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Why Quantum Mechanics?
- golergka 5y agoGuy works in the space for 25 years and asks random strangers on the internet for their ideas. That's the level of humbleness I wish more people had.
- dboreham 5y agoQ1: because that wouldn't be consistent with simulation. Q2: because that's how the simulator works. Joking aside, I wonder if there's some principle that: physics will always look like you'd expect it to look if it's a simulation. Perhaps that's what Yang-Mills Gauge Theory is about?
- jiggawatts 5y agoI'm the type of person that likes to visualise the space of all possible theories of everything like a surface. A table, let's say. I like to imagine placing similar theories together, like stacking papers. Likely candidates closer to the middle of the table, fringe theories physically further away, under a pile of other junk. I've never been able to mentally put the "we're in a simulation" paper away. It's always been persistently plausible, and refuses to budge. A friend of mine keeps insisting that a lot of the complexity we see in physics stems from floating point arithmetic rounding error.
- sdwr 5y agoI'm partial to that idea too. I don't know much about the nuts and bolts of QM, but on the surface, entanglement and the observer problem lines up nicely with our universe being a lazily evaluated simulation, crunching numbers at the last second for our benefit like a game engine. It's all personal though, a fisherman sees God in the ocean, why wouldn't a programmer see God in complex digital systems?
- astrange 5y agoThe problem is that it doesn't explain anything, and so it might not be a theory. For instance, what is the simulation in? Is not being in a simulation even possible? Btw, I recommend reading Permutation City.
- jiggawatts 5y agoI've already read through most of Greg Egan's works, but it's good to see like-minded people out in the wild! Simulations can have explanatory power and can potentially have falsifiable predictions. One prediction of a simulated universe is that any such computer would be built on a budget. As in, you'd expect all aspects of the the compute substrate to have finite "limits" that manifest at the extremes of the simulation. For example: 1. Finite resolution -- Plank length. 2. Finite information propagation speed due to simple "update next cell based on neighbouring cells" simulation -- Special Relativity. 3. Finite (maximum) information density -- black holes. 4. Finite precision -- particle decay, "inherent randomness", etc... You can even explain General Relativity by saying that simulation chunks that are busy due to highly complex content fail to fully update their state and hence fall behind, appearing to have a slower progression of time. Neighbouring cells also need to "check" the state of the busy cells, and hence they're slowed down a bit also, which explains field curvature. Etc...
- deltaonefour 5y agoThe answer to these questions is one of those things that are beyond human understanding. It's like asking why does probability work? Why does predicate logic work? They are axioms. We have never looked beyond these axioms nor will we ever in your lifetime. I mean we may find a deeper mathematical model for quantum mechanics but the question of "why?" will never be answered. It may not even be the right question.
- moonchild 5y agoThat is an assumption. We do not currently know of any process by which we might explain these axioms; but: 1. We may still glean insight by reflecting on them, and 2. There may be unknown processes by which we can explain these axioms
- deltaonefour 5y ago1. All axioms are assumptions. 2. You mean Logic? The foundation which axioms and theorems themselves rely on? Logic is like a recursive axiom. We assume logic is true (aka an axiom) then, logic allows us to create axioms themselves and build theorems off the axiom. The thing with logic is that it's almost a thought driven endeavor. We don't need to observe the world to go deeper. But we can't. The buck ends here. To answer the question "why?" we have to go deeper, but there's nothing left.
- bawolff 5y agoWe may not find the answer, but it seems really different than say predicate logic. It seems easy to imagine a non-quantum world. I can't imagine a world where predicate logic doesn't work.
- deltaonefour 5y agoThe universe seems to be built in layers. Science, Math, and logic in that order with logic at the very bottom. So logic is always PART of the answer as it's just a layer on the bottom of everything. The thing is, I would imagine the answer to the question "why?" is on some hidden layer below logic. But the buck stops there. Even the very thought of predicting that there's a hidden layer has to involve logic. To get at the hidden layer we have to remove the upper layer of logic and therefore the process of thought itself. How is this even possible? We can't go further. It's beyond us. But I get what your saying. You think the answer exists on the side or the upper layers. Science and beyond.
