# Neutrino discovery

Wolfgang Pauli, at the age of 30, had a brilliant idea for solving a difficult problem in nuclear physics. He proposed the presence of a neutral, light-weight particle to explain the apparent absence of energy in the decay of some atomic nuclei, thus preserving the fundamental law of energy conservation.

Pauli postulated that “neutrons” may emerge from decay processes, moving energy away while eluding scientific detection.

Pauli did not dare to disclose his idea without contacting any experimental physicists, fearful that no one would ever be able to witness this particle. On December 4, 1930, Pauli sent an open letter to a group of nuclear physicists known as the “dear radioactive ladies and gentlemen,” who were meeting in Tübingen, Germany, a few days later. Pauli got a machine-typed copy of the text from Lise Meitner, a well-known physicist who had attended the Tübingen meeting, in 1956.

Scientists expanded on Pauli’s concept in the early 1930s, concluding that the new particle must be exceedingly light and barely interact. The neutron was named after James Chadwick’s discovery of a neutral particle in 1932. However, the particle was too heavy to fit Pauli’s prediction. Enrico Fermi, who was working on a theory of weakly interacting particles, gave Pauli’s particle a new name: neutrino, which means “small neutral one.” Scientists discovered neutrino-matter collisions for the first time a quarter-century later, providing long-awaited proof of Pauli’s ghost-like innovation.