A tight-knit, high-powered group of scientists and engineers spent eight years building a satellite designed, in effect, to read the genome of the universe. Launched in 2001, the Wilkinson Microwave Anisotropy Probe (WMAP) reported its first results two years later with a set of brilliant observations that added focus, detail, and insight to our formerly fuzzy view of the cosmos.

For more than a year, the WMAP satellite hovered in the cold of deep space, a million miles from Earth, in an effort to determine whether the science of cosmology--the study of the origin and evolution of the universe--has been on the right track for the past two decades. What WMAP was looking for was a barely perceptible pattern of hot and cold spots in the faint whisper of microwave radiation left over from the Big Bang, the event that almost 14 billion years ago gave birth to all of space, time, matter, and energy.

The pattern encoded in those microwaves holds the answers to some of the great unanswered questions of cosmology: What is the universe made of? What is its geometry? How much of it consists of the mysterious dark matter and dark energy that continue to baffle astronomers? How fast is it expanding? And did it undergo a period of inflationary hyper-expansion at the very beginning? WMAP has now given definitive answers to these mysteries.

On February 11, 2003, the team of researchers went public with the results. Just some of their extraordinary findings: The universe is 13.7 billion years old. The first stars--turned on--when the universe was only 200 million years old, five times earlier than anyone had thought. It is now certain that a mysterious dark energy dominates the universe. Michael Lemonick, who had exclusive access to the researchers as WMAP gathered its data, here tells the full story of WMAP and its surprising revelations. This book is both a personal and a scientific tale of discovery. In its pages, readers will come to know the science of cosmology and the people who, seventy-five years after we first learned that the universe is expanding, deciphered some of its deepest mysteries in the patterns of its oldest light.

These lectures were first given during my tenure of a Walker Ames Visiting Professorship in the Department of Astronautics and Aeronautics at the University of Washington, November 2-12, 1964. I am grateful for the interest shown there and for the tranquil hospitality of Dr. JOHN BOLLARD and Dr. ELLIS DILL, which allowed me the leisure sufficient to write the first manuscript. I thank Dean ROBERT Roy and Dr. GEORGE BENTON for the unusual honor of an invitation to deliver a series of public lectures at my own university. Apart from the footnotes on pp. 49, 50, and 85, which have been added so as to answer questions allowed by the slower pace of silence, and the obviously necessary note on p. 106, the lectures of this second series are here printed as read, February 9-25, 1965. Thus I may call these, in imitation of a famous example, " Bal timore Lectures." Acknowledgment The first lecture is based largely upon my Bingham Medal Address of 1963, part of which it reproduces verbatim. The filth lecture may be regarded as a partial summary of my course on ergodic theory at the International School of Physics, Varenna, 1960. Much of the last lecture runs parallel to my article "The Modern Spirit in Applied Mathematics," ICSU Review of World Science, Volume 6, pp. 195-205 (1964), and some paragraphs are taken from my address to the Fourth U. S. National Congress of Applied Mechanics (1961)."

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, submillimetre-wave and gravitational wave astronomy. Each chapter contains full-colour figures, worked examples and exercises with complete solutions. Clearly identified key facts and equations help students easily locate important information. Suggestions for further reading provide jumping-off points for students aiming to further their studies. Reflecting decades of Open University experience in undergraduate teaching, this textbook brings students to the forefront of the rapidly developing field of observational cosmology. Accompanying resources to this textbook are available at: http://www.cambridge.org/features/astrophysics.