- guerrilla 5y agoI've always liked these kinds of questions. Myself, I always wondered why specifically three dimensions. (Please don't start telling me about string theory.)
- lisper 5y agoI wondered that for a long time myself and recently stumbled on what I believe is (or at least is a good candidate for) the correct answer: planetary orbits are stable in three dimensions, but not any other dimensions. The anthropic principle therefore selects for three-dimensional slices/subsets of the wave function.
- guerrilla 5y agoThey're really not stable in two dimensions? Hmm [1], and another answer [2] (mentioned by Hawking apparently) but that's less convincing since there could be a 2D universe with intelligent organisms that just have their digestive systems on the outside... 1. https://www.reddit.com/r/askscience/comments/q8fmo/what_would_orbits_look_like_in_a_2d_universe/ https://www.reddit.com/r/askscience/comments/q8fmo/what_woul... 2. http://ion.uwinnipeg.ca/~vincent/4500.6-001/Cosmology/2-D_Digestion.gif http://ion.uwinnipeg.ca/~vincent/4500.6-001/Cosmology/2-D_Di...
- chaxor 5y agoRight hand rule only works in 3d and 7d
- lordnacho 5y agoThat is rather fascinating, where can I read about this?
- octoberfranklin 5y agoIn the early chapters of the Feynman Lectures on Physics (volume II) there is a really good explanation of why cross product and curl make absolutely no sense in more than three dimensions. The fact that they can be defined unambiguously is a complete accident which occurs only in three dimensions. Not sure if this is what GP was talking about. But the explanation there is excellent. It's in the chapter where curl is introduced for the first time. After you read it, you'll get annoyed whenever you see curls or cross products. Also: https://en.wikipedia.org/wiki/Seven-dimensional_cross_product https://en.wikipedia.org/wiki/Seven-dimensional_cross_produc...
- breuleux 5y agoGiven the infinite number of ways the universe could have been, it seems kind of a mathematical truth that whatever it ended up being was incredibly improbable to begin with. I would tend to say that unless it is logically necessary for the universe to be what it is, the question of why it is what it is necessarily lacks an answer. We should expect the universe to be improbable.
- guerrilla 5y ago> I would tend to say that unless it is logically necessary for the universe to be what it is Well that's what he's asking and what I was asking with the 3D question: is it logically necessary? Maybe it is. It seems like it could be in the case of 3D.
- breuleux 5y agoThat seems extremely unlikely to me. There are 1D and 2D cellular automata that are Turing complete and could arguably support life if they were scaled wide enough. Any virtual reality you can simulate on a computer could have been a physical reality. There isn't any requirement for it to have a spatial topology, there isn't any requirement for it to support life or any kind of complexity. Reality could have been a sprawling Mandelbrot fractal. Why not?
- platz 5y agoThis assumes a differnt universe could have been possible. What pool are you sampling from? What notion of probability are you relying on? scott is not asking what other universes were possible. he's asking to explain why QM must be true in the universe that we do observe.
- Koshkin 5y agoA trivial answer is that the question is moot, as this universe is the way it is precisely due to the laws of QM themselves. (Conceivably, in other universes, ones that we do not observe, the laws could be different.)
- 6gvONxR4sf7o 5y ago> why complex values amplitudes? If you multiply the left and right sides of schrodingers equation by its complex conjugate, do you still get an equation that the real valued square of the wave function solves? Can you do QM with just the real valued probability distribution? If you can, why not say that that’s the “real” thing, and factoring it is just a convenient way to solve it, same as imaginary solutions to quadratic equations.
- sam-2727 5y ago> Can you do QM with just the real valued probability distribution? You can't. The key fact is that other observables, such as momentum, depend on the complex part of the wave function.
- 6gvONxR4sf7o 5y agoBut those have real valued probability distributions too, right? Does modeling the evolution of the joint distribution of all the observables not count?
