Talk:Copenhagen interpretation

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The flamewar is going out of control, so let's just stop. See Wikipedia:Wikipetiquette, particularly the section "How to avoid abuse of /Talk pages".

In summary, it has been suggested that the current article does not serve the layman well. An overhaul of the article was thought to have removed too much information, and was reverted. The best thing to do now w.r.t. the article is probably to merge the overhaul into the current article, avoiding any unnecessary deletion. The consensus seems to be that deleting the entire article is unnecessary deletion. To avoid controversy, it would be good to be extra meticulous. Before making a claim in the article, quote reputable sources, and document the references in a "references" section. Thanks. -- CYD

I lay that accusation against all the physics articles. You people need to find a layman who'll tell you what's comprehensible, what isn't, what's of no interest, what's irrelevant and what gratuitously creates confusion. And when you find that person, you should declare them Tyrant over all of the physics section. And if you're really smart, you'll also find a historian, a historian of physics if you're extremely lucky, to do the same job. Then you need to distinguish ontology, mathematics and history strictly.

So sayonara suckers and may a place be reserved for you in Gehenna.

--Ark, Friday, June 7, 2002

I don't have any objection to rewriting the physics pages to be comprehensible to the layman. My objection is that in the process of doing so, one absolutely, positively must not sacrifice correctness, and that the changes that Ark suggested did so.

Nobody understands quantum mechanics and no one is not confused by quantum mechanics. Much of the confusion arises from experiments that don't make any sense at all. The goal as I see it is to "present the confusion clearly" and explain clearly why it doesn't make any sense. -- RoadRunner

I removed the sentence:

The results of this experiment are particularly preplexing when one considers that this is not a thought experiment, but an actual real experiment that can be quite easily performed with photons, electrons, atoms, molecules, and even small viruses.

Firstly, regardless of whether or not this experiment in the form noted is "quite easily performed", it wasn't in fact performed until 1989 (using electrons; see double-slit experiment). Thus, for the greatest part of its life, it was indeed a thought experiment; just as Schrodinger's cat experiment was (although the latter has now finally been performed, I think in 2000 - no cats were injured in the process of the experiment :) ).

Secondly, to perform the experiment with "... atoms, molecules, and even small viruses" would require a coherent source of these objects - something none too easily acheived. Certainly we can imagine that the results would be the same; but that again is the domain of a thought experiment. -- Chas 18 Oct 2001 19:10 UTC

[edit] Contradicting Articles

Something of a problem: Sundry articles which link to this page, for example the EPR paradox page, claim that the Copenhagen interpretation treats measurement as significant and wavefunction collapse as an actual physical event or process (this is in fact the description that I have been taught, both by earlier articles at this location and by a couple of high school teachers). However, the article in its current state claims that collapse does not actually happen, and represents instead an approximation of the truth, which is (the article implies) that the particles has a definite speed and position at all times, which we are simply not aware of. Not only does this contradict summaries of this article present elsewhere, it is in blatant contradiction (as far as I can see) of the EPRB paradox. --209.30.128.163 23:17, 21 February 2007 (UTC) Minor edit a couple seconds later: Whoops, mislinked the EPR Paradox article. My bad.--209.30.128.163 23:18, 21 February 2007 (UTC)

The article should not say "Particles has a definite speed and position at all times", that is not Copenhagen and is contrary to almost every interpretation , in fact.1Z 01:24, 6 March 2007 (UTC)

I afraid I was taught Physics (graudate level) nearly 30 years ago, when Copenhagen was the only game in town. The waveform was presented as a "unreal" calculation tool. It wouldn't surprise me if a great deal of articles relating to this subject contradict each other, because (1) it is complex area, (2) a lot of the arguments surround issues of who said what (sometimes a single word or phrase in another language) and (3) even Great Minds contradict themselves. It seems to me (*** WARNING - opinion here ***) that the reality of the waveform is the late 20th Century equivalent to luminiferous ether, which seems to be making a comeback as well (sigh). The idea that a probability description is an approximation to the truth is not accepted by Copenhagen. What is truth? Positivist would say it is what is measured (or words to that effect). It is the only truth. That's why this topic is so difficult.

If there are conflicting views, the article should cover all of them (or at least the notable ones). The material you have been deleting has been appropriately cited. The material you have been inserting wasn't.1Z 01:22, 6 March 2007 (UTC)

---

??? The article should not say "Particles has a definite speed and position at all times", that is not Copenhagen and is contrary to almost every interpretation , in fact.1Z 01:24, 6 March 2007 (UTC) ???

No it doesn't. You will have to explain that one. It is not possible for an interpretation to be agnostic about whether the waveform is real or not; it is at the heart of any QM interpretation. I think that saying it is hard to reconcile the reality of the waveform with some of the statements of Bohr and Positivism is being kind. I also don't think that quotes work very well in this area, since it is possible to find a quote from someone backing up just about anything - a sea of contradictory quotes simply obfuscates. Some of the deleted material is just plain wrong: A probability description does not implies a hidden variable approach. It fails to understand the whole point of Copenhagen. The idea of "collapse" really originates with Von Neumann (I have the book ;-)). The use of a single word ("collapse" or "reduction") by Bohr or Heisenberg does not mean that user subscribes to the collapse of a real waveform. Using a quote to suggest otherwise is questionable. The term "Waveform Collapse" has aquired a specific meaning that I would argue it did not originally have. If QM is just rules for calculating the probability of outomes for a specific experiment, then once the measurement is made, the experiment is over and the "waveform" has served its purpose. I would argue that the "Waveform Collapse" now implies a real waveform, and from a pedagogic position, it becomes difficult to use that term without invoking images of a real waveform - something that is not part of Copenhagen.

