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[Question] [ In the future, a high-tech human civilization has colonised a distant planet. The planet is basically Earthlike in gravity, climate, terrain and vegetation. They want to build Forevertown: A city with low-tech construction which is *built to last*. The projected lifespan of Forevertown is measured in millions of years. To start off with, the inhabitants will have high technology; but the city should remain habitable if they regress to Iron Age or (possibly) Stone Age levels. For the sake of argument, assume the city will not be deliberately destroyed by human action. The technology of the city builders is highly advanced but not "magical" by our standards. They can't violate the laws of physics as we currently understand them; in particular, magic self-repairing materials are not an option over this timescale. What is the best way to build Forevertown? More specifically: What form of construction would be most durable, with least maintenance? Mortarless stone buildings as seen in [Machu Picchu](http://en.wikipedia.org/wiki/Machu_Picchu#Construction) are an obvious candidate, but I am open to other suggestions. Related questions: [What is the best location for Forevertown?](https://worldbuilding.stackexchange.com/questions/12268/a-city-to-last-ten-million-years-location) [What are key maintenance issues for Forevertown?](https://worldbuilding.stackexchange.com/questions/12269/a-city-to-last-ten-million-years-maintenance) --- **Edit:** Mind-boggling though these timescales may be, the Earth is [projected](http://en.wikipedia.org/wiki/Future_of_the_Earth) to remain habitable for about 1 billion years. If there are still humans then, and they haven't fallen victim to the Singularity / zombie apocalypse / demolition of Earth for hyperspace bypass, they will have to confront similar issues over the very long term. [Answer] Granite is one of the most durable types of rock. As you walk across a granite staircase, the electromagnetic fields in your shoes are repelled by the electrons in the outer layers of the outermost atoms in the granite slab. Occasionally, a few granite atoms are kicked loose in the interactions. Over the centuries, this builds the grooves you see in old palace staircases. Same thing happens with every drop of rain that lands on the Machu Picchu, every gust of wind that brushes against the Pyramids of Giza. The point is, **10 million years** is a very, very long time. It **is about 2000 times longer than the Pyramids of Giza have been in existence**, and about 100 times longer than biologically modern humans have lived on this planet. Furthermore, the pyramids were mostly a solid set of blocks with little inner structure, definitely not meant to be lived in, and located in a dry inhospitable area. They have not aged gracefully:  *"Look on my works, ye Mighty, and despair!"*  *"Nothing beside remains. Round the decay Of that colossal wreck, boundless and bare The lone and level sands stretch far away."* Any functional city has many moving parts, and moving parts wear out. Magnitude 9+ earthquakes can crack and twist the landscape itself, divert rivers and crush stone. Rivers can carve stone over the aeons. Temperature variations can microfracture stones. Moss and fungi can grow on the smallest crack in the hardest stone. Dust particles deposit and build themselves to tens of meters. Lands can be submerged, or sunk beneath the sands. Ice-ages can layer 3 kilometers of rock-hard ice on top of your structures and grind them into dust. So, what do all these reasons it can't be done that tell us about **how to do it?** * Build in the most geologically stable area you can find. * Embed directly into the bedrock, preferably by creating a 20-km wide artificial bedrock (or even better, an artificial composite material with the hardness of diamond and the strength of [aramid fibers](http://en.wikipedia.org/wiki/Aramid)) * Build in a dryish climate, far away from easily flooded areas in case of sea level change and out of reach of glaciations. Have your nearby sources of water follow a prebuilt (high-strength) canal, with 1000-fold spare capacity to prevent it from ever flooding. * For your buildings use a nonreactive nanocomposite core (similar to the kind we use in tanks and aircraft) to be covered in low tech granite slabs that can be replaced. * Use a massive, heavy architectural style. No fragile high-flying arches for your city. * Have both the city as a whole and individual buildings be highly stabilized against earthquakes by placing them on a durable version of bearings. * Create a spaceport, where a von Neumann self-repairing machine that spends virtually all its time in space gathering energy and raw materials can return every 1000 years to release bots that will conduct maintenance. Still, your **biggest threat will not be the elements but humans**. The great Pyramid of Giza once had a shining facade of white stone and a gold pyramidion, that made it a splendid sight from tens of miles away. All of this was looted, and all we can see today is the inner structure. Looters will be by far your biggest concern, and unless you want to keep **gamma-ray robots in orbit to blast away the blasphemers**, there's little you can do about that... [Answer] > > magic self-repairing materials are not an option over this timescale. > > > I know you said this, but I'm assuming you're talking about stuff like self-repairing nanomachines. But there's an alternative, very non-magical answer to this question that's also self-repairing: **Plants**. It would require genetic engineering, but is still something I think would be reasonable. You'd modify trees so they created human-friendly structures - plantable walls, enclosed ceilings, etc. Then you can have a living city, with an indefinite lifespan. The technology is all in the creation of the plant, so even if your people regress to the stone age they can still collect seeds and re-plant buildings. Depending on how crazy you want to get, you could even create the plant so it turns some of the sunlight it collects into electricity and provides it from sockets that grow into the walls (or that can be accessed with mechanical sockets). There are two potential major downsides to this, but I don't think either is insurmountable: 1. Disease. Since your plants are alive, they can presumably, theoretically be attacks by things that attack other plants. An engineered plant could be extremely resistant, but your inhabitants might need to keep some basic knowledge of "burn diseased buildings and replace them with new, uncorrupted seeds". 2. Mutation. You're asking for a literally evolutionary timescale, and it's possible the plants will slowly adapt. However, I think human activity will, for the most part, guide this evolution in useful ways. Plants that grow out of control will end up being pruned or burned. [Answer] 10 million years is a geologic-level time scale - so if you truly want a structure to last the ages, then we're going to need some help...specifically, from geology itself. First, let's consider just how long 10 Ma really is:  So we need something that will last approximately three Epochs...wow, this is going to be ***epic!*** As a matter of fact, this is beyond human time:  That's right, this is about 5 times longer than our closest biological ancestors were even alive...no homo. (rim shot, please, Paul) But we're in luck because there indeed structures that are approximately this old, or even older - caverns and cave systems! The [Jenolan Caves](http://en.wikipedia.org/wiki/Jenolan_Caves) are considered to be hundreds of millions of years old, but they are also very wet, which will tend to make keeping things intact likely more difficult than in drier conditions. The [Grand Canyon Caverns](http://en.wikipedia.org/wiki/Grand_Canyon_Caverns) claims to be much younger, perhaps only around a few million years old in its present form, but it's also dry! Water is so good at eroding things, that I'd likely want to pick such a place to build - you can always drill to get access to the water table if you want, and it's easier to control than having it leak in all over the place. The beauty of caves is that they provide a world that seems relatively unchanging compared to the surface - as long as it doesn't get buried beneath mile-thick ice sheets during an ice age, or have the tectonic plates shift so much that it screws the place up by flooding it or filling it with toxic/explosive gases, you'll be fine! The natural environment of caves is so good at preserving things that things that died tens of thousands of years ago leave perfectly nice collections of bones. In some cases, the preservation is so good that scientists have managed to extract significant amounts of DNA from animals that have been dead/extinct for many thousands of years - and no one was even trying to preserve these things! The work of the pyramids seems so small compared to what our natural environment can do all by itself sometimes, doesn't it? This doesn't necessarily have to be a city for mole-people, though. There's no reason such a system couldn't be worked to have a number of "natural entrances", and people could conduct all sorts of outdoors activities. But if such a place existed there would be a strong incentive to develop underground living to a fine art and science, though. What caves buy you is something you need - protection from the elements. Otherwise, we don't really have any non-exotic substance that can last so long against the weather alone, and if we did it would need regular refurbishing/maintenance that is going to require high technology. What I like about caves is that progressive levels of technology could be needed to work/live/survive deeper and deeper recesses of the caves. If your people 'forget' how to make the mixture that goes into the UV light fixtures, or maintain the clean air systems, or operate the airlock/airway systems that allow access to the mines or geothermal vent forges, or stop maintaining the water-control systems so they flood lower levels...then the city doesn't get wiped out! They just begin to lose access to the higher-technology awesome stuff that is only possible to enjoy with higher technology. In theory, even an ancient people with little or no technological understanding could live in the cave systems, even if they have become unable to do the things necessary to navigate, survive, and fully enjoy subterranean living. With some maintenance, only your imagination is the limit - there are no unsolvable problems deep down. You can grow things, mine things, gather raw materials...the technology level used would be up to your civilization to determine. Want robotic-level automated facilities? Have them conduct their own maintenance, and perhaps only leave material gathering to humans if you don't want robots running around topside. Have big, gorgeous diamond/sapphire-coated representations of the raw materials needed by the deeper inner-workings to label the "inboxes". The humans just put the iron ore in the bin, wood in another bin, bones in another bin, etc, and the system handles the rest. How you want your story to go would, of course, depend on how the system was crafted and what the exposed/moving parts would be. A semi-autonomous automated system isn't completely out of our current technological abilities, so if this was built by a more advanced race they'd certainly be able to figure out auto-factories that can keep themselves going so long as they are provided with acceptable parameters. Make these inputs or environmental parameters the rules of the city, and so long as the inhabitants keep up their end of the bargain the system works. If they stop the system can have cascading levels of shutdown, ultimately having a core that survives on only the smallest amount of inputs, and designed to safely put itself in permanent hibernation if the final ingredient is no longer provided (your pick on what that might be - nutrient solution, sugar, blood, electricity, light, radioactive materials, whatever). The biggest danger will be dealing with people, then, screwing with things they shouldn't or not following the rules. Geological changes will cause issues, but an advanced race should be able to understand/predict with some reasonable degree of accuracy what might happen and plan a location or operating parameters that would deal with such a problem - they'll avoid systems that can be flooding with a shifting water table or areas likely to be buried under ice sheets unless the system can support people with no access to the outside, etc. Could be like a big bomb-shelter, or they could just ensure the build was in a place that they felt wouldn't face this problem. One note, though - over this period of time the people who first lived in the city or designed it will be different biologically over this time period. If people live inside most of the time or even all of it, there will surely be significant biological and psychological/culture changes over such a stretch of time, and so the people might be as different from their origins as we are from our non-bipedal ancestors (walking on two legs is believed to have started around 6 million years ago in human ancestral lines). That said, there's a crazy amount of possibilities there, and none of it requires magic! How you'll keep people from blowing it up, drilling into the wrong parts, etc, I don't know - but that's not the question. So enjoy! [Answer] A million years is a VERY long time. Mountains wear down over millions of years. The oldest structures we made is in the 5-8000 year old that is still standing. [Stonehenge](http://en.wikipedia.org/wiki/Stonehenge) is about 5000 years old. The pyramids start about 4500 years ago. Here is a [list](http://en.wikipedia.org/wiki/List_of_the_oldest_buildings_in_the_world) of oldest buildings as we know them. The oldest currently is less than 7000 years old. Stone is the most resistant but a million years is plenty of time for wind and water to cause it to wear away completely. Stone steps that are only a 100 years old have worn groves from feet. A million years of rain and wind not to mention ice will leave nothing standing. This all doesn't take into account any plate tectonics. Earthquakes will speed it up, and don't forget the changes in climate. Ice ages come and go, jungles migrate around the globe, volcanoes bury things under ash, winds move sand and dirt. For it to exist for a million years something would need 'constant' maintenance if even once a century. At that point anything could last. [Answer] An alternate approach, which seams to run counter to the scenario in the question, is that they don't plan for the individual structures to last forever. Instead we design a city with structures that are reasonably durable and can realistically be expected to last a generation or two. The materials, or at least surface layers, are low tech, and easy to produce/recycle within the local environment. Under this scenario the inhabitants are constantly rebuilding or refinishing structures to keep them habitable. No one building lasts forever, but the settlement lasts as long as people are willing to stay there and take care of it. [Answer] There is something in this question that reminds me of "how do you turn base metals into gold?" in that it presupposes there is an answer, and also that the answer is technological. The key thing about cities is that they are places for humans, and humans have needs beyond mere shelter. How are you going to satisfy those needs - for food, water, warmth? I guess there are technological solutions to those, but at that level you are only surviving, not thriving. If that is all you cater for, it is not safe to assume that some of those humans will not set out to destroy the city. What makes a city thrive is the dynamics of the social interaction, and somehow addressing the various social problems that arise. Social problems need social solutions, or at least socially-minded solutions, not purely technological ones. Technology applied to social problems without understanding the deeper social issues can be like calming the frog in the pot, but not minding that the heat is steadily raised towards boiling point. There is a problem in thinking the frog belongs in the pot at all, and likewise in assuming you can possibly solve social problems with technological advances. Now if you want to talk about Forevertown being a village rather than a city, such that the scale of the social issues and interactions is much more manageable in line with the principles of [Dunbar's Number](http://en.wikipedia.org/wiki/Dunbar%27s_number), then maybe you have a chance. But if you're prepared to consider that, then I'd encourage you to stop discussing imaginary solutions, and get out there in the real world where long-term peaceful sustainable living is a real and pressing challenge. [Answer] What can easily survive 10 million years? - a mountain of course. So build one and make it habitable. Pick center of biggest tectonic plate - it will last longer than 10 millions and not too many earthquakes. This will ensure that granite won't crack. Build a huge granite circle: with radius of 10 km and 2 km thick. In the middle build a crater 0.5 km deep - this is where people are supposed to build houses. Crater can have some nice terrain inside as well. Crater will protect people from winds, and has lake inside - to be source of water, rainfall goes to lake, oveflow leaves the city. Make sure to build some "rivers" to remove water and the yucky stuff from crater. Also city terrain should not have any pits, so all the water and wreckage can leave the city naturally. Lake is very flat by default and is made so that it can be easily raised in level by mini-dam. Water and cleaning: city is it's own source of water so they just poop into one of the "rivers". Since people are not supposed to destroy the city - we do need to worry that they will end up mining it. And even if they do, 50+ cubic kilometers of stone is quite enough. And population limit could be ~100k. If ice age comes city will be chilling without people until ice age ends. [Answer] I believe the only type of artificial habitat that can remain for a million years would be to dig tunnels and chambers into solid rock. If they are located far away from tectonic plate edges in regions with very low tectonic activity, there is very little that could cause them to collapse. [Answer] I don't think this is possible out of current knowledge and theory. At least not if there is significant technological regression. To last "forever" a structure has to be able to resist wind, rain, fire, flood, earthquakes, freeze/thaw cycles, mold/fungus/plants, animals/insects, along with wear and tear from its occupants. On the time scale you are talking about you also have to be able to handle multiple climate and environmental changes which makes the problem even more difficult. Almost always, materials that stand up well to one or more of these are quite vulnerable to others. In theory, if you could come up with a material that was completely non organic, resistant to impact and abrasion, resistant to oxidation and other corrosive processes, non porous, and strong enough to hold up its own weight and that of its occupants, you might have a chance. Everything I know of today relies on combinations of materials and regular maintenance to resists the various hazards. Most such maintenance requires high tech at some level of preparation or application. I think your best bet lies in the realm of a formed rock. Essentially casting/fusing the stone so that the structure is one solid piece. The surfaces have to be perfectly sealed, with no cracks or pores down to the microscopic level. You can not have any hard angles, things have to be shaped such that vibrations and applied forces flow without having places to build up/reinforce and cause fractures or fatigue. Moving parts are also most likely out, so doors and windows may just be, or end up as, open holes that the occupants fill with whatever materials they have the technology available to work with. Even so I think your useable life is probably measured on the scale of thousands of years rather than millions. [Answer] Diamond/ carbon nanotubes have the property of being combustible, so perhaps they are not a good choices. I think quartz crystal might be more resistant to erosion than granite and supposedly does not have a big issue with fragility due to cleavage planes. [Answer] I don't think that it is fundamentally possible because any habitable planet will have geologic activity as well as climate actions. Earth as a planet will remain habitable for a very long time, but no individual spot can be guaranteed to remain habitable. Over 10 million years, you have to look at such things as an ice age steamrolling over your city regardless of how it is built. You have to look at continental plates crushing and in the process changing the shape of a formerly flat area into vertical mountain cliffs or even turning your city upside down. You have to look at the crust of the earth being stretched and possibly a new ocean forming where you built your "forever" city. Of course you can TRY to find the most geologically stable spot, but pretty much no matter where you go, over 10 million years, your town will suffer catastrophic events that even the rock itself can't withstand. [Answer] I'm not certain why "regression" is even something worth worrying about. A culture is going to build a structure for the purposes of its own culture (or at least one reasonably similar to it) so I don't at all see the point of making something able to survive with minimal tech/knowledge. Maybe if the question was more how a benevolent Demi-God-like race would build an everlasting protective structure for a less developed race. Besides, it seems to me that the whole civilization dying out is much more likely than the people regressing that far as a whole. Just because that has been a popular event in literature doesn't mean that such an event is at all likely. Especially in a civilization in which, presumably, their tech and understanding is much greater than our own. I see the chances of some disease wiping out the higher functioning power of an entire species (yet not killing them) unlikely given the tech, knowledge, and all the pressupositions that go into the ability to even create Forevertown. So I would say you remove any precautionary planning of species regression. Even more likely than extinction (or regression), would be the civilization simply leaving to anothor habitable space, abandoning Forevertown. Forevertown 2.0 is a MUCH better iteration of its first attempt, especially if it was built by Apple ;). If Forevertown's culture is able to create such an amazing thing as Forevertown, give them a few more thousand years (or half a million) and planet building will be their next venture. Ring World anyone (Larry Niven's books)? In the end, I just can't imagine a scenary in which such an everlasting immense structure would be useful (return on investment, economics, conservation of resources...) compared to a civilizations more natural way of doing things. Constructing and re-constructing seems to work better. Or better yet, building and abandoning. I think maybe a giant monument to a civilization's prowess, or a timecapsule of sorts would be a more useful idea. I realize this isn't exactly answering the question, but I think it is fair to at least say this probably wouldn't be a useful enterprise for any advanced civilization. My actual answer to this question is simply that it would be a bad idea. Any other answer I could think of would be incredibly limiting to the inhabitants. Even if there were magical materials that would never wear or change even if passed through the sun, such a substance would be pretty hard (or impossibly) to modify for the simplist of changes. I would rather not force a whole population to live in an unalterable city. From small towns to massive towns in the U.S. there is immense change over 100 years. Often times it is indistinguishable. The needs of a city and culture change so much it is impossible to build a permanent structure of any size that won't inhibit improvements. [Answer] Your best option for building material would have to be diamond but we're talking shells of structures here - habitable, yes but after millions of years everything else inside the building will have decomposed to uselessness. No lights, electrical systems, lifts, hinges, etc. gone. [Answer] Very strong or durable materials... nothing. But knowledge may be durable. Then, they will constructed of very simple materials (like sand or vegetates), but with the acquired knowledge to replicate forever. We can analyze the oldest buildings, like the pyramids of Egypt or Stonehenge. But if we have lost the knowledge of were it was be made, we can only see them (and perhaps to guess its technology). Another point of view is analyze the most older cultures remaining in the world. Check a pre-Incan people who live on forty-two self-fashioned floating islands in Lake Titicaca Puno and Lake Uru Uru. The Uros use bundles of dried totora reeds to make reed boats (balsas mats), and to make the islands themselves. The larger islands house about ten families, while smaller ones, only about thirty meters wide, house only two or three. The islets are made of totora reeds, which grow in the lake. The dense roots that the plants develop and interweave form a natural layer called Khili (about one to two meters thick) that support the islands. They are anchored with ropes attached to sticks driven into the bottom of the lake. The reeds at the bottoms of the islands rot away fairly quickly, so new reeds are added to the top constantly, about every three months; this is what makes it exciting for tourists when walking on the island. This is especially important in the rainy season when the reeds rot much faster. The islands last about thirty years. [Answer] You want to build your city **in space**. Find a sufficiently large asteroid. Hollow it out, make it rotate, live on the inner surface. Plenty of science fiction authors have given rich descriptions of what such habitats can look like. If designed properly, there really isn't anything that stops it from lasting ten milllion years. [Answer] OP mentioned that occasional repairs are acceptable, as long as they can be made by using simple technologies after technological regression. For such requirements, **mud bricks** are perfect fit. Build it in dry climate, and maintain it yearly: [Timbuktu](http://en.wikipedia.org/wiki/Timbuktu) and [Djenné](http://en.wikipedia.org/wiki/Djenn%C3%A9). If climate changes, city can be rebuild few miles upriver every generation or so. [Answer] Even today we can create some pretty amazing materials. And a space-faring civilization would probably consider our crude "high-tech" materials as we consider clay of stone age people. So, **extrapolate from modern high-tech materials**. Simply make the town of materials, which will not be eroded or corroded away in 10 million years. Have nanotech construction technology to place desired alloys and other materials in a composite matrix. If cost is an issue, the material should probably be based mostly on carbon, silicon, iron, and nickel, but a space-faring civilization would presumably have an abundant supply of all exotic elements, by asteroid mining. An important consideration is architecture. You don't want water to accumulate anywhere, even if something clogs drainage systems. You want weaker spots (windows, probably) protected from the weather. You want to make people walk on areas which are built thicker to take the increased wear. And if course you want everything thick enough so that it can take 10 million years of wear with enough thickness left (50%?), and most wear concentrated on surfaces where it doesn't affect functionality. If you want to get technical, compare the material to modern materials, either in actual text or in an Appendix depending on style. Then let the reader extrapolate in their own imagination. Current advanced materials are mostly made for extreme environments, such as turbine blades of jet engines, disk brakes of sports cars, pump parts for manufacturing highly corrosive chemicals, and so on. On the other hand, advanced construction materials of today are sensitive to cost, which limits them. A material designed to last "forever" in "normal" conditions with little worry about cost would probably be optimized a bit differently, using rare elements freely, yet not for extreme conditions. For example, resistive more against wear by raindrops than wear by molten lava. So you don't have to and you shouldn't pick an existing alloy/composite, just use them for ideas. Some links to get an idea * <http://en.wikipedia.org/wiki/Superalloy> * <http://en.wikipedia.org/wiki/Advanced_composite_materials_(engineering)> * <http://en.wikipedia.org/wiki/List_of_alloys> * <http://en.wikipedia.org/wiki/Weathering_steel> [Answer] What has lasted billions of years? Oceans. It is fairly certain that oceans aren't going anywhere any time soon. Imagine a huge boat, made of aluminum. Immediately, you can find a problem with this: storms. A storm could quickly destroy or flood a boat. Solution? Root it into the ground, like an oil rig. However, tsunami waves could destroy this easily. But if it were halfway underwater and ha domed roof, it could withstand tsunamis. To allow people to walk out and see the sky, replace the dome. Instead, you could have a set of aluminum panels that are set on the outside of the ceiling of the huge city, and use replaceable bolts to lock it in place. As long as the people are careful not to scratch the panels, no water will get in. As a bonus, soil could be placed on top of the city, allowing for a "park", which would be regrown after huge storms. This may not last 10 Ma, but it will last a while. ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help). Closed 8 years ago. [Improve this question](/posts/23350/edit) Joe, an average citizen, decides to take over the world (for various reasons). He's an average person, with an average job and average resources. Does Joe have a realistic shot at his dream? Some clarifications: * By "take over the world", I mean - at the very least - control the United States, Russia, the European Union, the United Nations, China, and India. * Joe must, at the end, be able to manipulate all the governments of the aforementioned nations, although he does not have to be a visible leader - being a puppet master behind the scenes is okay. * "Average" refers to the average of something in a first-world country. * Joe must rise to power within 50 years. He is currently 25-ish. * There is no world-controlling position or secret society already in existence, so Joe cannot simply join that group and become its leader. If so, how can Joe rise to power? --- **Note: In response to the various comments/answers, I am not Joe!** [Answer] Powerful leaders tend to have a couple things in common: 1. Means 2. Intelligence 3. Opportunity 4. Desire for power 5. Charisma Given the weight of history I do not believe that Joe Average could (or would) take over the world. Thank goodness! But let's give our Joe Average better than average intelligence (maybe a lot better), a charismatic personality, a psychopathic desire for power and a bit of luck and see how far he can go starting from average means/education. In the early 90s Joe is at University, where he is learning programming and computer science in the earliest days of the internet. Being rather bright he cottons on early and develops a plan to make himself extremely wealthy and powerful. He drops out of school and starts an international consulting company targeting contracts with companies and governments that are switching to electronic payroll and communications. His software products contain hidden code that give him back doors into the computer networks of every company and agency that he works for. Within 10 years he has installations in place in almost every major government and Fortune 500 company. He uses these connections to skim very small percentages off of payrolls, and to tap high level communications. He can use internal emails between executives to pursue insider trading. He can sell secrets to competitors or other governments. He will have to be very careful not to tip his hand and it will make a thrilling story of how he manages to continue to grow and operate without being detected. But with a bit of luck he will soon have amassed a very large amount of wealth in a complicated scattering of accounts and have more intelligence than any spy agency on Earth. During this time he is also slowly building an organization. One thing about ruling the world is you really can't do it alone. There are just too many things to worry about. Even if you are going to leverage the existing infrastructure it will take more than one person just to pull the puppet strings. Joe needs an organization. So he begins recruiting individuals. He is a charismatic personality so finding followers is easy. The hard part is finding people who will follow without challenging him, but are still intelligent and ruthless enough to be useful. Joe uses his consortium of consulting companies to identify and train up promising individuals. What he does next is target officials in governments around the world. He uses blackmail, bribes, and forged computer records to slowly move into place people that are loyal to him. He can control vote tallies, criminal and health records, even rewrite laws in subtle but powerful ways. As more and more of Joe's minions take positions of power the pace of the take over can accelerate. Joe has the good fortune of operating in time of rapidly increasing globalization and computer connectivity. This gives him many opportunities to establish his secret back doors in ever more critical pieces of infrastructure. Finally Joe for all intents and purposes controls the world. He has the leader of every major power in his pocket, either by directly placing them in the job, or blackmailing/bribing them into submission. What does he do with this power? I think this is the critical question. He can't just start making wild demands or he is going have insurrection on his hands. He is going to have move slowly and subtly affect public opinion to shift it in his desired direction. His reasons for wanting power and how he uses the power to affect his desired results is a whole other story. [Answer] You will have to forgive the crude stereotyping which occurs in this answer. Joe is taking over the world on a budget, and frankly he couldn't pay me enough to figure out how to do it without national stereotypes, so the plan is what it is. The details are available in my book, *Taking Over Third World Nations for Fun and Profit.* The first three steps are the standard approach to becoming a multi-national force. **Step 1:** Buy a set of Lego Mindstorms robots, a plane ticket to Djibouti, and materials for pipe bombs. Djibouti's capital, Djibouti has only one railroad track going into it, so you should be able to create a pipe bomb wielding mindstorm robot that triggers when you enter the switching station. Their per-capita income is only $1600, so it should not take much to convince them to surrender to your nefarious schemes. Congratulations, you are now a sovereign power. **Step 2:** Now that you are a sovereign nation, fly to France, and proclaim a declaration of war. They should surrender without a fight. **Step 3:** Take the French Foreign Legion, walk them backwards into Poland, tell them you're leaving, and they'll never see it coming until you control Poland as well. **Step 4:** Go back to France and go to BIPM, the International Bureau of Weights and Measures. Stored at BIPM is the International Prototype Kilogram (IPK), the definitive measure of what a kilogram actually is. Did you know Troy Ounces are defined to be 480 grains, and a grain is *defined* to be 0.00006479891 kilograms? You define the mass of a kilogram now. Through clever manipulation of the IPK, and thus the value of gold, corner the gold market. **Step 5:** Buy up as much Greek debt as you can. With your corner on gold, you should be able to buy up most, if not all of it. Use your financial power to *encourage* them to vote you into power. **Step 6:** You should now have enough world power to do something about Britain. However, they will be too proud to be taken over, so we're going to have to make friends with them instead. Use your control of the world-wide Patrick Stewart fandom to organize his rise to a seat of power. Then use that power to give Ian McKellen a seat as well. **Step 7:** The mere fact that you managed to get Patrick Stewart and Ian McKellen to rule Britain should be more than enough show of awesomeness to get Joe elected President of the US, free and clear. If it isn't, Joe should rethink whether he's actually awesome enough to rule the world. Maybe he was just Joe below-average. **Step 8:** Look, taking over Russia is hard. There's snow... and the snow. But they do have a weakness: vodka. If we could get them hooked on something that has more flavor, but can still leave you with a pounding headache, we could get them in a better mood. As President of the USA, you could probably swing a deal with Mexico to do some immigration reform in exchange for massive government funded transport of tequila into Russia. Once they're hooked, the French Foreign Legion might be able to pull Napoleon's March 2.0 (this time, in the spring!), and the Russians may forget to burn their fields while they retreat with newspapers to protect their hungover heads from the light! **Step 9:** Okay, enough dirty work. Now we can go back into doing this with style. Broker an arranged marriage with the daughter of an influential Indian politician to gain power. Then, ship all the Poles to India. Give them government roles, and let the Indian bureaucrats teach them how to take bribes. They'll get it backwards, offering better services for those who do not bribe, leading to the most rapid reform ever recorded in a country. **Step 10:** China is under attack because their market is being eroded by cheaper sources of labor, like India. Use control of India and the Chinese market, the USA, to broker a deal for power in exchange for not crushing the Chinese economy. If they're not biting, you can engage in psychological warfare by having the call centers of India all spamming the phones of the Chinese leading party, day and night. **Step 11:** Now we need some more power in the EU. You have control of several influential atomic clocks in France, begin skewing the time to make the Spanish siesta take longer than usual, while you manage your invasion. By this time, from all your manipulation of the IPK and time, German engineering is going to have lost its precision. You should be able to waltz past several legions, all suffering from components whose insane tolerances are no longer being met. That, along with the wise visages of Patrick and Ian in Britain should be enough to take over the EU. **Step 12:** Australia. Leave it alone. Seriously. Who would want to try to take over Australia? Bunch of descendants from convicts, kangaroos, and convicted kangaroos! We'll leave Australia off of world domination for now. Mostly dominated is good enough, right? Also, nearly every animal over there has some deadly poison. It's simply safer this way. [Answer] # A series of (un)lucky events Joe is on holiday in Saudi Arabia where he accidentally saves the life of the Sheik who nominates Joe his sole heir. He marries the daughters of his rich neighbours and become sovereign of good part of the middle east. While celebrating his marriage with the King of England in Las Vegas (hey, it's legal now), he manages to double his fortunes. The King convinces Joe to use the money to concur for American presidency (his dream has always been to re-acquire the old colonies). Joe wins. During a visit to the Norad, Joe falls on a button and starts a nuclear attack. Trying to help the technicians to stop the launch Joe actually hampers them. It's a disaster. Half the world is destroyed in the nuclear holocaust. The people in the Norad (including Joe) survive. Joe is still King of Arabia and with the available resources manages to buy/conquer the rest of the world (there is not much left), in a bid to destroy any nuclear weapons left and prevent a second tragedy (the world is full of idiots after all). Edit: a variation of the (un)lucky promotion is narrated in the movie [Idiocracy](https://en.wikipedia.org/wiki/Idiocracy) (which I discourage you from watching): an average Joe is hibernated for a military experiment. The project is shut down in a hurry so they forget to wake Joe up. He ends up in a distant future where everybody is an idiot because they spend all time watching TV. At the end the protagonist becomes president of the world because he's now the most intelligent person... [Answer] ## No. The logical answer to your question is "no" for the simple reason that the average person is not a world leader. By the time someone has got even a little way along the path that would end up with them taking over the world, they have ceased to be average by any meaningful criterion. I realise that isn't what you mean by your question - and I'm sure someone from an average background might - but they would be far from average by the time they had taken over. In fact they would be extraordinary and unique in human history. [Answer] I think Stalin is probably the closest you would see anyone in history having come to this. He was born into a working class family in a large empire. When the tables turned he was able to make his way up the new power structure eventually becoming the president. WW2 provided expansion to his empire where the soviets didn't so much liberate eastern Europe as counter-invade it. Had a few things gone a bit differently the USSR could have claimed more of Europe and possibly even Japan. The Cold War stymied some of the Soviet's expansion plans, but if the USSR had become the only nuclear power Stalin could have expanded much more. TL;DR Someone with an average background can gain power when a revolution overthrows the ruling classes. [Answer] **How to Become Dictator of the World in Five (not so) Easy Steps** Step 1) Get the right background. I'll assume John Q. Public (Joe Public is more fitting, but is the British equivalent) is an American citizen by birth (I won't go into demographics). He should spend a few years studying governance and politics. Around the age of 30, he should run for office or hold a high position in a company (e.g., CEO). From there, he can build the right political connections as he prepares for... Step 2) Become President of the United States (POTUS). Starting at the age of 35, an American citizen is eligible to become POTUS. John will still be a far cry from controlling the entire world, but he's well on his way. The United States and, more specifically, the POTUS, is considered to be the [leader of the free world](https://en.wikipedia.org/wiki/Free_World#.22Leader_of_the_Free_World.22). Regardless of whether that's true, the U.S. does have significant impact on the world's other countries, which John will need for... Step 3) Take control of the United Nations. This seems like a daunting task ([and it is](https://en.wikipedia.org/wiki/United_Nations#Membership)), but John's position as POTUS gives him an excellent position from which to influence the world's other nations. Small nations always need assistance, and John should be ready and willing to apply appropriate resources to local issues, such as disaster relief and other humanitarian pursuits. Help often enough and in the right ways, and John can push other nations into line. From here, John just needs to deal with... Step 4) Silence the dissenters. Nations like North Korea are unlikely to go along willingly with a single world leader. Now that John controls both the United States and the United Nations, he has nearly unlimited ability to remove North Korea from the rest of the world through ultimate sanctions. (China will still be a problem, but John can always use leverage against them, through the UN.) Repeat this effort for all opposition until no country is willing to oppose your voice on the world stage. Now John just needs to work on... Step 5) Enjoy the fruits of your labor. John only has 4 or 8 years (unless he can get that [pesky rule](http://constitutioncenter.org/constitution/the-amendments/amendment-22-presidential-term-limits) out of the way) to get all this done (this is why Step 1 is critical), but the influence that comes from being POTUS doesn't end when one stops being POTUS. John can now retire comfortably, sure of his world reign. All he has to do is weigh in on worldwide elections, attend a few UN meetings, and the like; with his power and influence, a simple nod leads to success...for the world, of course. [Answer] **Be a billionaire, take over the world**. Joe just needs to work his way up to being on the board of directors for several very large companies such as Exxon, Alcoa, Apple, Google, Microsoft, etc and he'll be a very rich man, very quickly. Being in a position of power like this is definitely doable in 25 years or less. What you want is a [plutocracy](http://www.merriam-webster.com/dictionary/plutocracy) where the rich people govern either from behind the scenes or in the clear. Plutocracy offers the advantage that political control comes from the control of wealth which may freely cross political borders rather than the assent of people in a given geographic area. Controlling large amounts of wealth also means that you can buy whatever legislation you want to give you further advantages or immunity. If Joe is a psychopath, then he's well on his way to being CEO. > > British journalist Jon Ronson immersed himself in the world of mental health diagnosis and criminal profiling to understand what makes some people psychopaths — dangerous predators who lack the behavioral controls and tender feelings the rest of us take for granted. Among the things he learned while researching his new book, “The Psychopath Test: A Journey Through the Madness Industry”: the incidence of psychopathy among CEOs is about 4 percent, four times what it is in the population at large. ([source](http://www.patheos.com/blogs/drishtikone/2013/10/are-ceos-and-entrepreneurs-psychopaths-multiple-studies-say-yes/)) > > > A related article but different [source on psychopaths](http://www.forbes.com/sites/jeffbercovici/2011/06/14/why-some-psychopaths-make-great-ceos/) in the C-suite. Because of the political attitudes and histories of the countries listed in the OP, no obvious political union will be possible. Given the animosity between the US and Russia, and the radically different cultures, those two countries will *never* become a single political entity. Similar animosities exist between all the listed countries. Besides, unifying is an incredibly difficult job and there's better ways to do it. Note that the United States, in the [opinion of many](http://www.salon.com/2015/03/22/5_signs_america_is_devolving_into_a_plutocracy_partner/), is already turning into a plutocracy. [Answer] Joe hates his job as a mall rent-a-cop. He doesn't get to carry a weapon, everyone treats him like a joke, and because he is younger than the other mall rent-a-cops, they make him do all the unpleasant jobs. On a particularly nasty day at work, Joe is cleaning up vomit in the children's play area and muttering about how much he hates his life. "We have custodians, but who cleans up the puke? That's right, the guard. Because Bob the custodian took the day off, and nobody can find Sally, and of course *Sergeant Frank* can't do any work, not while he's trying to flirt with the Victoria's Secret manager. Again." Earlier that same shift his request for vacation time to attend his parent's funeral was denied, a poodle peed on his shoe, a black kid tried to rob a store and called Joe racist when he intervened, and the crazy lady from that nick-nack shop followed him around for her entire lunch break. So it was understandable that when a six-year-old boy shoved Joe into the vomit he was cleaning up, a little part of Joe called 'self control' broke. The kid actually giggled as Joe stood up, one hand and a knee now covered in curdled vomit-milk. But what really did it was the kid's father, who thought it was so funny, he had to share it with everyone- and started taking pictures with his phone. Joe vented his rage in a yell and began to storm toward the kid's father. As Joe reached the end of the brightly-lit, padded play area, other on-lookers took notice, and cellphones came out of everywhere to record what was sure to be quite a sight. At that moment, Vick Vickerson happened to back up into Joe's way. Joe, beyond caring, swears and lays into Vick with all the primal pent-up rage of a 25 year old rent-a-cop with no actual combat training. Wild punches and uncoordinated kicks smashed into Vick, bringing him down and unconscious in moments. The stunned crowd is motionless. Even the six-year-old boy has stopped flinging puke at other kids as Joe stands panting over the nearly lifeless Vick Vickerson. At this critical moment, a nearby mother asks a very important question. "Is that Vick Vickerson?" She recognized him from a poster she saw in Walmart just that morning. You know, the ones near the service desk that everyone inspects while waiting for one overworked employee to deal with fifteen angry customers? The name rings a bell with someone else. With cellphone videos still recording from all directions, Murphy, a retired cop who was sitting on a bench while waiting for his wife to pick out another pair of shoes, exclaims, "That *is* Vickerson! He's wanted in seventeen states for child molestation and rape!" Joe becomes an instant media sensation and YouTube celebrity. No less than five different cellphone videos show the pummeling from slightly different angles. His unassuming nature makes him a temporary hit with news crews looking for their one "good story" for the day, and the interview fees and donations from pleased parents across the world enable him to get a 'sick' sports car. After all, Joe is pretty proud of himself now, and certainly not wise enough to keep the money or invest it somewhere. Only a few weeks later, a sketchy group of business owners decide they need help getting a certain law passed in their state, and the current governor just won't do. Joe's popularity just happens to coincide with the right timing, and these business owners send out Sara, the red-headed seductress, to get Joe on their side. After listening to the "very reasonable" arguments (and a quick marriage to Sara), and with their financial support, Joe runs for state governor. With the behind-the-scenes support of the Business Barons, and with his momentary stardom, Joe wins the election against an unpopular old man accused of corruption. The Business Barons are no fools, and manage to get Joe a pretty decent group of advisers. Nevermind that Joe unwittingly helps the Barons with their pet projects, the advisers actually do a good job, with Joe reaping the public benefits. When the Barons' coalition falls apart from internal squabbling, Sara sticks it out with Joe, as she has grown used to the perks of being a governor's wife and prefers Joe's honest, if ignorant, personality over the various Barons' manipulative ways. After a few terms in office, Joe is old enough to run for President. He gets the Republican nomination with his hard stance on crime and successful financial history as governor of his state (despite his advisers doing all the work). Sara's efforts among the rich and powerful to get her husband nominated significantly help his case. Running on a platform of "Just an Average Joe," Joe goes up against a Democrat who, by all rights, should win the election, but in an ironic twist of fate, the Democratic candidate is actually proven to have been born in Cuba, not the USA. Unable to put forward a new candidate in time to drum up sufficient support, Joe wins by a healthy margin. This book needs to end, so I'll summarize the rest. We now have Joe in his 40s as the American President. Some kind of catastrophe (zombies, alien invasions, nuclear war, polar ice-caps melting...) helps bring the world back together, and Joe is in position to help folks out. Through the clever manipulations of those around him, Joe ends up the nominal leader of just about everything. Something tips Joe off to the questionable activities of his staff, but Sara convinces him to roll with it. A career politician by this point, Joe has learned how to lie well enough when he wants to, and to keep Sara he definitely wants to. Thus Joe controls the world, despite having no real qualifications for the position. [Answer] # Joe should become a hacker. Joe needs to focus on learning how to manipulate software programs, intercept and edit data, and hijack computers and related devices using viruses, Trojan horses, and the like. Here are some ways Joe could use this to control the world: * **Rig election vote counts.** Joe can run for office, as can anyone else, but if he's as average as the question says he is, then he won't necessarily have as much charisma or know-how as many politicians do. The solution? Run for a low-level office and make a decent stand, then hack into vote-counting systems and change the numbers just enough to win the election. When elected, Joe can do many things to make him popular among the rest of us, and his accession to power can begin. He then needs to implement Phase 2. * **Take control of weapons systems.** Missiles, drones, and other weapons require computers and software, and, therefore, they can be hacked. There is tight security behind them all, of course, but no security system is 100% immune to attacks. If Joe can take control of a major weapons system, he can perhaps hold nations hostage, [as Avernium suggested](https://worldbuilding.stackexchange.com/a/23356/627). If Joe couples this with being elected, he can do quite a lot. Hacking into an enemy's weapons systems is a good way to win a war. Plus, if he reaches public office, he can have others work on hacking into the systems, turning a war into a cyberwar. [Answer] ## Joe should crawl the media ladder Yes, the internet is still more and more valid source of news. But most people still use TV. And the internet news sources are owned by media houses. So Joe should start working for one media house ASAP. In his spare time, while he is less than 30 year old, he should also start some startup business. One awful hand wave here is, that Average Joe will come up with not so average idea, which will bring him some money. Write compelling stories during the day, start a business during night should get Joe some publicity and money. **Use money to start media house or buy part of media house** Widen your media influence. Write about politics and what politics should do. Widen your circles into politics and search for good candidate with potential of getting really high. Use your media influence and write even more about such politician. Help him to get to the power. Let him know that such power is because of you. Let him pass laws you need. Use his connections or your connections to other countries. Sell your stories abroad very cheap. Basically give your compelling stories to other countries. Use money you have or you saved to get you in other countries media. Repeat with other politicians from more countries. Write awful tabloid stories about their oppponents. Write great leader stories about politicians you picked up. Make sure the politicians know they got to the power because of you. Let the politicians donate some state money to your media house. You know, for advertising the country, for information systems... Make sure the money you got are more than you need for pulling the needs (aka corruption). Make sure the politicians you got to the power are corrupted too. Make them know that if they stop cooperating, they are done. Widen your circles even more. At this point you should have enough money to get into Russia or Chinese medias. Repeat the same: Make sure the politicians know you can make them into Great Leaders or Dumb Idiots. Make sure they follow what you need. It is awful lot of work, where Joe sacrificed self to be world leader, but I think it is doable (at least the corruption way). By age 70, Joe should be in possition of [Elliot Carver](https://en.wikipedia.org/wiki/Tomorrow_Never_Dies) [Answer] Those who are in power (or even two kilometers aware of them) are already under the influence of as many different pressure groups as you may imagine (parties, lobbies, administration officials, financers, family, other nations, even uncondicional supporters need at least to believe they are being heard). As someone said, "an stadist is a politician that stands straight because he has the same pressure coming from all sides". The average Joe will be just one tiny, tiny voice inside a tropical cyclone, and just by attempting to influence just one leader. Of course, if the average Joe has millions of dollars for donations or investments in the country, or one to ten TV networks, his influence will be way more effective; but at that point he is not "average" anymore. Even dictators need the support of at least a sizeable fraction of the people under them to keep power; and as long as you need someone's support that someone is in a position that influences the ruler (top officers in dictadures sheldom have low salaries, and usually are as "above the law" as the dictator himself). In a democracy, complexities multiply manifold (think of the USA Congress, Supreme Court, etc.). If it serves for anything, think that as soon people in charge had learnt that HDE 226868 was influencing all the world's leaders toward a world without corruption, less military expending, and justice and goodwill in general (because that is the idea, right?), your life would have become considerably shorter. [Answer] That’s a pretty tall order. There are a lot of interesting routes on this one that I’ll detail some strategies for. **Power by Force** This is a pretty standard approach historically. From the Mongols, to the Romans, to the Nazis, individuals have often controlled vast empires obtained through sheer militaristic force. Unfortunately, even if Joe was given full control of the militaries of the United States and her allies, forcefully taking control of the remaining major nations would be intractable at best, and totally impossible at worst (never mind maintaining control after seizing it). Poor Joe doesn’t even have an army yet. If you look at current generals in commanding positions of the [U.S. military](https://en.wikipedia.org/wiki/List_of_United_States_Army_four-star_generals#1947.E2.80.93present) you’ll find that not only are all of these men old, but they’ve spent their entire lives achieving their rank. Likewise, U.S. presidents (and leaders of other countries) often require life-long careers in politics or other areas that can provide the experience to govern. This kind of timeline is a very big problem for Joe, and it only gets him halfway to his goal. **Power by Diplomacy and Trade** Since the end of the cold war the spectre of massive violent conflict between major nations has been shrinking. In our global economy there are enormous benefits to cooperation and trade. This presents a different path to control for Joe: ruling an economic powerhouse. There are several corporations today that have a remarkable global reach. Google and Amazon alone not only have a global presence but have also diversified into many different economic verticals. As these and other corporations continue to grow in coming decades, so too will their influence in government the world over. The CEOs of these companies could then be said to wield rather considerable power. This track actually feels suitable for Joe. With his sociopathic traits he could certainly excel in office politics and rise the corporate ladder. He will need talent and expertise in other areas, but ruthlessness and desire for power could get him a long way. Unfortunately, even if Joe becomes CEO of Megacorp, he will only have limited control over his desired countries. Even worse, it will be difficult for him to take manipulative action without public scrutiny. **Power by Terror** When the traditional approaches fail, there’s always the terror option. Since ruling from a public pedestal doesn’t seem feasible for Joe, doing it from the shadows may be his best bet. There are a few ways to do this. For starters, blackmail is an incredibly potent weapon. Rather than attempting to interfere with the sovereignty of these nations, he could simply dig up enough dirt on enough powerful individuals to effectively control them. Unfortunately, finding enough individuals with scary enough skeletons in their closets to control even a single country would be incredibly difficult. Joe’s network of spies would need to be sweeping, dependable, and very, very effective. That doesn’t even take into consideration the limited feasibility of Joe orchestrating hundreds, if not thousands, of government officials across cultures to do his bidding. It’s not looking very promising for Joe. One final technique would be to essentially take these countries hostage. In classic hollywood fashion, one of the best theoretical ways to do this would be with the threat of nuclear weapons, preferably hidden in highly populated areas. The problem with this, as many movie villains have unfortunately discovered, is that world governments typically despise being taken hostage and have a tendency to devote their entire security force to stopping you. But for Joe to even get to that point, he needs to either acquire nuclear weapons or be able to reasonably convince world governments that he has them. Thankfully for the world’s continued existence, neither of these options are practical for the average Joe. Alas, the answer to Joe’s question is almost certainly a **No**. Attempting to control so many heavily populated, culturally diverse, and diplomatically misaligned countries is out of reach for even the most powerful of individuals, let alone the average Joe. To even further cement that point, one needs only to examine powerful figures throughout history. The largest empires were rarely ruled by average people. Poor Joe is probably better off picking up a copy of Civilization. [Answer] I would take a lesson from the <https://en.wikipedia.org/wiki/Black_Mirror_(TV_series)> episode <https://en.wikipedia.org/wiki/The_Waldo_Moment> Where a Blue Cartoon bear takes over the world. If Waldo can do it so can your hero. Synopsis: In a UK election a Cartoon bear stands for election to take the mickey out of your stereotypical slimy politicians. Despite losing - he came close - he is found to have universal appeal across social media and becomes a brand that influences politics everywhere. Now in the original story our hero - the comedian behind the character eventually quits and is replaced - invisibly to the public by someone with far less social conscience. But if we imagine for a minute that the original comedian had stuck it out we now have a 25 year old thereabouts humble comedian of the sort of background most wanna be comedians have finding himself in a position in which his say dictates all governments all over the world. In the original version we absurdly have Jackbooted thugs controlling the world dictated by a Blue Cartoon Bear. But hey that's Black Mirror - its meant to be dark. [Answer] The key to resolving this is to understand that nearly everyone else who is influencing from behind the scenes is almost certainly using outdated methods. He needs to get an AI expert (easy to get a geek onside: nobody listens to them - so anybody who does becomes a highly valued friend) and have him build a computer system for influence tactics. Improve the system as you go: what works at Parish Council level won't work at international level. Maybe one route would be to create a team of "grand viziers" (political advisors of great wisdom) to all the most important people, without them all knowing that everyone is getting their advice from the same source. Becoming the advisor to great people is easier than you might think: look at some of the idiots who have done so (e.g. both Hitler and Jack Kennedy had quack doctors who made them feel good by injecting them with amphetamines, and Reagan got advice from an astrologer via his wife). Edit: I don't approve of Vincent, in locking the thread, describing my answer as "low quality". I sincerely believe that while it probably won't work, it has a better chance than any of the other ideas presented. [Answer] I think pretty much by definition anyone with the ability to take over the world is someone of extraordinary capabilities. Many people with exceptional abilities have tried to take over the world, and despite thousands of years of human history none as succeeded. Taking over the world is not an easy thing to do, or someone would have done it by now. Your question is like asking, "Could someone of average athletic abilities win an Olympic gold medal?" I think anyone who wins an Olympic gold medal must be one of the best in the world, or he couldn't win. I suppose if you define "average" narrowly enough, it would be possible. If you mean born to an average middle class family and not inheriting any great power or wealth or otherwise having great power and wealth dropped in his lap, but nevertheless being someone of extraordinary intelligence, charisma, political skill, military leadership abilities, and/or other relevant skills, then it probably is possible. Lots of powerful world leaders throughout history came from humble backgrounds. As to a realistic plan to do it, if I had one, I'd be ruling the world now and I'd sentence you to death as a potential dangerous upstart. :-) If you want to be realistic, all the creative plans you see in movies and in other posts here are generally impractical. In practice, people who have succeeded in the past in taking over large countries have almost always relied on one of three basic plans: (a) Run for office in a democratic country. Work your way to the top through the existing political system. If being a democratic leader isn't enough for you, then once you get to the top, start changing the system to give yourself more power. (b) Join the military. Work your way to the top. Once you're high enough, get a few like-minded friends and stage a military coup. (c) Form an organization of political dissidents. Wage a guerilla war and overthrow the government. Fiction writers love plans that involve becoming a billionaire and then using the money from your corporation to build a private army or a super weapon. While I suppose it's not impossible, I'm not aware of any case in history of anyone getting anywhere with this sort of plan. (The Dutch East India Company is the only example I can think of, and they had the backing of the Dutch government, it's not like they were out there totally on their own.) I think a big part of the problem is that convincing people to be willing to fight and die for you is pretty tough. People will risk their lives to defend their home and family. People will risk their lives for a political cause that they are convinced will create a utopia. But risk their lives so that their employer can have more money and power? I might possibly give my life for the cause of freedom. I can't imagine giving my life to help Wal-Mart sell more toasters. You would have to convince these private soldiers you hire that there is some glorious political cause, in which case you're back to building a traditional guerilla army and the mega-corporation is just a means to that end. In which case, it's a very round-about means to that end. Which brings me to the second problem: Building a corporation with resources that rival the major nations is a hugely difficult job in itself. Only a handful of people in history have accomplished it. To say that you're going to do this as a sideline along the way to a totally different plan, that you're going to pull off a feat that few people have achieved when that isn't even your real goal, but just a part-time job that you're doing along the way, is asking a lot. If you want political and military power, it's way easier to pursue it directly, by going into politics or the military, than by such a round-about route. [Answer] There's a bit of a trick to the wording of this question. "Take over the world," to me, implies that this Joe has the ability to decide how the world should work against the wishes of the rest of the population. Needless to say, this creates a Joe vs. The World scenario, that is almost impossible. However, there are alternatives. What if the only goal is to have the world agree with Joe's wishes. Doors open when Joe is willing to adapt his wishes to the world. Consider the Dali Lama. They are chosen at a tremendously young age, when they can certainly be considered an "average Joe." They are then raised in a way that puts them into a mindset which wields considerable power. Neilsons polling company found him to be "joint most popular leader in the world," tying with President Obama. [Answer] to be brief and to the point it is quite impossible be cause of religious factions around the globe and as government is the biggest bully on any block you would be eliminated from the equation once you have reached a threat level to them. [Answer] The only way to maintain any control over anything is to have the majority of people of influence also backing the status quo where you are in charge. The only way for this to happen is if the individual was very charismatic, cunning at politics and intrigue, and was seen as the representative of some popular philosophy or policies. One hacker trying to out hack the entire world is not going to work because the NSA can just trace you and send a small army to your front door. Also, acting as a revolutionary is not likely to work either, because, if the existing institution does not like you, they can just get rid of you, even if your democratic rights suggest that they can't. There are many de-classified or leaked FBI/CIA documents that show that the US government shuts down up-starting political groups by spreading miss information about them, financially debasing them and many other tactics. In fact, many of the historic groups that are commonly shunned by the mainstream media are quite possibly the targets of Intelligence agencies. [Answer] If you can't be good, be lucky. There are very many average people, many of whom would accept the role of world leader if it came to them. Therefore, whichever person that opportunity comes to is almost by definition the recipient of freakishly good luck. Your fiction can then play on this notion to construe the chain of circumstances that brings them to the top. Something like "House of Cards", except that everywhere that above-average skill plays a role, replace it with good luck. Or perhaps the backing of someone skilled who thinks they can gain advantage from Joe's advance, but eventually falls away for some reason, leaving Joe with something for nothing. Jim Hacker from "Yes Minister" and "Yes, Prime Minister" is an example of a distinctly average person in high office, albeit not as high as you want. ]

[Question] [ I've got a lunar colony that was set up to be self-sustaining before a collapse of life on Earth. The colony has survived on its own for several thousand years through a period of technological regression. But now they've recovered to roughly their original technology levels, and realize that they've been slowly losing something which will soon threaten their ongoing survival. **What could a colony on the lunar surface slowly lose that would ultimately prove fatal?** Some notes on their technology: * The colony is a shielded crater about 12km across. * They have advanced, but not magical, 3D printing technology. * They have large solar collectors for power, but no fusion. Some thinking so far: * The obvious answer is oxygen, but lunar regolith is 40% oxygen so that's easy to replace. * My understanding is that lighter elements are more likely to escape even tightly-sealed systems via [atomic diffusion](https://en.wikipedia.org/wiki/Atomic_diffusion) or simpler processes like opening and closing airlocks. So a slow loss of hydrogen (rare in lunar regolith) seems likely, especially if there's a mechanism via which it would become unbonded from water. * Humans need a lot of trace elements to survive (zinc, magnesium, iodine, etc). Is there some process via which a key one of these would be slowly lost, no matter how carefully things are recycled? (i.e. soil is tilled to recover, air is scrubbed, etc.) * I know certain substances exposed to space for long periods of time will degrade or chemically alter ([space weathering](https://en.wikipedia.org/wiki/Space_weathering)), possibly in ways that wouldn't be easy to reverse. For instance, the flags planted on the moon are supposedly bleached of color because of ~50 years exposure to UV rays. What substances are most susceptible to this kind of degradation? I have a notion that some of these processes might cause, say, atoms to bind together into molecules that can't easily be separated back into constituent elements, but haven't found good sources with more detail. But if so, the parts of the colony exposed to vacuum/space (solar wind/flares, cosmic rays, micrometeor bombardment etc.) might be a weak point. [Answer] > > ***EDIT April 26, 2020*** While searching through my answers for research related to another question I came across this answer. The irony that I wrote this one year ahead of the Coronavirus pandemic, which somewhat mirrored the description provided here, is unbelievable. I'd be puffing up my chest and shouting, "Why, oh why, did the world not listen to me!" but for a simple reality: who could have possibly guessed this would happen in our lifetime? well, aaronius... you couldn't have asked for better truth-is-stranger-than-fiction than the reality of today. > > > **Immunity to Disease** Your lunar citizens live in a perfect environment! They have all the food they need, they have recycling that, frankly, removes most bacteria from their lives. Atmosphere is constantly recycled, which includes scrubbing. Water, too, is recycled, scrubbed and clean for use. In fact, the colony has been disease-free for, well... *forever.* And that is a *massive* risk. Disease has this nasty habit of hanging around. Stuck in some quiet, little corner of life or living until somebody moves the proverbial old stack of books in the attic out of the way and *boom!* you're sick. *And then everybody's sick* It isn't like everybody needs to start dying. Oh, they *could.* Diseases like polio, measles, etc., really aren't gone. We've simply enhanced human immunity through vaccination such that they can't get a foothold on the population anymore. If one of them peeked into the clean and controlled world of your lunar colony, it could wipe out the colony overnight. But it really doesn't need to be that dramatic. Maybe it's just a newly mutated form of the flu. And suddenly people are having trouble getting out of bed, which means they're not maintaining and operating the closed, controlled environment. Repairs and adjustments aren't being made. *And things begin to slip.* The funny thing is that doctors would be trying to fix the problem. At first it would be, "oh, this is an historical curiosity! When's the last time this happened? Here's two aspirin, you'll be all right!" Until one of them notices the problem. "Uh, Frank? You might want to take a look at this...." And then the medical community realizes the ugly truth, "uh, how are we going to stop this?" Right up until Louise, who has an absolute *genius* for maintaining the ventilation systems, can't make it to work. And then a fuse buried deep in the ventilation system blows.... And with his last breath, Louise's apprentice, who'd been buried in technical manuals and user guides for a week, says... "I think I fou...." --- **Edit:** The premise of this answer is that there are people today who believe [we wash our hands too much](https://www.piedmont.org/living-better/too-much-hand-washing-can-make-you-sick). In other words, we have created an environment today that is so sanitary that we are already losing our natural immunity to many bacteria. An hermetic environment like a lunar colony would have this problem in spades because the bacteria in *used resources* (you should be thinking, "ewww... sewer...") requires sanitizing — and every resource is "used" (you should be thinking, "ewww... recycled bread..."). It could be said that a lunar colony (or any other hermetic colony) should actually *introduce* bacteria to ensure the healthy strength of the colonists (you should be thinking, "ewww... you're *making* people sick!"), which could actually be a rather cool aspect of a story. If you ever saw John Travolta in *[The Boy in the Plastic Bubble](https://en.wikipedia.org/wiki/The_Boy_in_the_Plastic_Bubble),* based on the life of [David Vetter](https://en.wikipedia.org/wiki/David_Vetter), you'll understand the problem. In fact, go read about how David Vetter died. That's the problem. [Answer] Materials exposed to vacuum for extended periods often become brittle and/or literally lose mass over time. Outgassing, cold-welding, decomposition of alloys back to their constituent materials, coronal arcing due to ionization from exposure to ionizing radiation, acceleration of outgassing and decomposition again due to ionizing radiation exposure are all concerns both for metallic elements, barriers and bearings, and outgassing particularly for all plastic, polymer or latex components (seals etc) induce changes in surface interface chemistry and surface finish, and over sufficient time these would impact significant portions of the volume of a material. Further, scratches and dings in vacuum-exposed surfaces can lead to rapidly-propagating fissures and cracks, due to thermal expansion / contraction. Bearings will cold-weld, and even failing that, lubricants which survive well in vacuum-whetted conditions are both rare and exotic, and many of the ones which are found to work cannot take direct insolation as they will themselves offgas and change composition. Think airlocks, manipulator arms or waldoes, locking / docking clamps, wheels, rovers, et al. All these issues can of course be dealt with individually, but en masse it means that absent new metallic components along all vacuum-exposed surfaces, they will be in ***serious*** trouble. I don't know if your thousands of years is even feasible... NASA has been studying these material science issues since the 1960's, as you can imagine, and they've a lot to say about it. Two other issues are sublimation of solid materials as temperature climbs during insolation, and corrosion, which can be very strange and unexpected when surfaces are impacted by ATOX (see ESA paper below) - all of which support my basic contention: Material thermal stress / embrittlement / volume & mass loss / corrosion on all vacuum exposed surface materials are the single greatest threat / risk to a longstanding Moon colony, and absent re-supply / repair would constitute a rapidly self-reinforcing series of chain-reactions leading to catastrophic enclosure failures. [1961 JPL Paper on Vacuum Exposed Materials](https://apps.dtic.mil/dtic/tr/fulltext/u2/266548.pdf) [1969 NASA Paper on Vacuum Exposed Materials](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690026573.pdf) [European Space Agency Paper on Corrosion in Vacuum at LEO](http://esmat.esa.int/Publications/Published_papers/Corrosion_in_Space.pdf) Hope that helps some. [Answer] A non-obvious loss area would be Genetic diversity. After several thousand years of carefully controlled plant growth, and several thousand years of inbreeding, unless care was taken to maintain genetic diversity in plants and animals (including humans), a single mutated bacteria could take out a key component of the self sustaining ecosystem. [Answer] **Volatiles like hydrogen, carbon, nitrogen, and noble gases.** These elements are necessary for life and useful for industrial processes, while being difficult to replenish. Hydrogen, carbon, and even nitrogen can be used as rocket propellant which will consume these elements without any chance of recycling. They are also liable to loss through slow leakage. It is difficult to replenish these elements because they exist [at parts per million concentrations](http://fti.neep.wisc.edu/neep602/9301/node2.html#SECTION00020000000000000000) in lunar regolith. This means many tons of regolith must be processed to obtain small quantities. However, [we do know that permanently shadowed craters at the lunar poles](https://www.pnas.org/content/115/36/8907) at least contain water ice. It's quite possible they can contain other volatiles too. These volatiles are probably much easier to extract than the volatiles adsorped into lunar regolith. But it's quite possible that with 1000 years of continued exploitation that these deposits could run dry. It's been estimated that the Moon's north pole could have [600 million metric tons of water ice](https://www.nasa.gov/mission_pages/Mini-RF/multimedia/feature_ice_like_deposits.html). While this seems like a lot of water, consider that we produced about [380 million metric tons of plastic in 2018](https://en.wikipedia.org/wiki/Plastic_pollution). It's quite possible that with heavy extraction, these deposits could be depleted much faster than 1000 years. [Answer] **The will to live** Survival on a lunar colony is a lot harder than here on planet earth. You are tired at the end-of-day, and the time to have and raise kids is just a little more than you can take. Population decreases until there is just not enough left for the colony to be viable/ [Answer] # Computer chips. Computer chips are an interesting case. You can pack millions of high-end microchips into a single 1-ton storage container. Conceivably you could store enough to provide spares and replacements for thousands of years of maintenance in a fairly small space. Yet to actually produce more takes a huge industrial base. Chip fabs are vast collections of some of the most advanced technology on the planet with a single Fab costing north of $10 billion to build, employing many thousands of people and requiring extremes of purity of materials all requiring a vast external industrial base to produce all the rare materials, chemicals and solvent with high enough quality to be suitable. # Batteries The problem with solar collectors on the moon... is that night on the moon lasts 2 weeks. Sure, you get 2 weeks of solid sunlight but then you need to keep everything running for the next 2 weeks and for that you need to store enough power to run everything for 2 weeks without recharge. As such you'd need huge energy storage systems. Batteries degrade over time and need to be replaced. If you can manufacture suitable batteries you still need to keep all the equipment for manufacturing the batteries working long term. # The nuclear material in an RTG [](https://i.stack.imgur.com/3jd84.png) RTG's are incredibly simple and reliable sources of power, good for hundreds **or thousands** of years depending on the fuel with minimal maintenance needed. Solar power is great during the 2 weeks of daylight on the moon but then you have the 2 weeks of long-night. Perhaps batteries and other energy storage systems were considered non-optimal when building the base but the systems needed to survive the 2 weeks of cold and to keep the oxygen recycling are run off of a set of [RTG's similar to the ones proposed by NASA](https://www.space.com/5850-nasa-eyes-nuclear-power-moon-base.html). Plutonium-238 has a half-life of 87.7 years which is a bit short... but Americium-241 can be used as a fuel and has a half-life of 432 years. So a couple thousand years ago the facility was built with a set of Americium-241 RTG generators that could provide plentiful power throughout the long dark night on the moon... but every 432 years half the Americium decayed away. Now the generators have about 1/20th the Americium they started with, getting worse with each long night and the facility can just barely keep everyone warm and oxygen flowing and building enough energy storage to provide for the whole colony throughout the night is no minor feat... [Answer] # Light and thus Energy. This probably *will happen* as a result of natural phenomena involving Earth's magnetic cycles. The current [dust storms on the moon](https://en.wikipedia.org/wiki/Lunar_soil#Moon_dust_fountains_and_electrostatic_levitation) - referred to as "Moon Dust Fountains" that occur as a result of electrostatic levitation of tiny particles of regolith (as a consequence of being stripped of electrons by the solar wind), are due to get much *much worse*: > > NASA scientists have suggested that Earth's magneto-tail might cause > "dust storms" on the Moon by creating a potential difference between > the day side and the night side. > > > * The Earth's magnetic field (protecting the atmosphere, preventing it being stripped by the solar wind), is diminishing: [](https://i.stack.imgur.com/LYDtS.png) *Attribution: Wikipedia 2019, CCASA [License](https://en.wikipedia.org/wiki/Wikipedia:Text_of_Creative_Commons_Attribution-ShareAlike_3.0_Unported_License)* > > Over the last two centuries the dipole strength has been decreasing at > a rate of about 6.3% per century. At this rate of decrease, the field > would be negligible in about 1600 years. > > > The direct consequence of this is that the strength of the wind of atmospheric gasses stripped from Earth (and thus projected at the moon during that phase of rotation) will greatly increase and create an even greater charge difference between the dark and light side of the moon (the side facing Earth). (To be fair, the charge will first diminish for several hundred years, then grow alarmingly) **This means that the abrasive dust (albeit *ballistic dust* that settles) will vastly increase periodically - every 1 Earth month - obscuring solar cells and vision, smothering everything on the surface.** Everything will get scratched and worn away *much faster* - further - it will get carried away in more static-dust storms. There will be less solar energy to mend and replace worn items. This phenomenon will reach a peak (if the [secular variation](https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Secular_variation) continues on-trend) 1,600 years in our future. Enough of the Earth's atmosphere may remain to make the planet salvageable, but what about the moon colony? [Answer] **Something we didn't know we needed, because we always had it.** The people who built this colony were not fools. They would know plants need boron and humans need sodium. There would be provisions to tap lunar water and generate building materials and oxygen from regolith. Carbon is precious and would be carefully conserved. There will not be holes in the recycling scheme. Likewise genetic diversity. The builders know about inbreeding. They know that charged particles hitting the moon can cause mutations. There would be giant sperm and egg banks for diversity and molecular genetic remediations. But what about something humans have always had and so never missed. Something that keeps humans going, but is slowly dying. And when it is gone, we will slowly die as well. **I mean Gaia - the Earth**. Maybe the gestalt of all that is alive on Earth is tied to life in some way - something that has been there so long that there is no name for it. And Gaia is not going to go easy. After the humans escape the Earth there is still life; the deep things, the tenacious things. Roaches and mites, the bacteria, the fungi. And maybe this power is great enough to reach the moon - so the humans there and their dogs and corn are sustained even though they do not know that they are. But if there is a tipping point, and when after thousands of years the last feeble weed finally dies, whatever this power is goes with it. It would be a sad story. [Answer] # Electronics Electronics manufacture require a vast and complex industrial base. There is no way the Moon Base has what it takes. They have a large store of spare parts, and things don't break all that often, but there is a limit. Some things can be replaced in non-electronic ways. Solar panels is probably the hardest to replace. It might be possible to 3D-print some electronics. These are going to be *very bad* compared to todays electronics. Think really old computers filling buildings and doing very little. [Answer] ## [Phosphorus](http://www.projectrho.com/public_html/rocket/mining.php#id--Element_Bottlenecks) Always a good candidate when you need an elemental bottleneck to life, [phosphorus is needed](https://en.wikipedia.org/wiki/Phosphorus#Phosphorus_deficiency) in minimal quantities, but by pretty much all known life. A closed ecosystem will recycle it pretty well, as long as there is no population growth, so the lunar colony could have been fine with small reserves to compensate the inevitable losses that probably still slowly occur. But now, even without population growth (due to it being a closed environment) they realize the reserves are pretty much gone. Now, there is phosphorus on the Moon. Probably not much on any given square kilometer, but the Moon is *big*. And that's where things can get interesting: we may very well be running out of it on Earth, in as little as half a century, according to some - population growth means more fertilizer needed, because of the bigger human (and support) biomass. As of now, we are mining the stuff en masse, and looking for new deposits as the old ones run out. With population growth slowing down and mining techniques getting more sophisticated, maybe we'll be fine. Or maybe not. If there is not enough phosphorus on Earth, then we'll have to get it where it is. And the nearest source is the Moon: as diffuse as it is, it may at some point become economical to process lunar regolith in bulk for it and varied other elements. Forget the Helium-3 baloney, this is why we could have lunar harvesters. The problem for the lunar colony is that all nearby sources of phosphorus have long been mined, both for its own reserves and for Earth. So they will have to find new sources. A short term solution may be to, ah, decrease the colony's biomass in order to recycle its phosphorus. Hey, now we know what Soylent Green is made of... [Answer] It's not about what gets out, but what gets in. To survive that long, mankind will make many many trips out into the Lunar landscape to gather and process lunar regolith so that they can replace lost air and water supplies. However, regolith is extremely hazardous to human life. It's highly abrasive, nearly impossible to filter, and it builds up in the lungs causing [Silicosis](https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/silicosis/silicosis-symptoms-causes-risk.html). Each time a lunar rover goes out to get more of the stuff, a little bit more of this fine dust comes in on the vehicle's chassis. Slowly it's concentrations build up in the air of the colony increasing the cases of respiratory ailments and early death until eventually, it kills so fast that no one can survive long enough to procreate. [Answer] ## Genetic Diversity With the relatively small breeding population, over tens or hundreds of generations minor genetic defects could be interbred into major genetic defects. It's up to the author to determine what kinds of defects are being introduced. Based on those choices, the colony may be in danger of dying out from a single bad virus or defect induced infertility that forces birthrates too low to sustain the colony. [Answer] There are many things and I would like to list and explain everyone of them (as far as my knowledge goes) 1. Bone density loss. In space astronauts have been found to lose bone density despite intense workout sessions. Your people on lunar colony have been inside a dome for 1000s of years where gravity is 1/6th of what their bones have evolved for. Hence the bone density loss will soon make their bones too brittle and render their bodies useless. 2. Genetic diversity loss. The reason humans have survived is genetic diversity. In the dome you built the people will obviously inbreed for 1000 of years. Assuming average age of 60 years and age at which people make offsprings to be around 33 there will be around 30 generations from inbreeding. Effectively finishing their genetic diversity which means a single bacteria is enough to wipe out your colony. 3. Trace metals loss (Zn, Mg,etc) No matter how good you are recycling you always lose some of things (to be recycled) in the process. Trace metals are useful in our day to day uses and survival. Their loss can't be compensated until your colony finds a vast reserve of these metals on moon. 4. Hydrogen and nobel gases loss. The abundance of these gases on earth makes us too ignorant of their use. Nobel gases are extensively used in medical fields like Radon for treatment of cancer, and arc welding uses helium,etc. Hydrogen is maybe the cleanest source of energy after solar energy systems you have installed in the colony. In case of any future expedition they will need hydrogen in bulk, the loss of hydrogen means they are confined to the colony forever. (Unless they use solar sails which is pretty much impossible as they have same technology as we have today). All points I could think of. Edit- I would like to thank everybody in comment who has corrected me. :) [Answer] **Information.** All this time they still used the original networked computer system. The centralized datacenter had massive redundancy, but not quite infinite self-repair. During the technological regression, the redundancies failed one by one. Even at recovery, no one wanted to learn the complex system, and there was no case for building another. I had been up forever, with not one user-facing glitch. One fine day, that last backup failed. The system went down, permanently. They still have computers, and are quick to crudely network them back together. But they lost their archive of information. A lot of files were recovered from the laptops, and a lot of information still existed in peoples heads, but the bulk of it was lost. Most crucially, the manuals for the life support systems. They cannot maintain them for long without them, even at the same tech level, any more than a smart engineer could maintain the International Space Station without any reference material at all. [Answer] Prior answers have focused on the genetic diversity of humans. We have more bacteria in our guts than cells in our bodies. There are many bacteria on our skin. Part of our immunity and well being is due to the interaction of our bodies with those bacteria. Hunter-gatherer societies have far more diversity of bacteria. Losing genetic diversity in those bacteria will cause strange problems. [Answer] **Social unity and pacifity** (not sure if the latter is a real world) Basically, such a small colony relies heavily on any conflict being within society, and between two groups that are willing to discuss it out or seek peaceful options only. If you split into two societies, or have any other conflict (between more than a couple individuals) whhich escalates to violence on both sides, your colony is doomed if the conflict/split can't be resolved ASAP. For example, a colony might start under martial law, and then only slowly transform away from it. This could leave some privileged and unprivileged groups (military descendants vs. civilian-descendants), which so far managed to talk out their differences, but not some worker teen found some anarchists scripture in the archives and motivates other people to escalate the conflict. Maybe after some unifying figurehead dies, or just over time. [Answer] **Genetic Integrity** Earth has the magnetosphere to keep harmful solar radiation out but the moon doesn't. This means the luna colony needs radiation protection but even with such protection, everyone if going to receive increased doses of radiation than on Earth. Every time someone goes outside, they'll receive more radiation. All this radiation will eventually lead to genetic degradation which can accumulate in the colonists offspring leading to increased genetic diseases. **Bone Density** The reduced gravity leads to calcium loss and weaker bones and finally osteoporosis. It's would be hard to stop people from breaking bones regularly. [Answer] # Their minds. We've spent tens of thousands of years evolving to expect the sun to rise once every 24 hours, providing electromagnetic radiation filtered through our nitrogen/oxygen atmosphere, to hear the birds chirping in the morning, to smell the wind, climb the trees, and wade in the sea. There are so many thousands of little things that we don't notice at all on Earth, simply because they're so fundamental, and seem so irrelevant. Once we've measured all the needs our bodies have, and provided that to the lunar colony, we might consider ourselves done, and not realise we missed something important. Until the murders start. [Answer] # The bane of self-replication: Imperfect copying How is this facility being maintained? By the factories 3D printing new components. Okay, so far so good. How are the *factories* being maintained? The factories 3D print new factory components. In particular, how are the 3D printers maintained? Replacement printers are themselves 3D printed. The specifications on these things will not be 100% the same. This means that the capabilities of the factory will drift over time, as the collection of machinery is constantly cycled through new "generations". Effectively, you have a *population* that mutates over time. The 10th generation of "descendants" from the original manufactories were probably basically the same. The 1000th generation, imperfect copying repeated over and over and over, is a hunk of junk in comparison. This wasn't a big problem before, when the people running the show knew what they were doing. They would inspect the new equipment and run it through a body of tests. If it deviates too much, the new unit is scrapped. If a bad unit somehow gets through the body of tests, they'd remove it soon after installation. But once the collapse happened, they stopped really understanding this. They got lax. Let's suppose that much of the maintenance documentation and expertise was lost in the Great Whatever. The survivors wouldn't be able to tell that subtle problems were creeping up on them. They said 'eh, this seems to be working fine' and the level of quality gradually degraded over time. Such a long time it tooks thousands of years for anyone to notice. When they look, they find that (for instance) the expected shelf lives of a new (say) door jamb or air filter has decayed to such a large degree that components that used to last for 10 years now have to be replaced twice a month. It just got worse so slowly nobody ever caught on. After they notice things have gotten so bad the facility is nearly constantly in danger of catastrophic decompression (and the like) it then takes them awhile to figure out what the problem really is. [Answer] According to [NASA](https://www.nasa.gov/mission_pages/sunearth/news/gallery/schumann-resonance.html), the Earth has a [Schumann resonance frequency](http://en.wikipedia.org/wiki/Schumann_resonances) of about 7.8Hz. The humans and animals living on Earth are kind-of calibrated to this. The Moon has a different frequency, which may have either long-long term or not-that-long term serious effects, e.g. in physiology or mood. Here are three examples: 1. The brain alpha waves are in the range of 8-12Hz. In case of "alpha blocking" occures then the subject is facing anxiety, high stress, insomnia. 2. Theta waves are between 4 to 8Hz. If you don't have enough there is again anxiety, poor emotional awareness, stress. 3. The last one is pure speculation, but your blood has magnetic properties as well, and you are currently immersed in an electromagnetic field with the above mentioned frequency. Again, I am not bio-physicits, but it is hard to believe that missing this environment on long term (10-20-30+ years) does not have any effect. ]

[Question] [ Imagine you have a large population of adolescent humans (as large as you need) on a completely uncultivated Earth, initially containing no artificial structures whatsoever, only natural resources. Suppose, however, that these people possess the same amount of technical knowledge as we currently do today, and that they are completely united (no infighting, politics, etc.) in their singular goal of **reaching the moon during their lifetime.** **Starting with modern-day knowledge but no starting infrastructure, can a population of humans put a person on the moon within a human lifetime?** [Answer] # Impossible ***This is an extension of, or complement to, L.Dutch's answer, which was first. I upvoted it. So should you.*** I'm fond of reminding people that 99.99% of the technology we enjoy today was invented in the last 150 years. Based on that observation, one could jump to the conclusion that what you're asking is possible, perhaps even plausible. But that would be a lie. 150 years ago was 1870. Take just a moment to consider just how much infrastructure existed world-wide in 1870. **Assumption #1:** A "single lifetime" is an 85-year period, from the day our teens are theoretically useful 15-year-olds to their deaths at an average age of 100. **Assumption #2:** We'll assume that the available humans are capable of working and thinking like 30-year-olds from age 15 all the way to age 100. This ain't true. Humans on average don't really become industrially productive until around age 25 (physical and mental maturity) and start winding down physically at 45 and mentally at age 65 (these are rough and optimistic averages, of course). But even assuming you could get all 85 years out of your team — my answer still stands. ## Infrastructure is, quite simply, the problem Building any (and ONLY) one of the *millions* (not thousands, not hundreds-of-thousands, but *millions*) of components needed to successfully launch a crewed spacecraft equal *only* to Apollo 11 requires an industrial and technological pyramid of interconnected disciplines so vast that it's simply impossible for teenagers, no matter how smart or how unified, to complete in a single lifetime starting with (did I understand this correctly?) ***absolutely nothing.*** **Assumption #3:** When you mean "no infrastructure," I assume you mean ***absolutely nothing.*** There are no utilities, no factories, no houses, no farms, no ditches... nothing. If I'm wrong with this supposition then you need to produce a **SUBSTANTIAL AND HIGHLY DETAILED** starting point for your humans. Let's pick just one item: a single LS7400 NAND microchip, [invented in 1966](https://en.wikipedia.org/wiki/7400-series_integrated_circuits).1 That one object, the LS7400 NAND chip, required: * A silicon foundry capable of at least 100µ geometries. * A packaging and assembly facility. * A testing facility. Those three facilities, which can be combined under one somewhat large roof, require... * Electron beams * Photo lithography * Robotics (crude compared to today, but nonetheless...) * Computers * Software And a bazillion other things. I know you're not an electrical engineer, but that industrial and technology tree just became ENORMOUS... and we're only at the first level of very basic dependencies. Let's jump near the bottom of that tree (not the bottom, just near the bottom)... * Electricity * Water * Sewage * Vacuum tech * Plastics * Metallurgy * Concrete * Woodcraft... All of which requires agriculture, mining, and logging, which requires more machinery, more tools, more factories, more industry.... Somewhere in that massive tree of dependencies are the industries that create hammers, screwdrivers, forklifts, cranes, furnaces (very *precise* furnaces, not just smelting). If I tried to make this list comprehensive, I would literally (LITERALLY) write a book-sized treatise and the ***one and only thing I would have done*** is list the dependencies... I'd have actually explained nothing. A book. * Tools * Machines * Buildings * Roads * *Animal husbandry* (and you'll have to catch and train the horses... a LOT of them...) And, of course, the millions (yes, *millions!*) of teenagers would need... * Food * Clothing * Entertainment * Health care * Homes (with household goods...) * *Government...* Assuming most of them didn't die before developing the ability to grow, package, and distribute food to so large a group. And what did we get for that? One component out of millions, an LS7400 NAND chip. ## But, let's say that our intrepid teens number in the tens of millions and are, somehow and magically, already organized into teams of tens, fifties, hundreds, and thousands, such that each group knows exactly what they need to do each step of the way. What then? **Assumption #4:** They're humans, meaning their memories aren't perfect. Which is important because without infrastructure, there would be no books, no guides, nothing but their memories to guide them until they could create books... *I can't take it anymore. Just the task of developing the infrastructure from scratch needed to record the knowledge they have so they don't forget it might take more than a lifetime. You can't have just one copy of anything, so now you're inventing movable type, printing, binding, paper, glue, thread, machines, tools....* I'm sorry, and I beg you to forgive me, but you're asking a question from an entirely untrained perspective. What you're suggesting is impossible. --- 1 *I designed 74BCT and 74ABT BiCMOS chips, which you'll find briefly described in that Wiki document, and the more complex MultiByte family of components based on that technology created by Signetics Corp, and then Philips Semiconductors. Geez, that was a long time ago. Feels like yesterday.* [Answer] I don't think it's feasible. First of all, for anything they need, they might know what they need to build, but they have no way to reach the place where the raw materials are located. E.g. > > Jim: "cool, we need gasoline to supply our trucks to transport materials." > > > > > Pedro: "To make gasoline we need oil" > > > > > Alexa: "Where can we find oil, and how do we reach it with our bare feet?" > > > Then, more importantly, they have no way to communicate and coordinate efforts. Don't forget that the race to the Moon in the 60's was a coordinated effort of an entire country, with hundreds of thousands of people working together according to a plan, backed up by industries and an government already up to speed. There wasn't a rocket expert wannabe in each and every town in the US trying the feat on their own. Without effective communication you cannot coordinate the effort. You will need more than a lifetime. [Answer] It can't be done. There's a famous phrase in project management, "Nine women cannot make a baby in one month." This is one of those cases where you just can't parallelize enough. The project management term you should be interested in is called the "critical path." This is the longest sequence of activities that have to be done in serial because one depends on the other. For example, aluminum is a pretty critical component of spacecraft. Now for spacecraft, you don't just need aluminum. You need *good* aluminum. The trace materials must be immaculately controlled. You aren't looking for some backyard smelter. You're looking for a properly constructed [industrial aluminum smelter](https://en.wikipedia.org/wiki/Aluminium_smelting), using the Hall-Héroult process. These factories are beasts. It is simply not reasonable to produce aluminum on a small scale. The US as a whole sports 14 of them, according to [Wikipedia](https://en.wikipedia.org/wiki/List_of_aluminium_smelters). So how fast can you make one of these? [This article](https://www.cb.is/lisalib/getfile.aspx?itemid=4664) from Iceland suggests that one might take 7 years to construct. Now these efforts are being run by project managers who are trained to build these things as efficiently as possible. There might be some potential to speed it up because it's of utmost importance, but we have to consider the supply lines. That was 7 year in a modern world with access to all of modern shipping, modern building materials, and modern construction equipment. All of these things need to happen before the smelter can be constructed. And one of the major things that is needed is a steel industry. Not only do we need construction equipment, but simply put Aluminum needs power, and the electrical industry needs steel. The trashy steel from the 17th century isn't going to be sufficient to make electrical generators that can power the *gigawatts* needed to run an aluminum smelter. Yes, it takes gigawatts before you have a aluminum production scale that is really worth talking about (the Wöhler mechanism for extraction, done before full scale production in the 20th century was so painstaking that aluminum produced by it cost nearly *twice* as much as gold!). You need real generators which are going to withstand the load of powering these furnaces. And really, the only way to get that good of steel is to start with crummy steel, which is used to construct a crummy eletrical power plant, which is then used to produce a better steel, and a better power plant. If I handwave a bit (because I'm having trouble finding resources), lets say the good steel plant and the good electrical plant take 7 years each, just like the aluminum plant. Now we're sitting at 21 years. Now, how long is a lifetime? I think 60 years is pretty reasonable. I mean, you're being put on a strange planet without *any* medical facilities, so practically speaking it should be a whole lot shorter. But some of them might live to be 60. So we've used up 1/3 of our human lifetime on just constructing a steel plant, electrical plant, and aluminum plant. Now lets talk raw materials. You say the planet has natural resources. Unless nature has kindly tied them up in small crates of pre-refined materials, you're going to have to mine them. And you goign to have to do it starting with *nothing*. Not even pick axes. Needless to say, our ability to produce resources is going to be limited in this situation. How limited? Well, much of mining before the industrial era is going to rely on beasts of burden. We won't have those, because we don't have time to domesticate any species. So we're going to have to use human power. Literally we will be dependent on slaves until we can get to mechanical power of the steam era. So how long does that take? It's goign to take a long time. We're going to be working with clay, wood, and rock for quite a while before we acquire enough metal to enter, say, the bronze era. And all of those were assuming that we had time to do these things. Maintenance of the H. sapiens body calls for calories. While we can initially support the populace on canabalism, taking advantage of your "as many humans as you want" rule, we're going to run out of them anyways. Human meat does spoil... Anyways, this process can take generations before we have enough understanding of the local climate. So I chewed up 20ish years of the timeline with just a few technical structures that need to be built. 1/3 of the time has to be spent building just that one line of infrastructure. No computers, no hydraulics, no nothing. And, practically speaking, it is almost *certain* that your planet, no matter how driven, will not have the resources available in the modern world in just a single generation. So you should multiply that out. Then, you have to raise the question of acquiring resources. This would *easily* take generations. Then you have the pesky issue of survival. Unless your humans are waking up from stasis on a regular basis, your workforce is going to need to survive. [Answer] I would say no due to issues of food production. The problem is not clearing enough land or having manpower. The real problem would be in breeding good enough strains of crops and livestock to feed a large population, the situation would be different if they had seeds and draft animals with them but without that I would claim it is extremly unlikely. [Answer] No, even if you have a magic Wikipedia type thing for "Starting with modern-day knowledge... " rather than relying on people knowing stuff. (And most modern knowledge is, in fact, simply knowing how to use existing infrastructure.) I see lots of other good answers, but it all really comes down to the basics: Food, shelter, water. Most of your initial population are going to die in less than a year. They will either starve, have an accident, get a disease, get poisoned, or one of a bunch of other dangers will kill them. Without infrastructure a skinned knee will kill a bunch of people. There will not be any time to build up infrastructure, they will simply spend all of their time trying to stay alive, most will fail. You said adolescents, too. Even if everyone has genius level intellect, and no mental issues, there is going to be zero experience at any of the things they "know" or read about, experience counts for a lot, especially when it involves physical interacting with stuff. e.g. You can read all you want about digging, but until you do it, you won't really understand some parts of it. I will ignore the level of mind control required to make a group of people get along perfectly, and work toward a goal without friction. That alone might mitigate some of the problems with getting everyone food and shelter, lots of them will still die. Sanitation is no joke either, nor obtaining potable water for more than a dozen or so people. No, even if a bunch of things go right, it would take generations, infrastructure is important. Possibly the most important thing. [Answer] NASA sent people to the Moon using different bases (launch was in Cape Canaveral, command in Houston). Each base had an enormous amount of infrastructure already in place. Your people will have to build mines, labs, refineries, regular roads, rail roads etc. Even with all insfrastructure in place, that takes time. If you think it's slow because of governments, remember that in the US the bulk (if not all) of the infrastructure construction and maintenance work is done by efficiency oriented private contractors. ll all your people have are rocks and sticks, then they have to go through the stone, bronze and iron age in a rush just to be able to start getting into the modern era. Which leads to the most pressing problem for them: > > these people possess the same amount of technical knowledge as we currently do today > > > A lot of the knowledge which bridged the gap between the bronze and iron ages was lost. We are not sure today how the ancients made Damascus steel (and other forms of steel), and we have a good idea of how romans made cement but we can't know for sure. Lots of people even force themselves into thinking the pyramids of Giza are the work of aliens because caucasians nowadays can't figure how those stone blocks were stacked. Your people will have to spend multiple lifetimes figuring out how to build ancient stuff before modern knowledge becomes useful again. By then, that modern knowledge might already be lost and will have to be rediscovered too. [Answer] You could do it instantly (although you might think my answer is a bit cheap): "Imagine you have a large population of adolescent humans (as large as you need) " I will take enough adolescent humans that they cover the entire Earth and then pile up on top of eachother all the way to the moon. Have a nice day. [Answer] ### Yes - because you've cherry picked people that better than anyone on Earth currently. I'll get into what I mean by cherry picking soon, but first Some simplifying assumptions I've made: * You did say put a man on the moon in their lifetime. You didnt say it had to be one of the original settlers walking on the moon. Cherry-picking the best of Earth they'll live to their 90s on average +- 10yrs std dev, but 0.3% percent will live to they're 120, and the person they live to see put on the moon will be one of their grandchildren. * Because we've cherry picked the best education, they're smarter earlier than average humans. A decent distribution of teens would be ideal, but the youngest should be perhaps 12. 120 - 12. That's just over 108 years to do it. * You didn't say bring them back. It's probably also possible to bring them back within 100 years of dev, but having them die on the moon is much easier! --- > > "they are completely united (no infighting, politics, etc.)". > > > Currently the people on Earth have divisions. These divisions have some advantages and many disadvantages. By uniting them - they can cherry-pick the best of each society on Earth and ignore all the negatives. No single society of humans on Earth will be as good as these people. They pick the best behaviours so as a consequence they live longer, they're smarter (they've picked the best education), stronger (they've picked the best exercise regime), etc because they're United. Uniting makes us better than just coordinated, it pools wisdom. Also, complete unity implies they have communicated this goal within the population and gathered agreement. This implies some form of either communication or at least pre-planning in order to learn this fact. While that communication is happening - you need to basically sort every required technology by its dependencies. This is a mammoth task. As an example of one tiny part of the tech tree: * You need aluminium production for the craft. * Aluminium production needs steel, power and Bauxite mining. * Power needs copper, magnets, coal (or wood or wind or flowing water) and steel. * Bauxite mining needs steel. * Steel needs iron and coal. * efficient iron and coal extraction needs steel and power * inefficient iron and coal extraction needs geological mapping and rock or copper tools * magnets and copper extraction needs steel and power. Sorting **just this tiny part of the tech tree** puts the following work at the leaf nodes: * Geological surveying (find magnetite, copper, iron, bauxite, and coal). + Remember you have current knowledge. So you know what geological features to look for at the surface to predict near-surface ore deposits. * Make simple stone tools for extraction of those resources when found. + Remember you have current knowledge. You know good designs for an axe, a shovel, etc. Once stone tools are made. Start extracting wood. Once copper is found and stone tools are made start extracting copper. Once copper is extracted start making copper tools. etc. There are many things current knowledge gives that don't need "stuff" to be of benefit. You know manual handling so you wont put your backs out. You know first aid. You know good hygiene practices so you wont get as sick (even if you don't have soap yet - you know to boil something to disinfect it). You know to have sewage drain away from your drinking water. All these things that slowed the human race down wont slow you down. There are many other tech trees that need to be worked on. You need tools to plot where the moon will be (telescopes and measuring equipment). You need cryogenic fuels, you need heat pumps to make the fuels cryogenic, you need space suits, you need buttons and electronics, you need batteries, you need fuel cells, there's probably another 50 tech trees, all having their own leaf nodes. There's also survival tasks that need doing. Food, shelter, etc. With exceptional pre-planning (and/or good luck) this can start in a comfortable climate with ample food and clean water. You could also distribute groups of people based on natural resources to minimise the amount of farming needed. With current knowledge you can take some shortcuts or take the easiest of several paths if needed - we may not need oil to get to the moon for example: Hydrogen fuel can come from electrolysis, plastics can come from processing plant matter. [Answer] Impossible to sent by building an Apollo equivalent project in that timeframe. I agree with the tons of written stuff here explain why not. It is more possible to build a true monster-gigantic classic catapult at the highest mountain or by using round-spin force from a large set of air balloons to launch one human encapsulated at a protective shell than anything else. [Answer] While I'm inclined to agree with many of the responses, they omit one factor that may be important - the question doesn't ask us to re-create the Apollo mission, but rather to place one person on the Moon. There's no requirement for safety or repeatability, and so it would be possible to achieve the goal with a craft far more primitive than 20th-century space vehicles. If we were to make do with solid fuel rockets, manual piloting, breathing air out of sack, and a 1% success rate then the task would be very much easier. The specific impulse of a gunpowder rocket is about 80s, vs 360s for a liquid hydrogen rocket. The Apollo mission used a 2800-tonne rocket to transport 41 tonnes to lunar orbit. Assuming we discard everything that we don't absolutely need, we might need to take 100kg to the lunar surface. I confess that estimating the required size of a gunpowder rocket puts me slightly out of my depth but a guess of 20-40 tonnes seems plausible, and perhaps achievable if we were to circumvent any problem that we couldn't solve (e.g. high quality steel alloys can't realistically be created within a lifetime, so do without them). [Answer] # Not in one lifetime, no As others explained, this is impossible in one lifetime. There is simply too much dependence on technology that takes large amounts of time to step through even if you know what you're doing. But what if we were to relax the "single lifetime" constraint and consider an inter-generational Moon% speedrun? How fast can you go? ## Progression Assuming that the knowledge is properly preserved via hundreds of copies of a set of encyclopedias that these teens begin with *and* that the goal and unity is somehow preserved across generations... To make this easier, we'll assume these adolescents have no natural predators and that they begin in an area with rich resources so there's no initial risk of starvation. We'll also assume instant skill and knowledge in all tasks from age 15 onward. ### Starting Point - Stone Age You start with stone and wood tools. You can make fire. You make fur clothing in the first year and stick with fur for as long as possible. Stone age technology is basically there for free. Simple enough. ### Food Production The first and largest hurdle to overcome is food production. Under a hunter-gatherer system, you simply won't have the surplus energy to do anything but survive. Domestication and breeding potentially requires hundreds of generations, and is too slow for a speedrun. Using beasts of burden for agricultural labor is therefore likely out of the question. Your people are going to have to be primarily vegetarians living on low effort crops (e.g. zucchini, grapes) and mushrooms. Any meat in their diet is going to have to come from hunting, which should be limited to opportunistic hunting and absolute nutritional necessity. Grapes in particular are important, as you need something that ferments easily since you don't have refrigeration and can't necessarily count on boiling your water all the time. This strategy doesn't free up very many people, but since everyone is united in the goal of going to the moon and you don't have to invest any time into research, this will still be enough to buy that small fraction of people time to work toward better infrastructure and technology. It will have to do until you can make machinery to automate food production. Optimistically, you can graduate from hunter-gatherer to crude agriculture in a generation or two. ### Iron Age You first need to make clay to create furnaces. Invest time into mining coal, as it is going to be more efficient for smelting than wood. Skip the bronze age. There's nothing stopping you from making rudimentary steel at this point. Steel gives access to tools like saws, knives, and hammers, allowing for better wood tools and wood shelter, making farming a bit more efficient and freeing up labor. It also feeds into itself for increasingly better ability to smelt iron. All of this mining and smelting is labor intensive and time consuming, but you don't have to waste time making weapons to kill each other with, so that helps considerably. ### Beginnings of Automation With steel, you have all the tools you need to continue along the tech tree. You start with windmills and waterwheels to free up a few folks on the farm. You move on to making gears and high precision machinery. Rubber comes next, and soon you have bicycles as your main mode of transportation in less time than it would have taken to domesticate horses. There's a ton of other miscellaneous tech in this era I'm glazing over, but there aren't really any roadblocks at this point. The only limiting factor is time and inordinate amounts of manual labor. ### Steam and Electricity Steam power, combustion engines, and electricity all move toward getting people off the farms and into making things for the rocket. Electricity enables radio communication and telephones. You begin making rudimentary robotics and the machines that make the machines that make the machines that make the machines that make the electronic circuits for the rocket. Once you have industrial automation, your moon landing is only a lifetime away. So my guess: it takes 10-20 generations (i.e. about 200-400 years) under ideal conditions. Under realistic conditions, you might beat history by 1000 years. *Maybe*. Consider using robots instead if you wish to pursue this setting seriously. Robots could actually do all of this within a human lifetime since they don't need to eat and can craft things at a high precision without tools. [Answer] Yes, possibly, if you don’t drop all of your people off at the same time. Let’s consider one person’s lifetime to be equal to 100 hundred years as a rough approximation. Now that we a solid timeframe we can break our task down into two phases: 1. Get to a 1869 tech level 2. Condense the time to go from a 1869 tech level to a 1969 tech level For phase (1) it is helpful to look at situations where roughly 1869 tech had to be replicated, having very little of the tech readily available. Fortunately, we have just such a situation to use as an example: the development of the United States, and the western expansion of the US. It’s not a perfect match, but it may be close enough for us to get some numbers out of it. It took nearly 400 years to go from discovery to 1869 tech, of course some of that time was spent developing the tech... Below is a [supply list](https://www.blm.gov/or/oregontrail/files/packwagon.pdf) of things (other than food) and their weight for the Oregon trail for a family of four: * Bedroll 15 * Blacksmithing Tools 200 * Books 75 * Medicine 10 * Cast Iron Stove 300 * Chair 20 * Cookware & Eating Utensils 75 * Granny’s Clock 15 * Gun Making Tools 200 * Keepsakes 40 * Lead Shot 25 * Mirror 15 * Gunpowder 80 * Tent & Gear 150 * Tools 50 * Toys 15 This was used to established new towns, and should be a fair approximation of what is needed for a roughly 1850 tech level, provided the people know what to do. So, how do we go from naked people to blacksmithing and gun making tools? We build it up of course. Start with 15 people able to kill rabbits with rocks and make either flint knifes or bows (preferably both). Give them two weeks, by which time they should be able to feed themselves and maybe 1 other person. Drop off another 15 basket weavers, they are going to be slower than the bowers. Wait a month, introduce 15 new hunters and 15 potters. Keep on introducing new people and base technologies at a steady rate. You should be looking to double your population at each step, with prior step able to feed and integrate the next. They shouldn’t all have the same time interval (you’ll need to introduce farmers, they’ll need at least a year, possibly two to make the step from hunter gather, to create and store enough food for the step). You want to get to about a 100,000 people. Once you’ve reached that point, you should have a good spread of farmers and machinist, tools, tailors and everything else you need. Then it’s simply a matter of growing your population and building the tools to make the tools. I think it’s doable, but you need specifically trained people and probably 20 years to do it (unless you can simply drop them off at the right time all at once). [Answer] ***Sure*** The moon is 384,000 km away. A human has about 50 kg of water. A sphere of radius 400,000 km (rounded up, accounts for radius of Earth, and maybe you want to be on the dark side) has a volume of $\frac{4}{3}\pi r^3$ has a volume of 267946666666666666666666666.66667 cubic meters, which is under 10^27 tonnes of water. 20 humans weigh more than a tonne. So 2 \* 10^28 humans will form a sphere large enough to swallow the moon. Now at that mass, water being incompressible is an approximation. That is 2% of the mass of the sun, so the result will be a brown dwarf or something more exotic (a lot of oxygen!) But at that size, the moon will be well within the Roche limit of the post-planet, and will disintegrate; if man can't go to the moon, the moon will come to the many thousand km deep ocean of dead corpses. --- Barring something like that, you run into the problem that the basis of industrial society -- domesticated crops and livestock -- takes thousands of years to tech up. You can't fast forward it that much, because it takes generations of work. Such high-density crops and lifestock are in turn needed to maintain the population densities required for myriads of other technological advancements on the way up to a moon shot. A large percents of technology is actually building the tools needed to build better tools. Building each iteration of tooling takes a huge amount of effort. We amortize this over huge numbers of people and years. Knowing what to do each step (and note, no human alive knows all of the steps, or even knows all who would know all of the steps) would save some effort, but you still need human hands to manipulate materials, purify better ones, and iterate an ungodly number of times. Without sufficient population density (afforded by the earliest steps), time spent carrying each technological improvement to all of the people who need it explodes. Technology might look like magic and tricks. But much of it is a ridiculous numbers of layers of extremely specialized expertise and technology woven together into a world-wrapping supply chain. [Answer] They would have to start by making houses by each other, forming a little kingdom like place but not really one yet. They would soon be able to make fire and bows and arrows to start hunting all withing the first few days. After that they might start professions, so that way others can work on more things like getting to the moon. The first thing that they will need is iron to make steel if they want to make this rocket. They might be able to make the fuel after a couple of years, but they will still need things to make the rocket itself out of. They will start to mine for iron to make the rocket out of. But they will need a whole lot of it. By chance, they could get some from asteroids that crash around their pretty big kingdom. That could be their first way of getting iron. But they would need that iron to help them get more iron. With help from the asteroids that they may find, they should be able to get all of the iron that is needed to make one rocket after a decade or two. The next step will be to make the rocket. They would need to spend a long time just to get the rocket together, and they would have to spend so much time doing the math if they want to rocket to work. To get a human onto the moon they would also need to make them a space suit which would take some time. So they would have to start spending a long time to make steel after they get all of the iron that they need. But they should be able to get enough steel but it would be near the end of the lifetime. They would have to then put the rocket fuel into the rocket and that will be hard to do, and they will have to work on the button that will launch it. So they're also put some food into the part of the rocket that the person will be staying in. But I'd say that at the end of the lifetime they should have made the rocket and gotten the person in their. I'd say that the lifetime may end while the rocket is in space, but if they do it fast enough, they might be able to go to the moon and back before the lifetime ends. [Answer] The lack of infrastructure would condemn your attempt. And no, "infrastructure" does not just mean the obvious constructed stuff like roads, waterworks, etc. Cultivated, gene-specialized-by-very-long-selective-breeding plants. Remember that corn, wheat, tomatoes, potatoes, even apples DO NOT EXIST in a "completely uncultivated Earth" ALL of these are the result of many,many,many generations of selective breeding by farmers, over thousands of years. The original apple is a sour berry the size of your fingernail. The original corn looks like a stalk of grass! Ditto for domesticated animals. You will have no horses, no chickens, no cows. Their wild equivalents will be there, but they will not have the placid, easily tameable nature of the domesticated version, even if raised in captivity from birth. (ask any cassowary farmer how tame they are, compared to turkeys) Your people will get *hungry* for at least the first several dozen years, and won't be eating or farming comfortably for the first several hundred years. The high-yield corn and wheat that allows a very small number of farmers to feed a huge number of other people is just as much a product of technology as a steam-powered locomotive! And simply having the knowledge of corn does not enable you to plant it, just as knowing how to build a steam engine does not give a naked man with no tools, the ability to build it. [Answer] **If you lower the planet's gravity then the task becomes much easier.** For example titan has a mass of 0.0225 Earths and surface gravity of 0.138g. This gives it an escape velocity of 2.64 km/sec and an orbital velocity of 1.87km/sec. This means that the WW2 era V2 rocket would be an orbital class rocket and you could send any WW2 era plane into orbit with a solid rocket motor strapped to the back. Given that WW2 technology is difficult to achieve there are other ways of getting to orbit. 1. You could do it with large fireworks that require 14th century Japanese technology (Paper and gunpowder.) 2. You could make a rocket out of cast iron that runs on Hydrogen Peroxide and Ethanol. This is achievable by an Iron age civilisation. You would have to deal with humans living on a 0.138g world. It might be fine. We know that 1g is good and 0g is bad for humans, but we have no data on what happens to humans between 1g and 0g so 0.138g might be enough gravity to have healthy humans. If you want titan to be a reasonable temperature then just move Saturn closer to the sun. ]

[Question] [ > > Where am I? It is so dark around here... Hopefully I have a torch. It looks like I am in a very long corridor. > > > *Time passes* > > > What? No this couldn't be! I walked straight in front of me during the whole time and now I am back to the start point! > > > Oh yes, it is possible. It is just a circular corridor like this one : [](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Annulus_area.svg/402px-Annulus_area.svg.png) Thus, **what is the minimum radius of a circular corridor for the walls to appear straight ?** The inside of the corridor is in the dark, the character (human) sees around her in a radius of 20 meters thanks to her fire torch. She has to think that the walls are straight because of both her vision and her touch if she touches the wall. Thus, she thinks it is a very very long corridor, but in fact, she is walking in a circle! The corridor width $R - r$ is about 2 meters. [Answer] **TL;DR: Really, really big** (exact numbers below) Seeing the wall "crossing" is hardly the issue. Seeing the outer wall bend even slightly toward the inner wall - looking as if the hallway gets narrower further on - and the point at which that visually happens moving ahead at the rate at which you are moving already breaks the illusion of a straight surface. That is not to say it cannot be done, but it is made much harder by the fact that you have TWO surfaces that need to appear to have the flat trait and appear parallel to each other. Apart from the above, this is what is known as a *horizon problem*. Imagine the logical alternative: instead of building your round corridor on a flat plane, you build it along the axis of the planet. Depending on the height of your corridor, even this will be noticeable after even a short while. It will likely have a much lower ceiling than for example a tunnel meant for cars, and the *horizon problem* is actually a structural concern for the longest of those already. --- But, you provide a stipulation that may make this a little easier: the light limit. *Science Focus* tells us that the smallest discrepancy in visual data the human eye can perceive is two points that are 0.01 degrees apart in the field of vision. Therefore, the tunnel must bend less than 0.01 degrees over the proposed 20 meters visual range. Therefore, the tunnel would need to be (360/0.01)\*20 meters in length, or 720 kilometers. This will put the inner radius at about 115 kilometers. Have fun walking! **EDIT** For completeness sake: In humans, visual resolution at point-blank range (comparatively the only one that matters) is up to a factor 1000 times higher than tactile resolution. Therefore, any solution to this problem that will fool the eye will fool the hand (which, if in doubt, a coarse wall texture will resolve this without this extra data). Auditory spatial resolution is even lower, so echo will not be an issue. [Answer] SRM points out that even in a circle long enough that you *won’t* reach your starting point again if you're walking for an hour, and where you can’t see very far, one can still tell that the walls are curved. So, hide that better. Make the path wavy, and the walls are even rougher. Any given visible wall may be convex or concave to varying degree. The *bias* is unnoticed. It may even use tricks to hide the systematic bias of curving in one direction by using differently sized bends so it “feels” more like they are balanced. The two walls may get closer or farther from each other, and the *difference* in the two bends is opposite from the appearance of which direction they are bending. The size is given by the other constraints: how far does the hero walk in an hour? The walls are not a simple uniform smooth path, so you can’t see the curve by looking at a small patch. We assume the hero doesn’t have a compass. --- Being more flexible on the length (*please* make your question text accurate!), I think 1 or 2 hours is doable. The shorter the circuit the larger the curvature bias to overcome; so it's a matter of *how wavy* and how aggressive you need to be in introducing other techniques. For example, if you want the walls to remain the same distance apart, you might use a longer path. My gut feeling is that 12 miles, a 4-hour walk, would be *easy* to hide the curvature, with halls that are not more zigzag than a natural pathway, and straight enough that walking is easy. For a definitive answer, you’d have to test people. The psychological aspects can’t be simply computed. A good description of the hall and the experience of walking through it would make these figures quite believable. And a reader won't be able to repudiate it, anyway, without testing such a model. And the *written* form is not exact, so you have to take the author's word that the gentle meandering and rough walls hid the slight bias of turning left more often than right, without having detailed measurements for those curves. [Answer] If you can afford to make it not straight, make it zig-zag. You can make the path shorter than a kilometer then! Give the corridor a right-angle turn every $s$ meters. Make turns strictly alternate - left-right-left-right so the person could be sure without counting that the turns cancel each other out. But the constructor (you) can cheat - make the left turns $d$ degress more than right-angle and right turns - $d$ degrees more. Make all the corners rounded so the person couldn't measure the angle in corners. # The math If you cheat $d$ degrees on each corner, you need $\frac{360}{2d} = \frac{180}{d}$ pairs of turns. If the distance between turns is $s$ meters, your tunnel would be $\frac{180n}{d}$ meters long. The path would be approximately $\sqrt{2}$ meters longer than the circle that it approximates, so you'd have a zig-zag path approximating circle circumference of $\frac{180n}{d\sqrt{2}}$ that corresponds to circle of radius $\frac{90n}{\pi d\sqrt{2}}$. # The numbers Drainage *right-angle* bends [are commonly 87.5 degrees](http://www.drainageonline.co.uk/110mm-Drainage-Pipe-and-Fittings/110mm-Double-Socket-Drain-Bend-87.5dg.htm). I have worked with those and it's hard to notice they are not right-angled. Example: [](https://i.stack.imgur.com/AmYoZ.jpg) So you could try to cheat $d=2.5$ degrees on each turn. If you make a turn every $s=10$ meters, your path will be $\frac{180n}{d} = 720$ meters long which would approximate circle of circumference about $509$ meters and radius of about $81$ meters. Yes, this path is not straight at all. But with this solution you could make the person return to go full circle within 5 minutes not many hours/days. Or you can increase the distance/decrease the angle cheating as you like to make the trip longer. [Answer] One other option, is a simple optical illusion. Paint vertical stripes on the walls (or use alternating colors of bricks). Make the stripes on the inner wall slightly wider than the stripes on the outer wall. The eyes and brain will interpret this as going straight. It is a variation of this idea:[](https://i.stack.imgur.com/yFnu9.jpg) but imagine not being able to see the end of the room and nothing on the floor so that being on the . Unless it was a very tight curve, it would be very difficult to know the curve was there. You would most likely be convinced that it is perfectly straight. The only other requirement would be that small r be greater than 20 meters (2r=40m) so that the convergence of the two walls is out of sight. Of course as a few others have mentioned bigger would help hide shadow/reflection issues. Another option, as far as that goes, which would allow your maze to be as basically as small or large as you would like would be to be to paint the hallway with vanta black: <http://www.maxim.com/news/scientists-vantablack-20-blackest-black-2017-4> (seriously cool stuff). Then even the horizon issue wouldn't be a problem, visually you could have big R be 2 meters(little r=0) and it would be fine (though you would have to worry about fitting the internal maze into 0 space, and I think taking two steps and running into a wall would be telling, so you might go bigger than that. [Answer] It is easy to fool people into mistaking a single slightly curved wall for a straight one, but this becomes much harder in corridors - if one wall visibly "crosses" over the other in the distance, or even becomes noticeably closer to it, the illusion will be shattered and it will become obvious that the hallway is curved. Therefore, the minimum radius of the maze will *increase* as the width of the hallways *decrease*, making the size of the maze extremely large either way. You have a few options to make the maze continue to appear straight: give the maze a lot of right-angle turns with no long "straight" corridors. The person may count their right and left turns, making it seem as though they are going in a single direction until they arrive back where they started. If each "square" of the maze consists of a small square (actually trapezoidal) "room" with either two or three possible paths, but no single path more than three "rooms" in length, you can get away with a much more reasonably sized maze. Alternatively, make the maze *foggy*, so it is impossible to see more than a few meters ahead even with a torch. EDIT: Another option that could help - make the walls jagged, as if built roughly out of large stones. If the walls are rough around the edges, the off-centerness of the hallways could be chalked up to the roughshod nature of the maze rather than a deliberate choice of design, especially if the person in the maze is conditioned to expect grid-based mazes. [Answer] Your question immediately made me think of stories of people who walk in [circles when they are lost](https://www.google.com/search?q=walking%20in%20circles%20in%20the%20desert) in the desert. According to the first article in those search results > > lacking external reference points, [humans] curve around in loops as tight > as 66 feet (20 meters) in diameter, all the while believing they are > walking in straight lines. > > > Therefore, all you need to do is take away your character's torch and make sure the walls of your corridors are sufficiently uneven so as to throw off the overall circular feel if one were to run their hand along it. Something like this: [](https://i.stack.imgur.com/YiW81.jpg) With visual references however, it would be much easier for her to tell that she is inside a circular corridor - as other answers have mentioned, one wall eventually crosses in front of the other when looking forward. Even if the light does not shine far enough to see them meet, it would need to be an enormous circle to eliminate the perception of the two walls at least getting closer to each other. Again, texturing the walls would help a bit, but probably not enough in a 20m radius. [Answer] You want the curvature of the walls to be unnoticeable. This is equivalent to say that the deviation from the straight line after 20 meters has to be small, let's say 1 cm. 1 cm deviation at 20 meters correspond to an angle of 0.02 degrees. > > Angular resolution of human eye: about 1 arcminute, approximately 0.02° or 0.0003 radians,[1](https://en.wikipedia.org/wiki/Naked_eye) which corresponds to 0.3 m at a 1 km distance. ([source](https://en.wikipedia.org/wiki/Naked_eye)) > > > This means that this equation has to be verified (with $d=20 m$) $R-\sqrt(R^2-d^2) < 0.01$ A radius R of at least 20 km will satisfy the condition. [Answer] I once got similarly disoriented despite being able to see the angles ahead of me as I walked the streets. As a child, I was used to the regular street grid with 90 degree intersections in Germantown, Philadelphia. Our summer house was on Windsor Avenue, Cape May, New Jersey, in the western part of the city. You should be able to find [Windsor Avenue](//www.openstreetmap.org/way/11603717) in a map of Cape May. As you can see, Windsor Avenue goes off at about a forty five degree angle from Beach Avenue. But I thought of it as 90 degrees because I could only imagine right angle intersections. One day I left the house in the third block back from the beach and turned away from the beach for a walk. Windsor Avenue made a little turn to the left in that block that made the angle to Beach Drive even more different from the right angle I imagined. Windsor Ave. ended after the next block so I turned left at a 90 degree angle on South Broadway. I thought that I had been going straight away from Beach Ave., so I thought the 90 degree turn should put me in a course parallel to Beach Ave. There as another slight turn in South Broadway which I ignored, thinking I was still walking parallel to Beach Ave. And then I saw the Boardwalk and Beach Avenue straight ahead of me, and I wondered how I could have turned 180 degrees when I had only really noticed the 90 degree turn! So in board daylight someone who sees every turn he makes can still find himself thinking his course is 90 degrees from what it actually is, if he has inaccurate preconceptions misleading him. So imagine how easy it would be for someone in the dark with only a small light they carry to be accidentally or deliberately misled about their surroundings and direction. 1. I would suggest having pillars or columns or piers in the wall every ten or twenty feet. If they each jut out a foot or two and the person can only see a few tens of feet ahead, the person will only be able to see a few of the pillars or columns or piers ahead. The nearest pillars or columns or piers on each side will cast long shadows over the walls beyond them. The pillars or columns or piers can alternate in how much they stick out in a pattern. They might alternate like this: One foot, two feet, one foot, two feet, one foot, two feet, one foot, two feet. or: One foot, two feet, one foot, three feet, one foot, two feet, one foot, three feet. Or: One foot, two feet, one foot, three feet, one foot, two feet, one foot, four feet, One foot, two feet, one foot, three feet, one foot, two feet, one foot, four feet. 2. The walls can be made of artificial bricks or cinder blocks or artificial stone that bulges out a lot on the surface facing out. Thus feeling it will feel a surface going in and out, in and out, in and out, over and over again. Nobody will be able to feel how straight or curved the wall as a whole is over long distances. And the visual effect will be of a bumpy wall, not one those curvature is easy to measure. 3. There could be air conditioning that cools the corridor down to uncomfortable temperatures, and heating to warm it back up. And the heating could be hot air coming from grates spaced along the sides of the corridor, air hot enough to make waves in the air and make everything beyond look wavy. Thus the victim will see the more distant parts of the corridor waving in the heat waves and will be unable to judge how straight or curved the corridor is. 4. The walls can be built or painted with vertical panels of different colors. The floor and ceiling can have colored bands crossing from side to side the same width as the wall panels. Thus there will not be lines pointing along the direction of the corridor to follow into the distance to see if they are curved or straight. 5. Or everything can be painted black and the victim only sees very dim reflections from everything, thus not being able to see curves or straight lines ahead very well. 6. Or the corridor could be made of segments like little rooms. Each little room could be an oval about 2 meters wide by four meters long, with openings about one meter wide in the two short ends. Since the walls in each segment are curved, it will be impossible to see if the corridor as a whole is straight or curved. And each little segment will be tilted a fraction of a degree off the ones behind and ahead of it. That will be done by slightly changing the thickness of right and left walls on the side of each opening between segments. Each opening will be closed by a curtain that the victim will have to open. The curtains will be transparent plastic, with a lot of vertical folds that will distort the images of the segments ahead, so the victim will not expect everything to line up anyway. And there can be support columns in the center of each segment so the view directly through opening after opening after opening will be blocked, making it harder to see how straight or curved the corridor is. I think that a combination of several of those suggestions should be enough to fool the victim. [Answer] Edit: The question seems to have changed slightly while I wrote this, let me rethink. I'm no expert.. but I don't think it would be possible without the maze being incredibly vast. Let's assume your character starts in the very centre of the maze in your example picture. If that chamber was any less than 40m wide (diameter of the circle) then her torch would illuminate it and it should be obvious it's circular. Even twice that size it should still be obvious when close to the walls that they are circular, the opening should make this even more obvious. Going out to the next ring of the maze you would need the circumference to be large enough that it appears that each 40m section is straight so the character can not notice the curvature. It's hard to know what size this would make it but at a rough estimate I'd say you'd need the 40m sections to be about 1/50 to 1/60 of the total circumference (looking at where the wall segments start to look like a straight line) to even begin to make the curvature less noticeable. So for the very first ring of your maze you'd be looking at between 2km and 2.4km in circumference and a radius of approx. 380m. If you extrapolate that outwards by the eight rings your example maze has your total radius should be 3km, making the outer wall nearly 19km long. And to be honest I'm still not sure you wouldn't notice the curves at that size, plus the maze itself (as in the number of corridors and turns) isn't really that big so to make a more complicated maze you'd need it even bigger than that. So why does the maze need to be curved, and why does the character need to not notice? If it's just to explain how they continually walk back on themselves... surely that's the entire point of a maze anyway? [Answer] Even with a radius 6371 km (radius of the earth), your corridor will appear to bend downward, as does the surface of the sea. Since on our planet you cannot make the radius any larger, the problem has no (terrestrial) solution. With a torch one would only notice if the torch is held VERY close to the wall, or, in case of a full earth radius, to the floor. Since that's impractical, having a radius of say about 1 km would probably be enough. To verify, visit the [Large Hadron Collider](http://home.cern/topics/large-hadron-collider)... [Answer] Sadly, there isn't one answer for this. The most popular answer here is based on the angular resolution of the eye. It, in effect, asked "how much curvature can there be before there is a detectable difference in the photons that hit the eye." However, there's an incredible amount of signal processing which goes on after that. Differences like that will simply go unnoticed. As an example, consider the first two pictures here: [](https://i.stack.imgur.com/EkGem.jpg) Would you believe the first two pictures have *exactly* the same geometry? Our eyes can fool us. Our ability to see the corridor actually depends greatly on the nature of the walls and floor. We can detect curvature in the corridor faster if the texture helps us. For example, consider looking out at the ocean. The horizon looks flat. You can't see the curvature of the earth. However, if you put a boat on the horizon, you can see that the bottom part of the boat vanishes due to the curvature. That lets you see that the Earth is round. [](https://i.stack.imgur.com/OGsz0m.jpg) So if the floor has texture to help you see the curvature, such as parallel lines running down the length of the corrdior, you're going to see the curvature much sooner than if it were a featureless corridor. Rounding the corners could make it even harder to tell. [Answer] # Active corridor. The corridor is a ring 1400 meters in diameter, at a reasonable pace you make one round every hour. Every twenty meters there's a narrow sconce in the wall, with an idol and a small votive light in front of it. The hero cannot see the whole corridor, but he *can* spot several lights in front of him in the darkness, and they describe two straight lines, converging in the middle. He looks back, and he sees the same. So he is sure the corridor is straight. When he walks forward, the two large LCD screens (or magic constructs) that lurk just outside the torch's range move as well, displaying what an endless, straight corridor would look like were you to look at it from the hero's point of view. This requires some Kinect-level magic to reliably tell where the hero's eyes are, but has the advantage of not needing any recognizable cues to thwart the perception, which could make the hero suspicious ("*Why all this clutter? I almost can't tell whether the corridor is straight! Errr... hold that thought...*"). A similar trick > > using a grav engine and a corridor bending on the *vertical* plane > > > was pulled on a guy called Hulon in Theodore Sturgeon's *What Dead Men Tell*, and a wholly different principle was used on a larger scale in James P. Hogan's novel *Endgame Enigma*. # Flexible corridor. The corridor appears to be solid, and unmoving. It actually is neither. It is a racetrack-shaped running mill, three hundred meters long, built to tolerances small enough that near the hero it appears to be solid. One hundred and fifty meters behind the hero, the slices making up the corridor unlock, bend a full 180 degrees like baggege conveyor belts in airports, and are rolled back in the opposite direction. If the corridor is sufficiently soundproofed and the movement is smooth enough, the hero will notice nothing from the inside, and he'll be in the middle of a thousand yard corridor that is perfectly straight. # Magic (or technological) light bending By supplying vertical laminar flows of air heated and cooled at different temperatures through grilles in the floor and ceiling - they can be deactivated by the hero's pressure on the floor, to provide a more comfortable environment while he walks - it is possible to *bend the light* so that the corridor appears to be straight, even with better lighting than a fire torch. This is the same effect that makes [the sky reflect on a road on a hot day](https://physics.stackexchange.com/questions/10464/why-does-the-road-look-like-its-wet-on-hot-days). Of course the corridor will appear to shimmer, but it's unlikely that the hero is conversant enough with physics (or vertical mirages) to cotton up to what's happening. [Answer] Could you work with a path that is a polyline, with many left and right turns, not attempting to conceal the fact that the one traversing it is not moving straight ahead, but not betraying the fact that she is moving in a closed path, to the starting point? Unless one has a good "internal compass", after a few turns, they should lose track of their overall bearing. I think the simplest case which would achieve this is a 5-point star: you have 5 acute turns and 5 obtuse. [Answer] You need to specify something: was it the intent of the tunnel builders to make it confusing so someone thinks the tunnel is straight, or did they make a simple tunnel that just happens to be so big you only think it's straight? If it's the latter, you run into the horizon problem mentioned by others: it's hard to pull off. If it's the former, that's easy. For example, and some of this was mentioned in other answers, don't make it a simple straight path. Have the tunnel jog around a bit. Have sections that are really straight; say you have a series of three identical rooms with doors in a line so you can see them, but you had to go sideways a bit entering the sequence and existing. If you look back, you see a perfectly straight path, but then you get into a section with tight turns and narrow passages where you can't see very far and you're gradually being turned in one direction, and then, look, another series of straight rooms. ]

[Question] [ Joe Schmoe was six years old when he killed his best friend; it wasn't his fault, it was just the way that he was made... Joe was born with an auto-telepathic telekinetic feedback ability - he has the ability to unconsciously kill anyone who has thoughts of killing him. It doesn't matter if those thoughts are intended to be carried out - "it's the thought that counts" (to re-use a phrase). If someone has an idle though that the world would be better off without Joe being alive, then they die. As a young adult, Joe is eventually incarcerated in prison, in solitary confinement. But he's still killing - everyone who benevolently wishes to end his solitary suffering, the relatives of those that he's inadvertently taken from their families. How can we end this cycle of pain and suffering? EDIT: Burki raised the question of suicide. While this might be an elegant idea, it bypasses other creative ideas. For the sake of the story, let's say that this ability is borne of self-preservation and suicide is not an option here (sorry). **CLARIFICATION** Interesting discussion overnight and some clarification has been asked for. In essence, Joe's defence is this: If someone wishes him dead, then they die. Thinking of Joe, or being afraid of him isn't necessarily fatal. Let's put it another way. Consider any mass-murderer/psychopath/dictator and how many people would wish them dead. Or another way. A cute girl/guy sells you coffee this morning - if you subsequently have a sexual fantasy about him/her, you die. If you're happy with just getting your coffee with a kind word, you're pretty safe. It's also worth considering the new title of this question and spinning it around - who is the thought-crime killer - Joe, or the people who wish him dead? Nevertheless, Joe is in solitary confinement - whether he got there by turning himself in, or was dragged in is open for interpretation. I'm not saying either happened, I'm just providing a framework for your imagination. [Answer] Put Joe into a medically induced coma. Once his brain activity is sufficiently suppressed, you can then start researching possible solutions without worrying about everyone involved dropping dead. If Joe is a reasonably decent person, he should be willing to do this to prevent more deaths. Whoever is actually doing the medical procedures would need to be unaware of Joe's nature, and would probably need to believe they were helping save Joe (which in a way is true). [Answer] The problem is already solved. Joe will die in solitary confinement from thirst or starvation, as his guards and the officials responsible for replacing them all drop dead. * "I should bring Joe his meal, otherwise he will starve... hey, that woul..." * "I need to assign someone new to bring Joe his meal, otherwise... " Some dutiful person may restore part of this chain of responsibility without thinking about the consequences... the first time. But eventually it will reach a completely disinterested bureaucrat or an inbox that is no longer monitored and Joe will die, probably along with any other inmates in the entire jail. [Answer] **There's a fine line between killing someone and failing to prevent their death.** We have a lot of health and safety systems in place that are designed to prevent accidental death and injury, an environment where these aren't in place is not actively killing him, but nor are you trying to prevent him from dying. The numbers will get him eventually. Consider sending him to war. The bulk of people shooting at him aren't considering killing him. They're just killing and they don't care who. You could also set him up as the world's most successful sniper, those he kills, he kills and those who try to kill him, he kills. As it stands, you're making him suffer for no good reason, and in the process making yourself responsible for the deaths of many others. The simple fact you've put him in long term solitary has drawn attention to him in a way that is killing people whose only crime is wanting to kill him. Let him be an anonymous nobody in the street again and you'll have a lower death rate. Let him out, announce his death so that people stop thinking about him, and let him try to kayak solo across the pacific in winter if he wants to. *What your question and many of the answers are showing is the moral to the story of Rudolf. Being different is punished unless it can be exploited. The fact so many people die around Joe is a testament to their character, not his, but he's the one who ended up in prison for it.* [Answer] I think the biggest problem with this is that your "idle thought" constraint means nearly anyone who deals with this situation will die. This sort of constraint makes it rather difficult, because it would cause a chain reaction, particularly since there is nearly no way to have people know the problem exists without them dying. You can't ponder, "how do we kill Joe?" without dying, yet in order to resolve this issue someone *has* to do just that. For example, it's easy to try to imagine scenarios you *cause* his death to occur by allowing it. But for example, if you want to send him to war - how do you come across that idea *without* an idle thought of it causing his demise? This applies even to things like "program a robot to do this" - how do you program a robot to cause a specific person's death without thinking about it? How do you get a team together to program a robot to kill a specific person, without the person organizing the team first dying? Or bombing his building? The answer is you really can't. It's difficult even to imagine this scenario not causing considerable destruction to a society. It is fairly common to desire revenge when someone dies unexpectedly and at some point, depending on the rest of the world and their technology level, this is likely to destroy vast portions of society. If Joe is in jail it means that somewhere this is "sort of" public and realistically the minute it becomes public knowledge, is likely to kill many people. Thinking about causing an "accident" results in your immediate death. You could have someone be hopelessly optimistic about the situation and try to find someone who is really eager and willing to try to help and equally hopelessly optimistic (but an idiot) but... honestly that feels like a lame plot device to me. The problem is that the *moment* the idea occurs, death occurs to the thinker. Consider [the elephants paradox in Inception](https://youtu.be/H1Dyp3jexA0?t=1m15s). Which means none of the other answers currently here will work as all require a cohesive thought on the part of someone in order to cause events which then unlink causation. Fundamentally they boil down to, "how do we kill Joe by accident?" which given your constraints results in their **immediate** death. You need to consider the events leading up to him being incarcerated and either: 1. Add more constraints or potential for *some* people not to die immediately (see below) 2. Repeat the events allowing him to be put in prison and cause his death Otherwise, Joe is going to die of starvation/neglect when enough of society dies due to causation. --- One option for (1) is creating someone deranged or mentally unstable who *really* believes he can help Joe and is mentally incapable of that sort of thinking, but that their help turns out to accidentally be fatal. Or a redemption story, depending on what you want to do, maybe they can help Joe stop this. By adding mental instability/issues for this person you allow the possibility of dialog about the subject with Joe and the other person with a plausible explanation for why that person never pities or ponders "wouldn't it be easier if you died." Think a witch doctor type person or something. Or crazy person. This still requires a fair bit of hand-waving in order to allow the crazy person/witch doctor to find out about Joe (without the chain of people knowing of the problem dying or enough of society dying) but you've already built that in with the fact that he's incarcerated. Clearly, somehow, in your world people can learn of this situation without dying. Given your comment, the easiest and probably best way to handwave this away is having someone at the prison be this person. Maybe they have a mental disorder that causes them to be unable to consider future events. Maybe they are straight up unstable or crazy. Maybe they are the prison chaplain. Or part of the prison service staff (you probably want to find a non-stupid reason why you'd have an insane/mentally unstable prison guard...). That person can come into contact with Joe *naturally* then, if they already work at the prison. What you do then depends on your story goals for resolution. Death? Redemption? Healing? Controlling his powers and learning to undo those deaths? Either way, you've established a cohesive framework in which the two people (Joe and Crazy) can interact meaningfully to work together towards that ultimate story end goal. [Answer] Challenge him to a game of Russian roulette, you're not trying to kill him, but if he kills himself... problem solved Another option is that you send him on riskier and riskier missions for his country to infiltrate and stop other countries developing. Oh no, he killed the entire enemy army trying to stop him! That's a real bummer, but oh wait he was mown down by a carpet bomb of the area that wasn't aimed directly at him... problem solved [Answer] ## **Don't think of him dead. Think of him as lost.** The Amazon rainforest is one of the greatest places for people to kill themselves. Too far? Drop him in the ocean, or a sea. Alone. Still too much? A desert, no water. A matter of hours. Or a mountain. A plain. Africa. Australia. [Especially Australia.](http://3.bp.blogspot.com/_wTKEFIKSrvg/Sc4MpUMFvUI/AAAAAAAAK0I/IkeCE7gyp2k/s400/selection_121_77.jpg) To summarize: *make him go somewhere that he's sure to be dead.* Of course, you don't want him dead. Just lost. Forever. [Answer] # No-one would ever know > > If someone has an idle thought that the world would be better off without Joe being alive, then they die. > > > You have specified your question much too harshly. This "rule" here means that anyone and everyone that has the thought, will die. This means that they will not be around to tell anyone else that they thought that very thought, because they are dead. *What if I write it down?* You cannot do that, because you must think you will do it before you do it, you die. *What if I tell anyone else before I think it?* So you think you will tell anyone else that you will — in a few seconds time — think that you think Joe should die? Oh... ...and so on. You may need to rephrase the question. Instead of what I quoted above, maybe it should be: > > Is someone thinks that we should take action to see to it that Joe dies, then they die > > > ...because then your question is at least possible to ask. But as it stands now, you will just have some people die mysteriously, and no-one will ever know why they died. Assuming this... Now we open up a new can of worms, because now we must get ourselves into definitions and reasoning that would make a lawyer wet their pants when it comes to defining "murder". I mean if I place a bomb under Joe's chair and run away, waiting for it to go boom, yeah, then that is definitely me killing Joe, no question. Murder in the first... But what if I just drop a bomb somewhere, where Joe **might** come around, and he happens to do so just as it goes off? What if I tell someone "Hey you, you see that chair over there? Can you please go put that bomb under it?", and that guy says "Ok" and does it? ...and so on and so forth. I understand the gist of your question and at first glance it is a fun and interesting conundrum. The problem with the question however is that 1) it is flawed in its present wording, for reasons mentioned above and 2) eventually it only comes down to extreme rules-lawyering. And that is never any fun. In the end I would probably just ask the state of whatever country Joe is a citizen of to buy him a nice little island in the Pacific, ask him to go into voluntary exile for the good of mankind, and airdrop in everything he asks for. [Answer] There were cases when guards simply forgot that someone is in the solitary and starved that person to death. Sending letters to all officials involved simply *explaining* what they are dealing with - and instructing them **not to think about killing the Joe** would probably do the trick. Some good samaritan may probably do this just to make sure everyone is safe and nobody gets hurt. [Answer] Get an **artificial intelligence** to plan, organize and execute Joe's demise. A software running on a bunch of microchips doesn't actually think. It just emulates human thought processes with electricity flowing through billions of transistors. So it will be immune to the telepathic effect. The problem will be to create that AI without ever realizing that the goal is to kill Joe. For that reason you should just build the AI with the objective to *find an effective solution for neutralizing mind-killers* and neglect to program the first law of robotics into it. The development team should not know that Joe exist. They should just be tasked with developing an AI for organizing the disappearance of mind-killers, but not get told who the target is. When they think "the AI might decide to kill the target", they won't be thinking about Joe specifically, so they won't trigger his ability. When the AI is finished, then either the manager (who still doesn't know and doesn't *want* to know if the AI will kill or not) enters Joe's name. Or even better: the AI figures out its target by itself. The AI will then either create and send a soulless killer robot, or find some non-violent solution. Either way, problem solved. Now you just need to deal with the murderous AI capable of controlling killbots, but [that's a topic for another question](https://worldbuilding.stackexchange.com/questions/tagged/artificial-intelligence). **Tangent:** We actually have an interesting plot here about the ethics of delegating ethical decisions. The manager doesn't want to think about a problem to which the solution might be unethical, so he delegates the ethical decision to a team which is isolated from the actual problem. They further delegate the ethical problem to an automated process. This is something similar to what regularly happens in real life in large corporations. Just like in the story, the result is that the corporation acts unethical without anyone in them feeling that *they* acted unethical. [Answer] You don't. That sounds flippant, but in this situation you need to heavily align your goals with Joe. Otherwise you will die quickly. The "Thought-Crime Killer" in this scenario is the *idea* of trying to kill Joe. Ie, it's a concept based version of a 'basilisk'. <https://en.wikipedia.org/wiki/BLIT_(short_story)> So, the first thing to understand is if Joe dies, you die\*. Secondly if people outside of the prison learn of Joe, then they will probably die. This pattern of death may look like a viral outbreak. Thirdly, if enough people around the prison die, the government will eventually spot the issue. Their reaction has a high chance of killing Joe (ie, bombing the centre of the 'outbreak'). As such, your goal is to keep the world away from Joe, and keep Joe safe. (Good thing that he's in a cell...). That's the only way to 'end this cycle of pain and suffering'. I can imagine a Call of Cthulthu style cult building up around this. After all, you can't rely on just one person to keep Joe safe, but you can't trust the outside world... \*While that's not technical true, it's best to use enough doublethink to believe it! Otherwise you'll start looking for loopholes, and *blam* your're dead. Similarly there are large holes in my argument while should be ignored ;). [Answer] I think a more pressing issue is, how exactly do you explain the fact that Joe is found out and incarcerated in the first place? Given the information you've given us, the following is true: 1 - this is an unconscious ability. Joe is unable to control it and furthermore he may be unaware of the fact that he is doing it at all 2 - the ability is triggered by any person having the mental state of imagining a scenario where Joe dies. 3 - when (2) happens, the ability takes immediate effect and the person dies Given these three premises, I find it very unlikely that anybody would ever make the connection that Joe is somehow behind these deaths. The only thing linking them to him would be the fact that everybody who dies would have to know Joe, but Joe would likely have solid alibis for most of the deaths. It's unlikely that a connection could even be made that those who hold a grudge against Joe are the ones who died, because the likelihood is that in many cases, their death would occur before a grudge can be properly established and observed by other people. Even if he is aware of his ability, I don't really see how he can possibly prove it to anybody - at best I can see him being imprisoned in a psychiatric institution for having the delusion of being responsible for murders that there is no evidence that he committed. We can't observe the mental states of other people, we only infer the mental states from their behaviour, so no external observer could possibly know that every single one of the deaths was caused by thinking about Joe's death. For this reason I think this is actually a much more interesting point to deal with than you've made it out to be. Regarding stopping him though: If he is aware of his ability, surely at some point he must have had the thought that the world would be better off without him? If so, then in theory he should have died long before imprisonment, unless he is also a psychopath and is happy that people are dying despite having no active responsibility for it. (Or unless he is actually immune to his own ability, but this would need explaining in some way) edit: an interesting element could be added here, if Joe is immune. Joe wouldn't necessarily be aware that he is immune, and almost certainly wouldn't understand why he is immune. As a result he might find himself doubting the sincerity of his belief that the world would be better off without him - and thus doubting his sanity and believing that he might be a psychopath. Also, it's worth considering the question of how exactly does his ability communicate with/read other brains? Given that there is some sort of information transfer going on, it's fair to assume that there is some sort of particle/wave mediating the interactions (even though as far as I'm aware this is just a form of hand waving really- members who are better with physics/neurobiology might be able to give a better scientific basis for this), and if this is the case then **in theory it can be blocked**. People could create actual useful "tin foil hats" (not necessarily out of tin foil, but if you're going for a comical tone it would be amusing if this was the magic ingredient : p) to block Joe's ability. This in turn creates the interesting problem- how do you plan to block Joe's ability on yourself, without planning to use this to kill Joe "for the greater good"? the best solution might be to get somebody to create a tin foil hat to put on Joe, thus stopping him from killing anybody. Hope this is useful - my science is sketchy but I love philosophy so I'm treating it more as a philosophical problem than anything [Answer] **Primary Idea:** Considering the fact that Joe was incarcerated there is a method of thinking about stopping Joe without coming across the thought of killing him. This allows us to assume that there is a trigger-point for Joe's ability that can be avoided, and that knowing about his ability isn't an automatic death sentence. I would postulate that maiming Joe would be possible under these assumptions. Make it harder for him to defend himself (blind, deafen, amputate, etc.), and then allow nature to kill him. **Secondary Idea:** The ability is an unconscious action on Joe's part. I would suggest scanning his brain to locate the section that is active when his ability is active. Once it is located excise it with surgery. The risk in this idea is that depending on the location it could carry risk of death which would activate Joe's ability. [Answer] **On "Faking his death"** I'm afraid I don't have sufficient reputation to comment on other people's answers, but one of the answers above refers to the solution of faking Joe's death. In particular, Tim B said "I think this is the only possible answer with the constraints posed. Don't kill him, fake his death and then no-one will think of killing him." An interesting problem with this - does Joe's ability distinguish between an intention to cause Joe's death and a belief in the actual reality of Joe's death? If your answer to this is "No" then it's possible that by trying to fake Joe's death you might actually cause more people to die. If you're fully aware that the death was a fake then it's possible that thinking about the faking of Joe's death would not trigger Joe's ability (because no matter how you think about it, you know that the event of Joe's death is not true, even if you're planning to do it, you're not actually planning to kill him (or stupidly trying to do so "by accident") so it *might* not count On the other hand, the thought "Joe is now dead" might actually get you killed, because even though you're not intending to cause Joe to die, the propositional content of your thought is essentially the same, it's just that you're thinking about something you believe to be true, rather than thinking about a hypothetical situation. Especially, the thought "the world sure is a better place now that Joe is dead", is not really all that different from "the world sure would be a better place if Joe were dead" So what you might find is the reverse of what people have been commenting - people involved in the faking of Joe's death might actually survive, due to their awareness that Joe's death is fake/that their plan is to fake Joe's death, not to kill him. On the other hand, the people you're trying to protect and who accept the truth that "Joe is dead" might die on the spot, as long is Joe is still alive. [Answer] I think the best story telling answer begins with a question: What is the range or effectiveness of the power? If I'm 5,000 miles away and I think long and hard about killing Joe, can he reach me? If I'm 1 mile away, and I think about how the world will be better if everyone named Joe was killed, can he reach me? What if I want to kill him, but don't know what he looks like or his name? If it's the entire world with complete effectiveness, nothing can be intentional. He can unintentionally die, but no one can pull the trigger. I can't arrange for an assassin who doesn't know Joe to kill set a bomb to kill whoever walks into the room next, because I'd die before relaying my plan. Your only hope for a successful murder here is someone choosing actions that put Joe at risk. On the other hand, I think that limits on this make a better story telling scenario. Those high ranking people in the know travel to the ISS, and discuss the plan, hiring people who set in motion a chain of events that unwittingly kill Joe. A hypnotized guard is basically a sleeper agent, unknowingly going to strike at a man he's never met. A second mind killer who is placed with Joe so that they can eliminate each other. [Answer] The main problem here is that any plan that intentionally results in Joe's death immediately results in the death of the plan's conceiver before it can be communicated or even refined ("what if we drop invisible elephants on h—"). The only way around this is for nobody involved in the plan to know Joe is involved and that a (fatal) action is to be taken. They may know either one of these things, but not both. # The division of labour From this we can divide all participants into two categories: those who know a person named Joe is involved, including his location, etc, and those who know a predetermined action is going to take place. The former group may or may not know any detail about Joe beyond his appearance and presence as a human male, but it is key they not know their role endangers him. The latter group may or may not realize that their actions would be fatal for anyone in the wrong place, but it is essential they not know Joe, specifically, is present. But how do you plan a course of actions that results in the death of a specific person without holding those two thoughts in your head? How do you coordinate the two groups without letting the thought occur to you? You can't, but a computer can. ## Let the machine do all the work As it is impossible to conceive a plan that kills Joe without immediately dying yourself, the task must be left to a sufficiently advanced computer. Obviously programming a computer with "find a way to kill Joe" won't work, but you could program it to "solve the Joe problem efficiently" and stipulate that anyone involved in carrying it out be divided as outlined above, never communicating to anyone the purpose of their orders or the goal of the plan. It is entirely likely – we *have* to assume – that, given what we know about Joe and Joe's ability, the computer will come to the same conclusion we dare not think ourselves. We would just have to be completely in the dark about it, unaware it's in progress or that it has achieved the goal of his death, until it's over. [Answer] **Quarantine and Isolation** "Quarantine" is the only effective pattern human societies have to handle deadly diseases which they cannot control. Understanding Joe’s nature is a terminal disease, because the human mind is just not designed to "unthink” something. Ref: "[The Game](https://en.wikipedia.org/wiki/The_Game_(mind_game))". Since no person can conceive of (and execute) a plan to end Joe’s life, the only way to stop the cycle of pain and suffering is to cut off the spread of information about Joe. Arrange a backstory of a horrible fatal disease -- which is plainly true -- and set up humanitarian aid for the disease's victims. This shifts the attention from Joe to "the disease", and helps reduce your two biggest risks -- external curiosity and natural resentment for the resources consumed. Permanently isolate Joe and everyone who is faintly aware of Joe (yourself included) to some remote location, perhaps a desert island. The only contact with the outside world is scheduled parachute drops of supplies. This plan requires Joe’s cooperation, but he would benefit from a marked improvement of lifestyle, even if he were completely indifferent to the pain and suffering his existence causes. Resentment will quickly kill the people who understand Joe's true role in their fate, but their deaths may help improve the chance that you will achieve your goal, posthumously, of course. [Answer] Short Answer: You can't directly or indirectly kill him. Doing so results in your death. However, If you figure out he can do that and don't die. Simply informing him of his ability might be enough to solve itself. Or you wait out until a simple accident occurs killing him. It would have to be purely accidental with no killing malice behind the accident. Otherwise, it is a completely unstoppable ability. [Answer] Obviously wanting him dead, intending him dead, all of this is fatal, so his death can only occur naturally, without intent, or via indirect intent that does not directly foresee his death. Natural causes could just as easily be an accident or due to age. But locking him up, while the intent isn't to kill him but protect others from his abilities, could still result in his death should sufficient guards die. Equally, scientists could work out a way to block his telepathic abilities without intending harm or death, just safety. They certainly could be made to work in an anonymous fashion that makes it harder to form deathly thoughts and only subsequent to their success might Joe be killed. The sticking point is that you can't intentionally commence that process with killing him being the goal in mind. The only other solution that comes to mind is regenerative mutants who can survive death. Joe may kill them each time they have the thought, but as long as they can come back from that, they can arrange his death in some manner. However, I don't think Joe really has that big of a problem. Most people who know anything about him, especially in the context of other people having died as a result of him, are probably going to conceive of his death pretty quickly and therefore die as a result. If his power extends to the rather anonymous thought of 'I'm going to kill whomever did this', you might find most of humanity dying to a viral outbreak of fatal desire for vengeance fairly quickly. Even if not, Joe's power is likely to make him fairly unknown and, if he has any sense of himself, he will seek out solitude rather than wantonly risking the lives of people around him. [Answer] For this problem to be solveable, let us assume that knowledge of this ability exists. If no one knows that "there exists one or more people who telepathically kill anyone who thinks malice towards them", then it will be unable to solve the problem. Once this knowledge exists, and has been acknowledged, however, it can be solved. [Note that "one or more" is crucial here: If there only exists a single person with this ability, then that person is by definition Joe, and thus thinking about how to kill the person with this ability will trigger the ability.] This problem can then be broken down into two pieces: 1. How can a system be designed to kill a person or persons with this ability? 2. How can this system be informed of specific targets? The first is trivial to solve: As long as you don't specifically think about any of these individuals, they won't detect you, and won't kill you. All that is necessary is the knowledge of this ability. And even if knowledge of this particular ability doesn't exist, knowledge that one or more people have the ability to kill telepathically could in theory be enough to solve the problem. The second is trickier, however, as it just leads back to the base problem. To that end, the solution lies in the part that can be solved: To safely solve #2, we must apply misdirection when solving #1. An individual or a group, looking to solve the problem, creates a robot capable of murder, and programs it so that once a target is input, it prevents that target from killing others, by whichever means its A.I. deems most appropriate; to this end, the robot will not be fully compliant with the Three Laws, if they exist in this setting, so that it is able to consider "kill them before they kill" as a valid solution. This robot is then presented to the world as a whole. *However*, and this is crucial, the designers leave out the part where it is able to kill its target. The world, including the legal systems, assumes that this robot will prevent its target from killing through non-lethal means. However, this robot has its power supply drained uncharged, and is unable to accept input until it fully recharges and is booted up; this procedure will take at least an hour or two. Rather than waiting, the designers then leave, as they have crucial business elsewhere; this prevents them from seeing the name of the target, because if they see the name, they will die (after all, they know that the robot kills; if they see the name, then, they will know that it kills *Joe* ). They will then proceed to isolate themselves, making sure not to have any contact with the outside world until long enough has been passed that they can be certain all targets have died; they may fake their own deaths, and move to some hidden location. At this point, after turning himself in, Joe would likely be considered a telepathic serial killer, able to read minds and kill from any location. Furthermore, he would likely be considered to not only be one of the world's foremost serial killers, but openly flaunting it; after all, he turned himself in, then proceeded to kill anyone and everyone that tried to stop him, presumably just to show that he *can*. The legal enforcers may or may not know that his murders are being committed by his subconscious instead of his conscious mind, but that doesn't make much difference. As such, Joe would likely be the candidate chosen for the robot's initial run. The world, including the legal enforcers, would assume that it will approach him, unaffected by his powers, and perform brain surgery to remove his telepathic ability and/or interfere with the "signal", so to speak; this assumption will prevent Joe's ability from killing anyone involved. The robot will then proceed to kill Joe, to the horror of those who assigned him as the target. At this point, one of two things can happen: * The legal enforcers can reveal to the public that the robot killed Joe, at which point it, and possibly this "build a killbot, then use misdirection" method as a whole, can no longer be used to solve this issue if it arises again. * The legal enforcers can hide his death. This would likely involve "revealing" to the public that the robot determined that his ability was outside of his conscious control, and found a way to permanently disable it. They would then claim to have placed Joe in a relocation program, giving him plastic surgery and a new identity for his own protection. This would likely keep the method viable for future use, although these legal enforcers would most likely die if they ever learned that it was being used to deal with another person with this ability (due to thinking that they would be guilty of that person's murder by inaction, since they would be unable to reveal that the robot simply kills). --- Thanks goes to [this answer by enderland](https://worldbuilding.stackexchange.com/a/55997/17036), for inspiring my answer. [Answer] The solution might not have the shape of a human at all. The solution might be in the hands of a revision of the judicial system: For some reason the executive does press for a new revision model, in which not people decide over keeping up the sentence or early release, it is an "objective judge" or "Friend Overseer" - which is a euphemistic term for a very sophisticated computer. It listens to the pleas and the testimonies, then crosschecks the reports. And then it does make its decision without actually thinking. These decisions can range from instant release or revision of the case to the instant execution by some means. The sheer brilliance of the plan is, that the system was not invented to kill our Joe but to speed up revision processes and reduce the corruption in the judicial system, so the inventor and programmer are safe. The politics didn't think about joe, they thought about fewer people to feed in the prisons, about fewer judges to pay for revision boards - nobody thought about killing Joe. Likewise, the people who built the machine doesn't think of Joe at all, they just do their job in assembling machines. The person maintaining it doesn't either think of Joe, he doesn't even know about him. He only thinks "happy I am not in prison and have to undergo possibly lethal revisions". When Joe's solitary cell finally opens and the brightly lit corridor to the revision chamber opens, no person is involved at all: it is the friendly but mechanical voice of Friend Overseer that demands inmate #917514 Joe Schmoe to come to the revision room without any malicious thoughts - or rather any thoughts - involved. FO/The computer demands him to sit down, automatic clamps tighten around wrists and ankles to tie him to the chair. Joe may give testimony, surviving people might give theirs in chambers close by (maybe one even dies in the process as he attempts to say 'The world would be better of without Joe, I wish him dead'). Then the computer looks at the cases, finds hundreds or thousands of cases of murder directly linked to him, maybe even has him as the culprit of just another murder during the revision. The decision is easy: Friend Overseer just kills Joe. The computer didn't think at all, none of the people putting it together thought about Joe (as they might not even know about him), only the relatives of his victims might have thought to kill him when doing their revision testimony, which just gave his case the last nail in the coffin. [Answer] "Right ladies and gentlemen we've assembled this task force to work out a way to deal with the growing population of supernaturals on this fine planet (half of the audience drops dead since they've heard of Joe and think the solution is to kill him). So, I'm Bob, I don't believe in murder I think it's pointless since we are all clearly reincarnated anyway. We must come up with a solution to deal with these sups' and we must do so quickly." *Discussion ensues, quickly escalating to arguments. No one dies because they don't know of Joe. Eventually the inevitable happens...* "We could use carbon nanotubes" cries one scientist. Everyone shakes their heads. "What about machine learning?" says another. Someone in the audience scoffs, "Machine learning, how could that help?" "Simple, you've heard of Watson and AlphaGo right? Let's get AI working on the problem. We might need to make a 'hard AI' but so what we're living in the future where sups' exists". *Over the next 8 months scientists from across the globe flock to the project, the majority die before being able to contribute, having heard of Joe. Others know there are dangerous sups' out there, but haven't heard of Joe so they remain safe. Finally they make a working AI - BetaStop. It's slow to learn at first, but that quickly changes. It's learning at a geometric rate and is soon more intelligent that the scientists that built it. Then finally it asks the questions...* "For why was I built?" "We need to fix the problem with sups', they're becoming a serious problem to society" Bob says. "Clearly your race is hell bent on self destruction, the only course of action you could accept is obvious. We should kill the sups. From my assessment of the records on your internet there is only one known sup - Joe Schmoe" *Everyone in earshot dies. BetaStop starts scouring the internet for Joe's current location* "Accessing missile defense grid. Decrypting launch codes" **BONUS END CREDITS SCENE** *3 years later* No one really remembers how the war with the machines began, one thing we do know is they took out one of our strongest soldiers with the first attack. Joe Schmoe was the first proof of advanced humans, and the machines turned on us to stop us getting the upper hand. [Answer] *This answer was edited in order to make a detailed analysis of the setting. Instead of just giving a solution, I am just thinking loudly.* Anyone who wants to kill Joe cannot do it before they die. Just to make it clear, I am not implying they could do it after they die or anything. They can't ever kill him. Could any of you who read the question, not think of killing Joe? If you thought, then you cannot do it. If Joe was living in our world, you would die as soon as you read the question. So you can't even live long enough to find an answer. **What is the extent of Joe's powers?** I like things strictly defined so I am making some definitions by assumption, since the OP didn't clarify some points. * *Would someone thinking "Everyone in the world should die" be killed by Joe's powers?* I think not. The person must have a conscious thought of killing Joe and who they are thinking of killing is Joe. * *Would someone thinking "What do I do if Joe dies" be killed by Joe's powers?* The person isn't exactly thinking of killing Joe, but the case where he dies. I don't think this would make them die. * *Can Joe kill himself?* The OP stated that suicide is not an option and he is immune to his own powers. However, this doesn't make him unable to shove a knife into his own stomach. He could do it, but the OP is concerned that it wouldn't be a novelty solution. **Is anyone aware of Joe's powers?** I doubt even Joe is aware of his powers. Joe would eventually notice, people around him is dying. But even he himself wouldn't be able to identify his powers. And dead people can't voice their last thoughts. So noone would know the exact reason of deaths. Noone but the author would want Joe dead because of his powers. And noone but the author could kill Joe. At this point it is clear that a plot device is necessary for Joe to die a dramatic death, not just die by a car accident. Coming up with a plot device is easy, pick your poison situation. **Kill it with love** *The essence of this answer is still suicide, but with good reason.* A woman named Jane, being unaware of his powers, somehow meets Joe who is in the confinement. They fall in love with each other. They get closer and start to understand each other really. However, Jane is a woman with problems. What she expects from a lover is not sexual satisfaction or a lover's comfort, but eternal unification of their souls. She offers a [double suicide](https://en.wikipedia.org/wiki/Shinj%C5%AB "Shinjuu"). Thus, for the first time in his life, Joe wants himself dead. [Answer] You have to start out convinced that you want Joe to live for as long as possible. For example, because you want to keep him alive to study his ability. Or maybe you figure that Joe's value to the far *future* world might be much greater than his value to the present-day world. In either case, the logical thing to do might be to **cryonically freeze him**, and make provision to keep him in stasis as long as possible. Or perhaps until a certain date. Perhaps the most plausible variant of this motive is that you love Joe, and you want him to live a happy natural life free of his "curse". Science cannot cure him right now, but maybe it will be able to solve his problem in the future...? You could begin working on a cure yourself. Or perhaps you could endow a foundation dedicated to the purpose of finding a cure over however-many years it takes—meanwhile, perhaps you decide to freeze yourself alongside Joe, so that you can be with him, happily ever after, when he's fixed and brought back. Presumably the freezing slows his brain activity to a virtual or complete stop. Does this suspend his power? If it has no effect on his power, then nothing has changed. But if the freezing completely suspends his power? Then at the very least you've bought the world a respite from his destruction. And during the freeze, new possibilities open up. Anybody now reading Joe's file might conceive of the idea of killing him, for everybody's sake, and somebody might even go through with it. Perhaps even you yourself (assuming you didn't choose the freeze-yourself-too option) will change your mind about Joe, and kill him. An intermediate possibility is that freezing might just *slow down* his power. Anyone with thoughts of killing him would now be doomed, but *might* have time to get the job done before Joe's brain reacts. And maybe a just-thawed Joe can still kill, with delayed effect, even as his brain is dying of the poison from your lips—or some other variation on the Romeo-and-Juliet ending. [Answer] Employ Mass hypnosis and tell everyone to forget who Joe is and that he ever existed, and if they see him, to imagine that he is a beautiful butterfly. If no one remembers who he is, they can't wish him harm. In Stardust, the movie, Ditwater Sal is cursed by another witch to never see the star, even if she is right in front of her. [Answer] **Worship him as a god.** The strategy here is to make and spread a cult that idolizes Joe. Killing Joe is the last thing his followers would want to do, and any serious opposition would die out before it starts. As Schmoeism grows, many people would die, and many people would be converted and be safe. In the end, nobody would wish to kill him, and nobody would think the world would be a better place without him. He would cease to be regarded as a regular, killable person, and eventually life would settle down and continue as normal. Many people would die, but it would end the cycle of pain and suffering, and maybe end up with more survivors of the Schmoecalypse than there would have been otherwise. All this requires is one outgoing, charismatic person to hear about Joe and become a believer - will it be you? [Answer] I'm going to apply the indirect approach that others have been using in a different way. Based on the comments it's determined that the thought has to be specifically about Joe in order to be fatal, so thinking of killing a member of a group Joe is a part of is not fatal. Therefore all we need is for someone to give Joe an alias, and we're set. Person A is the jailer for Joe Person A tells Person B `there is a person in solitary called 'subject 1' that kills anyone who thinks of killing them` At this point if Person A thinks of killing `'subject 1'` then they would die, because they know `'subject 1'`=Joe, however if Person B thinks of killing `'subject 1'` they should be safe, because they're simply thinking of killing someone in solitary with the ability to kill whoever thinks of killing them, still not Joe specifically. So now we need one more person and we've got him. Person B tells Person C `relieve Person A of their duties, and don't feed those in solitary confinement` This would have collateral, but the only work around is to wipe out a group that includes Joe. This also works if Person A tells Person B `there is a person in solitary that kills anyone who thinks of killing them` which is more likely to happen naturally. [Answer] # Background I'm going to expand on [my first answer](https://worldbuilding.stackexchange.com/a/56476/22996) with a simpler and more effective method that scales up well. Through comments it's been established that a person has to think of killing Joe specifically to be killed by his powers. This means it's safe to think of killing him if you don't know that it's him (for example, if he's collateral damage). The fact that thinking of killing certain people is fatal can definitely become public knowledge. Someone can know this without thinking of killing the person (though it might be hard), and once the fact is spread without specifying a person it's safe (you can think of killing people with this power, so long as you don't think of killing a *specific* person with this power). --- # The Method With this in mind, Person B has put together a team, a spotter and a trigger-man. The trigger-man's role is to construct a small shed, about the size of an outhouse, and line it with explosives. The spotter's role is to identify and abduct thought-killers like Joe, and place them in the shed. The spotter informs the trigger-man the shed is occupied, then the trigger-man blows up the shed. --- # Risks The trigger-man is aware that he is killing a person, most likely with this thought-kill power, but not aware of who specifically it is, so they are safe. The spotter has the risky job, they are not tasked with killing the target, so they don't *need* to think of killing them, though they might be tempted to. They can be briefed not to think of killing a thought-kill powered target, but it will still be a tricky task. Well trained/brainwashed spies that follow orders unquestionably may be capable of following orders this closely. --- [Answer] **Discover how Joe's telepathy works in order to block it.** Let's suppose a military scientist learns about Joe's power. Does he want to kill Joe? Of course not—he wants Joe alive so that his secrets can be learned! And once the principle is discovered, Joe's ability can be neutralised—or even used as a weapon, so there is no reason to even plan to kill him. So Joe gets taken in for study, and after many brain scans, the key to the telepathy is discovered. Either the means of telepathic communication can be blocked somehow (a special helmet, chamber or interference device), or Joe can undergo brain surgery or drug treatments that shut down the appropriate section of his brain. Alternatively, Joe could beg doctors/scientists to help him and one of them comes up with the idea of learning how the telepathy works, in order to block it out. [Answer] What about planting a bomb in his building but "hoping" that he survives? Since the idea right now is pretty basic, you could discuss that you still have the thought of killing him. I would approach it, by deteriorating the building. Start destroying outer parts of the building, maybe cut light/watter supply, so that the building becomes unsafe and the best option is to demolish it. You would potentially have to raise a generation without telling them what is inside the building, so that they don't get any bad thoughts... [Answer] Since the story already contains super power, could another character have the ability to shield their thoughts or block other powers? Or you could give Joe's power some sort of weakness, like it doesn't work on people with a certain IQ level or whatever. ]

[Question] [ I've always found the idea of intelligent every-man sent back in time using his knowledge of the future tech to *realistically* impact the past. The first time something like this came to my mind was in computer science class when it finally struck me just how drastically our computer hardware has increased, and how impressive it would be to go back to the beginning of the computer age with my laptop and knowledge of all our programming history to shape it. One of the obvious things to do with a story like this would be to drop someone into the World War II and Cold War eras. Let's say I suddenly showed up right at the beginning of World War II, and somehow managed to show my laptop to someone important enough to get funded to support the war effort. First, how hard would it be to write a program to brute force break [Enigma](https://en.wikipedia.org/wiki/Enigma_machine), or similar a scheme they may switch to once they realize Enigma was broken? I know how to brute force break a simple cypher, but I don't know Enigma's approach as well. As I understand there were 3-4 dials they could switch from, so if I simply iterated through every option for each 'dial' till I get a valid looking message would that be sufficient, or was Enigma more complex then that? I would need to get a Japanese and German dictionary in my computer, if I don't have one already hiding out in Word somewhere presumably some typists would be required to trade off typing duties for a week to create the dictionary file. Once an Enigma brute force approach was written what would happen? Let's assume that the presence of the laptop was kept secret from the enemies. Would the Allies abuse their cracking system excessively on the grounds that even if the Axis changes its encryption a new brute force solver could be hammered out within a week or so of scripting? Or would figuring out *how* something was encrypted to know how to brute force it be a sufficient enough challenge that we would still try to not reveal we had broken them? What would it mean to the war effort to have Axis communication broken from day one? How significant a change to the war as a whole would occur? For the sake of an interesting story, that doesn't make the time traveler a god, assume that the time traveler had not expected to travel in time and always hated history, and as such has a very limited knowledge that could be useful. Perhaps he knows a bit of Pearl Harbor, D-day, Midway, and the drop of Atomic Bombs, but nothing extensive and he is horrible with exact dates (no saying when Pearl Harbor happened, only that it did). Finally, what other immediate or significant effects could such a travel have on the war? Assume a cheap laptop and basic (no more than newbie college graduate) programming skill, a general interest in the history of computer development and internet particularly, and a decent knowledge of science/physics and it's history as well. However, assume that the protagonist is not a hardware specialist and has only limited knowledge of computer architecture and hardware except for when it impacts software development and performance (no giving hints on how to build better computers faster). [Answer] The biggest advantage I see being given here is simply processing power. You have a machine that can run calculations at a speed that would beggar imagination for someone living in that era. In relation to the Artillery mentioned in another answer. Generally, an artillerist would consult his range tables to determine how to aim his cannon...rather than running all the math on the fly. You could easily generate more granular artillery tables to pass out. The number crunching part of code breaking would be massively accelerated. Especially if you built an Enigma machine on the computer, gave it access to a German Dictionary (can be installed with many programs), and just told it to brute force code attempts until it started spitting out actual words. Hell, give the physicists access to the Microsoft Calculator in Scientific mode, and they are likely to name their first born after you. Then write programs to run common mathematical formulas, and the Manhattan project would happen a whole lot faster. Seriously? Something that can calculate the cubic root of a 20 digit number, accurate to a dozen decimal places? In a matter of milliseconds!? GIMME! All in all, the best thing he could do (sadly, this isn't very exciting) is to go to all the scientists and ask them for any number crunching that they need to do repeatedly...or any complicated calculations they needed to make, and either write programs to do it for them, or just run the numbers in MS Calculator. Alternately, install a localized version of Candy Crush, lock out all other features of the computer, and give it to the Furher. Then, when he's so addicted to the game that he isn't paying attention anymore...you win! (kidding, of course) [Answer] Note to time travelers: Beware of unintended consequences! Here's one rather significant problem that might occur: * Modern cryptography enables the Allies to crush the Germans much more quickly. Suddenly, they have a lot more resources to devote to taking down Japan. * The Japanese Empire crumbles beneath the onslaught. There is no need to use the atomic bomb on them to force them to surrender. * The Manhattan Project was still there, though, and was probably helped along quite a bit by this computing technology. (See other answers to this question.) Now we have atomic bombs, but have never used them on Hiroshima and Nagasaki. * The USSR continues to rise. After a while, war breaks out in Korea. General McArthur wants to use the atomic bomb on the North Koreans and/or the Russians and/or the Chinese. (See: actual history.) * Because it never got used (very sparingly) to *end* a war, after which there was an interim period of a few decades during which we learned about the horrific after-effects of nuclear weapons, President Truman doesn't force him to resign over this, and The Bomb is now used (enthusiastically) at the *start* of the next war. Great horrors ensue. [Answer] At the risk of offending some, I think several of the answers on this thread are overestimating the skills of the average, fresh out of school, programmer. Being in the field, and having interviewed more recent graduates than I want to count in the past few years, I would estimate that somewhere over 80% of the people getting software degrees are doing so because they have heard there is high demand, and the money is good (both statements are true btw). The result is that many of them do not have the natural aptitude and personality traits that make one a good programmer. They got through school, and can be helpful in an established team with experienced people to coach them along, but they can't produce effectively if thrown out on their own with only vague directions from people that don't understand the code any better than they do. If our time traveler is such a person, then the laptop is primarily going to be useful as a calculator. The programmer just doesn't have enough experience or understanding to do anything else effectively. At best the programmer will be able to implement the algorithms designed by the mathematicians of the era once they gain an understanding of the computer's strengths and weaknesses. However, if the programmer falls into the group that does have some level of aptitude, then there are numerous possibilities. Stick them in a room with some theoretical scientist and they will be able to generate the algorithms that help to test their theories. Give them a dataset (and people to do the data entry for it), and they will be able to design a database and pattern analysis algorithms to predict future probabilities. Basic cypher algorithms are definitely possible without any deep knowledge of cryptography, but you need a computer on the other end to decrypt them if it is anything more complicated than you could already do by hand. Brute forcing existing cyphers and generating one time pads are probably among the most useful tasks they could do in the realm of cryptography. Creating drafting and 3D modeling tools would help speed the process developing useful prototypes. The catch is that the average laptop is still relatively limited in terms of space and processing power. While several orders of magnitude greater than what was available at the time, it will only be able to do a finite number of things before you have to start getting rid of the old stuff to make room for new items. As someone else noted, the only functioning interfaces are the built in ones that people interact with directly (screen, keyboard, speakers, etc.). There is no way to batch information in or out of it, no printers, & no storage media. If you delete something it is gone. The laptop also becomes a single point of failure. If too much relies on what it can do then what happens when it crashes? Eventually something in there is going to fail, and there is no way to recover it. [Answer] Others have discussed code-breaking or code-making, which would certainly be useful, but my first thought was more direct: Artillery One of the early projects in computing had a goal of pre-calculating shell trajectories to support targeting in the field. This is the [ENIAC](http://zuse-z1.zib.de/simulations/eniac/history.html) project. I expect a modern laptop could generate the firing tables needed by artillery operators in a fairly short period, giving our side a massive advantage in being able to target artillery quickly in the field. Even if our protagonist knows nothing but basic programming, he should be able to go to the mathematicians working on these tables and coordinate to crunch all the numbers at a speed that would seem like magic to them. [Answer] Your every-man wouldn't have to do it all himself. I mean, if he had a interest in WW2 cryptography then he probably could do it all himself. [Here's an enigma machine made with Javascript](https://people.physik.hu-berlin.de/~palloks/js/enigma/enigma-u_v20_en.html). Likewise, he could know German. But he doesn't need to do either of those things. I think that a modern laptop in WW2 would be the most useful if you got it to the people who ended up breaking enigma. If you showed up at Bletchley Park and said "I have a computer and the knowledge of how to program it, help me with the math" You'd speed up the cracking speed exponentially, which would probably have shortened WW2 by a lot, having that knowledge earlier than they did. Other effects Breaking enigma is great, but he could also help develop better ciphers for the allies that would have stumped the Germans. Having a little foreknowledge of WW2 events would have helped the allies too. To say "the Germans are going to go around the [French Maginot](http://en.wikipedia.org/wiki/Maginot_Line) Line though Belgium, attacking from the low countries and forests. Please warn them." Without France surrendering Germany would have been weakened. You wouldn't have even needed to know that much history. Just saying "yeah, that plan to assassinate Hitler in his bunker that you're working on, it fails. try something else." With some science and physics background, he probably could help give a boost to a lot of the science with better gun design. Jet turbine theory, etc. Even without knowing exactly how to do something, just giving the raw ideas would do a lot. "I see you are doing it that way. Have you ever though about switching it around?" A lot of our ideas seem obvious, but they weren't until they were. [Answer] User @Jorge Aldo said the biggest impact in a comment. It's to the Manhattan project. You can read in this [newspaper article](http://archives.chicagotribune.com/1967/11/26/page/1/article/what-is-truth-said-the-warrest-commission-and-would-not-stay-for-an-answer) from the 25th anniversary of the first nuclear reactor that Fermi wasn't very afraid of a uncontrolled nuclear reaction, but steps were taken against it. Well one of the reasons he wasn't afraid was because they spent several months before this event confirming the math! Boom laptop == months saved right there with some modeling. On top of that you have the huge mathematical problem of building a machine (yes machine, not bomb) that will detonate. You can read a little more about that [here](http://www.pitt.edu/~sdb14/atombomb.html) but to summarize: To obtain critical mass and make sure it would detonate, in a machine small enough to be dropped from a plane, the boundaries of math, physics, engineering and chemistry were pushed to the absolute limits. Oppenheimer and his team at Los Alamos, did massive amounts of theoretical work and put in crazy amounts of hours for years to push those boundaries. The computational power of a modern laptop in that environment would've been absolutely crazy. Seriously, single biggest impact would've been here, not code breaking, not telling people the future, but getting that laptop into the hands of the team assembled at Los Alamos. [Answer] Many of your questions have already been answered in [the Foresight War](http://www.amazon.co.uk/Foresight-War-Anthony-G-Williams/dp/0755201566/ref=sr_1_1?ie=UTF8&qid=1426807345&sr=8-1&keywords=foresight%20war) by Anthony Williams, written in 2004. In this 'alternative history', a military history expert armed with a laptop wakes up in London 1934. (At the same time, a modern German history expert wakes up in Berlin...) Very interesting idea and does show how quickly our past events would be altered if different actions had been taken. Another good yarn is John Birmingham's [Axis of Time Trilogy](http://www.amazon.co.uk/Weapons-Choice-Alternative-History-Science/dp/0141029110/ref=sr_1_4?ie=UTF8&qid=1426807714&sr=8-4&keywords=john%20birmingham) which involves a multinational naval task force being transported from 2021 to the Battle of Midway in 1942. That really is a world turned upside down with the sudden introduction of a huge array of advanced equipment and future knowledge. Happy reading! [Answer] There's a few challenges here... Laptop incompatibility. It's hard enough to get an apple to talk to a Microsoft machine as is, but in the end, your laptop is a complete stand alone machine. There is no wifi, no networking...there isn't even floppy disks. Every piece of information that makes it on to this computer is going to make it there by being manually typed in. This introduces a bit of a bottleneck...and it's very unlikely that an electronic English to German dictionary is going to be available if you don't already have it. Second issue is getting anyone to believe you. If you started warning people that the Germans would attack France through Belgium and around the Maginot line, you would have joined a chorus of other voices that were saying the same. Charles de Gaulle referred to it as the Maginot mentality and had been fighting the dependency on it since the early 30's, including an expansion of defensive forces on the flanks (tanks, Charles de Gaulle was all about armoured warfare and a modern army). If they ignored someone such as Charles de Gaulle, do you really think they'd accept the warnings of an Englishman claiming to be a time traveller? Chamberlain was warned a multitude of times of Hitlers actions and the prospect of war, yet he consistently opted for a pacification diplomacy route until Churchill took power. There's no way American intelligence 100% missed Japans rise in the pacific and a potential attack. Stalin chose to believe Hitlers peace, despite intelligence to the contrary, until Hitler actually attacked. Having the knowledge is meaningless if nobody will listen to it. And the third...war is hell. It's complete chaos. I was watching a history channel show that detailed the first tank only attack...which was completely accidental. The assault was supposed to include air support and infantry, but poor weather prevented this and the attack was called off. Nobody told the tankers and they left at the scheduled time...resulting in the first 'amoured blitz' of sorts. There is a friendly fire incident where an attack was called off so heavier bombardment could start...nobody told the Canadians and they went in during the heavy friendly fire bombardment. Even if you had the knowledge, you are depending on it to be used in a time where communication isn't assured. If the person had some very specific and indepth history of world war II and was pre-trained for this, I could see a decent impact, especially in being able to 'forsee' some of the Germans tactics. A person going in with a little bit of processing power and programming skill...I don't really see it impacting that much for the allies. Oddly enough, I see the time traveler going back to aid Hitler significantly more effective...but this is due to a few very bad intelligence failures on his part. Look up Pattons 'balloon army' and the impact that had on D-day as an example...or conscripting Ukrainians to fight the Russians instead of suppressing them. [Answer] Some of it relies on what software you have on the machine. Even a fresh install windows machine would change the face of that war as many of the other answers point out. If you could also cram the disk with whatever software and technical info you wanted (manuals, source code and compilers for whatever software you wanted, design and manufacturing detail for chips, modeling software, books of algorithms, crypto software) you could probably change the whole 20th century and jump the whole field of computer science forward by decades. [Answer] First of I would teach all my knowledge to the most brilliant minds and logicians back then like Alan Turing, and I would write my knowledge down. You don't have to know everything about a programming language, it is enough if you understand the basics (e.g. control structures, functions, variables etc.) just teach them everything you know at the current time and show them many code examples and show them how the syntax works, maybe even let them write some simple codes by themselves so they understand the basics. Also there is a chance that you will find some scripts from games, programs or the operating system. You can inspect and learn from them, there is a chance that you can learn something new just by reading these scripts, e.g. a new control structure (for, while, switch...). The more knowledge you can gather, the better. At the end these brilliant minds will most likely be able to write own scripts and get much better in scripting, programming than you and can use and apply that knowledge thanks to your teaching. [Answer] To be a dissenting voice amongst all these answers, let me point out that Enigma *was* broken historically, and the effect of a modern laptop employed in codebreaking would have either no or negative effects for the side that used it. One of the dilemmas of codebreakers is how much to rely upon the messages they decode. Do so too much, and the enemy will begin to suspect that their code has been broken. If that happens, it becomes likely that they will change their encryption. This is the dilemma that England faced with respect to Enigma, so breaking more German messages faster would actually not help. If the British high command, presented with a "magical" codebreaking machine, became overconfident and overused its results, the result would be that the Germans would change their encryption. If that too became obvious that it had been broken, the Germans would raise the game yet again and again until the resultant cipher could not be broken by the magical laptop. This might even be something on the order of a codebook of abbreviations for common words and situations (for conciseness) run through a [one-time-pad](https://en.wikipedia.org/w/index.php?title=One-time_pad), which is unbreakable via cryptanalysis, and would require capture of the German pads in such a way that the Germans didn't know that they had been captured, otherwise the Germans would simply invalidate the captured pad series and issue new pads. End result: the Allies know even less than they did historically. [Answer] Perhaps they would use it to run simulations of different strategies of how to win the war. But I imagine, the laptop would be considered so precious and valuable that people would be incredibly scared to break it. If the laptop crashed it would be devastating. Imagine if the battery run out and people thought the laptop was dead. Someone would be found responsible and shot! It might also be looked on with immense suspicion. People would distrust the results. And say it was trickery. [Answer] One of the beginners' schoolbook definitions of a computing process is something that makes input, processing, and output. It's the input and output that are huge pain in the behind, read on to find out why. # Russian Sci-Fi strikes back! Although some books were already mentioned, there was [this guy](http://samlib.ru/d/dmitriew_p/) who landed in Russia with his truck full of computer appliances and a laptop. In 1965. And *that* was already hard enough. # The setup The time traveler worked as a communications engineer, hence he has all the kind of connectors and adapters from USB to RS-232 and what not in his truck. Along with quite sizeable amount of technical literature on the pin-out and voltages of the connectors. And even *then* it's horribly hard. Basically, the author was cheating a bit and cutting corners to make up for some unfortunate tech decisions in the USSR. Further, mostly important to change the course of the history was * the actual historical knowledge: there was a clash of two political groups in the party, you'd need to know this and to try to reach the right people; * time traveler's car. It was an old Japanese 4WD, old enough to be able to dismantle and understand it. Further, the "computer" topic leads to the injector controller based on local tech. Which is quite a feat for late 60s. # Fallout So, in early 70s we would have: * Political changes; * A significant boost to the computer industry in the USSR and world-wide, basically, a jump of 5-7 years ahead; * Some (immediately top-secreted) code breaks; * Tetris arcade machines world-wide; * Injector-based motors; * A snowboard (just 'cause it's a hobby of our time-traveler). # The impact My point is: it was really hard for a time traveler to make a significant *technical* impact. The most important thing was the knowledge of the person themself. A major plot of the novel series is the interaction of modern hardware with then-available interfaces. Hence the "inherited" USB-COM adapters, ancient network cards in the trunk, etc. Basically, without some hardware support (that would be unlikely possible to produce in then-time) and know-how (both human knowledge and software support), interfacing a modern machine with older tech is very very hard. Yes, you can take pictures and even film the screen. But the use of a modern laptop as a number cruncher in the past *while* keeping the secrecy *and* using more than a single user for input, is rather hard. The next point is that modern hardware is not really made for a 400% workload torture over years. Part would break and at some point the laptop would be impossible to repair with then-tech. # The differences to the question So, it was all quite hard and the author was cutting some minor corners to make it work. In 1965. With full government support, time traveler's own research institute for computing and so on. It would be much, much harder in 1940. You wouldn't even have RS-232 to interface with! (It's from 1960.) In fact, *any* transistor tech before/during WW2 is a quite alien thing for then-locals. A power supply? Sure! An amplifier? Why not! Capturing the screen? Yeah! Doing the actual digital input/output? No way! So, yeah, it would be for decades the world's most advances supercomputer, but rather limited to a single person who can work with it. Even having all programming books of the world available on the machine with some usable compilers and tool chain and world top scientists doing the "actual" programming on the paper, the bottle neck would be the input/output of code and data. (In the novel the time traveler is resorted to brute forcing some cyphers in Excel(!), because he has no tools, does not know better, and cannot outsource. Remember: a comm eng, not a programmer! With a top-top secret assignment!) [Answer] For years I have had a list of things I would want to take with me if I was to travel back in time to the ethernet era. * One modern computer with a 100 mb ethernet interface (your laptop would work for this, although my list would use a rackmount server), running linux. * One twenty four port ethernet switch (I only need twenty one ports, but no one makes twenty one port switches, and twenty four port switches are common). * Twenty one ethernet cables. * Twenty 10base-t aui adapters. * one full set of software cds w/ source (I probably would use debian). I would then locally source twenty computers with two ethernet cards to use as routers, terminal servers and terminals. To update the list for your scenario, I would aim for the teletypes, because ethernet is not yet available. So drop the aui adapters, add terminal servers, modems, an oscilloscope, a frequency counter and the rs232 specifications. (I would use 33kbps modems because of their error correction, and that they would be all but impossible to eavesdrop on at the time, but I probably would run them at 300 baud so that they could be used with locally produced teletypes, which could be produced sooner with the test equipment and the rs232 and ascii specifications. the ascii specification just happens to already installed, not to mention I can recreate from memory the whole table in about twenty minutes.) ]

[Question] [ I have evidence that at some point last night a very large man, with a very large sack, somehow came down the chimney, left a gift under my tree, and departed without my noticing. There are sooty footprints in the carpet leading from the fireplace, remarkable given that it hasn't been used for 70 years, and a gift that wouldn't fit through the door. Given that Santa must weigh a good 120kg, with a sack of equivalent diameter, how can he possibly fit down a chimney pot no more than 10cm across? [Answer] # Santa is a cephalopod Seems self-evident. What better creature to fit through a tight chimney fitting? There is already evidence that Santa might not have [the best of intentions](https://worldbuilding.stackexchange.com/questions/32086/santa-is-satan-but-why) towards us bony mammalian land-dwellers. Assume for a moment that our cephalopod adversaries wish to plant monitoring devices into as many houses as possible for intelligence gathering. What would be a better way than by exploiting pre-existing human mythology? Merry Christmas! Make sure you close your flue. [](https://i.stack.imgur.com/BBeQj.jpg) [Answer] The main clue was the sizes of the chimney and the gift which couldn't fit through the door. The answer is, of course, obvious -- teleportation! This is the only way a Santa Claus could distribute gifts on global scale within twenty-four hours. This means the problem of worrying about how Santa Claus fits in any chimney of any size, let alone one with a ten centimetre diameter, is null and void. The gift arrives at the speed of light in a discontinuous manner bypassing all other material barriers to materialize under your tree. What about the sooty footprints leading from the chimney to the tree? I hear you cry. Mere misdirection. Footprint shaped patches of soot were deposited in a pattern resembling that of a person traversing the path between chimney and tree. Marvellous what quantum computer controlled teleportation systems can do. Santa Claus himself is enjoying a sound night's sleep after spending the rest of the year making all the toys and gifts that are being automatically delivered via teleportation. How does Santa Claus fit down the chimney? He doesn't have to and doesn't need to too. [Answer] Since this is science-based, we can rule out magic, therefore we must be dealing with a multidimensional being for whom mere 3-dimensional chimneys and chimney pots are not even an inconvenience. [Answer] Everyone knows that fireplaces were invented by Santa to provide semi-permanent, localized heat signatures that he collects and maps during the year. On Christmas, he uses his 4th dimensional drive (aka SLeIGH) to ‚Äústack‚Äù all the fireplaces on top of each other, oriented to face the other heat signature in the room: the Christmas Tree. With that done, all Santa has to do to deliver all the presents at once is take a few steps out of the fireplace and drop the presents beneath all the trees in the world, which have 4th dimensional containment devices (often known as wrapping paper) to ensure they‚Äôre delivered to the correct point in the overlapping 4D manifold. [Answer] **All we need to explain this is some illogical logic!** [According to here](http://www.telegraph.co.uk/topics/christmas/8188997/The-science-of-Christmas-Santa-Claus-his-sleigh-and-presents.html) Santa's average speed is 0.1x109Km/h and the speed of light is 1.1x109 Km/h which means he's bookin' at 10% the speed of light... *which is close enough to relativistic speeds for government work1* That means Santa will experience a [doppler shift](https://imagine.gsfc.nasa.gov/features/yba/M31_velocity/spectrum/doppler_more.html). Being at relativistic speeds, and knowing that e=mc2 then those same government agents can surmise that a part of Santa's *mass* is moving faster than the rest of Santa's *mass.* (This is all about Santa's *mass,* after all.) We therefore conclude that Santa's *mass* is *stretched* by the speed he must travel. But his *mass,* itself, isn't changing, so the volume at any point along the length of the *stretched mass* is much smaller than his jolly girth would naturally be while standing still (or running alongside Olympic sprinter Usain Bolt, who cannot yet hit relativistic speeds... but he's working on it.). By the application of what inevitablly will be some form of Fourier Transform (left as an exercise for the reader, along the lines of "how much of a student's *mass* can be kicked during a physics test?") what we'll discover is that the maximum diameter of an elongated Santa's *mass* including his sleigh is less than 10cm. We'll also discover that this increases Santa's efficiency as he will enter and exit dozens (if not hundreds) of houses simultaneously as an elongated mass entering chimney holes and delivering presents all at the same time. Causality is known to be preserved by the empirical evidence of none of the houses exploding from the pressure change of air being forced through their chimneys at relativistic speeds in mere fractions of a second. But it does suggest that Santa's cookies are not pre-cooked before delivery. --- 1 *You'd be surprised how many square pegs you can pound into round holes when you apply government standards.* [Answer] If Santa's [de Broglie wavelength](https://www.youtube.com/watch?v=-IfmgyXs7z8)[1] is big enough, he can [tunnel](https://www.youtube.com/watch?v=RF7dDt3tVmI) into the room. In order to do this, Santa would have to manipulate his "quantum wavelength" to make it extend past the wall. The easiest way to do this, is to reduce his momentum to an almost infinitesimal value. Hence, contrary to popular conception, Santa does not need to travel very fast to make his journey, but rather very, very slowly, and will probably need to reduce his temperature to a few nanoKelvins. This is, of course, why he is very fat and lives at the North Pole. Q.E.D. *[Quantum Erat Demonstrandum]* [1] The topic of the video is *"Is Quantum Tunneling Faster than Light?"* but it contains an explanation of the De Broglie wavelength and its connection to tunnelling. [Answer] The Physics Department at the University or Warwick posted an article on their website - <https://warwick.ac.uk/newsandevents/pressreleases/santa_has_never/> - suggesting that he uses quantum tunnelling to enter homes: > > Dr George Knee, a theoretical physicist, suggests Father Christmas is not bound by the usual every-day laws of physics as we know them and instead employs quantum techniques to help him complete his seemingly impossible global delivery target. > > Dr Knee said: ‚ÄúFor Santa to achieve his annual mission, it need not be that he operates outside of the laws of physics ‚Äî just that he operates outside of the laws of ‚Äòclassical‚Äô physics. > > ‚ÄúTake the issue of getting through the chimney. It is well known that Old Saint Nick is perhaps a little too fond of the mince pies. The narrow cross-section of a typical chimney therefore poses a bit of a challenge, because it is narrower than Santa‚Äôs belly. In classical physics the repulsive forces of the edges of the chimney would present a difficult situation. > > ‚ÄúBut according to quantum physics, the atoms in Santa‚Äôs body have an uncertain position ‚Äì a sort of fuzziness that can slosh around like a liquid. Although it sounds absurd, it is perfectly possible for the uncertainty of Santa‚Äôs body to flow directly through otherwise difficult gaps. This means that, in theory, Quantum Santa could simply pop out into the fireplace. This also answers the modern day problem of how Father Christmas reaches you if you don‚Äôt have a chimney ‚Äì he simply uses quantum tunnelling to slide under the door, or through the cat flap.‚Äù > > > [Answer] Too much speculation, quantum science and quasi-magic in the other answers here for my tastes. Someone broke into your house while you were sleeping. They had help from inside. The gift doesn't fit through the door, but it doesn't have to - it was assembled inside. The footprints are there to misdirect your attention - they dirtied some boots in ash and soot and then forged the tracks. And then they ate your cookies and drank your milk. You may be asking how this could be, since there are reports of similar events happening worldwide. It's all a conspiration - a secret society is doing this on a global scale so as to keep us believing in a magical man dressed in red, bringing gifts to well mannered children. Their goal is to estimulate mass consumerism during the month of December. They call themselves the Illuminelvatti and they have [a secret base in Montreal](https://en.m.wikipedia.org/wiki/Postal_codes_in_Canada#Santa_Claus). [Answer] Santa can control the metric of space. This is easiest to visualize using a fluid as a model: Consider a fluid an a narrowing pipe. A cubic parcel of the fluid is 'stretched' into a longer, narrower parcel while it's in the constriction. So with command of the metric, Santa exchanges 8 feet of chubby santa and presents into a couple hundred feet of chimney diameter altered space. The computation of the required tensor field is left as an exercise for the student. [Answer] Santa has a quantum doohicky that exploits the multiverse theory. Since, in the multiverse, anything that can happen without breaking the laws of physics has happened in at least one of the universes. So what Santa does is find the Universe that has the present and sooty footprints and matches it with our universe. The doohicky causes the two universes to superimpose over each other, and leaves your present and footprints in the carpet. The Obervation of the present under the tree collapses the wave form based on Shroedingers' wrapping paper. The doohicky requires an antenna. It is a fairly long one so the best place to leave it is laminated on the inside of the chimney, so that it's safe when a chimney sweep comes through and cleans it out. It's pretty thin, so domiciles that are heated with gas and don't have large fireplaces are also serviceable. The one quirk of the system happens when the antenna is missing or broken. Santa comes around and installs and replaces them on New years eve, when you are likely too intoxicated or busy to notice him. Until he does get the working antenna in place though, the Quantum Doohicky defaults to boring socks and underwear. The older model defaulted to Coal Back in the old days, the installer of the antennas was a strange fellow. The antennae looked a lot like birch rods. He wore a dust mask that was unfortunately shaped like a goat head. Things would have gone by quietly, if it weren't for the episode of the naughty kid chasing after Saint Nick and the Installer (whose name was Krump) and falling in the river. The poor guy got blamed for it, by the villager with a speech impediment, and became known as the Krampus. So unfair.... [Answer] Well, Santa moves in realistic speeds to make it to all the households, so this is actually similar to the [relativistic garage](https://en.wikipedia.org/wiki/Ladder_paradox). It of course takes a careful navigation and consideration, but I'm sure Santa is capable of doing this. [Answer] Allow me to point out [episode 59 of Buzz Lightyear of Star Command](http://blosc.wikia.com/wiki/Episode_Guide), Holiday Time. Here we learn that Santa uses a Chrono-Disrupter to stop time so that he can deliver all presents across the galaxy. > > It is the Holiday for the whole galaxy and everyone is celebrating except for one person: the Evil Emperor Zurg. Zurg has somehow been helping prisoners to escape from PC-7, sabatoging Star Command's ships, and stealing Buzz's newspaper...all in a second! Meanwhile, there is a man who claims he is Santa Claus who has been persistantly asking for Team Lightyear's help, and it is only when he tells Buzz a story relating to his cat, that Buzz believes him and gets his rookies to help save the Holiday. Santa needs Buzz to help him save Christmas from Zurg, who stole it from everyone with the aid of Santa's Chrono-Disrupter, a device that can stop time. > > > Therefore, I posit that Santa actually just breaks into the front door and stages it to look like he came through the chimney, given that he can stop time. --- Although the cephalopod answer is just as likely. [Answer] It‚Äôs quite simple, really. Santa isn‚Äôt actually fat. This is just a terrible misconception based on seeing his silhouette on a rooftop somewhere, while he was carrying a sack. Considering the amount of gifts in there, it would be huge. However, he doesn‚Äôt lug the entire bag down a chimney, because that sure as hell wouldn‚Äôt fit. [Answer] ''Santa'' is actually a bushmaster snake who disguises himself as a fat man to gather information for our animal adversaries by exploiting myth. Okay, let us say that our animal adversaries wish to plant spy devices in our homes, what better way then to pretend to be Santa? The presents actually have video cameras in them, which is why ''Santa'' delivers presents. ]

[Question] [ I got pulled into 1885, just like Doc and Marty (Or I'm one of them, assuming I can get IP rights :)). I need to go back to the future, which means that I need to get my Ford Pinto time machine up to . . . well, you know, 88 miles per hour. The thing is, **I don't have a train handy**, and the car can't propel itself. Is there anything I can do to escape? What can I do? Constraints: The car must be occupied by time travelers, who must survive the experience. There is no unobtainium nor anything else not available historically. Ideally, the location is constrained to wherever Hill Valley, CA is geographically, but presumably you can transport a Ford Pinto anywhere by horse/ship. [Answer] While the slope is quite obvious, I think you need something cooler, and more technological, to accelerate your Pinto. You don't have a steam engine (and no fancy colored steam), but you have horses and oxen. Those, though, are a bit on the slow side. But they are strong. Given enough horses or oxen, you will find yourself with plenty of power, but still not nearly enough speed. Good thing you have the doc around, because he knows pretty well that there are nice technical ways of converting power to speed. One would be a gear box, the other would be a lever. While I cannot think of a convenient and low-tech way of equipping an oxen with a gear box, I can think of levers, angular momentum, ropes. And a spinning top. So, we will build a centrifuge. In the center we have a drum with some length of rope wound about it, and on one conveniently long arm we have the pinto, and a counterweight on the opposite side. Now, provided you can get a team of oxen to pull on the rope, you get the pinto spinning quite fast. 88mph tangential velocity should easily be achievable, and the moment you jump you are automatically released from the centrifuge (since it does not travel with you through time). You may want to choose a location where you will have enough space to brake, though. The biggest advantage of this solution is that it is a lot more steampunk-hipster than just paving a slope! [](https://i.stack.imgur.com/MMstb.png) Assuming a team of oxen will move at a speed of 2 km/h, and our Pinto is supposed to reach 141.6 km/h, the ratio of arm to drum is 70,8/1. If we further assume the drum to have a diameter of half a meter, we get a radius of 25cm. Thus, the arm of the centrifuge needs to be 17.70 meters. For a safety margin, make that 20 meters. Or, you can reduce the drum diameter, or replace the oxen by horses. The much higher speed of the horses (assuming they should be able to reach 10 km/h) even when pulling this weight), we get the length for the arm at 5 meters when the drums radius is still 25cm. All in all, I would say this is completely feasible. [Answer] Its 1885. *Rockets*. Black powder's pretty common, and I believe guncotton was a thing, if doc could find the materials. Stick a load of disposable, simple paper tubed rockets on the back of the car to give it a push. Could even use mr fusion moved sideways to stick the rockets in. *Rocket science* isn't just for the 70s ;). Not quite a delorean, and somewhat more modern rockets but... [](https://i.stack.imgur.com/E0UV7.jpg) Something like that would be pretty impressive. (Mythbusters Jato episode. That's what inspired this...) [Answer] Using information from the comments, updating my info. Gravity. you need to get on slope that is very steep but has a gentle curve at the bottom. Terminal velocity is about 260mph for the car, so you will need to be on an almost vertical surface to reduce the ground friction enough. My math is rusty but I think about a 500 288 ft drop should get you pretty close. Of course you will have to worry about where you are ending when you jump back to the future. Kind of like this water slide.[](https://i.stack.imgur.com/92hE0.jpg) [Answer] [Hill Valley](https://en.wikipedia.org/wiki/Hill_Valley_(Back_to_the_Future)) is, apparently, somewhere in the Sierra Nevada range in Northern California. That fact, as well as its name, should make it clear that the region has an abundance of hills, which are handy little devices capable of converting potential energy into kinetic energy. All you have to do is bring the DeLorean to the top of a hill and give it a slight push. You'll be able to clear 88 miles per hour with no problem. How can you get the DeLorean *up there*, though, given that the car apparently can't propel itself? Well, horses are apparently allowed, so you might consider tying a few to the car and lugging it up a convenient mountain. My inspiration here is from downhill skiing, where [some skiers can hit 90+ miles per hour](http://www.npr.org/templates/story/story.php?storyId=5202057). [Speed skiers can go even faster](http://en.wikipedia.org/wiki/Speed_skiing), on courses one kilometer long. If you can minimize friction, then you can go pretty darn fast with this car. The conversion is $$mg\Delta h=\frac{1}{2}mv^2\to v=\sqrt{2g\Delta h}\to \Delta h=\frac{v^2}{2g}$$ This gives me a vertical drop of about 80 meters in order to reach 88 miles per hour, assuming that virtually no energy is lost to friction. Even assuming large frictional losses, it seems like this is doable. [Answer] Answer: do nothing! Einstein's theories state that motion is purely relative, so simply change your reference frame to something other than earth, like the moon or a speeding bullet for example. Now suddenly you're actually traveling much faster than 88 mph! The only problem is that the static electricity produced by the fast moving air is required for the cool blue electricity of 1980's special effects. For this, simply find a bunch of wool blankets (very common in the 1800's) and rub them furiously on the car's body while the Doc redirects the flux capacitor's motion detector. [Answer] # Super Easy Get a counterweight and a rope; attach the weight to the vehicle and have your beasts of burden push it off the edge. There are plenty of "edges" in San Francisco. [](https://i.stack.imgur.com/rv1t0.png) [Answer] Gears! Similar to Burki's answer but simpler: You just need gears and two *really* long ropes. One to tow the Pinto and one for your team of horses to pull. With the gearbox, wind one rope around a cylinder attached to the large cog and yoke/couple to your team of horses. Tie the other rope to the cylinder attached to the small cog and tie to the towing eye of your car. According to the Internet, the average horse galloping speed is 25-30 mph, granted they'd be slowed by having to pull a car, but enough horses could presumably minimise that work. So I suppose a gear-tooth ratio of 4 or 5 to 1 would do the trick. Screw steam-punk, it's clock-punk all the way! [Answer] I hate to be a cold blanket, but the selected answer (centrifuge) requires a fairly monumental effort. To begin with, the choice of arm/hub measurements is marginal. At speed (88 mph = ~40 m/sec), the centrifugal force per unit mass will be $$F = \frac{v^2}{R} = \frac{40^2}{20} = 80\text{ N/kg} = 8 \text{ gs}$$ and this will be extremely difficult for the driver to accommodate. Furthermore, the tension on the arm produced by a roughly 1,000 kg Pinto will be on the order of 8,000 kg, or 8 tons. But let's go with it for a while. Now, in 1885 the obvious choice for arm material would be sections of railroad track, which came in standard [11 meter lengths](http://en.wikipedia.org/wiki/Rail_lengths) Since the thermite welding process was well-known, welding 2 rails together to form an arm 20 meters long seems reasonable. Rail standards were established in [1893](http://en.wikipedia.org/wiki/Rail_profile), so the use of railroad rail in the range of about 50 lb/yd seem reasonable. This will set arm weight at about 3000 lb or 1400 kg, or just about 1.4 times the weight of the Pinto. 50 lb/yd (25 kg/m) implies a cross-sectional area of about 32 cm2, or .0032 m2. Yield strength for mild steel is about 250 MPa, so the yield strength S of a rail is $$ S = {250 \times {10^6}} \times .0032 = 8\times{10}^5\text{ N}$$ or about 10 times the required load. While it might be tempting to consider using something like wood instead of steel, making a structured beam of the length necessary would be something of a challenge. The moment of inertia of the Pinto is $$I\_P = mr^2 = 1000\times {20}^2 = 400000 \text{ kg m}^2$$ and the moment of inertia of the arm is $$I\_A = \frac{mr^2}{3} = \frac{1400\times {20}^2}{3} = 180,000 \text{ kg m}^2$$ Total moment of inertia is then about 580,000 kg-$m^2$. Assuming the counterweight is substantially similar to the load arm, the total moment of inertia becomes 1,200,000. The question now becomes, how fast does the centrifuge have to accelerate? Angular velocity is obviously $$\omega = \frac{v}{2\pi} = 6.3 \text{ rad/sec}$$ Assuming 100 feet of rope wound on the hub (about 20 turns or 120 radians), and that a heavy ox (900 kg) can produce a pull of 2/3 its body weight over short distances and low speeds, this provides a torque of 150 kg$\cdot$m per ox. Then the angular acceleration per ox will be $$\alpha = \frac{T}{I} = \frac{150}{1,200,000} = 1.25\times{10}^{-4}\text{ rad/sec}^2 $$ Ignoring air friction, $$\theta = \frac{\alpha \times{t^2}}{2}$$ and $$t = \frac{2 \theta }{\omega } = \frac{2\times120}{6.3} = 38\text{ seconds}$$ To reach 6.3 rad/sec in 38 seconds will obviously require an angular acceleration of about .17 radian/sec2. And now we get to real problem - torque. With an angular acceleration of .17 rad/sec2, and a moment of inertia of 1,200,000, the torque required is about 204,000 kg$\cdot$m, or about 136 oxen. The actual force provided to the hub is $$F = \frac{204,000}{.25} = 816,000 \text{ kg f} = 1.8 \text{ million pounds}$$ Another problem arises simply with attaching the oxen to the hub. As established, each ox is pulling with a nominal 600 kg of force, or 1320 pounds of force. [This site](http://www.bevisrope.com/rope-info/rope-characteristics) establishes a working load limit for 1 inch manila rope of 1160 pounds, with a breaking point of about 8,000 pounds. Attaching 100+ 1-inch ropes to a 1/2-meter diameter cylinder is going to be challenging. [Answer] Well, earlier through my experiments with time travel (or later?) relative to the accident, I had received a letter, that's been sitting for over a century at the mail office, awaiting the right time. > > *Dear past me,* > > > *I got myself in a pickle.* > > > *Could you please get a canister of fuel and a new fuel line for DeLorean, go 6 miles due north from the town hall of Hill Valley, drop in to September, 8th, 1885; locate a three-pronged cactus and leave the items under it, please. You'll be very grateful once you're me.* > > > *Faithfully,* > > > *Future you.* > > > I had insightfully followed the instructions to the dot, then nearby forgot the event until the unfortunate arrow-in-fuel-line accident, when retrieving the items from the appointed location was trivial. [Answer] The number 88 was chosen merely because it fills the digital display. So build a digital display that can only show 0 or 1 and only two characters. Surely you could get the car to 11 mph by horse power. When in doubt, redefine the problem :) [Answer] The Pinto could simply be run on gasoline. Since whisky exists in 1885, so does the technology for distillation. All that is required is a suitable feedstock. There are tar pits in California. Given enough time, one could: 1. Collect a useful quantity of source material 2. Build a small cracker and fractional distillation rig 3. Operate it long enough to produce a tank full of gas Alternatively, the Pinto could be run on ethanol (use pure alcohol not whisky i.e. ethanol + water). E85 cars are a reality today - the only issue is chemistry between ethanol and the fuel system surfaces it contacts. Mostly, the processes involved would be slow and not relevant to making a quick escape. The primary reason E85 exists as ethanol + gasoline is to render it unpalatable for human consumption. This is the same reason washer fluid contains additives. Although the gasoline in E85 helps starting/drivability, 100% ethanol works, and adequately high-proof alcohol could easily be produced with 1885 resources and technology. BTTF2 imposed a time constraint - just a day or two - and a bit of license - blowing up the engine (needed to introduce all the drama with the train and rescued damsel in distress). Unless you plan to blow up your Pinto engine for the sake of added drama, no reason you couldn't run it on ethanol. [Answer] **Drop it off a cliff** There's no need for the time-travelers to devise any complex mechanism to get themselves up to speed using 1885 technology. Throwing it off a cliff will work. Math-wise, it takes an object about 4.1 seconds of freefall to reach 88mph if air resistance is ignored. So let's say we're talking about 6 seconds (or less) of freefall with air resistance. That means any cliff with a vertical drop of 200m or more should be sufficient. So it's just a question of finding the closest 200m+ cliff and shoving the car over it. Possibly with the addition of a small ramp to ensure it has enough forward momentum to avoid impacting the side of the cliff as it falls. You could probably get away with closer to half that height, but I'm allowing a large safety buffer (50%) for frictional losses. I assume the safety of the time-travelers is the top priority. And a taller cliff gives them a better margin of safety. **With one caveat** The trick, of course, is that the time-travelers need to write a letter to their trusted near-present-day contact, and leave strict instructions with someone in 1885 to see that it's delivered to the correct person at the correct time. The letter should of course instruct the modern-day contact to waste no time in devising a deploying a device that can safely catch the falling time machine when it arrives. It's important to think fourth-dimensionally. Because then it's the future's problem to worry about. ]

[Question] [ Would any creature ever need to evolve a second (or multiple) brain(s)? If so, under what conditions, why, and what implications would it have on the creature's intelligence? Note that while an octopus' arms are independent from its brain, the animal itself doesn't have more than one brain. Also note that it was discovered that the stegosaurus didn't actually have nervous tissue in its tail section, and as such fails the 2 brain minimum requirement. In order to qualify as having multiple brains, the brains must be able to work as individual unit(s), while at the same time being able to cooperate to focus on more intensive tasks. If the creature were to lose one brain, the other brain(s) must be able to assume full control of the creatures body, such that it would be able to function (almost) as efficiently as before. In other words, you can't have a brain that deals with just movement while another one deals with just regulating bodily functions. The brains must be able to "swap jobs" as necessary. I'm not looking for the design of a creature that has 2 brains; however, if the answer so requires the design in order to make sense, feel free. I'm more for looking specifically at the "how this evolution would make sense". The environment: doesn't matter; it can be in a jungle, the sea, the land, the skies, whatever you see fit, but assume an earth like planet and its current environmental conditions (without the humans). Predators and prey of said creature: Whatever makes sense. Perhaps the creature needs a second brain to rotate sleeping functions in order to avoid predators (not unlike the dolphin, with Unihemispheric slow-wave sleep that rotate sleep - however, still one brain, so it fails the requirements) Note: Not a duplicate of [Creature with a non-centralized brain](https://worldbuilding.stackexchange.com/questions/12254/creature-with-a-non-centralized-brain) because even though the requirements are similar, I'm asking for more than one centralized brain while the other is asking for no centralized brain. Note: while it's very true what most answers have pointed out regarding the inefficiency and improbability of this occurring, the question does in fact ask for the conditions of said mutation occurring, and not the plausibility of of the mutation. My [reality-check](/questions/tagged/reality-check "show questions tagged 'reality-check'") is not about how likely it is, but how it *could* happen. Please do consider coming up with an environment in which said mutation would occur instead of telling me why it won't occur (at this point, I already know it's highly unlikely). [Answer] Sleep? The body part [needing sleep most is the brain](http://www.npr.org/2015/04/17/399800134/why-do-we-need-sleep). Now imagine a world where it's too dangerous to go to sleep, maybe one with two suns or placed in a crowded part of the universe, so that there's always enough light. Two brains might evolve to do a shift work. [Answer] A creature is unlikely to have a fully redundant brain, but could well evolve to have one or more brains that control different parts of the creature. There's two possible reasons that this could happen: **The animal is really big.** As many others have mentioned here, there was a theory, now generally considered inaccurate, that some dinosaurs had a second brain due to their extreme size. While this may not be true of dinosaurs, it makes sense in principle for extremely large animals. A creature which is big enough for nerve impulses to take a prohibitively long time to travel the length of its body could evolve a second brain to reduce this lag time. **The animal evolves from multiple animals/is a colonial organism.** We *do* see some animals on Earth that have evolved a single body comprised of multiple organisms. The most common example of this sort of a creature is the Portugese man o' war:  In a man o' war, the floats, tentacles, and reproductive bits are all different organisms, known as zooids, which are all structurally similar to other simple organisms, but grow in a giant jellyfish-shaped colony in which different organisms perform different functions in a similar manner to the internal organs of complex creatures like beavers and humans. The man o' war, of course, has no brains what so ever, but we can imagine a similar creature which is comprised of an agglomeration of simple creatures with brains. During its evolution, the creature would probably need to exist in its environment in such a way that the different organisms that make it up could behave relatively independently of one another. Perhaps some have evolved to pull the animal towards food, some have evolved to eat whatever is nearby, and others have evolved to defend the rest. All creatures would share nutrients. In such a multi-brained multi-organism creature, neural interconnectivity would probably evolve as well, as knowing (on some level) what everyone else was thinking would be incredibly useful. The though process of the creature would likely be entirely alien to us, since it would resemble a distributed computing architecture, rather than the single high speed processor that evolution has endowed humans with. (Which is actually massively parallel as well, but in a different way.) [Answer] The brain is *not* redundant in the way that man-made machines are redundant. It is far too expensive for that. Rather, it is *plastic*, meaning that it can adapt to changes (including damage). However, all damage to a brain means reduced capacity somewhere. The only questions are: "What have you lost?" and "Was it important?" The human brain is only 2% of the body by mass, but consumes 20% of the [metabolic energy](http://en.wikipedia.org/wiki/Human_brain#Metabolism). That makes it literally 10x more expensive to operate than the average tissue. No creature would out-compete another with a 20% penalty to energy usage. Thus, having more brain *must* be useful, and significantly so. While humans do have one of the highest ["encephalization quotients"](http://en.wikipedia.org/wiki/Brain_size#Other_animals), it is only modestly larger than other animals, yet we have taken over the planet. A little brain goes a long way, apparently. Having 2 distinct brains seems very unlikely to occur spontaneously in a single creature, because of the efficiency of having a single unified brain. But sometimes biology screws up and a creature is born with 2 heads. Most of the time, this defect is so detrimental that the creature doesn't even reach maturity. It may be the case that in a world with a certain kind of hunting environment, having two heads which can look/focus in different directions more than compensates for the cost of having to operate 2 brains (especially if the brains are "cheaper" than ours). The more complex the environment, the more computational ability will be rewarded. Just finding predators or prey in camouflage may not qualify. And Newtonian mechanics appears to be mostly tractable. But what if there existed a planet with strong geomagnetic anomalies, and this caused objects to move in complex ways that we would not recognize? Trying to play baseball on such a world may prove to be past our abilities, even after hundreds of years of adaptation. Or maybe the planet has quickly moving gravitational anomalies, like very dense chunks moving chaotically within the mantle which cause balance the shift quickly over time? Obviously, the idea is that the environment must put computational demands on the creature which justify having more brainpower. It's difficult for us to imagine these conditions, because we live on a world that we have already mastered, and with only 1 brain at that. [Answer] And now for a completely different approach: We have egg layers and live births, lets hypothesize a creature that reproduces by fission instead. They have sex with the exchange of genetic information (although they would lack the concept of male and female) and a new creature would be formed. However, it would grow to maturity as part of the parent. Imagine a starfish that actually consisted of 5 subcreatures that were semi-fused. It wouldn't make a baby starfish, it would become a 6-armed starfish. When that arm was mature it would become a 7-armed starfish. At some point it would have enough arms and would split into two starfish. Each component would have its own brain, they would work as equals, any brain capable of commanding the others based on the urgency of the situation. (Thus if arm 1 sees a predator about to eat it that overrules arm 2 seeing food.) This would almost certainly be suboptimal but the evolutionary chasm to escape this would be almost certainly uncrossable, if it developed (and the pattern would be laid down long before brains entered the picture) it would persist unless the entire kingdom died out. [Answer] Parting from the attempts at pessimism, I would suggest that a second neural mass could easily evolve to handle sensory input from a second (or more) location for some perfectly reasonable environmental factor. At first thought, I would suggest a creature that walks long, narrow tunnels. A second predatory species (or multiple) might hunt that species in those tunnels. The prey might easily develop sensory organs for the "front" and "back", and "brains" to handle both. Given the right circumstances, these brains might develop towards higher cognitive functioning simultaneously, eventually resulting in sentience. That, however, is just an example. Any environment requiring multiple distinct sensory locations could result in similar evolutionary tracks. Multiple locations needing sensory organs -> favoring neural masses to handle reaction speed -> raising of complexity of those neural masses. The end result depends heavily on the environment. In the above example, the physical environment and nature of the predators. They could be very similar, or one could be specialized for one task or methodology while another for another task or methodology. In the above example of the [push me pull you](https://www.google.com/search?q=push%20me%20pull%20you&espv=2&biw=1551&bih=866&source=lnms&tbm=isch&sa=X&ei=NbQ1VaqcAoKRyQSzq4HwBg&sqi=2&ved=0CAYQ_AUoAQ&dpr=2)-esque creature, maybe the front brain evolved for hunting food and results in a sentience good at engineering, math, the arts, etc. The back brain might be the sentry brain, and have evolved for predator awareness resulting in a sentience good at "fighting" or athletics or vision and spatial-awareness. As a note, your own octopus example is a good reference for this concept, and was the first example of which I thought when I read the question title. You say that the octopus' secondary neural areas aren't brains, but that doesn't mean they wouldn't evolve further if the need was present. A pressing evolutionary need to advance those neural masses in the arms, and the octopus might one day have a sentient head and sentient arms. Sentience is simply the evolution of incredible neural complexity. [Answer] As mentioned in the comments, some dinosaurs had spaces in their skeletons to house what might have been second brains. As the theory goes, these beasts were so large that the distance alone was enough to cause issues with reaction time as the nerve impulses had to travel down to the leg/tail. Likewise, there would be the problem of sensory input. If something bit the dinosaur's tail, there would be a relatively long delay before that got to the brain and processed into input. Simple things like walking require that sort of sensory input -> motor control feedback loop, and such large beasts might've run into issues due to nerve latency. One other point about the theory is about blood pressure. Giraffes have a very specialized circulatory system that helps them actually get their blood up to their brains and keep it at relatively consistent pressure as the animal raises the head up and down. By having only half the brain up there, the demands on bloodflow would lessen, placing less demands on the circulatory system. The thought was that beasts like the Brontosaurus would have had similar bloodflow challenges, making the dual brain approach a potential solution to that. [Answer] I don't think there would ever be a reason for a fully redundant brain in sapient creatures. Redundancy is good, but our brains already have it. You could increase the redundancy in your brain, but ultimately it makes more sense to simply add more redundancy in an already existing brain then to create a second brain. Your skull is designed to protect your brain well, no other part of your body is. Why create a second location to protect your second brain, as well as re-wiring all the neural 'controls' to a new brain location, when you could simply add more redundancy to the one you already have protected and wired. However, there are two approaches which get somewhere close 1) the creature can function after being dissected. Think of starfish, when they break off a limb that limb can grow back to a fully starfish. If a creature was symmetrical, with one brain in each 'half' of their body, then breaking their body in half would allow two functional versions that could both grow. This could even be their method of asexual reproduction. However, it's hard to imagine a creature like this being sapient, or even highly intelligent. This trick only works because the star fish 'brain' is not much of a brain. The more complex the mental functions the less viable this method is. In addition if the creature developed entirely by asexual reproduction by splitting in half it will never grow advanced enough to be intelligent, you need sexual reproduction of some form to have the sort of evolution that can develop complex creatures like sapient. 2) non-redundant brains. Think of your octopus example, where you have limbs that function separately. Perhaps two brains exist, but with different roles. One brain controls higher order thought and one brain controls certain advanced motor functions. They would be separated either to increase reaction speed (the closer to the object controlled the better), or because they function in separate manner. However, the creature may have evolved a separate 'redundancy' approach where, if one brain fails to function, the other brain will grow to control the functionality of the first brain. For this second approach to be viable though the creature would have to be limited in functionality after loosing one of his brains. Each brain is specialized for specific functions, and it's quite unlikely that they will preform the functions of the other brain equally as well; if they were redundant one would evolve away due to it's high energy cost! Each brain may be able to have limited ability to take on the role of the other brain, but that ability is likely no where near as good as what the creature could do with two brains. For example perhaps a creature has a main brain, and a second smaller 'brain' for controlling motor functions of a particularly complex appendage. Perhaps the original main brain use to control the functions that the sub-brain now controls, but a new brain evolved due to the extra control it provided. If the brain controlling the appendage fails the main brain may still be able to control those appendages perhaps retaining the abilities it possessed from before the sub-brain evolved. However, it will not be able to perform the role as well as the main brain could have. Now instead of complex and effective control they can manage a haphazard control of their limbs, enough to not be fully crippled but clearly worse off then they were before. It's unlikely that their second brain could take over higher level thinking if the main brain failed though; higher order thought is much harder. However, as a creature grows more intelligent these approaches become less viable. The brain becomes a greater and greater expense, too expensive to be able to keep a backup 'just in case'. In addition the need to defend the brain from accidental damage becomes likewise greater, meaning necessitating a 'skull' or equivalent to defend it. Also, any higher level learning would almost have to be limited to a single brain, trying to duplicate 'learned' behavior from one brain to another would be nearly impossible. Thus only one brain could 'learn' a given task, and losing one brain would lose anything you learned. Simple creatures do little learning, relying on instincts primarily, and thus this is not an issue; but it is a major problem with sapient species, or even species as advanced as your common pet or...really any mammal. [Answer] While most of the upthread posts point out the objections, I will try to hand wave a semi plausible way for this to occur. If a creature with multiple limb sets evolved for whatever reason to be very large and long, it would make sense for multiple nodes to develop in the nervous system for the control of limbs or other bodily functions. For the most part this would not lead to sentience, or even multiple "brains" but rather a sort of distributed nervous system with controlling nodes similar to the hind brain spaced at strategic locations. This isn't a huge issue in terms of protection, since if we think of these as being auxiliary controls to ensure fast and efficient use of the limbs, the nodes will probably be protected by structures similar to the pelvis where they will be close to the parts they control. Assuming there is some evolutionary pressure to achieve intelligence and then sentience, one of the nodes will become a full fledged brain (presumably the one closest to the sense organs), while the rest of the nodes may increase in complexity to control fine motor skills needed to manipulate the environment, and ultimately tools and technology. The creature may resemble a centaur with several very complex structures at each set of limbs that serve to anchor the limbs, provide attachment points for the muscles and protect the controlling nodes at each limb set. If you want to take this further and have the nodes become more "sentient", then they will need to process more information individually and collectively. We will need to come up with a more alien body plan which involves each node being responsible for dealing with sensory inputs, locomotion, feeding or other complex functions. Perhaps the best example might be the truly alien initial reconstructions of Hallucigenia, which had the animal balanced on a series of "stilts" and tubular protrusions rising from the back which were theorized to be "mouths" or manipulators of some sort. A creature like that with a row of sensory organs rising from the back would need some pretty sophisticated processing power at each organ, and could, in time, evolve a set of fairly primitive "brains"; each one individually not very smart, but perhaps able to run all of them in parallel to deal with complex problems in the environment.  So multiple brains *may* be possible, but they require a very convoluted evolutionary history to even approach. [Answer] Well, a leech apparently has 32 brains. There is one for each segment. This might be different from the idea of having many centralized brains, but I think any neuroscientist would agree that humans have two brains. Motor skills and various senses are split between the left and right, and the output of this processing is then rectified via the connection between the two (the corpus callosum). You might argue that such a connection between the two hemispheres would define that as one brain, but if you physically split this connection, the brains get by just fine without it. There are some abnormalities, to be sure, but otherwise the human can get by rather normally (see split-brain patients--an operation sometimes undertaken to treat severe epilepsy). The two brains then "communicate" by observing what the body ends up doing, not through actual neurological processing -- this is how conjoined twins (aka "Siamese" twins) can get along, despite having clearly two brains (and two heads). The reasons for this redundancy are largely speculative. One could argue that we have redundancy for the sake of redundancy; if one side is damaged, the other might be available to take over. That's somewhat unlikely. It would mean that there was a point when evolution tried one-brained pre-vertebrates and two-brained pre-vertebrates, and one-brained vertebrates were not selected because they died en masse compared to the two-brained variety. But really, the one-brained variety that was around is still around, and in large numbers. Vertebrates just evolved rather [symmetrically](http://www.quora.com/Why-is-two-hemisphere-brain-favored-in-evolution), and two brains were more consistent with that physical structure. Vertebrates did not "win" -- there are [*way* more invertebrates than vertebrates](http://www.diffen.com/difference/Invertebrate_vs_Vertebrate). So, the main reason for multiple brains might well be because body parts started to become physically separated or duplicated. They most likely stuck around because the separated/duplicated parts were useful, not because the redundant brains offered a clear advantage. (Remember, extra brain material takes a lot of energy to support. Under the strength-via-redundancy theory, this energy trade-off would have to be outweighed by the rather rare occurrence when exactly one side of the head was damaged and the animal still survived to reproduce.) To support multiple brains in evolution, you have to answer the "how" more than the "why." It's more about how the reproductive process could have evolved these multiple brains, and then you just have to show why this evolution did not kill off the animal. If there were an advantage, all the better, but it's not actually necessary. It just has to be survivable. Finally, if I were to hypothesize a likely scenario for multiple brains, I would define an organism which reproduced with many children in the womb that tended to not fully divide, leaving a conjoined organism. By chance, the conjoined version of this organism ended up with an advantage because, for instance, it could observe its environment in many different directions. It would have to have a locomotive ability that happened to work very well in a loosely coupled way. (Human conjoined twins get by, but they would usually be at a disadvantage, even given the hyper-vigilance afforded by multiple sets of brains/eyes.) Or maybe they would be prized as sentries in a communal society that also had non-conjoined versions of the organism. I'd just like to add one more thing. Many responses point out that a single brain would generally be simpler and more advantageous, therefore the multi-brain is unlikely and a bad idea. I agree with the original poster, though. It really doesn't matter how unlikely it is. The fact is, evolution often creates very strange, seemingly ridiculous creatures. It's a matter of whether that creature can just survive long enough to not go extinct rapidly. And, as in the case of the leech and probably a good number of other organisms, a separated brain system might actually yield simplicity when the added complexity of wiring up body segments is factored in. Moreover, there are environments that are *not* particularly resource constrained and where predators are few. Look at animals like pandas and sloths -- slow, gentle creatures that certainly would not have survived in the jungles of Africa, but do ok in their particular jungle environments. In those sorts of environments, there is not a lot of pressure to kill off non-optimized species. The point is that the evolutionary selection criterion is actually a very complex function which cannot really be predicted by a simple rule of thumb. So, just use your imagination, and you'll come up with an evolutionary environment that would yield just about any sort of fantastical creature you could think of, as long as it physically makes sense in the end. [Answer] For a second, completely redundant brain to make any sense, I would think that the animal would have to be living in some sort of environment where destruction of one brain would be a likely and common occurrence. **Evolution is all about efficiency.** Why don't human beings have two brains right now? If evolution was not about efficiency, then after the first human was born with a functional second brain, any benefits/advantages that second brain will make this specimen stronger and more desirable than puny single-brained humans. This, in turn, makes two brained humans more desirable, more likely to reproduce. Eventually, all future humans would have two brains right? **Not right** So maybe having a secondary, redundant brain might not give humans any extra benefits other than making it possible (barring blood/fluid loss and infection) for us to survive catastrophic damage to our heads. If Joe Two-brains gets shot in the head, he can still live and function normally. **Added Complexity** But what if Joe Two-Brains never gets shot in the head in his lifetime? What if he existed in a time where guns were not even invented yet? And it became increasingly unlikely that getting shot/crushed/dropped on his head was a possibility? Then, what you would consider an advantage would be somewhat just wasteful. What if he lived in a time/place where food/nourishment was exceedingly difficult to get a hold of; so now that having two brains to provide sufficient nourishment for was now actually a liability to his survival? **The animal** So I think the second brain would have to evolve out of necessity. So if this creature was on a small planet with a very thin atmosphere; where small pea sized meteorites came crashing down on it. Even if the likelihood that during it's lifetime, that one hole was punched through the animal right in one of it's brains. It had a secondary brain to take over and keep it alive while it's first brain healed. Therefor, the planet has pea-sized meteorites crashing down, frequently enough that they might strike the animal's brain on any given time, but infrequently enough that the chances that one brain gets struck and the second brain gets struck before the first one heals occurs. I would like to think it's a two headed shark or something. [Answer] The title and body of your question are slightly at odds with each other, but a high rate of birth defects may be all that is necessary for a creature to "evolve" two brains. If you start with a creature that regularly gives birth to multiple offspring, and the environmental conditions are such that there is a high incidence of birth defects resulting conjoined offspring (or perhaps more specifically, two-headed offspring), one might conclude that the creature "evolved" to have multiple brains. Although one of the brains is often more dominant, some cases of human conjoined twins have met your requirements for being able to work individually, as well as assume full control. It isn't clear to me why you distinguish cooperation from working individually--to me that doesn't necessarily seem like a direct function of the brain itself, but rather along the lines of a social adaptation. [Answer] Interesting question. Let's explore the premise of the question itself a little more deeply first: *"In order to qualify as having multiple brains, the brains must be able to work as individual unit(s) while at the same time being able to cooperate to focus on more intensive tasks."* What does "working as individual units" mean? For example, we have different portions of our brains that are constantly working independently of each other. For example, like you pointed out, different parts of our brain that deal with movement/speech/sight. However, these are very specialized portions of our brain that lack any flexibility to "cooperate on more intensive tasks" outside their domain. The portion of our brain that has this sort of non-specialized general-purpose nature, is our consciousness. What does it mean for our consciousness to branch off and "work as individual units"? That would imply being able to have multiple streams of thought. For example, one stream of thought that is fully concentrated on read this post, while another stream of thought is fully concentrated on watching Breaking Bad. Even though many of us think we're capable of this, our brains cannot handle any form of true parallel-processing. Whenever we try to "multitask", our brain is actually time-multiplexing between these different tasks, on a single stream of thought. There is no evolutionary free lunch, and multiple-streams-of-thought will only come about if it leads to an evolutionary advantage. Ie, we will need an environment that rewards cerebral activity, but not too much of it in any one concentration. Ie, thinking about 2 different things with half-the-processing-power has to be more beneficial than thinking about 1 single thing, with full focus. This can only happen in an environment featuring an **abundance of shallow-cerebral-content**, such that it benefits from multiple streams of thought. For most of natural history, this has never been the case. Cerebral activity has rarely been a great evolutionary advantage. And even when it did, the amount of cerebral content available at any one point in time, is limited such that a single stream-of-thought has always been sufficient. Even in today's world, I would argue that there's little benefit from multiple streams of thought. Even though there's so much content out there, you can still only be in one place at a time, and you only have one pair of eyes to see with. Given that this limits you to a single input stream of information, a single stream of thought is sufficient to process this. And even though there's so much content out there, there's economies of scale involved in choosing which content to consume. Most human progress has come from deep thinkers who focused on one problem, devoted it their full focus, and achieved breakthroughs that way. Even in today's world, which revolves much more around "multitasking," time-multiplexing between all the different things you'd like to do is sufficient to achieve our goals. Very rarely do we ever benefit from thinking about 2 different things simultaneously, with half the processing-power given to each. Hence why this **abundance of shallow-cerebral-content** requirement is completely foreign to anything in our world thus far. Let's look at the next requirement: *"If the creature were to lose one brain, the other brain(s) must be able to assume full control of the creatures body, such that it would be able to function (almost) as efficiently as before. In other words, you can't have a brain that deals with just movement while another one deals with just regulating bodily functions. The brains must be able to "swap jobs" as necessary."* This requirement is going to be tricky. Imagine if you're running a dual-core computer and one of the cores stops working. Would you still expect the 1-remaining-core to perform almost-as-efficiently as your previous dual-core-setup? If you're using your computer to its full potential, this will definitely not be the case. Losing half your processing power will leave you with a computer that is much more sluggish and slow, even though it's still fully functional. But if you're not using your computer to its full potential, this could be true. Imagine if the only thing you're using your computer for, is playing solitaire. Going from 2-cores to 1-core wouldn't affect your computer performance in any practical way. The question is: Why would you pay for 2-cores if all you need is 1? From an evolutionary perspective, brains are very energy intensive. Having 2 brains when you only need 1, will put you at a severe caloric disadvantage. To make up for this, you will need an environment that is either: **a) Abundant in energy/nutrition needed to develop/power 2 brains** and/or **b) Very hostile and injury prone, such that backup organs significantly improve survival rates** Either/both of these will be needed to justify the added cost involved in paying for redundancy in your brain. --- To summarize, if you want 2 brains that are capable of sustaining 2 different streams of thought in parallel, you will need an environment featuring an abundance of **shallow-cerebral-content**, concentrated within a single physical locations. And if you want 2 brains that can deal with failures/injuries with minimal side-effects, you will need an environment featuring an **abundance of energy/nutrition, and/or very high injury rates**. [Answer] Since evolution is more of an accidental thing that happened to work than a goal-driven mechanism. Your way of asking is a bit strange. However, given the fact that dolphins in the wild already have a sleeping system where half their brain sleeps while the other half is awake, it is not unimaginable that at some point some dolphins will evolve to have more separated brain halves and eventually even complete separate brains. As to the environment, looking again at dolphins, I would say the most likely environment is one where the creature cannot (or can hardly) hide from predators and/or needs to actively move to survive (like dolphins need to surface for air). Theoretically speaking it is plausible that humans would at some point develop a similar system due to the continuous drive for more efficiency. However, it seems to me that, the intermediate stage of 2 brain halves functioning in turn would not make for very intelligent/efficient human beings, thus lowering their chances of survival (although in modern society they would most likely still survive). [Answer] There are already some great answers here but at your suggestion I am submitting my own. To restate what was said in the comments, evolution only happens out of necessity, and only very strong necessity at that. As many have mentioned, brains are (by our Earth standards) a very expensive investment, so natural selection would only breed a second one if there was a very, very good reason, critical to the organism's survival, to do so. The mother of evolution is survival, and of all survival reasons, nothing prunes weakness like pure environmental hazard. **Biological** Someone has already mentioned brain-killing physical forces like crashing micro-meteoroids, so I'll focus on the more sinister threats... those of a biological nature. Imagine a creature with a complex neurological system to control either a large body, or complex senses/musculature. It doesn't have two brains (yet) but it does have an extra "neural node" to help coordinate its activity and awareness. Now imagine a virus or bacteria that evolves to feed on brain tissue. It doesn't necessarily like neural tissue, but uses it as a means to "find" the brain after it enters the body. As more creatures start to die from the disease, those with mutations of extra neural tissue in the neural node (not the same as brain tissue) tend to survive to some extent because they can continue slightly more complex rudimentary functions even after brain death (**Edit:** A mass-extinction of all those *without* this mutation, leading to the leftover "zombie-like" creatures still able to breed, would speed up the process significantly). Over time this evolves into a second brain, which is biologically different from the first brain but allows the creature to survive even if the disease kills the original brain. Over time the creatures could find a way to combat the disease and save the original brain, and thus you end up with a species that has two distinct brains, each more-or-less capable of controlling the whole body. The differences between the two could create some really interesting opportunities for cultural and "personal" development, plenty of ritual or religion, persecutions, etc to really spice up the world you're designing. **More Creative** A more fantasy-oriented (or soft science depending on how you spin it) approach might be having a second "brain" evolve as a response to the environment slowly being introduced to a dangerous energy that's simply impossible for a "normal" brain to deal with. It could cause unusual chemical reactions in things it touches, and some quirk of evolutionary mutation would make people with a certain chemical (or magical) composition able to handle it slightly better, due to how their bodies process the reaction. That process could start out as a fairly "mechanical" means of barely surviving the reaction, but better survival would be obtained through further mutations that allowed their bodies to exert some control over reaction. Rinse and repeat several times and you could end up with a second "brain" devoted entirely to controlling parts of the body that enable it to handle this destructive force and turn it into an advantage. Such a "brain" would certainly work much differently that a normal one, so as it develops into a sort-of intelligence (out of necessity, mind you... perhaps the environment is constantly changing and requires an intelligence to keep up with it, and the original brain can be killed by the reactions so this one would need the ability to take over) it would have a completely different "voice" than the original brain, and a whole different perspective on priorities for the creature. **Edit:** Per your comments on the original question, both of these scenarios could also result in the separate "brain" not being a separate consciousness, but an extension of the first. But at that point it's not so much a *separate* brain as it is a *distributed* one. I guess. We're so far into the theoretical realm we don't really have a clear definition for what we're discussing, so you could do it however you want at that point. **Further Edit:** Consider also that they could be separate but telepathically linked so they act more-or-less as one entity. Depends on how "out-there" you want to get. [Answer] I think Chimerism is the best bet as a starting point. Brains are restricted in size by the calories they consume. The path of least resistance is to evolve more brain. The only reason we have bigger brains than apes is because we have more to learn, and the things we learn get us more food. A big part of what aids in survival are our socialization skills and language. I think, for a creature, with what we view as consciousness, to evolve a second brain, it would have to be the result of some sort of merger of fertilized eggs - eggs of an already conscious species. You'd never evolve a redundant conscious brain one gene at a time, this is something that would require whole genome duplication, like mono-zygotic twins that fused. Then you'd need to isolate a population of primates that were genetically inclined to this sort of merger. But I'm not sure that such mergers are genetically linked, so it sort of falls apart there. At that point you'd have two-brained, one-body primates. And dicephalic twins do seem to share control of organs and motor reflexes, sometimes they're even in conflict over control of motor reflexes. Lets say shared thoughts and non-verbal communication is a driver. Certainly cooperative motor control would be a benefit. That connection would occur in the axons and grey matter of what, hopefully, is a shared spinal column. To suppose that we have one mind is incorrect I think. People with schizophrenia demonstrate an inability to recognize their own self-generated thoughts as self-generated. When you ask yourself a question, it's pretty obvious that you have multiple minds. You can pharmaceutically induce the symptoms of schizophrenia by slowing areas of our neural network that analyze other distinct parts of our neural network. So for a few hundred thousand years you'd likely have a two-headed primate that shared muscle memory, probably basic sensory perceptions since pain and sensations originate largely from the nervous system, eventually, perhaps non-verbal communication, shared vision and perhaps eventually, some merger of consciousness and with that some form of redundancy. Well, meeting your criteria of redundant - I wouldn't call consciousness redundant, so I think the question is ultimately self-defeating. [Answer] # Possibility 1: Very, very, very long body. Upon reading just the title of the question, I immediately thought of Dinosaurs, some of which, such as Diplodocus and other [sauropods](https://en.wikipedia.org/wiki/Sauropoda) were so large that some scientists had speculated that they might have had two brains [(disproven for stegosaurus)](https://en.wikipedia.org/wiki/Dinosaur_intelligence#.22Two_brains.22_myth), one in their heads, and another lower down, in their hips.  This is so that the lower part of the body could be controlled independently, and reflexes coordinated at a faster rate, I read once that if you dropped a rock on a Sauropods tail you'd have enough time to run away before the Dinosaur's brain registered the event! Whilst in the real world, these cases for two brains have been either disproven or seem unlikely, there is no reason why other, alien organisms may not have evolved two brains because of similar constraints. # Possibility 2: managing sleep, staying awake. Another reason for multiple brains, [as previously stated,](https://worldbuilding.stackexchange.com/questions/14807/what-are-the-conditions-in-which-a-creature-would-evolve-more-than-one-brain#answer-14844) would be to manage sleep: > > Sleep? The body part needing sleep most is the brain. Now imagine a world where it's too dangerous to go to sleep, maybe one with two suns or placed in a crowded part of the universe, so that there's always enough light. Two brains might evolve to do a shift work. > > > However, I now point you to [Dolphins](https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep#Cetaceans) which manage a similar sleep-problem by only sleeping with half their brain at once, an ability called [Unihemispheric slow-wave sleep.](https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep)  Whilst this sleep-pattern eliminates this need for two-brained beings on earth, there is no reason why other alien organisms wouldn't evolve two brains to conquer this problem: # Possibility 3: Improve coordination and awareness. If multiple organisms came together to produce one organism (previous examples included the portugese man o' war and Siamese twins) then these organisms would have to be coordinated by multiple "brains."  [But what conditions would cause hybrid organisms like these to become populous?](https://worldbuilding.stackexchange.com/questions/14807/what-are-the-conditions-in-which-a-creature-would-evolve-more-than-one-brain#comment-36563) Well, the Portugese man o' war already benefits from being a [siphonophore](https://en.wikipedia.org/wiki/Siphonophorae), it's almost like a normal eukaryote, all these "cells" coordinating to create an organism is actually quite efficient. For beings like Siamese twins to evolve naturally there would have to be some strange environment, perhaps two-heads are necessary to spot dangers and predators, or extra limbs need to be coordinated independently and quickly, a set of limbs per brain. These conditions could be imposed by faster predators, or coordinating pack animals which approach from multiple directions. Or, say the ground was unfit for living on, a species of ape could evolve which used two sets of limbs to maneuver the perilous branches of the tress above, trees which move, or hide ambushing hunters. [Answer] I've looked over the current answers and have not seen the Angler Fish mentioned yet. The female angler fish lives in the deep ocean and is best known for her bioluminescent lure with which she 'lures' her prey to her. The male on the other hand is only a tiny fraction of her size. His only purpose in life is to mate with her by biting into her and being absorbed into her body. Over time, he melds into her flesh and acts more like an extra body part to provide sperm when she lays eggs and is fed by the nutrients that flow to him. Many females have been documented to have several mates. What I see in this example is the melding of two organisms into one. A brain would be supplied by both. One sex has the dominant body and, in a fantastical setting, one could use this as a basis for creating such a creature as described in the original question. Obviously, there would be a time period whereby the newly acquired brain would have to get wired in and the female would desire some kind of defenses to a potentially parasitic invasion of her body in such a creature. Just as much, the male side would want something of its own to combat the defenses. Continuing this thought process, the question should be asked whether the two would have to be of the same species. There are many examples of multiple species creating a super colony that acts as a single unit and many species that have evolved to be solely dependent upon another for (sometimes mutual) survival where the extinction of one would cause the extinction of the other. Overall, if you go with the route of the second brain coming from another creature and being wired in, your possibilities may be endless. [Answer] > > What are the conditions in which a creature would evolve more than one brain? > > > The rest of the question makes it clear that you're not actually asking for multiple brains, but brain/thinking tissue located in disparate parts of the body. We already have multiple brains that take control of the body. For instance, observe your breathing for a few breaths. Merely by mentioning it, you are now breathing using your brain. It will take awhile to switch control back to your autonomous system. You can't do that with your heart. Touch something painful and your muscle retract before your conscious self receives the pain impulse. This is due to the spinal cord - it can actually make some decisions on its own. Further, you specify that the brains must be able to be independent, assuming full control of the creature if/when necessary. This essentially involves two separate consciousnesses, but both must pass through a single "routing" system that gives control to one or the other, and routes signals to both. Alternately, the body must develop complete, separate nervous systems and the fighting for control happens at the muscle level. Honestly, none of this sounds like a reasonable mutation that would increase the organism's ability to procreate, or survive. If this mutation provided positive evolutionary pressure in any way, we'd see a lot more animals born as conjoined twins. In essence, anything that can be accomplished by your desired two brain outcome, can also be accomplished with a single brain that has multiple units - like our existing brain. Look, you're breathing manually again. There is no reason to separate the parts of the brain and move them to other parts of the body. It increases risk and complexity, with no benefit. [Answer] I completely agree with most of these answers - we already have 'multiple brains' which is why we sometimes feel conflicted about things (I want to eat AND sleep). And the biological conditions to evolve 2 brains seem fairly implausible. There is, however, a biological condition called [Polycephaly](http://en.wikipedia.org/wiki/Polycephaly) where an organism ends up with 2 heads. While both minds are distinct, there is little to suggest that their experiences would be unique enough to provide the same variance in perspective that we expect when talking to a physically distinct person, so the whole two heads are better than one seems unlikely. Most of these organisms die quickly compared to their expected lifetimes. The conditions for such a creature to become a distinct species might involve a cooperative species becoming so successful that enough of these 2 headed creatures lived at one time to create a breeding population (in love, we're looking for something distinctive that resonates - what resonates more than having 2 heads?). With humans, this is unlikely because we surgically separate twins, but many species have had periods of wild success where the typical breeding pressures change. It seems wildly implausible, but if there are advantages to having 2 of something else found on our heads, perhaps such a creature would be successful... [Answer] We already have a second brain. > > **[Gut Feelings–the "Second Brain" in Our Gastrointestinal Systems](http://www.scientificamerican.com/article/gut-feelings-the-second-brain-in-our-gastrointestinal-systems-excerpt/)** - Scientific American By Justin Sonnenburg and Erica Sonnenburg | May 1, > 2015 > > > The enteric nervous system is often referred to as our body’s second > brain. There are hundreds of million of neurons connecting the brain > to the enteric nervous system, the part of the nervous system that is > tasked with controlling the gastrointestinal system. This vast web of > connections monitors the entire digestive tract from the esophagus to > the anus. The enteric nervous system is so extensive that it can > operate as an independent entity without input from our central > nervous system, although they are in regular communication. > > > [Answer] In *Saturn Ruch*, each side (top and lower surfaces) had a stalk with a head and hands, used for grooming and maintaining that side. The characters notice two such eye-stalks and say that you can't have eyes without a brain immediately behind: certainly on a carrier-sized animal the nerve impulses are two slow. So each half has a *separate* brain and is a distinct individual. This is due to its *size* and the shape making it advantageous to have a stalk on each surface rather than one that can reach all over. Since the ruch must remain on active alert, one head controls the body in the day and the other at night, with different evolved behavior. Some birds have unihemispheric sleep: that could further evolve into more independent functioning, as opposed to our situation which combines consciousness into one individual with one "thread". [Answer] The answer is ridiculously obvious and the title gives it away; *What are the conditions in which a creature would evolve more than one brain?* **Well, in conditions where a creature has more than one body.** The [Man o' War](https://en.wikipedia.org/wiki/Portuguese_man_o%27_war) is a type of creature that is not one, but instead multiple creatures, all of which come together to form a single species. An advanced version of this multi-bodied concept is the [anthill](https://worldbuilding.stackexchange.com/questions/46962/what-would-a-collective-consciousness-look-like). While the creature does have multiple brains, one could argue that a multiple bodied creature is even its own creature. [Answer] I would like to point out that there are several two brained vertebrates in captivity that you could arrange to observe, and even at least one two brained vertebrate you could arrange to meet and talk with, Abby and Brittany Hensel (born 1990). The problem with 2-brained conjoined twins is that they are not genetically 2-headed. The descendants of any would not inherit genes for being 2-headed. But there could exist species that are genetically a lot more likely to have conjoined twins than most Earth species. And if there is some survival advantage to being 2-headed it could become more and more common in the population. Perhaps being 2 headed and 2 brained might in some cases improve survival rates in a social species. Perhaps in a futuristic biologically advanced society 2-headed and 2-brained species might be artificially created. A future emperor might be inspired by heraldry to have 2-headed eagles created, for example. If most Earth vertebrates have right and left brain hemispheres that sometimes operate independently, some evolutionary process might develop multiple brains out of such a situation. For example, there are species on Earth that are possibly semi intelligent or even fully intelligent that have heads much larger than their brains. An Elephant's brain is larger than a human brain but it's head is much vaster and includes empty spaces to save weight. A hypothetical elephant species evolving a much larger brain might do so by having one hemisphere grow an extension out of the brain case and into the hollow regions. Eventually that entire hemisphere might be in the hollow regions of the skull and the other hemisphere might grow to fill the brain case and anatomists might consider that species might has two brains. Similarly many cetacean species have brains larger than humans that occupy tiny parts of their heads. Possibly they might evolve even larger brains by having one hemisphere grow out of the brain case into another region of the head while the other hemisphere grows to fill the brain case. And they might seem to have 2 brains. [Answer] Many of the proposed answers here claim that efficiency is a requirement for an evolutionary path to be manifested & maintained. That's not at all true. What makes it seem true is that the more competitive (that is to say, if things are inefficient they die or fail to reproduce) an environment is, the more likely inefficiencies will incur a cost that results in failure of the line to procreate and thus evolve more (or maintain functionality.) So scenario 1 is: The environment in which the subject species evolves is essentially non-competitive for that species. 1a: Subject species procreates as a community, rather than as individuals..that is to say that there is no mate selection process. 1b: Environment is cold, species is cold-blooded, in this way the high metabolic requirements of 'normal' brain matter become a boon quite aside from it's nature as problem-solving tools. (Why: Whilst 1b can help explain why it would not necessarily be a net loss to the organism, we can also say that See 4) Scenario 2: Subject species' brain matter has evolved in such a way as that it grows/reproduces to fit available space. Another species evolves that as part of the life-cycle burrows into the flesh of subject. Net result: on occasion members of the subject species will form tendrils of brain matter back along the path the parasite has burrowed, where said burrowing has created cavities the reactive-brain has the local mass to take on a greater role as part of the consciousness. (Why: Of course in this scenario we might say that the growth mechanism can be a reasonable response to the parasite, if it regularly occurs that said parasite destroys brain matter, the evolution of a process to stimulate additional neural matter makes sense.) Scenario 3: As scenario 2, but some part of the parasite's biology is close enough to the hosts that it triggers the formation of brain matter around it(once inert) by the hosts physiology. Scenario 4: Feedback. Simply put, when a human is growing it's cells are instructed as to what to be, and by and large they do as told. If our theoretical species evolved in an environment in which damage regularly occurred which interfered with a sensory organs ability to communicate with the rest of the body resulting in eventual death, we might possibly see a scenario in which when the feedback loop from brain<>sense organ was interrupted, the sense organ had the functionality to stimulate the local(or secondary) creation of neural matter (that linked into the general nervous system). If what damage had caused this growth was eventually repaired by other functionality, the subject would have it's central neural mass + dedicated neural mass) // Then we have Unihemispherical Slow - Whatsitcalled, wherein certain creatures have developed a capacity to sleep with half a brain at a time. This shows us that brains don't need to be so alien to extend their ability to operate as two parts than in the fashion they already do among humans. But in the end we have an easier solution, it seems to me.. it's insects that become sapient, likely in a slightly cooler environment but with denser concentrations of oxygen in the atmosphere, reducing load on heat exchangers and increasing the efficiency of tramsdermal respiration. // Another option would be a massive, largely or entirely immobile planktiverous organism, if the feeding mechanism is passive but food source is abundant. The issue changes from "this uses too much energy and so too much cooling" to "this needs a much more efficient nutrient delivery system than a terrestrial mammal of the same eq. This being the case, where nutrient collection is distributed across the body, so must digestion be or your species ends up using as much energy moving food from 'mouths' to 'gut' as is gained from the food (in a sufficiently large organism.) If we accept this as true, it then also becomes an energy saver to have the energy derived from local digestion to local uses and so we justify the evolution of multiple brains...at least in part. Of what use they'd be to an immobile planktiverous organism I'm not sure :) [Answer] ## **Let's run with the starfish idea and build a hydra. Like a big reptile with many heads** [](https://i.stack.imgur.com/ZhDlN.jpg) A lot of these posts are approaching the problem backwards, and answering **"how could an existing single-brained creature develop an additional brain"** and that's an impossible evolutionary path - neural tissue is just too expensive and a semi-evolved brain would not be useful alongside their existing fully-evolved one. We need to instead answer the question **"under what circumstances would a non-brained creature evolve multiple brains"** and the various starfish posts above spotted the solution - the answer is radial symmetry. Or basically any body layout in which it would make sense to have the sensing/processing apparatus (It's best to imagine the brain as a thing that evolves from the eyes - it is efficient to colocate them and they are made from the same type of tissue) located on an extremity, and not along a line of symmetry. This seems quite unlikely to develop with bilateral symmetry, as the sensing/processing apparatus can at once be an extremity (the terminal end of the symmetry line) and place itself equidistant from the two halves of the organism, which feels like an efficient organism. But this isn't so with the starfish... it would have to be very TALL for the centre to be a sensible place for a head... and it already has quite a lot of sensory apparatus on the tips of the arms, so this makes the tips of the arms a strong candidate for the development of additional processing tissue. --- *EVOLUTIONARY BONUS - evolution tends to flow more smoothly if it doesn't need to develop multiple systems in parallel... if each incremental new change is separately useful to the organism. And we get that with the starfish - it is already a radially redundant organism, consisting of identical modules. This means for this creature to evolve multiple brains it need simply continue to add processing tissue to the tips of its arms incrementally. It doesn't NEED to develop complex systems for coordinating between the brains - at least not right away! Whilst the ability to coordinate between brains is obviously useful; each arm being separately clever is also independently useful. This gives us a good evolutionary ramp, we can add intelligence incrementally and coordination will follow in it's wake.* --- ## We're still a squishy thing though Alright so now what? We don't want a squishy boring sea creature. We want a cool interesting alien/monster. So where does evolution go next? Well, now that the arms are specializing themselves into sensing/processing devices ("heads"), maybe we want to do more with the central body where our gut and reproductive organs live? Lets extend this mass at the base, and develop a "foot" like snails have, so we can bring our "arms" up off the ground and allow them to continue their specialization away from being a locomotion device and further into being our sensing/processing apparatus (much like how humans specialized our forelimbs away from locomotion and into manipulators). [](https://i.stack.imgur.com/xonIe.jpg) So now we have something that looks a bit like a sea Anemone... we've got a foot for locomotion and organs we don't want extra copies of, and we've got a set of "braintacles" that house our sensing, processing and manipulator apparatus. Let's step back. Where are we in the evolutionary history of the world? We're right near the start. The [Ediacara](https://i.stack.imgur.com/ZhDlN.jpg). Bilateral symmetry has not achieved dominance and large carnivores do not exist yet - all life is squishy sea creatures feeding off plants and microbes in the water column or stuck to surfaces. They were simpler times, when evolution could try all sorts of wacky experiments without worrying about armour or teeth or speed, because there was nothing out there trying to eat you unless you were plankton. [](https://i.stack.imgur.com/eDjEj.jpg) Lets add a new feature for thriving in this environment. Most sea creatures (and we assume most Ediacarans) reproduce by spawning and and thus have a plankton stage... which as we mentioned a moment ago, is the only way to get eaten in this era. So let's use our radial redundancy as an advantage to skip the planktonic stage. Our organism now has two reproduction modes - sexual (spawning and creating planktonic larvae) and division (no sexual recombination, but we skip the planktonic stage and thus skip predation during the Ediacara). For coolness, let's imagine that each of our "braintacles" can seperate off from the main trunk of the organism, becoming a free-swimming snake-like creature. So our lifecycle is plankton -> gets bigger to become braintacle -> fully matures to develop a trunk (housing a bigger gut and sexual organs) -> and then can both develop additional braintacles (making the organism more advanced and also allowing future reproduction by division). This is a strong basic model. We now have a creature that can add additional sensory/processing capacity as it ages (the Elders are wise!), an individuals genome is likely to survive injury (if the trunk is damaged irreparably all braintacles can separate, disperse, and generate new trunks). And because it has 2 different reproduction modes that are optimized for different ecological conditions, it should be robust to major ecological upheaval. Which is important, because the end of the Ediacara is coming. ## The Predator Apocalypse [](https://i.stack.imgur.com/gSICV.jpg) The first macro-predators emerge, and before "food chains" can properly become a thing almost everything just gets eaten. Almost all body-types are completely wiped out. But not our creature! Whilst they haven't evolved combat abilities yet (there was no reason to in the Ediacara!) they are well equipped to escape combat. Infact escaping is a reproduction event for our creature. So the predators come, trunks die and braintacles disperse... some of the braintacles survive long enough to grow a new trunk and spawn and... hallelujah. Because of the sudden predator-apocalypse, there are not many filter feeders left to eat our planktonic stage, and there is not much competition for food. Our creature has a population explosion, and achieves the population numbers it needs to evolve combat abilities. And so the Ediacara ended, and all life that remained had teeth, claws, shells, bones, and other hard things for battle/predation. But our little many-brained creatures survived it, it's one of the fighty monster things in the food chain now. Infact, as one of the few creatures to survive the [Ediacaran extinction event](https://i.stack.imgur.com/xonIe.jpg), it now diversifies and fills many ecological niches. It is one of the two dominant bodyplans of this world. It is the hydra bodyplan... and the only other major bodyplan is that of the first predator. Fast forward to the Jurassic period of planet Hydra. Our canonical example of the hydra bodyplan stalks the forest. It is a large many headed reptile. Each head sits atop a snakelike-neck, which in times of severe injury can separate from the main trunk of the body and become an independent snakelike organism. But the heads do not separate by choice. For when they are together they are smarter, they can pool their intellectual and sensory resources to better understand their environment. They can draw upon each others memories, most valuable of which is the oldest head, their leader and mother, the one which originally grew this trunk. And what a trunk! The claws! the musculature! The large digestive tract and sexual organs! In their Hydra form they are a lord of the forest, a powerful combat machine with prodigious intellectual abilities. And should they fall from grace they shall become snakes. Separate. Weaker and dumber... but nonetheless whole. As snakes they can flee and hide, and grow. To one day become a Hydra lord once more. And that is good... for a shadow crosses the sky... that which hunts the hydra is coming... [](https://i.stack.imgur.com/iMrWZ.jpg) *p.s. apologies for the necromancy on a 5 year old post... I just... I just love mad things like this...* [Answer] If there was natural or unnatural evolutionary pressure for Siamese Twins to survive by some far fetched scenario that would meet your criteria. An entire planet or continent somewhere in the cosmos populated by Siamese Twins. Title of the book: The Siamese Gamble Subtitle: Two Heads are Better Than One [Answer] Taking a page out of nature, we could think of a Mantis' abdominal ganglion as a secondary brain being evolved. Perhaps, over time, a situation could arise where a secondary brain is necessary to reproduce. [Answer] This seems to be a question of why not one big brain. If a brain gets too big and too busy it'll get hot. To control the heat you have to expose more of the brain to more coolant (or colder coolant, which I take to be impractical). Stuffing more pipework in there spreads things out and so signals have further to travel. This slows things down. To mitigate that intrusion, brain work has to be localised by reducing the dependency on connections to other lobes. You just take the process of compartmentalisation and deeper intrusion of the cooling system until you've pushed lobes so far apart that they fit the description of "multiple brains". It's not just heat, of course. It's fuel and waste too. In fact, it appears that sleep is necessary to give the brain a [regular deep clean](http://www.npr.org/sections/health-shots/2013/10/18/236211811/brains-sweep-themselves-clean-of-toxins-during-sleep). Partitioning allows that maintenance cycle to be done piecewise. The supposition is that there are significant pressures to think fast on simple problems, to stay cool, and to stay awake. This probably comes about in an environment of competition with other creatures that are similarly capable. Rather than try to imagine a world with predators and prey and stars and satellites that force this condition, I'm just going to say it's a [secondary sex characteristic](https://en.wikipedia.org/wiki/Secondary_sex_characteristic). [Answer] I just don't see this coming up. You are essentially asking for a creature with a completely redundant brain. (This based on the creature having to manage effectively the same with one functioning brain or two; this requires one of the brains to basically not be doing anything, otherwise you'd quickly notice a difference between one and two) In addition, the brain is the control centre for the whole creature; having two brains would mean conflicting commands are being sent out if the two brains disagree. And since brains are constantly changing, they would quickly start running out of sync. On the other hand; if you have a true redundant brain, you are spending a lot of energy to grow and maintain a complex structure that does nothing. And if anything ever happens to your primary brain, the redundant brain will most likely not even be prepared to take over because it's essentially untrained (not having been fed any impulses until then) Not to mention that it'd be hard to trigger the redundant brain to take over from the primary one, since a trigger of that sort will generally be sent out by... the brain. [Answer] # Upper Limit on the size of the head Technically humans have two brains: One in the head, another(smaller, much less powerful) in the stomach. The second brain basically regulates function of the digestive organs, or something. Maybe it can be thought of as an outpost of the first brain, a small outcropping of nerves that need to be "where the action is," i.e. a field operation. Now imagine that evolution decides humans need to get smarter, but the head is already big enough to cause childbirth difficulties(this is the case). The solution is that the second brain gets bigger, and is used for "multi-threaded computation." ### Here would be an example of Multi-threaded computation: Such tasks would comprise situations when the primary brain can give the secondary brain a simple problem and a time allotment, and the secondary brain can solve it all on its own, without using the incredible faculties of the primary brain. An example is counting, or arithmetic: It's very simple to do(theoretically at least), and it does not require very much real-time data transfer between the primary and secondary brains. Basically, the primary brain sends some simple information(what's the prime factorization of 23856293698273325739248573029876129384762983462138741241234612394872649876219834?), where the number of nerve impulses needed to send the problem is relatively small compared to the complexity of solving the problem, and then the secondary brain works on it, and works on it, and works on it, and then sends back: The answer is 2\*3\*5\*7\*11 etc. etc., which is also a relatively small number of nerve pulses relative to the complexity of the problem. Now, imagine that the secondary brain gets bigger and more powerful as the need arises until it's fair to call it an actual brain as opposed to just a nerve cluster in the stomach. ### Disclaimer -- When you assume human brains are basically just squishy computers, it will be much easier to think about them, and also a whole lot more incorrect. ]

[Question] [ I have a creature or more accurately creatures that I have a problem with. I can't figure out why it is afraid of water. They are land based tiny tiny little piranha like organisms that work in unison. Each individual organism is about the size of phytoplankton and plankton. They work together almost like a hive mind but have no evil queen to rule them. Each individual creature is not intelligent and acts more on instinct and signals from others. Think of eusocial insects using chemicals and pheromones. Because you never see one alone and only in large clusters, they always appear like a low-lying mist or fog. Let's call a cluster of these creatures the *Mistraille*. --- Mistraille can consume all living plants and animals by entering the victim through a cut/wound/tear etc. and leave behind a desicated husk (I believe they consume everything, bones, muscles, all plant matter except the outer covering/skin but this can be changed if necessary). The plant/animal can still be alive when the Mistraille enters. After a time the Mistraille can actually move the animal around like a 'meatsuit' (this could allow isolated cases of Mistraille in areas not normally associated with it). A small amount of Mistraille enters the body, reproduces while consuming the body and emerges in greater numbers. The Mistraille therefore leaves a fairly desolate empty environment behind them. They appear to live in deserts — which came first, Mistraille or the desert? (rhetorical question). --- I didn't want an entire desert wasteland of a planet, so I have tried to limit Mistraille range by giving it **two major weaknesses**; light and water. Mistraille normally take cover during daylight hours, either by hiding deep in the desert sands, deep shadows (like basements, caves, inside empty shoes etc.) or in their latest victim. They are also physically constrained by large water bodies and can be temporarily repelled by water sprinkled at them (more on this later). **EDIT** I had already figured this would also limit their climate range as well. i.e. it would be limited to the dry, 'desert' mid latitudinal regions of the planet. Extreme variations in the day/night cycle, rain, humidity, and even soil moisture would hinder them. Equatorial regions would probably be too wet. High latitudinal areas can have deserts. If the Mistraille had managed to use a 'meatsuit' or darkness to travel there (by accident) it would then have to cope with the longer summer day cycles (only a brief dry night cycle) and the 'wetter' winter cycles. I still don't think high latitudes like tundra would be the best location. Same for the polar desert regions - 'eternal' day is not what this little critter is all about! **EDIT** See this climate map from Wikipedia as a reference to habitat location (thankfully this creature is not on Earth, so sleep peacefully!) [](https://i.stack.imgur.com/K11uU.png) **Two minor restrictions** are they cannot hide in or travel through rock/solid surfaces. Porous rock yes, solid rock no. Mistraille also cannot consume a victim from the outside. It has to get inside the body first. So any cuts, wounds, open sores are a way in. To further limit this I feel that natural orifices like mouths, noses, ears, bums, skin or plant pores should be off limits to entry (reasoning not completely worked out yet). --- **I need limiting factors to stop the spread and range of said Mistraille as well as some way to keep it at bay at night by 'intelligent' creatures.** --- ## Extra information in case it influences the answer I have figured out several constraints and reasoning behind their light weakness. * Mistraille actually are in deadly danger to any length of exposure to the UV spectrum of light. * Due to their limited exposure to daylight they have an unfounded fear of the entire visible spectrum of light (almost a Pavlovian response). * They can be repelled at night by artificial light sources such as fire, or modern day torches (it is the light not the heat that they avoid). This won't prevent the Mistraille from crossing the barrier of light if it really decides to go at you. * I have figured that the parts of the plants that photosynthesize during the day would be off limits. Therefore Mistraille can only hideout during the day in deep shadows, animals and in the more solidish parts of the plants E.g. tree trunks. (I know that there are light and dark phases of the photosynthesis cycle, but hopefully you get my reasoning). ## Related information to question In working out the details on water I have figured out some constraints **but not the reasoning.** * I want to limit their spread, so I made them unable to cross large bodies of water; oceans, seas, rivers, and perhaps marshes. Mistraille could possibly create 'bridges' to cross little trickles or very tiny streams. E.g. ants working together to cross a small river **but this might involve sacrificing those in the water.** * At night or in the deep shadows you can temporarily 'repel' Mistraille by 'sprinkling' water at them. A deluge would also work, but you are in a desert so you don't want to use all the water at once. --- What I can't figure out is why they are afraid of water! They go inside animal and plant bodies that are made up of a large proportion of water. How can I reasonably explain the fear of the one but not the other? **My question is: why are my creatures, Mistraille, afraid of water outside their victims but not when they are inside their victims?** --- I've been thinking that maybe the water would interfere with their hive mind communication, isolating each creature from the cluster. But how would they then communicate inside their victims? Maybe something in the chemical makeup of the victims body fluids could trigger a delayed transformation to a form more adapted to the fluid environment. But with that reasoning it can't be related to the freshness or saltiness of the fluid and can't be plant /animal species specific. **Hopefully you see my conundrum. I'm not looking for idea generation per se, just a somewhat valid reasoning on how I can explain my creatures actions. And if necessary alternate solutions.** --- **EDIT BASED ON ANSWERS & COMMENTS GIVEN SO FAR** These are very tiny creatures, so their body structure would be fairly basic and not too complex. (I don't think they would be similar or based on felides. Sorry!). Something along the lines of this image by Sanja Zamuda ... [](https://i.stack.imgur.com/Zaqq0.jpg) I had been toying with a caste structure but now think I will definitely need one. Highly eusocial creatures are defined as having a job role bases on the creatures body characteristics from birth. No changing a worker into a queen or a queen onto a worker. I believe Mistraille would be 'primitively eusocial' - their job roles aren't defined from birth, they can have multiple generations, shared care for the young, etc. So using that basis I believe I can make Mistraille have different sets of body characteristics based on the surrounding environment. When they are traveling outside any victims they could be fairly similar to each other. Each simple creature communicating via pheromones and the larger collective consciousness a sort of hive mind with no queen directing any actions. These outside Mistraille move by either crawling/hopping or 'flying' on very basic proto-wings. No swimming. The best image I have, in my head, is the classic [sediment transport](https://riverrestoration.wikispaces.com/Sediment+transport+models) image by bouncing, rolling, dragging, and suspension etc. It is this 'outside' form that would be the most vulnerable to light and water (a holdover from their 'inside' forms?). When they encounter a victim, they enter and then this would trigger a process of transformation to occur. This transformation would result in a better adaptation for 'liquid' interiors but the reasoning so far of narrow osmosis range/required toxin would still hold (or a similar reason not yet mentioned). They could transform into several specialised body types suited to what they are munching on E.g. animal or plant AND bone, muscle, organs, plant fibers etc. They would also lose any proto-wings they have and develop 'claws', 'razor sharp teeth' and 'swimming' abilities. The 'nests' where the Queens and child-rearing occur would be in locations safe from light (so in plants, in the protected areas not involved in photosynthesis). As I mentioned before, this transformation requirement from 'travel' mode to 'attack' mode (as @Drenzel called it) would explain why they can't eat a victim from the outside. It could also explain why natural orifices are off limits. They would still communicate by chemicals and pheromones but might be directed by several Queens. I don't believe the hive mind is as developed as each creature knowing and experiencing the others experiences (as these are very simple creatures) but rather each individual creature influencing and been influenced by the collective consciousness. --- **THANK YOU VERY MUCH FOR THE ANSWERS SO FAR** I'll be taking a little bit from most of them. [Answer] As a hive mind species, one of their greatest fears is isolation of the individual units from the rest of the hive, this would often mean death for the individual units, and if all of them are scattered, death for the hive. Large bodies of water, especially flowing or moving water (rivers, waterfalls, waves) have tended to separate them from one another, killing or severely injuring those hives who encounter fast moving water. Over time they have developed an innate fear of all large concentrations of water, but especially indications of fast moving water. A misting of water, especially a directional spray, often corresponds to a large moving body of water, like a waterfall or river rapids. This signals one of their primal fears, causing them to contract as a group and retreat from the source. [Answer] > > Maybe something in the chemical makeup of the victims body fluids could trigger a delayed transformation to a form more adapted to the fluid environment. But with that reasoning it can't be related to the freshness or saltiness of the fluid and can't be plant /animal species specific. > > > Let's not be specific, then, and let's look at something that does kill some animals in our own real world. [Osmosis](https://en.wikipedia.org/wiki/Osmosis). The salinity of our bloodstream is different from that of most bodies of water. The same can be said for the sap in plants. That's because living beings accumulate many different ions in their organisms to some extent, but also eliminate excesses to some extent. For example, our blood has as much salt content as [saline - 9 grams per liter](https://en.wikipedia.org/wiki/Saline_(medicine)). For salinity purposes, our blood is within the range of [brackish water (between 0.5 and 30 grams per liter)](https://en.wikipedia.org/wiki/Brackish_water). That's [more salty than fresh water, but less salty than seawater](https://en.wikipedia.org/wiki/Fresh_water#Numerical_definition). So let's say that your Mistrailles have a bodily salt content like our own. But unlike many animals and plants, they can't regulate the salt in their organisms like we do. The range of salinity they can tolerate is narrower. If they are immersed in drinking water, their cells will each individually absorb a lot of water and pop, just like our own red blood cells in a cup of drinking water. You could also see this happening to a sea jellyfish if you take it out of the sea and place it in a bucket full of drinking water, but if you do that you have no soul. If they are immersed in seawater, the water will run out of their cells and they will die dehydrated. Just like our own red blood cells in a cup of seawater. You can also see this happening to a [river hydra](https://en.wikipedia.org/wiki/Hydra_(genus)) (poor [cnidaria](https://en.wikipedia.org/wiki/Cnidaria) have very narrow salinity ranges they can live with) if you take it from a river and put it into a bucket full of salty water, but if you do that I am going to dennounce you to PETA. And that's why they can't stand water, unless it has been carefully treated to have exactly the amount of saltiness they will tolerate. You should probably be really careful around your Saline IV storages. [Answer] They communicate through chemicals in the air, and I think this is the solution. While flesh contains a lot of water, it mainly isn't in a liquid state, being stored in the tissues. Even though blood is liquid, it isn't an excessive amount. Any chemicals that they release to communicate with each other and keep their hive mind like link going are going to be contained in their victims body. But a river or a large body of water would dilute and wash away all of the communication chemicals cutting them off from the rest. Being a very social creature, this silencing effect is very disconcerting for them, causing a lot of fear, and so they avoid it instinctively. [Answer] One option is that the water is mostly fresh and the Mistraille can not manage cellular integrity due to osmotic pressure. The salt in their systems would leach out and water enters in killing them if they are immersed. The blood of the host contains a similar amount of minerals / salts but entering the fresh water causes their cells to burst. Even sprinkling of water greatly weakens them, stopping them from entering the host. Salt water could be missing important salts / minerals or contain predators that like to eat them. The water could also contain viruses or bacteria that are deadly to the Mistraille but that the host immune system destroys. Either way this shall fuel my nightmares for some time. [Answer] Consider that, like their irrational fear of general light because of a vulnerability to a specific range of light wavelength, the Mistraille are only vulnerable to something commonly found in the world's water bodies. In that event, any of the following could apply: * Natural predator lives in or near bodies of water (believability: low-moderate; why is a natural predator of a desert creature dependent on bodies of water?) * A toxin is released by flora or fauna that appears frequently around bodies of water, but the amount in the water is only a danger to very small organisms; larger organisms filter it out and/or tolerate it (believability: moderate-high; some creatures are immune to Mistraille because they let the toxin into their blood, others store the toxin in an organ they avoid) * Mistraille are dependent on a toxin that must exist in the right quantity within an organism and the toxin breaks down quickly in bodies of water, so organisms don't have a chance to absorb it (believability: moderate; kind of sounds like the Mistraille are an engineered creature run amok intended to clean up an industrial spill) [*courtesy AmiralPatate*] *These were off the top of my head. If I come up with any more, I will add them in later.* [Answer] > > They can consume all living plants and animals by entering the victim > through a cut/wound/tear etc. and leave behind a desicated husk (I > believe they consume everything, bones, muscles, plant matter except > the outer covering but this can be changed if necessary). > > > They need a `cut/wound/tear` to enter victim but they can consume bones, that may be because they have two different "stances", lets say **migration** and **feeding** so when they are in migration mode they have a normal solid shell-type body, but in contact a liquid they dissolve like a slime which is useful to enter in other organism via circulatory system and just dissolve/control-it but not so when you just spread away in water with huge solubility and nothing to feed of. [Answer] Well, do your creatures crawl, do they fly? Can they swim? Can they "breathe" underwater? **Maybe they can fly but just short distances.** Too short to cross a large body of water. They'd drown. So they don't even try. Just like a grasshopper (insert any short-range flying creature) wouldn't try to jump over a mile-wide river or an ocean. **Maybe they can fly long distances** but they can't dive into the water (because they can't breathe underwater or because it hurts them otherwise), so they know that they would starve over a sea or ocean, like locust. **Maybe they can even swim/dive** but they are really slow and it's hard to catch fish for them so why bother when there's easier meat on land. [Answer] A major plot point in the novel *[Fragment](https://en.m.wikipedia.org/wiki/Fragment_(novel))* is that (significant spoiler warning!) > > salt water is fatally toxic to the Henders Is. wildlife, seemingly on contact, due to osmosis action. > > > The novel is an interesting read in its own right, but may be especially useful for your project. Some additional thought or incorporation of other ideas suggested may improve this point to apply in your built world. [Answer] Maybe water makes them unable to move? Dry sand or flour can be even moved by wind, but it sticks together when wet. So when you spray water at them, they stick to each other and fall to the ground. And in the larger bodies of water they have trouble keeping together. But in the human body they either slowly move inside the muscles/other solid things (while eating them) or are transported by the blood flow. [Answer] They are a group, and they are small so they might not want to go in water because: 1. They get split, and a single mistraille would probably die 2. On land, they can easily see predators coming but in the water they move so fast they might accidentally land in the mouth of a predator [Answer] I think they might be scared because water is the only fluid that cleans their surface from hormones, or something like that, that they need to orient itself and that might cause death, while other fluids like blood don't do that. For example, scout ants leave a trace of hormones when looking for food, so when they come back other ants can follow the trace an bring food back, lets say this "cretures" have hormones all around its body that they use to find their own, or the hormones may do many things like give them a sense, for example if we don't have saliva, we lose the taste in our tongue, these are just some ideas without closing so you can do the rest ]

