James Watson Cronin
The Nobel Prize in Physics 1980
Born: 29 September 1931, Chicago, IL, USA
Died: 25 August 2016, St. Paul, MN, USA
Affiliation at the time of the award: University of Chicago, Chicago, IL, USA
Prize motivation: "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons."
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 left-right symmetry had already been proven violated when, in 1964, James Cronin and Val Fitch discovered that the matter-antimatter symmetry is violated when the neutral K-meson decays. Their experiment also proved that symmetry does not apply during time reversal: reactions going backward in time are not identical to those going forward.
Their work and discoveries range from how cells adapt to changes in levels of oxygen to our ability to fight global poverty.
See them all presented here.