# Universal Gravity: Lesson for Kids

Instructor: Shoshana Yarin

Shoshana has taught all grades with an emphasis in science and has a master's degree in science.

Have you heard of Isaac Newton? Maybe you have heard the story about him seeing an apple fall and discovering the law of gravity. There's a lot more to the story than that! Read this lesson to find out about universal gravitation.

## Mr. Isaac Newton

We all know about gravity. If you have ever fallen down or fallen from something high above the ground, you know about gravity! Did you know that gravity is a law that applies to everything in the universe? That's where Isaac Newton comes in. Of course, people knew about gravity, but he made it a law and figured out some important mathematical calculations.

It was around 1666 when Isaac Newton sat in a garden under an apple tree and watched an apple fall (so the story goes). He began thinking, how high up from the ground could an apple be and still fall back to Earth? Then he wondered if the moon was actually in somehow 'falling back to earth' in a pattern but it was just too far away to actually fall.

## What's Up with the Moon?

That would mean distance had something to do with the effects of gravity. Being the mathematician he was, Newton calculated how long it should take for the moon to orbit the earth if indeed it was in a falling pattern. Orbit means to travel in a circular path around another object. Guess what? His calculations were correct. It takes about 28 days for the moon to orbit the earth just like Newton figured. So the moon is always falling?

Watch out for that fly ball! Think about a baseball that has been hit high in the sky. It doesn't go up and come straight back down, but follows a curved path. Now imagine if we hit the moon so far up that the curved path of coming back down was just too large to ever come back down. That's kind of how it works. So universal gravity depends on distance, how far apart the two objects are.

## What Else Does Gravity Depends On?

Why would an apple or the moon even fall to the earth? Because the earth is so large and has lots of mass, it also has lots of gravity. The more mass something has, the more gravity it has. That's why the moon orbits the earth and the earth orbits the sun. The sun is so large it has 28 times as much gravity as the earth! Does that mean that everything has gravity?

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