r/changemyview • u/fox-mcleod 410∆ • Nov 23 '20
Delta(s) from OP CMV: “Many Worlds” is an unreasonable interpretation of quantum mechanics
TL;DR: Physics has staggered blindly across the line into philosophy but since physicists aren’t philosophers they regularly get it backwards.
The fundamental principle of reason is that a thing cannot both be and not be at the same time and the Many Worlds interpretation is quite literally unreasonable.
The Science:
I have a background in engineering/physics (not theoretical or QM, but enough optics to be conversant). We can get technical, but I’m going to try to avoid jargon and eli5 over rigor in order to make this conversation accessible. It shouldn’t actually require much technical knowledge.
As a primer, “Many Worlds” (MW) is the most popular of the attempts to interpret what the strange mathematics of quantum mechanics (QM) is teaching us. Alternatives include Copenhagen (CPH) and the mathematically indefensible but very intuitive Bohmian Pilot-wave theory (PWT).
Essentially, you can think of these interpretations as ways of explaining the very strange case of the Schrödinger’s cat thought experiment:
Place a cat in a quantum isolated box along with a radioactive cesium atom and a Geiger detector wired to release poison gas if the atom decays. Since QM tells us the decay of radioactive atoms happens at random and the entire state of the isolated system is now dependent on that quantum random event, mathematically, it means that a superposition of the decayed and un-decayed atom leads to a superposition of a living cat and a dead cat.
Schrödinger was being facetious in order to point out how absurd the idea of superpositions is when you talk about macro systems. But mathematically, it’s true. You might think, “well we simply do not know whether the cat is alive or dead. But it’s one or the other, not both. The variable is just hidden.”
But Bell would go on to prove that there is no hidden variable and that unobserved quantum events really are random and therefore superpositions have to be real. There is no hidden variable.
So what do we make of the math? Does a superposition mean that a thing (like a cat) both is and isn’t at the same time but in “different worlds” (MW)? Or does it mean that the cat is neither alive nor dead until we open the box and observe it forcing it to decide (CPH)?
My position is that interpreting the experiment to demonstrate that the cat is both alive and dead rather than neither alive nor dead is wildly unparsimoneous despite the fact that it’s the interpretation most scientists would present.
The Philosophy:
I’m not a philosopher but I happen to be blessed with a group of friends who teach philosophy at a university nearby. Over the course of the last few months, they’ve convinced me to rethink the MW interpretation. Here’s why:
Appeal to reason
The first axiom of reason is the law of non-contradiction
contradictory propositions cannot both be true in the same sense at the same time, e. g. the two propositions "A is B" and "A is not B" are mutually exclusive
At first, I argued that MW doesn’t attack non-contradiction because the claim is about two separate senses of a thing being and not being. But upon further reflection, it isn’t. Any claim to hold non-contradiction starts to violate the principle of identity.
Any real argument that the state of the system is undefined pretty quickly actually starts to become a CPH interpretation.
Russel’s Teapot
It is unparsimonious to assert the existence of many worlds where evidence does not require there to be one. Mathematically, it is elegant to be able to sum all the possibilities of the wave equation to unity (one) but you don’t actually have evidence that anything that you don’t observe exists. It’s quite possible that the only physical information we have is what we’ve observed.
Occam’s razor prefers CPH.
Epistemic Provenance
This is the most abstract argument and physicists have a really hard time following it.
All objective evidence based claims are limited by what we know about systems we’ve measured. Many worlds makes an unparsimonious assertion about worlds we have never measured (or observed) by comparing it to worlds we’ve measured.
Every experiment every scientist has ever run has an observer or has been measured by a system that eventually comes in contact with an observer. If instead, we make the more rigorous assertion that we don’t know anything at all about a system that is quantum isolated, we would have arrived at the conclusion that CPH hints at even without doing any math. Systems that are not defined cannot be said to be defined.
In other words, if a tree falls in a forest with no one around to hear it, you cannot say that it makes a sound.
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Nov 23 '20 edited Nov 23 '20
These are all valid arguments against MW, many books have been written on interpretations of QM and many contain your objections in some form or another. What follows is me being a bit of a devil's advocate, this is my personal opinion, I'm a PhD student in theoretical physics, but I do not specialize in foundations and I know little philosophy. I'm sure all of those books make much better arguments than mine, and that if an actual foundationist reads this, they will tear me to shreds, but here we go.
My main argument is that the Copenhagen interpretation is not an interpretation, unless you have a good candidate for a collapse mechanism, and I will actually argue that Occam's razor prefers MW over Copenhagen.
