Submitted by taracus t3_ygfptx in askscience
nooki1 t1_iu8rgu2 wrote
Reply to comment by Aseyhe in Is dark matter orbiting galaxies with the same speed as normal matter? by taracus
Maybe I misunderstood you but should regular mass drag any dark energy with it(or other way around)? Loosing or adding momentum due to gravity.
Aseyhe t1_iu8tn7l wrote
Ordinary matter and dark matter both exert gravitational forces on each other, so they influence each other collectively. However there is essentially no momentum exchange between individual particles. Such gravitational collisions are possible (e.g. the slingshot effect), but their importance scales inversely with the number of particles in the system. In the context of galaxies, the individual dark matter particles and ordinary matter particles (whether they be stars or atoms) are far too numerous for gravitational collisions to be important.
(Incidentally, you said dark energy, not dark matter. In case that was intentional, I'll note that we currently have no evidence that dark energy is capable of clustering, but that is an active research topic.)
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