Part 1 (2/2)
BESSEL detected a parallax of one-third of a second in the star 61 Cygni, and in the constellation of the Centaur HENDERSON found another star whose parallax amounted to one second. Of the million of fixed glittering points that adorn the sky, these are the only two whose distances have been calculated, and to express them, miles, leagues, or orbits seems inadequate. Light, whose speed is known to be 192,000 miles per second, would be three years in reaching our earth from the star of HENDERSON; and starting from BESSEL'S star and moving at the same rate it could only reach us in ten years. These are the nearest stars, but there are others whose distances are immeasurably greater, and whose light, though starting from them at the beginning of creation, may not have reached our globe!
The stars visible to the eye are about 3,000, but the number increases with every increase of telescopic power, and may be said to be innumerable. They are not of uniform l.u.s.tre or form, but vary in figure and brightness. Some of them have a _nebulous_ or cloudy appearance; and there are entire cl.u.s.ters with this dusky aspect, mostly pervaded, however, with luminous points of more brilliant hue. In the outer fields of astral s.p.a.ce Sir WILLIAM HERSCHEL observed a mult.i.tude of nebulae, one or two of which may be seen by the naked eye. All of them, when seen by instruments of low power, look like ma.s.ses of luminous vapour; but some of them had brighter spots, suggesting to Sir WILLIAM the idea of a condensation of the nebulous matter round one or more centres. But when these luminous ma.s.ses are examined by more powerful instruments many of them lose their cloudy form, and are resolved into s.h.i.+ning points, ”like spangles of diamond dust.” It is in this way several nebulae have yielded to the gigantic reflector of Lord ROSSE, and others with still greater optical resources may follow. This brings us to the first questionable and controversial portion of the _Vestiges_; namely,--the
NEBULAR HYPOTHESIS.
It is among the gaseous bodies just described, in the outer boundary of Nature, which neither telescope nor geometry can well reach, that speculation has laid its _venue_, and commenced its aerial castles.
LAPLACE was the first to suggest the nebular hypothesis, which he did with great diffidence, not as a theory proved, or hardly likely, but as a mathematical possibility or ill.u.s.tration. His range of creation, moreover, was not so vast as that of our author, which a.s.sumes to compa.s.s the entire universe, but was limited to the evolution of the solar system. The mode in which this might be evolved, LAPLACE thus explains:--
He conjectures that in the original condition of the solar system the sun revolved upon his axis, surrounded by an atmosphere which, in virtue of an excessive heat, extended far beyond the orbits of all the planets, the planets as yet having no existence. The heat gradually diminished, and as the solar atmosphere contracted by cooling, the rapidity of its rotation increased by the laws of rotatory motion, and an exterior zone of vapour was detached from the rest, the central attraction being no longer able to overcome the increased centrifugal force. The zone of vapour might in some cases retain its form, as we still see in Saturn's ring; but more usually the ring of vapour would break into several ma.s.ses, and these would generally coalesce into one ma.s.s, which would revolve about the sun. Such portions of the solar atmosphere abandoned successively at different distances, would form planets in the state of vapour. These ma.s.ses of vapour, it appears from mechanical laws, would have each its rotatory motion, and as the cooling of the vapour still went on, would each produce a planet that might have satellites and rings formed from the planet, in the same manner as the planets were formed from the atmosphere of the sun.
All the known motions of the solar system are consistent and reconcileable with this theory of LAPLACE, and upon it the author of the _Vestiges_ has enlarged and founded his wider scheme of physical creation. He supposes the void of nature to have been originally filled with a universal FIRE MIST (p. 30), out of which all the celestial orbs were made and put in motion. How this mist was put in activity, and resolved into the luminous and revolving bodies that we now see, and one of which we inhabit is the first urgent perplexity to surmount in the conjecture. It is manifest that if a mist filled the entire region of s.p.a.ce, a mist it must for ever remain, unless acted upon by some cause adequate to give it new action and arrangement. No sun, no stars or planets could spontaneously emanate from an inert vapour any more than from nothing. To meet this, his first difficulty, the author supposes that there were certain _nuclei_, or centres of greater condensation, a.n.a.logous to those still remarked in the nebulae of the heavens, and that these nuclei, by their superior attractive force, consolidated into spheres the gaseous matter around them:--
”Of nebulous matter,” says he, ”in its original state we know too little to enable us to suggest _how nuclei should be established in it_. But supposing that from a _peculiarity_ in the const.i.tution nuclei are formed, we know very well how, by the power of gravitation, the process of an aggregation of the neighbouring matter to these nuclei should proceed until ma.s.ses more or less solid should be detached from the rest. It is a _well-known law in physics, that when fluid matter collects towards, or meets in a centre, it establishes a rotatory motion_. See minor results of this law in the whirlpool and the whirlwind--nay, on so humble a scale as the water sinking through the aperture of a funnel. It thus becomes certain, that when we arrive at the stage of a nebulous star we have a rotation on its axis commenced.”
