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Our reality may be a sum of all possible realities
- bbayles 4y agoFor a contrary perspective, see https://www.math.columbia.edu/~woit/wordpress/?p=13367 https://www.math.columbia.edu/~woit/wordpress/?p=13367
- deleted 4y ago[deleted]
- indigodaddy 4y agoAs if I’m a ten year old, because I kind of am when it comes to this kind of stuff… how in the world could adding up all alternate realities end up with a single reality? How would that work?
- User23 4y agoMost of them cancel out. Think of it like summing an infinite array of an equal number of 1 and -1 and then a 2. The sum of that array is 2.
- travisjungroth 4y agoMight be easier if you start with the 2 :P
- whatshisface 4y agoIf we station ourselves outside of the quantum system, then the answer is that each reality puts a complex number on every outcome, which get summed into a single complex number. Then, the magnitude squared of that sum becomes the probability with which we will observe that outcome. If we put ourselves inside the system then saying anything about it comes with a lot of implied philosophy about what "we" are.
- jwuphysics 4y agoI don't have a good answer for you, but the best advice I'd say is to read Feynman's book "QED: the Strange Theory of Light and Matter" (it's really just a four part lecture series).
- krohling 4y agoThe path integral suggests that all of the possible realities are like waves. When these waves are added up, they can interfere with each other in a way that only one of the possible realities can be seen. It's like when you throw two stones into a pond at the same time. The waves created by the stones will interfere with each other and create a single pattern on the surface of the water. In the same way, the path integral suggests that all of the possible realities can interfere with each other and create a single reality.
- indigodaddy 4y agoGreat explanation, quite fascinating thanks!
- krohling 4y agoThanks for the kind response. I actually generated that comment by feeding parts of the article into ChatGPT and asking it the previous comment. If you would like to ask it more things about this article I have it searchable here: https://app.conifer.chat/threads/37321fdc-6a04-4c56-a857-21bc97d5e95d https://app.conifer.chat/threads/37321fdc-6a04-4c56-a857-21b...
- thriftwy 4y agoAlternative realities may have alternative people living in them - will they observe different laws of physics since their reality is not a sum of all realities, as opposed to ours? Or would they have the same conclusion about sum of realities? A) these realities can't have people - they're not real enough to be called that B) physics will be different - that would be a great scientific revelation C) physics will be the same - making the premise meaningless
- slewis 4y agoIt’s also surprising at first that infinite series can add up to a specific, finite number. If I go halfway to X, halfway again, and so on, where do I end up? All next realities are weighted based on their probability given the current one. The probabilities are based on our knowledge of the equations of physics. Some realities are more likely than others and adding this all up results in an average outcome. At the smallest scales the average outcome is not actually what happens, but time is a great equalizer.
- osigurdson 4y agoLots of things are like that. An infinite number of sine waves are needed to make a square wave for example. Taylor series expansion, etc.
- CamperBob2 4y agoAn infinite number of sine waves are needed to make a square wave for example. And even then it only really works if the waveforms are infinite in duration. Is there a Gibbs Phenomenon equivalent for path integrals?
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- jemmyw 4y agoThe problem here is the word "realities" because it doesn't in any way mean an alternate reality where you're there doing something else. This is from the math model where the resulting path of a particle can be figured out by finding all possible paths. Then what follows is the conjecture that because the math works maybe those particles really do travel by every possible path. There's no proof of this, and it's very hard to test because the result has to be the same. So maybe our reality is the sum of particles taking every possible path. Or may be it isn't. Wake me up when the article title is "Our reality IS the sum of all possible realities."
- nine_k 4y ago"Our" reality is not necessarily the only one, or is somehow special: under the many-worlds interpretation, every "quantum event" forks the universe. It should look somehow similar to "updating" a typical immutable data structure (a tree, a list) so that a new copy is created, sharing most data with the old copy. https://en.m.wikipedia.org/wiki/Many-worlds_interpretation https://en.m.wikipedia.org/wiki/Many-worlds_interpretation
- wyager 4y agoYou wouldn't necessarily end up with a single reality, but if there was some kind of process "sampling" a finite number of realities from the wavefunction (either continuously, e.g. if quantum collapse is ontic, or e.g. at some time in the distant future god takes a look at the state of the wavefunction) where the sample probability was calculated in the normal way (square of the wavefunction magnitude), that would explain how probability "gets into" quantum mechanics. This is kind of an open question, though - you can find plenty of papers (mostly bad) wondering out loud how you get the appearance of "discrete" realities with things like probability when quantum mechanics appears to be continuous.
