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One passage of Swedenborg's description of Jupiter is curious. 'Although on that earth,' he says, 'spirits speak with men' (i.e. with Jovian men) 'man in his turn does not speak with spirits, except to say, when instructed, that he will do so no more,'—which we should regard as a bull if it were not news from the Jovian spirit world. 'Nor is man allowed to tell anyone that a spirit has spoken to him; if he does so, he is punished. Those spirits of Jupiter when they were with me, at first supposed they were with a man of their own earth; but when in my turn I spoke with them, and thought of publishing what passed between us and so relating it to others, then, because they were not allowed to chastise me, they discovered they were with a stranger.'

It has been a favourite idea with those who delight in the argument from design, that the moons of the remoter planets have been provided for the express purpose of making up for the small amount of sunlight which reaches those planets. Jupiter receives only about one twenty-seventh part of the light which we receive from the sun; but then, has he not four moons to make his nights glorious? Saturn is yet farther away from the sun, and receives only the ninetieth part of the light we get from the sun; but then he has eight moons and his rings, and the nocturnal glory of his skies must go far to compensate the Saturnians for the small quantity of sunlight they receive. The Saturnian spirits who visited Swedenborg were manifestly indoctrinated with these ideas. For they informed him that the nocturnal light of Saturn is so great that some Saturnians worship it, calling it the Lord. These wicked spirits are separated from the rest, and are not tolerated by them. 'The nocturnal light,' say the spirits, 'comes from the immense ring which at a distance encircles that earth, and from the moons which are called the satellites of Saturn.' And again, being questioned further 'concerning the great ring which appears from our earth to rise above the horizon of that planet, and to vary its situations, they said that it does not appear to them as a ring, but only as a snow-white substance in heaven in various directions.' Unfortunately for our faith in the veracity of these spirits, it is certain that the moons of Saturn cannot give nearly so much light as ours, while the rings are much more effective as darkeners than as illuminators. One can readily calculate the apparent size of each of the moons as seen from Saturn, and thence show that the eight discs of the moons together are larger than our moon's disc in about the proportion of forty-five to eight. So that if they were all shining as brightly as our full moon and all full at the same time, their combined light would exceed hers in that degree. But they are not illuminated as our moon is. They are illuminated by the same remote sun which illuminates Saturn, while our moon is illuminated by a sun giving her as much light as we ourselves receive. Our moon then is illuminated ninety times more brightly than the moons of Saturn, and as her disc is less than all theirs together, not as one to ninety, but as sixteen to ninety, it follows that all the Saturnian moons, if full at the same time, would reflect to Saturn one-sixteenth part of the light which we receive from the full moon.29 As regards the rings of Saturn, nothing can be more certain than that they tend much more to deprive Saturn of light then to make up by reflection for the small amount of light which Saturn receives directly from the sun. The part of the ring which lies between the planet and the sun casts a black shadow upon Saturn, this shadow sometimes covering an extent of surface many times exceeding the entire surface of our earth. The shadow thus thrown upon the planet creeps slowly, first one way, then another, northwards and southwards over the illuminated hemisphere of the planet (as pictured in the 13th plate of my treatise on Saturn), requiring for its passage from the arctic to the antarctic regions and back again to the arctic regions of the planet, a period nearly equal to that of a generation of terrestrial men. Nearly thirty of our years the process lasts, during half of which time the northern hemisphere suffers, and during the other half the southern. The shadow band, which be it remembered stretches right athwart the planet from the extreme eastern to the extreme western side of the illuminated hemisphere, is so broad during the greater part of the time that in some regions (those corresponding to our temperate zones) the shadow takes two years in passing, during which time the sun cannot be seen at all, unless for a few moments through some chinks in the rings, which are known to be not solid bodies, but made up of closely crowded small moons. And the slow passage of this fearful shadow, which advances at the average rate of some twenty miles a day, but yet hangs for years over the regions athwart which it sweeps, occurs in the very season when the sun's small direct supply of heat would require to be most freely compensated by nocturnal light—in the winter season, namely, of the planet. Moreover, not only during the time of the shadow's passage, but during the entire winter half of the Saturnian year, the ring reflects no light during the night time, the sun being on the other or summer side of the ring's plane.30 The only nocturnal effect which would be observable would be the obliteration of the stars covered by the ring system. It is strange that, this being so, the spirits from Saturn should have made no mention of the circumstance; and even more strange that these spirits and others should have asserted that the moons and rings of Saturn compensate for the small amount of light directly received from the sun. Most certainly a Swedenborg of our own time would find the spirits from Saturn more veracious and more communicative about these matters, though even what he would hear from the spirits would doubtless appear to sceptics of the twenty-first century to be no more than he could have inferred from the known facts of the science of his day.

