Curiosities of the Sky, Garrett Putman Serviss [free novel reading sites txt] 📗

than one-twenty-fifth is due to stars separately distinguished by the eye. If there were no obscuring medium in space, it is probable that the amount of starlight would be noticeably and perhaps enormously increased.

But while it seems certain that some of the obscure spots in the Milky Way are due to the presence of ``dark nebulæ,'' or concealing veils of one kind or another, it is equally certain that there are many which are true apertures, however they may have been formed, and by whatever forces they may be maintained. These, then, are veritable windows of the Galaxy, and when looking out of them one is face to face with the great mystery of infinite space. There the known universe visibly ends, but manifestly space itself does not end there. It is not within the power of thought to conceive an end to space, for the instant we think of a terminal point or line the mind leaps forward to the beyond. There must be space outside as well as inside. Eternity of time and infinity of space are ideas that the intellect cannot fully grasp, but neither can it grasp the idea of a limitation to either space or time. The metaphysical conceptions of hypergeometry, or fourth-dimensional space, do not aid us.

Having, then, discovered that the universe is a thing contained in something indefinitely greater than itself; having looked out of its windows and found only the gloom of starless night outside -- what conclusions are we to draw concerning the beyond? It seems as empty as a vacuum, but is it really so? If it be, then our universe is a single atom astray in the infinite; it is the only island in an ocean without shores; it is the one oasis in an illimitable desert. Then the Milky Way, with its wide-flung garland of stars, is afloat like a tiny smoke-wreath amid a horror of immeasurable vacancy, or it is an evanescent and solitary ring of sparkling froth cast up for a moment on the viewless billows of immensity. From such conclusions the mind instinctively shrinks. It prefers to think that there is something beyond, though we cannot see it. Even the universe could not bear to be alone -- a Crusoe lost in the Cosmos! As the inhabitants of the most elegant château, with its gardens, parks, and crowds of attendants, would die of loneliness if they did not know that they have neighbors, though not seen, and that a living world of indefinite extent surrounds them, so we, when we perceive that the universe has limits, wish to feel that it is not solitary; that beyond the hedges and the hills there are other centers of life and activity. Could anything be more terrible than the thought of an isolated universe? The greater the being, the greater the aversion to seclusion. Only the infinite satisfies; in that alone the mind finds rest.

We are driven, then, to believe that the universal night which envelopes us is not tenantless; that as we stare out of the star-framed windows of the Galaxy and see nothing but uniform blackness, the fault is with our eyes or is due to an obscuring medium. Since our universe is limited in extent, there must be other universes beyond it on all sides. Perhaps if we could carry our telescopes to the verge of the great ``Coal-sack'' near the ``Cross,'' being then on the frontier of our starry system, we could discern, sparkling afar off in the vast night, some of the outer galaxies. They may be grander than ours, just as many of the suns surrounding us are immensely greater than ours. If we could take our stand somewhere in the midst of immensity and, with vision of infinite reach, look about us, we should perhaps see a countless number of stellar systems, amid which ours would be unnoticeable, like a single star among the multitude glittering in the terrestial sky on a clear night. Some might be in the form of a wreath, like our own; some might be globular, like the great star-clusters in Hercules and Centaurus; some might be glittering circles, or disks, or rings within rings. If we could enter them we should probably find a vast variety of composition, including elements unknown to terrestrial chemistry; for while the visible universe appears to contain few if any substances not existing on the earth or in the sun, we have no warrant to assume that others may not exist in infinite space.

And how as to gravitation? We do not know that gravitation acts beyond the visible universe, but it is reasonable to suppose that it does. At any rate, if we let go its sustaining hand we are lost, and can only wander hopelessly in our speculations, like children astray. If the empire of gravitation is infinite, then the various outer systems must have some, though measuring by our standards an imperceptible, attractive influence upon each other, for gravitation never lets go its hold, however great the space over which it is required to act. Just as the stars about us are all in motion, so the starry systems beyond our sight may be in motion, and our system as a whole may be moving in concert with them. If this be so, then after interminable ages the aspect of the entire system of systems must change, its various members assuming new positions with respect to one another. In the course of time we may even suppose that our universe will approach relatively close to one of the others; and then, if men are yet living on the earth, they may glimpse through the openings which reveal nothing to us now, the lights of another nearing star system, like the signals of a strange squadron, bringing them the assurance (which can be but an inference at present) that the ocean of space has other argosies venturing on its limitless expanse.

There remains the question of the luminiferous ether by whose agency the waves of light are borne through space. The ether is as mysterious as gravitation. With regard to ether we only infer its existence from the effects which we ascribe to it. Evidently the ether must extend as far as the most distant visible stars. But does it continue on indefinitely in outer space? If it does, then the invisibility of the other systems must be due to their distance diminishing the quantity of light that comes from them below the limit of perceptibility, or to the interposition of absorbing media; if it does not, then the reason why we cannot see them is owing to the absence of a means of conveyance for the light waves, as the lack of an interplanetary atmosphere prevents us from hearing the thunder of sun-spots. (It is interesting to recall that Mr Edison was once credited with the intention to construct a gigantic microphone which should render the roar of sun-spots audible by transforming the electric vibrations into sound-waves). On this supposition each starry system would be enveloped in its own globule of ether, and no light could cross from one to another. But the probability is that both the ether and gravitation are ubiquitous, and that all the stellar systems are immersed in the former like clouds of phosphorescent organisms in the sea.

So astronomy carries the mind from height to greater height. Men were long in accepting the proofs of the relative insignificance of the earth; they were more quickly convinced of the comparative littleness of the solar system; and now the evidence assails their reason that what they had regarded as the universe is only one mote gleaming in the sunbeams of Infinity.

Star-Clouds, Star-Clusters, and Star-Streams

In the preceding chapter we have seen something of the strangely complicated structure of the Galaxy, or Milky Way. We now proceed to study more comprehensively that garlanded ``Pathway of the Gods.''

Judged by the eye alone, the Milky Way is one of the most delicately beautiful phenomena in the entire realm of nature -- a shimmer of silvery gauze stretched across the sky; but studied in the light of its revelations, it is the most stupendous object presented to human ken. Let us consider, first, its appearance to ordinary vision. Its apparent position in the sky shifts according to the season. On a serene, cloudless summer evening, in the absence of the moon, whose light obscures it, one sees the Galaxy spanning the heavens from north to southeast of the zenith like a phosphorescent arch. In early spring it forms a similar but, upon the whole, less brilliant arch west of the zenith. Between spring and summer it lies like a long, faint, twilight band along the northern horizon. At the beginning of winter it again forms an arch, this time spanning the sky from east to west, a little north of the zenith. These are its positions as viewed from the mean latitude of the United States. Even the beginner in star-gazing does not have to watch it throughout the year in order to be convinced that it is, in reality, a great circle, extending entirely around the celestial sphere. We appear to be situated near