Popular Science Monthly/Volume 10/April 1877/World-Creations
By C. C. MERRIMAN.
THE New-World pioneers of the sixteenth century, when they first looked on the sea-worn shores and giant forests of New England, had in reality no compelling reason for believing in the veritable old age of this new-found land. They had no "first order of proof" that the shores were not recently upheaved there for them to land upon, and with the growth of the centuries on them for the trial of the manhood that was soon to reclaim them. But I think those sturdy adventurers, if they stopped at all to consider of scientific doubts, were not long in deciding that the scene before them was conformable to the laws and processes of Nature, and therefore must have been the slow growth of time.
In like manner, the geologist, looking into the bowels of the earth, and finding here and there the remains of a tree or a saurian, presumes that they once lived and grew in the same localities, and were buried and petrified under the rock-grindings of after-ages. But he really has no absolute proof of any such thing. They may have been created in the fossil state and laid away in the strata on the same day the earth was made. But I think the scientist, knowing laws of Nature by which, with sufficiently long periods of time, all these geologic results might have been gradually brought about, is justified in believing that they too were the slow product of Nature and of time.
So we, finding that the world has certainly at some time been subjected to a heat at least sufficient to volatilize nearly every known substance, and that there are laws of Nature by which, through periods of time immensely long, the earth and the planets might have been rolled up from a gaseous nebula and bowled off in their mighty revolutions, have just as much right to say that it was so, as we have to say that the American forests grew, or that the Triassic beds were deposited.
Geology has proved that the earth, up to the primary rocks, was once a molten mass. The crystalline structure of the unstratified rocks compels to this conclusion; for minerals insoluble in water can only become crystallized in large masses by cooling from a state of fusion. If, then, the earth was once an incandescent globe of melted rocks—for everything above the granite beds must then have been in a state of vapor—it is not unreasonable to suppose that it may have existed prior to that time in a still more highly-heated condition—even volatilized, and diffused through space as rare and attenuated gases; for this is the condition which all matter assumes under sufficient degrees of heat. In fact, we must either suppose that the earth was created as a fiery liquid globe, for which we have no warrant, or we must follow back to the time when its vapors were scattered in space, unreflecting and impenetrable to light—when the earth was "without form and void, and darkness was upon the face of the deep."
Let us start, then, with that condition of things which it is now very generally conceded must once have existed—the diffusion of matter in a nebulous form throughout all space. Calculations easily made show that the nebula must have been of extreme tenuity—such that the few grains taken up on the point of a knife-blade must have been expanded to fill several cubic miles. A heat so powerful—for we know of no other force which could thus hold apart the atoms of matter—would doubtless be sufficient to resolve every known substance into its simplest elementary constituents, perhaps into a very few primordial elements; for chemists are far from being satisfied that they have arrived at the ultimate forms of matter in their list of sixty-five elements. But, however this may be, we know that the atoms, whatever they were, must have been held so far apart that no combinations could possibly have existed. Neither were they drawn more in one direction than another by their mutual attractions, for they are equally diffused through all space. Therefore, heat, the great repulsive force, has overcome all the forces of attraction—cohesion, chemical affinity, and gravity.
Between such mighty contending forces we can hardly imagine a state of perfect equilibrium. Immense currents and world-wide surgings must be the long-continued if not the permanent condition of this state of things, especially if we conceive it brought about by natural causes. More condensed portions of nebulous matter would be formed—sections of space larger or smaller, in which the forces of attraction counterbalanced those of repulsion. Each such section would then have its centre of gravity, around which all the currents within its influence, by the law of the composition of forces, must eventually unite in one. This one flowing ever around and slowly toward the centre, like a ball rolling down an inclined plane, goes faster and faster, until the centrifugal overbalances the centripetal force, and it separates completely from the inner mass. Thus a ring is formed revolving around a central nucleus. Unless perfectly equiposed, and of homogeneous material, this ring would sooner or later break up into a number of globes, which, by the superior attraction of the largest, would ultimately coalesce into one. This globe, still contracting, and the nucleus also contracting, would throw off satellites and other planets, all revolving in nearly the same plane and in the same direction. All these processes are in perfect accord, not only with the conditions of the heavenly bodies so far as discovered, but with known natural laws. Many of them have been successfully imitated on a small scale in experimental illustrations, as in the rapid rotation of oil suspended in water.
We have here given only the simple outlines of the famous "nebular hypothesis" of Laplace. In later years, the discovery of nebulae in the heavens in all stages of world-formation, the evidence of the spectroscope on the unformed material of the universe, and other proofs, have compelled for the proscribed hypothesis a recognized place in science. We do not stop to consider these subjects more fully, because it is the purpose of this article to inquire chiefly concerning the forces that would be engaged in such a process of evolution; and, firstly, how from the preponderance of the repellent forces holding matter in universal diffusion there came the final mastery of the aggregating forces ever concentrating, combining, and working up the materials of the universe.
The first of the operations which have come to our notice in the progress of this evolution is the condensation of the gases. This, according to all experience, ought to evolve heat; but, instead, we find only that the flow of the currents—the motion of the masses—is proportionately increased. Is there a connection of cause and effect between these phenomena?
