Recreations in Astronomy Part 13

"A dark Illimitable ocean, without bound, Without dimension, where length, breadth, and height, And time, and place are lost."--MILTON.

"It is certain that matter is somehow directed, controlled, and arranged; while no material forces or properties are known to be capable of discharging such functions."--LIONEL BEALE.

"The laws of nature do not account for their own origin."--JOHN STUART MILL.

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IX.

_THE NEBULAR HYPOTHESIS._

The method by which the solar system came into its present form was sketched in vast outline by Moses. He gave us the fundamental idea of what is called the nebular hypothesis. Swedenborg, that prodigal dreamer of vagaries, in 1734 threw out some conjectures of the way in which the outlines were to be filled up; Buffon followed him closely in 1749; Kant sought to give it an ideal philosophical completeness; as he said, "not as the result of observation and computation," but as evolved out of his own consciousness; and Laplace sought to settle it on a mathematical basis.

It has been modified greatly by later writers, and must receive still greater modifications before it can be accepted by the best scientists of to-day. It has been called "the grandest generalization of the human mind;" and if it shall finally be so modified as to pa.s.s from a tentative hypothesis to an accepted philosophy, declaring the modes of a divine worker rather than the necessities of blind force, it will still be worthy of that high distinction.

Let it be clearly noted that it never proposes to do more than to trace a portion of the mode of working which brought the universe from one stage to another. It only goes back to a definite point, never to absolute beginning, nor to nothingness. It takes matter from [Page 182] the hand of the unseen power behind, and merely notes the progress of its development. It finds the clay in the hands of an intelligent potter, and sees it whirl in the process of formation into a vessel. It is not in any sense necessarily atheistic, any more than it is to affirm that a tree grows by vital processes in the sun and dew, instead of being arbitrarily and instantly created. The conclusion reached depends on the spirit of the observer. Newton could say, "This most beautiful system of the sun, planets, and comets could only proceed from the counsel and dominion of an intelligent and powerful being!" Still it is well to recognize that some of its most ardent defenders have advocated it as materialistic. And Laplace said of it to Napoleon, "I have no need of the hypothesis of a G.o.d."

The materialistic statement of the theory is this: that matter is at first a.s.sumed to exist as an infinite cloud of fire-mist, dowered with power latent therein to grow of itself into every possibility of world, flower, animal, man, mind, and affection, without any interference or help from without. But it requires far more of the Divine Worker than any other theory. He must fill matter with capabilities to take care of itself, and this would tax the abilities of the Infinite One far more than a constant supervision and occasional interference. Instead of making the vase in perfect form, and coloring it with exquisite beauty by an ever-present skill, he must endow the clay with power to make itself in perfect form, adorn itself with delicate beauty, and create other vases.

The nebular hypothesis is briefly this: All the matter composing all the bodies of the sun, planets, and satellites once existed in an exceedingly diffused state; [Page 183] rarer than any gas with which we are acquainted, filling a s.p.a.ce 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 ma.s.s, 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 Ura.n.u.s left in the next sun-ring, to make its four moons from four successive planet-rings; Saturn, with its eight moons and three rings not made into moons, is left in the third sun-ring; and so on down to Vulcan.

The outer planets would cool off first, become inhabitable, and, as the sun contracted and they radiated their own heat, become refrigerated and left behind by the retreating sun. Of course the outer planets would move slowly; but as that portion of the sun which gave them their motion drew in toward the centre, keeping its absolute speed, and revolving in the lessening circles of a contracting body, it would give the faster motion necessary to be imparted to Earth, Mercury, and Vulcan.

The four great cla.s.ses of facts confirmatory of this hypothesis are as follows: 1st. All the planets move [Page 184] 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 in the heavens which are not yet condensed into solids, but are still bright gas.

The materialistic evolutionist takes up the idea of a universe of material world-stuff without form, and void, but so endowed as to develop itself into orderly worlds, and adds to it this exceeding advance, that when soil, sun, and chemical laws found themselves properly related, a force in matter, latent for a million eons in the original cloud, comes forward, and dead matter becomes alive in the lowest order of vegetable life; there takes place, as Herbert Spencer says, "a change from an indefinite, incoherent h.o.m.ogeneity, into a definite, coherent heterogeneity, through continuous differentiation and integration." The dead becomes alive; matter pa.s.ses from unconsciousness to consciousness; pa.s.ses up from plant to animal, from animal to man; takes on power to think, reason, love, and adore. The theistic evolutionist may think that the same process is gone through, but that an ever-present and working G.o.d superintends, guides, and occasionally bestows a new endowment of power that successively gives life, consciousness, mental, affectional, and spiritual capacity.

