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Cosmo Novice
Nov22-11, 09:33 AM
P: 366
Quote Quote by Chalnoth View Post
Finally, as to Cosmo Novice's statement about homogeneity and isotropy, the fact of the matter is that these assumptions are known to be not completely accurate. They are approximations to the true behavior, and we know that these assumptions break down on small scales. It is entirely conceivable that they also break down on scales much larger than the cosmological horizon.
I can concede that they are assumptions, the difficulty is obtaining a burden of proof. If we proved space was anisotropic then job done, while the sizeable chunk we see is isotropic there will likely always be more to see and so the concept of isotropy can never be fully established.

That being said I think the empirical evidence and the sizeable chunk of homogenous U we can see gives a good indication of this being a cornerstone cosmological principle.

Chalnoth I am interested so can you please give further information on how "we know that these assumptions break down on small scales"?