Talk:Wave–particle duality

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Wave–particle duality has had a peer review which is now archived. It may contain ideas you can use to improve this article.

Wave-particle duality as MYTH

I added the link to paper Quantum mechanics: Myths and facts in the "External links". In this paper, the Wave-particle duality is taken as Myth. For more information read Quantum mechanics: Myths and facts. Lseixas 04:06, 24 December 2006 (UTC)

Yeah it's annoying how much this particular "meme" is propagated. Quantum entities are just that - entities that follow a particular set of rules based on quantized energy, the principle of least action, and various conservation laws. They aren't waves or particles, however it sometimes does help to think of them as one or the other in certain limiting cases. IMHO it's not myserious at all - it's just objects that obey math that we don't find intuitive. I agree very strongly with the school of "shut up and calculate" :) - JustinWick 19:21, 22 January 2007 (UTC)

I, too, think of duality as somewhat mythical. Yet I use it all the time, since in optics all the progagation part acts like waves and all the absorption/detection part acts like particles. So it's a useful myth. Dicklyon 21:47, 22 January 2007 (UTC)

The papers view that everything is waves is problematic in my view. Waves are medium phenomena (by definition, non particulate). However, one particular medium, the aether was laid to rest some while ago with the advent of Special Relativity. If waves exist, just what are they waving in? An alternative, is to simple state that everything is particles, but ones that obey non Newtonian laws of motion, as per L. Ballentine. It is an approach that seems to work. Kevin aylward 13:46, 10 September 2007 (UTC)

The idea that QM waves have a medium was laid to rest long ago, but that did not remove the need to treat particles as waves. QM waves propagate like light, at speed c, and relativity means there can be no medium for such waves. Dicklyon 16:57, 10 September 2007 (UTC)

But this is a meaningless statement. What do you actually mean by waves, if such a wave is not a disturbance in a medium? Please explain what such a wave physically is. Otherwise, all there is, is the word “wave”.

Additionally, as per the Ballentine view, physical waves are not needed in any QM explanation at all. That is, all observations can be consistently accounted for by the notion of discrete particles obeying non Newtonian mechanic. This is true for light, and for material particles, so the need to treat particles as waves has been removed by alternative arguments. Now apply Occams razor.

Secondly, on the country, SR explains exactly why that, in principle, an aether could exist, but that it can’t be observed as in a MMX experiment, e.g due to length contraction. The SR view is that, if it cannot be observed, than we can ignore it from our explanations. Einstein himself made this point.

Kevin aylward 09:14, 11 September 2007 (UTC)

Kevin, if you weren't such a twat [1], I'd think we would enjoy knocking back a few cold ones, doing some picking, and arguing over stuff like this ;-) Alfred Centauri 22:49, 11 September 2007 (UTC)

"What do you actually mean by waves, if such a wave is not a disturbance in a medium?"

it means that some solutions to Schrodinger's equation are what would typically be called wave equations, with characteristics like wavelength, frequency, phase and so on. 1Z 09:25, 11 September 2007 (UTC)

But that still doesn’t say really anything. I see it like this. We have two approaches to analysing the physical world, we can have a calculation model, that simple states what results of experiments are. That is, there is no one to one correspondence of what is written on paper to, that which is being modelled. The second, is that we make a statement that what is being modelled is physically real. That is we assume that there is a one to one correspondence with a mathematical symbol and some physical property such that we can claim that the wave is representing a real physical object. That is statements on the math are statements on the physical object. Of course, the math statement itself is not real in the true sense, its just lines on a bit of paper, but is is “as if” it is real. If you argue that a “wave” is just a solution to the SE, with characteristics, this is by definition, saying that the “wave” is a virtual, non physical mathematical construct. Therefor to then argue that the real physical world is all physical waves, doesn’t make sense to me.

The particle only view states that there are real, localised physical objects, made of some substance, that make patterns that are reminiscent of idealised waves when viewed from a distance. To make a statement that the physical universe is truly all *physical* waves, then one must, by assumption, have some physical material, with some properties that can manifest themselves as particles, e.g, sending a hump down a rope. Now this smells of an aether. The idea that we don’t physical move, e.g. substance at point x of wave goes up and down , when the disturbance goes left right, and its just an effect that moves, is an interesting idea, however, I don’t see that SE can be interpreted in that way.

So the question still remains, if the universe is all wave, what physically is the wave? Kevin aylward 15:11, 14 September 2007 (UTC)

But that still doesn’t say really anything. Can you really say what space time and matter are? What is the standard here? (And try actually answering the questions..)

We have two approaches to analysing the physical world. Actually we have three approaches:

1. empirical instrumental sufficiency, as per your first
2. stuctural/functional modelling isomorpohism (the structure of the theoretical model matches the structure of the "territory", the thing being modelled. "Black box" adequacy).
3. Full realism. Description of what something "really is" , beyond merely structural corespondence.

It is also often argued that physics never reaches 3, so singling out waves as a special case where we do no know "what is waving" is meaningless. It is also often arged that there is no 3 to be reached , that everyhting is just pur structure; which would mean there is no more to a wave than structural properties like frequency and phase; there is nothing to "wave".

So there are your problem areas; you are siding with the more-than-structure people against the nothing-but-structure people wihout presenting an argument, or even being aware of the dispute And you are singling out waves a special and problematical case, when they may well be -- if the structure-only proponents are correct -- just a another example of an ungoroudned, abstract structure like eveything else in physics.

The point is that there are formal. "virtual" grounds for syaign something is a wave as opposed to a particle (or any number of other things). The structure that characterises a wave may be entirely abstract (as in a sine wave) or it may be possessed by some real entity. There are perfect, mathematical squares and there are real objects which are more-or-less square. 1Z 16:02, 14 September 2007 (UTC)

The particle-only view does not have to state any more than that there the entities that make up the world can modelled by delta functions. Having a precise position is just as much a formal property as having a wavelength. There is no magic to the particle-only view that allows it to answer the question: "what is particling" (at least in any way that the wave-only view can't. "Fundamental matter-energy" works either way).

To make a statement that the physical universe is truly all *physical* waves, then one must, by assumption, have some physical material, with some properties that can manifest themselves as particles, e.g, sending a hump down a rope. That is a very unclear statement. We can explain how particles (localised entities) arise formally out of waves -- and vice versa. (This is even possible in classical physics, via wave packets). Neither formal explanation invokes "stuff". That does no mean there is no "stuff". The point is that the situation is symmetrical, the playing field is level. The particle formalism does not supply a noumenal, non-structrual explanation as an added extra.1Z 16:20, 14 September 2007 (UTC)

If the universe is all particles, what are particles made of ? What is particling? 1Z 16:21, 14 September 2007 (UTC)

I agree, that is a question that remains. It's not clear, however, that it makes sense to expect the answer to be within the domain of stuff that we have previously known as "real". There is no known way to relate the QM behavior of energy and matter to conventional stuff without some mystical level of "duality" or "randomness" or "non-causality." That's life, whether you try to make explanations out of waves only or particles only or a more typical dualistic formalism. But this is not really the place to discuss and debate these ideas. The talk page is for talking about the article and how to improve it, which needs to be focused on what we can say that is supported by reliable sources. Dicklyon 15:21, 14 September 2007 (UTC)

For the record

This may not belong in the article, but I just wanted to mention for the record that the whole issue basically goes away in modern quantum mechanics. The wave model was particular to early quantum mechanics. This is sometimes called "Wave Mechanics" today, to distinguish it from modern QM. Typically, undergraduate courses in quantum mechanics never get beyond this. Modern QM deals with states of quantum systems as abstract objects—points in Hilbert space, a complex vector space. These can be manipulated with various kinds of mathematical operators, some of which correspond to physical measurements that can be performed on the system. Like an ordinary 3D vector, the states can be expanded in terms of a set of basis vectors. One can extract the "wavefunction" corresponding to a particular state by expanding it in terms of the basis set of position vectors if you like, but you don't have to do this in general.

None of that probably belongs in this article, but my point is that in modern QM an object is neither a wave nor a particle. It is what it is. If you choose to describe the system in a position-space representation you can describe it as having wave-like properties. You're perfectly free to choose another basis set, however, in which case the description may be quite different even though the results are the same. There are an infinite (IIRC) number of basis sets to choose from, so there is nothing particularly special about "waves" or "particles", except that they are kindof intuitive.--Srleffler 01:57, 13 December 2005 (UTC)

• Actually, the section called "Theoretical Review", near the bottom of the article, was meant to contain such statements. I didn't feel like writing a grand review of what QM is, so I left it vague, but it is clear from previous edits to this article that many readers are thirsting for a technical rather than a historical presentation. Feel free to add or re-write that section; however, please don't oversimplify analogies, I'm sick of deleting "particles are like guitar strings" type content. You're scaring me with the "IIRC" comment.linas 15:23, 13 December 2005 (UTC)

• I agree with Srleffler's above setiments, however the statement about infinite basises - yes there are an infinite number to choose from, however the most useful ones tend to be eigenfunctions of important operators. The "wave" function space in free space is important because it is the set of eigenfunction (at least in nonrelativistic QM) of the momentum operator, which is of course very important. Same with the dirac delta being the engenfunction for the position operator. These choices are not merely intuitive, but mathematically necessary to study the results of these operators. I do agree, however, that the whole wave/particle concept is now pretty irrelevant, however to understand the history of physics, it is absolutely vial. I agree with Linas that the final section should be improved, but we do have to be sure to stay away from oversimplification. - JustinWick 15:43, 13 December 2005 (UTC)

Picture

I complied with your "Good Article" request, but it would be great if this article had a picture. I'm not sure what you could add a picture of, but it looks like this needs one. joturner 17:35, 25 December 2005 (UTC)

Objects

• JA: The word "object" does not imply tangibility. If you want to imply tangibility you say "tangible object". An object is an "object of discussion and thought" (OODAT). Some folks would add "object of consistent discussion and thought" (OOCDAT). So, for example, numbers are objects, even imaginary numbers. Jon Awbrey 20:45, 17 February 2006 (UTC)

• • object –n. 1 a material thing that can be seen or touched.

