The efforts that came to fruition with the detection of the free neutrino started at Los Alamos in 1950–1, when several of us who were engaged in the testing of nuclear bombs wondered if that man-made star could be used to advance our knowledge of physics. For one thing, the unusual object featured lots of fissions, followed by β decays; so why not use it as a source of neutrinos? After all, it is an extraordinarily intense pulse, and signals produced by such a source might be sufficiently copious and distinguishable from background. Some hand-waving and rough estimates led me to conclude that the bomb was, in fact, the best source. All that was required was a massive detector, measuring a cubic meter or so.

As it happened, Enrico Fermi was at Los Alamos during the summer of 1951, and I took the opportunity to talk with him about these matters. The conversation went something as follows: “I would like to talk with you a few minutes about the possibility of neutrino detection.” He was very pleasant, and said, “Well, tell me what is on your mind.” “First off as to the source,” I said, “I think that the bomb is best.” After a few moments thought he replied, “Yes, the bomb is the best source.” So far so good. And then I said, “But one needs a detector which is so big and I don't know how to make such a detector.” He thought about it further and said he didn't know either.