Talk:Philosophical interpretation of classical physics/Archive 1

Archive 1

Messiah, of course presents things for students starting from a classical point of view, but with the clear intention of showing that quantum mechanics is a satisfactory theory and is complete for whatever one can describe and calculate with it. Reviewing it thoughtfully, it is quite clear that he sees it simply as reality and has no difficulty with that point of view.

Analogy to Lamarckian evolution

Lamarckian evolution, with inheritance of acquired character, is a common misunderstanding of Darwinian evolution, in the popular mind. That the world evolves in a random way when we are not measuring it, though not such a simple or important mistake, is a similar misunderstanding, by even experts, of quantum mechanics. The probabilities are a property of experimental physics and not of nature. I wish I could make this as clear as Messiah did. I suppose biologists must have spent a lot of time learning to help people avoid that error. The way to avoid the random nature error is to speak correctly about the philosophy of science.David R. Ingham

According to the "shut up and calculate" doctrine, this doesn't matter because we can't calculate it anyway, but who knows, it might matter. Suppose Stephen Hawking had been right about entropy decreasing at the end of the universe. The fact that quantum mechanics is internally deterministic might help to explain how this could happen.

Another problem with thinking that way is that it keeps one from understanding where the probabilities really do come from. David R. Ingham 23:45, 22 September 2005 (UTC)

references?

you say '"Physics and the Real World" by Carlos Bustamante, Jan Liphardt, and Felix Ritort, July, 2005' but don't give a journal. a google search finds http://www.physicstoday.org/pt/vol-58/iss-7/contents.html , but the article author is George F. R. Ellis; Bustamante et al is the previous article. If so, please fix.

other ref by Herbert P. Broida , looks like you may have copied and pasted a reference with the "[1]", but it didn't get pasted. Needs the full ref. GangofOne 20:37, 19 September 2005 (UTC)

Does there exist a written record of Broida's ideas? GangofOne 21:38, 19 September 2005 (UTC)

I don't think so. He just said that the probabilities were all associated with the relation between quantum and classical physics, as far as he knew. They named a building after him. He had recently come from the National Bureau of Standards (NIST), where he lead a group. He did a wide variety of experiments and needed to be broad in his knowledge of that sort of thing.

From my own experience with nuclei, I know they are philosophically well behaved (except of course the uncertainty principle), even though three of the four type of interaction are significant in them, they have hundreds of particles and they are slightly relativistic. The theory is rather messy, but the experiments are more straight forward than Broida's molecular physics experiments. --David R. Ingham 23:29, 20 September 2005 (UTC)

The text states that the old ideas on this subject are refuted and refers readers to the references section. That section lists Messiah's text, but no volume number and page number. Some books have good organization and good indices, but some brilliant authors write all over the place and some non-expert readers may find only some relevant passages even if the index of a book is good, so it would be very helpful to readers to have the relevant pages listed out for them. P0M 01:42, 22 September 2005 (UTC)

The first sentence.

I think (or guess) that I understand what the first sentence is trying to say, and also why the average well-informed reader will get the wrong idea from it.

Philosophical interpretation of classical physics is used here to mean the consideration of the probabilities arising in quantum mechanical experiments from the point of view that quantum mechanics is reality and does not require further philosophical interpretation.

When I read this "naively", I think it is going to be about how people who are trying to be philosophers say things about classical physics. But that isn't your intent, right?

Let's take that part away, since the kernal of your meaning is apparently in the rest of the sentence, and so if I can get clear on that part the earlier part may come clear.

"Quantum mechanics is reality and does not require further philosophical interpretation." I think the mention of "philosophical interpretation" is problematical. I think it is kind of a "code word" for "talk to make it go away or at least make it palatable", and such an agenda should not be the agenda of the philosophy of science or any other philosophy conducted as a serious enterprise. And, to make a serious quibble, physics is something that talks about (in well-formed propositions) reality. It is "word and object" time again. How about:

Quantum mechanics closely maps reality and cannot be reduced to a mapping that is closer to natural language without making the representation of reality more imperfect.

Now let's work backwards. If we haven't already hit a snag, then temporarily maybe we can say:

We regard the empirical generalizations employed in quantum mechanics that involve probabilistic factors as mappings of reality that cannot be reduced to mappings closer to natural language without making our representations of reality more imperfect.

Please don't get hung up on the inelegance of the language. If this is the idea that you're trying to state, then we can refine it stylistically. But for now I want a gaunt body through which the bones all stick out. Is the above (leaving out your pejorative (?) use of the word philosophical) the basic idea you're trying to get across? Or have I demonstrated that we are on entirely different wavelengths (maybe even AM vs FM ;-)  ? P0M 05:49, 20 September 2005 (UTC)

I see your point, though it is not as clear to me how people will read it. How about, "If one accepts that nature (reality?) is quantum mechanical, then the meaning of classical physics needs to be considered." David R. Ingham 23:41, 20 September 2005 (UTC)