But Swedenborg was not content merely to receive visits from the inhabitants of other planets in the solar system. He was visited also by the spirits of earths in the starry heaven; nay, he was enabled to visit those earths himself. For man, even while living in the world, 'is a spirit as to his interiors, the body which he carries about in the world only serving him for performing functions in this natural or terrestrial sphere, which is the lowest.' And to certain men it is granted not only to converse as a spirit with angels and spirits, but to traverse in a spiritual way the vast distances which separate world from world and system from system, all the while remaining in the body. Swedenborg was one of these. 'The interiors of my spirit,' he says, 'are opened by the Lord, so that while I am in the body I can at the same time be with angels in heaven, and not only converse with them, but behold the wonderful things which are there and describe them, that henceforth it may no more be said, "Who ever came from heaven to assure us it exists and tell us what is there?" He who is unacquainted with the arcana of heaven cannot believe that man can see earths so remote, and give any account of them from sensible experience. But let him know that spaces and distances, and consequently progressions, existing in the natural world, in their origin and first causes are changes of the state of the interiors; that with angels and spirits progressions appear according to changes of state; and that by changes of state they may be apparently translated from one place to another, and from one earth to another, even to earths at the boundaries of the universe; so likewise may man as to his spirit, his body still remaining in its place. This has been the case with me.'

Before describing his visits to earths in the starry heavens, Swedenborg is careful to indicate the probability that such earths exist. 'It is well known to the learned world,' he says, 'that every star is a sun in its place, remaining fixed like the sun of our earth.' The proper motions of the stars had, alas! not been discovered in Swedenborg's day, nor does he seem to have been aware what a wild chase he was really entering upon in his spiritual progressions. Conceive the pursuit of Sirius or Vega as either sun rushed through space with a velocity of thirty or forty miles in every second of time! To resume, however, the account which Swedenborg gives of the ideas of the learned world of his day. 'It is the distance which makes a star appear in a small form; consequently' (the logical necessity is not manifest, however) 'each star, like the sun of our system, has around it planets which are earths; and the reason these are not visible to us is because of their immense distance and their having no light but from their own star, which light cannot be reflected so far as to reach us.' 'To what other end,' proceeds this most convincing reasoning, 'can be so immense a heaven with such a multitude of stars? For man is the end for which the universe was created. It has been ascertained by calculation that supposing there were in the universe a million earths, and on every earth three hundred millions of men and two hundred generations within six thousand years, and that to every man or spirit was allotted a space of three cubic ells, the collective number of men or spirits could not occupy a space equal to a thousandth part of this earth, thus not more than that occupied by one of the satellites of Jupiter or Saturn; a space on the universe almost undiscernible, for a satellite is hardly visible to the naked eye. What would this be for the Creator of the universe, to whom the whole universe filled with earths could not be enough' (for what?), 'seeing that he is infinite.' However, it is not on this reasoning alone that Swedenborg relies. He tells us, honestly beyond all doubt, that he knows the truth of what he relates. 'The information I am about to give,' he says, 'respecting the earths in the starry heaven is from experimental testimony; from which it will likewise appear how I was translated thither as to my spirit, the body remaining in its place.'

