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.
So first is to accept this is more philosophy/religious sort of discussion rather than science, because it's not falsifiable.
One thing is that we don't need to presume infinite recursion, just accept that there can be some recursion. Just like how a SNES game could run on a SNES emulator running inside qemu running on a computer of a different architecture. Each step limits the next and maybe you couldn't have anything credible at the end of some chain, but the chain can nonetheless exist.
If U0 existed, U1 has no way of knowing the nature of U0. U1 has no way of knowing 'absolute complexity', knowing how long of a time is actually 'long', or how long time passes in U0 compared to U1. We see it already in our simulations, a hypothetical self-aware game engine would have some interesting concepts about reality, and hope they aren't in a Bethesda game. Presuming they could have an accurate measurement of their world, they could conclude the observed triangles were the smallest particles. They would be unable to even know that everything they couldn't perceive is not actually there, since when they go to observe it is made on demand. They'd have a set of physics based on the game engine, which superficially looks like ours, but we know they are simplifications with side effects. If you clip a chair just right in a corner of the room, it can jump out through the seemingly solid walls. For us that would be mostly ridiculous (quantum stuff gets weird...), but for them they'd just accept it as a weird quirk of physics (like we accept quantum stuff and time getting all weird based on relative velocity).
We don't know that all this history took place, or even our own memories. Almost all games have participants act based on some history and claimed memories, even though you know the scenario has only been playing out in any modeled way for minutes. The environment and all participants had lore and memories pre-loaded.
Similarly, we don't know all this fancy physics is substantial or merely superficial "special effects". Some sci-fi game in-universe might marvel at the impossibly complicated physics of their interstellar travel but we would know it's just hand waving around some pretty special effects.
This is why it's kind of pointless to consider this concept as a 'hard science' and disproving it is just a pointless exercise since you can always undermine such an argument by saying the results were just as the simulation made them to be.
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.
I'm not sure about this. Our current universe is 13 billion years old. At one year to one minute, that would take over 6500 trillion years to simulate (I think).
The solar system will only live another few billion years or so. All the stars in universe will burn out in around 100 trillion years. So it would probably not be possible to run a simulation for that long.
You're mixing up nightmares now lol
Yes it's true that everything we perceive could be fake, when I turn my head to the left, the world that I was looking at before could disappear. That's not a new paranoia, it's been around for literally hundreds if not thousands of years.
The simulacrum hypothesis is a little different in that it tries to bring it up to date, and use statistical principles to show that our universe is very unlikely to be real.
The idea is that at some point, a life form will create machines so powerful that they can simulate the entire universe in a way that is indistinguishable from the real universe. There is a real universe in this vision, and it functions very much like the universe which we ourselves inhabit. We are not special in our simulated universe, just like the beings that do live in the real universe are not special. That is, every part of the universe exists in every simulation just as it does in the one real universe. By saying no beings are special, I mean that there are no shortcuts to fool one being (or group of beings) into thinking the universe is more complete than it really is - the entire universe is fully simulated.
You're assuming that:
I'm afraid you didn't understand what I wrote.
If it were to take 1 year to render each minute, it would take 6500 trillion years to simulate the universe from the big bang to now. That is, the parent universe which is running our simulation must run it for an impracticably long time.
As for your other point, yes each simulation has to be a similar universe to the one we ourselves live in. Only that way do you end up with vastly more simulated universes than real universes, and the conclusion that statistically we must be living in a simulated universe and not a real one.
If you don't have that part, then you do not have anything more compelling than Descartes' age-old nightmare that an evil demon could be deceiving us about everything we perceive.
I understood that. I'm pointing out that you're making an assumption that trillions of years is an 'impractically long time'. It is to us, but there's no reason it would be to another universe. Assuming time even works the same way and isn't just a cool thing they came up with for this simulation.
Firstly, the current discussion isn't about the probability of us living in a simulation. It's about whether it's possible to begin with.
Secondly, 'each simulation has to be a similar universe to the one we ourselves live in. Only that way do you end up with vastly more simulated universes than real universes' is in itself another assumption that doesn't necessarily hold true. The only thing the simulated universes need to have in common is that they contain sentience intelligent enough to continue the chain of nested simulations. The physical rules governing each simulation might be wildly different.
I didn't read the whole thing, just got far enough to understand one of their fundamental assumptions is that a universe outside a simulation follows the same fundamental laws of nature as ours
If we are in a simulation, anything outside of it is effectively unknowable. It would be like a self-aware sim in The Sims determining they are not in a simulation because it is impossible for computers to simulate anything -- computers only raise the entertainment stat (I don't actually know what they do in modern incarnations of the game)
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.
I am not really convinced. First, there are too many things in physics not yet understood (and they claim it will never be). Second, they assume that the entity that would "run" the simulation would work exactly like our universe.
Too many unknowns to claim a definitive end of the debate.
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.
As they say, sufficiently advanced technology is indistinguishable from magic.
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.
I think you might be confusing something. The simulation hypothesis is rooted in the concept of the Boltzmann Braun, which is exactly what I described: A simulation of reality as in "the perceptions of a being is simulated" not "all of reality is simulated".
I haven't heard a single time so far by anyone seriously into that topic that a simulation would need to simulate reality to a perfect degree. That wouldn't even really make any sense, neither from the argument, nor from the words. A simulation is always an abstraction, and since you bring up the world "simulacrum", a simulacrum is something that by definition lacks the detail and sophistication of the original. A plastic apple is a simulacrum of a real apple, and in no way does a plastic apple replicate the cell structure or the biological details of a real apple. It's just something that from a distance looks vaguely like the real thing.
And that's what all forms of simulation hypothesis are based around: simulate everything necessary for the conciousness living in the simulation to believe it lives in reality.
In fact, humans have a mechanism that does just that built right into their brains: dreams. While dreaming your brain doesn't accurately simulate reality down to the atom-level. All it does is simulate enough of your perception to make you believe you are experiencing what is happening in the dream.