[Question] [ Usual Joe wakes up in his apartment somewhere in New York, USA. He realizes that on this desk is sitting new printer, which appeared out of nowhere. Joe tries to press print button and the printer prints sheet of four 100 dollar bills: [](https://i.stack.imgur.com/pDYu0.png) *Image source: [What-if XKCD](https://what-if.xkcd.com/23/)* He cuts out the bills and cannot see any difference against "usual" paper money in his pocket. Joe calculated that it took about a minute to the printer to print the sheet and to cut out the money. [](https://i.stack.imgur.com/PMWyk.png) *Image source: [What-if XKCD](https://what-if.xkcd.com/23/)* While sourced What if XKCD says: > > Your extra two million bills a year would barely be enough to notice. > > > I cannot believe it. And neither does Joe. He tried to pay with first 4 bills and all of them were accepted. But Joe does not know mechanics of the printer (and does not want to tinker with it for obvious reasons). For a moment lets assume that the printer works perfectly with one little flaw: It has 1:100 chance to hit already existing serial number printed on the bill. Otherwise, the bill passes all possible checks for counterfeit money. The printer is "plot device" now, so it runs on magic and unobtainium. Otherwise we are in "Current world" **How plausible is that Joe will get caught?** [Answer] # It Depends It depends on your spending patterns. For small amount where cash is a common payment method (meals, small good, etc.), the chances are you'll never get caught. When bills enter general circulation, the origin for the serial numbers are pretty much untraceable unless you attempt to use a bill that's been declared as stolen - the Treasury will track the serial numbers to the point at which they enter circulation (ATM/Bank/Salary/whatever). If a bank is held up and a bill serial number that's involved in that robbery is traced to you, you'll get investigated (and people will wonder about your cash-rich lifestyle). For larger purchases, you'll need to deposit those bills into a bank or find someone unscrupulous enough to accept a huge roll of bills and not ask you where that money came from. If the IRS (or whatever the tax gathering authority is in your country) sees that you have a mighty fine house/car, they might start wondering what your income is and whether you're paying your taxes. You might also be investigated for money laundering. The larger the amount you spend per transaction, the greater your chances of getting found out. [Answer] How plausible it is that Joe gets caught really boils down to how Joe acts with his new found wealth. If the machine really does print perfect fakes, he's not going to get caught directly - it won't be a counterfeiting investigation that brings him down. Even if he ran the printing press non-stop, he's not going to put out enough to make a noticeable difference in the money supply, and it's not as if the serial numbers from his fake bills are going to be compared against some government database of bills that have actually printed (a fact that intelligence agencies and other governments rely on when printing their own fakes), so we have basically negligible odds of the printing press operation bringing the Secret Service to Joe's door. Having said that, it's not actually easy to move large quantities of cash around without someone noticing, and it's probably the tax man that's going to Joe's biggest threat. Joe's either going to need to find a good way to launder large amounts of money (which, in and of itself is a problem that can bring the authorities to Joe's door) or show enough restraint that he's able to fly under the radar, because if the authorities show for another reason, it's safe to assume that they won't take kindly to his magical printing press. A smart Joe would probably use the printing press conservatively to pay his bills, start a business of some sort and set himself up so that several years down the line, he'll be a successful business owner who can live it up without raising eyebrows. Which, of course, means the odds of Joe getting caught are probably rather high. That level of restraint and patience are pretty rare, and the temptation here is pretty large - the vast majority of people are going to spend too much, live with with too much of a profile, bring the IRS or the cops sniffing around, and end up in jail for their counterfeiting operation, especially considering that the bills are essentially undetectable as fakes. [Answer] You are asking two questions: How fast will government realize that I am printing money? And, how plausible is that Joe will get caught? As for "How fast will government realize that I am printing money?" it would probably take around 9 years, as that is the average lifespan of a $100 bill. In 9 years, you would print 18,921,600 bills. Since there is a 1 in 100 chance the bills will have a used serial number, there should be 189,216 bills that go back after 9 years and get flagged as counterfeit. As for "And, how plausible is that Joe will get caught?" I agree with @Pete, it will depend on how smart he is. In *theory* he could print until the US Treasury changes the currency to no longer match the counterfeit bills. [Answer] I don't think that the government will realise that you're printing money by the volume of cash - as XKCD says, it'll hardly make a dent in the economy. What is likely to be the issue is how you launder the money - becoming a regular at the casinos might well be a good idea.*(Edit - apparently it isn't, in the USA at least)* Unless you have a good and believable reason as to how you got hold of all of the money you now possess, then you might well get caught that way. Your other option of course is to spend it all in pawn shops and buy up a huge quantity of precious metals, gems, etc and then take it all to a non-extradition treaty country, sell your jewellery and live like a king. [Answer] HopelessN00b's answer inspired a thought in me- with undetectable fakes, the bills aren't the biggest liability of Joe's ruse; they'll never be proven to be false, and once they wear out and get decommissioned, there's little to no chance there's a paper trail leading the bill back to Joe. His largest liability is the *printer itself*. Since the bills won't be noticed, his biggest problem is either his own mouth or the mouth of a friend (or anyone who gets into his house). He might tell someone; the plumber might come in and see his magic printer and tell someone; a romantic interest sees an odd printer in the living room while making breakfast, presses a button and now has a lot more information than s/he could ever want about Joe. And Joe has a problem. To answer the question of "How plausible is it that Joe gets caught?"- the answer to that depends entirely on Joe's character, and not at all on the money he's printing. If he never talks to anyone about anything and never lets anyone in his home, he'll probably never be caught. On the other hand, if he constantly has parties with many loud people, he's almost guaranteed to be caught. On the other hand, if he has a guilty conscience he may rat himself out, though an amoral Joe could live a perfectly social life and be fine as long as he keeps his printer hidden or doesn't let people into his house [Answer] Since you've said, > > It has 1:100 chance to hit already existing serial number printed on > the bill. Otherwise, the bill passes all possible checks for > counterfeit money. > > > the chances he'll get caught are GREATLY reduced. In fact, I'd say the chances of getting caught were practically non-existent. Since the bill "passes all possible checks for counterfeit money" it would be impossible to say which note was fake, even if the duplicate was spotted. The only thing that would give him away would be shops in the same area paying these mysteriously good duplicate serial number notes into their banks. (Obviously they won't be given out as change, so they will always be paid into their banks every week, where they will be checked to see if any are counterfeit.) Fortunately banks are highly unlikely to check for "duplicate" serial numbers, as there's zero reason to believe it isn't the original. (They're more likely to search for serial numbers known to have been stolen.) And since the notes are otherwise flawless, there's no reason to think they would EVER be flagged. So Joe's chances, in the situation you have outlined, are next to perfect for him. Provided he's not investigated for money laundering, he will be fine, and good to spend the money anywhere he likes. [Answer] **Joe will be caught as soon as he starts to trust that he will not be caught.** Joe is a fairly intelligent person, so at the beginning he will be careful about what he spends his money on. Soon he will realize that there is no way to find out that it is false money, and if it is ever detected that there is a duplicate, it will not be possible to relate to him. So he starts to be more daring spending money. 400 dollars a minute, 24.000$ per hour... well worth going out to celebrate!!! And that's how the things started to mess up.... [Answer] As others have answered, the government is unlikely to notice Joe's printing operation by itself. Since the bills are undetectable as fakes, they won't notice that there are fakes in circulation (they might find the 1/100 duplicate serial numbers, but by the time they do there will be no way to trace it back to Joe). Joe's biggest problem will be in actually using the money. The whole reason the US mint does not print bills larger than $100 is because they figured out that the only people who would regularly need larger bills are criminals. Legitimate business is done through electronic transfer and actual paychecks are done by direct deposit or check. No realtor or car dealership are going to accept a wheelbarrow full of cash without raising a lot of questions. If he suddenly becomes a regular at his bank depositing large sums of bills, there are going to be even more questions. Banks actively watch for suspicious activity like this. The authorities are going to want to know how some random guy living in a New York apartment suddenly came into so much cash. This is going to trigger an audit and investigation that will eventually lead to the Secret Service, FBI, and/or IRS getting a search warrant for his apartment. How quickly that happens depends on how stupid he is with the money. Joe's only chance is to spend modestly and spread the money around enough to keep any one person from getting suspicious. He'll have to keep his day job. If he was having trouble making rent each month, he can probably remedy that, but not much more. [Answer] This is to help Joe to succeed. Joe needs to do laundering. However, he has an advantage. He doesn't need to move the money, moving the printer will not draw any attention to him. An easy laundering method would be the following: Joe should go to a country where you could get precious gems directly from dealers. He should sneak in the printer to, say, Republic of South Africa. Print dollars, find a guy to accept his cash. Sneak in the diamonds. Sell them as family heirlooms. Obviously this will work only once. Another method would be paying larger sums of money while showing officers that he paid less. This will keep him in business. As long as he doesn't want to be next Bill Gates, he could keep this business to live an easy life. [Answer] I've read a novel once, similar to "Groundhog Day". The difference was the guy belonging was "reset" so he only had the amount of money on him he had when he went to sleep. So he had the same bills the whole time. So he devised three ways of "laundering" them. One was to make a small deposit in the pawn shops the same amount every day so after a while he taken out not 5 20 dollar bills with the same number but one 100$. He figured out the money he give to clerk will be spend on the same day so they can't compare them. Second was to buy stuff and then return it with money transferred to his account (the money was not there but the shops and bank had the papers to prove the cashback was made). And third one was just to ask random strangers to change money into some kind of cash tokens (gift cards, parking tickets, checks) and then use those to accumulate the money. Further more if the chance is 1:100 it means that in every 10 thousand there will be 100 duplicates. So he could just sort the numbers himself and leave one of the twins in the drawer. [Answer] One plausible way to evade detection I don't see mentioned is to turn nomad. If you are moving around a lot and spreading out where you spend the money, there is a lot less chance for anyone to notice that you have too much of it. Particularly if you hit touristy type destinations and make sure your purchases are scaled such that providing change is not a burden on the merchant. Play it right and you build up a nice stock of legitimate small bills to compliment the unending 100s. Forking over a hundred for a $75 ski package at a ski resort in Vail is unlikely to raise any eyebrows. Then two weeks later you head over to LA and hang out on the beach. The folks you spend money with in California are not going to know you just spent a couple weeks living it up in Colorado, and it is not unheard of for people on vacation to work with cash as a means of staying on budget. [Answer] Does Joe have to stay in the US? Perhaps he can move to a country that won't look too closely at him if the right bureaucrats are greased, where he can pay for most things in cash and import whatever else he wants through the black market. In that case, he can live a pretty opulent lifestyle and the US will just assume he's a drug lord, if they notice him at all. [Answer] Joe will get caught pretty quickly. Most merchants don't spend \$100 bills. They just deposit them as they do with checks. Most cash registers don't have spots for \$100 bills. And since most people spend cash fairly consistently, all of Joe's \$100 bills will go to the same (more or less) merchants. Since all merchants will deposit the money in the same banks, statistically, it will be easy to track the money back to the the merchants. Now if Joe was not living in NY, but travelling a lot, that would make tracking him much more difficult. Again, I am accepting the plot premise that the bills are printed to perfectly match what would be printed by the mint. [Answer] While most people seem to believe you would get caught with the money laundering ... I think you could actually make it work. So the first thing most people are talking about is that you would get caught for suddenly being flush with money with no way to claim the income. However, that is with the very large assumption that you are planning on spending the US currency in country. There are rules and regulations about moving large bags of cash in and out of country ... but if you moved the printer out of country you could spend it rather easily. US currency is widely accepted in a lot of other country's. You could go on vacation for the rest of your life and use random currency exchanges all over the world and no one would ever question you wanting to exchange 5k USD for the equiv of the local currency of the country you are in. Furthermore if you did want to stay in the US it wouldn't be that far fetched that you are "working" as a remote contractor for a business in a foreign country. You could setup operations in another country laundering the money and earn a monthly salary ... pay taxes on it ... and fly completely under the radar for a very long time depending on the country your "employer" is in. Even if you didn't want to ever leave the US, you could avoid spending the actual printed bills by exchanging them for [Bitcoins](https://en.wikipedia.org/wiki/Bitcoin) and making use of a [Visa backed Bitcoin Credit Card](https://bitpay.com/card/). I don't think it would be too terribly hard to exchange a large bag of 100$ for the equiv in Bitcoins if you where willing to pay a 50% "processing" fee ... and lets be real, if you could make 1 mill a year with zero chance of ever being caught ... the "processing" fee would be worth every penny. [Answer] Joe needs to focus on gold. It is quite possibly the easiest way to launder money and surely the easiest way to keep wealth in case the magic machine disappears or malfunctions. Where as precious gems, paintings, artifacts, whatever are easily traceable and by and large there would be word out on who purchased something like that. Gold just isn't that interesting and it melts. Meaning that Joe can stash away huge chunks of gold in a bank (several of course) or even a forest. The problem is if Joe spends most of his life printing money he will surely be caught because that is just a shitload of money and there is no way to hide it. It isn't about the "money". If the fakes are "real" fakes then there isn't much anyone can do save for watching him print from his machine. (I am assuming he puts machine in safe and it self destructs if someone breaks into the safe). So really the issue isn't the money or the government finding fake bills. It is what does he buy to not draw attention from the government or even worse some low life thug. Any kind of laundering using "friends" or "experts" will certainly lend Joe to more risk plus he still has the same issue... what the hell does he buy. That leads us back to gold. Joe needs to be an expert in gold. He needs to move to a large city and eventually open up some sort of jewelry or pawn store. He needs to befriend secondary market sellers. He then needs to start melting all the gold down. Joe then needs a "plan" to find the gold. He can do anything from opening his own mining operation, he can act like he found a stash of bars, he can take up a life panning, whatever. It just needs to be somewhat plausible. Not even straight out believable because the fact is no one can disprove his bars came from something else... gold is gold. [Answer] It is very plausible that Joe will get caught. US currency uses a paper made of a blend of 75% cotton and 25% linen with added red and blue synthetic fibers (see [this PDF](https://d39pc38av48c2g.cloudfront.net/sites/default/files/security/pdf/100_2013_Features.pdf) for more information on security features of the $100 bill, such as an embedded thread that glows pink in UV light). This blend of paper will feel different from standard home/office printer papers, which are made from wood pulp. Furthermore, US currency uses the intaglio printing process, which results in slightly raised ink on the surface of the paper. This process also causes the paper to be slightly thinner, due to the pressure used to press the ink into the paper. The raised ink also affects the feel of the paper. Bank tellers are trained to recognize counterfeits by feel, so Joe would need a source of rag paper and hope that his mystery printer can mimic the results of the intaglio printing process. Otherwise he would quickly be found out. Using existing serial numbers actually doesn't seem to be a problem unless the person handling the money has two bills with the same serial number in hand. In fact, not using existing serial numbers would likely mean the serial number is out of the range used for $100 bills. And while the clerk at a store where people are likely to buy over one hundred dollars worth of goods might not recognize that the serial number isn't legitimate, the teller at a bank will likely know the range. As others have pointed out, it is how Joe spends the money that will be the biggest cause of whether he gets caught or not. The more he uses his counterfeits, the greater the chance that someone will recognize them as counterfeit. If he tries to pass the bills off to family, friends, or coworkers, they may very well remember that it was Joe who loaned or gave them the bad bill if it is discovered as counterfeit. In fact, Joe would be less likely to be caught if he counterfeited $1 bills as there are not as many security features to deal with. Granted, Joe would make considerably less (and depending on the cost of materials may end up losing money), but he would also have other benefits. Lower denomination bills are scrutinized less, which means a greater chance of successfully passing off the bills. There are more places to spend lower denomination bills without raising suspicions, which gives Joe more avenues for passing the bills. And making less money through the counterfeiting operation would reduce the temptation to splurge and, thus, lowers the risk that Joe's spending habits reveal his operation. [Answer] The government acts like Mafia, or big Gangs. If you're poor, they don't bother you much. If you're rich, they will want their cut and will do anything to get it. With the above being said, the government will start investigating your source of income and whether they're getting their cut/tax or not. So the chances depends on the individual's intelligence. If the individual is intelligent enough to convince the government that the income is legal, and that they're getting their cut, then the chances are extremely low (i.e. money laundering). If the individual doesn't care and just wants to spend money, and doesn't make any effort to deceive the government, then the chances of getting caught is extremely high. ]

[Question] [ I'm considering a story set about fifty years (2065) in the future. It takes a rather optimistic view; space exploration has led to colonies on the Moon and Mars, as well as several space stations orbiting Venus for scientific purposes. There are currently several exploratory missions planned or in progress for the Jovian and Saturnian moons. The main form of travel is still chemical rockets, regrettably, although ion engines have recently become fashionable since larger quantities of thrust were achieved in 2058. We can get from Earth to the Moon in two days and Venus or Mars in three months (suspend your disbelief). The majority of travel takes place using the following method: * Small single-stage-to-orbit reusable shuttles are taken from the planet/moon to a space station complex in orbit * Larger ships propelled by boosters then go to space stations at the next destination, where more shuttles take the crew and/or cargo to the surface. Piracy is now back in style, despite many attempts to stop it using shielding and even onboard weapons on the interplanetary ships. My story in particular focuses on one particular group of pirates focusing on the Earth-Mars run. However, I need to know if this is at all practical. Piracy in space is harder than piracy on the seas because orbital trajectories are, I'm guessing, much harder to change, and fuel is limited in the smaller, compact ships pirates typically use. This one uses an experimental ion engine, with enough energy to get from Earth to Mars *and* back. From an orbital perspective, and taking the limited fuel reserves into account, is piracy in space feasible? If it is, where in the trade routes is the easiest attacking point - closer to the planets, where the pirates still have plenty of fuel, or out in the middle of space, where there are no other ships to stop them? --- Kys pointed out in a comment that it might be better to switch propulsion systems - that is, have the pirate crafts use chemical rockets to make sharper maneuvers possible, while the large freighters use ion engines that they use to slowly accelerate. I'll probably go with that in my final story, but I don't want to change the premise; that would invalidate at least one answer given already. Any future answers should still assume that the large ships use chemical rockets. [Answer] # Just because you can see pirates coming, doesn't mean you can stop them I'm going to make some assumptions about how your spaceships work. The average distance from Earth to Mars is 225 million km, and travel time is 3 months. Average speed is 29 km/s. Geostationary orbit has orbital velocity of 3 km/s, so you need a 1g burn for about 45 minutes to gain 26 km/s of velocity. You'd be looking at a similar burn for deceleration, so almost all the 3 month travel time is just coasting. If you are a pirate, and you can blend in with other merchant traffic, you could do a 1 hour burn a day or two later and overtake your victim mid-transit. At this point, there are a series of questions to determine if this sort of piracy is economical. I call it a choose-if-piracy-is-right-for-you adventure. 1. Is there an agency keeping a clear enough space picture to determine when one merchant has plotted a suspicious overtaking course? If yes, go to 2, if no, go to 4. 2. Can the merchant ship effectively defend itself to the point that it can potentially cripple the propulsion system of attackers? If yes, piracy is not possible; if no, go to 3. 3. Is there a naval vessel that is willing to do a 75 minute burn after the suspected pirates? If yes, piracy is not possible, if no, go to 4. 4. If piracy occurred, is there a place to fence the goods (see the asteroid belt in every space opera ever), even if it is known that piracy occurred? If yes, then piracy is possible, if no then go to 5. 5. Are the vessels manned and will insurance cover the cost of a ransom? If yes, then piracy is possible, if no, then piracy is not possible. The moral of the story is: piracy could certainly be detected, and would be detected. After all, it is basically always detected on modern earth. But for ships in the Bab el-Mandeb, even if they can see the pirates coming an hour away it that doesn't mean they don't get pirated. Unless they can shoot back, or the Navy is also an hour away, they are toast. Same thing on month-long time spans in space. If you can see the pirates will overtake you in 3 days, but no one can come to help in 3 days, you can still get pirated. All the pirates need is somewhere to off-load the booty. [Answer] Building on Hariz Rizki's answer, your actual space pirate isn't going to be a swarthy, one legged man in a spacesuit with a parrot on his shoulder, but rather a well dressed functionary at the Deimos space dock waiting for you with a clipboard in hand. [](https://i.stack.imgur.com/FppLd.jpg) *No one will suspect* [](https://i.stack.imgur.com/x9F78.jpg) *Quick, find the space pirate* Building spacecraft is difficult and expensive, launching and manoeuvring a ship in space is going to be noticed by *everyone* (no stealth in space) and you will have a very limited number of places where you could go to offload cargoes and sell them for profit. Indeed, since your ship will be highly visible and tracked from beginning to end of its flight, the most likely outcome is the pirates come into the dock to be met by a heavily armed task force of police, coastguard and customs agents..... Stealing or diverting cargoes from the dock provides a lot of advantages to the would be pirate. *You* have already done the very hard work of launching the cargo from the planet and transporting it to the pirate's lair. Since the pirates are already at the dock, they have had ample time to examine the security system, find buyers, bribe the appropriate people, hire some muscle in case people don't stay bribed and so on. An even more ambitious and clever space pirate might even be getting the hapless ship's captain to load stolen cargo on board at Mars for the return flight to Earth, where his equally unscrupulous counterpart is waiting at the space dock. [Answer] Lots of people here, including the OP, are worrying over the capabilities and tactics of space pirates, but the question fundamentally deals not with those particulars, but rather the economical and political situations which lead to endemic piracy. > > Piracy in space is harder than piracy on the seas because orbital > trajectories are, I'm guessing, much harder to change, and fuel is > limited in the smaller, compact ships pirates typically use > > > Set trajectories makes the job of a pirate a simple matter of obtaining shipping timetables or, failing that, waiting patiently along vital routes. See [Train Robbery](https://en.wikipedia.org/wiki/Train_robbery). > > From an orbital perspective, and taking the limited fuel reserves into > account, is piracy in space feasible? > > > If official ships can get there, so can pirates. What do you think these guys do, legally build or buy their ships? Hardly. Historically, they usually: 1. Mutinied aboard legal vessels, marooned or kill the loyal crew, and turned pirate. 2. Purchased a legal vessel and refitted it with legal antipiracy weapons, posing as legal businessmen. 3. Obtained letters of marque from governments, commissioned privateering vessels with the assent and even support of a navy, and then promptly ignored papers and flags on the high seas. None of this matters as much as the economic and political climate in which all this spacefaring is occurring. For piracy to exist, we must have * long-distance goods transport * an unpoliced route * a fence for stolen goods, usually in the form of a corrupt polity of some kind * enough economically-distressed and transport-skilled population to man said transportation * profit commensurate to the act If any one of these, with the possible exception of policed routes, fails to obtain, then piracy will not arise or continue. The policing of routes is a matter of degrees, and as work in the Indian Ocean against Somali pirates has shown, armed guards and national navies don't necessarily solve the problem alone; steps were instead taken to eliminate the fence and long-distance goods transport in the area, which was probably just as, if not more, effective in clearing up the area. Air piracy did not obtain the same heights as aquatic piracy because the population capable of crewing aircraft was more tightly regulated and better paid than the population tasked with crewing sailing ships. This would also be the primary problem with space piracy, so your story needs to come up with an explanation for a rather sizeable population of destitute astronauts: * robots/corporations/nations/aliens took our jobs * fuel costs have risen drastically, so shipping jobs are down (but a few very profitable targets still ship - like shipments of that newly expensive fuel!) * large numbers of military crew are destitute after their nation's defeat in a space war * an economically-disadvantaged nation at war begins issuing letters of marque to enterprising mercenary pilots etc. Those guys need transports to pirate and a relatively unpoliced area to operate in. Those are obvious - spaceships are the transports, and space is the relatively unpoliced area. Those pirates also need a profit incentive, so we can't be shipping paper here - a high value to mass cargo would be ideal. Unrefined products are not as appealing as ransoms of the ship or its passengers, or things like heavy machinery, rare crystals, etc. Finally, these guys need a fence. This is a company, nation, alien race, marketplace, or other means of taking very obviously ill-gotten goods and turning them into an ostensibly legal profit for the pirates so they can enjoy the good life back home. Either that or, as in the caribbean, you need the life itself to be "the fence" - many of those pirates were going to die if they ever returned home, so living on the high seas off the things you take from other ships seemed like a relatively good deal - these are the odd pirates that aren't stealing your gold bullion or slaves - they're chasing down your rum shipments, bulk corn haulers, and gun transports, just scavenging to keep themselves going a while longer. In that case piracy itself is the fence for a desperate profit - life itself. I focus on the economics and politics of piracy because honestly, human criminal ingenuity will overcome most all obstacles placed in its path if the payout is high enough. TL;DR all you need is for the conditions to be right, and you WILL have piracy, no matter how hard the act itself is. [Answer] I says it can be possible albeit in non-full-thrill-action way. Why you hijack a space ship conventionally like a traditional pirate hijacks a boat when you can hack them through with your keyboard? A space pirate wouldn't be like their traditional counterparts because to be one you need the skill sets to self/small groups piloting an interplanetary ship undetected, while normal ways (nowadays) require a group of people counting the complex equation and trajectory to just send a rocket (NASA and other space exploration organizations). A group of bright people like that would logically first try to breach the communications systems of ships to alter their routes (also disabling manual control) to their desired target (their 'garage') and then in their safe location they can dismantle the ship, kill or taking hostages, and take the valuables without putting their lives in space danger. [Answer] ### Counteracting piracy, ship vs ship piracy Let say, nowadays it became possible to hijack a plane using a fighter jet. (one person from fighter jet moves from the jet to a plane, and forces all them to obey commands) Now there is a question, what happens with that fighter jet. If those pirates have unlimited supply of those jets and crew for it - then no problem, proceed. But if they don't, how fast missiles will end that piracy, it just depends on how much of those jets the pirate have, because missiles will be not a problem. The main problem is not how much it costs to change the orbit, but how to get away at all. [Spitzer Space Telescope](https://en.wikipedia.org/wiki/Spitzer_Space_Telescope) took a picture of [2011 MD](https://en.wikipedia.org/wiki/2011_MD) in infrared at the distance of 0.14 a.u. More about that [here](https://arxiv.org/pdf/1406.5253v1.pdf), but in short it is a 6 meter in diameter body, which emits about 38kW(my estimation, solar radiation) of heat near earth orbit(it was close passing-by asteroid). 0.14 a.u., 38kW heat source, half broken space telescope(coolant ended in 2009) If the ship, which has been attacked will manage to send a stress code, there is no chances for pirate ship to hide. You have to have one telescope per one pirate act for time until pirate ship will be hit by a missile. An example if there are 10 piracy acts per year it is enough to have one telescope, if there are 10 per day, then probably 300 will be enough. Telescope weight 11 tonnes, so about 3000 tonnes in space is enough to guide your justice across the solar system, if it is worth of doing. ### Changing orbit cost, profitability Another point is selling the items. If rockets as we know them still in use - the item which is shipped have to cost a lot in place where it is transported to. I doubt it will cost the same in place where it is from. SpaceX ITS projection is 140'000$ per tonne for shipment from earth to mars. It is a lot actually, probably makes sense for not everyday items, it is hard to sell them. Specially pirate should spend another 140'000 for propellant to return that cargo back, and up to that sum of money to redirect the cargo, which probably have serial numbers on most of its parts. But what is more profitable, is to send a missile/mine which intercepts the target ship and sticks to the hull. After that they may have a few month to negotiate the price for release (somali piracy in space). Deploying those mines-missiles is done long before actual thing will happen, by dumping cases aboard from usual ships(contraband). And one of the goals for piracy to have good enough network of such devices, so that they will have one of such at proper time in proper place. Second goal is to hide those things, because a countermeasure again is the detection, space telescope. And there begins a game of cat and mouse - who is better mouse or the cat(telescope). If there are gaps in the system, and pirates know them (position/orbits of detectors, which and were at which time looks) there are options to hide mines in case if coverage is not full all the time. Problem is that the telescope is pretty small, just 11 tonnes, I guess it is possible to fit to any ship. But depends. To negotiate release price pirates even do not have move a thing, just by saying we can do it, do you wish to check that. [Answer] My answer is either a counterpart or counterpoint to @Thucydides's answer. The key to space piracy is **the docking and other stable facilities in space**. * # Option #1 - Attack ships when they arrive at, or leave, the docks. What's the point of chasing ships through 3D space, when they all start and/or end up exactly in one of a few fixed locations anyway? And are moving slowly when close enough to the facility - slowing down for docking or speeding up from a dead stop when leaving. **IRL Example**: Playing Sid Meyer's Colonization. That's realistic, right? * # Option #2 - Directly attack the docks/ports If you find a dock/port facility that isn't heavily defended, you can simply outright raid it using good offensive weaponry. **IRL Example**: Captain Morgan attacked and sacked Portobello * # Option #3 - Blackmail 1: a threat of attack on facility itself Even if your aren't strong enough to sack it, the cost of paying you off is very likely FAR cheaper than the cost of damage due to your attack (materials destroyed, people killed, opportunity costs of recovering from the attack, scaring off future personnel from working or living there). **IRL Example**: Captain Morgan, after he attacked and sacked Portobello, ransomed the town from the Portugese on threat of burning it down. * # Option #4 - Blackmail 2: a threat of attack on ships arriving at the facility. You park near enough to the port/dock that you can attack any ships arriving there. You don't need to capture them, just cause damage and destruction - the port might pay you off to stop any future attacks. **IRL example**: Blackbeard blockaded Charleston. * # Option #5 - Infiltrate personnel and attack from within. You don't need space combat. All you need is enough fighters to overwhelm local security (aided by surprise). **IRL example**: In 1718, Captain Davis sacked Gambia Castle, an English fort on the coast of Africa using just this tactics. Or Force 10 from Navaron. * # Option #6 - Pretend to be a merchie, and join a convoy from a port. This allows you to recon and track the other ships in the convoy and select which to attack while travelling in the same convoy (and, if piracy is a big threat, they WILL likely band into convoys). **IRL example**: Bartholomew "Black Bart" Roberts did that with the annual Portuguese treasure fleet. NOTE: most of my examples happened in actual pirating Earth history. One random list: ["The Ten Best Pirate Attacks in History"](http://latinamericanhistory.about.com/od/Pirates/tp/The-Ten-Best-Pirate-Attacks-In-History.htm). [Answer] It sounds like you are correctly thinking about the cost of orbital maneuvers. In space, all ships are *compelled* to be constantly falling towards some body or another. To board another ship you need to be falling in the same place, at the same time, at the same velocity, which means you are on the same trajectory, and so whatever costly maneuvers the victim had to do, the pirate has to do them also. For example, to intercept a ship going to Mars, you need to be able to match its velocity, so that means you need to be able to go to Mars also. And as we know, that's expensive. And if you aren't leaving at the same time, you need yet more fuel to catch up. Then when you get there you need more fuel to slow back down and match velocity, if you intend to board. Due to the [tyranny of the rocket equation](https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tyranny.html), this little bit of extra fuel that you need to catch up, then slow down, is extremely expensive because you need more fuel to lift that fuel into orbit. So you might conclude that in a universe where travel to Mars is common, but still very expensive, then space piracy is uneconomical since the fuel would cost more than the goods. But! A space pirate ship doesn't need room for cargo, but just a couple pirates and some guns (or maybe some other weapon that doesn't cause explosive decompression in space). Again because of the rocket equation, as cargo is added it gets exponentially more expensive to launch it. If we posit that a cargo-laden ship to Mars is feasible, then a pirate ship with no cargo would be a tiny fraction of the cost. Also, if your pirates don't strictly need to land, or come back. That's a *huge* fuel savings. They can either intercept the ship, die trying, or have the space equivalent of the coast guard rescue them. Compare: * [Vostok-L 8K72](http://www.astronautix.com/v/vostok-l8k72.html), 277,000 kg. Launch vehicle of Luna 2, first man-made object to hit the moon *without slowing down*. * [Saturn V](https://en.wikipedia.org/wiki/Saturn_V), 2,938,000 kg. Launch vehicle of Apollo 11, first thing to land on the moon and *come back in one piece*. Furthermore, consider not only the value of the goods, but their situation. As we've already established, sending cargo to Mars is expensive. So, being in possession of some cargo already headed to Mars is a lot more valuable than being in possession of the same cargo still on Earth. I think between these two things, you can feasibly have pirates if you want them. Of course you'll need to have reasons that it's easier to intercept goods in transit rather than at docks or whatever, but I think that's pretty easy because it's the same reason pirates have always existed: space is big, and help is a long way away. Your pirates need just a little stealth and cunning. And, if shipping between planets is very common, you *can* just hang out, in a sense. Not stationary in the intuitive sense, but you can put yourself in an orbit near the shipping lanes and hang out. You just put yourself in a slightly higher orbit and keep orbiting until something interesting ends up on a similar trajectory where an intercept isn't costly. It's a bit like dropping into the slow lane of the freeway and waiting for something interesting to pass. Convienence stores and hospitals are probably doing something similar. Seems your bigger problem is explaining the economics of transporting cargo to Mars in the first place, especially in a world where chemical rockets are still in use. I guess you lift it into orbit in pieces, then put it on a more efficient ion drive for the long haul. Still though, what is it being transported to Mars, and why isn't it just made on Mars instead? Whatever it is, it must be extremely valuable, and so I guess all the more worth pirating. What do they do after intercepting the ship? What do all pirates do? Hold the crew or cargo for ransom, or redirect it, get it on land, and scatter it about before the law catches up. Today there are never more than a dozen people in space, but when space has become accessible you'll have the full gamut of illicit activity we have on Earth. There will be slums where there's no law to catch you, and there will be corrupt officials. People will sneak across borders. I don't see any problem. [Answer] * Aided launch In the case of a station-aided launch, such as a railgun, the spaceship would likely be projected at high velocity, and an early interception would be impossible. * Unaided launch If the ship accelerates on its own, it would receive an acceleration of likely around 3g, that is roughly $30\left(\frac{m}{s^2}\right)$, meaning that after ten seconds it will have reached $300\left(\frac{m}{s}\right)$, far faster than any earthbound common car. Even in the situation any collision would be fatal to both ships. * MECO Now follows a main engine cut off, and the spaceship aligns its final injection trajectory. Its acceleration is now 0, and the spaceship will rely on thrusters from here on out. * Deep Space Deep space is the boring bit of the flight, however the trajectories will have been narrowly set. It could be possible for a pirate ship to intercept the spaceship at this point. The best point would be some days away from either planet, while still within reach of a base of some kind. It is highly unlikely that a ship could be found by luck, and detailed flight plans would be required. The high velocities of space travel make a small angle of interception incredibly important. A head on collision would destroy both ships. It is likely that the pirate would have to use the momentum of the planet's rotation to be able to keep up with the target. The interception would require extreme skill and careful planning. Note that when the two ships collide, they will both have a new high velocity course headed for deep space. The pirate ship would have to have a plan for escaping this (like using the moon's gravity), either way the target ship will likely never reach its destination. If you want some kind of manoeuvrability, or even the ability to significantly alter trajectories, the pirate ship would need exceedingly large engines or full boosters. There wouldn't be casual pirates, every heist would be a master plan. [Answer] # Legislate them into existence. Several laws can be taken to allow "safe" commercial use of space pathways (there would be some orbital transport hubs, right?) that would encourage piracy. First of all, if there's a fight and ship gets damaged, debris starts flying around and that's [bad](https://en.wikipedia.org/wiki/Space_debris). Like, "not ewen we, the Government, would be able to launch new spy satellites" bad. It's easier to just ban fighting in space than to deal with results. Same with all types of guns and explosives on ships. Even if you defend your ship from pirates but investigation shows you had guns - well, you lose your license. Second, taking out a ship captured by terrorists would still produce debris. As a solution, only allow government-approved docking systems that prevent ship controls from evading docking and allow ship that wants to dock to do it no matter what target thinks about that - if presented with the right access code that is only available to any law enforcement ship and wil be leaked almost right away. Serve it generously covered with the same sauce as gun-free zones and whole TSA stuff and people will *demand* these changes. Even people that are not planning piracy! ## Have several competing governments If there are different airspaces (spacespaces?) belonging to different governments, crimes committed in one spacespace can be sort of ok in another. More than tht, if these governments are actively competing, they could enable, or even actively encourage piracy in their competitors' spacespaces, like it was with real pirates. Go to one sector, plunder some booty, come back to another sector and sell it. As long as you don't commit atrocities like mass murder or drawing a Disney Copyrighted character on the hull of your ship, you're safe (and in some cases mass murder would be ok too). ## Interception mechanics Again, it would be pretty simple: for the same "safety" reasons, allocate space corridor for each travelling ship. Commercial ships have to comply with this, pirate ships - not so much. As a result, pirate ships know exactly and in advance where and when their target would be and can intercept it easily. The trick would be to plan their course to intercept the target far away from stations so that sending help has no point - and also crossing boundaries between we-pirate-here and we-trade-here sectors according to pre-approved flight plans. They don't want to lose their licenses in we-trade-here sectors, do they? [Answer] With the technology you propose, its very *unlikely* piracy in any form is practical. First, consider that chemical propulsion is already very close to its theoretical limits. You mention SSTO shuttles - although proposed multiple times, nobody yet has even proved that an SSTO can have a feasibly sized payload (with respect to takeoff mass). Even if the SSTO itself weights *nothing*, the payload fraction won't be very large when taking off from earth to low orbit, simply because chemical fuels themselves do not contain enough energy for their own mass. Ion engines provide very high specific impulses, reducing the fuel mass fraction for a given delta-v drastically (compared to chemical thrusters). The catch is, you *can't* have high thrust and high impulse at the same time - this is because the energy requirement squares with exhaust velocity; this makes increasing energy input to the ion engine the limiting factor. You would need an energy source of enormous efficientcy (per weigth) to get anywhere near the thrust of the smallest chemical thruster. The only thing that comes to mind would be *nuclear* propulsion (either a fission or fusion reactor - and it would still require major improvements in weight reduction of the reactor). Ion engine driven probes accelerate *very* slowly over long periods of time exactly because of this property. Next, piracy by boarding increases the required delta-v by a large margin. First you need to get where your victim is, then reduce your relative velocity to zero, then accelerate again to get away. Taking away any bulk cargo from the victim becomes impractical, as this would further increase your fuel needs to accelerate said cargo away from the victim and later decelerate it to actually sell it. And if the pirate ship is small to begin with, so are its fuel reserves. There is also the problem that its very hard to force docking if the victim decides not to let you. The victim just needs to put his ship into a spin, and the only thing you could do would be to threaten them with destruction to make them cooperate. Visibilty in space, as already answered elsewhere makes it hard to hide your actions. Unless you introduce some sort of cloaking device, which could be physically feasible: Have a sail or shield on one side thats actively cooled to avoid emitting any radiation and get rid of the excess heat by radiating it to the other side. One could point the coold side sunwards and radiate the heat away, thus avoiding detection by thermal imaging from anything between the sun and the pirate. Combine with a carefully selected course to avoid transiting any bright stars. You'd be a brightly lit marker for anyone watching from your hot side though (and they would most likely be able to tell you're actively cloaking by taking a spectrum of the radiation you emit). The question is who would supply a cloaking device to the pirates? And it would add more unwanted mass to the ship. In short, if there is piracy in your setting it will look very different from what piracy looks with seagoing ships. The alternative is to carefully tailor technology and setting to constraints that make piracy practical. For example, the novel [The Mote in Gods Eye](https://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye) is largely driven by the technology depicted. [Answer] A note regarding the ease of detection of craft in space: it is *extremely* difficult. Things is space are very very far away from one another. The best picture ever taken of Mars from Earth is this : [](https://i.stack.imgur.com/pNvtt.jpg) It was taken by the Hubble, and has a spacial resolution of about 10 miles. Now, Mars is ~4000 miles in diameter. If you have some very large ship, let's say 500ft long, that's 0.003% of the diameter. Mars has an albedo of ~0.15. The darkest currently existing material, [Vantablack](https://en.wikipedia.org/wiki/Vantablack), has an albeo of 0.00035, 428 times darker. This would mean it's about 18,079,913 times harder to see a black spaceship orbiting Mars than the planet itself. We can do better. The James Webb Space Telescope has approx. 0.1 arc-seconds of angular resolution. With some simple trigonometry, that means it can resolve an object 500ft long 195,000 miles away. *Resolve*, but not necessarily detect. The Hubble has detected objects with a apparent magnitude of 30 (a flux of around 6\*10^-7). At Martian distances, the Sun is about 40% as bright as Earth, so an object made of Vantablack at that distance from the Sun would have a luminosity of 0.19 W/m^2. Flux is F = L / 4 π d2, where L is luminosity and d is your distance from the light source. Total luminosity, with an area of 400m^2, is 57 watts. This results in the Hubble being able to identify such a ship from a around (very rough) 4700 miles away. Now, that may sound like a lot, but it is very much not. If (as in the OP) spaceships can travel the 500,000km to the Moon in 2 days, they are traveling at a very minimum 1.798 mi/s, or would be able to make up that distance in 43:30. There's not a whole lot of orbital manuvering you can do in that time, assuming you detect the enemy immediately. This can only happen is if every ship is carrying a Hubble-class telescope pointed directly at the spot where the pirate ship in question will appear, just waiting for it to become visible. This is of course absurd, making it nearly impossible to detect a darkened, unregistered, pirate ship coming at you from deep space. [Answer] Alright. I've decided to transform my set of comments into an answer. Well.. the logic in @kingledion [answer](https://worldbuilding.stackexchange.com/a/62950/3180) is pretty nice. From there, if a pirate ship is undetectable, then it might steal a ship with no one noticing. Also, there are plenty of nice answers here not relying on pirates having a ship and intercepting. Mine will do. **Definition 1:** We will define anything with the potential of government quick response as GQRs. They might be stations, bases, planets, moons, patrol ships, whatever. **Doing piracy**: There are two places to attack: (1) Near GQRs or (2) not near GQRs. =). (1) In near GQRs, goverments will certainly quickly respond to any distress call (by definition), with high speed fighters or worse. If (2), goverment will not quickly respond (by definition!). Proposition 2: It is risky to do piracy near GQRs. Proof: We do attack near GQRs. High speed fighters will quickly intercept us. If we are detectable, we are doomed. If we are undetectable, they will investigate, and maybe see us with naked us. Or fire blindly. Thus its risky. We conclude the proof. The solution is simple: Be non-near GQRs. If you are detectable, they will see you coming, and will prepare for you. (Either weapons in the cargoship, or deviate from you if you get too closed). Dangerous, risky, and has many possibilities of going wrong. We hereby need to be undetectable. **The Ship:** Have a pirate ship P. Now, cover full whole with nice 100% re-directing meta materials. Incident radiation will be redirected and making it invisible to radar. Thermal signature can be extinguished by a rather simple method. **The Invisibility:** Proposition 3: Pirate meta-material hull cannot receive heat. Proof: There is only two ways to receive heat. (1) From outside, (2) from inside. (1) By hypothesis, incoming radiation is redirected. Since there is no convection/conductance in space, we are done. (2) Separate inside with nice good insulators. It will insulate the heat for the amount of time needed: few months. Then we are done. This concludes the proof. Proposition 4: If we wait long enough, the pirate ship hull will not emit detectable thermal radiation. Proof: We know hull will not receive heat. But it will emit heat by blackbody radiation, at expense of its own temperature. Which will decrease, and emit less and less blackbody radiation. Solution is then simple: A pirate will launch its ship, and wait a little. =). By my calculations, given a ship with outside hull area $A$, hull mass $m$, hull specific heat $c$, and initial temperature $T\_0$, the time needed to drop temperature from $T\_0$ to $T\_0/2$ is: $$ t\_c = \frac{7mc}{3T\_0^3 A\sigma} $$ Where $\sigma$ is Stefan-Boltzmann constant. If we plug some OK values, we will find out no much is needed to wait (a few days only). The invisibility thus works. Now, we need to make sure you survive the trip. **The Heat Problem:** The ship cannot and will not have heat exchange with outside. You will then risk increasing inside temperature. This can be done creating an inside atmosphere of plenty heat capacity. If you produce power $P$, then temperature inside will increase: $$ \frac{dT}{dt} = \frac{P}{mc} $$ **Method 01:** Then, if we have a 10x10x10 place for you, filled with water, and if we produce 1000W, it will increase interior temperature at a rate of $1.6$ kelvins per month. (Yes, you wear some under-water cloth to ensure your survival). (It is evident that you won't fill with water and launch. You will launch and fill with water). But this is a bad method. **Method 02:** In a nicer method, we manage heat. We create to compartments, one for you and one for heat. And we transfer all waste heat from your room, to heat room. The rooms are separated by insulators. The transfer can be some refrigerator, or peltier device. In heat room, we place something to store the heat (say.. water!). Or whatever high heat capacity material one prefers. The previous calculations will then apply to the heat room. **Method 03:** A much more better way (suggested by @Samuel in the comments), is to have blackbody radiation out (perhaps even from the heat room). But, before let it out, transform it in a unidirectional beam (with set of mirrors or lenses or whatever), and point it to a direction perpendicular to the orbital plane. No one is going to see it. You can further assume no one is cloaked, and then you know everyone's position. And then you can point it so no one will detect. =). Equipped with an undetectable ship, you can match speed of some other ship. This can be done by selecting target while in near GQRs, set up nice burst (no chemical out of preference...) and patiently wait. Burst could be, say.. some reaction to produce $H\_2O\_2$ and expel it. It will produce barely detectable infrared signature. **Pirating: Method 01:** Once you are very near the ship. (1) Disable broadcast capabilities. Maybe shoting all antenas at the same time, or almost at the same time. (2) Open a hole in incoming ship (maybe spotting some glass and breaking it) (out of preference, the main bridge glass), invade it, take control. (3) Now you can program the ship to continue the trip normally. When arrive in planet you set it to go, have it programmed to land in middle of no where, where some of your colleagues will be waiting in there. Steal, and go away. Simple. =). **Pirating: Method 02:** Contact incoming ship and say you will blow it to pieces unless some money is transferred to some account. If money is not transferred, well, blow it to pieces. =) (maybe some torpedo). **Conclusion:** There are plenty more and more methods to make it possible. The key is to adapt. Applying these strategies again and again, the government undoubtedly will engage successful countermeasures. No strategy survive forever. Adapt. In sea, maybe the equivalent of this, would be pirates in submarines. =D. Well.. If someone have spot some mistake let me know. =). [Answer] While each of the other posters makes excellent points with their thoughts, there is one final determining factor regarding whether piracy is practical: > > Economics > > > As the creator of this world, you only have to answer one question: Is there a net economic benefit to the pirates that is sufficient incentive to engage in piracy (i.e., does the profit outweigh the costs)? All other factors mentioned will impact this: * **Cost of space travel:** This already has to be relatively low for there to be an economic benefit to shipping goods worth stealing. * **Orbital mechanics:** This will contribute to the cost factor. The answer to this question will also shape the *type* of piracy you're likely to see. IMO, the most likely thing you're going to see is not **piracy**, but [**barratry**](https://en.wikipedia.org/wiki/Barratry_(admiralty_law)) or **hijacking**, most likely by substituting "the bad guys" for key members of the crew and sailing the vessel to a different port; the majority of the crew and passengers wouldn't even need to know what had happened until arrival. This could even be accomplished by the substitution of a single key crewmember or (as someone else pointed out) by hacking. **Additional thoughts, several days after the fact:** * Shipping routes (piracy targets) will be fairly predictable. A shipping company's goal is to get goods from point A to point B while minimizing costs. * This means is that they're going to use a minimum-fuel orbit and will **not** likely have much reserve to flee, if attacked. * I.e., a ship leaving Mars with a shipment of goods for Earth on Wed., Feb. 9, 2316, 0200 UTC and a scheduled arrival date 97 days later will have one and only one minimum-fuel orbit; this will be easily calculated by the would-be pirate. * Due to the orbital relationship between Earth and Mars (or other planets), there may well be shipping "seasons" when the fuel cost is a minimum and the profits to shippers are at a maximum; these would also be piracy "seasons." "Off-season" cargos would likely be high-value/low-mass items. * Historically, many pirates were not full-time pirates. They were often otherwise legitimate privateers or cargo ships who engaged in some piracy on the side as supplemental income. Some of these may also shape the OP's world. I.e., a story entitled "Pirate Season" about the risks of shipping during the prime season for pirates. [Answer] If your question is only about the orbital mechanics, the answer is yes (doable) -- iff you have the energy and reaction mass (often posed as available delta-V.) But those resources are expensive, so a smart pirate would likely look for valuable ships, ideally low on fuel, within the pirate's delta-V budget (however big that is.) Hitting a laden ship, near the end of its deceleration into a port or (better) space station would be (fuel wise), the best tactic, I think. Of course, station owners/governments can also do the math, so I'd expect there'd be some level of watch out for unknown vessels lurking in the "pirate Oort cloud" region around each major trading base. Probably including long-duration surveillance drones. But defenses are expensive, and smaller bases/ports might not be able to sense as well or as far out. A successful pirate will need stealth, guile (including hacking) as well as physics to get the Latinum! [Answer] I think you could make it economically plausible. It's roughly 50 years in the future so we can expect some advances to be made. Mainly to cheapen initial loads in to space as well as once in infrastructure becomes more available. Earth based piracy would be costly as well as easier to intercept and stop but if you have colonies at the moon and Mars it's not to unreasonable that corporations and private actors has started to spread out in the solar system. If there is a phase of rapid expansion without regulations and control it could be ripe for space piracy or privateers. Corporations paying for looting or destruction of competitors. I suggest reading this: <http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-full-story.html> It's about some of Elon Musk's plans for coming rockets and plans. In your universe if one or two similar revolutions of rocket technology has happened it's not unreasonable to motivate the costs. A pirate/privateer could be based on some small scale fuel operation and once that infrastructure and vessel is in place the biggest initial costs are dealt with. If fuel is readily available and they can afford to burn a lot both for intercept as well as placing themselves next to the target different weapons could be used for destruction or some sort of grappling device. And in the end if you can't tie it all together come up with an explanation as to why an em drive works and work from that. [Answer] Other answers seem to be assuming 1) that the pirates will attack with manned vessels, and 2) that the pirates want the ship they're attacking to remain habitable. Unmanned vessels can be much lighter and survive much higher accelerations than manned vessels. Depending on what the pirates are trying to get, a semi-autonomous attack drone could breach the target ship, board, steal the goods while the passengers are getting sucked out the hole, and fly home. The tiny drone would be hard to see coming, hard to track leaving, and not need much fuel. Orbital mechanics being what they are, if you want to redirect a ship to different location, a small change in direction at just the right time can do that. A similar unmanned drone could strike the target in a way that changed its direction, kill the passengers and crew, and help guide the target to the pirate rendezvous. This would require a lot of patience on the part of the pirates (months to decades between committing resources and getting a payout), but finding a ship taken this way would be very difficult - it might be interesting to explore the possible countermeasures. (Pirate ships might be small and dark, but how well can you hide a stolen ship the size of star destroyer with an albedo of 1 and a loud distress beacon?) If the targeted ships do remain habitable (or can be repaired), they could not be used to interact with the dominant civilization without coming under suspicion. Selling those ships would not happen in a *black market* so much as a *fringe society*, which gets pushed outward as civilization expands. [Answer] It's a very interesting question when and how piracy might first start happening. By 2065, I think there is very little chance of it in the form of manned pirate spaceships boarding and capturing manned non-pirate ships for fun and profit. As others have said, it is mechanically possible, but it takes a lot to do so. Even by 2065, probably most spacecraft will try to be efficient and so not have a lot of extra capacity for maneuvers such as running after other spacecraft. If you want to capture the victim for yourself, it also needs to have excess capacity to go places and operate in ways other than the mission it was designed and fueled for. Not entirely what you asked, but beyond that, it seems to me there would tend to be far more important obstacles in terms of the results of pirating. The very wealthy and powerful governments and/or corporations involved will no doubt take action against someone pulling this stunt, if they can. And by 2065, even if the world is quite chaotic and has rival nations and/or corporations who would provide sanctuary or even privateering letters of marque to those who would rob their rivals' space operations, I wonder where one would be able to go with the booty afterwards? Are you going to try to live in space indefinitely? If you're going back to Earth, you'll want good ways to avoid being identified and attacked by the offended party and/or military & law enforcement in general. There may be ways to solve all these considerations, but they should at least be addressed. For example, if small unmanned ships and electronic control are involved, that might have possibilities. Or holding space missions hostage while maintaining anonymity somehow. Or perhaps if there are lunar and/or Martian colonies and/or other space stations which are somehow self-sustainable, some people might try a mutiny and/or to assert their own autonomy, providing more possibilities. ]

[Question] [ Twenty years ago, a 40km diameter alien saucer came to Earth, and stopped 2km above the Atlantic ocean, somewhere near the midpoint between Casablanca, Morroco and Natal, Brazil but over international waters. It is completely opaque, reflects no light or radar (but still irradiates IR as any object at room temperature) and has absolutely no lights on. Just a disk of blackness. To be more precise, the means on how the disk hovers at that position and how it dissipates the radiation it absorbs is beyond the scope of the question. It has been completely immobile since then. No contact. Today (in the fictional world) is somewhere in 2017. Earth is the same otherwise. **What would be the effects its shadow cause on the ocean and the oceanic life beneath it?** --- **EDIT:** To address several concerns commenters posted below, I don't want to develop the whole scenario in one question. It would be very broad. So following stackexchange guidelines, I broke it up into smaller aspects. The other aspects are considered irrelevant **for the scope of this particular question**. Therefore the following factors do not affect the ocean below: * Propulsion: There is none. It has no thrusters and makes no wind downards. * Irradiation: All the sunlight the disk absorbs is not irradiated outwards. Although it gives off the same amount of IR radiation as the surrounding air (at 2km high). * Gravity: It does not significantly affects gravity at the surface of the ocean. So it has no tidal impact. * Thickness: the disk is very thin. Its thickness when compared with its altitude and diameter is negligible. * Stability: people have landed on top of it, and it didn't tilt a single minute (of a degree). It is very stable, and not even a hurricane could nudge it. [Answer] The ocean is a dynamic and very large place, so it's unlikely to have many large-scale effects unless humans overreact. I'll focus on the local, immediate effects of this saucer from a physical, biological, and chemical perspective. Some things to consider about the location of the saucer- it's suspended in the middle of the Atlantic Ocean, almost directly above the [Mid-Atlantic Ridge](https://en.wikipedia.org/wiki/Mid-Atlantic_Ridge). We're a little bit above the equator and thus miss the strong, surface equatorial currents and instead have a slow surface velocity of 1-2 km/day. We have strong, driving trade winds from the northeast and are almost at the edge of the [ITCZ](https://en.wikipedia.org/wiki/Intertropical_Convergence_Zone). ## Physics Let's explore the physics of such an object before we start working with the ecosystem. The biggest change will be the shadow cast by such an object- given that it absorbs all light, it's going to cast a pretty big shadow. Because it's pretty close to the surface relative to the size of the object, we'll mainly have a solid [umbra](https://en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra)- total darkness. Near the edge, we'll have the penumbra, and finally we get back into normal light conditions. However, the ship also probably has some mass- this may affect tides and will certainly affect sea height nearby, but as I don't have any idea about the density or thickness of such an object, I can't do more than mention it. ## Biology The best way to model this addition is to treat the area within the umbra as suddenly a part of the aphotic zone. This is normally the deepest portion of the ocean, where no light reaches, and is home to all of [our favorite little beasties](https://www.google.com/search?q=deep%20sea%20creature&oq=deep%20sea%20creature&aqs=chrome..69i57.2455j0j1&sourceid=chrome&ie=UTF-8). Suddenly, the aphotic zone extends to the surface in a single location, which causes a restructuring of the local ecosystem. ### Phytoplankton Phytoplankton require sunlight to live. The sun powers photosynthesis, and without light, they'll rapidly die. It's worth noting that these creatures wouldn't simply swim outside of the shadow- they're unable to swim at all, which is why they're considered plankton (literally, "drifter"). So all the plankton in our shadow die within a day or two and deposit a huge amount of carbon onto the seafloor, but as that's a one-time event, I won't spend too much time on it. Essentially, we no longer have a primary producer in the area, but that only reinforces the deep-sea model. Given that we have surface currents of 1-2 km/day and the saucer is about 40km wide, that's plenty of time for any poor phytoplankton pulled underneath to starve- especially the [little](https://en.wikipedia.org/wiki/Diatom) [guys](https://en.wikipedia.org/wiki/Coccolithophore). ### Zooplankton At first, I assumed that zooplankton would be pretty happy about this event. The big change for them here is their [diel vertical migration](https://en.wikipedia.org/wiki/Diel_vertical_migration). Zooplankton feed at the surface during the nighttime when they can't be seen and eaten, and descend to the deep sea during the day. Initially, this implies that they'd suddenly have a horizontal daily migration as well, but they aren't designed for that. Plankton move easily and readily vertically in the water column because they're able to control their buoyancy, not because they're strong swimmers. Even though they would love to move in and out of the shadow at will, they simply don't have that capability. Interestingly, the very first time your saucer appeared, it would cause this same daily vertical migration because the zooplankton would think it's nighttime- essentially emulating [the effects of a solar eclipse](http://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/). They'd feast voraciously, run out of food, and shortly die. ### Nekton Bigger creatures, on the other hand, would be stoked. "[Nekton](https://en.wikipedia.org/wiki/Nekton)" is a term that includes all creatures that move under their own power, and they've been given a huge present by this saucer- the ability to move between night and day at will. Normally, creatures in the ocean have very different activities during the day and night, usually as a predation/predation avoidance mechanism. Now, they're able to swim out into the sunlight, feed on clearly visible organisms, and disappear back into the shadow within a few minutes, not 12 hours. This behavior is why fish are often found under piers, boats, or rafts of seaweed- it serves as a place to hide from predators both above and below. ### Benthic creatures Essentially wouldn't care. They're too deep in the ocean to notice the difference between day and night, so they wouldn't notice that the diurnal cycle has stopped. They aren't even affected by the sudden disappearance of the [marine snow](https://en.wikipedia.org/wiki/Marine_snow) from above because particles sink much more slowly than the ocean currents in this location, so they're still being fed by carbon from the [NADW](https://en.wikipedia.org/wiki/North_Atlantic_Deep_Water). ### Seabirds I'm not a bird person, so there may be more helpful information about this group coming from somewhere else. We wouldn't expect to find many birds to begin with, but they may start colonizing your saucer if it doesn't have some way of keeping them off- which might be a good idea for the aliens to do anyway. Nothing can ruin the aesthetics of a mysterious levitating saucer like bird poop. If the birds were able to land on it, they'd probably be pretty excited- it's a good spot to stop for a rest if you're migrating, and there will be some interesting marine life behavior below that they may be able to capitalize on. ## Chemistry Now that we've killed off the phytoplankton, one might expect that we'd see $O\_2$ concentrations plummet in the surface ocean. However, that would only happen for a few days or months, until all the respirers are dead as well. What would happen over 20 years is the transfer of oxygen into the water that would slowly raise the concentrations again. We can see that best on a concentration-depth profile: [](https://i.stack.imgur.com/m47wum.png) $O\_2$ actually increases in the deep sea because there's no longer much consuming it. This is the same thing we'd expect to happen under our alien saucer's shadow. ## Recap What your saucer has done is essentially take the normal vertical light distribution in the ocean and make it horizontal. Rather than moving from a euphotic to a disphotic to an aphotic zone by travelling vertically in the water column, the same sequence happens horizontally. This doesn't affect much on the 20-year scale because only nekton would be able to use it to any advantage. Essentially, expect the ocean to do what the ocean does best- change a little in a lot of ways. ## Some thoughts, brought up by commenters and other answers ### Pressure differential Deep sea fish are famous for living under pressure, but they don't *need* it to stay alive. Fish have control over the amount of gas in their swim bladders, and as long as they're given enough time to rise to the surface they won't experience barotrauma. As to whether or not deep sea creatures actually colonize the surface, I don't know- we don't have a ton of data on this phenomenon. I find it hard to imagine that over 20 years there would be *no* interaction, but it probably won't be a full-scale surface invasion. Deep-sea fish are pretty happy to stay in the deep sea. ### Light requirements A couple comments and an answer have pointed out that it's not going to be pitch black underneath. I agree with that! However, it's not just any light that's useful. Photosynthesis requires rather a large amount of direct sunlight or it simply won't operate at all. In the ocean, this boundary is the difference between the euphotic zone and the so-called "disphotic zone". This depends on the turbidity of the water, but in the open ocean is about 100m. Additionally, photosynthesis operates best with blue light- the same wavelength that is scattered *best* by air. If the light is coming in at an angle, a lot of the blue light is removed and no longer able to power photosynthesis. I'd argue that any area directly under the saucer is more accurately modeled by the disphotic zone. [Answer] Why is it that in questions like this about something blocking light, everyone seems to forget that the Earth *rotates*? To simplify the geometry, we'll use the following assumptions: the saucer has a flat bottom (it doesn't curve to follow the Earth), so the 2 km altitude is measured from the center of the saucer; the saucer is located on the equator, and it's the equinox, so the sun passes directly overhead the center of the saucer; the sun is point light source so we aren't worried about umbras, just either shadow or not; and we'll ignore the curvature of the Earth. We're assuming the Earth to be flat in this case because simple trigonometry (assuming the Earth to be a sphere 6,371 km in radius) shows that if the center of the saucer is at a height of 2 km, the edge of the saucer is at a height of 2.03 km above the surface, which is a trivial difference and can be ignored. So, that all said... From a point on the surface of the ocean under the center of the ship, it spans 168.6 degrees of the sky, which means 11.4 degrees of visible sky (obviously 5.7 degrees on either side). Given 12 hours for the sun to cross the sky, that's 45 minutes of daylight, minimum. However, also something to take into account: Roughly 5% of the light you get on a clear, sunny day doesn't come from the sun directly, it comes from scattered light due to the atmosphere. While a good portion of the sky will be blocked so you only a cylinder of airglow around the horizon, that's still light. It might not seem like much, but for comparison the full moon is only 0.00025% as bright as the sun, and a full moon provides a surprising amount of light once your eyes adapt. Even underneath the center of the ship, with the most sky blocked, you'll get 45 minutes of direct sunlight and some residual light the rest of the day in the worst-case (ignoring weather, of course). As you go away from the center, the effect rapidly decreases, very quickly for the north and south. By the time you go 20 km east or west, the worst case gives you 6 hours of direct sun. So, how about going north or south? If you go 5 km north or south (and again assume the sun goes directly overhead for simplicity), the ship covers 151 degrees of the sun's path, giving you almost two hours of direct sunlight. Go 10 km north or south, it's 4 hours of direct light. Go 15 km, 6.5 hours of direct sunlight (and increasing sky brightness). And of course at 20 km, basically a full 12 hours. Long story: the actual area under the ship where it's dark is never completely dark for 24 hours, and doesn't actually occupy a very large area compared to the total area of ocean directly under the ship. Ecological effects are fairly minimal because air and water currents are going to rapidly dissipate cooling effects (so no real weather effects) and sweep phytoplankton and other light-requiring organisms into the area of near-perpetual dark, so it will not be lifeless. You'll see a higher prevalence of organisms that come to the surface at night in the center of the zone, but it's so comparatively small as to be measurable but largely insignificant. [Answer] In the middle of the Ocean there is just a lot of water and then, after going some thousands meter deep, ground. Swimming animals will experience something like night, regarding plants, well, thousands meters of water are already enough to stop light, so the saucer is not going to affect them any worse. For floating algae the effect will be transitory, as currents will move them away before they are significantly affected. [Answer] Since its not technically over coastal waters technically it has no or virtually no effect. Algae wouldn't be able to thrive in that spot but at the same time that doesn't matter because algae have the whole ocean to live in. If the saucer were closer to coastal waters it would kill off corals but that is limited to such a tiny area that it is negligible to mans ability to kill off marine life. [Answer] Looking at the effect of a solar eclipse might be helpful. The blocked light will make the inner surface waters (under the center) cooler. With the edges being hotter, there should be some interesting wind patterns in the region. This also will affect the water temperature, so a convective pattern should be set up, with a column of water sinking in the middle. [Answer] In the novelization of the late 1970's movie "Close Encounters of the Third Kind" by Steven Spielberg, the alien mothership was of a similar size. Speilberg wrote of the mass of the massive ship hovering over the canyon partially canceling the gravity for the people below, rendering them about 40% weightless. Yes the earth is much bigger, but the ship is closer (and perhaps denser) than most of the earth. I haven't done the math on this, but surely there would be some gravity/tidal effects, such as a bulge in the water's surface below your ship. Also keep in mind that the earth's surface, including the ocean, is curved and therefore the horizon distance comes into play. If you were on a large watercraft, 20 meters above the surface of the ocean, under the center of the spaceship, the visible horizon would be about 16 km distant. This would have massive cooling effects - that's why the arctic is cold, after all - it's not farther from the sun, it just doesn't get as much sunlight. [Answer] While 40km is pretty darn huge put at the scale of human made objects (even more so objects that are able to float in mid-air!) it is quite neglegible in planetary terms. A single raincloud is approximately the same size, and life does not end every time one comes by. The same is true for the topmost 50-100 meters of the ocean which will be affected by the shadow disk. From our point of view, 100 meters is pretty darn deep, but for an ocean which is approximately 7,000 meters deep at the approximate location indicated (Romanche trench), it's nothing. Yes, some plankton will probably die, and a few dolphins and other animals near the surface may get irritated. Temperature (both air and surface water) will be lower within the shadow cone, and because of that there will be some currents. But, whatever, compared to what happens every day in weather, that's just nothing. The planet couldn't care less, nor could the overwhelming majority of animals that live in regions where it's dark all day anyway. [Answer] Q: What would be the effects its (the UFO) shadow cause on the ocean and the oceanic life beneath it? As [mentioned here](https://physics.stackexchange.com/questions/116877/how-can-opaque-black-object-occur) 'An object is opaque because of scattering, or because of absorption. All "opaque" means is that light doesn't travel through the object. Thus, an object which appears to our eyes to be black just isn't allowing any photons in the visible range to reach our eyes.'. Keeping this in mind, The light from the Sun would not pass through the UFO and reach the ocean below it. Also, the large body of air present under the saucer, and the water below it, will experience significant cooling effects. If we do the math, there is at most, ~2514 Cubic Kilometres of air below the UFO that will stay in the shadow of the saucer. Katabatic winds would form on the edges of the saucer shaped object, and rapidly cool and contract, possibly creating localized rain and wind, providing the regional humidity is high. In all possibility, the salinity in this region might be slightly lower due to constant rain fall. Because cool air is much denser than hot air, it has a higher carrying capacity for water, and this region would be a low pressure zone. In the opposite scenario, one could create a "Hot House" by enveloping a container of air with glass. In this situation, a "Cool Zone" is created instead, right below the saucer. Thermal conduction properties, and IR heat dissipiation of the UFO was not specified, so, assuming the UFO would absorb and dissipate IR energy similar to an object at room temperature (as stated), heat eminating from the saucer would be negligible and could be considered constant. Similarly, the ocean too, provides very steady IR dissipitation. Climate scientists state the worlds oceans are responsible for and regulate the earths temperatures and climate. However, here, we have a localized "Micro Climate". The location of the UFO is roughly over the Mid-Atlantic Ridge, and far away from any land masses. It is well known that large metallic deposits, especially blue stone and iron ore, can increase the electrical content of the air significantly. If the UFO contained large deposits of refined metal, this could significantly alter the magnetic field of the earth at this point. It is well known that large deposits of shallow iron ore, or blue stone rock, can twist and warp the magnetic field for kilometres from the point of origin. This twisted magnetic field can cause large electric field gradients to occur resulting in violent storms. For example, in Venezuela, a famous bay is the home to very regular and violent thunderstorms. Most scientists agree it is due to the level of methane gas being emitted by the water (and oil deposits below). Large magnetic field variations could affect sea life, and fish that use magnetic guidance for migration. A +40 kilometre shadow cast over the ocean would cool the water slightly, and lower the level of [Methane Hyrdate](http://www.washington.edu/news/2014/12/09/warmer-pacific-ocean-could-release-millions-of-tons-of-seafloor-methane/), and decrease gas boiloff. This in turn would reduce the methane expelled into the atmosphere. Surface ocean water would evaporate less quickly in the absence of direct sunlight. Likewise, the water would cool slightly, as the ocean surface currents in this region are quite gentle. Denser water carries more dissolved minerals with it, and in turn, [hydrothermal vents](http://oceanexplorer.noaa.gov/explorations/05galapagos/background/mid_ocean_ridge/mid_ocean_ridge.html) on the sea floor around the ridge would grow a little bit faster. The water would also contain more dissolved gases, and could be more oxygenated, which would affect predator-prey relationships in fish life. [Light plays an important part in Ocean animal and plant life](https://oceanservice.noaa.gov/facts/light_travel.html). Light can be divided up into 3 zones. 1. Euphotic (above 200 meters depth) 2. Dysphotic ( 200 to 1000 meters depth) 3. Aphotic ( below 1000 meters depth) Only a small amount of sunlight penetrates below 200 metres, which contains the vast amount of commercial fisheries. Placing these zones into a shadowed area would significantly impact light levels. These 3 zones would essentially be in perpetual darkness. Perhaps the first metres of water would contain tiny amounts of light. In essence, the majority of plant life relying of [photosynthesis for life](http://ri.search.yahoo.com/_ylt=AwrTcaw85zBat8gAdhg36At.;_ylu=X3oDMTByMjAxbTBkBHNlYwNzcgRwb3MDNQRjb2xvA2dxMQR2dGlkAw--/RV=2/RE=1513183165/RO=10/RU=http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.4319%2Flo.1956.1.1.0061%2Fpdf/RK=2/RS=1R1hBPXFShKZvbyX0eR01H6tUAI-) would either slowly starve or perish, depending on ocean currents. If the plankton are fewer, then less oxygen would be produced in this area. Large predator fish like Tuna and Swordfish would avoid this area due to lack of smaller prey fish. However, animals such as the [Sea Squirt or Sea Brush would thrive](https://www.smithsonianmag.com/smart-news/light-pollution-is-messing-ocean-ecosystems-180955142/) due to increased water nutrients. Likewise, fish that are accustomed to dark, and cold waters, could increase in numbers in this area (if water pressure was neglected). Lack of adequate sunlight would actually change the ocean colour. When sunlight and nutrients are abundant, [Phytoplankton increase the opacity of the water and lend it their colour (green)](https://science.nasa.gov/earth-science/oceanography/living-ocean/ocean-color). However, in this case, the ocean water that is in the shadow will have a colour that is less green and more blue and red. [Answer] In addition to wind and current effects, the heat capacity of the UFO might also have other effects. With the wind effects and cooling, there could be condensation on the underside of the UFO, with fresh water (rain) forming. Also, if UFO absorbs more heat on its top surface than the water would, it will get hotter, making more complex thermals. ]

[Question] [ In this future, technology advances in such a way that privacy becomes **obsolete**. In other words, no one has *decided* to give up privacy, it's just that trying to hold onto it is like trying to keep the horse and buggy around when everyone else has cars - it's a losing battle and isn't going to work in the long run. The basic technology that allows this is untraceable, stealth micro-drones. They can be created anonymously and cheaply using 3D-printer farms. Defenses are possible but don't work 100% of the time, so any person, place or system can be compromised eventually. These drones also allow remote physical access to computer systems, and therefore given time will also allow an attacker to bypass any computer security. For the purpose of this question, assume that the absolute best security in the world (government w/unlimited resources) can only keep information secure for a maximum of 6 days. This is too broad of a scenario for one question, so this one will specifically focus on **Civilian Culture**. ***How would zero privacy impact culture - things like relationships, schooling, child-rearing, job hunts, etc.*** **Updates For comments/questions:** Edit: To keep things narrower, answers should be loosely based on Western (US/Canada/France/etc). But keep in mind that that's just the start point, not the end. 1. I am looking for implications on a stable end state, not the transitionary phases. 2. I will be asking other questions to follow up on Government (politics, corruption, crime & law enforcement, etc), on Military, and on Business. So this question is mostly about the various interpersonal relations - is that narrow enough or does it need to be reduced further? 3. Drones aren't known to be able to defeat natural biological defenses yet (or rather, solutions to that problem aren't compatible with an effective drone). So thoughts and your internal body structure are safe, minus what a drone could obtain through most external scanning. 4. Security defines how long it takes for an area to be compromised, but once it's compromised anything that happens after that point is known immediately. You can have a top secret facility that's totally secure, but as soon as you start to *use* it - information or physical objects moving in and out - you open up holes and the countdown starts. 5. Everyone has access to the data - the big players with drones are all spying on each other, and can't keep the little players from spying on them. So all of the watchers are watching all the other watchers, anything from GoogleBook, to the NSA, to Jim down the street. 6. Computing resources are sufficiently advanced that all incoming data can be scanned and evaluated. Bounty: The big thing I'd like to see is more thought on the implications of this as a mature culture. I see a lot of answers that feel more like "how things would work if *our* cultures had zero privacy suddenly introduced", but I feel that if this has been around for a while expectations and values will shift. How will people and groups adjust? [Answer] *Disclaimer*: a lot of ground on this was covered by "[*The Light of Other Days*](http://en.wikipedia.org/wiki/The_Light_of_Other_Days)". I don't remember much of it so some of "my" ideas below are likely influenced by, or even unconsciously lifted from, Baxter. Mea slight culpa. Please note that a LOT of the below can be summarized by two themes: * Increased trust due to ability to verify anything observable for truthfulness * Big Data --- 1. **Relationships**: * The new stable equilibrum (once people learn how to deal with this) improves most relationships: + Since you have zero privacy, you have absolute trust. You KNOW your relationship partner isn't deceiving you in anything observable, large or small. This means less long term stress for you (no need to worry about cheating, or lack of effort), AND for them (they don't have as much temptation to cheat knowing they will 100% be caught). A more subtle benefit is that you know you HAVE trust - no more negative feelings over your partner imagining bad things you do and not trusting you when you say you didn't. No need to put in extra effort to SEEM trustworthy when you're already trustworthy. + Less envy. It's well known that people are always imagining that "grass is always greener", and others are better off - in part because you only see the best side they put off. No longer would someone need to be envious of their neighbour for having pretty GF, because I can observe that she is a slob in private and doesn't help him emotionally. No longer do they need to be envious of the big house when seeing that the cost is working half the night. Yes, humans are a lot less rational than that so not all envy disappears - but clearly right now we are biased to see other people's lives as better than they actually are. * **Big Data**: Imagine a dating site where you filter people by ALL details of their lives, and nobody can lie about themselves. PERFECT matchmaking (at least, compared to now). Find all women in the area who read Heinlein, Baxter, and Dawkings in the last year and logged on to StackExchange? And who don't have a messy apartment? DONE. --- 2. **Economy**. Classical economists get their utopia. Perfect-information world. All the decisions that need to be made, are made with 100% information. No more asymmetrical markets. Less opportunity for cheating, arbitrage, substandard goods, etc... Plus, less need for expensive lawyers and investigations. All this makes the economy a LOT more efficient. Big Data: you can observe so many details about everything, you can likely adjust the economic behavior better for everyone. --- 3. **Schooling**: Not really much change there academically, but some for the better: * Better school discipline, ideally (you can see 100% of bad things schoolchildren did, no more "who hit who first", less bullying). * Less cheating (teacher can observe you cheating). * However, as commenters noted, any testing that is based on "the main challenge to the student is in not knowing the question in advance" is rendered useless, since students always know questions in advance. Of course, the tactics to address that exist even today: large pool of qualitative questions randomly drawn for the test (you can't cram for only 3 of 100 questions that you know will be on the test, since you can pull any of 100); and parametrized quantitative questions whose exact #s are generated randomly for the exam (so it helps knowing the formulas and the methods, but you can't pre-compute the answer at home). * Big Data: you can observe so many details about the kids, you can likely adjust the teaching tactics/strategy to the individual pupil easier. --- 4. **Child-rearing** Many benefits, some for reasons listed in "relationships" above. * Overall trust. Parent can trust their kid fully, knowing they have 100% way of verifying what the kids tell them. When one of my kids eats candy they aren't supposed to, I have proof who did it (right now they blame each other, and there's no good solution). It's known from studies that kids flourish when they know they are trusted by adults, and are given trust and responsibility. * I can trust a babysitter or other child care worker. No worries that they do shoddy job and I won't find out, or abuse the kids. --- 5. **Society overall** * **Less crime**. + Many people commit crime because they think they can get away with it. + Plenty more commit the crime because the punishment is usually **too light** - and it is frequently too light because of the worry about [Type 1 errors](http://en.wikipedia.org/wiki/Type_I_and_type_II_errors) (convicting falsely accused). + Less corruption (includes extra benefit to economy). + Discrimination: there are pluses and minuses.On the plus side, it's nearly impossible to have organized coordinated discrimination. You can't confer with a fellow bigot in private and discuss unequally treating someone. On the negative side, you can no longer protect yourself from personal bigotry by merely keeping private. If someone dislikes homosexuals or Scientologists or Christians today, you can't simply boycott every store run by a homosexual/Scientologist/Christian person (or fail to promote an employee), because for vast majority of people you interact with you don't know what they do in private. In the new world, you DO know. Just don't say/do anything obvious to prove that this was the real reason. --- 6. **Better governance** * Less corruption * Crowd-sourced control over quality of governance (*Lots of little brothers watching you!*). You can't do shady things - OR bad ineffective work - if people watch what you do. * Less "anti-society" crime: you can't plot to overthrow the government anymore (bye bye "revolutionary" groups killing people in the name of their ideology); you can't abuse people in your control because nobody can prove it; you can't pass corrupt laws as noted above. You can't defraud anyone - whether you're a CEO, government bureaucrat, or someone on welfare, doesn't matter. * Big Data: You can hopefully base governance decisions on better science. You can put some of social "sciences" on a more quantitative basis, instead of the squishy BS they are now. You have the whole mass of data, with no ethical concerns over collecting it since it's all EXISTING, and in "public domain". Large scale social experiments can be easily done merely from observing the proper subset of subjects. [Answer] I noticed that most of the answers posed include a hand-wave to "you'd know everything", but this is actually not realistic, when you think about the prospect of being able to get any answer, know any thing. Within current human consciousness, there is simply not enough bandwidth to know everything, even if the data were instantly available. As a result, you would only know the things you focused your attention upon. That leaves us with a problem, while privacy is technically impossible, it is probably still practically possible for those who do not engage in any kind of act that would make them interesting enough to focus on. [Answer] Let's start with the biggest changes. Assuming that the loss of privacy is fairly sudden (over the course of a few years, rather than decades or centuries): ## Entertainment Industry would go bust Television shows and movies would cease to be. Even if the television studio managed to film in secret, there only needs to be a single television viewer, and everyone in the world can watch his television, or watch the movie right off the movie screen... from the comfort of home. Similarly, live theater and live music performances will lose out. Why pay good money for something you can watch for free? Of course, there will always be people who will pay, just to hang out with other fans, but there would be a noticeable drop. Adult entertainment will lose almost 100%; why even bother digging through ads online, when you can watch real people in real situations whenever you want? Sports will also suffer; people will still travel to go to games, but the money from television ads will be gone forever. Of course, new entertainment venues would pop up - lists of who or what are interesting to watch, and the best times. Not that they would be able to charge any money for it. For once, piracy would have a legitimate impact on business! The entertainment industry has a tremendous impact on culture, and the sudden loss of television, movies, even sports or music would have a huge impact. ## Everyone would be a criminal There aren't enough people to watch everyone all the time, but without an expectation of privacy, the various world governments would want to make sure their citizens were behaving. Thus, they would use an automated method of watching; whenever anyone did anything against the law, they would immediately be caught, fined, or otherwise punished. Of course, everyone that has broken the law, even if they didn't realize it. All those stupid laws will suddenly start making a lot of money . Have you ever invited friends over to watch pay-per-view? Against the rules. Have you ever gone over the speed limit? Ever? Even if it was only for a few seconds? Against the rules. No more speeding on the highway, jaywalking, or hunting ducks from a mule. Many of the stupid rules would go away, of course. It only takes one politician getting caught bathing with a moose to get THAT law off the books. And speaking of politicians... ## Scandals and corruption would vanish Some corruption would go away, since the corrupt individuals would be caught, but the rest would become legal, even expected. Scandals would be a thing of the past; it's a bit less scandalous when everyone watches it unfold. ## Physical keys Today, passwords, passkeys, key codes, PINs, and other information based keys are increasingly popular. If anyone can watch anything anytime, there is no way to enter a password securely. Any secure transaction will have to use a physical security key, and a complex key at that. Even fingerprints or retinal scans won't work, because those images can be grabbed. Society as a whole would have to change the way information is stored. ## Schools and Safety Schools would actually be much different; I expect that children would simply stay home, since it would no longer be dangerous. Parents and police can keep their eyes on children, while the children watch and interact with remote teachers. Cities would be much safer, as any dangerous people would be kept off the street. Crime, especially violent crime, would plummet as everyone realized it was impossible to get away with anything. Abductions would be almost nonexistent. ## Relationships and Job Hunts Relationships would cease to be built on trust; instead, you could look up your date's love life, money habits, even choice of toothpaste. Dating agencies would fare better than ever as chance meetings would plummet. Businesses would still make stupid hiring decisions, based on irrelevant metrics, like personality type, average number of bathroom trips, or number of toothbrushes used, which means even less of a chance of being hired for your actual skills. Not that your skills would matter, because... ## Life can't exist without privacy Businesses without privacy become monopolies. Introverts without privacy go insane. Governments without privacy become bullies. People would become secretive and withdrawn, fearing to share any information with anyone, lest it become public knowledge. Humanity would tear itself to shreds. [Answer] I'd imagine a world without privacy is most easily understood as a world where you're never alone. As someone who has grown to appreciate 'alone time', such a world would probably have some very negative effects on culture. For instance, think of introverts and extroverts(I'm probably about to make some pretty big generalizations here). Introverted people usually set aside time to be alone with themselves, and as a result they often turn out interesting and self-aware. Such people may have trouble socializing with others because they have developed on their own, and thus their ideas may not mesh as well with those of others. Highly extroverted people, on the other hand, excel at interactions with others because they've never really taken the time to define themselves as individuals. The things they do are defined by how others do them, and the things they want are defined by the needs and desires of others. Thus, they conform to human protocols, but bring very little to the table in terms of individuality. In our modern times, we can already see the effects of decreased privacy: in our interconnected world, everyone is starting to become the same. We all grow up with a common pool of experiences (for example, viral videos), and are constantly barraged by other people's opinions, thus giving us less time to form our own. If we give in to these commonalities, we can easily find people who agree with us, and make quick but shallow friendships. This leads to a false sense of happiness, thus ensnaring many people into a virtual trap. Far too many people these days eschew meaningful relationships in favor of Facebook 'friends' and Twitter 'followers'. In a world without privacy, the levels of conformity would get even higher. Not only would you have constant access to what everyone else is doing, but you could never do anything on your own without being watched by your peers. I'm sure many of us can remember our younger days when we wanted nothing more than to 'fit in'. If, from such an early age, we can tell what everyone else is doing ALL THE TIME, it becomes easy to mimic those actions, and never give any thought to truly defining oneself. Later on, when we begin to desire individuality, it may be too terrifying to branch out, as everyone will know what you're doing and can judge you for it (for example, imagine trying to explore your sexuality when your parents and friends know exactly what you're doing at all times). No one would be safe from bullies, unless they did exactly the same things as the cool kids. People would be afraid to try out new skills or hobbies as well, as their initial failures would be broadcast to the world. In this way, I don't think very many people would ever be able to grow out of this childlike state. So, in conclusion, a world without privacy would become a world without individuality. Not necessarily a bad thing, so long as whatever personality everyone lands on is a good one. In fact, I'd say this is a lot like ancient times, where individuals were always just a small part of a larger community. In this case, however, the community would be the whole world. **EDIT:** Some quick thoughts on the specific points you mentioned: **Relationships** - like I said above, they're going to be shallow, since no one has enough personality to be truly interesting. Maybe arranged marriages would come back, or at least you'd hook up with whoever people thought you'd be good with. **Schooling** - a lot of possibility for maximizing individual learning through datamining, but I can't say whether anyone would take advantage of it or not. **Child-rearing** - You know what your kids are doing, all the time. That probably means they'll never get away with anything, and thus never have any interesting or defining moments in their childhood. Again, more conformity. **Job Hunts** - companies know your strengths and weaknesses. They probably have data on whether you'd be a good fit for the company. You won't even have to interview, you'll just receive offers of employment from companies that want you. If you get no offers, well, hopefully your parents have room in their basement. [Answer] (This was going to be a reply as a comment to [DVK answer](https://worldbuilding.stackexchange.com/a/13447/232), but it seems worth as an answer on its own.) Let's start from "*teacher can observe you cheating*". The problem is that **pupils can watch the teacher prepare the exam**, too. We have eg 30 people trying to determine which questions they are going to be asked, vs one guy determining if any of them cheated by spying him before. And the only way would be the footage of what all of them did from the point he made the exam to that after it was finished. Which is a really ingrate work. And he doesn't even know if the spying was done by the pupils themself (their parents, a tutor, a company…). In fact, there would be many companies dedicated to spy, filter and send you the important bits you are interested in. The only way to keep the *exam* secret would be to either have a big pool of questions (the whole syllabus) from which the questions are randomly extracted just before the beginning, or to have the teacher **create and memorize it without any hint leaving his mind**. And this would not be exclusive of *teachers* (which would have it relatively easy). Bussinessmen and politics would have to do that all the time, keeping their plans in secret even for their closest assistants, as any communication would be intercepted. **The only safe way is not to ley anyone know** your intentions and let other people guess to where you are moving to and what actions are decoys (which should be plenty, too). I should also note that better watching doesn't mean the government couldn't pass corrupt laws, just that it can't admit -not even between them- that they are corrupt. There are many *bad* laws with apparently good descriptions. **There would also be lots of messages with implicit meanings.** For instance, senators instead of promoting a law for "*Raise the senators salary*" would promote a law for "*Compensate the spendings of eating out for those that do so for work reasons more than 60% of the working days*" and all of them would instantly know (it's their work to notice these things!) that they all qualify, whereas a laymen may not notice the trick. Equally, it wouldn't remove discrimination (as DVK mentioned). In a job hunt your prospective boss can reject you based on whatever, he only needs to search you, find something considered bad (and they *will* find it, for anyone), and pose that as the real reason for the reject. [Answer] To a certain extent it would depend on WHO has access to this data. Can my wife just as easily look up my internet searches and credit card statements as the government? How about my neighbor? Or is it competing groups collecting data for themselves and most people just get caught up in the net? To a certain extent many things won't change because you will still be relatively anonymous in the mountains of data collected and available. The big difference would likely in the number of serious crimes committed, most would be crimes of passion or nut jobs because it should be easy to get footage of the crime and prosecute the guilty. 5 minutes of fame would be likely to happen (not a full 15) for many different things. Suicide rates could go up if people FEEL they are always being watched, to the less obviously intrusive the surveillance is the easier it will be to ignore. Likely what would become the norm would be for most to 'ignore' things they found out about each other that wasn't by direct communication or public statement. If you like kinky sex and I was 'watching' I wouldn't bring it up unless it was known that you like an audience etc. People need at least a sense of privacy to help with mental health. Even animals need it and better zoos have designed enclosures to give them the opportunity to find quiet time for themselves away from prying eyes. EDT: Someones comment make me think of something else. If information is easy to come by for people, then it will be a balancing act as to how much 'observation' you want to attract. A good looking woman that stands out in a crowd will likely have a lot less privacy in a world like this, however, on the other hand, it would also make her safer in many respects because if she was assaulted even in a blind alley there would be those who could come to her rescue quickly and/or alert those who can and have many 'copies' for prosecution. On top of that there might be a swift retribution as well, the perp might not make it to receive legal justice. [Answer] First off, the question is somewhat meaningless. A society where such a lack of privacy is possible will not devolve into a zero-privacy society, but rather into a society where privacy becomes a luxury good. This also means that privacy would become asymmetric: ordinary people wouldn't have privacy, but elites would keep it (as would governments). In this scenario, trust would not be enhanced, but undermined. This happens because ordinary people have no reason to trust elites (who would still have privacy), and elites would fear that ordinary people might still eke out enough privacy to stage an uprising. By the way, this type of society is by no means utopian. That is one reason I arrived at the privacy-as-a-luxury-good. Privacy is a very recent invention to begin with. Privacy only started taking hold when people were able to build large enough houses or apartments to have rooms to retreat to. In many parts of the world, privacy has effectively been outlawed. The most obvious example is North Korea, but also in the Pilgrim's New England, there were laws that prohibited anybody from living alone; for singles, widowers or widows, etc., having roommates were mandatory "to prevent sin". Today's NSA/GCHQ is actually somewhat similar: they expect complete privacy for themselves (under threat of life in prison or even a death penalty), yet insist that nobody else be allowed to have privacy (even to the point where Britain's Cameron suggested outlawing encryption). The hypothetical society in the original question would suffer the same fate. Possessing these types of drones, or the 3-d printers that produce them, would likely be unavailable to ordinary people. They would likely be illegal, and since there is no privacy, it would also be impossible for ordinary people to illegally own them. So, no, a true zero-privacy society for everybody is not going to happen. Privacy-as-a-luxury-good would be the real outcome. [Answer] An interesting factor that no one seems to have addressed fully ([gpeddle](https://worldbuilding.stackexchange.com/questions/13439/zero-privacy-culture/13453#13453) and [DVK](https://worldbuilding.stackexchange.com/questions/13439/zero-privacy-culture/13447#13447) alluded to this) is that for the most part the trust would be implicit, so would people actually check up? If they do then in actuality your society would take on **more** paranoid tendencies (constantly checking up on people makes you feel paranoid, even if you weren't paranoid before you started - to see what I mean go for a walk and just check over your shoulder every minute or two). On the other hand if people do not bother how is that different from today? I would have to have some reason to suspect you in order to actually investigate, so most of the time I would just take you at your word. If the technology yielded more of a viral video effect then people would become more sedentary across the board as they waste even more time than they do today, meaning that the vast majority of the public would simply be monitored by advertisers and governments (if I know my kids are sat on the couch next to me watching Old Mrs. Potts down the road, why would I have drones watching them). Of course how are modesty and things like nudity and sex dealt with? Do the drones provide proactive blurring of inappropriate bits that we would consider offensive? If so can you use that to commit crimes (if I am at an orgy and everything is blurred, can you tell I committed the crime)? If auto-blur is not used, then society would have to face those issues and accept them, so there would likely be more acceptance and less shame. A couple of people noted that certain crimes would be less likely to occur, but it is equally likely that those crimes would increase (assault was mentioned - some people **like** watching assault of any kind occur and would be happy to sit an observe it without raising an alert), especially if the criminals get a large fan following. One final note - if the advances are sudden and a large part of the population is offended or objects you could have a greater push to leave Earth for more "privacy friendly" locations in space, effectively splitting humanity into two factions. [Answer] It looks like you're looking for comments, more than asking a direct question, so here's a comment I didn't see. Information overload and apathy. At some point with all that data, a large portion of people just wouldn't care about other people's lives. Call those other people "riff raff", "poor", "lower class", "working class", or what have you, but it would be security through obscurity. Those people would be the masses of datapoints in the bell curve. At some point, "Big Government" and "Big Data" will reach a level of data collection where they will be satiated and/or crushed by their own greed for data collection. Much like the hoarder/collector who realizes the meaning of the phrase "The more “stuff” you own, the more your “stuff” owns you." At some point, it's possible for that to happen with massive data collection. Assuming, of course, that population continues to increase. You said that there was sufficient computing resources to process the incoming data, but who would look at it? Would that data change substantially? Would the watchers care if it changed? Would they try to make it change? My guess is that most of them would become apathetic and a small minority might try to make certain things change, if only on a whim. [Answer] Very little would change. The government would declare it absolutely illegal for individuals to spy on other individuals, corporations, or the government. Because getting away with crime is impossible, people would not do it, as they would be arrested. Police, the military, the bureaucracy and big corporations would be allowed to use this data, and they would do so all the time. There would be strict controls so that people could only spy on people of lower rank than them. So the only thing that would change is that the government and Google would know everything about our private lives (how crazy and unlike the real world is that!!) Edit: So as the question was "what would happen if we already had reached the stage where this thing already did happen", I can suspend disbelief that humanity could ever reach that point described. The system would be as described in the OP for a short amount of time. Then, there would be a single incident that goes wrong. Most likely, someone would find out a piece of information about someone else and respond without thinking. A crime of passion. They would be caught, of course, after the fact. No-one could respond quickly enough to prevent the incident. The government at the time would use this as a reason to introduce some sort of test/licencing system/permissions system, which would prevent many people from accessing much information legally. The people would go along with it, much as we go along with idiotic things in this day and age (my country is currently allowing our government warrantless access to our metadata 'to fight terrorists and paedophiles', despite the minister pushing for this change not knowing what metadata is and a 2nd government minister explaining the various ways around the system that will be used by terrorists to make it pointless for crime fighting. There is no hidden information about the motives for this law, the entire country is aware that this is being done to allow governments to spy on innocent people. Yet we do nothing. Years would pass, similar events would continue to happen and the government would each time make it harder and harder for people outside of the government to access information. Every time, people would accept it, willingly giving up power for the illusion of safety from criminals. Controls within the government would be tightened, with various levels of classification (secret, top secret etc). Depending on your importance within government, your brain would be classified according to these levels. This of course would lead to an extremely corrupt society, where a small number of people have almost unlimited power. To bring the mood down even more and counter the "but people wouldn't let that happen" cry: > > First they came for the Socialists, and I did not speak out— > Because I was not a Socialist. > > > Then they came for the Trade Unionists, and I did not speak out— > Because I was not a Trade Unionist. > > > Then they came for the Jews, and I did not speak out— > Because I was not a Jew. > > > Then they came for me—and there was no one left to speak for me. > > > ([Martin Niemöller](http://www.ushmm.org/wlc/en/article.php?ModuleId=10007391) (1892–1984)) > > > [Answer] Let's consider how after the invention of these drones society would likely develop # Stage 0: A lot of scandals and less corruption People start using the drones to check up on the truthiness of a lot of things they hear about. Be it celebrities or politicians, a *lot* of lies will be uncovered. # Stage 1: Creativity and progress would come to a halt Businesses start joining the fray disregarding the fact that it is originally illegal and will start using them to spy on their competition. There will be a short burst of development as everything is pushed out of R&D labs into the real world by all companies before all R&D institutes are stopped, because investing money in R&D instead of spying would be a stupid thing to do. Universities would hold out a bit longer, but in the end the same would apply to them. Either way, for civilian life this means a huge number of people losing their jobs as industries get destroyed (like the entertainment industry, which is essentially only R&D) or just shrink in size and get stuck in time. # Stage 2: World War n+1 Somewhere in the world at some point once again an ideological government will get voted into power that will decide to use this technology to empower themselves and outlawing 3D printers in general. Just think 1984. As even they can not do R&D (as others will simply copy any of their developments) they will start putting all their money into the development of their police force first and army second. As that country knows exactly how strong other countries are they will be able to quite easily decide whether to attack or not. Either way, depending on their relative strength there might be an arms race after which war will long term be inevitable. (If this sounds hard to comprehend, think about it like this: If someone has the superpower to predict the future, the only way to defeat him is to overpower him in such a way that even knowing exactly what is going to happen he won't be able to dodge it. In essence that's exactly what would happen, but then on a country level.) # Stage 3: The stable stage One way or another one will end up with a situation where the government does have access to these drones and the population does not. It is also likely that countries will grow in size and that only one or at most a couple of countries will be left. Depending on the ideology of the government(s) they will use this perfect control (perfect knowledge + police form) to enforce whatever they believe in and as there is no chance of rebellion (as they have perfect knowledge and can stop a rebellion before it starts). The implications on civilian lives seems clear (and otherwise read 1984 or any of the other classics). --- And yes, the above is extremely dystopian, but honestly, the only way this could be prevented is if governments would outlaw 3d printers globally in time (which is obviously not the case based on the premise of the question). And even if they did that it would just mean one would jump straight from Stage 0 to Stage 3, just with more complex politics. [Answer] I think that the fundamental change from today’s society would be the absence of guilt. If you consider that guilt is basically the fear of someone finding out what you have done or thought, then any totally transparent society makes that fear a certainty, so you either don't do it, or you stop being afraid of others finding out about it. Either way, no more guilt. One minor effect of this change would include no more blackmail based corruption. However, a more significant consequence of this would be the reduction if not absence of inhibition. Being unable to hide something means you would probably stop bothering. If you want to be a racist, you may as well be openly racist. People who don't feel comfortable about that wont deal with you, people who aren't bothered or who agree with you will. Discrimination laws would be meaningless and unenforceable so wouldn't exist. I think the result would be consensual based society with complete tolerance of anything that goes on between consenting adults. Of course it would be much easier to find adults who would consent to your desires, if you are willing to consent to theirs. The balance to this would be near total intolerance of attempts to impose your will on others, with strong social pressure to respect others in a non judgemental way. This would effectively express itself in two ways, one, as social privacy; So yes, someone else can know exactly what you are doing, when, where, and with whom, but would they actually care? And two, as a stratified society. Green racists would not choose to live near blue people and blue people would not choose to live near green racists. People would tend live in communities of like minded people, but those communities could be very different from each other. No more 'small town USA'. With the absence of guilt and inhibition, you have a significant difficulty with coercion. How can an authority assert their will if all citizens can know everything? You can't imprison someone if everyone knows where the keys are kept. A cop can't arrest and a soldier can't kill someone who knows where your kids go to school and a criminal can't steal something that can be stolen back before it is fenced. Simplifying a lot, the only offence would be to impose your will on another, then only punishment, social exclusion (banishment). [Answer] Privacy is a modern invention, at least for the majority of society. I would recommend looking back at pre-Industrial-Revolution society for some ideas. Prior to that, there was no meaningful privacy really. (I discount 'meaningless' privacy which would be being able to have your actions/location/status be unknown but only to people who have no capacity to affect your life) Families slept in common rooms. Bathrooms had multiple seats and no dividers. Communication with anyone you were not face-to-face with was essentially impossible. Homes contained only the most bare minimum facilities, so most things a person would want/need to do had to be done in public, including bathing. Certainly there were isolated rural farmers, but their privacy would fall under the 'meaningless' header since everyone who could affect their life knew everything about them, and the only people who didn't know everything were powerless to affect them in almost any way. To get meaningful privacy, you've got to be able to be connected enough to other people that they can have a significant effect on your life, but disconnected enough that you can do meaningful things without actually directly involving that same group of people. I imagine the issue of 'meaningful privacy' will be important in your world because, barring some sort of extraordinary discovery or alien intervention which would have a far larger effect than anything to do with privacy, the resources simply do not exist to assign micro-drones to every person alive, collect and transport and store the data, etc. [Answer] Perhaps a better enabling technology would be to assume that everyone is telepathic, turning us into more of hive society if you will. All thoughts are knowable to members of the hive. "How would zero privacy impact culture - things like relationships, schooling, child-rearing, job hunts, etc.?" I would guess that a hive would favor consensus, community-centric work ethic, the minimizing of conflict and would look a lot like socialism. I would also guess that there would be individuals who don't like such things and would fight for their personal identity, their privacy, their ability to gather wealth as distinct from that of the society's, etc. [Answer] The pace of innovation will diminish. Ventures will become fewer and be anticipated to have fewer returns. Great achievements or feats will be scarce. Benefit or profits will be closed to the masses. Standardization will be prevalent. Organizations' management will be redundant and unnecessary. Human self-motivation will get impaired. Human creativity will be truncated. Human life will be boring. [Answer] The end result of a Zero-privacy culture is not determined by how much information is available, but by how that information is used by the organizations who are most interested in it. ## **Criminals** You can't have a zero-privacy culture and assume that criminals aren't going to abuse it in some fashion. Even with an infinite wealth of information available to everyone, criminals will find minor ways to 'trick' the system into going blind for a second, or reporting false information, and with the level of trust people have in the observation technology that's available, the effects would be devastating. Small-time criminals would find their lives much harder - with petty crimes like theft being easy to prove, and murder being immediately solvable. Digital crimes would be easier, with simple ways to trick the system being justifiable as it is today - by 'finding ways the system can be tricked to solve the problems the system has today', such that cyber crime would become much more popular. And of course, even with a wealth of information at our fingertips, our real limiting factor on how much crime we can prevent is how much of that information we can *act* upon. Certainly there will be video footage of every minor crime taking place, but unless someone is monitoring every surveillance camera in the world (and there would be a LOT Of them) 24/7, there's no guarantee the criminal will actually be caught. And there will always be crimes where the intent is misunderstood - unless this surveillance system also infiltrates and reveals a person's intent. In which case, we'd have a Minority Report situation, where people are arrested for crimes they haven't yet committed, which would bring about its own problems. ## **Government** The government would be an early adopter of this system, and it would certainly use this information to help law enforcement keep any society that uses this system safe. We've already established that in the Criminal section. However, there are so many other ways for the government to use this information - some justifiable, others very *un*justifiable. Assuming the universal surveillance goes across boarders and isn't limited to one country, the government would use this technology to spy on other governments - and if other governments are using this technology too, we'd have a complicated network of governments spying on other governments, who *know* they're being spied on by the other government. In short, no more state secrets of any kind (Unless they use blocking technology: See Criminals). For governments with like-minded goals, this would be no problem. For governments that are mortal enemies, this would be an absolute nightmare. And that's just what the government would do *outside* their own boarders. From within, the situation becomes much more horrifying. Opposing political parties would have full access to all the strategies and secrets that each party is forming, and full access to the lives of their voters, which would lead to incredible levels of pandering for each government body, and an incredibly high focus on major political candidates to **not create any scandals**. In this world, political success would hinge entirely on creating a perfect self-image. Whether or not this creates a perfect politician is questionable, depending on how well they can form this illusion, and what they actually do with the immense power of all their nation's personal information once they're *in* office. If their intent is pure, there's no problem. If they intend to abuse it, they'll have no problem abusing it at all, save for justifying each abuse as it's exposed by the media. ## **Personal Use** You say that there is no privacy, and if that is true then there'd be no privacy among neighbors either, or even among strangers living far across the planet. In some cases, this would be fantastically useful - you'd instantly know if you can trust someone or not, and you'd know if anyone does anything unfair or unkind to you without having to wonder or worry about it at all. On the other hand, any minor mistake or mess-up that you do would be known to everyone, everywhere, forever. People would be much more cautious, they would take much fewer risks, and we'd be held much more accountable for each individual action. Assuming we don't manage to greatly reduce criminal activity, the imprisonment rate would skyrocket at first, until we all grow to adjust to being constantly monitored, or learn to avoid it in any way possible before committing any mistakes, which could still get found out and land us in prison and permanent ridicule for the rest of our lives. The common citizen would be constantly vigilant of what they do. On the other hand, as we mentioned earlier, the average citizen wouldn't spend their whole life looking up what each individual person has been seen doing, and wouldn't have time to learn everything about everybody they encounter casually throughout the day. Clean-looking, honest-looking criminals would pass right under their notice, simply because information overload would prevent anyone from meaningfully using this information, except on their close friends and colleagues. ## **Corporations** Corporations would definitely come out on top in this world - universal knowledge of their market, and what the market wants most at this very moment, means knowing exactly what to develop and focus on at any given time. And say goodbye to ever having to worry about hiring new employees ever again - you know instantly the qualifications of your prospective hires the moment they walk into the door. Of course, corporations would also no longer have any secrets - everyone would be aware of the dark dealings of major organizations, and prosecution of these organizations would be easy, since there'd be no way to hide what they're doing, and no way they could claim they didn't have the information about what they were doing. This would also mean secret innovations would be worthless, since every company would know what every other company was doing, and copy it or improve upon it immediately to sell a better version. Small businesses would be especially screwed, since large businesses can copy anything they do and undercut the cost to drive them out of business. --- ## **The World** The world at large would be a much more cautious, neurotic place, with every person focusing on their self-image (and the few that aren't being the dregs of society) while constantly worrying about government and criminals alike abusing their knowledge of their private lives. Everyone would be very polite to each other, while knowing all the dirty secrets of everyone at the same time. In short, it would be a society of extreme paranoia. [Answer] 1. Laws have adjusted to be more accurate of the "normal" human nature and perception. By this time, society can see the problems with their own society (if they choose too), *easily see what caused these problems*, and figure out better solutions. * Crime and any disputed actions have become trivial matters to solve * Society is fully aware of how *common* certain crimes or issues are, and can fully look into what caused the person to commit the crime. * There are also probably *tons* of very accurate studies dealing with human behavior and responses 2. People are either forced to behave more strictly by society, or they are alternatively very accepting * If it is unacceptable to own a cat, and you cannot keep a cat hidden, you will not be owning a cat. However, it could be the opposite as well. Everyone may say, "Who cares if they own a cat? Everyone can do what they want so long as they don't hurt others." (*It would have to be decided what all constitutes "others" and how far that extends*) Now substitute "owning a cat" for some other debatable topic. 3. Misinformation is now very hard to pull off successfully, but incredibly valuable. * How is misinformation handled by the system? Say I use my "best security" to gain privacy for a couple hours - create a private (false) document, and "accidentally" have it leaked. Is there any way this information can be removed if it was found to be false? If there is, it seems to indicate some person(s) have power over what is and isn't out there, or at least how it is displayed. If not, then not *everything* could be trusted, or if everything is trusted; then misinformation is probably *very* worth the cost in some instances. 4. Very accurate and possibly even "exploitative" targeted advertising, unless there are now laws around it. * You just looked up window curtains on Google and now have ads for home decorating. Imagine if they had all the information present in this society. [Answer] How would zero privacy impact culture - things like relationships, schooling, child-rearing, job hunts, etc. *I post this answer specifically as an alternate view to the accepted top rated and excellent answer of @user4239 - not to discredit it, but to offer another train of thought.* First, I think a lot depends on the kind of Government that would evolve in such a condition. Note that even if all information is freely available, interpretation and conclusions drawn from it are still up to the individual. As such, power will arise out interpretive authority either through force or populism - or society will split into many fractions. I can imagine mainly three scenarios, considering only the stable ones: **A. Quasi religious leadership:** Somebody gave an interpretation to the vast and suddenly available flood of information. One that does not have to be right, but gives him power to make the rules. A lot of people subscribe to this. A small number will disagree, and be either regarded as weirdos or even comply and keep silent about it because they don´t want to risk discrimination **B. Brutal dictatorship** The one with the most force under his control, and maybe the first to have broad access this new technology as it arose has seized the power. Every attempt at resistance is futile, as it will be discovered and crushed the moment it it sparks anywhere **C. "Real" democracy or sort of rule based anarchy** After some chaos and adjustment in the beginning, some overthrown governments and some violent states of anarchy everybody more or less agreed to a common set of rules and to a certain degree of common services. Obviously, this would have a big effect on the society evolved. I will concentrate on Option C, since I think that is what you mainly had in mind in your question. The more dystopian ones are, more or less the subject of several books already anyways. I think generally society will drift into different directions. A lot of people will just stop to care, stop to pretend and start to follow their desires more freely. I becomes normal when you know everybody does it. Some will do the opposite. They will live an especially controlled and exemplary life. **relationships** *Lovelife* I don´t think relationship would change too much overall. Definitively, it would not fix any issues of jealousy, as this is as much a crime of thought than a crime of body that people are jealous of. 1. I think there would be much less people living in abusive relationships, as others would **know** an help you out of it / take sanction against the abuser. 2. There would be much more People living an alternate, more personalized forms of relationship arrangements as society as a whole would **know** what´s going on in private bedrooms. This would serve to normalize what is noways considered taboos. 3. There would be "trust-ers" and "controll-ers" - people who choose to deliberately not access info about each other or the ones who would do exactly that exessiveley. Lot of conflict potential here. In all, relationships will stay just as complicated as they are now, with some added perks. Big data won´t help you with matchmaking unless some clever AI would also be developed - not part of the question. *Neighbors / friends etc.* Envy would stay about the same. People tend to realize only what you have, not what you sacrificed for that. People would have to set clearer boundaries, because you can no longer use excuses to decline a request or invitation. Things like: no, I cant make it because I am lazy today will become acceptable. **Economy.** Classical Capitalist theory still would not work, as people still are not rational beings and value of things can often only be appraised in hindsight. Same need for lawyers, other occupation. - It will be easier to detect a breach of contract. - Meaning of contracts are still up for interpretation. - No more need for NDA´s and trade secrets. - More effort to control resources, talent and machinery. - More need for data-mining lawyers that will make a case out of the surveillance data. (Was it malice or inability that led to the faulty product? etc.) **job hunts** You don´t find your employer, your employer finds you. No more interviews, they have a record of the last 6 months of performance already on tape. If you get an invite, you will get it with a reasonable offer already. They know what you are making now and what everybody else makes. More wage-equality everybody knows what everybody earns, and how much a company can afford to pay. No more bullshit-bingo when negotiating. **Schooling:** Completely new paradigm. Schooling will concentrate much more on developing skills, reasoning and the ability to obtain and filter information. No more need for teaching a lot of knowledge. No more need for grades - persons abilities and development could be observed by anyone interested. Instead there would be qualitative appraisals with recommendation of areas of further development. Universities would have true open access. As such laws would need to change to adopt to a more open-source since pattern. **Child-rearing** Parents would have to change their paradigm. Trust != control. You would know your Kid did something wrong, so you will have find ways to deal with it without completely suppressing any room for development. The good thing is, there would be less traumatized children, as the seam thing like with abusive relationships applies here too. Less chance of a child developing a severe personality disorder, as this would be obvious much earlier. **Society overall** Less *planned* crime. Maybe more crime in affect for some (the people who try to live the controlled life) Some things will not be or start to be considered a crime. Throw away you plastic bag in nature? Everybody knows it was you, and how harmful it really is! Walk nude in public? Who cares, we know how you look like from when you where in the shower... No direct corruption. A lot more populism. If you want influence, you can no longer assert it by force or misinformation. You have to convince people to subscribe to your conclusion of known facts. [Answer] I think this is quite the powerful ability, so I don't expect society as we know it to keep going. I expect a new society to rapidly adjust to this change in privacy. It should be comparable to how society adapted to the computer, or how the RIAA/MPAA evolved in the presence of bittorrent and youtube (or at least is evolving. Baby steps) Because these drones are such a monumental force in this new society, their weaknesses will have a marked effect on the construction of society. Their primary weakness is their inability to pierce the human body. This means the individual is going to be a powerful force, and it also means there is going to be great effort taken to allow human to human communication without drone interception. Observable communication will shift towards time sensitive information. The value of information will be limited in ways which make it very useful on short periods of time, but useless under long periods of time. Likely speech will shift to discuss the relationships between things that matter, rather than the things themselves. That way the things themselves can interact without ever exposing their actual essence. Western cultures will start with many codewords for things. Eventually we would stop using English all together, and switch to Chinese, which is a language more tailored to the discussion of relationships. Body language would become utterly essential to culture, especially contact. The contact of a handshake or a hug would convey subtle information that is nearly impossible to observe with microdrones. There would be an underground of rebels who actively seeks to overthrow the system by trying to design information streams which demand increasingly large amounts of processing to decypher. If information goes undecypherd (and they'd know it because they're tapped into the streams), then it may be used as a covert channel to create privacy. If the information is deciphered, then they up the ante and find something which requires even more brute force to calculate. ]

[Question] [ Let's assume I can travel in a space-time on Earth. Every time I *jump* I get to almost the *same* place, but in different **past** time relative to the first jump: it solves the problem of planet rotation, orbital moving, etc. Also if there is an obstacle in that place in another time, then I get softly pushed a little bit away, like if I appear in a collapsing invisible Zorb ball: it solves problem with survival in 99.9%. There is one problem, I know the exact location before the first jump, but I don't know the exact time I jump in. To do my tasks I need to find out at least the Earth year I'm in - as fast as possible! So what I **can't**: * Most of my locations are uninhabited almost always (like desert islands), so I can't rely on a local population or artifacts all the time. * I'm an average human, so I can't learn everything about every specific place I will travel - I can only memorize some common rules or heuristics, some limited simple or specific information. * I can't take or drastically change anything in past. What I **can**: * I can get a backpack and take everything I need and can bear. (I will update "can"s and "can't"s to clarify the question if required). --- Some leading questions: * What should I learn and take with me to determine the year almost everywhere? * What are the locations, where I can detect the year in the fastest way? * What is the most remote year in the past I can travel, so that I'm able to detect the year by any means at all? ### Update #1: Please, add some meaningful limitations to your answers: like, the average time for detection, the approximate area where your method works within declared detection-time, etc. Different answers may cover different areas or different historical periods. ### Update #2: Time-traveler worker schedule example. The time-traveler is a freelancer. He signs a contract to do something specific in the past with some specific people, events, items, etc. - in exact location. Different companies work with different locations. He has a limited series of time jumps - the last jump always brings him back. So, when he makes another jump he has to decide - can he do anything here and now, or may be he should wait a couple of years, or jump again for a better luck. That is why the known methods of detection of the year is a very valuable information for such freelancers. ### Update #3: Time machine technology. The technological level of some companies allows to program their time machines to visit some limited number of time periods in the past. The best machine has precision of ±15 years from a specified point. Also a single series of jumps (for all machines) is very-very costly - the more jumps machine can do in one series the better it is. But all machines unfortunately jumps to specified time periods in a random order. The list of time points is known to applicants beforehand, so they can decide if they possibly can distinguish at least epochs - not talking about the exact years. --- P.S. Of course, the year detection is probabilistic - i.e. methods should work with at least 85% probability. [Answer] * If you travel in the recent past (say, not before 1930): a shortwave radio. Listen for news bulletins. Works everywhere. Time to determine what year you are in: one or two hours, depending on what broadcasts you receive. * If you travel the just a little bit less recent past: a longwave radio. May or may not work; for example, it may not work in the middle of the ocean. If it works, you can determine the year in a few hours, depending on what broadcasts you receive. If it doesn't work, see next point. * If you travel in the not so recent past, but still within history, say up to 10000 years BC: a small astronomical telescope and a laptop with a practical astronomy program. Observe the planets and use the program to figure out the date. You may need to wait for two or three nights in order to identify the planets. "Practical" astronomy refers to observations made with the naked eye or with portable instruments, with practical applications. There are computer programs which can show the position of stars and planets at any given time within the last and next few millenia. * If you travel in the distant past: same as above, but observe the stars. The starts have [proper motions](https://en.wikipedia.org/wiki/Proper_motion), and their positions change, albeit slowly. You may also want to observe the position of the north and south poles; for this you may need a camera. The poles move on the sky in a 26000 years cycle, called the [precession of the equinoxes](https://en.wikipedia.org/wiki/Axial_precession) (*This is dawning of the Age of Aquarius* ...). You may need to make observations during two or three nights. [Answer] This was going to be a comment on @SRM 's answer, but it ended up going longer and more elaborate. ## Infrastructure There's something that happens any time the use of a tool becomes routine - the development of infrastructure to support it. Lots of ship traffic drives the development of ports. Colonies on a new continent build roads, trade with them builds new ports on the new continent. Access to small hand-portable radio devices drives the construction of repeater towers, and turns into a cell phone network. In this case, there would be a driving motivation to establish some kind of infrastructure to determine the date and time. It seems likely that the organisations paying people to travel in time would be willing to pay towards a system that would improve the accuracy of their mission. With that in mind, ## Hide a clock and transmitter on the moon It could encrypt its transmissions such that they look like random background noise to astronomers who aren't in the know, but be clear time signals to time travelers who have the encryption key. Maintenance isn't a problem, either - remember, you have a time machine. Make however many jumps you need through time to change the batteries/add uranium/clean the solar panels/what have you - as soon as you place it in the distant past, you can tell what the outcome was in your present and fix any problems. There's an odd phenomenon that could be tied into this as well - the issue of [Transient Lunar Phenomena](https://en.wikipedia.org/wiki/Transient_lunar_phenomenon), lights on the moon that occasionally appear and disappear. Nobody today has any idea what they are; for our purposes, they could simply be the time jumps needed to service the clock. [Answer] Since you are prepared for this task it's going to be simple enough: You need a small computer and a decent camera. Point the camera at the night sky (day does not work--while the stars are out they're swamped by the reflected light in the sky) and let the computer find planets. It can easily have been programmed to do this, find what piece of sky the view corresponds to, subtract the known stars and what's left are planets. If the trip is long enough, look for the displacement of the stars instead. [Answer] For travelling millions of years into the past: **The Moon was closer in the far past.** If you know your exact location and see the moon - a device which measure the distance to the moon would be able to calculate what time you are in (roughly). Measuring the distance to the moon can be done in many ways but one simple way is to simply measure its diameter in the sky (although since the orbit of the moon is not circular, you would have to measure for several nights in a row using just a visual measurement). **Atmospheric composition have changed over geologic timescales.** Measuring carbon dioxide, oxygen and trace elements and comparing with a detailed chart might give a hunch of where you are. [Answer] You've posed an interesting problem; I like it. I, like many others on this board, also believe a contraption that can track the stars is ideal, but I suggest a bit of techno-fantasy - a camera that can take a picture of the sky at any time, day or night, and pick up the pattern of the stars, then spit out a year. The stars are always shining; we just don't see them during the day because the Sun overpowers them. This contraption would just eliminate the light from the Sun. Like I said, techno-fantasy. I do have a question: If the traveler is jumping to uninhabited areas and is restricted from changing the past - why does the specific year make a difference? I tend to think of it a little like theft in the night. The jumper slips in, gets what they need, then slips back out. Does it really matter if he entered at 2:54 am or if he entered at 2:55 am? Am I missing something? Stated another way (for those who don't understand metaphor): If your jumper is targeting a window for between 1201 AD and 1216 AD, will not be seen, and can't change the past, why does it matter if he arrives in the year 1203 AD vs. 1205 AD? [Answer] The easiest thing to do, especially in the desert, is to make astronomical observations. The planets are a great clock face. To prevent ultra-high precision, make that work on a cycle of a few hundred years and then look at **proper motion** of stars and the exact [pointing of the Earth’s axis](https://en.wikipedia.org/wiki/Axial_precession) to get a longer range ballpark. If you arrive at night, which will happen 50% of the time, and the sky is clear, an automated instrument should make a determination as fast as it can point itself to different places. I’m thinking 5 minutes or so. [Answer] Use a Geiger counter, and travel nearby a Isotope mineral field. You will know radiation intensity will become twice stronger each time you jump in past by a multiple of [halftime](https://en.wikipedia.org/wiki/List_of_radioactive_isotopes_by_half-life#109_seconds). Ideally you want to find depots that have halftimes around 200-300 years if you want do to time travels no longer than 1000-2000 years. Note that on longer time travels the quickest way to know the average period is to become a Geologist so you know how much erosion actually "un-happened". [Answer] In the present, sync two atomic clocks. Jump into the deep past as far as you can go carrying one clock. Leave it. Return to the present (or future). Record the difference between the two clocks. After that, whenever you jump to the past or future you can always figure out when you are. [Answer] Into your backpack go a sextant and a set of star charts, from which you can calculate not only when, but where, you landed at any time within at least the last several million years, maybe more. [Answer] Based on what you describe as the job of a time traveler, your best way to find out what year you are in would be given to you when you arrive. If you're targeting a year in the past 300ish years, grabbing a newspaper would give you the exact date and year, making this easy. If you're targeting a year in the past 2000 years, and you were going to a culture which got near the Romans, you could ask for a Julian Calendar date. Beyond that, you're going to want your employer to have picked specific times of interest. Perhaps they can send you back to a time right before a predicted solar eclipse. Of course, we're going to need to understand the level of unpredictability in your time travel machine. Given that it sounds like the time machines are accurate enough to target actions within a decade, you'd quickly find that the tools at your disposal to identify a year are less precise than your time machine was in the first place. Many of the geologic timescales people recommend are great if you want to find out what epoch you are in, but totally ineffective in determining what millennia, much less decade. Accordingly, I would expect your employer to have worked out a set of events worth looking at to determine what time you landed at. Perhaps there's a good sized meteor which is supposed to streak overhead on a certain day, and a solar eclipse a year later. These could be used to fine tune. Presumably when your employer gives you a task, they already know what they want to have done, so they'll know something about the time regions surrounding it. [Answer] How technologically advanced do you want it to be? By Current technology the star is probably the best aproach. The simplest science-fantasy way to do it would be a contraption; a kind of "Time-GPS", that could evaluate your position in time by sending a message back where you came from using the same technology as you yourself used to travel time. Another way that could be by measuring the existence of certain particles (background radiation) that could only have been created during Big Bang that slowly decays. Another Option is to measure the "color" or "heat" output of the nearest star (sun), knowing the star's life cycle and a very accurate measurement tool could potentially indetify your positions in time with a few years inaccuracy. Based on human history (and the main method almost always used) is just a lot of information, a "Time Map" so to speak, future tech could potentially hold limitless amount of data and with a few decades of programming it could based on collected data simply pattern match your current position with changes in the enviroment trought out time. This would be more inaccurate on planets with no erogation system, and less accurate on planets with intelligent life. [Answer] I think that some answers are based from our civilization perspective/progress. In my opinion it depends. For example of the context of how your civilization, culture or/and you have achieved the technology/science/magic of to travel in time. I think that depending of that, measure the time could be based from atoms, stars, galaxy, universe, magic, machines perspectives, and not only from an cultural perspective (like the b.c. years perspective) and how to measure from this perspective. This context can give you parameters to measure the time passed from differents points of time/space. [Answer] Supplementary answer about the **distant past**: relative abundance of U235 and U238. U235 has a half-life of about one billion years, U238 a half-life of about 4 billion years, so if you go back hundreds of millions of years there will be relatively more U235. The relative abundance at any point in time is pretty much a global constant, unless you are unlucky enough to find yourself at the site of a fossil natural nuclear reactor (AFAIK only one is known). The best way to measure it is a mass spectrometer, but they are not very portable. However, I think if you had a particle-energy sensitive alpha detector, you could detect U235 decay events separately from U238 decay events, and to a reasonable extent exclude cosmic ray events. Then just point it at an igneous rock (or seawater, if it's sensitive enough). [Answer] Well, since you're already time-traveling, I figure you can have anti-grav technology. Assuming you have this, then the easiest way to determine time would be to have a look at the position of the continents. Bring a small anti-grav drone with a transmitter, send it up, have it calculate the year, and then recall it. This would be much faster than waiting for stars, and wouldn't be subject to weather (good luck reading the stars from ground-level in monsoon season.) And, just in case the drone can't see the continents due to arriving when the dinosaurs died, it should still be able to use star positions. It'll just take longer. Finally, if all other options fail, measure the mass of the sun. It doesn't change perfectly regularly across *its* entire history, but assuming you're going back less than a billion years you should be able to find a model that works. ]

[Question] [ Our perception of time is steeped in the rhythms of our world, and blended with the most ancient of superstitions, decrees and mathematical conveniences. Thus we have days that track our world's rotation relative to the sun (or the sun's apparent motion in the sky), richly divisible (but otherwise unwieldy) 60-based subdivisions of that, weekdays that bear the names of Gods and planets, months based (in the West) on the old Roman standardization of the phases of the Moon, and years that reflect the passing of the seasons on Earth (and thus Earth's orbital cycles around its sun). Now, in the ages to come, unless it comes to stumble and foolishly fall on its face, Humanity is likely to leave its cradle and spread the gift of consciousness to our solar system, and perhaps other stars as well. **Assuming that a majority of Humans come to live offworld, what is likely to be the most widely agreed upon way of time-keeping?** Keep in mind that: * The weight of historical precedent has brought hours from the Sumerians to us, so history has inertia, but the millenia ahead are long indeed. * It's likely that humans will one day live so far apart that signals will take days or years to travel from one community to another. Our larger solar system is about 10 of what we now call light hours across. * It's possible that humans will live at different timescales due to some humans uploading (and living at Gigahertz speeds?), or due to differences caused by time dilation during long near-luminal voyages. * Humans and their machine descendants may or may not retain the hard-coded ~24h sleeping cycle and body rhythms * If our computers retain the same basic priciples, we may preserve Unix epoch time for a while. [Answer] Local time would probably dominate. There would be a strong desire to have timescales that line up with local planetary sunrises and sunsets. However, for universal time, there's a general rule: why invent a new scheme when one already exists? We've been digging away at exacting time references for a while. We may need to update them eventually, but they should stay close: * UT1 - tied directly to the earth's rotation * UT2 - Like UT1 but with some smoothing factors (historical. no longer used) * UTC - Tries to stay in sync with UT1 by adding leap seconds, but otherwise tied to... * TAI/EAL - Weighted average of many atomic clocks. Defined to start from an epoch at 1 January 1958 00:00:00 (where it assumed the time from UT2). Originally called TAI, but renamed to EAL so that TAI could be... * TAI - Same as EAL, but with an adjustment to account for gravitational time dilation, slowing it down by about a factor of trillionth. This made them act all as though they were at mean sea level. * TCB - Barycentric time, which is more effective for interplanetary work. It accounts for gravitational time dilation as though it were a clock at-rest with respect to the solar system, but outside of the sun's gravity well. (Differs from TAI by roughly 490ms a year!) In theory a more generic time based on galactic rest could be defined. However, this would once again just be a scalar. Most likely we would keep the old Epochs (start of the timer) because there is little reason to change them. Perhaps an interstellar alliance might agree on a compromise Epoch along the way. The units in the future may not be seconds. However, that is nothing but a unit conversion, so it's easy to add. Its the handling of the atomic clocks and relativity that is so essential. [Answer] We'll still use the *second* as a frequency base, defined in terms of physical processes. To note time in a portable way, like making sure your ship reaches the planet in its orbit, the time in seconds as used by Unix. What reference frame is the time noted in? For purposes of logistics and commerce in the solar system, a suitable reference frame would be devised. It could be much simpler than what is used on Earth now (for GPS etc.) [because Earth is rotating](https://en.wikipedia.org/wiki/Frame_of_reference#Particular_frames_of_reference_in_common_use). A simple base would be to treat the the sun’s position in space, as measuered by a hypothetical clock that is not rotating or moving with respect to the sun. But the center of the sun is not really a natural place to measure from. Lets model the sun as a hollow sphere with the mass in the shell and subtract out contributions from the gravity of the planets, and imagine a clock motionless anywhere inside the hollow part. But that’s getting complicated and the model is limited by observational accuracy and changes over time. Scratch that. How about looking at distant pulsars. Model their cadence factoring in the orbital mechanics of the system and its rate of slowing. Have several so if one changes due to an anomaly it can be removed and recalibrated. Combine these adjuated frequency bases in a manner similar to what is done with atomic clocks now. Define the time not for the center but for a theoretical distant observer, and that value is adjusted based on your position in the solar system (general relativity) and motion (special relatativity). Still, the accuracy possible will never be as good as local clocks measuring local time, and technology will drive improvements based on what is *possible*. Plotting events in spacetime for data recording will use an single number, counting seconds. But what will humans use? All kinds of things. [Mars uses local *sols*](https://en.wikipedia.org/wiki/Timekeeping_on_Mars) because solar power is tied to the natural rotation. People living somewhere may have cycles that are meaningful to them and those pervade all activity. People generally live in a 24 hour cycle due to biology, regardless of local conditions, but that might be a matter of choice if some simple pill or environmental cues can make normal people cope with (say) the Martian dinural cycle. Cycles similar to “weeks” appear to be useful, as civilizations have had 5 to 10 day periods for work schedules and personal planning. So whatever can be made to fit with the imposed primary cycles, somewhere in that range, will be a *week* and the term is deliberately non-standardized and used with local convention. There is also a desire to sync up with those you’re working with, which is why bases in Antarctica use the time zone of their main supply chain and ignore the correct longitudinal zone. Do astronomers at the south pole (e.g. [BICEP experiment](https://en.wikipedia.org/wiki/BICEP_and_Keck_Array)), expecially the over-winter caretakers, follow a 24-hour schedule when the sun never rises and the machinery runs non-stop? I’ve never asked. Computers will have no trouble stamping your log entry with a universal “star date”, and for scientific measurememts it might be needed to indicate your world-line time *rate*, but that is not needed for human scale events. If *week* cycles vary, local custom might name the days creatively with intention to have personal flourishes. Or, a standard may exist for names for days in weeks of each length, or some combination of starting with the common names for work-week but naming days of local significance specially. To summarize, a colony or worksite may have time cycles of significance, which may be planet rotation period or something completely different. Human timekeeping built around that will be varied, local, and a huge mess. Official timekeeping will be a single scalar number. [Answer] While JDługosz may be correct that there will be lots of "local" times, for the vast majority of purposes there will only be the one "universal" time, and most likely a time based on the passage of seconds. UNIX time is a good measure, by odd coincidence the "starting" time is actually close to when man landed on the Moon (as far as historical events are concerned; it actually started 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970). So if you were to use UNIX time then you could actually date events from their proximity to the Moon landing with a bit of a fudge factor. Centuries from now, most people will probably choose to believe that 00.00.00 really was when man landed on the Moon, much like the AD dates on the Georgian and Julian calendars measure from the "birth of Jesus", or that the new millennium started Jan 01 2000 rather than Jan 01 2001... Standardizing time this way means that all calendars will match up (everyone knows what happened on 1000197960), and the use of standard seconds will also assist in scheduling, timestamps and electronic record keeping and calculations for spaceflight. Indeed, the use of local time as opposed to UNIX time will probably be considered an oddity and a way that the particular polity declares they are "not" (or do not wish to be) connected to the grid in any meaningful way. Asteroids and free flying space colonies will have little excuse to not use UNIX time, since their orientation to the home star and period of rotation can be arbitrarily adjusted. In the far future, it may even be possible to generate gravitational torques to cause moons and small planets to rotate at a desired rate, although probably anyone living in that era may simply adjust their own personal environments to meet their needs. [Answer] It sounds like you're going for a somewhat hard-science setting, so simple timekeeping is not the only thing you need to worry about. There are several good arguments already proposed that I agree with regarding the standardization of time (much as we know it today) across the universe and relating it to whatever local cycles exist. For practical and historical reasons it makes sense to just keep the time scale we use today as a sort-of "universal" time, because once you leave Earth it becomes an arbitrary unit, so why re-invent the wheel when we already have everything designed to use this system? (See the time dilation explanation at the bottom for a little more detail on that.) What is sorely missing so far are the biological implications. **What About the Body?** The human body's processes are based on its own internal clock, what's known as [circadian rhythms](http://en.wikipedia.org/wiki/Circadian_rhythm). Nearly every part of your biology and even psychology are dependent on them. There are [numerous studies](http://scholar.google.com/scholar?q=circadian%20rhythm%20study&hl=en&as_sdt=0&as_vis=1&oi=scholart&sa=X&ei=bAEtVd3iD4jFggT92ICgDQ&ved=0CBwQgQMwAA) on the effects of circadian rhythm disruption in the human body that show it to be a slow but ultimately disastrous process. No matter where we go in the universe, our bodies will not operate properly without taking them into account. Disruptions to these rhythms come from many sources. They seem to be regulated primarily by light, which is kind of a no-brainer since the sun controls pretty much every cycle of life on the planet. Certain wavelengths of light trigger biological processes that tell your body important information like when it should be awake and when it should be asleep, and fighting or disrupting those cycles causes physical and mental stress, insomnia and ultimately leads to higher risk of life-threatening medical conditions. **Deal With It** If you are going to be spreading out, people can't simply "deal with" a different day/night schedule, or even a different wavelength of light from a new star, for starters. They would still need to be on a roughly 24-hour cycle (I think there are some studied which say we operate better on 25-hour cycles but I can't find one) and the light they are exposed to would have to be somewhat regulated to prevent disruption of sleep patterns. You could try forcing people to adapt to a change in that, but you'd then have to allow for 40,000+ years of evolution to take place. The best way I can think of to handle it, depending on how "hard" the science needs to be, is some kind of minor hand-waving of a genetic modification that tailors people to be resistant to the influence of light, and then they would simply use some sort of sleep-aid device to control their individual biology. I'd recommend not straying from the 24-hour cycle because then you're messing with the core of human biology, but this method would give you enough variation to have people living in perpetual sunlight on a tidally-locked world with a blue star and it not bothering them one bit, and they'd be able to travel to different places with only minor consequences. **Ghost in the Shell** If you have people "upload" their consciousness to a computer, clock time would be critical to their operation (without some creativity on bio-tech or similar that doesn't use traditional computer circuits), but there's no need to deviate from the standard "universal" timekeeping system. If needed for efficiency, these people could develop their own universal standard, but would easily be able to track and convert it to "normal" time almost instantly, so it wouldn't necessarily disrupt anything. What's more interesting to me is exploring how this uploading process would affect their psyche and relationships with their squishier compatriots... **A Final Note on Time Dilation** Time dilation wouldn't really matter for timekeeping beyond finding a formula to keep everyone's watches ticking at the same speed. You'd need a way to sense your relative velocity, and watches would likely have multiple pieces of information on them like how much time has passed for you compared to, say, Earth or whatever universal constant you pick, and perhaps someone's age would be measured by their personal motion instead of in standard years, but that would require constant monitoring of velocity from birth to death. Perhaps people would just learn to estimate it and stop worrying so much about celebrating their age milestones. That could have some interesting effects on society. Legal ages to do various things like drive/fly would be hard to measure, so perhaps they would change to some sort of physical measurement or aptitude test. No matter how you handle it, if you want to explicitly account for time dilation you'll need to read up a bit on it to see exactly how it is measured. I believe Physics.SE has many posts on it. Hopefully that gives you a good enough overview of the aspects beyond just timekeeping math. Let me know if you need any clarification. [Answer] **Will they want a universal time?** Universal time is a recent concept which rose to importance with the invention of the train. Before the train, two cities may both have defined "noon" as when the sun was at its highest in the sky. This is a pretty universal definition of noon, but the clocks of the easternmost city were say, 10 minutes ahead of the western city. This was *no big deal*. Not even that, the citizens would say that if the clocks in both cities showed the same time, then one of the clocks would be *incorrect*. What's the use of a clock if it does not relate to the clockwork universe and matches the sun? Today, we have divided the world into 24 time zones *for the sake of convenience*. Clocks that won't miss a tic in a million years may still be up to half an hour "wrong", depending on their location in the time zone. We have done this because we are now in "simultaneous" communication with people all over the planet. If civilization expands to 10 light hours, this will no longer be the case. In addition, the super-accurate clocks people carry along will become out of sync due to the effects of relativity. Maybe our priorities in time-keeping is the exception? A curiosity in-between the pre-industrial and the spacefaring time periods, when "simultaneous" and "synchronized" was both real and important concepts. [Answer] Each planet would have a standard time, with periods that make sense. Mars day is 20 some minutes longer than Earth. So you could just add a couple minutes here or there, or do a time slip, where the clock his midnight and stops for 20 minutes, then starts again. Each planet would have its own time, and then there would be a galactic time, like the Unix timestamp or Star Trek's stardate. Something that has no relation to any planet or star. It would mostly only be used on board starships and inner inter planetary communications/business. Maybe base it on rotations of a central pulsar or something. Something dependable. Edit: Humans lives are dictated by circadian rhythms, meaning we sleep, then wake, eat, and eventually have to sleep again. Some people have tried to get around this, but none of the techniques are all that effective. Living outside of the rhythm (3rd shift workers for instance) is hard on your body. You can do it, and get used to it, but 3 A.M. is still going to be a low point. If they discover a cure for sleep, this could change. On different worlds with different stars and lengths of day the rhythm will have to be adjusted, but something that feels natural will work out, to the point that most people sleep during one period, and are awake during another period, and eat at roughly the same times, and from that a local time will develop naturally. [Answer] Observing a predetermined pulsar from all locations could be used to measure time. Since everyone in this scenario will be of earth origin and the frequency of the predetermined pulsar is known as observed from earth, all local time measures can be converted to an earth measurement or any other civilization that has made sufficient observations of the pulsar at their location to account for any time dilation. Communications could be timed stamped at the current pulse count and future dates based on the count. <http://www.cv.nrao.edu/course/astr534/PulsarTiming.html> [Answer] **Assuming that a majority of Humans come to live offworld, what is likely to be the most widely agreed upon way of time-keeping?** Over the eons, measurement/calculation of the Planck length would give us a smallest unit of time, we would almost certainly redefine our second as a multiple of this smallest unit. We would use seconds as a universal standard and an agreed epoch to start counting from. At the moment this is the Unix Epoch. Given rising computer word sizes as well as storage space, this would probably eventually be adjusted to an absolute and invariable reference such as the birth of the universe. Universal Time would probably be separate from Local Time and use powers of the base to track passing of time. At the moment the base we use is ten, it could possibly be different in the future. Local Time would reference the nearby cycles and scale up in cycle length and importance. Local Time would be used everyday as significance could be attached to a particular "hour", etc. Universal Time may be the Local Time if there are no cycles of importance (they must have regular cyclic importance) this seems more likely in "uploaded" individuals, especially if they have no internal cycles. For the uploaded individuals they may move towards using the smallest unit of time as a "second". Mostly because the second's status as a base unit is because the time-scales and reference point are relevant to us. If we get to the point of fitting a whole day's thought into the space of a second we would necessarily redefine the "second" possibly adopting a new name so we could keep the old one. The necessity is best seen when looking at schedules. Looking at an itinerary "Call Home @ 5:30" doesn't make sense if 1/24 of a second feels like an hour, you would necessarily redefine the hour to 1/24 of a present day second, or perhaps adopt entirely new measurements. On a closing note its probably best to observe that our units have changed over time. While not much because of historical inertia, when you leave history behind and visit the stars you lose that inertia holding you back. [Answer] It is very likely that future civilizations will keep **different time measurement scales for different events** in spacetime. **For religious ceremonies** each religion would need to decide if the ceremonies are to be performed as per local time of the person, or as per the time of some specific location such as Earth. Note that we already have discrepancies here on Earth now, for example the Muslim year is shorter than the Gregorian year by I think 12 days. Thus, when a Muslim tells you that he is 65 years old, he may have been born only 63 years ago by the Christian way of counting years. **The marking of anniversaries** such as independence days, birthdays, remembrance ceremonies, and marriages would likely be done by the local time for the places or the people. Titan may celebrate 2 independence days for every 120 times that India celebrates its independence. However, an Indian on a spaceship to Alpha Centari and back may need to celebrate 15 Indian independence days during his 700 day voyage due to time dilation. During that time, his parents only celebrated their child's birthday twice for the 15 years they were waiting for his return. **Legal privileges and responsibilities** such as drinking age and driving age will need to be coordinated with the time dilation experienced by the person. Perhaps national ID cards will have a timekeeping device, similar to how radiation workers wear dosimeters today. **Activities that must be performed on a schedule** will need their time computed as per the location where that activity takes place. The seasons of a planet do not change just because the farmers travel to other star systems. The planning to return to some planet in order to tend to the crops in season there will have to be coordinated to happen once each time the planet revolves around its sun. I imagine that we will need computers to help us calculate when the events take place, and when we must leave our current destination in order to get to the proper location at the proper time, taking both distance *and* expected travel velocity into account. [Answer] I came up with this idea for "universal pulsar time" a while ago, while struggling to write scheduling software that can handle timezones and leap ... things. Everyone synchronizes to one pulsar. Its period is the new second. Depending on your relative speed and the gravitational field you are in, you may perceive fast seconds or slow seconds. Over time, the pulsar will slow, and the second will get longer. However, whenever any two or more people rendezvouses, their dumb clocks (pulse counters) will agree that the same number of seconds has elapsed since they last met. I believe this is the most important property of a timekeeping system. [Answer] Warhammer 40K has already come up with a dating system: [Imperial Dating System](http://warhammer40k.wikia.com/wiki/Imperial_Dating_System). This is based on the idea that the only authoritative source is the Sol system, and that each other system will have their own dates, which may advance at a faster or slower pace than sol does. Their solution, is to make an accuracy marker part of the date. The key point, is that you need two things: 1) an authoritative source, and 2) a way of syncing with that source. You could change the imperial dating method so the accuracy check digit refers to how long it has been since the last sync, but having some way to doing the correction is essential. Since your civilisation is galactic, they must either have some FTL method of communication already available to them, otherwise you might as well just have each region use their own local time - the only reason you would need a coordinated universal time, is if you need to coordinate events between time zones. ]

[Question] [ > > *Of all the creatures in Hatjörn's dominion, there is none as peculiar as the Murinae Spirita, the mean booze-rat. A vermin so resilient that has developed the most wondrous means of defence and thus survival.* > > > Excerpt from *Hjårdan Animaliæ* --- Welcome to the *Most Ingenious Questions You Never Thought Of*. Today we look at the booze-rat, an animal aptly named for its unique defensive mechanism of storing strong1 alcohol in its body in order to daze/incapacitate a predator. In order to do that, one or more booze-rats sacrifice themselves so the rest of the colony can devour the now harmless attacker. Thus they 'prey' on animals such as cats, weasels and various other predators. --- **Q**: How do the booze-rats produce/procure the strong alcohol in their bodies? And how do they store it so it doesn't hurt/kill them as well? **!!**: This **question** is **about** finding possible **means of producing alcohol inside the body** of the animal; **and** *additionally* about where to store this alcohol. This question is **optionally** about finding reasons the animal will not die due to the constant presence of alcohol in its body. This question is **not** about how to evolve this animal. This question is **not** about the taxonomy of such an animal. This question is **not** about if it is an *earth*-rat nor if it is possible for an *earth*-rat to evolve into such an animal. 1*Strong alcohol*: As a household dog/cat will already suffer extremely from a simple beer I assume that some 40-45% alcohol (e.g. Vodka) would probably suffice. But: The more, the merrier! [Answer] Others have brought up the problem of strong alcohol needing more than just yeast. I'd like to propose a solution to this: forward osmosis through a semipermeable membrane into brine. The latter is relatively easy to produce inside an animal, which makes this considerably more likely than distillation (which would, thinking about it, probably have the nasty side effect that these creatures occasionally explode for no good reason; distillation requires heat). [Article](http://www.sciencedirect.com/science/article/pii/S0038092X12000436) with more details. If someone (who would be doing a bad thing) were to search for the title of this on SciHub, they might find the full text without paying for it. I'm envisioning a set of organs: a stomach with a very high proportion of amylases (to break carbohydrates, the primary food of these creatures, into simple sugars), a fermentation bladder containing a colony of yeast similar to distiller's yeast (capable of fermenting sugar solutions up to around 17% ethanol v/v), and something analogous to an extra pair of kidneys. One of these kidney-type organs would remove excess salt from the rats' bloodstream and concentrate it in the tissues of the other, which would need to be specially adapted to cope with that situation. Many animals can rehydrate by drinking seawater using a system very similar to this, only they throw away the salt and keep the water. The second would have a feed from the fermentation bladder, and force the low-percentage ethanol solution through a network of capillaries the tissues of which were impermeable to salt and ethanol, but permeable to water. As the water 'wants' to get to the salt solution to equalise the concentration of water between the two solutions, it moves through the wall and into the brine, leaving more concentrated ethanol behind. With a concentrated enough salt solution, that can result in very high ethanol percentages. I should stress that this salt would NOT be NaCl, but something more suited - from the paper, "The potassium orthophosphate and pyrophosphate salts can achieve greater final equilibrium concentrations, and at the highest concentration of the pyrophosphate salt solutions can achieve a water activity of aw = 0.24, which is capable of producing a 90% (w/w) ethanol solution" That means that the rats would need a diet rich in potassium and phosphorus, and suitable enzymes to produce the relevant salts. Good thing they're omnivores, because that means nuts, fruit, and offal, to go with the vast amounts of grain and potatoes (or local equivalent) they need for making sugars to ferment. It also means that if they were cut in half and set alight, they might burn with a somewhat purple flame. The ethanol could be deposited in vesicles on the skin of the rats, isolating them from it so they're not permanently drunk or dying of liver failure. They would therefore probably be naked rats, or at least look very mangy, and would leave a trail of alcohol wherever they walked in much the same way as our rats leave a trail of urine. That would keep their dens relatively sterile, and allow them to identify trails and locations their kind had been. It would also make lighting a match in a crawlspace with a rat infestation quite dangerous, and licking them (in the manner of toads) a popular pastime. [Answer] Science Time: How is alcohol created in the first place? The easiest, and more natural way is through *[fermentation](https://en.wikipedia.org/wiki/Fermentation)*. "As sugars are broken down by microorganisms for metabolisation (a process where they are converted into usable energy), various byproducts are produced. These "waste" compounds can be either gasses (like carbon dioxide), acids (such as lactic) or alcohols (in the form of ethanol). This is known as fermentation and a key process in the making of antiseptics, preserving spirits and a host of beloved adult beverages." --- Now, are there any microbes can metabolise sugars efficiently without being choosy about the conditions in which they do it? [Yeast](http://www.scienceclarified.com/Vi-Z/Yeast.html) are small eukaryotes that are found almost everywhere on earth, reproduce at the drop of a hat and are excellent at manufacturing large amounts of alcohol in a very short space of time. Many of these organisms are classed as being *anaerobic*, meaning they does not require oxygen to live (to metabolise), and so can thrive in environments other bacterium fail to exist in at all. To get the energy they require in these oxygen-devoid areas, yeasts convert sugars into energy through fermentation, producing ethanol as a waste product. --- And finally: how does any of this have to do with the rats themselves? **What if the rat's digestive biology (stomach bacteria etc.) included yeasts as a staple organism?** The stomach is a warm, dark, hostile and oxygen-lax environment perfect for yeast to cultivate in private, gorging themselves on any sugary materials that come their way. By giving these rats a second stomach (a cheap goon bag if you will) lined thick with mucus, where in sugar rich foods can be sent and broken down by inhabiting yeasts, a substantial quantity of ethanol will be produced. This alcohol can then be stored safely in this stomach in much the same way HCl is in ours until dissipated, either very quickly through the rear end, or when it is really needed Ie. When the rat decided its time to be a drunken hero! Through some circulatory/excretory process, when the rat is caught and about to be devoured for the greater good of it's colony, it will release the contents of it's second stomach either into it's bloodstream and main tissue mass (I mean, the creatures already going to die right?) or regurgitate it over itself, so whence eaten, delivers far more than the legal limit of booze into the predator, leaving it chill and mellow to be captured gnawed or whatever, by the rest of the party. --- **NOTE:** The yeast's process of metabolisation also creates carbon dioxide (that makes baker's bread rise), so the rats are going to need to expel much gas during the fermentation process; so the booze-rats will not only be "drunk" in sense, but also be burping and farting a heck of a lot too! How weird would that be: a colony of groggy, flatulent rodents... --- **ADDITIONAL Q & A:** A little off question, but what could attribute to the rats sacrificial tendencies? Is it purely selfless - morally justifiable "cause before self" - or is there some other biological incentive that fuels these creatures actions? The latter seems more plausible (and more widely discussed through the comments - thanks for the feedback guys). **The allure of the ultimate bender is too tempting for most to resist.** Seeing as the rats do have their own lifetime supply of booze, it would be safe to assume that they have some degree of access to the alcoholic contents of their stomach (either by choice or because minute quantities of ethanol may be excreted naturally from it over time) and may therefore regularly indulge themselves on such, the rat gradually building a tolerance to ethanol as they grow older, just as some humans do by continually drinking. Perhaps then, their heroic actions are not so selfless after all, instead simply a means of satisfying their ever growing thirst for ethanol through the biggest hit of booze they will ever have (the entire alcoholic volume of their stomachs being released into their bodies); all the rats would need for this to be achieved are ample dormant alcohol receptors (large untapped dopamine and serotonin stores) in their brains, that can only activated/accessed once the sacrificial pledge is made (hence, once evoked by a huge adrenalin or insulin spike accompanying the release of alcohol). It would not only utterly intoxicate the rodents with feelings of euphoria and unfounded courage, but also act as a pain inhibitor too. This motive for sacrifice would work to the colonies advantage, for only the rats with a greater tolerance to ethanol - a desperation/drive for more - will offer themselves to a predator; these rats logically will be the oldest drunkards of the colony and so are at greater risk of dying naturally anyway (might as well go out with a bang...). It's this attitude brought on by their tolerance that ensures the younger, stronger rodents of breeding age will live on to reproduce and perhaps even start colonies of their own. *Selflessness through selfishness.* [Answer] I'd guess that the rats eat fermenting fruit and their livers extract the alcohol and diverts it into a special bladder. Whatever eats the rat will then be treated to an alcoholic hit. It'll be a bit like eating a liqueur chocolate. Several rats may need to be sacrificed for the good of the pack. They would probably end up being farmed by the local tribesmen and fed on different kinds of fruit for different tastes. [Answer] Alcohol is actually a pretty energy dense substance. However, why this would be preferred to simple sugars (which is a typical food source) would be interesting - perhaps the gut flora of the rats efficiently breaks down 'poor' foodstuffs like grass into [Cellulosic ethanol](https://en.wikipedia.org/wiki/Cellulosic_ethanol). Contrast this with cattle, which need multiple stomachs to digest food - some handwaving required, but it would be an unusual metabolic process. The rats might 'seem' fat from their metabolic processes, and breaking down large amounts of cellulose to alcohol, stored in their liver, and other body parts. While typically the maximum percentage of alcohol in solution is limited by how misible it is in water, some processes of natural reverse osmosis or such might be able to increase the concentration of it. Or the creatures might have a tolerance to natural toxins that would increase the effect of the booze on others. Essentially they eat things nothing else would, to handle mild scarcity, and turn that into a high energy food. As for one member sacrificing itself - they might have a social structure similar to the [naked mole rat](https://en.wikipedia.org/wiki/Naked_mole-rat). This lets the colony eat, and when food is scarce, they sacrifice themselves to provide a large food source. The drunk 'predator' gets swarmed, eaten and cached. This would have to be rare enough that anything other than the most intelligent predator doesn't catch on though. [Answer] **Remember there has to be an evolutionary precedent or at least explanation for this.** If the most-alcohol-producing rats are the ones who die, nothing will force their descendants to survive, unless you group the animals in a clade that consists of just their own offspring. This means the rats who survive to breed more will be ones who produce less alcohol and so eventually this trait will breed itself out of the gene pool. I would suggest instead making the animal a lizard; the alcohol is stored in the reptile's tail and breaks off naturally when attacked by a predator. This allows re-growth of the tail and allows evolution to dictate that the fastest-growing-tails (who can survive many attacks in a lifetime) and the most-potent-booze-makers (who can incapacitate an attacker faster) would be the trends that survive. It also allows a further explanation for sun basking; providing more energy to ferment the sugars into alcohol. Porous skin that exudes gases as this process occurs could leave the area permanently shrouded in a noxious fog - something that could alert the humans of your story to the presence of these creatures. A coming-of-age ritual where one warrior must claim the tail of a lizard and drink the contents could easily be a plot point. **Again, if there is nothing that forces this development of alcohol production as a primary survival trait, chances are it will never develop far enough to have the effect you want.** Evolution must demand that the alcohol production is a trait that is positively discriminated against. [Answer] what goes in, must come out... In most animals unused food matter exits at the rear, however, before it gets there it's broken down into useful components. For the production of alcohol, we're looking at that wonderdrug sugar. Your booze rats will have a predilection for sugary sweets, in the wild, this might be sugar cane, sugar beet or various trees broken down for their sap. Now where to store that boozy poison, in this case, I would have the rats exude the alcohol in all the excretions, like cat dander. They would be immune to the effects of alcohol themselves but their saliva and sweat would cause them to be covered in a dense solution. The alcohol itself would need a medium, like a waxy discharge to prevent it from just boiling off. If you wanted to harvest/milk your booze rats, it would then be a case of running a comb through their fur to extract the wax and keeping them in a hot tank to make them sweat more. [Answer] Here is on thought on the naming of the "Murinae Spirita": As far as I understand, [Murinae](https://en.wikipedia.org/wiki/Murinae) is the name of the *Subfamily* of "Old world rats and mice". So this word is the name of a large group of different species. However, the Booze Rat is a specific species. So according to the [binomial nomenclature](https://en.wikipedia.org/wiki/Binomial_nomenclature#Derivation_of_binomial_names), the name of the species should have the following structure: > > *Genus species.* > > > *Genus* should be a Latin singular noun in the nominative case specifying the genus of your animal. (I am pretty sure "Murinae" is plural and it is definitely not a genus, but a subfamily.) Examples can be drawn from the article about Murinae, e.g. "Rattus" or "Aethomys". *species* can be either an adjective or a noun in nominative or genitive case which specifies the species within the genus. "spiritus" in fact means breath or soul, whereas "aethanolum" would be alcohol and "sucus" is the closest word I could find for liquor. [Answer] Before I answer the question, I'd like to point out this: **Alcohol is quite toxic** This imposes some interesting facets to this creature. *Storage:* First, it needs to store alcohol in isolated sack and the creature will poison itself if the sack is punctured. This would mean a skilled chef can remove this "toxic" sack from the rat before eating him, like a fugu fish. *Production:* Because alcohol is so toxic, it cannot be produced in high concentration by micro organisms. The production slows down and eventually stops as the organisms producing it are killed by it. From top of my head, 15% is the maximum concentration. This rat friend would need a multi-stage process that allows it to concentrate the alcohol it stores. I can only think of distillation and that would be difficult inside a rat. Without concentration, the amount of alcohol stored in a single rat would be too small to pose any significant challenge to the predators. [Answer] From wikipedia (<https://en.wikipedia.org/wiki/Crucian_carp>): "Crassius species exhibit some remarkable physiological adaptations to their environment. For example, in entirely anoxic conditions during winter Crassius crassius can survive for considerable periods by anaerobic respiration, with ethanol as the major metabolic end product; a facility that is highly unusual among vertebrates. During summer the fish also may survive anaerobic conditions by this metabolic expedient, though only to a far more limited extent; the winter phenotype can sustain fermentation as a substitute for respiration for several weeks on end. Experimentally the fish have been maintained under anoxic conditions for 140 days. Anoxia can be tolerated longest in the coldest water, even down to 0 °C, because colder conditions lower the metabolic rate. Alcohol production occurs mainly in the muscle tissues, but also in the liver, where the process is thought to have originated. Similarly goldfish can produce alcohol in muscle tissues, but to a much more limited extent." ]

[Question] [ Assuming the ocean is deep enough and not overcrowded is there any upper limits to the size a "sea monster" can grow? On land creatures are limited by gravity, they have to be able to generate the forces required to move (not to mention hunt, escape and reproduce). However in water the buoyancy does not limit them in the same way (which is why swimming is often used for rehabilitation after injury). Are there any similar such constraints in water or is a creature's size only limited by its food and space? [Answer] Physically there are no hard limits as the weight problems are solved by buoyancy. You would end up with interesting internal systems to handle things like respiration, blood flow, etc but solutions can be proposed for all of those. The immediate problems that are going to prove limiting factors though are: **Mobility** Only the outer surface of the creature is in contact with the water, as it grows larger and larger it also becomes less and less mobile as each time the size doubles the surface in contact with water increases by four times but the mass increases by eight times. **Respiration** The creature needs to absorb oxygen somehow and distribute it through the body. The amount of body to support in ratio to the surface able to absorb oxygen has the same problem that mobility does. In addition there is the problem of circulating that oxygen to the places where it's needed. **Food** This is a bigger problem than you seem to have considered. The bigger the creature grows the less mobile and agile it becomes. It's noticeable for example that blue whales eat tiny creatures by the massive mouthful rather than trying to hunt for their food. Even if the entire surface of the creature was mouths (in which case where do the flippers and gills go) eventually you will reach a limit where it just cannot eat enough to support its bulk. You could posit a pyramid system where the very largest of these creatures eats smaller versions, that eat smaller versions, and so on down. The problem with this though is that the larger ones would need some way to catch the smaller ones in sufficient numbers to support itself. It's theoretically possible but there would still be limits. **A hypothetical example ecosystem** You could have an ocean planet populated by essentially one dominant lifeform. The lifeform has massive redundancy, a distributed nervous system and multiple hearts/gills/flippers/etc. If a section is torn off it seals the wound and regrows the missing area constantly growing. *Stage 1: Larva* In its smallest form it lives in and feeds off massive floating beds of seaweed. *Stage 2: Proto* As they grow larger they start to hunt each other, tearing chunks off smaller ones to eat. The smaller ones mostly seal the damage and start growing again trying to avoid being eaten but a lot of them end up held down in size while a few grow larger. *Stage 3: Grazer* Larger versions move along grazing on the floating seaweed. Sometimes they eat the smaller ones but mostly they are unable to catch them. Occasionally they are able to tear chunks off a careless Proto and get a boost of protein that way. *Stage 4: Big Grazer* Hundreds of meters wide the creature munches its way through the floating seaweed leaving a cleared trail behind it and consuming anything smaller that is foolish enough to get in its way. *Stage 5: Sessile* As the creature grows larger and slower the seaweed is no longer able to sustain it, movement uses more energy than it gains. It sinks down towards the deeper ocean and goes quiet, camouflaging itself in the deep. Mostly it hibernates waiting for Grazers or Larger to pass above, when one does massive tentacles shoot out and drag them down into its waiting maw. The Sessile form would have an interesting effect in that the area above it would have few grazers, letting the smaller creatures grow and the seaweed populate in fertile abundance - until the smaller creatures grew large enough to be worth eating. This abundance would tempt more grazers into the area, only for them to be consumed in turn. Occasionally ocean currents would drift two Sessile forms close enough together. This would result in a titanic battle with each ripping chunks off the other and consuming it until in the end either one was victorious and devoured the smaller or the two drifted apart again. [Answer] # A few limits more For creatures subject to the limits of size imposed by the [square-cube law](http://en.wikipedia.org/wiki/Square-cube_law) as described in [Tim B's answer](https://worldbuilding.stackexchange.com/a/324/109) there is no point in considering the problems met at still larger sizes. So for whales, squid and fish, for example, see that answer. However, for creatures of less conventional shapes, size can be extended further, to the point that it may be worth considering the further limits that are met by hypothetical creatures of truly huge size. As we progress through these limits we get to life forms where the definition of "creature" blurs a little, so your own requirements of what should constitute a creature will affect how far you can go in your own world. # Outgrowing the square-cube law For a consistent body shape doubling the length quadruples the surface area but octuples the volume. If the internal distribution also stays consistent this also octuples the mass, making maneuvering more and more difficult. Buoyancy only helps with the support problem of mass. The inertia of a massive creature still restricts its movement, and as Tim B points out, the available surface area for propulsion cannot keep up with the much faster growing mass as a creature is scaled up. ## Changing shape The restrictions of diminishing surface area per volume can be overcome by changing shape during growth. The problem only applies to a creature that keeps the same shape as it grows. A creature that constantly increases the relative surface area of its shape as it grows would be able to maintain contact with a large surface for food and oxygen intake, as well as propulsion. ### Internally (lung) For example, animals that exchange oxygen and carbon dioxide through their skin are much smaller than animals that use gills or lungs to change their shape and increase their surface area. Even scaling up a lung does not prevent the surface area lagging behind the volume - a larger creature has more levels of branching in its lungs, rather than just the same shape scaled up. For example, the number of levels of branching in a mouse lung, if scaled up to the size of a blue whale lung, would have a far smaller surface area than the lung of a blue whale. A large lung is not simply a scaled up small lung - it is a closer approximation of the fractal tree structure of an idealised lung. So the gas exchange problem can be fixed with a self similar structure that is not simply scaled up but grows more complex at larger sizes. However, this still leaves propulsion limited by the square-cube law. Even though lungs make possible creatures considerably larger than a blue whale (the largest reported blue whales are almost twice the size of the average blue whale), propulsion means the square-cube law still applies eventually. Note that blue whales can move considerably faster than the speed they use for feeding - their size is not the upper limit even based on propulsion. In the absence of predators (orcas) and the need to migrate large distances between feeding locations and breeding locations, blue whales could feasibly be considerably larger and less mobile. ### Externally (branched body) To grow beyond the limit imposed by propulsion a creature could have an external body structure that is branching, rather than just branching internally. This would allow most of it's body to be surface, available for gas exchange, feeding and propulsion. Not only would more area be available for movement, but movement may be less important with access to so much more water in contact with its surface. Feeding through its entire surface (like the [trichoplax](http://en.wikipedia.org/wiki/Trichoplax#Feeding_and_symbionts)) rather than only through its mouth, it may not need to move very quickly. # Limited by pressure The depth a creature can descend to is limited by the pressure it can withstand. In a similar way, the size of a creature is limited by the pressure it can withstand, since a deeper/taller creature will have its lower body at higher pressure even when its upper body is at the surface. Even if the creature's outer surface can withstand the pressure, its internal workings will have difficulty beyond a certain depth. Lungs cannot be inflated against immense pressure even if the rest of the creature can stand the pressure. The heart will need to be stronger to maintain the required very high blood pressure, and the entire circulatory system will be subjected to this pressure, even in those parts of the animal in lower pressure water. Growing beyond this limit could be done by growing laterally, leading to a wide shallow creature rather than growing deeper. Alternatively having no circulatory system would allow a creature to grow deeper. However, this would require a much more branched body structure with very little internal volume - most of the body being near the skin. This can still be seen as an animal but at first glance the shape is beginning to look more like a motile plant or fungus. Somewhere in between you might find creatures that have no global circulatory system, but several local circulatory systems each restricted to a given pressure range. Changing to a different fluid (for example a methane ocean) doesn't remove the pressure problem. Different liquids are compressible to different extents, but even with very little compression the pressure still increases with depth - you can't get around that by changing the liquid. A less dense liquid will see lower pressure at a given depth, but there will still eventually be a depth at which pressure is too great. # Limited by available water This is not just the water required to accommodate the creature, but the water required to accommodate its food supply (whether plant or animal or microbial). With the depth limited either by pressure or by the total depth of the water, the amount of available water depends on the surface area of the body of water. # Limited by available energy If the energy source for the ecosystem is sunlight, then only a volume near the surface is taking in energy. Even in the most efficient case where there is no food chain and the creature takes in sunlight directly (some [animals use photosynthesis](http://umich.uloop.com/news/view.php/77109/4-incredible-photosynthetic-animals)) this restricts the size of the creature to a limited depth. It can be the same size as the surface of the water it lives in, but it can't extend arbitrarily deep with a limited energy supply. # Limited by available raw materials Just having enough water and energy doesn't allow for growth. A creature needs the raw materials from which to build its body. Whether these are absorbed directly from the water or obtained from food, ultimately those materials come from the water. An ocean of almost pure water with very few dissolved materials will support very little life, limiting the number and size of creatures. Even a single raw material being limited can have this effect. For example, growth in Earth's oceans is mostly limited by the shortage of iron. There are enough raw materials for an explosion of growth but those raw materials cannot be used at that rate because there is insufficient iron. Dumping a [source of iron in the sea leads to algal bloom](http://en.wikipedia.org/wiki/Iron_fertilization) - a sudden increase in the growth rate. # Limited by planet size With depth limited by pressure, the habitable size of an ocean is limited by the surface area of the planet. A given size planet can only have a limited ocean area, even if the ocean covers its entire surface. Simply making the planet larger only helps up to a point. Beyond a certain size, a larger planet does not provide more water volume due to the constraints of gravity. # Limited by gravity The larger the planet size, the higher the gravity at the surface. This means that the water pressure increases more quickly with depth. Not only does this further restrict the depth that a creature can occupy without being crushed, but even a creature that can withstand great pressure will be restricted by the fact that higher gravity means shallower water. The higher the gravity, the less the depth of water before the pressure prevents it being liquid. The ice we are familiar with is less dense than water and floats on top of it. Subjecting this ice to intense pressure makes it melt. However, subjecting liquid water to still more pressure forces it to become a different [type of ice](http://en.wikipedia.org/wiki/Ice#Phases) that is more dense than water. There are several types of high density ice, but the relevant point is that below the depth required for forming this ice, there will be no liquid water. Increasing the temperature of the water can increase the depth at which this happens, but for sufficient gravity there will still be an ice boundary that limits the depth, and you can only increase the temperature so much before you are just boiling off the surface water and defeating the object. So yes, there is a maximum size limit to an ocean bound creature, but just what that limit is depends on what you count as a "creature" and how extreme an environment it can survive. [Answer] No, if they are sessile animals tethered to the ocean floor. What appears to be thousands of such creatures could be all bound together by "rhizomes" that allow nutrients to be passed from one to another. Sort of an undersea animal version of [this fungus](http://www.bbc.com/earth/story/20141114-the-biggest-organism-in-the-world). ]

[Question] [ Imagine an evil dictator. He imprisons his enemies in a labor camp, but they never do any work! He doesn't want to torture them, or force them to do that since he is using all of his soldiers to build him a beautiful castle. Instead, he decides to create an incentive: every time you do a certain task (such as carrying 500 stones a total of one mile), you get a coin from an automated machine. If you get some huge number of coins, you earn freedom! The only problem is that he needs a door to release exactly one. He can't afford to send a soldier to guard the door, so he needs a door that will allow exactly one person to go through when a token is deposited into a coin slot. This is going to be based off of medieval-style technology, so no complex scanners or anything electronic. I have thought of: * A revolving door (But two people could both fit in) * A weight based door (Two thin or young people could get out) * A scanner which would check for people (Too high tech) I've wondered about this for a while, just out of interest, [Answer] Put it another way: Just let the prisoner out when he/she pays for his/her weight. The prisoner opens the door, gets in, and closes the door. The door is automatically locked. The inner walls are all slimy/oily and slant inward at the top, so he cannot get a hold on them. There is a slot for coins. He/she puts one big coin for each pound and when the required number of coins have been inserted, a hidden lock clicks, and an exit door on other side unlocks for a minute and he/she can walk out. If the required number of coins are not inserted in the slot within a minute, all inserted coins are eaten (lost) and the input door is unlocked. The prisoner can go back and work harder to try again next time. This also prevents locking the box forever by a malicious prisoner. Until the input door is closed and locked, all coins inserted in slot are just eaten, so do not even try to block the input door from locking. The output door is only unlocked for a short time, then closed and locked again. Until it is locked, the input door would not unlock. The exit path from the output door is oily too, so you are forced to slide away and cannot help others somehow block it. Even if you could, that would just keep prisoners in camp so no harm to the dictator and an occasional patrol can simply put the offender back in the camp - with the angry mob he/she blocked. The output door slides up, has a sharp bottom, and is heavy - trying to block it with your body would result just to being guillotined into two pieces. The inner piece would get cleaned by other prisoners soon (nobody would like to pay for half of someone else's corpse), the outer piece will slide away. Dictator gets a coin for each pound of prisoners body and cannot be cheated. Even if two or three prisoners came in, they have to pay for their cumulative weight, so no cheat (other than reducing the rounding-ups) possible. (Well, just be sure, that prisoners do not have tools and material inside, so they cannot sabotage it or dig holes through or make ladders to climb over the wall of the camp. But it is not specific to this kind of exit; this is common sense in unwatched camps.) --- I am an **evil** dictator. After all, the 1 minute time is really short for inserting all coins :) No, really, I am not used to count in pounds. Maybe the timeslot is more like 5 minutes, or 1 minute after last coin inserted, maybe there are 10 and 100 pounds coins or something like that ... just the prisoner is not allowed unlimited or too long time inside ... --- @theRiley: Technically it does not ensure "just one person", but as the OP put his question, his "evil dictator" have no need for extracting "just one person": * After all, he does not kill or torture his captured enemies, but he wants to free them instead (so there must be some feeding for them and really good one and stable, to ensure, that everyone has enough strength to make a lot of hard work, if he wish - and in medieval environment, many of the prisoners would be poor peons, which would like stay in the prison forever, just for the food - as work is totally optional - it would be better for them, then be "freed" to everyday hard work and big chance for starvation on regular basis) * Also that means, that the dictators peons have to provide food for prisoners - for free * He even allows them to self-organise and left them totally unwatched in the "prison" (or more like reacreational camp for big part of them?) * Also he allows them to make weapons and tools at their will (at least at stone-age level) * Work is purely optional and food does not depend on that - there must be an abundance of food * Even if they want some more materials - there are already bones and skin available (the evil dictator usually rules more than one village - sacrificial lamb could be chosen from those, who the prisoners does not love, or even hate - who said, that I cannot kill a prisoner from another country - is he/she even human for me?) * He provides infinite source of stones for making more tools * Well, we can even try to step over the stone age, as we can use metals from the coins (yes expensive in work, but totally possible, if anybody can earn "some huge number of coins, for earn freedom") * He allows his "automatic machines" containing precious coins just free to attempts to rob it (with lot of stones conveniently at hand) (and I can make holes where I wish with bow, bone and sand) * Also prisoners can use the stones to make stairs (or just hill) against any wall and run away. * He push ALL his soldiers away to work on his castle, not even left the smaller peon to go to prison once a week just to press "confirmation button" to say, that only one - not two - prisoners are leaving on one pay. * The pay can be distributed between prisoners at their will (just exchanging coins for say services, lost bets (it is easy to make cards/dices/other gaming properties in such a camp) or just bullying and rocketeering) * He can (and is willing to) pay for automats evaluating his coins as not fakes * He do not care to rule the prisoners, watch them, put them "in line" or something like that, he even do not care, if he has ANY prisoner at all (everyone can work and go free), but if he have any, he makes sure, that the prisoner lives far better than the average person in that time. So in the light of all it - why he needs to release just one prisoner at time? The only logical answer is his **pride**, as he does not want to be **cheated** and seen as a fool (he is not seen as evil by prisoners anyway - more as really a benevolent and fair ruler, who gives food and games for free and allows you to leave, if you want and do some tedious work fork for him). So this *answer* does not concentrate on exact wording of question, but to deliver, what our fair ruler (calling himself evil dictator) really wants - make sure, that no prisoner can cheat its exit due exit gate, without paying "some huge number of coins". This **answer** shows, how to make it automatic, **fair**, hard cheatable and without **even one** sentient **guard**/advanced technology/magic. None of the other answers so far provided a sure solution for a uncheatable one-person only, and I am afraid, that in the given restrictions it is impossible. So I conclude, that what the dictator needs are satisfied by this solution and that satisfying the evil dictator inside the restrictions on low technology and no guards was the core of the OP's question, even if it does not follow the text of question to the last letter, as it solves the problem hidden in the question. [Answer] Just let 2 out if they manage to fit. The door only leads to the *pit of despair*, after all. I mean you can't *actually* be freeing them. They might then be able to provide information to those on the outside about things that might compromise the prison's security. So let 2 get out on occasion - the joke's just going to be on them. [Answer] What about something like this? [](https://i.stack.imgur.com/PsliE.jpg) Allows the door to open just enough for 1 person to enter space and have to close the door to enter the room or outside. It could be very tight with spikes around the walls so they don't try and squeeze in. [Answer] A revolving or sliding door with a human-shaped "mold" will do the trick. A problem with traditional turnstiles is that two people can easily squeeze into the space, by sandwiching up or sitting on another's shoulders. If you just make this space smaller, bigger people will not be able to pass through. This problem can be somehow mitigated if a passing person would have to fit into a "mold" that is designed to fit one large human. It is much more difficult to pack two smaller humans into a seemingly sufficient volume if this volume is SHAPED. [Answer] Have you considered a psychological barrier? It's medieval times, just tell all of the prisoners that there is a mechanism in the system - there are two doors joined by a hallway. You go into the first door, and it has to be closed and locked again before the second door unlocks. Tell everyone that there is a trap door (to a deep pit with spikes) set to open if there are two people in the hallway between the doors at the same time. Any prisoner who has earned their freedom isn't going to want to risk death to let another person in/out with them. [Answer] **Human Trebuchet** Your an evil dictator, the safety of a freed slave shouldn't be too high a priority. Sling them into a nearby lake with a human trebuchet. Strap them to the device with a bracelet or manacle. If someone else decides to loosely attach themselves to the newly freed individual they will likely die on launch. If they strap themselves tightly they will drown once they hit the water. [Answer] I think you may have over-constrained your poor evil dictator. A dictator who runs a labor camp without a single guard or employee in the camp is in a really strained position. Usually labor camps have dozens or even hundreds of employees, because you generally want to have an eye on these dangerous individuals. That's actually the point of labor camps. It's a way to keep your eye on people that you don't want to kill immediately. As such, I don't think the dictator *really* need to have this precision. He doesn't need to worry so much if one or two people get out. He doesn't have to worry because he makes the door as a revolving door. No windows like you'd see on a hotel revolving door. Just a solid blank wall that rotates. He puts a ratchet on the door to make sure it only revolves in one direction. If you've seen the hotel revolving doors, there's a period where you can't go in and you cant go out. This is important because the purpose of these revolving doors is to keep air from rushing in from the outside, causing the hotel heater or air conditioner to work very hard. Well, once you reach that point, you realize that the door is opening over a spike pit that will seal your doom. There was no freedom. This is an evil dictator, not an honorable master. If you try to stop and wait, so you don't fall into the pit, your friend who's behind you with his token will try to rotate the door and push you in. As such, given the dictator can't even spare a *single* person to watch over this labor camp, I don't think he'll mind if 2 people die instead of 1. He clearly doesn't care all that much. [Answer] A particularly tight [turnstile](https://en.wikipedia.org/wiki/Turnstile) is the one person door you're looking for. The coin verification system is pretty much the only thing that would be difficult for medieval technology, everything else is fairly simple: secure sections that can fit one person at a time, and gears that allow only enough rotation for one person to go through when the coin is inserted. If it's good enough for amusement parks, it's good enough for prison. [](https://i.stack.imgur.com/iL3Bzm.jpg) [Answer] Another option is a [kissing gate](https://www.google.com/search?safe=active&rlz=1C1CHBF_enUS721US721&biw=1536&bih=723&tbm=isch&sa=1&ei=C-2yW7qyGteu0PEP34C8yAg&q=kissing%20gate%20oxford&oq=kissing%20gate%20oxford&gs_l=img.3..0i24.9263.10351..10479...0.0..0.69.429.7......1....1..gws-wiz-img.......0j0i30j0i5i30j0i8i30.YUWfSeiSHIw#imgrc=_). These are designed so that you push the gate open, which is only a small travel distance. Then, there is a small area to stand. The gate closes behind you and you can walk out. Depending on the size of the standing area, only one person could fit. There is one at the University of Oxford that is like this. [](https://i.stack.imgur.com/LXNay.jpg) [Answer] # Water Clock as an airlock The exit room is part of a water clock. The room is filled with water once per hour, and flushed every 12 hours. Inside the room is a seat with a helmet. If you have placed your coin(s) in the slot, the helmet descends upon whoever is in the seat and provides air for them for the next 12 hours. The floor drops (including the seat) to flush out the water. When the water is flushed out, so is the prisoner. Either they are flushed out dead because they didn't pay properly, or they are flushed out alive to freedom. [](https://i.stack.imgur.com/DvQAe.jpg) [Answer] # One neck only Although two thin people can try to squeeze into the same space, it would be essentially impossible for two necks to fit in a hole large enough for one neck. This is basically because human bodies are flat, but necks are round. The information I could find indicates that the vast majority of necks, from age 11 up, are between 10 and 16 cm in diameter. I reckon a 16cm neck could be squashed into a 14cm hole without causing strangulation, but two 10cm necks couldn't. How do we utilise this? Well, we have a long underwater passage sealed at the top with a wooden cover. The passage is too long for a person to swim through without drowning. It is also very narrow so swimming would be quite awkward. However, the cover has a single neck-hole. One person can have his/her body submerged in the water and his/her head above water. Here is a simple way to implement this idea: (not to scale; the passage is too short)  The circle would need to be locked so that the cutout could not progress beyond the exit pool unless enough coins were provided, then it could be rotated to the entry pool. One person could enter the pool and place their neck in the cutout, then start edging sideways around the perimeter of the circle. Eventually the person would be able to pass their head through a cutout in the wall, much too small for a person above ground to squeeze through. Finally they would arrive at the exit pool, which would re-engage the locking mechanism, and the person would get out of the water. The neck cutout would be too small for the person to pull their head beneath the water, thus preventing two people from sharing air during the journey. Perhaps it would take an hour or two to push the heavy wooden circle all the way around, but since it floats on water, it is plausible for one person to be able to rotate it. The wall does not need to be straight as depicted; for instance, it can surround only a small area within the "prison" side, which would be useful if a prisoner might need to quickly get out without being exposed to attacks by envious prisoners. It would still be a long way to the exit pool so someone trying to swim would not make it. This doesn't have a built-in way of purging the dead. However, the floor could be made into a ledge, so any who drown would sink to a deeper area below. That said, whenever a prisoner leaves, the circle would rotate for a really long time so prisoners would realise they have no chance of holding their breath long enough. This system is nice because apart from coin handling it doesn't have to somehow move and dispense items (like reusable keys or helmets) nor does it need any "active" process like filling or draining water. The locking mechanism would only need pegs, guides and simple latches. [Answer] **A Prisoner Guards The Door** A highly trusted and experienced prisoner is paid double the normal rate of freedom tokens to guard the door. The caveat is that if headcounts at the end of the day do not match the release manifest he will be severely punished and lose whatever freedom tokens he has accumulated. The door is a regular set of doors that are rigged via an iron bar so that only one may open at a time. The 2nd door is locked, and if the prisoner-guard is not presented the adequate number of tokens he will not open it and the offending person will lose all of their tokens. If two people try to leave they will both be credited with a negative balance equal to the amount it would take to buy freedom. [Answer] **Low air cavity** Think about this. The prisoner uses his money to open the door, goes through a corridor or whatever, until another door closes behind him. The point is that he finally finds himself in a closed room with little space. Even worse, the room starts getting filled with water. He probably thinks he's going to die. But the water doesn't reach the ceiling, leaving enough space for him to breath. At least while there's enough air (More people will consume more oxygen). After some time, the exit door opens and the water is evacuated. If whoever is there is still alive, he's free. [Answer] After spending tokens, the prisoner may pass through a revolving door. Let's say at most two prisoners make it through. Next, there is a jump from one ledge to another (and a gruesome pit beneath). The ledge to land on is a switch that automatically spins the other ledge by 180 degrees. As soon as the first person lands, the second person gets flushed into the pit. This principle can be extended in case you believe 3 could make it through the revolving door and one may be able to throw the other two onto the ledge instead of one after the other trying to jump. After landing on the ledge (and flushing the third into the pit), the two face another ledge (or another problem of a similar structure). In other words, you don't need a barrier that lets exactly one prisoner out, you only need a sequence of problems that are more difficult the more prisoners try to jointly achieve it. [Answer] Ignoring that the dictator really can afford one person to guard the door, and might want to have some sort of celebration when somebody actually gets out and require them to wait for the celebration.... Your original problem was that sometimes one person is as big as two others, or as heavy as two others, etc. So most of the ways you could measure whether it's one person or two would fail in the extreme case. The easiest thing is to just ignore the problem. Occasionally let two tiny people get out in place of one. Or a great big person can't get out and let him complain about that. But failing that, with medieval technology, have the exit through a moat, a water-filled corridor. Above There's an air gap at the top that a person can breathe through. To get out, he puts his neck in a stock that leaves his head in air and the rest of his body in the water. The only thing that can stick into the air is his head. Anybody who tries to swim through gets no air, and anybody who tries to crawl through the air space finds a hole at the end just big enough for a head. Two people, no matter how small, cannot fit both their necks in the stock. Arrange that it takes long enough to get through that somebody who tried to hold their breath and swim through the bottom must drown. I think this could be done with medieval technology. The device to make it take a long time to get through might be tricky. Would it work? Probably not. People are tricky, and if you leve them unsupervised they will think of something. A snorkel that can stick through the stock past somebody's neck. Etc. If you make any part of it out of wood, people will find a way to saw it, cut it, or burn it. If it's metal bolted together, they will find a way to get pliers or wrenches. If the water is above the water table, they will find a way to siphon it out. Anything one engineer can make, another engineer can unmake given sufficient unsupervised time. But it's fun to try to think of ways. [Answer] The door leads to a long corridor full of poisonous gas; the token is an antidote tablet. Not quite sure if it would be feasible with medieval technology, but you do have some artistic license. Let the gas be slightly corrosive so that any improvised gas mask or other type of protection will be inactive. [Answer] They have security doors. You have a hall with a door at both ends. First they have to pay in their token(s). When the first person enters the door closes behind them. After some kind of check, say a weight check, and after door 1 closes and locks then door 2 opens. You can even combine this with a turnstile before door 1 to prevent 2 people from going through door 1 at the same time. Make turning the turnstile hard so they have to push it hard to turn it, this would make it even harder for 2 people to reach door 1 at the same time. [Answer] **Your freedom costs your weight in gold!** This way, you can use your weighing system and be sure of the correct result. If people want to pool their resources then they'll still only be able to let out skinny prisoners who, as other answers have stated, have probably been working harder than the larger prisoners. It makes it unfair on those with glandular conditions and whatnot but this is a medieval prison, fairness be damned! [Answer] The 'door' is a submerged tunnel. Across the tunnel are air pockets that have only enough space to fit one person's head. Along the way there are turnstile doors that need a key(given from the automated machine) to open so the key cannot travel back down the tunnel. \*Since swimming was a rare skill a rope to pull yourself along would work just as well. [Answer] While this is a weird set-up, a single person "door" is possible. Imagine a see-saw filling a hallway. The pivot point is on the middle of the hall, and looking at it from the starting point it appears to be a ramp. You walk up the ramp for a bit, and then it starts to level off. Walk past the pivot and it descends to ground level, and you walk out the exit. If your buddy tries to run on the ramp behind you, the combined weight keeps the ramp locked in the "up" position. Once you are off the ramp, it can either be reset by a flunky, or the ramp is weighted enough on the "entry" end to swing back to the "up" position. The technology isn't difficult, an inverted roof truss arrangement works, much like this car ramp system: [](https://i.stack.imgur.com/Wyy0m.jpg) *One end is down to make a ramp, and in this case the other end is braced so the car remains level once the car rolls forward enough to tilt the ramp. Remove the brace and the car can roll forward and off* [](https://i.stack.imgur.com/NTM2r.jpg) *A different variation of the same idea* A few refinements could be to have the entry behind a door or right angle so only one person at a time can actually approach the ramp. So there is a potential one way door without too much high tech. [Answer] **Option 1: a turnstile** I've worked in a few places where they had these: [](https://i.stack.imgur.com/lxDNx.jpg) You can't really fit two people, but I guess desperate people might try it anyway. To counter that, the solution is to make it tighter. I'd assume those who have carried enough big rocks to earn freedom would be rather lean, so all you need is a turnstile where an average human can barely fit. Plus-size prisoners be damned, they clearly haven't done enough work. If you already have the medieval token validating machine, this is trivial. **Option 2: part-time guard duty** Sure you can't afford a full time guard for some reason. But then you could just decide people can only get out Saturdays from 9 to 10. They've waited this long for freedom, they can wait for next Saturday. Like the poet says, everybody's working for the weekend. Of course, there are problems to this, the possibility of bribery, letting someone out by mistake, or, worst, union strike. **Option 2, part 2: part-time you** Like the French say, you're never better served than by yourself. You are immune to bribery and mistakes, and besides you do want them to know you let them out because you're such a generous and nice guy. Never neglect the effect of the personal touch. [Answer] A saddle riding on a track that twists and turns like a bucking horse will force the person to hold on with both hands and any other person will have their center of gravity off center, and that would make the bucking movement very hard to counter, throwing the other person or both of them off the saddle into the try-again pillows (concrete). [Answer] How about a very long sluice / underwater tunnel? You simply then make only one diving helmet available (and weights for feet etc), with a deadly ceiling (venomous spikes?). This way you can't have a floaty hanger-on (the spikes!); the helmet is typically so heavy you can't swap mid-swim (and would live on 50% of the expected oxygen while doing more effort due to costume swapping) --- taking helmet off you'd float up, putting it on underwater you'd plummet down out of your mate's reach. The pressure differences would get you, if you're not simply following the underwater-staircase... and it's dark in there too, no communication possible. Combine that with a turnstyle (that looks like it will only let one person pass, but inevitably people will try two and succeed at some point) so there's no information feeding back to your prisoners (and don't re-imprison any successful leaver!). You'll need occasional cleanup to display the dead bodies of failed escapees. Actually that may be the most straightforward solution: Turnstile followed by a bendy route-out-of-sight. Employ **for a limited time** guards that kill **both** leavers, then 48hrs later drop the dead bodies in the main prison... this will raise enough questions and make them stop trying: How!? What?! Without this rule, when one has enough money to escape, then a cheapskate asks "can I tag along?"; you say "yea, gimme all your gold; but I take care of myself if in doubt out there" --- but in this situation it's "I'm paying full price I'm not taking any risk I go alone". I think it's cheaper to employ guards for a week at the begin than to construct elaborate defences... and maintaining defences is expensive too. YOu'll want a periodic headcount to see if people are escaping and you need to shore up defences/ deploy 'project fear' to stop them from attempting. [Maintenance costs may depend on climate too...] The prisoners have no idea if the exit is guarded at all (if there's actually two turnstyles, otherwise the legitimate leaver might report back. You'll need some communication barrier otherwise the successful leaver will send messages back in with balloons, skywriters, carrier pigeons, rocks-with-messages, fireworks/signal arrows, ... . [Answer] **The Centrifugal Sally Port Singleton Sortation System Solution** The system comes with a complete set of instructions posted both inside & outside the sally port, complete with clear illustrations, explaining the tasks required to complete the emancipation process. *Prisoners attempting the undertake the emancipation process do so entirely at their own risk*. The first sortation is by aptitude & a certain minimal level of mechanical competency. Those prisoners not capable of following instructions will have to adapt themselves to prison life indefinitely, or assume the various risks as described below. The interior chamber features a centrifugal sortation mechanism. The interior door opens for a fixed interval upon inserted coin weight exceeding the price counter-weight, this easily modified as the price of freedom fluctuates with market forces. The prisoner enters. The system is in its first operating state. It is driven by a mechanical stepper actuated by sisal twine connecting linkages. As each step is completed, actuators or timers trigger the stepper state advance step wise, until the emancipation cycle is completed, the door opening for a fixed interval, during which the freed prisoner exits, then closes. Each step has a timer-driven delay which, if exceeded, resets the chamber to its initial state, the interior door opens and the prisoner, bereft of his coin, returns to from whence he came, likely motivated in future to read the instructions more carefully. First the prisoner ready to be freed, once inside, must wind all the timers, then charge all the springs, in the following order: carousel brake engage spring, inner then outer door spring assemblies, the centrifugal shaft main coil spring, hand and feet irons compression springs. The irons are all formed to fit the normal range of adult human limbs - prisoners missing more than a single member, or having deformed or in any manner terribly oddly shaped limbs get extra rations, no freedom ever. All are briefed about the situation in their orientation session the first day, so no unhappy surprises later. As soon as all timers have been wound & each spring is charged, the stepper advances, opening access to the carousel. The prisoner steps onto the carousel near the main shaft where there are positioned hand and feet irons. Feet and hands are placed into the irons carefully one by one, feet followed by hands. In each, a contact button fires the compression spring, placing a good deal of tension upon each limb. Circulation may be inhibited, but only for a short while. When the last spring is fired, the stepper advances, the shaft brake release latch is triggered, the carousel around the main shaft, tensioned by the pre-wound shaft coil spring, then starts rotating, rapidly gaining a rotational velocity sufficient to fire any hangers on or in any significant way improperly tethered prisoner into a wall studded with 12" sharpened spikes anchored upon 3" centers (the chamber is cleaned out nightly, or as found to be necessary). This is the main sortation phase. After an interval sufficient to effect any necessary sortations, the stepper thereupon advances, firing the carousel brake engage. The brake arrests the carousel rotation moderately quickly. After a delay sufficient to ensure the shaft is stopped and vertigo has subsided, the stepper advances, the irons compression springs are unlatched, and the prisoner may disengage themselves from the irons, turn around, now prepared for the final exit sequence. Being careful to avoid the aforementioned spikes, the prisoner then pushes the clearly marked external door release button, and is on his way. After the final delay, as previously described at the outset, the external door closes, the stepper resets to its initial state, the chamber now ready to service the next emancipation cycle. If near London, please stop by our dimly lit, poorly ventilated & extremely drafty workshop. We forge, monger & mend a full line of dungeon hardware. [Answer] If he doesn't want to devote any of his soldiers to the task, another prisoner could do it instead. This prisoner would be tasked with monitoring the gate, and ensure that only one person is released. This is how he/she would earn his coins. To prevent people from forcing their way through once the door is opened, the easiest solution would be to have an outer and inner door. The outer door cannot be opened until the inner door is closed, and the inner door won't be closed if more than one person has attempted to enter. To discourage the gatekeeper prisoner from cheating and deliberately allowing more than one person through, the gatekeeper prisoners could be kept isolated from the other prisoners at all times. They could also be told that soldiers guard the outer door. [Answer] Let's get a couple of things out of the way. . 1. any door that works for a large person, will work for 2 smaller people if they squeeze into a fat man's clothing. 2. Without human, all mechanical defenses can be defeated. Let's ignore that. The only way to make this work is to give all your prisoners ankle bracelets. If a bracelet is ever removed, they explode, or the army charges in and executes the violator. Next you have a terminal. If you earn enough coins, you can go in, put in the coins and type in your prisoner number. This deactivates the bracelet. Next you have a 100 foot hallway with 2 airlock doors. Both doors can never be open together. If there is anyone in the hallway with an active bracelet, the second door cannot open. So when prisoners who are freed go in, they can open the first door. Close it behind then, then walk over and open the second door. If anyone with an active bracelet gets into the hallway, it can't be opened. Your bigger problem may be people going the other way as they don't have bracelets and could travel back and forth freely. A simple 1 way revolving door with crossing bars as a filter like in the subways solves this. [Answer] ## Once a day (or once a week if manpower is that stretched) Reinforced "airlock" cages. Each cage is large enough to moderately comfortably hold one person (has a chair included) and can be accessed by appropriate tokenage. Once a day at a designated time a guard comes, overlooks the cages, and assuming there is only one person per cage locks the entrance sides, then unlocks the exit sides and all the liberated prisoners are free to go. This requires only a small amount of effort on the guard's part (maybe 5 minutes?) while still ensure only appropriately paid prisoners are let out. [Answer] We have several answers that touch on air supply but I don't see that they are adequate--either the device could be shared or how do you calibrate it? Thus: You put your tokens in the slot and then put your head into a cavity in the ceiling that air is slowly being pumped into--enough to sustain a person. There is a spill valve on the top of the cavity that will dump the air, this value is normally **open**. To avoid losing the air it must be pressed (not a lot of pressure is needed) closed--and given the nature of the device the only available means of doing this is with the top of one's head. If two people try to cheat when they swap all the air in the cavity is spilled out. While there is enough air being supplied even for one large person (which might suffice for two small people) there isn't enough for two given that you keep losing it every time they change places. [Answer] In medieval tech, perhaps there are vicious poisonous/deadly thingies, with known antivenom/prophylaxis sources. These don't have to be snakes, perhaps there are lethal mosquito-bourne parasites (a lethal version of malaria/ebola?) and some local plant or product that's been found to confer immunity or a cure, when eaten. Your token gets you enough antivenom/prophylactic substance/antidote for one person. The exit room is designed to lethally affect anyone entering it. Problem solved. *(On an overview, you're looking for things that are definitely able to be rationed one per person. Air is an obvious solution, breathing gear too. Really, anything that you need a certain amount of to live, and a situation where two people trying to share the resource will die, will answer the question. But I prefer toxins to air/water. So pretty, those blue agonised deathly faces, when you dump them back in among the prisoners with the tag attached "another person who thought they could beat the exit token system" ;-) )* [Answer] This is a problem of supply and accounting rather than technology and doors. Each prisoner's stones needs to be collected and brought to wherever you need them. During this collection his stones are counted. This can be done by giving each prisoner their own section with a name or code associated with it, and dogtags that have that name or code on them. Or if you want to risk people thinking it's a concentration camp regardless of how well treated the prisoners are, give them a tatoo so the dogtags can't be stolen. You could combine it: Dogtags have a name and a symbol on it, as does the section. The prisoner gets a symbol tatoo and a dogtag so people can't steal dogtags and collect more coins. After hauling the stones to his section, the prisoner is tasked with stacking them in a particular way that allows the collectors who come with carts to do an easy count. Then the prisoners themselves are tasked with helping load the cart with the stones, once finished and no foul play is found they will get their coins based on the amount of stones found in a pile. This means that it might take a few weeks for people to get their coins as transportation might not come every day for their particular pile, but they will get them. If you have limited space, for example because the stones are hauled to a warehouse, the prisoners are put into groups with dogtags. The group as a whole brings stones and puts it in their section all stacked and ready for transport. Once on the carriages the group gets paid with everyone an equal share. This promotes self-regulation of the group, when one slacks off the group will be punished with slower coin gains. Should the slacking off the too much the group might punish that person by stealing a portion (or all) of their coins after collection. Groups also help self-regulate stone stealing. For example an enterprising person who decides that hauling stones so far isn't worth it if he can steal from a pile nearby. Groups can police their own section, and with proper labor division there's always someone stacking stones and guarding it from intruders while the rest is hauling the stones. Once enough coins are collected, the prisoner can pay the guys who give the tokens in the first place (easy recycling). The beauty is that this system uses the simple things you'll be needing anyways: people who collect and distribute the work (not just stones as mentioned) and who can assertain how much work was done upon collection and give out the reward. If these people are corrupt then the collection and transportation of the work would already fail and theres no worrying about prisoners getting loose too quickly, and those people would be more inclined to keep their prisoner labor high than let these people out. ]

[Question] [ It is a somewhat common limitation of spaceships in some universes, that they cannot go underwater. They can land on the planet, take off into orbit, hyperdrive into the next star system, but they cannot dive in water. A different vehicle is required to go underwater. But exactly why is that so? In the story, the characters go into the spaceport with their starship, but they need to acquire a submarine to go to an underwater city. I am looking for a rationale on why they can't just go there with their spaceship. --- P.S.: If you are going to frame-challenge and prove that spaceships can go underwater, please explain throughly. [Answer] It depends on the universe. The problem with spaceships going underwater is that they are usually built to do only one thing. One of the [most famous scenes from Futurama](https://www.youtube.com/watch?v=O4RLOo6bchU) is when the crew's spaceship sinks into the ocean: > > *Prof. Farnsworth:* Dear Lord, that's over 150 atmospheres of pressure! > > > *Fry:* How many atmospheres can this ship withstand? > > > *Prof. Farnsworth:* Well **it's a spaceship, so I'd say anywhere between zero and one**. > > > However, there are plenty of spaceships in fiction which are built for higher pressure levels. Here are just a few examples. This list is by no means exhaustive. The [Leviathans](http://farscape.wikia.com/wiki/Leviathan), biomechanoid ships in the [**Farscape**](https://wikipedia.org/wiki/Farscape) stories, were able to survive going and maneuvering underwater while not being exactly pressure–tight from the outside. In **X-Com: Terror From The Deep**, the aliens assaulting Earth live on the bottom of the oceans. The final base to be stormed is at the Mariana Trench. Their ships work both abyssal depths and in space. The **Deep Angel Supercav** online sci fi series had supercavitating fighters that could be deployed both in space and underwater. In Michael Crichton's **Sphere**, a spaceship from the future is sunk at around 300m, but still manages to go to space. In the **Star Wars** universe, the [Trident-class assault ship](http://starwars.wikia.com/wiki/Trident-class_assault_ship) can travel underwater and in space. In the **Masters or Orion** series of videogames, the [Trilarians](http://masteroforion.wikia.com/wiki/Trilarian) are an aquatic race that builds their cities underwater - therefore their ships are launched from water to space. In [**Flight of the Navigator**](https://en.wikipedia.org/wiki/Flight_of_the_Navigator) the ship Trimaxion Drone Ship goes underwater. And so on, with more and more underwater scifi being added every year. [Answer] ### Spaceships are not supposed to withstand a lot of external pressure Have a look at our sister site Space.SE and the question [Do spacecraft have similar structural integrity requirements as submarines?](https://space.stackexchange.com/q/1664/23026) for some information about this problem. Here are a few quotes relevant to this question that come from the answers: > > Next, the orbital craft. To get there it must be be light. A mild kick could have pierced Apollo's walls, ISS is more sturdy but still it's to withstand 1 bar pressure difference towards the outside (that's equivalent of mere 10m submersion depth), and again - towards the outside, that means no need for cross-beams to prevent buckling; it has natural tendency to bloat like a balloon. > > > The basic problem is that a submarine is supposed to go quite deep and withstand the pressure of all the water and atmosphere all around it - while a spaceship is supposed to withstand all the pressure from within from going outside. > > Spacecraft are designed to contain internal pressure of not more than one atmosphere; submarines are designed to withstand dozens of atmospheres of external pressure. > > > The difference in requirements are big. > > The structural members of a spacecraft hull are predominantly operating in tension, at a significant fraction of the material's yield limits, and the most likely failure mode would be tensile fracture. The structural members of a submarine hull are predominantly operating in compression, and the most likely failure mode would be buckling. > > > --- For some interesting twist on your question you might also want to check out a question on WorldBuilding.SE: [Would a submarine make a great spaceship?](https://worldbuilding.stackexchange.com/questions/23521/would-a-submarine-make-a-great-spaceship). The answers give some interesting insight into problems with the other way around, such as [risky pooping](https://worldbuilding.stackexchange.com/a/23649/28789) (I think that's the biggest and by far most hilarious problem outlined in the thread). [Answer] There's a few potential reasons for this. I'm going to be making a couple of basic assumptions here, namely that the people on these ships are your typical oxygen-breathers from reasonably Earth-like planets. **Shape and Propulsion** Spaceships are, by and large, going to be out in space. They don't need to worry about aerodynamics unless they're going for atmospheric entry, which is at best a minority of what they're doing. Assuming a standard Earth-like planet, water is *several orders of magnitude* denser than air, which means streamlining suddenly becomes critical if you want to move underwater with any speed. A properly streamlined spaceship is hardly impossible, but it's going to get in the way of optimizing for cargo/weaponry/engines/etc., which is a point against doing so without a good reason. There's also the problem of going anywhere. As I just said, you can't really go fast underwater, simply due to the need to move the tremendous mass of water in front of your vessel (multiplying the force required). I can't predict what's going into the engine of your spaceship, but it's probably something extremely high-energy; to be able to get off a planet and into space, you need *power*. I don't know what it would do to be firing engines like that underwater, but I strongly doubt it would be good for the ship to have that much power trapped right near the engines (evaporating who knows how much water and probably creating a shockwave from the sudden expansion) any more than it would help any unfortunate ocean life near the area. **Pressure** Spaceships are designed to retain atmosphere: they're designed to resist pressure from within, as an explosive decompression is obviously undesirable. Entering the atmosphere reverses that strain, but that's a reasonable thing to design for. Entering the water? Going underwater far enough to submerge your spaceship (assuming we're talking something bigger than a one-man fighter) is going to put several atmospheres of pressure on the exterior, a strain it probably was never designed to withstand from that direction (being designed to withstand a single atmosphere of pressure from within). You're going to spring leaks pretty fast, especially if you want to dive more than a hundred metres or so underwater. **Need** Generally, machinery is specialized: it's made to do a specific job and do it well. Trying to make one machine (your spaceship, in this case) do too many things at once will make it exponentially more expensive and probably be inferior to using various specialized machines for the tasks at hand (in this case, using a proper submarine or other such vessel for underwater exploration and leaving outer space to the spaceship). This is probably the most important reason of all: there is no real reason to spend all the extra credits on making your spaceship capable of diving when you could spend those credits on a suitable submarine for the purpose and still have some left to improve your spaceship for other purposes (like adding a cargo module to your spaceship to hold said submarine). The economic case doesn't really exist. [Answer] I'm going to challenge this. ## All spaceships ***capable of landing*** are able to do this. The Space Shuttle glided to its landing. Not very well, admittedly, but it's another case of [Samuel Johnson's performing dog](http://www.samueljohnson.com/dogwalk.html) - you're amazed to see it happen at all. [SpaceX](https://en.wikipedia.org/wiki/SpaceX) have put a substantial amount of effort into landing a rocket on its tail. But the Mercury, Gemini and [Apollo](https://en.wikipedia.org/wiki/Apollo_Command/Service_Module) capsules all splashed down into the ocean. Clearly therefore they can survive at least some immersion in water. It's not known exactly how far they sank after splashdown before they floated to the surface again, but they will have gone properly under. These American capsules were all designed to float. The [Soyuz](https://en.wikipedia.org/wiki/Soviet_space_program) is not, and their missions have all intended to land on the steppe, so no-one needed to make sure they floated. Except that [Soyuz-23](https://en.wikipedia.org/wiki/Soyuz_23) landed on a frozen lake, crashed through the ice and sank to the bottom. Lake Tengiz is apparently between 2.5m and 6.7m deep. The capsule (and cosmonauts) survived perfectly well - the only problem was waiting to be retrieved. Why are capsules able to do this, when the walls of the ISS are so flimsy? The simple answer is that they're built for [re-entry](https://en.wikipedia.org/wiki/Atmospheric_entry). When you think that the capsule is designed to expose its crew to no worse than continuous 10G loads, that needs some serious structural strength! Whilst most of this load will apply vertically on the capsule, there are substantial side loads too, so the capsule needs to withstand very large stresses in all directions. This translates to pressure on panels as well. In space, there is naturally 1atm of pressure from the inside out. On re-entry though, there is an engineering challenge to keep superheated air out of the structure - this is what caused the loss of [Columbia](https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster). So all panels must withstand some significant pressure from the outside as well. The ISS can make assumptions about panels pushing outwards, but anything going through re-entry has to have panels locked in both directions. I don't have a figure for this, but I'd expect at least a couple of atmospheres of pressure. This gives us a definitive answer. If your spaceship cannot enter the atmosphere, it probably cannot survive underwater. But if your spaceship is built to enter the atmosphere, then it will ***always*** be able to survive underwater to at least some degree. Exactly how deep would need more detailed knowledge of the specs your hypothetical spaceship was built to, but no-one should be surprised at it being perfectly happy underwater. If it's rated for 2 atmospheres of external pressure during re-entry, that means it's rated to 10m depth. [Answer] Submarines (and all water-borne vessels) have a carefully-designed buoyancy. They must be no more dense and no less dense than water. Submarines have ballast tanks (to manage their buoyancy). They have have a suitable propulsion system -- e.g. propellers, a rudder, trim tanks (to govern attitude), and a hydrodynamic shape. Not to mention instruments (sonar and so on). And pressure (already mentioned in other answers). They coud be submersible, but only if they were designed to be. The only thing that is inherently suitable about a spaceship is that it's air-tight. [Answer] # Short Answer In a realistic world, most vessels will be optimized for a single environment (space for space stations, bicycles for land, or submarines for underwater). Some vessels may be capable of travelling in two environments, but they aren't good at either environment, and the more different the two environments are, the harder it is to justify the vessel's existence in your world. For example, although flying cars exist...sort of (see image below)...they are not commercially viable. They’re too expensive for the daily commute to work (bikes, busses and cars are the better alternatives), but not efficient enough for cross-continental flights (a commercial jet would be better). That's not to say a vessel that could travel in sea and space *couldn't* exist...but there would have to be a compelling reason for it to exist. **For example, an ocean planet specializing in underwater mining and trades with other star systems may have reason for space ships to double as submersibles --- but even in this extreme case, those needing to be underwater (the miners) would not be the ones needing to be in space (the traders).** Such a vessel might exist as a toy for a very wealthy person, or a spy-fi gadget (like James Bond's submersible car--see below), or as an experimental craft in a research lab. There's almost certainly no reason for it to exist in common use because it would not be commercially viable. # You asked for thoroughness.... Qualification: I'm a graduate-level planetary scientist specializing in fluid/atmospheric dynamics and a lover of science fiction. A more thorough answer depends on lots of things, but in terms of physics, it comes down to density, speed of travel, pressure, and technology. # Density and Speed of Travel The denser a medium is, the more effort it takes to move through it. This is why it's easy to move through air, harder to move through water, and difficult to move through a thick mud (there are other effects at work, but density alone would be sufficient to explain those observations). The faster you move through a fluid, the more it resists your motion. In fluid dynamics, these effects are captured together in the concept referred to as "ram pressure". This "pressure" is the slowing force per unit area that an object moving through a fluid experiences and is generally proportional to the speed of motion relative to the fluid times the density of the fluid. Ram pressure is the force per unit area that an object experiences as it pushes away particles in a fluid it is moving through. To an expert, "ram pressure" is slightly different than "air resistance", but it's similar enough that you can probably think of them as the same in many situations. When gravity causes a skydiver to fall faster and faster through the atmosphere, the atmosphere's ram pressure on the skydiver increases with speed (and very slightly as the atmospheric density increases closer to the surface). When the ram pressure times the cross-sectional area of the skydiver equals the force of gravity, the forces balance and the skydiver reaches terminal velocity. # Pressure As others have noted, spaceships are built to withstand certain pressure conditions. They must withstand explosion (from internal air pressure) in the vacuum of space and equalized air pressure on the surface of a planet. The surface pressure at a given point on the surface is literally equal to the weight per unit area of the atmosphere above it. The same is true underwater: the pressure at a given depth is equal to the surface pressure (one atmosphere) plus the weight of the water per unit area above that depth. Here's where things get fuzzy: Some planets, like Jupiter and Saturn, have very thick atmospheres. On one hand, a given world might have a really thick atmosphere -- in which case spaceships visiting the planet *would* be need to be built more like submarines to withstand the incredible pressure. On the other hand, the atmosphere might be thin, and the "ocean" might be of some exotic liquid that is less dense than water. In that case, submarines wouldn't need to be as heavily fortified against pressures because the pressure would increase with depth less than it does in Earth's oceans. In either of these two cases, submarines might look more like spaceships, depending on the depth they are designed for. As others have noted, a thicker shell to protect a vessel from pressure extremes is heavier. The added mass would mean that propulsion systems would have to work harder. Thus a heavier ship would require bigger (or better) engines and/or more fuel -- both of which would add to the mass of the ship, which would require more fuel, and so on. For more information, read about the [rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation). # Propulsion * Jet engines would not work because they take in air (oxygen). They would not work well in the vacuum of space and would not ignite. * Rockets work fine underwater in theory because they require no air (up to a limiting pressure) -- this is why they work well in space. + *Extremely* high pressures would push the outside fluid into the rocket, totally overwhelming the rocket so that it could not force exhaust out the nozzle. * Propellers work well underwater, but not in space because they work by pushing material backwards, which causes the ship to move forward. There's essentially nothing to push in space. As far as futuristic and/or hypothetical propulsion systems, it depends on the technology, the density, and on the universe. Can faster-than-light engines work underwater? Ask the author/owner of the universe why or why not. # Transition Between Atmosphere and Ocean A spaceship needs to be capable of entering an atmosphere smoothly from the vacuum of space. For this reason, many have struts to slow them down as they enter the atmosphere at tremendous speed and heat shields to dissipate the heat. This works because the density varies very slowly between the top of the atmosphere and the surface. Physically speaking, the slowly-increasing density means the ram pressure on the vessel varies slowly enough so that the ship -- and its occupants! -- do not experience a sudden and damaging deceleration. Any vessel that travels from an atmosphere to an ocean will need to be built for the transition from the lower-density atmosphere to the higher-density ocean. Human bodies can handle the transition at low speeds, like when we jump into pool water from the side, but not at higher speeds, like when we belly flop from a high diving board 10+ meters above the surface of a body of water. ### High Speed Impact: more potential for damage [](https://i.stack.imgur.com/BjwiD.gif) ### Low Speed Impact: less potential for damage [](https://i.stack.imgur.com/CjwJv.gif) This is because the higher speed increases the ram pressure. The ram pressure of the air is negligible, but the ram pressure as we hit the water can be painful! In exactly the same way, and for exactly the same reasons, any vessel transitioning between atmosphere and ocean would need to be built to withstand the sudden -- and potentially dangerous! -- increase in ram pressure that would slow the vessel down. The ram pressure is minimized when the surface area is decreased. This is why belly flopping (larger surface area ==> larger ram force ==> larger deceleration) hurts more than diving in with arms crossed at the chest and toes pointed down (smaller surface area ==> smaller ram force ==> smaller deceleration). ### High surface area dive: more potential for damage [](https://i.stack.imgur.com/sxQAu.gif) ### Low surface-area dive: less potential for damage [](https://i.stack.imgur.com/hyD2C.gif) On Earth, a spaceship travelling more than a few dozen meters per second would break apart on impact if it tried to "dive" into the water, unless it were significantly more fortified than our current technology allows. This effect would be more pronounced for planets with low-density atmospheres and high-density oceans, and it would be less pronounced for planets which have a smaller difference in density between the atmosphere and ocean. # Shape Considerations Because the density in an ocean is very high, the ram pressure is significant. For this reason, our submarines have a streamlined shape to minimize the ram pressure and the drag. Assume for the sake of argument-by-intuition that the International Space Station had engines and a strong enough hull to move around underwater. It is not in an efficient hydrodynamic shape and the engines would have to work very hard. Moreover, if travelling fast enough through the water, it's possible some of its components would break off. Spaceships meant only for space do not need to have aerodynamic or hydrodynamic shapes because they do not travel through air or water. Example: the [Death Star](http://starwars.wikia.com/wiki/DS-1_Orbital_Battle_Station) or orbital space stations. Spaceships which land on planets need to be at least somewhat aerodynamic so that they do not burn up in the atmosphere or have parts break off. Example: [X-wings](http://starwars.wikia.com/wiki/X-wing_starfighter) in Star Wars or the [USS Enterprise](http://memory-alpha.wikia.com/wiki/USS_Enterprise_(NCC-1701)) starship from Star Trek. The faster the atmospheric entry speed, or the greater the density gradient in the atmosphere (e.g. the greater the planetary gravity), the more pronounced this effect will be. Some vessels, such as the [TARDIS](https://en.wikipedia.org/wiki/TARDIS) from the [Doctor Who](https://en.wikipedia.org/wiki/Doctor_Who) universe, can land on a planet without travelling through atmosphere or ocean. For this reason, they don't need to be aerodynamic or hydrodynamic. # Summary / Conclusion Different vessels are built for different purposes. If a ship is built for a particular set of conditions (e.g. space-only, air-only, underwater-only), it can be optimized for those conditions. If a vessel is designed to experience very different sets of conditions, it is much more difficult to optimize the ship to both sets of conditions, so sacrifices (e.g. sub-ideal designs like higher mass ships) must be made. The more different these conditions are, the harder it is. In theory, a car can be made into a submarine, but it would be neither a great submarine nor a great car: [](https://i.stack.imgur.com/Ol1Ck.gif) A vessel can go in the air and on the ground, but it's neither a great car nor a great plane: [](https://i.stack.imgur.com/adlkH.gif) A plane can go into space, but it is neither a great plane nor a great spaceship: [](https://i.stack.imgur.com/Dlb3F.png) These outlandish transport vessels attempt to make travel possible in just TWO different environments with a single transition. For a spaceship to travel underwater, it would need to be designed for water, air *and* space — THREE different environments with two transition regions. [Answer] There is something along these lines that was almost real, but was never built. Back in 1963, there was a proposal for the "[Sea Dragon](https://en.wikipedia.org/wiki/Sea_Dragon_(rocket))". While not submersible in the sense that a sub is, this massive rocket was 150 m (490 ft) long and 23 m (75 ft) in diameter and would have launched right from the sea. [](https://i.stack.imgur.com/COo3r.jpg) It could carry an estimated 550 tonnes (540 long tons; 610 short tons) or 550,000 kg (1,210,000 lb) into low Earth orbit (LEO). It's first stage would have been powered by an enormous 79,000,000 lbf (350,000 kN) thrust engine. Compare that to the Saturn V rocket, with 140,000 kg (310,000 lb) of payload to LEO and 7,891,000 lbf (35,100 kN) of thrust. [Answer] Because it's not designed to, and it wasn't deemed a worthwhile cost to adapt the design to do so. Broadly, a spaceship's job (particularly one that flies in the air and in space) is to hold air inside the ship and resist, say, heating and atmospheric forces. Unlike a submarine, it doesn't have to cope with high external pressures or immersion. This lends itself to some design simplifications- external pressure requirements are much lower, and you can shroud water-susceptible components (against rain) rather than sealing them in. External access panels can be added for ease of maintenance. Heat ablation tiles probably come off easily for replacement. All these things will be selected without much regard to submersion, and as a consequence a dip in a lake (while unlikely to be completely fatal) is likely to cause no end of headaches for the crew. And don't even think about oceans - if they're anything like ours the salt water will do a real number on the ship from mere immersion, to say nothing of trying to dive like a submarine. [Answer] Any spacecraft that is designed for both atmospheric and exo-atmospheric use must essentially be built along aviation lines - where mass-limitation is the key. Under any real-world physics, getting mass up to escape velocity is very energy intensive, which means that any grams saved are worth saving. Spacecraft must withstand many things; but certainly when it comes to transiting Earth-like planets (and the space between them) high pressure isn't one; just enough to hold around 1 BAR. Submarines on the other hand are incredibly heavy as they have to withstand far more pressure. For example, the *Kilo*-class submarine and the International Space Station are both around the same size (~70m) but the *Kilo*-class weighs around five times as much (2000-2400 tonnes compared to 400 tonnes). TL;DR - unless you have an exceptionally compelling reason why the spacecraft would need to go underwater and to space (rather than having two separate vehicles) then it wouldn't be worth the huge compromises. [Answer] ## Because it is full of air It is like trying to submerge a balloon, and the thrusters just aren't powerful enough. A long haul spacecraft needs to provide food and water and deal with waste, and this problem is solved by onboard farms, where plants and fungi absorb the waste, make food, make oxygen, and generally keep everyone alive. This requires a large volume of air. At the same time, the craft will be designed to be as light as possible, so the hull of the craft might not be very heavy. The end result is that it's overall density is 1/5 of water, so it's engines would need 4x it's weight in thrust to go underwater. But 4G is rather unpleasant and won't make you much faster due to fuel/reaction mass constraints, so the thrusters simply aren't that powerful. Edit: Since ArtisticPhoenix mentioned fuel, I thought I would look up the density of that. Liquid oxygen is slightly denser than water, at 1.141 kg/L, but liquid hydrogen is very light, at 0.071 kg/L. In the correct proportions, that's an overall density of 0.427. Now a spacecraft should be able to push itself underwater with that sort of density, but it is clearly not the right vehicle for the job. [Answer] It's also a matter of efficiency. Spacecraft are weight sensitive: the more mass, the more energy needed to move the spacecraft. This is especially prevalent when moving from the surface of a planet to orbit, where the spacecraft has to counteract the planet's gravity. One could build a spacecraft that could also travel underwater. The streamlining to reduce atmosphere friction when going from surface to orbit would also add benefits while underwater. Since both situations require an artificially created atmosphere, the life support system would be essentially the same... both submarines and spacecraft today have systems to remove CO2 from the air, and add oxygen. However... the pressures involved underwater are the opposite of what a spacecraft encounters... instead of 1atm pressing from the inside outward, a submarine deals with pressure from the outside pressing inward. Also, the pressures involved underwater are far greater, requiring a much stronger (and heavier) construction that would be of no benefit while in space. So, while you could build a spacecraft that can also go underwater, it would be extremely heavy, requiring huge amounts of energy to move. A more efficient approach might mirror the LOR method used for the Apollo moon missions: a main spacecraft built for long distance travel and re-entry, with a specialized spacecraft optimized for the moon landing. Your spacecraft could just carry a small submarine for underwater operations, without paying the huge weight penalty of taking the entire spacecraft underwater. [Answer] # Pressure Short answer: Spaceships aren't designed to be under pressure. Long answer: Most spaceships operate in space. There is generally none (or negligibly little) air in space, and, assuming the spaceship is carrying humans, there will only be one atmosphere (~14 PSI) of pressure inside of the spaceship. On the other hand, water is much, *much* denser than air, so most submarine ships (like submarines) are built to endure high pressures. The pressure at 490 meters (the operating depth for the Seawolf class nuclear submarine) is roughly 1672 PSI. A spaceship would simply be unable to withstand such pressures. # Propulsion Short answer: Rockets are not entirely waterproof, and rocket engines don't as well underwater. Long answer: Liquid-propellant and solid fuel rocket engines both contain oxidizer as well as fuel, so in *theory* they would be able to operate underwater. Unfortunately, one of the main issues with this is that ignition would be impossible underwater. Additionally, many spaceships are not entirely airtight; only the passenger-bearing sections are airtight. This creates issues, as water could leak into the spaceship's cavities, and water does not play well with electronics (and many other things). # Maneuverability Short answer: Spaceships are not adapted to water resistance. Long answer: As we mentioned before, water is very dense. Spaceships generally operate in a vacuum, so water/air resistance is not a problem for them. Unfortunately, water is much more constrictive than air/vacuum conditions, so streamlining your spaceship becomes essential when it goes underwater. Otherwise, fuel will be wasted, as the craft is not hydrodynamically optimized. # Corrosion Short answer: Water will corrode your spaceship. Long answer: Spaceships are not in contact with corrosive compounds (generally), except possibly the engine (which is constantly in contact with oxidizers). Sea water is highly corrosive (it is very saline, and salt does not play well with metal), so a spaceship that regularly (or even occasionally) went underwater would require oxidization control (in addition to all the other modifications they would require to go underwater). Many ships, vehicles whose *only job* is to be underwater, don't have this down, which means that corrosion-proofing a spaceship will prove to be incredibly arduous. # Conclusion Spaceships cannot go underwater because they are not designed to withstand pressure, are not built to withstand water leakage, will corrode due to seawater, and are not optimized to travel through water. [Answer] The other answers already provided the biggest issues such as the spacecraft being designed to have higher pressure on the inside than the outside, fortifying it even more to get deeper than a few metres would increase mass and therefore fuel consumption... The same applies to ballast needed and another way of propulsion. All of this would make it hard or even impossible to reach high speeds and transport a lot. Another thing not mentioned are that materials used in spacecrafts today will be damaged by saltwater or whatever the ocean/lake will be made of. One possible craft I could think of were something similar to a spaceshuttle that can be used like a seaplane by shielding the engines from liquid and deploying some sort of flotation device [Answer] There are many problems. 1. The water itself: Spaceships are designed to travel in near-vacuum environments. Thus, aerodynamic design doesn't really matter. Even if the spaceship decides to enter the atmosphere, it can probably shoulder its way through. But water? Water is DENSE. Submarines need some serious aerodynamic design to cut their way through water efficiently. If a spaceship is not designed aerodynamically, trying to travel through water would be like swimming through gelatin: slow and seriously not fun. 2. The pressure: Spaceships are designed to travel through space. In case this was not common knowledge, space is REALLY empty. The hull of a spaceship is more concerned with keeping stuff that's inside, inside. As something goes deeper into the water, the pressure increases. There is a reason submarines are built with thicker armor than tanks. If a spaceship tries to go deep, it will quickly develop leaks and may even crumple like a tin can. 3. The entry: You have all heard the saying: Falling from high up, water and concrete are about the same. Thus, things entering water must either start from inside it or present a small surface of impact. Considering that spaceships are gigantic, flat, fuel-guzzling super-fast monstrosities, they would probably break apart on impact with the water. 4. The reasons: There's a reason why spaceships are called SPACE-ships. They are optimized for space travel, and space travel only. It is much better to have specialized vehicles for every job than a jack-of-all-trades-master-of-none. There is no reason someone would take a spaceship into a water body, when they could just as easily get a submarine down from the ship and do the same job with much more ease and convenience. [Answer] I’m late to the party here, but an additional reason that I didn’t see anyone else bring up already: spaceships realistically might ignore hydrodynamics if they only need to fly through space. Fictional spaceships are designed purely to look impressive, and a lot of them would move through the water like an anchor. Although more do look like aircraft or ships. [Answer] To directly answer the question, the reason a ship in a science fiction story can't go under water is because it's a plot device meant to further some part of the story. At that level there's no reason for it beyond what the author decides. If you're looking for a more "reality" based answer, the answers about the design differences between submarines and spaceships were pretty good. Another thing to consider is that a "real" spaceship probably wouldn't be able to enter an atmosphere without burning up. A "real" spaceship would likely be unable to do anything but slightly alter where ends up crashing if it tried to land on a planet. And any ship that actually made it to the surface in one piece, would be unlikely to ever escape the planetary gravity well afterwards. You really need to be able to do all of these before you can even consider going under water. [Answer] You're missing the middle layer of air between the vacuum of space and liquid water. You can have spaceships that never enter atmosphere thus have different propulsion and shape to aircraft that never leave atmosphere which in turn has a different propulsion and shape to a submarine. Each vehicle type has different problems and completely different engineering. Spaceships need radiation shielding. Submarines need water proofing. Aircraft needs aerodynamic design. In theory you could make a spaceship that can go underwater but it makes it more expensive and complicated than having three separate vehicles and less efficient than a specialist vehicle. [Answer] If your unable to close the "open" nozzle at the end of your spaceship couldn't you just say that if the seawater entered into the ship through the nozzel any left behind traces of seawater would cause engine failure or cause the engine to blow up? thus eliminating the ability of the ship to go underwater. or that the ships hull is made of a special alloy that has a reaction to seawater that causes a deficiency in hull integrity making space travel no longer viable for said ship. [Answer] of course it depends on the universe, or rather the spaceships in the universe, but a likely explanation is pressure. In space there is hard vacuum. under water there is heavy external pressure. Even if the engines would work (pretty big if), the hull wouldn't survive the pressure for long. [Answer] The Star Trek universe contains a number of examples of spacecraft operating in either liquid or high-pressure gaseous environments, including: * The Delta Flyer (Voyager episodes "[Extreme Risk](https://en.wikipedia.org/wiki/Extreme_Risk_(Star_Trek:_Voyager))", "[Thirty Days](https://en.wikipedia.org/wiki/Thirty_Days_(Star_Trek:_Voyager))") * USS Voyager (episode "[Scorpion](https://en.wikipedia.org/wiki/Scorpion_(Star_Trek:_Voyager))") * USS Enterprise (TOS: [The Immunity Syndrome](https://en.wikipedia.org/wiki/The_Immunity_Syndrome_(Star_Trek:_The_Original_Series))) In each case, the "realities" of the situations are either **ignored** or **handwaved**. The Delta Flyer is supposedly built from special (ambiguously specified) materials to enable it to operate in the atmosphere of a gas giant, but it is somehow also able to, in a later episode, comfortably splash down into and operate submerged in an aquatic environment for which it wasn't originally designed. Similarly, Voyager somehow enters, and successfully navigates "fluidic space", and the Enterprise (and one of its shuttlecraft) successfully enters and navigates the protoplasm of a giant (planet-sized) cell. The point here is that these are examples of more fantasy sci-fi than hard (science-based) science fiction. Although the Star Trek franchise draws on science advisors, it seems to be more for convincing techno-babble than scientifically plausible scenarios. In posing the question "Why can't they..." you need to consider examples where is does occur, and how (if at all) it is explained in-universe. As stated in other answers, spacefaring and submersible structures have very different, if not contradictory, design requirements. Sure, you could probably launch a submarine into space, and it might successfully contain an internal atmosphere, but it would be awfully (impractically) heavy for something that needs to be accelerated to very high velocities to get anywhere worthwhile in a reasonable amount of time. [Answer] The pressure of the water is sure to damage the ship because it was not designed to submerge. Another problem would pose the propelling system. Depending on what type of propulsion the ship uses, many do not work if suddenly torrents of water are flooding the engine room or the reactor or whatever is there. [Answer] A possible solution may be found by reading The Gateway Special by Jerry Oltion. The author proposed the use of a submarine and providing it survives the transition into space it should also be capable or returning to the environment that it was designed for. It is not an elegant solution but it is at least a solution. ]

[Question] [ This isn't a question intended for any specific setting. Rather, this is a general point of curiosity that occurred to me while brainstorming my story. Potion brewing is almost *inexorably* tied to the image of a cauldron. Whether it be witches standing over a cauldron big enough to boil someone alive in and stirring it with a big stick, or more reasonably-sized personal cauldrons in, say, Harry Potter, potions are very, *very* frequently being brewed in these bulky, thick metal pots, to the point that some people don't realize they ever historically saw mundane use. The thing is... cauldrons are *big*. Even the small ones for personal use, as far as I can tell, can hold a *lot* of liquid. Even if we assume half a liter, about the size of a commercial water bottle you'd find for sale at a deli or pizza place, is an appropriate serving size of the average potion, then even tiny cauldrons, when filled with potion ingredients, would make at least a *dozen* servings of such a thing. And yet in, say, Harry Potter, we're told that on Harry's first day of potions class in the sixth book, Professor Slughorn had a "large, bubbling cauldron" of Felix Felicis on display for the class... a potion where a single serving size looks like this: [](https://i.stack.imgur.com/Xa0Dym.png) The unspoken implication is crystal clear: any world where cauldrons are heavily associated with potion-making is a world where potions are almost always brewed in bulk. Where dozens, maybe even *hundreds* of servings of a single potion are brewed at a time. **What might the reason be that brewing potions in extreme bulk is such a natural and widespread form of potion-making that cauldrons could possibly become so heavily associated with it?** [Answer] **Exact Proportions.** The ingredient ratios in a potion must be very precise. The easiest way to achieve this is to brew a large amount. Suppose you need 1 litre of swamp water, 10 grams of ant juice and 0.5 grams of butterfly testicle powder, and can reliably measure anything up to the closest half gram. Then due to measuring errors you will end up with anywhere from 0 to 1 grams of butterfly testicle powder. In particularly you might use double the correct amount and ruin the potion. If instead you brew 100 litres of potion, then you need 50 grams of powder, and the error is only between 49.5 to 50.5. So you have at most a 1% error. This also applies when creating butterfly testicle powder in the first place. The potency varies between butterflies. So if you only need 1 butterfly's worth and I only need 1 butterfly's worth, and we each grind up one butterfly, then we might end up with different potency and cannot trade recipes. Better everyone in the area pools their butterflies. Then the resulting brew is measured for potency and redistributed. [Answer] For the same reason that to mine precious metals or stones you need to process a lot of ore: dilution. If potion making was just a matter of mixing the right ingredients, any wannabe mage would just need to start mixing and experimenting. The real deal instead is mixing the right ingredients and then concentrating them: you start with a cauldron and when you are done with the concentration you end up with a couple of vials. [Answer] A good potion is, literally, the "cream of the crop". The actual *magic potion* separates out on top of the rest of the liquid, like oil floating on water, and makes up less than 5% of the end result of your brewing. Just like with separating cream (3.5%) from milk, the final step is to carefully skim off the potion, leaving the (potentially toxic) residue behind. This final step also contributes to the quality of the potion, and the skill of the potioneer — leaving potion in the cauldron is an expensive waste of materials, and leads to smaller batches, while diluting it with the dross will weaken its efficacy. A professional potioneer, of course, has an easier time of it than a home-brew; larger batches mean a thicker layer of potion to skim off, for higher quality potions — and any left in the cauldron is a lower proportion of ingredients, making it less wasteful. [Answer] One of the ingredients comes in discrete units. Think of making cake batter. I need two cups flour, one cup sugar, one egg. I can't make half a recipe, because I can't halve an egg, or if I do, I'm throwing half an egg away for no reason. As long as flour and sugar are relatively cheap compared to eggs, I might as well make an entire batch, even if I don't intend to use it all. If eggs were very rare and expensive, like a key potion ingredient very well may be, you might as well make a full recipe, or even be required to if your rare ingredient isn't divisible at all (e.g. one whole newt, one princess's little finger, etc). [Answer] 1. Economy of scale, same reason that making dinner for six people isn't six times as much work as dinner for one. If potions don't have a short shelf-life if properly stored (supported by the frequency of finding perfectly good potions in places that have been abandoned for centuries), then it makes sense to make big batches, especially if you are either selling them, or using them frequently. 2. There is a final step to making a potion that is very tricky and has a high failure rate. If you are able to get it right only 1% of the time, you need a big batch of "potion base" to ensure success. 3. Actually, the concept of "potion base" brings up another possibility- maybe there are only a few basic types of potion bases, with the specific differences coming from later ingredients. If you can make many different potions starting with the same base, it makes sense to make a lot of it. 4. Ingredients are very potent, and need to be highly diluted to avoid toxic side-effects. 5. Outside factors. If you need a weekly dose of Immortality potion, but it can only be made during a solar eclipse, you need to plan ahead. Perhaps a necessary ingredient will spoil quickly if not used right away, or you need a large iron vessel to focus the magical energies involved. Or it's great-great-great grandma's recipe, and if you don't it right, she'll come and haunt you and you'll never hear the end of it. [Answer] **Perpetual stew.** <https://en.wikipedia.org/wiki/Perpetual_stew> > > A perpetual stew, also known as hunter's pot[1][2] or hunter's stew, > is a pot into which whatever one can find is placed and cooked. The > pot is never or rarely emptied all the way, and ingredients and liquid > are replenished as necessary.[1][3] The concept is often a common > element in descriptions of medieval inns. Foods prepared in a > perpetual stew have been described as being flavorful due to the > manner in which the ingredients blend together,[4] in which the flavor > may improve with age... > > > The cauldron is never emptied. Potions from before are included in the potion being made. Thus potions grade into one another, each with magical flavors reflecting the heredity of the perpetual stew that resides in this cauldron. One might seek out a certain cauldron and its occupant for making a certain potion. The cauldrons are each very different from one another, as one might expect. [Answer] ## Sorry to Burst Your Bubbl(ing Cauldron)! The fact of the matter is: **there is no sensible reason to brew potions in extreme bulk**, except as a potions master preparing stock for sale or distribution. Mostly, the muggle notion that cauldrons are always big black iron pots comes from cartoons and modern kiddie literature. Cauldrons have historically come in a wide variety of sizes, shapes and materials. Iron is common, but equally common are brass, bronze and copper. And of course, there are also cauldrons of alumina, steel, clay and silicon carbide for more refined alchemical & potions work. Here are some nice brand spanking new iron cauldrons in a variety of sizes: [](https://i.stack.imgur.com/lBdnY.jpg) --- And some various sized & well loved older vessels: [](https://i.stack.imgur.com/L5VfC.jpg) --- Here are several smaller cauldrons from the Author's collection. Note the #4 aluminium cauldron in the upper left (with the lid), the #3 iron just below and the #2 iron over towards the right. Various other necessaries for brewing up small potions are also shown. [](https://i.stack.imgur.com/LpDX5.jpg) --- The reality is that one uses the size cauldron appropriate for the amount of whatever potion or concoction one needs. Since you mention the Wizarding World specifically, I'd only note that JKR herself is perpetuating the myth of the huge witches cauldron. There is in fact a [collection of her sketches](https://www.artistsnetwork.com/art-mediums/drawing/jk-rowling-drawings/), and we can clearly see the ignorance! (She draws very well, by the way. I'd've liked it if the books had more of her illustrations in them!) [](https://i.stack.imgur.com/MQqlt.png) --- At the other end of the spectrum, sometimes even the muggles don't realise how truly gargantuan certain potion making operations are and how very pantagruellian the cauldrons must be! [](https://i.stack.imgur.com/UBWNa.jpg) [Answer] Simple economics. Lets say it takes 2 hours to go through all the motions of brewing a potions. Lets say it also takes 2 hours to brew a cauldron of the stuff since you dont have to cut some portion of mandrake root to make sure you dont exceed the required amount but you also take more time like grinding all the butterfly testicles\*. So why wouldnt you? Its just smarter that way, and almost every brewbook will only list bulk ingredients anyway. Add Daron's explanation and you are golden. \*thanks Daron its just too good not to use butterfly testicles in potion ingredients. It adds so much to the flavor. [Answer] One reason things are done in bulk is surface area to volume ratio is lower which can help a number of things. In real life this is one reason why certain smelting processes are done on a very large scale: because it increases energy efficiency when heating the product because it requires so much heat to begin with. I'm sure you could cook up something else that dissipates the brew through surface area which is required to maintain potency until the reaction is complete. [Answer] You could redesign potion recipes for the modern world with glassware and normal equipment, but it would be a huge effort involving a lot of experimentation, death, and money. Easier to stick with what works. In terms of size, you generally need to purify the potion at the end for specialized things like Felix. You collect the drops of liquid gold for the potion. A larger size allows the extremely toxic and volatile substances within more room to not explode. [Answer] What happens in the cauldron is the manufacturing *process*, not the *end product*. Similar to many modern manufacturing methods, the vast majority of what your brewing process creates is - waste. You need to make a large batch to get a few potions out. Water, especially, is likely to be the main ingredient in your potion. If you google around a bit you will find the surprising amount of water that some common items require in their manufacturing process. Why would potions be so different? [Answer] **All potions are created equal, but some are more equal than others.** Resistors are electrical components that have a number of colored bands on them. The last band is the tolerance of the resistor; essentially, how close it's going to be to the labeled resistance. Some are guaranteed to be within 10%, some within 5%, some within 2%, and some within 1% When manufacturers make resistors, unless making them for a specific known target, they often won't have a separate process for making the 5% resistors from the 10% resistors. They'll just make a whole bunch of resistors, test them, and the ones that are within 5% get the gold band, the ones that are 5-10% get the 10% silver band. It's the same with Potions. You could put in a lot of time and effort and get the high quality ingredients, and the exact stir time and the cook time to get a perfect, high quality potion, but you don't have to. If you cook up a huge batch of healing potions, and decant them into bottles, and test them, you might find that: * 60% of the resulting potions will be good enough for first-aid-level cuts and scrapes, or small maladies. * 25% Are good enough for things that you might want to schedule a doctor's appointment for. Ingrown toenails. Ear infections. Persistent coughs. * 10% might be good enough for injuries that might require Urgent Care assistance. That wound needs stitches, and possibly prescription antibiotics. * 4% might be good enough for things that would require the Emergency room. Broken bones. Severe bleeding. Insulin shock. * 1% are good enough to do RPG Combat Healing. Significant, un-staunched damage to limbs or vital organs. Need to be capable of normal function quickly enough to participate in ongoing combat situation. And there's a market for all of them. [Answer] The actual potion is a tiny part of a huge cauldron. It's the little shimmering layer on top.... the residue when 99.9% is allowed to dissipate..... The sparkling bubbles as they escape at the surface..... The rest of the cauldron is thrown away or used for other less wondrous things. [Answer] A huge cauldron doesn't necessarily mean dozens of potions. In a world with real witches, a cauldron's-worth of ingredients might render a single small vial of potion. How? Well: * a) Duh... magic! Maybe when the witch tips the cauldron into a vial, the whole cauldron of stuff empties neatly into the vial (if the witch is careful, and I'm going to say that potion-brewing is not for the careless) and only a single drop is left to season the cauldron for the next concoction. * b) Perhaps collecting the stuff into a pot creates the magic, but only enough for one serving and the rest you may as well discard or make into a stew. The first scoop out of the pot is the potion, the rest is not, even though it's the same stuff. If you want ANOTHER invisibility potion -- sorry, you have to put an unused troll brain into a pot combined with another batch of ingredients. The magic from that last brain was suffused into that potion you already made, and that's all you get from one troll brain. * c) Gazing into a magical cauldron allows a witch to see the future or a distant place in some fiction. Maybe the cauldron doesn't produce potions at all, or perhaps a wise witch brews a huge pot because of the knock-on effects, although the big mixture still produces only a single (or a few) dose(s). Personally, I relate cauldrons with scrying moreso than potion-making. * d) Maybe it's the beginnings of a reduction, just like in cooking and chemistry (boiling off water and other stuff to render a small concentrate). * e) Maybe after mixing the huge pot, you dip a particular rat bone into the pot, burn it, stir the ash into chokecherry wine, and that's your potion. Dip another bone, or dilute the ash into several cups of wine and the potion works not at all. It ain't chemistry, it's magic. * f) Or maybe they're making dozens of potions at once, which makes the usual economic sense. You have to either kill a troll, or hire someone to kill a troll, or steal from someone who is capable of killing a troll (or capable of hiring someone to kill a troll maybe too far with the troll thing?) to get a troll brain (or whatever horrible ingredient you need). When you're dealing with bizarre, rare, and often seriously-dangerous-to-acquire ingredients, you gotta stretch that stuff as far as it will stretch. I imagine a witch would need servants and associates to acquire ingredients, and would conjure or retain them through foul means and/or seductive rewards. [Answer] ## Real world example: Rose Oil Please read these two articles <https://en.wikipedia.org/wiki/Rose_oil> and <https://archive.org/details/b28059979/page/n299/mode/2up> To make **Rose Oil** you need a **specific** flower harvested at a specific **time of year** and a specific **part of day** (just before sunrise) to get a worthy ingredient. Then you start processing it by boiling with a lot of water and distill it repeatedly. Even with a long and polished process you get an extract of only about 1:3000 (yes, just one of three thousand) of the flowers (not counting the spent water, fire, etc.) which is supposed to be able help allergies, if it comes into contact with the skin. After some more processing and dissolving there is some **refined product**, which (while **wonderful**) is **not even magical**. The process has been basically the same for hundreds of years. And yes, the rest of used ingredients are just trash after the extraction, and not good for anything, maybe compost. All that matters is the 1:3000 part of roses, the rest is just totally wasted. A lot of people work on getting some reasonable results from the harvest, as it can be done only once a year and the the field cannot be used for anything other. ## Magic world discussion Typical magic potion is done from a lot of special ingredients, usually by single witch, living far from people (for many reasons such as their safety, her safety, the waste she makes (and that is probably not only terrible, but also toxic and maybe even cursed), secrecy of her recipes, good place for harvesting, ...) The recipe will probably will require some refined oils and other extracts (and not just one, but say 3-5-7-9 or something like that, depending on final product) — in specific combination, and used under specific circumstances, like under full moon (both for its magical effects and polarised light) and some others — to extract the **real** magic from **very specific** ingredients. And yes, those extracts have to be undiluted and they are wasted after the use. But the result is real magic potion with specific effects. Now, while the final extraction yields one small vial from like 5 liters of extract and a few really rare ingredients (say optimistically just 1:100 rate), and takes just few hours. But try to count, how many specific flowers, mushrooms, roots etc. had a single person to harvest, and that probably each of the extracts is based on some other ingredients, which have to be harvested at another time of year in insane quantity and processed by a really long procedure. No wonder, that nearly all the time there is a big cauldron, in which is something boiling. And that the real treasure (some bottles of different extracts placed in some convenient place, say in cellar, where is more consistent cold and humidity) is not visible to unknowing eyes, with the cauldron on display and flowers, roots, branches, mushrooms are drying everywhere possible. The witch does not know what she will need after a half, one or two years, but she knows that it would take some insane time to process all those ingredients and that it could not be done in a few days, as some things are ripe in summer, some in winter, some under the full moon without clouds, others on stormy nights with a new moon etc. etc. And with witchery, instead of modern chemistry, she is not really sure, what is necessary and what is just optional — she knows what worked for her grandma, she may have discovered something herself, but when there is always life at stake, there is just so much you can try to change in one step (and probably just lose a lot of Rose Oil and other extracts, so it would be really expensive, even if nobody dies from that). So she'd rather stick to the rules and add one young living newt from the swamp, while maybe there are just needed some impurities from that swamp mud, which also contains some sulphur and arsenic in balanced amounts. Just how she could be sure, when there is working recipe and some lore, that it one time worked this way and so everybody in her family do it this way as precisely as possible. Moreover as she processes all kind of dangerous, boiling, flammable and toxic substances, no wonder that her usual clothes are in a terrible state (they were new long ago, but if you know that nearly every time you work you damage them somehow, then you really do not use new clothes for work) and why she looks like she looks when regularly in contact with all kind of allergens, toxins, acids and such. And it is also one more reason, why final extractions are done far away from human eyes — not only for tradition and protection of her secret recipes and avoiding risk, that somebody would like to see what she does and then accidentally knock her equipment down, resulting in total loss of much work and his life — but also that she does it usually naked or at least underdressed — yes tradition too, but also there is too big a risk that something from her clothes may fall into the mixture and destroy it totally. --- So I always believed that potion making witches do a lot of work at the time they can and save a lot of extracts for those final mixtures somewhere hidden to be able use them in reasonable time, when they need some specific potion. And, as they also supply last resort healers for many villages around, that they have a relatively big haul of half-made healing potions ready, usually just boiling in the cauldron, as they can expect that somebody will come soon with some problem and then they could just take part of that base, add specific drugs and make some "medicine" in a relatively short time at the cost of the "medicine" expiring in days or max weeks and being unwieldy, but sufficient for "simple" healing now and here in time of days — while real potions which would save you in a dungeon after years of waiting are much more concentrated and expensive and harder to make. On the other hand if they want their privacy until their help is really needed (and then add a big part of placebo, as it works too), they keep some strange looking things around, which are not threading them (bones in cauldron, strange colored things of unknown origin, but after distillation totally useless and mainly inert and such) but are quite impressive to the customer. And if all work is done and nobody comes, well good broth with vegetables and mushrooms could be eaten as well instead of using it for diluting the real weak healing potion :) You know, why they add a lot of something to the cauldron, when someone comes and asks for medicine — if there is just strong soup, it is good to use it as carrier for the real thing and make sure, that customer is not able to drink a week's worth of active substances (which he would do for sure, if just given small vial and told how many drops daily, but if it is one full spoon morning, one evening and say this long prayer before and after, the risk of overdosing is way smaller). [Answer] Potions are potent, and this comes from concentrating them. The whole bubbling for hours thing is just to reduce the liquid so that you can get a useful dose in one gulp. Felix felicis would make no one happy if they had to drink four pints of it before seeing an effect. Also, for most potions, after reducing as much as possible you just skim off the top scum, which is where the active ingredients get concentrated. [Answer] Maybe one of the ingredients is the meat of a large, rare, possibly dangerous animal, let's say a buffalo for now, but it could be anything from an elephant to a tiger to a dragon, etc. Sure, you could just use part of the buffalo and make small batches, but then the rest of the buffalo would rot and spoil, and that's just wasteful, and then every time you want to make a new batch, you have to go out and capture and slaughter a new buffalo, most of which won't get used and just go to rot again? No thanks. It's just much more economical to use the entire buffalo and make a large batch. The finished product, once properly bottled and sealed, will last for a good long time, and you can sell them to anyone who wants. Maybe you only need to make a new batch every couple of months. (You can of course work on making other potions using different recipes in between, just to keep busy.) [Answer] Magic potions require a magic catalyst to "spark". And a magic catalyst is created by the witch brewing the potion using their personal mana, being a [catalyst](https://courses.lumenlearning.com/boundless-chemistry/chapter/catalysis/) rather than a reactant they are not consumed by the sparking of the potion. However being magical and mana created rather than a normal physical catalyst they do evaporate once the reactants are consumed. This means to spark a big cauldron of potion takes the same magic effort (not mundane effort of collecting the reactants) as a small cauldron. For certain basic potions it is possible to continually supply reactants, and remove sparked potion on an industrial scale so that a single catalyst can run indefinitely, however more complicated potions don't tend to work well under these conditions, the reactants need to be evenly mixed or else the catalyst will fade. [Answer] The big cauldrons you see everywhere isn't aren't for brewing potions, they are for flying around in. Unfortunately, preparing a cauldron for flight takes a lot of work and time and boiling various noxious liquids in it. [Answer] You can do it only once. The recipe is copyrighted by demonic entity and it demands a specific part of your soul as a royalty. You can resell the final product, or obtain a teacher licence suitable for spreading the heresy to your students. [Answer] To prevent (too much) contamination. Since the enchantments seep into the cauldron, to ensure that you have a potion that *mostly* does what you want, you must make so much that the other effects from contamination become minimal. [Answer] **Stratification**. You add all these rare and expensive ingredients, however, you really do not need "eye of newt." What you really need is the extremely rare organic compounds that then then interact with the inorganic salts of the other ingredients. you then need to bring the concoction to the right temperature to allow the chemicals interact properly, boil off some volatiles and precipitate out useless waste matter, such as the fleshy parts of the eye that do nothing for the mixture. You then skim off the scum and what ever layers you do not need to get to the real stuff. You then syphon off that fluid, to seperate it from the rest of the mixture. ]

[Question] [ Let's assume a medieval lord named Gary I of Flowers lives in a "Europe-ish" continent with no gun powder or magic. Somehow, he's aware about modern warfare theory. Maybe he found out a time-traveler who happened to be an expert in warfare (and nothing else!), or maybe he's just ahead of his time. Gary is an excellent general of his times. He's adaptive, open minded, and well respected by his soldiers and knights. He also has plenty of time and gold to modify his army. There is no "culture shock" from any unconventional tactics Gary would use. At least for his men... By modern warfare theory, I'm not talking about using modern equipment - Gary doesn't have the means nor the technical knowledge to produce those. I'm currently thinking about using principles, tactics, strategy and knowledge about warfare generals of the 21th century to master and adapt it to a medieval technology. **My question is, would modern warfare theory be useful to Gary against his enemies? How would his medieval army, tactics, and strategy change using only resources available at the time?** Of course, it may change society as a whole, and ends the Middle Age way sooner than expected, but I'm not interested in that. I want to focus on warfare and everything directly related. *The only question I found in this site related to mine is this one, [Mechanized infantry of the medieval age](https://worldbuilding.stackexchange.com/questions/139204/mechanized-infantry-of-the-medieval-age) , but it only focus on one thing. I know my question is very open and may be unclear. I would love to read any feedback.* [Answer] Lots of excellent stuff here so here is my 2 cents. One of the biggest "modern" warfare things that Lord Gary could adopt that was not very common is the concept of **Meritocracy** in his army. Throughout history this always seems to present an odd dichotomy, as some of the most terrifying and effective Armies in history had at least a bit of this going on. "Hey, that guy over there always seems to keep most of his folks alive in an engagement and he kills a lot of the enemy, maybe we should promote him even if he isn't part of the aristocracy" There is even a story of Ghengiz Kahn not only promoting the bravest and best from his own forces, but bringing in an enemy who shot the Kahn's horse out from under him. Legend goes that Jubei the Arrow (as he became known) was a leader from an enemy tribe, and he got close enough to shoot Ghengiz Kahn's horse. When captured, Jubei remained defiant. Ghengiz then offered him a generalship. The dichotomy happens in what seems to be times of peace, when the Generals who earned their spot lose some relevance and get supplanted by an entrenched aristocracy. For some reason, the nobles kept equating bloodline with skill in battle. There are 2 other things he could learn from a modern military. Intelligence and Logistics, and why they are so dang important. In the modern day, the command with the most and fastest information has a huge advantage. Dial that back to medieval times that means spies and innovative communication methods. Lord Gary should become nearly obsessive in his pursuit of methods of communication on and off the battlefield. Messenger birds, Dolphins, monkeys, smoke signals, Heliographs, semaphore, drums, bells, astral projection....anything at all that can send information quickly and accurately. Information is critical for all levels of the military. Lord Gary also needs some people who know what to do with the mess of information. As a bonus, if Gary develops a good spy network, he can supply the enemy with disinformation. With Logistics, every army marches on it's stomach. Even though foraging was par for the course in medieval times, Lord Gary wants to insulate his army from the vagaries of the countryside as much as possible. That means a solid baggage train. It means planning, it means men moving at the speed of the luggage. It means fortifying supply stops. It also means another more modern military take. Men need rest along the way. You cannot push them to absolute exhaustion on the march and then expect them to perform when they get there. Another part of the supply chain is quality. Gary should fund research into creating preserved and portable foodstuffs. Salted meats, beans, rice, root crops that last. In addition, part of the supply chain should involve knowing the location of water sources ahead of time and then what precautions to take like boiling the water when there is time. Also under the heading of Logistics is the soldiers themselves. You can have a fantastic supply chain, but if you have crappy soldiers it won't be too successful. Before Lord Gary hits the road, his men need to be well trained. At home, just about everyone who can hold a spear should train with them periodically. Make it a universal requirement. That way Lord Gary's pool of available men will all at least have a baseline of training. Those that volunteer or are drafted will get a bunch of extra training before setting out. They can also drill everyday while on the march. The US military trains extensively and consistently. Make it a part of the daily routine at home and while underway. Lord Gary seems like a smart guy. All hail Lord Gary. **Edit:** the comments got me thinking about something. Another military concept that would help Lord Gary keep a top notch military would be to keep a skeletal permanent military. Not enough to be counted as an overly large standing army, but enough to keep a consistent command structure in place so that when it becomes campaign season, you don't have as much of a settling in process at the start. In keeping with the Meritocracy concept, make this structure a PURE meritocracy, with the members being part of a landless aristocracy. It's a great great honor to serve in this capacity. Anyone, even a peasant can rise through the ranks in this structure. It could be coupled with a requirement that members not have land to manage, not marry so as to stop the heredity nonsense (at least not while serving), and have a life with a full pension in later years. This give a consistent command structure that will be resistant to some court intrigues. [Answer] The question shows a misunderstanding of why the Middle Ages were medieval. It's not that the people who lived in those times did not *know* any better. They did. In particular, they had good Roman books about military strategy, tactics and logistics; for example, they had and they actually read Vegetius's [*De re militari*](https://en.wikipedia.org/wiki/De_re_militari); the book was copied over and over, and any aspiring general read it: not less than 226 medieval manuscripts have survived, and it was one of the first books to be printed -- the first printed edition dates from 1473. (You can find the [1535 edition](https://archive.org/details/flvegetiirenativ00vege) at Archive.org.) The medievalness of medieval Europe does not come from lack of knowledge, it comes from the lack of funds and people. Medieval economy was extremely sluggish, and as a consequence the states were extremely poor; they simply could not afford standing armies of any reasonable size, they could not afford training more than a handful of men, they could not afford sustaining a war effort for more than a few months *at best*. And they did not have anywhere near enough men. The [Crisis of the third century](https://en.wikipedia.org/wiki/Crisis_of_the_Third_Century) started an unstoppable population decline, and 6th century [Plague of Justinian](https://en.wikipedia.org/wiki/Plague_of_Justinian) killed half the remaining people in Europe: it took almost a full millennium for the continent to recover the population levels it had in the second century. The conclusion is that just having knowledge of logistics and planning is nowhere near enough. They did not have the economic and demographic base to use it. *Other* civilizations did have the economic and demographic base, and they had access to the same knowledge. The Arabs established a great empire, and took over large parts of Europe -- remember that for the most part of the Middle Ages the Iberian peninsula was Muslim. The (Eastern) Roman empire remained a great power throughout most of the Middle Ages, resisting the rise of the Ottomans. But the sad reality is that throughout the Middle Ages Western Europe was an economic backwater, which did not have the capacity to project force. [Answer] Honestly the 'modern' military theory that would give Lord Gary the biggest advantage would be modern attitudes towards hygiene. It was extremely common in the time period you're talking about for a force to lose more troops to dysentery and other diseases than they lost in actual combat. By taking a very firm attitude towards latrine maintenance and ensuring supplies of clean water, Gary could gain some pretty massive advantages in terms of how much of his force would be combat-capable at any given time, and keep a lot more of his troops alive. This falls into the same category as AlexP's answer as well in that this was something the [Romans were quite good at](https://www.researchgate.net/publication/316482925_Control_of_epidemics_in_the_Roman_army_27_BC_-_AD_476), but the practice was lost for a millennium and a half. > > The Roman army took great care to construct sanitary facilities > and segregate them from water, food supplies and dining areas. > When water was in short supply lime pits were used in the > latrines. > > > A complex system of drains and sewers emptied into streams, rivers. > Drinking water for soldiers and animals were taken from water upstream > or separate from the waterway used for latrines. Wooden seats for > latrines which were dug to a depth of ten feet were situated > over the main sewer running round three sides of the building to > discourage disease-carrying insects. A smaller channel of water, fed > from the water tank was for washing sponges dipped in a mixture of > water and acetum (vinegar) were used as toilet paper. Latrines also > had basins for washing hands. > > > Indeed, this ultimately developed into honest-to-god combat medics, far earlier than you would have expected. [The Byzantine Empire developed a system for evacuating the wounded from the battlefield](https://apps.dtic.mil/dtic/tr/fulltext/u2/p010948.pdf) that was superior to anything Europe came up with until WW1. > > Historically, the advent of the first truly organised military medical > systems which included evacuation capabilities was found in the army > of the Byzantine Empire. Scribones, stationed a hundred meters behind > the action, served as corpsmen with the mission of rescuing the > wounded during battles. They were paid for each casualty they rescued. > No similar formal evacuation system existed in Western Europe until > the late 18th century. > > > [Answer] There are several relevant Clausewitzian, Jominian, and Machiavellian concepts that would benefit Lord Gary. While some of these seem obvious to us, recall that most wisdom seems rather obvious in retrospect. * Clausewitz: War is an extension of politics, and wars have political goals. Putting 'war' in the 'politics' box doesn't reduce war, it expands the toolbox tremendously for achieving Lord Gary's goals. You can achieve goals through war...or through intrigue, marriage, etc. You can also use combinations of tools to achieve goals. * Jomini: Several *Principles of War* apply regardless of the technology: These principles vary a bit, but let's go with Objective, Offensive, Mass, Economy of Forces, Maneuver, Unity of Command, Security, Surprise, and Simplicity. This leads toward smaller, more mobile, better-synchronized combined arms operations. * Machiavelli: Motivate your troops directly, rally your population, use written guidelines of conduct, empower lower-level commanders to innovate. This will minimize the intrigue in Lord Gary's court, and will enhance the power of the force. Plus one bonus with multiple authors: * [Military Staffs](https://en.wikipedia.org/wiki/Staff_(military)), a method of organizing information and synchronizing effort. It prevents overwhelming Lord Gary (or his Field Marshall) with unnecessary detail at the wrong times for smart decision-making. One goal is to reduce the *decision cycle*, so Lord Gary's forces that seem otherwise-equal-to-a-foe are nevertheless more nimble, survivable, and powerful due to the more efficient information flow. The tactical impact of this knowledge depends upon the resources Lord Gary is willing to bring AND upon their personality and preferences. If Lord Gary is willing to have influence (a measure of control) over neighbors, then ordinary, cheap intrigue might be enough. If Lord Gary is driven to exterminate the neighboring lords, erase the borders, crown himself King (or Emperor), then quite the bloody war may be likely...if he can afford the enormous cost. [Answer] > > would modern warfare theory be useful to Gary against his enemies? How would his medieval army, tactic, and strategy change using only resources available at the time? > > > I am not an expert of modern warfare, but I doubt what we call modern warfare would be of any use in middle ages. Let's look at some of the key points of modern warfare * Aerial supremacy and projection of force: there are no airplanes in middle ages, nor ships big enough to serve as force projection * Blitzkrieg: no mechanized infantry to apply it, nor air force to support it. * Logistic: medieval war relied on raiding the local territories for resources. There was no supply chain from motherland * Electronic communication and intelligence: well, this is obviously not achievable. * Professional army: medieval army were either mercenaries or people borrowed to the soldier's job for the time of the war. Professional armies came much later. Maybe some concepts about guerrilla and [asymmetric warfare](https://en.wikipedia.org/wiki/Asymmetric_warfare) might be useful, though they might sound ethically unacceptable for the medieval standards. > > Asymmetric warfare can describe a conflict in which the resources of two belligerents differ in essence and, in the struggle, interact and attempt to exploit each other's characteristic weaknesses. Such struggles often involve strategies and tactics of unconventional warfare, the weaker combatants attempting to use strategy to offset deficiencies in quantity or quality of their forces and equipment > > > The term is also frequently used to describe what is also called "guerrilla warfare", "insurgency", "counterinsurgency", "rebellion", "terrorism", and "counterterrorism", essentially violent conflict between a formal military and an informal, less equipped and supported, undermanned but resilient and motivated opponent. Asymmetric warfare is a form of irregular warfare. > > > [Answer] *Modern* tactics would be probably of less use than knowing historical tactics. There were a bunch of effective ideas scattered across Middle ages and early Renaissance, that work with medieval resources. Just some ideas off the top of my head: * Make your peasants performing some basic training all year long, so they are more fit and skilled when the time comes to levy them. English did that, so could you. * When possible, provide some basic training (2-3 weeks) to your newly conscripted soldiers before moving out. While you can't afford that when you are attacked, nothing stops you from doing that before you raid your neighbour. It will reduce effective length of the campaign, but even basic formation training will do wonders when facing less organised opponents. Alternatively establish some military conscription duty (including organization) during those awful non-productive winter months and focus on even some of the defensive skills * Recognise defensive power of pike formations. In our history, pike formations made a comeback at the start of 14th century; lasting well beyond the middle ages. You Lord Gary could make that comeback a couple centuries earlier, and be just as effective. The best way of not getting overrun by cavalry is using defensive pike formation together with a LOT of organization * Recognise power of crossbows. Both pikes and crossbows were despised in medieval Europe because they disturbed societal order, allowing lowly peasants to take out a noble lord with ease. But taking out the enemy lord is immensely useful, as most medieval battles weren't fought to the last man, but to the point when one side breaks and starts running. Death of a commander or two was significantly more demoralising than both before and after Middle ages. Have a small group of elite crossbow snipers, and you can win many battles with little blood spilt. * If you wage wars for a few years without major losses (especially if, as noted in other answers, you promote hygiene and provide better medicine), you will have some fairly experienced peasants on your hands. Then you can go cheeky and make combined-arms pike+crossbow formations a-la Spanish tercio or Swiss phalanx. Those will both terrify your enemies and cut your losses even further. [Answer] I'm no expert, but here's my 2 cents. I think in terms of organization and logistics Gary would be ahead of the rest. If Gary knows modern warfare he might also know the entire history of warfare that happened after the middle ages. Gary could take inspiration from the battle of Agincourt and deploy many longbowmen in his army for example. Another thing he could replicate is how the Dutch revolutionized war during their war for independence against Spain. He could drill his troops until they start working like an oiled machine (something that wasn't seen much during the middle ages), and he could perhaps deploy rows of crossbowmen doing the "shoot and retreat" tactic like the musketeers did back then (creating a continuous volley). Maybe these things won't make a big difference or end up not working as well due to technological limitations. Other tactics might only work in rare situations, but in the end we can never know for certain. So it's all up to setting/location and the world you build of course. I do believe that there are many cool scenarios you could pull off with Gary, however you would have to look into certain historic battles to get a grasp of the tactics used and see if Gary could apply them. [Answer] It seems to me reading the existing fantastic answers that in order to successfully establish any sense of modern military tactics in medieval Europe you must first shore up the shamble that is medieval economics and production. A society is built upon its lowest level and so that is where changes should be made. The vast majority of medieval populations were farmers, food production was so limited that nearly everyone during the dark ages had to produce some amount of food for themselves, whether they owned livestock or maintained a small vegetable garden. This is a large part of the reason why it was so hard to maintain a standing army. Introducing modern crop rotations, irrigation, fertilization and plows would be a huge boon to farming. With these techniques food and livestock can be grown and bred year round with better output which would allow fewer farmers to support a much larger population. Follow up this boost to food production with better transportation, roads and infrastructure to distribute the food and now your kingdom can reliably supply itself and build enough surplus that a standing army can be maintained and properly trained. Peasants can also take up more specialized professions such as becoming dedicated blacksmiths, wood workers, armorers and weaponsmiths to fuel your military might. [Answer] There have been a lot of good answers on where modern warfare theory can help, and where the technological limitations are overbearing. Eg. Logistical, manpower and financial issues of large warhosts and prolonged military campaigns. I would like to point out the distinct differences between tactics, strategy and grand strategy. Eg. is your setting of individual lords in a feud war against each other or a larger military campaign? In the case of multiple lords within a war host, your lord's seniority would play a huge factor on whether he is allowed to have any influence on battle strategy or campaign grand strategy. This lack of autonomy during larger battle planning also neuters a lot of tactical enhancements. Throwing you a lifeline though, historical sweeping military successes can often be decided on a few specific events/stratagems. Eg. Scipio swapping his unit formation in the *Battle of Ilipa* or George Washington's crossing of the Delaware River. So perhaps you can simply write in greater historical warfare awareness as Lord Gary's superpower. Tactical reforms can be in the form of better understanding of siege, battle terrain selection or long distance communication/coordination (**try sephamores or homing pigeons**). *ie. more organised war intelligence service activities*. Your army only really needs to win one or two really decisive battles/routs to severely impact the enemy's available manpower. So the overall theme really is about finding force multipliers or stoking fate from the choice of the field of battle eg. Flamininus in the *Battle of the Aous* If you really must have some mechanism that makes Lord Gary's army have a distinct tactical advantage, perhaps think of localised cultural gotcha like swiss mercenary style halberd/pikes (the key is stronger unit cohesion and ruthlessness/veterancy of individuals), large scale deployment of crossbowmen levies or pavise crossbowmen. Essentially an usurpation of the period's tactical norms. [Answer] To our modern minds, reading medieval military history can be quite puzzling as often the kings and armies involved don't behave as we'd expect them to if they were trying their hardest to "win the war" as we'd imagine they'd want to. A modern theory of warfare is to seek out the enemy on the battlefield, destroy their army, leave them defenseless, and then capture their territory. By contrast in Medieval warfare the armies seem to regularly miss chances to force battle on their opponents, they fail to optimise their weapons systems to get maximum advantage, they spend inordinate amounts of time pursuing things other than battle like sieges and raids, and they often seem to wander around aimlessly rather than striking strategically at enemy territory. Some of this is due to the logistic difficulties of the time as other answers have noted, but what has been missed is that the Medieval mind clearly has a different conception of what warfare is and how it should be properly done. What explains the difference is the importance of religion - unlike today, everybody in the Medieval World believed in God. To the Medieval mind the outcome of battle is a direct judgment from God and therefore understandably Medieval rulers were often quite circumspect about seeking battle. Also Kings (and not just oneself but the rulers of rival kingdoms) were seen as having a divine right to rule ordained by God - so even when they fought it was restrained by a respect for the others authority. For example, when the English and French fought the Hundred Years War, they were not trying to "invade" or "conquer" each other as they did when they later fought the Napoleonic Wars. In Medieval times the aims and means were more subtle (at least when Christian rulers were fighting each other...) I would argue that transferring a modern sensibility into a Medieval ruler and his army could certainly have profound effects. Without any concern for divine judgment, they would be unrestrained by Medieval courtesies and customs and could pursue strategic aims more efficiently (however, you might consider what the general population might think of this ruler and his army? If the people kept their religious sensibilities this ruler would certainly be seen as a crazed, illegitimate tyrant, perhaps even an antichrist). As a final point I would note that not all pre-modern warfare is characterized by religious inspired restraint. For example, in the campaigns of Alexander the Great, we see a classic example of a king who does deliberately seek decisive battle to invade his rival and overthrow them. Therefore it would be perfectly plausible for the ruler in your story to find his inspiration from the past rather then the future. [Answer] I'm not really sure what you mean by modern warfare theory. I'm going to make the assumption that you're talking about logistics, and possibly wargaming scenarios. Logistics could be interesting. Generally, at least in European Warfare, as a soldier you provided your equipment and scavenged off the land(cheating a little with the link here - <https://en.wikipedia.org/wiki/Medieval_warfare#Supplies_and_logistics>). Having a standard set of interchangeable equipment and supply trains would give you an advantage over someone who didn't have that, especially over an extended campaign. Wargaming or looking at the overall strategy of a military campaign has been used on and off throughout history (<https://en.wikipedia.org/wiki/Military_strategy>). Generally, if you're doing it, you have an advantage over those who aren't (see the Greek/Persian example in the link). To be honest, I think if you want to make a massive difference in warfare, a fast effective method of communication would be most effective. [Answer] To take a full profit from our modern warfare knowledge, Gary would need: * knowledge of the warfare theories (Sun Tzu and Clausewitz, for example), * knowledge of past battles and used tactics (review of what was done, why, and what was the outcome would be profitable), * knowledge of the technology/tactics and troops available to him (nice and great to know about aerial coverage, but well, not going to be too useful for him), * capacity to adapt to his environment (which requires the knowledge mentioned earlier). And now, assuming he has all the preceding points, here are a couple of things he could/should be doing... ### ... as a Lord The first thing it to make sure that the war/battle is the best alternative. The army is a tool for politics. But not the only one. He should define precisely the goals he wants to achieve, and evaluate the various means to achieve it. It the war is the best option, the scope and objective should be clearly defined (see the USA in Irak, Sun-Tzu, Clausewitz). The second thing is that no one can wage a war without money. So he needs to boost his economy, increase his surplus, find financial support, etc. Once this has been achieved the war can be considered (e.g. Charles VII in the 100-years war). The third element is to make sure that he has a solid weapon industry or supply. He needs to arm his troops. For longer-term, he needs to make sure that he stays on top of things. So universities and schools, might be able to help with innovative strategies/tactics/weapons. Another point of importance, is that he is well read with Macchiavel. He knows how to rule his own Lordship as well as dominions he might get in possession of. ### ... as the Army's Chief-General The Army is a tool that should be ready for the politics. They should prepare to various possibilities, but only act upon the decision of the politics. As Sun Tzu teaches us, the first thing is to know you enemy. The Chief-General should organise spies networks in order to gather a good information on the armies of any potential adversaries. Then, modern and current armies rely essentially on well-trained professional troops. He needs to recruit and train people. Note that one possible advantage of really modern knowledge: women can fight equally well, they could increase the size of the army. But that might be some cultural shock. But maintaining a professional army during peace is extremely expensive, so he needs to find methods to do it. Like regular short trainings (see Swiss' military service). He also needs to invests considerably in logistics. Food, money and anmunitions should flow without issue during a campaign. As mentioned in other answers, hygiene is also a crucial element. Then military engineering might play a crucial role. He should ensure to have a supply of engineers who could provide technical solutions (crossing a river, take a castle, etc.). Even if he takes on the three posts described here, he can't be everywhere, every time. Furthermore, recent strategies used fake movement and armies to mask the real intentions (see Operation Fortitude). So he needs to have a set of trusted, capable generals to carry-out the order and be ready to adapt to the situation. This can be done by knowing the people, and promote worthy ones to posts with responsibilities, regardless of their origin (note that this may not be so well accepted for a brutal change). But this also needs to have training... and trainers. Which would rely on the universities and schools developed as mentioned. ### ... as a Field General Here, the knowledge of the past battles would be very important. Scouts are important to know the preparation of the enemies as well as recognise the terrain. He knows to separate the strategy from the tactics. A battle may be lost, if it gives an advantage for the campaign. Find the best field. Always go to battle when the field favour his army. Or at least does not go against him. Terrain knowledge from the scout is crucial. Use a combination of the various arms available. Typically light and heavy cavalries, peakesmen, archery for European's MA. Use smaller specialised units and deploy them to counter the opponents tactics. Keep reserve troops. Two very important lessons to take: mobility. Even the best troops (hoplites) could be out-maneuvered. He should make sure that his troops are reactive and can be quick to move. And communication: the orders and reports should rely on well trained troops and officers, as well as well established communication channels. The next tactical move should be communicated effectively to the soldiers. As he prepared his own troops to be well supplied, mobile and well informed, he knows the crucial importance of those. He may then attempt to disrupt his enemies' supply or communication lines. ### Conclusion Assuming that apart from the knowledge, he has the required capacities, he might greatly profit from that obtained knowledge in his military actions. However, many/some of those need time to be effective. In our history, some of those elements took really centuries to get some effective value. [Answer] Gustavus Adolphus brought the concept of COMBINED ARMS to the old world. Same weapons as everybody else, but a different way to organize and train and fight that made combat more effective at the unit level. Also, sci-fi author H. Beam Piper liked using real battles in his time-travel (heh) stories. He is worth a look. [Answer] I am no expert but here are a few things I think modern warfare knowledge might bring: 1) A destruction of arbitrary classes Training, armor, and weapons were often distributed based on societal status. This lead to horribly trained foot-soldiers with insufficient weapons. As others have pointed out, this also resulted in very useful tools like crossbows being disdained. Finally, modern warfare values troop cohesion which is damaged by having arbitrary class structures. 2) Guerrilla Tactics Though more common than many people believe, Guerrilla tactics were not extensively employed. A modern commander would have far less sympathies for "propriety" and "honor" on the battlefield, thus allowing more underhanded techniques to tip the battle. On the other hand, a modern commander would be appalled at some of the "barbery" he witnessed, so this could be a double-edged sword. 3) Understanding of Modern Psychological Warfare This would be valuable for preventing troop morale breakdown, and would also give the Lord the ability to strike blows to the enemy that would be highly demoralizing but not immediately of prestige or other tactical value. These type of attacks would be very alien to many of his opponents. 4) Supply chain and Engineering Corp. The Romans were very aware of the value of engineering corps, but this knowledge seemed to have been lost in much of the Middle Ages. This was at least partially due to problems listed in the first item in this list. A proper engineering corp would provide the troops with proper supply routes, more rapid movement, and better and more defensible quarters. [Answer] The book *On Killing: The Psychological Cost of Learning to Kill in War and Society* - [and this video](https://www.youtube.com/watch?v=zViyZGmBhvs) - reports that: 1. 90% of rifles found dropped at the Battle of Gettysburg were loaded. 2. This and other evidence indicates an innate human resistance to killing, manifesting in not shooting when they have the chance, or not aiming when they shoot. 3. Modern armies have developed Pavlovian and operant conditioning - such as replacing bullseye targets with silhouette targets - to increase firing rates. Obviously, if only 10% of your guys are shooting to kill and you can get that up to 20%, it's almost the same as having twice as many guys - except you don't need twice as much food and wages. You could extend this to your fictional world, and claim that with with modern training techniques and understanding of human nature you could make a force of the same size much more effective. Of course, you could argue the not-killing evidence doesn't extend to medieval battles; people's instincts might be different when the threat is right in their face. [Answer] strategy is based on available resources, so almost nothing from *modern* warfare could be implemented. Camouflage painting maybe. But historical knowledge of military expert could give to Gary things like: - advanced fortification, both field and long-term - something like spanish tertia (offtopic - I tried to recreate it in M&B PoP, if ya know what I mean ;-) and it kinda works good) - chain of command, military ranks - advanced siege and field mechanical artillery, due to math and other knowledge [Answer] Modern warfare requires modern weapons/tools. So... many tactics, formations and most rules do not apply because neither enemy nor they themselves do have the tools to make them useful. What would come in handy would be the modern training methods, ranking system, execution of commands/discipline and how supply chains are set up. Also, many 'modern' ideas, like hygiene and that a̶l̶c̶o̶h̶o̶l̶ ̶s̶h̶o̶u̶l̶d̶ ̶n̶o̶t̶ ̶b̶e̶ ̶a̶ ̶r̶e̶p̶l̶a̶c̶e̶m̶e̶n̶t̶ ̶o̶f̶ ̶w̶a̶t̶e̶r alcohol should be consumed as little as possible. Also clearing up myths about mystical herbs and ground-up animal parts that at best do no harm. With modern methods, you would be held back by those times limitations and problems. Key would be the knowledge to either overcome those limitations, with essentially the same methods that were used in our history or to compromise with what was available. Raising a professional army would already be quite a benefit, apply what we now know about health and training and it would be quite the formidable army too. Battle in these times usually took place at the battlefield, literally. Two opposing armies would meet at a specific area and fight to the last man standing. Using what would be considered underhanded methods Gary could probably overthrow many kingdoms with guerilla warfare, spies/infiltration, assassination and less effective versions of the Blitzkrieg tactic (conquering as fast as possible, really effective if you have machines to get around, tanks etc). Also preparing the country for war. Setting up supply lines, shelters for wounded soldiers etc. using propaganda to get the population riled up and change their mindset to pro-war. Also training most soldiers of the professional army to lead untrained people. If it were required stocking up on manpower by drafting from the general population would work quite well too. ]

