Providing a comprehensive and up-to-date treatment of observational cosmology, this advanced undergraduate textbook enables students to use quantitative physical methods to understand the Universe. The textbook covers recent developments such as precision cosmology and the concordance cosmological model, inflation, gravitational lensing, the extragalactic far-infrared and X-ray backgrounds, downsizing and baryon wiggles. It also explores the future missions and facilities likely to dominate cosmological research in the future, including radio, X-ray, submillimeter-wave and gravitational wave...