- ketozhang 5y agoYes you're right, every superposition of quantum systems have a real valued probability distribution for some observable variable. QM has very specific rules when it comes to how two random variables are dependent. That specific rule comes up when you have quantum interference and this is best described by the conjugate square of two complex functions A^2 + B^2 + A*B + B*A. This is just a special case of the union probability: P(A) + P(B) - P(AB).
- sam-2727 5y agoYes, but you have more variables than necessary. Why model all the observables independently when you can model the system with one complex wave function? It's the interaction between variables that is key.
- eigenket 5y agoThere is not really a meaningful joint distribution. Some quantum observables are incompatible with each other which essentially means they can't be assigned simultaneous values. More precisely a quantum observable is a map (a function) that takes in a quantum state and outputs a probability distribution, representing the probabilities of the various outcomes you could get if you measure that observable on that state. The equivalent statement is also true of classical observables and classical states. Under classical rules it turns out that if you have many observables acting on the same system you can come up with a joint observable, that maps a state to a joint probability distribution for all the observables. For incompatible quantum observables this is emphatically not the case. Given two quantum observables there is generally not a joint observable representing simultaneous measurement of them.
- AnotherGoodName 5y agoIf there's a loot box with a 50% chance of a cat in it, no game developer in their right mind would bother determining if there actually is a cat or not until someone checks.
- pishpash 5y agoSo some kind of efficiency principle at work? The universe does seem optimized in certain ways that make it mathematical.
- inter_netuser 5y agowhat are the optimizations you are talking about?
- rep_lodsb 5y agohttps://nethackwiki.com/wiki/Schroedinger%27s_Cat https://nethackwiki.com/wiki/Schroedinger%27s_Cat
- astrange 5y agoThat depends on if the developer wants to allow RNG manipulation speedruns or not.
- kolinko 5y agoActually, the opposite - a good dev would simulate two outcomes. Otherwise you may have a serious lag the moment someone opens up the box, because the system would need to simulate the cat’s behaviour for the past.
- trixie_ 5y agoRandomly found a link to this video on super determinism from his blog and found it super interesting. 100% agree, what is 'free will' anyways? A concept with no scientific definition. Why is it even used to explain anything in quantum mechanics? https://www.youtube.com/watch?v=ytyjgIyegDI https://www.youtube.com/watch?v=ytyjgIyegDI
- seiferteric 5y agoI think the question of free will is even simpler. It doesn't come down to determinism vs indeterminism because either way it's not "you" making a decision. At the lowest level (neuron or whatever) when a decision is "made" it is either deterministic (determinism) or probabilistic (indeterminism) based on physics but either way, where is the "you" in the process? Only way free will makes sense is if something supernatural is involved.
- GoblinSlayer 5y agoYou can't possibly hope for eliminativism to be meaningful? Like a computer is not on the level of a transistor, "you" is not on the level of a neuron, but on a higher integrative level.
- seiferteric 5y agoI mean I am saying it does not matter. If "you" is the sum of your experiences, genes and your environment programming your brain over time, but decisions are either deterministic or probabilistic, then "you" really had no input on how your brain/body would ultimately develop. It does not matter how complex your program is, each decision ultimately comes down to a process on the lowest level that you don't control.
- GoblinSlayer 5y agoPrograms have full input on what ultimately happens: the result completely depends on the program. There's no "you" on the lowest level, by looking there you don't see what happens to "you", so your claims about "you" aren't based on knowledge, but prejudice.
- kmckiern 5y agoSince boundaries can be very helpful: could many lower level theories ‘emerge’ to classical physics?
- cblconfederate 5y agoHe should consider the neuroscientific answer: The brain is a limited capacity model maker in a world that is only partially sensed. It was evolved to predict food and survival along the time dimension, not much more. Its model making is limited to extrapolating linearly (infinities) or nonlinearly (quanta) from initial conditions, and there is no guarantee it can make a full consistent theoretic universe. Even its notion of information is limited. It ponders many questions, mostly out of inertia, but not all questions are going to lead to useful answers, even the question 'why quanta'
- c01n 5y agoI will give it a shot :) Q: Because consciousness is all there is. Q2: Because you need consciousness to observe the universe as classical. Q3: Way over my head.
