Let's pretend that gravity stopped. It is only make-believe. It shows how much gravity does for us. Gravity is the invisible pull that makes things fall down. It keeps you on the ground. With no gravity, nothing would hold you there.

Your weight is how hard gravity pulls on you. The pull comes from all of Earth's mass. Your mass is the amount of stuff you are made of. It stays the same when your weight changes. On the Moon you would weigh about one-sixth of what you weigh on Earth. That is because the Moon pulls less.

When you throw something up, gravity pulls it back down. With no gravity, nothing would pull a thrown ball back. Everything that has mass has gravity. Things with more mass pull harder. Gravity also gets weaker the farther apart two things are.

Gravity holds down the air we breathe. So Earth keeps its blanket of air. Without gravity, Earth would not keep that blanket. The Moon's gravity pulls on the seas. That makes the ocean tides go up and down. Without that pull, there would be no such tides.

Gravity keeps the Moon going around Earth. It keeps Earth going around the Sun. The Sun's gravity keeps Earth at a comfortable distance. That distance is right for the Sun's light and warmth. Without gravity, nothing would keep the Moon or Earth going around.

The Sun is a giant ball of hydrogen gas. Gravity holds all of that gas together. It would take almost 1,000 Jupiters to fill up the Sun. Think about that for a moment. With no gravity, nothing would hold the gas together.

Astronauts on the space station look like they float. That is because everything inside is falling together. A roller coaster can feel a little like that. On a roller coaster, free fall gives you a brief feeling of weightlessness at the top of a drop.

Words to know

• gravity: invisible pull
• tides: rising falling sea
• mass: amount of stuff
• hydrogen: a light gas
• weightlessness: floating feeling