Hans Albrecht Bethe (French pronunciation: [ˈhans ˈalbʀɛçt ˈbeːtə]; July 2, 1906 – March 6, 2005) was a German-American physicist, and Nobel laureate in physics for his work on the theory of stellar nucleosynthesis. A versatile theoretical physicist, Bethe also made important contributions to quantum electrodynamics, nuclear physics, solid-state physics and particle astrophysics. During World War II, he was head of the Theoretical Division at the secret Los Alamos laboratory developing the first atomic bombs. There he played a key role in calculating the critical mass of the weapons, and did theoretical work on the implosion method used in both the Trinity test and the "Fat Man" weapon dropped on Nagasaki, Japan. For most of his career, Bethe was a professor at Cornell University. During the early 1950s, Bethe also played an important role in the development of the larger hydrogen bomb, though he had originally joined the project with the hope of proving it could not be made. Bethe later campaigned together with Albert Einstein in the Emergency Committee of Atomic Scientists against nuclear testing and the nuclear arms race. He influenced the White House to sign the ban of atmospheric nuclear tests in 1963 and the 1972 Anti-Ballistic Missile Treaty, SALT I. His scientific research never ceased even into the later years of his life. He is one of the few scientists who can claim a major paper in his field every decade of his career, which spanned nearly sixty years. Freeman Dyson called Bethe the "supreme problem solver of the 20th century."