The Riddle of the Universe at the close of the nineteenth century

by Ernst Haeckel

I.—MONISTIC COSMOGONY

The first attempt to explain the constitution and the mechanical origin of the world in a simple manner by “Newtonian laws”—that is, by mathematical and physical laws—was made by Immanuel Kant in the famous work of his youth (1755), General History of the Earth and Theory of the Heavens. Unfortunately, this distinguished and daring work remained almost unknown for ninety years; it was only disinterred in 1845 by Alexander Humboldt in the first volume of his Cosmos. In the mean time the great French mathematician, Pierre Laplace, had arrived independently at similar views to those of Kant, and he gave them a mathematical foundation in his Exposition du Système du Monde (1796). His chief work, the Mécanique Céleste, appeared a hundred years ago. The analogous features of the cosmogony of Kant and Laplace consist, as is well known, in a mechanical explanation of the movements of the planets, and the conclusion which is drawn therefrom, that all the cosmic bodies were formed originally by a condensation of rotating nebulous spheres. This “nebular hypothesis” has been much improved and supplemented since, but it is still the best of all the attempts to explain the origin of the world on monistic and mechanical lines. It has recently been strongly confirmed and enlarged by the theory that this cosmogonic process did not simply take place once, but is periodically repeated. While new cosmic bodies arise and develop out of rotating masses of nebula in some parts of the universe, in other parts old, extinct, frigid suns come into collision, and are once more reduced by the heat generated to the condition of nebulæ.

Nearly all the older and the more recent cosmogonies, including most of those which were inspired by Kant and Laplace, started from the popular idea that the world had had a beginning. Hence, according to a widespread version of the nebular hypothesis, “in the beginning” was made a vast nebula of infinitely attenuated and light material, and at a certain moment (“countless ages ago”) a movement of rotation was imparted to this mass. Given this “first beginning” of the cosmogonic movement, it is easy, on mechanical principles, to deduce and mathematically establish the further phenomena of the formation of the cosmic bodies, the separation of the planets, and so forth. This first “origin of movement” is Du Bois-Reymond’s second “world-enigma”; he regards it as transcendental. Many other scientists and philosophers are equally helpless before this difficulty; they resign themselves to the notion that we have here a primary “supernatural impetus” to the scheme of things, a “miracle.”

In our opinion, this second “world-enigma” is solved by the recognition that movement is as innate and original a property of substance as is sensation. The proof of this monistic assumption is found, first, in the law of substance, and, secondly, in the discoveries which astronomy and physics have made in the latter half of the century. By the spectral analysis of Bunsen and Kirchhoff (1860) we have found, not only that the millions of bodies, which fill the infinity of space, are of the same material as our own sun and earth, but also that they are in various stages of evolution; we have obtained by its aid information as to the movements and distances of the stars, which the telescope would never have given us. Moreover, the telescope itself has been vastly improved, and has, in alliance with photography, made a host of scientific discoveries of which no one dreamed at the beginning of the century. In particular, a closer acquaintance with comets, meteorites, star-clusters, and nebulæ has helped us to realize the great significance of the smaller bodies which are found in millions in the space between the stars.

We now know that the paths of the millions of heavenly bodies are changeable, and to some extent irregular, whereas the planetary system was formerly thought to be constant, and the rotating spheres were described as pursuing their orbits in eternal regularity. Astro-physics owes much of its triumph to the immense progress of other branches of physics, of optics, and electricity, and especially of the theory of ether. And here, again, our supreme law of substance is found to be one of the most valuable achievements of modern science. We now know that it rules unconditionally in the most distant reaches of space, just as it does in our planetary system, in the most minute particle of the earth as well as in the smallest cell of our human frame. We are, moreover, justified in concluding, if we are not logically compelled to conclude, that the persistence of matter and force has held good throughout all time as it does to-day. Through all eternity the infinite universe has been, and is, subject to the law of substance.

