The Unseen World, and Other Essays Page 3

  The ether, therefore, is unlike any of the forms of matter which we can weigh and measure. In some respects it resembles a fluid, in some respects a solid. It is both hard and elastic to an almost inconceivable degree. It fills all material bodies like a sea in which the atoms of the material bodies are as islands, and it occupies the whole of what we call empty space. It is so sensitive that a disturbance in any part of it causes a "tremour which is felt on the surface of countless worlds." Our old experiences of matter give us no account of any substance like this; yet the undulatory theory of light obliges us to admit such a substance, and that theory is as well established as the theory of gravitation. Obviously we have here an enlargement of our experience of matter. The analysis of the phenomena of light and radiant heat has brought us into mental relations with matter in a different state from any in which we previously knew it. For the supposition that the ether may be something essentially different from matter is contradicted by all the terms we have used in describing it. Strange and contradictory as its properties may seem, are they any more strange than the properties of a gas would seem if we were for the first time to discover a gas after heretofore knowing nothing but solids and liquids? I think not; and the conclusion implied by our authors seems to me eminently probable, that in the so-called ether we have simply a state of matter more primitive than what we know as the gaseous state. Indeed, the conceptions of matter now current, and inherited from barbarous ages, are likely enough to be crude in the extreme. It is not strange that the study of such subtle agencies as heat and light should oblige us to modify them; and it will not be strange if the study of electricity should entail still further revision of our ideas.

  We are now brought to one of the profoundest speculations of modern times, the vortex-atom theory of Helmholtz and Thomson, in which the evolution of ordinary matter from ether is plainly indicated. The reader first needs to know what vortex-motion is; and this has been so beautifully explained by Professor Clifford, that I quote his description entire: "Imagine a ring of india-rubber, made by joining together the ends of a cylindrical piece (like a lead-pencil before it is cut), to be put upon a round stick which it will just fit with a little stretching. Let the stick be now pulled through the ring while the latter is kept in its place by being pulled the other way on the outside. The india-rubber has then what is called vortex-motion. Before the ends were joined together, while it was straight, it might have been made to turn around without changing position, by rolling it between the hands. Just the same motion of rotation it has on the stick, only that the ends are now joined together. All the inside surface of the ring is going one way, namely, the way the stick is pulled; and all the outside is going the other way. Such a vortex-ring is made by the smoker who purses his lips into a round hole and sends out a puff of smoke. The outside of the ring is kept back by the friction of his lips while the inside is going forwards; thus a rotation is set up all round the smoke- ring as it travels out into the air." In these cases, and in others as we commonly find it, vortex-motion owes its origin to friction and is after a while brought to an end by friction. But in 1858 the equations of motion of an incompressible frictionless fluid were first successfully solved by Helmholtz, and among other things he proved that, though vortex-motion could not be originated in such a fluid, yet supposing it once to exist, it would exist to all eternity and could not be diminished by any mechanical action whatever. A vortex-ring, for example, in such a fluid, would forever preserve its own rotation, and would thus forever retain its peculiar individuality, being, as it were, marked off from its neighbour vortex-rings. Upon this mechanical truth Sir William Thomson based his wonderfully suggestive theory of the constitution of matter. That which is permanent or indestructible in matter is the ultimate homogeneous atom; and this is probably all that is permanent, since chemists now almost unanimously hold that so-called elementary molecules are not really simple, but owe their sensible differences to the various groupings of an ultimate atom which is alike for all. Relatively to our powers of comprehension the atom endures eternally; that is, it retains forever unalterable its definite mass and its definite rate of vibration. Now this is just what a vortex-ring would do in an incompressible frictionless fluid. Thus the startling question is suggested, Why may not the ultimate atoms of matter be vortex- rings forever existing in such a frictionless fluid filling the whole of space? Such a hypothesis is not less brilliant than Huyghens's conjectural identification of light with undulatory motion; and it is moreover a legitimate hypothesis, since it can be brought to the test of verification. Sir William Thomson has shown that it explains a great many of the physical properties of matter: it remains to be seen whether it can explain them all.

  Of course the ether which conveys thermal and luminous undulations is not the frictionless fluid postulated by Sir William Thomson. The most conspicuous property of the ether is its enormous elasticity, a property which we should not find in a frictionless fluid. "To account for such elasticity," says Professor Clifford (whose exposition of the subject is still more lucid than that of our authors), "it has to be supposed that even where there are no material molecules the universal fluid is full of vortex-motion, but that the vortices are smaller and more closely packed than those of [ordinary] matter, forming altogether a more finely grained structure. So that the difference between matter and ether is reduced to a mere difference in the size and arrangement of the component vortex-rings. Now, whatever may turn out to be the ultimate nature of the ether and of molecules, we know that to some extent at least they obey the same dynamic laws, and that they act upon one another in accordance with these laws. Until, therefore, it is absolutely disproved, it must remain the simplest and most probable assumption that they are finally made of the same stuff, that the material molecule is some kind of knot or coagulation of ether."[5]

  Another interesting consequence of Sir William Thomson's pregnant hypothesis is that the absolute hardness which has been attributed to material atoms from the time of Lucretius downward may be dispensed with. Somewhat in the same way that a loosely suspended chain becomes rigid with rapid rotation, the hardness and elasticity of the vortex-atom are explained as due to the swift rotary motion of a soft and yielding fluid. So that the vortex-atom is really indivisible, not by reason of its hardness or solidity, but by reason of the indestructibleness of its motion.

