1 - The standard model and beyond

Abstract

This chapter describes the idea of an expanding universe, without using the equations of general relativity. The success of the Big Bang rests on three observational pillars: the Hubble diagram exhibiting expansion, light element abundances that are in accord with Big Bang nucleosynthesis, and the blackbody radiation left over from the first few hundred thousand years, the cosmic microwave background. Standard model embodies all these three pillars. Although the three pillars put the Big Bang model on a firm footing, other observations cry out for more details. Because of the limits inferred from Big Bang nucleosynthesis, the dark matter, or at least an appreciable fraction of it, must be nonbaryonic. The most popular idea currently is that the dark matter consists of elementary particles produced in the earnest moments of the Big Bang. The last decades of the 20th century saw a number of large surveys of galaxies designed to measure structure in the universe. These culminated in two large surveys, the Sloan Digital Sky Survey and the Two Degree Field Galaxy. To understand this structure, one must go beyond the Standard Model.