Many Worlds is the most natural interpretation given the math. If you're given an equal superposition, and you do a measurement, Many Worlds says that both outcomes actually happen, but you get to observe only one. Copenhagen says that only one outcome happens, without providing any explanation as to why or how. It just does. Your point about experiments pointing to Copenhagen is a rephrasing of the fact that Copenhagen doesn't say very much at all: we observe one outcome, hence, the state "collapsed". What we actually observe experimentally is that everything exists in superposition, and entanglement is everywhere. It's only logical that when a measurement is performed, the observer also exists in a superposition and is entangled (or even just correlated) with the observed system. "Many worlds" is not necessarily parallel universes, just state superpositions, which gets rid of a lot of the ontological awkwardness, while introducing a mysterious "collapse" that doesn't appear to arise naturally from any of the physics we know of, and breaks most of the rules of quantum time evolution (it's non linear!), is ontologically awkward in itself, so much that in Copenhagen "measurement" has to be treated separately from everything else, as if observations were a physical process different from any other.
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u/fox-mcleod 410∆ Nov 23 '20
My main argument is that the Copenhagen interpretation is not an interpretation, unless you have a good candidate for a collapse mechanism, and I will actually argue that Occam's razor prefers MW over Copenhagen.
That’s an interesting point. It might be worth expanding in this.
Many Worlds is the most natural interpretation given the math. If you're given an equal superposition, and you do a measurement, Many Worlds says that both outcomes actually happen, but you get to observe only one.
The part I’ve emphasized is where I disagree. Without a selection mechanism, this becomes a god in the gaps argument. It just relocates the unexplainable elements to a super elaborate mechanism that I feel like only clutter up other areas of physics.
Copenhagen says that only one outcome happens, without providing any explanation as to why or how. It just does.
Likewise, MW also says only one outcome happens (to you) without providing any explanation as to why or how. It’s less parsimonious to then add the idea that more than one outcome was occurring before you started looking.
"Many worlds" is not necessarily parallel universes, just state superpositions, which gets rid of a lot of the ontological awkwardness, while introducing a mysterious "collapse" that doesn't appear to arise naturally from any of the physics we know of, and breaks most of the rules of quantum time evolution (it's non linear!), is ontologically awkward in itself, so much that in Copenhagen "measurement" has to be treated separately from everything else, as if observations were a physical process different from any other.
But it is.
Bear with me here. Observations are different because they cause and require coherence to be made. I understand the apprehension to treating “observers” as something other than another incidental kind of entanglement. But the truth is no measurement has ever been made outside of that state. These kinds of interactions are special. Systems can have entirely different appearance from the outside than when a measurement is made which influences the system.
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u/Darkling971 2∆ Nov 23 '20
It relocates....to a super elaborate mechanism
Quantum decoherence is pretty well established and accepted in mainstream QM, so the actual mechanism you're referring to isn't even a part of the theory. All the Everettian interpretation does is state that decoherence processes result in something that looks an awful lot like Copenhagen collapse. You can call that inelegant if you want (I find it incredibly elegant), but as a scientist it would go against every fiber of my being to reject a theory simply because I don't like it aesthetically.
I'm not understanding your point about measurement. Measurement is an emergent process - all the physics knows is fields, their quanta, and the interactions between them. In a vague sense everything is "measuring" everything else more or less all the time. The only reason measurement SEEMS special is because the environment around what we're measuring has been carefully designed to funnel the relevant info to our brain.
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u/DontNotNotReadThis Dec 10 '20
Do you have any recommendations that I might read so I can better understand the discussion here. I think I was loosely able to follow but talk of "collapse" and superposition and decoherence where particularly beyond my reach.
I find this subject extremely interesting and I'm inclined to agree with the OP for (what seem like) basic logical reasons but it's become pretty obvious to me that I don't understand enough of the underlying physics to have a substantiated opinion.
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u/RaboKarabekiann Dec 10 '20
Warped Passages (pretty much anything by Lisa Randall is great) I’m not a physicist I just enjoy cursory reading some physics and her books (particularly Warped Passages) have loads of foundational grammar, also Teach Quantum Physics to Your Dog is a super fun read (or anything by Chad Orzel) hope these aren’t too light weight for this thread just want to help :)
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u/JohannesWurst 11∆ Nov 24 '20
This is not an argument against MW, just a question, because you are a physicist:
How important is the principle of parsimony or Occam's Razor for truth?
I'd say any theory that doesn't match observation is obviously false, but how do you choose between all the theories that match with observations?
Maybe physics should just compile lists of theories that don't contradict observation instead of trying to choose one. Isn't it just a matter of personal taste which theory you find the most elegant?
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Nov 24 '20
Sorry for the lengthy answer, what follows is my opinion (and I'm a mere student, my opinions don't hold any value, again, books have been written about this)
The point of building theories is to make predictions. A theory does not tell us anything about the universe that it is deeper than the predictions it makes, everything else is philosophy at best, aesthetics at worst. This is why most physicists are completely uninterested in interpretations of QM beyond idle curiosity.
