Bullet Cluster
<p>Sep 27, 2011 09:33 PM
 
see Bullet Cluster... it provides the BEST direct evidence of dark matter and
is spectacular.
 
see overview.  great explanation...  the stars in both galaxies do NOT interact and
neither does the dark matter.   The dark matter's  distribution (location) as judged by
gravit. lensing seems to be where the regular matter is.   It is expected to be where the
gas is (the gas is left behind because the gas clouds interact using EM.
The fact that most of the lensing is located near the regular (star) matter suggests that
it is collisionless  (no EM interaction)... just like the stars.</p>