History of the Intellectual Development of Europe, Volume II (of 2) / Revised Edition

by John William Draper

Dominion of law in the universe.From what has been said, the conclusion forces [279] itself upon us that the general laws obtaining as respects the earth, hold good likewise for all other parts of the universe; a conclusion sustained not only by the mechanism of such motions as we have been considering, but also by all evidence of a physical kind accessible to us. The circumstances under which our sun emits light and heat, and thereby vivifies his attendant planets, are indisputably the same as those obtaining in the case of every fixed star, each of which is a self-luminous sun. There is thus an aspect of homogeneousness in the structure of all systems in the universe, which, though some have spoken of it as if it were the indication of a uniformity of plan, and therefore the evidence of a primordial idea, is rather to be looked upon as the proof of unchangeable and resistless law.

Ruin of anthropocentric ideas.What, therefore, now becomes of the doctrine authoritatively put forth, and made to hold its sway for so many centuries, that the earth is not only the central-body of the universe, but in reality, the most noble body in it; that the sun and other stars are mere ministers or attendants for human use? In the place of these utterly erroneous and unworthy views, far different conceptions must be substituted. Man, when he looks upon the countless multitude of stars—when he reflects that all he sees is only a little portion of those which exist, yet that each is a light and life-giving sun to multitudes of opaque, and therefore, invisible worlds—when he considers the enormous size of these various bodies and their immeasurable distance from one another, may form an estimate of the scale on which the world is constructed, and learn therefrom his own unspeakable insignificance.

Aids for measurements in the universe.In one beat of a pendulum a ray of light would pass eight times round the circumference of the earth. Thus we may take the sunbeam as a carpenter does his measuring-rule; it serves as a gauge in our measurements of the universe. A sunbeam would require more than three years to reach us from alpha Centauri; nine and a quarter years from 61 Cygni; from alpha Lyræ twelve years. These are stars whose parallax has been determined, and which are therefore nearest to us.

Clusters of stars. [280] Of suns visible to the naked eye there are about 8000, but the telescope can discern in the Milky Way more than eighteen millions, the number visible increasing as more powerful instruments are used. Our cluster of stars is a disc divided into two branches at about one-third of its length. In the midst of innumerable compeers and superiors, the sun is not far from the place of bifurcation, and at about the middle of the thickness. Outside the plane of the Milky Way the appearance would be like a ring, and, still farther off, a nebulous disc.

Distribution of matter and force in space.From the contemplation of isolated suns and congregated clusters we are led to the stupendous problem of the distribution of matter and force in space, and to the interpretation of those apparent phantoms of self-luminous vapour, circular and elliptic discs, spiral wreaths, rings and fans, whose edges fade doubtfully away, twins and triplets of phosphorescent haze connected together by threads of light and grotesque forms of indescribable complexity. Perhaps in some of these gleaming apparitions we see the genesis, in some the melting away of universes. There is nothing motionless in the sky. In every direction vast transformations are occurring, yet all things proclaim the eternity of matter and the undiminished perpetuity of force.

Limit of the theory of gravitation.The theory of gravitation, as delivered by Newton, thus leads us to a knowledge of the mathematical construction of the solar system, and inferentially likewise to that of other systems; but it leaves without explanation a large number of singular facts. It explains the existing conditions of equilibrium of the heavenly bodies, but it tells us nothing of their genesis; or, at the best, in that particular it falls back on the simple fiat of God.

Phenomena of the solar system.The facts here referred to conduct us, however, to another and far higher point of view. Some of them, as enumerated by Laplace, are the following:—1. All the planets and their satellites move in ellipses of such small eccentricity that they are nearly circles; 2. The movements of the planets are in the same direction and nearly in the same plane; 3. The movements of the satellites are in the same direction as those of [281] the planets; 4. The movements of rotation of these various bodies and of the sun are in the same direction as their orbitual motions, and in planes little different.

The nebular hypothesis.The nebular hypothesis requires us to admit that all the ponderable material now constituting the various bodies of the solar system once extended in a rarefied or nebulous and rotating condition, beyond the confines of the most distant planet. That postulate granted; the structure and present condition of the system may be mathematically deduced.

For, as the vast rotating spheroid lost its heat by radiation, it contracted, and its velocity of rotation was necessarily increased; and thus were left behind from its equatorial zone, by reason of the centrifugal force, rotating rings, the same result occurring periodically again and again. These rings must lie all in one plane. They might break, collapsing into one rotating spheroid, a planet; or into many, asteroids; or maintain the ring-like form. From the larger of these secondary rotating spheroids other rings might be thrown off, as from the parent mass; these, in their turn breaking and becoming spheroids, constitute satellites, whose movements correspond to those of their primaries.

We might, indeed, advance a step farther, and show how, by the radiation of heat from a motionless nebula, a movement of rotation in a determinate direction could be engendered, and that upon these principles, the existence of a nebulous matter admitted, and the present laws and forces of nature regarded as having been unchanged, the manner of origin of the solar system might be deduced, and all those singular facts previously alluded to explained; and not only so, but there is spontaneously suggested the cause of many minor peculiarities not yet mentioned.