Einstein's essay, On the Electrodynamics of Moving Bodies, introduces his famous “principle of relativity,” one of the twentieth century's most revolutionary concepts. In his introduction to this seminal work, the renowned physicist Stephen Hawking cuts through Einstein's mathematical complexities to explain this revolutionary concept in language that excites and informs the reader. This book features selections from a translation of the original essay, The Principle of Relativity, as well as an insightful biography of Einstein and Hawking's informative summary.