This book gives an accessible account of the history of the Universe; not only what happened, but why it happened. An author of textbooks on the early Universe and inflation, David Lyth now explains both cosmology and the underlying physics to the general reader. The book includes a detailed account of the almost imperceptible structure in the early Universe, and its probable origin as a quantum fluctuation during an early epoch known as the epoch of inflation. It also explains how that early structure is visible now in the cosmic microwave radiation which is our main source of information about the early Universe, and how it gave rise to galaxies and stars. The main text of the book assumes no knowledge of mathematics or physics so that it is accessible to everybody, while an appendix contains more advanced material. As a result the book will be useful for a wide spectrum of readers, including high-school students, undergraduates, postgraduates and professional physicists working in areas other than cosmology. It will also serve as "additional reading" for university courses in general astronomy, astrophysics or cosmology itself.

The origin and evolution of the primordial perturbation is the key to understanding structure formation in the earliest stages of the Universe. It carries clues to the types of physical phenomena active in that extreme high-density environment. Through its evolution, generating first the observed cosmic microwave background anisotropies and later the distribution of galaxies and dark matter in the Universe, it probes the properties and dynamics of the present Universe. This graduate-level textbook gives a thorough account of theoretical cosmology and perturbations in the early Universe, describing their observational consequences and showing how to relate such observations to primordial physical processes, particularly cosmological inflation. With ambitious observational programmes complementing ever-increasing sophistication in theoretical modelling, cosmological studies will remain at the cutting edge of astrophysical studies for the foreseeable future.

Enormous progress has been made in inflationary cosmology in the past few years and this book is the first to provide a modern and unified overview of the subject. Coverage examines every aspect of inflationary cosmology and carefully compares predictions with the latest observations, including those of the cosmic microwave background, the clustering and velocities of galaxies and the epoch of structure formation. Problems are included throughout to help the student develop a thorough understanding. An ideal introduction to what promises to be one of the most fruitful topics of research in science in the next decade, this volume will be of great interest to graduate students and researchers in astrophysics, cosmology, particle physics, theoretical physics and applied mathematics.