A: Gravity is very important. B: What is gravity? A: It's the force that pulls everything down. B: I don't understand. A: If you pour water into a glass, the water goes down into the glass. B: Of course it does. A: Without gravity, the water would go up. B: You're joking. A: Without gravity, you would go up. B: What do you mean? A: You would float into the sky like a balloon. B: That would be fun!