Time dilation from galactic gravitational mass

[strangerep]

Wouldn't the change in gravitational potential be significantly different for a 3D sphere (where the mass is evenly distributed in 3-space and as we move in 3 dimensions, the calculation is ^3) vs a flat surface (where the mass isn't evenly distributed in 3-space and so it's ^2)?

You can get a feel for the difference by just looking at the Newtonian case -- where the non-relativistic gravitation (Poisson) equations are solved for various mass distributions. This is explained in considerable detail at Bovy's Galactic Dynamics Online Book, especially ch8 et. seq.

 

[Ibix]

I wouldn't call it "solid". Not at all. See the Deur thread over in BTSM.

In the context of this thread I was merely meaning that it was a fleshed-out mathematical proposal from a serious physicist, as opposed to the "hey wouldn't it be cool if..." idea in this thread which can be dismissed with an order of magnitude calculation. I suspect I'm not qualified to have an opinion on Deur's idea's plausibility.

 

[strangerep]

In the context of this thread I was merely meaning that it was a fleshed-out mathematical proposal from a serious physicist, [...]

I don't think it's "fleshed out".

But I hope other people here with good proficiency in GR will take a closer look at it, and offer their well-considered opinions on this point.

 

[Vanadium 50]

The fact that "dark matter" is proportional to the visible mass is

This is not a fact. The mass-to-light ratio for galaxies varies by quite a bit: more than a factor of about 5.

 

[malawi_glenn]

This is not a fact. The mass-to-light ratio for galaxies varies by quite a bit: more than a factor of about 5.

Another missuse of "proportionality" :(

 

[Vanadium 50]

Well, you can always divide any two quantities A by B and say "look, they are proportional!" Just not sure where that gets you.