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#51




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#52




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The only thing that's weird is that we've been able to develop mathematics that in any way describes how the real universe works. That this mathematics doesn't have an easy and glib translation into common English and that it doesn't correspond to mundane reality is the most totally expected thing I can think of. It really is you who's at issue here. Or rather, it really is that you are merely human that's at issue. Humans never see the quantum world. It is what it is, without regard to any aspect of humanness. The universe is math, not culture. If you find math weird that unfortunately says more about you than it does about math. 
#53




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You're not grasping the underlying concepts of quantum mechanics and it's not something that any number posts on an Internet message board can correct. If you're really committed to understanding the topic there's a bounty of information available online and if you're the selflearning type you can even try OpenCourseWare from MIT that has some great courses/materials on quantum theory. 
#54




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It's kinda like the My Problems With Relativity thread, where someone thinks he's proved Einstein wrong. He hasn't, but he won't accept that. In order to refute a theory, you need to understand it first. Otherwise how do you even know what it is you're refuting? I mean, you know you're refuting a 3sentence description of what quantum mechanics is to you, but quantum mechanics is not a 3sentence description; it's a million equations, experiments, observations, and fulfilled predictions. Those are what you have to refute, not a soundbyte description you heard; and to refute them, you have to understand them very well indeed. You have to intimately know the equations, what they mean, how they were derived, how they are used. Then you can point out what's wrong with them. Last edited by Candyman74; 01032012 at 07:48 PM. 


#55




Ah, I understand now. I was thinking that you were referring to the numerical value of c.

#56




This is an excerpt from an English translation of S's paper The Present Situation in Quantum Mechanicswhich can be read in its entirety on linewhere the cat first appears. It helps to get to primary sources.
The intro graf helps get things going: That it is in fact not impossible to express the degree and kind of blurring of all variables in one perfectly clear concept follows at once from the fact that Q.M. as a matter of fact has and uses such an instrument, the socalled wave function or psifunction, also called system vector. Much more is to be said about it further on. That it is an abstract, unintuitive mathematical construct is a scruple that almost always surfaces against new aids to thought and that carries no great message. At all events it is an imagined entity that images the blurring of all variables at every moment just as clearly and faithfully as does the classical model its sharp numerical values. Its equation of motion too, the law of its time variation, so long as the system is left undisturbed, lags not one iota, in clarity and determinacy, behind the equations of motion of the classical model.the .... Inside the nucleus, blurring doesn't bother us.[ital mine] That the lack of the excluded middle is justifiable is discuused in almost identical language by Heisenberg on page 124 of Physics and Philosophy (entire book online in PDF). 
#57




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#58




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#59




I don't think anyone in the thread has argued that excluded middle is violated by quantum phenomena, including superposition.
And it's not. 


#60




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I was reading this. Did I get the wrong end of the stick? 
#61




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"Excluded middle does not apply" is not the same thing as "excluded middle is violated." What he's saying (and I agree) is that "dead" turns out not to mean the same thing as "not alive." Everything is either alive or not aliveS's cat is not a violation of this, nor is anything in quantum theory. For excluded middle to be violated with regard to the characteristic "alive," something would have to be both alive and not alive. This cat ain't that. 
#62




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Quaternions are another fun mathematical feature that I've had the pleasure to work with in the past, basically vectors in a four dimensional vector space that can be used to describe direction in three dimensional space regardless of a fixed plane, all using complex number (mathematicians, please correct any mistakes in the previous sentence.) I mean, try and wrap common sense around that? Screw common sense, is that I'm basically saying. 
#63




