Relativity, Richard Wolfson shows us, gave us a new sense of space and time, opening the door to questions about their flexible nature. Is the universe finite or infinite? Will it expand forever or eventually collapse in a "big crunch"? Is time travel possible? What goes on inside a black hole? How does gravity really work? These questions at the forefront of 21st-century physics are all rooted in the profound and sweeping vision of Albert Einstein's theory. Wolfson leads his readers on an intellectual journey that culminates in a universe made almost unimaginably rich by the principles that Einstein first discovered. Emphasizing the simplicity at the heart of the theory of relativity, he offers his readers clear scientific explanations and the historical and conceptual background of the theory.