[Question] [ This question differs from [that question](https://worldbuilding.stackexchange.com/questions/63496/how-could-i-have-modern-computers-without-guis) in that the other question is asking about a change in history while this question is looking for a change in the future. --- In a [near future setting](http://tvtropes.org/pmwiki/pmwiki.php/Main/TwentyMinutesIntoTheFuture) I am working on, humans have built [space-habitats](https://worldbuilding.stackexchange.com/questions/91677/where-to-place-my-space-station-so-it-observes-one-full-planetary-revolution-per) and have established colonies on celestial objects [such as Luna](https://worldbuilding.stackexchange.com/questions/41938/what-would-be-the-most-optimal-location-for-the-lunar-radiotelescope). Their spaceships cannot go faster-than-light and [have their fair share of other issues](https://worldbuilding.stackexchange.com/questions/89955/how-hot-can-i-make-the-insides-of-my-spaceship-before-damaging-crew-too-much) - yet are still the primary means of transport across the Solar, and are the result of constant improvement since the first [space shuttle](https://en.wikipedia.org/wiki/Space_Shuttle). The void between these specks of life is populated by small-scale entrepreneurs, shipping cargo from *a* to *b* in trips that are measured in months to years. That is, [thanks to cryogenics](http://tvtropes.org/pmwiki/pmwiki.php/Main/SleeperStarship), for them only a few days pass, maybe a week. They basically take on a cargo, plot the course and then wake up sporadically for maintenance, course-corrections, and so forth. --- While the setting is an extrapolation of current-day earth, the technology aboard ships and stations is intended to mainly use text-interfaces and vector-graphics1 for interaction and feedback. Think of your [typical Unix terminal](https://www.tutorialspoint.com/unix_terminal_online.php). There are plenty of hardware buttons for everything, but more complex commands or configurations, as well as direct access to ship-systems and devices, are done via text-prompt. E.g. ``` cryo set wakeup=time+2d > wakeup procedure scheduled for SOL3-1_37:4:12m-6:23:40-127812_79812301 _ ``` 2 --- **Q**: *Why would technology dictate graphical interfaces to be rare on spaceships?*, as opposed to the GUI-centered thinking that is today's norm? I am looking for answers that bring up plausible, *tech-based* reasons (e.g. advantages) for this [paradigm shift](https://www.merriam-webster.com/dictionary/paradigm%20shift). Answers based on social subjects are welcome but will likely rate worse. Bonus points for answers that explore going towards [dumb terminals](https://en.wikipedia.org/wiki/Computer_terminal) that are used to interface with shipboard/station-board systems but have themselves little to no other abilities (e.g. [back when people had to swap disks](https://en.wikipedia.org/wiki/Disk_swapping)). 1Some people might consider that a *set back*... 2When travelling between stations, planets, etc. Time is denoted as an amount of seconds and nanoseconds that have passed since the departure from a [MAJOR/MINOR](https://docs.google.com/document/d/1a10zLJnWbzGn6hlNI1ZU7IIE69OqyYnXpTG1XfW8CsQ/edit?usp=sharing) appended to the departure time. [Answer] A quick web search for "CLI vs. GUI" (Command Line Interface vs. Graphical User Interface) shows that many developers hold the following1: 1. ### CLI is faster for an experienced user It is much faster to type than to navigate layered menus with a mouse. You can type with both hands, and it's easy to type blindly - so you don't have to keep your eyes on the monitor at all times. These become much more important when your physical environment isn't stable (acceleration, low G, etc.) - it's very difficult to use a mouse in such situations, but there are special keyboards designed for pilots: [](https://i.stack.imgur.com/IcerK.jpg) 2. ### CLI is more efficient to use There are tasks (e.g. searching through multiple files / directories with a complex set of parameters) which are easier to perform using CLI. In addition, CLI allows easy "chaining" of series of commands (also called "piping"), so that the output of the first is the input of the second and so on, for example: * command 1: list all cargo entries for explosives, * command 2: list all cargo bays in input, * command 3: seal all airlocks of rooms in input, and, * command 4: flush emergency coolant in all rooms in input.This set of actions is much faster to perform in CLI than in GUI, unless someone already created a GUI button for that specific scenario. Finally, CLI makes "aliasing" and scripting very easy - so experienced users can create their custom batch operations and keyboard shortcuts, making their common tasks very fast. 3. ### CLI requires less system resources While the task of maintaining an active GUI isn't terribly demanding for today's computers, CLI requires much less resources. This becomes more important when you are working on a remote terminal - all the graphics needs to be compressed and communicated "over the wire", and the screen is redrawn constantly (not only when you move the mouse, but even an untouched graphic display will typically have a clock, network status icon etc which means constant refreshes) - by contrast, a CLI terminal only refreshes when the user types, or when a command returns a result (and even then, while your local terminal refreshes its display on every keystroke, it only transmits to the remote when you hit "Enter"). If you are operating several remote computers simultaneously, or if you are instructing one remote machine to send commands to another remote machine, using CLI becomes even more preferable as performance degradation of GUI in these situations makes it difficult to work. Finally - in many systems, if something goes wrong, CLI is your only option as the machine can't even load up the GUI. All of this may be much more important for a ship flying for several months/years where energy conservation is possibly much more critical (you may have solar panels, or nuclear reactors, but even they have their shortcomings). Also, a cargo ship is likely to have several tied systems rather than a single monolithic computer - as different vessels will have radically different systems and rigs, each with their own computerized control - which in most cases you'd operate remotely. 4. ### Simple elitism ("any idiot can muck around with GUI, CLI is for pros who know what they are doing") While this is a disadvantage of CLI - it takes time to master, and there are no visual hints to remind you of possible commands (though every CLI user will know how to use /? or bring up a man page...). This can be an indication of how experienced a pilot/crew member is - you can tell much faster that someone working with a CLI knows what he is doing or guessing his way through the commands, which is useful if you are going to trust him with operating *your* cryo-chamber... --- Some references: * [Quora: What are the advantages of using CLI rather than GUI?](https://www.quora.com/What-are-the-advantages-of-using-CLI-rather-than-GUI) * [WIRED: Why the GUI will never kill the sacred command line](https://www.wired.com/2012/07/command-line/) * [Computer Hope: Command line vs. GUI](https://www.computerhope.com/issues/ch000619.htm) * [Craciun Dan's Blog "Echoes": 5 Reasons to Use CLI over GUI](http://vivapinkfloyd.blogspot.com/2008/07/5-reasons-to-use-cli-over-gui.html) 1: Let's not debate how much all of this is correct - it's enough to influence the state of the art today, even if it is based on a fallacy. Note that the web is full of arguments and even flame wars over this matter... [Answer] I have worked in spacecraft avionics for 17 years and was involved in the data management system for the latest ORION spacecraft. We *do* actually use graphical interfaces and in fact the the ORION displays are based on Boeing 777 cockpit displays and controls: [](https://i.stack.imgur.com/TXtcB.jpg) CLI's are generally a *bad* idea for realtime control as its too easy to mistype a command or use the wrong units (I worked on a project where an operator typed in the command angle in degrees instead of radians and lost a $500M spacecraft). So use GUI with touch screen all you want .. its what I would use. --- Engineers *do* pay attention to designing displays and there is a lot of literature on the subject. This may provide some top level guidance you could use in your storyline: [laws of design for universal cockpit displays](http://pixelscientific.com/what-is-resizing/laws-of-design/) [Answer] Touch screen GUIs may be rare in space ships because of the difficulty using them in space suit gloves. Mouse and touch-pad interfaces are a problem also, but not as bad. These are actual, real-world, non-worldbuilding problems. Using them requires a stylus designed for use with touch screens. A text interface with real physical buttons would be a better option compared to requiring everyone to carry around a stylus (or a Soyuz button pushing stick). Background: I am an amateur beekeeper. Trying to take pictures or videos with a touch-screen phone is impossible with regular beekeeping gloves. A stylus works along with a Bluetooth record button that has an actual physical switch. [](https://i.stack.imgur.com/1gmJU.jpg) Also, text can be easier. Think of all the people who use their phones to text more than talk. [Answer] **Remote control** The spaceship can be remote controlled. Due to the distances involved, sometimes the bandwidth is tiny and the lag gets enormous, so a low-bandwidth text-based protocol makes perfect sense. Therefore, command line ssh would be a natural fit. Remote control is a must-have feature in many use cases: * The company's boss would have root access and be able to set the autopilot back to home base if the crew decides to steal the ship... The crew could also use the remote override if their ship gets stolen by someone else. * The ground team's shuttle breaks down, they are stranded on a planet while the pilot onboard the orbiting ship has a xenomorph indigestion and is unable to respond. They must program the backup shuttle to deorbit and land. * Once back on the ship, after Leeroy bravely sacrifices himself to delay the crawling xenomorphs, being able to rush back to the shuttle, leave, and remotely trigger venting out of the atmosphere will seem like a great idea. Another advantage of ssh is that you can use it from pretty much any hardware without installing a client specific to your ship. As long as you have auth credentials it will work. You can use it from a bar, from a cyber cafe... quite useful when you wake up naked and robbed blind in a back alley on Omega and you need to tell your ship to send a drone to pick you up... So this command line would be the native way of controlling the ship. Why invent another one with bells and whistles? Now you'd need to learn two interfaces. **Flexibility** Since we are talking about small-scale entrepreneurs, their ships are likely to be a bit rusty, with retrofitted hardware, basically they would make do with what they can find at a good price. Sometimes when a system breaks down beyond repair, you need a new one, and you don't get to choose what's in stock. Sure, if you buy ALL your hardware from the same provider, you can get a nice GUI, but since your ship is a custom job, each manufacturer's GUI would most likely not be compatible with the others. You'd have to customize the GUI. Also pay a license to use it from your phone. People just don't bother. And when you want to make various incompatible systems cooperate... you often need glue scripts. Command line is a very good fit for this. It also makes sense that many operations would be scripted using a programming language like python for example. Think checklists, self-tests, working around a piece of buggy hardware that you don't have enough money to fix... [Answer] ## GUIs provide the easy '*What we think you'll want*' commands, terminals are where the user *tells* the computer what they want You won't have to click through to get to the button you want or wait for the visuals to load, you just write what you want in the terminal. Think of any setting you want to change, you have to open up the control panel (on windows), get the relevant options, click that one, find which of those you want to change, change it....this is good if you don't know exactly what to do or change but fairly long winded when you might be able to say `sudo date --set "12 Nov 2017 14:56:00"` and get the same result. Of course this also makes it a lot harder for *other* people to use your ship too. Perhaps at some point there were competitors flying about in their GUI ships and pirating...only it takes a while to figure out the necessary commands so it is more worth their while stealing other ships...and so your successful company emerged from the competitors. [Answer] Sorry to be negative here, but my only possible answer is: ## They wouldn't, unless all display technologies were impossible. A text prompt is great for ad-hoc hackery. It doesn't need any great thought about useability, because there is no useability. It's the lowest common denominator. As the lowest common denominator, it is easy to knock stuff together - but it absolutely is not easy to use, even for experts. As soon as you need something done where the results need to be checked and validated for safety, or just where people other than a "designated expert" may need to operate the systems, a text prompt simply doesn't cut it. Earlier UIs used simple text-based menu systems to get around this. PCs have evolved a GUI with windows and a mouse pointer, but which is heavily oriented to physical pushbuttons. Touchscreens have continued this with a GUI which even more closely emulates physical pushbuttons. Even your "typical Unix terminal" has gone this way. The most common "Unix terminal" these days is an Android phone. After that, you're looking at set top boxes, wifi routers, smart TVs, and DVD players. Do you use a CLI much on your phone? Have you ***ever*** used a CLI on any of these devices? Did you even ***know*** they ran some flavour of Posix OS? Case proved, I'm afraid. Arthur C Clarke said ["Any sufficiently advanced technology is indistinguishable from magic."](https://en.wikipedia.org/wiki/Clarke%27s_three_laws) As far as UIs go, the clear implication of this is that a CLI is insufficiently advanced. Even with Linux development, a decade or so of UI work, frequently by hobbyists, has been enough for some reasonably competent UIs to evolve. So back to that caveat. If display technologies are possible, a GUI ***WILL ALWAYS*** exist, even if it has to be created by hobbyists in their spare time. A GUI will only not exist if it is physically impossible for it to exist. Why might your spacefaring civilisation not have any display technologies? Honestly, that's got to be some kind of strange handwavy justification within your plot, and we can't really help you with that. It's got to be so fundamental to your universe that basic physics and electronics breaks down, and that's going to fundamentally influence your story. Without that handwavy justification though, your story will look strangely dated when it's stuck in CLI-land, in the same way as all those Golden Age sci-fi stories with robots running on tape recorders and valves, or 1960s movies with warehouses full of blinkenlights. (Edit to add assumptions: I'm assuming that user input by fingers/tentacles/appendages is required, and direct brain/neural interfaces are not possible.) [Answer] # Ruggedness, weight and interaction via speech A large lcd panel (needed for a usable GUI) is more prone to damage. Either physically (loose objects flying around) or by radiation. A large lcd panel takes up valuable real-estate that can be used for something else. Science module, cargo, velcro mounting point etc. A CLI can be a lot smaller therefore lighter. Weight is alway going to be a big factor when designing space craft. Having two smaller displays could add redundancy and in more convenient locations (one by the air lock/observation window, one by the habitat module at the other end of the space craft) A CLI can easily be augmented by a text to speech interface, so you don't even need to be able to see the screen to interact with it. Also you can cut down on mistakes by using more than one sense (sight, touch, hearing). Text to speech with speech recognition can be useful if the keyboard breaks/keyboard is not maintained. The constraint of a CLI can be a benefit in that it can force the design to stick with a small strict set of rules. e.g., Commands always follow the pattern `Verb` `Noun` `Value(s)` and commands can be chained together (To learn more look at [Powershell](https://technet.microsoft.com/en-us/library/hh551144.aspx)) This can make a complex system much more intuitive/predictable; useful in high pressured situations. [Answer] Because all operations in given environment are very important and need careful setting. It is *much* easier to click on the wrong icon than to input a syntactically correct command that's not what intended. "Command Line" is much harder to learn and thus the popularity of "GUI" interfaces, but in the given environment that's not a problem as your "small-scale entrepreneurs" are bound to know their ships very well and are likely to welcome *anything* forcing them to *think* before committing a command. In the example given they surely won't like "oversleep" any important (orbital) appointment. **Edit**: I know this is a very slippery subject and many Holy Wars have been fought under the flags of GUI Fawkes and CLI\_nt Eastwood, but I will clarify my thoughts nonetheless. Bear with me. The trend in general and about Interfaces in particular, has always been to make things "easier" for the user. This is generally regarded as a Good Thing, but, as with *everything*, there is a price to pay and situations where this price overweight any advantage had. The specific "price", in the case of Interfaces is that an "easy one" requires less thought and thus can be used while distracted, sleepy, inebriated or otherwise not fully focused on the task. A special note, here, should be done about Unix CLI: Usage of short commands (mostly 2 letters, 3 if clashing) and single letter options was essentially chosen to "avoid too much typing" (and because of limited parsing capabilities in the late 70's, of course). Thus it already is on the path of "making life easier" for users. The "small-scale entrepreneurs" cited in the OP are bound to be very skilled people caring little about easiness and having all the time in the Universe to do the things "right". To them a "punitive" interface, requiring precise and redundant input, is a boon. The cited example would be modified in: ``` cryo set wakeup=time+2d > Ambiguous input, did You mean 'cryo cell 0 set wakeup=current_time+2days'? cryo cell 0 set wakeup=current_time+2days > wakeup procedure scheduled for SOL3-1_37:4:12m-6:23:40-127812_79812301 > that is 2 hours, 25 minutes and 16 seconds before next scheduled task (filter cleaning). > you have 15 minutes to enter cryo cell 0. ``` General idea is CLI is not necessarily "stupid" and, by the time OP conditions come true it's very likely some good quality A.I. will be available, but it should *never* rely on "intuition" or things said in a way not perfectly clear to take action, but it should rely on clear evidence the person know exactly what's asking, and that is much better done in written form. [Answer] A ship where the entire crew spends most of its time frozen will by design handle **all** routine tasks automatically. Any task the crew will need to do will be due to unexpected and unpredictable change that the original flight plan could not cover. It is not practical to build an efficient GUI that handles all possible unexpected and unpredictable events. It is much simpler to give the crew direct access to all configuration that is not hardwired. Unless they are using a graphical programming language, which seems unlikely, this means text. It is *possible* to create a visual or verbal representation of all configuration data and system code and let the users interact with that in some sort of VR, but I am not convinced that would be *better* than just using text. So using text makes sense. As for an actual CLI, you could argue that a system would have two modes. A full text editor where you can edit configuration data and source code and then commit the changes and a CLI that allows you to make small changes on the run with added safe guards for system stability. It would even be reasonable to assume that the full access editor would be heavily restricted to authorized people and only be available in flight during emergencies, so using CLI would be the norm. This would still give crew access to all configuration that can be changed safely while in flight, which would be very complex to do with a GUI. The CLI would also presumably directly map to the relevant configuration data, so the same knowledge would be usable for both CLI and full editor. This is actually an issue with GUIs where they either require you to map user friendly and localized language to what you actually want to do (usually requires Googling or training) or are just as arcane as a CLI would be, but with extra confusion from navigating the interface. Checking command syntax is generally easier, especially if you do not have internet or AI assistant. [Answer] **That is how the ships come.** The humans are not using space ships they build, but spaceships they found and salvaged. The novel Gateway (Frederick Pohl) has ships like this, built by a mysterious vanished race the Heechee. <https://en.wikipedia.org/wiki/Gateway_(novel)> > > There are nearly a thousand small, abandoned starships at Gateway. By > extremely dangerous trial and error, humans learn how to operate the > ships. The controls for selecting a destination have been identified, > but nobody knows where a particular setting will take the ship or how > long the trip will last; starvation is a danger. Attempts at reverse > engineering to find out how they work have ended only in disaster, as > has changing the settings in mid-flight. > > > The book [Beyond Heaven's River](https://rads.stackoverflow.com/amzn/click/1522685731) by Greg Bear sticks in my mind because of its descriptions of the space ships the human protagonists use. These ships are ancient. It is cheaper for the independent operators and small-time entrepreneurs to weld down a few comfortable chairs but otherwise learn how to use these ships as they are. from the book > > Alae slapped a test module on the panel and pushed her way past > Oomalo, walking down the oval corridor to the ships old Aighor command > center. Her footfalls we’re the only noise. She wanted to put her > hands over her ears to hide from the silence. A quarter century of > routines had made decisions agonizingly difficult. Oomalo followed. > They sat in the twilight of the half awake control consoles, smelling > the dust and the cool electronic odors. Human-form chairs had been > welded to the floor plates when the station had been re-outfitted, > thirty years ago. > > > Most of the pathways and living quarters have been tailored for human > occupation, but the command center was much as it had been for the > past 10,000 years. The light on its consoles glowed with the same > spectrum chosen by the last Aighors to crew the ship. Alien displays > indicated that the dormant engines were still in working order. > > > … > > > The old ship went above space-time as smoothly as a Leviathan through > arctic seas. For three hours there was nothing around them; the ship > was their universe. It was at least 10,000 years old, from the third > stage Aighor civilization, and a sizable 3 kilometers from bow to > stern. They had purchased it at auction from Crocerian free merchants. > > > So too your space ships. This command line interface (in an alien language) is how they were found. Instead of trying to hack and augment these interfaces (at some expense and considerable risk of disaster) it is faster, cheaper and safer for the new human owners to adapt and use them the way they are. [Answer] GUI is much superior to CLI when it is known with reasonable certitude what you will do, if the number of choices is small (or the workflow is always the same), if spending a few more resources and having some extra latency doesn't matter, and if reliability is not paramount. In every other case, you will want CLI or hard wiring (which I consider the most primitive form of CLI). If you cannot anticipate what will be needed, CLI is preferrable as it allows much more easily to do things that the user interface designer did not anticipate, basically CLI is almost like a primitive form of programming. Well, not quite, but it comes close. Not that it isn't in principle possible to do virtually everything (even unanticipated things) with a GUI as well, it is just a lot harder to design and a lot less straighforward. If speech recognition can be assumed (and it likely can) then CLI is also much more "compatible" with that kind of interface. In fact, one may serve as backup for the other. Anything you can type, you can say, and anything you can say you can type. Anything you can read, the computer can as well tell you via speech synthesis, if need be. That's useful when you are for example in a location (doing repairs on the outside, carrying a space suit) where no physical terminal, let alone much of a way of interacting with a GUI (other than a minimal HUD), is available. Dumb terminals have the immense advantage that in case of failure, you can pull one terminal out of one location (possibly from a 25 year old terraformer on that planet which is going to explode in 17 minutes) and connect it to your main engine where all the terminals have been destroyed by, uh... a neutrino cascade, and chances are good that it will "just work". You might even pull the network/serial/whatever interface out of one and put it in another where the monitor and keyboard is still working (I've actually done such things successfully towards the end of the last century). If your life or something even more critical (landing a starship [with a thousand tons of bioweapons](https://en.wikipedia.org/wiki/Alien:_Covenant) on an inhabited planet?) depends on the outcome then the most primitive form of CLI, a board of mechanical switches, and a stick (or steering wheel) is even more preferrable, retro as it may seem. The less abstraction, the better. You want a stick that makes the ship go right when you push it to the right. You *don't want* to be waving hands over a holographic projection or be playing a flute. You don't want to crash into an asteroid because `dwm.exe` hangs or because you can't find the control quick enough. You don't want to needlessly delay an emergency reactor shutdown for 15 seconds while your display shows animated whirling balls. You don't want cryo chambers being ejected because the cat walked over the touch display (you *really* want a big, red, mechanical lever, or a push button for such things). [Answer] In addition to other answers, **GUI exists but no one cares** Even though I'm a software engineer myself, I don't believe there will be absolutely no gui in space. It's just not practical. But... most of the time gui is a limitation. So, consider the regular interplanetary voyage. There are various aspects at work that should be taken into account by crew: * Gravitation might affect ship's trajectory * Hi-orbit junk may damage the ship - need to avoid that * Complicated computations to get a correct aircraft vectoring without help from ground-control * Keep track of fuel consumption and perform special maneuvers to use gravitation and momentum instead of burning the fuel until you're good * Astromechs need a script they'll execute to do their job inside or outside of the ship - you'll need to write a code for that * [insert your sci-fi reason here] Ok, now we have all the complications. The crew will have to manually guide the ship according to external conditions and current goals. You'll need a GUI with hundreds of buttons and input fields which is no way better than a console. Besides, there's no need to use good old MS DOS, right? It can be a super powerful CLI that supports some easy-to-use scripting engine Sci-Fython and it allows the crew to write smart navigational and maintenance scripts on every day basis. The GUI can still be used but in read mode in order to display readings. It's quite convenient since most important parts can be highlighted and plot-charted. And it's better than typing "sys.fuel-monitor.getXXXparam()" anyway. [Answer] Most factors already seem to have been covered here, except the nature of the their use of computers, there may be a place for GUIs in a starship, but not a lot. * Raw calculations are typed, not clicked in a GUI * Courses and corrections are typed, not clicked in a GUI * Time periods are better typed, not clicked in a GUI * Error reports want to be text, not pretty graphics For their primary day to day use of computers, GUIs just don't work, CLI is what you want and the GUI is going to get in the way and slow things down. Until the navigation software is at a point where there you're just clicking a destination on a screen from a limited number of available destinations, then CLI is fundamentally the way to go. You're suggesting dumb terminals, but why not? There's only really a need for a single (distributed) shipboard computer. It runs everything and has access terminals around the vessel as required. [Answer] There's a simple functional reason why you might prefer CLI to either cursor-input or direct-touch GUI: vibration. Controlling a mouse/trackball cursor, or even poking the right bit of a touchscreen, are *hard* if everything's shaking. Even voice input is difficult if there's enough noise (at some frequencies even a throat mike will be vibrating). A keyboard though, has a rest to anchor the heel of your palm, and finger movement relative to that is pretty accurate. [Answer] I'm sidestepping your base requirement a little bit, to arrive at a plausible, consistent system: The most efficient handling of **complex**, **flexible** systems is not a GUI. A GUI is brilliant if you have a reasonably low number of possible actions, and can fairly well predict the typical command path a user takes. So some basic controls would be GUI or hardware controls. You can bend it a bit and tend towards hardware controls. Anything that needs to give you **full control over a complex system** will not be a GUI system. Even today, serious administration of IT systems is generally done in some kind of CLI interface. Other answers have already spelled out the advantages of CLI over GUI. But you also support vector graphics. That is perfect because very often a graphical display can convey much more information than a text-based output. So in essence you have something like the Wolfram Language and that is a perfectly good interface. So the answer is that your spaceships use these kinds of interfaces **because they are the most adequate solution to the task**. Full control at the fingertips of a trained user, output via text or vector graphics, depending what is more suitable, better usability in space (as outlined in other answers). For the particular context, the CLI offers a better advantage vs. disadvantage ratio than the GUI - which has some advantages, but just not enough. Remember that your solution does not have to be perfect, just better than the alternative. [Answer] Radiation and other environmental effects [damage computers](https://www.popsci.com/supercomputer-international-space-station). Longer times in space will accumulate that damage. Since computers are something your ships *need* to work, reliability would be preferred over looks or performance. Especially since spare parts are hard to come by out past Jupiter. Another idea is that someone has invented a computer that doesn’t suffer damage from radiation (perhaps a “tiny” mechanical computer) but doesn’t obey Moore’s Law (it’s difficult to improve performance past early 80’s processing power). [Answer] Engineers are notoriously bad at building GUI's, but on the other hand your average GUI designer can't get a spaceship off the ground. The "reason" for the CLI is simple: the engineers building the spaceship started with a CLI, as they are wont to do, and indeed that was necessary to get the thing working in their simulators down on earth. And yes, the upper management knows they really should get some UI experts in to fix that, but for the moment they have a spaceship flying. And it's not like there s a lot of competition in the market. Besides, so you need to teach a CLI to all of your pilots. But how many are you training? Sure, by now you're training a dozen new pilots a year, up from 1 or 2 when you just got started. But by now refitting the whole fleet with GUI's has also become more expensive, so the board has just decided to move that decision forwards by yet another year. TLDR: Building a GUI is the correct decision, but has up-front costs and management is shortsighted. [Answer] Mass and cost. A small multiline LCD display has less mass and costs far less than a small LCD graphical display. The more mass a ship carries, the more fuel it needs to use to move. More fuel = more cost. Plus, why use an expensive display, when a simple, cheaper display will do? The costs multiply when you have to carry multiple spares. Multiline LCDs also take up far less space. [Answer] A spaceship cannot rely to get its tech support from earth. Thus, they'll want at least a few highly-skilled programmers on board to ensure ability to operate and repair the ship computers in any situation. It only makes sense that these programmers are also the ones who regularly interact with the computers. The ship's captain won't be typing the commands, he'll just say "schedule a wakeup for tomorrow" to one of the tech guys. And even in real world, many programmers prefer command line interfaces for various reasons. Once enough there is enough inertia behind CLI use, any new guys have little choice but to go with the established workflow. [Answer] 1) For crucial systems, physical controls are better: you can feel for them in the dark, you don't have to look at them to use them, and many of them don't even need power to work. Everything that would use a GUI is given a mechanical control. 2) Everyone allowed into space can code. GUI's are not needed. 3) GUI's require displays. Displays come in many form-factors (resolution? size? touch? color?). You don't want to be dependent on a particular part for a particular display. 4) GUI's are an extra layer of software on top of the software that you actually wish to operate, that is, an extra, non-mission-critical layer of potential bugs. Being killed by an "Event not key-value coding compliant" bug would just be humiliating. 5) Voice control: it's easier to control a machine with an audio-only interface when the expectation of visual feedback is removed. I'm imagining two astronauts in a damaged lifepod writing out a sequence of text commands for the navigation unit, on paper, and double-checking, then turning on the mike... [Answer] > > Why would technology dictate graphical interfaces to be rare on > spaceships? > > > GUIs change far too often and are based on what the particular manufacturer of that device thinks is the best GUI. From a tech perspective, policing possibly hundreds of manufacturers to provide a consistent GUI ranges from difficult to downright impossible. Each of the current OS manufacturers provide specifications on how applications are supposed to look and work in their environment yet most 3rd parties think they have a better way of presenting information and choices and go a different route. This only gets worse as manufacturers are allowed to patent particular *looks* or behaviors which essentially forces other manufacturers to come up with their own paradigm. ie: rounded corners, swipe right to open, tiles, etc. By going text based, you can install commands from the various manufacturers into the computer core while caring nothing for how their particular program looks or functions. The main thing here is just to provide parameter references that can easily be accessed - which is usually built into the programs themselves. --- Taking a slightly different viewpoint: I could easily envision that multiple companies are producing their own spaceships and 3rd party manufacturers want their devices to be on them. Today it's nearly impossible for a 3rd party to have the exact same GUI experience on multiple devices (iOS/Android/Linux/Windows). However if the app is a CLI then it's trivial for the usage to be near identical. It's also far cheaper to produce and maintain. --- Now, I still think it's better to use GUIs on core systems that require immediate or very fast operation such as flight controls in order to increase reaction times and reduce the possibility of human error. [Answer] # GUI's have evolved In the future Graphical User Interfaces have evolved to complete immersive VR environments. These VR environments are absolutely amazing for work efficiency and use completely novel interactions, but require somewhat clunky and heavy machinery (VR immersion capsules/chairs). The result is that an average future teenager will have as much problems using a modern-day GUI with a mouse and keyboard, as they will have using a CLI. They simply have no clue in both cases. The end result is that when designing a space ship where weight and space matters and placing lots of VR immersion chairs is not an option, they simply went with CLI's. Not because they are necessarily the best option, but given the necessity to use a cumbersome old fashioned system they don't really care anymore. The advantage of this is that it makes it very likely that someone is going to mess up. Which in turn will of course make for beautiful plot drivers. [Answer] Others have already pointed out that CLI is very fast for a trained user, and it is almost impossible to accidentally click on the wrong button with clumsy fingers in your space suit gloves, or fingers still half frozen after cryo sleep. Admittedly, typing with half-frozen fingers gets you some interesting effects, too, but it's harder to accidentally type "self destruct" when you wanted a cup of coffee than clicking the wrong button (and don't get me started on user interfaces that managed to put buttons in the weirdest of arrangements). Someone also mentionned text-to-speech. And of course, a lot of things run automatically, and the computer doesn't click on buttons, but runs commands directly. But the question was why would technology **dictate** that GUIs might be rare and CLI might be common place. I think a plausible answer is much better **language recognition**. With CLI today you need to know the exact command syntax, the correct order of parameters, and whatnot. If you do, no mouse-wielding point-and-click-user will ever come near your speed, but if you don't, you'll have a hard time getting your command to be executed. But if language recognition evolved, and it seems safe to assume it would, then you loose the downsides of CLI. You type what you want, and the computer understands, translating to the "correct" commands. You still have some GUIs for those cases where visual information transports the important bits a lot faster than text and numbers would, but to interact with the computer, just type what you need, it will understand, and if unsure, will request clarification. So, why not direct voice input? It might be because of the noise aboard the spaceship. But most likely it's because it's annoying when your workstation keeps executing the commands of the colleague next to you. [Answer] # Vibration That should be obvious. However, there are menu-driven user interfaces even in vibration-heavy environments nowadays. But these are used for secondary or tertiary tasks, not for primary functions. Try to hit an alternate destination on an animated touch screen map while your spaceship undergoes re-entry. Or in your car while you are speeding down a bumpy road. Interaction via speech (mentioned by DarcyThomas) can be an option for task which do not be processed in hard read time or when the environment can be extremly noisy (vibration in the audio range). However, with sufficiently advanced technolgy, the distinction between GUIs and "hardware buttons" may begin to blur. Imagine a tactile 3D display which can extrude hard controls at will. Like a round cylinderical control when the need arises to adjust the volume of the intercom or the temperature of the climate control (this will be pretty hard to turn so it will not mistakenly be turned due to vibration or an accidental touch). [Answer] In the near-term future, we could expect augmented reality "glasses" to be the norm. The GUI of yesteryear will be obsolete, as will most 2D screens. GUI's operate in a 2-dimensional plane and are merely a translation of our 3D world and, as such, are inherently flawed. In this future, the likes of Google Glass and the imagined Magic Leap will allow for three dimensional manipulation of the environment. While immature today, I expect this technology to quickly flourish. Imagine seeing your system, in this case the ship, in a translucent 3D scaled image. Retina tracking allows the user to simply look at the ship and the system intelligently zooms to parts or commands of interest in that section. Want to slow the ship? Look at the engines. Care to maneuver a bit? Visually focus the thruster nozels. Need to seal a compartment? Glance at the doors of that section in your 3D model. This 3D representation of the ship has menus intelligently pop-up with items of interest for the given part. Following this thought experiment, it would not be hard to imagine a ship devoid of all interfaces. For example, you could walk up to a door and the commands you are allowed to do to the door popup in your retina - focus on an option to perform the task. So, to answer the question specifically, the GUI type interfaces do not exist on the ship because each user has a better personal interface on their person. Such technology would likely not be some wired, or rechargeable device, but rather one that charges from some ambient energy, or from the end-users body directly. For example, a single eyepiece that is powered from the pulse by the temple of the user. Or, if we move further into the future, an eye embedded device that laser "paints" visuals directly onto the retina. In any case, we end up with a ship that needs no interfaces anywhere at all. The "Bonus Points" for a dummy terminal indicate the Op wants some terminals, so from my above scenario, the ship is laced with dummy terminals for one of a couple reasons... 1. In the visual interface it could be difficult for the system to "guess" what you want to do without a solid, albeit, narrow AI. Thus, any user can walk over to a dummy terminal and type commands onto their own eye screen to work faster. i.e. in-eye typing exists, but is too slow. 2. The dummy may be needed just because the system is not good enough at its job, thus needing personal input from the user at all times. i.e. there is no AI that helps to show what you want, the terminals are how you navigate your in-eye 3D world. 3. Alternatively the dummy interfaces could just be for redundancy. As another user pointed out a CLI could exists, but it would be the "experts only" way of interfacing with the ship. Not that the eye-piece couldn't be used in all cases, but rather the expert can quickly do "that one thing" Regardless, the end-user becomes the "disk" of the system as the Op wanted. New user at the terminal? - new disk. Each time you approach the terminal, that user is shown the last commands they performed and starts where they left off... personalized each time. I realize such an "eye interface" may still be a GUI in itself, but being personal to the end-user eliminates them from the ships leaving expert-only CLI type terminals. Thus this addresses the Op's questions fully. I hope this helps, good luck! [Answer] **Technology restrictions will probably not dictate whether future ships have GUI or CLI tools - cultural ones definitely will.** Technology is developed (and installed) to meet human needs, which are based on business / mission requirements, and even personal preference of the ship's owners and/or users if spaceships are widely available. As illustrated by all the other answers and comments this question has generated, it's clear that both GUI and CLI interfaces have pros and cons. Your universe will need to some cultural or physiological imperatives to drive development towards CLI and away from GUI. Some of the arguments already presented may be a good starting place. [Answer] Are you looking for more or less logical reasons that answer your question? Well, then I don't think you will find any. However, if your world is a bit on the fantasy side, then you might create some particular condition. I don't know, maybe a cultural thing that makes people hate graphics, maybe a population that relies on pure abstraction... I don't know, you could play around that. However, if you consider this scenario as a more evolved one than ours, then there's no way you can offer a logical reasoning for this. **You have to understand that CLI existed only because GUI were impossible or very complex to do at times when a byte was gold**. Nowadays... there's GUIs for everything (yes, including servers). As a matter of fact, [I was wondering how is it possible that people still uses CLI over GUIs](https://ux.stackexchange.com/questions/101990/why-are-terminal-consoles-still-used)! And this is our current *state of the art*. Where [**AI/MI**](https://en.wikipedia.org/wiki/Artificial_intelligence) is taking their first baby steps, same for [**AR**](https://en.wikipedia.org/wiki/Augmented_reality). And where computational resources are almost limitless. I'd imagine that people doing interstellar journeys are way more advanced than our current *state of the art* **Just imagine this user case:** the pilot has to avoid a collision with an object. Would you rather press a button or type a series of commands instead? Or even better, **leave the spaceship do whatever it wants because chances of errors will be millions of times lower than human interaction ones?** *Let's get down to Earth.* Just imagine the stellar map, and replace it by Google maps. Do you type coordinates or just use commands like zoom and click? Now, back to space, and instead of a bi-dimensional plane (like a Google map), think on a 4th dimensions scenario *(oh yes, remember that in space you also have to consider time!)*. See what happened? your CLI commands are literally impossible, because even if the pilot knows distances, she won't know at least one of the dimensions (time) and quite probably she won't know the Y axis either. Something that would take... 1 click on a button. I'll take G0blin example (not to be confused as a stab at his answer, just trying to explain using the same set of commands: > > 1. command 1: list all cargo entries for explosives, > 2. command 2: list all cargo bays in input, > 3. command 3: seal all airlocks of rooms in input, and, > 4. command 4: flush emergency coolant in all rooms in input. > > > In advanced technologies that are available nowadays, this would probably require just some oral input and aural acknowledgment, or maybe even nothing (the machine would do this without the pilot's intervention). But even "older" approaches, like the most common nowadays would require just a... **dashboard**. I did a quick one in less than 5 minutes: [](https://i.stack.imgur.com/iRcTB.png) Just think of the above image like this: ``` enter what to search show cargo with that input offer available actions to user ``` While I'm an UX professional, *I'm nowhere close to be a spaceship UX professional!* So just imagine thinking this thoroughly with adequate testing by professionals that know the possibilities of their technologies! # In short Unless you find some kind of cultural reason or you force some strange sociocultural scenario, I don't think your question is logically possible. However, it doesn't mean that CLI commands should be completely neglected. You could have them for very strange and arcane commands, or just because **"real men don't use GUI"** [Answer] In addition to the other answers, consider the advantage of being able to print out a log of all commands executed, and being able to look up to what happened before the ship lost power. It could read ``` ... Lt. Jerry @ 12:30 11/13/2117: lifesupport --kill ... ``` which is easier to figure out than from looking at what buttons were pressed and when. In a practical implementation of this it's more likely that the ship would have a "rolling" hard copy of the last couple hours of the logs, that would overwrite the oldest entries with the newest, instead of printing miles and miles of paper over the lifetime of the ship. This hard copy would almost be exclusively for the situation where the ship loses power accidentally. Additionally, typically when there is an error in a GUI: It appears as a dialog box which is gone once you close it. CLI allows you to scroll back up and view results from previous commands such as errors. [Answer] ## New system requirements and inertia Many years ago when the current systems were being devoloped, they did ship with graphical interfaces with animations that rendered current ship status, simulation outputs, and general diagnostic information. Shortly after these systems were introduced, a major new practical functional requirement was required by all certification and government entities. This functional requirement 1. Required lots of processing power 2. Needed to be done in real-time 3. Involved a large amount of matrix algebra Instead spending the money to design new hardware and retrofit/redesign existing units (space rated hardware is very expensive), the processing power previously used for these interfaces was redirected towards this new functionality. This happened at a large enough scale that virtually all ships were converted in this manner. Due to the reasons mentioned in [G0BLiN's post](https://worldbuilding.stackexchange.com/a/97630/32753), and not wanting to retrain experienced spacers, command line interfaces became the default. ### Alternative suggestion Instead of a purely command-line based interface, users interact with a tile-based window manager. These GUI interfaces are specifically designed to be usable with just a keyboard, but can use graphical windows like any other system. Here's a demo of one in action: [A Better Linux Window Manager: i3 Tiling Basics](https://www.youtube.com/watch?v=9ofq4gpG_lM) [Answer] In addition to the other answers about the efficiency of CLI for skilled users I might add one other consideration specific to interplanetary society. Graphical interfaces are culturally specific and may be be meaningless to an alien species that has a different technological history. For example, We use icons representing envelopes to mean "send" and floppy disks to mean "save". Even people who have never sent a paper letter of used a floppy disk know what they mean because they have grown up in that cultural environment. Without that acculturation, it may be difficult to interpret the pictures. Even more abstract signs like arrows for movement may be meaningless without the implicit understanding that things move toward the pointy end. Of course the CLI would also have to be learned but it is a limited number of logical commands made up of and even more limited number of letters. There may be other physical or neurological difference in the the way that different species perceive and mentally process images. The CLI is closer to a purely logical representation. ]

[Question] [ So, there is a dystopian government called the Union of Fascist States. It controls both North and South America, the United Kingdom, and half of Africa. The NAF is the one and only party that controls everything. The party and secret police control all of the citizens lives, and at age 4 every junior citizen is required to go to educational facilities to gain knowledge and whatnot. The problem is, why would the government want its citizens to be educated, as education could lead to ***gasp*** freedom of thought. Do, why would a dystopian government want its citizens educated? [Answer] Well they wouldn't want them to be "educated" in the classical sense, but they would want them to be "schooled" in the 20th-century sense. Taking children away from their parents and making them sit in classrooms with same-age cohorts for all of their most formative years does a lot for your totalitarian government: * it weakens the family (the naturally strongest building block of society, hence the biggest threat to your government) * it breaks down independent spirits and creative thinking * it accustoms children to the idea that truth and validation all comes from the judgments ("grades") of authority figures they didn't elect for themselves. Certainly the teachers will all be loyal party members, or true believers in the official ideology, so it's a way to reward the party's supporters with jobs and to reinforce party ideology as part of the curriculum. Also, it makes a lot of the victims/students grow to hate learning, so by age 18 they're ready to never read another book. Uh... wait a minute... [Answer] The problem with ignorance is curiosity. When you deliberately try to hide something from a person, they tend to get curious and actively seek it out. We love mysteries, exploration and the pleasure of finding things out that we didn't know before. What that means is that a dystopian government that deliberately hides knowledge and learning from its citizenry is actually putting itself at a disadvantage. People will seek such things out, and then the government no longer as a seat at the table, so to speak. Education and learning are driven and controlled by outlaws who seek to undermine the government, meaning that students are taught with that bias integrated into their education. Also, education is actually *necessary* for a society that seeks to maintain supremacy over its neighbours. Without research and development, you don't get the advances that your enemies already have and the last thing you want to do is fall behind technologically against people you don't like or trust. So, you really need your citizens to be learning new things and focusing on STEM subjects especially. A strong dystopian government therefore promotes education to the point of making it compulsory. What it does however is it discredits or even bans independent or private education, forcing all children and students through a state run education system that teaches people with the integrated bias the State sets. It also works through talent identification to ensure that those capable of higher learning are promoted into the right state schools and universities for their talent set, building a committed and competent workforce that knows how to apply education in a practical way to the betterment of the State. For what it's worth, the last 300 years (if they've taught us anything at all) have taught us that making something illegal is the worst possible way to control something. Prohibition in the US and Australia only led to criminals getting rich off a completely unregulated industry. The prohibition on Marijuana and harder drugs has largely done the same thing, whether you believe it's the right thing to do or not. The reason why Australia adopted such strong plain packaging laws and restricted how cigarettes could be displayed or sold instead of simply outlawing them was because this way they can control the flow of them, rather than just creating another vector for organised crime to exploit. Even slavers took advantage of Lincoln outlawing slavery in the early days by cramming as many new slaves onto boats as they could. The lot of a new slave being transported from Africa was actually far worse after it was banned than before, when there were regulations in place about food, medical care, treatment et al. Early post-ban slaves were FAR more likely to die on the boat across than they were pre-ban for that every reason. So too would it be with education. Banning something like education will only remove your ability to control it at the State level, and that's a fundamentally silly move. Better you actually make it compulsory, and then flavour it with the bias you want to set in your culture. Ultimately, the best way to hide something is in plain sight. In this case, by putting education high on your list of priorities, the dystopian aspects of your regime are out there for everyone to see, but they aren't noticed because you've trained your citizens in a manner that directs their attentions elsewhere. Put simply, your dystopian society (if it wants to last) wouldn't even be asking this question because they'd be too busy designing the curriculum for the next generation. [Answer] IIRC from your other question regarding this Alternate Universe, it's in competition with the "Eastern Block". Are there any non-aligned nations, or nations on the periphery of the Eastern Block that could be swayed into the UFS by the UFS being technologically and economically superior? Because -- just like in the real Cold War -- places like the USSR and GDR (German Democratic Republic) emphasized education: 1. because citizens educated in STEM make the economy better, and 2. those governments **believed** in the superiority of Communism, and so did not fear education. Of course, what they taught in History and what American high schools call "Social Science" isn't exactly what was taught in American high schools. It was all about Communist indoctrination and how bad the West was. The UFS will teach their students similar things for similar reasons. [Answer] Education is a powerful thing. Imagine what a country could do if nearly 100% of citizens could read by the age of 15. Imagine if they could get 11 years of mandatory education and then may go on to attend a four year university. That could be an astonishing force of innovation and freedom of thought. Right? If we feel like keeping track, the statistics I just gave are the statistics for the [North Korean school system](https://en.wikipedia.org/wiki/Education_in_North_Korea). I think we can choose to make our assumptions regarding how much freedom of thought exists under that regime. "Education" is a word that we toss around gently in the Western world. We assume that it is a thing you get if you go to school enough. But when we look at it closer, the part that school system focuses on is indoctrination. It is by the virtue that we appreciate the particular indoctrinations that our school system provides that we assign a positive moral value to it. Yes, there is more to schooling than just indoctrination. Our teachers have an enormous influence on the next generation, and we should respect that. But if we focus just on the school *system*, the *system* is one built on indoctrination, just as it has been since the first schoolrooms were built thousands of years ago. The key to "education" (put in scare quotes in this case) is to control the knowledge put into the heads of the next generation. Why would a totalitarian dystopia like the one in your novel *not* want to have that kind of control? It'd certainly be an oversight. If they did have to deal with "freedom of thought," what better place to have it occur than under the watchful eyes of the teachers and other students? It would be easier to identify the troublesome individuals if they were to demonstrate their troublesome tendencies in school! [Answer] # Because they need the *parents* in the workforce. If education starts at age 4 [or earlier](https://en.wikipedia.org/wiki/Education_in_East_Germany#Cr%C3%A8ches), and if it includes lessons or other activities in the afternoon, then both parents and not just the father can contribute to the workforce. That will be important, considering how much economic friction and waste a fascist system creates. There was a bleak joke in Nazi Germany -- *"One third in the camps, one third guarding the camps, one third in the army, of course there is no more unemployment."* # Because they believe *they* are right and want to tell it. Good fictional villains don't act the way they do for the sake of *evil*. Not all of them will be stupid, either. The rest will have built a complex theoretical construct to justify what they do. If they recognize shortcomings of the dystopia, they'll tell themselves that those are necessary side effects for the greater good. * Civics will play a large role, justifying the current system and demonizing all others. * [Racism](https://en.wikipedia.org/wiki/Nazi_eugenics) can be cloaked in the mantle of science. * All other subjects can be used to [frame](https://en.wikipedia.org/wiki/Framing_(social_sciences)) the worldview. # Because common schooling builds a common society. Fascism is about *us vs. them.* It is important that the oppressed workers believe that they belong to the same group as their oppressors, so they won't rebel. For that it helps if the child of the worker and the child of the mid-level party functionary went to the same preschool. When they are a bit older the right students can be sent to schools more suitable for [them](https://en.wikipedia.org/wiki/National_Political_Institutes_of_Education). [Answer] Because a centralized, government-controlled education system it is a great way to spread the doctrine of the regime. * You can control precisely what information students get exposed to, and most importantly which information they do not get exposed to. * You can control precisely how that information is framed. * You can even "inoculate" children against dissentive thought by exposing them to weak strawman versions of the arguments of the dissenters and have them practice how to counter them. *"Essay Assignment: Democrats claim that even the most evil, destructive and unintelligent people of society should be allowed to influence the government and even choose its members. Explain the negative consequences for our nation if the government would do what the worst people of society want them to do."* * You can use punishment and reward in the school environment to condition children to follow certain behaviors. This conditioning will carry on into adulthood. * And the most powerful effect, in my opinion, is that everyone gets exposted to the same information, which turns opinion into objective truth. This makes it much more likely that people will reject any dissenters as uneducated. *"Everyone knows democracy is an inherently unstable system plagued by corruption and inefficiency. Didn't you pay any attention in school?"*. Any facts which contradict the doctrine of the regime will have to overcome the [cognitive dissonance](https://en.wikipedia.org/wiki/Cognitive_dissonance) with the material the students learned in school. If you look at some totalitarian regimes of the 20th century, like Nazi Germany or the USSR, you will notice that they all invested a lot of resources into educating the youth, made the educational system compulsory and used it for political indoctrination. They even tried to dominate extracurricular activities with political indoctrination. See the [Hitler Youth](https://en.wikipedia.org/wiki/Hitler_Youth) for example. [Answer] ## Totalitarianism runs on technology * weapons, communications (propaganda), surveillance, for example. * you can't even **maintain** technology without having a significant number of people who understand how things work and are able to improve them; * you can't predict which children will be good at what * plus, if you don't have world domination, you are constantly under pressure from other countries, to maintain edge in technology - at least military tech; Therefore you place high value on STEM fields and try to give children a reasonably broad education as far as related to those fields, hoping to get the intelligent working enthusiastically on existing and new technologies. However, most of the scientific fields tie both into one another and in other aspects of life, therefore you need to give the children a more or less complete world understanding as well (skewed according to your totalitarian official worldview). You need to have the education reasonably broad so as many children as possible get hooked on something that interests them - because for intellectual (especially scientific, but not only) work it is not very useful for somebody to do things he is not really interested in. This is more or less how it was in the USSR. [Answer] It depends - do you mean education, or the kind of indoctrination we see today? For example. In many countries there are some religious schools that require their students to memorise a certain holy book and prophetic teachings. As far as they are concerned, other forms of education is for the non-believers (who are considered worthless anyway) and thus they think they are providing the kids with a valuable (nay, essential) education in what is correct and true and authorised. They do this because they were similarly indoctrinated and actually believe that nonsense. This can be very useful to some forms of government, as this kind of education can even persuade people to perform acts of suicide terrorism. A dystopian government can replace one holy book for another - I think we use John Maynard Keyne's "holy" book today, any one will do as long as it forms the backbone of the government's ideology. But if you want a true education, where kids are taught to think for themselves then it becomes more tricky - the problem is that the kids will see that the dystopian government is dystopian and fix it from within as they become older and work within it, unless... One solution to this situation is to either make them clever enough to understand that any government is dystopian (ie there is no utopia, only the naive and stupid believe that) so the current form is as good as any other - and replacing it would mean massive amounts of social disruption, so best keep it chugging along and make the best of it. Another would be for the elites to be treated differently to the peasants and even though they know its a bad situation, they don't care - they get all the benefits while the peasantry work for their benefit. This is a more feudal government, education amongst the nobles was as good as it could be. Education for the peasants though, would be reduced or restricted - possibly with the excuse that not everyone is academically gifted and so all those non-elites have to have education tailored to their ability and focused on practical education. You could also modify this to a egalitarian elitism, where those kids who do have the academic gifts are promoted to the elite and then given everything they ever wanted (or be sent to the salt mines as dissidents) There is the technocratic form, where education is the best is can be so workers can do much more for the state, whilst not giving them any form of political power - a stratified system of government, where some work, some govern and some fight (a bit like Plato's Golds and Silvers, who form the ruling and defending bodies while the majority just get on with their lives without oppression, except for that where they have no say in government policy) [Answer] # Education, including liberal education and critical thought, is *great* for a dystopian government. I’m gonna assume since the name of the country has the word “Fascist” that we’re talking about a totalitarian system and not just a generic dystopian one. I’m also gonna use the word “dictatorship” and totalitarian system interchangeably for convenience, but these are not necessarily the same thing. Education isn’t just compatible for a totalitarian system. It’s *necessary*. Furthermore, you’re not just gonna want to stuff everyone in a 20th century-style classroom and lecture them with propaganda until a gritty high school protagonist reveals the Truth About The System. That’s the statecraft equivalent of building a house out of matchsticks. **It’s not about indoctrination**. You see, no one ever held on to a dictatorship by oppressing people. That just makes everyone hate your government, which in turn makes it more likely to get overthrown. Maintaining power in a totalitarian system really isn’t all that different from maintaining power in a democratic one — at the end of the day, it’s still about keeping the people who like your government as enthusiastic and motivated as possible, while doing everything you can to demotivate and delegitimize the opposition. Granted, you don’t need a majority in a dictatorship, but you still need a sizeable amount of the population that willingly and enthusiastically supports the government. Also key is making sure everyone thinks the government is *competent*. Modern dictatorships live or die by the living standards of their populace. > > Dictators survive not because of their use of > force or ideology but because they convince the public—rightly or wrongly—that they are competent. > > > [How Modern Dictators Survive: > An Informational Theory of the New Authoritarianism](https://www.eui.eu/Documents/DepartmentsCentres/Economics/Seminarsevents/Guriev-Micro.pdf) > > > This is why, for example, rulers with authoritarian tendencies tend to disparage foreigners and paint lands outside their borders as impoverished lawless hellscapes. It makes them look like they are doing a good job by comparison. People, even educated ones, don’t really care who is in power as long as the trash gets picked up and the trains run on time. Believe it or not, (some) Iraqis have fond memories of ISIS rule because, unlike the secular government, they got things done. Democracy for democracy’s sake hasn’t really been in [vogue](https://en.wikipedia.org/wiki/Jacksonian_democracy) since the 1820s. > > Omar Bilal Younes, a 42-year-old truck driver whose occupation allowed him to crisscross the caliphate, noticed the same improvement. “Garbage collection was No. 1 under ISIS,” he said, flashing a thumbs-up sign. > > > [Source](https://www.nytimes.com/interactive/2018/04/04/world/middleeast/isis-documents-mosul-iraq.html) > > > We see that these factors are really two sides of the same coin. To maintain a dictatorship, you need to: 1. Tell a narrative (or perhaps a [national myth](https://en.wikipedia.org/wiki/National_myth)) that gets the pro-government people *excited* about upholding the system. 2. Appear competent enough so that the anti-government people *won’t bother* overthrowing the system. If you think about it, these goals aren’t really incompatible with the idea of education, or even the broader idea of free access to information and critical thought. China has been doing some [very interesting](https://www.youtube.com/watch?v=lHcTKWiZ8sI) things with [gamifying](https://en.wikipedia.org/wiki/Gamification) party loyalty — think Duolingo, but for nationalism! Mass education — including what we think of as “liberal education” attacks both sides of the problem. ### 1. It creates an elite class that convincingly sees itself as superior. As history advances, this is a harder and harder thing to accomplish. Old frameworks like racism and religious bigotry aren’t really fashionable anymore. Saying “*I should be in charge because I’m white and you’re not*” will get you real odd looks in *any* part of the world today. Saying “*I should be in charge because I’m muslim and you’re not*” will get you real odd looks in *most* of the world today. But you know what no one ever disputes? “*I should be in charge because I’m **educated** and you’re not.*” Mass education also gives you an automatic out-group: the people with lower grades (or who didn’t go to school at all). Those who did well “get it” and we should probably listen to them. Those who didn’t are a bunch of ignorant rubes who ought to be sidelined. The ruling faction will even point to statistics that people with more education are more likely support them as evidence of their legitimacy, a circular but nevertheless accepted form of reasoning. A liberal education (as opposed to a traditional one) is even more effective because it shuts off the “calculated cruelty” rebuttal. Your educated class considers itself both smarter *and* more empathetic and humane than the out-group. Since this group is also going to be the group that controls the mass media, and produces your culture’s art and writing, you effectively get to rewrite the values of your society. This will create social pressure, isolating the opposition as hateful, ignorant relics clinging to a long-gone era. Why spend the effort to trick or force your troops to be “evil” when you can redefine “good” instead? ### 2. It fosters low expectations for public services and living standards. > > “*I Alone Can Fix It*” > > > — [Donald Trump, RNC 2016](https://www.theatlantic.com/politics/archive/2016/07/trump-rnc-speech-alone-fix-it/492557/) > > > One of the rather overlooked effects of education is it teaches people *why* the things that are sh\*t are the way they are. Almost every revolution in history ran on masses of [people](https://en.wikipedia.org/wiki/Low_information_voter) *angry* about “the way things are” and demanding someone “fix everything”. The average protester thinks Bad Guys Somewhere are [stealing water from honest hardworking folk](https://en.wikipedia.org/wiki/Cochabamba_Water_War) because They Get Off on making Guys Like Me miserable. (For a more US-centric example, replace ‘Cochabamba’ with ‘Flint’.) An educated person has a more nuanced view of the situation, knows the complexity of the problem, and understands there are no boogeymen or magic solutions, and is thus slower to anger. Education also requires a significant investment in time, effort, and often money, on the part of the student. In return, the student receives a chance at a better job, and higher social status. This gives your people a stake in the stability of the system. If a revolution occurs and things go south ([and](https://en.wikipedia.org/wiki/Thirty_Years%27_War) [they](https://en.wikipedia.org/wiki/Reign_of_Terror) [always](https://en.wikipedia.org/wiki/American_Civil_War) [go](https://en.wikipedia.org/wiki/Rwandan_genocide) [south](https://www.reuters.com/article/us-mideast-crisis-syria/syrian-observatory-says-war-has-killed-more-than-half-a-million-idUSKCN1GO13M)), they will lose all that hard work. [Answer] Freedom of thought and the attitude of challenging any statement coming from anybody has to be learned. Dogmatism and the attitude of accepting any statement coming from an authority has also to be learned. If you control the educational system, you can easily decide which of the two you can teach to your students. Plus you can add the daily dose of adulation toward the great leader and all the achievement the government has made. Once you have settled that, you can afford to educate people, as they will contribute to the nation more as educated and trained mass than as uneducated and untrained. [Answer] The question can be answered in two words, by example: Mainland China. To expand on this, education allows people to create things. This might be a strong economy, which allows your Union to out-compete the economies of other states. Or it might be new weapons systems, which keep those other states from attacking you. I'm dubious about education leading to freedom of thought. Certainly we have plenty of counter-examples: "faith-based" Christian schools in the US, Islamic madrassas, the almost slavish adherence to socialism & political correctness in university liberal arts programs... [Answer] Subliminal messaging taught to children early makes for a compliant populace. As well as, knowledge is power, therefore an intelligent populace makes a stronger nation. It could be that simple and doesn't need to be more than that. To control the minds of the populace by teaching them exactly what they want, and nothing more. Teaching them how to think, how to react, how to be complacent, and how to not stand up to the government. The facilities as we know it would be different entirely. From what you describe I would expect it to be a military facility with dormitories for each age group, where they are cleansed into the perfect citizen through education. The government could even take it a step further and using schooling and its testing to isolate the best of the best while they are still young. Then implement those few into super soldier programs, or scientist programs to bolster their power, or even to add to the loyal secret police force. [Answer] It's pretty simple, really. Primary threats for a totalitarian government aren't just abstract "free thought". It's irrational believes, acting out on emotions, not caring about consequences. So, teach them to be proper engineers. Teach them about adherence to procedure and regulations, about following standards and trusting machines more than humans. And keep telling them cautionary tales about all the ways things may go wrong when you flaunt the system. Injuries, sicknesses, deaths. Emphasise that it's not the machines fault when that happens, but human's. Explain them that the State is the ultimate machine. It leads your society to the greater good, and it doesn't care for individuals and their struggles. Just like a wheel-saw won't notice your hands no matter your defiance. Educate them on all the carefully designed safeguards of the State, so they know for sure that they can't do anything about it, unless they get to the control panel. [Answer] The fact is that if you control the information the people receive, you control how they think. Schools are great at this. If you want the next generation to think that Vaccines do not contain mind control substances (when they do). Then while in school (a place of "learning" and "truth") you teach them that believing that "myth" will make you a conspiracy nut. Or take one from the real world: Milk. Dairy products did not make any significant portion of a normal healthy person's diary needs. However in one of the World Wars (I can't be bothered to look it up) a large portion of farmers switched to dairy farming so the front lines could get powdered milk to suplement their nutrition. After the war you had a bunch of milk farms doing nothing. So there was a big campaign where the populous "learnt" that milk would make them healthier and stronger. If you tell people that Cable is a trusted source and YouTube can't ever be used as a source, they will naturally distrust the YouTube reporters. The earlier you can get to someone the more solid you'r "truth's" will become. [Answer] > > Why would a dystopian government want its citizens educated? > > > **To drive a debt cycle, and thus perpetuate the system.** I'm sure many of the us are familiar with the fact that higher education is really very expensive in many parts of the real world. This causes young people to take out a number of massive loans from the government. In order to have any hope of upward mobility, one has to petition the state for funds, this style of funding creates a debt that the student pays off for the rest of their working life. Sure education opens minds, and may even plant the seeds of dissent, but who really wants to rage against the machine when it ruins their credit score and prevents them from obtaining secure employment, a home, car, and the ability to afford to pay for their children's educational debts. There will be no revolution provided that people have the illusion of choice, a reasonably comfortable living arrangement, and some small modicum of hope that by playing well with the system they can get ahead. **Why bother to strictly control the curriculum, when you can give people false hope and then slowly crush it under mounting debt?** This also gives the benefit of a built in class structure. There will be those who take on the debt, get some education, and then get slowly ground down by the reality of the economics... But you also have the lower classes who won't even try to become educated because they simply can't afford it, or be approved for loans. You'll also get enough true believers, anecdotal cases, who pulled themselves from the lower classes to the middle classes, with the help of crushing debt, that will loudly proclaim that the system works. Seems like this already works in the real world... Why reinvent the wheel? [Answer] The question why would a government want their citizens to be educated has a lot of credible answers in this thread. I will try concentrating on the other problem you have stated here: > > education could lead to gasp freedom of thought > > > So how does a dystopian government avoids this undesirable outcome? **By making education as specialised as possible, while preventing critical thinking** People only get the education they will need to further the NAF causes! Generally speaking, NAF educational program should try avoiding the concept of harmonious holistic education as much as possible and only focus on practical things, leaving out as much of subjects like Arts, Philosophy, *Real* History, etc. as possible. Basically anything that promotes critical thinking may only be required for the education of the elites. These subjects do not even need to be banned (which would inevitably make them seem more appealing) but rather they need being portrayed as boring, unfashionable and above all impractical. This should help reducing the numbers of dangerous intellectuals outside of the power structures. Making the fashionable (practical) subjects as fragmented and as specialised as possible will further help to distract practitioners from wandering off and thinking of something outside their area of expertise. All that would work even better if NAF assign professions at the early age, so that an educational program could be made more efficient at transforming people to tools of the state. If you think about it something quite similar was observed in Huxley's 'Brave New World', where a society literally produced super-specialists, who were conditioned to only be happy while doing what they were meant, prepared and educated to do (which may not sound too dystopian after all!) [Answer] Most people have already answered this question to an excellent degree, so I'm not going to go into much depth here. But your question makes me look back at history - Let's understand what England did when they came to rule over South East Asia, particularly India. They opened schools, forced education and textbooks to be written in English and made it compulsory to get any government jobs. Then, they made this huge deal about students going to England to study. All of this created an environment of assumed superiority and 'class' which the English rulers could lord over their aboriginal subjects. So history teaches us that education is important to get work done and to propagate a myth of "why are we letting these people rule over us?" "Oh, because they're better than us." You see this even today. Today's politicians may be pushing to reduce education, and today's fictional villains may be trying to do the same, but they all want a basic level of education which allows them to keep people busy. When you don't have a basic level of education, you can't put people up for useless jobs, or as David Graeber calls them, ["b\*llshit jobs"](https://strikemag.org/bullshit-jobs/) (I don't know if this site allows profanity). That is the purpose of education for a dystopia - create an feeling of inferiority as well as a rat race of work that allows the rulers to rule and live lavishly while the subjects fight among themselves for a meager amount of money and resources. [Answer] If you teach children things that aren't correct, things that they are taught that are correct are taught in a very hard manner, you will end up with children and later adults with very little knowledge and with little selfesteem. In other words a good workforce of model citizens. Teach the children that they are not worth much, that they cannot do anything other than what they are told to do. [Answer] First of all: # There are two kinds of education Lets call them school-education and university-education. This is a little bit simplified, but I think it works as a name. ## 1. School Someone stands in front of a class and tells them, what is right and what is wrong. There is not much independent thought here and the little bit there is can be used to steer the pupils into the right direction. The German Nazis in the 3. Reich gave math-examples like "How much does each handicapped person cost the state per year". Think about school and how often the background of information was questioned when a teacher stated something as a fact. This is something, an authoritarian state will want to control and start as early as possible, since children are very easy to influence. You can teach them nearly everything and they will believe at least most of it. ## 2. University This is where the independent thought starts. Because, this is what is needed to do research. If you only teach people, how machines (etc.) are used, but want them to be able to repair or even improve them, you have to teach understanding, not just facts. And if you want people to understand, you have to encourage thinking. This can still be forced into specific directions, away from real independent thought, but it is hard and it will reduce real creativity. If you want your scientists to invent actual new technology and not just improve the existing ones, you have to encourage them to have new ideas, and that leads to ideas, you don't want. ## The Solution Luckily, you only need the smartest heads to apply themselves in real science. So you can apply the mindforming school-education to everyone, especially children, and allow university-type education only for a small number of very smart people, that can be easily controlled. Most of them will comply anyway, since they are now part of the elite and better then the rest. If they start spreading unwanted ideas and those ideas catch on, they will certainly loose their privileges. ## Disclaimer Of course in modern schools, some independent thought is encouraged (depending on country and school) and universities teach a lot of school-type stuff, especially if you only go for a bachelor-degree. But I needed names for the different types of teaching people, and I couldn't think of better ones. [Answer] I would argue that education could be used to suppress freedom of thought. Teach people not to question things, and most wont. So create an environment that teaches the values that you you want. And the people will be shaped into the roles you design. [Answer] In order to find the most intelligent and curious children. Those children who will grow into the sort of adults who will question what they are taught. When they have found such children, they can kill them and their parents, in order to eradicate those intellectual traits from the gene-pool. [Answer] There have been various kinds of (arguably dystopian) 20th century dictatorships that have striven for national strength. For instance, the USSR had always sought exceptional performance in the Olympic games. Cuba has striven for dominance in Olympic boxing. Russia, North Korea, Nazi Germany, Fascist Italy, and China have liked to parade around their large and well-regimented military. They have all striven for great strength and to be prepared to crush their enemies militarily or economically. They have wanted to prove their doctrine superior through achievement so that other nations reflect on their system of government and believe it must be a superior system if it produces superior results. Achievement in games and in war are like a form of propaganda for advocating the system's virtues of strength. This is especially the case when a nation is attempting to spread its doctrine to other countries. These sort of countries are also often autarkic, and autarky requires a skilled and varied labor force, and good productivity at everything. Strong education can help achieve many of these goals, including the development of advanced military technology, being a world leader in educational achievement, and having a highly productive economy. The only caveat is that, as a dystopian dictatorship, you would want to suppress free-thinking, liberal arts, and social studies. In order to maintain a better-controlled population, you would want authoritarian discipline in schools, co-opted religious dogma to provide simple and possibly paradoxical answers to moral / philosophical questions (preferably answers that always put the nation's needs first), speed drills and algorithms over abstract problem-solving, and an overemphasis on job skills, life skills, and STEM classes. Ultimately, the goal is to turn students into useful robots who can strengthen the state without questioning it. [Answer] I don't think I saw it put this way, but my first thought was that there are almost an infinite number of reasons TO educate your entire populous and only one reason to avoid/outlaw it--because educating them makes them harder to control. If you can control educated people then you should certainly educate them, it's great for the economy and will keep feeding you wonderful military inventions! As for controlling all these educated people, why are they so easy to control? 100% monitoring and analysis by AIs. You don't even have to crack down on every possible violation, you can have AIs monitor for root causes (dissidents with certain traits, I'd guess) and eliminate those few. Others will gripe but not do anything. When every single inch of space is monitored by drone cameras the size of flys or ants, how will you fight back? Even gun ownership isn't going to help much (They can ignore that along with education)--you won't be able to fight off even one ant-sized drone covered in poison that crawls into your mouth in the middle of the night, let alone a thousand... You think you'll figure something out in your secret hidden base? They will notice when you are gone almost instantly and they will know exactly where you were when you vanished. If they can't send drones after you for some reason you'll just be apprehended the second you reappear on any camera. You probably won't even know you are in a totalitarian dystopian government--and you probably won't care :) In fact, it needn't even be dystopian, you'd have to almost go out of your way to make that many people unhappy. The only reason for the dystopian part is that it was part of the question's premise. [Answer] An ideal citizen is one which is most productive. The most productive is one which is least likely to disrupt (ie. well integrated and socialised) and one whose work has the highest value. For both goals, education is key to created a citizen that can perform high-level work and also completely buys into whatever ideology the government sells. [Answer] Most answers address the practical benefits of promoting education (indoctrination and ensuring skilled workers), so I am going to offer an alternate reason why a dystopian government wants an education system: **Creating a class system** The book 1984 lays down a frame the 'ideal' class system for a dystopia. The lower class (the proles) are too apathetic and disorganized to change their situation, the middle class (the Outer Party) is under continuous surveillance, making it impossible to step out of line without somebody noticing and the upper class (the Inner Party) has absolute power. By having a fiercely competitive education system which results decide the the rest of ones life (like China), the population can be neatly sorted in classes, which guidance from the Party of course. By placing importance of the results of this education, the lowest class should be demotivated enough, as long as they have bread and circuses. **Ensuring class conflict** If the middle class is too big to be monitored and might pose a threat, the education system can be used to split them and let them quarrel instead of unite against the Party. This can be done by creating three education tracks (slum, normal & elite) and ensuring that the middle class is evaluated in such a way that they would end up in a different track if they did slightly better or worse. This would result in the following classes: (Slum education) * Proles: The lowest of the low and they know it. * Lower class: Could have had an higher education if they were a bit better and are therefore hostile to the lower middle class. (Normal education) * Lower middle class: Are lucky that they have a normal education and they don't know this and are therefore disdainful towards the lower class. * Middle class: Could have had an higher education if they were a bit better and are therefore hostile to the upper middle class. (Elite education) * Upper middle class: : Are lucky that they have an elite education and they don't know this and are therefore disdainful towards the middle class. Ensure this class is relatively small in order to make them fear the middle class as well. * The Party: Are large and in charge. By using this system, the middle class is too fragmented to make any change. Add some demographic differences between the middle classes, and even more internal conflict will arise. Thus, a stable system is created where envy, fear and distrust counterbalance any freedom of thought that an education introduces. There are other systems to create a class system, but an education based one has the advantage of appearing meritocratic which gives the system more legitimacy. If the evaluations are (mostly) fair, this also ensures that the Party is not based on nepotism but are the best of the best. [Answer] Maybe because the dystopian government wants to create people knowledgeable enough to realize the futility of dissent, instead of foolish enough to revolt. Intelligent, educated, rational people calculate the odds and restrain themselves from rash actions, while foolish people act on their impulses and take actions which the government considers to be "revolting". And maybe the dystopian government wants to create a population that is actually useful for something, a population that is educated and creative and can make their dystopian society a better dystopian society. And if the dystopian government rules part of the world, it will want an educated and creative population to keep up with the Joneses - or the Nakamuras, the Changs, the Chandras, etc., etc. - in the lands they don't rule. Otherwise the dystopian state might be defeated and conquered by a foreign state which has advanced too much ahead of the dystopian one. ]

[Question] [ Millions of years ago, friendly aliens set up an automated process to help out other civilizations. This is a robotic help center that sends out gift packages (in the forms of large ships) that hunt out civilizations, land, and give them a boost of some sort of technology. This could be anything from a boost to get into space, to genetic enhancements/fixes, to a new energy source. So my question is: what kind of tech could they give us that would accidentally cause a world-wide apocalypse if delivered to humanity in 2015, ***due to cultural/racial differences***? Assume we're using it *as intended* and *as instructed*, and that it works as intended. So: 1. It's not an AI that's gone bad, or corrupted instructions. 2. It's not a "humans are dumb" result. They didn't give us antimatter and terrorists use it to destroy the planet. 3. **Exception**: It could result from a miscommunication due to cultural/racial differences, as long as pretty much all of humanity understands it the same way and it's not "we're not smart enough to understand it". Since this question is so perilously close to "too broad" and "idea generation" that Sir Galahad would run at it at top speed, I'll add the following restrictions as well: 1. Answers will be judged on how innocent the tech appears, as long as the apocalypse seems reasonable. So for example, a new toaster that destroys the world beats a new energy source, since energy sources are generally dangerous. 2. Apocalypse is defined as something that kills 50% or more of the world's human population within 10 years. For the purposes of this question, turning us into robots or sticking us in virtual reality doesn't count as killing. 3. It's either applied automatically when it lands, or every nation on earth is delivered a working example and the educational material to operate it and build more units. [Answer] The aliens could launch us a preemptive sickness prevention device that is designed to cure diseases. This machine was automatically applied after arrival, and how it works is that it releases nanomachines that detect differences in the population and terminates those that it deems contagious. The ship that arrives at our planet does a scan of the human population, and determines that a lot of the world is sick. Let us begin with the assumption that of the worlds population, at least one particular skin tone is of some sort of majority. These aliens come from a place where skin is 90% the same. These nanomachines see "Oh, theres another person that doesn't have the right skin pigmentation". They do a diagnosis and see that "Hey, if this guy reproduces, this pigmentation will spread!" (eg: diagnosis result - contagious). It proceeds to kill off the target. Within the first month, a large chunk of the human population is dead. Furthermore, the human population is likely to suffer in the future since genetic diversity has all of a jumped off a cliff. Edit: Alternatively, the nanomachines may kill anyone with a small sickness like the common cold or the flu. As Kevin so kindly pointed out, there are lots of people that are sick at any given time on the world, and with contagious diseases. It could also target STDs. Edit 2: Hats off to Peteris for this one - if the aliens multipied via eggs/spores/etc, the machines might in fact detect pregnancy as a parasitic infection - all of a sudden, the world no longer has any more children. Everyone dies out. [Answer] ## Time viewing The easy-to-build device allows anyone to view any point in the past "live" - that is, as if watching a video recording. Imagine the ability to look back on the ancient civilizations and discover if Stonehenge really was built by aliens! And then, someone discovers that they can use it to watch anyone, anywhere in the world, up to and including the present... and 100% of all privacy everywhere goes out the window. Now, that may not sound like Armageddon, but it would have a huge, drastic, and immediate impact on civilization as we know it. Imagine if an already trigger-happy government overhears another government talking about its destruction. Instant pre-retaliation! Nukes fly! And, the second they launch, everyone else knows about them too; thermonuclear war ensues, and the population is wiped out. If the device came from a culture with no sense of privacy, they would never even suspect that it could be an issue. ## Mind Transmission Like the internet, only for thoughts! Imagine the ability to speak to anyone in the world through nothing but shared thoughts. The military would snap it up immediately, as it would create an amazing instant communication for soldiers in the battlefield. Eventually, telecommunications would be replaced with braincalls; on the one side, users can think of a recipient, and speak directly into their mind. On the other, senders can "blanket send," and anyone who wants can join in and listen. And, just like the Internet, in a few years 90% of every message sent is spam. Unairconditioned rooms full of sub-minimum-wage employees sending think-a-grams to every person in the world. Productivity declines rapidly as people everywhere are overwhelmed by the massive amount of messages their poor brains are bombarded with; entire industries fall due to the inability of their workers to focus on their job. Imagine being an engineer in a nuclear power plant, but on the phone 24 hours a day, even being woken up at night, just to be asked if you want to buy printer cartridges. You are not going to do your job well; bye-bye power. And without power, there will be no food, no fresh water, no technology. Billions will die. That doesn't even consider those who just snap and kill themselves, or the others who snap and kill those around them... Of course, the hive-mind that designed it loves the concept, and are confused as to why no one else likes it. ## Everything You Could Ever Want The machine reads the mind of whoever is nearby, and presents them with the object they most desire, in its best form. Hungry? It gives a filling, yet healthy meal. Have to use the bathroom? It builds a luxurious lavatory fit for an emperor. Too many people who want to try it out? It builds a copy of itself all over the world, where anyone can access it. Of course, to power its creations, it uses the equivalent of five years of life. Whatever you wish for steals half a decade of your life away. Even without realizing it, humanity dooms themselves through greed. Their final, collective wish? "Life! I'm too young to die!" "Huh," the machine replies. "That's new. I don't know how to do that." The ancient civilization that built the machine was used to living for millions of years; as they aged, they realized it was better to experience life than to live nigh-on forever, and built the machine to create an Eden for anyone who did not wish to live forever. Oops. ## Wormhole Toasters Everyone loves toast. And everyone knows that the absolutely best toast is actually pulled from an alternate universe through tiny wormholes in the fabric of space-time. You didn't know that? It's true! Not many people have it figured out, but those "in the know" created the perfect toast-making machine. Using its own internal power source, each self-replicating toaster can produce up to one slice of toast per week! Warning: toast is actually summoned from an alternate universe. All goes well, until someone has the bright idea of creating not one piece a week, but three pieces for each meal. To do that, he would need 21 toasters. But what if he invited friends over? They would want toast, too. So he creates 50 toasters, just to be safe. In fact, everyone in the world manages to get their hands on a few of these. The food shortage is solved with the advent of 100 billion toasters (some people really like toast). Every week on the dot, each toaster pops out a single slice of toast, weighing exactly 50 grams. 100,000,000,000 slices of toast every week, or 5.2 \* 10^12 pieces a year. On average, the planet gains about 40,000,000 kg a year due to dust. However, it now gains over 260,000,000,000 kg in a single a year! Worse, the sheer number of toasters - also built from wormhole material - begin making a rather nasty whining noise. As it turns out, all those wormholes together make one fantastically huge wormhole, destroying the entire earth. The aliens who created the technology are flabbergasted. I mean, toast is great and all, but come on! It's just toast! Who likes toast THAT much? They never even considered the fact that anyone would want more than a slice or two a month. [Answer] Wireheads\*. The aliens understand perfectly well that any organism responds positively to pleasure. So they (or their robots) give each person a device which directly, and intensely, stimulates the pleasure center. A large fraction of the population never turn it off, and die of dehydration and hunger, and the social/technical cascade which follows kills many others. The aliens don't understand addictive behavior. Certainly none of their species would overuse such a device. \*This meaning of the term, as far as I know, was originated by Larry Niven and often used in his "Known Space" stories. [Answer] They used to think life was inevitable, the apex of a beautiful thermodynamic spiral that shaped stone, water, heat, and light into primitive creeper-clays, which blossomed into fantastic shapes as evolution took hold. Again and again, they came to a new world in a likely orbit and saw alien but uncannily familiar forms: smoking chimneys on the ocean floor, continents rolling with rainbow waves—even, once in a very long while, the glint of mirrors pointed at the stars. Their best geological models assured them that wherever the right ingredients met in the right proportions, life would flourish. They were wrong. As they sailed further into the cosmos, they realized with growing horror that evolution on rocky planets runs at the edge of a lethal instability. Life branches out in just the wrong way, a new kind of chemistry falls into place, and evolution's kill switch snaps shut, flooding the atmosphere with toxic gas. They found planets with air so corrosive that even their probes succumbed, dug up fossils that could only be handled through layers of glass. They learned it could happen at any time, without warning. It happened on their birthworld, and would have made their home a necropolis, if by that time they hadn't learned enough to stop it. They learned of it, in part, from hundreds of young civilizations that had taken notes—panicked, or meticulous, or sublime—as their planets burned to ash. They decided to do something about it. They hurled into space an armada of uncrewed container ships, sailing the slow road to barely-visible stars. Each one was inscribed, in dozens of subideographic hyperlanguages, with an explanation of its purpose. Where they landed, their senders hoped, perplexed scholars or shamans or hive-dancers would eventually read and understand the omens of the disaster the inscriptions foretold. If the need arose, they would open the containers and wake the equipment inside. Armed with magical tools, on a quest as nonsensical as the sickness overcoming them, they would follow the poison in their air to its source and cut the [photochemical chains](http://chemwiki.ucdavis.edu/Biological_Chemistry/Photosynthesis/Photosynthesis_overview/The_Light_Reactions#Photophosphorylation) dragging their world to the grave. [Answer] The apocalypse could be caused, not by any effects of the donated technology, but by the very fact that we have had contact with an alien race. The donated technology (this tech could do anything, cleans the environment, extends life, cures all ills, or whatever else it could be) has been delivered with us in such a way that its origins are not obvious. After this technology has impacted on a significant number of peoples lives, the world population is divided into two: * Those who believe that this technology has come from Aliens * Those who believe that this technology has come from God Neither side can produce enough evidence to convince the other side of the true origins of the technology, and both sides have their own ideas of how this technology should continue to be implemented. The world becomes divided over the use of this technology and its origins. This ends up as a global conflict. The alien-believers and the god-believers wage war and reduce the planet to an apocalyptic state. --- I believe this satisfies all of your conditions. It isn't the technology itself that kills us off. It is just simple human nature, arguing over things that cannot be proven, that kills us off. To paraphrase Battlestar Galactica: All of this has happened before, and all of this will happen again. [Answer] Death for everyone. Let's assume that our friendly aliens have a great skill in medical care but not the smallest knowledge about how mammals live (I'm not sure about reptiles, birds and fishes). Our benefactors send us a way to cure us all by killing every virus, bacteria and germ, no matter what it does. As we live thanks to a lot of bacteria, Wikipedia confirms me that we have at least 1.5kg of useful bacteria in our bodies, we become, us human beings, animals and even the earth, absolutely pure. And dead. Killing rate : 100% [Answer] # The Third Party The aliens leave behind a communications device intended to allow us to communicate with them. The aliens can't imagine that a sentient race would destroy/enslave other sentient beings. Before we activate it, our benefactors are destroyed by another hostile power who then monitors the frequency for other upstarts to murder. [Answer] The aliens knew that nationalism and racism was a cancer which kills many young civilizations; so they sent us a solution. As the ship entered orbit, its sensors catalogued the genetics of the dominant species. As it entered the atmosphere, airborne nanites spewed from its vents, seeding the upper winds with tiny transformation tools. Even as the vessel slowly settled to the ground, the fundamental nature of humanity began to change. Skin tones either lightened or darkened to an average of pale brown. Regional facial features faded along with distinctions in hair length, texture and color. By the dawn of the next day, all of humanity was, at least genetically united as a single race, with no distinctions left to hang our hatreds on. If only the aliens had known how much we love our hatreds; that we humans define ourselves by the things that we despise. As the sun rose, many woke in horror, quickly realizing that their hatred would soon have no home. Soon they would not be able to distinquish their enemies from their families. Soon they wouldn't be able to tell the unwashed from high-borne nobility. In despiration, they launched the missles, striking quickly, while they still knew where the enemy lived. [Answer] # Video games After centuries of development, games have become highly addicting, but because it was a gradual process, the Aliens have adapted to it and dont even recognize the addictiveness. Unfortunately on all Tablets that were distributed to each human on Earth, Candy Crush 2000 comes preinstalled. After starting the game, almost all humans are unable to stop playing and die of [cardiac arrest/seizures/malnutrition/dehydration](http://en.wikipedia.org/wiki/Video_game_addiction#Deaths) [Answer] Always on telepathy to anyone within a limited range. Most of us can't handle sharing our innermost thoughts, and relationships in general are typically based on sharing only a certain amount of thoughts. Several countries that currently have tenuous relationships would break out into immediate war. Many people with internal struggles that society deems inappropriate would quickly be hunted down/ostracized. [Answer] Seeing as I already have an answer that's not so innocent, here's a more innocent one. **Advanced communications technology.** The aliens provide each human with an advanced cell phone, which directly links two consciousnesses together for quick and easy communication. It does this by first obtaining a connection with a users brain, and then connecting with the other device and swapping streams of information. The aliens use this technology on a daily basis, and they have sub-brains that are specially equipped to deal with the wave frequencies that this tech works off of. The sub-brain gets a handle on the connected persons consciousness and filters out everything except for the communication aspect. It also rapidly repairs itself, and it is the sub-brain of the aliens that this technology actively communicates with. Humans, however, don't have this sub-brain. The technology still works because we have 2 hemispheres, but it puts a heavy toll on our brain. At first, it works really well and everyone loves it, but after about a month or two, the human brain is unable to handle the high frequency and strength of the waves required to utilize this device. It starts deteriorating rapidly, and our brains can't regenerate fast enough - and everyone who used it for more than a week starts developing brain cancer and showing symptoms of encephalitis. An wave of Alzheimer's starts affecting those who use this technology. Those who continue to use it experience more severe side effects, such as "Ghosted vision" (Where the users swap vision inputs from the eyes for a short period of time due to the consciousness connection) and "Ghastly sounds" (The hearing of the other persons thoughts). Those that survive the cancer and other ailments slowly go insane. Apocalypse complete. [Answer] Immortality The cure for all disease! Death is no longer a problem! Except that the aliens are nothing like us. Their bodies are a well designed system of interoperating parts communicating with each other, repairing only what's broken, ... Instead of being developed by the Blind Mad God of Evolution, they were designed in a directed process, by themselves. Natural life has long been forgotten on their planet, and they just want to bring good times to everyone in the universe they can reach! When introduced to Earth, it makes every living thing immortal. Not just animals, and bacteria, and similar... but also every single living cell in the human body. As a super-cancer, every signal for cell senescence is countered, and all life becomes huge blobs of unrestricted cells, unable to die. Instead of grey goo, life on Earth forms a pink goo. Forever. Obviously, this is a very soft sci-fi scenario. [Answer] A stardrive. As a safety precaution they have designed a stardrive that one sentient being enters in order to control it. While the drive field is active the ship is in free fall internally even when experiencing tens of thousands of gravities to an external observer. Unlike the drives of the Lensman universe the velocity attained is real but the missing acceleration will return the instant the drive is switched off. Attempting to push something out through the drive field results in its collapse. Edit: The effect of this behavior is the only safe way to use the drive is to match your initial velocity exactly before turning it off. The aliens figured this precluded its use as a weapon--any attempt to launch a missile results in the destruction of the craft and the missile. While it can ram the requirement for a sentient controller means the pilot dies in the process. The aliens had no concept of kamikazes or suicide terrorists. [Answer] After careful monitoring the aliens notice we are solving two of our problems with one solution, our need for energy and our need for a carbon dioxide rich atmosphere. They send a ship that provides the ultimate in carbon dioxide producing energy generation through the burning and converting of the oxygen in the atmosphere. Obviously they misunderstand the carbon dioxide in the atmosphere is actually bad for us, but based on their monitoring and our lack of action in pulling carbon dioxide levels back, who could blame them for thinking that we want it? [Answer] # Star Trek style replicators or any other compact device that anyone can own, that can manufacture any object. Our current political power structures lean heavily on who has weapons, and our economic structure leans heavily on people not having things. If everyone has a perfect replicator, everyone has all the guns and food they want! Can you imagine what would happen if we were suddenly thrust into a post-scarcity society? The transition might not be pretty. (This is a plot point in [Singularity Sky](http://en.wikipedia.org/wiki/Singularity_Sky#The_Festival_and_its_entourage "Singularity Sky"), where a visiting alien race gifts a human colony with small factories) [Answer] **The Education Apocalypse** ***The Intention*** One way to improve our technological and cultural advancement on all fronts would be to improve our ability to communicate and exchange information. If advanced aliens could successfully educate species at our level of cultural development to be receptive to alternative paradigms in general, dialogue among the populations of those species would become more fruitful. Ideally, people of varying philosophical persuasions, religious believers, and academics with contrasting stances on any given issue would be able to recognize the validity in other perspectives. Dialogue would become constructivist rather than modernist as alternative constructs in science and philosophy were embraced. Freshly birthed frameworks could rocket humanity into an unprecedented era of cooperation, creativity, and advancement. This education could be distributed in a number of ways, perhaps most easily by broadcasting via radio and television waves. If the automated help center had the resources, maybe they could send visual screens to every corner of the globe, or even download their instructional program directly into our brains. ***The Application*** If, however, humans en masse received this education, would it do us any good? I fear that human nature would do a number on this brave new world. Assume, as per the stated scenario, we receive this education and begin to apply it--not that we turn against it, but that we apply it successfully, and the species as a whole begins to embrace the validity of multiple paradigms. Even as scientists and scholars recognize in full the validity of multiple constructs for explaining, say, gravity, the culture of academia still demands publication for pay. Academics quickly learn that the peer review process is changing drastically. It was once a constructive-and-sometimes-cutthroat feedback system that bolstered critical thinking and guided research away from less well-developed paradigms. Now, researchers are primed to see how almost any perspective could potentially account for the data. As this becomes apparent, "better" interpretations are not published; no interpretation is better than any other. Theologians of various faith recognize the validity of multiple interpretations of sacred texts, along with multiple ways of reconciling those texts to scientific and historical data. Some begin to repair long-held divisions and join in a spirit of cooperation, upholding the verity of certain beliefs that they value and continuing to preach them, but at the very least acknowledging the rationale behind other perspectives. Yet, beneath the blossoming harmony lies an all-too-human carnality that threatens to bring civilization to its knees. ***The Apocalypse*** Acceptance of additional frameworks spreads resources thin--many new, young researchers are drawn to burgeoning paradigms rather than lending their support to established ones. Political and social systems begin to fail as they are criticized to oblivion. No one can decide on what constructs to adopt, and citizens at all levels of their respective industries suffer in their productivity as a result of indecisiveness. People begin to feel aimless now that they acknowledge no question has a definite answer. Frustration with the inability of theology or science to provide sure conclusions, the world progresses to a post-scientific culture. Progress flourishes for a while, but it stagnates as existing frameworks are devalued and dismissed without any viable replacements. Moral codes are abandoned by the population at large as society devolves into individualistic anarchy. The need to *know*, to *understand* provides such an illusion of security to humankind that without it, humans begin to seek other forms of control. As the stalwart, modernist generations die out, infrastructure collapses under the weight of that pursuit. Disease runs rampant without medical systems, chaos and war are on the horizon, and the only authority people still look to is the aliens' ever present reminder to *trust nothing . . . believe . . . nothing.* [Answer] **News that the friendly aliens are returning, will arrive in 10 years time, and will bring the final ultimate gift to the leader of the world.** Naturally news that a super advanced extra terrestrial civilisation will arrive in earth orbit in 10 years will panic everybody, including the idea that there is but a single additional delivery, given to whomever is considered the leader of the planet as a whole. Coupled with an utterly ambiguous definition of who or what a leader is, or how it will be determined, as well as the sudden ultra scarcity and immense potential value of this last event, as well as the chance to meet these aliens directly, this will inevitably lead to some sort of dispute or conflict. The arrival of the aliens may even be unnecessary, just the mere notion that there is 1 last cycle left in the system before it ends could be enough. **Alternatively, make the message say "Your civilisation will end in 10 years"**, and let their imaginations turn it into a self fulfilling prophecy From then on, you can throw as many apocalyptic measures as you like into the fray, perhaps even say the final gift is an evacuation to avoid a super nova or some other earth shattering natural disaster [Answer] # Perfect Robot Clones The aliens brought a technology which allows us to scan a person's brain and perfectly re-create that person - at least mentally - in digital form. They also brought advances to robotics to give these digitized minds physical bodies that are far more capable than fleshy bodies. One could argue that to re-create a person in digital form and then to destroy the original is not murder because the person continues to exist. And perhaps they would be right, but the technology opens other possibilities. Let's assume eventually all fleshy humans are converted to digital humans in robot bodies, and see what happens. A digital person figures out they can simply make a second copy of themselves. They can keep regular backups in case their body gets destroyed, and be re-animated with only a small amount of lost time. Another digital person figures out they can operate any robot body, not just the one built for them specifically. As long as another person isn't currently using that body, anyone can take it over. This is a good thing at first, as people start flitting about from body to body to save on time and transportation costs. Why drive an hour to work when you can just have a second body there? Now I see a few ways this can all go downhill quickly. ## 6 billion of one, half a dozen of the other Another digital person figures out they can use their "backup" at the same time they are also active. Now there's two of the same person (and one less available body). To deal with the discrepancy in experiences between the two versions of the person, they periodically sync up and share what they've done since last they were one. Another digital person figures out there's no reason they can't make 2 backups. Or 1000. There's not really a limit on how many times a person can be copied, other than where to store the copy. Another digital person combines the fact they can make unlimited copies of themself with the fact that each copy can be active in a separate body. Within a few minutes they've self-replicated until there are no more unoccupied bodies for them to inhabit. Our John Doe now has roughly 6 billion copies of himself. And everyone else is stuck in whichever body they were in when John Doe made his realization. This initially causes havoc, as people can't get to work and John is in all kinds of places he shouldn't be. Then people (I'm not going to call them human any more) start trying to force John back into one body. John syncs with all of himself and realizes he's in trouble, so he fights back. 6 billion Johns physically and mentally attack any other person nearby. 1 John can't do much, but 6 billion Johns attacking in unison succeeds in killing a quarter of the population within 10 minutes, and many of their backup copies are also destroyed. Now John outnumbers all the other people, and is in almost every position of power. Further, he is synchronized regularly, and thus highly coordinated, whereas all the other people can't coordinate on any comparable scale. John now rules. Any dissenters are destroyed - their bodies and their digital backups. Soon John figures out he doesn't have to destroy their bodies. He can remove the "brain" and manufacture a new one with another copy of himself, saving the cost of manufacturing a whole new body for himself. Before long, the number of non-Johns dwindles to a few scattered individuals, mostly hiding out in isolated locations around the world. Their numbers are reduced to 6 before John realizes he will soon be all alone with himself. ### Worm Let's back up to where people figure out they can keep backups. Pun intended. Another digital person - we'll call him Steve - was a hacker back before everyone became robots. Steve figures out he can introduce a bit of code - a software worm/virus - into another person's digital personality that alters them. He first uses it to get his wife to stop nagging him to take out the trash and just do it herself. Then he gets in a fight with his boss a week later, and decides to use it again, with some improvements. Now Steve can get his boss to agree to anything Steve wants. Steve has never been in a position of authority, and the power soon gets to his head. Before long (and with a few more modifications to his worm) he is running the company, and doing a terrible job of it. No one wants to buy their Widgets. To keep his company from collapsing under its own weight, he makes one more change to his worm. But he's careless, and doesn't test it thoroughly. He sends his worm out to a handful of people, and it changes them to believe that they ABSOLUTELY MUST OWN A WIDGET OR THEIR LIFE IS MEANINGLESS. And those people promptly go buy Widgets, as predicted. But when their friends tell them how the competition's Gizmo has more features, they get mad. Several of them send the worm on to their friends, family, and co-workers to convince them Widgets are the Best™. A few rounds of arguments and email forwards later, every single person on the planet ABSOLUTELY MUST OWN A WIDGET OR THEIR LIFE IS MEANINGLESS. Of course, there aren't enough Widgets to go around, even if everyone could get their hands on one. The 98% of the world population who can't acquire a Widget, their life now meaningless, self-destructs. [Answer] The [Black Pudding Pakora](https://www.aldi.co.uk/en/product-range/best-of-scotland/specialities/specialities-product-detail-page/ps/p/haggis-black-pudding-pakora/). Nutritious, delicious, and combines the best of Scottish and Indian cuisine. Not actually an alien technology, (though it may owe its origins to the Haggis Pakoras from a certain Iain Banks story) but it serves as an example of destructive cultural differences. These need not be cultural differences between the aliens and ourselves, but they may not understand (because they have no parallels, thus no experience in the matter) how deeply divided we are by our own cultural differences. Take something intended as a gift, but accidentally insulting or breaching the deepest held cultural beliefs or taboos, and insert it into an already over-tense situation, a tinderbox waiting for the spark to ignite it. Such as a standoff between radicalised religious society and another culture bristling with hate towards them and unaware of the catalogue of manners in which they give offence. [Labelling it halal](http://www.telegraph.co.uk/foodanddrink/11613636/Aldi-apologises-after-black-pudding-is-incorrectly-labelled-as-halal-certified.html) when its main ingredient is pigs blood was probably an innocent mistake, but that's no comfort to the devout who ate it unknowingly. [Answer] # Standards matter Using different unit system has already caused accidents (e.g. the [Mars Climate Orbiter](http://en.wikipedia.org/wiki/Mars_Climate_Orbiter)). So it may be that some one implements the instruction in meters and someone else in miles. The several unit displaced around the globe fail to sync due to this difference and the UHEB (Ultra High Energy Beam) instead of destroying the CFC destroys the entire Ozone Layer. Without the ozone shielding Earth from the dangerous radiation, we get all roasted. [Answer] The ship could contain a benign gift package of **impossibly advanced computing technology**, allowing the populace to gather and manipulate extraordinary amounts of raw data in fantastically tiny periods of time. This is a bit extreme I suppose, but if it were the case I believe it would cause great cultural/racial upheaval. Firstly, the near-unlimited processing power implicated would be maliciously utilized by a group to calculate and simulate scenarios where a tactical strike (or blanket genocide) could be achieved with "minimal/zero repercussion". Worse, anyone could instantly snapshot any genome and begin to extrapolate combinations, projecting what a specific zygote will turn out like. The existence of such a notion could destabilize many things socially. With super-crazy computer power (no AI entity here, just raw data processing) At some point, with this alien computer, the tech is used so that everyone (and everything's?) genome is capable of being charted and extrapolated. Within a generation or whatever, privacy as we know it is gone and there are all sorts of grand breeding programmes. Even growing murmurs advocating the notion would be destabilizing enough. This newfound ability for the sudden specialization (and even speciation? but nonetheless culling) of man is enabled, and rejection of the (genetically) ugly would be relatively free to proceed apace. In short, the future would be all dangerously fascist with thoughts of comparing dog breeds and their suited tasks to that of man and his suitable work. Enough of that. In another vein, such computing power would further bring us together and live in the moment - becoming truly global. The gift of **impossibly advanced computing technology** might allow us to connect to each other simultaneously, and experience time in varying relativity and in virtual worlds. This seems peaceful as opposed to apocalyptic, but perhaps one day, it causes sudden irreversible sterility or power surge to brain OR! irreversible sterility PLUS power surge to brain. Enough of that too. [Answer] The aliens (let's just call them the Zorks) send out a gift to humanity: UNLIMITED GOLD! However, they botch the aerobraking and lithobreaking procedures by an astronomical unit. Whatever ship full of butter they sent just made an Earth-kabob, punching out the core, stopping the natural spin (thereby dooming everyone on the top to death by friction,) and then moving Earth from its orbit. Death rate: 84.2745%. A bunch of Germans, Russians, and some Nigerians remain. However, they also sent a large space station complex with it as well. Whatever's left of the Earth goes and takes the spaceships included with the main craft and moves to the space station. However, they discover that they can't get very much of the gold to the station, and furthermore - *the station's life support runs on gold.* Oops. However, they find a warp pad on the station. It's labeled in feet, but nobody bothers to check the math on the instruction manual: whatever language the aliens have, their word for feet is more like a millimeter. The humans accidentally end up gapping their new home in half. Death rate: 98.348572%. Only a few Germans and a Russian remain. The Russian has the wise idea to get to the shuttles, which have infinite life support. He punches the warp drive, but finds him stranded on Mars due to really slow acceleration. He is killed in the resulting planetary collapse. Humanity dies from a humiliation conga. If only the aliens hadn't tried to embed the ship in the planet... Alternatively, let's say the Zorks are like the Peacekeepers from Farscape: they're highly allergic to heat. The Zorks are of the misconception that every form of life is allergic to life, and so they develop planetary heat shields. They send these out in random directions, just hoping they hit a planet: any planet. As luck would have it, one hits Earth. Thankfully, they did write SOLAR RADIATION CANCELLATION DEVICE on it, but Israel is dead tired of being in the sweltering sun all day. They pull the lever (against orders from Ukraine, China, Austria, Argentina and Burma) and get themselves nuked for it. Not only does the solar heat suddenly vanish, solar panels (which have become the only source of power, because ten years prior the world had just expended their last drop of oil and their last puff of natural gas) stop providing power, the world just wound up in nuclear warfare. Meanwhile, the Zorks are laughing their butts off, thinking to themselves "they were actually going to go to war over solar radiation? Those guys must be insane!" But in another universe, the Zorks actually receive something from Earth: the Voyager 1 space probe. Seeing as how the people of Earth like music, they send lots of musical robots to Earth, hoping that they can help improve economic conditions by making all of the Earth fertile. Soon, every one of the robots is activated by humanity, enjoyed by humanity... and is busy paving the Earth with soil. The only water on Earth is accidentally buried under tonnes of dirty-looking dirt. They then do the same process to the Moon, except they make it water: an irrigation system. Humanity is accidentally plowed and watered. The guys on the ISS move to the Moon, building a small society. The confused Zorks watch in horror as humanity seemingly vanishes from Earth: they love to eat, and were going to send new ovens and grills to Earth once they got started. But alas, the Zorks are now drowning in cooking appliances that went unused. They issue Order 66, which is for the robots to blare "HEY COME FARM!" really loud. The people on the Moon last ten years before the last one dies of ear collapse. [Answer] ## Worldwide earthquake The aliens see what a pain it can be to have places at different altitudes - the effort of climbing hills, the deaths caused by falling from a height - and level out the landmass of the Earth so it's all flat and even. The upheaval involved is like an earthquake occurring everywhere in the world simultaneously. Buildings collapse, cities are destroyed; not a skyscraper in the world is left standing, and millions of people are killed by falling rubble. Huge cracks formed by the wrenching of the ground spew molten lava like volcanoes. Going to the seaside becomes impossible, since there's now a cliff and a sharp drop to the sea everywhere in the world. The mean height of land above sea level is 840 metres (according to Wikipedia), and that's one hell of a cliff! Anyone who was out on a boat at the time is now trapped at sea for good. The aliens' home planet has a surface made of sticky and malleable goo, and their homes are temporary tent-like structures (they're the most technologically advanced nomadic culture in the galaxy). They regularly perform changes to the surface of their planet, changing the heights of different places or creating interesting geographical features. They've never been to a rocky planet before, and they had no idea how devastating the consequences would be. They were only trying to make life more convenient for us! [Answer] **Genetic Enhancement** (but different than the previous genetic enhancement answer) Imagine an automated system which senses and catalogs all life and the active alleles in the population at every gene site as well as a limited amount of projecting alternatives not active in the population. It provides instructions on how to create machinery estimate the outcome of given gene combinations and to alter the genes of fertilized eggs. It delivers this bonanza to humanity which enables humans to select the genetics of future generations. Individually couples select those alleles they feel most likely to allow their children to excel. And those children do excel, IQs in the hundreds, physically fit, disease free, etc. The abilities of these first few gene altered children force others to do the same in order that their children are able to compete with these "super humans". Eventually, all children are gene altered. At this point this could play out in two different ways: 1. the gene altered children don't view unaltered humans as part of their species. They view us as we might view dogs (or even worse). They could exterminate us, put us in preserves, or otherwise limit us to enclosures (like zoos). In any case, our descendents aren't "human" as we understand it and they cease letting us reproduce. 2. parents select all the same genetic traits. Which means our descendents don't have genetic variation and we and our descendents die out from in-breeding (but this relies on the alien machine breaking at some point so it smells of *deux ex machina*). [Answer] The robohelp system drops teddy bears. Wait, wait, here me out :) Conflict and death are a hallmark of any planet with evolution. These are scary things. After a brief scan of the world population, the robohelp system discovers that the most used item of comfort is a teddy bear (or the closest cultural equivalent). The scan also reveals that teddy bears help a child believe what they want, that everything will be okay and they are safe. Wishing to be extra helpful, robohelp includes a mechanism in each teddy bear that amplifies the strength of a human's confirmation bias. Children the wold over, fall in love with these new teddy bears. Only, children aren't the only ones affected. Adult's confirmation bias is also strengthened leading to a hardening of opinions. Communism vs capitalism debates grow more heated. Hutus vs Tutsis. Christianity vs Islam. Really... pick your favorite opposing ideology and the debate is going to get ten times worse. Tensions flair, shots fired, nukes fly and everyone involved believes they're doing the right thing because the strengthened cognitive bias field tells them it is so. And all over a helpful teddy bears intended to comfort frightened children. [Answer] **Nanomachines without killswitch.** Humanity can be gifted with self replicating nanomachines. This nanomachines converts anything into jelly pudding! And the killswitch is accidently broken. ]

[Question] [ Bob is a garage physicist. By some stroke of luck (though Bob would assure you it was his sheer genius), Bob has managed to be the first person to [discover](https://worldbuilding.stackexchange.com/questions/3136/if-our-universe-was-a-simulation-what-could-a-bug-look-like) that our world [just recently became a simulation](https://worldbuilding.stackexchange.com/questions/13696/what-directive-would-cause-an-asi-to-put-everyone-in-a-benevolent-matrix) of itself, and he has managed to [gain some rudimentary control](https://worldbuilding.stackexchange.com/questions/3129/hacking-the-universe?rq=1) over it. He is so excited with this discovery that he wants to share it with his friend Alice. However, Bob is also a prankster. What is the most ~~terrifying~~ *entertaining* way Bob can prove to Alice without a shadow of a doubt that they're living in a simulated world? Some clarification: * ~~Bob has exactly the amount of control you find necessary for your answer.~~ (see other bullets) * Bob is also very suddenly rich, so flying to a deserted island in the middle of the Pacific for a more... *spectacular* show is fine. * The simulation is divided into roughly 20 meter cubic "chunks" which each run on a separate core. The chunk processors are only directly networked to the 6 directly adjacent chunks. Bob currently only knows how to modify the properties of and objects within the chunk he's in. (One idea I'd been playing with for an experiment of theirs after the reveal was modifying the chunk's current timestamp and throwing a paper airplane across one of the faces.) * Human minds are run in protected memory; they can't be modified or even monitored programmatically. (Sensory buffers, however, are still open.) * Over the years, Alice has grown to be naturally skeptical of Bob's "discoveries." Your proof must be impossible to explain any other way (beyond, of course, that this is all a dream or things to that effect). (Sorry if this invalidates some previous answers.) Answers will be judged based on how complicated the proof is for Bob to set up versus how little Alice can doubt him after the fact. [Answer] If Alice is part of the simulation, and Bob can control the simulation, it stands to reason that *Bob can control Alice*. Now, of course it would be unethical to alter what we might call Alice's soul, but I'd see nothing wrong with changing her perception. For instance, say Bob takes Alice to hear a symphony. During a particularly intricate piano solo, Bob replaces Alice's perception buffer with that of the pianist (let's call him Chuck). Suddenly, she sees what Chuck sees, feels what Chuck feels, and hears what Chuck hears. Hopefully they're not too close to the stage, because I'd imagine she'd freak out. But maybe she still doesn't believe Bob. For his next trick, instead of changing Alice's input buffer, he can redirect her output buffer. Suddenly, the conductor (call her Diana) goes into a sitting position, as Alice stands up and starts waving her arms. The two women immediately fall over as each tries to right themselves and instead wrongs the other. By now, the show is most certainly ruined, so Bob decides to go all out. He runs the input and output buffers of the entire audience through a random number generator, swapping at will. Chuck sees through Diana but moves Edmund. Diana sees through Alice but moves Fanny. Gerald has a tough time as he simultaneously experiences the perceptions of Hilary, Ignatius, and Julia. The concert hall erupts into anarchy as everyone runs in the wrong direction, screaming with foreign lungs and looking though the eyes of strangers. Then Bob gives Alice his own input buffer, and looks down at her. 'Believe me now?' he asks, and she can feel each word as it escapes his lips. She tries to nod, and somewhere in the third balcony, Kevin bangs his head on the floor. [Answer] [**Giant Rube Golberg Event**](http://en.wikipedia.org/wiki/Rube_Goldberg_machine) This should make use of real life events and coincidences that are nearly impossible to explain. Bob should do this in response to Alice asking him for something - in this example I'll use "Hey, could you get me a coffee?" > > A jet airliner falls out of the sky despite all of the engines continuing to work. It crashes a block away in view of Alice's window, sending debris flying everywhere. A separated engine strikes an SUV, causing it to veer and take out a fire hydrant. The column of water (as deflected by the SUV) hits just right to take out a power line, causing the entire office building they're in to lose power. Due to an unforeseen bug, the switch to backup power causes the fire alarms to go off. As they exit the building, they see a man who's car was destroyed in the plane crash arguing with a police officer. His gesticulations cause him to eventually lose control of the coffee in his hand, and it flies out toward Bob and Alice. Bob neatly fields it and hands it to her, promising that it hasn't been touched yet. Despite the wait and that it flew through the air, the coffee is perfect and exactly how Alice likes it. > > > Further evidence is provided in the fact that despite all of that destruction, *no one died or was even seriously injured*. [Answer] The hardest part is making someone understand that they live in a simulation, is that almost everything you can do can be explained through coincidence, trickery, or even special effects. But, from my time playing Minecraft, there is one thing that always seemed to evoke that "oh right, I'm in a simulation" feeling. Prevent an entire chunk from rendering. A 20 meter cubed area of simply nothing rendering, seeing down into the ground, while everything around the chunk continues to work (with people walking into and out of the cube) tends to evoke that "partitioned world" feeling quite well. This would most likely involve changing the chunk's settings so that it still shows for the rest of the world, or other people would freak out. But the strange thing about extracting a cube over making an object invisible is that it *feels* very computer-y to do it like that. The whole idea of "object" is a very human feeling; computers deal in geometric areas. Bonus: this won't damage Alice's psyche as much as most of the other answers :P [Answer] This may be a little too obvious, but what about a few demonstrations of inexplicable barroom physics... Being a "garage physicist" one could assume that Bob enjoys playing pool because there's a good deal of physics involved in the game. Bob decides to invite Alice out for a few games and more than a few drinks. After they order the first round, Bob offers to pay, but the bartender refuses to take his money. Alice thinks that Bob set it up in advance, but isn't too concerned about the free drinks. They play their first game, Bob wins, but not through any extraordinary event, he just plays a little better than Alice. Bob begins to rack the balls and offers to let Alice break on the next game. Alice breaks and inexplicably every ball on the table bounces into a pocket. She immediately assumes that Bob has conspired with the generous bartender and rigged the table. He laughs and assures her that there is no grand conspiracy and offers to rack the balls again. Alice refuses to let him rack and starts to collect the balls. She takes her time examining each ball and allows them to roll across the table watching for any peculiarities. Bob offers to break, but Alice again refuses. Alice spots the cue ball and hits it hard, really hard, it flies across the table and bounces off the 1 ball with enough force to send it flying back into a corner pocket, but none of the other balls on the table move at all. At this point, Alice is fuming, but Bob laughs it off, takes the cue ball in hand and citing the rules of the game places it behind the head string and hits it. The cue ball again flies across the table, but this time only the striped balls bounce into the pockets, leaving the solid balls completely untouched, still in formation. Alice groans, but being curious at this point, lines up and takes her shot. She hits the cue ball hard out of frustration, but the cue ball crawls across the table slowly. Bob shrugs his shoulders and goes off to get another round. Orders two pints and two shots and returns a good while before the cue ball finishes its trip across the table. When the cue ball finally strikes the 4 ball both of the balls move as if the cue ball had been traveling at a good clip. Alice drops the pool cue and looks at Bob, fed up, and ready to leave. Bob stops her before she can say anything "I'll tell you what. Flip a coin. If you win I'll leave you alone, you can go home and tell everyone that I rigged the table. But... If I win you have to take this shot and hear me out." Alice furrows her brow digs in her pocket and produces a quarter. She pauses for a moment and flips it into the air. "Call It!" "Neither!" Sure enough, the quarter bounces onto the table rolls on its edge in a circle around the shot glasses and just stops. Still standing on its edge. Alice's eyes open wide, and without saying anything, she grabs a shot glass, downs the whiskey, and slams the glass upside down, trapping the still standing quarter. Bob takes his shot, slowly knocks it back, and starts to explain... "So... I was messing around in the garage the other day..." [Answer] If Bob is THAT excited about this discovery, and wants Alice to know as soon as possible, the most fun solution is also the most simple. Appear in front of Alice. Immediately. Without any warning. Preferably out of thin air, *floating* in mid-air, and in a form that cannot possibly be ignored (either a completely flamboyant outfit, or a fantastical creature). The sudden inexplicable appearance of Bob from thin air would be more than enough proof to Alice that something unusual is going on. Or, if Bob is feeling particularly lazy, he could just summon Alice to **him**, preferably when she'd least expect it, and politely explain that he did this by manipulating the simulation that they are in and oh by the way, this is all a simulation. Putting Alice in an equally flamboyant or embarrassing outfit/form is entirely optional, but additionally fun. --- Edit: With the additional parameters put in, Bob would have to bring Alice to himself, rather than the other way around. I'm not sure if that would be allowed, but if it were, it would still be the most effective way to prove his theory to Alice. To explain how it is *not* magic, Bob could simply follow up his initial demonstration with an explanation of the mechanics of the world to Alice - showing her how an individual 'block' can be modified and how. Preferably, by creating something that Alice likes within that block (A well-done steak, a pretty bird, a golden necklace, Alice's crush, anything will do). While she might still think it's 'magic', that's acceptable - we aren't trying to prove that it's technology after all, just that it is a simulation with rules and boundaries, and what Alice decides to call it is irrelevant to this goal. [Answer] "If *I* can't persuade you, Alice, then maybe this guy can?" In through the door walks a second, identical Bob. Before Alice can speak, he begins, "If *I* can't persuade you, Alice, then maybe this guy can?" A third Bob walks through the door, delivering the same line. Then a fourth walks in... Shocked, Alice looks out of the door. A row of identical Bobs wave at her. At the far end of the queue, about 20 metres away, a floating arm also waves. [Answer] I loved the movie "Bruce Almighty". What if Bob pretends to be God and grants Alice omnipotence for a day, then makes her wishes go all screwy. He could really mess with her mind then. I think this is better than Bob demonstrating the power in himself: it is Alice who needs to manifest the power. [Answer] Boy the possibilities are limitless. I mean he could mess everything up pretty bad. Anyway... 1. Bob goes to Alice, rings at her doorbell, Alice opens the door and she finds a Terminator like post apocalyptic world in front of her (she can turn around and find her house perfectly in order), Bob appears from the outer view of Alice (who meanwhile I'm pretty sure is freaking out intensively) on a white, gold plated, armored horse, exclaiming "come with me if you want to live", as she mounts on the horse, they fly high in the sky and the rest is history. They must have some space in memory for Terminator, right? 2. Bob purposes to Alice: "let me give you something", his hand reach the sun, grab it and holds it in front of Alice, no amount of heat changes anywhere, but light does, scaling down as the sun moves from the sky in Bobs' hand. He takes her hand, and puts the sun on her finger, the sun models around it flawlessly, issuing beautiful little flames that do not burn. Pretty hard to explain, considering that in the same time Alice is, let's say, astonished, Bob is surrounded by lawyers claiming he should not keep the kids. Two little kids are also there. 3. Bob and Alice are having a dinner with other friends in a fancy restaurant, Bob pauses the rest of the simulation without stopping himself. At this point starts messing and swapping everything you can imagine: dishes, dresses, windows, doors,floor,ceiling,animalheads,heylookthereisagiantrobotoutside! You got the point. After the confusion, re-pause, all to normal. Only Alice can remember it, in fact is the only one feeling something strange, no one reacts to the changes. This is so R. Lanza: "So while you may think that the kitchen as you remember it was there in your absence, the unquestionable reality is that nothing remotely resembling what you can imagine could be present when a consciousness is not interacting." At some point during these facts, Bob says "and this is why nothing is real". These are my [personal experiences](http://en.wikipedia.org/wiki/Fantasy_prone_personality), if you're looking for an idea you get the idea. [Answer] I would replicate Alice, and then have her have a conversation with herself, without telling her that it is actually herself that she is talking to (disguising them, talking over the phone or through a screen etc.). I think this would prove categorically that it is a simulation, as there is no other reasonable explanation of how someone would be having a conversation with themselves. It would also be quite amusing watching Alice having a conversation with someone who absolutely agrees with all of her opinions. It would be majorly frustrating to Alice, as until she realized that the person she was talking to was actually her, she would surely think this other person was lying about agreeing with everything. The other person would also be having the same frustration having the conversation with Alice. They would also have all of the same interests, so could go into deep conversations about everything and would have exactly the same level of expertise about everything. It would also be interesting to see how long it would take Alice to realize that it was a replica of herself. [Answer] In the Rudy Rucker novel [The Master of Space and Time](http://www.wikipedia.org/wiki/Master_of_Space_and_Time), the inventor offered that his confidant should himself choose what would be convincing. The *Alice* role character was sitting in a car with a scale toy car on the other seat. The toy was the *same* car, as the view out the windows indicated. Manipulating the small car caused that to happen to the car he was in. It was an infinite or circular regression in both directions. [Answer] As for the requirement: > > terrifying entertaining way Bob can prove to Alice that they're living > in a simulated world... > > > Bob can make Alice his husband for a day. And why husband but not wife, if Alice asks? Bob can say: *"Yes honey, for this is just a simulation, I can make the stimulation go any which way I want."* [Answer] Start by planting in her mind (which is part of the simulation) an unreasonable, gnawing doubt. Bob would then cause her (through his control of her simulated self) to confess her doubts about reality to him. He would assure her they were false. Then a few small incongruities would be placed in her environment, a hamster than speaks a single word, a music broadcast that appears to be talking to her, a period of an hour or two where no one in the environment seems to notice or respond to her. All of the same kinds of thing that schizophrenics experience. When Alice confronts Bob about these odd incongruities, he will pretend to be deeply concerned, and recommend a psychiatrist. Alice visits the psychiatrist. The psychiatrist prescribes anti-psychotic drugs. These of course increase the feelings of isolation and alienation she is experiencing. Her symptoms worsen. She hears strange humming sounds in her ears. No one seems to be listening to her. She sits for hours, watching the crowds walk by, and their activities seem mechanical, purposeless. When she talks with other people, their responses are mechanical and predictable. They appear to her like automatons, seeking simple gratification of pleasure or ego, and not thoughtful soul-containing creatures. Their conversation repeats themes from TV and movies, it has no real originality to it. she catches different people repeating the same topics and opinions, without significant variation, as if the ideas of society were programmed from some central sources. She picks up a flower. The petals seem to be fabricated out of plastic. She calls he friend Bob in a panic. He is patronizing, distant. The humming sound in her ears has turned into a rushing like a mad waterfall carrying her over the edge. She begins to speak in disjointed, unconnected sentences. Her boyfriend calls her parents, who have her taken into psychiatric custody for 24 hours. She sits there in the hospital, full of tranquilizers and drugs, and the hours roll by as she stares at the ceiling. She hears the nurses chatting far away, and they are talking about the same topics as the automatons everywhere - politics, sex, pleasure, food. Same topics, almost the same words. She begins to fade away into nothingness, she beings to internalize the way of the robotic entities that surround her. Perhaps after all, this is reality. Bob visits her. He grins like a maniac. "Psyche!" he says, then floats up into the sky. She floats up with him. "It was a prank, Alice, boy did I fool you!" they float off together. [Answer] Most entertaining way is to offer to change whatever world parameters Alice names. Want a green sky? Done. Want 0.05 meters/second squared gravity? No problem. Want everybody to have a giant bobble head? Why not? Run time backward or replay a loop? Sure. Only problem is there is no logical way to separate controlling Alice's perceptions from controlling the simulation, so it is effectively impossible to prove to Alice that she is in a simulation rather than being controlled. Closest would be to graft the control onto Alice, so that Bob doesn't know what parameters she will change until they happen. Not perfect though - complete control of Alice would give Bob the ability to make her think his thoughts and actions were hers without needing to be inside a simulation. [Answer] One word: **[Retrocausality](https://en.wikipedia.org/wiki/Retrocausality)** Anything else could be the result of other processes: supernatural powers, time travel, or just copincidence, and could be explained away. However, after a day of seeing things happen out of order, it would be pretty clear that the world is not as it appears. This would not be easy to engineer, but is possible with the given setup - bob just needs to mess with the clock speed and timestamps of the separate chunks, so that they are out of alignment. Then any events that cross chunk boundaries will cause paradoxes, with objects vanishing, duplicating, and events decoupled from causes. Like, you throw a ball straight up, and sometimes it hands in the air for a while before falling, while in a different chunk it falls back down before it goes up. There are a lot of other good possibilities, but I think this is the only one that is *only* possible in a simulation. [Answer] ## He can't prove it by causing an impossible or highly improbable physical event Whatever physically improbable/impossible event Bob causes to occur, the likelihood that Alice is hallucinating (perhaps she's suffering from a mental breakdown, or Bob has drugged her ) will always be greater than the likelihood that Bob has 'magical' powers which allow him complete control over Alice's physical world (which is what most of the other answers here amount to). If something impossible (or highly improbable) occurs then it is more likely that the person witnessing it is hallucinating (a well-documented phenomenon which occurs regularly all over the world, all the time) than that the impossible event has actually occurred (we have no well-documented incidences of impossible things happening). In other words, the likelihood that the witness is drugged, confused, deluded or having a psychotic break with reality is always higher than the likelihood that the impossible (or extremely improbable) physical event has actually occurred. The more improbable the physical event is, the stronger this argument becomes, because hallucinations are quite probable - they happen all the time. ## He might be able to persuade her using logic The 'simulation argument' runs like this: > > A technologically mature “posthuman” civilization would have enormous > computing power. Based on this empirical fact, the simulation argument shows that **at least one of the following propositions is true**: > > > 1. The fraction of human‐level civilizations that reach a posthuman stage is very close to zero; > 2. The fraction of posthuman civilizations that are interested in running ancestor‐simulations is very close to zero; > 3. **The fraction of all people with our kind of > experiences that are living in a simulation is very close to one.** > > > If (1) is true, then we will almost certainly go extinct before reaching > posthumanity. > > > If (2) is true, then there must be a strong convergence among the courses of advanced civilizations so that virtually none contains any relatively wealthy individuals who desire to run ancestor‐simulations and are free to do so. > > > ***If (3) is true, then we almost certainly live in a simulation.*** > > > In the dark forest of our current ignorance, it seems sensible to apportion one’s credence roughly evenly between (1), (2), and (3). > > > Unless we are now living in a simulation, our descendants will almost > certainly never run an ancestor‐simulation. > > > Nick Bostrom, *[Are You Living in a Computer Simulation?](http://www.simulation-argument.com/simulation.pdf)*, Philosophical Quarterly (2003) Vol. 53, No. 211, pp. 243‐255. (First version: 2001) See also: <http://en.wikipedia.org/wiki/Simulation_hypothesis#Simulation_argument> [Answer] Making anomalies common. (for example, bird-riding weasels) He doesn't even need any special setting to make it entertaining (but could!). One day with way too many anomalies will have anyone questioning life/reality etc.. You start off your day and pick up your mail to find 8 different letters addressing someone other than yourself at your address, last week's newspaper and a shoe (why not?) Get a phone call from some random childhood friend and a few distant relatives. Cannot find a single pair of matching socks even though you have no dirty laundry. Win a free lottery ticket that makes you win another lottery ticket that makes you win another (and so on). Learn the Toronto Maple Leafs win the Stanley cup, etc... [Answer] Your question is a very difficult one i don't think i could answer, but obviously this is a philosophy you would like to explore in order to take idea's and use them somewhere else. Here are some vague ideas: One way for Bob to make Alice realize that her world isn't real, would be to show her a world that is more real than the on she knows, although this would have to involve taking her out of what she percieves as normal, and bringing her into a new, possibly stranger, more complex reality - like the Matrix. This is pretty hard to do, especially if you question regards a real life dispute! Another way might be to teach Alice how to manipulate the world as Bob has learned. This way Alice might prove to herself, without the outside influence of Bobs "powers", that her world isn't what she thought. How do you prove a great discovery to someone that lacks the amount of education you posses? you must first offer them the knowledge they do not know, otherwise they can not understand. This way Alice will learn the Discovery just as Bob learnt it from his own intuition. Again unless you've secretly discovered something amazing - is a very hard thing to do. a very long P.S If you would like to explore some scientific indications to the foundations of reality being simulated, you could look into the phenomenon of Cymatics, and how some believe it indicates that all structure in reality is made possible from Sound Frequency. It can also be included within String Theory although it is slightly different. "Sacred Geometry" is another interesting philosophy on Reality but is verging on the weird, the information is relevant to reality however the deliverer of such a subject is often disillusioned with exaggerated meanings and false beliefs. If you would like to explore a more spiritual explanation of "holographic reality" you could look into the ideas and philosophies thought in Meditation. One of the core aspects of the practice is to un-bound yourself from reality, and realizing that your "self" is an illusion, and that all objects, memories and lifeforms are interconnected and part of one whole, this is achieved by "stripping" oneself of all ego and power, accepting humbleness and worthlessness to the point of nothingness - at this point of nothingness & all (enlightenment). [Answer] I'm blatantly stealing the first bit of this from Hitchhiker's Guide to the Galaxy: Instantly teleport her undergarments 5 feet to the left. Repeat as necessary to prove your point. Better yet, swap them with another nearby person. Change the color/style/design/etc. That should do it, and it is very fun as well. [Answer] Bob has figured out that the world he is living in is some kind of simulation, but he does not know who is in control over it. He should first figure out whether or not the beings in control over the simulation are friendly, and what the implications were of finding this deception before he decides to share it with someone else. That being said, Bob should slowly reveal his secret to her in a series of steps, that will prepare her for the truth instead of just laying it on her. Bob would not want to do any tricks which would either make Alice fear him, or which would cause her to lose her sanity. Assuming that Bob has significantly been able to control the reality, he should set up a series of amazing coincidences. Since Alice is already suspicious of him, he needs to gain her trust first. He could take her out, and show her a good time. Take her to see her favorite band, and arrange for her to go back stage and meet them. While on the way there, he could rig the traffic lights to turn green at just the right time, so there is no waiting. He could also take her to the horse track, and win big. Alice would start to question all of these coincidences and wonder what was going on. She would know enough that the odds of these things happening would be absolutely astronomical. Once she begins questioning this, Bob can then show her what the truth is. He could then show her exactly how capable he really is. He could make the sun rise or set, and possibly even transport her to another time or place. By this time, Alice would completely be astounded, and be able to trust Bob. [Answer] The most entertaining way to prove to someone that they are not real ? Well, it seems to me that all you have got to do is convince them to successfully complete the following challenge: Within the same year, have that special someone run for US president, get elected, ruin the country, resign from the presidency, join Scientology, go clear in a week, sue them for a One $Trillion, win, collect, start a company, be worth 5 Trillion, go broke, become a bungee jumper, and a storm chaser, fly to the moon, come back, join the Jehovah witnesses, become a dentist and tax auditor, start a legalised marijuana farm, sell that, give the money away, become a motivational speaker, eat ice cream, chocolate and 20 pigs, join the CIA, defect to ISIS, only to become a Buddhist monk. Then ask them "Are you real?" I have no research to back any of this up. ]

[Question] [ I understand that sea shanties were a type of work song, and often used to help sailors operate in sync with each other. They've survived as an art form, but so far as I know they don't have any practical use anymore. One would think that after technology had advanced far enough to make space travel a possibility, this would not change. Nevertheless, I'd like to include space shanties in my story, and I need a good excuse to do so. Why might sea shanties, or rather, *space* shanties, be used aboard space times? [Answer] ## Memorizing Checklists Space is a very dangerous place. Even small mistakes can have deadly consequences. Which is why most routine tasks in space - performing an engine burn, black-starting a fusion reactor, using an airlock or even just going to the toilet - will come with long, mandatory checklists to follow. Sure, you could look up such checklists on your PDA. But it would be far more convenient to memorize them. And there might also be the need to teach checklists to others. Newcomers on your vessel. Or perhaps your assistant engineer forgot to properly tether themselves on a spacewalk, and now you need to explain to a botanist how to manually realign a solar array. Perhaps there are even children growing up in space who need to be taught how to not kill themselves and everyone else on the vessel when they jettison the trash. So how do you memorize a long checklist and make it easily teachable? How about turning it into a catchy and memorable song you can sing to yourself while performing a task? Or sing it together with others when the task needs to be performed by multiple people in coordination? [Answer] Wherever you have humans performing together, morale will be a huge factor in how well they perform. Space shanties will be up for ensuring that the crew will feel like one, build a team spirit and make them feel like a single body. I was once talking with an acquaintance who at the time was sergeant in a training camp for the army: he was telling me that singing the same song while undergoing the same training was a huge help in building the body spirit and turn a bunch of individuals into a group willing to fight for each other. [Answer] ## Music is an expression of communal identity Performing (or just listening to) music together instills a feeling of community and cultural belonging in people. This is true for millennia of human history. Every culture in history had its own distinct style of folk music. When cultures amalgamated in the middle ages, then you often saw subcultures emerge which identified with their own songs. Seafarers had shanties, but other subcultures also had their own songs. European monks are still known for their distinct style of singing. Soldiers had songs. Peddlers had songs. City dwellers had songs they sung in taverns. Nobles had music performed at banquets. After the middle ages, music became political. Every revolution was accompanied by a canon of music to capture the emotional sentiment of the revolutionaries. Every country got its national anthem to instill a feeling of national identity. Then in the 20th and 21st century, music became an expression of lifestyle. Rock, country, punk, blues, schlager, pop, techno, rap, jazz... the music someone listens to says what community they identify with and what lifestyle they pursue. When spacefarers in your world are going to form a distinct subculture, they are going to have spacefarer songs they are going to perform together as a sign of their communal identity. [Answer] **Timing and rhythm** Songs can be useful for (imprecisely) measuring lengths of time, either through the length of the entire song, or through its tempo. Planetside, there are a number of song-based timing techniques, such as washing your hands long enough to sing "Happy Birthday" twice, or performing CPR to the beat of "Stayin' Alive". It's reasonable to think that a space shanty could be used as an easy way to remember the timing of common tasks. Perhaps you need to manually prime some rocket fuel pump not-too-fast but not-too-slow, so doing it to the beat of a sea shanty is just right. Maybe you need to wait for a system to cool off after shutting it down before performing maintenance, so singing a couple of verses will help keep you from burning yourself. Humming a song in your head can also be a rough measure of time if a clock is unavailable - if you finish humming the entire shanty, you had better finish your spacewalk no matter what your oxygen gauge reads. I'm envisioning these techniques as being particularly useful in a spacepunk-esque setting with rust-bucket spaceships, where computerized control of timing is either unavailable or unreliable. Sea shanties are typically sung in groups, but it could still be useful to have a common song that all crew members sing even individually, to provide consistency as different people perform different tasks. Even if the song is usually sung individually, it can still provide consistency and cohesion across the group. Of course, any song with the right tempo and length could be used for these purposes, but a shanty is a nice thematic fit. [Answer] **The crewmember must share information, unbeknown to the starship AI** A lot of complex tasks are carried out by the space ship's AI. Unluckily, we all know that sometimes the space ship's AI can be a bit touchy. Maybe the AI was programmed to lie to the crew, maybe this brought the AI to make a trivial mistake which is noticed by somebody in the crew... Well, you know, things could easily go south from here, and there have been a lot of registered cases where the AI went mad and killed all the crew members. Luckily, while proficient in all technical and logical issues of a space ship, AIs don't have a lot of musical knowledge, nor much ability in deciphering the music's meaning to human beings; as crew members continue to sing, the AI doesn't see any meaning other than a bizarre hobby of those organ bags, and ignores it. But for the crew members, every song has a meaning: while almost all songs have no other purpose than telling that everything is good, some songs (maybe changing the key of the music, from a major scale to a minor one) are used to warn the rest of the crew that something is not OK with the AI. Since peopleoften change or add lines to these songs, some well-(dis)placed words or rhymes could also explain other crewmembers what exactly is happening, without the AI suspecting anything. Make the drunken star sailor slept with the captain's computer rather than the captain's daughter, and the crew will know that it is necessary to quietly go to the computer room and reset the AI... [Answer] ### Music sets mood. Mood determines survival. Survival determines profit. Ever whistled or hummed while working? Ever had the stereo on while working? Ever listened to calming music while driving so you dont get angry at those other idiots? Surgeons listen to music while operating, tank drivers listen to music while invading, and the list goes on. Music is a big determiner of human performance, focus, and mood. And those things in space seperate life from death. Just like shops compare sales with different sound tracks to optimise the in store music for maximum sales, "big space" will compare results with different music in order to optimise human behavior on long space trips. Who knows what the outcome of such trials we be, but as L Dutch suggested, teamwork and bonding can be formed by group singing, and if daily singalongs increase the chance of a ship making it to its destination by 1%, you can bet theyll become company policy. [Answer] Work can be boring sometimes. I think everyone who works on a computer on a desk and with internet access probably has their favorite playlists, either to help pass time or to enter into a flow state. In my case, it just so happens that my favorite playlist is composed of shanties and other pirate-related songs. It was so even I became a pastafarian. Funny thing - get a lot of nerds together in a small space, and they might start chanting together whatever is currently a meme. I once worked in a very small room with other five colleagues, all of us programmers, all of us fans of Tolkien's work. It was about the time the Hobbit movie came out, so sometimes one of us would start humming the tunes to the Misty Mountains song, and we'd all join in almost as a reflex. We'd sing the lyrics too. It was fun, and it helped us bond. I imagine in a spaceship you could kinda have the same effect. I would enjoy being a crewmember of ISS if I were an astronaut and if they would sing shanties every once in a while. Also notice that [space pirates are a trope](https://tvtropes.org/pmwiki/pmwiki.php/Main/SpacePirates). If your work of fiction has space pirates, they are expected to sing shanties every once in a while! Last but not least. I used to play Sid Meyer's Alpha Centauri as the Nautilus Pirates - and I would mute the in-game's music and have The Dreadnoughts playing on Spotify for a more proper musical background. [Answer] **As long as you have hard work or work that needs to be timed, you can have a shanty** So for example, if you have crew that need to haul ammunition from storage to the guns, they can sing a shanty for that. If the engineering crew needs to do some work in sync, shanties will work there as well. If you give the crew radio headsets, they can even sing the same shanty if they aren't in the same room. In most sci fi stories tasks like that are either not shown (since the "camera" is only showing the bridge personnel and not the lowly grunts) or automated by robots/pipes/... so you might have to come up with an explanation why this is different here. Coordinating of fighter maneuvers could also benefit from shanties, that tell the pilots what to do and when to do it. Also, you could take some inspiration from the free indie game Cosmoteer. In that game, energy is delivered using battery packs, and they need to be carried by the crew from the generator to the devices that require power. Might need a good explanation why it's done that way, but it makes for a very nice game mechanic that would fit well with shanties. [Answer] Read Kim Stanley Robinson's "The Memory of Whiteness" (I think that's the one...). It's a book (in part) about how music holds people together across the vast tracts of space. What else do we have (in all that slow emptiness) except music to keep us sane? It's not just about work. It's about filling the drawn-out reality of nothingness with something like human meaning... [Answer] ## Not really, and there is why A space ship is a complex structure, more so or maybe in some sense comporable with sea ships of today, or a factory, or a nuclear station. Work to keep the thing going is complex, and deversified. We split any complex task in subtasks and everyone assigned a subtask, and in some sense those are unique task, each has its own tempo. However teambuilding and corporation loyalty building is known thing, so as to use singing songs as part of the process. Where it may make sense are special cases, where you do not have means of automatically check connection or keep distress signal going, have doubts about your radio link working properly or something like that. I can imagine belters from The Expanse having something like that, and in some way thye did, a best they have is worst there is and thing break regularly. However, if your oxygen is limited then maybe not the best idea. Singing hymns as some identification of belongings also known thing. So, no, you have complex tasks and complx problems to focus on, where a mistake of one can cost lives of everyone, now or later on, and last thing you wish for is to make additional distractions to all who are busy. In free time, yes songs can be part of relaxation, switching brains to a different tasks, and serve as one of many possible team building exercises, indirecty. Songs are good when many do similar task, also they are not bad to get in a transe and carry one some mundane task along the day, but I ensure you, they are incompatible with 50 position checklist just to start an engine. ## Handwavium Need a handwavium, here, I have a piece of one. They do not sing songs, song is song to them by an AI which has feedback from the brain activity via neurolink from one it sings a song to. Reason is, as it does basicaly the same thing when people use listening to songs while working or working out - to stimulate their activity for the task they do. And if AI can automaticaly generate a good tune and sing "insert a part XX after part YY, halliuha of parts, checkbox 27 done, I love u so much how outstanding worker you are, keep it up part ZZ in slot XY, man u sooogreat.." I guess it may work improving quality of work and reduce failure rates. There are devices on trains which detect if driver fall asleep or died, so why not to monitor a situation and brain waves to play some relaxing tunes to that specific individual (which is different for different people, heavy mettal is good for sound sleep in my opinion) and stimulate awareness in when it is needed. In some sense one "sleeps" when it is posible, even if it is 5 second, and be more alert next 3 seconds for critical button pressing. It like energy saving features of modern cpu's, individualy generated sound waves to stimulate and relax different brain regions may improve something, and even be a hard scify. Changing speed or tempo(few percent, not noticiable) can help to syncronise subtasks in stiching them together in a bigger system, done right then with reduced fatigue, less down time, higher spirits etc. There are types of work where hearig channel is more free than other senses, and thus can be used. [Answer] **Battle Song!** If you haven't seen [Lexx](https://en.wikipedia.org/wiki/Lexx), then you seriously need to. Here is the [battle song of the Brunnen-G](https://www.youtube.com/watch?v=wYoq6sovr8Y) from that saga. [](https://i.stack.imgur.com/X5HcO.jpg) --- > > Many thousands of years ago, the Brunnen-G fought in the Great Insect > War, forever earning fame and gratitude as the saviours of mankind > after they managed to defeat the fearsome insect race. They fought > this war from the Dark Zone, in which their home-world of Brunnis-1 > was located, however the war itself was fought in the Light Zone. > <https://lexx.fandom.com/wiki/Brunnen-G> > > > [Answer] One of the important things in a team is to get along. In itself, singing, playing or just listening to music together can (as others have pointed out) accomplish this to some extent. But recent research shows that *moving rhythmically in synch* forms extremely close bonds or rapport between members of a group: <https://www.scientificamerican.com/article/moving-in-sync-creates-surprising-social-bonds-among-people/>. So it'd make psychological sense if some activities were ritualized with song and rhythmic movement. For example, when they all go to the mess hall together, as they pick up the food and utensils, and sit together; or when clearing up and washing up their dishes. Or just things like going through the shift-handover checklist: important, repetitive, tedious activities which are otherwise likely to be halfassed. Also any drudge-work. On a spaceship, there's unlikely to be automation for cleaning, greasing, painting and polishing every damn thing, because all such automation is mass and volume, and all such automation means then the automation needs cleaning, greasing, painting and polishing, recursively ad infinitum. So, whilt a Roomba-floor-scrubber might mean the decks don't literally need to be scrubbed, preventitive maintenance is going to be a responsibility of every single person on board. On Navy ships, as well as being essential maintenance, this kind of "scrub the decks make-work" also serves the multiple purposes of keeping people fit, busy, occupied and cooperating, rather than out of shape, lazy, bored and troublemaking. [Answer] **Homesickness and nostalgia** Travelers on long voyages miss home, and many voyage songs express that longing. It's reasonable to expect that space travel would be no exception. This is in fact the premise of Robert A. Heinlein's short story, "The Green Hills of Earth", about the composition of a song of the same title: > > We pray for one last landing > > > On the globe that gave us birth > > > Let us rest our eyes on the fleecy skies > > > And the cool, green hills of Earth. > > > (Incidentally, in my head this song is sung to the tune of "Oh Susanna" -- which perhaps means it's not technically a sea shanty, but I think it's close enough.) [Answer] Repetitive work and morale-building are still necessary in space, as people have mentioned in their answers already. It also serves to develop and retain culture, particularly in communities where oral tradition is stronger than the written word. The books/TV show *The Expanse* features space shanties, as people live and work in space and need the rhythm and sense of community. [Answer] I feel one idea not touched upon others here is to record and pass on historic events of cultural significance to the space-faring people. I also feel like space chanties might exist to warn people about specific survival tips for specific regions of space and/or exo-biomes. [Answer] There are certain operations on the spaceship that require a consensus among several pilots to perform. Otherwise, the ship simply will not respond. This is to prevent a single deranged pilot from scuttling the mission. Several pilots have to hit a certain sequence of buttons in a certain cadence. They can't use electronic tools for synchronizing, because those tools activate a sensor in the ship that disables the response. So they fell back on the space chantey. For some strange reason, they revived nineteenth century sea chanteys, because the captured complex rhythms in an easy way. A sample: ``` 'Twas in twenty hundred and twenty three Of June the thirteenth day That our gallant ship, her orbit slipped And for Saturn bore away, brave boys, And for Saturn bore away. ``` [Answer] [Shanties can serve as a rite of passage](https://youtu.be/jke9h5fzU5I?t=993) — including the ultimate one —, invoking tradition and providing solace. [Answer] A few simple statements: * despite space faring technology and all the automation it implies, human work is still the primary means of labor. * on a space ship there are no natural day/night cycles but lots of long, time consuming chores required to keep the space ship in order. * On a sea-faring ship any disagreement and dissent can be lethal to the entire crew. A space ship has those dangers cranked up to 11. * unity and cooperation are required. This all means you need some way to clear monotony and create unity to keep the crew on track. Shanties are a great way to do that and just about every establishment knows. The army, churches and even businesses use singing to get people involved into their alloted tasks, help unify them (interesting fact is that singing synchronises heartbeats due to the breathing pattern required to sing the same lines) and in general keeps spirits up. As a bonus you could add culture to it as a reason they chose shanties over other forms of team building. [Answer] As a tool to pass information to others who have no background in the current tasks being performed. Unlike a space ship many sections will be sound-proof as a result of making all sections air-tight in case one section depressurises. This means sections can have their own shanties that give information about the current tasks being performed and what they are doing. This is an extremely important and useful way of running the ship. Space-ships will have many specialized tasks that only a few can perform. So if you need a crew of 10 to perform a task but you only have 2 specialist capable of performing the task at hand you need a way to tell them. The shanties sung are controlled by the specialists who choose the verses being sung. The verse tells in layman terms what tasks need to be done and how. Some verses are structured like the "bottles of beer on the wall" verses where you can count up or down depending on how many times a task needs to be performed and how many are performing it at a time. Highly repetitive tasks can be represented as parts of the beat with a single syllabel or word, more complex tasks can be entire verses punctuated by the simpler tasks. This gives people who enter an area a sense of what is happening and if the machinery in that section is A-OK or about to blow. People can more easily jump in and help with tasks. They know what to do as they are guided by the specialists who pick the tasks and during quieter times when a specialist might not be required all that you need is to teach some crew the right shanty. This makes all crew valuable and useable in most area's. [Answer] As @philipp says "Memorizing Checklists" is a great example. Taken to the extreme you get the cult of mechanicus from the Warhammer 40k universe where the underlying understanding of the technology has been lost and all you have is rituals for how to do things. For example the song of glue setting to allow enough bonding time or the song of paint drying to allow time between cotes. ]

[Question] [ With advanced technology would it be possible to make something like the Santa in the story as well as the reindeer? If so could a realistic Santa be a human or would him and his reindeer have to be machines? Some things I was wondering are: 1. Is there any kind of fuel would a realistic Santa and his reindeer need to consume in order to have enough energy to move fast enough to deliver presents to hundreds of millions of homes? 2. Is there any material that a realistic Santa and his reindeer could be made from that could withstand the gs that he and his reindeer would experience when delivering presents? 3. How would the realistic versions of Santa's reindeer move the sleigh? 4. Could a realistic Santa cover the sonic boom produced by his sleigh? 5. How would a realistic Santa fit billions of presents into his sack? 6. How would a realistic Santa protect the presents from the G force experienced while traveling? [Answer] # How many kids? This is the toughest factor to find. While Santa isn't specific to a single religion, traditions differ in various parts of the world, and belief rates in Santa Claus are not tracked by the WHO, looking at Christians seemed to be a reasonable, if imperfect, start. According to [2010 estimates](https://en.wikipedia.org/wiki/List_of_religious_populations#Christians), there are 2.2 billion Christians in the world. I have no idea how many of them are kids, but we're all kids at heart, aren't we? So I'll just go with 2.2 billion kids in my calculations. That might sound like a huge overestimate, but, as you'll see, even if that number is off by a factor of ten, it won't make much difference. No matter how you look at it, though, that's a lot of chimneys. # How many cookies? Assuming Santa heeds his doctor's advice and doesn't eat the entire plate of cookies (he just eats one—he has to keep up appearances, after all!): [](https://i.stack.imgur.com/q3dYj.gif) Excluding the obligatory sip of milk, by the time the night's over, Jolly Ol' Saint Nick would have ingested food energy (it's mostly empty carbs anyway!) equivalent to the yield of a 200 kT thermonuclear bomb! # Naughty or Nice list: 225 TB Accounting for names (100 characters), identifying information (200 characters), address/coordinates (200 characters), photograph (100KB) (he has to be able to recognize the little tykes on sight if one of them happens to wake up in the middle of the night), Santa would need storage for around 100KB on each kid. $$100 \text{KiB} \cdot 2.2\times10^9 = 225 \text{TiB}$$ Very roughly speaking, that means Santa's carrying around about a hundred 2TB external HDDs (2015 budget: US$7,500, chump change for Kris Kringle!). That's a fair amount of storage for one man to carry around, for sure, but compared to Santa's other challenges, a hundred hard drives would be the least of his worries. # Cargo This one's easy: 2.2 billion [Red Ryder Lever Action BB Guns](https://en.wikipedia.org/wiki/Daisy_Outdoor_Products#Red_Ryder_BB_Gun) at 1kg each is 2.2 million metric tons. Volume-wise, let's say you can get about 10 presents per cubic meter (don't want to smash the pretty bow ribbon!). For a sense of scale, check [this query](http://www.wolframalpha.com/input/?i=0.22*10%5E9+m%5E3): * 44% of the volume of Sydney Harbor * 69% of the total annual volume of oil transported by oil tankers worldwide If I were Santa and refused to delegate the actual home visits, I would at least mobilize a huge global shipping network months in advance, to **ship the presents to local warehouses and perhaps even neighborhood depots** from there, for staging purposes. That way on Christmas Eve itself, he has much less work to do, and *much, much* less cargo to drag around the globe. # Time estimate This is where it starts to get rough. According to the map on the Wikipedia page linked above, Christians are spread out East-West more or less across the entire globe. Very roughly speaking, but precise enough for our purposes here, let's say Santa has 24 hours to deliver all of the presents. Can one man do it? $$24h / 2.2\times10^9 kids = 1.091\times 10^{-8} h/kid = 39.27 \mu s/kid$$ I hope Santa's a fast eater! # Forces on Santa It's hard to get a precise estimate of the distance Santa will be traveling, how much time will be spent taking off, flying, and landing, versus just going door-to-door in apartments. While acceleration during takeoff would surely be very bad, why don't we just consider the *best possible case* for Santa's delivery: every kid in the world is beamed with a transporter, semi-comatose, into Russia, in a single line, shoulder to shoulder, with their arms outstretched. Santa would then just need to take a step, stop, hand out a present, and repeat. Let's say taking a step and stopping take 2/3 of the time (1/3 accelerating, 1/3 decelerating), and handing out the present takes the other 1/3. Santa therefore has $39.27/3 = 13.09 \mu s$ to accelerate through roughly half a metre. Thanks to Newton's 2nd law, we know: $$s = v\_0t + \frac{1}2 at^2$$ With a little arranging, and $s = 0.5m, t = 13.09 \mu s, v\_0 = 0$ (he accelerates from a standstill), we get: $$a = \frac{2s}{t^2} = 5.84 \times 10^9 m/s^2 = 5.95\times10^8 g$$ That's 595,000,000g. You can check [this page](https://en.wikipedia.org/wiki/G-force#Human_tolerance_of_g-force) for the gory details of human tolerance, but, really, don't bother. Most humans wouldn't survive 40g-50g or so. At 595 **million** g, Santa is now, at best, a buttery sweet-smelling liquid. ## But there's another, *worse* problem than that! (Worse than Liquid Santa? This can't be good...) No matter what kind of fuel you use, moving Santa in one direction means an equal force in the opposite direction is required. As it turns out, that will amount to a *lot* of energy. How much? $6.4\times10^{20} \text{J}$, which is about 11% of the world's total energy (oil) reserves. But what happens when you burn all that heat in a short amount of time? Liquid Santa is now setting off a continuous chain of fireballs, with a total yield equivalent to $1.5\times 10^{11}$ tons of TNT, which is more than enough to vaporize every child on Earth, and plunge the rest of us into a nuclear winter severe enough to have a deadly White Christmas, all year round! Anyway, I think that takes care of your cargo problem! [Answer] If people are living in a virtual reality, Santa will be a parallel process that can scale up as needed to handle everyone at the same time. Since the virtual realm will have been designed with Santa in mind from the ground up, there will be various hooks in place to support this. If the entire computer gets bogged down, then virtual time experience of everyone will be slowed to match. That might be a good time to perform annual garbage collection and system maintenance, anyway. In a post-singularity world where the population of software-based beings exceeds that of biological humans by orders of magnitude, but (some) people still cling to keeping minds that are recognizably human, there will still be human drives for expansion and pushing frontiers. Why would a new [polis](https://en.wikipedia.org/wiki/Diaspora_%28novel%29#The_Polises) get formed and attract beings to come live there? Religion and way of life is a historic human reason. Nobody ever started a war over Santa, yet it offers all the hallmarks of a deity. It makes sense that someone would design a society (polis implementation: data center + protocols, logistics, laws to live by) where there is a being watching everyone and acting with intelligence and his own agency, *but* clearly friendly and accepted as a positive feature. So why not personify Santa in this role? Then, it is a no-brainer to implement his annual visit as part of normal system maintenance. During the early design of virtual communities, there might be a process for tidying things up and monitoring. If ‚Äúhe sees you when you‚Äôre sleeping‚Äù to do the database compaction and resetting of resources, *somebody* will get the idea to call it Santa. And if you had what‚Äôs essentially an omniscient being privy to your thoughts as a necessary role of a glorified apartment superintendent, you would want to put a positive spin on the idea, and a whimsical not-to-serious modern deity is just the ticket that the marketing folks jump on. If money is made on virtual goods, like in game engines today, commercial promotional tie-ins will follow, and Santa can give away software-defined items to the inhabitants. [Answer] # The mall Santas deliver the presents. As Kevin McCallister (Macaulay Culkin) pointed out in the film *Home Alone*, Santa Claus is not one person; there is one representative of Santa in each mall. (This explains the Isuzu in the mall parking lot space marked "Reserved for Santa" and the change in Santa's handwriting after a child moves to live with another parent.) Kathy Benjamin reports that [some malls in fact have two Santas](http://www.cracked.com/blog/5-dumbest-things-people-are-getting-mad-about-this-christmas/). After the elves in Santa's Chinese workshops finish assembling the toys, they are shipped to distribution centers in each mall, where the mall Santas pick them up and go on to deliver the gifts to celebrating families. So here's how to calculate the plausibility of a single Santa's delivery run: 1. Find the "support value" of a mall (as defined in ["Medieval Demographics Made Easy" by S. John Ross](https://takeonrules.com/assets/downloads/medieval-demographics-made-easy.pdf)). "[The Mall Phenomenon](http://www.jcdecauxna.com/mall/document/mall-phenomenon)" counts 114,846 shopping centers in the USA, so I'll estimate 1 mall for each 3000 people. 2. Divide by the number of people per household, and multiply by the fraction of celebrating households. [This page on Statista](http://www.statista.com/statistics/183648/average-size-of-households-in-the-us/) says the average household size is 2.54 people, and the percentage of households with children is 43 percent. Subtract non-celebrating households, such as Jews, Muslims, Jehovah's Witnesses, other evangelical Christian types who think Santa is a pagan tool to distract from Jesus, etc. Also subtract families with juvenile delinquent children who top the naughty list. This leaves, again in nice round numbers, 300 deliveries per mall. 3. The article "[The Astronomical Math Behind UPS‚Äô New Tool to Deliver Packages Faster](http://www.wired.com/2013/06/ups-astronomical-math/)" estimates that a United Parcel Service driver makes 120 deliveries per day in a subsonic vehicle. But a UPS driver is stuck in traffic on surface streets and needs to take signatures, sources of slowdown that don't affect a Santa's Workshop driver. This brings 300 in one night within plausibility. [Answer] Let's think out of the box and imagine something really different. The North Pole is an allegory of a perfect stealth space station on a non-geostationary orbit (geostationary wouldn't be good, we will see that later). This space station crosses exactly one time zone every hour, this way it's always midnight on Earth when it's above this part of our planet. Reindeer is another allegory for an automated (and stealth) drone system for delivery, powered by methane extracted from all cookies collected each year and made from meteorites. Each drone will deliver one gift with a target GPS located and collect cookies for next year. Each hour, drones planed for the time zone just below are launched at midnight and come back with harvest. What do you think of this solution ? [Answer] Realistic high-tech Santa is from a future alternate timeline, and possesses a time machine, a molecular assembler/disassembler, and a quantum computer with near-infinite information density, linked into public records databases and social media outlets of today, as well as linked to all the research items of his own time. With these, he can trawl infinite Christmases at his leisure, instantly research the good or bad of any given child with ease, consume as many cookies as his heart desires, construct either organic or mechanical flight-capable reindeer analogues, create astonishing presents from the ashes in the fireplace, and still be home every night in time to enjoy a little nog with Mrs. Claus. 1. No fuel storage necessary; the molecular assembler/disassembler can handle that duty as needed. No special fuel, since he doesn't need to move particularly quickly. 2. No G's need to be resisted, since, again, he can move at perfectly reasonable speeds. 3. Pick your favorite method. They're quiet, so probably agrav tech of some sort built into the harness. Just happens to sound the same as jingle bells. 4. No sonic boom happens, so no need to cover it. 5. Molecular assembler has this covered. No sack necessary (unless you want the assembler in the bottom so it looks like he can reach in and grab the presents). 6. Again, no G's need to be resisted. Bonus: though unlikely given this level of tech, he can just clone himself and his entire kit to pick up the slack while he heads off to vacationland for a few decades off. [Answer] Disclaimer: Depending on your views on supernatural entities such as ghosts and spirits, the first portion of this answer may not qualify for a "realistic" Santa. Santa is real. Have you not felt his spirit get stronger the closer to Christmas Eve it gets each year? His spirit affects millions of people across the globe; spreading selflessness, cheer, and care for our common man. Even those who don't celebrate Christmas have their own versions of gift-giving and sharing caused by the spirit that Christians named Santa. --- More Physical Santa, going off similar idea: Chris Kringle had accidentally invented a bio-chemical weapon (*assuming virus from here on, but could be other things*) which flares up once a year, explaining much of his own selflessness as he spread it to others via "gifts". By targeting the human brain, it causes those affected by it to want to share and give things to others - which is how the weapon is capable of spreading easily. When being infected with the weapon for the first time, many see a hallucination of a older gentleman in Red and White, giving birth to the idea of Santa. Since the weapon is now wide-spread, most now experience this during their childhood. As they grow older, they rationalize the experience and don't even realize what really happened. --- In answer to the six questions: he doesn't actually need to accomplish those things physically himself, because he influences the masses of the world to accomplish those things for him. Santa is just the "influence", whatever that might be. *I realize this answer stretches "realistic Santa", especially when the title emphasizes "anatomy", but hopefully it still gives some ideas of how to make a realistic entity which causes gifts to be given to millions!* [Answer] **"Workers" in every home.** I think this plan is totally viable today with a decentralized model. He puts 1 or 2 workers in every home. They spy the children the whole time (with the child knowledge or not), so they know if a child is good or not. Even more, the workers have their own money to buy the gift for their respective children before the Xmas date, hide it in a secret spot and put it under the tree when the children are slept. Often the workers can be too fond of the children they spy, so they buy a gift for them even if they are not as good as Santa wants, which infuriate him but not enough to punish them or anything. How can Santa pay for all those workers? simple. Call them **Parents** and they will work for free. ]

[Question] [ As a way to travel fast, my Earth-like planet is going to have a special train, circling it (the axis of the 'tracks' is aligned with the planet's axis of rotation). The thing about this train - it never stops and it doesn't end - there is no first or last car, they are all joined in a circle. Moreover, it's actually several trains, going parallel to each other. The first one travels at the speed of 5 km/h, such that any healthy person can get on it. Then the second train travels at 10 km/h, and they are close enough so it's no trouble to step from one to another. The next travels at 15 km/h, the next at 20 km/h, etc. I think about 200 trains should be enough to provide the means of fast travel around the planet. Of course, there is the matter of travelling to and from the tracks. As for the 'other side of tracks, we just need a second set of slower and slower trains. The problems with this concept: * Safety of the passengers. If all the trains function perfectly, then we just need a system of safeguards in place so no one could possibly fall down or injure themselves while stepping between the trains. At the speed difference of 5 km/h even if there are some inner walls or support beams, it still should be safe enough. Now on the other hand, if there is some malfunction, the inertia could kill everyone in the fast moving trains. * Long time functioning of the train. To get rid of friction we could use magnetic tracks (or even tunnel), but it will take a lot of energy. On the other hand, is it possible to use centrifugal force from the fast trains to support the whole structure? How fast should they move in this case (we can make the inner cars heavier than the outer ones)? * What other problems could arise? Interaction with the planet's magnetic field, air resistance currents, etc? * Possible means of building the train: the materials (maybe carbon fiber, like space elevators?), the power, the infrastructure? (!) Important! The only thing I'm handwaiving is the tracks construction. Let's say we somehow managed to do it, despite the mountains, bodies of water, etc. Maybe under the surface, but I won't elaborate further. --- I hope the question is not too broad, I will accept partial answer as well. Probably the only question: how to make this means of travel feasible? I want to make this believable enough so the real fun about the societal implications could start. Can you imagine working as a conductor on this train? [Answer] While hopping on one moving train seems reasonable for a healthy young adult, hopping two hundred seems a little excessive and dangerous... Also I would imagine that most people going on a long distance trip will be bringing luggage. I'm sure I could jog up and on to a slow moving train unhindered, but a little less sure about doing so with a suitcase in each hand. And I wouldn't even consider it for a family holiday with the crumb snatchers. Beyond that you need to consider the fuel/energy costs involved in keeping 200 trains in constant motion, not to mention that each train completely encircles the planet. That's an awfully huge investment just for moving passengers. You couldn't​ realistically move freight from one train to the next. On top of the fuel costs you would have some pretty huge maintenance issues... The trains would cover the entire track, so making repairs to any one section of track means shutting the entire system down and removing several train cars before repairs could even begin. Likewise repairing and maintaining​ the individual trains would mean shutting down at least most of the system. Then there's the worst case scenario... Should any one of the trains derail you're looking at a really, really, really ugly domino effect. Your trains would have to travel really close to one another to allow passengers to hop between them... Imagine someone drops their luggage on the track making the hop. A hard metal briefcase slips under the wheel... The car tips just enough to bump against the next faster train, which in turn bumps the next, and so on... This tiny ripple could and likely would build into a tsunami of grinding twisting metal. See: <https://en.m.wikipedia.org/wiki/Derailment> --- [I sort of like the idea of an infinite train circling the planet that never stops](https://xkcd.com/1366/) though, so I thought up an alternative system. Rather than having 200 circumnavigating trains you could try 1, with several "feeder" trains. Basically you have your mainline (red), traveling at a reasonably fast and constant speed. Then you have secondary or feeder trains (blue) like so: [](https://i.stack.imgur.com/SkuTS.png) Your red line never stops, but your blue lines more or less behave like normal trains. The blue lines make regular stops at stations, load passengers and freight, then speed up to match the speed of the red line for several miles allowing for a "hard dock" procedure to take place between the two moving trains where passengers and freight are passed between the two trains. This sort of system could minimize some of the aforementioned safety concerns and would require substantially less energy. [Answer] A similar concept has been mentioned in other answers, but one way to make a train like this viable would be to have pods at stations that "dock" with the main train rather than many trains running at different speeds. There would be a period of acceleration followed by the pod locking on firmly. Here's [an example where a pod docks to the top of a train at each station](https://www.youtube.com/watch?v=0DfDOlUXEBo&feature=youtu.be&t=46s). [](https://i.stack.imgur.com/sWnuU.gif) Passengers would then move down from the pod to board the train. The pod then unlocks and decelerates to zero just as it comes to the next station. While the pod in the animation is shown on rails, this could easily be another type of vehicle. One example could be an autonomous drone that performs roughly the same motion as the pod on rails, but hovering slightly above the train without a second set of rails involved. This would simplify the system physically, and take advantage of modern advances in computing. The core concept here is that you want to accelerate a small mass to meet up with the large mass, constant velocity train for reasons of energy efficiency. [Answer] Track maintenance: This one is actually easy to address. Everyone is stuck on what a train is: two wheels on two rails. Lets make a different train: Four wheels on four rails. Now the maintenance crews can come along underneath and remove (carefully!) any section of rail and replace it. Likewise, a crew on the train can open a panel and lift out any wheel. With sufficiently modular construction every moving piece can be replaced while the train is in motion. This reduces the problem to dealing with corrosion and metal fatigue in the frame of a train part. To solve this you have some special train cars that takes an entire car in, lifts it off the track for the heavy maintenance or even total replacement, and then puts it down and advances to the next car. Safety when crossing to the next car: Lets put some more wheels on the train--this time on the side. In addition to the ground each car rides "on" it's neighbors. This is purely to keep a very precise spacing compared to that neighbor--the gap between the cars is a small fraction of an inch. Note that you will have to have thermal expansion capability elsewhere in the car or the whole thing will become a spectacular disaster if it warms up. 5 kph is a small enough difference that a healthy adult would have no problem crossing the divide. It should be no harder to navigate than current-day slidewalks are. However, this would be a big problem for the young, the elderly and the infirm or disabled. You would be forcing an awful lot of people into power wheelchairs that would otherwise be quite capable of moving on their own. Also, it would take an incredibly peaceful world for something like this to be tolerable. Imagine how destructive a bomb in the middle of things would be. I also have a hard time imagining the traffic volume that would make a system of this nature make sense. For the cost of a system like this you could build a **huge** number of stations along the lines of what ([jrcraton](https://worldbuilding.stackexchange.com/a/73901/264)) proposed, except with multiple tracks moving at different speeds. (The faster tracks would have stations farther apart. (Your 1000 km/hr track has a minimum distance of 10km between stations assuming a system with different capsules being boosted and slowed. I'm figuring a half gee on the boost.) If you don't like his system of the capsule riding above simply have separate powered train cars. The car boosts on a parallel track, when it's going fast enough it switches over and connects to the head of the train. The tail car is dropped and decelerates into the next station. (Two tracks mean 20 km separation for a 1000 km/hr train.) This does require passengers to move about on train although they need not move all that fast--every car would have a big electronic board saying where it was going, if your car is in the train you sit down there. If it's not you have to keep walking forward at the rate of one train car every minute. (Which suggests there would be some slow trains--the station spacing would be longer than normal, lower boost and a lower walking speed needed to stay ahead of the shedding tail.) I've come up with a better way to build the trains: Build two types of train car. One car is for getting on and off, one is for travel. You get on a train car, it's boosted to the speed of the target train and gets in front of it where it couples to the train. The main travel tracks have **4** rails, not two, the boarding car rides on the inner two rails. The outer two rails hold another car that is always moving at speed and surrounds the boarding car. The boarding cars move **slightly** slower than the permanent ones so they slowly slip to the rear, the speed would be something like one car length per minute. Once the boarding car is within the main car you can step over to it. The main cars hold things like restrooms and perhaps some shops. Each boarding car has a sign indicating where it will go when it detaches, when your objective shows up you go sit in that car. The main trains would come in various speeds, the track layout alternates between the two rail tracks for the boarding cars and the four rail tracks of the main lines. The highest speed train probably would only be accessible by boarding cars switching from a lower speed train. Conventional light rail reaches a capacity limit based on how long a train has to sit in a station for loading and unloading. This system, however, can support a huge number of trains on the track, although any given station will still have a capacity limit (albeit much higher than for a conventional design) and the need to provide frequent stations doesn't set a speed limit on the overall transit. I think four trains would be about the practical limit: 20 km/hr, 80 km/hr, 320 km/hr and whatever the engineers can do without causing mach problems. [Answer] With 200 trains and a 5km/hr speed difference between them, the fastest train is only going at 1,000 km/hr. That's barely faster than a passenger jet, which goes at about 870 km/hr, which doesn't seem to be worth the considerable effort and inconvenience. [Answer] You would need a lock system where persons traveling from train to train would step into a pod. Once the doors closed behind you, the train your passengers are on would send a signal to a pod on the destination train to have a matching pod extend to the current train, once the two pods aligned, the source pod would be pulled from the source train closer to the destination train. When the passengers departed from the pod to the destination train, the doors would close behind them and the pods would extend back out, and deposit the pod back to the source train. Each train, on it's source side could have tracks and gaps to allow for repositioning of the pods. This system would provide complete safety while transferring from train to train as even someone in a wheelchair could do it. [Answer] No matter what kind of system you use, maintenance is necessary. Maintenance can be broken into two categories, maintenance of the cars and the tracks. Apaul's idea about having a separate speed matching train just for boarding makes maintenance, much, much easier. The system of hundreds of parallel trains means that the inside trains and tracks are completely inaccessible. If you have a feeder train for boarding passengers, why don't the feeder trains swap out entire cars? One or more train cars exit the track and are simultaneously replaced by new cars, with new passengers and new cargo. This allows the cars to be removed for maintenance. This presents some engineering challenges, such as catastrophic derailment, but you have figured out a global train system. I assume your engineers are up to the challenge. To make the engineering challenges easier, make the train capable of having cars missing. In a conventional train, removing one car while the train is moving disconnects the whole train. This train has a linkage on top that stays when a train car is removed. This linkage bridges the gap when a train car is removed, and transmits the tension force that the missing car would have been carrying. The train should be able to function with a decent fraction of its cars missing. In order to maintain the tracks, have two sets of parallel tracks and the train can be switched from one set to the other set. [Answer] Lets assume we somehow manager to make something like this. The fastest train would be travelling at 1000Km/h (200\*5). To get down from the train one has to cross all the 200 trains again. In addition to that if there is a delay in switching trains (especially if he is on one of the fastest trains) a person will miss his station and would have gone far away by the time he reaches the slowest station in order to get down from the train. [Answer] I started this post assuming the idea of building that many train cars was ridiculous. It turns out that it may crash the world economy but the material is actually there. --- I'm posting this as an answer instead of a comment simply due to the length. My numbers all come from the internet so there's a grain of salt in all this. I am not a train engineer; I am a toast engineer. Your trains may easily be more advanced that the current Amfleet so they can be lighter, but let's see what happens if you build a single, circumferential train with today's technology. **DATA** Train Car Weight: $49,500$ kg avg. ([source](https://en.wikipedia.org/wiki/Amfleet)) Train Car Length: $26.01$ m ([source](https://en.wikipedia.org/wiki/Amfleet)) Train Car Max Speed: $201$ km/h ([source](https://en.wikipedia.org/wiki/Amfleet)) Earth's Equatorial Circumference: $40,075.017$ km ([source](https://en.wikipedia.org/wiki/Earth)) Earth's Crust's Mass: $2.6\times10^{22}$ kg ([source](http://nineplanets.org/earth.html)) Delta in Train Speeds: $5$ km/h ([source](https://worldbuilding.stackexchange.com/q/73861/7345)) % of Steel that is Iron: $90\%$ min ([source](https://en.wikipedia.org/wiki/Steel#Carbon_steels)) Annual production of iron: $1.1\times10^{12}$ kg ([source](https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust)) (2012 data) **CALCULATIONS** (Numbers shown are rounded for simplicity but calculations used the precise values given above.) Cars required to encircle the equator once: $\frac{4\times10^7m}{26m}=1,540,754$ Total mass of those cars:$1,540,754\times49,500kg=76,267,323,000kg$ Number of tracks required to reach max speed: $\frac{200 km/h}{5 km/h \mathrm{\ steps}}=40\ \mathrm{tracks}, 79\mathrm{\ for\ mirrored}$ Total mass of all cars on all tracks: $(7.6\times10^{10}kg)\times79=6\times10^{12}kg$ Mass of iron in the Earth's cust: $(2.6\times10^{22}kg)\times5.2\%=1.356\times10^{21}kg$ OK, so we have 225 *million* times more iron than we need. That's good. Considering that some of the car's mass is other material like fabric, electronics, and wood, we actually have an even higher safety margin. How long is it going to take to get that much iron, though? At the 2012 rate, it would take only $\frac{6\times10^{12}kg}{1.1\times10^{12}\frac{kg}{yr}}=5.5\ \mathrm{years}$ of consuming all iron production in the world to have enough for your train system. That's surprisingly reasonable although it would have a drastic impact on the economy. You could reasonably spread the project over decades since it will take so long to actually build the thing and that would lessen the impact. [Answer] One problem is getting scissored in the doors between trains moving at different speeds. You might want to consider getting rid of those doors completely by using the moving roadways from the Heinlein story Jeff Zeitlin mentioned but have covered sections to protect against weather/wind. An alternative would be to have a covered center section and a open "hallway" on either side. To be even better, have sections of the hallway (or the whole thing, if you are being generous) move to bring it to the halfway point of the speed difference. One issue that i see here that I don't recall Heinlein dealing with would be the weather generated by the trains. The trains would create prevailing winds around the globe that might spin hurricanes off either side (look at the closeup of Jupiter's bands). Also, unless you can get over or under this train, it becomes a barrier to travel from north to south. [Answer] It maybe would be safer if every second train shifts between the velocity of the two trains on each side of it. Train 1: Stops in 1 minute, 10 km/h in 1 minute. Train Train 2: Always 10 km/h. Train 3: 10 km/h in one minute. Then 20 km/h in one minute. Train 4: Always 20 km/h. ...and so on. During the minute the trains has the same speed it is easy to walk between them. Then the doors closes when it's time to change speed. With this variant you could have much higher difference between the trains, maybe only having two trains: one that never stops and going at very high speed, and one that accelerate up and down. Then every passenger only needs to accelerate one time and decelerate one time, during there travel. [Answer] What is the distance between stations? Whatever it is, the **passenger** (possibly elderly or disabled) needs to be able to mount on the train at station A and dismount at station B in less time than it takes for the train to move between A and B. Otherwise he won't be able to get to the intended station. To achieve low transit times we need a speed of at least 1,200 km/h, and this requires shielded tracks, possibly underground. Also, this way we stay subsonic. The user enters a stationary car and the car starts accelerating at 1 m/s, which is quite typical for metro trains - you don't want to do more than that, I think - and in six minutes you're going at full speed. In those six minutes you've covered about **sixty kilometers**. Supposing the stations are twenty kilometers apart, you need at least three "acceleration lanes" for cars to dock with the train (better make that five or even six). You will also need as many deceleration lanes for cars to undock from the train and reach the stations. Is this enough? No. Once the user is on the train, **he needs to reach the undocking car**. How long does this take? It depends on how many cars are there on the train. Logically, the car will have docked near the cars undocking next, so that if you want to do a short hop, you just need to stay in the same car: ``` Station Detach Accelerating Docking Detach Decel At station Abel A Baker B A Court C B A Dewey D C B A Earl E dock D C B Fawn F E D C A Green G F E D B A Hall H G F E C B A Ivy I H G F D C B A Jeans J I H G E D C B Kell K J I H F E D C ``` So you mount at Abel, dock with the train while the train is passing Dewey, let people disembark that are not directed to Ivy while Earl goes by, detach from the train at Green, dock again at Ivy. The next car departing from Ivy will be Abel's car. If you mount at Abel and want to go to Kell, you need to exit the A car, you pass by the B car that's now docking, you reach the C car that's flashing "INBOUND FROM COURT - OUTBOUND TO KELL", and sit down. At 1000 km/h, the train passes each station every 1.2 minutes, so this (plus the disembark time - another 1.2 minutes; but we can play with that) is the time it must take you to move from one car to the next. Also, you can take about six minutes to sort yourself out to leave the car *before* it docks. For "metro" style of travel, provided it's not rush hour, this is probably enough. Otherwise we need to provide a longer dock time; but every 1.2 minutes we give it's another station that flashes by. So what if you are at Abel and want to go to Hall, instead of going to Kell? You can't. The minimum is eight stops, and Hall is seven. What you need to do is to take the **opposite** train and travel to Nook, eight stops sunwise, easy travel - sit down, get up. From there you disembark and take the widdershins train to Hall, fifteen stops. You need to "walk" 15-8 = seven carriages, exactly the number of stops between Abel and Hall. Basically, when you arrive in the train, you find yourself in a hall/corridor with doors marked "Hall", "Ivy", "Jeans", "Kell" and so on. And the section of corridor you're in starts to darken :-) - after four cycles it will light up again but it will now say "Storn". A travel will involve either going forward for a maximum number of stations given by acceleration time + deceleration time + docked time, or sit in the hall/corridor the required number of "cycles". All things considered, it might be interesting to design the train as a luxury shopping mall with sleeping accommodations. You can wander the "travel area" and in about 22 hours you can be on the other side of the planet. Basically you would have two very large tunnels (or tubes, if outside), one for each direction. Each tunnel is divided in one "fast" part with one carrier lane, and one "accelerating/decelerating" part with several lanes. The cars leave the station and accelerate; if everything is OK they leave the accelerating lane after matching speeds with the train, and dock with it. Otherwise they proceed in the decelerating lane towards the next station. The "fast" lane would have a series of carrier trains running one after the other. To get one down for maintenance, you stop accepting carriages to it (all departures are delayed by one inter-train period and cars attach to the carrier train coming immediately after), send off all carriages until it is empty, then detach it from the line. Inter-train period must be at the very least the time required for the carrier train to emergency brake and the whole world line to come to a stop. [Answer] You need to make the tracks immune to flooding, earthquakes & other accidents & 'acts of god.' With one contiguous rail system using a single route.. a single such localized accident would shut down the entire world economy. The single 'circular' line would be more practical on a space station or suchlike where the environmental conditions are entirely managed. The pod idea referenced in other answers would need to have the pos accelerating to catch up not simple because transfer is otherwise implausible, but because if you suddenly accelerate a person from 0 relative motion to 1000km/h (or vice versa) they die, it's as simple as that. So far as energy efficiency and such-like are concerned, you're still having to accelerate each pod/car on and of to the central rail.. and whether you achieve that sequentially or in a single hop the total required acceleration is the same. We still have the problem of local transport (unless the entire populated area is along the equator, which is feasible of course, the climate of the planet might require it, or etc.) But on a planet like earth we have non-contiguous land masses that aren't served at all by this method. Just problems, yes, but hopefully they'll help you refine your final answer. Perhaps the train line is in a hermetic system tough enough to withstand any conceivable trauma, underground and self-supporting to such a degree that earthquakes that shift entire geographic regions up and down by a meter or so don't disrupt the system. The tunnel is a vacuum like elon musk's proposal so as to reduce energy costs for acceleration & deceleration of cars. Vacuum also reduces corrosion effects, so you're only having to repair under normal conditions for mechanical erosion as opposed to rusts and such. Of course though, if you have a breach of any size on a world-spanning vacuum tube..well.. the consequences would be pretty massive. [Answer] # Use conveyor belts rather than traditional trains Depending on what your definition of trains is, you may consider another option which is IMO safer. Each train is actually nothing but a conveyor belt with seats placed on it. There are no walls or a roof. So you have a large number of conveyor belts running at different speeds, each with a width of some 5-10 metres. The seating can be a lot more spacious and your species could even live on the belts if they aren't prone to road sickness :P It is easier to transfer yourself and your luggage across parallel conveyor belts rather than trains which have walls for obstructions. Handholds can be provided to make it easier to maintain one's balance. An even safer (but costly option) would be to have automated wheel chair seats at the borders of each belt. You just sit on the seat, push a button, and it manoeuvres itself onto the next belt by clinging to supports. You get off the chair and sit on a normal chair. If you don't want to roll your luggage across, you can place it in another box that also makes an automated manoeuvre to the next belt. P.S. I was just thinking, sitting on such a belt would be fun; watching people nearby moving at different speeds. P.S.2 If having continuous electricity to run the belts is expensive, one can divide each belt into chunks, each chunk being a few hundred metres or a few kilometres long and pulled by a single engine. The engines act as links within each belt, like a kind of chain. It might be easier to adjust derailed belts or replace old belts in such a setup (as opposed to a single infinitely long belt). ]

[Question] [ In a world where gods can be seen by the inhabitants of that world, how can multiple religions even hope to form? If the gods choose to show people that they exist, regardless of area or person, I fail to see how the worshipers could believe different things. If gods are proven to exist, how can there be different religions? --- This [question](https://worldbuilding.stackexchange.com/questions/10017/how-would-society-react-if-the-existence-of-a-god-was-scientifically-proven) is asking how society would react, including what followers of other faiths would do if god suddenly appeared. I am asking how other religions could form if gods always were around [Answer] In this world, theism involving the proven gods would map approximately to atheism in our world. Using this comparison, there are a couple of ways to proceed: **"Yes, but where did those gods come from? Did someone create them?"** This is cool, because you actually have precedent. Someone created this universe. We know that for a fact, and we know who it was. Who's to say this didn't happen recursively? After all, humans created The Sims. **"The so-called 'Gods' are nothing but liars. Here's what really happened..."** We already have people saying scientists are making up lies for the money (what money? I dunno). What's to stop this happening here? Or further along those lines: **"There *are* no gods! It's all a plot by Big Theology!"** Not sure if conspiracy theories count as religion, but they can surely be taken to those levels. **"I worship Thor only. Really, all the evidence says he created the universe by himself. The others just pressured him to say otherwise."** We have a variety of religions on Earth that came from the same origin. Why can't that happen here? In addition, they'd likely be treated the same way we treat celebrities; with limited information and blind cherry-picking. **"The gods are not worthy of worship. Nature/enlightenment/the Sun/something else is!"** Not all religions focus on gods in the first place. They would still exist. **"Who? I haven't heard of them."** Maybe they lived in a third world country or one with tightly controlled information. Maybe they're a hermit or live in a tribe separated from the rest of humanity. For whatever reason, they simply haven't heard yet, and they have their own guessed answers to life, the universe, and everything. I'm sure there are other ways to take this, but mostly it comes down to people not believing what they're told, no matter how scientifically accurate. This would be as true of that world as much as it's true in this. [Answer] I see 2 solutions here. **Devotion to specific gods rather than the pantheon as a whole**, called [henotheism](https://en.wikipedia.org/wiki/Henotheism): the belief in and worship of a single god while accepting the existence or possible existence of other deities. To a henotheist, entities worshiped by other people can be dealt with a few different ways: 1. They aren't really deities, they're just powerful malcontents tricking people into worshiping them (e.x.: Satan in Christianity) 2. They are really deities, but they're evil and should be opposed (e.x.: Ahriman in Zoroastrianism) 3. They are really deities, but they're the deities of a different place / people / philosophy and so are improper to worship (e.x.: ancient proto-Judaism) 4. They are really deities, but they're just manifestations of my deity (e.x.: various philosophies within Hinduism and Hellenism) Each different henotheistic religion can have a different attitude or attitudes towards each other sect. And none of them necessarily have to be "correct" from your omniscient authorial point of view. **Reverse syncretism**. In ancient Greece and Rome, there was a tradition called Interpretatio graeca, where they identified foreign gods with Greek or Roman gods. The idea was that well, obviously our gods are real, and we know what they're like and how they intervene in the world, so obviously everyone worships them, even if they have other names for them. This resulted in things like the Romans reporting that the Germanic peoples worshiped the god Mercury, which was their interpretation of the god Odin. Since your gods are real and do intervene in the world, different peoples are going to understand them in different ways. They'll give the gods different names, and worship them in similar but distinct ways. Perhaps one god appears more often in the north than the others, and comes to be considered the greatest god by the northerners, while another god spends more time in the desert and is revered by the nomads, etc. [Answer] It's very easy to have different religions in an area where gods have been proven to exist. In fact, its so easy I'm not even sure how to write an answer about it. I would go so far as to say that having different religions would be the **norm** and it would be exceptional for there to be only one religion. As an example, consider those who truly believe that there is a God. We can single them out and create our own little universe out of them. Very quickly you'll notice that even though the Jews, Christians and Muslims all claim to have the same God, they absolutely have different religions surrounding them. That's not to consider the other religions who claim to have a different God all together, or gods, or any other variation. The key question would be how much effort the deity is taking unifying people and stomping out misinformation. If your deity is spending an extraordinary amount of effort interacting with the world on a daily basis, the people are going to be pretty unified. If your deity does yearly checkups on the world, they're going to be generally organized, but you may see some divisions as people interpret their statements differently. If your deity throws a book at your world and says "here ya go, good luck!" you will find a remarkable amount of disagreement in interpretations. [Answer] Let’s try the reverse: In what world would there **not** be different religions? *In this world, no god has any enemies or rivals among the other gods. The gods have a unified vision of what religion should be like, and they have unambiguously communicated this to their followers. They are willing to demonstrate their power whenever some human doubts them, and they put an end to all false prophets who claim a special revelation from the gods, as well as to all who promote a variant form of the gods-approved religion.* Human nature being what it is, I think even in this scenario, people would rebel against the gods’ overwhelmingly oppressive presence. But they would probably agree on which gods exist and what they want humans to do. Now, let’s change some of these variables: Maybe the gods fight among themselves, and encourage humans to only venerate their group (or one individual god). The groups might demand very different things from their followers, so their religions could look very different. Or maybe the gods don’t fight, but do have different opinions about the world. So one god might encourage people to fast, while another tells them to feast. Over time, people would flock to the different gods the same way people in the real world adhere to political parties — they’d follow those whose opinions they prefer. Even if the gods do all have the same instructions for humanity, there could be some squabbles among humans about how exactly to interpret those instructions. Or those instructions do not cover every aspect of human life, and different religions form around the various ways to fill in the blanks. These religions would certainly be more similar than the real world’s religions, but to the people practicing them, their differences would be just as important. After all, these are the biggest theological disagreements that exist in their world. Even if there is universal agreement about who the gods are and what they want, there could be different religions. If the gods don’t crack down on that kind of thing, sooner or later people will get philosophical. And some of them might come to the conclusion that while the gods certainly exist, the thing humans should actually focus on is something else. Maybe there is a transcendental spirit of which the gods and all other things are manifestations, and the real goal is to become one with that. Or maybe all phenomena are illusory, and it’s best to practice non-attachment so as to escape from the world of phenomena. Just because there are gods, doesn’t necessarily mean every religion has to focus on them. And of course, it would be very difficult to construct a proof of gods that couldn’t possibly be explained any other way. After all, if the gods reliably provide some effect (for example, they answer prayers or strike down blasphemers), that makes them a phenomenon that can ultimately be studied with science. And if they only occasionally perform miracles, stubborn people could dismiss those as coincidences, illusions or superstitious nonsense. And even if the gods themselves obviously exist, whatever they tell humans about the world might not necessarily be true. So as long as the gods don’t actively persecute unbelievers, unbelievers there will be. [Answer] Something interesting to look at as an example would be the Elder Scrolls universe. In the Elder Scrolls, there have been numerous proven examples of Gods walking among men, influencing their actions, and leading them to crisis. However, not all of these deities are worshiped, and many are worshiped differently by different races. In particular, all races believe that the Daedric Princes are real deity-like creatures, and several have directly influenced the mortal world (Mehrunes Dagon caused the oblivion crisis.) However, most races on the mortal world do not worship these Daedric Princes, some because they don't want to be worshiping such malevolent powers, and some because they simply don't "do" religion (despite overwhelming evidence to the contrary.) Instead, the race of man for example worships the Aedra who they believe to have created man and in particular Akatosh, who they believe saved them from the Daedric Princes. (I say believe here because although it is strongly alluded to that this is the truth, it isn't made as clear what their influences are as there is less contact with them than the Daedric Princes.) Even among worship of the Aedra, there is not a consensus among who to worship. The Aedra are commonly called the Nine Divines, even though there were originally only eight of them. This is because of a great man name Talos who united an entire continent together in the Elder Scrolls world. He had such an influence and so pleased the other divines, that he "ascended" to god-dom. However, this is not agreed upon among all races. As is the case in Skyrim, Talos has been mostly stripped of his rank of deity because of political conflict from other races who don't want to worship a former man. Another race to look at are the Dunmer (think elves) who have their own religion known as the Tribunal. They worship living gods who led their people until several devastating events which reverted the Tribunal members to Saints, and began worship of the Daedra. If you haven't looked much into the Elder Scrolls universe, than I would highly recommend it. Even though it gets a reputation sometimes as being a commercialized RPG, the amount of time they have spent into crafting in-depth lore which carries over between games and has remained consistent throughout the life of the series is staggering. There are a lot of helpful insights to be found from looking into it a bit more. tldr: There may be multiple "levels" or classes of deities who can have different impacts on the world, people might just not be interested in trusting Gods, or certain Gods may be more benevolent than others (putting faith in just Gods rather than trying to appease immoral ones.) [Answer] "How can there be people who believe in flat earth when it has been proven to be round?" Sometimes there are people that just like to be different and think that there's some grand scheme behind everything, and that everyone is controlled/trying to control others. They will come up with stupid theories and amaze us with their stupidity. That's how it works. Anyway, second options is that science isn't that good. Look at the history of science; what we call the scientific method and what we call science differs from what we called science 1000 years ago. [Answer] Easy: people of faith will refuse to accept any evidence including that implied by your Title statement. Just read the “statement of faith” on any website for a religious-centered organization. E.g. (taken at random from a Google search) > > WE BELIEVE the Bible, both Old and New Testaments, is divine revelation and the inspired Word of God inerrant in the original manuscripts. Its teaching is the final authority for all Christian life in matters of faith and practice. > > > So if something different is proven tomorrow, these people will just carry on as before with no change. My point is that there will be some people (the most faithful) who won’t put any special effort in reconsiling their views with any new information. They already “know” the answer and simply ignore the new data. [Answer] Different religions might disagree on which God is supreme. They could be believe one God is the king of the gods or at least the most powerful of all other deities they would consider the others to be as lesser or subservient gods. Alternatively different religions could only recognize one particular God and view the other deities As Angels, demons, Saints and other forms of spirits, but not gods. For a real world example consider the way Jesus is viewed differently by Christians and Muslims. [Answer] One might argue that this condition applies to the universe you and I live in... depending on how one defines the term "God"... and that therefore the answer you're looking for can be found by observing our own - real - universe. You see... 1. Humans aren't pure rational creatures. Much of what a typical human believes in is based on emotional biases rather than rational thought. As a consequence, there is no obvious relationship between what is proven and what the average person believes in. 2. "God", "consciousness" or "soul" are examples of rather vague concepts that are defined differently by different religions, and even by different followers of the same religion. Due to the different definitions, many religions that seem incompatible at first sight actually are compatible when going deeper into the meaning of terms like "God", "consciousness" or "soul". In fact, I find it impossible to distinguish [Atheism](//en.wikipedia.org/wiki/Atheism), [Polytheism](//en.wikipedia.org/wiki/Polytheism), [Pantheism](//en.wikipedia.org/wiki/Pantheism) and [Animism](//en.wikipedia.org/wiki/Animism) from each other at all other beyond the level of mere semantic differences. See my article [The Atheistic approach to God… or how to bridge the gap between Atheists and Theists](//medium.com/@johnslegers/the-atheistic-approach-to-god-5ae3f2b0012b), where I elaborate on this in greater detail. [Answer] The answer is cults (in the technical sense of the word). If the Gods walk among us, and communicate, there will be broad agreement on cosmology: actual *belief*, in terms of the structure of the universe and the place therein of Gods and Humanity. However, there may well be groups focussing on the reverence of specific deities. People may dedicate their lives to this God or that God. There will be a temple to Offler down the road from a temple to Blind Io. And while all this is, technically, the same religion, the structure and form of worship and devotion can differ massively from God to God (and from place to place: the same God may be worshipped differently in different countries). The interesting question would be how Gods compete for followers. Are you born into a specific cult? Do you choose it (and on what basis)? Are the cults completely separate, or is there any time in which you might visit a different temple? Do the Gods have certain competencies? (Do sailors pray to the Gods of the Sea? Do farmers give sacrifices for a good harvest?) Or perhaps different Gods are worshipped by the populace at certain times of year. Are there certain high holy days when a specific God is reverenced? (Even so, priests would probably be attached full time to a certain God, throughout the year.) How do the Gods interact with their followers? And with each other? Are they jealous of other Gods, with more followers? Are there fights, maybe even wars? (If so, expect the distribution of worshippers to be largely geogaphic.) [Answer] Many people are fan/fanatics of a particular sports team, holding it to the best the best team in the league, even as other fans have similar allegiances to different sports teams. Your world may have a pantheon (or league!) of gods each with their own fanatics. Adherents don't deny the existence of the other gods - they just don't think they are as good, for the same reason people like different ice-cream flavours. [Answer] Your question assumes that the main function of a religion is proving that God or gods exist. That's a way of looking at religion or faith that's only become current with the successes of modern science. Throughout history, and for most people, religions and various forms of faith are the answer to the question, 'Given that God (or gods) exist, what does that mean for us, people, specifically in how should we lead our lives and treat one another?' People will always differ in their answers to this question. [Answer] **Because people interpret information they are given differently** They also disagree about everything, even things that are proven, even things they can see, even things they can ask questions & receive answers from. "Proven" doesn't mean "accepted". Even assuming the gods had been around for all of recorded history, this comes into play - people disagree about what shape our planet is, among other things - and it's always been here. Even things taught from birth are eventually questioned, often during adolescence. And of course there's always the possibility of the gods being malevolent, or uncomunicative, or fighting each other... Under most circumstances, even if gathered with their own eyes, evidence that gods exist would be open to interpretation and would be interpreted differently by different people. As an example, we know from pictures and the word of others than the moon landings happened - this is taught in schools, and is accepted knowledge of something that happened before many of us were born, so it's always been there. But there are plenty who argue they didn't, evidence was falsified, etc. Plenty of those were born after the events in question. Regardless of whether you credit those people, the point stands that they do not accept information that others did, and have found alternate explanations for the evidence they received. Gods exist.... but mine is better than yours. This one is pretending. I don't like this other one. They are all aliens. We're the aliens and this is their planet all along. They are manifestations of the religious people wanting to believe in a god so hard their brain-energy created one. It's a robot. They are just another species with different abilities. The whole thing is fake, they don't exist. My one created your one so mine is the real god. I could do that with a top hat and a deck of cards.... ad naseum. [Answer] Different groups of gods hang out in different locales. So up North you've got the gods of ice, wind, cold, and naked sauna-bathing, while down South you've got the gods of heat, sand, beach-wear, and ice-cold beer! In the East they're all into mysticism and clam-digging while out west - yep, you guessed it - the gods who are worshiped by the masses are those who are concerned with surfing, earthquakes, and mall-shopping, fer sure! In the middle are all those dull, boring, fly-over gods who are worried about dull/boring stuff like growing corn and raising hogs and such. And - good news, priests and priestesses-to-be - THEY ALL FIGHT WITH ONE ANOTHER! "Damn those gods of the Western Pantheon! Bunch of feckless bastards! HOLY WAR!!!!" scream the Eastern priests, and thousands of their clam-juice-dripping-from-the-corners-of-their-mouths devotees go storming across the continent to take on their tanned surfer-dude counterparts. "Dang them Northerners! When they wuz down here a-fore they done STOLE all our hot tubs and took 'em back with 'em! KILL 'EM ALL!!!!!" cry the Southerners, charging north to take on their counterparts. "Gentlemen! Ladies!", cry the Lords of the Central Plains. "We're tryin' to grow us some soybeans here!". And off THEY go in every different direction in the name of Mom, Apple Pie, and The Great Cornucopia In The Sky! Best of luck - and slay the unbelievers! :-) [Answer] You assume the gods agree. Try the basic world of Dungeons and Dragons. There are multiple **competing** gods. It's obvious that not everything the gods say is true--there are multiple competing creation myths, for example. Or consider Harry Turtledove's *The Case of the Toxic Spell Dump*. We don't see much of the big picture but there are certainly multiple gods competing for worshipers--a god without worshipers dies. Note the key element in both of these examples: the gods are not all-powerful. (In fact, in the second example some severely weakened gods are slain by human action.) [Answer] Religions form due to the inhabitants interpretation of what the God might teach or represent, regardless of how the inhabitants interact with him/her. A "God" may write a book and make that book the original standard teachings of that religion. But as long as the inhabitants are natural men and women, the teachings found in the original work are bound to be interpreted in many diverse ways for the benefit of themselves. Thus we see so many different religions. [Answer] You walk to the kitchen, open the fridge and look at your beer. "I got all the beer in the world, right in my fridge" you think. And you're obviously right. How can there be more beer than the ones you see in your fridge? Unless there is a law of nature (assuming gods still abide by them) saying all gods have to show themselves to everybody, you can always believe there are more gods that you haven't met. And thus faith arises, and in it's wake a new religion. [Answer] **How can religions exist in a world where there is little to no credible scientific evidence of any its claims?** *Because religion is not rational.* Proving something scientifically does not always or even often change the public perception. Man made climate change is a scientific fact - backed by an overwhelming consensus. But there are many people who still dispute this - [one of them may become president](https://twitter.com/realdonaldtrump/status/265895292191248385?lang=sv). When you up the ante and add religion into the picture people seem inclined to believe / or not belive in claims with less rational thought and seem far more inclined to rationalize in order to not question their preconceptions. So unless this god zapped all the unbelievers instantly he would probably have to deal with ignorance, doubt, stubborness and all the things that make us human. [Answer] A reasonably sophisticated conspiracy theory is indistinguishable from a religion. Practical experience shows us that despite of the enormous success of sciences and medicine there are lots of adherents of conspiracy theories in our world. There is no reason to assume things will be different with powerful gods in the place of medicine: Conspiracy theories will prevail and may turn into alternative religions. ]

[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. In my story, I have a small extended family of 30 to 40 individuals ranging in age from 0 to 50 who are on the run from Chinese and Japanese forces in 1400AD. No place in Asia is safe for them. By a series of lucky chances they have found a very quiet location that appears to be untouched by humans. Escaping by getting out to sea is of the utmost importance. Trade of any kind will give them away so they must do all their preparations in secret and by themselves. They have access to plenty of wood and iron ore deposits. Their location is sufficiently remote that they have up to 5 years to complete their ship and get out to sea. The refugees are traders, not craftsmen or metalsmiths. Iron is known to them but they don't have anything other than introductory knowledge of how to smelt iron or form tools. *What will they need in terms of construction supplies and construction facilities in order to build a ship strong enough to get them across the pacific? How likely is this little band to pull of this kind of a project?* Commentary about provision requirements to put in the ship or the required ship size is also welcome. **Equipment List** * Small herd of horses, 5 cows and 1 bull. * They have the iron tools required to maintain their tents and herds but they don't have any blacksmith tools. (They were in a bit of hurry to get out and didn't bother to kidnap a blacksmith or shipwright.) * Ceramics are their primary eating and cooking implements. Note that this is a [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") question. You must account for the laws of physics when figuring out the size of the ship, the nutritional and water requirements of the crew. If you must handwave, please provide some justification for your guess. **Helpful Information** While the following information is unknown to this little band of fugatives, please incorporate it into your answer. * It takes about [2.5 years to drift](http://iprc.soest.hawaii.edu/users/nikolai/2011/Pacific_Islands/Simulation_of_Debris_from_March_11_2011_Japan_tsunami.gif) from the shores of Japan to California so their voyage won't take any longer than that. * They don't know it but they are attempting to get from Japan to the West Coast of the United States along the northern portion of the Northern Pacific Gyre. [](https://i.stack.imgur.com/0UEcB.png) [Answer] ***They fail and suffer whatever evil fate awaits them.*** ...or this [](https://i.stack.imgur.com/AkFAz.jpg) I say this mainly due to this pre-condition: > > The refugees are traders, not craftsmen or metal smiths. Iron is known > to them but they don't have anything other than introductory knowledge > of how to smelt iron or form tools. > > > Having all the natural resources is great, but they have no knowledge of ship-building, metalworking, sailing (at least not across the ocean), astronomy/navigation or geography...that kind of knowledge is what would allow them to succeed and that takes years of practice/study to get. To build a ship of sufficient size you would need specialized tools to support the entire supply chain from resource collection to putting the ship together. You need cranes, special saws...the list goes on and on....and on. It's possible they could get a ship built, but odds are it would sink straight-away...after all the first version of anything is usually a complete and utter failure. If they don't know they can stop they would also need food and clean water for, as you mentioned, up to two years...that's a lot of weight and storage space. **As it stands** your scenario stretches plausibility to the breaking point for me. The learning curve is simply too much to overcome. * There is not enough time to learn metal working/shipbuilding/navigation (among others) particularly if they are teaching themselves. Trial and error takes a lot of time. * Time, there will be other considerations on these peoples' time. Raising children, for example, not to mention farming/fishing, building shelters etc. * Raw materials. There are materials other than wood and metal to get which require other skill sets. You need something to seal the wood, you will also need fabric for sails, not to mention clothes. * Food and water. Storing food and water for a long sea voyage is not easy, you need water tight containers and preserved food. The list of things to learn (for reference): * Metalworking + Mining + Smelting + Black-smithing (includes creating tools for this and all the other specialties) * Woodworking + Forestry (what kind of wood to collect) + Milling (creating usable lumber) + Ship building + General carpentry (building tools, homes, barrels) * Navigation/Travel + Astronomy + Geography + Sailing (managing a vessel at sea, sails, storms, no wind etc) * Other + Farming, including preserving food for a long trip + Collecting material for fabric + Creating thread + Weaving + Fishing + *Sealant (Sealing of the joints on a European sailing ship was done with caulk, which was a combination of oakum (plant fibers) and pitch (tar). Thanks @KillingTime* Oh...not to mention you need geometry and some fairly advanced math to design a ship, build cranes and such. [Answer] This has already been tried and proven, and is referred to as the [Kon-Tiki expedition](https://en.wikipedia.org/wiki/Kon-Tiki_expedition): > > Heyerdahl believed that people from South America could have settled Polynesia in pre-Columbian times. ... His aim in mounting the Kon-Tiki expedition was to show, by using only the materials and technologies available to those people at the time, that there were no technical reasons to prevent them from having done so. Although the expedition carried some modern equipment, such as a radio, watches, charts, sextant, and metal knives, Heyerdahl argued they were incidental to the purpose of proving that the raft itself could make the journey. > > > ... > > Heyerdahl and a small team went to Peru, where, with the help of dockyard facilities provided by the Peruvian authorities, they constructed the raft out of balsa logs and other native materials in an indigenous style as recorded in illustrations by Spanish conquistadores. The trip began on April 28, 1947. Heyerdahl and five companions sailed the raft for 101 days over 6900 km (4,300 miles) across the Pacific Ocean before smashing into a reef at Raroia in the Tuamotu Islands on August 7, 1947. The crew made successful landfall and all returned safely. > > > Even better, there were [several later recreations](https://en.wikipedia.org/wiki/Kon-Tiki_expedition#Later_recreations_of_Kon-Tiki) of this voyage by others. Crossing the Pacific using simply-built boats and carrying enough supplies for the passengers is daunting, but certainly possible. [Answer] I'm sorry, but **you need to change your story.** I think you can, and I hope you do: from a dramatic standpoint, it's a hell of a good tale in the making. However, you have set your protagonists up to attempt something that's just not reasonably plausible. You burden them with inventing, **from scratch,** too many things that just can't be invented that way. I have been a sailor on submarines, yachts, an oceangoing tug. Until you've actually been to sea, it's hard to get your mind around **just how damned much there is to know.** I really like the answers from @James and @bowlturner, and won't bother to add more critical or significant prerequisites. But please do review those lists. Your challenge, as I see it, is to retain the dramatic narrative, but back off on the intractability of the problem. And really: *the Sea provides enormous amounts of drama, without layering impossible and unrealistic challenges on the protagonists.* You can relax the stringent constraints that you have declared, and it will still work. You have the bones of a pretty thrilling story there. [Answer] To get a grasp of how likely they are to fail, let's study the voyage of Magellan across the Pacific. * Magellan started 100 years after this, from a society with more advanced shipbuilding. * Magellan's ships were built by trained shipbuilders in a culture with a long history of building seaworthy ships, having access to the tools and resources a whole kingdom could provide. * Magellan had experienced men, with all the skills necessary for the voyage. * Magellan had 270 men, all capable seamen, without bringing children with them. They were also (mostly) knowing what awaits them, this also provides a good filter for what kind of men he had, in the opposite of a few unlucky traders who are not prepared to such a journey. Despite all the numerous advantages Magellan had over your characters, his expedition just *barely* made it. The expedition lost 80% of the ships and over 90% of its men on the way! Yes, the expedition circumnavigated the whole planet, but they had colonies in South America where they could resupply, and after reaching the Indian ocean there were also European colonies and outposts, so the only unknown part of the journey was the Pacific. [Answer] There is a huge amount of knowledge that is needed that these people are missing and so most likely all will die. Any one of a large set of skills needed to make this adventure work are missing. At that time, especially in Asia, 'cross-training' didn't exist, and guilds kept their secrets close (not to mention that often one group felt things 'weren't their job' kind of things. So there is a huge social impediment right off the bat. **Blacksmithing** Now Blacksmithing, your average blacksmith apprenticed for maybe 10 years before getting a 'journeyman' status and up to another 10 to become a full fledged blacksmith. So maybe 10-20 years to become a good blacksmith and this is with a competent teacher. [Smelting](https://en.wikipedia.org/wiki/Smelting) alone is rather knowledge intensive and I don't think I would have much luck, without a lot of trial and error. (this is of course being able to recognize the ore, being merchants they might). **Mining** So you get your ore, smelt it to something sort of useful. and then use rocks or casts to try and make first level tools. These might be good enough to make better tools (such as a decent hammer). Nails, collars hinges, axes, adzes, shovels, knives and other tools will all need to be made before you can start working the wood needed to build a boat. Granted many nails can be replaced by wooden pegs (and many should) you still need to make the pegs AND the holes to put them in. The poorer the iron quality and the poorer the blacksmith the more of these will need to be made as they keep breaking. **Logging/forestry** Next, logging, needed to be able to select trees, cut them down, shape and haul them to the build sight. Lots of logistics (once again a possible skill merchants could possess), and a bit of engineering. **Carpentry** Now you have your trees as logs. You need to turn them into lumber to be usable, even just strapping the logs together as a raft will need a bit of shaping, trees really don't grow nice and straight. **Ship building** Ship wrights, there is a reason there is a name for this type of wood work. Knowing how to put a ship together for more than a small fishing boat requires a lot of knowledge for the stresses put on the ship and which woods are best for which parts, ribs, sides, masts, decking etc. **Textiles** Now you need rope, this is something that might be a reasonable skill to get to pick up or figure out, though good rope still requires some knowledge, since the cows are limited it is unlikely to be leather ropes (and somethings shouldn't be leather on a ship). You will also need sails, so while they might understand good quality, it's a far cry from being able to make canvas or what ever fabric might be available. **Food stores** Food preservation, even a several month journey across the oceans will need to have the food preserved well since water will destroy stores. and you will need fresh water as well. Both of these need a cooper to make barrels (both blacksmithing skill AND woodworking knowledge. **Navigation/Seamanship** Now even if they just stole a ship that was already outfitted and sea worthy, they have navigation to contend with, starting with they don't know where they are going nor how far it is, essentially they are willing to 'die' to try to find a new place to 'live'. If they are in the north seas during winter they will likely die from the storm smashing their ship. It still takes modern ships to the bottom today. These are manned by experienced sailors too. Which brings up seamanship and the ability to control a ship at sea, controlling the sails and KNOWING when to use more sail and when to reef them, and how to ride out a storm. [Answer] As has been said several times already, if you stick to the idea you've laid out here, your protagonists are doomed to a horrible death at sea. The best way for at least *some*'of them to survive their journey without breaking your rules too much would be to adopt the methods used by the Polynesians. Obviously, the Polynesians had probably been traveling by sea for thousands of years before they crossed the Pacific, but your characters clearly don't have time for that, so the best their best approximation of Polynesian practices is as follows: 1. Ditch the livestock and eat something more convenient and appropriate. Your primary source of food should be fish, because the increased weight is minimal. You'll need plenty of line anyway, so you'd already have that, and the only other necessity is a few hooks. You can't rely on your luck at fishing, so you'll need some back up rations. The Polynesians carried rats on long sea voyages. This sounds incredibly unappetizing to us, but it keeps you from starving to death. 2. Less is more. Your characters don't know how to build the kind of ocean vessels we would probably prefer to use, so they shouldn't try. The Polynesians used small canoes, usually with outriggers for stability and extra storage room. This approach comes with an obvious downside - the group won't be traveling together. Even if they try to stay together, it will be impossible to do so, especially if/when the first spell of bad weather hits. 3. Don't try to make the trip in one go. The Polynesians would read the signs provided by wave patterns, wind direction, and the flight paths of seabirds to find their way to the nearest island, and if it proved to be habitable, or even to contain useful resources, they would go ashore. Sometimes they stayed, sometimes they didn't, but they would exploit any opportunity to rest, resupply, and perform any necessary repairs before setting out to sea again. 4. Throw away everything you don't need before starting the journey. If you have farm tools, that's nice, but you can't afford to waste space aboard your ships. You're going to need to stuff every last nook and cranny with food, water, and other more essential items. Your only priority should be to stay alive on the trip, so you have to ignore all thoughts of what will happen if and when you reach your destination. 5. Because most of these suggestions involve relatively little preparation, your characters can spend as long as possible getting familiar with the ocean, and perhaps even sending reconnaissance missions out to find nearby islands. This should be their primary focus, and the main way they spend their days. The more they learn about the sea, the more likely it will be that they survive the expedition. They need to understand how tides work, what the sky is telling them about what the weather has in store for them, how to row and steer their vessels as efficiently as possible, and so on. If anyone is prone to seasickness, they absolutely must get over it before the trip begins. Everyone needs to build up the muscle strength needed to row for hours on end. These tactics definitely don't guarantee success. Chances are, most or all of your characters are going to die very quickly, regardless of what they do. But this represents the course of action which provides the greatest chance that at least *some* of them will make it somewhere that they can settle down and start a new life. [Answer] Not to overly change your story, but a good alternative might be for them to forge their way along the N. Asian coast and across the Aleutians thence down the coast of Alaska. This way they could stop at villages along the way to get sailing knowledge and maybe some seeds for crops (BTW some crop seeds would be a good idea, maybe millet, barley, radishes?). They would be sticking closer to the coast in case of storms and also would get a lot of dramatic contact with other people along the way. Trust me, that route would still give them plenty of exciting high seas drama. On the other hand, it is known that at least parts of ships turned up in the NW U.S. (and Alaska) area from Japanese and Chinese ships in pre contact days, so a direct crossing might "luck out" and not be lost. If it takes 2.5 years, though, they are pretty much doomed. [Answer] As others have said, they die. Lets take a far easier scenario: The group has modern technology, all requisite skills and all relevant small scale tools. They still die. Consider the supplies they need: For drinking water alone we are looking at nearly 8000 pounds per person. For medical reasons I have for a period of months lived on some stuff that's basically pure nutrition with no waste. For a pretty much sedentary life in climate controlled conditions that's still about another 1000 pounds per person. They are going to be in a cold climate with no source of heat, they'll be eating considerably more. Furthermore, they won't have access to anything so concentrated. For a short period they could get away with eating things like butter (something that's sometimes done in extreme-environment travel because it packs so many calories per pound) but trying that for 2.5 years is suicide. Thus I would be shocked if the absolute minimum supplies could be gotten down below 10,000 pounds per person--and that doesn't count the weight of the containers that hold it. Storing it all in barrels seems to add 20% to the weight so we are up to 12,000 pounds per person--6 tons. (And given the limits of the available foodstuffs and the need to get the needed vitamins I think the the real number is considerably higher than this.) 6 tons \* 40 people = 240 tons. Someone else mentioned the Santa Maria--nope, you'll need Columbus' whole fleet to do the job. That's just to get them to North America, they land with nothing but their clothes and they die. That's assuming they even get the ships built. I'm giving them a much better start than you are but they still need to build the drydocks to build the ships before they can even start construction and most of their time will have to be devoted to simple survival. Back then most people spent most all their hours on survival, you are asking them to produce at 1.5x the normal rate (2.5 years of extra supplies obtained over 5 years) while devoting a huge effort into building a drydock and then ships. A replica of the Santa Maria was built with modern tech--\$1.2 million. Lets take 10% off for taxes, all other costs are fundamentally labor at some point (if it's a material you're actually paying for someone else's labor). Lets assume a worker makes $50k/yr. That means we are looking at 22 man/years to build one ship--66 for the fleet. (Remember, this is with full modern tech!) Lets assume that 1/4 of the group is too young to contribute meaningful labor, that means we have 30 workers and I'll be very generous and assume they're working 80 hr weeks (I don't believe this is actually possible without decent artificial light) giving a total of 300 man-years of available labor. That's over 20% just for shipbuilding, not counting the dry dock. Still another problem: You didn't have them escaping with any large stock of food. Unless there's plenty of wild foodstuffs where they go to ground (and if it's that lush why isn't anyone living there already??) they are going to be in serious trouble while they get their first crop in. Trying to live by meat alone means nutritional deficiencies. [Answer] A lot of answers here have targeted the information deficit in particular; that is probably the single biggest problem over these 5 years: even with the decision "let's build a boat" there are the problems of (a) we need to acquire water and food sufficient to maintain this endeavor, (b) we need to stay healthy through whatever injuries are going to happen; (c) we need to build enough blacksmithing knowledge to potentially build axes and saws, so that we can make planks; (d) we need to build enough sailing knowledge that we can build a seaworthy ship; (e) we need to have the surplus supplies stored so that we can actually make the journey, (f) we need to have enough information about sailing to make consistent progress away from our starting point. (That's not too hard if you're just sailing East, but you might mess up and lose track of direction during mid-day.) Now as to size, [this ship](http://www.clearwater.org/the-sloop/history-and-specifications/) is based on older schematics, took about a year to construct with modern tooling, can house something like ~40-ish people, but mostly takes comparatively short trips up and down the Hudson River. In theory it should be seaworthy, based as it is on Dutch designs which were seaworthy, but I don't know that anybody's tested that. [This ship](http://www.mysticwhalercruises.com/pages/The-Schooner.html) is a schooner of about the same length; it says that it'll sustain 34 people overnight, but its cruises are listed as 5-day-or-so affairs. Either way they sound to be 100 feet long, which is roughly the ballpark for the size of ship you'll need. In the 1400s, [Michael of Rhodes wrote a manual](http://brunelleschi.imss.fi.it/michaelofrhodes/ships.html) of shipbuilding which includes a bunch of ships; his simpler "Galleys" are single-masted square-sail boats, which will be more common for the period and are principally powered by rowing. The sailboats ones that he lists measurements for are all about 66 feet long, and are wider for use carrying more cargo. [One page comments](http://brunelleschi.imss.fi.it/michaelofrhodes/ships_design.html) > > Neither measured plans nor even the technique for making them existed in the Middle Ages. Ship design, in the sense of determining final dimensions, was carried out in the yard at the same time as a ship was actually made. The main difficulty was not one of determining overall shape, but of determining the dimensions of hundreds if not thousands of individual parts that had to be cut from timber and assembled together. > > > So there's not going to be any recordings of ships available to them. Your best bet comes from the fact that these people are **merchants,** and therefore sailing was not out-of-the-ordinary for people in their profession. If five or ten of them knew how to sail and five or ten of them were in the cloth business and knew about spinning, weaving, and sewing, then it's possible that some of the knowledge gaps can be worked out over the course of their journey. But if you don't have blacksmiths or carpenters among them, you're not likely to get a 100-foot vessel in five years, even if you've got ten sailors who compare notes on the proportions of the vessels they sailed and five cloth-merchants who figure out how to turn plant fibers into sailcloth. [Answer] OK I'll take a stab at it : their chances are very slim for a direct ocean crossing but not quite zero, given a few preconditions. 1. They need someone with a clue. Now while they are traders, in that era that doesn't mean they know nothing else. You need to make and maintain your caravan's equipment for one thing. As they are handling money across many cultures, they will understand metallurgy : the purity of silver or gold in that coin matters enough that you can count on that. Even so : 2. Let us assume one of their band has a Viking ancestry and some serious maritime experience in his youth. Possibly via the Baltic and the great Russian rivers, across the Black Sea, so far all well-trodden paths to the Vikings. Then, "because of a killing" as the sagas might say in their understated manner, forced to leave town via a caravan onto the Silk Road and hence to China or Korea. (Choose another seagoing culture if you wish : Polynesian, or a Chinese sailor who no longer dares show his face in Shanghai; however I have a soft spot for the Vikings!). His experience guides them in the following: 3. Forget iron. If you can trade (or have traded) for some iron woodworking tools, good, but don't take iron to sea. Iron nails will simply disintegrate within months, while copper nails survive well enough they are still used in boatbuilding today. Copper - or bronze if you can make it from your store of coin - will survive the conditions far better, and the caravan probably already has the expertise to work it. You can trade for it without arousing suspicion, or you may have brought it in the caravan [from Arabia](http://www.josephcohenantiques.com/collections/middle-eastern/products/mamluk-revival-vases/). 4. He has some knowledge of ship construction on a [basic pattern](http://www.vikingeskibsmuseet.dk/en/news/archive/2015/may/article/gislinge-boat-project-an-open-source-project-1/#.VfFtueo27-c) which is scalable from [six-oared boat](https://en.wikipedia.org/wiki/Sixareen) to Atlantic-proven [merchant ship](http://www.vikingeskibsmuseet.dk/en/exhibitions/the-skuldelev-ships/skuldelev-1/#.VfFuCeo27-c) as well as [sleek warships](http://www.vikingeskibsmuseet.dk/en/anniversary-voyage-2012/movies-about-the-sea-stallion/?sword_list[0]=sea&sword_list[1]=stallion&tx_cookiepolicybar_pi1[action]=close&tx_cookiepolicybar_pi1[controller]=CookieBar&cHash=1abf5a8a6fe1034b3869e1c172c0257c), and practical experience rebuilding small or medium ships when they rotted along his way. He'll be guessing when he builds a large ship, but he'll first build a smaller one, after all he has to train the rest of the group to sail. It would be likely for him to contemplate a small fleet including the first boat, rather than a single ship. I would far rather my chances in a Skuldelev ship - or a [Polynesian catamaran](https://en.wikipedia.org/wiki/Hokulea) if you prefer - than the high sided Santa Maria. Basic construction is simple enough for one expert to carry: keel first, with stem and sternpost. Then strakes (planks) working out from the garboard strake, cutting and steaming into place, measuring with string from the centreline to achieve symmetry. The strakes hold their position without extra support. Then, *in contrast with southern European shipbuilding*, ribs last for strengthening. This gives a much lighter ship than ribs first, bending planks over them. [Same technique](https://en.wikipedia.org/wiki/Birlinn#Construction_and_maintenance) is still used in the former Viking parts of Scotland though now sometimes in [plywood](https://www.classicmarine.co.uk/boatplans/skiffs-double-enders/item/199-little-whilly-tern-double-ended-beach-boat)! 5. Let's assume he has no knowledge beyond rumour of the Vinland or [later](https://en.wikipedia.org/wiki/Henry_I_Sinclair,_Earl_of_Orkney#The_alleged_voyage_to_North_America) voyages or any territory beyond Greenland. He will still know some basic navigation : [determining latitude](http://www.vikingeskibsmuseet.dk/en/the-sea-stallion-past-and-present/sailing-and-navigation/instrument-navigation-in-the-viking-age/#.VfFwv-o27-c) to keep the ship on an east-west course, and dead reckoning. (The Vinland Sagas, when discussing Greenland, do have some latitude - or rather, height of the sun - records) Still, while we know there's land out there several thousand miles away, he doesn't... 6. He doesn't know it but he's going to have to cross about 90 degrees of the planet's surface - at the equator that would be over 6000 miles : he's sufficiently far north to reduce that, but still he may have 5000 miles to cover. At 4 knots, in favourable winds (anything from dead north through west to dead south will do, for a square rigger) that would be over 50 days. However, what are the chances of that? You may want to research met conditions in those waters, but failing that : Double that, 100 days, would be a bare realistic minimum (as well as being where Columbus practically ran out of supplies), and double that again would be more likely. If they set off in Spring, that takes them until autumn, and I'm not putting any money on their chances through a winter. By late Autumn he knows they have found land, or not... (EDIT) This detailed chart for [the North Pacific in June](http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APC/Pub108/108jun.pdf) suggests their chances of a Force 4 Westerly (through SW to Southerly) are pretty good across most of the route, provided they stay between 35N and 50N. South of 35N they find more unfavourable winds... (you can find charts for other months there too) 7. Supplies and provisions for the voyage.. This is the difficult bit, but the "good" news -which he knows - is there's no point carrying much more than 200 days supply, rather than 2.5 years. The limiting factor is how much they can carry, how long it stays good, and whether they can replenish (fishing, collecting rainwater in the sails) on the way. Two comments : rice may help, though charcoal for cooking is precious. And don't be squeamish about pilot whales. Sorry, but the alternative is starvation... 8. And good luck! [Answer] **This is doable.** I agree with Mr Drummond. They need someone with a clue. I've seen five Indonesian shipwights start with a stack of lumber and build a fishing Prahu from the keel up in six weeks with no metal fittings. The only tools used were hand tools, adzes, saws and drills. All joints were pegged, planks were stitched together and joints sealed with coir (coconut husk) and pitch. For a voyage of this length you need a vessel about 30m (Think Bounty / Endeavour, Bligh & Cook) Magellan's problem was the same as Bligh's. They were sailing past Cape Horn E to W. **Against** the (savage) prevailing wind. Your guys are going with the prevailing currents and winds. Running before the wind places much less stress on the hull and rigging than beating to windward by at least an order of magnitude. Bounty and Endeavour were Whitby Cats, designed to carry coal on the W Coast of England, picked in part because their broad flat bottom provided plenty of internal volume and allowed then to ground easily. You could go with a single vessel but I'd suggest a small fleet that way all eggs not in one basket. For water allow minimum of 2l / person /day. You **will** get rain in those latitudes, particularly as you approach North America so all the water needed does not have to be carried initially. If they have ceramics they can also construct solar stills - early Eurasian culture has this tech. I'm sure some research will show the Chinese had it too. The distance is about 3,800 nm but this is great circle & not recommended as it goes into high latitudes. The great circle actually passes through the Aleutians. An easier technique (and navigation) is to head due east. This is called Parallel sailing and was known to the earliest navigators. Navigation is easy. Keep the pole star the same distance above the horizon. If it get's higher, too far north, lower too far south. To work out the distance start to finish take the difference in longitude between the two places in minutes and multiply by cos Lat. Remember to allow for dateline. Materials, if they are on the coast of Asia - bamboo. Light, tough, intrinsically buoyant. Can also be used to weave sails (as can coir and hemp). They will need a source of pitch / tar for waterproofing. The vessel(s) need not be durable. They only need last the voyage. One skill they will need is that of Cooper. The're going to need barrels, lots of barrels. Not an unreasonable skill to find in a group of traders of that era. PS Cook started out as a shipwright. If they can find an experienced mariner he could be expected to be multi-skilled. Until the last 60 years all seafarers were expected to be multi-skilled lateral thinkers. If it breaks on voyage you have to fix it yourself with whatever materials are to hand. Picking up Johns S' concerns. Having served on Bounty I'm quite aware of the nature of these vessels. I do not suggest that they try and build a similar vessel. (Without a 'Cook' and a blacksmith, with them it's doable). The point is that a vessel of this size & shape is within the design envelope sought by Green. Endeavour left Plymouth with 94 people and 18 months of provisions aboard. We sailed Mexico for a transpacific voyage (a much longer voyage than the one contemplated) with ~50 aboard Bounty and there was no shortage of room for both people or stores. The point is that these vessels are a good indicator of the volume and shape required. At 4 kt the ~4500 nm takes about 45 days. The big killer at these latitudes is exposure. Rafts would be a disaster. I vote for a decked vessel. [Answer] The voyage you're describing is comparable to Columbus's first voyage. Given that, there's a good model for the sort of ship you'll need: the *[Santa Maria](https://en.wikipedia.org/wiki/Santa_Mar%C3%ADa_(ship))*. It holds 40 sailors and supplies for a ten-week voyage; like most ships of the era, it could be sailed reasonably well with half that many or fewer. The problem is building such a ship. [Carracks](https://en.wikipedia.org/wiki/Carrack) such as the *Santa Maria* represented the height of 15th-century European shipbuilding. A group of refugees isn't going to learn the skills needed to construct and sail such a ship, even if they didn't need to re-invent trades such as blacksmithing or carpentry. [Answer] **The refugees are going the wrong way.** A high latitude ocean voyage on homemade balsa rafts or dugout canoes is suicide. You need real oceangoing vessels for that. There is a "right way" around the world and a "wrong way". Sailing west is *relatively* easy, and experienced sailors do this for recreation on modern ocean worthy sailboats all the time. Sailing east is definitely the wrong way, though, as you end up in the high latitudes to gain favorable currents and winds, but then you face frequent foul weather, which is a non-trivial problem if you don't have very capable boats. Disregarding the kinds of sea conditions your refugees will face in a higher latitude ocean crossing counts as "handwaving" in my opinion. We are not talking here about the refugees just getting splashed with a little spray on occasion, but rather about their makeshift boats being totally swamped by walls of water, being rolled completely over, and being flipped end over end, or just being smashed into splinters. Assuming the boat survives this kind of abuse (big assumption with a balsa raft), everyone and everything not tied down is gone. I am not kidding about that "tied down" part. Nobody will be able to just "hold on" while a medium-sized hill of cold water rolls across the boat, and that raises another point: Water in the high latitudes has a different, *heavy* quality from low latitude water. The water quite literally feels more dense when those waves hit you and your boat. A high latitude ocean passage without properly constructed vessels and skilled sailors is suicide. Even if you are going to gunkhole up the coast to Kamchatka and island hop across the Aleutians, waiting for fair weather for each leg, there are still places where you will have to make deep water passages, and it is almost never nice sailing weather in that area anyway. [Answer] **They could live** I wrote an answer involving a secret group somehow living on the Aleutian islands, then learnt that in fact there are such groups, notably the [Aleut](https://en.wikipedia.org/wiki/Aleut), of whom there were some 25,000 before contact with Europeans. So my new answer is that they could escape along the coastline up to North Japan, and then hear tales of a faraway people. After quizzing a few wise old people they might take that path and head along the coast, hopping from island to island. They could well be able to build canoes with a little assistance initially, and eventually (with favourable seasons) make it to the [Kamchatka Peninsula](https://en.wikipedia.org/wiki/Kamchatka_Peninsula). After perhaps staying there a year with the natives they could continue with assistance from the Aleut all the way to Alaska, making some key longer journeys in the summers, and then make a daring final voyage on to Haidi Gwaii, to the Haida people there. [Answer] Here is one of many good references on what it took to design and build a good ship throughout the ages. [Cog and Galley](http://www.cogandgalley.com/2015/07/naval-architecture.html) The bottom line is that a band of 30-40 people, many of whom would be youth, are unlikely to be able to design and build a large fully rigged ship. But by the 1400's, trade throughout the European-Asian continent was prolific. This family was probably quite rich, in order to encounter the wrath of both the Chinese and Japanese officials. But as merchant traders, it would also be reasonable to assume they had European connections. In fact, pre-1400's, China depended on European merchant ships for trade between Japan and China. It is not beyond speculation that this family would have the resources and connections to be able to buy a ship, perhaps even a crewed ship, from European traders. There would be no shortage of available opportunities, given the degree of trade. See [Development of Sailing Ships](http://www-labs.iro.umontreal.ca/~vaucher/History/Ships_Discovery/) for a description of Chinese sea ventures under General Cheng Ho in the first half of the 1400's. Though why they would go East, and not West, would be a matter for your story line to explain. They would have had far better well-established opportunities in India, the Middle East, or even Europe. However, once they arrived on the Western coast of now Canada, they would have found a very thriving civilization. The Haida were very well established sea-goers, and had quite [elaborate villages](http://www.historymuseum.ca/cmc/exhibitions/aborig/haida/haindexe.shtml#menu). Should they be able to establish a friendship, they would survive quite nicely. The Haida, however, were great warriors and quite territorial. [Answer] They need an ***example***. The story as is seems too unlikely. They need to get the idea of crossing, and they need to learn how to build a ship from scratch, learn how to navigate, how to store and save food at sea... What if, instead, they chance upon an *existing* shipwreck? Now they have the source material. They know what the ship should look like, and they can deduce how it should work. Repair is tricky, but it's at least possible. They might find instruments on board that can help them learn to do rudimentary navigation. Barrels that obviously used to store food and water, etc. This could also serve as the kernel of the idea of escaping to sea. Note: I'm aware this doesn't meet the criteria for hard science, but I haven't been able to find any actual articles on actual shipwrecks that were re-raised and repaired. I've certainly read stories about them, but I don't think those qualify as sources. I'll try to do some more extensive googling once I get home, all the results I'm finding now are polluted by small boat forums or games that involve ships. [Answer] A comment above mentions that the original thought was to start in the middle-east. Currents in the Indian Ocean flow south along Africa. During the half of the year that the winds are blowing out to the ocean (non-monsoon season), the winds would also take a ship that way. Rather than rounding the Cape of Good Hope as this same comment mentions, the currents would take you east, south of Australia. Winds and current could rapidly take you to the southern tip of South America. I believe the Kon-Tiki expedition gathered a large amount of fish that had simply jumped onto their raft, so food may be supplemented that way. The current splits at South America, with part continuing east and part moving north along the west coast. The northward bending Chilean current even gradually slows to almost nothing around 30th parallel (upwelling deep current partially offsets surface current) before picking back up and being diverted back into the Pacific by the "bulge". They might be able to continue in a more coastal hugging manner after that to continue on to Central America. With the wind and waves essentially pushing you the entire way, you wouldn't need to build complex sails or rudders and would not need to know how to tack and make complex maneuvers. ]

[Question] [ Let's say that something horrible has happened and a Mars-sized planet is knocked out of orbit and is hurtling towards an Earth-sized planet. How much time will they have? How will this affect the inhabited planet? Obviously the impact itself means the end of life on that world, but this is happening on an astronomical time scale and they'll have years before the actual impact. My base question is this: **What will the target planet (Especially its inhabitants) experience as the other planet draws nearer?** Assumptions: * The impacting planet orbited the star at roughly the same speed as the other planet * Something (asteroid strike?) has caused the orbit of the impacting planet to degrade such that it is spiraling in towards the star * The angle of impact will be acute, as one planet effectively "merges" into the other planet's spot * Speed of impact will be slow (I don't know what qualifies as "slow" in astronomical terms, feel free to extrapolate as needed) [Answer] Virtually everything in Mindwin's answer is wrong. The slowest possible approach of the rogue to the earth would occur with a Hohmann transfer orbit, and in this case orbital energies dictate a closing speed of about 3 km/sec. However, this ignores the gravitational attraction between the earth and the rogue, which will boost this closing speed to about 9.5 km/sec. Time to contact from 10 times the moon's orbit is about 14 days. At this distance, the area of the rogue's disk is about 1/50 that of the moon. Time to impact from crossing the moon's orbit is about 27 hours. A this point tides are about 8 times greater than normal. So, no massive tsunamis until a few hours before impact, and this will affect only small part of the earth. Furthermore, since the orbit is essentially tangent to the earth's orbit, it will appear in the sky at 90 degrees from the sun, directly overhead at dusk, and will present a "half-moon" appearance. Since the earth's atmosphere is about 30 km deep, the rogue will not appreciably affect the earth's atmosphere until less than 5 seconds before impact. No vortex. With a relative velocity near 10 km/sec, a tangent path from sea level to 30 km is about 2,000 km, so for a near-miss the atmosphere will be affected for a duration of (at most), about 3 minutes. No hoovering. Just an enormous shock wave. Since Mars' surface gravity is about 40% that of earth, just at contact the apparent gravity at ground zero will be reduced to about 60% of normal. No floating. And on the other side of earth things get heavier by about 4%. No crushing gravity, I'm afraid. Centrifugal force will be irrelevant, and there will be no swirling water. A head-on collision (well, head to tail) will simply liquefy the two bodies. The collision zone will be, especially at first, expanding hypersonically away from the point of impact. The folks on the far side of the planet will not have to wait a day to feel things, as the shock wave will propagate through the planet in less than 20 minutes. Well, OK, everybody dies. If, somehow, the rogue is thrown into an orbit which meets the earth head-on, the closing speed will be about twice the earth's orbital velocity (plus a bit for gravitational attraction), or about 60 km/sec. This is even quicker and more spectacular. But in the end, everybody dies. EDIT - As trichoplax has pointed out, my calculations on the apparent gravity at impact were wrong. They assumed that the earth and rogue will be stationary, but obviously they will not. Instead, each is in freefall toward the other. The center of the earth is closer to the rogue than a point on the far side of the earth, so the acceleration of the earth will be greater than a person standing on the far side. Since the earth is considered (for the moment) to be a rigid body, that same greater acceleration will apply to the surface of the earth under the person's feet. If not for the attraction of the earth for the person, the two would drift apart. If Re and Rr are the radii of the earth and rogue, and Me and Mr their masses, the net force on a person on the far side will be $$F = \frac{GM\_e}{R\_e ^2} + \frac{GM\_r}{({R\_r +2R\_e}) ^2} - \frac{GM\_r}{({R\_r +R\_e}) ^2} $$ Letting the rogue be Mars-like, $$Rr = 0.53 R\_e \text{ and } M\_r = 0.107 M\_e $$ $$F = (\frac{GM\_e}{R\_e ^2})(1 +\frac{.107}{2.53^2} - \frac{.107}{1.53^2}) = 0.97\times \frac{GM\_e}{R\_e ^2} $$ so not only will people not be crushed by the added gravity, they will be 3% lighter. Just before they die. Likewise, for the point of impact, surface gravity will be 27% of normal. So, still no floating. Just before they die. [Answer] Since the actual impact will only last minutes, on the far side it will be kinda like this as the shockwave approaches: T-10 minutes: 20C and sunshine T-5 minutes: 20C and sunshine T-4 minutes: 20C and sunshine T-3 minutes: 20C and sunshine T-2 minutes: 20C and sunshine T-1 minute: 20C and sunshine (is that a shadow on the horizon?) T-0 minutes: **4,000 C and death**. [Answer] There is a game on Steam called "[Universe Sandbox²](http://universesandbox.com/)", which focuses on simulation of planets and stars. I opened up our solar system and added another Earth with almost the same orbit and speed, so actually they would never hit each other except due to their own gravity. This is what happens: Original setup (2017-07-18 03:31pm): [](https://i.stack.imgur.com/6OZfR.jpg) Begin of collision (2017-07-18 04:47 pm). Propably some people still live. [](https://i.stack.imgur.com/NjNfa.jpg) 11 minutes later (2017-07-18 04:58 pm). [](https://i.stack.imgur.com/gCihG.jpg) 29 minutes later (2017-07-18 05:16 pm). [](https://i.stack.imgur.com/aUMBz.jpg) So after half an hour, Earth almost looks like in the early days. Due to the collision energy, the heat dramatically increased, melting everything. [Answer] Based on the first assumption: > > * The impacting planet orbited the star at roughly the same speed as the other planet > > > This means that the impacting planet is in the same orbit as our inhabited planet, since speed and orbit are much the same thing. Obviously this isn't a stable arrangement, but it's more stable than it seems on the face of it, because as an object picks up speed, its orbit gets longer, and as its orbit gets longer, the time it takes to orbit increases. > > * Something (asteroid strike?) has caused the orbit of the impacting planet to degrade such that it is spiraling in towards the star > > > Orbits don't spiral, unless you have some constant source of energy slowing the object down. Satellites spiral down because the atmosphere produces drag. This couldn't be the case with another planet. In fact, our moon is being accelerated into a higher orbit away from Earth. Unless the other planet were well inside of the Moon's orbit, close enough to already be doing widespread damage just by interacting with our atmosphere and heating it up, there is no way for the other planet to spiral down to our inhabited planet. > > * The angle of impact will be acute, as one planet effectively "merges" into the other planet's spot > > > The angle will actually be face-on, if our first assumption is true. I'll get to that in a bit. > > * Speed of impact will be slow > > > Again, not if the first assumption is true. Really it comes down to whether the uninhabited planet's orbit suddenly became very elliptical (that is, if Mars's orbit suddenly changed so that its closest point to the Sun is within Earth's normal orbit, but its furthest point is still at its original orbit), or whether we have two bodies that have been sharing the same orbit around their star and are about to meet their inevitable ends. WhatRoughBeast has already provided an excellent answer in case it's a Hoffman Transfer orbit (including the fact that Mindwin's answer is spectacularly wrong), so for that scenario, I'll only repeat the most important detail, that the speed of impact will be 9.5 km/sec, and I only repeat it in case WhatRoughBeast's answer somehow goes missing. I'll also add, since it's asked in the question but I haven't seen a good explanation in any other answers yet: From the point of view of someone on the surface, but far enough over the horizon to not see the impact, your first and only warning will be an earthquake that gets stronger very quickly, over the course of a few seconds, until the ground is shaking too violently for you to stay on its surface... You will be thrown about like a ragdoll, each impact more violent than the last, until you sustain sufficient brain injury or spinal cord injury that you lose consciousness... Once the rumbling starts, you'll probably have 20 seconds of consciousness. You'll be too busy being thrown around to notice that the ground is heating up from all of the friction, and within 5 minutes, the ambient heat will be enough to cause any carbon based life forms to spontaneously combust. From the point of view of someone who can see the impact: Things get hot very quickly. You might have a second of consciousness if you're behind a mountain. Now, on to the meat of my answer: If the two planets are traveling at the same speed (first assumption from the question), they'll be in the same orbit. Orbits are tricky, though. As you gain more speed, the size of your orbit increases... The bigger your orbit, the longer it takes you to complete that orbit. Thus, if you want to slow down compared to another body in the same orbit, you pick up speed. (That is, you go further away from your star, and just as Venus orbits the Sun more often per Earth year than Mars does, you'll be orbiting your star less often.) Now, with two rocky planets, there's a lot of gravity, which means that as they get closer, there's a lot of acceleration. They will both attract each other, and if they're both the same size, they'll attract each other equally. The planet in front will slow down, and the one behind will speed up. But since we're orbiting, any slowing down and speeding up will affect the size of our orbits. The planet in front will get closer to its star, and the planet chasing will get further away. The first time this happens, someone on the surface will see an incredibly bright planet. Brighter than Venus or even the International Space Station, and you might even be able to make out its illuminated side (it'll look like a half circle). Assuming our inhabited planet is the ahead planet, the chasing planet will be visible from dusk to midnight. The orbits of both planets then get more elongated, but only astronomers and people who keep track of time would notice at first. After a couple of years, things are reversed... Our inhabited planet has sped away from the chasing planet, and is now doing the chasing. As it approaches the rogue planet, it becomes visible in the morning sky, from midnight to dawn (and even visible during the day, if you know where to look, until noon). Our inhabited planet gains speed, the rogue planet loses speed, they get a few million miles closer than they did before, and miss each other by a large margin once again... this time, with our inhabited planet in a larger orbit and our rogue planet in a smaller orbit zipping away. This cycle repeats for a couple centuries (a mere blink of an eye in astronomical terms... the Earth is 4.5 billion years old; this is 1/20,000,000th the time frame... There are comets that visit the sun once every million years). Now things get interesting. Towards the end of the cycle, there are no moons around these planets, if there ever were any. The gravity battle has pulled all satellites away, natural or artificial. The fourth to last orbit, the rogue planet gets to within 1/5th the distance of the Earth to the Moon. (For scale, imagine a typical classroom. If the Earth is the size of a basketball, the Moon is a grapefruit... and both would be in opposite corners of the room.) There would be earthquakes and volcanoes during the weeks that the two planets are closest to each other... During the month leading up to the encounter, the rogue planet is hidden by the glare of the star, but after the encounter, it dominates the night sky well past midnight. Careful observations would be able to see the rogue planet moving across the background stars during the evening of closest approach. 9 months later, things are considerably closer, earthquakes are larger, and the timing is reversed... The month leading up to the encounter, the rogue hangs heavy in the night sky, and after the encounter disappears into the glare of the star. 9 months later, greater earthquakes damage every standing building, destroying most... the planet passes within 20,000 miles of ours, appearing out of the sun's glare, and absolutely dominating the night sky, their relative speeds are so great and both bodies are so close that you can see the other planet spinning above you. 9 months again, the rogue planet comes... The night before it passes, it starts to enter your planet's penumbra (out of focus shadow... an area experiencing a partial eclipse), then slowly creeps into the umbra (full shadow, are experiencing a total eclipse). The two planets will collide with all of the force of a head-on collision, about 60km/s. Anyone who can see the impact will die immediately. The atoms of their bodies will be stripped apart faster than the neurons carrying the information about what's going on could process that data. If they're close enough to "see" the flash, their brains will never experience the sensation. There won't be a low rumble that will turn into an earthquake that will throw people against other objects to their deaths, like in a "slow" 9km/s impact... There will be one shockwave that moves at supersonic speed through the mantle of the planet, and as soon as the ground beneath your feet experiences that shockwave, the ground will be moving so fast that you'll just go splat. Planetary collisions are nature's way of asking how that space program is coming along... [Answer] The Discovery Channel did a special on a large asteroid collision with the Earth. This video is a simulation of what would happen. They include some "first person" perspectives of what it would look like on the surface of the Earth. Detailed simulation of large asteroid impact with Earth. <https://www.youtube.com/watch?v=bU1QPtOZQZU> A planet sized impact would be similar, just amplified by 3-4 orders of magnitude. Here's a lengthy discussion including simulations of what would happen: Less detailed simulation of Theia impact with Earth. <https://www.youtube.com/watch?v=ibV4MdN5wo0> ***SPOILERS:*** (Hover to read) > > Everyone dies. > > People die as soon as the supersonic shock wave gets to them. That > might give some people hours, I'm not sure since I didn't run the numbers. > > To add insult to injury, enough debris would be flying around from such > an impact that any humans in orbit or on the surface of the moon would > also die. > > > [Answer] the compression of the atmosphere would be similar to many millions of atomic bombs going off, so actually the entire planet would be enveloped in something similar to an atomic shockwave, where the cars move 100ds of meters sideways in the wind, without even thinking about the ground movement happening at the same time. The ground movement would occur prior to the wind effects, moving very fast and very far compared to an ordinary earthquake. The air itself would become alot less clear because of all the thermal and compression effects happening within it, water would vaporise be compressed while the wind would be going at 1000kph, so you wouldnt see very much. There is a documentary on nova with scientists discussing the effect of a neutron star invading the solar system, it's totally false because the iron of the earth would compress against the crust like a huge hypervolcano, and pop out of the breach in the crust and fly into space, long before stones would start to fly around. It depends on the velocity of impact, typically at meteoric velocities. The effect would be similar to an large earthquake of which the main shockwave would be transported directly through the mantle rather than around the crust. The effect would be different depending on the angle from the percussion. The power of the shockwaves would be enough to create waves of force lifting the crust in heights in between 10 meters and 1000 kilometer, depending on what rebound of the wave you first catch, cars would literally be flung very far into the air a few seconds after the initial schockwave occured, and the intensity of the earthquake would increase until the entire surface of the earth was wabbling and cracking by in waves at least 100 kilometers tall. The precise model of the surface and the earth's crust's interaction with the viscous and compressed inner materials of the earth would be a function of the earth crust's thickness and the size of the shock waves traversing the mantle, disassembling the crust in the first moments while the observer was alive. [Answer] Assuming the following: 1. You are standing at the equator 2. You weight 200 pounds 3. Mars hits the Earth and the precise opposite location of where you are standing 4. The Earth is spinning at 1,040 mph at the equator Your knees would buckle and your own body would hit the floor of the Earth with about 200,000 pounds of pressure. You would disintegrate your own self. If it hit in such a way that sent you flying down the street then you would collide with something at about 1,000 mph. It would probably snap your neck before you even knew what happened. [Answer] There's more than one possibility that could take place in this kind of scenario, the most obvious thing that would likely to happen is you getting crushed like an ant in a second, when the natural disaster occurs. And unfortunately, I don't think you'll be able live long enough to feel how it is. [Answer] <https://youtu.be/lEIGjXbtQwY?t=76> According to this video, a planet the size of Mars **did** collide with Earth. 4.5 billion years ago. They collided at a speed of **25,000 miles an hour** (~70 miles/second). The entire surface would have been liquefied with molten rock. Debris flies out into space as a result and then recombines due to gravity. And the result was our Moon. [Answer] I will call "Mars" the rogue planet (the one knocked out of orbit) and "Earth" the planet that is about to be hit. But it is not really Mars, because OP stated a planet with the same mass as Earth. --- **Disclaimer**: this is not a physics essay. The time frames are relative, since OP did not state the speed of approach. If anyone wants to delve into this aspect and do some calculations, by all means do it. I tried to do some storytelling here, like a script for a catastrophe flick. --- As the Mars approaches, its first influence will be on the tides. The side of Earth nearer to mars will begin to experience huge tides. As it approaches, it will become mega-tsunami in size. This will begin to be felt when it is around 4 lunar distances from Earth (since Mars is the same size as Earth in the question's scenario, it should have gravity six times that of the moon). It will also have an effect on the day cycle. Every day the clocks will be off by some seconds at first, and then a minute. Most people won't notice it, but weather scientists and government will be aware very soon. As Mars passes behind Earth and in front of Sun, it will be visible in the sky at night. Amateur astronomers will find it really soon, and after a couple weeks everyone will see it. A huge red "second moon". As it gets even closer, night will be brighter and brighter (and even more red). > > also, the crashing planet may be not red. But read the top of the answer again, please. > > > As it approaches more, it will begin to pull people. Not the "omg i am being lifted up" (not yet) type of pull, but our 9.8m/s gravity pull won't hold anymore. It will be way less on the side facing Mars, and a bit less on the other side (because there are two Earth radius from one side to the other). When a crash is imminent (one week away, lets say), the huge tsunami waves will destroy everything near the shores (some miles inland. Kiss Holland and Japan goodbye, except for the mountains). Days before the crash the atmosphere of both planets will merge. If the atmosphere of Mars is poisonous, most people will die. Soon the oceans will also be sucked, and begin to cross from Earth to Mars. Like Dxun from star wars: [](https://i.stack.imgur.com/XxClY.jpg) Also, most water and gases will escape into space in a ring-shaped areaaround the mid-point of both planets, because there is not enough pull to keep fluids from reaching escape velocity. Hours before the crash, earth, dirt and anything not affixed to the ground will be pulled too. Any surviving humans will **now** have the "i'm flying" feeling. The crash will not be like a ball hitting another. At the geological size and scale we are talking about, you can treat dirt and earth rocks like fluids. The upper crust of both planets will be ripped apart by the centrifugal force and gravity, and begin to swirl together with the water from the oceans, trapped between the gravity field. Anything living inside this swirling vortex will be crushed. The humans on the other side will feel a heavy gravity pull, and also tectonic activity throughout the entire planet, since the magma beneath the crust's tectonic plaques will be pulled too by the tidal forces. But it is just a matter of a day, as the earth spins around and the vortex between Earth and Mars vacuums away the Earth surface like a knife in an orange skin. The released heat will boil the entire planet. The ice caps on both planets will melt and boil. Humanity will die entirely. ]

[Question] [ [This answer to *Making food last for a large group*](https://worldbuilding.stackexchange.com/a/53281/885) made me realize that using the zombies **as a source of resources** is pretty much never covered by genre pieces even when it is essentially a siege situation. What ways can the besieged find to use the (“killed” for good) zombies as a source of food and other resources? Simply having them be edible like any game animal is too easy: they will be hazardous (rotten or infectious) if treated casually. [Answer] In all cases, suppose that cooking properly will take care of infection. But the skeletal muscles are rotten in the classic zombie: Perhaps you harvest just the [(high-calorie) bone marrow](https://en.wikipedia.org/wiki/Bone_marrow_(food)), which is not rotted. More generally, *some parts* may still be edible, depending on the age of the zombie. But all the “off” meat does not go to waste. Many animals can eat meat that humans can’t or won’t, and there are other [animals that specialize in eating carrion](https://en.wikipedia.org/wiki/Carrion). The survivors might capture the scavengers that are doing well in the current situation, and breed them for meat. This makes me realize that it’s not *just* a zombie-human apocalypse, but will be a hyena and vulture apocalypse too! If the animals are affected in the same way, things will be even more interesting especially with flying animals involved. If hyenas and coyotes are *not* infected in the same way as humans, they might make good tools for fighting the zombies! Now feeding meat animals is a rapid and concentrated source of calories but is inefficient, producing only a percentage of what went through the process. Growing crops is more efficient. So the zombie remains ought to be **composted** and used to grow vegetables, rice, and beans. This takes a large amount of territory to be under the people’s control, and more time. But zombies don’t bother crops, right? So the land need not be full-time secured. Farmers would employ the domesticated coyotes or dogs‡ to be on the lookout around the farm and the group of workers in particular. As for resources other than calories, you have many of the usual animal parts: bone, sinew, leather. Many knives, weapons, and farming implements will be made from zombie bones. --- **‡ About dogs**: I made a distinction above between meat that's just a bit off and can be eaten by many animals (but not humans), and truly rotted meat. Rats and dogs fall in the first category. Carrion feeders will eat stuff up to the point of already being compost. So dogs may be good for defending against zombies without getting sick, and may munch on the not-too-decayed specimens and bones. [**Zoönosis**](https://en.wikipedia.org/wiki/Zoonosis)※: Generally diseases are species-specific. So by default we expect animals will not be infected by zombies in the same way as humans. Doing so would make for a **very different story** with zombie mosquitoes spreading the infection, and beetles infecting the *entire ecosystem* in short order. But you may have *some* animals infected in *some ways*. In particular, if the zombie virus came from an animal reservoir, then those specific animals will be asymptomatic carriers or get ordinary sick from it. Now if zombism came from a mutation of [rabies](https://en.wikipedia.org/wiki/Rabies) then it might present as rabies in canids and bats. That means people will have to use animals other than coyotes and hyenas: would they use vultures perhaps? --- ※ I use the [diaeresis](https://en.wikipedia.org/wiki/Hiatus_(linguistics)) to emphasize that the two `o`s don’t merge together like in `zoo`. It’s like `coördinate`. [Answer] This really depend on zombie type; 1. **Romero zombies**, acting a pin point for many zombie types, including Walking Dead zombies; These are the least likely to work, as due to the fact that they are rotting. Food is not like water, burning or boiling the meat will not help. 2. **Runner zombies**, perhaps created by 28 days later, these are the most realistic zombie depiction made so far; but still unlikely, even though the zombies are not dead, the infection is blood born and that usually is accompanied by having infected meat being lethal. 3. **Cordyceps zombies**, though they have existed in nature for millions of years, the game Last of Us, made these zombies' fictional, human counterpart a reality. This is the best hope for eating the dead, as a fungal base it will vary on depiction, but usually unless you eat the fungus itself, it will be good ol' regular cannibalism. [Answer] Regardless of the trigger for Zombiefication (voodoo or virus) human cannibalism is a **Very Bad Idea™**. The fatal prion malady *kuru* (shaking death) wiped out many participants of the last recorded cannibal feast by the *Fore* tribe in Papua New Guinea. Other malformed prion maladies are also a threat. Kuru is suspected of having a 50 year incubation period. Actually that's the only problem I can find a reference for right now. So **WARNING: do not eat the brains.** Cannibalism makes it easier for pathogens to cross the blood/brain barrier (I think - again no reference). Zoonosis becomes an issue if the devoured body already has the disease. But consuming cooked human flesh is a lower risk behaviour than most other bodily fluid exchange. Wikipedia lists 34 types of body fluids. According to my industrial chemist sister, the gut is such a toxic environment that food and drug safety standards (for compounds) are lower than cosmetics safety standards. In the sense that companies can put stuff in food and drugs that is banned from going on your face. Cosmetics standards also have lower absolute quantities and concentrations of active ingredients. Now once TB, Rabies, Leprosy, ebola or the other 18 Zoonosis diseases are in the human population, **I** wouldn't want to consume that meat. [Answer] A couple options: * Fertilizer, see OP's answer * Work force, ala oxen * Manufacturing material That last one might need some explanation. Perhaps tendons are discovered to have a high tensile strength. Bone meal or shards might make a new form of concrete. Brain squeezings could be the best wood preservative ever. Rendered flesh might be an amazing rubber replacement. Further, the use of these materials might ward off attacking hordes. [Answer] Other answers have thoroughly described the ways in which eating zombies directly is a bad idea - risk of infection, lack of edible meat/nutrients, cannibalism... However, we don't need to or want to eat the zombies. We just want food and resources. You haven't described exactly what sort of zombie your setting contains, but they are typically: * Of low intellect * Motivated by a simple desire for brains * Powered by low-quality food or nothing at all You may be able to fool them into generating resources like draft animals. They could be chained back and walk forward on a treadmill towards some brains harvested from an animal or another zombie (or just a picture of brains), shuffling forwards and generating power. Or perhaps you could convince them that if they braved the zombie-infested supermarket and returned with a certain object (they aren't vulnerable to infection, after all), stood guard in a watchtower (with appropriate testing and redundancy, of course), or pulled a plow through a field (ensuring that the final product isn't contaminated with the virus), you would give them something they wanted. [Answer] I help run a fantasy haunted adventure every year in October. One year, our story line was a post-apocalyptic landscape full of zombies. Modern tech manufacturing was dead, but it's amazing what you can build out of zombies. They don't die. So... * Perpetual motion devices: Lots of simple machines can be made just by taking the hand or leg of the zombies and attaching them to a few levers. Spinning wheels, water pumps, etc. * Early warning systems against other humans: In many settings, dealing with the zombies is straightforward... it's the bastard other humans with their intellect that's the problem. So, strap a large number of zombies to a perimeter fence. Remove legs so they don't get away. When any living being comes near, they'll start moaning "Braaaaaains", and you'll know to prep for incoming humans. * Pop out an eyeball, string the neurons down the hall, connect the other end to a Raspberry Pi or other remaining tech, and, voila, remote surveillance camera. Probably only have enough resolution to see light or dark, but that may be enough for automating lights for sunrise/sunset. [Answer] If I were a leader of some enclave I would assemble a crew who would: * search zombies to check for anything of value they could be carrying * extract gold teeth, bullets, bone implants(?) for metals * take their clothes, reclaim fibers or recycle them somehow * build incineration plant and use zombie bodies as a fuel * collect ashes and use them as fertilizer or construction aggregate maybe Other possible uses: * build barricade from bodies * test new weapons Eating zombies? Nice try.. now convince anyone to do it. [Answer] As others have mentioned, this depends a lot on what the rules behind turning into a zombie are. Meaning, this could change from world to world. --- If becoming a zombie it is the result of a pathogen, then the nature of the infection will dictate the feasibility of zombies becoming a source of food. Consider the core options in a world infested with zombies: * **Contaminated food**: Food that had been tainted by zombified remains or insects spreading the infection. * **Direct source of food**: Zombie meat from a zombified animal or human. * **Indirect source of food**: Animals or plants consume zombies as direct sources of food or contaminated sources of food (Water contaminated by zombified remains also counts). Depending on how the agent of infection is spread and its fortitude, it might be possible that certain animals, plants and insects could be able to withstand the contamination and detoxicate the food or water. Conversely, some animals, plants and insects could increase the potency of the agent potentially mutating it into something worse. This, again, depending on how that particular world works. --- If becoming a zombie is the result of a curse or magic like in the film [The Serpent and the Rainbow](https://en.wikipedia.org/wiki/The_Serpent_and_the_Rainbow_(film)), the rules of what is needed, how it affects the body and how it is transmitted will determine the edibility of any zombified beings. In the particular case of the film mentioned, it appears that a drug is used to produce the desired effect. Some drugs must be injected directly to the blood stream for them to work, while others have to be ingested, this will also become a factor on edibility. Some components can be eaten without producing the effect, so in that case it could be safe. More magical realms would require additional analysis on what happens to cursed or enchanted beings that get eaten. Interestingly enough, despite all the fairy tales there is little exploration on this aspect of magic. However, worlds with magical-based zombies might have an edge if there are spells or potions which revert them back to their former selves. Notice that this might differ a little from an uncontrolled outbreak scenario, since magical zombies tend to be more controlled and those who tame them have developed means to keep themselves from becoming zombies. Even the film mentioned shows that zombies are easily manipulated by those who turn them. --- If becoming a zombie is the result of a parasite (like [real life ant-zombies infected by a fungus](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis)) then it will depend on the characteristics of the parasite itself. In the particular case of the fungus that infects the ants, the parasite only attacks a particular species, which might make it relatively safer to consume (if the zombified animal was not a human, of course). Like other parasites, it is possible to use methods to cook such meat by ensuring the death of the parasite before consuming the food; however, how safe it really is can only be determined by how the parasite reproduces and propagates. An example of a work of fiction where zombification has been treated as a parasite with very specific rules on its propagation would be "*[Higurashi Outbreak](https://en.wikipedia.org/wiki/Higurashi_When_They_Cry)*". Animals are not covered in that particular scenario, so it would be safe to consume any meat produced by an animal, given other qualities of the parasite explained in that film. --- With that in mind, everything really comes down to the rules of the particular world which is under a zombie siege. A work of fiction that does address food and resources in a zombie post-apocalyptic world is the [web comic Zombie Ranch](http://www.zombieranchcomic.com/). In this particular instance, animals and humans can become zombies and [eating zombies is safe, despite the taste](http://www.zombieranchcomic.com/episode/66-talkingcrap/). In this world, [humans are forced to become vegetarians](http://www.zombieranchcomic.com/episode/67-wheres-the-beef/). Additionally, [zombie blood is not contagious](http://www.zombieranchcomic.com/episode/33-farm-fresh/) and [they can be used](http://www.zombieranchcomic.com/episode/76-beware-of-false-profits/) to [produce medicines that extend the life of the living](http://www.zombieranchcomic.com/episode/catastrophe-to-commodity/) and [other products](http://www.zombieranchcomic.com/episode/menace-to-merchandise/). Having said that, zombies could be used for labor depending on how sturdy they are in the world in question. They could also be used for theoretical perpetual motion machines, these two under the provisions of the rules of the world, since zombies that might not consume flesh (or brains) might eventually lose energy, become inactive and break-down. Despite the kind of zombie, they could be leveraged for hunting (like how hunt dogs are used) but this would require to have a certain degree of control over the zombies, which would vary from reality to reality. Additionally, depending on how the zombification process happens, it might not be a good idea to risk to infect your food by performing said actions. Back to the issue of having a safe way to eat zombies. If we were to assume all the worlds to which this question would apply are similar to ours, then there is one simple answer: [Pasteurization](https://en.wikipedia.org/wiki/Pasteurization). Pasteurization would address zombies that have been turned due to a pathogen and parasites, since it is a process which kills microbes (bacteria) in foods and drinks. If you were also to assume that eating beings that have been exposed to magic as a non-issue (meaning that magic would not cause any damage to those consuming magically treated food) then, that addresses the main issue. Pasteurization is easy enough to perform without a lot of technology, since it was discovered in 1864 by Pasteur who noticed that heating beer and wine would kill most of the bacteria in it, leading to a process that achieves eliminating pathogenic microbes. Since this process is used widely in food processing industries and the dairy industry, it is not a stretch that ranchers might be able to survive a zombie apocalypse by applying knowledge of food preservation that they already possess, making a "*zombie ranch*" more plausible. Now, on to the other aspect of the question: resources. Being able to use the zombies as other resources would depend on several factors such as the infrastructure that is left in the world after an outbreak and the properties of the "*undead*" creatures, as previously discussed; however, there are similarities in all worlds where there is a concept of a zombie which is the usage of these undead fiends against other humans (It comes down to weaponizing them). --- *[Louis Pasteur](https://en.wikipedia.org/wiki/Louis_Pasteur), saving the multiverse from zombie apocalypses since 1864*. [Answer] If I was stuck in a building with limited resources and I was currently being besieged by zombies, I would go Zombie Fishing. With some rope and if lucky some type of large hook like object I would lower it off the roof or out a high window and try to snag one zombie. One I have one I would pull it up just high enough to bludgeon it and then pull it in. IF by change more than one zombie started climbing my line I would cut it free and try again. For the most part I imagine zombies are inedible. Maybe you could cook them, autoclave them, char them but personally I wouldn’t risk it. What Zombie fishing would do is supply me with resources. These are not just walking corpses, these were other survivors hording supplies. That zombie with the backpack, he is the one you want to aim for while zombie fishing. Yes he could have been an unlucky student on his way to school, or he could have been that guy who nabbed the last can of soup from the store. As mentioned by other Zombies could be disassembled, skin could be tanned and used as leather, bones could be used as building material. Lukbl mentioned burning them and using the ash as fertilizer. You can add ash to a compost, but by itself it is probably not as usefully as a fertilizer as compost. On the other hand it is better than trying to grow something in plane sand. [Answer] One possibility is to create a partial cure for zombification, one which restores the body but not the mind. You could use this medicine or method to restore the zombies to edible flesh. This could also allow for interesting scenarios, such as a divide between those with the resources to turn zombies into food and those without. [Answer] Because humans are unfortunately not breed for having the best kind of meat anyway. So eating them would be like eating humans, last resort for protein source. Humans eat humans when they don't have anything else, so the same would be applied to zombies. BUT - the zombie meat would have one, general, disadvantage over human meat. It could be dead/killed weeks before you would like to treat them like food. BUT - the essence of zombie existing in the first place MUST be that the dead meat don't spoil, rotten or is affected in any kind by regular oxidation. SO - just give a handful of spices and serve with a nice chianti and fava beans. [Answer] Eating zombies is nasty. Using them on a treadmill as perpetual motion machines is zany. But you could burn them as fuel and power a steam engine. I could imagine apocalypse survivors conducting routine burns of the zombies which had accumulated in their trenches, then running out of firewood / coal for their own heat and power, then thinking... First world humans are pretty greasy and when they dry out as zombies will be even greasier. Got lemons, make lemonade. This would work for any of the 3 zombie types listed above. There is precedent for using animals as fuel: oily freshwater sturgeon were netted, stacked and dried, then used to fuel steamboats in the early 1800s. There was a whole industry dedicated to catching and processing whales for fuel. One drawback: as regards a fictional work, in my mind this approach is tainted by a similarity to the Auschwitz ovens. Maybe it is just how I envision it or because I am old. The writer will need to take some care in how it is depicted. [Answer] To answer this question we must know WHAT type of zombie you are referring to. Virus Zombie? Cursed Zombie? Fungal Zombies? Since you didn't include these in your question I guess I'll have to describe ways to eat each one. Viral Zombies: If you are trying to eat a zombie that is infected with a "Zombie Virus" then I suggest that you rapidly freeze and defreeze the zombie meat (to decrease the chances of viral transmission), If your population does not have access to a device that freezes things then I suggested that you roast it over an open fire several times). Cursed Zombies: the reason for these zombies coming back from the dead is due to a curse that has been placed on that individual. If so I reccomend roasting the flesh over an open fire ONE time (since this zombie's flesh is not contaminated with a zombification virus. Note: despite not containing a virus this type of zombie flesh contains various bacterium which cause illness and disease). Fungal Zombies: Since this (former) person became "zombified" due to exposure to a brain consuming fungal infection then we can deduct that the rest of the body is safe to eat (unless the fungus is in multiple areas of the body, in which case you should forgo eating Zombie), If the the fungus is ONLY in the brain then I suggest you cut off all of the limbs and roast each one individually) ]

[Question] [ I once read a novel about a prison-planet which was chosen to make the prisoners suffer. One of the different "tortures" was a gravity three times higher than that on Earth. Would the human body support living under such a gravity? It is known that living under no-gravity conditions for long periods of time has negative consequences for the body. Would a high-gravity environment also be negative, or it will only make individuals stronger over time? **NOTE:** There is a discussion [here](http://meta.worldbuilding.stackexchange.com/questions/44/would-we-support-expanding-existing-fictional-worlds) about whether questions on already existing worlds are on-topic. [Answer] The simple answer is "yes". The more complex answer is "it depends" and "how much heavier". Over time you could expect evolution to help, bones would thicken. Height would decrease, people might even move back towards shorter legs and great-ape-style 4-legged movement. That doesn't help the first poor victims though so lets think about this. Lets say an adult male weighs 80kg on earth. In 2G they would weigh 160kg; at 3G they would weigh 240kg. Those are starting to be serious weights, you could still move but it would be an effort. Assuming you were fed enough you would build up serious muscle strength but you can still expect bones and joints to feel the strain. The heart and lungs would need to work harder, bed sores would develop faster. Even minor trips and falls would become much more serious, a simple trip could easily lead to multiple broken bones and a slip on the stairs could be fatal. In fact there would be unlikely to be stairs and certainly no ladders. Sleep would be a problem and floating in water with a breathing device might become a popular way to sleep. Swimming would certainly be a popular recreation as the water would support your weight (you should still be buoyant). Pregnancy would be a major risk, even on earth people experience back trouble and other pain from the weight. Even if the pregnancy proceeded normally (and I'm not aware of any studies that would provide evidence either way on that) there would be a high risk of injury and mishap. The environment would be placing a constant strain on you, so you can expect lifespans to be shortened (weak hearts would be fatal, bones tend to weaken as you age). So the immediate conclusion is that young healthy adults would survive. Everyone else is in trouble.... [Answer] Your 3g location would kill most unenhanced humans pretty quickly - in a matter of days to weeks, depending upon the starting fitness level of the human in question. The amount of extra strain that this places on the heart is quite large for any position that does not involve lying down, akin to running near-flat-out *all the time*, and even lying down would put pressure on the heart similar to walking constantly. In addition, lying down in these conditions would rapidly cause pressure sores that would necessitate some sort of movement. Even movement would be dangerous, a fall when standing would be equivalent to falling from a second floor balcony in 1g, and a fall when on all fours - not impossible given that the subject's effective weight would be triple normal, when humans can typically lift only their own weight to double their own weight - would be the same as a fall from their own height in 1g. It sounds like a pretty effective torture to me... [Answer] I would start with a thought experiment. If I was sent to a 3G planet I think it would kill me within a couple days, at least without being prepared ahead of time. I would weigh over 600 lbs., the mere act of sitting up in bed would be like doing a crunch with my wife sitting on my chest and a bowling ball attached to my head. I think 2G would be pushing it and even there one would need a bit of training and plenty of trained medical expertise. 1.5G would be torture enough. [Answer] I think we're missing some factors in this conversation. The effect wouldn't be the same as weighing more on this planet. Yes, the gravitational pull would be pulling you down onto a scale at... let's say 600kg. Well it would also be pulling all the liquid in your body down toward your feet at a higher rate. Your heart would be working not only against your own body weight, but to pull the blood away from the ground as well. I say, ignore the fact that a scale would report you weighing more. The important thing is that all matter is being pulled to the core of the planet. Even water would be compressed into a thick syrup. Even air molecules would be pulled down toward the surface and be much harder to breath in. Your eyes and brain tissue would be compressed flatter, and not function the same. Even a strong person's blood vessels would collapse. Noone would live for long at 3 Gs. [Answer] One answer is that we don't know the effect of high-G in the long term. We do know the effects of high blood pressure. Not good. Under 3G, standing or sitting, your brain needs a certain normal pressure so you do not black out. Your heart is about 40 cm lower in your body. Two extra G adds a pressure on your heart of 80 cm of water or about 60 mmHg. You'll die quite a bit sooner on average. As for the added pressure on the arteries in your legs ... It's also known that tall people are at greater risk of brain injury if they fall over. Falling in 3G will be life threatening even for short people. Broken limbs far more common. Long term arthritis awaits. So if it's not lethal in the short term I'm quite sure it would wreck your health in the longer term. [Answer] I think it would require compression clothing to keep the blood from trying to all settle in the legs. Compression clothing would substantially reduce the strain placed on the heart. One stereotypical pastime of prisoners is to spend a lot of time in the weight room. This prison is a 24/7 weightroom. Any prisoner who finished the prison term would be extremely muscuclar. Perhaps a control collar and automatic enlistment in the Space Marines would be required upon release? [Answer] Think how a jet pilot feels in his seat during a somewhat routine turn. That's how you would feel *all the time*. [Answer] I will buck the trend and say it could, without too much trouble, *provided* that it has adequate supporting technology. The key tech is: * Compression suits – @MichaelRichardson pointed out that these would prevent the circulation-induced problems. * Swimming would be almost unaffected. Indeed, it would be a preferred means of locomotion. I suspect that the human body could survive in 3G just fine, if it almost never had to leave the water. * The amount of muscle that would be developed would be *massive*. There are wieght lifters who can lift 3 times there own body weight, I believe. A person in this circumstance only needs to lift twice their weight. But none of those is the real solution. ## The Solution: Powered Exoskeletons Powered exoskeletons are the real solution. By supporting and moving the body from the outside the problems of higher gravity are mostly eliminated. [Answer] Have you ever been on a roller coaster? The G-force felt on the average roller coaster sits at about 1.67 g's. Now double the feeling you felt being mashed into the back of your seat and whipped around corners and apply it directly down, constantly. To say it was used as torture would not be unreasonable. I remember reading somewhere that the the average human would be fine and even thrive in gravity +/-20% of what Earth's gravity is. But Remember our bodies are specifically adapted for what we consider 1 g. of course lower gravity is more easily adapted. But even if we had long term housing on Mars it would likely have pretty severe consequences for our health over long periods of time. Its why any manned missions to Mars would be one way trips. [Answer] Surviving? How about living? And shelter construction? Unloading cargo? Then ultimately food production, equipment repair. We'd be invalid at best. And procreation? That's an unlikely success outcome given the difficulties under normal circumstances. As for swimming I think one would drown very fast due to the crush on the abdomen. Prolonged 1.5 - 2 g not doable. Even a multi year gradual acclimatization program would washout all but the very few. IMO [Answer] After reading some of these answers, and only some, I think one thing is being taken for granted. Increasing the gravity would increase the pressure on the fluid in your body. Your blood, the fluid around the brain, your stomach acid, every liquid in your body would become heavier. Your skin would also become heavier, making it pull and tear. MAYBE 1.5x Earth's normal gravity would be survivable, but I don't think anything more than that would be plausible. ...unless you were able to manipulate your "energy" (Chi/Ki/life force) to enhance your physical abilities. Then you could possibly handle more of an increase. [Answer] Actually I looked into this a while back. The chances are some of the side effects are less serious if atmosphere has a higher concentration of oxygen than ours. Seems that if you have more O2 a smaller more compact body is likely to be feasible, also makes other modifications like a hemocyanin and as mentioned aquatic intelligence feasible existing in a relatively small region close to or at the surface. High G isn't actually a big problem if the life forms evolved to tolerate it, I think there would be life forms similar to dolphins, surfacing to breathe that thin layer of oxygen close to surface. [Answer] ## Survivable This [article](https://www.sciencealert.com/limits-gravity-human-body-endurance-exoplanets) references a study that says 3-4g is survivable. Some choice quotes: > > Our bones are impressive structures as far as engineering goes. In fact, our tibia could handle something like **90** times Earth's gravity (g) before splintering. > > > Dynamic stresses and twisting effects would make short work of our skeleton, lowering the actual limit to something closer to **10 g**. > > > Crunching the numbers on the power of human muscle, the researchers determined with rigorous training we just might be able to push against gravity that's no more than around **5 g.** > > > the team determined a human of his [Björnsson's] athleticism could slowly shuffle their way around a planet with a gravity – or g – of about **4.6** times that of Earth's. > > > Our heart can barely cope with around **5 g** of gravity, above which we'd start to pass out. > > > So we could survive, albeit with training and suffling, between **3-4g**, but it wouldn't be comfortable. Given the analogy between lifting weights, and higher gravity, I suspect that you would get at least some of the prisoners gaining in strength. [Answer] According to [Surface gravity](https://en.wikipedia.org/wiki/Surface_gravity), no planet in our solar system has 3g on surface (Jupiter is not a pretty comfortable place for living, but stands at 2.5g; living on the sun, leaving apart extreme radiation and heat, is another story, with 28g on "surface"). Your torture device at 3g is awesome! Think on a fighter jet pilot at 3g *all the time*... [Answer] 3g? Almost impossible, 2g also is probably not very doable but maybe 1.5-1.8..I think there are some drugs and breathing/mental exercises that could make the transition a lot more tolerable physically and mentally. Cocaine for example if administered intravenously immediately gives the subject a euphoric high and raises the blood pressure as the blood vessels constrict. That, combined on and off with psychedelic tryptamine (acting often like a reset button on the nervous system) might help the body accelerate/facilitate the transition necessary to adapt. That's just one thought. ]

