The brilliant trailing beauty of fiery comets has inspired fear, wonder, and awe since the dawn of human history. Brighter than stars, moving and disappearing in their own singular orbits, comets have been among the most mysterious elements in the sky, eluding our understanding until very recently. With the aid of space probes, scientists have discovered that these swiftly moving chunks of ice and carbon are more plentiful and far more dangerous than suspected. Scientists are also beginning to realize the monumental role played by comets in the development of the Earth and solar system. David Levy describes in dramatic detail the thrilling yet often devastating effects of comet collisions. In the dawn of our solar system, the Earth was barraged with comets that may have carried the materials necessary to lay the foundations for life on this planet. Levy also presents compelling evidence for later comet collisions, including those of the age of dinosaurs. Great impacts, Levy asserts, not only caused the extinction of the dinesaurs, but ushered in new species of life. As Levy so clearly explains, scientists are realizing that comet collisions are virtually inevitable. Levy reveals possible future collisions with the Earth and describes the terrible risks to life they would pose. He even shows how we might prepare to withstand the impact of large comets in the future.