Mass–energy equivalence (E=mc²)

Hello! Can you guess who I am? I am the wiggle in your toes when you dance and the giggle in your belly when you laugh. I help you run super fast at the park and build the tallest block towers. I am the warm sunshine on your face and the bright light from your lamp at bedtime. I make toy cars zoom across the floor and help airplanes fly high in the sky. I'm a secret power that's everywhere, making everything go, go, go! I am a special kind of magic that you can feel all around you, every single day.

For a long, long time, people felt me but didn't know my name. They felt my warmth from the crackling fire that cooked their food and kept them cozy. They saw me push their big boats across the water when the wind blew with a big whoosh. A very smart person named James Prescott Joule, way back in the 1840s, noticed something special. He saw that when things get warm, I am there, and when things move, I am there too! He realized that I could change from one thing to another, like a superhero changing costumes. I could be the heat from a fire or the push that moves a train down the tracks, choo-choo!

Have you guessed my name yet? I am Energy! I can be quiet, like the yummy food you eat that helps you grow big and strong. I can be loud, like the bang from a big drum. I can be bright, like the screen you watch your favorite cartoons on. I can’t be made and I can't disappear, I just change from one thing to another, like magic! Today, I light up your home, I keep your school warm, and I power all the amazing toys that help you learn and play. I will always be here, helping you explore the world and dream up new, wonderful adventures!