The discussion centers on the absence of detectable dark matter (DM) in the solar system despite its prevalence in the universe. Participants conclude that DM does not clump like baryonic matter, which results in its even distribution across vast spaces, making it difficult to detect. The consensus is that the solar system contains significantly less dark matter than expected, with estimates suggesting it has a mass equivalent to a small asteroid, dispersed throughout the solar system. The most widely accepted model for DM is that it consists of weakly interacting particles that follow Keplerian trajectories, contributing to the minimal detection of DM particles.
PREREQUISITESAstronomers, physicists, and cosmologists interested in the nature of dark matter, its distribution in the universe, and its implications for gravitational theories and cosmic structure formation.
Bandersnatch said:
Bandersnatch said:
First, the distribution of matter in the universe is NOT the same as the distribution in the solar system. For reasons I'm not sure are even understood, there is much less dark matter in the solar system than you would expect from the normal ratio of baronic matter to dark matter. The best estimate of the amount of dark matter in the solar system is that it has a total mass equivalent to a small asteroid, but it is spread out over the entire solar system. Even if it were baronic matter it would be too little to detect.Leonardo Muzzi said:
The reason is because DM doesn't clump. I think that's pretty well understood.phinds said:
Yeah, that's reasonable. The solar system is, on average, much more dense than the density of the Milky Way galaxy. DM is spread out evenly whereas solar systems are clumps within the galaxy.Bandersnatch said:
Really? Did you read this article: https://arxiv.org/pdf/0910.4272.pdf ?phinds said:
Why streaming? Do you remember our conversation: https://www.physicsforums.com/threads/gas-like-dark-matter.958333/ ?Bandersnatch said:
I don't understand the relevance of the questions. Please elaborate.DanMP said:
You wrote thatBandersnatch said:
and I need to know why do you think that DM particles are behaving like this. What experimental/theoretical evidence suggests that DM particles are "streaming by"?Bandersnatch said:
The most widely assumed model for DM is weakly interacting particles (i.e. collisionless gas), affected solely by gravity. As such, each particle follows Keplerian trajectories in gravitational fields. I.e. they're 'streaming by' on the basis of theoretical predictions of their assumed properties.DanMP said:
DM without qualifiers should refer to DM as used in the concordance (LCDM) model - because that's what's implicit in the question in the OP. This type of DM is collisionless.DanMP said:
Am I thinking that? They might not be. This has no bearing on the fact that, for a collisionless DM with required densities, the flux on the scale of the solar system must be tiny.DanMP said:
No, that is a very poor analogy. "Clear like glass" implies a macro-sized object. The consensus is that DM is particles and it is not a meaningful statement to say a particle is "clear like glass".Wes Tausend said:
Your point is sort of valid but totally irrelevant. You are ignoring the fundamental fact that DM interacts only by gravity, so there is no "built that way" that would allow us to detect it with nothing but human senses.Vibhu said:
Since such a shock wave would only affect normal matter, I fail to see what it has to do with the distribution of DM. Am I missing something?Nik_2213 said:
I see you have enough posts that you should be well aware about the PF rule on speculation.Nik_2213 said: