David Levy brings these 'ghostly apparitions' to life. With fascinating scenarios both real and imagined, he shows how comets have wreaked their special havoc on Earth and other planets. Beginning with ground zero as comets take form, we track the paths their icy, rocky masses take around our universe and investigate the enormous potential that future comets have to directly affect the way we live on this planet and what we might find as we travel to other planets. In this extraordinary volume,