Confirmation of the eclipse measurements – In 1919, Einstein received a telegram from Hendrik Lorentz [L-Lorentz, 1919] reporting preliminary confirmation of light deflection predicted by general relativity. Encouraged but cautious, as reflected in a letter to his mother [L-Einstein, 1919a], Einstein waited for more definitive results. A few weeks later in Leiden, he learned from Ejnar Hertzsprung that the data matched his prediction exactly [Clark]. Elated, he wrote to Max Planck [L-Einstein, 1919a,b]. The findings, later announced at the Royal Society, made Einstein a global celebrity [Landau, 2019].

Einstein’s admiration for Newton – Though general relativity replaced parts of Newtonian physics, Einstein revered Newton as one of history’s greatest scientific minds and admired his discovery of nature’s hidden laws. The reflection quoted here comes from his Autobiographical Notes which he wrote years later [Schilpp]. Given the moment’s significance, it is plausible such thoughts were already stirring in Einstein’s mind that evening in Leiden.