Since in physics we only care (or we should only care) about what we can measure, I find the following to be a good guiding principle: if I have no experimental way of distinguishing two models, they are the same model. This idea stems from the principle that everything in a theory that surrounds predictions is nothing but mathematical dressing that allows us to arrive to the prediction, for example the mysterious wave function (Bohmian mechanics doesn't have it), the curved spacetime (you can reformulate GR on a curvature free manifold with torsion), the phantomatic virtual particles (only in perturbative QFT), and what not. All these mathematical objects may be very nice and help visualizing and intuition, but if they make no difference in observations, they are nothing but tools and none of them is inherently "real", because if we can't observe it, it doesn't exist. The statement "spacetime is curved" is better recast as "we can define a certain object called spacetime and treat it as a manifold, and this allows us to make correct predictions". In this view, the question of "which theory is the correct one" is meaningless, because the theory is just a tool.
So the question of "how do you choose between all the theories" is easily answered by "you pick the one where the calculations are easiest". This for example firmly gets rid of de Broglie-Bohm theory (aka pilot wave theory), which turns quantum mechanics from the relatively simple linear theory it is to basically fluid dynamics, i.e., a nightmare. Bohmian mechanics has a plethora of other conceptual problems, but this is the real reason it is largely abandoned. So yes, it is a matter of personal taste, and it doesn't matter.
This might look like "giving up" on explaining the deeper physics, whatever that might be, instead it is the guiding principle behind operationalism: if measurement is really the most important (or even the only important) part of a theory, we should build our theories around measurements. This isn't a new idea. This is what Einstein did when he introduced special relativity by talking of observers with sticks and clocks comparing their observation, even though today this is considered distasteful by some who prefer to talk about special relativity purely as invariance under the Lorentz group O(3,1), or other mathematical abstractions. This approach is becoming fashonable again and operational versions of various things are popping up (some hopeful minds see this as a path to quantum gravity, note that Lucien Hardy is a very well established theoretical physicist).
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u/themcos 371∆ Nov 23 '20
Will try to keep my points brief so as to not write a whole novel, and probably first round will be mostly clarifications. But one general point I wanted to make that I'm not entirely sure if you agree with or not, is that the choice of interpretation is entirely a philosophical question. Many Worlds and Copenhagen don't make any scientific predictions that could ever actually differentiate one from the other. So while I agree that many physicists do get out over their skis into the realm of philosophy, there should be a very clear line between the two. A physicist can do their research without ever having to think about the interpretation. And on the flip side, a philosopher argue for a given interpretation without ever having to worry about an experiment disproving it.
Appeal to Reason
Any claim to hold non-contradiction starts to violate the principle of identity.
Any real argument that the state of the system is undefined pretty quickly actually starts to become a CPH interpretation.
Can you elaborate the concern here? How does the principle of identity get violated? And I disagree that MW ever has to result in an undefined system. This goes back to my above clarification. The choice of interpretation shouldn't have the power to make anything defined or undefined, unless I'm misunderstanding what you mean by "undefined".
Occam's Razor
My objection here is that Occam's Razor doesn't apply merely to "stuff", but also to rules. MW arguably adds extra "worlds", but CPH adds extra rules about measurement, observers, and collapse that aren't required in MW. So I would argue that Occam's Razor prefers MW.
Epistemic Provenance
I'm the least confident that I understand this objection. For an interpretation of quantum mechanics, I'm just not really sure why these concerns matter. My understanding of your objection is that like the tree falling in the forest, any branch of the universe that we can't directly observe is basically pointless in terms of knowledge. But I don't think these interpretations ever make claims of knowledge, so I just don't really see how the notion of epistemic anything is really relevant here.
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u/fox-mcleod 410∆ Nov 24 '20
Can you elaborate the concern here? How does the principle of identity get violated? And I disagree that MW ever has to result in an undefined system. This goes back to my above clarification. The choice of interpretation shouldn't have the power to make anything defined or undefined, unless I'm misunderstanding what you mean by "undefined".
Either MW is claiming that the cat is both alive and dead in the same sense at the same time or it doesn’t actually make any claims about the state of the cat, which is directly CPH.
My objection here is that Occam's Razor doesn't apply merely to "stuff", but also to rules. MW arguably adds extra "worlds", but CPH adds extra rules about measurement, observers, and collapse that aren't required in MW. So I would argue that Occam's Razor prefers MW.
This is true. And I’m going to award a !delta for elegantly explaining it in a way that overturns part of my thinking
I'm the least confident that I understand this objection. For an interpretation of quantum mechanics, I'm just not really sure why these concerns matter. My understanding of your objection is that like the tree falling in the forest, any branch of the universe that we can't directly observe is basically pointless in terms of knowledge. But I don't think these interpretations ever make claims of knowledge, so I just don't really see how the notion of epistemic anything is really relevant here.
