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If we wanted to model the universe as a set of equations or a cellular automaton, how complex would that program be? Could a competent software engineer, even
by jagrsw 2y ago
If we wanted to model the universe as a set of equations or a cellular automaton, how complex would that program be?
Could a competent software engineer, even without knowing the fundamental origins of things like particle masses or the fine-structure constant, capture all known fundamental interactions in code?
I guess I'm trying to figure out the complexity of the task of universe creation, assuming the necessary computational power exists. For example, could it be a computer science high school project for the folks in the parent universe (simulation hypothesis). I know that's a tough question :)
- dmos62 2y agoStephen Wolfram has been taking a stab at it. Researching fundamental physics via computational exploration is how I'd put it. https://www.wolframphysics.org/ https://www.wolframphysics.org/
- cjfd 2y agoHe is basically a crackpot. Any attempt at fundamental physics that doesn't take quantum mechanics into account is.... uhm.... how to put this.... 'questionable'.
- russdill 2y agoThat really seems to be mischaracterizing his work. The idea is that the quantum effects we see will eventually emerge. Most people in the field don't think his research will be fruitful, but that doesn't make him a crack pot
- momoschili 2y agomost people in the field believe his research isn't even capable of being wrong
- dmos62 2y agoSomeone seems to say something demeaning like that about him whenever he comes up, and I don't really know why. Which is fine, maybe it's a subjective thing. For what it's worth, the few times I read something of his, I loved it.
- cjfd 2y agoWell, one can love playing chess and that is all fine and good and so on but if someone says that chess is the fundamental theory of the universe, how much sense does that make? There might even even be truth in that statement, who could possibly know? All we can be quite certain about is that to actually demonstrate the hypothetical truth of the statement 'chess is the fundamental theory of the universe' some number, presumably larger than 5, of nobel price level of physics discoveries need to take place.
- gowld 2y agoYou are making an unscientific criticism. Wolfram's claim is that Cellukar Automata can provide as good or better mathematical model of the universe than current current theories, by commonly appreciated metrics such as "pasimony of theory" (Occam's Razor). He's not making claims about metaphysical truth.
- cjfd 2y agoWell, the question 'is this Wolfram guy doing science' is as such not a scientific question. And the answer is a resounding 'no'.
- 7thaccount 2y agoIt's a complex issue. He is obviously extremely intelligent and at least a decent business man. If you've never used Wolfram Mathematica before, I implore you to pick up a raspberry pi and play with the educational version. It's nothing short of magical in many ways. I still prefer Python in a lot of ways (least of all with Python being free/open), but Mathematica notebooks are nuts. You can do anything from calculus to charts, geographic visualizations, neural networks, NLP, audio processing, optimization, text processing, time series analysis, matrices, and a bazillion other things with a single command or by chaining them together. It has its warts, but is very polished. He also did some important early work on cellular automata if iirc. Then he wrote "A New Kind of Science", which reads like an ego trip and was not received well by the community (it is a massive tome that could have been summarized with a much smaller book). He also tried to claim discoveries from one of his workers due to some NDA shenanigans (or something along these lines iirc). The latter doesn't make him a crank, just a massive egotist, which is a trait nearly all cranks have. Sabine Hossenfelder did a video on him and how he only publishes in his own made up journals and generally doesn't use the process used by all other scientists. I think a lot believe where there is smoke, there is fire. To his credit, she also mentioned that some physicists gave him some critical feedback and he did then go and spend a bunch of time addressing the flaws they found.
- UltraSane 2y agoI sympathize with your opinion of him being a crackpot but he is also a genius and the idea is that the graphs in his theory are more fundamental than quantum mechanics and it would emerge from them.
- xwkd 2y agoI'm not even able to hold a candle to Wolfram intellectually- the guy is a universe away from me in that regard. But: Given a cursory look at his wiki page and Cosma Shalizi's review of his 2002 book on cellular automata [1], I feel fairly comfortable saying that it seems like he fell in the logician's trap of assuming that everything is computable [2]: >There’s a whole way of thinking about the world using the idea of computation. And it’s very powerful, and fundamental. Maybe even more fundamental than physics can ever be. >Yes, there is undecidability in mathematics, as we’ve known since Gödel’s theorem. But the mathematics that mathematicians usually work on is basically set up not to run into it. But just being “plucked from the computational universe”, my cellular automata don’t get to avoid it. I definitely wouldn't call him a crackpot, but he does seem to be spinning in a philosophical rut. I like his way of thinking (and I would, because I write code for a living), but I can't shake the feeling that his physics hypotheses are flawed and are destined to bear no fruit. But I guess we'll see, won't we? [1] http://bactra.org/reviews/wolfram/ http://bactra.org/reviews/wolfram/ [2] https://writings.stephenwolfram.com/2020/04/how-we-got-here-the-backstory-of-the-wolfram-physics-project/ https://writings.stephenwolfram.com/2020/04/how-we-got-here-...
