Frederick Reines

Frederick Reines (1918-1998) American physicist and co-winner of the 1995 Nobel Prize in physics for his confirmation of the existence of the neutrino, a type of subatomic particle. The 1995 prize was divided between Reines and American physicist Martin L. Perl.

Reines earned his Ph.D. at New York University in 1944, then joined the Manhattan Project in Los Alamos, New Mexico, helping to produce the atomic bomb. He remained at Los Alamos until 1959, when he joined the faculty of Case Western Reserve University in Ohio. In 1966 he took a position at the University of California at Irvine.

Neutrinos were first described in 1930 by Wolfgang Pauli, winner of the 1945 Nobel Prize in physics. In his studies of radioactivity, Pauli found that during the decay of a radioactive atomic nucleus, the energy of the electrons emitted did not account for all of the energy loss that he observed. He invented the concept of a new, uncharged subatomic particle that also was emitted from the nucleus during its decay. His reasoning was based on a fundamental law of physics—the law of conservation of energy. This law states that the amount of energy in the universe remains constant—it cannot be created or destroyed. Reines believed that this law held true even at the atomic and subatomic level. In the 1950s, Reines and his colleague, physicist Clyde L. Cowan, Jr., designed an experiment involving the collision of atomic particles in water. After almost a year, Reines and Cowan had collected enough evidence to conclusively announce in 1956 that neutrinos do exist as free particles. As Pauli had suspected, the neutrinos are emitted with electrons during radioactive decay.