1 upvotes, 2 direct replies (showing 2)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
I understand the concept of looking at the light from the oldest known galaxy gz-11 and the time it takes to reach us is 13 or so billion years and therefore we are looking into the past. Are we looking back toward the location of where the big bang happened? Is this how to think about the big bang? Im struggling to understand our position in the universe when it comes to looking back in time. In my mind gz11 can't possibly be 13 billion light years away, because surely the event isn't that far away from us in light years. We were also part of the big bang.
If gz11 also had a telescope on it looking at us, would it see us in our present state or us 13 billion years ago?
I appreciate I'm finding it very hard to even articulate this issue. I hope someone understands roughly what I'm getting at!
Comment by Wooden_Ad_3096 at 14/09/2022 at 22:16 UTC
2 upvotes, 1 direct replies
The big bang didn’t happen at a single point, it happened everywhere.
So someone in gz11 would see us as we were 13 billion years in the past.
Comment by prappleizer at 15/09/2022 at 05:09 UTC
1 upvotes, 1 direct replies
I see exactly where you’re coming from and it is challenging to understand. An analogy I’ve found useful when explaining this is the follows: if you imagine we lived not in a 3D universe but a 2D one, and that surface was the surface of a balloon. At t=0, Big Bang occurs, and someone begins blowing up the ballooon. Suddenly, every other point on the balloon (remember, we look only along it’s outer surface) is getting further away from us as the material stretches. And further things are moving away faster (more stretch).
In this scenario, we’re all expanding away from a central point that all of us in 3D space can visualize. But to people for whom the universe is the 2D surface of the balloon, that central point is a mathematically determinable but physically inaccessible point. Up everything by a dimension and you get our universe. We look in *all* directions and see the CMB (afterglow of the Big Bang), but that doesn’t conflict with the Big Bang being a thing that happened at some point — it’s not a point within our spacetime fabric itself.