What is the current evidence for dark matter?

[Simon Bridge]

Discussion from the MoND guy.
http://www.astro.umd.edu/~ssm/mond/moti_bullet.html
We have known for some fifteen years now that MOND does not fully explain away the mass discrepancy in galaxy clusters. (See e.g. the 1999 paper by Sanders: http://xxx.lanl.gov/abs/astro-ph/9807023, but there have been quite a few others discussing this before and after, starting from 1988). Even after correcting with MOND you still need in the cluster some yet undetected matter in roughly the same amount as that of the visible matter. Call it dark matter if you wish, but we think it is simply some standard matter in some form that has not been detected.

 

[Chalnoth]

Is the collision separation phenomenon 100% proof of dark matter? if so, why is that some scientists still doubt their existence.. even astrophysicists... and they even have data that suggest it is opposite to dark matter predictions. see:

http://www.sciencedaily.com/releases/2009/05/090505061949.htm

any familiar with what they are talking about?

There's no such thing as 100% proof. But it is compelling evidence that makes MOND-type theories hard to support. The CMB is even more compelling evidence, but that's a little bit more difficult to wrap your head around as to precisely why.

Here's more recent the suggest MOND is more appropriate.. so how does it still support dark matter?

http://www.sciencedaily.com/releases/2011/02/110223092406.htm

The claim here still requires a form of dark matter to fit the data. In this case, they use an undetected heavy species of neutrino in the fit (we know the three neutrinos we know about can't have that much mass). So they have a much more complicated model than just having dark matter: they've got both dark matter and modified gravity. Occam's Razor suggests that this is rather unlikely.