Musings on the Initial Singularity

For those of you who do not know, the so-called initial singularity is an artifact of Big Bang cosmology implied by the expansion of the universe. If all points in spacetime are moving away from each other (not the matter within spacetime, just the spacetime envirnment-sort of like a river flowing, things in the river flow with it, but are not pulled apart), then it seems reasonable that everything had to start at a point. This time reversal leading to something that looks like a black hole was the subject of Stephen Hawking's thesis around 40 years ago. Other people have studied this time reversal process and have speculated about the dynamics of this singularity. The only problem is that they treat it as a spacetime singularity, like that of a static black hole.

The problem is, it could not have been a spacetime singularity! Spacetime did not yet exist before the Big Bang happened, so there could not have been a spacetime singularity.

This is, of course, one of the reasons why we need a truly quantum theory of gravity. This realization destroys any real chance for unification of the forces, since without spacetime curvature there can be no gravitation; and radiation pressure becomes dominant during the inflationary period. At the moment of the Big Bang, the strong, weak, and electromagnetic forces cause a rapid expansion. Spacetime starts to expand, but without a quantum theory of gravity we cannot understand this process since it is entirely in the regime of quantum mechanical distances, even if the energy densities are huge.

A very deep problem, and one that can only be solved by quantum gravity.