•The Horizon
Problem
–The
cosmic background in all directions has the same temperature, yet opposite sides of the sky are not in “causal contact”
(they are outside each other’s
horizons). The largest COBE structures are also larger than their own horizons!
•The Flatness
Problem
–The geometry of the Universe now appears to be flat. But it has expanded by a factor of 1060, so at the beginning it had to be flat to within a
factor of 10-60! And yet it had to have enough density fluctuations to
produce today’s structure. How was that
arranged?
•The Matter
Problem
–Matter and antimatter should be created in exactly equal amounts, but they weren’t (by a tiny bit).
•The Creation
Problem
–How did spacetime suddenly spring into being, with lots of mass and energy, and violently expand?