Part 7

It may be the case, answered I; and we have another way of giving them relief. There are some parts of China which from their situation ought to be very hot, and yet, even in the month of July and August the weather is so cold that their rivers freeze. This coldness arises from the quantities of salt-petre with which the countries abound; the exhalations, drawn up in great abundance by the heat are of a cold nature. Mercury, if you please, shall be a little planet made of salt-petre, and the sun, by attracting the cooling exhalations, will thus prevent the evil it would otherwise be the cause of. However, we may rest assured that nature would not place beings where it was impossible for them to exist; and that habit, and ignorance of a better climate, render this situation agreeable: Mercury therefore may perhaps do very well without salt-petre, or abundant rains.

After Mercury, you know, we find the sun. We cannot possibly place inhabitants there: the _why not_ fails in this case. We conclude from the earth being inhabited that other bodies of the same nature must be so too: but the sun does not resemble the earth, and the rest of the planets. He is the source of all that light which the planets only reflect to each other after they have received it from him. They make exchanges, if I may so express myself, with one another, but none of them can bestow an original light. The sun is the sole proprietor of that treasure; which he distributes freely on every side. The light, thus issuing from the centre, is reflected from every solid body it meets, and from one planet to another it proceeds in bright streams that intermix, and cross each other in a thousand directions, forming a splendid tissue of the richest materials. The grand luminary by being placed in the centre is in the most advantageous situation for animating each planet with his heat and radiance. The sun, then, is of a peculiar nature, but what that nature is, we find it difficult to imagine. Formerly it was believed to be a pure fire, but lately we have been undeceived by observing spots on the surface. As certain new planets had just before been discovered, (I shall give you an account of these planets hereafter;) which entirely engrossed the attention of the philosophers, a sort of mania for new planets seized their minds, and they immediately concluded these spots were some; that they performed a circle round the sun, and necessarily concealed some part of his light by turning their dark side towards the earth. The learned already, through these planets, complimented the different princes of Europe. Some gave them the name of one prince; some of another, and perhaps in time there would have been a great contest to know who had the best right to name these spots.

I don't like their plan, said the Marchioness. You told me, the other day, that the different parts of the moon were named after learned men; I thought that very proper: as princes monopolize the earth, it is but fair that astronomers should have the sky for their share, and not suffer princes to intrude on their domain. Allow them, however, I replied, if territory should be wanting, to consign to them some planet, or some part of the moon. As to these spots on the sun, they can make no use of them; for instead of planets, we find they are only clouds of smoke or dross arising from the sun. Sometimes these clouds are greatly accumulated, sometimes we see little of them, and at other times they totally disappear. Sometimes a number of them are combined together, then they are separated into small parts; at one time they are very dark, at another they grow pale. It appears as if the sun was some kind of liquid; many people think it is melted gold, in a continual state of ebullition, producing impurities, which the rapidity of its motion casts up from the surface; they are afterwards consumed and others produced. Only think what amazing bodies these are. Some of them are seventeen hundred times[34] larger than the earth, for you must know, the earth is more than a million times smaller than the sun.[35] Imagine therefore what must be the quantity of this liquid gold, or the extent of this ocean of light and fire!

[Footnote 34: The largest of the sun's spots are scarcely three times larger than the diameter of the earth, or twenty-seven times its bulk.]

[Footnote 35: The earth is only a hundred, or to speak with more exactness, a hundred and eleven times, smaller.]

Other philosophers say, and with great plausibility, that the spots, or at least the greatest part of them, are not newly produced, and then destroyed after a certain time; but large, solid, masses, of irregular forms, always subsisting; sometimes floating on the surface of the sun, sometimes partly, or entirely buried in the liquid substance, and presenting to our view different projections according to the size of the part that remains uncovered. Perhaps they may be parts of some great mass of matter which serves as aliment to the fire of the sun. However, let the sun be what it will, it does not by any means appear habitable.[36] It is a pity; the situation would be advantageous: placed at the centre, its inhabitants would see the planets going round them in regular orbits, whilst to us their motions seem to have perplexing varieties, which are merely the effect of our not observing them from the best place; that is, the centre of their circles. What a sad thing it is: there is but one spot where the study of the celestial bodies would be extremely easy, and at that spot there is nobody to pursue the study. You forget yourself, answered the Marchioness. Were any one placed on the sun, he would neither see the planets nor the fixed stars; would not the light of the sun efface every other object? The inhabitants would doubtless think themselves the only people in existence.