  Supposing, now, that we adopt provisionally the vortex theory,--the great power of which is well shown by the consideration just mentioned,--we must not forget that it is absolutely essential to the indestructibleness of the material atom that the universal fluid in which it has an existence as a vortex-ring should be entirely destitute of friction. Once admit even the most infinitesimal amount of friction, while retaining the conception of vortex-motion in a universal fluid, and the whole case is so far altered that the material atom can no longer be regarded as absolutely indestructible, but only as indefinitely enduring. It may have been generated, in bygone eternity, by a natural process of evolution, and in future eternity may come to an end. Relatively to our powers of comprehension the practical difference is perhaps not great. Scientifically speaking, Helmholtz and Thomson are as well entitled to reason upon the assumption of a perfectly frictionless fluid as geometers in general are entitled to assume perfect lines without breadth and perfect surfaces without thickness. Perfect lines and surfaces do not exist within the region of our experience; yet the conclusions of geometry are none the less true ideally, though in any particular concrete instance they are only approximately realized. Just so with the conception of a frictionless fluid. So far as experience goes, such a thing has no more real existence than a line without breadth; and hence an atomic theory based upon such an assumption may be as true ideally as any of the theorems of Euclid, but it can give only an approximatively true account of the actual universe. These considerations do not at all affect the scientific value of the theory; but they will modify the tenour of such transcendental inferences as may be drawn from it regardi
ng, the probable origin and destiny of the universe.

  The conclusions reached in the first part of this paper, while we were dealing only with gross visible matter, may have seemed bold enough; but they are far surpassed by the inference which our authors draw from the vortex theory as they interpret it. Our authors exhibit various reasons, more or less sound, for attributing to the primordial fluid some slight amount of friction; and in support of this view they adduce Le Sage's explanation of gravitation as a differential result of pressure, and Struve's theory of the partial absorption of light-rays by the ether,--questions with which our present purpose does not require us to meddle. Apart from such questions it is every way probable that the primary assumption of Helmholtz and Thomson is only an approximation to the truth. But if we accredit the primordial fluid with even an infinitesimal amount of friction, then we are required to conceive of the visible universe as developed from the invisible and as destined to return into the invisible. The vortex-atom, produced by infinitesimal friction operating through wellnigh infinite time, is to be ultimately abolished by the agency which produced it. In the words of our authors, "If the visible universe be developed from an invisible which is not a perfect fluid, then the argument deduced by Sir William Thomson in favour of the eternity of ordinary matter disappears, since this eternity depends upon the perfect fluidity of the invisible. In fine, if we suppose the material universe to be composed of a series of vortex-rings developed from an invisible universe which is not a perfect fluid, it will be ephemeral, just as the smoke-ring which we develop from air, or that which we develop from water, is ephemeral, the only difference being in duration, these lasting only for a few seconds, and the others it may be for billions of years." Thus, as our authors suppose that "the available energy of the visible universe will ultimately be appropriated by the invisible," they go on to imagine, "at least as a possibility, that the separate existence of the visible universe will share the same fate, so that we shall have no huge, useless, inert mass existing in after ages to remind the passer-by of a form of energy and a species of matter that is long since out of date and functionally effete. Why should not the universe bury its dead out of sight?"

  In one respect perhaps no more stupendous subject of contemplation than this has ever been offered to the mind of man. In comparison with the length of time thus required to efface the tiny individual atom, the entire cosmical career of our solar system, or even that of the whole starry galaxy, shrinks into utter nothingness. Whether we shall adopt the conclusion suggested must depend on the extent of our speculative audacity. We have seen wherein its probability consists, but in reasoning upon such a scale we may fitly be cautious and modest in accepting inferences, and our authors, we may be sure, would be the first to recommend such modesty and caution. Even at the dimensions to which our theorizing has here grown, we may for instance discern the possible alternative of a simultaneous or rhythmically successive generation and destruction of vortex- atoms which would go far to modify the conclusion just suggested. But here we must pause for a moment, reserving for a second paper the weightier thoughts as to futurity which our authors have sought to enwrap in these sublime physical speculations.

  PART SECOND.