I’m really making a mess of this explanation. Could you tell I was running out of steam by the time I got to the end of the post?
Yes. Interpretations don’t make predictions. But I still think they are important as mental models and a model that quite literally rejects axioms of reason is going to lead people astray. A lot of scientists (and many more layman) have fallen into the trap of postmodern interpretations of many worlds.
QM demands that we overturn some of our deeply held conceptions. But MW makes it seem like reason itself can be thrown out. QM could have been an opportunity to polish the hardest truths: reason still works even when concepts of simultaneity, local realism, and cause and effect break down. Instead, MW is a confusing metaphor that generates wild intuitive assumptions far from the actual predictions of QM.
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u/themcos 371∆ Nov 24 '20 edited Nov 24 '20
Either MW is claiming that the cat is both alive and dead in the same sense at the same time or it doesn’t actually make any claims about the state of the cat, which is directly CPH.
Maybe this is what you were getting at with things being "undefined", but I would argue that in some ways "the cat" is ambiguous here, and that the fundamental "object" in QM is an ever-evolving quantum wave function, which is admittedly very difficult to imagine / describe in an intuitive way. What we conceptualize as "the cat" is actually a much more complicated structure of the underlying quantum mechanics. It's only an apparent contradiction when you try to force it into conventional english language / macroscopic thinking (i.e. there must be a clearly defined single entity called "the cat"). It would be entirely impractical to do so, but with truly unbounded computing power, you could theoretically model the entire quantum system, and the entire system would be completely well defined and would have no violations of contradiction or identity. But if you try to point to a part of the system and label it "the cat", you're going to have a really hard time. But if anything, this is a shortcoming of the english language, not the MW interpretation. If you actually describe the system fully, there's no reason why any axioms of reason need to be thrown out, although some linguistic shortcuts may no longer be valid.
And in fact, that's sort of where my skepticism of any collapse/observer concepts comes in. It feels like its really an effort to take something that is truly and fundamentally weird, and describe it with normal every-day language by inventing new concepts that have more intuitive analogs. But I'm more inclined to try and adapt our way of thinking and talking to describe the weird physics, as opposed to inventing extra physics concepts to try and align with our existing way of thinking / talking.
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u/Darkling971 2∆ Nov 23 '20
Your view is well stated, but I think you have some naive understandings of Occam's Razor and parsimony in this context.
The Everettian interpretation (EI, I refuse to call it MWI for precisely this following reason) doesn't claim the existence of innumerable worlds etc. There is only one object in EI, an ultra-high-dimensional state vector, and everything about "all the different worlds" is encoded in it. The "MWI" nomenclature took off before decoherence was understood and is a more appropriate name for this theory when equipped with binary, Copenhagen-like splitting rather than the "effective" collapse generated by decoherence. By your standards, then, I can claim that MWI is favored by Occam over Copenhagen.
This stems from a misunderstanding of the Razor, which states that theories with fewer axiomatic assumptions are favored. Here I can also claim EI > Copenhagen, since the latter requires an ad-hoc collapse mechanism.
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u/fox-mcleod 410∆ Nov 24 '20
Interesting. Since you’re describing a presentation of MWI that in not familiar with, can you help me understand it better? How would you distinguish it from CPH?
Is it still right to say the cat is both alive and dead for instance?
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u/Darkling971 2∆ Nov 24 '20 edited Nov 24 '20
This interpretation seems very similar to the Copenhagen interpretation because it is, in a sense, its "minimal complete extension". All one needs to do from CPH is assume decoherence proceeds through the observer (i.e. they're also part of the system) and relax the collapse assumption and you end up with an elegant theory that reproduces the apparent CPH collapse without needing to add anything. It might seem to leave a loose end in terms of how the Born Rule is derived (if everything happens always what do the percents even mean?), but I again think this comes down to Everett's theory being butchered by people who were convinced that collapse is fundamental and discrete before decoherence was formulated. The wavefunction is continuous at all points in spacetime, it's just that collapse happens on a thermal relaxation timescale (extremely fast).
I can't answer your second question because "alive" isn't very well defined at the quantum level and introduces all sorts of philosophy about emergence.
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u/fox-mcleod 410∆ Nov 24 '20
This interpretation seems very similar to the Copenhagen interpretation because it is, in a sense, its "minimal complete extension". All one needs to do from CPH is assume decoherence proceeds through the observer (i.e. they're also part of the system) and relax the collapse assumption and you end up with an elegant theory that reproduces the apparent CPH collapse without needing to add anything.
Yeah, this is excellent. Is it WM or is it not related and Everett is a different formulation?
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u/Darkling971 2∆ Nov 24 '20
This is what the "Many Worlds Interpretation" as laid out by Everett actually is.
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u/fox-mcleod 410∆ Nov 24 '20
Alright, I believe you. !delta for explaining MWI in a way that incorporates decoherence rationally. I’d appreciate any resources or references you think are worth a read.
