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It was now so late in the day that further conversation was postponed, and after a plain but exceedingly enjoyable supper we were shown to luxurious rooms, where we spent our first night in Mars in great comfort.
In the morning Thorwald told us we would reach our port in a few hours, and so we sat down as early as we could after breakfast for a short talk.
The doctor furnished the text by opening the conversation with this remark:
"It is wonderful to think we should find on this planet a race of people so advanced, when so little thought is given, on the earth, to the idea of life in other worlds."
"What has been the general opinion among you on that subject?" asked
Thorwald.
"The subject has not had standing enough to call forth much opinion," the doctor answered. "There is an almost universal indifference in regard to the matter. I think the common notion is that the earth is about all there is in the universe worth considering."
"But what are your own views, Doctor?"
"I have been one of those," he replied, "who believed the notion of life outside the earth to be a beautiful theory without one shred of scientific basis. We knew the earth was inhabited and the moon was not, and there we stopped. We did not know, and thought we never could know, anything that could be called evidence pointing to the existence of life in the other planets or elsewhere, and we held that there was no advantage in speculation. We thought it unwise to spend much time or thought on a subject about which we could know nothing. On coming here and finding you I have learned that Mars is inhabited, but I do not know any more about the other planets or stars."
"Does not the mere knowledge that there are two life-bearing bodies lead you to believe that there are more, among the vast numbers of worlds which you have not visited?"
"I don't see why it should. How can we believe anything without evidence? No one has ever come to us from those distant globes, and they are too far away for us to see what is taking place on their surface."
"It seems strange, Doctor, to hear you reason in that way, but I suppose some of our race were just as narrow, if you will pardon me for using that word, as you are, before our wonderful successes in astronomy. I believe you have not properly considered the subject, for it seems to me you had knowledge enough, before you left the earth, to justify you in holding to a strong probability of life beyond your own globe.
"Let us see what some of that knowledge is. You know, to begin with, that one world is inhabited. Then if you should find other bodies as large as the earth and bearing any resemblance to it, there would be no improbability in the thought that they or some of them were filled with life. The improbability is certainly taken away by the knowledge that one such body, the earth, is inhabited.
"You start, then, without prejudice, on a voyage of discovery, aided by your telescope and your reasoning faculties.
"First you find, within distances that you can easily measure, a small group of dark bodies, which you have called planets, all apparently governed by a common law, in obedience to which they are circling around a large body of quite different character, which gives them light and heat. Of these dark bodies, which shine in the sky only by reflected light, the earth is one, and, you are surprised to find, not the most important one, judging from all you can discover. Some of the others are much larger and are attended by more satellites. In fact, the earth is indistinguishable in this little group. While it is not the largest, neither is it the smallest. It is not the farthest from the sun nor the nearest to it. It is merely one among the number. And how much alike the members of this family are. Your telescopes do not point out any material differences, although each has its individual characteristics. Let us enumerate some of the many points of resemblance. They all turn on themselves as well as revolve around the sun. All see the night follow the day, and in most of them there must occur the regular succession of seasons. To each one the sun is the source of light and heat, many of them have moons, and all can see the stars. Nor does the resemblance stop here. For you have discovered that one has an atmosphere, another is surrounded with clouds, while on the surface of our own globe you see the polar snows increase in winter and melt away in summer. Is it not probable that if you could get nearer to these globes you would find still closer resemblances? And if they are like the earth in so many ways, is it at all unlikely that they may, at some period of their existence, be the abode of intelligent life? For what other purpose were they made, Doctor?"
"They make very pretty objects for us to look at," replied my companion.
"Yes, those that can be seen," said Thorwald; "but is that all? Were those great worlds, some of them hundreds of times larger than your own globe, created merely to add a little variety to your sky, and to give you the pleasant task of watching their movements under the pretty title of morning and evening star?" "Speaking from the knowledge I had when I left the earth," the doctor answered, "I can say I never heard that they were put to any other use. No one ever came down to us from any of them to tell us they were inhabited."
"And do you think," asked Thorwald, "that the myriads of stars were also made simply to delight the eye of man?"
"How do I know that they were not?" the doctor asked in reply.
"Because of the absolute unreasonableness of the thought, if for no other reason," answered Thorwald. "But now let me recall to your mind more of the knowledge possessed by the inhabitants of the earth. I think I know about what that knowledge is, from my acquaintance with the present state of your development. Astronomy has been our master science, and I can remember fairly well the extent of our knowledge when we had reached your stage. If I should fall into the error of attributing to you more than you have already discovered you can easily correct me.
