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If dark matter is thought to constitute the majority of the matter int he universe - so much so that it is thought to be the reason that galaxies don't pull apart when they spin..
Wouldn't dark matter be orbiting in galaxies and solar systems too
why don't massive objects (like the Earth) attract it gravitationally? Wouldn't dark matter fall into the gravitational fields, adding to the mass of objects, or bringing it here into range for observation?
I have also wondered why dark matter wouldn't coalesce under gravitational attraction with itself.
thermal equilibrium at 2.7 K
would the "weakly interacting" part inhibit thermal equilibration?
If dark matter is thought to constitute the majority of the matter int he universe - so much so that it is thought to be the reason that galaxies don't pull apart when they spin - then what form/size does this matter take?
Are there planet-sized lumps of it? Surely not, as this would block out the light from stars etc. behind it.
So are we talking about dark matter particles?
If so, could this have such a profound effect as that described above...and why does it not, then, interact with itself and 'clump' together...
what form/size does dark matter take?
Nobody knows for sure.
Some astronomers are hoping that if dark matter decays, or interacts with matter with some characteristic energy (even if infrequently), then a large space telescope looking for this specific energy signature may eventually be able to map the distribution of dark matter in our galaxy, and nearby galaxies.
But for now, we have to rely on computer simulations, which can render the (simulated) dark matter visible to the programmer. Some of these models end up with a distribution of visible matter that is similar to what we see in space; this suggests that the model also represents a distribution of dark matter which is similar to what occurs in space.
On the large scale, these models seem to point to a structure like soap bubbles or a sponge, where the galaxies and dark matter are clustered in the walls of the bubbles, surrounding large amounts of seemingly empty space.
IMHO the issue with that is that they've been talking about WIMPs for thirty years now, but there's no evidence for them whatsoever,
and meanwhile relativity has had no airtime.
I suspect that part of that is because the WIMP guys want everybody to think that theirs is "the only game in town".
No problem. The problem is with the assumption that dark matter must consist of particles. There's just no justification for that. That's doing physics as if relativity never happened.
This isn't actually true. Even if one considers only the evidence from the CMB, that is significant evidence for the existence of something like WIMPs. The evidence from the CMB indicates the presence of mass in a form that does not interact through electromagnetism or self-interact to a great degree. Even if other candidates for dark matter are viable, they have to be very, very much like WIMPs.
This is also not true. All the gravitational calculations done by contemporary cosmologists, be they from the WMAP project, the various supernovae projects, the large-scale structure projects, and so on, are relativistic calculations. Only by not actually looking at these projects and their publications can someone be ignorant that they are using general relativity--why someone would want to throw baseless allegations at these scientists, I do not know.
A look at the WMAP results can see that they are open to different kinds of dark matter from their very first official published results (Spergel et al., "FIRST-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP)1 OBSERVATIONS: DETERMINATION OF COSMOLOGICAL PARAMETERS", The Astrophysical Journal Supplement Series, 148:175194, 2003 September). There are many different teams proposing different kinds of dark matter; these teams do not do so in ignorance of the available evidence.
Again, this seems like a baseless insult entirely unrelated to the facts. There have been a couple of papers that attempted to show that relativistic effects could account for the phenomena associated with dark matter at the galactic level--all these attempts have failed. All the work of contemporary cosmology is done with general relativity.
Perhaps the poster would like to show us an example of a specific paper that ignores general relativity?
Perhaps the poster would like to present an alternative theory to those of contemporary physicists working in the field that one could compare to observations?
There is no evidence for WIMPs, or for something like WIMPs. None whatsoever. If you'd like to dispute that, then provide a link.
I'm not throwing baseless accusations at cosmologists or relativists,
I'm saying that there are dark-matter particle physicists who wilfully ignore relativity along with "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy".
Some do so in wilful ignorance of the fact that it's energy that causes gravity rather than matter per se. They perpetuate the myth that matter particles causes gravity.
Provide the references.
quote author=PhysBang link=topic=54299.msg450805#msg450805 date=1424440041]Perhaps the poster would like to show us an example of a specific paper that ignores general relativity?
a subset of the Wikipedia article saying this "According to consensus among cosmologists, dark matter is composed primarily of a not yet characterized type of subatomic particle". There is no such consensus. What there is, is a propaganda campaign.
Quote from: PhysBang on 20/02/2015 13:47:21Perhaps the poster would like to present an alternative theory to those of contemporary physicists working in the field that one could compare to observations?No, but I can refer you to http://arxiv.org/abs/1209.0563 which concerns inhomogeneous and interacting vacuum energy. You will be aware that a concentration of vacuum energy will have a gravitational effect, and that space expands between the galaxies but not within. Given conservation of energy, every galaxy must be embedded in a region of space where the vacuum energy is higher than the surrounding space. That energy would have a gravitational effect. And yet most of the media reports on dark matter do not mention this, because they originate from particle physicists who want to persuade the public that theirs is the only game in town.