Dear Radioactive Ladies and Gentlemen!

On of the few innovations in science to emerge from correspondence, rather than any kind of scholarly publication, the neutrino got its start in a timid letter. In 1930, Wolfgang Pauli, thought he may have had the solution to why energy seemed to be missing from the beta decay process. But he was afraid to propose it publicly for fear that observing his suggested neutral particle would be impossible. (Since it took 20 years to do to observe it at all, and another 30 to do it well this concern seems to be well-founded.) Symmetry, that slick monthly of particle physics has an article about his original letter, sent to nuclear physicists of the day, about to convene at some important conference. It is this letter for which he is credited as the father of the neutrino, even though the theory was mostly developed by Fermi. They have translated this neutrino Declaration of Independence.

I have hit upon a desperate remedy to save…the law of conservation of energy.

But so far I do not dare to publish anything about this idea, and trustfully turn first to you, dear radioactive ones, with the question of how likely it is to find experimental evidence for such a neutron…

I admit that my remedy may seem almost improbable because one probably would have seen those neutrons, if they exist, for a long time. But nothing ventured, nothing gained…

It is interesting to see how cautious and guarded Pauli is regarding the invention of a particle whose existence now seems obvious. The prevailing alternate solution to the beta-decay missing-energy problem at the time was that momentum was not conserved. Considering that people argued this seriously, it is amusing that somebody suggesting a light neutral particle would worry about sounding ridiculous.