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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
From our text:  Horizons, by Seeds