Could our Universe be a simulation? How would we even tell?
arstechnica.com
arstechnica.com
The more interesting question is where are the laws of physics located? How does an electron 'read' their rules?
In our case, the "headset" could be something in the brain. There are too many quantum fuckeries going on within neurons (and plants, for that matter) for me to fully rule this out.
Is there anything you'd do differently if we're conclusively determined to live in a simulation?
Not that this definition of simulation matches what most people think when this question gets asked.
The answer is no you can't tell no matter how hard you try. Quantum behaviors should be enough proof that our reality can act way outside our sense of things at very small scales. Any kind of "eureka!" claims about our universe being a simulation can more easily be explained as it just being how our universe works and of course it doesn't line up with human common-sense notions of causality/physics/etc.
And not that it is even an interesting question but my take is no this is not a simulation. Way too much detail. Even if some civilization had the resources to run a simulation the size of our universe it would be a massive waste to do so. The most efficient computational system for simulating a universe with the high fidelity our universe has is to create a universe and let it evolve.
That's just as plausible as those beings waiting for us to evolve our present level of understanding, and shutting down the simulation out of disappointment that we didn't try to contact them, or hack our way out of it.
This whole discussion - not just the one we're having, but probably most discussions on this topic, here on HN and elsewhere - is the nerd equivalent of trying to figure out how many angels can dance on the head of a pin.
Wasn't that a parady of silly theological questions in general? Or maybe a "it doesn't matter" analogy?
The nerd discussion on this sim question is totally serious.
Edit: Oh. Ye. There is no upper limit on the size of a needle, so there is no upper limit on the amount of angles that can dance on its tip no matter their size, if they can intersect or what not. Anyhow, at least one, should cover any set of boundary values to the problem.
Yes, but just as likely to result in a useful outcome as trying to count angels.
What I'm trying to say is that unless someone in this discussion is maybe a high-energy particle physicist, or astrophysicist, all we're really doing is the equivalent of trying to deduce what happened to the Holy Prepuce, or what Hermione Granger's canonical ethnicity is.
Which isn't to say that it's not a fun thing to talk about; but we should recognize that we're just sitting around the fire with a couple of beers and bullshitting, and that we can't make any really definitive statements here. We're at the Greek Philosophy level of being able to talk about this stuff - all thought experiments without much actual data.
I also don't think we live in a simulation, but if we did, how can you know anything about the outside universe, leave alone its resource limitations? Perhaps what we consider to be huge and complex (our own universe) is the equivalent of a simple Conway's Game of Life to the outside world.
I always find it fascinating to think about that, when we would be living in an simulation, they could shut the whole thing down for let's say 1 million years, turn it back on and for us it would be like nothing ever happened. Like, I sit here write this comment, in the middle of it they shut it down, wait for "a while" to power it back on, and I wouldnt even know. :)
If I spend my life doing it and there isn't a console I'm an idiot :P
My nonscientific best argument is that it explains how we came to be and how we end.
How can there be -nothing- and then there is matter, and then there are stars. Our understanding of time is linear. ¹
If we are a "sim-city ULTRA" game, then the users starts it, plays it and closes it. That all makes sense.
Thinking about being a simulation I find it amusing to think it of as fractal. Whenever we discover -the- final element/particel the game creates another layer.
¹ I am aware of scientific theories explaining why there was nothing and then something. I personally do not find them satisfying. Do have the multiple doctorates to make a scientifically informed decision? Probably not. I know someone, possibly Hawkins, was irritated when people asked him "what was before" it wasn an absurd question that made no sense. I do not think it is an unreasonable question. All we do in daily life is dependent up on a linear timeline. But yes experiments on particles may show us a different world.
I am drawn to the conclusion that a simulated universe must be of lower fidelity than host universe based on my experience simulating ecosystems within an ecohydrology model. Our model was really detailed, but still our ability to model things like soil physics is in the end limited by our inability to observe soil properties at smaller and smaller spatial scales. So the model necessarily simplifies the soil physics to the point where the model produces results that statistically match what we can observe. As a result, there are some things in the model that we can’t quite model and some things that don’t quite make sense in the model.
