Thank you. I observe the same sentiment of unjustifiable certainty with so many deep issues among popular journalists and scientists. Simulation theory, the potential disaster(s) of AI, not to mention political topics. When even smart people are blind to weaknesses in their position, I despair, and go back to funny gifs.
Arguably it would've been better to say "The universe may not be a simulation" but calling this clickbait and evidence of a decline in quality because of such a minor detail seems an overreaction. Unless there's more you object to than the first 6 words of the article.
There's no mention at all of the "universe is a simulation" theory in the article, unless I managed to skip a paragraph.
So title is entirely clickbait, surely? It's not "We're Getting Better at Universe Simulations" that is the content given. I was hoping to find some discussion of the simulation theory and perhaps reasons found that it may not be possible. That's why I clicked and read.
The title is just poking fun at the "The Universe is a Simulation" articles that keep popping up, I mean sure it technically makes an irrelevant claim, but in context it's clear that the main part of the article is supposed to be about how we can simulate the universe.
I agree it's kind of weird to raise something in the title and not address it at all in the main article, but that's a minor flaw in what's clearly intended as a joke.
There is a essentially a proof by induction that if several properties hold (such as the 2nd half of this headline) then our odds of being in the unsimulated universe are approaching 0, making the first half of the sentence a remarkable finding given the 2nd half. I.e. that one of the other prerequisites has been proved false.
"The universe may not sit on top of a giant turtle."
I'm so sick of these bullshit theorists coming up with unverifiable imaginations out of thin air. Produces lots of clicks and laymen books but doesn't do jackshit to help move science forward.
Is the "Universe is a Simulation" more than a dreamy internet theory, though? Like, are astronomers and physicists taking it seriously? I don't know either way, I just assumed the headline was basically saying "no, this isn't some sensational new post about how we're all in a simulation, this is hard data leading to realistic results". Kinda defensive more so than click-bait-y.
It is the internet misinterpreting some perfectly valid scientific investigations. A rational discussion of quanta and quantization, how observable information is coded in our universe, morphs into talk of whether that universe actually exists inside a big computer. To correct such rants one must explain quantum physics, something nobody wants to do anytime soon. It made for a half-decent Doctor Who episode.
I don't think any scientist should take it seriously. It is at the level of "maybe this is all just a dream". Well perhaps, but we have no way of knowing. It is an unfalsifiable hypothesis so it is outside the scope of science.
> Is the "Universe is a Simulation" more than a dreamy internet theory, though? Like, are astronomers and physicists taking it seriously?
There is no practical way to falsify that so yes, it is just a dreamy theory.
Unlike some other dreamy theories (creationism and astrology come to my mind) nobody has come up with any practical uses for the dreamy theory either, so that would be a second reason why nobody takes this dreamy theory that seriously.
But if this is a simulated game, I would be keen to know how this is scored and how many lifes I have left before game over...
Considering that you don't know this already... if the Universe is a Simulated Video Game its very unlikely that it was created for you to play.
It's much more likely that you are just an NPC waiting to be harvested for some aliens experience points.
The most you can hope for is that you are destroyed in an interesting way, and perhaps your memory lives on in a highlight reel on that aliens stream.
I've often wondered if God existed at one point and we were just his video game. But now God found a more interesting game to play and we are just a forgotten game in chugging along in his steam account. I don't think there is a better explanation for the miracle of the pyramids, or the invention of magnets.
> Considering that you don't know this already... if the Universe is a Simulated Video Game its very unlikely that it was created for you to play.
Well, if I think from bayesian point of view, given that only creature here that I personally can be somewhat confident actually having any sentience happens to be me, then it would feel quite likely me being a player. Especially as this can be single player game as well...
I think you are saying that it would be cruel to create a game where the scenery has real consciousness or sentience.
But just because something could be cruel doesn't make it less likely. I think we are basically talking about the plot of West World. And pointing out that it doesn't make sense to give an active inner life to characters that exist only to fill out someone else's designed game experience.
But just think about it. If Sims 2099 is capable of giving consciousness to its characters, or at least something so much like it that the characters believe the are conscious, don't you think its very likely players will ask for it? Regardless of the ethical implications.
I guess that last paragraph shows the temptation, our wish for meaning and some meta mechanism around us beyond a couple of rocks we can see flying around. We are unable to deal with the concrete mundanity of reality. (learning how things work is fascinating, but watching most processes for a prolonged amount of time is... not)
Yes, it is a serious theory, taken seriously by serious scientists, and seriously investigated by them.
It can be hard to tell through the popular science stories, where the author is typically unable to relay anything about this research without adding "woo woo" sounds and wiggling their fingers, but it's a real theory.
One thing that may be worth remembering is that in the real theory, the "simulation" is not necessarily running on "a supercomputer just like what we have, only way bigger", which is actually a silly idea for various reasons, and we also do not know that the simulation is literally simulating every particle and every cubic inch of space in the most accurate possible way (i.e., for all we know, far away galaxies could just be a few megabytes in size, rather than fully simulated to the nth degree). The "Great Simulator" is not required to run anything remotely resembling our physics. What seems an absurdly large computation may be smaller than it appears, and may not be an absurdly large amount of a universe running on fundamentally different physics.
(Occasionally when I'm bored, I noodle around with a theory of cellular automata in which the universe has infinite computation power by virtue of being able to split a cell in half or quarters, that then runs at double-speed relative to the outside. If this is done recursively the universe has arbitrary computation abilities relative to the "top level". I've never worked it into anything usable, but I think it can give a flavor of why we should not be sure that our simulation host is necessarily as staggered by the computation as we would be. We are not even capable of saying that they aren't running an exponentially-expensive quantum approximation algorithm with the entire universe actually arbitrary-precision integers under the hood. The staggering amount of computation that represents may not bother them at all.)
It is not a theory that is, strictly speaking, falsifiable thanks to Church-Turing equivalence, but there are ways in which it could potentially (to any arbitrary degree of confidence you may want) be confirmed if it is true. To take one degenerate case, if the Great Simulator broke silence and starting wildly breaking the laws of physics to get our attention, that would certainly put a lot of probability mass on the "we're a simulation" theory. There are less extreme cases we could conceivably pick up on, that just fits into an HN comment nicely.
Well, along with the religion case that whatshisface points out, there's also the problem that any theory of the nature of the universe has this problem. The problem here is not with the theory of the universe per se, but the fundamental limits of science itself.
Despite what seems to be a popular opinion, we are not actually obligated to curl up into a ball on the floor and cry about our inability to know anything just because science can't be definitive on some point. We just need to be aware of the limits of our knowledge. We have no choice; even in just our day-to-day lives, we are required to make all kinds of decisions for which science is either quiet, insufficiently informative, or (and this one may really hurt to think about too much) simply wrong.
> Despite what seems to be a popular opinion, we are not actually obligated to curl up into a ball on the floor and cry about our inability to know anything
I have no idea what you are referring to here. Can you be bit more specific about what viewpoint or philosophy you are satirizing?
Well, it's a little more complicated than that. It's only not falsifiable because nobody has devised a test. It's a hypothesis without an experiment. That doesn't mean that people aren't trying [0]. If it is a simulation, you're not going to clip through the wall by running against a corner and jumping for an hour.
The thing is, we don't know where this line of reasoning would even lead. I mean, people used to think that light had to travel in little packets through luminiferous aether [1] and look where that investigation led: Einstein, special relativity, atomic weapons and power, nuclear medicine, etc.
Let's say the universe is fundamentally indistinguishable from a computer simulation. What consequences does that have? What does that say about the types of math that can be used to describe the universe? Or, perhaps better, the types of math that shouldn't be used to describe the universe? What does that say about our ability to model a portion of the universe and therefore predict outcomes? Does it have implications for stochastic processes? Indeed, where is the stochasticism coming from? Is everything predictable or is there some fundamental randomness?
On the other hand, what if we can show that the universe is distinguishable from a computer simulation. What does that mean for our understanding of the universe as it exists? Does it reveal a fundamental aspect of reality that we have missed, or a limitation of our mathematics, or a fault in our computer models or design, etc.? We're dogs learning calculus here, and the universe isn't obligated to make sense.
