CHAPTER III.
DIFFICULTIES IN ASTRONOMY.
These objections, so far as they are based or supposed to be based on ascertained facts, are very few and insignificant. The chief of them are as follows:—
1. Moses describes light, and the division of night and day as existing before the Creation of the Sun.
2. Moses describes the firmament as a solid vault.
3. Moses speaks of the stars as created on the fourth day, only two days before Adam, whereas astronomers have asserted that many of them are so distant that the light by which we see them must have been on its way ages before Adam was created.
That part of the first objection which refers to the existence of light prior to the creation of the Sun, appears so extremely childish that it might have been thought unnecessary to notice it, had it not been solemnly propounded in such a work as "Essays and Reviews." [Footnote: Page 219] Anyone who is in possession of a telescope of but moderate power may satisfy himself of its futility on any starlight night. He has only to turn his telescope to one or two of the more conspicuous nebulae; the Great Nebula in Orion, for instance, or the Ring Nebula in Lyra, and his eye will receive light which has not come from any Sun, for it is a well- ascertained fact that these nebulae are nothing but vast masses of incandescent gas. And this objection is singularly inappropriate in the mouth of the opponents of the Mosaic Record, inasmuch as the Nebular hypothesis is with them the favourite method of accounting for the present state of things. The view which they bring forward as an alternative to the Mosaic account assumes the very state of things which, when, alleged by Moses, they denounce as impossible. The other part of this objection, which refers to the division of day and night, will be more advantageously discussed when we come to consider the actual accounts of the first and fourth days' work. It will then appear probable that the statements which Moses has made on this subject, instead of being indications of ignorance, are the result of a profound knowledge of the subject on which he was writing.
Next, it is alleged that Moses describes the firmament as a solid vault.[Footnote: Essays and Reviews, p. 220.] "The work of the second day of creation is to erect the vault of heaven, which is represented as supporting an ocean of water above it." That the Greek and Latin translations in this place do seem to imply the idea of solidity seems indisputable; and from the Latin the word "firmament" has passed into our own language. But there is no reason to think that the Hebrew word has any such meaning. It is derived from a root signifying "to beat out—to extend." [Footnote: May not this root, [Hebrew script], have some connexion with [Hebrew script], "to be light," from which is derived the Aramaic "Raca" of Matt. v. 22?] The verb is often applied to the beating out of metals, but not always. It is a new doctrine in etymology, that the meaning of a verbal noun is to be deduced from the nouns which often supply objects to its root, instead of from the meaning of the root itself. But even if it can be shown that the word did originally involve such a meaning, that would be nothing to the purpose. It would only be in the same case with a vast number of other words, which, though etymologically untrue, are habitually used without inconvenience, because they do convey to the minds of others the idea which we intend to convey, their etymology being lost sight of. Probably, the very persons who bring forward the objection do sometimes use the word "firmament," though they know the error which is involved in it. Nor would they be any more accurate if they substituted for it the Saxon word "heaven," since that also involves a scientific inaccuracy. The word used by Moses was the commonly recognized name for the object of which he was writing; and no objection to his use of it can be maintained, unless it can be shown that in using it he rejected some other word equally intelligible to all, and which was at the same time etymologically correct. But there is no ground for the assumption that any such word existed in the time of Moses or at any subsequent period.
The third objection, of course, ceases to have any force if the days of creation are no longer regarded as natural days. But the objection is in itself, apart from this condition, of no consequence whatever. For, in the first place, it is by no means certain, or even probable, that the stars referred to in the fourth day's work are the fixed stars. The Hebrew has no word for planets as distinguished from the fixed stars, although, as we know for certain, the difference between the planets and the fixed stars was recognized from a very early period. In every case, then, the context must determine the sense to be given to the word. In this case, the fact that these stars are mentioned in connexion with the sun and moon, combined with our knowledge that the planets, like the moon, are dependent upon the sun for their light, would lead us to infer that they are meant.
But even if the fixed stars were meant, the objection would be no longer tenable. It rests on certain estimates as to the supposed distances of the fixed stars and star clusters, which were formed by the late Sir W. Herschel from what he designated the "space- penetrating power" of his telescopes. Starting with the assumption that the stars were of tolerably uniform size and brilliancy, and that the difference in apparent brightness was the result, and therefore a measure of their distances, he proceeded to apply the same process to the star clusters, which, even in a fair telescope, present only the appearance of faint nebulous spots of light, but are resolved into clusters of stars by more powerful instruments. In many cases, he found that a certain proportion existed between the telescopic power by which a cluster was first rendered visible, and that required for its resolution, and by this means he formed what he considered a probable estimate of its distance. Other clusters there were which only became visible in his most powerful telescopes, and which, therefore, he could never succeed in resolving. These he placed at a still greater distance, and from this estimate he deduced the conclusion that their light must have been in some cases as much as 60,000 years in reaching the earth.
