How the 1922 solar eclipse in Australia proved Einstein right

Astronomers came from the United States, Canada, New Zealand, India and Britain – traveling to places so far away that many Australians had never heard of them before. their names are only starting to appear in the press.

The scientists weren’t there just for the show, but also in the hope that their observations of the eclipse would validate Albert Einstein’s then controversial theory of general relativity, postulated seven years earlier.

Einstein’s theory, in general, suggests that gravity can warp the very fabric of space-time itself. One possible way to test this was to photograph the background of stars before and during an eclipse. The Sun’s gravity is expected to bend the light of distant stars as it passes them, causing them to appear in a slightly different position – and the eclipse would allow astronomers to make this observation by usefully erasing glare from the Sun.

War and weather

World War I prevented astronomers from studying Einstein’s 1915 prediction. But a total solar eclipse on May 29, 1919 offered the first decent chance to prove him right. Britain has organized two separate expeditions in the hope that at least one of them can make the necessary observations. In Sobral, Brazil, the team led by astronomer Royal Frank Dyson suffered an equipment failure. But on Principe Island off the west coast of Africa, Arthur Eddington, despite the inclement weather, successfully photographed the event.

Dyson, after viewing Eddington’s photographic plates, said “there is no doubt that they confirm Einstein’s prediction.” But many skeptics remained skeptical.

The next suitable eclipse was in Australia on September 21, 1922. The famous Lick Observatory in California had used its 12-meter camera to photograph several previous eclipses, and director William Wallace Campbell was determined his observatory would solve “the problem. of Einstein ”in Australia.

The location chosen by Campbell – Wallal, on the WA coast about 200 miles (320 kilometers) south of Broome, was remote and almost inaccessible. But there was virtually no chance of clouds, and the eclipse would last there the longest, providing five full minutes of totality.

Shallow seas meant that the expedition ships could not get close to shore and instead had to carry equipment ashore at high tide with the help of local indigenous peoples.

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