(“Hear hear!”)
“Given these generalities, gentlemen, it is easy for me to embark upon my subject and determine—with some precision, I hope—the true relative ages of the planets. Let us go back to the creation of our system—and take note, gentlemen: although we have not been able to see that primitive epoch, others certainly have.
“Imagine yourselves, in fact, to be in a very distant solar system presenting at this moment the same physical characteristics as the Earth. Light travels, as you know, 298 million meters per second.28 Now, for the inhabitants of that world, if it is distant enough, the formation of our world will have taken place millions of years ago, and yet they will only now be able to observe it in that regions of the heavens. It is a simple matter of distance. It is necessary for the light that links the worlds in this sector of space to have time to reach its inhabitants. Thus, at this very moment, many astronomers lost in the oasis of the heavens can only witness the birth of our system.
“What happened? As always, a vaporous cloud is advancing through space at an extremely high temperature: a balloon of superheated vapors. At length, cooling takes place; the vapors contract and condense at certain points, obedient to the resultant of the forces that hold the in equilibrium. Where before there was only an opaline globe of hot vapor, new little globes form, less hot and more condensed, partly solidified, in exactly the same way that water vapor spread through the air forms a multitude of droplets as it cools.
“The initial cosmic matter is resolved into a rain of red hot drops: a rain of stars of worlds. We see them all around us; they fill the surrounding space again.
“Our Sun is but one scarcely-condensed drop of that fiery primitive matter; the planets are little droplets that sprang forth at the same time or condensed close to it. The initial motion that impelled the ensemble is conserved by each of its component parts, and all the worlds thus formed have continued to advance through space as before, rotating in the trajectories that the atoms were following before their agglomeration.
“Thus, in my view, it is established that the Sun and the planets have absolutely the same origin. In the beginning, at the moment when the cosmic rain condensed, they had the same constituents of uniform matter and the same quantity of motion—that which animated the entire system. The similarity was complete.
“Let us now follow these heavenly bodies through their transformations, through their evolution.
“Is it not perfectly clear that the quantity of movement that each one of them possesses cannot remain the same? If one considers it after a certain period of time, one will find it different. Is it not determined by the sum of free and independent primitive atoms, multiplied by the velocity with which these rudimentary heavenly bodies describe their trajectories?
“Now, we know that each petty atom inevitably loses its velocity over time, but that it loses it harmonically—which is to say that the loss is redistributed to every other atom. The more of them there are, the slower the loss of velocity is; the fewer there are, the more rapid it is. In other words, the loss of quantity of motion, which is the cooling of a heavenly body, is proportional to the sum of the atoms that constitute it—proportional to its mass. It is worth noting that this is no more than a translation of a principle well known to ordinary people: that the smaller a body is, the more rapidly it cools. From the preceding argument, gentlemen, you will immediately see this important consequence emerge.
“The rapidity of the evolution of a heavenly body, the duration of its life, is linked to its mass. Its life will be longer or shorter in proportion to the greater of lesser magnitude of its mass. From that emerges a method permitting the measurement of the age of a planet, and of forming an idea of the biological phenomena of which it has been the theater.
“Is not that which emerges from this reasoning process what common sense indicated in the first place? Why should you assume, gentlemen, a different plan of construction for every heavenly body? Why should not the Earth be hardened from the same clay as any other planet? Why should Venus be blonde and Jupiter brunette, Saturn chestnut, Mercury red and Mars albino? Why not the same constitution everywhere? What is here is there, what is there is here; once more, matter everywhere passes through the same evolutions. The only physical difference that the heavenly bodies present is in their age, the period of their transformation—that is all…”
The President: “Mr. Greenwight has just given a very clear summary of my idea—and that, I think, of all philosophical geologists—of the genesis of worlds. I…”
Mr. Greenwight: “I have not finished, Mr. President; the subject is large, and unless you have personal objections to address to me, I still implore the benevolent attention of the assembly.”
Mr. Haughton, the geologist of the thorns and roses: “I request the floor.”
Mr. Newbold: “I merely wanted to ask Mr. Greenwight to continue his account of geological evolution on another occasion. The floor, on that occasion, will be given to Mr. Haughton—but the advanced hour obliges me to ask my savant colleague to leave the conclusion of his interesting dissertation until tomorrow.”
The session ended at 7 p.m.
LETTER VI
On the age of heavenly bodies. A means of determining it. By which it is shown that not all worlds can be inhabited. Objections. Elements of our solar system. Relationships that seem to exist between the volumes, masses and densities of planets. Different aspects. The necessary conditions for two worlds to resemble one another. The floor continues to be held by Mr. Greenwight.
Mr. Greenwight: “I showed in the last session that if worlds present different appearances, we must seek the cause solely in the greater or lesser rapidity of their evolution. In the epoch in which we see them, they are more or less advanced; they are younger or older, according to their initial mass.
“We might envisage them as different members of the same family. Each of them, save for a few characteristic and similarly-originated particularities, will at some time present the same form and the same appearance—but when they are all seen together, one is young and another old. It is the same with worlds. They are alive; they have all passed, or will pass, through the same phases, like every natural individual. It now remains for me to apply these considerations and to draw conclusions therefrom.
