What's the shape of the universe? Mathematicians use topology to study its shape and everything in it

When you look at your surrounding environment, it might seem like you're living on a flat plane. After all, this is why you can navigate a new city using a map: a flat piece of paper that represents all the places around you. This is likely why some people in the past believed the Earth to be flat. But most people now know that is far from the truth.