Question - the Size of the Universe

[Ash_]

I've just been watching a video about Black Holes here;



In it the narrator discusses objects 18b light years away, I thought that we can only see objects around 13b light years away (the age of the Universe as we understand it?), so how can we know there are things beyond that? Secondly, if the Universe is only 13b years old, then it stands to reason that any objects further away than that would have travelled at greater than the speed of light to be where they are, which we all agree isn't possible (with known physics)?

I don't get it, please go easy on me with this, I very much appreciate that my brain isn't big enough to figure this stuff out and understand the theories behind it.

[Ash_]

So, does that mean that the total width of the Universe is 26b Light Years (13b LY in each direction from it's origin), and we can only see back 13b Light Years to the beginning of it's existence, so we'll never really "see" it all?

[Ash_]

SpudLink said:

The universe may (or may not) be infinite. The observable universe is over 40b LY in each direction (says Google).
That’s because the early stars that were formed 13b LY ago and 13b LY away, are now much further away due to expansion.

Just to add, distant objects are not travelling faster than light, but at extreme distance they are moving away faster than light. Expansion is the thing to get your head around.

Edited by SpudLink on Tuesday 10th May 15:47

Ah OK, that helps a lot, so the observable universe is 40b LY (I thought it was 13b LY, or the same as the age of the universe as we understand it, which made sense to my brain). But yes, I now get the expansion idea, if they're travelling at .51c, and the expansion is 0.51c, then to us it's greater than c and we'll never see them?

[Ash_]

Thanks all

[Ash_]

jimPH said:

Welcome to Kergesagt! Great channel!

It is indeed, I learn loads from it, with a few videos that have my mind blown (without further explanation such as I got above, which helped greatly).