Feynman, Richard Phillips (1918–1988)
Richard Feynman was an American theoretical physicist who shared the 1965 Nobel Prize in Physics with Julian Schwinger and Shinichiro Tomonaga (1906–1979) for their independent work on quantum electrodynamics. He also realized, independently of Murray Gell-Mann, that protons, neutrons, and other hadrons must be composed of smaller particles, which he called 'partons'. Later, it was recognized that Feynman's partons and Gell-Mann's quarks (together with gluons) were effectively the same thing, but arrived at by different methods.
Feynman helped to develop the atomic bomb during the Manhattan Project, before going to Cornell University with Hans Bethe where he began his great work on quantum electrodynamics. He was professor of physics at the California Institute of Technology from 1950 until his death. With Gell-Mann, he developed a theory of weak interactions (see weak force), such as those that occur in the emission of electrons from radioactive nuclei. His invention of Feynman diagrams (see below) greatly facilitated theoretical work on elementary particles and their interactions. In 1986 he was a key member of the committee that investigated the Challenger space shuttle disaster.
A Feynman diagram is a depiction of a possible process in the interaction of several elementary particles. Feynman introduced these diagrams in the 1950s.
Quantum theory assigns to each Feynman diagram the probability amplitude for that process to occur. The total probability is proportional to the square of the sum of the amplitudes of the possible processes, each of which is depicted by a Feynman diagram.