- puzzledobserver 4y agoI skimmed the article, and admittedly didn't understand much. Action principles and path integrals are unfortunately one step above where my knowledge of physics stops. But seeing a headline that reads, "Our reality may be a sum of all possible realities", I wonder whether the point is to (a) explain new experiments, (b) develop simpler mathematics, (c) close the gap between intuition and theory, or (d) whether this is all unfalsifiable speculation. A charitable interpretation might be (c), but a skeptic within me thinks that this might be (d).
- whatshisface 4y agoPath integrals are for (a) and (b), but take that with the knowledge that Feynman came up with them maybe 70 or so years ago, so that anything we say about it now tends towards (c) and (d) by virtue of a lot of the (a) and (b) questions already being taken care of.
- babyshake 4y agoSometimes the discussion I observe among scientific experts resembles the type of discourse I've seen from Marvel fans debating the finer points about multiverses and incursions within their comic book canon.
- skissane 4y agoI think one problem here - physics and the philosophy of physics are two different things, but a lot of people (even professional physicists) fail to treat them as distinct in practice. So long as we are talking about math, observation and experiment, that’s physics. But many of these “multiverse theories” are moving beyond that into philosophy, because they are not about the math, but rather how to interpret it; not only are existing observations or experiments are insufficient to determine their truth or falsehood, but we often have no idea of any practically feasible way to test them. There’s nothing wrong with doing philosophy-but let’s be honest when we are doing it, rather than pretending it is still just physics. Furthermore, your average professional physicist has indubitable expertise in physics, their expertise in philosophy (even the philosophy of physics) is much more variable.
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- adamnemecek 4y agoSounds like a convolution.
- lukeplato 4y agoIndeed, then the fundamental object would be a kernel much like the cosmological polytope or amplituhedron
- adamnemecek 4y agoFunction composition is convolution of unit impulses.
- consilient 4y agoThis is approximately right, time-evolution of a spatially homogeneous system is convolution of its initial state against the propagator `K = \int e^{iS[x]} Dx` over all of space - with the caveat that none of this is quite true. These aren't really integrals, `Dx` isn't really a measure, and fully rigorous interacting QFTs in 4d may or may not exist.
- juliangoldsmith 4y agoEach year is just another round of stochastic gradient descent, optimizing for the darkest timeline.
- User23 4y agoIt was Feynman’s excellent QED (basically the ELI5 for quantum physics) that introduced me to the concept that the photon I shine on my wall with a flashlight did a few orbits around Jupiter too, it just cancelled out. I believe the “dippy” process to do that is called renormalization. Feels like it’s time for a reread.
- CyberDildonics 4y agoYou think that when you turn on there are actual photon particles that traveled 48 minutes to jupiter and back?
- evanb 4y agoOne absolutely astounding aspect of the path integral is that it ascribes amplitudes to trajectories that don't obey the (classical) equations of motion. If you like: the classical paths are at turning points of the action (loss function) but all other paths have some associated imaginary loss. In the path formalism we sum every possible path, weighted by the imaginary loss. Since the classical paths are at turning points, small deviations around that path tend to sum coherently, while large deviations tend to have neighboring paths that contribute with opposite phases. If you write the amplitude for a photon going from your flashlight to your wall, the path integral tells you to sum up all possible paths, not just the classical ones. So yes, the path integral formalism really does say that a photon goes from the flashlight, around Jupiter, and to the wall. But not in 48 minutes! In time = (distance to wall)/c! It goes every which way without caring about the classical law. The "insane" ones cancel. Well, if all the insane ones cancel, what's the point of all this? Just forget about them, they're a huge surplus of nonsense in the theory! However, it's perfectly possible to construct experiments where it's clear that photons really do "smell out" alternatives. Diffraction gratings, the double-slit experiment, etc., all show this quantum weirdness.
- CyberDildonics 4y agoAre there any other household appliances that emit photons that circle around any other planets?