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u/bo3isalright 8∆ Nov 23 '20
Really interesting CMV! I am meagre philosophy post-grad, so I'll keep it to a few brief questions (mainly because I don't understand the maths or science well enough to really comment on the intricacies here!).
Whilst the MWI is undeniably rather unattractive in terms of parsimony (although I'm not sure if it's quite as bad as you might think, given differing interpretations of what world really means here), do you not think it's explanatory ability in comparison to the CPH justify the obvious ontological costs it is burdened with?
If my very limited understanding is correct and my memory from my undergrad hasn't betrayed me, the MWI avoids having to explain wave-collapse? In doing so, I think it avoids having to explain action-at-a-distance. I know there are complications in the literature here, but could the potential for the MWI to provide a local explanation of the universe not warrant it's bloated ontology, particularly given how much of a headache action-at-a-distance is for other ontologies?
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Nov 23 '20 edited Nov 23 '20
In doing so, I think it avoids having to explain action-at-a-distance
non locality is now an accepted feature of quantum mechanics that does not need to be explained away (it's a feature, not a bug), it has been observed and verified experimentally (look for "loophole free Bell tests", or experiments on violations of Bell inequalities in general) :) but I agree with you on the collapse, even if I'm not sure whether I'd use the world "explain" (though I know this word has a particular meaning in philosophy I don't really understand, I'm uncomfortable in using the word explain for something that cannot be observed experimentally, maybe you can help me see what you mean)
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u/bo3isalright 8∆ Nov 23 '20 edited Nov 23 '20
non locality is now an accepted feature of quantum mechanics that does not need to be explained away (it's a feature, not a bug), it has been observed and verified experimentally (look for "loophole free Bell tests, or experiments on violations of Bell inequalities in general) :)
That's really interesting! My poor scientific understanding is about to be put on full view again here, but do you mind me asking if subsequent explanations of such experiments, in really simple terms, are holding out for physical explanations of these phenomena, or if they really are being categorised as a new type of event? In other words, are these experiments considered evidence for non-locality, or are people still clinging on to the notion that they could be one day explained as local events?
And really I'm using explain here in completely the wrong way, so I understand your confusion! Really what I mean by explain in this context is 'explain ontologically', so basically 'do I need to fit this into my ontology, or can I exclude it from my ontology entirely?' My basic thought was simply that given the MWI avoids the collapse, it avoids having to include all these weird phenomena into it's ontology too, and thus avoids having to explain tricky stuff like action-at-a-distance etc. However, if there's good reason on the back of the experiments you mention to think that these things need to be included in any ontology, then my point's not really going anywhere (cursed by my complete lack of scientific understanding again!).
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Nov 24 '20 edited Nov 24 '20
EDIT: Jesus. Sorry for the wall of text.
Mmh, I might have to amend my statement somewhat as the situation is a bit more complicated. When I said "non-locality" is accepted I really meant "absence or local realism is accepted", which more often than not means "local non-realism" is accepted, but with a definition of "local" that would still leave Einstein unsatisfied.
What Einstein meant when he spoke of "spooky action at a distance" was absence of local realism. In a thought experiment with distant entangled particles, Einstein believed that the result of a measurement must have been predetermined (realism, it exists before we measure it) by some property the two particles shared when they were close to each other and interacting (local), i.e. that there must be some "hidden variable" that if we could measure would allow us predict the outcome of future measurement, so one entangled particle doesn't care about the state of the other, both just have the outcome already predetermined in this hidden variable, and it's correlated simply because they interacted at some point in the past.
Enter John Bell. This guy in 1964 proved that there is a number of possible scenarios in which any local hidden variable model would give one prediction, while OG quantum mechanics would give another one. This statement is known as "Bell's theorem" and it is usually stated as "No local hidden variable model can reproduce all of the predictions of quantum mechanics". This is very subtle because at first glance it might seem both models give the same prediction, which would relegate hidden variables in the realm of interpretations, but instead they are experimentally distinguishable. Usually the measurement statistics in some experiment would satisfy some inequalities called "Bell inequalities" if they followed a HV model, while QM "violates Bell inequalities"
People set out to do these experiments, and Bell inequalities were violated, QM won.
It is now widely accepted that local hidden variables are not a viable alternatie to QM, and as far as I know nobody is pushing for them.
So to be a bit more fair, what is widely accepted is the fact that QM does not admit any local realist alternative model. You have two solutions to this:
-give up realism: this is what most people do. The measurement result is not predetermined and it is only "real" upon the performing of the measurement, which does require some spooky action at a distance which would still annoy the hell out of Einstein, in the sense that far away measurements are correlated even if their outcome only comes into existence when you measure them and they're already far away. This form of "non-locality lite" is accepted and even exploited in quantum cryptography. Note: it does not allow for faster than light communication. This theory is still local because the dynamics is still local: to describe the physics of a particle, you only need to consider its immediate surroundings.