The Concise Oxford Dictionary of Current English, 8th ed., Ed. R.E. Allen, Oxford: Clarendon (1990).

--Srleffler 01:47, 19 February 2006 (UTC)

• JA: Oh, surely it's not that concise. Jon Awbrey 04:08, 19 February 2006 (UTC)

• • Of course not. There are several more meanings. My point, though, was that the first meaning, the most common one, specifically implies tangibility contrary to what you asserted. In general usage it is not necessary to add "tangible" to distinguish from other meanings. The usage in philosophy might be otherwise, but this article is about physics and the common usage of object is just fine here.--Srleffler 05:07, 19 February 2006 (UTC)

• JA: (A => 1 or 2 or 3) <=/=> (A => 1). If they are still using logic in physics, and if they are still using numbers in physics, then object does not imply tangible, even in physics. Jon Awbrey 05:14, 19 February 2006 (UTC)
  • Sorry, but that just doesn't make any sense. It's perfectly valid to use a word in its most common sense, notwithstanding the fact that the word may have other senses.--Srleffler 06:19, 19 February 2006 (UTC)

• JA: Yes, but the word does not "imply" the meaning that its most common use has. It implies only the meaning that all of its uses have in common. Jon Awbrey 06:26, 19 February 2006 (UTC)

• • OK, so then what was your point? Why should we care what the word "implies"? The word is used correctly in the article.--Srleffler 06:30, 19 February 2006 (UTC)

• JA: That was my point. Someone expressed some doubts, and I was trying to soothe them. That's evidently more difficult than it sounds. Jon Awbrey 06:38, 19 February 2006 (UTC)

Probability density

The magnitude of the square of the wavefunction is a probability density, not a probability. Probability densities can exceed 1. I believe the article should reflect this mathematical fact - probability density is not that difficult and there is an entire article article on it for those unfamiliar with the term. - JustinWick 05:06, 23 February 2006 (UTC)

I don't believe probability densities can exceed 1. What gave you that idea?--Srleffler 12:26, 23 February 2006 (UTC)

Certainly they cannot exceed 1, but this is merely a result of semantic nitpicking. Probability densities have the dimensions of inverse distance, and so may not even be compared in magnitude with a dimensionless number. However, for all intents and purposes, there is really nothing wrong with saying they can exceed 1, as there is nothing to stop a probability density from being as large as you like, e.g., one can have a probability density of something like "one billion per meter", as long as this density extends over no more than a nanometer. - Expensivehat 04:41, 6 March 2006 (UTC)

good article?

I've removed this article's good article status. The reason is that the only theoretical explanation that this article provides of wave-particle duality is that quantum systems are solutions to differential equations. That condition is neither necessary (there are quantum systems which exhibit the duality which are not solutions to diff eqs) nor sufficient (there are classical systems which are solutions to diff eqs which do not exhibit the duality) as an explanation of the phenomenon. A historical treatise on the evolution of whether light was modeled by waves or particles is interesting, but certainly not the primary reason purpose for this article. As such, not only is this not a good article, it is a bad article. -lethe ^{talk +} 23:01, 7 March 2006 (UTC)

Hi, well, as I'm repsponsible for the current state of the article, this remark catches my attention. I am rather totally unclear on what you are trying to say here. Is there any sort of definition of wave-partcile duality aside from random handwaving and appeals to history? To the best of my knowledge, there is no such thing as a "theoretical explanation of wave-particle duality", beyond the usual overheated argumentas about the interpretation of quantum mechanics and local realism. What do you have in mind? linas 00:45, 8 March 2006 (UTC)

Observables in quantum mechanics are represented by operators on a Hilbert space. If two observables do not commute, then the spectra of the two operators exhibit complementarity. We understand waves as momentum eigenstates and particles as position eigenstates, then wave particle duality is described by the noncommutativity of X and P. In relativistic field theory, there is no position operator, and instead we will talk about localization operators. None of this is mentioned in the article, instead there is talk of differential equations, the relevance of which I fail to see entirely. I also don't see the relevance of any discussion of local realism or interpretations of quantum mechanics. As far as I know, all formulations of quantum mechanics exhibit wave particle duality, which shows that this is not dependent on the interpretation. -lethe ^{talk +} 01:29, 8 March 2006 (UTC)

Complementarity has nothing to do with wave-particle duality. Complementarity just says things with momentum p have a wave number hbar k. But what's a particle? To talk about particles in QM, you have to talk about "wave function collapse", and that's thin ice. There are questions: when I measure a wave, why don't I ever see two half-particles? At its heart, QM is a wave theory, and no more. At least in QFT, you have the idea of creation and anhilation operators, and so finally you get back to something that can be called a particle. Anyway, you are right; the theory section is lacking; and someone should revise it. I have just about zero interest in writing a "theory" section for this article, mostly because I can't think of anything lucid to say about the theory aside from "shut up and calculate" (or rather, shut up and hit the books). linas 01:43, 10 March 2006 (UTC)

Perhaps you should take a look at complementarity. It is not the principle p = h/λ. I don't agree with much of your comments. I suppose the best solution would be for me to undertake to rewrite the article. Perhaps someday I will. -lethe ^{talk +} 04:14, 10 March 2006 (UTC)

I agree; I think Linas is referring to the de Broglie hypothesis. I've added a section on the Heisenberg uncertainty principle, explaining that it follows from the application of de Broglie to classical field theory, which may answer some of your earlier concerns about misleading statements about its derivation. --Michael C. Price ^talk 14:23, 29 November 2006 (UTC)

Wavelengths of human sized objects.

The article says "One does not observe the wave-like quality of everyday objects because the associated wavelengths of people-sized objects are exceedingly small." But can a human sized object be described by a single wave? There's no object of that kind of mass that is composed of a single fundamental particle. So wouldn't the non-wavelikeness of large objects be due to the fact that they are made up of lots and lots waves with wavelengths much smaller than the physical size of the object?

You don't have to be a fundamental particle to exhibit a wavefunction. For example, protons have wavefunctions, and atoms, and even some molecules exhibit a little bit of quantum interference. Furthermore, for certain systems like Bose-Einstein condensates and superfluids and superconductors, quantum effects are manifest even though there are a macroscopic number of particles. However, you're still right. The presense of a whole bunch of particles tied together greatly suppresses the quantum effects, if the particles are thermalized, meaning they are randomly arranged with no possibility of coherence of their wavefunctions. In this case, the large numbers make the objects behave classically, and this phenomenon is known as decoherence. So macroscopic objects do not exhibit quantum effects for two reasons: 1. h is too small, the wavelengths are completely unobservable, and 2. because of the large number of thermal particles, all quantum effects get averaged out through decoherence. -lethe ^{talk +} 05:15, 27 March 2006 (UTC)

Standard Quantum states that there is only *one* “wave function” for an ensemble of particles , not a sum of individual postulated wave functions of each particle.. This immediately dispenses with the daft idea that particles are also “waves”. QM states the probability of finding *particles* in regions of space. End of story. The “wave nature” of particles is simply that fact that particles don’t obey Newtonian Mechanics. Waves, as clearly shown manner times, are just the statistical collection of individual particles. 217.155.191.217 12:50, 8 February 2007 (UTC)

Mathematically Possible

If at all, how is the dual nature of light mathematically possible?

--203.200.220.71 11:20, 7 August 2006 (UTC) My question is why do we have to introduce photons for explaining the photoelectric effect? would it not be sufficient to say that only light waves of a certain frequency and above can knock off electrons? --203.200.220.71 11:20, 7 August 2006 (UTC)

I have expanded the explanation at Photoelectric_effect#Einstein:_light_quanta. --Michael C. Price ^talk 12:08, 7 August 2006 (UTC)

The introduction of photons, or quantized light energy, to explain the photoelectric effect, is historical and conventional. Einstein proposed it, got the Nobel prize for it, and it worked. But it is not the only way. One can explain quantum transitions between electron energy levels (which the photoelectric effect is a special case of) by the quantum electromagnetic interaction of the electrons; the transition involves a mixture of states, so the wavefunctions of the two states, differing in frequency by the frequency that corresponds to the energy difference, will make a "beat" in the electron distribution, which will allow it to couple electromagnetically to other subsystems of the universe that are at zero space-time interval (i.e. with other atoms that can absorb the photon when it gets there, if you want to put it back into photon terms). The details of this view of quantum transitions is explained by Carver Mead in his book Collective Electrodynamics: Quantum Foundations of Electromagnetism. Einstein was unhappy with the "random" results of his proposal, i.e. the Copenhagen interpretation that led only to probabilities; but he did not make the bold step of retracting the quantization of light, putting all the quantization into electron eigenstates instead, and finding the alternate view that the apparent randomness is due to all the other bits of the universe that every photon event is potentially coupled to. Wheeler and Feynman did a bit of that, but backed off; Mead picked it up later, as did Cramer, in his transactional interpretation of QM. Dicklyon 19:51, 7 August 2006 (UTC)

Revert by afshar

Ashfar removed my comment in the intro about how photons were the first to be seen as both waves and particles. I gave the explanation that they are "both", and that in a double slit experiment, a detector detects points - and over time diffraction patterns show up.

