The Cosmic Rosetta Stone

Abstract
Today the universe is characterized by a richness of complexity. Structure exists on scales from stars to superclusters of galaxies and beyond. Ordinary “baryonic” matter, in the form of protons, nuclei and their accompanying electrons, is found in stars, diffuse hot gas, cold gas and other forms; the admixture varies greatly with environment. Microkelvin variations in the cosmic microwave background encode a wealth of information about the origin and composition of the universe.