"Sakharov looked wryly at the composition of an average cubic metre of Universe. ...a billion quanta of radiation, one proton and no antiprotons. Tracking... to just after the Big Bang... [we] should have had... a billion antiprotons, and a billion and one protons. ...Why the odd proton? ...[A]ntimatter had slipped off the map of the Universe ...Sakharov put forward a three-point explanation."