The Big Bang model is now both theoretically and empirically well established, although it does not explain the mystery of the very beginning of our universe. Over recent years, however, new developments open up the exciting prospect of going "beyond" the Big Bang and even of finding a physical explanation for it. Surprisingly, the ancient idea of a past-eternal universe is being revived, but a variety of other fascinating new approaches -- from the Holographic Universe to Cosmic Natural Selection -- are also being pursued. This book provides an up-to-date overview of each of these competing scenarios with original contributions from the world's leading researchers in cosmology, who describe their own work and results in a manner understandable even to non-specialists. "The stellar line-up of contributors to this volume are working at the cutting edge of cosmological research, and are poised to take our understanding of the universe beyond the big bang into an even stranger realm." - Paul Davies. "This book provides a wonderful overview of current ideas on these ultimate cosmic questions, written by scientists working at the forefront of cosmological research."-- Alex Vilenkin.