I think all the physicists and philosophy of physics people and even populizers (going all the way back to George Gamow's One, Two, Three... Infinity) would agree with your substitute sentence, but I'd like to stick with what I had worked out as a paraphrase for your original sentence. I want to be sure that you are accepting my clumsy paraphrase as being essentially what you are trying to get at because when I first read what you wrote I had an entirely different idea, and my attempt here is to work out a language in common with you and also a language that will not unintentionally mislead the average well-informed reader. If what I said isn't what you meant, then there are problems somewhere even though we can agree on the vanilla version. P0M 01:24, 21 September 2005 (UTC)

The trouble with the second one is that it implies that quantum mechanics is probabilistic. My central point is that the probabilities are the fault of classical physics (and therefore also of natural language and other intelligent activity).David R. Ingham 21:43, 21 September 2005 (UTC)

O.K., that is a major problem, so let's go back to the original statement:

Philosophical interpretation of classical physics is used here to mean the consideration of the probabilities arising in quantum mechanical experiments from the point of view that quantum mechanics is reality and does not require further philosophical interpretation.

Since what you are saying is quite different from what most people have been led to believe, it might be best to state the nub of the issue point blank.

Descriptions of events made by using quantum mechanics do not include terms that denote probabilities, however, when a given quantum mechanical account of an event is expressed in ordinary language and even in the terms of classical physics (Newtonian physics) one is forced to introduce probabilistic terms.

If that much is correct, then the next thing to do will to present a telling example that shows how the probabilistic terms emerge. P0M 01:04, 22 September 2005 (UTC)

I just check the article and discovered that you had changed the first sentence.

Quantum mechanics closely maps reality and cannot be reduced to a mapping that is closer to natural language without making the representation of reality more imperfect. Accepting this, a Philosophical interpretation of classical physics is needed to explain the probabilities arising in quantum mechanical experiments.

Sentence one seems o.k. to me, but the next sentence seems to me to introduce two problems. (1) Why would anyone want to interpret classical physics except to say that if Planck's constant is arbitrarily set to zero then we get classical physics from quantum physics? (2) The passage now speaks of probabilities as though they are inherent in quantum mechanics. Another problem is that you are using the word "philosophical" in a way that I don't understand. To me it sounds like you mean some kind of linguistic sugar coating or rationalization has to be applied to make the alien stuff of quantum mechanics digestible or at least palatable to the average non-initiate. That's not what philsophy is supposed to do, as I understand the subject.

So how about:

Quantum mechanics closely maps reality and cannot be reduced to a mapping that is closer to natural language without making the representation of reality more imperfect. Descriptions of events made by using quantum mechanics do not include terms that denote probabilities, however, when a given quantum mechanical account of an event is expressed in ordinary language and even in the terms of classical physics (Newtonian physics), then one is forced to introduce probabilistic terms.

P0M 01:24, 22 September 2005 (UTC)

The reason it is philosophical is that we are discussing "reference to terms for which there are no true referents". The reason for the title is so that people who are looking at the article Interpretation of quantum mechanics or the similar material in the quantum mechanics article will recognise it as an alternative view of the same subject. Maybe we should expand the physics section and call it "The probabilities in quantum mechanical measurement" with a redirect. It seems our language is getting too phylosophical for people to understand. That should be "(Newtonian and Maxwellian physics)". Before I changed it, the indrocuction to Quantum mechanics mentioned only mechanics, while Messiah makes the point that one can't use quantum mechanics for massive particles with classical electromagnetism, because anything classical would allow classical measurements which would violate the uncertainty principle. David R. Ingham 16:11, 22 September 2005 (UTC)

Analyses of problems caused when people attempt to think using "terms for which there are no true referents" are indeed grist for the mill of philosophy. But one doesn't make a "philosophical interpretation of classical physics" exactly. That would be like advocating that somebody make a propaganda analysis of political science. (And I do think the correct word is "analysis" and not "interpretation.") P0M 17:25, 22 September 2005 (UTC)

On the measurement paragraph

Ħ Sentence by sentence, here are things I understand to be problematical:

Any process of measurement involves the application of outside forces to the object being measured, as when photons are directed at something and the paths of the photons are subsequently noted.

Ħ That is a very strong claim, hence it is difficult to maintain. How about measuring the dimensions of an object that radiates light by exposing photographic paper near to it and using similar methodologies?

If photons, electrons, or other quantum-scale entities used in the measurment process are described quantum mechanically, then the measurement process results in a deterministic description, i.e., a description that contains no probability factors.

Ħ It would be very helpful to have an operational definition of how a quantum mechanical description of a photon, electron, etc. is to be prepared.

However, to get the information into a notebook or (non-quantum) computer, it must be brought to the human scale where maintaining phase coherence is impossible.

Ħ Several items of information might be meant by “the information”: (1) The thus far undefined quantum mechanically defined (described?) photons or whatever that are used to make the measurements, (2) The measurements made. What does it mean to “bring them to the human scale”? If that were not enough, the reader is given no indication of why maintaining phase coherence would be desirable and why it is impossible.

Ħ Why would a quantum computer be a better choice? If the mention of a quantum computer is a little joke here, then it will generally only serve to puzzle the average well-informed reader.

Because the classical approximation does not conform to the uncertainty principle, it must make mention of information that the quantum system, which does conform, cannot supply.

Ħ This statement promises much but delivers little to the average well-informed reader who cannot guess what information must be mentioned in a description made in terms of classical physics, nor does it even suggest how the inability to discuss one kind of information forces the fabrication of a second kind of information.