I've even heard it stated by physicists that the Bekenstein bound helps to prove the feasibility of constructing a simulation of a universe within the size of our universe - but alas, I am not a physicist and this is merely armchair conjecture.
If it is a simulation, it must be doing some very clever lazy evaluation to avoid thinking about every quark in every atom in every star in every galaxy, while still producing results that astronomers can't distinguish from physics on earth.
How so? What if the goal of whoever is running said simulation is something else besides simulating life and civilizations or whatnot, and we are here because an unexpected result?
We can't know for sure what would interest simulation runners, but they must come from a technological civilization and would presumably find other civilizations more interesting than dust clouds.
What if the simulation is done in a way like we render video game graphics. We never render stuff that is not "visible", well mostly to spare GPU and CPU cycles. What stops a super advanced simulation to simulate only stuff we can "see" or stuff we observe. If no one is looking at the Andromeda galaxy, no simulation needs to "render" it, saving processing cycles. Or maybe, the nature of the probabilistic aspects of quantum physics is an indication that that the simulators are trying to simulate in a "lossy" way, kind of like MP3 vs FLAC files.
That's very relative. That never stopped us either when overcompensating with hardware. Now imagine some very advanced quantum computer (or something 10 generations after it) that can scale infinitely after you just run the big_bang.sh. Who knows, they maybe even make it more scalable an stable as it progresses, by some self-scaling optimizations, which always play catch-up with chaos.
You would still need some giant factory sized next-gen quantum computer but maybe that's just worth their budget, after extracting discoveries from civilization x or y.
I think the hardest part, if this ever happens, is to fast-forward just enough an cherry pick from gazillions of civilizations, all while hoping that they to not evolve quick enough to escape your quantum VM. This and maybe the part with shutting it down and becoming a destroyer of worlds.
Yeah, um... about that assumption...
This solves the "too much detail" problem by assuming that they have magic hardware. That's absolutely not realistic in any way.
I mean, this whole thing feels like a substitute for God for those who don't believe in God. It's Someone who existed before the universe, and created the whole universe out of "nothing" (nothing pre-existing in this universe, anyway). Now you're giving Him infinite resources (or miraculous ones that can scale to infinity, which amounts to the same thing).
Maybe our full universe fits predictably in some pre-allocated space of such an advanced machine/project and 1 million years on our part is a days worth of disk space on their side. An then there are retention periods too...
Regarding the "substitute for God" part... good point, but what if we really come up ourselves with such simulations? It doesn't mean we are gods (literally), it doesn't even mean we are ourselves in a simulation. Just that we found clever ways to simulate the process into replicating something that we judge as correct (ironically). Like a game nowadays but a trillion times more complex. Looking at how much AI improved recently, what is to say that 100 years from now we cannot simulate this and then cheat our future with data extracted from other civilizations, rinse and repeat, to evolve exponentially.
Besides that, I think we’re assuming too much about their motives and capabilities. Who’s to say simulating dust clouds isn’t the point, and we’re just an accident? Or that the point is a survey of the evolution of astronomical systems, or an attempt to predict the fate of the universe? And, since any technology that could simulate even this planet is completely beyond human comprehension, why should we expect them to scale up only about as efficiently as humans do, rather than, say, orchestrating some reaction that results in a computer that grows exponentially and boundlessly? Or that the purpose or mechanism are as beyond our comprehension as a machine that could simulate Earth? Or, if they do have a point of limiting cost, why should we have any idea where that is, and where the cost is so low that resources are spent like they’re free?
How so?
It is kind of impressive when I go into the city and see all the NPC AI running in real time. But the whole Trump plot arc is too stupid to be real.
Just kidding. Futurama must hold some kind of record for sheer number of series finales.
Of course this is all conjecture, and assumes that there is no effort to conceal the facts, but at least it is a solid, actionable starting point.
For example: My eyes can focus on this word on my screen: "Hello".
I don't know how many bits of information this word contains. I can see the shape of the four chars quite clearly. Maybe that is 100 bits of information or so?
So I would say the universe probably is at least 100 bits large.