An interpretation can be agnostic about anything. Shut-up-and-calculate is often said to be a popular interpretation, and it is agnostic about everything.

As explained in the article, the development of wave mechanics by Schrod. made it easier for Heis. to take a realistic stance. There is more than 1 person involved, and their views changed over time.

You must be unique among wikipedia editors in being able to easily find quotes. Most articles are planted with "citation needed" tags.

The article explains that collapse started as a formal procedure and became more ontological.

Using a quote to suggest otherwise is the only way of establishing the facts. 1Z 00:20, 7 March 2007 (UTC)

Can I emphasise again that there is no justification for removing relevant, sourced material from an article. If you disagree with it, that is just your WP:POV. If you can find contrary sources, there is a controversy, both sides of which should be reflected in the article. Please read and understand Wikipedia:Five_pillars

1Z 00:27, 7 March 2007 (UTC)

I am not defacing this article. I am editing it. Your quotes are misleading. One of the aims of this encyclopedia should be clarity. Some of your material is just plain wrong. You seem to think a probabilty description implies hidden variable.

You need to explain which passage you are referring to.

You use this as justification for "defacing" (your term) my entry.

editors don't own entries.

I will make an attempt at explaining why this is not so.

Kant (greatly paraphrased): We perceive the world through our senses. We build mental models of the world and apply logic to them. But the "real" world is "unknowable". And the mental models are not "real". Kant was talking, not about QM, but the division between science and meta-physics (including religion). In Kant's time, philosophers readily made pronouncements about God, Heaven etc. The Kantist division between Science and Religion is now well entrenched. Science is knowable, because it relates to what we can "sense". God and the great beyond is unknowable because we cannot sense it. Positivism goes even further and rejects all religion as meaningless since it cannot be sensed. The Copenhagen Interpretation is regarded as a Positivist (Sir Karl Popper) interpretation, or possibly Kantist. (Do a search on the web).

I have already studied both Kant and the CI.

The idea then is the the whole world we reason with is a mental model. A good mental model means that real world as experienced through our senses does what we expect. Newtonian Gravity was "real" after Newton, but not after Einstein, in that the model was so good that it is easy to forget it was a model. That's why people like Einstein define what they mean by "reality".

Copenhagen says that all we can know about the world is obtained by measurement. It is an operational view + elements of Positivism and/or Kantism. It may be that the best "operational" mental model possible is probabalistic, but that does not imply underlying hidden variables or other such nonsense.

I don't know who you think does believe that.

The other side of the measuring devices (senses) is unknowable (Kant, Bohr). I hope you understand the quote from Aage Petersen better now.

Copenhagen is subjective in the sense that different observers have different knowledge (their mental models are in different states - e.g. Wigner's friend), but objective in the sense that the model is a good one (the best possible) and so different observers in the same situation would have the same expectations and experience of the world.

That is your version of CI. Other people think differently. The various authorities I have cited are not wrong just because they disagree with you.

Summary: (1) Probability descriptions do not imply hidden variables. Your assertion that it does is nonsense. As a result your analysis of EPR is faulty.

I do not know which assertion you are referring to. You can be uncurious or agnostic about the fact that the observations of different observers correlate, but if the correlation is caused by anything, it is caused by something real. You still have the option of non-interpretation, as the article states ("A subjective approach is left with the claim that the observers have subjective knowledge that isn't knowledge of anything. But the knowledge of the observers is still correlated. It is just that without either an ontologically real wave function, or local hidden variables, the correlation cannot be explained")

- CI: The other side of the measuring device is "Unknowable". It might not be hidden variables, it might be angels with pins, or elephants all the way down. I think you miss the whole point of Copenhagen.

(2) By normal definitions of "reality", the Copenhagen waveform is not real.

I reserve the right to edit material which is just plain wrong and misleading.

Your rights are defined in the wikipedia guidelines. Editors are required to make verifiable

claims, not just express personal opinions. 1Z 01:24, 7 March 2007 (UTC)

[edit] Criticisms

I dont see how quantum entanglement or quantum superposition in any way lends any support to Many Worlds. In fact, Many Worlds has problems with EPR (quantum entanglement) Nor do I see how Bells Inequality is a problem for Copenhagen - it is a problem for hidden variable theories.

The choice between interpretations "is not as a matter of personal taste" - it should be based on a judgement of the difficulties associated with each interpretation.

