Hans Bethe

Hans Albrecht Eduard Bethe (/ˈbɛθə/; German: [ˈhans ˈbeːtə] ; 2 July 1906 – 6 March 2005) was a German-American physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics and solid-state physics, and received the Nobel Prize in Physics in 1967 for his work on the theory of stellar nucleosynthesis. For most of his career, Bethe was a professor at Cornell University.

In 1931, Bethe developed the Bethe ansatz, which is a method for finding the exact solutions for the eigenvalues and eigenvectors of certain one-dimensional quantum many-body models. In 1939, Bethe published a paper which established the CNO cycle as the primary energy source for heavier stars in the main sequence classification of stars, which earned him a Nobel Prize in 1967. During World War II, Bethe was head of the Theoretical Division at the secret Los Alamos National Laboratory that developed the first atomic bombs. There he played a key role in calculating the critical mass of the weapons and developing the theory behind the implosion method used in both the Trinity test and the "Fat Man" weapon dropped on Nagasaki in August 1945.