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was a German-born theoretical physicist who developed the general theory of relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modernphysics[2][3] and the most influential physicist of the 20th century. While best known for his mass–energy equivalence formula E = mc2 (which has been dubbed "the world's most famous equation"),[4] hereceived the 1921 Nobel Prize in Physics "for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect".[5] The latter was pivotal in establishingquantum theory within physics.
Near the beginning of his career, Einstein thought that Newtonian mechanics was no longer enough to reconcile the laws of classical mechanics with the laws of theelectromagnetic field. This led to the development of his special theory of relativity. He realized, however, that the principle of relativity could also be extended to gravitational fields, and with hissubsequent theory of gravitation in 1916, he published a paper on the general theory of relativity. He continued to deal with problems of statistical mechanics and quantum theory, which led to hisexplanations of particle theory and the motion of molecules. He also investigated the thermal properties of light which laid the foundation of the photon theory of light. In 1917, Einstein applied thegeneral theory of relativity to model the structure of the universe as a whole.[6]
He was visiting the United States when Adolf Hitler came to power in 1933, and did not go back to Germany, where he hadbeen a professor at the Berlin Academy of Sciences. He settled in the U.S., becoming a citizen in 1940.[7] On the eve of World War II, he helped alert President Franklin D. Roosevelt that Germany mightbe developing an atomic weapon, and recommended that the U.S. begin similar research; this eventually led to what would become the Manhattan Project. Einstein was in support of defending the Allied...