Did Hubble can it wrong?

[Alex K]

If we took two identical stars that are at different distances from us, the amount of gravitational redshift should still be the same if we're sufficiently far away. If the universe was not expanding, then this gravitation redshift would be the main component for the redshifts and we would see the same redshift. However, we see different redshifts.

The gravitational redshift depends on the difference of the gravitational potential. If two identical stars are at different distances, they will be in different gravitational potential, hence will exhibit diffrent redshifts.

Also, if you look at whole galaxies that have different total mass but are at the same distance away from you, you would expect different amount of redshift if the universe was not expanding. We see the same amount.

If you look at equation 10, d = H Δv, you need to know the mass and the size of the source. And so my argument is that this will be the same for every galaxy. I've put an appendix on my blog to illustrate that. Check it out again: http://soi.blogspot.ca/

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I'm confused: cosmological redshift and doppler redshift are different phenomena, no? One measures the relative speed during emission, the other the total expansion of the universe since the emission. In GR far away galaxies don't really move away in space, but the in between space expands according to the friedmann equations. Or do you claim that both are equivalent?

Yes, both are equivalent, since they both are described by the same equations.

I don't see it yet. Do you talk about cosmological redshift via spatial expansion at all in your notes?