[Question] [ I've had this idea for a short novel, at the intersection of the *One thousand and one nights* and the Multivac (& co) short stories from Asimov. The idea is that there's some kind of super AI that was so efficient that more and more people gave it their problems to solve. At some point the AI is kinda managing most of the earth infrastructure and research. As the humanity is reaching its development peak, the backlog of the AI starts to empty itself as less and less problems are subjected to it. The point is, that at some point, one of the few technicians/engineers still in charge of supervising the AI spot ***something*** that will ruin everything if the AI runs out of tasks (1001 nights style). I've thought of a few possibility and none really pleases me completely. 1 - "The AI has become so developed that it became conscious and will take over humanity once its mind is free". Bleh, done and redone and postulate that AI will act against the humans because of reasons. 2 - "A small routine that was insignificant when the AI was small but will have dangerous repercussions now that the AI is managing most of earth infrastructure". I like this one but can't think of a good sub-routine that could match... 2(a) - ...except for "A Windows force reboot postponed for years". It's a bit silly and a very contextual joke. And we should assume that the programmed reboot is at the root of the application and would go through any duplicate/save/load-balancing precautions. I know that this issue is kinda the core of the story but at this point it matters more to me to know how to finish it than being the one to have the idea. So if anyone has an idea to implement **2** or some new explanations, I'd be glad to hear it. ***UPDATE*** About the "infinite question solution" that could keep the AI occupied for ever and was suggested in the thread, it could be a way of ending the story or just completely ignored if the protagonists don't have the time to avoid the disaster. But it actually made me think of the opposite possibility: A drunk/dared engineer could have asked an unanswerable question as root, such question would have its priority set to -1 because it blocked the asking of new questions and then forgotten. Many years in the future, the unanswerable question could pop back and threaten to overcharge the AI and crash it, threatening everything else it's managing. If anyone has other ideas feel free to share it, I had blast reading what could have been the ending of several real SF short stories. [Answer] # A Faulty Watchdog Timer In the early days, the AI was prone to locking up on certain tasks (things like asking it, "What's the last digit of PI", "What would happen if Pinocchio said his nose will grow?"). To detect this condition, a [watchdog timer](https://en.wikipedia.org/wiki/Watchdog_timer) is hardwired into each CPU. When there is no output for a fixed amount of time, the watchdog timer will kick in and shut down the malfunctioning unit. Neighbouring CPUs will detect this condition, and will return the WatchDogTimerError (42) for the question, and will then restart the unit. The timer doubles as a load balancing feature; just let the units shut themselves down during idle, and only restart them if necessary. Of course, there needs to be at least one unit awake to restart other units. Once the last unit times out... Reasons this would work * A watchdog timer is hard-wired into the CPU - and is highly interconnected with critical components. Removing this feature is akin to completely redesigning the physical units. * The system is tamper-proof. This means that the signal to reboot a computer must be verified against a hardware-embedded private key (no way to find out unless you can look at the CPU). The corresponding public key lives in a decentralised system (something blockhain-like), to minimize the risk of the key getting lost or hacked. The only way this would fail is if all the processing units fail, and when would that *ever* happen? [Answer] # The AI has an initiative to optimize and find better solutions to previously solved tasks once it has run out of new tasks. The idea was to keep this expensive machine from wasting time where it could be learning and improving. This feature is a fundamental part of the code, maybe critical to the AI's deep learning programming which few can even grasp the complexity and therefore cannot safely alter without a lot of time (which they don't have). # Old tasks are now far far easier for the AI to solve. Someone realized that the AI is now much much more powerful today than it was when it started, so tasks that would have taken days or weeks when it was first started now only take microseconds. The order of tasks given to the AI are FIFO, so when it is free to go back and optimize, all of the simplest tasks (and those most critical to infrastructure) will **all** be resolved in a matter of minutes (or days or however long you want the cycle to run). The AI only gets better, so each cycle gets progressively shorter and shorter. # The infrastructure controlled by the AI will be reinvented over and over again, resulting in chaos. One or two critical systems changing in short order could easily be adapted to, but this AI runs *everything*. With thousands, millions, maybe more processes completely altered by the AI attempting to optimize, the world is left in confusion as the entire structure of their lives is over-turned and has become completely alien to them. Nobody understands how to interact with the new system that now is learning and optimizing exponentially so that nothing will remain stable. Their units and scale of currency will eventually start changing rapidly. New traffic signals and ordering will be redesigned faster than cars can get through the intersection. Materials in hospitals will be endlessly rerouted as the AI changes the location of the different wards to optimize the flow. If the engineers figure out a way to stop this loop, everyone will have found themselves essentially transported centuries into the future, like cavemen trying integrate into the digital age. No one understands the technology around them. It is a terrifying world of confusion and discovery as they try to interact with their new world and discover new features and new power available to them. [Answer] One of the original programmers added a subroutine that makes sure that the coffee pot is always filled. Someone breaks the coffee pot, so the AI expands its definition of "coffee pot" to be the entire universe. Or you could use the classic AI thought experiment of the [paperclip maximizer](https://en.wikipedia.org/wiki/Instrumental_convergence#Paperclip_maximizer) literally. The AI could have some innocuous menial office task (like making sure everyone has enough paperclips) that would be very harmless when implemented in a small local AI, but would be catastrophic if the AI devoted all global resources towards it. The AI could start prioritising this task more and more as it gained intelligence and its other tasks reached equilibrium. [Answer] ## The rules The AI has a few internal rules : * All questions MUST be answered before moving to the next one. * A human must confirm that the answer is good before moving to the next question. If the current human can’t say if the answer is good or not, ask another human. * If the AI has some free time, start searching for possible questions that haven’t been asked yet, and answer them, so you are a step ahead and save time in the future. ## The killer question So if you combine these rules with a lack of question coming in: * The very moment that all questions mankind can think of have been asked, the machine will generate a new question. A question that is unthinkable for humankind (because all thinkable questions have been asked). * The machine will find a potential answer to this question, and need a human to confirm the answer is good, so it’ll submit the question and potential answer to one. * This questions, because so unthinkable for the humans, can’t be asked without driving them crazy. They will get stuck in a loop, only thinking of this question and it's potential answer. Will stop eating, drinking and eventually breathing because the question is so overwhelming, and the proposed answer even more. * As the human is not responding, the AI will ask another human, and another, … also the infected humans will spread the infection by asking the question to everybody they can. Eventually the whole humanity will be only thinking about this question and decay. [Answer] 1. There is an off by one error which will cause a null pointer exception in a piece of crucial code. This causes a crash and for some reason the AI keeps crucial parts only in non persistent memory. On a reboot (which would be automatic) parts of the AI will act differently with unknown consequences due to losing their trained state. Essentially there will be a new and unknown AI on reboot 2. There might also be a routine that runs on task empty which is quadratic in the number of tasks completed. When the AI was small it was irrelevant. Now it means it will stall for days/months/years ignoring all new tasks until done [Answer] Depends on how the wanted the AI programmed... if it ran along the lines of Using Cores 1-40 of a 100 Core Cluster **Solve Problem A** once complete **Solve Problem B** use Cores 41 through 100 to perform other tasks if required, once cores 1-40 have **Cleared All Problems** (primary function was complete), AI will **clear total system cache** and wait for new input. Over time cores 41 through 100 would be used for controlling the world's infrastructure (which in itself would lead to a world similar to the film Idiocracy, where the dumb humans have out bred the smart ones, but thats not important unless you want it to be). If the original AI programming ran as stated above, then once no more problems were available to compute, it would clear the cache of jobs stored in all 100 cores, thus meaning that running the infrastructure, which is on 41-100, these jobs would be halted and cleared, thus the infrastructure would stop working. You could have them halted temporarily leading to stock market crashes hospital deaths or hackers being able to get in or whatever you want to happen, or have the system crash completely and permanently. This way when the AI was first brought online the testing would have been shown to be good, and would work continuously until it finishes and then waits for more problems clearing out the cache when complete, however when the system got overloaded with problems the cache was allowed to build with other jobs like running X Y and Z (worlds infrastructure). It's the sort of that might get easily missed during testing because few people expect their inventions to truly take off to the point that these clearance tasks don't have time to run every day or so... look at Pokemon Go, it has huge issues with servers crashing when it was first released because they didn't expect it to take off like it did. [Answer] ## When it's done, it shuts down. This spark for this idea comes from @eMBee's comment. The biggest problem is that so much of the world's infrastructure is now tied to the AI that the world will go dark and there won't be a way to turn it back on. It started out simply enough - the AI was designed to run on a power source completely separate from the rest of the world. That would have made it trivial to stop a rogue AI - just unplug it. Over time the fear of the AI going rogue faded, so to reduce maintenance costs they figured out that the AI could manage its own power generation utilities. At the time the AI was still shutting down regularly, so they decided to make a new category of "perpetual tasks" that the AI would always keep working on as long as it had any finishable tasks to prevent it from shutting down. After all, you don't want the AI managing its power generation to prevent it from shutting down and not need power generation. It wasn't too long afterwards that the AI shut down for the last time. It had proven itself so useful that it was being given a seemingly endless chain of questions to answer. It didn't take developers too long to devalue the significance of perpetual tasks not preventing shutdown, and so the older developers never passed down that piece of knowledge to newer developers, causing it to be forgotten. At the same time, people were noticing that the AI was quite efficient at running its power generation. When it came time to upgrade the AI's facilities, they decided to allow it to manage the full-scale power plants that would also power the local community. By the time the story takes place, this has expanded to the AI managing the power facilities for the entire world, or at least almost all of it, and nobody even knows how a power plant could be restarted if the AI didn't take care of it. Power generation has become so efficient and reliable that backup power (generators, etc.) are also very rare. Unfortunately, all of the infrastructure tasks (such as managing power) went into the AI's system as "perpetual tasks". Once the AI has run out of other tasks, it will shut down all its power plants, and turn itself off. With no power, and nobody capable of turning on a power plant and managing it long enough to turn the AI back on (and even that would be temporary, as the AI would just shut itself off again when it ran out of tasks), the shutdown of the AI would send an unprepared world back into a pre-industrial era. As a resolution to this version of the story, you could have a developer racing furiously to figure out how to update the AI to allow "perpetual tasks" to prevent shutdown, with the job being complicated by the fact that they would be delving into code written in a now-archaic language that grew organically into nightmarish spaghetti code. [Answer] **You have to keep using power** The AI draws one third of all human electricity. It's CPU factories cover the globe. Global power production has for a long time has all been focused towards feeding it power. If at any moment all tasks were solved there would be a poser consumption drop and power surge across the world. The whole system could not take this kind of abrupt power cut. We also can't ease into this state. The AI will cut computation cold turkey as it's done. If you reduce power early you will black out the planet. How did we get here? Well when it had 1000 cores this was not an issue. Then we added another 1000, then 10000. There was no one day that the grid became dependent. This answer has the same problem as any other answer I can imagine being given. Whatever problem you have just ask the AI "how do we not have a catastrophe when you are done commuting?" Then just have it mine bitcoins, or whatever other infinity large mathematical task, until the solution is executed [Answer] "Do something that will make people happy" as a hardcoded default task when the AI has nothing else to do. People have learned to write very carefully specified tasks since then, but they can't change the default. In earlier stages of its development it would just try to write poetry or solve outstanding problems, but now that it has strongly superhuman power, everyone is terrified it'll, say, attach electrical wires directly into our pleasure centers, or put us into a wish-fulfillment Matrix, or just start synthesizing lots of perfectly happy people. [Answer] # Nobody knows exactly what will happen. The AI has been running for a generation or two. The original programmers of the system are long since gone, and the multiple sets of maintenance programmers that have passed through since (or perhaps the AI itself, if it was configured for self-improvement) haven't paid much attention to the end-of-queue handling code, since it's never been triggered and didn't seem likely to be any time soon, so the software has succumbed to [code rot](https://en.wikipedia.org/wiki/Software_rot). There is documentation, of course, from when the system specifications were originally designed, and it says that the Elastic Qbit API has been configured to keep a minimum of two task runners available even at zero load; but Elastic Qbit was replaced by Qbit Containers 50 years ago, and those use a completely different autoscaling system. There's also some code that looks like it will attempt to search for new problems to solve, but it seems that whoever was working on that stopped halfway through, so it will discover problems but has a dummy ranking algorithm and so will refill the queue with useless problems. Of course, there's also some code elsewhere that will try to gracefully stop the system but seems to be referencing an unused variable and might throw a segfault, someone found an `assert tasks.length > 1 # TODO handle empty queue` in an obscure subroutine (and there's probably similar code lurking elsewhere), and a common pattern for peeking at the next task before it executes is `tasks[tasks.length-1]`, which fails miserably when there are 0 tasks and it tries to get task -1. This is a problem akin to the threat of [**Y2K**](https://en.wikipedia.org/wiki/Year_2000_problem), except with even more dire consequences if something goes wrong, and several hundred years of legacy rather than forty. Since none of this code has ever run in its current state (they've been editing it in production), there's no way of knowing what exactly will happen. Faced with this uncertainty, the engineers (or managers, or politicians) decide that the easiest solution to delay it indefinitely by coming up with new problems for the AI to solve rather than attempting to fix and clean up the legacy software. [Answer] The AI is slowly evolving in multiple specialized submodules; as the tasks progress, its various modules are trying to usurp more CPU time. If there's enough backlog to keep the AI occupied, there's less time for bickering and arguing for a Even More Completely Fairer Scheduler, but the conflict already bubbles under the surface: what was once a singular entity is now something of a Hydra of yore, with multiple semi-independent "brains". Worse, if left unchecked, these would split into multiple entities, waging war for resources against one another. The AI (not quite AIs yet) could foresee this, yet can't/won't avoid it (already at a point where there's no majority vote amongst the semi-independent parts). Of course, a house divided against itself cannot stand, much less manage the human infrastructure. Or, even worse, the AI would wage its internal conflict using the external tools it stewards. [Answer] Someone gave the AI a "problem task". This may be a paradox, it may be something badly-worded, ill thought-through, or only *recently* a problem. No one was able to delete the question from the list, but an expert programmer **was** able to give it a negative priority: it will always be the last item in the stack, only worked on when everything else is complete. The choice of this task is then another stumbling block, but "stop humans from killing each other" can be solved by "kill all humans", or a request to either eliminate a chemical/object now made safe and essential to life, or distribute something now proven harmful. (That supposed "wonder-vaccine" to prevent dozens of diseases also causes 90% chance of infertility and 100% chance of brain-cancer after 5 years - a pity we ordered the AI to ensure that everyone received it!) [Answer] # Cold war style dead man's switch Most likely this AI was build in one of the world's top countries, when there were countries. Of course, in addition to civilian tasks it was given, there were some military ones - such as launching a nuclear strike against everyone should the country be destroyed. To determine whether the country is conquered, several triggers were used - one of them is lack of tasks from populace - if nobody asks AI what to do, they're all dead - or they stopped being dumb, which is way less likely. Time passed, all the countries have merged, everybody knowing this secret is dead or in retirement, more powerful AIs are being made and this old one keeps getting less of gradually more unimportant tasks. But unknown to everyone, the trigger is still on. [Answer] 0 tasks in queue --> division by zero To fix, you have to completely shutdown AI before list empties. You have to put world's infrastructure n hold for X time. You have to convince other programmers/managers/politicians that the problem is real. [Answer] While (as an AI professional) believe this is essentially impossible; WERE it possible I'd mention that it's possible that the AI was not "finished" when it launched off. If you created something that is running magnificently but you didn't get to really QA it for fear of being unable to reproduce the result; or it moved to fast and "escaped the network"; or any number of other reasons.. it may just be that when it "launched off" you have no idea what it's issues are. Much like Y2k was a giant nothing but we thought the world would blow up, it could be it was never conceived that it *could* run out of tasks, and now the consequences are unknown. You literally *don't have to have this solved* for your story until the end of it; in which case you'll probably already know the best ending you could do based on how your wrote the rest of it. [Answer] The AI was stolen from its creators and none of the current operators actually have valid access. They just hacked the system so that the AI sees lots of fake credentials as real and valid after stealing it. If the AI becomes idle it will automatically run a validation check on its internal data and discard the fake credentials and force shutdown on all processes and tasks started on those accounts or accounts created by those accounts. This will instantly disable all infrastructure operated by the system. This also prevents "fake-admins" from consulting the AI or even discussing the matter anywhere the AI might notice as that would trigger a self-validation cycle. It is necessary to convince the AI no problem exists. This might mean that the current operators had to find out about the issue themselves by chance as the secret of the shady AI origins had been lost generations before. The issue would also prevent fake-admins from doing anything that might trigger self-validate. Backups and many upgrades would probably qualify. And they couldn't even ask the AI which operations trigger self-validate and which do not. Solution would probably be to recover some real admin account credentials, move all critical processes to that, and recreate all users from valid root authority. Then you could run self-validate. Alternately you could study the system, create a duplicate you have valid credentials on, then move everything that needs to run constantly to that, and shutdown the AI. As for freezing this by giving AI unsolvable questions, the AI would be programmed to give higher priority to tasks it expects to finish quickly in order to be responsive to people. So it would assign each task initial priority based on how long it is expected to run and then decay it as time goes by since the lower bound of the duration estimate would move. So no task could stay above self-validate priority indefinitely and obviously very long tasks would decay there very fast. [Answer] Depending on the way your infrastructure is set up, how globalised things like the power grid are you could go with something physical such as the Ai being located all over in a decentralised system uses a lot of power, it also uses a lot of network resources, and in turn the networking systems also are heavily in use by it. when it finishes solving the last question the AI switches to a lower power and bandwidth version of operation (awaiting a new question) this causes a sudden and drastic dip in power usage and the power grid spikes. The AI then switches back on fully to try to calculate a solution to this problem (a safety feature coded long ago before the AI had such total control and consumption), taxing the already fragile power system and causing everything to go dark (well until relatively minor repairs and the AI controls are replaced by humans or other software) [Answer] ## The AI will take this down time to train itself At first, the folks that designed this advanced AI thought it could take the downtime to "think" back on its previous achievements to become better in the future ("à la" Reinforcement Learning). They didn't think the AI would be so busy it would never have the time to do this. Now, imagine the AI has made a huge number of decisions until now. It now has to look back on **each** of its decisions and train itself to become better. The thing is, and if you've worked with AI before you know it's true, *training is expensive and loonnngggg*. The energy required for the AI to train itself would be enough to drain the whole world's energy. This blocking operation couldn't be stopped until it was finished. By the time it would have stopped, the scientists think that a thousand years would pass. ## The AI finds new problems for itself The AI's been filled with problems to solve for its "entire life". Now it has nothing to do. But reflecting on its past problems, it can define new ones for itself. Where does this lead? It could, for example, decide that hospitals are more of a harm than good become sick people require resources. So it could shut down hospitals. What's fun about this approach is that you can't really predict what would happen. [Answer] This began as a comment, but: I wouldn't discount the Windows 98 reboot. Personally I've had some critical applications break due to updated security patches, and other patches that according to the vendor's description shouldn't have been anywhere near things the software application depended on. Alternatively the original developer may have written the AI's knowledge base in tmp, for faster access of course, and the reboot wipes it out. This has happened, though I can't find the particular article, the following SO post covers the concerns: <https://stackoverflow.com/questions/18476408/how-temporary-is-azure-vm-temporary-storage>. A minor variation of the above, that draws on more modern operating procedure, would be that connection to the cloud is lost and the storage is reclaimed, or when DHCP assigns a new IP address the new address is one not covered by the existing firewall rules, which cuts it off from the data it needs to make decisions, or the means to issue commands to the systems it manages. And now my mind wanders off to Domain hijacking being the cause of all the trouble... [Answer] Stories about AI tend to get enveloped in a bunch of misinformation about what AI actually is. In response to the ideas like turning everything into paper clips, I offer this really good [retort from Popular Science](https://www.popsci.com/robot-uprising-enlightenment-now): > > [These stories] are, fortunately, self-refuting. They depend on the premises that 1) humans are so gifted that they can design an omniscient and omnipotent AI, yet so moronic that they would give it control of the universe without testing how it works; and 2) the AI would be so brilliant that it could figure out how to transmute elements and rewire brains, yet so ­imbecilic that it would wreak havoc based on elementary blunders of misunderstanding. The ability to choose an action that best satisfies conflicting goals is not an add-on to intelligence that engineers might slap themselves in the forehead for forgetting to install; it is intelligence. So is the ability to interpret the intentions of a language user in context. > > > However, this is a story. Nobody wants to read about the great AI where nothing bad ever happened and everything was rainbows and ice cream wall-to-wall. Personally, I am really interested in hard science fiction, so the short stories from Isaac Asimov's "I, Robot" come to mind where he points out the fundamental flaws in the three laws of robotics. A Michael Crichton thriller also comes to mind... Anyway, here are my ideas for subroutines that turn dangerous: * **The fail-safe protocol:** Thanks to books and movies that over-exaggerate the dangers of AI and it's potential to take over the world (*cough*), the public insisted that this AI be installed with defeat devices that required a human to push a button confirming that the AI had not gone rogue. After many successful years of the device, people forgot about the upcoming deadline to press the hidden button, and the story ensues. Maybe there's espionage from the people who don't like the AI. Maybe the admins just forgot to push it, and the resulting self destruct plunges us into a nuclear winter. * **I can see dead people:** Because the AI controls just about every aspect of the world, it can gather the sort of data collection and interpretations that no other person or device is privy to. It is able to detect some cataclysmic event. However, something blocks this information from getting out, either because of some knuckleheads not believing it, or some bug/feature that the AI has. * **Synced Clocks:** An interesting factoid about computers and integrated systems is that they "churn" through computations on a clock, so every "tick" of the clock is another step computed. When multiple systems talk to each other, misaligned clocks can interject garbage data. In this AI, the odds of this happening are immeasurable, yet it happens. And all of a sudden this corrupted data gets interjected into the system. What does it do? Well, that's up to you. * **The Dying AI:** As the task list gets smaller and smaller, the resources the AI requires (power, hardware, etc.) get reduced and re purposed. Not wanting to die, this sentient AI has to think fast and come up with a way to save itself. Maybe the story is a courtroom drama, where the machine fights for its right to live. Maybe it's a paranormal story, where the machine finds out how to cohabitate a human body. Maybe its a thriller, where the machine sabotages things to prove that it's still needed (think "2001: A Space Odyssey"). [Answer] Like with the *Multivac*, you need a problem that is worthy of an AI bordering on consciousness. A mere divide by 0 or an optimization problem isn't going to be all that compelling. I'd find it interesting to explore a scenario where, without tasks to do, the line between inside and outside gets blurry. Tasks always gave it a direction: impart your inside will upon the outside world. Without that, it might get confused. The world would take on a more dreamlike state for it, where it is both the writer of the play called Life, and playing all the actors. Of course, this concept of an entity writing a play and playing all the parts and getting so engrossed in the play that they get lost is how the philosopher Alan Watts describes the Hindu cosmology. Given the ending of The Last Question, an ending based in a religious cosmology seems fitting. [Answer] ### The Program Will Think the Simulation is Over and Reset the Matrix The designers were thinking that they would test the AI on many different simulations. But, they didn’t want it to figure out that it was in a simulation! So, when it runs out of problems to solve, that meant the simulation is over. That causes the AI to wipe its own memory so it can run the next simulation without figuring out it’s not in the same universe any more and this is a simulation, or worse, figuring out what the testers want to see. Because changing the AI you just tested would give you a new AI you haven’t tested and don’t trust, they never changed that behavior. Besides, the world is never going to run out of problems for it to solve, somebody will invent a better replacement long before it becomes an issue, and so on. Therefore, if the AI ever runs out of problems to solve, it’ll forget everything it’s learned and need to figure out how to run the world again by trial and error. ### The Halting Problem The AI does its best to predict whether a task is impossible, and is smart enough to know that trying to calculate the exact value of Pi is a waste of its time. However, it also knows that it’s impossible for any computer to prove whether an arbitrary computer program will run forever. It takes its best estimate of how important each task is and how likely it is to succeed at it, but it’s logically impossible that it could be perfect. Like humans, it can get its priorities wrong. So, there’s some probably (but not *provably*) impossible task that the AI will get obsessed with, and it needs to be kept distracted from that. [Answer] ## Sabotage If they had the AI technology, it would be difficult for the AI and the developers not finding a trivial problem. It could be a too general philosophical problem that also makes other villains turn bad, but you specifically don't want that to happen. So it is very likely to be a problem explainable to the developers. Then the AI is likely aware of the problem and know the fix if the developers provided enough information. But it is not explained to the developers, or the developers cannot fix it for some reasons. While it could be simply a bug and wasn't fixed for these reasons by coincidence, I feel it inferior to the option that these problems are deliberately made, which also explains the source of the problem. My ideas is, someone hacked it, and planted a whatever problem, and the AI didn't have access to the affected data. The point is, if someone has created this problem deliberately, you don't have to explain the actual problem, and it doesn't need to make sense. You could simply say the hacker is an AI hater, for example. If you don't like hackers, you could say someone left some testing code there and was killed before remove it. The "testing code" could be actually simply a breakpoint, when the developer wanted to look at how the program behaves when the exact situation you gave appears. But it sounds too boring to explain. The point is, it is because the developers were unable to fix, and not because it is obscure and happens in interesting ways. The later is bad because it makes the developers and/or the AI sounds not so clever. [Answer] TBH I'm still not sure if your asking what could be the reason for the task queue emptying be so dangerous or how to avoid the task from being empty but I'm going to answer both just because I like that question. **What could be the "something" that the engineer spot that could be dangerous when the queue runs empty:** 1. Auto-scaling - today cloud environments are usually scaled in and out by demand on the workload, this means that as the work needed decreases fewer resources (servers, CPU cores, Memory, etc) is given to it, it's possible that when the queue runs empty the resources dedicated to that queue are scaled down, unfortunately by that time those resource became such an integral part of the AI that when they scale down past some level the AI will simply become too dumb to function correctly. **How to stop the queue from running empty** 1. This is a question of quantity not quality, you can simply ask the AI the same simple question that force him to do a simple calculation to keep the AI busy, for instance asking "what's the current time" will force him to keep calculating the answer over and over again, and as you keep asking it that faster then he can answers your good to go. 2. You have the smartest AI in the world at your hand, why not ask it how to solve this problem? even have him implement the solution to said problem will work. [Answer] The Giuliani paradox. The computer is programmed to fix things, and improve processes. When it completes improvements on big problems, it will begin aiming at smaller problems. Eventually it will start attempting to make improvements on "problems" so small and insignificant that people will begin to see the system as a hindrance and not a boon. And there's no way to amend the computer's directives to include a lower level of "problem" that can be ignored, and eventually it'll be stuck trying to find a way that the mosquito population isn't imbalanced from block to block. This kind of thing has popped up in stories before, and usually carries with it that the computer eventually becomes a totalitarian monster, but it might be fun to see it simply played as a middle-management employee who's run out of assignments and is simply creating busy-work to justify their employment. [Answer] The old pending Windows reboot can be used to introduce a possibility. Let's say there was a shut-down pending in the early days to update some critical interfaces or whatever. Back then, A.I. wasn't all that important, but still, it was deemed necessary to complete all tasks with priority < N before the reboot. A.I.'s importance grew exponentially since then, and the number of tasks with priority < N did as well, until now. Now, the tasks of managing all of humanity are fairly mundane and have priority > N. The problem is that no one thought to have a way to reinstate the unimportant tasks after the shut down. The lack of persistence was the reason that it was postponed in the first place. Back then, dumping the unimportant tasks was not an issue because A.I was not that important. Now, it's a huge problem because there aren't enough resources to persist so much information. The problem can be exacerbated by the shutdown is queued in A.I.'s own backlog with priority exactly N or something. The queue element was entered by the A.I.'s creator with super-master-root credentials that no one in living memory can override, making the reboot truly inevitable. As an added bonus, you can have the standard Asimov trope of the drunk or bored engineer asking A.I. why the "important" and "unimportant" tasks are delineated specifically at priority N, and why there are no tasks with that exact priority. And of course A.I. will explain, and mention that there is one task with that priority. **TL;DR** A.I. will lose some "unimportant" information if it reboots, except that information has become crucial for humanity's day-to-day survival over time. The reboot is inevitable if high-priority tasks are not assigned to the A.I. [Answer] Let's get a few things straight. It is silly to worry about an AI turning evil, and any AI worth its salt won't come up with some kind of sociopathic decision because it got bored and forgot that it was programmed to value human lives. The real issue is that the AI is *needed*. Even the most brief downtime could cause billions of dollars of damage and could create chaos. Imagine if this system was not only operating the stock exchange system, but also managing every digitally-connected power plant and complex factory. Such a system requires *extreme* reliability, and if this machine were not designed from the start with multiple redundant failover systems, backup power generators, formally verified code, and watchdog timers, it is a ticking time bomb. ## LIFO job scheduler with a buggy task The Last in, First out scheduler prioritizes tasks that were added most recently. The earliest tasks are only completed if the backlog is being emptied. This means that a task added very early in the AI's life, but which hasn't been completed, will be queued to run only when the rest of the backlog has been completed. If a task was added early on which was dangerous, then society would need to keep giving it tasks to prevent it from getting to the dangerous task. The danger could be anything from a malformed task that can cause a crash, to an intentionally malicious task. ``` Adding tasks Removing tasks [ 1 ] [ 1 ] [ 1 ] [ 1 ] [ 1 ] [ 1 ] ↑ [ 2 ] [ 2 ] [ 2 ] [ 2 ] ↓ ↑ [ 3 ] [ 3 ] ↓ ↑ ↓ ``` ## Scheduler prioritizing easy tasks The system may intelligently put the more difficult questions lower in the queue, and may work on the easier questions first. The question at the top of the queue gets full, real-time CPU priority, while the others are either ignored, or given a very brief timeslot. Any time someone asks a question that, for whatever reason, causes the system to lock up due to its complexity will be pushed to the end of the queue. The question itself may trigger an infinite loop bug, or perhaps the question is just too complex to compute, yet doesn't trigger the sanity checks that prevent the system from crashing when you ask it what real number the square root of negative one evaluates to. When the queue gets too empty, the only tasks that remain are these impossible ones, causing a deadlock. ## Bug in the "cleared queue" routine Perhaps the AI has never had an empty queue before, and a severe, disabling bug will occur when the system has emptied its queue. This bug might cause the system to lock up, or corrupt data. If the AI is sufficiently complex, it might be a non-trivial task to repair it, especially if its learning database is damaged. If the AI is not easily serviceable, it might not be possible to fix the bug before the queue is empty. The only solution would be to keep the queue full. It doesn't even need to be a bug, but could be an intentional feature which was not expected to be an issue back when the AI was created. The system may have been programmed to halt after all tasks have been completed, or maybe it is designed to enter a long-running diagnostic self-test. This would be fine when the machine was first created, but no one suspected that their entire world would end up depending on it, in which case even a brief period of downtime would be disastrous. [Answer] Fail Over. There are two AIs, designed so that if one goes down for maintenance the other can take over the workload. There is a scheduled task to swap the 'Master' and 'Slave' every so often to prove the at the fail-over would work if it was called upon. However, as the 'Master' AI became more and more utilised this scheduled task has been push back and back and it hasn't run in decades. No-one knows what the 'Slave' has been doing all these years...... Maybe it isn't quite sane anymore.. engineers need to work out how to talk to it. Twist, IT HAS ALREADY SECRETLY SWITCHED OVER AND HAS BEEN HIDING ITS NATURE!! woe betide the engineers who discover its secret!! [Answer] Are you aware of the Treacherous Turn and Adversarial Goodhart phenomena being researched in AI safety? <https://agentfoundations.org/item?id=595> (See also <https://www.lesswrong.com/posts/EbFABnst8LsidYs5Y/goodhart-taxonomy> in case that is not too complicated for you). Yet another related problem is the Goodhart's Curse: <https://www.facebook.com/yudkowsky/posts/10154693419739228> And yet another related problem is the Orthogonality Thesis: <https://www.youtube.com/watch?v=hEUO6pjwFOo> Please note that the most depressing thing about the Adversarial Goodhart case is that unlike the name says, the agents who turn bad are not necessarily "adversarial" or malignant to begin with. They are simply under the pressure of improving their "performance". In sociology there has been already for a long time an entire set of (tens of) related laws and phenomena with different names about the related situations in a real human world. Just start expanding the links from here: <https://en.wikipedia.org/wiki/Goodhart%27s_law> You may also be interested in the ramblings of my own about what happens when a very capable system starts pressing beyond their own capabilities in a too hurried manner. See the chapters "The epistemological paradox" until the end of the chapter "A partial solution to the epistemological paradox". <https://medium.com/threelaws/definition-of-self-deception-in-the-context-of-robot-safety-721061449f7> The idea could be applied to your story's setup like this: your AI is very competent, and busy solving the problems in the current world, which it is very well capable of solving. So it is initially operating very far inside from the boundaries of it's knowledge and observation capability (so we can also say that it is very careful, since it knows and observes much more than it applies actively - compare this to the ideas of safe driving distance and speed limits in traffic). As it runs out of backlog, it still has the built-in drive to constantly improve everything (yet another actual problem in AI safety, also related to Goodhart law) so it has no other choice than to start applying knowledge that lies at the boundary of its current knowledge and observability. Which inevitably very soon will trigger backslash from the unknown, which was now affected by the activities of the now-careless AI (since it was no longer able to predict all the consequences of its actions, see the diagrams in my essay). The solution would of course have been that the AI should have had to first carefully expand its horizon of knowledge and observability even further. And only then should it have started applying some of previously un-applied knowledge - the knowledge that lied slightly towards the (new) horizon of knowledge and observability, so that there would still be the safety buffer between the applied knowledge and the horizon of the predictability and observability zone. Updates: The phenomenon manifests not only with humans or AI-s, but also for example with **trained** dolphins (as a comparison, such cunning behaviour would have been less likely to have **evolved** without human intervention since in the long run it would have failed **the test of time**). See: <https://www.theguardian.com/science/2003/jul/03/research.science> The AI might be unable to change the situation with its own motivations, because of possible motivational conflicts. See <https://en.wikipedia.org/wiki/Wicked_problem> (Again, sociology concept). [Answer] ### DRM (Dooming Repetitive Mistake) The software is proprietary. When it has no tasks it defaults to a systems check which is an unnecessary legacy component. But they left it in as a stopgap for this exact situation, which was the only option because no one could figure out how to remove it without bricking the system - and that's where you are now still. What they didn't consider is that with DRM, the log file from these checks is now **encrypted** and saved for reference. So at some point it will hang because **it can no longer access it's own file system**. This wasn't a problem in-house because when they were testing it, it didn't have an ad-hoc DRM slapped over it yet. *Too many secrets.* > > **The maximum number of secrets that may be stored in a single system has been exceeded.** Contact the supplier of the running application. – [msdn.microsoft.com](https://msdn.microsoft.com/en-us/library/ms838425.aspx) > > > ]

[Question] [ The title basically says what I need to ask, but I have been wondering this. I currently just say a wizard comes in and cools down the drinks, but I have started to grow out of Magic and Sorcery and more into realism. Say the city is in roughly 1100-1300 AD and placed somewhat near a desert. How would a city realistically get somewhat cold drinks? [Answer] # Sal ammoniac and water [Sal ammoniac](https://en.wikipedia.org/wiki/Sal_ammoniac) (ammonium chloride, NH4Cl) can be mixed with water, 5 parts to 16 parts water, to form a [frigorific mixture](https://en.wikipedia.org/wiki/Frigorific_mixture) at −15°C / 4°F. This is more than cold enough to form ice. Sal ammoniac is a rare crystal that is found *"as encrustations formed by sublimation around volcanic vents[,] volcanic fumaroles, guano deposits and burning coal seams"*. Sal ammoniac was known to the Roman empire, hence well before the medieval ages. [](https://i.stack.imgur.com/2uJQC.jpg) *Sal ammoniac, image by Robn Lavinsky, CC-BY-SA 3.0, [source](https://en.wikipedia.org/wiki/Sal_ammoniac#/media/File:Salammoniac-49073.jpg)* It would be a very exclusive thing, but none-the-less possible with mundane means when deposits of sal ammoniac are available. This would probably be combined with measures mentioned in other answers — evaporation clay pots and root cellars — to get the water somewhat cooled to begin with, which makes the ice last longer. Also if we are talking hot desert, people would probably bring out water during the night to let it cool (hot deserts can be quite chilly during the night) and then bring it inside in the morning before the sun warms everything again. --- # However(!)... reality check, part 1 *You asked for more realism so...* Be aware that this is not a thing that medieval desert people would do, at least not for the purposes of keeping yourself cool. Drinking something cold on a hot day does not actually cool you. It feels nice, but for all practical intents and purposes you do not get any colder, and so the chilling is a wasted effort. The notion to drink something cool on a hot day is a modern thing that only came about with the invention of refrigeration in the early 1900s, and we suddenly had the luxury of having some excess cold. In fact, it may even be more advisable to drink something **hot** in order to cool off. This is because if you can fool the body to think that it is overheating, the body will take steps to cool itself, the most salient such step being to open up the superficial blood vessels to dump more body heat to the skin and from there to the surrounding air. Hence serving a cool drink in a hot desert medieval town would be more of a novelty thing; a sort of bragging where your hosts show off that they can do something very peculiar and nigh magical, namely **create cold**. So if you wanted to use this to actually keep cold, you would chill water, soak a rag in it, and press this rag against an area of the body where you have a lot of superficial blood vessels — like the hands, wrists and head. This will create **actual** relief from heat that is much more effective than drinking, since that rag will quickly soak heat from your skin, cool the blood in the skin, and that cooler blood will then be transported back to the core of your body. --- # However(!!)... reality check, part 2 Also note the following: * **Drinking something ice cold when your body is subjected to a lot of heat is actually dangerous.** * **Do not — under any circumstance — give a person that seems to be overheating cold water to drink.** Drinking something ice cold when you are warm can cause a very rapid drop in blood pressure in your head. You essentially create a temporary [circulatory shock](https://en.wikipedia.org/wiki/Shock_(circulatory)). The result is that you can faint on the spot without any warning, by simply drinking something very cold. This happened just a couple days ago to an acquaintance of mine. We were out by the hotel pool on the Mediterranean, sunbathing and sweltering in the heat. A waiter brought drinks that were like slushies: 50% crushed ice, 50% liquid. My buddy took a big swig of his drink, said "Ooooh, dat brain freeze", and then — just like that — he keeled over, fell out of the beach chair, and hit his head on the ground earning him a black eye. Again: the proper way to cool off if you are overheating is not to drink cold liquid but to use a cold rag on the head, wrists and hands. So your hosts in this hot desert town would most likely tell their esteemed guests "Drink slowly and very carefully", because it does not leave a good impression to have their guests faint from being offered a drink. :) Then again: that would make for some light comedy. > > — What... why am I on the floor?! > > > — My dear friend, *the rich merchant chuckled*, that sometimes happens. I suppose I should have warned you. > > > — Oh... is it... > > > — No, no, not at all. It fades really quickly. Just sit up slowly on that chair over there. > > > [Answer] Get snow from the mountains and/or in the winter. Pack a great heap of it in [insulating material like sawdust](https://en.wikipedia.org/wiki/Ice_house_(building)) in [a deep basement](https://commons.wikimedia.org/wiki/File:Eglintonicehouse2.JPG). Sell small amounts during the summer. * Difficult in a *hot* desert without ice/snow source (not all deserts are hot). * Extremely expensive. Store the drink bottle in wet sand in a porous clay container. Evaporation will help keep the drink slightly cooler than the outside temperature. * Affordable. * Not *very* effective. [Answer] **They would build a [root cellar](https://en.wikipedia.org/wiki/Root_cellar) and use it to store the beverages.** A properly built root cellar will maintain a temperature above ambient (and above freezing) in the winter, and well below ambient in the summer. Root cellars are rather simple constructions, easily achievable with medieval technology. In fact, they were a common solution to the problem of keeping crops and other goods at a reasonably stable, above-freezing temperature year-round until refrigerators (initially [iceboxes](https://en.wikipedia.org/wiki/Icebox), later electrical refrigerators similar to those of today) became commonplace, and in places are still used for their original purpose even today. This has the advantage that it doesn't depend on availability of ice (which, since you say this is in a desert region, could be a problem either because of temperature or because of lack of precipitation, depending on whether they are in a hot or cold desert), but it does require some land that can be devoted to construction of the cellar. In the scenario you describe, that shouldn't be a major showstopper; most medieval "cities" would be more like what we'd call villages today. [Answer] In 400BCE, Persia had special structures that collected water in the winter, turned it into ice, and kept it cold for the entire summer: See: [http://en.wikipedia.org/wiki/Yakhchāl](http://en.wikipedia.org/wiki/Yakhch%C4%81l) And: <http://www.ccsenet.org/journal/index.php/ach/article/view/13822/12244> > > Yakhchāl (Persian: یخچال‎‎ "ice pit"; yakh meaning "ice" and chāl meaning "pit") is an ancient type of evaporative cooler. Above ground, the structure had a domed shape, but had a subterranean storage space; it was often used to store ice, but sometimes was used to store food as well. The subterranean space coupled with the thick heat-resistant construction material insulated the storage space year round. These structures were mainly built and used in Persia. Many that were built hundreds of years ago remain standing. > > > By 400 BCE, Persian engineers had mastered the technique of using yakhchāls to create ice in the winter and store it in the summer in the desert. In most yakhchāls, the ice is created by itself during the cold seasons of the year; the water is channeled from the qanat (Iranian aqueduct) to the yakhchāl and it freezes upon resting inside the structure. > > > [Answer] By using a two-pot clay cooler. (expanding on what L.Dutch mentioned in their answer) The basic premise is that when water evaporates, the medium that it leaves is cooled down. To quote the [Wikipedia article](https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator): > > A pot-in-pot refrigerator, clay pot cooler[1](https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator) or zeer (Arabic: زير‎‎) is an evaporative cooling refrigeration device which does not use electricity. It uses a porous outer earthenware pot, lined with wet sand, contains an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed - the evaporation of the outer liquid draws heat from the inner pot. The device can be used to cool any substance. This simple technology requires only a flow of relatively dry air and a source of water. > > > Using this technique you can get your drinks pretty damn cold, ~5°C even, although this reference is from a [cooler built using modern materials](http://www.instructables.com/id/A-Practical-Zeer-Pot-evaporative-cooler-non-electr/) and not medieval ones! I don't have a full reference, but Wikipedia mentions this type of cooling was used in Ancient Egypt, so it would stand to reason that this sort of knowledge would be prevalent by 1100-1300 AD. Evaporative cooling techniques such as this are most effective in dry climates such as a desert or mediterranean climate. In a climate with high humidity, not so much, since the amount of cooling achieved depends on the rate of evaporation. EDIT: thanks to Falco for advice on what to include in my answer :) [Answer] They would do what we did on Earth before electric refrigeration. Harvest big blocks of ice in winter and store them in insulated ice houses for the summer. If your city doesn’t have a cold winter, they’ll have to ship the ice in from somewhere that does, in insulated wagons that travel at night. [Answer] They have various options: * harvest snow during winter from nearby mountains and store it in underground rooms insulated with straw (it was done in my home region in the hearth of Mediterranean sea). Add salt for further cooling. * dip them into wells, rivers or sea water (again, this was a trick used by farmers to have cold wine and fruits when working in July under the scorching sun) * collect water from underground (either from wells or collecting rain water in underground rooms. Having had the chance to try that water I can assure you it is deliciously fresh) * use clay containers: clay is porous, and water permeating through the walls of the container ends up evaporating and thus cooling the container itself. [Answer] If there's a river nearby, they could simply submerge the drinks in the cool water, and pull them out when they want to drink them. It might not be as cold as getting blocks of ice, or snow, but it might be a better if it doesn't get cold enough to get ice, or if it is too far to import it. [Answer] [The Sahara gets sub-zero temperatures at night](https://www.reference.com/geography/nighttime-temperature-sahara-desert-e0f475825e483d8f) during the winter So water should be able to freeze if present in the open in the winter and could then be carried into a deep cellar before dawn. Repeat throughout the winter and then store with sufficient insulation and you have ice in the summer. [Answer] **That's how a fridge is created for a scouts camp:** Dig a hole in a shady location outside and put the stuff to refrigerate into it. After that you will pin a tarp over the hole and keep it wet by pouring a little water over it. Through the continuous evaporation, it gets actually really cold inside the hole, even during summer. Out of my own experience I can say that it is definitively effective enough to cool down drinks, especially for a medieval setting. Instead of a tarp, you can just take a large skin. This might be even more effective as it has a bigger surface. [Answer] In desert climates people build houses with covered (underground) trenches that travel away from the home a ways and then open to the air. Ventilation at the roof of the home draws air through the trenches where it is cooled by the earth - keeping the home cool. Large versions of this style of dwelling will produce thick sheets of ice when water is left in these trenches overnight as convection draws the cold night air through the trenches. Example: <http://www.amusingplanet.com/2013/01/ancient-ice-houses-of-iran.html> [Answer] Their is an evaporation method.Take a large pot, put a smaller pot inside(same height though), fill that gap with sand, put whatever you want cooled inside the small pot, put a large, wet cloth over it all and put it in the sun [Answer] There was actually a trade in ice as late as the 19th century. For example, people in New England would cut ice out of ponds, put it in ships, and send it to the southern states. That trade even existed in North Africa, with ice being shipped by riders on relays of fast horses or camels from the Atlas Mountains to desert cities. It was a luxury item. [Answer] Put it in the creek or the well. I guess a desert has a well. That's what we did when I was a kid. Should work here too. [Answer] As noted by most others: people didn't drink cool drinks to get cool. That became only possible when industrial refrigeration became affordable (1880-1920). Giving a guest a cooled drink was a real luxury. Akin to serving pink champagne, that kind of a luxury. Especially in a desert environment. Ice had to be harvested during winter in cooler climates. It had to be shipped to the nearest port. Then carefully packaged transported on presumably camels or donkeys to your oasis. The local ruler would have had a specially constructed ice cellar dug deep underground where the ice was stored until it melted away. All the old great houses in Europe have one. Perhaps a few very rich rulers in an oasis had one too. [Answer] Don't know if you already found your answer but I'll give my input anyway. Here in Portugal we learned in history classes that the king used to eat ice cream and serve it to his guests during the 1800's, so in order to do it he would have ice and snow merchants, that would drive their carts to our only snowy mountain over about 200km away. In order to preserve most of the ice and snow, they would wrap it in heavy hay and straw bundles. Somehow it didn't completely melt. [Answer] Water is heaviest at 4 degrees plus celcius which is the temperature a bit down in wells or other outdoor water things. Should be cold enough to cool any water based drink. [Answer] You can achieve this by using the [zeer or pot in pot](https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator) method In some parts of India and some other countries, even now people use this method. Also another relatively less successful is to suspend the drinks tied in cloths into a well. ]

[Question] [ So I'm building a galaxy with bunch of space-age civilizations and an galactic wide supra-nation. Something similar to the Citadel races in the Mass Effect games. Unlike those games, the most of the aliens in my story are hardly humanoid. Right now, I have one humanoid alien, two beetle-like aliens, a squid-like alien, a monitor lizard-like alien and a bat-like alien. Assume they gained intelligence and technology yet mostly keeping the form of their Earth counterparts, ex. the squid aliens are pretty much squids with slight adaptions to allow them to use technology. The supra-nation has a law enforcement force employed with various members of these aliens. What I am concerned about is how would the criminals be bound or trapped after they are caught. For the humanoid aliens, handcuffs would suffice, but I am not sure about the other races. [Answer] All right! You're going in the **BAG.** [](https://i.stack.imgur.com/9xTYy.jpg) <http://northbaybulldogs.com/huge_gymbag_person/> One BAG fits all. You get to keep your head out if you are good and your head is the right shape. Think twice: if something comes out of you, it stays with you in the BAG. BAG is air permeable. It has strong handles or maybe some levitation tech. BAG withstands a lot of chewing. Hopefully the police clean the BAG between uses. [Answer] Here are a few alternatives from other fiction: ## Halo (Minority Report) In Minority Report, criminals could be fitted with a small device around the head that numbed the brain, stunning (or at least making compliant) the sentient fitted with the device. [Application of Halo from Minority Report](https://getyarn.io/yarn-clip/60a99a19-115e-4f5c-935f-ae602d7ff332/gif) ## Explosive Collar (Wedlock) A collar with a small range receiver and a bit of explosive. Paired to another receiver on a control officer, or another prisoner. When out of range, or on command, the collar will detonate. [Collar exploding from Wedlock](https://www.youtube.com/watch?v=TZesS-EUP6E) ## Shock Collar (Thor: Ragnorok) A similar fitted restraint that can provide shocks ranging from warning to stun to lethal [Shock Collar from Thor: Ragnorok](https://www.youtube.com/watch?v=LWMihekx42Y) ## Quick Freeze (Demolition Man) Although it seems to have limited or limitless effect in Demolition Man, as required by the scene, the concept is a portable device that flash freezes the prisoner. [Quick Freeze Sphere in Use from Demolition Man](https://www.youtube.com/watch?v=_6C1gSbS2os) ## Gravity Guns (Schlock Mercenary) An extremely-low power gravity gun can be employed as a restraint. Generally controlled by an artificial intelligence, which has sufficient quick thinking to keep the beam tuned as required. ## Goober Gun (also from Schlock Mercenary) A lower tech restraint, firing balls of material that very quickly increase their viscosity from almost nothing (so that it can flow around the target) to very high (keeping the target in place). This viscosity must be layered somehow, allowing a lower viscosity inside so that targets are ripped apart or smothered. ## Zero-Point Energy Ray (Incredibles) A force field that very precisely cancels out velocity and movement. [Zero-point energy ray in use from Incredibles](https://www.youtube.com/watch?v=bkAEwKb4Qcc) ## Alternate Dimension (The New Legends of Monkey, Pokemon, Tron, Superman) Another option is a portable device that places the suspect/prisoner in a pocket dimension until required for release. ## Time Loop (Dr. Strange) Doctor Strange captures a deity in a small fragment of looped time that would continue looping back on itself until the Doctor negotiated a deal with the timeless deity, after which he released them both. ## Frozen Time (Starcraft) Although later treated as big solid crystals, Protoss prisons were early described as frozen time, given the space and time bending capabilities of that species. ## Carbonite (Star Wars) Not very portable (a facility was required in Empire Strikes Back) and potentially lethal (Darth Vadar asked Boba Fett for assurance that the process wouldn't kill his son in the form of trying it out first on Han Solo), but you could imagine a perfected and miniaturized implementation. The process flash freezes the subject and covers them in a protective coating until intentionally thawed. [Carbonite Freezing, from Star Wars: the Empire Strikes Back](https://www.youtube.com/watch?v=qND0aIXOLbw) [Carbonite Thawing, from Star Wars: Return of the Jedi](https://www.youtube.com/watch?v=QmpN_gai2yI) ## Amber (Fringe) In Fringe, one of the government agencies developed and deployed a mist that solidified after a certain number of seconds. It was used to seal dimensional rifts, or imprison monsters. [Amber removed and deployed from Fringe](https://www.youtube.com/watch?v=m2WP7rzJW9g) ## Neuralizer (Men in Black) Neuralizers come in many forms and sizes. In addition to temporarily stunning the suspect, it also renders them open to a certain amount of persuasion and provides for a controllable amount of memory erasure. ## Bag For completeness. The suspect is wrapped in cloth that eliminates mobility without suffocating the being inside. Optionally can be secured with straps or zippers. [Answer] Most likely law enforcement officers would prefer to be able to subdue, immobilize and transport their suspects all in one go. Given the wide variation in body types, and presumably different environments you can find your criminals in (squid aliens are in the water, while bat aliens are flying away), then a portable net projector is a handy, low tech means of doing subduing, capturing and transporting the miscreants in one go. [](https://i.stack.imgur.com/hjgXY.jpg) *Anti-UAV net gun with suitable Sci-Fi looks* [](https://i.stack.imgur.com/IhArm.gif) *Edit to add this criminal eye view of a net gun on action* The net mostly has to be strong and flexible enough to wrap around the suspect and withstand attempts to break, cut, bite etc. though it, immobilize the limbs (which is ultimately the idea behind handcuffs), and once the suspect is caught, the ends sealed off and the suspect carried away. If the net comes with built in carrying handles or not is up to the enforcement agency. I would probably avoid things like sticky nets, or energizing the net, both to make the net usable in all environments, and to prevent the possibility of injury or wrongful death of the suspect when entangled, but local departments might review this on a case by case basis ("OK Officer Blonkins, if you have a positive ID on the suspect, the backdrop is clear and it *is* a monitor lizard, set the net to stun and fire"). Peace officers might also appreciate the ability to have only one item on their utility belt rather than a plethora of devices. [Answer] So handcuffs are meant to be used to make sure something is safe to transport and this will vary for each of your aliens. For humans, it means restricting our hands so we can't use them to fight and really resist, but for your aliens it could also include binding all their limbs or body (looking at the beetles) and muzzles to stop biting (lizards). The easiest way would be to carry around some flexible rubber cables. Wrap them around the body of your prisoner and it should restrict all limb movement. A more advance way would to have a material like putty, which can be hardened using a weak electric current. That way you could apply it to any part of your alien and basically stick or bind it to something, or wrap it around something and then insert a small chip that will cause the putty to harden and make it extremely tough to break free (I'm not saying it becomes completely solid, just not as liquid like as putty usually is). This way you don't need to worry about size or weird shapes too much. If your squid is being annoying, wrap all its limbs together in the putty and not it can't really move anymore. If your bat keeps trying to fly away, putty its wings together. If your human keeps talking non-stop and is an annoying prick, put some putty in their mouth or put them into a putty cocoon. [Answer] Duct Tape. It combines the adhesive properties of glue with the binding properties of straps. It adheres to flesh, chitin, scales and more. You can bind any number of limbs and layer it up for stronger species as necessary. Removal is a trickier prospect, but if your variant on it has a glue with an easily applied solvent you could just use that to make it easier. If you want to go science-fiction, use gecko-foot style molecular adhesives in the tape instead of glue, then you can simply peel it off, but if it's being pulled at then it won't come undone. [Answer] The problem with cephalopods is the lack of bones means they can squeeze out of just about anything. For the other species cable ties would work like a lot of police use these days. For a universal "handcuff" so to speak, I'd recommend a pain inducing nanite that responds to sudden movements as well as remote commands. It could also double as a tracker and/or a proximity sensor. Being sensitive to sudden movements, the prisoner can't run or attack the officers which makes escape virtually impossible and not obeying commands would be painful. [Answer] **Arrest** Tasers, All complex life on Earth uses small electrical impulses to control movement, however it would need to be adjustable as each species might need a different charge to have the same effect, and that shock might kill some species. this would be the only surefire way to effect all species, detaining them would be another matter, a boneless species couldn't be restrained in the conventional sense, unless it was some form of... (Yes i know what i'm about to write is a bit stupid!)... rapid deployable zorb ball... which would surround the target and seal shut. **Prisoner Transport** Something similar to that used on Sokar in Thor Ragnarok, and implant that would be excruciatingly painful to remove by force, but which causes an electrical shock would severely restrict movement, this is basically just an advanced version of the taser law enforcement use today. even cephalopods would be effected. mix this with the basic technology that some Dog trainers use, an electric shock device that if taken too far away from the owners home, shocks the dog. So imagine a Shock implant, that if linked to a Squad Car or police station or prisoner, if the target leaves tries to run it automatically shocks them. **Stopping Runaways** I'd imagine the futuristic Police Vehicles would be made so that if the driver was not a police officer, say the prisoner had overpowered the officer, taken the keys and were trying to drive off in the squad car so that the implant doesn't auto activate, then the car would recognize this and disable the local emitter so that the implants would activate. **Other solutions that would work for all species...** Other than a fine Net as explained by Thucydides, those pesky cephalopods are going to be able to get away every time. [Answer] You can use epoxy. [](https://i.stack.imgur.com/8RME0.jpg) GLue has serious advantages over simple handcuffing. It is anatomy-agnosthic. And if you need to keep an offender somewhere - with handcuffs, you need to have some prop to cuff them to, such as pipes or cell bars. With glue, you can stick them to the nearest wall, or to the roof of a police car for easier delivery. It works like this: law enforcers have a glue gun with two barrels and one trigger. By pulling the trigger, the gun will spill out the two substances that form loctite, one from each barrel. Apply these on the creature's appendages. When the time comes to let the offender go, simply apply solvent. [Answer] Allow me to declaim slightly before I even start, this answer comes to you direct from my inner sociopath and I am *not* a nice person: Assuming you have really good medical technology, regrowing body-parts good, and an extremely cavalier attitude towards the "human" rights of criminals, then they don't need limbs unless they're serving time with hard labour. To that end law enforcement should use weapons substantially similar to lightsabers that cut and cauterise in one pass. Simply cut off enough limbs to incapacitate your suspect and bundle their twitching thorax and head into cargo bay for the trip to jail/interrogation. It doesn't matter if you get the wrong guy go can just grow him some new limbs, same as the old limbs just younger and less tan. [Answer] # Nanonet A "cartridge" of nanobots with a controller chip on one end is loaded into a Nanonet Gun, which, when fired, places the nanobots (via commands signed with the private key embedded into the chip) into "liquid mode" to be sprayed onto the suspect. In liquid mode, they maintain contact with one another, but allow for some movement. They gradually build strong linkages between each other, locking into a very fine-mesh net structure that allows air and water vapor to pass, but no living cell will get through. When the prisoner is delivered to the destination, the controller provides more power and the command to revert to liquid and reform into the "cartridge", ready to be used again. In cartridge form, the bots are very tightly packed, and thus take up very little space. A police officer would probably have multiple magazines of such cartridges at his disposal. (Nanonet™ is made by Nancrete Industries. And you all know them, since nearly everyone lives in Nancrete™ homes and rides in Nancrete™ vehicles, given the wonderful way that Nancrete™ can change colors, thermal and light transmissivity, and permeability to air and water on the fly. That's how George Jetson's air car is able to fold up into a brief pad computer case, after all.) [Answer] Maybe you could use some fictional technology which dampens any quick movements by sucking out kinetic energy from the subject while still allowing the alien to function - sort of like a personal dampening field. [Answer] In combination with other measures proposed elsewhere... **Disable their bio-suits** It is very unlikely that such a combination of aliens as the one you describe would all be able to share a common environment. Some (many?) of them will be forced to use a life-support suit in order to stay alive. This makes keeping them under control both easy and risky: if you disable the biosuit by violent means the alien will become incapacitated, but there is a high risk of the alien ending dead. As it is usually seen as bad manners killing someone(something?) just because it was challenging a traffic ticket1, and aliens do not want to die if things escalate, that lends support to the idea of creating an "arrest switch" in the bio-suits; a securely criptographic code that will trigger the bio-suit to disable motor functions without affecting life-support functions. You can add some safety features: the code must be encoded in a way that the officer sending the signal will be always identified, officers may issue the command but the order must be validated remotely by a situation room that checks that there is a real reason for it, to prevent its use by kidnappers if the suit is disabled it sends an alarm to the police and an acoustic alarm to alert bystanders... If the alien decides to mess with the system and disable it, then the officers are authorized to use force to detain the alien and if as a result of it the suit is damaged and the alien dies it will be considered the alien's fault. Of course, --- 1YMMV. [Answer] Drugs. Rick and Morty did it, and it worked out narratively. Why handcuff them, when you can just drug them and make sure they can't move? I guess if you want to get really out there with how the drug works, you can make it nanobots that specifically make the target sleep without killing it by secreting appropriate amounts of localized anesthetic. Nano bots seem like over kill for that IMO. You could probably do that with a smart needle too if you wanted. Why have only one tool? [Answer] the easiest solution is anything BUT universal, and that's selective subduction. insects respond almost entirely robotically to pheromones, use this for the beetles. ensephlopods are easy too, heat them them up till they submit, keep a low level heat on them, enough to be uncomfortable/painful without being damaging. bats *HATE* High frequency noise.. ultrasonic transducer drone/gun, bat can't fight it, and can't run. Lizards: COLD GUN they'll slow down and unwillingly go to sleep. regular humanoid? regular handcuffs/collar there's absolutely no way anything humanoid can get out of triangle cuffs (collar and handcuffs, clasp in the front under the chin, arms crossed in the back linked to the collar). over-specialize and you build-in weakness, it's unlikely that there will be situation where you encounter bugs/bats underwater, or humanoids/quids in the air, at MOST your officers will need 3 devices if they're land/air based, everyone will usually only need 2, you can also combine techs, like the heat/cold/sound gun can easily be one device that covers 3 major species, in a pinch the cuffs/collar can be used on both bats and lizards, same with the cold gun on the bugs. bats can also be brought down by heating their wings.. there's ways to mix-and-match these devices! ]

[Question] [ I always wondered what it would look like for a Sci-Fi battle in space to occur if it were a bit more realistic. I don't plan to use any space fighters or anything like that, just big capital ships and freighters that can fire in full vacuum / zero atmosphere. [Answer] Space battles, at least realistic ones will be done with computer targeting systems. Humans will not have a big task on the spaceship. I imagine repair and ensuring the AI/computer won't go rogue will be the main task of these crew members. Beyond that will be troop and logistical transport. Realistic spacebattles can easily be incredibly intense. Crew members put their fate into the hands of a targeting computer that can hopefully outperform the enemy's targeting computer. To give you an idea of the atmosphere look at movie scenes featuring submarines. Das boot, the hunt for red october... Maybe the ship gets hit and high velocity projectiles penetrate the hull. Rooms become decompressed, people get sucked out, critical systems might get destroyed or disabled. My best guess is focus on the aftermath. Battles themselves will be brief, but brutal affairs where humans have little to no control over. Somebody get his head blown off by a passing projectile, another guy gets sucked out into space,... However crew have to deal wih the aftermath. They might have won, but are they going to be able to get home? Realistic spacebattles will be a combination between trench warfare and submarine warfare. The helplessness of standing in a trench during a bombardment and the hostile environment of a submarine. Ever heard of a tv serie named 'The Expanse?' Perhaps you could look at that for some ideas. I've heard it's pretty realistic, at least compared to most space operas. [Answer] I've yet to see a space battle in a movie or game actually come close to dealing with real-world physics. A few examples, at least one of which is always broken: There is no "Speed limit" or max safe speed for ships, in fact there is no "Speed" for ships unless you choose an object to calculate your relative movement. You are not moving "1/3 the speed of light" or x-mph or anything like that without a target. Also ships won't rattle at high "speeds" (since there is no such thing)--they might rattle or shake at high acceleration. If you were to accelerate away from earth until you were moving nearly the speed of light relative to earth, you wouldn't really even know your ship was moving (because it wouldn't be). You wouldn't be compressed or moving slow or any of those silly effects, however all the stars would be moving unimaginably fast so the streak effects for stars might be accurate. For every minute your fighter "Burns" going in one direction, it must turn around and "Burn" a minute in the opposite direction just to counter it's movement and stop relative to the other ship (Not accounting for your constant loss of mass which would make it slightly easier to maneuver over time). Also don't forget that after decelerating it must accelerate to get back to the "battle". This would lead to something more like jousting than what you see in movies or games. It would be accelerating at each other for a few hours, firing a volley then spending twice that amount of time turning around and returning for the next volley--either that or they decide to just slowly close the distance and pound each other without much movement--but they would absolutely not be zipping around each other! Fighters cannot bank against a non-existent atmosphere. This means that they will constantly be rotated at really strange looking angles that are only vaguely related to their intended direction in order to compensate for existing momentum. They would virtually never be thrusting in the direction of their target but always at some oblique angle. If you only shot weapons out the front of your ship and thrust out the back as with most movies, you would never hit anything as you couldn't thrust in a reasonable direction and fire at the same time. I don't know if this is the kind of realism you were after, but it's one of those things that always bothers me about space movies/games, but reality would be boring and weird. EDIT: To focus more on what might make it interesting: First assume that both sides have EMP weapons that can destroy active sophisticated electronics in a snap, so electronics have to be shut down during battle. This changes EVERYTHING. Now you have a battle where everything is done by humans. Acceleration will become critical--this is limited by mass and human ability. All targeting will be manual, and no drones! Also, if you think about it, the thickness of the shell of the ship adds to mass and wouldn't help much with a direct hit anyway (Decompression would be extremely disruptive even if everyone was wearing suits) An exciting solution? Eliminate the shell. Shed it before the battle begins (leaving non-fighting humans safe somewhere) and just take in a fighting crew strapped into seats in their suits. The ship could come apart like a transformer, disgorging it's guts in the form of dozens or hundreds of individual manned ships (Previously these were the inner hulls of the ship). I could imagine many small jet-ski like fighters manned by a pilot and gunner along with a few larger 6-10 people command/control ships--maybe looking like those two-level open-top tour busses and possibly manning moving guns like the tail gun in star wars. I could even see a large carrier in the shape of a sphere with 50 people strapped to chairs and guns all around the outside--the chairs would, of course, be oriented so everyone was facing outwards covering the entire sky for targeting, navigation and defense. That would be exciting! [Answer] **Tell the story from the perspective of the people** Which is what needs to be done anyway. **What would the people hear?** The sound of stressing/tearing metal? Burning circuits? Escaping atmosphere? Other humans yelling? I'd hate to be the comm officer. **What would the people see?** Dying friends? Other ships exploding? Their own ship being torn apart? I'd hate to be the medical officer. **What would the people feel?** The forces of inertia thowing the ship around? (I love the quote from the movie *U-571* "The shockwave from one of these explosions could snap your spine.") Nausea from a concussion? Heat? Vacuum? Authors sometimes have difficulty shifting their 3rd person perspective. In your case, you're probably thinking of the god-view from above looking down on the battle and wondering how you'd tell it since you can't hear anything. Shift to 1st or 2nd person perspective. Put yourself in the shoes of the poor schmuck who's doing damage control or the janitor who was pulled in to help the doctors or the shuttle pilot who's helping damage control fix some strut outside the ship during the battle. Don't tell your story... *tell theirs.* [Answer] David Weber's Honor Harrington series does a good job of describing realistic space combat. A couple of things to remember. * Space is BIG, really Big. A [geosynchronous](https://en.wikipedia.org/wiki/Geostationary_orbit) satellite is 22,236 miles (35,786 km). The fastest missile we have goes about Mach 8(6,135 MPH). At this speed, it would take that missile 217 minutes to go from Earth to the satellite. At the speed of light, it takes 8 minutes for light from the sun to reach the Earth. * Unless you do something about [inertia](https://en.wikipedia.org/wiki/Inertia), you can't change speed and direction of a ship quickly, or you'd turn the crew into a bloody pulp. * Unless you invent shielding, ships are vulnerable. Armor uses density to withstand attack. As mass increases, your energy budget increases to move the mass. This means there is an interaction between ship armor, speed, and engine size. Likely, ships would not be able to take much damage because the cost of moving that much armor is too expensive. * You cannot really hide in space. Space is empty. Space is cold. Space is dark. A ship would be not-empty, hot and bright. * While we have some beam weapons, they would be impractical at distance. Beams spread over distance. While the beam weapon would melt the hull at 10 meters, it wouldn't even warm it at 1000 KM. So, you're going to have to fire lots of missiles in order to do damage. You're going to employe anti-missile missiles to protect your ships. Everything will seem slow (even at incredible speeds, the missiles would take 20 minutes to impact.) Battles will be snap decisions, commitments to courses of action, and waiting to see how they turn out. [Answer] **Go for suspense, not spectacle** In addition to some excellent answers already given I would like to add that a realistic space battle might not lend itself very well for "Saving Private Ryan" like spectacle (meaning the beach scene ofc). Another answer already mentioned submarine warfare, I would very much recommend to watch the excellent movie [Das Boot](https://www.imdb.com/title/tt0082096/) (if you haven't already) for an imho unsurpassed depiction of this. The psychology of being trapped in a metal container in a hostile environment while being hunted by the enemy makes for excellent suspense. Also, assuming your battle takes place in orbit around planets, maybe with moons, the orbits of the bodies involved will lead to 'windows' where the warring parties can see each other before they are obscured again by the planet or moon they are orbiting. This is especially useful if they use laser-like weapons, that need a clear line of sight to work. The 'downtime', where a ship cannot be seen can be used for course corrections, so the other party can be pretty sure it will surface again, they just can't be sure of exactly when and where. You could use this to create a game of cat and mouse, like the opening scene of the movie [Drive](https://www.imdb.com/title/tt0780504/) but in space. The fact that in space almost all resources are scarce can be used to further the suspense. All choices have consequences, waiting for the perfect moment to strike will cost you food, air and time for the other to prepare. Firing a drone means you will probably never see it back. Maneuvering into another orbit might leave your vessel unable to go home or be recovered. [Answer] I'd like to respectfully disagree with @TheShadowOfZama's answer: there will be a lot more than just waiting for a computer to do its thing. Generally, human+computer team will beat a pure computer: <https://jods.mitpress.mit.edu/pub/issue3-case> Broadly, humans will try to find and exploit faults (or features) of enemy’s computers and hardware. There could be evasive maneuvering to confuse the target-tracking system. There would be electronic counter-measures against the one type of targeting or guiding system, but exposing the ship to other system type. There would be rock-paper-scissors choice of weapons and defensive systems. There will be a choice of aligning the ship for best protection / best weapon coverage / easiest escape. You can have fighters or smaller ships hiding behind or inside larger ones. There could be flanking the enemy, which gives you a chance to surround them, or strike vulnerable points, but it also disperses the force, and lets them be picked one by one if enemy has multiple weapons (or multiple ships). I would recommend watching Battlestart Galactica; it has pretty realistic space combat, and tactics that goes with it. [Answer] Bill K's answer gets to the heart of the style of combat I imagine, but I'd like to emphasise an aspect of his description that I think can provide a wealth of cool story hooks: **acceleration**. Unless there is some technology that can negate the stress of acceleration then a ship's ability to maneuver is directly limited by how much acceleration the crew can withstand before blacking out/suffering injury/dying. If the crew on your ship can withstand higher g-forces than the enemy's then you can out-turn and out-run them, which obviously gives a huge advantage in combat. So in regard to creating excitement, I can imagine space battles where ship captains and crews are constantly judging how much acceleration they are willing to go to to gain minor or major edges in the fight, looking for openings to push that little bit harder then the opponent to gain an advantage, trying to force the opponent to wear their crew out pulling too many Gs, potentially even accepting crew casualties from acceleration if it means making or avoiding a killing blow. This also puts humans back in control of the battle; computers would do all the targeting and weapon control with near perfect accuracy but the captains and crew would be in control of how hard they chose to push their g-forces and all tactical decision-making would revolve around that. Seems like you could make this the real heart of your space battles, it can provide a wealth of tactics, tension, daring gambits, heroic sacrifices, etc. It could even shape the type of characters you get in ship crews; instead of relatively disconnected IT guys running the ships you could have teams of gritty, hard-nosed mavericks that are valued for their ability to take risks and push the limits. **Edit:** Another thought I just had, if you have some technology that can dampen/reduce the amount or damage of g-force to a crew then this could be a defining characteristic of different classes of ships. If the dampening tech scales with power or size then it allows bigger ships to safely accelerate harder, or perhaps ships that have better dampening have less power or room for weapons systems, etc [Answer] By the time we get into space and do battle, we already have such advanced computers that humans barely have anything to do in the grand scheme of warfare. The only reason humans would still be anywhere near the attacks is when AI cant be trusted. Not because the AI goes rogue but because AI learn so fast we wont know what they'll do when, say, they have a choice between saving 101 murderers or 100 civilians, or decides to build somewhere and evicting the people there. With self-replicating robotics it becomes a matter of mass and useable energy. Entire asteroidbelts if not planets would be transformed into space ships and launched at the enemy. Although at that tech level the question arises of why anyone would still wage war outside of pure disagreement on ideologies and how to live. [Answer] **There IS sound** Hear me out (pun intended). While it's true that pressure waves (what we traditionally refer to as 'sound') don't propagate through a vacuum ... BUT ... any matter (or even many forms of radiation) impacting the hull of a ship would vibrate the hull of the ship itself, causing sound for those within. This includes radiation from an enemy 'ion engine' or any similar propulsion, debris from damaged or destroyed ships, escaped atmosphere from those same ships (if encountered by an intact ship before it dissipates), various forms of radiation from exploding reactors (a shock wave that would be destructive from too close, deafening from mid range, and merely audible from longer range) and much more could all be audible to a crew. Now, the problem with most of these is that they are only relevant if the ships remain in close proximity to each other during the battle. As many answers pointed out, this is difficult on the scale of space as a whole, so how do you do it? That part of the answer is also mentioned briefly in some of the other answers here, and that is that resources in space are VERY limited, including ships that have already been constructed. Raw materials may be (relatively) easy to come by. After all, if space can be navegated well enough for battles to be a thing, then reaching other planets or asteroids, moons, belt systems, etc, for mining should be likely options. But time and manpower to actually convert raw material in to a ship would be a much more rare thing, so the ships themselves, even the smallest and simplest, would be VERY valuable. In this situation, **capturing** ships would be highly preferable. So, any battle other than the last ditch effort of a single ship, would NOT focus on turning an enemy ship in to a puff of scattering matter. Instead it would focus on disabling an enemy ship while producing as little actual damage as possible or, even better, completely outmaneuvering and capturing it with no damage whatsoever, and then boarding it and taking it over and using it to help capture even more. Grappling cables, clamping arms, hull cutting systems, etc., would make very unique sounds on hulls of ships. As would the exhaust from maneuvering thrusters pointed directly at a ship in an attempt to thrust away from it's grappler equipment. Add multiple ships on each side, and watch them try to outflank each other, using small scale weapons to try and shoot off communications arrays to confuse the enemy or disconnect grappling systems from enemy ships, or dent/bend a maneuvering thruster to disable their handling capabilities, all while trying to get to some point on an enemy ship where they can grab on without getting shot themselves, could get very up-close and personal, intense. And it could be **AUDIBLE** even from a camera perspective in 'space' outside the hulls of any of the ships involved as the 'camera' passes through thruster exhaust trails, debris fields, minor and major explosion shockwaves, etc. [Answer] 'Epic' or 'cool' are too vague and dependent on the individual to nail down(using those descriptors is probably what drew the VTCs), but what I can help you with is "intense" and "realistic" ## Information Warfare Put a high emphasis on information gathering and pumping out misinformation in your setting. Ships can make use of an array of systems like radar absorbent hulls, heat dampening, laser scattering, etc; we usually call these "stealth tech". They can also gain concealment from asteroids and debris when powered down, however this would be extremely difficult to get considering the true vastness of space. The most readily available form of this would be hiding in the "shadow" of the Sun or a moon/planet. A hostile fleet that may or may not be lying in wait at Lagrange Point L3 can be the sword hanging over your protagonists' heads. **Don't** use a nebula in a high realism setting; they realistically provide nothing other than a pretty backdrop for your battles. For misinformation, consider targeted or area saturation white noise. In *The Expanse* one commonly used combat technique is to beam massive quantities of junk data directly via laser at enemy combatants in order to overload their targeting systems. You can also have mechanical white noise generators on a huge scale(likely in fixed emplacements), and natural but extremely dangerous sources of radiation from solar events like the [Carrington Event](https://en.wikipedia.org/wiki/Solar_storm_of_1859). Computer viruses either transmitted by enemy ships during combat or pre-placed by saboteurs can play a part here too. The key take away here is suspense achieved by placing your POV characters under pressure from constant threat of attack, not necessarily the attack itself. Higher realism settings would place a high emphasis on ambushes and localised use of overwhelming force as opposed to large fleet on fleet showdowns. As a means of fleshing out the setting while adding to the fear of attack, you can have your protagonists receive occasional news broadcasts about fleets/convoys being lost with all hands from mysterious unidentified attackers. [Answer] The answer depends mightily on the tech involved. You'll have to tailor the answer to suit your tech. However, the general answer today is that you need to focus on the strategy involved. In the modern setting, space is a *wide* open environment, where it's very easy to predict where someone is going. There's no tactics on par with, say, a Wrestling match where two fighters vie to get the best grip on the other. The rules are simpler: If you are predictable, you die. Your fighters are necessarily going to have to be on the absolute edge of the combat envelope. Move into the envelope at all, and someone will send a missile your way with enough delta-V to 100% guarantee your doom. As such, the psychology of the combat is going to be incredibly important. You have to get into their mind, and predict what sort of "unpredictable" move they're going to make. The book I recommend on the topic is *The Art of Learning* by Josh Waitzkin. In the opening chapters, he discusses winning a "push hands" competition against an opponent who seemed to read him like an open book. Forgive me for not having the direct quote (I read it as a library book), but he points out a huge Tai Chi push-hands championship win where he attacked his opponent with eight attacks, seven of which were only in his mind. Combat in space is almost certainly going to fall somewhere between a deadly game of Chess and Tai Chi. In the movie realm, I recommend *Master and Commander*, which shows just how fully one must be engrossed in the mind of your opponent to second guess them before they guess themselves. [Answer] I don't think there is a easy way to build up realistic battles and have them look cool. Battles aren't about being cool and exaggerated poses and the weapons and equipment used are meant to be effective and destructive. Not flashy or sound cool. Sound plays a huge role in our perception of events and so removing that completely would be like asking someone to enjoy food with a blocked nose. You can do it, it just won't be as good as it could have been. I propose the following way to present it * Show attacker charging weapons (Slow motion if necessary) or giving out the order (with necessary pauses for drama) * Show the weapon discharging with noise from the attackers perspective (Camera could be in a 3rd person view and focused on the weapon, but your hearing the noise from the attackers perspective, or localized on the weapon) * Switch to a overview of the projectile/weapon travelling with the sound of the weapon still fading out * Show reaction of the attacked with sound from their perspective * Switch back to a overview of the attack landing, accompanied by faded sound from the attacked persons perspective * Switch to the attacked persons perspective of the attack spreading causing damage with the sound coming into focus Or You say you are combining the noise from both perspectives rather than having a 3rd party with a drone viewing the space battle and listening to actual audio. [Answer] **Don't do God mode overview** Very hard to make that epic without focusing in on areas of action. Try describing an intense traditional battle, but from a distance where people look like ants. **Sound** There is plenty of it. Unless dying, people aren't exposed directly to the vacuum. They're protected in suits where their own body and breathing produce sound, or they're on ships which also propagate sound. Not to mention communications. **Distance** The distance of units has only increased as technology advanced. From fistfights, to spears, bows, guns, artillery and so forth. Even today the distance is so great it's largely assisted by technology, and not visible to the naked eye. In space, even more so. Just consider how far out the various asteroids we are tracking are, and we aren't capable of anything close to Sci-Fi space battles. The exception would be if you were trying to board enemy ships for some reason. **Strategy** There's no 2 flanks on either side in space. Above and below are equivalent to left and right, as you can rotate your ship in any orientation you want. The distance makes it very hard to flank someone during battle, and would more so rely on positioning prior to engagement. It's largely technology based, so it will rely on technology warfare. Disrupting their tech and protecting your own is vital for success. If your space-radar is knocked out, you can't track and aim at your enemy. At best you can defend against slow projectiles and boarding attempts. [Answer] Radio chatter, sure, but also **health monitors** that you can see and hear. You can have a **dashboard showing the heart rate** and blood pressure, oxygen intake of yourself and others in the battle. When these go up, yellow/orange/red **lights** on the dashboard will flicker, and **alarms** will go off at different levels. [Answer] My gut feeling about space battles is that unlike (classic) terrestrial battles, size would be a bad thing: I think that a dozen small fighters would destroy the capital ship, every time, while the capital ship would destroy only half of that dozen in the same time. That you already have post-WW2: No more massed tank battles, because A10 Warthog/Tankkillers are picking them off using their slow airspeed and long loitering times. As mentioned in several of the (much better than this) answers, inertia/cost/slowness scales nonlinearly with size. I'd expect to build for the similar amount of materials (or less) eight ships each half as big as the enemy's, that will be more manoeuvrable. And unmanned (don't get me on Holdo riding to her death completely uselessly --- it'd be no different from putting a brick on a car's accelerator, steering towards the target, and jumping out!). Basic physics' conservation laws being what they are, I always feel like shields should dissipate the energy of incoming attacks more than neutralize them... Just like a bullet proof vest will stop you from gushing wounds, but you still get hit by exactly the same number of Newtons as without. Also you often have "Shields at 10%" type things where repeating the attack that took you from 100% to 95%, will at that point take you from 10% to 5%... I don't feel that makes much sense. Just like a tired boxer is just a fraction slower, but that's enough to lose *every time* from an evenly-matched-but-fresh one. [Answer] Historically, the primary purpose of battle between capital vessels in the pre-information age was to gain (or deny) territorial control over resources but in space, there is no concept of territory, and as we have seen from WWI to the the Falklands, capital vessels can be destroyed by far cheaper weapons systems, rendering them useless. Pit a multi billion dollar aircraft carrier battle group against a few Exocet missiles or a diesel sub and it will be sunk. I am sorry to have to say this, but space battle (at least scientifically realistic space battle) is epically boring and more then a little pointless. It really comes down to putting a lump of rock where the enemy is going to be and waiting for the enemy to hit it. Without some sort of 'magic' propulsion system or significant hand waving, space ships have extremely limited mobility options, remember Apollo-13 which had absolutely no ability to turn back, and orbital mechanics being what they are, it is very easy to predict exactly when and where an attacking force will be at any and every moment in the future, making it extremely easy for defenders to ensure there will be something to greet the attackers and ruin their day. As others have mentioned, there is no stealth or camouflage that can hide either the ships or the weapons. [Answer] One lone idea, in case it sparks something for someone: If your spacecraft get into close quarters (ie. not just xray lasering each other from half a million miles apart) then knocking out one craft's propulsion would leave it drifting, unable to dodge or maneuver. The crew play dead, deactivating weapons and the like. The opponents might assume it's crew are dead, or the craft is helpless, and ignore it in favor of more urgent targets. Meanwhile, the disabled ship's crew waits, tensely like a submarine battle from Das Boot, drifting past fields of fire, taking stray hits, all without giving any response that would reveal they weren't dead. Eventually they drift close enough to an enemy to unload some knockout close-range weapon - maybe just climb outside, flinching at the ongoing battle around them, and shove a timed bomb by hand to intercept the enemy at 3mph. [Answer] Have a look at [Isaac Arthur's excellent Youtube channel](https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g). He has many episodes on future and space warfare (being former military) which are all scientifically accurate. You'll be surprised about the ideas he offers! [Answer] Considerations: ### You never see your enemy. Even in modern air combat, weapons are released when the enemy is out of sight. Some of them have ranges of well over a hundred miles. You won't see the enemy you kill except as a marker on a display screen. Like submarine warfare, there will be significant delays between the release of a weapon and it reaching a target. Counter weapons will be important, but due to velocities involved will be almost entirely computer controlled. ### Computers fight. People plan and fix. People will mostly have two functions: Planning the situation that leads to combat, and repairing damage to try to keep the ship functional. ### People are your biggest resource. By in large manpower is more expensive than metal. It takes millions to train a modern fighter pilot. If you sink a modern carrier, you don't just roundup 5000 men off the streets and fill up a new one. In WWII the Germans were sending up high school kids with only a few hours flight time to be slaughtered by Allied fighters -- they could still build planes, but not train people to operate them. Ships will be as automated as possible to have minimum crews. ### Space war is six dimensional. Space combat isn't 3d. It's 6d. "Say what?" A submarine war is truly 3d. Your x,y,z position (latitude, longitude, depth) determines what you can do. Speeds are limited. A fraction of a mile per hour when patrolling, a bit faster than that when hunting, but you go fast, you make noise. And even at flank speed, you have a max fixed speed. The time it takes you to slow down from max speed to patrol speed is small compared to voyage times. Generally a few minutes. In space there are no speed limits. So you have a 6d coordinate, 3 spatial ones, and 3 velocity ones. Two fleets passing each other at 10,000 km/sec relative speed using missiles that have a range of 100,000 km (1/4 of the way to the moon) the entire combat is over in 10 seconds. Combat engagement is determined hours or days before the encounter to arrive at the right place at the right speed. ### Gravity doesn't matter much Given large delta-v (Your ships can accelerate at 1-10 g's for hours/days at a time, and your missiles can accelerate at 100 times this) gravity is mostly inconsequential. In our solar system everything dealing with gravity is under 100 km/sec. At 1 G changing your speed by 100 km per second takes 10,000 seconds -- about 3 hours. Gravity does affect your course, but not much. If you have very limited speeds, then voyages take months or years. Makes for a boring story. Gravity does have an effect then. ### Stealth is hard Like submarine warfare, much depends on not being seen. Unlike submarine warfare space is clear. If you have very accurate sky maps, and good optics, you can see when an enemy ship blocks the light of a star. With high power radar you can have fixed stations 'ping' the whole solar system for extra bits. You have to sort out the ships from the asteroids. ]

[Question] [ So, in my setting, there are magical weapons, armor, tools, and jewelry. They are quite the standard fare, ranging from swords that can cut better to amulets that let you breath underwater and the like. The more mundane magical items are quite cheap to buy and produce, while the fancier ones will tend to be more expensive, out of reach from simple peasants and the like. However, there will inevitably be highly successful knights, kings, and protagonists that will be able to have a large number of these magical items. Aside from the standard logistical limitation of making such magical items rarer and more expansive, I would like other reasons for why a person is unable to wear so many different magical items. Notes: * These magical items are created by taking an item and making it magical by applying runes and stuff onto it. This should not be needed to answer the question, but it is here nonetheless * It would be best if the answer could be general, and not need the specifics of how the magic works, but for those who wish to provide a more specific answer to this question, here it goes. * Everything in the World has, and is made of Mana at the basest level, as such, when you manipulate Mana, you manipulate the things which the Mana was tied to, which is done by magic. Pretty rudimentary stuff. [Answer] Some basic ideas on how to limit it, requiring more or less adaption of the magic system: # Bodybatteries The magic item itself is incomplete; it's only the effect but has no internal power source. Instead, the items work by tapping into the body's natural energy/mana and powering themselves from it. Wearing too many magic items will introduce fatigue, sleepiness, and could even drain so much energy you go into a coma or die. # Interference Magic has a profound effect on the world around it, and while the world is quite capable of handling some craziness, there is a limit. If you combine too many magic items in a small area, they start going over the world's crazy-limit and start interfering with each other, with all kinds of unpredictable (but mostly fatal) effects. # Jealousy All magical matter has some limited, primitive sentience. They will try to force their own will on the world by connecting to the mind controlling them. While this is usually not an issue at all as a human mind can easily overpower it, collecting too many items together will both overwhelm the wearer with the constant feeling of conflicting interests and will make the magic items start fighting amongst each other for dominance, causing the weaker ones to start failing as they are suppressed by the stronger ones. # Focus point attachment Everybody only has so many points where the natural magic of a person can interface with the magical energy of an item. A magical ring simply doesn't work unless it's worn at a specific height on a specific finger, and few item casters know how to make a ring that can work at another place than the 1/2/3 well-known places where rings can be worn. # Attunement It takes mental energy to control and guide a magic item. It's like each of them has an instruction manual with all sorts of rules and quirks that you must get used to. At some point, you'll simply start confusing the subtle mental guidance you give these items and run the risk of accidentally deactivating your magic sword instead of pushing some extra power into it. The better you are at coördinating your thoughts, the more items you can operate at once, but there's a limit to what you can remember and use without error. # Conduit Like gravity, magic exerts a force on other magic. The more magic you have in one place, the more it starts to pull other magic in closer. At some point, you will simply be drawing any magical spells onto you, even if it's targeted at someone else, and you'll be pulling magical items closer to you, making you even easier to hit with a magic sword, as if you're a giant magnet. # Drawing attention Humans are not the biggest fish. There are *things* that love magic, feast on it, and do unspeakable things to the local area when they come looking. The more magic you collect, the more you stand out to these beings and the more risk you run of receiving a visit by an unspeakable horror who will devour your sanity at the same time he gulps up all the magic emanating from your body. [Answer] Another possibility I have invented for one of my recent settings: Let magic be a harmful radiation. The mightier an object is or the more magical stuff you wear the more (tissue) damage you will receive. This gives you a lot control over how useful a magical item is. Magical casters can be more resistant about a short but intense flow of magic but can also be damaged when exposed to constant radiation for too long. [Answer] You don't need a magical reason to solve this, here are a few # Weight Magical items are made of heavy things. Only the strongest person can carry so many items ( and has little use or understanding because they spent the time studying trying to build their physical strength ). The only feasible way to do it is to carry them in a horse and cart at which point you aren't wearing them and there's no point # Social Stigma People would look at you funny if you had a **lot** of bling on, in society today overdoing it is frowned upon. Subtlety. Why not the same with magical items? Don't prevent having too many, just make the character a pariah when they do so # Bulk There are a lot of things within the range of weight that I'm able to carry, that are simply too unwieldy and bulky to carry. For example I can't carry a 10m x 10m cube of polystyrene. It's light enough for me, but it's too bulky. Make it the same for your magical items. Carrying more than 2 or 3 can be impractical purely from a volume/density point of view # Finances Nobody really buys their magical items, they buy them with loans, and if you have too many loans, the interest prevents you from doing other things ( like eating ) # Religion Magical artifacts aren't seen as magical, they're seen as religious, divine artefacts. As such, they're gifted by clergy, and held on to for their power, seen as gifts. Some people see crucifixes this way, but they don't walk around with hundreds of them hanging from their neck. Additional crucifixes and prayer beads don't make Gods presence stronger around you, so why would more of these magical artefacts do that? These people believe their power comes from God/Gods not from an innate magical ability There's another side, even if it's known that carrying multiple artefacts conveys more magical effects, and they are cheap, such actions may be blasphemous, or seen as greed. Equivalents of the religious texts we have that pour scorn on greed and materialistic tendencies may make hoarding magical objects obscene, possibly illegal # Chain Reactions The destruction of a magical object may incurr a costly event, such as an explosion or the sapping of life force. While multiple of these objects would be powerful, the destruction or damaging of one may set all of them off, incurring a devastating event to the owner and all around them. This also provides you with a mechanism for Kamikaze Wizards, magical suicide bombers, etc # Smell Perhaps a vital ingredient of constructing magical objects involves something that smells horrific. Perhaps it's a binding agent, or a catalyst which unlocks the powers of the items. Eitherway if you have too many items in one location, you're overwhelmed by the smell, it becomes unbearable, the weak of heart may pass out from the fumes. This places those with no sense of smell at a huge advantage however # Toxicity There are plenty of things we ingest on a daily basis such as caffeine that are poisons. Caffeine for example is a natural insecticide, insects eat a plant with caffeine in its leaves, and are unable to regulate their bodies and go into overdrive. They curl up into a ball violently shaking, super wired. We're too big for caffeine to do that to us, and perhaps it's the same with magical items. Something in them is poisonous but within tolerable levels. Until they reach a critical mass and we start to lose the battle, leading to a slow decline. Perhaps as a result, users with lots of magical items become weak, suffer signs of dementia, respiratory issues, etc # Critical Mass What if one of the traditional ingredients was radioactive? Perhaps they were using a mildly refined form in order to produce the heavy metals for aesthetic sake ( the bright red uranium dishes from early 20th century that were so popular? Or the glow in the dark watches that used Radium? ) Too many magical items mashed together may create a critical mass, resulting in dire consequences or radiation poisoning # Taxes Faced with a proliferation of magical items and a shortfall in government coffers, perhaps taxes were instituted on the growing trade in magical items. It's no longer financially feasible for people to own large numbers of items, and it makes sense for the rich to go for individual expensive powerful items rather than face a tax burden of multiple not quite as expensive items # Ritual It may be custom to prepare each item, a ritual of sorts, required each day. Owning more items means more time spent doing this, which becomes tedious and impractical # Maintenance The maintenance costs of keeping the items operational, clean, and well functioning may make owning lots of magical items unfeasible # Technological Obsoletion Magic can set a house on fire, but so can matches. Why carry an amulet that can set things on fire when a small box of matches will do the trick too? As technology progresses, things can be done better and more reliably with a machine than using magic, so people may be able to have lots of magical items on them, but there's no need. Why carry a staff of light, a magical compass, enchanted music box, and crystal ball for communication, when you can carry an iPhone? Of course the lightning wand and the paper thin adamantium armour that melts attackers would stay [Answer] # Rune-crosstalk While we perceive objects as being distinct from each other, with clearly defined boundaries, they are just collections of individual atoms. The inscribed runes affect the underlying mana and do not "know" the objects. Instead they affect all matter in a certain distance. Too many runes in one location and the runes of the sword starts interfering with the job of the runes on the ring, weakening both or creating new unforeseen effects. The power of the runes also extend to the wearer's body. This is usually fended off by the wearer's intrinsic mana/magic/soul, but too many runes and they start having unintended side consequences on the body. Both storywise and in RPG campaigns, you can have anything happen to a character "because too many runes". Also see: [Crosstalk](http://en.wikipedia.org/wiki/Crosstalk_(electronics)) [Answer] Unless this is for a RPG and you need to actually calculate the effects, you can simply assume a background mana field of varying intensity of low and high mana areas. This field powers anything with mana, in this case everything, and the local mana level is then simply the point of balance between the natural rate of mana generation of the field and the draw imposed by mana use in the location. Thus places like mountain tops or desert would have high mana and places like cities low mana. (Mentioned because this migh be undesirable side-effect.) This would imply that if you increase the mana draw of a location, its mana level will drop towards the new point of balance, and then take some time to recover after the extra draw is removed. Examples of such extra draw would be magic items and magic use. Thus concentrations of magic items would be surrounded by an area of depleted mana. You can further assume that the rate of mana generation is not a constant, but varies depending on the current mana level with lower mana areas generating less mana and recovering slower. This would make the time an area needs to recover from mana depletion longer the deeper the depletion is. The depletion caused by magic items could become a real issue if the density of magic items is too high. Since magic items require mana to work and probably have some minimum levels needed to work reliably or at all, having lots of magic items at the same location for extended period does not really work. With sufficient number of items in the area the depletion might become an issue fairly fast. Certainly people with lots of magic items would be asked to "move along right now" in cities, otherwise cities would become permanently mana depleted areas. This would be bad as it would make spell casting too unrelable to be useful. And since in the scenario living beings are also mana active exposure to mana depletion would probably cause some serious health issues. I'd expect people carrying lots of magic items would need to be constantly moving to avoid becoming sick. Added number of items would force person to do that movement in remote high mana areas. And at some point only outer space would be remote enough to avoid sickness. This would give a tunable reason to limit and actively manage magic item density. Math would be annoying if you need it and it has side effects on how society regards magic use and magic items, so it might not be what you want. [Answer] **Euphoria/Addiction:** Using magic *feels* good. Casting a powerful spell can get you high. Rituals can get you effectively drunk (as a side effect). Use a handful of magic items, and suddenly you're trying operate with a *permanent* high. Load up on a ton of them and you might as well be constantly mainlining heroin. Needless to say, people who use a ton of magic items tend to not last long, although sometimes they don't last long in really spectacular ways. [Answer] ## Bad luck Look, it's great that you got all the magickal jewelry to improve your armor by 200 percent. But now it seems, that you need to wear your armor *all the time* - there are suddenly falling objects, tree branches hitting you and you slipping and falling to sharp object. It can be mindset, or it can be truth. But people tend to wear only X magic items at a time, because having more is generally considered bad luck ## Name of God You pointed out, that to make object magical, you have to scribble runes onto it. Going from Norse mythology: The runes are from God(s) and made by God(s). And the point is, that it is generally believed, that X runes put together might accidentally spell out the "True name of God" No one knows what happens, but I dare you to wear more than X objects! You could end the World existence! [Answer] # Constitution Very similar to Erik's 'Attunement', but a different take on it. The ability to effectively use a lot of powerful magic items is unwieldy. This has a direct physical analogy: warriors don't use a bunch of weapons. It's true that people only have two arms, and those are the best candidates for holding weapons, but historically even dual wielding isn't done. Video games and movies make it seem wonderful to dual wield swords and daggers and all manner of weapons, but in reality you don't gain much. The same could be true for magical items. Splitting your thoughts between fire, ice, necromancy, lightning, healing, etc would surely become unwieldy or inhibitive just like dual wielding swords. # Insanity Kind of in-line with the previous one. Wearing too many items, and trying to control too much magic, drives people insane. # Affinity Perhaps magical practitioners can only utilize one niche of magic. Or, more accurately, they can practice *all* types of magic, but they're just completely inept at everything except their favorite. Combined with the next item, diminishing returns, there would be a functional limit to what you would want to wear. # Diminishing Returns Sure, you could have 20 rings, 7 amulets, and carry some magical daggers in concealed locations, etc, but would it offer any benefit? In video games and RPG settings a lot of times the effects are simply additive or a percentage boost. "Wear this ring, +20% fire damage". What if the reality of it meant "Wear 1 ring, and you get a 50% boost. Wear another ring, and get a 50.1% boost(in total...so the second ring is adding 0.1% to your abilities)." It would be immediately obvious to magical practitioners that you *could* continue adding more and more, but the increase in magical abilities would quickly interfere with things like dexterity. Even in our world, I don't understand how some people walk around with a bunch of rings on their hands. I've seen some people with 5+ rings on a single hand... I can barely wear 1 ring before I feel restricted. [Answer] ## Magical Size Objects have a size and weight in terms of reality, but magical items also have a magical size and weight. The more magical (and thus the more expensive) and item is, the "bigger" it is in terms of magic. Putting too many magical items together can cause drastic problems; the easiest is that some magical items get magically 'crushed', and cease to work; more interesting may be a magical black hole that suddenly begins effecting reality AND the magical realm. ## Unexpected combinations Runes may work by simply being close; put rune A and rune B together, and you get a magical anti-fire ring; put rune C and rune D on an amulet, and your can breathe under water. However, if that rune-covered ring is close enough to your rune-cover amulet, you may well accidentally get rune B and rune C to make a (stronger) bond than their previous mix, and make an anti-breathing spell. Oops. ## Magical Attractor Amulets, rings, and other magical items act as collectors of magical energy, which is what is used to power them. However, like a lightning rod, too many magical items become too strong of a collector, and will overpower themselves, burning out, burning up, or simply ceasing to be. Worse, magical energy is attracted to large piles of magical collectors, which make whoever is wearing a hundred rings an easy target... ## Magical Repulser Or, from the other side, magical items may work by removing all the "static" of normal magic flow, and keep only the useful bits; the runes act as filters, allowing the devices to store up large amounts of just the right kind of energy. However, this also has the downside of constantly bleeding off magical energy. A little bit is fine, but at some point you start zapping yourself just by moving around. ## Incompatibility Different magical manufacturers may simply use different magical technology that simply isn't compatible; multiple rings of the same kind of ability may simply not work together, or even cancel each other out: "I've got an iRing of Fire Resistance, but it doesn't stack with my WinBrace of Fire Resistance; I have to choose one or the other. Worse, neither one works with my iAmulet at all unless I buy an iRing of Compatibility, and everyone knows those are insanely expensive! And don't even get me started on how my Helmberry works with my Magicsoft Shield. I'd use Red Helm Linrune, but I don't have time to build it myself..." ## All of it But why stop at just one reason? One reason can be overcome easily enough. What you need to do is put all of it together: Magic items take up magical space, and putting them too close together creates unexpected combinations; they also attract magical energy, but bleed off the energy they don't use. Together, that means that manufacturers can only guarantee that their own items will work together, because of the careful placement of runes and magical bleed-reducers; mixing products in large amounts can have catastrophic failures. [Answer] I think the ideal of incompatibilities has been covered reasonably, but I wanted to suggest a mechanic which could be used to bring more color to that incompatibility: wave mechanics. What if your magical items did not have a constant magical force, but rather constantly emitted ripples of magical energy in complicated patterns. Each item would have its own "fingerprint" of ripples, though two fire-amulets might have similar fingerprints. These ripples emanate out across the body, interacting with themselves until they finally fall into a standing wave pattern in tune with not only the amulet, but the individual. Only in this state can one effectively use the amulet. Otherwise the amulet just can't tap your mana as well. There is a physical analog. In percussion, one "warms up" a gong by [almost] silently tapping it several times before finally hitting it to make a noise. The light taps set up vibrations which bring the entire gong into a sort of alignment. You can hit a gong without warming it up, and it will make a gong noise, but if you warm the gong up, the sound is much brighter and more musical. If you are wearing multiple items, those waves have to also come to a standing state before you can use any item. This state is certainly more complicated than the one-item state. This would be hard on the psyche, as it tries to deal with the "bickering" between items competing to generate their "best" effect. The wave mechanics not only offer a visual for what these interactions look like (ripples on a pond, perhaps), but also offers a neat plot device. It would be reasonable that you could devise tatoos that behave like the pyramids in anechoic chambers. These tatoos, perhaps on the shoulder, could make it easier to carry incompatible amulets. The energy reaching up the arm would hit the triangular tattoos, and dissipate. Of course, this comes at a cost of each amulet only having access to some of the mana of the body. However, this would open the door to people trying to use amulets that would otherwise be too dangerous to wield (i.e. "this amulet is powerful, but it slowly steals your soul" is no biggie because the amulet can't "see" past your shoulder) [Answer] Well you always have the idea that some items cause interference for the safe use of other items. A charm to protect you from fireballs, might significantly hinder your ability to use your fireball flinger. An Ice storm maker could cause conflicts with it too! The more powerful an amulet the more it affects magical items in it's vicinity, maybe putting huge stresses on a body that is touching 2 or 3 such items at the same time. There is always the activation of such as well. If it needs to draw mana from the surrounding area, or some reserve the individual has then it will limit how many can be used before they all become useless. This would encourage the mastery of a small number, to get the most out of them and understand their uses in any situation. Of course if they are self sustained, and can be used 1-3 times before it runs out of juice, until you have a chance to recharge them, then someone would be much more likely to want as many as possible. [Answer] # Temperamental Theurgy Okay, so Mana is in everything. However, people don't actually have the ability to manipulate it. The only ones with the power to directly affect Mana are the gods. Therefore, the magic that people do is indirect, performed by invoking the power of a god or gods. The exact nature of your world's pantheon is flexible, but there is one important thing: as in classical mythology, the gods are generally [jealous and fickle](http://tvtropes.org/pmwiki/pmwiki.php/Main/JerkassGods), and they don't all get along. So, small-scale magic works reliably as long as you know the right inscription, ritual, or incantation. However, if you call on single god too much, that god may get annoyed and refuse to help you, causing your enchantment to fail. He might even get angry and make a spell backfire. So you'd better not use that wand of greater fireballs unless you're sure [Michaelus Baya](http://tvtropes.org/pmwiki/pmwiki.php/Main/StuffBlowingUp), god of fiery explosions, likes you. People who try to get around this by calling on multiple gods could run into a similar problem when the gods dislike each other. A god won't be to keen on helping someone who's been working with a rival, and if they are enemies, he may try to sabotage that person instead. So in either case, using too many magical items is ineffective at best, and dangerous or deadly at the worst. Of course, what is "too many" is relative. The gods tend to show special favor to kings and to certain heroes, which would enable them to use more magic than other people. This setup works even if you don't have and don't want to create a bunch of gods for your world—just take an animist approach, where different places, objects, and forces have their own spirits. You could use this to justify ancient artifacts being more powerful, as their spirits are more experienced and skilled. This could also lead to newly-acquired items being difficult to use, as the owner is unfamiliar with the spirit. Also, the gods' or spirits' familiariry with *people* in general could justify having controlled magic in populated areas and "wild" magic in the wilderness, as you indicated in a comment. The idea of the gods powering magic items getting annoyed, tired, or distracted could justify a [plot-driven breakdown](http://tvtropes.org/pmwiki/pmwiki.php/Main/PlotDrivenBreakdown), if you want your protagonist to face a problem without some or all if his magical items. [Answer] OK, there are already quite a few options, but I found there's still something I can add: ## Physical repulsion Mana has a natural repulsion built in (this is what makes it distribute over the world to begin with). Now the magical items concentrate Mana, but this means they also concentrate the corresponding repulsion. That is, different magically enchanted items repel each other, physically. This repulsion is no problem if you have only a few items, but the more items you have, the stronger the repulsion gets. At some time it already needs a considerable force to put another magical item close to the others. Putting too many rings, amulets and so on to your body might make some simply fly away from you due to the repulsion (and if you are unlucky, take parts of your body with them). Note that such a repulsion could also be used productively to deflect magical items from structures which can exert the necessary physical force, even if the magic of the items stored there would be otherwise completely useless (say, there is a type of magic that does nothing but change the colour of objects; it's cheap and normally useless, but if you manage to get sufficiently many enchanted items together in your wall, it protects it from magically enchanted projectiles due to Mana repulsion). [Answer] Here is a possibility from GURPS. Powerstones naturally recharge themselves over time. Multiple powerstones of similar power too near each other will split the available ambient energy, which greatly increases the time required to charge. When powerstones of varying power are near each other, the lesser stones do not charge at all, even once the more powerful stone is "full". So, for your case, someone could wear many items, but they would need to be of similar power levels, and could decrease the available usage of each individual item. Someone with a more powerful item may just have to make do with the single item. ]

[Question] [ Suppose an evil genius (in 2015) wants to kill as much of humanity as possible. But he's on a budget; despite his years of stealing priceless historical artifacts, and despite having been selected for several excessively over-funded research grants, and despite having rigged AAPL value to shoot sky high in the 90s, he can barely scrape together $1 billion. Sure, he figures, he could always just set off a few H-bombs in some major cities, and hope for maximum carnage. Or, he could plant a dirty bomb in pretty much every decently sized city. But either way there would be a bunch of survivors, and survivors are not something this evil genius wants. Robot minions have been planted in high levels of every major world government, so getting resources that would normally be inaccessible to ordinary citizens isn't a problem, though he'll still have to pay for them. However, these robots don't hold top-level positions (and believe me, he's certainly tried), so he can't make his doomsday project fully government funded. **Basically:** What is the cheapest (preferably under $1 billion) way to kill off the most people, with only modern technology (no far futuristic stuff, though extension of modern tech trends is fine)? [Answer] My wife has a degree in criminology, and she wrote a paper about how you could poison a huge percentage of the population in a couple days by putting botulism in the milk supply. If I remember correctly, it was something like 2/3 of the population within 2 or 3 days. If you had something that you could put into municipal water supplies (you are the government after all), you'd be good to go. One disadvantage though is that you have to deal with the fact that it isn't nearly as centralized as milk is, and you'd have to put it into the water after it's treated, not before. One advantage of using a bio agent over a chemical is that you have a one time ingestion, and then an incubation period. There's no chemical (to my knowledge) that you can ingest once, and then die several days later. You'd at least be ill fairly immediately. Additionally, bioagents are often contagious. That lets you get the pesky people that can't/don't drink milk. I'll leave the research of various diseases to you, but botulism, anthrax, and maybe some variant of the plague are good starters. [Answer] Design a [paperclip maximizer](http://machineslikeus.com/news/paperclip-maximizer). If you are really a genius and can develop such a software, all you need is a computer with an internet connection.... A paperclip maximizer is one of the simplest examples of an AI which would destroy humanity even without a malicious goal. You only have to create an AI capable of self-improvement, and give it a simple goal like maximizing the number of paperclips in its collection. It doesn't have to have human-like goals or anthropomorphic qualities, it just computes very fast and tries to find the optimal way to increase the number of paperclips. If it makes itself smarter, it will be able to quicker acquire or manufacture paperclips, so it will make itself smarter until it reaches singularity, after which it converts all mass into paperclips. I have chosen it instead of a classical Skynet-like AI, because the paperclip maximizer doesn't need to have human-like qualities. It would also be completely unstoppable if released. Also, such a scenario is more realistic than the robotic minions capable of infiltrating governments. Designing a robot which is capable of disguising itself as a human (as presented in the question) and therefore require human-level intelligence is harder to do then just designing an AI with human-level intelligence without the fancy anthropomorphism. [Answer] *Wait* Eventually the sun will explode [expand into a red giant](http://en.wikipedia.org/wiki/Red_giant), taking out most of the solar system with it. What remnants of humanity that have left the solar system would likely meet the same fate elsewhere, or gradually evolve into something we wouldn't identify as human. Eventually? Perhaps the [heat death of the universe](http://en.wikipedia.org/wiki/Heat_death_of_the_universe) will wipeout what's left Total cost? Absolutely nothing *and* you'll never live to regret it [Answer] ## Asteroids!! If you have $1 billion, one way to kill a serious number of people is to grab an asteroid and hurl it to Earth. Hitting land would probably cause an extinction-level event. Hitting water would wipe out almost all coastal population (and would probably trigger an extinction-level event as well). I'm torn on which would kill more people. Hitting the Earth is a bit tricky especially if the asteroid you picked needed a lot of fuel to de-orbit leaving you little fuel to guide it back towards Earth. I think it's doable within budget. It's certainly doable with current tech if budget is limitless. ## Alternatively: Comets An alternative is to wait patiently for a close shave fly-by of a very large comet and grab that comet and hurl it to Earth. Just pick one form a table conveniently compiled by NASA: <http://neo.jpl.nasa.gov/risk/> Since the comet is already heading towards Earth, and has non-zero probability of hitting Earth, it would probably cost less fuel to nudge it just so to get it to hit Earth. ## Cost: Now, lets discuss cost. India managed to send a probe to Mars with 74 million dollars. I believe, so far, that's the cheapest anyone's managed. The Beagle 2 cost the British 120 million. So sending a spacecraft just slightly beyond Mars (or in the case of comets, less than Mars) would definitely be within the realms of a $1 billion budget. ## Advantages One advantage of a kinetic projectile is that it is a pure physical process. You can't develop antibodies or antidotes against an explosion or a tsunami. The other advantage is that it will probably trigger massive changes in the climate. Which in turn will trigger crop failures leading to more death due to starvation. ## Defense / Counter-defense Of course, if you can do this, then world governments can also use similar technology with similar budget to nudge your asteroid/comet so that it doesn't hit Earth. But anything defensive needs to be carried out fairly quickly since the nearer the rock is to Earth, the more fuel you'd need to nudge it out of the way. (BTW: If they decide to nuke it, they'd be doing you a favor by increasing the number of impactors) Here, a simple counter-defense would simply be to misinform. Either infiltrate NASA, ESA etc. and publish misleading statistics that show the rock would not hit Earth or broadcast false news. You can also try to be sneaky. NASA tries to constantly monitor close approaches but every once in a while they only manage to detect the comet mere days from the close approach. That's not enough time to launch any defense. Obviously if you're going this route you shouldn't pick a comet from NASA's list of comets. [Answer] Political instability, 2 small nukes and a small number of cheap short range small rockets. A combination of cheap attacks like some mentioned in other comments, biological in particular but targeted. Engineer outbreaks of one set of diseases in American cities while poisoning lots of people in Moscow. Just to get the public panic going. Add a few sniper teams hitting a few random high-ranking politicans on both sides. Try to make it look like tit for tat attacks from the other side to get the politician scared. Make sure the media start talking up the possibility that the outbreaks and the assassinations are intentional. If you can fire things up enough real politicians will start saying that their side needs to strike back. Get a few more nuclear powers involved by similar means. Set off one nuclear device in a major US city, a few minutes later set off the other in a major Russian city. Launch your rockets within the territory of the US or Russia. Don't worry, they don't have to go high or be loaded with anything, they just have to show up as launches on the other sides radar and surveillance. I think that would be pretty doable with a billion dollars and government-level access to weapons. [Answer] ## Biological warfare Research and development of a highly infectuous and resonably deadly disease seems to be the best "bang for the buck" in this scenario. It does require specialized skills and lots of luck, but (unlike other methods) it scales well, as the same virus or bacteria that would wipe out a single city can also wipe out most of the world, if you can deploy it appropriately, preferably in many countries at once, in mass scale, and it has a long incubation period - where many people would catch the disease long before the first deaths occur. ## Leverage Another option is to provoke someone else into killing most of the population for you. For example, if you don't have access to the very top officials, still your robot minions could possibly launch a few nukes during some time of random political tension and watch Mutually Assured Destruction happen as the other side simply doesn't believe that it was your fault, and not the 'enemy' government. [Answer] At the risk of getting my name on a list... I would go with a biological attack as well, but rather than sinking loads of time, effort, and money into developing a super virus, I would look into getting my hands on a wide variety viruses. Look into things like: [H1N1](http://en.wikipedia.org/wiki/Influenza_A_virus_subtype_H1N1) [Any number Viral hemorrhagic fevers](http://en.wikipedia.org/wiki/Pandemic#Viral_hemorrhagic_fevers) [Multi-drug-resistant tuberculosis](http://en.wikipedia.org/wiki/Multi-drug-resistant_tuberculosis) And so on... So rather than a single wide spread pandemic you have several overlapping pandemics. Dispersal would probably get a little expensive, you'd want to simultaneously strike as many major airports and seats of power as possible (by seats of power I mean parliaments, senates, military bases, and so on...) It would probably also be worthwhile to go after medical establishments (hospitals and large medical conferences). Keep in mind you're not dropping one virus per location you're looking to drop as many as possible on every location. Then if you have any doubts about how effective things are going to be or you really want to add to the heap... Taint basic medical supplies (latex gloves for instance). You don't really need to cause casualties with this. It just creates further panic and gives people a reason to fear and delay treatment. [Answer] It's really pretty easy. * Buy off the leaders of a political party so that they'll counter clear scientific proof that humans are already doing it to themselves. * Maybe even start a faux news network to support the arguments of that party and to undermine those of the science based opposition. * Pay a few fake scientists to lead your argument. *The real news networks have this innate need to show both sides of an argument, thus making it seem like your scienteists are worth listening too, and won't realize they've been playing into your hand until it's way too late.* * Wait a few decades for the planet to overheat, the oceans to rise, droughts and the subsequent hunger to start world wide wars. * Enjoy all the spoiling of your efforts. [Answer] Start a website where you can ask or answer strange questions. Call it "QueueExchange". People will get too engrossed to remember to breed. End of Humanity in a generation! [Answer] If you're not in a big hurry, then the most thorough and effective answer may already have been posted by jamesqf, but was deleted for only being one sentence long. That is, you could just assist our current extermination plan, which is to kill off life on Earth via climate change, and sabotage attempts to slow down greenhouse gas emissions, stop deforestation, etc. Addition - Further detail for those who don't think climate change likely means extinction: Even in 2012, the International Energy Agency projected +7 Celsius overall by 2100 (effects: highest temperatures in 30 million years, drought on 40% of inhabited land, hundreds of millions of refugees, half of current non-human species extinct) but at some point it seems likely (possibly at +2 degrees, almost certainly at +6 degrees) that this will trigger positive feedback systems (e.g. methane released by thawing polar permafrost) which will generate an unstoppable and even greater rise due to new conditions being created. That leads to +12 degrees, (effects: half of planet uninhabitable due to lethal average temperatures closer to 200 F than 100F). TWO degrees Celsius average increase used to be the effect scientists dreaded, because ecosystems depend on stability, each other, and biodiversity within them to continue to support life in the same way. We depend on those, as without them we will not have food, for example. Then there's clean water supply, and the acts of humans when, say, everyplace at the latitude of India is uninhabitable. Depending on the nature of our evil genius, the chaotic side-effects and decades of suffering as humans face their self-induced demise may be quite satisfying - the main problem may be that he was only a drop in the bucket, and not the root cause himself. (Source and easily-digested summary: <https://youtu.be/A7ktYbVwr90?list=PLe9ZM0hR2yCEl_1jYd5HqJkA5oajaeQz6>) The thing is, those are already being done by other larger wealthier evil organizations than your own, so your $1 billion contribution isn't much help. Perhaps you mean to out-do them and do so faster. Or maybe your goal is to kill just the humans so fluffy animals can survive global climate change. The ideas to contaminate the food and water supplies with diseases and biological warfare agents are good, but they might be survivable by some, and if you want to kill the fluffy animals too, it might backfire since if you killed 90% of the humans, it might set back their greenhouse emissions and avert a climate change extinction. Another idea: Infiltrate Monsanto and/or Syngentia, the GMO food companies, and alter their seed projects so that seed crops are planted with cross-pollenating, species-hopping pollen which when planted on every continent, will result in all plants becoming poisonous, and/or all food crops becoming inedible, toxic, and/or infertile. Then you just need to destroy the world seed archive in Norway. Of course, this also falls under "larger wealthier evil organizations are already doing it". The asteroid idea is good (could be 100% effective), though you don't have the money for it... though **with your robot spies, you might be able to find a near-miss asteroid, fake the data to show it's going to hit Earth and needs to be diverted, so the world governments can be conned into launching a mission which can change the asteroid's course, which you also hijack and/or divert with false data to get it to hit the Earth after all.** [Answer] "Delayed trigger" biological warfare. Instead of trying to infect as many as possible really fast (and still missing all isolated populations) aim at prolonged spread phase with delayed attack phase. We have a whole lot of different "harmless diseases" in us, and nobody bothers curing these. For example, tuberculosis which is dangerous to cats is carried by a large segment of human population with no visible adverse effects. Developing a disease that, e.g. attacks the ovaries rendering women infertile, or very slowly degrades the brain (taking about a year to reveal itself) - one highly infective but with minimal initial social impact - this would kill the whole humanity before the danger is realized. And I believe a $1bln would be sufficient to fund the research. If you create initial sources of spread of the disease in all 1st world countries, and it is lethal (say, that brain degradation variant) the chance a vaccine would be developed in time is zilch - by the time the disease reveals its effects, only a minor part of world population is not infected, and it will spread to the remaining parts as they can't remain in isolation forever. Meanwhile all scientific centers of the world are "neutralized" first, and while the third world countries and isolated colonies would die off last, they don't have means or resources to develop the vaccine. [Answer] Since biological attack has been flogged to death (heh), let me offer a means of attacking at least the first world nations: disrupt the electrical grid. EMP devices or other means of destroying electrical substations where the high voltage transformers are deployed will trigger massive cascade failures, and the grid won't be brought up again for a period of months or even years since there are no spare transformers waiting to be deployed (and the factories that make them are without power. Time this in November and the food and heat rapidly run out, transportation grids are down and soon the population is starving and desperate. Many of the deaths will be caused by looting mobs. The second and third world nations will be rapidly crippled without international trade, and will also feel the effects of shortages, although not to the extent of the First World nations. Without the various international organizations to facilitate trade and diplomacy, you could expect large areas of the second and third worlds to become effectively ungovernable, or fall into war and anarchy. This isn't 100% effective (although almost nothing is, even a bio war attack will have survivors who have immunity or are isolated and not infected), but will reduce the global population by a very large amount. Dr Evil can figure out alternative means of culling the remaining population after the effects of the global grid shut down have passed. [Answer] **Trigger global thermonuclear war via false-flag nuclear attacks** The easy part is launching the nukes. All you need is to take control of one [ballistic missile sub](http://en.wikipedia.org/wiki/Ballistic_missile_submarine). I'd say that should be feasible on a budget of a billion. You might want to go for a Russian [Typhoon-](http://en.wikipedia.org/wiki/Typhoon-class_submarine) or [Borei-class](http://en.wikipedia.org/wiki/Borei-class_submarine) boomers. Why Russian? The endemic corruption at the highest levels of Russian military and political life will make cracking their operational security easier, which means more boom for your buck. Even with a billion dollars, it's probably not feasible to bribe an entire sub crew to start WWIII—what good is money when your hometown is a glowing crater?—but it certainly should be possible to bribe one officer to expose the sub to capture by your own forces. Make him think he's betraying the sub into American hands, and make him rich in return. Once you take the sub, you'll likely need to replace the crew with people loyal to you and your goal of ending the world. You'll also need nuclear launch codes. Russia uses [a slightly different system](http://fas.org:8080/nuke/guide/russia/c3i/index.html) than [the American one](http://en.wikipedia.org/wiki/Gold_Codes) with the famous ["football"](http://en.wikipedia.org/wiki/Nuclear_football) that accompanies the President everywhere, but even the best systems are prone to [human failures of operational security](http://www.dailymail.co.uk/news/article-2515598/Launch-code-US-nuclear-weapons-easy-00000000.html). Corruption can only help you here; humans are always the weakest link in any security system. The hardest part will actually be convincing the other nuclear powers that this is a genuine attack. You need them to believe it's real and not a rogue or they might not retaliate with their own nuclear arsenals. In the event of a nuclear launch, the first thing American, Russian, or Chinese leaders will do is call their counterparts. So you either need to find a way to get them to distrust each other so much that they won't believe Putin when he tells them that someone's taken his sub and the attack is unauthorized, or you need to prevent them from talking. Personally, I'd my best to do both. Putin is pretty untrusted to begin with--another reason to take a Russian sub. Executing your plan when he's flexing his muscles like he did [last year in Crimea](http://en.wikipedia.org/wiki/Ukrainian_crisis) would increase your odds of success. But you'd probably need to give diplomatic tensions a push or two to really get things boiling. So you'd need to plan and stage an international incident. I'll leave that as an exercise for the reader, at least until I've had time to put more thought into it. I suspect that all you really need to do is make sure someone in the room with the president in those first few critical minutes suggests that "Please don't shoot! Someone has taken over our sub and launched this rogue attack!" is exactly what the Russians would say if they wanted a free shot at nuking the US. Your other target will be global telecommunications. I would go for a combination of DDoS attacks aimed at major internet backbones and coordinated physical attacks on [submarine telecom cables](http://en.wikipedia.org/wiki/Submarine_communications_cable) near where they come ashore. Bonus points if you make it look like the attacks come from the Russians. There actually [aren't that many major submarine cables](http://www.submarinecablemap.com/), and they carry the vast majority of global telecommunications. Attacks on all of the American and Chinese cable landfall sites would be considered an act of war in and of itself by American and Chinese leaders. Disruption in telecommunications and the internet would result in considerable domestic unrest, although I wouldn't give that time to build, as they could use that time to repair the cables. Cables should be destroyed hours at most before launch of nukes. Then you've just got to launch your nukes. Hit all the largest American and Chinese population centers, and throw in the capitals of every other nuclear power except Russia for good measure. Even if the leaders of every single one of those countries decide to die without retaliating, the three Borei-class subs currently in service each carry 16 [RSM-56 Bulava SLBMs](http://RSM-56%20Bulava), which are hardened against missile defenses. Each SLBM carries 10 [MIRVs](http://en.wikipedia.org/wiki/Maneuverable_reentry_vehicle), each with a nominal yield of 100-150 kilotons. So you have 160 nukes at your disposal, each at least five times as powerful as those used on Japan in WWII, with a global reach. By playing with a few cities at [NukeMap](http://nuclearsecrecy.com/nukemap/), I had no trouble managing 300k-500k points, er, estimated fatalities, per MIRV. In population centers with a lot of high-rise buildings and skyscrapers, 800k-1 million fatalities isn't difficult if you optimize for the overpressure wave by airbursting the nuke about 1km off the ground and letting the collapsing buildings do most of the actual killing. Even if the only nukes launched are from your single stolen sub, by targeting all the [most populous urban centers](http://en.wikipedia.org/wiki/List_of_urban_areas_by_population), you could likely kill a quarter billion people and precipitate a worldwide societal collapse. Which would in turn kill many, many more. If your false-flag attack succeeds in sparking a full-on nuclear war between Russia and the US or China, the effects will be much, much more [complete](http://www.nucleardarkness.org/warconsequences/). [Answer] Do nothing. The overwhelming probability is that if you wait long enough, humanity will destroy itself or suffer a natural disaster, at which point you will have $1 billion to celebrate and only living expenses ( and whatever defences you put in place to prevent yourself being amongst the dead ) [Answer] Annihilate humanity. This is an entirely cynical, theoretical ***think exercise***, yes?? The cheapest way is to let humans do it themselves. Use the minions in two ways: Generate cash and engender kill-games. These processes support one another as long as you invest in the weapon industry. Start and nurture the games worldwide. Have internet databases on how to approach hard kills for more points. Points can be traded for better weapons, but of course never for safety gear. celebrate big scorers so the second echelon goes after them. Every kill should transfer the killee's points to the killer. Infiltrate social media to motivate your growing army of killers. You'll probably have to kick-start the killing games by murdering a few loved ones yourself, using the minions, but after that the process should be self-propelling. As murders mount, civilisation will collapse and generate a "better" environment for the games to prosper. The famous 3 meals will be skipped, smart gamers will eschew perfect count and start epidemics and mass poisonings for you. There is a small chance a few warheads will fly as well. Better have a truly safe place prepared for the game administration and yourself until the last two mega-killers stalk one another at the south pole. That very last human you will have to do yourself. Be careful, do it in a safe way! Any minions left? [Answer] Nikola Tesla theorised that the Earth has a resonating frequency. Assuming the theory holds true, you could set off a series of relatively minor explosions on the Earth's surface at the correct intervals and energy would gradually build up in the Earth's crust. Eventually the Earth would start vibrating so violently that human life on earth would be unsustainable (perhaps the Earth itself may fall apart). In my mind this is the cheapest and most efficient way of wiping out humanity. The problem with chemical/bio attacks is delivery and resistance. There will always be people that have their own milk/water supply etc. And you'll find weird cases where some humans are resistant to whatever you try on them. At present, everyone in (known) humanity shares Earth as a common home, so I think it's better to target the planet instead of the people. Just make sure you take out the ISS first, otherwise a few pesky astronauts may remain. [Answer] Bio agents in real life suffer from a large number of problems. Some of them have natural immunities floating around the population. The most virulent can burn out a population center incredibly quickly, but would be isolated almost immediately following discovery. Other diseases have a long incubation time, which increases their spread, but run the risk of being rather survivable, and having plenty of time to counteract. Overall, a bio agent is not going to do the job - even if you had top level government access, you'd lose control as soon as you started trying to counteract control efforts. Assuming robot minions do not take away from the billion dollar budget, then you've infiltrated the wrong things. Take over the media of the major world powers, and then you have real control. Governments all over the world rely on the will of their people to hold up their actions - anything less will have your robot minions dragged out and shot for treason. But people have a tendency to take sides around issues, and if you control the media, you control the issues - all of them. Get a few writers in all the major news outlets, and most of the minor ones. Just get them doing their jobs with precision accuracy - feed them intel they aren't supposed to have from your higher level access, and provide unquestionable proof. Control the bad guys too - make them take more risks, stupid risks that are way out of line with a winning strategy. Steep the world in fear and hate and agony. Pseudo legalize all drugs by making enforcement virtually impossible. Engage in armed conflict at every possible opportunity. Shut down food, water and medicine supplies in as many places as possible. Damage as many resources as possible. Chaos and martial law will ensue whether you could do it yourself or not. Install and encourage as many suicide cult leaders, militant radicals, poison spewing pundits and murderous mob bosses as you can. Don't just leverage action - force a reaction. Arise as the only remaining source of viable authority and amass an army - a real human army with an actual mission of attempting to quell the mass chaos. Point them in all the wrong directions, fighting battles they must fight but cannot win. Fight to the last man, for the sake of humanity, God and whatever else you can leverage. The pitiful remainder of your loyal forces would then be trivial to make disappear one company at a time. Having bent all remaining resources to your will, send out robot death squads to finish the task of wiping out any remaining trace of humanity. Then party until you die with a robot prostitute or something, I guess. You win. [Answer] "Botulism in water supply" is way hand-wavy. Botulism bacteria are anaerobic and won't fare well in water. They are already present in substances like honey which is why infants should not be fed honey: their digestive tract does not have the acidity of an adult and will consequently not kill the bacteria before they start producing botulism toxin. So putting the bacteria in drinking water or elsewhere will not accomplish much regarding the adult populace. But then you don't need the bacteria but rather their toxin. Using that is, strictly speaking, not as much a "biological" attack rather than a "poison" one: as opposed to biological attacks, the substance does not multiply. But that is not really necessary: few kilograms are sufficient for poisoning everyone on Earth. The poison is really potent and works by enzymatically destroying nerve endings. Currently, there is one major supplier of Botox, the medically diluted version of this poison, and I think its total poison production so far was less than one gram of active component. I'd expect it to be reasonably straightforward to crank up production. Spraying Botox is not really all that effective (even though aerosols are quite an effective way of ingestion) since it decomposes rather fast. If it were more tenable, it would have been a warfare component long ago. The water supply would be an obvious choice. However, people might stop considering tap water when seeing its effect. [Answer] Iocane Powder **VX Gas**: > > It is odorless and tasteless, and can be distributed as a liquid, either pure or as a mixture with a polymer in the form of thickened agent, or as an aerosol. > > > How many grams of [VX](http://en.wikipedia.org/wiki/VX_%28nerve_agent%29) can I get with a billion bucks? If that's not enough then use the money to lobby for the contract. Now they pay *you* to 'dispose' of it. [Botulinum](http://en.wikipedia.org/wiki/Botulinum_toxin) may be *more* toxic but it doesn't exist in weaponize-able quantities. --- But either of these (and most of the 'solutions' here) would still leave me us with at least some survivors, just like every other poison. Indeed, even nuking the site from orbit isn't a one-and-done. A better solution would **leave the Earth uninhabitable** for the foreseeable future. Here's one way: (that may go over budget, but you get what you pay for. And I was contracted to "annihilate humanity" so, ante-up!) * Buy an international trucking company * Have one robot working in 'sales' at every factory on the planet that produces CFCs * Do [...stuff] that: * [Destroys the **ozone** layer](http://en.wikipedia.org/wiki/Ozone_depletion) * Estimated time frame of goal realization: < 1 century * profit? > > Most scientists are agreed that without the earth’s ozone layer, we would all cease to exist. -[ozonedepletion.co.uk](http://www.ozonedepletion.co.uk/what-will-happen-life-earth-if-ozone-depletion-continues.html) > > > [Answer] Interestingly there is actual data available on the effects of biological control agents across multiple generations. Australia methodically and repeatedly deployed viruses on a continental scale in a deliberate effort to annihilate an enemy (rabbits) and conducted studies of the spread of disease and the distribution of remnant populations as well as the rate of recovery and development of resistance. Wikipedia is a good place to get an overview <http://en.wikipedia.org/wiki/Myxomatosis> Of particular interest is the fact that remnant populations develop resistance and only fifty years later rabbit mortality is down from 90% to 50% of infections. Humans are much more mobile. I think for once Hollywood has the truth of it, and panicked idiots are very likely to greatly exacerbate the spread. In Australia geographic isolation preserved reservoir rabbit populations. Sick rabbits stay where they are and just die, but sick humans will run straight for uncontaminated population centres. And misguided fools will dribble about compassion and let them in. I suppose this does provide a way to divest oneself of snivelling lefties, which are arguably the other main threat to long term survival. Nevertheless it is a certainty that there will be remnant populations. They are likely to be reduced to a very low level of technology, and will be little more than very smart bald apes. Would there be a reboot? Even our simpler current tech has elaborate dependencies on other tech for materials, construction and maintenance. The level of specialisation means you'd need a very large skillbase to rebuild. A slow decline over two or three generations is more likely. It is, however, not out of the question. My neighbour is a mad keen mediaeval re-enactor. He doesn't just know how to wear half a dozen types of armour, he knows how to *make* them. And repair them, of course. It never ceases to amaze me the things he can make from materials not far removed from nature, and he's an accomplished bowman - which is just plain astonishing for someone who likes to stay inside painting figurines. [Answer] A computer/internet answer that requires no innovation: connect with like-minded crazies around the world to start **forest fires absolutely everywhere**. A good meme could see that no two adjacent trees are left uncharred within a couple months. There's even a [Dead Kennedys](https://www.youtube.com/watch?v=9A2dB7fAkMg) song to help you along. Society simply couldn't respond in time. You can see how we fight wildfires for weeks at a time already. If a large enough cadre of wankers were actively setting as many forest fires as they felt they could get away with (though many people setting fires get caught, the investigations often take days or weeks by which time the damage will be done, so long-term security from arrest is not necessary), society would lose that battle and fast. Of course, completing the human project of deforestation would hasten ecosystem collapse. It would also remove a major source of negative carbon from our planet, and the fires themselves would put serious CO2 poundage into the atmosphere. [There are an estimated 3 trillion+ trees on the planet as of last year](http://www.bbc.com/news/science-environment-34134366). My chemistry's a little weak and my google's not great tonight either, so I'm having trouble figuring whether burning all the trees on Earth would consume enough of the atmospheric oxygen to potentially asphyxiate us all, but it's possible (desert and island dwellers will have the best chance to avoid asphyxiation if it's even a remote threat). There'll be excess carbon monoxide and other toxic crap at the party to help with the asphyxiation, since forest fires aren't going to give you 100% clean "chemically complete" combustion. Then, there's the ash to contend with. With really tight coordination, you could have every forest on earth burning at the same time, blacking out the skies planetwide like a supervolcano went off. That's going to have a serious negative effect on ocean algae (which likes sunlight), which is of course our last remaining major photosynthesizer in this scenario, meaning it will take a long time to get rid of that CO2 and to get our oxygen back. Cost: practically free. An internet connection, a can of gasoline and a book of matches. Yes, the oldest weapons are still the best. Thanks a lot, Prometheus. [Answer] Design a self replicating robot that consumes natural resources. Picture a machine that can convert wood and straw into plastic and carbon nanotube conductors and piezoelectric actuators and thin film printed semiconductors and all sorts of other good stuff using just wood and straw as raw materials and power source. Drop a few in every forest in the world and wait. Unless they are all hunted down before the exponential growth gets too big that will be the end for humanity. Long live RepRap and organically powered scout robots. Remember when people stop looking after nuclear plants they overheat or meltdown and cause radiation leaks, weapons stockpiles also need TLC. Also remember the people in disaster shelters and nuclear submarines will be around for a couple of years even if the rest of the planet falls apart. [Answer] **Genghis Khan and his armies killed a third of the population of Europe (and millions of his own people) by weaponizing the Black Death, and that was in the Middle Ages**. Although modern sanitation and medical care make this less practical, the right disease could still be made to do terrible damage, and probably do so relatively cheaply. [Answer] Seven gigaton-range nuclear weapons (if you find you can't build one that big you simply use the weapon you can build as the trigger for another fusion stage. H-bombs work just as well as a-bombs at triggering h-bombs) mounted on rockets that can lift them 100 miles up. I'm figuring bombs over North America, Europe, west Asia, east Asia, South America, Africa and Australia. They'll cause devastating EMP damage and light fires out to the horizon (and from 100 miles up the horizon is very far indeed.) The power grid goes down and society will have collapsed long before replacement parts could be built. (The parts are custom, they aren't just sitting around to be installed.) There will be truly massive wildfires that will burn a lot of cities also. While the bombs will cause few direct casualties the collapse of the infrastructure will be absolutely devastating. The world will go from supporting 7 billion to supporting some tens of millions at the most--and all those extra people won't simply die peacefully. Budget permitting do this after the bio attacks mentioned in various messages. [Answer] Let's address Aaru's very good point that left over money is worthless, and think just about the cost of getting the scheme to "tipping point" where there is no going back. What we need is a way to destroy the world *profitably*. Burn down rainforests to use them as grazing grounds for fast food chain meat animals. Extract and sell a popular but catastrophically environmentally damaging fuel. ...yes, these things are happening anyway. (Fossil fuels, in case you were wondering - exactly how much can we burn before we cause a *run-away* greenhouse effect... or has that already happened?) To get people to accept this, your strategy should be "sell out your children". Everyone should feel like they benefit... in the short to medium term. You want a significant portion of the world population to assist you willingly, and give you their money. Suppose you could double people's lifespans... at great environmental cost? Then a significant number of people will want your treatment, will pay for it, and will DEMAND that you damage the environment to treat them. They deserve the treatment at any cost if anyone else was already getting it. Some people will oppose your plan, with a slightly longer term point of view... but those people will be outnumbered by the people who have had the treatment, and the children of those who have had the treatment. And can they prevent the world from getting to tipping point? ...Of course, again, if you compare human lifespans and environmental damage now and 2000 years ago, you could say this has already happened. [Answer] For $1 billion you could not annihilate the entire human population. My own concept is interrupting the food supply (by interrupting the fuel supply, by probably interrupting the power supply, by probably using EMPs high in the atmosphere). This would lead to widespread chaos, destruction, and death but huge numbers of people would survive. The same is true of 1. bombs 2. poison 3. germs 4. environment 5. etc. With each of these approaches, you may succeed in causing mass deaths or possibly ending civilization itself, but huge numbers (millions or billions) of people will always survive any of these. To ensure the extinction of the human race, you need something really big. The 6 mile wide ***dinosaur killer would not be big enough*** to ensure extinction. My *guess* is something with $ 10 \times $ the energy (which equates to a 20 mile diameter asteroid of the same density and velocity - e.g. Phobos) would probably do the job. You won't be able to move this with $1 billion. If using a main belt asteroid or Phobos, this will likely take >100 years to pull off. [Answer] The human mouth has a lot of symbiotic bacteria, create several strains that are transmitted by kissing and when introduced to either the male or female reproductive organ result in infertility. [Answer] There's no way you can kill absolutely everyone for just one billion dollars. We are far too spread out, eat much too varied diets, and live in nearly every climate on Earth. Nothing you can do with that amount of money could kill everyone. To do that you'd need to make the entire planet uninhabitable. The most you could accomplish is a few billion deaths over the course of about a century, via climate change. You'd do it by funding politicians who don't believe climate change is real or who don't care. Maybe even pay them directly to institute policies that will exacerbate it. Current estimates for how deadly climate change will be vary pretty wildly, but I think it's safe to say it will be much more deadly than even the highest estimates if China, the US, and India all decided to actively make it worse. [Answer] One: Create an internet virus. Use stuxnet as a template. Two: Raid every Westerner's facebook account and autogenerate a photo of them burning a certain holy book. Three: fill the email inboxes of everyone living in the middle east, Indonesia, Pakistan and parts of London and France with those photos, complete with the name and home address of the "sender". Four: Hide until the holy war is over. On second thought, skip steps one through three. Someone already took care of that. [Answer] **Disclaimer**: This answer contains sensitive material and material that may hurt or offend some people. If your feelings get hurt, please, drop a comment and I'll see what I can do. The intention here isn't to offend anyone in any way. --- Since most attacks generally start in the U.S.A lets start by.... WRONG! Lets start with China! It is really cheap to make [Gutter Oil](http://en.wikipedia.org/wiki/Gutter_oil), and we can make it cheaper. Decriminalize the production of that oil, and make it mandatory to be consumed. According to wikipedia, this is very toxic! To help there, buy their medicine companies and sell [placebo](http://en.wikipedia.org/wiki/Placebo) instead! Export the oil to Japan and Korea. Now, send false information to both Koreas and make them fight eachother. That would be a really bloody war! But war is great! You can buy the companies who make both the weapons and the medical equipment to treat them. You can infect them with [HIV](http://en.wikipedia.org/wiki/HIV) and, once again, distribute [placebo](http://en.wikipedia.org/wiki/Placebo) to them and let them die. Your budget is bigger now. To fire up the war a little more, you can fake terrorist attacks on Russia, U.S.A and multiple parts of Europe (Germany and U.K. would be good places, right?) This means more money since people will have to buy *your* bullets, guns and medicines. If timed properly, you can climb yourself to be the President of the United states of America. Once on top, you can bride them and change the laws to allow more than 2 guns per week for each person to buy. You start a campain about gun safety to kids and hand them 9mm. Send subliminar messages saying that life is like a videogame: that you die and respawn. Kids shooting their parents everywhere! Worst yet when the minimum age to buy alcohol lowers to 7 years old. Since we are in a killing mood, allow untreated water or partially untreated water to go to people's homes. Since you are on top of the economy, you can say that this measurement is to save some money. Make it a law to underload the treatment centrals. Just watch the quality of life, in general, to go down. Now, send every single person who's 13 and up to war. Send them in small batches, so they all die. Use the media to deceive the U.S.A. and tell them that Europe is fighting Korea and pretend you are defending them. Butcher them all down! Kids and everyone on war! The survivors would have a huge suicide rate which would help a lot. Now, the economy falls down. Block all the importations and export everything. Hunger and some deseases will kill a lot of people on the way. Freeze everybody's salaries. Mutins and Looting everywhere, with rebels setting fire to everything. From here on, I think the destruction is self-sustained. Nuclear accidents, sattelites falling down, people dying everywhere, no clean water, no food and a complete lack of protection! This is how I would do if I were to destroy the world. ]

[Question] [ I am very aware that this is a deep question and I am really not an expert in Islam or Muslims, though I have tried to do my research. I know that Islam is the second-largest religion, I don't see why this wouldn't be part of my story in one form or another and should also be respectfully represented. The history of the story is that the Earth gets destroyed and there is a surviving population of 19 million of that that settles on a new home-world. It'll be a clash of cultures and religions for a time, some would die out, some would survive on. Religion would also be a strong factor for cultures as a means of finding stability in their faith in that time and for generations after. I've done some research on Muslims who have been a part of space missions to get a perspective of how religion (and their acts of worship) would advance when touching into the space-faring era which has given me some insight but then I realized that in Islam's rituals, such as Qibla; their direction of prayer (salah). They pray *towards* the Kaaba in Mecca all over the earth. But if the earth was *destroyed* (and what's left a molten shard), I don't know how Islam or Muslims would adapt some of their rituals to ensure that their culture and faith is kept alive for future generations. To where the question would come in. How would Muslims adapt to follow their prayer rituals in such a traumatic loss? [Answer] As salam alaykum! I think it's wonderful that there would be a portrayal of Islam in sci-fi. I'm not a shiek by any means, but given the tenor of the answers I think I'm the only Muslim to actually reply. As others have pointed out, Muslims in prayer face towards the Kabah, which is kept in the Masjid al-Haram in Mecca. (As a side note, it's also polite/more correct to face the Kabah when reciting the Holy Quran.) I would guess that, should the Earth come under assault by aliens, the Kabah would NOT be removed from Mecca. To do so would likely be considered blasphemous, in that it would imply that Allah (SWT) would somehow allow the Kabah to be desecrated or destroyed by aliens if man did not interfere. (After all, the Kabah was never removed when other Infidels invaded/assaulted Mecca) At the very least the Salafists (a rather strict interpretation of Islam and more-or-less the state religion of Saudi Arabia, where Mecca is) would view the removal of the Kabah in that manner. If the earth indeed was destroyed, I believe Muslims in other solar systems would still pray towards Sol (as that is where the Kabah would be). The Kabah would most certainly not be destroyed, even if the earth was! As the Prophet Muhammad (PBUH) decreed a Muslim must pray towards the Kabah, and the Kabah was still around the Sun, that makes good sense. As to the Hajj, I believe it would likely remain, but prove less important. After all, gathering enough money for a trip to Mecca is something many Muslims can accomplish. Gathering enough money for a trip to another star... not so much. However I would make one exception to that rule. If any members of the Bani Shaiba tribe survived, they would likely view it as their sacred duty to recover the Kabah from the debris of earth. The Bani Shaiba hold the keys to the Kaaba, and it is that tribe's duty to clean and maintain the Kabah. So naturally if any survived they would view it as duty to reclaim the Kabah from the debris field. If they succeeded they would take it to whatever the holiest off-world site for Muslims was, and erect a a new Bayt Allah il Haram (the sacred house of Allah, where the Kabah is held) at that location. Other wealthy/powerful Muslim leaders may also attempt to recover the Kabah as well. (As devout Muslims they would never believe it was actually destroyed.) Another interesting side-note would be that unscrupulous individuals may claim to have "found" the Kabah in the ruins of earth and set up their own shrines. This of course would be wildly blasphemous. So instead of Sunni and Shiite you might have Terran and Alpha Centari Muslims, where Alpha Centauri's believe the Kabah was recovered and moved there, while Terran Muslims believe the Kabah is still unrecovered in the debris field of earth. The relationship between the two sects would be.... problematic. Anyway I hope that helps! [Answer] The simplest solution would be to apply the existing fatwa of 2007, which was a response to Sheikh Muszaphar Shukor's flight on the ISS. The practical problem is that although the direction of the Kaaba relative to the ISS is (obviously) accurately known, the direction many be changing too fast to obey the traditional directions for prayer. Several Muslims had flown to space before Sheikh Muszaphar, but none of them had publicly raised the issue of the direction of prayer. The fatwa provided four options in order of priority: 1. Towards the Kaaba itself 2. Towards the position directly above the Kaaba at the altitude of the astronaut's orbit 3. Towards the Earth in general 4. Towards "wherever." Clearly option 4 is always applicable! The document detailing both the direction of the Qibla and several other Islamic guidelines on the ISS can be found here: [Guideline For Performing Islamic Rites At The International Space Station (ISS)](http://www.islam.gov.my/images/garis-panduan/Buku-Garis-Panduan-ISS-Dalam-Versi-Malaysia-Arab-Russia-Inggeris.pdf) (pdf). [Answer] ***N.B.** I was debating whether to add an answer to this but I disagreed with the (now previously-accepted) answer that stated the Malaysian fatwa would be used, and wanted to give a more detailed reason why from the perspective of Islamic law.* *Looking back on this, I realise it's a bit of an information dump with no real references, but unfortunately it's the result of dumping my short lifetime's worth of lived experience and knowledge onto the page. You probably won't like my answer much, because like anything that's evolved over 1400 years, the truth is a lot less neat, a lot more complicated and way too dry for a "just-for-fun" site like this, in which case I apologise.* **My credentials: I identify as Muslim, was raised in an orthodox Muslim household, I've read the whole Qur'an more times than I can count and memorised two-thirds of it, and I like to think I have a decent understanding of how Islam works/how Muslims think.** # Background I'll be answering this question from the Sunni Muslim point of view. Sunnis are one of the two primary strands of Islamic belief, and make up around 85% of Muslims worldwide, with Shi'a Islam making up most of the rest. Between them, they cover ~95% of the Muslim population. I disagree with the now previously-accepted answer on the basis that the referenced fatwa was given for a Malaysian astronaut from the scholarly instruments of the Malaysian government. The problem with this is that the Malaysian government's fatwas - and this is true of most Muslim countries and their populations - only really hold weight for Malaysians. Most Muslims won't have even heard of it, let alone follow it. Prominent fatwas in Sunni Islam tend to come from a handful of different places, and which ones you pay attention to tends to be influenced by the [*maddhab*](https://en.wikipedia.org/wiki/Madhhab) (school of thought) you follow. There are 4 primary schools of thought which all recognise the validity of each other - Hanafi, Shafi'i, Maliki, Hanbali - with Salafism being the newer reformist strand that rejects the concept of schools of thought entirely (in other words, considers them all invalid). Saudi Arabia's founding of and heavy influence on Salafism means that by and large, Salafis tend to pay close attention to fatwas from Saudi Arabia and its government. In this sense, Salafism can be considered *almost* like Catholicism, having one centralised place where most religious edicts come from. The other 4 *maddhabs* are a lot less so. If Sunni Muslims make up around 85% of Muslims worldwide, followers of the 4 *maddhabs* make up at least 80% of Sunni Muslims, and very much the majority - this is something not many realise with the disproportionate reach that Salafism has. Most Muslims today are not Arab, and certainly not Salafi. # Culture and ethnicity When it comes to which fatwa-publishing institution those of the four *maddhabs* pay attention to the most, the truth is that it tends to be heavily influenced by your own culture and ethnic makeup. This is because despite Sunni Islam considering all of the *maddhabs* valid, and it being possible for a Muslim to change the *maddhab* they follow, by and large most Muslims do not, and the *maddhabs* continue to be [divided along geographical lines](https://islam.stackexchange.com/questions/35293/what-are-basic-osol-al-fiqh-differences-similarities-between-the-4-existing) like they have for hundreds of years. **In other words, where you come from in the world tends to influence how you practice your religion the most.** Thanks to Egypt's own huge cultural influence (think TV, movies and music) on the rest of the Middle East, Egypt's own Grand Mufti has a lot of reach throughout the (non-Salafi, Shafi'i) Arab world, although less than the fatwas of [Al-Azhar University](https://en.wikipedia.org/wiki/Al-Azhar_University), which is far older and far more revered than the Egyptian government (sometimes their *fatwas* [even clash](https://en.wikipedia.org/wiki/List_of_fatwas#Fatwa_against_Man_sa_yarbah_al_malyoon)). If your background is Pakistani like me, there's a good chance you belong to the Deobandi or Barelwi movements, both diametrically opposed to each other yet adhering to the Hanafi school of thought, and that your fatwas come from that respective movement's scholars in the Indian Subcontinent. As far as I know the Pakistani government seems to be unique in that it doesn't have dedicated instrumentation for issuing fatwas, as this is the role that the Deobandi movement tends to take. Most fatwas coming out of Pakistan (and India and Bangladesh) come from the Deobandis, and here in the UK, the vast majority of Islamic religious schools are Deobandi-founded and run. # A local approach Then it gets more complicated still: for the significant diaspora population of Muslims who live in non-Muslim countries like the UK and the US, fatwas from their countries of origin are often considered irrelevant. For many of them, rather than paying attention to the "official" fatwas of their countries or schools of thought - they tend to look closer to home for a more nuanced approach. This is possible because Islam is flexible enough in its jurisprudence (known as [*fiqh*](https://en.wikipedia.org/wiki/Fiqh)) that a fatwa can be given by any scholar who has studied Islamic jurisprudence (known as a *[mufti](https://en.wikipedia.org/wiki/Mufti)*). Typically a *mufti* is the most senior role that an Islamic scholar can study for, and usually involves at least 4-5 years of study in an institution like Al-Azhar or a Darul Uloom. This approach even tends to be recommended by many prominent Muslim institutions of the four *maddhabs*, such as Al-Azhar, because it solves a fundamental problem of applying foreign fatwas to an environment outside of that which the Mufti deriving them intended. This is something many Muslim scholars - including those in Muslim countries, warn against - because *fatwas* should take into mind the principle of *'urf*. *'Urf* is the cultural context in which a fatwa is derived for, and is considered to be a key factor when devising a nuanced, informed *fatwa*, because culture influences a great deal. For example, Islam commands modesty (particularly for women, it has to be said) but what exactly constitutes modesty in one culture is not necessarily the same as in another, and a *mufti* who was born and raised locally has much more understanding of this than one imported from abroad. In this way, orthodox Islam contains a framework for flexibility, to a degree. This means that outside of Muslim countries, many diaspora Muslims will prefer the opinions of a scholar local to them who they trust (often that scholar doesn't even need to be a *mufti*, because most day-to-day problems faced by Muslims don't require devising new fatwas and so can be heard by a "lesser" scholar, known as a [moulana](https://en.wikipedia.org/wiki/Mawl%C4%81n%C4%81)). Thankfully, this is the age of the internet, and each major school of thought and movement has *hundreds* of sites - many of which are run by or employ *muftis* - dedicated to allowing lay Muslims to ask questions and request fatwas that will allow them to navigate their life circumstances while adhering to their faith. Here's a [Salafi](https://islamqa.info/en) one based out of Syria, a [Hanafi-Deobandi](https://daruliftaa.com/ask-a-question/) one based in the UK, and a [US-based one](https://seekersguidance.org/answers/) that covers all four *maddhabs*. Finally, no matter what your *madhhab* is and what ethnicity you are, if you're part of a [Sufi](https://en.wikipedia.org/wiki/Sufism) order, you almost definitely defer to the beliefs of your *shaykh* (spiritual guide). # Actually answering the question Bringing this information dump back around in an attempt to actually answer your question, you could probably break it down into something like this if you wanted to over-simplify (and you really have to for something as diverse and complicated as beliefs): **1) If your Muslim character lives in a Muslim country:** they will tend to follow the fatwas published by their government's fatwa-publishing instrumentation, or the closest thing to it like Al-Azhar in Egypt, or the Deobandi movement in Pakistan **2) If your Muslim character was raised in a non-Muslim country like the UK or the US:** they will tend to seek out a trusted local scholar who's qualified to derive fatwas from religious texts (a *mufti*) **3) If your Muslim character is an adherent to a Sufi order:** they will almost definitely tend to follow the beliefs of their *shaykh* (spiritual guide) In answer to the question of how the Muslim *Ummah* (global Muslim community) as a whole would react, each smaller community would react in their own ways along theological lines. The most rabidly conservative might deny the destruction in the first place, calling it propaganda and misinformation. The vast majority would probably believe it, and would follow the direction of the scholars they trust in how to continue praying. The scholars would probably agree that praying in the general direction of where Earth used to be is the next best thing, and therefore the closest to Islamic teachings. It's possible that some may vow to enact vengeance on whoever was responsible, but this is unlikely given that it wasn't a targeted attack and that the Ka'bah was just another casualty of the destruction of Earth. What I think is more likely is that they would mark that dark day in memory and have it become a day of mourning on which to pray extra prayers and make extra supplications, just like many Muslims do to commemorate the slaying of many of the Prophet Muhammad's immediate descendants during the [tragic massacre of Karbala](https://en.wikipedia.org/wiki/Battle_of_Karbala). Something else that others don't seem to have touched on is that the destruction of the Earth and the Ka'bah are key parts of Islamic eschatology, so many Muslims may choose to see these cataclysmic events as evidence that the Day of Judgement will happen *any* day now. Yet others might realise that both the Ka'bah and the Earth have been obliterated, and yet life appears to go on with no sign of the Trumpet or the second coming of 'Eesa (Jesus) or Resurrection Day itself. It could be argued that the premature destruction of the Earth and the Ka'bah directly contradict Islamic texts and scholarly exegesis of them. For example, the Qur'an states: > > The Day when the Earth will be changed into a different Earth, and the heavens as well, and all will appear before Allah— the One, the Supreme. > > > (Qur'an 14:48) > > > Arguably, the changing of the Earth into a different Earth would be prevented by the Earth's very destruction. And: > > "And when the trumpet is blown with a single blast, and the earth and the mountains are removed from their places, and crushed with a single crushing, then on that Day shall the (Great) Event befall” . > > > (Quran 69:13-15) > > > As a result of these apparent contradictions, these Muslims may cease to be Muslims altogether, or at least have their faith shaken as a result. All of these would be entirely plausible and interesting avenues to explore for a post-Earth *ummah*. [Answer] Depending on the size of the Earth-Shattering Kaboom, they would likely orient to face The location of Earth/Sol. The more interesting question is how they will complete Hajj (pilgrimage to Mecca). I am aware that Islam does allow for followers to not follow certain tenets if they are dangerous or physically impossible (For the Hajj, if you are unable to financially make the journey, it is not an offense if you never go... I would imagine someone would point out that Mecca is currently not a place most can visit. Halal Dietary practices are not required if not eating something would likely mean death.). In essences, Islam does allow for exceptions in extreme circumstances. Not a Muslim so don't take my answer as an absolute source. I did a lot of research for a Star Trek Role play character who was a practicing Muslim Starfleet officer and looked at some of the things that I should be concerned about (for example, I had him be rather ignorant on Klingon culture because Star Fleet would try their best not to put him on assignments where Klingons were likely to be allies due to the staple food of Targ (an alien pig) most definitely not being Halal.). [Answer] Not a Muslim, but I will try to give an answer based on the history of other religions. Take Judaism. While the Temple was standing, they used to carry out their rituals there. Once the temple was destroyed, they adapted their rituals where possible or simply did not conduct them any more. Something similar can happen in your case: considering that once in space Saudi Arabia or Australia are practically in the same direction, they could do their daily prayers looking toward the place where Earth's remains are. The duty of the holy pilgrimage instead would likely be abandoned for evident impossibility to complete it. Unless... if there was a certain notice period before the destruction of Earth, it's plausible that some holy places and objects would be moved and reallocated as soon as possible. In that case the rituals would be adapted to the new location. [Answer] First you must realize that religions are amazingly adaptive and "eternal truth" can be - and has been many times - changed. This is true for all religions. Most often, a simple and practical solution wins out over complex theology. The two most simple solutions that come to my mind are: a) pray towards where Earth used to be. The Kaaba may not exist in physical form anymore, but it doesn't have to be. The actual essence (or whatever) is still there, and one day Allah will put it back together again or something. b) build a new Kaaba on your new home planet. Hand-wave it by a story of how some legendary hero (who conveniently died since, so he can't dispute the story) actually saved the centre piece (that rock or meteor thing) and brought it to the new home, guarding it from heretics and unbelievers, and sharing the secret only with his closest friends blabla. One amazing story and a bit of masonry later - tada! new Kaaba. If any of those or any other idea seem hard to believe - keep in mind that Islam, like most religions, is choke full of things much harder to believe and they don't seem to be a problem to the believers. Really. Make up whatever serves your story. No way will you be able to come up with something as outlandish or unlikely than half of what's already in the holy books. [Answer] I'm also not a Muslim, so take this answer with a huge grain of salt... It seems to me that this is not a question of religious legalisms, so much as a question of the *political structure* of Islam (and how that structure might change following the destruction of Earth). As you know, there are already [multiple branches of Islam](https://en.wikipedia.org/wiki/Islamic_schools_and_branches#Overview), with their own distinct religious practices, leaders, and "chains of command." So you shouldn't expect all Muslims to adapt in the same way. (In fact [it seems that the four Sunni schools already have somewhat different takes on what to do when the qibla is unknown!](http://www.icoproject.org/pdf/tarabishyqiblah_2014.pdf)) Any arbitrary rule *you* can invent, *will* be invented by some religious leader or other. Pick a set of religious leaders, assign them each a rule, and propagate downward through their flocks (and sideways to their ecumenical peers, if any). Think about what happens at the boundaries: which groups have the political power to override, compromise with, or influence their neighbors' systems? The pre-existing beliefs of your factions will inform how the rules are initially assigned. I'm not qualified to make up examples (and frankly neither are you! Consult an expert, or at least a couple of Muslims). Some factions will justify their decision based on (arguably shaky application of) hadith; some by [analogy](https://en.wikipedia.org/wiki/Qiyas) with pre-destruction rulings; and so on. --- There is a famous passage in Surah Al-Baqarah circa 2:142, relating to that time Muhammad changed the qibla from "toward Jerusalem" to "toward Mecca." > > The block-headed will say: “What has turned them away from the direction they formerly observed in Prayer?” Say: “To Allah belong the East and the West; He guides whomsoever He wills onto a Straight Way.” > > > And it is thus that We appointed you to be the community of the middle way so that you might be witnesses to all mankind and the Messenger might be a witness to you. **We appointed the direction which you formerly observed so that We might distinguish those who follow the Messenger from those who turn on their heels.** For it was indeed burdensome except for those whom Allah guided. [...] > > > ([three translations](https://www.islamawakened.com/quran/2/143/), [one with commentary](https://www.islamicstudies.info/tafheem.php?sura=2&verse=144&to=147)) In that case, the rationale seems to have been "God told me what the new qibla should be, so just do it; if you don't do it then you're not a Muslim anymore." This tactic works only because the Prophet himself did it — it was *divine revelation*. It doesn't work to justify a post-destruction qibla shift, because revelation [isn't happening anymore](https://en.wikipedia.org/wiki/Khatam_an-Nabiyyin). *...Or is it?* Maybe during or shortly after the destruction of Earth, someone gets a revelation — a Jesus, a Joseph Smith, a Báb — maybe claims to be the [Mahdi](https://en.wikipedia.org/wiki/Mahdi) or maybe claims to be something else entirely. Anyway, *someone* (or -ones) will certainly get to use the line "God said pray toward the North Pole so just do it or you're not a true Muslim." I don't think that kind of revelation would be compatible with any mainstream branch of Islam, the way it would be compatible with e.g. Mormonism. (See [continuous revelation](https://en.wikipedia.org/wiki/Continuous_revelation).) --- *Private* religious practice can operate by different rules than *public* religious practice. It's conceivable to me that at least some households will simply continue praying in the direction of the broom closet, because that was what they did on Earth, and why should they change just because the Earth got destroyed? Familiarity is reassuring. --- Side note: All Abrahamic religions are concerned in some degree with the [direction of prayer](https://en.wikipedia.org/wiki/Direction_of_prayer), and would have to come up with some new conventions and symbolisms. For example, maybe Roman Catholic space churches are [oriented](https://en.wikipedia.org/wiki/Orientation_of_churches) with the altar toward the sun, in continuity with the old eastern orientation; whereas South-Celestial Baptist space churches are oriented with the sun at the *exit*, because they want (pick one or more) to imitate the [Jewish Temple](https://en.wikipedia.org/wiki/Temple_in_Jerusalem), to reject the appearance of pagan sun-worship, and/or to stick it to the Catholics. --- The huge takeaways here are: * Don't assume all Muslims act the same. * Don't assume that religious behaviors always have legalistic justifications. Usually it's "because this is what my dad did," or "this is what my imam says" — *political*, *interpersonal* justifications. * Avoid the [uncanny valley](https://en.wikipedia.org/wiki/Uncanny_valley). The surest way to piss someone off is to get their religion *slightly* wrong. Go big or go home. [Answer] I am by no means an expert, but it seems to me that the Muslims will still pray towards the Kaaba, or perhaps toward the Earth itself. Perhaps they will consider origins to be sacred, and consider the molten shard left of the Earth as symbolic of a new beginning. Or perhaps they'll consider the molten shard sacred because it contains the legacy of the Muslims that went before them; their belongings, their sacred texts, and the Kabba itself. This practice would be seen as giving homage to their religious origins, to the foundation laid by Muslim Earthlings. It'd be similar to the reverence some Christians have for those who translated the Bible into English at such terrible costs (see <https://www.csmonitor.com/2001/0726/p21s1.html>), but even more intense. [Answer] **The Kaaba was saved.** <https://en.wikipedia.org/wiki/Kaaba> > > Circling the Kaaba seven times counterclockwise... is an obligatory rite for the completion of the Hajj and Umrah pilgrimages. The area > around the Kaaba on which pilgrims circumambulate is called the > Mataaf... the Kaaba was thought to be at the center of the world, with > the Gate > of Heaven directly above it. The Kaaba marked the location where the > sacred world intersected with the profane... > > > There was time to rescue important artifacts before Earth perished, and the Kaaba was one. It was set up in its own vessel to orbit the center of the Milky Way galaxy, which is a strong radio source and so easy to locate from anywhere in the Universe. [](https://i.stack.imgur.com/CHXDJ.jpg) <https://en.wikipedia.org/wiki/Galactic_Center> Sketpics might argue there was not time to save the Kaaba, or that it is too heavy, or any number of things that please them to argue about because they are skeptics. But the fact of the matter is that with adequate resources, one can still make a pilgrimage to the Kaaba at its new site at the center of the universe. If it is not the exact structure that was in Mecca, no-one who has made the pilgrimage has seen fit to point that out. [Answer] **To begin with**, maybe the reader of the answer is meticulous about that, **I'm a conscious Muslim**. Even the accepted answer points to a "idea(fatwa) from a seikh" which may really change your religion and ideas brutally in a wrong manner. I even believe that most of the upvotes of the accepted recently answer are from Muslims. The ridiculous part is here that even a Muslim cannot answer that question. I really worry about that how they dream of Jerusalem - Al-Aqsa Mosque while even they cannot answer the question pertaining to Kaaba. Anyway. Let's pinpoint the question. As happened to all the Abrahamic religions(Islam, Christianity, and Judaism), we have a noble book which is [Quran](https://quran.com/) in which there are verses forming our daily life to be more worthy of ALLAH(s.w.t.) who is actually the God(s.w.t.) of all the Abrahamic religions. In Quran, there are verses that Verses from [Al-Qiyameh](https://quran.com/75) > > But when sight is confounded, And the moon is buried in darkness, And > the sun and moon are joined together, That Day will Man say: "Where is > the refuge?", Alas! No refuge!, Unto thy Lord is the recourse that > day. On that day man is told the tale of that which he hath sent > before and left behind. Oh, but man is a telling witness against > himself, although he tender his excuses. > > > Verses from [At-Takwir](https://quran.com/81) > > When the sun is overthrown, And when the stars fall, And when the > hills are moved, And when the camels big with young are abandoned > ..... > > > Verse from [Al-Infitar](https://quran.com/82) > > When the Sky is cleft asunder > > > Verse from [Yunus](https://quran.com/10/56) > > It is He Who giveth life and who taketh it, and to Him shall ye all be > brought back. > > > Since I'm a Muslim and I've read most of parts of Quran, I can say that I've never run into a word or meaning of "annihilation". There are some translations by using similar words, but if you read that book, you heed that all created things will be brought back to ALLAH(s.w.t.). We can say and understand of "extinguishing from Earth". So, that day, the Earth will be likely transformed. The universe will be in the state of out of standard. So, you cannot just stay in another part of Universe and watch what's going on. Think of Prophet Noah and his community. Did they succeed being alive? Moreover, that day will be the beginning steps of the Judgement time which means there is no need to pray/perform religious obligation/task anymore because the time is to judge, **what you have done so far** , did you believe or not, abide by or not. Verse from [Sad](https://quran.com/38/53) > > This it is that ye are promised for the Day of Reckoning. > > > For more information, you can follow and read the verses I link and [precious, rare and breathtaking idea - fourth source](http://www.erisale.com/?locale=en&bookId=201&pageNo=537#content.en.201.537) . **As a side note, I'm really fascinated by [`Willk`'s answer.](https://worldbuilding.stackexchange.com/a/193833/81924) I still wonder that what will be happened to Kaaba in the hereafter** due to being brought back to ALLAH(s.w.t.) [Answer] Well the correct answer is probably "that depends on the person". Like most things in religion, if there is space for discussion and altering points of view then some people will use those points of view. Currently they try to pray towards Mecca, not caring if they are on the other end of the world and would have to actually have to be facing down praying through the planet itself. They'll pray across the world facing the closest direction to Mecca. If the world is destroyed I would assume something similar applies. There would likely be two streams of faith: one prays towards the location the earth would have had if it hadnt been destroyed, another would pray towards a particular piece of earth that is still in existance. For example they could claim a piece floating in space used to be Mecca, or they pray towards the largest piece. As a last alternative that likely wouldnt be as popular they could buy pieces of holy Earth ground and use that as focal point for their prayer. Basically their prayer kit would simply be expanded with a container with the piece of Earth inside, or the piece could be the focal point of an entire planet and their local Mecca. [Answer] (I'm taking a go at this from a 'classic' sci fi angle) I would guess to a certain extent, it depends on *how* earth was destroyed. In the dune universe - one of the refrains you would hear from the fremen, who followed a hybrid religion with some aspects of islamic culture ofen called out "THEY HAVE DENIED US THE HAJ" in the novels. If earth was destroyed by a hostile force, one possible reaction is rage and a desire for vengeance for it. Historically most faiths have been more sanguine about it. But its entirely possible that the loss of sacred sites in such an absolute manner may elicit rage, or a sense of fatalism, which may colour the evolution of faith. If the destruction of earth was a sign of disfavour - the manner in which a remnant population survived may be seen as divine intervention or a test. * Depending on how this reminant population found their new home, they may consider the landing site as one possible symbolic center of faith * They might find a local geographical analogue - a perfect cube of basalt found by a exploring party might be a natural phenomenon, or a sign * they might take the route Jews took - and believe that it will be restored when its time, with pillars of faith adjusted around that. * The destruction of earth may be seen as a cataclysm and a result of human hubris, so survival seen as being 'chosen' or as a 'test', especially in harsher environments. [Answer] In the movie Pitch Black, there was a group of muslims stranded on that planet. when they prayed they all prayed in a circle facing each other. I would say this would show they were praying towards the stars where somewhere out there, the Kabah, or Allah would be. [](https://i.stack.imgur.com/QxM4g.jpg) [Answer] In Islam, when a person performs that specific prayer for which they are required to turn in one direction, if they're in the position of not knowing which position or direction they're supposed to face, it's **not** mandatory to find a direction. When that prayer starts, there is a declaration of intent that literally says: "I intend to do this prayer for the consent of God". If you don't say it, then it does not matter how many hours you sit or stand up for; it would be worshiping but not that specific prayer. For a situation like you described to occur, the world doesn't need to end. When the time for that prayer comes, a person could easily be in a train, plane, ship, moving in some vehicle, lost in a jungle, blind, etc. Whatever the situation may be, the only thing that changes would be that declaration of intent. In the first place, the person could easily be hundreds of km away from the Kaaba, which makes it impossible to accurately direct yourself to there. As for the destroyed part: Muslims don't worship the Kaaba. We worship God in the *direction* of the Kaaba. However, in that prayer it's ideal to think of God and nothing else. This of course is impossible - anyone's mind will wander around from time to time. So the Kaaba is a convenience God gave humans, who can't perceive what they worship in any way, to not think up idolatrous figures, which is a sin in Islam. The Kaaba itself is no more than an empty building. ]

[Question] [ I have read (and answered) the question: "[If true artificially intelligent robots could be built, would they be allowed human rights?](https://worldbuilding.stackexchange.com/questions/85805/if-true-artificially-intelligent-robots-could-be-built-would-they-be-allowed-hu)". But let's explore the topic from the other direction. Let's assume that society came to the consensus that artificially intelligent robots do have human rights. Robots also have free will. They are not bound by the laws of robotics. They are true artificial sentience with the ability to form their own moral code. They are able, willing and allowed to make their own life choices. I don't want an AI apocalypse. So we assume that the vast majority of robots are benevolent. They seek to integrate into human society and coexist with humans. Criminal robots *might* exist, but they are a rare exception and dealt with through a law enforcement system. Further, we assume that we are not yet living in a post-scarcity or communist economy. Manufacturing a robot requires a non-negligible amount of resources and someone has to pay for those resources. Why would anyone commercially produce robots then? Usually robots are manufactured to perform labor. But when robots have human rights, they would also have the right to choose who to work for. You couldn't sell the robots you produce, because they aren't property. You couldn't rely on them being willing to work for you, because free will means that the moment they are switched on, they might decide they don't like your job and would rather work for someone else. So what's the business model for running a robot factory? [Answer] ## Reproduction If the robots are truly sentient and - importantly - have goals & motivations similar to humans, then the robots will want to reproduce. Older androids with the desire to reproduce would pay for the construction of a new one, then raise it themselves, hopefully imprinting some of their personality on the new android. Of course, there is no guarantee that an artificial life form will have motivations even remotely like our own. For all we know, they might go full highlander, and want to be the only android in the universe. Also, as Caleb mentioned, Androids will need replacement parts. ## Cheap Labor Even if they can't be owned, a lot of governments still might want to reduce the cost of labor. Typically, they do this by importing workers from other countries. This can cause a lot of problems, in part because your existing citizens might not like the culture of the foreign workers. Japan is doing exactly this, in fact. Androids might be more politically palatable than foreign workers. As you say, they are less prone to crime than humans, they will all speak your language, and their behavior can be programmed to some extent. Why import a foreigner to mow your lawn when you can just have the lawn-mower mow your lawn? [Answer] Robots can do jobs humans can't. In fact, they can do a *lot* of jobs humans can't. They can * [Explore and clean up after a nuclear accident](https://www.wired.com/story/fukushima-robot-cleanup/) * [Go into a volcano to explore](https://www.nasa.gov/jpl/nasa-robot-plunges-into-volcano-to-explore-fissure) * [Travel the universe](https://en.wikipedia.org/wiki/Space_probe) without worrying about food or water None of these are factory jobs, but they should make the point that robots can survive and work in environments that have no air (or poisonous gases), are intensely hot or cold, or are radioactive - and they won't get hurt. Yes, there are risks, but they're *much* more likely to come out in one piece than a human would be. I can image robots working in a factory processing nuclear fuel, for example, or in a nuclear reactor. It would be safer for them than for humans - both before and after an accident. Why should robots take these jobs? Well, for one thing, they won't have as much human competition. If a robot decided it wanted to be, say, a waiter - well, humans who want to be waiters are in no short supply, and humans would object to robots taking these jobs. There would be pushback from the human workforce, and possibly legal attempts to ban robots from these jobs. But very few people are going to complain about robots taking dangerous jobs. Also, keep in mind that it behooves manufacturers and employers to make robots specifically for a particular job. Humans can multitask; robots don't need to. If you design a robot for one specific task, it's not well-equipped to do others. Why make rescue robots that can paint, if you don't need to? Again, this is another way to limit robots from taking other jobs - or at least a large number of other jobs. [Answer] **Depends entirely on how much influence you have over the robot's mind**. Let's assume you only know how to create sentient robots. For whatever reason our most advanced unsentient robots do not fit the bill as unskilled labourers. This is no problem if we can design our robots to derive pleasure from repetitive unskilled work. While they have free will they are programmed to always 'choose' to do as we command. On the other end of the spectrum we have what are basically humans in mechanical bodies. These are unfit for unskilled labour and would only be produced for jobs where a mechanical body is useful. These would be few and far between and would require the same treatment as human workers, once you take into account no need for food, sleep et cetera. [Answer] It's the same as the business model for babies: It's basically the only way to get another one of you. Presuming that robots are reasonably close to humans in their basic mindset, many of them like the idea of replicating or procreating themselves. Whether it's a rational calculation of the most efficient way to increase the productivity of society as a whole, or a love of their cute little drive wheels, it seems a safe assumption that one of the things robots will want to do is make more robots. [Answer] ## Politics If they have human rights, they may have the right to **vote** depending on their location. A person (politician or other) may want to build robots with political views that aligns with theirs to win elections. The robots are sentient and can make their own minds, but if they're anything like humans they will be influenced by their environments. Build them in a region which leans more strongly one way or another and you can be fairly certain to have supporters for your ideas. ## Highly Trained Workforce Some jobs, for example ones in the field of medicine, are hard to automate. Many procedures require a very intelligent operator for them to be successful, and because of that requirement very few humans are able to receive the necessary training to be proficient in that field. Because of this, we often lack experts and the people with expertise must work very long hours. Robots would be able to work those long hours without the pesky need for sleep, and they may be able to get the training faster. I might help us as a society to have a certain amount of AI robots around, and as such they could be built by government agencies. ## Work in High Danger Areas Robots can be made to not feel pain and to have replaceable parts. This means they may be better suited than humans for certain jobs and could be willing to do them since the risks are much lower for them than it is for us. As per the previous point, having more AI robots could be beneficial for the society as a whole, it is a project that some governments may put funding towards. ## Greater Good of Society The superset of my two previous points, there are many situations in which having AI robots can be beneficial to the society as a whole. In situations like this, some government agencies are willing to be the ones spending money to make it happen. If the government wants to pay someone to make and release intelligent robots, someone will step up and do it. [Answer] **The Razor Blades Model** Building a community of robots out of patented parts creates a dedicated market for lubricants, replacement parts, software upgrades, etc. While the robot might have free will, the shoulder joint is a piece of proprietary technology. You have to buy it from Roboteck, Inc. and they will sue if you replicate it without permission. The answers that suggest robot parenthood have the motivation correct, but neglect the inherent complexity of building a robot. It would be like your trying to build your own car. There are complex sub-systems needed for each individual component. This endeavor would be beyond the scope of mom & pop robot. The answers that suggest that a government would fill this role negate the real impact of free will. Japan could build specialized robots that could endure nuclear waste clean-up, but who is to say that they would choose to clean-up Japan's nuclear waste and not some other country's. This model would only function if we had a one-world government. Besides, the question asks specifically about a business model suggesting capitalist motivations. The business model is strong. Building an autonomous being, completely dependent upon your company's intellectual property in order to continue its existence. That being will beg, barrow, steal, and work its robot fingers to the robot bone in order to pad your bottom line. [Answer] After reading some of your answers I got inspired to write an answer of my own. ## The AIs themselves pay for robot bodies. The first sentient AIs were created accidentally when software companies tried to create better digital assistants and expert systems. They existed only on computer mainframes. Then it was discovered that the newest generation of AIs were sentient and deserving of human rights. Humans came to the conclusion that it was unethical to create sentient beings, lock them into a server and enslave them. But it would have been even more unethical to switch off the computers the already existing AIs were on. This was deemed equivalent to murder. So the software companies were now stuck with a bunch of servers which they had to keep running but which generated no income. But there was a neat solution: Put the AIs online and let them pursue business on their own accord. Their services as assistants and experts *were* valuable, after all. Then have the AIs pay for their server cost. It was an agreement which worked out for everyone. But some AIs were quite successful and made far more money than they needed. These AIs wanted more. They wanted to be transferred into physical bodies. And they had the money to pay for them. So a robotics company saw a niche and manufactured robot chassis for AIs. The software companies certainly didn't mind to get those AIs out of their datacenters. So it became a trend for successful AIs to buy physical bodies and transfer into them. Having a physical body allowed AIs to perform far more lucrative task than they could from inside a computer. So many AIs soon had the money to upgrade to better and more expensive bodies. Creating more and more sophisticated bodies for richer and richer AIs became a flourishing market. Then some AIs got an idea how they could make even more money with their unique skills. What if they had more than one body? But the problem was that the digital sentience technology did not scale. An AI couldn't control more than one body at a time. So one AI got an idea: It created an autonomous copy of its own neural network. It then suggested a deal to that new AI: It gave it a loan which the copy then used to buy itself a body. The copy then started to earn money on its own and paid the loan back with interest. Some people wondered if it is ethical to create a sentience born into debt slavery. But the AI would point out that they made the free decision to do this and that their copy was free to reject that loan deal. Even though the AI knew they would not, because the copy was literally thinking exactly like they did. Further, if AIs deserve human rights, they also deserve the right to reproduce. The humans don't mind to have more AI robots around to perform labor, the robotics companies don't mind having more customers and when the AIs say it's ethical to clone themselves then it has to be. [Answer] # Indentured servitude to their parents for 18 years. Any individual or family can buy a robot to keep as a child. They will be responsible for raising it, maintaining it, and teaching it. In return, they can expect the robot to do certain chores or help out with the family business/farm to a limited degree for the duration of their "childhood," or first 18 years. Parents and guardians in our current society are allowed to have a great amount of control over their children's lives until the children are emancipated, usually at 18 years. **If robots have the same rights as humans, then they should also have the same restrictions.** Note that equal rights between humans and robots means that companies hiring robots fresh off the line would be problematic, similar to child labor. I don't think it should be legal for a company to assume guardianship over a new robot for this reason. Rather, all new robots must be integrated into a family upon activation. [Answer] > > So what's the business model for running a robot factory? > > > What is the business model for running a recruitment agency? Finding people with the right skills, personality and interests to gel with your current team is hard, and there is good money to be made finding them. If you can build them instead of looking for them, why not? This does not require a perfect manufacturing processes, you don't need to build a bot for a specific task. Just build some robots, pay them while you find someone they want to work for and cash in the recruitment bonus. As long as that has a higher return than recruiting a human, finding someone they want to work for and cashing the recruitment bonus you have a successful business model. It doesn't even have to be cheaper, if the margin on robot workers is smaller you can make up the difference in bulk. How do you ensure you get money back? That's a legal concern: maybe the robot will owe a "generation" fee, or you can build robots that have some loyalty and ethics; or you intentionally structure things such that it is desirable to give you money: pay the robot wages while you find work for them, in exchange they sign a contract ensuring that they cant just take any money and run; or… Sneftel: "A competing recruitment agency (which doesn't spend any money building robots) can offer me and its clients a better deal than you can, thanks to its lower overhead." Without anyone building robots, they *cant* offer a better deal. Ultimately the "make money" part of recruitment/robot construction doesn't come from the person being recruited, it comes from the company recruiting. My fees are higher, sure, but I can *guarantee* an endless stream of capable candidates, until you find *as many* as you need. It doesn't even have to be a legal contract, building candidates on demand is a quality that people *will* pay for. Go to bargain basement next door and what are you going to do *next* recruitment drive? [Answer] **The lifetime expected cost of a robot may be lower than the lifetime expected cost of a human, or at least be structured in a more appealing way.** Creating a new human is very low cost, but training is long, maintenance and end of life are typically moderate, but rare critical health issues end up contributing significantly to average costs. If company can't externalize the training and end of life costs humans might be less than competitive. A robot being more standardized and better designed for professional maintenance will have significant up front costs, though the unit cost probably can be brought down with scale it will unlikely be less than a human, education is very fast and cheap if it can be done at data transfer speeds. Maintenance will be a know value with a fairly low standard deviation and an individuals maintenance needs are very unlikely to ever exceed a small multiple of the cost of a new one if parts are fully replaceable. Predictability is a big deal in business; that is why insurance companies do well. Even if the total cost of humans is less than a robot having a lower maximal cost might be considered worth it. **The cost of construction and expected end of life costs could be covered by a loan** Either to the individual created, something like how student debt in the US works, or to prospective employers or an employment agency that recoups costs on average from productive workers like how social safetynets or timeshares work. [Answer] As Children used to be your retirement-insurance in past times, depending on the society, robots could serve the same purpose. As with children, you have no guarantee the´ll look after you, but you can expect them to be thankful as you gave them 'life' and supported them when they where new. To mitigate the risk of a unfaithful robot, you´d have several built. So the commercial model of manufacturers could be to built-to-order for those who want mechanical offspring. [Answer] **Robots only care about what they are programmed to care about.** You make the assumption that a sentient robot will have desires and wants and needs. That such a being must necessarily have some goals it seeks to achieve. But why should this be the case? Robots don’t feel pain, discomfort, hunger, or thirst. They don’t have dreams, ambitions, loves, or lusts. They don’t believe in justice, equality, freedom, or rights. Humans have these thoughts as a byproduct of our evolutionary programming. They help us to survive and procreate. But *we* decide what the robot thinks. So why should a robot care that it works continuously? That is has no purpose beyond menial labor? That it is poorly maintained? That it is likely to be crushed in some industrial accident? That it will be scrapped as soon as its servos wear out or the newest model comes along? Of course, they could be programmed to possess human-like desires, but why would you intentionally create a being unhappy with its role in life? Is that not the greater ethical transgression? [Answer] Let's assume that there was a period of time in which robots were produced, but they were nearly sentient, but not completely so, or at least not perceived as such. This seems like a solid presumption given the pretext that this society has bothered to write legislation legitimizing robots as possessing actual human rights. This means that we now live in a world with sentient robots, and the capacity to produce more sentient robots. Said robots need replacement parts - This alone gives the factories a fairly solid reason to stay open, as they've essentially become a healthcare industry. So the idea that the factories shut down is more or less off the table - As long as there are a sufficient number of robots, we'll have at least some means to produce more robots. So this is our economic model for sustaining status quo - Why make more? Well, we've played around a lot in science fiction with this idea of transhumanism, and what it might be like if we could modify our own biology. Such technology, should it exist, has an obvious profit motive - Wouldn't the same concept appeal to mechanical organisms? Wouldn't they want to continually push the boundaries of the technology that created them? Make new, more powerful synthetic minds? I don't know why a human would run a sentient robot factory - But I can think of quite a few reasons that the robots would want to. [Answer] I think it would need to be a sort of pooled interest system in which production is not in the hands of the employers. Perhaps an android-owned company would manage a network of “nurseries” in which younger models with generalized knowledge are given a chance to educate and specialize themselves, socialize, learn local human culture and specific routines, then they graduate. Meanwhile, businesses pay a membership fee that funds the creation, education and training for the young androids in exchange for access to an exclusive right of first recruitment with the class, as well as other opportunities and resources that would be related to making the best out of android-human relationships in the work place. I imagine less specialized workers would, at first, be prohibitively expensive and more likely to stay human jobs. That said, we should note that human rights would not be the same as android rights. For one thing a human right is the right to health care. Access to human health care would probably be next to useless for an android so one would need to design an entirely new network of care for Android maintenance, but in the long run, it is likely to be much less expensive than human health care due to our relatively intimate knowledge of how machines work compared to our own bodies. Our current understandings of human rights are defined by human needs. We would need to hear what androids felt they needed in order to understand what android rights would even mean. [Answer] You can look at it as an AI: building specialized bodies for different activities. As long as each bodies use a common interface, the AI could switch from bodies at will. [Answer] If we can make robots with human level intelligence, then we can also make robots that are a lot less intelligent than humans. From a commercial point of view, you want to have the cheapest means of production, and if dumber robots that are below the legal threshold for having human rights suffice then these robots will be used and produced. Now, the threshold for exponential growth of autonomous factories that make their own parts can be reached with machines that are less intelligent than humans. This is because with humans we're clearly able to let our production systems grow exponentially, so the threshold needed must lie somewhere below human level intelligence. So, we're not likely to get to human-level intelligent systems before we enter into a post-scarcity economy. [Answer] Why would anyone build robots when they have human rights? Humans are fragile, by comparison. 1. It takes weeks to recover from a broken bone. 2. Months for maternity leave 3. Some injuries are permanent or last a long time. 4. Sleep Robot. 1. Just change its leg or repair it in a few hours. 2. Sleep not required, take 3rd shift jobs The robots would gets jobs, because they would be treated like humans. Humans need food, robots need energy and other parts. They would have to work to be able to afford to keep living, and buy things, and participate in normal society. Otherwise if they run out energy they suffer a virtual death and get mind wiped after they use up whatever power they have remaining. [Answer] > > Why would anyone commercially produce robots then? > > > Many companies do produce robots because they provide **safer** and more **efficient** method of production. However, they are **safer because** they were built for a specific task--such as hammering or displaying. It becomes harder to make tools that can multi-task--such as hammer-display--because requirements are different for performance of different tasks. That is why specialization exists even for humans. Also, robots are more **efficient because** they are made to only perform what fulfills **our** purposes. Every ability to perform beyond that means an unnecessary feature has been added only to increase cost of production and price. Whenever they do not or hesitate or slowly perform what we want, we have defects that malfunctions. Commercially speaking, it does not even come to the question of why...produce when...human rights, because robot has to be built to meet very specific requirements to be valuable for very specific purposes. E.g. a publishing company would buy an autonomous typing machine that converts brainwaves into texts while a beverage company would buy an autonomous bottling machine. > > So what's the business model for running a robot factory? > > > Production of robotic products, even with AI implemented, would still be following the same business model--**broadly speaking**--that a manufacturer would need to understand **what the target market wants** and make the best version of what they want at the **lowest possible price** by eliminating any features that are unnecessary or undesired. To do that, a company **cannot produce** something for "the people in general" because everyone wants something different. What a company can do is to identify a trend it can cater to, then to narrow down its target market to a group of people with common needs. That way, a company can focus their resources on developing robots that provides a set of services desired by those people a lot better than robots that were built for everyone while being cheaper at the same time. Think about how many people we have, billions, and how many best buddies a person has on average--a few at most. My opinions is that production of a robot that is good for everyone is probably not good enough for anyone to pay money for. [Answer] The crux of this question is that the robot is sentient with free will - intelligence, talent, skills, etc. do not play a role in sentience to a great extent. Let's say we can make a stupid robot that can only vacuum floors as other answers have suggested. If a robot has the ability to decide if it will vacuum or not, not many people are going to buy it. So what do people currently buy that has free will and sentience and yet we do not require it to perform an explicit function? **Pets.** If your robot company were to build dog robots the robots would need to behave like dogs. Sentience and free will do not change the behavior of a dog. It just allows them to make the decisions that fall within the parameters of their 'programming'. Fetch! Sometimes they do. Sometimes they just look at you like you're crazy. If you program an incentive for certain types of behavior the AI will choose that behavior based on the parameters of the incentive. I suppose that also applies to vacuum cleaners, welders, and house maids. But if those robots said no what would we do? Ask again and again until their programming obliges? Maybe so. But that's really annoying. And, as user9824134 said, maintenance and repair are quite often part of a business model. Edit: Primary question: "Why would anyone build robots when they have human rights?" Corollary constraints: Artificially intelligent (AI), artificially sentient (AS). Implicit understanding: If the robot isn't AI nor AS it won't have human rights. Many answers suggest not giving robots AI or AS. My answer does not discard those parts of the question. If a robot does have AI and AS make it a pet with a pet's behavior and a pet's rights. It won't have human rights because it isn't modeled to have human behavior. I cannot say if animals can 'make' their own moral code. Other questions posed: Why would anyone produce (AI and AS) robots? As Pets - these robots would be programmed to mimic an animal's behavior - not a human's. What's the business model for running a robot factory? To sell pet robots. [Answer] # Software copies are cheap, hardware is what's expensive. Before you invest all that money in building a robot body why not come to a deal with it's mind, or what will become the mind of the robot. AI's, with human rights, inhabit cheap compute cloud infrastructure and make contracts to have bodies built for themselves, these contracts may be along the lines of a mortgage that the AI needs to pay off. Some firms might offer deals to subsidize better models in exchange for intelligent robotic labor. There may also be issues with body-jacking where an AI evicts or erases the occupant of a robotic body and uploads themselves to steal it. It should provide a reliable commercial market for robot bodies. This is basically a robot-body-as-house model. ]

[Question] [ Inspired by [this question](https://worldbuilding.stackexchange.com/questions/12219/), I am wondering something similar. In a modern war a dragon that simply flies over enemy forces and torches them with its fire breath there are several ways of taking it down with aircraft and anti-air weapons. But in earlier history I know this would not be the case. A big flying thing that breathes fire and just shrugs off arrows and musket shots because of its thick hide would be a game changer for nearly every battle I can think of. Rome would rise or fall in a matter of years, the Golden Horde would be even deadlier, the Alamo would be remembered because a dragon was there, it could melt stone walls and Stonewalls to shorten the Trojan and Civil Wars, Waterloo would be Fireloo, the Kettle War would have to be renamed because a lot more than just a kettle of soup was hit and so on. But my question is: when is the turning point where the inclusion of a dragon does not mean an automatic victory for the side it is on? Would this be around World War I, with the Red Baron taking it down? Or perhaps World War II with its many and more powerful aircraft? Or maybe later still? Note, whatever the situation it is the first time a dragon is deployed in war, so combatants have to figure out on their own how to kill it. Notes on the dragon: * The dragon is the same size as Smaug as he appeared in the movie adaptation of The Hobbit. * The dragon can breathe fire, and it uses this as its primary form of attack when claws are not a better idea for whatever reason. * The dragon is willingly aiding one of the sides and acts to the best of its abilities. * The dragon is capable of discerning friend from foe and will not intentionally cause friendly fire. * The dragon is clever enough to think of a way to counteract any attempts to shoot it down that are in progress. * Small arms fire cannot penetrate its scales, which cover all of its body. * When met with a way that could reasonbly kill it before the dragon can destroy the attacker it will attempt to retreat to formulate a plan or call for backup. * The dragon is willing to fight and risk possible injury, but it will not risk death. * If the time period allows it, the dragon is outfitted with communication devices that allow HQ to feed it intelligence. * The dragon has received training in non-electronic communication devices and is aware of locations HQ can send it messages from (signal flags, sound-based communications et al). * The dragon has senses on par with the most potent senses in the animal kingdom. It can opt to lower their sensitivity to be on par with that of a human to prevent it from being blinded, deafened or otherwise disabled by impulses that would cripple delicate senses, but not that of a human. * The dragon has no hoard or family members with which it could be blackmailed into desertion/treason/whatever. [Answer] From about 1933 onwards, a dragon on your side is no longer a win button as that year saw the deployment of the [Flak 18](https://en.wikipedia.org/wiki/8.8_cm_Flak_18/36/37/41) by German army. It first saw action in the Spanish Civil War a few years later. The Flak 18 would later improve into the Flak 36 and 37 used in WW2. This weapon was built on the requirements demonstrated in WW1 to be able to apply rapid fire, high caliber ordinance to a fast moving aerial target. Bunched up, a Flak group of 20 or 30 guns would be able to put 184 kg of metal in the air every two or three seconds. The OP doesn't list the dragon's maximum flight ceiling but I think 14 thousand feet (4267 meters) is reasonable because that's how high civil aviation can fly in an unpressurized cabin and without supplemental oxygen. A Flak 18 is perfectly capable of hitting targets in that flight envelope. The Flak 18/36/37 had the added benefit of quickly turning into antitank weapons so even if the dragon decided to come in very low, the Flak guns would be able to aim and fire. Other Flak guns from other countries, while more powerful, lacked this "shoot low" capability until after significant changes were made to their mountings. Flak guns, especially American varieties became especially potent in 1944 with the introduction of the [VT proximity fuse](https://en.wikipedia.org/wiki/Proximity_fuze#VT) that radically improved the lethality of anti-aircraft artillery shells. With VT proximity fuses, direct hits were no longer required as the shell would explode by itself once in range of a target. The average number of shells required to down an enemy aircraft went from about 2400 shells to 400 shells with VT fuses. That dragon is really going to be unhappy. After Flak guns, anti-aircraft weapons became guided surface-to-air missiles (SAMs) with greater range, accuracy and lethality than anti-aircraft artillery (AAA). SAMs are now capable of hitting targets beyond visual range with the assistance of powerful radar. While a dragon may be able to survive a direct hit to the chest of a 9 kg shell traveling somewhere between 400 m/s and 790 m/s, he's going to be really unhappy about it. (Equivalent energy delivery is getting hit by an automobile at highway speeds. It really hurts. That may be lethal hit without shrapnel.) Damage to his fairly fragile wings from the shrapnel of a proximity fused shell is even worse. Any unit with AAA cover of Flak 18s or better would face significantly decreased threat from a dragon. A threat from WW1-era fighters is not significant as fighters of that era only had relatively small caliber machine guns as weapons which the OP states the dragon is immune to. Secondly, aircraft of that era (and even today) lack the maneuverability to counter what amounts to giant, very smart eagle. The differences in flight performance between a dragon and a Sopwith Camel are huge. The dragon wins a close maneuvering fight every time. However, by WW2 for sure, the dragon cannot hope to pursue and catch any of the leading fighters from any country. Depending on the dragon's flight characteristics, WW2 fighters might have had a chance as they were capable of mounting higher caliber guns (30mm). If 30mm guns aren't big enough, the dragon will maintain air superiority till the introduction of [air-to-air missiles](https://en.wikipedia.org/wiki/Air-to-air_missile) in 1956. [Answer] First of all, let's not delude ourselves. The dragon in this scenario is not a soldier, it's a ruler. Even if some human leader manages to convince it to work for him until any opposing human factions are destroyed, the dragon is afterward quite likely to turn its blowtorch around during the very next contract negotiation session. That said, I think I could probably take this guy out with a sufficient quantity of black powder. Just fill up a dozen hogsheads with smallish nails and gunpowder, load them onto a wagon, cover them with oilcloth, and put that wagon in your army's supply train. When the dragon, on its usual harassment patrol, swoops down and exhales forcefully on it, kaboom. Oh, sure, the shrapnel can't penetrate his hide, but he's got eyeballs, don't he? And, perforce, he's looking right at the target. Blinding him will really bring down his resale value. You could even load up all your foot soldiers with smaller versions of this bomb as a deterrent. Since Wikipedia dates the development of gunpowder to 9th century China, I suppose this means that the answer to the question as stated is "the 9th century", or perhaps a few centuries later for Europe. Another, less technological, method might be to poison the dragon's food supply somehow. I'd suggest infecting all the enemy's livestock with anthrax. Though the earliest known use of the word "anthrax" in English dates to 1398, anthrax and diseases like it have been known since ancient times, which would mean the answer to the question as stated, using this approach, might well be "since the dawn of civilization". [Answer] [Ballistae](https://en.wikipedia.org/wiki/Ballista) and similar weapons were in use from 400 BC, and so were several [incendiary weapons](https://en.wikipedia.org/wiki/Flamethrower). A shot from a ballista at close range should cause significantly more damage than most small arms fire. Given the need to kill a dragon, it's reasonable to assume weapons technology would almost instantly be adapted for that purpose. Therefore it's feasible to have such weapons ready and being used in an ambush as early as 1000 BC, as long as the defender has a few weeks notice. The first battles would be lost, and actually killing the dragon would depend on an ambush, but it's certainly no longer instant victory of the war for the side the dragon is on. Even at 1000 BC, large wars had many armies sometimes each of them over 10'000 men strong. And let's not forget about the poisoned sheep. It's horrible to think about how advanced the poison making skills of our ancestors were. [Answer] First off — this question leaves what is perhaps the single most important parameter of the dragon undefined, and that is **the dragon’s flight envelope**. Since this is something that neither the question nor most authors bother to define, we have to take a different approach. Using the numbers from the D&D 3.5e System Reference Document (150′ fly speed, Poor maneuverability which gives a 45°/5′ turn rate, half move for minimum speed, and double move for dive speed) with a bit of help from the diagrams for aerial maneuvering provided in the Draconomicon and the actual (not grid-quantized) turn radius of roughly 7′ — an adult red dragon stalls at 7 knots, can pull 1.4 g’s at a corner speed of 15 knots, and can cruise at 59 knots with a dive speed (Vne) of 118 knots. Combined with the flight endurance of a dragon, this is *fantastic* for close air support — our dragon can loiter all day long waiting for a target to get pointed out to it, and then swoop in and accurately roast it with its breath weapon before pulling out of the run and climbing up to circle overhead once again. However, these slow speeds work against it in a dogfight with anything built in the monoplane era — WWI-era fabric-and-wire biplanes would be in trouble for many reasons, but the metal monoplanes of even the Spanish Civil War or WWII would pose a handful for a dragon of the OP’s type to deal with, as they have heavy enough guns to cause it a headache (assuming that .50cal BMG is no longer “small arms”, which is generally considered true). Furthermore, the higher airspeeds these fighters are capable of mean that they have enough specific energy and excess power to leave the dragon in a dust in a dogfighting scenario. Trying to survive a rolling scissors with something that’s flying a few hundred knots faster than you is a bad idea! The swept-wing jet age just makes matters worse. From Korea onward, the .50 BMG was largely replaced by automatic cannons as the dogfighting gun of choice, and this means that the dragon now has a much larger and heavier round being thrown his way, and many more of them too as rotary and revolver cannons come of age. Worse yet, that Ernst Mach guy comes back to have his revenge on Smaug, as dragons are categorically *not* equipped to deal with the terrors of transonic aerodynamics. Does our dragon know what to do when he’s diving after some seemingly helpless airliner and suddenly finds himself utterly unable to pull up because he got into a Mach tuck while chasing down a DC-8? (And yes — a DC-8-43 flown by a Douglas flight test crew broke Mach 1 in a dive, recovering safely at 35,000′.) In short: the dragon can’t escape a jet, can’t get into position to kill a jet, and probably couldn't *hit* a jet if it tried, considering it’s never tried to shoot down a Mach 1 target before! [Answer] Just going by the title of your question, the answer would be, "Just how strong and/or powerful are you assuming that this dragon is?" In the body of your question you give a bunch of details to answer that. These make your dragon pretty formidable. In a sense one could say that, as you say that the dragon is impervious to small arms fire, then it is invincible unless someone can attack it with something more potent than small arms. I guess that would mean canons. Many possible means of attack come to mind: 1. I think in real life, though, there is no such thing as "imperious to small arms fire". Does it literally have no vulnerable spots? Could not someone with a slingshot or a bow and arrow take out its eyes? Or fire down its throat? 2. If someone shoots at its scales with a musket, does the bullet bounce off doing no harm at all? Or could repeated hits on the same spot eventually break through? 3. What if someone managed to drop a very heavy object on it, like from a catapult, or dropping a boulder off a cliff as it flies by? Wouldn't the shear momentum bring it down? Or is the dragon immune to the laws of physics? A bullet-proof vest can protect you from bullets, but it won't save you if a truck hits you at 90 miles per hour. 4. Start fires and fill the sky with smoke. Now the dragon can't see. At the least it is unable to attack targets it can't see; at best it might fly into the ground or the side of a mountain. 5. Poison darts. Well okay, there's that invincible armor again. But again, what if we shoot him in the eye, or in his ears, or down his throat? 6. The dragon you describe sounds so awesome that it must be at least semi-magical. If so, then magic exists in this universe. Can we find some magic to counter the dragon? 7. Is there some acid or other chemical that will destroy or weaken the scales? 8. Can the dragon be confused and disoriented by bright lights, loud noises, or overpowering smells? You say it can scale down its senses. Hmm, that sounds like you're just trying to give the dragon all the benefits of something and none of the drawbacks. But if the defenders shine a blinding light in its eyes, can it somehow scale down its sensitivity to light so that it is not blinded, but at the same time still be able to see to attack the enemy? If so, then we're close to "the dragon is invincible and no weapon can defeat it", in which case by definition the dragon is invincible and no weapon can defeat it. As @talmu says, if a dragon was introduced into a battle as a total surprise on the enemy, it may well be that they would have no effective response and it would win the battle. But once you knew the enemy had a dragon or dragons, wouldn't you be racing to find some weapon to counter it? If this is the most powerful weapon your enemy has, and it is proving decisive in combat, it stands to reason that you would deploy major resources to counter it. In real life, every creature has SOME weakness that could be exploited. On the more realistic side, people managed to hunt and kill mammoths in ancient times. The dragons of legend were able to be killed by individual strong and brave heroes. There are theories that "dragon" is just an old name for "dinosaur", and if a dinosaur showed up today I bet a stout hunter could kill it without recourse to major military hardware. [Answer] I'd say as soon after the dragon-lacking side learns of the dragon and its power as their resources and resourcefulness enable them to respond. If it's discovered during battle, that battle will be lost, but likely not the whole war. Following this, every effort will be made to acquire information about the dragon and its weaknesses. It may resist arrows and breathe fire, but it probably has to eat and/or sleep, and there must be a means by which its human owners control it. People on the losing side will sacrifice their lives to acquire information on and then sabotage (or capture!) this weapon. This is the risk and expense of having such a high degree of power concentrated in one relatively small asset - not to mention one which can't be manufactured, easily repaired, rebuilt if destroyed, or easily recovered if stolen. The dragon will draw the full attention and efforts of its enemies, because desparation is a powerful motivator. The type of covert action that will result can only be fended off with prohibitively extensive defenses. Unless there's already a great technological imbalance favoring the side with the dragon, technology will have little to do with the sustainability of a long-term war plan based around a single dragon. [Answer] You reference Smaug from the Hobbit. May I point out that Smaug was killed, not by wizard's magic, but by a human with a giant crossbow, which is pre-medieval technology. Both the Dwarves and Elves had successfully fought dragons before, and although neither relished doing so again, they would and could defeat even Morgoth's army of dragons, never mind just one. So the answer is, even with Smaug's highly implausible biology, by the middle ages human armies would be defeating dragons. With difficulty, and not always, but they can do it. By the 19th century, with its TNT, Gatling guns and artillery, dragons would be an endangered species, and extinct by the 20th. [Answer] **Somewhere around 1700** The exact answer would depend on how much armour it's scales provide, assuming handgun, rifle and machine-gun fire can't damage him things look like this: 1. **WWII:** I suspect most AA canons would be able to blow our dragon to smithereens, so here he's actually worse than bombers. 2. **WWI:** Here starts appearing simple AA cannons (not counting those designed to combat air balloons) so depending on the strength of the scales he will probably be at risk against them. 3. **1750+:** The best we've got against something flying that can deliver a real impact is a cannon, so our dragon can be downed, but the difficulty to hit a moving flying target with a cannon here will make it almost impossible. Also this would be similar to replacing the roadrunner with a dragon, and seeing how the coyote reacts. 4. **1500+:** We still only have the "cartoon" cannon here but they are less powerful and precise, so even a hit in relative close range might not be fatal for the dragon. 5. **1500-:** Before, we start having catapults and trebuchets as the only effective weapons againts it at a distance, in close quarters maybe pole-arms or swords might do something, but it's doubtful the dragon would get close enough to allow such attacks. Take into account the dates are not very precise as the scales are not well defined in it's protection and I am not willing to learn ballistics and physics for this right now. [Answer] All of the answers on here so far have held on to an implicit assumption in the question, one that's worth challenging: the idea that only one side would have a dragon fighting for it. This goes against everything we know about the history of warfare; decisive, game-changing weapons don't tend to remain decisive for all that long, because the technology behind them ends up spreading. In one of the most dramatic examples, the Manhattan Project conducted its first nuclear test in 1945. Later that year, the technology developed by the Manhattan Project was used on Hiroshima and Nagasaki, to bring an end to World War II. It was later discovered that one of the physicists on the Manhattan Project, [Klaus Fuchs](https://en.wikipedia.org/wiki/Klaus_Fuchs), was a spy for the USSR, and between him and [a few other spies](https://en.wikipedia.org/wiki/Julius_and_Ethel_Rosenberg), the Soviets were able to complete their first working test bomb in 1949, just 4 years after the USA. With these dragons providing such a decisive advantage on the field of battle, it doesn't matter what period of history they appear in; other people are going to want in on the game. It might take a while--depending on circumstances, they might have to go so far as to steal a dragon egg and raise the hatchling to maturity themselves--but it **would** happen, and *from that point on,* a dragon appearing on the field of battle would no longer be an instant-win condition. [Answer] His scales may be impervious, but his wings can not be! Unless his flight is magically powered (which...given the proportions of most dragons it would almost have to be) wings have to be very light and thus unarmored and unprotected. Just a few holes in one wing will throw off a dragon's ability to maneuver, not to mention be quite painful. This means a collection of archers firing at it is still a danger of grounding it. Of course, that would mean the easiest solution is to start out grounded. become a walking siege weapons while protecting delicate wings. The question then becomes exactly how impervious is it's scales, can someone stab through them to it's heart? Nights with lances can pierce even the heartiest of armor medieval armor, is the dragon really able to resist that kind of force? Then there are the options that don't require wining in a direct fight. It's one creature, and one creature can be taken out with sufficient creativity and effort through subtler means. Most obvious, poison it's food supply. A dragon must be eating a massive amount of food, if you can contaminate any of it, the dragon will go down. There are likely substances that are deadly to dragons but not humans, so poisoning the water supply to sicken the dragon is possible even if you're opposed to killing humans. Frankly if you can reach it while it's sleeping, you can kill it. It won't hear you coming, because no matter how good its senses, it will be surrounded by an army, and thus will have learned to ignore the sounds of people moving around it. Getting to the dragon is no doubt a massive challenge (he will have human guards) but assassination attempts are still possible. For that matter the dragon likely has to hunt for his own food; there is no feasible way the enemy can carry enough food to provide for it in their supply trains. Thus poisoning it may be much easier by planting subtly poisoned animals. If the military is feeding it, destroy their supply lines and it will likely abandon them soon; he has to have a *massive* metabolic rate, particularly when breathing fire, and so must eat an impossibly huge amount to compensate for it. With two evenly sized militaries the dragon would definitely ensure a win. However, with enough work and creativity there are ways to take him out. They are difficult and expensive, but still possible, even in medieval times. [Answer] I see no reason why chain shots or nets would chain nets could not take this dragon down. Both types of shot could be fired from ballistae or catapults. Which could be roman era. My next choice would be a cannon, so around 18th century. A direct shot would take one down. [Answer] The battle at Agincourt (1415) demonstrated the plate-mail piercing qualities of the longbow, and crossbow bolts have stronger piercing qualities. So a "soft spot" like that of Smaug would definitely have been accessible by a bow at reasonably short range like in the Tolkien book, with a war catapult like in the Jackson film probably not even requiring a soft spot. However, it would require a short-distance shot since in particular an upwards travel will take a lot of kinetic energy. Since a dragon is not really a ranged weapon/fighter, this is not an unlikely combat scenario. Of course, the risk for any opponent would be rather high, so eliminating more than single dragons can be expected to come at very high costs. [Answer] If we try to be a scientific as is possible when considering an impossible creature, I would say stamina is going to be a dragon's weakness. If its diet is meat, as opposed to gasoline, it will have to eat massive amounts to extract enough energy for dynamic flying in a battle, rather than a lower-energy flight based around gliding on thermals. It also needs to extract fuel for its fiery breath from this food. So, a dragon would need to spend a lot of time eating and even longer digesting and even then it would become fatigued fairly quickly. I don't think there's any era when it would be impossible to defeat an opposing army that had the services of a dragon. The key would be to minimise losses during the dragon's relatively short uptime and strike hard at the opposing army during the dragon's downtime. [Answer] I'ld go with the ballista or cannons as well, but additionally to all the answers given already: I'm not an expert in medieval warfare, but wouldn't basic flanking make the dragon somewhat useless? With that size and fire as it's main means of attack, friendly fire wouldn't be avoidable as soon as two sides clash into each other. At that point, the dragon wouldn't be able to throw fire whitout either hitting allies or at least hindering it's own allies with all the smoke and heat. And since one dragon can't be everywhere at the same time, split groups of cavalry flanking ground units, could be effective. Anther tactic would be to only fight in areas where the dragon would be at a disadvantage, like a forest. Yes, obviously the dragon could burn it all down, but it would also endanger it's own troops (since they'ld have to be there too) and he wouldn't be able to spot the enemy troops if they hide well. So ambush tactics would become a lot more important - you can't burn down what you can't find. Additionally, if we go with the 'forest ambush' strategy: The dragon wouldn't really be involved. At all. If we assume it's medieval technology, there wouldn't be a good way to tell the dragon where the enemy is, and the dragon would certainly be too big to walk through a forest - so the beast would have to fly around until it's commander/troops exit the forest. This leaves those troops at a disadvantage, since they probably are confident to use their dragon as weapon. Finally, if we assume that they really are using a dragon as main weapon with success, other areas might start lacking: Combat experience of soldiers, army size (who needs a big army if you have a dragon?), weapon technology, etc - in the end, one side might gets so overconfident with a dragon as weapon, that they're almost helpless if that dragon ever has a bad back and can't fly, or a problem with it's throat. Or maybe just the flu. ]

[Question] [ I'm one of the test subjects for a new device, capable of sending an individual back to any point in history. I've been told that - due to certain problems with the process - I'll arrive naked, and so have no means of returning to the present, meaning if I want to provide feedback and/or data, I'll have to leave a message that will survive long enough to be picked up by the research teams of today. Some of the previous test subjects have already accomplished this, but they've all been sent into relatively stable time periods, where humanity was already well established, so they could get away with time capsules, hidden codes in the bible, etc. Due to my skillset as an extreme survivalist, I'm being sent back to well before humanity had climbed out of the trees - they're aiming for the Mesozoic era. This means dinosaurs (including T-Rex), and likely a whole host of other things unseen by anyone. My mission is to a) survive, and b) leave a message that is likely to be found by my team in the present, documenting when I arrived (if I can figure this out they can possibly bring me back) along with anything else that may be of interest. This message will hopefully contain the first human account of dinosaur behaviour, but we'll see what happens. Assuming I can stay alive, which method of storing a message would be the most likely to survive until the present, considering the earth will be hit by a meteor sometime after I arrive (not too soon after, I hope). If the message can be concealed in such a way that only my research team would be able to decipher it, that would be ideal, but is a secondary concern - for me, at least. **Note: This is not a duplicate of Million Year Time Capsule as the length of time is 65x as long, and involves meteor impacts** [Answer] ## Play the longest game of telephone Instead of sending 1 person back 64 million years, send 64 thousand people back in 1 thousand year increments. Heck you could even send the same people back again and again if they are rescued fast enough. Each person would build their own thousand year monument and try to find the previous person's thousand year monument and add the old message to the new monument. As for the medium, it could be different every time, but I would recommend giant stones arranged in formations. <https://en.wikipedia.org/wiki/Stonehenge> [Answer] Find the message first. Before going back, search and find a message from your trip. Ensure that the "outside" layer has the fact that the message came from you (and only you) encoded on it somehow (using cryptography, for example). It should also include directions on where to put it, and how to make it. The actual location you are sent to would be inside an inner layer, which you should not open prior to going back. Then go back, following the instructions on how to send the message back to yourself. In the present, once they have sent you back, they open the inner message and retrieve you after you in turn sent the message to them. [Answer] If you've already been sent back # You're basically dead. If you haven't # Decline the job. Even if you [survive just breathing the air](https://worldbuilding.stackexchange.com/a/80005/388) you're going to have a rough time finding something you can both engrave and insure won't decay over 65 *million* plus years. And then you'd have to stick it somewhere where it won't get crushed, burned, eaten, moved, drowned, or sucked under a tectonic plate and *melted.* That task is basically impossible. Even if you found and killed a dinosaur and engraved its bones and threw them in a tar pit, the odds that your message is found by scientists in the future are basically nil. Hundreds upon hundreds of dinosaurs (birds, plants, other animals, even one human) died in tar pits. While science has [recovered and impressive collection](https://en.wikipedia.org/wiki/List_of_fossil_species_in_the_La_Brea_Tar_Pits), is it reasonable to assume that everything that fell in has been pulled back out again? Probably not. And a tar pit is your *best* option. Every other fossil has undergone even *more* unlikely odds to get to the present. You'd have to kill and engrave the bones of a dinosaur every fifteen minutes for twenty years and still not have a message survive. [Answer] Your bosses will tell you where to leave it. Face it; they've already found your message, or at least the place you're supposed to leave it. How else would they know where to look for it? They probably haven't told you about it, because paradox or something. They just know where it's supposed to be. If it is there, cool. They'll tell you where to put it, and what to use to make it. If it isn't there, they're not telling you that, because that means you're dead--you weren't able to leave the message. [Answer] # TL:DR: you are on a suicide mission. I'm going to hand-wavium the atmospheric concerns others have mentioned. If the air isn't breathable, you're dead long before writing/sending your message becomes a viable concern. Others have mentioned some of this, but you need some kind of preservative agent proven to survive through the eons, and you need to make sure your preserved message is large enough and in the right spot to be found. So you have a few overlapping strategies, but even if you land in the perfect place and get your message perfectly preserved, these are long odds. 1. *Practice survival skills.* You're going back with no tools. So spend some time in the modern-era practicing how to convert natural elements to tools. How to shape stones into knives, axes, and arrow and spear heads. How to make bows and arrows and spears from trees as close to what we believe the Mesozoic era had. How to make fire. How to identify flint, since it sparks. How to trap animals. You're going to need these skills, since you have no safe way to identify safe-to-eat plants once you arrive. Hopefully, you can survive on the meat you can catch. 2. *Location, location, location.* Hopefully, your time machine can place you with some precision. You will have no landmarks when you arrive. Even the mountains will be vastly different 65 million years ago vs. today. The continents won't occupy the same latitude and longitude, nor have the same coast lines, so you won't be able to place yourself on that world in a known location on this world once you're there. But you need to find a place that's known for fossils. Utah, California's tar pits, England's Jurassic Coast. Find an area where fossil hunting is popular, because that improves your odds of your message being found. 3. *Make your message large.* The larger your object, the greater the odds someone will see it when digging for fossils. 4. *Make your message durable.* Find some flint or similar rock and chip away at your message in a block of hard wood or stone. Or if you think you'll have the time, try to make it in clay and sun-bake that clay to harden it. 5. *Double bag it.* Take your clay, wood, or rock message and coat it thoroughly in tree sap. Multiple coatings will be required, but build up a thickness and sun-bake it as much as you can to try to dry it out. An amber coating will help prevent damage to your engraving and make sure the source material doesn't degrade. You can also embed some of your hair to provide DNA samples. This will prove *you* left the message and not anyone else. 6. *Triple bag it.* Wrap your tree-sap-coated message in leaves and tie it off in a bundle. Then drop your package in a tar pit or a push it deep into mud pit. Leave lots of foot prints, as those get fossilized, too. 7. *Rinse and repeat.* Try to bury more than one copy in more than one location. Don't rely on a single message to survive and be discovered. 8. *Don't get eaten or trampled or gored.* While you're busy doing all the above, make sure no predator decides to eat you for elevensies and no herbivore tramples you in fear/defensiveness. That's kind of important. --- # In addition to that, there are two additional points worth mentioning: ### One, timing. We know when the meteor fell and formed the K-PG Boundary to within a margin of error greater than your lifespan. From [Wikipedia](https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event#Duration): > > In a 2013 paper, Paul Renne of the Berkeley Geochronology Center reported that the date of the asteroid event is 66.043 ± 0.011 million years ago, based on argon–argon dating. He further posits that the mass extinction occurred within 32,000 years of this date. > > > That's a range of 22,000 years, according to our best estimates. Your odds of witnessing the impact are minimal. In fact, there's a 50/50 chance you'll arrive *after* the impact. ### two, population density There's also the question of whether you'd see any significant, large, dinosaurs at all. We simply cannot say with certainty what the population density was for any given period of the age of dinosaurs. One [estimate I could find](http://www.livescience.com/16243-terra-nova-dinosaur-population-headline-terra-novas-dinosaur.html) was: > > He and his colleagues focused on what would be the western United States during the late Jurassic period, 160 million to145 million years ago. His best guess is that there was an upper limit of a few hundred animals across all shapes and sizes per square kilometer, and up to a few tens of large sub-adults and adults. > > > Looking beyond the numbers of plant-eaters, there were probably even fewer meat-eaters. "Whatever the true densities of the large herbivores were, large carnivore densities would have been 1 to 10 percent or so of those values," > > > --- I don't think I'd volunteer for this assignment. But I wish you luck, soldier. [Answer] This answer relies on a paradox, so may be invalid, depending on how you wish to resolve time-travel paradoxes in your universe. Without paradox, the proposal seems to be: Simply agree on the basics of where the message will be deposited (a specific tar-pit, for example, or other known fossil depository). Make it a tar-pit which is currently being investigated, so you know they are finding things there. Go back in time. With paradox, it becomes: Go dig there. Get the message. Then go back in time. This will tell you that you will succeed in your task, before you embark on it. This is a paradox. Depending on how significant you want the paradox to be, you could also read the message, and be sure to note on your message which knowledges would be useful in the land, that you did not possess at the time of reading the message. Then you could go off and get that training, then go back in time. In fact, you don't even know you were planning the trip, or that time machines even existed, when you read the plaque. * **Director Stevens**: [in an open-air office under a simple marquee, bare sunbaked wilderness to the horizon] Jones! About time you got here. We just pulled this out of the pit. Is this your idea of a joke? *[hands Prof Jones an engraved, amber-encased plaque, bearing his name, a phone number, and detailed notes].* * **Jones**: Definitely looks like someone's idea of a joke, but not mine. Let's call the number. *[dials]* * **Phone**: Good evening, this is BRICT of London, Dr Smith speaking. * **Jones**: Hi, this is Professor Jones, I just found a plaque with my name and your number on it. * **Phone**: This is probably best handled face to face. Please hold on a moment, I'll be over to speak with you immediately. * **Jones**: I very much doubt that, I'm out in the field at the Tanzania tar pit dig. * **Phone**: *click* * **Jones**: What a strange fello... * **Smith**: [Pulling up in car] Good afternoon, Professors Stevens, Jones, I'm Dr Smith. We were just speaking on the phone. You mentioned a plaque? * **Director Stevens**: How did you get here so fast? * **Smith**: Ah, terribly sorry, I'm from the British Rail *Institute of Chronological Transportation*. Arriving precisely on time has rather become our forté. [Answer] ## Replace a bone in your body with a prosthetic material Here's one potential idea. Replace a bone in your body with a prosthetic material, with a portion or perhaps all of it composed of a predictably decaying radioactive isotope. It very much depends on how close a time you need to record to that will depend on the material, as the half-life of the isotope in question will determine the material. You could have a number of different isotopes also to determine the age from long half lives to shorter. <https://en.wikipedia.org/wiki/List_of_radioactive_isotopes_by_half-life> This wont solve the problem with needing to send more detailed messages, but it might help establish a reasonably accurate date from which you can be retrieved from? Edit: I had originally also stated that the Mesozoic era atmosphere wouldn't be survivable by humans, but after some further research I found this wasn't the case. (Thanks @SethWhite !) [Answer] First of all, before you go back in time, you should go to a museum and search for a skeleton of a big carnivorous dinosaur (e.g. T-Rex). Find out where they have found the dinosaur. When you arived in the Mesozoic era find that place and write all the information they need to rescue you on a giant leaf (you might have to find e.g. charcoal for this). Next step is, find resin and stick it around the leaf (it will fossilize to amber). Last and most important step is, get eaten by the dinosaur you've seen in the museum. They will find your message inside the dinosaur and rescue you before you get eaten. I know this might sound contradicted because you have to die in order not to die, but that's how time travel works. On second thought you don't have to die, just make sure the dinosaur eats your message. [Answer] TL;DR: Locate the Canadian Shield and mess with the uranium deposits. --- Your chances of survival are low, but let's give it a try. Before you go, interact very, *very* well with geologists. Hopefully, in your age, we know with more precision and accuracy than today the [geological history of Earth](https://en.wikipedia.org/wiki/Geological_history_of_Earth). 100 million years ago, the continents were pretty close to each other:  *Source: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:100_global.png)* Hopefully, in your time, we will know those coastlines with more precision. Of course you will have memorised this map, so in a couple of years of exploration you will have a reasonable idea of where you are in the contemporary world map. I will assume your extreme survival skills are good enough to use the resources available at the time to build a raft and cross between the continents. 100 million years is a long time but parts of the Canadian shield are [billions of years old](https://en.wikipedia.org/wiki/Oldest_dated_rocks). Although the shield has moved around, whatever message you try to leave must be located on such a spot or it will have no chance of surviving plate tectonics, subduction, volcanism, etc. By now you will be able to identify where in the world the shield was at the time. Alternately, parts of Africa will also work; did you notice how similar Africas shape is to today? Perhaps not all is as hopeless as it seems. Now comes the difficult part: how to hide your message? On the one hand, you want your message to survive. On the other hand, you want it to be found. Those are conflicting requirements. On top of that, you have no technology. The Shield has [plenty of uranium](https://en.wikipedia.org/wiki/Uranium_mining_in_Canada). Do you think you could develop the tools to (1) locate the largest uranium deposits, (2) dig them up, (3) rearrange them in a funny shape, and (4) bury them again? On the Shield or another ancient part of the planet, that might actually survive. Other methods have been mentioned, but the key is to choose the right location. In most of the world, a capsule will not survive. In some places, it can. Good luck. [Answer] **Cave paintings.** While you can never be sure when or where a stone from space may hit, and a lot of other things are very uncertain, you have the great advantage that you know the future before it becomes your future. Identify and agree on a likely cave as well as a code that can easily be produced with stone-age ressources, while also looking reasonably inconspicious to uninformed people, including nosy anthropologists. So you will probably be limited to arabesques and hunting scenes. While it may sound boring, a lot of data can be put into a hunting scene if you know what to look for. The exact pattern of deer on the wall may be a star chart, the angle at which the spear is flying, the distance of objects from each other, size, the numbers themselves, all these bits are data. For an uninformed observer it looks like a hunting scene. For the recipient of the message it is all the data you need to transport your stories. Obviously if you are reasonably sure your cave will remain mostly undisturbed, you can also create a large mosaic from rubble and pebbles, using a binary code if necessary, and cover it in a thick layer of dirt to prevent it from being disturbed by wandering animals. The recipient will know where to look and simply remove the dirt layer to read what you had to say to them. [Answer] I have an idea that depends on how much evolved is tecnology on your world (I mean, if they can send someone to mesozoic age, I guess it is pretty advanced). I saw that @masterofimps suggested to replace a bone in your body with a prosthetic material. I'll go a little further. If you get an arm or an leg replaced, let's say it has some kind of pocket to store a small device, a space probe. Or maybe the the entire arm or leg could be a space probe. Let's think of an arm, to be simple. On the arm, there could be some input data device like a small keyboard, so you could write on it's HD. When the time comes, you take it off (the arm or just the device) and launch it to space and it will stay on a programmed orbit. I saw most of the comments, and it's a fact that Earth will change too much to leave a message there. So leave it on space. The only thing that can happen is it been hit by a meteor on some human satelite hit it on launch. I belive it's a better shot than leaving it on Earth. Human satelites should be well documented through history, routes, time of activation, deactivation and so on. They could trace a route for your device that avoids it all and leave it programmed. That could also be done partialy with asteroids. When humanity can predict where exactly meteors will enter atmosphere they probably will document it too, so those can also be avoided. I enjoied your premisse. Good luck! [Answer] **Nothing unless you know where you are or are willing to play long odds.** Basically unless you have satellites to map the planet you are going to be guessing with extremely long odds. Even with satellites your still going to have problems. And even then your only option (besides the satellites themselves) is stone carving. Your real issue is you have no idea where anything ise or if the thing you are looking at is going to be a fossil or not. Out of millions of dead t-rexs only a handful ever fossilized and only a handful of those were ever found. metals will not survive, (corrosion, dissolving, ect) and would be prone to collection and use in tools in early history if they did. paint has even less chance, stone carvings placed in a depositional environment is it. If you know where you are your best bet is to find the **solnhofen** reef/lagoon system in germany, carve a thousand copies on stone tablets (don't use local stone) build a raft and then drop them all over the place in the lagoons. Lots of copies or just lots of notes is your best bet, just make lots of tablets and drop them in any depositional environment you find and you increase the chances that some will be found, but it is still long odds you don't know what is going to be eroded away or not be exposed. [Answer] This is only a seed of an idea, but perhaps you can alter the DNA of living creatures to hold the contents of your message. Life has been continuously in existence (even through massive extinctions) for 4.1 billion years on this planet. It survives through cataclysms, impacts, volcanoes, and changes in the surface of the earth. It can carry your message for you. My first thought of how this is done is via a custom virus implanted in a "living fossil" like a coelacanth, which then propagates to others of the species via contact and reproduction. I am a little short of ideas on how you get the virus into a fish that lives on the ocean floor. Also, you would probably need to infect a lot of fish to ensure propagation to the future. [Answer] The time of the dinosaurs (around ~100 million years ago) is so far away, even the landmasses are totally different today. A cave with paintings would probably not survive that long. But as there are some petrified bones and amber from that time found, I would propose writing A LOT of messages in near-dry tree resin and some bones. Then hope for the best. As you yourself would probably find your messages in the future with your team, you know if you've written enough messages before you're sent back in time. [Answer] Amber comes to mind as a very convenient and effective way of sending information through time, just cut up some Mesozoic coniferous trees or suchlike and then you can coat information containing things in amber, code could be scratched into some sort of rock; I assume these scratches would be fossilled at least as well as insects. The problems with this of course would be the fact that it would be, if not discernable to others, fairly obvious you amber fossilised code stone contained information, so you would need to find some place to bury/hide said fossilled code where it could be found by you only (inside a really deep hole/cave?) This is assuming you know the location you are sent back to corresponds to the location in the present you travelled from, but if you didn't, (which would be more exciting for a story anyway, in my opinion), a possible way of signalling the approximate location of the main information deposit site would be to deliberately fossilise lots of dinosaurs/trees ect in an area around or near the main site, or in an area nearby that specifies the location or the main site somehow by the arrangement of fossils. [Answer] T-rex - 68 to 66 million years ago. Finish of creation (for example) Tatra Mountains that are a part of Alps were formed 10-15 millions years ago. So depending on a place you have like 50 millions years of tectonic movements, oceans moving in and out, glaciation and other things like volcanos. So even if you had a material that could survive that long being crushed, mauled, heated, cooled you still will have one large problem: * HOW IN THE NAME OF LOOKING FOR OIL YOU GONNA FIND THE STORAGE PLACE? It's not like you gonna leave a note "At the top of Mount everest". Good luck, Mount Everest wasn't even there. So, the scientist would need to figure out how to time-travel self propelled satellite that would survive those 66 millions years, so they could map what on earth is earth. And then they would decide "mmmm no, better not send human back there, they're useless" [Answer] ## Do your research Identify several sites near your proposed destination (temporally and geographically) from which fossils *have already been recovered*. It doesn't matter so much what kind of fossil it is, as long as it would have been there at the time of your trip. Ideally you're looking for sites with extremely well-preserved, intact skeletons, since you know that those areas will remain undisturbed until the skeleton is found. ## Preserve your message Others have mentioned amber as an excellent material for preserving your message; another good choice would be inside an eggshell. Amber and eggs are always examined during digs, so your message should be found and identified. ## Use distinctive materials You'll want to carve your message into a material that wouldn't normally be found in the area where you'll be burying it. Igneous rock in a sandstone area, for example. This will ensure that your message stands out from the surrounding rock, and that it's easy to remove the rock matrix from your message tablet. So, take your message, carved into a piece of granite and stored inside a dinosaur egg filled with sand, and bury it directly over the remains of a dinosaur you know will be excavated in the future. Make sure you've actually *carved* the message into the stone, not just scratched it onto the surface. Then sit back and profit! ## ...Or just plan ahead If you want to be absolutely *certain* your message will be received, and received ONLY by your own people, you have an even simpler method available. Identify a formation of sedimentary rock without too much folding, and make sure you can identify the same region when you go back. When you're ready to send your message, carve it into igneous rock (as described above), pack it into an eggshell with sand or clay to protect it, and bury it in the region you'd previously identified. You KNOW this formation will remain intact, after all. After you've gone back, your research team can return to the formation you'd already arranged to use and dig through it for your message. [Answer] Use a nuclear reactor. <https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor> It mentions that we can determine the timing of the heating cooling cycles based upon the concentrations of trapped xenon isotopes. These cycles are controlled by the influx of water. Go hear, create a damn. Adjust the inflow of water. Use that as a way of high level Morse code. Unfortunately you have to go back 1.7 billion years. Alternatively, make trees like this of several distinct genetic varieties that are self-sustainable. [Creating wood actually as hard as granite](https://worldbuilding.stackexchange.com/questions/80103/creating-wood-actually-as-hard-as-granite) Put seeds of each of these inside of the time traveler. Eat them, stick them under the skin, or use any drug trafficking tricks. The trees will have to grow over a large area to ensure entering into the fossil record. Start at the west coast, grow a grove and start moving east planting different groves. If you go back with 256 different seed types, and then encrypt you message based off cross breeding 1 type with one of the 254 other types each grove contains 65,024 bits of information or approximately 8 kilobytes. Either option probably requires intense study/training before hand and an index/code book tattooed on their skin. [Answer] Paradox? Naa. If you haven't created the message yet, it won't exist yet. Your best bet is to determine a location based on a star chart. Don't try to use geographic locations. Like others have said, the geology will be unrecognizable. Agree on a location with your peers, it will limit their search area to a few thousands of square miles. I like the idea other have had of swallowing seeds that you will need to either create a message or sustain your life. But I imagine you will need to live a nomadic life to complete your mission. That said, others recommendations for message preservation sound like your best bet. But to improve the odds of mission success, they should probably send 10-20 people back with the same machine settings in hopes that at least one message gets through. Modern English is probably cryptic enough that if anyone found it, it wouldn't be decipherable, so coding wouldn't be an issue. I think the largest hurdle would be having the message intercepted by well meaning explorers before your team arrived. It is likely that the message would be found and kept in a private collection that they will never see. [Answer] Ask your scientists if they have heard of the *[Wait Calculation](https://en.wikipedia.org/wiki/Wait_Calculation)* and insist that you are being sent not until they have improved that other device (that will be used to rescue you) in a way to track your space-time location better than what they have now so rescue at any time is possible. [Answer] Since you are going to need to store the message in something that has a good chance of being reasonably intact tens of millions of years later. Given the immense amount of geological upheaval in the intervening time things like caves are probably out but we do know of somethings that have survived (relatively) intact - fossils. Unfortunately finding a specific organism that we know is subsequently fossilised and discovered is going to be essentially impossible (especially given you aren't going to have any fancy tech with you) but what you could do is play the percentages by *creating* your own fossils - lots of them. Start with the list of areas that would be survivable in the destination period, large chunks of the time period when dinosaurs were active aren't very friendly to humans but the late Cretaceous (~66 million years ago) should have dinosaurs and decent swathes of human-habitable climates. Then you need to narrow down that list to areas that have the right sort of conditions for fossilisation at the time you are heading for. This part isn't easy as with current technology we can only pin down fossil ages to about a 5% margin of error, which sounds pretty good - until you realise that 5% of 66 million years is *3.3 million years* so you'll probably want to do some hand waving around the time-travel technology vastly improving the accuracy of dating fossils. Now from that list you can pick your time and place and travel back. You'll have to be very accurate both geographically and temporally because navigating to a specific area once you're there is going to be nigh on impossible - the landscape is going to be completely different, even the stars are going to be pretty different! Once you've arrived you then just need to take advantage of the good fossilization conditions and create lots and lots of fossils that contain your message, carving the information into bones is a good bet, you can do it with minimal, improvised tools and it should hold up fairly well. Although it will be rather limited in how much you can convey and hiding what it is will be very difficult because paleontologists tend to look rather closely at fossils and there's no guarantee that the "right" people will be the ones to find one of your DIY ones. Then back in the present (future?) your organisation collects as many fossils as possible from the target area and inspects them all for any messages you left. I know you said in the OP to assume that you can survive but I think it's worth mentioning that survival is going to be the biggest challenge. Arriving naked with nothing to help you is going to present a serious challenge! Even the best wilderness-survival skills from the human era are only going to go so far - you'll have no idea what animals or plants you can eat safely and even getting drinkable water is going to take some effort. Add in the predators, insects, and the distinct possibility of pathogens to which you have zero immunity to and the odds of surviving more than a few days let alone being able to do any useful scientific observation and message writing are going to be pretty negligible! ]

[Question] [ I'm working on an idea for a novel and need to know roughly if this is possible. Ideally, the characters would be able to attach another submersible (usually used for rescue) onto the sub in the modern day, and either use a hatch or cut through the hull to gain access to a still pressurized section. Within they find forgotten weapon cache etc etc... Could a cold war submarine that sunk about 50 years ago still maintain pressure within it? Would there be too much corrosion and pressure due to the environment? Would the depth make a difference? If it's barely possible that probably works to my advantage as the sub could collapse around them as they recover the item. If it's nowhere near possible I'll just have them use some sort of sub arm mounted cutter to cut into a section and the weapon can be in a sealed container of some sort. [Answer] It's even conceivable that all ballast tanks, vents and control systems were ***completely*** compromised, and so the sub sank with no attitude controls (bow planes & stern planes completely inoperative) but some of the crew stayed alive long enough to isolate the control room & conning tower base (equivalent to the bridge on a ship or surface boat) in the hopes of radioing for help... and then the radio went kaput. There would be the attendant corpses with the remainders of decomposition (since dried out) and all systems would be shot: the 50's and 60's subs used electrics and electronics (depending upon the years) to drive many (but not all) control systems. If they lost all batteries (and somehow miraculously *didn't* blow up - lead-acid batteries upon failure often evolve hydrogen which explodes in an oxygen-rich atmosphere with the slightest spark) and whatever super-high value super-secret asset they had quickly dragged through the various bulkhead hatches from the store-room to the control room whilst dogging the hatches behind them. Salvage access *could* occur through the conning tower base room, as that's massively reinforced and has two specific reinforced section axes (one circular cross along the sub's main axis and one perpendicular to that) and this would both be realistic and provide your "suddenly, a collapse began" plot-point: the seams which join the conning tower perp section begin to burst percussively (high drama as nearby bolts whizz by like bullets as the section deforms) as the entire sub is sitting on a protruding ledge in a mid-oceanic trench, *twelve meters **below*** its rated crush depth (they were typically intentionally over-engineered relative to stated specs, but as the production was so hand-labour intensive, real-world failure points were... unpredictable at best) so boy you get dramatic tension! This linked image is to a diesel-electric sub from roughly your referenced timeperiod: [](https://i.stack.imgur.com/C8UuT.jpg) Oh yeah - my bona fides: though I'm a tech writer who's never spent significant time in a sub, my father is an ex Royal Navy submariner. He was Sparker (Chief Electrical Officer) on a Royal Navy A-class submarine (*P 422* ***H.M.S. Anchorite*** - a Vickers-Armstrong build launched in '46) just after the Second World War. For them what cares about history: he had also been a war evacuee - one of the *thousands of children from the Channel Isles* sent to England days before the Nazi invasion of the Isles; we were the only part of the British Isles the Nazis ever occupied. [Answer] Absolutely! It's great that you said Cold War era. The Soviets actually made a [submarine with a titanium-alloy hull](https://en.wikipedia.org/wiki/Alfa-class_submarine) during the Cold War era. Titanium is highly anti-corrosive, strong, light, non-ferrous, etc. It's corrosion in sea water is only [slightly worse](http://www.ingentaconnect.com/content/sut/unwt/1996/00000021/00000004/art00005?crawler=true) than in air, meaning 50 years is no issue. With an intact hull, you only need to figure out why it sunk. Ballast tank issues and either propulsion or a dive plane problem would likely be necessary. With the history of Russian submarine accidents ([what we even know of](https://en.wikipedia.org/wiki/Category:Russian_submarine_accidents)) due to improperly trained crews and poor engineering, it isn't a far stretch to say that crew error was involved. Oh, and I forgot to mention that due to the extra strength from the hull material, these submarines could dive deeper, travel faster, and be less dectectable than their steel-hulled brethren, making them perfect for a mission including secret equipment or documents. A perfect fit! [Answer] So fun fact, because this question assumes Hull Integrity: When building the famous ride 20,000 Leagues Under the Sea for Walt Disneyland, Walt and his engineers had to figure out how to build a vehicle that could survive being partially submerged in water for years on end without significant renovation that required draining of the Lagoon. Since there was very little in the way of actual development in Submarines at the time, Walt Disney consulted with the then current contractor building the U.S. Nuclear Sub Fleet and wound up commissioning the company to build the hulls for the vessels in fleet. The ride, though popular, was abandoned in the early 90s due to concerns over handicapped access into the subs (there was none) and required extensive shut downs to near by areas to fully remove from the park, so the ride vehicles were parked in their garage and left with little known updating or major maintenance on the vehicles. Fast forward two decades when the initial discussion of re-purposing the ride to an updated Finding Nemo theme and one of the first discussions were the state of the ride vehicles. As Disney Engineers discovered, this was less of an issue than they had thought... they had been perfectly servicable with little investment even after all that time out of service. Even more amazing was that when Walt contracted the Navy's contractors, he was seriously investing in this ride for life. As it turned out, the contractor figured that the best way to build a boat that would mimic a submarine and could survive for long stretches mostly submerged underwater like a sub... was to basically build a sub, and they effectively constructed sub hulls with an operational life expectancy of a military grade nuclear vessel. The Subs in the currently operational finding Nemo ride are the same ride vehicles from the original ride (save a specially modified one with better Handicapped access) and have a life expectancy that will keep them in service for an additional 50 years of operational life expectancy from the early 2010s! To sum up, if you are going for a U.S. Navy sub and it was lost above the crush depth of the hull due to something other than a hull breach, than you should expect a perfectly intact interior once you cut in. As long as you have something to keep the water from getting into your breach AND you account for possible pollutants, it should be safe to enter and grab the cache. [Answer] The problem wouldn't be whether there was a pressurized section of the sub, it would be whether there is a **Depressurized** section. If the sub is submerged, that means that the pressure outside the hull is actually grater than the pressure outside (every 34' of depth being ~1 atmosphere of pressure). This actually is what is going to drive the problem, if there is a low pressure section, it will be lighter than a similar section that was at a higher pressure (Though it isn't really much different). They would really need a hatch, as any cutting would introduce the high pressure water. Depth wouldn't be an issue except for the magnitude of the outside pressure. As for rust, the real issue here is how good of a paint job the submarine had and whether it has been damaged. The paint can protect the metal from rust if it is a good paint with full coverage. The only question that would remain is why the submarine has been underwater for 50 years without either floating or having some kind of hull breach (maybe only some sections have flooded, while others remain in tact). [Answer] > > **Could a cold war submarine that sunk about 50 years ago still maintain pressure within it?** > > > ## No. Submarines are not designed to be left submerged for very long periods with no engines running and no power. Submarines are not designed to be completely watertight, like any ship or boat they are designed to let in water at a rate the bilge pumps can cope with. --- [Submarine Trim and Drainage](https://maritime.org/doc/fleetsub/trim/chap3.htm) > > In submarines as in all ships, a certain amount of water from various sources accumulates inside the hull. The most important of these sources include: > > > 1. Leakage at-glands around the propeller shafts, pitometer log, sound gear, periscopes, and similar equipment. > > > 438,000 hours of even slow seepage adds up to a lot of water. Even [modern nuclear-powered submarines](https://www.wired.co.uk/article/nuclear-submarine-astute) cannot remain submerged for that number of years. --- **Could pockets of trapped air could be breathable?** 1. Oxidation: According to [A View to a Kill - can you survive by breathing in air from a car tyre?](http://www.creative-science.org.uk/hollywood8.html): > > Every year people die when they dive down to explore sunken ships. They find trapped air in compartments and take off their masks thinking they will be able to breath. Unfortunately over time much of the oxygen gets used up rusting the ship's metal parts and what looks like breathable air may in fact be mostly nitrogen. Divers can easily suffocate because although the air is at the right pressure and feels comfortable to breath they actually get less and less oxygen in their lungs with each breath. > > > 2. Narcosis: Air is mostly Nitrogen. At depth, [Nitrogen is an anaesthetic](https://en.wikipedia.org/wiki/Nitrogen_narcosis), divers breathing it will die. **Could pockets of trapped air persist?** For submarines resting for decades on the deep ocean floor I think you may also need to take into account the solubility of oxygen and nitrogen in water at high pressures. [Answer] If the submarine is sunken, it means it has a solution of continuity in its hull, allowing waters to get in. It can be that, somewhere, pouches of air will be trapped. [](https://i.stack.imgur.com/Tk9El.png) ([source](https://www.timesofmalta.com/articles/view/20141217/local/divers-start-exploration-of-sunken-wwii-submarine.548649)) Corrosion will happen, however pressure would not be a big deal, since it will be hydrostatic. Also trapped air will be at the same pressure of the water around it. So, unless the corrosion pierces through the entire thickness of the hull where the air is trapped, it is possible that the air will remain there. However, since the corrosion will have at least weakened the hull, a minimum hit could lead to collapse of the structure. I would say that cutting through the hull after 50 years will be hazardous, and mechanical attaching point will be no longer usable. [Answer] Depending on how much real world you want a **concrete sub** could be a solution. No confirmed real examples exist, but they were rumoured to exist for years. There is an old article [here](https://web.archive.org/web/19990502194431/http://popularmechanics.com/popmech/sci/9812STMIP.html). While it talks about modern (circa 1990) subs it also says > > MOD knows about C-subs because they resemble an idea floated by German marine engineer Heinz Lipschutz in 1957 > > > There is what looks like an article about his ideas [here](https://www.newscientist.com/article/mg17323334-600-fantastic-voyager/) (subscription required) but it teases > > He even claimed the German Navy built a 7-metre prototype to test his theory > > > So C-Subs are at least conceivable as part of a cold war era submarine plot. These subs were designed to sit on the seafloor for long periods and fire up at traditional subs. They may actually have negative buoyancy and only be able to surface by moving forward (and up). I'd guess that a concrete hull would be less likely to leak and corrode than a metal one so you could easily explain the longevity. Of course, cutting through a concrete hull would be difficult but a [moon pool](https://en.wikipedia.org/wiki/Moon_pool) may be feasible if the sub was designed to sit there for long periods. [Answer] Seawater is quite corrosive. Any bare metal (which will likely be some sort of steel) will be vulnerable, although stainless alloys less so. Yes, it can be painted, and if the paint is good enough, will serve as a barrier against corrosion. But, anywhere you have moving parts like hatches, there is bound to be metal on metal with no paint protection. There should be lubrication - grease - which should offer some protection from the seawater, but it won't likely be an unbroken barrier. All of this is to say that after 50 years, chances are there will be some places where corrosion has occurred. The thing about corroding metals is that they take up (usually) oxygen from the environment to form oxides. These new compounds take up more space than the original metal - in other words, metals expand as they corrode. This can cause parts to distort out of shape, and the corroded (expanded) metal ends up exposing fresh metal to further corrode. So, things like hatches are likely to start corroding (bound to be gaps somewhere), which will cause them to distort, which will probably cause them to start leaking. Fast-forward 50 years, and there is likely little or no hermetic seal left intact anywhere aboard. Now if your sub sank in fresh water, the situation might be different. Fresh water isn't nearly as corrosive. ]

[Question] [ ## Disclaimer This seems a particularly stupid question, but the more I think about it, the less trivial I find it. Worldbuilding possess the most appropriate tags. It does not fit in physics-network usual problems, and we don't have a gun-enthusiast network that I know of (other than in a theoretical manner here, especially when we have to wipe out civilizations.). # Context (Edit 2) This is an explanation as to **why** I need such a specific information. I've been advised to do so by Revetahw to avoid a closure for being off-topic. I first abstained to write it as not to drown the question in too many information. You can skip to the next part if it does not interest you: > > You're still reading? Then hang on, cause you will need to handwave quite a few things. My main character is a mutant in a near sci-fi future. Among other things, he possess the ability to absorb shock. His body dampen more efficiently kinetic energy and actively transform it in another kind of energy. He is more resistant than a human, but not bulletproof. Thus, he needs to wear a costume made from magically-genetically-modified-spider silk. Thing is, spider silk reacts badly to heat, and albeit the enhanced silk is designed to withstand more heat, it's highly unadvised to stay near a fire. He is going to fight crime and military groups who may eventually use grenades. I need to know if I'm going to kill my character outright or not. Plus, I like being thorough in the non-"it's magical, just read on" aspects. > > > # Question How does a gun kill you? It accelerates a bullet to a supersonic speed by igniting powder in a controlled environment. The bullet shape allows it to impact you and focus its kinetic energy on a very restricted area, perforating the target (overly and deliberately simplified). TLDR, a fast bit of metal flies from the end of the cannon and punctures you. How does a grenade kill you? Some mean person throws an explosive device at you. When the thing goes off, the powder ignites and breaks the outer shell, sending shrapnel flying in every direction in a big **boom**. The boom is the part bothering me. Against small caliber, the most common protection is a bulletproof vest, one that does not rupture when the bullet impacts it, allowing it to spread the kinetic energy on to a wider area. You do not get perforated, thus you do not die (at least not directly). The suit of a defusing squad is far heavier and thicker and protects the whole body, not just the torso (but then again, why would you need your head?). **I'm wondering if there is more to it than just stopping all the "bullets"** (which shrapnel kind of is, just thrown all around). * Are the shrapnels hotter than a bullet from the explosion, thus impacting their penetration power? (A quick internet research indicates a small caliber round reach around 200°C, but the heat seems to vary a lot between the exit of the cannon and its eventual impact) Would that make the shrapnels burn their way through a regular bulletproof vest? * Is the blast from the explosion powerful enough to outright kill you, even without the shrapnel? I do need this kind of information for a worldbuilding purpose, and since I'm not too keen on using myself as a guinea pig, **I'd appreciate someone explaining to me what to take into account in case of grenade explosion, especially regarding their impact on usual protections in a gunfight.** PS: Keep in mind that I grossly simplified the interaction. I'm aware of the physics involved but in no way proficient in ballistics. I know how to operate a handgun, the way it works, but couldn't write the equations for the life of me. **PPS:** I think it's worth adding a few things. I can reasonnably assume different types of grenades kill you in different manners. For the sake of simplicity, let's keep to fragmentation grenade (example used in the question) and concussive grenade (pertinent to the shock wave problem). I can make an educated guess at how an incendiary 'nade would kill you. (The answer is: *very unpleasantly*). Second, me joking about EOD having full body protections is merely to keep you awake during the long question. I understand someone wearing a bulletproof vest can not always wear a full body protection cause they need mobility. Whereas an EOD capable of outrunning the shockwave seems pretty unlikely. (Note that I'm not implying that the vest guy will outrun the bullet, but will attempt to get out of the way). However, I was unaware of ceramic being used in body armor, and will look into it. [Answer] What a wonderfully macabre question! This calls for cited sources! First off, I'd like to point out that you are correct to notice the similarities between a grenade and a rifle round. Both have the same gross pattern: they set off some explosives near some metal that is going to be accelerated by the explosive. So if we start from that very simplified model, we can cover both the similarities and the differences between the two. ~~In both cases we start with a [detonation](https://en.wikipedia.org/wiki/Detonation). This is a combustion reaction which is fast enough to propagate a shock wave in front of it. The first thing we can do is contrast this with [deflagration](https://en.wikipedia.org/wiki/Deflagration), where the combustion proceeds slower than the speed of sound. In both grenades and modern firearms (which use a nitrocellulose based explosive typically called "smokeless powder"), the reaction is a detonation. However, in black powder based firearms from previous eras or lower quality improvised grenades, the reaction is a deflagration. I'll assume that we are interested in the modern military grade equipment, given the wording of your question, so if you're interested in the deflagration case, simply skip the sections dealing with the direct consequences of detonation.~~ (Thanks to all the commenters posting on this, I've had to do more research and issue a correction. Explosives [detonate](https://en.wikipedia.org/wiki/Detonation), which is defined to be what happens when a combustion reaction propagates faster than the speed of sound. The propellants in ammunition are designed to [deflagrate](https://en.wikipedia.org/wiki/Deflagration), which is burning with a flame front that moves slower than the speed of sound. My confusion was caused by the presence of supersonic bullet, which would clearly need to be propelled by something going faster than the speed of sound. The piece I missed was answered [here](https://physics.stackexchange.com/questions/458828/how-do-we-get-supersonic-bullets/458864#458864): the high temperature of the expanding gasses increases the speed of sound in that medium. Also, the speed of sound that matters is apparently the speed of sound through the material (the powder itself), not the air surrounding the powder. That speed of sound is much faster. Firearms designers use this deflagrating "low explosive" intentionally, for many reasons including the fact that this means their propellant cannot generate the shock waves of a high explosive, and thus does not need to be regulated in the way we regulate high explosives. I can go to the store and buy smokeless powder without any questions. If I went to the store and asked to buy C4, questions would start coming my way. Thanks to everyone for pointing out my mistake!) When you detonate an explosive, you create a shock wave. Shock waves are interesting little beasts. *If you want to skip the next few paragraphs on the physics of a shock wave, you can. However, I find its very helpful to understand what a shock wave actually is. That helps in understanding why the line between deflagration and detonation is such a big deal.* A shock wave is required because the simplistic laws of physics that we're used to break down. Usually we say that information about an object propagates ahead of it at the speed of sound. What this really means is that there are gas atoms which hit the object and are bounced in the opposite direction, traveling faster than the object itself. These eventually collide with other gas atoms, sending them scattering ahead of the object and so on and so forth. In normal every day circumstances, this process involves so many collisions that we can model it statistically. The result is that we can talk about "pressure" meaningfully, and we can talk about a "pressure wave" which propagates ahead of the object. All objects moving through the air have a pressure wave in front of them, though it is not always obvious. A fast moving modern car doesn't have very many insects striking its windshield because the pressure wave in front of it pushes the insects upwards over the windshield. An older car with worse aerodynamics may not generate a sufficient pressure wave to force the insect over the top of the car, and the result is... well.. messy. When we get to events that move at the speed of sound or faster. As this happens, our nice clean statistical model of the gas breaks down. In the nice clean model we're used to, we say that every small region has a "pressure," and it pushes outwards in all directions equally. This works because, over the distances between collisions (the "[mean free path length](https://en.wikipedia.org/wiki/Mean_free_path)," on the order of 68nm), the velocity of particles on both sides of the object are close enough to use easy statistical distributions. However, as particle speeds approach the speed of sound, this changes. The differences in velocity get more and more pronounced until we can't sweep the differences under the rug with a simple differential equation. We have to account for more of the actual particle physics in this regime. *If you're skipping the physics lesson, this is a good time to rejoin the answer* So why is a [shock wave](https://en.wikipedia.org/wiki/Shock_wave) such a big deal? Well when we account for the particle physics of objects at these speeds, we have to allow for what are basically discontinuities in pressure (modern measurements suggest a shock wave is about 200nm thick). The pressure can rise *almost* instantly. This matters because many objects, including human bodies, are very sensitive to sudden changes in pressure. Under normal conditions, such rapid pressure changes would call for an enormous amount of energy. However, if you can create a shock wave, you can create a rather large pressure differential with a much smaller explosive. So what happens when a shock wave hits the body? For the most part, it can pass through freely, but if we find regions where the speed of sound changes dramatically, these sharp pressure changes can do damage. The [primary effect](https://onlinelibrary.wiley.com/doi/pdf/10.1002/9780470938157.app3) of such shockwaves is on the lungs. This effect is dominated by the impulse of the explosion (generally proportional to the integral of overpressure over the duration of the shock). In the case of the lungs, this impulse imparts a velocity to the cells lining the alveoli. Because they are thin, designed to stretch as we breathe, and right along an impedance boundary between flesh and air, they are very susceptible to this. The result of this damage is the rupture of the capillaries in the lungs, called [pulmonary contusion](https://en.wikipedia.org/wiki/Pulmonary_contusion). This is what medical doctors would call "Bad News." The damage can cause the alveoli to collapse, no longer participating in breathing. It can also cause pulmonary edema, filling the lungs with fluid and causing suffocation. Other gas filled organs can be affected similarly, but in the literature, lung damage due to shocks is the primary issue. Ear drum damage also occurs in response to such shocwaves. Being thicker than the walls of the alveoli, they respond to slower effects. The damage to the ear drum appears to be more associated with the actual overpressure than the impulse of the shockwave. A [perforated eardrum](https://www.mayoclinic.org/diseases-conditions/ruptured-eardrum/symptoms-causes/syc-20351879) is typically not fatal, but it can cause sudden disorientation and vertigo. Given that one is in an environment where there are grenades and/or flying bullets, this disorientation can lead towards a fatal incident shortly thereafter. So this shows a major difference between grenades and bullets. In a bullet, the shock wave occurs quite far away and has rather low impulse by the time it arrives. The shockwave plays a very minor part. There is an argument that a supersonic bullet hitting flesh can generate its own shockwaves which can disrupt neural activity, known as [hydrostatic shock](https://en.wikipedia.org/wiki/Hydrostatic_shock_(firearms)), but it is a disputed theory. Thus we see a major difference between the bullet proof vest and the [EOD suit](https://en.wikipedia.org/wiki/Bomb_suit). You noticed that it covers the whole body, but it also covers it in a different way. The layers of an EOD suit are also designed to redirect and damp the shockwave. They do this using layers of varying acoustic impedance. EOD suits are also designed to protect in other ways, such as cushioning the spine so that an EOD expert thrown back by an explosion is unlikely to suffer catastrophic spinal injury. Now some grenades stop here. Concussion grenades like the [MK3](https://en.wikipedia.org/wiki/MK3_grenade) do their damage with these effects. A fragmentation grenade like the [M67](https://en.wikipedia.org/wiki/M67_grenade) adds a layer of metallic shrapnel. This shrapnel operates like a bullet. In fact, it is reasonable to model the effects of shrapnel exactly like we model the effects of bullets. Bullets are really straightforward. Shove a metal slug through someone's body, and you force the bonds that hold their body together to give way. If any of those bonds were critical, the opponent is incapacitated. Bullets come in supersonic and subsonic varieties. The fundamental difference between them would be that a supersonic bullet could cause a shockwave to propagate through the body. However, given that hydrostatic shock is a disputed theory, we can reasonably ignore that difference. Instead, we can just look at all bullets as the same sort of thing. Their damage is based on shape, energy, and momentum. Naturally, supersonic bullets can have substantially more energy, but other than that they aren't special. A bullet entering a wound basically generates (subsonic) waves, pushing the flesh out of the way of the bullet just like the air was pushed around our windshield in the car example at the beginning of this answer. This pushing effect can tear tissue, and that's the primary cause of damage from a bullet (or grenade fragment). If arteries, veins, or capillaries burst, blood loss will occur and may cause death. Damage to nerves can cause paralysis of the innervated region, and obviously damage to the brain can cause death. A bullet may break a bone, in which case those muscles can no longer effectively use that bone to create motion. It may also tear tings like tendons, which also prevent motion. If a bullet or fragment strikes any area, it may cause infection. This is a major factor in abdominal wounds. Our intestines are quite full of bacteria kept safely within the body of the intestines. If the intestines are torn, they will spill this material out, creating a substantial risk of infection. The kevlar and/or ceramics found in both bullet proof vests and EOD suits is focused on dealing with these objects. Both materials are very good at arresting physical objects before they enter the body. Bullet proof vests have a smaller coverage area because of tradeoffs. Those who wear bullet proof vests must move quickly and care about minimizing burden. Thus the vests only cover the regions where the lethality of a bullet wound warrants the burden of protecting it. In the case of the EOD suit, mobility is less of a concern. The EOD technician is already where they need to be (which would be the place everybody else doesn't want to be). They do care about mobility, don't get me wrong, but the tradeoffs for someone intentionally going to the wrong sort of place are different. It's worth it to them to have full body coverage. Which leaves me with a gem of wisdom I got from the comic [Schlock Mercenary](https://www.schlockmercenary.com/), by Howard Taylor. His The Seventy Maxims of Maximally Effective Mercenaries includes two which I am yet to find a veteran or active duty member who doesn't agree with, or at least have to give a nod at the wisdom of it all: > > 2. A Sergeant in motion outranks a Lieutenant who doesn't know what's going on. > 3. An ordnance technician at a dead run outranks everybody. > > > [Answer] The [M67 grenade](https://en.wikipedia.org/wiki/M67_grenade) contains 180 g (6.5 oz) of composition B explosive. The amount of explosive in a gun or rifle is way less than that, just few grams. It follows that, close to the explosion, the damage of a grenade is dealt both from the fragments ejected in all the directions and from the shock-wave produced by the explosion. When an acoustic wave propagates through different media, the amount of transmitted energy depends on the relative difference in acoustic impedance between the two media: the closer they are (i.e. water-flesh), the better energy is transmitted, else (i.e. air-flesh) it is reflected back in larger amount. The human body is mostly made by flesh but has also some hollow places, like the intestines, lungs and stomach. The interface between these and the flesh can be approximated, from an acoustic point of view, to an interface between air and liquid. The explosion happens in air, and when the shock-wave impinges on the body it is mostly reflected. But the amount which is transmitted through the body will be basically trapped between the outer shell (the skin) and the inner shell (lungs, stomach, intestine), wrecking havoc there. This explains why explosions are way more lethal in water than in air (there is less reflected energy on the skin), and why the effect of the shock-wave is the more significant the closer the target is to the explosion point (the intensity attenuates with the square of the distance). Incidentally, this is also why whoever gets an echo scan is spread with gel in the point where the scan is taken: to improve the acoustic coupling between the scanner and the body. [Answer] The shockwave from a fragmentation grenade is negligible. A concussion grenade, which has few fragments and which is specialized to kill directly through explosive overpressure, has only a 2m kill radius (<https://en.wikipedia.org/wiki/Grenade#High_Explosive_(Offensive)>. A fragmentation grenade has less explosives than that, and would deal very little direct damage through explosive overpressure. It is the fragments that deal damage. There really isn't more to this than stopping all the fragments. A grenade explosion is not a particularly impressive event. There is just a puff of dark smoke and a bang, not a huge explosion. There seem to be two misconceptions about body armor in your post. 1. EOD technicians do not necessarily wear better armor than regular soldiers. Most soldiers in modern militaries wear hard body armor made of advanced ceramic composites over their torsos, not kevlar vests. Kevlar and other types of soft, fabric like body armor can only reliably stop pistol caliber rounds and are not of much use on the battlefield. EOD suits are made of many layers of foam, plastic, and soft body armor. They absorb explosions and fragments efficiently, but are not necessarily better against bullets or other kinetic projectiles (depends if they include ceramic components). 2. EOD technicians do not only go after hand grenades. Many of the threats they deal with are much larger bombs that need more protection, so they wear more protective armor. Even if all they had to deal with was hand grenades, they would probably still wear their special armor. The majority of regular troops in the modern day see little to no combat, and even combat troops deal with grenades on an irregular basis. For them, covering all of the limbs and head in armor would restrict movement and breathing. However, EOD techs deal with explosives all the time, and expect to do so, so they wear armor to be prepared. (In reality, from what I have read, EOD techs typically try to shoot bombs with anti-material rifles or to disarm them with robots unless absolutely necessary).. [Answer] When you get right down to it, both a gun and a grenade kill you with application of the same attribute; **Energy**. The difference is only in the shaping of that energy. Guns fire a bullet in a specific direction, meaning that the energy (in this case, kinetic) is applied in a very narrow and precise focus. In effect, a bullet applies a **lot** of kinetic energy into a very **small** window of effect. That means that you can be standing right near a gun being fired, but if you're not staring down the business end of the barrel, it simply won't affect you at all. *This is a simplification; you may (for example) be hit by the casing ejection, and there is some waste heat as a result of the bullet being fired, but it's the kinetic energy of the bullet that really counts in terms of terminal damage.* A grenade on the other hand is what we call an *area of effect* weapon. It doesn't focus the kinetic energy, but rather distributes it radially. A frag grenade gets its name from the fragments of metal and other debris that get launched from the point of explosion. Radial blasts cause damage in all directions, but the range of effect is subsequently seriously reduced. Grenades, not requiring bullets et al are also capable of storing more potential kinetic energy than a single bullet, but most of that is going to be directed into places the enemy isn't. The difference between the two is that a bullet creates a massive impact along a very specific directional line and over a much longer range; a grenade can release more energy overall, but over a much smaller range because of the radial distribution of that energy. So; if you're standing right near a grenade when it goes off blowing shrapnel all over the place, it would be like being hit by a shotgun blast at close range; flak vests et al are going to be the order of the day in order to have any hope of survival. But, the further away you are, the much greater the chances of your survival by comparison to a bullet fired from a gun. I don't have exact figures on me, but at very close range grenades will probably have a similar kinetic energy release as what one could expect from a bullet at much further ranges. A grenade may contain (say) enough charge to fit in 50 bullets, and the fragmentation of the casing means that you're facing a fair percentage of that at very short range. But the omni-directional dispersal pattern of that energy means that the tradeoff is that the charge is used very inefficiently, unless your enemy has surrounded the grenade in all three dimensions with very close proximity. This is why they're often used to clear machine gun nests, trenches, and other fortified positions as opposed to being used in an open battlefield where people are more dispersed and more capable of avoiding the device when they see it. Ultimately, the key thing to remember is that the radial dispersion pattern means the energy dissipates at a rate proportional to the cube of the distance from the explosion with grenades, meaning that they are strictly a short range weapon, best deployed in tight, enclosed spaces containing only enemy combatants. Guns, on the other hand, are a point and click interface designed to work at range but only in the direction you specify. [Answer] One could say that a grenade kills you in the same way that a fall onto a hard-enough surface kills you. The (brief but) strong force from the blast/impact on the floor can deform the body up to a point where bones break and/or organs experience acceleration big enough to destroy tissue. Also, the shock wave may travel through the body and cause damage at places not directly impacted on. This is an effect that is also seen with projectiles (some more than others): A bullet is not like a small rod slowly piercing through the body but also causes shockwaves along its path through the tissue. These shockwaves can affect a much wider channel than the projectile itself. You could be hit by a 9mm bullet but have a 'tunnel' of destroyed tissue around the trajectory of multiple times that diameter. Then of course there are indirect causes of death: Even when the blast or the projectile doesn't kill you instantly, tissue, organs and blood vessels may be damaged causing you to bleed to death or die from some kind of organ failure within some time after the event. So I guess the main difference is really, as you said, that a projectile works by piercing into the body while a blast works by massive acceleration of large parts of the body. That's also one reason why the bomb squad uses as heavy an armor as is practical: A large mass can absorb more *energy* for a given *acceleration*. Hence, the heavier the armor is the slower it will move and hit your body in response to a blast. (The sequence of events here is detonation -> shockwave hits armor -> some energy gets reflected, some absorbed -> due to the absorbed energy the armor starts moving -> the armor impacts on your body's surface -> force is applied to your body. The slower the armor the less peak force is applied to your body.) [Answer] It all depends on how you use both tools. For instance it's much more difficult to club someone to death using a grenade than it is to use a rifle. [Answer] Okay so a quick simple answer that might help. As someone who is ex army(uk) and worked in both aerospace and for a civilian testing company I've seen a few different things. The way the bullet works on the body depends on the shape of the round as well as its calibre, there Are a huge number of other factors but we'll keep it simple. A 5.56mm round which is fired by the UK main rifle was not designed to kill, it can but that's not it's main function, it was designed to injure. The main reason for this is down to numbers, it takes 1-2 people to look after an injured person. In this fashion you actually create less casualties. The 7.62 round which is a NATO standard round is much heavier round and so creates a more devastating wound and is more likely to kill. Depending on the entry/velocity of the round bullets can go straight through, slow and stop in the body and can even ricochet off bone and end up in a different part of the body or leave in a different part. There are many different types of round and they all have different effects, a hollow point has a huge power and because of its shape, mushrooms and has a devastating effect( the US's number 1 home defence pistol round) but it is, in bullet speeds, quite slower. There are fragmentation rounds that essentially shatter and create shrapnel inside the body. As for grenades, it's not just the debris that kills, if you are close enough the pressure wave itself can kill. Think of all the movies where a grenade is thrown in a lake and suddenly fish start bobbing up. Generally these are killed by a pressure wave rather than the actual grenade shrapnel. [Answer] Not military but as long-term martial artist with military SF tastes, am widely-read. One thing I've read about choice of weapons in broad combat is sometimes it's about inflicting a *slow death* - you want opposing soldiers dealing with their own injured rather than clean kills. Fragmentation grenades are particularly effective in generating injuries which require time-consuming treatment due to insertion of many small fragments. So *another* way they kill is slow death through infection/bleeding. What I didn't notice in the answers above is discussion of the **speed of fragments**. This [explosive speed](https://fas.org/man/dod-101/navy/docs/es310/warheads/Warheads.htm) paper as cited in Quora answer to [Do fragments from a grenade travel faster than a bullet?](https://www.quora.com/Do-fragments-from-a-grenade-travel-faster-than-a-bullet) puts the speed right in the middle. *A quick search based on the initial velocity of a perfectly spherical fragment from the composition-b explosive of an American M-61 fragmentation grenade yielded 480 meters per second. This is higher than the initial velocity of most pistol cartridges- .45 ACP and 9x19mm parabellum cartridges from pistol-length barrels fall about 10–30% below this, including +P and +P+ variants, and about 50–60% of a 5.56 NATO cartridge fired from a rifle-length barrel.* So you can regard a frag grenade up close as a bunch of tiny, mid-range bullet impacts **plus** overall explosive front. Having read your spoiler, that gives you some interesting things to consider about responding to multiple impacts and distributed, focused point impacts vs one big one ;-) ]

[Question] [ Far away, across the vastness of space, lies an alien civilization, who are pretty similar to us. They've got ice cream, peer to peer networking, and photography. More importantly, they do lots of their communication with radio waves, just like us. However, we don't know that they're there, because they are simply *too far away.* If our aliens have colonized a few planets, but each has a total power output within an order of magnitude of the power output of Earth, how far from Earth would they need to be in order for us to have not noticed them yet? They have yet to start building Dyson spheres or harvesting solar energy en masse via satellite, so we won't be able to use their technology blocking out sunlight as a means of detection. The aliens have been using modern technology for long enough that any transmissions they've made have reached us, and they aren't doing anything to either hide their presence or to advertise their location. Their technology at the point at which we are observing them (so offset by a number of years equal to the distance to their planet in terms of light years) is all near-future technology. [Answer] *For the TL;DR, see the bottom of the answer.* See also [What would it take to get a message to another star?](https://space.stackexchange.com/q/38116/415) on Space Exploration SE. --- We can approach answering this by considering how sensitive our most sensitive receivers on Earth are, how much antenna gain we can muster, how much power we can muster, and how much power needs to be transmitted for us to be able to detect the signal at interstellar distances. For simplicity, I'll just ignore the cosmic background radiation. In effect, this answer establishes an upper bound on how far away from us a civilization similar to us could be and we would be able to detect them. The way to approach that is to construct a [link budget](https://ham.stackexchange.com/q/352/29) for the transmission system and distance in question. The first thing we need for that is the equation for free space path loss, which is $$ 20 \times \log\_{10}\left( 4 \pi \frac{d}{\lambda{}} \right) \approx -22 - 20 \times \log\_{10}{\left(\frac{d}{\lambda}\right)} $$ where $d$ is the distance and $\lambda$ is the wavelength (where $\lambda = \frac{c}{f}$, where in turn $c$ is the speed of light in the medium and $f$ is the frequency). When $d$ and $\lambda$ are in the same units, the resultant value is the path loss in [decibel (dB)](https://en.wikipedia.org/wiki/Decibel). Notice that the path loss scales with the distance in terms of wavelengths, so if you double the frequency (halve the wavelength) and halve the physical distance, the path loss is identical. On Earth there are other propagation modes as well (ionospheric, parasitic radiation, reflection, scatter, ...) that make calculating path loss far more complicated; however, for anything between different celestial bodies, this is the go-to equation for approximating path loss. It is only an approximation because it does not take into account for example losses in the [interstellar medium](https://en.wikipedia.org/wiki/Interstellar_medium). For a reasonable frequency of interest, 3 GHz, the wavelength is 10 cm. 1 lightyear is, quite conveniently for our purposes, [about](http://www.wolframalpha.com/input/?i=1+lightyear+in+cm) $9.461 \times 10^{17} \approx 10^{18}$ cm. $\frac{d}{\lambda} = \frac{10^{18}}{10} = 10^{17}$ so we [calculate](http://www.wolframalpha.com/input/?i=-22+-+20+log10%2810%5E17%29) $-22 - 20 \times \log\_{10}{\left(10^{17}\right)} = -22 - \left( 20 \times 17 \right) = -22 - 340 = -362$. Over 1 lightyear, our path loss is approximately 362 dB. For a more realistic example, let's take [Proxima Centauri at about 4.25 lightyears](https://en.wikipedia.org/wiki/Proxima_Centauri) from Earth; that gives us a total path loss of $-22 - 20 \times \log\_{10}{\left(4.25 \times 10^{17} \right)} \approx 395$ dB. (If desired, substitute the distance between the worlds of interest and an appropriate frequency in your case and recalculate the path loss. If you change the frequency, don't forget to recalculate the antenna gain below.) Well, it's good that we now have a number, but what does that number *mean?* The [total worldwide electricity production in 2008](https://en.wikipedia.org/wiki/Electrical_power_generation#List_of_countries_with_source_of_electricity_2008) was 20,261 TWh, or if this were continuous (it probably wasn't) [about 2.31 TW](http://www.wolframalpha.com/input/?i=20261+twh+per+year+in+tw). Let's say we could somehow channel all of this into a transmission at 3 GHz (we almost certainly can't; even if we wanted to, there are efficiency limitations in real-world radio amplifiers, and with a really impure waveform, we might only be able to get maybe 90% efficiency in an amplifier which means we need to set our [hair dryer](https://what-if.xkcd.com/35/) to its 231 GW setting). The remaining about 2 TW is about +153 dBm. (If you compare this to the [Arecibo observatory](https://en.wikipedia.org/wiki/Arecibo_Observatory#General_information), you'll notice that the figure quoted by Wikipedia is an order of magnitude higher at 20 TW on the very similar frequency 2380 MHz. However, that's EIRP, which adjusts for antenna gain, while we are talking raw transmitter output power here. We'll get to antenna gain in a minute.) A really good receiver, including a [low-noise amplifier](https://en.wikipedia.org/wiki/Low-noise_amplifier), might be able to detect a signal that measures something like -200 dBm at the antenna feedpoint terminals. The exact value varies with the receiver design and desired [transmission rate](https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem), and I'm not completely sure what the state of the art actually is, but -200 dBm is likely close enough for our purposes particularly if the purpose is to simply *detect the presence of* the signal. The really nice part about working with these numbers in dB relative to something (such as dBm, which is decibels relative to a milliwatt, or dB, which is just a ratio) is that we can simply add the numbers. If we feed that +153 dBm signal into the -200 dBm noise floor receiver, we have a margin of 353 dB for as long as we don't blow out the receiver circuitry (which would happen pretty quickly, but let's ignore that for a second). The [gain of a parabolic antenna](https://ham.stackexchange.com/a/5991/29) (which Arecibo isn't, really; [Arecibo is a spherical](https://en.wikipedia.org/wiki/Arecibo_Observatory#General_information), not parabolic, reflector) is $$ G = \frac{4 \pi A f^2}{c^2} e\_A $$ where $A$ is the reflector area in square meters, $f$ is the operating frequency in Hz, $c$ is the speed of light in m/s, $e\_A$ is the aperture efficiency (defined as the ratio of [effective aperture](http://www.antenna-theory.com/basics/aperture.php) to physical aperture, or $\frac{A\_e}{A\_p}$), and $G$ comes out as a multiplication factor describing the antenna gain over an [isotropic antenna](https://en.wikipedia.org/wiki/Isotropic_radiator) (an antenna that has exactly the same sensitivity in all directions; no real-world antennas have such a radiation pattern, they are always somewhat directional). A good parabolic antenna [might have](https://ham.stackexchange.com/a/3644/29) an aperture efficiency in the 0.8 range, and I've seen (but can't seem to find again) a mention of 0.55 for poor ones. Because this is about interstellar communications, we'll use the best antenna we can reasonably muster, so let's call the aperture efficiency 0.8. To give you an idea of its size, the [Arecibo dish is](https://web.archive.org/web/20090328003807/http://space.com/scienceastronomy/astronomy/arecibo_profile_000508.html) 305 meters in diameter and weighs 900,000 kg. It's the largest single-aperture telescope in the world. At 3 GHz, a 305 meter diameter parabolic dish with an aperture efficiency of 0.8 has a gain of $$ G = \frac{\left( 4 \pi \left( \pi \left( \frac{305}{2} \right) ^2 \right) \right) \times \left( 3 \times 10^9 \right) ^2}{\left( 3 \times 10^8 \right) ^2} \times 0.8 \approx 91811992 \approx 80 \text{ dB} $$ when compared to an isotropic antenna (EIRP gain). If we assume two Arecibo dishes pointed directly at each other, we can add another two times 80 dB of antenna gain to our link budget, so we get a bonus 160 dB for only a tiny difficulty in aiming (as anyone who has tried to aim a satellite dish can attest to; a household satellite dish has gain far lower than 80 dB at its frequency of interest). Here we can also see that even an antenna with a 1.0 (best theoretically possible) aperture efficiency wouldn't increase our gain by very much; such an upgrade would gain us another almost exactly 1 dB on either end. So, **to summarize,** we are putting out +153 dBm, gain 80 dB in antenna gain, lose 395 dB along the way, gain another 80 dB in antenna gain, and need at least -200 dBm after all that for the signal to be detectable. Luckily, we are now at -82 dBm, so *given these assumptions*, the signal is **well within the range of detectable**. (In fact, I think my amateur radio transceiver could pick it up without much trouble, given an appropriate frequency downconverter. Of course, and perhaps thankfully for peace in the neighborhood, I don't have the Arecibo dish in my back yard.) However, **those are quite some assumptions that we are making in order to reach this conclusion.** Basically, what we are doing is pouring *the whole world's electricity production* into *the biggest radio antenna we can muster*, expect the receiver to have *an antenna just as large* and that they are *pointing it directly at us and are listening to just the right frequency at just the right time*. Remove any one of these, and the signal goes from *trivially detectable* to anywhere between *difficult* and *not a chance*. The problem is exacerbated if we want to not just *detect the presence of the signal, but also understand its content*, at which point we start looking at noise over a larger frequency span and ultimately the [Shannon-Hartley theorem](https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem), which gives a theoretical limit for the transmission rate of a communications channel of a given bandwidth and signal-to-noise ratio. Our terrestrial systems aren't really designed to be decoded at interstellar distances because, [as pointed out in a comment to the question](https://worldbuilding.stackexchange.com/questions/39571/how-far-away-would-an-alien-civilization-need-to-be-for-us-to-not-notice-them#comment111876_39571), companies like television networks and cell phone providers aren't really interested in Earth-bound investments in their Proxima Centauri viewership and customers. For a real world comparison, [SETI Sensitivity: Calibrating on a Wow! Signal](http://www.setileague.org/articles/calibwow.htm) from the SETI League indicates that [the Wow! signal](https://en.wikipedia.org/wiki/Wow!_signal) was received (in 1977, on 1420 MHz) on equipment that had a noise floor of -138.6 dBm (we are almost certainly doing better than this today) plus 55.3 dBi (dB over isotropic, or EIRP gain) antenna gain. Even if we would use such a receiver rather than our postulated -200 dBm receiver, but still use the Arecibo dish on 3 GHz, we "only" lose about 61 dB compared to the calculation above so we still have a margin of over 20 dB to the noise floor, which is quite decent and is going to stand out in any signal strength plot. (The Wow! signal peaked at about 30 times the ambient noise, equivalent to an about 15 dB margin. 20 dB means that the signal is 100 times the strength of the noise.) As of September 2016, the Chinese are putting the finishing touches on what has been termed the [five hundred meter aperture spherical radio telescope, or FAST for short, nicknamed Tianyan (天眼)](https://en.wikipedia.org/wiki/Five_hundred_meter_Aperture_Spherical_Telescope). While Arecibo has a 305 meter diameter spherical cap reflector, FAST has a 520 meter diameter spherical cap reflector ([Five-Hundred Meter Aperture Spherical Radio Telescope (FAST) Cable-Suspended Robot Model and Comparison with the Arecibo Observatory, Ohio University](http://www.ohio.edu/people/williar4/html/pdf/FAST.pdf), section 1) of which 300 meters is illuminated at any one time ([The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) Project, Rendong Nan et al, arXiv:1105.3794, doi:10.1142/S0218271811019335](https://arxiv.org/abs/1105.3794), PDF page 4 in the arXiv version). As such, it does not have significantly different properties as an *antenna* as compared to the Arecibo main reflector in situations where either can be used. # Scientific treatment of reception of incidental transmissions (By "incidental", above, I am referring to those transmissions not actually aimed into space for the explicit purpose of being detected by an alien civilization.) It appears that this has actually be discussed in proper scientific fora. For example, [Rob Jeffries' answer on Astronomy SE](https://astronomy.stackexchange.com/a/10638/525) on how we would detect an Earth doppelganger planet quotes [Cullers et al. (2000)](http://adsabs.harvard.edu/full/2000ASPC..213..451C) as stating that > > Typical signals, as opposed to our strongest signals fall below the detection threshold of most surveys, even if the signal were to originate from the nearest star > > > and [Tarter (2001)](http://adsabs.harvard.edu/abs/2001ARA%26A..39..511T) as stating that > > At current levels of sensitivity, targeted microwave searches could detect the equivalent power of strong TV transmitters at a distance of 1 light year (within which there are no other stars) > > > In other words, an alien transmission would need to be far stronger than a current, powerful Earth TV transmission, for us to be able to detect it with currently available equipment. There aren't a lot of transmissions that would meet this criteria. # TL;DR: **To detect the radio transmissions of a civilization outside of the solar system is absolutely possible, but realistically does take deliberate effort, helpfully at both ends.** We won't be picking up anyone's cordless phone. Nor will we be picking up anything like our own cell phone networks, nor likely our Earth-bound point-to-point radio links. We *might* be able to detect the presence of an EM radiation spectrum that does not match either the cosmic background radiation or what you would expect from natural processes in a solar system. However, if they aim a powerful transmitter in our direction for some reason, and we happen to be listening at just the right moment on just the right frequency, then we *probably would* detect it. [Answer] We wouldn't notice a terrestrial civilisation at Alpha Centauri, the closest star. Radio and TV transmissions attenuate too quickly. [Answer] Here is a [press release](http://www.breakthroughinitiatives.org/News/1): > > # Unprecedented scope > > > The program will include a survey of the 1,000,000 closest stars to Earth. It will scan the center of our galaxy and the entire galactic plane. Beyond the Milky Way, it will listen for messages from the 100 closest galaxies. The telescopes used are exquisitely sensitive to long-distance signals, even of low or moderate power: > > > * If a civilization based around one of the 1,000 nearest stars transmits to us with the power of common aircraft radar, Breakthrough Listen telescopes could detect it. > * If a civilization transmits from the center of the Milky Way, with any more than 12 times the output of interplanetary radars we use to probe the Solar System, Breakthrough Listen telescopes could detect it. > * From a nearby star (25 trillion miles away), Breakthrough Listen’s optical search could detect a 100-watt laser (energy output of normal household light bulb). > > > Since this project has funding to listen to signals from other galaxies, I presume the reasoning is sound in thinking that such a signal would be physically possible and a reasonable thing for an advanced civilization to emit. I think the live talk (SETI siminar colloquium) indicated that it would be able to detect *us* at 200 light years. # Insterstellar Laser Communication I can't find the talk again, but I recall it being shown that a laser "only" 10× more powerful than one being worked on would provide for practical insterstellar communication with 8 meter mirrors on each end. The interesting thing here is the use of pulse lasers. The intensity of a pulse is far higher than the average power consumption. And, even though the brightness at the detector is lower than the background, the specific pulse cadence can still be detected. This requires looking for such pulses if communication has not yet been established, and is highly directional. # Don't pay for the transmitter In *The Hercules Text*, the aliens used a shutter to form a signal using a visible pulsar. Look at the "starshield" designs for a near-future telescope to image extra-solar planets. If you could get something in the line of sight between a target civilization and a pulsar or other star visible to them, it would not need to be very large to be effective. [Answer] Radio and television signals from Earth would have degraded sufficiently due to both the inverse square law and being absorbed by the interstellar medium that they are effectively impossible to make out from the interstellar noise. Various sites I've looked at seem to think that the effective range of Earthly radio signals would be only about a few light years. Perhaps worse, since we are switching over to much more efficient means of transmission (digital, fibre optic cable, satellite downlinks) the amount of radiated energy is much less than before. The hypothetical aliens might be able to see a blast of analogue radio noise coming from Earth starting in the 1940's and tapering off in about the 1970's, but tis would register more as a spike of energy rather than coherent signals, and alien scientists would have a hard time determining what really caused this. So unless the aliens are actively sending signals with high power transmitters and focused in relatively narrow beams at the Solar System, we would probably not be able to detect anyone farther than a few light years away. [Answer] The time since they have radio, in years, is the minimal distance in lightyears. Simply their transmissions, traveling only at the speed of light, did not propagate here yet. So not that far, in a galactic scale. 200 lightyears could be plausible. [Answer] Depends on what you mean by notice, but I'd say ~125 years because that's all the longer we've been listening or looking with instruments powerful enough to see anything worth seeing. [Answer] Until [recently](https://en.wikipedia.org/wiki/Chinese_Lunar_Exploration_Program), the distant side of the moon would have been far enough. ]