- UltraSane 2y agoWolfram really loves to talk about computational irreducibility.[1] But I think his articles about Machine Learning are excellent. [2] [1]https://www.google.com/search?client=firefox-b-1-d&q=%22computational+irreducibility%22+site%3Awritings.stephenwolfram.com https://www.google.com/search?client=firefox-b-1-d&q=%22comp... [2]https://writings.stephenwolfram.com/category/artificial-intelligence/ https://writings.stephenwolfram.com/category/artificial-inte...
- Aardwolf 2y agoI do wonder if you'd want to implement a sort of 3D game engine that simulates the entire universe, if somehow the weird stuff quantum physics and general relativity do (like the planck limit, the lightspeed limit, discretization, the 2D holographic bound on amount of stuff in 3D volumes, the not having an actual value til measured, the not being able to know momentum and speed at the same time, the edge of observable universe, ...) will turn out to be essential optimizations of this engine that make this possible. Many of the quantum and general relativity behaviors seem to be some kind of limits (compared to a newtonian universe where you can go arbitrarily small/big/fast/far). Except quantum computing, that one's unlocking even more computation instead so is the opposite of a limit and making it harder rather than easier to simulate...
- drdeca 2y agoI don’t think the “not having an actual value until measured”, properly understood, would seem like an optimization. I don’t know why so many people feel like it would be an optimization? Storing a position is a lot cheaper than storing an amplitude for each possible position. One-hot vectors are much more compressible than general vectors, as you can just store the index. Also, it is momentum and position that are conjugate, not momentum and speed.
- Aardwolf 2y agoUgh, I just listed things from the top of my head, no rigorous correct physics! I'd be interested to know where those so many other people who feel that would be an optimization are, because I don't often see opinions like this at all, only either rigorous physicists posting equations and papers, or people not knowing anything about it at all to even philosophize about it.
- jules 2y agoThe universe is already modeled that way. Differential equations are a kind of continuous time and space version of cellular automata, where the next state at a point is determined by the infinitesimally neighboring states.
- mannykannot 2y agoMy first thought was 'ah, yes.' My second thought was 'but what about nonlocality?'
- harha_ 2y agoHow complex? I'm no physicist nor an expert at this, but AFAIK we aren't really capable of simulating even a single electron at the quantum scale right now? Correct me if I'm wrong.
- kergonath 2y agoWe can simulate much more than that, even at the quantum scale. What we cannot do is calculate things analytically, so we only have approximations, but for simulation that’s more than enough.
- whatshisface 2y agoOur present best guess is that cellular automatons would be an explosively difficult way to simulate the universe because BQP (the class of problems that can be related to simulating a quantum system for polynomial time) is probably not contained in P (the class of problems Turing machines can solve in polynomial time).
- canadianfella 2y ago[dead]
- zmgsabst 2y agoThe scales get you: You can’t simulate a molecule at accurate quark/gluon resolution. The equations aren’t all that complex, but in practice you have to approximate to model the different levels, eg https://www.youtube.com/playlist?list=PLMoTR49uj6ld32zLVWmcGXaW7w2ey7Vh4 https://www.youtube.com/playlist?list=PLMoTR49uj6ld32zLVWmcG...
- jcranmer 2y ago> Could a competent software engineer, even without knowing the fundamental origins of things like particle masses or the fine-structure constant, capture all known fundamental interactions in code? I don't think so. In classical physics, "all" you have to do is tot up the forces on every particle and you get a differential equation that is pretty easy to numerically work with. Scale is a challenge all of its own, and of course you'd ideally need to learn about all the numerical issues you can run into. But the math behind Runge-Kutta methods isn't that advanced (really, you just need some calculus to even explain what you're doing in the first place), so that's pretty approachable to a smart high schooler. But when you get to quantum mechanics, it's different. The forces aren't described in a way that's amenable to tot-up-all-the-forces-on-every-particle, which is why you get stuff like https://xkcd.com/1489/ https://xkcd.com/1489/ (where the explainer is unable to really explain anything about the strong or weak force). As an arguably competent software engineer, my own attempts to do something like this have always resulted in my just bouncing off the math entirely. And my understanding of the math--as limited as it is--is that some things like gravity just don't work at all with the methods we have at hand to us, despite us working at it for 50 years. By way of comparison, my understanding is that our best computational models of fundamental forces struggle to model something as complicated as an atom.
- cjfd 2y agoHorribly complex and/or impossible. (1) quantum mechanics means that there is not just one state/evolution of the universe. Every possible state/evolution has to be taken into account. Your model is not three-dimensional. It is (NF * NP)-dimensional. NF is the number of fields. NP is the the number of points in space time. So, you want 10 space-time points in a length direction. The universe is four-dimensional so you actually have 10000 space-time points. Now your state space is (10000 * NF)-dimensional. Good luck with that. In fact people try to do such things. I.e., lattice quantum field theory but it is tough. (2) I am not really sure what the state of the art is but there are problems even with something simple like putting a spin 1/2 particle on a lattice. https://en.wikipedia.org/wiki/Fermion_doubling https://en.wikipedia.org/wiki/Fermion_doubling (3) Renormalization. If you fancy getting more accuracy by making your lattice spacing smaller, various constants tend to infinity. The physically interesting stuff is the finite part of that. Calculations get progressively less accurate.