First of all, quantum mechanics does not violate classical logic. This is straightforwardly demonstrated through the possibility of socalled 'hidden variable'interpretations, like Bohmian mechanics. They do have unusual properties (nonlocality, contextuality, etc.), and they essentially refer to 'surplus structure', i.e. unobservable stuff that the OP (rightly) has a problem with, but it's always at least possible, if perhaps inconvenient. In such interpretations, one can always reason classically about every observable, and weirdnesses of quantum theory are indeed only apparent, and due to our ignorance of the hidden variables.
Nevertheless, you can also choose to look at quantum theory using a logic different from classical logic; however, in this case, it's not the principle of the excluded middle that goes, but rather, distributivity. This is known as quantum logic (and while it has been proposed that it should replace classical logic as the 'proper' logic, because of the above argument, that doesn't actually follow). The reason for this is socalled complementarity. Two propositions are complementary roughly if both can't simultaneously be known exactly. This is the basis of the uncertainty principle, which thus provides the classic example of why quantum logic does not distribute. First of all, the principle itself says that the accuracy of both position and momentum can't exceed a specific threshold  the formalization is typically: ΔxΔp > h, where Δx and Δp are the uncertainties in position and momentum, respectively. One can translate this into the following proposition: z: The particle's momentum is in the interval Δp, and its position lies in the interval Δx. Now we can think about the following three propositions: p: The particle's momentum is in Δp, q: The particle's position is in Δx_{1} r: The particle's position is in Δx_{2} Where Δx_{1} and Δx_{2} are just the, say, left and right halves of the interval Δx. Then the following proposition: p ˄ (q ˅ r) (where ˄ denotes the logical and, and ˅ denotes the logical or) is clearly true, because it is equivalent to z, and thus, just a restatement of the uncertainty principle. However, the proposition: (p ˄ q) ˅ (q ˄ r), which is equivalent in classical logic, fails to be true, as both p ˄ q and q ˄ r are false; each asserts a proposition incompatible with the uncertainty principle, e.g. 'the particle's momentum is in Δp and the particle's position is in Δx_{1}', which would mean Δx_{1}Δp < h. Now it is in this complementarity that the key to superposition lies. Let's say there's a property, which can obtain either of two values (typically, this is a particle's spin along some axis), which is complementary to a similar property (spin along another axis, for example). If the particle thus has a definite spin along one axis, its spin along the other axis must be fully indeterminate  which means, it must be in a superposition of both possible values. Now Schrödinger's cat just consists in coupling the welfare of a macroscopic being to such a superposition  in principle, it's a straightforward consequence of the theory. The superposition is then not of the logical form 'A and notA', i.e. it's not a violation of the principle of the excluded middle. Rather, if 'A' is 'alive', it's just 'notA'  the cat's twovalued property doesn't have a definite value along the alivedead axis (so it's certainly not alive, but also not dead  one way of viewing this is simply that alive and dead don't exhaust the possibilities in the quantum world, but one can get rather tangled up thinking about it this way). It's interesting that almost all of quantum theory follows from the existence of complementary propositions  the way you can 'build' ordinary probability theory on classical logic, you can build quantum mechanics on quantum logic, too. I've written up a sketch of how this works (it will contain a lot of redundancy if you're familiar with classical logic, set theory, and probability, so you can probably skim those parts), and also of how thinking about quantum mechanics in terms of such a novel theory of probability illustrates the origin (and meaning) of interference effects, such as in the classical double slit experiment. And for the complete threefer, I discuss superpositions in the beginning of this bit on quantum entanglement in the light of what's known as 'Zeilinger's principle' (who, in a word, considers the origin of complementarity to be the finiteness of information in any given system  once something about it is known perfectly, there simply isn't enough information to decide its other properties). In the interest of openness, however, I should mention that my perspectives probably can't be considered entirely mainstream. So much for shameless selfpromotion... 
#64




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More specifically, I don't think there's an equivalence between: P: The particle's position is in deltax and Q: The particle's position is in deltax_{1} ˅ The particle's position is in deltax_{2}. For P's being true does not require that the position have any property of being in any smaller interval than x. The position is spread out, in a sense, over the whole of x. 


