12.3. Local Dark Baryonic Matter
The baryon density estimated in the Ly at z 3 and in local clusters of galaxies are both similar to the that from SBBN using low D/H. This implies that there is little dark baryonic matter in the universe . This result seems conceptually secure, since there is little opportunity to remove baryons from the IGM at z < 3 or to hide them in dense objects without making stars which we would see , and the clusters are believed to be representative of the contents of the universe as a whole today. However, the numerical estimates involved are not yet accurate enough to rule out a significant density (e.g. 0.5 b) of baryonic MACHOS.