Anyways, I'm not sure what is wrong about it. I skimmed the article on Complementarity (physics), and it doesn't seem to contradict me. Whats specifically wrong with the paragraph? I thought it would help clarify what wave-particle duality means, and especially what it means for something to "sometimes act like a wave and sometimes like a particle. Fresheneesz 10:17, 23 April 2006 (UTC)

• Dear Fresheneesz, you must be careful not to say that photons are "both" unless you qualify that by saying "but never at the same time." Bohr's Principle of Complementarity posits that both wave and particle natures of quantum systems (including photons) are equally important but are not both present in the same experiment. Although, I have performed an experiment that violates Bohr's assertion, I would not support such declarations without mentioning the controversial nature of my findings. My results are still being critically studied, and until the dust settles one way or another, it would be irresponsible to declare simultaneous presence of wave and particle behaviors for photons or any other particle. It is however allowed to talk about wave-particle duality in the sense presented by the de Broglie relation in which both wave (wavelength) and particle (momentum) properties show up. I hope this explanation helps. Regards.-- Prof. Afshar 03:48, 25 April 2006 (UTC)

Hmm, what experiment have you done that you mentioned? I believe that slit-experiments involving a single particle at a time imply that photons are in fact both waves and particles at the same time. A particle will hit somewhere on a detector, but throughout the length of the experiment, the particles will eventually hit in a pattern that is predicted by wave diffraction. Saying that the photon acts like a wave sometimes, and a particle sometimes - doesn't quite work in this case. The effects wouldn't show up unless the photon is both, at the same time. Fresheneesz 03:31, 26 April 2006 (UTC)

The experiment shows that discrete particles have a characteristic number, that is usually associated with “waves”, conventionally named lambda (wavelength). This lambda number can be calculated by examining the statistics of the locations of the particle spots. That is, an average “wavelength”, with a standard deviation for that wavelength, can be calculated. This wavelength can be nominally assigned to a particle, but it only has real meaning, when discussing an ensemble of particles. Thus, the experiment indeed shows particle and “wave” nature together. There is of course, no real wave in any medium. The wave is an illusion, just as a water wave is an illusion, brought about by the statistics of large number of water molecules. Wave-particle duality is completely bogus. Standard QM is about particulate objects that follow non Newtonian laws of motion. End of story. Kevin aylward

If wave-duality is such a load of shit then please describe how a radio antenna measures the signal frequency in terms of radio particles. (And please time-date stamp your signature for further replies.) --Michael C. Price ^talk 18:31, 28 October 2006 (UTC)

See Afshar experiment for Afshar's experiment. He claims that he measured a violation. I agree with Afshar that such a claim doesn't belong at the top of this article, and I appreciate his modesty. -lethe ^{talk +} 04:11, 26 April 2006 (UTC)

Wow, very interesting. I'm honored. I still don't understand why a single photon double-slit experiment also doesn't contradict complimentarity. Fresheneesz 06:55, 26 April 2006 (UTC)

Basically, complementary says you can not both see the diffration pattern and determine which slit the particle went through. In the two-slit experiment with both slits open, you get the diffraction pattern, but no idea which slit a particle went through (because it had to go through "both" to interfere); with one slit closed, you know which slit the detected particles when through, but you lose the diffraction pattern. That's all the duality is. Afshar's experiment can be interpreted as saying that the hole through which the photon went is determined, at the same time as a wave pattern is determined (somewhat indirectly); exactly how it relates to the formal principal of complementarity is subject to considerable dispute. Dicklyon 23:41, 30 May 2006 (UTC)

so the short answer, Fresheneesz, is that the single photon double-slit experiment does contradict complementarity as defined by Afshar, since the photon exhibits wave behaviour by going through both slits and particle behaviour when it "collapses" onto a single sliver-bromide emulsion grain. Of course most people do not accept Afshar's definition of complementarity he gave above as implying that wave and particle properties "are not both present in the same experiment". Rather the conventional view is that pure wave and particle behaviour may not be present at the same space-time event, as quantified by the Heisenberg uncertainty constraints. --Michael C. Price ^talk 18:23, 22 June 2006 (UTC)

Dear Michael, Once again you have misrepresented the facts. I have never said that the single photon interference experiment violates Complementarity. In fact I have specifically mentioned on page 3 of my original paper (if you care to read before making uninformed statements) that: " It is noteworthy to mention that quantum mechanics does not forbid the presence of non-complementary wave and particle behaviours in the same experimental setup. What is forbidden is the presence of sharp complementary wave and particle behaviours in the same experiment. Such complementary observables are those whose projection operators do not commute [1]." Projection operators for sharp which-way information and interference qualify as complementary observables. A simple interference pattern contains no which-way information, thus it is not subject to Complementarity. Please read the paper by [1] Bandyopadhyay, Phys. Lett. A 276 (2000) 233, you may learn a thing or two on the subject.

As regards Bohr's statement concerning Complementarity, here's what he himself has said: "...we are presented with a choice of either tracing the path of the particle, or observing interference effects…we have to do with a typical example of how the complementary phenomena appear under mutually exclusive experimental arrangements."[2] N. Bohr, in: Albert Einstein: Philosopher-Scientist, P. A. Schilpp, Ed. (Library of Living Philosophers, Evanston, Illinois, 1949). There is no mention of the requirement you impose above that the measurements be made "at the same space-time event." In fact, it is impossible to see an interference pattern if the measurement is supposed to be made at the same spacetime event, as the pattern only builds up over time, which means it requires great many space-time events to register as interference pattern. Sorry to burst your bubble, but you really need to read up on the subject before you embarrass yourself any further. You can start with my paper, and references therein. On the other hand, if you are deliberately spreading disinformation on my work, you should expect to see some repercussions. Regards.-- Prof. Afshar 16:11, 28 October 2006 (UTC)

If you're saying that the Schrodinger wave equation and complementarity are incompatible then just come straight out and say it; get the claim published in a peer rewiewed credible journal and I'd be very surprised. What Bohr meant by complementarity is explained over at complementarity; there's no evidence that he doubted the Schrodinger equation as a non-relativistic model. PS please give the full Bohr quote. --Michael C. Price ^talk 18:31, 28 October 2006 (UTC)

Apparent paradox?

The paradox article says "A paradox is an apparently true statement or group of statements that leads to a contradiction or a situation which defies intuition." What then is an apparent paradox? Is the article wrong? Is there a source/reference for Lethe's interpretation "paradoxes are apparently true but lead to contradiction. apparent paradoxes look like they should lead to contradition, but are actually only counterintuitive"? Dicklyon 17:21, 21 June 2006 (UTC)

The second part ("which defies intuition") makes my case weaker, so I won't revert if you remove the addition again. I restored the word "apparent" because the person who removed it a month ago only did so in order that it would support an argument he was having with me, and I don't that's a good reason to change the article. I am having an rfc with him, and so was reviewing his edits. -lethe ^{talk +} 19:02, 21 June 2006 (UTC)

OK, I found other definitions that agree (not just copies of the wiki def), so I'll take it out again. Don't want to step in that other mess... Dicklyon 04:16, 22 June 2006 (UTC)

Particle and its definition

The opening sentence did not have an internal link to the articles known as "elementary particles" or "composite particles" so I added the needed brackets. Be that as it may, my quick read of the article on "elementary particle" is one that is internally cyclic and does not really define what constitutes a "particle". Is anyone ready to tackle this task? Bvcrist 03:57, 14 August 2006 (UTC)

This point concerns me as well. The article doesn't seem to say explicitly what it means to "behave like a particle". I don't know if my thoughts can be worked in somehow, but here they are. To me, "behaving like particles" means the amount of that thing is quantized. You can have one photon in a box as a standing wave, but you can't have a quarter that much energy. I think the confusion arises because a lot of people hear "particle" and they (understandedly) think "localized". It's impossible to reconcile "wave" and "localized", so that leaves people confused. I say emphasize that "particle" refers to the quantization but does not imply the thing is a small dot. A single particle can extend over a large volume. Spiel496 05:20, 14 October 2006 (UTC)

Modern interpretation

Someone has been putting in and taking out the attempt at a "modern interpretation":

Quantum mechanics was and is still a controversial sicence. It "evolved" throughout the years, but somehow, old interpretations are still used and being taught.

Light and matter seem to both exist as particles. What behaves like a wave is the probability of being at a certain place. The wave function is said to be to be a mere mathematical abstaction.

The big problem with this attempt is that it represents only one POV, and doesn't say whose it is. Phrases like "is controversial" and "is said to be" are non-encyclopedic. If an interpretation is be discussed, we need to know whose it is, and we need to include other ones as well. Dicklyon 16:17, 20 August 2006 (UTC)

Kevin aylward 12:53, 25 October 2006 (UTC) The big problem with your reply Michael, is that this modern interpretation IS the correct modern impetration. The whole idea of wave particle duality is completely bogus. All graduate level academic physics text books state quite clearly that QM is about the probability of, for example, locating a particle in a specific volume. Do a web search on “postulates of quantum mechanics”. This interpretation is not controversial in the slightest, and is universally held by professional physicists.

And more appropriate at interpretation of quantum mechanics. --Michael C. Price ^talk 18:37, 20 August 2006 (UTC)

Wave behavior of large objects

I recently deleted the last paragraph/sentence in the "Wave behavior of large objects" section.

"Whether objects heavier than the Planck mass (about the weight of a large bacterium) have a de Broglie wavelength is theoretically unclear and experimentally unreachable; above the Planck mass a particle's Compton wavelength would be smaller than the Planck length and its own Schwarzchild radius, a scale at which current theories of physics may break down or need to be replaced by more general ones."

1. The paragraph before this one in the section is pretty spectacular. Going to the Planck mass just weakens a potentially good argument about decoherence (which should be linked internally to Wikipedia def of decoherence).