The article gives the impression that Many Worlds in the alternative to Copenhagen - it is not. Oz 19:56, 13 Sep 2003 (UTC)

If you post a criticism can you please outline that criticism. Just saying XXX says it gibberish is not a criticism. (My mum thinks Copenhagen is just fine). Also, a paradox such as Schrodingers Cat deserves analysis rather than a comment that it is intended to show how "absurd" something is. Oz 20:26, 13 Sep 2003 (UTC)

My Messiah textbook is good but old. I have not found the time to get and read a newer text, but I found a very good and up to date source in Physics Today and have quoted it in this article. Weinberg said there has been recent work, which may help to explain why my material from my older source did not satisfy some. The summary given in the quote is close to what I learned in graduate school, but better worded and supported by more recent physics. David R. Ingham 02:46, 14 May 2006 (UTC)

[edit] Query

Did Bohr use the term "collapse of the wave function"? Oz 23:02, 13 Sep 2003 (UTC)

Answer: No, he did not. A second "collapse" evolution is foreign to Bohr's account. It has its roots in von Neumann's version of QM, and should probably not be considered part of the Copenhagen Interpretation. PeterBokulich 18:43, 17 January 2007 (UTC)

[edit] "Mainstream"

Luminek, the study you cite provides the following poll results for the preferred interpretation of QM:

Copenhagen: 13

Many Worlds: 8

Bohm: 4

Consistent Histories: 4

Modified dynamics (GRW/DRM): 1

None of the above/undecided: 18

I removed the words "the mainstream" because that implies clear dominance over all other interpretations. While the Copenhagen interpretation is more accepted than MWI or any other specific competitor, it doesn't have a greater-than-50% majority. When more people report "undecided" than "Copenhagen interpretation", that should be a clear sign that it's not the mainstream interpretation. It's a mainstream interpretation, along with MWI, Bohm, and consistent histories. A 1995 study of 72 leading physicists reports that 58% believe MWI is true, so it appears this varies from study to study as well. While Copenhagen may indeed by the most-accepted interpretation, I feel the words "the mainstream interpretation" gave the false impression that all other interpretations where somehow non-mainstream, which is why I'm removing the phrase now.

I understand that, in the past, the Copenhagen interpretation did in fact have the sort of crushing dominance this article presently describes, and will make note of that. -- Schaefer 02:59, 28 Nov 2004 (UTC)

[edit] Interpretation of classical mechanics

It seems to me that the question of interpreting quantum mechanics was settled in the 20th century and is now historical: It is reality. Any remaining discussions should be called the "interpretation of classical mechanics". --David R. Ingham 22:16, 16 August 2005 (UTC)

I don't understand your comment David. Are you saying that there is still no controversy over the interpretation of quantum mechanics? If that's what you're saying then I totally disagree. Trious 13:10, 25 September 2005 (UTC)

Exactly: its interpretation belongs to *metaphysics*. It's therefore also misleading to have the opinion of *physicists* presented as if it represents an expert opinion - physicists are generally poorly educated about metaphysics. The only expert opinion about interpretation that I have read is that of Popper, and he rejected it. Consequently, I'll change the opinion header to "opinion of physicists"; only if a similar poll on people such as him is included, can the specification be scrapped. Harald, Lausanne, 14/10/2005

It seems to me that the trouble with the philosophy of science is that not even most physicists, let alone philosophers know enough physics to attempt to interpret it. I think that when one studies the early chapters in physics texts, instead of just doing the home work, it all becomes clear. David R. Ingham 03:33, 15 October 2005 (UTC)

David, when you say that the interpretation of QM was settled in the 20th century, what exactly do you mean? The word 'settled' suggests that a concensus of sorts was reached. Can you explain what this concensus view is?

Judging by Mr Ingham's comments elsewhere, he thinks interpretation boils down to a binary "QM is real, or QM is not real". In fact, of course, there are at least 8 major interpretations of quantum mechanics.1Z 16:00, 21 January 2007 (UTC)

[edit] Misinterpretation of the Bohrian view

I believe that this article incorrectly attributes a positivist slant to Bohrs interpretation. Although this is indeed the view taken by his student Heisenberg, and is often taken as being representative of the copenhagen interpretation, it is not true of Bohrs ideas (regardless of whether they make it into the definition of the cophenhagen interpretation). I myself still struggle to come to terms with Bohrs relationist notions of measurement and reality, but I am certain that it is unfortunately not as simple as a positivism.

Also with regards to whether interpretations of QM is a subject for physics or metaphysics, it is as much physics as Einsteins deriving of the lorentz transformations (ie. special relativity). Both attempt to clarify and extend an existing operationally adequete although conceptually incomplete theory by questioning what relation the theory has to reality.

Nic.

[edit] Introduction

As Wikipedia becomes more detailed, I suggest that interpretation of quantum mechanics be changed to Philosophical interpretation of classical physics to make this article more up to date. I think that, when the philosophy is settled, we should change that to "interpretation of classical physics" or "scientific interpretation of ordinary language". Language, being imprecise and restricted to common experience, by nature, cannot, without loss, interpret physics, which has become precise and general. David R. Ingham 09:12, 27 February 2006 (UTC)

[edit] Made a few corrections

Mainly POV things.

I removed the phrase

"Einstein's Relativity demonstrates that "instantaneous" has meaning only for observers sharing a single reference frame. No universal time reference exists so the "instantaneous wave function collapse" of the Copenhagen Interpretation is left undefined."

since it builds on the misunderstanding that the wave function collapse should be understood as a physical process (it should not). The "instantaneous wave function collapse" is not really a problem in quantum field theory or relativistic quantum mechanics, and in the various "delayed choice" experiments as well as in Einstein and Rosens article on the subject from 1931 we see that the shift involved in the observation/reduction of the wave function is so fundamental it actually stretches backwards in time.

[edit] Shut up and calculate

About the famous quote "Shut up and calculate", usually attributed to Feynmann and in the Copenhagen interpretation article attributed to Dirac: http://www.aip.org/pt/vol-57/iss-5/p10.html Can someone provide any source proving that this quote is actually Dirac's?

