Other Worlds<br />Their Nature, Possibilities and Habitability in the Light of the Latest Discoveries, Garrett Putman Serviss [reading diary .txt] 📗

We found the density of Jupiter astonishingly slight, but that of Saturn is slighter still. Jupiter would sink if thrown into water, but Saturn would actually float, if not "like a cork," yet quite as buoyantly as many kinds of wood, for its mean density is only three quarters that of water, or one eighth of the earth's. In fact, there is no known planet whose density is so slight as Saturn's. Thus it happens that, notwithstanding its vast size and mass, the force of gravity upon Saturn is nearly the same as upon our globe. Upon visiting Venus we should find ourselves weighing a little less than at home, and upon visiting Saturn a little more, but in neither case would the difference be very important. If the relative weight of bodies on the surfaces of planets formed the sole test of their habitability, Venus and Saturn would both rank[Pg 189] with the earth as suitable abodes for men.

But the exceedingly slight density of Saturn seems to be most reasonably accounted for on the supposition that, like Jupiter, it is in a vaporous condition, still very hot within—although but slightly, if at all, incandescent at the surface—and, therefore, unsuited to contain life. It is hardly worth while to speculate about any solid nucleus within, because, even if such a thing were possible, or probable, it must lie forever hidden from our eyes. But if we accept the theory that Saturn is in an early formative stage, and that, millions of years hence, it may become an incrusted and habitable globe, we shall, at least, follow the analogy of what we believe to have been the history of the earth, except that Saturn's immense distance from the sun will always prevent it from receiving an amount of solar radiation consistent with our ideas of what is required by a living world. Of course, since one can imagine what he chooses, it is possible to suppose inhabit[Pg 190]ants suited to existence in a world composed only of whirling clouds, and a poet with the imagination of a Milton might give us very imposing and stirring images of such creatures and their chaotic surroundings, but fancies like these can have no basis in human experience, and consequently can make no claim upon scientific recognition.

Or, as an alternative, it might be assumed that Saturn is composed of lighter elements and materials than those which constitute the earth and the other solid planets in the more immediate neighborhood of the sun. But such an assumption would put us entirely at sea as regards the forms of organic life that could exist upon a planet of that description, and, like Sir Humphry Davy in the Vision, that occupies the first chapter of his quaintly charming Consolations in Travel, or, the Last Days of a Philosopher, we should be thrown entirely upon the resources of the imagination in representing to ourselves the nature and appearance of its inhabitants. Yet minds[Pg 191] of unquestioned power and sincerity have in all ages found pleasure and even profit in such exercises, and with every fresh discovery arises a new flight of fancies like butterflies from a roadside pool. As affording a glimpse into the mind of a remarkable man, as well as a proof of the fascination of such subjects, it will be interesting to quote from the book just mentioned Davy's description of his imaginary inhabitants of Saturn:

"I saw below me a surface infinitely diversified, something like that of an immense glacier covered with large columnar masses, which appeared as if formed of glass, and from which were suspended rounded forms of various sizes which, if they had not been transparent, I might have supposed to be fruit. From what appeared to me to be analogous to bright-blue ice, streams of the richest tint of rose color or purple burst forth and flowed into basins, forming lakes or seas of the same color. Looking through the atmosphere toward the heavens, I saw brilliant opaque clouds, of an azure color, that reflected the light of the sun, which[Pg 192] had to my eyes an entirely new aspect and appeared smaller, as if seen through a dense blue mist.

"I saw moving on the surface below me immense masses, the forms of which I find it impossible to describe. They had systems for locomotion similar to those of the morse, or sea-horse, but I saw, with great surprise, that they moved from place to place by six extremely thin membranes, which they used as wings. Their colors were varied and beautiful, but principally azure and rose color. I saw numerous convolutions of tubes, more analogous to the trunk of the elephant than to anything else I can imagine, occupying what I supposed to be the upper parts of the body. It was with a species of terror that I saw one of them mounting upward, apparently flying toward those opaque clouds which I have before mentioned.

"'I know what your feelings are,' said the Genius; 'you want analogies, and all the elements of knowledge to comprehend the scene before you. You are in the same[Pg 193] state in which a fly would be whose microscopic eye was changed for one similar to that of man, and you are wholly unable to associate what you now see with your former knowledge. But those beings who are before you, and who appear to you almost as imperfect in their functions as the zoophytes of the polar sea, to which they are not unlike in their apparent organization to your eyes, have a sphere of sensibility and intellectual enjoyment far superior to that of the inhabitants of your earth. Each of those tubes, which appears like the trunk of an elephant, is an organ of peculiar motion or sensation. They have many modes of perception of which you are wholly ignorant, at the same time that their sphere of vision is infinitely more extended than yours, and their organs of touch far more perfect and exquisite.'"

