In Search of a Son

by William S. Walsh

"Yes."

"Well, I am obliged to tell you that it does fall."

"Ah, that is another matter!" cried Miette.

"Yes, it is another matter, as you say; and it is necessary that I should speak to you of that other matter. Without that how can I make you believe that the moon does not fall and that it does fall?"

"That would not be easy," said Miss Miette.

"Well, then, imagine a ball shot by a cannon. This ball would go forever in a straight line and with the same swiftness if it were not subject to gravity, to the attraction of the earth. This attraction forces the ball to lower itself little by little below the straight line to approach the earth. At last the time comes when the force of attraction conquers the force which shot the ball, and the latter falls to the earth. This example of the ball may be applied to the moon, which would go forever in a straight line if it were not subject to the attraction of the earth. It shoots in a straight line, ready to flee away from us; but suddenly the attraction of the earth makes itself felt. Then the moon bends downward to approach us, and the straight line which it had been ready to traverse is changed to the arc of a circle. Again the moon endeavors to depart in a straight line, but the attraction is felt again, and brings near to us our unfaithful satellite. The same phenomenon goes on forever, and the straight path which the moon intended to follow becomes a circular one. It falls in every instance towards us, but it falls with exactly the same swiftness as that with which it seeks to get away from us. Consequently it remains always at the same distance. The attraction which prevents the moon from running away may be likened to a string tied to the claws of a cockchafer. The cockchafer flies, seeking to free itself; the string pulls it back towards the child's finger; and very often the circular flight which the insect takes around the finger which holds it represents exactly the circular flight of the moon around the earth."

"But," said Miette, "is there no danger that the moon may fall some time?"

"If the moon had been closer to the earth it would have fallen long ago; but it is more than two hundred and thirty-eight thousand miles away, and, as I have told you, if attraction or gravity acts upon the planets, it loses its power in proportion to the distance at which they are. The same attraction which forces the moon to turn around the earth obliges the earth and the planets to turn around the sun; and the sun itself is not immovable. It flies through space like all the other stars, bearing us in its train, subject also to universal attraction."

Monsieur Roger stopped a moment, then he said,—

"And it is this great law of universal attraction, this law which governs the universe, that Newton discovered when he asked himself, 'Why does the apple fall?'"