Question: How large is our universe?

Monique Henson answered on 17 Nov 2015:

We don’t really know – we can’t even see the whole thing! When astronomers talk about the Universe, they’re normally talking about the observable Universe – that means the part of the Universe that we can see. Since the Universe is only around 13.8 billion years old and light can only travel at a particular speed, there are some parts of the Universe that are so far away that light hasn’t had time to travel to us yet. When we talk about the observable Universe, we’re only talking about the parts of the Universe that are close enough that light from them has had time to reach us.

How big is the observable Universe? Pretty huge. It’s around 10^27 metres – that’s a 1 with 26 zeros after it.