Quote:
Originally Posted by Brian W
Ok Craig I follow your argument with a few questions
(1) when I used to go sailing there were times that I was out of sight of land. Anyone else that was sailing out of sight of land would see basically what I was seeing. I get the idea that it all looks the same.
But I still do not see that that means there is no single spot where it all begins. Unless one was to take ethnocentricity to it ultimate limit.
(2) please explain to me the co-relationship between having a centre and not expanding.
It seems to me that there can be a centre in an ever expanding anything.
Brian
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Hi Brian;
Please excuse the sharpness of my responses (I'm a bit rushed today).
Ok. So … I guess there can be a centre in an ever expanding 'anything', if one chooses to go with the models originally suggested..
However, two testable consequences of the cosmological principle are homogeneity and isotropy. Homogeneity means that the same observational evidence is available to observers at different locations in the universe. Isotropy means that the same observational evidence is available by looking in any direction in the universe. A universe that appears isotropic from any two locations (for eg), must also be homogeneous.
If the universe is isotropic, the distance to the edge of the
observable universe is about the same in every direction (ie: appears as a sphere - confirmed by CMBR observations in different directions). But every location in the universe sees the same view ... which may, or may not, overlap with our Earth centric view.
So, if every observer sees the same expansion (with redshifts) how can one determine where the centre is ? (I don't think this is possible).
I think the point here is, one either goes with the observable evidence, and model, and accepts that there is no identifiable centre, or one believes otherwise, with no observable evidence supporting that belief.
The original model of the BBT suggests that the original universe started from an infinitely small, infinitely hot (energy dense) point. It expanded into nothing. It's location or its centre is not determinable, if one goes with the Standard Model concepts of homogeneity and isotrophy which are based on observations.
Cheers