Secondary source

Hello there. You can’t see me, but I am everywhere. I am like a big, invisible hug from the whole world. When you drop your favorite red ball, who makes it fall down to the floor. That’s me. When you jump up so high, who brings you back down to the ground. Me again. I hold everything close so it doesn't float away. I am Gravity.

For a long, long time, nobody knew my name. People just knew that things always fell down, down, down, and never up, up, up. One sunny day, a man named Isaac Newton was sitting under a big, green tree. He was very curious. Plop. A red apple fell from a branch and landed on the soft grass. Isaac looked at the apple and wondered. Why did the apple fall down. Why not sideways. Why not up to the sky. He thought and thought. He realized a special, invisible pull was bringing the apple to the ground. That pull was me, Gravity. He was the first person to understand how I help hold the moon and the stars in the sky, too.

I am always working to keep you safe and sound. I keep your yummy juice inside your cup so you can drink it. I keep the warm, splashy water in the bathtub. When you build with your colorful blocks, I help your tower stand up tall instead of floating away. I am the Earth’s special hug that holds you close. So the next time you jump up and down, just remember I will always be there to bring you gently back home.