All this had been investigated by Willy Fowler and his collaborators at Cal Tech. All... he investigated all nuclear reactions which would possibly occur in the stars, experimentally by using an accelerator, and so we knew all these. So it was the idea of Willy Fowler and his student John Bahcall, that maybe one could observe the neutrinos that are made in the sun. I should mention in this connection that actually I believe the first person who had this idea was Pontecorvo, a former collaborator of Fermi's in Rome who was involved in Fermi's study of neutron absorption in nuclei. But, at any rate, Bahcall was the person who kept the ball and investigated this in more detail and came to the conclusion that indeed it probably would be possible to observe neutrinos from the sun. There would be many of them, but of course we knew the cross section was extremely small but there were some of relatively high energy and the cross section of neutrinos interacting increases with the energy very rapidly. So an experiment was set up by Ray Davis at Brookhaven National Laboratory, to observe the solar neutrinos by... he got a tank... car full of cleaning fluid, a carbon, chlorine, hydrogen compound, and chlorine contains one isotope, chlorine-37, which by absorbing a neutrino can transform into argon-37 which is a radioactive nucleus, a neutrino goes in and an electron goes out. You can't observe that electron, it's too weak, but you can observe the argon-37. Unfortunately that again doesn't emit very energetic radiation but it does capture its orbital electrons and then emits a converging gamma ray after such... such capture, and so you get from this X-rays of a few KeVs. These X-rays come out with the decay time of argon-37, which I think is something like a month, and so what Davis set out to observe was these electrons.