This non-physical information is generated randomly.

Ħ Surely this is not something done by the experimenter with some kind of random number generator. But you’ve been speaking in terms of human intervention between physical system and human-intelligible report with words such as “must make mention.”

In addition, phase information in the quantum description cannot be represented classically, and is lost.

Ħ If there is “information” or data, how can it be “lost”? Surely you must be talking about some feature of any experimental apparatus that can be used, but the reader has been totally misled up to this point

One of Messiah's examples involves measuring the position of an electron with light.

Ħ Citation, please.

If the light's wave function is not known and hence cannot be included in the system wave function, then the predictions of the electron's position can only be stated in terms of probabilities, because the light photons exchange amounts of momentum with the electron which would then be unknown.

Ħ What if the light’s wave function is known?

Ħ And when you say “which would then be unknown,” you have a pronoun that has an ambiguous referent. Do you mean that the momentum of the electron would be unknown?

Ħ I could try to guess appropriate ways of resolving all of these problems, but I would rather have the author’s response. P0M 15:08, 22 September 2005 (UTC)

Yes, I like the first paragraph now. Is the other one you changed clear now?

I will be gone for two weeks to help my wife's family recover from Hurricane Katrina. David R. Ingham 22:50, 22 September 2005 (UTC)

Good luck (whatever that means in QM terms ;-). When you get back, please do provide citations to Messiah's book. I am working with our library to get the book back from someone so I can check it out. Volume 2, which I got today, does not seem to have the parts to which you refer. I could start going through a dozen or so books that I have on hand, but even if they disagreed with you that might not be as useful as my understanding exactly what and how Messiah has stated things. By the way, did Francis Weston Sears ever write specifically on this subject? I cursed my way through Sears and Zemansky, but the problem was not with the original work by Sears but because Zemansky had systematically reduced every bit of wonderful clarity in the original to a puddle of goo. So I would like to see how Sears handles it. Haven't found anything so far, however. P0M 04:36, 28 September 2005 (UTC)

Unintended consequence of unclarity

A recent addition to the section on measurement says:

Some of the early failures of classical physics were direct consequences of its failure to limit the degree of detail in nature.

Physics cannot limit nature. P0M 17:38, 22 September 2005 (UTC)

I mean its description of nature, of course. Fixed now? David R. Ingham 22:53, 22 September 2005 (UTC)

Clarification of 'interpretation' needed

The current introduction mentions the need for a new "philosophical interpretation" of classical physics, due to quantum physics, which is fairly clear.

Later, however, the article mentions a "direct interpretation"... but does not say what this means, or even what is being interpreted here--are we still talking about interpretations of classical physics or have we slipped into something else? Does "direct interpretation" mean probablistic interpretation of quantum physics?

I suppose this is confusing to me because I am used to hearing about different interpretations of quantum physics, not different interpretations of classical physics. In my opinion, the article needs more precision when talking about interpretations, especially using when using new terms. Perhaps you should also mention which interpretation of quantum physics you are using, or whether this new interpretation of classical physics would be needed regardless of your interpretation of quantum physics. WhiteC 20:33, 28 September 2005 (UTC)

Thanks for fixing the problem, and making the article in general easier to read. I would say you could get rid of the 'too technical' flag now, but I don't know who put it there in the first place. WhiteC 19:19, 7 October 2005 (UTC)

point by point (1)

"Some of the early failures of classical physics were not dynamical at all ..."

There is a link for "dynamical," but it does not clarify the problem for the general reader which is: what kind of problems or failures are "dynamical"? What does this word mean in this context? What would be a synonym for it? P0M 23:24, 23 September 2005 (UTC)

Do you mean that Time_evolution is not the problem? or what? P0M 04:48, 28 September 2005 (UTC)

I mean that these things come purely from the description without any use of interactions. A world described by classical physics cannot resemble ours, whatever one does with the "laws". David R. Ingham 22:46, 7 October 2005 (UTC)

Please paraphrase the original statement then. P0M 20:25, 8 October 2005 (UTC)

I think this sentence is o.k. now. P0M 01:19, 18 October 2005 (UTC)

Kudos for Albert Messiah

I have been mining Albert Messiah's Quantum Mechanics for citations and quotations. I am extremely impressed with the lucidity of his writing and recommend his book to others who may be interested in helping with this article.

By the way, the conceptual difficulties that lie behind the need for this article also come up very clearly in quantum entanglement discussions. The common stumbling point is our macro-world assumption of the inevitability of simple location. Twins may become identical, but tickling the one in Africa does not make the one in S. America laugh, and between diving board and pool neither one of them will fail to move in a continuous manner as a function of time. If one individual disappeared from the starting block and "materialized" at the finish line a very short time later, one would quite naturally suspect twins. (Especially if his time was d/c for the mile ;-) P0M 18:26, 1 October 2005 (UTC)

" highly refined instruments of modern physics"

Quantum mechanics was discovered by the instruments of classical physics, just a chemistry was discovered with the instruments of alchemy and the first chicken hatched from an egg laid by some other type of bird.David R. Ingham 23:39, 7 October 2005 (UTC)

Radar example

I saw the same error made by radar engineers when I was working for Lockheed Martin:

The same error as what?