- pbj1968 4y ago[flagged]
- osigurdson 4y agoIf true, the most important thing for us is to find out how to construct a filter such that the bad realities are suppressed.
- Rinum 4y agoSounds like the TVA - https://en.m.wikipedia.org/wiki/Time_Variance_Authority https://en.m.wikipedia.org/wiki/Time_Variance_Authority
- LargoLasskhyfv 4y agoOr https://en.wikipedia.org/wiki/The_Adjustment_Bureau https://en.wikipedia.org/wiki/The_Adjustment_Bureau , https://en.wikipedia.org/wiki/Timecop https://en.wikipedia.org/wiki/Timecop , https://en.wikipedia.org/wiki/Val%C3%A9rian_and_Laureline https://en.wikipedia.org/wiki/Val%C3%A9rian_and_Laureline , https://en.wikipedia.org/wiki/The_One_(2001_film) https://en.wikipedia.org/wiki/The_One_(2001_film)
- dclowd9901 4y agoWe can’t even agree on an objective version of reality and you want someone to determine which ones are “bad.”?
- flangola7 4y agoI don't see why that should be any harder than the AI alignment problem
- osigurdson 4y agoEverything must be objectively awesome in one of those realities. I'd pick that one.
- crazygringo 4y agoI read Feynman's QED back in high school and was fascinated by it, but always had a lingering question. Sure the math works out by summing all possible paths, and then most of them usually cancel each other out, and so you're left with the ones that mostly contribute to the actual probabilities, as complicated as those can still be. But I always suspected... surely that just has to be one mathematical way of looking at it. That at some point we'd discover that turns out to be mathematically identical to something else that would be a bit more local, a bit more intuitive, a bit more straightforward. That never even had to deal in the first place with the infinity of paths that all wind up cancelling each other out anyways. So now that I'm on a forum with smart people, the kind I didn't have access to back in high school... has there been any progress towards something like this at all? Are there any directions for this? Or is there a conceptual reason I'm missing why this fundamentally isn't possible, why the sum of all possible paths is the only way to account for certain behaviors?
- whatshisface 4y agoYou are never going to get the locality you're hoping for, because of Bell's theorem.
- elteto 4y agoI think the current state is very much “the formulas work, don’t get too philosophical with them though”. IANAP.
- andreareina 4y agoThat's more about Copenaghen vs Many Worlds vs Pilot Wave... The infinite path integral is heavy mathematical machinery so it's avoided if possible.
- evanb 4y agoThe path integral is used for computational approaches all the time.
- zeroonetwothree 4y ago
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- vouaobrasil 4y agoThis title really irks me. Basically it is saying that quantum states or possible paths are realities. But the very definition of reality is what we experience, so how can a quantum state, be a separate reality? The article mentions reality 5 times, not explaining what it even means by the word "reality". While there may be some philosophical content to the statement, it is not a well-defined physical statement and moreover, the article doesn't show any "evidence" for it assuming that there is even a valid way to interpret the title. I've come to expect this type of artilce from Quanta Magazine though.
- 3np 4y agoThe title irks me for a different reason. An improvement would be "Reality Considered As a Sum of All Possible Realities". This is an interpretation/model you can choose. It doesn't seem falsifiable or provable. "The sweater I wear today may be a sum of all sweaters is my wardrobe" - yeah, it is if you choose to think of it that way.
- Rury 4y agoIt irks me, because I find the title reads similar to: "Our possibilities may be a sum of all possible possibilities". Or shorter "What's possible is the sum of all that's possible". It's like, well no duh? If it doesn't read like that, then I too find it irksome for the aforementioned reasons.
- goatlover 4y ago> But the very definition of reality is what we experience If you're an anti-realist when it comes to science. I suspect a lot of scientists think there's plenty of reality we don't experience, such as quarks, dark matter or the interior of black holes. Or what lies beyond our light cone (probably a lot more of the same), given the flat topology that's been measured. Sean Carol has argued for the Many Worlds Interpretation being a true description of reality, even though we can only experience the decohered branch (world) we're on.
