# At the Big Bang, when everything was close together, why did it not “collide”, violating Planck length or Pauli Exclusion Principle?

How could so much matter, or "all" in fact, have been concentrated in a smaller universe without being in the actual same place? Why did this not result in undercutting the Planck Length or violating the Pauli exclusion principle?

• See e.g. "Did the Big Bang happen at a point" and "Does black hole formation contradict the Pauli exclusion principle" on Physics.SE. – David Moles Jul 3 '20 at 21:46
The big bang model relies on classical General Relativity. When we go back to scales where quantisation of space might become important (i.e. Planck length scales, corresponding to the first $$\sim 10^{-43}$$ s of the universe) then GR needs to be replaced by some quantum theory of gravity (which we don't have).