2. I believe the deleted sentence to be logically flawed. (The de Broglie wavelength depends inversely on velocity. Where/why does the Compton wavelength enter the sentence? Slowing to pm/s velocities to measure fm de Broglie wavelengths of complex micron-sized objects seems adequate support for unreachability.

3. If it is meant as stated, it seems to be a bogus method of getting to Compton wavelengths and the Swartzchild radius. Why pick the Planck mass for any other reason?

4. The paragraph weakens an otherwise good article. Those who don't know any better won't get anything out of it. Those who do know, see something amiss.

5. I am concerned about the issue since I was planning on referencing the article in a general physics paper.

AQM2241 —Preceding unsigned comment added by Aqm2241 (talk • contribs)

If you're thinking about referencing a wikipedia article as a source, you'd better think again. Wikipedia should never be used as a source, though it can be helpful in finding sources. If you find things that are not right, don't be surprised, but find a source for the right answer, fix it, and reference the source. Dicklyon 23:19, 16 June 2007 (UTC)

FULLERENE AND SCIENTIFIC RIGOR

I would like to know if the infamous fullerene experiment has been reproduced elswhere in the world by more mainstream scientists. —Preceding unsigned comment added by 70.81.162.66 (talk)

What do you mean by "mainstream scientists"? Are you suggesting that the IQOQI is not a reputable establishment and Anton Zeilinger is a charlatan? That would be funny. So giving you some credit, what are you saying? Frure (talk) 14:59, 7 November 2008 (UTC)

Duality expressed via uncertainty?

The article says:

Wave-particle duality is often expressed via the Heisenberg uncertainty principle

but it does not explain this. It doesn't say how this is expressed, only that it is expressed. How are HUPrinciple and WPDuality connected? For example, is it the inherent uncertainty in the momentum that makes the wave-particle is more wave-like, and the inherent uncertainty in the position that makes the wave-particle more particle-like? 145.97.205.193 05:56, 14 June 2007 (UTC)

All objects exhibit duality?

From my understanding, there isn't any actual proof of wave-particle duality on larger objects. The largest objects experimentally proven to exhibit such behavoir are fullerenes. The lead section leads readers to believe that all objects exhibit such behavoir. I propose the article to be reworded state this more clearly. For now, I'm putting the citation needed tag on such sentences. The discussion that spurred this can be found here [2]. --Android Mouse 22:37, 19 June 2007 (UTC)

There is no reason to suppose that WP behaviour ceases at just the point where we cease to be able to observe it. The mechanism that might curtail it is wave function collapse, but that is a very ill-understood area. 1Z 00:13, 20 June 2007 (UTC)

Exactly. It's an ill-understood idea. We're talking about quantum phenomena, and it's really not clear when messy compound objects are outside the realm to which QM ideas apply. Dicklyon 02:08, 20 June 2007 (UTC)

We can't draw a clear line between "realms. All systems are quantum systems. Classical-ish behaviour emerges from some of them. 1Z 07:49, 20 June 2007 (UTC)

Why won't you provide a reference in support of such strong claims when you make them? Dicklyon 17:40, 26 June 2007 (UTC)

I personally don't think a citaiton on those statements is really necessary. It can be found in almost any text. — Laura Scudder ☎ 23:05, 19 June 2007 (UTC)

So it's mostly accepted that wave-particle duality occurs in all objects, not just quantum? --Android Mouse 23:12, 19 June 2007 (UTC)

All the books I found talk about wave-particle phenomena as quantum effects. It makes no sense to talk about wave-particle duality outside the context of QM. Dicklyon 02:08, 20 June 2007 (UTC)

Exaclty what is the "context of QM"? 1Z 07:49, 20 June 2007 (UTC)

Hard to say. Probably it's the realm where "objects" display quantized behaviors such as wave-particle duality. Dicklyon 14:24, 20 June 2007 (UTC)

But (near enough) classical behaviour can be understood as emerging from quantum behaviour. But the quantum behaviour does not disappear. So in fact everything is in the "quantum context" and some things are also in a classical context (or at the classical limit). 1Z 16:51, 24 June 2007 (UTC)

So all quantum objects exhibit wave-particle duality, and a quantum object is an object that displays wave-particle duality? It seems then that "quantum object" is not a meaningful term then. — Laura Scudder ☎ 15:54, 21 June 2007 (UTC)

Yeah, I'm hoping someone will jump in with a sourced answer to this. I doubt that practioners of QM think that their methods apply to objects such as a "cheeseburger". But if they do, I'd like to read where they say so. Dicklyon 23:57, 21 June 2007 (UTC)

There is a difference between saying, that for practical reasons, you wouldn't apply the Schrodinger equation to a cheeseburger; and saying that a Cheeseburger is some entirely different entity to the quarks and electrons that make it up 1Z 16:51, 24 June 2007 (UTC)

I'm not sure I see the difference. I don't deny that a cheeseburger is made up of atomic and subatomic particles. But it seems to be clearly outside the domain to which QM applies, since it is not even possible to dilineanate what the cheeseburger is in terms of such constituents, and therefore to talk about a cheeseburger as having wave properties or particle properties is absurd, even though its low-level constituents have such properties. Dicklyon 17:39, 26 June 2007 (UTC)

I don't think it's so well accepted, and prefer to see citations from more serious texts; but start with an "almost any" is OK, too. It's applicable to "quantum objects" whatever that means, sort of by definition; but what about big messy compound objects like cheeseburgers? How can they be said to have a wave behavior? Keep in mind that statements without citations are always fair game for removal (or revision with citation, more productively). Dicklyon 23:33, 19 June 2007 (UTC)

If Schrodinger's equation is applied to large objects in noisy environments, it doesn't predict wave-like behaviour in any classical sense, but it doesn't quire predict a single classical, positional universe, either. 1Z 00:13, 20 June 2007 (UTC)

And my point is that it's not clear that Shrodinger's equation is applicable outside the realm of QM. Dicklyon 02:08, 20 June 2007 (UTC)

Exactly what is the "context of QM"? S's E does not indicate its own limits. 1Z 07:49, 20 June 2007 (UTC)

Precisely the problem. I've yet to hear anyone propose a limit where things suddenly become "quantum objects" as opposed to "normal objects". There's no point to the last sentence in the lead if we expect size limits to the theory. — Laura Scudder ☎ 15:54, 21 June 2007 (UTC)

I've been looking for a ref for this "all objects" concept, and having trouble finding it. Here are a bunch of books that mention "all objects" and "wave-particle", but as far as I can find, only one book on Data Compression (hardly a reliable source for this topic) makes the claim that all objects exhibit wave-particle duality. If we're going to emphasize all in the lead, we really need a reliable source. I'll take it out unless something can find one. Dicklyon 16:01, 24 June 2007 (UTC)

Here's a likely resolution: there seems to be lots of support for the idea that all particles are subject to wave–particle duality. This makes a lot more sense, since the the math suggests that as the wavelength gets very small the particle nature dominates, so things that can be considered to have a particle-like nature, which is what is suggested by "quantum object", I think, come within the theory. A cheeseburger is not a "particle" in this sense. Dicklyon 16:07, 24 June 2007 (UTC)

But a cheeseburger is composed entirely of particles. Why would an individual particle display duality but not a group of those same particles? --Android Mouse 17:01, 24 June 2007 (UTC)

Its particles will individually display wave-particle dualiity, because they are particles. I'm not familiar with a wave–group-of-particles duality, which is why I was questioning all this in the first place. But more to the point, it's not about what you or I think, but about what reliable sources say. Dicklyon 17:08, 24 June 2007 (UTC)

Don't photons exhibit duality both individually and as a large group? Also, I realize the article has to go off of reliable sources, I'm just asking out of curiosity. --Android Mouse 17:20, 24 June 2007 (UTC)

I'm not sure. Yes, I think it's likely, since coherently-behaving photons like in a laser are all in one quantum state, one wave function; but I'm not sure what particle aspect that would exhibit under such conditions. Another example would be a Bose–Einstein condensate; one state, so probably it can be treated as one particle with one wave-function. But here we're still talking of what I'd call "quantum objects", not objects of the "ordinary" sort. The difference may well be just in how cleanly the "object" can itself be defined; a cheeseburger is constant giving off vapors and fumes of all sorts, and can't really be defined as distinct from the environment around it; such "ordinary" objects are not the things that quantum theory applies to. Dicklyon 19:19, 24 June 2007 (UTC)

Why not say that: "according to quantum mechanics all objects can in principle exhibit wave particle duality" and then go on to qualify why in practice its difficult to detect inteference phenomena when the objects become large (i.e. decoherence etc.)? Count Iblis 20:31, 24 June 2007 (UTC)

So far, why not is easy: we don't know a source that claims that. They claim "all particles", not "all objects", as far as I can find. The lead already mentions the "conceptualization" that all objects in our universe exhibit properties...; isn't that plenty? Dicklyon 20:53, 24 June 2007 (UTC)

Basic Reference: P.A.M Dirac, the principles of quantum mechanics. Wave-particle duality is a consequence of the formalism of quantum mechanics which is assumed to be universally valid... Count Iblis 14:38, 26 June 2007 (UTC)

Over what universe or domain? Does it include cheeseburgers? It means nothing. Dicklyon 15:08, 26 June 2007 (UTC)

That would be the universe. 1Z 15:20, 26 June 2007 (UTC)

Last I heard, we don't have ANY theory that can yet consistently describe the physics of the universe. At a large scale, where gravitational forces dominates, QM has little to say about how things are, since it has no gravity in the theory at all. So I don't see why you say that. Sources? Dicklyon 17:46, 26 June 2007 (UTC)

What do you consider objects to be made of? 1Z 21:10, 24 June 2007 (UTC)

Excellent rhetorical reductionist question! Dicklyon 22:20, 24 June 2007 (UTC)

