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Trying to observe neutrinos from the sun


How to observe a neutrino
Hans Bethe Scientist
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Peierls and I, back in '34, said that the only way one could observe a neutrino is if you capture it again in a nucleus. Well, that's correct, and that was actually observed after the war when... when very powerful nuclear reactors were built which emit tremendous densities of neutrinos. Fred Reines and Cowan observed the neutrinos emanating from the Savannah River nuclear reactor. So that showed that neutrinos can be observed, and then in the last 10 or 20 years when we had high energy accelerators, much higher energy neutrinos were formed and neutrinos were observed, for instance, in Fermi's lab, or in CERN in Europe, coming out of these very high energy accelerators. But once neutrinos had been observed, it was a nice, interesting idea that maybe you could observe the neutrinos which are made in the sun. I mentioned the proton-proton reaction; you make a deuteron and a positron and with the positron comes a neutrino and that reaction is then followed by a lot of others. You make beryllium-7 which captures an electron and again emits a neutrino and once in a blue moon the beryllium-7 gets further enhanced and becomes boron-8, which emits neutrinos of very high energy up to about 14MeV.

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: Savannah River Site, CERN, Fermilab, Rudolf Peierls, Frederick Reines, Clyde Cowan

Duration: 2 minutes, 36 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008