Part III, Chapter IV of "Uranie"
THE CENTER OF GRAVITY OF THE UNIVERSE -- FORCE.
THE recollection of Uranie and the celestial journey on which she had taken me, and of the truths she had helped me to divine, the history of Spero and his researches on the system of the Universe, his apparition and his account of another world -- all these things occupied my thoughts, and kept constantly before me those problems which we have as yet only partially succeeded in solving. I felt that I had gradually attained to a clearer perception of the truth, and that the visible universe is indeed but an appearance under which we must look for the reality.
Everything is but an illusion of the senses. The Earth is not what it appears to us, Nature is not what we think it to be.
In the physical universe itself, where is the center of gravity, the point at which the material creation is in equipoise?
The plain and direct impression we receive from the observation of nature, is that we dwell upon the surface of a solid and stable globe placed in the center of the Universe. Long centuries of study, and a boldness in scientific speculation bordering on rashness, were necessary to free the minds of humanity from this natural impression, and enable them to comprehend that the earth, on which we live, hangs without support in space, and revolves with velocity around its own axis and around the Sun. But for the ages anterior to scientific investigation, for the primitive peoples, and for three-quarters of the human race today, our feet rest on the solid earth, fixed immovably beneath the heavens, its formations laid in eternity.
From the hour, however, in which it was settled beyond doubt that it is the Sun which rises and sets every day, and that the stars and the constellations revolve around the Earth, men were compelled to accept as an incontrovertible truth the fact that there is underneath the Earth the space necessary for the stars to move, from their rising to their setting. This first step in knowledge was of paramount importance. The admission that the Earth moves in space was the first great triumph of astronomers. It was not only the first, but the most diffficult step. To sweep away the foundations of the Universe! Such a thought could never have occurred to any mind were it not for the results of astronomical research, conducted under favoring conditions. Under a perpetually cloudy sky the old idea would have remained fixed to terrestrial soil like the oyster to its bed.
The Earth once proved to move in space, the first step was taken. Before this revolution in astronomic knowledge, the philosophic importance of which is equal to its scientific value, every imaginable form had been given to our sublunary abode. At first the Earth had been regarded as an island emerging from the bosom of a shoreless sea, and resting on foundations laid in the depths of infinite space. Then it was believed that the earth, with its oceans and seas, had the form of a flat, circular disk, on whose edge rested the vault of the firmament. Later it was successively supposed to be a cube, a cylinder, a polyhedron. The progress made in nautical knowledge, however, at last established the fact that the Earth was a sphere, and when it was proved, beyond question, to be surrounded on all sides by space, its spherical form was accepted as the natural corollary of the earth's motion, and of the revolution of the heavenly bodies around a globe supposed to be central.
The terrestrial globe once known to be surrounded on all sides by space, to put it in motion was not difficult. Previous to this time, while the sky was regarded as a vast dome, covering a plain of limitless extent, it would have seemed as absurd to suppose that the Earth moved, as it would have been impossible to prove the fact of its doing so. But from the moment in which we conceive it as a globe, revolving among the heavenly bodies, the idea that this globe might revolve on itself, and thus save the entire Universe the trouble of performing that daily operation, would naturally occur to the minds of the thinkers. And in fact we find hints of this theory of the diurnal rotation of the Earth among the writings of the older civilizations -- the Greeks, the Egyptians, the Indians, and others. It is only necessary to read a few chapters of Ptolemy, Plutarch or Surya-Siddhanta to be convinced of this.
But the new hypothesis, although the way had been prepared for it by the former one, was no less daring and opposed to the innate feeling of mankind of the reality of the apparent world. The thinkers of humanity were compelled to wait until the sixteenth century of our era, or rather until the seventeenth century, to know the true position of our planet in our universe, and to know by incontrovertible proof that it moves with a two-fold motion, around itself daily, and annually around the sun.
Dating only from this epoch, the epoch of Copernicus, Galileo, Keppler and Newton, has Astronomy existed as a science.
This, however, was only a beginning, for the great reviver of the system of the world had no knowledge of the other movements of the earth, nor of the distances of the stars. It was not until our own age that the distances of the planets were computed, and it is only in our own day that astronomical discoveries have afforded us the necessary data to enable us to form some conception of the forces which maintain creation in equilibrium.