His progress in his first star-hunt was to the right, and continued for about two hours. He found the boundary of our solar system marked first by a white but thick cloud, next by a fiery smoke ascending from a great chasm. Here some guards appeared, who stopped some of the company, because these had not, like Swedenborg and the rest, received permission to pass. They not only stopped those unfortunates, but tortured them, conduct for which terrestrial analogues might possibly be discovered.

Having reached another system, he asked the spirits of one of the earths there how large their sun was and how it appeared. They said it was less than the sun of our earth, and has a flaming appearance. Our sun, in fact, is larger than other suns in space, for from that earth starry heavens are seen, and a star larger than the rest appears, which, say those spirits, 'was declared from heaven' to be the sun of Swedenborg's earthly home.

What Swedenborg saw upon that earth has no special interest. The men there, though haughty, are loved by their respective wives because they, the men, are good. But their goodness does not appear very manifest from anything in the narrative. The only man seen by Swedenborg took from his wife 'the garment which she wore, and threw it over his own shoulders; loosening the lower part, which flowed down to his feet like a robe (much as a man of our earth might be expected to loosen the tie-back of the period, if he borrowed it in like manner) he thus walked about clad.'

He next visited an earth circling round a star, which he learned was one of the smaller sort, not far from the equator. Its greater distance was plain from the circumstance that Swedenborg was two days in reaching it. In this earth he very nearly fell into a quarrel with the spirits. For hearing that they possess remarkable keenness of vision, he 'compared them with eagles which fly aloft, and enjoy a clear and extensive view of objects beneath.' At this they were indignant, supposing, poor spirits, 'that he compared them to eagles as to their rapacity, and consequently thought them wicked.' He hastened to explain, however, that he 'did not liken them to eagles as to their rapacity, but as to sharpsightedness.'

Swedenborg's account of a third earth in the star-depths contains a very pretty idea for temples and churches. The temples in that earth 'are constructed,' he says, of trees, not cut down, but growing in the place where they were first planted. On that earth, it seems, there are trees of an extraordinary size and height; these they set in rows when young, and arrange in such an order that they may serve when they grow up to form porticoes and colonnades. In the meanwhile, by cutting and pruning, they fit and prepare the tender shoots to entwine one with another, and join together so as to form the groundwork and floor of the temple to be constructed, and to rise at the sides as walls, and above to bend into arches to form the roof. In this manner they construct the temple with admirable art, elevating it high above the ground. They prepare also an ascent into it, by continuous branches of the trees, extended from the trunk and firmly connected together. Moreover, they adorn the temple without and within in various ways, by disposing the foliage into particular forms; thus they build entire groves. But it was not permitted me to see the nature of these temples, only I was informed that the light of their sun is let in by apertures amongst the branches, and is everywhere transmitted through crystals; whereby the light falling on the walls is refracted in colours like those of the rainbow, particularly blue and orange, of which they are fondest. Such is their architecture, which they prefer to the most magnificent palaces of our earth.'

Other earths in the starry heavens were visited by Swedenborg, but the above will serve sufficiently to illustrate the nature of his observations. One statement, by the way, was made to him which must have seemed unlikely ever to be contravened, but which has been shown in our time to be altogether erroneous. In the fourth star-world he visited, he was told that that earth, which travels round its sun in 200 days of fifteen hours each, is one of the least in the universe, being scarcely 500 German miles, say 2000 English miles, in circumference. This would make its diameter about 640 English miles. But there is not one of the whole family of planetoids which has a diameter so great as this, and many of these earths must be less than fifty miles in diameter. Now Swedenborg remarks that he had his information from the angels, 'who made a comparison in all these particulars with things of a like nature on our earth, according to what they saw in me or in my memory. Their conclusions were formed by angelic ideas, whereby are instantly known the measure of space and time in a just proportion with respect to space and time elsewhere. Angelic ideas, which are spiritual, in such calculations infinitely excel human ideas, which are natural.' He must therefore have met, unfortunately, with untruthful angels.

