[Blue-Eyes White Dragon]

Quantum mechanics has proven that all energy is quantized; in other words it is not infinitely divisible. Gravity is a form of energy, therefore it must be quantized. But if gravity is quantized, then there must be a smallest space and time over which gravity can act, such that when you get smaller than a single "graviton," the force of gravity no longer functions, which means the gravitational force will stop operating before a singularity is produced.

As to what did cause the Big Bang... I'm not sure.