Relativity For All

This little book is written, not so much for those who wish to understand a physical theory from the point of view of a physicist, as for the large body of intelligent men and women who look on physics as one of many avenues into the secret of the Universe, and wish to know its windings in their relatio . n to the larger field of human inquiry. The dominant aim throughout the book has been to make the ideas definite and intelligible to the ordinary mind. All other considerationsstrict philosophical phraseology, literary graces, conventional forms of presentation everything, in fact, but truth-have been subordinated to b v vi RELATIVITY FOR ALL this end. Between the Charybdis of inaccuracy and the Scylla of abstruseness, the come is narrow and the sea is rough. The vessel will hardly escape buffeting from either side. It is hoped, nevertheless, that . in the present voyage a passage wiU be made without fatal mishap. Those who wish to pursue the subject more deeply, from either the philosophical or the scientific standpoint, are recommended to the works of Professor A. N. Whitehead, F. R. S. The author is glad to acknowledge his deep indebtedness to Professor Whitehead for invaluable help and unwearying kindness in unveiling the mysteries of a difficult subject. H. D. IDIPERIA CO L L LEGE OF SCIENCE, AND TECHNOLOGY July 1921 CONTENTS PART I THE FOUNDATIONS OF SCIENCE CHAP. PAGE I. HOW T HE THEORY A ROSE . . . I 11. SPACE, TIME, AND MATTER . . I0 IV. THE VELOCITY O F LIGHT . . 32 PART I1 THE LAWS OF NATURE V. WHAT I S A NATURALL AW. . 39 VI. THE WORK OF NEWTON . . 45 VII. RELATIVITY A ND THE MOVEMENTS O F BODIES . . . . 53 VIII. SOMEP ROBLEM O S F RELATIVITY . 63 INDEX . . . 71 viiRELATIVITY FOR ALL PART I THE FOUNDATIONS OF SCIENCE CHAPTER I HOW THE THEORY AROSE Space is thoughts, and the wonders thereof, and the secret of space Is thought not more than the thunders and lightnings shall thought give place Time, father of life, and more great than the life it begat and began, Earths keeper and heavens and their fate, lives, thinks and hath substance in man. W HEN Swinburne wrote these words, he was thinking what a wonderful being he was. That they would ever come to be a poetical expression of cold, scientific ideas about matter, time, and space, was probably the thought farthest from his inaccessible mind. Yet SO it is. The new doctrine of e l a t i v ietn ta ils a complete uprooting of the conceptions that I have formerly been held to lie inviolable at the foundations of thought and experience. The theory is not merely a metaphysical speculation. It has arisen in order to explain certain facts of observation, which seem to point to it as the most probable statement of the nature of the Universe which we perceive. 1 Let us think for a moment of the way in which we are accustomed - tacitly, almost S ubconsciously-to regard the physical world. We think of it as a number of pieces of matter. These pieces of matter exist in space. We do not generally take the trouble to define to ourselves exactly t what we mean by space, but we understand one another quite well when we refer to it in convertion. I t is a sort of receptacle, without limit in any direction, in which the material of the world exists and moves about. When we say a certain object is there, we have a clear idea of what we mean, and we feel confident that, provided the object does not move, it will alwaysbe there, no matter what we do ourselves...