I came to that conference and was very astonished and pleased by Strömgren's long talks telling all of us about the internal constitution of stars and how it worked very well with hydrogen and helium, and that was very convincing. It was convincing also for another reason because with Eddington's old idea of a high temperature and the heavy atoms in the sun, he never could agree with the calculated opacity of material, opacity being the tendency of matter to absorb light and then to emit another quantum after the absorption. Now with the hydrogen helium it worked exactly right, the opacity was just what quantum theory predicted and so everybody was happy. Now, at the conference most of the discussion was about the build up of elements and I thought Weizsäcker had been there, but looking at the roster of the people at the conference, he wasn't there; it was Gamow reporting [for] Weizsäcker, and they had fantastic ideas that there should be neutrons made by beryllium and that would build up other elements and that all sounded to me wrong. In addition to that Strömgren made clear to us that heavier stars than the sun, for instance Sirius A, have a much higher energy production, not only total energy production but also energy production per unit mass. So one needed a nuclear reaction which would increase rapidly with increasing temperature. It was known from the theory of Eddington and Strömgren how the temperature would increase with the mass of the star, quite slowly, less than linearly with the mass of the star, and that was certainly not enough with the proton-proton reaction to explain the very high luminosity of brilliant stars like Sirius.