Meet the Universe's
Main Attraction...
Gravity

animation of baseball falling down repeatedly

If you throw a ball into the air, it will return to the ground. Why?

Earth has invisible pulling power called gravity. In fact, our planet isn’t the only place with gravity. Every object in the universe — stars, planets, moons, even you—has gravity.

Gravity is a force of attraction between all objects.

illustration of Isaac Newton holding an apple

Isaac Newton

How does gravity work? There are two ideas you need to know. These ideas work throughout the universe.

1. The more massive an object is, the more gravity it has.

2. The closer two objects are, the stronger the gravitational pull between them.

So, putting these rules together, the more massive and the closer two objects are, the greater the gravitational attraction between them.

What does gravity do?

animation of feet landing on the ground repeatedly

Earth’s gravity pulls you back to the ground when you jump in the air. Otherwise, you’d fly out into space.

animation of feet landing on the ground repeatedly

Earth’s gravity pulls you back to the ground when you jump in the air. Otherwise, you’d fly out into space.

animation of Earth orbiting around the Sun

The Sun’s powerful gravity keeps Earth in orbit around it.

animation of Earth orbiting around the Sun

The Sun’s powerful gravity keeps Earth in orbit around it.

planets in a our solar system. one planet has 3 arrows repeatedly pointing and moving towards the center.

Gravity pulls stars and planets into round shapes called spheres. Did you ever see a square planet?

planets in a our solar system. one planet has 3 arrows repeatedly pointing and moving towards the center.

Gravity pulls stars and planets into round shapes called spheres. Did you ever see a square planet?

What would happen if...?

To understand the universe, scientists sometimes do “thought experiments”. They take a familiar situation and ask, “What would happen if we changed something about it?” Then they apply the laws of the universe and see how the situation would be different.

Try a thought experiment!

Look at this picture of a carnival. Then ask yourself: What would happen if the force of gravity were suddenly “turned off” in the whole universe?

Try a thought experiment!

Look at this picture of a carnival. Then ask yourself:  What would happen if the force of gravity were suddenly “turned off” in the whole universe?

circus illustration with a rollercoaster, ferris wheel, flying hot air ballon, magician letting doves fly, and child on trampoline
Image Credits:
apple background pattern, Amanda Zaldivar; baseball, © AMNH; Isaac Newton, by Amanda Duffy; landing feet, by Jim Paillot; Earth orbiting the Sun, by Jim Paillot; planets and gravity, by Jim Paillot; circus scene, by Chris Van Dunsen.