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 veloci............