To which the answer is? 1Z 23:25, 24 June 2007 (UTC)

Some objects are made of beef and cheese; others of sub-atomic particles. Just depends on what you have in mind by the too-general term "object". Dicklyon 03:45, 25 June 2007 (UTC)

Beef and cheese are made of..? 1Z 10:25, 25 June 2007 (UTC)

My two cents - There is a well-developed quantum mechanical theory of particles, and a well developed method of extending this theory to multiple-particle systems. A cheeseburger is a multiple-particle system, so in principle, there is a quantum mechanical description of it. This description is not at odds with any observations of the cheeseburger. In other words, quantum mechanics is consistent with the observed behavior of the cheeseburger. That is not to say that quantum mechanics is valid for the cheeseburger, for that we would need an experiment to detect, say, the wave nature of the cheeseburger, which is beyond present day technology. There may be a realm, presently beyond our ability to detect, at which quantum mechanics breaks down. Its hard to say (obviously). PAR 12:46, 25 June 2007 (UTC)

I disagree with your assertion that a cheeseburger is a multi-particle system. A fullerene molecule is a multi-particle system. A cheeseburger is a real-world messy object that has no conceivable connection to the kinds of objects that you can describe in QM, in my opinion. Your "in principle" is OK for the "conceptualization" line, but to say that a cheeseburger has wave properties or particle properties is a bit beyond what is supportable, isn't it? I'm not saying that QM breaks down, just that there are "objects" to which it applies and other "objects" that are just outside its domain. Dicklyon 17:55, 25 June 2007 (UTC)

If a fullerene particle doesn't exist in the real world,where does it exist?

Fullerenes certainly do exist in the real world, so I'm not sure what you're asking. Maybe whether they can be considered "particles" in the sense of QM? Probably so, but I'm not clear on whether those results have been substantiated and duplicated, so there may remain some question even there. Dicklyon 18:50, 25 June 2007 (UTC)

I don't see why you think it is important that anything should be a "particle in the sense of QM" sinece QM is readily applicable to ensembles.1Z 20:30, 25 June 2007 (UTC)

I understand that QM applies to ensembles, but I would argue that it is absurd to try to treat a cheeseburger as an "ensemble of particles"; it's just not possible to take an ordinary messy object with all kinds of evaporation and stuff going on and force it into the mold of something that QM is applicable to. Dicklyon 17:46, 26 June 2007 (UTC)

If QM doesn't break down in some cases, in what sense does it fail to apply?1Z 18:30, 25 June 2007 (UTC)

It doesn't "fail"; it's just doesn't apply. Just like it doesn't apply to psychological concepts, linguistic concepts, farts, and other "objects" outside its domain. Dicklyon 18:50, 25 June 2007 (UTC)

With enough reduction, it could apply to all of those. It can't be practically applied to those domains because of the vast amount of detail involved in making the reductions. But that is not to say there are separate domains of objects, just different levels of complexity. 1Z 20:30, 25 June 2007 (UTC)

Do physicists really believe that? Find us a source. Dicklyon 20:38, 25 June 2007 (UTC)

For a start, there must be a page on reductionism. 1Z 22:50, 25 June 2007 (UTC)

I have no problem with reductionism, except when it's taken to ridiculous extremes or to the exclusion of more sensible approaches. Dicklyon 22:54, 25 June 2007 (UTC)

Forget the cheeseburger

Do physicists believe that the formalism of quantum mechanics is valid for macroscopic objects? Yes! The few physicists who work on alternative ideas know that if their ideas were proven to be correct then that would be "big news", while if quantum mechanics were shown to be universally valid, then that would not make headlines. The altenative ideas include e.g. the hypothesis by Penrose that gravity causes wavefunction collapse and that this is somehow important for consciousness.

This is why black hole evaporaton via the Hawking process is such a hot item in theoretical physics. If the Hawking radiation is really thermal in the sense that it doesn't contain informaton about the particles that formed the black hole, then the laws of quantum mechanics cannot be exactly valid. According to quantum mechanics the initial state of a collapsing gas cloud and the final state of the radiation and matter, that forms after the black hole (formed by a supernova of the star which was created by the gas cloud) evaporates, are related by a unitary transformation.

So, this article should not give the impression that physicists are neutral about the validity of quantum mechanics in the macroscopic world. If one could show that, in principle, wave particle duality does not hold for cheesburgers (via indirect means or using entirely theoretical arguments) then that would really be earthshattering news. Count Iblis 14:24, 26 June 2007 (UTC)

OK, I think that's equally absurd. What sense does it make to say a theory "does not hold" in a domain to which it is not applicable? It's like proving that QM does not hold for Freudian psychology; makes no sense. Dicklyon 17:49, 26 June 2007 (UTC)

Actually, If I remember correctly, David Deutsch, who is a pioneer of the field of quantum computing, deviced a thought experiment involving a conscious entity simulated by a quantum computer. You could set up an interference experiment using that quantum computer where the conscious entity would evolve from one state to another state, but it can take two or more paths causing interference effects...

Anyway, if we say "QM does not hold" then that is not a trivial statement like "QM does not apply to Freudian psychology, Law, Theology, Rhetoric, etc.". What we mean is that a clear cut prediction of QM for the outcome of some experiment would be proven wrong if that experiment is actually performed, regardless of whether one can actually perform that experiment in practice. Quantum mechanics, of course, does not tell us whether Paris Hilton should have been sent to jail or not.  :) Count Iblis 19:04, 26 June 2007 (UTC)

Exactly, just as QM makes no predictions about cheeseburgers. Dicklyon 20:01, 26 June 2007 (UTC)

Nonsense. If QM is correct, it most certainly applies to cheeseburgers. A 1/4 pounder will have a wavelength of around 4.9e-33 when thrown at Paris Hilton at 1m/s.Kevin aylward 13:32, 10 September 2007 (UTC)

QM makes predictions about cheeseburgers in principle, but you wouldn't use it in practice. However, in-practice issues are not enough to found an ontology on. Different species is might have different limitations, but they live in the same universe with the same ontology. 1Z 07:44, 28 June 2007 (UTC)

Particle Only View

I have reinserted the Ballentine view, but corrected from my original. I see no reason for its deletion. It proposes a valid explanation as to the alleged wave-particle duality. Kevin aylward 13:26, 10 September 2007 (UTC)

If it is to stay, it should be balanced by the wave-only view as espoused by, for instance, Carver Mead. 1Z 22:25, 10 September 2007 (UTC)

I agree. The quote by Ballentine is not really very interpretable, and the interpretation that was there was unsourced. We've got a whole article about duality and a section on one guy who doesn't like it. I'm more with Carver Mead's side, since he can explain essentially all of electrodynamics by treating electrons purely as waves (but with charge quantized). I don't really see Ballentine's point, but I do very much see Mead's point. Dicklyon 23:05, 10 September 2007 (UTC)

I looked at the interview link (laputan) of Curver Mead. It seems to me that he was just saying the standard stuff, i.e. the wave of the SE, is the particle i.e. the shape of the wave function is the shape of the particle physically, like “ten foot electrons” with hills and valleys. Maybe I have misunderstood his view, but this particular well known idea is refuted by the Ballintine argument/experiment I cited below. If a photon is physically spread out, then it should trigger two detectors at once. Kevin aylward 19:45, 14 September 2007 (UTC)

You have misunderstood his view. Get the book. Dicklyon 20:14, 14 September 2007 (UTC)

Then explain what you mean by the word "wave". What is waving? what physically is it?

[I assume this is an unsigned comment by Aylward]1Z 09:13, 12 September 2007 (UTC)

---

(c) Suppose, finally that the object emitted by the source S, is a single particle, and that |psi(x,t)|2 is the probability per unit volume that at time t the particl will be located within some small volume about the point x. since the particle cannot be in two places at once, the triggering of D1 and of D2 at the same time are mutually exclusive events. Thus, the probability of a coincidence will be zero, as shown in (c)

Although this experiment is practical and of considerable importance for the interpretation of quantum mechanics, it does not seem to have ever been performed for electrons or any massive particles. However, an analogues experiment has been done for photons by Clauser (1974 ) and the result is only consistent with interpretation (c)

The result is only consistent with (c) out of the intperpretation Ballentine chose to mention.

The result is also consistent with an interpretations he chose not to mention; wave funciton collapse occurs randomnly on detection. Since the WF must become entirely localised at one of the detectors, the probability of coinididence is 0 as required.

Sure, and this is not in conflict with the quote. The mathematics of CI also effectively deny that there is a real physical wave. For example, the postulates of QM says the wave function is a mathematical function that gives the *probability* of finding a *particle* in a *volume*. Real, physical waves are not defined at all in the CI. Anyone that believes in a real probability current, has serious understanding issues, imo. Kevin aylward 07:46, 12 September 2007 (UTC)

The results of the experiment are consistent with interpretations where there is both a real physical wave and a real process of collapse. Whether you want to consider that a variation of the CI or something completely different is neither here no there; the point is that Ballentine has not exhastively shown that realism about waves is mistaken. He simply has not considered the full range of interpretations.1Z 09:13, 12 September 2007 (UTC)

Ballentine, of course, addresses other views in detail. In fact, very few text books address the interpretation of QM at all. However, it us a bit much to type out all the relevant quotes from his book that support the arguments here. I would suggest that you buy a copy. Its a great book. In fact, without the book, its hard to understand the full argument as to why callapse of the wave function is redundant. A key idea is occams razor. Like, remove any unnecessary assumptions, esspecially ones that can't be measured.