Even if we can never find a useful test for this hypothesis, the line of thinking itself potentially leads us into new areas of discovery.
The problem is...you can even define what it means for the universe to be a simulation. You might as well argue like George Berkely that all sensations are signs and symbols directly from God - it is not even wrong. It is fundamentally unknowable - unless God or The Simulator choose to reveal themselves directly to us.
The luminiferous ether was a falsifiable theory - indeed it was a breakthrough for physics because it was falsified (experiments failed to detect it) so new theories had to be developed. So this is completely different from unfalsifiable metaphysics.
It is falsifiable if you consider that a simulation would have limited resources allocated to it. The null hypothesis would be the universe runs in a way where a simulation couldn't cheat by performing a rough calculation at the hard parts, thereby spending a tiny fraction of what would be needed and produce the same observable result.
The idea that quantum fields exist in multiple states simultaneously until observed become evidence for a simulation, since a simulator could be deferring calculations on things not observed.
Also, the very program this article is referring to could be considered as evidence for it, since if a rough simulation can be made where the observable result is indistinguishable from a result where every atomic element in the entire universe was simulated, then, again, a simulator with limited resources would make do.
The law of conservation of energy is built the same way. There is no way we can test ways that energy is transferred that we don't yet know about, but this law is still considered true, because we have so many examples of it working.
Well I guess you can disprove particular forms of simulation - e.g. since a computer with 16GB RAM can be adequately simulated, we can reject the notion that the current universe is simulated on a computer with 16GB RAM or less.
> The idea that quantum fields exist in multiple states simultaneously until observed become evidence for a simulation,
How is that evidence? Current physics can model that without relying on a simulation hypothesis. Adding a simulation hypothesis does not simplify the model, and it is unfalsifiable.
Why did you quote half my sentence, leaving out the part where I explain why, and then ask why?
> Adding a simulation hypothesis does not simplify the model, and it is unfalsifiable.
I explain this. It's falsifiable if it can be shown there is some extremely large and complicated process that be observed to be different than any possible rough calculation that could be accomplished by a simulator with very constrained resources (constrained in comparison to all the supposed atomic particles in the universe)
The notion that all forms of energy must be conserved, even undiscovered ones, has been used as the basis for the theory of Hawking radiation, isn't it? Yet claiming that undiscovered forms of energy are conserved, just as known ones, is unfalsifiable, too.
The law of conservation of energy, including undiscovered ones, is in the same boat as the theory that the universe is a simulation.
Until we find a form of energy that isn't conserved, it is simpler to assume all types of energy are conserved.
Similarly, until we find a process that is of large enough scale that it couldn't be simulated on a computer with resources much more limited than the size of the universe, and be observable identical to a process taking much more resources, it is simpler to assume it all is being simulated in such a way.
> Why did you quote half my sentence, leaving out the part where I explain why, and then ask why?
Sorry I just didn't want to quote the whole comment, didn't mean to imply I was only responding to the first part of the sentence.
I understand you can hypothetically prove that a simulation of the universe would require a simulation engine of at least a certain complexity. But since the simulation engine does not exist in this universe, we have no idea about what limitations or laws of nature (if any) it is subject to. You will never be able to prove or disprove the existence if this hypothetical simulator.
Well, a Turing complete computer is about as abstract as you can get, and so is the concept of memory, regardless of the natural laws of some outer universe, it'd probably be a good starting point to consider a turing computer except with limited memory.
The point is not to prove one way or another whether the universe is a simulation, just like there is no point trying to prove the law of conservation of energy as universal for all forms of phenomena, discovered and undiscovered.
It's just if we can show that all known phenomena can be the result of a very limited simulation, then when analyzing new phenomena, we can also expect it to be runnable on a very limited simulation,
too.
It's the same as assuming that the law of conservation of energy would apply to any new phenomena we discover. There is no proof, but it's a good starting point.
You cannot through experiments prove that the law of conservation of energy holds in all cases. Indeed you cannot through observation prove that any law of nature holds in all cases. But you only need a single counterexample to show that a law doesn't hold in all cases. This is exactly the rationale behind the principle of falsification. You cannot prove through observation that all swans are white. But you can prove that not all swans are white by a single observation of a black swan.
The bottom line is that it is possible to devise experiments or observations which would give different outcome if the theory holds and if the theory doesn't hold.
But you cannot devise an experiment which would give different outcomes if the universe is a simulation versus if it isn't. More specifically, you cannot imagine an observation which would prove that the universe isn't a simulation. Therefore it is not a legitimate scientific theory. At best it is a fun thought experiment.
> But you cannot devise an experiment which would give different outcomes if the universe is a simulation versus if it isn't.
I've already mentioned 5 times in this thread that the theory I'm talking about is of a simulation with very limited resources, but you seem to be ignoring this point.
Show that a particular phenomenon can't be simulated using extremely limited hardware (compared to the size of the universe) and you can falsify this theory.
> But you cannot devise an experiment which would give different outcomes if the universe is a simulation versus if it isn't.
Does this or does this not apply to a simulation with very limited resources (compared to what it would take to model all the atoms of the universe) or not, then?
But it effectively wasn't for the first 150 years of it's existence. The theory originated in 1720 and it wasn't disproven until 1887. It took that long for someone to come up with a conclusive experiment. Nevertheless, for those 150 years the luminiferous ether theory was widely held, shaped the field of physics, and the research had to go into finding an experiment to test the theory.
Similarly, the idea that atoms might do things when high energy particles hit them was all theory until Wilson's cloud chamber became the first particle detector and suddenly physicists could see what these particles were doing when they hit things.
> The problem is...you can even define what it means for the universe to be a simulation.
You're confusing something that hasn't been done with something that can't be done. Indeed, what they're trying to do is exactly trying to define criteria to test that the universe is a simulation. It's the first day of school and you're complaining that Newton doesn't have his Principia and Gilbert doesn't have his De Magnete.
Theories often predate the knowledge of how to test them. This isn't weird.
In order for a theory to be falsifiable it first have to be a theory! The simulation hypothesis is not even a theory (i.e. it makes no verifiable predictions), so it is not even falsifiable in principle.
The great simulator doesn’t even need to be great. It only needs to be good enough to simulate heavily time-dilated reality for one individual. A highly detailed, highly realistic first person game only needs to simulate the immediate draw of the player character to be useful - you don’t have to draw every NPC’s worldview - they just need basic path finding, at best.
Of course it is falsifiable. If you can't specify in what way you recover physics from your simulation and what computation actually occurs in your simulation then, apart from the word "simulation" making no sense, you don't have any theory to either formulate or test at all. There, falsified for you. In particular cellular automata fit that description. It has been beaten to death since the 80's and leads nowhere, unless of course anybody counts Wolfram a (new kind of) scientist.
Same problem we have in quantum gravity. We just can't recover known physics from anything at all, any combination of theories at all it seems. That includes all known instances of computation, it just blows up.
Also, Church-Turing has nothing to do with basic problems here, in particular because eventual simulating computation would be unlike computation we know (which again, makes the word lose any meaning here).
That is not what falsifiable means. Falsifiable means that an experiment can be devised which could result in observations which contradict the predictions of the theory.
Falsification is a philosophical issue. Some say it's important. Some could live without. See Feyerabend.
None of that matter if there is no theory in the first place. Much was tried. 't Hooft got as far as holographic principle. And there's still no theory at all.
> Is the "Universe is a Simulation" more than a dreamy internet theory, though?
It's a theory that predates the internet. In the expanded view, the theory goes back to antiquity.
The modern version is a thought experiment more in line with the drake equation than a dreamy internet theory. It's an idea born of some assumptions and mathematics.
> Like, are astronomers and physicists taking it seriously?
Some are, most aren't. But then again, most astronomers and physicists don't take SETI seriously as they have their own work to focus on. But it certainly isn't anything to be dismissed just like the drake equation or SETI.
It may or may not be a dreamy internet theory, but "Universe is NOT a simulation" is just as strong and difficult to prove of a statement, perhaps even harder as it's a negative.
There are a few scientific reasons to believe that the universe is simulated;
One has something to do with the information in black-holes, i can't remember the details but it suggested to me that '3d space' was fundamentally artificial.