Is there any proof that it is larger?
Is there any way it could be smaller?
If it can't read your mind then the universe external to it must necessarily be much larger, since it can consistently hold much more information than you're able to recall.
But is there a proof that time exists?
I can "remember" something, but that act of "remembering" is happening in the now. I don't know if there really was a past.
When I look at "Hello", I don't remember something at the same time. The shape of the four "Hello" letters are all I can hold in my mind. So from that perspective, "Hello" might be all there is and all there has ever been.
So the siutation with the two Hello's might be just as simple (My rough estimation: 100 bits) as the situation where I focus on the shapes.
That's why my feeling is that the lower bound for how complex the universe is, is 100 bits.
Then you slowly start to realise that all of this activity on Earth could be happening on other planets elsewhere too.
Then you observe the stars, and combined with the mental models/theories from our brightest physicists, you might conclude that the universe is really fucking big, and there must be a shitload of other Earths out there.
But again, we can't really prove it concretely can we? For all you know, i'm an NPC and so is everyone else. You could the subject of an alien crackintro - where they try to simulate whole worlds in 100 bits or less.
While I look at the shape of the 4 letters "Hello", I can't interact with other agents. I can't even imagine such an interaction without losing the full grasp of how the four chars look like.
So I would say I don't know if anything else exists. Except of the 100 bits of information or so which I can witness.
I just have an experience of a certain complexity, which I roughly estimate to be 100 bits or so of information.
But it's even worse. I might be an NPC. If so, I am just a machine, with no true personality of my own. No free will, either. This pushes me towards living like an NPC - just going through the motions, rather than actually living. Even though it doesn't actually kill me, it destroys life.
This stuff isn't just an intellectual exercise. If you take it seriously, it can drain all the joy out of living.
Fully agreed. I've been down this rabbit hole before. There's a fine line between the thought of us being different ways for God to experience things in this dimension, and the pure and utter delusion.
It's so much easier to accept being human, along with all the limitations that may bring.
I've heard of a couple of methods that are almost purely computational:
Measure the randomness of something like radioactive decay, try to figure out the PRNG used in the simulation.
Measure all those very basic constants of the universe to a large number of decimal points. See if they indicate register size of the simulator.
Absence of evidence is not evidence of absence
We can at least conclude complex life is exceedingly rare.
To add to what @ethanbond said about space-time vicinity:
---------------
Article, subTitle: We have been broadcasting for over 100 years. Now a new 3D map of the galaxy reveals the stars these signals have reached that can also see Earth:
https://www.discovermagazine.com/planet-earth/our-radio-sign...
“1,715 stars within 326 light-years are in the right position to have spotted life on a transiting Earth since early human civilization, with an additional 319 stars entering this special vantage point in the next 5,000 years,” they say.
-----------------------
A microscopically small amount given the total number of stars in our own galaxy, the total number of galaxies in the Universe.
The odds of life are 1/N. We don't know how big N is, but it might be much larger than the number of sub-atomic particles in the universe. Perhaps N is (10^100000)^10000000000.
I'm, of course, not arguing we should stop searching or having philosophical arguments. (Although, to whomever it may apply, we could stop down voting comments that make objectively true philosophical arguments like postingawayonhns.)
(postingawayonhns: "We can at least conclude complex life is exceedingly rare.")
I wouldn't have downvoted a comment like that (or the comment you made). In fact, there's a large part of me that grudgingly agrees with you both. It's sad to think about and worthy of discussion.
I did a quick search because the other part of me - the one that doesn't want to believe we are alone in the Universe - had to find... hope.
The article I linked wasn't just a reply to OP but it's something I, myself, found eye-opening. I wasn't aware about the 3D map and the limited number of stars we've reached at this point. Especially the expected number of star systems we're expected to reach in the next 5,000 years (it's quite low a figure).
It was disheartening but helped hammer home just how vast the Universe is. It also leaves the door open for the hopeful...
My reply was meant to help drive discussion forward. (Downvotes suck and can change the way a message is received).