Secondly, until someone explains just what they mean by a “physical wave”, wave is just a meaningless word. For example, we know that water waves and their properties (refraction, diffraction etc), are not really due to water being a continuous substance with peaks and valleys, because it isn’t. Its made up of particulate molecules, and it is the interactions between molecules that, presumably at an approximate classical level of explanation, explains such apparent continuous wave phenomena. So for me, I don’t see true waves existing in the classical universe, so why should they exist in the quantum universe? Kevin aylward 10:43, 12 September 2007 (UTC)

If Ballentine addresses other views, you as an editor need to summarise them in order to make a good contribution to the article -- as well as representing a range of other opinion, for balance. I personally suspect that Ballentine's arguments are circular; the thinks collapse is redundant because he doesn't beleive in waves; and his argument against waves is based on disregrading collapse.1Z 15:50, 12 September 2007 (UTC)

Explanations are much simpler in the ensemble view. The issue here, as I have noted, you haven’t read the Ballentine book, so you only have limited idea of what the full Ballentine arguments for that are. By itself, this is reasonable, however, you can’t expect that I can copy all relevant information to eliminate all potential misunderstandings. One should appreciate that Ballentine, although not necessarily correct, has professional examined QM foundations in considerable detail, over 30+ years, so its unlikely that he will have missed any potential major refutations of his approach. Most of the editors here, like myself, are still only amateurs.Kevin aylward 15:13, 12 September 2007 (UTC)

If you cannot summarise LB's argument in a way that doesn't have obvious gaps, it would be better to just allude briefly to his conclusions. That would leave more room for other POVs.

As far as I am aware, LB's work has not been considered sufficently noteworthy for anyone to attempt to refute it. The Ensemble Interpretation is a dead duck for most physicists. 1Z 15:50, 12 September 2007 (UTC)

I don’t think most physicists even know about the Ballentine view. Most physicists don’t care about interpretations. I am sure that you can appreciate, to my knowledge, that around 90% of the worlds physicists are semiconductor physicists working at semiconductor manufactures, as that is actually were the real jobs and the readies are.

There is no realistic chance that Ballentines ensemble interpretation can be refuted as it is mathematical identical and equivalent in all ways with the CI as far as verifiable results go. The essence is simply that the state vector applies to ensembles, not to individual systems. To varify QM, one needs to do repeated experiments and see if the probabilities agree.

Despite what physicists say, in practise, they essentially use the EI unbeknown to them. The reality is that QM says not a lot about a single experimental run. You see, its all in the postulates, like, the *probability* of an observable being within a given range. To calculate and verify probabilities, you *must* run ensembles of experiments, like standard deviations to wit. There is no way to verify for example, a claim that the state vector refers to an individual system, because the postulates state that the result of any and all measurement must be a single eigen state with single eigen value. Any such claims to the single system are mere, experimentally unsupportable pontifications, imo. Kevin aylward 15:58, 14 September 2007 (UTC)

There is such a thing as a "wave equation" in maths even if the physical interpretation is unclear.

Yes, but it is meaningless to say that there exists, real, physical waves, if such physicality can’t even be described in even a basic sense. There is a claim that in QM, there are real physical waves. Well Habeas Corpus. What is this wave? Kevin aylward 15:13, 12 September 2007 (UTC)

What are these non-Newtonian dynamics? "What is X really" questions are hard to answer for any number of values

of X. But at least the wave realists have a predictive theory, and empirical resutls that conform to it.1Z 15:50, 12 September 2007 (UTC)

"So for me, I don’t see true waves existing in the classical universe, so why should they exist in the quantum universe?". That is a non-sequitur. Obviously, classical and quantum physics are different. Why shouldn't

that be one of the differences?

Oh dear, you miss the point. If classical waves are ultimately the result of particulate behaviour, i.e. true waves do not exist classicly, they are an illusion, then why should real waves magically appear in QM. Since QM can be explained from the particle point of view, why invent a truly new unit, the wave, which never previously existed even classically. Occams razor.

I haven't missed the point. You have made the same error again. Waves should non-magically appear in QM because QM is a different theory and that is one of the differences. There is nothing in CP to show that waves are absurd or impossible. There just happens not to be no such thing as a matter wave in CP, although there are energy

waves, as in Maxwell's EM theory. 1Z 15:50, 12 September 2007 (UTC)

The particle-only "explanation" of QM is a mere promissory note, since you have no maths to support it. S's E is a wave equation.1Z 15:50, 12 September 2007 (UTC)

Pardon again. I have no idea what you are on about here. The support is all in Ballentines text book. Every lock stock and barrel of QM is explained from the ensemble view point. Why don’t you get the book?

In any case, you are still not addressing the editorial issues, such as lack of balance. 1Z 11:19, 12 September 2007 (UTC)

This appears to be well accounted for by the other editors “balance” [unsigned comment presumably by KA]

No-one has so far added material to balance your contributions. Editors are suppsoed to balance their own contributions as far as they are able. 1Z 15:50, 12 September 2007 (UTC)

I am not saying the Copenhagen Interpertation is necessarily correct. However, it is clearly the case that it has not been disproved in any widely accepted fashion. 1Z 13:03, 11 September 2007 (UTC)

From the extended quote that Kevin added, it's clear that Ballentine's objections have little to do with what is meant by the wave nature of matter. He's saying that a photon is not a wave packet, and that's true, but it's not what duality of this article is about. Dicklyon 15:16, 11 September 2007 (UTC)

Of course it’s relevant to duality. Its fundermental. The wave packet is how one actually calculates all of the wave properties on an object. Without the existence of a wave packet, there would be no wave–particle duality at all, because there would be no wave like properties that would have caused the invention of the wave packet concept. It would all be de-facto particles. dah...Kevin aylward 07:46, 12 September 2007 (UTC)

Wave behaviour has an empirical foundation too.1Z 09:03, 12 September 2007 (UTC)

Yes, but invented when people did not know about molecules. After the fact, we now know that classical waves are pure fiction. Classical wave properties are strictly the result of particulate behaviour. There are no continuous disturbances in any real medium. Show me some empirical evidence that a continuous substance exits, as apart from an approximation to a continuous substance.

Objections to a theory are relevant if they are notable, but the PO section is not balanced or well-expressed. It should be called "controversy", for one thing 1Z 15:30, 11 September 2007 (UTC)

It should only be called controversy if there's a reliable source that says there's an active controversy. This sounds more like an item for interpretations of quantum mechanics. Dicklyon 15:39, 11 September 2007 (UTC)

There is an abundance of information on the controversy, see the Bohr-Einstein debate for instance. 1Z 09:03, 12 September 2007 (UTC)

I don't see why. interpretations of quantum mechanics is an overview page, it does not explain controversies in detail. And jsut about every aspect of QM is subject to active contorversy 1Z 16:03, 11 September 2007 (UTC)

That was just my idea of a better place. If you have a source discussing wave–particle dualiy as a controversy, you can talk about it. My impression is rather that the "interpretation" of the duality is where the controversy is, or was; see [3] or [4]. Dicklyon 16:49, 11 September 2007 (UTC)

There is controversy about where theory ends and interpretation begins, too. 1Z 18:54, 11 September 2007 (UTC)

Great; find a source about that controversy and let's mention it. Dicklyon 22:35, 11 September 2007 (UTC)

Ok, I will leave the Ballinine quote here for now. I think it is an important view on wave particle duality. I will wait for Dicklyons response as to the reasons why he claims that the actual nature of wave packet is irrelevant to wave particle-duality. It certainly has me banging my forehead on the wall.Kevin aylward 07:59, 12 September 2007 (UTC)

Ballentine says nothing about the "nature of the wave packet", since his "non-Newtownian dynamics"are unspecified. 1Z 09:03, 12 September 2007 (UTC)

Pardon? The experiment, which he is describing, says that the wave packet is most certainly not a real physical object that, for example, gets split in two. Therefore he is addresing the claimed true nature of the wave packet, that is, it is a virtual construct. The non-Newtonian dynamics are indeed specified, by the shrodinger equation, that is, the probability that a discrete particle will have a position and momentum within some range of values. Its not “his” mechanics, it’s, essentially, standard QM as far as the sums go Kevin aylward 10:23, 12 September 2007 (UTC)

His argument against a realistic interpretation of wave function is invalid for the reasons already given. Solutions to the S.E are wave mechanics, at least as far as the mathematical form goes. (The question of the mathematical form is of course separate to the question of the ontological interpretation). A solution to the S.W.E is not "dynamics" in the sense Ballentine requires; it does not describe forces acting on a point particle causing it to swerve from a Newtonian course. 1Z 11:08, 12 September 2007 (UTC)

Ballentine On Wave packet

Ballentine continues, p.101, by describing a coincidence experiment. This apparatus consists of a source emitting particles described, by a wave packet towards a semitransparent, semireflecting barrier with transmitted and reflected being detected by D1 and D2, and the coincidence detector, C12. He notes:

(a) Suppose that the wave packet is the particle. Then since each packet is divided in half, according to the solution (4.4), the two detectors will always be simultaneously triggered by the two portions of the divided wave packet. Thus the records of D1, d2, C12 will be identical, as shown in (a)

(b) Suppose that the wave function of (4.4) is a physical field in ordinary space, but one that is not directly observable. However, it leads to observable effects through a stochastic influence on the detectors, the probability of a detector recording a count being proportional to the integral |psi(x,t)|2 over the active volume of the detector. Since the emission probability within an interval dt is p=rdt, and since the wave packet divides equally between the transmitted and reflected components, the probability of D1 recording a count during an interval dt is p/2, as is also the probability for D2. If two the detectors (and hence the two wave packets) are sufficiently apart, the triggering of D1 and of D2 should be independent events. Therefore the probability of a coincidence will be c =p2/4

(c) Suppose, finally that the object emitted by the source S, is a single particle, and that |psi(x,t)|2 is the probability per unit volume that at time t the particl will be located within some small volume about the point x. since the particle cannot be in two places at once, the triggering of D1 and of D2 at the same time are mutually exclusive events. Thus, the probability of a coincidence will be zero, as shown in (c)

Although this experiment is practical and of considerable importance for the interpretation of quantum mechanics, it does not seem to have ever been performed for electrons or any massive particles. However, an analogues experiment has been done for photons by Clauser (1974 ) and the result is only consistent with interpretation (c)

Thus the idea that the photon is a spread out “wave” in some manner is claimed to be refuted experimentally. The suggestion is that, just as the wave properties of light can be experimentally varified as the statistical nature of photonic laws of motion, the wave properties of material particles are explainable by the statistical nature of non-Newtonian laws of motion. Thus, the claim that there is no wave-particle duality, only particles. Kevin aylward 07:29, 12 September 2007 (UTC)

Don't think this belongs. Apart from anything else, it doesn't stand on its own. What is a reader supposed to make of being referred to equation 4.4? Or (a) ... as shown in (a)? William M. Connolley 10:42, 12 September 2007 (UTC)

This section was removed from the main page prior, however, you also removed a valid sub section, the particle only view. I have re-added it. If someone wants to put a wave only view in, fine. The above section forms an alternate to the overwhelming bias on the page that there is a wave-duality issue.

