The Meaning of Relativity

THE MEANING OF RELATIVITY FOUR LECTURES DELIVERED AT PRINCETON UNIVERSITY BY ALBERT EINSTEIN Lecture I Space and Time in Pre-Relativity Physics Lecture II The Theory of Special Relativity Lecture III The General Theory of Relativity Lecture IV The General Theory of Relativity (continued) The theory of relativity is intimately connected with the theory of space and time. I shall therefore begin with a brief investigation of the origin of our ideas of space and time, although in doing so I know that I introduce a controversial subject. The object of all science, whether natural science or psychology, is to co-ordinate our experiences and to bring them into a logical system. How are our customary ideas of space and time related to the character of our experiences? The experiences of an individual appear to us arranged in a series of events; in this series the single events which we remember appear to be ordered according to the criterion of \earlier" and \later," which cannot be analyzed further. There exists, therefore, for the individual, an I-time, or subjective time. This in itself is not measurable. I can, indeed, associate numbers with the events, in such a way that a greater number is associated with the later event than with an earlier one; but the nature of this association may be quite arbitrary. This association I can define by means of a clock by comparing the order of events furnished by the clock with the order of the given series of events. We understand by a clock something which provides a series of events which can be counted, and which has other properties of which we shall speak later. These four lectures constituted an overview of his then controversial theory of relativity listen to Einstein go deeper into his famous General Theory of Relativity. A Must Read, Enjoy!