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Fritz Kirchner's work on the charge of the electron


Albrecht Unsöld's work on stars
Hans Bethe Scientist
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Perhaps the most important other student was Unsöld who then went into astrophysics, and he... during my studies discovered that the sun and other stars mostly consist of hydrogen and not of the same material as the Earth. Astrophysicists before him, especially Eddington who really put astrophysics on a firm basis, had assumed that the same elements prevail in the sun as on Earth, and that gave Eddington a terribly high temperature at the center of the sun, about 40 million degrees. Then came Unsöld, and at the same time Russell, Henry Norris Russell in America, who said well... the spectrum of the sun and of other stars is richest in the lines of hydrogen, therefore it is very likely that hydrogen is the dominant element in all stars. And this was then taken up by Eddington and Strömgren who independently made a star, mostly made out of hydrogen. So this was probably the most important student at my time.

The late German-American physicist Hans Bethe once described himself as the H-bomb's midwife. He left Nazi Germany in 1933, after which he helped develop the first atomic bomb, won the Nobel Prize in Physics in 1967 for his contribution to the theory of nuclear reactions, advocated tighter controls over nuclear weapons and campaigned vigorously for the peaceful use of nuclear energy.

Listeners: Sam Schweber

Silvan Sam Schweber is the Koret Professor of the History of Ideas and Professor of Physics at Brandeis University, and a Faculty Associate in the Department of the History of Science at Harvard University. He is the author of a history of the development of quantum electro mechanics, "QED and the men who made it", and has recently completed a biography of Hans Bethe and the history of nuclear weapons development, "In the Shadow of the Bomb: Oppenheimer, Bethe, and the Moral Responsibility of the Scientist" (Princeton University Press, 2000).

Tags: Albrecht Unsöld, Arthur Eddington, Henry Norris Russell, Bengt Strömgren

Duration: 1 minute, 43 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008