The wave function is pretty obvious in 4.4, but yes it is hard to be complete. Kevin aylward 15:57, 12 September 2007 (UTC)

Bias is dispoportionate over-or-under representation. It is perfectly legitimate for a most of a page to be devoted to the majority view on a subject. 1Z 16:02, 12 September 2007 (UTC)

What is a wave? What is a particle?

The article needs clear answers to theses questions. 1Z 23:59, 14 October 2007 (UTC)

Those answers should exist at wave and particle. --Michael C. Price ^talk 00:15, 15 October 2007 (UTC)

"Agreeing on a single, all-encompassing definition for the term wave is non-trivial". 1Z 10:47, 15 October 2007 (UTC)

I'm not disputing that, just questioning whether we need to repeat the same points *here*, when they should be covered somewhere else that we can link to. --Michael C. Price ^talk 11:06, 15 October 2007 (UTC)

That was a direct quote from wave. So it is not covered elsewhere, in a simple and clear way.1Z 11:11, 15 October 2007 (UTC)

That doesn't alter the fact that is where it should be covered, as I originally said. --Michael C. Price ^talk 11:38, 15 October 2007 (UTC)

That doesn't alter the fact that the lay reader is not going to be well informed, because the article plunges itno a discussion of W/P issues without laying out the groudn rules.1Z 14:30, 15 October 2007 (UTC)

If it is linked to, then why should the reader be confused? I do read the links on subjects I know little about. --Michael C. Price ^talk 08:27, 19 October 2007 (UTC)

The reader should be confused because there is not a clear explanation in the link, as I have demonstrated by direct quotation from it.1Z 14:29, 20 October 2007 (UTC)

If that's the case, then the logical next step would be to edit the wave and particle articles to make them better. --Steve 16:21, 20 October 2007 (UTC)

Exactly. --Michael C. Price ^talk 17:14, 20 October 2007 (UTC)

All objects?

We've been over this before, but with no good resolution. Has anyone found a reliable source in support of the "all objects" assertion? I think it differs from de Broglie's "all matter". The matter that matters is the matter that's quantizable. The terms "objects" is just too vague, and tends to make popularizations go off on the deep end and talk about the wavelength of things that do not have a wave function per se. So let's stick to what's verifiable in reliable sources, OK? Dicklyon 18:06, 17 October 2007 (UTC)

Eh? "all matter" covers everything, including all objects. What you mean by the "things that do not have a wave function per se" leaves me baffled, since everything can be ascribed a wavefunction. According to de Broglie everything with a momentum has a wavelength. Now what "things" don't possess momentum? --Michael C. Price ^talk 21:10, 17 October 2007 (UTC)

As mentioned in the article, a bacterium (for example) will have a de Broglie wavelength smaller than the Planck length, and most physicists agree that "space" isn't well-defined at that scale. I don't think the de Broglie hypothesis has even been formulated (let alone widely accepted by the physics community) in the Planck-length, quantum-gravity, string-theory regime.

Perhaps the article's opening could say, "According to traditional formulations of non-relativistic quantum mechanics, all objects...", or something like that.--Steve 21:43, 17 October 2007 (UTC)

Not just non-relativistic quantum mechanics: de Broglie is relativistically valid. --Michael C. Price ^talk 12:40, 19 October 2007 (UTC)

I think you didn't read what I said. I'm not talking about special relativity, I'm talking about general relativity and quantum gravity. Wavelengths smaller than the Planck length are quite possibly meaningless, and there's certainly no consensus among physicists in that regard. --Steve 15:49, 19 October 2007 (UTC)

I read exactly what you said: "non-relativistic quantum mechanics". You were talking about string theory/ QG elsewhere.--Michael C. Price ^talk 22:38, 19 October 2007 (UTC)

Regardless of what you understood me to have said, the point remains: You said above that "everything...has a [de Broglie] wavelength". According to string theory/QG, objects larger than the Planck mass do not. --Steve 03:38, 20 October 2007 (UTC)

No, not "according to string theory/QG". They are merely unfinished quantum theories about which no definitive statements can be made with complete confidence. --Michael C. Price ^talk 06:45, 20 October 2007 (UTC)

Sure, it would say that; if we had a source. Dicklyon 00:44, 18 October 2007 (UTC)

Sources:

• "Fundamental formulas of Physics" by Donald H Menzel gives the de Broglie wavelengths for electrons, protons and neutrons; protons and neutrons are composite particles.
• Brian Greene, The Elegant Universe, page 104 "all matter has a wave-like character"

There are gizzilions of other sources, by reliable physicists, that ascribe wavelengths to even larger composite objects. --Michael C. Price ^talk 08:59, 19 October 2007 (UTC)

No argument that composite objects can be quantum objects. But I've searched and not been able to find anything about "all objects". What about the object of my desire? Too abstract to have a wavelength, I bet. If Greene has it in his book, I can't find it; check here and maybe you can point it out, or quote it from your copy. Dicklyon 15:23, 19 October 2007 (UTC)

I'm happy to quote Greene as I have. "All matter" is sufficient for me.--Michael C. Price ^talk 15:28, 19 October 2007 (UTC)

PS I'd be interested to hear of what you consider a non-quantum object. --Michael C. Price ^talk 15:30, 19 October 2007 (UTC)

Well, the example I used before was a cheeseburger. There's just no way that such a messy object can be in the space things to which QM is applicable. Even a bacterium is highly questionable, not just because it's wavelength would be so short, but because it is not really quantizable; it has molecules coming and going all the time, so there's no way to pin down what it is the degree of precision needed for QM to be applicable. "All matter" is better, but it seems to leave out the pure-energy objects such as photons. Dicklyon 17:46, 19 October 2007 (UTC)

Again you claim that QM is not applicable to messy objects. Bollocks. As for photons, I think no one doubts that they exhibit wave properties -- de Broglie extended the wave-particle-duality from photons to all matter.--Michael C. Price ^talk 22:42, 19 October 2007 (UTC)

QM applies to all matter and photons, yes. I don't mean to say that it doesn't apply to the matter in cheeseburgers. But it's absurd to say that cheeseburgers have particle or wave properties, because QM doesn't apply to the cheeseburger as an object. Dicklyon 23:33, 19 October 2007 (UTC)

Still completely wrong. QM applies to everything. --Michael C. Price ^talk 06:45, 20 October 2007 (UTC)

Sure it does, in a trivial sense. That doesn't mean that "everything" has a wavelength. Dicklyon 07:04, 20 October 2007 (UTC)

Yes it does, since wavefunctions always come with complex phase factors. --Michael C. Price ^talk 07:06, 20 October 2007 (UTC)

But I still doubt that you'll find a physicist who says that a cheesburger has a wave function. I keep waiting for someone to find a source, but I don't see it. Dicklyon 07:08, 20 October 2007 (UTC)

If you need a source that specific then you are sadly deficient. You won't find a source that says that woolly mammoths had wavefunctions. Neither will you find a source that says they didn't have wavefunctions. Work it out. --Michael C. Price ^talk 17:24, 20 October 2007 (UTC)

Obviously, nobody is asking for a source on wooly mammoths or cheeseburgers having wave functions. I'm asking for a source that implies they do by saying "all objects" in a way that does not exclude such messy non-quantizable objects. Dicklyon 17:38, 20 October 2007 (UTC)

There are no "non-quantizable objects". And look up quantum cosmology. --Michael C. Price ^talk 07:32, 21 October 2007 (UTC)

OK, good. What's your source for that? Dicklyon 08:06, 21 October 2007 (UTC)

Of course, having a (theoretical) WF, and displaying (empirically observable) wave behaviour are two different things. 1Z 14:35, 20 October 2007 (UTC)

Of course. But that's not what's at issue here. Dicklyon 17:38, 20 October 2007 (UTC)

Isn't it? What are your grounds for denying that a theoretical WF can be applied to macroscopic objects? 1Z 15:28, 21 October 2007 (UTC)

I'm not so much denying it as asking for a source for it. The only conditions I know of where QM applies to macroscopic objects in the sense of treating them as waves is when those "objects" are behaving coherently. For example, the light in a laser, the collective electrons in a quantum Hall device, the bulk of a Bose–Einstein condensate, etc. I've never heard a physicist claim that "all objects" have wave functions, but these examples do; and so far nobody has found a reference to that effect, so let's don't claim it. Dicklyon 15:45, 21 October 2007 (UTC)

There is a difference between "wave function" and "wave", too. Localised particles still have WFs. So the question of coherence is not particularly relevant. 1Z 19:05, 21 October 2007 (UTC)

All fundamental equations are quantum equations.--Michael C. Price ^talk 18:56, 21 October 2007 (UTC)

Redirect

Why, when I seek "Wave-particle duality", am I redirected to http://en.wikipedia.org/wiki/Talk:Wave%E2%80%93particle_duality ? I don't know what "%E2%80%93" represents, but if it's not a hyphen, it's wrong. Just look at the conversation on this talk page. Does anybody use any other character in that position than the hyphen? Of course not. Unfree (talk) 11:22, 24 December 2007 (UTC)

People don't usually bother to type the correct character for connecting two equal concepts, which is an en dash. The title is correct. Dicklyon (talk) 16:16, 24 December 2007 (UTC)

de Broglie's parodox

Quantum Mechanics considers the duality wave-particle through the interpretation proposed by de Broglie. The diffraction has been detected for the elementary particles, as electrons, protons, neutrons, molecules. Considering these experiments, we show here that there is a grave incompatibility between this solution of Quantum Mechanics and the Michelson-Morley experiment, if we replace the light by protons, and Michelson’s interferometer is replaced by a crystal.