#65




Similarly, the statement "Line segment X is in interval [a, c]" does not require that it be true that "either line segment X is in interval [a, b] or line segment X is in interval [b, c]" (where, of course, b is in between a and c).
As far as I can tell, the sense of 'the particle's position' which makes your statement z true in QM is better modeled by line segments than points. 
#66




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Nevertheless, the failure of the distributive law in quantum logic is, as far as I can tell, the accepted view (that's at least how it seems to be regarded both by wiki and the Stanford Encyclopedia of Philosophy), so I think it's the appropriate position for GQ. Also, particle positions are not really wellmodeled by lines, since in measurement, one can measure them arbitrarily well (at the expense of arbitrarily bad knowledge about momentum), which would be impossible for extended objects. The bottom line is that there's really no unambiguous structure 'behind' the quantum formalism, not one of points, and neither one of lines  there's a lattice of propositions about these properties, which happens to be nondistributive. Last edited by Half Man Half Wit; 01042012 at 08:40 AM. 
#67




To be clear, by "in" I meant "contained entirely within."
As for the mainstream status of the view, note the article you linked to does not claim that QM violates distributivity. It says some philosophers have thought so, while (it seems to me) being careful to neither reject nor endorse this view. And it says that there are nonclassical logics which do not validate a theorem we might recognize as encapsulating a "distributive property," and which model QM well. But none of that means QM violates distributivity. 
#68




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Last edited by Frylock; 01042012 at 09:13 AM. 
#69




Put yet another way (sorry): The fact that subtraction isn't commutative doesn't mean that the physical phenomena we model through subtraction "violate commutativity." It doesn't mean that somehow the commutative properties of addition and multiplication are false or invalid.
Similarly, the fact that quantum logic isn't distributive doesn't mean that the phenomena modeled by quantum logic "violate distributivity." It doesn't mean that somehow the distributive properties of the "and" and "or" of propositional logic are false or invalid. 


#70




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What no one seems to be addressing is that we are dealing not with quantum mechanics, but with the Copenhagen interpretation of said mechanics. That particles exist in a superposition that collapses upon measurement is not something that has been scientifically proven, and the OP is right to reject that it has been. The interpretation of quantum mechanics is the realm of philosophy, not science. There are many interprettions of what is going on. In particular, whether a superposition is a mere mathematical entity or an actual value is hotly debated. Or to put it in the terms of the paradox: whether the cat alivedead, or is its value merely undetermined is actually an open question on the quantum level. And let us not forget that there is no theory of everything, so even asserting that quantum mechanics is true is not without peril. In fact, many physicists refuse to do anything but say that quantum theory works, and even refuse to interpret the results. 
#71




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Again, think about the example in terms of 'empirical semantics', where by 'the particle is in [a, c]' one just means 'experiment will find the particle within [a, c]'. From this point of view, it's clearly true that 'experiment will find the particle within [a, c]', and 'experiment will find the particle within [a, b] or within [b, c]' are equivalent  one can just check one's measurement records afterwards, and it will always be the case that the particle was found within [a, c], and it will always be the case that the particle was found in [a, b] or [a, c], since it was always found at some point in [a, c], and the union of [a, b] and [b, c] is just [a, c]  thus it was always found at a point in [a, b] or [b, c]. Or, consider another case, a computer build using a threevalued logic. This does not violate twovalued logic, since one can build a computer using twovalued logic that emulated it; but nevertheless, threevalued logic is an obviously valid and equivalent description (you could just as well use the computer based on threevalued logic to emulate a twovalued logic computer  neither is any more fundamental). Again, to be perfectly clear, I don't mean to say that quantum mechanics 'violates' distributivity in that distributivity is now somehow wrong  fundamentally, distributivity is just a way to regroup symbols on a page, and you can do that according to whatever rules you may want to use. But for quantum mechanics, a set of rules in which distributivity doesn't hold appears to be particularly apt, because it models complementarity well. You can use classical logic for the task  see the first paragraph of my first post in this thread , but one can argue against this on different grounds (Occam's razor is sometimes put to this task); you can also use threevalued logic (as Reichenbach did), or fuzzy logic, or nonlinear logic, or other kinds of rules one might come up with. There is just no one true right system handed down from above, its rules set in stone  we have to make do with what we can come up with (and that's a good thing, because if there were one true set of rules, where'd they be supposed to come from?). 
#72