- feoren 5y agoYou seem to be asserting the anthropic principal, but in doing so you're assuming that quantum mechanics is required for consciousness. But that's not really an answer to this post -- he explicitly calls that out as a possible answer, but why is QM required for consciousness?
- naasking 5y ago> Q: Because consciousness is all there is. But then the question becomes, why exactly is consciousness manifesting in exactly this way as quantum mechanics? There is no escaping addressing this question somehow.
- cortexio 5y ago
- amelius 5y agoShow me a simpler theory that can explain chemistry. Without QM, slow electrons would just drop into the nucleus all the time. The question is odd and makes it seem almost like Aaronson knows all about theoretical QC, but little about actual physics.
- simonh 5y agoI think you misunderstand the post, he's not arguing against QM in any way at all, this isn't QM denial. He's just asking _why_ the universe is built that way.
- Koshkin 5y agoI think you may have misunderstood GP's point. Isn't asking "why" equivalent to asking "what if not"? There is indeed a subtle, but still a difference, from "arguing against."
- amelius 5y agoYou need something like QM to explain chemistry. And you need chemistry to explain life. To make a comparison, the laws that determine the movement of celestial bodies are closer to classical physics. There is no order in these bodies: galaxies all look very different. But molecules all look very similar, thanks to QM. You need this property for life to exist (you need e.g. replication, which can only happen if things easily turn out to be the exactly same, as with molecules). Therefore, my question: show me a theory simpler than QM that can explain chemistry. And then we can talk.
- simonh 5y agoThere isn’t one. I’ll say it again, he isn’t doubting QM. That isn’t what this is about.
- MichaelRazum 5y agoIm just taking the easy course of QM by Suesskind. He had an example like you have two coins and give them randomy to your kids. The they move far away. Then one kid discovers what it got, it knows what the other has. So what I dont get is why QM you could argue that there is some hidden shared state. Guess this is a typical question. But anyway I‘m somehow not convinced that it is really random.
- dskloet 5y agoYou'll be convinced once you understand the EPR paradox and Bell's inequality. So look those up if you want to be convinced.
- jiggawatts 5y agoI did, and they make perfect sense if you look at them through the lens of MWI, which however seems weirdly unpopular in QM circles. I was taught the Copenhagen interpretation, which is just... madness.
- bondarchuk 5y agoWhich interpretation seems to make the most sense depends a lot on the framing of the explanation, and not very much on the experiments themselves. This comment [1] really drove home the Copenhagen interpretation for me, I quote: >It's painfully easy to have a clear intuitive picture of quantum physics. You just have to ditch one concept. >Universe is not made of little balls. [1] https://news.ycombinator.com/item?id=29756842 https://news.ycombinator.com/item?id=29756842
- dskloet 5y agoThen I don't think I understood your question. I agree the Copenhagen interpretation doesn't make sense, mostly because I listen to Sean Carroll's podcast.
- Schroedingers2c 5y agoYou can think of scenarios in which any classical state (i.e. the shared state is completely specified by the local states of the two kids) does the task with some success probability that is upper bounded, say by 75%. And you can even include some unspecified hidden variable in your classical state and could even allow the two kids to share some classical randomness (think: each of them has a button that returns the same random number for both kids). This hidden variable could be anything (a single unknown property, a whole collection of unknown properties or whatever really) and represents possibly incomplete knowledge, for example due to imperfect microscopes or equipment. Since you don't specify what this hidden variable is, it encapsulates anything that is allowed by classical physics (remember we started out with a classical state). Now lets allow entangled states between the kids (states that can only be specified if you have both subsystems, locally if you measured such a state your result will look at least a bit random or even completely random). Then you can prove that the two kids can do the task (that has classical success probability 75%) with success probability ~85% all of a sudden. You can write down general inequalities that describe such behaviour and that's what Bell inequalities are. The fact that entangled states in quantum mechanics violate the classical bound (which you cannot break if you demand your two kids can only share states allowed by classical physics, even if you allow unspecified hidden variables), proves that nature is not classical. It doesn't prove that nature is quantum, it just proves that nature is not classical. Bell inequalities have also been unambiguously experimentally verified [1]. In conclusion, nature allows for two-party (or multi-party) states that cannot be described by just describing the local parts of it. There is no information in the local parts, but if you look at both parts together then there is information. Think "the whole is more than the sum of its parts". Classically, the whole is the sum of its parts. Classically, you read a book page by page. If your pages are entangled with each other, you could only read your book by looking at all pages together, because if you looked a single pages separately anything written there would look like random garbage to you. The question that remains is: Where is the information then, physically? In some sense you could say it does not exist before measurement, because only when you look at the correlations between the local measurement results of the two kids will you find out that the underlying state must have been entangled (which you get to know if the state violates a Bell inequality). But that is just one possible interpretation, there still is a lot of scientific debate about what quantum mechanics really means. These are exactly the scenarios that make quantum so weird but fascinating at the same time. [1] https://www.nature.com/articles/nature15759 https://www.nature.com/articles/nature15759
- galaxyLogic 5y agoThere is a simple answer to the proposed question(s): Parallel Universes. Some of them might have classical physics only.