Another has to do with quantum entanglement, the explanation for spooky action at a distance could be that the two particles are still in the same 'bit of memory'.
And lastly the Uncertainty principle is thought to act a lot like an on-the-fly loading frame in an RPG.. As silly as that sounds there is not really a satisfying explanation of why things are less certain when we are not interacting with them.
Its worth noting that even if the universe is simulated, it might not be simulated by intelligence, we don't know enough to say its not 'naturally simulated', that might seem paradoxical but 'simulated' and 'artificial' are very loaded words; A reflection of the moon in a pond is in some way an artificial simulation of a moon..
The one-electron universe[1] was also a dreamy theory, but it inspired some groundbreaking ideas in quantum mechanics.
I think the universe as a simulation is less interesting as it's really just taking the notion of materialism to its logical extent. But in fairness to it, it's now part of culture, so if it's causing us to think in ways we wouldn't be aware of, it's harder to see it influencing someone than if he's Feynman getting a sudden phone call from Wheeler.
Many thought experiments can also be useful insights into nature of things. The idea of a Boltzmann brain[2], for instance, challenges your intuitions of infinity and thermodynamics.
If the Universe is a simulation (or might be) what is it simulating and who's simulating it? I'd be more interested to know about -that- than the arbitrary details of some measly little simulation itself. You might say something hand-wavy like, "it's simulating itself"... but OK, when I look at our "simulations" they are always highly referential to the external real... er... possibly real... world. Dwarf Fortress could be called a simulation (perhaps one of the better ones!) ... and while I'd be hard pressed to point to the outside world and say it's simulating any one thing with high fidelity, I can point to trees, mountains, water animals, etc. where the creative element is really just tweaking the attributes of these otherwise externally real things. It's hard to simulate what you're you're completely unaware of, unconscious of ... in fact to be conscious at all is to be conscious "of something" and insofar as simulations are conscious efforts at creation, it's difficult to not have some concrete reference that exists outside of a "simulation".
Of course, perhaps, it's the great mystery of God which I'm always told is beyond mere human understanding. Or maybe its simulations all the way down. Or maybe any explanation talking about simulations requires greater leaps of faith and greater acceptance of more and more unlikely scenarios of reality than just saying the Universe is perhaps a metaphysically real place that doesn't require an appeal to "simulation" for explanation.
I think I'll just stick to the simple minded idea of the Universe is a real place and not a simulation. That part of the title is so likely to be true that the author need not feel bad about the assumption.
I can't help but think the two options (we're in a simulation vs. we're not in a simulation) are equally likely without any information from outside our own universe. That said, it doesn't matter either way - we're not going to escape the simulation (certainly not anytime soon, probably not ever); knowing whether we're in a simulation has little bearing on individual lives (as far as we can tell, attempting to interact with the being running our simulation has no effect - or there is none, and this is indeed "reality.")
The fidelity of the simulation is not an argument for or against: assume we're simulated and it seems likely to me that perceptions by beings within simply wouldn't have the ability to notice a lack of fidelity; or whomever owns this simulation has the computational power to simulate sufficient fidelity to convince inhabitants that their universe is "real."
Because we don't yet have evidence either way, I'd go with 50/50 odds.
I disagree with your first sentence about two options; if we're to give credence to the idea of a simulation, there are other options we should give, in the absence of evidence, equal weight to... maybe the universe is the dreamlike state of some being, maybe the holographic principle can be extended to encompass greater questions of existence. Just because something like "simulation" is known to us as humans living in our time, and is something we can relate to, shouldn't limit the possibilities. Outside of some reason to believe the metaphysical nature of the universe is one thing or another, there are likely infinite possibilities, including many we couldn't conceive of. As to your main point in that paragraph, I agree: it doesn't matter.
I agree that fidelity of a simulation doesn't inform us as to whether or not there is a simulation involved at all. I'm trying to point out that a simulation is a simulation of "something" external to itself at some fidelity. If that's the case, the larger reality would be external to the simulation since 1) the simulation would be a simulation of something, 2) the simulation would simply be a component part of that larger reality. This may all depend on how we define the term: "Universe". If we mean universe to mean the metaphysically complete reality, then a universe by that definition couldn't be a simulation since it would be simulating something outside of itself. If we mean some smaller sense of the word Universe, like the observable universe or the perceivable universe, then perhaps.
I think trying to explain the universe or reality as a simulation or similar is nothing more than humans doing what we have done since long before recorded history: we're projecting existence (and its "causes") onto some explainable, graspable concept with which we are comfortable. This is nothing more than the motivation that created every religion on earth and is at least as likely to be a correct vision as any of those. In the old days we created Gods which resembled us, but had exaggerated qualities and powers to manipulate the universe and act as its cause... today, we feel much more comfortable with modern concepts such as "simulation"... but we have no more justification to make that claim than our ancestors did to mysterious thunderers high up on mountains.
The question of "Is there a God?" or "Is there a simulation?" is not a 50/50 proposition. The default position is the negative: there is no God until proven otherwise, there is no simulation until proven otherwise. We can start to believe and question as evidence mounts, but right now, I don't see much for a simulation (unless perhaps you want to argue that a quantized universe is just a pixelated one as we'd see in our own simulations).
Again, the author is justified in their claim that the Universe Is Not a Simulation until there is sufficient evidence to question it otherwise.
I’m of the opinion it’s two options (“real” vs “not real”) regardless of how the “not real” option is implemented: simulation, dream states, shared illusion, whatever.
Could someone elaborate on how accurate the results of these simulations are generally considered to be by the broader scientific community? It seems to me that the universe is so insanely complex that any simulations we can currently make would be fairly inaccurate because of lack of knowledge. Couldn't that cause a problem of building a whole base of theory on unproven guesses? I guess the researchers all know that but I'm just curious what the actual attitude towards this kind of work is.
Skimmed through the article and couldn't find any mention of the first part of the title which was the initial reason for reading it as it's a subject of great interest to me. I wasn't expecting this from quanta. Very disappointed.
I sometimes read hn as the discussions here can add to articles on topics I find interesting but have limited knowledge on, but the 3+ top comment threads (so far) discussing the title and not content of this article is somewhat disappointing.
I'm sorry you feel disappointed. But do you also feel like you've been bamboozled? Because this is how I feel after reading the whole article thinking that somebody managed to refute the 'simulation hypotheses'. Interesting article, of course, but I would have not read it at all if the titles was accurate. So I feel bamboozled.
There is nothing in the article to refute the conjecture that our universe is a simulation – and in fact the rapid progress it reports in simulating simplified universes could be seen as further support for the idea that universes like ours may be simulated.
Some combination of the holographic principle and the the information overhead of classically representing a quantum state? (I don't know, I'm not a physicist.)
Surprised that the currently exponential overhead for simulating a quantum system is a distant second in commenter objections here. "Simulating the universe" in the holistic manner that I feel such a phrase entails would require at least clearing that bar (say, with a quantum computer? Or at a longer shot, showing BQP = P?), and that's before thinking about the status of quantum gravity.
That's not even my second objection. My second objection is the rate of Entropy of the computer that would be using to make that computation, the amount of mass of the computer that would be required to use and how long it could continue to make computations before the heat death of computer. Also you would have to consider the fact that as performing multivariate calculus of the expanding universe that is completely gravitationally bound would require that the computer that is performing the calculations that govern the simulation to expand at a rate faster than the simulation that it is computing. Eventually what ever the rate of Entropy is in the Universe of the computer that would be simulating our Universe is would exceed the capability of it to exchange information from one end of the machine to the next as it eventually starts to expand faster than whatever the equivalent of the speed of light would be in the simulating universe.
There's a lot of subjectivity to the "we can simulate the universe" variety of claim stated by the article, but I'd tend to forgive considerations of the scale of the entire universe in that claim. It should be obvious that simulating the trajectory of every last particle is straight up impossible. (Even in principle: you could probably even show outright impossibility on logical grounds with a diagonal argument a la the time hierarchy theorem.)
