“And what is it?” asked Lucy.
“If things away from the earth can not move themselves to it,” said her father, “there can be no other cause of their falling than that the earth pulls them.”
“But,” said Lucy, “the earth is no more animate than they are; so how can it pull?”
“That is not an ordinary question, but I will try an explanation,” said her father. “Sir Isaac Newton discovered that there was a law in nature called attraction, and that all bodies exert this force upon each other. The greater the body, the greater is its power of attraction.
“Now, the earth is an immense mass of matter, with which nothing near it can compare in size. It draws therefore with mighty force all things within its reach, which is the cause of their falling. Do you understand this?”
“I think that I do,” said Lucy; “the earth is like a great magnet.”
“Yes,” said her father; “but the attraction of the magnet is of a particular kind and is only over iron, while the attraction of the earth acts upon every thing alike.”
“Then it is pulling you and me at this moment!” said Lucy.
“Certainly it is,” replied her father; “and as I am the larger, it is pulling me with more force than it is pulling you. This attraction is what gives every thing weight.
“If I lift up any thing, I am acting against this force, for which reason the article seems heavy; and the more matter it contains, the greater is the force of attraction and the heavier it appears to me.”
“Then,” said Lucy, “if this attraction is so powerful, why do we not stick to the ground?”
“Because,” replied her father, “we are animate beings, and have the power of motion, by which, to a limited degree, we overcome the attraction of the earth.”
“Well then, father,” said Lucy, “if our power of motion can overcome the attraction, why can not we jump a mile high as well as a foot?”
“Because,” replied her father, “as I said before, we can only overcome the attraction to a certain extent. As soon as the force our muscles give to the jump is spent, the attraction of the earth pulls us back.”
“Did Sir Isaac Newton think of all these things, because he saw the apple fall?” inquired Lucy.
“Yes; of all these and many more. He was a man of great knowledge. The name by which the force he discovered is generally known, is the Attraction of Gravitation, and some time you will learn how this force keeps the earth, and the sun, moon, and stars, all in their places.”
* * * * *
en’vy, wish one’s self in another’s place.
doffed, took off, as an article of dress.
blithe, very happy; gay.
fee, what is received as pay for service done.
boast, object of pride.