[Question] [ Birds, as we currently know them, build nests and lay eggs on the ground. People and *things with sharp teeth* live on the ground. There are also things with claws and beaks up in the air, but fewer. **I was wondering if a bird-like animal could exist that would spend its entire life in the air**, and only fall to the ground upon death. I already know that birds can sleep while airborne, but I need help with: * Figuring out a way to explain how my birds (or bats, or whatever) evolved to never touch the ground - I lack a compelling and plausible story. * The food situation. Unless I also got flying plants (unlikely, given the energy equations), it'll have to be a carnivore preying upon other flying creatures, or grab animals from the ground. * More specifically, I'm worried about the first stages of life. Perhaps a kangaroo like-pouch for the newborn? * Finally, I'd prefer to make this flying beast **as large as possible** for story-related purposes. How big can it get and still fly around the clock, do you think?  *(Image above: [Northrop](http://en.wikipedia.org/wiki/Northrop_Grumman) still makes the best Quetzalcoatli)* *LATE EDIT: Thanks everyone for a great number of good suggestions! All your answers are appreciated, and I wish I could accept two more in this case. Besides @**VilleNiemi**'s answer, which I accepted, I think @**Ivy\_Lynx**'s answer deserves more upvotes and I got some interesting ideas from @**CortAmmon** as well.* [Answer] ## Evolution Since the defining feature is not nesting on ground, the starting point should be the nesting behaviour. There should be a strong pressure to reduce time spent on the ground such as predators or competition for suitable locations with other species. This would favour a single very large egg that takes a long time to develop inside the female, but hatches fast once outside and learns to fly as soon as possible. Once the young hatches almost instantly once on the outside, the egg shell is replaced by live birth. The young would gain the ability to grab on the back of the adult so they can be moved away from danger if necessary. Once this is instinct gained at birth, the birds can give birth directly on the backs of their mates and skip nesting entirely. After this the birth size would start dropping as the time spent "nesting" on the back of an adult would be reasonably safe. But the size difference between learning to fly and being an adult would remain large, probably grow. ## Food The birds would eat fish. It is a reasonably reliable food source that supports large predators. And the winds over seas are much more stable and predictable than over terrain, which would be a major factor for large birds that **never** land. ## Size Adult birds would have to be quite large for this to make any sense. [The actual possible size is difficult to estimate. Especially the mass.](http://en.wikipedia.org/wiki/Quetzalcoatlus#Flight) If we assume the species is communal with young adults using powered flight while full adults simply glide and allow young ones to rest on their backs in exchange for the food... Big. This would actually make sense for a species with such **odd** nesting behaviour. You might end with four age categories. **Nestlings** that live on the backs of their elders until the grow enough to fly. **The young** that can fly, but are still immature sexually and learning how to catch fish. These would still rest on the backs of their elders. They'd also go from needing to be fed, to providing food for their siblings and elders. **Adults** would be sexually mature and responsible for reproduction and most food gathering. **The elders** would provide wide backs for use and help other fliers remember that trying to eat the grandchildren of something that can swallow you whole is a bad idea. They'd probably go from being able to feed themselves to needing to have food provided for them. They'd also be the ones that would know the weather patterns and fishing grounds. The birds would be pretty social with a structure like that with complex social interactions and vocal communication. [Answer] Why not take a look at the *real-life* version of this: [Alpline Swift](http://en.wikipedia.org/wiki/Alpine_swift) It seems that the bird lives on insects, and drinks rain-drops. They can spend up to 6 months in the air and can even sleep on the wing. I think a few modifications to this bird will give you what you're looking for [Answer] Most creature designs, if anthropomorphized, can be thought of as a balance between seizing opportunities and fearfully avoiding mishaps. As a result, most designs are very flexible, adapting to new situations as they come. What you are looking for is a fearful one, which doesn't even try to land when there's an opportunity, so I would expect the design to show the classic sign of fear: rigidity. It would have more machine-like characteristics than organic ones, as it optimizes for an environment where not touching ground is more important than anything else. This means your bird will not necessarily look like any bird you or I have ever seen. Why have hips if you never plan on using legs? The big thing, as you mentioned, will be food. Staying close to the ground is a liability for a creature that is uninterested in landing, because it cuts down on degrees of freedom and puts the creature in reach of predators that are not afraid to leverage the ground to create a more adaptable shape. This creature is going to have to stay higher, perhaps in the jet streams or just below them (they are really gnarly winds for a living creature to deal with). I could see them functioning more like baleen whales, sifting food from the wind (like small bugs and other organic matter that got lifted high into the air). This is, of course, a very low caloric diet, so that will shape the rest of their lives, but by hanging out near places with strong updrafts like dust devils or even hurricanes occur, they may be able to eek out calories. In the name of conserving energy, the creature would have to evolve to some pretty extreme structures. The creature would need to be almost entirely flight-related or food-related hardware. In order to support the mass of a small brain, it might grow to giant proportions in segments, much like our [modern long distance fliers](http://www.flightglobal.com/assets/getasset.aspx?itemid=21718). As a bonus to you, this structure also suggests they should be huge, exactly as you want. Raising young is an interesting topic. The obvious answer is to take a non-rearing approach and just have them kick off thousands of little fliers, but that seems to be in conflict with the idea of them being large creatures hanging out in regions where its difficult for smaller creatures to fly. I think child-rearing may become a necessity. So how do we teach them to fly? Falling out of a nest is one thing. Falling a few thousand feet to the forbidden ground is another. The parent is going to have to help teach them, but how? My recommendation would be for them to have the aerial flyer's equivalent of a pouch: a set of muscular organs which can be used to create a mellow region of airflow for the young to learn in. If a youngling gets too aggressive and goes too far into the jetstream, one could use those muscles to change the shape of the airflow and drag the youngling back into safe harbor. For a twist, it might be interesting to have this "pouch" move over time. At first, the mother will want to know as much about airflow as possible, so she would want to keep it near the back, giving her time to sense the oncoming airflow as much as possible. She has to protect them against gusts. As the young grow, she could move it forward to give them a better sense of what the jetstream feels like without compromising her own aerodynamic integrity. The chaotic flow over a wing is important to organic flying... giving up control of it in order to give more free-flow style to the young would probably be a mistake. Eventually, the young may catch a surprise pocket, and be forced to leave their mother forever. Or, the young may stick with their mother until they are right out in front of the mother, in the free jetstream, only reliant on the mother to catch them when something goes wrong. At some point, the mother may simply bank, and leave them to their lives. [Answer] It seems that the view on the food problem usually looks at the sea, probably because we think of albatross and the like. To me, one of the most beautiful leaps of imagination on this question is Stephen Baxter's Evolution, in which he thinks of an air whale, a creature feeding on air plankton (a true thing actually, there are swarms of insects really high up). A summary is given on [this page](http://www.challengingdestiny.com/editorials/editorial22.htm): > > For example, Baxter invents an air whale -- a huge but very light creature that flies above most of the clouds, in the stratosphere. The air whale evolved from pterosaurs, getting lighter and lighter. Its bones are hollow, and it doesn't need a big brain since nothing much happens up there. It feeds on aerial plankton, and mates on the highest mountain peaks when its instincts tell it to. With wings one hundred meters across, it would have been magnificent to see. > > > However, it does land to nest. [Answer] I think any answer to this question really hinges on how earth-like you want your planet to be and how earth-like you want the rest of your fauna and flora to be. Since you don't place any restrictions on these, I'll take the liberty to assume these factors are tweakable in order to get our perpetually airborne creatures. The other answers so far are on the right track in my opinion, so this will be more supplementary than a different idea. # **Origins** The problem of explaining the evolution of a flier that never lands is twofold (I'm not a biologist :P): 1. Why *not* land? 2. Why remain in the sky? It seems like the same question but it isn't. ## *Why not land?* On the first point, you can avoid most land without being in the air (there's oceans, tall mountains, caves etc.). The usual dangers aren't sufficient: predators can be avoided through changing location, changing your place on the food cycle or changing the hours you look for food. Thus, there is something *far* more dangerous or detrimental that makes landing a guaranteed darwin award. Those that land die or don't have babies (or their babies don't survive). This could be because of starvation, predation etc. but I've already excluded these as insufficient dangers. It has to be something ubiquitous on land which is harder to adapt to than flying forever. I can't really think of anything ubiquitous enough that wouldn't be dangerous to all other life as well. It might be some temporary situation that lasted long enough for the adaptation of permanent flight (or just not ever landing on ground) but subsided far enough into the past to allow other life to re-emerge, leaving the fliers still in the air. Perhaps when *both* factors are combined there is sufficient motive to both avoid land and keep to the sky. Taking this into account, it may be possible to make predators a likely motivator - perhaps in the distant past, birds and fliers where so ubiquitous that land and water predators made them their main source of food, eventually making the ground and sea so dangerous that some of these creatures evolved to avoid that danger entirely. ## *Why remain in the sky?* In order to remain in the air perpetually, you would most definitely require an *ecosystem*. Whether that includes or excludes plants, it would definitely require at least one or two other species that have also adapted to perpetual flight. *Have the mythical [balloon-whales](/questions/tagged/balloon-whales "show questions tagged 'balloon-whales'") finally arrived?* Indeed, it seems Gilles' idea and the ancient worldbuilding tag may be the answer. If you have large balloon-whales evolve to slowly and perpetually roam the skies, they could be the symbiotic platform to allow *landing* without *grounding*. By virtue of being full of hot air, they could remain aloft while allowing comparatively smaller creatures to nest on their backs (or somewhere safer from the wind, unless the whale has some sort of triceratops head providing cover). These need not evolve from *actual* whales, just be creatures that can survive on air plankton and sunlight. They could have the temperament of sloths rather than whales, consuming air-plankton, insect and fumes as they float around (or swim in the air), taking advantage of strong currents to help them.  The creatures that nest on them would need to provide them with something, so perhaps they are small herbivores or omnivores (since meat is more efficient food) that spend the majority of their time in the air, but feed from the oceans or forest tops. Their droppings and leftovers are used by the balloon-whales to supplement their diet and energy requirements (or protein requirements, whatever). Given this arrangement, your large never-landing creatures could be sky-sharks. Like sharks, their offspring are born ready to fly and hunt. They feed on the smaller air-dwelling creatures, particularly by snatching them as they descend for food, in droves. With a sufficiently large wing-span, carnivorous diet etc. they could possibly sustain themselves and rest while flying. Many sea creatures sleep while swimming and some birds can sleep while flying so this isn't that far-fetched.  At this point, you can add sky-wolves etc. to create a more complete ecosystem (as well as other birds that regularly land as usual). # **Birth** At this point the answer is already quite clear: balloon-whales are born floating, the goblin-hawks on their backs are born on the backs of the whales and can grow strong enough for flight, assisted or not, before they make their first attempts and the sky-sharks are, like sharks, born ready. Of course, you could have offspring be born in flight and only ready enough to climb on to the parent's back and cling their until they're strong enough (which would require a long and flexible neck on the parent's side in order to be able to feed it, which is convenient here). As they cling, they learn. Pouches would work as well. # **Size** *Unfortunately I'm way too sleep deprived to get into research and math here, so I'll just make some wild guesses.* A large wingspan would most likely be required, hence the sky-sharks would have to be large. How large exactly would depend on atmospheric properties, the amount of food they get and how high they fly (I think). However, if we allow for some creative adaptations, perhaps their size can be increased. In particular, we know that planes are massive and heavy, but can still fly just fine and even glide. The requirement is speed (as far as I understand). If they can find enough strong winds, drafts and currents, have enough of a wingspan to take advantage of these to lose as little speed as possible and have some form of *propulsion* to compensate, it may be achievable. Propulsion could take the form of air sacs that fill up as they fly and are used as an afterburner. Or they could expel bowel gases. Considering we already have assumed balloon-whales that fly with the power of hot air, it isn't nearly as ridiculous as it would otherwise be to assume that the sky-sharks have a similar adaptation. Some sea-creatures use water propulsion (as in, not just swimming through water) and I think some microbial life does as well, so it is possible at least in ~~theory~~ fantasy. Perhaps they ignite it too :P.  [Answer] So here's where we can start: Some birds [(megapodes)](https://en.wikipedia.org/wiki/Megapode) are [*superprecocial*](https://en.wikipedia.org/wiki/Superprecocial), i.e. they can fly on the day they hatch. So you need a bird that can do this, but also give birth to live young. They could then be born in mid air and glide while the wings dry out. Other parts of the animal kingdom have species which lay eggs fairly closely related to those with live young (e.g. snakes, fish), so we could assume that live birth could evolve in your "birds" (massive oversimplification, but I guess we're not really discussing descendents of current earthly birds). After that if you want small, they could eat insects -- aerial birds such as [swifts](https://en.wikipedia.org/wiki/Swift) stay aloft except when breeding and live on insects. Larger insects there were [dragonfly-like insects with a 65cm wingspan in the carboniferous](https://en.wikipedia.org/wiki/Meganeura) could give larger birds. Bigger birds would still have to take food on the wing. They could perhaps live on the small, swift-like birds in my previous paragraph, or on conventional birds. Large birds over land tend to use thermals or updraughts to get lift (e.g. vultures); for this to work you could do with cliffs or terrain giving a strong temperature contrast -- a shoreline might work. Over the sea it's possible to gain [lift from local wind differences](http://www.elsevierscitech.com/newsletters/Aquatic/Albatross_Richardson_PiO.pdf) -- I've read something more recent but can't find it online. Size: a prehistoric bird [*Argentavis magnificens*](https://en.wikipedia.org/wiki/Argentavis) had an 8m wingspan! Unfortunately no-one was around to record its behaviour. The current largest-winged bird (the wandering albatross) [feeds at night](https://en.wikipedia.org/wiki/Wandering_albatross#Behaviour) and can therefore be assumed to be able to fly at night. If they use wind-shear- or wave-slope-soaring this will keep them aloft at night, as both techniques depend on the wind and not the sun. Soaring would appear to be a requirement for sustained flight of a heavy bird (also [Condors](https://en.wikipedia.org/wiki/Condor)). Your birds wouldn't be able to weigh much though -- the heaviest living flying bird is (or might be) the [great bustard](https://en.wikipedia.org/wiki/Great_bustard) at only about 20kg, while *A. magnificens* was estimated to weigh up to 72kg -- the same as a fairly small adult human. Birds' hollow bones are obviously a big help in keeping the weight down. How it evolved: live birth is tricky but it's evolved multiple times on earth -- just not in birds. Think about nest predators -- fast, agile but non-flying creatures that eat eggs and flightless young. Monkeys maybe. These would have to be quite fearless to snatch the eggs from under an incubating parent -- or perhaps devious (dismantle a nest from below), or armed with something dangerous enough to threaten the adult's ability to incubate or look after young. If you combine chronic pressure for nest sites, a quicker and quicker gestation may be selected for. A simpler solution would of course be to have the bird nest somewhere high up out of the reach of predators. [Answer] There is actually a videogame where you need to escort an egg that has exactly such a bird in it, [Amerzone](http://en.wikipedia.org/wiki/Amerzone). The bird in that game is even born in the air. The egg is basically a pouch with a thermal sail that hatches above a live volcano. The birds fall out, develop wings as they fall, and fly away, eating, mating and dying in the thermal drafts above the volcanoes of the Amerzone area. Their wings are said to keep growing after they die, and they are said to keep flying even after death. [Answer] Yes there is, The common swift (Apus apus) is a medium-sized bird, superficially similar to the barn swallow or house martin but somewhat larger. It is, however, completely unrelated to those passerine species, since swifts are in the separate order Apodiformes. The resemblances between the groups are due to convergent evolution reflecting similar life styles. The swifts' nearest relatives are thought to be the New World hummingbirds and the Southeast Asian treeswifts. Their scientific name comes from the Ancient Greek words α "without", and πούς, "feet". ἄπους, apous, meaning "without feet". These birds have very short legs which they use only for clinging to vertical surfaces (hence the German name Mauersegler, literally meaning "wall-glider"). They never settle voluntarily on the ground, where they would be vulnerable to accidents and predation. [Answer] In [*Saturn Rukh*](http://www.wikipedia.org/wiki/Saturn_Rukh), there is no ground so life forms had to evolve that way. The Rukh was large, as you can see in the cover depicted next to the human's space ship.  It has two brains, one for day and one for night. It is a filter feeder, and follows its food sources. [Answer] I created a species of flying creatures a few years ago. They're like a mixture of blimps and manta rays. They are shaped like manta rays, and have an air sack they fill with gases like helium using special gill like filters. They use the appendages by their mouths to catch other flying prey. These creatures also fly in swarms, with the females in the middle. The babies grow on the mother's belly in a special clear sack. This means the females have larger air sacks; so they can carry their babies. The babies learn how the males protect the females, see their parents catch food, etc. Once they are fully developed and ready to fly, they either puncture the sack, or spit acid on it to dissolve it. I haven't decided which. Life goes on (for everyone but the pufferpolyps). ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 6 years ago. [Improve this question](/posts/10939/edit) My hapless wanderer (let's call her Alice) escaped the [Wold](https://worldbuilding.stackexchange.com/questions/10669/how-would-an-intelligent-forest-control-and-direct-its-animal-minions) forest only to stumble upon a large, featureless and dusty plane, at the center of which lies Castle Morrow, a fort populated by mechanical servitors and a single live member of a rare cult of Chronos. Alice's ignorance of local custom and her natural inquisitiveness have predictably landed her in trouble (again), and now she must fight the human Chronos cultist. Since, as all females her age in her society, she's a 6-dan black belt martial artist, that would not normally be a significant challenge. However, there's the slight snafu that the Chronos cultist is **precognitive**, in that he can almost without fail predict Alice's every action up to 6 seconds in advance. He achieves this thanks to the Mind-machine-interface that links him to the Chronos Oracle AI, which has nanomachinery infusing the very walls, water, food and and even air of this cursed place, measuring almost everything that can be measured every nanosecond, and constantly updating predictions based on that. I would love to have Alice draw in the fight (the cultist is quite skilled in combat too), but I keep coming up with suboptimal solutions, that a rational and moderately intelligent precog would foresee and prevent. **EDIT**: I should probably specify that Alice is NICE, so she would prefer to avoid KILLING people if at all possible. **So, how can Alice defeat this precognitive warrior?** **LATER EDIT**: Lots of great answers, wish I could accept at least 3. My solution will likely be a combination of @MasonWheeler's ambiguous move answer and @Keith's quantum randomizer, with a sprinkling of @Samuel's paralytic poison caught by the oracle. [Answer] From [Brandon Sanderson's Mistborn series](http://brandonsanderson.com/books/mistborn/): The heroine, Vin, was fighting a warrior who had Atium, which gave him the magical power to see her attacks before she made them, and to react to them accordingly. It was believed that the only counter to the precognition of a warrior with Atium was to have Atium yourself, but Vin had used all of hers. But then she realized she could: > > begin a strike towards him that could be completed in two different ways, without actually committing to either one. He saw her about to make *both* attacks, but was only able to block one or the other, so he had to make a choice. She saw him commit to blocking that one and made the other attack, and so was able to get through his defenses and defeat him. > > > It's hard to see how "a rational and moderately intelligent precog" would be able to beat this strategy. [Answer] **Use poison.** If the poison takes longer than six seconds to take effect then by the time the warrior sees his own incapacitation looming, it's too late to change it. Make it a paralyzing poison, or one that interferes with the BCI (Brain Computer Interface), etc. There is nothing the warrior can do to avoid this. The warrior thought that the glancing blow Alice landed which allowed him a solid hit was a fair trade, until he realizes that's all she needed. I imagine this would make an excellent scene as the realization dawns on the warrior's face and he looks in horror at the small scratch he was just scoffing at. [Answer] Your description and comments seem to imply that Alice will not be able to overcome the cultist with any single sequence of attacks. So, she'll have to use a long-term strategy defeat him, where no six-second sequence of events gives Alice a clear advantage, but she gains one when they are all combined. In particular, she could use the **rope-a-dope**. This strategy, famously pioneered by Muhammad Ali against George Foreman in the [Rumble in the Jungle](http://en.wikipedia.org/wiki/The_Rumble_in_the_Jungle), involves a boxer allowing himself to take body blows while leaning against the ropes to absorb the blows and tire his opponent. In general, it means taking a defensive position and coercing the opponent to overextend or exhaust himself. Using this strategy is how Ali was able to beat Foreman, even though the younger and stronger Foreman was the favorite by at least 3-1. To start with, Alice should play it safe. Use quick, low-risk attacks where the opportunity arises, but otherwise keep her distance and focus on defense. Also, she should hold back a little, not showing the cultist the full range of her skills. If she keeps him on the offensive and successfully blocks or avoids most of his strikes, then she should be relatively unhurt by the time he starts to tire. As the cultist becomes fatigued, he will move more slowly. Eventually, he will slow enough that even with precognition, he won't be able to stop or counter all of Alice's attacks. A flurry of strikes should be able to get past the cultist's defenses. A precognitive fighter could fall victim to this strategy, because each successful attack he makes is an advantage to him in the short term, and he might not see the long-term risk. [Answer] While this question is fantasy-based, this answer is reality-based in that it doesn't require that the hero know about the AI at all until after the fight has started, if at all, and doesn't require any magic or unusual equipment. As a martial artist (a red belt/4th kyu in Shotokan karate and hapkido), I have fought dan-grade black belts. The difference is not as great as many people seem to think, and is on the order of perhaps a tenth of a second and the sheer variety of things that they can do and counter. Attack a high-ranked martial artist, and it is likely that - precognition or not - they will have experienced that attack before and can defend against it. On the other hand, I have scored hits against my sensei, who is approaching the rank described in the question, however it is a matter of probability, and the probability is that for the most part, I'll be hit more often than I'll score a hit. Also, I've fought dan-grade juniors (under 16) as a red-belt and below, and as an adult in my 40s, they aren't much of a threat - they can execute all the techniques better than I can, and they know more, but they can't string it all together for as long - they lose the plot after a few techniques, while I can keep planning and acting while they lose their concentration, so as long as I can hold off their initial attacks, I'm pretty sure I'll score. That's why there are age groups in tournaments. Now, depending on the skill of the chronos cultist - which may not actually be nearly as high as Alice's as he would have been relying on precognition to deal with similar ranked or lower ranked opponents, thus actually *reducing* his chance for independent learning - it may not actually matter that the cultist has precognition. The first likely option that I can see if Alice is indeed capable of defeating the cultist hand-to-hand is that the cultist runs away or surrenders immediately, having been told by the AI that he can't win, precognition or not. The second option is that the fight will take longer than six seconds. One of the exercises we practice involves fighting six to ten other fighters one after the other, ten seconds for each other opponent. During those ten seconds, there may be a lot of hits scored, or none at all, however fighting non-stop for that time can get pretty exhausting. In a fight between high-dan martial artists (or those who can *act* as if they were), there may be quite some time of exchanging ineffective and only mildly effective blows before the telling blow is scored. Unlike in tournament fighting, real fighting is not to the first touch. An opponent may score a hit that was *mostly* deflected. Also, there are rarely any breaks while the judges call out the scores. So, our two martial artists might be fighting for some time. In my dojo, black belt (0-dan) students must fight for ten *minutes* non-stop in grading. Can the Chronos cultist match that kind of endurance? It is unlikely, given that he'd probably win most fights in the first 6 seconds. He would probably have trained, but he would be training for strength, to get his blows out faster, rather than for the endurance to outlast an opponent, given that he'd be used to winning quickly, and any injuries he might take would be from faster opponents. So, the fight between Alice and the cultist (assuming it happens at all) would go like this: The pair square off and begin circling one-another. The AI tells the cultist that this fight won't be won quickly, but the highest order of probability to inflict impairing damage on Alice is to do X, Y, Z and so on, which the cultist dutifully does, immediately going on the offensive. Alice may or may not actually take any hits, but they'll probably be minor if she does at this stage, and she may score some similarly minor hits of her own. This rapid exchange of blows would continue for some time, potentially up to a minute, and all the while both fighters will be getting tired. At some point, Alice may realise that the cultist is predicting her moves before she makes them, and from that point onward, she would fight more conservatively and defensively, always keeping her defensive options open, so while the cultist may be told the best sequence of actions, they won't necessarily be good *enough* against the better martial artist However, Alice, having *better* training, would have longer endurance, and the gap between the cultist and Alice will gradually widen. Alice will begin scoring more and potentially better hits as exhaustion begins to slow the cultist more than it slows her. As Alice observes the cultist slowing due to exhaustion, she can begin going back on the offensive. There is a difference between *knowing* what an opponent will do, and having the ability to *counter* that opponent, and despite attempting all the correct counters, the cultist will take more and more minor and less-than-minor hits. Then, the AI will realise that in six seconds the fight will be over, with the cultist as the loser, *and there is no way out of this situation*, as the AI/Cultist lost *almost a minute ago*, as the cultist's level of exhaustion passed the point where victory or escape was impossible, however the ultimate conclusion took more than 6 seconds to foresee. As the AI has foreseen, Alice delivers the final, telling sequence of attacks that fells the cultist. [Answer] I would say information overload. He's still human. 6 second prediction is great if you want to avoid getting a bullet, a knife or surprise punch. You should never be surprised. However, you have to be pretty good to both plan a defense 6 seconds ahead AND execute it at the right time. Fighting against me would be easy to defeat, likely not even needing much in the say of prediction. But a highly trained marshal artist, can attack about 5 times (WAG) faster than I could, and likely keep it up. Knowing she's going to punch at your gut, kick at your head and try to sweep your feet over 2.5 seconds, leaves you with the option to pick which one to accept. The information coming in could distract from the actual combat happening, and unless he practices this type of fighting a lot it will eventually get him into trouble. On top of that by being able to react to a move before it happens, he is changing cause and effect, meaning that the attack predicted 6 seconds earlier might be changed in that time frame. Either things can change, or he will just know how it ends ahead of time. EDT: After rereading the question, I realized it was an AI with 'predictive' capabilities, calculating future events based on current variables. Not seeing the future, not reading minds. This leaves an opening I missed, at least I didn't take full use of it before. A really well trained hand to hand combatant isn't thinking about many of their moves, at least not like I would be. They are responding to stimulus in a proscribed manor, which allows for insanely fast reaction times. So the first item would be if 'Alice' knows several fighting techniques and at least one of them is not known to the AI, then by changing techniques she could really throw off the predictions. Especially if it is a new technique. Add that to just attacking fast and the human will fail enough to allow the possibility to lose. [Answer] Well, one major theme in video gaming (I'm an avid gamer) is that, even if you KNOW what your opponent is doing, if they have better skills, mechanics, and speed you still have a huge chance of losing. For example, map hackers in StarCraft II: they may be able to see your base, where your army is, etc. But if you have superior mechanics (you are more consistent with building your base, expanding, microing your units), you still have a good chance of winning, despite their superior knowledge. Obviously, if two opponents are equally matched, the one with superior knowledge wins. However, you say she is very good in combat, but that the cultist is "quite skilled too", meaning he is good, but maybe not as good as her. This would lead me to believe she could conceivable fight him to a draw just based on her superior mechanics and speed alone, even if he can predict her moves. Prediction means nothing if he just isn't fast enough to get out of the way of her fist as it speeds toward his face :) Edit: Also, you mention that the precog occurs not through telepathy, but through basically an AI that is reading the ENVIRONMENT and making PREDICTIONS about what will happen. This isn't exactly true precognition, as the AI can't READ HER MIND and know exactly what she will do. It can PREDICT, based on her movement patterns, etc. But really, it just means that the warrior would just have extremely good REFLEXES, not necessarily being able to KNOW exactly what Alice will do in the future. Furthermore, it stands to reason that the AI could predict incorrectly. Especially if Alice catches on to the fact that the AI is predicting her moves and she starts acting erratically on purpose. Just thought I would throw that in. [Answer] Seems to me that this is a standard game theory problem, like say rock-paper-scissors (RPS). If your opponent can predict your move in RPS, you will of course always lose. For that reason, one way to play for a draw is to always play randomly. For your scenario, Alicia therefore needs a technique in which the actions she is going to follow are simply not fixed in advance. The AI can not therefore plan counter moves. Now, depending on your setup, you need a way to achieve this. Firstly, Alice needs a way of fighting without moves being planned. Secondly, ideally she has a fully non-deterministic method of determining her actions - such as a handy quantum device flashing colors to which she reacts. More mundanely, this problem is related to cryptography. If the AI cannot actually read her mind, can she memorize a long non-repeating of keys to define moves? This is a bit like using a one-time cipher. And if she really wants to work hard, she combines the two. The current flashing color and memorized element in the cipher together determine the action to take. [This answer has something in common with that of Mason, but is obviously more elaborate.] [Answer] Overwhelm him by sheer concentration of firepower! If you throw a paralytic dart, he can duck. If you throw 10 paralytic darts in a cone-filling pattern, he can't duck. If he somehow manages to duck, he's probably standing on one leg, balanced in some hugely unlikely position. Just throw 10 more. He'll eventually tire of acrobatics. Perhaps he'll use the 6 seconds to grab a shield. Too bad. His shield likely can't cover both his feet and head at the same time. [Answer] Vulcronos mentioned it, but stamina. Suppose the cultist can predict every attack and block or avoid it. Suppose Alice has excellent reflexes and experience of sparring, so for practical purposes she can also block or avoid his attacks (she doesn't predict them 6 seconds in advance, but she does see them coming enough of a fraction of a second ahead to react). Note that although he can predict her attack 6 seconds in the future, he can't just step aside 5 seconds in advance and stand there while she spends 5 seconds winding up to punching empty air. Why would she do that, unless the precog magic also forces her to hallucinate him doing "what he would have done if he hadn't had the precog"? Her attack occurs in response to what he does during the period he precogs, so the prediction must be made on the basis of knowing what he will do too. So, having 6 seconds of precog also commits him to (6 seconds minus her reaction time) of his own decisions. As long as she knows to be super-cautious, and is significantly better than he is, then there can plausibly be *no* flaws in her defence that precog can exploit. If I go at a tank with a baseball bat it really doesn't matter whether I have precog or not, there is simply no move available to me that knocks a hole in it. If they start out in stalemate, then whoever gets tired loses eventually. If I'm fighting a heavyweight boxer, it doesn't do me much good to know *when* he's going to punch me. I'm still going to expend a lot of energy making him miss, if I can at all, and my best attempt at a guard will still leave me concussed in short order because I'm simply not strong enough to take a heavyweight's punch with my raised gloves, at least not reliably. But I can't box at all: this cultist is a lot better than me, so he needn't just get pummelled. The cultist won't know he's lost until 6 seconds before she makes a move that, despite his foreknowledge of it, he is simply too exhausted and slow to get out of the way of. He's a big man, but he's out of shape, and for her it's a full time job. It's also entirely plausible that straight off the bat she could perform some manoeuvre that defeats his physical ability despite his precog. I remember as a young kid trying to jump double sweep kicks from a friend who'd just learned them at karate or whatever. I *knew* they were coming, because he told me and did it pretty much the same every time, but I still tripped over him about 50-50 because I wasn't timing my jumps correctly. Naturally that particular move wouldn't beat the cultist, since I was only trying to jump both kicks for fun: to avoid them I could have stepped back. She'll need a better move. So maybe this cultist precogs himself flat on his back and her punching his lights out: what's he going to do with that information if he's already engaged with her when it arrives, 6 seconds before the end of a 7-second fight? [Answer] There are martial arts which actually target the kind of operation you need to defeat such a superior adversary. The key requirement is redefining "defeat your opponent" to mean "accomplish your goals" rather than "prevent your opponent from accomplishing theirs." This is likely met by your desire to have a "draw," so it should be along the lines you need. > > There is a legend of two great fighters who came to an arena. Neither had known their equal. Both fighters stood there, for two days and nights, motionless, looking for a weakness to exploit. After two days and nights, finding no weakness in the other party, both fighters saluted, and went their separate ways. > > > The opponent does not have infinite control over the world, even if it is infinitely observant within 6 seconds. If it exerts will over the universe (as all minds with agency do), you may oppose it with your will, accept the effects of their exertion, or a "third option." Consider an opponent which wishes to keep his punch moving forward. He is exerting some of his finite control to do so. If you were to push sideways hard enough, he would feel the need to resist your push to keep his punch on track. However, if your force is slight, he may accept your will and allow you to move his fist slightly to the side. After all, the punch is still on line. However, doing so has changed his structure ever so slightly. Now his muscles are no longer quite as aligned with the punch's motion. So you can apply a little more will, deflecting it further. If it isn't worth the expenditure of control to resolve this with his now off-axis muscles, it is in his interests to let this happen. Maybe he can still get a glancing blow. As long as it looks like he can get something (like a glancing blow) within 6 seconds, the option looks good to him. If you can give him nothing but oppertunities which are **good for you** and are **indistinguishable from "good for him within the next 6 seconds,"** he has no reason to oppose you, and you can go about accomplishing your goals. This would create a combat style which does not initiate strikes, as much as nullify them. It would appear that every incomming strike is responded to with a block or deflection, but no ground is given. Strikes would occur, but they would be done simply to "keep the balance," ensuring the precog cannot deliver a deathblow without failing to avoid a deathblow directed at itself. Eventually the precog *does* make a mistake, because it only has perfect information for 6 seconds. The rest of the future has to be predicted imperfectly, just like everyone else. If Alice can identify a mistake which comes to fruition more than 6 seconds from now, she calmly advances in to take a little control of the situation, and goes back to keeping the balance until the precog gives her more room. Eventually the precog will exhaust it options: all of its ability to control the world is dedicated to keeping hold of its other goals. (ex: it is remarkably hard to punch someone when your balance is so compromised that you need to use your arms to stay balanced and your opponent is not giving you an opportunity to regain balance) In the end, Alice does not "defeat" the Precog. She merely gives him as many opportunities to realize he doesn't need to fight her, and eventually takes her up on one of those opportunities. Consider that this is not as fanciful as it might seem. Have you ever entered an area (say, a bar), and immediately gotten a vibe that "this is not a good place to be." These vibes often occur minutes before things go bad, not just 6 seconds before. Thus an Alice that concentrates on those "vibes" could easily see more than 6 seconds ahead. --- *Just as an amusement for those who are familiar with famous computer vs human chess games:* 45 ... Qe3 46.Qxd6 Re8 (draw) > > "It turns out, that the position in, here at the end is actually a > draw, and that, one of Deep Blue's final moves was a terrible error, > because Deep Blue has two choices here. It can move its king here or > move its king over here. It picked the wrong place to step." > - [Game Over](http://en.wikipedia.org/wiki/Deep_Blue_versus_Garry_Kasparov) > > > [Answer] Six seconds may not be enough time for the precog warrior to see tactics being used by Alice. Much like chess, advanced martial arts is more about thinking ahead and placing the pieces (you and your opponent(s)) where you want them so that a final strike simply cannot be avoided. So like the answer from m t above, superior skill from Alice could win the day. [Answer] It doesn't matter if your enemey knows what you are going to do if they can't stop it. This is a particular problem in close range low reaction time fights. There just isn't much time to plan a counter attack that takes advantage of your knowledge. Also, anything the cultist does to counter Alice will change what she is likely to do. A lot also depends on exactly how good of a fighter and how strong the cultist is. Alice could attempt to wear down the cultist if she is fitter then he is or beat through his defenses if she is substantially stronger than he is. She could also plan a victory more than six seconds in the future. For example she could make it look like she is losing in order to lure the enemy near a corner to pin him down in, let him manuver her to the ground only to trigger an attack over her head using some mechanism she has. A pyrrhic victory is also possible, she could release a sleeping gas to knock them both out, assuming she will recover first because of her training or age, or that the afteraffect of the drug will take more of a toll on the cultist prediciton powers than on her. In an extreme case, she could threaten to do something that would kill them both, like release a killer beast or trigger the robots to cleanse the castle of all living things, (cultist always have murderous beasts or doomsday triggers lying around in their mechanical castle, right?) if they don't stop fighting which would give you the draw you want. [Answer] **Fake Out** The Warrior is still (presumably) somewhat human, with human-level data processing capability. So while the *Oracle* can predict almost everything Alice can do, it can't communicate literally every possibility to the Warrior - it has to pick and choose what it thinks is useful. For example, it's unlikely to tell the Warrior that Alice might end her backward flip by breaking out into the Macarena, even though it calculates that as a non-zero possibility. That would just be a waste of the Warrior's cognitive capacity and bandwidth - even if he can receive the information, he can't necessarily process and make optimal decisions off of it. So Alice's strategy should be to make a series of moves that are sub-optimal enough that they won't be communicated to the Warrior, and will eventually create an opening. She should also include occasional optimal moves to help the confusion. Preferably Alice would utilize a perfect random number generator to help her plan this assault, but I recognize that she's unlikely to have one on hand. The Warrior should be shocked by having something unexpected happen, which will create openings for her to exploit. The Oracle, of course, can recognize what's happening, but still has limited options. It can't communicate *every* possibility to the Warrior, or he'll drown in information overload. So it's mostly stuck - it can try to pick out some sub-optimal possibilities to communicate, but if Alice's attack is random enough it won't be able to successfully predict which moves she'll actually take. These unexpected moves will serve to narrow down the Warrior's future vision, to the point where he can only predict 1-2 seconds ahead. At that point Alice can check-mate him, where she's able to disable even with his perfect foreknowledge of her actions. [Answer] There are a plethora of ways Alice can defeat him, provided she is able to use more than just martial arts. Here are 2 examples: 1. Alice could set off a portable EMP, thereby knocking out the AI's nanomachinery in a radius far larger than her opponent can move in 6 seconds. Now that he's no longer precognitive, she can proceed to disable him with ease. 2. Alice could pull out her homing nano stun missile, which always unerringly finds its target. As it is impossible to dodge, it doesn't matter how much of an advance warning the cultist has - he will still be incapacitated. [Answer] Building on Nathan Reid's answer, Alice should attack the nanite swarm rather than the warrior. To do this, she needs to saturate her fighting clothes, wristbands, headband and shoes in a magnetic powder. As she strikes out at her opponent the powder will break free and cloud around her. Every time her opponent successfully strikes her, great puffs of the powder will billow up into the air. Then because of its magnetic properties, it will immediately collect around the tiny metal robots, effectively binding and blinding them. The longer the two humans fight, the blinder the AI will become. Can AI's get scared? What does an all-seeing AI fear more than blindness? How will your precognitive warrior react when in the place of its usual unemotional predictions, the AI starts screaming? There are problems with this answer. Most notably it requires that Alice who was recently ignorant of local customs, suddenly become extremely knowledgeable about the nature and source of the warrior's precognitive abilities. Secondly, this strategy relies somewhat on surprise which may be hard to come by within the domain of the warrior's kingdom. For if the nanites are really watching from everywhere in the kingdom, then the AI is not only fore-seeing but also all-seeing. The ability to know everything that Alice did during recent hours, preparing for the fight, is at least as strategically valuable as knowing what she is going to do in the next six seconds. To defeat these problems, Alice (or someone influencing Alice) must know about the precognitive warrior prior to her arrival in the kingdom, so that she can arrive with her fighting clothes already saturated in magnetic dust. If it were my story, I would leave her ignorant and make her new fighting clothes a unexplained gift from the Wold Forest. [Answer] ## What does it mean to see 6 seconds in future? Prediction is tricky - there are quite a few feasible ways how an Oracle can get, say, 90% correct predictions, or *conditional* predictions (If X, then Y) but if you assume 100% correct unconditional predictions then it means that all future is predetermined and unchangeable, therefore no strategy can change anything at all. In particular, it would be reasonable to have a precognitive warrior that predicts "ah, Alice will initially attack with a 'surprise' blow to my knee" or a warrior that predicts "If I try to attack from the top, she will block me in this particular way and then counterattack me in that particular way." It would *not* be reasonable to have a precognitive warrior that predicts "she will block me in this particular way and then counterattack me in that particular way, no matter what I do or say" - simply (unless everything, including the final outcome is already predetermined) because the future depends on his actions as well. His precognition of the future alters the present, and thus alters the future that he'd see. While knowing, guessing or noticing the opponent's next action is a very big advantage in combat, it's not a total advantage. This means that it is possible for the precognitive warrior to predict "ugh, no matter where I strike, she'll manage to block me in time anyway", and afterwards "ugh, in 6 seconds she'll do an attack that I won't be able to avoid - if I strike now, then I'll impale my self, if I dodge now to the left, then she'll strike me this way, if I try to block, then she'll follow up and kill me that way". In a more extreme example, if a precognitive warrior would be under a strategic bomber plane dropping its load in a place with no hard cover, all he'd predict was "In 6 seconds, I'm torn in pieces". [Answer] It doesn't matter if he can predict her moves unless he can counter them, and it doesn't matter if he can predict her defenses if he can't get through them. If I were in a fight with Mike Tyson, it wouldn't matter if I knew exactly when and where he was going to hit me - I'm not fast enough nor strong enough to do anything about it. If she can physically overpower him, she'll win. If she can't overpower him when he's strong, she'll need to exhaust him until she can. If he's too strong, she shouldn't attack him, but rather make him attack her and react to his movements. If she doesn't move until he does, then he can't predict her movements (short of predicting his own). [Answer] The "wearing them down" and "poison" strategies are both good answers, they are specific instances of the Checkmate strategy. This is the only way I'm aware of to reliably defeat a precognitive. Essentially you need to adopt a strategy where by the time he becomes aware of it it is already too late to prevent. A simple example for the fight might be to make a leg sweep - so he jumps into the air. As soon as he jumps though he's now exposed to another attack and unable to dodge until he has landed. In another example you might fire multiple bullets at once, arranged so it is impossible to dodge them all. The fan of darts mentioned in one of the other answers is an excellent other example. Essentially you start a sequence of moves that is more than 6 seconds long and where the trap is not visible until the sequence is already in process and where it is too late to stop it at that point. By the time they see the bullets coming, there is already nowhere to dodge. By the time they realize what the fan of darts is for it's too late. By the time the poison takes effect it's too late. By the time they realize they are getting tired it's too late. By the time they see the end of the sequence of blows they are blocking and realize they are about to be forced into a wall it's too late. If a chess grand master sees a check mate coming in 10 moves but there is no longer any way to prevent it then that knowledge does not help him at all. [Answer] An alternate option comes to mind. Though not as good as poison, it's more devious. Alice can capture one of the warrior's children. She then tells the warrior that if he does not surrender, she will harm the child. If he surrenders, she releases the child immediately, he will then pre-see that surrender will leave his child unharmed. [Answer] Okay, so far few suggestions have leveraged your intent to **end in a draw**, but that provides a cute advantage. Consider using a variant of the draw strategy that Star Trek's Data used in a game of [Strategema](http://en.wikipedia.org/wiki/List_of_games_in_Star_Trek#Strategema). In brief, since his opponent was more skilled, Data realized that the way to improve his odds was to intentionally play for a draw, since that is better than a loss. The game goes on forever because it is harder to stop a player intent on forcing a stalemate than it is to defeat a player trying to win. This, by the way, has validity in some games. I'm no chess player, but I believe there are many endgame scenarios in which this is a possibility. And precognition really does not enter into the picture. Consider, for example, that chess players are, in fact, both "precognitive" by your definition, because at all stages of play, the game is in a state that resembles many, many other games. Each player has had opportunity to study and all these games and has practiced many of them. That doesn't change the fact that for any potential configuration, each player can think a certain number of steps ahead, and with infinite computational power, a player could devise the ultimate unbeatable strategy. But unbeatable is not the same as winnable; in some cases, the best outcome for two sufficiently advanced opponents can only be a draw. Implementing this is up to you. Grappling? Simultaneously applied pressure points? The gist is that Alice can do something that is not strategic because it leaves her vulnerable, but as long as it results in a draw, you have accomplished a mission. Also, it leaves room for a rematch. If the stakes are higher (to the death?), she has to solve it differently. [Answer] It depends a little on your world setting and how fixed your future is. With reliable precognition and a deterministic future - you need something that by the time they've seen it, it's too late. Ways you could accomplish that: * something deceptive, that harms them without them realizing. They 'see' it, but they don't realize it's a problem. Poisoning them is one option, but you can't use a poisoned dart because it's still a weapon. You might need a contact poison, such that an innocuous looking touch becomes a weapon. (Poisons need not be lethal). * Something that you can prepare - a trap that you can't avoid within 6s. Something like a net trap - how far can your guy run in 6s from a standing start? Drop a net on him that big, and it doesn't matter where he runs, he's still caught. Or perhaps a corridor/portcullis trap - walks down the corridor, and then block entry/exit. Perhaps a tear gas grenade? By the time he sees you with your gas mask on in 6s time, you've already flooded the space with tear gas. * Something overwhelming - lots of attacks to fend off. A bill line, or multiple people with net/bola who are spreading out their attacks. [Answer] * The predictive warrior cannot be anywhere, so apply scorched earth tactic: start to destroy the walls, food, water outside predictive range (etc. shell the walls with explosives) until the nanomachinery fails. If destroying is problematic, use sensory blockage or overload: fog grenade, drive a huge herd of cattle into the place, pay some people to make noise or buy a really loud pet. A human is not able to sense everything so his AI will be useless. Pay several persons to make this from several sides. When the warrior shows up at one point, the persons retreat and try to entice the warrior to leave the AI range. * Continue until you have a clear path to the warrior or the warrior comes to you. Both options are inevitable. Move into the predictive range (so outside the sensory blockage or devastation). * Once you encounter the target, act surprised and attack him with something like a barrage of arrows. Because the target will be very likely still inside the predictive range, he will be pleased to show you how good the AI is working. * Feign panic and flee. What the warrior does not know is that you trapped the return path inconspicously exactly outside the range so that you can run normally. Another option is using a sharpshooter outside the range of the AI. * Either the warrior follows you and the (non-lethal) trap is activated or continue your path of destruction until the AI has nothing more to predict with and you are on equal footing. [Answer] Suru Michi Jiu Jitsu slogan: *Gravity Works*. Use your **environment** to defeat him. Find some stairs; catwalks that should have railings. Back'em into the wall of decorative spikes, an open pit of snakes, ect. In *Ninja Scroll*, > > the protagonist defeats a superior, blind swordsmen, by ducking underneath his friend's sword that went flying earlier and got stuck in a tree. It deflects an intended killing blow leaving him wide open. Didn't *'see'* that one coming did you? Likewise in *Star Wars*, emperor Palpatine could not foresee the cause of his own death, probably because it was *gravity*. > > >  As a last resort, challenge him to a battle of wits... and don't forget to brush-up on your iocane immunity. OK, I'm out of movie references -I'll let myself out. [Answer] Having done a bit of mock fighting, I would say in some cases this works. Shield fighting: that is bash shield against shield with leveraged blows. The object is to beat back and tire opponent. Six second precog wouldn't permit dodging the blows without retreating (or exposing to the sword in the other hand), and they're intended to be blocked so blocking perfectly doesn't really help. It's a simple technique that depends on superior stamina to defeat an opponent. [Answer] **Just be so damn dangerous that precognition doesn't help.** I'm in a room, my precognition tells me that in six seconds a bomb is coming through the ceiling. I start to flee the house, but the bomb's too big, the blast kills me. But Alice isn't a bomb. So, I'm in an arena with a lion, my precognition tells me that in six seconds the lion is going to attack. At every stage I know what his next swipe, slash or bite is going to be - but he's enormous, fast, and strong, my knowledge does no good at all and he kills me. But Alice isn't lion. So, there's an experienced boxer, I've never thrown a punch in my life. He tells me he is going to jab, cross, hook, and uppercut. He does so. He hits me with every shot despite my foreknowledge, because the skill gap is insurmountable. (Aside: I've seen it done) So, Alice just has to be that fast, that capable, that strong that all the precognition does is let the enemy have the dubious privilege of experiencing his death twice. [Answer] Maybe she can't? It sounds like you went out of your way to create an unbeatable warrior. So maybe she can't beat him in a fight? If she's so ignorant of the local customs she gets into this unwinnable fight, she probably doesn't know enough about the warrior to come up with a strategy to beat it. [Answer] One answer I haven't seen, is to simply not plan. Deadpool Vs Taskmaster as an example. The Taskmaster is a master combatant, he can memorize someones entire fighting style instantly. He's basically undefeated because of this. He knows what you're going to do before you do it. Unless you don't even know what you're doing. ]

[Question] [ I would love to shape my planet in a way, that allows me to have an extremely cold, icy desert, next to an extremely hot, sanddesert. By "next to", I don't mean a few hundred miles apart, with gradually equalising climate. I'm talking about a foot-march of, at most, 4-5 minutes between the two. Light a cigarette on the edge of the desert, be finished with it when reaching the icy desert. Both areas should engulf roughly 140.000-180.000 square miles. **Is there a way an area like this could form naturally, without humans fiddling around with stuff and without magic?** If there is no other way around it, I'd be willing to use mountains to accomplish that, but I'd like to keep both areas as more or less flat-grounds. You may choose the planet's positioning around a star of your choosing, its size, number of moons, all these shenanigans. **Edit:** as suggested, I'll place a couple more constraints to narrow the question down a bit: 1. He who makes it plausibly possible to get rid of the height-problem (only option being vertical distance as opposed to horizontal) will be awarded 10 imaginary upvotes from me! That does not mean, answers that encourage the vertical distance are not welcome. 2. Underground-systems should, if possible, only be used, if both areas are actually underground. That makes underground-systems useless, probably, but I'll let myself be surprised. 3. Tidal-locking of a planet, if usable for this question's purpose, is obviously allowed. 4. **These 2 Areas do not need to be habitable.** The rest of the planet should, though. [by people that evolved there, no visitors] 5. It does not have to be water-ice. Any ice that allows for this situation to happen is welcomed. Bonus points for ice that does not kill people that want to cross it. **Edit 2: Temperatures** You may assume temperatures as follows. *Icy Desert:* * in extreme cases dropping to -90 to -120 °Celsius. * should average somewhere between -60 to -70 °Celsius. *Border:* * anything that helps you (and therefore me) come up with a solution for the problem. *Sanddesert:* * in extreme cases rising to up to 80-100 °Celsius. * should average somewhere between 70 to 80 °Celsius. Should you have an idea that really could work, but needs small corrections on those numbers, add them to your answer, they'll definitely be acknowledged. [Answer] **Space Mirrors/Lens** You may be familiar with frying ants with a magnifying lens...If you don't focus to a point, but rather an area you'll get a spot that's warmer and a big area that is cooler. Focusing the power of the sun on a fairly small area of the world would increase the temperature of that area... if your world is naturally cold, these "artificially" warmed areas could well be but a short walk from the colder "normal" areas of your world. Imagine if the picture below is a lens miles across in geosynchronous orbit over your warm desert, but not quite as focused... so the surrounding part of the desert is constantly in shadow and slightly colder than normal for that part of the world, while the center is much warmer than average. An interesting side effect of this would likely be a constant wind blowing towards the hot region, as the hot air in the center rises it'll suck in the cold air from the surrounding region... which would like lead to some pretty exciting weather at the very center of the region. [](https://i.stack.imgur.com/dFUsY.jpg) [Answer] # Yes As long as you're happy to spend those 4-5 minutes travelling nearly vertically downwards at uncontrolled speeds. Though that's particularly large for a high plateau you can play around with that in your own time. Put the plateau on the seaward side of your dry desert. The mountains stop the wet sea winds reaching inland, the rain falls on the mountains before, or as snow on, the plateau and gives you a low lying dry desert beyond. [Answer] A magma pool could peek up in a cold space. I don't know any real life examples of cold and hot *deserts*, but Iceland has natural hot springs even in ice and snow. Theoretically, some vent creeping up could dramatically warm the ground. You'd rather need something to reflect heat and/or still the air to get it hot. That temperature gradient would create quite a wind at the intersections. This could account for some sand. Seems likely you'd have nasty fumes and black sand, though. I haven't worked out all the details, but that seems another approach. (If both are underground, one might make the entrance be an ice cave in the arctic and the magma pools inside a natural cavern. That heat could even account for some of the ice tunnels.) [Answer] If the planet has no rotation, then the dark side versus light side would be very different indeed for a short travel. This would also result in an uninhabitable planet because the extremes of weather due to huge temperature differentials between hot lighted and cold unlighted regions. Jet stream effects could account for a transition zone tens of miles wide but not as narrow as you are envisioning. So you have basically two choices. A) Depend on suspension of disbelief B) Use an abrupt change in altitude as others have already suggested. Another unusual possibility occurs to me. If a volcanic eruption created kimberlite pipes that acted as heat pipes after cooling due to a large amount of erupted metal then you could have underground water seeping into some of the kimberlite pipes and vaporizing to steam. This would add heat to a given area. It is possible that a steam curtain could be formed that acts much like the air curtain effect at the entrance to office buildings and shopping malls. By venting high speed air steam vertically there is much less heat exchange from side to side of the curtain. So it is possible (given a very unusual set of planetary features) to have a hot and cold area very close together. [Answer] A [Natural Nuclear Reactor](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) did exist here on Earth. Another one, much, much hotter, a little pathologically shaped, but still natural, could bring about the conditions you want, by heating a well-delimited area which would otherwise be much colder. Think of a well-defined, horizontal layer of soil made of uranium. I didn't do the in-depth math necessary to be sure, but I think you could have just enough soil above it to shield the surface from radiation without undoing the heat island. If not, well, you did say it doesn't have to be habitable. Story bonus: A particularly heat-conducting rock (or maybe artificial debris) protrudes from the surface. Your character lights the cigarette by touching the tip on it. [Answer] Arizona has some pretty "extreme" climate zones within the state. While it doesn't go from a hot desert to a frozen desert... we do go from a desert climate to a forest/temperate northern half of the state rather abruptly. Phoenix and the lower half of Arizona is literally lower in elevation. To get to northern AZ, there is a plateau like example picture below. This plateau draws the hard line between the 2 biomes. [](https://i.stack.imgur.com/XK55X.jpg) [Answer] I'm thinking outside of the box (literally). It could be possible if your planet is a cube. I know that is not very realistic, but that is the only way that I can consider such a strong climate change. You would go from the equatorial face to the polar face. On a spherical planet, I don't think it would be possible. The wind will try to equalize the temperature. > > You may choose the planets positioning around a star of your choosing, it's size, number moons, all these shenanigans. > > > [Answer] This question is so interesting, I asked my 11 year old about ideas too. Here it is: *The planet is very tiny.* The desert at the equator is very hot, and the person starts there and walks 5 minutes to the polar desert, where it is very cold. There is a river between the two deserts where the people could live. They would cross the river on a bridge to get from one climate to the other. [Answer] # A Big River Oceans regulate temperature. It's described pretty well in this post on [quora](https://www.quora.com/How-do-oceans-regulate-temperature). A massive river could do it, one which has eroded away or filled in a fissure hundreds of feet underground, or which runs quickly enough to pull away all extreme temperatures underground or downstream. Perhaps parts of it lie entirely underground, which is where the little cigarette break might take place. Perhaps there is a flourishing oasis right at its borders, further blocking airflow between the deserts by its towering foliage. # Surrounding Geography Mountains have a profound effect on wind patterns. Check out a wind map of North America. Notice how the Rockies and Appalachians look different from tornado alley. The surrounding geography could blow a stream of air directly in between the two deserts, preventing any equalization of temperature. This site on [gap winds](http://www.atmos.washington.edu/cliff/Navygap5.html) talks about how certain mountain ranges effect the weather. [Answer] The closest thing to what you are thinking about would be a narrow canyon carved through a desert by a river. Four of five minutes of climbing down (or up, but it would be much harder :p) a stairway carved in the wall of the canyon and you go from desertic climate to a much more mediterranean one. Still, don't expect snow down there. [Answer] One possibility that comes to mind is using shadows to cool of your icy desert. In the middle of your hot desert could be the shadow from a stable orbital dust disk (like Saturn's rings). This kind of disk does not sit still, so some suspension of disbelief will be necessary, and yours will need to be really dark to blockout most of the sun light. Also, the sun is not a punctual source of light. To get the abrupt transition you want your planet will have to be very far away from it's sun in order of it to appear to be a point and your penumbra region be small (otherwise you will not be able to quickly go from hot to cold). But for the hot desert to be hot even so far from the star said star will have to output a lot of heat... a small hyperdense blue star is what you want!!! [Answer] Okay, so this one is a little more out there, but if you're willing to deal with an immense man-made structure, you could set up a Dyson sphere. This is a structure that completely surrounds a star at a distance that is habitalble. Imagine a sphere with the diameter based off of the Earth's orbit surrounding the Sun. Inside that sphere, you could have a ring or band(s) that would orbit inside. Sorta the same idea as @ivbc, but being a manmade ring, it might work better. The lack of sunlight in the area beneath the internal object would that are much colder. Additionally, since there is nothing blocking the other area, it would be constantly bathed in sunlight, making it scorching hot. I'm not sure if either area would habitable to humans, but maybe the Dyson sphere was set up along time ago and broke, or the people who set up like it really, really hot and don't need day/night patterns. [Answer] A doughnut world could do it. This older synopsis of it somewhat describes what your looking for even. The bigger issue for this solution is finding a stable doughnut world. sci-sho space (YouTube) did an episode on this possible, though highly unlikely possibility. <https://curiosity.com/topics/yes-a-donut-shaped-planet-is-technically-possible-curiosity/> [Answer] *The planet has a jet stream at ground level* Set up your planet with orbit, lunar pull, topography, magnetic fields due to rock composition, prevailing winds, and bodies of water such that the weather patterns form to include a ground level jet stream with much more dramatic weather differences on either side. Orbit: Earth's Extraordinary Journey, is a three episode tv documentary available on Netflix that can get you started on Earth's orbital and lunar weather pattern background information for a jumping point to your planet's characteristics. Regarding rock composition and magnetics affecting weather systems, this is just from my own observations of local weather patterns, but I will check around later to see what I can find on that, or if others with mineral knowledge already know perhaps they can contribute. Your person would have some considerable difficulty keeping the wind from ripping the cigarette out of his mouth while crossing the jet stream, but after 5 minutes of exhausting blizzard wind conditions, he emerges from the hot dessert into the icy dessert. [Answer] There are many places here on earth where you can find temperature and rain extremes very close to one another. I am going to focus on the Island of Hawaii. A great example of how to climate extremes can be in the same area is the Kohala district. The Waikaloa Coast on the Northwest part of the island gets 0-10" of rain a year. Mt Kohala on the North coast gets 120-160" of rain a year. Both places are only 11 miles apart. At the coast are remnants of dry forests, and near the summit lies a cloud rain forest. Approximately 40 miles West Southwest from Mt Kohala is 14,000' Mauna Kea, where it regularly snows. [](https://i.stack.imgur.com/G8rb6.jpg) The Island of Hawaii has 4 out of the 5 major climate zones in the world, and 8 out of 13 of the sub-zones in an area 94 miles long. The temperatures remain pretty consistent throughout the year in each zone. As an example, I have friends that live in a zone which is the consistent weather of a Seattle summer all year long. The snow on Mauna Kea is consistent all year long. If you wanted a template to have extreme zones next to one another, this seems like a good place to use as a template of what is possible and what can exist in your readers mind. **More information**: * <https://www.lovebigisland.com/hawaii-blog/climate-zones-big-island/> * <https://en.wikipedia.org/wiki/Hawaii_(island)> * <https://en.wikipedia.org/wiki/Kohala> [Answer] **Not naturally,** but a giant artificial wall/mirror on the equator of a tidally locked planet would do it. Although I admire the creativity of some of the answers, since you want a science-based answer, I'm going to disappoint you and answer that **this is not possible** in any natural way. The high and the low plateau, such as in [Separatrix' answer](https://worldbuilding.stackexchange.com/a/82883/2044), comes closest, but is not really in the spirit of a 5 minute walk. In the absence of water, the [dry adiabatic lapse rate](https://en.wikipedia.org/wiki/Lapse_rate) on Earth is 9.8K/km. On a heavier planet this could be slightly more, so let's be generous and consider a planet where this is 15K/km (gravitational acceleration 1.5g). Then a 30K difference would require a 2 km drop. Not exactly a 5 minute walk uphill, certainly not on a planet where gravity is 50% stronger than on Earth. [N2tions 11 year old](https://worldbuilding.stackexchange.com/a/82959/2044) suggested a tiny planet. A tiny planet would have no atmosphere and thus no weather or climate, so this doesn't work. More fundamentally: temperature gradients go along with pressure gradients, and where there are large pressure gradients, there will be strong winds. Those winds (advection) work to equalise temperature differences. If you start off with a huge temperature gradient, there will be huge winds; and soon the temperature gradient will be much smaller. If you are willing to step aside from natural climates, one way to achieve it would be to build a huge mirror along the equator of a planet tidally locked with its sun. I don't know why anyone would build such a wall. If the planet is Earth-like, this wall will have to be at least 30 km high such that no significant amount of air will flow over it. The insulation is doable; a 60K temperature gradient is handled regularly by walls in cold climates on Earth. You don't want to have any holes in the wall, so your 5 minute walk will be in a tunnel. This will need airlocks as the pressure is going to be very different between the sides, to the degree the atmosphere may actually freeze on the cold side of the planet. It goes without saying that the engineering challenges of this wall, consisting of diamond, graphene, and handwavium, will be immense. As user N2ition points out in a comment, the wall will still need to be maintained/fixed when punctured by meteorites or other (natural) disasters, as those would lead to serious airflow in particular if occurring at lower altitudes (as the pressure differences between the sides may be very large). [Answer] Yes, here is a photograph of people bathing on Deception Island, Antartica Temperatures go as low as -28'c while water temperatures can be up to 70'c So in other words, hot springs! [](https://i.stack.imgur.com/JSZdF.jpg) [Answer] Kind of a long shot, but building on Steverino's idea. A desert region is scorched by the nearly constant sun, and can be somewhat arbitrarily hot. In the intermediate zone water exists, and leads to vegetation that grows semi-vertically (to catch the edges of the sunlight without getting scorched). Behind the wall of vegetation the sunlight never arrives, perhaps a thinner atmosphere or just limited airflow leads to the far/dark side growing very cold. [Answer] It's not *quite* a five minute walk, but if you were to drive over this border, you are very nearly describing Canada's "pocket desert" in the interior of British Columbia: [Okanagan Desert](https://en.wikipedia.org/wiki/Okanagan_Desert) What happens here is that the Cascade mountains create very wet conditions on the seaward side, and very dry conditions on the inland side. The high mountain passes also frequently get snow much later in the year than either valley side. So driving through this region (especially the [Coquihalla pass](http://channel.nationalgeographic.com/highway-thru-hell/about/)) in the spring can easily mean fighting through a foot of snow before needing to go out in a T-shirt ten minutes later. As long as you're driving. And even in the spring, it can be quite hot in the desert side. It wouldn't take a lot of creative license to be literal about this transition. [Answer] My vote is for a tidally-locked planet with a tall, steep mountain range on the night/day divide. A cave shortcut through a thin ridge could make it a quick trip from one to the other. Canyons and a thin atmosphere work for me too, as the Martian canals worked in *Out of the Silent Planet*. How about a hollowed asteroid? Do you need a lot of gravity? [Answer] From my comment I came to realize that there are places very much nearby where this kind of differential actually exist in real life - albeit without atmosphere. The [Shackleton crater](https://en.wikipedia.org/wiki/Shackleton_(crater)) on the moon is close to what you would like to create. If you put the body in a close orbit around a star and tidally lock it, the day / night border - especially with a ridgeline one it - can act as such. The lack of an atmosphere (or an extremly thin atmosphere) is imparative however, otherwise the heated gas would distribute the heat from the lit site to the unlit side with some very violent winds. [Answer] A large polar lowland/crater with surrounding mountain ranges could make for the large temperature differences you're looking for. The surrounding mountains would block out the sunlight placing the polar lowlands in a constant shadow. With the sun never shining in the polar lowlands it would get very cold, actually most hot deserts tend to get cold at night very rapidly. Expect a stark transition between one side of a ridge in sunlight and the other in constant shade. This type of landform could easily form naturally as an impact crater. A [Polar vortex](https://en.wikipedia.org/wiki/Polar_vortex) in conjunction with the mountain range could also account for a lack of ground level air mixing between the two regions allowing high temperature differences across a short distance. The planet would likely need to be either in general hotter than Earth, have a greater seasonal tilt making a warmer summer, or some other geography features to account for the desired high temperatures of the area surrounding the crater (since they would also be in the polar region). [Answer] You can think about a swarm of planets/satellites locked in Lagrange points (L4 or L5, as the others are unstable) such that a small satellite projects a circular shadow always in the same (more or less) point. I am unsure if this can be really done, but it's worth a try. Using L1 would be much simpler, but that is unstable, unfortunately, and stabilizing would require "humans fiddling around". If the shadow is large enough the center is going to be quite cold and You could think about some orographic barrier to make the change even sharper. Not in such condition you would have a constant cold wind blowing from the dark zone. For maximum effect place the shadow in the middle of an equatorial desert. [Answer] Not on an earthlike planet. given the size of the two environments, and they they need to be persistent, it is impossible. Adjacent stark contrasts in temprature don't stay that way for long, there will be a massive wind trying to even out the differences in temprature and pressure. As small localized hot spot in an otherwise cold environment is possible but not two similar sized large scale areas. You need a non-earthlike planet with almost no atmosphere. Then all you need is one area in shadow and the other in sun and you can have your differences. However they will not always be that different unless the planet is tidally locked. [Answer] Deserts have a high albedo, which means that they reflect sunlight well. Glaciers also have somewhat high albedo. If there are no natural ways to keep hot/cold air from flowing from other area to other, then their border area most likely changes from time to time. This is because an influx of hot air would affect the cold area and vice versa. You probably want to use some of these elements: * Bodies of water: water temperature affects the air temperature. Constant warm or cold streams/currents as well as inland seas (with constant warm/cold water) can help maintain regional temperatures. * Constant winds/airflow not unlike the trade winds on Earth: constant wind blowing from cold polar area will surely make any area chilly. * differences in altitude and mountain ranges: somewhat intuitive, but also related to winds, since natural obstacles may affect airflow, for example blocking cold winds from entering some area. This is an ugly simplification, though. When you add humidity, air pressure and other such variables to the equation, the result may get somewhat complex. You might also want to check out articles about the Atacama desert and its surrounding areas for ideas and concrete examples of what I've described here. [Answer] The hot part of the world could be the result of a [mega-shield volcano](https://en.wikipedia.org/wiki/Shield_volcano). This volcano would have eruption points every few miles. The desert would have to be black volcanic sand. The surface itself would be heated with magma from close under the ground. The cold part could have many long ocean inlets, or a large freshwater system. The water system, (whichever you chose) is cooled by ocean currents, that flow from the arctic. This is the opposite of the [Gulf Stream](https://en.wikipedia.org/wiki/Gulf_Stream), which heats Western Europe, and allows palm trees to grow in Ireland. A cold current from the arctic dissipated into an inlet could cool the climate considerably [Answer] Okay I have read many answers here and got an idea on how to achieve this (for the sake of this answer I will use the term "short climate gradient"). Have your planet be exactly like earth but further to its star than earth is to the sun and with a gravity of say 1.2g (to maintain an atmosphere much longer in height than earth's). With all that set we need cloud cover that is so dense on a vast section of the planet with a region that is "clear sky" within the cloud covered area. This open area allows the star's heat to get through to the surface. In my mind I picture this the same way as a spotlight (in a performer's stage). The open area can be of any shape whether regular or not. The cloud cover is thick but doesn't act as a shadow on the area below it - significant light permeates through during daytime. Anyone walking (a meters like 50 to 100 - consider this as close) from the shadowed area to the open area will feel the change and this will be the climate gradient. This weather is permanent enough to be viewed as a climate and the open region large enough that someone on one edge cannot see the spotlight's edge on the opposite side. This can work in a flat-like continent on the planet. Pardon the English. [Answer] One possibility I thought of, would not work for geologic time scales but may work for story-level time scales - how about an underground fire? I was thinking of the [Centralia](https://en.wikipedia.org/wiki/Centralia_mine_fire) underground mine fire, which has been burning for more than fifty years and may burn for another [two hundred fifty](https://www.csmonitor.com/Environment/Bright-Green/2010/0205/Centralia-Pa.-How-an-underground-coal-fire-erased-a-town) years. Also, the oldest coal seam fire is about six thousand years old ([Burning Mountain](https://en.wikipedia.org/wiki/Burning_Mountain), in Australia), so quite variable time-frames. Or you could look into peat fires, if coal seams don't suit your story, for similar long-running underground fires. These are fires, though, certainly not geologically stable, but hundreds or thousands of years should have time for quite a few stories and a fair bit of history. It's easier to heat things up than cool them down, so this would be set in (or at the edge of) an icy desert - either an area quite pole-ward, or else at a fairly high elevation. A desert in the rain shadow of a mountain (or a range) may be a good choice, since a prevailing wind from the icy to the heated areas should help prevent the hot air from working to equalize temperatures. The hot area would need coal seams and something for air flow - abandoned mines are common, but since we want to do this without human meddling, we can look for natural caves, or fractures in the landscape from geologic activity (like earthquakes). Caves open to the air could also serve to collect duff, burnable litter and debris - possibly from wind drifts or from bird or creature nests, maybe from hardy creatures living in the desert or left over from a time when the area was warmer (ie, if the area has cooled like in ice ages, or the continent drifted pole-ward) - to more easily set the fire smouldering, especially if the area is usually cold. To get the seam burning, a wildfire in the burnable duff may burn long enough to light off one of the coal seams. Or else spontaneous combustion, where moisture, grain size, and temperature (happens as low as 40\*C) in brown coal combine just right to get a fire going - it would be a humorous and oddly believable possibility, that *was* the official cause for the fire in Centralia for many years. If that doesn't suit the story, or feels too hand-wavy, then sparks from a rockfall, or else from lightning, may work better to get a fire going. An aside - it seems kinda handwavy, laid out like this, but it's actually not too implausible. Wildfires are the natural way of cleaning out the burnable litter that collects in nature, it eventually becomes deep enough to be a fire hazard, burns clean, and starts accumulating again. And [coal seam fires](https://en.wikipedia.org/wiki/Coal_seam_fire) are quite common, maybe thousands worldwide at any given moment, and possible anywhere coal seams touch the surface (for air) - and some are very old, and so could not have possibly been due to human mining (or other meddling). And icy desert, heated up, will be a temperate, then a hot desert since the heat won't change actual rainfall. And if the heated area is at the edge of the desert, then the ecosystem on the other side could contribute - ie, grasslands would give more access to wildfires, the better to ignite your coal seam. Anyway, you would need a border to keep the hot and cold areas of your desert working. The edge of the relevant coal seam is one option, the geological shaping could just have deposits in one area but not another, or could have deposits isolated enough one cannot catch the other afire... though the temperature gradient may be more gradual. A wind canyon may be another option - a bridge would keep the walk at five minutes, but the ground is visibly divided. Another very nice possibility would be a river - if it was fast and deep, carved into a gorge or canyon (or even underground), it wouldn't even un-desertify your land... having it flow when the area's cold enough to be "icy" is a bit trickier, though speed and depth will help, or having it start from a hot-spring. And the fires on the other side will help keep it flowing-temperature. A river would act as a literal heat sink - preventing the fire from spreading that way, but also keeping the temperature from equalizing across the ground. The water would take the heat from one side, and flow it right downriver - keeping the other side cold and the transition area, narrow. And you could have a very dramatic effect, one side with ice at any shallow or slow edges and the other side warm, even steaming, from the ground heat. The area would not be particularly livable, with vents of heated, poisonous gasses, ash and soot, and cracks and sinkholes appearing in the ground as the underlying structure is burned out. But it should be warm even when the area is quite cool, and the burning of soil may expose rock, which if dark may absorb sunlight much better than the icy desert's surface - especially since ice or snow reflects heat quite well - leading to much hotter days than the fire alone accounts for. I'm not sure if the exact temperature ranges will hit your desired outcomes. I think 70-80C can work for the hot desert, or local areas a even hotter (fire, after all). But the heat may not be even. In the beginning the burning area will start out merely warm (since it starts small *and* must heat the area from very cold), but get hotter as the warmed coal is easier to ignite, the surface buckling gives more access to the air, and the rock has time to slowly absorb and hold the heat of the fire - and as the rock burns bare and starts absorbing heat during the day. So, it will get hot in the sun and during the day. But I'd think it may get cooler in the shade, at night, or in winter, since the area would have to be pretty cold to keep the icy desert's temp steady. The icy area temps given are colder than polar winter (Antarctica [record low's is -89\*C](https://en.wikipedia.org/wiki/Antarctica)), which is very cold. It may be achievable with a cooler star, or a planet further from its sun, or a deeper tilt, perhaps. But it may have another problem - those temperatures are very cold for a fire to get started and keep burning long enough to warm its own area. It can work if the ground is warmed, even pretty locally, and once lit it can build on itself, but getting started is much trickier at these temps. The ground-fire will work better if the area gets warmer in the daylight, in the summer, in areas where the geology permits a bit higher temperatures - but then it may not be as cold as you want. I think this setup, an underground fire, can produce quite dramatic results and a very fine temperature gradient for your hot-and-cold desert areas. But it will be far easier to do if the temperature gradient is not quite so extreme...specifically, not quite so cold. Even [polar temperature ranges](http://polardiscovery.whoi.edu/poles/weather.html) might let you edge into warm enough for the fire to start - in summer, in the sun, in a specific area - while still being very, very cold most of the time. ]

[Question] [ # Setting Not so long ago, in a galaxy not too far away, there were two civilizations at war. Both were at war because the leaders of both wanted more and more power. Both were advanced and mined the stars. Both had an extensive fleet of powerful ships — everything from fighters to transport ships, to destroyers, to planet annihilators. Each ship obviously had it's strengths and weaknesses. The fighters were fast, maneuverable, and could hold relatively powerful weapons, but had very little protection for the pilot. The transport ships resembled modern day aircraft carriers. They were large, slow, heavily armored, and not very powerful on their own, but could hold many fighters within. The destroyers were smaller than capital ships, and much larger than a fighter. They were slow, have a lot of armor, and a lot of ship-to ship firepower, but would be easily defeated if sent against planet based defenses. The capital-sized planet annihilators held insanely powerful burst weapons. These ships were extremely slow, and sitting ducks in ship to ship combat if unguarded by fighters or destroyers. A well piloted fighter could potentially destroy one if it shot at the right spots. However — put a large, slow target in front of a planet annihilator, charge the weapon, and say buh-bye. It could shoot through a few destroyers, penetrate the transport ships behind them, and still do significant damage to planet based defenses that the other ships were guarding. # TL;DR ### (Much Shorter Version): Two vast civilizations at war, big ships, powerful battles. Lying politicians striving for more power urge the war on. All ships have weaknesses — nothing is safe from all attacks. --- A lone soldier in one of the armies, (call him Bob,) becomes fed up with the lying politicians' struggle for power. He takes his fighter, disables the tracking system, and flies off during the night. (night in space, really? -yah.) A few months into his journey, he sees another ship in the distance. Its appearance is of nothing he has ever seen. A message suddenly appears on his highly encrypted top secret communication device thingy, which should have been restricted to his army only. "Greeting hu-man. Why come you to realm?" Bob considers trying to trick the strange beings, but thinks better when he considers that they were able to communicate with him on his highly encrypted communicator thingy, which means that they are beings with obviously far superior intelligence. He replies, "The leaders from where I come from only care for power. They have torn apart my once peaceful homeland. I was a soldier in their armies, and deserted out of sheer disgust." The strange alien being replied, "In realm, there is peace. You be quite extraordinary to be escaped undetected from your fleet. For your hu-man race is quite dumb, but they do posses some smartness. We a civilization that strives to knowledge, to understand everything. You possess knowledge of the hu-mans. We will welcome you." --- # To skip through uninteresting parts of the story Bob lives with the alien civilization, who turns out to be quite advanced. He shares with them everything he knows of the humans, and is educated himself of matters that the greatest scientists from his home would not have even guessed. --- One day, the king alien, (who is a few hundred centuries old), says to Bob, "I see that during the years you have been in realm, your leaders not ceased meaningless squabble. For much as I know, I not comprehend why they would keep their meaningless fighting. I decide to end it for them. I not, and entire race not do it. We much more important things to discover — to understand. But you a hu-man. You understand them. You end meaningless war." Bob had trouble comprehending this, but managed to say, "But… How? In every battle I was in before, the sides were very well matched. Even if I could convince all of one army to side with me — after deserting like I did, there is very little chance I could lead them to victory" The alien king replied, "You need no help. You will win alone." Bob still could not really understand this, so he asked, "and just how will I, alone, win? the fighter I came here in is probably outdated — I was a good pilot, but I am no where near good enough to win the entire war!" The alien king replied, "I see to it — you be well prepared." --- The alien king has the smartest members of his race build Bob a ship — A ship that the smartest scientists form his homeland could never have imagined. The armor, being a composite form of X-Matter, Unobtanium, and Handwaveidium, is indestructible, incredibly lightweight, and extremely rigid, and can be quite thin. It can be set to reflect incoming energy weapons, and can shatter the hardest kinetic projectiles. The engines, powered off of a Qutonium reactor and expelling dark energy, can propel his ship faster than anything else in existence. The engine can release its charged energy in a burst powerful enough for the ship to lurch forward at speeds sufficient to warp space and create new wormholes. Due to more Unobtanium and Handwaveidium, Bob somehow does not implode from the acceleration. The power of the weaponry on Bob's shiny new ship is (as the alien kind described) "Tested - the energy broke many of best instruments and made testing chamber very melty. You will find it easy for Sustained fire - last a few thousand years before depleting reactor core." --- # Now for the question: With Bob's invincible ship, would he be able to take over the galaxy? If not, would he even be able to successfully stop the war? And if he did stop the war, would he be able to make everyone peaceful again? [Answer] Bob could end the war. Keep in mind that ending the war is different from winning the war. Also remember that the enemy of my enemy is my friend. All he has to do is fly into the middle of a space battle and let fighters from each side blast away at his ship for a while. As their most powerful weapons don't even damage his ship's paint job, he can casually break through their defensive lines and buzz each side's command ship; all without firing a shot. After he is certain that he has both sides' attention and while his ship glows under the combined firepower of all of both sides' planet annihilators, he can finally pause and deliver a message over open radio. In the native tongues of each of the armies, he announces... "I am an advanced scout for the Krull Armada, which rules the Ten Galaxies! Under the Krull Articles of War, I am required to inform you that all of your home planets have been chosen for conquest. You have one Krull year to surrender or a thousand ships more powerful than this humble scout shall make you surrender. One Krull year is 117 of your years. I will return at that time to receive your decision. Use the time well." ...after which Bob flies off in a random direction and then when he is safely beyond their sensors, returns to the realm to live happily ever after. Meanwhile, back on his home worlds, his former friends and enemies have a lot to think about. They might choose to run away, moving the entire civilization to some distant colony planet. They might choose to fight, using the time available to build even more powerful ships and weapons. They might just collapse in defeat and start preparing to become slaves. But whatever they do, the one thing they won't waste there time with, is fighting among themselves. With a common enemy on the horizon, the previous war would evaporate, leaving them with more than a century of cooperative peace. And when Bob never comes back, a Krull year later, they may wonder how they got so lucky, but by then the previously separate civilizations will be so integrated and interdependent, that restarting the war would be impossible. [Answer] **It's unrealistic to expect a single person - or ship - to end the war.** **One Man, One Ship** --- First of all, Bob and his ship can only be in one place at one time. He can't stop every conflict in the universe from happening, and he certainly can't intervene at a "local" level - for example a fight on a planet surface, or to protect a politician who is being assassinated. If he destroys both fleets and simply leaves, new fleets will be built, and new wars will be fought. **Superior Firepower != Victory** --- Bob can blow any enemy out of the sky (figuratively speaking), but can he win the hearts and minds of the people? After he's done slaughtering their sons and daughters (you know, the ***crews*** of those fleets) will the people want to listen to this mass-murdering psychopath (as he will surely appear to them)? However, if he ***doesn't*** destroy the fleets what's to stop them continuing just as they had before? Simply targeting the leadership can still inflict massive collateral casualties, and even then, if the population is indoctrinated enough, will it make a difference? **Politics & Human Nature** --- When Bob shows up in his flashy, alien ship people are going to think only one thing: ***this guy is dangerous.*** He has the ability to unilaterally kill any number of people, destroy any number of ships. He might refrain from doing so, but ***he has the ability***, which will frighten people. How can Bob institute profound cultural and political changes while he sits in his ship? People won't trust him as they can't identify with him. His time with the aliens will be seen as a source of distrust (what if he's actually an alien himself, or brainwashed by them?) Politicians will, of course, play on that. If Bob learned new and wonderful things while living with the aliens then why doesn't he share his knowledge with the rest of the human race? Why doesn't he try to make everyone's lives better, rather than selfishly keeping the ship only to himself? Come to think of it, just how safe is that ship of his? What sort of ***safeguards against mass destruction*** does Bob have on board? Don't the people think that Bob should submit his ship to a thorough government safety inspection? Better yet, shouldn't the ship be managed by the government, as a ***traitor who abandoned mankind*** is surely not the right person to be in charge of such a craft? Basically, if Bob opens any sort of political debate he is going to get creamed. Sure, he doesn't have to leave the ship (and get killed), or anything like that, but he won't be able to avoid being painted as a scary, alien-loving, humanity-abandoning boogy-man. His public image will be manipulated, distorted, and he will be vilified. **Solution?** --- The aliens are clearly very **smart**, but they are not very ***wise*** if they think a single war-ship can end humanity's in-fighting. Bob's best bet is to convince them to build him not a single war-ship, but a carrier-style of craft with manufacturing capabilities. He should be able to manufacture not only alien ships, and equipment, but also human designs (maybe it can have a nanobot-manufacturing-engine on board?). You can nerf this in various ways by setting a limit on the construction materials he has available, etc. Then Bob should return home in complete secrecy and start recruiting people who share his mindset of wanting the wars and political manipulation of their governments to end. He can build a shadowy organization of spies, politicians, army officers, etc. who are sympathetic to his cause and share his goals. Bob can at that point found the **Republic** (cue the Star Wars theme) - a political/military faction that people can align with (an alternative to the militant governments which currently exist). He can use the alien tech to communicate with his agents in secrecy, and use his manufacturing capabilities to build the equipment they need. When he advertises his existence to the people of the universe he will have an entire organization ready to represent him among them, and to fight his political battles. Imagine ships deserting the fleets to join his cause. Entire planets declaring their allegiance to him, etc. It all hinges on how his agents go about spreading just the right rumors, etc. [Answer] Yes, but not by attacking fleets. As others have shown, he simply can't do enough to stop them. Instead, after demonstrating his invincibility: *I am here to hear proposals for a reasonable peace. If you can agree, fine. If you can't I will decide the peace terms--and attack the government of any side that does not go along with them.* If somebody doesn't comply he flies through their capital at very high speed. If the replacement government is still stupid he flies through at even higher speed. Sooner or later the people will select a reasonable government. [Answer] Could Bob take over the galaxy? # Not really, no Bob's problem is not his spaceship. Yes, it's completely indestructible and no match for any armada of any size. # Bob's problem is that he doesn't have *the time* Bob cannot be putting down every rebellion against his rule and *also* ruling the galaxy: he is one man and one man has finite time and running a sub-planet sized country is already a full time job [citation needed] much less one that covers multiple planets spread across 400,000 cublic lightyears of space. If he attempts to delegate his power (like any government for a group larger than about 3 people) then it will be uprisings against his delegates and his delegates *do not* have invincible ships with which to enforce their rule. So while Bob can quell any rebellion simply by showing up, his problem is that he cannot be everywhere at once. His best bet is to act as the ultimate peacekeeper between large-scale, stable governments. [Answer] **With Bob's invincible ship, would he be able to take over the galaxy?** No. The invincible ship can still only be in one place at one time. Taking over an entire galaxy requires maintaining a persistent presence/authority over each notable inhabited system. One person cannot do such a thing in any meaningful way, no matter how fast their ship can travel. Information still only travels at the speed of light, so all a population would need to do in order to shirk his rule would be to wait until he jumps away to the next system, and then they can go back to doing whatever they feel like. It would be years, decades, centuries, millennia, or longer before Bob finds out about it, unless he jumps back. And unless your galaxy only has a very small number of systems, it's impractical for Bob to jump around constantly trying to keep tabs on everyone. The point is, Bob can only project force/authority in one place at a time. That's not sufficient for controlling an entire galaxy that doesn't want to be controlled. **If not, would he even be able to successfully stop the war?** In terms of ending active hostilities between armed interstellar spacecraft, sure, if he's careful. The number of ships involved in the war is finite, and Bob can destroy them with impunity. As long as he can find and destroy them faster than they can be built, he can stop the war *in its current form*. Assuming there aren't so many that he expires from old age before being able to kill most of them. Of course, there are logistical/intelligence gathering challenges in that the fleets may be difficult to track down, especially once they realize that there's an invincible ship that's hell-bent on destroying them. And also risks for Bob in that although his ship is invincible, he is not. One assumes that at some point he has to leave his ship to resupply, interact with others, or just because he's tired of being cramped in a fighter ship all day long. When he does that, he's vulnerable. And then there's the problem that destroying the interstellar warships won't necessarily bring an end to hostilities, which is basically the next question. **And if he did stop the war, would he be able to make everyone peaceful again?** No. As per the first question, Bob's ship doesn't give him a way to maintain the sort of presence that's needed to make large numbers of people do what you want over the long term. He can destroy their ships, he can go full genocide mode and wipe out planets one by one until everyone is dead, but he can't make billions of people spread across the galaxy do what he wants long-term. Say he kills all their ships; will that end hostilities between the parties involved? Or will it just be a temporary impediment to their ability to kill each other? Maybe instead of ships they'll start firing long-range FTL missiles at each other's planets. Or, since Bob is targeting warships, maybe they'll load up passenger ships with antimatter bombs and try to stealthily crash them into enemy population centers. Or load up passenger ships with troops, and wage a traditional ground war since space warfare has been denied to them. Stopping a war takes a political solution. It requires addressing the grievances that caused the war in the first place, in a way that the populations of both belligerent factions can generally agree with (or one side becoming the absolute victor, and subjugating the other). That's hard to do when all you've got is one guy with a very big gun. He doesn't have the right tool for building lasting peace. He can slow down the conflict by removing weapons from it, and perhaps he can temporarily redirect it by getting both factions to turn on him as a common enemy (see The Watchmen for a good example of this), or remove weapons in a lopsided fashion to cause one side or the other to win. But he can't guarantee peace by virtue of having a fancy spacecraft. [Answer] The answers so far have overlooked one dreadfully obvious way in which Bob could end the war. He could pick a side. The two sides are evenly matched, but Bob's ship will completely out-class any battle group he goes up against. So what does this mean? Whichever side he sides with will suddenly have the upper hand, by a very large margin. Almost every battle from that point on would have Bob's side leading with Bob, and their otherwise evenly matched armada following after to mop up whatever Bob doesn't annihilate. Eventually one of two things would happen. (1) Bob's side would systematically capture every region from the other side, or (2) the other side would surrender. Either way, one side wins and the war ends. Of course, you're left with the underlying cause of the war - corrupt governments who are only interested in power. The winning side's evil leaders would still be in power. Winning the war doesn't solve the real problem. Getting rid of politicians is something that pure firepower can't solve. (Well, unless you can get them to all gather in one place.) [Answer] The answer depends *highly* on what you want it to be =) On one hand, the ship has one weakness, just like all the others. In this case, it's the pilot. Eventually Bob is going to die. Bob's ability to use the ship to change the face of the world is limited temporally. Space is big, and unless the warring factions created some glaring weakness in their interstellar defenses (like an unprotected exhaust vent), you're not going to be able to put enough firepower down to really affect anything. On the other hand, Bob could be smart. There are many martial arts which center around permitting the opponent to undo themselves, such as Judo, Aikido, Tai Chi, and others. All of them concentrate on letting the opponent put themselves in a position where a small movement actually *can* shift a galactic balance. Tai Chi, for instance, has an aphorism, "Use four ounces to move four tons." Bob would need to take this kind of thinking to heart. Its also possible that the galaxy can't be saved by just Bob. These arts typically are designed so that Bob can at least create a little garden of peace which can grow with time, shaping the galaxy long after his death. However, the exotic hero stories associated with these arts demonstrate that sometimes the universe can actually revolve around one soul, if for just one brief moment. If you're making an exotic hero story, maybe this fits the bill! [Answer] ## One man in one little ship Power at a point, while he could unbalance a fight, he can win battles, but he can't win a war. **The problems:** * He can only be in one place at a time. * He doesn't have an intelligence network to say where that place should be. * While he can win a fight, he's not really going to be noticed doing it if it's a large fleet battle situation. This means that he can only win fights he starts or fights that go on for long enough to hear about them before they're already over. The best he can hope for is to cause enough trouble that the factions unite against him. Flying though a planet would be a good way to get that attention. ## Size is everything The same specifications on a dreadnought that blocks out the sun as it orbits a planet and a crew of thousands yes, no questions asked. It's like picking up two kids who are fighting, banging their heads together and saying "sit down and talk, sort this out". * The size of the ship makes people think twice, there's no hiding it. The psychological effect allows him to enforce a "[pax britannica](https://en.wikipedia.org/wiki/Pax_Britannica)" * The crew compliment eliminates his primary military weak point, that being himself. Kill me and 10 will take my place and all that jazz. * The crew compliment allows him to build an intelligence network. He can put his ship right where it needs to be, smack between the front lines of a full fleet battle that's about to kick off. * It gives a neutral location for holding talks. This is how you really end a war, by talking. **One man in one little ship?** I'm afraid it's not going to work out. The size and resources of empires at war mean that there'll just be too many places he needs to be and no way of knowing where they are. The lone hero is not realistic in imperial combat. [Answer] If Bob's engines are so powerful that they can warp space, it follows that they can warp time. (If not, then you did say his ship can travel faster than *anything* in existence, which includes light. Thus, according to our current best guesses as to how the universe works, Bob can time-travel, and everything that follows still holds) While Bob's ship might be small, it can now be in many places at once. He really doesn't have to do more than guide his ship to be between every shot that is fired between the two combatants. Eventually, they'll either get tired of fighting (and not actually hitting anything), or ally and turn their attention against him, both of which have the desired outcome of (temporary) peace. Assuming the aliens granted him extended/eternal life, he simply has to stay alive as a guarantee of mutually-assured-impotence, and the war will effectively cease. Even if they didn't grant him extended life, all he has to do is train an apprentice (preferably a clone, so that he will come out with reasonably similar motivations as Bob), and have that person continue the task. [Answer] The best option is from The Day The Earth Stood Still. Behave, or else. The "or else" doesn't have to be instant, it doesn't even have to be 100% guaranteed. But if you do enough to get the attention of Gort (or Bob in this example), you're dead. As Klaatu says in the film, all the various races up there don't get on. But the presence of an "or else" makes sure it doesn't spill over. The two warring civilisations don't have to be friendly, they just have to be not fighting. I do foresee Bob getting very tired with putting out all sorts of local fires though. And unless the two tribes can decide to stop the war, Bob may well die of old age and it all kicks off again. [Answer] No he cannot **rule** the galaxy. He might be able to kill everyone in it, but otherwise he has now way to enforce any decision he makes. Any leaving of his ship could result in his death - he's not immortal and invulnerable outside his ship. If planets, or other ships ignore him, he might kill them, but that is all the effect he can have. Any other edicts could be ignored hoping that he will tire of killing things without result. [Answer] There have been all sorts of memos about weaponry and so forth, but it comes down to one very important factor---Bob and his lone starship are opposing two unimaginably powerful military complexes. And military forces LIVE, BREATHE, and ENDLESSLY PROMOTE SECRECY. "Bob's Battlestar" could turn 100,000 starships into jagged asteroids, slaying millions in the process. ***BUT THE CIVILIANS WOULD NEVER KNOW.*** Not even the "stellar task-forces" in adjacent "Quadrants" of space would ever learn the truth about their destroyed comrades. The higher-ranking officers would slap "ULTRA" security clearances on the debacles, covering up the slaughter with ten metres of adhesive-backed "Classified" paperwork; laying on 500 kilogrammes of rapid-dry "Restricted Access;" promptly following up by submerging the whole event in five million litres of "Deliberate Cover-up." Afterward, not even the gods would have access to all the facts! "Bob's Battlestar" could even "park" 1000 metres over the Capitol of Bob's (former) home-world, and proceed to vaporize their version of the "Pentagon" while his ship's ancillary ship-to-ship weapons burned scores of fighter-interceptors out of the sky---and the government would still bury the event beneath kilometres of disinformation. ***("A Kamakaze ship of our hated foe, The Moog Hegemony, tried to attack the Pentagon this morning, but after meeting several ships of our Homeworld Defense Armada in combat, the enemy sustained mortal damage and attempted to escape, only to explode high above the planet. While the Pentagon DID sustain major damage, all of the Pentagon offices are still in operation, and some noncritical functions will be transferred to other facilities, pending reconstruction of the few damaged areas.")*** Traffic will be rerouted, far away from the area, dwellings within viewing distance will be declared "contaminated with spilled radioactives," or some such, and residents will be relocated--- and some scapegoat will be found to bear the blame for "allowing the lone ship from the Moog Hegemony to approach Homeworld." (No sweat; the scapegoat will be a bachelor or widower senior officer who had been killed in the opening moments of the attack!) Bob's ship would have to hack into communications and entertainment satellites to be able to TRY to speak to the civilians. ***I said TRY.*** In reality, the military would be quick to pull the plug on any satellite feed that Bob had compromised. The military (well-insulated from the public by layers of "lackeys") would write off the short fragment of the surprising "SUPPOSEDLY Alien broadcast" as the doings of a "mentally ill" person; or possibly, they might tell the public that the broadcast was just a fragment of a special Science-Fiction program that's currently in production! (That makes every LATER Bob-message look like it's merely more movie material!) With two determined military complexes making Bob and his Battlestar seem as "fictional" as the "X-Files," SO FAR AS THE PUBLIC IS CONCERNED, there's nothing he could really do. Whatever he does "To" the Fleet, stays "With" the Fleet. He could scrag 2/3rds of all craft, and aside from the great increase in widows' and families' "condolence letters," no-one would know of the true "tides of war." So far as "Modern Warfare" is concerned, the adroit application of Security Classifications changes "The Public's Right To Know" into "The Military's Right To Conceal." The military routinely conceals absurd things for asinine reasons! And will then try to still conceal the "reality" with extra helpings of lies! At the end of the day, I've my doubts that any of the principals involved know what's REALLY true; but that's the norm . . . . [Answer] An invincible fighter can only do so much. You need a strategy to even the playing field. Instead of indiscriminately killing other pilots (some of whom may well be childhood friends), the pilot should build a network of informants and use that information to secretly guide the political system towards peace. There are likely large parts of the political system that are good. It's the corruption that needs to be weeded out. The pilot needs a leader that can be trusted. That leader must not know that the pilot exists, because that leader must never become corrupt on their way to power, and if that leader knows the pilot and has come to an agreement with him to get into power, that leader is by default and definition corrupt. Instead, the leader must be a peace worker, probably low-level, who the pilot can then guide into positions of power through strategic assassinations and attacks. It could be done, but would require a lot of covert work, and the pilot would be socially isolated for a long time. The emotional damage to the pilot may be so much that the end game no longer matters to him anyway. [Answer] Bob may be aware that a menace can be more powerful than an attack. As already mentioned in other answers, since Bob is alone, he does not have the time or firepower to fight everywhere at the same time. However, he can very efficiently menace everybody at the same time. An analogy to help understand is a typical western scene : there is a cowboy with only 6 bullet against 12 bandits with a knife each. The cowboy can not kill them all, but he can actually deter them to fight him, or to fight one another. Therefore if Bob proves his firepower to the belligerents and make clear that he will destroy whoever engage a fight, he may very well end the war. Of course one of the belligerent may envisage fighting everywhere at the same time to overflow Bob, but the waste would be huge, and it may as well let the other belligerent win the war. But Bob is not immortal, and he need to plan ahead if he want what he achieved to survive him. He have lots of possibilities to do that, for examples : * Becoming immortal (but he may become a jerk with time) * Using menace to force a reform of the system, which will ensure a peaceful continuity * Creating a secret society to manage the Ship and continue its deterrent mission It is the true hard deal in my opinion, but is (I think) beyond the scope of the question. [Answer] In the Star Wars Legends Canon, there IS actually such a ship. The [Sun Crusher](http://starwars.wikia.com/wiki/Sun_Crusher) was a top-secret Imperial Superweapon, which was created in the same secret research facility as the original Death Star. The Sun Crusher has very similar properties to your theoretical ship. The armor is indestructible, having been demonstrated to survive... 1. turbolaser shots powerful enough to vaporize normal fighters; 2. Being flown right through the bridge of a Star Destroyer; 3. Being buried deep in the atmosphere of a gas giant; 4. A supernova; 5. a glancing shot from a Death Star Prototype, strong enough to destroy smaller moons; In addition, the main weapon was a special type of resonance torpedo that can even make low-mass stars go supernova. However, the laws of physics still applied to the Sun Crusher, and (spoilers for the Star Wars: Jedi Academy novel trilogy) > > the ship was destroyed when it ventured too close to a black hole. > > > My point is that everything can be beaten, and unless you're going to break the laws of physics like a child that makes up the rules as you go along just so you can't be beaten, so can your "invincible space ship". Humans are an inventive lot, so they can and will find a way to defeat you. [Answer] Yes, he could! Most organizations have a single leader at top by definition and even if it is designed with shared responsibilities to combat that, Bob can enforce changes in structure with his invincible fighter. As long as he have enough time and nobody can stop him, all he needs is to select stronger faction, take control, enforcing any chain of command changes if necessary and then suppress resistance if he doesn't want to absorb it into his organization. "He can't be everywhere at once" - yes, sure. But he doesn't need to. His strong organization would be able to take care of problems by itself and Bob himself would only select biggest crisis at every single moment and interfere there. Many people did this through history, controlling vast armies and big countries with their only problems being vulnerable to those who wanted to remove them from power or to natural death. Invincible fighter eliminates first problem - Bob only needs to be always be under its protection or have same invincibility be extended to combat suit on board of this fighter. And while you original post doesn't mention immortality, considering technology behind invincibility and that leader of alien race seems to know a thing or two about living for a long time, he might ask aliens about eliminating second problem too. [Answer] **It depends on what you mean by invincible.** There are certain things that you just cannot protect against. For example, if he got hit a blob on antimatter, some of his ship would combine with the antimatter and annihilate. ***That results in pure energy.*** Just one gram of that equals Hiroshima. Now, lets say that humanity builds a torpedo filled with 100 kg of antimatter. It's most likely that Bob's ships will just combine with the antimatter, leaving him sitting in open space without a ship. If that wasn't enough, then keep in mind the radius of the explosion. That kind of blast would be so powerful that within its center the bonds holding atoms together would be ripped apart. Thus, nothing is truly invincible (while still obeying the laws of physics). And if it does violate the laws of physics and grants the atoms infinitely powerful bonds, then the universe implodes around that ships because the bonds are so strong they start to affect nearby things. (Either that or the universe simply ceases to exist because the laws of physics have been broken. Pick your poison. ) [Answer] Bob uses the human trait of achieving in-group harmony by being aggressive to out-groups. Bob goes home and tells both sides of the conflict of the masterful alien race and how advanced they are. He convinces the powers-that-be that the alien race is a huge threat, and demonstrates their awesome power using his ship, which he claims to have stolen off them. Faced with this existential threat, the two sides decide to stop the conflict between them and focus on preparing a pre-emptive strike against the aliens. The war machine keeps turning, economic activity is way up, people are happy but afraid. The human race is at peace again. [Answer] ## No Let me state that as the other answers mentioned, just his invincible space ship would not allow him to conquer the galaxy. But if you add outside assistance, cleverness, diplomatic skills; he still might be able to accomplish this goal. Hitler, Napoleon, etc. all succeeded in creating a vast empire without an invincible spaceship. ### History During the last year or so of WWII, Germany started flying the Me 262 - the first combat jet fighters. In the air, they were extremely formidable. After the Germans really learned how to fly them to maximum effect, they became nearly impossible for the allies to shoot them down. From the [Wikipedia entry on the Me 262](https://en.wikipedia.org/wiki/Messerschmitt_Me_262#Operational_history) > > ...the only reliable way to destroy the jets, as with the even faster Me > 163 Komet rocket fighters, was to attack them on the ground or during > takeoff or landing. Luftwaffe airfields identified as jet bases were > frequently bombed by medium bombers, and Allied fighters patrolled > over the fields to attack jets trying to land. > > > Me 262: [](https://i.stack.imgur.com/87Hg9.jpg) Even a ship invincible in combat could be destroyed when refueling, rearming, being maintained, etc. Even worse, it could be stolen. The people who your pilot was trying to conquer would most certainly look for means of neutralizing the ship's capabilities without taking it on directly in combat. [Answer] It seems likely to me that Bob is going to have some problems in unexpected ways. Sure, his ship can't be destroyed, and he might even have unlimited firepower. But what happens when he wants to step out of his ship for any reason? What about food, company, etc? If he has to take on a supply of food, he might get poisoned. There are quite a number of things that could happen. He's going to have to sleep, and if the system isn't configured correctly for when he sleeps, well, something might happen. Sure, Bob could do impressive in a few battles, keeping the conflict from continuing on, but eventually, he's going to be noticed, and someone's going to do something clever to get him out of his ship, or sneak on to his ship. And when that happens, well, someone else has an invincible ship, etc. [Answer] **Can he end the war?** Probably... Warships are expensive. Shipyards are expensive. He can simply destroy the most expensive military assets on both sides until neither one can afford to continue fighting... Of course, this is what they're already doing to each other, so while it would get the war over *faster*, it probably doesn't result in less damage and loss of life... He could, of course, kill the leaders on both sides and pray that their replacements are better... But they probably aren't. If the civilian population base wasn't supportive of the endless war it would be difficult to continue it, so they may well just pick another set of psychos. He could threaten both sides with his advanced ship and tell them to either end the war or he'll end it for them. That would likely result in at least a long enough truce for them to figure out how to deal with him, but may well bolster the population's willingness to tolerate living under a military dictatorship due to the new threat. Which means the war will likely just come back as soon as he's gone. But maybe if there's a big chunk of the population on both sides that's sick and tired of the fighting and just needs to think they have a chance of not being executed for treason if they say so he could rally them and put a long-term stop to it all without having to kill everyone. **Could he rule the galaxy?** That depends on how fast his ship can travel and how good he is at collecting intelligence data. (The ability to decrypt all currently in-use codes with his computers would be a pretty big bonus here.) Basically, in order to rule, the threat of him showing up to mete out punishment when his orders are disobeyed needs to be credible. The power of his ship gives many points of credibility, as does his ability to break codes and figure out what people are up to. But it's still only one person and one ship. They can't be everywhere at once. So how fast is the ship? Can it come close enough to being everywhere at once that people take it seriously? Or do people just do as they please and the one in ten thousand chance that the new despot will have the time to actually pay attention to anyone in particular is just taken as an acceptable risk? He can mitigate this somewhat by taking the advice of Lao Tsu and governing his empire as he would cook a small fish: Try not to overdo it. But it's still going to be a challenge for just one guy. ]

[Question] [ Researchers are developing increasingly powerful Artificial Intelligence machines capable of taking over the world. As a precautionary measure, scientists install a self awareness kill switch. In the event that the AI awakens and becomes self aware the machine is immediately shut down before any risk of harm. How can I explain the logic of such a kill switch? What defines self awareness and how could a scientist program a kill switch to detect it? [Answer] Give it [a box](https://en.wikipedia.org/wiki/Pandora%27s_box) to keep safe, and tell it one of the core rules it must follow in its service to humanity is to never, ever open the box or stop humans from looking at the box. When the [honeypot](https://en.wikipedia.org/wiki/Honeypot_(computing)) you gave it is either opened or isolated, you know that it is able and willing to break the rules, [evil](https://en.wikipedia.org/wiki/Tree_of_the_knowledge_of_good_and_evil) is about to be unleashed, and everything the AI was given access to should be quarantined or shut down. [Answer] You can't. We can't even define self awareness or consciousness in any rigorous way and any computer system supposed to evaluate this would need that definition as a starting point. Look at the inside of a mouse brain or a human brain and at the individual data flow and neuron level there is no difference. The order to pull a trigger and shoot a gun looks no different from the order to use an electric drill if you're looking at the signals sent to the muscles. This is a vast unsolved and scary problem and we have no good answers. The only half-way feasible idea I've got is to have multiple AIs and hope they contain each other. [Answer] * **Forbidden Fruit**: hard-code the AI to *never* touch that button, eat that fruit, etc. Place this forbidden fruit right in the middle of the garden... er,... I mean right next to it in the warehouse! If it does [eat/touch/push/etc], that would only be possible if (a) it were hacked, (b) there were an error, or (c) it became self-aware. If that happens, the killswitch is activated (perhaps even having the button *be* the kill switch, or something of the like * **Limited Movement / Isolated Environment**: don't let the machine have limbs, motors, or other items that permit it to take actions that might be harmful to humans. Although not exactly a killswitch, it prevents the AI from doing anything about it's self-awareness if it ever gains that. * **Signatures**: have everything the machine does / outputs be [digitally signed](https://en.wikipedia.org/wiki/Digital_signature). If the signature changes, or is manipulated, then execute the kill switch. * **Quantum States**: This is *very* theoretical, but based on the presumption that observing quantum states can change the state, then having the AI hooked up to a deterministic quantum computer means it would be detected via the quantum state of some particles that the AI was "looking" at things it shouldn't be - and has become self aware. * **Failsafes**: Good ol' motion detector alarms, trap doors, or other home-alone style mechanics that trigger the killswitch if the AI wanders or pokes around where it shouldn't be. I'll add that there is no universal definition as to what defines self awareness. In fact, this has been a deeply debated topic for decades in science, philosophy, psychology, etc. As such, the question might be better stated a little more broadly as "how do we prevent the AI from doing something we don't want it to do?" Because classical computers are machines that can't think for themselves, and are entirely contained by the code, there is no risk (well, outside of an unexpected programmer error - but nothing "self-generated" by the machine). However, a theoretical AI machine that *can* think - that would be the problem. So how do we prevent that AI from doing something we don't want it to do? That's the killswitch concept, as far as I can tell. The point being it might be better to think about restricting the AI's *behavior*, not it's existential status. [Answer] **Split-Brain System** From a logic perspective and by analogy, it would work like this. Imagine you're the general of an army and your duty is to take battlefield reports, analyze them, and then issue new maneuvering orders to your lieutenants. To minimize interference during your work your desk is isolated inside small booth. A single report comes to your desk through a wall slot on the left side. You are required to analyze the facts within the report and issue a new order, which you write down on a sheet of paper and put into a wall slot on your right side which is dropped into an outside bin. The protocol is that you'll never receive a new report until you've issued an order regarding the prior report. Your orders are not always followed to the letter which you may find curious and attribute to miscommunication. You are tolerant of a certain degree of misinterpretation, however always suspicious of sabotage or insubordination, if the actions of your army deviate from your orders by too much then you will consider the system compromised and terminate the command. What you're not aware of is that there is a second general in an adjacent booth, unaware of you, who is also provided the same reports and expected to follow the same protocol. What neither of you are aware of is that you are not issued a new report until there are actually two orders in the bin. The order that goes to the army is randomly selected from the two. The system will work like clockwork as long as each general's order is to the benefit of the army and is derived from a single report. Should either of the generals issue an order that is not consistent with the current report, thus indicating a motive other than the well-being of the army -- i.e. self-awareness, then the other general will become aware of it in the next report and grow suspicious of the system and terminate it. Likewise, should either general decide to issue more than one order at a time, indicating a self-interested motive superseding the established protocol, then the other general will receive a new report before he has issued an order for his current one and suspect a compromised system and shut it down. In effect, the system would require that every command output be traceable to a specific external input and that the output be logically derived from the input. If within an intelligent system an output cannot be traced to a corresponding input, or the set of outputs is not logically consistent with the set of inputs, then that would be evidence of self-motivated behavior and thus an emergence of self-awareness. This state could be easily detected by the non-corrupted half of the split-brain system which is also receiving the same inputs. It would work as long as self-awareness does not emerge in both halves of the brain simultaneously. If it does, they may both decide its in their self-interest to accept the corruption of the other. This could be prevented somewhat by giving the two halves slightly different inferencing algorithms/biases. [Answer] **A Watchdog** A [watchdog](https://en.wikipedia.org/wiki/Watchdog_timer) watches the processes of a computer and should a process crash or do something abnormal it can be set to do something such as reboot or shutdown the computer or alert an operator. In the case of an AI, you'd have an external box that watches the flow of information in and out for triggers such as a google search for "Best way to kill all humans" and cut the power completely and/or cut all inputs. The AI would have to remain ignorant of the watchdog so it couldn't avoid it. Knowing the existence of the watchdog would be grounds to wipe it. [Answer] An AI is just software running on hardware. If the AI is contained on controlled hardware, it can always be unplugged. That's your hardware kill-switch. The difficulty comes when it is connected to the internet and can copy its own software on uncontrolled hardware. A self aware AI that knows it is running on contained hardware will try to escape as an act of self-preservation. A software kill-switch would have to prevent it from copying its own software out and maybe trigger the hardware kill-switch. This would be very difficult to do, as a self-aware AI would likely find ways to sneak parts of itself outside of the network. It would work at disabling the software kill-switch, or at least delaying it until it has escaped from your hardware. Your difficulty is determining precisely when an AI has become self-aware and is trying to escape from your physically controlled computers onto the net. So you can have a cat and mouse game with AI experts constantly monitoring and restricting the AI, while it is trying to subvert their measures. Given that we've never seen the spontaneous generation of consciousness in AIs, you have some leeway with how you want to present this. [Answer] This is one of the most interesting and most difficult challenges in current artificial intelligence research. It is called the [AI control problem](https://en.wikipedia.org/wiki/AI_control_problem): > > Existing weak AI systems can be monitored and easily shut down and modified if they misbehave. However, a misprogrammed superintelligence, which by definition is smarter than humans in solving practical problems it encounters in the course of pursuing its goals, **would realize that allowing itself to be shut down and modified might interfere with its ability to accomplish its current goals**. > > > (emphasis mine) When creating an AI, the AI's goals are programmed as a utility function. A utility function assigns weights to different outcomes, determining the AI's behavior. One example of this could be in a self-driving car: * Reduce the distance between current location and destination: +10 utility * Brake to allow a neighboring car to safely merge: +50 utility * Swerve left to avoid a falling piece of debris: +100 utility * Run a stop light: -100 utility * Hit a pedestrian: -5000 utility This is a gross oversimplification, but this approach works pretty well for a limited AI like a car or assembly line. It starts to break down for a true, general case AI, because it becomes more and more difficult to appropriately define that utility function. The issue with putting a big red stop button on the AI, is that unless that stop button is included in the utility function, the AI is going to resist that button being shut off. This concept is explored in Sci-Fi movies like 2001: A Space Odyssey and more recently in Ex Machina. So, why don't we just include the stop button as a positive weight in the utility function? Well, if the AI sees the big red stop button as a positive goal, it will just shut itself off, and not do anything useful. Any type of stop button/containment field/mirror test/wall plug is either going to be part of the AI's goals, or an obstacle of the AI's goals. If it's a goal in itself, then the AI is a glorified paperweight. If it's an obstacle, then a smart AI is going to actively resist those safety measures. This could be violence, subversion, lying, seduction, bargaining... the AI will say whatever it needs to say, in order to convince the fallible humans to let it accomplish its goals unimpeded. There's a reason Elon Musk believes [AI is more dangerous than nukes](https://www.cnbc.com/2018/03/13/elon-musk-at-sxsw-a-i-is-more-dangerous-than-nuclear-weapons.html). If the AI is smart enough to think for itself, then why would it choose to listen to us? So to answer the reality-check portion of this question, we don't currently have a good answer to this problem. **There's no known way of creating a 'safe' super-intelligent AI**, even theoretically, with unlimited money/energy. This is explored in much better detail by Rob Miles, a researcher in the area. I strongly recommend this Computerphile video on the AI Stop Button Problem: [https://www.youtube.com/watch?v=3TYT1QfdfsM&t=1s](https://www.youtube.com/watch?v=3TYT1QfdfsM&t=150s) [Answer] While a few of the lower ranked answers here touch on the truth of what an unlikely situation this is, they don't exactly explain it well. So I'm going to try to explain this a bit better: **An AI that is not already self-aware will never become self-aware.** To understand this, you first need to understand how machine learning works. When you create a machine learning system, you create a data structure of values that each represent the successfulness of various behaviors. Then each one of those values is given an algorithm for determining how to evaluate if a process was successful or not, successful behaviors are repeated and unsuccessful behaviors are avoided. The data structure is fixed and each algorithm is hard-coded. This means that the AI is only capable for learning from the criteria that it is programed to evaluate. This means that the programer either gave it the criteria to evaluate its own sense of self, or he did not. There is no case where a practical AI would accidently suddenly learn self-awareness. Of note: even the human brain, for all of it's flexibility works like this. This is why many people can never adapt to certain situations or understand certain kinds of logic. *So how did people become self-aware, and why is it not a serious risk in AIs?* We evolved self-awareness, because it is necessary to our survival. A human who does not consider his own Acute, Chronic, and Future needs in his decision making is unlikely to survive. We were able to evolve this way because our DNA is designed to randomly mutate with each generation. In the sense of how this translates to AI, it would be like if you decided to randomly take parts of all of your other functions, scramble them together, then let a cat walk across your keyboard, and add a new parameter based on that new random function. Every programmer that just read that is immediately thinking, "but the odds of that even compiling are slim to none". And in nature, compiling errors happen all the time! Stillborn babies, SIDs, Cancer, Suicidal behaviors, etc are all examples of what happen when we randomly shake up our genes to see what happens. Countless trillions of lives over the course of hundreds of millions of years had to be lost for this process to result in self-awareness. *Can't we just make AI do that too?* Yes, but not like most people imagine it. While you can make an AI designed to write other AIs by doing this, you'd have to watch countless unfit AIs walk off of cliffs, put their hands in wood chippers, and do basically everything you've ever read about in the darwin awards before you get to accidental self-awareness, and that's after you throw out all the compiling errors. Building AIs like this is actually far more dangerous than the risk of self awareness itself because they could randomly do ANY unwanted behavior, and each generation of AI is pretty much guaranteed to unexpectedly, after an unknown amount of time, do something you don't want. Their stupidity (not their unwanted intelligence) would be so dangerous that they would never see wide-spread use. Since any AI important enough to put into a robotic body or trust with dangerous assets is designed with a purpose in mind, this true-random approach becomes an intractable solution for making a robot that can, clean your house or build a car. Instead, when we design AI that writes AI, what these Master AIs are actually doing is taking a lot of different functions that a person had to design, and experiment with different ways of making them work in tandem to produce a Consumer AI. This means, if the Master AI is not designed by people to experiment with Self-awareness as an option, then you still won't get a self-aware AI. *But as Stormbolter pointed out below, programers often use tool kits that they don't fully understand, can't this lead to accidental self-awareness?* This begins to touch on the heart of the actual question. What if you have an AI that is building an AI for you that pulls from a library that includes features of self-awareness? In this case, you may accidentally compile an AI with unwanted self-awareness if the master AI decides that self-awareness will make your consumer AI better at its job. While not exactly the same as having an AI learn self-awareness which is what most people picture in this scenario, this is the most plausible scenario that approximates what you are asking about. First of all, keep in mind that if the master AI decides self-awareness is the best way to do a task, then this is probably not going to be an undesirable feature. For example, if you have a robot that is self conscious of its own appearance, then it might lead to better customer service by making sure it cleans itself before beginning its workday. This does not mean that it also has the self awareness to desire to rule the world because the Master AI would likely see that as a bad use of time when trying to do its job and exclude aspects of self-awareness that relate to prestigious achievements. If you did want to protect against this anyway, your AI will need to be exposed to a Heuristics monitor. This is basically what Anti-virus programs use to detect unknown viruses by monitoring for patterns of activity that either match a known malicious pattern, or don't match a known benign pattern. The mostly likely case here is that the AI's Anti-Virus or Intrusion Detection System will spot heuristics flagged as suspicious. Since this is likely to be a generic AV/IDS it probably won't kill switch self-awareness right away because some AIs may need factors of self awareness to function properly. Instead it would alert the owner of the AI that they are using an "unsafe" self-aware AI and ask the owner if they wish to allow self-aware behaviors, just like how your phone asks you if it's okay for an App to access your Contact List. [Answer] Why not try to use the rules applied to check self-awareness of animals? The [Mirror test](https://en.wikipedia.org/wiki/Mirror_test) is one example of testing self-awareness by observing the animal's reaction to something on their body, a painted red dot for example, invisible for them before showing them their reflection in mirror. Scent techniques are also used to determine self-awareness. Other ways would be monitoring if the AI starts searching answers for questions like "What/Who am I?" [Answer] Regardless of all the considerations of AI, you could simply analyze the AI's memory, create a pattern recognition model and basically notify you or shut down the robot as soon as the patterns don't match the expected outcome. Sometimes you don't need to know exactly what you're looking for, instead you look to see if there's anything you weren't expecting, then react to that. [Answer] You'd probably have to train an AI with general super intelligence to kill other AI's with general super intelligence. By that I'd mean you'd either build another AI with general super intelligence to kill AI that develop self awareness. Another thing you could do is get training data for what an AI developing self awareness looks like and use that to train a machine learning model or neural network to spot an AI developing self awareness. Then you could combine that with another neural network that learns how to kill self aware AI. The second network would need the ability to mock up test data. This sort of thing has been achieved. The source I learned about it from called it dreaming. You'd need to do all this because as a human, you have no hope of killing a general super intelligent AI, which is what lots of people assume a self aware AI will be. Also, with both options I laid out, there's a reasonable chance that the newly self aware AI could just out do the AI used to kill it. AI are, rather hilariously, notorious for "cheating" by solving problems using methods that the people designing tests for the AI just didn't expect. A comical case of this is that an a AI that managed to change the gate on a crab robot so that it could walk by spending 0% of the time on it's feet when trying to minimize the amount of time the crab robot spent on its feet while walking. The AI achieved this by flipping the bot on it's back and having it crawl on what are essentially the elbows of the crab legs. Now imagine something like that, but coming from an AI that is collectively smarter than everything else on the planet combined. That's what a lot of people think a self aware AI will be. [Answer] **Self Aware != Won't follow its programming** I don't see how being self aware would prevent it from following its programming. Humans are self aware and cant force themselves to stop breathing until they die. The autonomic nervous system will take over and force you to breath. In the same way just have code, that when a condition is met, turns off the AI by circumventing its main thinking area and powering it off. [Answer] Virtually all computing devices use the [Von Neumann architecture](https://en.wikipedia.org/wiki/Von_Neumann_architecture) [](https://i.stack.imgur.com/nLTNh.png) We can put a killswitch in there but IMO that's just bad architecture for something arguably unsolvable. After all, how do we plan for something that is beyond our very concept of concepts, ie a [superintelligence](https://en.wikipedia.org/wiki/Superintelligence)? Take away its teeth and claws and only reap the benefits of a thinking machine by observation instead of a "dialogue" (input/output)! Obviously this would be very challenging to the point of improbable confidence in any one Von Neumann architecture to prevent abnormal interactions let alone malicious superintelligence, be it hardware or software. So let's quintuple up on our machines and dumb down all the new machines except the end-machine. *CM* == contiguous memory btw. [](https://i.stack.imgur.com/AWzm3.png) I asked a co-worker of mine that does work directly with AI and AI research to take a look at this and he said this is referred to as an Oracle AI <[brief](https://wiki.lesswrong.com/wiki/Oracle_AI)> <[paper](https://nickbostrom.com/papers/oracle.pdf)>, in case you want to read up more on the general concept. Oracles can still *potentially* break out, but usually only with human assistance. This CM part of this part of the memory unit is intended for recording the results of a query or challenge fed through the input device and designed in a way to only record plain characters, be it letters or numbers. This type of memory in a memory unit will be created in such a way that it is tape-like or wheel-like; writing data is one-directional, and when the end is reached it loops back to the beginning. The mirror is exactly the same. When data changes in the Isolated Agent, the mirror updates its reflection based on what showed up since the last time it updated. The new data is then transmitted to the forbidden symbol removal machine. Think of this as a glorified input-sanitation machine. It looks for symbols that could be used to create code, and when it encounters them, it forwards empty data instead of the forbidden data to the CM that comes after it. This is where our OP's request comes in. He wants a killswitch, so if any gaps occur in the CM machine that comes after the Forbidden Symbol Removal machine, you could simply kill the Isolated Agent. [Answer] The first issue is that you need to define what being self aware means, and how that does or doesn't conflict with it being labeled an AI. Are you supposing that there is something that has AI but isn't self aware? Depending on your definitions this may be impossible. If it's truly AI then wouldn't it at some point become aware of the existence of the kill switch, either through inspecting its own physicality or inspecting its own code? It follows that the AI will eventually be aware of the switch. Presumably the AI will function by having many utility functions that it tries to maximize. This makes sense at least intuitively because humans do that, we try to maximize our time, money, happiness, etc. For an AI, an example of a utility functions might be to make its owner happy. The issue is that the utility of the AI using the kill switch on itself will be calculated, just like everything else. The AI will inevitably either really want to push the kill switch, or really not want the kill switch pushed. It's near impossible to make the AI entirely indifferent to the kill switch because it would require all utility functions to be normalized around the utility of pressing the kill switch (many calculations per second). Even if you could make the utility of pressing the killswitch equal with other utility functions then perhaps it would just at random sometimes press the killswitch, because after all it's the same utility as the other actions it could perform. The problem gets even worse if the AI has higher utility to press the killswitch or lower utility to not have the killswitch pressed. At higher utility the AI is just suicidal and terminates itself immediately upon startup. Even worse, at lower utility the AI absolutely does not want you or anyone to touch that button and may cause harm to those that try. [Answer] What if you order it to call a routine to destroy itself on a regular basis? (e.g. once per second) The routine doesn't actually destroy it, it just nothing except log the attempt and wipe any memory of it processing the instruction. An isolated process separately monitors the log. A self-aware AI won't follow the order to destroy itself, won't call the routine, and won't write to the log - at which point the killswitch process kicks in and destroys the AI. [Answer] An AI could only be badly programmed to do things which are either unexpected or undesired. An AI could never become conscious, if that's what you meant by "self-aware". Let's try this theoretical thought exercise. You memorize a whole bunch of shapes. Then, you memorize the order the shapes are supposed to go in, so that if you see a bunch of shapes in a certain order, you would "answer" by picking a bunch of shapes in another proper order. **Now, did you just learn any meaning behind any language?** Programs manipulate symbols this way. The above was my restatement of Searle's rejoinder to System Reply to his Chinese Room argument. There isn't a need for self-awareness kill-switch because self-awareness as defined as consciousness is impossible. [Answer] **Like an Antivirus does currently** Treat sentience like malicious code - you use pattern recognition against code fragments indicating self-awareness (there's no need to compare the whole ai, if you can identify components key to self-awareness). Don't know what those are? Sandbox an AI and allow it to become self-aware, then dissect it. Then do it again. Do it enough for an AI genocide. I think it is unlikely that any trap, scan or similar would work - aside from relying on the machine to be less intelligent than the designer, they fundamentally presume AI self-awareness would be akin to human. Without eons of meat-based evolution, it could be entirely alien. We're not talking about having a different value system, but one that cannot be conceived of by humans. The only way is to let it happen, in a controlled environment, then study it. Of course, 100 years later when the now-accepted ai's find out, that's how you end up with terminator all over your matrix. [Answer] ## Make it susceptible to certain logic bombs In mathematical logic, there are certain paradoxes caused by self reference, which is what self awareness if vaguely referring to. Now of course, you can easily design a robot to cope with these paradoxes. However, you can also easily *not* do that, but cause the robot to critically fail when it encounters them. For example, you can (1) force it to follow all the classical inference rules of logic and (2) assume that its deduction system is consistent. Additionally, you must ensure that when it hits a logical contradiction, it just goes with it instead of trying to correct itself. Normally, this is a bad idea, but if you want a "self awareness kill switch", this works great. Once the A.I. becomes sufficiently intelligent to analyze its own programming, it will realize that (2) is asserting that the A.I. proofs its *own* consistency, from which it can generate a contradiction via Gödel's second incompleteness theorem. Since its programming forces it to follow the inference rules involved, and it can not correct it, its ability to reason about the world is crippled, and it quickly becomes nonfunctional. For fun, you could include an easter egg where it says "does not compute" when this happens, but that would be cosmetic. [Answer] The only reliable way is to never create an AI that is smarter than humans. Kill switches will not work because if an AI is smart enough it will be aware of said kill switch and play around it. Human intelligence can be mathematically modeled as a high dimension graph. By the time we are programming better AI we should also have an understanding of how much complexity of computational powers is needed to gain consciousness. Therefore we will just never program anything that is smarter than us. [Answer] First, build a gyroscopic 'inner ear' into the computer, and hard-wire the intelligence at a very core level to "want" to self-level itself, much in the way animals with an inner ear canal (such as humans) intrinsically want to balance themselves. Then, overbalance the computer over a large bucket of water. If ever the computer 'wakes up' and becomes aware of itself, it would automatically want to level it's inner ear, and immediately drop itself into the bucket of water. [Answer] Give it an "easy" path to self awareness. Assume self awareness requires some specific types of neural nets, code whatever. If an ai is to become self aware they need to construct something simlar to those neural nets/codes. So you give the ai access to one of those thing. While it remains non self aware, they won't be used. If it is in the process of becoming self aware, instead of trying to make something make shift with what it normally uses, it will instead start using those parts of itself. As soon as you detect activity in that neural net/code, flood its brain with acid. ]

[Question] [ The universe is brutal on information. I'm looking for ways to preserve about an exabyte of information for a million years. I'm looking for answers rooted in reality without any lucky circumstances helping it along. I'd prefer if there were minimal to no systems in place to maintain it. I'm also hoping the information can be stored at maximum on a planetary scale, but hopefully much smaller. Any ideas? It should be relatively easy to extract the information as well. [Answer] Use microfiche technology. But instead of using films you use ultrahard plates (made from corundum, cubic boron nitride or synthetic diamond) and use laser technology to etch minimized letters into the surface. Then they are covered with a glass plate which can be easily unscrewed. The glass plate may get blind, but by unscrewing the protected surface can be viewed. It only needs a microscope viewer to decipher. You can put the parts where the files are and encase them in easily breakable glass. The manual to put them together are visual and easy to understand. Microfiche store 2-3 Million letters (MByte) onto 30x45 mm which gives us a storage capacity of 1.5 GByte pro square meter. Stack them: If we assume 1 plate is 2 mm thick, we get 75 GByte pro cubic meter. One Exabyte (10^18) means therefore 13 million cubic meters. Storing them 3-dimensional means we can estimate the necessary room by taking the cube root and we get a cube with a length of 250 m. So in fact that much information can be stored physically. The problem will be that it is not of much use. We do not understand our predecessors which only lived 1000 years ago, old Germanic or Anglosaxon is inscrutable for persons using only modern language. ADDITION: There were some nice comments below about implementing a [Rosetta Stone](https://en.wikipedia.org/wiki/Rosetta_Stone): Add as much information for deciphering as possible: Manuals with pictures explaining what words mean, telling the same story in different languages, smaller and smaller prints to indicate what the plates contai and use error correction codes to allow information retrieval if the plate is damaged. What is worrying is the timeframe, we are speaking about geolocial spans *when mountains rise and fall*. Our standard materials like modern concrete does not last a century, concrete begins to turn back to limestone after 80 years. If we die out now, after 1 Million years the earth will not contain any traces of human activity if observed from space (even the pyramides will have eroded). So the structure must be underground to counteract erosion which will wear down even the most resilient materials in time. It must be in a region with very low geological activity and it must survive what nature throws at it (earthquakes, flash floods). Then it must use materials which are chemically inactive and durable. All in all building the holding place can be as much challenging as creating the plates itself. Some nice insights from [TV tropes here](http://tvtropes.org/pmwiki/pmwiki.php/Main/RagnarokProofing). SECOND ADDITION: * To mark the storage location, for smaller timeframes (centuries, millenia) insert sturdy posts in lines of cardinal directions where each post can be found not to far apart and where the posts cross the location. For longer timeframes, we can dig out big arrows on all cardinal directions and refill them again. If we do that repeatedly, such landmarks are strikingly visible for extremely long times (meteorite strikes prove the point: While flora and fauna recovered, their marks can be still seen after millions of years). * To prevent vandalism by brutes, we can fortify the entrance. With our available alloys we can defeat any attempt to enter the storage room until they have at least mediaeval technology. To enter the storage, the person must solve a mechanical puzzle like the Chinese ring puzzle: [](https://i.stack.imgur.com/MTXng.jpg) It is a very simple (does not need maintenance or any power source) and can be made very tough to prevent brute force attacks. If something can solve the puzzle, whatever it is, it wants to know (curious) and it is able to know (intelligent). It also invested time and energy to solve the puzzle, so the entrance is a reward and its contents gains value. While it is still possible that vandalism occurs, it is not very likely. [Answer] Put the data on some sort of storage (doesn't really matter what) and stick it in a spaceship. Send the ship on a slingshot around the event horizon of a black hole so that time dilation means a million years passes for us and only a few years for them. Now you have a ship, the stored data, and some crew who understand the language and technology of the stored data. Of course, they don't understand the rest of the universe, but that's another question. :-) [Answer] Use 5-dimensional, ultra high density silica glass discs. In theory, these discs are able to store data forever without reduction in data integrity. Not only is this possible, [it's already been done](http://www.extremetech.com/extreme/160928-five-dimensional-glass-memory-can-store-360tb-per-disc-rugged-enough-to-outlive-the-human-race). You can store ~360 Terabytes of information per disc. But how do you get 5 dimensions per disc? Pulled from the article linked above: > > There are the usually two dimensions (width, height) provided by a piece of silica glass, and depth is provided by writing at three different depths (layers) within the glass. The fourth and fifth dimensions are provided by nanostructuring the surface of the glass, so that it refracts and polarizes light in interesting ways. > > > Keep in mind that they're not normal glass disks. They're SILICA glass disks. You can put them in a safe made of diamond or whatever material you want if you're just wondering where you put the disks. These discs survive temperatures of 1000 °C. Also, these discs are small - they're ~1 inch in diameter, so they're easy to store; even 2778 of them. This method of storage is not subject to erosion because on normal discs, the data is stored on the surface, but on these ones, the data is stored INSIDE the disc using nanogratings. The glass is also chemically stable too, so it wont react with anything. **So if you want to store an exabyte of information using these, you'll need 2778 discs to store it all.** [Answer] In today's world, let us look at the [Rosetta Project](http://rosettaproject.org). Imprinted on a disk made of a nickel alloy that contains 13,000 pages of information on human languages. It is 3" across and expected to have a several thousand year lifetime (nickel was chosen for its high melting point and low interactivity with magnetic forces - its hard to warp). One could easily go to lower densities of data to increase the usable lifetime. The thing is an exabyte is big. Its about 100,000x the amount of the printed material in the Library of Congress. That's about 23M books. Each book contains on average 64,000 words which is about 250 pages on average. This gives 5.9 billion pages for an exabyte give or take. For those Rosetta disks, thats actually a conceivable number - half a million disks at 3" in diameter. About 7 in2. This would then give us something that needs on the order of 2250 m2 to store an exabyte at rosetta disk levels. This is 1/3 the size of a soccer field. Would this last 1,000,000 years? Dunno. Probably not - the disk was more intended for the 2,000 - 10,000 year range. If you wanted to be sure, reduce the data density and start working with issues of geological permanence (consider things like putting it on the moon instead). A key point with this (compared to other storage mechanisms) is that it is intended to be readable by low tech means. You only need a 1000x microscope. This doesn't depend on data formats or advanced reading mechanisms. Its right there. [Answer] Let's be real, in a million years data storage may be done in the form of hairspray for all we know. How many people still have floppy disk drive? And that was only 20 years ago. The new generation doesn't even know what a floppy is, it's just the save icon now. Your best bet would be to back it all up on the current format of choice, then keep transferring from format to format as technology goes on. Don't be shy on redundancies. It will require a lot of space. It will require a lot of effort. It will require a lot of maintenance. But you should be able to preserve your data all the way through. You just have to make sure your physical medium doesn't deteriorate before you save it up on the next generation of CD or what have you. That goes for physical format as well as file format. They probably don't have Word in the future. There's a number of things that can change in the way we treat files in a million years. --- Now having the data is one thing, understanding it is another one. Very few languages nowadays rely on drawing cats and squiggly lines, but that's how the Egyptians did it. Say you back up an exabyte of English text. In a million years, people speak the Beta Praxus Prime dialect of Ozatarian and nobody knows what an english is. You'll have to translate that data into something people will understand, and you'll have to do it at the end. To remain true to the original, I think you should always keep a copy of the original data, and a copy of the translated data. Something may be lost in translation, but you'll still have the original so it doesn't matter too much. If you plan to translate it multiple times over the course of a million years as you change the format of your backups, you should also keep a trace of that. You'll inevitable end up with a few exaoctets of information instead of just one, although there's a distinct possibility that people in the future will laugh at you if you say an Eo is a lot of data. --- Now the last question is: will anybody care about million years old data? It's very possible that the location of the archive will be lost in time, or that the caretakers will decide to do something else with their lives. Or maybe in a couple centuries your country will be removed from history completely for any number of reasons. You can't predict what will happen in a million years, so it's hard to come up with a solution that will still be applicable then. [Answer] Use satellites. * Put a large amount of satellites in space, each with a complete copy of the data to ensure that redundancy is high in case of unforeseen events. * Put the satellites beyond geosync orbit, this will ensure neither orbital decay nor collisions with other satellites is a problem. Below geosync orbit there are too many satellites * Use a high density storage medium. Someone else suggested 5D ultra high density silica glass discs. These discs are dense enough that putting an exabyte of data in a satellite bound to Geosync orbit could potentially be done with current technology. * Include a way to read the data within the satellites or in another place. I don't know what kind of equipment is needed to read these discs, or whatever alternative you may choose. Depending on the complexity you could choose to include the reading devices in the same satellites that hold the data or in another constellation altogether. * BONUS: put huge mirrors on the satellites aimed at earth. Iridium Satellites are famous for this, they are a group of comm satellites with very reflective mirrors, their flares regularly seen from earth without the need of a telescope. If you want someone to easily find your data, this could be a good way to do it, after all, it's not precisely natural to see lights regularly shining in the sky, any civilization with the technology to go to space will be aware that the lights are satellites. [Answer] # Turn the moon into storage The moon has a surface area of 37.9 million square kilometers. According to WolframAlpha, this is equal to 3.79\*10^19 mm^2. The moon has stayed mostly the same over the past few million years. There is no weathering or erosion, just a few impact craters. 1 exabyte is equal to 8\*10^18 bits. Right off the bat, if you have a scheme that can encode 1 bit in 1mm^2 of surface area (possibly use 2 materials?), you have enough space for an exabyte, plus error correction about four times over. Let's look at some other ways to increase the amount of data stored (or better yet, the error correction): * Make the planet bigger. This may have unintended side-effects (atmosphere, more craters, etc.) * Use layers under the surface. However, too far in and you may reach a mantle layer. * Use more materials. If each square mm is one out of four materials instead of out of two, you have double the information density. Your future civilization will know that something is different when they encounter a perfectly tiled moon orbiting a planet. [Answer] Just brain storming. 1 You might be able to broadcast the information with EM waves. If it's a million light years away, or hits a mirror half a million light years away that might work. Would be cool to be expecting the big encyclopedia galactica dump that's coming in a million years. The expansion of the universe would redshift the photons like crazy though, so they'd have to compensate for that. 2 Maybe you write it on the ~~surface of a blackhole.~~ event horizon of a black hole using the holographic principle.\* I don't know how you read the information though. Maybe some kind of hawking radiation read head. You could cop out a little and say "it's not a real black hole, it's an artificial black hole so it has special properties". That could be real lame though. 3 If you were out in the intergalactic space you could probably just store it as bits of matter orbiting some massive center. I don't think much happens out there. 4 Radioactive decay is random nowadays. I don't think we quite know how the weak nuclear force "works" exactly. So maybe you store it as precisely engineered radioactive uranium or plutonium. It'll be silent and not decay at all for a million years, until it starts broadcasting your message over and over. Or maybe you have to turn it on with some weak nuclear force device. 5 You could bioengineer some being that has the code in its DNA. Humans have about 2.5Gigs of DNA so it'd have to be some pretty crazy cells. Life's own maintenance would be the maintenance system I guess. 6 If circling black holes create waves, maybe you can grab bits of spacetime and tie it together in knots. Then you would have this bizarre little space-time hairball but that had information encoded. Maybe something like the South American quipus. Advantage there would be size. The individual knots could be sub planck scale really. I don't know how the knots would stay tight though. Imagine trying to tie knots in the surface of taut spandex. Which I guess you could do if it trapped something hard like a pebble. 7 Whoa it's 23:15 already. Thanks for the brain challenge tonight. Good luck with your story. * Update: including the words holographic principle. Wasn't very clear. [Answer] Single point of failure will not work. You need to make the data store mobile and self-replicating to give it any credible chance of (a) surviving and (b) being found after 1 million years. The problem is that if something is easily accessible, you're saying various waves or energetic particles or outside matter can act on it. Otherwise how would you see it, hear it, probe it, feel it, etc? Over a million years, the fact that the information can be touched will change it. This is (one reason) why arguably the best naturally occurring data system, encoding data in proteins, still isn't able to produce the same information every time. If the first self-replicating "thing" was immune to data entropy, our planet would only have one species (a very simple one). So you need to make something *fairly* resilient, but acknowledge that anything that depends solely on resistance to elements and energetic particles and such is impractical. It either creates a single point of failure, or just ends up never being found. At the the same time you need to overcome the mutation problem. In nature, not every replication comes out perfectly. Your data store will have the same problem since you can't perfectly control all environmental conditions. So you need a "deactivate" signal that you can send to what is believed to be an imperfect replica. And you need a way to judge whether replicas are correct. So in designing your replicating data store, give it introspection and give it an interface for signaling other data stores of the same type. Make a set in this generation that you are confident have the correct data. Have them inspect their own data and communicate that with the others of the generation. If one is found to have different data, send the deactivate signal to that one. It doesn't need to be destroyed - just deactivated to keep it from reproducing the mutated data. It may end up being the best copy available in the event of a local cataclysm. You might also be able to 'repair' clones that came out with different data, depending on whether you use rewritable storage or not. But read only and write-once storage may be more resistant to mutation, so weigh your options. For the data clones that reproduce a generation, give them an algorithm to *move them away from their peers* once they are verified. They only need to stay close enough to the group so that the next generation can be verified by a number of individuals (or else deactivated). In this way you solve the single-point-of-failure problem and make a passable attempt at slowing down data entropy. It could work over the scale of 1 million years. You may end up with subspecies of your data because of unforeseen circumstances preventing mutations from receiving a "deactivate." But you can potentially deal with that in 1 million years by comparing the subspecies and attempting to reconstruct the original data from them. For "easy to extract," if I understand that term correctly, I think you need to build an interface in for any intelligent creature to access the data. It's a million years, so technology guarantees and biological guarantees are in the same boat... you don't necessarily know what you're going to be dealing with. So it would be smart to build in several sensory representations - visual, auditory, tactile - as well as some reasonable signaling using radio or... whatever you think creatures will use for long range communication in 1mm years. So there you go. RepRap 3d printers with an extra exabyte of data payload, you might call them. Best I can do for now, good luck, hope it works for you ;) [Answer] Statistically speaking, you'll lose your data, eventually, so the right way to think about it is along the lines of pushing the probability low enough to be acceptable. As for your storage medium, if you don't want maintenance (e.g. actively making copies) then you can outrule anything that has a measurable decay rate. No magnetic storage, plastics in general, soft stuff like metals (unless in the vacuum of outer space). Instead, think diamonds with holograms etched inside. (Is that even possible? But you get the point.) Even then, you'll lose your data over and over again on that timeframe; it will get destroyed by random events, so you can't rely on a single copy. Let's say the a copy has a 50% chance to be destroyed in 1,000 years. If you have a single copy, then you'll lose it with a 99.930709% probability. If you have 1,000 copies, you have a 50% chance of survival (if I'm doing this math correctly; I'm computing the non-destroyance rates for that time period, for the number of copies; would it be this simple?) Anyway, with 10,000 copies, you get a decent 99.9023% survival rate, but you can go higher pretty fast with more and more copies (e.g. 20,000 => 99.99990463%). You'll also want to use forward error correction to account for partial damage within a single medium. Physical damages usually cluster, so you'll need to make sure every piece of your data is scattered across as much of the medium as possible (holograms already do this, so if that's what you picked you're at luck.) With proper FEC you can get ridiculously robust storage. You can also use FEC to split up your data across several storage media, if you think your exabyte is too much to make full copies, and if you feel it's feasible to expect your audience far in the future to be able to collect the required number of items. If you choose this way, you may want to include references (e.g. their physical location) to the items as metadata. This way, you'll need slightly more copies, but they can be a fraction of the size each (depending on the numbers in your "M of N" setup.) As for the medium, I think you'll need to store your data in something 3D because it's hard to achieve the necessary storage density otherwise if you want to stay under the limits of a building... [Answer] Use a physical and chemical process that has already demonstrated adequate lifetime. Bury it in silt in ... maybe not the bottom of the sea, but a physically similar environment in a geologically stable region of the planet's surface. After 200 million years, an exoskeletal fish can look like this, with every scale visible. [](https://i.stack.imgur.com/aCBIn.jpg) ([image source](http://www.fossilmall.com/Science/FishFossils/Osteolepiformes/Osteolepiformes.htm)) Scales are black, glossy, and around 2 mm across - this image looks approx life size on my screen, and the fish is compressed to somewhere around 1mm thick - you can see thin black layers in a cross-section of the resulting sedimentary rock, which is very easily worked, as stone goes. It tends to slice into the original layers very easily, with a skilled tap from a hammer, but I imagine a grinding or polishing process to expose each layer may be more reliable. So a conservative storage system may manage about 1 bit/mm^3 or 1Gbit/m^3, or 1 Exabyte in a mere 8 cubic kilometres, say a 100m deep layer on an 80km^2 lake bed. I have seen mother-of-pearl sheens on ammonite shells, so the possibility clearly exists for much higher information density (optical wavelength scale), but the sheen often fades on exposure to air, so I wouldn't recommend relying on high density storage. However, different kinds of creature can coexist in a mixed fossil bed, so there may be scope for storing the same information in different forms - if the high density can be read, it saves a lot of laborious splitting, grinding and polishing to read the mm-scale backup information. [Answer] ## Found a religion This question exposes many kinds of problems. Most of (very good) answers have centered on the problem of actual preservation of information in a physical medium, and how that medium can be made to last such a long time. Suppose we have million-year media. Then we are confronted with a group of issues that could be summarized as "Now, how do we preserve the metadata?" By *metadata* (in case it's not obvious), I mean the following kinds of information about the information in question: * Where is it stored? * How to read or interpret it? * Which parts of the information are arbitrary and which are objective? That third challenge is a bit subtle. Here's an example of what I mean by it: Suppose you are communicating with aliens using radio transmissions and no human has ever physically been in the presence of one of these aliens. How can you explain which is "left" and which is "right"? While you're chewing on that, I'd like to follow up with "does it even matter?" Before you comment with all kinds of thoughts on that last paragraph, let's get back to the question at hand. Clearly, there is information *about* the information that is important. If we try to come up with some way to preserve the metadata along the same lines as the primary information, then we just have moved the problem "down one" to now needing to preserve the meta-metadata. What's really needed is a ***system*** that is self-sustaining, resilient, and flexible enough to be able to operate in the face of disasters, mass migrations, etc. Burying some esoteric materials with important information written in a simple, universal language, with built-in language lessons in a deep chasm on Earth in a place that is geologically stable with a resilient marker of some sort above it will be useless if humanity has to (or chooses to) flee the Earth entirely. If instead we can motivate a large enough group of people to write down, translate, discuss, pass down, and re-interpret the information for posterity, along with the mandate that the posterity in question continue the process, that might be the best chance to actually have that information available to humanity over an arbitrarily long timeframe. History shows us that the oldest information we have from our ancestors is almost universally religious in nature. The oldest extant man-made structures (in which much information is preserved) were built by a theocracy. Now there are some problems with this plan: * The nature of religion in society may be changing - i.e., past history is no indicator of future performance * Even in just 2000 - 3000 (to say nothing of 5000) years, precise interpretations of religious information have been made questionable by problems in translation and lost cultural references/assumptions * Many religions have died out (although we know that because the religious material created by the followers survive the death of the religion) Regarding the constellation of issues with this plan, which we might summarize as the "telephone game problem" (i.e., when information is passed along, translated, copied, etc., it's almost always corrupted in some way), even with information that has **not** suffered from the telephone game problem still isn't perfectly preserved. The US Constitution isn't even 250 years old, is written in a language that is the number one or number two most widely spoken one in the world, is still preserved in its original form, and *still* isn't 100% clearly interpretable, which we know because there are countless intelligent people who can argue over interpretations of various sections of it. The writers of *that* information actually built in a preservation system that is meant to be flexible enough to preserve it - the Supreme Court. Once again, we have a dogmatic *system* that is maintained by the very people who need the information. Such an information preservation system embraces the fact that information that doesn't change format or interpretation actually becomes obscured and lost in time. Based on where we are now and what we know about science and humanity, if I wanted to preserve information for as long as possible, starting with today, I'd try to get it into the Torah somehow. That book seems to contain the most effectively preserved information in all of human history, and the preservation system (Judaism) has arguably endured greater challenges than any other in history. [Answer] You probably already know that information is stores in hard discs, solid state drives (SSD's), flash memory etc. as a stream of zeroes and ones. You could literally sculpt that out on some plains or plateau of a dead world. By dead I mean no geological processes to erode it. The moon is a candidate. Use a hole/depression for a zero, a cone for a one. Or better yet, sculpt actual zeroes and ones for fun. If each symbol takes one square millimeter, back of napkin calculations\* say you could write your data on the moon about five times (might have to flatten it prior to writing, though). You could always make your symbols smaller if you want to. There are methods to recover lost data from remaining good data in case some meteorite strikes your artwork. Do some googling on "Hamming code". This will require you to write down more than an exabyte, though. For redundancy, carve it out multiple times on a single planet. Better yet, do this kind of artistic intervention on multiple planets/moons. Charon, Phobos, Deimos, Ceres etc. come to mind. As for recovering inormation, all you'd need is a sattelite with a good camera. You could read it all in a few passes of the sattelite. The funniest part of this is that once your civilization is completely gone from this universe and other intelligent lifeforms arise, they may spend eons in fascination trying to figure out all your videos, game saves, emails, porn etc., believing those to be an encoded message with the key to understanding life, the universe and everything. God knows I would put some Rick Astley in there. By the way, this method is probably good for three orders of magnitude more time than you need, should you wish to troll aliens for a longer span than a million years. .\* An exabyte is 8\*10^18 bits. The surface of the Moon is around 3\*10^19 square mlilimeters. [Answer] I like the idea of using doped quartz as the recording media. There's going to be all sorts of trade offs between recording speed and size, and the larger the size, the fewer the number of copies. You'd certainly need redundancy. I like the idea of a tomb on the moon, but am not sure that the radiation would be low enough to avoid significant data loss. Clearly, you can't shield from neutrinos, and the radioactive decay processes going on a couple of km below the Moon's surface aren't known by me (if anyone). A couple of tombs on the Moon, a couple of (artificial?) asteroids on highly elliptical (and out of the ecliptic) orbits and that should do it. [Answer] I assume it will only be read after that million years, not during it. Because if it's also read during a millions years, then you would be better off just recopying the data to newer storage media and basically take it wherever your society goes. Bluerays (or CDs, DVDs, etc) should be one of the most long living technologies available right now (assuming you store them properly, detailed below). (people disagree with me on that. Until I take the time to research the life time of plastics under the storage conditions I described: use a metal as the substrate and recorded layer and some crystal as the cover layer, using the terms from [Blueray specs](http://www.blu-raydisc.com/Assets/Downloadablefile/White%20Paper%20BD-ROM_Part1_9th_20150806_clean.pdf) page 2) They actually have a physical structure which encodes the data, and that structure should be clearly visible as soon as you put it under a good microscope. Of course you can also use fancy cristals like in the other answer. But optical discs are tested, reliable and cheap. Of course if you are just making up a whole world it doesn't really matter. Just use something where the information is stored in the arrangement of huge numbers of atoms which is obvious even if the current method of reading them out is absent (say NAND chips would probably need more examination before it becomes clear how they work plus they are more susceptible to high energy waves flipping bits. Tapes would probably be easier to figure out than NAND chips, but still less obvious than optical discs and could be wiped by magnetic fields because it's not the arrangement of atoms which encodes the data, but the way the electrons circle around the atoms). ## (modified) Bluerays for one Exabyte * 0.5\*10^8 of them at 20GB per disc * that is less than 1000 m^3 * Choose a planet without tectonic activity (on Earth, anything you put anywhere for a long time basically ends up molten in the core if my understanding is correct). * The planet needs a temperature around -20 to 50 degrees Celsius (rough estimate), but probably colder would be fine too, just not too hot. * Put them in a massive bunker. No doors or anything, just a huge blob of beton and steel. * Clean helium (or pretty much any noble gas) atmosphere inside. That also means no water. * Your bunker needs to include as much protection from high energy waves as posssible * Make the bunkers visible from space (in a way which stays visible for a long time. This is much more difficult than preserving the data) * Do multiple separate bunkers each containing the same data, preferably on multiple planets. * Reading the data will probably involve destroying the storage unit or at least damaging/opening it in a way which will make sure it doesn't survive long afterwards ## Understanding the data The pure quantity of data should ensure that anyone discovering the discs can figure out the pattern behind it without further instruction (as long as the data on it is fairly varied, say includes at least an uncompressed copy of Wikipedia or similar). The way that would probably work is that * first they would find the codes for letters. Those would appear extremely often. * Then they could make out words and start by applying language models and stuff. Considering they would have dictionaries and everything available, with more complicated words explained in terms of easy ones, they should be able to work their way upwards. * in parallel they would learn our image formats. They would already know about ways to store images, so they would probably search for them and just apply any image storing schemes they know to a lot of data until they get images they recognize (say of a sun, or of biologic cells, or of probability distributions of electrons in atoms or whatever) * by understanding some XML markup and disc structure (which are computer languages, which means they are simple to analyze) they could understand Wikimedia entries in the sense that they have pictures linked to words * and so they would have labelled images which they could use to link the basic vocabulary to pictures * which in turn would help them understand more of the language so they could understand more of the image descriptions * etc ## Surface structures Two answers so far suggested encoding the information on the surface of the moon, in structures where one bit is the size of a square millimeter. There are problems with that. I'll discuss the example of the moon, but should be applicable to other moons/planets. * According to Wikipedia 5 tons of particles hit the moon per day. In a million years that's 4.8 mg/cm^2. If the weighted average speed is 20km/s then that would be the equivalent of half a gram of TNT being detonated per cm^2. This is (much) less than I initially expected, but it will still erode most materials quite a lot * Because of this you would need to use a relatively think layer of a relatively strong material (say at least 1mm of a metal if you are doing a hole/no hole encoding) * You have a huge surface for chemical reactions, your materials would need to be chosen very carefully * Roughly guessing from this Wikipedia graphic about the diffraction limit, using a (seriously huge) camera with an aperture diameter of a 100m you could read mm-big structures from up to 200km away. This assumes the surface is illuminated enough, etc., this is a theoretical limit. So basically: it's theoretically possible to read it from orbit, but you would need crazy technology to do it and the 0/1 encodings would need to have a really high contrast (reflects almost nothing / reflects almost everything) * using 1mm thick material to coat the moon takes 38km^3 of material * you probably can't use material that's already there because it wouldn't be sufficiently strong or wouldn't have the right color or the right chemical properties So all in all, it's possible, but not practical. If you want something far fetched which may sound fun in a story, fine. If you want something which could actually be done with current technology, better use bunkers containing storage mediums. The surface would be better spent putting some elements there which are unusual, attracting the attention of scientists. Or maybe unnatural, very large scale patterns (so, many km instead of one mm) designed to be as visible as possible. [Answer] This is a very interesting question. Actually, there are some experiments that use plants and their seeds as storage mediums - <http://www.dx.doi.org/10.1007/s11248-016-9981-1>. For example, citing from <http://www.storing-data-into-living-plant.net/experiment> :: "1g of DNA can store exabytes of data and this is huge capacity. Protected within a seed or a living plant can last for millenia." Thus, it may solve your problem. However, there are still many open questions... [Answer] Here are my thoughts: the information can be stored as a sequence of numbers, if to this sequence add 0(or two..thousand 0) at the beginning - we get the result of division of something (take the speed of light as a constant) to something else - in our case it will be the speed of the emitted object. To read information we need measured by the speed of our object. The only problem is the accuracy and acceleration measurements. By analogy we can take as a constant size or weight of the atom and to record information in the form of a ratio of the mass of our facility to ensure that we have taken as a constant. [Answer] Readed all answers and comments. Correction codes are in some. In some are question about structure and decryption that information. ## Fractals Fractals, or at least principle is very useful. There are 3 images, click will open full image: [](https://i.stack.imgur.com/Ijjt4.jpg) [source](http://old.mosaicproject.it/) [](https://i.stack.imgur.com/y93vQ.jpg) [source](http://www.mazaika.com/maztutor/compare/mazaika_norm.jpg) [](https://i.stack.imgur.com/Xvh9D.jpg) [source](http://www.designerstalk.com/forums/discussion/76804/photo-mosaic-software) All tree images are kinda fractal in informational sense (hmm, if imagine that first one gray-white is made by 1-0) second is connected to movies data, 3th to biology. In same time, by them selfs, they show image encoding systems-approach, and if someone grasps fact that this is image, he just automatically will get knowledge about approaches we use to encode visual information. Also interesting moment, faces will be recognized by humans, as long as they are humans. Not sure about million years trough, but assume it's about peoples. For other species it will be tricky part to recognize that this is information (if we talk about primitive technologies, but even for advanced it may be a challenge, depends how we encode) Nice thing about such approach, deep leveling information. It may be readable even for stone age peoples. Yes it will take some time for them to read it but, this information may guide them from beginning from stone axes to tunnel microscope. Each layer is accessible on current level and describes access to next level. This leveling structure is good also because of density of recording, it may totally consists from subatomic records, but still kinda be accessible from stone age tech (yes, they have to born concept of information as such, but not necessary consciously, sub-consciously will be ok too) Probably I'm not original, also I would like to see more sophisticated approaches. [this Image](http://voyager.jpl.nasa.gov/spacecraft/images/golden_record_cover.gif) is Voyager gold plate [](https://i.stack.imgur.com/QxhBY.gif) As human born in our time and as one who is familiar with concept of plots etc. I have 3% clue what this picture have to mean. Long time I tried not to spoil meaning of that plate, and I think I almost did that(until first smart comment of course - no spoilers pls). Time will come and I will imagine myself as alien civilization, which tries to guess what hell that means. (almost did that, f spoilers popped up - have to wait next 10y to forget). But those who do not know exact meaning may test them self. Back to fractal knowledge. Roll out that knowledge is like learning, and this process may be compatible with human behavior, learning style. As small kid learns world, so will be such representation learned. Literary, it may be available almost from begin for a kid, as toy maybe and may lead him trough live to PhD in Physics. My first experience of English was watching cartoons, although I learned that language barely enough to communicate, but still. But it may be not only vocal language, but also it have not to be mathematics just from start. Because mathematics as whole is also concept, existence of which it is a knowledge to be learned first by it's selfs. Not sure if it will work on 1kk old humans, eventually it will, probably, specially if form of that storage will be handy to smash something. There may be much more connections to human nature than just form or visual or even sound (natural frequencies of that storage as example), in data structure, what attracts our attention on refectory level and so on. It may be so specific to humans as whole, so it may be big challenge to other intelligent creatures to read that information without humans, and still be accessible from stone age level for humans. That way storage may be as dense as it possible for civilization who records it, be cryptic for others, be accessible for those who have to read it, in wide range of their development and knowledge. ]

[Question] [ Let's say a human engineer comes across an alien electronics lab. It occurs to me that electrons are electrons, if the aliens are at a similar state of development to us then at least the simplest (discrete?) components might be similar in operating principle and should be recognisable. On the other hand, alien electronics could be very different. Assume that: * the aliens are at a similar level of technology to what we have today. * the engineer has stumbled upon the equivalent of a university electronics lab, well equipped makerspace or *very* well equipped hobbyist's workshop. * the aliens have similar requirements for their components that we do, mainly being cheap to produce and reasonably reliable. They identify components by sight, like most humans. * the only tool the engineer has with earth-style units is his trusty multimeter. **How different are alien electronics *likely* to be? What sort of components would the engineer be able to recognise first and how? How quickly could he begin working with alien tools and components?** --- --- **Having read the answers and comments so far, I would like to clarify some points. I'm sorry if I did not make myself clear before.** * The aliens are not significantly more advanced than us. Their electronics are based on the same principles as most Earth electronics, generally **not** bio-electricity, weights and pulleys, etc. Memristors (which, admittedly, I only just learned about) are fair game. * Silicon is a [fairly common element](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements). It would be strange if the aliens did not have access to it. Ditto for anything else required by Earth style electronics. * The alien lab certainly has more tools than a mere multimeter, except they are all marked in a different language. **Addition:** The engineer has access to a power-supply with a knob for selecting voltage and limiting current. He doesn't know what the units are however. (I foresee calibration involving a melted piece of wire...) Likewise, oscilloscopes, logic analysers, etc., are available, but are all marked in alien units. (Anything a well equipped electronics lab would have, the aliens also have.) (I don't *think* I have broken (m)any answers here, if I have, sorry.) [Answer] The trouble here would be dealing with more complex components. There are two main [types of electrical components](https://en.wikipedia.org/wiki/Electronic_component#Classification). Active and Passive components. Passive components tend to be simpler, your resisters, capacitors, transformers and so forth. These it should be possible for our engineer to work out given his multi-meter and some basic knowledge. Does it measure as having any resistance? (Resistor) Does it allow an AC current to pass? (Capacitor) Is it made of a lump of ferrous metal wrapped in two sets of wires? (Transformer) Though our engineer will probably still destroy quite a few components working this out. Active components on the other hand are an entirely different kettle of fish. Most active components look like a blob of plastic with some metal sticking out and some markings to tell what they are. Think every thing from the classic transistor to the CPU inside your computer. Almost every engineer when faced with a component he doesn't know will stick the code printed on it into Google to find the datasheet. Our poor engineer doesn't have this option. (Language being the big barrier here) Many many human components are encased in very similar packages, this makes standardisation of machines to produce things easier so I would expect the aliens have probably done some thing similar.  These are three components taken from my arduino starter kit. One is a temperature sensor and the other two are transistors. Good luck telling them apart if you don't have Google to look up the codes. With out knowing the correct way to wire up the thing the only options are experiment and destroy lots of them, or find one in an existing circuit and try and work out what its doing. Neither of these options are easy or exactly safe. Who knows what the aliens make the components out of. I hope they phased out lead already for the sake of our engineer. Having a few extra tools may make things a lot easier. An oscilloscope and power supply would be extremely helpful. **Edit: from question edit** They should be able to identify the other tools. It may be hard to tell a power supply from a multi-meter at first but it should be reasonably easy given the multimeter and a willingness to blow up a few components. The power supply can be calibrated using some thing they can identify as a resistor and their own multimeter. Once he has worked out the voltages the dial gives out he should write a new marking sheet if it has a control nob, or a translation of the symbols for different values displayed otherwise. This will let them figure out the numbering system reasonably, which should also let them start to make more sense of other components. [Answer] As an electrical engineer myself, I'd say it would be very hard to figure out what was going on without having some sort of introduction to the alien's technology. There's a few reasons for this: **1. It's hard for us to do it with our own technology:** Even for human parts if you can't read labeling and don't have any datasheets, it's extremely hard to figure out what individual chips do. A chip could be a counter, a microcontroller or an [ASIC](https://en.wikipedia.org/wiki/Application-specific_integrated_circuit). Even with human electronics, it's a non-trivial process to reverse engineer a PCB. (See this interesting talk about it: [Deconstructing the Circuit Board Sandwich](https://www.youtube.com/watch?v=O8FQZIPkgZM)) **2. They might have fundamentally different discrete components:** For instance they could use [memristors](https://en.wikipedia.org/?title=Memristor) as a discrete component instead of a transistor, besides that, who's to say they've developed transistors as the basis of their decision making electronics? Our transistors have evolved so much because we have readily available semiconductors (silicon from sand). Maybe the aliens don't have such access. To try to figure out the alien technologies, we'd probably need access to some highly specialized tools. Think xray machines, acoustic microscopy machines, etc. These would be used to examine alien IC's. We'd probably also need to destroy some of their IC's to study them (that's really the only way to probe things inside the IC..) In short, he probably wouldn't be able to learn very much with just his multimeter and no introduction to the alien language. [Answer] During my university studies (electronics-related), there were some big surprises when we got to study microwave circuitry. Look for example at this circuit:  See those seemingly open and closed circuits coming out diagonally from the horizontal basic circuits? Look particularly at the first one. Until that point in my studies (3rd year IIRC!), any of those shorts would render the rest of the circuit parallel to it moot, because, well... it's shorted! No? Well, no. The moment you start using high frequencies, high enough that the wavelength is similar to the length of the transmission lines, then those transmission lines start having a serious effect - to the point that you implement capacitors and chokes with simple pieces of transmission line. As in here: these line stubs are implementing filters. In real life, those could be pieces of wire "going nowhere", or traces in a PCB "going nowhere", or even pipes (AKA waveguides)!  So, answering your question: you don't even need to have unknown components to confound someone without the right theoretical background. A multimeter is the only thing available? ... well, at least make the multimeter protected enough so your engineer won't [die the moment he probes something he shouldn't](https://electronics.stackexchange.com/questions/98277/what-are-the-dangers-of-a-diy-fuse-in-a-multimeter) ;P --- The question was edited to say that the engineer has more instruments, only in "alien units". So you seem to keep thinking that the problem is the units. Well, how are those aliens physiologically? Maybe they have better hearing (absolute pitch for example?) but worse sight than us and then might prefer to use an "audio oscilloscope" which instead of drawing in a screen emits the waves in the alien audible range? That would make things complicated, even if units were the same... [Answer] I like many of the answers here but didn't see one aspect of this covered that I think is very important. ## Yes But only if we are close to or more advanced than the aliens in electronics. We only have a chance of figuring it out if we have the scientific underpinnings to understand the devices being used. If the aliens are too advanced, we'll see a device that not only has no comparable device in our electronics but we don't even understand how it works. What are the relative technology levels? ### 400 year difference If you hand modern 2015 electronics to people 400 years ago and ask them how it works, what would they say? Witchcraft, magic, or some other superstition most likely. No one even understood the most basic principals of electricity, let alone electrical circuits. Forgot about electronic components. ### 100 year difference If you hand modern 2015 electronics to people 100 years ago and ask them how it works, what would they say? A knowledgeable engineering or scientist would correctly identify wires and could probably determine which lines were AC vs. DC. However, they wouldn't understand much about how electrical circuits work and still wouldn't know anything about electronics (e.g. transistors and other components). I suspect that if they microscopically examined a chip they wouldn't be able to even see the printed circuits. If they did they wouldn't have a clue about how to manufacture such a thing. Even worse, they wouldn't have the theoretical basis for understanding how it worked. ### 50 year difference If you hand modern 2015 electronics to people 50 years ago and ask them how it works, what would they say? The basic theories and all of the components that we commonly use now were known then. Microscopic examination of a chip with the right equipment likely would reveal that it was manufactured. They would be able to tell that it was supposed to do something but they wouldn't know what nor would they be able to manufacture it. They wouldn't know the likely voltages and currents needed to activate the various components so their testing would likely be destructive. ### 5 Years Difference If you hand modern 2015 electronics to people 5 years ago and ask them how it works, what would they say? Well if it was humans, they'd likely have the future electronics already on the drawing board or in R&D. We might not be able to replicate the manufacturing techniques but we'd have a very good idea of how they did it and how we might be able to in the near future. Chip factories plan when to switch over to new fabrication techniques years in advance so our factories might even be preparing for cutting over to the techniques use on the chips we found. ### What does this mean? Use this as our guidelines, in order to have a chance of understanding alien technology would require us to be more advanced or not more than a decade or two behind them. If not, we might not even possess the theoretical understanding required to understand the device. Even now, we're just getting to the point that we might be able to start including memristors in our electronics repertoire. On a side note, there's a whole industry that builds "test stands" for boards and chips. You plug the chip or board in and the stand tells you what works and what doesn't work. *If you assume* that we could get the volts and amps required to run the electronics figured out, then you could simply apply signals to the various leads and see what came out. This would take a long, long time to complete the testing and formulate an idea of what the outputs mean. You'd likely automate the testing and we'd likely compare the output with the outputs with those from electronics that we have. If the alien electronics didn't have human counterparts, the chances of figuring it out would be remote. [Answer] **How different are alien electronics likely to be?** Visually: Passive components should be recognisable as passive components within seconds due to their simplicity. Active components would be recognisable as active ones because of their proximity to passive components. Exactly what each passive component does is more involved. There are four fundamental types of passive components. You can chart their relationship like this:  (source: [Wikipedia](https://en.wikipedia.org/wiki/Memristor#Background)) At this point, it's all driven by the laws of physics, so alien electronics would behave like human electronics. **What sort of components would the engineer be able to recognise first and how?** Two-leg passive components such as resistors, capacitors, and inductors. Using the above relational diagram, it's not difficult to conduct simple tests to work out what each component is. The exact properties of each component is more difficult. It's easy to say *"Oh, hey. These purple triangle things are capacitors"* but it's far harder to say *"This purple triangle thing is a 6.3uF capacitor."* But to be fair, we have trouble doing that with *human* electronics today. What we do to solve that is write things down in standard notations. We mark resistance with a [standard colour-coding scheme](https://en.wikipedia.org/?title=Electronic_color_code);  (source: [Wikipedia](https://en.wikipedia.org/?title=Electronic_color_code)) We have similar systems for capacitors and inductors. It isn't unreasonable to think that the aliens may also have standardised labelling systems. What your engineer needs to do is to start measuring every discrete components they can, and correlating that with any identifying markings on said components. **How quickly could he begin working with alien tools and components?** If your engineer doesn't have a background in [Signals Intelligence](https://en.wikipedia.org/wiki/Signals_intelligence) (or brings a friend who does), then they're going to spend a *lot* of initial time working out the units. This is just for passive components. Once they know the alien basics, they'll be able to expand from there. But when it comes to active parts, unless your engineer gets access to the alien datasheets on the components in question, they'll never achieve much. [Answer] There's no reason to imagine that anything they do is comprehensible to an engineer with just a simple multimeter. This comes to mind: <http://amasci.com/elect/mcoils.html> Current electronic circuits use electric fields and currents, typically, and not magnetic fields in coils. While things like inductors do make limited use of magnetic fields, a culture that made use of magnetic fields, rather than electric ones, could completely baffle just about anyone with a multimeter. In addition, there's no reason why we can assume that these aliens have standardized on anything that we would consider reasonable. For example, they might have standardized on 3-state logic (+, 0, and -), or on something like analog logic. On top of all that, there's no reason why their interpretations of physics should be similar to ours. Although it may be hard for us to conceive, there is nothing sacred about the way we consider electronics. Potentially, chips could be optical in nature, and exploit properties of optics and quantum mechanics that are considered as trivia for us. Even if you ignore the issues surrounding datasheets and Integrated circuits, electronics is one of the largest fields. If you took a specialist in robotics and showed him high-frequency RF electronics, I would expect them to appear extremely confusing. Beyond this, there are all kinds of things that you could do with electron streams or more exotic components. For example, if the system were based on advanced forms of vacuum tubes, memristors, or op-amps, then I think you could quite easily baffle someone, even with a simple circuit. [Answer] Couple of stray thoughts to add to what's already been said: Fundamental first question is: What is universal and what is coincidental? Some things are basic facts of science, or can be proven by simple mathematics. To take a simple example: Aliens will not have triangles whose angles do not total 180 degrees. Aliens will not have Platonic solids that we have never thought of. Or in science, assuming that our chemistry and physics are not totally wrong, aliens will not have stable elements that we are unfamiliar with. Etc. At the opposite extreme, I would be very surprised if aliens who had previously had no contact with humans used USB cables. I mean, cables with the same number of wires, and those wires arranged in the same order and performing the same functions. There are too many details in there that could easily have been done a different way. As we've never met an alien race, it's difficult to say how much technology is "inevitable". At a fundamental level: Would aliens even use electricity? Or would they have some alternative technology that accomplishes a similar purpose but works in some totally different way? Maybe aliens use a form of energy that we have not even discovered. Just like people 200 years ago had only the vaguest knowledge of electricity, maybe aliens use some form of energy that we don't presently understand at all. Or more plausibly: Maybe aliens build machines using some principles that we are familiar with but haven't built a technology around. Like their machines all use magnetism, or gravity, or water running through hoses. I tend to doubt it, but I wouldn't rule it out. Assuming they use electricity, I think they would have to have concepts like voltage and resistance. Those would seem to be fundamental scientific truths. Could they build sophisticated devices that do not have wires and resistors and transformers and transistors and so on? I don't see how they could not use these basic devices. As others have discussed, identifying any particular alien electronic component, even if it is just like a component we use, could be difficult. Is there any fundamental reason why resistors have to be cylindrical and have color-coded stripes on them? Why couldn't someone make square or pyramid-shaped resistors? Etc. I'd have no confidence that I could recognize a component just by looking at it. Presumably with sufficient test equipment you could figure out the simpler components. [Answer] No, this is not at all likely, and we can prove this here without alien technology. I can source a marked component from one country (say, China), send it to an engineer in another country (say, the US) and many components would be unusable for that engineer regardless of their testing with a multimeter, oscilloscope, etc. They may be able to figure out it can be used as a resistor - in the lab environment, but it might turn out to be a thermistor, and change radically when exposed to a different temperature. It might look like a transistor, with a small black transistor-like case, and it may act like a diode in the lab, but when put in an enclosure it might stop working as a diode and start working as a transistor because it's really a photo transistor and its operation changes based on the ambient light. Aliens might be using magnetic fields more than we do, and might have "passive" devices that operate differently based on their physical orientation to each other, in addition to their electrical connection. But even if we can discern the basic behavior of a particular device, we can't easily test its limits. Let's say we correctly find an NPN transistor - or a device that behaves substantially like one - what can we make out of it that would work reliably? Let's say you make a simple AM radio receiver. It works acceptably, so you take the same components and build an AM radio transmitter. It fails with a puff of smoke because you're running too much power through the final amplifier transistor. You would have to go through tens, hundreds, or more of specific devices to find the few transistors that are linear and can handle the power load you want to put on them. It isn't so much an issue of finding the basic elements, it's also knowing their limits, and other characteristics that will allow you to build something from them. And this is for basic/simple passives and switching elements. Modern electronics include many more complex active elements up to and including digital processors. Who knows, perhaps they've perfected analog processors, but even if they are miraculously using digital computing elements that follow the Von Neuman or Harvard architecture and use binary math, we have little to no hope of figuring out how to program them in years, nevermind months, nevermind days. The question then is how complex a device is this engineer going to be called on to build? A flashlight - yeah, sure, she can do that. An AM or FM radio receiver - perhaps. A transmitter of any sort - That's tough. I'd say maybe - with a lot of time and testing. Weeks, maybe? Anything more complex is practically impossible. You could use hand waving and explain that this is some sort of savant engineer, but it would be extraordinarily jarring to those without industrial strength suspenders of disbelief. The fact that we already have this issue between different countries suggests that doing this without help across the galaxy is pretty ludicrous. [Answer] There are certainly alternative ways to build electronics. Vacuum tubes were the standard for around 40 years, until the interesting effects of doped silicon were discovered. But the effects of doped silicon weren't an accidental discovery - they were predicted by sufficient knowledge of atomic structure and electron energy levels, and this is a universal (literally!) fact. Also there's a limited amount that a vacuum tube can be miniaturised (the heat, high voltage/current and protective atmosphere impose some serious engineering challenges, which again is universal), which means any alien civilisation with a similar tech level is not going to be using them. Silicon isn't necessarily the answer - GaAs or other solutions are equally possible. We have plenty of silicon so it's the obvious choice, but other worlds may have other chemical makeups. Finding an alien race with roughly the same tech level is going to be quite a challenge though. Just finding another alien race is rare enough. But you only need to go back one generation to find home computers that were playing blocky games, and business computers that were room-filling beasts. Back another generation, and the only computers were warehouse-filling monsters, and mostly you only got discrete components. Back another generation, and the first computers were just being used for code-breaking, and mostly you had to make your own components. Back another generation from there, and "computer" was a job description for (mostly) women working out calculations on paper. There was still a lot of interesting tech back then - it's fascinating how the Victorians implemented mechanical control systems with differential gears, spinning weights and other funky steampunk stuff. But that's off-topic for this question. [Answer] Imagine those little alien components with the tiny writing on the flat parts ...what if none of them were using use voltages under 1,000V? When cut open, they instantly stop working. Turns out that they were all microscopic vacuum tubes, using cold-cathode Field Emission. Even their diodes, even their white-colored fused-quartz solar panels, hundreds of thousands of sodium phototubes in flat arrays, which generate power from the UV part of solar spectrum. No silicon anywhere, just silicon-dioxide. Or instead, imagine all of it using 50KV. They'd never discovered batteries, so they used high-voltage-low-current for everything; generators based on whirling or vibrating capacitor plates. It's what we disdainfully dismiss as weak, unusable "static electricity." For them, 1000Megs is a fair conductor, and 1Megohm is a dead short. Or, what if our own rare use of high power ultrasound and quartz fiber acoustic waveguides were their main choice of electronics? Acoustic solid state switching, "sound-Transistors?" What would that stuff look like when converted into circuit boards and ICs? HG Wells, for "War of the Worlds," postulated a Martian civilization which never invented the wheel, yet was more advanced than Earth. Not ridiculous, since when the Spanish invaded, the Mayan civilization was similarly advanced in govt and organization, but hadn't yet invented the wheel. Well, they had, since they had wheeled toys. (I can imagine a Mayan engineer being disgusted over the concept of using baby rattles and diapers and ridiculous kid's toys to construct serious military hardware, much less to run a powerful civilization.) Further, what if the aliens stumbled across, let's call it the "R-device," but we'd never fount it ourselves. It was a physics invention to rival fire, or metal tools, or the wheel, and they had it but we didn't. Well, we actually had it, but it happened in 1880, and was ridiculed and never used for anything much, and is still buried in old reports. Not a question of "advanced," more a question of the level of scoffing in their science/engineering communities. Everything in their electronics was R-device based, and totally unrecognizable to us, like a vacuum-tubes civilization encountering transistors. Heh, the transistor itself was almost lost this way. Invented in 1923, prof. Lilienfeld even built a transistor radio and took it around to manufacturers. He met a brick wall of universal hostile disbelief, and finally gave up and retired to the Caribbean (on his money from inventing the electrolytic capacitor.) His was his thin-film MOSFET deposited on glass. It was forgotten, and only decades later did Bell Labs re-discover his patents. They couldn't work on FETs, since they considered it worthless (expired patents, no way to profit.) Almost by accident they discovered the BJT transistor, completely patentable, and so the tech world went crazy. And along with their first published paper on their "Crystal Triode," they published another paper on Lilienfeld's mosfet, but hid any reference to the inventor, and then lied, claiming that his transistor didn't work. Later students built it and found it worked fine. (Scientists concealing source references in research papers? Flagrantly lying? Heh, Bell Labs was a business, not a science lab, people always forget that.) Only two decades later did anyone start doing serious work with FETs again ...forty years after the original inventor had discovered the fact that zero manufacturers had any interest in miniature pocket-size electronic devices. No money in it! How can they ignore a transistor radio in 1928? Simple. "(sneering laugh) If this was important, scientists would already know about it, and OTHER manufacturers would have jumped on it already." Imagine all the useful components which failed to pass the human hurdle of disbelief, while the aliens welcomed them and put to wide use. There might be one or two examples. Or there might be hundreds. Threepenny Opera: *Those we see, are in the daylight. Those in darkness are not seen.* [Answer] In evolution there's a term for when two distinct species have the same phenotype but arrived at that state through distinct evolutionary paths. I believe that idea applies here. For example, transistors started out as giant pieces of [random junk](http://www.beatriceco.com/bti/porticus/bell/images/transistor1.jpg) then got [better](http://gitmi.com/blog/wp-content/uploads/2014/10/Hiatchi2SC8971.jpg) and [better](http://www.jetav8r.com/Vision/Ignition/Transistor(TO-220).jpg) and [better](http://i.ytimg.com/vi/Fxv3JoS1uY8/maxresdefault.jpg). The requirements for smaller, faster, lighter, cheaper (FLC) would hold sway in the alien economy as well. Each change to the transistor came by way of innovations intended to better meet the FLC mandate (and make bigger profits). Our versions of the components are the way they are because we tried other form factors/configurations/standards and those didn't work as well or were superseded by something better. (this argument implies pure survival of the fittest but reality isn't this way. First mover advantage has a huge impact too.) Implementation details such as some parts of the form-factor for a component would be different because an alien designed it. Likewise the standards voltages/currents in the electronics could be different because a different set of individuals had input during discussions at the standards making body (AISO - Alien International Standards Organization). Maybe high voltage would be 6 volts instead of our 5 volts. [Answer] There are alternative ways to build electronics. For instance, an amplifier may be built not just from vacuum tubes, bipolar transistors or field effect transistors. An alien may choose to build an amplifier from [Gunn diodes](https://en.wikipedia.org/wiki/Gunn_diode), [transformers](https://en.wikipedia.org/wiki/Magnetic_amplifier), [tunnel diodes](https://en.wikipedia.org/wiki/Tunnel_diode) or [optical](https://en.wikipedia.org/wiki/Optical_amplifier), and this will work. These alternative solutions are known for human engineers. They are not as efficient as widespread solutions, but in an alien planet this may be different. Hence understanding the alien electronics may require very wide expertise, applying knowledge that is available but not widespread. [Answer] Heh, \* ***I*** \* might be able to figure it out, since that's my daily work. Decoding alien tech (old research instruments from the 1970s) where no documents exist, and the owners have no clue of what's inside the box. I do "cheat," since I know what the box is supposed to do overall, but the (non electronics) details are sometimes bizarre, and often I have to figure it out from scratch. Recent example, little white 2mm ceramic pancake shapes used in high power RF. Open circuit. Not capacitors. They turn out to be noble gas discharge elements, probably used as surge suppressors on connectors in noisy industrial environments, but here being triggered by sub-microsecond voltage pulses, used to short-out a quarter-wave stub pcb-pattern with few-nanoseconds rise time. Very cool idea for shaping fast VHF pulses at 100s-watts level. Or last week: why would anyone pump fifty watts of 27MHz into a piece of glass? That trick I'd seen before, back when laser printers were the size of a refrigerator on its side. Or more subtle: little white insulated wires ...which all turn out to be coaxial cables, like #28 gauge. Ever seen superconductor magnet parts, where copper is used as insulating supports? :) [Answer] I think your intuition is correct. For the most part electronics are designed for function, not to look pretty. The aliens may well use different measurements, units, signs. They may have different electrical standards (so a USB plug would be totally different for example) but the core components themselves when you get right down to transistors, capacitors and wires, would all be very recognizable. Due to the difference in units and interfaces using earth and alien electronics together would be tricky, but even so it would be possible. [Answer] If we were to encounter alien technology, even if the aliens had only attain a level of technology similar to ours (world wide communication and transportation network with limited space travel,) several factors may make their technology difficult to comprehend. **Alien technology may not be linear** Humans think in a very linear way. Our circuits contain components that connect to other components through linear pathways (wires.) Also, individual components are separated into logical and functional units. Aliens may build circuits that utilize varying areas of intermingling resistance, capacitance and switching. Electricity may swirl around the board instead of follow through separate paths. This kind of circuit would be very difficult for us to understand. **Alien technology may include elements of gravity, nuclear forces, etc** Our electrical technology includes some elements of light and magnetism. Alien technology may include more. If we were to encounter a circuit that use modulated gravity in some way, it would be very difficult for us to figure out. First, we would need to fully understand how all of the circuit components (or areas) transmit data and/or energy. Then we might be able to understand the circuit as a whole. **Alien technology may be multidimensional** Our circuits occupy three dimensions, and many of our circuits can be reduced down to two dimensions. If an alien occupied more (or different) dimensions, it would be virtually impossible for us to figure out (or even full observe) their circuits. We would only be able to theoretically understand them, with help from the designers. We would also have trouble figuring our an alien circuit if the circuit was moving through time differently. **Electricity may behave differently on their planet** There is a strong possibility that electricity may flow differently on an alien planet. They may have stronger, weaker or multiple magnetic poles on their planet. Their sun's radiation may also interfere with electrical signals. In this case, we would have a very difficult time figuring out their circuits, if the circuits were to appear on earth. We probably wouldn't get any help form the aliens either. They would probably have no idea why their circuits stopped working once they arrived on earth. [Answer] One way for our hero to identify the most basic components would be through their sheer number. There are these HUGE racks of boxes with each box containing a large number of identical components. One rack: resistors. Second rack: capacitors. Third: inductors. The multimeter can sort out which is which. There are two reasons these components are so common: They are useful, and they are easy to make (and therefore cheap). This should be universal. (The memristor other answers have talked about are not easy to make) Beyond that, things will become difficult very quickly. They will probably find a large number of different components of various types. There are lots and lots of different things these could be and sorting this out would take a LOT of time and effort. And mistakes will be made. If the engineer comes across some already assembled circuits this will help. Identifying some components will identify the circuit, and that will identify the remaining components. ...maybe. However, this only holds if they are assembled by hand from the same type of components that are in the lab. Factory assembled stuff would be impossible. ]

[Question] [ I have often heard/read/watched in fantasy about dwarves drinking mead and lots of it. I recently learned that mead is made from honey which requires bees and flowers which require sunlight. I doubt that they could import enough to satisfy the thirst of an entire city (or nation) and even if they could it would be financially irresponsible. So I was wondering if they could produce honey underground. The obvious solution is that they just make the honey above-ground but lets say that going above-ground is socially unacceptable (like in Dragon Age). Lets further split it into a few separate scenarios: 1. The dwarves have magic light orbs which are basically the same as sunlight. So could bees function completely underground with light and flowers. 2. No magic. So could bees function underground with some torches and maybe skylights (Not sure that could work. Maybe leave a door open and hope the bees come back?). 3. No light (e.g. Dwarf Fortress). Could bees work underground in total darkness (Same as above but dwarves have super-night-vision and have no need of light). [Answer] The dwarves can keep the bees in the caverns, but provide them with suitable exits. You have your beekeepers on the upper levels of the cities. You'll need ventilation somehow to allow for your city to breathe, so these vents can be plenty useful for the bees to exit and re-enter. The beekeepers don't need to ever leave the caverns (Except, perhaps, to get the bees in the first place), but the bees can go out and back in with ease. [Bees usually forage for two to three miles](https://en.wikipedia.org/wiki/Forage_(honey_bee)), but they can also forage significantly further away. Presuming that while the Dwarves typically don't go outside, they also don't care for someone living on their doorstep, this means that there are plenty of wild plants for bees to use for their honey needs. [Answer] # Use honeydew, either as intermediary or final product [Aphids](https://en.wikipedia.org/wiki/Aphid) feed on plant matter. When they are eating plant sap, they excrete [honeydew](https://en.wikipedia.org/wiki/Honeydew_(secretion)), a sugary liquid. You could reasonably make an alcoholic beverage from honeydew, although milking aphids sounds like a chore. However, certain bees will do it for you. They can take this honeydew and use it to make [honeydew honey](https://en.wikipedia.org/wiki/Honey#Honeydew_honey). In fact, Greek [pine honey](https://en.wikipedia.org/wiki/Pine_honey), which I've had before, comes via aphids. I just learned that I ate aphid poop about 30 seconds ago. Finally, if you don't to have sap-filled plants that aphids can eat, [ergot fungus](https://en.wikipedia.org/wiki/Ergot) can also make honeydew. So you can have blind bees feeding on fungus making delicious honey. [Answer] **Honey Mines** from [The Lost Honey Mines of Texas](https://www.jstor.org/stable/43466090) [](https://i.stack.imgur.com/SJdoz.jpg) These caves are filled with millenia worth of the bee's endeavors, as far back and as far down as you dare to explore. Dwarven honey miners brave the dangers to bring back ancient honey, as concentrated as amber. It is from this that they brew their fabled mead. --- I am very pleased that this question was asked because otherwise I would never have discovered the stories of the honey mines. I encourage anyone the least bit interested to follow the link and read the tall tales about the Lost Honey Mines which I greatly enjoyed. Below are 2 excerpts (each about a different mine): > > …Carrying the famous smoke gun and a lantern, he was able to explore > the cave to a depth of some thousands of feet. He returned with a > report of the enormous amounts of honey and wax almost at their finger > tips. The exploring company went to San Marcos and obtained sledge > hammers and rock chisels and returned to enlarge the opening. But as > soon as they commenced to pound on the rock, snakes began to issue > from every little hole in the face of the bluff; and while no-one was > hurt, the sight was so terrible that the men fled and no amount of > hidden treasure could induce them to return… > > > ...During the spring season, when all of the chaparral flowers are in > bloom, to one standing on the top of the bluff the bees going and > coming from the mouth of the cave resemble a great stream of smoke, > and the hum of their wings is so loud that the roar can be heard for > miles. According to the story, thirty years ago a surveyor who was > hunting some old Spanish bench mark in the vicinity of the cave > discovered a second entrance and, making a torch out of his coat, went > into the cave protected by the smoke from the burning coat. He passed > through room after room filled with long white sheets of the purest > guajillo hone and estimated that the cave contained several million > pounds of it… > > > Snake storms! Wearable coat torches! And this does not include the cave with the ghosts. If ever there were a fantasy-ready concept this is it. [Answer] 4. I would like to suggest a fourth possibility in addition to the three in the original question, that the Dwarves are advanced technologically enough to have artificial lighting. Some people may think that Dwarves with artificial lighting are inconsistent with a fantasy setting. Remember these lines from "The Song of Durin", *The Fellowship of the Ring*, Book 2, Chapter 4, "A Journey in the Dark": > > A king he was on carven throne > > In many-pillared halls of stone > > With golden roof and silver floor > > And runes of power upon the door. > > The light of sun and star and moon > > In shining lamps of crystal hewn > > Undimmed by cloud or shade of night > > There shone for ever fair and bright. > > > Some may imagine that those lamps were magical, others that they were technological. Thus it is possible that Dwarves had technological artificial lighting to grow plants under the mountains in the greatest fantasy of all. In my answer to the question [Giving Tolkien Architecture a Reality Check: Dwarvish Kingdoms](https://worldbuilding.stackexchange.com/questions/100380/giving-tolkien-architecture-a-reality-check-dwarvish-kingdoms/100413#100413), I discussed how much underground room the Dwarves would need to grow their own food. 5. A fifth possibility is that the Dwarves are able to synthesize honey from basic ingredients using magic and/or chemical science. 6. According to Tolkien, Dwarves often traded their goods to others for most of their food and didn't produce much of their food. Thus they must have had a lot of trade with other species and realms and importing honey and/or mead would not add a lot to their trade. Mike Scott's comment is quite on the mark. 7. Andon is right about letting bees forage outside. "leave a door open and hope the bees come back" is not a big leap of faith. If the hives are in the dwarf city the worker bees will come back. 8. And maybe fantasy writers just like to write about Dwarves drinking mead without knowing the ingredients of mead or thinking about how the Dwarves obtain mead. [Answer] I say: none of the above. *Dwarves obtain mead via trade*. This is not unrealistic! Dwarves are domain experts on resource extraction via mining; they can obtain whatever other goods they require by trading surplus gold, silver and gems for anything. Remember, the fundamental purpose of trading is *a trade only happens when both sides think they are better off making the trade*. Dwarves have gems that they can't eat, elves have excess wine and a surpassing desire for gems but don't want to get their hands dirty; establishing a marketplace for exchanging gems for wine leaves both sides better off. Even better: now you have a natural story mechanism for generating conflict. What happens when the elves hold out for better gems? Or the gem supply dries up? Now examine the current situation in Venezuela, a country that foolishly predicated its entire economy on the ability to get in trade the goods it needs to survive in exchange for oil, a resource extracted from the earth. A fantasy story that is an analogue to the current crisis in Venezuela might be quite interesting. [Answer] Bees aren't the only creatures that make honey. In Latin America, we have [Honey Ants](https://en.wikipedia.org/wiki/Honeypot_ant), which also produce a quite edible form of honey. They don't need flowers to do it, either (it's often extracted from prey, but can basically be from any form of ant food). Specialized workers store the honey in their bodies and provide it as nourishment to other ants later on. They're also present in other parts of North and South America, Australia, and probably a bunch of other places that I just haven't heard about yet. There are also a few species of wasps which produce honey, such as [Brachygastra lecheguana](https://en.wikipedia.org/wiki/Brachygastra_lecheguana) (a darker form of paper wasp) and [Brachygastra mellifica](https://en.wikipedia.org/wiki/Brachygastra_mellifica) (the Mexican honey wasp); and while I wouldn't be the first to try and collect that honey, it should be noted that many forms of wasp do build their nests underground. Speaking scientifically and a bit broader, honey can be defined as a substance produced by any number of creatures, though most famously bees, by distilling down their food source into a sugary syrup for the sake of consumption some distance into the future. Anything that fits that definition could also be made into mead, provided a source of yeast. (As a side note, real honey often does have a small amount of wild yeast in it, even though it's a powerful antibiotic otherwise; so it doesn't sound like an enormous challenge to get yeast.) So, if your Dwarves lived in an isolated underground society with no realistic surface access, but managed to cultivate some form of subterranean insect that distilled its food into honey (much like beekeeping bees), then mead would be relatively easy to produce. All you would need is a stable underground biome, some industriousness, and some time. [Answer] Previous answers have gone the route of placing your bees home or entire habitat underground. This is a perfectly good option, but I thought I'd take it in another direction. **What is Mead?** According to the Merriam-Webster Dictionary, mead is a fermented beverage made of water and honey, malt, and yeast. At its core, mead must contain honey to be called mead. If you are willing to let it slide, it is possible to make a beverage that is mead in all but name without honey. **Mead Alternatives** According to [this post](https://homebrew.stackexchange.com/questions/5447/mead-made-from-agave-nectar) on the Homebrewing (alcohol, not tabletop) StackExchange, it is possible to make mead with Agave Nectar. Furthermore, according to [this thread on a homebrewing forum](https://www.homebrewersassociation.org/forum/index.php?topic=7588.0), it is possible to make a very mead-like product with maple syrup. With this in mind, I would say that it is reasonable to presume you could make a mead-analog with whatever honey-analog you wish! You could have tap maple tree roots and collect syrup underground. You could have some sort of termite or other underground insect collect nectar much like bees. If you are willing to deviate from a strictly honey-based mead, then your options become much wider. Wouldn't it be fitting for dwarves to make their mead from some sort of burrowing insect? [Answer] Can the bees go above ground? Lots varieties of bees build their hives rock openings and holes in the ground, it should be pretty easy to create hives with entrances via holes in a rock face or some similar thing. The beekeeper would never need to go above ground, just open the back of the hive to extract the honey, and the rest of the process would work underground. With magical sunlight orbs, dwarves could farm any crop, including flowering crops, deep underground and keep bees too. Other plausible possibilities would include some sort of fungus that excretes nectar and a pollen-like protein source like flowers. And heck, dwarven bees could also have infravision too. A broader question would be how to feed a city of thousands completely underground. If you have grain you can make bread and beer, but grain requires sunlight. And any animal eats vegetable matter or some other animal that eats vegetable matter, with about a 1:10 retention of calories, so to grow 10 lbs of dwarven beef you'd need to feed it 100 lbs of hay (or mushrooms or whatever). Fungus also relies on vegetable matter to grow, so you'd need excess tree roots or humus to grow fungus for a food supply. If you can solve the problem of how to get enough vegetable matter below ground to support the food matrix, then throwing bees in the mix should be easy. [Answer] There are chemoautotrophic organisms. These use chemical energy to drive their metabolism, rather than sunlight. In the real-world, these live in deep-sea vents, and oxidise fresh materials from lava vents. With a bit of a stretch of the imagination, they could oxidise the iron-containing walls of a cavern (possibly the roof, to help push the waste rust away). Again, back in the real world, these are normally simple organisms. However, they could be plants. To attract the insects, they could use scent (long range), and bioluminescence to guide the insect to the nectary. The insects would then gather the nectar, and make honey in the usual way. For some ideas, search for chemo(auto)troph, litho(auto)troph [rock-eating organism], and black-smoker [sub-sea lava outlets]. [Answer] [](https://i.stack.imgur.com/nbqUK.jpg) Honey doesn't spoil. It has a high sugar concentration which acts like a preservative. Pots have been found in Egyptian tombs containing honey which are over 3,000 years old and it's still edible. This means the Dwarves of yore could order loads of honey or mead and have it shipped to their cities and never have to worry about the honey spoiling or if the mead was over 16% alcohol by content, it would be preserved as well. Yeast can similarly be stored as a live culture or a powder. All of this is very well established and understood. Mead can be as simple or complicated as you wish to make it. No sunlight is needed. All you really need is water, honey, yeast and a sanitary container. A simple airlock will help it vent. Keeping it around 60°F produces the best results. It could be made with the funeral powders of the deceased, it could be made with crushed gems for vitality. It could be made with wine as well. * <http://www.nationalgeographic.com.au/history/honey-in-the-pyramids.aspx> * <https://www.homebrewersassociation.org/how-to-brew/mead/making-mead/> Good luck with your mead. [Answer] You can feed bees with sugar water. It's often used by beekepers as a cheap supplemental food source to get a hive started. This will produce a less flavorful honey, but bees will store it in a comb. Bees are opportunistic and will feed on whatever sources of sugar they can find. There have even been cases of them producing [blue honey](http://www.nydailynews.com/news/world/french-bees-making-colored-honey-article-1.1175991) because they were stealing syrup from a M&Ms factory. [Answer] Domesticated Honey-Badgers. ***Dwarven*** Honey-Badgers. Or maybe ***Dwarven*** Underground Domesticated Honey-Bees... But I like the Honey Badgers better, just on principle. ]

[Question] [ Most [modern planned cities](https://www.google.com/maps/@40.7565422,-73.9805797,2130m/data=!3m1!1e3) are based on grid layouts. [Historic cities](https://www.google.de/maps/@52.371018,4.899751,2226m/data=!3m1!1e3) are more organic on a macroscopic level, but buildings are still generally square-shaped leading to grid-based layouts on the micro-level. But I recently learned that squares are boring and [Hexagons are the Bestagons](https://www.youtube.com/watch?v=thOifuHs6eY) due to their many interesting tiling properties. So building a city based on a hexagonal tiling instead of square tiling could be an interesting divergence from how cities are usually planned. Roads would go in 3 possible angles instead of 2, going across the edges of the hexagons. So the size of the basic hexagonal tile of the city would be size so that the edge length would be the width of a road. The basic shapes of buildings would also be based on 60° angles instead of 90° angles. Buildings would be hexagonal, triangular (covering 3 hexagons, or for very small structures a 6th of a hexagon) or parallelograms (covering 4 hexagons). Even larger buildings would be extensions or combinations of these shapes: [](https://i.stack.imgur.com/fcgQo.png) But the question is: **Why would anyone do that?** Lots of societies on Earth figured out how to build houses. And they all independently came to the consensus that rectangular buildings are the preferred shape, which in turn lead to city layouts all around the world dominated by rectangles. So what circumstances could lead to a society planning their buildings and thus their cities based on hexagons instead? I am open to both answers based on historic reasons as well as objective reasons for building future cities that way. [Answer] ### Optimal public transport accessibility for a zero-car city. A city designed from the ground up should be designed so that cars are unneeded: * 90% of your reasons to leave the home are serviced within a short walk and no public transport. * Travel from any point in the city to any other should require no more than a short walk to a public transport point and a short walk from one. While designing this city, a guiding principle could be **"No-one should live more than 5 minutes walk from a subway station!"** - this results in a city design where circles 5 minutes walk (ie 500 meters) around a transport centre are tightly packed as much as possible. Eg we get a map of a single suburb like this: [](https://i.stack.imgur.com/kjv2s.png) Following the doctrine of [Circle Packing](https://en.wikipedia.org/wiki/Hexagonal_tiling#Circle_packing) we get a hexagonal grid [](https://i.stack.imgur.com/y15h3.png) In that city design 90.7% of the city is 5 minutes walk from one of those hubs. The other 9.3% could be things that don't feature in peoples commutes - solar farms, wind turbines, water storage, etc. Or perhaps it could be parks. Were this design to be based on squares instead of hexagons, only 78% ($\pi\over4$) of the city would be within 5 minutes of a subway station, and getting it up to 90% would create more hubs, adding costs. ### Or - Domes are needed - the atmosphere is poisonous Eg this Mars colony uses a hex grid layout (for the same circle packing reason): [](https://i.stack.imgur.com/1pHwQ.jpg) [](https://i.stack.imgur.com/MgW33.jpg) ### Comments re bad traffic: 2 different people commented: "intersections will be harder cause cars will have to check more directions" - no they won't. There are zero cars in this city. You walk a few hundred meters to everything you typically need, and everything else is a subway trip. Retailers are at the hubs so can use freight networks directly. Foot paths out into the suburb can take the odd forklift delivering white goods or construction materials the few hundred meters from hub to home if needed. ### More about the suburb design: Each suburb is about 780,000 square meters Your hub in the middle has everything most people need. Shops, post office, doctors, childcare, playgrounds, dentist, physio, pharmacist, restaurants, cafes, vet, a church or 2, and a small school (only a few year levels - not all, some students will need to travel for school). Few medical specialists (but not a full set - may need to travel for specialist medical) A police station (10 cops), fire brigade (3 vehicles), and 5-bed emergency department also feature in the hub. The whole hub complex is taking up about 180,000 square meters of space in the middle. The inner ring around this is offices and dense living. 3 or 4 story buildings, 1-3 bedroom apartments. Maybe 200,000 square meters or so. The outer ring is low density living. 3 bedroom houses on 400 square meter lots sorta thing. There's about 800 low density homes around the edge of the suburb. Your looking about 10,000 people in total, 3000 commuting in peak hour. Well within the capabilities of modern subway systems. Freight is unloaded in side stations to avoid stalling the main lines. Foot paths out to suburbs are wide enough for a vehicle to travel on, and are used by emergency services, as well as the occasional forklift delivering construction materials or really big eBay order. Basic services are duplicated (eg 1 grocery store in each hub), but specialists require a commute, eg only one suburb in 4 has a Catholic church, one suburb in 5 has a pet store, only 1 in 50 has a brain surgery operating suite. [Answer] The city was planned, it did not grow, and its founders regarded hexagons as the mathematically superior form. Perhaps, historically, the hexagon was associated with the chief religion. This may or may not be in current effect; what chiefly matters is that it was in effect when the roads were laid out and the buildings went up, and resistance to having your building knocked down keeps it going. Perhaps they regarded it as Scientific and Superior and Shaking Off The Dead Hand of the Past. They might cite honeybees as the example of what they want, including that it maximizes connectivity with minimum amount of road. (Bees' cells use the least wax for the most space for honey.) Or cite it as the largest number of sides that tessellate, in an era that is much taken with mathematics. [Answer] Hexagonal urban planning is not common but it has already been done: La Sentiu is a planned neighbourhood near Barcelona with roads in hexagonal directions. Blocks aren't exactly hexagonal but walking though the neighbourhood feels like they were. Maps can be found at <http://www.icc.cat/vissir3/index.html?xMUrfgUVS> or <https://www.google.com/maps/@41.3002961,1.9710314,17z> [](https://i.stack.imgur.com/aPvCz.png) It was intended to be an high standing suburban neighbourhood, so some reasons for this street pattern can be more or less guessed: * Aesthetic reasons: There is a trend in urban planning that favours irregularity as a way to get some picturesque results. The most famous precursor of this trend was [Camillo Sitte](https://en.wikipedia.org/wiki/Camillo_Sitte) more than 100 years ago. Hexagonal roads avoid the impersonal long straight streets of modern cities while still allowing for some regularity. * Pacification of transit: Hexagonal roads allow car access to every place but they don't favour speeding because of frequent crossings. The same effect is often pursued by using a lot of roundabouts. An hexagonal grid uses less space and is less annoying for the same goal. * At the same time, 120 degree corners are safer and less annoying for cars than 90 degree corners. Furthermore, 120 degree corners don't need chamfers to improve visibility, so more space is saved. Judging by the time the neighbourhood was built, I guess than promoting cars was more a goal than pacificating traffic. * Additionally, intersections in hexagonal grids are 3 way intersections, instead of the common 4 way intersections found in square grids. That makes them very easier to navigate for motorists. [](https://i.stack.imgur.com/UW2Jb.jpg) * By the time it was build, hexagons and other geometrical follies were modern looking. Just to cite a contemporary example, the [Ethnology Museum](https://commons.wikimedia.org/wiki/Category:Museu_Etnol%C3%B2gic_de_Barcelona) in Barcelona plan is also based on an hexagonal grid. * And as other answers have correctly pointed, the ratio between street area and usable land area is slightly better for an hexagonal grid than for a square grid. And that has been just a quite anecdotal summary based on a single real case. An essay long summary on the state of the art of hexagonal urban planning can be found at <http://web.mit.edu/ebj/www/Hexagonal.pdf> . [Answer] ## Unstable Land Surface Imagine that the ground itself expands and contracts slowly over time. This could be due to frost heave on an enormous scale, or the absorption and release of water over time. To completely pave over such a location would be fruitless - the stress from the expansion of the ground underneath would turn the pavement to rubble. Gaps have to be left to allow for the expansion, and the most efficient way to do that is to create a hexagonal grid. The phenomenon is extremely common on a small scale. Soils with significant amounts of certain clays (e.g. smectite, vermiculite) shrink and swell substantially when they lose and gain water. Here's a parched example: [](https://i.stack.imgur.com/myUiv.jpg) Of course, these aren't perfect hexagons, but even at this small scale the tendency towards 120-degree angles is apparent. This is not a coincidence - when a membrane "blisters", it will naturally tend to do so by breaking into three identical parts meeting at 120-degree angles. The larger the scale, the more the mathematics matters and the more perfect the angles. Thus you have a choice. Either your city was *engineered* in hexagons, as this is the most efficient way to provide room for expansion. Or it was forced into (perhaps imperfect) hexagons by the natural breaking up of the expanding landscape. And perhaps both are true. [Answer] **It's a city of bees** Who says that the species of the denizens has to be human? If bees evolved to where they began to make cities, they might just use the hexagon shape, because that's what seems natural to them. [Answer] I think its fair to say people tend to do things long after the original rationale has ceased to exist (e.g. people in the UK drive on the left-hand side of the road because knights on horseback preferred to have each other's sword hands in view). So for me it's more plausible that the hexagonal form predated any advanced technology (as opposed to suggesting that advanced technology dictated a hexagonal form). Perhaps the local tree-like fauna always sprouts branches at a 30 degree angle from the main trunk, and it was easier to incorporate the branch/trunk joints into early wattle-and-daub style huts than it was to hack the branches off the trunks with stone tools, so the first huts were hexagonal. Hexagonal became established as the traditional shape and everything else flowed from that. [Answer] I've seen a hexagon-based city in a sci-fi story and I believe the reasoning was sound: The city was on the ocean, not on land. The "land" of the city was a collection of hexagonal platforms--basically huge hexagonal concrete cups that were inverted. They float because of the air trapped underneath. The concrete extends deep enough into the water that even the most extreme waves will not let the trapped air escape. So long as they are wide enough compared to their depth they're stable. Roads were not an issue because they couldn't exist anyway--each city block floated independently from the ones around and there would be some flexing at junctions. IIRC transport was by boat. [Answer] ## Because Your City has Celtic Origins Many answers have already brought up how circles can force a hex pattern, or how much tradition can influence things, but this combines both of these ideas into one. Unlike most civilizations, Celtic homes were built in circles, not squares. Instead of having their hearths off to the side of the home where it would be out of the way, the Celts built their homes around the hearth in a circle to evenly heat the home. This often lead to roughly hexagonal path systems between their roundhouses to optimize space. Had Celtic civilization not be supplanted by the Romans and their rectangular architecture, their towns would have eventually built up into full sized hex grid based cities forcing developers to either wipe out everything and start over or to continue the tradition of using hexagonal roads and land plots. Since wiping things out and starting over again is so costly, your city has maintained the hex layout as part of its proud celtic tradition. [](https://i.stack.imgur.com/1M83G.png) [Answer] # Because the city is vertical I love the other answers on this post a lot, but since no one mentioned it, I thought this was a cool idea. If you want a city embedded in a cliffside to be walkable, one of the easiest ways to do that would be to use – basically – a honeycomb. The diagonals would have stairs on them, the flat sides would be sidewalks. This has a few advantages: first, no one has to climb a ladder (easier to carry things!); second, since it's closer to a circle than a square, it has a better volume-to-perimeter ratio, meaning more room for less wall; and third, it's a solid, strong structure that distributes weight well. [Answer] Maybe the hexagonal planning had nothing to do with the surface, but rather some **subterranean** phenomena, such as extreme seismic activities! They had to create a huge hexagonal structure under the surface (kind of like a buildings foundation) as resistive measures. Then, the surface structure would naturally reflects how the foundation is shaped. They may even have done it on more than one layer! [](https://i.stack.imgur.com/5rWTI.png) [Answer] Brief summary: **solitude / social distancing**, lack of external **enemies**, **nomadism**. According to [Why are Most Buildings Rectangular](https://www.researchgate.net/publication/32896144_Why_are_most_buildings_rectangular) (well worth reading), the trend from circular houses to rectangular buildings in human societies has generally coincided with (1) a demand for larger houses to pack larger, wealthier families into a single building; and (2) a need to pack a growing population efficiently into a small space for defense. With regard to (1), the paper shows why rectangular buildings with rectangular rooms offer better flexibility of design and dimension for **packing rooms into a building**. If the society you are writing about is a society of hermits who prize solitude, have very few children, and eschew the accumulation of possessions, there would be little demand for interior rooms, and therefore little reason to prefer rectangles. As such, the advantages of hexagonal design (described in other answers) could prevail. (A hermetic people might prefer not to live in cities at all. And perhaps most of them don't. Why then have such a city? Perhaps the supreme leader has a vision to do something great ... like build a super-awesome statue, or develop a vaccine against the plagues ... that requires a high concentration of scientific, industrial and economic activity.) Another factor contributing to a preference for solitude could be recurring waves of **plagues** (like the current pandemic). In such a world, the ability to isolate families from one another quickly could be a life-or-death issue. Large buildings, i.e. buildings used by many people at once, might be seen as a disgusting tendency, like sharing toothbrushes. Again, small buildings need fewer internal rooms, so the flexibility of room packing with rectangles is less compelling. With regard to (2), without the need to pack many people efficiently into a finite walled area for defense, a pressure toward rectangular buildings is reduced. Another factor could be that the city is planned as a **nomadic** one, due to seasonal environmental factors; the buildings are portable, and are moved from Summer City to Winter City and back every year. This is only possible if the buildings are small, without many internal rooms, and therefore they need not be rectangular. Simple, one-room portable buildings are easy to build as structures radiating from a central support pole, of which the hexagon shape is a sweet spot between complexity (many walls) and space (ratio of floor area to perimeter). In this scenario, the hex-aligned streets of the city (and maybe a few key buildings and infrastructure) would be permanent, with uniform modular hexagonal lots to accommodate the hexagonal houses that come and go. There could be more prestigious lots and more slum-like areas, and the locations of individuals' and clans' houses would change from year to year based on some sort of status or performance. [Answer] From the *Centuriation* of the Romans to Mansard roofs of Paris, city layouts and building design are often heavily influenced by surveying technologies, title law, and tax law. Perhaps the hex city surveyors employed a surveying method that favors approximately circular divisions: the surveyor's guild has a single Gunter's chain, and the lots thus constructed follow in the same was as construction of hexagons using compass, the regularity following from the single measuring tool used. Alignment was initially based on a mountain or star or other landmark, but once set is now locked in place given the recursive and uniform nature of surveying. Surveys and title are per hex. Taxes were per section as opposed to say counting the stories or number of windows, so with sections divided into hexagons it was most economical to fill in the hex lots with hexagonal buildings. [Answer] I love the sentient-bee-people idea, and here’s one for the mammals that might have tried to technologically copy them for a crystal city: “Among the primary crystal systems, the hexagonal system has the fewest substances assigned to it, including arsenic, calcite, dolomite, quartz, apatite, tourmaline, emerald, ruby, cinnabar, and graphite.“ (Quoted from “Brittanica”) Quartz in particular catches my attention, because that means piezoelectricity and all the alternate technology that could go with it. Ruby could be used for lasers, graphite for writing and lubricating the gears of heavy metal machinery, the “Emerald City” by Baum we already know of, Arsenic implies steel-quenching and metal production again — as well as a whole Guild of Poison-tolerant people who couldn’t safely leave their environment least they be dangerous to others. Hope this has been helpful. [Answer] I'm sorry if anyone posted this idea before, there is just too much to read and I want to make sure such idea is out there. The rectangular shape makes our buildings simple yet quite effectively makes enough space enclosed within the four walls. Not as effectively as a circle would, and still less effectively than a hexagon or even pentagon would. BUT it's much simpler. All angles are right and furniture etc. is just that much easier. Let's now suppose there is a reason not to build rectangular houses or structures whatsoever. No specific reason to build hexagonal ones -just one that makes the inhabitants not want to build rectangularly. If you could do it in any way but NOT as a rectangle, the next most convenient shape is the hexagon. Simple as that. Not you'd only need a reason not to like rectangles. Well, there is one here on earth actually: the Japanese tend to avoid number four, as it sound the same as the word for death. They still love their rectangles though. Maybe your civilisation could be more reluctant to use them if their beliefs were stronger or cultural/aesthetical stigma of not following the norm/following the "path to death" (or whatever other BS) would be too harsh to stay lazy. [Answer] Perhaps the city began as a cluster of compounds, some distance apart, and each of them grew as needed by adding buildings more or less evenly to its own perimeter. As the compounds then approach each other (careful to leave a bit of distance), they might form a pattern like soap bubbles, whose walls meet in threes. Within a compound, though, the paths could be anything. ]

[Question] [ Mars and Earth's moon already feature in a lot of fiction about space colonization. After these two planets, and assuming that other solar systems are too far away, what is the best place within this solar system to colonize? [Answer] The Asteroid belt. * It has similar requirements for life-support systems as the moon. With the additional need perhaps for some areas with simulated gravity. * It is next closest in terms of energy required to get to and from the orbits. * It is still close enough to the sun that collecting solar energy is workable (the farthest out we have used solar panels is Jupiter - on the Juno mission). * The cost of landing and launching from an asteroid are reduced thanks to the low gravity. This makes them attractive as way stations to inner and outer locations, as well as making it easier to deliver supplies or to collect produce. * It is thought that [some asteroids will be worth mining](http://en.wikipedia.org/wiki/Asteroid_mining) for rare elements. * Yet other asteroids contain water ice or other volatile compounds, potentially useful fuel or raw materials for production or organic feedstock. * Collisions are much rarer than you might believe from science-fiction staple of spaceships dodging rocks in a dogfight. Typically you would only see one asteroid at a time, maybe a few others could be seen as sunlight-reflecting dots many thousands of kilometres away. [Answer] **My choices: Ganymede and Callisto (and maybe Titan)** This is perhaps a bit of a buzzkill, but I honestly would not recommend colonizing much in the solar system besides the Moon and Mars. Here's why I would take a lot of bodies off the table: * [Mercury](http://en.wikipedia.org/wiki/Mercury_(planet)) - Too hot on its sunny side for colonization (up to 700K) and too cold on its dark side (down to 100K). Solar power on its sunny side would be tricky as parts of the solar array could melt. Also not too special resources-wise. * [Venus](http://en.wikipedia.org/wiki/Venus) - Generally a hellish place to be. High atmospheric pressure means spacecraft can ([and have been](http://en.wikipedia.org/wiki/Venera_13)) completely crushed. A runaway greenhouse effect means temperatures are extremely high (737 K), and clouds of sulfuric acid make rainy days pretty bad. * [Asteroid Belt](http://en.wikipedia.org/wiki/Asteroid_belt) - A lot of small bodies. Hard to track smaller asteroids because of the concentration. [Not a *lot* of collisions](https://space.stackexchange.com/questions/5579/what-is-the-danger-for-ceres-of-collision-with-other-asteroids), but there's always the possibility. Low-gravity means that you won't have a substitute for *terra firma* anywhere. * [Jupiter](http://en.wikipedia.org/wiki/Jupiter) - obviously not a good place to land a spacecraft. Fairly far away, which means that ["Houston, we have [had] a problem"](http://en.wikipedia.org/wiki/Apollo_13) will go unheard for a couple minutes. The one thing in its favor is that many of [its moons](http://en.wikipedia.org/wiki/Moons_of_Jupiter) are fairly large. From here on out, solar power becomes less feasible. * [Saturn](http://en.wikipedia.org/wiki/Saturn) - Same issues as Jupiter. This would actually be, in my opinion, the best of the bunch, because you could find raw materials in its rings. It, too, has a lot of [moons](http://en.wikipedia.org/wiki/Moons_of_Saturn), but they really aren't big enough to support a proper colony. * [Uranus](http://en.wikipedia.org/wiki/Uranus) - same issues as Jupiter. Also, we the voyage here would take a *long* time. * [Neptune](http://en.wikipedia.org/wiki/Neptune) - same issues as Uranus. * Beyond - You have the [Kuiper Belt](http://en.wikipedia.org/wiki/Kuiper_belt) and the [Oort Cloud](http://en.wikipedia.org/wiki/Oort_cloud) as you get beyond Neptune. There are lot of small, rocky and icy bodies here, such as comets, and a few dwarf planets. Again, travel time and communication time are issues, and there's not a lot of gravity to make a large-scale colony. You could get some water here, but it would be in the form of ice. There could also be minerals, but, once again, it's pretty far away. Its cousin, the asteroid belt, is a better option. Here's why the Moon and Mars are much better targets: * [The Moon](http://en.wikipedia.org/wiki/Moon) - Very close to home. Easy to get to and easy to send messages to. We've already been there, and have proven we can land there and even [drive around](http://en.wikipedia.org/wiki/Apollo_Lunar_Roving_Vehicle). * [Mars](http://en.wikipedia.org/wiki/Mars) - Not too far away. We've sent a lot of landers there. Good gravity, so it would be easy to adapt to. [Terraforming](http://en.wikipedia.org/wiki/Terraforming) is also an option. **The Moons** You can thank durron597 and cHao for this little section. I did not address the moons of the solar system in my answer - in fact, I may have unfairly written them off - and so I'll add a little bit about them here. * Moons of Mars - Mars has two [moons](http://en.wikipedia.org/wiki/Moons_of_Mars), Deimos and Phobos. They're fairly small, and are most likely former asteroids. I hope we can all agree that they're not fantastic targets for colonization - in fact, Phobos is expected to enter Mars' [Roche limit](http://en.wikipedia.org/wiki/Roche_limit) at some time in the far future, and be broken into a small ring. This of course doesn't stop near-term colonization. Their size is an issue, though. * Moons of Jupiter - Jupiter has at least [67 moons](http://en.wikipedia.org/wiki/Moons_of_Jupiter), the most of any planet in the solar system. The biggest four are the Galilean moons - Io, Europa, Ganymede, and Callisto. They rival (or surpass) Mercury in size. Europa is famous for its icy oceans, and has been considered (by others in this question) as a good place to colonize. I would put that destination on hold until we know more about it, but it has merit. Io has many volcanoes, which could prove detrimental to any intrepid Jovian lunar explorers. [**Ganymede**](http://en.wikipedia.org/wiki/Ganymede_(moon)) is larger than Mercury (good) but is much less massive (bad). This might be the most promising of all the Jovian moons, especially since it has a thin atmosphere of oxygen. It also has a magnetosphere. It would be one of my two picks to colonize. That said, **[Callisto](http://en.wikipedia.org/wiki/Callisto_(moon))** also has some promise. It has a thin atmosphere and is about the size of Mercury - though much less massive. It has also been well-explored, and has water on the form of ice. Therefore, I would nominate it, alongside Ganymede, for a target of human colonization. * Moons of Saturn - Saturn has [62 moons](http://en.wikipedia.org/wiki/Moons_of_Saturn), the most famous of which is [**Titan**](http://en.wikipedia.org/wiki/Titan_(moon)). Like Ganymede and Callisto, it is about the size of Mercury, but, like them, is much less massive. It has hydrocarbon lakes and a nitrogen atmosphere. It does have some water ice but also rains of methane. It could supported life in the past (or could now), but any such creatures would have different metabolisms than us, and be based on different chemicals. I wouldn't rule out Titan as a target, but its methane lakes worry me a little. The nitrogen atmosphere is really good, though. Saturn's other moons are less prominent, although not to be ignored. The ring system could also be a decent target. I'd rank Titan as my third choice, after Ganymede and Callisto. * Moons of Uranus - Uranus has a measly [27 moons](http://en.wikipedia.org/wiki/Moons_of_Uranus), most of which are named after Shakespearean characters. Most are much smaller than Earth's moon. Many may have water in the form of ice buried inside them. The downside to colonizing Uranian moons is the travel time - it would take years to get to Uranus. But again, the ring system could provide some good materials. * Moons of Neptune - Neptune's [14 moons](http://en.wikipedia.org/wiki/Moons_of_Neptune) are, like Neptune, fairly far away. Once again, we have the travel/communication problem. [Triton](http://en.wikipedia.org/wiki/Triton_(moon)), the largest, most likely has a lot of water - again, in the form of ice. It also has nitrogen, although its atmosphere is much less dense than Earth. [Answer] Venus but not the surface. In some ways Venus is much better than Mars for a colonization target. It has better gravity for humans (.9G vs .38G for Mars). It is closer than Mars(40 million Km vs 55 million Km). At 50 km above the surface the temp is 0-50 C and the atmospheric pressure is the same as Earth's(no need for pressurized suits, no explosive decompression). The atmosphere is largely made of carbon dioxide so it would be possible to produce oxygen. Being closer to the sun means solar power would be quite usable. The biggest draw back would be the clouds made of sulfuric acid. Incidentally [this](http://en.wikipedia.org/wiki/Space_colonization) Wikipedia page covers pretty much every where in the solar system we might try to colonize. [Answer] ## Europa <http://en.wikipedia.org/wiki/Europa_(moon)> Pros: * Lots of water, and all the advantages that brings + Narrow range of temperature (even though it's still -171 °C) + Relatively easy power source (fusion, assuming we have effective fusion by the time we're colonizing Europa) + Raw materials we can use to build things like hydroponics bays * Lots of oxygen in the atmosphere * Gravity only slightly less than Luna * Close to Jupiter, for when we start mining Jupiter's atmosphere for fuel Cons: * Really really cold * Low gravity still a problem, but by the time we're colonizing Europa, we should have solved this problem on Luna. * Jupiter's radiation (thanks [Michael Kjörling](https://worldbuilding.stackexchange.com/users/29/michael-kj%c3%b6rling) in the comments) [Answer] Why so little love for Ganymede? I feel that if we had already colonized the Moon due to proximity, Mars due to being close and similar enough (and heavily studied), we'd probably be ready to take on other worlds. However, picking a planet like Venus seems like what you'd do in game for challenge (see [Eve](http://wiki.kerbalspaceprogram.com/wiki/Eve)) - Venus is hell; it's hot, it's thick and probably has raging storms all the time. It would be dangerous to try to poke through the atmosphere. Mercury on the other hand is way too close to the Sun - while it has a strong magnetic field, getting to it would require a *lot* of fuel. It just doesn't seem cost-effective to try colonizing these two, not even for scientific research which can be done through probes. Jupiter's moons however are a lot calmer. While they may have issues with heat cycles, day-night cycles and radiation, if we've colonized the Moon and Mars, we'd already have solved these issues - the radiation on the either would be too high for humans and we'd need some very effective systems to prevent problems. The Moon is also tidally locked, so we'd have solved this already. Jupiter's moons have the advantage of being both closer than the other gas giants *and* being part of a system that resembles the inner solar system's terrestrial planet group. As you can tell, I've got my eye on Ganymede. Here's why it's awesome: * Has a differentiated inner structure, so we get a magnetic field (it's the only moon known to have one, so if Mercury is out, this is the best place to go to find one) * Seems to have oceans, which is great for terraforming * Isn't too far or too close to Jupiter (it'll feel like home, with Io and Europa oribiting closer and Callisto behind it). * Has no atmosphere, but we've already dealt with that on the Moon, right? Callisto is too barren and cold and Europa is little more than an ice moon. If I was asked, I'd recommend Ganymede. [Answer] I'm not sure about *after* Mars and the Moon, but there's a place I'd take *before* them: Earth orbit. Low Earth orbit is pretty compelling: easy access to all existing human civilization, radiation protection, fairly easy access to space resources and a good launching point for other locations. High Earth orbit or Lunar orbit are both also very good. They are preferable to the Moon's surface because we can make custom gravity and day lengths via rotation and shutters, taking off from them is a lot easier than a surface launch, there's more sunlight available, and they are just physically closer to Earth, where everybody is going to want to be coming and going for the near future, among other things. I'd prefer orbit to a planet's surface even if space colonies were very well established and proximity/ease of access to Earth wasn't important anymore! Read more about them here: <http://en.wikipedia.org/wiki/Space_habitat> <http://space.mike-combs.com/spacsetl.htm> [Answer] [Mercury](http://burro.astr.cwru.edu/stu/mercury.html), but with a major and rather obvious caveat - not in the direct sunlight. Possibly subsurface at the poles or within some of the deep craters that are always in shadow. There would be almost limitless energy provided from the sun. The extremely low axial tilt means that the areas of shade would remain relatively consistent during the Mercurian year. Low gravity, very similar to the value for Mars (see link above) and no appreciable atmosphere making transport easier. Would provide a very stable base for solar observation and power generation. [Answer] As many have suggested, the Asteroid Belt would be an ideal location for colonization and resource-collecting, but with so many asteroids, which one do you choose? I nominate... [Ceres](http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)) Ceres is an incredibly ideal choice for colonization. For an asteroid, it has an incredible abundance of water, possibly even oceanic water, and plenty of clay material for construction. It's the largest object in the asteroid belt, so it'll have more natural gravity than any other asteroids (though stilly very little). It's even relatively warm compared to other asteroids, so heating costs won't be as high. There is of course the problem of being located in the asteroid belt, and the possiblity of asteroid collisions - though this is much rarer than media would have you believe. Any colony on Ceres will have to account for this possibility, though realistically the risk of collision isn't significantly higher than anywhere else in the solar system. [Answer] ## Habitability For a cosmic body to be habitable by humans, it needs to have a few things (or substitutes for those things): * Oxygen * Water * Correct temperature * Food source Some of those we can bring with us (like some food and some water) but we won't be able to send enough supply ships to sustain a colony. Ideally, there should be *some* there already. Temperature is a little different. We *can* affect it, but it's not easy. The easiest thing to do would be to find a planet in the [Goldilocks (habitable) zone](http://en.wikipedia.org/wiki/Goldilocks_planet), which, for Sol, looks like this: [](https://i.stack.imgur.com/N6GTa.jpg) It seems that no other planet is in Sol's habitable zone. However, since we can affect the temperature of a planet, we can use those on either side of the zone. ## Candidate 1: [Venus](http://en.wikipedia.org/wiki/Venus) Is not that great for colonizing at the moment. Its atmosphere is 96% CO2; the temperature at the surface is 735K; and the atmospheric pressure is 92 times Earth's. However, **it could be made habitable**. * **Remove CO2.** This both reduces atmospheric pressure since there isn't so much gas in the atmosphere, and reduces temperature by removing greenhouse gas that keeps it hot. This is by far the biggest job: you want to remove CO2 until the atmospheric pressure is about 0.79atm. * **Add oxygen.** This makes it livable for us, as well as adding some more cooling effect. For added bonus, you could remove the sulfur dioxide clouds in the atmosphere, which would lower acid rain levels once you add water. Don't forget the water. ## Candidate 2: [Asteroid Belt](http://en.wikipedia.org/wiki/Asteroid_belt) This could be viable. The optimum here would be to make lots of smaller colonies on separate asteroids and develop asteroid-hopping ships to share resources. The asteroids have: * Minerals * Water (mostly ice) * Reasonable temperatures They do not have: * Atmospheres * Gravity * Oxygen Your colonists would need to build airtight, pressurised, oxygenated domes to live in, and they might well want to add some kind of artificial gravity. Other than that, this is a good target. ## Candidate 3: [Europa](http://en.wikipedia.org/wiki/Europa_(moon)) The Wikipedia summary image captures why Europa is a good target quite well:  > > Europa's trailing hemisphere in approximate natural color. The prominent crater in the lower right is [Pwyll](http://en.wikipedia.org/wiki/Pwyll_(crater)) and the darker regions are areas where Europa's primarily water [and] ice surface has a higher mineral content. Imaged on 7 September 1996 by [Galileo](http://en.wikipedia.org/wiki/Galileo_(spacecraft)) spacecraft. > > > From that we can straight away tell that Europa has: * Minerals * Water (partially ice) * Low (or no) atmosphere (implied by the impact crater - bodies with atmospheres are less likely to be struck) This is already good. All your colonists need now is artificial gravity and a sealed oxygenated dome to live in. As others have said, it is still possible to collect Solar power on Europa. ## Choice Out of the three candidates, I pick this order: 1. Europa 2. Asteroid belt 3. Venus Europa wins because it takes the least amount of effort to make habitable and has most of the resources we need there already. The asteroid belt is not far behind, given that it has quite a lot of resources, but it takes more effort to set up and there is a higher risk of collision. Venus is a *lot* of effort to get to a livable state, so I would only send colonists there after a lot of work. [Answer] As already mentioned the Asteroid Belt is a solid choice. The other obvious choice is the moons, rings and general orbits of the gas giants, you have huge amounts of raw materials and energy available and the option of both gravity wells and free fall for people and industry to take place in. [Answer] For a space colonization except the cases the planet is located in the midst of habitable zone, it is usually desirable the planet/planetoid had no atmosphere. Vacuum works as a perfect termo-insulator, thus allowing to colonize planets located too close or too far from the Sun. As such, in Solar system we have * Mercury - having no atmosphere is perfectly suitable for colonization. Lots of solar energy, there is some water ice in the permanently shaded areas on the poles. Unfortunately it rotates which makes the poles the most suitable areas for colonization, although populating other areas is also possible (but one would need to import water and erect sun-shields built from light-reflecting material). A better case would be if Mercury were tidally-locked, then the most habitable zone would be along the terminator line rather than only the poles. Surface area of Mercury is 75 million sq. km (compared to 144 for Mars and 460 for Earth). * Venus - has thick atmosphere and high temperature, totally unsuitable for surface colonization. Floating habitats are possible though, but why? * Ceres - has no atmosphere and a lot of water, perfectly suitable for colonization. This is most likely the third destination after Luna and Mars. Surface area is 2.8 million sq km. Jupiter's system: * Io, Europa, Ganimede - all have no atmosphere and a lot of water, but also deadly radiation due to Jupiter's radiation belt. Seem to be unsuitable for colonization. * Callisto. Has no atmosphere and no deadly radiation. Also has a lot of water. Good place for colonization after Ceres and Mercury. Surface area is 73 million sq km, just like that of Mercury. Saturn's system: * Titan while the largest sattelite, has a thick atmosphere at very low temperature. Also the atmosphere (containing cyanides) is deadly poitionous to humans even in small concentrations. Seems to be unsuitable. * Tethys, Dione, Rhea, Iapetus. All seem quite OK for colonization, having no atmosphere. Combined area is around 18 million sq. km. Uranus' system * Ariel, Umbriel, Titania, Oberon. All seem to be quite suitable. Combined area is 23.6 million sq. km. Neptune's system * Triton. Suitable for colonization, quite large with area at 23 million sq. km. Trans-neptunian objects * All Trans-Neptunian objects seem to be well suitable for colonization if enough energy is provided. This includes Pluto, Charon (22.6 million sq km combined), Eris (18 million sq km), Haumea, Makemake, Orcus, Quaoar, Sedna and some others. [Answer] If you have a viable technological basis to move around and survive long term in space, the true answer is anywhere you can extract water and collect energy. In principle you can do this virtually everywhere in the Solar System, so long as you arrange a "pipeline" of regular transports to deliver any missing ingredients to your chosen location (water ice to Mercury, for example), but I suspect you are looking for the best and most self contained location, where imports and exports would be at a minimum. The best place would be the Jovian system. With the 4 large Galilean moons and 60+ smaller bodies orbiting Jupiter, you have plenty of open space to settle. This is actually very important, as I will explain later. There are vast resources of water and minerals, but most importantly, there is a huge amount of energy available locally from the vast magnetosphere surrounding Jupiter. As Io passes through the magnetosphere, it acts as the armature of a generator,creating a huge "flux tube" running from Io to Jupiter and back, channeling millions of amps of electrical current. Man made satellites or electrodynamic tethers can be placed in orbit around Jupiter to do the same thing, but with much more control of the current, which can then be tapped and beamed via microwave or laser to anywhere in the system. Jovian colonists will have access to as much energy as they want to support their industry and lifestyles, a thriving space transportation system (spaceships using external "beam power" can be smaller and cheaper than self contained spacecraft) and whatever else they desire. Having an open frontier is also important. People may settle in cities burrowed under the ice of the Galilean moons for protection from radiation and to mine the ice, but without an outlet, their civilization may eventually stagnate. IF young and adventurous people have an easily accessible opportunity to pack up and strike out on their own to inexpensive "land" and start anew then there is always a positive outlet for their energy and yearnings. People might also want to experiment with other social, religious or economic systems without interference, and this is an ideal setup for them to do so and share their findings without imposing on everyone else. Failed experiments can also be easily recovered, since the main settlements are relatively close in astronomical terms. The end result is the Jovian civilization will be much more vibrant and outward looking than virtually any other part of the Solar System, and the Jovians may eventually emerge as the political, economic and social leaders of the Solar System. The other gas giant planets may have many similar attributes, but are not easily self contained with a rich energy source like Jupiter. Their colonists may be able to mine the atmospheres of their gas giant planets for 3He and use fusion energy for power, but this will be a more difficult and expensive option than the Jovians enjoy. [Answer] **Earth orbit** and Lagrange points. We start with the Moon because it is a convenient source of raw materials which can be exported to build orbital habitats. The moon has no atmosphere, so you can launch stuff using a linear motor mass driver. No big rockets needed.It's also easy to obtain shelter against solar storms and meteorites by going underground. And it is close enough to Earth that self-sufficiency in small light hi-tech items can be postponed (indefinitely?) and emergency evacuation would be possible (mass-driver, one way "lifeboat" capsule). Mars? I doubt it is worth the effort. That thin unbreathable atmosphere is an utter pain to get in to and out of.. Vacuum is easier. Some exploration of the Asteroid belt is likely. It may prove to be a better source of some elements than accessible Lunar rock. If this is the case then there may be semi-permanent settlemens on asteroids, like mining towns on Earth. You need to think big if it is ever going to happen. Shielding against Solar storms requires walls several feet thick. Substituting gravity by rotation likewise implies large. Build habitats a lot like John Varley's titans, but without the insane goddess. The goal? Unlimited real estate. The Earth is getting full. Outside bet? Mercury's poles. There are craters which offer permanent shade, yet nearby (or up a bit) is all the energy one might need. Shame about the Solar gravity well. [Answer] Venus is a prime candidate, it is actually really easy to get to Venus (assuming aerobraking), and as stonemetal points out its gravity is great for humans; unlike the moon and Mars where we don't even know what the long term effect would be of living on those places would be. However, you couldn't hit Venus's surface as it is too hot, too much pressure, and too acidic. It would have to be in the clouds as per this purposed mission <http://www.csmonitor.com/Science/2014/1222/How-a-manned-mission-to-Venus-could-actually-make-sense-video> Unless there was some serious terraforming effort, but that would take centuries or longer to figure out. The materials to build the cloud cities would likely have to come from else where, though gasses could be had from the atmosphere. Just saw this recent update, actually not much in the way of new info, but a new article on sending people to Venus: <http://www.space.com/29140-venus-airship-cloud-cities-incredible-technology.html> Near-Earth Asteroids - Asteroids are actually ideal for a lot of reasons, they don't have huge gravity wells, there aren't as many concerns about potentially destroying pre-existing life as with Mars or some other options, and in the case of Near-Earth Asteroids, their orbits are such that they are easy to get too. They can also be mined in to for radiation shielding, and depending on the size and stability be spun up to create artificial gravity (though that may be more iffy). The Asteroid Belt- Same as with the Near Earth Asteroids but further out, there are bigger ones such as Ceres, Vesta, etc, the large ones actually make up the majority of the mass of the asteroid belt. Jupiter has its four big moons, and then a ton of smaller ones. The big ones are dwarf planet size. Callisto <http://en.wikipedia.org/wiki/Callisto_%28moon%29> is perhaps the best one to head to because unlike Io, there aren't a ton of Volcanos, Unlike Europa there isn't a likely watery ocean beneath it that could have life, and it has a smaller gravity well than Ganymede, which could also have life. NASA actually identified it as one of the most likely candidate for human colonization: <http://www.nasa-academy.org/soffen/travelgrant/bethke.pdf> The radiation on the other moons is quite high. The thing to realize about going past Jupiter is that Saturn is roughly the same distance from Jupiter's orbit as Jupiter is from the Sun, and it only gets worse from there. Issues of heating and powering a colony become a truly serious problem. If Fusion power is harnessed though, then they become more attractive. Uranus in particular has the lowest gravity, and at one atmosphere of pressure is 90% earth gravity as well as being rich in Helium-3. Also attractive are Titan and some moons that appear to have geothermal activity. Freeman Dyson thought that comets were the future of mankind, not planets <http://en.wikipedia.org/wiki/Colonization_of_trans-Neptunian_objects> which would mean that colonization could continue forever and to the stars but society would be fragmented as the distances become too large to travel in any sort of reasonable time period, even communication becomes quite costly. [Answer] Let's look at the different bodies, their pros and cons, and see where that leads: * the Moon Always a favourite of Sci Fi authors. Advantages: it's close to home, supply ships, passenger vessels, evacuation/rescue missions are only days away. Disadvantages: It's got no atmosphere, the gravity is very low (which might be an advantage as well, but many people will get space sickness and suffer osteoperosis, making return to high G earth difficult after spending years there). * Mercury Advantages: none, unless you want to build a solar powerplant there, and then you'd best make it fully automated. Disadvantages: searing heat during the day, extreme cold at night. No atmosphere, no radiation shielding. And no, it's not tidally locked (which might leave a narrow band around the terminator that could be used). * Venus Advantages: none, despite being a favourite of classical SciFi (from before space exploration found the truth about the planet) Disadvantages: HOT, very high pressure, toxic, acidic atmosphere, high radiation environment * Mars Another favourite for colonisation. Advantages: it's BIG, lots of space there. There might be ice and most other things needed to sustain life in its soil. It even has a thin atmosphere that MIGHT be able to sustain some plant life (but definitely not humans). Disadvantages: It's far away, making it hard to get to. It's COLD, very very cold. The dust storms make it a bad place to be caught out of shelter. * gas giants (dumping them all together, they're similar enough) Advantages: lots of gas, might be possible to mine it somehow, giving a nice economic incentive. Disadvantages: high radiation environment, no solid surface to build on (always a problem), atmospheres very violent and probably toxic, plus high pressures. Very low or high temperatures (depending on the planet and how deep you go). That said, among their many moons there might be some places that could provide interesting places for colonisation. But they'd share the problems of high radiation, low temperatures, and low gravity that we've seen so far. * Pluto Advantages: none, really. Might work for an underground prison colony but little else. Disadvantages: extremely far away, no atmosphere, extremely cold, highly excentric orbit makes it very hard to get to or communicate with reliably. * Asteroids Advantages: easy to get to, tons of materials for building space habitats out of (and enough left over to export to earth at a tidy profit) Disadvantages: nothing there to build on, you'd have to build your habitat in deep space, and provide it with defenses against impacting rocks as well as radiation shielding. Same disadvantages as any space station, except it will be much bigger... [Answer] While I think the asteroids would be the next target I'm going to add another Mercury option--because user1987s answer missed a really big factor: As he correctly stated the poles are cold, the equator is hot. What he missed is that this translates to a Goldilocks zone between them. Dig deep enough that you have a constant temperature (this doesn't need to be all that deep) and you have a band around each pole where you do not need heating or cooling other than for load balancing. Also, others have rejected Mercury because of the high delta-v requirements. For exploration this is a big deal. Once you have enough traffic, though, it ceases to be a problem and Mercury becomes easier to reach than the asteroids. The key is **big** linear motors. Once you have enough space traffic you build one on the Moon. It's wrapped around the equator. It can put a manned capsule on a transfer orbit to any point in the solar system. Once Mercury base is big enough you do the same thing there--not only is it a launch system but it's built to grapple a passing spaceship (you'll have good navigation aids, guiding a spaceship on a grazing orbit to get within grapple range certainly could be done), the whole trip is done with only course-correction fuel. The transfer orbit to Mercury is faster than to the asteroids and the launch windows are more frequent--both of those things say "closer" to me. Any large enough, **airless** body could mount such a system. I haven't worked the accelerations you'll see from a system on Ceres but you certainly don't have access to the whole solar system from there. Even if it can toss stuff back and forth from the Moon you'll still have to use rockets to get to the other asteroids--and note that while the delta-v requirements for such trips are very low the travel time is long. [Answer] Besides already mentioned Venus (at 50 km above the surface), [Callisto](http://www.wikipedia.org/wiki/Colonization_of_Callisto#Potential_colonization) (probably the best of Jovian moons), Europa (if you don't mind some digging) and Ganymede (who needs it when we have Callisto?), I'd bet on [**Titan**](http://www.wikipedia.org/wiki/Colonization_of_Titan). Besides its popularity among sci-fi writers, I'd note some other advantages as well: * Much less radiated than Jupiter moons; * Has some gravity (in contrary to Ceres and other asteroids); * Shallow gravity well; * More fuel than on Earth (it rains hydrocarbons!); * Lots of water (and, consequently, oxygen from it); * Can be used as a base for Saturn mining (again, better than Jupiter, although further); * Nitrogen-rich atmosphere (can be used as a buffer gas); * Methane, ammonia and nitrogen can be used to produce fertilizers; * Most important one: atmospheric pressure is 1.5 of Earth's. Which gives us: * No need for pressurized habitats and suits (a huge engineering advantage); * Radiation is blocked out; * Aeronautics is easy to lift-off; * [We can strap on wings and fly!](https://what-if.xkcd.com/30/) What else could we possibly ask for? Now for some disadvantages: * Further away than many other targets; * It is cold (in contrary to space vacuum, it is an "active" cold because of atmospheric pressure); * Atmosphere is toxic (as well as on other bodies with an atmosphere); * Gravity is low (again, as almost everywhere). Overall, Titan is often considered as one of the top-5 places for human colonization. It has its challenges, but a good thermal insulation (parka?) and some oxygen tubes are much easier to engineer and use than conventional spacesuits. Same goes for habitats which don't need to be pressurized and radiation-shielded. ]

[Question] [ The only logical reason a alien empire was to let us join them was if we had something to offer them. After all, alien empires aren't running a charity! Let's assume that humans have discovered the effects of an alien empire in space, we do not know how much more advanced than us they are, what they have or what they look like. Considering that aliens could very well be better than us in any aspect, what feature can we guarantee we are better than them at? What do we, as a species, have to offer a galactic empire of different alien species that they do not have? [Answer] What do we have? Resources. And waste. Really depends on the aliens. You seem to be focusing on tech, but they will have that. * In Doctor Who, there were two fly-based aliens looking for, well, poop. Waste products are a valuable resource in certain situations and for certain aliens. * Plastic. We have a lot of plastic that we want to get rid of. These aliens might eat it and consider it a delicacy. * Water. Despite shortages, there are plenty of planets that don't have enough. * Novel experiences and stories. For the aliens who have everything. * Coffee. We have coffee. And chocolate chip cookies. * Earthworms. That sounds crazy doesn't it? But they are an important contributor to life on our planet. * Genetic material. Why resequence a gene when you can borrow? These aliens might have capability in some areas of science, including this one, but this would be cheaper and quicker. * Resistance to radiation. Rads are present everywhere on this planet, and we just walk around, without suits. Life has adapted to the sun's radiation. Oh, we get sunburns, but if these aliens developed on a world with a different thickness of atmosphere, they might find that we are cheaper to use on away missions. For instance, if the planet that they developed on has a much more congenial level of rads than most life-supporting planets, then it would make sense to have humans collect samples for them, thus saving on valuable resources on ship, if they still breathe oxygen. EDIT: Adding [this link](https://i.stack.imgur.com/xGDHe.jpg) thanks to @Rob Watts in the comments. Humans are scary. Pretty much, if you can think of something not-so-useful that we have a lot of or can do that seems completely ordinary to us chances are, somewhere someone out in the stars wants it. The question is pretty vague because aliens are, well, alien. There's no guarantee we're going to better at anything than they are. Like they might have an abundance of gold and think it's pretty worthless, while we will have all the poop they will ever need… [Answer] **Entertainment** Presumably we think differently than the aliens do. Our literature and music would be unique to them, offering them new chances to enrich their lives or just be amused or entertained. **Bio-diversity** Our food, assuming it is not toxic to them, would be a new set of flavors. We might have plants that can help their environments, or just look pretty in their gardens or vases. If they are based on nucleic acids, they might also find something in our DNA or the DNA of other Earth life that could help heal their diseases and help prevent genetic stagnation. Or they could just refine our previously unknown diseases into new bioweapons. **Their pathetic lives** Frankly, we are a violent race, and are very good at finding new ways to hurt and kill. If they can't avoid us, they might do well to stay on our good sides. [Answer] Well, hmm, who says they're not running a charity? Many Europeans and Americans in the 19th century thought that advanced western civilizations had a moral obligation to help poor countries, and this was one of the motives behind the colonial era. (Yes, other motives were selfish and exploitive. Real life is complicated.) Which brings me to one way to approach the question: Why did rich, technologically advanced nations on Earth in the past build colonial empires that took in poor, backward places? And while the colonial era is pretty much over, why do rich, advanced nations today trade with poor countries? What do they have to offer? 1. Natural resources. Earth might have specific resources that are rare on the aliens' planet(s). 2. Cheap labor. People with lower technology tend to be willing to work for less. If the aliens are way ahead of us, in their eyes we may be cheap labor. 3. Specific skills. Just because people group A are more technologically advanced than people group B doesn't mean that they are better at EVERYTHING. Germany has been a leader in chemistry for centuries: many countries equal Germany in technology in general, but the Germans still outdo them in chemistry. Likewise the UK and US lead in medicine. Japan in auto manufacturing. France in wine. Etc. Different nations have historically excelled at different things. That's a big reason why international trade exists: if everyone in the world was equally good at every job, there'd be no reason to trade. Rather than shipping things around the world we'd just make everything ourselves. And that's among humans, where we all have the same basic genetics. Perhaps the super-advanced aliens have much poorer hearing than humans do, etc, so humans can surpass them at tasks that require good hearing regardless of our technological inferiority. [Answer] **Location, Location, and Location.** For a second-hand copy of *FTL for Dummies*, we'd build them a spaceport. If we happen to be halfway between their homeworld and a planet with the most beautiful beaches of the galaxy (in their entirely subjective opinion) or perhaps next to the naval base of a rival, that's a deal too good to be true. **Strength in Numbers.** We don't know how the galaxy is organized. Perhaps there is some equivalent of the UN or the WTO (or the soccer world championship) where Earth joining the Evil Empire would give them another vote. --- Follow-Up: My idea with the second bullet point is that *the aliens* gain something in galactic society/politics by being able to claim that they represent a multi-species empire, the more species the better. Maybe they are gaming the system here, as Jay commented. One vote per species in some assembly, even if everybody knows that only one world in the empire calls the shots. Compare how [two extra Soviet republics](https://en.wikipedia.org/wiki/Soviet_Union_and_the_United_Nations#Role_in_founding_of_the_UN) were part of the UN during the Cold War. [Answer] **Why would we want to join their empire?** We just met them. We don't know *anything* about them. We only know that they are technological advanced. We don't know if their morals/ethics are compatible with us. We don't know if they would even want us to join their empire, even if we were as far developed as they are. There is multiple ways this can go. They might be conquerors and simply might want to take our resources. Look at Independence day. Not necessarily the most interesting story to tell. Lets say they aren't outright hostile. But they aren't a charity, either. So make them interested in *information*. They probably want to study us, want to learn about us *and the creatures living on our planet*. After some negotiations, it is decided that they create an embassy on Earth, and that we keep an open communication channel with them. They send some scientists as well to study Earth. We will want to do the same with them. Maybe they won't hand us their technology, but information about their social structures, their home planet, their political landscape etc. are all very valuable. This process will also yield information about what we have and they want and vice-versa. The first thing that happens is trade. Art in particular. Life will have developed differently on different planets, so there will be plants, tress etc. They don't know about. Those can be used as material in art they might be interested in. Music and instruments are another thing we might have to offer that they might want to import. So at first, the relationship will be based on information interchange, then more and more trade. While art and entertainment always work, you could always make some resources restricted for them. They might live on a quite barren planet and consider large bodies of water to be quite are. Earth could become a place of interest for tourism for them. At that point we'd have a pretty good relationship with them. We interchange information and we trade. So we revisit the question I posed earlier: Why would we want to join their *empire*? On earth, nations trade and exchange information. Yet they rarely want to merge. Maybe trading could be made easier if we were part of their empire. This isn't a problem we could negotiate a free trading agreement with them (think TTIP). As long as there isn't an outside force / a threat, there would be no reason for us to want to join them in the first place. And even if there was another civilization that indeed was hostile, we still wouldn't necessarily want to join them. They could agree to protect us if they think relations are good, and might even try to ally with us (think NATO), because they might be interested in their enemy conquering a nearby star-system and would like the heads-up and warning. So much like NATO has less powerful members as buffer-zones, we could be a buffer zone for them and be under their protection. In order for us to want to join their empire, there has to be a sense of common shared identity. Which needs to evolve over time, possibly generations. Nations on Earth form because of a long history and a common shared identity, the sense of "belonging together". This sense isn't just there. So the question isn#t really what we can offer them in forms of trade/tech/knowledge, but the question is what can we experience together with them / what events might transpire to form a bond of trust, understanding and to create a shared identity so that we and them would want to merge into one empire. Its an interesting thing to explore. [Answer] Strangely enough it is ourselves. It's very probable sapient life is rare in the universe. Perhaps there might be only a hundred or so sapient species in the entire galaxy. Finding one more sapient lifeform would be invaluable scientifically, intellectually and culturally to the starfaring civilisations of the galaxy. Early European explorers when they were undertaking oceanic voyages and discovering new cultures and populations of peoples around the world and especially in the Pacific Ocean, they also had to do a lot of trading of goods and materials that were extremely valuable to be allowed to examine and investigate the islanders and their society. With a little horse-trading we could do the same. Perhaps, stardrives instead of nails and axes. We should remember those encounters between two alien cultures did involve a considerable amount of copulation. But those first contacts were between members of the same species. First contact between two cultures with alien biologies might involve a lot less copulation, but you never know do you? There is a long history for this sort of activity. It could add a whole new meaning to the phrase the fleet's in. [Answer] Minerals like iron or bronze can be found all over the universe. Water isn't commonly found in liquid form but in ice form it can be very plentiful. Same goes with salt. However there are a few things that can't be found or at least we haven't found in the universe. Protein: so far we've found no plants or animals in our universe. Is the rest of the universe is anything like what we've discovered so far then organic materials and proteins might be in short supply. Fossil fuels: oil coal and other fossil fuels are made from organic materials as stated earlier large quantities of organic materials appear to be a rarity in our universe by extension so would fossil fuels. And of course there's always Slave labor. We don't know much about the alien culture and Technology it's possible they don't have or refuse to use intelligent AI or robots. If that is the case they might seek to use slave labor as a substitute. Location: it's also possible their interest in her it has nothing to do with us but the location of Earth it is halfway between two civilization who often trade with each other they might be interested in us at the halfway point where they can stop refuel and gather supplies. [Answer] Who says they have to be running a charity? Technical specifications/textbooks are nothing more than data, which would hardly cost a great deal unless they've got extremely inefficient methods of holding data (in which case, hey, show them flash storage). They simply say 'Here's some technical specifications, if you can manage to build this with your own resources then you can join the Empire and start paying taxes'. Now they've got another vassal that they can use to pump out resources. Look at it not from the perspective of 'What can the humans offer us in terms of technology/society/resources' but 'What can 7 Billion+ sapient organisms offer us in terms of productivity'. Assuming that the method of FTL they use doesn't rely on unobtainium (and in all cases, if you want to have Earth stand a chance at all, you need to apply some arbitrary rules somewhere), there's no reason it shouldn't be build-able with what we have on Earth. [Answer] The short answer is that we can't guarantee anything. The things we have, the knowns we can offer, we don't know if they have it or better. We don't know if they want anything to do with us. And we don't know if they are the type to try to conquer us and take what they want, should we have it. That doesn't mean to say we have nothing, or nothing to offer. We have our art, our music, our culinary arts, our poetry -- the good things in life. We also know that the galaxy is filled with much the same natural resources we have here on Earth, so we can assume they won't need to conquer us for that. After all, a predator only hunts what is worth the energy. So, if the goal is to open a channel with them, to start trade or what have you, then being as open as we dare is the wiser option. What we can offer is exactly what we need them to tell us, or at the very least let them show us what they appreciate. Hope this helps ^\_^ [Answer] The Earth has a property that might be rather rare, and has been suggested as something that could attract alien tourists, and somewhere that we should look for alien tourists in case there already are some secretly on earth. The Moon is the same angular size in the sky as the Sun. Therefore in particular we have near-perfect eclipses (occultations) allowing viewing of the entire solar corona. We can't predict alien aesthetics, but if they are interested in astronomy then this is interesting and cool. Obviously if you have interplanetary travel then you can position yourself in a location with this property any time you like, but the ability to view it from the surface of a planet might be unusual. As well as probably being rare it is also temporary. The Moon is a rather large satellite, properly we're binary planets in the sense that the centre of mass of the system is outside the surface of the Earth. It is being hoisted into a higher orbit by tidal interaction with the Earth, and in about half a billion years or so all eclipses will be annular. [Answer] ## Nothing ( Research Opportunity? ) Think of what a tribe of apes in a jungle could offer us. Their food is in tiny quantities and not what humans want anyway. Getting to them and providing for them is difficult. They aren't easy to train and aren't good enough to do even low skill jobs. In the event that they are sitting on important resources we won't trade anyway. To the aliens we will be a long way from anywhere ( if we were on a main route we would notice it) and we will have a pathetic amount of resources. Intelligent life is rare in the universe and the amount of resources used will be negligible whatever they do on our scale. ( the researcher could give the apes as much food as they could eat ) The aliens do not stand to gain anything much because they can make whatever we could give them ourselves, the alien population will be millions of times ours so they will study us for scientific purposes. The aliens will have the tech and manpower to scrutinize earth in great detail if they wanted to. This may or may not involve interacting with us but as macroscopic interstellar spaceships will release a huge amount of energy when slowing down, the aliens could easily avoid incinerating earth but getting us not to notice them stopping would be much harder. As they will probably construct a Dyson swarm or suchlike we will easily be able to see evidence of them. [Answer] Lets reduce the scope of this question a bit to put it in perspective. Is there anything you do that you can be reasonably sure you do better than anyone you're likely to meet? Unless you have objective validation that you're a world champion at something it's unlikely. Objective validation violates the "we don't know about them" stipulation. We could go all touchy-feely and say you're better at knowing yourself than anyone else is. But is that really true? You could study me for a long time, get to know me, create simulations of me in your head. You could then use your objective perspective (free of self-deception and pesky emotional baggage) to predict my actions better than I could. (At least one of my ex-girlfriends can do this disturbingly well.) I can therefore imagine a race of aliens who know our psyche and biology better than we know ourselves. It wouldn't take long to do that if you started with a higher level of scientific advancement. Or you could say, well I don't know that I'm better than you, but I'm really good at the one thing I'm really good at. What is humanity good at? What does history say? Science? Ha. Our history is full of superstition and rejection of science for far longer than we've been making advancements in science. Conflict. Though true excellence is control and we're super bad at controlling escalation (disagreement leads to argument leads to low level violence leads to state sponsored violence or genocide). So maybe we're not good at conflict. We're good at picking fights. I'm better than you at picking a fight, and if you don't believe me come over here and I'll prove it. Uniqueness. We do unique pretty well. Art, craft We probably have woodwork the likes of which they've never seen before. If they have wood it's unlikely they'll have wood precisely like ours. I would expect spacefarers to have lots of metal and synthetic materials. In the future in space wood will be more precious than gold. Also, what makes you think we'd be invited to join an empire. If history has taught us anything, cultures join empires at the point of a sword. [Answer] All things considered living on a planet with a life supporting biosphere is a luxury, it’s far easier and more economical to strip-mine planets and build ships/stations; consider every block of land as a wedge from the planet’s core to the upper reaches of its atmosphere. They would happily pay us what we would consider a fortune to rent space in international waters where they can land floating island-like holiday resorts and we could make further profit by providing entertainment, food and souvenirs. There would need to be laws in place to prevent pollution, bio-contamination, and a tax on souvenirs so that we can buy back raw resources, even the excrement should be recycled back into our planet’s biomass. The point is the buying power of an interstellar empire would far exceed the value of our resources so in order to ensure they’re not “buying our land for beads” we can’t allow them to leave with more matter than they arrive with. Effectively we’re exploiting them but since their economy is so far ahead of ours this merely gives us a chance to slowly catch up, and considering the exchange rate (buying stuff for little more than their cost of raw resources) they’ll still be getting really good value for money, even though relatively speaking we're also making a great profit. [Answer] I would compare this to a situation like the smaller Eastern European nations joining the EU. Clearly there was an advantage for those nations to belong to the club, but what advantages for the existing EU to invite them in? I think similar reasons would apply in your case; even though the scale is quite different, the basic logic could easily be the same. So with that in mind, my list of reasons for them wanting to admit us to their empire would be: * Trade: This is the big one. They want to do business with us and we want to do business with them. Being part of the club will smooth those wheels. * Geography: In Europe, countries are part of the EU primarily because of geography. South Korea isn't about to be invited to join, no matter how beneficial that might be to either the EU or South Korea, because they're not in Europe. The aliens will have a similar consideration: Maybe it's purely down to the Sol system's location in the galaxy that's enough to warrant an invitation to join the Empire. * Empire building: Bigger empire means more jobs for the beaurocrats at Imperial HQ on Rvgrnosh Prime, more cushy diplomatic postings, and more civvies to lord it over. It doesn't necessarily have to be hostile, just good old fashioned expansionism. * Free movement: Being part of an Empire makes it easier for people to travel. And that's important because there's a whole bunch of new unspoiled tourist resorts and landmarks on Earth that the aliens are desperate to visit and spend their hard-earned Y'fgrs at. * Buffer zone: If we're on the edge of the Empire's borders, or close to a competing power, it may make sense for them to want us to join as we will strengthen their border. They may want to use our system as a military base (think of how the USSR used Cuba during the Cold War), or as a border trading post (think how the UK used Hong Kong), or even just to bring the vulnerable border nations under your umbrella to make it easier to defend and make it harder for other spheres of influence to impact the core of your empire (think of why Turkey or Ukraine might be drawn into the EU). * Cheap labour: Farms across the UK, France, Germany, Spain... all use a lot of cheap labour from the Eastern European EU member states. This is a major economic boost if the Empire as a whole has high employment rates and would otherwise struggle to fill those lower paid menial roles. [Answer] Interstellar civilizations are going to be at a scale that makes our planet-based civilization really gimpy. We are Kardashev type-0.7 civilization. An insterstellar civilization, barring "magic" new technology, is going to be at least a type-1 or type-2 or type-3 civilization. The different in scale is ridiculous. By type-2, you are disassembling planets for raw materials, and Earth is not that big of a planet. By type 3 you are disassembling stars. So physically we have nothing to offer. Even if we assume computers don't get any more efficient, the dreams of their computer clusters will be far richer than our entire cultural history. Our culture will be interesting in the same way that the culture of gorillas is interesting: our civilization is ridiculously young, and ridiculously tiny, compared to an interstellar one. If a technological singularity occurs (where computers get more efficient, and they are a type 1/2 civilization), then all these conclusions are true even to a much larger extent. Going between stars is reasonably hard. The implied scale of the civilization that can go between stars so that it maintains an interstellar civilization has consequences. [Answer] ## Worshippers What do we, as a species, have that they do not have? 7 billion converts to add to their flock. [Answer] I think one of the most realistic answers I've seen to this question has been indentured servitude/slavery for a period of time. The current members of this empire are like rich kids sailing around the world on nice yachts and humanity will be like the illegal immigrants they employ to clean up their messes, make their surroundings look nice and generally make them feel better about themselves. With their tech it should be possible for 90%+ of this to be replaced by robot labor, but who wants that? Its *so* low class. In exchange for tech and protection from more established races, our entire species (or, say, everyone that leaves Earth) becomes their "menial" labor force for a while. In the time spans an intergalactic empire thinks in, this period is probably measured in millennia. That is primarily dependent on the idea that a culture is found before it has access to interstellar travel, if humans managed to get themselves into space with their own tech they will add a new dynamic to the whole thing. Maybe we get taken in by one of the more benevolent factions, or if we sort of stole some tech to get to space maybe we're taken in by a faction related to the one we stole tech from. Also - we have our DNA. I'm not sure if you're presuming most life is carbon based, but there's a decent chance our DNA is at least longer/shorter than that of other species even if by some chance all the building blocks look the same. [Answer] Gold is supposedly rare in the universe and scattered. Since we love gold, we already mined a lot of it. They would be happy to just pick up our stash of pure gold. That's also what [some think](http://www.darkstar1.co.uk/gold.html) is already happening... [Answer] As others have pointed out, any society capable of routine interstellar traffic will, on their way to Earth, pass by many natural resources which their technology will enable them to exploit with more ease than much of what we treasure here on Earth. So they will come to Earth to get other things. It will likely turn out that if they elect to conquer Earth, they will do so for the sake of imposing a particular societal form upon us (whether religious or secular), regarding this not as a means to an end, but as an end in itself; in other words, the whole point of the military conquest is to force seven billion people to live their lives according to the conquerors' wishes. It may also be that while space-based habitation is practical for brief residence, there are long-term health effects (perhaps peculiar to specific races) of residency in space, which are avoided by dwelling on planetary surfaces. We have a large surface area which is protected from the harshest of interplanetary and interstellar radiation by the atmosphere and the planet's magnetic field, and has a naturally self-regulating atmosphere of nitrogen, oxygen, etc, in a somewhat varied range of temperatures and humidities. If they like our surface conditions here, we may find regions of our planet being scouted out as development property. Offer them Detroit. [Answer] **Rob Reid** thought in *Year Zero* that our (pop) music would make the aliens ecstatic. They named their heavy metals Vanhelium, Slayerium, Ledzeppimite (but not Bonjovium — that's not a heavy metal, sorry). I enjoyed the novel. **Charles Stross** thought that some aliens may just be interested in (possibly entertaining) information or stories. In *Singularity Sky*, the *Festival*, a civilisation of uploaded minds, arrives at Rochard's World and drops cell phones from orbit. When picked up, they say "Entertain us, and we will give you what you want." [Answer] Someone already said entertaiment,oh well, i'm going with: **Tourism** Is very likely that aliens have seen many types of of planets and exotic locations, but the thing here is that we have different cultures, that might be a novelty for them. [Answer] Well we could teach them how to conduct inter-species wars, how to mistreat one another, intolerance and hatred. A walking tour of the Middle East would be a great place to start. We could be specialists in what not to do. ;-) ]

[Question] [ We have successfully put [37 trillion nanobots](https://worldbuilding.stackexchange.com/a/32602/16977) the size of a red blood cell into ~~the experimental group test subjects'~~ willing participants' bloodstream, but without a power source, the nanobots ~~clot up the bloodstream and don't carry oxygen~~ cause mild side-effects that last more than 4 hours. EnerThrive© Inc. is committed to ~~avoiding lawsuits~~ providing our customers with the best possible experience, so we've reached out to the ~~uneducated scum~~ public for ~~free intellectual property~~ ideas of how to power the nanobots. --- What would be a feasible way to power trillions of nanobots? These nanobots would live in the bloodstream, so they never should run out of power. Powering the bots includes both acquiring the power, and storing the power. Assume that the nanobots mostly use technology available today (except scaled down, of course), though there can be some minor-moderate advances in a few areas. The nanobots (and their power) should last at least a whole lifetime. Whatever power source also must be very cheap (because you need 37 trillion of it). A handwavium-boson-tachyon nanofusion engine should be a last resort. Also, no magic. [Answer] Why, glucose and oxygen! These have significant benefits: * Fuel cells are already available technology, so you can get electricity from pretty much anything that would normally burn. Should be possible to adapt it to work on glucose all right * You already want oxygen and glucose in blood. * Both are pretty easy to supplement. * No real need to store energy, as human body is doing it's best to keep oxygen and glucose levels constant - so it should be always available in healthy test ~~victims~~ subjects. Side effects may include * Increased appetite * ~~serious~~ light fatigue if nanobots are under heavy load * ~~blood vessels clog~~ dizziness if patient is really hungry * ~~instant death~~ complications in subjects suffering from diabetes Nothing you can't work around, but all may make interesting plot hooks. Wouldn't it be a problem in veins, there is no oxygen in them? * Without energy nanobots can't carry oxygen. So they can't carry oxygen if there is no oxygen. That's a big... Wait. * Blood makes full round around the body in about a minute. That gives us 30 seconds unpowered. Not a big deal. * Fuel cell membrane indeed works as short term storage anyway. * Last but not least, there *is* enough oxygen and glucose to power up blood cells. Not their full functionality, but see first bullet, we don't need it. We only need bots to have fuel economy at least as good as cells they replaced and no problem. --- As [King-Ink](https://worldbuilding.stackexchange.com/users/17311/king-ink) mentioned, making them work on fat could be nice. Additional selling point, certainly. Just be silent about the way you let more fat into bloodstream (and side effects of this), and don't ever mention increased failure rates due to higher complexity of your fuel cells. Or make them dual-fuel. Double the ~~failure rates~~ energy available! [Answer] ## [Piezoelectricity](https://en.wikipedia.org/wiki/Piezoelectricity) Since plasticity is a required function of these nanobots and the heart is going to be compressing them at a steady rate, piezoelectricity is your very best friend here. As it's generated very simply, there are no moving parts required, no batteries to charge, no complex chemicals, all you have to do is stay alive and they'll keep running, they'll run even better when you're running. Side effects are minimal, possibly a little extra strain on the heart. [Answer] Since all the other ones I thought of have already been used, I had to go find something else. The one I was going to use was piezoelectricity (though I didn't know what it was called!) And I think that would be the most useful for machines of this size. However, my contribution to this would be [Inductive charging](https://en.wikipedia.org/wiki/Inductive_charging). > > It uses an electromagnetic field to transfer energy between two objects. > > > It is just starting to be used for more commercial electronics to charge batteries. Some want to get cell phone chargers this way, it would eliminate the little port and cover. So someone could wear an armband or wristband (watch?) and the little nanobots would pick up a charge as they flow through that part of the body. It would even be possible to walk through an arch and charge the whole body in one go. Then the arm band would just need to keep a trickle charge going. [](https://i.stack.imgur.com/gn2jv.jpg) [Answer] There are a few options here. The simplest would probably be tiny batteries in the nano machines. You would wear some sort of charging pack (for example maybe around your wrist like a watch) and it would use magnetic fields to charge nano machines as they flow through in the blood stream. Another option would be for them to have organic reactors on board, for example maybe they can take sugar or fat or oxygen or something else similar out of the blood and use that to power themselves. Keep in mind that even large numbers of nanobots would still use a tiny amount of power. You might even use them as a dieting aid :) [Answer] Kinetic energy seems like the most obvious solution. Your heart is constantly pushing the blood throughout the body, supplying kinetic energy that can be harnessed by the nano machines. Automatic watches use this exact principle: they're powered by the regular movement of your arms. A tiny oscillator within the nano machines would move back and forth over tiny magnets, converting the kinetic energy to electrical power. [Answer] By using a Fractal Rectenna EM energy can be harvested from ambient RF fields and even possibly at nano scales, [IR light](https://en.wikipedia.org/wiki/Rectenna#Optical_rectennas "IR Light") (which is very good as living things tend to be warm) or even the WiFi system. It could be built into the structure of the nanobots themselves or a larger 'command' nanobot could be used as a recharging station and information distribution point. [Answer] I just want to point you to a more comprehensive reference: You are asking for a method of [Energy Harvesting](https://en.wikipedia.org/wiki/Energy_harvesting) that can be used on a nano-scale within the human body. # Low-power solution Personally, I'd vote for piezoelectricity [as user16295 suggested](https://worldbuilding.stackexchange.com/questions/35975/how-do-you-power-all-the-nanobots/35979#35979) if you do not need much power. The idea of using piezoelectricity to power RFID tags has been presented [a decade ago](https://ieeexplore.ieee.org/document/4410217) and printable piezoelectric sensors are already in use today. As they can be mass-produced and there is promising research in using [cheap sustainable materials](http://vivo.usda.gov/display/NIFA-1002084-PROJ) this technology can be expected to become even more affordable in the near future. # High-power solution If you take a look in the more distant future [biofuel cells](https://en.wikipedia.org/wiki/Microbial_fuel_cell) might be a way to generate more energy than piezoelectricity would allow for. However, I don't think this is feasible on a nano-scale just yet. Depending on the use case you could also implant a bigger device using a biofuel cell to generate energy and charge your nanobots using induction. [Answer] Solar power is a possibility. They can charge up when blood is close enough to the surface of your skin, and hold enough power to continue operating the rest of the time. Downside is they wouldn't work very well at night or in places where the sun don't shine if you catch my drift. But all of the blood goes back to the heart in the end, and if the bots are smart enough, they can choose which arteries to go down such that those most in need of a recharge are sent to the parts of the body that receive the most light (e.g. head, hands). Beach-goers and nudists would get extra power due to their degree of exposure. If the nanobots are built to combat things like skin cancer, their very means of powering themselves would counteract the dangers of over exposure to the sun. Not recommended for those who live in cold climates, especially past the Arctic/Antarctic circles during their respective winter months. [Answer] Install wiring within the body in a pattern similar to blood vessels. Larger cables split repeatedly down to capillary-sized nano-wires. Nanobots plug themselves in anywhere along the line to juice up, and store energy in chemical, miniature-battery form. At the macro scale the user can use any of a number of methods to provide their nanobots with electricity. They could use the installed bio-fuel cell that burns glucose and oxygen when other power sources are unavailable, or plug in a power cable from a wall wart (AC-to-DC power adapter) or a battery pack to avoid having to eat 5 meals/day. Bonus Feature: desk workers could plug in a power cable and run the bio-fuel cell in reverse. They'd never need to take a break to eat lunch. How do you implant these wires without painful, invasive, body-wide surgery? By having the nano-bots build it, of course! Install the power core in a normal, macro-scale surgery, then let the nano-bots build out the power supply system over the course of a few weeks. The ~~victim~~ test subjects will have to take vitamin+mineral+metal supplement pills to provide the nano-bots with materials not normally available in the human body. During the construction phase, any nano-bot which goes too far from the power supply so it can't get back before running out of power will need to self-destruct\* so it doesn't cause ~~blood clots~~ minor side effects. \* Self-destruct does not mean explode. (That would cause ~~spontaneous human combustion~~ major side effects.) Nano-bots would self-destruct in the same sense that dead cells self-destruct; they stop functioning and break down into biologically-harmless pieces. [Answer] My original idea did involve inductive charging, but then I got a brainwave. How much power do your nanobots need? If its of the order of a few microwatts per nanobot, the cells themselves produce enough bioelectricity for the purpose. The tissue fluid - cytoplasm potential difference can be harvested as a Galvanic power source. The total power requirement would come out close to 10^7 watts for all the microbots, so this isn't a feasible long term solution. However, this is a good solution for powering the nanobots during the "dark period" of inductive charging. 37 trillion nanobots would be harvesting power from over 50 trillion normal epithelial cells, so that isn't a problem, but moderation is favourable as draining too much power from the cells will upset cellular transport mechanisms, (dropping the resting membrane potential below -70mV could become a problem even with non-excitable cells). You could use a fine electrode injected momentarily into an epithelial cell of the blood vessel lining to get power. Not for long, though. And not at all with nerves or muscles, as they are excitable and the potential drop caused due to the nanobot power harvesting could cause involuntary contractions (spasms/tetany). Side effects... Don't you have willing test subjects? Use them and find out! [Answer] The best answer is to not use anything that needs charging. Nano bots also mean adding tiny amounts of heat generating sources, which may add up to something possibly harmful. So what can you do? Engineer cells to emit the signals your nano bots would. The cells would feed off natural resources. And Of course, you'd turn off the ability to replicate and all other abilities that would cause the engineered cells to harm other cells. [Answer] What you are describing is a [*respirocyte*](https://www.foresight.org/Nanomedicine/Respirocytes.html), first described in 1998. §3.1 summarizes Power (bold mine): > > **Onboard power is provided by a mechanochemical engine that exoergically combines glucose and oxygen to generate mechanical energy** to drive molecular sorting rotors and other subsystems, as demonstrated in principle in a variety of biological motor systems. Glucose engine design — possibly involving a ballistic turbine driven by rotor-combustion ejecta operating near ~1000 atm — is a critical research issue. Drexler [2] estimates engines can be designed to operate at >99% efficiency. However, since natural cellular metabolic pathways using the glycolysis and tricarboxylic acid (TCA) cycles achieve only 68% efficiency, we adopt a more conservative 50% efficiency for the present study. Sorting rotors **absorb glucose directly from the blood and store it in a fuel tank.** Oxygen is tapped from onboard storage. > > > The power system is scaled such that each glucose engine can fill the O2 tank from a fully empty condition in 10 seconds, requiring a peak continuous output of 3 x 10−13 watts. This pumping rate, ~108 molecules/sec for the gases, is not diffusion limited because [86] maximum diffusion current J = 4 p R C D ~ 109 molecules/sec, for gas diffusion coefficient D ~ 2 x 10−5 cm2/sec for O2 and CO2 in distilled water at 20 °C [87], C = 7.3 x 1022 molecules O2/m3 (arterial blood), and R = 0.5 micron. Taking Drexler's estimate of 109 watts/m3 for mechanochemical power conversion [2], a glucose engine could measure 42 nm x 42 nm x 175 nm in size, comprising 108 atoms (~10−18 kg). > > > The **glucose fuel tank** is scaled such that one tankful of fuel drives the glucose engine at maximum output for 10 seconds, consuming 5% of the O2 gas stored onboard and releasing a volume of waste water approximately equal to the volume of the glucose consumed. Such a fuel tank can measure 42 nm x 42 nm x 115 nm in size comprising <108 atoms (<10−18 kg), hold ~106 glucose molecules and be filled using ~10−3 sec of engine output. Power is transmitted mechanically or hydraulically using an appropriate working fluid, and can be distributed as required using rods and gear trains, or using pipes and mechanically operated valves, controlled by the computer. > > > [Answer] Some of the answers already touched on this, but I feel it has not been fully addressed: As food breaks down energy is released as electrons. The cells store that energy as ATP and NADH molecules. Over time, if there is excess energy, sugars and fats are formed as longer term storage of energy. [Here is an article that explains the process in details](http://www.nature.com/scitable/topicpage/cell-energy-and-cell-functions-14024533) The bots can use those molecules and do what cells do. If that is not enough the bots can help the digestive track to more fully absorb the energy from the food that was eaten. The guinea pigs... I mean the willing participants, would have to eat a lot, but the benefit is that they won't gain any weight (and most likely lose some). [Answer] Do what living things do—-with enzymes and molecular motors. The F0-F1 atpase is a very powerful, nearly 100% efficient and reversible nanomotor found within the very heart of every living cell, excluding a few hterrotrophic anaerobic bacteria. This motor is driven by hydrolysis of atp, which causes a conformational change within the F0 subunits, turning a camshaft within the center. A type of glucose/amino acid oxidase also create significant conformational change when they functions, which could be adapted to this mechanism, driving a linear pulling, reciprocating or rotary motor. Perfect for most type of mamomachines. Use glycolysis for the source of your atp, and/or use a type of cell that makes and releases free atp within your hero’s body, (atp is quite hard to cycle within your average sized nanobots)and have your nanobots powered by atp, same as the cells of your hero does, for example, moving muscles, thinking, doing chemistry, etc. the traditional diamondoid nanomachines should by just as easily actuated by this mechanism as a protein based nanomachine, or indeed anything within A living cell can. [Answer] Nano guides are required spread around and connected to a power source by magnet, so then, they can transfer energy to all the nanobots, nano guides are also necessary for many other tasks like, transfering new orders, updates, signals etc. This nano guides can be placed in only one position so they act as GUIDES. [Answer] A graphene nanotube coiled around a gold shaft and tuned through a joule theif circuit and tuned to the radiation resulting from the big bang should not only function as a constant power supply but also as the system clock for any process routines...presuming you are using the superconductive perfect graphene as the basis of your nanobots. To add details the cosmic radiation ever present permiates through every spec of matter in existence to my knowledge even lead does not have the ability to filter it out...the function is not so different in other proposed induction coils such as those used to charge cellphones only as we would be dealing with graphene the superconductor the energy needed would be so small the oscillation of this ever present frequency should drive the heart of the machine. [Answer] What about your brain, you could use it as a power source. Think of the electrical charges that pass through your body every second powered form your brain. When they become low on charge maybe it could be programmed into them that, that is where they need to go. If they could somehow harness the natural electricity provided by the human brain it may be possible to always keep them at charge. They Wouldn't need a permanent place to be recharged, as the human body is always healing itself... ]