- layer8 4y agoOne way to look at this is that there is no difference between possibility and reality. If there was, then the question would arise why only this one particular possibility is real, while the other possibilities aren’t. If there is a necessary reason for why this particular possibility is real, then that would mean that the other possibilities aren’t actually possible after all. If, on the other hand, there isn’t any such reason, then that would mean that the fact that this particular possibility happens to be real is fundamentally arbitrary. Personally, I find it more plausible, in a parsimonious Occam’s razor sense, that everything that is logically possible actually exists, because the only other option is arbitrariness, the lack of any explanation even in theory. Whether summing up path integrals makes sense, is however a different question.
- elecush 4y ago"the whole is greater than the sum of its parts" - Aristotle a long time ago
- mewse 4y agoInterestingly, Zeno had said the exact opposite, a hundred years earlier -- that since a 'whole' could be divided into an infinite number of smaller 'parts', which themselves could be divided ad infinitum, that these infinite parts when summed up must be far greater than the whole. Which was the basis for nearly all of his popular paradoxes. (And then Newton and Leibnitz, some two millennia later, spoiled everybody's fun by developing the integral calculus such that whole categories of amusing philosophical conundrums became utterly mundane mathematical word problems with rigorously defined correct answers)
- neom 4y agoDoes that make me the mean me? Am I the most mediocre of me's? Or does this mean I'm the best me? Is everyones reality discreet to themselves? Or is this the sum of all possible observable realities by everyone?
- lukeplato 4y agoPeter woit recently wrote on this topic in 'The Trouble With Path Integrals': - https://www.math.columbia.edu/~woit/wordpress/?p=13319 https://www.math.columbia.edu/~woit/wordpress/?p=13319 - https://www.math.columbia.edu/~woit/wordpress/?p=13367 https://www.math.columbia.edu/~woit/wordpress/?p=13367
- wyager 4y agoIt seems like Woit is kind of intending this to serve as a refutation of PIF, but I don't really see why - this sounds more like a description of some problems that are hard in PIF, rather than anything wrong with the underlying theory.
- consilient 4y agoAs an organizational scheme for approximate numerical calculations, the path-integral formulation is fine. But path integrals can't serve as a rigorous foundation for QFTs, because for the most part they don't actually exist. The high-frequency behavior Woit describes is one obstacle; the fact that no infinite-dimensional Lebesgue measure is possible is another. There are others. Presumably there's some mathematical object out there that captures all the data a path integral ought to have without its pathologies, but no one knows what it is yet.
- laserbeam 4y agoIf you're going to talk about Feynman's equations and use the double slit experiment as an illustration instead of using Feynman diagrams (good explanation by pbs space time here https://youtu.be/fG52mXN-uWI https://youtu.be/fG52mXN-uWI), I'd say you're doing the concept a disservice. Extrapolating that to philosophy is usually risky, especially when doing it to a general audience. Also, I feel we should stop trying to explain quantum physics approximately AND do philosophy based on it in short articles. It's too hard to convey that "a possible reality" may mean something else than you traditionally expect in quantum mechanics, or that it's an interpretation of what the math implies. A general public always leaves with an inaccurate impression of what was written.
- superposeur 4y agoThere’s an aspect of path integrals that’s always bugged me. They rely on an underlying classical field configuration space to integrate over. But, this seems problematic to me, since properly the objects of classical physics should emerge as limits of quantum physics. Shouldn’t we be able to start with “pure” quantum mechanics (a state space, a Hamiltonian operator), with no mention even of “paths” and get out classical physics? I.e. it seems backward to speak of a particle trying out different paths since a “path” is a classical notion; it’s as though quantum mechanics is merely a superstructure on top of an underlying classical layer rather than the other way around. Know what I mean?
- mlloydw 4y agoQuantum and Newtonian physics are both just conceptual models to help ourselves understand and predict the things around us. They're useful for describing reality but neither of them are accurate representations of the real deal. All models break down at some limits. To imagine one model "being merely a superstructure" on another implies that the limit doesn't exist and the two models are, in fact, the same thing. If you expand that idea to all other models, they would all eventually merge into one grand unified theory that accurately explains every single occurrencence in the universe. A nice idea conceptually, but we're at best no where near that and at worst have brains that will find the nuance of the universe impossible to comprehend in totality. Any model that is useful for understanding and predicting the universe is worth sticking with, as long as you understand the limits where it applies. If path integrals happen to unlock some new insight that seems evidentially correct, it doesn't really matter if it ties into other theories.