"If, now, you leave the little group of dark bodies which are so like the earth, and go out still further into space, what do you find? At distances so great that only the speed of light can be used as a measuring line, you discover vast numbers of self-luminous bodies, which you call stars. Your natural eye can tell but a small fraction of their number. For example, look at the constellation you have named the Pleiades and you see six or seven stars. View it through a three-inch telescope and you can count perhaps three hundred. Now attach a photographic plate to the telescope, and with an exposure of four hours the light coming from that small patch of sky falls upon the sensitive film with a cumulative effect until you have a picture of more than two thousand three hundred stars."
"Yes," broke in the doctor, "you are gauging correctly the state of our knowledge. Our largest telescopes reveal in the entire sky, it is said, one hundred million stars."
"Then," answered Thorwald, "if the glories of the heavens were made merely to delight the eye of man, why was not the eye created of sufficient power to behold them? As it is, only a small proportion of the stars can be seen without the aid of instruments too costly and too delicate for general use.
"But have you the means of establishing any likeness between the earth and those distant bodies? You have discovered that the law of gravitation is universal and that the motions of the stars resemble those of the solar system. Have you made any discoveries tending to prove the existence of other systems like our own?"
"Yes," replied the doctor, "our recent investigations of the periods of some of the variable stars show irregularities in brightness, period, and proper motion. A close study of these irregularities has convinced some of our astronomers that there are invisible bodies near them, evidently planets circling around a central sun. The theory is that the dark bodies cause slight perturbations in the star, which account for the irregularities in period, motion, etc. So Neptune was discovered by the effect it had upon the observed movements of Uranus. This is the first evidence we have had tending to prove that there are other groups of worlds like ours, and it is considered quite significant."
"I can readily believe it," said Thorwald, "and I know how helpful every bit of evidence is, in your search for knowledge. But if I mistake not you have the aid of another instrument, which is destined to play an important part in your future studies. You get much nearer those distant orbs when a spectroscope is placed at the end of the telescope, and the ray of light coming from sun and star is widened out into a band of color, which tells a marvelous story. That light, that has been for years, and perhaps for centuries, on its way to you, now discloses the very nature of the substances which compose those fiery globes. And what are those substances? It must have been a startling truth to the man who first read from the spectrum of the star he was studying, that it contained matter with which he was familiar, materials of which the earth itself is made. By this science you have learned beyond doubt that many of the commonest elements of the earth's crust exist also in other worlds, and, what is of great significance, that the materials most closely connected with living organisms on the earth, such as hydrogen, sodium, magnesium, and iron, are the very ones which are found most widely diffused among the stars. I think I am not wrong in assuming that you are somewhat acquainted with the spectroscope and have made these discoveries."
"You are quite right," said the doctor. "This branch of scientific investigation has already been carried so far with us, and the results of the experiments are so constant and uniform, that when it is asserted, for example, that such and such a metal is present in a state of vapor in the sun's atmosphere, it is estimated that the chances in favor of the correctness of the assertion are as 300,000,000 to 1."
"You are helping my argument, Doctor," resumed Thorwald. "But now let me call your attention to another field of inquiry, in our search for evidence to establish a likeness between the earth and the other parts of the universe. You told me, a while ago, that you have the fall of meteorites on your globe. Have you considered the striking evidence they bring you? Let us imagine we have a meteoric fragment here. Take it in your hand and think of it a moment. You have few things on your earth as interesting as this piece of metallic stone. What a world of questions it starts! What is its composition? Whence comes it? Once it was in existence, but not here. Where, then, was its home? Out, out in the depths of space, where burning suns roll and comets have their dwelling place. The stars have fallen indeed, and here is one of the pieces. Before it came to us as a messenger from the sky did it have an independent existence, or is it a fragment of a shattered world? How long has it been whirling in its unknown orbit, and what story has it for us from its distant birthplace? If we can discover whence meteorites come, and of what they are composed, I think you will agree with me that they furnish valuable testimony in our inquiry. You have no doubt had many theories as to their origin."
I was just about to make answer to this implied question, when Thorwald rose and eagerly scanned the horizon. After a moment he exclaimed:
"We shall have to break off our conversation for a time, as we are nearing our port. I knew by other means that land must soon appear, and now I can see it."