Why did Einstein win a Nobel Prize for the photoelectric effect, but not for relativity?
Einstein supported unpopular causes. The year he moved from Switzerland to Germany, he joined a group of people opposing Germany’s entry into World Was I. He joined both socialist and pacifist causes. He opposed the Nazis, and when Adolf Hitler (1889–1945) came to power, Einstein moved to the United States. He took a position at the Institute for Advanced Study in Princeton, New Jersey. Some years later he became a citizen of the United States. After being urged by other physicists, Einstein signed a letter to President Franklin D. Roosevelt (1882–1945) pointing out the danger posed by Germany’s work on uranium that could lead to a dangerous new kind of bomb. The letter helped to launch the Manhattan Project that lead to the development of the atomic bomb.
Although Einstein did not actually work on the bomb, after the defeat of Germany, and knowing the death and destruction that dropping the bomb would cause, he sent another letter to the President urging him not to use the bomb. The letter was never forwarded to President Harry Truman (1884-1972). After the war Einstein spent time lobbying for atomic disarmament. At one point he was even asked to head the new Jewish state of Israel. Einstein, both for his scientific works and his social and political views, became an international icon.
Einstein was a controversial person. He was Jewish and a strong supporter of pacifist causes. In addition, his approach to theoretical physics was very different from physicists of that time. He was repeatedly nominated for the Nobel Prize, but members of the Prize committee, despite his public fame, refused to grant him the Prize, most likely for political reasons. The 1921 prize was not awarded. In 1922 the committee found a way to compromise. Einstein was awarded the 1921 prize for the photoelectric effect because of the way it could be tested experimentally.