From this great progress of astronomy and physics, which mutually elucidate and supplement each other, we draw a series of most important conclusions with regard to the constitution and evolution of the cosmos, and the persistence and transformation of substance. Let us put them briefly in the following theses:

I. The extent of the universe is infinite and unbounded; it is empty in no part, but everywhere filled with substance.

II. The duration of the world is equally infinite and unbounded; it has no beginning and no end: it is eternity.

III. Substance is everywhere and always in uninterrupted movement and transformation: nowhere is there perfect repose and rigidity; yet the infinite quantity of matter and of eternally changing force remains constant.

IV. This universal movement of substance in space takes the form of an eternal cycle or of a periodical process of evolution.

V. The phases of this evolution consist in a periodic change of consistency, of which the first outcome is the primary division into mass and ether—the ergonomy of ponderable and imponderable matter.

VI. This division is effected by a progressive condensation of matter as the formation of countless infinitesimal “centres of condensation,” in which the inherent primitive properties of substance—feeling and inclination—are the active causes.

VII. While minute and then larger bodies are being formed by this pyknotic process in one part of space, and the intermediate ether increases its strain, the opposite process—the destruction of cosmic bodies by collision—is taking place in another quarter.

VIII. The immense quantity of heat which is generated in this mechanical process of the collision of swiftly moving bodies represents the new kinetic energy which effects the movement of the resultant nebulæ and the construction of new rotating bodies. The eternal drama begins afresh. Even our mother earth, which was formed of part of the gyrating solar system millions of ages ago, will grow cold and lifeless after the lapse of further millions, and, gradually narrowing its orbit, will fall eventually into the sun.

It seems to me that these modern discoveries as to the periodic decay and re-birth of cosmic bodies, which we owe to the most recent advance of physics and astronomy, associated with the law of substance, are especially important in giving us a clear insight into the universal cosmic process of evolution. In their light our earth shrinks into the slender proportions of a “mote in the sunbeam,” of which unnumbered millions chase each other through the vast depths of space. Our own “human nature,” which exalted itself into an image of God in its anthropistic illusion, sinks to the level of a placental mammal, which has no more value for the universe at large than the ant, the fly of a summer’s day, the microscopic infusorium, or the smallest bacillus. Humanity is but a transitory phase of the evolution of an eternal substance, a particular phenomenal form of matter and energy, the true proportion of which we soon perceive when we set it on the background of infinite space and eternal time.

Since Kant explained space and time to be merely “forms of perception”—space the form of external, time of internal, sensitivity—there has been a keen controversy, which still continues, over this important problem. A large section of modern metaphysicians have persuaded themselves that this “critical fact” possesses a great importance as the starting-point of “a purely idealist theory of knowledge,” and that, consequently, the natural opinion of the ordinary healthy mind as to the reality of time and space is swept aside. This narrow and ultra-idealist conception of time and space has become a prolific source of error. It overlooks the fact that Kant only touched one side of the problem, the subjective side, in that theory, and recognized the equal validity of its objective side. “Time and space,” he said, “have empirical reality, but transcendental ideality.” Our modern monism is quite compatible with this thesis of Kant’s, but not with the one-sided exaggeration of the subjective aspect of the problem; the latter leads logically to the absurd idealism that culminates in Berkeley’s thesis, “Bodies are but ideas; their essence is in their perception.” The thesis should be read thus: “Bodies are only ideas for my personal consciousness; their existence is just as real as that of my organs of thought, the ganglionic cells in the gray bed of my brain, which receive the impress of bodies on my sense-organs and form those ideas by association of the impressions.” It is just as easy to doubt or to deny the reality of my own consciousness as to doubt that of time and space. In the delirium of fever, in hallucinations, in dreams, and in double-consciousness, I take ideas to be true which are merely fancies. I mistake my own personality for another (vide [p. 185]); Descartes’ famous Cogito ergo sum applies no longer. On the other hand, the reality of time and space is now fully established by that expansion of our philosophy which we owe to the law of substance and to our monistic cosmogony. When we have happily got rid of the untenable idea of “empty space,” there remains as the infinite “space-filling”-medium matter, in its two forms of ether and mass. So also we find a “time-filling” event in the eternal movement, or genetic energy, which reveals itself in the uninterrupted evolution of substance, in the perpetuum mobile of the universe.

