The present book is intended, as far as possible, to give an exact insight into the theory of relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics. The text is divided into three parts which deal respectively with the special theory of relativity, with the general theory of relativity, and with considerations on the universe as a whole. The special theory deals with the physics of elementary particles while the general theory is concerned with the force of gravity and its effect on the other forces of nature. These two theories, while exceptional in their explanations of their particular focus, are inconsistent with each other, and it has long been an aim of the science of physics to help resolve these inconsistencies. Einstein proposed that, rather than discarding these two principles for being conflicting, the rules of time and space should be completely revamped and rethought in order to find a way to make these two principles work in harmony. It is Einstein's work on relativity which would earn him the 1921 Nobel Prize in Physics and establish his legacy as one of the most famous scientists of all time. This edition is translated by Robert W. Lawson and is printed on premium acid-free paper.