Albert Einstein and his wife 1921 Einstein, Albert Swiss-US (German-born) physicist; moved to Switzerland, becoming Swiss citizen 1900; examiner in Swiss Patent Office in Bern 1900-1907; discovered special relativity 1905; discovered mass-energy equivalence 1905; correctly explained photoelectric effect in terms of light quantization 1905; correctly explained physical cause of Brownian motion 1905; enunciated principle of equivalent reference frames 1907; correctly formulated Maxwell's equations in presence of gravitational field 1914 (early version 1907); returned to Germany 1914; discovered general relativity 1915 (published 1916); predicted possibility of stimulated emission 1917, anticipating operation of lasers; hailed as world's preeminent physicist upon experimental confirmation of key prediction of general relativity, confirmed by Royal Society's expedition to Principe Island in Gulf of Guinea to observe solar eclipse 1919; Nobel Prize in Physics 1921; upon Adolf Hitler's rise to power, left Germany, renounced German citizenship, and immigrated to US 1933 (naturalized US citizen 1940); rejected probabilistic nature of quantum mechanics and unsuccessfully attempted to develop non-probabilistic unified theory; upon learning of Otto Hahn and Fritz Strassmann's successful fission of uranium in Nazi Germany, wrote letter to Franklin Roosevelt urging initiation of US atomic-bomb research (Manhattan Project), though taking no direct role in bomb research; following World War II, strongly advocated pacifism and arms limitation; offered presidency of Israel following death of Chaim Weizmann 1952, but declined _1879-1955