193 1 year, Pauli boldly put forward his own scientific hypothesis-he assumed that there was a new particle, which was emitted from the nucleus together with the beta particle, but the mass of this particle was very small, not more than one tenth of the mass of the electron, uncharged and stable, thus satisfying the conservation of energy in each beta decay event. In order to keep the spin in β decay, he also assumed that the spin of this particle was 1/2. 1932, Fermi called this particle "neutrino", which means "tiny neutral little guy".

After Pauli's neutrino hypothesis was put forward, it convincingly explained the whereabouts of the missing energy in β decay and solved this contradiction satisfactorily. But neutrinos are as mysterious as "ghosts" because they have no charge and no mass.