As a body which has been set in motion continues to move as long as no external agency interferes with it, the idea was conceived long ago of constructing an apparatus which should illustrate perpetual motion. The fact was overlooked that every movement meets with external impediments and gradually ceases, unless a new impetus is given to it from without and a new force is introduced to counteract the impediments. Thus, for instance, a pendulum would swing backward and forward for an eternity at the same speed if the resistance of the atmosphere and the friction at the point it hangs from did not gradually deprive it of the mechanical kinetic energy of its motion and convert it into heat. We have to furnish it with fresh mechanical energy by a spring (or, as in the pendulum-clock, by the drag of a weight). Hence it is impossible to construct a machine that would produce, without external aid, a surplus of energy by which it could keep itself going. Every attempt to make such a perpetuum mobile must necessarily fail; the discovery of the law of substance showed, in addition, the theoretical impossibility of it.

The case is different, however, when we turn to the world at large, the boundless universe that is in eternal movement. The infinite matter, which fills it objectively, is what we call space in our subjective impression of it; time is our subjective conception of its eternal movement, which is, objectively, a periodic, cyclic evolution. These two “forms of perception” teach us the infinity and eternity of the universe. That is, moreover, equal to saying that the universe itself is a perpetuum mobile. This infinite and eternal “machine of the universe” sustains itself in eternal and uninterrupted movement, because every impediment is compensated by an “equivalence of energy,” and the unlimited sum of kinetic and potential energy remains always the same. The law of the persistence of force proves also that the idea of a perpetuum mobile is just as applicable to, and as significant for, the cosmos as a whole as it is impossible for the isolated action of any part of it. Hence the theory of entropy is likewise untenable.

The able founder of the mechanical theory of heat (1850), Clausius, embodied the momentous contents of this important theory in two theses. The first runs: “The energy of the universe is constant”—that is one-half of our law of substance, the principle of energy (vide [p. 230]). The second thesis is: “The energy of the universe tends towards a maximum.” In my opinion this second assertion is just as erroneous as the first is true. In the theory of Clausius the entire energy of the universe is of two kinds, one of which (heat of the higher degree, mechanical, electrical, chemical energy, etc.) is partly convertible into work, but the other is not; the latter energy, already converted into heat and distributed in the cooler masses, is irrevocably lost as far as any further work is concerned. Clausius calls this unconsumed energy, which is no longer available for mechanical work, entropy (that is, force that is directed inward); it is continually increasing at the cost of the other half. As, therefore, the mechanical energy of the universe is daily being transformed into heat, and this cannot be reconverted into mechanical force, the sum of heat and energy in the universe must continually tend to be reduced and dissipated. All difference of temperature must ultimately disappear, and the completely latent heat must be equally distributed through one inert mass of motionless matter. All organic life and movement must cease when this maximum of entropy has been reached. That would be a real “end of the world.”

If this theory of entropy were true, we should have a “beginning” corresponding to this assumed “end” of the world—a minimum of entropy, in which the differences in temperature of the various parts of the cosmos would be at a maximum. Both ideas are quite untenable in the light of our monistic and consistent theory of the eternal cosmogenetic process; both contradict the law of substance. There is neither beginning nor end of the world. The universe is infinite, and eternally in motion; the conversion of kinetic into potential energy, and vicissim, goes on uninterruptedly; and the sum of this actual and potential energy remains constant. The second thesis of the mechanical theory of heat contradicts the first, and so must be rejected.

The representatives of the theory of entropy are quite correct as long as they confine themselves to distinct processes, in which, under certain conditions, the latent heat cannot be reconverted into work. Thus, for instance, in the steam-engine the heat can only be converted into mechanical work when it passes from a warmer body (steam) into a cooler (water); the process cannot be reversed. In the world at large, however, quite other conditions obtain—conditions which permit the reconversion of latent heat into mechanical work. For instance, in the collision of two heavenly bodies, which rush towards each other at inconceivable speed, enormous quantities of heat are liberated, while the pulverized masses are hurled and scattered about space. The eternal drama begins afresh—the rotating mass, the condensation of its parts, the formation of new meteorites, their combination into larger bodies, and so on.