- dojitza1 5y agoI'd go as far as to offer an explanation like this: The universe/multiverse is infinite in every (by our brains) comprehensible and incomprehensible form. Both on a macro and a micro level. Our existence is finite in nature, both in space dimension (objects have edges) and time (they change form). It is understandable we have trouble interpreting some of the rules of our universe that we are unable to comprehend. I say quantum mechanics (and perhaps natural science in general) are our attempt to make sense of something fundamentally not comprehensible.
- _Nat_ 5y ago> 4. To keep the discussion focused, in this post I’d like to exclude answers along the lines of “but what if QM is merely an approximation to something else?,” [...] imagine that, as fantastical as it sounds, QM were not only exactly true, [...] Seems like an absurd, conceptually-crippling stipulation, analogous to asking why [the fine-structure-constant is exactly 1/137](https://en.wikipedia.org/wiki/Fine-structure_constant#Numerological_explanations_and_multiverse_theory https://en.wikipedia.org/wiki/Fine-structure_constant#Numero... ). I mean, while one might reasonably wonder why alpha~=1/137, wondering why alpha=1/137 exactly doesn't seem like a simplification but rather a different question that'd invite a different sort of reasoning.
- octoberfranklin 5y agoDude, what are you talking about, the fine structure constant is exactly 1/137. The TimeCube [1] told me so. [1] https://en.wikipedia.org/wiki/Time_Cube https://en.wikipedia.org/wiki/Time_Cube
- rocqua 5y agoThis limitation is not because Scott things to know with certainty QM is true. This limitation is because Scott is wondering "Is there a way to explain QM in a way that makes QM an obvious conclusion". That is an interesting question regardless of whether QM is true.
- platz 5y ago#4 isnt about the accuracy of the fine structure constant. #4 is about limiting the discussion to QM as opposed to dealing the claim that QM is incomplete - that maybe the only reason it gives us probabilities for events is because its incomplete, and maybe theres a deeper theory that would supersede QM; this line of reasoning would not be productive to scott's initial question, which is focused on the nature of QM, given that it is true in a fundamental way.
- Dumblydorr 5y agoQ1: Why didn’t God just make the universe classical and be done with it? What would’ve been wrong with that choice? Why mention God? If you're attempting a scientific stance, starting your initial question with an unproven deity who doesn't want us to eat meat on Fridays part of the year, why? Why include that, it's an instant turnoff to any evidence-based reader.
- messe 5y agoI think you're reading far too much into that. Anecdotally, I'm as atheistic as they come, and I don't have a problem with that. It even echoes Einstein's famous quotation "God does not play dice with the universe".
- criddell 5y agoMany evidence-based readers don't mind when a bit of poetic language creeps into technical or scientific writing.
- MathCodeLove 5y agoI think your assumption that he meant the Christian monotheistic god may be the problem. Maybe that's precisely what they meant, but I find more often in these kind of discussions its meant as a placeholder for "The event/entity/unknown source of the universe." I'm an atheist myself and find no issue in the use of the word God here. We don't know with any certainty how the universe was spawned into being, using God as a sort of shorthand to state as much isn't a problem.
