“Stars that oversprinkle all the heavens seem to twinkle
With a crystalline delight,”
and sweep with his gaze all the concave hemisphere of the sky, and then compare the light which is radiated around him with the gorgeous effulgence of the noonday summer sun, he can pretty closely compare the relative attraction of gravity which all those distant suns together can exercise upon our earth with that of our own sun. Under control of the latter, the earth sweeps around in her orbit at the rate of about twenty miles per second; all these suns could not give our solar system even a minute fraction of that. Of this starlight Professor Ball says, “The sun certainly must receive some heat by the radiation from the stars; but this is quite infinitesimal in comparison with his own stupendous radiation.” Any such attraction, of course, could not control the motions of our solar system, and much less that of many of the others.
“The night has a thousand eyes, and the day but one,
But the light of the whole world dies when the day is done.”
We can also demonstrate the fact mathematically by an exceedingly rough calculation, which, however, will be sufficient for our purpose. Of the Milky Way, which comprises only the stars of our own sidereal system, Professor Ball says, “One hundred million stars are presumed to be disposed in a flat circular layer of such dimensions that a ray of light would require thirty thousand years to traverse one diameter.” (The most recent estimates make the number of the stars which compose the Milky Way several times one hundred million, occupying a correspondingly greater amplitude of space. The number in any case is sufficiently stupendous.) Our solar system is located in space at the apex of a vast transverse cleft, and nearly at the center of this disk. Let us leave out of consideration the lower half of the Milky Way, as we look upward on a starlit night, and conceive this galaxy to extend only across the midnight sky above us like an archway, with fifty million suns, visible and invisible, exposed in the field of our vision. The nearest of all the fixed stars to us is that known as Alpha Centauri,—not visible, however, in our northern skies. This star is about two hundred and thirty thousand times as far from our sun as is the earth. If of the same mass as our sun, it must exert upon us an attractive force of gravity one fifty-three-billionth that of our own sun. Next in distance is the star No. 61 of the constellation Cygnus. This may be three times as distant, and is certainly not less than twice. The light of the former will reach the earth in three and one-quarter years; that of the latter in not less than six and one-half years, perhaps much more. These are our nearest stellar neighbors. While the former will attract us with only one fifty-three-thousand-millionth that of the sun, the latter will attract us with less than one two-hundred-thousand-millionth that of our sun. Conceive, then, a square pyramid extending radially upward for three thousand times the mean of these distances to the upper probable limits of the Milky Way, a light-distance of fifteen thousand years, and that this pyramid expands according to the squares of its distances, so that it will contain within it, equally distributed, all the stars (fifty million) of the upper half of the disk of the Milky Way; the sum total of all these attractions could not reach one twenty-millionth part of that of our sun upon the earth. If we continue to pile galaxies, in the same perpetual recession, behind each other to all infinity, we still could not engender sufficient attractive force to control the observed movements of the multitudinous stars of space. The very statement of the law of gravitation itself disproves it; for if we multiply orbs and systems according to any principle of aggregation that we know of in the way of distribution of such systems, or anything possible, with due regard to their own mutually interacting movements in space, we could never reach the inside limits of such a sphere of control, because the piling up of orb behind orb adds but an infinitesimal fraction to the force of gravity, for as the orbs themselves multiply in distance progressively by hundreds, their relative attractions inversely diminish by ten thousands. No possible increase of suns directly in mass could compensate for such an inverse ratio of squares, even if all intergalactic space were peopled with suns, instead of being, in fact, like a vast ocean, with a few small clusters of islands scattered here and there throughout its illimitable extent.
Of these vast realms of space, Professor Ball asks, “Is our sidereal system to be regarded as an oceanic island in space, or is it in such connection with the systems in other parts of space as might lead us to infer that the various systems had a common character? The evidence seems to show that the stars in our system are probably not permanently associated together, but that in the course of time some stars enter our system and other stars leave it, in such manner as to suggest that the bodies visible to us are fairly typical of the general contents of the universe. The strongest evidence that can be presented on this subject is met with in the peculiar circumstances of one particular star. The star in question is known as No. 1830 of Groombridge’s catalogue. It is a small star, not to be seen without the aid of a telescope …. We shall probably be quite correct in assuming that the distance is not less than two hundred billions of miles …. The velocity is no less than two hundred miles per second …. The star sweeps along through our system with this stupendous velocity …. The velocity being over twenty-five miles a second, the attraction can never overcome the velocity, so that the star seems destined to escape.” Of the star Alcyone he says, “Doubtless that star is thousands of billions of miles from the earth; doubtless the light from it requires thousands of years—and some astronomers have said millions of years—to span the abyss which intervenes between our globe and those distant regions.” And yet these stars, these galaxies, and even all the nebulæ we see or ever shall see, are merely in the vestibule of space; we have scarcely even yet lifted the outer curtain at the entrance of those vast realms. That the popular, but pseudo-scientific, idea of a series of ever-widening concentric orbits, increasing at every new expansion by an inconceivable ratio, is incredible we can well understand, and it is a satisfaction to know that such a wild hypothesis finds no warrant in the dicta or the demonstrations of science. And it is in the failure of gravity to control over the intervening space which lies between those vastly distant centers that we may hope to find the inklings of a more far-reaching law, by which nebulæ like that of Orion crystallize out into separate star systems, just as in the rocks, whether igneous, metamorphic, or sedimentary, we find the attraction of cohesion yield to that of crystallization, until the whole cleft rock blazes with countless garnets in the schist and quartz crystals in the gneiss, or reveals the yellow specks of olivine in volcanic ejections.
We shall find in the processes concerned with the development of living things the workings of a similar great law, perhaps the same. Wherever there is the possibility of life, there we find life. There seems to be an all-pervading vital tension, so to speak, an energizing force, which drives the evolution and ascent of life forward and upward by successive leaps, as it were, from type to type, from race to race, and even from nation to nation. In this universal forward movement we may dimly discern the primordial creative and developing impulse, constantly acting, but manifesting visible change only at intervals as gathering forces accumulate and equilibrium is disturbed. It manifests itself in all the fields of nature,—vital, chemical, molecular, molar, systemic. It is the ever-acting, eternal past, present, and future, the macrocosm and the microcosm, the panurgus, the Brahma, the Ancient of Days, and cannot be silenced or evaded:
“They reckon ill who leave me out,
When me they fly I am the wings.”