  UP to this point, however remote from ordinary every-day thoughts may be the region of speculation which we have been called upon to traverse, we have still kept within the limits of legitimate scientific hypothesis. Though we have ventured for a goodly distance into the unknown, we have not yet been required to abandon our base of operations in the known. Of the views presented in the preceding paper, some are wellnigh certainly established, some are probable, some have a sort of plausibility, others--to which we have refrained from giving assent--may possibly be true; but none are irretrievably beyond the jurisdiction of scientific tests. No suggestion has so far been broached which a very little further increase of our scientific knowledge may not show to be either eminently probable or eminently improbable. We have kept pretty clear of mere subjective guesses, such as men may wrangle about forever without coming to any conclusion. The theory of the nebular origin of our planetary system has come to command the assent of all persons qualified to appreciate the evidence on which it is based; and the more immediate conclusions which we have drawn from that theory are only such as are commonly drawn by astronomers and physicists. The doctrine of an intermolecular and interstellar ether is wrapped up in the well-established undulatory theory of light. Such is by no means the case with Sir William Thomson's vortex-atom theory, which to-day is in somewhat the same condition as the undulatory theory of Huyghens two centuries ago. This, however, is none the less a hypothesis truly scientific in conception, and in the speculations to which it leads us we are still sure of dealing with views that admit at least of definite expression and treatment. In other words, though our study of the visible universe has led us to the recognition of a kind of unseen world underlying the world of things that are seen, yet concerning the economy of this unseen world we have not been led to entertain any hypothesis that has not its possible justification in our experiences of visible phenomena.

  We are now called upon, following in the wake of our esteemed authors, to venture on a different sort of exploration, in which we must cut loose altogether from our moorings in the world of which we have definite experience. We are invited to entertain suggestions concerning the peculiar economy of the invisible portion of the universe which we have no means of subjecting to any sort of test of probability, either experimental or deductive. These suggestions are, therefore, not to be regarded as properly scientific; but, with this word of caution, we may proceed to show what they are.

  Compared with the life and death of cosmical systems which we have heretofore contemplated, the life and death of individuals of the human race may perhaps seem a small matter; yet because we are ourselves the men who live and die, the small event is of vastly greater interest to us than the grand series of events of which it is part and parcel. It is natural that we should be more interested in the ultimate fate of humanity than in the fate of a world which is of no account to us save as our present dwelling-place. Whether the human soul is to come to an end or not is to us a more important question than whether the visible universe, with its matter and energy, is to be absorbed in an invisible ether. It is indeed only because we are interested in the former question that we are so curious about the latter. If we could dissociate ourselves from the material universe, our habitat, we should probably speculate much less about its past and future. We care very little what becomes of the black ball of the earth, after all life has vanished from its surface; or, if we care at all about it, it is only because our thoughts about the career of the earth are necessarily mixed up with our thoughts about life. Hence in considering the probable ultimate destiny of the physical universe, our innermost purpose must be to know what is to become of all this rich and wonderful life of which the physical universe is the theatre. Has it all been developed, apparently at almost infinite waste of effort, only to be abolished again before it has attained to completeness, or does it contain or shelter some indestructible element which having drawn sustenance for a while from the senseless turmoil of physical phenomena shall still survive their final decay? This question is closely connected with the time-honoured question of the meaning, purpose, or tendency of the world. In the career of the world is life an end, or a means toward an end, or only an incidental phenomenon in which we can discover no meaning? Contemporary theologians seem generally to believe that one necessary result of modern scientific inquiry must be the destruction of the belief in immortal life, since against every thoroughgoing expounder of scientific knowledge they seek to hurl the charge of "materialism." Their doubts, however, are not shared by our authors, thorough men of science as they are, though their mode of dealing with the question may not be such as we can well adopt. While upholding the doctrine of evolution, and all the so-called "materialistic" views of modern science, they not only regard the hypothesis of a future
life as admissible, but they even go so far as to propound a physical theory as to the nature of existence after death. Let us see what this physical theory is.

  As far as the visible universe is concerned, we do not find in it any evidence of immortality or of permanence of any sort, unless it be in the sum of potential and kinetic energies on the persistency of which depends our principle of continuity. In ordinary language "the stars in their courses" serve as symbols of permanence, yet we have found reason to regard them as but temporary phenomena. So, in the language of our authors, "if we take the individual man, we find that he lives his short tale of years, and that then the visible machinery which connects him with the past, as well as that which enables him to act in the present, falls into ruin and is brought to an end. If any germ or potentiality remains, it is certainly not connected with the visible order of things." In like manner our race is pretty sure to come to an end long before the destruction of the planet from which it now gets its sustenance. And in our authors opinion even the universe will by and by become "old and effete, no less truly than the individual: it is a glorious garment this visible universe, but not an immortal one; we must look elsewhere if we are to be clothed with immortality as with a garment."