De sphaera mundi

De sphaera mundi was a book that was written a really long time ago by a smart person named Johannes de Sacrobosco. The book was all about the Earth and how it moves around the Sun.

Imagine that you are standing in the middle of a big room with your family and some toys. You can move around the room and everyone else can move around too. Now imagine that the Earth is like that big room and it's moving around the Sun. The Earth is always moving, but you don't feel it because you're moving with it.

The book talks about how the Earth is a ball and how people used to believe that the Earth was the center of everything and that the Sun and all the other things in the sky moved around it. But Johannes de Sacrobosco showed that the Earth actually moves around the Sun and that the Sun is the center of everything.

It was a really important book because it helped people understand how the Earth and other planets move, which is really useful for things like navigation and understanding the universe. Even though it was written a very long time ago, people still study it today because it has helped us understand so much about the world we live in.