o (Omega-"naught") is the ratio of the
density of the universe to the critical density. If Omegao equals 1
, the universe is FLAT. If Omegao is LESS than 1, then the univers
e is OPEN. Current theories favor
an Omegao less than one.. For this lecture, we are going to assume that our universe is OPEN. An open universe will expand for ever..