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However, as he only considered the effect of deflection around a single star, he seemed to conclude that the phenomenon was unlikely to be observed for the foreseeable future since the necessary alignments between stars and observer would be highly improbable.

Several other physicists speculated about gravitational lensing as well, but all reached the same conclusion that it would be nearly impossible to observe.

In 1936, after some urging by Rudi W. Mandl, Einstein reluctantly published the short article "Lens-Like Action of a Star By the Deviation of Light In the Gravitational Field" in the journal Science.

In 1937, Fritz Zwicky first considered the case where the newly discovered galaxies (which were called 'nebulae' at the time) could act as both source and lens, and that, because of the mass and sizes involved, the effect was much more likely to be observed.

G. Klimov, S. Liebes, and Sjur Refsdal recognized independently that quasars are an ideal light source for the gravitational lens effect.

It was not until 1979 that the first gravitational lens would be discovered.

This gravitational lens was discovered by Dennis Walsh, Bob Carswell, and Ray Weymann using the Kitt Peak National Observatory 2.1 meter telescope.

In the 1980s, astronomers realized that the combination of CCD imagers and computers would allow the brightness of millions of stars to be measured each night.

In a dense field, such as the galactic center or the Magellanic clouds, many microlensing events per year could potentially be found.

This led to efforts such as Optical Gravitational Lensing Experiment, or OGLE, that have characterized hundreds of such events, including those of OGLE-2016-BLG-1190Lb and OGLE-2016-BLG-1195Lb.

This means that the light from an object on the other side will be bent towards an observer's eye, just like an ordinary lens.

In general relativity the speed of light depends on the gravitational potential (i.e.

Light rays are the boundary between the future, the spacelike, and the past regions.

The gravitational attraction can be viewed as the motion of undisturbed objects in a background curved geometry or alternatively as the response of objects to a force in a flat geometry.

A search for gravitational lenses in the northern hemisphere (Cosmic Lens All Sky Survey, CLASS), done in radio frequencies using the Very Large Array (VLA) in New Mexico, led to the discovery of 22 new lensing systems, a major milestone.

This has opened a whole new avenue for research ranging from finding very distant objects to finding values for cosmological parameters so we can understand the universe better.

A similar search in the southern hemisphere would be a very good step towards complementing the northern hemisphere search as well as obtaining other objectives for study.

If such a search is done using well-calibrated and well-parameterized instrument and data, a result similar to the northern survey can be expected.

The use of the Australia Telescope 20 GHz (AT20G) Survey data collected using the Australia Telescope Compact Array (ATCA) stands to be such a collection of data.

As the data were collected using the same instrument maintaining a very stringent quality of data we should expect to obtain good results from the search.

The AT20G survey is a blind survey at 20 GHz frequency in the radio domain of the electromagnetic spectrum.

Due to the high frequency used, the chances of finding gravitational lenses increases as the relative number of compact core objects (e.g.

This is important as the lensing is easier to detect and identify in simple objects compared to objects with complexity in them.

This search involves the use of interferometric methods to identify candidates and follow them up at higher resolution to identify them.

Full detail of the project is currently under works for publication.

Microlensing techniques have been used to search for planets outside our solar system.

A statistical analysis of specific cases of observed microlensing over the time period of 2002 to 2007 found that most stars in the Milky Way galaxy hosted at least one orbiting planet within 0.5 to 10 AUs.

In 2009, weak gravitational lensing was used to extend the mass-X-ray-luminosity relation to older and smaller structures than was previously possible to improve measurements of distant galaxies.

While it remains the most distant quad-image lensing galaxy known, an even more distant two-image lensing galaxy was subsequently discovered by an international team of astronomers using a combination of Hubble Space Telescope and Keck telescope imaging and spectroscopy.

The discovery and analysis of the IRC 0218 lens was published in the Astrophysical Journal Letters on June 23, 2014.

Thus, a probe positioned at this distance (or greater) from the Sun could use the Sun as a gravitational lens for magnifying distant objects on the opposite side of the Sun.

A probe's location could shift around as needed to select different targets relative to the Sun.

This distance is far beyond the progress and equipment capabilities of space probes such as Voyager 1, and beyond the known planets and dwarf planets, though over thousands of years 90377 Sedna will move farther away on its highly elliptical orbit.

The high gain for potentially detecting signals through this lens, such as microwaves at the 21-cm hydrogen line, led to the suggestion by Frank Drake in the early days of SETI that a probe could be sent to this distance.

