the redshift from recession or expansion

[micomaco86572]

Almost all textbooks tell us that the cosmic redshift is arised from the cosmic expansion rather than the recession of the celestial objects. I think the conclusion is basically based on the assumption of Copernican Principle, i.e. there is no favored position in the whole universe. But what if we give up this assumption? Can we still lead to the conclusion that the redshift is caused by expansion?

thx.

[Chalnoth]

Almost all textbooks tell us that the cosmic redshift is arised from the cosmic expansion rather than the recession of the celestial objects. I think the conclusion is basically based on the assumption of Copernican Principle, i.e. there is no favored position in the whole universe. But what if we give up this assumption? Can we still lead to the conclusion that the redshift is caused by expansion?

thx.
It's largely just a matter of the description of reality rather than actually being a physical discrepancy. If you so choose, you can select a different coordinate system where the expansion appears to be primarily due to the recession instead of the expansion. The math is just easier in the coordinate system where the expansion is the cause of the redshift.

[micomaco86572]

It's largely just a matter of the description of reality rather than actually being a physical discrepancy. If you so choose, you can select a different coordinate system where the expansion appears to be primarily due to the recession instead of the expansion. The math is just easier in the coordinate system where the expansion is the cause of the redshift.

Thank u, Chalnoth. I understand it, now.

[Naty1]

lots more detail here:
http://www.physicsforums.com/showthread.php?t=522587