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"
Field: particle physics
Prize share: 1/2
For a long time, physicists assumed that different types of symmetries characterise nature. In a kind of mirror-world, the physical laws should be the same if right and left are exchanged and if matter is replaced by antimatter. However, for certain decays of elementary particles the equality of the laws was questioned, and Chen Ning Yang and Tsung Dao Lee formulated in 1956 a theory stating that the left-right symmetry law is violated for the weak interaction. Measurements of the decay electrons from a cobalt isotope confirmed the symmetry violation.