ABSTRACT
The atmosphere was quite tense on that Thursday, the 6th of November, 1919, at the seat of that most venerable British scientific institution, the Royal Society. All of the leading British scientists had come that day to Burlington House, where a joint session of the Royal Society and the Royal Astronomical Society was to be held. The president of the Royal Society, Sir Joseph John Thomson (famous for his discovery of the first elementary particle, the electron), opened the session. He recalled that the aim of this joint meeting was to present the results obtained by two British astronomical expeditions which had gone to observe the total eclipse of the Sun on May 29, 1919. The observations made by these expeditions consisted of photographs (taken by day) of the field of stars around the Sun at the moment when the eclipse was total and allowed the stars to be seen. These photographic plates were then compared to photographs (taken at night) of the same field of stars, at a moment when the Sun was far from the field. The aim of these observations was to confirm or invalidate a prediction made by Einstein in November 1915, which was a consequence of his new conception of gravity based on a generalization of the theory of relativity of 1905.
