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this post was submitted on 31 Oct 2025
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It would be interesting to see someone with the background to understand the arguments involved in the paper give it a good review.
That said, I've never brought the simulation hypothesis on the simple grounds of compute resources. Part of the argument tends to be the idea of an infinite recursion of simulations, making the possible number of simulations infinite. This has one minor issue, where are all those simulations running? If the top level (call it U0 for Universe 0) is running a simulation (U1) and that simulation decides to run its own simulation (U2), where is U2 running? While the naive answer is U1, this cannot actually be true. U1 doesn't actually exist, everything it it doing is actually being run up in U0. Therefore, for U1 to think it's running U2, U0 needs to simulate U2 and pipe the results into U1. And this logic continues for every sub-simulation run. They must all be simulated by U0. And while U0 may have vast resources dedicated to their simulation, they do not have infinite resources and would have to limit the number of sub-simulation which could be run.
You're making a few assumptions there which aren't necessarily true. Firstly, that U0 obeys the same rules of physics and reality that we do. They might be orders of magnitude more complex, the same way that a Sims game is a vastly simplified version of our world.
Secondly, that time is progressing at the same speed in both universes. It's possible to simulate an even more complicated universe than the base layer, provided you don't care about the frame rate. It could take a year in U0 to simulate a minute in U1, and so forth, and we wouldn't notice it.
A couple other possibilities, which don't come to mind right now
There’s a book be Greg Egan called Permutation City which postulates something similar to this.
There exists a simulation. It works well but, due to the unbelievable complexity it runs something like 10 times slower than the real word.
They do a series of experiments on someone in the simulation. They count to ten a number of times and ask him if he perceived anything unusual. He didn’t. But what happened outside the simulation is that they did the computations for the simulation in various different ways. They parcel out the data in all kinds of ways and,, for example, send different packets of data to different locations in the world, process it in each different location and then send it back and recompile it. Or they run the data packets in reverse temporal order before recompiling them.
Since the guy in the simulation didn’t notice anything unusual, they determine that time and space is irrelevant when it comes to processing the data of a simulation, at least to the people in the simulation.
So, either through some very clever realistic physics that i didn’t pick up on or, as is far more likely, some science fiction hands-waving, they decide that you can treat every point in space and time as a bit and the presence of matter as a 1 and the absence of matter as a 0. And you can then consider them one giant stack of code and data and how far each point is separated in time and space can be ignored, and therefore you can use all of time and space as one computer and run an effectively infinitely large simulation with it.
It’s a pretty silly idea, but also a clever one. And it makes for a good story.
We understand the universe as complex. Honestly though, I wonder if a True understanding of how the universe works—from the fundamentals of which all things may emerge—is rather simple.
For example: within U0, you would control the spacetime simulation of U1. Therefore, what could be a single moment of simulation by U0s standards, could be experienced as trillions of years from within the perspective of U1. They control the frame rate.
They could simulate the fundamentals, fast forward to the end of the universe, and here we are somewhere in the very early part of that having no idea someone hit fast forward because everything is relative for us.
The short reply to that is that it's turtles all the way down. The slightly longer reply is that you're making assumptions about how energy works in a system that you're recognizing is not the same as our system. The even longer to reply is that if you're hypothesizing a system then neither looks nor functions, anything like our current system, then our current language simply cannot describe it properly and therefore we have no good way to speculate about how it would or wouldn't work.
So, if the higher level universe works by magic, then the theory is fine.
Sure, I'm making assumptions that any universe simulating our own would have finite energy and resources. Also that they would make a simulation that is at least close to their own (making theirs close to ours). Those seem like reasonable assumptions to make, otherwise we might as well just say that our universe is a pocket dimension made by magic and the whole thing becomes absurd pretty quick.
Very simple fix for that perceived contradiction: A simulation doesn't need to simulate everything. All it needs to simulate is the inputs and outputs perceived by a single human being, the observer, me.
For me it would be indistinguishable if the universe I am living in is real, if it's a simulation or if it doesn't exist at all and instead only the things I can perceive are simulated.
Simulating the perception of a single human being should be in the reach of our current calculation power.
Kind of how in a computer game only areas around a player are simulated.
"In order to bake an apple pie from scratch, you first have to create the universe"
If you don't create the universe, then you aren't really making an apple pie from scratch. In the same way, what you're referring to doesn't simulate the universe - not in the way that it is simulated in the simulacrum hypothesis.
In the simulacrum hypothesis, the entire universe is simulated. You exist entirely inside the simulation rather than being merely plugged into it, and so do I and so does every other consciousness that exists.