Hans Bethe

Hans Albrecht Bethe (; July 2, 1906 – March 6, 2005) was a German-American nuclear physicist.
Bethe made important contributions to astrophysics, quantum electrodynamics, and solid-state physics. He who won the 1967 Nobel Prize in Physics for his work on the theory of stellar nucleosynthesis. 
For most of his career, Bethe was a professor at Cornell University. The notes of his classes are on nuclear physics and applications of quantum mechanics.
During World War II, he was head of the Theoretical Division at the secret Los Alamos laboratory that developed the first atomic bombs. There he played a key role in calculating the critical mass of the weapons. He and others developed the theory behind the implosion method used in the Trinity test and the "Fat Man" weapon dropped on Nagasaki in August 1945.
After the war, Bethe also played an important role in the development of the hydrogen bomb, although he had originally joined the project with the hope of proving it could not be made. Bethe later campaigned with Albert Einstein and others against nuclear testing and the nuclear arms race. He helped persuade the Kennedy and Nixon administrations to sign treaties limiting nuclear tests.
His scientific research never stopped. He published papers well into his nineties. He published at least one major paper in his field during every decade of his career, which in Bethe's case spanned nearly seventy years. Freeman Dyson, once his doctoral student, called him the "supreme problem-solver of the 20th century".