Question - the Size of the Universe
Discussion
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.
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.
There’s a thread somewhere discussing the expansion of the universe.
If the light has taken 13b years to reach us, it would have moved further away during that time.
Someone who knows what they are talking about will be along shortly.
Edit: Not the thread I was thinking of, but worth a read...
https://www.pistonheads.com/gassing/topic.asp?h=0&...
If the light has taken 13b years to reach us, it would have moved further away during that time.
Someone who knows what they are talking about will be along shortly.
Edit: Not the thread I was thinking of, but worth a read...
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Edited by SpudLink on Tuesday 10th May 15:37
There was a program on (I think) the Hubble Telescope on telly a month or two back and it explained some of this.
Like you, my poor little brain simply can't cope with, or really understand, the vastness of space.
I'll see if I can find it - pretty sure it was a Horizon program on BBC.
Like you, my poor little brain simply can't cope with, or really understand, the vastness of space.
I'll see if I can find it - pretty sure it was a Horizon program on BBC.
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.
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
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.
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?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
Ash_ said:
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?
Yes. If we invented a lightspeed ship today, we could never travel fast enough to see what has already moved beyond the observable distance.pincher said:
There was a program on (I think) the Hubble Telescope on telly a month or two back and it explained some of this.
Like you, my poor little brain simply can't cope with, or really understand, the vastness of space.
I'll see if I can find it - pretty sure it was a Horizon program on BBC.
As I thought, it was a Horizon programme - Hubble: The Wonders of Space Revealed. Was to celebrate the 30th anniversary but appears to be no longer available. There are a few short clips on iPlayer though - some of the imagery is simply stunning.Like you, my poor little brain simply can't cope with, or really understand, the vastness of space.
I'll see if I can find it - pretty sure it was a Horizon program on BBC.
Ash_ said:
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?
There is no widthWhichever direction you look in, if you can see far enough, you are seeing the Universe earlier and earlier in time.
James Webb will take us closer to seeing big bang than ever before.
SpudLink said:
The Hitchhiker's Guide to the Galaxy said:
Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
I don't want to worry anyone but....
https://www.bbc.co.uk/news/science-environment-614...
26,000 light years
Don't black holes compress space and time?
To quote Sam Niell in the excellent documentary 'SPACE'
We have a monster in our galaxy!
https://www.bbc.co.uk/news/science-environment-614...
26,000 light years
Don't black holes compress space and time?
To quote Sam Niell in the excellent documentary 'SPACE'
We have a monster in our galaxy!
Edited by anonymous-user on Thursday 12th May 19:56
digimeistter said:
I don't want to worry anyone but....
https://www.bbc.co.uk/news/science-environment-614...
26,000 light years
Don't black holes compress space and time?
To quote Sam Niell in the excellent documentary 'SPACE'
We have a monster in our galaxy!
It’s been known for some time there is a huge dark monster at the heart of the galaxy, and probably most galaxies. It might even be the gravitational glue that holds the galaxy together. Or a result of the galactic mass?https://www.bbc.co.uk/news/science-environment-614...
26,000 light years
Don't black holes compress space and time?
To quote Sam Niell in the excellent documentary 'SPACE'
We have a monster in our galaxy!
Edited by digimeistter on Thursday 12th May 19:56
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