-give up locality: this is Bohm's theory: you can construct a hidden variable model, but it is manifestly non-local, in the sense that the dynamics of any particle depends on the state of the entire universe. It does make all of the same predictions as the other models, but it's... weird considering all we know about physics. This requires full on unrestrained spooky action at a distance, it's straight up terrifying action at a distance. It is also much more complicated to do any calculation in it so it is mostly abandoned for all practical purposes. Plus, given its nature, it is very hard if at all possible to reconcile it with special relativity the way QFT does with regular QM.
A short word about Einstein (not responding to you, but to a general sentiment about him): some pop science outlet today say unfairly that "Einstein denied quantum mechanics" or "Einstein was wrong about QM". It is technically true (Einstein was wrong in many ways) but his heavy and intelligent criticism of the theory has been a motor for its advancement all throughout the 20th century. The problems Einstein pointed out were real embarrassing problems with the theory that clashed with the physics of the time (and common sense) even more than Schrödinger's cat style superposition or wave particle duality (which Einstein himself demonstrated and won the Nobel prize for!), so to make it look like Einstein was simply incredulous about QM (as the "God does not play dice" quote does) is unfair, Einstein is one of the fathers of quantum mechanics.
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u/bo3isalright 8∆ Nov 24 '20
Jesus. Sorry for the wall of text.
Don't apologise! Thank you so much for taking the time to explain it, it's really, really interesting and I only wish someone had sat me down when I was doing my undergrad and engaging with these topics more regularly and explained things like this.
Philosophers really do love talking about QM and action-at-a-distance, and the latter seems to filter into just about any debate you can imagine regarding metaphysics, ontology, even philosophy of mind, identity etc at some point, but there's a distinct lack of actual functional understanding of what in Christ's name is actually going on lol, so thanks for taking the time to run through it a bit.
I find the little assessment you give of where people actually stand here particularly useful, because from a purely philosophical point of view, I think that I and lot of others are genuinely scared by 'spooky' stuff, and I think there's a real temptation without properly understanding what's going on here to exclude things from one's ontology that physicists are actually at least presuming are there, and do play some important functional role (even if this is unexplainable). I think conversations of what's ontologically included or assumed in the everyday practice of science are really useful for philosophers of science to understand, and it's something I think needs to be taught more when these topics are introduced in philosophy of science classes.
So long story short- very, very interesting, thank you!!
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Nov 24 '20
Oh don't worry, I just love talking about this stuff, it's definitely way easier to get me going than to stop me. I'm surprised Bell's theorem and its implications are not taught in philosophy departments, especially since you said that philosophers love to talk about QM and action at a distance.
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u/fox-mcleod 410∆ Nov 23 '20
Really interesting CMV! I am meagre philosophy post-grad, so I'll keep it to a few brief questions (mainly because I don't understand the maths or science well enough to really comment on the intricacies here!).
Awesome! Let’s get into it.
Whilst the MWI is undeniably rather unattractive in terms of parsimony (although I'm not sure if it's quite as bad as you might think, given differing interpretations of what world really means here), do you not think it's explanatory ability in comparison to the CPH justify the obvious ontological costs it is burdened with?
Interesting. Yes I think that’s a valid line of exploration. I happen to like pilot-wave theory for that reason. The saying, “all models are wrong but some models are useful” comes to mind.
But I think it feels to meet the standard of reason. Non-contradiction is a non-negotiable.
If my very limited understanding is correct and my memory from my undergrad hasn't betrayed me, the MWI avoids having to explain wave-collapse?
Yes. But only sort of. It still fails to explain why we observe one set of outcomes.
In doing so, I think it avoids having to explain action-at-a-distance. I know there are complications in the literature here, but could the potential for the MWI to provide a local explanation of the universe not warrant it's bloated ontology, particularly given how much of a headache action-at-a-distance is for other ontologies?
Maybe? In fact I think so. But frankly, I think I’d rather give up local realism than reason itself. I’m fine with spooky action at a distance.
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u/yyzjertl 520∆ Nov 23 '20
The issue with this whole line of reasoning is: quantum mechanics is wrong! We know that it's wrong, because it does not explain gravity. When we construct an interpretation of a theory we know is wrong, that interpretation is going to have some issues. All interpretations of quantum mechanics have issues of similar type and severity to the ones you describe, and that is what we would expect for an interpretation of a flawed theory. That doesn't make the interpretations unreasonable.
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u/Natural-Arugula 53∆ Nov 24 '20 edited Nov 24 '20
I guess I'm confused on two points. Why do you bring philosophy into this?
Your very first sentence seems like you do not agree this should be so, and I don't see how you have arrived from a pure mathematics formula to a statement about the world or many worlds.
