Is an assumption of the theory that the universe is a simulation that the simulating universe is fundamentally more complex than our own?
The Long Version
As a programmer, I find the argument that the universe is a simulation unlikely for a number of reasons, and the idea that we'll be able to simulate any reasonable facsimile of any significant portion of reality (say, a cubic inch of water) by 2050 to be untenable as well. We may be able to simulate single proteins by then, but probably not entire networks of them, and almost certainly not something as complex as a bacteria.
But the woeful state of simulation aside, the real issue I have with this theory is the question of scale: if I want to simulate a protein and all its behavior, it's hard to see how this could be done without having at least as many particles involved in the simulation as there are particles involved in reality.
So if the universe being simulated has a much lower resolution than the one doing the simulating, I can see how the simulation would be feasible, but I don't see any even vaguely theoretical way that a computer in our universe with fewer actual atoms than are present within a few miles of the Earth's surface could simulate the planet.
Proponents have dismissed this problem without apparently addressing it--the idea is that eventually, a post human civilization will have enormous resources available to it, certainly enough to build a universe simulator that could simulate the universe. But given the size of the computer required, and the fact that the universe might not be possible to compute anyway, and the fact that there are problems of energy consumption and engineering that might make it theoretically impossible to even build the required computer, I don't see why people think that it is more probable than not that these problems must be solvable. What am I missing? To me the whole idea seems silly, but smart, well educated people seem to think it is more likely than not. What am I missing here? Can you model a particle without using a particle? Or is the assumption that we are living at a much lower resolution than the simulating universe?
I have this question here in physics because this is a theory that is advanced by physicists. To me, the things that are being ignored in advancing the theory seem fundamental and simple (like, I need enough matter to model the matter I'm modeling, I need to exert energy to model exertion of energy, etc). Assuming that the physicists who advance the theory aren't completely naive about computer science and engineering, the reasonable conclusion is that I'm missing something about the theory. My question is: what is it that I'm missing that makes this seemingly ridiculous idea not ridiculous?