#OTD in 1919.
Albert Einstein's theory of general relativity is tested by Arthur Eddington and Andrew Claude de la Cherois Crommelin.
The Eddington experiment was organised by the astronomers Frank Watson Dyson & Arthur Stanley Eddington in 1919. The observations were of the total solar eclipse of 29 May 1919 and were carried out by two expeditions which aim was to measure the gravitational deflection of starlight passing near the Sun.