Is this world-theory true? and if so, is either of the [Page 185]

evolution theories true also? If the first evolution theory is true, the evolved man will hardly know which to adore most, the Being that could so endow matter, or the matter capable of such endowment.

There are some difficulties in the way of the acceptance of the nebular hypothesis that compel many of the most thorough scientists of the day to withhold their a.s.sent to its entirety. The latest, and one of the most competent writers on the subject, Professor Newcomb, who is a mathematical astronomer, and not an easy theorist, evolving the system of the universe from the depth of his own consciousness, says: "Should any one be sceptical as to the sufficiency of these laws to account for the present state of things, science can furnish no evidence strong enough to overthrow his doubts until the sun shall be found to be growing smaller by actual measurement, or the nebulae be actually seen to condense into stars and systems." In one of the most elaborate defences of the theory, it is argued that the hypothesis explains why only one of the four planets nearest the sun can have a moon, and why there can be no planet inside of Mercury. The discovery of the two satellites to Mars and of the planet Vulcan makes it all the worse for these facts.

Some of the objections to the theory should be known by every thinker.

Laplace must have the cloud "diffused in consequence of excessive heat," etc. Helmholtz, in order to account for the heat of the contracting sun, must have the cloud relatively cold. How he and his followers diffused the cloud without heat is not stated.

The next difficulty is that of rotation. The laws [Page 186] of science compel a contraction into one non-rotating body--a central sun, indeed, but no planets about it. Laplace cleverly evades the difficulty by not taking from the hand of the Creator diffused gas, but a sun with an atmosphere filling s.p.a.ce to the orbit of Neptune, and _already in revolution_. He says: "It is four millions to one that all motions of the planets, rotations and revolutions, were at once imparted by an original common cause, of which we know neither the nature nor the epoch." Helmholtz says of rotation, "the existence of which must be a.s.sumed." Professor Newcomb says that the planets would not be arranged as now, each one twice as far from the sun as the next interior one, and the outer ones made first, but that all would be made into planets at once, and the small inner ones quite likely to cool off more rapidly.

It is a very serious difficulty that at least one satellite does not revolve in the right direction. How Neptune or Ura.n.u.s could throw their moons backward from its equator is not easily accounted for. It is at least one Parthian arrow at the system, not necessarily fatal, but certainly dangerous.

A greater difficulty is presented by the recently discovered satellites of Mars. The inner one goes round the planet in one-third part of the time of the latter's revolution. How Mars could impart three times the speed to a body flying off its surface that it has itself, has caused several defenders of the hypothesis to rush forward with explanations, but none with anything more than mere imaginary collisions with some comet. It is to be noticed that accounting for three times the speed is not enough; for as Mars shrunk away from the [Page 187] ring that formed that satellite, it ought itself to attain more speed, as the sun revolves faster than its planets, and the earth faster than its moon. In defending the hypothesis, Mitchel said: "Suppose we had discovered that it required more time for Saturn or Jupiter to rotate on their axes than for their nearest moon to revolve round them in its...o...b..t; this would have falsified the theory." It is also a.s.serted that the newly discovered planet Vulcan makes an orbital in less time than the sun makes an axial revolution.

In regard to one Martial moon, Professor Kirkwood, on whom Proctor conferred the highest t.i.tle that could be conferred, "the modern Kepler," says: "Unless some explanation can be given, the short period of the inner satellite will be doubtless regarded as a conclusive argument against the nebular hypothesis." If gravitation be sufficient to account for the various motions of the heavenly bodies, we have a perplexing problem in the star known as 1830 Groombridge, now in the Hunting Dogs of Bootes. It is thought to have a speed of two hundred miles per second--a velocity that all the known matter in the universe could not give to the star by all its combined attraction. Neither could all that attraction stop the motion of the star, or bend it into an orbit. Its motion must be accounted for on some hypothesis other than the nebular.