Instead I'd take it as meaning something like, "any slice of physical phenomena there is to observe in the universe, we can simulate given reasonable resources to do so." So, put an imaginary box around some reasonably isolated plot of reality, pick your precision and your time scale, and you could replicate what happens in that space with a "reasonable" computational resource overhead. That's what elevates the quantum simulation overhead objection to number 1 in my mind.
There are some assumptions that we can make about an upstream computers physics, things such as the Fundamental Constants. Not that the constants would be the same in upstream but that those constants need to be defined in order for a fine-tuned universe complex enough to have something like a computer.
I ascribe a high likelihood that our universe is infinite in extent, so my answer would be ∞. But for any finite volume, the Bekenstein bound will give you an upper limit.
I may be incorrect but the radius of the upper bound of the Bekenstein bound would exceed the length of the lower bound of the whole universe. I came up with my number using the observable universe as the radius and the planck length as the volume. Your number would far exceed mine, I think.
Edit: Ah I'm reading this wrong. You are making the argument that an informational density that large would cause a singularity. You are correct, probably.
Right, but adaptive refinement is bread and butter of today's physics simulations. I imagine that in order to simulate our Universe, you'd go down to elementary particle level only when some of the simulated folks run their accelerators, etc. But for an in-simulation billiard game you'd use a plain impulse-based rigid body dynamics.
The problem isn't particles, its particle interactions and the orders of magnitude in time these events occur at. There is a reason why planck length is shortest theoretical measurable time interval. I'm sure you are aware of the equation E=mc^2, at the planck length the value of c=1. Therefore a planck length, cubed, of the universe can be considered to be 1 bit, for the purposes of storage for a universe, or at least this one.
to see how strongly it conflicts with what you have written about it.
Among other things catalogued there, the Planck length has dimension of [Length], rather than [Time], and per Bekenstein [1973] (doi:10.1103/PhysRevD.7.2333) "1 bit"[0] relates to the minimal increase in the area of the event horizon of a hairless, monotonically growing, stationary, spherically symmetric (or with some further assumptions, axisymmetric) black hole into which matter is being thrown. This remains contentious because black hole mass is continuous and not discrete (one can throw almost arbitrary wavelength photons in, for instance).
By contrast with what you wrote, if you look at it (e.g. via sci-hub) Bekenstein's PRD paper sure doesn't assert that a horizon area on the order of Planck area would contain "one bit", especially as he was aware of the content of the about-to-be-published Nature paper, Hawking [1974] (doi:10.1038/248030a0), which details the "explosion" of black holes with small horizon areas (and was additionally the first Hawking radiation paper).
Finally, if you don't like wikipedia and sci-hub, your favourite search engine will surely supply numerous discussions among working physicists (including peer-reviewed publications) of the Planck length and whether it is physically significant in any context other than Bekenstein's or close relatives (e.g. Loop Quantum Gravity requires that all surface areas are quantized, although not to integer multiples of the fundamental quantum, which in turn is roughly on the order of the Planck length cubed).
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[0] A modern semiclassical statement of this is: to leading order, the entropy of a black hole is proportional to its event horizon area at one nat per four Planck areas.
https://en.wikipedia.org/wiki/Nat_(unit)
Let us begin with a maximally dense object, a black hole. It will be assumed that the entropy is found on the horizon and that no more than one bit per Planck area can
stored there.
The only thing I stated incorrectly was planck cubed instead of square.
The metaphorical name of the principle (’t Hooft, 1993)
originates here. In many situations, the covariant entropy bound dictates that all physics in a region of space is described by data that fit on its boundary surface, at one bit per Planck area
An important implication of the holographic principle is that all the information in a given region can be encoded on a surface B, at a density of one bit per Planck area. We can now ask ourselves if the information contained in an entire spacetime can be encoded on a certain
hypersurface, which we will call a screen.
What's that you were saying? I can't hear you over the sound of how right I am.
And why is a planck area one bit?
Because at the planck length, h=G=c=k=1. Where h is the Planck constant, G is Newton's constant, c is the speed of light and k is Boltzmann's constant. Or if you like some Einstein. E=mc^2 reduces to E=m
I'm not sure what you're trying to convince anyone of, other than that you have read at least some of several documents dealing with gravitational physics. That's promising, so I'll react. I'm not a string theory fan, but don't let that discourage you from digging deeper into the field.
> "no more than one bit per Planck area can be stored there"
Sure, that's a postulate to help clarify the Susskind's string theory argument about the information content of his 2d holographic screen at infinity from the black hole with all of the above in a 3d spacelike hypersurface at t=const. Being a postulate, the sentence fragment you quote is not proven in the paper, it's just assumed.
Changing the number of states at the horizon in that spacelike hypersurface to an arbitrary finite number does not really frustrate his gravitational argument (but see below about his matter GUT argument), while arguments about the upper and lower limit of states at the horizon are available in Bekenstein [1973] op. cit. and many subsequent papers.
It is perfectly normal for gravitational arguments to set c = G = 1, and possibly normalize some other terms to unity too; the choice of what to set to unity depends on the trade off between ease of writing down formulae and the difficulty of checking their dimensionality. The reason Susskind uses Planck units, and relevantly to our discussion the Planck length, is because it's convenient in analogies as he develops his argument further down the paper using units where the string length is set to unity.
(The majority of the Susskind paper is heavy (pardon the pun relating to scaling of interaction with momentum) with non-gravitational string physics, and I have no expertise on that, but his gravitational arguments are low energy ones, and there I am comfortable).
> The only thing I stated incorrectly was planck cubed instead of square.
You wrote, "shortest theoretical time interval". The word "time" is incorrect since it is a unit of length (this matters in a Lorentzian spacetime), but changing it to "spatial" does not let you claim that the Susskind paper supports your statement at all, for the reasons above.
You can certainly make arguments about states on a stretched horizon (Susskind does in the paper you found) -- complementarity is wildly popular with string theorists. However, their entropy:information argument, as also repeated in the Bousso paper and the master's degree thesis you found, does not set a minimum length scale rather than fixing a limit on the number of microstates you can squash into an area before the macrostate resembles a hairless black hole, the idea being that any sparser region's macrostate grows gently, and moreover that you can with some care use the macrostate to describe all the internal microstates (which is the core content of SUGRA theories, essentially, where the care one takes is in the choice of a conformal field theory to represent the evolution of the macrostate).
> "a planck area [is] one bit [b]ecause at the planck length, h=G=c=k=1"
No. More on that in the paragraph after the following one.
You also wrote "the equation E=mc^2, at the planck length the value of c=1", which is a bit confused. All Planck units set five constants, c = G = hbar = k_e = k_B = 1. Any quantity measured in Planck units will have c = 1 (and also Boltzmann's constant = 1 and the Coulomb constant = 1 etc.). The partial dispersion relation you provide has nothing to do with it, other than that you can solve it for an appropriate system in Planck units just as in S.I. or cms units, and you can simplify by dropping the term normalized to unity, just as your version has already simplified from the fuller special relativistic relation by normalizing momentum to zero.
In the stringy arguments, the reason there is supposedly four nats or one bit or a small finite number of microphysical degrees of freedom or whatever per unit ar...
Even though your two-link reply seems like an obvious "I don't want to talk any more", I'll leave you with three things.
Firstly, there is nothing special about natural units compared to any other system of units, except that some popular formulae can take on especially simple forms in that system of units, provided one takes care not to lose dimensionality:
You (still) are confusing two different dimensions, length and time. Again, this matters in a spacetime like ours, where the difference in dimensionality gives us a system of causality[1] and a reasonable setting in which to do time-series physics[2]. It also matters when switching from natural units to a different system of units in which c != 1, such that we cannot omit the conversion constant (or change of sign when calculating spacetime intervals [3]).
Changing a physical system like a black hole from one system of units to another does not change the physics of the system, just how we describe them. It is enlightening to do so in general, because it is easy to fall into the trap of treating as physical a condition that vanishes upon switching to a different set of units. A quantity that is a ratio of two dimensionful quantities (area and information) surviving across changes of units on one or both dimensions may be interesting. In the case of black hole complementarity, which earlier you found links for, it's a (near-horizon) density that (according to some string theorists) corresponds directly with a (interior) density (states / volume) taking into account the Ricci tensor's effect on interior volume but removing the physical singularity through string interactions in a "fuzzball" or something similar[4].
