Originally Posted by Darkness
I prefer the pressure theory. Basically, when you accurately expand the equations for gravitation, pressure becomes a source of gravity. In the everyday world, it's insignificant. In the early days of the universe with very little entropy, everything was very tightly bunched together such that the pressure term of the gravitation equations was much more significant than the 'regular' terms from gravitation. The thing is, the pressure term of gravitation induces a repulsive force, where normal gravity (following newton's laws for macroscopic objects) is an attractive force (it induces a pull).
So, basically, the theory suggests that gravity caused the big bang. Because it is gravity, and not some other mysterious unknown entity (gravity obeys the speed limit of the universe, the speed of light) the big bang acts as a single well defined event with respect to absolute space time (as opposed to basing it off of relative time or whatever).