Philosophiæ Naturalis Principia Mathematica

Hello. Before I had pages with words, I was a thought. I was a big, big question in someone’s mind. Have you ever wondered why a red apple falls down from a tree instead of up to the clouds? Or why the Moon loves to dance around the Earth but never floats away? I am filled with the answers to these wonderful questions. I am a very special book, and my name is Philosophiæ Naturalis Principia Mathematica. That's a big name. You can just call me the Principia.

A very smart man named Isaac Newton made me. He was my friend. Isaac loved to look at the world and ask 'why?'. He thought and thought for a very long time about how everything moves. On a warm summer day, on July 5th, 1687, he put all his big ideas onto my pages for everyone to see. He drew circles and lines and wrote down special rules. He called them 'laws.' One law is like this: if you push your toy car, it will keep rolling until you stop it. Another law, his most famous one, is about a secret force called gravity. It's like an invisible string that holds the Moon close to the Earth and keeps your feet on the ground when you jump.

When people read my pages, their eyes got wide. 'Aha!' they said. For the very first time, they understood how planets zoom through the sky like race cars on a track. My ideas helped people build amazing things, like big spaceships that can fly all the way to the Moon. I am still here today, and I have a secret to share with you. The world is full of magic. All you have to do is look around, ask big questions, and never, ever stop wondering.