Well, N. David Mermin is pretty sure that the remark is Feynman's, but is looking for evidence (or was, back in 2004, cf. http://www.aip.org/pt/vol-57/iss-5/p10.html), because he had found the remark attributed to himself (cf. https://faculty.washington.edu/seattle/physics324/preface.pdf, page v).

Charles Francis wrote in the sci.physics.research newsgroup in 2000, "Dirac's statement that we cannot speak of what happens prior to measurement is perhaps the beginnings of the 'shut up and calculate interpretation', but I don't believe that that is what he really meant." (Retrieved from http://www.lepp.cornell.edu/spr/2000-09/msg0027974.html)

I found a blog where someone quoted this remark and attributed it to Dirac, but he did so in the precise wording found in Wikipedia. I also found several people who wrote that it must have been said by Dirac because Wikipedia says so (I'm not bothering with citations here).

In absence of better evidence, I think it would be safe to change this article so that the remark is attributed to Feynman, not Dirac. --Swwright 23:27, 24 January 2007 (UTC)

Or perhaps it is not as simple as one would desire. I just came across an attribution of this remark to Hans Bethe (with a note that it is frequently mis-attributed to Feynman). I found this at the end of L.G. Sobotka's notes for a physical chemistry course he teaches at Washington University (St. Louis, Missouri); cf. Physical Science in 12 Problems --Swwright 20:09, 25 January 2007 (UTC)

[edit] Outsider View

I'm a mathematician and philosopher, not a physicist. I find Many worlds and Consistent histories both east to understand as they are presented on WP, but after reading this article I can't say I'm any closer to understanding what the Copenhagen interpretation is. OK that's maybe an exaggeration but it certainly took a few reads. What is needed I think is for the first sentence of "The meaning of the wave function", with the two bullet points to be clearly separated from the rest of that section (ideally it should be the first/second sentence of the whole article) and the ambiguity over whether that sentence represents merely the "starting point" for the Copenhagen interpretation or the contents of the interpretation itself, needs to be removed. ("The Copenhagan interpretation merely states that ...") As an outsider it's hard to see that sentence as staking any claim at all really. It is ambiguous over whether it allows the selection of the result of a measurement to be amongst a probability distribution of probability distributions, or whether it always assumes that an observation produces a classical certainty. In the latter case as a non-physicist I would assume it was just wrong (?) and in the former I fail to see why Many-Worlds say would be inconsistent with it (?). If someone like me with a degree in the two subjects closest to but not covering this issue thinks it is unclear, then I can't imagine there is much hope for those with no background even remotely related to the question. --cfp 01:19, 8 August 2006 (UTC)

Thank you for your comment. The point you make is very good. The trouble with many writers is that they will be satisfied if they predict to themselves that they will be able to make a good defense of the validity of what they have said should anyone challenge them. The very top physicists are also frequently the best writers for the average well-informed reader. They manage to say something in English that will give any reader a clear (and perhaps only qualitative) description of some phenomenon or theory, and yet they will not say anything that their colleagues who are well acquainted with the subject will take amiss. P0M 07:24, 10 August 2006 (UTC)

Let's look at the top of section one:

The Copenhagen interpretation assumes that there are two processes influencing the wavefunction:

the unitary evolution according to the Schrödinger equation

the process of the measurement

While there is no ambiguity about the former...

This way of discussing matters assumes that the reader has clicked on a previous link to "wavefunction" and now has internalized it well enough to know what the first sentence in this quotation means. In addition to that rather dubious assumption, the sentence hypostatizes or reifies the wavefunction. It implies that we already have an account according to which a mathematical function is such a perfect mapping of some thing (a proton, electron, etc) that we can speak of the one as the other and not get in trouble. The problem is that the Copenhagen interpretation is an explanation (one of many) of what the mathematics really tells us about the outside world. The mathematics tells us that at any given time we are more likely to observe an interaction between the proton, electron, or whatever and some other entity (such as a detection screen) that is placed at the points indicated by the theory -- provided that there is something there for it to interact with. But generally there are several points of high probability for "manifestation" along a continuum of points of lesser probabilities. We cannot fill out gaps in the theory and predict which of the high probability points it will actually "choose." The theory describes something about the "potentiality for manifestation" or "probability of materialization" (like a ghost "materializes" somewhere), but the theory does not take account of a physical barrier. It describes how a photon's probability distribution looks as time progresses, but it doesn't say anything about the presence of a physical barrier to further progress.

So, if we are looking at an electron in a double-split experiment, we do something to cause an electron to be emitted, we wait for a while, and then we see a sign that the electron has impacted somewhere on a capture screen. Why did it hit at point A instead of the center point directly across from the emitter and perpendicular to the screen containing the double slits? What do we make of the fact that x% of the time an electron will manifest itself at point B, y% of the time it will manifest itself at point D, etc.? Where was the electron in the interval between emission and collision? Did some unknown factor force the selection of one point rather an another for the electron to interact with? Did the electron actually show up at all points, but in our universe it ended up at one specific point, and all other impacts created separate universes in which those probabilities were realized. That kind of question involves "interpretation," i.e., saying what all the math says about the world of real things.