“I therefore propose to you a simple introductory stroll through our neighbor worlds; I hope to be able to specify their biological characteristics, their conditions of habitability.
“Firstly, before setting out, are they all habitable?
“Evidently not, gentlemen. The French scientist Arago,29 and so many others who followed him, who placed inhabitants everywhere, even in the Sun, had no notion of the true laws that preside over the destiny of worlds.
“By an inhabitant—for it is necessary to define everything in order to avoid misconceptions—I mean some sort of animal, a living organism. Now, an organism can evidently only exist in a condition of being partially composed of liquids and solids. Liquids are generally the vehicles of life. For us, blood and the humors are absolutely necessary to the sustenance and the refinement of our organs. One cannot imagine any kind of creature solely formed out of solid materials; it would be inert. Such a body would belong to inorganic nature, here and everywhere else.
“That said, we arrive inevitably at this consequence: that no living being can exist on any world while the quantity of motion possessed by that world—which is to say, its own heat—is sufficiently elevated to vaporize the organism’s liquids. Conversely, every organic creature will disappear from its surface when its heat becomes low enough to freeze the organism’s liquids. Those are the two extreme limits of life.”
Mr. Rink: “But how can Mr. Greenwight tell whether the liquids of some heavenly body or other might not be able to resist high temperatures—and how, in consequence, the biological limits determining the appearance and disappearance of living beings can be determined?”
Mr. Greenwight: “Mr. Rink is a trifle has
ty; everything cannot be said at once. It is evident that, at first glance, one cannot see why liquids might not have different properties of cohesion in the heavenly bodies of a system.
“A liquid’s boiling point is linked to the pressure that it supports and its composition. If the pressure and the composition were significantly different, liquids might exist on each world at widely different temperatures, as Mr. Rink quite rightly says—but I have good reasons to believe that it is not so, and am drawn to the opposite conclusion.
“Yes, without a doubt, on Earth and elsewhere, pressure has varied since the time of origin; it must be more considerable at the beginning, and, in consequence, liquids could only evaporate at a higher temperature than they do now. Yes, I also think that the pressure might perhaps be slightly variable between stars, but within very narrow limits. In conclusion, though, considering the pressure that now exists on Earth and the neighboring worlds, recalling the unity of origin of heavenly bodies, and judging the past by the present, one is bound to admit that the composition of liquids of the same nature is much the same everywhere. We shall, moreover, return to this point soon and enter into some new explanations. Since composition and pressure remain almost identical, it can be presumed that the limits of existence are almost the same everywhere.
“At what temperature are the liquids of terrestrial organisms volatilized? About 80 degrees.30 The pressure being much greater in the beginning, we shall extrapolate that initial temperature to 100 degrees. By the same token, we shall extrapolate to 30 degrees below zero the ultimate temperature—that at which freezing occurs in spite of the heat produced by vital activity. From 100 degrees to minus 30 degrees is 130 degrees; those are the degrees of life, the normal limitations circumscribing the existence of organisms.
“Thus, gentlemen, any world that possesses a surface temperature of 100 degrees cannot be inhabited. Any world that has cooled to below minus 30 degrees is similarly incapable of sustaining life. Conclusion: not all worlds are habitable.
“Let us see now which of those around us might be inhabited; let us seek to determine the age of each planet.
“The quantity of motion for each world, as we have already said, depends primarily on its mass. The different planets that surround us were doubtless absolutely similar for a fairly considerable lapse of time,31 during the entire period when they were still in a vaporous state, but they soon began to cool unequally, and since then, the conditions of existence and vitality have changed in each of them. Some have moved forward, others have remained far behind. Let us examine the matter.
“In order not to abuse the patience of the commission, I shall only take the worlds that surround us, those for which verification is to some degree possible—to wit, the Sun, Jupiter, Saturn, Neptune, Uranus, the Earth, Venus, Mercury and Mars.
“Here are the approximate masses of these worlds, as deduced by means of Newtonian attraction, in given in proportion to the mass of the Earth:32
The Sun 354,930.000
Jupiter 338.034
Saturn 101.411
Neptune 20.879
Uranus 14.789
The Earth 1.000
Venus 0.885
Mercury 0.175
Mars 0.132
“Here now are the volumes of these worlds, their density and the intensity of the solar light and heat at the surface of each; elements of which we shall have need:33
Volumes in cubic myriameters:
Sun 1,520,976,847,653,880
Jupiter 1,528,718,930,570
Saturn 793,742,722,600
Neptune 113,604,675,800
Uranus 88,600,521,920
Eart 1,080,863,240
Venus 1,034,348,528
Mars 151,320,850
Mercury 64,851,800
Density:
Sun 1.4 Jupiter 1.3
Saturn 0.7 Neptune 1.8
Uranus 0.9 Earth 5.5
Venus 5.1 Mars 5.4
Mercury 6.8
Intensity of solar light and heat relative to that of the Earth:
Jupiter 0.04 Saturn 0.01
Neptune 0.001 Uranus 0.003
Earth 1 Venus 1.9
Mars 0.4 Mercury 6.9
“If we consider the first of these tables,34 it is evident that we shall find therein the order in which the worlds can be arranged according to the sum of their quantity of motion; we shall have their quantity of life, or, in other words, the duration of their existence.