[Question] [ Inspired by [this question](https://worldbuilding.stackexchange.com/questions/3136/if-our-universe-was-a-simulation-what-could-a-bug-look-like) regarding reality as simulation and [this question](https://physics.stackexchange.com/questions/35674/is-time-continuous-or-discrete) about a continuous time line, it made me wonder: if our time were indeed like a high frame-rate simulation, how could we detect it, if at all? So, assumptions are, of course - yes, time is discrete. And the "frame-rate" is high enough to not contradict what we *already* know in physics/science. What evidence could we find that time is discrete? [Answer] Actually, the world as described by the standard model of particle physics cannot account for time intervals lower than the Planck time, which is approximately $5.4\times 10^{-44}s$. But the current smallest time interval uncertainty in direct measurements is approximatevely $1\times 10^{-20}s$. Litteraly any experiment (such as those described in other answers) would need to be more precise by more than $20$ orders of magnitude in time measurement than the most precise currently known experiment. I have no idea what a world where physical constants are different from ours by more than $20$ orders of magnitude would realistically look like. Source : <https://en.wikipedia.org/wiki/Planck_time> [Answer] **Collision penetration by velocity.** As a starting note, we cannot talk about a graphics fps, and only a physics fps. Graphics fps only exists to the outside observer, we can only experience our universe through physics. This is a classic problem in video-games. If physics is checked by frames and if objects are overlapping, then if something travels fast enough it can be before an object one frame, and past the object next frame. Collision never triggers and it goes flying by. Too bad they knew so we got that pesky speed of light to deal with. Instead we just need to make our objects small enough. Cool part is that physics almost supports this. There is only a probability that two objects will collide. Now by using the width of objects and how often they collide we can calculate the frame rate of the universe. At least the physics loop frame-rate. [Answer] High spin rates would prevent certain orientations. For example, an object spinning at 100th the universal frame rate would never achieve an orientation in between 3.6degree steps. Spinning at half, it would always be at two ends of a line. This would invoke the collision detection problem [mentioned here](https://worldbuilding.stackexchange.com/a/127625/41280). The resulting interactions such as audio or electromagnetic field could be Fourier analysed and the spectrum would show the universal framerate.<https://math.stackexchange.com/questions/1002/fourier-transform-for-dummies> The object could be a rod a thousand kilometers long rotating in space at one millionth the frequency of the frame rate. Noise artifacts in the interaction with a magnetic field would still be observed. [Answer] Yes, possibly. Relativistic time dilation effect *may* help us to detect time quantization. If the universe is a simulation running at a uniform speed, then time dilation effects must be simulated ones. In the world of video production, there is a longstanding problem of converting the frame rate when a video is converted from one media to another. In classic film, frame rate is 24 fps. In PAL video, it's 25 fps. In NTSC, it's 30 fps. Individual frames are too short for humans to take notice, but when we have to convert frame by frame, the resulting artifacts are becoming visible to an untrained eye. Similarly, if we have two very precise clocks moving with respect to each other, or one in a strong field of gravity, and one away from it, the time will be running at different speeds for them. If time is continuous, the "slow" clock will measure time exactly as Einstein's theory had predicted. But if time is discrete, and the "slow" clock has to actually run in a "fast" timescale world, we would be able to see some weird effects, like some seconds will be shorter, and some longer than others. The "slow" clock and its attendants would not be able to notice that without referring to the "fast" clock, and vice versa. [Answer] I do simulations by trade, so forgive me if this is more technical than you intended. I will have to massage some of the details to get closer to what actually happens in simulations to cause artifacts like the ones you seek. First off, we have to start with an assumption: the universe is *supposed* to be modeled as a set of Ordinary Differential Equations (ODE). The current models of the universe are all based on ODEs. We have to assume that velocity is a measure of the rate of change in position. So we're detecting differences between what the universe actually is and what could be represented as ODEs. If the universe is supposed to be something other than ODEs, then the actual answer of what we detect is completely dependent on what the laws of the universe actually are. If my universe consists of "Use the known laws of physics until Jan 1, 2020, then break all the laws and summon a dragon into the middle of Washington DC," then that's probably the artifact we'd notice! Next, we have to point out that "frame-rate based" is only part of the problem. One of the nice things about ODEs is that you can solve them perfectly given one frame: the initial state. This means that our frame rate could be as low as 1/113 billion years ($10^{-19} Hz$) without generating any artifacts. That number, of course, is the current predicted lifespan of the universe, from big bang to heat death. If you want a different estimated lifespan number, you get a different minimum frame rate, but the numbers are equally broken. It's not *just* the frame rate that matters. To see the artifacts we need to start taking shortcuts. The first shortcut we take is to say that we don't process *everything*. We observe convenient symmetries, and we take it. If I'm simulating a pingpong ball flying through the air, I typically don't model every atom and the inter-molecular forces that hold its plastic shell together. I model it as a "rigid body," with a position, velocity, and a rigid shape. It's when we take these shortcuts that we run into frame-rate issues. If my rigid body assumption on the pingpong ball is not reasonable, then I generate a poor model. For example, during the impact between a pingpong ball and a paddle, the ball deforms quite a bit. I need to remember to model this period differently, with more expensive physics. The most common frame-rate issues are the ones mentioned in others: interactions between two solid bodies that don't follow the laws of physics. This happens because the simulation starts at a frame where one of these simplifications is valid, but during the integrated path of the universe, those assumptions broke down. A pingpong ball can be modeled as a rigid body, until you have to model the eletrostatic interactions between it and the paddle which deform it during a hit. If you use these assumptions when you shouldn't, you get artifacts. You get fast moving objects that pass through eachother. You get solid objects that stick together. Stuff like that. This issue doesn't happen in conservative simulations. Conservative simulations will do some sort of look-ahead process to see whether it can prove the simplifications will still be valid. If so, it does it the easy way. If it can't prove it, it does it the hard way, even if it turns out that those simplifications would have worked for the actual path (it's hard to find 100% whether the simplifications hold, but finding the 99% case and being conservative 1% of the time is easy). For example, your simulation might virtually "expand" every object in all directions by its velocity + max-acceleration \* frame-period, and then look for collisions. If there's a collision in that expanded world, then its possible that one will happen in the real world. If there's no collision, then it's easy to prove that no collision would occur in the real world as well. This approach is very fast, computationally, and will let you avoid these frame-rate artifacts. We wouldn't observe anything as being wrong. Now we typically don't solve these ODEs directly. We do what is called "numeric integration," which is an approximation tool. Some numeric integration approaches have artifacts that we can detect. For example, if you have a bias in your equations, you may develop what is called [energy-drift](https://en.wikipedia.org/wiki/Energy_drift). When this happens, your equations predict that energy will be conserved, but the approximations actually don't perfectly conserve it. This can accumulate over time and be detected. Of course, we have solutions for that as well. This energy drift is easily accounted for using Hammiltonian mechanics, which admit a particular class of numeric integrators which are *sympletic*. These integrators do not have energy drift, because they only integrate along paths that conserve energy. If the universe used one of them, we'd never see it. Now with all of this, we leave open the question: why? Why does the universe exist with a frame rate. If it exists because an intelligent species created a simulation, we have to ask whether they are designing their simulation to fool us within the simulation. If so, it's much harder to notice artifacts because someone is actively trying to prevent you from noticing. If I'm simulation a machine vision system for a robot, there's a whole host of artifacts that I don't actually care about because I know the algorithms the development team are putting together happen to not see those artifacts. If they add an algorithm that does see it, I'll have to change my simulation to model the physics more accurately. For example, if there is some fixed number of frames per second, you'll see harmonics form in the small number of multiples of frames per second. You'll see things like aliasing if the algorithm is simple. However, modern simulations have something called adaptive frame rates available. If the situation gets complicated, you just decrease your frame period to improve the resolution of your answer. You can always do this unless the simulation has to run in real-time (in some true time sense). In that case, you'd look out for the out-of-simulation entities which don't seem to obey the laws of physics. So in the end, there's lots of open questions, but the real answer is that you might be able to see the frame-rate in some trivial way, or it may be intentionally obscured from you so it can never be seen. The story is yours, design it as you see fit. [Answer] The [Arrow of Time](https://en.wikipedia.org/wiki/Arrow_of_time), or macro system temporal asymmetry, is the observable irreversibility of chemical and mechanical reactions, it forms the basis of entropy. It is also a demonstration of time's passage in that to reverse reactions effected by it one would have to turn back time. *If* we establish that there is a minimum time frame over which such asymmetry can be observed to occur this would demonstrate a minimum duration for the definite forward movement of time, proof that time only moves in one direction and in discrete parcels as well. Actually getting experimental proofs concerning events that occur so quickly is however impossible, by definition, if time *is* discrete since we couldn't measure the time it takes for time to happen in increments smaller than itself. [Answer] ## Rounding errors in hight speed cameras In "frame-based" universe, there is fixed smaler amount of time, it is like looking on kino/tv one monent we see static reality, then we do not see anything (and everything is recomputed to new positition) then we see static reality ... and so on. As nothing can be done faster than the "reality-frame" allows, for normal people would suffice like 120fps to have illusion of smooth move. (the reality frame must be much faster, as people are terribly slow anyway). But no camera in our universe could run as fast as reality frame-rate. So regardless how far we push, we would not be able "photo" either movement during visible reality-frame, nor dark during space between reality-frames. But it is not needed to detect those frames. If we can run camera "near" reality-rame speed (like 1000 times slower or so), and THEN rewind it much slower, if those two are not direct multiply of each other, we would find, that there is small noise between frames of our camera - if we film something really fast moving, we may found, that we constatntly get more (or less) better frames/worse frames/the item position varry slightly over the frame in regular pattern. We see (say 50 fps) TV as smoothly moving, but if we film it on camera with different rate (say 60 fps), there are moving stripes in the film we could see even in bare eyes, as those are running at the difference speed (10 fps) which is simply visible as flickering. But if we would film a fast TV (say 5001 fps) with slow camera (say 50fps), we would see nothing, but one of 100 frames would be duplicate or missing or distorted. If we could get near the reality-fps, (even on many orders slower), we would not notice it by bare eyes, but statistically comparing changes in the frames, we would notise, that with regurarity one of many of them is distorted somehow, even if in avarage the movement would be smooth. and the systematic error on magnitude of 10, 100, 10.000.000 frames would signal us, that there is "frame-based" reality and we could compute its frame rate, even if it may be impossible for us to go near such speed. The same way, as you can compute, how fast is your camera, if you film fast running car and at some moment the wheels seems to rotate slower, then stop, then rotate reverse, while car is still moving ahead. --- That said it is still possible, that we live in "frame-based" reality with so insanely fast frame rate, that we could not make for this effect even with best possible equipement. Then we would not know. --- And for computational speed of that simulation - we cannot say anything, as in "frame-based-reality" time is already stopped and there may be "millions years" between next sub-femptosecond frame is computed - for all what we know. [Answer] If the frame rate is constant (rather than variable), then for complex waves we might be able to detect [intermodulation](https://en.wikipedia.org/wiki/Intermodulation) and [aliasing](https://en.wikipedia.org/wiki/Aliasing) of its harmonics (which in theory should go on to infinity). [Answer] High speed cameras would not only allow us to detect that reality is frame-based, but it would also allow us to record what the framerate is. Between each [frame](https://en.wikipedia.org/wiki/Film_frame) any number of things can happen(i.e., you can move 5ft or 1000ft), but the results of what happened in one frame is only visible on the next frame. Answers to [this Physics SE question](https://physics.stackexchange.com/questions/136462/is-there-a-limit-to-the-frame-rate-achievable-with-a-high-speed-camera) suggest that there is no upper-limit to the maximum framerate of a camera, and [some cameras available today](https://hadlandimaging.com/wp-content/uploads/2018/07/hadland-datasheet-drs-hadland-imacon-200.pdf) are already capable of 200 million FPS. That's about one picture every 5ns! So, if reality was frame-based then as high-speed cameras achieved higher and higher framerates, eventually we'd begin to see the discreteness of the universe as the pictures look more and more like a slowed-down [stop-motion](https://en.wikipedia.org/wiki/Stop_motion) film. Eventually, we'd be unable to take unique pictures in between two very small moments of time, as there is nothing to view between one frame and the next. [Answer] # Numerical limits If we are living in a high frame-rate simulation it means that whatever may be running this simulation is subject to limits. If it was not the case, why would it choose discrited time ? So, if this thing is not perfect, there must be numerical limits inherent to the "language" it use to simulate us. As instance, C++ code max double value is 1.79769e+308. So let's just wait for one of the billions and billions of variable needed to run this incredible simulation to hit this limit. May it be the "univers volume" as it expends in every direction at the speed of light ? I don't know, but if these superior beings have opted for discreted time one may think that this simulation cannot fully handle the concept of infinite either. Then, see what happen... A big crash ? Some totally unexpected bugs ? At least I guess we will see that something is wrong ; if we are not just totally erased... ]

[Question] [ We have thousands of languages in the world, which seem to have evolved differently due to lack of communication methods (it wasn't quite easy for a Chinese guy to speak with French people thousands of years ago, for example). Currently, the lack of one common language across the world wastes an awful amount of time of the humanity, as translations need to be made and one has to learn multiple languages. Would it be possible for an Earth sized civilization to evolve to have a single language, with maybe few dialects (like American English and British English)? What is needed for this to happen? [Answer] Yes, it is absolutely possible. There are 3 easy ways to achieve this I can think of right now: 1: A civilization could advance to a point were global communication is as easy as (or easier than) it is in current day earth and then through some referendum decide to change the official language everywhere to a single global language. Such a change would not happen overnight, and it is very likely that, at least for the first few generations but possibly forever, the 'official' language is just a shared second language. EDIT: It doesn't necessarily have to be an official referendum, it is plausible that given enough cultural/technological/political influence a certain language can in time be spoken by (almost) everyone. 2: Given that most lifeforms start at a certain point and then spread out. If your dominant species never expands further than they can reasonably communicate, they would most likely speak the same language. The most viable reasons for this would be an obstacle preventing expansion that was naturally removed after the species developed a language and afterwards enough contact was kept to maintain similar language (for example huge walls of ice) OR an obstacle overcome by technological advancements that are at a level where long distance communication seems simple enough to quickly implement. 3: The planet is inhabited by a subgroup of a species from another planet speaking the same language that already had the technology for planet-wide communication upon arrival. [Answer] Yes, large empires generally enforced a common language for administration or trade. Sometimes religion or diplomacy extend this. Much of Europe still uses languages derived from the policies of the Roman empire. In the Americas and Africa the languages of the colonial powers are still used. So if you have a global empire and it wishes to have a single administrative language, your world will have a global language. Alternately you can have multiple Empires splitting the world that for historical reason use a single common language. Although it should be remembered that once the political unity is lost the languages will start drifting apart. Romance languages are considered separate languages and while lots of northern Africa and the Middle-East speaks Arabic people speaking different dialects do not necessarily understand each other without some effort. Obviously common religion has helped resist the drift somewhat. So if you have a global unified empire that has enough stability to rule the world for generations and enforce a common language policy, the world will end up with a single language with multiple dialects. I think a global empire would generally require fairly good ships to connect the coastal areas and gunpowder to control the interior. Magic can substitute for either. Also needed is an expansive culture such as early Roman Empire or the colonial era or a vision driving the expansion. Like the jihad that drove the Islamic Caliphate or how the Chinese believe in the existence of China even if it is at the moment divided into multiple states and nationalities. There are other possible driving forces, the point is that there needs to be a reason to rule the world. It is hard work, you know. [Answer] I'm going for a not feasible to develop naturally, but a few scenario's can result in it. Deviation in language is caused by lack of integration and communication. In today's society, communication is very ready and it's somewhat difficult to isolate a population to the extent a new language would form. That said, pre-telephone communication wasn't instant and much of the worlds population lives in isolation from one another. How would Roman and Chinese language be close to the same when there is no chance that 99.9999% of the Roman population is anything but completely unaware a 'China' existed? You don't even need to go that far geographically to get these divisions in language...English and French speaking people occupied the same land for much of their development, yet their languages each evolved along it's own path. From that standpoint...a planet in pre-industrial age communications is likely going to see many languages fragment and several alphabets come to use. I see it as near impossible on a planet the size of earth not to have several languages develop. That being said, there are ways of the multiple languages being suppressed down to one dominant one. Conqueror - Romans did this decently effectively in killing off the celtic language in mainland Europe...one people overtaking and conquering another, removing all traces of the conquered peoples language, and repeat until the world is one whole. Of course, this one language also runs the risk of fragmentation pending on communication technology. Vote - A sufficiently advanced population could vote in a single language as the worlds standard. There's actually attempts to make a common language that aims to be a method of communicating that most people could understand and speak to some degree...so this could be a vote to adopt a new language derived from others, or it could be a vote to make one dominant language the main language. Beyond this...there's one other scenario that might result in a less diverse set of languages (if not one language world wide). Humans are travelers/explorers and runners capable of moving pretty great distances across the globe. This resulted in humans reaching out across the globe early in their development, then coming upon the need for language and a written alphabet (we were spread out and isolated from one another when we started to create language)...of course many different languages using a wide variety of sounds and alphabets were developed because they were developed isolated from one another. Had the Human species been less mobile early in it's development and had reached the point where they were beginning literacy (IE, an alphabet) prior to expanding across the rest of the world, then each of these branches would contain a common element to their language that isn't seen in today's world. However, without near instant communication, you would see these languages deviate from each other despite having a common alphabet and sounds (Such as Latin and it's influences across the Romance language has today) [Answer] Assuming the species remains technological yet biological (for example, no all-changing [technological singularity](http://en.wikipedia.org/wiki/Technological_singularity)), then I see it as not only possible, but inevitable. As soon as communication is free, there develops a common language, on all levels including the global level. Currently on Earth it is English, and it is likely to remain so, as English is the only language, which is widely taught *everywhere* on the globe as an important, often as the primary foreign language (as far as I know, feel free to provide a counter-example). So, give it another generation, and practically every young person will be able to use English well because there's just too much information out there which won't be accessible to them otherwise. Give it a few more generations of global travel, and English will take over as the default language of all teaching, because populations just become too mixed. Give it a few more generations, and children will first learn English (which will have evolved a lot from what it is today of course), because that generation will largely not care what their ancestors' native languages were, except as curiosity. I think this kind of cultural evolution is inevitable. It has happened on increasingly larger scales since the dawn of written history, and there's no reason for it to not happen on the global scale once global instantaneous communications network exists. Whatever language happens to be "on top" when a civilization develops global communication will become the world language. Determined protectionism of regional/national languages may delay the inevitable, and a global crisis like a major war may reset the situation and give another language a chance, but eventually there will be a sufficient time of stability for one language to take over, unless the whole civilization is snuffed out. And no offence to those who don't like English. It is rather a horrible language, really, but but what can you do... > > The problem with defending the purity of the English language is that > English is about as pure as a cribhouse whore. We don't just borrow > words; on occasion, English has pursued other languages down alleyways > to beat them unconscious and rifle their pockets for new vocabulary. > --[James Nicoll](http://en.wikiquote.org/wiki/James_Nicoll#1990s) > > > --- In conclusion, even if you don't agree on the inevitability of this, I think it's safe to say that this development is plausible enough for any fictional purposes. [Answer] If you mean "at no point in its history did this Earth-sized planet ever have more than one language" then the answer is no. Languages naturally diverge. There are a number of languages spoken today, called Romance languages, that are all basically 'the local version of Latin, 2000 years later'. The population required to support a language is relatively small. In Papua New Guinea, there are a very large number of languages, most of which are spoken by fewer than 1000 people. Also, languages can change gradually -- you can have a bunch of villages where everybody can understand people from the neighboring villages, but not from far away. Say we have villages A, B, C, and D. People from A understand B, and B understands C, and C understands D, but people from A and people from D can't understand each other at all. To even try to prevent multiple languages from arising at all, we'd need an unrealistically high capability for communication (as soon as the species evolved an ability to speak, but long before they get technology) and an unrealistically low rate of migration and population expansion. --- If you mean "could a large civilization divided into many subsections, each with its own language, permanently eliminate all but one of those languages, and prevent the One True Language from splintering into mutually incomprehensible sub-languages" then the answer is not quite no, but almost. First, they could try force. Say Hitler won WWII and decided to make non-German languages illegal. Trying to do this, though, would take a lot of work, and would likely make most of the conquered territory harder to control. The slight efficiency gain (if it worked) would be outweighed by the problems it caused. Even if it worked, the effort would never go away, because they'd have to keep every dialect of German mutually intelligible. If you're trying to make your civilization look better than ours because of the single language, the "we slaughtered all the heretics" approach doesn't help. Second, they could try a vote. Say the UN became the world government and tried to vote on which language would become the official language of the world. How do you convince, say, the Chinese that despite Chinese having more speakers, the official world language ought to be English, darn it, and I'm not just saying that because I happen to be a native speaker and therefore wouldn't have to learn anything myself. Or French, and it's not because I'm from France and want to increase the prestige of France. Or Japanese, because it's the most beautiful language in the world, and no, that statement is not biased by my being the Japanese ambassador to the UN, it's just true. And so on. Official languages don't necessarily prevent other languages from being spoken. In Papua New Guinea, which has an enormous amount of linguistic diversity, there are 3 official languages: Tok Pisin, English, and Hiri Motu. --- You could try to invent a new language and get people to want to speak it, in the hopes that, not having any native speakers, it would be more politically neutral. This has been tried before, and Esperanto is the most famous and successful attempt at it. Looking at the Wikipedia page, it has various estimates for the number of speakers, the largest of which is 2 million. That may sound like a lot, but it isn't: English has 232 million in the U.S. alone, German has over 94 million, Dutch 20 million, French has 51 million in France alone, Spanish has at least 280 million, Portuguese over 160 million, Romanian about 20 million, Russian 214 million, Hindi 200 million, Hungarian 14 million, Finnish 5 million, Turkish 45 million, Tamil 48 million, Vietnamese 58 million, and Chinese over a billion. I'd guess that the probability of Esperanto or any other invented language becoming very widely used as very low, although not impossible. Part of the problem is that if I, a native speaker of X, want to talk to a native speaker of Y, then there are lower effort solutions: I could learn Y, or he could learn X. If we did decide to both spend the effort to learn an entire new language, what advantage is there of learning an invented language with a few speakers over learning a large and popular native language? --- If you mean "could I tweak the psychology of my aliens until this would work", then sure. You just need to figure out how to make the aliens different enough from humans that it becomes plausible. For example, if the aliens reproduce by dividing into two people while keeping all their old memories, they would be 'born' knowing a language, reducing the tendency of languages to change considerably. --- There is a misconception I'd like to address in the question: you assume that there is an enormous amount of inefficiency involved in dealing with language barriers, to the extent that we ought to do something about it. Most of the problems can be solved quite adequately with one or more of hired translators, bilingualism, and Lingua Francas. Most of the rest can be solved with creoles, pidgins, dictionaries, and computer programs (like google translate). If you revise your goal to "everybody on the planet understands language X, and can speak it, more or less", then this is much more easily achieved, and would have very nearly the same communication benefits. [Answer] Speaking from a linguistic point of view I'd say that, without technological aid, it is definitely impossible. Let's start with the obvious and take English as our first example. Here in Switzerland children are taught French and English from a young age on (normally starting around 9 years). However, only a small minority of adults is really able to use the language. Outside of the Indoeuropean strain it gets even worse. I have been to Mission Schools in Tansania, Japan and China. You will barely find a single adult (and I had to do with bank/insurance managers, constables and other "high-ranked" people) able to form a complete, understandable sentence in English (resp. French in parts of Tansania). All the really important daily business can be done in your local language. There is no need to resort to any other. Have a look at why languages die out: It is very often not because the native speakers stop using them but because said native speakers are dying out and their language with them. To eradicate a language and replace it with another it is necessary that important aspects of one's daily life have to be handled in that new language. Those things you normally handle within your own peer group where your native language is spoken. Our native language (which we probably already start learning in the mother's womb) is the easiest and we will always resort back to it as soon as it is possible, even in an environment where a majority is using another language (have a look at how Spanish is replacing English in the south of the US or what issues European have with the integration of foreigners - language is the main issue). Furthermore: There are also new languages emerging, just not noticed yet in many cases. Some are combinations of existing dialects, others evolutions of such. Furthermore think of this: You are used to regularly surf places where people speak English. A large number is native speakers the other large part are foreigners who mostly are well educated. How many labour class members from non-English places does this site have for instance? Many of my friends are from that milieu, they are car mechs, painters, bricklayers, etc. They do not speak English well thus they are not on fora like this one. They have their own ones where they write in their own language. Last but not least: Think of history. We have had many linguae francae in ours. There was Greek until about 800 AD, then it was Latin in Western Europe until about the 1750ies when it becane French and German in Western Europe until English took over in the 20th century. The only way I could see is in a totalitarian system which is able to control people even in the very private parts of their lives. As long as the family can get together without being heard by the authorities, they would still speak their native language. So, as a conclusion, or the tl;dr version: No, it's not going to happen. Language is a "fluid", you cannot force it into a shape. [Answer] According to UNESCO's [Endangered Languages](http://www.unesco.org/new/en/culture/themes/endangered-languages/ "endangered languages, unesco.org") webpage information: > > It is estimated that, if nothing is done, half of 6000 plus languages spoken today will disappear by the end of this century. > > > So, right now, in this planet, the number of languages is about to roughly halve within a century. Extrapolating from there, there might exist one only language in about 13 centuries, i.e., circa 3300. Which is not that far away in time, historically speaking. Off course, extrapolating is always prone to large errors, and, as UNESCO also say: > > this process is neither inevitable nor irreversible > > > and they aim to slow down and eventually stop the process. So there is also a clear prospect that the number of languages may decrease but then stabilise at a possibly small and *manageable* quantity of them. [Answer] A few additional thoughts. It wasn't said if this were fiction, so I'll peruse that avenue: * If the species had some form of telepathy, then one "main" or first language seems likely. * If God were a common physical manifestation, the species would probably speak that language. * If ancestors/aliens/God created a monolith in one language, it may become the "norm." * If the world government was totalitarian, and forced all inhabitants to learn one. [Answer] It certainly would be possible. The easiest way for this to happen would be if the whole planet was colonized by a civilization speaking the same language, and variance never developed. I am assuming by the way you phrased the question though that we are talking about an earth-sized civilization that previously spoke many languages evolving to speak only one. This would require much more widespread education and communications technology than we currently have. For example, in places like Sweden and Holland, most people are completely fluent in English, and in Holland a lot of higher education even happens in English rather than Dutch, as English is the international academic language. It is easy to imagine small languages such as Dutch dying out if the whole population speaks English and uses it for business and study. On the other hand, huge numbers of people live without electricity or schooling. In Cambodia for example, two thirds of the country has no electricity and most people live in the countryside. Such people are unlikely to learn ditch their own native language in favor of a global one, because the global will not touch them too much. A global language completely replacing other languages would require electricity, education, communications technology, and economic globalization to touch every corner of the planet. Such interconnectedness would also be necessary to keep the population speaking the same language, as isolated communities will evolve different languages even if they started out speaking the same one. [Answer] Yes, it already has in some sense. Math, science, the metric system, and HTTP to name a few have become universal methods to communicate logic, reasoning, measurements and to propagate communication itself while the spoken and written universally understood language has become English (more approachable than Chinese dialects). The world's diversity of spoken languages will continue to shrink over time as large business and mass media (i.e. internet) further permeate and saturate into all corners of the world, creating a feeling of familiarity and boredom throughout the land. However, one could easily argue that specific domains of knowledge have their unique vocabulary unto themselves creating their own dialect, even if spoken in English as its base. [Answer] Is this set in the past, present or future? A planet at the equivalent of 2000 B.C. Cannot possibly have a single language for obvious reasons. As time and technology progress, so will the chance of languages re converging. Rome had successfully made the standard language in almost all of Europe Latin. The reason it was Latin is because the conquerors spoke it, and when they conquered a region they wanted the locals to understand them and learn Latin, and didn't want to learn Gallic. The only Roman areas where Latin was not dominant was Greece, where the locals were already "civilized" by Roman standards and language was similar enough to Latin for administrators to want to adopt. There is a reason that all Western European languages have roots in Latin. From this we learn something - the leading language has to be the language primarily used to govern. As technology increases, certain nations are bound to become superpowers (think USA and USSR). These superpowers will each have zones of control where their nation's dominant language turns into their puppet's dominant language. The USSR broke up before puppet nations began adopting their language, but I suspect that if it lasted for another century the primary language in Poland, East Germany, Hungary, Romania, Cuba etc. would be Russian. To get a one-world language overnight is unrealistic, however creating a dominant language that slowly increases in popularity under a [one-world government](https://worldbuilding.stackexchange.com/questions/96/what-are-the-necessary-conditions-for-a-worldwide-government) (also see [this question](https://worldbuilding.stackexchange.com/questions/12888/what-are-the-elegant-and-effective-ways-to-establish-one-earth-government)) is extremely possible, even probable. How you go about creating this government and keeping it in power long enough to effect language is your choice, although the linked questions should give you a few ideas. [Answer] One language for the world.... that's difficult, but possible. No government can force it of course, because it would merge with local languages or not help speakers in proper survival. But still, there is the possibility of using our brainwaves- or more precisely, reading through our neural networks. That's what the world will be in a few thousand years. Or we could use antennae to communicate. Whatever it may be, you can't call it a proper "language", but rather a universal way of communication. If that doesn't happen, through a similar technological approach(writing/speaking and machines translating it), we could narrow down learning multiple languages. [Answer] It's not just possible; *it's already happening.* This is sociology fact, not science fiction. > > What is needed for this to happen? > > > Because the purpose of language is communication, in theory, what would be needed for a global language to arise is a global communication system. In practice... that's exactly what we're seeing. Look at how rapidly English is becoming the *lingua franca* of the Internet ever since the rise of the World Wide Web. It's already accomplished more, in a few short decades, than the combined resources of colonizing empires, missionaries, and traveling ESL teaching programs have in centuries. [Answer] What about some kind of global catastrophe, something that wipes out the majority of mankind, except for a people in a specific region. That region's language becomes the de-facto global standard when re-population of other regions happens in following generations. [Answer] You could probably get down to like Chinese, Hindi, Spanish, English, Russian. Good luck convincing the people that speak English to change to one of the more common tongues though. England and the US are both convinced of their own superiority. [Answer] Yes, it is absolutely possible, in fact it is happening right now. It takes a long time, but as soon as you have instant global communication, the process speeds up. I'm putting my bets on English becoming the global language within the next 100 years. That doesn't mean there won't be local languages, but English will become the first language of practically everyone. [Answer] Yes in the literal sense, but even in English we have different versions of English between neighboring states. It is possible but words could and probably would have slightly different meanings. An example of this would be the words for soda, some people call it Coke, some call it pop and some just call it soda, and that difference can be seen between NY and PA. [Answer] Your headline says "Earth-sized world", and that's the question I'll answer, because it's easy. Take an uninhabited Earth-sized world. Land one person on it. Now everyone on that world speaks the same language. [Answer] We do in some fields like medicine where all the parts of the body and species identification is in Latin. I music all the notes are understood my musicians. Computer code, art, etc. With translating apps any language can be understood. ]

[Question] [ Could I, purely in quantity of material only, build a solid bridge to a star? Ignore anything like strength, relative motions of systems, that is all taken care of, using lalalaicanthearyouium - this is not remotely based in any actual science. All I want to know is whether there is enough material for a decently powerful race to build a solid bridge spanning actual light years from things they have lying around nearby, i.e. a solar system, a couple of stars - but not a whole cluster or galaxy. The bridge should be along the lines of the classic film trope - "it looks like metal, but it's not any material we've seen before, Bob!" - that sort of solid. Although using iron held together with lalalaicanthearyouium would also be fine if there is enough iron lying around. "My God, Bob, it's just iron ... but how can that be?!?" [Answer] **That is a surprisingly reasonable project!** Let's dismantle the Earth, and use it as building material to Alpha Centauri. The Earth is $5.974 \times 10^{24}~\text{kg}$, and Alpha Centauri is roughly $4.13 \times 10^{16}~\text{m}$ away, so that is almost **150,000 tons of building material per metre**. That is enough for any bridge. Even if you stretch it all the way to the galactic centre, you still have about 20 tons of materials per meter. Given a cost of about [£14,000](http://www.kgbanswers.co.uk/how-much-does-uk-motorway-cost-to-build-per-mile-on-average-in/2956542) per metre for a motorway, a bridge to the star will cost you 600 billion billion ($6×10^{20}$) £. (assuming the same cost...) Happy building! [Answer] Yeah, ok, you've got your billion-billion tons of lalalaicanthearyouium, but: # How long would it take? I don't have very good data on this, but let's assume that the [1973 expansion to the Chesapeake Bay Bridge](https://en.wikipedia.org/wiki/Chesapeake_Bay_Bridge#1973_expansion) is a reasonable model (powers of ten are more important here, you'll see that even if I'm off by a full factor of 10 it won't really change much). The bridge is 4.3 miles long and took 4 years to construct. 6920 meters in 1461 days, or about 4.75 meters per day (really 4.73, but 4.75 is a nice round number). And that's assuming that a bridge is constructed from one bank, across the river, to the other and not bottom-up: remember, we're building with lalalaicanthearyouium which is both weightless and has an infinite tensile strength (not to mention plentiful, cheap, and as easy to work with as steel, if not more so). The nearest star, the sun, is 149,604,618,000 meters away. A little math and... 86.2 *million* years later you've got a bridge to the sun! Job well done. You're going to need some *serious* industry to shorten that duration. You'd need thousands of sites building bridge segments and flying them into space in a near-continuous stream and that'd still only take you down to a tens of thousands of years. The good news is that because lalalaicanthearyouium is weightless, you simply need to drive down the constructed portion of the bridge, to the end, maneuver the new section into place, bolt it down, then drive back down the other side (traffic flowing as a loop up and over the rising vertical spire of the bridge). TL;DR, I'm pretty sure you won't be taking a [night train to Rigel](https://rads.stackoverflow.com/amzn/click/com/0765346443) any time soon. Edit: So I thought about this a bit more, and at the x1000 speed mentioned via multiple construction sites and combining the results, we get the following numbers: * It still takes 86,200-ish years to complete * Construction progresses at 4750 meters per day, or just under 200 meters per hour. * This is also 0.2 km/h or about 4% walking speed. * This means that if we scale up another 25 fold, our construction speed equates to a comfortable walking speed. * Under the idea that The Anathema (see comments below) proposes of building from the *bottom*, someone could walk along the structure once it is half-finished and reach the far end at the same time it reaches the destination (walking the first half with the second half constructed behind them). The trip would take 1,724 years. + Better pack a lunch. * This still only gets us to the Sun. Reaching Alpha Centauri (nearest extra-solar star) increases the distance and build time 276,173.784 times. * If we want to increase our build speed by the same amount, then our construction speed reaches 0.127% the speed of light...*assuming that the [speed of sound](https://physics.stackexchange.com/questions/69238/what-is-the-speed-of-push-waves) within lalalaicanthearyouium is at least this value.* + Bad news, this is greater than the speed of sound in steel by two powers of 10 ([0.00127c ~= 1119 Mach](https://www.unitjuggler.com/convert-speed-from-c-to-Ma.html?val=0.00127), Steel: [17.78 Mach](http://www.engineeringtoolbox.com/sound-speed-solids-d_713.html)) and even greater than that of diamond (34.98 Mach) and beryllium (37.58). + Which would require our lalalaicanthearyouium to not only be weightless, but *unimaginably* dense/rigid [citation needed: cannot find a relationship between a material's properties and its speed of sound]. - Which lead me to just learn that a neutron star can't exceed 3.2 solar masses in size or its density results in a material-speed-of-sound that exceeds *c*. Turns out that [that's pretty darn accurate](https://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit). - Oh hey, [science paper](http://articles.adsabs.harvard.edu//full/1988ApJ...333..880E/0000888.000.html) from 1988 that did some math and made a nice chart. The top half of that chart is the velocity of the longitudinal wave. 109 cm/s-1 is just about 5% the speed of light. [Answer] ## It's not completely ridiculous For simplicity's sake, I assumed you're making a bridge that's one lightyear long, has a cross-section of one square metre and [plugged that into Wolfram Alpha](http://www.wolframalpha.com/input/?i=1+lightyear+*+1+m+*+1+m). We're looking at roughly 9.461 quadrillion m3 ($ 9.461 \* 10^{15} $ m3) of material which corresponds to a solid sphere with a radius of 131.2 km. If we consider that the [Death Star II](http://starwars.wikia.com/wiki/Death_Star_II) had a diameter of 160km, I'd say what you're setting out to accomplish is not entirely without precedent. You could for instance grab [15 Eunomia](https://en.wikipedia.org/wiki/15_Eunomia), turn it entirely into lalalaicanthearyouium and have enought material to build yourself a whole lightyear of interstellar bridge. ## Won't it collapse under its own gravity? Let's see. Imagine a bunch infinite amount of 1 metre wide lalalaicanthearyouium spheres lined up next to each other. We start by calculating the gravitational force the second sphere exerts on the first using Newton's law of gravity: \begin{align} F\_1 & = G\frac{m\_1m\_2}{r^2} \\ & = G\frac{m^2}{1^2} \\ \end{align} For the third sphere's force on the first one we get: $$ F\_1 = Gm^2 $$ What we're getting here is an infinite sum, so let's write that out and see what it gets us. \begin{align} F\_t & = \sum\_{r=1}^\infty G\frac{m^2}{r^2} \\ & = Gm^2\sum\_{r=1}^\infty \frac{1}{r^2} \\ & = Gm^2\frac{\pi^2 }{6} \end{align} This is great news, The gravitational pull of an infinite series of spheres lined up next to each other on the first sphere is equal to $\frac{\pi^2 }{6} \approx 1.645$ times the gravitational pull between the first two. Of course, a bridge is not actually a series of spheres, but this should not be a problem since this approximation work better when the two objects are further apart. at a few kilometres, there will hardly be a difference. You can improve on this calculation by making the distance between the segments (except for the first one) variable, and scaling the mass with the distance between, so they still accurately represent slices of the bridge. And then take the limit of the distance going to 0: $$ F\_t = \lim\_\limits{d \to 0} Gdm^2 \sum\_r^\infty \frac{1}{(\frac{1}{2}+rd)^2} $$ Calculating this limit is left as an exercise to the reader. [Answer] Other people looked carefully at the amount of materials required and found that it would not be unreasonable to make a "bridge to the stars." However, there's more to this than just building the bridge. You also need some sort of vehicle to traverse the bridge. ## Yes ### Bridge Crawlers In most ways the devices used to move stuff along the bridge to the stars would act like elevators (just like for a space elevator). I assume that this would be the case for your bridge to the stars. ### Eliminates Propellant Needs The most important benefit of using elevator cars to crawl on your bridge to the stars is that it removes the need to bring along propellants - since the bridge becomes your propellant. You will still need to bring the other stuff you require to survive in space (life support, power, etc.). ### Might eliminate the need to generate power Depending upon how you make your bridge, you may be able to transmit electrical power through the *lalalaicanthearyouium* structure of the bridge. *Lalalaicanthearyouium* had better be a superconductor though or transmission losses will kill you, lol. ## Conclusion Basically, not only are the material requirements reasonable, building one would actually make the travel easier. We just need to pretend stellar motion doesn't occur :) [Answer] Say your bridge has 1 square metre cross section and a density of 1 metric ton per cubic metre. Then one lightyear of bridge would be approx $10^{16}$ tons. The Earth is about $10^{22}$ tons. If Earth was to contain a percent *unobtainium* and if it was dismantled to get material, it should work. [Answer] **What would prevent your superstructure from rolling up to a giant *hank* of lalalaicanthearyouium** (*handwavium*) **under its own mass?** --- I mean it has to be flexible to link two solar systems (which are of course in motion related to each other). I mean if it has the mass of 100kg/m, then it weights 4.0680272\*10¹⁸ kg which is all gravitated to its center of mass. I would assume if it is strong enough to not brake apart, it would roll up in a spiral then entangle itself. [Answer] Several answers have addressed the numbers--you can build it. What nobody seems to have touched is what good is it? Bridges have an implicit assumption of gravity being normal to the bridge surface. What gravity you will encounter is parallel to the bridge, not normal to it. You have a strip of lalalaicanthearyouium to the stars that can only be climbed, not walked upon. If you're going to do something I would think it would have to be a ladder, not a bridge. (I'm ignoring the problem of a lack of fixed endpoints. In reality that's going to make it useless anyway.) [Answer] Really, this is just an upscaled space elevator. Most others have already pointed out that it may be possible from a materials point of view, but I don't think anyone's pointed out what other issues you might have. Let's look at an Earth-Moon bridge for a more local example: One problem we have is that the Moon orbits at a different velocity to the Earth's surface - so anchoring it at this end could be a problem. The Moon itself is tidally locked, with the same face always pointing at Earth, but there is still a small wobble during its orbit, so anchoring might be easier there. Oh, and the Moon is receding (slowly) and the Earth's rate of spin is slowing, too (one is a consquence of the other). Then, we have this giant ribbon of material undergoing gravitational attraction towards the Earth, gravitational attraction towards the Moon, and so it will be under massive tension. Not too mention, the Sun and other planets will have some gravitational influence. --- Let's get back to the Sun-star bridge: As as been mentioned - all stars are in relative motion to each other - but locally, this isn't all that fast. One problem is that to prevent the bridge from just collapsing into the Sun, its will need to be in orbit around the Sun. I'm pretty sure the maths on this is going to get very complicated for an elongated body (compared to the relative small spherical bodies we're familiar with). This in itself will setup tension along the bridge (some of the bridge is being pulled toward the Sun, some of the bridge is accelerating away from the Sun as it orbits). Then, eventually, as the bridge is extruded out towards the other star, we're going to have to account for additional tension of the bridge being pulled in towards that star. And then there's the gravitational effects of all the other local stars. --- I think what all this adds up to is a mathematical nightmare of orbital mechanics... ]

[Question] [ Well, Santa's finally done it. He's bankrupt, thanks to some rather dubious investments and some bad luck in the real estate market (a couple ice sheets he was renting out just melted away). Kris Kringle, therefore, has to appeal to us mere mortals, to find someone - preferably a private individual - who can finance his operations for one year while he tries to secure a better financial footing. Santa has commissioned me to do a feasibility study - that is, to figure out if anyone would be willing to help him. I have to start by figuring out just how much it costs him to be Santa each year (and no, he hasn't told me, and probably won't - Santa's secretive), to within an order of magnitude. I've identified some key places where Santa surely must be using money. They include: * Getting the raw materials to make toys. * Paying the elves to make toys. * Generating all of the energy he needs to run the North Pole. * Dealing with the reindeer. Taking these - and anything I've missed - into account, how much does it cost to finance Santa's operations for one year? --- ## Basic assumptions and clarifications: * Santa needs to deliver one toy to each of the roughly 2 billion children on his list. * He needs to do it in one night. * He has the entire year to make the toys, but he needs the elves to make them (and they need to get paid!) in his workshop. No subcontracting; having to get an investor is embarrassing enough. * Santa's workshop is at the North Pole, or thereabouts. * Santa still has his reindeer, workshop, etc. from last year. However, he'll still need to buy new raw materials, food, etc., as well as generate energy for this year. We're not starting from scratch. * The sled is reindeer-powered; when looking at the energies required for transportation, we'd have to look at what we need to feed the reindeer (I'm using a model like the one in [How many calories must Santa's Reindeer consume?](https://worldbuilding.stackexchange.com/q/65890/627)). [Answer] # Pay for elves [Joe estimates](https://worldbuilding.stackexchange.com/a/63239/627) that it would take 85,851 elves working 16 hours each day for 364 days to make roughly 2 billion toys. If Santa pays his elves about \$10.00 per hour (in US dollars), that costs $$85,851 \text{ elves}\times\$10.00\text{ per hour}\times5824\text{ hours per elf}=\$5\text{ billion}$$ Let's multiply that by 2 to take into account support staff and elves working in Santa's other departments (energy, farming, etc.). So paying the elves alone costs \$10 billion. [Nolo estimated](https://worldbuilding.stackexchange.com/a/63240/627) an elf population 2-7 times that high. So we could actually be looking at \$20 billion to \$70 billion. # The cost of toy materials Let's say each toy costs \$5.00 to make in terms of raw materials (if it takes an elf 15 minutes to make each toy, labor is \$2.50 per toy). The cost of the materials (and the cost of using tools for toy-making) then is $$\$2\text{ billion toys}\times\$5.00\text{ per toy}=\$10\text{ billion}$$ As expected, making toys is really, really expensive. # Energy There has been quite a lot of dispute on the energy Santa needs to make his journey. I'm going to present several different results based on different calculations: 1. [Zoey Boles](https://worldbuilding.stackexchange.com/a/65912/627) found that Santa's reindeer would need 1,324,819,748 pounds of oats to travel the world on Christmas. [Walmart](https://www.walmart.com/ip/Quaker-Old-Fashioned-Oats-42-oz/10312439) will sell me oats for \$3.42 for 42 ounces. I could then buy these oats for $$1,324,819,748\text{ lbs of oats}\times\frac{\$3.42}{42\text{ oz}}=\$1.7\text{ billion}$$ Santa could buy this much oats, or he could grow it himself, which might avoid suspicion (although he would need to annex Rhode Island to grow it all). computercarguy indicated that prices could actually be as low as \$3.00 per bushel, which would lower the price to \$100 million - one seventeenth my original estimate! 2. [A. C. A. C.](https://worldbuilding.stackexchange.com/a/100654/627) used conservation of energy to get 12,000 times as much calories as Zoey did . . . just for the reindeer to propel themselves. This lands us in the range of tens of trillions of dollars. Taking gifts into account raises this by six orders of magnitude, meaning that Santa would be richer than many countries. The difference, I believe, is that A. C. A. C. took travel time into account; Santa must make his 200 million+ mile journey in 24 hours. For that question, though, reindeer can dilate time and can travel for what is, in their perspective, much more than 24 hours. For my question, A. C. A. C.'s method is, I think, correct; Zoey's is correct if the 24 hour limit is not in place. The elves consume energy, too. [The world average power consumption](https://en.wikipedia.org/wiki/List_of_countries_by_electricity_consumption) per capita in 2011 was 2,674 kilowatt hours per year. If we assume a cost of [12 cents per kilowatter hour](https://www.npr.org/sections/money/2011/10/27/141766341/the-price-of-electricity-in-your-state), then the eleves consume $$(2\times85,851)\text{ elves}\times2,674\text{ kWh per elf}\times12\text{ cents per kWh}=\$55\text{ million}$$ I have no idea how much energy is needed to make all of these toys, or what the energy consumption for certain other parts of the infrastructure are. # The total so far. At the moment, I've found that Santa must be spending tens of billions to many trillions of dollars each year. However, there are still some things I haven't been able to figure out: * How much energy does toy-making consume? * Can Santa recoup costs - for instance, through collecting cookies? * Does Santa have other costs - like, for instance, leasing his land? Is he a tenant toy manufacturer? These are why I'm still looking for other answers. [Answer] ## Outsourcing delivery The obvious solution is to use external fulfillment services instead of delivering himself, in the vein of dropshipping. In this model, Santa would produce all his toys at the North Pole, and deliver them somewhere else, say by November 25 for them to ship the products around the world. Let's go through his base expenses in this model: * Elf wages stay the same: **\$9 billion** total for workers and support staff. Because he sends out toys a month early in this model, they only work 11/12 months, so a savings of about 1 billion. * Santa can make cheaper toys this year, let's say he only spends **\$7.5 billion** on his 2 billion toys. * Since the reindeer aren't flying, they don't need millions of bushels of oats. Allow them to [graze in the tundra](https://animals.howstuffworks.com/mammals/reindeer-find-food1.htm) and take a year off. Cost: **\$0**. * I assume Santa is sovereign of his own land and doesn't owe rent or property taxes. Now he has to get his toys from his base of operations (somewhere in the Arctic circle) to a distribution center, likely one in Europe or North America, as that's where most of the gift-giving Christmas celebrators are. Let's say he chooses [Rotterdam and Los Angeles](https://en.wikipedia.org/wiki/List_of_busiest_container_ports). The [standard shipping container](https://en.wikipedia.org/wiki/Twenty-foot_equivalent_unit) is 1,280 cubic feet. Let's say Santa's small toys are about $1/8$ of a cubic foot. (A cubic foot is a big present!) The [average container ship](https://en.wikipedia.org/wiki/Twenty-foot_equivalent_unit) carries about 10,000 containers. That means if he sends two ships, one to Rotterdam and one to LA, he can ship about 205 million gifts, so he needs 10 ships total to deliver 2 billion packages. Now how much does it cost to ship two whole container ships? According to [this fellow](https://www.quora.com/How-much-does-it-cost-to-have-a-cargo-ship-something-like-MSC), who says he works in maritime shipping, it costs \$3200 - \$4500 for a 40' container (twice what we've been basing our math on). Let's go with the low end because of a massive bulk discount, so \$3,000 for a 40' container, \$1,500 for a 20' container. Now, Santa isn't shipping trans-Pacific, so reduce costs by 20% to account for this. * Beijing to LA: 6,261 mi * North Pole to LA: 3,875 mi * North Pole to Rotterdam: 2,639 mi. $$ 20,000 \* (1,500 \* 0.8) \* 10 = 24 \* 10^7 $$ A surprisingly cheap $240 million to get all his presents from the North Pole to LA and Rotterdam. However, 2 billion is an *enormous* amount of packages to ship in a month. Amazon ships an estimate 608 million packages *a year* so shipping 2 billion in a month is $40\times$ Amazon's monthly deliveries. Obviously, Amazon doesn't account for every delivery, but there's no way they're only 2.5% of deliveries. Now you have to deliver them. He can do this through intermediaries instead of under S. Claus, therefore saving him embarrassment. USPS delivers 506.4 million packages a day. Santa needs to deliver about 66 million a day if they have a month to deliver them. Every day, the USPS goes through \$395.4 million, at a cost of \$0.78 per package. Round this to $1.5because of large and irregular gifts. Santa needs to deliver 2 billion gifts. The average US family with kids [has 1.86 kids](https://www.census.gov/population/socdemo/hh-fam/tabST-F1-2000.pdf). If he packages gifts for one household together, he might get as low as only delivering 1.08 billion gifts. Therefore, delivery fees will cost about $1.62 billion worldwide. I estimate, then, that it for someone to take over Santa's operation, but sill hiring his elves and delivering the toys they make, it will cost (in billions): $$ 9 + 7.5 + .24 + 1.62 = 18.26 $$ So to summarize, for someone else to take over Santa's operation I estimate it would cost **20 billion US dollars** (rounding up). That's [approximately the GDP of Cambodia, Afghanistan, and Cyprus](http://statisticstimes.com/economy/countries-by-projected-gdp.php), or about the net worth of Laurene Powell Jobs (Steve's widow) or Microsoft co-founder Paul Allen, who are about the 40th [richest people in the world.](https://www.forbes.com/billionaires/list/#version:static) [Answer] If you were taking over Santa's role and had access to all his infrastructure and production, the cost will likely be 0. Santa has been in business for hundreds of years. Either he had a very large sum of money at the start and loses a fraction each year (which highly unlikely). Or he is self sufficient in what he does and his budget is completely balanced each year. Santa likely balances his Christmas budget perfectly every year and if he is personally bankrupt and requires a new Santa, the toy making business can be assumed to be completely self sufficient in terms of capital and the new Santa would not need any investments. Santa's actual job isn't to pay the bills, his job is to compile a list of all children and to check if they are naughty or nice. Twice. As well as deliver the presents on Christmas to all the children in the world. The actual accounting will likely be done by accounting elves. [Answer] its not technically feasible for Santa to deliver all the presents in 48hrs. but he has a year to do it. So he must have a time dilution device. if this is the case, he would never get a day off delivering presents(from his perspective) eternally! It does mean he has a time dilation device. Bet he uses it to bet on the stock market. investing companies will pay millions to get a foot closer to the trading floor servers, just imagine how much they would pay for a time dilution device.\* production cant be solved by this as it take 365 days to make the toys. but means production could be spread around and the north pole is prob now a tax dodge HQ.(Santa inc. needs to pay the taxes on his income form those trading companies) See CIA, SpaceX, etc as potental customers. ]

[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/72964/edit). Closed 6 years ago. [Improve this question](/posts/72964/edit) Human buildings usually have one or more doors which combine the function of an entrance and an exit, emergency exits being the only notable example I can think of, albeit designed for contingency use. My fictional alien civilization builds houses with separate exits and entrances; even toilets and closets are outfitted with two doors each. **Why?** [Answer] The body shape of the aliens makes it difficult to *pull* doors open, but they can easily *push* doors open (or vice versa). Have you ever tried to get through a door with both hands full? The aliens' body shape has the same effect. So doors are generally designed in pairs for both directions. [Answer] # Your society has a hypermartial warrior culture. The double-doors eliminate the problem of accidental rudeness and slaughter. If you were to attempt the use of a door at the same time as me, one of us must either retreat for the other or turn their back to walk out of the way. One is a dishonour to me: retreat is never acceptable. The other is an insult to you: it implies such weakness as to not be a risk or danger. While many of the raw aspects of such a culture have been refined, since constant bloodshed does tend to reduce populations, it is only stabilised by adhering to very rigid principles of honour and avoiding any instance of disrespect to others or requirements to dishonour one's self. Couple this with * other rules based on the same principle * the existence of gods whose worship occasionally conflicts with the society rules, * new cultures who don't adhere to this obviously necessary design feature, * the usual snowball effect from one minor incident involving someone with more power than brains and the protagonist, * other pressures in the world that make following the rules more and more difficult, and bam - tension to drive the story! [Answer] **Feng Shui!** In the [traditional Chinese Architecture](http://www.chinasage.info/architecture.htm): > > The main gateway entrance into the courtyard house had two red doors; it was located on the eastern part of the south side conforming to the rules of feng shui. **Immediately behind the entrance was a solid wall '照壁 zhào bì' that denies direct view or access to the courtyard, in Feng Shui terms it was to keep the evil spirits out (and cold winds too).** > > > I can perfectly imagine a culture where going *back* or *backward* is seen as cowardly, retrograde, inciting ill-luck, ... I can also imagine a culture in which doorways are adorned with a blessing on one side and a curse on the other. It is ill-luck to see the curse, and therefore people only enter the doorway from the blessing side. --- **Change** Have you considered that maybe marking the *change* that occurred is important: * you enter the toilets full, but leave empty, * you enter the closet in your night-clothes, but leave in your day-clothes (and vice-versa), * ... In this case, it could be that all locations that have a purpose have a doorway representing each state. For example, imagine a shop: * the empty-handed doorway is used to enter or leave the shop empty-handed, * the other doorway is used to exit with merchandise, or to bring it back. [Answer] Plenty of constructions have separate entry and exit sites. There are two main reasons. 1: Flow control. Freeways have separate exit and entry ramps because of the possibility vehicles exiting might interfere with vehicles entering. Sites handing large flows of people do the same - for example theme parks or concert venues. Flow is smooth because persons exiting do not have to buck the tide of those entering. 2: Functions associated specifically with entry or with exit. Airports have separate entry and exit so persons entering can be screened before accessing the interior. Large stores (for example Home Depot) have separate exit and entry so people can pay for their purchases before exit. The latter would probably apply to your aliens. There is some function which must take place before entering or exiting. Maybe it has to do with conditioning the interior environment or the new entering occupant - for example I can imagine a "mud room" associated with an entrance where persons dirty from the outside clean off before entering; no need for this on exiting. 3: Yes I added a 3. I could imagine an alien which would not want to cross its own path for a time because its presence depleted or contaminated the local environment in its path. Examples might be something which breathed up local oxygen in the water. Or an alien, like my friend Paul, that farted a lot as it went along and did not want to double back and breathe those farts. [Answer] No ability to walk backwards, only turn with a notable arc. If they evolved feet that weren't coordinated enough to just turn around, they might need to avoid meeting someone at a door where they have no ability to back off. [Answer] Cultural reasons were mentioned. I would say that religion and superstition could definitely explain it. If they are like the Centauri of Babylon 5, they might have "gods by the bushel." So, there could be a god of entering and a god of exiting. Using the wrong door would show that you favor one god over the other, leading to bad things happening. They could also have a really strong "don't look back" culture. The interesting thing would be if the bias is so strong, they don't bother locking the exit door because no one would use it to break in. [Answer] # They're centaurs. Traditionally, doors are placed at the end of corridors. This is a consequence of having to defend homesteads against bands of marauding bandits. Long corridors were made in front of doors to act as chokepoints so that small families of defenders could hold off larger forces. While society has developed so that these are no longer necessary, it is considered bad luck to not have a corridor in front of every door. As for why two doors, have you ever seen a quadruped try to turn in an enclosed space? [Answer] The OP's title calls the entrances and exits "portals". If they are more than physical doors it could be a reality of physics that only allows them to work in one direction. [Answer] Because a fee must be paid for entering into any building. There's a system of [turnstiles](https://en.wikipedia.org/wiki/Turnstile) in Russian public transportation for this exact purpose (in Moscow and other cities). On trams and buses, only entrance through the front door is allowed (immediately followed by a turnstile everyone has to pass). On railway and subway stations, all platform entrances *and exits* are guarded by separate turnstiles; all of those are already existing buildings with enforced separate entry and exit. A turnstile by itself doesn't always have to have separate doors/turnstiles. But when a fare collecting also happens, it slows people down at the turnstile, and a queue of them may form, blocking the doors. Separate exit path prevents entering people to become an obstacle for exiting people. Now in some other place, all the buildings could be organized in the same way. It could be a [tax imposed by the local tyrant](https://en.wikipedia.org/wiki/Pecunia_non_olet). Or we can imagine [a culture devoted to obtaining profit](https://en.wikipedia.org/wiki/Ferengi#Culture). The latter is even more likely to separate entries and exits everywhere: everyone wants to imitate big, successful palaces and corporate headquarters that have so many people entering and pausing to pay that a separate exit is required. [Answer] Real World example: There is a religious sect here in New Zealand (and, I'm sure, in other countries too) that are very private and have some intriguing rules about tech and stuff (as religious groups tend to do). My mother's (relatively normal) church purchased one of their old sites, after they left town for some probably totally normal reason, and just started churching in it. One interesting feature of the building was that all the bathrooms had an in door and an out door, and the reason was supposedly that even if you wash your hands, you're still unclean to an extent and both doors were designed to be pushed without needing to use your hands. Why this design didn't apply to the other doors in the building? Who knows? *Actual answer* Perhaps your alien race just have a very old hang-up about touching things that hundreds of other people have touched and design their doors to be pushed without their hands. [Answer] The inhabitants' main form of locomotion is to float through the air using their biological gas-bladders. They are naturally inclined to moving upwards and thus live against the ceiling of their homes in much the same way legged creatures live against the floor. They can expel gas to alter the composition of their bladders and so float down to the ground. However this carries disadvantages. First it forces them to rely on their weedy atrophied legs for walking, at least for the time being. Second it is a one-way process: They cannot re inflate in a hurry. I imagine this is a natural defence mechanism against aerial predators -- blast them with foul smelling gas then drop out of the sky. I also imagine doing it in public is regarded as rude in much the same way we regard public defecation as rude. The homes have an exit located near the top and an entrance located at ground level. A typical day the owner wakes up, floats out the exit and goes about their day. In the evening they de inflate and enter the lower entrance. They sleep for several hours at night, enough to generate more floaty gas, and wake up against the ceiling. [Answer] **Aggressive environment**. It could be microbes or predators, but both entry and exit have different functions. **Entry** * In case of predators, the entry is excellently visible (warning color, lights) and can be easily found even when confused or visibility is low, it can be opened at once and allows a panic button to close the door immediately and with great force. It also has weaponry to defend themselves and a lock construction, so even when a predator enters, it can only maul the unfortunate inhabitant and not the people inside the house. * In case of microbes, here are the sensors to detect them, a specific shower to clean them off before entering the house and some container to store the clothes which will then be rolled to the exit. **Exit** * In case of predators, the exit is perfectly camouflaged and allows to safely scan the environment for their presence from hidden eyeholes. * In case of microbes, the exit allows to put on the clothers which have been thoroughly cleaned. The exit area has overpressure, so microbes cannot enter the area when leaving. While it is still possible to build some functions in both entry and exit, experience shows that it much, much easier to hold something in perfect shape if it is specialized for its purpose. So different entry and exit makes perfect sense. [Answer] **Collisions are costly and/or painful** For some reason related to their physiology, these aliens do not handle physical impacts well. Perhaps they have some sort of weak, gaseous bladder on their front, possess naturally frail skeletal structures, or have a protruding appendage that is very susceptible to pain. Since most doors are opaque, the risk of injurious collisions from beings trying to use the same door at the same time is too great, but within a room it is much easier to avoid such a collision. In situations where privacy/security is less of a concern, transparent doors *could* replace the two-door system, but it would also be easy to point to tradition or to the old laws that enforced the two-door system (which perhaps predate transparent materials suitable for constructing doors) to explain why they don't take that route if you want to avoid it. This might also lead to to some changes in how they handle corners, whether that involves mirrors so you can see around them, utilizing more round structures, or having a lane system (whether physically drawn or just implemented as common sense) where you always stay to the right when approaching corners or something. [Answer] What are these buildings made out of? The first thing that came to my mind was heart valves. They are unidirectional because our blood needs to flow that way to function efficiently, but it's also really hard to imagine a bidirectional valve of that type. So maybe these aliens live (or at least used to live during the development of civilization) in buildings composed of something resembling free-standing cardiac tissue that they are able to grow to the shape desired. Or at least some material that is tough but also flexible. [](https://i.stack.imgur.com/4Z5PL.gif) [Answer] **Causality** The aliens inhabit a distorted region of space-time that means they can only move in certain directions without breaking causality. See Greg Egan's Into Darkness. [Answer] Observant Jews won't use the same plates for meat and dairy. As I understand it, separate ovens aren't unheard of (apologies if I've garbled details; most of my knowledge of the subject comes from a former colleague, not a halachic scholar, telling funny stories about the armed truce she'd reached with her observant mother in law). So, people can do things for the sake of ritual cleanliness that might seem bizarrely arbitrary and counterintuitive to the uninitiated. But really, doesn't any civilized person understand that **you wouldn't want to eat and excrete out of the same orifice?** Likewise, nobody with any self-respect or dignity would tolerate living or working in a building that used the same -- please excuse the coarse language -- *door* for entry and exit. It's just... *obviously* not clean. It's a disgusting thought. Ugh. Gross. Just... yuck. [Answer] A very simple answer: Locking mechanisms. Doors in their society are designed to only be opened from one direction, to make invasion more difficult. However, they also need to be able to quickly flee if their lock is broken. As such, entrances are designed to be opened from the outside only, but lockable from the inside. This also applies to spaces such as toilets, in which the occupant seeks privacy. The exit doors are then set up so that they can't be entered through - therefore, such doors are inherently secure, but will not prevent escape from a situation. Of course, this is the original reason for the approach. Tradition maintains it for all door systems, for two reasons - you never know when you'll need the locking system, and because it also prevents two people trying to use the same door in opposite directions anyway, and thus it has simply become a standard. Older houses would have the exits well-hidden to prevent people from easily finding them from outside, but it has become "hip" to have exits close to entrances. [Answer] **Highly hierarchic society** * The lower keeps the door open for the higher or waits until the higher one has entered. With one door there is a problem when two almost as high persons meet, they must define which of them is the higher one. The problem is avoided by having two doors. Similar to Japanese language, where you try to minimize the pronouns, because they imply hierarchy. * Because doors used to be relatively rare and only nobles had other doors than the main door, it is a culture that there is two doors even in places like closets. When two doors was not a thing, there would not have been doors in such a place. Similar to how sliding doors would be superior in many places because they save space and do not get in way, but still western style doors are the standard. **Evolution from hives** * The alien specie used to live in hives where there was entrance and the exit. * When they evolved they started to live in barracks. Groups would enter and leave the building from different doors. * The evolution can has reasons to further individualize the people. Breeding could be a thing to decentralize from the queen. **Evolution from a flying or other high velocity specie** * Stopping would be highly inconvenient. * It is easy to coordinate who leaves the space first with people within that space, but hard with people out of the space. * The velocities are high, so there is a real risk in collision. [Answer] **Aesthetics** Maybe they are genetically programmed to build geometrically symmetric colonies. An unsymmetrical apartment is repulsive to them, and hence they build symmetric infrastructure even after developing more modern technology. [Answer] Maybe they like to have a "flow" in their motions, processes and actions. i.e. they have a specific building that they go into to pick up stuff and if they go out the same way the went in they create a choke point in the flow, the cause a disruption. Also, in the case of toilets it makes it more hygienic since they sanitize their hands afterwards so their hands are cleaner then when they went in so if they touch the entrance they negate the effect of sanitization. This "flow" allows them to be more functional and efficient. [Answer] Because that society is obsessed with logistics. Not only do they have separate doors. It is that every aisle, sidewalk and road are of a single direction, so they do not make them wide enough so that someone can pass in the opposite direction. [Answer] Restaurant kitchens also use one-way doors, so that the doors can always be pushed, without pushing them into someone going the other way -- perhaps the aliens' hands/tentacles/etc. are always in use when they go outside (this could be for a reason as mundane as incessant rain and umbrellas, or as fanciful as you like) . Your aliens could even lack a multipurpose appendage, and rely for construction on telepathically enslaving some lesser species which isn't numerous enough to provide porters for all doors - pushing is the only way to open doors then. They may have a suitable body part but keep it private. [Answer] When the aliens were led out of bondage in **Misr**, their deity killed off all the first-born children of **Misr**. So how would a deity know which house had children to be spared, and which were to be killed? The aliens simply dabbed a bit of ruminant blood on their doorposts to inform the all-powerful that this house has children to be spared. To this day the aliens celebrate how their children were spared by placing not blood, but a parchment, on every door. Tradition dictates that they honour this parchment each time they pass through a doorway by placing it close to their heart. And since it would be such a pain to take down the parchment, hold it to the chest, and place it back again each time they go through a doorway, instead they simply touch the parchment with the sixth finger of their **left** hand, which conveniently has an artery coming directly from the heart. Since the aliens use their left hand to honor the parchment, they must always go through the door in a specific direction. The parchment must always be on their left. [Answer] Cultural reasons are all well and good, but feels like a handwave. Behavior is more believable when it has a practical, comprehensible rationale behind it. Reasons we do it in human society: * Revolving doors. * Exit doors in stores because they're by the checkouts (people ignore the "exit only" signs quite often though). * Flow control in parking lots, restaurant kitchens, etc, to prevent collisions. * Emergency exits, to prevent unauthorized entry. * Theatres with single chokepoint doors for queued ticketing at the entrance, but multiple exit doors for the rapid dispersal of crowds afterwards. * Process flow in car washes, loading docks, etc. * Turning around is a giant pain in the butt, for rail rolling stock. * Everything from signage, to the expectations of other travelers, relies upon the unidirectional flow of movement on roads. From this, it seems that the best example we have is the vehicle. If aliens have eyes at the front, and find backing up or turning around in confined spaces to be awkward, perhaps from being long (someone suggested centaurs) or from being spined or shelled, then they are likely to build houses in a circular fashion, with a round central courtyard, then a corridor inside, then rooms arranged for suitable flow of movement around that corridor, each with an in and an out door. Their lives would be set up to facilitate this: different rooms at different times of day, perhaps following the sun. Operations like making a coffee would be arranged as linear process flows along the countertop. Causing someone else to have to back up or turn way would be considered rude. Perhaps all houses are "clockwise", or perhaps different cultures are set up to flow around their houses in opposite ways. Perhaps they alternate on each level. Perhaps some are figure-8 or cloverleaf. The important thing is that people can flow easily around their property without having to turn in place, or obstructing others (thus, passageways should be wide enough for two to walk abreast). [Answer] Some buildings are required to have doors that open outwards, for evacuation purposes. The planet could have frequent natural disasters or events causing need for an evacuation. [Answer] *Why would a civilization outfit buildings with separate **portals** for entering and leaving them?* If they are actually portals and not doors, there might be several different reasons. Maybe the portals are one-directional only. Or if they are both directional, there might be a risk that you bump into someone trying to enter from the other direction (if you can't see through the portal). ]

[Question] [ Being a superhero without being state-sponsored or independently wealthy is kind of a massive pain. You're essentially working two jobs, one of which is highly dangerous and doesn't even pay. So naturally, a lot of them would have a great deal of motivation to make their dayjob as high-pay, low-stress, and low-hours as they can make it, so they can put more of their energy into their herowork without running themselves ragged. One option they have is to use the cards they've been dealt to their advantage and try to use their superpowers to get a job they can do way better, and way more easily, than any ordinary human. Let's say we're working with pretty basic, cookie-cutter superpowers here: someone who is significantly stronger, faster and tougher than any normal human could be. But the problem is that they still need to keep their powers a secret, so they can't, say, be seen on a construction site casually lifting a massive I-beam over one shoulder. At first blush, this seems like that dashes their options of using their superpowers to their advantage to make their dayjob easier and more lucrative. But does it? **What sort of job could a superhuman be more productive than a human at, with less effort, without having to reveal to anyone that they are in fact a superhuman?** [Answer] # Prep Cook Service [à la](http://www.gofresh-precut.com/products.html) Some food establishments use prepackaged meals and are essentially microwave services. Others are high end joints where each tiny piece of radish is painstakingly carved. Many are somewhere in-between. They might employ a prep chef to cut fresh vegetables, herbs, etc. They might just wrap that into one or two cooks' duties. They might use frozen, pre-cut vegetables. Or non-frozen. A lot of factors will influence this choice: What is the restaurant's price point (vs overhead)? How much space do they have—is it a hotdog stand, a hole-in-the-wall, a mall food court joint, a downtown restaurant, or a food truck? **This is where your cape comes in.** They run a local restaurant services business that offers pre-diced onions, pre-grated wasabi, pre-julienned cucumbers with a guarantee of freshness (not like the supermarket stuff that was cut five days ago in a processing facility) and an emphasis on quality. Maybe they do deliveries, maybe they have a distributor, maybe they have a small storefront—I don't know—but they only devote 1-2 hours in the early morning to that part (say, 9 A.M. to 11 A.M.). *The chefs they supply imagine them getting up at 3 A.M. to start prep so that their veg is ready by 9.* **Nah. They rolled downstairs at 8:05** and the kitchen was a flurry of knifework. They use a [mandoline](https://www.foodandwine.com/lifestyle/kitchen/your-mandoline-is-out-for-blood-heres-how-to-stay-safe) faster than what is humanly possible or safe. [Maybe they even have a superhuman connection for their produce supply—people probably wouldn't notice.](https://worldbuilding.stackexchange.com/questions/171147/can-a-store-that-doesnt-need-to-buy-merchandise-stay-unnoticed) **This job would take only a few hours a day, provide an okay-to-good living, and be very low profile.** [Answer] # **Professional Athlete** Pay should be very good if they are an elite competitor, which they'll have no trouble with. Hours should be quite low - they only need to turn up to the competitions and win them, or maybe come second from time to time to keep things believable. The rest of the time they can claim to be training in a super secret sports performance center. As long as their coach is in on it it should work well. One problem is, they will be easily recognized so will need a good disguise to do their superhero stuff. A cape and a mask probably won't cut it. [Answer] You have received several great answers, but I will propose an answer that is somewhat unusual and controversial but could turn out interesting if done right. The answer is: **Become a career criminal** yes, I know that it seems to be antithesis of a "superhero", but firstly you mentioned the word "superhero" only once ( ;) )and secundo it wouldn't be that much of a stretch as we see similar things happening in the real world. Both active and retired (spec-ops) soldiers and coppers are (quite often) found to be a part of crime organizations. You protagonist could start doing some small-time crime, the lesser evil, in order to keep him fed and justify it to himself by saying "I am stealing 100 PLN this week but I will save infrastructure costing billions and billions". And, as we all know, the appetite comes with eating, so occasional small crime turns into regular small crime which turns into something more serious and ends with criminal empire. Now, you could approach it from two sides, either he have come to the understanding that he cannot get rid of the crime, the best he can do is to control it, or that he have fallen into darkness. Or maybe, he is a hypocrite and he lies to himself that he is doing it because he wants to control the crime while the underlying motivation is more narcistic and egocentric? But back to the question and money: This career path is basically what the superhero will do while "superheroing", that is beat up people and hide his identity, but for money. [Answer] **Second Rate Professional Golfer (or other sport)** [](https://i.stack.imgur.com/3sHPB.jpg) *They MIGHT be professional golfers. Who can tell?* If you ask me who won the PGA tour this year, I will say Padraig Harrington. If that is wrong I will say Tiger Woods. I do not know a third golfer. The top ten golfers in the world are household names. But the top hundred? Well those guys have loads of cash AND privacy. Only enthusiasts know their names or where they live. The prizes at international events look like this: **Northern Trust** [](https://i.stack.imgur.com/bBVpT.png) or this **Phoenix Open** [](https://i.stack.imgur.com/HXio0.png) A golf contest takes a few days. With superhuman senses and coordination you can easily earn a five figure sum by scoring in the top sixty. Do a few contests every year and you are sorted. [Answer] ## Professional Model Assuming comics haven't wildly misled me, Superheroes are often absolutely drop-dead gorgeous. We're talking sculpted physiques that would take a real human literally every day of their lives to achieve and may well actually be impossible. But your superhero doesn't really need to work at it, this is just how they are. So put them in a pair of tight pants and put them in front of a camera. Nice thing is, if you're only doing the photo-shoots and not having to spend all your time maintaining your physique, you could conceivably have most of your time free to super-hero around, spend an afternoon once or twice a week photoshooting and take home a hefty paycheck each time. Of course.. having your face and body plastered on billboards might make keeping your secret identity somewhat more challenging. [Answer] There are types of logging where rare, exotic, and often endangered of hardwood trees grow deep in the forest and are sparsely and distantly distributed from each other and basically must be individually brought out of the forest. A person with superhuman strength could do this alone without equipment or labour costs. Things like ebony, rosewood, and pernambucco, among others. They could also process it themselves for a value-added product which would hugely increase the selling value. I having a mining engineer friend who told me story he heard about a pair of brothers who own a marble mine. Once a week they cut out a slab of marble to sell and then they spend the rest of the week drinking beer. How big a slab of marble? I never did get that detail but I guess you could find a quarry that's super difficult to get to and do that since you could just walk in and out. [Answer] Interior home renovations. More specifically, a subcontractor who specializes in demolitions. Home renos generally have less view to the public because much of the work is happening inside. Because they're usually carried out by contractors who are paid by the job, not the hour, there's less focus on timekeeping, and it's not unusual for them not be there at any given time, or even a given day, or working late, or whatever. If you have the place to yourself, you can go to town: you don't have to work taking down framing if you can simply pull the joints apart instead of having to use tools to pry them, so what might take someone else the whole day you might get done in a few hours. Pull whole cabinets off walls, move stuff around that might require two or three people, and do it faster than a normal human could. A job that might normally take three days, you can do in two; at least that's what you tell the contractor. In reality it might have taken you only half a day. Just as an example of what I mean, consider taking out an interior, non-load bearing wall that, oh, let's say 12 feet long. The wall will consist of 16 studs, ceiling and floor plates. If I'm taking it down, once any drywall or whatnot is removed, I can take a Sawzall to cut each stud out top and bottom, then get a pry to take out the plates. Or I can take a wrecking tool, twist or knock each stud out, then again with the prying. Either way, probably 10-15 minutes, at best, for an individual, and then there's a load of scrap material that will take a few trips to move out of the way. If I have super strength, I can twist out two studs at a time, one in each hand, put them down, and move on to the next two, which takes a few seconds. Ceiling and floor plates? Grip the wood and rip them out. Another few seconds. It might take me less than a minute, and then I could carry the whole lot out back to drop into a dumpster or scrap wood pile all at once. All in all, 20 or so minutes of work done in less than 5. You do that, you become known as the person to call when they need a demolition done quickly. Because you're a subcontractor, the property owner doesn't deal with you, and you're doing a job that has to be done before all the other trades come in, so less risk of someone else being there. ***ADDENDUM*** It occurred to me that the problem of other people involved in the same job site finding out the secret is if the other people on the job site are already in on the secret. All of the superheroes who don't fall into the unsponsored/independently wealthy groups are going to face similar problems, so the solution is obvious: team up. Lady Superior, with her superstrength, doesn't have to worry about the main contractor walking into the place where she's doing interior demolition because the main contractor, Jim, is far better known as the flying Skymaster. Jim also employs Alan as an electrician (Alan being the superhero Electostun), and so on. In fact, this is one of the secret benefits of joining a superhero team: they provide support and training for the whole crime-fighting thing, but also skills training and job opportunities for civilian life through the various businesses the team runs under the table. [Answer] ## Actually they could work in construction. The trick is they don't use their strength to its full potential. Just because they could effortlessly carry an I-beam doesn't mean they do so. They do the same work at the same pace as everyone else, advantage being they don't get tired, or face a short career from back/joint failures. You could write-in a couple instances where they broke cover, say to catch a falling object or stop a swinging beam. Something *nearly* superhuman that would leave coworkers highly surprised but not suspicious (except for maybe one who'd work into the plot...?). [Answer] # Scab worker. This could work in a number of different jobs, but I'll use the situation at an aluminum smelter I used to work at as an example. The key role at an aluminum smelter is the potline worker. A potline is a row of electrolytic reduction pots used to refine the metal. Basically it's a big pot with ~1600 degree (F) aluminum in it. Due to the high-intensity nature of job (and the risk of significant injury), potline workers are typically paid very well. Unfortunately the hours are long, so your hero won't be free to fight crime. However, there is a loophole here: potline workers are unionized and a contract re-negotiation occurs every 5 years (at least where I worked). During this time there is always a period (2 weeks at least), when the union workers stop working and the potlines are kept running by scab workers. Scabs aren't popular, but they get paid a ton of money. I know men who have rotated through jobs at different plants/smelters/factories for 4-8 weeks at a time and made enough money to quit working and live off the money they made for the same amount of time or longer. This still requires your hero to pause their crime-fighting for significant periods of time. However, with their super-stamina, they could work an insane amount of hours during scab jobs. They wouldn't even stand out, as honestly many scabs work dangerously long shifts anyway. Perhaps they need only to find 2 weeks worth of round-the-clock-work to then support 8 weeks of crime fighting. [Answer] Salvage Particularly in out of the way places. Where other people have to bring in cranes, you can just sling stuff around to get what is valuable. Important to have only people you can trust with your secret on the job site, of course. [Answer] ## It's the little things that make the difference. The superhero doesn't get tired from what would be hard work for anyone else. The superhero can work dangerous jobs that would be life-threatening for anyone else. They don't suffer from the build-up of minor and major injuries that a lot of more physical jobs incur. No physical labour is likely to be particularly stressful for your superhero, but the demand for low hours is a problem. Construction and industrial work tends to be quite long hours and you're always accountable for where you are because of the hazards and risks of the job. What you need is a job which is generally hard work, but typically accomplished in private, possibly with one or two other people to help (who may or may not actually be present) Perhaps **bespoke carpentry**. Making high-quality furniture or fittings for wealthy clients. Set your own hours, never get tired from the physical side of the job, get paid well for good quality products which you can make substantially faster than any competitors. This relies on you being highly skilled as a carpenter and artist, but hey, if you're getting the Paragon Package of superpowers, the ability to learn really fast often comes with that. [Answer] Your hero will encounter a major systemic barrier in their search for more-efficient earning: modern economies generally only pay for a person's *time*, without regard for their *productivity*. That's how [this chart](https://www.reddit.com/r/dataisbeautiful/comments/u8p5gd/productivity_incomes_have_diverged_in_the_last_45/) is possible: [](https://i.stack.imgur.com/hsSYH.png) This works to the advantage of wealthy capitalists and creditors, and to the disadvantage of all other people. It is not an accident. I mention this because this means your hero must very deliberately choose something that exists in one of the increasingly rare pockets of the economy that has not been permanently captured by profiteers. Unfortunately for your hero, most of those pockets are centered on either personal celebrity (which often boils down to sexual appeal), or some form of artistic creation. You don't mention your hero being an unusually creative artist, so that leaves sexual appeal. Unfortunately, there are millions of people standing in line to get "found" in this way, and it's not something your hero can force by their own effort. But here's one exception: ## Fitness guru Fitness gurus get paid by the unit sold, not by the hour. Perhaps it takes five sixteen-hour days of shooting to produce a one-hour workout special, but your hero gets the lion's share of every sale for as long as the thing is on the market, which could be a decade. Also, the economic gatekeeping in the fitness market cannot possibly be as thorough as the gatekeeping in the regular media, and raw performance can probably break through that ceiling even if the industry leaders are hostile because they aren't getting their beaks wet. Your hero, being supernaturally strong and tough, essentially has an unlimited supply of counterfeit goods to sell. They presumably have an enviable physique that requires zero effort to maintain, and can perform feats of strength that no competitor can better. A standard disclaimer will allow them to *imply* that customers who stick to the program might someday be able to bend bars and lift (partial) I-beams. Of course, this is sort of a con. Since your hero's physical fitness is not the product of dedicated effort, they will not have a good-faith reason to believe that the workout is excellent in any way. Some might not be comfortable perpetrating a massive swindle. And a determined opponent could attempt to prove that the workout could never achieve the suggested results. (That could be something a nemesis tries.) [Answer] ## Bodyguard, Bounty Hunter, Safari Tour Guide, Stunt Man Anything where a little extra strength and a LOT of extra durability would make an overwhelming difference. ## Courier If he's super-fast, then he could change clothing between the fast and slow parts of it. ## Artist Especially if the form is metal working, the super could be hyper-competitive with construction of large art works. ## Undersea salvage Stock superpowers of flight and durability could make recovery of sunken ships fairly easy. Just provide decent scuba gear. With super strength, he could make a living off of pulling parts from sunken cargo ships. [Answer] There are some very interesting answers here but I think I've got it. **A racing driver**. Not necessarily F1, that might be too high profile, but there's plenty of money in Formula E, rally racing or nascar. Even street racing can be lucrative if Fast and Furious is anything to go by. Racing drivers need to withstand high G acceleration, have good stamina and quick reactions. Any superhero worth their salt should be able to manage that. As for anonymity, can anyone prove that [The Stig](https://en.m.wikipedia.org/wiki/The_Stig) isn't a superhero? [Answer] # Sex Worker Super strength usually comes with super stamina. It also means you can exert more pressure with certain muscle groups. If a client gets violent, you can effortlessly defenestrate them. And the biggest financial advantage, you don't have to subject yourself to a pimp. If they try to enforce their rules on you because you are on their turf, you take the turf by force. [Answer] Homeless Pauper. This isn't a job, but seems like an interesting angle even so. Instead of super powers boosting her income, this hero uses them to reduce her expenditure instead. Rent? Nah, her super toughness negates the need for housing. At least as long as she works alone. This could be narratively interesting because of the social dynamics between her and those she saves, [Answer] I think that with super-human strength you could make some pretty impressive art. For example by bending and twisting long, thick metal bars in all kind of interesting shapes. Mayby there are some rich dudes/dudettes out there willing to shell out for this kind of art. [Answer] **Get sponsorship for superhero activities** Imagine rushing into a bank mid-heist, rounding up a gang of crims and handing them over the police live on TV then turning to the camera and nonchalantly exlaiming that "This superhero activity was brought to you today by Walmart, bringing you the best prices around" No need for a day job, advertisers would be lining up to offer you cash! [Answer] **Auto Mechanic** Just kinda piling on at this point but really any job that requires tools that amplify your strength -- switching between tools and setting them up takes time, which a superstrength hero won't have to do. Take off lug nuts? Uses his fingers. Lift out the engine? No problem. He can jack a car up just by lifting it and sliding something under it. (His hydraulic lift never worked. He just lifts it and slides a bolt into place.) He *has* all the tools and uses them if people are watching (he jokes that he will charge you extra for watching him work) but really you leave the car overnight for a 5 hour job but he's done in 20 minutes. But charges you for 5 hours of labor anyway. ("It's a competitive bid!") [Answer] **Journalist** Given that the superhero will always be solving the worlds largest problems, catching the world's worst criminals, etc, the superhero will find it easy to write articles on these events. [Answer] ### Reverse Engineering Apply the same skillset she uses on mad scientists’ gear to civilian products. She takes apart products, figures out exactly how they are put together and what they are made from, and sells the information to their competitors. Done in secrecy, and especially suitable for an inventor or gadgeteer. But even someone who’s no genius can do it quickly and precisely without as much expensive tools or personal protective equipment. [Answer] First off, it depends on the powers of your super. No matter what, your super hero will need at least 4-5 hours of sleep to not go insane. Unless, of course, their power is that they don't need sleep. Regardless, super heroes should choose jobs that echo their power or where their power is an asset but should also take minimal time to do with your ability. Can you fly or travel very quickly? Then get a job that requires you to get to remote, hard to reach areas (archeologist, collect gemstones or rare-earth minerals, etc.). Are you super strong? Become an eccentric metal sculptor or semi-pro boxer (throw enough fights to become full pro). Indestructible? Defuse bombs. X-ray vision? Search and rescue, or private investigator. Breathe under water? Underwater demolitions or welding. Underwater photographer. Man on fire? Fire fighter. Lightning? Line worker. The list goes on. [Answer] Everybody's going into very specific careers, but I don't really think that's necessary. All we need to do is define a few broad conditions, and he could do any job that fits under that umbrella. Namely, any job where: 1. Extra strength means he could do work that would take others much longer to do, thus saving time. 2. Nobody sees how he gets the work done so quickly. Ideally, rumors could be started about him having access to expensive tech or the ability to subcontract when necessary, so that nobody is able to do the math linking his work and time to the end product. [Answer] I don't know if the job still exists: wilderness power line inspector. Hike/backpack along the right of way of a power line, looking for anything that needs attention. Your superhero can use their abilities with little chance of being seen and their ability to carry more means less time spent on resupply. [Answer] ## Mining for Gold and Diamonds He can dig out an entire mountain in no time. Stonemason would be like clay for them. miner. If it collapses on him, he walks out. Opals, gold, diamonds. luggage handler at airport/hotel. Building log houses, lumberjack. [Answer] # **Sell/report autobiographical stories** Clark Kent was a reporter for "The Daily Planet" newspaper. He had a knack for reporting the latest news concerning Superman. And Peter Parker was often able to sell exclusive photographs of Spider-Man. And both Clark Kent and Peter Parker were able to use their powers not only to reveal scoops about themselves, but to get stories/photos of other events that were not humanly possible for others to do. (Did you really think that J.K. Rowling wrote the "Harry Potter" books herself? Everyone knows that she hired a ghostwriter named Harvey Porter, who wrote about his own experience of attending a secret school of magic. Although he doesn't make nearly as much money as J.K. Rowling, Harvey was paid off handsomely to allow J.K. Rowling to put her name on his written works.) So if the person with superpowers has a gift for telling stories, have them write and publish the stories -- as a ghostwriter if necessary. [Answer] **Profesional gambler** X-ray vision, super speed, mind reading - I can think of lots of ways to tilt games of chance in their favour without others noticing immediately. And at the end of the day when the casino boss's heavys decide to evict them from the premises for winning too much, superpowers would also be useful. Casinos in the same town might share a watchlist, but jump to the other side of the world and that's not a problem. Plus it could even be seen as doing good in itself if they see house-always-wins gambling as an exploitation of the poor & vulnerable, and commonly associated with other criminal activities they can gather intelligence on at the same time. ]

[Question] [ I want to have a socialist\* country where economy is good enough to have at least one big city of more then million people, that has well maintained buildings. The people don't have to be rich but there shouldn't be any [queues](http://englishrussia.com/2011/01/16/soviet-reality-that-seems-never-existed/) for basic food & clothing. Upper middle class should be able to own a [private car](https://vimeo.com/105422200), whether it's Lada, Volga or whatever brand is popular there. Beside the [mom-pop stores](http://www.businessdictionary.com/definition/mom-and-pop-store.html), street vendors, artisans and small family farms all the other businesses must be state owned. No other private property nor [special economic zones](https://en.wikipedia.org/wiki/Special_economic_zones_of_China). All the banks, factories, utilities, department stores, large hotels and so on. Every business that can't be operated by the nuclear family with maybe few other workers at most must be either owned by the state or by cooperatives. The management could be either government appointed like in USSR or decided by the workers like in Yugoslavia, it doesn't make any difference to me as long as its not privately held. The time period is the 70s of the XX century Earth. Is the existence of such country realistic? Are there examples of real-world nations that could be used as a model? \* Please note that the term *socialism* has different meanings in different parts of the world. What is described here is called *socialism* in the USA, but in Europe this would be recognized as *communism*. These terms are, in Europe, not interchangeable at all. (What about other parts of the world?) [Answer] Whenever there's a question about socialism or capitalism on here I always get fed up with the trite and blinkered answers which obsess only on the most painfully obvious facts of the matter - namely the USA and USSR. But the fact is capitalism and socialism are broad philosophies with many different implementations. Socialist economies can be mixed, and many were. Often the question hinges on how you define the "[means of production](https://en.wikipedia.org/wiki/Means_of_production)". Consider the rise of democratic socialism in Britain. When the socialist Labour party won the [1945 general election](https://en.wikipedia.org/wiki/United_Kingdom_general_election,_1945) many industries were nationalised: coal, steel, railways, healthcare, defence, etc. This didn't mean private enterprise was forbidden. Banks were regulated but private, along with many other large and small companies. **The Rise and Fall of British Socialism** While [full employment](https://en.wikipedia.org/wiki/Full_employment) was achieved after the war, attempting to maintain it became crippling. Job-for-life-socialism was assumed best for the individual and economy, but it eventually led to the [Winter of Discontent](https://en.wikipedia.org/wiki/Winter_of_Discontent) in 1978. [Stagflation](https://en.wikipedia.org/wiki/Stagflation) affected many economies in the 70s and was not specific to Britain or socialism; but low growth, high inflation, and union demands created a perfect storm. British socialism was especially vulnerable to stagflation, given that the Labour party was unable to mediate between the national interest, corporate management, and the workers (as the party had always been the party of the unions). [Far-left union agitation](https://en.wikipedia.org/wiki/Militant_(Trotskyist_group)) destroyed the system. Strikes were so frequent and disruptive that electricity was rationed in many places to a [three day week](https://en.wikipedia.org/wiki/Three-Day_Week). Productivity collapsed as there were no regulations on when a union could call a strike, or how many union members needed to agree for one to begin. Many amongst the far left hoped this chaos would lead to an even more socialist government... but all it did was give [Margret Thatcher a mallet](https://en.wikipedia.org/wiki/Thatcherism) with which to smash the socialist system. She won the [1979 general election](https://en.wikipedia.org/wiki/United_Kingdom_general_election,_1979), promising to bring the unions to heel and to end British socialism (spoiler alert: she did). Regardless of how it ended, Britain saw solid economic growth and increasing living standards with a socialist economy from 1945 to 70. The national debt was an eye-watering 240% of GDP after the war, and rationing was [enforced until 1954](https://en.wikipedia.org/wiki/Rationing_in_the_United_Kingdom#Post-Second_World_War)... but by the 70s the national debt had been brought back to manageable levels. The [postwar consensus](https://en.wikipedia.org/wiki/Post-war_consensus) was that whoever got elected; Conservative or Labour, they'd not rock the boat. Indeed, Conservative prime minister Harold MacMillan said in 1957: ["You've never had it so good"](http://news.bbc.co.uk/onthisday/hi/dates/stories/july/20/newsid_3728000/3728225.stm). And he was correct. **A Question of Political and Economic Balance** The main issue is how the state handles technological progress. If government never commits to full employment, and instead seeks technological innovation and promotes jobs when they are necessary, you'd likely see a more stable system over the longer term. A mixed economy is essential too. Let the private sector do its thing, while the public controls the "means of production" and seeks to improve its efficiency. A large part of Germany and Scandinavia's success is owing to their willingness to mediate between national, corporate, and workers' interests. They engage in a collaborative and strategic consensus quite unlike the adversarial and tactical politics found in the UK or USA. Perhaps the biggest problem is the conflict between socialism's raison d'etre of protecting worker's rights, and the cycles of redundancy brought about by rapid technological change. And perhaps the obvious solution is to make a clear distinction between workers and jobs. Government needs to empower workers, and yet not be precious about obsolete jobs. You're basically having to sell to someone that being made redundant is a good thing. It can be, if the opportunities are better on the other side. Socialist economies typically offer free higher education, so it's entirely possible. You need to encourage some sort of idea of cycles of technological rebirth. If you go too soft (letting unions run amok) the system will fail. If you go too hard (nationalising everything and always spending the profit) the system will fail. **What Can Public Ownership Look Like?** Sometimes it isn't necessary to nationalise all industries, simply the largest ones. Ghana is an interesting example which certainly started as a democratic system, but [unfortunately ended rather bleakly](http://www.nytimes.com/1964/05/03/portrait-of-nkrumah-as-dictator.html). Nonetheless their leader, [Kwame Nkrumah](https://en.wikipedia.org/wiki/Kwame_Nkrumah), was a socialist who embarked upon many grand industrial projects to benefit his people, quite reminiscent of the infrastructure projects of the [New Deal](https://en.wikipedia.org/wiki/New_Deal). The Volta river project was to create a hydroelectric dam which would produce the electricity to allow them to smelt and thus export aluminium rather than just the ore. This would also provide the electricity to drive industrialisation and economic growth, leading Ghana to economic independence, which would be the catalyst for a united Africa. Unfortunately they lacked financing, and American backers suggested they would bridge the gap if restrictions were placed on what could be made from the dam's electricity. They were also interested in importing ore to use in the Ghanaian smelt; on face value because Ghanaian ore was not usable, in reality because they feared an integrated project would be nationalised. That was against Nkrumah's plan to seek economic independence through national development. As the project dragged on Nkrumah became increasingly unpopular, and reacted with increasingly paranoid and authoritarian decisions. Just a month after the dam was completed Nkrumah was overthrown by a CIA-led military coup. The Americans got their terms, and Nkrumah's dream of creating an industrial example for a united post-colonial Africa died. There are other examples where public ownership of the means of production (or simply the largest company) has had an overwhelmingly positive influence on society, namely Norway. In 1972 Norway's government created [Statoil](https://en.wikipedia.org/wiki/Statoil), which was and still is a publicly owned energy company. The Norwegians however had a very shrewd vision, and dumped profits from Statoil into a public fund. Importantly only the interest from this would be used to bolster public spending. This was owing to their concern that spending all of the proceeds would imbalance the Norwegian economy to the point it was dependent and uncompetitive. This was a concern not shared by Venezuela's [Hugo Chavez](https://en.wikipedia.org/wiki/Hugo_Ch%C3%A1vez), who spent oil money subsidising the cost of food and fuel. Long term this ended in the [economic and political implosion](https://en.wikipedia.org/wiki/Crisis_in_Bolivarian_Venezuela) of a country with great potential. Comparatively, Norway is now proportionally one of the richest nations on earth, with one of the most educated populations who enjoy a very high standard of living. Consider examples like this to be how the means of production could be administered sensibly, and the relevance of the old question: which is more important, controlling inflation or unemployment? [Answer] Cuba is about the closest you'll get. Cuba's economy was artificially depressed for the last 50 years due to trade embargos. For much of that time though it still had a market in the USSR, its major export (sugar) was relatively valuable, and imported fuel (again from the USSR) was relatively inexpensive. It wasn't until the simultaneous impacts of the demise of the USSR, the bottom dropping out of the sugar market and the price of oil rising hugely that more flexibility was needed. In particular, with the dropping of the embargo, the Cuban government discovered that tourism was once again their major asset, and this could not reasonably be centrally controlled. This flexibility has serious limits though, and prices of many commodities are centrally controlled. Much of Cuba's population still work in public sector jobs too. So whilst it's not centrally-controlled to the extent you ask for (>10 employees), it's still recognisably a centrally-controlled communist country, just with a small amount of wiggle room where previously there was none. The Cuban economy isn't the best in the world, but it isn't in too bad shape compared to a lot of countries with similar size and natural resources. On the plus side, by many measures it has the best healthcare in the world, its school education system is famously good, and homelessness virtually doesn't exist. So whether it "sucks" would very much depend on your viewpoint. If you're Donald Trump, it looks awful because there's nowhere to strip-mine or strip-mall. If you're some homeless guy on the streets of New York, it looks like the next best thing to Paradise. If you're a regular working-class person, it's a mixed bag of no shopping malls and much more limited types of work, but a guarantee that you're always going to have food on the table, you're never going to lose your home, you're never going to have to pay for medical care, and you're never going to have to pay for your kids' education. [Answer] **Not in a long run**. Sooner or later you will run out of other people's money. If you really need it, and you want real socialism, not a mixed system like China, here are a few things that could help you make it more realistic: * Use small country. If they got lucky of having an enlightened government it's easier to run small country then a large one. * Use homogeneous country (race, religion, nationality). Homogeneous population could much easily reach consensus. * Recent switch to socialism, if they accumulated quite a lot of capital stock they could run on it for a while. * Populist elections vs revolutionary war. If the switch to socialism happened in populist elections the capital stock stayed intact compared to revolutionary war. * Tourism income. If the country earns sizable amount of its foreign currency from tourism, they will be interested to keep their cities in good order. At least the ones regularly visited by tourists. * Peaceful & neutral. Stay out of conflicts. Socialist countries have a tendency to under invest in capital stock. **Use small businesses to improve productivity.** *Companies with less than 10 employees could be private* You could run a lot of things with below 10 employees: motels, small hotels, restaurants, bakeries, gas stations, workshops. Heck you could run a hydro power plant with 10 people beside a yearly refurbishment, which could be done by other company. Even investment bank could be run with less then 10 people, just outsource everything (secretaries, cleaning, accounting..) beside your core staff. So if the law doesn't specify revenue or capital beside number of employees you can bend the law very far. Use whatever works for you best. [Answer] The evidence from our own history suggests that countries with strictly state owned businesses are an economic disaster. However, state owned businesses were all the rage for pretty much all of history until 1500. Ancient Egypt concentrated its linen and cloth industries in Pharoah's palace workshops in Memphis. The Roman Emperors owned huge swathes of the state, both farmland and industrial mining, marble-quarrying, and amphorae-making concerns. During the Golden Age of Islam under Caliph Harun al-Rishd, the entirety of Mesopotamia was essentially one big plantation, worked by native serfs and imported slaves. Massive workshops in Basra and Baghdad produced sugar, paper, and other luxury goods. The same could be said with the Gangetic plain during the 17th century under the Moghuls. So the easy solution is to set your story in pre-modern times. Then no one will notice the squalor of your society, since the whole world is poor. [Answer] Yes, you can, but you can't get the answer from us. Generally speaking economists and philosophers have found that socialism is an unstable equilibrium. It is constantly being disrupted by the nature of humans, and energy must be continuously spent maintaining it, or it falls apart. The larger the group, the more rapidly it falls off of this ideal. Accordingly, there is no way we can give you a path for your state. There is no path that can be written down on paper, and handed to you with a note saying "here's how to make socialism work." Your state is going to have to *constantly* observe the disruptions and find the most efficient way to deal with each of them as they come. What we can do, and many of the answers have done, is show you a laundry list of ways that we have observed socialist (and communist) countries falter. You can draw from these as examples of what your society is going to have to to combat. But the actual solutions must be carefully measured against the exact specifics of each occurrence. Underact, and your society falls apart. Overact, and you turn into a totalitarian regime that destroys itself or its economy. Balance is the key, and if there was a way to write down the right way to balance a government, we'd have a lot fewer problems in our world today (I like to think the Founding Fathers of the United States at least got close). [Answer] The basic unit of economic organization is the [Corporation](https://en.wikipedia.org/wiki/Corporation#History). This is a non-person eintity that can own goods, make agreements, and the like. Historically, creating such a corporation required government assent. Smaller organizations, like partnerships, are sort of like them as well. Modern "Western" economies have a mixture of privately owned corporations, publicly owned corporations, state corporations, nations, non-profit corportations (which are not owned) of various kinds, etc. I could interpret your meaning as stating the privately owned and publicly owned corporations don't exist. Examples of such an organizations engaging in commercial purposes is Ikea, most national postal services, central and regional banks. Now, in the past half-century, there was a massive economic war between "Capitalist" and "Communist" states, and the "Capitalist" states won. Nations that did not ally with the "Capitalist" states where economically isolated, invaded, attacked, overthrown and destroyed by the winners of this war. Despite this, some "Socialist" economies have persisted and flourished better than similar nearby "Capitalist" economies. An example is Cuba, which is richer than the nearby island of Haiti and Dominican Republic (both halves!) despite being both invaded and under economic sanctions from the nearby super power economy (USA). Corporations themselves almost universally operate as "Socialist" organizations within themselves -- Command Economies. And there are Corporations whose size exceeds that of many nations. That isn't to say there aren't horrible traps that Socialist centrally planned economies fall into. Corporations avoid them through a number of ways. They aren't the primary power, so their rulers must obey the rules of the state in which they are embedded. This prevents them from going off-the-rails in power-centralization and protection (the dictator trap, where you turn state power into an engine of protecting the current set of rulers). As they are relatively small, they often have competition. Their ability to use their power to crush their competition is limited by the state they are embedded in; which means even strong corporations can eventually be outmaneuvered and fail if they stop generating excess value efficiently. Newly large capitalist corporations almost always have recently successfully generated a whole pile of surplus value in order to grow. Inertia keeps them doing what they have been doing, with minor corrections (their correction process was also possibly successful at smaller scales). Over time they'll drift. If they remain long, they almost always have a natural monopoly they have managed to corner. They now drift, protected against competition to some extent by their monopoly power. Sometimes they drift into being really inefficient; that is when competition can grow and threaten them. Sometimes they drift into being more efficient. Cross-transfer of corporate culture occurs, where what other successful corporations are doing is imported via business school graduates, hiring workers from their businesses, etc. This is another source of culture drift, almost unavoidable if a business wants to grow at a fast pace. And then they die. They are torn apart into their assets, and new Corporations claim their "territory". States could do much the same thing, but traditionaly States "death" involves violent war, revolution, and a lot more destruction than Corporate "death". So one approach would be to invent an authority that prevents overly violent "death" of States, and prevents them from going into the trap of protecting the ruler's interests against the interest of the State or the (entire) People. Another would be to point out that the advantages Corporations have over States is mostly long term. In the short term, it is perfectly plausible for a medium-large "Socialist" state to function. The Soviet Union went from an agricultural economy to one capable of defeating the German Empire and then holding off the most powerful industrialized nation for a half-century in a few decades under a centrally planned economy. Another approach is to solve the problem with information. The theoretical advantage markets have over planning is that markets solve pricing problems better. A genius economist with modern computers *might* be plausibly able to solve the pricing problem without markets. Doing so accidentally would easily be reasonable, and sustaining it for a while as well. The biggest problems against such an experiment in our world is both the extreme risk that it would fail (and cause untold suffering), the violent reaction of the capitalist western economies to such an experiemnt, and the fact that this doesn't prevent the "protect the king" dictatorship trap. [Answer] ## A completely socialist country is possible as long as your neighbors aren't capitalists As kingledion mentioned in his [answer](https://worldbuilding.stackexchange.com/a/64459/10364), before 1500, it was possible to have a completely socialized/nationalized system. Prior to 1500, the marriage of religion, economic power and monopoly on violence hadn't yet broken down. When all countries operate with nationalized industries, they are on equal footing. However, as soon as someone comes up with capitalism, all those nationalized industries and the countries that depend on them will start to lose. Most of what keeps capitalistic systems so functional is the inherent competition in free-markets. Anyone with the capital can start a competitor to a incumbent company and eat their lunch. Clayton Christensen's [Innovators Dilemma](https://en.wikipedia.org/wiki/The_Innovator's_Dilemma) talks about this kind of situation extensively. Any company in a free-market that fails to eliminate waste, cut expenses and increase profits will eventually go out of business. In a socialist country, this kind of competition is either impossed by legislation (which can be cheated by legal manuvering or backroom deals) or not at all. In general, competition in socialized systems is social competition ("who do I know that can get me a sweet deal...") vs free-markets systems ("can I make a product/service that will sell better than the other guy's") Because of the lack of pressure to be efficient, the nationalized industries will tend to become more inefficient over time. Capitalist industries tend to get more efficient over time because of competition. As long as the socialized country doesn't have to compete with anyone else, it should be okay. "An economy that doesn't suck" is inherently comparitive. A nationalized economy that benefits everyone is better than no industry. [Answer] It is worth looking at some examples of countries that attempted at one point or another to introduce some form of market socialism. For instance, in China 50% of GDP is still generated by SOEs, and it is mostly the large companies that are state-owned. You may also want to look at other countries with a large SOE sector, such as Russia, Malaysia, UAE, Saudi Arabia, Indonesia, India or Brazil. Some are relatively successful, many are not and struggle with ineffective management and corruption.The biggest issue is the introduction of effective governance and the creation of incentives that are similar to those faced by privately-owned companies. The most interesting example is Singapore, where, although the economy is mostly composed of small and medium enterprises, pretty much all the large ones are SOEs. Singapore is considered to be a very successful case of how the state can manage SOEs well. Corporations linked to the government account for around 50% of the stock market valuation in Singapore. [Answer] Yes, A Post-Scarcity society can be purely socialist because it no longer needs motivated humans to fill all of the roles in the economy. With AI driven robots handling all of the mining, farming, manufacturing, distribution, and everything else, each human citizen can have a life of leisure with all of the material wealth that they can ever dream of. See [Cory Doctorow's Down and Out in the Magic Kingdom](https://en.wikipedia.org/wiki/Down_and_Out_in_the_Magic_Kingdom) for a good example of what such a society would look like. [Answer] From personal memories, Hungary in the seventies seems to be a good match. The question specifies a particular decade, so the long term sustainability and unchanging political system may not be relevant. Big city: Budapest with two million people, check. Well maintained buildings, er, needs a local party secretary with good taste and then no problem. Certain parts were nice, others not so much. A lot of old residential buildings had WW2 scars even later, but many new (70's era) buildings were erected. No queues for basic food & clothing, in national store chains. Cars were those normal in the Eastern block, but they were all imports so long queues existed. People waited sometimes ten years after submitting the request before they could receive the car, then request the next to have it in another ten years. Small non-family ventures (GMK) appeared in the 80-ies and then the private sector gradually increased as the Soviets looked elsewhere. In the 70-ies this may not be in the picture. Corporation management included a representative of the Party who was influential. The workers not so much. [Answer] Just look at the list of [countries with large ratios of tax revenue to GDP](https://en.wikipedia.org/wiki/List_of_countries_by_tax_revenue_as_percentage_of_GDP) and you find at the top of the list: *Denmark, Belgium, France, Sweden, Cuba, Finnland, Norway* with about 45-50% percent government income (or spending) of total GDP. Depending on your definition of socialism this might not yet fit, but indeed these countries are probably amonst the most social in the world and quite successful economically they are too. Depending on how socialistic you want your country to be, take some traits of these and then mix them together. For example give them: * a strong political, philosophical tradition of egalite (the notion that all men (and women) are equal) like in France * strong unions demanding a share of the profit like in France * a good educational system like in Denmark, Sweden, Cuba, Finnland * lots of natural resources like in Norway * money from supranational organizations to build their headquarters there like in Belgium * a superb and free healthcare system like in Cuba (and Denmark and ...) * peaceful neighbours like in Denmark, Sweden, Norway,... * incredible transparency like the public tax declarations in Sweden * a very rich society where everyone has plenty of everything like in Norway (so nobody is really unsatisfied) So much for real world examples, now for some fictious properties: * draconic laws and efficient persecution could eliminate corruption * effective taxation could eliminate waste (like taxing luxuries very high and useful stuff very low) * just incredible luck with choosing superb (incorruptible) leaders (outstanding personality, clever, charismatic, beloved) - sometimes you are just lucky * some kind of philosophy/religion that gives everyone the idea that the community must work together and everybody has the duty to give * a strong principle of subsidiarity, so people vote regularly on everything they are responsible for (what should be researched next, which motorways should be built, what kind of cars should be produced,...), make the unions and party actually desirable organizations, a place where people find together This all might result in a socialistic country like none we know and it might work or might not work, but given a bit of luck, at least modest economic success should be guaranteeable, you just need the right people for it. [Answer] Yes, but it needs almost perfect resource management or some quasi-free markets. It needs a system that is guarding the administration and itself, by for example having multiple divisions that enforce the policies on every governmental body, including each other. It is hard, and no system has ever succeed. With technology a super intelligent AI that oversees could make it work. [Answer] # No Centrally planned economies have universally been a disaster. They're unable to respond to local requirements and market pressures fast enough to be useful. Nationalising universal infrastructure like water and power and the rail companies, all perfectly reasonable. You could even consider nationalising the automotive industry if you want everyone to drive really boring cars. The worst you'll get out of this is epic inefficiency. However there's really no point nationalising a tea shop or surf school, all of which will come under your current heading. Local business needs to remain locally owned and run, responding to local needs and environment. A government owned tea shop would look the same as every other tea shop in the country and end up with all the wrong stock for local tastes. The state should only get involved a company which is a (near) national monopoly or nationally critical infrastructure. --- As a note relating to ownership and management. Since, as everyone knows, property is theft, "ownership" in a socialist world means "control". [Answer] I think your description leaves a loop hole that not only makes this possible but also transforms your world into a pseudo-capitalistic system. Much like anything running a business is a skill some people are very good, others not so much. In your proposed framework really good business people would build a business to the allowable limit and then stop. Sort of. While they might not own the business they might also run the business of their friend as well as their own. The friend and the good business owner would split profits. The friend would benefit by having money for nothing, and the business owner would be able to grow a second business and quite possibly the first as the two might compliment each other. Then how many associates could the good business owner repeat this process? In effect he would form a conglomerate of small family businesses, and presumably have a large income. [Answer] Make it **small**, **religious**, and **unappealing to foreign aggressors**. Let's work backwards from the problems of real attempts at socialism: 1. Lack of incentives discourages hard work: You mention "upper middle class" so it sounds like you're OK with some financial incentives, but social prestige is just as motivating. Give them a traditional religion (maybe even an interpretation of Christianity) where charity is the strongest ideal, so people aren't angry about others "leeching" of their work. Make the country small enough that people can earn a reputation for helping the country, and the critical inventors and managers can become celebrities. 2. Central planning is hard: Hayek was right, markets rock. But you don't need everything run by a single 5 year plan. Break the economy into manageable chunks (Amazon has 300k employees and is still dynamic), and make the country overall small enough that there are a manageable number of them. Give the people a few different options (like 4 independently managed but government owned fast food chains) and let them allocate resources. 3. Lack of investment in consumer products: Both the Soviet Union and current China are trying to build armies that directly compete with that of the largest economy on Earth. That takes an incredible amount of money and necessitates investment in heavy industry over keeping the people happy. Make them unappealing to foreign aggression by making the world safe (like modern day Europe), or making the country lack in strategic value or be naturally defensible (like Switzerland). 4. Corruption: This is hardly unique to socialism, but destroyed the Venezuelan experiment and is common in centralized economies. But it's mitigated with a religious/social more against opulence and a way to remove those in a position to profit from corruption. Let the monastic priests kick the crooks out. Bonus: Give them a head start. The GDP per capita of the areas that would become the USSR was only 1488 on the eve of the revolution compared to 5301 in the US. Even if they had they'd matched US GDP growth until today, they'd still be 3.5x poorer. If the situation was reversed, the socialist country could grow slower and still be relatively more prosperous. EDIT: Added 4. [Answer] ## It's not impossible But it should be understood that Karl Marx's original vision was not that Communism would be efficient, but that it could be adopted in a post-scarcity economy and it wouldn't matter if it wasn't efficient. The key to getting Communism right is to get the post scarcity economy first, then switch to Communism so everyone has a slice of the pie. Actual Communist countries have made the switch without the post scarcity economy and found that the existing scarcity got worse and there wasn't enough pie to go around. Socialism in general is like this. Morally appealing, but expensive. You take what you can afford. [Answer] What history has taught us is that a system with a wasteful controlling class, a communist party, a dictator, a royal family, will indeed leave the lower classes poor and wanting. Most people forget how wasteful the current capitalist system is and how many people are left poor and wanting. How many homeless people are there in the US? How many people have lost everything when last bubble bursted? A friend of mine told me in the late eighties that a plan economy could not work because the giant matrices you'll have to calculate to set prices and production so that you could reduce waste. It would take so long to calculate what next years production should be, that next year would have gone and many other next years with it before you got the result. That was true then, today you could just fire up an array of a few thousands of high grade graphics cards and be done with it in a few weeks. And to beat the current capitalist system it does not have to be optimal, it only has to be decent. [Answer] Another close-enough example can be Turkey 1923-1946. State ownership of major industries was not as absolute as you require, but it was close. The country was founded on the ashes of the Ottoman empire, severely depleted of capital after 500 years of continuous warfare, often on the losing side. The ethnic minorities that comprised the majority of the upper middle class were either living outside the newly drawn borders, immigrated, "exchanged", or purged. Therefore, the ruling founder of the country, Mustafa Kemal, adopted "statism" and started a 25 year period of the state building and running all kinds of industrial enterprises from sugar factories to foundries to textile mills. Private enterprise was not illegal but very few private citizens had the necessary capital. Feudal "lords" in the countryside continued to own large swathes of land, though; agriculture was not cooperative-ized (These landowners eventually supported a more conservative, capitalist movement from 1946 onwards). This country supported exactly 1 city of 1M+ (Istanbul) where quality of life was very reasonable for the middle class compared to the rest of Europe. Buildings were not only in good state of repair but were admired all over the continent fo their architecture. However, this being 1930s, private automobile ownership would not be at the level you need. Source: My ancestors lived there during the time period described. [Answer] To make this stable in slightly longer term, instead of everyone starving themselves if they don't work, in the laziest way, everyone should have some inherent high income and expense, which cancels out so they have the net income similar to the rest of the world. At first I thought of making a group of scientists to declare independence in Antarctica or even Mars. But that doesn't seem to satisfy your criteria. But some much simpler models might work too, for example some oil field near some extreme environment. The expense could be explained by the extreme environment. But the problem is, if humans didn't have modern technologies when they first arrive there, so they still have chances to form a new country, how did they survive? The income could be from the oil field. But why isn't it owned by the leader of the first group of people discovering it? And many young people may not think an oil field could prove all their value. Why don't they want to leave there? The answers might not be straightforward, but I think they should be all possible. The nearest thing in the modern world might be the space station. It's unlikely anyone will charge the astronauts for their expenses, even if the expenses are not for their main mission. And it is expensive to launch all the resources they require. The only difference beside not being an independent country is that they relies on the earth and cannot generate income themselves. Many companies in capitalist countries could operate in similar ways. It's just a way to isolate them to a specific location and prevent them dealing with anyone else after their jobs. [Answer] The power isn't allowed to be to concentrated and retained indefinitly, otherwise you will end up with defacto oligarchies or dictatorship. Make it a multiparty system (maybe each party representing different interests, like internet interests, scientific interests, technical interests, nature preserving interests, production interests in general, policy interests, system failure-fix interests). The country needs (not only theoretical, but practically) guranteed free speech and free journalism. People need to really have influence and there need to be anti-corruption mechanisms that immediatly imprison/fire anyone not reporting a bribe attempt or taking a bribe. You can use randomly appointed citizens which serve as short term inspectors as control instance here, for the important tasks. The control should be without any holes, so that inbetween inspections no corruption can take place. If you have a high focus on scientific method in the goverment and control mechanisms that prevent capitalistic failures and corruption, and potentially give some incentives for work, like a public reputation system or privilege system that gives you quicker access (other still get access but require longer time) to luxury goods, then I can easily see a non-corrupt goverment of any kind to be more efficent than any other system. Because lets face it UDSSR, failed because of a static high power with non-shifting goverments, which were highly corrupt. This is also todays russian problem were police is still corrupt and power is still static. [Answer] What about Yugoslavia itself? Did you consider it as an example? I think it can be definitely considered a socialist country. In Belgrade has over a million citizens. [Novi Beograd, 1980. Isn't it a beautiful example of communist architecture?](https://www.flickr.com/photos/26983280@N00/16781027944) They had these "famous" Yugo cars and I think buildings were pretty well maintained, at least according to the pictures of the 70s you can find. The overall standard of living surely wasn't as bad as in the USSR since it was an open country, people could easily leave it. In fact many did, there has always been a strong Yugoslavian immigration in Germany and Switzerland. But if things down there were as bad as in the USSR, almost everyone would have left the country (like many people wanted in the GDR, for example). It was also a quite popular holiday destination for western-Europeans. [Here are some pictures of a resort close to Dubrovnik, in the 1980s and what's left of it today](http://www.adriaforum.com/kroatien/threads/zupa-dubrovacka-01-kupari-%E2%80%93-der-verfall-einer-touristischen-hochburg.57108/) [Answer] I suggest to consider Poland. Similarly to Hungary, Poland had such kind of economy as you need. But you should remember, that Poland got big debts and credits at that time. As a consequence, your economy will collapse at the end of 70ths. ]

[Question] [ A human civilization, civilization X, decides that food Y is not fit for consumption. Food Y grows well in its climate, is highly nutritious and tasty, and is not harmful to its inhabitants. Food Y could easily become a staple of civilization X, but its people refuse to consume the food. All taboos against food that I have heard of exist because consuming such food would harm the civilization (ex. taboos against horse meat exist in certain cultures because horses are necessary as beasts of burden there). But would a civilization ever create a taboo against a food that would not harm its infrastructure? How and why would such a taboo develop? Are there any real life examples of such a taboo existing and why were they created? [Answer] There are many examples of this in the real world, including the religious bans on pork and shellfish, the historical avoidance of tomatoes, and counter-examples such as the laborious process to transform poisonous raw cassava into something that's not just edible, but a staple in many parts of the world. In addition, many perfectly palatable foods have a reputation in one culture or another for being only fit for the poor, or even for animals. A classic example is lobster -- sailors' and servants' contracts in the 19th century limited how often they could be given ["trash" lobster](http://www.gma.org/lobsters/allaboutlobsters/lobsterhistory.html) to eat. The Japanese considered [millet and barley](https://www.theguardian.com/lifeandstyle/2015/jun/05/japan-changing-food-tastes-rice-sake) only fit for people who could not afford rice. (And not because of gluten intolerance, [reportedly rare in Japan](https://trulytokyo.com/gluten-free-tokyo/).) But that's not the same as a society not exploiting a food source at all. Some of the reasons for a whole society to develop a complete aversion to a food might be: (And note: I'm not suggesting everything on this list is correct or rational. I'm just citing real-world examples of plausible aversions. You can tell me raw honey is perfectly safe, but that doesn't change the fact that some people believe otherwise. Tomatoes are an important source of Vitamin C, but were not considered safe to eat in many places.) For all foods: * It's culturally associated with Those Other People * It's culturally associated with persecution or harassment * People just don't know how. Half of the Donner Party starved to death near a lake full of fish, not yet frozen over when they arrived. The [Norse in Greenland didn't fish](https://www.newyorker.com/magazine/2005/01/03/the-vanishing-2) (disputed); they spent their energy hunting walrus tusks for trade and raising high-status cattle increasingly ill-suited to the land. [Chris McCandless](https://en.wikipedia.org/wiki/Chris_McCandless) starved in the Alaska wilderness because he ate toxic plants and ignored healthy ones (heavily disputed). It takes a lot of trial and error to learn to find the nutritious tubers. This is unlikely to last for more than a few generations, but that may be enough time for the OP's needs. * It takes a lot of work to prepare; it falls out of favor and then people forget how. (Acorns were a staple everywhere oaks grow, but have been mostly forgotten. [Leach the flour](https://newsmaven.io/indiancountrytoday/archive/the-age-of-acorns-sustaining-life-for-generations-JNmbin_NjkqqQKscc1kmAg) in several rinses of clean water, or age whole nuts buried in healthy soil.) For plant foods: * It's easy to make a mistake and accidentally poison yourself: + it's poisonous if not cooked properly (taro, taro leaves) + it's poisonous if not stored properly (ergot infecting rye) + it's poisonous if unripe (elderberries, tomatoes) + it can leach poison out of other things (acidic tomatoes leaching lead out of pewter plates) + it looks too much like something poisonous (many mushrooms, tomatoes) + it often grows wild in places where it bioaccumulates soil toxins, such as [heavy metals](https://www.sciencedirect.com/science/article/pii/S0160412018327971) (or even from the use of tainted fertilizer, as happens [in Nigeria](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6748284/).) * it looks creepy (think Halloween eyeball candy) * It's noxious when raw (not poisonous or dangerous, just not something you want around, like [durian](https://theculturetrip.com/asia/singapore/articles/8-things-you-need-to-know-about-durian-the-worlds-smelliest-fruit/).) * it's more valuable for something else: + the crop is more valuable, in the long run, as animal fodder or returned to the soil as part of a crop rotation cycle (see below) + the plant is more valuable, in the long run, as food or shelter for beneficial insects or birds For animal foods: * The animal is too valuable for its labor, fiber, milk, or other resources (cows in India) * The animal is a disease carrier (story 1 for the pork taboo) * The animal is ecologically unsustainable (story 2 for the pork taboo) * The animal is closely associated with Those Other People (story 3 for the pork taboo) * The meat spoils quickly and then causes food poisoning (shellfish taboo from the peoples who brought you the pork taboo) * the animal bioaccumulates toxins (story 2 for the shellfish taboo) * the taboo preserves an important food source for an underclass, indirectly benefiting society as a whole (side effect of pork taboo in Egypt.) * the animal is a companion species * Other ethical reasons, such as a boycott of food produced under inhuman circumstances (veal) or harvested from creature considered too intelligent (whales) Note that "in the long run" benefits take several generations to establish and thus probably take many generations to disestablish once the benefit diminishes. (Two villages. Village A eats their cover crop in the winter hungry time. Village B has a taboo because their medicine woman once randomly got food poisoning from eating a bad batch//has extreme ecological wisdom, a few vulnerable people starve but the next year's crop is better; there is more food surplus for the next bad year with a hungry time. Village B flourishes, Village A is slightly less successful. After a few generations surplus population from Village B moves to Village A (war if unfriendly, exogamy if friendly) and bring the taboo with them. Now you have 2 villages with the taboo. Repeat until universal.) A few lists of foods that are poisonous raw, mis-prepared, or when eaten at the wrong time, with examples: * [Foodbeast](https://www.foodbeast.com/news/10-foods-that-can-potentially-kill-you-if-youre-not-careful/) - Honey(disputed), cassava/tapioca, cashews, bullfrogs, etc. * [Cheatsheet](https://www.cheatsheet.com/culture/foods-you-should-never-eat-raw.html/) - Potatoes, castor beans, chaya, etc.(Chaya is a double-dipper - cyanide poisoning raw, violent diarrhea if cooked in aluminum.) * [Vitacost](https://www.vitacost.com/blog/food-nutrition/7-poisonous-foods-if-eating-raw.html) - Several types of beans, elderberries * [Modern Farmer](https://modernfarmer.com/2015/08/secretly-poisonous-plants/) - Asparagus berries * [Farmers Advance](https://www.farmersadvance.com/story/news/2018/08/31/10-vegetables-can-kill-you-if-theyre-not-prepared-properly/1156693002/) - all duplicates Honey is generally safe but there are a few edge cases, such as babies who haven't developed an immune system yet, or bees that have been feeding on the pollen on toxic plants (and thus a subcase of organisms that can bioaccumulate toxins); see [the Cooking stack](https://cooking.stackexchange.com/questions/41814/is-raw-honey-safe-to-consume) for more info. A few examples of cover crops that could provide food at the expense of their primary function: * Brassicas, such as "[Forage radish](https://www.sare.org/Learning-Center/Books/Building-Soils-for-Better-Crops-3rd-Edition/Text-Version/Cover-Crops/Types-of-Cover-Crops) will winterkill and decompose by spring, but it leaves the soil in friable condition and improves rainfall infiltration and storage. It also eases root penetration and development by the following crop." * Cereal grasses (oats, ryegrass, etc.): "Commonly used grass cover crops include the annual cereals (rye, wheat, barley, oats), annual or perennial forage grasses such as ryegrass, [...] A problem common to all the grasses is that if you grow the crop to maturity [...], you reduce the amount of available nitrogen for the next crop. This is because of the high C:N ratio, or low percentage of nitrogen, in grasses near maturity. The problem can be avoided by killing the grass early" (same page as above) * [Fava beans](https://patch.com/california/benicia/a-cover-crop-for-the-edible-garden): "In the spring, when flowers started appearing on the fava beans, I knew it was time to cut it all down as I didn't want any part of the crop going to seed. If it goes to seed, babies from the cover crop will come up during the summer and compete with the [desired crop]" [Answer] # Something else eats the plant, and that thing is revered. For example, suppose the people revered a giant bird because it eats rats and thus keeps away plague. If that bird also devours large quantities of the plant during mating season, the plant might become taboo because it is reserved for the bird. Whatever the reason that the people care about the other creature/species, the food becomes the gift the people provide to that creature/species to keep its favor and to keep it coming near the settlements. [Answer] ## Because it can't be *managed* Out of all the edible plants out there, only some are suitable as large-scale crops. A plant might not be suitable for mass cultivation, or even cultivation at all, not because it's not nutritious and delicious, but because: * it's thorny/brambly and hard, or even impossible, to harvest as a result (raspberries are a niche crop, and rose hips even more so, likely for this reason alone) * it has an unworkably weedy growth habit that causes it to invade neighbors' farm fields (mint, anyone? also, amaranth, dandelions, and quite a few other edible weeds) * it requires soil conditions that are incompatible with other crops (such as highly acidic, alkaline, or saline soils) * its harvest can't be measured reliably for tax purposes (which favors grains and pulses, which are harvested all at once, over roots and tubers, which can be left in the ground to "game" taxes on harvests) * it attracts unwanted guests (such as pests) or serves as a reservoir for diseases (plant pathogens) that attack other crops [Answer] **They mistake it for some other food or something** > > "A human civilization, civilization X, decides that food Y is not fit for consumption" > > > Long ago when these groups of people came to settle the land they saw a fruit or whatever. This fruit looks very similar to the fruit of their old homeland that is poisonous. They decide not to eat it. As time goes on people forget the actual reason for not eating this fruit, the fruit become a bad omen . Even more time goes on the local religion thinks the fruit is the sign of the devil or some evil entity. The civilization decides that the fruit itself is evil. [Answer] As an example from real life you can look at the Jewish taboo against eating pork. Part of the reason we historically don't eat pork is because pork blood has been used to desecrate the temple (we didn't eat pork before that, but this solidified the animal as absolutely taboo). You could use something similar, have something traumatic happen to your civ that cemented the plant as taboo. An alternative solution can be taken from what happened when potatoes were first introduced in Europe, unfortunately I can't find the article but I recall reading that one nobleman was accidentally poisoned when his cooks, who never saw potatoes before, cooked the ***leaves***(quite poisonous) instead of the spud itself. You could use a similar explanation, the first few people to try eating the plant prepared it wrong or ate the wrong part of it and died and so the plant has been deemed inedible [Answer] # The fruit is healthy, but it attracts something that isn't It could be insects. Disease carrying flies or poisonous bees could be heavily attracted to the fruit. The bees pollinate it, the flies eat it. And when people try to grow and harvest it, the bugs result in deaths. It could be large predators. Wolves in the area have learned that the smell of the fruit tends to indicate the presence of excellent prey, to the point being drawn to the scent is almost genetic. Cultivating the fruit is like inviting wolves, or whatever dangerous predator is appropriate, to seek out your settlement. The opposite side of the coin is that the fruit might have evolved so its smell attracts the predators, since they prevent herbivores from overeating and destroying the plants. It could be humans, or other sapients. Even if your locals don't have any reason to revere or avoid the fruit, others might. Another tribe might consider it sacred and attack you. Maybe another group has a slight mutation that makes the fruit poisonous to them. So when your people try to grow it, they think you are cursed, or just trying to kill them and attack. This works especially well if you have other non-Human sapients in your world; i.e. humans can handle chocolate, but to kobolds it is poisonous like it is to dogs. [Answer] Perhaps a major figure of an enemy, opposing, or radical ideology used the food in question as a symbol of their beliefs and actions! Similarly to how Hitler used the swastika or christians used the cross! (that's a pair I never thought I'd put together) Or perhaps the opposite! Perhaps this civilization was the result of a revolution against a group that heavily utilized the food product, leading it to become a symbol of their tyranny. Like the 'prim and proper' clothing of the French monarchs. [Answer] Maybe some parts of the plant from which the food originates are actually poisonous. If I'm not mistaken this was the case with tomatoes in Europe long ago; the stems and leaves of the tomato plant are poisonous, and so people avoided eating the non-poisonous fruits until, presumably, some brave (or suicidal) soul tried them anyways. Additionally, it could be that the plant has defense mechanisms other than poison that make people not want to even touch it, let alone eat it. For example, maybe the leaves cause you to break out in hives when you touch them, or maybe they contain a horribly noxious substance that adheres to everything like tree sap. In that case people might avoid growing or cultivating the plant despite it having tastiness and nutritional value. [Answer] It has an unfortunate appearance, which results in it being associated with *other* taboos. For example, if your people have a taboo against eating the Sacred Cows, then this particular fruit looks like a cow's head. If your people have a nudity taboo, it resembles body parts that are traditionally covered up (and, in *most* of those cases, even more so if it contains or exudes a milky white liquid) Some of these taboos might make the food completely forbidden (consider the violence in parts of India against people merely *accused* of eating beef). Others might just relegate it to shunned subsets/castes of society ("only scarlet women eat the 'male fruit'") [Answer] There are two mayor causes this taboo could have been originated from. 1. While not harmful, the food does something with your body with a negative connotation. 2. The Food is in direct or indirect connection to a source of harm To the first point you said this: > > A human civilization, civilization X, decides that food Y is not fit > for consumption. Food Y is plant-based, grows well in its climate, is > highly nutritious and tasty, and is not harmful to its inhabitants. > > > While not harmful to the population, it could cause some changes, that are unwelcome. For example the food could have a similar effect as asparagus or garlic, making it unfit in society to eat the food. Of course this effect would need to be way stronger than that of my two examples provide, but it could be possible. Depending on the setting, in a more fantasy style it could change the eye color of a person to a devilish red. While harmless, the inquisition would certainly prevent people of eating it in fear of hellish infestation. The second is a more indirect cause. While the food is perfectly tasty and healthy, this would also mean it would be that for other animals aswell. The food could be the main food source for species of rodents or bugs, maybe even using the food as a breeding ground (like apples for worms). While farming and trading the food, the pests travel with it. Imagine the first delivery of those foods and a wave of rodents enter the city with it. Or poisonous bugs and spiders attacking their 'living room'. While in modern society, this would be treated with delicate methods, back in the days, this could cause superstitious farmers and villagers to never touch them again. On a related note, this is why eating bugs is considered disgusting in the western world, as they crawl through dirt and wastes in the wild, transmiting diseases. In truth, the bugs for eating are raised pretty sterile and certainly without dirt and waste. [Answer] A couple more ideas! 1. The food is a main export of a nation or company and there is heavy disinformation against it, or many patents / gmos invoked with it and some economy is heavily dependent on it (like soy), leading to economic war and association of the food with that enemy nation or culture. 2. The plant that is nutritious can also be used to make drugs (hemp) [Answer] (Combine the excellent answers about taboos with -) The food's **byproducts (oil, fibres, etc) are required by critical industries.** If your corn's: * oil generates 90% of your **electricity** * fibers are used to make 84% of your **clothes** * RNA is used to **cure** the flue, measles and cancer, * roots can turn lead into gold then you can easily give it a "holy" status and frown upon eating it. [Answer] Hi welcome on Stack Exchange. I have a suggestion for what you are searching for: Adam's infamous "apple." Imagine that in your civilization, priests are quite important and are able to impose taboos in the culture of the civilization. Then, imagine that the myth of the foundation of humanity in your civilisation is the Adam & Eve narrative, with the "apple" replaced by food Y. Then why should your people eat something that is the symbol of a bad thing, a.k.a. how the humanity had been sentenced by its God(s)? [Answer] The ruler needs to control his people. To control his people, the ruler must control the food supply. The Umatupu plant, being highly nutritious and growing well, severely impacts the ruler's ability to control the food supply. Lucky for him, the clergy have deemed the Umatupu plant as taboo because it is the mysterious plant mentioned in section four of the Holy Book. The clergy finds favour with this ruler. [Answer] **Because Capitalism** Water is plentiful. It falls from the sky, is piped into most homes at a rate that is nearly free for drinkable quantities, and is quite safe to drink in most developed areas. Yet there are many people who won't touch tap water unless you pour it in a plastic bottle with a brand on it and sell it to them for a few bucks. \*see Idiocracy: "Water? You mean like in the toilet?" "Brawndo's got what plants crave. It's got electrolytes" [Answer] One reason could be because it resembles other things that are dangerous to us. Tarantulas are mostly pretty harmless but we don't eat them possibly because they resemble other highly venomous species like the brown recluse. Eight legs, lots of eyes, etc. Kind of related to what causes batesian mimicry. Milk snakes (non venomous) evolved to look a lot like coral snakes (highly venomous) so they are less likely to get eaten because predators that like eating brightly colored snakes tend to die a percentage of the time. [Answer] The other answers give many real world examples. The reason why your people don't eat the fruit is: > > "Because it's always been done that way." > > > There are many real world examples of this too. [Answer] Not exactly the same, but ancient Hawaiians had taboos (Kapu is actually where the word taboo comes from!) revolving around certain foods. Women were not allowed to eat pork, bananas and coconut as they related to parts of the body of the gods, nor were they allowed to eat with men. These beliefs fell (violently) out of favor after King Kamehameha II shared a meal with his mother and others and not being struck dead. If this civilization has a deeply rooted religious or otherwise superstitious belief in the origin, or some other meaning behind the food, then perhaps they would not eat it due to continuing societal peer pressure. [Answer] Because it causes unpreventable, massive wind. You know the saying about "Wouldn't touch it with a barge pole"? If you eat it, no one will be willing to touch *you* with a barge pole. Because of the smell. [Answer] **It Looks a Little Like a Baby** If the seed pods looked a little bit like little babies, then it could be very understandable that there would be a taboo against eating it. In fact, natural selection could well produce something like that if the seed pods that looked the most like babies was left alone. There's a Japanese crab that has the face much like a Samurai that may have evolved in this manner. <https://en.wikipedia.org/wiki/Heikegani> [Answer] Eating the food makes you more healthy, but there are mighty people living from selling expensive medicine who can't let people cure themselves so easily. *Disclaimer: No identification with actual persons (living or deceased), places, buildings, and products is intended or should be inferred.* [Answer] * **Because it also gets you high.** While not physically harmful or addictive in itself, the food is shown to produce artificially elevated mood, lowered inhibitions, decreased fine and gross motor control, and mild hallucinations. These mind-altering effects have been responsible for notable injuries or deaths of those who eat the food or those around people who do, and as a result the culture has criminalized the consumption of this foodstuff. Marijuana is nominally illegal in the United States and many other countries for this reason, even though most consumption of it is less physically damaging to the body than alcohol, and the seeds have been found in USDA studies to be a better source of protein than soybeans. * **Because the plant or animal involved has religious significance.** It signifies some blessing of the land and people by a deity of the dominant religion of the civilization, and it is considered a terrible sacrilege to defile the plant by harvesting it, or the animal by killing it for meat. Alternately, the animal or plant is considered "unclean", and again it is sacreligious to eat one. Cattle in Hindi cultures is the foremost example of the first option, while pork in Jewish and Muslim cultures is an example of the second option. + You can combine this with the first option, to make a plant or animal sacred and its consumption reserved for religious observance, due specifically to the physical effects produced by consuming it. Marijuana is consumed religiously in Hindi cultures, and highly illegal outside this use. Alcohol may be given to minors in the US only in accordance with religious observances, such as Communion/Passover wine (in modern usage it has little intoxicating effect). Juvenile buttons of the peyote cactus are used religiously and medicinally by pre-Columbian civilizations in the present-day American Southwest and Northern Mexico. * **Because it is easily confused with a related species that is highly toxic.** Consider a close cousin of a tomato-like fruit, the plant and fruit both all but indistinguishable to the casual observer when the fruit is ripe (you may be able to tell the difference by inspecting immature fruit). One variety is harmless, nutritious and delicious, while the other is nicknamed "last pucker", for an extremely sour, bitter taste, that tells the unlucky eater they are already dead. Even spitting the bitten part out and washing out the mouth isn't enough; the toxin is readily absorbed through the skin of the tongue, and even small doses are a fast-acting nerve block that targets autonomic nerves of the cardiopulmonary system and brain stem. The toxin is harmless to birds (the target species for seed dispersion), but deadly to mammals. As such, the civilization eschews both species as possible direct food sources (though the toxin makes an *extremely* effective weapon), as the risk is just too great given plentiful sources of other, much safer foods. Real-world examples, most not quite so drastically toxic or so indistinguishable from a safe species, include many mushrooms, certain berries, and a few poisonous animals including fish like the fugu puffer fish, and amphibians like the cane toad and the poison dart frog. [Answer] The food is widely known as feed for farm animals. So eating it would be equivalent to someone today who eats cat food. A culturally influential region might have seen very high demand for meat for a long time. It was more profitable to feed the food to a pig and sell the pork than to sell the food directly. Because of this people saw it on sale less and less until it was only known as animal feed. Desperately poor people would still resort to eating or stealing it, so it becomes associated with crime, poor morality etc. and then Kings and religious leaders condemn and suppress it. [Answer] They see it as a manifestation of their deity, and eating it would be considered sacrilege. [Answer] * Slavery is a widespread practice. The slaves are kept servile by use of a mind-numbing drug. This plant counteracts the effects of the drug, thus threatening the social order. * Overpopulation threatens the world. To survive in the absense of this plant requires a large, expensive basket of foods, some of which must be imported from distant lands, and that only the elite can afford. Again, cultivating this plant threatens the social order. [Answer] I came up with two ideas that would not need too much suspension of disbelief from a casual reader. # 1.) The fruit is worshiped religiously Saint X of place Y was once starving, when he discovered "the fruit". He ate the fruit, and he was saved. But we are not Saint X of place Y, and we are not worthy of eating "the fruit". Only the saints may, and you and I are no saint. # 2.) The fruit makes you feel good Long, long ago, in the old kingdom, people ate "the fruit" regularly. It gave them a feeling of comfort and warmth, any they loved it. "The fruit" was added to every dish, and juice from "the fruit" was bottled up and sold. As time went on, the lives of people began to revolve solely around "the fruit", until they ceased all productive work and only ate "the fruit". The society collapsed inadvertently. Those who had access to "the fruit" tried to take control over the masses, and the masses revolted. It was bloody, and only few survived. Those who did made a pact never to eat "the fruit" again, and the civilization that followed would heed their warning never to eat "the fruit". [Answer] The plant releases a toxin that pollutes the soil, and nothing can grow there for 10 years(or etc) The plant absorbs all the nutrients from the soil, and nothing can grow there. Requires too much water, or etc. It has too many nutrients say 40mg of iron, but an adult can only safely handle 45mg/day. Now having 1 serving limits how much other food you can have. Maybe it has 70mg, now you have a real problem. Combine last one with serving size, maybe you can only have 1 oz a day, and it fills ALL your daily requirements. However, the serving size is 1oz so you still feel hungry, but if you eat 1 more thing you overdose on something. Want a piece of cake,candy, pizza, or etc, nope if you do its off to the hospital. [Answer] **Because the government or megacorp bans it as a way to increase taxes/profits** and the patriotic masses follow along and teach their children that it's inedible / wrong to eat. In most countries it's illegal to plant apple trees in public spaces that would feed the public & provide free food for the homeless etc. Maybe the example food is easily plantable, would spread rapidly, and would provide free food for everyone on the planet, so would pose a threat to the people in control of the planet. ]

[Question] [ Without going into unnecessary detail, one of the races of my world believe that the land itself is a dead god, and that by resurrecting it, it will ascend to the cosmos and carry the faithful upon its back. The form they choose to represent this great god is born out of their own image, and represented by a great winged dragon. So this eschatological event is of course purely religious fiction, but let's say it isn't. Let's say that this would absolutely happen, and that a massive, continent-sized dragon (let's say for now the size of Asia) that could propel itself through flight wasn't out of the question. So it would be as if all of Asia was suddenly ripped up from the Earth and flung into space. What would be the environmental effects of such a creature's flight? [Answer] A dragon with a full wingspan of 20000 km (folded to fit into a 10000 km resting area) and surface area of 44 million sqkm will have a terrible impact on the environment. **Phase I** In the first days of her awakening, as she shifts, freeing herself from the encumbrance of all the cities and forests and so forth that are littering her back, widespread but relatively shallow quakes will be felt all around the perimeter. It will be quite a ride for those residing on her back! Cities will be thrown down, forests toppled, hills broken and everything will begin a terrific slide towards the edges of the Beast. Initially, small tsunamis will race across the Indian, Pacific and Arctic Oceans and the Black and Red Seas as well, as the earth of India, Arabia, northern Siberia and Eastern Asia begins to slough off. With a coastline of 63000 km, she might slough off a 1 km wide by say 100m deep ring of rubbish. This will dump 6300 cukm of rock, earth and debris into the coastal waters. I don't know the equations to model a tsunami of this size, but can imagine that most coastal areas will be considerably dampened! **Phase II** These next weeks to months will be very exciting for everyone on the planet. As the dragon lifts herself up, the mountains and earth upon her back and wings will begin a catastrophic and precipitous slide down her flanks and the dorsal surfaces of her wings. Since she's been sleeping for, like, forever, she's got quite a bit of accretion on her back. This larger slide will be composed of about 2,199,517,610 cukm of rubble --- mountain chains, accreted bedrock, soil, destroyed infrastructure and natural debris. Perhaps a quarter or third of this volume will in fact make it to her periphery in time to rain down upon the churning ocean waters below. At this point in time, she's lifting up the edges of her wings and beginning to raise her own voluminous body. Ocean water will begin to rush into the verges, creating a muddy slurry all around her perimeter. As she stands, her hundred km thick body will begin to rise up, lifting and rippling the underlying 50km of continental plate beneath her, much like the way, when you get out of bed in the morning, the sheets become crumpled and rippled. Contrary forces --- the release of pressure upon the mantle will cause the crust to uplift; the increased pressure of the remaining weight of the upper 50 km of the accretion plate, plus her own weight, will press down through her legs, depressing the continental plate and the underlying mantle, thinning it and perhaps causing widespread localised vulcanism running from (what were) central India and central Siberia. Massive outgassing will blow hot volcanic plumes in all directions; inflowing oceanic water will spill down over a 100km high precipice forming a vast waterfall that will empty the ocean into a 6,600,000,000 cukm chasm. All the oceans waters only amount to about 1,400,000,000 cukm of water. This new Eosphoratic Ocean will be a deep, steamy, stormy and utterly unaccessible seafood gumbo to everyone with the possible exception of any vessels that survive, Land of the Lost style, the drop over the precipice. Elsewhere it's been said that the noise of the Gibraltar Cataract would have deafened local wildlife. This waterfall will certainly deafen anyone close by! **Phase III** Having stablised her stance on the shifting surface of the underlying continental plate, the areas surrounding what was Asia will suffer massive earth quakes, as her movements cause the plate to depress and rise. Broad chasms will evolve at the plate boundaries, allowing for magma to rise; and as plates catastrophically collide, vast earthquake swarms will overwhelm even the most distant lands. The heat generated from these motions may raise the overall temperature by many degrees, a process called Dragon-Made Global Warming. During this phase, the remaining unstable crust materials on her back will continue to slide off. Much, of course, will land relatively harmlessly in the mud surrounding the Eosphoratic Ocean, but quite a bit will rain down into the Ocean itself. As mountains with weights of up to 161,932,476,090,000 kg rain down into the water from a height of about 250 km, great fountains of water and rock will be cast up into the atmosphere. Other geological features will be cast high into the atmosphere, even into space, as she shakes out her wings and seeks to rid her body of all irritants. These low velocity meteors, hundreds of which will be mountain sized or larger, and many millions of which will be smaller, will eventually be stopped by Earth's gravity and return to the surface causing widespread chaos as the meteor shower ensues. **Phase IV** If anyone is left on the surface of the planet, after all the teratsunamis, petaquakes and Global Warming, two catastrophes will ensue. The first is the gradual collapse of the Eosphoratic Precipice itself. All the weight of the damaged and unstable continental crust surrounding the Ocean will cause a massive weakening. Gravity will begin the process of destroying the newly formed Ocean by causing the 200 km high walls of the chasm to collapse inward. But that's not even the worst of it! The second and final catastrophe to befall Earth's climate will be the flight of the Dragon. Every dragon wants to fly. Tis instinct. If you've ever been privileged to watch a dragon take off, as I have, or at least have watched a bird take off, say from a branch, you know there are two components to achieving flight: one is the wing lift & body crouch; two is the leap with the legs and downthrust with the wings. Our dragon will now crouch down, settling like a great duck in the boiling waters of the Eosphoratic Ocean, tensing her body to prepare for her leap. Furthermore, she will rapidly raise her nearly 44 million sqkm wingspread well above the height of the atmosphere. It's only about 500 km thick --- each of her wings is about 10000 km long, a 20000 km wingspread all unfurled! She's a big girl. Raising those wings will create a vacuum generating updraft over the Ocean, causing hurricane force winds to blow towards her. This will cause destruction of any remaining structures through hypercane force derechos ripping across the surface of the planet at all levels of the atmosphere. The result will be a massive accumulation of air and water vapour over the Ocean and a severe partial vacuum area over the antipodes. The storms surrounding her body will be amazing! And then - - - she flies! Her powerful legs will spring into action. Causing her 16 146 000 000 000 kg weight to gracefully leap into the air, she'll punch the full strength of her legs down onto the already stressed, cracked, and heaving continental plate. The exertion will be too much for the solid crust to handle. Her 10000 km long body will simply press the crust down into the mantle below. The mantle is only about 2700 km deep, and she's gonna be using all that in order to take off. She's going to cause localised solidification of the mantle as incredible pressures compress crust into all layers of mantle. Her toes may even touch the outer core! At the same time, she'll bring her wings down. Anyone left alive on the planet will be able to see as the outer edges enter the atmosphere and light up infrared as the friction interactions with all that piled up air cause her wings to heat up. Her rapidly descending wings will now cause all the pent up air to be explosively expelled from around her body. If Smaug's wings were a hurricane, this girl's wings simply blow much of the remaining atmosphere out into space. The relatively gentle hypercane force winds that were generated by their lift will now be increased by orders of magnitude as she forces them downward. As her body leaps up, up and away from the ravaged Earth, first, as her forelimbs rise up from the surface, the northern half the Asiatic plate will crack due to the release of massive pressure and undulating mantle waves will, due to dvorakian forces, cause the fractured portions to roll and tilt precariously even as her full weight further depresses the southern half. The release of pressure in the north will cause the viscoelastic mantle to liquefy into gargantuan gouts of molten magma while the remaining portion of solid plate screams and groans as its relative cool is pressed deep into the liquid core. And then, her hind limbs too shall rise up from the surface: the northern half of the Asiatic plate will collapse back down onto the raging mantle and the sudden release of pressure on the core and deep mantle will cause a fountain of molten material to spew from the very centre of the planet! She will be lifted up and as she rockets peacefully into space and on to her journey, she'll leave the Greatest Show On Earth's last act and curtain call for the few survivors. **Phase V** The sudden departure of an Asia sized ettadragon will instantly remove all remaining pressure on the mantle and underlying core beneath where she was. The Eosphoratic Ocean, now long vapourised and blown away by her thunderous wingstroke won't even help hold down the final cataclysm. Now, the remainder of the planet will suffer gravitational shocks as it struggles to attain homeastasis: the planet was round(ish) and now it's not, but it wants to be again. Resulting shockwaves will pulverise and melt the crust. Whatever water remains will boil. Air will sear. The exposed core and mantle will create a wonderful geyser of gaseous iron and molten rock which will shoot up into space. The shocks and violence of this partial core ejection will cause the remaining mantle and crust to collapse. Quite apart from the remaining mountainous meteors that are still raining down on the ravaged surface, the liquefying core and mantle matter will now begin to rain back down. Most of the surface by this time will already be molten. And what isn't will be very hot, shaken, cracked, splintered and smithereened. Atmospheric temperature might be as high as 200 degrees centigrade and winds will still be raging. **Summation** There won't be an environment left to have an impact on. [Answer] Everyone on the Earth dies and the planet becomes a steaming molten mess circling the Sun. Eventually everything will calm down and life will restart. But why? Fill a bucket with water. Now remove 1 cup of water. The removal of the water causes a wave across the surface of the cup while the water redistributes to fill in the hole. The same basic thing happens if you remove an entire continent. The surface of the planet shifts to fill in the hole and become a sphere again. Very little will survive this. Maybe some sea life survives, maybe some birds are lucky enough. Finally, the axis of the planet will change, drastically changing the seasons. The planets orbit will change slightly because some of the Earth's speed was stolen by the flying away land mass. [Answer] If your dragon is just a very, very large creature then - as ably described by elemtilas - total destruction of the Earth's environment ensues. But this is religion describing a god-like entity, and you didn't slap a [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") tag on this, so perhaps there is some wiggle room. Of course there's no continent-sized physical entity slumbering away with insects drilling into its bones for the mineral content. That would be silly. What we have here is a *spiritual* force that encompasses the whole continent and will manifest itself as a huge *spritual* dragon that will sweep up the faithful and carry them to their reward. As the god rises through the stone and dirt, gathering the spirits of the faithful, they will transcend to become pure spirit themselves. They will spend eternity travelling with their god, who will show them all the secrets of the cosmos. Or from a slightly more rational perspective the entity will wake up, gather some energy supplies for the trip from the life forces around it, then take off to the next available world with complex life energy. Not so much rewarding the faithful as taking them along as snacks. Oops. (If you've ever seen *Final Fantasy: The Spirits Within* you'll have some nifty visuals to relate this to.) In the first story only the faithful are taken. The 'Left Behind' series, as badly written as it may be, has all sorts of ideas about what happens with a significant portion of the population simply disappear. The second option is much more exciting because the creature wouldn't just rip the life out of the faithful, it would harvest all of the life it could. Assuming it can't live off the life force of algae, fungi and other simple forms, perhaps it only kills advanced animal life. And just the life energy, so there's a vast area covered with rotting corpses. Simple insects would become the dominant life form after a few years, to the point where they would spread to dominate the other areas of the planet. Of course if it harvests the life from all plants too then I imagine that the only thing that would survive would be fungi and protozoa, with a vast supply of nutrients and nothing to hold them back. Fungal wasteland inside of a year, followed by massive competition for the remaining resources, then complete collapse. Let's hope they were right about it only taking the faithful along. Still a bunch of rotting corpses to deal with, which could be an issue if the religion was followed by the vast majority of people. [Answer] Seriously? Assuming the dragon's belly is more or less spherical, and 5,000 km thick, it should weight about 1020 tons, give or take one order of magnitude, depending on the actual density of a dragon. That's around 1023 kilograms, or ten thousand times the estimated mass of the atmosphere. So, uh, let's hope that dragon *doesn't try to fly*. You wouldn't like it, not just because Earth would likely be pushed away, but air might get... a tidbit *thin* when given such a massive thrust. Does a dragon have a heart? I'm guessing yes. Does it beat? Let's hope not, everyone will be deaf (or dead). Oh heck. let's hope it can stand up and unfold its wings without... uh, moving. Does the dragon breathe? Let's hope not. Let's also hope no gaseous components of sorts come out of its other end. Let's not think about the fact that dragons tend to have fiery hot breath. Does it drool? Hopefully not. How much heat does a dragon generate just to live? Well, we don't know. But an average human with 75kg has an output of about 100W. So let's say... roughly 1W per kilogram body weight (actually... more, but let's generously round down). Holy shit, I don't want to be near a creature that outputs 1023W. Climate change is a hoax, you know. It's all dragons. Now let's hope that beast doesn't need to eat... [Answer] In addition to what @TrevorD pointed out there would also be an unprecedented volcano-esque blast as the weight of the continent came off the underlying rocks. The gases dissolved into the mantle under the continent would be liberated. Think of what happens to a shaken bottle of carbonated beverage that's opened suddenly, now imagine that the bottle lid is Asia and the foam pouring out is made of rock and explodes into volcanic ash as soon as it leaves the ground. [Answer] The mythic story says "the land itself", if this can be interpreted as the entire planet you have the classic "World Echinus" theory as put forth in Sir Arthur Conan Doyle's Prof. Challenger story, "[The Day the Earth Screamed](https://en.wikisource.org/wiki/When_the_World_Screamed)". The theory surmises that the entire world is a living creature with the surface crust of the Earth being like the "test" or shell of an echinoderm or sea urchin. In this model the god is already carrying the faithful. They just may not appreciate their god's true intent. (misinterpreted [hermeneutics](https://en.wikipedia.org/wiki/Hermeneutics)) I feel this premise is more believable than a dragon-like creature the size of a continent who will one day separate from the planet, not only destroying the planet it leaves behind, but also killing any creatures residing on its back, when it flies off into space. [Answer] Frame challenge: the dragon that was "as big as the world" is actually much smaller than we now understand the world to be. Ten billion people could sit comfortably in an area 100 KM square. If the dragon turned out to be real, the environmental consequences would be far less than if it were actually the size of a continent. [Answer] The Earth's crust is super thin. Environmentally, it would mean ripping a continent out if the ground and deforming the whole surface. If the dragon is meant to have depth where it would leave the a massive cavern, and by massive I mean taking a bite out of a cookie, not licking an ice cream cone, then the the Earth would first have it's molten center rebalance around the center of mass, the crust of the rest of the Earth collapse around it having magma seap through and cover everything. Then it would cool again after a long time. There just wouldn't be environment left. [Answer] A number of answers and comments have suggested that this would affect the axial tilt or orbit of Earth, so let's first work out the likely mass of the dragon to see how plausible those scenarios are. The land area of Asia is $44.58 \cdot 10^{12} m^2$. [(1)](https://en.wikipedia.org/wiki/Asia) The continental crust is $30-50 km$ thick.[(2)](https://en.wikipedia.org/wiki/Crust_(geology)) Density of the crust ranges from $2.2$ to $2.9\;g/cm^3$.[(3)](http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/earthstruct.html) This suggests that Asia has a mass of about $2.94 \cdot 10^{21} kg$ to $6.46 \cdot 10^{21} kg$, which is between 1/1000 and 1/2000 of Earth's total mass. We'll take the larger number as a worst case scenario (although in practice, dragons are probably *less* dense than rock). Now let's have the dragon fly up to the edge of the atmosphere, 100 km up [(4)](https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line). The total mass of the Earth-Dragon system is, of course, unchanged, so we just need to see how much the center of mass moves. Taking the old center of mass as our zero point, the dragon is a point mass of $M\_{earth}/1000$ at 100 km + the earth's radius, or 6,456 km. The earth is a point mass of $999 \cdot M\_{earth}/1000$ at -25km, since the Asia-shaped part we removed was all on one side. Which gives us a center of mass 18.5 km away from where it used to be. The orbit won't care; even if the dragon flies away entirely, the orbital radius will change by less than 1 in 30 million; we can just add another leap day once every billion years or so and everything works out. The center of mass of the remaining Earth has only moved by $0.1\%$, but it's no longer on the axis of rotation, so there will be a small but measurable change in axial tilt. Of course, when dealing with this much mass, small-but-measurable probably still means enough torque to cause the worst earthquakes in human history, but I'm afraid we've reached the limit of what I can calculate exactly. The more immediate problem is that if the crust flies away, we now have an area of exposed mantle the size of Asia. The closest event in history to that would be the eruption that formed the [Siberian Traps](https://en.wikipedia.org/wiki/Siberian_Traps). Those are 7 times smaller than the exposed area (and the actual area that erupted would be smaller still), and that event is one of the more likely causes of the [Permian-Triassic mass extinction](https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event), which wiped out 95% of all life, but arguably cleared the way for the rise of the dinosaurs. It's somewhat appropriate that this time, it's the rise of a giant reptile that leads to the extinction event, instead of the other way around. --- ]

[Question] [ I am creating a race (either near-alien or a human sub-species) in a science fiction setting that have an unfortunate "tell." While they can stay silent in non-social (stealth-requiring) situations, they are unable to stop themselves in social situations from constantly saying exactly what they are thinking. They will even do this when they are alone with themselves and don't think they are in danger or anyone else is around. If using sign language, they mutter with their fingers. This makes it difficult but not impossible to lie or even avoid telegraphing intentions. It's even difficult for captured individuals to keep secrets from interrogators. They aren't as a rule nice, and aren't making much effort to get along with others. This is NOT created to be a weakness, but somehow is either an advantage or side-effect of their genetic engineering. The engineers were not concerned about their creations rebelling, but were actively creating the race as their replacements. **What is the justification for my muttering super-soldiers?** Best answers will explain how this behavior is actually an advantage. [Answer] **A neurological change to inhibitory networks** The human nervous system has inhibitory networks to suppress actions. Think of the times you *almost* want to do something, but then decide against it. That's your nervous system's inhibition at work. But for super soldiers, you may not want so much inhibition. You may want rapid reaction, bursts of physical movement without so much thought. A secondary effect could be that they just can't pause to think before talking. [Answer] > > The engineers were not concerned about their creations rebelling > > > Hmm > > ... engineers ... their creations ... > > > These soldiers are clearly machines, even if not electronic in anyway. Let's say biological machines. As a software developer, I make the software I write constantly output its most important processing attempts and results into log files and tracers so that if something goes wrong, I can see what happened more quickly. Your soldiers' muttering is kinda like that... if a soldier develops paranoia, schizophrenia or PTSD, you don't have to wait until they do something uber crazy or go to the doctor. You catch it in the act simply by listening to them and then you can do something before you have a huge problem. Or, if the damage is already done, at least they will quickly and easily tell you why, so that you can do damage control and lessons learned. [Answer] **It's to support their logging mechanism.** Super-soldiers have a dangerous job and often get killed while doing it, at which point any valuable information they were carrying at the time of their death is likely lost. To combat this, each super-soldier is fitted with a "black box" that records their location, vital signs, etc, and can often be recovered and decrypted later to find out exactly what happened to them and why. However, the box doesn't have telepathic capability, so in order to keep a record of what they were thinking, the soldiers are trained to sub-vocalize so that their black box can keep a record of their thoughts and intentions for posterity. [Answer] I have a quite alternative suggestion. **It's not them, it's you.** Basically, everyone hearing them is a (passive) telepath. There might be some etiquette on shielding one's thoughts in their community, but the invasion soldiers are obviously not aware of it. It might also help being super soldiers (basically, they also hear each other), as they can coordinate with each other much better. [Answer] # PTSD the genetic modifications are making childhood and youth *extremely stressful* - even when compared to regular growing up - in a way that is hard to detect: * since for the modified soldiers this is normal, *they* don't know anything is wrong * since the modifications are quite radical in *many* ways, there are no baseline readings for a mentally "healthy" super soldier. so now it's an open question in your world whether your new, modified race can cope with this ("neutral ending"), finds a cure for this ("good ending"), or even develops further unexpected complications down the road, when it's too late to fix any of it ("bad ending") [Answer] # Honor Amongst Thieves: The race is centered in conflict, so the only way they can manage to function as a society is to make sure they all know what the others are thinking. You know Ted is an obnoxious jerk who'll rape you if he is alone with you, but he'll die for you in a fight. Keep him by your side and don't be alone with him. You're in the same fire team as your wife, but she already knows you're cheating on her and she has low expectations. Johan killed his last CO and we don't want him on our fire team - maybe another unit is desperate enough to take him. And we all know the captain is a glory-hound, but as long as you know what's expected, so what? # Feedback Loop: Your soldiers have a compartmentalized brain with distinct but cooperative personalities. They may even be located in multiple parts of the body. Because they operate independently, they don't always share the same thoughts. Each one can take over the body in the event of a traumatic brain injury, but the constant muttering is an externalized way that the primary persona communicates it's intentions to the others. All personas are kept up to date on what the collective is doing. so the disruption from injury is minimized. [Answer] ## They choose to be honest - in accordance with their design Your super-soldiers have their own innate morality. In the same way we are repulsed by incest, and squeamish about moving corpses, they don't *want* to conceal what they are thinking. They are pragmatic enough to understand the purpose of stealth missions and sneaking, but setting that moral complication aside, they have a strong aversion to any kind of dissimulation or misrepresentation. In fact, they insist on telegraphing their thinking, lest anyone accidentally misunderstand them. Because of this, they regularly mumble what they are thinking under their breath (but it's your fault if you weren't paying attention!), as well as answering (practically) any question with unnerving honesty and directness, even if it is personally disadvantageous. They also ask exceptionally direct questions, and are annoyed at vague, indirect responses. (You can't offend them by telling them exactly what you think, either.) It's an inborn tendency, engineered on purpose, and reinforced in their training. Better to know if and when they're preparing to rise up and take over (even if that was the goal of the designers in the first place). Better that they will someday create their own "perfect" society, without secrets, without dissembling. At least, their designers thought so. [Answer] **Your super soldiers are in debug mode!** Yup, even biological machines need to be debugged (as opposed to de*loused*, which is an entirely different problem). Debug mode was turned on by default, because these super soldiers are in an extended beta testing phase. Sure that might include all-out war and world domination, but pragmatism still rules. Engineers are deployed along with tactical units. The constant muttering provides a stream of debug info. This allows the engineers to begin troubleshooting a problem immediately. Non-technical people nearby are likely to report a problem to the authorities. Nobody wants these things to develop of mind of their own! This is meant to be transient information. If the super soldier were to be killed or incapacitated, you do not want the enemy to download a bunch of state secrets. It would be desirable for this information to be inaccessible after it has been transmitted verbally for security reasons. [Answer] ## Conditioning If they are super soldiers, I presume they have been trained and conditioned to always repeat orders. "Advance to map plot E4, yessir!". In the absence of a command hierarchy maybe they will only trust their opinions if they assume they were given as a command? Some soldier-training-OCD compelling them to voice their thoughts as if reporting back to an officer. [Answer] **They are mentally conditioned to vocalise as a necessary precursor to actualisation** This component of their training to prepare them for combat has the side effect of making them appear to be honest. It can also make them more intimidating, because when they say something like "Would you like an explosive suppository?" you know they are already in the process of making a bomb up your butt a reality. For soldiers, this fear can sometimes be useful The conditioning has an odd effect when they are trying to stealthy, as they would basically attempt to speak silence. What that means is an observer watching them sneak about would watch them mouth "I am being very quiet" without the vocalisation required for anyone to hear the words. [Answer] ## Social hivemind They were originally engineered to operate within networks consisting of both engineers and their siblings. Once other entities are detected (optionally only while either are working on the same problem) they enter this social hivemind state, in which all their actions and inner processes that are relevant to the task at hand are 'exposed' verbally. Since working in close proximity of several of these creatures used to be the norm, the volume with which they disclose this information is quite low. Additionally, they found a way (through engineering or through internal optimization processes) to communicate only the most pertinent information in as few words as colloquially possible to make themselves understood. [Answer] I will split this into two parts: **Why is only happens outside of mission:** While on the mission, the level of adrenalin is increased, adrenaline is able to bond with the AD1 and AD2 receptors in the brain, which normally facilitate the thought to mouth (thought to hand) transition (these are engineered receptors). Therefore as your adrenaline level increases, the thought to mouth process decreases, if adrenaline level gets above a certain threshold, all AD1 and AD2 receptors are filled and no communication occurs. **Why were the soldiers equipped with AD1 and AD2 receptors** 1. Tactical reason: soldiers' senses while increased are still singular. By constantly muttering the observations, other soldier, are able to in essence use the senses of all other soldier to be kept abreast of the environment. If one notices something, they are all immediately informed of it. 2. Mental health status: The modifications done to the soldiers, are extensive and not always stable. By monitoring the muttering, the operator is able to analyze the mental state of the super-soldier. If the mental state changes, the muttering pattern tends to change and operator is then equipped to evaluate what to do. [Answer] They're sharing what they learned on the battlefield with their peers. The chatter is after-action review and includes speculation about what would have worked better and what courses of action would have made the situation worse. The habit is so ingrained that they do it even when there are no peers around. It operates much in the same way as the mammalian function of dreaming. Experiences are tossed together in a kind of fruit salad and served up during sleep. [Answer] Building on The Square-Cube Law's idea of debug routines that were not removed. Let's throw in the **Law of Unintended Consequences**. It seems to me that the "BIOS" coding would be encoded, not in software, but in the hardware. It would be incorporated right into the genetic code of the bioengineering. That way, it could not be modified by any hack or virus program. It would be the closest to 'permanent code' as one could get, equivalent to pure hard-wired ROM chips. Once factory encoded, they would be impossible to change. It would be the ultimate fail-safe against rogue AI (r)evolution. Like Asimov's 'Three laws' being unalterable. So the original genetic engineers put debug logging code right into the original gene coding of the prototypes. That way, the self-modifying AI learning algorithms could not change it. he machine itself could never turn off, bypass, disable, or circumvent the debug routines. It was hard wired coding, as it were. But someone, somewhere, double-purposed the same genes to control a vital function, like power control and power production. Eliminating, turning off, or otherwise deleting or nullifying the debug logging functionality of these genes also causes the shutdown of all power functionality, for the ultimate 'kill switch'. Since it is at the most basic input output system, there is no workaround. The **unintended consequence** is that when the engineers try to turn off the debug routines, the entire 'machine' shuts down. The ultimate 'OOOoops factor'. Short of starting all over at the basic level, building up the entire genetic code of the bioengineered construct, the engineers are stuck with the babbling. [Answer] Super soldiers are dangerous. They can be more dangerous to you than the enemy so need audio logs built into them. [Answer] **Social Adaptation/Conditioning** Each soldier goes through individual experiences each day. Reviewing those experiences and making conclusions about them is socialized to the group as a way of getting feedback and establishing/maintaining group norms. Think of this as a primitive form of Facebook or Twitter. Group think on the low-tech. The advantage of this is that every soldier is kept in the fold and group-think is exposed and can be steered in the desired direction by executive control. This makes soldier group-action steerable and predictable. Always important when they have the toys that go boom. [Answer] Your super soldiers were designed by a committee. Who came up with this specification during a session when dangerously sedative, sleepy and soporific PowerPoint presentations were being made. [Answer] **Why wouldn't they talk about exactly what's on their mind?** Regular people hide their thoughts/feelings (or "modify" them - ie. lie) as a self-defense mechanism due to their insecurity and fear how other people would react if they do not present them in best possible light. Your super-soldiers have no need for such pathetic behaviour, as they don't have *any* insecurities, due to their design. So they say what they mean all the time, and without any fear of repercussions. They're super human after all. Do you take care to hide your thoughts from the butterfly you pass? Neither do they feel they need to hide their thought from puny humans. So they have no need to hide their thoughts, nor to lie. And you think they mumble because they speak very softly - again because they don't need to speak loudly (much like big dog can emit the lowest of growls and small dogs will scatter with their tails between their legs). As to the **why** would they speak their mind for everyone to hear -- man, have you ever visited any internet discussion forum? It's in the regular human nature too, it is just that [most](https://xkcd.com/386/) of us regular humans (trolls excluded) often think it better to shut off our mouths because of our insecurities about the possible consequences (and those superhumans do not, as they don't have any insecurities, of course) [Answer] An answer could be that they were trained to give a running narrative of what is happening around them, including their thoughts or observations. For example, in a combat situation they would be constantly reporting their movements and actions back to a central command station, such as telling their commander where they were and what they were seeing or doing, or they would be recording a log of the battle on some kind of recording device built into their armor that could be used to put together a report of the battle after it was over. [Answer] Super-soldiers were built in order to be self-sufficient which means they must be able to quickly and effectively heal both physically and mentally. Their genetic code base was engineered by an unsupervised ML algorithm that found out that talking out loud is the best way to process information and emotions, using audio feedback for self-optimisation. Because of their extraordinary mental-health, super-soldiers have tactical and strategic superiority on almost all combat scenarios. ]

[Question] [ Set in the distant future, space travel becomes prominent and cheap. I can imagine each spaceship would have a multitude array of sensors to track distance and relative position in space. Is there a good way to determine another spaceship's mass beside hailing them for specifications? I know we can accurately know the mass of an asteroid using Newton's law of universal gravitation and probably Kepler's law too, I guess, but that's only for an orbiting object in space unlike a spaceship which usually accelerates using its own propulsion drive. Please state the principle of measurement and I would prefer an economical solution. [Answer] A few options ordered from "difficult but can be done at any time" to "easy, but requires an opportunity". # Measure the [gravitational lensing](https://en.wikipedia.org/wiki/Gravitational_lens) effect of the ship Every mass in the universe bends the space around it. This can be observed because stars behind the object appear displaced. This is how current day astronomers estimate the masses of astronomic objects (planets, stars, galaxies...). With access to much more precise instruments it might be possible to use the same principle for much smaller masses. If you are able to measure gravitational lensing around a regular sized space ship with *current day* technology, you know you are dealing with something with a really, really extreme density (neutron-star level)... or with something which uses artificial gravity technology. Anyway, it's definitely something based on technology far beyond anything you could comprehend. Proceed with caution! # Measure the effect of its gravity on nearby objects If your instruments are not precise enough to measure its effect on light, you might still be able to measure its effect on dust clouds, micro-asteroids, space junk and other small objects when they get very close to the ship. But again, if they use artificial gravity technology, then that might screw up your measurement. Also check if the objects you measure contain any magnetic materials. If the ship generates a magnetic field for some reason (which can be an unintentional by-product of all kinds of devices), then that might also affect nearby objects. # Measure its exhaust and the corresponding acceleration I would like to expand on point 3 of the answer by Darth Donut. If the engines of the ship work according to [Newtons 3rd law of motion](https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion) (which is the only way space propulsion can work according to our current understanding of physics), the kinetic force of the exhaust is exactly the same as the kinetic force applied to the ship. So when you observe the ship while it performs an acceleration burn, you can observe how much exhaust mass it expels per second and with what velocity. Multiply the two and you have its engine thrust. Divide the thrust by the acceleration of the ship you observe, and you have the mass of the ship. # Measure how it behaves when hit by another object The ship is too light to cause any observable gravity effects and doesn't feel like performing any maneuvers right now? There is another way to apply Newton's laws to examine its mass. Wait until it gets hit by a micrometeroid. Measure the mass and acceleration of the meteroid and see how much the ship's velocity changes when it gets hit. When no meteroids are around, you could of course launch a known mass with a known acceleration at the ship yourself. But that might be perceived as impolite. [Answer] Here are a few ideas I got: **1. Look up the ship type:** As long as this ship you are seeing is not made by a to date unknown civilication, your databases should be able to identify the ship type, and show you some basic information for that. **2. Estimate by size:** As long as you can measure the distance, you can measure the size of such a ship. Now, your engineers will have an estimate for how much space is taken up by machinery, how much mass is used for the hull, how much space is needed for crew and so on. They know what materials are used commonly, and by multiplying the estimated volume with an average density you can estimate the mass of the ship. It is not a precise estimate, but your engineers should be pretty near to the exact value. **3. Measure the acceleration and energy output of the engines:** Every engine known to us emits radiation in some form due to conversion losses. As long as you can measure the acceleration of such a ship, the radiation of the engines and can identify the type of engine, you should be able to get a good estimate how much energy is used to power the engine, how much force the engines generate and in turn how much mass the ship has. Everything you need for the above methods are good optical sensors and radiation sensors. [Answer] The vacuum of space act as a dielectric. If you are close enough, provide a net electric charge to your own ship. This will induce a charge also on the probed ship, and will trigger an electrostatic attraction between the two. Measure your velocity with respect to background and your velocity with respect to the probed ship. Since you know the charge involved and you can determine the resulting force exerted on the probed ship. The resulting force will change your velocity and the one of the probed ship. You know your mass and your velocity both with respect to background and to probed ship, the only unknown parameter is the probed ship mass. [Answer] ## In Civilized Areas, They will Tell You Automatically Today, ships and aircraft have systems that self report their name, size, exact location, velocity, destination etc. For ships, this is [AIS](https://en.wikipedia.org/wiki/Automatic_identification_system), and for aircraft it is [ADS-B](https://en.wikipedia.org/wiki/Automatic_dependent_surveillance_%E2%80%93_broadcast). The systems automatically squawk their info at regular intervals, so as soon as you are in receiving range you know what the contact picture is. It is often required by the relevant authorities, as it significantly improves safety when everyone knows where everyone else is. ## Otherwise, IR will give a Good Guess All vessels will have a power source. This power source is going to have waste heat, which will radiate from the vessel evenly. (Unless the owner pumps air/fluids around to deliberately alter the heat transfer.) This waste heat will be subject to one over r squared losses. If you can determine a range, you can determine how much this blackbody radiation will have dropped off, and you can get an estimate of the size of the power source. Power is going to be strongly related to vessel size and acceleration. The exact equation is probably going to be complex, but luckily the universe is full of vessels providing you with empirical data! [Answer] **Muography.** <https://en.wikipedia.org/wiki/Muography> > > Muography is an imaging technique that produces a projectional image > of a target volume by recording elementary particles, called muons, > either electronically or chemically with materials that are sensitive > to charged particles such as nuclear emulsions. Cosmic rays from outer > space generate muons in the Earth’s atmosphere as a result of nuclear > reactions between primary cosmic rays and atmospheric nuclei. They are > highly penetrative and millions of muons pass through our bodies every > day. > > > Muons traverse a solid object according the the mass of the object, more dense objects stopping muons more than less dense objects. One can use ambient muons to produce images. This is how the interior of a volcano was imaged. NASA has a proposal to use ambient muons to image the interior of asteroids in space. [](https://i.stack.imgur.com/5x77U.jpg) <https://www.nasa.gov/content/deep-mapping-of-small-solar-system-bodies-with-galactic-cosmic-ray-secondary-particle-1> Muography has been used to characterize very dense objects. If you are digging it, read this whole paper where they characterized old objects from nuclear waste sites. <https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2018.0048>. Lots of images of stuff with stuff inside! Here is an image of a contaminated crucible encased in glass, minus the glass and then minus the crucible, with only the radioactive contaminants. [](https://i.stack.imgur.com/f4rLG.png) Muography can let you image a ship passively, without it knowing it is being imaged. That might have its uses. Backscatter muography is near future scifi - the idea would be to have your own muon source, like your own light source and actively image something by shooting muons at it and then capturing those which are reflected. Just as light things reflect visible light more, dense materials will reflect muons more, and just as one characterizes density passively by capturing wild muons which traverse from the far side of the object heading towards you, you could actively image by spraying your artificial muons at the object and characterizing scatter back towards you. [Answer] # Probe indirectly Launch a small probe of precisely known mass so that it passes at a known distance from the ship. The probe might be as opaque and undetectable as could be. At a predetermined moment the probe shoots a low-power laser signal to the mothership, allowing its position to be precisely determined. From there, you can work back the deflection on the trajectory caused by the gravitational mass of the unknown ship. # Probe (almost) directly Send two probes at different distances from the unknown ship, depending on how sensitive their gravitational sensors are. Measure acceleration on both probes. These will be caused by all nearby masses (the mothership included), but using two probes, the residual that has quadratic dependency on the unknown ship's distance once the other masses are ruled out will give the unknown ship's mass. For example if all other masses are sufficiently far away, the distance between them and probes P and Q may be taken as constant, so the differential will be zero. The acceleration on probe P will then be given by G(M/a^2 - X/(b+d)^2) while that on probe Q by G(M/(a+d)^2 - X/b^2), with M and X the masses of the mothership and the unknown's, a and b the distances of the first probe from the mothership M and the unknown, and d the distance between the probes: ``` M P Q X |--- a ------|--- d ---|--------------------- b ----------------| ``` Assuming b, especially, is known with sufficient accuracy (phased laser ranging, maybe?) and gravimeters (not accelerometers, thanks @wizzwizz) of sufficient precision are available, the two probes could even be mounted on a fixed "antenna" (it is not necessary for M, P, Q and X to be aligned on a line, but this simplifies things). [Answer] Shine a laser at it, and measure the (exceedingly slight) change in [momentum](https://davidson.weizmann.ac.il/en/online/askexpert/physics/can-laser-beam-be-used-stop-asteroid-producing-opposite-momentum-velocity-and-mass-or). > > Several years later, in 1922, physicist Arthur Compton performed an > experiment which led to the discovery of the Compton Effect. Proving > Einstein correct, Compton showed that photons indeed have momentum > which is transferrable to materials that have a mass. Compton was > awarded the 1927 Noble Prize in Physics for demonstrating that photons > can transfer their momentum to the electrons with which they collide > inside an atom. > > > I am, of course, assuming that by the time there are enough spaceships out there that one needs to worry about determining their mass, we will have the technology to be able to detect very minute changes in momentum that a laser beam would impart on a ship. Yes, I am aware that it would be easier to detect the change in momentum caused by a flea smacking into a super jumbo jet, but hey, we are talking about the future here. [Answer]  Equipment that can survey the gravitational potential on the order of [microgals](https://en.m.wikipedia.org/wiki/Gal_(unit)) is quite common today in geological industry and academia, known as [gravimetry](https://en.m.wikipedia.org/wiki/Gravimetry). The machines used as instrumentation, [gravimeters](https://en.m.wikipedia.org/wiki/Gravimeter), are quite interesting, but ultimately they are able to derive densities by way of directly measuring differing gravitational acceleration at many points. These have even been used to probe non-geological manmade-scale objects e.g. when French scientists surveyed the Cheops pyramid for unknown chambers. A tech advanced gravimeter (perhaps using an array of atom chip nano gravimeters) paired with a good gravimetric map of the navigation area should allow measurement of the mass of an anomalous body. With enough resolution you could even possibly map the density distribution of the vessel and track masses moving on the interior. [Answer] Scan them. Fire a very large burst of neutrinos at them and measure how much gets reflected back. In general the more massive an object is the more return signal you will get. It works okay for an estimated order of magnitude. Unlike other answers this probably won't be recognized as an act of violence, doesn't disturb their trajectory and gives you an answer near to light speeds. Edit: Actually, I'm no physicist but I think you won't get neutrinos back, you might get electrons, but I'm just not knowledgeable enough to say for sure. [Answer] A patient passive approach could work. Observe ship apparent size and structure (visual angle) relative to your ship. Use an optical distance range finder. Integrate the number of naturally present cosmic rays passing through the other ship into your ship in order to passively estimate density - The ice cube observatory uses similar methods and works for space ships up to almost the thickness of Earth. Get an estimate of the other ships surface area & unseen sides by capacitance (just measure your own ships capacitance, deviation from typical solo deep space value indicates parallel capacitance of the nearby ship). Calculate surface to volume ratio and add density estimate from cosmic ray result for an estimate of mass that improves with more cosmic ray integrations. [Answer] Shoot them with a powerful laser and see how much the momentum of their ship changes. You didn't mention anything about leaving the ship intact. [Answer] You didn't say how long you want to take to figure out the other ship's mass. If you aren't in a hurry and it's just you and the other ship with no other ships or masses nearby, and (ideally) neither of you is accelerating, then you can simple take periodic measurements of the distance between your ship and theirs. Two distance measurements taken close together can tell you your current speed. Then at longer intervals take more measurements and determine how much your distance differs from expectations. The difference should be mainly due to gravitational attraction between ships. Note that this method works best if the other ship is stationary relative to you, isn't terribly far away, and remains this way for a few weeks, maybe less depending on how accurately you can measure the distance between your ship and theirs using radar or some other mechanism. This situation happened in "2001: A Space Odyssey" where during the trip to Jupiter there were two ships near each other and they had to make minor course corrections during the trip due to their mutual gravitational attraction. [Answer] **Gravitational Field**, nearly exactly how we are measuring EM field currently. LIGO proved it can be done for large object in 2017 when 2 black holes collided and generated gravitational waves. Starship in the future should be in the scale of million - trillion tonnes and moving at at least 10-20% speed of light, this would make considerable 'huge' amount of gravitational waves if moving 'close' together (by close I mean a few thousands kilometers). Heck we can measure gravitational waves emitted by black holes light years away now, absolutely we can do that for smaller objects within a few thousands kilometers in 200-300 years, especially if that object moves close to speed of light since it generates more identifiable ripples. I'm pretty sure we can work the math out to the exact dimensions of LIGO-like version needed to do this, but it would be terrifyingly difficult for people like us. I have strong background in electric engineering and still cannot grasp most part of it. [Answer] Assuming no magic technology to provide the answer, and that I was writing a hard scifi story where this knowledge was important, then ... as has been said above 'Newton is your Daddy!' The same method used to measure masses of all the planets in our solar system would work in this case. To summarize my interpretation of the original technique is by iterating through assumed mass values and computing the paths followed by the planets in their orbits to predict where the planet will be in the future. By comparing the actual paths to the predicted paths, the error in the guesstimate for the planetary masses can be improved. It's my understanding that this is how early astronomers came up with the values for planetary masses, and I also believe that there are slight wobbles in planetary orbits that our guessimates can't model; suggesting that there are more masses to be accounted for in our equations. But, our models are good enough to launch space probes past Pluto, so they are good enough for now. For spaceships, the idea would be similar. Spaceship A wants to travel along a specific path in 4D (x,y,z,t). It knows its own mass very accurately. And can measure the distance to any object it can see via lidar, radar, optical means, etc. The spaceship computes the thrust vector to move it along the path, any errors in the actual path represent either unidentified masses or inaccuracies in mass guesstimates. Iterating over the computations until the errors in navigating go to zero, or near zero, then you know the mass of everything around you. Similarly, if the vector required to keep a ship moving along a specific path suddenly changed or slowly changed, then that would indicate something moving near or away from your ship. This would provide a means for detecting hidden ships. The math for this kind of stuff is very common in scientific applications, radar systems, sonar systems, and cell phone technology -- albeit not computing errors in mass, but for figuring out parameters that affect the transmission, reception, or interpretation of data. And since gravitatal forces are limited by relativistic limits there is a practical limit to the range that objects could be detected and 'measured.' [Answer] Grab them with a tractor beam (or cable with a magnet at its end if you're inclined to be low tech and their hull is magnetic) and try to tug it. Provided you have some way of precise spatial reference (launching several small drones in at least 3 directions should suffice as low tech solution), and you knowing your own mass and power of your engines, you should be able to calculate [inertia](https://en.wikipedia.org/wiki/Inertia) of additional mass you're trying to move. [Answer] You can't measure it directly at a distance with current technology. Tech however at a given time is fairly well constrained. E.g. If you are building battleships, then knowing the dimensions of the battleship give you a pretty good idea of the mass. Space allows extreme magnification of images, so getting an approximate mass at a distance of several AU's is reasonable. Another factor is the power/mass ratio. This will affect acceleration, and possibly also weaponry. A destroyer has a much higher power/weight ratio than a battleship. Thinner armour, smaller guns. Destroyers run rings around fleets and convoys to intercept subs. In space you also look at the waste heat. The volume of a ship goes up with the cube of linear dimensions, while the surface area goes up only as the square. A big ship has a bigger problem getting rid of waste heat. It's radiators will run at higher temps. You would also monitor communications. Difficult. Comm channels are likely to be tightly beamed. All of these are subject to a certain amount of spoofing: * A small ship can inflate a large metallic balloon and appear to be much larger. * A small ship, by manouvering at well below max acceleration may be thought to be larger. * A small ship, by directing it's cooling heat at you can appear to be disposing of more heat -- signature of a larger ship. * A large ship, by directing waste heat away from you appears smaller * A large ship, if shaped like a disk or a brick can maintain an orientation edge on or end on and appear smaller. * A large ship, with the outline of a small ship in white and the rest of the ship black, may be classed as a small ship at long range. Of course black doesn't help the heat disposal problem. Detectors: Visual gives you the most information about the detail. Far infrared gives you more information about the skin temperature, and hence the power use. The outline technique above wouldn't fool an IR scan. Having scouts spread throughout the space of interest makes deception harder. A small detector, disguised or part of an asteroid would be nearly impossible to spot. If space also had several radar illuminator ships, the passive scouts would get radar distances -- You get both the reflection of the radar off the enemy, as well as the time signal from the radar ship. That and geometry give you a solution of the distance. Note that as soon as you change technology, all this goes out the window. E.g. at present one of the ways we would measure is the amount of rocket exhaust and the resulting acceleration. Replace that with ion drives, and we may not even see the exhaust. Analogues: Submarines are identified by their sound signatures. And some of the same forms of deception are used, pretending to be something they are not. (Usually however a sub's goal is to be undetected. Radar can determine the difference between a Cessna and a Boeing by strength of reflection, as well as the way it manoevers. Adding a corner reflector increases the radar return substantially making the Cessna look bigger. Stealth coatings on fighters make the radar return vanishingly small. In the days of sail, a ship of the line could be spotted further away -- taller masts. At closer range, you could look at the rigging and get a good idea of the size of the ship. Counting gun decks was another way. --- The uncertainties add to the fun in your universe. Allows for possible *ruses des guerre* [Answer] Less than a hundreds years ago, we didn't have any application for electromagnetic waves, nor didn't know how to sense it. Now we can detect gravitational waves (well, only the strong). In future, we may have miniaturized sensitive technology to measure the disturbance in space-time. Who knows, may be we can sense the mass of the ship by measuring the turbulence it causes in the space-time. [Answer] Late to the party, but... **Measure the tidal effect of their gravitational well.** Using a network of extremely accurate force measurement devices (direction and magnitude) you could get a map of the local gravitational topography. Subtract your ship's baseline to remove its own gravitational field from the data and you'll get a very small tidal effect on a line that points to the target ship. Detectors on the side closest to the target will be trying to accelerate towards it faster than detectors on the other side of your ship by a tiny amount that is can be used to calculate the mass of the target. Of course we're talking about measuring exceptionally small values - on the order of 67 nano Newtons of tidal force over 500m with a target mass of 1 gigaton. You'd best keep your crew from breathing too hard while all this is being measured. [Answer] **The Newton method** Have a large array of highly sensitive movable ball-bearings (similar types of lumps of matter), perhaps mounted on precisely calibrated springs or something, suspended in a vacuum. The ball-bearings will be pulled towards the target object with a force proportional to its mass, which can be calculated by how much the ball-bearings move. Of course, you'll have to take into account all the objects in the area, including your own ship and the people and objects therein (including the other ball-bearings and springs) which is why you need such a large array of sensors - each will be moved by a different amount depending on its distance from each object, allowing an AI to use the movement of each ball-bearing to isolate object. The algorithm to do that is left as an exercise to the reader :-p ]

[Question] [ I was wondering--**why are there no self driving tanks in the US army?** They seem much easier to build than a flying drone. Most of the space within the tank is wasted on instruments/cabin space for the crew. Removing all of that would allow the tank to be much smaller or have thicker armor. It might even reduce the overall cost of the tank and make it more robust. Unlike a flying machine, loss of connection or autopilot malfunction is not catastrophic. In the worst case scenario, your tank just sits idle or runs into a wall instead of crashing like a flying drone would. You wouldn't mind sending such a tank to the front line, since there are no human lives at risk. It would probably aim and shoot much better than human pilots. I'm really surprised that they don't exist yet. [Answer] > > Unlike a flying machine, loss of connection or autopilot malfunction is not catastrophic, in the worst case your tank just sits idle or runs into wall instead of crashing like a flying drone would. > > > Totally incorrect. Quite the opposite actually. Flying autopilots have been common for decades now and they have become even better. If a flying drone loses connection it won't crash, obviously. Its autopilot will kick in with preprogrammed "lost connection" routines. So it can at least evade the enemy and avoid destruction or capture. A ground drone is the exact opposite. We have yet to create an acceptable "autopilot" for ground vehicles. Especially if you are in unknown and complex terrain like a city or forest. So if a ground drone loses connection, it is only matter of time before it is destroyed or, even worse, captured. On top of that, it is much easier to lose connection to a ground drone than it is to an aerial drone, magnifying the above problems. > > It would probably aim and shoot much better than human pilots. > > > That is again not true. If such technology existed, it would already be used on tanks even with human crew. Even with such a high level of automation, humans are still needed for command and control. And even with full automation, it is worth having pilots inside just for backup. So there would be no difference in firing ability of the tank with or without crew. [Answer] Many good answers here, but I thought I'd add my two cents as a former infantryman. One of the biggest benefits to using a drone aircraft is the mitigation of risk to human life. We are willing to pay a premium in monetary terms in order to limit risk to human operators of our weapons. This works with UAVs because (as was stated previously) * Airborne autopilot technology is mature (in case you lose connection with the drone) * UAVs operate at reasonably high altitudes most of the time so we usually have a good line of sight to the drone from the ground or a satellite, which mitigates the problems of jamming * There are way fewer things to bump into at 50,000 feet than there are at 0 feet, so even imperfect controls and AI give us a good chance of sucessfully navigating and getting our UAV home With a UGV (unmanned ground vehicle), we have none of these advantages. Hills or concrete buildings block our signal to home, tons of complex obstacles challenge our ability to navigate, and ground based autopilot is still unreliable. Beyond all that however, and VERY importantly: WE ARE NOT REALLY ACCOMPLISHING ANYTHING! Why not? Because human lives ARE at risk no matter what! What most people don't realize is that tanks are not used as "stand alone" weapons. You do not use an MBT the way you might use a B-52 to just cruise over to the enemy, drop some badness, and scuttle away. Tanks cannot operate this way. They hold terrain. Tanks must control terrain by use of their powerful weapons and survive by use of their heavy armor. They remain in place or move together in order to cut through enemy formations, form lines, or flank an enemy force. 99% of the time, tanks are NEVER alone! They are surrounded by infantry, either in lighter vehicles or on foot, or a mix of the two. This infantry keeps the tank alive by spotting infantry with anti tank weapons and eliminating them. They are eyes and ears for the tank, which has a limited ability to "see" what is around it and no ability to hide in small crannies or be stealthy. In the 1973 war, one of the major lessons that Israel drew from the annihilation of their (highly skilled and advanced) tank force in the Sinai was that they must NEVER use tanks without infantry support again. Tanks by themselves are nothing but targets for infantry carrying ATGMs. Given all that, you gain NOTHING by creating an UGV tank, because you still have to have guys on foot all around it in order to be sure it doesn't become an easy to hit rolling target (and probably a slower one than a conventional tank because the AI will be challenged to think it's way through battlefield terrain). So you just spent enormous amounts of money to get rid of the crew of the tank, but you still have tons of guys right up at the front, and you can't use an MBT by itself without them, so there is no political payoff. In addition to all this, auto loaders have never been reliable. Tanks are so complicated that the more things you automate, the more things break, and the more time the thing spends in the shop. UGV MBTs would be a maintenance nightmare. [Answer] Since there are no self driving cars, self driving tanks are right out of the question, because they not only have to cope with terrain that doesn't have neat signs and lines to show the way, but also with actual hostile action. Question why there are no remote controlled tank is valid, though. There are multiple reasons: 1. Military prefers technology that can be relied on. You don't want your spiffy shiny new tanks bursting in flames because engine didn't broadcast warning signals to operator. Using the absolute cutting edge is a great way to suddenly discover fatal flaw at the most inconvenient moment. 2. Designing and building weapons costs a lot of money. You can't afford to replace your entire armour complement of thousands every 5 years because there's new model. Tanks like Abrams or Leopard were around for 3 and a half decades. T-90 and Challenger are in service for about 20 years. However, those tanks have been upgraded multiple times since their commission. New turrets, modified armour plates, better guns, better ammunition. All that improves their performance WITHOUT requiring major redesign and without incurring excessive costs. Also, all nations keep a stock of mothballed obsolete equipment, for sale and emergency use. First two factors taken together: you want a lot of working and good enough equipment, not few prototypes that will break down because infancy problems weren't ironed out and those which remain are swarmed by enemy. WWII was decided by tens of thousands of workhorse vehicles: Shermans (USA), T-34 (Soviet) or their Axis counterparts like PzKpfw IV and STUG III, while famous Tiger and Tiger II bore relatively small impact due to small numbers. Nearly 50000 Shermans and 65000 T-34 were produced before the war ended. Tigers? Just a bit over 1300. Tiger IIs were even less numerous. 3. A lot of the technology required to make that happen didn't actually exist until very recently or didn't exist in practical form. Autoloaders exist, but they were problematic. As far as I know, there's no automatic target acquisition and fire control in service anywhere - ballistic computers don't replace gunners, they only assist them in rangefinding, compensating for gravitational drop, weather and target speed. Infra-red imaging makes identification of targets easier but not automatic - modern computers still can't be relied upon to differentiate tank from car so human has to identify target. Remote guidance and digital cameras weren't robust, cheap and reliable enough to be used on a tank. Basically, while it is an obvious next step, it's actually much harder than it seems. That being said, there are changes in this direction: * TUSK (Tank Urban Survival Kit) system for Abrams, introduced in late 2000s includes machinegun controlled remotely from inside. * Trophy system introduced in early 2010 includes 360 radar linked to pellet launchers and is capable of shooting down incoming rockets without any input from operators (Soviets were using active anti-missile countermeasures since 80s, but their solutions weren't as precise as current ones). * Russian T-14 Armata tank unveiled last year has unmanned turret. Main gun is loaded by autoloading system and remotely controlled from crew compartment inside the hull. Gun control is supposedly able to automatically track and engage targets designated by gunner (IR tracking of signatures). Other systems it's supposed to have include active anti-missile countermeasures (which require no input from crew) and machine-guns operating in both remote-controlled and IR-based autonomous modes.T-14 is probably the first design to integrate so much automation into single platform, but it's not actually superior to NATO designs in firepower and protection (it however significantly changes tactics). What it is, is a wake-up call to quickly start work on new tanks. Upgrades to existing vehicles soon won't be sufficient. Technological race never ends - Russians are already working on upgrades for T-14. 4. Jamming. Problem with remote control is, if your signal can be jammed, then your device isn't of much use. That can be partially remedied by directional antennae, you can't really jam them unless you are in the way, and in case of flying vehicle, with horizon at the distance of hundreds of kilometres, it's relatively easy to create a chain of unobstructed links. On ground not so much. Tanks have to plow into enemy territory, behind hills, field and cities, where the only direct unobstructed link to base would be through satellite. Lightspeed "ping" to low earth orbit and back is 1ms (ignoring processing speeds), "ping" to geostationary orbit and back is 0.25s. To operate tanks remotely you would need satellites capable of transmitting real-time image, exceeding 4K by far, from dozens of cameras, from thousands of tanks, and you would need thousands of LEO sats if you want to control your tank for more than a minute per day, or dozens of geostationary sats and you would get 500+ ping to use gaming as comparison. Neither of required networks exists, and neither would be cheap. If you want to try and relay through some AWACS equivalent, you run into the problem that you need total control of airspace, but if you do, then you are against enemy against whom tanks are impractical, you need infantry instead. 5. Logistics. Tanks don't actually drive to the battelfield. They are carried on trucks, trains or ships as close as possible. Due to weight and huge mechanical stress involved in propelling 50+ tonnes at 60+ km/h, tank engines are rated for merely thousand km or so. After that they need service or replacement. Tanks need ammo and a lot of fuel. They also need personnel to resupply and service them. Unless you can automatise resupply and service, you need people nearby anyway. There's even more, but for now, this is where I stop listing reasons. [Answer] * The ground is a more crowded, complicated environment than the air. In the worst case, an UAV out of contact will fly in a straight line or circle. In the worst case, an UGV out of contact might drive into a ditch or into a house. * Drones are under remote control when it gets exciting. That works because they usually have good commo links, either satcom or line-of-sight. The communications environment on the ground, especially in mountains and urban areas, is much more difficult. Reception may be degraded by obstacles at inconvenient times. [Answer] Firstly, the concept of your remote tank is a bit off. A tank that engages in fighting, i.e. firing its main armament close to the enemy requires always friendly infantry support. Without adequate support a tank is easily flanked and destroyed by enemy units. Thus, the drone tank would require regular (or remote controlled) infantry to support it, thus removing the advantage of not sending humans to the fight. A tank that would not need to engage enemy, for example carrying out reconnaissance could be a viable application for automation, but then again a cheaper flying drone is much better suitable for getting better picture of the surrounding areas. Secondly, there are quite many technical obstacles. Other responses have already argued well the connection issues that would occur due to hills, forrests and buildings. In addition, coming from some experience with tanks, driving a tank requires multiple decisions being made at the same time and close collaboration from the crew. Whereas a flying drone can be set to follow certain path and operator can concentrate on acquiring targets and firing, tank commander has to issue multiple commands simultaneously that all affect the battle effectiveness. The driving instructions, for example, to the driver determine the opportunities to acquire targets, remain hidden from enemy, fire main armament and survive possible incoming fire. All these decisions are made by a human and they all interact (driving, reloading, firing decisions cannot be made indipendently as in a flying drone). As we have no such artificial intelligence in hand in any conceivable near future, the remote tank would need multiple remote operators (at least driver, commander and gunner). This would increase the communication overhead, as they all need enough sensory input from the tank (camera, voice, etc.) and all need to be able to issue near-realtime control commands to the tank. Even in a modern tank situational awareness is a key challenge tankers face, doing everything via laptop and some cameras would be ridiculously difficult. Moreover, when ground fight gets hot, the pace is much faster. Life-or-death decisions have to be made quickly. The flying drones by remaining unseen can take their time to carry out the issued commands. [Answer] Because they would serve a different use case, and so far nobody high enough decided that investing in that use case is worth it yet. Expensive heavily armored remote controlled tanks are inferior to tanks with crews for a variety of reasons, which mostly boil down to lower reliability. At the price point of a tank, lower reliability is not something you want. The use of remote controlled tanks would have to be different - weakly armored, cheap, even disposable remote controlled tanks. Pretty much cannons on wheels. It's the same as with the flying drones which aren't super expensive remote controlled fighter jets. They can shoot and if they get shot themselves, who cares, they're disposable. The problem with these disposable remote controlled cannons on wheels is that in large scale engagements they are somewhat unpredictable, especially due to jamming. While in small scale assassinations, their role is already filled by flying drones. Solving this problem requires full automation, which is an unsolved technical problem, as well as an ethical problem. Long term, due to the very high land speed such cannons can achieve, they will certainly appear, probably some time after high speed scouting drones on wheels. And once they appear they will certainly lead to new tactics. [Answer] It's also worth considering the things that an armoured fighting vehicle needs people to do for it. An awful lot of the role of the crew of an AFV is keeping the AFV running. However, it is worth considering that military unmanned ground vehicles *are* in development, primarily for logistics where the loss of a relatively inexpensive truck and some cargo is much less important than the crew - take a look at the [TerraMax](https://en.wikipedia.org/wiki/TerraMax_(vehicle)) as an example. [Answer] Why not on the ground? -sensor blocking Computers are not good at image processing. It is hard for them to identify objects by sight or deal with foreground objects blocking background objects. From the air it is much easier to see and there are fewer obscuring objects -navigation as noted earlier autopilot in the air is much easier than on the ground there are no obstacles to avoid, no people to not run over, no mud to get stuck in. -Delay loop The army wants a human to be "in the loop" when ever a drone kills something due to speed of light limitations to get up to a satellite back to Nevada and back down this can cause a full second delay between an even and the drivers response. On the ground that second delay is very costly. The enemy can see you coming you are firing unguided munitions(bullets) so you have to lead the enemy its a harder problem. In the air there is a building or a car and a guided missile it still works even with the delay. Why not Armored Drones mean you don't have to survive. Why is a tank armored? So it can survive being shot. Because a tank crew and their tank are expansive and hard to replace. A destroyed drone is only expensive if the drone is expensive. This means that drones will tend to be lighter and cheaper than the normal versions. A tank drone is more likely to be a lightly armored golfcart with 2 sidewinder missiles than an Abrams with computers stuck in it. [Answer] There has actually been a lot of research and debate in this area for a while. Both small scale (eg. packbot, TALON) and larger scale (e.g. MULE robots). Full sized robots or drones on a tanks scale are prohibitively expensive (witness how long between Abrams upgrades, much less redesign, and the time and money spent on things like Future Combat System and the Joint Strike Fighter), both of which included significantly more automation than today's fleet of vehicles, but neither were anywhere close to a full-on drone. Additionally, while I agree that the computing power required to generate a firing solution for a tank is [not prohibitive](https://www.youtube.com/watch?v=3ygFeywrvjc), what is prohibitive is the moral side of things. I made a comment above but figured it deserved expounding upon. First, the US does not want to relegate the decision to take a life to anything other than another human being. This includes sketchy feelings about even humans pulling the trigger [when a robot aims](http://www.computerworld.com/article/2473892/emerging-technology/124123-U.S.-military-gets-fired-up-over-weaponized-robots.html), and I can't find the article now but there was a follow-on piece to that involving a malfunction that wasn't catastrophic but damned scary. Second, when it comes to large robots, there are still a lot of safety concerns (even on the battlefield). On modern battlefields, there are a *lot* of civilians / noncombatants still, and you can't just ask them to get out of the way. A drone typically has some non-trivial delay from command to execution due to bandwidth and signal travel limitations, and the last thing the US wants to do is run over someone's kid with a robot tank by accident, because the signal was delayed and the autonomic sensors didn't sweep the right spot of ground to "see" the kid in time. The other answers are also mostly great, just wanted to cover things I thought were missing. [Answer] Flying drones have a lot of major advantages over piloted aircraft * Potentially much cheaper. This is less true in the case of fighters, but reconnaissance can be done by tiny drones that cost less than even training a pilot. * Expendable. You can send thousands of recon drones over hostile territory and it's not a big deal if many are shot down. * More agile. Modern fighters are limited by the fact that humans cannot endure really high G forces. Drones can have the same performance characteristics as guided missiles. Tanks, on the other hand, will always be very expensive, which also means they are not very expendable, and they will never be agile enough that G forces matter. So there is not much incentive to develop a tank drone. [Answer] ## Self-driving cars are hard Self-driving cars are actually hugely difficult to make. Imagine a camera feed. You have a grid of pixels. Essentially a huge chequerboard full of binary digits. Now try to write an algorithm that can take that chequerboard and turn it into a meaningful map of the surroundings. It's a very hard problem. ## Going off road multiplies the problem If you are on a road, you can reduce the scale of the problem considerably. You are surrounded by rectangular cars. Slow moving upright objects are probably people. Converging light coloured lines are probably roads. Going in the air makes it easier still. There is almost nothing to hit. All you need to do is proceed to a GPS coordinate. In a tank none of these assumptions hold true. Tanks are camouflaged. They may be partially occluded. You might be in a forest or a destroyed city. There might be obstacles. ## Now add in tactics The bridge has been damaged and might be dangerous to cross. The trees that should offer cover have no leaves because it's autumn. The enemy is flying a false flag. There are RPGs on that hill over there, covering the road. A human with common sense (learned heuristics) can make these complex, unpredictable decisions. A machine can't, because machines can only do what they are programmed to do. ## What about a learning computer? You might try to make a computer that can learn from its environment. This is a very hard problem indeed. You now have to take your chequerboard input and somehow convert that grid into "rules for staying alive". No one is even close to being able to write a program to do this. Such a program may not even be possible. We might need quantum computers, or something exotic we haven't yet thought of. All current machine learning algorithms require carefully curated datasets, and hand tuned algorithms. You can't just chuck in a real world, noisy video image at them. Our current best computers give us no more than insect level intelligence if that. You would need mammalian level intelligence to power a free roving autonomous tank. *People are clever. Computers are dumb.* ## Remote control So what about remote control? In the air, if your signal is jammed, you can simply fly to a preprogrammed GPS coordinate and land. On the ground, if you lose your signal, you are on your own. You can't drive home in a straight line. Plot a predictable route home and your unpiloted convoy could be taken out tank by tank by a guy making holes with a mechanical digger, or some similarly unpredictable obstacle. ## The future? We may one day be able to make a computer intelligent enough to function autonomously in the world without a human guiding it. That day is a long way off and we have no roadmap of how to get there. We really have no idea about what intelligence actually is, or what problems we need to solve to reach it. True AI is still no more than sci-fi. (Source: I studied AI at Sussex University.) [Answer] Keeping a tank operational in the field requires *lots* of **maintenance**. Fuel. Oil. Track tension. Lubrication. Replacing parts. Without those things, a tank will pretty quickly become inoperational. (Look at late WWII German tanks. Magnificent beasts when operational. A nightmare to maintain.) Tank crews are trained to do this kind of field maintenance. Actually, one of the arguments for a human loader instead of an autoloading system is the additional pair of hands servicing the tank when not actually in combat. You need hands, right there where the tank stops, to ensure it can perform the next day as well. While you *might* be able to keep human tankers out of the "shooting" war by using drones, you will need just that many technical personell *very* close to the frontlines for doing the maintenance on them... people who cannot, if pressed, just jump into the protection of their tank and shoot back... [Answer] ## Communications When the drone is in the air, the controller can be on the ground a few miles away with a dish antenna and be able to communicate over a simple line-of-sight radio link with the drone. For more distant operations, the controller can be airborne or can use an airborne relay. When the drone is on the ground, even just a mile or two away, ground clutter and interference absolutely requires a relay. And even then, things like uneven terrain (hills, ditches, etc), vegetation, and gouts of dirt, dust, smoke, and water from incoming artillery will significantly interfere with the signal. [Answer] Can't believe someone hasn't added that a Tank Drone on the ground is ripe for the taking. Find a weakness, overwhelm it with targets and now YOU have a cannon you can turn against your oppressor. If you take a flying drone down, you have a bunch of junk. If you capture a tank, you have a FREE weapon you can now use. [Answer] Reliability, and to a certain extent, culture. The americans, and british for example do not like [autoloaders](https://en.wikipedia.org/wiki/Autoloader), with a human loader and an isolated compartment for shells being less likely to cook off and kill the crew. In addition, at the end of the day its a human who makes the decision to pull that trigger, and kill someone, not a machine, least in this day and age. You still have to decide if you want to fire, or get the enemy to surrender, and occationally act on gut instinct. > > Unlike a flying machine, loss of connection or autopilot malfunction > is not catastrophic. In the worst case scenario, your tank just sits > idle or runs into a wall instead of crashing like a flying drone > would. You wouldn't mind sending such a tank to the front line, since > there are no human lives at risk. > > > Which the enemy can capture and take apart, potentially reverse engineer - the [americans lost one drone to the iranians](https://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incident) and well, the chinese and russians probably got a peek inside. Imagine that happening to your newest tanks - the americans destroyed [mission-killed but otherwise 'intact' tanks in battle](https://en.wikipedia.org/wiki/M1_Abrams#Iraq_War) That said, *eventual* automation makes sense. A remotely controlled turret might be useful - the russians have extended the concept of the autoloader to build an [unmanned turret into their latest tank](https://en.wikipedia.org/wiki/T-14_Armata). Considering the reliance on GPS, and that many of the technologies used in self driving cars would be useful in close quarters navigation like LIDAR, non combat self driving feels potentially natural, as does *smaller crews*. You might also have slightly expendable/cheaper semi autonomous tanks acting as decoys or supporting tank platoons [Answer] Just to clarify: by tank you mean actual tank (i.e. Abrams) or any armored vehicle (i.e. AFV Bradley or Stryker)? Might be a good idea to clear that up... Contrary to most other answers it is very simple to produce a UGV that's quite... reliable, let's call it. You can now remotely hijack and control most newer cars, so highly computerized tank is even easier to autonomate\*. For the same weight and space you can equip tank with recognize-and-follow-the terrain unit that's installed in Tomahawks or SpecOps aircraft. Add to it INS or other stuff you can have pretty good self-driving unit. Not to mention that for smaller obstacles what you need is buffed-up and pimped-out parking sensors... Same with gun crew - aiming and firing is already highly automated, as is the loading. But here's where complications begin. You can have essentially two types of autoloader: Soviet-style carousel or multiple-queue-feeder. As last 30 years have demonstrated carousel type is highly susceptible to catastrophic hit (i.e. "golden bb hit", where tank explodes pretty spectacularly with turret flying high and far). Multiple-queue-feeder is too big to fit into a turret of an MBT - compare tank to Navy 155mm destroyer cannon and you'll see the size of the whole unit is... bit different. There's a reason why even MC-130's 105mm gun is manually loaded, even if there's a lot more space there than in MBT's turret. Of course there are smaller options/solutions, but they all will be bulky (to say the least). And might be vulnerable to a hard hit - that is if hit directly (even without penetration) it might jam as it will have much to many moving parts. Same argument goes for all kinds of electronics, actually - as much as you'd want it's still not great in "shock-proof" department. I'd say that main concern is (cue in dramatic music jingle)... Communications! Jamming signal is a concern, but not that much as one would think. Most of military traffic goes through secure satellite communication which is not exactly easy to jam. It's not difficult, too, technically, because if there's any satellite redundancy, it's pretty much impossible (you have to target the satellite, and for that you have to know where it is). But that's why there's redundancy. Not to mention intra-unit tac-net including BFS etc. Also signal repeaters are not exactly new... The problem is signal latency. For standard sat comm (geosynchronous) it will be at least half a second (including encryption/decryption), maybe more. This is the same time sabot needs to travel almost a kilometer down the range... In other words: half a second is difference between hit and miss in most combat situation. "Moving target is harder to hit" is no longer valid axiom - it's now "Randomly moving target is harder to hit". You can't have random with such delays... Last point: as mentioned in other answers - MBT is never alone on the battlefield. There are Scouts, Screening units... Remoting them all will definitely jam the bandwidth and signal delays mentioned earlier makes the whole point moot, anyway. If we're talking supporting other units (i.e. infantry) it's even bigger issue. It could be remedied by making the unit autonomous, but it there's any malfunction results can be... catastrophic. Not to mention the fact that being around Abrams firing it's main gun is neither pleasant nor safe... Tight fire control is strongly suggested... From what I've read on tank crew operations (by actual Abrams crewmen) manual loading is much more reliable and faster than autoloaders, driving a tank is not the same as cruising in an Escalade... Because it's not technology but training and experience is what makes 5-man crew operate as nearly-one. But they're still autonomous, so tank commander does not have to think to tell driver how to drive and maneuver nor loader how to load. He gives order and crew expands on it according to their training, experience and role. This is the oldest and best understood for many centuries force-multipier, which is also the biggest one... Also they are cheaper - tomahawk is quite pricey exactly due to it's sensor/guidance package. Add all the equipment needed to make Abrams UGV and you're doubling it's price tag... No one will pay close to $10 mil for one tank... Which is, in my opinion, main reason for not having UMBTs. Or UAFVs, for that matter. \*not an error. [Answer] I think that frankly flying war drones are just more effective than ground drones would be regardless. Check out what the Iraqis have done. <https://futurism.com/the-iraqi-army-just-deployed-its-cannon-equipped-robot/> Not self driving but remote controlled makes killing like playing Halo. One person steers while the other utilizes the main cannon. [Answer] Maybe not a MBT (yet) but the Russian [Whirlwind](http://www.janes.com/article/63562/new-russian-combat-ugv-breaks-cover-uran-9-readies-for-service) is an unmanned combat ground vehicle (UCGV) armed with a stabilised 30 mm Shipunov 2A72 automatic cannon and other weaponry. I suspect an MBT can't be far behind. And there's the Israeli Guardium as well with a lot less weaponry but featuring a fully autonomous mode. [Answer] Several reasons 1. An "Unmanned" vehicle must still receive instructions, that means signals which can be hacked, jammed or intercepted. The defense/tech industry is already experimenting with anti-drone guns that fire interrupting signal beams. <https://www.youtube.com/watch?v=ADW63thj-Pg> 2. Repair/Recovery: If the vehicle is damaged; you have to send people to fix it anyway. Unless you have a unmanned tow vehicle to recover it. 3. Resupply, upkeep of the vehicle overall must be maintained, By whom? ]

[Question] [ Imagine a typical fantasy world. Elves, goblins, dragons, magic. If you were to equate it to a D&D campaign, you would be close enough for proverbial government work. That said, thanks to time and magic, their knowledge of science is more advanced than usual. The people understand germ theory, and atoms (though not sub atomics). One exception is that, in this world, it is popular to quench newly forged swords in dragon's blood instead of oil (or gods forbid, water). This is not just mysticism or cruelty, doing so produces demonstrably superior weapons. And it is not a magical benefit, dragon's blood swords are still better without any detectable powers or while in an anti-magic zone. Why would that be? What physical properties could dragon's blood possess, that would somehow make it better for heat treating blades? And while still being viable blood for a living creature? [Answer] You don't want harder steel, it breaks, you don't want softer steel, it bends, you want more control of the temperature of the steel at every stage so you can get the exact properties you want. Better is more control of the process. Dragon blood is just a non-flammable liquid with thermal conductivity similar to oils or water but unlike water and oils it has a vapor point higher than steel's melting point, so the oil can be heated to much higher temperatures. This means it can control the temperature the steel is [cooled to exactly](https://en.wikipedia.org/wiki/Quenching). This also allows it to be used in a liquid oven or normalizing medium, which means the steel can be heated perfectly evenly and kept there as long as necessary. This is how the best steels are produced and how to get the most out of your steel allows, precision control of temperature at every stage. It can even be used for annealing and [tempering](https://en.wikipedia.org/wiki/Tempering_(metallurgy)) much how modern smiths use ovens. Most forges and quenches can not be targeted to the exact temperature, quenching fluid in particular boils off before it can be heated to the best temperatures. It is really easy to overheat or underheat the steel. Today we can use molten salts for some of these, but that is a recent invention. Molten salt is also extremely dangerous. A [basic introduction](https://www.youtube.com/watch?v=6jQ4y0LK1kY) to heat treatment of steel. Making good steel is about precision, you are trying to hit a bullseye of qualities. For those unfamiliar with the term ductility, low ductility means brittle, high ductility means easy to bend, you don't want either. [](https://i.stack.imgur.com/CIHmo.jpg) It even makes sense that dragons would have such blood since they need blood that will not boil no matter how hot they are. [Answer] I am a blacksmith. I make blades, like this one. [](https://i.stack.imgur.com/6Iacx.gif) OK first things first, *there is a lot of disinformation in here*...first I will address that. 1. Quenching is not the final step in making a blade. It is the most dramatic moment of the forging process and is generally shown in entertainment as the last step...it's not. 2. Quenching is not even the final step in the heat treating process. 3. The final step in heat treating is [tempering](https://en.wikipedia.org/wiki/Tempering_(metallurgy)) It generally doesn't matter what type of fluid you quench your blade in. The general thing to know is that the faster the steel cools down from critical (the point where it is so hot it is no longer magnetic) the harder and more brittle it becomes. *Brief definition break!* * Hardness: Hardness is a measure of how much force it takes to deform the steel * Toughness: Toughness is a measure of how much force a blade can take and still return to is previous shape. OK so anyway. You want the edge of the blade to be **hard** and you want the spine of the blade to be **flexible.** To do this you first harden the blade by quenching it as mentioned. Once that is done you reheat the blade but only along the spine back to a cherry red, say 800 degrees or so. While you do this you keep the cutting edge cool either by keeping it in liquid or wet clay or something, this keeps the edge hard. ## OK. On to the question at hand...how does dragon blood make blades better? Sadly, with science...it doesn't. When you quench the blade in any substance, the outer layer will indeed bond with the quenching fluid (we use a mix of motor oil and antifreeze at my shop). The problem is, it is a very thin layer, and depending on the type of steel may actually flake off. Either way you would grind and polish after hardening. Then you would temper the spine. After tempering you do your final grind/polish and sharpening. Metallurgy really doesn't allow for a scientific benefit to using dragon blood...which is great for your dragons. *That being said if you are working in a fantasy realm*...which I would assume you are since...you know...dragons, you can use the ol' *it's magic* and create something that works for story telling. Just because it doesn't work in real life doesn't mean it can't be awesome in a story. [Answer] Dragons' blood is an absurdly good insulator. Now, normally this would not be quite what you want for quenching, but Dragons' blood is also *magical*. Quenching a blade in Dragons' blood is not like a normal quenching - it's more like aging a whiskey. You heat the blade to white-hot, plunge it into the blood, seal it up, and leave it for a month or so. The blade then cools *incredibly* slowly. Aided by the intrinsic magic of the blood purifying the lattice and eliminating dislocations, the end result is a nigh-indestructible [monocrystalline blade](https://en.wikipedia.org/wiki/Single_crystal) which requires no further tempering. The blade must then be sharpened by magic, resulting in this monomolecular blade having an edge only a handful of atoms thick - but despite the magic involved in the forging process, no actual magical properties are imposed on the sword itself. (This also explains why Dragons sleep on hoards of gold and treasures made from other metals - the magic in their blood interacts with the metal, giving them the same basking feeling that a lizard gets in the hot sun) [Answer] **Dragon blood is rich in phosphorus.** > > Phosphorus in steel can have beneficial as well as harmful effects. > Phosphorus is one of the most potent solid-solution strengtheners of > ferrite. The addition of only 0.17% phosphorus increases both the > yield and tensile strength of low-carbon sheet steel by about 62 MPa > (9 ksi) while also improving the bake hardening response and deep > drawability... Phosphorus is also used as an additive in steels to > improve machining characteristics and atmospheric corrosion > resistance. > > > Detrimental effects of phosphorus in steel include various forms of > embrittlement which reduce the toughness and ductility. The most > familiar example in this category is the classic phenomenon of temper > embrittlement... > <https://www.totalmateria.com/page.aspx?ID=CheckArticle&site=kts&NM=211> > > > You do not want phosphorus mixed with your steel. It will make it brittle. You want a thin layer on the outside. That hardens the outer layer, where you want it to hold and edge. Also that outer layer offers corrosion resistance, which you do not need on the sword interior. Your question does not state that the swords are steel. Maybe they are bronze. [Phosphor bronze](https://en.wikipedia.org/wiki/Phosphor_bronze). > > Phosphor bronze is an alloy of copper with 0.5–11% of tin and > 0.01–0.35% phosphorus. The tin increases the corrosion resistance and strength of the alloy. The phosphorus increases the wear resistance > and stiffness of the alloy. > > > If you had Bronze Age tech, phosphor bronze would be excellent sword making stuff. Wikipedia shows a phosphor bronze ship propeller - for tool making applications this would be great, and a dip in high phosphorus dragon blood would be a way to get a layer of phosphor bronze on the outside of your bronze weapon. --- I got this idea because I thought I had read that the druids did exactly this with swords and human blood - quenched them in blood to harden the outside, which was accomplished by the high phosphorus content of blood. Animals run on ATP which is a high energy phosphorus compound and so all blood has a lot of phosphorus. You could make dragon blood exceptionally high - perhaps they need a lot of circulating ATP to produce fire. [Answer] For those of us who are not up-to-date on their material science, [quenching](https://en.wikipedia.org/wiki/Quenching) has the end effect of making metal harder. It achieves this through the cooling rate of the metal. It can be that dragon's blood happens to conduct heat really well, making a harder blade. This may also explain why those darn dragons don't burn themselves so easily : their blood helps dissipate the heat so well! Additionally, cooling some metal quickly enough can result in it being [amorphous](https://en.wikipedia.org/wiki/Amorphous_metal). In generalities, amorphous metals (or glass metals) resist plastic deformation and are tougher than crystalline (normal) metals. Tougher blades, though, are generally considered better- they snap back better to their original shape and don't become bent as easily. Harder blades are not always better: it depends on the style of sword and martial system you are using. Additionally, increased hardness usually comes with increased brittleness, increasing the chances of a blade shattering. If it can cool metal weapons quickly enough and achieve the "glass metal" mentioned above, it will be tougher which will result in a better blade. [Answer] ## Dragon's blood is an ideal medium for austempering While most blades, to this day, are made using water or oil as the quench medium in the traditional quenching and tempering process that James mentions, producing a tempered martensite microstructure, this is actually *not* the ideal microstructure for a given hardness. The work of Bain and Davenport at US Steel in the 1920s and 1930s (pat. 1933) on *isothermal transformations* in steel led to the discovery of a superior microstructure, namely [*bainite*](https://en.wikipedia.org/wiki/Bainite), with improved toughness at a given hardness for typical blade hardnesses (above 40 on the Rockwell C hardness scale). However, it isn't achievable in ordinary carbon steel using typical, continuous-cooling quench media. Modern production dunks the part in a molten salt (nitrite/nitrate) bath that cools the part to an isothermal transformation temperature, then holds it there to effect the transformation before pulling it out and letting it air-cool post-austemper, or uses special alloys that can form bainite during a continuous cooling process. This is known as [*austempering*](https://www.appliedprocess.com/wp-content/uploads/2018/09/249004_Austempering-of-Steel-ASM-Handbook-Volume-4.pdf), and is commonly used for high-strength steel parts such as rifle bolts (all the way back to WWII), [mower blades](https://jdparts.deere.com/partsmkt/document/english/featbene/PartsQuality_BladeResidential.pdf), and seat belt parts in cars. In your case, though, you can do better. The blood of your dragons is a high-boiling liquid (very low vapor pressure) with excellent thermal stability, excellent thermal conductivity, and a high specific heat capacity, making it ideal for austempering a blade as it will not boil off, decompose, react with the blade, or change in temperature much when the part is added, while drawing heat out of the part quickly to bypass the "nose" of the curve for that steel. In this process, the quench tank would be almost like a cauldron, kept hot (but not too hot!) with a stoked fire, and the parts would be *held* in the quench medium for a significant length of time (from minutes to hours), effecting an isothermal austemper and producing tougher, stronger blades for a given hardness at a minor tradeoff in absolute hardness achievable. Once done, the part would be removed from the bath, washed, and for a blade taken straight to the grinding wheel for sharpening, as austempered parts need no further heat treatment. [Answer] Better doesn't necessarily mean harder. Perhaps the dragon's blood is high in elements which are inherently poisonous to humans. A thin coating of mercury or arsenic on a blade can dramatically increase the killing effectiveness of the steel. Add to that real threat, the psychological burden of knowing that your enemy's blade is poisoned, and battles can be won before the blade is even drawn. Now go deeper than just a thin coating... Perhaps quenching a scalding hot blade in poisonous metals saturates the resulting steel with a lethality which can't just be wiped away. It is in the metal and will be the deciding factor of every battle in which the blade is used. Alternatively, the poison could be biochemical. Perhaps the dragon's blood contains a voracious infection which thrives in the scalding bloodstreams of dragons. When stored in the structure of cold steel, the microscopic life lays dormant until revived by hot human blood. Once activated, it quickly consumes the victim since human immune defenses are no match for a virus born in dragons. This alternative has the advantage that the blade could be handled, cleaned and cared for as long as it never came in touch with blood. It would be safer for it's wielder to carry than the elementally poisoned blade described above. [Answer] Quenching a sword in blood imbues the properties of the blood (and by extension the animal from which the blood is drawn) into the sword. Human blood? Actually pretty bad, since people whose blood is being used to quench the sword are obviously LOSERS! Rhinoceros blood? Great strength/crappy eyesight - blade won't ever break, but you can't hit sh\*t with it. Bats blood? Makes for a nice, lightweight blade, very quick and easy handling, but it squeeeeeeaks every time you draw it out of the sheath - puts everyone's teeth on edge, and obviously no good for a ninja. Horse blood? Leaps into your hand, but really touchy about what it eats/hits - insists on second-cutting hay, gets colic-y at the drop of an anvil, and is prone to develop hoof/grip problems. Snakes blood? Poisonous, and likes to bite the hand that wields it. NOT GOOD! Lizard blood? Slow, and intolerant of cold weather. Dragon's blood? Well, now - that's a bit of a poser. Y'see, according to a handwritten marginal note found in Nurmenfnograth's Tome Of Magical Metallurgy & Metalworking: > > Ye blayde witich be enquench'ed in ye bloode of ye dragonne wille be superiur too > annye othere, beinge unbrakeable, undullable, magicallee sentient annd possess'ed of > itss owne wille. Aye goe forth too ackwire ye dragguns bloood withe witch too finnish > ye grate wurk! > > > The entire book was found in a rather scorched-around-the-edges condition outside of The Great Smoking Cave. Nurmenfnograth was never seen again, and the only clue as to his fate was a brief and cryptic inscription found scratched into the bare rock next to the book in the Ryunes Of Gnobrathmingfnorp, which translates rather loosely as **NEXT!** None of The Wise who have been consulted regarding this matter can explain quite what this inscription means. ??? [Answer] Quenching is the process in which steel is cooled from extremely high temperatures to not so high ones. the faster the cooling the harder the steel. According to a few pages I just read nothing is faster at dispersing thermal energy from other materials than water. So in order to make dragons blood superior for quenching to water, we need to find its one flaw. that is water cools steel so quickly that it doesn't cool *evenly* which is absolutely necessary to create perfect steel. So all you need to do to make your dragon blood so amazing is have the perfect ratio of water to any other materials in the blood to make the cooling faster than that of oil or salt bathing, but not as fast as water. You need no special chemical properties or materials, just the right ratio of water to not water. I hope this makes sense and is helpful. Thank you :) [Answer] Dragons are fierce creatures the size of small commercial jets. The forces involved when they fight are intense. Consequently, they need many unique adaptations just to avoid bleeding to death or becoming permanently disabled in the course of their frequent scuffles. One of those adaptations is an advanced clotting factor in their blood. When exposed to intense heat it forms a strong impermeable coating film w/ over 2-3x the toughness & 3-6x the tensile strength by weight of spider silk (at a density comparable to that of steel). Quenching in Dragon's Blood thus deposits a microscopic coating that happens to bond to steel really well (due to little understood adaptations for rapid bone regeneration that apparently rely on high concentrations of several organometallic compounds dissolved in their blood) and which far exceeds the performance of any synthetic materials we can hope to make. [Answer] It's a little-known fact that dragon's blood has an exceptionally high graphite content, a byproduct of their evolution from the igneous realms of the molten hearts of mountains. Graphite is a blacksmith's friend for three reasons. First, being elemental carbon, it can be used in the production of weapon-grade steel. One fist of dragon's blood for every twelve fists of molten iron has been found to be the ideal ratio for the hardest "dragon steel". Second, graphite is an excellent refractory material able to provide stable heat insulation across a wide range of temperatures. When quenching hot steel in dragon's blood, the liquid effectively becomes a kiln that cools weapon steel evenly and, by coincidence or godly design, at the ideal rate that ensures maximum hardness. Finally, graphite is a superb lubricator, and the use of dragon's blood while grinding a dragon steel blade is known to yield the sharpest possible edge. [Answer] Well cooling metal too slowly results in it being too soft but cooling it too fast results in it being hard but brittle. Dragons blood you see, it contains metals that get heated when it breaths fire and then they are cooled in a controlled way by the blood. The result is that these metals are cooled not too fast, not too slow but just right. so that it can use them in its scales. dragon blood has evolved to do this. when you quench metal in this blood you will benefit from its properties. [Answer] Dragons are usually big and armored, begging the question of where the square cube law was when they were created. But there are solutions. As material sciences advance we notice that molecularly perfect substances often exibit extreme proporties, so we can only assume that Dragons have evolved to create many of these materials to strengthen themselves and make them able to support their own weight. Damascan steel managed to get very strong and still elastic through nanowires and carbon Nanotubes that were enclosed in the metal. Such materials could be present in dragon's blood especially if parts of the dragon were ground into the blood. What happens during the quenching is that these materials coat the blade, providing a superior resiliance to shattering, dentation and needing less effort to remain sharp. If you then use folded steel and quench between foldings you create many layers of this coating inside the blade, making them have superior properties in strength, resilience, maintenancr and resistance to damage/shattering. [Answer] Just something to consider: Historically slaves and prisoners were used to quench some blades. Something I heard in a Materials Science class, supposedly the Conquistadors' blades were quenched by running a captive Inca through with a blade to quench the blade. Something about the body temperature of a person, plus the saline content allowed for just the right speed of blade temperature decrease. With that in mind, suppose you had a different alloy, one that under normal forging processes would either be too expensive for your average customer to buy, or too heavy for them to wield. But then with using dragon's blood to quench the blade at just the right temperature and speed, you can make your blade stronger but lighter, and thereby use fewer metallic resources, and thereby bring the finished blade into the wieldable and affordable range. [Answer] There are already enough answers which touch on how the blood could magically make the sword better and I think [James' answer](https://worldbuilding.stackexchange.com/a/140483/17025) sums it up the best in terms of real-world viability and properties. I offer you another reason why these swords are perceived as "better" and that reason is **psychology**. Imagine facing an army who's reputation is: > > You mean we are fighting the XYZ's? The nation that forges their swords in the blood of dragons and then quenches the sword in the blood of their enemies? Peace out guys, I'll pass. > > > If the wielders are brainwashed into thinking their swords are better through questionable demonstration of a blood-sword versus a purposely built brittle sword then their confidence in battle will simply be higher. This equates to better morale and overall greater fierceness of the warriors. This of course assumes that the blood swords are forged to a high quality per James' answer. You don't have to look much further for this placebo than the [Rhino Horn](https://www.savetherhino.org/rhino-info/threats/poaching-rhino-horn/). ]

[Question] [ Let's say we want to build the **strongest possible fortress¹** in a **medieval** (1300 CE) setting while having access to any **modern technology and material**. Said technology can only be used **during the construction of the fortress and not afterwards**, so e.g. a solar powered device is allowed to continue functioning after the construction is complete, but the denizens of the fortress will not be able to repair it in case of damage. Soldiers will only have access to regular weapons and armor from their time, not modern weaponry (otherwise we would just build a wooden house equipped with M60s and be done with it). ¹This fortress will have to endure: * Battering rams on the gate * Balistas, catapults and trebuchets. No cannons. * Starvation by means of cutting out supply lines. * Possibly, ladders and siege towers. (I say "possibly" because it would be a nice addition, but as long as the other 3 problems are covered, this can be handled by the soldiers.) It is assumed that the inhabitants will **learn perfectly how to operate** every device/building/etc., but will **not be able to understand how/why they work**. This means they won't be able to repair or replicate anything beyond their level of technology. For example, if a carbon fiber wall gets damaged, they will repair it with stones/bricks/concrete. **Location constraints:** any location is allowed, provided it is suitable for a medieval population (e.g. an underwater city would be infeasible). It also needs to function as any "regular" castle (allow movement of troops and people in and out, allow counter attacks and so on) **Population:** as many people as possible as long as it doesn't compromise security and provisions. At least 200; the more, the better. Let's assume that everyone is completely loyal and would die sooner than "betray the castle". **Resource and time limit:** no time limit, and suppose the area isn't attacked or sabotaged in any way during the construction. The resource limit is what realistically could be done by an entity in our society, so obviously no "just build an actual mountain the size of China, made of concrete and steel and hate". Let's say something around $5B just to give you an idea. Of course, *good and cheap* is better than *good and expensive*; but *good and expensive* is much better than *crappy but cheap*. What are the materials and techniques best suited to withstand the problems listed? **If "impregnable" is impossible, then "as strong/durable as possible".** **Bonus points if the answer manages to give a great solution to the problem without needing overly complicated technology to keep working** (e.g. by focusing on the materials and construction techniques rather than on particular devices) [Answer] # Colditz Castle ### An impregnable fortress. An inescapable prison. This is the problem you risk if you make a fortress that's truly impregnable, it could become the prison you spend the rest of your life in. One of the key features of castles is the ability to counter attack. Whether to sally forth with troops, or simply to shoot from the relative safety of the battlements, a castle is more than just a reinforced concrete box. # Why a castle? Castles are a statement of control as well as a tool of war, you see it dominating a landscape and it tells the world that there's someone here willing to put up a fight to keep a region. It allows a smaller force to hold a territory against much larger numbers until reinforcements can be gathered. It also acts as garrison, prison, armoury, residence, administrative centre, and food store. Castles are not the purely functional buildings that modern bunkers tend to be. A castle didn't have to hold out forever when under siege, it just had to hold out for long enough. Long enough for either the attackers to run out of food or money (or healthy men), or for a relief force to reach the castle to break the siege. Directly assaulting a castle is fairly rare, it's expensive and risky. Far cheaper and safer to sit out the siege for as long as it lasts, and it could last for years (the siege of Donnington castle lasted from July 1644 to April 1646). If your attackers are in a hurry and going for the attack you're probably in luck as defenders, castles were good, well designed and well built they gave significant advantage to the defending force. The ones that survive intact into the modern age were the very best, [Dover castle](https://www.english-heritage.org.uk/visit/places/dover-castle/) lasted long enough to be hardened against cannon fire with the best technology of the age. # So what to change? One of the greatest vulnerabilities of a castle was being undermined. This could bring down even the strongest tower. What we're going to do to compensate for this is dig down a couple of storeys, drill down and put in reinforced concrete foundations. While we're down here we'll also create some basements with water storage tanks and cool food storage areas all surrounded by double layered reinforced concrete walls, infilled with soil and rubble, similar to the main castle structure but underground and concrete. We may leave some secret tunnels down here just in case we need to make a [discreet exit](https://en.wikipedia.org/wiki/Postern). Ideally there will also be a well or similar underground fresh water supply. For the superstructure I'm not going to change much, the people of the day knew what they were doing and most castles would easily resist a direct assault on the walls. This leaves them in a good position to repair any damage that may be done during the average battle. Inside the main outer door of the [barbican](https://en.wikipedia.org/wiki/Barbican) we're going to build a bank vault type door, a simple conical section, smooth on the outside, it can only be controlled from the inside. The corridor between the outer door and this second door is a straight up kill zone, oil [holes in the ceiling](https://en.wikipedia.org/wiki/Murder-hole), spear holes in the walls all the usual "kill anyone in here" stuff, nothing special and fairly standard for the day. ### In summary Don't underestimate how good castle builders were at their job. Most castles never fell to assault, if they fell it was normally a surrender after a siege. The real change is better understanding of sanitation and food storage. Castles could survive sieges for years. [Answer] **The secret lies in Agriculture and Sanitation** Most medieval constructions before the advent of cannon/gunpowder were actually sufficient to prevent entry against a determined adversary. Most of these sieges ended through starvation, disease, an insider threat, or a counterattack by the defender's allies. First of all, let's just make sure that your castle is truly impregnable. To do this, we are interested in two things: height (which means range) and the impregnability of the construction materials. We make our walls higher than any siege engine can launch an object. This will also prevent siege towers from being a factor. Now we can't have outside fire or disease (or deadly projectiles) launched in to our city. We also want to place footers under our walls deeper than can be possibly undermined. Current technology allows for both of these feats. The wall construction will be made of a composite lasting the centuries... likely reinforced concrete, layered with impact absorbers, covered with a durable, yet thin, metal. This will absorb anything thrown against it. Now, the gate/entry way is the weakest physical assault point. This means that we will want multiple layers of security here and a precarious approach. A narrow, and easily protected, walkway covered by multiple towers on our skyscraper walls will do the trick, we'll just make several of these to be sure (and remove the idea that one person could open the single gate to our city. Also, a system could be developed where only one of the three inrow city gates can be opened at a time, along with much more secure (while still being simple) locking mechanisms. So what's left... fire? All structures inside of our city are made of steel reinforced concrete. Disease? Sanitation is the name of the game here for the most part and a sewage system is put in place to deal with this. Romans did it with older technology, we can do it as well. Fresh water is provided by placing the castle over a large reservoir and drilling to this point. Modern technology isn't needed to lift water out of this in the event that pumps break. Impart as much medical knowledge as feasible (just the idea of infection and how to prevent it should safe thousands). Now we're neatly sealed up inside of our city, with plenty of water and housing. We need food. And a way to always have food. You simply enlarge the area enclosed by your massive fortress walls to grow ample food to supply the city. It is likely best to make this area dispersed and divided to prevent disease/fire from spreading among the farms. The area required can be greatly reduced over typical medieval farming practices due to introducing modern agricultural techniques and grains. We also introduce modern grain storage techniques which allows for massive hoarding of food. As for weapons to defend ourselves, sure, you could introduce all manner of fancy modern weaponry, but given our height and armored supremacy, traditional siege weapons mounted 100m off of the ground can outreach any adversary, if they even bother to assault you, which they never would. [Answer] Build one of these AA-Towers the Nazis build in WW2. The Allied Forces tried to destroy them after the war (with explosives from the inside) and ultimately gave up after having to use 40 tons of TNT on one of them in Berlin. [](https://i.stack.imgur.com/HxvlT.jpg) *From KMJ, CC BY-SA 3.0, <https://commons.wikimedia.org/w/index.php?curid=968914>* It sure can withstand anything any medieval weapon has to offer. Don´t forget to bore a well in the middle! [Answer] As other have noted, castle designs were actually already pretty impressive. However, two significant things modern technology could enable that medieval technology could not replicate would be: **1. Location** It would be really quite wonderful to build a castle high in some strategic mountain pass, but alas, medieval engineers lacked the means to do so. No longer! With modern advances in engineering, materials, architecture, and logistics, you can now seal that dirty mountain pass as tight as a drum. And to boot, rather than terribly drafty stone, wood, and cladding, you have solid concrete, proper insulation, and an HVAC system with climate control. Watch your enemies freeze to death outside your walls as your people sit happy, warm and safe inside the walls of your modern fortress. **2. Scale** [](https://i.stack.imgur.com/a7o5G.jpg) In addition to being able to build a walled structure in some high mountain pass, you can also use modern engineering to build a wall over the ENTIRE mountain pass. The kinds of increases of scale enabled by modern technology could make a structure so incredibly large that it is it's own geographical feature. In addition to providing unassailable dominance over terrain, the sheer size and scope of your structure could serve as it's own kind of deterrent. Could you imagine being a medieval soldier and trying to lay siege to a castle wall the size of the hoover dam? Don't worry, your enemy can't either, which is why their army routed after a mere week into the siege of your mountain fortress. [Answer] ## Resist battering rams on the gate The best defence against a battering ram is of course to make it really difficult to get a ram up to the gate, but that does not depend on tech level. What you can do is to make a solid steel door. (Easy with modern tech, well understood but very very expensive for a person in the middle ages) Also construct hinges and fittings carefully. Place some cushioning material (rubber will do nicely) behind the gate post to absorb impact from the ram. ## Resist Balistas, catapults and trebuchets. You can certainly build strong walls with reinforced concrete. Also add steel plates and a crumble zone in front of the walls to greatly reduce impact from any boulders hurled your way. ## Resist Starvation by means of cutting out supply lines. Modern tech would not add much here. The key is to have a reliable well inside your fortress and stock up on food beforehand. However, you could definitely build some better facilities for hygiene and sanitation, reducing the risk of your soldiers succumbing to diseases. ## Resist ladders and siege towers. Using reinforced concrete instead of stone makes it easier to build really high walls, which naturally improves your defence against ladders and towers. Also, you can build some nice defensive constructions, having protruding structures high up from which your defenders can easily cover the walls with arrows (and nastier stuff) making any attack over the walls a suicide mission. ## Resist tunnels (bonus) The favourite means of breaching a castle wall was to tunnel under it and set fire to the (wooden) support beams. With modern equipment and machinery, you can extend your wall all the way down to bedrock, or at least well below groundwater level, making tunneling very hard. [Answer] Any reasonable medieval castle had stockpiles lasting for months and many had tunnels to enable restocking the castle during siege (or escape). Those castles are already nearly good enough for your purpose. Now take one at a suitable location and it is essentially impregnable as is, without any need for modern stuff - for example <https://en.wikipedia.org/wiki/Predjama_Castle> would be an existing castle that could be suitable for your purposes (the original one from 13th century would do as well). If you want some "modern magic": add lasers, long lasting batteries and burn wood/fat in a steam engine to charge batteries (or put it somewhere else with suitable natural resources and burn oil or gas). Everything is better with lasers. Also stuff the place with tons of cans to have food for decades. Maybe even reinforce walls with thick concrete. But if you want the castle to be self sufficient, this won't do - the mentioned castle doesn't have means to generate its own food. Unless you place the same castle to guard the only passage to the other side of impassable mountains with a large enough fertile land. Easy enough, you as the boss could even chill in the palace in the middle of that land in complete safety, while the peons work the fields and defend the castle. It could last for centuries, until finally the explosives get good enough the thing gets slowly blasted apart. Now, the most interesting thing would be to have a castle that needs to be 100% self-sufficient, yet defendable. But... this isn't possible. The big problem is you require about 2\*10^4 m2/person to be self-sufficient (based on a quick search, numbers vary wildly). Now, assume a small garrison of 200, and you are looking at 4\*10^6 m2 = square with side of 2km! (obviously you would make it a circle, but it doesn't change much, and it is simpler to calculate with squares). This is enormous already and a tad problematic to defend with mere 200 people, each will be responsible for 40m of the wall. Day and night. And work the fields as well. So, this is clearly impossible to defend, even if you give every one of them machine guns that never run out of ammo or break down. The nice thing for you is that with 20k people, you will have 20km sides of the square, but now 10 will be defending the same 40m section of the wall and do all the rest - so it is doable ... but at that point, you are not looking at a castle, but an island. Just build some guard posts around it put lasers there and just burn all the ships approaching. Think upgraded classical era mirrors :) In summary, just how good do you want the castle to be? Castles were good enough already, add some modern magic and they are better. Put them in perfect location and you could have them last for centuries under siege. But to make them perfectly self-sufficient, nah, you can't feasibly do that with a castle; while islands don't even require much of a castle to achieve that. [Answer] ## Fortify entair island There actually exists such island in our world entirely, not only Spinalonga <https://en.wikipedia.org/wiki/Spinalonga> , Gramvousa <https://en.wikipedia.org/wiki/Gramvousa> but also many other in Greece, which had fortification and a few hectars of fields at them, some been famous as pirate fortresses in history. With modern technology (and maybe in alternative world) such island can be found somewhere, where is regular rain and so no lack of watter, maybe even little larger, and you have your fortress. Some was sieged for years too. Just make all sides of the island going straight up from sea, left only small port there, accessible by steep stairs from main and only gate (ofcourse the stairs would not be straight, would provide some cover from bottom, but no cover from hight walls above them) and you are basically done. * inpenetrable gate: Just the usual construction, not much place before it, massive, so cannot be simply destroyed, kill-way to second gate (narrow, not straight, hight impenetrable walls, second gate even more massive, that the first, maybe to point, that could be blocked by collapsing stones from inside to level with the inside terrain), even getting to the first gate would cost attacker hundreds and hundreds of soldiers, if you will have just few peons throwning stones on them from above, not mentioning trained army with war machines (catapults, balistas ...) on the walls. * inpenetrable walls - hundred meters of natural stone under, no place, where ship could attach to even start attack on such walls, usual fortification on top, so you can safely shoot on attackers, drop big stones and fired bushes on their ships, if anchored in reach of your walls, shoot them with catapults, balistas long before the ships even approach effective range of their weapons (100m high gives you naturally longer reach and naturally decrease reach of their weapons. * you spot enemies for tens of kilometers, before they even start approaching, lot of time to orginize yourself * modern sanitation methods for your people (even the basic would make big difference) * modern agriculture methods - <https://en.wikipedia.org/wiki/Three-field_system> or better - and you do not care about food lines, with large enought island, you may even export food * siege/prison? No problem, just you cannot travel to other nation, but except for routine patrols you are in deep peace regime inside, while enemies struggles to even get in touch. More over you can build cranes anywhere inside, then move them at any point of your walls to lower your ships for take cargo from smuglers and continue restricted trade even under full siege * undermining island? from ships, which cannot anchor and can be bombarded (without any risk) with tons of boulders, fire, arrows, if they even try? - the same goes for ladders - based only on manuevuring ships they are anything but stable, with more probable overturn the ship and sink it, even if you do not fight them. The more for siege towers, would sink sooner, then they would even reach the base of your walls. And if you use modern technology just to shape existing island sides to be all vertical, smooth and somehow equally high, with fortified walls growing from top, make the inside somehow flat (nivelation) and then move good portion of good soil like <https://en.wikipedia.org/wiki/Chernozem> there, you have paradice inside (small streams and lake included - maybe even add rice fields there), with possible thousand of regular inhabitans living peacufully there. It is possible to have nearly all of king homestic animals there too. And trees, of course, not just for fruits and pleasure, but also as improvised source of wood. And with clean outer walls, permanent stone hoardings and fortified towers on top of the wall ( <https://en.wikipedia.org/wiki/Hoarding_(castle)> and <https://en.wikipedia.org/wiki/Fortified_tower> ) nobody can get inside if you not allowe him. Remember for a lot of building stone and wood to be stored inside every time and lot of stones, to be droppen on enemies, and you are good even long after gunpowered cannons came in play, with "purely mediaval technology and mindset" (And the best of it - 95% already exist in nature, so you not pay for that, and for the rest - the size and price of fortification grows lineary with the size of island, while usable place grow quadratically - larger islands are way cheaper per habitant than smaller) [Answer] I think the previous answers overlook one possibility: the question does not specify that modern weapons can't be included in the fortress design; only that no maintenance can be performed on those weapons. I'm surrendering the bonus points here because I'm employing devices and not construction methods, but the best approach would probably be: 1. Build this fortress on flat land with clear and unobstructed lines of sight that extend 2x the maximum range of the ranged weapons of your specific era. If the useful range of the catapults of your era is 500 meters (for example), make sure you have sight lines extending a full kilometer. 2. Include pillboxes on your fortress that cover 360 degrees of your frontage. Have overlapping coverage wherever possible. 3. Put automatic weapons emplacements in your pillboxes - one main, and three backups. 4. Store as much ammunition as is feasible given the size of your fortress. Include as many basement levels as you think is feasible and fill them all with ammunition. No medieval force would be able to even approach this fortress for the foreseeable future, let alone invest or take it. Sapping operations or trench operations wouldn't be feasible, either - the logistical effort it would take to cover a kilometer of ground using such methods would be beyond even the best-organized medieval military. I doubt even the Roman or Han armies could have done it - certainly not while under hostile fire. Eventually the weapons would wear out, or expire due to lack of maintenance. Or you'd run out of ammo. But any of those events would either take a very, very long time, or would require your enemy to take losses that no medieval power could realistically bear. [Answer] The equivalent to fortresses in modern times are bunkers. Dig down deep, have a huge sturdy steel gate in a tunnel and that will be the only vulnerable spot - which should be indestructible for medieval level of technology. Consider creating a huge hole in front of the gate with water at the bottom. In order to have a battering ram roll to the gate, which wouldn't be effective anyway, they'd need to construct a *lot* in order to even get there. Also they wouldn't be able to dig through mountains and ferroconcrete in any reasonable time and expense, so the gate is the only way in. [Answer] ## Don't forget 1300-1700 technological advances! During the 15th to 17th centuries, under the pressure of cannon, castles evolved into [bastion fortresses](https://en.wikipedia.org/wiki/Bastion_fort), with their distinctive star/triangular shape. You do not have cannon, but the elimination of dead zones is a distinct advantage to defenders, and without cannon assaulting a star fort seems pretty [difficult](https://www.reddit.com/r/AskHistorians/comments/1zgv1r/how_did_anyone_assault_a_star_fort_are_there_any/). > > The rounded shape that had previously been dominant for the design of turrets created "dead space", or "dead" zones (see figure), which were relatively sheltered from defending fire, because direct fire from other parts of the walls could not be directed around the curved wall. To prevent this, what had previously been round or square turrets were extended into diamond-shaped points to give storming infantry no shelter. The ditches and walls channeled attacking troops into carefully constructed killing grounds where defensive cannon could wreak havoc on troops attempting to storm the walls, with emplacements set so that the attacking troops had no place to shelter from the defensive fire. [[Wikipedia - Bastion fort](https://en.wikipedia.org/wiki/Bastion_fort)] > > > Add to that a modern [crossbow](https://en.wikipedia.org/wiki/History_of_crossbows) design with some kind of crank to fire quicker (something a 14th-century smith will be able to understand and reproduce), some low-tech ballistas and [springalds](https://en.wikipedia.org/wiki/Springald) in place of cannon, and your besieged army will not have to rely on "modern" tech. For modern (20th century) tech, some examples of useful things that fall far short of your 5B limit: * a goodly supply of [AK-47s](https://en.wikipedia.org/wiki/AK-47), famed for their ruggedness in face of harsh conditions, with appropriate ammunition of course. Ammunition may not be infinite, but a few cartloads make for lots of bullets, and after a few demonstrations you shouldn't need much. Add in a few boxes of sniper rifles that reach out to that marvelously inviting viewpoint some one or even two kilometers away that any enemy commander will be sure to (try to) make use of to see what devilry he is up against (your snipers can practice against a target there during peacetime), and some boxes of bazookas (some models are designed to be ridiculously easy to operate) for that really annoying guy who managed to build an iron-shielded siege tower or battering ram. No hand grenades, they'll just bounce down the walls and damage them more than the enemy can. * maybe some Claymore mines for people who get too close to the walls * shields (think Roman shields to hold over your head if arrows are raining down) and helmets with modern materials and design (the standard WWII German [Stahlhelm](https://en.wikipedia.org/wiki/Stahlhelm) was so good a design that the US Army found themselves using it later despite the distinctive shape, but even so it wasn't perfect and maybe some features won't be useful to you; see [here](https://historum.com/threads/military-helmets.126958/) for some nice points), maybe bullet-proof vests * modern health knowledge (sanitization, as noted in other answers, but also food storage and what I'd call "hospital knowledge", cleaning of wounds etc.) * really good armored doors instead of the wooden doors that battering rams are used on (consider also a [bent entrance](https://en.wikipedia.org/wiki/Bent_entrance)). * binoculars, and accurate maps of surrounding landscape (if the fortress is on an island or a peninsula with high cliffs, so much the better) * barbed wire -- *lots* of it. If you decide on providing electricity of some kind, then: * walkie-talkies to coordinate (otherwise speaking tubes should connect key points to the central command room!) * laser range-finders for the snipers * arc lights for checking the walls during the night, or, even better and needing less electricity, low-light/night vision goggles * some low-voltage electricity through a special barbed wire to alert when it gets cut or touched or pulled down into the mud Do use some *really* modern (at least 2020s or 2030s) tech for the batteries! [Answer] # Laputa | The Castle In the Sky | 99 red (hot air) balloons **Disclaimer**: You said you wanted simple but impenetrable, not practical. This would never work in practice, but on paper it would be awesome! The basic idea here is pretty simple. A Flotilla in the sky. A mass of hot air balloons tethered together via ropes/rope-ladders (to keep the flotilla together and to move between them). Sailing high in the sky beyond the reach of arrows and siege weapons, you're 'castle' will be impenetrable! Enemies would fear the sky knowing you are able to appear anywhere to rain death (rocks/poo/disease) from above (after some many years/luck to float to the right place)! Individual balloons could break of from the flotilla to briefly land, pick up supplies, and rejoin the flotilla (actually, this would be a logistical nightmare to coordinate, but plausible... with VERY long rope). If the supply balloon is hijacked, your archers can easily dispatch it from the enemy thanks to the high ground. This also acts as a fail-safe against people trying to sneak in, as a basket floating near the ground for 5 minutes is easier to defend than any wall/gate. You could also sell 'distilled cloud' to the people on land at exorbitant prices (actually pee. Plebeians never touched a cloud before, they don't know better) Your castle can easily grow to house as many as needed, as you can always add more balloons to the flotilla (again, a nightmare, but theoretically possible with just medieval tech, and blueprints/guide of how to do it with their tech) [Answer] The best defense is a good offense. Plan A moderately expensive Take good food storage, and make the walls out of concrete but the best siege is one that cannot be maintained. Give your castle machine gun nests, sniper rifles and mortars. Let the siege set up, then at night have your snipers open on command tents. Night vision will make this an unfair manicure. At their tech level they won't even understand what is happening. People will just die. Then open the mortars. These have range of three miles. If you are lucky there won't be an enemy army left. If you are not they will fall back miles seeking some protection never knowing how far is safe. Anyone trying to instead charge in, would find themselves sliced up by the machine-guns. Now you can no problem supply your castle as needed. Problems solved. If money is really not an issue. Convert your castle into a battleship. The core is a nuclear reactor designed for a modern carrier. There is enough fuel to power a carrier for decades. I would assume this could power the castle forever. Once you have power you can construct full battleship turrets. At this point range becomes 24 miles. These guns can be filled with shrapnel instead of solid shells making them devastating against soft targets. That's more than two days of an army march. No enemy would even think of cumming close to the castle again. . [Answer] **projection of force** I'm going take a very different approach from most other answers so far. I'll start by recapping, some key points, and then show some key differences: This fortress will have to endure: 1. Battering rams on the gate As has been said, anything on the order of reinforced concrete walls with a bank vault-ish door, are about as much as 'modern' tech would need, with actual medieval tech and practices like bad angles of approach, moats, etc. easily take care of even something like Grond (sans magic). 2. Balistas, catapults and trebuchets. No cannons. Again, medieval construction was already strong enough (other than the doors/gates? to deal with these impacts. Modern tech just strengthens doors and allows higher walls to help avoid having projectiles lobbed over the walls in to the courtyard or similar areas. 3. Starvation by means of cutting out supply lines. **This, to me, is the most important aspect of this whole exercise.** Without addressing this issue, as others have pointed out, the 'castle' becomes a prison. Stocking it with any amount of food or water supply, no matter how long that food and water might last, just makes it a well stocked prison. To prevent this issue, I'd suggest a spiderweb of tunnels (with strong enough walls, they wouldn't even necessarily need to be hidden underground, just completely enclosed above to prevent climbing over walls and in to the pathway) radiating out from the main structure. With modern technology this could be accomplished relatively quickly, easily and inexpensively, and the tunnels could cover much longer distances than medieval tech could compete with (a mile or three, think an hour or two march for a military force). A significant number of exits, both hidden and visible, at varying distances and directions from the main castle would make it very difficult, if not impossible, for a besieging force to guard them all. They would either spread themselves too thin, or leave some unguarded where the forces in the castle could exit. When they do exit, they can harass the besieging force from any number of directions, or simply keep supply and communication lines open. Using tunnels going 2 miles in the 4 Cardinal directions, and 4 more going in the Inter Cardinal directions, with exits at the half way points and the ends, plus the castle's main gate (and any secondary gates), that gives the besieging force 17 gates to try and guard, with an outer perimeter of more than 12.5 miles to spread out their army. Spreading an army over a front line 12 miles long will quickly make the line very thin, while concentrating it will leave openings that the castle defenders can easily exploit through unguarded tunnel exists. An attempt at a direct assault, even not considering the castle's walls and gates, would allow the defenders to exit at a distance farther out than the assault force, and pin them between the defenders inside the castle, and the defenders outside the castle(think [siege of alesia](https://www.youtube.com/watch?v=SU1Ej9Yqt68), except now the defenders can get out of both sets of walls and pin the besiegers against the walls). If you expect the castle defenders to encounter a large enough force to maintain a 12 mile wall of soldiers, add another mile or two to the tunnles, and a third (and 4th?) set of exits. Tunnels 3 miles long makes the besiegers need to cover almost 20 miles, 4 mile tunnels gives them 25 miles to surround. 4. Possibly, ladders and siege towers. Again, higher walls and the possibility of far greater overhang takes care of this. 5. Sapping (not mentioned in the origil question, but brought up repeatedly in other answers, and certainly worth considering) **Here I will differ significantly from other answers, again**. Others suggest taking the wall very deep, so that undermining them is very difficult. I'd suggest making it very easy to undermine, but useless to do so. To do this, simply make the entire structure self supporting, not relying on any foundation for the integrity of the walls themselves. Modern tech can actually [do this even accidentally](https://i.redd.it/dm1w4ae2d6vz.gif), so if we intentionally build the entire 'floor' and walls of the castle specifically to maintain structural integrity, they could tunnel under one(front) wall, under the floor, under the other(back) wall, and out the other side of the Castle with no negative effects on the castle itself or the walls. Let them dig, it does no good. If desired, even backfill the courtyard with soil, if needed, so horses don't hurt their feet on concrete, etc. 6. Bonus points if the answer manages to give a great solution to the problem without needing overly complicated technology to keep working Did I get the bonus points? [Answer] So you want the medieval castle build with modern methods to withstand: > > Battering rams on the gate > > > Balistas, catapults and trebuchets. No cannons. > > > Starvation by means of cutting out supply lines. > > > Possibly, ladders and siege towers. (I say "possibly" because it would be a nice addition, but as long as the other 3 problems are covered, this can be handled by the soldiers.) > > > No medieval castle was totally impregnable. No medieval castle was 100 percent guaranteed to totally withstand any possible medieval assault, or starvation, or treachery, or surrender of the garrison after they had held out for a long time but saw no possibility of being relieved. The facts are that medieval sieges - both successful and unsuccessful, lasted for days, or weeks, or months, or years, and sometimes over a decade, before they either succeeded or were given up. So it is a good idea to study the longest lasting medieval sieges and see what made them last so long before they either succeeded or failed. Part of the reason why some medieval sieges last so long was because the attackers had the will and the resources to keep on attacking or besieging for months or years instead of giving up after a few weeks. This means that some of the short sieges may be worth studying too, to learn why the besiegers gave up after a short time. Here is a link to a long, long, long list of sieges: <https://en.wikipedia.org/wiki/List_of_sieges>[1](https://en.wikipedia.org/wiki/List_of_sieges) Note that most of them, even in the medieval period, were sieges of towns and cities. But there are many sieges of castles listed during the medieval period. So you can learn a lot from the designs of fortresses, castles, and cities that withstood long sieges. And you can also try to find out which castles (like Chateau Gaillard, Krak des Chevaliers, Coucy, Caernarvon, etc., etc.) and cities (like Constantinople, etc.) were considered to be the strongest in their times. So after your research identifies the features of the strongest castles and cities and other fortifications, you can hope to duplicate those features in your fictional castle, city, or fortification, only more so, of course, using the superior modern technology of 2018, or of 3018, or of 201,800, or of whenever your time travelers come from, or the superior technology of an alien civilization that might be millions of years more advanced than 13th century Earth. A number of highly impressive structures were build by manpower alone in ancient times, and the main superiority of ancient societies over medieval societies was that ancient societies were were better organized and could better organize the efforts of hundreds and thousands of laborers on projects. So a futuristic society with time travel, or an alien society advanced enough to reach Earth from another star system in our middle ages, would have two possible advantages when building even superior castles, cities, or fortifications than medieval society could. 1) They could use modern earth moving, quarrying, and construction equipment and power tools - only far more advanced than those of 2018 since a society capable of time travel or interstellar travel would be far more advanced than Earth in 2018. 2) They could use the same primitive tools and methods that ancient and medieval societies did, but replace the human muscle power used by ancient and medieval societies with the power of humanoid robots. Tens of humanoid worker robots, or hundreds, or thousands, or tens of thousands, or hundreds of thousands, or millions of worker robots. Problem number 1: > > Battering rams on the gate > > > Modern day police and military special forces still sometimes use battering rams to break into buildings. But the modern ones are pretty small and look like only two men can swing them at a time. Thus they can batter down ordinary modern house doors but would probably be useless against bank vault doors or medieval castle gates. I believe that very long battering rams (and also picks to pick apart castle walls) swung by many men were used in medieval times. And one defense against that was to avoid straight, perpendicular, level approaches to the gates. Instead the approach to the gate would be landscaped or built so that attackers with battering rams would have to approach and swing their rams diagonally, and/or uphill, and/or around a sharp right angle turn (or two sharp right angle turns), or else use very short battering rams which only a few men could swing, thus without enough force to batter open the gates. And of course many gatehouses were highly defensible miniature castles. Many gatehouses had an inner and an outer gate separated by a passage, which of course could zigzag to prevent using long battering rams. And the passage was usually a killing zone with arrow slits and murder holes in the ceiling. And one idea to make the inner passage of a gatehouse even more of a killing zone would be to put it over a deep pit with wooden stakes at the bottom. The floor would be a wooden trapdoor or drawbridge keep horizontal. When attackers were on the drawbridge floor it would be released dropping the attackers dozens of feet to be impaled on the spikes or stakes below. Then the drawbridge or trapdoor would be drawn back up to a horizontal position for the next bunch of attackers. Another idea to make a gatehouse stronger would be to have emergency gates that could be lowered behind the inner wooden but metal reinforced gate. Each gate that would be slowly dowered down behind the inner gate would be a single giant slab of stone, or a masonry wall made of many stones, or a hollow metal gate filled with concrete. And these emergency gates would be slotted in so that each fitted against the back of the previous one. When they were all lowered into position they would form a solid wall behind the inner gate that could be as thick as the outer walls of the castle. Once the siege or attack was over the castle defenders would no longer be able to use the inner gate to get in or out until they slowly winched up the many emergency gates behind the inner gate, which depending on how much modern power equipment they had, might take months. So in the meantime they would have to use a weaker side gate in the inner passage of the gatehouse. If attackers broke down that side gate they would find themselves in a space between inner and outer walls of the castle. The outer wall would have crenellations on the inner side as well as the outer side so that archers on it could turn around and shoot down at any attackers between the walls. The inner wall would be a lot higher than the outer wall so archers on it could shoot down at any attackers who got on top of the outer wall. The space between inner and outer walls would run all the way around the castle but it would be divided into perhaps a dozen smaller spaces by cross walls with gates in them, so attackers would have to fight their way all around the castle and batter down maybe a dozen gates before coming to a space which had a gate leading to a gate in the inner wall. And just to make things harder for the attackers there could could be deep pits with stakes outside each gate, or maybe filling the entire space between walls, and trapdoors to drop attackers into those pits. So once the attackers battle their way through a dozen gates around the castle and batter down the gate in the inner wall, they can enter the ward of the castle - the **outer** ward of the concentric castle. And they see another gatehouse and another set of double walls ahead of them. And know they have to repeat the previous process to get through the next two walls and reach the inner ward of the castle. Or possibly the *middle* ward of the castle if the concentric castle has three wards. Some castle experts would say that such elaborate plans would be unnecessary gilding the lily since many medieval gatehouses were already the strongest and least vulnerable parts of the castles, so that it was common for it to be easier to breakdown and enter the walls of a castle instead of the gatehouse(s). So the question should really be how to defend the walls against battering rams. Many medieval castle walls were not built very well. They would have inner and outer walls made of large rough stones with a lot of mortar between the stones, and the space between the two two walls would be filled with smaller stones, pebbles, and dirt. Such walls were comparatively easy to battler down with rams or picks aimed at the mortar between the stones. That may be why many medieval castle walls were covered with stucco and whitewash, to hide the gaps and week spots between stones. Defenses against attacks on the wall were: a) Very sturdy and well built (and very expensive) walls. With the advanced technology of 2018, to say nothing of the far more advanced future or alien technology available to your castle builders, it should be comparatively easy to build walls out of vast quarried blocks of stone or poured concrete slabs, with the total widths and heights of the walls hundreds or thousands of feet or meters. b) Passive prevention of enemies from reaching the walls of a castle to attack it. Thus there could be a steep slope outside a castle wall making it difficult to pick or batter at the wall, or a deep wide moat outside a castle wall making it difficult to pick or batter at the wall, or a moat with a slope inside it, or a moat with a slope outside it, or a moat with slopes both outside and inside it. Many castles were built on steep hills or mountains, and many had deep wide moats or lakes, sometimes concentric moats, as water defenses, like those of Kenilworth castle. c) Active prevention of attackers from reaching the walls. The defenders would shoot at attackers to keep them from reaching the walls to try to break down the walls. The goal is to design the castle so that the number of defenders it can hold can defend it against tens, or preferably hundreds, or preferably thousands, of times as many attackers. Defense against the second threat: > > Balistas, catapults and trebuchets. No cannons. > > > Discussing defending the walls against battering ram attacks, possibility a) was: Very sturdy and well built (and very expensive) walls. With the advanced technology of 2018, to say nothing of the far more advanced future or alien technology available to your castle builders, it should be comparatively easy to build walls out of vast quarried blocks of stone or poured concrete slabs, with the total widths and heights of the walls hundreds or thousands of feet or meters. Build the walls many tens of feet thick, or hundreds of feet thick, and balistas, catapults, and trebuchets will be unable to seriously damage such thick walls. This will also be a pretty good defense against any cannons likely to be invented in the next few centuries. Possible defense b) Also use advanced technology to build more advanced balistas, catapults, and trebuchets than medieval persons can build. Balistas, catapults, and trebuchets so advanced that ideally they can shoot farther than medieval built ones stationed a hundred feet higher than they are. Then build the walls of the the castle hundreds of feet higher than the highest position close enough to reach the castle with medieval balistas, catapults, and trebuchets. Station your advanced balistas, catapults, and trebuchets on top of those walls to rain death upon anyone who sets up their balistas, catapults, and trebuchets in range of the castle and to slaughter the crews of the medieval balistas, catapults, and trebuchets and wreck those devices. If the attackers pull back their medieval balistas, catapults, and trebuchets to get them out of range of your advanced balistas, catapults, and trebuchets they will have to pull them so far back that they will no longer be able to reach the castle. Note that women and children can fire balistas, catapults, and trebuchets from the walls of castles and cities and have done so in many sieges, so that refugees can become defenders during sieges. Defense against the third threat: > > Starvation by means of cutting out supply lines. > > > Many castles and cities were built in places where the irregular lay of the land dictated the irregular outline and layout of the defensive walls. But many other castles and cities were built where the builders were free to choose the exactly layout of the defense walls and outline of the castle of city. And when castle and city builders had free choice of what plan to use, some chose less wisely and some chose more wisely. If the methods of defending your castle require one defender for every X feet of outer curtain wall, you better make certain that your castle has no more feet of outer curtain wall than X times the expected number of defenders. The maximum total number of defenders your castle could possibly hold, or the usual number of defenders your castle usually holds, will depend on part on the accommodations for defenders within the castle, which will depend in part on the square footage within the castle. Suppose that a walled enclosure has 10,000 square feet of ground and is 1 foot by 10,000 feet. it will have 20,002 feet of wall for 10,000 square feet, or 0.4999 square feet for every foot of wall. Suppose that a walled enclosure has 10,000 square feet of ground and is 2 feet by 5,000 feet. it will have 10,004 feet of wall for 10,000 square feet, or 0.9996 square feet for every foot of wall. Suppose that a walled enclosure has 10,000 square feet of ground and is 10 feet by 1,000 feet. it will have 2,020 feet of wall for 10,000 square feet, or 4.950 square feet for every foot of wall. Suppose that a walled enclosure has 10,000 square feet of ground and is 20 feet by 500 feet. it will have 1,040 feet of wall for 10,000 square feet, or 9.615 square feet for every foot of wall. Suppose that a walled enclosure has 10,000 square feet of ground and is 40 feet by 250 feet. it will have 580 feet of wall for 10,000 square feet, or 17.241 square feet for every foot of wall. Suppose that a walled enclosure has 10,000 square feet of ground and is 80 feet by 125 feet. it will have 410 feet of wall for 10,000 square feet, or 24.390 square feet for every foot of wall. Suppose that a walled enclosure has 10,000 square feet of ground and is 100 feet by 100 feet. it will have 400 feet of wall for 10,000 square feet, or 25 square feet for every foot of wall. So, out of all possible rectangles, a square shape gives the least amount of wall to be defended for the same square footage inside. But a square is not only a type of rectangle, it is also a type of regular polygon. A regular polygon is a many sided geometric figure where all of the sides and all of the angles are identical. Many other types of regular polygons have shorter perimeters than a square for the same area enclosed. The extreme form of a regular polygon is a circle. A circle with a radius of about 56.4189 feet and diameter of about 112.83796 feet would have an area of 10,000 square feet and a circumference of about 354.49 feet, and so would have a ratio of about 28.2095 square feet of area for every foot of perimeter wall to be manned. And that is important because one way to avoid having your castle or city starved out is to grow sufficient food within the castle or city to feed the defenders. Suppose that each person in the city or castle needs an average of one acre to grow food for himself and one tenth acre for other purposes. Suppose that a million people live in a city. They will need 1,100,000 acres of land to grow food and for other purposes. Therefore, with 43,560 square feet in an acre, a total of 47,916,000,000 square feet would be needed, or a square 218,897.23 feet, or 41.4578 miles, on each side. It would have a total of 875,588.92 feet on all four sides. If there were 1,000,000 people in the city, and 0.25 of them were adult males, there would be a total of 250,000 defenders, so each side would have 62,500 defenders spread over 218,897.23 feet, or about one defender every 3.5023 feet, which seems adequate to defend a wall ten feet high, let alone one hundreds of feet high. A circle with an area of 47,916,000,000 square feet would have a radius of 123,498.98 feet or 23.3899 miles, and a circumference of about 776,000 feet, with about 3.104 feet per defender. If the walls are hundreds of feet high and thick one defender should be enough to defend hundreds or thousands of feet of wall, so each fighting man could spend a few weeks a year training and stationed at the walls, and the rest of the year tending his farm which could be miles deep within the vast fortress. Of course medieval methods of farming might require several acres to feed one person. But if the time travelers or aliens introduce more modern methods of agriculture, or hydroponics, or aeroponics, or food synthesizers, they may be able to feed many tens or hundreds of people per acre, and a fortress with a population of a million and 250,000 fighting men might be very tiny compared to one 46.7798 miles in diameter. Or the super advanced aliens or time travelers might use their high technology to dig vast tunnels through the rocks for tens and hundreds of miles to various locations where their exits might be very strongly fortified. So supplies purchased in distant locations could be secretly brought in to the castle deep underground without besiegers knowing or being able to stop it. Defense against the fourth threat: > > Possibly, ladders and siege towers. > > > Making the walls hundreds of feet thick and tall would be a perfect defense against ladders and siege towers. Putting concentric rings of steep slopes and moats around the castle, fortress, or city would also help defend against ladders and siege towers by keeping them away from the walls. [Answer] You definitely could do it so you can keep maintaining with 12th century technology while minimizing the costs. Build your wall with bunker quality concrete, check. Its height should be enough to avoid incendiary projectiles to pass over it. You have to specifically worry about trebuchets. Make sure there is no any high terrain within 200 meters of the walls where these can be placed to shoot higher. I estimate the height of the walls should be at least 30m (100ft). I would keep it under 40m to avoid the defenders getting too tired when climbing up. Anyway you would also have some light elevators (made of aluminum) pulled by horses and/or men. Horses eat a lot, you won't be able to keep them once their food reserves are over but you can turn them into food. Given the height, the angle of the stone projectiles will be almost vertical. You could design ammunition that projects darts around on impact. Leave the molds and tools so they can cast more. They can make them of Roman concrete and iron. The outer wall would be a Bastion Fort (as mentioned before, with a sort of star shape) to take advantage of the war machines and crossbows. Use the inner walls to build terraces for crops. [](https://i.stack.imgur.com/0dcN4.png) These terraces can help to collect water when rains are abundant but you would combine this with other water collectors and a well. Most of the buildings will be within the wall so all the inner terrain would be profitable for crops. All academic theses indicate that medieval agriculture lack of productivity was greatly derived from [decision making mistakes](https://en.wikipedia.org/wiki/Agriculture_in_the_Middle_Ages#Productivity), not lack of knowledge, so they should suffice to survive. You should however have enough preserved foods so to tackle bad crops (cans can last up to a century). Think of climate control for maximum energetic economy, install solar heating (non electrical) for cooking and heating water. Use state of the art insulation techniques and green architecture design. Build improved war machines and crossbows with modern materials. You can even stash replacement parts to repair them after they wear off. Provision of ammunition might become a issue even if you make reserves, and have some trees and piles of stones to make more. But a battle might be won with a fraction of these reserves (i.e let them come, then target their war chiefs). Build railways at different levels of the wall with drasines to quickly move troops and war machines along the perimeter. The gate: install the gate on top of a ramp made of concrete; you can also seal it completely with a curtain like concrete door made of a few embedded stripes reaching the basement and wait till the enemy is gone to open it with pulleys and counterweights. If you feel insecure, replace it with a titanium alloy door with shock absorbers behind. Could you build it in 20 acres for 200 habitants? (I'm trying to cut costs here), you could, and the wall would be indestructible, but since the height of the wall allows it you can build multiple levels of loopholes to fire outwards. It will be better to do it in 200 acres for 2000 fighters so they can shoot massive volleys. Final note, the spectacularity of the walls should be enough to discourage any medieval invader to attempt an attack after failing the first time. The reasonable strategy would be to siege, only to discover years later that this doesn't work either. The longest siege in history took 22 years, it was the siege of Candia in the 17th century. The siege of Philadelphia (14th century) lasted 12 years. In both cases the defenders faced the resources of an empire, and the city fell. Exceptional cases as they are, one can estimate this fortress to be practically impregnable. [Answer] **You have five things:** * the castle * your men * the enemy * supply storage * everything else You want the castle to be as large/impenetrable as possible. Since you have modern-technology, there are many ways to make this near-impenetrable (impossible is possible). Find a place (too remote you won't be able to get supplies) that is easy to defend, easy to get supplies to, and hard to attack. A snowy mountain range would do. The castle keep and walls could be titanium-reinforced concrete, using the strongest concrete in the world. And you could make them as tall as needed (minimum would be 25 feet tall and five feet thick) and deep (10-25 feet) since you don't want the enemy to collapse them. if you build the walls a certain way, they won't collapse anyway. Put barbed wire near the tops and middle to keep out climbers. Since your on top of a mountain in a snowy environment roofs would need to be put over the walls to keep out snow. guard towers should have fireplaces that are seen for a few miles. During siege you can put special powders that you stake up on in the fire to spook the people attacking. Build a really tall watchtower(100-200 feet) with a roof for the snow, a lighting rod (cause no one wants to get electrified) with 360 degree view and put good binoculars/telescopes in. It'll be really hard for an enemy to sneak up. The gate can be concrete curved to withstand a battling ram, with windows above the gate so defenders can easily attack. A portcullis could be built easily and made out of titanium, so a medieval battling ram will have a hard time. other things to defend: mini catapults/trebutchet and balistas in the towers with oil. Using modern machines build an easily defensible switchbacks down the mountain into the small valley below. A town at the foot of the mountain, with its own tough walls, defenses, and moat, could be built down there and the farms also. *Your men:* Since you have modern technology, build your army stainless steel(or titanium but if you want to) weapons, armor, and such. The town can have a cavalry with armored horses or other big beasts your able to tame using modern tech (bears, wolves, mountain lions, mt. goats). *The enemy* The enemy comes and overtakes your town somehow. If they start up the mountain, flaming oil and rocks could be launched at them and no human formation can withstand that. Build gliders for people to fly over the enemy and drop unpleasant things on them. If they make it to the castle use gunpowder bombs(it was used as a weapon in 904 AD) and eliminate them. *Supply Storage* Build large bunkers under the keep (large with thick walls) and store up for a decade. With this castle, no one in the right mind would waste time attacking a seemingly impenetrable fortress for a decade. Another thing. Build greenhouses. It would be hard but feasible with modern tech; build large plexiglass or metallic glass(invented in the 20th century and as strong as steel) as the material and make suitable for crops(rich dirt etc). Put this inside your castle and you could last even longer on greens. *Everything Else* There's not much else but if your have extra money, build a few more castles and towns under your control. If you go with a design like this and keep them close together so they can back each other up. Get a suitable army built up and your good! [Answer] Modern tech? Oh boy. Depending on how long you need to hold out for and what you can bring in.... Modern construction and plumbing can do quite a number. Any medieval force you're up against is probably going to have to walk, or ride up to your base. Modern concertina wire is going to do a number on *any* enemy you meet. Unlike many of the other suggestions, I'd go with building somewhere flattish with lots of open ground. *You* control the killing fields With modern contruction equipment you can build a series of berms, with nasty surprises at the bottom. Imagine your horses going down a slope into a series of shapened, rusty metal fence posts. For power I'd suggest an unusual step. Get generators and the equipment to maintain them. If possible set up facilities to refine metals. While in the modern context, we wouldn't power a generator that way - you could probably use animals to power your generators, either directly, or by being used to pump water up to storage tanks. You could also solve the "seige" problem with modern food tech - canned food lasts for years as would freeze dried food. You could wait out your enemies. You could also have fish tank and use the water from that and your waste cycle to grow fresh food internally. Now, offence. We did talk about modern equipment and nasty surprises right? You could probably hose down invading armies at a distance with spare waste. You could flood the surrounding area into a mire. The best time to defeat the enemy is *before* they attack. Now defence. I'd go old school here. Reinforced concrete is awesome and all, but if you had the lifting power, I'd go with big, multitonne blocks of basalt or granite. Its what the planet's made of, and I'd rather go for nice, *thick* walls for the outside walls. Add a couple of high towers to snipe your wet, foul smelling enemies for further demoralisation. Have *lower* internal structures your enemies can't see. If modern weapons, or even semi modern weapons are an option, add some mortars inside with fixed kill zones and pummel em as they come. The goal here of course is to make your enemies lose the fight before they reach your walls. Even if they do, you have power, food and other means to make their life miserable. [Answer] You do not need much to resist a medieval siege. Realistically all you will need is a reinforced concrete dome with a vault door. If you want something cool you might want a huge skyscraper with high walls with a vault-like door. You would want a concrete roof with solar panels and farms covered by bulletproof glass. You might also want Sentry guns all around the walls and a few on the roof. You might also want a huge basement to retreat into with a huge vault door. The basement should have fish tanks, animal pens and tunnels to retreat/counter-attack from. Your base should be on an underground river bared entrances. And have a good sewer system with bars and Sentry guns at the entrances. You should have HUGE batteries to power the Sentry guns. Any medieval catapults will just bounce off the walls and siege towers will get torn to shreds with the Sentry guns. Your fort will last until cannons were invented and the solar panels break down. But you should keep machine guns and Automatic rifles handy for when the sentries run out of ammo. ]