- russdill 2y agoTo go down this rabbit hole, the deeper question is about the vector in Hilbert space that represents the state of the universe. Is it infinite dimensional?
- cjfd 2y agoYes, but that is not saying very much. Just one single harmonic oscillator already has a state space that is an infinitely dimensional Hilbert space. It is L^2. Now make a tensor product of NF * NP of these already infinitely dimensional Hilbert spaces defined above to get quite a bit more infinite.
- IIAOPSW 2y agoWell, Newton thought he could do it with just 3 lines, and we've all been playing code golf ever since.
- mrguyorama 2y agoTo be fair, his universe was much simpler than ours. He didn't need a nuclear reactor or particle accelerator to transmute lead into gold in his theory.
- UltraSane 2y agoStephen Wolfram is trying to model physics as a hypergraph https://www.wolframphysics.org/universes/ https://www.wolframphysics.org/universes/
- gus_massa 2y agoYou (sorta) can! https://en.wikipedia.org/wiki/Lattice_QCD https://en.wikipedia.org/wiki/Lattice_QCD The trick is (as the sibling comments explain) that it involves an exponential number of calculations, so it's extremely slow unless you are interested only in very small systems. Going more technical, the problem with systems with the strong force is that they are too difficult to calculate, so the only method to get results is to add a fake lattice and try solving the system there. It works better than expected and it includes all the forces we know, well except gravity , and it includes the fake grid. So it's only an approximation. > Could a competent software engineer, even without knowing the fundamental origins of things like particle masses or the fine-structure constant, capture all known fundamental interactions in code? Nobody know where that numbers come from, so they are just like 20 or 30 numbers in the header of the file. There is some research to try to reduce the number, but I nobody knows if it's possible.
- Jach 2y agohttp://oyhus.no/QuantumMechanicsForProgrammers.html http://oyhus.no/QuantumMechanicsForProgrammers.html gives a flavor of one possible shape of things. It's pretty intractable to actually compute anything this way.
- UltraSane 2y agoOne of the real promises of Quantum Computers is being able to simulate quantum systems better.
- jfengel 2y agoThe formulas are really not very complex. The Standard Model is a single Lagrangian with a couple of dozen constants. https://visit.cern/node/612 https://visit.cern/node/612 You can expand that Lagrangian out to look more complex, but that's just a matter of notation rather than a real illustration of its complexity. There's no need to treat all of the quarks as different terms when you can compress them into a single matrix. General relativity adds one more equation, in a matrix notation. And that's almost everything. That's the whole model of the universe. It just so happens that there are a few domains where the two parts cause conflicts, but they occur only under insanely extreme circumstances (points within black holes, the universe at less than 10^-43 seconds, etc.) These all rely on real numbers, so there's no computational complexity to talk about. Anything you represent in a computer is an approximation. It's conceivable that there is some version out there that doesn't rely on real numbers, and could be computed with integers in a Turing machine. It need not have high computational complexity; there's no need for it to be anything other than linear. But it would be linear in an insane number of terms, and computationally intractable.
- baxtr 2y ago>The Standard Model is a single Lagrangian with a couple of dozen constants. I hear it's a bit more complex than that! https://www.sciencealert.com/this-is-what-the-standard-model-of-physics-actually-looks-like https://www.sciencealert.com/this-is-what-the-standard-model...
- jekude 2y agoI've always thought that gravity exists because without it, matter doesn't get close enough for interesting things to happen.
- tmiku 2y agoI'm surprised that more sibling comments aren't covering the lack of a unified theory here. Currently, our best understanding of gravity (general relativity) and our best understanding of everything else (electromagnetism, quantum mechanics, strong/weak force via the standard model) aren't consistent. They have assumptions and conclusions that contradict each other. It is very difficult to investigate these contradictions closely because the interesting parts of GR show up only in very massive objects (stars, black holes) and the interesting parts of everything else show up in the tiniest things (subatomic particles, photons). So we don't have a set of equations that we could expect to model the whole universe in any meaningful way.
- whatshisface 2y agoAt the level of writing a program to simulate the universe as we see it, ideas like classical gravity (see Penrose) would probably work.
- dumah 2y agoThey definitely wouldn’t work because we have strong evidence that relativity is a more accurate theory and significant evidence that either gravity does not obey an inverse square law or our estimation of the distribution or nature of dark matter is incorrect. https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation#Observations_conflicting_with_Newton's_formula https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gr...
- abecedarius 2y agoLess ambitiously, how small and clear could you make a program for QED calculations? Where you're going for code that can be clear to someone educated with only undergrad physics, with effort, to help explain what the theory even is -- not for usefulness to career physicists. Maybe still too ambitious, because I haven't heard of such a program.
- whatshisface 2y agoWolfram actually got his start writing these.
- antonvs 2y agoRephrasing what some of the other answers have said, with a decent knowledge of math you could write the program, but you wouldn’t be able to run it in a reasonable time for anything but the most trivial scenarios.