A multipurpose probe SETISAIL and later FOCAL was proposed to the ESA in 1993, but is expected to be a difficult task.

If a probe does pass 542 AU, magnification capabilities of the lens will continue to act at farther distances, as the rays that come to a focus at larger distances pass further away from the distortions of the Sun's corona.

A critique of the concept was given by Landis, who discussed issues including interference of the solar corona, the high magnification of the target, which will make the design of the mission focal plane difficult, and an analysis of the inherent spherical aberration of the lens.

In 2020, NASA physicist Slava Turyshev presented his idea of Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravitational Lens Mission.

As a result, the shear effects in weak lensing need to be determined by statistically preferred orientations.

The primary source of error in lensing measurement is due to the convolution of the PSF with the lensed image.

The objects in lensed images are parameterized according to their weighted quadrupole moments.

For a perfect ellipse, the weighted quadrupole moments are related to the weighted ellipticity.

KSB calculate how a weighted ellipticity measure is related to the shear and use the same formalism to remove the effects of the PSF.

KSB's primary advantages are its mathematical ease and relatively simple implementation.

However, KSB is based on a key assumption that the PSF is circular with an anisotropic distortion.

This is a reasonable assumption for cosmic shear surveys, but the next generation of surveys (e.g.

Institute of Applied Mathematics, The University of British Columbia.

Cohen, N., "Gravity's Lens: Views of the New Cosmology", Wiley and Sons, 1988.

Wittenberg ( , ; Low Saxon: Wittenbarg; meaning White Mountain; officially Lutherstadt Wittenberg (Luther City Wittenberg)), is the fourth largest town in Saxony-Anhalt, Germany.

Wittenberg is situated on the River Elbe, north of Leipzig and south-west of Berlin, and has a population of 46,008 (2018).

Wittenberg is famous for its close connection with Martin Luther and the Protestant Reformation, for which it received the honorific Lutherstadt.

Several of Wittenberg's buildings are associated with the events, including a preserved part of the Augustinian monastery in which Luther lived, first as a monk and later as owner with his wife Katharina von Bora and family, considered to be the world's premier museum dedicated to Luther.

Wittenberg was also the seat of the Elector of Saxony, a dignity held by the dukes of Saxe-Wittenberg, making it one of the most powerful cities in the Holy Roman Empire.

Today, Wittenberg is an industrial center and popular tourist destination, best known for its intact historic center and various memorial sites dedicated to Martin Luther and Philip Melanchthon.

In 1260 this village became the residence of the dukes of Saxe-Wittenberg, and in 1293 the settlement was granted its town charter as a free-standing town.

Wittenberg developed into an important trade centre during the following several centuries, because of its central location.

When the local branch of the Ascanians died out in 1422, control of Saxe-Wittenberg passed to the House of Wettin.

This town became an important regional political and cultural centre at the end of the 15th century, when Frederick III "the Wise", the Elector of Saxony from 1486 to 1525, made his residence in Wittenberg.

Several parts of boundaries of the town were extended soon afterward.

The second bridge over the Elbe River was built from 1487 through 1490 and the castle church (the Schlosskirche in German) was erected from 1496 through 1506.

In 1502 Elector Frederick founded the University of Wittenberg, which attracted some important thinkers, such as Martin Luther—a professor of theology beginning in 1508—and Philipp Melanchthon—a professor of Greek starting in 1518.

On 31 October 1517, according to legend, Luther nailed his 95 theses against the selling of indulgences at the door of the All Saints', the Castle Church – an event taken as marking the beginning of the Protestant Reformation.

The Anabaptist movement had one of its earliest homes in Wittenberg, when the Zwickau prophets moved there in late 1521, only to be suppressed by Luther when he returned from the Wartburg in spring 1522.

The Capitulation of Wittenberg (1547) is the name given to the treaty by which John Frederick the Magnanimous was compelled to resign the electoral dignity and most of his territory to the Albertine branch of the House of Wettin.

In 1760, during the Seven Years' War, the Austrians bombarded the Prussian-occupied town.

The French took control in 1806, and Napoleon commanded the refortification of the town in 1813.

In 1814 the Prussian Army under Tauentzien stormed Wittenberg; he received the title of "von Wittenberg" as a reward.

In 1815 Wittenberg became part of Prussia, administered within the Province of Saxony.

Wittenberg continued to be a fortress of the third class until the reorganisation of German defences after the foundation of the new German Empire led to its dismantling in 1873.

