Journey to the Sun, page 17
“However, by means of the changes that take place in the intensity of the light of certain stars, among those called ‘variable,’ it is easy enough to deduce the time of their revolution. For instance, one of the most remarkable is placed in Cetus and bears the designation Omicron;69 its period is 334 days. ‘The star conserves its maximum brightness,’ Herschel says, ‘for about a fortnight, and sometimes appears then as a beautiful star of the second magnitude; it then decreases for about three months until it becomes completely invisible for approximately five months; then its brightness increases for the remaining three months of its period.’
“I conclude therefrom that during half of its course it is moving away from us, and that it is approaching during the other half, that it describes an ellipse, one of whose summits is orientated in our direction, and that during the fortnight that it appears bright to us its travels the curve formed by that summit. The constellations of Perseus, Cepheus, Lyra, Antinous. Hercules, Serpentis, Hydra and Sagittarius each offer us a star analogous to that one; Cygnus and Leo each present two.”
“I’d like to believe,” said the Solarian, that that is a demonstration and that the stars are moving through space, but it doesn’t prove that, like my Sun, they have planets rotating around them.”
“I’ll try to establish that. Algol is a star in Perseus that appears to be a star of the second magnitude for sixty-two hours; then its brightness suddenly decreases, and in the space of two and a half hours it is reduced to the fourth magnitude; it then starts increasing again, to resume its habitual brightness in three and a half hours, the full extent of its period being approximately two days, twenty hours and forty-eight minutes. Goodricke, who was the first to observe the phenomenon,70 thought with reason that an opaque body, consequently a planet, is circling the star and comes periodically to interpose itself between it and us.”
“Is it necessary to conclude that there are, in visible space, as many planetary systems similar to ours as there are stars?”
“Not at all. Those planetary systems don’t all resemble ours, because there are some that have two suns, and we only have one.”
“Two suns! That seems singular to me.”
“However, it is demonstrated today by twenty-one years of observations made by William Herschel between 1778 and 1803, and observations that his son has continued to the present day. It results therefrom that between thirty and forty have been found of these systems with two suns rotating around one another, accomplishing their revolutions in various lengths of time, one in 1200 years, others in 628 years, 80 years, 43 years, etc.; but what is most extraordinary for those who do not know the law of complementary colors is that the two suns are never the same hue; if one is red, the other is green; if one is yellow, the other is blue. The inhabitants of planets illuminated by them must, in consequence, have red days and green days alternating with white, tallow or blue days and obscure nights. Truly, if all that had not been mathematically proven, I would think that I were traveling in an enchanted land to which a beautiful dream had taken me.”
I was at that point when we saw arriving and rising over our immense horizon a very large globe that was advancing toward us with such rapidity that one could easily follow it with the eye; it was moving in space while rotating about its axis, just like a ball launched by a vigorous player of skittles. Its color was pale white, like the Moon when one perceives it during the day.
I confess frankly that I did not recognize it, because I had never seen anything similar from Earth. In my disappointment, I turned toward the genius, who smiled at my embarrassment, and then said: “What you see is Mercury, the planet closest to the Sun, and it’s because you’re looking at it from this globe—which is to say, from approximately three times closer than from Earth—that you see it nearly three times as large; it also appears to you to be traveling more rapidly for the same reason, and also because it’s velocity really is more rapid than that of any other planet, which it owes to its greater proximity to the Sun. If its glare is less bright, it’s because you’re placed at the source of the light it receives.
“Mercury is 13,361,000 leagues from the Sun and its diameter in 1,200 leagues, or two-fifths of that of the Earth. Its days are 24 hours 5 minutes 2 seconds, and its years 87 days, 23 hours 15 minutes 44 seconds—which is to say that it turns on its axis in a little more than 24 hours and completes the ellipse that it describes around the sun in nearly 88 days, which, given its distance from the star, means that it its traveling at forty thousand leagues an hour as it moves along its orbit.
Chapter VII
The Planetary System
“Let us pass on to the most beautiful of the planets, which has been named Venus because of its brightness, and which has also been called the Shepherd’s Star, because it sometimes shows itself in the morning and sometimes in the evening, at the time when pastors are bringing forth or taking home their flocks. Its mean distance from the Sun is 25 million leagues; its size is slightly less than that of the Earth, for it is some 2,800 leagues in diameter; the velocity at which it travels in its orbit around the Sun is less than that of Mercury and more considerable than that of Earth, for it advances at 29 thousand leagues per hour. Its days are 23 hours 21 minutes 19 seconds and its year is 224 days 16 hours 49 minutes. The orbits described by Mercury and Venus are enclosed within that of the Earth. Let us now pass on...”
“Pardon me, Monseigneur,” I said to the demon, “but it seems to me that you’re abridging singularly, and if you go at that pace, we’ll soon be at the far end of the world.”
“My intention,” he said, “is to pass in review for you the entire planetary system, in order that you can get a clear and precise idea of it to begin with; then, as I’m going to take you to all those worlds, you’ll have time to study them in detail. However, I can extend myself a little on the one you perceive as a little, rather bright star, around which another bright dot is turning, which seems to be touching it. You’ll deduce that it’s a matter of the Earth and the Moon.”
