Through the Earth/Chapter XXV



IF Mr. Curtis had been in the car at that moment, especially if he had been in the direct path of the knife, he would have freely acknowledged the fallacy of his theory; for the knife, far from clinging to William's hand, as predicted, sped off like a shot to the ceiling, its velocity being much greater than it would have been if thrown from the surface of the earth with the same force. Bounding back from the cushions, it returned to our hero, who dexterously caught it and put it back in his pocket.

William laughed heartily at this result. "I guess there must be something wrong with Mr. Curtis's reasoning," he said, "though I hardly see where his mistake is. I know that on the earth a ball stuffed with wadding could be thrown only a short distance, while a good heavy base-ball could be thrown out of sight. The same thing ought to be true here in the car, because here all objects are stuffed with wadding instead of with weight, so to speak; yet my knife flies around here better than it would up there. I can't understand it at all!"

After a moment's pause, our hero continued:

"If the knife had even a small amount of weight, I could understand why it is possible to throw it around; but I know that objects in the car have no weight at all, because I can stay up in midair if I want to, and this would be impossible if I had weight. Besides, among the instruments on the wall there is a spring balance with a pound weight in the pan. At the present moment the needle in the balance points to zero. This shows that the pound weight does n't pull on the spring at all, or, in other words, the same piece of iron which on the earth would weigh a pound has no longer any weight. Just for the fun of it, I weighed myself on the balance, too, but even I did n't weigh a single ounce. Consequently it's certain that bodies in the car have now no weight, and that makes it hard to understand why that knife flew around so nicely."

At this juncture William remembered that there was a second experiment which Mr. Curtis had asked him to try.

"He said that as soon as I lost my weight I should no longer be able to smash anything. He said that even if I had the most delicate glass vase in the car, I could hit it with my fist, or stamp on it with all my force, and yet I could n't break it, because, of course, neither my hand nor foot would have any weight.

"I thought he was joking at first; but he explained that, on the earth, if we took a body without weight, or even a very light body like a feather, and threw it down with might and main on top of a delicate glass vase, the feather could not possibly break it. So he claimed that when bodies in the car lost their weight they would be lighter than the lightest feather, and said I could take a heavy piece of iron and throw it down with all my force on the most brittle vase, and yet I could n't smash it.

"I promised to try; but the only thing I see to experiment on is the tumbler that is hanging up by the water reservoir, and I don't want to run the risk of breaking that. Besides, I should n't like to have any broken glass flying around loose in the car. Perhaps I may find something in the drawer of the table."

Acting on this idea, our hero opened the drawer; but the only object he found in it was a light wooden box containing various odds and ends. William decided that this box would answer his purpose, and ruthlessly dumped out the contents into the drawer. Then he placed the box beside him in the air, about a foot from the ground, and, supporting himself by one of the handles on the lounge, he drew back his foot and brought it forward with all his strength, giving the box a violent kick that shivered it into fragments and sent the pieces flying in all directions.

"Gracious!" exclaimed William, as he gazed at the flying fragments. "It's mighty lucky I used the wooden box instead of the glass tumbler. Otherwise the car would now be full of flying pieces of broken glass that would n't make very pleasant traveling companions. I guess there's something wrong about Mr. Curtis's mechanics, and I'm glad there are no more of his experiments to try. They don't seem to turn out as expected." William's studies in physics helped him to understand the reason for the two occurrences which had just puzzled him.

"I understand the whole thing now," he said, a light dawning on him. "I have been confusing weight with mass. The weight of bodies has nothing whatever to do with the question as to how far you can throw them, or the amount of damage they will do when thrown; it is their mass that decides this.

"Mass is the amount of matter a body contains, while weight is the force with which it is attracted to the earth. My mass here is just the same as it was on the earth, although my weight has entirely disappeared, and hence I can do as much damage with my hands and feet here as I could in my native land. The reason we can't throw a feather far on the earth, or smash a glass vase by throwing a feather at it, is not because the feather has little weight, but because it has almost no mass; that is to say, it contains very little matter."

These two experiments being satisfactorily terminated and explained, our hero now turned his attention to a third one which occurred to him, and that promised to afford no end of entertainment.