During the last twenty years, dramatic improvements in methods of observing astrophysical phenomena from the ground and in space have added to our knowledge of what the universe is like now and what it was like in the past, going back to the hot big bang. In this overview of today's physical cosmology, P.J.E. Peebles shows how observation has combined with theoretical elements to establish the subject as a mature science, while he also discusses the most notable recent attempts to understand the origin and structure of the universe. A successor to Peebles's classic volume Physical...