They tried to measure a highly resonant target with a short pulse radar system, to range-gate out other objects in the radar range. They couldn't understand why they didn't observe the single frequency cross section.

In this case, h bar cancels out in calculating the relation and there is no definite limit to what can be measured with continued measurement and signal processing, but the relation between a function and its Fourier transform is the same. David R. Ingham 00:13, 8 October 2005 (UTC)

We may not be talking on the same wavelength. Remember the joke about the man who dropped his Rolex overboard in the middle of the lake and quickly marked an X on the bottom of the motorboat so that he could bring divers back to that very spot. He had one idea of position, but it wasn't a very useful idea as far as telling the scuba guys where to go. To communicate the location of something in a way that is useful to the general community we not only have to have a reliable way of determining position (which the Rolex guy obviously didn't have, but he was a joke anyway), but we also have to be able to communicate the idea clearly and unambiguously to other people. Otherwise we are likely to end up having, e.g., people going to different places because one person is speaking in terms of true north and the other person is speaking in terms of magnetic north.

It is possible to state the location of a macro object with good enough precision that members of the general community can locate it. We can have many levels of precision, in practice, anything from, "It's over there, about two bow shots away," to a reading from a military satellite-based position finder, etc. But saying, "I know exactly where it is" is often really the promise of being able to perform some actions that haven't been done yet. Saying that a photon has a location depends on analogous procedures.

Anybody can affirm that the body of Jimmy Hoffa has a position, but that claim in itself may not be subject to empirical verification. In other words, that claim cannot be proven and it cannot be disproven unles we can go "there" to check it out because we have specific travel instructions of some kind. Somebody might argue that his body must be somewhere, but the meaning of "somewhere" would be very diffuse if the body had been reduced to plasma and blown out the window to range, spec by spec, all over the globe. P0M 21:03, 8 October 2005 (UTC)

Quantum computer?

Our use of notebooks and (non-quantum) computers depends on the classical approximation to the operation of these devices and to the information stored in them.

This statement seems to be intended to say that quantum computers could be used to obtain reliable predictions regarding quantum phenomena that could not be obtained by our current crop of computers. If a classical computer can accurately simulate a quantum computer, and the difference between classical and quantum computers is one of speed and scale of operations that can be performed, how would moving the problem to a quantum computer give a fundamentally different kind of result? P0M 01:24, 11 October 2005 (UTC)

(See http://www.cs.caltech.edu/~westside/quantum-intro.html for a discussion of what a quantum computer actually is.) P0M 01:30, 11 October 2005 (UTC)

We need someone who knows more about quantum computing. As I understand it, there is no direct translation between quantum and classical information, just as there is no direct correspondence between classical and quantum descriptions of nature. One can translate, but not without loss of information.

All I said in the article is that I am not sure the same discussion of experiment would apply if one used a quantum data acquisition computer. That is not a proposal of an experiment, it is just that I am not sure. David R. Ingham 04:24, 11 October 2005 (UTC)

Footnotes needed for Messiah's book

I still think that it is essential to provide readers with volume number and page number whenever Messiah is claimed as the authority for some statement. P0M 01:34, 11 October 2005 (UTC)

Maybe but it is not that simple. The page numbers must not be the same in different additions and there isn't anywhere he exactly says that quantum mechanics is reality. He says more like that it is an adequate description of reality, and proceeds to explain why. I did give the section heading, "Uncertainty Relations and the Measurement Process", not only for that reference but as a place to start looking in other such books. David R. Ingham 03:51, 11 October 2005 (UTC)

Page numbers will still help. If there should happen to be one version with 594 pages in volume 1 and you were to cite page 332/594 and quote a sentence or two it would be no great problem to find the material. In the version I have, the section to which you just made mention turns out to begin on p. 139, and once I knew that I was actually looking for a section by that title it wasn't hard to find even though it is not exactly at the beginning of the book. P0M 08:02, 11 October 2005 (UTC)

Dynamics versus kinematics.

No, I don't think [1] helps at all. It is not a matter of experiment. The point is that classical physics not only does not provide a framework for expressing interaction. The very description of nature itself leads to contradictory or at least ridiculously unphysical predictions without even including any forces or other interactions.

Is "It is not a matter of experiment" basically what you wanted to say? That it is essentially a matter of a conceptualization that fails so badly to fit the reality it was intended to describe that it produces only nonsense?

I am thinking that this should drive home the point that one should not seriously think in such a way. David R. Ingham 03:53, 11 October 2005 (UTC)

What is the intended referent for "this"? What is the intended referent for "such a way"? Sorry if I appear thick-headed, but I have found that assuming I can guess what somebody else intended to say is a fairly reliable way to get myself even more confused. P0M 08:41, 11 October 2005 (UTC)

Request for citation

The article currently says, "One of Messiah's examples involves measuring the position of an electron with light. If the light's wave function is not known and hence cannot be included in the system wave function, then the predictions of the electron's position can only be stated in terms of probabilities, because the light photons exchange amounts of momentum with the electron which would then be unknown." Where does he say that? Thanks. P0M 01:17, 13 October 2005 (UTC)