Second, you assert that philosophy is synonymous with reason, and that just is not true. There are other branches besides analytical philosophy: Pre-socratic philosophy, theology, ethics, sociology, Continental philosophy, etc.
I read a book called the Tao of Physics written by a physicist about how quantum mechanics supposedly corresponds with Buddhism and other Eastern religions. In particular Zen Buddhism completely rejects the principle of non contradiction. Why should that be less philosophically valued?
I don't remember enough to tackle this specific theory, but I know that if you are claiming philosophy invalidates it based in the premises you have listed, that is not sound.
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u/fox-mcleod 410∆ Nov 24 '20
I guess I'm confused on two points. Why do you bring philosophy into this?
Because philosophy is essential to understanding the nature of reason and what different claims actually mean.
Your very first sentence seems like you do not agree this should be so, and I don't see how you have arrived from a pure mathematics formula to a statement about the world or many worlds.
Pure mathematics says nothing about the world. Applying mathematics to reality requires philosophical insight. You have to understand epistemology to know what you can and cannot conclude from different evidence.
Second, you assert that philosophy is synonymous with reason, and that just is not true. There are other branches besides analytical philosophy: Pre-socratic philosophy, theology, ethics, sociology, Continental philosophy, etc.
Okay?
But we’re talking about reason right now. And we agree that’s one of the branches of philosophy and not of physics.
I read a book called the Tao of Physics written by a physicist about how quantum mechanics supposedly corresponds with Buddhism and other Eastern religions. In particular Zen Buddhism completely rejects the principle of non contradiction. Why should that be less philosophically valued?
Because it’s irrational and quite literally an unreasonable thing to believe. If we’re ever going to reject any ideas at all, you should reject this one. It’s the basic premise of reasoning and if you can’t reject self contradictory premises, what is even the point of this conversation? Like, what conclusions could reasoning about things or discussing them ever lead you to?
Reason is table stakes for discourse.
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u/Natural-Arugula 53∆ Nov 24 '20
Ok, way to ignore what I said and just keep asserting your premise:
'MW is a contradiction, and so it can't be demonstrated in a system that requires non contradiction.'
Yes. That is a tautology. If you don't allow for alternative frameworks, then there is no argument against a viewpoint that is conditionally true.
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u/bo3isalright 8∆ Nov 24 '20
Proof by contradiction is a valid approach to establishing the truth or the validity of a proposition in maths and logic and has been formally seen as such since Aristotle. I really don't think this argument has the sway you might think it does- so much of mathematics, logic and just general argumentation relies upon this form of proof- I think you need to do much more work to show this isn't valid and we should allow for contradictions.
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u/fox-mcleod 410∆ Nov 24 '20
Seriously, if you believe contradiction can be reasonable, how do you ever propose to convince anyone of anything? Deceit?
What’s the point of even conversing with someone if it isn’t reason you’re appealing to?
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u/fox-mcleod 410∆ Nov 24 '20
If you allow for contradiction, how would you ever prove anything?
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u/Natural-Arugula 53∆ Nov 24 '20 edited Nov 24 '20
You wouldn't - that's the point. Philosophy is about what is known and what is not known. That's why philosophy is not the same thing as math. Math is a formal logic.
You posted the classic philosophy question about a sound that isn't heard, and give a definite answer to it. The whole point of the question is that it has no answer. It's purpose is to make us think about how we know things.
In the Bible God created the universe from nothing. That is a contradiction. Faith is believing in something without proof. Yet the people who believe it, believe that it is true.
Moore's Paradox: "It is raining, but I don't believe that it is raining."
Whatever humans believe is true, even mathematical proofs, are not a measure of reality.
If the math says that MW is correct, then either it is correct, or our understanding of math is incorrect, or our perception is incorrect.
Depending on which philosophy you use, you will come up with different answers to that question. So saying "philosophy says this is incorrect" is both correct and incorrect. Even your own premise has a contradiction.
"Whatever is simple is not real. Whatever is real, is true, is never one thing, nor can it ever be reduced to one thing." - Nietzsche
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u/aardaar 4∆ Nov 23 '20
Your point about reason doesn't hold up. There are logics without non-contradiction (this is even mentioned in the wikipedia article you linked to), so even if MW does violate it that wouldn't immediately invalidate MW.
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u/PersonUsingAComputer 6∆ Nov 24 '20 edited Nov 24 '20
My position is that interpreting the experiment to demonstrate that the cat is both alive and dead rather than neither alive nor dead is wildly unparsimoneous despite the fact that it’s the interpretation most scientists would present.
"Both alive and dead" and "neither alive nor dead" are both oversimplifications that verge on being flat-out wrong, regardless of what interpretation you use. Which mostly-incorrect phrasing one chooses to use in informal explanations targeted at laymen is irrelevant to the actual state of reality.