The old idea that the earth rested on foundations extending down into immensity, could not, it is plain, be altogether satisfactory to earnest minds seeking for a knowledge of the truth. It is absolutely impossible for us to form a conception of a material column of the same diameter as that of the earth, which should reach down into infinite space, just as it would be impossible to conceive of the existence of a stick that should have but one end. No matter how far our thought may descend toward the base of this material pillar, there must come a point where the end of it is to be found. Astronomy had sought to obviate the difficulty by materializing the celestial sphere, and placing the world within it, occupying its lower part. But, on the one hand, the movement of the stars thus became difficult to prove; and on the other, the material universe, shut up in this immense globe of crystal, was itself supported by nothing, since space must extend around it on all sides, above as well as below. The first thing for men of science to do was to free their minds from the vulgar idea of weight.
Floating in space, like a child's balloon floating in the air, but still more helplessly, since the balloon is carried along by atmospheric currents, while the spheres move in the void, the Earth is the sport of the invisible cosmic forces which she obeys -- a veritable soap bubble blown about by every breath. We can easily convince ourselves of this if we take a glance at her eleven principal movements. Perhaps they will help us to find that center of gravity, which it is the ambition of astronomers to discover.
Moving around the sun at a distance from it of ninety-five millions of miles, and performing, at this distance, her annual revolution around that body, she moves as a consequence with a velocity of 19,229,000 miles a day, or eight hundred and four thousand miles an hour, or eighty-nine thousand feet a second. This velocity is eleven times greater than that of a lightning express, moving at a rate of 60 miles an hour. It is a ball moving with a velocity seventy-five times greater than that of a shell -- moving ceaselessly on without ever reaching its goal. In three hundred and sixty-five days, six hours, nine minutes and ten seconds the terrestrial ball has returned to the same point in its orbit, relatively to the sun, from which she started, to begin anew her course. The sun, on his side, moves on in space, following obliquely the annual movement of the Earth, directing his course toward the constellation Hercules. From this it follows that, instead of describing a circle, the Earth describes a spiral, and, since its creation, has never passed twice through the same point in space. To her motion of annual revolution around the Sun, then, is added a second attraction, that of the Sun himself, who draws her, together with the whole solar system, in an oblique direction toward the constellation Hercules.
Meantime, our little globe revolves upon its axis in twenty-four hours, producing the succession of days and nights. Thus we havea third motion, her daily revolution.
She does not revolve on her axis vertically, as a humming top spins around on a table, but inclined, as every one knows, at an angle of 27° 27'. And this inclintion is not always the same; it varies from year to year, from century to century, oscillating slowly for secular periods. Here we have a fourth species of motion.
The orbit in which the Earth moves annually around the Sun, is not circular, but elliptical. This ellipse itself varies from year to year, from century to century; at times it is nearly circular; at times markedly eccentric. It is like an elastic hoop more or less pulled out of shape. This is a fifth variety of the motions of the Earth.
But this ellipse is not a fixed path in space, but turns around on its own axis in a period of twenty-one thousand years. The perihelion, which at the beginning of our era was at 65 degrees of longitude, reckoning from the spring equinox, is now at 101 degrees. This alteration, every hundred years, of the line of the apsides, makes a sixth complication in the movements of our planet.
Here is a seventh. We said just now that our globe moves, not vertically, but with an inclination on her axis, and every one knows that the imaginary prolongation of this line would end at the North star. But this axis itself is not fixed, it makes a revolution in 25,765 years, preserving an inclination of from 22 to 24 degrees; so that its prolongation on the celestial sphere describes, around the pole of the ecliptic, a circle of from 44 to 48 degrees in diameter, according to the periods. It is owing to this alteration of the pole that Vega in twelve thousand years, will be the north star, as she was fourteen thousand years ago. Seventh species of motion.
An eighth motion, due to the action of the moon on the equatorial regions of the Earth, that of nutation, causes the pole of the equator to describe a small ellipse, in 18 years and 8 months.
