How far can we observe

[Ermac]

Since the universe it roughly 13 billion years old, I guess we can't observe (by any means) objects further than 13 billion light years away...there hasn't been enough time for light from those objects to reach us.

What are the implications of this in terms of how well we can know the spatial extent of the universe?

When we use available technology to "see" as far back in time as possible...to see the early early universe...what are we observing in a spatial sense? Is it appropriate to say we're looking into the "core" of the universe as we look back in time? On one hand, this would seem to make sense because the universe was smaller then. On the other hand, if the universe doesn't really have a center per se (or does it?), then what it does mean, spatially, to look into the earliest stage of the universe?

:E :upstare: :cheers: :x

 

[Member17]

(QUOTE
I guess we can't observe (by any means) objects further than 13 billion light years away...there hasn't been enough time for light from those objects to reach us.
)

Correct – this is a direct result of the inflationary period in which all the matter/energy in the universe was carried along with the expanding space. Some believe this is a prelude to faster than light travel, however the matter/energy was not actually moving at those speeds – space can expand as fast as it wants because its expansion rate is not determined by the same laws that govern matter and energy.

(Quote:
What are the implications of this in terms of how well we can know the spatial extent of the universe?
)


The implications are such that it is most likely we will never see the very early universe back to the inflationary period or even close to it. However, we can speculate through mathematics and observations of existing matter and energy based on the effects they have and the metrics of GR. The CMBR’s temperature and its fluctuations play an important part in trying to understand this era.

As well, we must keep in mind our reference frame – the universe has been expanding for billions of years. According to GR, the ‘curvature’ of the universe was much greater in the past – the light emitted from that time has expanded along with the universe (hence we get redshift) making our views of the universe frame dependent.

We must therefore measure this light and plug the values into the metric to determine what the universe may have resembled from that reference frame.

(Quote:
When we use available technology to "see" as far back in time as possible...to see the early early universe...what are we observing in a spatial sense? Is it appropriate to say we're looking into the "core" of the universe as we look back in time?
)

Not really, the core of the universe is all around us. If everything in the universe was at one time a single point, then every place one could possibly be in the universe could be claimed as being the core, or the center. That is why the concept of a core or center of the universe really doesn’t mean much in cosmology in this regard.



(Quote:
then what it does mean, spatially, to look into the earliest stage of the universe?
)

I think you need to expand on this or perhaps choose different terms. In order to “view” the entire universe, we would have to invoke an absolute frame of reference, which does not exist according to relativity. Again, we must invoke the mathematics from the metrics of GR to explain much of these concepts.

 

[Shodan]

That signature is likely to get you.... le banned....:|

 

[Ermac]

Going off topic will likely get YOU banned.

 

[dream431ca]

There is something really wrong with your logic. When you say "look back in time" what your really saying is looking so many light years away. We think we see back in time but in reality we don't. If we were to travel 16000 light years away then use a very big telescope to look at earth and actually see what's on the earth..we would not see earth 16000 years in the past. To get back to the quesion on how far can we observe..that's a question of how far we want to observe. The universe is predicted to be 13 Billion years old, but nobody knows exactly how long it's been there. What will happen if we keep on look farther and farther and farther?? We wil just see more stars and Galaxies. Remember the big bang is an explosion and we are on one side of the explosion. The other side we cannot see because it's too far away, Very far away.

 

[jondy]

Going off topic will likely get YOU banned.

Ermac, he's been here longer than you and he still hasn't managed to make an ass of himself, which is more than can be said for you. So less of the lameness.