Re: Size of the universe question ?

"No_Spam" <no_spam@xxxxxxxxxxx> wrote in message news:47d9310c$0$21899$a9266ab1@xxxxxxxxxxxxxxxxxxxxxxx
OG wrote:
"No_Spam" <no_spam@xxxxxxxxxxx> wrote in message news:47d84ea1$0$21837$a9266ab1@xxxxxxxxxxxxxxxxxxxxxxx
Andy Hewitt wrote:
No_Spam <no_spam@xxxxxxxxxxx> wrote:

[..]
According to this:

http://www.atlasoftheuniverse.com/bigbang.html

The matter was already there, the Big Bang just caused it to expand.
Ok, I've read that. Far easier than I thought.
What this says (answer 6) is that it's possible the the speed of expansion can exceed the speed of light !!
In a way I can sort of see that working. If nothing with mass can
move faster than the speed of light it seem only reasonable that that
nothing (having zero mass) CAN move faster than the speed of light...
The way I read it, it only appears to be travelling faster than light.
But it has to be expanding faster than light. The universe is 14 billion years old, we can detect object as far away as 90+ billion light years. Even if the rate of expansion was just under the speed of light the diameter should be no more the 28 billion light years. So no matter where we where it would be impossible to see object 90 billion ly's away...
And anyway, if an object is 90 billion light years away that implys that the light has been traveling for 90 billion years, which it plainly can't have been!


When you talk about objects that ARE 90+ light years away, what do you mean?
We can't see the sun NOW, we can only see the sun that WAS 8 minutes ago.
We can't see the Andromeda galaxy NOW, we can only see the galaxy that WAS 2.2 million year ago.

We don't see Andromeda AS it is - likewise, we don't see it WHERE it is.

Did you read the pages I suggested ?
Ahh, now I see (sorry, missed a bit !).
OK, I see how how the math works (just), but I can't get to the 90+ billion light years (which is the max distance that the furthest object detected so far is that I can find info on). The page you reference states that the max distance is 47 billion light years... Although, looking at those numbers it's possible that I miss read and it said that the diameter was 90 + (47x=94 ?). I agree that logic might not hold as the universe isn't a sphere (at least in the conventional sense), at least the models I've seen aren't.



Yes, the obvious confusion is over "radius" and "diameter". The calculation on Ed Wright's page is for what you would describe as radius, and the 90+ GLY was for diameter. These terms do not have their everyday Euclidean meanings over extremely large distances.

Small differences, e.g., 93, 94, etc are due to rounding errors or changes in the best values of Universe age, Hubble parameter, etc as more data comes in from the WMAP and other experiments.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

.

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