The Solar System And Its Origin

THE SOLAR SYSTEM AND ITS ORIGIN THE SOLAR SYSTEM AND ITS ORIGIN by HENRY NORRIS RUSSELL NEW YORK THE MACMILLAN COMPANY 1935 CONTENTS PAGE PREFACE v CHAPTER I. THE DYNAMICAL PROPERTIES OF THE SYSTEM 1 II. PHYSICAL AND CHEMICAL PROPERTIES OF THE SYSTEM 44 III. THEORIES OF ITS ORIGIN 93 INDEX THE SOLAR SYSTEM AND ITS ORIGIN THE DYNAMICAL PROPERTIES OF THE SYSTEM THE unsolved problems of Nature have a distinctive fa Qffiation, though they still far outnumber those which have even approximately been resolved. It may therefore be permissible to discuss the present situation of one of these, even though the outcome should no more than justify the conventional resolution to re port progress and turn to other matters. Speculation on the origin of our solar system is cen turies old much older, indeed, than the recognition of those dynamical and physical laws upon which alone any rational hypothesis must be based, or than the knowledge of facts enough to serve as adequate tests of such . theories. In a present-day survey of the field it is well to reverse the historic order, and consider first the known properties of the system, and then the theories which have been advanced to account for them, their successes and their limitations. 1. First among the characteristics of our system is its extreme isolation. Imagine a map, drawn accurately to scale, on which Pluto, at its remotest, is a foot from the Sun. The Earths orbit would be half an inch across 1 2 THE SOLAR SYSTEM AND ITS ORIGIN and Jupiter an inch and a quarter from the Sun but the nearest star would be a full mile away A generation ago, when few measures of stellar dis tances had been made, there was hope of finding nearer stars. But amongthe thousands of stars which have now been investigated for parallax one little one has been found, half as far away again, and two more not quite twice as distant as Alpha Centauri, which re tains its primacy. Since special attention has been paid to those stars which give promise of being our near neighbors, it is now practically certain that if any nearer star exists, it must be exceedingly faint. These studies have shown that interstellar distances are usually as great as this, so that the Sun is no lone lier than its neighbors indeed, it is a very common place star, dwarfish, though not minute, like hun dreds, nay thousands, of others. By accident the brighter component of Alpha Centauri which is dou ble is almost the Suns twin in brightness, mass, and size. Could this Earth be transported to its vicinity by some supernatural power, and set revolving about it, at a little less than a hundred million miles distance, the star would heat and light the world just as the Sun does, and life and civilization might go on with no radi cal change. The Milky Way would girdle the heavens as before some of our familiar constellations, such as Orion, would be little changed, though others would be greatly altered by the shifting of the nearer stars. An unfamiliar brilliant star, between Cassiopeia and Per seus would be the Sun. Looking back at it with our telescopes, we could photograph its spectrum, observe DYNAMICAL PROPERTIES OF THE SYSTEM 3 its motion among the stars, and convince ourselves that it was the same old Sun but what had happened to the rest of our planetary system we would not know. For the planets are so small, in comparison with stellar distances, and shine so feebly byreflected light, that even the best of them would be hopelessly invis ible. Jupiter itself would be too faint to be seen at all, or even photographed, with a hundred-inch telescope. A two-hundred-inch aperture might barely reveal it, if it stood alone on a dark background but the glare of the Sun, five hundred million times brighter, and only four seconds of arc away, would drown it out utterly in any telescope which human skill dares even to imagine...