The 2008 Nobel Prizes in Physics

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2008 with one half to Yoichiro Nambu "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics," and the other half jointly to Makoto Kobayashi and Toshihide Maskawa "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature." Nambu's early work began a "paradigm shift" in particle theory in which we think of the "vacuum" not as a state of absolute nothingness but the ground state of an infinite, multi-particle system which by its very nature breaks the symmetries inherent in the laws of physics. These ideas flowered in what we now call the Standard Model in which a complicated array of particles is brought into existence by this spontaneous symmetry breaking. Part of this picture depends on the realization of Kobayashi and Maskawa that there must be three generations of quarks and leptons. These discoveries will be reviewed in the context of modern particle physics theory.