Thursday, February 2, 2012

Hans Bethe, Bomb and Fusion

"I am not a Philosopher"
Hans Bethe (1906 – 2005)

Wikipedia writes:
Hans Albrecht Bethe was a German-American nuclear 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 astrophysics.

During World War II, he was head of the Theoretical Division at the secret Los Alamos laboratory which developed 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 and he was publishing papers well into his nineties. He is one of the few scientists who can claim a major paper in his field every decade of his career, which spanned nearly 70 years. Freeman Dyson called Bethe the "supreme problem solver of the 20th century."

Stellar career until old age

Wikipedia continues:

In 1967, Bethe was awarded the Nobel Prize in Physics "for his contributions to the theory of nuclear reactions, especially his discoveries concerning the energy production in stars. His postulate was that the source of this stellar nucleosynthesis was thermonuclear reactions in which hydrogen is converted into helium.

Bethe was also noted for his theories on atomic properties. In the late 1940s, he provided the first way out of the infinities that plagued the explanation of the so called Lamb shift. Although his calculation was a non-relativistic one, it provided the impetus for later work done by Richard Feynman, Julian Schwinger and others which marked the beginning of modern quantum electrodynamics.

Bethe continued to do research on supernovae, neutron stars, black holes, and other problems in theoretical astrophysics into his late nineties. In doing this, he collaborated with Gerald Brown of the State University of New York at Stony Brook.

In his 80s, he wrote an important article about the solar neutrino problem in which he dealt with the conversion of electron neutrinos into muon neutrinos that was proposed to explain the discrepancy between theory and experiment. Physicist Kurt Gottfried says that he does not know anyone in the history of modern physics who has done work of such calibre in his 80s.

Cornell University respects him for example by naming the West Campus House System Hans Bethe House.

Hans Bethe's Nobel foundation biography is in this link

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