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For over a decade, physicists had been plagued with the problem of beta-particle emission. Beta particles might be fired out of a nucleus with all the energy to be expected from the loss in mass as one nucleus broke down into another. Generally, though, they came out with less energy, and to an unpredictable degree. They sometimes emerged with very little energy, in fact, and some physicists, in despair, felt that the law of conservation of energy simply didn't hold in connection with beta-particle emission.

In 1931, however, Pauli, who had worked out the exclusion principle (see 1925), suggested an explanation that did not violate energy conservation. He suggested that, along with the electron, another particle was given off, and that the energy was divided between the electron and the other particle in a random manner.

Since the electron had all the electric charge available, the other particle had to be electrically uncharged, or neutral. Since all the kinetic energy of an electron could be converted into only a tiny quantity of mass, the other particle would have little or no mass.

The next year Fermi, who had devised a mathematical treatment for electron distribution (see 1926), named the other particle the neutrino (Italian for "little neutral one").

Since it lacked both mass and electric charge, the neutrino was sure to be very difficult to detect, assuming it existed at all, and for a quarter of a century it remained a kind of "ghost particle," with theoretical reasons for existing but backed by no observational evidence.

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Author:Asimov, Isaac
Publication:Asimov's Chronology of Science & Discovery, Updated ed.
Article Type:Reference Source
Date:Jan 1, 1994
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