You don't mean the discussion starting on p. 45 that discusses how the wavelength of light that would be useful in such an attempt would be in the x-ray range, and then discusses the difficulty of measurement purely in terms of how strong a perturbation would be produced on an electron by that radiation, do you? P0M 02:37, 13 October 2005 (UTC)

Repeated call for clarification

The expression "brought to the human scale" needs an operational_definition by means of which the original imprecise and misleading formulation might be redone. As it stands it does not have any clear meaning. P0M 20:27, 8 October 2005 (UTC)

I was hoping that "Our use of notebooks and (non-quantum) computers depends on the classical approximation to the operation of these devices and to the information stored in them." would clarify it. Physics experiments usually use electronics, so the experimenter himself may not directly handle the data. However the design and use of notebooks and computers depends on the classical approximation, and they store bits and not q-bits, so the classical approximation appears to be completely unavoidable. David R. Ingham 04:05, 11 October 2005 (UTC)

Unfortunately, what I would like is a clear expression of the steps that one takes to "bring something to the human scale," and the fact that computers and notebook paper express things that are formulated "on the human scale" does not at all clarify what readers need to get clear on. At present I have no certainty, from what you have said, what this quantum-scale something is, nor have I any idea of how you would propose to take that something and convert it into something that could be written into a three-ring binder or typed into a computer. Let's take something that the average well-informed reader could do on his/her desktop and a laser pointer, a double-slit experiment, tell what the description is on the level of quantum mechanics and how that description is "brought to the human scale." P0M 08:35, 11 October 2005 (UTC)

What I think David is trying to get at is that quantum states are indeterminate in some sense. A wave-function's value is not determined until it is collapsed by assuming that X is a particle and not a wave. The fact that the scale of quanta is extremely small may obscure this, but trying to measure individual quanta (rather than ex: whole light-waves) with particle-measuring sorts of equipment (as opposed to wave-measuring sorts of equipment) just assumes that the quanta actually HAVE determinate values for position and velocity (I think those are the 2 values that people try to measure for particles anyway)...

Let me know if I got something wrong, or if my comments aren't very clear. I'm not really sure what a wave-function's value actually tells you, but I think the assumption under question is that it can be collapsed to give a particle's definite position and/or velocity somehow, and that many measuring instruments do this. How, precisely, I couldn't tell you, though. WhiteC 02:58, 12 October 2005 (UTC)

I think you are likely to be incorrect. At first I would have agreed with you but I compared what David wrote with what Messiah says: "A quantum system isolated from any external influence evolves in an exactly predictable manner." It is not the "quantum states" that are indeterminate. That's David's whole point. David says, "If photons, electrons, or other quantum-scale entities used in the measurement process are described quantum mechanically, then the measurement process results in a deterministic description, i.e., a description that contains no probability factors. However, to get the information into a notebook or a computer, it must be brought to the human scale where maintaining phase coherence is impossible." When I read this description, I think of a quantum-mechanical experimental apparatus such as a double-slit experiment. The quantum-mechanical part, the part that doesn't find an appropriate explanation under the terms of Newtonian physics, extends from the time of emission of one quantum of light, a photon, to the time that one quantum of light is detected by its physical interaction with the detection scheme. According to David, and he is certainly not alone in maintaining this proposition, the "laws" of quantum dynamics are absolutely determinate. So whatever happens between t1 and t2 is going to be the same in all cases. However, the part about "getting the information into a notebook..." elides a crucial part of what must be a clearly described operation that can be reliably repeated in any laboratory. Moreover, it makes it seem that there is information that exists in one form that presumably behaves like any information that one could discuss in information theory, and that it is nevertheless information that must be translated and falsified in some sense in order to be written down in pen and ink or typed into a computer. If that is really what David means, then we have one kind of problem. If that is not what he means, then we have another kind of problem. I don't want to create a third kind of problem by guessing about what he may intend to convey.P0M 03:55, 12 October 2005 (UTC)

The discussion of the measurement/observation issue is very clearly discussed in The Elegant Universe by Brian Greene, p. 208ff. Particularly interesting is his statement on page 212: "Even though decoherence suppresses quantum interference and thereby coaxes weird quantum probabilites to be like their familiar classical counterparts, each of the potential outcomes embodied in a wavefunction still vies for realization. And so we are still left wondering how one outcome 'wins' and where the many other possibilities 'go' when that [measurement/observation] actually happens." To put that in terms of the double-slit experiment, there are only probabilities to be inferred from the psi function of the coherent radiation, but the photon doesn't manifest itself 10% in one place and 30% in another. It manifests at only one place. There is no hidden information that tells us why it has "chosen" to show up at one place or another in this run of the experiment. We, however, are left unsatisfied by this result since every analogous event in our macro environment has an explanation. If we shoot a gun at a target we expect to be able to account for any deviation of the bullet from an "ideal" path. For instance, we might find that a powerful magnetic field deflected the steel bullet. P0M 23:04, 12 October 2005 (UTC)

Another very clear discussion is given by Einstein. See the "The Fundaments of Theoretical Physics", included in Reading in the Philosophy of Science (Edited by Herbert Feigl and May Brodbeck), p. 259f. P0M 03:28, 13 October 2005 (UTC)