Telescopes only recently have been able to detect signatures of life relatively close to Earth. There have been very recent possible discoveries. But may not be able to confirm without going there.
There is no systematic search for radio waves. We would only be able to hear anyone for short distance. Advanced civilizations would be rare so not hearing doesn’t say anything about life.
The one thing we haven’t seen are megastructures like Dyson Spheres. Those would be visible for long distances and we haven’t seen any in our galaxy.
If these are true, they do have genuine implications (eg., a world with such a god is different than one without). However, I shortcut all this with a simple meta-epistemic principle: I will never believe one of those propositions on the basis that it could never be rational to do so.
I take it is the most rational belief in this case is simply to presume they're all false, since there are an infinite number and i think some argument can be made that theyre certainly largely false since most are contradictory (etc.)
So, no the universe is not a simulation; nor a dream of a demon; nor one of any of these propositions. If you think it is, then why not draw randomly from a similar set? Why not the wish of an alien honoured by a angel?
These kinds of propositions are "failure modes" of rational thinking that cannot be addressed in their own framing (consider, by analogy, "is the king of the US bald?"). The response has to be about what it means to think at all, to believe something is true, and so on.
This is also how to address conspiracy theories. The issue with them is their belief in classes of propositions of this kind (eg., that all "official" claims are false).
>If these are true, they do have genuine implications (eg., a world with such a god is different than one without).
What? Which one is it?
If the universe can be evaluated in a simulation, then the computer carrying out the simulation is not actually necessary. In fact, even defining the rules of the universe is not necessary, because the contents of the universe with any given set of rules are not changed by the act of writing the rules down. Mathematical truths are true, even if they're never discovered. If a universe can be simulated, then it has a mathematical description, which means all of its configurations, and all of the events within it, are determined from the mathematical description.
(As an inhabitant of the universe, you may experience non-determinism, but this is because you are limited to experiencing one path at a time. For example, you can make a mathematical model of the outcomes if you flip a coin 20 times in a row, and even though the outcome of any given path is non-deterministic, all of the possible observations are determined purely by the rules, and all are equally true regardless of how many times you flip the coin, or whether you even bother flipping the coin at all).
By analogy to Conway's game of life:
The outcome of any given configuration in Conway's game of life is fully decided regardless of whether anyone actually runs the simulation, regardless of whether anyone writes down the rules, regardless of whether anyone even thinks of the rules. The outcomes of Conway's game of life didn't become decided at the point that the first simulation was executed. The outcomes were always there.
No observer inside Conway's game of life has an experience or lack of experience due to the simulation being evaluated on a computer. Evaluating the simulation has no effect on the outcome. Evaluating the simulation allows someone outside the simulated universe to inspect its state, but it has no effect whatsoever on the observers inside the simulated universe. They were there all along.
The observations made by observers inside the simulated universe are decided by the specification of the universe, and are the same regardless of whether there is any computer outside the simulation actually evaluating it.
All of this is to say that IF our universe can be simulated, then we don't need the simulator. The fact that it can be simulated is enough to create all of our experiences. And in fact I think this is the "true" explanation (whatever that means) of why the universe came to be: we exist just because mathematics says we can. (And, further: every possible universe "exists" - as far as the observers inside it are concerned - and every possible experience is experienced).
I wrote a short story about why: https://nothingtrue.substack.com/p/discovered-a-secret-messa...
Why are we sure that mathematics is not completely a part of this time-space bubble?
Let's say there is an "outside" for the mathematics similar to warp space in wh40k.
A "something" where natural numbers, for example, cannot exist, there will be no space or time in such a case, but it may still exist in some weird sense of undivided consciousness.
In such a case for this outside you need a proper rule based bubble to say that there exists a mathematical possibility for our universe to run in according to rules defined inside that bubble.
That would be "simulation space", if we contrast it with the "outside".
I hope I've got my thought across, because I am pretty rusty in my English writing skills.
There are other ways to define mathematics, sure, and if those ways allow universes that our ways don't, then those universes "exist" too.
I am not sure that this is the case, for math to be it needs a set of axioms.
Axioms have to mirror some sort of universe. I am really curious what can be done if we remove all the axioms.
