eli5-how do we know for sure how big space is? and how do we know we are right about everything we know in space?

Question

eli5-how do we know for sure how big space is? and how do we know we are right about everything we know in space?

In: Planetary Science

Answer 1

Short answer to both questions is: we don’t.

1. We don’t know how big the Universe is. It can be infinite. It could also have a curvature and be of limited size. We are unable to measure that curvature yet, so we can give some _lower_ boundaries on how big the Universe is (if it was smaller we would be able to measure the curvature).

2. This is an even bigger “we don’t know”. Best we can do is to provide some models, that can explain some of our observations. But these models are sometimes contradictory and sometimes we make observations that they can’t explain.