“It is thus easy to see that the Sun is still only at the beginning of its evolution; it is in its infancy. Jupiter comes next, then Saturn, etc. The duration of the existence of these worlds is approximately expressed, taking the earth as unity, by the following figures: Sun 335,000; Jupiter 339; Neptune 20; Uranus 14; Venus 1; Mars 0.13; Mercury 0.17—which signifies that if the Earth were only capable of existing for a century, the Sun would last for 335,000 centuries, Jupiter 339 centuries, Neptune 20, Uranus 14, Venus only one, etc.
“It is, however, necessary not to lose sight of the fact that this is only a matter of individual existence, for the various worlds that are individually dead will still remain aggregated until the complete separation of the group to which we belong, exactly as dead terrestrial matter still subsists for a long time before eventually turning to dust.
“The second table shows that the volumes occupied in space by these different worlds decreases with their mass, but not proportionately. Thus, Mars is less dense that Mercury even though its volume is greater.
“None of this should surprise anyone. We see similar phenomena on Earth and among small things. A body can diminish in mass and increase in volume, and vice versa. You know, for example, that as water freezes it increases in volume; ice is less dense than water. Bismuth is similar. Everything, in fact, depends on grouping: the arrangement of the constituent molecules. Now, you can explain these differences by going back to the genesis of the worlds. All of them were in a vaporous state. Each of them lost motion, and therefore heat, and, according to the rapidity of that loss, the atoms became grouped in one manner or another. The simplest combinations correspond to the most rapid cooling and, on the other hand, the variety of combinations must increase with the slowness of the evolution of the world.
“It is similarly impossible, gentlemen, not to recognize that the duration of each world’s rotation on its axis must have had an influence on the greater or lesser condensation of its molecules. The centrifugal force dependant on the speed of rotation tends to disperse matter and increase the volume of the world; the proximity of the central nebulosity and its consequent attractive action must also have modified the phenomena of grouping, of atomic combination. There must therefore be a certain dependency between the density of each world, the duration of its rotation and its surface gravity. The speed of rotation disperses atoms, but the central attraction brings them closer together.
“Going back to the third table, which lists the densities of the planets, and setting them in relation to the duration of rotation and gravitation, one has:35
Density Duration of Rotation Gravitation
Mercury 6.8 24h5m 5.63
Earth 5.5 23h56m 4.90
Mars 5.4 24h39m 2.1
Venus 5.1 23h23m 4.65
Neptune 1.8 5.00
Jupiter 1.3 9h55m 12.49
Uranus 0.9 5.44
Saturn 0.7 10h18m 5.34
“These seemingly-unrelated numbers are, on the contrary, a faithful translation of a general law of mechanics.
“It is, in fact, necessary to observe that not only does the speed of rotation play a large part in the disposition of atoms, but also the volume or radius of a world. The centrifugal force depends directly on its radius. By taking account of these various elements, not forgetting that the intensity of solar heat given in the third column as also played its part in modifying the grouping of molecules at the surface, we can arrive at the cause of the apparent anomalies that seem to exist in the densities of planets.
“A world, it may be mention
ed in passing, will be as rich and as highly-developed as the quantity of life it has and the time of transformation it has before it.
“Why, then, is Mercury denser and smaller than Mars? One sees immediately that Mars rotates a little more rapidly and that its surface gravitation is much less. For these two reasons, the molecules have a tendency to lesser aggregation, or greater volume. One similarly sees that, relatively, it is on the surface of Mercury that the greater force of molecular grouping must exist—and, indeed, it is that planet that has the greater density. Equally, and for the same reasons, we find that the force of aggregation diminishes for the Earth, Mars, Venus, Jupiter and Saturn.
“These remarks are not without value, if one recalls Mr. Rink’s objections. What tells you, our noble colleague asks, in effect, that the liquids on each world do not have a very different force of cohesion, which might permit them to resist high temperatures? And, indeed, when one sees that the forces of aggregation are so manifestly different, Mr. Rink’s question is perfectly justified. We should, therefore, go on to point out that the age of a world has a disproportionate influence on the force of aggregation; the two are linked. We should not compare the force of two planets of widely different ages; the comparison is only admissible for worlds that have manifestly arrived at the same point of their evolution.
“On thus examining the Earth and Venus, whose masses are very similar and which have in consequence almost the same quantity of life, we evidently find the same density, the same speed of rotation, the same volume, the same gravitation. Here we may affirm that liquids behave as on Earth.
“Taking, by contrast, Earth and Mars, whose masses are in the proportion 1:0.13, the quantity of life being very different, a direct comparison is no longer possible. The density of Mars ought, in the first place, be greater than that of Earth, since Mars is more condensed—but it is very nearly equal. The fact is explained by observing that the surface gravity is less than half of what it is on Earth; it is absolutely necessary to take account here of all the elements that might modify the problem.
An Inhabitant of the Planet Mars Page 6
