Originally posted by Tranquility Base:
Tell me more about the spiral arm quantization - it's not due to the fact that one arm is moving towards and the other away in those cases?
You're starting to worry me, TB. Have you been reading any of the links in this thread? Are you following any of the subtleties of redshift quantization discussed here?
Percy brought this up a long time ago...
The next step involved examining the rotation curves of individual spiral galaxies. Such curves indicate how the rotational velocity of the material in the galaxy's disk varies with distance from the center.
Several well-studied galaxies, including M51 and NGC 2903, exhibited two distinct redshifts. Velocity breaks, or discontinuities, occured at the nuclei of these galaxies. Even more fascinating was the observation that the jump in redshift between the spiral arms always tended to be around 72 kilometers per second, no matter which galaxy was considered.
and Setterfield does, too...
However, when it is considered that the quantum jumps in redshift values have been observed to even go through individual galaxies [Tifft, 1977, p.31], it becomes apparent that the redshift can have little to do with either space-time expansion or galactic velocities through space...
So it seems that Tifft's older work is the source of this observation. Have these data been superceded or discredited since? I don't know. Maybe you could look into it.
If these data hold up, then a strictly Dopplerian interpretion of redshift is completely untenable. Therefore, galactocentrism based on redshift 'shells' falls apart.