- fluffycookie 4y ago[dead]
- fuzzfactor 4y ago>Our reality may be a sum of all possible realities OTOH I would say there's a number of possible realities that never did add up. Some of the actual realities also.
- k__ 4y agoThat's what the article says. If they're too different, they cancel out.
- malthaus 4y agoi'm way too dumb to understand quantum mechanics and all its implications but i love to believe in quantum immortality and surfing all those possible realities to infinity - the most optimistic, while somewhat grounded in science, approach to thinking about life & death imho
- deathgripsss 4y agoQuanta really is one of the best science websites around these days
- hartator 4y agoCan someone explain why "the future is already written" theory doesn't work to explain quantum effects? If we see the world as a book and we are in the middle of it, we don't need string theory, multiverse, or this new theory to explain quantum effects.
- fallingfrog 4y agoWell, that seems vague, but here are some of the things about quantum physics that people find odd: 1) We intuitively think of the past as certain and the future as unwritten. You seem to be suggesting that both are written. But quantum physics says that both are unwritten. So it's exactly the opposite. Just as there are many possible futures from this point, there are also many pasts leading to this point, and that's why you get interference patterns and so forth. So, it's not that there is one past and many futures, nor is it the case that there is one past and one future. There are many pasts and many futures, and they are all mathematically, measurably, equally real. (But not all equally probable) 2) Probabilities in quantum physics have a phase angle, which is why they can sum or they can cancel out.
- peteradio 4y agoIt's not a predictive solution. It could very well be revealed to be true by some god type creature, but it defies the fundamentals of conducting the scientific method.
- naasking 4y agoWhy does it defy the fundamentals of the scientific method? I don't see what fundamentally changed just because that search is deterministic. Given all finite theories are recursively enumerable, and we clearly have enough degrees of freedom to enumerate all such theories, what's the problem exactly?
- peteradio 4y agoThe scientific method is hypothesis testing. You must be able to make a hypothesis that is testable. What method are we using to make testable hypotheses?
- averagestudent3 4y ago[dead]
- taeric 4y agoCalling it an "imaginary hack" is frustrating to me. Imaginary numbers are called that for derogatory reasons already, leaning in on that bias is ridiculous in the modern world.
- oprahwindfury 4y ago[dead]
- sashank_1509 4y agoWell if it’s about QED I’m always drawn to the paper : “There’s something rotten about the state of QED” by Oliver Consa (https://arxiv.org/pdf/2110.02078.pdf https://arxiv.org/pdf/2110.02078.pdf). Since I’m in CS, not physics could anyone let me know if the paper above is making stuff up. If not, then it does paint QED in a very bad light and indicates something wrong with that field
- naasking 4y agoYes, there are historical issues with that calculation, and field theories in general. I've become very suspicious of continuous formalisms period: https://arxiv.org/abs/1609.01421 https://arxiv.org/abs/1609.01421 I think many problems in physics will be solved by moving to more discrete formalisms.
- rstuart4133 4y agoErrr, that reminds me of a paper I reviewed. It was a favour for my daughter who doing a post-doctoral Uni course, who was asked to write a review of it for an assignment. She could not make head nor tail of it, which was surprising as she is is pretty strong at maths. After maybe two days or dusting off my old statistics text books and numerous google searches I came to the conclusion the statistics they used were, as far as I could tell, complete rubbish. It looked like someone got themselves a (very small) data set by posting out a questionnaire, crunched the data by mashing together a grab bag of sampling techniques + distributions + significance tests, polished the result them by using the usual academic style of a numbered lemmas and "proofs", and served up the result which happened to match the latest management fad. But we were both full of self doubt - why would a Uni course ask read something like this? Fortunately her father-in-law had a PhD in statistics, and had lectured at a major Uni for a while. So we asked his opinion. It was the same. Which left us in a difficult position. We both suspected the point of the assignment was to demonstrate she could read complex material and learn from it. I' afraid I wimped out with "I'm an engineer, I'm not cut out for this sort of thing". I'm not sure what she wrote, but she got a distinction for the assignment. Oddly, I now think it was a good learning experience in management. But the maths of QED has always been beyond me so I always just taken what the physicists said about the accuracy of their models at face value. If I had of read "calculated that the sum of all positive integers is not infinity but -1/12 ... and this is precisely the value that is used in the equation of the Casimir effect" a little earlier, I might have been a little less sanguine.
