Cronin, James Watson 1931-
US physicist and Nobel Prize winner

Born and educated in Chicago, he worked at the Brookhaven National Laboratory before moving to Princeton University, becoming Professor of Physics there in 1965, and at Chicago University from 1971. Tsung-Dao Lee, Cheng Ning Yang and others had shown to the surprise of physicists that neither charge conjugation nor parity was conserved in weak interactions between subatomic particles. In 1964, together with Val Fitch, J Christensen and R Turlay, Cronin made a study of neutral kaons and discovered that a combination of parity and charge conjugation was not conserved either, thus violating CP-conservation. Since it was known from the CPT theorem that a combination of parity, charge conjugation and time is conserved, this important result implied that the decay of kaons is not symmetrical with respect to time reversal. This is still not understood today, but the idea of CP violation has been used to explain the domination of matter over antimatter in the universe. Cronin and Fitch shared the 1980 Nobel Prize for physics for their work in particle physics.