Photo from the Nobel Foundation archive.
Val Logsdon Fitch
Born: 10 March 1923, Merriman, NE, USA
Died: 5 February 2015, Princeton, NJ, USA
Affiliation at the time of the award: Princeton University, Princeton, NJ, 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, Val Fitch and James Cronin 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.