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Hans Bethe - How to observe a neutrino (145/158)

937 views · Published 26 June 2017 · 2:36 · Indexed 30 October 2026

Channel: Web of Stories - Life Stories of Remarkable People · 2017 · Science & Technology

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To hear more of Hans Bethe’s stories, go to the playlist: https://www.youtube.com/watch?v=LvgLyzTEmJk&list=PLVV0r6CmEsFyUDSroBQVEcbnNud7I9xom

German-born theoretical physicist Hans Bethe (1906-2005) was one of the first scientists to join the Manhattan Project, later strongly advocating nuclear disarmament. In 1967, he was awarded the Nobel Prize in Physics for his theory of stellar nucleosynthesis. [Listener: Sam Schweber; date recorded: 1996]

TRANSCRIPT: 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.

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