Universe's missing matter "located"

[nick c]

"light slows down" Doesn't this slowed down light result in red shift?

I think that Wal thought (a la Arp) that a portion if not all of the red shift was intrinsic to the object and probably was a better description of its age. Quasars, which are young objects or the seeds for future galaxies, have high redshifts and are often found to have a physical connection to a lower redshift (parent) galaxy.