To spot the rare neutrino collisions, you need a lot of stuff for the neutrinos to run into. So the international experiment uses 12.5 million gallons of water. The tank, as tall as an eight-story building, is lined with sensors that spot the tiny bursts of light given off by the collisions. There are electron neutrinos, muon neutrinos, and tau neutrinos. Physicist Wolfgang Pauli hypothesizes the existence of neutrinos to account for missing energy in particle decay experiments.
Theoretical physicists speculate that neutrinos oscillate from one type to another.
In a South African gold mine, Reines and his collaborators are the first to observe naturally occuring neutrinos. The Kamioka experiment is built in a zinc mine in Japan. The Kamioka and IMB experiments detect a burst of neutrinos from Supernova 1987A, heralding the birth of neutrino astronomy. The observation sets many limits on the properties of neutrinos, including mass. After analyzing more than 500 days of data, the Super-Kamiokande team reports finding oscillations and, thus, mass in muon neutrinos.