Published online by Cambridge University Press: 09 March 2010
During its early evolution, the hot, dense Universe provided a laboratory for probing fundamental physics at high energies. By studying the relics from those early epochs, such as the light elements synthesized during primordial nucleosynthesis when the Universe was only a few minutes old, and the relic, cosmic microwave photons, last scattered when the protons, alphas, and electrons (re)combined some 400 thousand years later, the evolution of the Universe may be used to test the standard models of cosmology and particle physics and to set constraints on proposals of physics beyond these standard models.