Einstein in mid-century: Eclipse tests of General Relativity from 1929 to 1973

By the late 1920s most astronomers and physicists were satisfied that the light deflection test conducted by several eclipses expeditions had conclusively falsified Newtonian gravity, leaving Einstein’s theory of General Relativity (GR) as the only viable theory of gravity. In the next half-century however, repeated testing would raise some doubts about the accuracy of the confirmation of GR and the emergence of rival theories (such as Brans-Dicke theory) would raise the stakes for new attempts to perform the test. Astronomers from several countries would perform the test at multiple eclipses, all agreeing with Einstein’s prediction. At the same time levels of precision of the test failed to improve as logistical challenges associated with the challenges of traveling to eclipses continued to confound even the best prepared expeditions.