Having thought about this some more, I think the easiest way to present the Copenhagen interpretation (if I've understood it) would be by direct contrast to the many worlds interpretation. E.g. something like:

The equations of quantum mechanics describe the probability of a certain result being obtained from a measurement. The many worlds interpretation postulates that the notion of probability is a broadly frequentist one. However as any measurement may only be performed once (indeed it is arguable that it could only be performed once), instead of counting occurrences across time or space, those who believe in the many worlds interpretation count frequencies across the same measurement in different "parallel" universes, which means that the particular measurement we obtain is just a result of the universe we happen to be in. Thus in the classic single-photon light diffraction experiment, the many worlds theorist believes that photons are taking every possible path, according to the predicted probability distribution, but in different universes. Those who believe in the Copenhagen interpretation on the other hand view the process of measurement itself as a "physically significant" operation. They believe that prior to a measurement the system is in a superposition of states, i.e. in the single photon slip experiment, the photon (in some sense) occupies every position in a triangle between the slit and the card. Measurement (they believe) just collapses the superposition into a single result, randomly, according to the probability distribution that gave the superposition. The chief point of contention between the Copenhagen interpretation and the many worlds one then is whether measurement does play this "selection" role (as in the Copenhagen interpretation), or whether the "selection" is made prior to the measurement (as in the Many Worlds interpretation, our own universe is selected). There is by definition no physical experiment that could decide between these two interpretations, since any attempt to see "if the selection had occurred yet" would involve a measurement, which, in either case, would result in a selection being returned.

What do you think? --cfp 15:28, 10 August 2006 (UTC)

It seems o.k., except for "frequentist," which doesn't mean anything to me (except that I can guess from the total context of this discussion). Then there is the problem of how to explain "collapse of the wave function." One of the things that is clear from the double-slit experiment is that when there is an interaction between a photon or an electron and something in its path, then that determines one "event," i.e., we know that something was emitted because (1) we have a fairly reliable emitter device and we know how to trigger it, and (2) we saw something happen at the other end. (Something flashed on a screen, an electrical potential was jogged up a notch, etc.) That's what happens, for instance, if we put a detector in a slit in the double-slit apparatus. If a photon or electron triggers the detector and if a photon or electron continues on from that point and is detected on the screen, the wave function appropriate to the first half of the trip is different from this new wave function, and that is why there will be no interference effect. So wherever we say we "make a measurement" what we are really saying is that we get the absorption of one photon or electron, some change in the detector, and the subsequent emission of another one.

So what does "collapse of the wave function" mean? It really just means "termination of the wave function." Why does it terminate here rather than there? I believe that many people insist that there must be a reason for its "collapse" (or the manifestation of the particle) at one point rather than another. But if that were the case then it seems to me that we should be able to disturb the probabilities by some simple manipulation of the detector screen. If I am flying a spinnaker from my sailboat and arrange a set of explosive devices that enables me to cut all connections to the boat at the same time, then I could throw the sail forward and it could impact a screen ahead. What part of the spinnaker hit the screen first would be fairly random, and over time I suppose that a fairly consistent pattern of hits would develop. Probably the sail would tend to hit the screen first at the center. But we should be able to change the most likely point of impact by slanting the screen so that the right end was closer to our boat and the right edge of the sail wold be more likely to hit it than the center or the left edge. But as far as I know nobody has ever suggested that the detector screen has to be exactly parallel to the screen containing the two slits. Does a pebble surface of the detection screen make any difference? But every screen is pebble surfaced. P0M 19:14, 10 August 2006 (UTC)

For frequentist see Frequency probability. Should have linked it sorry. That sentence wasn't very clear in any case. And if I was going to mention frequentism for many worlds I should have mentioned the rival theory (Bayesianism) for the Copenhangen interpretation. As this is a specific philosophy of science article I was assuming some general philosophy of science. Maybe I shouldn't have. Anyway as for angling the screen, just think of what happens when you do it with a multi photon beam rather than a single one. You can think of the waves as spreading out from the slits (think of ripples). As you change the angle of the screen you will change the point at which you are cutting the "ripples", so the pattern will change in a predictable way. It's not really an issue I don't think. --cfp 21:36, 10 August 2006 (UTC)

The pattern changes in a predictable way, and one pattern is a mapping of the other pattern, no? I think we are saying the same thing in different ways. People who are wedded to the idea of hidden causal factors claim that there are real causal reasons for why a particle "chooses" the path it uses in each case. But if that were true it seems to me that people could easily find some way to mess with these hidden factors and change the experimental results. But I'm just speculating. Have you studied http://plato.stanford.edu/entries/qm-copenhagen/? P0M 01:53, 11 August 2006 (UTC)

Nope I hadn't seen that page. Looks like there's plenty to base an article on in there. Like I said I'm not a physicist so I don't know what I'm talking about. All I was saying was that this page needs a lot of work. --cfp 19:20, 11 August 2006 (UTC)

I started out as a physics major and got seduced to the dark side of philosophy and Chinese language, so I'm not the ideal person to write an article like this even though I've maintained an interest in physics. On the other hand I am less likely than some to assume that I can't understand something because I'm too stupid. If the article does not make sense to you at some point then it is probably either wrong or else the writer knew what s/he was trying to say but it is not coming through right. P0M 20:41, 11 August 2006 (UTC)

[edit] New material on Quantum reality

Here is some new source material:

[edit] Penrose

From The Road to Reality by Roger Penrose, 2004, section 21.6, (top of p. 508 in my copy):

If we are to believe that any one thing in the quantum formalism is 'actually' real, for a quantum system, then I think that it has to be the wavefunction (or state vector) that describes quantum reality. (I shall be addressing some other possibilities later, in Chapter 29; see also the end of 22.4.) My own viewpoint is that the question of 'reality' must be addressed in quantum mechanics—especially if one takes the view (as many physicists appear to) that the quantum formalism applies universally to the whole of physics—for then, if there is no quantum reality, there can be no reality at any level (all levels being quantum levels, on this view). To me, it makes no sense to deny reality altogether in this way. We need a notion of physical reality, even if only a provisional or approximate one, for without it our objective universe, and thence the whole of science, simply evaporates before our contemplative gaze!

