Dark Matter or Field

  • B
  • Thread starter bluecap
  • Start date
  • #1
396
13
For the universe extra source of gravity, why don't they propose some kind of field connected to our matter instead of dark matter?
 

Answers and Replies

  • #2
Bandersnatch
Science Advisor
2,933
1,852
To account for the bullet cluster and for BAO peaks you'd need to construct a field that is separate from baryonic matter. TeVeS does this, but in the end you just get dark matter by a different name.

The latter part of the following talk covers this issue:
 
  • Like
Likes Mary Space
  • #3
Jonathan Scott
Gold Member
2,294
991
For the universe extra source of gravity, why don't they propose some kind of field connected to our matter instead of dark matter?
The standard mainline theory of gravity is General Relativity, in which no such additional field exists.

There are alternative theories, such as MOND (Modified Newtonian Dynamics) and its later refinements, which assume modifications to the laws of gravity. MOND leads to a beautifully simple rule with only one universal parameter which is remarkably successful in predicting rotation curves of galaxies, but it is extremely unsatisfactory from a theoretical point of view (for example the force caused by two masses on each other is unequal, and a star or star system as a whole somehow moves differently from the particles which make it up). It also apparently fails to explain the motion of galaxies within a cluster. More complex theories exist (such as TeVeS) which have a similar effect to MOND, are more theoretically self-consistent and can provide a better fit for observations, but they do this by having many more parameters and they are still not very satisfactory from a theoretical point of view.

The "Bullet Cluster" is often considered to provide strong evidence against any modified gravity theory because observations appear to show that there is a concentration of invisible matter which is not in the same location as the visible matter.
 
  • #4
Garth
Science Advisor
Gold Member
3,574
105
The 'Bullet Cluster' showed DM still associated with the visible matter after two galaxies that had 'colllided', that is the two galaxies passed through each other but with a X-ray source that had been left between them.

This is interpredted as the non-interacting DM staying with the stars of the galaxies, which passed by each other, but the two galaxy-wide clouds of interstellar gas had collided and combined with each other and so heated to over ~ 106 oK, thus emitting X-rays, and this combined cloud was left behind in the centre.

Garth
 
Last edited:

Related Threads on Dark Matter or Field

Replies
14
Views
1K
  • Last Post
Replies
8
Views
6K
  • Last Post
3
Replies
68
Views
9K
Replies
0
Views
403
Replies
5
Views
153
  • Last Post
Replies
13
Views
5K
  • Last Post
Replies
20
Views
2K
  • Last Post
Replies
13
Views
2K
  • Last Post
Replies
7
Views
4K
Top