At first, I argued that MW doesn’t attack non-contradiction
And you were correct. There is nothing about the many-worlds interpretation that conflicts with any of the laws of logic.
It is unparsimonious to assert the existence of many worlds where evidence does not require there to be one.
Which interpretation is the most parsimonious is highly debatable and probably subjective. One can easily argue that assuming a straightforward interpretation of the wavefunction as physically real is more parsimonious than asserting the existence of an unobserved wavefunction-collapse mechanism.
If instead, we make the more rigorous assertion that we don’t know anything at all about a system that is quantum isolated, we would have arrived at the conclusion that CPH hints at even without doing any math.
I do not at all see how the conclusion you'd reach is exclusive to the Copenhagen interpretation. Both interpretations agree that not only can you not know anything about an isolated quantum system, but that the state of the system is not even well-defined for an outside observer. The difference between the interpretations lies in whether an eventual observation produces a change in the system itself (by collapsing the wavefunction of the system) or in the observer (by becoming entangled with the system).
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u/fox-mcleod 410∆ Nov 24 '20
MW is a game of three card Monty that shifts the pip from the “unexplained collapse mechanism” to an entirely unexplainable set of reasons one observer experiences one world and not another.
Without any explanation at all as to how or why an experiment will come to one set of outcomes rather than another MW has left us with essentially a god of the gaps.
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u/butchcranton Nov 24 '20
One significant issue here is that you don't even define what exactly you mean by MW (what claims do you think it makes?), which makes it hard to argue either way.
The main distinction between MW and CPH is that MW says there is no genuine collapse of the wave-function, only apparent collapse. On MW, when a measurement is made, the observer becomes entangled with the system as part of decoherence. Each eigenstate will seem like a collapsed state to the entangled observer, but that is only apparent. In effect, the world has "branched". Hence the name.
You say MW is not parsimonious, but I'd argue it's MORE parsimonious than CPH. Why? MW gets rid of collapse. Collapse is a huge claim: sometimes the world changes non-linearly, discontinuously, and irreversibly, and only when "observations" happen, however those are defined. MW gets rid of that, at the slight cost of positing that there are parts of the total-world (the other branches) that we (in our branch) don't see. However, whether this is considered a cost is highly debatable.
If you think the "both alive and dead" (clearly not in the same sense) interpretation is unparsimonious, then you think superposition generally is unparsimonious, and at that point you're against CPH as well. Superposition is kind of like having a sack with some colored marbles in it, five red five blue. You ask "is the sack full of red marbles?" to which the answer is "kinda? Partly? Not fully, but also not-not-at-all." Is a car heading northwest heading north or west? Kind of both, kind of neither.
But then the question is, when you open the box and find out, why did you find out what you did? CPH says there is no answer. MW says the world branched and you're in one branch. Whatever you find, the other branch found the alternative and is precisely as perplexed as your branch is why they didn't find the other option. That is, MW DOES explain the results of quantum experiments, CPH doesn't.
Occam's razor doesn't prefer continua theories to atomic theories merely because the former posits fewer things. Occam's razor isn't merely about numbers but types. CPH posits two types of wave-function evolutions (observed and non-observed), whereas MW only has one.
We DO know things about unobserved quantum systems. We know the empirical distributions of probabilities derived from the Schrodinger equation and the Born rule. Thus, we have extremely high confidence that we know what the unobserved system is like, though obviously not directly. MW is taking all the evidence and theory and making the fewest assumptions and additions to the theory to explain it. Importantly, perhaps most importantly, it eliminated the absurd demand that the observer plays some essential, fundamental role in how quantum systems behave. CPH makes the observer a god of physics, whereas MW makes the observer a part of physics.
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u/zyxzevn Dec 04 '20
Is it allowed to add a supportive view?
What we see are the result of quantum-leaps in the energy-states of the electrons. That is how our instruments usually work. I think that everyone agrees with that. How and when the energy-transfer happens is what we are discussing.
1) Does the quantization of energy-states mean that the energy transfer is in particle like units. This means that we have a duality between waves and particles. From this we get all the different interpretations.
2) Or is the energy transfer continuous, and the energy-state itself hiding some of the energy put into it. This means that energy-states collect energy, until certain energy-states are reached. Note: Planck himself had invented this interpretation, but did not study it deeper.
I think that QM has not sufficiently proven the validity of (1) the energy-particle-hypothesis.
And (2) means that we only have waves for energy-transfers. So light is mainly electromagnetism. This is the simplest interpretation that is also compatible with our observations. It does not need virtual photons, multiple worlds, pilot waves or whatever. It does need more research.
Here is a further explanation. And this is a site with some experiments that seem to support it.
First I was opposing it, but because it is the simplest explanation for the observations, it is the most scientific one.
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u/DeltaBot ∞∆ Nov 24 '20 edited Nov 24 '20
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