The Einstein Theory of Relativity A Concise Statement by Prof. H.A. Lorentz of the University of Leyden NOTE Whether it is true or not that not more than twelve persons in all the world are able to understand Einstein's Theory, it is nevertheless a fact that there is a constant demand for information about this much-debated topic of relativity. The books published on the subject are so technical that only a person trained in pure physics and higher mathematics is able to fully understand them. In order to make a popular explanation of this far-reaching theory available, the present book is published. Professor Lorentz is credited by Einstein with sharing the development of his theory. He is doubtless better able than any other man--except the author himself--to explain this scientific discovery. The publishers wish to acknowledge their indebtedness to the New York Times, The Review of Reviews and The Athenaeum for courteous permission to reprint articles from their pages. Professor Lorentz's article appeared originally in The Nieuwe Rotterdamsche Courant of November 19, 1919. INTRODUCTION The action of the Royal Society at its meeting in London on November 6, in recognizing Dr. Albert Einstein's "theory of relativity" has caused a great stir in scientific circles on both sides of the Atlantic. Dr. Einstein propounded his theory nearly fifteen years ago. The present revival of interest in it is due to the remarkable confirmation which it received in the report of the observations made during the sun's eclipse of last May to determine whether rays of light passing close to the sun are deflected from their course. The actual deflection of the rays that was discovered by the astronomers was precisely what had been predicted theoretically by Einstein many years since. This striking confirmation has led certain German scientists to assert that no scientific discovery of such importance has been made since Newton's theory of gravitation was promulgated. This suggestion, however, was put aside by Dr. Einstein himself when he was interviewed by a correspondent of the New York Times at his home in Berlin. To this correspondent he expressed the difference between his conception and the law of gravitation in the following terms: