A new edition of this introduction to modern physics, provides new material on the most recent experimental tests in relativity, and a fuller treatment of the space-time interval and the Kennedy-Thorndike experiment. It treats the quantum theory of specific heats, with material on synchrotron radiation, a modernized treatment of the electron microscope and a preview of quantum mechanics. Features include additional historical, philosophical and biographical material reflecting important published research of the past decade, along with a significant expansion - nearly double - in the number of problems, thought questions and worked-out examples. The book also includes references, summary tables and illustrations.