It contained a prisoner of war camp from 1914 to 1918.

During the typhus epidemic of 1914-1915, conditions were harsh.

The camp medical officer, Dr. Aschenbach, was awarded the Iron Cross for his part in the epidemic.

The use of dogs to attack POW’s was criticised by American Ambassador James W. Gerard in his book “Four Years in Germany”.

Unlike many other historic German cities during World War II, Wittenberg's town centre was spared destruction during the conflict.

The Allies agreed not to bomb Wittenberg, though fighting took place in the town, with bullet pock-marks visible on the statues of Luther and Melanchthon at the market square – or so the popular version of the town's history goes.

In actuality, the Luther statue was not even present in the town square during much of the war, but in storage at Luther Brunnen, a roadhouse a few kilometres north of the town.

Wittenberg's reputation as a town protected from Allied bombing is largely accurate.

However, just outside Wittenberg the government had built the Arado Flugzeugwerke (the Arado Aircraft Factory), which produced components of airplanes for the Luftwaffe.

This war factory was worked by Jews, Russians, Poles, political prisoners and even a few Americans—all prisoners engaging in forced labour, including POW’s who were supposed to be exempt from this sort of labor.

American and British planes bombed the factory near the end of the war, and in destroying it killed over one thousand of the prisoners and POW’s placed by the Germans in this war plant.

At the end of the war, Soviet forces occupied Wittenberg; it became part of East Germany in 1949.

During the East German period, it formed part of Halle District.

By means of the peaceful revolution in 1989, the communist régime dissolved and the town has been governed democratically since 1990.

Wittenberg is currently characterized by renovation and new construction work, an economic recovery and tourism development as a "place of pilgrimage for the Reformation".

With the Luther Decade starting in 2008, the city began preparing for the 500th anniversary of the Reformation, which took place in 2017.

Numerous buildings have been restored, the infrastructure has been partially renewed and numerous new attractions have been created in the city (e.g.

On the doors of All Saints' Church, the Schlosskirche ("castle church", built in 1496–1506) Martin Luther is said to have nailed his 95 theses in 1517.

It was seriously damaged by fire in 1760 during a bombardment by the French during the Seven Years' War, was practically rebuilt, and was later (1885–1892) restored.

St. Mary's Church, the parish church in which Luther often preached, was built in the 14th century, but has been much altered since Luther's time.

It contains a painting by Lucas Cranach the Elder, representing the Last Supper (with the faces of Luther and other reformers), Baptism and Confession, also a font by Hermann Vischer the Elder (1457).

In addition, there are numerous historic paintings in the church.

The ancient electoral palace is another of the buildings that suffered severely in 1760; it now contains archives.

Martin Luther's home, the Lutherhaus, where he studied and lived both before and after the Reformation, is now a museum containing many artifacts from his life.

Melanchthon's house and the house of Lucas Cranach the Elder, mayor of Wittenberg, can also be found here.

Statues of Luther (by Schadow), Melanchthon and Bugenhagen embellish the town.

The spot outside the Elster Gate where Luther publicly burned the papal bull in 1520 is marked by an oak tree.

On 27 June 1293, Wittenberg was granted town rights by Duke Albert II.

There then arose a mediaeval town whose highest governing body was its council.

This council, known to have existed as early as 1317, was given the job of administering the town in its care through law and legislation, and of handling the town's revenue.

For documentation, the administration used its own seal.

One version of what is believed to be the town's oldest town seal, which the council used, and which dated from the first half of the 14th century, set the pattern with its elements for various civic coats of arms down to the present day.

The coat of arms symbolizes, with its crenelated wall and the towers within and each side, a town that was already strongly fortified by 1409.

The shield on the left is the Wittenberg district's arms.

In 1356, Emperor Charles IV bestowed upon the Duke of Saxony-Wittenberg the honour of Elector.

The shield with its crossed swords stands for the office of "Arch-Marshal of the Holy Roman Empire" inextricably joined by the Electorate, brought to Wittenberg by Rudolf I.

Both coats of arms continued to be used by the Wettins after the Ascanians died out.

The flowing water at the foot of the shield symbolizes Wittenberg's location on the River Elbe.

The fish is a salmon, which were once abundant in the Elbe.

The whole area of the industrial park covers more than 220 hectares with more than 1,500 workers.

Wittenberg is also the headquarters of the eco-friendly web search engine Ecosia.

Wittenberg is one of the top destinations in Saxony-Anhalt.