All motion that we are familiar with requires the expenditure of heat. The combustion of coal supplies motion to the steam-engine. The evaporation of water by the sun's heat causes the rain-clouds and the mill-streams. The oxidation of certain elements in the food we eat is the combustion which supplies our bodies with powers of motion. Recent discoveries have shown not only that motion is heat transformed, but that to produce a certain quantity of motion an invariable certain quantity of heat is required.
Again, the cessation of motion evolves heat. It is well known that by skillful blows with the hammer a cold iron bar can be made red-hot. Two wheels revolving in opposite directions, and touching at the circumference, become highly heated; and factories have been warmed solely by this transfer of motion into heat. Friction is but another name for the arresting of motion, and, as we well know, always produces heat. There is also here the same equivalence as in the other case. The stoppage of motion evolves just the amount of heat that was required to produce that motion.
The greatest triumph of modern science is the splendid induction that all the forces are correlative and indestructible. Not an impulse of motion, of light or heat, or any force, is ever lost. It may be communicated from one body to another, or transmuted into some other form of force, or become for a time latent or imperceptible; but it always exists, and is reclaimable back again into the same, in mode and quantity, from which it started.
The grandest exemplification of these truths will be found in what we are now considering, the origin of the celestial revolutions. The condensation of gases gives out heat in direct proportion to the contraction of volume. The attraction of gravitation, not only between masses but between all the particles of matter, increases in the inverse square of the diminishing distance. From these two principles it can be mathematically shown that in the contraction of each great world-nebula heat would be set free in the precise proportion of the increase of atomic attraction; or, in other words, that it would take the exact amount of heat-force that had been released, to separate the atoms again to their original distance apart. But in this instance the heat-force is not really set free; it is transformed into the motion of the mass from which it came. Instead of holding the atoms apart, the work which it now has to do under the form of motion is, to prevent the masses from falling into each other. It is this motion—the celestial revolutions—which keeps the worlds apart, and allows each to work out its destiny under the aggregating forces, without interference from any other. Up to a certain point of condensation, which is previous to the radiation of heat into space, if this motion were at any time stopped, it would be resolved into just the amount of heat necessary to expand the mass again to its original dimensions.
The attractive forces, gravity, chemical affinity, and cohesion, whether these forces are many or one, are inherent properties of matter. Every atom has its definite capacity of attraction, which may be exercised or not according to circumstances. For it is evident that an attracting body may be at the same time drawing toward itself a million other like bodies, or none at all, without change of its power of attraction. In like manner the magnet has a definite lifting power whether it is actually holding up a weight or not. If this attribute of matter is not operative, or but partially so, it is because heat, or motion, or some repellent force, is holding the atoms or the masses at a distance from each other, and thus opposing the exercise of it. The sum, however, of the attracting power belonging to the world of matter is as fixed as the quantity of matter itself. And I think it is in the highest degree probable that there is in the universe precisely enough repulsive force or heat to overcome all this inherent power of attraction. When all motion of the masses and of the atoms is resolved into repulsive energy, and brought to bear on the elements of matter, I imagine that they must completely fill the bounds or the infinity of space. Then, if there were perfect equilibrium or rest, no further changes or effects could ever be manifested. Such a condition, however, could probably never result from natural causes, for the time necessary to the perfect balance of the forces must be as infinite as the space through which they extend, and to "set bounds to space" has puzzled philosophy from a very ancient date. If, on the other hand, the universe of matter was created in a state of absolute rest, we have the further and necessary provision that the Spirit of God moved on the face of his creation, and thus unbalanced the forces. But the equilibrium once broken, in whatever manner, from that moment evolution must inevitably proceed. For, let there be an overbalancing of the aggregating force in ever so little or much, an equivalent of the opposing force must thereafter find some other work to do, and the field is effectually given up to the mighty agency that combines, and constructs, and brings order out of chaos.
So long and in proportion as the forming worlds continue to contract their dimensions, the rotations and revolutions increase in their velocity. Thus in the rapid and ever-speeding movements of the heavenly bodies there is stored up the ever-increasing reserve of heat that is liberated from the great contest with gravity. But in the progress of concentration there comes a time when the atoms of matter have approached each other sufficiently near for other forces of attraction, equally correlative of heat, to come into play—chemical affinity between molecules of unlike nature, and cohesion between those of like kind. Under the latter term are included all the changes of state which are the result of cooling. By these attractions heat is set free in such abundance and under such conditions that it cannot be stored away in the motion of the masses. It is then, probably for the first time, that heat becomes a wave-force, and is radiated into space as light and radiant heat—not, however, lost, for that is impossible, but moving ever onward and outward to the day and the place of its final reclamation.
