Photo from the Nobel Foundation archive.
Chen Ning Yang
Born: 22 September 1922, Hofei, Anhwei, China
Affiliation at the time of the award: Institute for Advanced Study, Princeton, NJ, USA
Prize motivation: "for their penetrating investigation of the so-called parity laws which has led to important discoveries regarding the elementary particles."
Prize share: 1/2
For a long time, physicists assumed that various symmetries characterized nature. In a kind of "mirror world" where right and left were reversed and matter was replaced by antimatter, the same physical laws would apply, they posited. The equality of these laws was questioned concerning the decay of certain elementary particles, however, and in 1956 Chen Ning Yang and Tsung Dao Lee formulated a theory that the left-right symmetry law is violated by the weak interaction. Measurements of electrons' direction of motion during a cobalt isotope's beta decay confirmed this.