This illustrates my contention that the word "interpretation" in this article is a poor choice. The interpretation is clear: It is reality. This article is about how to make use of this theory, using our classical minds and notebooks and tools that we can only describe classically. David R. Ingham 04:06, 16 August 2006 (UTC)

[edit] Weinberg

I put this into two articles' discussion pages some time back, but it is also relevant here.

Physics Today, April 2006, "Weinberg replies", p. 16,

... but the apparatus that we use to measure these variables—and we ourselves—are described by a wave function that evolves deterministically. So there is a missing element in quantum mechanics: a demonstration that the deterministic evolution of the wave function of the apparatus and observer leads to the usual probabilistic rules [Copenhagen interpretation].

So the "Copenhagen interpretation" is not philosophy nor is it basic physics. It is an empirical rule, that has not yet been fully justified theoretically, for using the classical approximation in quantum experiments. David R. Ingham 04:22, 16 August 2006 (UTC)

[edit] Short,Sweet&CONCRETE: EXACTLY What Copenhagen Interp Claims Set Comprises; BONUS: (after the concrete), PROFOUND INSIGHT: Isomorphism (identical structure) Bayesian Statistician & Copenhagen QMer

The Coppenhagen interpretation of QM says that nothing EXISTS in the world such as position and mometum -- NOT UNTIL A SENTIENT BEING MAKES A MEASUREMENT. It is not that there is uncertainty, it is that such a thing does not exist. The sentient creature capable of measurement does a GOD-LIKE act of CREATION when s/he/it performs the measurement and COLLAPSES the wavefunction. Prior to the measurement, yes, the wavefunction was "in a superposition of states" but what EXISTED was indeed that wavefunction. The wavefunction (by multiplying itself by its complex conjugate) becomes a probability distribution, but the WAVEFUNCTION ITSELF IS WHAT EXISTS in the world. The wavefunction exists in the world whether or not a mind ever existed, whether or not a measurement is ever made, whether or not the wavefunction ever gets collapsed by a creature wishing to do his/her God-like act of creating a magnitude into the world. So, Einstein, you focused only on what did NOT exist in the world without a mind -- which is what so riled you up about those Copenhagen folks. But Einstein, you forgot that the Copenhagen folks were just as vehement about the wavefunction EXISTING independent of any mind (like you greatly prefer) as they were about the magnitudes NOT existing until a mind collapsed the wavefunction. In short, Einstein saw the glass as half empty and then totally forgot that he was focused on only half of the glass. Another summary: as idealist (non-existence without mind) as the Coppenhagen folks were about magnitudes (position, momentum etc), those same Coppenhagen folks were total realists about the wavefunction's ontological status.

A BONUS ON UNDERSTANDING BAYESIAN STATISTICS

To the Sampling Theory statistician, the truth is a pure number. The unknown parameter, if given an audience with God, could be stated as e.g. 3.452. The data, however, are random variables. To the Bayesian, just the opposite is true. The Bayesian says, "waddaya mean my data are random variables? I got 2.17. What's random about that?" To the Bayesian, the parameter, the truth, is a probability density function. There are many implications for statistics, terminology, and computation procedure, but here the philosophy part of the Sampling Theory - Bayesian dichotomy is aided by a one-to-one correspondence of the Bayesian with the Coppenhagen interpretation of QM. When the Bayesian says "I got 2.17! What's random about that?", that is isomorphic to the Coppenhagen QM'er saying "That was the measurement result. I collapsed the wavefunction." When a Bayesian talks about the parameter, the truth being a probability density function, that is isomorphic to the Coppenhagen QM'er saying that "what really exists in the world is the wavefunction". When the Coppenhagen QM'er talks of this wavefunction being in a superposition of states, that is isomorphic to the Bayesian talking about the prior distribution on the parameter. Bayesian statistics may seem weird (in some ways: truth is a probability density function) but in other ways not (which I can't go into). But clearly the Bayesian Statistician's isomorphic ontology with the Coppenhagen QM'er makes Bayesian Statistics in a sense, well, sensible. Sampling Theory statistics is Newtonian; Bayesian Statistics is specifically Coppenhagen QM.199.196.144.11 19:24, 21 March 2007 (UTC)

That seems an inaccurate representation of Bayesian ideas. He thought that all possibilities exist simultaneously or that possibility is the fundamental nature of reality? I got the impression that it was more about updating your calculation of a probability to account for incoming knowledge, and recognition of the fact that there can always be stuff we don't know, so we have to identify our prob. calculations as representations of our beliefs rather than of objective reality. Bleedingcherub (talk) 08:25, 27 April 2008 (UTC)

[edit] Internal Questions

"But the knowledge of the observers is still correlated. It is just that without either an ontologically real wave function, or local hidden variables, the correlation cannot be explained."

