“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.”