Abstract

The Cosmic Microwave Background (CMB) is the left-over heat from the Big Bang. When we observe this radiation, we see the universe when it was only 370,000 years old. Now, 14 billion years later, it has cooled to microwave frequencies. The CMB is nearly uniform. The slight variations of 1 part in 100,000 in its temperature, hotter or colder than the average, reflect initial inhomogeneities in the matter and radiation that later collapsed due to gravity to form clusters and galaxies. These fluctuations carry information about the origin, composition and evolution of the universe, and theories of the origin of the universe make detailed predictions about their statistical properties.

Given the extreme conditions in the early universe, the CMB is our best hope of uncovering fingerprints of the physics operating at very high energy scales, inaccessible to Earth-bound particle accelerators. But what created these primordial inhomogeneities? Current cosmological data are, for the first time, precise enough to allow detailed observational tests of models of the very early universe. I will describe how data from next generation cosmological surveys such as ESA ’s Planck CMB satellite will help us move beyond a phenomenological description of the early universe, and uncover the physics at hitherto-unexplored energies.