Thoughts on the multiverse, simulation theory, and the singularity

This thought stream stemmed from contemplating the possibility of time travel, and if it were possible there would in hand have to be a computer set to calculate the outcome of any changes made. Say you want to go back in time and kill Hitler, but somebody even worse comes into total world power years down the road as an outcome.

Assuming that at this point technology would have advanced to the point of being able to replicate consciousness (currently in the works), this computer would then run simulations of the entire universe from start to finish, calculating every possible outcome for everything that’s ever happened or could possibly happen within the defined physical laws.

Some of those “created” universes would then get to the point where the very technology producing it is being created, then running the same calculations to create a whole new set of infinite universes, infinitely, and fractally inward. Including you, and me, and everything that’s ever happened, in detail indistinguishable from reality.

I know this sounds like lunacy, but it would have been damn near impossible to explain a cellphone, and everything it does, and why to somebody a few hundred years ago.