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Hans Bethe - Working on a theory of deutron disintegration (43/158)

2,939 views · Published 27 June 2017 · 3:08 · Indexed 6 November 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]

TRANSCRIPT: Peierls and I went to Cambridge to discuss this with Chadwick and Goldhaber, which was very interesting. And Chadwick then said to the two of us 'Well, I bet you, you cannot make a theory of that.' So there was a five hour train trip back from Cambridge to Manchester and during that train trip Peierls and I solved the problem of the theory of this disintegration, and we then wrote a paper about that. Having... when we assumed I think we had thought of that before, and I believe also Heisenberg had thought of that, that the range of the forces between neutron and proton, the nuclear forces, must be very short, very short compared to the size of the deuteron, and that made it very easy to write down the wave function of the deuteron. In fact we could write it down on the train still, and it's beautifully simple and knowing that we could also solve the problem of the scattering of neutrons by protons that was being experimented on, and we calculated to start the cross section for that scattering was very closely related to the binding energy of the deuteron. And from that we calculated that the cross section should be about 3*10-24 cm2. 10-24 cm2 is called a Barn. For a nucleus it's the cross section as big as a barn, as one of my later colleagues at... at Cornell invented, and so we calculated 3 Barns. The unfortunate thing however was that people did [the scattering] experiments on it, many of them at Columbia University, and they found about 20 Barns instead of 3 Barns, and that 20 Barns was obtained even after Fermi had shown that there is a correction for the binding of the two deuterons in the molecule. The actual figure the experimenters had found was 50 Barns, but Fermi's correction brought it down to 20. So obviously our theory of this scattering was very beautiful but unfortunately wrong

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