Four years after Albert Einstein published his theory of General Relativity, the British astronomers Frank Watson Dyson and Arthur Stanley Eddington organized two expeditions, one to Africa and the other to Brazil, in order to test this theory during the solar eclipse. total of May 29, 1919. Thus it was possible to measure, for the first time, the deflection of the light of stars from the background, caused by the gravitational field of the Sun. The talk describes this decisive experiment and its consequences.