In , Professor Lisa Randall, one of today’s most influential theoretical physicists, takes readers on an intellectual adventure through the history of the cosmos, showing how events in the farthest reaches of the Universe created the conditions for life—and death—on our planet. Sixty-six million years ago, an object the size of a city crashed into Earth, killing off the dinosaurs, along with three-quarters of the planet’s species. Challenging the usual assumptions about the simple makeup of the unseen material that constitutes 85% of the matter in the Universe, Randall explains how a disk of dark matter in the Milky Way plane might have triggered the cataclysm. But does more than present a radical idea. With clarity and wit, it explains the nature of the Universe, dark matter, the Milky Way galaxy, comets, asteroids, and impacts. This breathtaking synthesis, illuminated by pop culture references and social and political viewpoints, reveals the deep relationships among the small and the large, the visible and the hidden, as well as the astonishing beauty of the connections that surround us. It’s impossible to read this book and look at either the Earth or the sky again in the same way.