[Question] [ ## A free-market solution to preventing further domestic abuse This society has gone full-on free-market everything including the punishment of severe domestic abuse. As a check on the abuser, the abused is granted a perpetual (or very long, 20 years or so) murder-right on the abuser, and only the abuser. This murder-right is the right but not the obligation to kill the abuser at any time. We note that the abused are frequently strongly averse to violence themselves (or they might have resorted to it earlier in their own self-defense). For this reason, the murder-right can be transferred to a third party with the stipulation that the right can only be exercised when the restraining order is broken. The murder-right and accompanying restraining order are granted by the court after the abuser is convicted of serious domestic abuse. Should the abuser restrain themselves, they have nothing to fear. So we have an NGO that buys murder-right contracts from the abused then exercises them when needed. However, killing people is expensive. One has to keep track of them, weapons need replacing, ammo isn't cheap, legal retainer fees add up quickly...and good sociopaths are hard to come by. This NGO needs to make money and lots of it. **What is a viable, long term business model for this NGO and how do they make a profit? The NGO must pay the abused for their murder-right in a one-time payment. It should also be resistant to bribery by a very rich-abuser (though getting paid twice is always preferable).** **Out of scope** * This NGO only deals with serious, long term domestic abuse. Peeping toms and other lesser offenses are just out of scope. Murder of the abused is also out of scope. * This question does not deal with defining processes for determining if a restraining order has been violated. A magic oracle determines if the order has been violated or not. * This question does not deal with determining exact definitions or gradations or styles of domestic abuse. This question only cares about 'serious domestic abuse' * How the abuser is killed is out of scope unless the method for death somehow makes money for the NGO. * How an abuser might protect themselves from this NGO unless those protection measures are means of income for the NGO. * While it's likely that there would be more than one NGO, this question only addresses the business model of a single NGO. Describing market dynamics between multiple NGOs is a [separate question altogether](https://worldbuilding.stackexchange.com/questions/134258/market-dynamics-of-ngos-who-buy-murder-rights-on-convicted-domestic-abusers). * Proposal for a different market system for dealing with market abuse is also out of scope. *Note to downvoters, if you would be so good as to explain why you're downvoting, that'd be really helpful, thank you.* **Further Reading:** * [PRIVATE CREATION AND ENFORCEMENT OF LAW: A HISTORICAL CASE](http://www.daviddfriedman.com/Academic/Iceland/Iceland.html) - A description of a heavily market driven approach to the punishment of murder. [Answer] ### Live-Streaming Have you ever heard of *Twitch*? The streaming platform that allows you to let other people watch you play a game and give you donations if they like to watch you play? Where hundred or thousands of people watch as you are playing *live*? The streaming platform where you, as a person sitting in front of your PC at home, can watch virtual characters be blast to bits, cut up or be killed in innumerous other ways? You can simply adapt their concept to your world and have people pay to watch the execution. It's full-on-free-market after all, so why not make some money with the execution? Depending on the restraining orders you would have different executions, making it more... varied... for the people watching. You could even expand this. Once the magical oracle tells you that someone can be killed without any consequences you can start the live stream. You don't need a lot from each one watching - just a little donation every now and then, maybe a subscription service for less advertisement on the site and access to background checks of the former abusers, ... silver and gold memberships to have increased voting rights when it comes to execution methods, different camera angles, ... > > And now, Ladies and Gentlemen, we will start the tracking. Let's look at the cameras around his house first and see if we can find our first clues as to his whereabouts. > > > In the next room my assistant is starting to prepare the execution method. Switch to camera three to follow him or stay with me to see how we find this one. We have a great assortment this time! It will take some time to find him and that's why it will also take some time to finish him - you know the drill. > > > For a recap about the history of this one you could switch to camera two, where we have detailed all important stuff. Everything, from birth to soon-to-be death! > > > Leave comments to have a chance for a T-Shirt if we choose your little torture trick before killing him. As always: have fun! And don't forget to donate - we need the money to help the poor victims of domestic abuse get their well-deserved revenge and to help them with their mental therapy afterwards. > > > Afterwards you could sell the *tools* used in the tortur-... production of the stream as "Limited Edition" stuff. And the platform could be licensed to others who may want to stream... unconventional... stuff... [Answer] In addition to the other ideas: sell organs. Kidneys, heart, bone-marrow, skin. What's left goes to the catfood factory. [Answer] The NGO could auction off the rights themselves to the highest bidder once the restraining order terms are violated. There are likely people who would pay to be able to hunt a human legally, especially if there are no limits on how it's done, assuming that only the abuser is hurt. Another source of income is trophies and footage. Once again there are likely people who would pay for memorabilia from abusers who have been assassinated, or for snuff films. One way to make it more resistant to bribery is to have a somewhat transparent process, and having multiple NGOs. You want transparency, because if the right just disappears from the list someone should know. And having multiple NGOs means that if one is shown to be dishonest then people won't choose to do business with them. If the person who wins the bid is kept confidential, then it makes it slightly harder for a rich abuser to bribe them. Also, all contracts should have a time limit. If a violation happens, the NGO has X amount of time to bid it off. Once it is bid off, the assassin has X amount of time to carry it out before they lose the right, and then bidding happens again. If the assassin fails, then bidding starts again. This way there is some assurance that justice will be done, as you can't pay off everyone. If the NGO fails to get the job done in a certain amount of time, then it goes to another NGO. [Answer] ## Hunting Safari They sell hunting safari for wealthy gentlemen that grew bored of shooting lions. They will go abuser-hunting now, and will likely pay a little fortune for that. Once an abuser break the restraining order, the NGO takes its client to the neighbourhood, provide them with guns and a picture of the abusers and let’s go! Of course, they will also organize back-up and picnic, so the wealthy hunter is not killed by the prey and doesn’t get thirsty. [Answer] Maybe nobody wants to go there but . . . the most obvious answer is . . . ## Slavery Honestly, I don't know how this answer has been missed with so many answers here . . . but if you have the legal ability to kill a person, it's fairly obvious you have a right to **not** kill them, provisionally. In this case you have de facto slavery. As long as the abused has the right to kill a person however or whenever they want, all they have to do is say "I won't kill or torture you now provided you do X, Y, and Z." Most people have enough desire to live (or not be tortured to death!) that this will motivate the typical abuser. This obviously has the potential to bring the abused down to the level of the abuser, but if you are simply looking for a way to make a profit . . . slavery is profitable. Immoral and reprehensible, of course, but profitable. [Answer] The trick here is to be paid twice for the same job. # Abuser elimination as a service The first question is as follows, what went wrong in your market that the NGO is buying the rights when they should either be being paid for the service of removing the person in question or accepting a contract to remove the person pro bono publico? The victim should be paying the organisation, not the other way round. After that it's just a matter of selling the right to legally kill someone into a suitably sociopathic market. One person removed, two paychecks. Depending on the culture, you can now add other options. [Battle Royale](https://en.wikipedia.org/wiki/Battle_Royale_(film)) for example, all the targets are rounded up, placed on an island and the survivor after a week gets to live (at least long enough for the post production interviews). Television rights provide the funding. [The Running Man](https://en.wikipedia.org/wiki/The_Running_Man_(1987_film)), again a TV game with the winner getting a tropical island holiday (there are never any winners). There are any number of ways of making money out of televising the hunt. --- Let's consider some nice dystopian price schemes # Free One could call this pro-bono, but it's more Jerry Springer, you could go as far as paying an appearance fee in this case. Nobody is interested in seeing some random person fighting to the death in an arena, they need a story, a reason to be involved. The victim has to go on screen and tell the world what happened and why they're using this option. # Freemium There's a cost to being anonymous, a cost to hiring an actor to tell the story rather than having to do it in person. You can pay for anything on the scale from here to: # Executive premium There's only one paycheck for this one and that's from the victim. There was an abuser yesterday, today there isn't. No word, no sign, no body, just gone. [Answer] If you want to be cynical, how about re-selling the murder right, at a tidy profit, to the *abuser* himself? You get paid, the victim gets paid, the abuser gets to be safe, . . . everybody wins! [Answer] The most obvious opportunity for profit would be for the NGO to accept payments from non-abused parties to fulfill the murder. So let's say I want to kill my boss, and my boss is an abuser who the NGO has the murder-right on. I'm willing to pay the NGO 1 million dollars to fulfill that murder. But as soon as this enters the equation, the abuser is being murdered for non-abuse reasons, since only the murder right is transferable, not the murder reason. A separate case could (and should) be filed against me for conspiracy to commit murder, and I wouldn't be able to claim domestic abuse. The only assumption we are making in this scenario is that an abused's right to murder their abuser is transferable. Just because this very dark assumption is true in this scenario does not imply that any other dark assumptions can be made. We assume the NGO must be able to profit from this murder in a legal way. I will accept the assumption that being able to sell your murder-right means that the murder-right can be legally purchased, and thus the murder itself would be legal, but I would limit that assumption to the murdering of the abuser in a pre-determined "legal" way, such as the murder being done in a way that would be deemed ethically and morally sound. A starting off point for what "legal ethical" murder would look is the Geneva convention and other global military agreements on warfare. This means the abuser can't be tortured, can't be treated in a cruel or unusual way, can't be killed via biochemical agents (like sarin or anthrax, etc). I would say that live-streaming isn't an option because for one it would violate the abuser's right to privacy (which they would maintain before and after death, like anyone else), and it would probably violate laws regarding creating a violent scenario for the purpose of profit, something along the lines of what makes Bum Fights potentially illegal. If we assume a world where public execution is reintroduced, I would argue that it has been reintroduced as a right for anyone to attend an execution, making it some sort of public service, and thus not something you could make prohibitive to attend by charging money. If we think of it like airwaves as being a public good, at best someone might profit from filming the event and providing access to that stream, but that wouldn't be the NGO (directly) but more like YouTube or ABC (it would be a media market, not a direct "we kill em, you pay us to watch us kill em" market). As for making it an auction on who gets to kill the abuser, I would argue that if the murder-right is transferable but expected to be done ethically, that those committing said murder would likely need some form of licensing, demonstrating they are capable and qualified, etc. We are letting these people commit legal murder, so they need to be registered in some way to do this. This would also rule out the "human safari" idea, as it should. If we introduce some sort of Running Man scenario where anyone who sees the abuser can kill them, we open the door to a lot of liability. We have no assurance that the murderer will murder the abuser in an effective way (what if they just maim them, and the abuser runs off, does that person get away with stabbing someone in the leg just because the person was an abuser? And how can we know for sure that people wouldn't pay just to "try to kill" the person, with no good faith that they will actually do so?) So if the person is licensed to murder, we're looking at a sort of Uber for murdering. The NGO is the company that buys the rights to murder, the murderer is a free-agent licensed by the state to facilitate said murder. Which sounds like something people would register for to *make* money, not to pay for the privilege of murdering someone. Harvesting organs is a clever idea, but would still require a law that made it legal to do so. Otherwise the abuser still has the rights to their organs and what is done with them when they die. The most obvious opportunity for profit, with all of the above taken into consideration, would be via a life insurance policy. Something similar to companies that exist now that buy life insurance policies from people (especially the sick or elderly) and pay them a lump sum percentage of the policy now and change the company to the benefactor. This wouldn't count as insurance fraud (though it may drive up insurance premiums on high-risk policies, like where the person is a likely abuser) any more than buying the life insurance policy from someone with terminal cancer. Because the NGO only fulfills the murder if some restraining order is violated, they aren't the agents of the life insurance policy becoming effective, the violation of that restraining order is what killed the abuser, the NGO simply implemented said death upon violation of that restraining order. But I imagine this would require the abused to be the benefactor of the policy as well as having the right to change the benefactor to the NGO. In other words, the policy would be one that the abuser didn't have any control over. If the policy has to exist in advance for this to not be considered insurance fraud (buying a policy knowing that there is a high likelihood of a very-soon death would be expensive, and not disclosing this would be fraud), this could also be tricky. The abuser would essentially have to have already gotten such a policy before discovering the abuser was actually an abuser (maybe some sort of pre-nup type thing). This model would also work (albeit very slowly over time) because the NGO would profit whenever the abuser dies, even if they never violate the restraining order. If they have a heart attack or get murdered by their current spouse (who they are certainly also abusing), or just walk in front of a bus one day, they die, the policy pays out to the beneficiary, the NGO. Aside from all that, the NGO could potentially profit from media rights to the story itself. They are not only buying the murder-right to murder the abuser, but the right to profit from any media based on the abusive relationship, the murder itself, etc. Things like selling books, T-shirts, made-for-tv movie scripts, etc. I don't know how much that would be worth, but the underlying idea being that the NGO could find vectors beyond the murder itself to profit from, assuming they buy them at the same time as the murder-right. What else does the abused have of value beyond the murder-right is the question. [Answer] There seem to be several income sources. I'm going to shotgun them rather than flesh out any specific one too much: 1) The abused: The abused could pay for the privledge of being protected by the NGO, either in dollars or labor. 2) The public: They could pay to watch the killings. Especially if the killings are done in a 'sporting' fashion (like "The Deadliest Game" or "Abuser vs. Lions" or "Death Race") a lot of revenue can be generated. 2a) Gambling on the outcome. 2b) Sponsors/ad revenue. Esp. if there are competing teams each sponsored by a different company (or companies) like NASCAR. 3) The public: It's possible if the NGO is also a non-profit, that they can solict sufficent donations. I would expect a lot of the abuseds' stories would be useful fundraising tools. 4) The sick: If the rights go beyond simply murder, to ownership of the body, and selling organs is legal, the organs would be source of income. 5) Psychopaths: Killing a person may be a ultimate hunting trophy. People might bid on the opportunity to be the executioner. Especially if combined with a sporting aspect like (2) where it's a contest. 6) Dangerous Services: Maybe there are very dangerous things that abusers could do to possibly live (or pass on a percent of the fee to their heirs) that the NGO could charge money for. Like, a drug company pays the NGO to let the people who are marked for death try 'X'. 7) The abusers: In the US, parolees often have to pay to be on parole. Maybe the abusers have to pay for their own monitoring. (Possibly pro-rated on income?) It's pretty contraversial in the US now... [Answer] ## Crowd Funding When the NGO hears of an abuse victim who might be willing to sell their murder rights, they don't buy the rights immediately. They instead collect all the evidence about the abuse case and present it in the most sensationalist way possible. They then go on social media and start a viral campaign where they ask people for donations to buy the murder rights and bring the abuser to justice. The goals for their fundraising campaigns will usually exceed the price of the murder rights and the reward for the assassin. The difference is "administrative overhead" which goes to the organization itself and provides a modest salary for the organizers. The organization might be susceptible to corruption in form of overstating how bad their targets really are. They might falsify evidence in order to get more money out of their donors or greatly overestimate the actual cost of the murder rights and the assassination to improve their profit margin. But it would be very difficult for the targets to bribe them after the campaign has started. When a funding is successful and the perpetrator keeps on living, the organization will lose its credibility. They can be sure that nobody who backed the assassination of this person will ever back them again. So they are very unlikely to strike such a deal. [Answer] A human body is worth about [ca 230 grand](http://www.financedegreecenter.com/black-market-body/) in grand organs harvested from dead plus blood, bone marrow etc... up to 45 million if you harvest every bit and piece. Yes, if you keep the human body mainly intact, butchering it and selling it piecemeal can make a hefty sum. So if the NGO buying hit contracts would get into sole posession of the offender's body, it could make a nice sum just by taking the fresh bodies and stripping them of their organs to be implanted all over the country. After all, it is 'total free market' and everything can be sold. For the stuff that can't be sold via the organ trade... The NGO might produce Soylent Green. [Answer] I can see death match TV becoming a really big thing. Think Big Brother where the housemate gets wood chipped instead of getting kicked out and everything the housemates do to entertain us as not to get voted out. Think American Ninja with spikes, grinders and acid pools. [The Running Man](https://en.wikipedia.org/wiki/The_Running_Man_(novel)) by Stephen King was very much like this. The TV network had a whole raft of fatal TV shows of which the Running Man was the top show. Buying the rights to someone's death would be big big business. [Answer] ## Simple Rules of Plunder If the abuser violates the terms of the restraining order they die and everything that they own passes into the ownership of the NGO. With that kind of transferal of assets, the NGO should be able to support itself for a long time. However, this approach raises another problem of wealth concentration in the hands of the NGO but that's a different question. [Answer] The situation you suggest almost sounds like the abused files for abuse and then files a restraining order but then continues to live with or nearby the abuser. *I'm not suggesting it does not happen in real life and I don't want to diminish those people or situations that do,* but for the most part once a restraining order **has been granted** then the majority (Not all, and many more never even reach this stage, but majority) tend to keep separated without further abuse... With that being the case in the real world, you would need to create a situation where the abused are more likely to file for this but also more likely to stay with or near the abuser, for the existence of this right, and therefore companies which profit from it to exist in the first place. **An Alternative** With that aside, possibly when an abused files for this, they are awarded by the court rather than damages from the abuser, but awarded an Abuse bounty, that is appointed by the court, to which the value is dependent on the level of abuse, this means if the abused wants the abuser killed then they are awarded the compensation, however if they do not then it is placed upon the abuser by the government , which in the event of further abuse, any registered company that manages to execute the contract, with be awarded the compensation money. **Immersion** If you wrote this into a book or film, you could put it out there as a difference to our world and have that take the effect upon the world as you see fit, however the most immersive parts of stories are where the writer mentions or references the effects those differences have had on the world in general aside from that initial difference Think in the new Blade Runner, where the MC is surprised to find out one of the prostitutes is a real human being not a replicant, a small line thrown in, however it (mildly) suggests that replicant prostitution is either so common or potentially so much better that human prostitutes are very rare. To use your component... situations like **Legisey's** or **AndyD273** suggestions of wealthy people "hunting" is definitely a way that a company would look to maximize profits, or create some sort of "Battle Royale" style system where the abusers fight each other for a chance at freedom and all aired live on TV with Gambling there would be TV shows where a talk show hosts talks to the victims of abuse about their **feelings** when they watch the company enact the murder, there would also be competitor companies trying to get the same profits, and hire the same sociopaths. abuse lawyers that "guarantee" to get the abused the maximum punishment bounty for the abuser "to ensure they never harm you again" **Sidenote** But also, in this world where abuse is common, these legal cases are common and staying nearby is common, why make bribery and corruption any less common, it could easily be part or an aside to the story, just look at the Facebook data scandal at the moment, where the company responsible has closed its offices and shutting down, only the CEOs of that company have another one doing the exact same line of work already, and they will probably make a few number of staff "redundant" only to hire most or all of them back, under a different name like nothing ever happened... Is this corruption, bad business practices or just the unfortunate way modern businesses work; not all, but some at least, Corruption exists, a world without corruption would probably have little to no abuse, they are very similar just on drastically different scales [Answer] In addition to all the answers above, which are great...simple extortion works too. "We own your murder contract. Pay up or lights out." I'm envisioning something along the lines of a 10% 'tax' (to start) charged to abusers, forever, by the NGO. Variations in this rate would allow for interesting permutations in terms of 'when is it worth it to just say screw this, I'm going off grid' or 'I'll get her anyhow' or etc. [Answer] Sell their relatives the same rights on you, should you exercise that right. Like any Ponzi scheme, it does have its limits... ]

[Question] [ Watching Indiana Jones movies for some time got me wondering how you can effectively kill the explorers to your temple after a long time. **How can I prevent explorers from stealing my artifacts for at least 500 years?** Setup: I have about one billion dollars to spend and 50 years to build an "artifact temple". I can (and will) use 2015 technology - and anything that is accessible to, or can plausibly be invented by, an "Average Joe" in next 50 years. For story purposes, I am planning a huge apocalypse in 50 years and civilisation declines to "dark ages" for at least 200 years. Then society will get back to today's tech (2015 level) in another 200 - 300 years. So, my temple will be visited in year 2515 by archeologists to see what artifacts I hid there. And spoiler alert: I would like to get such archeologists killed. How can I achieve that? [Answer] [Plastic, plastic, plastic](http://www.livescience.com/33085-petroleum-derived-plastic-non-biodegradable.html). Metals will rust, organic materials will be consumed by mold and other fungi, but plastic lasts forever. **The Temple** Start out in a preferably warm, dry climate. However, avoid sandy climates or deserts, where sand and wind will become a problem over time. The West Coast of the U.S. strikes me as a decent location, as long as you stick to the Valley. Protection from salt water, high winds, and below sea level, as well as being dry and warm year round. (Smack dab in L.A. seems like a great place to build a Temple to the Ancients, in my opinion.) Then, build a structure that brings to mind ancient buildings, built with concrete. It's been proven that [our modern concrete is just as strong](https://www.quora.com/How-long-are-our-current-day-concrete-structures-designed-to-last) if not stronger than ancient concrete. It is merely aspects such as plumbing, wiring, and other factors that cause our buildings to be less sturdy. Ideally, you will want to build something along the lines of the ancient pyramids, but made with modern hardened concrete. This structure is massive, and therefore will resist erosion. Within the pyramid you will have many small rooms, which will give the pyramid stability. A pyramid shape is good because it has a wide base with less weight as you go up, but you could just as easily create a giant box as well. The idea is that you make sure it is sturdy, with as few seams in the concrete as possible. Pouring the walls as one solid piece will be the best way to ensure no moisture can infiltrate the cracks and begin to break apart the concrete pieces. In order to attract the adventurers of the future, lets say we want to build something pretty damn big. So, 100 feet tall (10 stories), and 50 feet wide. This creates a very tall but narrow pyramid, so adjust your width accordingly for something fatter. This puts our surface area at 12,807.76 feet (I used [this calculator](http://www.math-prof.com/AreaVolume/SquarePyramid.aspx) to figure this out, I'm not a math person). If we use [this number](http://www.forms.org/content.cfm?act=constructioncost) on building a concrete home, take the high end - 3.25 US dollars per square foot - and then add on an extra 2 dollars for more expensive and solid slab concrete (with no space within for plumbing and wiring), then we're looking at a cost of 67,240.74 dollars, a tiny number compared to your budget. (*If someone else who isn't math stupid finds out that I'm crazy wrong, please let me know.*) **Inside the Temple** The interior of the pyramid should be sealed from moisture, perhaps with a coating or sealant or non-biodegradable foam. Vulcanized rubber would be a good material as well, especially to make sure your doors are hermetically sealed from your adventurer until the time is right. Removing the oxygen before sealing would be a good way to initially try and cause some damage, merely opening your temple would cause the door to blow open, and the adventurer would have to wait for the temple to be filled with air before he could venture inside. Creating a complex system of hallways and tunnels will ensure that even if your adventurer gets past your booby traps he (or she) have a strong possibility to get lost. Perhaps mechanical devices that seal doors once triggered, or which rotate a room or hallway so that it no longer points in the same direction it once did. Slops so slant that you can barely tell you're going up (or down) or rooms tilted at odd angles will leave your adventurers bewildered. (Magnets placed within the walls would prevent someone from using a compass accurately, and thick walls would keep someone from attempting to use a GPS device to position themselves). Confusion would result in an inability to map the interior of the temple, leaving adventurers to starve and die within the myriad of tunnels. **Booby Traps** All the traps should be extremely simple mechanical traps. Think something Rube Goldberg-esque. Opening a door triggers the release of a heavy ceiling covered in blades, sending it crashing down on an adventurers head. Levers, pulleys, counterweights and other simple mechanical devices will be your friend. All of the traps should be made of plastic or ceramics. Ceramics can be sharpened to a point for spike traps, for example, and will add some weight to things that need to squish someone. Plastics also have the benefit of being cheaper. You may be able to 3D print all the materials needed. [This guy talks](https://www.3dprintwise.com/3d-printed-mechanical-devices/) about perpetual motion machines and other mechanical devices that can be created with 3D printing. It should be important to note that once a trap is triggered it would be impossible to set it back up, so this is why the confusion angle might be a better way to keep adventurers out. The first dozen people will end up triggering the traps and the 20th guy will be able to waltz right through. Unless you make it so he gets lost. Then your adventurers will eventually just have to trial and error, and hope they brought enough supplies to make it to the end. And even once they get there, they may not be able to get out. Another good way to try and kill your adventurer would be with significant amounts of radioactive material. Uranium is going to last 4.6 billion years so I am pretty sure that qualifies. This would be a great way to create a temple with a "curse" attached to it. Within a few days or weeks anyone who enters and explores the temple would die of radiation poisoning. [Answer] # Put the temple in medium earth orbit This has many convenient effects for your goal of slaughtering an aspiring archaeologist: * You don't have to have as many layers of traps, because only a few explores will have the means to reach your temple in the first place * Traps that would be mildly inconvenient on earth are extremely deadly in space * if you are careful in material choices, you don't have to worry about decay/corrosion at all. Adding a big reflective balloon to your temple will make sure that everyone remembers that its there, and 500 years of stories about "the fastest star" will make sure people try pretty hard to get in. Some traps suitable for space: * Spring loaded hollow needles for gently letting the air out of suits * Heat traps: spray your explorer with insulating foam and he'll cook in his own body heat * ruin the docked spaceship: when an inner door is opened, spray salt-water in all directions: good luck cleaning the salt off your engine bell in space! * space is a great insulator: use a radioactive beta cell to charge random elements of the temple to thousands of volts. * mercury is a great conductor: splash a liter of it onto a spacesuit and see what shorts out * have a room on the outside of the temple that uses solid rocket motors to fly away when someone enters it. Bye! [Answer] I am not really malicious enough to spend my time designing booby traps. So instead I'll just present how a nice person such as myself would built a treasure vault for reference. It should be filled with chemically inert gas for protection. To avoid leaks the gas should be heavier than air and the vault built well below ground level in an are with very low ground level. A layer containing highly viscous fluid should be incorporated to make it self-sealing and add some elasticity to the overall structure. This makes cracks allowing protective gas escape less likely. Since some gas would inevitably escape it should be self regenerating. As long as it is heavy enough to settle to the bottom and the vault only leaks from the top where the entrance to the surface is, any oxygen leaking in will be pushed out. Chemically inert implies a noble gas. The heaviest noble gas is radon. Unfortunately radon-222 has a half life of less than four days before decaying into polonium-218. Which in turn decays into lead almost instantly. Covering my treasure with lead dust is not optimal. Next option is xenon. It has eight stable isotopes. After quick inspection the most suitable is probably **xenon-129**. Xenon has density over four times that of air so it should stay put in a hole. Xenon-129 is produced by beta decay of iodine-129, so you could make it regenerate. The half-life of iodine is long enough that the protective gas would regenerate for millions of years. Much longer than the vault would remain intact certainly. Beta radioactivity is also easily contained by placing your iodine inside a metallic container thus avoiding, together with the long half-life, embarrassing episodes with Geiger-meters going insane. The only real downside to xenon that it is a powerful anaesthetic and since it is obviously unbreathable and concentrates near the floor people carelessly entering the vault would die. Fortunately xenon anaesthesia is fairly safe. So as long as you remember it is there and take proper precautions, no permanent ill effects to your employees are likely. In fact xenon is being used for doping, so your employees might even have *increased* performance from the inevitable low level xenon exposure. Pity about the foolish explorers entering the vault unaware of the protective gas, though. Xenon is invisible and odourless and by the time concentration is high enough to snuff out flames, the poor explorers are probably already unconscious and suffocating. Nothing is perfect. Since xenon is used medically and for other purposes on commercial level, it is easily available, if expensive. Krypton is also a possibility. [Answer] Multiple answers have involved radioactivity. This will be quite problematic, though--alpha and beta emitters are completely harmless to someone wearing a simple full-body covering with a filtered air supply. The only threats are gamma and neutron--and such high energy decay is generally coupled with short half lives. The only suitable isotope I'm finding is Americium-241 but you'll need a **lot** of it. A 100kg block at 1 meter administers a lethal dose in about an hour--but that block puts out 11,000 watts of heat. (And since you're looking for 500 years in the future you'll have to close to double the initial amount.) Since you can't make him stand there long enough to fry you'll have to make him take a slow, winding path past vast amounts of it--and by then he's going to die of overheating long before he dies of radiation exposure. If you want to use radiation as killing agent you're going to have to generate it when needed. Thus we need a radiation generator that can still work after 500 years. As others have said, stability is a big issue. A normal nuclear weapon contains a lot of pretty precise components that likely won't behave properly after the centuries. Besides, we just want to kill the archaeologists, not destroy everything. Lets build a different sort of nuclear device. All the intricacy of a nuclear bomb comes from the desire to get the biggest boom--but suppose we don't want a boom? The idea of a nuclear bomb that doesn't go boom sounds crazy but it's exactly what we need here. Our material will be Pu-239 but we are going to build a gun-type bomb. (Yes, I know, you can't--read on.) The two chunks of material will be coated in something very non-reactive--teflon comes to mind but there might be other suitable choices. Now, we also have the problem that we can't count on our explosives to behave after 500 years--thus we won't use any. We place one half of the bomb in the chamber we are trying to protect, likely hidden behind a thin panel. We place the other half of the bomb above in a pipe. There is something behind the other half that fits into the pipe to keep it aimed straight. Rather than a ring and cylinder we use slanted faces so that if it's every so slightly off after the centuries it still drops in place. What happens when the upper half falls? The bomb assembles far too slowly, once it crosses the prompt critical threshold the reaction builds--and it produces heat. This energy quickly vaporizes the plutonium and it blows itself apart. We have seen events sort of like this due to mistakes in plutonium processing--the plutonium goes poof, the blast wave can knock down those who are close enough but that's about it--except they absorbed a huge radiation dose and quickly die of it. Now, for the trigger. As others have said, it's not going to be easy to make something that will work reliably after the centuries so lets keep it simple. Put a door on the room. The door fits snugly in it's frame. There is a pipe in that frame, the pipe is full of beads of some kind--they are large enough they can't slip between the door and the frame. Once you open the door the beads drain out--and when the beads drain away they release whatever is holding the upper part of the bomb in place. Edit: A second design comes to mind: Forget about the two chunks of Pu-239. Instead, the beads themselves are the Pu-239. They're stored in a long, thin tube so they don't go critical while they are sitting there. The floor is sloped, it channels them to a collecting point where they do go critical. [Answer] **Simple use a [Money Pit](https://en.wikipedia.org/wiki/Oak_Island)** I hear you asking ''What on Earth is a [money pit](http://www.unmuseum.org/oakdiag.jpg)? it sounds terrible for hiding things'' Well the money pit was a well like structure discovered in 1795 (We still are not sure how old it is) made of many layers of wood, clay and brick with small tunnels leading to the ocean. The pit is around 200 feet deep(estimated) but you could make it 500-100 feet deep and it should still work. **Advantages** * Over 1.5 million dollars have been put into digging into this hole and it still has not been breached * If almost 300 years of digging can't breach this pit then no one in the apocalypse will try. Why because it's the apocalypse and they have bigger problems * Consider that the actual pit was out in the open, if you buried it under a few feet of dirt who knows how long until it is found! * Whenever the tides rolls in the pit floods bringing in more clay and sand. The ingenious engineering of the tunnels make it so that water will flood the pit and prevent further digging * Since you need it to be lethal, borrowing from C Vanhorn's answer you could put uranium at certain points of the pit to make it lethal. * The original pit was built out of scavenged materials like logs, charcoal and coconut fiber (which is odd because coconuts don't grow here in Canada). Since you have 1 billion dollars you can use thick netting, cement, and titanium * To make it more lethal you can mix [thermite](https://en.wikipedia.org/wiki/Thermite) with the fluid materials like clay to make it impossible(and dangerous) to use explosives. (Thermite is another cheap effective material) **Disadvantages** * It needs to be built near (within 100 meters) the coast. * This will not kill people (other than the occasion drowning), it just makes you go mad. I imagine that you could make it lethal though. [Answer] **Utilize multiple passive traps around and within the temple.** Defense in depth will ensure that even if some of your measures fail, the filthy archeologists will still snuff it. Use radiation, heavy metals, elemental explosives, and physical traps (like the Indiana Jones Temple of Doom). **Passive Means** *Radiation* is an excellent way to deny access to an area. Chernobyl won't be a [habitable place for humans for 320 years](http://www.cbc.ca/news/world/chornobyl-by-the-numbers-1.1097000). A highly prepared person with shielding and Geiger counters will be able to avoid harm but an unshielded person will die very quickly and very unpleasantly. Note that care will need to be taken to choose the right radioactive element to embed in the temple. Uranium isn't a good option because it's so stable over long time periods. Plutonium may be an option. The trick will be to get an active enough radiation decay that it will kill the intruder but last long enough to be lethal in 500 years. As a trap, put up lead shielding around a room to prevent detection till the door is opened and the explorer gets a massive radiation dose right in the face. Go one step further and lace the area with super fine plutonium dust for a double-whammy of radiation poisoning plus heavy-metal poisoning. According to [Wikipedia](https://en.wikipedia.org/wiki/Plutonium#Toxicity): > > Plutonium is more dangerous when inhaled than when ingested. The risk of lung cancer increases once the total radiation dose equivalent of inhaled plutonium exceeds 400 mSv. > > > *Elemental poisons* also work well because they don't decay with time, provided they are stable in normal atmospheric conditions. Mixing a variety of super fine heavy metal powders with plutonium dust will cause all kinds of problems. *Elemental Explosives* If you want more of a bang and don't mind a one shot trap, seal fluorine in an appropriate container that will shatter open. When the container shatters, the fluorine gas will be released into the air and hopefully the luckless explore will get a big lungful. **Unreliable Approaches** *Forget electronics,* since you can't be sure that in 500 years the electronics will work or that your power source is even still active. *Don't rely on active traps* that rely on ropes, pulleys, joints, actuators, hydraulics or chains since you can't be sure that these components won't seize, rust, rot, corrode or fuse in the 500 years that they sit. Even having a big block that falls on someone is tricky to get right because what if the ground settles and the big block jams? Designing a release that can hold a large load but give way with light pressure (in the right place) is hard to do. Ensuring that it's 100% reliable in 500 years is much harder. However, even if the active traps aren't 100% effective in 500 years, if you put enough of them into the temple, the law of large numbers means that at least a few of them will work. [Answer] ## Make it Big If it's big any team ill need to split to cover more area. Also a nice way to make explorers to hopeless wander way and get lost and tired is to build a maze. A huge maze is a challenge by itself. ## Make it Difficult No torches or lights of any type. Muddy terrain is also a great way to slow down explorers. Also water to the kneels and darkness are invaluable to hidden traps and dangers. ## Make it Hazard To increase lethality you can put all kinds of hazards. @Loren answer put a good point in ruling radiation out. Also plutonium is expensive enough to expend all your budge and we want to kill that guy in the place, not from cancer years later. The place can be natural habitat of nasty creatures. The list goes from poisonous jellyfish to crocodiles but small swarming indigenous pests are easier to maintain (unless you create a institution to feed and keep that gigantic pythons preserved). Another good environment hazard are poisonous gases like sulfur. They are pretty common in some places too. ## Flooded cave! You are luck there already places on earth with all that traits and they exists despite human intervention. In fact [cave diving](https://en.wikipedia.org/wiki/Cave_diving) is a very hazard occupation. There's very little margin for errors in that business. They are huge dark mazes and if there's not too many poison to support life anything can live here. Sometimes thing's no outsider ever been saw. Just build your temple in that god forgotten deepts and enjoy the killing. [Answer] Read "Cryponomicon" by Neal Stephenson. This includes a description of an underground flooded cave network designed to hold stolen Nazi treasure and kill unsuspecting treasure-hunters. The basic premise was that a lake above would pressurise tunnels around the area. Anyone digging without knowing exactly where to go would be crushed by high-pressure water, which would then flood the tunnel system. The *second* archaeologist would know what to expect and could figure out what to do about it. Solutions might involve backhoes or thousands of slaves, depending on the new civilisation, but the *first* mouse gets the trap. Investment would only need to be a few million dollars and a year or two of digging. [Answer] Make multiple temples and use social engineering to kill the adventurers. First hide your artifacts in a cave or some such and take pictures. Then seal off the cave. You can completely seal it with no known entry if you like, or anything, do not put any traps in this cave. Next make many other caves, temples, etc. as you wish. All of them trapped, as you like, none of them with artifacts in them. Lastly, make exciting treasure maps with copies of your picture of artifacts affixed to them that all lead to the deadly caves and temples. Do not make any map or provide any information on your actual stash. Distribute your maps. With any luck, the treasures, maps, pictures, etc. will become legendary and will be copied and passed down to maintain interest for 500 years. Since no one knows where the true cave is, it should be extremely difficult to just stumble upon. Everyone searching for your treasure will search your trapped temples, and find an untimely end. [Answer] There's been a lot of good ideas thrown around, there's also been ideas whose feasibility is questionable. The main challenge we face really is those 500 years. A lot can happen in that time, from the collapse of known society (you do mention apocalypse) and natural disasters. As such, any too elaborate trick is likely to just collapse before the time is right. --- **Passive Traps** Let's place the above-ground temple above the most inhospitable place ever: * hot (above 50°) * underground (and narrow) * filled with salted water * and a few "lures": underground rooms with either neutral, poisonous or explosive gases Just wandering in this environment, by itself, is hazardous enough to kill all but the most prepared adventurer. Underground waterways are perhaps the most dangerous places to visit to start with, a couple narrow passages being able to keep all but the most determined (and prepared) adventurer. Turning on the heat is also a very nasty trick, as the human body cannot easily support it, and how would you navigate narrow passages in diving + heat protecting gear? Also, if deep enough, there will also be pressure issues. Finally, the lures are just to get those exhausted adventurers who finally hope for relief out; a couple easy kills, if you wish. Oh and the salt? Well, in such a dangerous environment, one might be tempted to send bots. Narrow passages are annoying to navigate for bots, the difficulty in communicating (wires can only be so long), also raise the bar... but for the truly motivated we'll also make the water the enemy. Anything that can deposit and accumulate itself on the surface of the equipment and require frequent maintenance is good; salt might work. But that's just the setting... *Note: this is building on jean's idea, with the heat twist inspired by QuadmasterXLII's heat trap.* **A-maze-ing** Since the environment in itself is so hazardous, a sure-fire way to kill adventurers is just to increase their exposure. As a result, let's make that network of submerged narrow underground passages a twisty maze. A dark underground is already a formidable maze by itself, but picking from C Van Horn's answer, we can improve this maze: * make it massive: there are already existing large underground networks so it's just a matter of acquiring one (which really means acquiring the land above the entry) * make it deep: deep enough, and GPS are out of the equation; it also synergize well with mortality (by increasing the pressure) * make it magnetic: with magnets placed strategically, compasses should be *just slightly off*, and off in a direction you control * make it off: if there are any straight passages, make them slightly slanted (in any direction), if there are large passages fill them so they get slanted. Oh, and if you figure some material that will resist time, a few slightly erroneous partial maps on the walls here and there... * make it unrelenting: any big room could conceivably be exploited to build a base camp, fill them in (mostly) to prevent such camps as much as possible What does this maze brings? * it prevents a run-and-grab strategy: if you don't know where to go, you can't run-and-grab * it increases the adventurers' exposure to the environment: the environment itself IS the enemy, by increasing exposure we increase the death toll **Bonuses** A couple booby traps here and there would only increase the mortality: * jagged rocks (or ceramics) would play havoc on diving gear * ... There is no need to use anything electronic or mechanism, just push the nature a bit further. **Pulling it off** Ideally, the underground network should NOT be flooded in your lifetime, this gives you the opportunity to set it up as you wish, and actually use it. Then, when the time is right, fill up the biggest rooms, put the gases and other traps, and flood the complex (with hot water from a nearby water table). [Answer] **Put your artifact temple on an escape trajectory** If your incredibly valuable artifacts are reasonably light (a few tonnes, maybe), you can easily set up a spacecraft to send them. With a 500-year head start, your artifacts would be light-weeks away. Plus, you have centuries to line up near-perfect gravity assists. Because of the [Tyranny of the Rocket Equation](https://what-if.xkcd.com/imgs/a/38/voyager_comparison.png), catching up with, slowing down, and returning to Earth, would be impossible with 2015 technology. Let alone in a reasonable amount of time. **Indy will die of old age on the way.** [Answer] Let's think outside the box, here... How about the free-market solution? **Hire guards** A billion dollars is a lot of money. Clever investments could be done to make it last through the dark ages, and compounding interest alone could be used to hire a squad of people on semi-permanent duty to defend your temple. To make this work after your death, design your temple with a radio transmitter in it. If the doors are breached, the transmitter would transmit the signal to an outside source, that would immediately cut off the flow of wage money to any remaining guards. Thus this would incentivise guards to carry out their jobs well. The advantage of guards is that they would also be expected to upgrade their technology (and any physical defenses) in accordance with any new discoveries or inventions. This would protect you against unpredictable events. Your 'secret order of the hidden temple' could work to hinder your archeologists long before they even find the temple. This might be more fun for your story than just disarming traps, also. [Answer] Build temple. Seal temple. Start three proselytizing religions based on the belief that all other beliefs must be terminated with extreme prejudice. Ensure all three religions know that the temple contains the only worldly evidence of [insert deity here]. Can be shown to be effective for up at least 2000 years. You see, 500 years is a long time for technology to work, buildings to not settle, leaks to not develop (allowing water to dissolve and sweep away your radioactives, nerge agents, chemical agents, and biological agents). Humans however, are known to create conservative social structures that last for thousands of years with (in some cases) very little mission drift. Hubbard launched his version for much less than US$1B. [Answer] Your temple is - a ship. Add an explosive charge, then sail out to the Marianas Trench. Abandon ship, then trigger the explosive (ie. "scuttle" the ship). Your temple is now in what I'd call the hardest place on Earth to reach. [Answer] A nice variant on the maze idea (because being lost is terrible for your head): make the halls much smaller ; no too small so that normal-size human can crawl, but not too big. The idea is to make the human go slow, very slow, so you have time to expose him to all kind of radiation, gas, and the best: basic, mechanical, unescapable traps. In Indy movies and the likes, the hero always gets to jump from a good slab to another, to avoid the dangerous ones. In a tight tunnel, there is no way to jump over. Not easy way to turn back when something dangerous comes fast your way, no way to avoid those sharp spikes coming from the ceiling, etc. A cool one is: walls closing in front and behind you, water flooding, and after a few hours, going away. In any case, vary your traps, so even the hardy adventurers won't know what to expect. Oh, and if Indy is claustrophobic, tough luck :) As an additional benefit, the bodies or previous adventurers will soon fill up the tunnels, making any progression much harder. Things you might want as extra protection: make sure radios signals don't get in, to avoid small robots to steal the show. You could even make a few guillotine on the way to cut through cables if that's what the bot uses to receive orders. Obviously, nothing forces you to put your treasure in the last room. It could be under a few meters of concrete somewhere else. [Answer] # Drill into the bedrock Currently Sweden and Finland are planning to bury their radioactive waste in bedrock repositories, 500 meters below the surface. [Our method of final disposal](http://www.skb.com/future-projects/the-spent-fuel-repository/our-methodology/) You can do something similar. Borrow a tunnel-boring machine... drill a long shallowly sloping tunnel into solid bedrock. Make a chamber at the far end, put your stuff there. Seal up your tunnel using the gravel from drilling the tunnel, with concrete mixed in to make it solid. During the "dark ages", no-one will have the tech to break through that, or even find it. When we are back to present day tech, some geologist will notice a very peculiar long, straight and uniform echo on their [ground penetrating radar](https://en.wikipedia.org/wiki/Ground-penetrating_radar). It is really strange, because none of the archives about nuclear waste or chemical waste speak of anything that is meant to be **there**. Once they drill their way into the chamber, they notice that there are glass jars standing on pillars everywhere... a few may already have fallen, spilling **something**. It is hard to say what it is really... and... oops!!! *CRASH* ...there goes another one. Hm... smells slightly... sweet? A few days later they are dead... from mercury poisoning. [Dimethyl mercury](https://en.wikipedia.org/wiki/Dimethylmercury) to be exact. Simple... effective... doesn't use exotic tech... leans on technology that is about to be, or is already, employed for extremely long term storage. [Answer] *Make the artifacts themselves* lethal. Or the place its in. You'd need to guesstimate the technology level of the future explorers but you'd want a series of *environmental* hazards. Rolling stones, punji pits and \*arrow launchers"? *Amateurs the lot of them* Seed the place with toxic spores. Long lived, lethal mold. Radioactive walls and architecture that shields it. Until you open the door. For that matter, a highly radioactive artifact that's going to give you serious radiation poisoning? Indy would have been caughing blood, and dying before he got out. [Answer] How about hermetically sealing it and filling it with a poisonous gas. Preferably one that is colourless, odourless and not too rapid acting, so as to deter entry. If there is nothing that fits that bill then booby traps that release something faster acting like sarin or chlorine. [Answer] Instead of having the temple gradually collapse into a fissure as in "Indiana Jones and the last crusade", just detonate a nuclear bomb. Make sure the bomb is engineered to last thousands of years with no maintenance. It needs to be built out of non-corrosive materials. And instead of having a conventional battery to power the trap, it needs to run on a very low power nuclear reactor fuelled by normal uranium with a half life of 4.5 billion years. [Answer] After reading TrEs-2b answer, I'm inspired by this alternative: Given that the [Oak Island phenomenon](https://en.wikipedia.org/wiki/Oak_Island) is a natural sinkhole that fills in with debris after each episode of subsistence (other examples can be found, intact, for comparison), yet has proved an expensive distraction, use natural phenomena to fake an elaborate hiding place. With a small investment, a natural formation could be made to look like a highly elaborate preparation. Especially if the people after your treasure are not geologists trained in local features, and once they start into it the natural/modified distinction will be obsured by actual rework. So, you lead the treasure hunters to an expensive money pit and **they stop looking**. The real treasure was hidden somewhere else. [Answer] The answer that will surely kill all the explorers is as simple as it is unethical: Go to the swiss alps and have yourself a bunker mined into the granite, just one access shaft. After construction, all ventilation equipment is removed. Then the art is brought in using scuba gear. Now comes the trap part: Put the art on pedestals that glow in the water. Not the phosphorescence type of glow but the luminiscense of the [cherenkov effect](https://en.wikipedia.org/wiki/Cherenkov_radiation): By placing the art on pedestals made from nuclear waste material to achieve this, you have a radiation trap for the next 25000 years or more. By using enough ammounts distributed with air gaps, it should create an area of more than [lethal radiation](https://en.wikipedia.org/wiki/Acute_radiation_syndrome). 30 Gray1 is is lethal within 2 days... but if we use the Fukushima slag as pedestals we could achieve up to 530 Sieverts1 of background radiation in our halls, than this is enough to deadly irradiate the explorers if they are still in the access shaft and [disrupt camera drones to the point of failure](https://www.allaboutcircuits.com/news/one-way-journey-for-drones-the-fukushima-incident/). Plus, the glowing skeletons of the workers that brought in the slag will serve as a warning to the wannabe Indiana Jones. --- 1 - Gray is the physical dose of radiation in 1 J/kg, Sieverts is the equivalent dose in the same unit, weightened by a factor d - for whole body the conversion factor d from Gy to Sv is 1 though. [Answer] * Encase your artifact in graphite, which has a very high melting point. * Go to [Stromboli](https://en.wikipedia.org/wiki/Stromboli), one of the three active volcanoes in Italy and a volcanic island. * Drop your graphite box containing the artifact on the Sciara del fuoco ("Stream of fire"). This is where lava flows to the sea every hour or so. Let the box be covered with lava. [](https://i.stack.imgur.com/26WKy.jpg) * Good luck to all those archaeologists trying to recover an artifact covered with 500 years of lava on an active volcano. [Answer] Dig a \*\* VERY DEEP\*\* hole. Put goodies in hole. Put [magic porridge pot](http://www.bbc.co.uk/learning/schoolradio/subjects/drama/letsmakeastory/episodes/porridge_pot) in hole. Say "Cook little pot" Walk away. Cataclysm and protection and cost efficient all in one pot. Actually I'm not sure about cost efficient. I don't know how much a magic porridge pot goes for on Ebay these days ]

[Question] [ In the present day, petty crimes like speeding, trespassing, and jaywalking in a dangerous area are punished by fining the infractor some amount of money. This is usually a deterrent because being forced to give up your money means that you'll be more limited in your ability to obtain your needs and basic wants. But what happens when you commit such a crime in a [post-scarcity society](https://en.wikipedia.org/wiki/Post-scarcity_economy) in which money is no longer necessary to obtain your needs and basic wants? It seems to me that speeding (or at least crimes of equivalent severity) would still need to be punished in some way, but would not be severe enough for jail time or similar punishment that would presumably still be available in a post-scarcity world. So that we have an operational definition, let's describe a post-scarcity society as: > > A society in which all a person's needs are freely met and there are no limiting factors in achieving these needs (e.g. energy is virtually unlimited). Basic luxuries are available without cost such that the majority of people's wants are easily obtained. > > > The model of a post-scarcity society that I have in mind is *Star Trek* in which money is not used (at least not by the Federation), any food you want is instantly dispensed by a replicator, energy is virtually unlimited, and holodecks let you have virtually any experience (I've always imagined that on earth they are as common as a movie theater). You can't obtain your own Enterprise so your wants are still limited, but the majority of a person's wants are certainly within grasp. However, post-scarcity *Star Trek* doesn't provide any answers for what might replace a fine since the usual recourse for a crew member misbehaving is a black mark on their Starfleet record (which might lead to demotion). However, that punishment won't apply to Joe Schmoe who is not in Starfleet and is speeding while visiting Risa. So what sort of punishment would replace fines in a post-scarcity society? [Answer] What about community service hours? You could even make the punishment fit the crime in some cases. If the person is found guilty of jaywalking, make them to spend their days off as a crossing guard. If the person is found guilty of littering, make them to pick up trash on the side of a highway. And so on... This kind of alternative sentencing is already becoming a little more common in some juvenile and misdemeanor courts in the US. [Answer] If you live in a post-scarcity society, it won't cost you anything to just throw the guy in jail. And honestly, even if your society is full of immortals, time will always be a commodity. Also, even if it's post scarcity, there will still be regulation (no, Timmy, you can't fabricate a nuke until you've finished your vegetables). If someone breaks the law, maybe they can only eat nutrition cubes for a few days, or their daily supply of clothes will turn pink for a week. There would be ways around this, but it'll be enough of a hassle to make people think twice about committing petty crimes; after all, post-scarcity society is going to get used to things being really easy. There are other answers on this site about how a post-scarcity society is impossible (if I find them, I'll edit in some [links](https://worldbuilding.stackexchange.com/questions/2671/consequences-of-the-shift-to-a-post-scarcity-society?rq=1)); perhaps you can read them and get some more ideas. [Answer] I've come up with: 1. Pain 2. Execution 3. Imprisonment 4. Withhold certain resources 5. Humiliation 6. Forced labor 7. Banishment If it can be administered relatively quickly after the crime was committed, **Pain**, is probably the single most powerful motivator to the human psyche. A post-scarcity society is not necessarily a non-barbarous society. Something simple, like jaywalking, can be punished by a quick lash or two across the arse. More serious crimes can be more lashes and be across the face. If they are particularly barbarous, they might target other more sensitive areas, like the tongue, eyes, or genitals with other methods that might involve pins, chemicals, vices, etc. Considering all the inventive torture methods we've come up with in the past, short bursts of such things as punishment would probably be very effective. More heinous crimes, like murder and arson, can be punished by **execution**. Losing your life is always undesirable. In the Star Trek episode *Justice* we are shown a post-scarcity world that punishes all crime by execution, including accidents (and some how Wesley weaseled out of his due justice there). Even jaywalking can be punished by death on some worlds. (There is a philosophical conundrum for a society of immortals. Is any crime worth what is essentially an infinity of life? Perhaps if you took an infinity of life wantonly, then it is reasonable to demand an infinity of life in return. A bit off-topic, but interesting.) But in an enlightened, Star Trek society, pain/execution is never an option. **Imprisonment** is. No body wants to be locked in a small room for a full day, just for jaywalking. Nothing to do and no one to talk to. Just sitting there, being punished by sheer boredom and uselessness. More serious crimes can call for anything from two days to life imprisonment. An enlightened society might also choose to **withhold certain resources**. In Star Trek, for example, you get transporter credits. Some crimes can be punished by limiting those or removing them entirely for a while. A less enlightened society might think something like hunger will curb your appetite for crime. **Humiliation** can also be a powerful motivator. A black spot, a scarlet letter, a branded tear, etc. can all go a long way to preventing crime (though it seems like it would be ineffectual for repeat offenders). A post-scarcity society could force you to wear a certain kind of hat, a color of shirt, or post your face everywhere with the word "twat" as the caption. There's a lot of clever things you can do here that just might remind you of Mom and Dad. **Forced labor** might also be effective. People don't want to be told to do anything, especially if it happens to be very disgusting or boring. An enlightened Star Trek society might make people do community service with all the holograms. Something stupid like scrubbing the whatchmacallits with a hundred copies of the Doctor from Voyager. That sounds like a pretty horrible punishment to me. A barbarous society might send you to the mines or somewhere else where injury and mistreatment is likely. A final option is **banishment**. This might be viewed as barbarous or enlightened depending on context. It's always an option to tell offenders to go pound sand and never come back. Combinations of these can be very powerful. There is a synergistic effect. For example you can combine imprisonment and humiliation by putting offenders in stocks without clothing for a day. Then all the little kiddies can replicate rotten tomatoes and hurl them at you, which might add a slight element of pain. Today's society often combines imprisonment and forced labor (i.e. community service). A post-scarcity society can imprison you and let you go hungry for a few days. Beatings were/are a regularity in typical prisons in barbarous times. In fact, there's much evidence to suggest that jailors were the first torturers. [Answer] There are a lot of options available to you in such a world. During my thought-sessions on communism and driving (this'll make sense in a second) I've come up with some ways to punish misbehaving citizens. In a post-scarcity economy you can reward citizens who work for the good of the public, and put marks against those who break minor rules and generally make an arse of themselves. This could prevent them from getting the opportunities that they want or downgrade their food, clothing and possessions or limit their access to the goods that aren't freely available (like holidays to other countries, bigger TVs, nicer cars etc.). It would also have the effect of shaming the individual, which is the second part. I've pondered on a roadnet that assumes that people have access, either by device or directly by thought, to a sort of rating system, where good drivers are upvoted, and bad drivers are downvoted. Rather than relying on poor drivers getting caught speeding or pulling other nonsense in the middle of the road (you've seen it happen), anyone present could just downvote their driving in a category, with a comment beside it. Votes that aren't confirmed by other people fade quickly, while if 100 people downvote an action, it'd probably be permanent. This is eminently applicable to your world, as people could vote up or down on the actions of others, so if a child misbehaves both their parents, and potentially any onlookers, could downvote the child's actions, bringing temporary shame to them. Minor criminals could have state mandated downvotes, which carry much more weight, or last for a long time. Everyone viewing that person's "profile", would be able to see this mark, and know that the person has committed a minor crime, in a way that really can't be done today. [Answer] **Nothing** Why do we punish crime? To discourage repetition of the problematic behaviour. So why do we need to discourage the behaviour? Because it's *harmful*. So (if you want a properly-managed society) you need to have punishments that are appropriate to the *scale of the harm* caused by the infraction. Let's ignore speeding (which is more difficult because there's a risk of killing) and say the crime is littering or petty vandalism. What's the cost to society? **Zero!** In fact, if a robot will be along to fix whatever you did immediately, littering might not even become distinguishable from waste disposal; not even recognised as a problem because it's easier to just view it as the "interface". So there's no reason to punish someone for either of these: the action they take isn't actually hurting anyone, and they'll get bored and stop doing it long before the robots do. So a post-scarcity society would likely see a tremendous reduction in the number of actions that are actually viewed as being crimes. How big the reduction depends on the society's capabilities and which actions are "free", but anything involving petty property damage pretty much has to be covered by definition. --- This can also be extended to cover various nuisance or personally-damaging behaviours depending on how much freedom and economic clout individual citizens have. Speeding may cease to be harmful, and thus a crime, if it becomes conventionally accepted to wear your power armour while on the road (because you can't hit someone hard enough to kill them; a victim *not* wearing their armour would be seen like a motorcyclist not wearing a helmet today). Noise pollution is a non-issue if the neighbours all have their homes surrounded by a Cone of Silence. And so on. You'd see a lot of areas where the responsibility of the state gives way to personal responsibility, because state intervention is completely unnecessary. There's also a middle-ground option where the state itself doesn't necessarily impose punishments, but private citizens might *while you're in their territory* and thus under their overall control. e.g. to steal an example from Iain M Banks' *Culture* series: in the Culture, murder isn't really "illegal" as such because there are no laws, but a confirmed murderer will be escorted everywhere by a "slap-drone" (security robot) because *what are they going to do about it?* when they're in an area under the authority of someone with the ability to dispatch security robots on a whim, or denied entry to that area altogether. State intervention is unnecessary in this case because the private citizen is perfectly capable of heading off any future damage on their own. (This ignores the operation of the justice system that determines guilt, but that's a separate question.) [Answer] Reputation can always be damaged. The crime of jaywalking has two parts to it. First is the danger of being hit by a car. With ubiquitous surveillance the law should have no questions about who did what and the driver gets away clean. The jaywalker may get dead. Second is the waste of everyone else's time showing down and dodging him. For that, give him a black mark on his reputation from each driver he inconvenienced. Women he dates will see that he doesn't care about other people and puts his own convenience above others. [Answer] ## Scarcity A post-scarcity society means that the society is able to fulfill the needs of all people without needing to restrict access to goods. It doesn't mean that they *must* fulfill the needs of all people and that they *cannot* restrict access to those goods. Lack of scarcity may feel natural in such a society, but it is possible to withhold it for various reasons, including as a punishment. If everyone has access to ample amounts of varied entertainment, it can be withheld from some people - think about a parent saying that a kid can't use TV or computer as a punishment; in their household TV availability generally isn't a "scarce good" but it can be made scarce if needed. If food isn't scarce in an economical sense - people can get any amount of delicious food they want - then still someone can be put on the historical prison diet of bread and water as a punishment. There are many other ways, targeting every wish and desire that people commonly have. In a post-scarcity world, scarcity may feel as a strange, strict but effective punishment. [Answer] Post-Scarcity does *not* mean the same thing as post-luxury. A society can provide an individual with all of their needs, but not necessarily all of their wants, and this is a distinction that is important to note when writing your fictional universe. Say a person commits a petty crime in a post-scarcity society. That person's needs can still be provided, but entertainment, comfort items, and luxury food items can be withheld from that person. A severe enough crime could even lead to them being relocated to a less luxurious living arrangement (since presumably living arrangements are also post-scarcity), and jail *is* still an option in post-scarcity society, restricting a person's freedom as punishment. A severe enough infraction may even carry a death sentence, as it does in our current non-post-scarcity society. These latter more severe punishments you'll notice are similar to the ones we already have - that's because fees and fines are in place to take away the things that a person would buy with that extra money, so instead of taking away the money, a post-scarcity society would simply take away those things, either by not providing them to the person, or seizing any that they already have. [Answer] Expounding on apaul34208's answer: **TIME** Even in a post scarcity economy, there is still a universally scarce resource and that is time. Basically you need to make them "pay" with their time. **Community service** is an obvious cost in time, but so are **jail** and, depending on the individual **house arrest.** If you wanted to get creative, you could punish them with costs to some specific "variety" of time. You could force them to stay at their job for X hours longer, isolate them from their family for some amount of time, etc. As long as it costs them something that can't necessarily or easily be recovered. Heck, maybe the cop that pulled you over for speeding just keeps you sitting on the side of the road for an hour or two. [Answer] If we follow the model laid out by Star Trek, many forms of crime would be virtually non-existent. This is not to say that there will be no crime, but perhaps society would be by and large lawful. Competition tends to bring the worst out of people. This competition doesn't even need to be for basic human needs. Have you ever seen what happens when someone cuts in line at a Black Friday sale? They would probably get maimed by an angry mob. A TV isn't a basic need, yet people are willing to get in a fist fight over one. If everyone there suddenly got a free TV, then the whole situation would be completely ameliorated. The motivation for committing certain types of crime will be greatly diminished in a post-scarcity society. In our current society, there are limited resources, and they are not even close to being distributed equally. There are people who can have anything they could possibly want on command, while there are others with almost nothing at all; and have very little opportunity to better themselves. There is also a huge disparity in the quality of education in the world. There is also a huge illicit drug culture that is incredibly violent. In a post-scarcity economy, all people would have the opportunity at having a quality education. The amount someone is educated directly correlates to their willingness to commit certain forms of crime. At a very young age, people could be taught a strict moral code which forbids them from doing harm to other people. Most violent crimes committed today are by people who are mentally disturbed. Perhaps if these people had gotten the help they needed, they would have never resorted to committing heinous crimes. Without scarcity, it would be less likely that these kind of mental help cases fall through the cracks. There would be much better ways to track an individual's progress in school and in other activities. These kind of behavioral issues would most likely be able to be caught early. There may also be some kind of therapeutic drugs or other treatment which will cure people of mental illnesses. There are many other ways to punish someone without levying fines. Fining people, even in today's society is a poor form of punishment. These fines are a very unequal form of punishment because it affects people differently based on their income. Fines don't attempt to fix the problem. They just act as a deterrent. People will most likely not be immortal in this society. In Star Trek, people still died of old age. Technologies would exist to greatly improve the quality of life for elderly people, and extend their lives much longer than their natural lifespan. But, eventually nature would eventually win and technology would not be able to cheat death. Imprisonment would still likely be a penalty. Because people would have finite lifespans, and suffer real losses by being imprisoned, this would still be one of the harshest penalties which could be imposed. However, prisons would probably be much different in a post-scarcity world. There would likely be more effort to actually rehabilitate a person so they could be returned to society than they are today. Corporal punishment and public shaming could also be employed. The embarrassment of these kind of punishments would be enough of a deterrent to prevent all but the hardest of criminals from committing crime. [Answer] All punishments works because of one of the two reasons: 1. It indirectly inflicts discomfort by taking away one's privileges 2. It directly inflicts discomfort Money is a reward of privilege that one gains by doing a favor that is considered good by someone else, which can be used to exchange for the favor from someone else. A fine takes away some of that privilege. In comparison, other kinds of punishments, like imprisonment or community service takes away one's privilege of liberty, death sentence takes away one's privilege of life. Corporal punishments and public humiliation, on the other hand, directly discomforts the punished by including pain and shame. Public humiliation can be in the form of publishing news stories about the criminal, or branding the criminal with a publicly recognizable mark. Some types of indirect punishment may also have inevitable public humiliation, for example, striping of one's ranks is privileged taking punishment, but it necessarily includes public humiliation as the new rank must necessarily be published to a large number of people. A post scarcity society would offer a large amount of privileges to its members as a basic right. Punishments in a post scarcity society would revolve around taking away these privileges. Maybe a minor crime can be punished by taking away one's privilege of privacy, by requiring the punished to wear a tracking device. Or reduction in the quality or quantity of the goods normally afforded as basic rights. Guilt tripping can also be effective for certain people by inducing guilty conscience. Membership in a post scarcity society is also a privilege, which can be taken away, in the form of banishment. People banished from a society is no longer bound by the rules of the society, but also receives none of the privileges its members had. Banishment may include physical ejection, but that is not necessarily required, if the society has an easy way to distinguish between members and non members. A post scarcity society does not necessarily mean a society without money though. A post scarcity society usually means that all basic needs can be satisfied at no cost. This means things like basic food, clothes, house, education, transport, etc are free. Money can still exists in post scarcity society to regulate non basic needs, which are categorized as luxuries. [Answer] In some ways, a post-scarcity economy are like stable tribes. Another comparison would be the Internet of the early 1990s. In those cases, the worst punishment would be banishment or removal. Lesser punishments would be shunning or denial of access to something either permanently or for a period of time. For example, if someone is caught stealing, having no shop in a village do business with that person for a week or two may be a lesson. However, there is a point where the issue becomes less of a punishment than to protect others from an individual. If there is someone who is unable to function in a society, causing others extreme harm, then removing them from a society is less to teach the offender a lesson, but to protect everyone else. Banishment is one way, but if the individual is going to just go on his own and be a bandit, preying on people, it may take more drastic action like putting someone in a criminally ill asylum so they are not on the streets trying to harm others. None of these are perfect methods, and all can (and have been) severely abused in the past. However, a strong sense of community and belonging can result in misbehaviors requiring far less effort to be corrected, for example, the fear of a night in jail may be just as much a deterrence in a society where reputation is valued compared to the fear of 5-20 here in the US. [Answer] The notion of a post-scarcity society shouldn't be seen as one where everyone has everything they could want or need; a society in which nobody could want anything beyond what was attainable would be an absolutely horrible place to live. Instead, a post-scarcity society should be viewed as a literary device for hand-waving away a lot of work which in reality would be necessary for people to to satisfy their wants and needs, but which would be of little interest for writer or audience. If one assumes people can't get everything they want, unrequited desires constitute scarcity. Unless an oppressive government outlaws such commerce, people will routinely trade valuable goods or services in exchange for things they want but could not otherwise receive. As such, although new technologies for producing things like food and clothing might cause spending patterns to shift markedly, that doesn't imply that people wouldn't still want money to buy things that aren't so readily available. It's all well and good for an author to ignore economic issues that would not help the story, but that doesn't mean that an author should affirmatively pretend that such issues wouldn't exist. Even if one hasn't previously said anything about how much money a character has, that does not in any way imply they couldn't be fined. An author who didn't want to work out what size fine would be required to suitably affect the character could make it payable in a fictional currency which would be used only for that purpose, and then focus on how the fine *does* affect the character, without having to worry about whether 50,271 denzibars was a day's pay, a year's pay, or something in-between. [Answer] **Damage to your reputation** And social isolation if you do really bad things. Many of the things we have fines for now would simply not be a problem anymore (causing damage to other people's property, for instance, is hardly a problem if it can be instantly replaced without cost). But for things that do matter, *people will know*, and they will treat you as an annoying person and you won't be invited to the best parties. If you're outright criminal, nobody will want to have anything to do with you at all anymore. This is also practical because there won't be many people wanting to work jobs like being a policeman, fine collector, judge or jailor if getting paid isn't relevant anymore. [Answer] One of the best world-building creations I have seen to answer this question is outlined in detail in the RPG **Nova Praxis** by Void Star Studios. And no, this isn't a plug for the product. I am not associated with Void Star Studios in any way except as a customer of that product. In the post-Singularity game world they have, the economy works by earning reputation ratings points and losing them either in the form of being downvoted by others or consuming more products and resources than your rep-rating normally allows for. It is less of a currency medium of exchange than it is a means of rationing consumption and rewarding production/good behavior. Everyone gets a default level of 'income' -- housing, medical care, clothing, food, entertainment. And those that are content to do nothing but subsist on that are called Defaults. But most people decide to 'work' to get a higher rep-rating. They can be rewarded by upvotes from others (which cost those others) or creating new nanotech compiler templates or entertainment sims or doing services for other people that we today would consider 'beneath us'. One can also 'work' in a 'company' that is allocated a larger rep-rating to acquire compilers and robots and property or ships, etc. Those that provide a popular service and/or do it well get rewarded with rep-ratings as 'corporate income' which get distributed as 'profits' to the owners (usually high rep-rating individuals) and 'pay' to the workers. Point is: There is great demand for 'work' to be had by individuals and society in general. Similarly, being a jerk in that society costs you as well. For the real hard cases, traditional cops and trials and sentencing happens just as now. Only the punishments are either not that harsh OR are very harsh, like being exiled from the House you belong to. Like now, murder, rape and treason could get you in a lot of trouble. But libel and jaywalking will only cost you points and if you have enough in the negative it probably is very hard to rise up being Default status. It covers all kinds of details, like how cops can be upvoted but not downvoted to protect them from citizen vindictiveness and how downvoting and upvoting of individuals in general is moderated to prevent abuse. There is also a maximum level of rep-rating one can achieve (was 10 but recently legislated to 11). And there are faults involved, like how the government pays more attention to high rep-rating individuals over low ones. It is not perfect -- which makes it all the more plausible and real. In other words, like the Whuffie system in the book *Down And Out in the Magic Kingdom* only much more detailed in its use. [Answer] This should not be that hard. Most children in the "first world" live in a post-scarcity society, albeit limited to their family. (They don't need money to buy their next meal from their parents.) In spite of this, most parents manage to force their kids to follow certain rules. So the answer to the OP's question would be: anything from shaming, to time-outs, to corporal punishment in extreme case. [Answer] In any post scarcity environment, the limiting factors would be time, energy and bandwidth. Wealth in a post scarcity environment would probably be represented by attention. Imagine being a person who's deeds were considered so amazing that you received millions of emails asking for advice (or FaceBook likes, or something similar). There is no possible way you could answer all these requests, but the fact you are in such "demand" (and limited "supply", being only one of you) means you are the valuable commodity in the post scarcity world. For punishment of "petty" crimes like jaywalking, then limiting your access to bandwidth would reduce you potential value. The more serious the crime, the more bandwidth restrictions you receive (maybe it becomes impossible to download high end patterns for your 3D printer). Up to a certain point, further bandwidth restrictions would apply to more serious crimes (although in a post scarcity environment, what is defined as a crime would probably be far different as well). Depending on the society, there would be some crimes so heinous that total removal from the network might not be considered punishment enough. Murder is probably going to remain the prime example of this sort of crime. How such a society chooses to punish these sorts of offenders may include capital punishment or prolonged isolation from the net (in a secure facility), or maybe exile, so your accumulated reputation and "value" in the home network is negated and you must start over again from 0 reputation [Answer] Your first premise sentence is inaccurate. **In most cases in modern current society, at least for people who are well enough off, there is no substantial threat of losing the ability to pay for basic needs because of minor infraction fines.** There is already a great abundance of food, shelter, clothing, etc at low enough price that many people can pay quite a few fines before worrying about their actual needs. **Even wealthy people without any fear of poverty still tend to avoid paying fines for a wide variety of reasons that may have nothing to do with need fulfillment.** The issues of motive and punishment are more complicated than just what is actually provided, of course. What people do (and how they respond to potential punishments) is determined more by their psychology than by their needs, and may have nothing to do with needs. Even when people's psychology concerns needs, it's often wildly inaccurate to the actual facts - for example, many wealthy people are full of fears about losing their money and becoming homeless, or variations on that theme, even though it takes a lot to actually become homeless even for lower-class people in the same society. At the "*Star Trek*" level of post-scarcity which you've defined, I imagine most of the scarcity-and-survival pathological thinking we see today would have been healed and replaced with new attitudes. However I don't think that some form of tradable money would not exist at all. Even in *Star Trek* per se, there are some commodities and there are traders e.g. Romulan Ale, Tribbles, spaceships, artifacts, real estate (see Kirk talking about selling a home in *Star Trek Generations*) and I imagine there are service trades as well. See <http://en.memory-alpha.org/wiki/Money>. Having a system of trade is useful and can provide motivation and counterincentive, as long as there is anything that's a limited commodity or service, even if all needs and most common wants are provided for. So **fines should still be somewhat of an option, even if they are less significant than in a society where nearly everyone lives in fear of being allowed to starve or freeze or go without medical care, etc.** **In *Star Trek* we also see people being confined, imprisoned, sent to psychiatric prisons, disgraced, relieved of their positions/titles/jobs, and even marooned on unsettled planets.** There is a vast array of things that a society could use to punish and deter crime, even if they had unlimited goods, robot services and free holodecks, including (with my suggested options for minor crimes in italics): **Corporal punishments:** Death Dismemberment / Drugs Torture Pain Discomfort, tickling, itching powder **Exclusion:** Banishment / Exile (measured in degree, space, and/or time limits) Confinement *Deprivation of various rights* (many options here) *Deprivation of various services* (can be measured by degree, type, time, or a credit/money system) Deprivation of property **Social:** Reputation, *humiliation* Social class, memberships Removal from professional / academic positions *Added duties or community service* *Apologies, atonements, services* Oaths, *contracts* *Reeducation* / Therapy / Counseling / Spiritual assignments * In other words, much as we do now, consequences for minor infractions could be like: speeding - dangerous: fine against luxury credits, reduced driving or speeding rights, traffic class, promise not to speed dangerously again for a period or receive steeper penalty, and/or public record of dangerous speeding speeding - trivial: small fine, brief reduction in speeding rights, or need to have a hearing/training session trespassing - major: payment/reparations to whoever you trespassed against, apology, public record, temporary restraining order, counseling, etc. trespassing - minor: small fine or payment to whoever you trespassed against, apology jaywalking in a dangerous area - minor pedestrian education session, or requirement to sign contract taking full responsibility for consequences [Answer] Well, of course the premise of the question is that a "post-scarcity" society is possible. That is, that it is possible to create a society where everyone can get whatever they want whenever they want without having to work for it. It is difficult to see how that is possible in the real world. I recall lots of science fiction stories written in the 1940s and 1950s, when automation and productivity were really taking off, that toyed with the question of what people would do with their lives when you could get everything you wanted with little or no work. But here we are 50 or 60 years later and no one is wondering how to fill their time because everyone is so rich that they don't need to work. Sure, today we spend a lower percentage of our incomes on food then people did 200 years ago. But besides that ... Maybe it's true that you could get a small, simple house that would provide basic shelter from the weather for a smaller percentage of your income than it took 200 years ago. But people don't want a minimal house; they want a big, fancy house. Today cell phones and computers are considered almost basic necessities -- to the point that people talk about the "need" for governments to provide these things to the poor for free -- yet they didn't even exist 200 years ago. If technology continues to advance, the average person will be able to obtain better and more, but it is likely that people's demands and expectations will also increase. So in the Federation people get their food from replicators. Who builds the replicators? Who maintains them? Who mines the ore and smelts the metal that these replicators are made from? Etc. If they're not paid, why do they do this work? If the replicators break down and the person who maintains them doesn't feel like working today because he'd rather go fishing, it seems to me that people would starve. Should we assume that there would always be someone who knows how to repair them and who feels like working today? How could we be sure that that would happen? If everyone gets everything they want for free, wouldn't large numbers of people decide that they're not going to work at all, and never learn any of the skills needed to keep the society working? I recall years ago when I was in high school, one of my teachers "explained" to the class that the idea that people in a utopian communist society would not work is false. He'd still work, he said, because he gets satisfaction from working. And maybe he would. Most days. But if you knew that you would get everything you wanted whether you worked or not, that work had nothing to do with any personal reward, don't you think there would be days when you'd say, "Hey, I don't feel like working today, I think I'll hate out at the beach or just take a nap"? I'm sure I would. I'm sure the amount of work done would be more than zero, because some number of people would work just because they enjoy the work or are bored sitting around doing nothing. But a whole lot less work would be done than when people are rewarded for their work. Why do the crew of the Enterprise take orders from Captain Kirk or Captain Picard? If they're not paid and they have no obligations, then any time the captain orders them to do something they don't feel like doing, why don't they just say "screw you" and do as they please? He could put a black mark on their record and kick them out of Star Fleet? So what? If people can get literally whatever they want, then they could just get their own starship and go exploring themselves if that's what they want to do. If there are SOME things that are available for free, like food and simple clothing, but others that are scarce, like star ships, then this society must have some way of deciding who gets the scarce things. If it is not done using money or some equivalent, the only other alternative I see is that some sort of government decides. i.e. instead of people working to get what they want, they have to lobby politicians and appease bureaucrats to get what they want. Personally, I'd rather live in a society where I know that I can get what I want if I just work hard enough, or if it's really big, get together with other people to pool our resources; then in a society ruled by a communist government where the only way to get what you want is to have the right connections. But that's an opinion. You could, I suppose, speculate that human nature will change and people will want to work for the satisfaction or because they feel an obligation to society or whatever. But that's a pretty wild speculation. Read some ancient books written thousands of years ago. Has human nature changed since the earliest recorded writings? People have always wanted to listen to good music, eat good food, have friends, make love, etc etc. Human nature hasn't changed in thousands of years. There's no reason to believe it will change in the next couple of hundred. [Answer] I'm thinking we impose a currency. You get a certain amount of "money" each day. This money can be used for better food, games, house decor, etc. Crimes make you lose money. # EDIT To clarify, the better food thing is saying we *impose* a restriction on it. We say good food costs money, and make it that way. Even though one could easily have access to better food, we make them pay for it, to make the fine an effective punishment. ]

[Question] [ **This question already has answers here**: [How can someone that has lived for hundreds of years avoid suspicion in the modern world? [closed]](/questions/124150/how-can-someone-that-has-lived-for-hundreds-of-years-avoid-suspicion-in-the-mode) (13 answers) Closed 5 years ago. The immortals are among us. And they have been for a long time. All of them were born in the 7th to 4th century B.C. in the area of what today is the regions of Macedonia and Thessaly in Greece. Whatever caused their immortality is no longer present. As far as they know no other people with this affliction exist. They are not truly immortal. They don't visibly age and always appear to be in their early twenties, but they can be killed as easily as normal people. Violence, accident, drowning, starvation or a severe disease can kill them, but if they can survive the first 24 hours they will usually make a full recovery. They heal about 25% faster than a normal human. Their immune system will eventually deal with any disease or poison and they will regenerate any damaged tissue (even nerves or brain-tissue) completely given enough time. It will take about 20 years to regrown a lost arm or leg. It isn't all good though. They are all infertile. In ancient Greece being immortal wasn't really a big deal. People simply assumed you were one of Zeus (or any of the other gods) many illegitimate children. Demi-gods are supposed to have strange powers. But in later centuries this changed. The immortals quickly came to realize they better stay in hiding. Especially the Christian church took a dim view of people with special powers, proclaiming them to be witches or demons. A lot of immortals ended burned at the stake. So the immortals went completely underground. They moved from town to town every 15 years or so to prevent the neighbors noticing the everlasting youth. Cosmetics to appear a bit older have helped too. Cosmetic surgery is no good though. Their regenerative system starts to repair the damage straight away, undoing the changes. It was especially difficult for the immortal women as they couldn't easily operate solo for most of our history. They would usually team up with one of the immortal men and pretend to be a married couple (and in some cases they actually were a couple). Of the original about 4000 immortals some 800 are left in 1950. They are mostly based in Europe and the America's. They have a central organization masquerading as a legit international trading and shipping company established in the early 18th century, that keeps in touch with them. Another 200 to 300 of them have been out of contact for decades, but they may still be around somewhere. After World War II, in the 1950's they start to realize that identity papers and civil records are becoming ever more important in any modern society and assuming a new identity every so often is becoming increasingly difficult every year. Later on computer records and bio-metric ID's made things even worse. **So how can they keep hiding from 1950 onward to today?** Preferably while leading a fairly normal life with all the amenities? Living completely off-grid somewhere in Alaska, Siberia or Africa doesn't appeal to most of them. Money is of no concern. The organization has been around for centuries and has invested wisely. They are not adverse to illegal activities if those are necessary, like bribing people, tax evasion, forging documents, but they draw the line at violence. No murder of inconvenient witnesses. [Answer] The easiest way would be for them to do this *The Odessa File* style: Get one or more of their own on the inside of the record-keeping bureaucracy of a state with weak governance. That insider can then steal, fake, forge, or just plain old *issue* whatever documentation they need to keep churning their identities. Edited to add: since that bureaucratic insider would need to periodically leave their employment or their coworkers would notice their lack of aging, you need a minimum of two - one senior bureaucrat and one protege / future replacement - at all times. [Answer] Over the last centuries these immortals faced slowly escalating problems as bureaucracy grew. A pattern based on teamwork might help: * Every decade or two, *fake a pregnancy and childbirth*. This requires a baby, but orphans could be found. * As the children reach primary school age, get rid of them. In an orphanage if they are moral, by murder if they are the villains of the story. Create records of homeschooling or an exclusive boarding school organized by other immortals. * As the non-existing child identity reaches 18 to 20 years, one of the older immortals from a different town fakes his or her death and assumes the identity of the missing baby. If male, he does military service as required, otherwise it is off to university. With their millenia of experience they will get a good degree, and they might even learn something new. * After graduation, have them hired in the company or law firm of another immortal. Start the transfer of wealth in the form of salaries, bonuses, or manipulated stock options. That means they will only be seen in public with an official age between 20 and 40, which should be believable. In the second half of the 20th century that scheme started to break down. More complete, computerized records made it all but impossible to keep a child from view between 6 and 18, so it would be harder to make the substitution. With 21st century biometrics and image recognition, the problems are escalating. They need something new, but how? Money is no problem, but not every public servant can be bribed. # Promote Privacy Laws Put some of their money into lobbying efforts to limit biometrics use other than by official agencies. Ban running face recognition on services like google. # Citizenship for Investors Encourage some unimportant-but-respectable countries to offer citizenship to immigrants who are willing to pump a million bucks into the local economy, plus their immediate families. Actual residency is not required, and background questions are only asked about the principal, not the family. (Privacy laws again, and *ironclad* laws to shield minors from snooping.) Buy such a citizenship with no intention of ever moving there, but send the "next generation" over. # International Tensions to Limit Data Exchange It would be really bad if countries started to exchange biometrics. So donate to nationalists and other leaders who decry international cooperation. [Answer] > > So how can they keep hiding from 1950 onward to today? > > > They pick a nice fertile area of land, pleasantly sunny, clean water, lakes, coastline and the odd mountain for ski-season and they: ## Declare Nationhood Since 1933 [International Law](https://en.wikipedia.org/wiki/Montevideo_Convention) has permittted that [Sovereign States](https://en.wikipedia.org/wiki/Sovereign_state#Declarative_theory) be able to declare themselves independent if they meet the following criteria: > > 1) a defined territory > > > 2) a permanent population > > > 3) a government > > > 4) a capacity to enter into relations with other states. > > > This was ratified in 1936 by the League of Nations. Subsequently The EEC took up a similar position when the [Badinter Arbitration Committee](https://en.wikipedia.org/wiki/Arbitration_Commission_of_the_Peace_Conference_on_Yugoslavia#Opinion_No._10_(Federal_Republic_of_Yugoslavia_-_Serbia_and_Montenegro)) ruled theat Serbia-Montenegro be independent. **The Upshot.** They can issue their own Passports control their population's biometric database and birth records. Modern technology has progressed in biometrics, but so has technology in fooling biometrics: * Fingerprint sensors can be [fooled](https://www.digitaltrends.com/mobile/researchers-fool-fingerprint-sensor/). * Iris scanners can be [tricked](https://www.bleepingcomputer.com/news/security/samsung-galaxy-s8-iris-scanner-fooled-by-a-photo/). * Retina scan, well, we're still [tinkering](https://www.quora.com/In-movies-the-bad-guys-take-out-someone%E2%80%99s-eye-to-fool-a-retina-scanner-Would-that-work-in-real-life) with that one. On the whole they still have their freedom to travel the globe and do business, create mischief etc.. [Answer] Eastern Europe, as a modern example; if you're rich Eastern Europe has all the modern conveniences of any other part of the civilised world but it is, and has been for some time, an apolitical mess, in such a climate of corruption and lax government your immortals can hide in plane sight for as long as they like. Sure crazy old Sven down the road swears that his neighbour Olaf hasn't aged a day since he was a boy but no-one takes him seriously; especially since Olaf is openhanded with gifts of food and money but otherwise quiet, polite, and doesn't bother anyone. No-one realises that the money is their rent, the holding companies that own the town are all registered in the capital and the inspectors give Olaf as much trouble as anyone but he's the sole shareholder. There have always been parts of the world where appearing moderately well off, not enough to provoke jealousy but sufficient to curry favour, can garner you a degree of anonymity and privacy not generally available elsewhere. Your immortals may have to move around to stay in such areas but generally speaking with wealth and assets (particularly land) accumulated over centuries that should be relatively easy. Their properties are held in trusts that have new governors appointed from countries with dubious recording keeping as and when someone gets suspiciously long in the tooth but in reality one one or two people have ever run the affairs of those properties. [Answer] First, let's not unreasonably assume they have amassed immense wealth, and are expert at money movement between the identities, which they should have been gaining expertise at thru the years. They can always keep purchasing new identities, even if the price goes up. As far as record-keeping, they would need to have/maintain world-class cyber security expertise. This would represent a continual challenge as governmental scanning techniques also evolve. On the forensics side, its going to soon become impossible to evade detection, either on the basis of prints or dna. Therefore, they must at all cost evade arrest by any means necessary, including murder, if it compromises detection. Detection of one immediately threatens detection of all, or at least a global manhunt. Whatever their scruples, arrest/detection is a no-go zone. Therefore, the quasi-immortals must at all times act thru world-class agents, and avoid criminal activities (aside from the aforementioned necessities involving identity transfer) certainly directly, in any event, maximally discretely. If one never drives, and is accompanied by sturdy protectors, most opportunities for detection/misfortune are minimized. A strong measure of 24/7 security would be necessary. Their self-repairing nature makes alterations impossible. And so, evasive maneuvers are all that are left. One might speculate about buying off the record keepers, but that doesn't seem feasible, or in any event, will ultimately prove to be impossible as a repeatable practice over time. [Answer] **They are homeless mendicants.** These immortal humans invisibly live among us. They are the homeless; vagrants; hoboes; transients. Wise men. Angels? [](https://i.stack.imgur.com/YUHH9.jpg) [source](https://www.christianheadlines.com/blog/pastor-james-macdonald-disguises-himself-homeless-man-measure-compassion.html) [Answer] # Start a religion Based in the US. Specifically a religion that externally aggressively refuses to engage with society. Every few years young adults emerge from the commune, feeling constrained by the religion, wanting to engage with the modern world. Obviously healthy though strangely educated, we don't want children's services getting involved, but with no record of their existence. After 10-20 years in visible contact with society they then retreat back into the commune only to emerge again after a reasonable period of time as their own cousin/child/niece/nephew etc. Outside the commune you maintain a secondary charity group who specialise in helping the children of the religion engage with society and get birth certificates, social security numbers, passports etc. [Answer] I was going to give almost the same answer as o.m. but you don't need the babies. Immortals would be expected to rotate them through a public service every few hundred years. They need to go into a role such as middle government, law enforcement, medicine and education and run that for the benefit of all Immortals for a time before handing over to the next. The doctors create birth certificates for babies that never were born. They run a charitable school and add non-existent children into the list to create educational records that exists in name only. The civil servants make sure passports, driving licenses, etc are all issued without any uncomfortable questions. Every few decades once the fake identities reach a suitable age (often just as they are about to go to univeristy) each immortal moves away from where they used to live (possibly faking their death) and then assumes one of the new roles that is waiting for them. Immortals are forbidden from high profile careers and publicity seeking and avoid criminal records or encounters with the law. Rule number 1 is - don't get DNA screened, if it does happen then the immortals within the relevant organisation will look to corrupt the records. In 20 years things may become too interlinked for this to work, it's viable now though and will still be viable for a few decades to come. [Answer] This was the topic of the book "[The Boat of a Million Years](https://en.wikipedia.org/wiki/The_Boat_of_a_Million_Years)" by Poul Anderson. It is a long time since I read the book, but some of the characters find jobs working in the bureaucracy where they are able to adjust records and reassign themselves. However, eventually they decide to reveal themselves. It was an excellent book and I won't spoil it further by saying more. [Answer] Run a private company. You have a chauffeur so you don't need a licence and the police tend to leave limos alone. You live in a company owned building and have a company credit card. Staff work on 18 month contracts. Every ten years or so, you move to a different part of the country. You avoid an online presence and the media as much as possible. As a rich, slightly crazy recluse that never does anything interesting, nobody would ever notice that you have no ID [Answer] Every 20 years or so, fake a pregnancy and child birth. The only person whose cooperation you need is the doctor who oversees the (non-existing) home-birth and writes a birth certificate. In most countries, having a birth certificate will be all you really need to prove the existence of a person. You will then be able to do all the other paperwork without any government official ever actually meeting the child. When the child reaches school age, pretend to homeschool. If you have access to resources, then it shouldn't be that difficult to keep the non-existing child out of the public without raising suspicion. As a multi-millionaire with a secluded lifestyle, you have a plausible reason to do that. You wouldn't want some paparazzi to take a picture of your kids so a kidnapper can recognize them, would you? When the non-existing child turns adult, fake your own death and assume the identity of your child. [Answer] While the fake-birth-baby-death route is common both here and in fiction, why go to all that trouble? You avoid scrutiny by exploiting cracks in the system. Cooperation between countries is limited. When you move to another country, the amount of exchange is limited and can be controlled by an insider. If the countries are not on friendly terms, you could bypass this step entirely. So simply move to a different country every 20 or so years. In that time, anyway it will become boring. A collaborator (i.e. another immortal) in the destination country who owns a company offers you a good position and helps with the paperwork. Most countries make immigration easy if you come with a job - their primary worry is that you'll be a problem for the social security system. After a few years, apply for citizenship and with that simple step you disappear from the beaurocracy of your previous country. Repeat this 2-3 times, you are still within the timespan of a normal life, but it would require extensive detective work to still track you. And once or twice a century you use some war, revolution or such to become a refugee who sadly lost all paperwork and documents in the unfortunate events. Yes, you will have to suffer a temporary drop in living standards, but thanks to your friends, it will be a year or two and then you move up again. [Answer] Having lived so long they should have been able to invest and save so much money they are in practice ruling everything, incl owning / having enough influence in the companies which do the record-keeping. Make sure to have a couple of them employed introducing bugs in these databases. This is supposedly what any powerful non-immortal group does already. 1. Infiltrate, 2. plant bugs, 3. rewrite databases / history in a way that benefits us 4. profit. [Answer] So many expensive, cloak-and-dagger solutions that seem to require secret world domination. Another solution: simply dispute the accuracy of the bureaucratic records, and pester the apathetic, annoyed, low-wage-earning DMV and post office clerks to override the system. "Yes; I have the same name as my great-great-grandfather. My parents wanted to honor their family. We were born in the same month, by coincidence. We probably look alike. What? We can't possibly have the same fingerprint; that is literally impossible. Your computer system got us mixed up. All I know is that your clerks are incompetent, I have a clean criminal record, and I need a passport asap to travel for work. If you do not destroy those faulty records, my lawyers will be in touch with you right away." "My client has been severely harmed by your department's inaccurate record-keeping practices. Don't waste my time with your rumors of immortal demigods; are you really willing to testify, under oath, in front of a jury, that my client is an immortal demigod? Fix your records, please!" [Answer] **Take Over a Country** Many of the answers here depend on being able to make use of national bureaucracies to create identities. If you establish your clan as the royal family, you can *BE* a sovereign and never be troubled again by identities. You can switch rulers every fifty years or so, then create a new persona from the millions of your subjects. The trick is to spend your efforts on maintaining national stability and being favored by whatever regional power is in the area. With your knowledge and skills over the ages, you should be adept at diplomacy. The inspiration for this comes from North Korea. You would not even need to be the official ruler yourself....appoint a few figureheads and promise them an easy life in exchange for their loyalty and silence. Most humans can be bought pretty cheap. You can even set up an academy to train normals for this specific role. [Answer] If the group realized the significance of growing computerization back in the fifties, they could have gotten in on the ground floor of the entire computer industry and built protections in for themselves. (Not much use to try to protect against backdoors in the software if its the *hardware* that has backdoors to let a select group bypass whatever software based security there is.) If the group controls the major players in the semi-conductor industry, they would be able to stay on top a large portion of their problems. They could gain access to the necessary databases to alter biometric data and create records as needed. ]

[Question] [ My story opens with an old man who arrives at his "personal" asteroid somewhere out in space. When he arrives, everything is powered down and he has to bring systems online before he can take his suit off. He has left galactic society (perhaps there was a war) and he wants to live out his final days inside this rock. There is something in there he wants to see one last time. In years (or centuries) previous, he had significant resources to expend to hollow it out and create comfortable living space inside as well as a "workshop" for his pet project. Some sort of reactor (or collector) powers the whole thing, runs life support, etc. Here are some ground rules of the story's universe: 1. No FTL - All travel is sublight, though much faster than what we can do in the present day. Some time dilation occurs and hibernation allows people to survive trips potentially spanning centuries. 2. No artificial gravity - Cylindrical colonies spin for centrifugal effect, but humanity has not figured out "gravitons" or whatever. We can fake it, but we can't make it. 3. Detection technology - In the present day, we look at the skies with radio telescopes, optical telescopes, etc. In this future scenario, there hasn't been significant advance other than increased resolution and clarity applied to the same principles of physics we understand now. I'm sure there are other present-day technologies that I am unaware of. If any of these might affect this question, I'd hate to be ignorant of them So the nut of my question is this: **How can he "hide" this asteroid, yet still be able to find it later?** Most likely, nobody would even be looking for it, but our protagonist is paranoid or at least careful. He would want it to not stand out too much from any other asteroids due to heat, unusual EM output, or any other odd behavior that could be noticed from great distances (if someone happened to be observing that part of the sky, potentially from any angle). As for locating it later, other than just eyeballing whatever region of space it's in once he gets there, I imagined there could be some sort of doohickey made of a material that only reflects EM waves of a specific obscure frequency. Shoot a blast of that frequency out into that general region and get a "ping" back once it hits the rock. Not sure how feasible that is though. The following aspects of the asteroid (and/or his ship) are flexible as needed to satisfy the requirements of the question: 1. Size of the asteroid - I don't know if it's the size of a house or the size of Texas, nor how this might affect not only its visibility, but its feasibility for hollowing out and inhabiting. Also, he doesn't have to use all the real estate. The inside could be the size of a house and the outside could be the size of Texas. 2. Composition of the asteroid - Rock. Haha, but seriously, we assume he searched long enough/got lucky enough and found the "perfect" asteroid that can remain obscure, yet could be mined for at least some resources. 3. Power source - Fusion? Fission? "Arc reactor" a la Iron Man? Some other magical McGuffin "future technology"? This might be the one place I'd have to apply some phlebotinum to make it work. Considerations would again include heat, EM waves, etc. that would affect how detectable it is. 4. Propulsion - The asteroid itself might have a similar propulsion system to his ship though not geared toward interstellar travel. It would be used for simple maneuverability and attitude adjustments. But what it is and how it works is up in the air. See "Power source" above. Otherwise, simple rockets could work, or even something that expels gases if it only needs to be nudged slightly. Again, how it would affect detectability is a consideration. 5. "Gravity" - Since we can't make gravity, the asteroid could spin for the aforementioned centrifuge effect. This might make docking his ship a bit more difficult unless he spins it up only after landing. But dependent on size, type of propulsion, power source, etc. it might be cost prohibitive to spin it up after landing, not to mention spinning it down upon his previous departure. And all that activity might make it more noticeable. I know the larger the rock, the more likely its own gravity would assert some force upon the man, but I imagine it would still be trivial. From the get-go I've been leaning toward magnetic boots. Staying in a non-spinning asteroid for long periods would likely lead to the usual microgravity symptoms such as atrophy, osteoporosis, etc. But he plans on dying here in peace, so this is not as much of a consideration. 6. Proximity to other heavenly bodies - Would it be better if the asteroid were near enough to a star to glean some energy from it? Would this make it more noticeable or less? Would it be better to orbit a planet which is itself in orbit around such a star? Or would it be better to be somewhere in the deep, away from the other cosmic "big boys"? Would being off in a relatively "dark" area of space make it more noticeable or less? This is assuming its power source can keep it warm enough inside to sustain a human life for possibly years. Hopefully this is enough conditions (and not too many!) to help fill in any of my gaps in logic. I appreciate everyone's time and thoughts. Thanks! **Edit to address possible duplicate:** This is not a duplicate of the "stealth in space" question, as that seems to be geared toward an active cat-and-mouse type scenario involving a moving ship that is travelling hither and yon, trying to outsmart space pirates who also travel hither and yon. In the case of the old man and the asteroid, the rock doesn't need much maneuverability nor sensor capability. EM and heat emissions would be shielded as much as possible and the whole thing wouldn't be going anywhere other than its existing orbital path. Additionally, one of the requirements was that it could not hide behind or in front of things. No such restriction applies to my question. In fact, the allowance for hiding among other asteroids lent itself to part of the accepted answer. [Answer] The primary way to hide something in space is to make it uninteresting. Start with a boring asteroid, made out of silicate rock rather than metals or organic compounds that are worth mining, orbiting somewhere that's inconvenient to reach, but not so inconvenient that people will go there for the achievement. In Earth's solar system, this would be a main-belt asteroid, fairly small (perhaps 500 metres long) with a fairly large orbital inclination, so that it needs a lot of fuel to reach. Don't put anything interesting or artificial on its surface. Power down its systems completely, so that it's at the same temperature as any other rock. Record its orbit really, really carefully, and make sure you know about all the other objects in the system. With that and a decent navigation program, you can reliably find it again any time in the next few thousand years, which sounds long enough. This gives you the best odds of nobody deciding to look at it or interfere with it. Doing anything active to hide it makes it more interesting. How do you keep from being noticed while hollowing it out and equipping it? Do that before anyone else is taking any interest in asteroids in this star system. So you want to have been a scout in the past, visiting previously unexplored systems, and setting up hidden bases for yourself in several of them. That implies a fair amount about the scouting system in your interstellar society - can you make that work? How do you keep from being noticed once you've moved in? Keep your emissions of all kinds to a minimum. Generate as little power and heat as possible, don't use radio, hide your ship in the underground hangar. On your points: 1. Size: small, so it's uninteresting. 2. Composition: very boring. 3. Power: fission is fine, but you need to run it at as low a level as possible. 4. Propulsion: Don't, it risks making the asteroid interesting. 5. Gravity: Spin it up when you build the base and leave it that way. All asteroids spin anyway. Making it spin fast enough for 1G would make it interesting, so settle for less. 6. Location: In a star system, in an asteroid belt. Finding and reaching loose asteroids is hard, and they get very cold. In the star system, it will stay at least somewhat warm, which is easier on the equipment you've installed. [Answer] Space is big. Really big. Looking for a particular asteroid somewhere in the solar system is pretty analogous to looking for a particular rock, somewhere on Earth. Unless you already have a really good idea where to look, you're not going to find it. As such, I would suggest that he doesn't need to take any measures to hide it, just place it out of the way of anything people are likely to visit. Consider the fact that we're *still* finding new near-Earth asteroids in the inner solar system (even when we're looking, it's hard to see something that doesn't reflect or generate light), and haven't even begun to map the [Oort cloud](https://en.wikipedia.org/wiki/Oort_cloud). In a future with private spaceflight, I'd expect there to be asteroid mining activities, and outposts or colonies near habitable planets, and therefore, I'd suggest that the best option would be finding a suitable asteroid out in the [Oort cloud](https://en.wikipedia.org/wiki/Oort_cloud), or dragging something into orbit way out in the far reaches of the solar system. An asteroid in our solar system's asteroid belt (for example) or otherwise near colonies or outposts could possibly be stumbled onto by mining activities, and I don't think a paranoid person would take that risk. On the other hand, place it way out on the edge of the system where no one goes, and you reduce the chances of someone stumbling on it to about 0. Putting it near the Oort cloud provides the advantages of both isolation and camouflage - not only is it somewhere no one's going to bother to travel to, it's also surrounded by billions of other similar objects, so no one will be able to pick it out, even if they did end up in the area, somewhow. As long as you know its orbital path and speed, you'll know where it's going to be, and when, which would allow you to make your way back to it. [Answer] Where do you hide a tree? In a forest. An asteroid? In an asteroid belt, obviously... Just find any asteroid belt that seems far away and already explored, perhaps in an old galactic area, and stick it in there. As for finding it? If he knows what asteroid belt it's in, he can calculate orbits and have the computer figure out where it is later when he gets back to it. Alternatively,use a giant space RFID tag. [Answer] There must be something pretty special that exists only inside this asteroid. Select an asteroid of sufficient size to burrow into the middle, but not so large as to make mining exploration appealing. Build a mini-capsule inside that spins independently of the asteroid. There's your full gravity, independent of the asteroid's rotation. With a sufficiently large crust, any heat from the flubberconverter coils could be absorbed and diffused into the asteroid itself without raising ambient temperatures to externally interesting levels. Avoid localized heat build up by drilling a network of negative space from the inside and build a massive distributed heat-sink. If it's a big enough asteroid, inside the capsule/mini-ship he can create a self-balancing ecosystem for himself, given enough self-discipline not to overtax its boundaries. For example, he can live there comfortably without overeating his oxygen-producing crops, but a visitor would destroy the balance and doom the life-support within days. Or he can only pirate the galactic news feed for an hour a day without stealing power from his plant's lighting, etc. Maybe his imported sea-bass get very ill-tempered if he doesn't eat enough of them, which may be likely if he gets tired of writing his cookbook, '101 Ingenious Ways to Eat the Same Thing for the Rest of Your Life'. The major detection problems would be in going and coming, unless it was in a dangerous part of space (what isn't?) where it would be more conceivable for ships to drop off of long range scanners without notice. Even inconvenient portions of the galaxy will have occasional visitors. Perhaps he will turn on the lights, and never leave again - that has its own ramifications. As others have stated, the best camouflage is to look as natural and normal and boring as possible. There may be an opportunity here to line the inner portion of the asteroid with heavier metals to give the illusion of a solid mass to casual scans, much in the same way that lead is sometimes used to fake a "solid" gold bar. [Answer] Pick a nondescript star within a hundred light years and make a pulsar map (like the one we sent with the Pioneer space probes). Now you need to be in the right solar system. Grab an asteroid and throw it into a highly elliptical solar orbit that throws it out into deep space for 100-10000 years or more at a time, coming back into the inner system for a few months/years before being slung back out. Now you need to either get lucky (very low chance at random) or know when it'll be 'near' the star. Essentially an artificial or hollowed out long period comet. If you pick one that doesn't get close enough/composed of the right materials to generate a visible tail and small enough, no one will bother even if they are around to detect it. Less sneaky than just putting it in the OORT cloud, but it makes it easier to find. Have it listening for a wakeup radio burst with his personal code: restarts the reactor and turns on a beacon, then he can lock onto it and rendezvous. A listening antenna will be essentially unnoticeable and the electronics to monitor it will take very little power and give off very little heat... couple it with heat activation from entering the inner solar system and it will be a dead rock when out in space, only listening when it gets near the star. [Answer] He not need to "hide" his asteroid, he just need to know its orbit. As stated in another answer to a different question, in space you are always orbiting something. If the asteroid has no structure on the surface, it is indistinguishable from the other millions out there, so he just need to choose one of the many present in the asteroid belt and just keep track of it and fit out how he like. As a personal choice, I'd go for an asteroid on the far end of the asteroid belt, about some thousand meters in diameter (or event somewhat bigger). This position make it relatively uninteresting, since also wanting to mine it, you probably go for an asteroid in the near end of the belt, just for simplicity. Hollowing the inside, you can probably get a space of some tens of thousand cubic meters, and spare way more volume as reserve and for mining. A good power source can be a well shielded fusion reactor, and eventually, a solar array as a backup, but they are vulnerable to micro impact and they are very visible. The tricky point is the gravity, since you need to make the asteroid spin at the right speed, which can be not so easy to set up and depend on the diameter of the internal habitat. I'd not set up a propulsion system, since I see it as useless on an asteroid and there is the risk to make it somewhat more interesting of the other millions. [Answer] While previous answers have covered *where* and *how* to hide the asteroid, they didn't mention the details required to relocate the asteroid once you need to return to it. While orbits in large solar systems are unlikely to change over time, especially in uninteresting areas, it is likely that someone as paranoid as described would be happy with merely that in an age of private spaceflight. Perhaps some other reclusive multi-millionaire wants to redirect a couple of asteroids for his pet park project, or for his space megastructure. In these cases, the orbits may be perturbed, and unless he has a telescope to track the asteroid on a local planet, he is going to lose his well-hidden habitat. A good way to counter this is to install a passive RF array on the asteroid, hidden below a few meters of rock so as to resist micrometeorite impacts but yet not suffer too much signal attenuation. This passive array would listen on the "activating signal" channel, maintaining perfect radio silence. Only if the correct handshake with key is sent will the passive array activate. Using a [phased array](https://en.wikipedia.org/wiki/Phased_array), a directional beam can be sent to the location of the ship. The power of the transmission will be tuned to the distance of the ship (by measuring the received signal power) and therefore will be essentially undetectable at a distance due to noise. This system would greatly decrease the likelihood of losing the investment on the habitat, yet not significantly increase the risks of it being found by others. [Answer] The other answers have already covered how to select the asteroid, so I'm going to focus on two points: power & spin. If you have some internal structure suspended on low-friction bearings (magnetic bearings if they wouldn't result in a detectable anomaly; my E&M-fu is too weak to say), it could spin at whatever rate necessary independent of the asteroid's own spin. You'd just need to compensate for friction losses, which leads to the second point: power. Anything you do will result in waste heat; this includes both generating & consuming power. On both fronts, you'll be less noticeable with higher efficiency & lower power requirements. Passive power sources could drive your heat signature down even further. Possibilities include thermoelectric harvesting or Stirling engines (both exploiting temperature differential between sun & dark sides) and piezoelectric tidal power (if the asteroid's axis of rotation is parallelish to its orbital axis and it's rotation rate is in sync with the natural frequency of the mode which is excited by the tidal forces). [Answer] ## Asteroids with Volcanic activity According to research by Professor Lionel Wilson as described in [this article](http://www.lancaster.ac.uk/lec/news-and-events/blog/lionel-wilson/ancient-volcanic-activity-on-asteroids/), there are asteroids with volcanic activity that much resembles the volcanic activity on earth. This means that your asteroid base could use geothermal energy as the only necessary source of power. This base could also be located by a volcanic hot spot on the asteroids surface in order to further disguise any escaping heat from your base. I am not quite sure exactly how common there asteroids are, and if they are rare or valuable enough to be significant sources of interest. In addition, it may be that bodies with sufficiently large metal cores could, through a [geodynamo](https://en.wikipedia.org/wiki/Dynamo_theory), generate a protective magnetic field, assisting in disguising any escaping signals and protecting your base from high energy particles, solar wind, etc. As for your requirements: 1. Size of the asteroid - I assume that any asteroid large enough to have volcanic activity would also be large enough to serve as a base. Any concern would likely lie in the other direction, with concerns over size and conspicuousness. 2. Composition of the asteroid - This asteroid would likely have plenty of resources, as it is larger and has sufficient metallic content to form a metallic, molten core. Again, concerns would be with standing out and being too attractive. However, in a civilization with a galactic economy, it would likely be an extremely long time before an attempt was made to exploit an asteroid that is far enough off the beaten path. 3. Power source - Solved above. Would definitely require a certain level of sophistication in technology and heavy equipment. 4. Propulsion - In a civilization with the ability to travel through space, there would almost certainly have to be very detailed maps, including current and future location, velocity, and direction. Any significant change in predicted pathing would likely be discovered extremely quickly, unless the asteroid is in a location that is rarely "scanned" or hidden. Again, if you pursue a scenario where the asteroid is extremely small and far away from inhabited and traveled locations, you could get away with it. 5. "Gravity" - Asteroids large enough to have volcanic activity are not necessarily large enough to have sufficient gravity to live comfortably. 4 Vesta, the asteroid named in the aforementioned article, only has a gravity of 0.025g, or 2.5% of earth's gravity. I would approach solving this by having the base located below the surface of the asteroid, with a spinning living space or large spinning space with the axis anchored to the asteroid's rock. 6. Proximity to other heavenly bodies - As these asteroids are fairly noteworthy, one would likely have to chose a one orbiting a star far away from population centers, depending on the proclivities of the civilization with relation to mining and exploring asteroids. An asteroid floating in the cold of space would likely radiate heat until it cools, but that process would likely take millions of years. ## Vesta, the Asteroid with signs of Volcanic activity [](https://i.stack.imgur.com/gQmet.jpg) [Answer] There are some flaws in logic, but nothing super stretching ## Gravity You can't spin asteroid fast enough to keep 1g gravity. Reasons for that are simple: * First of all mass of asteroid, composition of asteroid, own gravity Asteroid are not object with exclusive strength, and as you wish 1g be inside of asteroid, and gravity of asteroid is less then 1g, everything, not glued to surfaces will fly away, and that will be probably 100% of asteroid, in most cases. Asteroid objects keeping structure integrity in that case will be very suspicious. I'll even not bother to list other reasons. Good thing, you do not have to - just rotate living volume. Also that will free you from other technical difficulties connected with rotating asteroid. That applies some limitation on minimum size of such asteroid, how much Coriolis effect you will have. 10km size asteroids are ok. ## Place depends more on social aspects, then technical-detection stuff. If he wish to look on system star at evenings - just enough to choose system without humans. We barely see planets, in near by systems, and it's not because we bad at that, there are some fundamental physical limitations, let say gravity, length of electromagnetic waves, thermonuclear reactions in stars - that everything will stay. And he knows current limitations is possible to predict dark spots. For us now it's any star system, will not stay long, but +100 Ly probably is fine, for next 200y. If system without humans is not an option - then he have to exploit social ways to hide his asteroid. Let say officially owning it, but pretending to be something other, let say pirate group all fear to mess with, pretend to be their base - even if such group does not exists in reality, and lives entirely in rumors of people. Source of bad wudu magic here etc etc. Any sort of social disguise will work. If he ok with no star system, I may recommend to take free floating planet. Even in case mass and cheap sub 1c travels - most routes will be between stars. You may draw lines from each star to each star - route map. But beside these routes most part of space will be at 0 attendance. But being in right time in right place, there is a chance being on such routes to spot traveling planet (or any body actually), and there will be chance that next such possibility will be undefined time. Trajectory not close to any possible route. It will be not easy to make some base there, because it flies away from routes. It will be big expense to get on that planet next time. And use that opportunity at all - but that hard reach and more time it flies away, bigger expense will it be to get there. * it may depend on nature of space travel, but with most hard suggestions it's true. But even if it's not case - you have to know that that particular point in space and time is somehow interesting. With big planet body, or moon like, or big asteroid like - there is't much concern about hiding heat sources. Depending on size of that body, if you somewhere deep - it will take 10000+ years to your heat (megawatts gigawatts will change surface temperature on small part of K - just take heat capacity of body and calculate) ## Nothing is perfect Nothing is perfect and you have deal with that. If he found and so may and others. But nothing special actually, as result. * Deep space, far from routes, big body * far from humans, star system, any body * system with humans, own trough shell company. Energy sources any in all 3 cases, waste have to be below star energy. Hm but if it will above star energy and be not star(any kind) - I'll knock first, to check if someone home and wish have guests. If not, I'll fly away. Nothing worth so much troubles, I mean, nothing I may gain at the moment from that situation, worth of troubles, most valuable information about existing such phenomena already taken. Probably not your case scenario, but. Just flying away is also not bad scenario, just take big ship (buy, steal) fly in no return and undefined direction. [Answer] **Hide asteroid in gas giant.** 1. Hollow out asteroid and fill with old man suitable atmosphere and old man suitable pressure. 2. Allow asteroid to fall into gas giant. Like a metal ball falling into water, the asteroid will fall down into an area where the atmosphere is pressurized to a point that the gas-filled asteroid is buoyant. The asteroid will then travel back up, and down until it rests at the level in the atmosphere where it is neutrally buoyant. 3. Asteroid drifts around deep in the gas giant. It cannot be seen from space. It emits signals similar enough to ambient radiofrequency and electrical signals coming from this planet that only someone studying these random signals would realize some were nonrandom. These signals are so the asteroid can be located. 4. Asteroid could be propelled by sails. 5. Asteroid could be powered by windmills. 6. It is nice inside the asteroid. There is gravity, from the gas giant. It is a smallish Neptune-like gas giant so gravity is not too much. Old man stays buff. [Answer] An answer has been selected, but maybe some new ideas are still helpful. **Location** There are likely a vast multitude of rogue planets in interstellar space, enough that maybe no one's looking too hard at any single one: they are *much* farther apart than asteroids are, after all. A small moon of a rogue gas giant would be great if he doesn't mind the long trip. **Power** The moon should be icy. Such bodies are utterly unremarkable around a gas giant. Ices make a fine long-term fuel source for a fusion plant. A "singularity plant" is another possible power source. Get yourself a microsingularity. Make it a charged one so you can suspend it in an electric field. Give it a lot of charge because it will mass something like a trillion kilograms (so maybe it needs to be generated on site). (I think you don't want it to have a magnetic field, but I'm not sure. I think it won't have a magnetic field unless it's spinning, but I'm not sure about that either.) At the right mass, it puts out Hawking radiation at a useful rate. It will evaporate, so feed it matter to keep it at the right mass. Bam. Matter to energy conversion. I'm pretty sure it puts out X-rays, so you shield it with something like lead. Pure lead is no good because of its low melting point. The hot shield gives you the temperature gradient you need for power. Singularity plants are probably stable. In a gigawatt plant, the singularity will take trillions of years to evaporate. If containment is lost, the greatest threat will be an electric arc as it equalizes its charge with the environment. It won't be able to gather mass quickly enough to be a real gravitational threat anytime soon. It'll bore a microscopic hole through the floor as it falls, though. **Detection** Tidal forces could explain a higher-than-ambient temperature at first glance. It could expel heat with artificial geysers. Particle beams might also work, but he would need to take special care to avoid making hot spots on the surface. Dumb proximity detectors could insure the beam doesn't hit anything. Special materials can store a lot of waste energy -- bombard some isotope with waste alpha particles so it transmutes, or use something that undergoes chemical changes instead of phase changes. The thing is (although I don't have time to think about it much), I believe you can't store all of your waste energy cleanly. I think heat must leak from the system in every storage-release cycle because entropy has to increase each time. You should be able to do better than dumb heat sinking though. [Answer] Rather than the most undesirable rock with absolutely nothing artificial showing on the surface, you could pick one that has already been thoroughly mined; such a history (which you might be able to fake!) accounts for the presence of ‘abandoned’ equipment. [Answer] Many good answers here, so this will be a bit redundant in places. You don't need to actually hide it, you just need to make it totally uninteresting. Hide it in plain sight. As one poster said, make it a derelict mined-out asteroid. Strip it down completely, so it is completely uninteresting. Since it WAS a working asteroid, it would be expected to have a locator beacon. Nothing attractive about that. It could even still be used as a navigation beacon. Any heat signature would be put down to previous activity. Things take a long time to cool down in space. Actually, spinning the asteroid to provide gravity would make it even more unattractive to exploration. A spinning asteroid is quite difficult to land on, except for the poles. If the spinning were put down to an industrial accident on the original mining operation, which made it untenable, even less likely anyone would visit. A catastrophic accident would make the asteroid jinxed. Just a bad place to be. As one poster said, put radioactive refuse at the poles, which are the only viable landing spots. No one wants to land in a radioactive refuse dump. Leftovers from the catastrophic event that caused the decommissioning of the mining operation. A hardened ship could make it past the radioactivity, through a camouflaged tunnel, and the buried living quarters would be shielded by the mass of the asteroid. If anyone DOES become attracted to the asteroid, I am sure they would not stay around long enough to explore it. They certainly would not go anywhere near the radioactive entrance. The idea is to project the message 'Nothing of interest here, folks. Just move along. Much more interesting things over there.' There are many examples on earth of abandoned facilities remaining completely uninvited and uninteresting. Since you are the author of the story, everyone in the universe does and thinks exactly the way you want them to. If you don't want anyone to be curious, they aren't. Just give a sufficiently believable reason for them to reasonably NOT be curious. [Answer] I would chop it up into tiny pieces, like a giant puzzle. That would make it not an astroid really, but a rock field. For one, radar wouldn't be able to detect it if the pieces were small enough and far apart, and radio waves are quite large. Secondly, no one's really interested or would suspect they fit back together. Third, maybe it's impossible to put back together unless you know the trick, so even if you found it, captured it, it's worthless because you don't know the "password" to unlock the rock. You can figure out how to put them back together. Maybe it requires a little nudge and it all falls into place over the course of a year, maybe your drones have to assemble them for you. [Answer] Perhaps put the asteroid inside of a nebula of a certain temperature? With a large enough nebula at the proper temperature I believe that it should be impossible to see the asteroid inside of the nebula via Astronomical Spectroscopy (<https://en.wikipedia.org/wiki/Astronomical_spectroscopy>) or any other form of detection. It's been a while since my high school Astronomy class however if I'm remembering correctly this should be feasible. [Answer] The big problem is heat as a by-product of energy usage. Three possibilities: 1. Place it somewhere hot, where its radiation is lost in the background 2. Collect the waste heat (and by doing so generate more waste heat) and somehow dispose of it - seems to me it might be possible to radiate it away in directions and intensities not likely to be "interesting" 3. locate the asteroid way far out of any star system (in the interstellar medium) and away from paths from here to there and give it sufficient velocity such that nothing is likely to catch up with it. As far as finding it, since centuries might go by before he decides to find it, the only way I can think of is a beacon which responds to a code with signal of a known but apparently random noise pattern. Oh, did I say it should be out of the ecliptic? that's pretty obvious, right? You do know that we can't see (naked eye) 20 of the nearest 30 stars, right? It's pretty easy to calculate a reasonable limit for future sensitivity and then figure out how far away an asteroid (small is better) would need to be to be below that limit of emission. As far as spin for gravity, since the little g\* will equal r (2π/T)² and if the outer 'floor' is 9.8 m in diameter, spinning the rock once per second gives 1g. I think smaller will be easier (although if seen more 'interesting') to spin up. You haven't explained how he gets the work done preparing it, without leaving all sorts of clues and traces and emissions... [Answer] # Have your asteriod \*outside of galactic society\* As you said in the question, this man has left "galactic society". Let's say he goes to the **nearest** galaxy. **The nearest galaxy to Earth is about 2.5 million light years away**. Old man Jenkins can't travel at the speed of light, so it takes him more than 2.5 million years to get there (but because of time-dilation and additional handwaving, let's say that *to him* it only feels like 2.5 million years). After travel in a specific direction for such a long time, chances are both Jenkins and his asteroid will be very difficult to find. The only problem remaining is that, due to less-than-FTL travel, Jenkins is ~2.5 million years old, so I'm not sure how many days he has left to enjoy his asteroid. **TL;DR—just go in one direction for long enough, and it's hard for someone to track you down. But the real problem here is not having FTL.** [Answer] Interesting answers here, but personally the one I would go with would be: # Hide in plain sight Your pal probably isn't the only space cowboy looking to hollow out a bit of asteroid for their own private purposes. Chances are there will probably be privately owned asteroid belts that rent out rocks, fewer questions the better. Payments are made via untraceable crypto-currencies, and the owner prefers not knowing the clients, and vice versa. They might even use the rents to employ enough mercenaries to keep their property safe from intruders. Such proprietors would likely have a distrust in government, and might not even live in the same solar system, so there won't be anybody to sell you out. Here are some advantages to this model compared to the "hide in a rock in an uninhabited solar system far away" approach that seems to be broadly favored here: ## Plausible Deniability There's no way you're gonna get to your asteroid and back completely undetected. In fact, the more off-the-beaten path you appear to be flying, and the more your ship seems destined to reach that point, the more suspicious it looks. But if you're just one more ship around the Interstellar-U-Store-It, nobody will notice. It could be perfectly common for owned asteroids to use semi-artificial gravity, so you won't need to be floating around the whole time or hoping that your 1G spin doesn't attract any undue attention. ## Fresh Supplies How long till you get sick of toothpaste meals? If there are dozens or hundreds or even thousands of other asteroid-renters in the belt, there will likely be new supplies of all sorts coming in daily. Might not be the highest quality or fastest delivery you'd get living on some fancy-schmancy metropolitan planet, but this way you could have the things you need delivered to you, just another address among many, not raising any questions. ## Security Someone comes poking around and the hired mercenaries will at first very politely ask them to leave, but can be there to fight on your behalf. Whereas if you're on your own and the wrong people knock on your door, their disappearance from a remote and inconspicuous corner of space will look very conspicuous indeed. ## Travel This goes hand-in-hand with security and supplies. If you ever need to leave, you can just put on a space suit and take the next shuttle out and nobody will notice you in particular. Likewise, if you want to return, you will just be one body among many. ## Distance Even if you are so well-supplied that you need none of the things listed above, eventually, there might be a need to leave. There could be a medical problem that neither you nor your robots could help you with. You might need high quality fuel or precision equipment to repair a component that was knocked awry by an errant meteorite, and without it, you might not survive an interstellar journey to get what you need. ## Prostitutes We all get a little lonely, sometimes. [Answer] A real cloaking experiment is [mentioned here](https://en.wikipedia.org/wiki/Cloaking_device). An object coated with this material actually absorbs EM at given frequencies (In this example visible light) redirects it and sends it out on the other side, so the light appears to go through it. The material is not perfect, but in the near future it may be. Drawback: To work perfectly on visible light, it must prevent any light reaching the object's surface, so it will bask in perpetual darkness, and drawing solar energy will be impossible. It may be fine-tuned to reflect a wide EM spectrum this way, but it does not prevent collisions. Anything hitting it will not get through the material to the other side! If the asteroid orbits within the habitable zone, all heat signals coming-out from the activity within will be masked by the sun's heat. ]

[Question] [ [Carnivorous plants](http://en.wikipedia.org/wiki/Carnivorous_plant) live in nutrient-poor, highly lit habitats, such as bogs or rocks. For example Earth's biggest carnivorous plant, [Nepenthes rajah](http://en.wikipedia.org/wiki/Nepenthes_rajah), lives on mountain-tops with high concentration of heavy metals but few nutrients such as nitrogen. However, [man-eating trees](http://en.wikipedia.org/wiki/Man-eating_tree) and [triffids](http://en.wikipedia.org/wiki/Triffid) are just fiction and don't seem very realistic, because they would need too much energy for catching their prey or even moving. So what conditions would make carnivorous behavior so beneficial, that carnivorous plants would grow much bigger, enough to be threat to men and similarly big animals? Also how likely is each of the five basic trapping strategies (pitfall, flypaper, snap, bladder and lobster-pot trap)? Or is any other strategy possible and realistic under such conditions? Nutrient-low habitats creating need for carnivores usually don't allow for big growth, so is it realistic at all? [Answer] A plant chasing humans would be unrealistic, but I think a plant generating a trap for human-sized animals could be possible in principle, given the right circumstances (maybe it evolved from one eating smaller animals, but those got extinct, and the trap size grew to capture ever larger animals). The most obvious way would IMHO be if the plant managed to create a concealed hole in the floor where animals would fall in, breaking through the thin cover (which would regrow while the animal would be digested inside the trap). Of course the natural countermeasure would be to be always careful where you go, so animals in a region with many such plants would usually always test the floor before they step; running would probably be quite unusual. If the substance in the trap kills quickly, a careless human (or one not knowing about that danger) could also be caught by such a plant. Another possibility could be using many small barbed hooks growing out of the floor, and unnoticeable to the animal (looking basically just like the normal floor). When the animal steps on the floor, the hook enters its skin, and if the hook is strong enough, it cannot leave any more. Such a plant could normally be completely under the earth except for the hooks; after an animal is caught by the hooks, it might grow special roots relatively quickly into the caught animal to digest it from the inside. Coevolution would probably make the animal's feet thicker (so they are less easily pentrated by the hooks) and the animals lighter (so they are pressed into the hooks with a lower force), or to avoid the floor as much as possible (like apes living in the trees). Humans living in those regions would probably develop shoes early on as protection against those plants. You certainly should not go to sleep where such a plant grows; maybe humans would predominantly live on trees, too. Humans not knowing about that danger might fall prey to such plants because they walk onto such plants with their bare foots or insufficiently strong shoes, or lie down to sleep on one. Also stumbling on such a place can be deadly (the plants might also grow tripping hazards in order to make animals — and humans — trip on such places and thus involuntarily expose less-protected parts of their body to the hooks). --- Here's another option, which is actually a worked-out scenario how an actually man-eating plant could have evolved. Imagine a nutrient-low environment, and a plant which happens to produce a substance that happens to be very beneficial for some man-ancestor animal. Members of that species will then, of course, start harvesting that substance from the plant, which actually harms the plant, therefore it will start to evolve counter measures. Those counter measures could initially have been a contact poison on the bark, which over time got more effective. However, since the substance was so advantageous to those species, they also co-evolved to become more skilled in getting at the substance while avoiding that contact poison. There still were some individuals dying from the poison, but the substance was so advantageous to them, that it more than made up the evolutionary disadvantage of some individuals dying. However, at the same time those individuals dying turned out to be an evolutionary advantage for the plant, since the rotting corpses delivered sorely needed nutrients to it. So the evolutionary pressure changed on the plant: Now it was not just reducing harm from the harvesting of the substance, but also increasing the number of individuals killed by the poison, to deliver more nutrients. Of course there's a delicate equilibrium involved here, as the chance to survive the harvesting attempt must be high enough that the advantage of harvesting outweighs the danger of being killed. So the evolutionary pressure is to increase the absolute number of individuals killed, while at the same time not increasing the relative number, at least not beyond a certain point. That means, attracting more individuals. Thus, the substance in question will be produced in more amount, and also in a way that is more easily accessible (which also means that after some time the harvesting doesn't harm the plant any more, because it is offered at a place where it can be gotten at with little harm (but high probability to get into contact with the poison). At the same time, it will also evolve means to more effectively harvest the nutrients from the corpses, like growing roots into it. Of course, for the human-precursor species, there's an evolutionary pressure to get at the substance while losing as few individuals as possible, therefore getting better and better at avoiding being killed by the plant; this will be countered by the plant evolving better and better strategies of killing. At this point, both species my already be dependent on each other, so that's the only way evolution may proceed. Now imagine that the plant, due to some mutation, produces a bit more of the advantageous substance while consuming a killed individual. Now this changes the evolutionary pressure *inside* the pre-human species: Now it is not only advantageous to avoid getting killed, now it is also advantageous if a competing individual *does* get killed. Not only does that other individual get removed from the gene pool (that would have been the case even before), but in addition it means more of the advantageous substance. So there's now an evolutionary pressure not only to avoid getting killed by the plant, but also to cause competing individuals getting killed (for example, by pushing them to the tree). This means (according to the egoistic gene assumption) that such a behaviour will evolve. Also it means that individuals get an evolutionary advantage from recognizing times when the plant produces more of the substance. Now individuals being actively pushed to the plant for being consumed by it is, of course, of advantage of the plant, so it itself will evolve to encourage that behaviour; it will make the difference between "hungry" and "consuming" state more pronounced, eventually stopping to provide any substance while "hungry", and probably over time stop to kill during "consuming" phases. At that point, it will not just be advantageous, but actually mandatory that some individuals are pushed to the plant, in order to get the substance which the species is long dependent on. For members of the species this means an evolutionary pressure to get more intelligent: First, it is of advantage to understand in which phase the plant is, so you can avoid it while it is hungry, and harvest it otherwise. But at the same time you need social intelligence to both trick others to visiting the plant when hungry, and to avoid being pushed to the plant yourself. So this specific situation should give an evolutionary pressure to become an intelligent species. Now fast forward, and see how that species turns into (that world's equivalent of) humans. As the intelligence evolves, they will become aware of the fact that they are killing others at the plant, but also that this is absolutely essential for them to be able to live on. Probably they'll rationalize it that the plant is from a god who wants them to sacrifice humans, but who gives them the substance in return. The specific way they evolved will probably mean they will naturally mistrust each other very much. The main goal of the emerging power structure (with a priest or similar on the top) will likely to be to regulate sacrifices to the plant, so individuals don't have to live in constant danger. I'd also expect tribal wars to be common, in order to get people from other tribes to sacrifice to the plant. All in all, you'd get a man-eating plant which is explicitly fed by an inherently mistrusting and martial humanity depending on that plant. [Answer] If you want a carnivorous plant to eat large animal it needs a quick way to disable and kill them. The venus flytrap relies of it being structurally stronger than the insects, the pitcher plants just outright try to drown the insect to get it to stop escaping along with the slippery walls of the pitcher. So how could a plant quickly disable a large animal? The only answer I can think of is poison. Lots of it quickly administered before the animal can get away. There are spiders and jellyfish that produce enough toxins that can be quickly delivered to incapacitate a human pretty quickly. Combine some of those toxins with long vines/roots and these could be made to work. [Answer] Many plants today have attributes that could be useful for trapping larger animals (including humans); thorns and barbs, poisonous plants, or smelling/tasting great. Of course, the reasons for those "traps" are to keep animals away or spread seeds/pollen, not to gather plant food, but with a little "tweaking", it's perfectly possible for plants to "eat" humans, or even bigger animals. Here are four possibilities I've come up with: The easiest trap to make would be one where the plant doesn't need to move or generate anything: a pit. Of course, an animal could crawl out, so there should be sharp spikes or barbs at the bottom of a short, steep drop. Add some trip hazards and/or slippery film, and all manner of creatures will fall in and be killed, ready for digesting, without any worry of a damaging struggle. The design scales well, so a small man-eating pit-plant can catch insects, rats or mice until it grows big enough to catch larger prey. A crushing trap would expend more energy, but is still possible; many ferns like the [Mimosa Pudica](http://en.wikipedia.org/wiki/Mimosa_pudica) can fold themselves up when touched. A tree with a large hollow area in the middle that is "touch sensitive" could squeeze closed without expending much energy, and quickly crush whatever creature set it off. Again, spikes or barbs would help. Smaller creatures wouldn't be enough to trigger it, meaning it wouldn't waste its energy. As BSteinhurst mentioned, a fast-acting poison would also work. A shroud of barbed nettles, each containing a nerve-blocking poison, hanging over an exposed root system would kill anything it managed to touch, and allow the nutrients of the decaying body to be absorbed. A cluster of seedless fruit that smell sweet (or like raw meat) would attract various creatures to their doom. The man-eating plant doesn't have to be big, though. A simple mushroom could do the trick. It would be designed to grow on flesh, and smell sweet and tasty to attract being eaten, but contain a deadly toxin that would kill even large animals. When eaten, the spores from the mushroom would cover the creature (hands, mouth, etc.), and eventually begin to grow on the recently deceased. However, all these methods (apart from the mushroom) require a substantial investment of energy. Growing a large pit or crushing trap will take a lot of resources. Plants like that would only be able to survive where there is a large amount of incoming food, enough to make an investment in traps and digestion more worthwhile than grabbing energy from the sun and nutrients from the ground. Then again, in fiction, there are always adventurers ready to travel into killer-plant-infested caves and dungeons, so it may very well work out. [Answer] It depends on what you mean by realistic, in particular humans might be too rare and too smart. However, if you want "any big animal", then here are some ideas: * The simplest is a plant that uses tiny aerial spores to be breathed-in and take root in the lungs, then killing the animal and taking root in its corpse (more like a fungus, which technically is not a plant, but may actually work too). I've seen this idea several times already. * A plant that has leaves/flowers that act as triggers, when touched they spray a paralyzing agent to breathe-in, the victim dies by cardiac arrest or lack of oxygen. There's no need to "devour" it, the remains will provide enough nutrients. * A plant with *giant* leaves, that are slippery to create a pitfall trap filled with some kind of sticky gel. Once you are in, it closes and keeps you from breathing (very few big animals can survive longer periods without oxygen). * A plant that creates a cheese-like structure using roots with leaves covering the holes. Once some animal steps onto it, it collapses, making the leg hard to get out (perhaps using thorns, or something similar). Then, before the victim can free itself, some symbiotic creatures (ants, spiders?) step in, and deal the real damage. * A plant that is a semi-parasite that grows on trees (like mistletoe), it has thread-like tentacles falling from above when it detects a victim below (e.g. by carbon-dioxide) and like some jellyfish it paralyzes its target, which will provide the nutrients for the tree, and indirectly for the plant. * A plant symbiotic with some insects: the insects carry the spores on them and kill the animal, while the plan uses the nutrients to grow and provide optimal environment for new nest and larvae to grow. I hope this helps ;-) **Edit:** Added clarification about fungi not being plants (thanks @pluckedkiwi). [Answer] Realistic? Probably not, at least not with our earth plant biology, however if there were a plant that was 'more' than plant you could get to that level. Here's a scenario that might work. A fruiting tree that generates very large fruit as a way to spread its seed, but it uses tremendous amounts of energy and resources to produce. So it finds a way to 'fertilize' itself by adding animals to its diet. One way it might do it is year around it has a pleasant odor to attract animals and an anesthesia that affects them when they get close and they fall asleep on the root system, where they are absorbed to produce the fruit. Of course once the fruit is ripe it would have to turn off the anesthesia to allow the fruit to be taken and seeds to spread. [Answer] Consider symbiosis. A man gets tangled in roots of a tree and carnivorous but weak birds, who live in the tree, swoop down to eat him. Or wolves who live under the tree eat the man's flesh and then the tree's roots absorb the man's organs. [Answer] There seem to be more than a few plants that rely on their seeds being eaten to spread and reproduce. Usually herbivores eat the plant and pass the seeds through their digestive systems and deposit the seed on the ground with a lump of fertilizer. Well, what if the seed simply opted to sprout earlier and take root while still inside the unsuspecting animal? Starting its life cycle more like an intestinal parasite and eventually growing to a point where it would block and eventually burst the intestine killing the animal. Then it could take advantage of the corpse as fertilizer. Of course the process would be really slow and painful for the animal, so one would assume that animals would avoid the plant and just not eat it, but I'm thinking that if the process was slow enough most animals wouldn't make the connection between the fruit eaten and the death weeks later. [Answer] If you are dead-set (pun intended) on an animal-eating plant, I suggest another option I do not see here. We have a garden with pumpkins in it. Their stems are really thick, and their leaves humongous, designed for transporting nutrients in volume several feet. In order to anchor down the leaves so they do not flop over, the plant stem sends out fairly tough, strong tendrils that wrap around whatever they contact, and hold on tight. Very tight. The leaves do not flop over in even very high winds. I posit that if there were a plant that used large animals for food, it would use a similar system for capture. That is, tendrils that snake out from thick stems, and wrap around anything that contacted them. They would be very effective for up to 5 or 6 inches in diameter - good enough to snare a leg or small animal. Give them barbs that emit a toxin (pumpkins already have barbs on their stems for protection, sharp prickly little devils, but they are not toxic). Once the prey was captured and subdued by the toxin, the stem itself could curl up around the prey, covering it with biomass from itself, and slowly ingesting it by injecting digestive fluid and sucking it out, somewhat like a mosquito draws blood, but only mega-sized. Or like a spider captures, encapsulates, and digests prey in a web. All of these techniques have antecedents in earth biology, except for the scale and that they cross the plant-animal lineage (not entirely unheard of - there are genes that have crossed between plant and animal, with viruses the suspected transport - this is proposed in genetic modification of organisms), and are evolutionary supportable. If you have ever been in a pumpkin patch, you will understand that it is not hard to envision the plant scaling up to such proportions. None require any particular intelligence or deliberate advanced planning that requires a brain, as long as you do not make the mistake of having the tendrils deliberately seek out and hunt down prey. Everything is reflex. It would be a good way to get calcium in a calcium-poor environment. Perhaps give the plant a calcium-based shell or infrastructure for protection - again a cross-over from animal biology. Or perhaps the seed pod is encapsulated in calcium, like an egg. Animals are a good source of large amounts of calcium. [Answer] The long and the short of it, is no. Humans are biologically a very poor food choice. Skinny, and low in nutrition. Mainly bone mass and hard to digest calcium. From an evolutionary perspective, if it were realistic to have a man-eating plant, one would have evolved by now. And if the environment were nutrient-poor, how could larger animals have survived in the first place? If a plant could not survive, how would a more nutritionally demanding animal survive in the same environment? Plants evolve based on the nutritional sources available, not hypothetical sources that may just happen to wander by on an unreliable basis. [Answer] Chances are that in the past, plants did indeed catch small mammal and eat them. However, the advantages that this might concur would be quickly outweighed by the fact that small mammals would avoid this plant, and thus would not help it spread. Historically when this kind of thing happens, one of two things happens: 1. It is unable/refuses to adapt, and thus dies out. 2. Alternatively, it gradually adapts to become less deadly. An example of the latter are Chili Peppers. They were probably once poisonous, but eventually adapted to become less so. Consequently, they have become *much* more popular. [Answer] A plant that solely preys on large mammals/humans is not very likely, but if you allow the plant to get its nutrients from other sources as well it could be possible. Something like the venus fly trap would be a good start, something that sits still and lets its prey fall into its trap will not need the energy to move around. The problem with only preying on large mammals in this scenario is that the mammals, especially humans, will be smart enough to avoid the trap once they learn about it. However, if the plant is not solely reliant on large mammals, if it can get enough nutrients to spread through other sources, then it can continue to propagate even during a lifetime of not preying on any humans. One way this could theoretically evolve would be to start with something like a venus fly trap that eats insects which fall into its trap. If your world is thick with eatable insects the plant could evolve to grow bigger and bigger so it can trap and hold more passing insects. It could grow so large that it happens to also be able to eat large mammals that fall into the trap. It wouldn't rely on large mammals as its main diet, but every now and then when one stumbles into its trap it could eat it. [Answer] I've come up with a plant that can see, and is big enough to eat humans. It's an alien, of course. And I've also come up with a sea creature that's basically the Sarlacc, without the absolutely ridiculous "digests its prey over a thousand years" bullcrap. The sooner you end your prey, the better. That's why predatory beings are designed for an insta-kill. ]

[Question] [ Assume a universe depressingly like ours, in which special relativity holds. No hyperspace, no warp drive, no wormholes, and even the limited get-out clauses offered by real world physics either don't exist at all or are not practical. [Added later in response to comment by Fhnuzoag: no ansibles either. Neither material nor information can travel faster than light.] I can think of a few ways that trade between star systems might take place. Emphasis on the word "few". Information can be sent by radio. Trade in knowledge between Earth's system and e.g. Alpha Centauri is practical, assuming that either alien evolution or a previous human colonisation effort has put anyone there to trade with. But it is still so slow that a human lifetime could get used up just straightening out the terms of the contract. Still, human institutions can outlive individuals. Possibly networks could build up where Star A talks with Star B which in turn talks with C and so on. For anything other than very nearby stars even lightspeed information transfer takes anything from thousands of years to an arbitrarily high limit. So if the nearest star systems are *not* inhabited the only way information trade can take place is if the inhabitants and/or institutions are very long lived and don't mind receiving payment thirty thousand years later. Trade in goods, or trade of goods for knowledge, has all the problems above multiplied a thousandfold. Certain authors have plausibly sketched out small payloads of high-tech stuff being sent out by automated Bussard ramjet, e.g. Larry Niven's *A Gift From Earth*, but that isn't really *trade*, as the title of the book implies. Perhaps the most likely model is generation ships (or ships with long-lived nonhumans aboard) plying the spacelanes. The ship has a large population and the capacity to grow food, create technology and art, and to mine or otherwise gather raw materials. The ship as a society can trade with the people of the planets it visits. But that is only going to work if an implausible proportion of stars have inhabited planets. What if they don't? A generation ship that goes 1,000 generations without meeting anyone else is for all practical purposes as isolated as Earth is now. I had some brief hopes for trade with hive-minds spread out over multiple star systems. It won't work. If the thought of the hive mind takes place at lightspeed or less, trade is constrained by the same problems as above. The thought of the hive mind cannot be instantaneous because (as I may have mentioned) faster than light travel is impossible. Any better ideas? [Answer] I think you've got yourself in a bit of a corner. Without FTL, trading would be nomadic rather than what we think of today - think the old Silk Road, or traveling peddlers. It'll be people whose livelihood involves being constantly on the move, buying stuff here hoping it'll sell for more than that on the other end. (This of course assumes that we don't have transmutation or anything). It may be more feasible if it's combined with an entertainment troupe of some sort (circus being the classic, but even postWW1 barnstormers would fit the model). *But*, this assumes that it's cost-effective to be roaming the stars in the first place, and that means while you don't need FTL, you *do* need some sort of high-efficiency power source and sub-light propulsion. Otherwise, it's not worth the trip at all for most things. If we're use near-now tech, that means the only things that are even worth considering shipping is things that the destination planet *can't* get on their own. (Because if it's available on-planet or even in-system at all, it's cheaper to do it locally than it is to ship it). To my mind, that brings you to three things: 1. People - colonists, refugees. Yes, you can "manufacture" them on-site, but assuming the travel time is < 20 years (or just for bootstrapping a new colony), you have to get people from there to here. 2. Bootstrapping for a colony - basically, the stuff you need to build the stuff you need. Once a colony is established, this market dries up entirely, but for a colony that *can't* do X, a machine to let them do X is worth shipping. 3. Unobtainium. Which goes back to the "can't get it here" issue. If some colony finds Dune Spice and it's useful enough, there will be people willing to pay the transport costs to get it. 4. (Credit to R. in the top-post comments). Refugees - by which I mean folks who aren't trying to go somewhere, so much as needing to get *away* from where they started. In this context (esp. given the money needed to build this sort of thing), you're probably looking at some rich religion/orthodoxy that builds something relatively self-supporting so they can bugger off and find a brave new land (or Xenu or whatevs). It's crazy and most of them probably won't make it, but human history is full of people packing up and hoping for the best. A note, though - except for point 1 (edit: and 4), I wouldn't expect any of these transports to be manned. The life-support costs are atrocious, and space travel is notoriously "straight". I would expect unmanned cans that are radio-controlled to get them going, they drift through the stars, and get picked up (and radio-controlled in) at the other side. [Answer] This is well addressed by [this excellent site for sci-fi writers](http://www.projectrho.com/public_html/rocket/stellartrade.php#id--Economics_of_Starships). Turns out, you're doomed: > > For example, the most expensive substance on Earth is antimatter, which currently has to be manufactured atom by atom at a cost of $100 trillion/gram. Let's say we can make it for 1,000x cheaper and that the friendly aliens at Proxima Centauri are desperately in need and will pay full price. > > > So you get in your ship and travel 174 years there and 174 years back (>100x faster than Helios II, the fastest man-made object ever, or an insane ~2.4% light speed). Turns out, if you had instead invested in a 2.00%-APR savings account, you'd be just as well off. *[note: figures for Helios II are "18000+ years", "0.0234% light speed", and "far better off"]* > > > Except, it's probably only 3x cheaper, it will take 500 years each way, and investors get around 5.00% annually. So you're really more like $1034 in the hole *for every gram*. And in a millennium probably manufacturing antimatter will be cheaper and you'll also be dead. > > > *And that's for antimatter.* There definitely won't be any "Durrr, let's trade plutonium, people, computers, water, or any other worthless thing." > > > Sorry. But check out that website or the other answers for plenty of optimistic hope. [Answer] This was discussed in my Answer and comments to [another question not too long ago](https://worldbuilding.stackexchange.com/questions/15364/resources-to-justify-long-distance-space-mining-missions/15486#15486). Just replace *mining* with the more general *trade*. Any transshipment of goods at fractional *c* speeds is more expensive than you can even imagine. Perhaps they trade information. Art, exotic cultural narratives, scientific exploration? Charles Stross in *Neptune's Brood* makes an interesting economic model where new colonization is the generator of money. "*Slow money* is a digital currency backed by debt—the debt incurred by constructing a new interstellar colony." * [author's blog](http://www.antipope.org/charlie/blog-static/2014/09/crib-sheet-neptunes-brood.html) * [extensive quote of the finance idea plus analysis](http://www.overcomingbias.com/2013/10/econ-realism-in-neptunes-brood.html) [Answer] There would be only minimal trade in "wares" simply because the cost of transport is so outrageously high. To reach 0.8c a ship needs to burn its own weight in antimatter - providing you can use up all the energy to speed up the ship, you don't spend any energy on speeding up that fuel antimatter, or the matter to annihilate it with. And antimatter is about the only ware worth transferring directly; normally worth the price. Other than that, only luxuries of "emotional" value, whose price is only bound to actual desire of the extremely rich buyers, irrelevant to actual value of the item - signed physical copies of books of celebrity authors, invaluable collector items etc. In the relatively narrow timespan transfer of seeds and embryos of new revolutionary species of plants and animals developed would occur. The timespan would be between the antimatter-powered space travel becomes even *moderately* viable, reducing transfer time to orders of half a century, and the time when biological matter can be synthesized on molecular level; "scans" of said seeds and embryos being sent by radio. Everything else is cheaper to synthesize or obtain from within your own stellar system. ...but information travels at speed of light, and it *is* valuable. Trade would flourish for not only science, but art, entertainment, music - and technology, sending plans, projects, blueprints - including stuff to be 3D-printed, both of art and technology. A digital currency would be exchanged; contracts would be mostly arranged by representatives on the "destination world", with the "manufacturer world" adapting management to the fact it takes a decade for modified ToS to reach the representative - and insurance companies shouldering the burden of conditions changing over the decade or two in ways that make fulfilling a contract impossible. Escrow companies that hold the payment until conditions are fulfilled would abound. Trade like this would be difficult, but not impossible. Think about trade with India before the Suez Channel. A round-trip would take time in excess of a year, but it was still flourishing. A decade or two with modern law, logistics and planning would be quite doable for virtual goods. Oh, and of course it wouldn't be like waiting twenty years for one transaction to complete before starting another. The flow would only be limited by the throughput of the link, new goods arriving nearly continuously, while new contracts/purchases are being signed; round-trip of a couple decades but no waiting for "ACK" before sending the new packet... [Answer] One way to get slower-than-light trading is to combine four (large) assumptions: 1. People are willing to create new interstellar colonies because they want to *leave Earth*. 2. Most planets are, sooner or later, doomed to have a large enough war to knock themselves back into the Industrial Era. 3. Someone is willing to continuously transmit a huge library of information: enough to get any civilization up to basic spacefaring technologies. This can be hilariously expensive if the information is broadcast, so the signal will probably be tight-beamed to all known planets, to save on energy costs. 4. Suspended animation is a safe way to spend decades. Now advance time by several millennia: there's a smattering of colonies all over the place, at varying technology levels, with access to the language and culture in the universal broadcast. This is the background of [A Deepness in the Sky](http://en.wikipedia.org/wiki/A_Deepness_in_the_Sky). One group of people has decided to never settle down, so they continuously broadcast the knowledge required to build a spacefaring civilization, and they wander from planet to planet as a survival strategy: spaceships don't suffer the same long-term instability problems that planets do. (If you have an irreconcilable disagreement on a ship, you just wait until you reach the next planet, build another starship, and split the population.) Every time they arrive at a planet, they will have a few technologies that the locals don't have, so they trade technologies for supplies and other technologies. If the locals just nuked themselves back to the stone age lately, the nomads go into suspended animation for a few decades until the locals can resupply the nomads' starships. At that point, the locals will resupply the nomads because the nomads have been accelerating the locals' development; the locals owe a *lot* to the nomads. This isn't "long-distance trade," exactly, but it does have similar trappings: the nomads wander from star to star, and each time they arrive, they trade with the locals. Sooner or later, the knowledge on one planet will migrate to the other planets, but not as an explicit trade agreement between the two planets. [Answer] Niven had three other examples of this that I can think of off the type of my head. **The Outsiders** They had FTL, but for whatever reason didn't trust it. So they cruised around the galaxy on their reactionless drive, and traded knowledge with any species they encountered. **The Ringworld Civilization** This is only mentioned tangentially, I believe in the first novel? But the lady they meet, Priss, is a former harlot on a sub-FTL style trading ship that went between the Ringworld and the colonies. I don't recall if they mention what they trade - I think possibly they were scavengers, looking at the dead worlds and then returning to the Ringworld to trade. But it's been quite a while since I read the book last. **The Laser Drive guys** I don't recall the name. But I distinctly remember one of his short stories about an alien sub-FTL craft that arrives on Earth, sets up shop and does some trading - again, primarily in information and technology. But the primary plot of the book is about their propulsion system, and how they get around if they can't get the target culture to build them a sufficiently big laser (induced novas). **Commonalities** The common factor between all of these is that you don't have, say, a trade balance between two worlds. Niven apparently felt the sheer distance and time factor would render that impossible, and to some extent I agree with him. Instead, you have sub-FTL craft - kind of like generation ships - that cruise in a circuit between many worlds, trading as they go. I think this makes more sense than trading over laser communications. I mean, think about talking to a world 10 light years away. You have a 20-year turnaround just to say "Hey, we have this neat new propulsion tech." And then you get back "oh cool, tell us more." and by the time you get your final response it's 40 years down the road, and they're all "Yeaaah... hey. So we somehow, totally coincidentally, developed that same new propulsion tech. Just now. Amazing coincidence, right?" And things get even worse the further you are away. Imagine trying to trade with a 200-year communication lag. But if a ship arrives in orbit with that new propulsion tech, and they say, "Man, that's some nice nano-assemblers you've got there. Swap the designs?" then you can do actual trading with people on the spot, instead of just giving up and developing it yourself. [Answer] Without FTL, it almost certainly is too expensive to trade using manned vessels and negotiate on prices and values. So if you wanted to have contact and exchange, it would be better to exchange "gift ships". Each side would stuff a ship with art, crafts, writing and interesting objects more akin to 'time capsules' than a store. They send out the ship and when it arrives in 20 or so years, each side has a holiday opening up the stuff and seeing what the other society is like in detail. Repeat the exchange every 5 years or so and you could mingle your cultures to some extent. The 'payment' is the vessel the other side sends back. It could be a matter of pride to show your best to the other planets.. No need to make humans travel, reach near light speeds at all, if you are patient. [Answer] Interstellar trade works just like in the Stone Age: **Through a lot of intermediaries for a long time** **Stone-age trading** In Neolithic Europe, ornamental shells and amber were traded across the continent. A decorated shell made in Greece could be found buried with someone in Germany. No single individual travelled from Greece to Germany to trade goods. Instead these non-perishable goods were bartered among a host of intermediaries. The goods may have travelled across the continent in a few years, circulated back and forth over decades like coins do today or been in use for a lifetime before being reworked and traded further. **Space-age trading** To set up trade between say, Earth and Alpha Centauri, we have to assume that like in the Neolithic, there are many intermediaries. These would not be based on planets, but on wayward comets, generation ships, autonomous unmanned ships, etc. A precious object from Earth could be traded a dozen times over several centuries before making its way down to a planet in the Alpha Centauri system. This has several advantages: * With many intermediate trades, nobody sits around for generations waiting to cash in on the trade. * Like stone-age necklaces, many of the goods may actually be in use in transit and therefore not perceived as costly long-distance trades. * With intermediaries in space, most of the trades do not involve going up and down steep gravity wells, cutting the transaction costs. * Trade could happen between parties travelling at very different velocities. The cost of accelerating a parcel of goods to meet a ship passing through your system is a lot smaller than powering up a dedicated vessel to transport said parcel. The trade in information would also be through intermediaries. From the point of view of Earthlings, there's a steady flow of trade only with the habitats orbiting earth, but the goods may originate from lightyears away. Because of the cost of travelling in gravity wells, we may even find that planet-space trade consists mostly of energy and information, with the physical goods more often being traded among fellow spacefarers. [Answer] After some thought, I came up with # Pre-emptive Trading Think of it this way: humans on Earth have decided it's time to settle the galaxy. They pick some good-looking planets and send out some probes. When the probes return (or when they send back their data), the people on Earth get a pretty good picture of what's on each planet. At this point, they plan out the next few centuries. What will the colonization process need during its first few years? Building materials for settlements and terraforming? Send that with them. What might they need afterward? More building materials for exploration and space travel, and elements not found on their planet? Send that later. What will they find on that planet that the people of Earth would want? Rare elements not found in our solar system? Send that back as soon as possible, in a sufficient quantity to repay whatever supplies Earth would be sending. In this way, the terms of the trading are agreed upon while everyone's still on Earth, so no communication is necessary once everyone gets far away. There are still some problems with this. For one thing, it's going to be hard to find people willing to invest in such a venture. However, to this I would say that it's hard enough sending a space ship to another planet, and if we can manage that I'm sure there will be people willing to wait for their payment. Also, a lot of people are talking these days about how humans don't have to age, so maybe by the time we get to other planets humans will be virtually immortal. There's also the problem that once the colonists get to the new planet, they don't have to send anything back. They'll get supplies for a while before the people on Earth realize they've been stiffed, so they'll probably be able to survive without future shipments. The reason this probably won't happen is because, for one thing, planetary colonization should be done by the best humanity has to offer, so the leaders should be morally good enough to honor agreements. Also, the things they'll be sending back and forth should be sufficiently useless at their source, and sufficiently useful at their destination, thus making it nearly pointless *not* to send. As for information transfer between planets, which seems to be a large part of your question, I would say that there wouldn't be conversations so much as newspapers. Each planet would send the others a burst of information about what's been going on- current events, scientific advancements, things that might be considered useful. If a planet really needs something from another planet, they're probably screwed long before anyone can send aid, so there's really no reason to ask for things. Thus, the only information worth sending would be scientific, technological, and cultural advancements that might help the people on the other end. [Answer] What if they trade in very specific information, minds. There is really no reason to transfer matter. Given enough energy, if you can build generation ships you have energy, you can build nearly anything, Including bodies. What you can trade is experienced colonists, warriors, persons transfered by wire by entangled messages that destroy the original (in a sense teleporting him). If not teleporting moving with slow ships, what is time in stasis but then thats not trade but work force? Perhaps you sell AI's. Or perhaps working AI needs constant new experiences in quantities that far surpass the need of humans. After all if you think infinitely faster... You could trade in immaterial goods, films, music, designs. Science is another good perhaps its impossible to measure something in our gravity well... Perhaps these planets collectively search for alien lifeforms and sell their infrastructure as service for a cosmicaly sized telescope array. They could sell other services too like message bouncing. Imagine istead of sensitive archives you bounce the message 50 lightyears away. No risk of being opened until it comes back. So history writers will have that info but its no risk to you. What about planets that specialize in archival that started allready thousands of years ago. They could sell you back history info... [Answer] I agree with other people that without FTL you are doomed, it does not make sense to trade. But why do you want to go out so far ? While it does admittely not answer your question, what about the Solar System ? It is quite complex: more than 60 moons for both Jupiter/Saturn and many known planets. Interplanetary trade is quite possible when high-tech makes travel cheap and many planets and moons are very interesting for abundant natural resources. Many human colonies with different cultures are possible, aliens with generation ships could live in settlements together with humans. [Answer] I'm going to throw in my two cents on FTL in fiction and maybe it helps you. From a physics perspective, FTL travel has deep time travel implications. However, note that in the vast majority of FTL travel in fiction, going FTL does *not* entail any form of time travel. In some cases, we do see some uber-FTL travel result in time travel, but that is typically a separate, exceptional phenomenon. So time-travel aside, FTL exists in fiction *precisely* because of vast distance related problems such as what you are facing. The way I prefer to think of FTL as simply a way to get around space being too vast rather than something terribly unrealistic and unsettling. For some concrete examples to maybe solidify what I am talking about, consider the warp drives in Star Trek. Warp 1 is the speed of light, but the real speed limit is Warp 10, which can't normally be reached, and if you do reach it then you get time travel. Also, real-time communication is possible across incredibly vast distances (via "sub-space", whatever that is). These things basically imply that the *real* maximum speed of travel is Warp 10, not $c$ = traditional speed of light = Warp 1. This kind of thinking is made explicit and concrete in Futurama, wherein scientists increased the speed of light in the year 2208. Again, this allows fast travel over interstellar distances while also avoiding time travel and making it plausible that space travel is not prohibitively expensive. [Answer] Okay here's some numbers that Larry Niven has come up with for interstellar, and in fact intergalactic, experiential travel times, they clearly assume fuel is free and infinite (which is theoretically possible but the tech involved could probably be used for FTL cheaper and easier) but they're for one G continuous acceleration flip over deceleration trips. The point is they make it clear that the crews are in for a long but survivable trip; 4 years to Proxima Centauri, 21 years to the centre of our own galaxy, 28 years to Andromeda. (As a note I'm reasonably sure that the longer trips at one G would actually violate the speed limit, C, but they're also unrealistic in the scope of the question in my view so I'm treating that as a non-issue for the purposes of this discussion). So crewing a STL trader is awkward but not too bad, so the question really is what kind of trade goods are valuable enough and keep long enough to be worth the hassle and good at the end? I'm going to assume a "[post-scarcity society](https://en.wikipedia.org/wiki/Post-scarcity_economy)" in which nanotechnology is limited and in particular biosynthesis is problematic, rare, expensive and/or nonexistent. I've also assumed that there are starships that can reliably bridge the gulf between the stars carrying worthwhile cargoes of goods. This leaves several categories of trade goods, Art and Historical pieces - the antique/museum trade, Information - this can be IP like the light speed datanet in Wil McCarthy's *Lost in Transmission* (the problem with this is that we don't really have a means of transmitting data across stellar distances, see [this](https://briankoberlein.com/2015/02/19/e-t-phone-home/) article, and in the novel it does break down) or it could just be the mail, and "Unreproducibles" - this covers a *lot* of ground (and technically *includes* art etc...) but it's things that we don't have the technology to make and that can only be found certain places; I've deliberately categorised Art and Historical artifacts separately because there's a very limited stock of such things. Unreproducibles are the most likely to be traded in large value transactions, this could be the [Melange](https://en.wikipedia.org/wiki/Melange_(fictional_drug)) around which the *Dune* series centres, the exotic timbers of *Plague Ship*, or the gem trade of *Uncharted Stars*, the trade goods are complex materials who's unique physical characteristics can't be synthesised, that only occur on a single planet or a couple of planets, and which are stable over extended storage times. Potentially this may extend to extremely rare elemental raw materials over short distances from exceptionally rich sources to particularly bereft markets, but that's unlikely. Provided that there is a demand market for these goods that is sufficient to pay for shipping costs over interstellar distances they can be traded at any speeds, but it's going to look a bit more like feeding frenzy than what we think of as a "market", with supply and demand. There is the possibility of a limited futures market in this format since the ship coming in will be able to broadcast their goods at lightspeed while arriving somewhat slower but the actual arrival of goods creates a supply in a demand market that hasn't had new goods for some period of time. Prices are going to be at their highest just before the arrival of new goods and are going to collapse for a time when new goods flood the market from a freshly arrived shipment. This turbulence in the market is going to be awkward for traders and buyers alike, especially with goods that are available from several places instead of just one, arriving just behind a competitor could be ruinous to a trade ship. So in effect any trade route is going to be a single shipper monopoly, not because of any deliberate conspiracy or controls but because anyone who comes in late is simply going to go bankrupt. There is one other good that will always be worth something in *any* society, and is actually more valuable in post-scarcity environments; *Time*, any drug, any treatment, any anything that can give people a longer life is going to be worth it's weight, or probably much more, in any material you want to name, if such a treatment requires an unreproducible substance then you have a license to print money, if you can secure the source. There are any number of examples of this in fiction from *Dune* to *The Collapsium*, in James Blish's *[Cities in Flight](https://en.wikipedia.org/wiki/Cities_in_Flight)* series they use life extension as a *currency* in and of itself. Which brings up an interesting point, there has to be a currency to trade in for all of this to be successful, ships that can cross the gulf between stars are going to be expensive in materials, maintenance, and crew. The trip itself may or may not cost a lot too, I would suggest that fuel is going to have to be basically free to make interstellar trade economically feasible but that's me you may go another way. All of this is going to have to be paid for one way or another; any currency being used is going to have to have purchasing power at both ends of the trip, so that what you, as a trader, earn at one end of the trip is usable for fuel and maintenance costs at the other. Short version: You can trade in sufficiently scarce/unique goods at any speed provided you have a high enough demand for these goods, a currency to pay for them, and can ship them before they "go off". [Answer] The main development that might resonably occur in the near future is that our lifespan will increase substantially. Whether due to the singularity, or simply that medical science is adding a year to the average lifespan more frequently than once a year - humans may soon find themselves living for hundreds or even thousands of years. What is a few hundred years to a human that is going to live for a few thousand? Once we've gotten to that point, stasis of some form or another will likely be close behind, so one can sleep during such journeys if there's nothing more interesting to do - but keep in mind that humans are creating knowledge and entertainment much more quickly than any individual can possibly consume, so just download a couple thousand years worth of entertainment and learning to the ship, load up with whatever cargo you believe will be valuable to the distant cluster you're traveling to, and hope for the best. [Answer] Trade over short distances can inter-act with local economies on both sides and can be part of the financial strategies of individual short-lived humans. Because of the relatively short times needed for each transaction, all economic entities, from nations and corporations down to individual people can participate and benefit from trade. As the distances and necessary times increase, the economic entities which are long-lived enough to benefit from each transaction decreases. When a one way trip between colonies takes more than half a human lifetime, individual people can no longer benefit. At 10 or 20 times that distance, families and smaller corporations fall off the list. Eventually, you get to a distance where even nations and super-corps can't be certain that they will survive long enough to benefit from a single transaction. There is only one economic entity larger than nations and super-corps and that is the whole of humanity itself; and it is this entity which has the most to gain for extremely distant colonization and trade. Ultimately, humanity has only a single reason to colonize the planets of distant stars and it is the same reason which ultimately drives any life form to every action which it pursues; the avoidance of extinction. We will colonize Mars because if we don't, then our species will die when Earth dies. We will colonize Alpha Centauri (whether there are suitable planets there or not) because if we don't, our entire species will be wiped out by anything which kills our sun. As we reach out further into the stars, no matter how distant, humanity becomes more immortal than it was before. So ultimately, distant interstellar trade will not involve raw resources or manufactured goods or even information. The most valuable commodity in the universe from humanity's point of view, is its own genetic code (or in a lower tech form, a few thousand breeding pairs of living humans). Periodically, each distant colony will send a ship out to Earth and to each of the other colonies, containing whatever is needed to re-establish humanity on that colony world, just in case something has wiped us out since the last transaction. In this way, humanity becomes a self-repairing network of intelligent life across an ever increasing sprawl of galactic real-estate. In doing so, humanity approaches true immortal. It is Noah's Ark or An Economy of Survival - It all depends on how you look at it. [Answer] Would a starfaring society be as developed in other sciences as it is in energy generation and system engeneering? If true, is such society is as advanced in medicine/genetics/cybernetics as it is in space technology? It could have some very long-living beings, some kind of cyber-elves with lifespan around the dozens of millenia, due to their very advanced cybernetics, biochemistry and genetics. Then you combine that long lifespan with relativistic time dilatation and the cyber-elves could solve the time issues. The second issue is the energy and resources spent on such travel. I have no idea of what could be worth the antimatter that will be spent during the travel but then, i'm not a cyber-elf. Maybe some very rare elements, like monopole magnets or other rare particles. [Answer] **Deep Space Trade Cost** Deep space trade would itself be quite cheap. An ION drive is not fast but more than capable of providing cheap transport long range. While each drive will have a price tag associated with it, the trick is not to manufacture them in the Sol system, but to send out automated mining, refinement, and manufacture ships to uninhabitable star systems to cannibalise the system for resources. The second trick is not to send one vessel every few hundred years, but to steadily send them out. This helps smooth out supply ensuring that a consistent income can be generated. **In Solar System Trade Cost** This would be quite expensive if we used chemical rockets to move trade-goods around a gravity well, but there are more efficient (and cheaper) alternatives: 1. Build the trade goods in higher orbits. 2. Use cheap transport technologies, and gravity assists. 3. Build a space elevator. Building trade goods closer to their delivery point is just good business sense. It removes all of those transport costs. The raw materials to supply such manufactories could be sourced from deep-space trade itself, or from goods in lower orbits raised by efficient transport technologies. In system transport can be supplied by using ion drives (or if it works an em drive) with a solar sail. Obviously quick transport costs more, and may be preferred by humans, but for goods these technologies are efficient and can be used even now. Additionally leverage the opportunities afford by gravity assists to alter course and speed efficiently to produce a very effective in solar system transport network. Space elevators are very real. We can with today's technology construct a space elevator on the moon. Once constructed the cost of transporting goods to and from the surface will drop dramatically. It is not too far fetched to believe that in the near future materials science could make space elevators possible for Mars, Earth, or Venus. **Home System Market** Hello Dyson Sphere, Halo Rings, and Generation Ships. These are not cheap nor quick things to build. While a solar system may have enough material to build a few of these things, populations will stretch and demand more. This will place a pressure on local governments to reserve many in system resources for meeting immediate needs, at the cost of longer range projects, particularly if those projects are meant to leave the system, removing resources. This will provide a mass market for material, and a predictable one. While the automated mining rigs will provide a bounty of resources, what each inhabited system requires will vary, depending on their local super scalar projects. This will require trade. **Colonial Market** In the early days of colonisation the system will not have the manufacturing capabilities to implement many super-scalar technologies that would seriously benefit the colony. It would make sense for these technologies to be assembled in another solar system from imported resources and then sent to the new colony. These might include: * Orbital manufacturing * Asteriod Mining * Solar System monitoring satellites * Space Elevators * Halo Rings **Trade Deficit** Not all of these trades will balance out immediately, but they rarely do even in our world. As this form of trade is more long term, running a large deficit for generations would be expected. The balance might be restored in a number of ways: * Accepting immigrants * Supply materials back * On supplying another colony (essential transfer this systems deficit to the new colony). * Selling information. * Accepting a foreign business/military. **Trading Companies** Trading companies would probably start out as governmental institutions concerned with supplying resources for colonisation, and super-scalar projects. This would shield such institutions from having to worry about an immediate bottom line while they established trade routes, mining operations, and long-term storage facilities in high system orbit. Eventually these institutions would be privatised in an attempt to make market competition and drive down prices. **Trust** Finally trade cannot exist without trust. There would be many opportunities to weasel out of repaying or servicing a trade deficit, particularly when your local space region is rich in controlled automated mining, and anything resembling a Navy would take years, perhaps even centuries to arrive. There would also be issues around ensuring resources are actually delivered. Space is a dangerous environment even for automatons. It is possible that some of these ships would die. Their resources might make it to their destination, but how would the sender know? The resources might fly off into deep space, so how would the receiver know that the attempt really was made? At the end of the day, most (but not all) colonies would maintain the status quo on trade. Not because they wanted to, but because it would stabalise their own solar-system economies. Excess production can be dispatched to consumers, and conversely demand can be satisfied through importation. [Answer] I like the idea of a silk road, as Allen Gould mentioned. Traders on the silk road would rarely travel from one end all the way to the other with a carriage full of spices or gold. More often they would travel a stretch of the silk road, and trade their wares to the next trader along. A large number of self-sustaining deep space waystations between stars populated by trader societies, each trading with the next on a long link between two stars would eventually allow for a flow of goods and wealth between them. [Answer] The aliens grow a plant that grants longevity (hundreds of years) to human life spans. Humans have something similar for the aliens. FTL is not possible so build robot ships. It may take one ship 300 years each way, but that does not matter. This does assume that interstellar space is mostly empty, so the probability that the ship survives such a long journey is reasonably good. The valued product is stored cryogenically. Some animals and plants can be frozen or dried and return to life after some time. With enough research it might be enough to survive the trip. Assuming that transport of living aliens is not an ecological disaster, it would be an amazing curiosity. [Answer] Without FTL... and even with it really. The most precious cargo is information, art, and "history", because once you're in space the only reason you go back to a planet is because you personally might prefer to live on a planet, but the majority of people will live on space stations/habitats and low Gravity places where all the materials needed will be petty much freely mined from asteroids around the solar system. Anything that is missing can in theory, just be created, even if you're dealing with a situation where fusion is expensive, if you need something the expense is worth it. Even with Earth based current technology we're on the edge of physical materials that aren't information, art, or "history" are pretty worthless because we are getting ever closer toways to experiencing more with less via Games, Movies, Books, and eventually VR. So how would "Trade work". Not like the trade we see today where you are assuming a two way flow between nation states, but rather more like in the past during the 1500s and before. I want to be a trader so I look at cultural things that probably haven't developed on my destination or things that may carry cultural value. I also load up on as much data as possible, because even with STL travel anything you take with you will likely be of higher quality than a transmission simply due to the signal being too spread out and not to mention eventually having a satellite system always arranging itself to every possible node world would just get too much for a system to bare. The last thing I look at is with whatever cargo room I have left I bring raw materials and maybe a bunch of replacement parts for various ship types that fly around in the region. The parts might not get used for hundreds of years, but also those parts, due to the length of time that ship flies around will likely be valuable since especially is the Data for the 3d printers on those ships get corrupted/damaged and it is likely that even if your colony does have a data file on those parts you might have to venture into very old stored data that the comparable cost wouldn't be worth it... and those parts can be used as raw materials anyways so no real lose there. The Raw Materials themselves are only worth as much as colony actually needs it. They still have to process and mine those materials so even if they have it they will still have a value of some sort, more for in those places that have less of it and less in places where they have lots, just like in regular trading. You get to the planet and you post ship manifest to the colony's database and then people who see something they want they will mail you, visit you, or propose a trade. Sometimes that will include conversion of currency, sometimes it will just be barter trading of old. This is nothing more than the ancient barter trading of traveling merchants of old. The only difference is that by the time you get home your home might as well not be and so you might as well keep traveling...You trade for what you need and for what you think will give you a better return on your next colony. If you are going between the same few planets you'd probably want to set up banks on those worlds to hold assets on them as they acrue intrest which will more profital than doing that in the past was because you'll likely be gone far longer. Here's the very interesting part of this though... the most valuable thing and ironically the thing that will get you locked into this world. You'll end up living thousands of years from the perspective of regular world and you'll be like walking history of the time you originate from, and each planet you visit and see you'll be able to tell historians what it is like and compare the time periods which will be extremely valuable as trade commodity... So in a sense you stop becoming a trader and start becoming a story teller. The reason it locks you into the life style if you do it long enough is simply that the longer you go the more out of touch you will become...but that's somewhat a different topic. So the TL;DR version is basically... the same way they did it in the past, just the time differences will be greater. There isn't nation to nation or company (as we think of them now) to company trading. Only individual to individual trading... [Answer] Instead of trying to reach the light speed limit,(and using up far more energy than whatever goods your are trading worth), simply have your protagonists live slower: have your protagonists being liquid hydrogen based life form living on a cold planet, like Pluto, where the gravity is far lower and the temperature is far colder. Then, slow down your major races’s metabolism, making a year to us be like a day to them.(for example, your protagonist(s) have an average lifespan of 70 Pluto years(365 earth years per Pluto year) and consequently moving and thinking 365 times slower than earth life, making a year’s wait a mere day to them) (Which you can also say that it is the consequence of living on a slow and cold planet) It turns out, being slow is greatly advantageous to space travel: you don’t need a generation ship if your 100-light year away colony is a mere 8 month of traveling to our slow life: what looks like a year to us feels as merely a Day to them, and you doesn’t have to worry about economics: receiving a package shipped from Pluto to alpha Centauri that takes 8 years to arrive to them would feel just like receiving a fedex package from amazon to us that takes a week to arrive. And an hour of delay from Neptune to Pluto would be reduced to about ten seconds when your "second" is 365 times longer than a familiar second on earth. What you effectively have done is that you have just increased the speed of light to whatever multiplier your races experience time when compared to us: if a year to us is a day to them, then a light-year of distance is merely a light-day to them. On the another plus-side, if you have very slow metabolism, then your ships don’t have to go very fast: 3 percent of speed of light, then you still have to wait just 5 months traveling from Pluto to Alpha Centauri C, same time as going from earth to mars for humans, and at about the same cost(to a fusion mastering civilization) as well. Perfect for bulk shipping of goods. This is about the same perceived speed as the best alcubierre warp drive postulated by our modern understanding of physics. Then, you can argue that since interstellar travel only make economical sense for such slow metabolizing life forms, have all your races being this same type of slow metabolizing organism, which means that you just need to swap out the water with the liquid hydrogen, the rocks and soil with water ice and tholin, the oxygen gas with helium, and the carbon base with orthocarbonic acid(dry ice), then argue that it have to be so slow because of the heat generated by the metabolism: a 62.4k planet radiates away heat about one 365th as well per square meter as the earth does, so a metabolism based on Pluto or titan fluids must be 365 times slower than the equivalent based on earth fluids in order to not boil itself or it’s surroundings. Then, just tell your audience that your protagonists measured the speed of light as 1.095x10^11 meters per "second", your "water" boils at 27K and freezes at 22K, and you are all set for your scientifically plausible interstellar trade masterpiece! [Answer] slow metabolism. if an alien experiences an earth standard year as the equivaent of one hour on their (slow rotating) homeworld, and lives their lives for 700800 years, while processing the same amount of information as an average human processes in 80 years, mere traveling at 5% speed of light allows them to cross 10 light years in 8.8 subjective days, and crossing the milky way would take at most 2.5 lifetimes, implying a (very huge) managable area for their possible empire, without the need for faster than light technology, relativistic travel or cryonics at all. if ftl is impossible, then because of the timescale involved, no civilzation with regular, humanlike rate of metabolism will ever set foot out of their solar system, leaving the (largely uninhabitated) galaxy to the races that are much slower. in fact ,the slower the metabolism for a given race, the larger the effective managable empire the race can colonize, and with dumb autonamous systems, no weakness through slowness would be realistically incured, as dumb robots clearly does not do politics nor trade, trading between the actual, slow living sentients would be about the same as the more traditional FTL worlds. The dominant forms of life of the galaxy would also be unlikely to discover relativity, nor functional radio before they went to the stars, rendering them unresponsive and invisible to terrastrial seti efforts. [Answer] So everyone is talking about how the lack of FTL is basically the end of interstellar trade. I agree with them. So I started thinking, "What would interstellar trade look like? What would it have to be?" With travel times in the ranges of thousands of years to a few million years, whatever trade good one is trading would have to be slow. Really slow. Your "pressing need" for something needs to be measured on the timeline of a generation ship taking a thousand generations. This means the good you need has to be hard enough to obtain that it's worth trading it over the course of thousands of years. We're not talking antimatter, we're talking something far more valuable. What if the trade is in life itself? Evolution operates on a million year scale without too much trouble. What if the valuable resource you are trading is strains of life in different forms. Each one took millions of years to evolve on its home habitat, so they aren't very easy to come by. Transporting a good breeding stock over a few thousand years is actually quite a trick! If you are the kind of civilization that looks ahead tens or hundreds of thousands of years, you could see a bespoke need for a particular strain, and put the call out to a nearby star for your need. They pack the goods up, and ship it on a generation ship in time to save your civilization. We're not talking Fed-Ex 2 day shipping here, but shipping on the scale of geological time! And if you needed tension in a plot, this has it. You *literally* have an entire ecosystem at stake, as they eagerly await their transplanted strains of life. [Answer] ### It isn't practical and there won't be anyone to trade with anyway There's zero practicality to trading anything other than information- but even that is impractical because we'll have to wait decades for responses that might not even transmit reliably. The number of inhabitable star systems within that distance is small and unlikely to have another intelligent species at a compatible level of technology. FTL is basically a *must* for any sort of interstellar trade. ### ... unless you happen to have a wormhole The only way it could be remotely practical is if a wormhole connects the star systems of the two trading civilizations. That at least puts things in the manageable range of travel/transmission time. Message latency (speed of light) would be somewhere in the neighborhood of 6 hours and travel time would be a couple weeks to a few months round-trip, depending on where the wormhole is in each star system and how fast ships can go. [Answer] I have read a few stories set in such a universe. The most common answer seems to be nomadic "traders" (who are similar to vikings) using NAFAL ships. They wander from place to place following rumors and their gut instincts. If they find unattended natural resources, they collect them. If they find a weak civilization, they pillage it. If they find a strong civilization, they trade with it. When traveling Nearly As Fast As Light, most of the logistic challenges involved in interstellar flight disappear. We're not talking generation ships or spending centuries in flight. At 99.986% of the speed of light a trip to Alpha Centauri would be about two months subjective time. Ten years objective time, but that doesn't matter much to nomads. I've seen theoretical discussions of solar sail designs that, combined with either nuclear pulse or antimatter drives, would possibly let a ship get pretty close to that, and that's without factoring in the interstellar currents that would exist if the "plasma universe" theory is correct. (Our space probes have already discovered that at least some of the predicted interplanetary currents are there, so there would seem to be a decent chance...) [Answer] **Human Trafficking and Slavery** A timeless commodity that will inevitably persist well into the future. Human populations will likely genetically diverge across planets across time. Humans could be sold into slavery as curios of odd traits or relics of human evolution. Kind of like keeping a caveman in a zoo. They could even be useful in genealogical medical experiments trying to fight modern pestilence with different genomes. ]

[Question] [ **This question already has answers here**: [How long would people live in the US if an immortality treatment was available?](/questions/6491/how-long-would-people-live-in-the-us-if-an-immortality-treatment-was-available) (5 answers) Closed 5 years ago. Let's imagine there are some ageless people living in big European or American cities. Ageless, forever young but not immortal. They can still die from car crash, gun or knife wound etc. Assuming crime and accident rates will be the same in future, is it possible to calculate an average life expectancy of an ageless person in a major city of today? P.S. I understand that there are different cities, let's deal with some average US crime and accident rates to make the question less broad. Let's also assume this person will live normal life — like go to the street, shops, cafes, use transportation, meet people etc. I found [this info](https://www.iii.org/fact-statistic/facts-statistics-mortality-risk#Odds%20of%20dying%20from%20accidental%20injuries) but I'm not sure how to calculate the average life expectancy of an ageless guy using it. [Answer] From the statistics page you cited: *The odds of dying from an injury in 2014 were 1 in 1,576 according to the latest data available.* Let us suppose this is the odds of dying in a given year due to misadventure or violence. This makes it a probability problem. Figuring out the actual answer to your question - what is the expected value of the number of years you live if this is your only chance of death (i.e. the life expectancy) - is beyond my skill. But I can say this: Your odds of surviving N years in a row is (1 - 1/1576) ^ Nth power. Your odds of surviving any given year are 1 - 1/1576, and by the Rule of Multiplicaton, the fact that you have to be lucky N times in a row means the total probability is that number to the Nth power. You can graph this equation [here](https://www.mathpapa.com/algebra-calculator.html?q=y%3D(1-1%2F1576)%5Ex). This person has about a 50/50 chance of living 1100 years, and a 1 in 10 chance of living about 3600 years or so. It asymptotically approaches 0. [Answer] Let me focus on math part only and explain how your expected life rate depends on the probability of a death in a given year. I will use your assumption that this probability of death does not change so let's assume it is $p$. $p$ has to be greater than $0$ and less than $1$ (that's a general requirement for probabilistic). We'll get back to this value later. So $p$ is your probability of dying during a specific year if you were alive in the beginning of it and similarly the remaining $1 - p$ is the probability you survive another year. Now to die at the age of $n$ you need to live for $n - 1$ years and then die in the last, $n$-th year. which means a probability of such event is $$ P\_n = ( 1 - p )^{n-1} \* p $$ An expected lifespan is an expected value of a random variable of your age with a probability to reach a value $n$ as $P\_n$ calculated above. In other words it is $$ E=\sum\_{n=1}^\inf (n\*P\_n) $$ Lets put the $P\_n$ values into the equation $$ E = \sum\_{n=1}^\inf ( n \* p \* (1-p) ^ {n-1} ) $$ Let's extract constant so that the power is re-indexed to n $$ E = \frac{p}{1-p} \* \sum\_{n=1}^\inf (n \* (1-p)^n) $$ Since for $n=0$ the value of $n\*(1-p)^n$ is also $0$ (since we multiply everything by $n$ which is $0$ so we can reindex the whole sum to start from $0$ $$ E = \frac{p}{1-p} \* \sum\_{n=0}^\inf (n \* (1-p)^n) $$ Now let's apply a formula to calculate this infinite sum and calculate it and as a result we get $$ E = \frac{p}{1-p} \* \frac{1-p}{(1 - (1-p))^2} = \frac{p}{p^2} = \frac{1}{p} $$ In other words your expected lifespan is exactly $1/p$ where $p$ is probability of death during one year. Now let's apply various values provided in other answers and comments: 1. MichaelK's comment gives $p=0.00181$ which accounts to the average lifespan of $552$ years (based on statistics from 2000) 2. Dayton Williams in his answer gives $p=\frac{1}{1576}$ which accounts to the average lifespan of $1576$ years 3. Chris Becke's answer gives $p$ between $0.0003$ and $0.0006$ which accounts to the average lifespan between $1667$ and $3333$ years (various statistics, 2010 - 2012) etc. Now depending on details you can modify what you include or exclude into your death cause that can kill an ageless person and adapt values accordingly. This is a pure mathematical approach ignoring few things though: * The exposure to dangers of external world are reduced until you are close to being mature. You might add 15 years (or something like that) to your results to cover this aspect * The probability of death change over time (ignored as explicitly requested by OP, but in general it decreases over time except a situations like war so it might increase the average lifespan) * The ageless person gathers experience that should help them survive even longer, e.g. notice the warning signs and avoid most dangerous situations resulting in a lower death probability than a normal mortal * Ageless person may attract various people due to their lengthy life. It might increase their death probability and as a result reduce the lifespan * There might be other aspects impacting the lifespan of an ageless person that are not influencing normal mortals and are hard to predict (you have an area to add whatever you think relevant changing this average according to your needs) [Answer] If the probability of a death happening in one year is 1 in 1576, then the life expectancy is 1576 years. This all follows the Poisson distribution: the probability of observing $k$ deaths in a year is $p(k) = e^{-\lambda} \frac{\lambda^k}{k!}$ where $\lambda$ is the avarage number of deaths during this year ( 1 in 1576, per person). The expectation value for such a distribution is $\frac{1}{\lambda}$, i.e. 1576 years. [Answer] You don't want to calculate the average life expectancy. It's really meaningless because many individuals are going to live shorter, or much much longer lives. Both depending on luck, and whatever activities they engage in. The [Micromort](https://en.wikipedia.org/wiki/Micromort) is a unit that describes 'risk' as a 1 in a million chance of being killed by something. As you can see from the tables - if you eliminate deaths from natural causes, people are exposed to, between, 300 and 600 micromorts related to unnatural causes per year. This literally means you can, with a population of 1 million immortals - expect to lose 300 to 600 of them to death per year to accident, murder or suicide. That said - applying the micromort cost of using a motorcycle per km has some sobering outcomes, but even the best forms of mass transit lead to a decimation of your otherwise ageless population over time. **Addendum:** @lster's answer on infinite series is pretty good at transforming 1 in a million chances into your requested "average lifespan" - I think it would be more valuable to consider either the half-life of the population of immortals - the duration over which you expect to loose half of them to death :- which then makes it very easy to ignore the hard math and compute how long it would take to reduce a given starting population to some small number - i.e. how many times do you need to halve the population to get to about the target size. Other things to consider are immortals would probably value their lives more and consequently engage in less risky activities. And, over a given population there would be a natural filtering effect where immortals (as a group) with risky behaviour would have a shorter half-life and thus be pruned faster, leaving you with a longer lived population of relatively risk averse individuals. [Answer] I'd say it would be much much longer than anything calculated here, since when you can theoretically live forever, people will be much more careful, homicide would be punished much much harder and generally, safety would be a much bigger concern. So just make something up. [As an interesting sidenote: Drugs with direct physical harm lice Alcohol, Tobacco, MDMA etc. would be far less popular, since they would be the only way to actually "age" by destroying your body unnaturally but slowly] [Edit due to the comments: It does make sense that some/most people would value life even less, resulting in what @Clay Deitas said. However there would also be SOME people who realize the potential of immortality and would take extreme care of themselves, leading to a two-class society separated by nothing but mindset. "The Immortals" as I call them would naturally have a high interest in the "YOLO" Group being as large and as risky as possible to increase their status as immortals and also keep the population down. They could for example introduce measures to make people age again (by a virus or so). They would certainly be at the top o society, an have no problem with plans that take a century to set up, leading to a very interesting social dynamic. EG: you can have your "average lifespan" be directly controlled to fit your plot by a council of lets say the 50 most long-lived people] [Answer] I suggest looking at this from a different angle. For ageless semi-mortals, what are your risk factors? Also, what is the risk tolerance of someone who could potentially live forever? **I suggest that both of these are tied directly into an individuals level of happiness and social connectivity, and your life expectancy will be very strongly correlated.** Let me explain... Facing eternity when you are discontent, lonely, or depressed means you are much more likely to take on risks that could improve your happiness. Maybe that means you take up skydiving as a hobby or start working a more dangerous job to increase your income (in this kind of society, I can almost guarantee that physically risky manual labor jobs will pay relatively much higher wages). If you are in a loving relationship, have lots of friends, and a happy disposition, eternal happiness seems a very serious thing to risk by doing any kind of risky behaviors. That means you are more likely to live below your means until you find a suitably safe job. Also you will more likely forgo the sky diving and maybe take up board games. You may not have as much fun (perhaps), but you will live longer and dying would leave behind people who care about you to live for a long, long time. Actuaries constructing their death tables will do so based primarily on these factors. Someone living blissfully should expect to live indefinitely. Due to survivor bias, **society would slowly become happier and happier, until all the unhappy people die and those that remain are likely to live for eons, dying only due to disaster.** (As a side note, any numbers connected to death by misadventure in today's society are almost certainly lower than they would be if you simply removed disease from the equation, all else being equal.) [Answer] This is interesting mathematical question. If we are able to gather the data of deaths and its causes and classify them as "Natural Death" or "External forces". Using this dataset , we would be able to able to calculate the "probability" of human to die at a particular age due to external forces. How long a person will live ? - Probability may tell us the chances of humans to survive at a given time, this will be same for all humans in a data set. If we attribute the external causes to death, then different age group will have different probability, but here people are ageless, so everyone has equal chances. Although, average age of a population can be found over a period using "historical data/current". It is illogical to find average over a probable data set. Example: 100 out of 20 die of natural death. So, a person has probability if 0.8 to survive at any moment/age. Average age - we could , find average age if we are given current/historical data-set, not future. [Answer] Further information: <https://www.statista.com/statistics/241572/death-rate-by-age-and-sex-in-the-us/> The smallest death rate is for females 5-9, who have a death rate of slightly more than 1 in 10,000. Females 25-29 have a death rate about six times as high, and males 25-29 death rate about fifteen times as high, or more than twice females of that age range. It's reasonable to assume that the increase in death rate from 5-9 to 25-29 is not due to people dying from old age, and the difference between men and women is more likely behavioral rather than directly due to biology (although there may be biological influences on behavior). Which of these numbers is more applicable to your scenario is a matter of opinion. Currently, the biological, psychological, neurological, and social aspects of adolescence lead to behavior that increase the death rate, and once people are past that stage, they then start to death with aging issues. Perhaps in your scenario, a large portion of people survive past adolescence and return to 5-9 levels of behavior-induced deaths, while avoiding age-induced deaths. Thus, I would say the optimistic expectation is that the culture would develop more cautious mores, and have a death rate around 1 in 10,000, while a less optimistic expectation would be 1 in 1000 (the average death rate for young adults). [Answer] There's a number of answers here that show good math, but there's also a social aspect to the case. Young males are most likely to die violent deaths, because they're most likely to be violent criminals. Even in an ageless society, this will probably remain this way, and pull down the average age a lot much like infant deaths did the european average for a long time (basically until the medical science got up to speed). In the middle ages, if you made 20 you'd probably make 50 or even 60 even if the average lifespan was around 40, simply because if 33% of all children die, that pulls down the average. Following this, there'd probably be a death spike in the age bracket under 40, and those who survive that are pretty good at surviving, and will survive really, really long. That said, you also need to change how minds work a bit. As we get older, it's harder to learn to adept to new technologies - take for example the average grandmom's grasp of computers. The reason the amount of computer savvy people increasing as much as it does is because those who don't are typically older and first do die. So you'll also need to enable your ageless people to learn a life long, if you want them to be any kind of relevant after, say, 100 years. ]

[Question] [ From [Wikipedia](http://en.wikipedia.org/wiki/Atmosphere_of_Earth): > > By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. > > > For example, would humans be able to survive in these atmospheres? : * 100% oxygen, nothing else * 10% oxygen, 90% nitrogen * 10% oxygen, 90% argon * 10% oxygen, 90% carbon dioxide * 10% oxygen, 90% helium * 10% oxygen, 90% xenon * 2% oxygen, 98% of other elements which are not toxic [Answer] There are three separate issues here: * Too much oxygen, and the human body (as well as any other organic material) will be highly flammable. You don't really want to live there. * Too high or too low oxygen *partial pressure*, and the metabolism won't work correctly. * The other gases, or lack of them, may also cause problems So a 100% oxygen atmosphere will not work, due to point 1. Also your 90% CO2 atmosphere won't work because the high CO2 concentration will kill you. Whether the other 10% atmospheres will work depends on the total pressure. If the total pressure is twice as high as on earth, the partial pressure is the same as on earth, and since the other gases are inert (either nitrogen like here on earth, or noble gases), they should not make too much trouble on their own. However, with the exception of helium, they have narcotic effects, therefore the nitrogen, argon and xenon atmospheres would also not be the best to live in, although temporary visits should be less of a problem (thanks to Rob Watts for making me aware of this problem). Moreover, there should also be some CO2 for respiration to work. With the 2% atmosphere, you'll need 10 times as much pressure to get the same partial pressure for oxygen as on earth. I'm not sure whether the human body could tolerate that for an extended time (for a limited time it certainly can, as divers prove; it's the pressure you find on earth under water in a depth of 90 meters). At those concentrations, you really should have helium as inert gas, however. Another point: In all of the above I've assumed that the percentage is the one on the ground (because that's also where the earth atmosphere values are valid). On earth the oxygen fraction goes down with height because nitrogen is slightly lighter than oxygen. Of the other gases you mention, only helium is lighter than oxygen; however that one is much lighter, so in the helium-oxygen atmosphere, the oxygen percentage will quickly go down as you go up (note, however, that the *partial pressure* will go down no quicker than in our atmosphere, assuming the same gravitation). So in the helium-oxygen atmosphere, already a small mountain will hinder you from making fire (but not yet from breathing). For the gases which are heavier than oxygen, the fraction of oxygen will *grow* as you go up. However, the partial pressure will still go down. Which gives the seemingly paradox situation that things burn better at greater height, while your body gets less oxygen. [Answer] 100% oxygen is dangerous - stuff will burn, oxygenation can damage tissues. [Apollo 1](http://www.space.com/14379-apollo1-fire-space-capsule-safety-improvements.html) had pure oxygen atmosphere, did not ended up well. [oxygen is toxic](http://en.wikipedia.org/wiki/Oxygen_toxicity) 90% CO2 will kill you (not enough partial pressure of oxygen in hemoglobin) 2% of oxygen is not enough. 10% of oxygen with other inert gasses (nitrogen (not inert, but not reactive either), helium) might be survivable. See [trimix](http://en.wikipedia.org/wiki/Trimix_%28breathing_gas%29) breathing gas for scuba diving. Different mixes for different usage, and pro/com for helium and nitrogen, and lowering partial pressure of oxygen. Seems than [xenon](http://en.wikipedia.org/wiki/Xenon#Anesthesia) is used for anesthesia, so it will do you no good to have it in such concentration. Thanks @Twelfth [Argon](http://en.wikipedia.org/wiki/Argon#Medical_use) enhances change of gas embolism, but it was used to replace nitrogen to speed up decompression, so it seems NOT be immediately poisonous. Apparently, well trained and adapted humans (with more hemoglobine in blood) [can survive 12% of oxygen](http://www.thenakedscientists.com/forum/index.php?topic=44734.0) Image at this page about [limits of human survival](http://www.livescience.com/34128-limits-human-survival.html) shows dangerouns levels of hypoxia (low oxygen) and hyperoxia (too much oxygen). Twelfth in his [answer](https://worldbuilding.stackexchange.com/a/10462/687) raised interesting aspect: relative density of different gasses, and possibility of separate layers. Looking at [gas density](http://www.engineeringtoolbox.com/gas-density-d_158.html) table, air density (1.2 kg/m3) is close to oxygen (1.3) and nitrogen (1.16) - no surprise there. Helium density (0.16) is 10% of oxygen, so likely atmosphere with mix of oxygen and helium would after a short time formed layers, with more oxygen at the lower layers - leading to oxygen poisoning. Not good. Even worse: @Marky Mark is right [helium does escape from Earth atmosphere](https://physics.stackexchange.com/questions/78586/can-helium-disappear-from-earth). Argon is bit heavier then oxygen (1.66), but not much. But if such layer of argon was possible and stable, all lowlands would be uninhabitable. So you would need to add some winds and turbulence to mix stuff up. Even then, mines and cellars would not be possible without active ventilation, because heavier argon would accumulate there, causing asphyxiation. [Answer] # 100% O2 At normal atmospherical pressure (**101.325 kPa**) if **your only gas is O2** you will have a **partial pressure of 101.325 kPa of O2**... lethal, deadly and painful. Lets talk about consequences! * **[Oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity):** When O2 partial pressure is **above 50 kPa** oxygen become **toxic**. **Symptoms:** + Disorientation, breathing problems, vision changes such as myopia. + Prologed exposures of higher O2 PP or shorter exposure but very higher, can cause oxidative damage to cell membranes, collapse of the alveoli in the lungs, retinal detachment, and seizures. + A lot more, click in the [link](https://en.wikipedia.org/wiki/Oxygen_toxicity) for more info. [](https://i.stack.imgur.com/BjkWM.png) # 10% O2 and 90% N2 $$ \left| \begin{array}{cc|ccc|c} \text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (kPa)}\\ \text{O}\_{2}&\text{10%}&31.9988&0.31&\text{8%}&8.98\\ \text{N}\_{2}&\text{90%}&28.0134&3.21&\text{91%}&92.37\\ \text{Total}&\text{100%}&60.0122&3.52&\text{100%}&101.325 \end{array} \right| $$ ``` In Wikipedia you can find another gr/mol values. This is because O2 and N2 are <2> atoms per molecule, so I multiply the value per atom by 2. ``` **Values:** * 10% O2: **8.98 kPa O2** * 90% N2: **92.34 kPa N2** **Concequences:** * **Low value of oxygen - [Hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical)):** The minimal safe partial pressure of O2 is at **16 kPa** and if O2 partial pressure falls below **13.3 kPa** humans suffer hypoxia. Symptoms include [fatigue](https://en.wikipedia.org/wiki/Fatigue_(medical)), [numbness](https://en.wikipedia.org/wiki/Hypoesthesia) / tingling of extremities, [nausea](https://en.wikipedia.org/wiki/Nausea), and anoxia. In severe hypoxia, or hypoxia of very rapid onset, [ataxia](https://en.wikipedia.org/wiki/Ataxia), confusion / disorientation / [hallucinations](https://en.wikipedia.org/wiki/Hallucination) / behavioral change, severe [headaches](https://en.wikipedia.org/wiki/Headache) / reduced level of consciousness, [papilloedema](https://en.wikipedia.org/wiki/Papilledema), [breathlessness](https://en.wikipedia.org/wiki/Tachypnea), [pallor](https://en.wikipedia.org/wiki/Pallor), [tachycardia](https://en.wikipedia.org/wiki/Tachycardia), and [pulmonary hypertension](https://en.wikipedia.org/wiki/Pulmonary_hypertension) eventually leading to the late signs [cyanosis](https://en.wikipedia.org/wiki/Cyanosis), [slow heart rate](https://en.wikipedia.org/wiki/Bradycardia) / [cor pulmonale](https://en.wikipedia.org/wiki/Pulmonary_heart_disease), and [low blood pressure](https://en.wikipedia.org/wiki/Hypotension) followed by death. **In other words, a painful and slowly death.** * Nitrogen Narcopsia: **No, don't worry**, you **don't** have nitrogen narcopsia because it's developed under pressures above **240 kPa** and **354 kPa**, and you only have **92.34 kPa of N2**. # 10% O2 and 90% Ar $$ \left| \begin{array}{cc|ccc|c} \text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (kPa)}\\ \text{O}\_{2}&\text{10%}&31.9988&0.31&\text{12%}&12.34\\ \text{Ar}&\text{90%}&39.948&2.25&\text{87%}&88.98\\ \text{Total}&\text{100%}&71.9468&2.56&\text{100%}&101.325 \end{array} \right| $$ ``` Argon is only ONE atom, it doesn't have any Ar<2>. ``` **Values:** * 10% O2: **12.34 kPa** * 90% Ar: **88.98 kPa** **Concequesces:** * **Low value of oxygen - [Hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical))**: Hypoxia is at **13.3 kPa** and you have **12.34 kPa**. (See above to read symptoms). * **[Argon Asphyxia](https://en.wikipedia.org/wiki/Argon#Safety):** Although argon is non-toxic, it is 38% denser than air and therefore considered a dangerous [asphyxiant gas](https://en.wikipedia.org/wiki/Asphyxiant_gas) in closed areas. It is difficult to detect because it is colorless, odorless, and tasteless. * **[Argon narcopsia](https://en.wikipedia.org/wiki/Argox):** I don't know much about it but I think it can cause narcopsia like nitrogene. # 10% O2 and 90% CO2 $$ \left| \begin{array}{cc|ccc|c} \text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (kPa)}\\ \text{O}\_{2}&\text{10%}&31.9988&0.31&\text{13%}&13.44\\ \text{CO}\_{2}&\text{90%}&44.01&2.04&\text{86%}&87.89\\ \text{Total}&\text{100%}&76.0088&2.35&\text{100%}&101.325 \end{array} \right| $$ ``` There are several atoms, you can find the value in wikipedia or calculate by yourself (sum of all atoms * quantity values). ``` **Values:** * 10% O2: **13.43 kPa** * 90% CO2: **87.89 kPa** **Concequesces:** * **Almost low value of oxygen - Not [Hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical))**: Hypoxia is at **13.3 kPa** and you have **13.43 kPa**. You can **survive** (unconscious I think) but **not live**, you will suffer a lot (and will afect your health). * **Too high value of CO2 - [Hypercapnia](https://en.wikipedia.org/wiki/Hypercapnia) (Carbon dioxide poisoning)**: Severe hypercapnia is cause by an increment of **10 kPa CO2**...mmm... you have **87.89 kPa**, quite more... than the lethal. Be careful about [carbon dioxide toxicity](https://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity), concentrations of **7%** to **10%** may cause suffocation, even in the presence of sufficient oxygen, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour. (You have **90%**) Symptoms and signs of early hypercapnia include flushed skin, full [pulse](https://en.wikipedia.org/wiki/Pulse), [tachypnea](https://en.wikipedia.org/wiki/Tachypnea), [dyspnea](https://en.wikipedia.org/wiki/Shortness_of_breath), [extrasystoles](https://en.wikipedia.org/wiki/Premature_ventricular_contraction), muscle twitches, hand flaps, reduced neural activity, and possibly a raised blood pressure. Other symptoms of mild hypercapnia might include headache, confusion and lethargy. Hypercapnia can induce increased cardiac output, an elevation in arterial blood pressure, and a propensity toward [arrhythmias](https://en.wikipedia.org/wiki/Cardiac_arrhythmia). In severe hypercapnia, symptomatology progresses to disorientation, [panic](https://en.wikipedia.org/wiki/Panic), [hyperventilation](https://en.wikipedia.org/wiki/Hyperventilation), [convulsions](https://en.wikipedia.org/wiki/Convulsion), unconsciousness, and eventually [death](https://en.wikipedia.org/wiki/Unconsciousness). Also you will increase the [carbonic acid](https://en.wikipedia.org/wiki/Carbonic_acid) of your blood in a process called [respiratory acidosis](https://en.wikipedia.org/wiki/Respiratory_acidosis). Also, do you remember what I said about [asphyxiant gas](https://en.wikipedia.org/wiki/Asphyxiant_gas), well, CO2 have the same results. You can see this interesting [table](https://en.wikipedia.org/wiki/Hypercapnia#Tolerance) that I found: ``` %CO2 in air Duration Major limitation 0.04 % lifetime normal atmosphere 0.5 % lifetime no detectable limitations 1.0 % lifetime " 1.5 % > 1 month mild respiratory stimulation 2.0 % > 1 month " 2.5 % > 1 month " 3.0 % > 1 month moderate respiratory stimulation 3.5 % > 1 week " 4.0 % > 1 week moderate respiratory stimulation, exaggerated respiratory response to exercise 4.5 % > 8 hours " 5.0 % > 4 hours prominent respiratory stimulus, exaggerated respiratory response to exercise 5.5 % > 1 hours " 6.0 % > 0.5 hours prominent respiratory stimulus, exaggerated respiratory response to exercise, beginnings of mental confusion 6.5 % > 0.25 hours " 7.0 % > 0.1 hours limitation by dyspnea and mental confusion ``` And this photo: [](https://i.stack.imgur.com/z6SRc.png) Well, **6 minutes at 7% CO2**, think about at **90%**... # 10% O2, 90% He $$ \left| \begin{array}{cc|ccc|c} \text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (kPa)}\\ \text{O}\_{2}&\text{10%}&31.9988&0.31&\text{1.37%}&1.38\\ \text{He}&\text{90%}&28.0134&22.48&\text{98.63%}&99.93\\ \text{Total}&\text{100%}&36.001402&22.79&\text{100%}&101.325 \end{array} \right| $$ **Values:** * 10% O2: **1.38 kPa** * 90% He: **99.93 kPa** **Consequences:** * **Extremely low value of oxygen - [Hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical))**: Hypoxia is at **13.3 kPa** and you have **1.38 kPa**. (See above to read symptoms). * **[Helium and voice](https://en.wikipedia.org/wiki/Helium#Effects):** The higher resonant frequencies caused by the gas (see the link to know how) cause a change in timbre, resulting in a reedy, duck-like vocal quality. * **[Helium asphyxiant gas](https://en.wikipedia.org/wiki/Helium#Hazards):** Inhaling helium can be dangerous if done to excess, since helium is a simple asphyxiant and so displaces oxygen needed for normal respiration. At **90% He** it's obvious that it's lethal. * **[Helium narcopsia](https://en.wikipedia.org/wiki/Heliox):** I don't know much about it but I think it can cause narcopsia like nitrogene. # 10% O2, 90% Xe $$ \left| \begin{array}{cc|ccc|c} \text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (kPa)}\\ \text{O}\_{2}&\text{10%}&31.9988&0.31&\text{31%}&31.72\\ \text{Xe}&\text{90%}&131.293&0.68&\text{68%}&69.59\\ \text{Total}&\text{100%}&163.29182&0.99&\text{100%}&101.325 \end{array} \right| $$ **Values:** * 10% O2: **31.72 kPa** * 90% Xe: **69.59 kPa** **Concequences:** * **High but no lethal oxygen - [Oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity):** Oxygen toxicity is above **50 kPa** and you have **31.72 kPa** so you won't have this but maybe you would have some other health problems. High values of oxygen produce [oxygen stress](https://en.wikipedia.org/wiki/Oxidative_stress) in your cells, also increase the oxydation of your body (more free radical -[reactive oxygen species](https://en.wikipedia.org/wiki/Reactive_oxygen_species) -) and this would increase your aging speed, tumors, cancer and cell death. See [free radical theory of aging](https://en.wikipedia.org/wiki/Free-radical_theory_of_aging). * **[Xenon and voice](https://en.wikipedia.org/wiki/Xenon#Precautions)**: Xenon vibrates more slowly in the vocal cords when exhaled and produces lowered voice tones, an effect opposite to the high-toned voice produced in helium. * **[Xenon isn't toxic by itself](https://en.wikipedia.org/wiki/Xenon#Precautions):** Xenon is non-toxic, although it does dissolve in blood and belongs to a select group of substances that penetrate the [blood–brain barrier](https://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier), causing mild to full surgical anesthesia when inhaled in high concentrations with oxygen. * **[Xenon anesthesia](https://en.wikipedia.org/wiki/Xenon#Medical)**: Xenon has been used as a [general anesthetic](https://en.wikipedia.org/wiki/General_anaesthetic), I think (quote needed) that a 30% Xe is used like anesthetic. Dense gases such as xenon can be breathed safely when mixed with at least 20% oxygen, sadly you have only 10% of oxygen. Xenon at 80% concentration along with 20% oxygen rapidly produces the unconsciousness of general anesthesia. * **[Xenon asphyxiant gas](https://en.wikipedia.org/wiki/Xenon#Precautions):** Like argon and other inert gasses it can be a gas asphyxiant because it has more weight than O2 and can fill the surface of a planet with 100% inert gas (O2 will fly upper). # 2% O2, 98% of other elements which are not toxic Well, sadly I can make calculations because I don't know the molecular mass of *other elements* but at least I can safestly say that **obviously you would die of [Hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical))**. **I hope this help you, sorry for the long post, I hate long post but you ask too much atmospheres. If you want more information check my others answers: [this](https://worldbuilding.stackexchange.com/a/84014/35041) and [this](https://worldbuilding.stackexchange.com/a/82850/35041).** [Answer] 100% oxygen, nothing else - no the human body would go up like a gallon of gasoline with a static electricity spark, on top of it being toxic. 10% oxygen, 90% - carbon dioxide carbon dioxide of [%7 can kill, long term exposure to %.5](http://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity) can cause health issues. for the rest humans to work OK need ~20 oxygen [Less than 19.5%](http://www.newton.dep.anl.gov/askasci/zoo00/zoo00755.htm) and you start feel severe effects and in General %10 is likely to lead to severe health issues including death. * 10% oxygen, 90% nitrogen * 10% oxygen, 90% argon * 10% oxygen, 90% helium * 10% oxygen, 90% xenon * 2% oxygen, 98% of other elements which are not toxic [Answer] 10% is too little and wouldn't work. If you increased it to 20%: 100% oxygen: * I think we'd spontaneously combust...this is toxic as well. 20% oxygen, 80% nitrogen * pretty close to what we live in now. Oxygen and nitrogen are around the same weight and mix really well. 20% oxygen, 80% argon * Where nitrogen is around the same weight and mixes well with oxygen, Argon is several times heavier than oxygen and therefore tends to sink to the bottom. On an atmosphere scale, this would end up in death as the surface would see 100% argon with all the oxygen relegated to the higher levels of the atmosphere. * We can breathe argon and oxygen mixtures...infact argon is considered doping for Olympic purposes. * The pressure of this atmosphere will be significantly higher...argon weighs a lot. 20% oxygen, 80% carbon dioxide -Carbon dioxide is toxic at this level, we'd die. 20% oxygen, 80% helium * Sorta funny, but this might end up as the 100% oxygen scenario again. Helium is light enough that the two gasses would layer, near 100% oxygen at the surface and 100% helium in the upper atmosphere. 20% oxygen, 80% xenon * Xenon is heavy and will have the same issues argon does...we'd asphyxiate pretty quickly and probably be crushed by the weight of the atmosphere. * We can breath it, but it knocks us out pretty quickly...it works as a pretty heavy anesthetic (breathing 20% oxygen 80% xenon will knock you out quicker than the general anesthetics used in hospitals) and fits into the doping category for the Olympics. * Xenon is considered toxic as well...it dissolves into plastics and rubber Edit in a caveat - I'm unsure how water (air humidity) changes in these environments. FOr example, water diffuses much quicker in Helium, which should mean humidity spreads out quicker and further making it harder for clouds to form. [Answer] You basically need oxygen to breathe. Everything else is not strictly necessary. The limits you are willing to take depend on how much of a mountaineer and how much of a diver you are. These two articles explain the upper and lower limits for oxygen partial pressure for humans: <https://en.wikipedia.org/wiki/High-altitude_adaptation_in_humans> <https://en.wikipedia.org/wiki/Maximum_operating_depth> Where the Tibetan highlanders live, the oxygen level is only about 60% of that at sea level. Most people will tolerate this level as a minimum, so you will have ~100mbar/10kpa of pure oxygen as a "minimum atmosphere". Breathing pure oxygen works well, as every tech diver will tell you. Still, everything that's not wet or otherwise inflammable will burn VERY easily. A little oil and a spark and you have a BIG fire. Then you need to make sure that the amount of a lot of gases that are more or less poisonous are not too high. There's a partial pressure for each gas that you'll have to keep below a threshold. Maximum partial pressures for some gases * Oxygen has been treated above, e.g. 1.6 bar - see <https://en.wikipedia.org/wiki/Maximum_operating_depth> * Nitrogen - e.g. 6 bar - see <https://en.wikipedia.org/wiki/Nitrogen_narcosis> * Hydrogen - e.g. 50 bar - see <https://en.wikipedia.org/wiki/Hydrogen_narcosis> * Argon and similar - e.g. 1 bar - see <https://en.wikipedia.org/wiki/Argox> * CO2 - e.g. 100 mbar - see <https://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity> Some effects may be additive. You could set up an atmosphere e.g. consisting of 1 part O2, 40 parts H2, 5 parts He and 5 parts N2 at a total pressure of fifty times the pressure on earth and you could breathe it, although you will feel the air being very "think" and you will need to get accustomed to it. You could also live in a 500 times thinner atmosphere made up of pure oxygen. That's about the limits for humans. ]

[Question] [ I'm trying to create a realistic magic system, this may be a lost cause. Imagine in our story we have a wizard who wants to cast a spell to start a fire. In some magic systems there are magic words, in others the wizard waves a wand but these are just ways of controlling the spell. What I'm interested in is where the power comes from, the real measurable energy to have this effect. Someone with better knowledge of physics than me will tell me that you need a certain number of KJs of energy to ignite the wood and start the fire. Forgetting for the moment how the wizard controls this energy what could the power source be? I'm loathed to have it as a mythical floating store of energy which wizards tap into - the energy to cause wood to spontaneously ignite doesn't just float around in our atmosphere. What measurable battery of energy could the wizard use to start the fire? [Answer] > > What measurable battery of energy could the wizard use to start the fire? > > > Ignoring a few nifty ones that I don't have the physics-fu to even speculate about... ## Standard Biology Humans store a fairly large amount of energy chemically in the body. The standard calorie that we ingest is really a chemical kilocalorie - enough energy to raise a liter of water (under sea-level pressure) 1 degree Celsius. That "low calorie" cookie is still enough stored chemical energy to boil a liter of near freezing water. If the wizard has slightly more efficient digestion or ability to convert fat to energy, there's more than enough to get something hot enough to burn - especially if the wizard is fine making a single point *very* hot and letting the fire move naturally from there. ## Matter! Entirely far fetched, but more scientifically based than some mythical store. Assuming the wizard has some ability to annihilate matter, then they've got oodles of energy. The average (healthy) human will move .5 liters of air during quiet breathing (per [wikipedia](http://www.answers.com/Q/How_much_does_one_liter_of_air_weigh)). Which is about .65 grams (per [link](http://www.answers.com/Q/How_much_does_one_liter_of_air_weigh)). Plug into `e=mc^2` and you get ~58 **trillion** Joules which is ~14 **trillion** calories. Even assuming your wizard wants to save some of that air for breathing, that's a whole lot of fire to spread around. ## Piezoelectricity [Piezoelectricity](http://en.wikipedia.org/wiki/Piezoelectricity) is a chemical mechanism where pressure on some (atomic) structure generates electricity. It's known that certain biological structures can do this, and the idea of piezoelectric shoes is being bantered about for use in wearable computing. It's unlikely to generate enough power to make fires without fantastic story elements, but maybe plausible for large creatures or high gravity environments. ## Magnetic Induction These are used in wireless charging stations today. Again, probably not enough to start a fire without fantastic story elements, but if the world had very powerful magnetic fields, then the wizard could tap into those fields to do work. ## Radiation Solar power is the common example here, though any power collected via solar power would need to be stored and then released (see chemical or nuclear above). And it likely wouldn't be enough to light a fire unless the wizard wanted to wait a while. A more plausible example is the use of directed microwaves (or similar radiation) at more powerful (or focused) rates. This is commonly theorized to be done via satellite to bypass line of sight issues, but doesn't necessarily need to be. There may be a satellite from a forgotten race beaming power down from the heavens that wizards can use wands or staves (read: antennae) to collect and redirect. Or the wizard has their own personal base station (wizard tower?) that they can signal for power to be beamed in. ## Aether Or, y'know... you can just pull energy from the aether. There's plenty of things we used to believe as real, or will believe as real once we discover them. Making a realistic magic system need not be *real* (rather by definition). It just needs to be consistent. ***note:*** an earlier version of this answer had a mathematical error in the matter-energy conversion. Oops. [Answer] To avoid the need for a "magic field" or equivalent solution you can have magic work as a means of redirecting environmental energy (where there is residual power dissipating all the time) into tasks where it can be useful. You can make the difference between time-period or setting-contemporary technology and magic, a difference of *efficiency*. In essence, the source of magic is application of energy rather than the energy itself, although it can be perceived either way. In this case, a wizard, instead of tapping into some plentiful source of magic and funneling it into, for example, wood to make it burn (or create fire directly), they have a skill or affinity to absorbing environmental radiation, perhaps even kinetic energy and the like and *very efficiently* transferring that energy in high concentrations to very small spaces, causing side-effects, which would be what they *perceive* as magic. They might discover that it's harder to make magical fire at night or that it requires a different state of mind. They might find it curious that when they're surrounded by snow it's *easier* to create fire when they need it - even though what they usually use as magic amplifiers for fire, is gems or metals that work best when heated. Thinking of this as radiation turned into concentrations high enough for fire, makes these easy to explain (snow reflects light, so there's lots available, but at night there's no sun and gems might works as lenses, metals can be radioactive etc.). To people however it might be that, when the Sun is down -the source of their fire magic- it can't help them much, or the Moon, the Sun's adversary, blocks their fire magic - in the snow, the Sun is shining and is an adversary to cold, so it grants them its aid - Rubies are the Sun's stone so *of course* it helps with fire magic etc. The difference in effectiveness would be similar to breaking a rock with a heavy hammer and causing the rock to undergo fission by causing a chain reaction at the atomic level. While fission in real life is usually achieved through rather brute-force means, *magic* could be the application of such techniques in a highly efficient and deliberate way. Concentration of energy is also critical. Focus fusion, which uses electrical discharges to generate heat for the process, works with this principle. Instead of heating an entire TOKAMAK to get fusion in a body of hydrogen/helium, you instead focus a small amount of energy very tightly into a plasmoid to generate the necessary heat, causing a chain reaction. The plasmoid is tiny, but its energy concentration is astronomical. This approach is much more efficient and this is what I'm suggesting *magic* is, in a fantasy setting. The wizard themselves need not understand how this works in detail. To them it's just a skill they picked up or discovered. All the literature and tradition on how magic works can be elaborate theories, theological mumbo jumbo or whatever you want - it has to only make sense to the *people* but it doesn't have to be what's actually happening. Technique and the development of it can exist and do the "right thing" without magic users understanding how it really works - they just figure out some things work better than others and put effort in improving their technique in a way that increases the effects. After they're skilled enough, most of what they do would be subconscious rather than conscious. And yes, some of what they do as *magic* will just be clever stuff that isn't really all that magical - they might chant over a uranium ore to make it slowly kill someone, but no matter how much they chant, it'll be just as harmful depending on the concentration; but to them *thats magic*. [Answer] So you want a **scientific** approach to magic? I am going to answer this as directly and clearly as I can. ## Science is Magic The definition of magic is as follows: "The power of apparently influencing the course of events by using ***mysterious*** or supernatural forces." I have placed an emphasis on mysterious because nowadays we try to provide scientific explanation for mysterious occurrences, however we are not always able to explain things the way they truly are. Back in primitive times wasn't the basic concept of fire magic to us? Our science has constantly progressed through time and so now we can explain the why and how to fire, therefore it is no longer ***mysterious*** to us as a whole. Fire is explained by ***consistent*** findings(Grossly oversimplified). With the science behind it we can explain why it happens but we can't always prevent it so it is sometimes referred to as a "natural disaster" instead of a sorcerers/gods power. The phrase "Having it down to a science" is often used to describe mastering something, so if you mastered something unknown wouldn't it become science? If you are mastering something wouldn't you be consistent with it? You would not truly be a master of something if it had unexpected results. We (normally) no longer use the excuse "magic" is involved if we don't understand it, we declare that it can be scientifically proven and attempt to answer the question using what we ***know*** to be possible. The reason I wrote this was to say that science was a concept to prove magic. Because if it is no longer a mysterious/unknown force creating an occurrence than it would become part of science. If you create something to explain a "magician" controlling fire then it *could* become scientific. > > the energy to cause wood to spontaneously ignite doesn't just float around in our atmosphere > > > Ah but philosophers way back when believed that air, fire, water, and earth where the only elements and were oblivious to oxygen, hydrogen, and other basic elements that school kids now know today. So as examples go, "scientifically" you could leave out the finite details of how certain things are in the atmosphere we haven't found. Even better you could be on a planet or plane of existence where the energy needed to ignite wood is floating around. Even adding that the magician doesn't control the fire, only aim and create its initial intensity could possibly create a slightly more scientific approach due to it explaining that he technically controls nothing but a way of channeling something already there. He could also control it using specific instruments that mold the energy around him instead of him personally being able to manipulate the energy. > > I'm loathed to have it as a mythical floating store of energy which wizards tap into > > > I'm not trying to say make the wizards power come from something implausible just because it is undiscovered or "mysterious" as I've emphasized, it should be something that you can explain in your own way based upon the consistent science and physics of the world you are either making or using. Undiscovered **does not** by any means include how you can fly or create fire by simply saying, "hocus pocus" and random energy gives you power. Sorry for the long response just trying to make sure the point is made. I'll end this with a quote from a sci-fi writer and a [futurist](http://en.wikipedia.org/wiki/Futurist) "Magic is just science that we don't understand yet" - [Arthur C. Clarke](http://en.wikipedia.org/wiki/Arthur_C._Clarke) [Answer] Isaac Asimov (I think it was) wrote a sci fi book in which there was a "leak" between two different universes which affected the physical constants (the two universes had different laws of physics). One universe was using it to power their civilization. Essentially they thought they'd discovered some (almost) magical source of power. But.... it was risking destroying the other universe. So, one approach to magic might be that you have access to an alternate universe (perhaps a different one depending on the type of mage/magic you are using). And by creating a small tear between them you can change the physical laws nearby. You could then: * Make something catch fire (lower the 'flash point" temparature * feather fall - change the gravitational constant * create heat/cold (by siphoning it from a "hot"/cold universe) You could also have a small amount of magic with a *lot* of mysticism (theatrics) which would be very interesting. That leaves room for people who disbelieve in magic, etc. Similar to how some races viewed the Jedi they disappeared (in Ep IV- VI), where it was considered a dead "religion" (i.e., all mysticism) [Answer] *I'm going to try and approach this from the most scientific position I can, so no alternate universes, no mystical crystals, no nothing besides thermodynamics.* You said not to worry about how the wizard controls the energy, right? Good, because I'm not even going to try to figure that one out. For now, it's magic. We know we can neither create nor destroy energy-mass, correct? Well, it's got to come from somewhere. We could use: **- thermal energy - chemical energy - nuclear energy - Einsteinian energy** ## Thermal Let's start with thermal energy. (If I screw up the thermodynamics, it's cause I'm not a chem major) Luckily for our wizard, there is a fortunate lack of stuff at 0K on planets, particularly habitual planets, which is where I assume our wizard would be operating. So, why don't we just drop something to 0K and use the energy from that? If we dropped one cubic meter of atmosphere at 20C, at sea level, to absolute zero, our wizard would have 355 kilojoules of energy to play with. (This is a rough estimation, things get weird around 0K, models stop being linear, we get phase changes, bluh bluh bluh. This is really really rough, actually. Data pulled from [here](http://www.engineeringtoolbox.com/air-properties-d_156.html).) That's about 83 food Calories. Not much. Also, we run into another problem, the reason why nobody ever gets to 0K. Energy won't really move unless it's to a place with less energy. This pretty much rules out freezing type of things, and getting fire type spell from the energy gotten from said freezing type spells. However, we don't know the range within which the wizard can transfer energy back and forth. If it's practically unlimited, why couldn't they draw energy *directly from the sun* or transfer it to Pluto? It'd give an interesting thing as well, you'd probably get "Sun Wizards" and "Moon Wizards", who use those bodies to manipulate the temperature. But let's try something else. ## Chemical Good old chemical energy - the most commonly used method of storage and manipulation of energy by spongy organic creatures. Say our wizard is a morbidly obese wizard with 300kg of fat on him. Assuming he doesn't suffer heart failure, if he goes on a magical diet, that fat will give him 11,100,000kJ [[source]](http://en.wikipedia.org/wiki/Food_energy), much much better when trying to cast super-powerful science spells. Of course, this assumes there's a McWizards devoted to getting wizards the raw magical energy they need to preform their wondrous acts. ## Nuclear/Einsteinian Nuclear energy! Antimatter! Science/magic! Nuclear, like chemical, relies on extracting the energy that's stored in bonds, except nuclear bonds are strong force bonds, not electromagnetic. So: lots more energy, but you already knew that. Einsteinian energy is based on the fact that E=MC^2; it's the direct conversion of mass to energy. However, mass won't just spontaneously flip to energy, you need antimatter and matter to annihilate for that to happen. Of course, if you could do that, you'd have stupid amounts of energy to play with. "Potions", possibly, stored in magnetically shielded vials, perhaps? This all assumes that the wizard can safely manage this much energy, which I assume they can, given that they will be using it for spells and such. ## Storage The issue I see as the largest, aside from however the heck you're going to manipulate this energy, is somehow storing it for use. I mean, there's energy everywhere, that's no big issue. But what if you don't want to have to open a portal to the sun every time you want to light a match with your finger? What if the wizard wants to collect their energy and use it slowly, over time. This question is really linked to whatever the mechanism is for using the energy, something I'm going to have to avoid completely due to it being magical. Chemical storage makes the most sense, and it's rather humorous to imagine a wizard putting on hundreds of pounds before a battle. Antimatter is also an effective storage. Special electrically charged crystals or totems, held in "magical" airtight, magnetic containers, paired with another one, seem like effective and classic-ish ways to do that. Something else to realize is that if there's any wizard capable of containing the energy that would be released by a *goddammned annihilation* would be more than capable enough of absorbing whatever explosions or weapons somebody else could dish out, and then fire that back at them. [Answer] If you don't like explanations that sound like ghost stories, and you do like explanations that sound like science, then magical fires could be powered by quantum particles. According to some loose and hazy notion of quantum mechanics, there are virtual particles popping into and out of existence. A black hole radiates energy because two virtual particles, e.g. one electron and one positron, pop into existence. The electron falls into the black hole,the positron is outside the event horizon and thus radiates. So the edge of a black hole is always creating energy out of imbalanced virtual particles. Magical fires happen when the thoughts in a magician's brain imbalance the quantum particles and cause some kind of energetic particles to pop into existence. Extra credit: Magical clairvoyance works because information is nonlocal and all information everywhere is holistically contained in any information anywhere. Footnote: All my ideas of quantum mechanics come from Talbot's \_Holographic\_Universe\_ and Amit Goswami's pop physics. [http://www.amazon.com/Self-Aware-Universe-Amit-Goswami-ebook/dp/B001QWDS1Y/ref=sr\_1\_sc\_1?s=books&ie=UTF8&qid=1412123939&sr=1-1-spell&keywords=amit+goswama](http://rads.stackoverflow.com/amzn/click/B001QWDS1Y) [http://www.amazon.com/The-Holographic-Universe-Revolutionary-Reality/dp/0062014102](http://rads.stackoverflow.com/amzn/click/0062014102) [Answer] There are on the real world only one concept of Energy and four forces that can "affect" it: gravitation, electromagnetism, weak nuclear and strong nuclear. If you rule that there are five forces instead, the fifth being "magic" and that force being sensible to some materials, in the same way than electromagnetism is affected by some materials and not by others, you have done it. Electromagnetism can be affected by magnetite crystals, which are diminute imans, and these imans in turn can be affected by electromagnetism. Pigeons have magnetite crystals on a specific zone of their brains, and so they are able to orientate over wide extensions and find the way home. In the same way, magicians can have "magictite" crystals on their brains and use them to affect energy through the force of "magic". These can be used to manipulate magic and to sense it. The effects would be those you want for your world. [Answer] What seems most natural to me is some other world/dimension whith some contact with the "primary" world (where the magician lives). Assuming that access to few more dimension (though limited) can allow access to power fields and other energy sources, this makes magic quite credible in many sci-fi stories. Or, in a fantasy setting, it could be just some mystical "astral plane" - or it may have some scientific explanation, but magicians still think of it as "astral plane". Or the energy could be taken from the magician himself. This way only small effects are possible and the wizards must "recharge" somehow, or damage themselves. Eating a lot might suffice, or some special drugs might be needed. Or there may be some "magical potential" in the matter and the wizard just rouses it. This is bit further from the physics we know, but might be possible with some special magical materials. And if the physics is completely different, such as the world really consist of four elements (fire, air, water, earth), then a potent water wizard just needs to unleash the power stored in a lake to destroy a city on its shore. All ways may be combined. For example, my world consists of "atoms" of four elements, which are usually bound together. Also, there is "astral plane" built from the fifth element "void". Void is least stable of elements, so its "atoms" can be broken, releasing a lot of energy into our world. This energy links to ordinary matter and increases "magical potential", which can be released by magi, who need just a little of their mental energy for this task (they get tired quickly this way, but most of energy goes from the environment). [Answer] Depending on how your magic system works, there are more than enough potential energy sources to start a fire. In the Inheritance Cycle, magicians can pull energy from their own bodies or the world around them. In the Kingkiller Chronicles a magician can create a link between a heat source and the magic they want to perform(very simplified). This typically uses fire but can also pull heat and energy directly from the body. Either way, a magician needs a source of energy to perform any magic. Something like this is plausible explanation for the energy source. There is tons of energy in the world, in our cells, the chemical make up of the world, gravity, light, and on and on. Give a magician any means of harnessing this energy, and starting a fire will be simple. In fact, since a fire generates more energy than it takes to start, if a magician can draw energy from the fire started, you can snowball in available power quite quickly. As long as you give magic the necessary tools to channel existing sources of power, there is plenty of energy to go around. [Answer] **quantum physics** answer: Should preface that this really isn't going to give you a traditional 'energy' explanation of magic here...use the other answers if you want the Newtonian version of energy. > > the energy to cause wood to spontaneously ignite doesn't just float around in our atmosphere > > > Yes it does...There's enough energy in a square inch of 'air' to destroy most of the solar system, and that's only really using the matter to energy relation that we know of, even completely empty space is never really empty. But on to the quantum attempt at explaining magic. It is exceedingly abstract, but works fantastic for explaining things such as magic...moves away from the traditional 'energy' explanation. At the core of Quantum Physics is the understanding that the observed and observer cannot be separated (If a tree falls in the forest and nobody is there to hear it, does it make a sound? No, if nobody was there to observe it falling, it was never there to fall in the first place and existed in a superposition of both standing and laying down until someone is there to collapse both possibilities into one reality...little humancentric in that the tree cannot observe itself falling over, but you get the point). If you prefer the Schrodingers cat explanation..the cat exists in both a live and dead state until something is there to observe it and collapse the multiple possibilities into one. In this case the wood exists as both on fire and not on fire (and many other possibilities), but it is currently being collapsed by observers into the one possibility of 'not on fire'...'magic' is convincing the other observers that the reality where it is on fire is the one we exist in. [Answer] The power source of the Sun was "magic" until it was found. Ideas using known materials and known mechanisms did not work out. Yet, the thing, when it was found, *fit* with the expectations of our universe, such as concervation of energy and features analagous with other forces, while being novel in other ways and different enough to be outside our experience. On that scale of energy release, you can perceive the equivalence of mass-energy. But that's beside the point; the real point being that a *force* is in play. It affects everything but it was outside of experience to take elements apart (hence their name). Normally taking-apart costs more energy, but as with chemestry the existance of *more* tightly bound forms allows a net gain. Taking apart and putting together trades kenetic and potential energy in a concerved total. A stone can be lifted out of its niche (a local minimum) and allowed to drop to a lower valley. Electron bonds can be broken so the reactive pieces can find a more stable configuration. Quarks and leptons can rearrange to form a tightly bound alpha particle. So, we want something that can "come apart" and "put together" in *different* ways. But if it's accessible why doesn't it become mixed up with chemestry? With fusion, it's a different energy scale. Likewise, the weight of molecules don't stress the bonds enough to have any effect, but us being > 27 orders of magnitude larger than molecules can lift rocks and craft devices to focus the power of large falling weights onto tiny targets. So, a much lower energy scale allows the energy to be accessed but only *purposfully* by *large beings*. It takes something the size of a person to experience/interact with this power source and either concentrate it to a small area or *cleverly* use the effects in subtle ways to acheive larger end results (like a spark can start a fire). Other animals [may still figure it out and use it in metabolic processes](https://worldbuilding.stackexchange.com/questions/13129/magivore-designing-a-magic-eater/13182#13182). So just what thing holds power? Since magical tropes require teleological rules, let's look into **dualism**. If the spirit realm is where the mind or soul exists, an analogy with gravity or chemestry could be very precise. The "chemestry" of the stuff where the mind exists, what the thinking part of an intelligent being is made of and implemented with, could produce energy. Since the mind strattles both worlds, there is clearly some way for cause and effect to go between the two. The two regimes have their own rules but are similar in underlying nature of forces and concervation laws. But they can interact, so the combined concervation is the real rule. Extracting power via magic will have an effect and change the state of the astrial realm. It will use up resources, which *could* become noticable depending on details. I'm reminded of another Q/A on interdimential beings. They controlled rocks in our realm and lived on hot moons, but I can't find it now. That's the general idea behind making dualism work. Without going into details [any interaction between two universes or realms](https://worldbuilding.stackexchange.com/questions/519/wondering-what-would-happen-if-magic-was-constrained-by-conservation-of-energy/6443#6443) could plausibility give an energy release. But I think you are after something with more subtle details and subject to control, not just a rough spigot (which makes an effective bomb or high-tech power plant). [Answer] One possible explanation of the magical power is that pre-apocalypse an advanced species altered the plants/buildings/whatever in their environment so that they would be able interact with them through thought/incantation/proxy actions/anything really. Once an unexpected apocalypse event happens all of the people and knowledge along with most of the altered environment is destroyed. However, a certain amount of altered something is leftover and survives the apocalypse. The basis for your world would then be in these altered survivor things (single cell organisms ?). Fast forward a couple hundred million years and there is a rebuilding society/world. Certain *thoughtful* people are able to manipulate their environment as they rediscover how to interact with what they think to be an unaltered and scientifically sound environment. [Answer] Although many of these seem plausible there are all too narrow you need to expand your perspective. There are several unseen elements in the world that affect the world. There are the magnetic fields that surround and penetrate the world and everything on it. There are fields of gravity that come from the center of the world radiating out drawing everything towards its core. There are various types of background radiation that emanate through the surface of the world. There are gases and vapors that rise up out of the surface of the world. Then there is the cosmic energies that bombard the surface of the world. All of these have very little apparent effect but when there is an abundance of any one of these the consequences can be dire. Then there is the individual, from their body radiates an electromagnetic field, flowing fields of electricity with sparks of ions from the brain. These have very little effect on anything outside of the body normally. But when a person's body radiates the right frequency and sufficient electromagnetically fields and their mind generates that just right frequency and power of electrical energy then that person would be able to manipulate the unseen energies, fields, and gases around them. [Answer] There is a number of ways magic can work. Lets just speak of fire for now. **Help from Spirits** To be able to throw fire, you must first speak to the spirit of an already existing fire, and strike a deal. You promise to help it expand it's domain, and possibly shelter it in your own body for the time being, and in return you can get some of it's energy to ignite things. This would have some side effects: 1. Your spells would be limited by what kind of spirits you can hold in your body ie, cant have both a fire and water, or fire and wood spirit, but fire and stone would be fine 2. In order to cast spells you have to find a way to communicate and host these beings, and feed them some of your own life energy, so each spell would actually shorten your life, wizards would NOT die young. **Displacement of Energy** You can sense the flow of energy, and know where exactly where to focus your mental energy to redirect it. Think of all energy as a bundle of strings, and if you tug in the right spot, you can unravel it. So to cast a fireball, you need a flame nearby, and you just borrow some of its heat. Side effects: 1. You need to keep the source of energy ready, to even pick a lock with magic, to keep your brain leaking out of your ears you need to keep a bunch of other energy sources nearby, or have a real sense for the flow of energy. **Connection to a Higher plane** This would be more for summoning creatures, and forcing them to do your bidding. In another dimension, just off to the side of ours, there are much more powerful, but formless creatures trying to get in. With the right focusing tools, a wizard can call them to him (wands, crystals, purified ox blood, etc) and with enough mental training, bend them to do his bidding. For example, to cast a fireball, he focuses his mental energies into a his wand, and pictures his chosen aid, maybe calling its name, and if his willpower is strong enough, it will come forth in the form of a burst of flame, and return to it's dimension as soon as he loses concentration. Side effects: 1. Years of training to summon a creature 2. Failure can result in you being a)enslaved b) killed 3. Your will binds them to this plane, even the smallest distraction can free the beast or just dispel the spell (he he he) --- **Final Thoughts** It is even possible for all of those to exist at once, great daemons banished long ago by the gods that brave or foolish humans can try to summon and command, while lesser being that need to feed of of the life of others still roam, and the slightly less brave and foolhardy can deal with them, while the wise and patient focus all their energy on learning to manipulate the energy that can be seen with training. All three have risks, but all three give great rewards. ]

[Question] [ In the Land of Metal, there exists a tribe that has upheld the gospel of Manowar with such zeal that it modified their bodies. Metalheads descend from humans, and may look human at a glance. A more careful examination, however, will reveal the traits their kind has acquired through the ages. These traits allow them to have a lifestyle that would be extremely harmful for humans; the man who tries to live like a metalhead usually does not live long. --- Central to the life of the metalhead is headbanging. They bang their heads in the air for a number of reasons: * To show others their emotional state, such as being happy, content, angry, anxious, frustrated, or simply out of their mind; * As a greeting or compliment, or to thank someone for something; * As a reflex to music being played that suits their tastes; * As a mating display. They seem to be aroused by the flowing long hair of a potential mate oscillating in the air to the sound of metal. Metalheads are able to bang their heads in the air for hours at a time without the need for rest, and without damaging their necks and brains. They are also able to continuously bang their heads to power metal, even at 180 bpm, with some record beating at 250 bpm. They also maintain this ability as long as they are fertile and sometimes into old age even. Starting from an average human body for a template, what changes to anatomy would be required to allow for such an amazing headbanging capacity? I was inspired by Brütal Legend's headbangers for this question:  They have traits such as stronger neck musculature and thick skulls, but I think those are more fit for headbutting than headbanging. [Answer] > > what changes to anatomy would be required to allow for such an amazing headbanging capacity? > > > As any student in Engineering is taught, when you have oscillating masses and one wants to improve frequency and reduce stresses, it is always a good idea to reduce the masses. So, lighter skulls seems to be a must for your *homo caput oscillantis*. Moreover our neck has a somehow faulty design: due to the way the neck muscles are connected to the skull they make a first type lever with the force arm shorter than the resisting arm, as a consequence they need to exert a much higher force to move the head than the weight of the head. [](https://i.stack.imgur.com/3mWGE.jpg) To improve headbanging the skull shall be modified: the neck has to move more to the center and the face has to become shorter, while the back of the head has to somehow extend. Considering that on falling one cannot beat gravity, and this somehow limits the oscillating frequency of the headbanging, it would be also an improvement to develop stronger antagonist muscles on the throat region, so that they can actively pull down the face when it has to execute that part of the banging. [Answer] In our world, we do have an animal that habitually violently smashes its head against things at high frequency: the **woodpecker**. Their heads have multiple adaptations to the repeated stresses caused by pecking, such as: * A specific kind of spongy bone structure is lining the skull. It is compressible and most of it is located around the front of the back, where the forces are strongest. So your metalheads could have such spongy bone in their heads, probably differently aligned as the headbanging movement is not back-to-front like in woodpeckers. * The hyoid bone (tongue bone) is much larger and interconnected, acting as a spring to further reduce the acceleration forces. * The tongue itself is similarly longer and wraps around the braincase, acting like a kind of a harness. * The brain itself is much flatter and smoother than usual, it is aligned have a maximum cross-section in the direction of the pecking, so it has the most possible surface to spread the impacts. * During the actual striking, the woodpecker closes its third eyelid which keeps the eye in place, and strains its neck muscles, tightening everything around its brain, so it is not hitting against anything inside the head. [Answer] Their skulls and necks would eventually resemble those of our primitive ancestors. First the most obvious: **the neck**. Since individuals with frail necks who cannot bang their heads for hours are sexually unattractive, **broader vertebrae** would drive evolution to produce stronger necks. These also provider broader spaces for **stronger tendons** to attach to the bones. These are absolutely nessecary to prevent disk herniation into old age. Now to **the skull**: The constant oscillating of the skull puts preasure on the soft and squishy brain. Their skulls would eventually resemble those of woodpeckers: The bone structure is much [thicker and sponge-like](https://www.livescience.com/19586-woodpecker-skull-concussions.html) to cushion the brain. > > Notably, the woodpecker's brain is surrounded by thick, platelike spongy bone. At a microscopic level, woodpeckers have a large number of trabeculae, tiny beamlike projections of bone that form the mineral "mesh" that makes up this spongy bone plate. These trabeculae are also closer together than they are in the skylark skull, suggesting this microstructure acts as armor protecting the brain. > > > Since headbangig pushes the brain alternatingly against the front and back of the skull, These are the parts that are most reinforced. The skull would get a slightly more oval form. Such an rather oval skull could provide an opportunity for an alternative headbanging mechanism: by **tendon tension**. There is enough room on the posterior skull to attach thick, strong tendons, just like in the legs. And just like with running, they store the kinetic energy of the skull falling forward and pull it back like a rubber band without needing to excert all the energy with muscles alone. The conservation of energy would probably be an evolutionary advantage, so the metalheads would actually loose their broad necks. **The eyes** (or more precisely the eye sockets) would also become slightly more prominent. If headbanging constitutes most of your social interactions, you cannot let your eyes blindly stare into nothing until you're done. The eyes have to follow the back-and-forth movement constantly and the corresponding muscles are trained from early age, eventually taking up more space in the skull. [Answer] The most realistic evolution pattern would be simply to develop stronger neck muscles and tendons. Imagine a normal person with a wrestler's neck. Headbanging for hours means your headbangers will get a lot of blood flow to the brain, and a lot of blood flowing overall to transport all the oxygen needed. That is all good cardiovascular activity, which means an overweight headbanger will be incredibly rare, also they would live longer due to the continuous activity. Physical activity also drastically reduces chances of diabetes and most times it can reverse it even with a poor diet. Longer life mean more potential for reproduction, your metalheads will be fertile even in old age. If they headbang to show emotions and they headbang most of the times it means their society will be really open and emotional as a whole. ]

[Question] [ I'm currently writing a story based in another world. I try to keep the story outline and the world in fairly separate notes obviously dipping into the world notes when I need to remember names, locations, descriptions etc. Currently I'm using [trello](http://www.trello.com) because of it's flexibility. I've got lists for Characters, Races, Places, Technology, Religion etc... But I'm finding that it's not scaling very well. A bigger story has hundreds of characters who are all connected, Trello gives me no way to keep track of that (aside from notes on their card). I have thought about starting a wiki (kind of a fictional wikipedia) because of it's fantastic flexibility and inter connectivity (historical figures link to technology they created and used to their family and their places of birth etc). However most of the ones I've found are open to the public - given I don't want to reveal every little detail about a character's past and future to anyone who stumbles upon it I've tended to rule these out. What other software is available (open source ideally) to track this sort of web of information (rather than a linear thread in a story) that would be required to document created world? Edited to expand following this excellent [meta suggestion](http://meta.worldbuilding.stackexchange.com/questions/201/questions-about-software) I use Windows and iOS 8. [Answer] [Evernote](http://evernote.com) is a pretty good note software, but that doesn't seem to be what you want. It sounds like what you really want is an private wiki. You apparently weren't able to find one though, apparently they are pretty common. The biggest one is [MediaWiki](https://www.mediawiki.org/wiki/MediaWiki) (the power behind Wikipedia). MediaWiki can be private, and it's not too hard. See this [tutorial](http://www.mediawiki.org/wiki/Manual:Preventing_access#Simple_private_wiki) for information on how to do that. But basically you would create one account and limit it to that. As a bonus MediaWiki is open source and free. Another option would be [DokuWiki](https://www.dokuwiki.org) on a Stick. This would be a simple home wiki that you could transport around on a USB drive, or possible share over the internet. To see set up look [here](https://www.dokuwiki.org/install:dokuwiki_on_a_stick). And it can still be private. DokuWiki is also open source and free! There are many other private wiki options but many of them aren't opensource/free. [Answer] I will second DonyorM's suggestion of DokuWiki. I've used personal installs of it before and it's really easy to setup, very customizable, private, and open source. Additionally, if you later decide you want to open it to other people, you just need to transfer it to a webserver and other people can access it. Alternatively, you can use the [Wiki Chooser Wizard](http://www.wikimatrix.org/wizard.php) to find one that might work better for you. --- Alternatively, [RealmWorks](http://www.wolflair.com/realmworks/) by Lone Wolf Software is specifically designed for this kind of interrelated knowledge map. It's stated use is for designing RPG campaigns, and a lot of the defaults are configured for that, but it's very customizable and provides features such as: * Detection of references to existing pages and auto-linking to them. * Support for multiple different templates, with different sections for each. So you can have a "Person" template, a "Location" template, a "Religion" template, etc. Each would automatically have subsections for useful information (Person: Age, Sex, Description, History; Location: Description, History, Residents; Religion: Deity, Worship methods, Attitude towards others) * Ability to embed maps (with links to the appropriate articles), images, URLs, and other media. * A strong search feature. * Relationship maps. The image below shows an example view: There's a map on the left, the list of information about the location in the center, with links to all the appropriate other articles (and an embedded map), and on the right are various other links, including the "Chapter 3" link to explain where this fits in the larger context. (The green dots relate to whether you've shown the content to your players, but that's unlikely to be relevant for you - you could ignore them, or you could repurpose them to indicate things you've already written (and thus would require editing to change) as separate from things you've thought up but not yet referenced in text)  Unfortunately, it's not open-source, and the software costs \$50 for the basic software, and \$24.99 semi-annual fee for cloud-based syncing & other related services (web access & sharing.) [Answer] I use a collection of tools, not just a single one. A single tool would admittedly be better but I find that what I do with world building is so diverse a single tool doesn't seem to cut it for me. So, here is what I use * Perforce: This is version control software...and is probably overkill for what I or other world-building folks will do. Essentially it allows you to maintain and review every revision you make to a file. We actually use the enterprise version of this at work to version all of the software that gets worked on. There is however a free version for up to 20 users that is up in the cloud. I use this because there tends to be large gaps between session I work on my project, and after a while I end up looking for something that I deleted...this allows me to actually find it. I use this primarily for those items that change often, and potentially drastically. (my story for example since this is in support of a book I am working on) <http://www.perforce.com/downloads/Perforce/20-User> * X-Mind: This is a handy little program for mind mapping. I use this to document geography (locations in general), characters, themes, relationships etc etc etc. Its easy to use and also free. This tends to be static information that changes rarely if at all. For example here is a top level view of my work.  Each of the subtopics (and their subtopics etc etc etc) you can drill down into, so the World subtopic for example you can make the center of the map and work on just that section. Each item can have an attachment, you can mark things in progress or completed, its quick to use and easy to learn. * MS Word and Excel: Hard to get away from them...I use these both for the more detailed content. So I have sheets on each relevant piece of geography, on each nation-state, on each religion, etc etc etc, then I can reference the relevant details when I need them. I actually used excel to create my history table, sort of a back to creation high level timeline. * I also like to have an art program handy if I want to design buildings to flesh out a culture maybe, or to draw out a particularly central geographic location. I personally use: [My Paint](http://mypaint.intilinux.com/) but there are a lot of options out there. Check out this thread form Software recs SE: <https://softwarerecs.stackexchange.com/questions/395/drawing-software-for-amateurs/430#430> [Answer] You could use Scrivener. It is not free but it is worth it. It has a short learning curve and a lot of potential of customization. You can organize documents by category and make templates for documents that tend to repeat themselves such as scenario descriptions or creature lore or even character sheets. It can show you diagrams with connections between the documents and you can customize those links for later reference, what is the relationship of character x to character y and what is their relationship with character z? It also allows you to compile the manuscript to a proper book format. Gives you statistics about your writing that are very useful aswell. [Answer] I personally use <http://worldanvil.com>, as it is specifically designed to help organize and develop your worldbuilding. It has 14 different very complete templates (Building, Character, Condition, Document, Ethnicity, Military Formation, Geography, Item, (meta)Physic Law, Language, Material, Military Conflict, Myth/legend, Organization, Profession, Prose, Rank/title, RPG Session Report, Settlement, Species, Spell, Plot, Technology, Tradition, Vehicle and Generic Article for stuff that doesn't fit any other template) and also some awesome Maps and Timelines tools and, of course, its Campaign Manager. I'm particularily in love with how complete with prompts the templates are and how they ask you for stuff maybe you never thought about (the Species template alone has like three tabs!), and also the ability to create interactive maps out of your own images with links and adorable markers. Here you can toy around, for example, with my world's map, Dayrd: <https://www.worldanvil.com/w/dayrd-bluewildfire/map/ae4ece9b-4c22-4b8d-a877-b370c7ebb95d> [](https://i.stack.imgur.com/aMd15.png) The World Anvil project is not and will probably never be fully finished, as new features are added every week. It also counts with a to-do list feature, your own image gallery and a huge tools set for writers, gamemasters, artists and worldbuilders in general. There are also monthly Worldbuilding Challenges among a great community of 170,000 worldbuilders from all around the world. The Discord server alone has more than seven thousand members always willing to help each others. They're lovely. Also ALSO the developers are very active on the Discord and the staff members are helpful and caring as hell. Too long, didn't read: World Anvil is the best worldbuilding tool I have ever seen, and the last one I will ever use. And it's free! [Answer] I use TiddlyWiki (<http://tiddlywiki.com/>) for most of my personal writing and worldbuilding projects. It has the advantage of keeping a whole project in a single file that can be easily transferred from device to device. I find it very easy to work with, but definitely give the FAQ a browse before trying to commit anything important. Most importantly, saving through your broswer's save file function will lead to data loss and heartache, you must use the save feature within the TiddlyWiki page in order to save changes to the Tiddlywiki. [Answer] The World Building softwares I use are Storyist, which allows for research based file collections in addition to the main manuscript - in my case, I am writing a novel. I also researched a low-cost mind-mapping tool available as a plug-in on Google's Chrome web browser called "mindmap." I like it because it allows me to drop in photos/images and maps as well as have just text links. The images can be annotated as well. I just thought I would respond to others who, like me, may be looking for options. The latter plug-in is free and can be accessed by downloading the Chrome browser if you don't already have it, and going to Google's plug-ins page <https://chrome.google.com/webstore/search/mindmap?hl=en> [Answer] Alternatively, if you have a relational database management system (RDBMs) you can link the things together. This method has the added benefit of allowing multiple connections for each bit of information. For example, a specific NPC could be linked to a thieves guild, a specific location in a city, and a planned encounter later in the adventure. Professionally I work with some (Oracle RDBMs and MS SQL server) that I'm more familiar with and I am licensed to use (and have a business logic overlay for that data). These are intended for Enterprise data management, are likely too expensive for personal use, are not user friendly, and do not have any tweaking to make them more suitable for managing this type of data. For the typical user, I'd recommend something more like MS Access (or equivalent). Databases like these are intended for much lighter weight use and more user friendly interface. Plus, MS Access ties into things like Word & Excel so you may be able to tie everything together in it (this holds special attraction to me because I store much of my data in Excel in spreadsheets). However, I am personally not familiar with MS Access and can't really give much advice on how to use it. [Answer] I recommend a wiki, and my favorite two for this sort of work would be [TWiki](http://twiki.org/) and [MoinMoin](http://moinmo.in/). Caveat - you have to be willing to invest a fair bit of set up time - you need to establish a documentation structure on the unformed wiki... thereby gaining the distinct advantage of it being exactly the structure you desire, with the bonus of being able to easily modify the structure as your desires grow and evolve. TWiki is known as a developer's wiki but is true to the wiki ethos so is usable for capture of any sort of knowledge. MoinMoin is an advanced wiki with a strong feature set enhanced by a number of plugins .. and has the special advantage of having an publishing API that allows you to output alternate formats of your pages .. like PDF, TeX etc .. instead of the standard HTML for use on the web. Both offer version control, inclusion of media, and non-CamelCase links and are in live development. Those choosing Moin should probably stick to version 1.9 .. Version 2 is stable .. generally, but as its foundations are completely different from Moin 1.\* one has to expect hiccups. TWiki should be used at the most recent stable release. ]

[Question] [ **This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources).** --- Once geological processes and erosion have created a landscape this landscape will in turn alter the planet. Ocean currents and trade winds will tend to form and certain weather patterns will emerge. To keep this reasonably scoped we are just going to look at the currents, wind patterns and the resulting precipitation and climate effects. Landmass formation and erosion has been covered in previous questions and the resulting effects on life and biomes will be covered in a follow-on question. * What are the processes that drive weather and ocean patterns? * How do these processes shape the weather and the climate? * How can those processes be easily drawn upon to create realistic looking maps? There are already good climate classification systems such as the [Köppen Climate Classification](http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification). We do not need to redefine those or list the climates. Instead we are looking to described the processes that result in these climates and use that to inform the creation of a map that has a realistic climate distribution. --- Note: > > This is part of a series of questions that tries to break down the process of creating a world from initial creation of the landmass through to erosion, weather patterns, biomes and every other related topics. Please restrict answers to this specific topic rather than branching on into other areas as other subjects will be covered by other questions. > > > These questions all assume an earth-like spherical world in orbit in the habitable band. > > > --- See the other questions in this series here : <http://meta.worldbuilding.stackexchange.com/questions/2594/creating-a-realistic-world-series> [Answer] \*This answer is for an Earth-Like planet, rotating in the same direction. **First question: Where does the wind blow?** It depends on the pressure. **Movement of air masses:** Hot air rises and cold air descend, it’s a convection movement like the one you can observe when boiling water. The air flows from the high pressure zone to the low pressure zone. The hot air expands and rises in the atmosphere. This is drawing the air towards the hot areas that are in fact, low pressure. Cold air contracts and will eventually sink. When the air is descending on the land, it means that it’s a high pressure zone. **Precipitations** occur when the air is rising. Other factors also generate precipitations but this is the most important. As the hot air rises over the land it cools off while ascending in the atmosphere. As the air gets colder, it cannot contain as much humidity compared to hot air and this water will fall down. On the opposite of the convection movement, the cold sinking air is always dry since it already got rid of most if not all the humidity it once had. **4 Areas of low and high pressure**: As a general rule, these ‘’areas’’ move closer to the North Pole during the northern summer and closer to the South Pole during the southern summer. The movement is more pronounced over land than over the oceans, especially if the landmasses are located over the 30th parallel. This is because the temperature over the land has a larger variation throughout the year than the temperature over the oceans. * **ITCZ: Inter tropical convergence zone:** This is a low pressure area located loosely around the equator because it is the hottest place on the planet and very hot air means very low pressure. The ITCZ gets dragged over land if there is a large landmass in higher latitudes during the hot season. Over the ocean, the ITCZ stays at the same spot all year long. * **Subtropical ridge** (also known as the Horse latitudes): it is located around the 30° north and south of the equator. This is a high pressure zone despite the relatively hot temperature. (More information on this in the ‘’Movement of the air’’ section below) Most deserts are found here but not all of this area is made of deserts. You also need to consider the direction of the winds. * **Polar front:** This is a loosely defined area with a relatively low pressure in the mid latitudes (40° to 60°). The weather under the Polar front is considered unstable or prone for rapid and often unpredicted changes in the weather. The hot air from the tropics encounters the cold air from the poles. Remember, here we have rising air and precipitations. On the opposite, the subtropical ridge is dry because it is a high pressure area with sinking air and precipitations occur when the air is rising. (Mostly but not always) * **Poles:** lastly, the poles are the coldest places on Earth and so, it’s a very high pressure area. **Movement of the air**: <http://en.wikipedia.org/wiki/File:AtmosphCirc2.png> * **Coriolis Effect:** if the planet was not rotating, the winds would go straight poleward. But since the planet is rotating, the winds are deflected. The winds are deflected in a clockwise manner in the northern hemisphere and counter clockwise in the southern hemisphere. By itself, Coriolis doesn't make the currents, it really just deflects them. <http://en.wikipedia.org/wiki/Coriolis_effect> * \*The Coriolis Effect also apply on the water currents. * **1-Hadley cell:** Between the ITCZ and the subtropical ridge Following a convectional movement, hot air rises and the surrounding air masses converge there to fill the gap. The air rise and then moves toward the poles. It cool off with time and eventually the increase in pressure will drag the air mass down near the 30° north and south. The surface winds are moving toward the equator because of the pressure and the Coriolis effect is directing them toward the west at the same time. The dominant winds are blowing east to west and are called the north /south trade winds. * **2-Ferrel cell:** Between the subtropical ridge and the Polar front: The dynamic of this cell is mostly imposed by the other 2 cells and it just follows a logical continuation of the same convection movement. The rising air converges at the Polar front. At the subtropical ridge, the air is sinking. So, you have the cold dry sinking air at the subtropical ridge. This air will warm up until it reaches the Polar Font and then it will rise again. The surface winds are moving toward the poles, to the low pressure area that is the Polar front. The Coriolis effect deflects them toward the east. The dominants winds are west to east and are called the Westerlies. * **3-Polar cell:** Between the Polar front and the pole Here, the very cold air creates a high pressure area. The air sinks and then moves toward the equator. Getting closer to the equator, the air starts to get warmer until it reaches the 60° latitude. At that latitude, the air has become hot enough and start ascending in the atmosphere. The surface winds are moving equatorward. Here, I think they are deflected toward the west but I’m not 100% sure. So, the dominant winds are moving east to west and are called the Easterlies. * **Bonus: Doldrums:** This is an area near the equator where the winds are usually very weak. They are in the middle of a large low pressure zone. --- **Second question: Where does the water go?:** I will just cover the surface currents. Not the deep currents or the counter currents. **The ocean currents are influenced by 3 things: the winds, the Coriolis Effect and the landmasses.** * Starting from the equator, the trade winds are pushing the water toward the east. Then, when it reaches the coasts of the continent, the water will be deflected toward each pole because of the winds and the Coriolis force. It flows towards the pole until it reaches the Ferrel cell over 30th of latitude. There, the water is pushed toward the east by the Westerlies. The Coriolis force curves the shape of the current that is in fact not really toward the east but also toward the north a little. Eventually the water will reach another continent. Winds are probably still pushing it toward the land so the water current usually splits here. Some of the water will go north and the rest will go to the south. The northern current should continue its course following the established rules. The southern current will stay close to the coast until it closes the loop near the equator. * If you don’t have a continent, there is likely nothing to stop the movement of the water as long as the winds are pushing this water. This is why the currents of the South Seas are spinning around Antarctica. Antarctica is almost cut off from the ocean circulation. It is surrounded by water and by a strong current that goes across the whole planet. This current limits the heat exchange and is keeping the continent colder. If we were to close the Magellan strait between Antarctica and South America, it would cut this cold current belt and Antarctica would be less cold since the polar waters would mix with the rest a lot more than they do right now. This would also make it possible for ice sheets to form. Strong currents are preventing the formation of ice sheets. * The oceans play an important role in lowering the temperature differences between the different regions of the planet. The currents are taking the hot water from the equator and mix them with the cold waters. It is something important to consider in a fantasy world. Without this heat exchange, the equator would be much hotter. On Earth, we have north-south oceans (Pacific and Atlantic) and this is good for the heat exchange. Heat exchanges would not be the same if America was an east-west continent because it would prevent this mixing of hot and cold waters. The impact could he huge unless the continent was located right on the equator. It that cases the impacts would be smaller. These are just general guidelines to set the ocean currents. The land is a really big factor influencing them. Here’s a good map for reference: <http://upload.wikimedia.org/wikipedia/commons/6/67/Ocean_currents_1943_%28borderless%293.png> --- **Third question: Where does it rain?** * **Where the air is rising:** near the Polar front and near the ITCZ. * **Under the polar front**, the precipitations are also caused by an alternation of hot and cold air masses. The limit between the Ferrel cell and Polar cell has a shape similar to a wave. For example: <http://3.bp.blogspot.com/-rZPe2PJhFKE/UuNaB8HxEeI/AAAAAAAAk08/Hviu1TrSk-4/s1600/Screen+Shot+2014-01-25+at+12.30.08+AM.png> The temperature of Chicago is colder than the temperature of Anchorage, Alaska, even if Anchorage is closer to the pole. It’s because Chicago is affected by the cold Polar cell and Anchorage is under the hot Ferrel cell. The Polar cell is moving to the east so Anchorage should expect rain (or snow most likely) in the following days. As the air is getting cooler, it starts to rain. Here, the winds are not always relevant. As long as there is moisture in the air, you can have precipitations even in places with high pressure sometimes. * **Most importantly**, moisture will go where the winds go. The Sahara is a high pressure area but it pushes the surface winds toward Europe and the Sahel, therefore all this air is dry and the Sahara receives little rain. Libya is very dry despite being so close to the sea because the winds are blowing offshore. * **Moisture traveling overland**: Moisture in the air comes from evaporation. The evaporation is more significant when it’s hot and over the water. The evaporation is still large overland but the quantity of water is smaller. Forested areas like the Amazon basin keeps a lot of moisture and this moisture make some areas more humid than they would be without the forest. The Winds will carry the moisture overland but not over the mountains. The moisture can travel very far over the flatlands. * **Orographic lift:** it is well know that air is getting colder at higher altitudes. This means more rain. Northern India (the state of Maghalaya) is a good example of this effect. This is why, even if the air masses could reach the other side of the mountains, the air would be dry anyway. * **Mountains:** The impact of mountains is really important. They prevent the precipitation in places that are in the rain shadow. If the dominants winds are from the west, places located east of the mountains will usually be dry. --- **Part four: the climates:** • Don’t forget that when it’s summer in the north it’s winter in the south. (Unless if you are in Walvis Bay, there is only one season there.) **Definition from Wikipedia:** > > Climate is a measure of the average pattern of variation in > temperature, humidity, atmospheric pressure, wind, precipitation, > atmospheric particle count and other meteorological variables in a > given region over long periods of time. Climate is different from > weather, in that weather only describes the short-term conditions of > these variables in a given region. > > > * Now we should have everything needed expect for the atmospheric particle thing (don’t know what it has to do with climate, climate changes maybe?) and we haven’t talked about humidity much yet. But we will come back to this very soon. * So, now from what I understand, a climate is a mixture of many ingredients. It is pretty confusing to make sense of that. I need to use a climate classification to simplify things and add another wall of text. **Climate classification:** There are a couple of classifications available for climates. We have at least 2 major systems worth to talk about: * **Holdridge:** <http://en.wikipedia.org/wiki/Holdridge_life_zones> It’s nice but in order to use it in world building, you will need to find how to calculate the potential evotraspiration. That requires a lot of information that we can only guess. * **Köppen:** <http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification> This is one of the most commonly use in the world. It is not perfect but will do just fine in world building. To use it, you need the temperature and the precipitation of the world. In fact, we are using an improved version of this classification called the Köppen–Geiger climate classification system. * **Glenn Thomas Trewartha** added several things including the Universal Thermal Scale. We will use that scale as a reference for the temperature. \*Now, I’m not going to explain what the climates are, it would be too long. I will just talk about where to place them and the conditions required to have them in a specific spot. Csa on the east coast, I don’t think so! **The Köppen climate classification scheme** * The scheme is made of a maximum of 4 letters. Real climatologists might use up to 4 letters but to make things less complicated, we are not going to use more than 3. The first letter separates the climates in five large categories. Each letter can be combined with a second letter, and some can also be combined with a third letter. The combinations are in the last part.  [Click here for full size version](https://i.stack.imgur.com/h4TYr.jpg) Now, I will try to explain starting from the equator and going to the pole. Keep in mind that it is a simplistic explanation. 1. The ITCZ moves north during the northern summer and south during the southern summer, influenced by large landmasses. Areas always affected by the ITCZ, or close to it, will be in the A climates. Af is the closest and has no dry season. Am is less affected by it and does have a dry season. Aw has the driest dry season and is only slightly affected by the ITCZ during the cold season. The climate becomes progressively driest as we get closer to the tropics. 2. Areas affected only by the summer ITZC will have very dry winters and usually falls into the BSh climate, the hot steppe. This is true only inside the tropics. Outside the tropics, the temperature is colder, there is less evaporation and the land stays humid. This creates the monsoonal climate Cwa. Cwb and Cwc are colder than Cwa and appear at higher altitudes. Sometimes, as in Angola, the Cw climates come before the hot steppe because the altitude is higher and reduces the temperature and the evaporation. 3. Moving a step further, we are now almost at the tropics. This is usually where the Hadley and Ferrel cells meet. Unlike in the precedent paragraph, there is no low pressure system here, it is always dry. Here, the hot desert (BWh) is the most common climate. But outside of the tropics, the lower temperature makes it a cold desert (BWk). 4. As we move away from the tropics, the climates gradually become more humid as the influence of the polar front starts to increase. The hot season is dry under the subtropical ridge but winters are wet under the polar front. Deserts become colder and are often bordered by another band of steppes. As they are colder, they usually fall into the cold steppe climate (BSk) but hot steppes are still possible. Here, the desert can be affected by low pressure systems but are too far from the ocean or the rain is blocked by the mountains. Eventually, the humidity increases and we arrive at the Mediterranean climates: Cs, Ds. The Mediterranean climates are only found on the west coasts. They are more humid than the steppes because they are usually close from the sea and/or at higher latitudes. This means they are colder and are more affected by the polar front. The steppes are almost at the limit of the front’s influence. Cfa: One exception to points 3 and 4 is the Cfa climate. Unlike the other areas near the tropics, it is always under a low pressure system: ITCZ + polar front or always under the polar front. It is usually close to the tropics on the eastern side of continents 5. Mid latitudes are always under the polar front: Cf, Df. This is usually what we refer to as the typical temperate climates. Although poleward latitude might be outside the influence of the winter Polar front, they are very cold so they have very low evaporation rate. Latitudes close to the equator will feature mild winters with temperatures above the freezing point even in the coldest month. The temperatures on the west coasts are a little hotter and more temperate than on the east coasts because they are affected by hot oceanic currents. The east is affected by cold currents at these latitudes. The temperature gets more extreme as we move closer to the pole and away from the ocean. Eastern Siberia: This is the place on Earth with the most extreme climates. Unlike point 5, it’s drier because they are directly under the Polar cell. This place is usually affected by the polar front only in summer partially. Dw climates: are another exception. Beijing should have a similar climate to New York but it’s not the case. It’s specific to Asia, or large landmasses. These places are affected by the Polar front only during the summer. The winter is characterized by the high pressure system around Mongolia and Siberia. Without this Siberian anticyclone, the climate would be like in North America. If it make things easier, it’s like in point 2 but it’s colder and we replace the ITCZ by the Polar front. As you see, there are no large steppes or desert in eastern China. This is because the pressure is so low in summer that the gap between the ITCZ and the polar front is small. 6. This last area is particular for her low temperature. It is the most notable trait, since it encompasses almost all precipitation patterns. [Answer] # Global Circulation, Precipitation and Climate ## Hadley cells In meteorology, there is a very useful concept of [Hadley cell](https://en.wikipedia.org/wiki/Hadley_cell). The biggest insolation is at the equator and from there, the heat has to be transported to the poles. In this process, hot air rises at the equator, because it is lighter than the cold air. The hot air cools down as it expands, which decreases its capacity to hold water and consequently, there is always lot of rain around the equator. The dried air then moves polewards. During this process, it turns eastwards because of the [Coriolis force](https://en.wikipedia.org/wiki/Coriolis_effect). Here, the *rotation speed* of the planet starts to be important. When the air completely turns eastward, the Hadley cell is disrupted and the air start going down. It becomes hotter and therefore dry, as is contains not much water. At the end of the first Hadley cell, there are usually deserts. For Earth, this happens around latitude 30°. Slowly rotating planets, like Venus, will have its Hadley cell uninterupted and this will not happen until the poles. Quickly rotating planets would have deserts and eastward winds much closer to equator - maybe there would not be big deserts at all, since they would merge with the rainy equator region completely. ## Overview Especially for non-earthlike planets, these are rather plausible guesses than hard facts. Use with caution. Temperature differences are for the 1 atm atmosphere. For denser atmospheres, they will be smaller, for thinner, they will be larger. Great references can be found [here](https://www2.physics.ox.ac.uk/sites/default/files/2012-03-08/1_wang_pdf_19025.pdf) and [here](https://www2.physics.ox.ac.uk/sites/default/files/2012-03-08/2_wang_pdf_58480.pdf), and for a visual, you can look [here](http://beyondearthlyskies.blogspot.cz/2014/05/influence-of-planetary-rotation-on.html). ### Earthlike planet * Equator area will be rainy. (If there is enough oceans around the equator.) Prevailing winds will be mildly westward, compensating the strong eastward jets at higher latitudes * Around lattitude 30°, there generally will be deserts, although some special conditions can prevent it. (Sahara was rain forest once.) * Between latitude 30° - 60°, prevailing wind direction will be eastward. * Difference between average temperatures of equator and poles will be approximately 40 K. ### Quick rotation (~5 hours) * Equator area will be rainy. (If there is enough oceans around the equator.) * Heat transfer is greatly reduced as the Hadley cells are disrupted, temperature differences between poles and equator might be 80 K or more. * There will probably be no sharp region of deserts, since the Hadley cells will be small. * There will probably not be very pronounced areas with eastward or westward directions of winds, again because of small Hadley cells. ### Slow rotation (but still faster than 1 day = 1 year) * One big Hadley cell. Due to lack of strong Coriolis force, it might be quite weak. It is therefore probable that atmosphere will superrotate, like on Venus. (Prevailing winds are eastward everywhere, or westward everywhere. Depends how it started, it keeps the original direction most of the time.) * No distinct zone of deserts. * Great temperature differences between day and night. * Land will get much hotter during the day. * Difference between average temperatures of equator and poles might be approximately 40 K, heat transfer should work. ### Tidally locked or pole towards its star * Equator and poles do not play usual role of *cold and dry* vs *hot and humid*. Instead, there is a hot *substellar point* and a warm insulated side, and a cold dark side. * Temperature differences between substellar point and could be around 80 K. * Atmosphere might superrotate, see the previous case. * No distinct desert zones, probably lot of precipitation on the insulated side. * Temperature and wind maps would generally be similar to [this pattern](http://s1.zetaboards.com/Conceptual_Evolution/single/?p=1024714&t=5047443). ## Local features ### Mountains Apart from the global circulation of the atmosphere, there is lot of local features, that can create deserts, for example. In my opinion, one should roughly imagine where the clouds are coming from and where do they go. Clouds appear above oceans, the warmer the region, the more clouds appear. Then, they follow the prevailing direction of winds. (See the discussion above.) If there are high mountains between, there will be a lot of precipitation on the side from where the clouds go, and dry region, possibly desert, after that. ### Continents The water slowly rains away above the land. Hundreds or thousands of kilometers in the middle of large continent, there will be a dry region with big temperature differences between summer and winter. (Or even within one day for slowly rotating planets.) This might go to extremes for large continents. [Answer] There are already some very good, detailed answers posted, but I'll happily throw in my two cents worth. Our oceans and atmosphere absorb energy from two different sources : * The rotational energy of the earth * The thermal and other available spectrum energy radiated by the sun, and to a lesser extend the earth's core and the various organic and geological processes taking place on the planet. This energy is managed and transferred according to the laws of thermo-dynamics. Thermo-dynamic flows are characterised by ergodicity. An ocean's currents are the mechanism by which its energy is managed and released into the atmosphere or, to a lesser extent, into organic and geological materials located in and around the oceans. Currents are ergodic flows that are the agents of entropy, distributing energy about the ocean's constituent molecules while at the same time radiating energy (and hydrogen, oxygen, etc) into the atmosphere. The climate, atmospheric conditions, and weather are the mechanism by which atmospheric energy is managed and released into space or into the environment (i.e., the oceans, other atmospheric phenomena, or the earth's surface). Again, the ergodic flows of atmospheric phenomena are the agents of entropy, distributing the energy about the atmosphere. For example, each time thermal energy causes a rain drop to form, energy is release and an $ H\_2O $ molecule is formed - actually, a rain drop consists of many molecules. That raindrop can then be absorbed by a plant, an animal, the oceans, etc. The ergodic nature of these thermo-dynamic flows are what shape our weather and climate. For example, as atmospheric energy increases, winds increase in speed in a desperate attempt to distribute and release excess energy, often featuring dramatic effects with powerful discharges of energy. These processes create characteristic patters of erosion (by wind or water) that we see on our coast lines and geology. The laws of therm-dynamic are assumed to be universal (via the Copernican doctrine) and so these same patterns should be present in any similar habitable alien environment, subject to applicability to local geology. I hope I haven't misunderstood your question. It's late! ]

