Additional evidence is provided by gravitational lensing observations, the most spectacular of which is the Bullet Cluster: http://apod.nasa.gov/apod/ap060824.h

Additional evidence is provided by gravitational lensing observations, the most spectacular of which is the Bullet Cluster: http://apod.nasa.gov/apod/ap060824.html http://apod.nasa.gov/apod/ap060824.html