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Last edited by Frylock; 01042012 at 11:00 AM. 
#73




Well, you could translate what I wrote into classical logic, using for example a hidden variable theory, where particles simultaneously do have a welldefined position and momentum, and we're just prohibited from finding them out. Thus things only appear to be nondistributive due to conspirative dynamics that keep us from accessing the basement layer, which is classical and distributive  this would essentially amount to emulating quantum logic within classical logic. (Something like this was done, for example, by Edward Moore in his somewhat famous paper 'GedankenExperiments on Sequential Machines', where he used automata nowadays called 'Moore machines' to construct an analogue of the uncertainty principle.)
But you can just as well not do that, and just use quantum logic, and only the properties and relations between them quantum mechanics dictates; for those, it is indeed the case that distributivity does not hold, meaning that classical logic, without 'embellishments', just isn't the right tool to do the job of modelling the behaviour of quantum systems (which does not mean that it's wrong anymore than the insufficiency of real numbers to model quantum dynamics means that the real numbers are 'wrong'; this kind of question is just not an empirically decidable one). 
#74




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People are far too concerned with this alivedead cat. This thought experiment was NOT intended to be a way to explain the Copenhagen interpretation to people. It was actually an illustration of the differentiation between the quantum world and our everyday interactions. 


#75




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Hidden variable interpretations get rid of the superposition, but replace it with quantities that are subject to the same criticism that the OP makes about the superposition itself  that we're introducing these fundamentally nonobservable things. (Plus, due to Bell's theorem, they need to be nonlocal, which buggers up relativity, too). 
#76




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I'm untrained but I hope any response to me here is a serious refutation, not a frivolous comparison with "purple cows." In the Bell's paradox, twin photons are created on Monday, then read Tuesday and Wednesday on distant asteroids. Note that the Tuesday is not preferentially "earlier" than the Wednesday reading, since each is outside the other's causeeffect cone. Yet in the Paradox, the reading on one asteroid seems somehow telepathized to the other asteroid, faster than light, or even Wednesday's filter setting can be seen to affect Tuesday's reading. The paradox disappears if you consider that the paired photon is a single photon, arriving from some future point beyond the Wednesday asteroid, travelling backward to the actual pair creation event, then forward in time to Tuesday's asteroid. Causeeffect behaves trivially: Wednesday's filter setting is imparted to the photon, and the polarization is "later" detected by the Tuesday receiver. Is there a flaw in this argument? WheelerFeynmann argue, IIRC, that reversecausality photons of the type described imply "advanced" radiation waves whereas only "retarded" radiation waves are observed. On the other hand, wouldn't advanced waves be quite hard to detect? (I am not quite espousing the traditional Transactional model: it has an unnecessarily complex notion of causation, though I won't try to synopsize mine in this post.) Just as rising entropy is a consequence of the happenstance that we inhabit a world of low entropy, couldn't the prevalence of retarded waves be an artifact of the same thermodynamic state? Probably not, or geniuses like Feynmann would have seized on the elegance of this solution. Still, it would be nice to understand where the model fails. 
#77




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(1) I think you are talking about the EPR paradox. (2) A description that attempts to prevent a causality problem by positing that the information is routinely transmitted backwards in time is somewhat defeating the purpose. If we posit that we can sent information backwards in time, why not just send it between the measurements directly. (3) The FeynmanWheeler description of "particles going backwards in time" is a description of antimatter. I.e. that an X with its timedirection reversed is an antiX. That means your description is fine for entangled photons, or particleantiparticle pairs, but entanglement is not limited to those kinds of particles. There is nothing in principle stopping an electron from being entangled with another electron, or a proton, or something else, which can't be described the way you have it. 
#78




