Time dilation from galactic gravitational mass

In summary, there is a negligible relativistic effect between the center of the galaxy and the outside, which cannot explain the size of the "delta" in galactic acceleration. Effects of speeds of this order magnitude are measurable in experiments, but are of a similar order of magnitude to the effects of gravitational time dilation on the applicable scales.
  • #36
marcosdb said:
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.
 
  • Informative
Likes PeroK
Physics news on Phys.org
  • #37
strangerep said:
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.
 
  • Like
Likes Dale and PeroK
  • #38
Ibix said:
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. :oldsmile:
 
  • #39
marcosdb said:
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.
 
  • #40
Vanadium 50 said:
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" :(
 
  • #41
Well, you can always divide any two quantities A by B and say "look, they are proportional!" Just not sure where that gets you.
 
  • Like
Likes vanhees71 and PeroK

Similar threads

  • Special and General Relativity
Replies
4
Views
1K
  • Special and General Relativity
Replies
7
Views
2K
  • Special and General Relativity
Replies
7
Views
1K
  • Special and General Relativity
Replies
5
Views
1K
  • Special and General Relativity
Replies
11
Views
953
Replies
35
Views
1K
  • Special and General Relativity
2
Replies
37
Views
3K
  • Special and General Relativity
Replies
12
Views
1K
  • Special and General Relativity
Replies
1
Views
650
  • Special and General Relativity
Replies
9
Views
198
Back
Top