[Footnote 36: Some natural philosophers have however thought that the sun might be the cause of heat without being itself hot; and that there was a possibility of its being inhabited. M. Herschel believes its population very abundant. Trans. Philos. 1795. Décade Philosophique.]

I acknowledge my error, I replied: I was thinking of the situation of the sun, without considering the effect of such an excessive light: but although you have so properly corrected my mistake, yet you must allow me to tell you that you have fallen into one yourself. The inhabitants of the sun would not see any thing: they would be either incapable of enduring so immoderate a light, or, were their eyes sufficiently strong, of receiving it unless they were at some distance; therefore the sun could only be a habitation for people without sight. In short, we have abundant proofs that this luminary was not intended to be a dwelling-place; and therefore we may as well continue our planetary journey. We are now stopping at the central point which is always the lowest part in any thing that is round; and, by the way, I should tell you that in going from our world to this centre we have travelled thirty-three millions of leagues. We must now return the way we came. We pass by Mercury, Venus, the Earth and the Moon; all which we have visited. Then we arrive at Mars. I don't know that there is any thing remarkable in this planet. The days there are about half an hour longer than ours; and the years twice the length of ours, except a month and a half. Mars is four times less than the earth,[37] and the sun appears rather smaller and less brilliant than it does to us.--In short, Mars contains nothing calculated to arrest our attention.

[Footnote 37: Its volume, or bulk is five times smaller.]

But what a beautiful object is Jupiter, surrounded by his four moons, or satellites! These moons are four little planets which, whilst Jupiter revolves in twelve years round the sun, constantly go round him as the moon does round the earth. But, interrupted the Marchioness, how is it that there are planets which go round other planets, no better than themselves? It seems to me that there would be much more regularity and uniformity in assigning to all the planets but one sort of orbit in which they should move round the sun.

Ah! madam, I replied, were you but acquainted with the vortices of Descartes; those vortices, so terrible in name, and so charming in the ideas they give rise to; you would not talk in this way. My wits must all go, said she, laughing. I must know what these vortices are. Make me quite mad at once: now I have dipped into philosophy I can't trouble myself about the care of my senses: spite of the world's laughter, we will talk of the vortices. I did not know you had so much enthusiasm, said I; 'tis pity it has no other object than vortices.

What we call a vortex is a quantity of matter, whose detached parts move all in the same direction, but allowed at the same time to have some little movements peculiar to themselves, provided they still pursue the general course. A vortex of wind, for instance, is a vast number of little particles of air, turning all together in a circular direction, and involving whatever comes in their way. The planets you know are borne along by the celestial fluid, which is prodigiously subtle and active. All the celestial matter, from the sun to the fixed stars, constantly turns round, carries the planets along with it, and makes them proceed round the sun in the same direction, but in longer or shorter periods, according to their distance from the centre. Even the sun is made to turn on his axis by being exactly in the midst of this moving matter; you will therefore observe, that if the earth were in the central situation she could not be exempted from this rotation.

Such is the great vortex of which the sun is master; but the planets, at the same time, form little vortices in imitation of the sun. Each of them whilst turning round the sun, turns likewise on itself, and carries in its motion a certain portion of the celestial matter, which is ready to receive any impulse that would not prevent it from following the general course: this is a vortex of any particular planet, and it extends as far as the motion of this planet has any influence. If a smaller planet comes within the vortex of a larger one, it is irresistibly carried round that larger one, and altogether, the large, and the small planet, and the vortex that encloses them, perform their revolution round the sun. Thus at the commencement of creation we obliged the moon to follow us because she came within the influence of our vortex, and was by that mean subjugated to our will. Jupiter, the planet we were speaking of, was more fortunate, or more powerful than the earth. Four little planets were in his neighbourhood, and he became master of them all; and we, who are a planet of some importance, would probably have felt his power if we had been near him. He is a thousand times larger than the earth;[38] and would easily have drawn us into his vortex, and made us one of his moons; instead of this we have a planet to attend on us: so true is it that the situation into which we are thrown decides the fate of our lives.

[Footnote 38: We may even say thirteen hundred times.]