After descanting upon the advantages of Saturn's position for surveying some of the phenomena of the solar system and of outer space, and the consequent immense advances that the Saturnians have made in[Pg 194] astronomical knowledge, the Genius continues:

"'If I were to show you the different parts of the surface of this planet you would see the marvelous results of the powers possessed by these highly intellectual beings, and of the wonderful manner in which they have applied and modified matter. Those columnar masses, which seem to you as if rising out of a mass of ice below, are results of art, and processes are going on within them connected with the formation and perfection of their food. The brilliant-colored fluids are the results of such operations as on the earth would be performed in your laboratories, or more properly in your refined culinary apparatus, for they are connected with their system of nourishment. Those opaque azure clouds, to which you saw a few minutes ago one of those beings directing his course, are works of art, and places in which they move through different regions of their atmosphere, and command the temperature and the quantity of light most fitted for their philosophical[Pg 195] researches, or most convenient for the purposes of life.'"[11]

But, while Saturn does not appear, with our present knowledge, to hold out any encouragement to those who would regard it as the abode of living creatures capable of being described in any terms except those of pure imagination, yet it is so unique a curiosity among the heavenly bodies that one returns again and again to the contemplation of its strange details. Saturn has nine moons, but some of them are relatively small bodies—the ninth, discovered photographically by Professor Pickering in 1899, being especially minute—and others are situated at great distances from the planet, and for these reasons, together with the fact that the sunlight is so feeble upon them that, surface for surface, they have only one ninetieth as much illumination as our moon receives, they can not make a very[Pg 196] brilliant display in the Saturnian sky. To astronomers on Saturn they would, of course, be intensely interesting because of their perturbations and particularly the effect of their attraction on the rings.

This brings us again to the consideration of those marvelous appendages, and to the statement of facts about them which we have not yet recalled.

If the reader will take a ball three inches in diameter to represent the globe of Saturn, and, out of the center of a circular piece of writing-paper seven inches in diameter, will cut a round hole three and three quarter inches across, and will then place the ball in the middle of the hole in the paper, he will have a very fair representation of the relative proportions of Saturn and its rings. To represent the main gap or division in the rings he might draw, a little more than three eighths of an inch from the outer edge of the paper disk, a pencil line about a sixteenth of an inch broad.

Perhaps the most striking fact that becomes conspicuous in making such a model[Pg 197] of the Saturnian system is the exceeding thinness of the rings as compared with their enormous extent. They are about 170,000 miles across from outer edge to outer edge, and about 38,000 miles broad from outer edge to inner edge—including the gauze ring presently to be mentioned—yet their thickness probably does not surpass one hundred miles! In fact, the sheet of paper in our imaginary model is several times too thick to represent the true relative thickness of Saturn's rings.

Several narrow gaps in the rings have been detected from time to time, but there is only one such gap that is always clearly to be seen, the one already mentioned, situated about 10,000 miles from the outer edge and about 1,600 miles in width. Inside of this gap the broadest and brightest ring appears, having a width of about 16,500 miles. For some reason this great ring is most brilliant near the gap, and its brightness gradually falls off toward its inner side. At a distance of something less than 20,000 miles from the planet—or perhaps it[Pg 198] would be more correct to say above the planet, for the rings hang directly over Saturn's equator—the broad, bright ring merges into a mysterious gauzelike object, also in the form of a ring, which extends to within 9,000 or 10,000 miles of the planet's surface, and therefore itself has a width of say 10,000 miles.

In consequence of the thinness of the rings they completely disappear from the range of vision of small telescopes when, as occurs once in every fifteen years, they are seen exactly edgewise from the earth. In a telescope powerful enough to reveal them when in that situation they resemble a thin, glowing needle run through the ball of the planet. The rings will be in this position in 1907, and again in 1922.

The opacity of the rings is proved by the shadow which they cast upon the ball of the planet. This is particularly manifest at the time when they are edgewise to the earth, for the sun being situated slightly above or below the plane of the rings then throws their shadow across Saturn close to[Pg 199] its equator. When they are canted at a considerable angle to our line of sight their shadow is seen on the planet, bordering their outer edge where they cross the ball.

The gauze ring, the detection of which as a faintly luminous phenomenon requires a powerful telescope, can be seen with slighter telescopic power in the form of a light shade projected against the planet at the inner edge of the broad bright ring. The explanation of the existence of this peculiar object depends upon the nature of the entire system, which, instead of being, as the earliest observers thought it, a solid ring or series of concentric rings, is composed of innumerable small bodies, like meteorites, perhaps, in size, circulating independently but in comparatively close juxtaposition to one another about Saturn, and presenting to our eyes, because of their great number and of our enormous distance, the appearance of solid, uniform rings. So a flock of ducks may look from afar like a continuous black line or band, although if we were near them we should perceive that a consider[Pg 200]able space separates each individual from his neighbors.

The fact that this is the constitution of Saturn's rings can be confidently stated because it has been mathematically proved that they could not exist if they were either solid or liquid bodies in a continuous form, and because the late Prof. James E. Keeler demonstrated with the