I am sorry if I sound dumb, I don't know much, but it is really interesting.
I don't think that's true. There is much more substance to the universe than just its mathematical description, and you need the computer to run the simulation to provide all the flesh and character the math does not.
The flesh and character are just emergent properties of enormously complicated mathematical structures.
They are not just emergent properties, they are one of many possible combinations of possible emergent properties, just lie you yourself are.
The math is always abstracted and doesn't contain the full detail, the meat and flesh.
I think you are dismissive of that, but you shouldn't be. It's very significant. Crucial, even.
If it can't be described mathematically, it can't be simulated mathematically.
And if it can be simulated by a computer (i.e. mathematically), then it can be described mathematically, and the computer isn't adding anything to the experience of any observers inside the universe.
They could be instructions not constructions and rely on any number of data not in the descriptions themselves.
> If it can't be described mathematically, it can't be simulated mathematically.
You're missing the point. You can say everything running on your PC right now can be described mathematically, and that's fine. But it's also highly dependent on how you have used it, configured it, what you have installed at. The initial mathematical description wouldn't account for the things that are a result of environment and your input.
> The entire state of the computer can be encoded and manipulated using mathematics. If that weren't possible, the computer wouldn't work.
I don't disagree, but 'can' is not the same as 'is'.
Absolutely everything can be modeled and described mathematically with enough variables, but that isn't always feasible, and describing all modeling all instances of something with practically infinite permutations probably isn't. Besides, if they already had that information they wouldn't really need to simulate anything.
The point is that the simulation gives the parameters for the simulation but then lets it go its own way and doesn't already have all that information of the path it ended up taking.
The path it ends up taking is the result of numerous complex variables, (i.e. all the choices we make in the simulation) which were not and could not be modeled ahead of time (unless you want to argue that infinity would not be so in some kind of higher dimension).
Thus, actually running the simulation, to generate that flesh and meat, is the point of running the simulation, and why I think your original point that anything that can be simulated need not be simulated is wrong.
My point is that you don't need someone to actively describe it. The fact that it can be described mathematically (even if it's infinite!) means it already exists within the structure of mathematics.
> The point is that the simulation gives the parameters for the simulation but then lets it go its own way and doesn't already have all that information of the path it ended up taking.
Everything that is implied mathematically from the starting state is implied just as well even if you never evaluate it.
You're taking the natural numbers to be your starting state, and declaring that the results of arithmetic operations on them are created by the simulation, whereas I'm saying the results of arithmetic operations were always there, because they can be defined by rules.
Running the simulation doesn't create anything inside the simulation that wasn't already implied by the initial configuration. Running the simulation "generates the flesh and meat", only in the sense that it makes it visible to someone outside the simulation. Inside the simulation, it is impossible to tell whether it has been evaluated or not.
This is absolutely meaningless though. The structure of mathematics is infinite. Just because it exists as something unrealized does not at all mean it is equivalent to something manifested with substance as you suggest.
> Everything that is implied mathematically from the starting state is implied just as well even if you never evaluate it.
Well that's kind of horseshit, because you don't know what input to give.
And you can't practically compute all outcomes for all possible inputs since it's an infinite address space.
So the point you're trying to make, your conclusion doesn't follow from the premise, and the premise while technically true is completely irrelevant for any and all practical purposes.
> Running the simulation doesn't create anything inside the simulation that wasn't already implied by the initial configuration.
When you play an FPS game, nothing that happens in the game isn't "implied by the initial configuration", yet you can't have an accurate output of how each match will go.
> whereas I'm saying the results of arithmetic operations were always there, because they can be defined by rules.
You're saying it is not a simulation at all but a detailed description where every outcome is already known. Nothing is being simulated. That's quite a different argument and proposal from considering if the universe is a simulation or not.
> The structure of mathematics is infinite. Just because it exists as something unrealized does not at all mean it is equivalent to something manifested with substance as you suggest.
Being "manifested with substance" is something you experience from the inside of the universe. How do you know there is substance? Because you experience it with your senses, that's all.
> you don't know what input to give.
