From time to time scientists have proposed ideas that seemed to be absurd or senseless when they were suggested, only to have them turn out to be brilliant breakthroughs. Such is the case with the first mention of the neutrino by Wolfgang Pauli in 1930.

The problem with which Pauli was attempting to deal was the apparent violation of the law of conservation of energy that occurs during beta decay. According to quantum theory, the amount of energy carried off by an electron during beta decay ought to have specific, discrete values, reflecting specific, discrete energy changes in the nuclei that emit them. Instead, research shows that the energy carried off by beta particles emitted from any particular sample of radioactive material covers a complete spectrum. This discrepancy between theory and observation so troubled some physicists that they began to consider the possibility that energy conservation is not, in...