Up to this, however, the author has proved nothing. The existence of the fire-mist and nuclei are a.s.sumptions only, and the way by which he tries to account for rotatory motion is clearly erroneous. The aggregation of matter round the nuclei by gravitation would have no such tendency; no more than a perfect balance would of itself have a tendency to move about its fulcrum, or a falling stone to deviate from its vertical course. Gravitation would indeed compress the particles of matter, but its tendency and entire action is towards the nucleus; it compresses them no more on one side of the line of their direction to the centre of force than on any other side; and hence no _lateral_ or _rotatory motion_ would ensue. Rotation, therefore, is yet unaccounted for; though the author says _it is a well-known law in physics_ that when fluid matter collects towards, or meets in a centre, it establishes a rotatory motion; and then for ill.u.s.tration refers to a whirlwind or whirlpool. No such effect would follow the conditions stated, and an entire ignorance is betrayed of the laws of mechanical philosophy. In the whirlpool and the whirlwind the gyration is caused by the fluid pa.s.sing, not _to_ the centre, but _through_ it and away from it; in the whirlpool downwards through the place of exit, in the whirlwind upwards to where the vacuum has caused the rapid aggregation.
LAPLACE was too able a mathematician to commit these elementary blunders; he did not a.s.sume to account for rotation by inapplicable laws, but took for granted that the sun revolved upon its axis, and thence communicated a corresponding motion to the bodies thrown from its surface. But our author has sought to advance beyond his teacher, and in this way has shown his ignorance of physics by an egregious mistake. At this point we might stop, without following the ulterior steps by which the solar system is made to evolve out of heated vapour. Having got rotation, though by an impossible process, the author falls into the ill.u.s.tration already given of the theory of LAPLACE. The rotation of each nucleus or sun round its axis produces centrifugal force; that force, by refrigeration, increases beyond the centripetal force of gravity; in consequence rings are formed and detached from the surface, whose unequal coherence of parts mostly causes them to break into separate ma.s.ses or planets, partaking of the motion of the bodies from which they have been separated, and these primaries in their turn becoming centres of gravitation and centrifugal force, throw off their secondaries, or _moons_.
In this way the solar system and other systems upon a similar plan of arrangement, it is conjectured, may have been formed. According to the author the generative process is still in progress, and new worlds are in course of being thrown off from new suns in the confines of creation.
These nebulous stars on the outer bounds of s.p.a.ce, of varying forms and brightness, are supposed to be the centres of new systems in different stages of development, like children of various ages and growth in a numerous family. This is the author's own ill.u.s.tration (p. 20), and after giving it he proceeds:--
”Precisely thus, seeing in our astral system many thousands of worlds in all stages of formation, from the most rudimental to that immediately preceding the present condition of those we deem perfect, it is unavoidable to conclude that all the perfect have gone through the various stages which we see in the rudimental.
This leads us at once to the conclusion that the whole of our firmament was at one time a diffused ma.s.s of nebulous matter, extending through the s.p.a.ce which it still occupies. So also, of _course_, must have been the other astral systems. Indeed, we must presume the whole to have been originally in one connected ma.s.s, the astral systems being only the first division into parts, and solar systems the second.
”The first idea which all this impresses upon us is, that the formation of bodies in s.p.a.ce is _still and at present in progress_.
We live at a time when many have been formed, and many are still forming. Our own solar system is to be regarded as completed, supposing its perfection to consist in the formation of a series of planets, for there are mathematical reasons for concluding that Mercury is the nearest planet to the sun, which can, according to the laws of the system, exist. But there are other solar systems within our astral systems, which are as yet in a less advanced state, and even some quant.i.ties of nebulous matter which have scarcely begun to advance towards the stellar form. On the other hand, there are vast numbers of stars which have all the appearance of being fully formed systems, if we are to judge from the complete and definite appearance which they present to our vision through the telescope. We have no means of judging of the _seniority of systems; but it is reasonable to suppose that among the many, some are older than ours_. There is, indeed, one piece of evidence for the probability of the comparative youth of our system, altogether apart from human traditions and the geognostic appearances of the surface of our planet. This consists in a thin nebulous matter, which is diffused around the sun to nearly the orbit of Mercury, of a very oblately spheroidal shape. This matter, which sometimes appears to our naked eyes, at sunset, in the form of a cone projecting upwards in the line of the sun's path, and which bears the name of the Zodiacal Light, has been thought a residuum or last remnant of the concentrating matter of our system, and thus may be supposed to indicate the comparative recentness of the princ.i.p.al events of our cosmogony. _Supposing the surmise and inference_ to be correct, and they may be held as so far supported by more familiar evidence, we might with the more confidence speak of our system as not amongst the elder born of Heaven, but one whose various phenomena, physical and moral, as yet lay undeveloped, while myriads of others were fully fas.h.i.+oned, and in complete arrangement. Thus, in the sublime chronology to which we are directing our inquiries, we first find ourselves called upon to consider the globe which we inhabit as a child of the sun, elder than Venus and her younger brother Mercury, but posterior in date of birth to Mars, Jupiter, Saturn, and Ura.n.u.s; next to regard our whole system as probably of recent formation in comparison with many of the stars of our firmament. We must, however, be on our guard against supposing the earth as a recent globe in our ordinary conceptions of time. From evidence afterwards to be adduced, it will be seen that it cannot be presumed to be less than many hundreds of centuries old. How much older Ura.n.u.s may be, no one can tell, far less how much more aged may be many of the stars of our firmament, or the stars of other firmaments, than ours.”
