Putting Albert Einstein’s theory of general relativity to the test.
In February 1919, Frank Dyson of the Royal Greenwich Observatory and Arthur Eddington of Cambridge University arranged for two teams of astronomers to observe and photograph a solar eclipse that was to occur in May of that year as it moved across South America, the Atlantic Ocean, and Africa. One team was based in Sobral, Brazil, and the other on the small island of Principe off the West coast of Africa.
The object of the expeditions was to put Albert Einstein’s theory of general relativity to the test. Published in 1915 after years of mathematical trial and error, the theory had - perhaps unsurprisingly - proven divisive and controversial among the scientific community at the time.
One of the predictions of general relativity was that light passing by an object like the sun would appear to bend. Because of their size, Einstein’s theory posited, astronomical bodies would cause a distortion in space-time so that even light waves – which travel at the absolute cosmic speed limit of 186,000 miles per second (300,000km per second) and in perfectly straight lines – would distort as well.
The darkness of an eclipse presented the astronomers with an opportunity to observe the stars that appear closest to the sun from Earth’s perspective, as they would otherwise be completely washed out by our star’s brightness.
The teams’ mission was a success. Having taken photos of a cluster of stars known as the Hyades, located in the constellation Taurus, they compared the images with reference shots of the same cluster that had been taken at night, to calculate any potential difference caused by the sun’s presence. In November of that year, both Dyson and Eddington announced that their findings supported the theory. The skeptics had been silenced and Einstein and his work were instantly catapulted to fame.
General relativity can be described without hyperbole as one of the deepest scientific insights into the universe that humanity has ever worked out. After Eddington and Dyson announced their results, the physicist J.J. Thomson reportedly described Einstein’s theory as, “a whole continent of scientific ideas.”
Scientists are still exploring the topography of that continent. The curving of light around massive astronomical objects is just one odd physical manifestation the theory describes.
If you’ve ever found yourself perplexed by the ideas expressed by general relativity, you’re in good company - the theory essentially keys humanity into the fact that space is bendable and the universe is weird. While perhaps an ungraceful description from a technical perspective, that is the essential truth of the environment that everyone and everything inhabits.