But the whole foundation on which this long chain of inference rested has now been shown to be evanescent. In the first place many of his irresolvable nebulae have been proved by the spectroscope to be true nebulae—masses of luminous gas, and not star clusters at all; and, in the next place, the actual distances of a few of the fixed stars have been approximately ascertained, and it is proved beyond all doubt that the different degree of brightness exhibited by different stars is no test at all of their distance. Of all the stars in our hemisphere whose distance has thus been measured, the nearest to us is one which can only just be discerned by a practised eye on a favourable night, 61 Cygni, whilst the most brilliant star visible in England, Sirius, is at a considerably greater distance. The most competent judges estimate the magnitude of Sirius as about one thousand times that of the sun [Footnote: Mr. Proctor in Good Words, February, 1872.]. In addition to this, many stars of very different magnitudes are found to be related to each other in such a way as to show that they are in actual, and not merely in optical proximity. The clusters which were formerly supposed to consist of large stars at enormous distances from us, are now, upon very solid grounds, believed to be formed of much smaller stars, at much more moderate distances, so that it is very improbable that there is any object visible in the heavens whose light has taken so much as 6000 years, instead of 60,000 years to reach us.
THE NEBULAR THEORY.
We come now to the consideration of the Nebular Theory of Laplace, in so far as it is opposed to the Mosaic account. It must be remembered that, after all, this is only a theory. Even if it could be satisfactorily established, it would only point out a way in which this world MIGHT have been formed. That it could not have been formed in any other way is an independent proposition, in support of which no single argument has ever yet been brought forward. There may be a greater or less probability that the earth was formed in this particular way, that probability depending on the extent to which the theory accounts for observed facts. This it does in many cases, and it has in consequence been accepted AS A WHOLE by many scientific men, as a substitute for the Scriptural account. As will be seen hereafter, there are strong reasons for admitting it as a supplement to the brief account given by Moses; but our business now is to ascertain, whether it has any just claim to be received instead of that account.
The theory seems to have been suggested by certain speculations of Sir W. Herschel. In his telescopic examination of the Nebulae and star clusters, he found that in a great number of cases, when a nebula was rendered visible by a certain amount of telescopic power, it would be resolved into separate stars by a telescope of a little higher power. But there were some nebulae, visible in very small telescopes, or even discernible with the naked eye, such as those in Orion and Andromeda, which could not be resolved even by his great four-foot reflector, the largest telescope that had then been constructed. And these nebulae exhibited a great variety of forms. Some of them were vast shapeless masses of faint light; others, which he designated "planetary" nebulae, exhibited a regular form—a circular disc more or less clearly defined, often brightest in the centre. Others seemed to be intermediate between these two classes. Hence he was led to the idea that these were worlds in the process of formation, and that their varying forms indicated varying stages of that process.
This suggestion was eagerly adopted by the members of the French Academy, who were at that time on the look-out for anything which they thought would help them to account for the existence of the world, while they refused to acknowledge a Creator. It was taken up by one of their number—Laplace—a man who stood in the very foremost rank as a mathematician and physical astronomer, and moulded into shape by him.[Footnote: There is a very full account of Laplace's hypothesis, extracted from the works of Pontecoulant, in Professor Nichol's System of the World, pp. 69—86.]
He assumed, that the Solar System existed at the very earliest period as a shapeless nebula, a vast undefined mass of "fire- mist;" that at some time or other the separate particles of this fire-mist began to move towards their centre of gravity, under the influence of their mutual attractions, and thus assumed a spherical shape; that by some means or other a motion of rotation was originated in this spherical mass, which increased in rapidity as the process of condensation advanced. The effect of this rotation would be a flattening of the sphere; the equatorial diameter would increase while the polar diameter, or axis of rotation, diminished; and when the centrifugal force thus produced had reached a certain point, a ring would detach itself from the equator, but would continue to revolve about the common centre. He supposed that a succession of rings were thus thrown off, which finally broke up and accumulated into one or more spherical masses, forming the planets and their satellites, while the remainder of the original sphere was condensed into the sun. The planets and their satellites would continue to revolve about the centre as the ring from which they were formed had done, while the different original velocities of the particles of which they were formed, some having been in the outer, some in the inner part of the ring, would cause them also to rotate on their axis. As the condensation advanced, the heat which had originally existed in the "fire-mist" would be condensed also, so that all the masses when formed would be in an incandescent state, but the planets and their satellites being comparatively small would soon cool down, while the sun, owing to its greatly superior bulk, still retains its heat.
