First prediction from Big Bang model: Cosmic Background Radiation
					• Look out (and back in time) to place  where H became neutral • Beyond that the high density ionized H forms an opaque “wall” • Originally 3000 K blackbody radiation • The material that emitted it was moving away from us at extreme speed • That v produces extreme redshift (z=1000), so photons all appear much redder, so T appears cooler • With red shift, get 2.7 K Planck blackbody • Should be same in all directions