The American astronomer Carl Sagan (1934-1996) was one of the best-known scientists of his time. A prolific writer and television personality, he was creator and host of Cosmos, an enormously popular television series that explained the wonders and intricacies of astronomy to millions of television viewers. Gifted with the ability to communicate difficult scientific concepts to the average person, Sagan opened up the wonders of science to hundreds of thousands more through his many books and magazine articles. But in addition to his talents as a science popularizer, Sagan was a first-rate scientist. Ever persistent in exploring the possibility of life on other planets in the Universe, he was a pioneer in the field now known as astrobiology, a major thrust of NASA's current planetary explorations This book takes a fascinating look at all aspects of the life of Carl Sagan: Sagan the working scientist, who was an inspired and creative participant in the forefront of the new and exciting era of astronomy opened up by the technological breakthroughs of the space age; Sagan the advocate for science, who could expound on the beauties and joys of science as well as point out the follies and foibles of pseudoscience; and Sagan the activist, who helped raise our awareness to the perils of the Nuclear Age that threatened all of us. Following the arc of Sagan's personal and professional life, this book examines both the man and the provocative ideas he brought to this new era, always seeking to capture the infectious enthusiasm and love of communication that infused Carl Sagan's life and work.