Reines, Frederick (1918-1998), an American physicist, discovered a fundamental particle called the neutrino. The most notable qualites of the neutrino are that it is extremely resistant to interaction with other particles and has virtually no mass. The existence of neutrinos had been suggested many years before by the Austrian physicist Wolfgang Pauli, but it took 25 years to prove their existence experimentally. For his work on the neutrino, Reines was awarded half of the 1995 Nobel Prize for physics.
In 1930 Pauli had suggested neutrinos to solve a problem in beta decay (the emission of electrons or positrons by a particle). Since 1914, scientists had known that not all the energy shed by a decaying particle was emitted with the electron or positron. Pauli suggested that the remaining energy was carried away by an unknown particle. He worked out that this particle must be neutral (neither positive nor negative), extremely light in mass, and extremely elusive. It came to be called the neutrino, meaning little neutral one.
Reines, along with colleague Clyde Cowan, discovered the neutrino through Project Poltergeist, which involved a large tank of liquid containing dissolved cadmium chloride. Enormous numbers of neutrinos passed through the tank every second. Out of this flood, a tiny number of neutrinos reacted with particles in the tank. These reactions produced other particles, some of which could be detected. The experiment detected about three neutrino reactions per hour.
Reines was born in Paterson, New Jersey. He graduated in engineering, and then took a master of science degree in mathematical physics, at Stevens Institute of Technology. He obtained his Ph.D. at New York University in 1944. That same year, Reines joined the Manhattan Project, the Allied nuclear bomb program, and continued working as a theoretical physicist on US nuclear weapons for 15 years. See Manhattan Project ; Nuclear energy (The development of nuclear weapons) .
Reines later discovered neutrinos in the Earth’s atmosphere. They were produced by high-speed collisions between particles in the atmosphere and cosmic rays from the depths of space. His experimental equipment was located at the bottom of a deep mine, to filter out all other particles.
Reines was a professor and administrator at the University of California, Irvine from 1966 to 1988. His neutrino group was one of two that, in 1987, made the first observation of neutrinos given off by a supernova, a distant exploding star.
See also Neutrino ; Pauli, Wolfgang .