A ninth motion, due also to lunar attraction, ceaselessly changes the position of the center of gravity of the globe, and the position of the Earth in space; when the moon is in front of us she accelerates the motion of our globe, when she is behind she retards it, acting thus as a rein -- a monthly complication in the movements of the Earth, added to all the preceding ones.
When the Earth passes between the Sun and Jupiter, the attraction of the later, notwithstanding his distance of 465 millions of miles, makes her deviate 2' 10" beyond her orbit. The attraction of Venus makes her deviate l' 25" on the other side. Saturn and Mars exert their attraction also, but more feebly. Here are external perturbations which make a second kind of influence to add to the other movements of our celestial boat.
The united mass of the planets being about the seven hundredth part of the mass of the Sun, the center of gravity around which the Earth annually revolves is never at the center of the Sun itself, but distant from it and often outside its circumference. But, speaking with exactness, the Earth does not revolve around the Sun, but these two bodies, the Sun and the Earth, revolve around their common center of gravity. The center of the annual motion of our planet changes its place constantly then, and we may add this eleventh complication to the preceding ones.
We might even add to these several others; but this will suffice to give an idea of the extreme lightness with which our island floats in the atmosphere, subject, as we see, to all the fluctuations of the celestial influences. Mathematical investigations go much deeper than this brief statement; they have discovered in the moon alone, that seems to move so tranquilly around the earth, more than sixty distinct causes of different motions.
The expression, then, is not exaggerated: Our planet is the sport of the cosmic forces that guide it in the fields of space, and the same thing is the case with all the worlds and everything that exists in the Universe. Matter obeys blindly the law of attraction.
Where then is the center of gravity which it is our ambition to discover?
In point of fact our planet, formerly supposed to be beneath the heavens, is sustained in space at a certain distance from the Sun, whose attraction causes her to revolve around him with a velocity corresponding to this distance. This velocity, caused by the mass of the Sun, sustains our planet at the same mean distance from the sun -- a lesser velocity would cause the force of gravity to exert too powerful an influence on the Earth and draw her into the Sun. A greater velocity, on the other hand, would gradually and ceaselessly remove our planet from the source of heat and light that animates it. But the velocity resulting from the amount of attraction exerted is sufficient to keep our wandering abode in permanent stability. In the same way the Moon is sustained in space by the force of gravity of the Earth, which causes it to revolve around her with the requisite velocity to maintain her constantly at the same mean distance. The Earth and the Moon thus form a pair of planets sustaining themselves in perpetual equipoise under the sovereign sway of solar attraction. If the Earth were alone in the universe, it would remain forever motionless in that point in infinite space where she had been placed, without ever having the power either to rise or set or change her position in any way whatever, the expressions to rise; to set; right or left, having no positive signification. If this same Earth thus alone in the Universe had received any impulse whatsoever, had been set moving with any degree of velocity whatsoever, in any direction whatsoever, she would move eternally in a straight line in that direction, without ever having the power to stop, or to slacken her motion, or to change its direction. It would be still the same if the Moon were alone with her in the Universe. They would both turn around their common center of gravity fulfilling their destiny in the same spot in space, hurrying on together in the direction toward which they had been projected. The Sun, however, having been created and being the center of his system, the Earth, all the planets and all their satellites depend on him, and their destiny is irrevocably joined to his.
The center of gravity we are in search of, the solid basis we seem to desire in order to assure the stability of the Universe, is it then on the colossal globe of the Sun that we shall find it?
Assuredly not, since the Sun himself is not at rest, since he draws us on with all his system toward the constellation of Hercules.
Does our Sun gravitate around an immense Sun whose attraction extends to him and rules his destinies as he rules those of the planets? Do our astronomical researches give us reason to suppose that at some point situated at right angles to the Earth as she moves towards Hercules, there may exist a star of such power? No; our Sun is influenced by the attraction of the stars, but none of them seems to dominate over the others and rule our Sun with sovereign sway.
Although it is quite possible, or rather certain, that the sun which is nearest to our sun, the star Alpha, of the Centaur, and our own sun mutually attract each other, yet we cannot regard those two stars as forming a pair like binary stars; in the first place, because all the systems of binary stars known are composed of stars much nearer to each other than those; and secondly, because in the vastness of the orbit described according to this hypothesis, we must not lose sight of this attraction exerted by the neighboring stars; and, finally, because the actual velocity of these two suns is much greater than would be the result of their mutual attraction.
