In the century since the publication of the special theory of relativity, there remains a tendency to venerate Einstein's genius without actually understanding his achievement. This book offers the opportunity to truly comprehend the workings of one of humanity's greatest minds. Acclaimed by Einstein himself, it is among the clearest, most readable expositions of relativity theory. It explains the problems Einstein faced, the experiments that led to his theories, and what his findings reveal about the forces that govern the universe. The concepts of relativity and the fourth dimension unfold with all the vivid excitement of research into the unknown, in language anyone can readily understand.