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The SAGE experiment


Stanislav Mikheyev and Alexi Smirnov's theory
Hans Bethe Scientist
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It remained a big puzzle. Finally this was solved, at least to my satisfaction, by two Russian theoretical physicists, Mikheyev and Smirnov, making use of a theory previously developed by Wolfenstein of Pittsburgh for a completely different purpose. Namely Wolfenstein said that when you have some very dense material and have neutrinos going into it, then there could be a transformation of the neutrino which we know, the electron neutrino, into another type which is associated with the µ-meson. And the two Russians took up that theory and said that's probably what happens in the sun; the neutrinos which are formed in the sun are interacting with the very dense gas of electrons in the sun and are converted into µ-neutrinos. Those you cannot observe on earth because in order to observe them by the methods so far used you have to have neutrinos of energies equal to the mass of a µ-meson because a µ-neutrino being absorbed by neutron or proton will give an electron... a µ-meson plus the other nucleon. Well, that is a very attractive theory and it was brought to my attention by Davis who had done the experiment, and it immediately captured my interest and I... revised the Smirnov paper into one that is a little easier to comprehend and I became convinced that indeed the Smirnov theory is correct and that electron neutrinos are converted in µ-neutrinos.

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: Mikheyev–Smirnov–Wolfenstein effect, matter effect, Stanislav Mikheyev, Alexei Smirnov, Lincoln Wolfenstein

Duration: 2 minutes, 55 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008