The little constellation of Perseus, especially, may exercise an influence more powerful than that of the Pleiades or of any other cluster of stars, and constitute the center of gravity of the movements of our sun, of Alpheus, of the Centaur and the neighboring stars. Seeing that the constellation of Perseus is situated not only at right angles with the tangent of the Earth's path as she moves toward Hercules, but also in the great circle of the principal stars, and precisely at the intersection of that circle with the Milky Way, with its eighteen millions of suns, of which it would be daring indeed to seek the center of gravity.
But what is the whole Milky Way compared to the myriads of stars our thought contemplates in the bosom of the sidereal heavens? Does not this Milky Way itself move like an archipelago of floating islands? Is not each nebula, each cluster of stars a Milky Way moving under the influence of the gravitation of the other universes who call to it and beckon to it across infinite night.
Passing from constellation to constellation, from system to system, from region to region, our thought is brought face to face with the stupendous magnificence of the spectacle of heavenly bodies revolving with a velocity which we have begun to appreciate, but which already surpasses all conception. The yearly revolution of the star Alpha in the Centaur is more than 549 millions of miles. The revolution of star 61 Cygni (the second sun in the order of distances)is equivalent to 1110 millions of miles a year; or about three millions of miles a day. The star Alpha of the Centaur approaches us in a straight line with a velocity of 1500 millions of miles a year. The motion on its axis of star 1830 in the Catalogue of Groombridge attains a velocity of 7770 millions of miles a year, which is equal to 21 millions of miles a day, 115,000 kilometres an hour, or 320,000 yards a second! Those are the minimum calculations, as we observe the stellar motions measured obliquely, not in a straight line.
What projectiles? Suns of millions and millions times greater density than the Earth, launched into the fathomless depths of immensity with a more than vertiginous velocity, revolving in space under the united action of all the stars of the universe! And those millions, those myriads of suns, of planets, of constellations, of nebulæ, of worlds which are beginning, of worlds which are coming to an end, rush with similar velocity towards an unknown goal, with an energy and intensity of action compared with which powder and dynamite are like the breathing of an infant in the cradle.
And thus they all rush through space, perhaps for all eternity, without ever approaching its limits, which do not exist. Everywhere motion, activity, light and life. Happily so, no doubt. If all these innumerable suns, planets, earths, moons, and comets, were fixed motionless, kings petrified in their eternal tombs, how much more awe-inspiring indeed, but how much more deplorable also, would be the aspect of such a universe! All Creation arrested in its course, congealed, mummified! Is not such a thought inconceivable. Is there not something ominous -- something unsupportable in such a thought?
And what causes these motions? What sustains them, what guides them? The force of attraction everywhere reigning, that invisible force which the visible universe (that which we call matter) obeys. A body attracted from infinite space by the Earth, would attain to a velocity of 11,300 yards a second; thus a body projected from the Earth would never fall. A body attracted from infinite space by the sun, would attain a velocity of 608,000 yards; a body projected from the Sun with this velocity would never return to its point of departure. Certain constellations can cause a velocity of motion still greater, but which are explained by the law of attraction. It is enough to cast one's eyes over a chart of the motions of the stars on their axis, to understand the variety and grandeur of these motions.
Thus, the stars, the suns, the planets, the comets, the shooting stars, the uranoliths -- in a word, all the bodies that constitute this vast universe, rest, not on solid foundations, as the primitive and childish conception of our ancestors supposed, but on invisible and immaterial forces which govern their motions. Those myriads of celestial bodies owe their stability in the universe to their respective movements, and mutually sustain each other in the void that separates them. The mind that could divest itself of the notion of time and space would see the Earth, the planets, the Sun, the stars, falling in a shower from a heaven without bounds in every imaginable direction, like drops drawn into the vortex of a mighty whirlwind, and drawn not by one force, but by the attraction of each and all of them; each of those cosmic drops, each of those worlds, each of those suns is carried with a velocity so great, that the flight of a cannon-ball is rest in comparison. It is not a hundred, nor five hundred nor a thousand yards: it is ten thousand, twenty thousand, fifty thousand yards a second!