There is no doubt much to be said in favour of this theory, which may be more advantageously considered hereafter, when we shall have to consider it as supplementary to the Mosaic account. At present we are only concerned with it as it claims to stand alone, and to be accepted as a substitute for that account. Viewed in this light, as a substitute for a Creator, as showing us how the universe might have come into existence spontaneously, it utterly breaks down in three points.
1. It gives us no account whatever of the origin of matter, but assumes that it was already in existence at the time from which the theory takes its point of departure. But some account of it must be given. Either it was created by some higher power, or it was eternal; for the idea of its being self-originated is manifestly untenable. If it was created, there is an end of the theory—the act of creation assumes the existence of a Creator; and the only question left is, whether that Creator did more or less. But the very object of the theory was to dispense with the existence of a Creator. This alternative, then, it must reject, and there is nothing left but to fall back upon the other, and to assume that it existed from all eternity. But it is certainly not less difficult to us to conceive the possibility of inert matter being self-existent and eternal, than it is to recognize the existence of an eternal and all-powerful Spirit. Our own consciousness helps us to realize the possibility of the existence of an Eternal Mind, and of the exercise of power by that mind; but we have nothing to help us to a conception of self-existent matter.
In addition to this, the idea of eternity precludes from its very nature the idea of possible change. If there is change there must be the distinction of before and after, and so of the succession of existence, which involves the idea of time. That which is subject to change, and this theory assumes a change in the condition of matter, cannot be eternal.
2. The next failing point is, that this theory assumes a change, of the origin of which it can give no account. The assumption is, that matter which had existed from all eternity, or for an indefinite time, in a state of perfect rest, suddenly began to move towards its centre of gravity. A body, or a system of particles, can remain at rest only under one of two conditions. Either it must be acted on by no force at all, or all the forces by which it is acted on must be in perfect equilibrium. If matter existed under the first of these conditions, whence did the force suddenly emanate? Force cannot be self-originated any more than matter. But if the other alternative be adopted, how was the equilibrium disturbed? It is a fundamental axiom of mechanics that "a body (or system of bodies) at rest will continue at rest till it be acted upon by some external force." But the theory supplies no such external force, for it could only originate in that which the theory ignores—the will and power of some intelligent Being.
3. The third defect is, that the theory does not give any satisfactory account of the origin of the motions of rotation and revolution. Laplace does not attempt this. He simply assumes that a motion of rotation was set up somehow; but many of his followers, perceiving that the theory broke down here—though they passed the other two defects unnoticed—have attempted to supply the deficiency in this point. Some have attempted to account for this motion by analogy. It has been suggested that it was of the same nature, and produced by the same causes, as the vortex which is formed when a vessel full of fluid is emptied through an orifice in its bottom. Pontecoulant, in his account of the theory, enters more into detail. He assumes that in the process of agglomeration large bodies of matter impinged obliquely on the already formed mass, and so imparted to it a motion of rotation.
A consideration of the mechanical conditions of the problem will show the unsoundness of Pontecoulant's views. It is of course assumed that the forces by which this rotation is said to have been produced are identical in their character with those with which we are familiar, for the introduction of any force peculiar to that time would be equivalent to an admission of a directing power. The following propositions then seem unquestionable:—
1. The nebula must be considered as a system of particles acted on by their mutual attractions, and by no other force.
2. When two particles of matter, a and b, attract each other, it is a fundamental principle of mechanics, (commonly known as the "Third Law of Motion") that whatever amount of momentum is produced in a, an equal and opposite momentum must be produced in b. Hence if the mutual action remain undisturbed, the two particles will approach each other and finally meet. On their union, the two momenta being equal and opposite will neutralize each other, and there will be no tendency to produce motion of any kind. 3. The same law will hold good with reference to any number of particles, and therefore with reference to the supposed nebula. Every single particle will produce a certain momentum in each of the other particles, and at the same time will have impressed upon it by each of the other particles an equal and opposite momentum. Hence when all the particles are collected into a single mass, each individual momentum will be balanced by an equal and opposite one, and there can be no resultant motion.
The analogy from fluids flowing through an orifice fails, because—
1. The particles of the fluid are acted on by forces other than their mutual attractions, and in many cases affecting them unequally, e. g., friction against the sides of the containing vessel and the orifice.
2. Because the orifice is not a point, but a finite area, and consequently the particles of the fluid are acted on by forces which do not pass through the same point.
Considered then as a substitute for the action of an intelligent Creator, Laplace's theory utterly breaks down in three points, which, as they will have to be referred to hereafter, it is well to recapitulate.
1. It does not account for the origin of matter.
2. It does not account for the emergence of the force of attraction.
3. It does not give a satisfactory account for the motion of rotation.