The real source of Swedenborg's inspirations will be tolerably obvious—to all, at least, who are not Swedenborgians. But our account of his visions would not be complete in a psychological sense without a brief reference to the personal allusions which the spirits and angels made during their visits or his wanderings. His distinguished rival, Christian Wolf, was encountered as a spirit by spirits from Mercury, who 'perceived that what he said did not rise above the sensual things of the natural man, because in speaking he thought of honour, and was desirous, as in the world (for in the other world every one is like his former self), to connect various things into series, and from these again continually to deduce others, and so form several chains of such, which they did not see or acknowledge to be true, and which, therefore, they declared to be chains which neither cohered in themselves nor with the conclusions, calling them the obscurity of authority;' so they ceased to question him further, and presently left him. Similarly, a spirit who in this world had been a 'prelate and a preacher,' and 'very pathetic, so that he could deeply move his hearers,' got no hearing among the spirits of a certain earth in the starry heavens; for they said they could tell 'from the tone of the voice whether a discourse came from the heart or not;' and as his discourse came not from the heart, 'he was unable to teach them, whereupon he was silent.' Convenient thus to have spirits and angels to confirm our impressions of other men, living or dead.

Apart from the psychological interest attaching to Swedenborg's strange vision, one cannot but be strongly impressed by the idea pervading them, that to beings suitably constituted all that takes place in other worlds might be known. Modern science recognises a truth here; for in that mysterious ether which occupies all space, messages are at all times travelling by which the history of every orb is constantly recorded. No world, however remote or insignificant; no period, however distant—but has its history thus continually proclaimed in ever widening waves. Nay, by these waves also (to beings who could read their teachings aright) the future is constantly indicated. For, as the waves which permeate the ether could only be situated as they actually are, at any moment, through past processes, each one of which is consequently indicated by those ethereal waves, so also there can be but one series of events in the future, as the sequel of the relations actually indicated by the ethereal undulations. These, therefore, speak as definitely and distinctly of the future as of the past. Could we but rid us of the gross habiliments of flesh, and by some new senses be enabled to feel each order of ethereal undulations, even of those only which reach our earth, all knowledge of the past and future would be within our power. The consciousness of this underlies the fancies of Swedenborg, just as it underlies the thought of him who sang—

 
There's not an orb which thou behold'st
But in his motion like an angel sings,
Still quiring to the young-eyed cherubim.
But while this muddy vesture of decay
Doth grossly close us in, we cannot hear it.
 

V.
OTHER WORLDS AND OTHER UNIVERSES

If any one shall gravely tell me that I have spent my time idly in a vain and fruitless inquiry after what I can never become sure of, the answer is that at this rate he would put down all natural philosophy, as far as it concerns itself in searching into the nature of such things. In such noble and sublime studies as these, 'tis a glory to arrive at probability, and the search itself rewards the pains. But there are many degrees of probable, some nearer to the truth than others, in the determining of which lies the chief exercise of our judgment. And besides the nobleness and pleasure of the studies, may we not be so bold as to say that they are no small help to the advancement of wisdom and morality?

—Huyghens, Conjectures concerning the Planetary Worlds.

