How do we know how big is the universe?

Question

How do we know how big is the universe?

In: 3

Answer 1

We believe the universe as a whole is infinite, because it seemingly has no intrinsic curvature (as opposed to local curvature, ie gravity caused by stars etc). Something like a ball with curvature can’t be infinite, but a flat piece of paper can.

We know the size of the *observable* universe because we can see the stuff at the edge.