- platz 5y agoReligion isn't relevant to the question scott is pursuing and neither is your aversion to it.
- GuB-42 5y agoWhy assume a specific deity? There is nothing in that text that assumes that this is the god Christians believe in. For all we know, it could be the Flying Spaghetti Monster. I don't think there is a problem in mentioning God as a shorthand for "whatever caused the universe to be the way it is and cannot be proven". Like axioms in maths, you need some unproven assumptions to do something, otherwise you get ridiculous situations like Boltzmann brains. Q1 could be understood as "why is the universe so weird as to require quantum mechanics?" It is undecidable, just like god is, but it makes the point that quantum mechanics may take us a bit too far. For example, it may result in said Boltzmann brains, and once you get to that point, the science become meaningless. The maths of quantum mechanics check out, this is unquestionable, but the article is about the deeper implications, at the limit of philosophy. If you are in the "shut up and calculate" camp (which is fine), it may be meaningless to you, but I don't think it is an unscientific debate.
- stared 5y ago> Why didn't God just make the universe classical and be done with it? What would've been wrong with that choice? I hear it over and over and still don't understand the premise. Classical mechanics is not something sacred. It is our first serious model of physics. Our first approximation is based on the scales at which we operate and our senses as humans. Furthermore, even "regular" quantum mechanics is a non-relativistic, low-energy approximation of Quantum Field Theory. It is like asking why God created clouds, not just "waters above the filament"? That said, Q2 minus Q1 is an interesting question.
- platz 5y agoIt seems like you misunderstood the actual question. It attempting to get at why QM might be inevitable, not why classical mechanics is
- stared 5y agoWell, the very quotation treats classical mechanics as a reference. Q2 minus Q1 is much more interesting: why this specific theory (i.e. quantum mechanics), rather than anything else.
- platz 5y agoQ1 answers the anything else part, not Q2 which is only limited to variations of properties of QM.
- naasking 5y ago> Well, the very quotation treats classical mechanics as a reference. Yes, as a reference for an alternative possible world. Other alternatives discussed are cellular automata.
- stared 5y agoTo elaborate on this a bit: One may argue that "a state" is a simpler concept than "a superposition of all state". Even in pure mathematics [1], I don't think that (say) real numbers are less fundamental than natural (unlike Kronecker in "Natural numbers were created by God, everything else is the work of men"). What's true for the set theory route, does not need to be true for any possible mathematics, including those created by other species. For me, it is perfectly conceivable that some aliens use Hilbert space, and for them natural numbers are a particular concept (finitely dimensional vector -> n=1 -> zeros of sin(𝜋z) = 0 & Γ(z+1) is finite, or something in that line). In this sense, if you understand quantization as a map between a set (e.g. {0, 1}) and a vector space over a set (e.g. |psi> = a |0> + b |1>), then it is harder within this conceptualization. For aliens, "a basis state" (i.e. |0> or |1>) might be not an object worth studying on its own. When it comes to the path from classical to quantum physics - yes, it is full of question marks. The only hints I know come from "Quantum principle of relativity" by Dragan & Ekert (previously on arXiv with a more inflammatory title, "Why devil plays dice?"). Yes, there is a contrast with cases, in physics, in which a more advanced theory could be deduced purely with the elimination of inconsistencies, or strive for mathematical beauty, e.g.: E/M -(symmetry)-> Maxwell equations -(Minkowski transformation)-> Special Relativity or non-relativistic quantum -(SR)-> Dirac equation -(Klein paradox)-> QFT At the same time, I think it is a wild hypothesis that "any physics theory point to a more advanced theory only with its own ugliness and inconsistencies". Furthermore, like almost anyone, I used to believe that it is always possible to reduce a "more advanced" theory to a "less advanced" one. Sure, for SR you take v/c << 1 and you are done. For anything dealing with emergent phenomena, well - it is (IMHO) not as straightforward as it may seem at the first glance. Decoherence is one of these cases. For even simpler ones - how to turn molecules of water into their macroscopic properties (temperature, pressure, viscosity). Yes, we can do it (well, with T and p, but still - not viscosity); but if we haven't seen any field in our life, we would not ask such questions in the first place. Even the concept of temperature would be some arbitrary, made-up quantity. Anecdote on a students' conference there were two talks after each other - one on bubbles in beer, and the other - C-star-algebras. The latter claimed that it is the more fundamental, ergo better, way of dealing with physics. Iwo Bialynicki-Birula (theoretical physics) smiled and asked the second speaker: "And how would you derive the beer bubble from C-star-algebras?") [1] Disclaimer: I believe that mathematics is created by humans, not something existing on its own. An abstraction of our language, and our sensory experiences. If we were a slime mold, maybe we wouldn't come with the idea of integers at all. Evolutionary speaking, integers are an abstraction over counting own offsprings, and perhaps - estimating strengths of groups when hunting or protecting. As a side note, it was really fun to have a longer conversation with Penrose, having very different views (also: I am Everettian, and have a naturalistic view towards consciousness, in the spirit of Dennett). After that, I got a clear idea that "the root of all misconceptions" is the assumption that mathematics exists beyond a human concept.
