I'm not sure what you said refutes his point. It still doesn't require the entire universe to be simulated. If you observe the Nile, then yes it becomes an inp

I'm not sure what you said refutes his point. It still doesn't require the entire universe to be simulated. If you observe the Nile, then yes it becomes an input, so that then would need to be simulated. This could take however long is necessary to do. It still does not necessitate simulating the entire universe down to the minutiae. Perhaps if the people in the simulation purposefully set out to "observe" somehow their entire universe in one timestep, in such way that _necessitates_ the complete simulation of their universe (like, say, running an experiment that involves all atoms interacting with all other atoms in their universe), then maybe it will be a problem. Then again, maybe the parent universe just has more atoms & computing power to throw at it, or it will generate a simulation that is "close enough" to the real thing that the people in the simulation will not be able to distinguish.