You don't have to. Nobody needs to give any input. It's enough that if a given input were given then a given output would arise. The output would arise from the input regardless of whether anyone ran the simulation.
It is true that 123+456=789, even if nobody ever calculates it.
> you can't practically compute all outcomes for all possible inputs since it's an infinite address space.
It doesn't matter that it's infinite. I'm saying you don't need to compute it, the outcomes were already there. Computing the function doesn't change anything. That's why if the universe can be simulated it doesn't have to be.
> When you play an FPS game, nothing that happens in the game isn't "implied by the initial configuration", yet you can't have an accurate output of how each match will go.
You don't know how any individual match will go because it is non-deterministic (like the coin-flipping example), but the set of all possible outcomes can be inferred from the starting state based on the rules. They're all already there in the vast structure of all that is possible in the game. You just only simuulate one path.
(The main caveat in my argument is that it begins with "IF the universe can be simulated" -- if you don't think it is possible to define a computable function that would simulate the universe given arbitrary time and space etc., then the rest of my argument is irrelevant).
No worries! I'm interested in the discussion and really this is meant to be about healthy exchange of ideas to better understand different view points anyway. Apologies for taking so long to reply, hopefully you still see this.
> Being "manifested with substance" is something you experience from the inside of the universe. How do you know there is substance? Because you experience it with your senses, that's all.v
I don't necessarily disagree, but this isn't refuting my point. I'm not denying that if we are a simulation we have a mathematical description, i'm saying most of the substance of this simulation, whether it be experienced by us or described as math, came about as a result of the simulation, and was not described in the initial model.
> You don't have to. Nobody needs to give any input. It's enough that if a given input were given then a given output would arise. The output would arise from the input regardless of whether anyone ran the simulation.
This is only relevant if you can predict all possible outputs for all possible inputs, and you can't. No one can.
> I'm saying you don't need to compute it, the outcomes were already there.
That's the problem though. You do need to actually compete and run it to generate any meaningful data i.e. substance.
Your argument, if I understand it correctly, is analogous to saying you don't need to play a game of CS to know how it will turn out, because you can generate all the possible scenarios. CS scenarios don't have an infinite space of possibilities, just a very large one, but even then it's more than we could compute, and it may still not capture everything (while everything in the game could be mathematically modeled it doesn't mean every aspect would be being recorded or considered significant). When you take that to a simulation with basically infinite inputs, it becomes unsolvable and impractical at least in any way we can understand.
> You don't know how any individual match will go because it is non-deterministic (like the coin-flipping example), but the set of all possible outcomes can be inferred from the starting state based on the rules. They're all already there in the vast structure of all that is possible in the game. You just only simuulate one path.
So you're saying our simulation is more like a match being replayed where everything is known? That's not really a simulation then, is it, but a replay. The point of running a simulation is generally to gather data. If, as in your scenario they (whoever 'they' may be) already have all the data, there would be no reason to run the simulation.
> (The main caveat in my argument is that it begins with "IF the universe can be simulated" -- if you don't think it is possible to define a computable function that would simulate the universe given arbitrary time and space etc., then the rest of my argument is irrelevant).
I certainly think a simulation is possible, I disagree on how predictable or known ahead of time the outcomes of that simulation would be.
However, it's a different question whether this is a 'simulation created by conscious beings' or a 'natural simulation', e.g. some kind of natural process in a different kind of universe which somehow results in a simulation of our universe. 'Conscious being simulation' theory is just kicking the can further, rather than solving the origin problem, if we assume that their universe is similar to us.
What isn't allowed is for the total matter and energy within the universe to increase or decrease. But if we're talking about the creation of the universe itself along with its matter and energy, then there are no laws of physics that forbid it happening from literally nothing. The state of there being nothing is not within the scope of physics, which deals solely with what happens inside our own universe.
It's like if you have an MMO where money can be neither created nor destroyed, but when the server was first booted all the money supply already existed within the world. A player seeking to explain where the money came from could not appeal to the rules of the game, because the rules only apply once the game is already running.
That's true in our universe, not necessarily in others and certainly not in a universe containing our universe.