- HeartTicker 4y ago[flagged]
- 93po 4y agoAlternatively, just program the characters to be incapable of perceiving the gaps in the simulation. Which is totally possibly happening considering we are far from understanding the entirety of how the universe works.
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- biomcgary 4y agoArticles on this topic always remind me of Leibniz's philosophical optimism, which stemmed from considering all possible worlds through the lens of his theological motivations (https://en.wikipedia.org/wiki/Gottfried_Wilhelm_Leibniz#Theodicy_and_optimism https://en.wikipedia.org/wiki/Gottfried_Wilhelm_Leibniz#Theo...). This was famously criticized by Voltaire in Candide. But, even earlier, the Scholastics wrestled with alternatives to reality as we know it, which seems to have found its best articulation by Luis de Molina (https://en.wikipedia.org/wiki/Molinism https://en.wikipedia.org/wiki/Molinism). Even Calvin seems to resurrect his influence through superdeterminism (most recently championed by Sabine Hossenfelder). I'm not claiming that these thinker prefigure modern physics, only that intellectual history sometimes rhymes, even if it doesn't repeat.
- RyEgswuCsn 4y agoMy interpretation of the double-slit experiment has been that the presence of physical matters in a certain configuration imposes some sort of probabilistic "reality field" that propagates at light-speed. The superposition of these "reality fields" at a certain point in space(-time) determines the probability of the particles' behaviour at that point, not unlike how support vector machines with a RBF kernel work. This interpretation has the benefit (I think) of bypassing the problems with the "observers" --- any apparatus that is able to discern the path a particle had taken just so happens to impose a field such that, when superposed with the original "reality field" the double-slit imposes, the mixture field no longer exhibits the interference pattern. Of course I am not a physicist by training, so the above could be completely nonsense (or it could have already been an established theory).
- 93po 4y agoI would love for someone to clarify this for me: My understanding is that the physical act of observing, as in, with the specific machine we use, is what causes photons to suddenly behave different. Like if decided to gently touch a marble rolling down a ramp in darkness to measure how fast it was rolling, the act of touching changes how the marble rolls. It's not that we're actually observing the marble's behavior, is that's we're interfering with its behavior when we measure it. Is this accurate? Or is the observation of the photon not physically impacted by our observation, and through some magic of quantum behavior, it somehow "knows" it's being observed and changes because of that?
- RyEgswuCsn 4y agoI'd thought direct observation of the photo would mean physically interact with it (and thus changing its behaviour). My understanding is that there are also other experiment designs which allow identifying which path a photon went after it passed the slits; in such cases the interference pattern disappears too.
- consilient 4y ago> It's not that we're actually observing the marble's behavior, is that's we're interfering with its behavior when we measure it. There's no difference: observing something without interacting with it isn't possible.
- 93po 4y agoWhat's up with all the weirdly typed dead comments here? Is someone unleashing a GPT bot for commenting?
- amai 4y agoSee https://en.wikipedia.org/wiki/Consistent_histories https://en.wikipedia.org/wiki/Consistent_histories and the last paper from Murray Gell-Mann (published posthumously) https://arxiv.org/abs/2110.15471 https://arxiv.org/abs/2110.15471
- anthlax 4y agoWhat I am not understanding is if all paths have an equal amplitude, and there are infinite paths, shouldn’t all paths cancel out? I’ve heard an example of throwing infinite stones in a pool, and the ripple that forms is what we perceive as reality. But how does our reality not have a counter-reality that cancels it out?
- neuralzen 4y agoThis short story "Divided by Infinity" is a great exploration of similar ideas/ particularly the Quantum Immortality thought experiment. Definitely worth a read. https://www.tor.com/2010/08/05/divided-by-infinity/ https://www.tor.com/2010/08/05/divided-by-infinity/
- lazyeye 4y agoThis is absolutely true as long as you define all possible realities as what our reality would be the sum of.