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Pleasing results from the experiments


The SAGE experiment
Hans Bethe Scientist
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How can you prove it? The way in which Bahcall made it very plausible is by showing that probably the neutrinos which arrive on earth have different properties according to their energy. The high energy neutrinos which come from boron and which are observed in Kamiokande are converted halfway into µ-neutrinos. The medium energy neutrinos, however, don't get out of the sun at all, they're practically all converted into µ-neutrinos and therefore are not visible. And he concluded that by comparing the result of Davis in chlorine with the result of Kamiokande, the comparison of this... these two shows pretty definitely that the beryllium neutrinos do not come to the earth. The beryllium neutrinos should be seen by Davis. And then a third experiment was done using gallium, again I think suggested by Bahcall. In gallium you can observe the primary neutrinos which are made in the fundamental reaction making two protons coming together and forming deuterons. And... and now, this reaction has the great advantage that we know exactly how much there is of this reaction, namely this reaction after all feeds the energy of the sun, and therefore if we just look at the luminosity of the sun we can tell how intense this proton-proton reaction must be. And the proton-proton neutrinos can be observed with gallium. It was first done in Russia by a Russian-American group known as the SAGE Experiment, Soviet American Gallium Experiment, and then repeated in Italy by a European group.

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: Kamiokande experiment, Homestake experiment, SAGE experiment, John Bahcall, Raymond Davis

Duration: 2 minutes, 58 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008