American Physical Society, New York. Leon Lederman announces the severe violation of parity in our universe. Pion decay creates a muon and a neutrino, which can have spin +1/2 or -1/2, but there are twice as many of one type as the other. The universe is slightly left-handed. (In other words, the laws of physics at the quantum level change when a reaction is mirrored, that is, when spatial coordinates are reversed. Therefore, unlike macroscopic reality, it is possible at the quantum level to tell whether an image is the real one or the mirrored one.) Why does this matter? When the universe formed in the Big Bang, it should have generated matter and antimatter in equal amounts, if nature treated them exactly the same, leaving behind nothing but energy for mutual annihilation. Yet, our matter-dominated universe exists. CP (Charge and Parity) violation is essential to explain this imbalance, although there are still many unsolved aspects.
