Newton's Ball

Have you ever wondered how satellites in the sky stay in orbit? Before there were satellites, Newton asked himself the same thing about objects such as the moon:

thought bubble with the words Why do things stay in orbit?

Get your brain on the ball and explore Newton's question with the thought experiment below:

Question:  Can you throw a ball so hard that it never falls to Earth?

person standing on Earth throwing a ball with trajectory that shows the ball only went one quarter of the way around Earth, then half way around Earth

Example: Imagine you are on a mountain and throw a ball in front of you.

Logic: Think about what happens if you throw a ball softly. It goes a bit and then falls to the ground. If you throw the ball harder, it will go farther before it hits the ground, right?

person holding a ball and winding up, then person standing on Earth throwing a ball with trajectory going all the way around Earth

Prediction: If you throw the ball hard enough, it will never hit the ground and continue to follow a stable path around the earth. This path is called an orbit. (If something is going a certain speed around Earth, it will stay in orbit around the Earth .)


Conclusion: By combining his theory of gravity with his theory of motion, Newton came up with a formula that showed how fast an object has to go to stay in orbit. He was right! Today, scientists use his formula to put satellites in orbit.

Who said science couldn't be a ball?

Image Credits:

Photos: satellite: courtesy of NASA; Illustrations: Newton's Ball and Light Speed: Eric Hamilton