A very interesting article in the latest SciAm on dark matter and dark energy.
http://www.sciam.com/article.cfm?cha...CA562C33C4F03C
It points out how the Universe as we observe it, principally the large scale filamentary structure, as well as galaxy evolution, is sculpted by dark matter.
The underlying assumption is the cosmological principle the the Universe, and the forces of gravity and space/time, are the same everywhere.