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2. The information doesn't magically travel back in time; it just follows a normal causeeffect relation, but with timesense reversed. Counterintuitive? Of course. Problematic? Perhaps; I'd like to understand the specific objections. But the beauty of the scheme, if it is at all workable, is that quantum mystery disappears. 3. Au contraire, haven't Feynmann et al themselves modeled electrons as positrons going backward in time? 
#79




septimus, perhaps the discussion of your idea would be something for a separate thread? Personally, I don't see where you differ from Cramer's transactional interpretation, and as with that interpretation, I'm not sure I really see the need. As leahcim notes, interpretational problems of EPR experiments mainly focus on how to save causality in the presence of apparently faster than light 'spooky actions' (which I consider neither spooky nor 'actions' in most senses of the word). To just throw out the notion of causality does seem like cheating somehow. And of course, the problems you get are those you get with any retrocausal proposal, such as paradoxical influences on the past, causal loops (i.e. A caused B retrocaused A), and of course, there's also the problem of how our experience of a unidirectional arrow of time comes about; the usual argument of 'entropy was lower in the past' doesn't work, since for every point in time, if causal influences propagate in both time directions symmetrically, one should expect that entropy is higher both towards the past and towards the future, as the dynamics that generate entropy increase work in both directions equally well.



#80




I think I see where whc.03grady is misunderstanding something...
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Our observations lead us to the idea that these wave/particle things exist in a superposition of states. It's not, like you seem to be saying, that we base these ideas on simple ignorance of what may be really happening. Further, the Geiger counter that triggered (or not) the breaking of the vial of poison, is itself an observer. Last edited by CurtC; 01052012 at 10:12 AM. 
#81




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Don't worry, I'm good. 
#82




Is if just me, or are the usernames whc.03grady and tomh.4040 reminiscent in style of each other?
One being "I've figured out what's wrong with quantum theory" and the other being "I've figured out that Einstein was wrong about relativity"? 
#83




I don't think so. To me, it seems that whc.03grady has shown himself both more knowledgeable and corrigible on his topic, plus we haven't yet seen any inane thought experiments intended to expose errors in the thinking of some of the smartest people in the world for nearly the past 100 years that can ultimately be reduced to trivial misunderstandings based on biased readings of popsci arguments...

#84




Many posters have recommended researching the topic to get a better understanding of the strangeness of quantum phenomenon that is being illustrated by the story of Schrodinger's Cat. That is the best approach.
I think the heart of the matter is the difficulty in accepting the quantum view that the world seems to be inherently probabilistic. As a nonphysicist I have gotten a lot out of the various Feynman lectures available online. This series is a good place to start: http://vega.org.uk/video/programme/45 He talks about the idea of understanding at 20:15. 


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#86




Fundamentally, Schrödinger's point about the cat was that the Copenhagen interpretation of quantum mechanics led to results which seem intuitively absurd. About that, he's right. But there are many different possible interpretations of quantum mechanics, all of them exactly equivalent in the sense that they predict the same sets of observations, and not all of them lead to that particular absurdity. The tricky part, though, is that all of them lead to their own particular absurdities: Bell's Inequality proves that any model which does not lead to one of a variety of things we consider intuitively absurd, cannot be consistent with the results of the measurements we've actually performed. So somehow or another, there's something about physics that we consider intuitively absurd (which should, of course, be taken as a flaw in our intuitions, not as a flaw in physics), but we can't actually say just what the absurdity is.

#87




Chronos! Where the heck you been, man?

#88




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I think I'm going to search for some similar jokes. It's been a while since I heard any. Out to find the one about the physicist and the engineer fighting a kitchen fire ETA : Immediately found some here. The one I was searching for and couldn't remember being the first one. Not really helpful for the OP, but still... Last edited by clairobscur; 01062012 at 08:19 PM. 
#89




Visiting my mom (who has lousy internet access) for vacation. But I'm back in the land of broadband now.



