Question: What are the boundaries of the Universe?

Struan Simpson answered on 18 Mar 2020:

Good question! Unfortunately, the answer is very complicated.

To answer this, we need to distinguish the universe, and the “observable” universe. What’s the difference? The observable universe refers to the amount of the universe that we can actually see using things like telescopes. In order for us to see stuff in the universe, it needs to have spent time travelling to us from its source. That means we can only see things that have had enough time to reach us – in other words, we haven’t seen a lot of stuff that’s very, very far away because the light from them hasn’t had enough time to get to us!

Because we can’t see outside our observable universe, we have no idea if the universe as a whole has a boundary. It’s difficult for us to know for sure without being able to see it! We currently don’t think it has a boundary, but we think it’s finite. It’s tricky to think about what this means exactly, but basically we think there’s only so much stuff in existence, but if you kept travelling in a certain direction, you’d never reach any “fence” that separates our universe from another.

If that’s still confusing, let me know – I can try and explain it another way!