How does it happen that collisions do not take place in the midst of such perpetual movement? Perhaps they do. The stars that appear and disappear, as if perpetually renewed from their ashes, would seem to indicate it. But, in point of fact, collisions could not take place because space is infinite relatively to the dimensions of the celestial bodies, and because the movement of each body prevents it suffering passively the attraction of another body and being drawn into it. It keeps its own motion, which cannot be destroyed, and glides around the center of light and heat that attracts it, as the moth circles around the fire that attracts it, but without burning itself. And then, speaking with exactness, those movements are not rapid.
In fact, all those bodies rush, fly, fall, roll through space, but at such distances from one another that they all seem at rest. If we were to place in a space the size of Paris, the stars of which the distances have been measured, up to the present day, the nearest star would be placed at a distance of two kilometres from the Sun, from which the Earth would be distant one centimetre, Jupiter five centimetres and Neptune 30. The star 61 Cygni would be distant four kilometres, Sirius 10 kilometres, the North star 27 kilometres and so on, and the great majority of the stars would remain beyond the department of the Seine. Now, putting all these bodies in motion with their respective movements, the Earth would take a year to pass through its orbit -- no larger than the centimetre of a ray of light, Jupiter twelve years to pass through his, measuring five centimetres, and Neptune a hundred and sixty-five years. The proper motion of the Sun and stars would be in the same proportion; that is to say, they would appear to be at rest even through the magnifying glass. Uranie reigns calm and serene in the immensities of the universe.
But the constitution of the sidereal universe is the same as that of the bodies we call material. Every body, organic or inorganic -- man, animal, plant, stone, iron, bronze -- is composed of molecules perpetually in motion, yet never touching each other. Each of these atoms is infinitely small, and invisible, not only to the naked eye, not only through the magnifying glass, but even to the thought, since it is possible these atoms are no more than centers of force. It has been estimated that in the head of a pin there are not less than eight sextillions of atoms, or eight thousand thousand millions of thousand millions, and that in a cubic centimetre of air there are no less than a sextillion of molecules. All these atoms, all these molecules are in motion, acted upon by forces which govern them, and separated, relatively to their dimensions, by great distances. We may even think that there is, in principle, but one species of atoms, and that it is the number of primitive atoms, simple and homogeneous in essence, their modes of arrangement and their movements, which constitute the diversity of molecules. A molecule of gold or of iron would differ from a molecule of sulphur, of oxygen, of hydrogen, only in the number, the disposition and the movement of the primitive atoms which compose it; each molecule may be a system, a microcosm.
But whatever idea we may form of the constituent atoms of bodies, the fact accepted today and never again to be disputed, is that the imaginary center of gravity sought for, exists nowhere. Archimedes may ask in vain for a point of support for his lever to raise the world. Worlds, like atoms, rest on the invisible, on immaterial force; everything moves, acted upon by the force of attraction, and as if in search of that center of gravity which flies from us as we pursue it, and which has no existence, since in space the center is everywhere and nowhere. Those pretended positivists who affirm with so much assurance that only "matter and its properties exist," and who smile disdainfully at the researches of thinkers, should tell us first of all what they mean by this much talked of "matter." If they carried their investigations beyond the surface of things, if they could imagine that appearances conceal intangible realities, they would doubtless be a little more modest.
For us who seek the truth without preconceived ideas, and without having a theory to support, it seems to us that the principle of matter remains as much unknown as the principle of force, the visible universe not being at all what it appears to our senses. In fact this visible universe is composed of invisible atoms; it rests in space, and the forces which govern it are themselves immaterial and invisible. It would be less daring to suppose that matter did not exist, that force is everything, than to maintain the existence of a universe exclusively material. As to the physical foundations of the world, they have disappeared, by a curious contradiction, precisely with the triumph of mechanics which proclaims the triumphs of the invisible. The center of gravity disappears in the balancing of forces everywhere, in the ideal harmony of the vibrations of ether; the more we seek it, the less we find it, and the final effort of our thought has for its final support, for supreme reality, the Infinite.