Richard Feynman with Yang Chen Ning, American physicists, c 1950s.

UNITED STATES - MAY 14: Feynman (1918-1988) was a theoretical physicist whose work on the development of the new theory of quantum electrodynamics (QED) led to his being awarded the Nobel Prize in 1965. Yang Chen Ning (b 1922) is best known for his role as co-discoverer of parity violation. In the mid 1940s he joined the University of Chicago where he collaborated with T D Lee (b 1926). In 1956 they proposed that parity is not conserved when particles interact via the weak force, such as in beta decay. This was proved correct in 1957 and they were awarded the Nobel Prize for Physics in 1965. (Photo by SSPL/Getty Images)