How the Sun is radiating?

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HANS BETHE

70 - How the Sun is radiating?

In 1938 Teller and Gamow decided to do astrophysics rather than plain theoretical physics, and I was really not interested in that, and I said I would skip this conference. But Teller persuaded me to come and it turned out to be very interesting. I had known Eddington's theory of the interior of the sun, and I had known that he predicted the temperature at the center of the sun to be 40 million degrees. Well I should probably mention first one thing that preceded that conference, namely Gamow had proposed his graduate student Critchfield to do something about the energy in the sun. And Critchfield found the suggestion by von Weizsäcker in Germany that maybe two protons could get together to form a deuteron with the emission of a positron and a neutrino. But neither [von] Weizsäcker nor Gamow thought much of this process. But Critchfield decided he'd do it anyway, and he started calculating it and it came out pretty well. So then Gamow told him 'Now really you should get together with somebody who really knows about the deuteron, namely Hans Bethe.' And Critchfield showed me... sent me his calculations, which looked quite good and I could somewhat make his calculations of the deuteron a bit more elegant, and so reduced the number of assumptions which he had put in. And so we wrote a paper together, making energy at the center of the sun by this reaction. Now this is quite a miracle because anything involving emission of electrons, positive or negative, is an extremely slow process. Beta decay of nuclei takes seconds or hours or days or years, whereas nuclear processes in general take something like 10^-22 seconds, maybe as long as 10^-20 seconds. And of course Fermi had explained that by his theory of beta decay and so the interaction, the weak interaction which makes beta decay is really just what it says, exceedingly weak. And so it is rather a miracle that such a weak interaction can give you enough energy to keep the sun radiating all the time.