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Mike Garrard asked the Naked Scientists: Please can you explain the current theories on why we don't detect dark matter stars? Why doesn't the dark matter halo of one galaxy start pulling the visible matter out of another colliding galaxy? Why can't we detect any local solar system effects? When dark matter is mentioned, the proof always appears to be the rotational pattern of galaxies. Surely there is more? Thanks Mike GarrardWhat do you think?
@ Graham:1. Can you support that electromagnetic, strong forces and weak forces are required to bind aggregate together? Gravity would seem sufficient up to the point where the particles are orbiting up to the speed of light. If we ran a model of particles where the only force was gravity, would you not expect them to clump?2. You start with the assumption that's it's thinly dispersed then use that to explain lack of interaction for galaxies. I'm asking why it's thinly dispersed. Running some numbers, for lack of interaction it has to be pretty even in interstellar space. What is your theory as to why a grativationally active particle would remain evenly distributed? In the link, the bullet cluster is used as evidence: yet the gas clouds lag the galaxy clusters *because* they are thinly and evenly dispersed: they interacted whilst the galaxies missed each other.3. See #2. My question is why is the density low.4. I'm not disputing the existance of dark matter. I'm asking why it doesn't clump.
Latest NS podcast has Dominic quoting a paper on DM: within earth radius it implies equivalent mass of 1.5 mile diameter asteroid, pretty small. However DM does appear to be in the plane of the galaxy.
"particles cannot lose energy by collisions": this must be a requirement to feed models that match (lack of) observation?
"tiny cross sections involved": do you mean relative to the average density, or is the theory of lack of interaction based upon the size of the particle?