And how do we know, answered the Marchioness, that we shall always remain where we are? I begin to tremble lest we should be foolish enough to approach such an enterprizing planet as Jupiter, or that he should come to us, for the sake of drawing us into his vortex; for I can't help thinking, from your description of the agitated state of this celestial fluid, that it must move the planets irregularly, sometimes urging them nearer together, sometimes sending them to a greater distance. We may as well expect to gain as to lose by such an eccentric motion, said I; perhaps we may make a conquest of Mercury or Mars, which are smaller planets, and incapable of resisting us. However we have no occasion for either hope or fear; the planets will remain in their places; and, like the former kings of China, they are forbidden to aim at conquest. You have observed that when oil is mixed with water, the oil swims at the top. Put any substance that is extremely light on both these, and the oil will support it, so that it shall not touch the water: but put a heavier body, of a certain weight, it will pass through the oil, which is too weak to stop it, and keep falling till it meets the water, which has sufficient force to bear it up. Thus two liquors put together, being of unequal weight, will not mix, but place themselves in different situations; and neither will one rise, nor the other descend: pour on these other liquors which are of a nature to remain separate, and the same effect is still produced. In like manner the celestial matter which fills this grand vortex, is in separate strata, encircling each other, and of unequal weight, like oil and water, and some other liquors. Some planets likewise are heavier than others,[39] each therefore stops in the layer which has the degree of force necessary for supporting it, and keeping it in a state of equilibrium; and you must be convinced that it can never go beyond this stratum.

[Footnote 39: The Cartesians carried their illusion so far as to believe that so solid a mass as a planet could be steadily supported by the ætherial fluid, the most subtle of all fluids.]

I understand, replied the Marchioness, that the different degrees of weight are sufficient to keep them in their proper ranks. I wish with all my heart there was some such regulating power among us, that would serve to fix people in the situation most suitable to them! You have quite removed my uneasiness with regard to Jupiter. I am very glad he will let us remain quietly with our little vortex, and single moon. I feel very well contented with one attendant, and do not envy him his four.

You would do wrong if you did, said I; he has no more than are necessary. He is five times farther from the sun than we, that is, a hundred and sixty-five[40] millions of leagues distant from it, consequently his moons receive, and reflect, but a feeble light: the number therefore compensates for the little effect produced by each: were they not separately so inefficient, four moons would appear unnecessary, as Jupiter turns on his axis in ten hours, and of course the nights are very short. The satellite which is the nearest to Jupiter, performs its circle round him in two-and-forty hours; the next in three days and a half; the third, in seven; the fourth, in seventeen; and by the inequality of their progress, they form a most pleasing spectacle for this planet. At one time they rise all four together; then, almost immediately separate; sometimes they are all at the full, placed in a line, one above another; afterwards they are seen at equal distances in the sky; then when two are rising the other two will set. Above all I should like to see the perpetual variety of eclipses among them, for there is not a day passes in which they do not eclipse each other, or the sun.[41] Surely as eclipses are so familiar to the inhabitants of that world, they must be considered a subject of amusement, rather than terror, as they are here.

[Footnote 40: Calculating with more exactness, 179.]

[Footnote 41: Or; we may add, in which they are not eclipsed by the shadow of Jupiter, which happens the most frequently.]

You will not fail, I suppose, said the Marchioness, to people these four moons, though they are only little subaltern planets, intended merely to give light to another during the night. Undoubtedly not, I replied. These little planets are not unworthy of inhabitants because they are unfortunate enough to be subjected to a larger planet.

I think, then, answered she, these satellites ought to be like colonies to Jupiter; that their inhabitants should, if possible, receive from him their laws and customs, and in return, render him some degree of homage, and always consider the great planet with respect. Would it not be needful, said I, for the moons occasionally to send deputies to Jupiter, who should take an oath of fidelity to him? I must own the little superiority we possess over the people in our moon makes me doubt whether Jupiter has much influence over the inhabitants of his satellites, and I think the only superiority he can aspire to is that of impressing them with awe. For of what a terrific size he must appear! To the planets nearest to him he looks sixteen hundred times larger than our moon appears to us.[42] Truly if the Gauls in ancient times were afraid the heavens would fall and crush them to death, the inhabitants of this moon may with greater propriety apprehend the fall of Jupiter. Perhaps, she replied, that is the subject of alarm to them instead of the eclipses, which you assure me they see without fear;[43] for as they are exempt from one folly, they must be subject to some other. Undoubtedly, answered I. The inventor of a third system, which I mentioned the other day, the celebrated Tycho Brahe, one of the greatest astronomers that ever lived, felt none of the vulgar terror at an eclipse; he was too much accustomed to study the nature of such a phenomenon; but what do you think he was afraid of instead?--If when he first went out of doors the first person he saw was an old woman; or if a hare crossed the path he had taken, Tycho Brahe thought the day would be unfortunate, and returning in haste to his apartment, he shut himself up without venturing to engage in any occupation whatever.

[Footnote 42: Thirty-six times larger than we see the moon: and they receive from him one thousand two hundred and ninety times more light.]

[Footnote 43: Their solar eclipses are of much longer duration than ours.]

It would be unjust, said she, if such a man as he could not with impunity overcome the fear of an eclipse, for the inhabitants of the satellite we were speaking of, to be exempted from it on easier terms. We will not spare them: they shall submit to the general doom; and if they escape one error they shall be liable to another.

A difficulty has just occurred to me, continued she, you must remove it if you can: if the earth is so small in comparison of Jupiter, are we visible to the inhabitants of that planet? I am afraid we are unknown to them.

Really I think so, answered I; the earth is certainly too small to be distinguished by them.[44]

[Footnote 44: The earth at that distance must appear only three seconds and a half in diameter, as the planet Herschel does to us; but our nearness to the sun necessarily prevents them from seeing us at all.]

We can only hope that in Jupiter there may be some astronomers who, after taking great pains to compose very excellent telescopes, and availing themselves of the finest nights for making their observations, may at length discover a very little planet which they had never seen before. At first the learned give an account of it in their journal; the rest of the people either hear nothing about it, or laugh at it when they do; the philosophers are discouraged and resolve not to mention it again, and but a few of the inhabitants who are more reasonable than the others will admit the idea. By and by they examine again; they see the little planet a second time; they are then assured of its reality, and even begin to think it has a motion round the sun. After observing it a thousand times, they find out that this revolution is performed in a year: and at last, when the learned have been at great pains to investigate the subject, the inhabitants of Jupiter know that our world is in the universe. The curious eagerly look through their telescopes, and with all their looking, can scarcely discern it.

Were it not disagreeable, said she, to know that from Jupiter we can only be seen through telescopes, I should amuse myself with the idea of all the glasses being pointed towards the earth as ours are towards him, and the mutual curiosity with which the two planets examine each other, and enquire, _What world is that? What sort of people inhabit it?_

Your imagination is too rapid, I replied; when the astronomers of Jupiter become acquainted with our earth, they do not become acquainted with us: they will not suspect the possibility of its being inhabited; if any one should venture to express such an idea, how they would laugh at him! Perhaps they would even persecute any philosopher who should maintain the opinion. After all I think the inhabitants of Jupiter are too much occupied in making discoveries on their own globe, to concern themselves about us. Jupiter is of such extent, that if they are adepts in navigation their Christopher Columbus must be fully employed. The inhabitants cannot know, even by reputation, a hundredth part of the other inhabitants. In Mercury, on the contrary, they are all neighbours, living familiarly together, and hardly considering the tour of their world more than a pleasant walk. If we are not visible to Jupiter, much less can Venus be so, who is at a still greater distance;[45] and Mercury must be most out of its reach of all, being the smallest, and the most distant. However, the inhabitants can see Mars, their own four satellites, and Saturn with all his moons. Surely then they have planets enough to perplex their astronomers; nature, in kindness, has hid from them the rest.

[Footnote 45: Venus is not farther from Jupiter, but more concealed by the rays of the sun.]

What! cried the Marchioness; do you consider it a kindness? Without doubt, answered I. This great vortex contains sixteen planets; nature to spare us the trouble of studying the motions of so many, let us see but seven: is not that a favour? But not feeling the value of this mark of consideration, we have, with great pains, discovered the other nine, which had been concealed from us: our curiosity brings its own punishment in the laborious study which astronomy now requires.

I see, she replied, by the number of planets you mention, that Saturn must have five moons.[46] You are right, said I; and it is but just that he should have so many, as he is thirty years in going round the sun; and in some parts the nights last fifteen years, for the same reason that on our globe, which turns in a year, there are nights, beneath the poles of six months' duration. But Saturn, being at twice the distance that Jupiter is from the sun, consequently ten times farther than the earth; his five moons, faintly as they are illumined, would not give sufficient light during his nights, he has therefore a wonderful resource, the only one of the kind we have discovered in the universe: 'tis a large circle or ring[47] which environs the planet, and which, being sufficiently elevated to escape almost entirely the shadow of Saturn, reflects the sun's light on the darkened parts, and reflects it more strongly than all the five moons, because it is not so high as the lowest of them.

[Footnote 46: He has seven, and Herschel six. In all there are twenty-five planets, without reckoning ninety-one comets known in 1800.]

[Footnote 47: Its exterior diameter is sixty seven thousand seven hundred leagues.]