Lutherstadt Wittenberg station is the main railway station.

It connects Wittenberg hourly with Berlin to the north and Leipzig and Halle (Saale) to the south.

The station was rebuilt to be more environmentally friendly and re-opened in December 2016.

The Central German State Theatre (Mitteldeutsches Landestheater) reached a great importance in GDR times.

Since 1996, the town has staged open-air theatre shows based on the Lutheran history still alive in many historical places of the ancient town.

As highlights, in 2001 and 2005, Fernando Scarpa became the artistic director of the "Bühne Wittenberg" (Stage Wittenberg), a project for theatre, art and culture in the whole of Germany which attracts many visitors to the town and whose success is known European-wide.

On 2002 and 2003 Stefano Vagnini, Italian composer and organist created the music for Thesys and Luther Stories.

Prince Hamlet is said to have studied in Wittenberg and it was the supposed home of Dr. Faustus.

Wittenberg is seat of the Leucorea which is part of the Martin Luther University of Halle-Wittenberg, the largest university in Saxony-Anhalt.

Georgia is a state in the Southeastern region of the United States, bordered to the north by Tennessee and North Carolina; to the northeast by South Carolina; to the southeast by the Atlantic Ocean; to the south by Florida; and to the west by Alabama.

Georgia is the 24th-largest in area and 8th-most populous of the 50 United States.

Its 2020 population was 10,711,908, according to the U.S. Census Bureau.

Atlanta, a "beta(+)" global city, is both the state's capital and its largest city.

The Atlanta metropolitan area, with a population of more than 6 million people in 2020, is the 9th most populous metropolitan area in the United States and contains about 57% of Georgia's entire population.

Founded in 1732 as the Province of Georgia and becoming a royal colony in 1752, Georgia was the last and southernmost of the original Thirteen Colonies to be established.

Named after King George II of Great Britain, the Colony of Georgia covered the area from South Carolina south to Spanish Florida and west to French Louisiana at the Mississippi River.

On January 2, 1788, Georgia became the fourth state to ratify the United States Constitution.

From 1802 to 1804, western Georgia was split to form the Mississippi Territory, which later was admitted as the U.S. states of Alabama and Mississippi.

Georgia declared its secession from the Union on January 19, 1861, and was one of the original seven Confederate States.

Following the Civil War, it was the last state to be restored to the Union, on July 15, 1870.

In the post-Reconstruction era of the late 19th century, Georgia's economy was transformed as a group of prominent politicians, businessmen, and journalists, led by Henry W. Grady, espoused the "New South" philosophy of sectional reconciliation, industrialization, and white supremacy.

During the mid-20th century, several Georgians, most notably Martin Luther King Jr., were prominent leaders during the civil rights movement.

Atlanta was selected as host of the 1996 Summer Olympics, which marked the 100th anniversary of the modern Olympic Games.

Since 1945, Georgia has seen substantial population and economic growth as part of the broader Sun Belt phenomenon.

From 2007 to 2008, 14 of Georgia's counties ranked among the nation's 100 fastest-growing.

Georgia is defined by a diversity of landscapes, flora, and fauna.

The state's northernmost regions include the Blue Ridge Mountains, part of the larger Appalachian Mountain system.

The Piedmont plateau extends from the foothills of the Blue Ridge south to the Fall Line, an escarpment to the Coastal Plain defining the state's southern region.

Georgia's highest point is Brasstown Bald at 4,784 feet (1,458 m) above sea level; the lowest is the Atlantic Ocean.

With the exception of some high-altitude areas in the Blue Ridge, the entirety of the state has a humid subtropical climate.

Of the states entirely east of the Mississippi River, Georgia is the largest in land area.

The British colony of Georgia was founded by James Oglethorpe on February 12, 1733.

The colony was administered by the Trustees for the Establishment of the Colony of Georgia in America under a charter issued by (and named for) King George II.

The Trustees implemented an elaborate plan for the colony's settlement, known as the Oglethorpe Plan, which envisioned an agrarian society of yeoman farmers and prohibited slavery.

The colony was invaded by the Spanish in 1742, during the War of Jenkins' Ear.

In 1752, after the government failed to renew subsidies that had helped support the colony, the Trustees turned over control to the crown.

Georgia became a crown colony, with a governor appointed by the king.

The Province of Georgia was one of the Thirteen Colonies that revolted against British rule in the American Revolution by signing the 1776 Declaration of Independence.

The State of Georgia's first constitution was ratified in February 1777.