LIGHT OF LIGHT

Hokitika Guardian, 6 November 1920, Page 4

LIGHT OF LIGHT

EINSTEIN’S THEORY. t CLEARLY EXPLAINED. \ (By H. W. Wilson in London Daily Mail). Professor Einstein’s theory of iclativity lias attracted so much attention that many will be anxious to read a clear popular account of what it really means. His book, published to-day (“Relativity: tbe Special and the General Theory; a Popular Account,” by A. Einstein, translated by R. W. Lawson j Methuen, 5s not), is of great valuo but it 'does not give such a popular exposition. It is often difficult to. follow, and requires considerable mathematical knowledge. Here is a fair extract: “Owing to the alteration in direction of the velocity of rotation of the earth in the course of a year, the earth cannot be at rest relative to tlie hypothetical system K throughout tbe whole year. However, tlie most careful observations have never revealed such anisotropic properties in terrestrial pliycical space, i.e., a physical non-equivalence of different directions.” This is as tough as Joey Bagstock; luit that is, perhaps, because the ideas with which it deals arc exceedingly abstruse, so that even Sir Oliver Lodge, one of our greatest physicists, said they will, if accepted, give physicists “a terrible time.” What then, is the theory, reduced to the simplest terms? It is this—that matter has length, breadth, height, and also- time; that size and mass depend on speed of movement (which is space covered and time taken in covering it), and that mass increases at very high velocities. The earth and all on it are supposed, by the ordinary accepted theory, to move through an ether stream at a rate of 100 miles a, second. The ni asc and size of any object should be greater when moving in the direction of the stream than when moving across it. SHRINKING YARD MEASURE. From this it follows that a yard may be really longer when measured in the direction of the stream than across it. But we should not know, because the yard measure, which is our standard, would alter, expanding when we measured with the stream and contracting when we measured across it. If we lmd anything absolutely stable and unchanging, a yard measured north and south should differ very slightly from a yard measured east and west. Professor Eddington, in a study of the theory, has supposed the people in a room to be carried vertically upwards through tlie ether at 161,000 miles per second (the speed of light is 186,000 miles per second). At that speed a yard measure, Held vertically in the direction of tbe movement, would contract to lift, if bold horizontally across the direction of the movement, but that contraction would be' invisible to us. Tbe less the speed of movement tbe smaller tlie contraction would be; but it would always elude notice because we have nothing by which we can gauge it —no fixed and' stable object—and because everything expands or shrinks in tbe same degree. Though tins theory gives some very startling results, it cannot be rejected offlmnd. For centuries mankind was content to believe that the sun went round the earth. When Copernicus concluded that this theory no longer explained the facts, anil asserted that the earth* really went round* the sun, be was greeted with a shout of indignant incredulity. But bis theory holds the field to-day. BENT LIGHT. Einstein’s theory cannot be said to have been proved, but two important predictions based on it have been confirmed. The first of these was that light from distant stars would bo bent, when passing near the sun, to a definite extent, which lie calculated. The British, eclipse observations last year proved that there was bending, and to the extent predicted. The second pro diction was that a certain variation in the orbit of the.. planet Mercury would take place. That variation is now. established and exactly coincides with the prediction. Further, tlie theory explains a number of obscure phenomena in eleetroc'yi'.nmics and optics. It explains, why the electrical masses , which. .are sup-. po-.ed to constitute the eleclrm (tlie basis of all matter under the present -.!(< trieal ,theory of matter) do. not scatter. By Einstein’s theory they contract in consequence of their movement, and this contraction holds them together. , .... ~.*... .. Into tiie remoter consequences of tbe theory it is not necessary to go here. But it supplies a new explanation of gravitation, new ideas of space .as curved, new ideas of planetary movements, and some, dim insight into the tremendous mystery of* the Fourth .Dimension, which has puzzled so many thinkers in the past. .