ar X iv : h ep - p h / 06 11 20 9 v 1 1 5 N ov 2 00 6 BBN And The CBR Probe The Early Universe

Big Bang Nucleosynthesis (BBN) and the Cosmic Background Radiation (CBR) provide complementary probes of the early evolution of the Universe and of its particle content. Neutrinos play important roles in both cases, influencing the primordial abundances of the nuclides produced by BBN during the first 20 minutes as well as the spectrum of temperature fluctuations imprinted on the CBR when the Universe is some 400 thousand years old. The physical effects relevant at these widely separated epochs are reviewed and the theoretical predictions are compared with observational data to explore the consistency of the standard models of cosmology and particle physics and to constrain beyond-the-standard-model physics and cosmology.