This last paragraph is nonsensical. It contains internal questions which are not answered

It does; it is amounts to a criticism., that subjectivism does raise quesitons it cannot anser. 1Z 12:55, 20 July 2007 (UTC)

[edit] Philosophical Ramfications?

I visited this article about a year ago and seem to recall there was a section entitled Philosphical Ramifications (or something to that extent). I would like rationale as to why it was removed. I have noticed an addition of a "consciousness collapses wavefunction" article which attempts to do the job of articulating what was written in this article before yet there is no direct link to this page. Futhermore, it seems that this concept has been seperated entirely from the Copenhagen interpretation article although it is a philosophical consideration that extends from the Copenhagen Interpretation.

Sadly, there is currently no article on "Quantum Philosophy" which explains these concepts as considerations to quantum mechanics; in lieu of "quantum philsophy" is a redirect to a very biased article on "quantum mysticism". —Lehel Kovach (talk) 23:23, 12 January 2008 (UTC)

[edit] Is Wikipedia intended to Confuse?

Is Wikipedia intended to Confuse?

[The following discussion was posted to the POSITIVISM talk page as a complaint against ambiguity. It serves as my example of what happens when a difficult to understand (imho) article refers to an ambiguously explained (imho) article. Also, how unfair it is to the reader. All this before I read the historical controversy about the Wikipeida "Copenhagen Interpretation" on this talk page. I now chastise myself. With all the contradictions, controversies, paradoxes, and unfullfilled desires expressed, does it occur to anyone that frantic attempts to get closer to truth are like attempts to hasten one's own death; they are against human nature, and inherently self-limiting? Or that calls for ever more precise language rendering of these ideas approach their own uncertainty limit? Perhaps the idea that every internally-consistent logical system of sufficient size contains theorems which, in principle, cannot be proven either true or false?

If the only things certain to be true are death and taxes, then I'm not sure I want to know the truth of my own death yet, and, by the way, my taxes are not done yet, either. By extension, frantic desires to learn the truth of how to release the vast amounts of energy contained within the most indivisible components of matter, without adequate consideration of the human consequences to self and others, might be more sensibly referred to a refresher course in "All I really need to know I learned in kindergarten", or the gentle human ways humans act to humans.

Once again, I now chastise myself. But rather more gently, I give myself credit for apologizing, and ask for your understanding and forgiveness. In the heat of the moment, human rants happen to humans...]

I got here from the "Copenhagen Interpretation of the Quantum Theory", section "The meaning of the wave function", wherein I quote,

"The Copenhagen Interpretation denies that any wave function is anything more than an abstraction, or is at least non-committal about its being a discrete entity or a discernible component of some discrete entity.

There are some who say that there are objective variants of the Copenhagen Interpretation that allow for a "real" wave function, but it is questionable whether that view is really consistent with POSITIVISM (link emphasized) and/or with some of Bohr's statements. Niels Bohr emphasized that science is concerned with predictions of the outcomes of experiments, and that any additional propositions offered are not scientific but rather meta-physical. Bohr was heavily influenced by positivism. On the other hand, Bohr and Heisenberg were not in complete agreement, and held different views at different times. Heisenberg in particular was prompted to move towards realism.[3]"

I came to understand and evaluate the validity of a train of scientific thought regarding "Zero-Point Energy" before I or my correspondent died. I understand there exists no general guarantee I will understand any particular topic by reading about it.

If I accept a wave function as a wave function, then I can use the wave function as like. Does the wave function hinder or enhance my functioning by its existence? I do not know. Does it predict things others feel do not exist, or only that which is generally accepted? Why should I care, until it matters to me? But, views put existence to work, so now I am left with the question of trying to imagine a situation where "Zero-Point Energy" could work as described. And, Wikipedia refers me to an article that describes (quoted below) how humanity (thus man) must go thru a three-stage process to reach the Positivism view that allows me to deny that the wave function of Zero-Point Energy, in reality, exists. The three-stage process is: accept received "facts", then respect humanity's rights (also a received "fact"), then accept the idea that one can achieve anything based on one's individual free will and authority (while respecting humanity's rights) (another received "fact"). Thus, by my Positivistic development of acceptance (Is this contrary to the skeptical nature of scientific inquiry?) , I can disprove a scientific theory. Or, scientific proof only works for those who respect human life?

But, at the Risk of Screaming, I state the main premise of my contribution here, "I AM NOW MORE CONFUSED THAN WHEN I STARTED." Is this the intent of Wikipedia? Is Wikipedia intended to confuse?

At the least, the following passage calls for some restriction or qualifications to the sentence "There is no higher power governing the masses and the intrigue of any one person than the idea that one can achieve anything based on one's individual free will and authority." Why can this sentence be confusing? Let me count the ways.

