THE EVOLUTION OF WORLDSFROM NEBULAE.
THE EVOLUTION OF WORLDSFROM NEBULAE.
The theory of world-formation as conceived by the Nebular hypothesis has been briefly stated by Dr. H. W. Warren in the following words: “All the matter composing all the bodies of the sun, planets, and their satellites, once existed in an exceedingly diffused state; rarer than any gas with which we are acquainted, filling a space larger than the orbit of Neptune. Gravitation gradually contracted this matter into a condensing globe of immense extent. Some parts would naturally be denser than others, and in the course of contraction a rotary motion, it is affirmed, would be engendered. Rotation would flatten the globe somewhat in the line of its axis.
Contracting still more, the rarer gases, aided by centrifugal force, would be left behind as a ring that would ultimately be separated, like Saturn’s ring, from the retreating body. There would naturally be some places in this ring denser than others; these would gradually absorb all the ring into a planet, and still revolve about the central mass, and still rotate on its own axis, throwing off rings from itself.
Thus the planet Neptune would be left behind in the first sun-ring, to make its one moon; the planet Uranus left in the next sun-ring; and so on down to Mercury. The outer planets would cool off first, become habitable, and, as the sun contracted and they radiated their own heat, become refrigerated and left behind by the retreating sun. The four great classes of facts confirmatory of this hypothesis are as follows: 1st. All the planets move in the same direction and nearly in the same plane, as if thrown off from one equator; 2d. The motions of the satellites about their primaries are mostly in the same direction as that of their primaries about the sun; 3d. The rotation of most of these bodies on their axes, and also of the sun, is in the same direction as the motion of the planets about the sun; 4th. The orbits of the planets, excluding asteroids, and their satellites, have but a comparatively small eccentricity; 5th. Certain nebulae are observable which are not yet condensed into solids, but are still bright gas.”[1]
The nebular hypothesis above stated was advanced by astronomers early in the eighteenth century, and later established by Laplace on a mathematical basis, who at the same time advocated the theory as materialistic. It is accepted quite generally by astronomers at the present day, though in a greatly modified form; for there are many difficulties in the way of a full belief of the theory. Sir Robert Ball in a late work says of Herschel’s belief of the transmutation of nebulae into stars; “To establishthis theory it would be necessary to watch the actual condensation of one single nebula from the primitive gaseous condition down to the stellar points. It may easily be conceived that such a process would require a vast lapse of time, perhaps enormously greater than the period between the invention of the telescope and the present moment. It may at all events be confidently asserted that this condensation of a nebula into a star is a process which has never been witnessed.” Concerning the theory of Laplace he tells us that it is “almost incapable of receiving any direct testimony;” and gives as the verdict of science, the words of Newcomb; “At the present time the nebular hypothesis is only indicated by the general tendencies of the laws of nature.”
According to this theory,—if all the planets are of the same substance as the earth on which we live, and of the greater sun from which they have ages since been separated,—there must once have been material heavy as rock and earth after condensation, filling the space around our sun in every direction for 3,000 millions of miles. If we could learnhowthis material of fire-mist originated we could better understand the mystery of world-making. A theory that would explain the formation of our own solar system should explain the formation of all the suns in space, a state of fire-mist for one implying the same for all. Let us consider whether there may not be other explanations of the phenomena in question fully as credible as the one given, and quite as consistent with all the known laws of nature.