“Permit me, Monseigneur: I see all those planets round and bright over their entire surface, like full moons, and yet on Earth, I’ve often seen Venus and the Moon present themselves to my eyes as silvery crescents. Why is that?”
“Because from Earth your eyes embrace both a part of those bodies turned toward the Sun and struck by its rays, and another part in shadow, turning its back to the sun, to make use of a vulgar expression; whereas from here, being placed at the center or source of those rays, they travel the same lines through space as your sight and necessarily fall on the same points.”
“One more question. Mercury is smaller than Venus, and Venus smaller than the Earth, and yet I see the Earth much smaller than Venus, and Venus much smaller than Mercury...”
That’s because objects, in accordance with the laws of optics, appear to us to diminish in size in proportion to their distance from the viewpoint from which one is looking at them. Astronomers have taken advantage of that fact and deduced useful consequences therefrom in order to determine the movement of certain heavenly bodies by means of their apparent size, increasing or decreasing, compared to their actual size. But let’s get back to the Earth.
“You doubtless know that it’s nine thousand leagues around, which gives it a diameter of nearly three thousand leagues; but as it is not precisely round, bulging slightly toward the equator and being slightly flattened around the poles, the diameter is not exactly the same everywhere. For example, a line passing through the Earth from one pole to the other passing through the center of the globe, would be 2,800 leagues of 2,280 toises each; the same line passing through the equator would be 2,870 leagues, and would, in consequence, be ten leagues longer. The flattening at each pole is thus nearly five leagues, or, if you want more precision, 10,600 toises. If the line passed through France at the forty-fifth degree of latitude—through Lyon, for example—it would be 2,864 leagues.”
“I knew that the Earth is flattened at the poles, and I even know why.”
“Bah! Tell us that.”
“It’s because when our globe was in fusion, the liquid matter, by virtue of the effect of the centrifugal force resulting from the rotation, must have flowed away from the poles and accumulated toward the equator.”
“Ha ha! It’s my turn now to take lessons,” said the genius, smiling. “Are you going to tell me how it came about that the globe was in fusion?”
“Nothing is easier. Launched into space by the Sun, of which the matter composing the Earth is merely the froth...”
“Now you’re going to say silly things again. Remember that at this moment we’re on a mountain on the Sun, not in a furnace.”
“My God! I was thinking about that. That’s true. How can it be that some of our astronomers simultaneously admit two contradictory facts: to wit, firstly that our globe was once incandescent, and still is in its interior; and secondly that the Sun isn’t. Come on, let’s seek the explanation elsewhere…ah! I have it. In the beginning, the Earth was encountered by a comet that set it on fire, and...”
“One moment. Comets are incapable of setting anything on fire; they have little or no heat of their own, and are not even luminous, as is proved by the phenomenon of polarization.”
“However, it’s necessary that one or other of these causes liquefied the globe.”
“Why is it necessary to liquefy the globe to explain the flattening of the poles? Are not water and the matter that it holds in solution, the air and the molecules of matter that it carries, and the light bodies that are constantly forming or organizing on the Earth’s surface obedient to the mechanical laws of rotation as well as pebbles in fusion? Are they more firmly attached to the nucleus of the Earth than any other matter in fusion? Could they not have drawn away from the poles just as easily as molten lead?
“In addition, my dear, there’s another little difficulty. Let’s admit that the Earth in fusion was launched from the Sun—you don’t suppose, I hope, that it was spherical in form, that it was detached from the furnace with its globular form?”
“Certainly not. It owes that form to its movement of rotation.”
“If its rotation was able to impose the form of a ball upon it, the laws of mechanics must not have been the same then as they are now, because, supposing the material to be liquid, it would have taken the form of a flat disk, not a sphere. Not at all: it has taken the form of a globe; then, when that sphere was well rounded, mechanical law changed in order to deform the ball and remake a disk by flattening it at the poles. You can see that it’s not possible.”
“I don’t say that it first took the form of a perfect sphere, but that of a flattened globe.”
“But then there would have been two laws of mechanics diametrically contrary and operating simultaneously, one to make the formless splinter a sphere and the other to make it a disk.”
“I confess that that’s very embarrassing; I hadn’t thought of it. Are you, who know so many things, going to tell me how the Earth, as well as Saturn and other planets, are flattened at their pole if they’ve never been in fusion?”
“My dear, if anyone asks you that you can reply that you don’t know, and you’ll be sure of not being mistaken—all the more so because, if you go on to give other mechanical reasons, you might be put into embarrassment by being asking why other planets that have, like the Earth, a rotational movement, are nevertheless not flattened but perfectly spherical; why Ceres and Pallas, which also rotate, are neither flattened not spherical but irregular in form, etc., etc. And if you say that it’s because those planets have never been in fusion, you’ll be asked what necessity there is for the Earth ever to have been molten, when that necessity doesn’t exist for the others.”