This is one possible parsing (forgive me if you think there exists a msitake here - I admit, the longer the sentence, the greater the possibility I make an error of understanding):

(There) is (no (higher (power))) (governing ((the masses) and (the (intrigue (of (any (one (person))))) than (the (idea (that (one) (can achieve) anything (based on (one's individual ((free will) and authority)))))))

a) too many clauses -> Can these be restated in separate sentences? b) "anything" is undefined -> Supposing one has the authority to violate human rights (stage 2), can one's free will achieve this violation and still be Positivist? c) Sentence construction is negative ("no higher power") -> can this be made more positive (Positivist?) d) The ambiguous nature of the common English usage of the word "and" ("both X and Y" versus "either X or Y, possibly without completely evaluating one or the other"), calls for breaking this long rambling sentence into separate sentences, with more specifics and examples. e) "any", "anything"-> Is it possible to think clearly in such expansive generalities? f) "one", "person", "achieve" -> Do these need to be defined? g) In order to even think concretely about this sentence, the following undefined variables need to be evaluated (matched) to the reader's known interpretation:

1) powers, higher than, negated, that could possibly govern 2) masses (which permution of six billion, currently) 3) persons, (which, of six billion), capable of which intrigues, 4 and 5) one (twice) times (which, of six billion) 6) anything, which is achievable 7) the idea 8) based on 9) one's individual (Is this redundant? Does anyone have group free will?) 10) authority 11) and (and its ambiguous interpretations)

Since most people can only think about a maximum of two to seven different things at a time, this sentence cannot even be read without significant thought, if at all, for the preceding listed reasons, namely it is too ambiguous, redundant, or hard.

CAN IT BE CLARIFIED ENOUGH SO I CAN DETERMINE THE DIFFERENCE BETWEEN BOHR AND HEISENBERG? [IN CAPITALS TO RESTATE MY GOAL, NOT TO SHOUT. (PARDON ME)]

Specifically, can the proposed content of this article be made relevant to our current shared existence? Can the historical develoment background be made understandable in a current events context? Can the opinions of the participants of the recent 2007-2008 presidential debates be characterized from a Positivist viewpoint? Is Positivism, as defined, too ambiguous to do so? Are the opinions, as stated, too ambiguous to do so? Does the Wikipedia Positivism explanation fail when brought to the specifics of defending the human rights of terrorists, at the expense of the safety and freedom of thought of the masses or any one person and their individual free will and authority?

In short, does this Wikipedia entry make sense to anybody outside of college philosophy majors?

Referenced Quote from this "Positivism" article: "The theological phase of man is based on whole-hearted belief in all things with reference to God. God, he says, had reigned supreme over human existence pre-Enlightenment. Humanity's place in society was governed by his association with the divine presences and with the church. The theological phase deals with humankind accepting the doctrines of the church (or place of worship) and not questioning the world. It dealt with the restrictions put in place by the religious organization at the time and the total acceptance of any “fact” placed forth for society to believe.[2]

Comte describes the metaphysical phase of humanity as the time since the Enlightenment, a time steeped in logical rationalism, to the time right after the French Revolution. This second phase states that the universal rights of humanity are most important. The central idea is that humanity is born with certain rights, that should not and cannot be taken away, which must be respected. With this in mind democracies and dictators rose and fell in attempt to maintain the innate rights of humanity.[3]

The final stage of the trilogy of Comte’s universal law is the scientific, or positive stage. The central idea of this phase is the idea that individual rights are more important than the rule of any one person. Comte stated the idea that humanity is able to govern itself is what makes this stage innately different from the rest. There is no higher power governing the masses and the intrigue of any one person than the idea that one can achieve anything based on one's individual free will and authority. The third principle is most important in the positive stage.[4]

These three phases are what Comte calls the universal rule – in relation to society and its development. Neither the second nor the third phase can be reached without the completion and understanding of the preceding stage. All stages must be completed in progress." —Preceding unsigned comment added by SalineBrain (talk • contribs) 20:14, 11 February 2008 (UTC) SalineBrain (talk) 20:16, 11 February 2008 (UTC)

[edit] that damn cat again...

How can

"The wave function reflects our knowledge of the system. The wave function $(|\text{dead}\rangle + |\text{alive}\rangle)/\sqrt 2$ simply means that there is a 50-50 chance that the cat is alive or dead."

be right? Isn't it self-contradictory? You don't know the state the cat's in, so he ought to be in a superposition, both dead and alive (not either or), according to "The wave function reflects our knowledge of the system". But if one would consider the cat an object incapable of being both alive and dead, surely, the first part would be false, for the wave function reflects the cat's point of view, and thus, we'd run into all sort of trouble.

Schrödinger's_Cat#Copenhagen_interpretation seems to agree with my point of view that it should be discussed that it's hard to tell whether the cat is a classical observer or in superposition, so I suggest we do the same thing here. Besides, that was the whole point of this experiment! Boreras (talk) 00:01, 3 March 2008 (UTC)

[edit] Run-On

This is a run-on in the 3rd paragraph. It is very hard to understand.

Bohr and Heisenberg had stepped beyond the world of empirical experiments, pragmatic predictions of such phenomena as the frequencies of light emitted under various conditions and the observation that a discrete quantities of energy must be postulated in order to avoid the paradoxes to which classical physics inevitably led when it was pushed to extremes, and found a new world of quanta of energy, entities that fit neither the classical ideas of particles nor the classical ideas of waves, elementary particles that behaved in ways highly regular when many similar interactions were analyzed yet highly unpredictable when one tried to predict things like individual trajectories through a simple physical apparatus.

I would just fix it, but I don't know enough about the subject to reword this correctly

--Vonce (talk) 22:03, 20 April 2008 (UTC)

[edit] Expert Attention Needed?

Is this a fair claim? How many people working on this article are seriously in this field, anyway? Bleedingcherub (talk) 09:43, 27 April 2008 (UTC)