What is the void? What remains when you take all the matter away? Can empty Space--nothing--exist? To answer these questions, eminent scientist Frank Close takes us on a lively and accessible journey that ranges from ancient ideas and cultural superstitions to the frontiers of current research, illuminating the story of how scientists have explored the void and the rich discoveries they have made there. Readers will find an enlightening history of the vacuum: how the efforts to make a better vacuum led to the discovery of the electron; the understanding that the vacuum is filled with fields; the ideas of Newton, Mach, and Einstein on the nature of space and time; the mysterious aether and how Einstein did away with it; and the latest ideas that the vacuum is filled with the Higgs field. The story ranges from the absolute zero of temperature and the seething vacuum of virtual particles and anti-particles that fills space, to the extreme heat and energy of the early universe. It compares the ways that substances change from gas to liquid and solid with the way that the vacuum of our universe has changed as the temperature dropped following the Big Bang. It covers modern ideas that there may be more dimensions to the void than those that we currently are aware of and even that our universe is but one in a multiverse. The Void takes us inside a field of science that may ultimately provide answers to some of cosmology's most fundamental questions: what lies outside the universe, and, if there was once nothing, then how did the universe begin?