he third paper in 1905 concerned statistical mechanics.After 1905 Einstein made important contributions to quantum theory, but he wanted to extend the special theory of relativity to phenomena involving acceleration. The key appeared in 1907 with the principle of equivalence, in which gravitational acceleration was held to be indistinguishable from acceleration caused by mechanical forces. From then on, gravitational mass was identical with inertial mass.1909 recognized Einstein as a leading scientific thinker and in the same year he resigned from the patent office. He was appointed a full professor at the Karl Ferdinand University in Prague in 1911. Also in 1911, Einstein was able to make preliminary predictions about how a ray of light from a distant star, passing near the sun, would appear to be bent slightly in the direction of the sun.Einstein received the Nobel Prize in 1921 but not for relativity, rather for his 1905 work on the photoelectric effect. At approximately 1922 he made many international visits. He visited Paris in 1922 and during 1923 he visited Palestine. After making his last major scientific discovery on the association of waves with matter in 1924 he made more visits in 1925 to South America.In 1940 Einstein became a citizen of the United States. He made many contributions to peace during his life. In 1944 he made a contribution to the war effort by handwriting his 1905 paper on special relativity and putting it up for auction. It raised six million dollars. The manuscript today is held in the Library of Congress.One week before his death, Einstein signed his last letter to Bertrand Russell in which he agreed that his name should go on a manifesto urging all nations to give up nuclear weapons. It fit him that one of his last acts was to argue, just as he had done all his life, for international peace....
