Richard Phillips Feynman, (; May 11, 1918 – February 15, 1988) was an American
theoretical physicist known for his work in the
path integral formulation of
quantum mechanics, the theory of
quantum electrodynamics, and the physics of the
superfluidity of supercooled
liquid helium, as well as in
particle physics for which he proposed the
parton model. For his contributions to the development of quantum electrodynamics, Feynman, jointly with
Julian Schwinger and
Sin-Itiro Tomonaga, received the
Nobel Prize in Physics in 1965. He developed a widely used pictorial representation scheme for the mathematical expressions governing the behavior of
subatomic particles, which later became known as
Feynman diagrams. During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal
Physics World he was ranked as one of the ten greatest physicists of all time.