Secondly, your second link says of Planck time, "Presumed to be the shortest theoretically measurable time interval (but not necessarily the shortest increment of time - see quantum gravity)", which does not really support your position. Rather than reinvent the wheel for you in qualifying that, which I think would be wasteful given your previous few replies, I'll direct you to physics se and in particular to Lubos Motl's 85 point comment at : https://physics.stackexchange.com/questions/9720/does-the-pl...
Finally, I don't know what you're trying to accomplish although it seems you're set on convincing yourself and perhaps some people who know even less physics than you do that you know what you're talking about. Hopefully it's more optimistic and instead you're trying to learn more than you already do and are just going about it inefficiently.
[2] https://arxiv.org/abs/1505.01403 (section 4) - sadly the wikipedia has only scattershot coverage of it in e.g. the short and/or not very accessible pages on the ADM and BSSM formalisms, and on Canonical Quantum Gravity (which is a quantization of the Hamiltonian formulation that is "only" an effective field theory good to one loop, and provokes the question of "the problem of time"). Unfortunately most introductory material about 3+1 formalisms in general is already highly technical (e.g., textbooks aimed at graduate students).
this is highly naive of me to ask, but "in theory" if we could simulate the universe, would familiar stuff like living organisms/'societies'/'humans' potentially just emerge within such simulations?
just super cool to think about even if not the case/unrealistic.
My understanding of Tierra and its successors like Avida are that the "digital organisms" are written beforehand and then systematically (pseudorandomly) mutated. Because the initial "organisms" are written, it would be a stretch to say that "life" developed in these systems. A statement like "the process of evolution by natural selection was simulated in an artificial system" would seem to be more accurate.
Yes, this is true, however I think the distinction is irrelevant. The initial VM was created with the intention of encouraging this evolution, had the original intent included spontaneous emergence of a-life as a goal I'm pretty confident that would have happened.
Seems like that's an assertion begging for an experiment. Take the software that manages experiments in Avida or Tierra, but don't supply pre-written organisms. Bit-flip randomly and see if something develops. Unfortunately I don't know the implementation details of those systems at all, so I can't say whether or not that would be feasible.
Actually, when you found out it was a simulation, we scrapped the current data, we had to restore it to the last valid snapshot and adjust local simulation parameters so that you wouldn't find it out. It's all reported in the post-mortem of the incident. Service levels are now fully restored.
Yes. We have some guard code in place for when this happens and it's getting really good at catching it before or right after it happens and doing all the rollbacks automatically, but they can't catch every possible situation.
It's now down to one minor outage every couple years. We are aiming at five nines on the next major release.
well.. the guys who figured out that we are not in a simulation had a caveat that is was "with classical computers" meaning, we are not being simulated in some version of AWS somewhere.
It specifically does not rule out other forms of computers.
In Charles Stross's "Accelerando" (strongly recommended!) astronomers suspect that the inhabitants of Andromeda Galaxy converted all its baryonic matter to computronium (here: configuration of matter capable of the most efficient computation as per the laws of physics) and are using it to run a massive side-channel attack, trying to verify if the Universe runs on a virtual machine (and I guess maybe break out of it).
On a different note, here's a sobering thought for the Universe-as-simulation optimists: while it's possible the simulation's Creators wish us well, e.g. will store your soul/mind and let you live carefree in a Paradise... it might rather work like our current massive simulations (e.g. the Millennium Run [0]). It generates enormous amounts of data, but only some small amount (like a state snapshot every 100M years) is actually captured and analyzed. I.e. the "dumb" computing power at the Creators' disposal is far greater than their mental capacity. The whole existence of humanity might go unnoticed, just a side-effects of the simulation's fidelity.
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[ 5.3 ms ] story [ 184 ms ] thread> The Universe Is Not a Simulation
That's based on what? Author of the article opinion? That's cool but then it should be "In my opinion.." and "here's my reasoning".
So title is entirely clickbait, surely? It's not "We're Getting Better at Universe Simulations" that is the content given. I was hoping to find some discussion of the simulation theory and perhaps reasons found that it may not be possible. That's why I clicked and read.
I agree it's kind of weird to raise something in the title and not address it at all in the main article, but that's a minor flaw in what's clearly intended as a joke.
I'm so sick of these bullshit theorists coming up with unverifiable imaginations out of thin air. Produces lots of clicks and laymen books but doesn't do jackshit to help move science forward.
There is no practical way to falsify that so yes, it is just a dreamy theory.
Unlike some other dreamy theories (creationism and astrology come to my mind) nobody has come up with any practical uses for the dreamy theory either, so that would be a second reason why nobody takes this dreamy theory that seriously.
But if this is a simulated game, I would be keen to know how this is scored and how many lifes I have left before game over...
It's much more likely that you are just an NPC waiting to be harvested for some aliens experience points.
The most you can hope for is that you are destroyed in an interesting way, and perhaps your memory lives on in a highlight reel on that aliens stream.
I've often wondered if God existed at one point and we were just his video game. But now God found a more interesting game to play and we are just a forgotten game in chugging along in his steam account. I don't think there is a better explanation for the miracle of the pyramids, or the invention of magnets.
Well, if I think from bayesian point of view, given that only creature here that I personally can be somewhat confident actually having any sentience happens to be me, then it would feel quite likely me being a player. Especially as this can be single player game as well...
But just because something could be cruel doesn't make it less likely. I think we are basically talking about the plot of West World. And pointing out that it doesn't make sense to give an active inner life to characters that exist only to fill out someone else's designed game experience.
But just think about it. If Sims 2099 is capable of giving consciousness to its characters, or at least something so much like it that the characters believe the are conscious, don't you think its very likely players will ask for it? Regardless of the ethical implications.
It can be hard to tell through the popular science stories, where the author is typically unable to relay anything about this research without adding "woo woo" sounds and wiggling their fingers, but it's a real theory.
One thing that may be worth remembering is that in the real theory, the "simulation" is not necessarily running on "a supercomputer just like what we have, only way bigger", which is actually a silly idea for various reasons, and we also do not know that the simulation is literally simulating every particle and every cubic inch of space in the most accurate possible way (i.e., for all we know, far away galaxies could just be a few megabytes in size, rather than fully simulated to the nth degree). The "Great Simulator" is not required to run anything remotely resembling our physics. What seems an absurdly large computation may be smaller than it appears, and may not be an absurdly large amount of a universe running on fundamentally different physics.
(Occasionally when I'm bored, I noodle around with a theory of cellular automata in which the universe has infinite computation power by virtue of being able to split a cell in half or quarters, that then runs at double-speed relative to the outside. If this is done recursively the universe has arbitrary computation abilities relative to the "top level". I've never worked it into anything usable, but I think it can give a flavor of why we should not be sure that our simulation host is necessarily as staggered by the computation as we would be. We are not even capable of saying that they aren't running an exponentially-expensive quantum approximation algorithm with the entire universe actually arbitrary-precision integers under the hood. The staggering amount of computation that represents may not bother them at all.)
It is not a theory that is, strictly speaking, falsifiable thanks to Church-Turing equivalence, but there are ways in which it could potentially (to any arbitrary degree of confidence you may want) be confirmed if it is true. To take one degenerate case, if the Great Simulator broke silence and starting wildly breaking the laws of physics to get our attention, that would certainly put a lot of probability mass on the "we're a simulation" theory. There are less extreme cases we could conceivably pick up on, that just fits into an HN comment nicely.
So in what ways is it a "serious theory"?
Despite what seems to be a popular opinion, we are not actually obligated to curl up into a ball on the floor and cry about our inability to know anything just because science can't be definitive on some point. We just need to be aware of the limits of our knowledge. We have no choice; even in just our day-to-day lives, we are required to make all kinds of decisions for which science is either quiet, insufficiently informative, or (and this one may really hurt to think about too much) simply wrong.
I have no idea what you are referring to here. Can you be bit more specific about what viewpoint or philosophy you are satirizing?
People defend it with a straight face?
The thing is, we don't know where this line of reasoning would even lead. I mean, people used to think that light had to travel in little packets through luminiferous aether [1] and look where that investigation led: Einstein, special relativity, atomic weapons and power, nuclear medicine, etc.
