>>1
Do you mean indexing universes? If the universe is fundamentally discrete in both time and space, then true. I suppose if you wanted to be fancy you could design some mind-bogglingly huge code to specify all particles and trajectories and then embed it in the decimal expansion, which probably amounts to the same thing.
Of course, at that point, you may as well say that the natural numbers can be mapped to the same set, and go home.
If it isn't discrete, then it's probably undecidable in ZFC. It sounds equivalent to the continuum hypothesis although fuck me if I know how I'd actually frame the problem rigorously.