8 5 6 A P P E N D I X E conception that inert mass was nothing else than latent energy. The doctrine of the conser- vation of mass lost its independence and became merged in the doctrine of conservation of energy. Physical Laws and Relativity “The special relativity theory, which was simply a systematic extension of the electro- dynamics of Maxwell and Lorentz, had consequences, which reached beyond itself. Must the independence of physical laws with regard to a system of coordinates be limited to sys- tems of coordinates in uniform movement of translation with regard to one another? What has Nature to do with the coordinate systems that we propose and with their motions? Al- though it may be necessary for our descriptions of nature to employ systems of coordinates that we have selected arbitrarily, the choice should not be limited in any way so far as their state of motion is concerned (General theory of relativity). The application of this general theory of relativity was found to be in conflict with a well-known experiment, according to which it appeared that the weight and the inertia of a body depended on the same constants (identity of inert and heavy masses). Consider the case of a system of coordinates which is conceived as being in stable rotation relative to a system of inertia in the Newtonian sense. [Article continued in 23 November 1922 issue of the Osaka Mainichi] “The forces which, relative to this system, are centrifugal must, in the Newtonian sense, be attributed to inertia. But these centrifugal forces are, like gravitation, proportional to the mass of the bodies. Is it not, then, possible to regard the system of coordinates as at rest, and the centrifugal forces as gravitation? The interpretation seemed obvious, but classical mechanics forbade it.” Geometry and Physics The lecturer, then, by a series of sketches on the black board proved how a generalised theory of relativity must include the laws of gravitation. But all that seemed, and actually did, contradict Euclidean geometry. In other words, the laws, according to which material bodies are arranged in space, do not exactly agree with the laws of space prescribed by the Euclidean geometry of solids. This is what is meant by the phrase that “Euclid is wrong.” The fundamental concepts “straight”, “plane”, etc., accordingly lose their exact meaning in physics. In the generalised theory of relativity, the doctrine of space and time, kinematics, is no longer one of the absolute foundations of general physics. The geometrical status of bodies and the rates of clocks depend in the first place on their gravitational fields, which again are produced by the material systems concerned. Gravitation Thus, the new theory of gravitation diverges widely from that of Newton with respect to its basic principles. But, in practical application, the two agree so closely that it has been