Let's say the universe is fundamentally indistinguishable from a computer simulation. What consequences does that have? What does that say about the types of math that can be used to describe the universe? Or, perhaps better, the types of math that shouldn't be used to describe the universe? What does that say about our ability to model a portion of the universe and therefore predict outcomes? Does it have implications for stochastic processes? Indeed, where is the stochasticism coming from? Is everything predictable or is there some fundamental randomness?
On the other hand, what if we can show that the universe is distinguishable from a computer simulation. What does that mean for our understanding of the universe as it exists? Does it reveal a fundamental aspect of reality that we have missed, or a limitation of our mathematics, or a fault in our computer models or design, etc.? We're dogs learning calculus here, and the universe isn't obligated to make sense.
Even if we can never find a useful test for this hypothesis, the line of thinking itself potentially leads us into new areas of discovery.
[0]: https://gizmodo.com/5950832/how-to-tell-if-the-universe-is-a...
[1]: https://en.wikipedia.org/wiki/Luminiferous_aether
The luminiferous ether was a falsifiable theory - indeed it was a breakthrough for physics because it was falsified (experiments failed to detect it) so new theories had to be developed. So this is completely different from unfalsifiable metaphysics.
The idea that quantum fields exist in multiple states simultaneously until observed become evidence for a simulation, since a simulator could be deferring calculations on things not observed.
Also, the very program this article is referring to could be considered as evidence for it, since if a rough simulation can be made where the observable result is indistinguishable from a result where every atomic element in the entire universe was simulated, then, again, a simulator with limited resources would make do.
The law of conservation of energy is built the same way. There is no way we can test ways that energy is transferred that we don't yet know about, but this law is still considered true, because we have so many examples of it working.
> The idea that quantum fields exist in multiple states simultaneously until observed become evidence for a simulation,
How is that evidence? Current physics can model that without relying on a simulation hypothesis. Adding a simulation hypothesis does not simplify the model, and it is unfalsifiable.
> Adding a simulation hypothesis does not simplify the model, and it is unfalsifiable.
I explain this. It's falsifiable if it can be shown there is some extremely large and complicated process that be observed to be different than any possible rough calculation that could be accomplished by a simulator with very constrained resources (constrained in comparison to all the supposed atomic particles in the universe)
The notion that all forms of energy must be conserved, even undiscovered ones, has been used as the basis for the theory of Hawking radiation, isn't it? Yet claiming that undiscovered forms of energy are conserved, just as known ones, is unfalsifiable, too.
The law of conservation of energy, including undiscovered ones, is in the same boat as the theory that the universe is a simulation.
Until we find a form of energy that isn't conserved, it is simpler to assume all types of energy are conserved.
Similarly, until we find a process that is of large enough scale that it couldn't be simulated on a computer with resources much more limited than the size of the universe, and be observable identical to a process taking much more resources, it is simpler to assume it all is being simulated in such a way.
Sorry I just didn't want to quote the whole comment, didn't mean to imply I was only responding to the first part of the sentence.
I understand you can hypothetically prove that a simulation of the universe would require a simulation engine of at least a certain complexity. But since the simulation engine does not exist in this universe, we have no idea about what limitations or laws of nature (if any) it is subject to. You will never be able to prove or disprove the existence if this hypothetical simulator.
The point is not to prove one way or another whether the universe is a simulation, just like there is no point trying to prove the law of conservation of energy as universal for all forms of phenomena, discovered and undiscovered.
It's just if we can show that all known phenomena can be the result of a very limited simulation, then when analyzing new phenomena, we can also expect it to be runnable on a very limited simulation, too.
It's the same as assuming that the law of conservation of energy would apply to any new phenomena we discover. There is no proof, but it's a good starting point.
The bottom line is that it is possible to devise experiments or observations which would give different outcome if the theory holds and if the theory doesn't hold.
But you cannot devise an experiment which would give different outcomes if the universe is a simulation versus if it isn't. More specifically, you cannot imagine an observation which would prove that the universe isn't a simulation. Therefore it is not a legitimate scientific theory. At best it is a fun thought experiment.
I've already mentioned 5 times in this thread that the theory I'm talking about is of a simulation with very limited resources, but you seem to be ignoring this point.
Show that a particular phenomenon can't be simulated using extremely limited hardware (compared to the size of the universe) and you can falsify this theory.
Does this or does this not apply to a simulation with very limited resources (compared to what it would take to model all the atoms of the universe) or not, then?
But it effectively wasn't for the first 150 years of it's existence. The theory originated in 1720 and it wasn't disproven until 1887. It took that long for someone to come up with a conclusive experiment. Nevertheless, for those 150 years the luminiferous ether theory was widely held, shaped the field of physics, and the research had to go into finding an experiment to test the theory.
Similarly, the idea that atoms might do things when high energy particles hit them was all theory until Wilson's cloud chamber became the first particle detector and suddenly physicists could see what these particles were doing when they hit things.
> The problem is...you can even define what it means for the universe to be a simulation.
You're confusing something that hasn't been done with something that can't be done. Indeed, what they're trying to do is exactly trying to define criteria to test that the universe is a simulation. It's the first day of school and you're complaining that Newton doesn't have his Principia and Gilbert doesn't have his De Magnete.
Theories often predate the knowledge of how to test them. This isn't weird.
It's worth noting that most religions are in exactly the same situation.
Edit, oh, duh.
Yeah, my main take is that there should be evidence for it being a simulation, and in lieu of said evidence it should be assumed untrue
Same problem we have in quantum gravity. We just can't recover known physics from anything at all, any combination of theories at all it seems. That includes all known instances of computation, it just blows up.
Also, Church-Turing has nothing to do with basic problems here, in particular because eventual simulating computation would be unlike computation we know (which again, makes the word lose any meaning here).
None of that matter if there is no theory in the first place. Much was tried. 't Hooft got as far as holographic principle. And there's still no theory at all.
What does such a theory have to do with astronomers or physicists? Its a philosophical issue
It's a theory that predates the internet. In the expanded view, the theory goes back to antiquity.
The modern version is a thought experiment more in line with the drake equation than a dreamy internet theory. It's an idea born of some assumptions and mathematics.
> Like, are astronomers and physicists taking it seriously?
Some are, most aren't. But then again, most astronomers and physicists don't take SETI seriously as they have their own work to focus on. But it certainly isn't anything to be dismissed just like the drake equation or SETI.
One has something to do with the information in black-holes, i can't remember the details but it suggested to me that '3d space' was fundamentally artificial.
Another has to do with quantum entanglement, the explanation for spooky action at a distance could be that the two particles are still in the same 'bit of memory'.
And lastly the Uncertainty principle is thought to act a lot like an on-the-fly loading frame in an RPG.. As silly as that sounds there is not really a satisfying explanation of why things are less certain when we are not interacting with them.
Its worth noting that even if the universe is simulated, it might not be simulated by intelligence, we don't know enough to say its not 'naturally simulated', that might seem paradoxical but 'simulated' and 'artificial' are very loaded words; A reflection of the moon in a pond is in some way an artificial simulation of a moon..
I think the universe as a simulation is less interesting as it's really just taking the notion of materialism to its logical extent. But in fairness to it, it's now part of culture, so if it's causing us to think in ways we wouldn't be aware of, it's harder to see it influencing someone than if he's Feynman getting a sudden phone call from Wheeler.
Many thought experiments can also be useful insights into nature of things. The idea of a Boltzmann brain[2], for instance, challenges your intuitions of infinity and thermodynamics.
[1]: https://en.wikipedia.org/wiki/One-electron_universe [2]: https://en.wikipedia.org/wiki/Boltzmann_brain
If the Universe is a simulation (or might be) what is it simulating and who's simulating it? I'd be more interested to know about -that- than the arbitrary details of some measly little simulation itself. You might say something hand-wavy like, "it's simulating itself"... but OK, when I look at our "simulations" they are always highly referential to the external real... er... possibly real... world. Dwarf Fortress could be called a simulation (perhaps one of the better ones!) ... and while I'd be hard pressed to point to the outside world and say it's simulating any one thing with high fidelity, I can point to trees, mountains, water animals, etc. where the creative element is really just tweaking the attributes of these otherwise externally real things. It's hard to simulate what you're you're completely unaware of, unconscious of ... in fact to be conscious at all is to be conscious "of something" and insofar as simulations are conscious efforts at creation, it's difficult to not have some concrete reference that exists outside of a "simulation".