The interest with which astronomy is studied by many who care little or nothing for other sciences is due chiefly to the thoughts which the celestial bodies suggest respecting life in other worlds than ours. There is no feeling more deeply seated in the human heart—not the belief in higher than human powers, not the hope of immortality, not even the fear of death—than the faith in realms of life where other conditions are experienced than those we are acquainted with here. It is not vulgar curiosity or idle fancy that suggests the possibilities of life in other worlds. It has been the conviction of the profoundest thinkers, of men of highest imagination. The mystery of the star-depths has had its charm for the mathematician as well as for the poet; for the exact observer as for the most fruitful theoriser; nay, for the man of business as for him whose life is passed in communing with nature. If we analyse the interest with which the generality of men inquire into astronomical matters apparently not connected with the question of life in other worlds, we find in every case that it has been out of this question alone or chiefly that that interest has sprung. The great discoveries made during the last few years respecting the sun for example, might seem remote from the subject of life in other worlds. It is true that Sir William Herschel thought the sun might be the abode of living creatures; and Sir John Herschel even suggested the possibility that the vast streaks of light called the solar willow-leaves, objects varying from two hundred to a thousand miles in length, might be living creatures whose intense lustre was the measure of their intense vitality. But modern discoveries had rendered all such theories untenable. The sun is presented to us as a mighty furnace, in whose fires the most stubborn elements are not merely melted but vaporised. The material of the sun has been analysed, the motions and changes taking place on his surface examined, the laws of his being determined. How, it might be asked, is the question of life in other worlds involved in these researches? The faith of Sir David Brewster in the sun as the abode of life being dispelled, how could discoveries respecting the sun interest those who care about the subject of the plurality of worlds? The answer to these questions is easily found. The real interest which solar researches have possessed for those who are not astronomers has resided in the evidence afforded respecting the sun's position as the fire, light, and life of the system of worlds whereof our world is one. The mere facts discovered respecting the sun would be regarded as so much dry detail were they not brought directly into relation with our earth and its wants, and therefore with the wants of the other earths which circle round the sun; but when thus dealt with they immediately excite attention and interest. I do not speak at random in asserting this, but describe the result of widely ranging observation. I have addressed hundreds of audiences in Great Britain and America on the subject of recent solar discoveries, and I have conversed with many hundreds of persons of various capacity and education, from men almost uncultured to men of the highest intellectual power; and my invariable experience has been that solar research derives its chief interest when viewed in relation to the sun's position as the mighty ruler, the steadfast sustainer, the beneficent almoner of the system of worlds to which our earth belongs. It is the same with other astronomical subjects. Few care for the record of lunar observations, save in relation to the question whether the moon is or has been the abode of living creatures. The movements of comets and meteors, and the discoveries recently made respecting their condition, have no interest except in relation to the position of these bodies in the economy of solar systems, or to the possible part which they may at one time have performed in building up worlds and suns. None save astronomers, and few only of these, care for researches into the star-depths, except in connection with the thought that every star is a sun and therefore probably the light and fire of a system of worlds like those which circle around our own sun.

It is singular how variously this question of life in other worlds has been viewed at various stages of astronomical progress. From the time of Pythagoras, who first, so far as is known, propounded the general theory of the plurality of worlds, down to our own time, when Brewster and Chalmers on the one hand, and Whewell on the other, have advocated rival theories probably to be both set aside for a theory at once intermediate to and more widely ranging in time and space than either, the aspect of the subject has constantly varied, as new lights have been thrown upon it from different directions. It may be interesting briefly to consider what has been thought in the past on this strangely attractive question, and then to indicate the view towards which modern discoveries seem manifestly to point—a view not likely to undergo other change than that resulting from clearer vision and closer approach. In other words, I shall endeavour to show that the theory to which we are now led by all the known facts is correct in general, though, as fresh knowledge is obtained, it may undergo modification in details. We now see the subject from the right point of view, though as science progresses we may come to see it more clearly and definedly.

When men believed the earth to be a flat surface above which the heavens were arched as a tent or canopy, they were not likely to entertain the belief in other worlds than ours. During the earlier ages of mankind ideas such as these prevailed. The earth had been fashioned into its present form and condition, the heavens had been spread over it, the sun, and moon, and stars had been set in the heavens for its use and adornment, and there was no thought of any other world.