Our own solar system has already progressed far in this stage of aggregation. All the planets and satellites have become crusted over, and have ceased almost entirely to radiate heat. But the sun, the great central body, the one which should last of all become cold, is still in active combustion or chemical combination. Immense quantities of light and heat are still radiating from its surface—so immense that the little fraction which our earth catches as it flies through space gives us all the motion, and life, and beauty, which we enjoy. But the sun is not even now the glowing orb that once it was, as the rock-records of our globe testify. Its bright radiance is slowly but surely fading. Those huge, black incrustations, often twice as large as the whole surface of the earth, that float awhile on its photosphere, and then are suddenly broken up—they were not always there. And, if they have grown upon it, the uncomfortable conviction arises that they will continue to grow and darken more and more its life-giving face. Old age is certainly being written on the solar brow. It may be millions of years hence—for time is not one of the economies of Nature—but the period will surely come when light and heat will all have departed from the sun, as they once ceased to be radiated from the earth and the planets and the numerous stars that have gone out within the records of astronomy. A pall of darkness will gradually overspread the universe as one by one the stars of the firmament shall fade away and sink into gloomy, lifeless sleep. A day in the mighty calendar of creation has passed, and a night has followed, cold and dark as the tomb of expiring Nature.
But is there no awakening, no morrow to this night of the universe? Is the contest over, and never to be renewed? For answer, let us seek out in this case, as we did once before, the condition and movements of the great contending forces. Those of attraction have now in each world expended their utmost possible energy, and are holding all the forms of matter combined and compacted in a cold and rigid embrace. The forces of repulsion have entirely abandoned the contest, and are either vibrating through the unknown realms of space, or are locked up in the swift and complicated motions of the heavenly bodies. It is probable that by far the greater part of the repulsive forces thus exists in the form of motion. It has been estimated, no doubt with a near approximation to truth, that, if by any means the earth could be suddenly arrested in its rapid course, its mass would thereby be raised to the enormous temperature of 23,360° Fahr.—a heat sufficient to vaporize and dissipate every known substance. If then, as would be the case, it should fall into the sun, this heat would be increased by the fall four-hundred-fold. Now, it makes no difference in the aggregate evolution of heat whether this cessation of motion is sudden or gradual; and if we can find in Nature any agencies tending to retard the revolutions of the planetary bodies, they must inevitably sooner or later fall into the sun. In such a case it can hardly be doubted that we have found a cause sufficient to produce again the disintegration and diffusion of matter.
The wave-theory of light and radiant heat presupposes the existence of an ethereal medium pervading all space. It must be a medium of material atoms held in equipoise by a balance of forces, for it is evident there could be no wave-motion unless there was something to move, and something, too, having the attributes of matter in a state of extreme mobility or fluidity. There is no other conceivable way by which light could reach us from the sun and stars except through this all-pervading form of matter. And if there is a material medium, of whatsoever exceeding tenuity it may be, still it must pre sent something of resistance to everything passing through it. It resists the passage of light eight minutes in 90,000,000 miles, thus proving its materiality by its resistance to force, which is one of the definitions of matter. If one could conceive of any force passing through an absolute vacuum, it could only be conceived of as passing instantaneously—there is absolutely nothing to detain it. Again, heat and its allied forces are only effects, and the subject is and can be only matter. There is no physical truth better established than that the forces can exist only where matter is in some form. It is not essential that this form of matter be subject to the ordinary laws of gravitation. The probability is, that it differs entirely from anything that we have experience of. It would seem that the atoms composing the ether of space, instead of attracting each other like those of ordinary matter, must repel each other. At least this supposition would account for what there is remarkable in connection with the ethereal medium. But, whatever theories we may adopt in regard to it, this is certainly true, that the revolutions of the heavenly bodies must be continually opening passages through it, and that a certain part of the force of those revolutions must be expended in pushing it aside. The centrifugal force is thus lessened, and the bodies are drawn nearer to the sun. In consequence, the periods of their revolutions are shortened. This has not as yet become noticeable in the case of the planets, from the fact that the slow contraction of their bulk by the loss of internal heat through volcanoes, thermal springs, and other sources, has the contrary effect of increasing the velocity of revolution, and thus counterbalancing the retardation of friction. The fact that the two effects are thus nearly counterbalanced proves the retardation, for otherwise we know that the acceleration would be observable. In the case, however, of the light cometary bodies, it has been shown that they suffer a very considerable retardation in their passage through space. Encke's comet formerly came regularly back into the field of the earth's orbit once in every three years, but with a period shortened six hours each time. The whole planetary regions seem to be filled with collections of matter—star-dust and meteorites. They are all revolving about the sun in eccentric orbits, and are doubtless slowly circling toward it. The zodiacal light is supposed to be only an immense aggregation of this material. Thus the thickening stratum as these strange bodies draw near to the sun shows that they are all slowly gathering to that great centre of attraction.
The evident effect of the fall of any of the planets into the sun would be the diffusion of highly-heated vapors far out into the spaces that surround it—probably far enough to reach the next outlying planet, and thereby to increase its retardation and hasten its fall into the mighty caldron. So one by one the planets dissolve and their elements fill the void of space. The expanding gases catch up the waves of radiant heat that have long been wandering from planets and suns; and the nebula is again seething and surging with its mighty contending forces. Sun-system reaches out to sun-system, and star-galaxy mingles with star-galaxy, till through all the abysmal depths matter is again "without form and void, and darkness is upon the face of the deep." Chaos has returned once more, again to be breathed upon by the Omnipotent Spirit that reforms and recreates.