Yet another useful analysis is given by Hans Reichenback, "Principle of Anomaly in Quantum Mechanics," ibid, p. 515. P0M 03:53, 13 October 2005 (UTC)

http://en.wikipedia.org/w/index.php?title=Philosophical_interpretation_of_classical_physics&curid=2690589&diff=25388356&oldid=25323074

I don't think "implies" is the right word. David R. Ingham 03:15, 15 October 2005 (UTC)

Fixed. P0M 01:03, 18 October 2005 (UTC)

Point by point (2)

The expression "brought to the human scale" needs an operational_definition. P0M 06:52, 30 September 2005 (UTC)

This statement, too, needs to be redone. As it stands it does not have any clear meaning. P0M 20:27, 8 October 2005 (UTC)

My intention is that it help to guide understanding of the rest of the phagraph. David R. Ingham 23:08, 19 October 2005 (UTC)

I understand what your intent is, however, I do not know what the statement means. If you know what it means then it should be possible to explain what it means to other people. As it stands it cannot guide understanding. It serves only to obfuscate the discussion. P0M 23:24, 19 October 2005 (UTC)

Moving forward

I have been getting no answers to my questions, only reactions to changes that I actually make, so I have started to restate the most problematic section on the basis of my "intuitive" understanding of the intended meaning.

(I have also archived the first half of the discussion. Nothing has been lost. If anybody wants anything, please cut and paste to bring it back in at the top of this page.) P0M 22:34, 18 October 2005 (UTC)

Maybe my "Analogy to Lamarckianism" comment was too outlandish to stay up top. David R. Ingham 23:49, 19 October 2005 (UTC)

Archiving old talk pages need involve no judgments on the material archived. Some users need to conserve bandwidth and as files grow over 32 k they may take too long to load and/or be too big for older browsers to edit. Generally when talk pages are archived the decision is a simple one: archive all discussion before a certain date. But if the talk page has "forked" into several discussions growing at the bottom of several sections then archiving can be a problem. From experience I know that it is important to cut information from the archive file and paste to the current discussion file when restoring portions of archived material for continuing discussion. If you don't do it that way you end up with much duplication and much confusion.

Another principle that can be used to archive discussions is simply to archive all discussions that seem to have reached a natural stand-still. I am at the point of archiving my "point 1" for instance, because it's already been resolved. P0M 00:36, 20 October 2005 (UTC)

Point by point (5)

The article says:

Because the classical approximation does not conform to the uncertainty principle, it must make mention of information that the quantum system, which does conform, cannot supply. This non-physical information is generated randomly.

How can nature make mention of something. This way of saying things seems almost solipsistic. Maybe that is not quite the right word except that human intelligence seems to be implicitly pictured as behind the change from the quantum physics picture to the Newtonian physics picture. The quantum system has no information on X (whatever that is). The classical system needs an X for some reason, so "it" plucks an X out of a random number generator somehow. Without knowing what the author of these words had in mind it is hard for me to imagine how to make them less vague. But let me try to provoke a correction:

We have set up a double-slit apparatus. Our X in this case is the measured physical position of a photon. We have done a good job setting up and testing our apparatus, so we know that we can kick off one photon from some emitter of photons. We've done that job enough times with no barrier between the LED and the detection screen that we can be pretty sure that we will get a good run of the experiment often enough to be useful. We put in the double slit barrier. At t[0] we fire off one photon. "It" "goes through" the two slits resulting in a superposition of two ψ waves. Between t[0] and t[1] (when a photon shows up on the detection screen) we have no information on the position of the photon. When the photon interacts with the screen we must have a single position. Photons in this apparatus show up at points that are statistically in accord with quantum theory, but the order in which they hit the various positions on the screen is totally random. P0M 04:14, 19 October 2005 (UTC)

Sounds good to me. Much clearer than the original. WhiteC 20:28, 19 October 2005 (UTC)

I don't see why you think nature makes approximations. That sounds "Lamarckian" to me. I think the paragraph does need work, but that sentence seems nearly right as it stands. It needs the actual source of the random information, which is what the "hidden variables" people need. David R. Ingham 21:42, 19 October 2005 (UTC)

I don't think nature makes approximations. You are the one who wrote: "This non-physical information is generated randomly." I was trying to paraphrase the text that I quoted. I'm not a mind reader, so I may have paraphrased it the wrong way, but when you write unclearly then that is the risk that you incur. You are also the one who spoke of nature "making mention" of something, which seems even more questionable to me.

If your last sentence above means that the paragraph in question needs to indicate the actual source of the randomness, then I agree. And, by the way, on what page does Messiah discuss measuring the location and momentum of an electron? P0M 23:43, 19 October 2005 (UTC)

Several places, I think.

I have asked several times. Please tell me where. P0M 00:40, 20 October 2005 (UTC)

Yes, it doesn't occur to me when I am writing that people might read it in ways like that.

