 Nolan (1997) examines these questions in the context of the discovery of the  neutrino.[19]  Physicists in the 1930’s were puzzled by certain anomalies arising from experiments in which radioactive atoms emit electrons during so-called Beta decay. In these experiments the total spin of the particles in the system before decay exceeds by ½ the total spin of the (observed) emitted particles. Physicists’ response was to posit a ‘new’ fundamental particle, the neutrino, with spin ½ and to hypothesize that exactly one neutrino is emitted by each electron during Beta decay.