Edit TL/DR

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?


closed as primarily opinion-based by ACuriousMind, Ryan Unger, Kyle Kanos, John Rennie, Qmechanic Jul 15 '15 at 14:07

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ What you're missing is that smart well-educated people agree with you, and don't think it's more likely than not! $\endgroup$ – John Duffield Jul 14 '15 at 18:05
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    $\begingroup$ I don't see how this is a physics question. If we are in a simulation, we have no clue how the laws of nature in the world simulating us work, and if there even is the concept of "particle" there. $\endgroup$ – ACuriousMind Jul 14 '15 at 18:19
  • $\begingroup$ There is the vaguely-formulated but quite reasonable-sounding hypothesis that nature is the most efficient computer of its own state. I'm having trouble finding references though. $\endgroup$ – user10851 Jul 14 '15 at 18:44
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    $\begingroup$ The core problem with the whole idea, is that we have no way---whatsoever---to constrain the physics of the host universe. Just like we don't have to write simulated worlds that are faithful to the one we live in. So you're stuck unless you want to simply assert some facts to be assumed about the host universe; and people do that which is fine as far as it goes but doesn't tell us anything. You are basically assuming that the host universe must be similar to our own. Fine. But why are you assuming that the host universe is the same size? Maybe the host universe simple has more particles. $\endgroup$ – dmckee Jul 14 '15 at 22:00
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    $\begingroup$ Next question to ask yourself: why are you assuming that the distant stars (or even the sun and other planets) are simulated at same high resolution as the local volume? Why can't all the parts of the universe not in the immediate vicinity of me or you be running a course-grained, effective theory? Everyone else is a NPC, of course. For that matter you have to assume that I am a PC. $\endgroup$ – dmckee Jul 14 '15 at 22:28

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