The nebulae which we are able to observe are not altogether confirmatory of the hypothesis under consideration. They have the most fantastic shapes, as if they had no relation to rotating suns in the formative stages. There are vast gaps in the middle, where they ought to be densest. Mr. Plumer, in the _Natural Science Review_, [Page 188]

says, in regard to the results of the spectroscopic revelations: "We are furnished with distinct proof that the gases so examined are not only of nearly equal density, but that they exist in a low state of _tension. This fact is fatal to the nebular theory._"

In the autumn of 1876 a star blazed out in Cygnus, which promised to throw a flood of light on the question of world-making. Its spectrum was like some of the fixed stars. It probably blazed ont by condensation from some previously invisible nebula. But its brilliancy diminished swiftly, when it ought to have taken millions of years to cool. If the theory was true, it ought to have behaved very differently. It should have regularly condensed from gas to a solid sun by slow process. But, worst of all, after being a star awhile, it showed unmistakable proofs of turning into a cloud-mist--a star into a nebula, instead of _vice versa_. A possible explanation will be considered under variable stars.

Such are a few of the many difficulties in the way of accepting the nebular hypothesis, as at present explained, as being the true mode of development of the solar system. Doubtless it has come from a hot and diffused condition into its present state; but when such men as Proctor, Newcomb, and Kirkwood see difficulties that cannot be explained, contradictions that cannot be reconciled by the principles of this theory, surely lesser men are obliged to suspend judgment, and render the Scotch verdict of "not proven."

Whatever truth there may be in the theory will survive, and be incorporated into the final solution of the problem; which solution will be a much grander generalization of the human mind than the nebular hypothesis.

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Of some things we feel very sure: that matter was once without form and void, and darkness rested on the face of the mighty deeps; that, instead of chaos, we have now cosmos and beauty; and that there is some process by which matter has been brought from one state to the other. Whether, however, the nebular hypothesis lays down the road travelled to this transfiguration, we are not sure.

Some of it seems like solid rock, and some like shifting quicksand.

Doubtless there is a road from that chaos to this fair cosmos.

The nebular hypothesis has surveyed, worked, and perfected many long reaches of this road, but the rivers are not bridged, the chasms not filled, nor the mountains tunnelled.

When men attempt to roll the hypothesis of evolution along the road of the nebular hypothesis of worlds, and even beyond to the production of vegetable and animal life, mind and affection, the gaps in the road become evident, and disastrous.

A soul that has reached an adoration for the Supreme Father cares not how he has made him. Doubtless the way G.o.d chose was the best.

It is as agreeable to have been thought of and provided for in the beginning, to have had a myriad ages of care, and to have come from the highest existent life at last, as to have been made at once, by a single act, out of dust. The one who is made is not to say to the Maker, "Why hast thou formed me in this or that manner?"

We only wish the question answered in what manner we were really made.

Evolution, without constant superintendence and occasional new inspiration of power, finds some tremendous chasms in the road it travels. These must be spanned by the power of a present G.o.d or the airy imagination [Page 190] of man. Dr. McCosh has happily enumerated some of these tremendous gaps over which mere force cannot go. Given, then, matter with mechanical power only, what are the gaps between it and spirituality?

"1. Chemical action cannot be produced by mechanical power.

"2. Life, even in the lowest forms, cannot be produced from unorganized matter.

"3. Protoplasm can be produced only by living matter.

"4. Organized matter is made up of cells, and can be produced only by cells. Whence the first cell?

"5. A living being can be produced only from a seed or germ. Whence the first vegetable seed?

"6. An animal cannot be produced from a plant. Whence the first animal?

"7. Sensation cannot be produced in insentient matter.

"8. The genesis of a new species of plant or animal has never come under the cognizance of man, either in pre-human or post-human ages, either in pre-scientific or scientific times. Darwin acknowledges this, and says that, should a new species suddenly arise, we have no means of knowing that it is such.

"9. Consciousness--that is, a knowledge of self and its operations--cannot be produced out of mere matter or sensation.

"10. We have no knowledge of man being generated out of the lower animals.

"11. All human beings, even savages, are capable of forming certain high ideas, such as those of G.o.d and duty. The brute creatures cannot be made to entertain these by any training.

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"With such tremendous gaps in the process, the theory which would derive all things out of matter by development is seen to be a very precarious one.

The truth, according to the best judgment to be formed in the present state of knowledge, would seem to be about this: The nebular hypothesis is correct in all the main facts on which it is based; but that neither the present forces of matter, nor any other forces conceivable to the mind of man, with which it can possibly be endowed, can account for all the facts already observed. There is a demand for a personal volition, for an exercise of intelligence, for the following of a divine plan that embraces a final perfection through various and changeful processes. The five great cla.s.ses of facts that sustain the nebular hypothesis seem set before us to show the regular order of working. The several facts that will not, so far as at present known, accord with that plan, seem to be set before us to declare the presence of a divine will and power working his good pleasure according to the exigencies of time and place.

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X.