How far can we see?

[modest]

Michael, I've answered you in your Bang/Crunch Revisited thread.

~modest

[maddog]

Originally Posted by sman

I'll try to state my problem with parsimony:

When we look a Barnards star (for example, ~15 light years out) we see it as it was 15 years ago. When we look 1 million ly out we are looking at a scene from 1 million years ago. So I think I understand it when astronomers say that looking very far away is equivalent to looking very far into the past.

I've heard of telescopes that see BILLIONS of light years away. Here's my problem: the universe is only ~15 billion years old. So if we are looking at something 15 billion ly away, we are looking 15b years into the past - at that time when whatever we are looking at should've been RIGHT HERE.

Maybe we just can't see that far, but still, the farther we look the closer we come to the point where all mater was in the same spot. This is the paradox: the FARTHER it is away from us, the CLOSER everything sould be to everything else.

I'm sure I'm missing something here that someone can fill in. I'd appreciate any comment.

In your statement is the dilemma as a hidden assumption. That being the "yardstick" you
use to measure everything "from here to there". You imply it is static. As Modest has
stated in his posts to this thread, the conventional wisdom of BBT has this is not necessarily
the case. Alan Guth in 1980 published his Inflation Theory. This in essence says that
early in the BB time scale -- that yardstick went from {1 yard} to {10e6 or 10e7 Light year of yards}.
This being done so in a matter of seconds or so. Thus Space and Time being created.
In the recent period a rival Theory being VST or Variable Speed of Light Theory. Both
explain some things yet do not answer all questions (I forget the Portuguese Physicist's
name). I have not heard a definitive debunking or validating of either so far.
So if Inflation/VST were true -- Yes the Universe could be "MUCH" bigger that about
15 Billion LY in size.

maddog

[enorbet2]

The name of the Portuguese theoretical physicist is Joao Magueijo and he has an interesting site here
João Magueijo's Big Bang : Science Channel

Perhaps more important than his VST is his early recognition of structure within WMAP. There is a linear anomaly he calls "the axis of evil" brcause it can be interpreted many ways. Most BBT advocates think it is simply due to our motion within the local group. Joao begs to differ. Cool controversy

An excellent site for questions and answers or at least info and insights is here (example specific to why we don't see a speck as we look way out)
Curious About Astronomy: When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter?

There are also good sections on measuring distance, the size and shape of the universe there, and also here
http://en.wikipedia.org/wiki/Distanc...res_(cosmology)