Transcript: The fact that quasars are at large distances and have huge luminosities depends on the cosmological interpretation of their redshift. There are some crucial distinctions between galaxies and quasars as far as redshift goes. For galaxies they follow a Hubble relation where distance indicators such as Cepheids within the galaxies or supernovae in more distant galaxies reliably indicate distance and are correlated well with redshift. Quasars have no property that correlates well with redshift. The luminosity varies by a factor of thousands between different objects, and the light from the quasar is variable on timescales of weeks, months, and years. So the redshift itself is used as a distance indicator. In many cases the redshift is high enough that the host galaxy cannot be seen. Quasar redshifts begin at a few tenths, and beyond a redshift of a half the host galaxy is usually not visible. The highest quasar redshifts are six or seven, an age when the universe was only ten percent of its current age and seven times smaller than it is now.