Robert Geroch builds on Einstein's work with commentary that addresses the ideas at the heart of the theory, bringing a modern understanding of relativity to the text. He elucidates how special relativity is a reconciliation of the contradictions between the nature of light and the principle of relativity; he expands on Einstein's treatment of the geometry of space-time and the fundamental notion of an "event"; he explains in detail, but without technical language, the equivalence of inertial and gravitational mass, a cornerstone of general relativity.
Roger Penrose is a world-renowned physicist at Oxford University. He is the author of The Road to Reality.
Albert Einstein (1879–1955), one of the greatest thinkers of the twentieth century, was born in Ulm, Germany, to German-Jewish parents. He published his first great theories in Switzerland in the early 1900s while working as a patent clerk.