#90




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Three umpires answering a furious coach: Umpire 1: I calls 'em what they are. Umpire 2: I calls 'em as I see 'em. Umpire 3: They ain't nothin' till I calls 'em. 
#91




Why is it so hard to believe that science has proved the existence of zombie cats?

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I can't wait to watch the next three lectures. Thanks. 


#95




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http://research.microsoft.com/apps/t...uva/index.html 
#96




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I do not "throw out the notion of causality" nor are there "faster than light actions." Yes, the Wednesday and Tuesday events are outside each others' causality cones, but information can tunnel(!) using the "advanced action" path from detector to entangler at the speed of the electron or photon. I'll agree there are probably severe constraints on what kind of information can be exchanged, but information is manifestly exchanged in the case of EPR and GHZ paradoxes. Yes, we give up the fixity of time's arrow. But where is that written in stone? In the the 2nd Law of T ΔS≥0 which Mr. Wit mentions in concluding ("causal influences propagat[ing] in both time directions"): I certainly admit the possibility of boundary conditions, just as other models do, e.g. Big Bang Hypothesis, or for that matter 19th century physicists like Boltzmann. It is, apparently, the extremely low entropy at 13 Gigayear — however this boundary constraint arose — which leads to the causality arrow so clearly experienced by human brains. (This much is stipulated, I think, even by some who do not also propose retrocausality.) 
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In contrast, in ordinary quantum mechanics, you merely need to give up the assumption that all measurements should obey a joint probability distribution. Quote:
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#98




I feel that a lot of quantum mechanics is still a manufactured framework to enable people to work in that difficult realm. It has not yet fully reflected the reality of what is going on. I liken it to navigating with two dimensional maps before you know the world is a sphere. You can make it work. But you need to invent rules in order to do it. A little creative math to straighten or curve things to plot the best path that works in the reality that you do not yet know. Many places where there be monsters.
That doesn't mean it does not work. We use flat maps all the time and get where we want to go. Quantum mechanics is a developing map. It helps explore that world. The explorers may at some point see it for what it is. Possibly far outside the boundaries of their map. 
#99




To clarify for other users due to the use of various terms in this thread.
EPR experiment nor any other quantum experiment has demonstrated that fasterthanlight signaling is possible. The lack of transfer of usable "fasterthanlight signaling" or what is commonly also called information has not been demonstrated. Because of this lack of useable information the speed of causality is not violated at this date. While a lack of a unifying theory may make these paradoxes fairly confusing as there is a significant amount of unsettled science the restriction on the speed of causality is related to communication faster than the speed of light and not other aspects of our universe. In fact in the future even the expansion of the universe is expected to exceed the speed of light. This does not imply that the particles themselves are superluminal, but that the distances between them will be. As of this date the nocommunication theorem is still firmly in place. 


#100




Alice and Bob each take one of an entangled pair.
Alice reads the Z spin on one of the entangled pair but Bob doesn't have a way to detect that she did. Alice can't control what the value is that will be read, she reads a "random value. Alice my read an up or a down. Bob will read a complement of Alice's "random" value, to Bob it appears random as well. Bob would need a way to know that Alice has actually performed a measurement or if he is the first one to measure a member of the pair. Bob's statistics for his particle alone look the same either way. If Alice and Bob are not local to each other they cannot tell if something is random or due to entanglement. It is easy to confuse tests that do have locality and non FTL communication with thought experiments that describe how entanglement interactions are FTL but to reference Kedikats post remember that most of the math is in done in Hilbert space or other Euclidean spaces and thus will not apply to space like intervals. While our theories are incomplete, any violation of the speed of causality is purely theoretical and there is no experimental proof for "fasterthanlight signaling" but only for "fasterthanlight interactions". I do want to address this from the OP: Quote:
http://physicsworld.com/cws/article/...visibleobject Last edited by rat avatar; 04222017 at 02:24 PM. 
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