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Perikles
2009-Jun-12, 01:57 PM
A really basic question, possibly rather stupid considering all the specific questions posed here. Apologies if asked before.

I assume that apart from local variations, observations from earth show that the density of matter in the universe in a direction A is more or less the same as in the exact opposite direction B, with the furthest visible objects moving away at around 0.4c. An observer in some galaxy at A will then see us moving away from them at the same speed, and behind us, they see B travelling away at an even greater speed, (I've forgotten the factor applied, but less than twice 0.4c).

What does the observer at A see when looking in the direction away from us? Do they see an equally dense universe, or do they see themselves on the edge of it?

I suppose the question really boils down to: Does every observer see themselves as at the centre of the universe? (Apart from those with an inflated ego)

Cougar
2009-Jun-12, 02:07 PM
Well, it's hard to say for certain, since travel to distant galaxies is so darn difficult, but yes, that is one of the assumptions, that the universe is isotropic (http://en.wikipedia.org/wiki/Isotropic).

solomarineris
2009-Jun-14, 11:17 PM
I suppose the question really boils down to: Does every observer see themselves as at the centre of the universe? (Apart from those with an inflated ego)
No one can answer your Q. better than Hubble's Deep Field picture, it peers into 13billon LY, I downloaded this huge picture, it looks like our neighbors of today.

Cougar
2009-Jun-15, 02:32 AM
...it looks like our neighbors of today...

Well, the most distant galaxies in Hubble's Ultra Deep Field are not so well formed, lots of 'tadpole' and other odd shapes... They're much earlier in their evolution than our neighbors. Same raw material.

Fiery Phoenix
2009-Jun-28, 03:24 PM
According to the Cosmological Principle (http://en.wikipedia.org/wiki/Cosmological_Principle), yes. Basically, any observer in any galaxy sees the same general features of the Universe as any other. Based upon homogeneity, isotropy and universality.

nokton
2009-Jun-28, 04:25 PM
A really basic question, possibly rather stupid considering all the specific questions posed here. Apologies if asked before.

I assume that apart from local variations, observations from earth show that the density of matter in the universe in a direction A is more or less the same as in the exact opposite direction B, with the furthest visible objects moving away at around 0.4c. An observer in some galaxy at A will then see us moving away from them at the same speed, and behind us, they see B travelling away at an even greater speed, (I've forgotten the factor applied, but less than twice 0.4c).

What does the observer at A see when looking in the direction away from us? Do they see an equally dense universe, or do they see themselves on the edge of it?

I suppose the question really boils down to: Does every observer see themselves as at the centre of the universe? (Apart from those with an inflated ego)

Your evaluation of the density cannot contend.
My contention is, the relative gravity of the observer, and the observers speed,
would influence the observers measurement if different from from ours.
My point is, density apart, the speed of galaxies moving apart is determined
by the time frame of the observer, an observer in galaxy A, (assume ours),
would be different to observer B, if observer B observing in a higher gravity field.
and or, moving faster than we are.
The true observer realises we are not the centre of the universe.
A few hundred years ago, one would have been burned at the stake for ideas
like that. One was.
Nokton