- ninkendo 5y ago> As in, “I’m 100% fine with living inside a Matrix … I just want to understand why it’s a _unitary_ matrix!” Best quote from the article right there. I love Scott's writing style... highly recommend his book "Quantum Computing Since Democritus" if you're into his blog.
- platz 5y agoagreed!
- cannabis_sam 5y ago>Why didn’t God just [MAKE THE PLANETS ORBIT AROUND EARTH] and be done with it? What would’ve been wrong with that choice? Okay then, can you explain the math behind that solution? How in the world does the words “God”, “just” and “be done with it” in anyway whatsoever help elucidate this issue…?
- platz 5y agoYou're either getting caught up in the incidental religious reference, or failed to interpret Scott's conciseness. See this comment for elaboration on exactly what kind of counterfactual Scott is asking https://news.ycombinator.com/item?id=30117928 https://news.ycombinator.com/item?id=30117928 . He's asking about a hypothetical alternative in a very specific way, which is to see whether it sheds any light on the logical foundation of QM, not just to consider alternatives for the sake of considering them in themselves. Scott's aim is to understand QM better.
- cannabis_sam 5y agoAlso, can you at least attempt to mathematically explain a QM+“god” argument?
- cannabis_sam 5y ago>he's asking about a hypothetical alternative in a very specific way, which is to see whether it sheds any light on the logical foundation of QM Could easily be done without any references to an omniscient, omnipresent and omnipotent concept with exactly zero scientific evidence. Even worse the whole concept of God literally defies logic, so mixing god into this discussion is laughable, if it didn’t come from an authority in the field of QM. I have a lot of respect for Scott, but IMHO he would be more persuasive if he left his religious beliefs out of this argument. >Scott's aim is to understand QM better. How does referencing god help with this endeavor? Btw, the comment you linked commits the exact same fallacy of assuming anthropomorphic qualities behind whatever created the universe…
- Eratosthenes 5y ago> Why didn’t God just make the universe classical and be done with it? He did. Physicists just never managed to properly grapple with the concept that classical mechanics involves action-at-a-distance.
- simiones 5y agoNothing in classical mechanics can explain the double-slit experiment; nor the relativity of simultaneity. Furthermore, action-at-a-distance (non-locality) makes classical mechanics inconsistent even with itself, so it's a non-starter (it implies grandfather paradoxes).
- Eratosthenes 5y agoFundamentally, orbital mechanics still relies on the same old action-at-a-distance that plagued Newton. You can look under the hood of any software that simulates orbits and see that this is the case. No time delay is assumed for gravitational interaction. Celestial bodies effect each other's orbits instantaneously (the Poynting-Robertson effect also makes this obvious). IF you assume that photons have mass and interact gravitationally (there are good reasons for making this assumption), then you can explain the double slit experiment classically via gravitational interaction.