Of course, perhaps, it's the great mystery of God which I'm always told is beyond mere human understanding. Or maybe its simulations all the way down. Or maybe any explanation talking about simulations requires greater leaps of faith and greater acceptance of more and more unlikely scenarios of reality than just saying the Universe is perhaps a metaphysically real place that doesn't require an appeal to "simulation" for explanation.
I think I'll just stick to the simple minded idea of the Universe is a real place and not a simulation. That part of the title is so likely to be true that the author need not feel bad about the assumption.
The fidelity of the simulation is not an argument for or against: assume we're simulated and it seems likely to me that perceptions by beings within simply wouldn't have the ability to notice a lack of fidelity; or whomever owns this simulation has the computational power to simulate sufficient fidelity to convince inhabitants that their universe is "real."
Because we don't yet have evidence either way, I'd go with 50/50 odds.
I agree that fidelity of a simulation doesn't inform us as to whether or not there is a simulation involved at all. I'm trying to point out that a simulation is a simulation of "something" external to itself at some fidelity. If that's the case, the larger reality would be external to the simulation since 1) the simulation would be a simulation of something, 2) the simulation would simply be a component part of that larger reality. This may all depend on how we define the term: "Universe". If we mean universe to mean the metaphysically complete reality, then a universe by that definition couldn't be a simulation since it would be simulating something outside of itself. If we mean some smaller sense of the word Universe, like the observable universe or the perceivable universe, then perhaps.
I think trying to explain the universe or reality as a simulation or similar is nothing more than humans doing what we have done since long before recorded history: we're projecting existence (and its "causes") onto some explainable, graspable concept with which we are comfortable. This is nothing more than the motivation that created every religion on earth and is at least as likely to be a correct vision as any of those. In the old days we created Gods which resembled us, but had exaggerated qualities and powers to manipulate the universe and act as its cause... today, we feel much more comfortable with modern concepts such as "simulation"... but we have no more justification to make that claim than our ancestors did to mysterious thunderers high up on mountains.
The question of "Is there a God?" or "Is there a simulation?" is not a 50/50 proposition. The default position is the negative: there is no God until proven otherwise, there is no simulation until proven otherwise. We can start to believe and question as evidence mounts, but right now, I don't see much for a simulation (unless perhaps you want to argue that a quantized universe is just a pixelated one as we'd see in our own simulations).
Again, the author is justified in their claim that the Universe Is Not a Simulation until there is sufficient evidence to question it otherwise.
The rest of your comment makes fine arguments.
http://gasoline-code.com/
http://bluetides-project.org/
I sometimes read hn as the discussions here can add to articles on topics I find interesting but have limited knowledge on, but the 3+ top comment threads (so far) discussing the title and not content of this article is somewhat disappointing.
Proof left as exercise for the reader?
Surprised that the currently exponential overhead for simulating a quantum system is a distant second in commenter objections here. "Simulating the universe" in the holistic manner that I feel such a phrase entails would require at least clearing that bar (say, with a quantum computer? Or at a longer shot, showing BQP = P?), and that's before thinking about the status of quantum gravity.
https://web.archive.org/web/20171111160807/http://fab.cba.mi...
https://www.amazon.com/dp/B000GCFBP6/ref=dp-kindle-redirect?...
Also read the references.
Instead I'd take it as meaning something like, "any slice of physical phenomena there is to observe in the universe, we can simulate given reasonable resources to do so." So, put an imaginary box around some reasonably isolated plot of reality, pick your precision and your time scale, and you could replicate what happens in that space with a "reasonable" computational resource overhead. That's what elevates the quantum simulation overhead objection to number 1 in my mind.
https://en.wikipedia.org/wiki/Bekenstein_bound
Edit: Ah I'm reading this wrong. You are making the argument that an informational density that large would cause a singularity. You are correct, probably.
https://en.wikipedia.org/wiki/Planck_length
to see how strongly it conflicts with what you have written about it.
Among other things catalogued there, the Planck length has dimension of [Length], rather than [Time], and per Bekenstein [1973] (doi:10.1103/PhysRevD.7.2333) "1 bit"[0] relates to the minimal increase in the area of the event horizon of a hairless, monotonically growing, stationary, spherically symmetric (or with some further assumptions, axisymmetric) black hole into which matter is being thrown. This remains contentious because black hole mass is continuous and not discrete (one can throw almost arbitrary wavelength photons in, for instance).
By contrast with what you wrote, if you look at it (e.g. via sci-hub) Bekenstein's PRD paper sure doesn't assert that a horizon area on the order of Planck area would contain "one bit", especially as he was aware of the content of the about-to-be-published Nature paper, Hawking [1974] (doi:10.1038/248030a0), which details the "explosion" of black holes with small horizon areas (and was additionally the first Hawking radiation paper).
Finally, if you don't like wikipedia and sci-hub, your favourite search engine will surely supply numerous discussions among working physicists (including peer-reviewed publications) of the Planck length and whether it is physically significant in any context other than Bekenstein's or close relatives (e.g. Loop Quantum Gravity requires that all surface areas are quantized, although not to integer multiples of the fundamental quantum, which in turn is roughly on the order of the Planck length cubed).
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[0] A modern semiclassical statement of this is: to leading order, the entropy of a black hole is proportional to its event horizon area at one nat per four Planck areas. https://en.wikipedia.org/wiki/Nat_(unit)
Let us begin with a maximally dense object, a black hole. It will be assumed that the entropy is found on the horizon and that no more than one bit per Planck area can stored there.
The only thing I stated incorrectly was planck cubed instead of square.
https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.74....
The metaphorical name of the principle (’t Hooft, 1993) originates here. In many situations, the covariant entropy bound dictates that all physics in a region of space is described by data that fit on its boundary surface, at one bit per Planck area
https://lib.ugent.be/fulltxt/RUG01/001/787/483/RUG01-0017874...
3.5 Holographic screens
An important implication of the holographic principle is that all the information in a given region can be encoded on a surface B, at a density of one bit per Planck area. We can now ask ourselves if the information contained in an entire spacetime can be encoded on a certain hypersurface, which we will call a screen.
What's that you were saying? I can't hear you over the sound of how right I am.
And why is a planck area one bit?
Because at the planck length, h=G=c=k=1. Where h is the Planck constant, G is Newton's constant, c is the speed of light and k is Boltzmann's constant. Or if you like some Einstein. E=mc^2 reduces to E=m
> "no more than one bit per Planck area can be stored there"
Sure, that's a postulate to help clarify the Susskind's string theory argument about the information content of his 2d holographic screen at infinity from the black hole with all of the above in a 3d spacelike hypersurface at t=const. Being a postulate, the sentence fragment you quote is not proven in the paper, it's just assumed.
Changing the number of states at the horizon in that spacelike hypersurface to an arbitrary finite number does not really frustrate his gravitational argument (but see below about his matter GUT argument), while arguments about the upper and lower limit of states at the horizon are available in Bekenstein [1973] op. cit. and many subsequent papers.
It is perfectly normal for gravitational arguments to set c = G = 1, and possibly normalize some other terms to unity too; the choice of what to set to unity depends on the trade off between ease of writing down formulae and the difficulty of checking their dimensionality. The reason Susskind uses Planck units, and relevantly to our discussion the Planck length, is because it's convenient in analogies as he develops his argument further down the paper using units where the string length is set to unity.
(The majority of the Susskind paper is heavy (pardon the pun relating to scaling of interaction with momentum) with non-gravitational string physics, and I have no expertise on that, but his gravitational arguments are low energy ones, and there I am comfortable).
> The only thing I stated incorrectly was planck cubed instead of square.
You wrote, "shortest theoretical time interval". The word "time" is incorrect since it is a unit of length (this matters in a Lorentzian spacetime), but changing it to "spatial" does not let you claim that the Susskind paper supports your statement at all, for the reasons above.
