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Volume 53, 1921
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Presidential Address: “Science and the Principle of the Relativity of Motion,”


The aim of the address is not to give an adequate account of Einstein's theory of relativity, but to pick out therefrom certain features which should serve to fit the subject on to familiar scientific conceptions, and thereby render the most important results of the theory intelligible, perhaps even acceptable, to the non-specialist. The metaphysical notion of void space involves the relativity of all positions, directions, and motions, including rest, or zero motion. But the scientific conception of space has for ages past been more or less inconsistent with this view. The latter, however, has, during the progress of science, vindicated itself with regard first to position and direction, then in regard to uniform motions, and, within the past few years, with regard to all motions. Each such vindication has constituted a sudden and remarkable increase of intellectual power, and has involved a notable reconstruction of scientific conceptions. The conceptions chiefly affected by the recent intellectual advance are those of space and time, natural geometry, gravitation, and the other natural forces. Besides these, a new dominating conception has been introduced which, when it is once mastered, allows of a much more accurate and simple representation to our minds of what is really happening in the external world.

Events referred to this entity, which has four dimensions, lose certain refractory inconsistencies which they undoubtedly present when they are described in the usual terms of space and time. Just as ethereal radiation is put forward by science as the real external event giving rise to our subjective experiences of light and warmth, so our movement in this four-dimensional continuum is put forward in the address as giving rise to our subjective and other experiences of the measure of space and time which we associate with natural occurrences. The conception affords us a truer apprehension of what is really going on in the external world than we can receive directly by our space-and-time experiences, which have been found by modern science to vary with our relative motion in a most confusing and irreconcilable manner. The satisfactory unification, as seen from the new point of view, of previously unrelated facts, especially of the facts of gravitation, inertia, and centrifugal force, was described in the address; and, since non-Euclidean geometry is used in relativity investigations, a short popular account was given of what such a thing may be.