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How Many Worlds? - Harper's


"Professor," asked May, "are there more worlds with people on them like this one of ours?"

"That is a hard question," said he. "For many ages it was believed that there could be only one. More recently, when astronomers learned by the aid of their telescopes the countless number of the heavenly bodies, it began to be doubted whether such an immense creation could be destitute of intelligent creatures like man; and it was argued that most likely the Almighty had supplied the heavenly bodies with inhabitants, but had for some good reason thought best not to reveal the fact to us, perhaps because our attention might be too much drawn away from the truths that He wished us particularly to remember. At last, however, men of science, continuing their researches, seem to be settling back in the first opinion."

"Why is that?" asked Joe.

"Because they find reasons for thinking that our earth has had human beings on it only a very little while in comparison with its own existence. And if this world was millions of years without man, then, of course, any or all the heavenly bodies may still be without any such creature on them."

"Is there no better reason than that?" asked Joe.

"Yes, there is considerable evidence that the bodies nearest to us can not be inhabited by any creatures at all like man. On the moon, for instance, there is no air to breathe and no water to drink. And without air and water there can be no grass, trees, or plants of any kind, and no food for any animal. And besides starving, all creatures that we know of would immediately freeze to death; for the moon is excessively cold. The nights are about thirty times as long as ours, and allow each portion of its surface to get so cold that nothing could live."

"How did the moon get so cold?" asked Joe. "What became of the heat?"

"It went off into the surrounding space, which is all very cold. Empty space does not get warmed by the sun, whose heat seems chiefly to lodge in solid bodies and dense fluids."

"But some of the planets are larger than the moon, are they not?" asked Joe.

"Yes, Jupiter, for instance, is very much larger than the moon and the earth; and Professor Proctor tells us it will take Jupiter millions of years to become as cool as the earth, while the moon was as cool as the earth millions of years ago. Here is a picture of the planet; but its surface is changing so constantly, that it seldom appears the same on two nights in succession. Jupiter at present is wrapped in enormous volumes of thin cloud that rises up from a melted and boiling mass in the centre. Professor Newcomb supposes that there is only a comparatively small core of liquid, the greater part of the planet being made up of seething vapor. So you see it would be about as difficult to live on Jupiter as in a steam-boiler, or a caldron of molten lead. Since last summer a great red spot has been noticed on the surface of the planet, which has attracted much attention. Some think it is an immense opening, large enough for our earth to be dropped through."

"Are the other planets such dreadful places?" asked May.

"Saturn seems to be in about the same condition as Jupiter. Mars is thought to be solid, and to have land, water, and air. It has also two brilliant white spots on opposite sides, which are supposed to be vast fields of ice and snow. But the water seems to be disappearing; and the time when the planet could be inhabited is thought to be long gone by."

"Where does the water go?" asked Joe.

"Probably it sinks into the cracks or fissures which form in the crust of the planet when it begins to shrivel up with the cold."

"Then it must be like a great frozen grave-yard," said May. "But is there no other planet that is pleasanter to think about?"

"The one that seems on the whole to be most like our own is Venus, and so Professor Proctor calls it our sister planet. It is so close to the sun that it is hidden most of the time, being only seen for a while before sunrise, and at other times a while after sunset. In the one case it is called the morning, and in the other the evening star. Also there is Mercury, still nearer the sun, and hidden almost all the time."

"Then," said May, "there seems to be no way of knowing anything about there being people like us in other worlds; and the more we look into it, the more uncertain we become."

"That is about the way the case stands," said the Professor. "But if science continues to make as rapid progress as it has lately done, we may hope that it will yet throw more light on the question."

"How many planets are there?" asked Joe.

"Until quite recent times there were supposed to be only the five we have mentioned. Since the beginning of the present century about two hundred little planets, called asteroids, have been discovered between the orbits, or paths, of Mars and Jupiter. Then there are Uranus and Neptune, very far off from the sun and from us, so much so that the latter was mistaken for a fixed star."

"Professor," said May, "you mentioned the moon as being near to us. Can you explain to us how its distance is measured, so that we can understand it?"

"And then, Professor," said Jack, "I would like to know what parallax means."

"There," said Gus, "is another big word of Jack's—pallylacks, knickknacks, gimcracks, slapjacks!"

"Hush, you goose."

"I think," said the Professor, "I can answer May's and Jack's questions both at once, as they are very closely connected. Suppose that at night, when you look down the street, you see two gas lamps, one much farther off than the other. Then if you go across the street, the nearer lamp will seem to move in the opposite way from what you did. Thus, in the diagram, when you are at A, the nearer lamp is on the right of the other, and when you go over to B and look at it, it is on the left. This change in direction is called parallax. Now we can imagine the nearer one of the lights to be the moon, and that an observatory, or tower with a telescope in it, is located at A, from which the direction of the moon is carefully noted at six o'clock in the morning. Then by six in the evening the earth, spinning round on its axis, will have carried the observatory about 8000 miles away from A, and placed it at, say, B. If the moon's direction be again noted, it is very easy to calculate her distance by a branch of mathematics called trigonometry, which Jack, I have no doubt, has already studied."