Trying to write from a quantum mechanical point of view, it was incorrect or misleading of me to say simply that the extra information is generated randomly. In principle, if the whole laboratory and physics journal were described quantum mechanically, there would be no probabilities in the prediction and that description would closely correspond to a particular classical description of the result and the journal article. The outcome only seems random when the experiment is viewed classically. It comes from the assumption that the apparatus is known, when really the classical description includes no phases. David R. Ingham 00:18, 20 October 2005 (UTC)

Point by point (4)

The article claims: "The Copenhagen interpretation holds back from declaring quantum mechanics primary and from downgrading classical physics to the status of an approximation that uses terms for which there are no true referents." (Emphasis is mine.) What terms without true referents does it use? P0M 01:01, 18 October 2005 (UTC)

Does my addition fix it? David R. Ingham 23:41, 19 October 2005 (UTC)

No. If you are going to claim that there are terms (words) without true referents, then you have to be willing to say what those words are. What words that classical mechanics uses have no true referents? Mass, energy, momentum, position in space, position in time? Name a few, please. P0M 02:41, 20 October 2005 (UTC)

Explanation

This section is, of course, why I, perhaps optimistically, deleted the "too technical" symbol. Probably, for most readers who make any sense of the article at all, this will be the understandable part.

Perhaps it might be more conventional to put the easiest part at the top, but I like getting to the point first and explaining it below, as is done now.

In this context, the statistical mechanics paragraph is a bit technical and not essential, but I like it because it makes the point that it was the classical description of nature itself that first failed, not just its incompatibility with the accurate dynamical forces. This seems to me to drive home the theme of the article. -- Ingham

I know where I got the information that I put in this section and can easily add citations. As a matter of fact, most of what I added is so much a commonplace of the discussions on quantum mechanics that multiple citations could be provided. But we have to be willing to try to live up to the standards of someone like Greene who can write about these matters with perfect clarity, and we have to be able to give accurate citations. P0M 02:56, 20 October 2005 (UTC)

Difficult to understand

Not only is this page difficult to understand but it is original research as the essay does not provide verifiable sources for the claims that are made, etc. I think this article should be deleted, but I am willing to see if it can be improved to something that is both understandable and verifiable. Trödel|talk 00:44, 20 October 2005 (UTC)

Thanks for the suggestion. I can easily supply citations for the garden variety stuff I have tucked in here and there. Do you have suggestions for citation style? I think there is a way to make regular footnote superscript numbers and have them pop the reader down to a section of notes at the bottom of the article. P0M 03:00, 20 October 2005 (UTC)

No, it is certainly not original research, unless you mean educational research. It follows the sources listed and other standard sources but presents it in a way that is more oriented toward philosophy and depends less on mathematics. Perhaps we should list more sources, but Messiah is really all that is needed, as he devotes so much space to the subject. He is not always easy to understand either and can't be read in short sections. What are you having trouble verifying? If you are really worried about the content, I suppose you should put in disputed flags.

An article that "presents it in a way" that has an orientation other than the neutral point of view is by definition a work of original research. Encyclopedic articles should present the information available on a subject not provide a new orientation to the subject at hand. If Messiah is the only source then there should be an encyclopedic article on him where this is one of the items discussed. Trödel|talk 03:27, 20 October 2005 (UTC)

My opinion is that the point of view of quantum mechanics texts must be considered the neutral point of view on quantum mechanics. Messiah is by no means unusual in this point of view, only in the space devoted to it. It is the observation that this most conventional point of view was under-represented in Wikipedia that motivates this article. As we find relevant parts of other sources we will add references.David R. Ingham 16:02, 20 October 2005 (UTC)

What originally motivated me is that people are still putting quantum mechanics on the defensive after a century of uninterrupted verification. The things that were originally considered absurd are nearing the engineering stage. More specific is that people are still thinking as though nature continually generated probabilities by converting back and forth between quantum and classical descriptions of itself. That is clearly contradictory to what Messiah says.

I just now have been working on the Explanation section, which is our attempt to make it understandable. Of course no-one should expect the subject to be easy to understand, no matter how it is presented. I understood some of these things very early in life and am trying to remember how to look at them without using much mathematics. I took off my "too technical" flag because it seemed we are doing as well as can be expected, not because it wouldn't be good to further increase the potential readership. You are welcome to put it back if you like. 03:06, 20 October 2005 (UTC)

I am of the opinion that if something can not be explained well to an educated person (in my case an educated college graduate with a B.S. in Physics) then it needs more editing. However, I am not sure that this article would survive a AfD vote since it is too much like original research. Thus I am not willing to invest the time in trying to more clearly articulate the ideas for intelligent non-scientists unless it will survive a challenge to its verifiability (and generally one source is not enough to create an article on). Trödel|talk 03:27, 20 October 2005 (UTC)

When there is only one reputed source, and repeated requests for page numbers are met with claims that it "is all in there somewhere. Just worry about making it correct and clear," then there does not seem to be any way to go forward. P0M 16:39, 20 October 2005 (UTC)

Footnote style

I looked up footnotes. The one I just added seems good to me. I hope Interpretation of quantum mechanics will adopt the same style. Or are there other suggestions?David R. Ingham 18:09, 20 October 2005 (UTC)

The measurement process

There is not yet a clear division, here, between the quantum and classical descriptions of the measurement process. The classical description must have been studied closely, in the dawn of quantum physics, to argue the uncertainty principle, but is less interesting now. The quantum description may be an active subject of research, because of its complexity and its relevance to entanglement and to quantum computing.David R. Ingham 05:55, 21 October 2005 (UTC)

Toward agreement on a neutral point of view

Suppose we rename Interpretation of quantum mechanics to History of the interpretation of quantum mechanics, rename this article to "Subtleties of the relation between quantum an classical descriptions of nature]], and archive this entire article and re-write it, closer to its text book sources but without plagiarizing?