“Well, let’s not talk about the flattening of the poles any longer, but leave me my little theory of the liquefaction of the globe, for it’s almost proven by a host of geological experiments. By means of thermometers placed in the depths of artesian wells, mines, subterranean caves and other profundities, it has been found that the Earth’s heat increases by one degree per ninety feet as one descends into its entrails, and after work done with as much talent as care, one of our scientists has published the contention that the augmentation is one degree for forty-six feet. According to him, the entire mass of the globe, with the exception of a crust that is no more than twenty leagues thick, is composed of molten lava, entirely similar to that which springs from volcanoes, and he considers the latter as the ventilators, or rather as the safety-valves, of our globe.”
“That hypothesis is certainly ingenious, but let’s see whether it can stand up to criticism. Let’s first occupy ourselves with the facts that serve to establish it. Geologists have studied what they call the mineral crust of the Earth, and in accordance with the phenomena that they have observed there, they’ve deduced the general phenomena of the globe. You realize that it has been concluded on the basis of probabilities, and that they’ve been obliged to establish for that a kind of statistics of chance.
“But the mineral crust observed or supposed to be known is, so far as I know, no more than 1,700 feet in depth below the surface of the Ocean; at least, what is certain is that no thermometric experiments have been carried out below that depth. 1,700 feet, neglecting fractions, are 283 toises; now, in proportion to the radius of the Earth, 283 toises is one in 11,531. It is, therefore, on a rather slight knowledge of one eleven-and-a-half-thousandth of the thickness of the Earth that geologists claim to judge the totality of the globe. It’s as if I wanted to judge the interior of a ball nearly fifty feet in diameter by a fraction of an inch of the thickness of its surface. You’d tell me what people say to fools, that it’s necessary not to judge a tree by its bark, especially when that bark is exceedingly thin. If we were prepared to believe these gentlemen, there would be boiling water only 8,212 feet beneath Paris—which is to say, a little more than a quarter of a league beneath the ground on which we tread so tranquilly.
“And that, however, is what they call facts and observations. If these observation were even identical everywhere…but they aren’t. That increase in heat, fixed at one degree per 46 feet by one, is fixed at one degree per 24 or 37 feet by another, one degree per 56 feet or one degree per 90 feet by the majority. That is because the increase in heat is not submissive to the same law all over the Earth, because experiments have proven that it can be two or three times as great in one place than another. They ought, it seems to me, to have compared the figures to find their average, and concluded quite naturally that such variable heat cannot have come from a common source.
“Thus, the facts invoked to produce the incandescence of the interior of the globe prove nothing, for the reason that it is not sufficient to know one eleven-and-a-half-thousandth of a composite body to know the totality of the body and determine the species of phenomena associated with it.
“Now let’s reason differently. At a hundred degrees on the centigrade thermometer, water boils and evaporates. No refractory substances are known, including diamond, that do not melt or volatilize at a temperature that never surpasses three or four hundred degrees—let’s say five hundred to accord a generous margin. It follows that any body heated to five hundred degrees and above, whatever its nature might be, will have passed from the solid state to the liquid, or vaporous, or that of gas, and sometimes all three, according to its nature. In a gaseous state, it will occupy a greater volume as it experiences more heat, and its volume can then be several times greater than when the substance was in the solid state. That posited, let’s see what follows.
“Admitting, like the scientist of whom we spoke just now, that the internal heat of the Earth increases at an average of one degree per 46 feet, that of the center of the globe ought to rise to the prodigious temperature of 252,580 degrees. Now, even if the Earth were made of diamond, it would not be liquefied, but in a gaseous state, and that gas would be so rarefied that, in a mass equal to that of the atmospheric air, it would occupy perhaps a thousand times more volume. Even supposing that the force of expansion doesn’t make our poor globe explode like a shell, it would follow that the entire Earth, not including its solid crust, would be composed of less matter than perhaps Mont Blanc or the Puy-de-Dôme, and then, compared to its volume, it would be a thousand times lighter than a feather of the lightest down, for the caloric that would form the immense part of its mass is imponderable.”
“But nothing proves that the heat increases with the same intensity all the way to the center of the globe,” I said to the demon.
“For the phenomenon to occur as I describe it,” he replied, “there’s no need for it to do so. It would be sufficient for it to increase in that progressive proportion until a depth of five leagues, at the most.71 Now, far from the Earth being as light as a feather, it’s five times heavier than water, heavier than lead. How can you enable me to understand that at an equal volume, a gas can be as heavy, or even heavier, than the substance that furnished it by expansion?”
“I confess that the proposition is not sustainable. Well, I’ll grant you that the interior of the globe is in a solid state, but at least you’ll agree with me that in the beginning it was in a state of fusion.”
“Not at all. Since that dilates substances, on cooling they must shrink and lose volume. However, it’s certain that the Earth, more than three thousand years ago, was exactly the same size as it is today; thus, it has not been subject to cooling.”
“How can you know that?”
“I know it by virtue of ancient astronomical observations, and I’ll demonstrate it to you, although I don’t believe you’re intelligent enough to understand the demonstration perfectly at present. This is it. If the volume of the Earth had varied by the effect of dilatation or contraction, the motion of the Moon would also have varied; now, that hasn’t happened, for the duration of the sidereal day is exactly the same today as in the most remote times, and we have several thousand years of observations that prove it.”