All this is ingenious and fluently expressed. The author has an easy way of surmounting his difficulties by the use of such little auxiliary phrases, as ”of course,” ”it may be surmised,” ”it is reasonable to suppose,” and so on; which, though trifling in themselves, help him in their connecting inferences through many embarra.s.sing perplexities. But his hypothesis is yet unproved; his fire-mist is only a conjecture; his nuclei, scattered like so many eggs in s.p.a.ce out of which future suns and worlds are in process of incubation, is of the same description, and rotation, the first step in his process of creation, would not ensue under the conditions he has a.s.signed. Without dwelling on these shortcomings, we shall terminate this portion of the author's inquiry with a few general strictures. First, on its inconsistency with what we know of the solar system; and, secondly, on its inadequacy to explain the facts of which we are cognizant on our own globe.
In the first place, for the hypothesis to be applicable to our system, it is requisite that the primary and secondary bodies should revolve, both in their orbits and round their axes, in one direction, and nearly in one plane. Most of the bodies of the system observe these laws, their orbits are nearly circular, nearly in the plane of the original equator of the solar rotation, and in the direction of that rotation. But there are exceptions; the comets, which intersect the equatorial plane in every angle of direction form one, and the most distant of the planets forms another. The satellites of Ura.n.u.s are retrograde. They move from east to west in orbits highly inclined to that of their primary, and on both accounts are exceptions to the order of the other secondary bodies.
Our author is so perplexed by this inconsistency that he first doubts the fact, and next tries to explain it by alleging that ”it may be owing to a _boulevers.e.m.e.nt_ of the primary.” What is meant by the _boulevers.e.m.e.nt_ of a planet none of his critics seem to apprehend, nor do we. But that the moons of Ura.n.u.s are contrariwise to those of the other planets, Sir JOHN HERSCHEL has indubitably established; so that the author at any rate upon this point has sustained a boulevers.e.m.e.nt.
Our own moon forms a third exception to his theory. According to his system, this satellite is a slip or graft from our planet, and in const.i.tution, it might be inferred, would partake of the elements of the parent. But the fact is otherwise. The moon has no atmosphere, no seas, or rivers, nor any water, and of course totally unfit for human inhabitants, or organic life of any kind. It must, then, have had a different origin, or be in some earlier stage of development than that through which our earth has pa.s.sed.
Leaving these exceptions, we may next inquire into the relevant purposes of the nebular hypothesis, supposing its a.s.sumptions acquiesced in. Like the fanciful theories of the ancient philosophers, it seems only to involve a profitless topic of controversy, without solving natural phenomena. It does not unravel the mystery of the beginning, brings us no nearer to the first creative force. Like a good chemist, previous to a.n.a.lysis, the author first throws all matter into a state of solution; but granting him his fire-mist and nuclei in the midst, how or whence came this condition and arrangement of nature? What was its pre-existing state? or, if that be answered, how or whence was that preceding state educed, for it, too, must have had one prior to it? So that the mind makes no advances by such inquiries, is lost in a maze that can have no end, because it has no beginning; and, like Noah's messenger, for want of a resting place, is compelled to return to the first starting point.
Easier, and quite as satisfactory, it seems to believe, as we have been taught to believe, that the celestial spheres were at once perfect and entire, projected into s.p.a.ce from the hands of the maker, than that they were elaborated out of luminous vapour by gravity and condensation.
Hopeless inquiry is thus foreclosed, an inquisition that cannot be answered, silenced, and removed out of the pale of discussion.
It is not from any attribute of the Deity being impugned that the hypothesis is objectionable. Design and intelligence in the creation are left paramount as before, and our impression of the skill exercised, and the means employed, only transferred to another part of the work. He who produced the primordial condition the author supposes, who filled s.p.a.ce with such a mist, composed of such materials, subjected to such laws, such const.i.tution, that sun, moon, and stars necessarily resulted from them, appears omnipotent as ever. But it does not advance inquiry, nor a.s.sist us in explaining the wonders we contemplate in our own globe.
Suppose a planet formed by the author's process, what kind of a body would it be? Something, as Professor WHEWELL suggests, resembling a large meteoric stone. How after wards came this unformed ma.s.s to be like our earth, to be covered with motion and organization, with life and general felicity? What primitive cause stocked it with plants and animals, and produced all the surprising and subtle contrivances which we find in their structure, all the wide and profound mutual dependence which we trace in their economy? Is it possible to conceive, as the _Vestiges_ inculcate, that man, with his sentiment and intellect, his powers and pa.s.sions, his will and conscience, were also produced as the ultimate result of vapourous condensation?
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