You can certainly make arguments about states on a stretched horizon (Susskind does in the paper you found) -- complementarity is wildly popular with string theorists. However, their entropy:information argument, as also repeated in the Bousso paper and the master's degree thesis you found, does not set a minimum length scale rather than fixing a limit on the number of microstates you can squash into an area before the macrostate resembles a hairless black hole, the idea being that any sparser region's macrostate grows gently, and moreover that you can with some care use the macrostate to describe all the internal microstates (which is the core content of SUGRA theories, essentially, where the care one takes is in the choice of a conformal field theory to represent the evolution of the macrostate).
> "a planck area [is] one bit [b]ecause at the planck length, h=G=c=k=1"
No. More on that in the paragraph after the following one.
You also wrote "the equation E=mc^2, at the planck length the value of c=1", which is a bit confused. All Planck units set five constants, c = G = hbar = k_e = k_B = 1. Any quantity measured in Planck units will have c = 1 (and also Boltzmann's constant = 1 and the Coulomb constant = 1 etc.). The partial dispersion relation you provide has nothing to do with it, other than that you can solve it for an appropriate system in Planck units just as in S.I. or cms units, and you can simplify by dropping the term normalized to unity, just as your version has already simplified from the fuller special relativistic relation by normalizing momentum to zero.
In the stringy arguments, the reason there is supposedly four nats or one bit or a small finite number of microphysical degrees of freedom or whatever per unit ar...
https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(time)
Firstly, there is nothing special about natural units compared to any other system of units, except that some popular formulae can take on especially simple forms in that system of units, provided one takes care not to lose dimensionality:
https://en.wikipedia.org/wiki/Dimensional_analysis
You (still) are confusing two different dimensions, length and time. Again, this matters in a spacetime like ours, where the difference in dimensionality gives us a system of causality[1] and a reasonable setting in which to do time-series physics[2]. It also matters when switching from natural units to a different system of units in which c != 1, such that we cannot omit the conversion constant (or change of sign when calculating spacetime intervals [3]).
Changing a physical system like a black hole from one system of units to another does not change the physics of the system, just how we describe them. It is enlightening to do so in general, because it is easy to fall into the trap of treating as physical a condition that vanishes upon switching to a different set of units. A quantity that is a ratio of two dimensionful quantities (area and information) surviving across changes of units on one or both dimensions may be interesting. In the case of black hole complementarity, which earlier you found links for, it's a (near-horizon) density that (according to some string theorists) corresponds directly with a (interior) density (states / volume) taking into account the Ricci tensor's effect on interior volume but removing the physical singularity through string interactions in a "fuzzball" or something similar[4].
Secondly, your second link says of Planck time, "Presumed to be the shortest theoretically measurable time interval (but not necessarily the shortest increment of time - see quantum gravity)", which does not really support your position. Rather than reinvent the wheel for you in qualifying that, which I think would be wasteful given your previous few replies, I'll direct you to physics se and in particular to Lubos Motl's 85 point comment at : https://physics.stackexchange.com/questions/9720/does-the-pl...
Finally, I don't know what you're trying to accomplish although it seems you're set on convincing yourself and perhaps some people who know even less physics than you do that you know what you're talking about. Hopefully it's more optimistic and instead you're trying to learn more than you already do and are just going about it inefficiently.
- --
[1] https://en.wikipedia.org/wiki/Causal_structure
[2] https://arxiv.org/abs/1505.01403 (section 4) - sadly the wikipedia has only scattershot coverage of it in e.g. the short and/or not very accessible pages on the ADM and BSSM formalisms, and on Canonical Quantum Gravity (which is a quantization of the Hamiltonian formulation that is "only" an effective field theory good to one loop, and provokes the question of "the problem of time"). Unfortunately most introductory material about 3+1 formalisms in general is already highly technical (e.g., textbooks aimed at graduate students).
[3] https://en.wikipedia.org/wiki/Metric_signature
[4] ____a ↗ Is there a good book that covers primarily or at least secondarily the ideas behind the universe being a simulation? I'd like to learn more. psetq ↗ There's several links in the wikipedia article which can make for good jumping off points: ur-whale ↗ Is it just me or all that talk of "codes" combined with all-uppercase names is exuding a potent whiff of fortran :D ? freshhawk ↗ Not knowledgeable in the field really, but I have a bunch of old school friends who do this for a living. krrishd ↗ this is highly naive of me to ask, but "in theory" if we could simulate the universe, would familiar stuff like living organisms/'societies'/'humans' potentially just emerge within such simulations? ada1981 ↗ If we could simulate it past a certain fidelity threshold, it would seem so. AnIdiotOnTheNet ↗ Depends on how you define living, really. It's a philosophical problem, what makes one collection of matter "alive" and another "not alive"? pouta ↗ The 'I Am A Strange Loop' covers this beautifully. rotexo ↗ My understanding of Tierra and its successors like Avida are that the "digital organisms" are written beforehand and then systematically (pseudorandomly) mutated. Because the initial "organisms" are written, it would be a stretch to say that "life" developed in these systems. A statement like "the process of evolution by natural selection was simulated in an artificial system" would seem to be more accurate. AnIdiotOnTheNet ↗ Yes, this is true, however I think the distinction is irrelevant. The initial VM was created with the intention of encouraging this evolution, had the original intent included spontaneous emergence of a-life as a goal I'm pretty confident that would have happened. rotexo ↗ Seems like that's an assertion begging for an experiment. Take the software that manages experiments in Avida or Tierra, but don't supply pre-written organisms. Bit-flip randomly and see if something develops. Unfortunately I don't know the implementation details of those systems at all, so I can't say whether or not that would be feasible. NVRM ↗ Because you can chroot doesn't mean that you are not in a virtualized container. Actually this tend to say the opposite... rbanffy ↗ Actually, when you found out it was a simulation, we scrapped the current data, we had to restore it to the last valid snapshot and adjust local simulation parameters so that you wouldn't find it out. It's all reported in the post-mortem of the incident. Service levels are now fully restored. stabbles ↗ There is another theory which states that this has already happened rbanffy ↗ Yes. We have some guard code in place for when this happens and it's getting really good at catching it before or right after it happens and doing all the rollbacks automatically, but they can't catch every possible situation. [deleted] ↗ (comment deleted) kjeetgill ↗ That explains the slack outage. earenndil ↗ In the beginning, the universe was simulated. This has made a lot of people very unhappy and is widely regarded as a bad move. [dead] joeldg ↗ well.. the guys who figured out that we are not in a simulation had a caveat that is was "with classical computers" meaning, we are not being simulated in some version of AWS somewhere.
It specifically does not rule out other forms of computers. gattr ↗ In Charles Stross's "Accelerando" (strongly recommended!) astronomers suspect that the inhabitants of Andromeda Galaxy converted all its baryonic matter to computronium (here: configuration of matter capable of the most efficient computation as per the laws of physics) and are using it to run a massive side-channel attack, trying to verify if the Universe runs on a virtual machine (and I guess maybe break out of it).
https://en.wikipedia.org/wiki/Simulation_hypothesis
And if so, I'm wondering if any of that stuff runs on GPUs or if we're still talking about "traditional" supercomputers?
Anyone knowledgeable in the field care to share?
Your ability to detect Fortran is apparently excellent.
just super cool to think about even if not the case/unrealistic.
Since at least Thomas S. Ray's work on Tierra in the 90s we've been creating universes in which things that could be called "life" have developed.
It's now down to one minor outage every couple years. We are aiming at five nines on the next major release.
On a different note, here's a sobering thought for the Universe-as-simulation optimists: while it's possible the simulation's Creators wish us well, e.g. will store your soul/mind and let you live carefree in a Paradise... it might rather work like our current massive simulations (e.g. the Millennium Run [0]). It generates enormous amounts of data, but only some small amount (like a state snapshot every 100M years) is actually captured and analyzed. I.e. the "dumb" computing power at the Creators' disposal is far greater than their mental capacity. The whole existence of humanity might go unnoticed, just a side-effects of the simulation's fidelity.
[0] https://en.wikipedia.org/wiki/Millennium_Run