3. MICHELSON-MORLEY EXPERIMENT FOR PROTONS

When an electron crosses a crystal, it can suffer diffraction according to the Bragg’s relation, which is: nλ = 2.d. senφ .... [2.1]

Davisson, Germer and Thomson made experiments with φ = 65^o , d = 0,91Å , and electrons with kinetic energy 54eV.

Through the expression 2.1 we get: λ= 1,65 Å .... [2.2]

The wavelength of de Broglie, for the electrons with energy 54eV used at the Davisson-Germer-Thomson experiment, is:

λ = h/p = 6,6x10-34j-s/4,0x10-24kg-m/s = 1,65 Å .... [2.3]

Electrons with kinetic energy 54eV have approximately a speed 4.000km/s. As we see, the postulate of de Broglie gets the same result of the Bragg’s relation. According to the authors Robert Eisberg & Robert Resnick[1], the electron suffers diffraction into the crystal because “there is a constructive interference of waves spread by the periodic arrangement of the atoms in the planes of the crystal ”. So, this constructive interference is a consequence of: d=0,91Å within the crystal, and the electron’s speed 4.000km/s.

In the experiments of diffraction electrons are used with speed 4.000km/s. But instead of using electrons we can replace them by protons. As the proton has a mass 2.000 times greater than the electron, then de Broglie’s wavelength of a proton with speed 2km/s will be 1,65Å. Then let us imagine Michelson-Morley experiment, made with a proton with speed 32km/s.

We will consider the Sun as a reference at rest. And in order to simplify the explanation, let's consider that the Earth's translation velocity around the Sun is 30km/s. So the crystal in our laboratory has a speed of 30km/s with regard to the Sun. But the Bragg’s relation does not depend on the speed of the crystal, in order that through his relation we get the value λ=1,65Å.

Now let us submit the protons to the experiment, when they are emitted in two directions. Let us analyze the two different directions of the proton’s motion in the experiment.

Michelson-Morley experiment for protons:

1- First let us consider that the flux of protons is emitted with 32km/s in contrary direction of the Earth’s motion. The speed of the protons with regard to the Sun is 32km/s - 30km/s = 2km/s. So, by de Broglie’s relation we get a wavelength λ=1,65Å , and by the Bragg’s relation we also have λ=1,65Å. This means that the proton shall be submitted to the diffraction effect into the crystal, and we can detect the proton’s duality by the experiment.

2- Now consider the flux of protons emitted with 32km/s in the same direction of the Earth’s motion. The speed of the protons with regard to the Sun is 32km/s + 30km/s = 62km/s. Then, the proton has a de Broglie’s wavelength λ=1,65Å/31 = 0,055Å, while from the Bragg’s relation for the crystal λ=1,65Å. Therefore such proton cannot suffer diffraction into the crystal.

This is the result that we have to expect from the concepts of Quantum Mechanics. But suppose that we make this Michelson-Morley experiment for protons, and we get a result showing that the speed 30km/s of the Earth does not have influence on the proton’s diffraction, no matter the direction of the flux of protons with regard to the Earth’s motion. Clearly this experimental result does not fit to the concepts of Quantum Mechanics, as has been shown above. One can say that there is no paradox, because it is necessary to consider the velocity of the crystal with regard to the proton, i.e., actually it would be necessary to consider the relation λ= h/m(V-v), where V is the velocity of the proton, and v is the velocity of the crystal. With such argument, actually we are introducing the Doppler effect between the proton and the crystal. However such argument is valid only for pure waves, it is not valid for the de Broglie’s idea of duality. Let us show why.

Consider a proton with speed 30km/s. Its wavelength h/mv is λ= 0,11Å. And if we use a crystal with distance d= 0,06Å , from the Bragg’s relation we get λ= 0,11Å, and therefore in the laboratory we must detect the proton’s diffraction. This is the prediction according to de Broglie’s interpretation. But now consider that we make such experiment with the proton going in contrary direction of the Earth’s motion around the Sun. Therefore, with regard to the Sun, the velocity of the proton is Vp= 0. In such experiment, the proton is at rest, while the crystal has a velocity Vc=30km/s toward the direction of the proton. Unmistakably the proton is stopped with regard to the Sun, and this means that it does not have wave feature. The proton with Vp= 0 is 100% corpuscular, and therefore it cannot suffer diffraction into the crystal. So, the de Broglie’s interpretation is wrong.

Obviously we have a paradox. The duality, according to the interpretation of de Broglie, is not compatible with the Michelson-Morley experiment for protons. Let us call it Michelson-deBroglie Paradox. It shows that it is not correct the de Broglie's interpretation for the relation λ=h/p.

Instead of being a property of the matter, it's possible the duality wave-particle may be a property of the helical trajectory of elementary particles as the electrons. The helical trajectory is known as zitterbewegung, which appears in the Dirac's equation of the electron .

From such new interpretation, the duality wave-particle is not a manifestation of the matter. Actually it's a property of the helical trajectory. —Preceding unsigned comment added by 200.149.61.68 (talk) 03:48, 15 April 2008 (UTC)

For some sources about this, including some that resolve it, see here. It might be sensible to add something to the article, as long as it's well rooted in reliable sources. Dicklyon (talk) 05:04, 15 April 2008 (UTC)

Complementary Principle

I read the article Copenhagen interpretation. It mentions the Complementary Principle (it is capitalized in the article, perhaps to differentiate it from other principles that are complimentary to one another). I checked to see if Wikipedia had an article titled, Complementary Principle or complementary principle, but it did not. I then searched for "Complementary Principle" with Google. The results I got paired the Complementary Principle with wave–particle duality (the Copenhagen interpretation article mentions it, too, of course). Therefore, I redirected Complementary Principle to this article. If that is inappropriate, feel free to delete it or redirect to another article. If the redirect is acceptable, then I think it would help those who are redirected to mention the Complementary Principle in this article, if only in passing. I do not know enough about the subject to do it myself. Thanks, Kjkolb (talk) 07:16, 9 September 2008 (UTC)

If someone hadn't misspelled complementarity principle in Copenhagen interpretation you wouldn't have gone off on that wild goose chase. I'll redirect your new complementary principle accordingly. Dicklyon (talk) 15:23, 9 September 2008 (UTC)

Feynman quote

I want to emphasize that light comes in this form—particles. It is very important to know that light behaves like particles, especially for those of you who have gone to school, where you were probably told something about light behaving like waves. I'm telling you the way it does behave—like particles.

Quoting this part alone seems to imply that Richard had a non-mainstream opinion about the wave–particle duality. But later on on that book, he says:

In fact, both objects [photons and electrons] behave somewhat like waves, and somewhat like particles. In order to save ourselves from inventing new words such as "wavicles," we have chosen to call these objects "particles," but we all know that they obey these rules for drawing and combining arrows [representing complex numbers] that I have been explaining.

So I think it's better to remove that quote, because it is very likely to be misunderstood, especially given its place in the article. --A r m y 1 9 8 7 ! ! ! 21:10, 17 September 2008 (UTC)

Better would be to include both quotes. --Michael C. Price ^talk 07:11, 18 September 2008 (UTC)

I think you missed my point. The introductive paragraph of the "Particle-only view" subsection calls it "an offshoot of determinism", but I don't think Feynman was a determinist (or, at least, he didn't give a damn about the issue). "I am not going to explain how the photons actually "decide" whether to bounce back or go through; that is not known. (Probably the question has no meaning.)"; "you can have all the philosophical worries you want as to what the amplitudes mean (if, indeed, they mean anything at all), but because physics is an experimental science and the framework agrees with experiment, it's good enough for us so far." So there is no point why he should be included in that section in the first place. A r m y 1 9 8 7 ! ! ! 09:21, 18 September 2008 (UTC)

Since you didn't make the point, no wonder I missed it!

However the quotations(s) seem to merit inclusion the article somewhere. --Michael C. Price ^talk 10:43, 18 September 2008 (UTC)

Well, that was I meant by "Quoting this part alone seems to imply that Richard had a non-mainstream opinion about the wave–particle duality." But now I realize that that was not very explicit; indeed, that would mean what I meant to mean only if no mainstream scientist believed in determinism... A r m y 1 9 8 7 ! ! ! 14:37, 18 September 2008 (UTC)

I've added them back into the section with some contextural comments. Also tidied up the stuff about the pilot wave and added a comment into the "wave only" section about many worlds. --Michael C. Price ^talk 11:10, 18 September 2008 (UTC)

Yes, that's all right, thank you. A r m y 1 9 8 7 ! ! ! 14:37, 18 September 2008 (UTC)