But while this was the general belief, there was already a school of philosophy where another doctrine had been taught. Pythagoras had adopted the belief of Apollonius Pergæus that the sun is the centre of the planetary paths, the earth one among the planets—a belief inseparable from the doctrine of the plurality of worlds. Much argument has been advanced to show that this belief never was adopted before the time of Copernicus, and unquestionably it must be admitted that the theory was not presented in the clear and simple form to which we have become accustomed. But it is not necessary to weigh the conflicting arguments for and against the opinion that Pythagoras and others regarded the earth as not the fixed centre of the universe. The certain fact that the doctrine of the plurality of worlds was entertained (I do not say adopted) by them, proves sufficiently that they cannot have believed the earth to be fixed and central. The idea of other worlds like our earth is manifestly inconsistent with the belief that the earth is the central body around which the whole universe revolves.

That this is so is well illustrated by the fate of the unfortunate Giordano Bruno. He was one of the first disciples of Copernicus, and, having accepted the doctrine that the earth travels round the sun as one among his family of planets, was led very naturally to the belief that the other planets are inhabited. He went farther, and maintained that as the earth is not the only inhabited world in the solar system, so the sun is not the only centre of a system of inhabited worlds, but each star a sun like him, about which many planets revolve. This was one of the many heresies for which Bruno was burned at the stake. It is easy, also, to recognise in the doctrine of many worlds as the natural sequel of the Copernican theory, rather than in the features of this theory itself, the cause of the hostility with which theologians regarded it, until, finding it proved, they discovered that it is directly taught in the books which they interpret for us so variously. The Copernican theory was not rejected—nay, it was even countenanced—until this particular consequence of the theory was recognised. But within a few years from the persecution of Bruno, Galileo was imprisoned, and the last years of his life made miserable, because it had become clear that in setting the earth adrift from its position as centre of the universe, he and his brother Copernicans were sanctioning the belief in other worlds than ours. Again and again, in the attacks made by clericals and theologians upon the Copernican theory, this lamentable consequence was insisted upon. Unconscious that they were advancing the most damaging argument which could be conceived for the cause they had at heart, they maintained, honestly but unfortunately, that with the new theory came the manifest inference that our earth is not the only and by no means the most important world in the universe—a doctrine manifestly inconsistent (so they said) with the teachings of the Scriptures.

It was naturally only by a slow progression that men were able to advance into the domain spread before them by the Copernican theory, and to recognise the real minuteness of the earth both in space and time. They more quickly recognised the earth's insignificance in space, because the new theory absolutely forced this fact upon them. If the earth, whose globe they knew to be minute compared with her distance from the sun, is really circling around the sun in a mighty orbit many millions of miles in diameter, it follows of necessity that the fixed stars must lie so far away that even the span of the earth's orbit is reduced to nothing by comparison with the vast depths beyond which lie even the nearest of those suns. This was Tycho Brahe's famous and perfectly sound argument against the Copernican theory. 'The stars remain fixed in apparent position all the time, yet the Copernicans tell us that the earth from which we view the stars is circling once a year in an orbit many millions of miles in diameter; how is it that from so widely ranging a point of view we do not see widely different celestial scenery? Who can believe that the stars are so remote that by comparison the span of the earth's path is a mere point?' Tycho's argument was of course valid.31 Of two things one. Either the earth does not travel round the sun, or the stars are much farther away than men had conceived possible in Tycho's time. His mistake lay in rejecting the correct conclusion because simply it made the visible universe seem many millions of times vaster than he had supposed. Yet the universe, even as thus enlarged, was but a point to the universe visible in our day, which in turn will dwindle to a point compared with the universe as men will see it a few centuries hence; while that or the utmost range of space over which men can ever extend their survey is doubtless as nothing to the real universe of occupied space.

