Hans Bethe

Aravind Bharathi bio photo By Aravind Bharathi Comment

Who developed the formula to calculate the explosive yield of the first atomic bomb?

Hans Bethe was born in Strassburg, Germany on 2nd July 1905. He studied at the Universities of Frankfurt and Munich, where he earned his Ph.D. under Arnold Sommerfeld in 1928. He made important contributions to the theories of electrons in crystals, the negative hydrogen ion, and the passage of charged particles through matter and wrote major review articles on one-and-two electron atoms and electrons in metals before leaving Germany in 1933 for England.

He began working in nuclear physics, and he and Rudolph Peierls developed the theoretical model of the deuteron shortly after its discovery. Bethe was at Cornell University from 1935 to 2005. His three review articles in the late 1930s became known as “Bethe’s Bible” and formed the first real textbook of nuclear physics.

In 1938 he developed the detailed model of the nuclear reactions which power the stars. He worked out the reaction rates for the CNO cycle, which he introduced, and which powers the more massive stars, and (with C.L. Critchfield) of the proton-proton chain, which had been suggested earlier by others, and which is more important in lower mass stars such as the sun. At the beginning of World War II Bethe, on his own, formed a theory of the penetration of armor by projectiles, and, with Edward Teller, produced a major paper on shock waves. From 1943 to 1946 Bethe headed the theoretical group at Los Alamos, where the first nuclear bomb was designed and built.

After the war he worked on nuclear matter and meson theory and was the first to explain the Lamb shift in the hydrogen atom in an early and important contribution to quantum electrodynamics. He was an influential advisor to government agencies on both defense and energy policies, and he wrote widely about arms control and the need for new energy policies.

After his official retirement he returned to astrophysics, and he continued to do research on solar neutrinos, supernovae, neutron stars, black holes, and other problems in theoretical astrophysics into his late nineties.

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