Tess and Harry on the Dock
“Is there gravity on the moon?” asked Tess.
“Of course,” said Harry.
“Then how come when you showed me that video of the men on the moon, they could take giant leaps and soar through the air?”
“There isn’t any air on the moon.”
“You know what I mean.”
“Every object in the universe has gravity. The moon just has less than the earth because it’s smaller. The amount of gravitational force exerted by an object is proportional to its mass.”
“You mean how big it is?”
“In simple terms.”
“But even a tiny object has gravity?”
“That’s right.”
“Even these two rocks have gravity?” Tess set two small, smooth stones from the beach onto the dock about a foot apart.
“Yes.”
“If they both have gravity, shouldn’t they pull each other closer?”
“Very good, Tess. They should do exactly that. And how strong that pull is depends on their mass and how far apart they are from each other. Objects that are very far apart have only a tiny gravitational pull on each other.”
“But these stones are close together.”
“But they also have very small masses. The earth has enough gravity to keep you from floating away, but compared to the mass of the earth, these stones are miniscule.”
“Miniscule?”
“Extremely small.”
“But even a very small force should bring them together eventually.”
“That’s right. But only if there are no other forces acting on them.
These stones have to deal with the gravitational pull of the earth, the friction of the dock, the resistance of the atmosphere, and the impatience of a little girl.
But if we could take all those forces away, eventually, in a very long time, these two stones would be drawn to each other by gravity. ”
“And you said that the closer objects are to each other the greater their gravitational pull?”
“Correct. That’s why stars that are millions of light-years away have almost no gravitational effect on the earth even though they might be thousands of times as massive as our sun.”
“But the closer the object, the greater the pull?”
“You’ve got it.”
“So, if I’m close to something…or someone…eventually I’ll be even closer?”
“I think it’s time for bed.”
“Is that why you and me are pulled together on the dock every night? Because of gravity?”
“You and I.”
“Answer the question.”
“No, we’re pulled together by a much stronger force than gravity. We are pulled together by love.”
“Love is stronger than gravity?”
“Love is the strongest force in the universe.”