A classic of twentieth-century theoretical physics, this book provides a comprehensive and approachable overview of the principles and concepts that underlie modern physics. Kompaneyets covers a broad range of subjects, from relativity and quantum mechanics to statistical physics and astrophysics, with clarity and precision. A must-read for anyone interested in the foundational ideas of physics and their implications for our understanding of the universe. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.