Yang Chen Ning (1922– )

Chinese-born US physicist who, with Lee Tsung-Dao, overthrew a long-standing principle in theoretical physics called the conservation of parity. This principle states that physical laws are the same in all mirror-image systems. The work of Yang and Lee showed that the weak nuclear force caused particles called K-mesons to decay in a way which violated parity conservation. They shared the Nobel Prize for Physics in 1957 for their investigations of weak interactions between elementary particles.

Yang also established the basis of modern quantum field theory. In 1954, with Robert Mills, he elaborated the methods needed to describe elementary particles by using mathematical entities called gauge-invariant fields. He also made contributions to statistical mechanics.

Yang was born in Hefei, China, and was the son of a mathematics professor. He was educated at the National Southwest Associated University in Kunming. In 1945 he travelled to the USA to study under Edward Teller and Enrico Fermi at the University of Chicago. He received his doctorate in 1948. In 1949 he went to the Institute for Advanced Study at Princeton, New Jersey, where he worked on the theory of elementary particles and the weak nuclear force. In 1951 he and Lee started to study the unusual decay pattern of K-mesons. By 1956, they had concluded that parity was not conserved in the decay. This result was quickly confirmed experimentally by Chien-Shung Wu, a physicist at Columbia University, New York. Yang was made professor of physics at Princeton in 1955. In 1966 he was appointed director for theoretical physics at the University of New York at Stony Brook.