http://en.wikipedia.org/wiki/Massive_Compact_Halo_Object http://en.wikipedia.org/wiki/Massive_Compact_Halo_Object Basicly, there is not enough baryonic matter

http://en.wikipedia.org/wiki/Massive_Compact_Halo_Object http://en.wikipedia.org/wiki/Massive_Compact_Halo_Object Basicly, there is not enough baryonic matter (stuff like protons and neutrons) in the universe to explain the observed effects of dark matter without invalidating a lot of other observations.