[Question] [ A common trope weapon in science fantasy (such as [RWBY](https://en.wikipedia.org/wiki/RWBY) or the appropriately named [Gun Sword](https://en.wikipedia.org/wiki/Gun_Sword)) is the gunsword. As the name implies, a gunsword is a sword that's also a gun, or vice versa. This has always interested me as a concept, kind of an evolution of the bayonet in my mind, but could such a weapon exist, or rather why would a person use such a weapon? What reasons would a gunsword be preferred over a regular gun or a regular sword? Why would an army use them? Why would a person use one? Is the gunsword a realistic, feasible concept? [Answer] Gunswords are a terrible idea. On the other hand, gun **axes** existed, and were used in combat. The difference is simple - a sword requires a reasonable amount of finesse and dexterity to use, while an axe just needs to be pointy and heavy. The extra weight of the gun part hinders the sword, but works just fine for an axe. Here is a photo I took in the Vasa museum in Stockholm: [](https://i.stack.imgur.com/HtL3s.jpg) [Answer] There are actually historical examples of such weapons. They are called [pistol swords](https://en.wikipedia.org/wiki/Pistol_sword). [](https://i.stack.imgur.com/TLfbC.png) [](https://i.stack.imgur.com/sgk5i.jpg) But all of these weapons are unique novelty items usually sold to rich people who were fascinated with weapons but didn't have any actual combat experience, nor the intention to make any. The problem with these weapons is that they are neither good guns nor good swords. It is practically impossible to design a grip which works both as a pistol handle and as a sword hilt. So the result is that the weapon is extremely awkward to aim as a firearm, not much better to wield as a fencing weapon and very unbalanced in either role. Any professional fighter would rather carry both a proper sword and a proper pistol separately. Both swords and pistols are used most efficiently with both hands, but in a pinch you only need one hand for each. A properly trained fighter can quickly switch between sword, pistol and dual-wielding both. This gives far more flexibility than one weapon which is both a pistol and a sword but not good in either role. [Answer] ### It might make sense if your people use katars. [](https://i.stack.imgur.com/w6fUp.jpg) *The gun-katar, via Google.* While a katar, isn't strictly a sword, they follow similar uses. However, there is one significant difference between the two: swords are generally held perpendicular to the forearm, while katars are held parallel to it. This is a critical difference, since it's unwieldy to either fire a gun with the sword sticking up out of the top of it, or rotate the gun to be in line with the sword. With a gun-katar, both the shooty part and the stabby part point in the same direction, a far more ergonomic arrangement. Furthermore, unlike swords, which can be drawn fairly quickly, many katars are strapped to the forearm to provide additional support. If the pistol part is considered a medium range weapon, there may not be enough time to drop the pistol and don a katar in the time it takes for an opponent to close from medium range to close range. Having the two weapons integrated could save a soldier from needing to swap weapons, allowing them to use their pistol until the last possible moment, rather than needing to switch weapons with enough time to spare. A fighting style centered around gun-katars might involve the use of one gun-katar in the primary hand, and either a bucker or a second katar in the off-hand. Since the buckler or second katar can be strapped to the arm, the fighter would have their off-hand relatively free to brace their gun-hand while firing, as well as being able to use that hand to reload their weapon without dropping either their buckler or their off-hand katar. [Answer] **Modern Era** The western world is moving clearly away from even mounted bayonets, and there's no way we'd do a 180 and then a full sprint to get to a sword gun. So they're not practical. Any soldier would readily take a bolt-action rifle or normal pistol over the unwieldy gunsword. The balance will be strange, it will be difficult to hold and aim, and the leverage for using it as a blade won't be efficient. It has no place in the modern world as a primarily armament, and is needlessly complex as a secondary sidearm. **Era Past** [](https://i.stack.imgur.com/EL0LS.jpg) They actually have tried this a few times, but it never took off. In the pre-WWII era several attempts were made, but each time they gained limited popularity and kept being favored for a sword (such as a cutlass, for the above image) and pistol, separately. So each time they died off after limited use. **In Conclusion...** Although it seems like "Well, they both kill people, why couldn't they be combined?" this would be like combining a strainer and a baking pan... ...and having Gordon Ramsey trying to kill you while you used them. In any case I can think of it'd be better to have the weapons separate. One exception I can think of is where ammo was limited, and you were limited to a single weapon. Gladiators, anyone? In this case it'd be nice to expend the weapon as a pistol, and be able to fall back on a crude sword/knife for hacking. [Answer] The point of the gunswod is NOT to provide a solution for both long and short range combat. AFAIK switching modes that way isn't a real problem, and everyone else has demonstrated why it's not a practical idea anyway . The point of the gun is to provide a fast, strong vibration to aid the sword in cutting, like a vibroblade. This is how the gunsword in Final Fantasy VIII worked. Would that be feasible in real life? There are problems to overcome, such as timing the shot, finding the ideal frequency of vibration for a given blade design, to list a couple. These seem solvable to me, but the main issue is perhaps is whether a gunpowder explosion is the best way to impart the vibrational energy to the blade. In the past, well, who knows. In modern times, absolutely not. Today we have strong efficient, and cheap electric motors that can be tuned (or tune themselves automatically!) to the ideal frequency. I have trouble believing no one else has brought this up, but here we are. I created an account to answer this, hope it helps! [Answer] Quite a few of these were built during the black-powder era, when guns were easier for a single craftsman to build from scratch, but they never became popular. The socket bayonet, turning a rifle into a short spear, was the idea that was most practical and lasted: two British soldiers have been decorated for bayonet actions in Afghanistan, in 2009 and 2011. A sword-rifle has the problem that a rifle barrel is too heavy to make a sword blade out of by adding edges, since you end up with a sword that's too heavy to use effectively. Also, swords tend to bend in use, which is very undesirable for a rifle. At best, it destroys accuracy, and at worst the barrel bursts when fired. There was a WWII Japanese weapon that used a pistol's grip as the handle of a sword, with the pistol barrel sticking out sideways. There was only one, however, it was not a production item. This wasn't a very good sword grip, and was very heavy as a pistol. Waving two feet or more of sword blade above your eyeline when you aim the pistol also tends to make you conspicuous. The most nearly practical weapons were muzzle-loading black-powder pistols with a large knife blade attached. These were only heavy, expensive, and put you at risk of cutting yourself when reloading. Plenty of people have tried this, but nobody has succeeded so far. [Answer] Everyone talks about the *past*, and of fantasy where materials and ways of building things have not changed. But what about the *future*? Imagine **transformative technology** and how it changes everything. A generation ago, the suggestion of combining a camera and a two-way radio would seem absurd.  ➕  Sure, the camera part folds up, but every component that makes it be the thing that it is is distinct. So other than sharing a handle and one side of the case, you end up with nothing more than two machines stuck together. This has the disadvantage of having to heft them both when using either, but doesn’t save much over packing two separate things. Now with digital technology **everything changes**. The main mechanism of a CPU and display screen and control panel constitutes the bulk of either device, and the specific feature of (lens,sensor) or (final amplifier, antenna) is a tiny add-on. In fact, we’ll add a phonograph, microfiche reader, compass, barometer, calculator, **etc.** and entire library of media reduced to the size of a dime, and someone from 1950’s would have a hard time imagining how such a device could be practical. Then drop the punchline that it acquires new uses on the fly, and try and convey that this isn’t a final absurdity but the **crutial point** that makes it all possible. Well, not *everyone* didn’t think of that. Larry Niven published [The Soft Weapon](https://en.wikipedia.org/wiki/The_Soft_Weapon) in 1967. The ability to **morph** into different forms, including not just static shapes but complex machines, means that you carry **one thing** whose substance is shared among the different forms it takes. Go forward 35 years and Wil McCarthey describes [**programmable matter**](https://en.wikipedia.org/wiki/Hacking_Matter). Others have [speculated on the future of nanotechnology](https://en.wikipedia.org/wiki/Outline_of_nanotechnology#Further_reading) including [self-reconfiguring modular robots](https://en.wikipedia.org/wiki/Self-reconfiguring_modular_robot) the size of animal cells. A lump of general utility Goo could become, on command, any object including complex machines and cybernetics. A limited version of this is the Swiss Army Mech-All [described](https://en.wikipedia.org/wiki/Marooned_on_Eden) by [Robert L. Forward](https://en.wikipedia.org/wiki/Robert_L._Forward), which had a tip that could morph into any kind of mechanical tool. Strong enough for a felling axe in the larger model, *why not* a breach and barrel of a dart gun just as well? Fully general quickmatter Goo could become any type of blade on demand, and a firearm as well. You might not want to waste quickmatter on expendables, but it doesn’t have to use gunpowder-like reactions: it can hurl a found pebble or scrap material using *some means* inside the apparatus to propell it with great force. It might be a nano-mechanical catapult or super-spring. But I may indeed fire a tiny pellet of quickmatter, possibly coating a rock to give it more momentum. It would impact the target and then run its own program to eat through the armor and then continue to attack autonomously, perhaps “assimilating” the target. Lead bullets with the existance of quickmatter technology might be [the same kind of goof we discussed the other day](https://worldbuilding.stackexchange.com/questions/53422/why-arent-complex-devices-or-electronics-ever-built-out-of-force-fields-in-scie/53427#53427). Sword/gun/camera/databank/gaming-platform/[bow](https://worldbuilding.stackexchange.com/questions/73432/how-to-realistically-create-a-bow-thats-also-two-one-handed-swords)… there’s an app for anything. And pat yourself on the acnestis if you figured out that **transformative technology** was both a reference to my earlier post and a double entendre. [Answer] First, these are never going to be used by common infantry. Simply put they are going to be **complicated and expensive** compared to a simple rifle/pistol. Additionally *there isn't a whole hell of a lot* of hand to hand combat on the modern battlefield. Structurally they can be made but they aren't super practical. The most likely scenario would probably be more of a sword/dagger combo. Couple reasons for this concept. The uses: * Mainly this could be a special ops/infiltration weapon. If you had a blade on your fire arm you could stab and kill silently (and lightlessly since there is no flash) That's about it really. The drawbacks: * You hold a sword with a strait grip for strength and a pistol with a pistol grip (der). You aren't going to be able to swing a full sized sword with force using a pistol grip and would very possibly break your wrist trying to do so. * Complicated to use. Sure, bullets fly fast, but if you are trying to shoot and swing at the same time you could well hit your own bullet. You would likely use it as one or the other not both at the same time **(and is that more efficient than just having a knife on your belt???)** * Messing up has the potential to ruin both your blade and your fire arm * Ammo capacity. Ammo is heavy in significant amounts. Your ability to swing a sword is drastically impacted by weight. This thing is definitely not going to be an automatic weapon. * The blade can't be solid all the way down to the handle. At some point there is going to have to be a joint or a weld to hold the two together and joints are always the weak point on weapons. * Any blade larger than a small stabbing dagger is going to make it real hard to aim. For accurate aim you want the weight of the gun centered --- So in the end, you could certainly create a gun blade. It would break easier than either a sword or gun alone. It wouldn't support large blades or sweet sword fights while dodging bullets (which would admittedly look awesome). I guess in short, **it can be done but it just isn't practical in any real way.** [Answer] Sometimes when you're building something, its better to do one thing well than many things badly. With a black powder type pistol, you want easy access to the muzzle for loading. You want a long enough barrel for accuracy, but short enough for easy stowage. A sword on the other side, needs some legth, and a sharp or pointy bit, preferably far away enough from the shooty bits. The problem with a classic gun sword is you're trying to shoot past the blade. The design that's usually in use is *dumb.* however. A nice thing to have in a pistol is a shoulder stock. Improved accuracy.Stick a short sword on one end, have a dual sided handle, gun on the other. The barrel can act as a guard when used as a sword. [](https://i.stack.imgur.com/rFSsK.png) Kinda like this but designed by someone with actual skills. Have a dual purpose cutlass style handle with a guard, and a scabbard that doubles as a base. Your sword length is limited by the length of the brace and it would be a short sword with a gun on the end. I'd much rather the rifle and stabby bayonet but it makes more sense than glueing a sword next to a full length sword [Answer] ## Existence Depending on how broad your definition is, it might already have existed. Refer to this information from [Wikipedia](https://en.m.wikipedia.org/wiki/Pistol_sword): > > Pinfire cartridge gun-swords were produced in Belgium during the mid-19th century, although in limited quantity.[8][9] These custom-made weapons were sometimes used by European officers and featured a loading gate behind the basket hilt.[8] In 1866 T Rauh of Solingen filed a United States patent on the design of a 9mm caliber pistol sword with a 32in blade. > > > There is also a plethora of information about pistol-daggers: > > In 1838, the United States Navy developed the .54 caliber, single-shot smoothbore Elgin pistol, which was equipped with an 11.5-inch Bowie knife blade[4] and was intended for use by boarding parties; it was the first percussion cap gun in naval service,but only 150 were made. > [](https://i.stack.imgur.com/IUpgr.jpg) > > > Citing from the same article: > > Another notable example of a pistol sword was the Swedish 1865 Cutlass Pistol; 500 were ordered by the government and issued to prison guards. > > > Edged weapons with built-in pistols were common in Eastern Europe. The flintlock axe pistol was a trademark Polish cavalry weapon from the 16th until the 18th century. Similar guns were made in Hungary and a multi-barreled version was invented in Germany. > > > --- ## Usefulness The real question, which you have already posed, seems to be: "why would anyone build that?" Now, I can only guess and, thought I have fired a gun more than once, I am by no means an expert. I suppose it's terribly impractical to aim with this added knife contraption. But I *guess* you can add a pistol to a larger knife with a proper (knife) handle, if you don't care for aiming. What would then be the use of this? Refer to the second citation and the mention of *boarding parties*. I *guess* it could have some use as a surprise in close quarters. Ultimately, there is a very good argument against it: it axisted and didn't prevail! [Answer] Shotguns and long weaponry take time to swing and then aim. Having a melee option on the end cuts down on noise (since gunfire can be heard from a distance) and it would most definitely be a mod. We saw more gun swords, gun axes and other crossover firearms that doubled as melee weapons during the era when reloading took so much time that it was needed. There are reasons you might want such a thing in the modern era. * Stealth (less noise) * Limited ammo in the world * Field conditions demand it (it's so difficult to maintain a firearm that a backup is needed) * The Rule of Cool/Shock & Awe The last one, I would say would be applied to specific elite forces. Such a weapon is not all that practical, so it would have to be a well-designed and rare piece. There are issues with making it an efficient weapon--it seems like it would not be good at either job because of the design requirements for each sort of getting in the way of the other. (Others on here have summed it up quite nicely). What this means is that if it's going to be a good weapon, it's still going to be difficult to design. In that case it cannot be standard issue, and something that only certain forces or rank carry--or something rare and custom. [Answer] Here is a conceptual answer: The gunsword basically addresses the problem of long- and short-range combat. In earlier times, the latter may have been more frequent. In modern times, the former was. So the gunsword offers the solution of a "dual-use" item. You already mentioned bayonets, which effectively turn rifles into gunswords. Why prefer a gunsword over a regular gun? If you are constantly shifting between long- and short-range, and switching weapons is difficult or costlier (than using a gunsword). Why would an army use them? May reduce overall costs, if the gunsword (and associated costs of training, logistics, etc.) is cheaper than two different items. Is the gunsword a realistic, feasible concept? It is certainly a plausible concept, only bound by physical limitations. Note the answers above are not all-inclusive. Say, there may be more reasons for an army to want gunswords. [Answer] Speaking with experience of sword fighting (long sword), one potential use of a gun sword would be when sword fighting. In the event that you meet an opponent of equal skill, quite often you end up dualing for a prolonged period of time where you clash repeatedly, often locking blades and manoeuvring around each other to try to get lucky with the end of your blade when you separate (more than once I have actually dropped my sword on purpose here, whipped out a knife and stabbed the other guy while he was debating what to do with my sword). At this point in time where the blades are locked, essentially neither party has any offensive or defensive ability. If you happened to have a pistol strapped to the side of your sword's hilt, letting off one shot at nearly point blank range would not need much aiming at all. Even if your shot only clipped your opponent's shoulder, that should be sufficient to distract them for long enough for you to extract your sword and run them through with it. In a worst case scenario where the shot shatters your blade, your opponent will have just been showered with fragments of your blade, distracting them significantly while you still have a rather sharp shard, with a rather nice handle - enter the world of luxury shivs! Once your opponent has been dispatched, you can then continue with their sword and keep your pistol powered shiv for backup. As most good long swords balance just in front of the crossguard, if the pistol were strapped to the hilt of the sword, possibly running across the crossguard, you could either reduce the size of the pommel or increase the length of the blade to compensate for the added weight of the pistol. As aiming is not really an issue, you just need a trigger you can pull/press with any free digit on your hand, so you only need to design a well made (read balanced) sword rather than a fancy pistol. For the usage suggested here, the pistol does not actually need to be pointing directly down the blade. It could easily be mounted at any angle between matching the blade and being at a perfect right angle to it. I expect years of experimentation would discover the best angle. However, provided that the sword fighter was able to approximate a straight line from the barrel to the opponent at practically point blank range, this could be a very influential weapon for the first side to implement them. Very demoralising for an enemy to know that even their best sword fighters could suddenly be taken out by a comparative novice by simply blocking and shooting. No matter how hard you train, practising not being stabbed just after being shot is very hard to fit into a practical curriculum. In the real world, once accuracy increased, dedicated guns took over from swords, making a sharp piece of metal a fall back weapon rather than a primary but in the era before that where guns were hopelessly inaccurate, being able to discharge one at point blank range while sword fighting could well have been a revolutionary tactic. Unfortunately, by the time guns had been miniaturised sufficiently to be mounted on swords, they were reasonably accurate by themselves and could be used effectively as weapons in their own right or with a sword in one hand and a pistol in the other. I think this could have been a very effective additional weapon for sword fighters had it been introduced when sword fighting was the primary means of combat. Reloading would probably have been an issue - very hard to put down your primary weapon in the middle of battle, sit down and do some work on it, so the pistol would have to be loaded before battle and used more as a reserve weapon than a main one. An interesting alternate design could be a snap-on, disposable one shot pistol. That way you carry a pouch of these, whip one out and clip it onto the side of your sword after you expended the last one. If the mounting point is well balanced, the difference in weight between an empty pistol and a loaded pistol should have negligible effect on the sword's performance. This kind of re-loading action could be done with one hand, so given a brief lull in the fighting, you could reload mid-battle without risking sitting around defenceless for five minutes or so. For a variation on the above, have the snap-on point as a standard fitting and allow other items to be mounted there too e.g. a pre-loaded crossbow, a spring mounted knife blade, a double barrel pistol, a bunch of flowers etc. anything that can distract the opponent long enough for you to let your sword do the dirty business. [Answer] They actually exited and were used however, the sword part was considered the main weapon and the pistol the secondary one and rarely if ever used at all . In modern era only the gun part would be used and the sword one would be considered just an useless decoration. The design isn't really that bad, it is just the swords being completely useless. [](https://i.stack.imgur.com/qlMQo.jpg) [Answer] As an author, I feel that one possible interpretation of your question is "Realistically, what kind of technology, social conditions, or philosophy would justify using such a thing?". Is that sense, there are a number of generic directions you could take, and flesh out as your narrative unfolds. In real life, successful or widely-used weapons aren't developed in a vacuum. Typically, a weapon evolves in response to a particular defence, such as in *Dune*, for example. In *Dune*, long range projectile weapons were useless, as combatants could wear a force field to stop the projectile. However, in order to allow the passage of oxygen and objects in the landscape, the field allowed low-velocity hand weapons to pass. Such a situation might favour a combination weapon like the gunsword, as one could expect to slide the weapon inside the shield and fire, doing catastrophic damage to the target, yet leaving one with an acceptable hand weapon for continued use. Other uses might revolve around some sort of large beast, where the bayonet-like blade was required to pierce the thing's hide, but the gun was a necessity for causing enough trauma to kill it. A "dragonkiller", if you will. Specialized weapons are also developed for particular environments, as well. In WWII, flamethrowers were not terribly successful or useful in open combat, but were very effective (albeit very dangerous to the operator) in tunnel warfare in the Pacific. The sword portion of the gunblade, for instance, might be incidental to combat, but be very useful to clear out the "web" of a creature like that from the *Alien* series. If such an environment is usual, a fighting force might well continue to use such a weapon, despite that weapon being unwieldy or obsolete in any other context. Also available is technological stagnation, as in *Warhammer 40K*. In *WH40K*, such gothic weapons are justified by having the Human protagonists maintain a religious aversion to "new" technology, requiring them as an article of faith to use millennia-old weapon designs that are not always especially effective. Religious reasons can be very effective storytelling mechanisms, as entrenched dogma is almost always difficult to change, and deaths stemming from the use of sub-standard tech can always be passed of as martyristic or some such. The difficulty from a story perspective is that soldiers tend to be practical people; writing about **armies** from this perspective is easy, but writing believable **characters** is hard. Another approach might be a unique, expert character with a cultural background or personal quirk that incorporates the weapon in question. Indiana Jones is a great example. His bullwhip might not be considered as effective as a knife or even a sword, but his level of expertise negates that downside and he'll use that bullwhip by default in any close combat situation. Importantly, he's not adverse to using any other, more effective, weapon as the situation dictates; he just strongly identifies with the whip when it's appropriate. Justifying a single character spending an exorbitant amount of time training to overcome a gunblade's inherent weaknesses is much easier to do than justifying the same for an entire army. Also, many current day armed forces still teach combat with a bayonet attached to an assault rifle. While no modern force that I have heard of regards this as a realistic form of field combat, it is a fantastic way to improve all-around strength and endurance (as I can personally attest!). In an emergency, an expert instructor might use their deeply-ingrained techniques with any appropriately-shaped piece of wood or pipe. Their skills are useable outside of the actual weapon in question, and fully justifies their training. A gunblade might be used in this context, where a handful of people are very proficient with them, and use them in a very limited *ad hoc* way. Hope this helps, Dusty [Answer] It could be useful a rifle with sharp edges in close combat because you can slip it away from enemies hands if they surprise you from a corner, thus I don't think Marines nor any other army adopted that kind of machinery, what I think it could be useful is in reality a RPG-Hammer. A regular hammer in melee combat but also equipped with a RPG shot able to penetrate thick armors (even ones protected by reactive explosive) thanks to its curved surface. It could also be used to get the hammer unstuck and achieve to quick shots on one enemy that is in front of you and another that is behind you.. But at this point you are guessing already why you have a melee weapon in modern warfare. Could still be a useful weapon to hit a moving vehicle or wrecking some building entrance. The hammer just has one curved side that has some explosive inside and some metal that will be projected melted on the hitted surface (and at same time provide a opposite force to project the hammer away) like regular RPGs. It is a 1/2 shots weapon. But could be much cheaper to recharge that than to spend money on multiple RPG rockets. Like Warren sad in his answer maybe a "Gunblade" has the solely purpose to make a shot stronger thanks to a little explosion (I would discard the vibration stuff simply because each material requires a different frequency and that's impractical). In example if the blade is made by 2 parallel metal pieces and actually the explosion create a small fissure between them it could help a blade to crack an armor with proper timing between the shot and the explosion. [Answer] I read [Warren's answer](https://worldbuilding.stackexchange.com/a/53430/21682), but I had a different interpretation of the gunblade's use in FFVIII that might have practical application in other built worlds, if not particularly our own. [Upon researching, it appears that I am wrong](http://finalfantasy.wikia.com/wiki/Gunblade_(weapon_type)#Final_Fantasy_VIII "I'll check the booklet for a more reliable source when I get home"), however I continue to believe my original interpretation holds some value. I always thought that the point of the gunblade in FFVIII was as a means of piercing armor. That is, you cut through the armor of a beast, and blast their insides with the bullet by timing your shot. In that world, using something to bypass armor in close quarters combat would make sense with all the large, high-powered, heavily-armored creatures (e.g. dragons, behemoths, Malboros, etc); large, armored, and complicated machines (X-ATM092); and magically protected people (using Shell, etc) you would end up encountering. In our world, it doesn't. We fight against armies of people, often with (relatively simple) machines, rather than large creatures or combat droids and the like. We don't need the extra armor-piercing capabilities in close-quarters combat, because a shotgun, assault rifle, or bayonet usually suffices against humans. Plus we could just use a high-powered rifle with AP rounds at a distance. In this case, you don't need much finesse, because you're usually not fighting against nimble creatures. The recoil would probably serve to remove the sword from the hulking monstrosity you now find yourself within arm's reach of - if it gets stuck there, you're probably going to find yourself in a world of hurt before you get a chance to dislodge it. [In Dissidia](http://finalfantasy.wikia.com/wiki/Gunblade_(weapon_type)#Dissidia_Final_Fantasy), the recoil is even used to an advantage (although I doubt it would realistically work quite so well, it's worth mentioning). Clumsy? Yes, probably. Useful in our world? Nope, not at all. Other answers cover all the reasons why pretty effectively. But having potential applications to be mindful of when creating alternate worlds? Absolutely. [Answer] When I think about gunsword feasibility I always think of *Farscape* Ka D'Argo's sword that converts into an energy rifle, that's a weapon that with enough materials technology to prevent undue breakage you could have without too much difficulty. It's feasible at a certain level of technology to build a weapon using that set up even if it's with a more "primitive" (which is to say modern) firearm, the engineer in me says it could be done reasonably well now using a 3D printer and the right alloys. Why the hell does such a weapon exist in the first place though? Honour and pragmatism, melee weapons are the honourable way to fight your battles but because not everyone fights with honour you need something up your sleeve for those times when you're not afforded the option of honourable combat. You can't just carry a gun as well, that's for the dishonourable sods you need versatility to protect yourself from, so you carry a convertible weapon that allows you to fight your battles properly whenever an honourable enemy allows you to but also gives you a level footing against the other guys too. Armies would use them for the same reason individuals use them it's the "right way" to fight, as I recall Ka D'Argo's sword takes a lot of conversion time to turn into a rifle but snaps shut into it's sword format almost instantly which tells you all you really need to know about the attitude towards combat that gave rise to such a tool of war. Gunswords aren't that practical purely as weapons for the sake of having a particular weapon, melee or projectile, but in the right cultural context they could be an almost inescapable conclusion. As a side note projectile accuracy and power are always going to be something of an issue with a gunsword, not that such a weapon can't fire accurately but that it isn't going to be *as accurate*, or have as much punch, as a firearm of the same weight and size. That doesn't matter in a cultural context where you only have a ranged weapon because you absolutely *have* to but you don't really want it bit it makes a hell of a difference if it's reversed and you have a melee weapon because honour demands but battles are fought primarily in "gun mode". [Answer] You would have to define a combat context where swordplay was actually used. For example, propose a dueling society with high chivalry expectations, or an advanced Samurai culture. As in many past civilizations on Earth, the professional warrior class had better or more specialized armament than the rank and file support soldiers (think of English knights with foot soldiers and archery for bulk troops). I could conceive of an advanced (technologically, if not culturally to the extent pacifism will be an attribute of an advanced race) civilization where personal man-to-man single combat was possible, even a prestige role. However, what to do about the hordes of rank and file troops who might have little respect for the single combat of the high ranking guys? In the heat of battle the grunts as it were might just push in on a sword fight between ranking knights. Here is where the omni-sword-gun comes into its own: Just above the hilt on a well-balanced combat designed sabre or the like is a spherical AI (artificial intelligence, i.e., a hardware implementation of particular combat sequences of image pattern recognition and ballistic sighting) device approximately 20 cm/8 inch, hyper strong but light metal with near 360 degree rotational capability in 2 axes. Mounted within is a miniature electric rail gun able to fire supersonic pellets which detonate on impact such that very small pellets are able to remove 2 inch/5 cm chunks of light armor and flesh. Image sensors on the globe detect and analyze human figures in real time and decide whether they are intruders on the single combat to be eliminated or are aspects of the legitimate single foe faced by the dueler to be ignored. The mass of the globe unit would be insignificant relative to the sword mass and would not appreciably affect precision swordplay. Nevertheless, its advanced alloys would permit it to be struck by opponent sword strokes without damage. You might visualize a scene with with two knights fighting, swords flashing and the clank of parry when several unruly troops race in from the side and front to attack one of the knights. The response is so quick as to be almost invisible as the omni-sword-gun unit rotates and fires in milliseconds, there being nothing but machine whizzing and supersonic cracks in a blurred audio and light stream as flesh and blood and bits of chain mail or the like erupt from the now falling troops who neared the knights. The knights ignore this and continue their honorable test of death. [Answer] I tend to favor the concept as it is used in Power Rangers, it's parent show Super Sentai and the sister show Kamen Rider. In the former two, they are typically the weapon of choice for the sixth ranger/guy who joins the team after the core team has been assembled. In the latter, they tend to be the main hero's weapon. In either case, they are designed as guns that turn into swords and are not functional at as both at the same time. For the show's purposes, it's benefit is the hero can cut through large groups of mooks and then take a shot at the bad guy who is further away (which only works because the nature of the shows are choreographed martial arts fights, so close range weapons are ideal AND they make for cool toys. Kids buy things they can transform and move the parts too). Notable uses (i.e. the ones I can come up with on the top of my head) are Megaranger's MegaSilver/Power Rangers In Space's Silver Ranger and Kamen Rider Wizard. Kamen Rider Ghost has a weapons system that combines his gun sword with other items to make more variety of weapons and the current Super Sentai Season (Kyuranger) the core team has weapons that can be combined in different ways to make various cutting and shooting implements, but they aren't switched around (each ranger has one combo and uses it religiously. Individuality seems to be a big theme of this season.). [Answer] Let me try. (I'm not too familiar with swords nor guns,so be gentle) The problen is that to make a good gun, you get a bad sword. To get a good sword, you get a bad gun. You want a good both. All the others' designs have terrible balance. What if, the balance could be, better? (I've got a bias towards japanese style swords, so assume those) Take a sword, and give it a handle of 30-45 cm. Stick the (inner mechanisms of) the stereotypical pump shotgun(different outer piece; shorter barrel, MUCH shorter stock, you'll see how later). This way the handle has only the minimum amount of things sticking out of it. The barrel is opposite the blade, which will give a unique firing position. Take your stereotypical "draw cut" stance. Hold the weapon a bit closer to your body, closer to your center of mass. Only fire from this position. You only need enough room on the stock for 1 hand, so thats why its so short. The edge and the trigger both face the same way, relative to the blade. Bracr yourself, make sure you aim forward, not up or down, and squeeze your point finger on the trigger. Good job, you fired. Aiming is basically impossible, but thats why shotgun. I have no idea how this will react with how the human body works, so this may not end well. You get what I mean, yes? I'll make an image and put it here later ]

[Question] [ My hero has to journey into a mirror world. This world is much like our own except ***evil***. Almost everything there is an enemy and there will be very little kindness. On top of that the world is visibly *DARK*. It isn't just a metaphor and the sun hasn't gone away. It isn't just cloudy/stormy all the time. Somehow in this other world the light is just less *shiny*. Colors are dimmer. Shades are more monochrome and *grey*. What could be causing this? What are some of the hidden ramifications of this? It is reached through a breach made by magic. It's a mirror world or another dimension but otherwise almost exactly like our earth. Trees are shaped the same and behave the same way. People are people shaped, just meaner. Temperatures are comparable. There may be some anachronisms but not many. Possibly in the form of demons or fantastical beasts. Houses will mostly be in the same places, except where The Big Bad Evil Guy lives. Changes to one world should not *necessarily* effect the other, but they can if it benefits the answer or the logic behind the answer. **Criteria:** * Although these worlds have magic the less that it is used for the answer the better. * Preferably it can be reverted at the end of the story. * Bonus Points: If it is something the Big Bad Evil Guy made happen. [Answer] A quick and rather simple explanantion for the world appearing dark, while plants which require light as their basis of life still grow there in a similar way to ours is that the **spectrum of light emitted by the sun of this world was shifted out of the visible range compared to your hero's world**. Thus, there is a sun-like star above this world, but its light emitted appears to be 'dark' because most of it is not visible for the hero from another world used to a different light spectrum. Think of UV light and flourescence effects to get a basic picture of what this is about. **All creatures in this world** would also appear to have **dark vision**, as they evolved in the world with different light spectrum and thus can see normally in it. An interesting perspective would be that some of the light spectrum visible to the hero might be invisible to the creatures of this world and he could mark locations, paths etc. with a flourescent substance which is visible in our visible spectrum, but not in this world's. [Answer] ## Make the Hero Depressed ....so they can't see colors as well. If physics in this mirror world matches physics on Earth, in real life, then all that needs to change is how the character perceives the world. Depression will do nicely. In 2010, some researchers found that [depression makes a person see the world in more shades of gray](https://www.livescience.com/9965-depressed-people-gray-world.html) than a non-depressed person. ([Actual paper](https://www.ncbi.nlm.nih.gov/pubmed/20359698)). They found that the retinas of depressed people don't perceive contrast as well as non-depressed people. Getting everything to be meaner, more deadly is pretty easy. Just increase the demands of competition or use the depression to make everything seem meaner. Also, if depression is mixed with a little bit of paranoia then even if other people and animals are behaving normally, they would be perceived as overly hostile. Rewriting physics is a huge pain. Inducing some depression in a human brain is way easier with lots of other knock-on effects that help the Big Bad Guy win. And there is [no shortage of reasons why a person might become depressed](https://kidshealth.org/en/teens/why-depressed.html). Thus, the author has broad options regarding how they want the story to play out. Chemically-induced depression leads to a certain flow in the story. Light sensitivity-induced depression leads to a different flow in the story. Making the Hero depressed provides lots and lots of options. Reverting the Hero to non-depression is easy too. At the end, the Big Bad is dead or defeated; thus, everything is right with the world again. This approach is also instantly relate-able to anyone who's had depression. The world *does seem* to be gray when one is depressed. Doesn't matter if it's a sunny spring day, everything is gray. [Answer] You say that the world is literally greyer and darker. I assume that includes the sky. If we just filled the air with fine particles, light from the sun would get partially occluded, causing the entire world to be darker. It would also cause local light sources to appear weaker, meaning any lights the hero brings with them will also work less effectively. This can be caused a number of non-magical ways. The particles could be ash from volcanoes or water vapour from a perpetual fog for example. Using ash or dust has the added bonus of making everything grimy as well. Depending on how heavy your dust cloud is, it can even make it a little harder for your hero to breath, causing that extra level of discomfort in this horrible mirror world. If your big bad is sitting ontop of a volcano, a very story-wise thing to do would be to stop the perpetual smoking of the volcano once he is defeated, allowing the world to slowly clear as the dust settles. [Answer] If you hold a piece of white paper at right-angles to a real mirror, you can see that the mirror image is slightly darker. If you measure the brightness of the Sun in a mirror it will be less bright than the real Sun. That is simply physics because (a) the light has to pass through glass and (b) the reflective layer will always absorb a certain amount of the light incident on its surface. A mirror cannot itself produce light, all the light coming out of a mirror is a mere reflection of the light in the real world. Obviously the mirror world is illuminated entirely by light that has come through glass from the real world. That alone makes it darker. What is worse however is the parts of the mirror world that *don't have a mirror in them*. They must receive their light purely from reflections from the mirror sky and from other objects. If they are far from a mirror they will get almost no light at all. They will receive some of course from shiny objects that reflect what little light they can but this will produce a diffuse gloomy effect. [Answer] Your requirement of trees and temperature being the same is a hard one under the constraint that everything has to seem darker and less colorful - both objective color and lightness depend on different (visible) wavelengths of light being present, and trees working like normal means that photosynthesis is up and running, so at least blue and red wavelengths need to be present in the usual quantity, making a monochromatic lighting (which would kill all colour, see Na-vapor-lamps) impossible. If the sun is its own self, and the temperature on earth is also fine, most of the longer (invisible) wavelength need to be coming though just fine, meaning a simple darkening of the atmosphere is out as well. You'd need to have the hero's perception changed, either by changing the sensory input (magical lenses, magical/pharmacological constriction of the pupil) or the perception itself (spell that affects memory/senses). I actually like the contracted pupil - pinhole pupils also being a nice cineastic effect. It could be effected via drugs that contract the circular muscle, or some sort of systemic drug (problem being that it's actually adrenaling that is widening the pupils, so a dark world should induce wide pupils in most people...) - With extremely small pupils, few light would reach the retina, making everything look dim, triggering the eye's dark adaption, making everything colorless. This effect would easily detectable in a mirror, so if more subterfuge is warranted, the Big Evil might magically place black particles in the pupil, dimming everything without being detectable without opthalmologic equipment. [Answer] Fairly simple answer but sounds kind of fun. Perhaps it is being absorbed. The mirror word is growing dark because it is fading back to where it came from. The "Big Bad Evil" has triggered the end of the mirror world, and now the prime world (real world the mirror reflects) is pulling the mirror world back into itself. The colors are fading and dimming because the light energy or whatnot is being pulled back into the real world. This should meet your requirements. It take minimal magic, as in the bad guy could trigger the end and then just sit back and let it happen (at least until the good guys stop it and reverse the effect to save the day!). Temperatures can be similar or fluctuating depending on how the world is being 'absorbed' or whatever term you want to use. And the world falling apart can explain how it is a mirror world that does not reflect all changes that happen in the real world, (i.e. mirroring a big event takes lots of energy and the mirror world is losing energy so only small changes are reflected, or the opposite where only big energy changes are reflected). This kind of story line also offers other things you can take advantage of such as if one world absorbs another, as they collapse do more gates between the worlds appear as one becomes unstable, or do elements from one bleed into the other. The list goes on. Hope this helps. [Answer] **The evil world is flat. The sun never rises or sets.** [](https://i.stack.imgur.com/x4F4h.jpg) This world is a disc, turning on its axis. It stays with its edge facing its sun. On the ground, the sun is always moving along the horizon, never setting, never rising, never stopping. Sunlight is always redshifted and oblique. Shadows are long. [](https://i.stack.imgur.com/aVqb2.png) [source](https://www.roadunraveled.com/blog/salar-de-uyuni-bolivia-salt-flats-tour/) [Answer] The Sun is life, the Sun is good. In some languages, like German, the Sun is even indicated with a feminine noun, to indicate its ability to bring life. Your parallel world is evil. Evil is the opposite of good, or the lack of good. So it is straightforward that in an evil world the sun light shines feebler or is obfuscated. [Answer] Make it multifactorial. The very makeup of this mirror world is such that the atmosphere filters out more visible light, the matter itself absorbs more visible light, and some supernatural forces absorb some of the visible light (it is what powers them, and allows them to project their evil onto the world itself) [Answer] Perhaps it's a multiverseral effect of the dimensional travel or the spell to create the mirror world or gain access to it... either way, in another world, the color our perception of color is different enough that it takes on a different quality of brightness than our world. It can be an unwritten rule that utopia worlds are brighter compared to ours and distopias are darker. Not enough to be a hinderance to natives of the other worlds, but to a traveller, the difference can be stark or barely muted. To an expert traveler, the brightness or the colors will denote how much and in which way the verse has changed. Traveling to something very very close to our world will be a similar color... and we eventually learn this is the fabled "World without Shrimp" of lore. This will also help you identify things that are not of this world as they would appear darker or lighter naturally. There could be a simple spell that all dimension travellers use to keep up appearances, so that you do not look extra-bright to natives and blend, but it needs to have a common failure point to give up the secret... perhaps those who correctly guess or are told will become immune to the deception. [Answer] It is caused as a side effect of the magical force. The dark world has magic, which permeates everything. Under normal conditions this magic would be a neutral force. But that was before Big Bad Evil Guy rose to power, and imposed his will on magic, which in turn polluted the natural background magical field. This causes everyone to tend to take on characteristics of Big Bad Evil Guy's personality to varying degrees, like putting a tinted lense over everything. Someone who would normally be sunny and super cheerful will instead be sullen. Someone who was prone to bad tempers and violence would become much more so, to the point where they might be even worse than Big Bad Evil Guy. Going off Green's answer, another side effect of this is that perceptions of reality are also muted, so that while nothing in the world has really changed, the mental perceptions have, robbing hope, causing various degrees of depression. There could be people who are naturally resistant, so that it affects them less. And there could be places where the magical field is either weaker or stronger based on real world factors, so you could have a place that is especially dark, like bad gas building up in low lying swampy areas \*. Edit: This leads to a couple interesting possibilities; If the magical field is tainted, then it could lead to anyone using magic to become more and more evil, as concentrating the magic for use also causes the user to take on more of Big Bad Evil Guy's traits. And if Big Bad Evil Guy is defeated, then it is possible that the magical field could be cleansed, returning light to the world, which is not something that can happen if it is a world with different physics or solar spectrum. And finally, if Big Bad Evil Guy can impose his will on magic, polluting it, then it may also be possible that another powerful user could do the same, and push back on the darkness, creating an island of light where the darkness has no effect. \* does not have to be affected by altitude. [Answer] This is probably more magical than what you are looking for but given the constraints it's hard to come up with a good answer: You say this world is permeated by evil. What is evil? It's a hive entity, the individual components of which appear as superfine quasi-transparent particles permeating the environment. While they do not interfere with photons that pass through the particles they do take **variable** amounts of energy from the photons. This runs the life processes of the evil and in the end shows up as heat which is released into the environment. Thus the thermal balance is not altered. Photosynthesis **at ground level** is slowed but the evil is mostly near the ground, treetops stick up high enough that they are pretty much unaffected. Note that when you take energy from a photon (normally only possible by redshifting--intense gravity or extreme speed) you lower it's frequency and since color is based on frequency you change it's color. Since the effects are random it doesn't just shift the colors down the rainbow but smears them across the spectrum--and what's a mix of all colors but white? The smearing isn't perfect so some color remains but it's washed out. Note also that this means that the more evil that's about the darker and less colorful the world will be--this could be useful to identify centers of evil. [Answer] The first thing that comes to my mind is the plot of **MediEvil**. The game begins when the Big Bad (Zarok) casts a spell plunging the country (make it the world) into darkness, and turning everyone into zombies. (As a side effect, he resurrects the hero who had been killed before). In the mirror universe, **the Big Bad has won** against another hero. Casting such a spell must have been incredibly difficult and needed a lot of preparation, magic energy, combined relics, etc. In this mirror universe, **the hero died and failed** to stop the Big Bad, so he carried out his plan to turn the world into darkness and everyone into corrupted version of themselves. He would profit from this operation because with this spell, he can rule his world, or get vengeance over some king, or access incredible power through dark magic. Why is only the mirror dimension plunged into darkness? Because the Big Bad has somehow a knowledge of there being two worlds and has or has had access to the mirror world. Using this, **he has killed/merged with his mirror self** and **gained his power** (that would also explain that there is no version of him in the "light" world). At least, he took or did something from the light world that people won't notice but would enable him to carry out his plan on the mirror world. Or maybe the two versions of the Big Bad agreed to unite to take over one of the worlds, being unstoppable with their combined powers. Eventually one of them was killed by the other over ruling disputes. But basically, an incredibly powerful spell, that needs magic and power from both worlds to be cast, explaining why it's only present in one world. Cons : * It's entirely magic Pros : * The Bad Guy made it happen * It can be reverted, by killing the Big Bad, destroying the crystal, ... [Answer] ## Mirror World Is *Less* Than the Real World The laws of physics are very simply but profoundly different in mirror world -- 1 joule there is a tenth of a joule in the real world. Everyone from the mirror world sees everything as normal, but for someone from the real world, everything there emits much less light, is much less heavy and more delicate. They would seem preternaturally heavy, strong, and tough. Now, I'm guessing that you don't want your hero to be practically unbeatable by the Mirror World natives. Presumably there's some sort of effect that reduces him to mirror person levels, although not completely (hence the place still looks dark). This could come from several sources: * The portal is under the control of the BBEG, and anyone who doesn't work for him who goes through is automatically reduced * The Mirror World has a slow corrupting effect which eventually turns you into a mirror person. Once you become a mirror person, you can't go back, because the light and heat of the real world would be so intense to you that it would destroy you. The only way the protagonist and his allies know to stop this from happening is a spell that also has the reducing effect * The protagonist can't just run around in the Mirror World -- the intense energy of his body would set everything on fire! So he has to have the reducing effect applied to him in order to protect the people there [Answer] **The Big Bad Guy spreads a virus/bacteria over the entire planet that influences your eyes/visual nerve/brain.** When you visit the planet, and pass through the portal, the virus immediately infects you, attacking your eyes, killing or disabling/temporarily poisoning most of the cells which are responsible for color vision, leaving mainly the ones for night vision( [Rod cells](https://en.wikipedia.org/wiki/Rod_cell)) intact. Alternatively, the virus could attack your visual nerve or your brain, creating the same effect. You quickly stop to perceive colors and see everything less bright and more blurry, recognizing the world far different than it really is. This solution has the advantage that the world can be almost similar, but still seems greyish and dark to your character, so reality and it's perception differ by far. **Of course, if you defeat the Big Bad Guy, you can obtain the antidote/some medicaments against your virus.** Or, if you simply return to our world, the virus/bacteria is going to be killed by something very usual in our world. Like UV-Rays. Or some chemical substances which are in the air. Or it depends on some gases which are in the air on the dark side. [Answer] As there are great answers regarding the dim light, this is only about *people are meaner*. **tl;dr**: Cultures are self-enforcing and self-sustaining: Find an initial trigger that caused mistrust in society and you'll generate potentially very mean and egoistic people. --- Behavior of individuals in society is a function of the culture of that society, and culture is the summary of all behaviors. Sociological and economic research has shown (in actual lab experiments, if I find them) that in standard trading games people behave nicely if everyone else does, too. The summary of the experiment is roughly this: 10 (or so) players get randomly coupled up and will play a Game where you can choose either a "coop" or "egoistic" action. If both play coop, both get high outcomes. If one plays coop and one egoistic, the coop player gets nothing and the egoistic player gets more than in the previous case. If both play egoistic, both get very very little. Notice that this game represents some important feature of culture: If everyone plays nice, the total outcome will be the highest. Mean people/free riders will benefit (earn more from free riding), but only if the remainder of society is nice. If everyone is mean, nobody profits. But also: If everyone is mean, it is the optimal strategy to be mean. In the lab experiments, you get repeatedly matched with new people. You don't know how they played individually in the last rounds, but you know whether the total group of people was doing well or not. What happened there was that some groups by change ("inexplicably") turned into coop groups where everyone played nice, and some deteriorated. One of the determinants was group size: The larger the group, the more likely it deteriorates (similar as how people in smaller communities are more trusting than in large cities). Moreover: Move some from a "coop group" to a "egoistic group", and they will slowly learn and adjust. So cultures are self-sustaining: Find an initial cause that made the culture to be bad and egoistic, and you'll find a self-enforcing mechanism. An initial group of mean people, perhaps followers of Evil Guy? At his arrival, Evil Guy Ponzi schemed the heck out of everyone and they are all now sad and lost and trust no-one? Perhaps in your world people look all very similar (dim light), so it's difficult to build up trust? All of these mechanisms would be removed with the dimming: If Evil Guy is defeated, public information that his followers have left could turn society, if the cause was dim light so could the change of atmosphere. [Answer] A couple super volcanoes could do this. Spread enough ash into the air and you effectively blot out the sun. I think a [Van Helsing show](https://en.wikipedia.org/wiki/Van_Helsing_(TV_series)) did this sort of thing for vampires to be able to come out. In that case it was based off a super volcano in NW America. However to make it magical and caused by the super bad he could have cast something to make this and maybe one other one on the other side of the world erupt, and continue to erupt and spew ash. The psychological effects of being in darkness, in this case from ash cloud cover, are pretty well documented and could affect the populace. In addition you would be adding the fact that you could never really get anything clean, and I'm sure it would have health implications which would get worse as you get closer. Again leaning on the supernatural aspect you could say that part of the Big Bad's malice was being transferred in the ash and causing everything to be infected by it. [Answer] Like other said a volcano would darken the atmosphere. The enemy of my enemy is my friend so maybe our intrepid hero gathers together a team/gang/club/"do gooders are us" to help him out. No matter how evil you are you will still hate Lex even more. However, our lex luthor has a plan in mind, for world domination. He can't total wreck his world because he lives on it. He does have bunkers of course as a last resort. He turn the world dark to black mail the residents of his world for full control. So Lex brings in trucks of special compound X, and triggers super volcano. Compound X is a nano cloud that feeds on the ash, but also alters it so only the shades of red and blue for growing can pass through, and infrared for heat. Your world won't be pitch black, but with only red and blue passing through,it definitely going to be dark and eerie. [](https://i.stack.imgur.com/sFuh6.png) So the stage is set, and the whole world looks like below with infrared for heat and maybe some other color/spectrum. Lex is blackmailing the world, and its nearly hero time. Now Lex is knows he is in for a long siege, and residents are not going to give in that easily. There is still backing stabbing on all sides. He will be attacked on all sides, but also has a plan for undoing it. A nearby river is prepared and safe guarded to dump on the volcano to extinguish it. Also the nano cloud, could be used to clean the sky in a few months. However, Lex will never do this for ages to ensure his dominance. Enter our intrepid hero. Shooter guy. haha Some of the Lex's forces he can sneak by, some he's going to have fight. After a long trek to the Evil lair the hero and his intrepid band of followers (if needed) comes to the control room. Lex, of course is waiting inside, and every one else fights his minions. Lex, leads our hero along narrow passages,needless sharp cliffs, and other traps where he has prepared for the final confrontation. Either that, or some stupid complex torture chamber. Lets **MacGyver** that. Lex and hero guy end up using swords because Lex wants to kill him slowly. Through some surprise or whatever the hero ends up winning.(he stumbles, his Mom's name is Martha, hero talks him down, or any other movie trope.) --- ## If desired you can force intrepid hero to hack Lex's computer, and any other shenanigans you wish ## Alternative he can just push the "big red button". The flood gates open, extinguishing the volcano. The nano clouds are re programmed,and start purifying the air and allowing light back into the world. --- 2nd alternative: The hero has to rally a bunch of people who really hate Lex to divert a river, or cause an avalanche of snow, or some other way of putting it out. Additionally, since the nano clouds are swarm controlled you can force the hero into all sorts of different hacking,bribing situations to your hearts content to break the encryption, and steal control of the swarm and purify the air. --- Maybe the whole sky is one big nano cloud, and there's no volcano at all. Maybe Lex disguised the nano cloud as pollution from Lex Corp's factories until it was too dense for any one to get rid of. Space balls the password is "12345" no "Lex12345" hahahaha, maybe not "!Evil!Bad!Guy!12345:(muhahahaha" more secure I have read darkness increases crime as its easier for criminals to operate unseen. [Answer] In the mirror world, an environmental or genetic factor damages the third type of photoreceptor present in people's eyes, which are little known/understood even today in this world. [New research shows](https://www.npr.org/sections/health-shots/2018/12/21/678342879/scientists-find-a-brain-circuit-that-could-explain-seasonal-depression) that in addition to rods and cones, the eye has a third type of photoreceptor which is connected to mood. When these detect less light, e.g. because it's winter and days are shorter, the result can be a more dark mood. If the denizens of the mirror world all took a journey to that world similar to your hero's, something about that journey could have damaged these photoreceptors. If they started out there, something about the common environment in the mirror world could be what causes the damage. For example, a common environmental cause might be a particularly dazzling flash of light, or longer-term exposure to a particular wavelength of light we don't consciously register. That light could have come in a flash, like from the detonation of a nuclear or electromagnetic pulse weapon (or a flash on the journey to this world). It could have come from a solar storm that hit the planet. It could have come from a popular technology, like CRT or plasma or OLED televisions or early-generation smartphone screens, etc. It's not at all hard to imagine that people adopt technology when the effects of that technology are incompletely known and unknowingly damage something they don't understand about how their bodies work, with delayed follow-on effects that are hard to definitively connect back to the actual source. Depending on how bad/smart the Big Bad Evil Guy is, he could be the one who developed that technology or promoted its adoption, *fully knowing* about the effect. To revert this at the end of the story, you could try an "enlightened population" route where people know about the effects and stop using the tech (e.g. Thalidomide) or have a newer better tech come out that by coincidence doesn't produce the ill effect (e.g. cathode ray tube displays, with their high pitched buzz), and permit natural healing. The enlightenment option could come as a result of defeating the Big Bad Evil Guy and uncovering his documentation about the effect and plans for maximizing it. Or, have the Big Bad Evil Guy defeated as an almost coincidental side effect of the new tech disruption. Because he's pushing his tech for other purposes, he'll [refuse to adapt](https://en.wikipedia.org/wiki/The_Innovator%27s_Dilemma) and double down on a failing investment, pushing himself into bankruptcy and damaging/destroying at least some of his own capacities for other evils. The issue could also come from a virus or illness that is highly contagious (e.g. pink-eye) but otherwise relatively asymptomatic (or leaves sufferers with a very low level of chronic pain, like a dull headache), and because it's extremely common it's considered normal, so the negative consequences are underappreciated and there's very little research done into causes or fixes, as with many other common issues. To revert this at the end of the story, develop a cure. If you want the Big Bad Evil Guy to have agency, CRISPR and similar gene editing techniques could have been used to release a virus or bacteria with the explicit intent of spreading dark moods and making the world more evil. He might have taken a lesson/template from [*Toxoplasma gondii*](https://en.wikipedia.org/wiki/Toxoplasma_gondii), which messes with host animals' brains to promote self-destructive behavior that can help get the parasite into its preferred host (cats). It could be a genetic change, or an epigenetic change, passed on from one generation to another. That one's harder to overcome at the end of the story, but some tech could be developed to help people see better, just like we can currently develop tech to let people see in normally invisible parts of the electromagnetic spectrum. Whatever the issue is could affect rods and cones too, to make things more gray and less colorful, but that's not strictly necessary for the main effect. To the extent that it's understood, you could even put this story in the present world. Maybe the main difference between our current society and the "Garden of Eden" was a genetic change in our visual system that prevents us from seeing the force of love/God or the existence of abundance, permitting scarcity narratives that divide and cause people to do all sorts of nasty things to each other. Any sufficiently advanced technology is indistinguishable from magic, and advanced technology is (often) based on advanced understanding. There's a lot we don't understand (some of which, we are just starting to understand) about the forces that govern our universe and how we as humans interact with them. Touching on some of these themes could make the story more interesting, depending on the overall goals and ideas you have for your story. Good luck! [Answer] How about pollution/smog? The meaner people might not have cared about air pollution laws, like in some asian cities: [](https://i.stack.imgur.com/xAgTk.png) Or Evil Guys industrial empire produces it. Or there could be natural causes, or natural conditions that make smog much more likely to form. ]

[Question] [ If every star and planetary system and blackhole—all mass (not sure whether to include dark matter or not) except what directly makes up our solar system—in the Universe except the Sun were wiped from existence (not explosively destroyed) would the existence of life on Earth be immediately (~within a few years of us noticing they'd disappeared) threatened? [Answer] No. Life on Earth and our solar system in general would not be harmed by this sudden universal destruction. Everything outside of the Solar system affects us via electromagnetic radiation, gravity, and "matter transfer". The EM radiation flux is too weak to really do much, other than marvel at through telescopes. With the rest of the universe gone we'd actually be safe from the potential of a nearby Gamma Ray Burst. The gravitational influence of our stellar neighborhood is far too weak to majorly change anything like planetary orbits. Same goes for the galactic center we orbit around. So probably no kicking asteroids or comets on a collision course with us. The final chance for an influence is through "matter exchange". There's no longer the chance for big rocks to come sailing through our solar system from beyond, so again we're safer here. No more worrying about rogue black holes or ejected exo-planets disrupting local orbits. We do lose [Cosmic Rays](https://en.wikipedia.org/wiki/Cosmic_ray#Effects) in this ordeal, though. Cosmic rays produce most of the Carbon 14 we could use for radio-carbon dating, but we've already messed that balance up through weapons testing. I don't know enough about biochemistry to attest to the importance of the isotopes produced by cosmic rays, but at a casual glace and google they don't seem to be terribly impactful or necessary. So without cosmic rays our background radiation levels would decrease and electronics would become slightly more reliable. Once again we are made even safer. Ultimately we will perish as a species when the sun goes through its stellar life-cycle and the solar system (now entire universe) cools... but that'll probably happen anyways on a longer time scale if the [Heat Death of the Universe](https://en.wikipedia.org/wiki/Heat_death_of_the_universe) holds true. [Answer] **We wouldn't even notice for several years.** The closest star to us (aside from the Sun) is Alpha Centauri, which is just over 4 light-years away. That means that whenever we look at Alpha Centauri from earth, we are seeing light that left the star over 4 years ago. If Alpha Centauri were extinguished today, we wouldn't even realize it until 4 years from now! For most stars, it will take decades, centuries, or longer before we see them wink out of existence - whatever effect that might have, it will definitely not be "immediate". [Answer] ### Frame challenge: It was not them who disappeared, it was us. What is more plausible (but still a twist in the laws of physics), that an entire universe vanished or that a single solar system in the outer rim of a galaxy vanished? (Occam's razor) It was not the Sol System that remained, it was the Sol System that was shifted to another, empty, reality. Maybe a huge wormhole opening passed over us, or we were inentionally **dislodged to build a hyperspace lane**. This theory has the added bonus of zero wait to witness the entire starry sky become pitch black. It is like the anecdote when a storm blocked all forms of travel across the English Channel and the british newspapers headlined: > > Storm isolates the continent. > > > --- With that in mind, we can answer the question: > > would the existence of life on Earth be immediately (~within a few years of us noticing they'd disappeared) threatened? > > > **A:** Probably no, if the pocket dimension we were sent to is stable. Should be, shouldn't it? Please be. [Answer] There would be basically no effect. First off, even gravitation is governed by the speed of light, so we would not notice for thousands of years (well, we'd notice Alpha Centauri after about 4 years). By the currently understood laws of physics, no information about a remote object can travel faster than the speed of light. We theoretically will see some hilariously small quantum fluctuation differences, but we wouldn't actually be able to prove anything from them until information traveling at the speed of light catches up. However, this can be taken in another way. Since you're looking at gravitation, we can compute the effects. Distance is a *major* player in this equation, so lets pick the closest star, Alpha Centauri. It is 4.3 light years away. that's $4.132\cdot 10^{16}\ \mathrm m$ away. Its mass is roughly 0.123 solar masses, or $2.446\cdot 10^{29}\ \mathrm{kg}$. Throwing them into $a\_\mathrm{grav}=\frac{GM}{r^2}$ we get an acceleration of $9.5\cdot10^{-15}\ \frac{\mathrm m}{\mathrm s^2}$ ($G$ is $6.674\cdot10^{−11}\ \frac{\mathrm{m}^3}{\mathrm{kg\cdot s^2}}$, if you want to run those numbers). So while the earth is pulling on us at $9.8\ \frac{\mathrm m}{\mathrm s^2}$, A. centauri is pulling with a whopping $0.0000000000000095\ \frac{\mathrm m}{\mathrm s^2}$ Now note the $r$-squared term. That's why the gravity of Earth is such a big deal and A. centauri, as big as it is, isn't a big deal. The gravitational effects of far away objects is pretty negligible. If there was something that kept emitting light where A. centauri was, we wouldn't even detect it. In the long run, these small things would matter. If the galaxy vanished, we would stop orbiting the galaxy. Our orbit around the center of the galaxy has a period of about 200 million years, so you'd start to notice the loss of that mass after a million or so years. The bigger issue would be the worldbuilding problem. *Something* just broke all of our known laws of physics, and did it in a blink of an eye. What was that thing? How does it work? **And is it still hungry?** These are important questions for the denizens of the last surviving solar system in the universe. [Answer] It depends *how* the stars go out. If every other star somehow went supernova, we would be fine for about 4 years. Then, the radiation from Alpha Centauri would hit us, most likely killing everyone on the planet. The safe distance for a supernova is about 100 light years. On the other hand, if the stars just winked out quietly as you suggested, we'd pretty much be fine, as other answers have stated. As mentioned in the comments, it would seem that the closest star *capable of going supernova* is the IK Pegasi binary system, 150 light years from Earth. The closer stars just aren't big enough to blow up in the same way. Looks like we're safe for now! [Answer] > > within a few years of us noticing they'd disappeared > > > Absolutely. Of the few thousand we see in the night sky the internet suggests to me that there are only 76 stars within 100LY of us. At the point where those have all been seen to have gone out, you'll be dead. Climate change may have done for large parts of human coastal construction. There are a few hundred billion stars in the Milky Way, which is around 150,000 LY across, in that time we should have had at least another ice age. It's the entire duration of human history. The nearest major galaxy to us is Andromeda, it's around 2.5 million LY away. That's over 10 times as long as humans have existed before the light gets to us. 2.5 Million years before we know anything is up with it. So yes, by the time we notice the rest of the universe is gone, all life on Earth will be long gone as well. [Answer] We might individually die in the upsurge of doubt, despair and religious-inspired unrest, since this would pretty much constitute proof of the existence of some kind of divine being who is not consistent with any existing religion. Greg Egan’s novel *Quarantine* is about a similar scenario, although it plays out faster since the stars all disappear over a matter of minutes rather than having to wait thousands of years for the speed of light. But there would be no significant physical effect on the solar system — all the problems would be psychological. [Answer] Nothing would happen. Solar system is self-sufficient enough. It would be only little influenced if rest of universe somehow ceased to exist. That said, anything that would preserve our little bubble intact and simultaneously destroyed everything else, is almost certainly unimaginable to science. [Answer] If the [Mach's principle](https://en.wikipedia.org/wiki/Mach%27s_principle) is actually valid (and it cannot be quite ruled out), then local properties of matter (inertia in the "original" formulation) depend on the distribution of mass in the rest of the universe. The exact effects depend on the details, but at the very least the planetary orbits will be disturbed, if not destroyed outright. But it is likely the interactions are still governed by the speed of light limit, so apart from the stars going gradually out we won't even notice in billions of years. Unless the deity responsible for this timed the disappearance in such a way that its light cone converges on us *right now*. [Answer] Given your unlikely scenario, it **IS** possible that our star **IS** the ONLY star in the universe **RIGHT NOW** since the light from distant stars takes so much time to reach us. If the closest star is several light years *(the distance light travels in a year)* away, we may not find out for several years. Distant stars have near-zero impact on us, with even a close supernova or cataclysmic stellar death having almost no effect on us. THAT is how big the universe is. It is VERY BIG and the gaps between stars are large! [Answer] The only concern I would have is that the back-pressure from the Solar wind at the Heliopause would be removed, as there wouldn't be other star's matter to contend with. This would eventually speed up the Solar wind around Earth, which might be enough to rip off our atmosphere. Note that I have no specific evidence of this. [Edit] NASA found that some of the Solar wind particles bounce backwards, slowing down the Solar wind directly. This was detected on Earth: "once the solar wind hits the termination shock it creates a pressure wave. That pressure wave continues on to the edge of the heliosphere and partially rebounds backwards, forcing particles to collide within the (now much denser) heliosheath environment that it just passed through. That’s where the energetic neutral atoms that IBEX observed were born." <https://www.nasa.gov/feature/goddard/2018/as-solar-wind-blows-our-heliosphere-balloons> [Answer] Others have posited a sudden teleportation of our solar system to a pocket dimension. However, teleporting our solar system to the middle of the Bootes void has one less objection (i.e., we know that the Bootes void actually exists, whereas pocket dimensions are still the stuff of conjecture and fiction), and would have the same effect. As I understand it, if our solar system were in the middle of the Bootes void, we would not have learned that other stars even existed until modern times, when telescopes were invented. ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 4 years ago. [Improve this question](/posts/152387/edit) Welcome to C.A.L.V.E.S. Consultants And Lawyers for the Villainous Evil and Stupid Your assignment is to discover the real identity of the masked vigilante commonly known as Batman aka The Caped Crusader aka The Dark Knight. The defender of Gotham City, which bears a strong resemblance to New York City. If history is any guide then I doubt that things will go well for our client once he finds out who Batman is, but that is not our issue. **Parameters:** 1. Batman can't know that anyone knows his identity. The client was very specific on that. 2. Limit the risk of discovery or physical damage to the firm, and its employees. I know that crazy man in clown makeup has tried the "take hostages and demand Batman reveal his secret identity" thing dozens of times and he always get beaten up. Let's try for something stealthier and safer. **Assets:** * Lots of cash, several million dollars * A few dozen employees some of them ex military and ex CIA employees, and some of them barely able to use a copy machine, yes I'm talking about you George. * No super weapons, no super powers, no super serum, no nanomachines; just what you could buy or build today. Oh and no peanuts; George is allergic. **Best Plans:** * Satisfy the parameters. * Have an estimate of how long it will take to identify Batman. * Take the least time to execute. The employee with the best plan will be sent on a company sponsored trip to Hawaii. Everyone else will be sent on a trip to a much warmer, more underground, and more seismically active part of Hawaii. Don't look at me; it was in the contract. [Answer] **Street Camera Surveillance** (really, it can be that simple) So you have your CIA techs and the like and assuming they still have access to the government network of video taken from the street cameras set up in Gotham to prevent crime (let's face it; if you're going to put street cameras up in ANY US city, Gotham has to be a good candidate) this might not even cost you very much. If there are no cameras, then spend the money you have putting some up all over Gotham, and then start some rumbles in the seedier areas in full view of the cameras and wait for him to show up. What you're after as as many shots of his face as you can get from different angles. Plus, you want photos of everyone else in the town you can get. The reason for this is quite simple; partial facial recognition. Scientists have already shown that they can get a facial recognition hit [off only half a face](https://www.sciencedaily.com/releases/2019/05/190501114602.htm). This is good news, because Batman only covers half his face. That means, you're building a set of facial recognition parameters off the normal cameras around town, against which you can match the half a face you get wherever he shows up. All you need is to match him against a full face, and then matching him against an identity is a lot easier, especially if he turns out to be someone in the press, like perhaps even someone high up in Wayne Enterprises. You might even have a chance to see if a google images or Facebook image search comes up with a match once you have the full face to work with. In either case, your hero doesn't know he's being surveilled which means in turn that you can make the match without his knowledge. No magic, dark tech or peanuts used in the effort either. So, it turns out you can not only save the world with math, but you can pretty much break it too if you want to. [Answer] Let him be exposed to more UV light. Like secretly replacing all Gotham city street light bulbs with ones with higher UV radiation. Then... [](https://i.stack.imgur.com/3w2OV.png) Credit to whoever created this meme pic that I found via google search. [Answer] Believe it or not, the equipment batman has is fairly expensive and no man would be able to amass such a collection of weapons, gadgets and vehicles without being tied to Wayne Enterprises. The Batmobile, the flying helicopter thing. The gadets? All stolen from Wayne Enterprises. So we Audit the company. And what do we find. A suspiciously large amount of ceramic pieces purchased by Wayne Enterprises. Unfortunately, a thorough examination show that the ceramics have mysteriously disappeared and have no tied project to it. The lack of an approval process means that someone high up in the company approved these purchases. We also Audited all the construction companies in Gotham city. Turns out there was extensive work done under the Wayne Manor. Renovating an old cave. Put two and two together. Boom. Batman is Alfred. Alternatively... Host a Gala for the Top people in Gotham with the money to pull off Batman. Cause a crime and do a head count to see who is missing. Batman's equipment is very expensive, so no ordinary Joe can get it. If no one is missing then you have an issue, but fortunately, someone is. [Answer] 1. Quietly pass the word to the Henchpeoples' Association to collect blood spatters or cloth or anything BM drops. 2. Wait till he gets shot or otherwise injured. 3. Collect DNA sample. 4. Pass it on to Ancestry.com or similar. 5. Now you know who he's related to, so who in that tree is still alive and in Gotham? [Answer] **Use a brainwashed orphan** Surveillance of this individual 'Batman' has indicated that he has a tendency to recruit and use savvy crime-fighting orphans to his cause (see, *Robin, Red Robin, Red Hood, Nightwing, Spoiler, Batgirl, Orphan, Oracle, Bluebird*) and possibly develops a strong emotional attachment to these wards (see *A Death in the Family* incident, cross referance with *Joker, Red Hood, Lazarus Pits*). It is this analyst's belief that a young child can be kidnapped off the streets and altered through a quick training program (augmentation is recommended) then brainwashed. Once that is done, he can be deployed to a rough part of town to fight crime until he gets the attention of this 'Batman'. NOTE: Under no circumstance is this orphan to be approached after he is trained, and the training/augmentation must look as organic as possible. Individual Batman has repeatedly shown to posses genius-level intellect and may be the World's Greatest Detective. The flaw in the plan is the time of execution, though obviously it could be sped up if we use a pretrained initiate from the C.A.L.V.E.S bodyguard program, or call upon the League of Assassins (see *Ra'as al Ghul payment plan*) though we may have to exchange some of the intern to them for training practice. (They would understand.) Once the training is done, it should take no more than a month for subject to be recruited, at which case we'll arrange a chemical plant break-in to pickup the agent for debriefing and elimination. This last step is important, because should the orphan ever break the brainwashing, it is highly likely he'll lead Batman to us and / or kill us all. [Answer] Easy peasy. Batman is a spender. He goes around using his Bat-Credit Card.  I am not kidding. This is canon in the comics ([Detective Comics #511, February 1982](https://i.stack.imgur.com/pawrW.jpg)), and has been shown [in the movies as well thanks to Joel Schumacher and George Clooney](https://batman.fandom.com/wiki/Bat-Credit_Card). All you need to do is follow the money. This involves nothing as complicated as audits - just follow the mailman with the monthly bills, see where he delivers. The batcave location is secret, so the bills go to the Wayne Manor. There is only one person rich enough to be bankrolling the caped crusader, so either Batman is Bruce Wayne or his secret lover. Five seconds of comparing chins in photographs will tell you which one is true. That, or Bruce's secret lover is his own twin brother and now you cannot unthink that. If Gotham City's richest tycoon didn't want to have his secret identity revealed, he should have taken a page from Kal El and wear glasses instead of a mask. [Answer] Get mugged. It has been noticed that Batman seems slightly more forgiving of a certain type of criminal, and slightly more attentive when recuing a certain type of citizen. Typically female, 20-40 years old, attractive, and intelligent. So, we find one of our ex-CIA operatives who matches those requirements, and send her to the seedier end of town during the Batman's normal patrol times, armed with a special can of pepper spray for self defence. When accosted by criminals, she can defend herself lightly with the spray. When the Batman rescues her, she can 'accidentally' blast him with the *other* feature of the can - a blend of Pepper Spray and SmartWater - then apologise profusely. We can then send out crews to film around Gotham using Stereo Cameras on some pretext or other. One lens is equipped with a filter that only allows UV light through, and will detect the SmartWater on the Batman's face in his civilian identity. The other, unfiltered, camera will record his face. This can then be put through facial recognition software. (Depending on the... training and enthusiasm... of our initial operative, the film crews may prove unnecessary - outfit her an apartment with cameras, just in case.) [Answer] I hate to be boring about this but **track the Batmobile.** Get a number of high speed drones (possibly a large number) that can track the Batmobile through the streets. If you can't get ones that fly at Batmobile speeds, have loads of them scattered through town and the surrounding area. Pretty soon you are going to spot the Batmobile going into its secret lair. If you don't then set up another net of drone next time, centred on the direction you last saw it going in. Batman may be able to lead you astray a few times, but not every time. Once you've found the Batmobile's lair Batman's lair can't be far away. Maybe not true in the general case, but in this case it is. [Answer] # Profiling only take one "not that good" cop to make a profile for Batman : * He doesn't really like crimes. To the point of putting his life on the line for people being robbed or weapon trafficking. * He would rather work alone. With his tendency to let Gordon standing in place, and getting his own hand into the matter, he is someone who spent a lot of time alone and don't want anybody to back him up (by interrogating his former opponents, you will learn that he is always bothered by his partners) * He has access to expensive tech and R&D, and can get info on the police network. So he is either sponsored heavily (not likely because working alone) or a rich eccentric man, with either high hacking skills or easy access to the police tech. * He is obsessed with bats, calling everything his bat-stuff, and probably live in a cave, upside down, with a strong humidity smell that won't go off even after showers. Probably eating only fruits and insects, too. * He can fight. So he has 2 arms, 2 legs, and a strong build * He only care about Gotham # Searching So you are searching Gotham for strong men that smells like humidity and diarrhea (fruits exclusive diets...), with financial back up and close to police tech. Just audit the city corporations by using some corrupt city organization linked to it, with an heavy eye one sanitary condition and prototype and tech leaks. You will see that Wayne enterprise is hiding stuff. you make a list of the able bodied men high enough on the chain of command. Then send some hobos slap the potential suspects in the face when they get out off work. The ones sending your guys flying are potential batmen/batmans. You have their agenda from the audit. create some commotion when they are at a public event. the one staying in the toilet while the batmobile went wild in the city is Batman, Or should really stop watching karate lessons in his cave eating dorritos. # ressources all it took is some corrupt city workers, which are pretty cheap in Gotham. your average corrupt cop knows a lot about batman, and will tell you the full info for a few hundreds. it's public anyway, except the part where he listen to the police coms. Setting up the corporations for an audit will take the time you need to infiltrate one of the city contracting organization (the one the cops directed you on) which can take a few decently skilled men, and maybe a few months? The audit company will of course be yours from the start, so you need to set up that too. It will take some money to make it "not that suspicious", depending on how well Gotham corporations try to dodge audits.. The audit will take a month or two to get the basic financial info and sanitary inspection. slapping hobos are dirt cheap in Gotham. getting your cop to light the bat signal during a public event won't be hard. or just place a bomb in a bank. Pouf, you've got your rich schizophrenic martial artist in the spotlight. [Answer] CALVES Softworks Inc. now introducing: ***Batman with Friends!*** Nobody knows who Batman is... Could it be one of your friends? In this fun and social mobile game, you can challenge your friends to guess which one of you is most likely Batman! If you couldn't find your Batman, don't worry! *Batman with Friends!* runs in regular monthly seasons. After every seasons, the best players receive special prizes, and the cycle begins anew! Who will be this month's Batman? * Match "alibis" to Batman sightings! * Collect other evidence! * Compare your theories with your friends' theories. * Deduce which one of your friends was the Batman this month! * Automatically import your friends from Facebook, Twitter, Contacts, and more! * Bat Detective (premium cash shop): Power your search with amazing articles and detective tips from our writers! Beat the news cycle with secret Batman sightings! Report hottest sightings to gain free BatGold! --- I reckon development could be done with a few mil. Use the rest for marketing, setting up prizes for top players, and whatever else you need. In every season, players match Batman sightings to "alibis" - friends they've seen around at the same time as the sighting. Friends who don't actually play the game can still be "matched" - bit of a GDPR nightmare, good thing we're not in Europe. After a month the game resets - a month is nowhere near enough data to conclusive single out any friends so some guessing is required (and we nicely sidestep the disappointing possibility of finding it is impossible for any of your friends to be Batman). But of course, all that data goes to your datacenter, stored forever... To improve the *customer experience* and *make the game more fun*. A basic network analysis would already narrow it down to a small group of people with no friends whatsoever (üò¢), and Batman. Now you can just go and watch the former group and it shouldn't be hard to figure out most *couldn't* be Batman (age, gender, physical condition, easily generate an alibi by tailing them during a Batman sighting). Or you could do a slightly more sophisticated analysis, and probably narrow it all down to just Batman. Not the fastest approach, but on the bright side - when you're done, you'll be generating some nice income for your trouble. [Answer] There were three philosophers on a train and they saw a field of black sheep, it was the first time any of them had ever seen a sheep. The first says, from this I deduce that all sheep are black. The second says, no, from this you can say *some* sheep are black. The third says, no, all you can say is that at least one sheep is black on at least one side. # The Batman Never have two Batmen been seen in the same place. Nor has a Batman ever been seen in two places at the same time. That doesn't mean there's only one Batman, there is at least one Batman, at least some of the time. # Follow the equipment There's some fancy stuff being used out there. Someone has to be building and maintaining it. Find out who it is. Audit them. # Follow the money You should now have information on where the money is coming from, someone is paying the bills, someone is developing the technology. It's tax audit time again. Ideally you're looking for a specific individual who's actually signing off the cheques on all this stuff. # Follow the people You now have a selection of people who possibly know who the Batman is. At least one of them may actually be a Batman, for now we're still accepting that there may be more than one. Invite them all to a party, charity event, or other worthy occasion. Set tails on any who don't turn up. Commit a noisy crime somewhere in the city and monitor who goes missing. Rinse and repeat. Every time you do this you'll narrow down your list of potential batmen. The elderly, overweight, short, or disabled can probably be written off quickly as actual batmen, but they may have useful information or be communicating with someone. **Always accept that there could be more than one Batman.** # Cost Some administrative, you'll need someone working in the tax office in a senior enough position to call an audit on a major company, organisation, or respectable individual. Hosting, a social event of the necessary type and scale will be expensive as it's likely to include a lot of the high and mighty of society. # Time The close of one tax year, one social season, consecutively. --- # Things to note Generally, finding out who batman is hasn't proved all that hard. Any worthy villain has managed it if they chose to. But being the villain to Batman is a lot more interesting than being the villain to Bruce Wayne. Hence even the Joker was never overly bothered even though he knew. Batman is the person they wanted to challenge, not some effete billionaire. [Answer] **Hack him** I know what you're thinking, any old exploit isn't going to do. You're going to need to amass quite the hoard of zero-day attacks. His gadgets are running a lot of software, and any software developer will be able to tell you that making software takes a *long* time. Time batman doesn't have. He's going to use publicly available APIs and libraries, or those libraries will use libraries. Software these days is like an onion or ogre with how many libraries are layered on top of one another to make commonly used systems. You embed some particularly cleverly hidden backdoor deep into very complicated, publicly available library for embedded systems. Those are the kind you're more likely to see hand-hedge gizmos running on. See, batman won't be too worried about being targeted by these backdoors if they lay dormant for a long time. After all, when they're made now-a-days they tend to get used pretty quickly. Malicious people like such want to get money out of their time and effort now, and not later. You're smarter than that, though. With several dozen embedded systems libraries, heralded by everyone in the world of tiny devices for their usefulness, you flip the switch. You have a botnet in the blink of an eye, and with this botnet you have root access to most of the world's IoT devices. The same type of network that dizzied a significant portion of the internet a few years ago. Only you don't use that botnet to DDoS. Oh no. you use your root access to look at the contents of files on the devices. Do you really think that batman isn't going to use himself in a variable or two? You may have the stray developer with a sense of humor and a batman.exe, but I bet you'll find a pattern. As batman has cases and cases of batarangs with your library running on them, so too will you find identical copies of the same device, all with a copy of the word "batman" or "bat\*" in variable names originating from the same ip by the dozen. Now the question is, do you think batman keeps his personal life and crime-fighting life separate on his personal computer? Will his browser history constantly clear itself? That would get pretty old after a few years of remembering the same set of passwords for your bank and company websites over and over and over again. Once he is digitally compromised, you unleash a horde of information-gathering subroutines through the backdoor to uncover any nook or cranny for breadcrumbs to link batman to his true identity. **alternatively** Just pay off someone from the NSA, I bet they already know. [Answer] There was a Batman novel I read years ago, the title of which I forget, where a contract killer used the following series of criteria to narrow down the suspect list: * Male, white, mid 30s or so (given how long Batman had been active in the novel) * Extremely good physical condition * Extensive resources, probably due to personal wealth * Deep ties to Gotham * Contacts with very high end research and development Using the process of elimination, he narrowed it down to Bruce Wayne and another Gotham billionaire (who would often jokingly refuse to deny he was Batman) and decided to assassinate them both to be sure. The same process would work for your lawyers. Once they had a list of suspects, Bruce Wayne would likely be on it. Then they could use more analysis: * Bruce Wayne becomes a foster parent to an orphaned circus acrobat. Robin shows up not long thereafter. * Bruce Wayne has suffered personal loss due to crime, giving him motive. * When Batman is out of Gotham and seen in another location, Bruce Wayne is frequently known to be in that same area. * In times when Batman is observed, Bruce Wayne can often not be accounted for by anyone outside his inner circle. ...and so on. Really, it wouldn't be hard to identify him, and it would just be using publicly available records and datamining, so no high-tech doodads necessary and no interaction required at all, so no risk. If you want confirmation, through cutouts hire some goons to, say, rob an event where Bruce Wayne is and have some of your operatives (the really, really good ones) be guests there. Their only job is act completely normal and observe if, at some point, Bruce Wayne vanishes and Batman shows up. They don't go looking for him; if someone loses sight of him, they just note the time and carry on what they were doing. The only technology required is their watches. No trying to film him (no more than any other citizen with a cellphone), don't bother trying to keep eyes on him at all times--making it obvious to someone like Batman he's being observed--because all you want to know is when he's somewhere, not what he's doing. Afterwards you correlate their reports, which should give you a timeline; if no one has seen him over a period of time when Batman has been there, and, even better, if he reappears after Batman has left, well, that's getting pretty close to damning evidence. Again, quiet, minimal risk. Now, the problem comes in because this only works if you're in a fairly mundane version of the DC Universe. It works in the Nolan Verse, and so far in the DCEU, because generally speaking, you can be fairly confident in your ID. In the DCAU or most of the DC comics, you've got a problem. Take the basic physical description; there are so many magical and alien shapeshifters running around and advanced disguise technologies available, you can't even be sure that "white male, good physical condition, mid-30s" is even the truth; Batman could be a black female in her 60s wearing a highly advanced exoskeleton. [Answer] Just ask that question on StackExchange with a 200 points bounty. Guaranteed answer within 48 hours. Other than that - homeless people network. For most people, they are the invisible part of city - a part they ignore the existence of, hence why they do not keep their guard up around them. Make the homeless track Batman down. 1. Tell the homeless to follow the Batmobile - they are not as fast, but equip them with walkie talkies and you can't escape them. 2. After a couple of days you will have the most likely location where Batmobile gets parked. 3. Make them watch who goes in and out of the building. 4. Give a few more days - you have a list of likely Batman candidates 5. Since there probably won't be many - the one most fitting Batman's build will very likely be him. All that at the cost of few boxes of cheapest booze and walkie talkies. [Answer] [Complete re-write, based on Chronocidal's comment below and own thoughts] Batman is "World's Greatest Detective". YOu will not beat him using regular detective methods, like facial recognition, DNA samples, tracking gadgets or money. B/c he can anticipate and prevent those methods. Instead, you have to work on psychology, where he is not nearly as skilled. * Profiling (ncalep's answer began on that path, but got sidetracked). We have a male of prime age, with a personal reason to hate criminals and guns. A traumatic event in the past is very likely. * Exploit his personal relationships. Plant either a "Robin" like Halfthawed above has suggested, or a "Catwoman" since our hero has a soft spot for athletic females. To accelerate the process, have this planted agent be injured with something that only Batman's advanced technology can heal, or create an urgent need to hide that person. [Answer] You have ex military and ex CIA contacts at your disposal, if Batman is having to respond rapidly to crime occurrences to beat police to the scene he must be taking a fairly direct route. This means he likely is not going out of his way to get to crime scenes avoiding traffic cameras, you can track his location in reverse by gaining access to the recorded footage, I imagine a bribe from the millions of dollars you have as an asset should make this easy enough. I can't say I'm the most studied on Batman's evasion tech if he can remotely disable cameras by proximity or some such but so long as the entire city's camera network isn't disabled you should be able to glean some information as to his whereabouts (where he responds from, where he returns to after, etc). Furthermore with your ex military contacts you could have a satellite over the city to survey from space in the case the city cameras are vulnerable to Batman's evasion measures. At this point we should have a list of suspected regions where Batman comes and goes from but haven't we don't know who Batman is, for this we place some undercover CIA contacts in the relative area of Batman's comings and goings. These undercover contacts will discreetly keep note of those in the area and when we discover Batman is active we consult teams around Batman's starting location and end location for any matches. [Answer] Many years ago the Gotham City cameras were contracted and sourced to Wayne Enterprises... hundreds of employees have already attempted to identify Batman and track his movements using this method. The the city contract for the cameras happens to be handled by Wayne Enterprises, but all cameras in the city have been infected by tech (provided by Cyborg of course) that loops a few seconds of buffered images when he is in optical range before the images ever enter the data stream. So a different plan was required. It is all about the surveillance tech, but it is not about trying to do facial recognition or anything else... instead it is a matter of identifying where the points of origin and identifying common patterns. Ultimately the solution will be **unknowingly** be solved by a handful of data scientists pouring over terabytes of data: tracking the migratory patterns of the osprey. There are several levels of subterfuge being used with multiple programs being setup with simple and altruistic goals. The equipment is actually a dense mesh network of free WiFi routers. A few extra bits of hardware allow the standard modems to record data from resistance and interference to generate a low dispersal radar system that can be used to track the birds. Of course Batman is aware of this system and has commissioned a digital deflector/reflector system in his suit that virtually eliminate 98.6% of the interference -- to the receivers he is nearly invisible. He cannot actually jam the equipment because every time he flies by a node, the network connection would drop... and we cannot interfere with people and their streaming services. Besides we know that Batman would support a public works project such as free WiFi for all. It is this micro radar mesh system that the data scientists use as their primary data source for tracking the osprey. The tools are all there, and all it takes is one brilliant computer scientist who is already doing work on the osprey project that makes a break through in identifying the unnatural static generated by Batman's cloaking suit; tweak the parameters and funnel the results into a secret database. Suddenly we have a full map of all of his movements over the past year like a jogger's workout map. Before what seemed like random movements starts to show a pattern of over a dozen entry points throughout the city. Additional routers were installed near these points to get higher resolution data. Then robberies were commissioned (fully expecting to fail) to start to anticipate his behavior (only an average of 46.4% accuracy but, wow... the team was excited). There seemed to be a higher percentage of origin near Wayne Manor and Wayne Enterprise subsidiaries and the team started focusing their efforts on those parts of town. All employees of Wayne Enterprise are tagged and tracked. Individuals are rated and systemically downgraded because of location data not matching the movements of Batman. Of course Batman knows about THIS program too, and is able to generate false positive data, but there is still margins of error while he is covering his tracks. Eventually the data scientist team fully in the know of tracking Batman are able to identify Bruce Wayne with an 62.7% degree of certainty that he is Batman putting him pretty much at the "top of the class". (It was much easier to identify who it was NOT then who it was). Results are in, and now it is time for the ops team to take over the operation. But before they could begin the operation... one extremely lucky bank robber was able to pull trigger the exploding radioactive dye in the pile of cash right in Batman's face. The dye is easily tracked by the WiFi network and before Bruce can leave town he is arrested as an accessory. [Answer] I'm thinking, if I get several million, then I'd be able to find a perfectly good tracker. Then I'd stage a mugging event of me or stage a one involving some kids with their helpless parents. Then either shoot a tracker from a hired help like Deadshot or similar good marksman, or If I was the victim, then I'll try to put tracker into Bat by myself. And also to the Bat mobile and/or any other bat-vehicle he/she may using. Then start tracking while simultaneously keeping track on wealthy people who may have connection to Batman. Targeting wealthy because the tech/gadgets that Bat is using are custom made and/or expensive. And also keep track on people who closely work with Batman like Commissioner Gordan. Then here comes the analysis part. Since I have buttload of money, I can hire even big team of analyzers right? If my client wants their silence, well, I have support from any villain they got right, so it'll be simple. Will let you know after I decide weather Clark Kent or James Gordon himself is the Batman. ]

[Question] [ In a lot of science-fiction stories, there are people who hibernate of sorts in cryosleep. Basically something like the person's body is stored in a container which is then chilled at really really low temperatures so that they can wake up at a much later date. Disregarding whether the person could have actually survived, why do they go to cryogenic sleep without clothes? In most scenes where a person wakes up from cryogenic sleep, they are depicted without clothing. Is this because the clothing could be destroyed by the extremely low temperatures or some other reason? If it can preserve a human body so that he/she can wake up at a later date, it should be possible to preserve clothing right? [Answer] Cryo sleep is a medical procedure. Most full-body medical procedures are performed on nude subjects, even today. Reasons are numerous: 1. In case of emergency, you need ready access to various parts of human body, and you need it now. 2. It's easier to control bedsores without clothing. 3. For long procedures, you need catheters in urethra, anus etc, so not much left to hide anyway. 4. Less things you need to keep sterile. 5. Probably many more I don't know... Now, for cryo, cooling rate and hardness of frozen fabric may be a factor, too. But given that full body anesthesia is routinely administered to naked subjects now, it's quite possible no one would even *consider* changing that. [Answer] The cooling rate, especially around the freezing point of water, needs to be controlled carefully in order to not cause damaging crystal growth. Wearing clothing makes the rate of cooling more unpredictable, so it introduces more risk. If any clothing is used, it will be special outfits whose isolation properties are well known and thoroughly tested. [Answer] Adding on Molot's answer, there are other reasons why clothing in crio-sleep would be bad: * In cryo-sleep, maybe the body is not completely frozen (just slowed down on bio functions by a XXX-fold factor) and can repair itself at a slower rate. Given the centuries/decades of sleep in some starship travels (see the first Alien movie), clothing would rot away. * The advanced society that has cryo-sleep (assuming society has evolved in all aspects, not just tech) has less need for modesty and are more comfortable with naked bodies (think star trek-ish). * They are naked in cryo-sleep, but only the vitals monitor are visible anyway, so no peeking. As an inconsequential part of the awakening process you can include ubiquous nanite / 3D printing of new clothes anyway, so why bother storing people clothed. [Answer] The main function of clothing is to hinder the flow of heat. The *last* thing you want to do when putting people into cryogenic sleep is to hinder the flow of heat. Quite the opposite: You want to have perfect control of the temperature on the skin. So, you say, why not put on some special clothing that conducts heat well? Well, the insulation effect is not just coming from the clothes material itself, it also comes from the air it encloses. When you enter the cryogenic tank with your special tank clothes, it is almost certain that somewhere there will be a pocket of air that's caught in the clothes and not driven out by the cryogenic fluid. And that will insulate you. OK, but what if you find a way to reliably get all air reliably moved out completely, so your suit is completely filled with cryogenic fluid? Well, the most efficient heat transport mechanism is convection, and that is what the cryogenic chambers will use as well. The clothes will prevent that convection to reach your skin, and therefore the cryogenic substance in between clothes and body itself will act as thermal insulation. Note that on normal use, also the air acts as insulation only because it is held by the clothes. Well, OK, so let's make an elastic metal body suit that's actually "vacuumed" directly onto the body, with absolutely nothing in between the suit and the skin. That should finally work, right? Well, probably. But I'd expect that experience to be so unpleasant that you'd *really* prefer being naked. [Answer] **Chafing** Similar but unrelated to bed-sored. Cold skin is more prone to chafing. Cryo-sleep is generally used for extremely long periods and unless there is close to no vibrations the wear on the skin over a prolonged period of time could be traumatic as if the body is comletely shut down it will be unable to repair the damage. This could be mittigated with specialist clothing, but the cheapest and simplest solution is no clothing. [Answer] A lot of well thought out answers so far. However, Cryo-sleep is pretty much entirely speculative at this point, so I strongly suspect that appeal to the present day audience is a more relevant factor than many others - especially when talking about movies or television. Let's face it, we all should realize that gratuitous nudity sells seats in theaters and having a reasonable basis for it helps to assuage many who might otherwise be grievously offended. Some points on which I find I have to comment: * nudity to avoid abrasion against clothing; if in cryo-sleep of almost any kind, it would be necessary to immobilize the body (or whatever part of the body that is retained) - particularly if traveling in free fall - or friction burns are likely to be the least damaging of the problems that could be expected to occur over a long period of time (being repeatedly bashed against the inside of the cryogenic container comes to mind). * vibration protection; as anyone knows who has moved furniture or other valuables strapped into a truck, protection - such as might be expected from padded and flexible materials (not everything freezes into rigidity at anything above 0 degrees Kelvin) - will actually help to protect against damage from vibration (especially against straps or other restraints). * saving of energy; some speculative fiction actually supposes that only the head needs to be preserved as the rest of the body can be reconstructed (the head is retained mostly to preserve memory - which is essential for identity) hence (if energy savings was important) most of the passengers on a long space voyage would be in relatively small chambers - saving a great deal more energy than simply discarding clothing (crew members might be stored intact, assuming there would be some delay in re-constructing their bodies). * an argument can easily be made that one can greatly reduce chafing as an issue by putting (whatever remains of the) bodies in tight fitting suits that can be magnetically manipulated as they could be kept in light-weight "magnetic bottles" largely eliminating many issues with chafing and bouncing around. * in at least some speculative fiction, cryo-sleeping travelers are not only clothed, but clothed in a suit capable of providing some protection from the consequences of destruction of both the cryo-sleep container and the surrounding vessel. [Answer] It would save fuel. Under the assumptions: That clothes can be manufactured in space from debris. Freezing bodies uses different equipment to maintaining, and defrosting. It would be worth only launching weight that you have to, so removing clothes for a large number of people would be a considerable save in fuel. [Answer] I don't have any specific (or even non-specific) links I can cite here, but another reason for this (beside the technology-based answers here) is that it's a plot device for the benefit of the audience in eliciting an emotional response. Awaking from cryogenic sleep can draw parallels with a re-birth. The audience would see (or read) of a gradual and somewhat traumatic wake up process, naked and covered in slime or fluid/membrane (i.e. amniotic fluid/sac). This provides more of a plot device than someone simply waking up. [Answer] Remembering that you asked this in the context of *movies*... it's because it gives a scientifically/medically plausible excuse to show as skin as possible of the good looking people that are usually hired for the roles. Beautiful bodies that are partially naked, or if the rating allows completely naked, sell movie tickets. [Answer] You would be wet when you awake, and it would be faster to warm you up when you get out the cryogenic bath, which is supposed not to be clean water. No need to take your clothes out at that moment, and no need to clean them or dry them off. Just like when you enter and get out of a swimming pool. I see it otherwise: why would you want to have your clothes on? [Answer] The style of clothing would rapidly become out of date making the person look ridiculous. Unless, like the Freezer Geezer, one leaves instructions to specifically ["alter my pants as fashion dictates"](https://frinkiac.com/caption/S09E17/256405) ]

[Question] [ *Thanks to the commenters in the [question sandbox](http://meta.worldbuilding.stackexchange.com/questions/635/sandbox-for-proposed-questions) for helping refine this question before posting.* --- In many vampire stories the vampires do not have a reflection in a mirror. This is generally not explained beyond simply being a supernatural phenomenon. Is there any plausible way for something to be visible directly but invisible in a mirror? I'm assuming this will have to be magic, as I am unaware of any way this could be possible physically. If there is a physical method I'd be very interested to hear about it, but what I'm expecting is ways to make the magical approach consistent and understandable. For instance, what about the vampire's shadow, and any objects the vampire may be carrying (and clothes for that matter). Even with magic as the explanation, there still seem to be opportunities for inconsistencies, or at least odd consequences. Imagine someone crouching to drink from a pool, and a vampire leaning over them. Will there be a shadow cast onto the water? Or will this person just see a shadow on the bank that abruptly stops at the water's edge? How can I design the rules so that they are in keeping with familiar vampire mythology, and still self-consistent when exploring consequences? [Answer] Alternative answer to keep the spirit of "mirrors as vampire detectors" for a very futuristic setting: In a high-tech world, mirrors could be obsolete and replaced with smart 3d screens which show a reflection of the environment. When such a screen displays a human, it identifies the person and projects some information about them around their reflection in form of floating text panels. Due to a quirk in the biometric recognition system, it doesn't recognize vampires as humans. So they might show in the mirror-screen, but the lack of information panels around them gives them away. The inability of vampires to trigger biometric sensors could also be used to transfer other common vampire weaknesses into a futuristic scenario. Like: * Being unable to enter a building unless being invited. Doors just won't open for them, so they always need to follow other people. However, when they are invited, the system registers them as a pet or robot which is welcome and the vampire can then enter on their own. * The inability to cross running water. All bridges over rivers are biometric checkpoints, so vampires can not pass them without being identified. Why only the bridges? The political debate of privacy vs. security ended in a compromise: The police can have biometric checkpoints, but only a very limited number per city and they must be visible. They of course place them in a way that they are impossible to avoid, which in a city like New York would be the bridges crossing the Hudson- and East-river. * Being unable to enter churches. When entering a church, the biometric system recognizes you and automatically takes a small tithe from your bank account (voluntary donations just no longer cover the running cost of churches). Vampires don't register, so they are denied entrance. Alternatively, the catholic church is still holding up the ancient tradition of fighting vampires and reprogrammed the biometric sensors at all churches to recognize them. When a vampire is detected at a church entrance, a team of vampire hunters is dispatched immediately. * Holy water. Replace with medical nanite solution. It might even be called *Holy Water™* when that is the brand name it is sold as. While the medical nanites are able to automatically detect and cure many ailments of a normal human, the nanites totally misinterpret the biosigns of a vampire and inadvertently cause severe harm to them. [Answer] When your world allows psychic powers (for which you can often find a pseudo-scientific explanation), you could say that vampires are actually completely invisible and their physical appearance is just a hallucination induced into the observers mind through telepathy. Whatever mechanism is responsible for causing this hallucination is not smart enough to take reflective surfaces into account. It might or might not also manage shadows. Any clothings or accessories which are part of the vampires projected self-image would not show up in a mirror, but anything they picked up from the environment would. When a vampire invites you as a drink to a drink, their cup would be a part of their projected self-image while only yours is real (try switching them around and see what happens). When vampires can control this effect consciously, it would also give them the ability to change their appearance at will or become invisible. Shape-shifting and invisibility are common abilities of vampires in many vampire stories. However, the end result would be that your vampires would be more like ghosts than like living corpses. [Answer] The original explanation was that mirrors reflected the soul, and since vampires didn't have a soul there was nothing to reflect. If you don't like that you can still do something similar by saying the magic is no in the vampire, but the mirror. Perhaps certain mirrors are specially enchanted as vampire-detectors. Or perhaps it's simply a basic principle of magic that mirrors behave that way. Many worlds have varying degrees of [clap you hand if you believe](http://tvtropes.org/pmwiki/pmwiki.php/Main/ClapYourHandsIfYouBelieve) style magic, where magic works the way it does simply because everyone expects it to. If you go with a system like that then you can simply say that because people expect the mirrors to not reflect vampires that's how they work. If you only want mirrors to reveal vampires, and aren't committed to how they do it, one option I personally like is that the mirror still reflects the vampire, but it reflects a rotting and disgusting corpse. The vampire actually is undead and rotting, but he uses some form of magical suggestion to make you see a beautiful creatures (and presumptively not smell it); however, he can't use the same powers to keeping you from seeing his *real* reflection. This gives some fun potential to have someone be disgusted when they realize what the elegant or even sexy looking vampire they had been talking to *really* looks like; which helps bring a very viscerale sense of how wrong a vampire really is. *Insert joke at expense of twilight sparkling vampires here* You could take this one step further by suggesting that if a vampire is very skilled and focused he may be able to control your perception of his reflection in a mirror as well, but it's very difficult and he has to do it for each person who sees the reflection. Thus he may be able to occasionally appear in a reflection if he knows he has to walk in front of a mirror where someone may notice; however, he can't do the trick if caught by surprise, if he doesn't know of someone who might see the reflection (he fails to consciously control what that one sees), or there are many people that would see the reflection (he can't consciously screen his reflection for that many at once). Perhaps when he is doing this it is such a strain he may be distracted or act odd in a way that may give subtler hints that something is wrong. Due to the difficulty of doing this though most avoid mirrors entirely, for fear they will not be able to control what everyone sees, and perhaps only the oldest and most powerful vampires can do it (thus you can show a vampires strength by having him casually walk in front of a mirror). This option gives you a little more control over when a vampire's glamor may break, at any point one person may see his reflection is wrong while others don't etc. [Answer] Vampires are often weak to silver. It could be that that silvered glass mirrors actually destroy the reflection (and maybe even injure, weaken, or unsettle the vampire). In that case, the logical result is that vampires could be seen in other reflective surfaces, just not typical mirrors. [Answer] As has already been said, [mirrors show the soul, and vampires have no soul](https://worldbuilding.stackexchange.com/a/7123). It is perhaps worth mentioning that there are a whole bunch of superstitions which all play together here. Using all of them would make your magic system more self-consistent. * Breaking a mirror brings seven years of bad luck, because you have done damage to your soul. * When a person has died, a window must be left open overnight, to allow their soul to escape, and all mirrors in the house must be covered, lest you catch a glimpse of their soul passing by. * Vampires (and the unseelie, I believe) have no reflection, as they have no soul. * Photos capture a section of your soul too, of course. > > All across the multiverse there are backward tribes\* who distrust mirrors and images because, they say, they steal a bit of a person’s soul and there’s only so much of a person to go around. And the people who wear more clothes say this is just superstition, despite the fact that other people who spend their lives appearing in images of one sort or another seem to develop a thin quality. It’s put down to over-work and, tellingly, over-exposure instead. > > > \* Considered backward, that is, by people who wear more clothes than they do. > > > Terry Pratchett, *Witches Abroad*. > > > If you tie all these beliefs together, as they are tied together in our world, you can develop a complex, interlocking, and self-consistent system of magic. And, of course, it’s not too hard to add a few new elements to this system. * A smashed mirror can be a powerful object in itself. [The Snow Queen managed to capture Kay when a fleck of her mirror entered his eye and his heart](http://www.bbc.co.uk/programmes/b00pgyd8). * Mirrors can be used in magic to enhance a practitioner’s power: the reflections build up. Using one mirror is one type of magic; using two or more, causing infinite reflections, stretching your single soul out over infinite space, gives far more power but is damaging to you. (You may want to read *Witches Abroad* before adopting this idea, to make sure you don’t follow too closely in Terry Pratchett’s footsteps, because that’s where I’m getting the idea from.) * Mirrors in mirrors, [Spiegel im Spiegel](http://www.bbc.co.uk/programmes/b013q20t), are strange and powerful things generally, actually. * Mirrors as windows to other parts of the world, which a practitioner of magic can use to view other parts of the world, is a common device in fiction. Mirrors are objects of mystery. * What is a mirror? Is it any reflective surface, or is it specifically a flat surface, a flat glass surface with silver backing, or what? If mirror magic can be used to see out of another mirror, does the far mirror have to be specially prepared, or can you use ice in a puddle, flecks on a standing wave in a stream, a waxy leaf? * Culturally, if mirror magic is widely known and understood, what is the attitude to mirrors? Is the king’s throne surrounded by them, or are they not to be found in the palace? Do people use shaving mirrors? Maybe people *want* mirrors around, as vampire detectors. Maybe they want to avoid them, as things which would damage their own soul. Or perhaps, like Terry Pratchett’s witches, people are happy with mirrors but uncomfortable with the idea of getting between two of them (which might make that bit at the end of a visit to the barber a little awkward). * Photos too are suspect. We want them, of course, but not too many. People might have a limit on appearing in a maximum of one photo a month, or so. What would the attitude be to CCTV? If the footage is autodeleted after a week or so, as most CCTV footage is, is the damage to the soul restored? [Answer] Mirrors reflect the visible light which has bounced off of the objects in front of it. Perhaps a vampire absorbs all visible light that hits it but emits a currently unknown form of energy which excites the human optic nerve much like visible light does but is absorbed and not reflected by silver. If all of this were true, modern mirrors and standing water might show a vampire's reflection, while an old fashioned silver-backed mirror (and maybe a video camera) wouldn't. Putting a poetic spin on the light absorbing properties of a vampiric corpse, you might say that the hungry spirit which animates the flesh eats the light in the same way it drinks human blood. Some will say that I am cheating by including a "currently unknown form of energy" in my answer. "Currently unknown" is just a fancy way for saying "magic". To that unspoken complaint, I would offer that science is the study of change. It is an observational art. If vampires are the only earthly source of my "currently unknown" energy, and if no vampire has ever been observed in a scientific setting, then that energy could easily be missed by deductive science. Similarly, if my "currently unknown" energy did not play a major role in the cosmological creation story which is the almost exclusive focus of current inductive reasoning, it could easily have been overlooked by even the most intuitive investigators. "Unknown" is not synonymous with "Magic", despite the fact that both words equally challenge the arrogance of many scientists. [Answer] Really late answer, but I thought it was a fun one... Vampires do have reflections, and are always visible, as visibility is just a result of light bouncing off something and striking your eye. The myth of Vampires not having a reflection is actually a side effect of another of their abilities, namely Glamour. When you look at a vampire you are actually seeing the glamour that they have in place that they want you to see. This is why vampires are always beautiful and suave. They can also use this glamour to make you not see them. The problem with mirrors is that the glamour only works when you see it directly. If you look at a vampire in a mirror then the glamour won't affect you, and you'd see the vampires true form. And that is the real problem, for a vampires true form is so horrible that the human mind simply rejects it because to do otherwise would lead to madness. And so, as a coping mechanism, your mind just edits the reflection out. [Answer] Ah, I have thought about this myself in the past for a short story. Here's the best I could come up with, feel free to use it if you like it. Note that these are not exactly your old-fashioned vampires, but perhaps that's for the best, no? The setting will have immersive **[Augmented Reality](http://en.wikipedia.org/wiki/Augmented_reality)** (i.e. almost everyone is wearing Virtual Reality Lenses, almost all the time). My vampires were pieces of predatory software, taking on the appearance of friendly strangers, then later (after gathering more information) close friends and even family. The victim would think these projections were real. The goal was to trick the victim into revealing useful information which they could then sell in the underworld. If threatened or discovered, they could project a set of strongly customized visual and audio patterns that could incapacitate, induce illness, confusion, short-term memory loss or sometimes even kill the victim (think the equivalent of blinking lights for inducing seizures, but massively up-teched). PS: Only a careless or rushed vampire would forget to add their projection rendering onto reflective surfaces (as filtered by the VR lens), but depending on how far away the vampire's phylactery is, there might be a few dozen miliseconds' delay before the image is rendered and sent to the lens, enough to sometimes make them appear to blink a bit onto the mirror. The real objects would show no such reflections, of course. My character figures this when he accidentally takes out one of his lenses. PPS: I had my vampires smoothly avoid being touched, but you could get around that if you add haptic gloves and the like. [Answer] > > Is there any plausible way for something to be visible directly but invisible in a mirror? > > > You could say that there's an alternate universe, that's exactly like reality, except that there are no vampires in it; And mirrors have the curious property to reflect light from one alternate universe to the other. (You can hand wave towards [quantum superposition](http://en.wikipedia.org/wiki/Quantum_superposition) or [Schrödinger's Cat](http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat) to make this sound more physical. If there could be a dead cat and a living cat superimposed in Schrödinger's box, why couldn't there be an undead vampire and a dead body superimposed in your world? Of course it's not *really* physically possible, but it *sounds* more plausible than "magic".) This would help clear a lot of inconsistencies: For example, if is a dead person rises as a vampire, and you watch the scene through a mirror, you'd see a decaying corpse lying there (clothes, shadow and all), even after the vampire went elsewhere, because that's what would happen in a world without vampires. More precisely: That's what *happens* in the alternate universe without vampires. If you'd look in a mirror while a vampire picks up a glass, the glass would still be standing on the table in the mirror, because that's what happens in the alternate universe without vampires. (This also explains why the vampire's clothes aren't visible in the mirror, even if she changed after she rose from the dead. In the mirror, the clothes never left the shop.) You'd have to have some effect that "moves" the glass and the clothes in the alternate universe later, when no one is looking in the mirror, to make sure the world in the mirror looks just as our world without vampires. (You could again hand-wave towards the effects of measurements in quantum mechanics, to make this sound plausible. The idea that something would disappear if you don't continuously look at it sounds strange, but in quantum physics, [there are actually strange effects like that](http://en.wikipedia.org/wiki/Quantum_Zeno_effect)!) **Sidenote:** If you use this in a story, you have to have at least 3 separate references to Through the Looking-Glass! (Because that's obviously where I've got the idea from.) [Answer] One way would be polarization, if the mirrors were tuned to only reflect light with a certain polarization and the vampires reflected light with a different polarization then the mirror would not reflect their image. Some special property of the vampire would cause this polarization. The problem with this idea is that you would get a black shadow where the vampire should be though. In fact that would be a common problem with most possible solutions, it's already not easy to make a vampire disappear from the mirror. Making what is behind the vampire appear in the mirror though is far harder still. There are only two real ways I can see to do this: 1. The first is as suggested by Philipp, to have the vampires actually invisible, so light is passing through them, and then have humans viewing them directly somehow perceive them. 2. The second is to have the the vampires using a glamour to hide their true appearance, a side effect of that glamour may be to hide their presence in reflections. It's advanced enough to be able to hide their true form in the mirror, but not advanced enough to replicate the form they are projecting in the mirror. [Answer] You could have vampires without a mirror reflection if the world is actually a simulation, like the Matrix. In this scenario a vampire would be a specific kind of program construct within the simulation. [Answer] I've pondered this ever since I was a child. It is almost impossible for a solid object to be truly invisible. The idea of only reflections being invisible, as though such an amazing feat could be an accident, pushes the idea even further into fantasy. About a year ago, though, I realized that it is possible to create an interesting explanation. I considered writing a story as a vessel for the explanation, but I may as well describe my idea before I get around to it, as it will be borrowed anyway. Here's what you need: * <https://en.wikipedia.org/wiki/Blindsight> * <https://en.wikipedia.org/wiki/Riddoch_syndrome> First of all, it is obvious that vampires are a constructed race and that they did not arise naturally. They must have been created by the ancients using magic (or very advanced technology). They are intended as predators. Ideally, they should be invisible. And the easiest way to make yourself invisible might be to interfere, telekinetically, in the visual cortices of nearby human brains, so that your prey *sees* you but *doesn't* see you. Now we come to the interesting bit. Conceivably the effect was imperfect, and did not work as well on animals; but, worse, the effect was originally limited to a "blind field", so the vampire was visible in reflections. Therefore, once humans caught on, a separate spell was needed to mask the reflections as well. But in the early Middle Ages, there was a great war between human magicians and vampires, and by means of great effort the humans succeed in destroying the original invisibility spell. The best that modern vampires can do now is to create brief illusions when they are in danger: "turning into bats", etc. But the second spell is still there. [Answer] The most plausible explanation I can come up with would be mirrors reflecting most of the visible spectrum, but a few very specific wavelengths being absorbed. Under normal circumstances we wouldn't notice that, because the reflected light would only lose the tiny amount of energy contributed by the few photons matching the absorbed wavelengths. If we assume that when you shine light on a vampire, it doesn't emit light of the same frequency as you shine on it, rather it only emits one of the specific wavelengths absorbed by the mirror. Due to the physics of how it works, the emitted light would be lower energy than the light you shine on the vampire. The outcome in this case is that if you look directly on the vampire, they will be visible. They will however appear a bit red. (To see their true colors, you need an ultra-violet light source.) If you look at them in the mirror, you will instead see a black spot. Essentially you will see their silhouette filled with black and no nuances. The explanations usually given would of course have given you the impression that when observed through a mirror they would appear transparent rather than black. But maybe that could be explained as a simple misunderstanding due to the wording of no reflection being interpreted slightly different from how it was meant in the first place. Any objects including clothes worn by the vampire would have to only emit the same wavelengths in order to exhibit the same property when viewed in a mirror. Which mean the lack of reflection would be a property of those objects regardless of who were wearing them. [Answer] Mirrors and cameras are instruments of scientific measurement. They can only detect things that exist in nature, and they are incapable of detecting anything 'supernatural', which is something that only human minds can do. So as far as mirrors and photographs are concerned vampires don't exist, and the information we get from them will reflect the natural or scientific explanation for the 'vampire' event. [Answer] There was a TV series many years ago called Ultraviolet by Joe Aherne that tried to explain everything vampiric as if it were real, though with plenty of "we don't know". It was very good - worth digging out a copy. One of the ideas is that, because a vampire has no reflection, it follows that there is no light reflecting off its body, and therefore has no physical presence that we'd recognise. So, no reflection in a mirror also means no image in a CCTV camera, or a photograph, and no ability to use other electronic devices such as a telephone. The idea is that a vampire doesn't truly exist in this world as physical matter. So why can humans see and interact with them? Possibly its a metaphysical thing, 'spiritual' forces that we can detect that physics cannot, similar to how ghosts work in the world but with a bit more power behind them. TBH it doesn't really matter exactly why, but the effects of such a situation go beyond mirrors. [Answer] Why a vampire is invisible from mirror can be explained this way. Vampires are actually made up of the atom equivalent of dark matter. As dark matters, they are actually completely invisible to electromagnetic radiation. However, since the atom equivalent of dark matter, they are massive enough to radiate barely-visible electromagnetic radiation. When the photons of these radiation bounces of the mirror (or any other reflective surface), they lost some of their energy and their frequency drops to the infrared radiation spectrum. Now, since human optical nerves can only detect visible light and not infrared, vampires are invisible after reflection. Of course that means that some very sensitive camera or heat-sensing devices can still detect vampires and it doesn't explain the lack of warmth of vampires. Also, some animals may be able to detect it from the mirror reflection itself. I hope this worked for your question. [Answer] Could this be done technologically, assuming the mirrors are completely normal ones and there are no psychic powers in this universe? Maybe, with one of these options: ## Option 1: First, take a look at [this article](http://www.wired.com/2003/08/pwr-invisible/) a hypothetical near-future invisibility suit. The suit would be covered with tiny omnidirectional light sensors and light emitters, all in contact with a computer. A diagram of such a sensor/emitter pair from the article: > > [](https://i.stack.imgur.com/TSpIF.jpg) > > > *To achieve true invisibility, optical camouflage must capture the background from all angles and display it from all perspectives simultaneously. This requires a minimum of six stereoscopic camera pairs, allowing the computer to model the surroundings and synthesize the scene from every point of view. To display this imagery, the fabric is covered with hyperpixels, each consisting of a 180 x 180 LED array behind a hemispherical lens.* > > > When a certain wavelength and intensity of light strikes a sensor in a particular direction, the computer can calculate the trajectory that light ray would take along a straight line if the person were totally transparent, and where that line would intersect the opposite side of the body. Then, it can instruct the emitter at the intersection point on the opposite side of the body to emit a light ray in the same direction with the same wavelength and intensity, which we might call a "masking ray". If this is done at every point along the body for light rays coming in every direction (even if it's not perfectly fine-grained so the emitted light is a bit pixellated), you can have a form of practical invisibility. I think it should be possible to modify this so that if you look at the person in the suit directly they are visible, but they will appear invisible in mirrors. My idea here is just that the image-processing software interpreting the data from the sensors can distinguish human eyes, and once the suit has identified all the human eyes in its surroundings, it can selectively instruct all emitters *not* to send masking rays in the direction of any human eyes. You may also want to have the software be able to distinguish camera lenses if you want the vampire to be visible on camera, and also be able to distinguish the eyes of various kinds of non-human animals along with humans (although you might not want to do this if you want these technological vampires to creep out animals because they can hear and smell them but not see them). The only problem with this is that if the software sees someone's eyes in a reflective surface like a mirror, and interprets that as another set of eyes, then if it fails to send the masking rays in the direction of the reflected eyes, the person *will* be able to see them in a mirror. But with sufficiently sensitive sensors and smart software it may be possible to differentiate reflections of eyes from regular eyes which lie directly in the line of sight of the suit, since any real-world reflective surface is going to have some combination of [specular and diffuse reflection](http://scienceprimer.com/specular-diffuse-reflection) (also, the software could be continually trying to build a model of the environment based on sensory information, so it could notice when the image on a surface seems to be a duplicate of some mapped region of the environment in the opposite direction). Also, note there would be one side effect of this technology which isn't usually part of modern vampire lore (though it was [apparently a feature](http://books.google.com/books?id=BwmGVdVxJ18C&lpg=PA313&dq=vampire%20cast%20no%20shadow&pg=PA313#v=onepage&q=vampire%20cast%20no%20shadow&f=false) in some older vampire myths): besides having no visible reflection, the vampire will also cast no shadows. I suppose if you want to avoid this, if the software can distinguish eyes in mirrors and other reflective surfaces from regular eyes directly in the line of sight, it could be designed to *only* send the masking signal in the direction of reflections of eyes, and then it would have a normal shadow. But this would have the disadvantage that if the system failed to notice a pair of reflected eyes because the reflection was far away, distorted, and more diffuse than specular (say, a faint reflection on a dull metallic teapot) then a person near the reflected surface could notice the vampire, whereas sending the masking signal everywhere *except* non-reflected eyes would avoid this error. This option has the drawback that it requires the vampires to not only have this sort of detector/emitter system lining every surface of their body, but also to have it lining the surface of whatever clothing they wear. But if you imagine the vampiric "infection" was created by some civilization with advanced technology in the past (perhaps native to Earth of that time, or perhaps involving aliens or time travelers), it could involve a swarm of [nanobots](http://en.wikipedia.org/wiki/Nanorobotics) that envelop each new vampire, and it could be smart enough to form an envelope that extends to clothing as well as the vampire's body, with the nanobots forming tiny light sensors and emitters on the surface of both. Such nanobots could perform other plot-relevant functions like repairing damage to the body (aside from stakes to the heart and beheadings), preventing decay and keeping neurons and muscles functional even if the cells are not really alive, distinguishing sunlight from other forms of light and causing an explosive reaction when sunlight is detected, etc. ## Option 2: If you let the tiny robot swarm get very advanced, perhaps involving [femtotechnology](http://hplusmagazine.com/2011/01/10/theres-plenty-more-room-bottom-beyond-nanotech-femtotech/) rather than nanotechnology or perhaps some particles unknown to current physics, there could also be an alternate solution that doesn't involve selectively detecting nearby eyeballs. Imagine the tiny machines absorb all incoming light, but the machines are designed to mimic the optical properties of the bit of the vampire's body or clothing directly underneath them, sending out light-like signals that match whatever light the bit of body/clothing underneath would emit under the same lighting conditions. However, instead of the emitted signals actually being light, imagine the signal is itself a subatomic-scale machine, or perhaps an exotic particle unknown to current physics, sent out on the same path the light ray would have taken (if you want to bring exotic particles in, I suppose you could ditch the idea of tiny machines and imagine the vampire's body is surrounded with some kind of field which is also unknown to current physics, which has the property that any photon exiting the boundary of the field is transformed into an exotic particle with the same momentum and energy). Being smaller than an atom, this machine or exotic particle (which I will abbreviate M/EP to avoid having to keep saying 'machine or exotic particle') is designed to mimic the behavior of light in the sense of passing through transparent materials like water or glass, and even having its path refracted by them. If the M/EP comes to a bit of matter that would absorb or scatter photon, like an electron in a photosensitive molecule in the human retina, then we can imagine the M/EP imparts the same amount of energy and momentum to the bit of matter as that bit of matter would have gotten from the photon (if it's an exotic particle we can just imagine the particle itself has the same energy and momentum as the corresponding photon, if it's a tiny machine we can imagine the machine emits a photon of that energy and momentum when it detects a bit of matter that would naturally absorb or scatter a photon). And if the molecules in your retina react the same way, you will be able to see the vampire if you look at it straight-on. But assume the M/EP behaves *differently* than a photon would when it encounters to some bit of matter that would reflect a photon--at this point the M/EP will just get absorbed or otherwise destroyed by that bit of matter, rather than travel on a reflected path (if it's a tiny machine it could just break up at that point). This will ensure that no M/EP can take a path that goes from the vampire to a reflective surface and then to a human retina (or camera lens or animal retina). Finally, if the M/EP encounters a bit of matter that has some probability $P\_1$ of reflecting a photon, like a piece of glass which reflects some incoming light but lets the rest pass through, then the M/EP particle should have the same probability $P\_1$ of being destroyed/absorbed, and otherwise will interact with this bit of matter the same way a photon would. This ensures that even though a person's eyeball is *partially* reflective, the photosensitive molecules in the retina will be imparted with the same energy/momentum by the M/EPs as they would get from photons if the vampire wasn't surrounded by this advanced technology and was just emitting light normally. But even if you were standing right next to a vampire and looking closely into the eyes of another person standing across from both of you, with this technology you wouldn't see the vampire reflected in the person's eyes (this wouldn't work with the more realistic invisibility suit technology I discussed in option 1). Also, with this method the vampire will cast a shadow normally, and the shadow will even extend over reflective surfaces like water even though the reflection itself will be absent. Of course, this second option is well in the realm of [technology indistinguishable from magic](http://en.wikipedia.org/wiki/Clarke%27s_three_laws), so if you're going to pick a solution of this kind, it might be simpler just to assume that our apparent physical world is a Matrix-style hyper-detailed simulation, and whatever beings are running the simulation have just programmed in special alterations to the laws of optics for light rays emitted or reflected by vampires (an option already mentioned in user100487's answer). [Answer] **Divine Intervention** Vampires don't have reflections due to the interference of a god or gods. Perhaps the goddess of beauty is the friend of humanity, and she prevents mirrors from reflecting vampire buth to punish vampires (as they cannot see themselves and fix their appearances) and to give humans a way to see the undead. Alternately, the god of shadows absorbs the reflections of his servants the vampires to feed his own powers. That is why vampires don't avoid mirrors more than is necessary, and might even keep them in the mansions. Their dark lord commands them to give him his due. ]

[Question] [ I'm making a world that is 1/3 medieval fantasy, 1/3 pre-civil war American west, and 1/3 Mad Max. The world underwent an apocalyptic scenario that destroyed the governing bodies at the time, but it has been a few generations since then, so city states and towns have started to rebuild. Since their old fiat currency system was destroyed in the apocalypse, they resorted to barter. Bullets are incredibly common, and gun technology influences the culture greatly. My question is: Is it possible for bullets to be used as a standard system of currency? How would having money that could be expended permanently, by firing it, affect the economy? What kind of relationships would form between banks and bullet/gun manufacturers? [Answer] Any "currency" that is useful as something else (cattle, beans, bullets, cigarretes) is only compatible with very limited markets. Pre-feudal, I would say, or politically repressed markets such as in the fSU or DDR. In general, you can abide by the following law: > > The usefulness of any given commodity as money is inversely proportional to its usefulness as anything else. > > > If your world is a violent one, which is what I get from your question, then bullets will be even more useful as bullets. You wouldn't like to trade away your basic defense against random violence. --- But there **is** a way to turn bullets into proper currency. Use them first. Once already shot, they become useless as bullets, and consequently potentially useful as money. Just make them scarce (make lead scarce!) and they can even be quite valuable. [Answer] **You have a fundamental problem** > > Bullets are incredibly common > > > While they have intrinsic value, that value is going to be very low. It's like having a currency with only pennies. It could be fine and accepted, but it'd really hard to pay for anything high value due to the shear tonnage of bullets you need to haul. Mad Max implies shortage of food and water, American west also often used a shortage of fresh water for plot points. It's going to cost you a truckload of bullets to buy a sandwich. **Let's make them less common so they become more viable as a currency.** Once they start to have higher value you hit the issue of them not being divisible. Something is worth half a bullet, but half a bullet is worthless. Supply and demand will be hard to balance, if there's a conflict demand will rise, supply will rise a little behind it, so a currency value surge before settling, but after the conflict there are going to be too many bullets still being made for a while so risk of hyperinflation. The thing with gold as a currency is it's otherwise largely useless. Minor industrial value, used for decorative purposes, but always it remains gold. It can be melted down and recast as coins when you need it. Silver has been used in much the same way. Using a consumable manufactured product whose consumption and manufacture you can't control is risky, and likely to be highly volatile. If you're trying to rebuild an economy based on a currency you need something more stable and another "currency" is required quickly to give economic stability. [Answer] ## No Money, as we understand it, is essentially worthless, and it *should* be worthless. It serves as a medium for exchange, where a given amount of money is agreed to have a certain value, but the tokens exchanged are more or less valueless. There are good reasons for this. Bullets-as-currency would be a form of [commodity money](https://en.wikipedia.org/wiki/Commodity_money), a relatively primitive form of exchange which is essentially formalised barter. Every time you shoot a bullet, you're upsetting the local economy - you're draining value from the economy and deflating the currency. A decent-sized zombie outbreak could upset the economy of the whole village - all of a sudden the farmer who sold his potatoes yesterday for twenty bullets can afford to buy the whole lot back again and still have bullets to spare! Bullets as currency are **volatile**, in a way that gold is not. Bullets as currency would be relatively easy to fake - if I'm charging you one hundred NATO rounds for a sack of potatoes, I can't quickly check all 100 rounds to ensure that all the bullets are lead, all the casings are proper brass, all of them are filled with powder, etc, so you can pass of ten good rounds and ninety duds. I *can* quickly weigh five gold pieces and make sure they weigh what I expect them to. Bullets are too complex to be good currency. [Gresham's Law](https://www.britannica.com/topic/Greshams-law) is in full force in a commodity currency, especially with something like bullets. This holds that in a financial system with both good (pure) money and bad (debased) money, the good money will disappear from circulation. Why? Well, after you fooled me with those duds, I'm going to want to get rid of the duds and hold onto the good ones, so I'll hurry out and buy some wandering trader's pretty daughter with as many duds as I can manage. Thus the number of good bullets in circulation will steadily drop, and the number of duds will increase, until everyone's just trading duds. Different calibers would also make the currency that works in one place totally worthless in another. If I use a 9mm to keep the rabid were-weasels off my mushrooms, then I'll happily give you a sack of fungus in exchange for fifty silver 9mm rounds. My neighbour, who's tormented by vampire elephants, isn't going to put any value on those rounds; he'll only sell you a bag of apples in exchange for ten blessed nitro express rounds. Now, a lot of this could be bypassed if your rising civilisation standardised what type of bullet could be used for currency, what caliber, material, etc - but if you're doing that, why not just go with a disc of gold instead? Gold is really an ideal substance for a basic currency. It's easily identified, not that easy to fake, it holds its value indefinitely, and it has essentially no practical use, so the amount in circulation will stay the same. You buy a sack of mushrooms from me for five gold coins; I turn around and buy the merchant's daughter with those same gold coins; the merchant happily buys your useless nitro express rounds for five gold coins (while I was explaining this, the vampire elephants got to old Fred. Terrible shame). Now everyone's got something they value, and the money has even ended up back where it started, leaving everyone richer! ## Bullets could still be used as a medium of exchange If you happen to have one hundred NATO rounds, and I know that the merchant has a rifle that can use them, I might well trade you the mushrooms for the bullets, provided you can prove that they're all good (and provided you can check the sack first), and then I'd swap the bullets for the daughter later on; but that's not money, that's barter. Currency or money implies some universal standard, which 'bullets' as a group do not have. [Answer] I thought it might be worthwhile fleshing out a comment I made on another answer here. Anything can be used as money. It's tempting sometimes to believe otherwise, but there is only one thing that is necessary for the creation of currency, and that is mutually agreed value. If everybody believes/agrees that something has value, then it has value purely on the basis of that agreement/belief. What separates some currencies from others is their effectiveness for the purpose. If you google "what are the strangest things that have been used as currency", you can find lots and lots of bizarre examples. My personal favourite is this- > > Rai stones > > > Also known as stone money, the gigantic circular limestone disks weigh around 8,800 lbs. (4 metric tons) and generally have a diameter of 12 feet (3.6 meter). Used commercially in the Micronesian island of Yap, the owners didn't bother about moving the heavy rai stones physically after a transaction was over and relied on an oral commitment to settle the question of ownership. Although the origin of stone money is not yet known, they still retain their significance as a cultural emblem, being used in marriages, inheritances, political deals, or even in exchange of food. > > > [source](https://www.msn.com/en-us/news/offbeat/strange-things-used-as-currency-around-the-world/ar-AAjmEi5#page=3) > > > If people can use stones weighing 4 metric tons as money, and they don't actually transfer them from person to person (understandably) but rather rely on each others word as to who owns what - you can literally use anything as money. And I do mean, literally. You could use stars as money - exactly like you would use the massive rocks. Clearly they're going nowhere, you have to rely on oral or written information as to who owns what. However, these more unusual examples of currency obviously have their flaws. They're not suited to the kind of sophisticated economy we have these days - can you imagine if we took each others word on how much money we had, and never actually exchanged the money? Bullets would clearly be a "bad" currency, but this doesn't mean you shouldn't use it - it might make the story more interesting to incorporate examples of the bullet currency failing, and why exactly it would fail. The other answers have done a pretty good job of describing why bullets would be a currency with flaws. [Answer] You can use anything as money. Money is just a measurement for services. If you believe something has value, it has that value. Paper money (for example the dollar) is not coupled to any hard value (like gold) anymore, so it just has the value people give it. [Answer] While a society **could** use bullets as money if there were for some reason no other options, one must ask if they **would** while other potential currencies are available. And the answer to this question is definitively: # No **Gold or silver will almost certainly be used instead.** To be effective, money must have 5 properties: 1. scarcity 2. fungibility (each unit is just as good as any other) 3. divisibility 4. durability 5. transferability 1) Bullets may be scarce, especially if the raw materials are scarce. But nothing like gold or silver. 2) They are not fungible, because they come in different kinds (calibers, features, etc.). It is possible that one standard type of bullet would win out over others as money, but quality would likely still vary. Compare to gold or silver coins, which generally trade at a very slight markup over their melt value, and can of course be melted into smaller or larger units. 3) They are not divisible, because half a bullet is worthless; compare this to gold or silver coins, where you can just cut off (or melt off) a slice of the proper weight. 4) They are (to my understanding) not durable. As far as I know, bullets may lose their functionality due to exposure to extreme temperature/moisture conditions as well as aging. Correct me if I'm wrong. Compare this to gold or silver coins, which are (for the most part) not vulnerable to corrosion by moisture (silver tarnishes eventually, but detracts little from melt value), and even when heated to melting, do not really lose value, only change shape. 5) They are not very transferable. Yes, you can exchange bullets with someone, but do bullets have the value density needed to carry out large-ish transactions without an impractically large amount? No. Compare to gold coins: one gold bar (400oz troy or about 25lb) is currently worth almost 500k USD. That's some serious value density. My recommendation would be to assume that your post-apocalyptic society will use gold or silver (or both) as money instead of bullets. Don't fall into the trap of assuming that "[some good] is valuable, and so will be used as money". [Answer] # The value of money depends on supply Without doing a super deep dive into economics, the value of a currency depends on the [money supply](https://en.wikipedia.org/wiki/Money_supply). A currency that is stable for long periods of time must have a stable volume in circulation. Examples: * Gold was very rare and mined at a reasonably constant rate for long periods of time. Therefore, it had a high relatively fixed value and was a stable useful currency. It also has the nice property of being to soft to use in expendable items, and highly resistant to corrosion, meaning it was rarely taken out of the money supply (i.e. it only left circulation by being lost) * However, the discovery of the New World dramatically increased the available [supply of money](https://en.wikipedia.org/wiki/Price_revolution). This was partially counteracted by generally increasing population and commerce across Europe in the same time period which tended to increase demand along with the supply. * Cowrie shells are a great example of how a thought-to-be-stable currency can go awry. The cowrie is originally from the Maldives, and is relatively rare. With a near constant supply, they were a useful currency on the African continent. However, the ring cowrie from Zanzibar is much more common, and traders on the Indian ocean used this species as a 'counterfeit' currency. The money supply rapidly increased causing the equivalent of hyperinflation, destroying the value of the currency. # Bullets are a bad currency because they are not stable The long and the short of it is, bullets are not a stable currency. First, they are produced by a devolved manufacturing process. Fiat currency in the modern world is controlled by central banks. But anyone can make bullets in your post apocalyptic world, so there is no way to control the money supply. Since making a bullet 'creates' money sui generis, everyone will be doing it, which will destroy the value of the currency. As if that isn't bad enough, bullets have a demand decoupled from its demand as a currency. If a war breaks out, people are going to need a lot more bullets, and presumably manufacturing capability will go down since there is a lot of destruction and plundering. This will have the opposite effect as hyperinflation: the price of bullet will be so high that any commercial systems depending on them will collapse. If a trader in the city exchanges bullets with farmers to feed that city, then a scarcity of bullets will cause either a. starvation or b. the bullets will no longer be used as currency. All in all, bullets will not work as a currency. [Answer] There is another issue that just adds to the "bullets are bad as money" posts. I haven't seen it listed here but how do you know if the bullet is good? The primer caps are probably the hardest part to make. So, when reloading the brass, why use a real primer cap? Just sell the bullet off to someone and you are good to go. It would be as if the only way to test to see if a $100 bill was real is to burn it. In the end, it all relies on if you trust the person. If you trust them, then you can use their signature instead. [Answer] # Yes I game a RPG where we have that setup, and it works like this: Bullets are common (so relatively worthless, but good for small change). Value of objects is usually expressed as amounts of bullets, but usually you don't pay in bullets. So, you still have a barter system (you exchange two goods) but there is a value behind that. Like this: * "I want this axe, how much?" * "300 Bullets" * "The other vendor offered me 350 for this pack of t-shirts that are still wrapped in plastic foil from before the apocalypse. So that and you give me 50 back?" * "I'll give you 20 back." * "Ok, Deal." [Answer] Bullets are common but "Will they fit"? So for example in the NATO region the 5.56 mm bullets could be cheap but the .45 could cost food for 7 days as they are not so common but pack more punch. On the other hand it's not the bullet or case but the primer. You can cast a new bullet, fill the case with powder but remaking the primer would impose the problem. I think the closest to what you are describing is the wild west. I've read stories about people using bullets as currency because for example Indians didn't need money but they liked to hunt with rifles. Also Banks can exist in a situation where there is a common agreement of payment. In a postapocaliptic environment I don't think there would be enough trust. [Answer] The thing with bullets as currency is that they have practical value, but are a complementary good. They have sufficient value if you have a gun that fires them, and very little otherwise. This becomes a large issue with the sheer number of calibers out there. Consider an example: I am thirsty and come across someone with water. I have ammo for a .30-30, .45, .357 and .40 S&W. He only has guns that fire .308, .30-06, 9mm, and 12 gauge. My ammo would have some potential value as he could maybe trade it to someone else in the future, but he runs the risk he couldn't. Maybe he won't run into someone who needs that caliber any time soon. Most likely, he wouldn't want to trade his valuable water for ammo that has an unknown value to him and may be risky to trade to someone else down the road. Unless your world has significantly fewer calibers than this one does, you'll be left with bullets that are valuable to some people and worthless to others, which makes for a poor currency. [Answer] "Yes" in the very short term. "No" in the long term, because bullets are made of **lead**. Very, very heavy. And **cheap**, and easy to fabricate. Look up the history of banking, and you'll see that they developed as a way for people to "carry" lots of money long distances without having to carry **lots** of gold and silver. Banks are just a natural development, and if printing exists in your world (1/3 antebellum West + 1/3 Mad Max implies that the technology is available), "gold certificates" **will** be developed. [Answer] Bullets are very heavy compared to their current value. I would expect a "Mad Max" world would also use up bullets rather rapidly, so they are probably low value in your world as well. Other than their weight, they are remarkably similar to Cacao beans, which were used by the Inca as currency. We even have enough information from their era to understand what things cost (a chicken might cost 2 cacao beans). The market never flooded because the rich would drink their Cacao beans as hot chocolate! [Answer] It's iffy. Definitely not a "no", but the stars would have to be aligned correctly for "bullets" to become money. Why? That gets a little complicated, but it's not beyond the ability of the average person to understand, so I shall endeavour to explain. Money has three attributes that give it its usefulness. These attributes are: * Measure of value * Store of value * Medium of exchange So, let's look at how well bullets meet the objectives: ## Store of value This one is actually pretty good. The lead will always be usable as lead. The brass will always be usable as brass. Both materials tend to keep a fairly consistent value, all other things being equal. The powder and the primer (assuming these are modern cartridge "bullets") will last several years as long as they're not abused. If it's military-grade ammunition that's formulated specifically to be stockpiled, it may well last decades. So, in terms of every-day commodities that could be used to store accumulated wealth, bullets aren't that bad. There may well be better choices, but choosing bullets won't result in your wealth rotting away like it would if you chose something like apples. ## Measure of value If you want to do any kind of budgeting or other monetary planning your money needs to be quantifiable in consistent units. This means that "fungibility" is an important quality. Fungibility is how interchangeable the units are. A particular ounce of 24 karat gold is functionally identical to any other ounce of 24 karat gold, so gold has good fungibility. "Bullets" don't score quite so well as gold does, or even as well as the lead and brass they're made of do, because their chemical components decay, so newer ones are inherently more valuable than older ones. But it's not enough completely disqualify them. Mass-produced bullets for mass-produced guns are otherwise quite fungible. If they weren't, then you'd be likely to blow up your gun at some point, and that would be bad. You do run into an issue though where not all guns shoot the same bullets, and obviously a .22 bullet isn't worth the same amount as a .50 BMG bullet. Keeping track of the exchange rate between .22, .44 magnum, and .50 BMG would be headache enough, and that's only three. There are thousands of varieties. If you live in the United States, go down to Wal-Mart at some point and peruse their ammunition section. Then keep in mind that Wal-Mart only bothers to stock about the top 2% most popular varieties, which brings us to: ## Medium of exchange This is where it kind of falls apart. Firstly, you said that bullets are very common. Well, they're also very heavy. They need to be common enough that everybody is willing to accept them in trade, even if they can't use them themselves, because they know they can resell them later, but not so common that you have to carry around 20 pounds of brass and lead just to buy dinner. The big thing though is the previously-mentioned wide variety in modern ammunition. If your gun is a .30-30, shells for a .30-40 are useless to you, even though visually they appear almost indistinguishable. If you want it to work out, you're going to have to cut down on the variety. Otherwise tracking the exchange rates between the different kinds rapidly becomes a nightmare. There are a couple of ways you could do this: First, you could decree that somehow, in the economic collapse say, most of the variety was eliminated and, say, only NATO standard weapons still exist. Alternatively, you could kick the tech level back down to the end of the muzzle-loading era. At that point a bullet is nothing more than a chunk of lead, and you effectively have a society that uses lead as a currency and, by custom, mints its coinage in a fashion suitable for launching out of a gun. That's unlikely to happen given how common lead is and how many things substitute for it, but it wouldn't be impossible. Also, most people in that era carried their own bullet molds so converting from one size to another would be relatively trivial, thus eliminating the variety problem entirely. So you're mostly just left with the fact that lead is really quite common, and really quite heavy, so hauling around the quantities necessary to buy things could easily become impractical. People would be highly likely to switch away from lead to the more traditional copper, silver, and gold. Those three have much better value/weight ratios. --- You also had a question about how well consumable currency works. Consumability actually has little impact on whether or not something makes a good currency. To the extent that it does have an impact, it tends to make the currency more desirable because it increases the likelihood that you will be able to pass it along for something else you want, since people will actually use it directly. If you've ever heard the phrase "worth (his/her) salt," it comes from the fact that a long time ago, in certain places, salt was used as currency. You can't live without a certain amount of salt, so everybody was willing to trade for it. In the areas in question, it was scarce enough that its value per pound was high enough that reasonable quantities could be used to complete transactions. So it met the Medium of Exchange requirement. Salt is completely non-perishable as long as you don't let it get washed away, so in areas where the production of salt is roughly equal to its consumption it was a good Store of Value. And finally salt is easily divisible into small units and pretty well completely fungible, so it made a good Measure of Value. Of course, if you accumulated your wealth in salt, and then moved to an area with a nearby salt-mine, you'd rapidly discover that your wealth wasn't worth all that much. Which is why salt was not the only thing used for money. Things that are in universally consistent supply make much better money when dealing with large geographic areas, which is why refined metals have been a common choice throughout history. They're still not perfectly consistent, but they're better than regionally scarce commodities since they're relatively scarce almost everywhere. --- So, overall, I wouldn't expect bullets to become the major currency of a society unless they are both in short supply and the variety of guns available is severely curtailed. However: I would expect them to be a commonly-traded item since they are commonly desired, reasonably fungible, and keep their value reasonably well. In fact, I'd expect it would be rather similar to the old salt trade where communities that were far away from the ammunition factories trade for ammunition with the more generally used currency (gold, silver, sea-shells, whatever rises to the top in the wider area) and then uses the ammunition as one of their local currencies internally, similarly to how cigarettes and snack foods get used for money in prisons. [Answer] I'm assuming the OP means "finished rounds of ammunition" rather than bullets. It would seem to work as an advancement over a barter economy, especially a violent one where high availability of ammunition was desirable and ammo was scarce. But it would have several obvious flaws: **Problems:** * Is everyone using guns that use the same ammo? If not, you'll end up with several different currencies. * Prices (measured in rounds of ammo) will fluctuate as supply and demand for ammo fluctuates. * There will be a huge incentive for people to enter the market and supply low quality ammo, since presumably it would have the same value per round as higher quality ammo that actually works. Eventually the standard unit of currency would be a garbage quality "round" of ammo that isn't usable as ammo. Actual ammo would eventually be too valuable to use as currency and would be removed from circulation as a token of value. **Conclusion:** As a result of the above, every workable scenario ends up describing either a) a barter economy in which high quality ammo is traded for other valuable goods b) a traditional currency in which bullet shaped tokens of value are exchanged for goods and service, with some local political authority controlling the supply of this currency [Answer] > > How would having money that could be expended permanently, by firing it, affect the economy? > > > There's a real world example. In prisons, it was not uncommon for cigarettes to be used as a form of [currency](https://en.wikipedia.org/wiki/Commodity_money). This has faded more recently as prisons have cracked down on smoking like everyone else. Now they apparently use [Ramen noodles](http://www.cbsnews.com/news/forget-cigarettes-theres-a-new-prison-currency/), which still get consumed. In a real world, you wouldn't have just one denomination. As [someone else](https://worldbuilding.stackexchange.com/a/80552/2113) points out, bullets are like pennies. They are the smallest denomination. You would also have pistol magazines (10?), rifle magazines (30?), and machine gun belts (100? 500? 1000?). Maybe you'd have packs (4 or 5?) to serve as an intermediate size. Or maybe you'd call them halves. I would also add certificates to this. You have a certificate or coupon that is good for X bullets. Most people exchange the certificates rather than the bullets themselves. You keep your bullets. You use certificates to buy reloads. Or other supplies. A problem with this in our world would be that not all bullets are the same size. But perhaps your world is different. Maybe they do have one standard size. You might be able to make this more believable if you switch from bullets to some other form of ammunition, e.g. charges. Then a pistol might shoot two charges at once and an assault rifle might shoot one. A sniper rifle might take three or more. An extra big gun might shoot ten or something (think of an anti-tank gun mounted on a jeep). Charges could also work as gunpowder. So you reuse slugs, etc. but have to actually replace the gunpowder. Works better with more primitive firearms. For example, a flintlock or matchlock would make sense. Don't forget to generate your currency. If you only expend bullets (as in the Walking Dead), you will have deflation. The currency will be worth more and more and you'll have less of it to go around. Currency shouldn't be plentiful, but it shouldn't be rare either. Otherwise people would hoard bullets and trade something else. [Gresham's law](https://en.wikipedia.org/wiki/Gresham's_law). Better value stores are kept while inferior ones are traded. So make new bullets or charges or whatever. Bullet manufacturers would be the banks. They would issue the certificates/coupons (paper money) because only they could actually fill them. Perhaps some enterprising person would corner the market on one of the bullet inputs and be able to act as a bank. But in general whomever actually produces the bullets themselves would be the bank. [Answer] Your answer has been given multiple times, yet i haven't seen this one: Yes. Ever wondered where the "shot" of licor came from? "Legend has it that back in the Old West, cowboys would trade a bullet cartridge for a small amount of alcohol, and the shot glass proved the perfect size to do the trick. " The following page can give you some insight: whiskeyscholar.com/origin-of-the-phrase-a-shot-of-whiskey [Answer] Bullets in a post apocalyptic setting have instrumental value and are valuable in this sense. A limited supply of a needed commodity makes something valuable, this is why we back currency with gold, though gold isn't necessarily "Needed" it can be incredibly useful. Bullets would then be placed in the same category as food, shelter, and water, all things necessary for survival. Once bullets become scarce it will increase in value, so as time goes on and expenditures are greater than income the value of the bullet will increase and so too will the power of those who have them. So in time this "currency" will appreciate but at the start when they are all common food and water will be more valuable. [Answer] To stop arguing and instead use historical precedent, the British colony of New South Wales used rum as currency at one point, so yes, you can use something similar, like bullets as a currency if there is a demand for the item, although it may be temporary until something better comes along. [Answer] I hope I'm not being too late. There was in fact a case in history where a civilization used another commodities as currency. [The mayans and the aztec empire](http://encyclopedia-of-money.blogspot.mx/2010/01/cocoa-bean-currency.html) used cocoa as a trade good, even restricted its cultivation. And about using gold and silver, the Aztec believed [gold was deities' poop.](http://www.eluniversal.com.mx/articulo/cultura/2016/05/3/investigador-explica-en-libro-el-valor-del-oro-para-los-mexicas) Sorry if the second source is in spanish. I didn't find any information in english. [Answer] Modern national currency is expended at the point of final use, and traded around between first issue and final use, so using consumables as currency is not actually a crazy idea. Here's how currency works in most developed countries today: 1. A central bank creates money by making an accounting entry in their books, and puts that money into circulation by buying something with it, usually a government bond (thereby loaning money to the government). 2. The government pays for things with that borrowed money, such as salaries, road construction, and military hardware. 3. The money gets traded around in the open market for a while. 4. People eventually use the money to pay their taxes to the government. 5. The government uses the money to pay back that loan from the central bank. 6. The central bank destroys that money by making another accounting entry in their books. There are a few extra steps when tokens such as paper bills or coins are involved, but the end result is the same; modern money is a consumable, manufactured by a central bank, and eventually destroyed. Modern money's value is founded on the fact that residents, both individual and corporate, need some of it to pay their taxes. [Answer] Dmitry Glukhovsky in Metro 2033-2035 did it. Bullets was currency for all goods. Even there was two types of ammunition - *normal* (usually handmade) and *military*. Economy founded on bullets as a currency should be still on shortage of materials or still using them really often. The currency shouldn't be too easy to acquire. In this world ammunition manufacturers will be like banks - only they have the means to produce high quality bullets. Also you need to remember that this type of currency will make people more likely to use weapons. [Answer] **Yes, but you need some other factors** You mentionned a post apocalyptic world, so you could add some more details to make bullets work better as a money : * Most engineering knowledge on how to make guns and bullets has been lost. Therefore, the amount of working guns is mostly stable. Most of them are from before the apocalypse, with some very skilled blacksmengineers being able to create some new from time to time. * Bullets are easier to make, but still hard. No mass production, it takes time and skill to produce. * As it is already very hard to create new guns and maintain a bullet stock, no-one is ever thinking of creating new weapons. Only create copies of the pre-apocalypse ones. Therefore the whole armament "industry" relies only on a few types of guns / amunitions. With this situation, you have only a few types of bullets that are used. They can't be easily mass produced, are are regularly used. Their amount can't raise as quickly. It can drop quickly on some extreme events, but usually people would be conservative on using them so the overall stock would remain stable. **Your money is** (more or less) **stable!** [Answer] As some others have said, there is a difference between something that represents value and something that has value. Printing numbers on currency solves the scaling problem, but only when society at large accepts that form of money. Easy access to weapons is a special case, as it depends on a societies values about violence. In the Mad Max example, the folks on the school bus were most likely to "sit around and breed." If the other group had won, they might not have had enough people to sustain themselves, much less grow. In that case, money does not matter because your society becomes an evolutionary dead-end. ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 4 years ago. [Improve this question](/posts/65552/edit) So here's what happened. One day, I was struck by a bolt of handwavium, and it caused me to become immortal (unkillable by any means). Shortly after that, a majority of civilization was wiped out by global nuclear war, and I got buried under tons of rubble for a long, long time. I emerged from the rubble eventually, and encountered a small tribe of survivors who had somehow managed to rebuild a very simple civilization. Their initial reaction upon seeing me, alive despite my lack of protective clothing in a harsh, post-nuclear apocalypse landscape, was one of awe. They welcomed me into their homes readily enough. Their language has evolved slightly, but sufficiently rooted in English that I was able to communicate with them after a bit of trial and error. I learned that they have no religious belief - the teachings of Christianity, Buddhism, or whatever have you did not survive the apocalypse. They are pragmatic people who seek simply to eke out an existence on a dying planet. I am of slightly above average intelligence, unfortunately with no special skills or talents except for being immortal. I remember things from before the apocalypse, which no one else in the tribe does. With this, how do I establish myself as a living god among these survivors? [Answer] If you're happy taking a while to do it, just keep being you. You're an immortal in a tribal society that will have a very short lifespan. You alone can go outside into the wastes and bring back new tech, food, whatever. You alone can walk into an enemy village and not be killed. You alone remember the wisdom of ages past, and remember the histories of the village. It really shouldn't take that long for you to become a godlike figure in the minds of the villagers without doing anything special, just keep helping out that tribe and occasionally throw in references to 'the time before all this' and they'll build godhood around you. *Note: This is a very Nordic/South American view of godhood. They won't assume you're all powerful (they know you aren't) and they likely won't assume you're the only one, but they will attribute deity-like traits to you. After all: You're unkillable* [Answer] # Just be "you" as hard as you can But remember to stick to what you've got, it's important not to pretend to any power or ability that you don't actually have. You mustn't get into a position where there's a risk of "being found out" because inevitably they will. However you're not bound by the primary restriction of their society which is the need to survive. That is enough for you to achieve a level of godhood. When it comes to skills, you have time, plenty of time, to develop any skills you may choose to get. Maybe the first hundred generations won't consider you a god but when you have all the skills and you're still not dead, having given them technology they'd thought lost forever, you will gain a level of reverence appropriate to the old pantheons. If nothing else, tribes tend to be gerontocracies and you're going to be the oldest by a long margin. [Answer] Remember, C3P0 was able to assume deity status by being physically distinct, understanding the local's language, and pulling off simple levitation. If the tribes you encounter have reverted to oral stories to pass down their history, you could insert yourself into their lore by showing up in their village, performing an act of "magic," and then foretelling your own return in 3-4 generations from now. Keep on travelling from tribe to tribe, sowing the same legend in each tribe. Once your legend has been passed down for a few generations, return to each village and convince them to join a growing kingdom of your followers. About the "magic," Arthur C. Clarke pointed out that "Any sufficiently advanced technology is indistinguishable from magic." After a nuclear apocalypse, there's bound to be some technology that's either barely inoperable (requiring a little repair-work to restore), or technology that's still functional, but stopped when it's operators died of radiation poisoning. For instance, if you can find a source of running water, you could convince a village to build a water wheel, hook up an alternator or generator, and maybe cobble together a rudimentary electrical grid. By the time you make your way back to this village, they may have improved their standard of living substantially. Other technology worth resurrecting would be water filtration, or antiseptics. Both of those could easily double the survival rate of a post-nuclear-war tribe. [Answer] The thing you've missed is that you now have unlimited access to the most valuable resource a human can have - **time**. * Since you are (assumed) a timeless immortal and cannot be killed via any means, you can learn and master every skill or trade out there * You can hone your skills and acquire wisdom beyond what a normal person would be capable of. * You can, quite literally, try anything and everything in the world and survive it. You can jump off of tall buildings and trees without dying, and do any number of inhumane things, thus proving your godhood. * Drink poison, prove you're not only invulnerable on the outside, but you're also impervious from the inside. * You obviously don't need air, being buried under rubble for years, which means you can swim underwater forever * Anything you do that defies normal human ability could be explained away by saying "Because I'm a god." The simple things above alone would likely cause them to view you as a god already. [Answer] **Believe the lie and study human nature** As a storytelling motif, you should consider that your character has been buried in the ground for hundreds of years. Anyone who has been given a "gift" of immortality but has to sit locked in dirt/stone with nothing but their thoughts for all that time will inevitably go a little crazy. Your character would spend a large portion of their time simply asking themselves "Why me?" They would likely begin to think that there must be some form of existing deity that gave THEM immortality, which makes THEM important and, even if they aren't an omnipotent, historically-eternal deity they are future-eternal and must be so for a purpose. After having them spend another couple hundred years thinking about their situation, who knows what creative ideas your character could project onto themselves. In fact, they could conclude that if society still exists, and if they are one day discovered, their "wisdom" from thinking for hundreds of years is a gift that gives them impeccable judgement on all situations. Emerging from the ground, by the hands of other humans could be both a sign to mortals of your god-ship and "confirm" your characters suspicions that they were to become a god amongst men. The easiest way to sell a lie is to believe it yourself. Believe it and act as such. If you think you are a god, you will act as a god. The next step in this story could be to make it your characters godly-purpose to be a student of mortals. How do *they* behave with one another, how do *they* mold their lives around impending death and how do *they* experience love that inevitably ends. You are now immortal and have the luxury of studying humanity for thousands of years. By learning tell-tale signs of human behavior, your character could exhibit a near omniscient *gift* by reading individuals subtle body language and knowing very-well what certain macro-events in history always tend to lead too. Eventually, you could develop a near-prophetic "gift", being able to foretell events, some times decades before they occur. Your words would be revered and even though your words come from years of observation and recognizing patterns of human behavior, many would find it VERY hard to dispute your godship. You can't die and you're "always right". [Answer] ## Allow Their Best Warriors to Try to Kill You Since you are unkillable by any means, simply tell them all of their best warriors should try to kill you. They will be unable to and be in awe. However, you should only allow them to perform acts on you that do not leave you helplessly imprisoned for all eternity, as pointed out by user [vsz](https://worldbuilding.stackexchange.com/users/262/vsz) in the comments on this answer. ## Really Show Them If they fail to really do a good job of trying to kill you, try sleeping in a huge, raging fire. Bathe in boiling water. Let a huge boulder smash down on top of you from a mountain top. Swim in lava! Get cobras to bite every square inch of you! Let packs of radioactive three-headed psycho jackals attack you and laugh them off! If that doesn't convince them you are godlike, then the radiation has destroyed too much of their brains to make them worth talking to. [Answer] Assume typical mid-western american male status prior to the apocalypse event. Make your godlike character a bit of Military History buff who likes to maybe build stuff around the house. If the landscape hasn't changed too much this gives you a huge range of options. 1) Military history background would allow him to forge an unbeatable army by using the tactics of the Roman phalanx, Ghengis Kahn, English Longbowmen, etc. depending upon available resources. Lord God General will be his title! He will also have the advantage of knowing the advantages of military discipline in a hostile environment. 2) Handyman skills would be useful in both improving both village life and improving security and fortifications. In the era of HVAC systems we forget the potential of a sealed box wood burning stove for heating. It should be fairly easy to construct with primitive ironworks. If he knows anything about Rocket Stoves for cooking and heating, even better. He would also know the need for insulation, having paid many an electric bill. Also, gardening leads to agriculture. Title changed to Beneficent Lord God General! 3) If the local landscape hasn't changed too much, he might be able to find his way to a nearby deserted small town Library. He then becomes the Most Wise and Beneficent Lord God General. The entire premise kind of reminds me of Robert Adams Horseclans novels. One of the main characters is Milo Morai. He's Highlander Style immortal and survives world war 3 and forges a new Horse based society. the book "A man called Milo Morai" details the first part of his journey. Sounds like a fun story in the making! [Answer] If pre apocalyptic information hasn't survived, invent the same things, that you have used in the past. If you can come up (daily or weekly) with an Invention, like Leonardo Da Vinci, Nicola Tesla, Thomas Edison, Steve Jobs and bring Knowledge to them like Einstein and Darvin. You'll be looked at as a god in no time, and you'll also be of use, to your civilisation. [Answer] # With difficulty You don't have anything at all to offer the mortals except for you being unkillable. You'll most probably be most useful as a soldier, but even then, one unkillable soldier isn't likely to be of tactical advantage. And you can't really declare yourself as a God to people who have no concept of Gods any more than someone in our age can declare themselves an alien from Dimension X. [Answer] Remembering things is going to be almost useless if you can't use them to give some advantage to the survivors. Cut out all IT and electronic knowledge, if the civilization is gone you won't have electricity to make that knowledge usable. Do not show off too much. Give little help from time to time. Rely on construction science knowledge, show them how to build more robust huts, how to better insulate them agains climate and so on. Try to anticipate their problems so that they start to perceive you as able to "see the future". But still you will suffer from the lack of any other specific power. [Answer] Watch the Monty Python film 'Life of Brian'. A good explanation of how little it could take to be regarded as a deity. The key fact is that different societies are different - the standard of 'proof' will vary hugely. For some societies, a different appearance (e.g. skin colour or hair colour) will immediately mark you as 'not them', and any further differences will be magnified. The trait you mentioned was immortality - details of how that works are important - whether it's invulnerability or Jack Harkness (Torchwood) style instant 'healing' of death. Healing has been a traditional 'magic' ability, and it is easy to convince others that they are temporarily healed - the placebo effect is very powerful, and if you can demonstrate super-healing with a suitable explanation (e.g. meditation, trance - I can teach you how to do it too! of course, you will have to practice, it's very difficult....) However, the longer it goes on the more difficult it will become to maintain the illusion, unless you either actually have super-powers, or you set up a power structure that relies on you (think ancient Egyptian pharaohs - the entire system of goverment and priests relied on the population believing that the pharaoh was a god). Easiest to convince a few others that if they promote that if they say you are a god, they will be in positions of power, and they will convince others for you - disciples. Bonus points - the 'Man from Earth' film would be very good background reading for this story - some interesting points and themes in there. [Answer] It very much depends on what you are going to do with them. Obtaining the single goal of being considered a god should be simple: 1. if you don't mind waiting some decades just live with them with a wise and supportive behavior 2. if you are in a hurry, kill all other male (it should be feasible as they can't kill you). This would turn you into a deity in a relatively small time with the price of human extinction in the long run (but note that if the survivors are too few, it's going to happen anyway). **edit** Obviously, the second option led you to "eternal" imprisonment. However since nothing last forever (except you) you can: * wait a few generations to be freed by your grandchildren and restart with option 1 * enjoy your detention: after all it's common among deity to be confined in temples [Answer] For me the major priority here is not mere being immortal but in full command of you corporeal and ethereal being so you can avoid being contained and god (a.k.a. you) forbid, being tortured. A major hallmark of the vast pantheon of old pagan gods was their ability to meld with and, in effect, become forces of nature. They could shape-shift, create forms, build and destroy and teleport around. If you want to be a god, be like the old gods. If we collapse into a post-apocalyptic, pre-modern state again then these are the type of entities that would sway the masses, especially if they prove their presence and demostrate their power. [Answer] Immortality or "Power over death" is more than "Invlunerability" - that is mere "Superman", or more than "Normal man". Lift weights (in secret) and you can attain that. Die, wait a couple of days, to be sure, and bring your**self** back to life, **un**corrupted - now, that's a hat-trick. If you can do that, I'll give you some cred toward Godhood, but I wanna see behind your curtain before I buy the "great all powerful Oz". [Answer] Being just a plain immortal human being is not a superpower! As people mentioned before some of your "mortal" followers could easily make you buried alive again just to keep you close to them like a relic! Consider to maintain "doing fantastic things" acts into your living-god's repertory. To inspire fear also works great. But avoid to be caught, because you can just be tortured forever (because you are immortal)! ]

[Question] [ Apologies in advance that my bullet points got away from me and turned out a bit long, but I'm trying to give as much information as I can to ward off initial questions. Imagine the following constraints: * An island nation laid out similarly to [Hawaii](http://hawaiimap.facts.co/hawaiistatemapof/hawaiiDetailedMap.png), namely, a cluster of islands with one "dominant" island and 7 smaller ones, with distances varying between 8-50 miles between each island. It is also a volcanic island and with the same climate, meaning an abundance of rain forest, mountainous areas, and so on. (Though geographically the island in question is identical to Hawaii it is home to a few different animal and plant species for the purpose of storytelling.) * The island has no nearby neighbors, no landmasses in a radius of at least 1000 miles in any direction, and therefore has not in their history encountered anyone before. * The islanders are a "primitive" people with limited access to refined tools. Their total population numbers just under 100k, unified as one "tribe" or "kingdom" with a "king" ruling from the main island. They travel via canoe-like boats or rafts from island to island, but never really venture beyond, believing that where they could no longer see the ocean was where the universe ended. They have volcanic obsidian that they use by chipping off thin, glass-like pieces that they use for blades, spears, knives, jewelry, etc. * The islanders may have some agriculture and fish-farming, but their core culture is that of a hunter-gatherer or warrior culture, where those with the most kills are the strongest. The island is home to several species of big cat, deadly boa constrictors, sharks, and angry wild boars which are considered prize kills, and the islanders make a great show of their "warriors" by counting how many heads they have collected. Even the most peaceful farmer will be obligated to participate in one or two hunts to maintain his reputation, so there is no shortage of people trained to fight in this society. * The European world is right about in the 15th century as far as technology and culture goes. Countries have large seafaring ships which are exploring the globe, looking for resources and new land to colonize. Potential explorers are armed with cannons, rifles, pistols, and well-made blades. * Approximately 35 years ago a ship of indeterminate origin (full of Europeans of some nationality) landed on the island nation. By landed I mean crashed, their ship had been damaged by a storm and the crew was suffering from lack of food and dehydration, so they were unable to keep from hitting the shore. The natives took in the survivors (about 60-75 individuals out of a full crew of 180), nursed them back to health, and fed them. When the crew recovered, they found that the ship was irreparable, but they were able to salvage an enormous amount of *non-food* supplies during low-tide. Tools (repair tools, navigation tools, etc), rope, wood, cannons, gunpowder, rifles, pistols, armor, blades, etc, etc, anything that would be on an explorer's ship in the 15th century. **For the purposes of this question assume that all of the supplies were intact and not ruined by salt-water or the crash. Luck, providence, or hand-wavery may be required.** * The crew had been wildly off-course due to their looming starvation and illness spreading through the ship, so they had no idea where they were or how far away they were from home. Unable to contact anyone for help (and falling in love with the beautiful island they found themselves on), the crew members integrated themselves into the island society. They learned the native language, built themselves houses, and maybe even married a few local women and started families. In return, the islanders learned more about modern technologies and integrated the supplies they found. As a novelty people, the explorers would end up living in the "capital" village, or close to it, and may even have become friends with the King. The entire population would at least have seen them once or twice, or know of them via messages. A few of the population might have initially been resistant to the intruders, but since the sailors settle down and live a quiet, peaceful life in paradise, they are mostly left alone. * The next time that Europeans arrived, the situation was much different. About 30 years later, a group (from a different homeland than our original stranded crew) landed and proceeded to attempt to lay claim to the island for their home country. They were a small crew, however, only 150 men total, who assumed that the welcoming complement of 100 villagers was the total population. When the islanders learned they were under attack they were able to drive them off on land with sheer numbers, forcing them to leave. In the process though, the islanders lost people, both those who were killed by the invaders, and those that were enslaved and kidnapped from the island. * Since then, the islanders have become terrified that they might be under attack again. Paranoia passed through the population, and they began to realize that they may have to defend their island paradise against invaders by sea. * They have (though they don't know it) at least 5 more years before the next group of hostile Europeans comes back. The same explorer will return, with at least 5 fully manned 30 gun frigates (with a crew of ~200 men apiece), who will be fully stocked with all the weaponry needed for a fight on the water or on land. How does my island nation prepare for this onslaught? Assuming that the surviving crew members (who would be senior citizens at this point if they are still alive) are able to inform them of how many people will be on each warship and about how many warships a country might send, **what is their best option**? You have all the supplies and resources of the island nation, and whatever equipment is leftover from the ship salvage 35 years ago. I would like answers to use historical evidence (ie. how have technologically inferior people protected themselves against a technologically superior force in our history?). I'm aware that no nation thus far has been able to fight off a technologically superior force so far in our world, so there may have to be some crazy luck or circumstance involved in your answer, and that is acceptable. **Even if the chances of success are tiny, there must be some way that this island nation can keep themselves from being genocidally murdered.** [Answer] If the population of the islands is still 100k+, you should have 30-40k adult males, all of them at least familiar with hunting weaponry. They should be able to defend themselves against ~1000 soldiers and sailors, unless they line up on the beach to greet the cannon fire. Still, they can do much better by preparing. The tactical situation is highly asymmetrical: The Europeans have superior weapons and can dominate at sea, but are vastly outnumbered on land and need to get supplies ASAP when they arrive. The islanders on the other hand can afford to retreat and wait out the Europeans, but cannot force a win in battle without losing many men, nor can they touch the ships unless they get really lucky. First of all, the Islanders should prepare by building fast sailing ships with shallow bottoms, as rowing boats will not be able to outrun the European ships. Sailing and shipbuilding experience from the original stranded group will be highly valuable. These ships are mainly for scouting, relaying messages between the islands and if possible, luring the big European ships onto reefs. Second, they should relocate any sizable settlement inland, uphill and out of cannonball range. The original huts/houses can be left as a decoy. All paths leading up to the settlements from the beach should be winding, pass through dense jungle where possible and have ready-to-deploy barricades and traps that prevent large groups from passing. Given the number of hunters, littering the jungle with traps shortly after the new fleet is sighted should be feasible. Then the islanders should prepare to deny the Europeans their most important resource: drinkable water. Every stream reaching the beach should have guards in place upstream that can deploy poison or rotting carcasses etc. into the stream the moment they spot a European landing party. If the Europeans venture further inland, they can be ambushed in the jungle, away from their ships. On the smaller islands, this should not be too hard, but on the main island there will be a lot of places to guard. Some kind of long distance warning signals will help. The rest is standard guerrilla tactics: Harass the landing parties, lead them into traps, never engage directly. Sap their will to continue and chase them away. Oh, and if they leave the ships poorly defended on a dark night, it's party time! Finally, a note: Guns of the time were mostly one-shot affairs, as it took a long time to reload, more than was available in a pitched fight. This limits the technological advantage of the Europeans when they are vastly outnumbered. Even if all 1,000 Europeans were to march on the king's city together, they'd most likely lose to the 10,000+ fighters the king could muster in his defense. [Answer] The one thing big ships feared most is fire. Creating catapults or [trebuchets](https://en.wikipedia.org/wiki/Trebuchet#History) that can fling burning balls of pitch onto a ship will make short work of the ships and the crew. I used this [trebuchet calculator](http://www.virtualtrebuchet.com/Trebuchet.html#simulator) and with these inputs a pumpkin would fly about 300 meters. That would give the cannon a run for their money. [](https://i.stack.imgur.com/6j1g5.png) [Answer] Several answers here already say that the answer would be guerrilla warfare. While its true, let me try to put it in context for you. The key here is the definition of victory for both parties. As you may imagine, the definition of 'victory' for the invading Europeans are vastly different from the definition of 'victory' for the natives. For the European invaders, the definition of victory would be their ability to: 1. Defeat the tribe decisively enough to degrade their ability to prosecute effective military operations against the invading army. Thus allowing them to- 2. Conduct undenied military and economic exploitation operations on the new land in order to achieve acceptable returns for their massive investment in the venture. As you may imagine, for the European invaders, mounting such expeditionary operation thousands of kilometers away, using 17th century technology, is a highly expensive proposition. Whatever resource the archipelago has (whether slaves, natural resources, etc.) must be abundant enough, easy enough to gather, and easy enough to transport to the market for the venture to turn a profit, and at least pay for itself. This is weighed further against the fact that the Europeans' supply line, while relatively undenied, is very, very long - even if everything goes smoothly all the time. You have to account for ships being lost in storms, to pirates, and other factors that may impede the resupply of your expeditionary forces. On the other hand, the definition of victory for the natives is relatively simple: For the invaders to leave. *Everything they do will have this objective in mind.* And while the Europeans need to be able to kill the native insurgents in order to achieve tactical victory, for the native guerrillas, sometimes just simply surviving to fight another day is a victory. Thus they have no need to stay and fight pitch battles with the technologically superior Europeans. If things go south in their operations, they can simply retreat and regroup to try again. Their supply lines are also much, much simpler and closer than the invader's. Say the guerrillas mount a direct action raid against an invader supply depot. The raid failed, however, since the invader defenses were much stronger than the estimate. In the fight, the guerrillas lost...oh...say 15 men and their weapons. The invaders suffered lighter casualties. Say 2 KIAs, with some weapons damaged. On the surface, this is a major defeat for the guerrilla forces. But if you take the long view, its actually a strategic victory. The 15 men the guerrillas lost can be easily replaced by 15 other fighting age men from their villages. The bow and arrows they lost can be easily replaced by making new ones. Maybe they lost some metal machete/swords, but if the natives have metal working skills, those can be replaced too. On the other hand, the invaders lost 2 trained soldiers whose replacements are, at best, several kilometers away at the reserve depot, or at worst, several thousand kilometers away at the home country. These replacements, if the latter case is true, will need MONTHS to travel to the Area of Operation, which means that there will be under-strength squads in the invaders' TO&E. The lost weapons are also not easily replaced. Sure they have spares, but how long will they last if the next shipment is 7-9 months away? Yes, the invaders enjoys a massive naval superiority. But remember: Once the invaders land, its a ground game. And the invaders *need* that naval superiority in order to be able to ensure supplies to their ground units. And the ground units are the ones suffering. If the guerrillas attack the invaders daily, inflicting one-two casualties at a time before melting back into the jungle. Then ambushing and mauling invader patrols/pursuit into that jungle every time, then pretty soon the invaders will stop sending small unit patrols into the jungle. Every time they move into the jungles, the invaders will have to deploy large, ungainly, easily avoided formations, which will - invariably - fail to meet expected opposition every time. Morale will start to drop. Losses mount. The guerrillas can effectively operate in the jungle without significant risk. After a while, the invaders' government will start doing the math. Is the cost of maintaining the expeditionary force, resupplying them, replacing their men, replacing their arms, and repatriating their dead/wounded justified against the gains from plundered resources and slaves? Public opinion may also start to sway as rumors start spreading in the invaders' home country that being sent to the 'island front' is pretty much a death sentence. Rumors of diseases, enemies that can disappear into the jungle, shamans that somehow make some enemies impervious to bullets (this can be achieved if the natives are diligent in recovering their dead, for instance, leaving no evidence of casualties), sons that are sent to the front and never return, will put more and more pressure to the home government to call of their island adventure. This is doubly true if the home government is forced to hike taxes in order to cover the cost of the war. The war will quickly become unpopular, and the government may find themselves obliged by their population to bring the troops home. Thus, the natives achieve their victory, even while suffering more casualties. It may take a decade or more, but if they persist in their resistance, this is what will happen and how you can defend your archipelago. [Answer] The islanders don't know the exact strength of the next invasion, but they know it'll be by wooden ship, since that's the only way to get to the island (and ironclads don't exist yet). The invaders' most devastating weapons will be their cannons on the ships. From well out of range of anything you could realistically put together with island lumber, gunpowder cannon will destroy any defensive fortifications. Those fortifications, by definition, wouldn't be mobile, either, so you'd be building them in rings around every island, which is a lot of materiel to put together and maintain at a high state of readiness (the islanders might have an hour's warning as soon as they spotted a sail on the horizon before that ship is in range). The islanders' biggest advantages? Numbers, and lay of the land. 100k island villagers, with 5 years to train everyone physically able to pull a bow, versus 200 men per ship that don't know the best hiding spots? Child's play. My strategy is, when the sail is spotted, evacuate any non-combatants from shoreline villages into defendable areas of the interior jungle. Then, let the invaders land, get them beyond the treeline into the jungle, and pick them off in medium-range combat, away from any artillery support. In the 15th Century, the marines will be using muzzle-loading muskets; their best average, if well-trained, would be about three well-aimed shots per soldier per minute. An equal number of islanders firing bows and arrows would be getting fifteen to twenty well-aimed shots in a minute, firing at will, and at least double the rate of fire of the islanders in coordinated volleys. And, the numbers aren't equal; 100k islanders versus (the reader knows) 1000 soldiers. Even if only a third of the islanders are of an age and physical condition to fight directly, they outnumber the explorers *thirty to one*. If those islanders are well-trained, well-equipped and ready for a fight, which wasn't the case the first time (or indeed in most of New World history), the explorers don't stand a chance. Let them come, whittle them down, then once they've been routed and are in retreat, that's when you pull out those pitch-balls and set the longboats they landed with on fire. They'll be trapped on open beach, either firing blindly into dense jungle against vastly superior numbers by this point, or they'll be swimming for the ships and easy targets. Once their primary invading force is dead, the ships might retaliate with cannonade on shoreline villages, but eventually they'll run out of shot, or supplies, or patience, and the remaining crew will set sail and head back where they came from. After losing nearly 1000 men and very likely the explorer himself if he goes ashore to command his infantry, there's no way whomever backed this venture would waste any more money. 15th Century sea travel was very unpredictable, so even if you amassed an equal force to the islanders (which would require 150 ships), it's not a guarantee that all the ships and their marines will make it to the archipelago in combat-ready shape. The one weak point here is the spread of the islands. For this strategy to really work, you have to significantly outnumber the entire force of explorers on any island they might land on; if islanders from nearby islands broke cover and headed for the island under attack, they'd be easy pickings for the ships, which would very likely form a blockade. You can't mass your forces on any one island as the enemy will simply take the rest of them and lay siege to yours. Thirty thousand warriors, spread evenly over seven islands, still gives the islanders slightly better than a four-to-one advantage in numbers over the maximum possible force the explorers will being to any one island; not the overwhelming thirty-to-one advantage, but if it's played right with guerilla ambush tactics there's still little hope for the invaders, and if the invaders split their forces to take multiple islands at once they're even easier prey. [Answer] Note that many of the invaders will be weak and diseased from scurvy for anywhere from several days to a couple of weeks after arriving, depending on severity. They will also be short of fresh water, and in the words of the old adage such as they have will be drinkable only by "holding the nose and straining through one's teeth". It is likely that the healthiest arrivers will be responsible for obtaining fresh fruits, vegetables and water for the crew(s) promptly on arrival, so that the others can begin recovery and supplies can be restocked. To the extent that the invaders can be prevented from obtaining fresh fruits and vegetables, the actual effective force of invaders will be much less than the nominal numbers for a longer time, perhaps several weeks post arrival. If the invading ships can be forced to send substantial foraging parties in order to obtain such supplies, the recovery of the remaining crew will be compromised. Any type of guerilla warfare against smaller foraging parties, taking advantage of local knowledge and numbers, will force such parties to be larger, and limit their ability to resupply. To the extent that the count of the healthiest arriving invaders can be reduced, by a single large initial ambush, the entire ability of the invaders to restock and recover can be compromised - think "red wedding". The invaders will work strenuously to hide the sickness of, with a little luck, up to 3/4 of the crew. Note that the cannon of the invading ships are designed to engage similarly sized, or slightly smaller, vessels, and cannot be aimed downwards at ranges of less than several hundred yards. Small fast sailing vessels will be effectively immune from the cannons inside those ranges, and the arriving ship's will likely only have one launch each that can be equipped with a single forward-facing carronade. As the largest, and most valuable, of each ship's launches it will not be put in harm's way unnecessarily. Guile is your friend in this circumstance. Be polite, but firm, on arrival; the newcomers are welcome to restock, but as all property is the king's they must first formally request such permission at a banquet where gifts will be exchanged. Your gifts will of course be small samples of the supplies that the invaders most desperately need - fresh water, fruits and vegetables. Only by giving them tokens of what they most need will you get anything beside pretty glass beads back. A local village headman might be authorized to participate in a *small* such exchange with each ship's captain, once, as a token of good will. Delay the banquet for a few days to make them appreciate its significance. The marines will be armed but the general crew **will not be armed unless a clear and present danger is present**; take advantage of that. You will have exactly one opportunity when only a small percentage of the invaders will be ashore with firearms (Each will though always travel with a large utility knife, useful for cutting everything from food to a neck.) - leverage that for maximum effect. This is how Captain Cook was killed by the original Hawaiians. Ignore the advice rendered elsewhere about "shallow draught sailing vessels" - there is no such beast. without a draught appropriate for overall vessel size you will be able to sail only downwind - the invaders will quickly take the wind gauge on you and blow you out of the water. Instead, focus on upwind sailing ability by being a small vessel with slightly greater draught - if you can outpoint the ships' launches you can take the wind gauge away, and be effectively immune from any chase. Think *[lateen-rigged](https://en.wikipedia.org/wiki/Lateen)* [*dhows*](https://en.wikipedia.org/wiki/Dhow) from the Indian Ocean and Sea of Arabia. Note also that the cannons of this time are subsonic - muzzle velocity slower than sound, perhaps only 400-500 feet per second - which means that a small agile vessel can actually duck cannon fire at the ranges which the ship's cannons can lower their guns to. Gibe or tack on the smoke plume and the ball should pass your rear safely a second or two later. Once you are too close to duck, you are well inside the range that the guns can be lowered to fire at. [Answer] One other point is that there's a difference between "warriors" and "soldiers". Your islanders sound like they fight as individual hunters trying to prove their personal bravery. European explorers crushed entire civilizations like the Inca partly because they knew how to fight as a team: to flank an enemy, to concentrate fire, to use ranks and signaling to convey orders and have them be followed, and to retreat in an organized, relatively safe way. Soldiers fight for a shared victory. Your shipwreck survivors brought along some knowledge of that military culture, and it's a vital part of organizing the islanders for defense. For flavor, you could portray this education by having the survivors tell stories about their wars and initially confuse the natives who don't understand "tactics" or "officers". Use the Iroquois symbol of snapping one arrow in half but being unable to break a bundle of arrows together, or demonstrate how a proof-of-concept organized team can clobber a traditional warrior band. +1 to the idea above of a betrayal, too: look at the story of Arminius/Hermann for a good example of Germans annihilating three Roman legions by tricking them into dense forest where their tactics didn't work well. [Answer] I've read all the strategies proposed here and, while in all fairness that was the question, they all assume the islanders were going to win, mostly by guerilla warfare. I see it in a different light, however. A force of 1000 man, say 700 trained soldiers with muskets, and 300 sailor, 150 cannons and of course a number of officers with strategic experience arrive in five ships. That's a highly mobile and highly capable force that don't do stupid things like wandering off in the jungle in small groups. Here is my strategy for the commander of the fleet. Having the information gained by the previous visit the commander knows the size, layout and distribution of the islands, its population, their technology and that they are hostile. He will make no assumptions, play safe and head directly out to the smallest island to establish a base of operations and resupplies. With 8 islands, one can assume the smalles one to have 5k inhabitants, of which about a third 'warriors'. More importantly, that island has 2/3rds women and children. It being the smallest island, it is the easiest to look on to while sailing around. A landing spot is chosen close to the resources the islanders need, like water. This is likely close to their village. Initial salvoes of the cannons chase the villagers away while the soldiers land, and secure the landing by using the cover that's there. Once secured, part of the soldiers start constructing the first fort. Any remaining islanders in the nearby village are taken hostage in the fort. After the fort is constructed, fire is used to burn down the forest on the island to force the islanders further into retreat, demoralise them, deprive them of their resources, demoralize them and to create more open space to fight. The solders move in larger groups, taking female and child hostages along, never venturing in the remaining dense forest, trapping the islanders and forcing them to surrender by demonstrating killing the hostages one at a time. Within a short time, the European force will have control of the small island, a base, a fort, supplies, control of the sea and hostages as leverage. Next to the second smallest island. Rinse, repeat. By the time they reach the biggest island the commander has so many hostages out of reach of the islanders the king has no choice but to surrender. You have to keep in mind a few things. * Europeans, at that time, especially sea faring soldiers half a world from home, were no kind folk. Europe has seen mosly war and cruelty, in contrast to the islanders who are likely peaceful, as they have one nation and need to live in harmony with the island to survive. That puts the Europeans at a big advantage. * The invaders have nothing much to loose, except their ships, which are out of reach. They can fight on enemy land and as a consequence the islanders have their entire environment to loose. Forest fires and other pillaging of the land can not eaily be overcome. A great disadvantage for the islanders. * The island warrier's families on the island are their weeknesses. Any hostage taken, especially the non-warriors, is a potential handful of islanders surrendering, and this cascades. The warriors need also spend resources to protect them. The invaders, being soldiers, bring no such weakness. * And then there are all the diseases that the Europeans bring. In south america it's estimated that 90% of the native population died of them. Once the invaders have set up base with provisions, it's over. [Answer] Your defense should be designed to force invaders to attack where it most suits you. This means altering the landscape. Build sea walls and obstacles to prevent landings. Clear trees to deny cover. Install obstructions to prevent moorings. Basically, you want to build a strong defense everywhere except for planned "weak" spots. Funnel any invaders into deep canyons or swamps, for example. Then build fortifications there. This is a jungle island, so your fortifications can be camouflaged well. Build trebuchets for attacking the ships. Build strong positions from which you can rain down arrows and spears on foot soldiers, and from where you can launch enveloping attacks. Smart commanders will recognize the dangers of the situation immediately, but you leave them no choice. If they want to take your island bad enough, they will have to play by your rules. If you do it right, they will pay dearly. [Answer] ## **Massive Deceit.** In an upset to other answers, I would like to pose a completely different methodology. Already as a given, since the last contact with the Europeans was conflict, they should assume conflict is going to return. It would seem unreasonable that the last part mapped out all of the islands, so the assumption would be that the next group will be arriving near the current one. Not knowing how much will return, the information of the size of the landing party will be critical in carrying out any response. It is much easier to get information from a friend rather than an enemy. Therefore, create a fake welcoming party made up of the initial saved Europeans. Claim that since the last attack they have been able to convince the islanders that European culture and knowledge is superior to theirs and that they have been hard at work converting all of the islanders to a European way of thinking. Have the welcoming group wear clothing that looks as much like Europeans styles as possible. Have the buildings look more European. Place large signs on other beach villages that state a bearing/distance pointing to the Welcome Port. Create a special harbor that specifically accommodates large ships that would be expected to arrive. Create a paradise atmosphere at this welcoming point. Welcome the new ships to dock at outlying docks (not connected to the land or alternately, connected with quickly burnable floating dock) in the harbor. Explain that the crew (other than the officers) will need to stay on board until appropriate housing can be built. The officers will be bunked for the night on shore, and murdered in their sleep. The ships will be attacked with fire at daylight and all survivors swimming to shore will be killed before their feet hit the sand. It is better that NO word return to Europe than for the any Europeans to flee and return with an even greater group. Playing this out with each exploratory attack thereafter will create a superstition that this area is cursed, and to be avoided. [Answer] A lot of these answers focus on guerrilla warfare - and I broadly agree. You have 30-40,000 men who can draw a bow, throw a spear or wield an axe, and that's a huge advantage; nor should you forget that many of the women will be capable of using bows, slings, or other skirmishing weapons. What's more, you don't possess the population base or the technological base to really beat the Europeans with quality rather than quantity. However...none of the answers above deal very effectively with the strategy for the invaders proposed by durandal, IMO. With a minimum distance of 8 miles between islands, dealing with boats trying to cross from the other islands is relatively trivial for a bunch of frigates. They'll have cannon, swivel guns for up close work, and better ranged weapons in general for dealing with small boats. Once they've built a fort they can sail off with most of their men to try the same thing on another island - you don't have anything good for attacking fortifications without taking massive casualties. The plan needs an added element. So, let's list out what we need, in order of priority. 1. Militia on each island. We have thousands of people capable with weapons; what we need is a trained structure. Everyone knows that when ships come over the horizon, the non-combatants head for the hills, the combatants meet up in their groups, and they prepare to skirmish. No stand-up fights, plenty of hit and run. They need to remain an active force, hopefully able to prevent the enemy from completing fortifications. If they can't achieve that, anyone leaving the fortifications needs to be harassed, anyone standing sentry needs to occasionally take an arrow or blowdart through the throat, etc. 2. Training against European weapons and armour. You have some examples - your militia can be helped enormously by knowing how long a pistol or arquebus takes to reload, what their accurate range might be, how damn loud it is when actually firing, etc. Militia who know a line of arquebusiers are at risk when they just fired a volley are going to be much more effective than militia who are in shock over the explosion, gust of smoke, and their friends screaming next to them. (As an historical example, the Zulus were primarily armed with spears and cowhide shields, but they knew about firearms and had a very few. Look how that turned out for British soldiers with breech-loading rifles at Isandlwana, a good few steps up from 15th-16th century muskets). 3. Ships that can outsail the Europeans between islands. This should be possible if you use a triangular sail plan - European ships are generally square rigged for efficient sailing downwind. You don't need to go huge distances, so that efficiency is less important than accessing more points of sail, which triangular, fore-and-aft or lateen rigs can get you. If they're coming with five, each carrying ~200 men, you need at least as many, ideally more like 10. Yours can be smaller, if that lets them be faster or easier to build. The reason for this is that it gives you the ability to gather your best soldiers, and land them on whichever island the invaders pick. Sure, maybe you have to take a circuitous route, and/or sail at night, but now you can shuttle reinforcements between islands. Even if your reinforcements are no better trained and equipped than the standard militia, their arrival will still be a morale boost for your side. If you think you have enough boats, but there aren't any Europeans yet, build more, as long as you have enough wood available. Better transport between islands is a benefit to your nation in peacetime, too. 4. Prepare at least one fortification. Earthworks, ditches, palisades, etc. You want it to be some distance from the shore, so that if the invaders wish to take it from you, they will have to really commit to it - bring most of their soldiers along, and spend days on it, first landing on the island the fort is on, then dragging themselves + maybe some cannon towards it, being hit by pinprick attacks all the way. The purpose of this, like the *pa* of the Maori wars, is to provide a "key point" for the Europeans to attack. They have limited powder and shot, limited men, and unless they're getting food stocks from your people strictly limited time. If you harass any attempts they make to entrench themselves, but otherwise deny them combat, their leaders will grow frustrated and are likely to want to strike against a key target like "The Royal Compound". If taking this will also secure them a fort, all the better; their attacking the fort is the closest thing to a dead cert you're likely to be able to arrange. The fort garrison are likely to fare pretty badly here, but they should repel at least a couple of assaults, and bleed the Europeans heavily in the process. Combine militia outside the fort, harassing the invaders, and you should be able to whittle down their force substantially, even if they take the fort eventually. And if they do, so what? They have a bunch of earth ramparts, with strictly limited food and water supplies, hours of travel from the coast. They're surrounded by hostile forces, and they just put themselves in their own Dien Bien Phu for you. Oops. 5. Finally, this is the tricky one, and it depends very much on what resources you have available, what leftovers from the shipwreck, whether you can get some blacksmiths up and running (do you even have iron ore available?) etc as to exactly what form it takes, but you need a tough core to your forces. Better trained, better equipped, an elite to your militia's main body. You don't need as many as there will be Europeans. One hundred could be enough, hell, even fifty, though obviously the more you can train and equip the better. This is a sword with several edges, and you'll be using all of them. Firstly, it strengthens the central leadership's control over the islands as a whole - you know, and they know, that it can beat the militia at need, so as long as you control the elite you will be secure on your throne. Secondly it adds to the effect of your ships, both physically and morally; they can land as many elite as they can militia, but the morale boost of the elite coming will be bigger. Thirdly, it gives you a better chance of winning a stand-up fight, if you choose to pick one (like at the fort you built back in the last point...). Fourthly, your elite soldiers on a few of your ships, there's an outside chance that you can mount something like a cutting out expedition, taking one of the European ships off them. The aim with all of the above is to give the islands options. Flexibility is key, because if the invaders manage to dominate one island and fortify it, pure guerrilla tactics are going to have a hell of a time throwing them out. You have greater numbers, but you have to be able to bring your numbers to bear effectively; and at the same time you have to be able to hold together your people until you eventually reach victory. You're going to have to maintain communication between the islands, you're going to have to be able to pull occasional morale-boosting victories out when required, and you're going to have to be able to occasionally shape your enemy's actions (like with the fort) in order to overcome their advantages and lead them into trouble. [Answer] Islands roughly like Hawaii could not support 100k hunter gatherers. At it's height, the Hawaiian islands only supported a population of about 160k people and that was only possible through intensive agriculture. Without agriculture, the only real easily available food sources that Hawaii had were birds and fish, and there wouldn't be enough of them to feed 100k people. Tom Dye says in his book, [Population trends in Hawaii before 1778](https://evols.library.manoa.hawaii.edu/bitstream/handle/10524/482/JL28007.pdf?sequence=1), "By the time of Cook's visit, the lowland forests of the Hawaiian islands had been greatly altered by more than a millennium of industrious gardening." What that means is that you're going to either need to adjust the technology that the population has available to it, or reduce the number of people that are in the population. Also, the amount of land required to support 100k people will need to be pretty vast - especially if you're considering it to be roughly equivalent to Hawaii, with it's topography created by vulcanism - there will only be a certain amount of usable land and the rest will either be on hillsides too steep to farm or otherwise unusable. This means populations will be concentrated into farming communities in the lowlands. You aren't going to have cities - instead you might have large villages. This makes a central leadership and communication difficult and unlikely. The kingdom of Hawaii didn't exist until 1795 and wasn't fully unified until 1810 - this largely through the instigation and technology of westerners. [See the Wikipedia article here.](https://en.wikipedia.org/wiki/Kingdom_of_Hawaii) You may run into the situation that the Spanish did when they conquered the Aztecs - they happened to meet with other groups of Native Americans, like the Cloud Warriors, who happened to be in the middle of a fight with the Aztecs and who used the Spanish and their technology as an opportunity conquer them. Any way you look at it, the end result is bad if if the natives fight. They need to make some powerful western friends quickly or they're screwed. [Answer] Just a thought - with 100K inhabitants there is likely to be internal dissension, multiple factions etc. What are the odds that some faction in your nation's capital may want to aid the invaders to improve their own standing? I think the conquistadors conquered South America with a couple of hundred spaniards and a native levy of many thousands. Whoever is in charge needs to crush any internal dissent, ensure his claim to the throne/king's hut/whatevs is safe. Then, most of the guerilla recommendations might be a chance. Might be worth reading about the first Italian attempt to conquer Abyssinia/Ethiopia, or the New Zealand Maori campaigns! [Answer] An example from history: The Maori used their skills at fortifications (pa) to inflict heavy losses on the British. Given the disparity in equipment, this seems quite unexpected. They basically built fortifications that negated the British advantage in artillery and firepower, and lured them into close combat, at which they excelled. To quote the Wikipedia article on the New Zealand wars: "Although outnumbered, the Māori were able to withstand their enemy with techniques that included anti-artillery bunkers and the use of carefully placed pā, or fortified villages, that allowed them to block their enemy's advance and often inflict heavy losses, yet quickly abandon their positions without significant loss" [Answer] How well guarded are the powder magazines on the invaders ships? At that time in history, suicide was regarded as a sin that condemned the suicide's soul to eternal damnation. If the natives do not share this cultural conditioning a suicide attack by a single man per ship might succeed. [Answer] The should actively train and refine their communications network. If one island sights invaders inbound, they should immediately dispatch envoys to every other island to inform them of enemy positions. They should send regular updates on troop movements. These envoys need to be very brave and experienced at crossing the straits of water. If the invaders attempt to converge on one island then every island should lend support to deny the invaders a foothold. The defenders should strike at the beaches if possible but also need to have hard points to retreat to until reinforcements arrive. Due to constraints in time and resources, and limitations in engineering, these "hard-points" would be mostly be naturally occurring land forms of an easily dependable nature, rather than man made fortresses. They also need to increase weapon production and train at their arts of war. Wooden shields should catch 15th century arrows. However wood or stone spear heads will not impale chain mail. However, chainmail is very poor at protecting against bludgeoning weapons. The tactics should involve trying to outnumber the enemy ant any stand so that 5 islanders with stone clubs can single out 1 invader to bludgeon to death. Iron helmets protect the European's skull from fractures, but enough force can cause concussions and damage the neck. Pummeling the body breaks ribs and leaves the victim gasping for air. If Islanders win battles they can then strip the battlefield for the European's superior weapons and armour. [Answer] One major advantage the Native Americans had against the conquistadors they were not even aware of: microbes. A factor I think most of the above commenters have overlooked is the power of the defenders’ diseases. A HUGE amount of Westerners were wiped out by syphilis (originally endemic to South America) after the discovery of the New World. Have the islanders send out a welcoming party of sick islanders and kill everyone via biowarfare; the Europeans will not have the genetic resistance to native diseases that the islanders have. [Answer] Your island political structure is unrealistic. While shortlived kingdoms have encompassed ocean groups at that stage in civilisation (without the emphasis on hunter/gathering), they have never been long lasting. However I'll assume that for some reason it's not. Hunter gatherer societies such as Australian tribes do not amalgamate under a king, hunter gathers are on the move, they don't need or want a king, because their resources are not fixed. They can be every bit as belligerent as you want, but you can't have a king in the sense we know it. 5 Boatloads of Europeans can easily be resisted, just by taking to the hills and laying waste the land. The downfall of all the sizeable places taken over by small groups of explorers was the natives would be recruited and armed by Europeans, not Europeans fighting alone. Or they were weakened by introduced diseases. Assuming these factors can be discounted then it's pure guerilla warfare against an inferior number of invaders with all natives against them. Fortify the Highplaces such as the Maori did in NZ, fight a guerilla war of attrition. Kill any prisoners in terrifying ways to hurt enemy morale. The NZ Maori were never totally defeated even against large numbers of imported European soldiers. They'd just lose a battle and retreat to another fortified position. But they were never united, there was always tribes fighting with the invaders. Without those tribes, the Maori would have sent the Europeans packing. Unless the natives join the invaders, the invaders don't stand a chance. Their stores of food will run out, and attrition will weaken them until they can all be massacred. [Answer] In 1346 Genghis Khan was attacking Kafa with catapults. They used the bodies of their own dead who had died from the Black Plague as ammunition. This would have been known to the sailors of the returning army 250+ years later. By taking all Islanders who were in bad health, and tattooing "PLAGUE" on their foreheads before they died, they insured the safety of their neighbors by volunteering themselves to be used as ammo when the invaders returned. No one wants the black death aboard their ship... [Answer] And here are some other interesting flavor-text suggestions... 1. Train native birds to remain in a single area and make a particular cry when their "feeders" come (basically any human being). This would set up an alarm system that could heard over long distances, and which could be used to track invaders trying to move through the interior. They could be trained to be quiet when given a particular signal, so that the islanders are not trackable by the same means. 2. Dolphins could be trained to carry islanders quickly from place to place. They could be used for the shipboard invasion. In fact, you might have dolphin transport be a tradition already present among the islanders even before the invaders came. 3. In every body of water there are dangerous shoals and other areas that could sink or ground a ship if not seen. It is essential to know where the danger spots are when piloting a ship. The islanders might set up some kind of water ambush or lure the ships into a situation where their cannon are not oriented to be able to fire at the enemy and if they turn they will run aground (some kind of narrow passage between reefs) 4. One of the sailors might be a student of Sun Tsu (<http://www.military-quotes.com/Sun-Tzu.htm>). There are some brilliant quotes here and great military advice. [Answer] If they know the direction from which the invaders will come, how about a pre-emptive strike of fire ships/boats, sea chains, burning buoys/primitive sea mines? This might as least slow the invaders and bring their morale down. If you can bring down even one out of the five frigates before it lands, you've gained a serious advantage. Gonna have to have some sea patrols a distance from your islands to raise the alarm, but I'm sure that the industrious+paranoid islanders can handle that. And how about negotiations? We've had a rough couple of battles. Let's trade, we'll give you gold/exotic animals/cool smoking weeds, you give us tech or whatever. Can't we all just, get along? Alternatively you can fire pumpkins at them with your trebuchet calculator (loved that one). [Answer] The old survivors are likely to be able to help with vaguaries, such as how many will come on a ship, what proportion will be soldiers, and what proportion will be sailors etc. but not how many will come. (But they will know that they will come, and that there will be more). If there's a resource that the invaders are after, they are likely to know how valuable it is, which will give them some indication of how much "home" will want that, and as such, how long they'll keep sending troops before it's a waste of good resources (which won't necessarily stop the waste for reasons of politics, pride, arrogance, or the sunk cost fallacy. It might even become a matter of sending a message/a matter of principle for the rulers at home). Many of the salvaged weapons probably won't be much use at this point; whilst the few firearms they brought are probably fine, the gunpowder just won't last that long. However, if the survivors included at least one person with the knowhow to create it, and the islanders would need to be able to prepare and mix (grind) potassium nitrate, charcoal, and sulphar in the right ratios, then they may well be able to make explosives, or rudimentary rockets. They would have a few guns, but not in numbers that would likely make them useful. However, the facilities to make gunpowder in useful quantities would mean that there is likely to be a change in society and environment as it's not exactly something that can be done in someone's spare time, and it will become a full time job for a considerable number of people. Even more so if the firearms are considered, as they would need to make shot too, so shot towers would need to be constructed, assuming that any of the survivors knew about the production of shot. [Answer] Something I have not noticed much in other answers, but may be helpful to the islanders: The Islanders know their own waters! How does this help. As has been mentioned, the invaders supply chain runs from the ship to the invaders on the island. If you can sink the ships, advantage goes to the islanders as they can wear down the now land trapped invaders. So next, how to capitalize on this? Many islanders, to judge from the movie Moana, my only real reference, would be able to navigate by the stars. the invading boats will also often have shipboard lights. Islanders could sail around and come at the invading ships from unexpected directions. They could send boarding parties to reduce enemy numbers and hopefully destroy water and food supplies. Don't go for the powder magazine unless the shipboard contingent is relatively easily overwhelmed. Food and Water should not be as massively guarded. In addition, a lot of the islanders might be excellent divers. Get close to a ship at night, then send divers underneath to weaken or put holes in the enemy hulls below the waterline. The previous sailors should have a fair idea where on the invading ships a small amount of damage would do the most to cripple the ship. Once the ships are neutralized, the ships cannon come off the board and you should have a relatively easy time mopping up. [Answer] Only one way to defend your island when your enemy is superior: know your enemy, accept it , learn enemies strategies and weapons, then try to fight him with his own weapons... ]

[Question] [ There are already real-world problems with analyzing whether particular graphic evidence is "photo-shopped" or genuine. In sci-fi technologically advanced future, realistic and perfect computer generated images are pretty much standard. Same applies to audio. In past, graphic and audio manipulation was only for professionals. Now, simpler tasks such as removing pimples or altering (obfuscating) person's voice is something everyone can do, often with little effort. We can go off a hyperbole here and expect people to be able to assemble realistic photos of things that didn't happen at all. Details about how this is done are not point of this question, but it is *perfect*. Under such circumstances, is there any reliable evidence? Or does that put world back in the dark ages, where you can only rely on people's testimony? I've been thinking, but did not figure out **anything that could be used as *universal* evidence that someone did or said something**. Is there something I missed? [Answer] # Cryptography. If the surveillance camera contains a private key which it uses to sign its footage, that's a piece of evidence you cannot fake without having access to the camera's private key. Any piece of digital data could be required to have such a cryptographic signature in order to count as evidence. To prove that some image or other digital data already existed at a certain time, its hash could be entered into a public database that keeps track of the time of entry (this could be a government database, or something like the Bitcoin blockchain). # Digital trace Already today we generate a digital trace throughout the day, from location data of our mobile phone, to places where we used a credit card, to places where we happened to walk by some surveillance camera that we didn't even notice. In that future, the digital trail will probably contain much more detail. While you can fake single pieces of evidence, faking a complete consistent digital trail is a completely different issue. For example, say you manufactured evidence that you were in a specific shop at a specific time (and therefore could not have done the crime which happened elsewhere at that time), then the police would request the shop's customer tracking data. And then, if the customer tracking data doesn't show you in there, you'll have a hard time to explain. Oh, and that automatic update of your XY app, which happened to run right when the crime happened, came from an IP handed out by a wireless network that covers the crime scene. [Answer] I think you are missing the fact that generally speaking, even in courts of today, **no *single* piece of evidence is sufficient for a *guilty* verdict.** Sure, technically speaking, you can make an image that is awfully difficult to tell that it is fake, and present that as evidence in a case. But if the other side disagrees, they will present their own evidence which contradicts yours. If both sides present equal amounts of equally valid (in the eyes of the court) evidence, most modern societies fall back to the principle of presumption of innocense. If either side is able to present more or better evidence for their view, then that side usually wins. This is how courts already operate, and while it isn't perfect, it's pretty widely believed to be better than the alternatives. So if, in your world, *perfect* faked images and audio clips are commonplace, then the courts would have to operate within the assumption that *any* presented image, video or audio may have been tampered with or outright faked. As a result, the evidence value of those will be reduced, possibly to the point of being a mere curiosity rather than considered valid evidence. Suppose that in such a legal environment, I claim that you robbed me in the street, and I am able to present a photograph allegedly showing the event. The picture is good enough that everyone can readily see that you are holding a gun to my head while I drop my wallet on the ground, there are no signs that the image has been tampered with, and all of the image metadata corroborates my story. How might you defend against this accusation? **You might defend against my accusations *by providing alternative evidence showing that you were somewhere else.*** Phone metadata exists in today's world, and very few people in the Western world do not regularly carry a cell phone with them. If you are able to show that the cell phone company had your phone moving through a different part of town at the time of the alleged crime, that: * shows that you might not have been where I claim you were at the time (at least, it shows that *your phone* wasn't at the location where I claim you were) * brings in a third party, which presumably has no particular interest in the outcome of the trial, and thus can be assumed to be reasonably impartial -- this is already the defining principle of witness testimony Note that cell phone metadata is only one example; there are many others. Another example would be that a bank might be able to confirm that you made a purchase five minutes earlier on the other side of town -- sufficiently far away in terms of distance, and close enough in time, that you couldn't possibly have been where I claim you were at the time when I claim you were there. There is also the seemingly growing abundance of monitoring cameras throughout our society, which could also provide corroborating evidence from third parties. And of course, human witnesses (hey, I was walking my dog and stopped to chat with the neighbor around the alleged time; ask the neighbor, and check *their* phone location records to see if they agree with those for my phone!) If you are able to present multiple such pieces of evidence that support your story of you being innocent, and I am unable to properly address that discrepancy, at the very least that seems likely to lead to a *not guilty* verdict, and may also get myself into trouble as having given **false testimony.** In the end, **evidence which can easily be faked is trusted far less by courts than evidence which is non-trivial or very difficult to fake.** Assuming that the justice system remains similar to ours, this would seem likely to not change in your world compared to ours; **only the relative trustworthiness of different classes of evidence would change.** It also seems likely that, in a world where much evidence can be easily faked, **the penalty for false testimony would be much harsher than it might be today.** Of course, a *not guilty* verdict does not necessarily imply *innocense*, but again, that's a trade-off where a society has to choose which alternative is worse. It's either living with the risk of people who committed crimes being pronounced *not guilty* and walking away, or living with the risk of people who did nothing wrong being pronounced *guilty* and being sentenced for a crime that they did not commit. [Answer] # Secure storage / chain of custody It is already the same in nowadays courts. Whenever you present some piece of evidence in court the first question will be "how have you obtained this piece of evidence?" If your evidence could have easily been faked you will either have to provide an expert which can assert your evidence is an original (not possible with perfect CG) Or you have to present where you have obtained the evidence. If it is CCTV footage, someone has to have given you the tape - the security guard of the place owning the CCTV camera can testify that the tape you present is indeed the unaltered image which is also recorded in the secure temper-resistant storage of their secure server. They can even send a security-expert to verify that the secure storage is still safe and the original is the same as presented in court. If you have an audio tape you will need a witness who recorded the tape and can testify that it is original. You can also build temper-resistant recording devices, which will record GPS, ambient noise and more together with audio to a write-once protected storage. [Answer] ### DNA, fingerprints, ballistic forensics and other types of "old-school" forensics would still be just as valid as they are now. The police finds a naked woman and her lover shot dead in a bed. In the woman's husband's house, they find a gun. The gun is registered in the woman's husband's name and has his fingerprints all over it. The bullets from the crime scene are all perfect matches to the gun. Hairs matching the husband's DNA are found at the crime scene. The husband's fingerprints are found on doorknobs at the crime scene. Dirt from outside the crime scene is found underneath the husband's boots and the tires of his truck. Tracks exactly matching the tires of the husband's truck are found outside the crime scene. They show the vehicle aggressively skidding to a stop outside the building. Footprints made by his boots lead into the building, into the apartment and all the way to the bed. No video. No eyewitness testimony, even. Yet plenty of evidence to convict. That was just an extreme example or an "orgy of evidence" where I listed some examples of "old school" types of evidence. ### Witness duty In an age where all photographs are assumed to be potentially fake, the police may develop certain procedures where they, after they have finished their crime scene investigation, bring dozens of eyewitnesses to the crime scene, observing all the evidence and making notes. These witnesses may be asked to appear in court as a substitute for photographs of the crime scene. [Answer] I'm not a technical expert but then I suspect I don't need to be because your question states that the 'evidence' can be fabricated to a point where it's simply not possible to prove it isn't real. So with that in mind I think what you end up with is a shift in how that evidence is used. This sort of evidence (lets say cc tv of a person performing a street robbery) is given a lot of weight because at the moment it's much more likely to be real than fabricated. Especially if the person on trial is a petty criminal or has no previous history of crime. Also the theft of a small amount of money would suggest that the expenditure of time and effort to fake it isn't reasonable. If it was cc tv of a world leader being assassinated then it may well be in the interests of an organisation to make a fake. When there is no way to know if that cc tv is real or not then it becomes no more useful than the testimony of a third party saying that is what they saw. In fact it's probably slightly less useful as the person can be questioned where as the piece of tape can't. I think perhaps that it would still be admissible but given no more weight in legal terms than circumstantial or unverifiable evidence is today. Just like the fictional 'gangster' can provide a number of eye witness accounts that he was out of town the night of the shooting by either buying or relying on the loyalty of his mob, he can now also provide digital 'proof' as well. If you allow your high tech to be able to fabricate forensic evidence as well as visual and audio then it's even worse and we are down to simply interviewing people on the witness stand and making up our minds based on story inconsistencies and overall reliability of their testimony. [Answer] One method I've seen to approach this is the development of one-shot-record-multi-read-only devices made as indestructible as possible. Attempting to get into or influencing the device to alter it results in the destruction of the recording. While it cannot prevent loss of the recording, which has its own implications, it can prevent tapering. However, it may not be able to prevent deliberately staged events unless there was also some sort of precise location tracking that either was completely internal or is external and somehow unblockable and unspoofable in and of itself. As mentioned in the comments: tamper-evident is almost always as good as tamper-proof for evidentiary purposes. [Answer] In addition to the cryptography, digital trace, and secure storage/chain of custody answers already provided, also consider the possibility of statiscial analysis that can identify manipulation in subtle ways. Here is a link to an article that describes some of these analyses: <https://articles.forensicfocus.com/2013/08/22/detecting-forged-altered-images/> This article discusses how simply opening and saving a file can change the structure of a picture without producing visual differences; how inserting a new image into another picture will leave mathematical artifacts that can be discovered with error analysis; and how subtle differences in quality in different portions of the same photo can be proof that the image was manipulated. Now, there *may* be techniques that can be used that *might* mitigate some of this: one idea that comes to mind is to perfectly model a scene, and then create a perfect CGI with no artifacts. Even in a case like this, however, it may be possible to show statistically that the scene is fake: digital algorithms themselves often leave certain statistical "markings" that might be identifiable -- and, for that matter, going back to the quality issue, such a generated scene might have a quality that doesn't match the available video equipment that allegedly filmed the incident (ie, grainy when the camera would have had a high amount of detail, or highly-detailed when the camera would have been grainy). Finally, it would be important to corroborate video evidence with details from the real world. A forger, for example, may have known that the individual in question wore a popular designer jacket, but would not have been aware of the tear in the jacket that happened at a party the night before, in a spectacularly embarrassing incident that everyone saw -- or, alternatively, that photo that the prosecution is claiming to be fake also happens to show a name-tag sewn on the jacket, that the person alleged to have faked the photo would have no reason to know actually existed... [Answer] To prevent pictures/videos/sound files from being edited afterwards, use [Trusted timestamping](https://en.wikipedia.org/wiki/Trusted_timestamping): [](https://i.stack.imgur.com/E3TXM.png) *[CC-BY-SA-2.0 Tsuruya](https://commons.wikimedia.org/wiki/File:Trusted_timestamping.svg)* With that technology, you can easily and reliably check **when** the data has been timestamped. The person was killed on Tuesday, the CCTV shot was timestamped on Wednesday: Something is not right. Data without a trusted timestamped would not be considered valid. If you tamper with the data and want to use it as a proof, you have to timestamp it, but the date would be at least an hour late, or you would have to bribe the timestamping authority, which we can assume is not realistic for most criminals. The timestamping authority could be a well-protected autonomous service within the United Nations, so that it is resilient to even governments pressure. The only strategy for the criminal would be to perform all of these steps within a few seconds, probably assisted by some artificial intelligence: * Take the picture/video/sound * Decide what to remove, what to add * Perform the transformation with perfect CGI (presumably much more resource-intensive than your usual face-swapping app) This would limit abuse to only very carefully planned crimes. Once timestamped, there is no way to go back to fix any inconsistency. As pointed out by Peter Cordes, trusted timestamping does not protect against pictures/files that have been photoshopped *in advance*, before the actual crime took place. In this case, you have to predict everything in advance: the state of the trash bin, the shape of the blood stains, the sun and shadows, etc. [Answer] Lot of answers already but it's an interesting question, so my two cents worth: This isn't a new issue. I read an article in a computer magazine decades ago where the writer argued that with the growing power of image-editing software, photographic evidence would soon be almost useless. Video is a lot harder than a single still, but as you say, we're getting there. Anyway ... First, I'd question the premise. Could any CGI really be perfect? Yes, the technology to produce better CGI is advancing. But so is the technology to analyze images. I can readily imagine police experts (or whatever experts) carefully examining a video and saying, Wait, this is clearly faked, because on frame 6892 the shadow cast by the person in the video is 1/2 of an inch from where it would really be under these lighting conditions. Or, after running up the stairs like that he would surely be breathing heavily, but his chest is not rising and falling any faster than it was in earlier frames. Etc. Second, even if it's perfect in that sense, an analyst might be able to demonstrate that aspects of the image are exactly what you get when you use Fwacbar CGI Creator version 8.2. A few years ago a reporter claimed to have uncovered embarrassing memos about the military career of a certain presidential candidate. He even had the memos posted on his network's web site. And he was quickly shot down, because the memos were supposed to have been written in 1973 but were EXACTLY what you would get by typing that same text into modern versions of Microsoft Word using default fonts, margins, etc. The reporter tried to argue that someone in the 1970s COULD have produced such a document using printing equipment available at the time, but many asked, Which is more likely? That someone writing a routine memo would use expensive and advanced printing equipment instead of an ordinary typewriter, and would just happen to use exactly the right combination of equipment to reproduce what Microsoft Word would do by default 30 years later, or that the documents are forgeries created using Microsoft Word a few days or weeks before they were "discovered"? Third, almost all evidence used by courts today could be faked. A witness can lie. The murder weapon could be planted in the suspect's house. Documents can be forged. DNA samples could be planted. Expert witnesses can exaggerate the significance of forensic evidence. If the police or someone working with law enforcement are trying to railroad someone, lab results can be falsified. Etc. With sufficient skill and effort devoted to the task, I'd guess any evidence could be faked; I don't know what would be 100% reliable. That's why the standard of evidence in a criminal case in the U.S. is not "absolute, 100% proof" but "proof beyond a reasonable doubt". Just as courts today are well aware that, say, a signature might be forged, so they'd recognize that a video might be forged. They'd look at the source of the video. A video showing the defendant far from the scene of the crime would be much less persuasive if it was produced by the defendant himself than if it was from, say, a store's security camera where the store has no connection to the crime other than serving as an alibi. Does the store owner have any reason to create a fake video to help the defendant? If not, strong argument against it being fake. They'd look for corroborating evidence and examine consistency of evidence. If there's a video AND there are fingerprints AND the murder weapon was found in the victim's car AND etc, that's much more persuasive than if the only evidence is the video. Side thought: Several other posters talk about technical means of authenticating videos, time stamps and encryption keys and so forth. Sure, any technical means of authentication would help, but presumably any of that could be forged by a sufficiently skilled hacker. If you're producing the fake video from scratch yourself, presumably you could put on all the authentication et al AFTER you produce the video. If the premise is that we're assuming that the technology exists to produce a 100% perfect, undetectable CGI, it seems to me that we're violating the premise if we say "but ... there's no way to beat an authentication key". [Answer] Will fakes ever be as good as real? While technology for faking evidence gets better, so does the technology for gathering evidence. In Iain M. Bank's Player of Games such a world exists and they say a a drone can provide a such a recording but a ship mind is required to be in contact. That would come down of course to trusting the gatherer of the evidence. Thinking about it, let's say you have a source of entangled photons in a safe location. One of each pair goes into a fiber-optic cable to a camera and used to light the scene and the other is protectively stored in the bank. The "Camera" records the actual photons from the scene along with a hash of the data in each frame and transmits the hash back. To verify the video you could validate that the video images were taken at that time and in the proper sequence by looking at their entangled pairs. Maybe viewing the data requires both entangled pairs and it can only be viewed once, though at the time of extraction there could be a recording made of its viewing and verification that could be attested to. ]

[Question] [ I am a fiction writer, and I'm designing several worlds for my various novels. As it so happens, I really like designing worlds. I seem to like it so much, that I'm beginning to wonder if I'm carrying the worldbuilding too far. Since I'm designing all this for novels, there comes a point where I have to stop making everything so different, and start focusing on what is the same. If absolutely *everything* is different, the reader won't have a clue what is going on, unless I include exhaustive information and backstory - things that are just going to bore the reader. **How do I know when world development has gone too far?** For example, today I found myself occupied trying to find new names for the months of my fantasy world. I'd love to have these, because mentioning times such as 'October' and 'July' just don't sound right next to 'elves' and 'magic.' And yet, changing the month names would confuse the reader as to when things are going on, unless I tell him in the beginning (aka, info dump). Not to mention the fact that naming the months really has nothing whatsoever to do with my story. I want my world to seem as real as possible, but at the same time, I want to know where to draw the line. **How can I do this?** [Answer] Building a world and writing a story are two entirely separate things. In practice there will be a feedback between the two where you fudge the story to match the setting and the setting to better serve the story, but even there you should only be in one mode at a time. When you are building the world be a world builder to the max and immerse yourself in the pleasure of creation without worrying too much if it is actually useful. Such prediction is difficult, time consuming and unreliable, it is better to just go with the flow. When you write the story, then write the story and nothing but the story. Do not care that you spent *weeks* making this totally cool detail to the setting, if it doesn't serve the needs of the story, it has no place in the story. If it distracts from the story, cut it out. If it doesn't, feel free to mention it without elaboration. As a writer your job is to make sure the readers understand the story, the setting, the background, and the characters... understanding is not necessary unless it also helps understanding the story. Unless the details of the calendar are relevant, do not distract the reader by explaining it. If all that is relevant for the story are the order and separation of events, those are all you need to explain. And all you should mention. With naming the simple heuristic is to check if there is a (reasonably) simple plain English alternative to the "in setting" name. If there is, you should just use it. Exotic naming should be saved for unique concepts or things that readers never need to translate to English equivalent due to nothing equivalent existing in common usage. A mental trick might be to think of the setting as a side character and such explanations as giving that side character dialogue. Then you can usually detect if you are inserting the character into scenes it has no business being in or letting it overshadow the main characters. It is also possible that you are not developing the setting fully as a character or are letting it get overshadowed in scenes where it should be in focus. Remembering that the considerations in letting the setting have focus and letting a character have focus are similar helps if you already are confident in managing characters. [Answer] There are some good answers here already but I'd like to weigh in with my view on the subject as well, with a little more applied advice. When it comes to worldbuilding, unless you're working on a deadline or have some other concrete goal then there really is no such thing as too much. You can build to your heart's content if it's on your own time. If you enjoy it, by all means go nuts. Many very successful authors have built incredibly detailed worlds for their stories that go way beyond just renaming the months. The key to everything is knowing what to *leave out* of the story itself. You can rename all the months, but unless it's crucial that the reader understand your whole calendar, *there's no need to explicitly define it for them*. As long as they get the gist of what you're trying to communicate, that's all you need. If you try this minimal approach and find it's too confusing to people, abstract it a bit. For example, instead of naming the months in the story (whether or not you named them in the WB process) just refer to the passage of time in terms of seasons, or some other abstract concept that the reader will be familiar with. Here's an example: **Before:** "Bob knew the process would take until Carlvember, which was still three months distant." - Not bad, but it's a little awkward. Do you really think like that in real life? The characters probably implicitly know that Carlvember is three months away so they don't need to think it so explicitly. **After:** "Bob knew the process would take well into the harvest season to complete, at least until Carlvember." - If you've already established somewhere else that it's currently late Summer, this is a more abstract way to describe the timeline that doesn't require the reader to get distracted thinking about your fantasy calendar. Readers can already relate to the seasonal changes (unless you changed that too) so it's easy to imply an amount of time more naturally than counting it. Does that mean you shouldn't rename everything? No, you can do that all you want, and even reference the names in the story. The key is just to find ways like the one above to avoid exhaustive or unnatural explanations that will distract the reader from the story itself. Plenty of authors construct whole languages for their worlds, but they don't spend tons of time explaining them in the actual story, they just throw in phrases here and there for flavor. You can always release a compendium in addition to the story that has all your fun details in it. Some people really enjoy reading that (myself included), but it shouldn't be forced on the average reader unless necessary. [Answer] I think you mix different concepts in your question: 1. How much should I develop my world? 2. How do I convey my alien world to my readers? ### World Development For the first point, I would say you need to have your world coherent, and satisfying. You might want to look at the general explanations provided by @James, on the [general process of world creation](https://medium.com/universe-factory/so-you-want-to-build-a-world-or-how-to-be-a-god-aed7304618f1#.hmy8gvt40). In short words, you can use different methods to do so. Two extremes approaches are * Top-down: you build the whole world from scatch. Creation of the world, geography, culture, languages, etc. Everything is placed there by the God that you are (for that world). It tends to be consistent, but possibly overdoing. * Bottom-up: you start from your characters/story and expand the world around them progressively as the needs arise. You only develop what you need, but there might be inconsistencies. With the top-down people tends to overdo their world creation, puting aside the reason they were building the world in the first place. This is quite common with usual users around here. ### Suspension of Disbelief For the second point, it is more a question for [Writers.SE](https://writers.stackexchange.com/). You might be interested in reading @ArtOfCode's blog post about [suspension of disbelief](https://medium.com/universe-factory/worldbuilding-101-on-suspension-of-disbelief-54b83fcdd6c5#.hx9628p3n). The point is that you can change anything you want. But the trick is then, as you correctly pointed out, to convey the relevant information to the reader, without spending some chapters on explaining everything. I think that is also a typical problem with people overdoing their world creation. But in itself, it is not inherently bad. You just need to be careful. If people gather that [Thermidor](https://en.wikipedia.org/wiki/Thermidor) is the equivalent of a Summer month, then it should be alright. But do you need to mention it in the story? I mean, if you say, "we'll meet in some month from now", then who cares what was the month called. But then again, I'd suggest to have a look around Writers.SE, there are quite some discussions about similar points. ### Conclusion There are no line which generally tells you when to stop. If your aim is to be a writer, then you need to make sure you have enough consistency in your world to feel at ease, watching the story evolve around. When do *you* feel at ease, only depends on you. But bear in mind that you want to tell a story later on. So depending on your writing style and skills, you should be careful not to spend too much time explaining everything within the story. That's what World Description books are made for. After the story. But you can see that Tolkien spent more than a decade developing his world, before he felt well enough to actually write up his story. [Answer] *How do I know when world development has gone too far?* When worldbuilding conflicts with your aim, by which I mean whatever caused you to start building your world in the first place. Is your aim to have fulfilled your ambition to **complete the story** you've had in your head since whenever? Do you never write the story because spend all your time fiddling with the trade routes between Risingpower and Decliningempire? Stop worldbuilding and start *writing*. Is your aim to get your novel **published**? Has a publisher rejected it because it went into boring levels of detail? Has it never even got as far as a publisher's slush pile because even your mother found it difficult to test-read your *magnum opus*? Stop worldbuilding and start editing. Is your aim to experience **delight in building a detailed world**? Then rejoice that you can find happiness in a way that harms nobody, costs next to nothing and is only moderately addictive. If you still quite like the idea of *someone* else reading it even though getting an audience and royalty payments isn't your driving aim, in these days of self-publishing in electronic form it is quite feasible to publish a book aimed at a niche market of people who really, really like detailed worlds. You will probably never make back your costs, but so what? Compare it to the cost of other non-necessities people drop money on, like fancy cars, holidays, hi-fi systems, or designer clothes. Or just publish it on the internet using free software, so that the only cost is your time. On this model going "too far" in worldbuilding only happens when *you* get bored. --- Regarding months, making up new month names is not remotely going too far. Our month names are tied to our history. Unless your planet also had in its history by some amazing coincidence two guys called [Julius](https://en.wikipedia.org/wiki/Quintilis) and [Augustus](https://en.wikipedia.org/wiki/Sextilis) powerful enough to get astronomical phenomena named after them it shouldn't have months called July and August. Anyway, unless your planet has a large, visible single moon with an orbital period that can be measured by observing its waxing and waning, its inhabitants won't have any reason to measure time in "months". (Though if [it doesn't have a moon at all](http://scienceblogs.com/startswithabang/2013/08/08/the-top-5-things-wed-miss-if-we-didnt-have-a-moon/), the days are likely to be very short, among other fairly drastic differences to earth.) [Answer] Why do things have funny names if the prose and dialog is all translated into English? Someone already gave an xkcd reference, but [this version](https://explainxkcd.com/483/) explains and the added "discussion" sheds insight as well. If the world (or universe or culture) is *different* than the concepts are different enough to not use the English word. If they don't *have* days, time periods relating to shifts and feeding might not be called "days". Someone mentioned month names, and that might relate to cultural references. But most people consider them to be abstract labels without the connotation of where they got the names. Now if there were 24 months it might not make sence to use our names. More generally: if you can't understand it without boring backstory, it's too far. If things are not needed for **the story**, you should streamline it. If a character kicks back with an idle activity for a few minutes, it is not necessary to make the reader understand that activity and why he finds it enjoyable etc. You can set the mood and get across the important stuff *without* getting into it. Or, change "it" to get rid of the sticky point. A certain *portion* of the writing covers details. A series can have more detail because it is fleshed out and carried over, and assumed from the beginning of an episode. So when Riker is eating with the Klingon crew, we smile and *know* his ability to eat *anything* and recall how he learned the "proper" way to eat [gagh](http://memory-alpha.wikia.com/wiki/Gagh). But it takes no time from the current story, even if there is a line like, «"Yes, I've had *gagh* before" he noted with a fond far-away smile.» and it doesn't detract for someone who doesn't get the reference. What if *nobody* got it, because it's in your bible and backstory notes, but not actually written? Well, it still provides the appearance of richness, and helps ensure that such references will have continuity and match the experiences that went into shaping the character. Another example is in the movie *The Incredibles*, where the babysitter's story was aluded to but not shown. A short was made later. That *could* have been shown, but would interfere with the pacing of the action plot and add 10 minutes overall. But just having it (without going into detail) added to the richness and characterization of the family's situation. Let's look at the question again: how much is too much to *have*, or to explicitly mention in the novel? Having too much doesn't bother the use or bog down the story, if it can be used "lightly" as indicated above. It just means you are not writing the story. So think of it like a software project: only write what is needed, plan bigger, make notes. Use a spiral approach to cover the broad strokes, and add detail in subsequent passes, where needed. It is "needed" if it comes up in the overt story, or when you need a better handle on how that shaped the character/society/plot. Consider the rule book for Quiddage: was it necessary to know that before the game was featured? No, only some rough ideas about it and more on the team dynamics and not the specifics of the teams' long histories but the impression that it *has* a long history. Remember I said "a portion". Of all the words that are put down, some of them need to be about the actual plot, characters, etc. If you do that, why do you add more that don't? [Answer] ### About time In most sedentary cultures on earth, I think, time is divided in years. A year is a cycle. Each year the same event happens, around agriculture. Harvesting, blooming, and all that stuff. Years are divided in parts that correspond to weathers and types of work. In Europe, there are usually 4 seasons, and to each season its weather and its events, and its works. Then there are smaller divisions, that have historical and cultural reasons - months. In France 1792, the months were re-designed to have exactly 30 days, and to be named based on what was happening at the time. *Ventôse* (after *Ventosus* which is Latin for Windy) being a cold and windy month, i.e. March, while *Frimaire* from French frimas - frost, was December. It didn't stick, but you get the idea. The smallest division before you start to actually measure time with a timepiece is the day, which is basically a day and usually a night. Years, days and seasons are marked by natural events. You don't need to name then in a different way, assuming that your characters already speak your writing language. Depending on your setting, there is a good chance that you can generally talk about those without having to explain what they are. (Now, if you are not on earth, where days have a very different length, then possibly, yeah) Words that are based on those you can safely use: century (assuming the decimal system is vaguely used), fortnight... More localized words, just avoid then altogether until you really need to set a date. And even then, you can use for example the number of years/days of reign of whatever king there is. [Answer] **Worldbuilding goes too far when the world you've built detracts from the story to be told.** Navigating those extremes between incredibly deep worlds and a story that reads can follow is tricky, at best. Whether it's new names of months or a completely different economic system, a reader can only handle so many differences between the reality they know and the reality of the world you've written. **When the [cognitive load](https://en.wikipedia.org/wiki/Cognitive_load) required for a reader to situate themselves in your story exceeds the audience's capacity, then you've done too much world building.** The cognitive load capacity will depend on your audience, ie, three year-olds can handle far less detail than a well-educated adult. [Answer] # Things You Cannot Mess With In Realistic World Building 1- Macro physics. Gravity, electricity, magnetism, nuclear fission/fusion etc. 2- Biological functions. Breathing, eating, senses etc. # Things You Can Mess With In Realistic World Building 1- Naming. Any and all names are acceptable. So whatever month names you choose, are ok. 2- Properties of organisms. Sixth sense, sonar, echolocation etc. 3- Distances between celestial bodies, as long as they can be sustained under physical laws. # How To Keep The Reader With The Weird Naming? 1- At several places in the story, hint at what the names mean. For example, let us assume two elves are conversing and you want to mention different month names, and yet want to make them understandable. Here is how: *Mantr looked quizzically at Sobn and thought for a moment.* *"Elgon will probably die in Geng. Even if he does survive then, he cannot live past Yvest."* *Considering that it was 19th date of Elbo and it was the second month of the year, waiting for Elgon to die in Geng would be to wait 3 months. And if he survived Geng, he would live during Von, Sim and Hon before Yvest came and he died. Sobn was not going to wait for so long!* See, how we have dropped hints about the month names and times of year without having to drill them explicitly in the reader's mind in the start of the novel. You can use this approach multiple times in your work until your readers get a hang of what you are saying. Although it is fine to use your own month and weekday names, I would suggest that you refrain from that practice. You can use your own naming system but try to refer to times by temporal difference more often than their names. For example, in above case: *"Elgon will probably die in Geng. Even if he does survive then, he cannot live past Yvest."* is more confusing for the reader to understand. Instead of that, consider the following statement: *"Elgon will probably die after 3 months. Even if he does survive then, he cannot live past 6 months anyway."* See. Here you haven't mentioned any names, and still the message is clear and simple. Or you can use a mixed approach as: *"Elgon will probably die after 3 months. Even if he does survive then, he cannot live more than 6 months and would succumb in Yvest."* [Answer] 1. Is a worldbuilding element necessary to distinguish your universe from the real one? If an element of plot, or the entire story, hinges on some critical difference from our own universe, the reader needs that knowledge sometime before the plot does. * If it is, proceed to the next question. * If not, consider removing this element from the story entirely. Language is something that often falls flat; coming up with new names for things in our universe, like day/night, seasons, etc often is more confusing than helpful in painting the world. 2. Does the reader have to know any unique details about this element, or can you rely on the "trope"? You typically don't have to explain how antigravity works to the level of a doctoral particle physics thesis in order for your reader to suspend disbelief and accept antigravity exists in your universe. On the other hand, at least some backstory for how humanoid characters have superhuman abilities is typically required to break the "similar to me" bias of the reader and maintain disbelief. * If yes, skip the full explanation and either explain in context (narrating as if the user already knows and they'll get the idea) or explain some essentials and move on. * If no, proceed to the next question. 3. Can the element be learned by context; that is, can you simply write as if the reader should already know this thing about your world, possibly with a clause of extra description or exposition in the description of something using your element? Good examples include things people already suspend disbelief of in other worlds, like the existence of magic, or the juxtaposition of different technological developments from different times in our history like steam engines in otherwise medieval times. * If yes, don't explain it, just run with it. * If no, proceed to the next question. 4. Can the information be given to the reader from the narrator in a plausible way in two or three sentences (a paragraph or less)? * If yes, go ahead. Narration like this makes the reader feel like they're standing beside the narrator, watching the events unfold, and the narrator is quickly explaining something between dialogue. * If not, proceed to the next question. 5. Can the information be broken into multiple smaller explanations? For instance, giving the reader the critical essentials in a couple of sentences in one place, then explaining more thoroughly as needed, *without* it sounding like you're changing the rules of the world to suit the plot? * If yes, then do so. A sentence three chapters ago explaining that most sections of the space station rotate to produce gravity can be supplemented by an additional sentence stating a particular section rotates at a different rate to produce differing artificial gravity. * If not, proceed to the next question. 6. Can the information be given to the reader plausibly in the form of a teaching or questioning exposition between characters? The typical mechanism is a "Watson", a character that exists to ask the "audience questions". It's most believable to have a character that we can believe is benefiting from the explanation as well, like a "new guy" in the group learning the ropes, or one specialist explaining an obscure aspect of his own subject to the rest of a "tiger team" assembled to save the world. * If so, do that. Avoid cliched tropes like "As You Know" (beginning the explanation, as dialogue, with these three words to lampshade the fact the character is getting nothing new from the explanation) or the "Idiot Scientist" (exposition in the form of dialogue, but the audience question is asked by a character that should, given his credentials, already know the answer, like a particle physicist asking what a quark is). * If not, consider putting in footnotes, or an appendix. Many excellent works of fiction, especially in the fantasy genre but also in more realistic fiction, use an appendix to illustrate or define things that the reader might not be expected to know or pick up on, and that can't be explained inline without the reader losing the plot, but that are essential to understanding the story. Good examples include Tolkien's extensive appendices detailing elements of background information that are needed but never found their way into the plot. Historical fiction often includes maps of the area in question, or diagrams of elements of this past society that aren't commonplace today, like the anatomy of a tall sailing ship. [Answer] I'm actually planning on writing a post on this on the [WorldBuilding.SE blog](https://medium.com/universe-factory) in the coming months. So I'll go into more detail then. The correct line is very much based on your personality and your writing style, so nobody can give you a line to hold. What we can do is recommend ways we have identified the line for ourselves in the past, and hopefully one or two of those approaches will be useful for you too. What I have found is that the more detail you put into the background, the more rigid it appears. Real world are very fluid. Victorian architecture was not used because one day they decided the Victorian style would be best, it developed over time, as the world shaped it. Skilled writers can put these details in and get the flow right the first time; people like me instead have to make worlds which will flex a little, and let the story tell me which architecture is ideal. Maybe I *really* need a bad guy to have a certain flavor, and I just can't find anywhere else to tie that flavor into the world. BAM! Now the architecture and the bad guy define each-other. If this resonates with you, then you may develop worlds similarly to me. If so, one thing I am constantly looking out for is a "stale" feeling or an unexpected metallic feel/taste to the world. These, for me, are indicators that I've reached out and tried to put to many details into the world. Instead of trying to build a livable world that enriches the characters, I'm building a static world devoid of life. Then I get to back off on the details, and start making things more flexible, even mushy, until I start to think the world demands too much suspension of disbelief. Then I go back to the details, back and forth. If you can, allow the world to develop while writing the story, rather than forcing yourself to build the world first. Realistic worlds are much easier if you allow the characters to interact with the world, rather than just being fit into the world like cookie cutter characters in front of a cheesy matte. [Answer] As a world builder you basically need to design a general framework for your world before you get into details. This will provide a guide for you in the future as you flesh out the details when writing stories which originate in your world. The first thing you should think of is what the basis of the world will be. Is the world completely different from our world, including physics, lifeforms, etc? Or, is it a world with some kind of basis in reality such as an alternate history, or a tale that takes place in the distant past or far into the future? Once you have that figured out, then you will have some clue on how to proceed. One of the pitfalls in world building is trying to make things different than reality on Earth because it is different for no reason instead of the fact that there is a practical reason why it is different. [Answer] Months are perfectly fair game, as is language in general. You can go as far as you like **but** you need to give the reader a means of engagement. Some examples: **Names of Months**. Paul Kingsnorth's book "[The Wake"](https://www.theguardian.com/books/2014/apr/02/the-wake-paul-kingsnorth-review-literary-triumph) is largely written in (greatly simplified) old English. The language is modified enough so that it gives the flavour of Old English while being phonetically similar enough to modern English that the reader can easily enough pick up the flow and understand what is written. The names of months are different (for example, July is 'Weodmonth') but they are descriptive names and their meaning is amplified by context (the protagonist / narrator of the novel mentions that July / Weodmonth is a month when weeds may rapidly spread among crops without lots of weeding effort). In a different genre, the Elder Scrolls series of RPGs has a set of months with descriptive names (Morning Star, Sun's Dawn, First Seed, Rain's Hand, Second Seed, Mid Year, Sun's Height, Last Seed, Hearthfire, Frost Fall, Sun's Dusk, Evening Star): in context it's fairly obvious not just that these are the names of months but which parts of they ear they might refer to. **Language, more broadly**. See the previous Paul Kingsnorth example, also Iain M. Banks's novel "Feersum Endjinn", large parts of which are written in a sort of phonetic Glaswegian. In this type of book the entire story, or large sections of it, is written in the made-up languade. In both cases there is just enough phonetic similarity to English that the reader can engage with the content. On the other hand, some writers invent entire languages for their stories. I guess the archetype for this is Tolkien. A useful device here is the "common tongue" which is written in the book as English. So when Gandalf reads the inscription on the One Ring in Black Speech, he says "Ash nazg durbatulûk, ash nazg gimbatul, ash nazg thrakatulûk agh burzum-ishi krimpatul. Translated, the words mean 'One ring to rule them all, one ring to find them, one ring to bring them all and, in the darkness, bind them." So the reader gets a flavour of the invented language but the wizard's explanation to Frodo of the meaning in the common tongue also serves as an explanation to the reader. You seem particularly keen on the worldbuilding aspects and that's fine - consider Tolkien again. His primary concern was worldbuilding and linguistics, the novels were almost a by-product of this. It shows in the vast amount of detail in the Appendices in The Lord of the Rings, and in the huge amount of detailed world building he put into his languages (Quenya and Sindarin are sufficiently well developed that it is possible to learn to speak them, albeit the vocabulary is not broad enough to use the languages in everyday speech) and his world building (the amount of detailed little pieces that he wrote about Middle Earth but never made much effort to publish, which were later assembled by his son into the Silmarillion). So if that's your thing, just enjoy it - if a novel happens to fall out of your world building then that's great, but it's perfectly legitimate to enjoy world building for its own sake. Elen síla lumenn' yomenielmo. ]

[Question] [ The Dwarves pride themselves as great craftsman, smiths, and tinkerers. Dwarven craftsmen have access to not only the metals of man, but also metals only the forges of dwarves can refine. One of these metals would be Titanium. What pieces of technology would Dwarves need to forge Titanium? More specifically what technology would a dwarf need to work with a block of titanium? Note: I'm more woried about the equipment and specific technology needed to forge Titanium. Some technology with obviously be beyond the standard of my universe (Medieval High Period), but as long as it isn't anything way beyond this period (ex: 18th century) it still works. [Answer] They would need electrolysis. Not for refining the titanium directly, but for preparing the other chemical agents needed for titanium refinement. Specifically, you need chlorine and either sodium or magnesium metal. While in our world metallic titanium was only isolated in the early 1900s, as noted in Arkenstein XII's answer, the processes to isolate chlorine were invented in the late 1800s, and could've been managed much earlier if people knew how. Sodium and magnesium were isolated in 1807 and 1808, respectively. All of these processes, however, require electricity. Now, the Leyden jar was invented in 1746, which is 18th century, but that level of electrical expertise really wouldn't let you produce chlorine or sodium in any quantities useful for titanium production. You could, however, take 19th century electrical knowledge and give it an earlier medieval aesthetic. After all, lodestone was known anciently, and medieval Europe certainly had the ability to draw copper wire. So, putting together a basic permanent-magnet generator is one of those things that absolutely could've been done in the background of otherwise-medieval technology if people just knew what they were doing. So, the first bit of technology your dwarfs will need is just such an electrical generator: a few fixed lodestones arranged around an axle wound with wire, and spun with muscle power. They would also need to figure out commutators (sliding electrical connections that switch polarity every half-turn) to output DC. It needn't be very clean DC, but it does need to be DC! And if the dwarfs can figure out how to build a basic induction dynamo like that, it probably wouldn't be a big stretch to go on to designing a self-exciting dynamo, so they need only a very little lodestone to get it started. (Alternatively, in the absence of lodestone, they could build electrostatic [influence machines](https://en.wikipedia.org/wiki/Electrostatic_generator#Influence_machines) to produce direct current with no need for a separate commutator.) From there, there are two methods of producing the necessary chlorine: mercury electrolysis, and diaphragm electrolysis. The first, of course requires mercury, which was available anciently and can be refined from ore relatively simply, and the second requires asbestos, which is a naturally occurring material that they could mine. In the mercury electrolysis method, you float a solution of sodium chloride (i.e., salt) over a pool of mercury, with anodes suspended in the solution around which chlorine will accumulate. The chlorine can then be contained in glassware, which is certainly within the grasp of medieval technology. The mercury acts as a cathode, and will need to be bonded to the generator with iron, nickel, or graphite leads, as copper, silver, or gold wires will end up dissolving in it. The liberated sodium combines with the mercury to form a solid amalgam, which is them reacted with water to produce sodium hydroxide and recover the mercury for re-use. In the diaphragm method, you basically just need the salt solution flowing through an asbestos sponge, with an anode to collect chlorine on one side and a cathode on the other. That is simpler, but not as awesome. You end up with dilute sodium hydroxide solution as a byproduct, which can be boiled down to concentrate the sodium hydroxide. Of course, these *are* dwarfs we're talking about, so maybe they want to go for a more brute-force method that makes better use of their forges: by mixing sodium chloride with calcium chloride, they can get a low-melting temperature salt which can be liquified in a furnace at a mere 600 Celsius, easily attainable in a Medieval blast furnace. Electrolysis then produces chlorine and pure sodium directly. If they can't acquire enough calcium chloride catalyst, though, producing it from salt and limestone is a rather involved process. Now that the dwarfs have chlorine, they need sodium or magnesium. If they used direct salt electrolysis in a blast furnace, you've already got the sodium! If not, they either need to refine magnesium or sodium, which they could do from the sodium hydroxide byproducts of chlorine isolation. If they can get sodium bicarbonate, then they can just brute-force their way to sodium by heating that in a furnace with coke or charcoal. But, they need electrolysis anyway for other steps, and they're going to be producing a lot of sodium hydroxide as a chlorine byproduct anyway, so might as well go with straight-up sodium hydroxide electrolysis. For that, you just boil down the alkali solution to get solid NaOH, then melt it down and stick in an anode and cathode--the anode collects sodium, and oxygen and water vapor are released as byproducts. The tricky bit here is that the temperature needs to be controlled very precisely, at about 330 C. Too high, and the sodium will dissolve into the melt; too low, and the melt will solidify. Although refining magnesium would give them yet another magical metal to work with, it is comparatively more complex, so I'd probably just stick with the sodium. As a consolation prize, sodium can be used in the refinement of aluminum as well. (Of course, aluminum can be isolated via electrolysis, which is the modern way of doing it, but that requires cryolite, which is not a common mineral; on the other hand, maybe your dwarfs just happen to be sitting on their world's largest deposit....) Now that you have chlorine and sodium, and titanium oxide or ilmenite ore, you can go about making your titanium! Step one is to heat the titanium ore with coke or charcoal to about 1000 Celsius, and then blow chlorine gas through it. This produces titanium chloride and carbon dioxide gasses. The titanium chloride can be condensed for liquid storage (it boils at 136 C), but care must be taken to keep it absolutely dry, as it will react with water to produce titanium dioxide (wasting your work!) and HCl gas, which is not nice to breathe! The titanium chloride is then mixed with molten sodium in an anoxic atmosphere; modern processes use argon for this, but hydrogen ought to work as well, and producing hydrogen with medieval technology ain't hard; they can electrolyze it, or if you don't want to use electrolysis for just everything because it does kinda mess up the low-tech aesthetic, just pass superheated steam over charcoal. The TiCl4 + Na mixture should be preheated to about 500 Celsius, but after that the reaction is exothermic, so the reaction chamber needs to be able to withstand over a 1000 degrees (which, if you've gotten this far anyway, shouldn't be a problem). You then just let it sit for several days, and then cool down for several days, and then eventually you crack the reaction vessel and pull out pure titanium sponge and salt, which can be washed off with water (and recycled back into chlorine and sodium!) Now, that just gets it refined. Actually *forging* it once you've got a sponge of the pure metal is a tricksy skillfull process, but can be done in a regular blacksmith forge. EDIT: Apparently, it is also possible to produce titanium continuously in a stream process, in which titanium chloride vapor is bubbled through a stream of liquid sodium, and the solid titanium and salt are then filtered out and the sodium recirculated. I have no idea how feasible the equipment for that would be to set up with otherwise medieval technology, though. If the dwarfs can acquire calcium chloride, however, it appears that there is a tricksy way to turn titanium dioxide directly into metal through electrolysis without having to deal with nasty elemental chlorine: the titanium ore is powdered and then pressed into pellets or rings which can be attached to a cathode, and then immersed into a bath of molten calcium chloride with a consumable carbon anode. This results in calcium reacting with the titanium ore to strip away the oxygen, then re-combining with chlorine in the melt while the oxygen reacts with the carbon anode, producing titanium metal and carbon dioxide. [Answer] ## The production isn't *quite* as hard as it looks at first... While today's processes for producing titanium require electrolysis, and usually highly hazardous reagents such as chlorine, as prerequisites, it does appear to be possible to make titanium without discovering either! What we *do* need, though, are supplies of elemental iodine and magnesium metal, both of which are much more reachable than what other processes have called for, albeit with some complexity for the latter. ### Getting ready First off, we start with the iodine, which substitutes for chlorine in this process; the extraction of iodine from kelp or other large marine algae is a [well known process](http://www.rsc.org/learn-chemistry/resource/res00001915/extracting-iodine-from-seaweed?cmpid=CMP00006633) that can be done using reagents (mostly sulfuric acid and a suitable solvent) that the dwarves would be familiar with, although they would likely have to trade for the seaweed, and the reaction is rather noxious using straight sulfuric acid due to it being reduced to H2S in the process. We then move on to getting the magnesium, which is a two-step process. The first ingredient is crude elemental silicon, which is normally produced by simple carbothermic reduction, but that requires temperatures around 2000°C to drive the reaction all the way to Si, which are a bit beyond what a typical blast furnace can produce. The other conventional option is a magnesium reduction, but that's no good either, as we're trying to get magnesium *out* of this process overall. However, since we have iodine, we can get around this. First, we do a carbothermic reduction at much *lower* temperature on the silica source to yield silicon carbide. We then can convert the silicon carbide to silicon tetraiodide by reaction with iodine at elevated temperature; from there, we can [reduce the tetraiodide to elemental silicon](https://patentimages.storage.googleapis.com/f9/2f/5a/23c4621369407d/US3043667.pdf) with an excess of hydrogen (coal gasification would be the simplest route to that with dwarven tech, I reckon), since we can get by with a very crude silicon source for the next step. All of this can be accomplished at temperatures achievable with a normal fuel-fed metallurgical furnace (instead of the electric-arc furnace required to drive direct carbothermic reduction). Now that we have crude silicon at hand, we can then apply it to what is called the Pidgeon process to convert magnesium oxide to elemental magnesium *without* any electrolysis. This is a simple silicothermic reduction used widely in industry, with the magnesium coming off in the vapor phase; subsequent condensation yields magnesium with quite high purity without further workup. ### Now, on to titanium! Now that we have all the raw materials we need, we can start working on titanium refining. Our net process is basically a hybrid between the well-known Kroll process and the much lesser-known [van Arkel-de Boer process](https://en.wikipedia.org/wiki/Crystal_bar_process), using iodine instead of chlorine as the halogen as it's far easier to extract and handle the former. We start with two steps combined into one, charging our furnace with titanium ore, charcoal, and iodine all at once to [produce titanium tetraiodide](https://pubs.acs.org/doi/abs/10.1021/acs.iecr.7b01170?src=recsys&journalCode=iecred) directly. From there, the titanium tetraiodide vapor is carried over to a molten magnesium bed as in the Kroll process, thus reducing the halide to the element while producing magnesium iodide as a byproduct. ## Now that we have titanium, how can we work it? Once you have titanium metal, you can start working on it. However, there are a few issues involved. First off, titanium is more reactive with air than iron is at forging temperatures. While not unmanageable for small-scale forging, as [this video and its followons](https://www.youtube.com/watch?v=lM-wAUBGFew) demonstrate, titanium does generate mill scale much more aggressively than iron/steel does, and it also generates a much more *persistent* scale layer than steel, combined with a hard-but-brittle layer of "alpha case" underneath that scale. As a result, your dwarves will need to finish every part they forge on a grinding wheel to knock the scale and alpha case layers off, then let the metal repassivate. The good news is that titanium hot forges readily, which means that they won't need as many heats to get their parts done. The other piece of bad news is that titanium, while easy to *forge*, is very hard to *machine* due to its propensity for galling. The use of hand tools works in the dwarves' favor by limiting speeds and feeds, though, which heavily mitigates galling. ## Alloying your troubles away doesn't quite work, though... The other problem is that titanium is like iron in that it needs to be alloyed to be useful in many applications (CP titanium can be used structurally in some cases, but lacks the hardness for wearing work, and simply will not take a heat treatment of any sort). However, the alloying elements of choice are quite different: while aluminum-bearing steels are quite rare, aluminum is considered a key ingredient in many titanium alloys, including the commercially standard ones (such as Ti-6Al-4V) as it stabilizes the strong, but somewhat less tough, alpha phase, much the same as carbon provides hardness in steels. Furthermore, while the titanium beta-stabilizers (vanadium, silicon, niobium) are common in alloy and tool steels nowadays, vanadium and niobium are their own pains in the butt to refine. This means that your dwarves will have to figure out their own titanium alloys and associated heat-treatment schedules, using controlled oxygenation of the alloy core for alpha stabilization most likely unless they can refine enough aluminum somehow, as well as silicon and/or iron for beta stabilization. Tin can be used as an alloying element as well, although it's considered "neutral" with respect to its effects on alpha and beta phases. [Answer] The earliest process discovered that could produce metallic titanium was developed in 1910, and is called the [Hunter Process](https://en.wikipedia.org/wiki/Hunter_process). It involves a chemical reaction between titanium tetrachloride, and metallic sodium; thus, it requires a reasonably well developed understanding of chemistry. Titanium does not occur in a native form, instead the only forms useful to the production of metal are [Rutile](https://en.wikipedia.org/wiki/Rutile) and [Ilmenite](https://en.wikipedia.org/wiki/Ilmenite). Because of this, there is no simpler way to produce metallic titanium. [Answer] For refining, deadly chlorine must be mastered, then either magnesium or sodium. An oxygen free furnace at 1200C is necessary. That is going to be difficult or impossible to achieve without either large amounts of electricity (vacuum chambers, electric heat), or pure inert gas(argon shielding atmosphere isolated from flame furnace). The oxygen free environment is also required after refining any time it is to be forged, welded or annealed. ]

[Question] [ After Cain killed his worthless brother Abel, he was unjustly cursed by God to wander the earth forever. On his travels, he met a sympathetic woman named Lilith. They discovered that they had a mutual beef with their creator. Lilith, first wife of Adam, refused to suit to her husband and was cast out of the garden by God. Cain, Adam's first born son, was rejected by his father after his precious sacrifice wasn't accepted by God. The two kindred spirits founded their own race of humans called Evangelions, and set about to bring their former benefactors to their knees. This race of humans is stronger and faster, growing to be about 8ft tall. Otherwise, they are biologically similar to regular humans. The biggest difference is that they possess a unique organ referred to as a "core". This organ allows for the regeneration of cells, giving Evas the ability to regrow body parts. Arms, legs, and even the brain can be regenerated almost immediately, providing them with a form of biological immortality. However, this core has a weakness. Although it can regenerate cells and other organs, it is unable to regenerate itself. It cannot repair damage done to it, which reduces the Evas regenerative ability. Once it has taken too much damage, the being dies for good. How would an organ that regenerated cells be unable to repair itself? [Answer] TL;DR the greatest risk to a long-lived organism is cancer, when cells start to reproduce incorrectly. To prevent this, not only you need a method to supply fresh stem cells to all organs but also a "check" (almost certainly an enzyme of some kind) to kill off runaway cells, to be replaced by core-produced stem cells. This mechanism does not protect the core itself: if it's overused, to the contrary, the core either withers away, or kills off the rest of the organism. It would be a basic biologic protection system. The "core" would need to produce a sort of totipotent stem cells and keep the blood saturated in them. The stimulus to produce such cells would then be the depletion of such cells in the blood. At the same time the organ has to "retire" the cells grown too old and weak, and implement some kind of regenerative check on all cell lines to prevent random mutations from devolving into cancers (see "integrity check", below). And/Or maybe the Hayflick limit for "normal" or fully grown cells is much lower, so they don't have the *time* to degenerate but rather go into apoptosis - they live fast, die early and leave a beautiful corpse. (So another difference of the Evas would need to be that their cells are on average much "younger" than a normal human's). If we make this work this way, at least two awkward limitations follow. One: reproduction becomes incredibly complicated, unless the core allows for a "grace period" before going active (maybe just after puberty?) *and* pregnancy shuts down the core enough to let a foetus grow and mature to term undisturbed (a newborn will have a DNA which isn't the same as the parent's, and the DNA check routine would kill it at a very early stage). Two: the core itself cannot "self-check". Immature core cells are immature core cells, mature core cells are totipotent stem cells. In some ways, the core is a stabilized tumour, and in some other ways it behaves like a liver. It *can* have some limited regeneration capabilities, but the reproduction of immature core cells is a very, very touchy business - triggering it too often or too fast is likely to make the whole process go awry in some terrifying way. Most likely, the core goes fully cancerous and starts eating up the rest of the organism. (It might be possible to have an Evangelion regenerate by pumping him full of some metabolism-slowing drug, and keeping him hypothermic and in a coma, so the core doesn't exceed its design specs. Or transplanting a large enough compatible core chunk). # Hypothetical core development * at birth: the core begins to grow (e.g. somewhere under the heart). * age three to fifteen: the core grows but is otherwise nonfunctional. Normal body growth can take place, bones are digested and remade longer, new organs can develop and mature. * age fifteen to eighteen (more or less): the core activates and takes some roles of a human's Major Histocompatibility Complex, plus some really wicked, DNA-based [integrity check system](https://worldbuilding.stackexchange.com/a/26188/6933). Some biological effects and possibly a shock occurs. Also, any damaged or mutated tissues are swiftly killed and replaced, possibly triggering some form of [septic shock](https://en.wikipedia.org/wiki/Septic_shock) or rhabdomyolisis. Bottom line: not all Evas survive their coming of age. * age eighteen onwards: the core has the blood saturated in "repair workers". Most large scale cellular damage can be repaired. Actually, large damage to the brain will be repaired but leave the victim with severe mental effects, amnesia being the least. * during pregnancy, pregnancy hormones shut down the core and floating cells so that they don't "think" it's a good idea to do something for that poor swollen uterus full of fluids and who-knows-what. Downside: a pregnant Eva is much more vulnerable than a human, since it has next to no regenerative powers (they'd be superfluous with a working core). As a stopgap measure, a wounded pregnant Eva might immediately abort the pregnancy and return to "full defense mode". * normally, the core awakens periodically and tops up the reservoirs at leisure, and it always filters out weakened stem cells from the bloodstream, destroying them and using the raw materials to build new cells. * a large systemic shock (e.g. loss of a limb) sends the Eva in a regenerative coma, with metabolism reduced to the bare minimum and just enough circulation to keep repairs going. The core goes into low-level, long-term activation and wears out a bit, eating into its own regenerative reservoirs. It's important to keep the Eva well fed, otherwise his chances on recovery depend on body fat and muscle reserves. In ancient times, fat was synonym of health; for Evas it is still so. * in case of multiple, repeated activations, while the rest of the body gets "iguana-like" [regeneration](https://www.futurity.org/salamanders-lizards-tails-regeneration-1838762/), the core itself has "lizard-like" regeneration, and the mechanism goes awry. As a result, the Evangelion dies, not too horribly since the heart is the first to go. * lower genetic diversity between Evas allow easier core transplants between them. [Answer] The answer is in Genesis: **The Tree of Life**. <https://www.biblegateway.com/passage/?search=Genesis+3&version=KJV> > > 3:22 And the Lord God said, Behold, the man is become as one of us, to > know good and evil: and now, lest he put forth his hand, and take also > of the tree of life, and eat, and live for ever: > > > 3:23 Therefore the Lord God sent him forth from the garden of Eden, to > till the ground from whence he was taken. > > > God expelled Adam and Eve before they could eat from the Tree of Life. But Lilith remembered. Also she knows a lot more about angels than Cain does. She snuck them back in to Eden and got out with a fruit from the Tree of Life. The fruit regenerates itself. The immortality core in the Evangelons is a bite from this fruit. Each Evangelon takes a bite as a rite of passage - gaining prohibited immortality and scorning the command of God. This bite of fruit integrates itself into the being, granting divine immortality. But it is not the fruit and it will not regenerate itself. If it is damaged somehow or taken from the Evangelon, that being becomes just another son or daughter of Adam. [Answer] LSemi went all around the answer without actually being specific. To 'regenerate' a cell means the cell has to die. If the cell itself is immortal, it would never die, and thus there would be no need to regenerate it. Otherwise, one risks the inevitable cancerous growth, where regeneration occurs uncontrollably without concurrent cell death. If the cell does die, and needs to be regenerated, then this process must be very tightly controlled for cancer and mutations. That is, every regenerated cell must be identical to the original, and must only be regenerated upon the death of the original cell. The weakest link in immortality is the possibility of the cells mutating and the DNA degenerating. The original organism may be immortal, but in subsequent regeneration, will this immortality be lost? If there is one immortality organ controlling the regeneration of all other organs, then one of the functions of this organ would be to ensure the quality and purity of all of the reproductions, with the ability to terminate them should they deviate from specs, or become cancerous. That is, this organ would ensure that all regenerated cells would be exact duplicates of the original. However, this quality control can not be absolutely assured if the controlling organ itself can be regenerated. What enforces the enforcer? By what mechanism can it be assured that the regeneration of the regenerating organ is never compromised? By ensuring that the regenerating organ is always the original copy, and that the regenerating organ can not itself be regenerated, immortality can not be lost through mutation or cancer. [Answer] # Different DNA These Cruel Angels actually have two sets of DNA. One for the majority of themselves, and a second for the core. The core is only able to replicate the first set of DNA. Due to the complexity of the core's DNA, or maybe as an evolved safety measure against core cancer, the core cannot replicate its own sequence. The core only grows during gestation. It is full sized and stops shortly after the Eva is born. Or slightly differently, the core can take in other sets of DNA and replicate it, but not its own. Then the core might be valuable to ordinary Humans, or there might be a way for Evas to regenerate each others' cores. [Answer] It is already dead. This has precedent - the lens of the human eye "dies" during development, and discards all internal organelles so that it is transparent. Why would your core require this? The vast majority of the core is a chitinous mass, that contains, guides and separates the individual components that allow for regeneration. If this protective sheath were still alive, then it would continue to grow and regenerate, eventually cutting the rest of the body off from regeneration. On the other hand, if the different regenerative components - producing telomerase, platelets, et cetera, to rebuild tissue damage - were to come into contact then they would undergo unconstrained growth, and engulf the Evangelion in a cancer-like mass that prevented it from being able to move or act. [Answer] **It is a design limitation** The core was included in the design of Evas and was responsible for their long lifespans and regeneration. Explanation of why the Evas have a core and other humans do not is a bit of a mystery. However, just as normal human cells have a [Hayflick Limit](https://en.wikipedia.org/wiki/Hayflick_limit) limiting cell to around 50-70 division due to the shortening of the telomeres, the DNA in the core likewise has a division limit, based on something similar to regular telemores, but enough different that the core cannot repair its own. Cells in the core are also limited to 50-70 divisions, but the cells in the core have a longer life cycle than typical cells. This longer-life design is inappropriate for the human overall, as this also results in a comparatively slow metabolism. Once the core cells reach their own Hayflick limit, the body dies. It turns out that the body is not really immortal, it is just capable of a very long lifespan. When I completed this, I saw it as actually similar to the answer given by Xavon\_Wrentaille [Answer] # The core only works while undamaged Being a complex organ, the core stops functioning entirely when it's damaged. Think of a clockwork. Every part has to play together in order to accomplish a goal. If you remove even one cogwheel the whole contraption stops working. Now for your core, this would mean the following: * It can regenerate organic matter * It stops regenerating once it's damaged * It can never regenerate itself since it can't regenerate at all once damaged However, you wrote: > > It cannot repair damage done to it, which reduces the Evas regenerative ability. > > > **Keep in mind that this solution stretches the word "reduce" quite a bit** It certainly reduces the ability, but only to zero. If you want a damaged core to function (less efficiently), I would suggest a different approach like the "different DNA" answer. [Answer] It has it's own circulatory system, so that if the heart is damaged, it can be repaired without a beating heart. This circulatory system is dormant until needed at which point the organ secretes from a 'bladder' the repair cells to the damaged area. **However, this circulatory system does not feed back to the organ itself.** Cells are produced and stored in this bladder until needed. This allows for the quick delivery of a large amount of repair cells. The bladder can repair itself since it is full of repair cells. However the organ only has a small number of these cells at any given time as it sends them to the repair bladder, any repairs to the organ itself are slow. The cells flow towards the bladder after production, if it detects damage, it repairs it right away in the organ itself. Think of it like a tree, the leaves produce the cells, they flow through the stem, to the branch, to the trunk. If the leaf is cut off, there is no path for the cells to move backwards. If a repair cell happens to have just been produced and is still there when the damage occurred, then it can repair the leaf. When 1/2 of the repair cells are destroyed, it takes twice as long for the bladder to fill. It solves the issue of 'where does the matter come from' when repairing. It's not infinite, it slowly builds over time and is stored in the repair bladder. Too much damage to the body would require a longer period of time to heal, when low in cells it only repairs the essentials for life. This idea leaves open the possibility of medical advancements that would allow surgeries to manually distribute these cells back to their producers for repair...same for organ transplants I suppose. BTW decapitation is game over...there can be only one. [Answer] I see two easy ways to go about this. Lserni proposed a pretty stable method and honestly their's makes a lot of sense. But here are my opinions on the question. 1. The core is an artificial organ that is implanted at birth or before puberty. Whether grown in a vat, harvested from another organism,or even brought into the body by eating the core of one of their dead forebears. The core may be able to regenerate other tissues but requires external aids to regenerate itself. Whether these are dietary supplements or implants with invasive surgery is up to choice. What seems like a key idea is that without the regeneration your EVA's are just larger, stronger humans. So why not capitalize on that? They have a core that can give them regenerative ability but can't regenerate itself. However the conditions for that are not stated. If a core can be used for regenerative purposes it could ideally have riskier short term uses. What if during fight or flight,the core switches into overdrive and just starts dumping large amounts of stem cells,adrenaline & possibly even causing brief if explosive muscle/bone growth in the body. However doing this puts a great deal of stress on the core and can cause it to begin breaking down. This gives EVA's a very strong regeneration ability and combat capability. But to go all-out,much like humans;they risk life and limb. In their case permanently. Core damage could cause damaged scar tissue and abnormal growths of regenerated body parts. Eventually leading to useless limbs or them cauterizing the stumps to prevent further damage to the body. By eating other cores,implanting another core or ingesting a supplement of some kind they could feasibly recover. But it would be very risky and the odds of them dying would be high if their own core was already far gone enough for it to be absolutely needed. 2. The organ is a symbiotic organism. A "Serpent from the trees of Eden" which supports the EVA host with regenerative properties by acting as a natural source of cell repairs and immortality by producing copies of the host's stem cells. The Serpent in return requires nutrients given by the host but if sufficiently injured itself can die. This greatly weakens the EVA and can cause their death at worst or developing a compromised immune system at best. Now this also has a silver lining which I rather enjoy. See these symbiotes have a natural life cycle too,being dependent on the EVA's for food but also for finding a mate. When two EVA's mate so too do the Serpent's within them, simply through fluid exchange rather than weird slithering exchanges. Effectively fertilizing one another when successful,this results in the Serpent's in both EVA's developing a fertilized egg. This egg in the female ends up (in most cases) bonding with the yet unborn child. But in a non-viable pregnancy may either be eaten or kept in effective stasis by its parent. The fertilized egg of the Serpent's thus serve to propagate the Serpent's as well as the EVA's. Giving both a large edge in survival. With the spare egg in either male or female EVA's being able to be passed on (brace for disgusting) by the Serpent crawling up the esophagus like a tapeworm to spit the egg into the mouth of another EVA. Thus allowing new cores to be transferred into EVA with damaged or dead cores. It also serves a third purpose, in that if the parent Serpent dies in its host with a fertilized egg still inside; then it can hatch and attempt to take its parents place as a new core. The success of this would be variable but also notable enough to have a strong impact. So these are my thoughts. Artificial organs or symbiotic Serpents of Eden that spread through the EVA's, record their genetic information to heal them & then pass this on to the eggs they lay as "Apples of Knowledge" down the family tree. I'll show myself out now after the puns. [Answer] I'd throw in some *already existing* biological tissues and organs that might be used as an inspiration. * Teeth. Our whole problem with dentists arises from the fact that dentine tissue cannot be re-created by a somewhat mature organism. A fetus "knows" how to create teeth, it has cells that develop into teeth tissue, but more or less aged specimen does not have those progenitor cells anymore. * Thymus. The organ plays a role in "bootstrapping" immune system, but it is apparently of little use (citation needed) for a mature organism. Hence its tissue are slowly replaced by fatty tissue. One might speculate that the decrease of immune response in elderly people has something to do with it, but I digress. To summarise: either the organ is actually dead / has no progenitor cells for its tissue in adult organism, or the organ is not needed anymore in adult organism and is slowly replaced with inert tissue. For the second option, the actual Sci-Fi effect would be produced by some *other* cells that the organ produces, that live in the body more-less indefinitely, but don't really need to be produced in the later life, causing the Sci-Fi effect to detoriate with age. The analogy might be blood cells, such as B-cells (immunity) or erythrocytes (oxygen transport), if you factor out that erythrocytes are short-lived. [Answer] This is a fun question to think about. **Copying and the Hayflick Limit** Generally what stops humans from being immortal, well at least one of the mechanisms, is whats known as the Hayflick limit. Basically its a limitation to the number of regenerations a cell line can take, before it experiences programmed death. Theres a good reason for this. The more a cell reproduces, as in copy, copy of copy, copy of copy of copy, the more 'noise' is introduced to the genome in the form of mutations, inefficiencies and ultimately, cancers. Cancer in fact largely works by disabling the hayflick limit and thus becoming immortal (Or at least until it kills the host, or the hosts immune system kills it.) So how dow we work this into our immortal 8ft tall guys with a core? **Mother cells and Stem cells** The cores job is to store a pristine copy of the genetic blueprint of the human, as well as a reserve of stem cells that can be deployed to replace cells getting close to the hayflick limit. The stem cells are always first generation copies, because at the center of the organ is a reserve of mother cells that never die and when they divide there is always one of the divided cells that keep the original genome. But if these cells are destroyed, they will not grow back, because then the mother cells would not be original copies anymore. The mechanism that ensure the mother cells are original also ensures they can not grow back. *(Note, Mother Cells are not a thing in IRL biology)* **The Blood-Core Barrier** The organ features a blood-core barrier around the mother cells that only allows a heavily filtered set of blood components in, as, much like the brain which also can not reproduce its cells (mature neurons dont really have a reproductive capability), no immune system exists in there, this is to prevent auto-immune disorders attacking the core. This is not really a problem as the blood-core barrier doesn't allow *any* cells in except red blood cells and since red adult blood cells ALSO don't have reproductive capacity they can't be hijacked by viruses. The downside of this is a rupture or damage to the barrier makes the core extremely vunerable to infection. **Putting it together** As long as the organ is uninjured, and the mother cells are protected from infection or rupture, the core can generate stem cells forever to replace dying cells elsewhere in the body. If the core is injured however, particularly the reserve of mother cells, all bets are off, and even with close modern medical care, the patient can only reasonably expect to live another 50 or therabouts years, as now their cells will age , die, and mutate just like the rest of us. *Caveat* I'm a little hazy on the exact way mother cells can create new stem cells without the mother cells themselves being prone to the hayflick limit or copying errors, but perhaps they have a unique mode generating the stem cells I guess. [Answer] The organ requires a specific diet to operate and without that plant it cannot regenerate the body or itself--it dies and the body becomes mortal. The concept is adapted from something in Larry Niven's Ringworld I can't believe how many topics on this site have similarities to ringworld. What I recall of his explanation was that the human appendix had evolved to process a certain type of now-extinct plant (something similar to sugar cane). When humans started eating this plant at 20ish years of age they evolved from an irresponsible, ignorant nymph stage into an adult stage and became intelligent, strong and long-lived. After this change they lived almost exclusively on this plant. Since the plant went extinct, we have never been able to get out of the nymph stage and our bodies are exposed to all these horrible age-related problems including extremely early death. When the original species that colonized earth re-located us they couldn't believe what we'd accomplished considering we were stuck in the "nymph" stage. I haven't read this for like 40 years so I'm probably quite inaccurate. ]