29.Similar reasoning applies to the moons of Jupiter, and it so chances that the result in their case comes out exactly the same as in the case of Saturn; all the Jovian moons, if full together, would reflect only the sixteenth part of the light which we receive from the full moon. It is strange that scientific men of considerable mathematical power have used the argument from design apparently supplied by the satellites, without being at the pains to test its validity by the simple mathematical calculations necessary to determine the quantity of light which these bodies can reflect to the planets round which they travel. Brewster and Whewell, though they took opposite sides in the controversy about other inhabited worlds, agreed in this. Brewster, of course, holding the theory that all the planets are inhabited, very naturally accepted the argument from design in this case. Whewell, in opposing that theory, did not dwell at all upon the subjects of the satellites. But in his 'Bridgewater Treatise on Astronomy and General Physics,' he says, 'Taking only the ascertained cases of Venus, the Earth, Jupiter, and Saturn, we conceive that a person of common understanding will be strongly impressed with the persuasion that the satellites are placed in the system with a view to compensate for the diminished light of the sun at greater distances. Mars is an exception; some persons might conjecture from this case that the arrangement itself, like other useful arrangements, has been brought about by some wider law which we have not yet detected. But whether or not we entertain such a guess (it can be nothing more), we see in other parts of creation so many examples of apparent exceptions to rules, which are afterwards found to be capable of explanation, or to be provided for by particular contrivances, that no one familiar with such contemplations will, by one anomaly, be driven from the persuasion that the end which the arrangements of the satellites seem suited to answer is really one of the ends of their creation.'
30.The reader who cares enough about such subjects to take the necessary trouble, can easily make a little model of Saturn and his ring system, which will very prettily illustrate the effect of the rings both in reflecting light to the planet's darkened hemisphere and in cutting off light from the planet's illuminated hemisphere. Take a ball, say an ordinary hand-ball, and pierce it through the centre with a fine knitting-needle. Cut out a flat ring of card, proportioned to the ball as the ring system of Saturn to his ball. (If the ball is two inches in diameter, strike out on a sheet of cardboard two concentric circles, one of them with a radius of a little more than an inch and a half, the other with a radius of about two inches and three-eights, and cut out the ring between these two circles.) Thrust the knitting-needle through this ring in such a way that the ball shall lie in the middle of the ring, as the globe of Saturn hangs (without knitting-needle connections) in the middle of his ring system. Thrust another knitting-needle centrally through the ball square to the plane of the ring, and use this second needle, which we may call the polar one, as a handle. Now take the ball and ring into sunlight, or the light of a lamp or candle, holding them so that the shadow of the ring is as thin as possible. This represents the position of the shadow at the time of Saturnian spring or autumn. Cause the shadow slowly to shift until it surrounds the part of the ball through which the polar needle passes on one side. This will represent the position of the shadow at the time of midwinter for the hemisphere corresponding to that side of the ball. Notice that while the shadow is traversing this half of the ball, the side of the ring which lies towards that half is in shadow, so that a fly or other small insect on that half of the ball would see the darkened side of the ring. A Saturnian correspondingly placed would get no reflected sunlight from the ring system. Move the ball and ring so that the shadow slowly returns to its first position. You will then have illustrated the changes taking place during one half of a Saturnian year. Continue the motion so that the shadow passes to the other half of the ball, and finally surrounds the other point through which the polar needle passes. The polar point which the shadow before surrounded will now be seen to be in the light, and this half of the ball will illustrate the hemisphere of Saturn where it is midsummer. It will also be seen that the side of the ring towards this half of the ball is now in the light, so that a small insect on this half of the ball would see the bright side of the ring. A Saturnian correspondingly placed would get reflected sunlight from the ring system both by day and by night. Moving the ball and ring so that the shadow returns to its first position, an entire Saturnian year will have been illustrated. These changes can be still better shown with a Saturnian orrery (see plate viii. of my Saturn), which can be very easily constructed.
31.Not 'of course' because Tycho used it, for, like other able students of science, he made mistakes from time to time. Thus he argued that the earth cannot rotate on her axis, because if she did bodies raised above her surface would be left behind—an argument which even the mechanical knowledge of his own time should have sufficed to invalidate, though it is still used from time to time by paradoxers of our own day.
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