[halter73]

That's funny. The parent's NASA link uses the high relative velocities as "direct evidence for dark matter and supports the view that dark matter particles interact with each other only very weakly or not at all, apart from the pull of gravity." The lack of friction seems obvious with this view of limited interaction between dark matter particles.

[MrPatan]

That's also how I understood it. No photons, no electrical interaction, no friction.

[floxy]

Chandrasekhar dynamical friction is just a function of gravity:

https://en.wikipedia.org/wiki/Dynamical_friction

[MrPatan]

Well, ok, but that means there's still _less_ friction with those particles because they don't interact electrically, right? So I still would expect the same result of the 4 blobs in different positions in space.

What's wrong with that view?