- simiones 5y ago> IF you assume that photons have mass and interact gravitationally (there are good reasons for making this assumption), then you can explain the double slit experiment classically via gravitational interaction. No, you can't. The double slit experiment has nothing to do with mass or gravity. It is well known that it happens with electrons, protons, and has even been demonstrated with some large molecules (thousands of atoms). Gravity can't explain anything about it though. And even if I can imagine some gravitation-based interactions in the case of a stream of huge numbers of particles (though not the actual quantitative explanation), the double slit experiment has been reproduced with things like 1 photon emitted every hour - over the course of a few days, the same interference pattern emerges IF the photon's path is NOT observed; but NO interference pattern emerges if the photon's path IS observed. > You can look under the hood of any software that simulates orbits and see that this is the case. No time delay is assumed for gravitational interaction. The fact that simulation software takes shortcuts to make its computations feasible is not proof that this is how the world works. Einstein's GR equations are famously intractable to solve in their base form, and approximations are strictly necessary. But given the distances and observational precision for the positions of planetary objects, I would bet the effect of gravitational waves having a finite speed is negligible for most predictions. Not to mention, we have actually measured the speed of gravity: we have detected gravity waves and they are moving at the "speed of light", or as near to that as we have been able to determine. Definitely not instantaneously. > the Poynting-Robertson effect also makes this obvious That is a General Relativity effect, which assumes that gravity is a local interaction (i.e. no action at a distance). That is precisely Robertson's contribution to the Poynting-Robertson effect, per the WIkipedia article (Poynting first understood the effect, but described it in terms of the luminiferous aether).
- Leary 5y agoBecause we're in a simulation. And they used a quantum computer to run it.
- YeGoblynQueenne 5y ago>> By my age, Einstein had completed general relativity, Turing had founded CS, won WWII, and proposed the Turing Test, and Galois, Ramanujan, and Ramsey had been dead for years. I fee confused when an article begins with a blatant exaggeration about a subject I am cognisant in right off the bat because then Idon't know how much I can trust it when it speaks of subjects I don't know. To wit, Turing did not win WWII and didn't found CS. Turing wrote a seminal paper in early computer science, but he didn't found the field of research called "computer science". To be honest, I have no idea who would rightfully deserve to be recognised as the founder of computer science, when there have been many contributions of the same value as Turing's, the most obvious examples being Church and Von Neumann, less well-recognised ones being Charles Sanders Peirce and Henry M. Sheffer, Claude Shannon, Conrand Zuse and others (Church described a theory of computation equivalent to UTMs; Von Neumann proposed the accursed Von Neumann architecture; Peirce and Sheffer described logic gates and showed the completeness of the NAND gate; Shannon proved the completeness of Boolean logic circuits; Zuse made the first programmable computer -Babbage only designed the first). And so on. In my mind, trying to ascribe feats to heroes that they never performed, diminishes, rather than exalts, the hero. Turing doesn't need any extra serving of praise for things he didn't do to be known for ever as one of the greats of CS.
- ericpauley 5y agoPerhaps this comes down to having more context on Scott Aaronson's work and writing, but this section to me came off as humorous front matter, not some attempt to precisely characterize the history of computer science. See the front matter of his book (Quantum Computing Since Democritus) for more context on this. On the actual meat of the post, Scott Aaronson is a definite authority figure (among others) on these topics especially as they relate to computing.
- YeGoblynQueenne 5y agoMnyea, you're probably right and that just flew over my head. No surprise- I remember being told that my sense of humour was removed at birth...
- dekhn 5y agoHuh. What he's not talking about is QM, he's talking about the enormous math industry that built up around QM. Actual QM is experiments in labs with lasers and cryocooling. You can sit around with your complex amplitudes and fancy math but none of that is really necessary to appreciate or make forward progress in the actual underlying physics. Sort of like string theory. Not exactly, but sort of.
- GoblinSlayer 5y agoApplied physics doesn't work without fundamental physics. Can you prove experimentally whether FTL communication is possible? How would you make progress there?
- dekhn 5y ago"Prove" FTL impossible? No. however, based on everything we know today, superluminal communication will remain impossible, and if it does become possible, will raise all sorts of interesting implications.