Spacetime Expansion in Big Bang 100% Certainty?

[Alfrez]

In Big Bang theory, Spacetime itself expands from Planck size to the universe today. This means there is no existing space before the bang.

But what if we assume space and time already existed in the universe and the Big Bang was an explosion of just matter. Is there no cosmology theory or model that can ever support this? If so. Then it means spacetime geometry being elastic is a law of physics set in stone and not irreplaceble with anything else forever and a categorical finality with 100% certainty??

 

[BillSaltLake]

100% certainty is a tall order, especially when talking about something that's so remote from current lab-testable physics.

 

[Alfrez]

General Relativity is in severe conflict with Quantum Mechanics. Does it mean that it is still possible General Relativity is wrong?

 

[BillSaltLake]

GR is an approximation, and it's also not a complete theory of everything. It doesn't make predictions about QM, so that the behavior of gravity in the QM realm is not (yet) known. In the sense that GR is an approximation, it is by definition not completely "right".