There is good historical material in that other article, but its title, as it is, is misleadingly outdated. Its category would change from physics to history of physics.

Part of the objective for the new article should be to help understand entanglement, if possible.

Text book authors work hard to make it believable to people who did not grow up understanding quantum mechanics, and maybe there is much more of that quality that can be taken without adhering too closely. This would allow this article to be checked sentence by sentence against its sources, as people here want, but would still be representative of a modern view. David R. Ingham 10:50, 26 October 2005 (UTC)

As I mention on the Wikipedia:Articles for deletion/Philosophical interpretation of classical physics page, this article is mis-named, as it fails to mention any topic that is normally discussed when the "philosophy of classical mechanics" is discussed. This article seems to be enitrely about quantum. I would think the the Stanford encyclopedia of philosophy might provide a good example of what this article should look like. linas 15:17, 26 October 2005 (UTC)

For example [2] and [3] and [4] and [5] for a 'mainstream' view of classical physics philosophy.linas 15:25, 26 October 2005 (UTC)

Introduction

There were problems with the old introduction, but this one fails to identify the central point that the classical description includes more information than can be observed.David R. Ingham

Trying to fix that, I see that we have deviated from the issue. Sorry if I don't always have time or express myself clearly enough to keep things on track.

The subject is not just the verbal representation of classical physics, it is that the mathematical form itself contains untestable information. This is the point that is philosophical in nature. (Quantum mechanics does not suffer from this problem, in this case.) The uncertainty principle is a failure of classical physics and not of quantum physics. (Perhaps my previous sentence is all that is needed for than introduction.) As Feynman puts it, the fact that the information is not testable does not in itself condemn classical physics to the status of an approximation, what does is that its predictions are wrong. The statistical mechanics examples show that some of these failures follow directly from the classical description itself.

• page 2-9 of The Feynman Lectures on Physics, Vol. III
• Albert Messiah, Quantum Mechanics, English translation by G. M. Temmer of Mécanique Quantique, 1966, John Wiley and Sons, p. 45

David R. Ingham 21:23, 30 October 2005 (UTC)

Ħ: re:Messiah, 45-50

Ħ: Messiah says that the old quantum theory contained mention of things for which there are no observations, for instance: the orbit of an electron (because any measurement of low orbit electrons would distort their orbits beyond recognition, like trying to locate a fly with a fly swatter). He agrees with many others that our expectations should not be carried over from our everyday experience and make us expect or demand that electrons be discrete entities with planet-like orbits.

Ħ: This kind of situation is one that the philosophy of science deals with as almost a matter of course. We must always guard our thinking against unconscious assumptions, preconceptions, prejudices, etc., and philosophy is the category where we put analytical tools that we have designed for this kind of serious housekeeping task.

Ħ: The problem implicit in this part of Messiah's book, as in many others, is that familiarity with the macro scale phenomena successfully described in classical physics prepares us to misunderstand micro scale phenomena successfully described in quantum physics. The title "Philosophical interpretation of classical physics" does not prepare the average well-informed reader for the contents of the article that Ingham wants to present. Something like "Pitfalls of the classical mindset" would come closer to what is being discussed.

Ħ: It is a practical mistake to say that classical physics descriptions "include more information than can be observed". Readers will interpret that statement to mean that there is true information known and included in the descriptions of classical physics, but it happens to be information that is learned by some means other than by direct observation. The truth is that classical physics descriptions sometimes allege to be reports on things like planetary electron orbits for which there is no evidence.

Ħ: In the Interpretation_of_quantum_mechanics article, there is a chart of several interpretations. Ingham seems to me to want to take the Bohm position as the correct one and claim hidden variables, variables that are there and that determine, e.g., in which position a photon "show up" in a double-slit experiment. To prefer one of those several viewpoints fails to meet the requirement that we maintain a neutral point of view.

Ħ: As Messier says in a footnote on the fourth page of chapter 2,

After violent controversies, [the Copenhagen interpretation] has finally received the support of the great majority of physicists. However, it had (and still has) a number of die-hard opponents, among which one should notably list Einstein, Schrödinger, and de Broglie. The controversy has finally reached a point where it can no longer be decided by any further experimental observations; it henceforth belongs to the philosophy of science rather than to the domain of physical science proper.

Surely the Bohm or any other interpretation is no more sacrosance.P0M 23:21, 30 October 2005 (UTC)

I think you may be starting to learn some physics, POM. That introduction may be an improvement. I am not sure why we were both looking at the same page in Messiah at the same time.

The section on the measurement process is in need of help too. Please see the discussion page for the rfd where I have listed problems. P0M 04:45, 31 October 2005 (UTC)

I agree that we should end up with a different title, but I started with this one to balance "Interpretation of quantum mechanics", because a poor fit between a theory and its approximation belongs to the approximation and not to the theory. As I said, somewhere, we should talk about the history of when physicists still thought classically and talk about physics from a contemporary point of view. I want this article to permanently do the latter but also at present to lead people away from seeing viewpoints as contemporary, when they are not.

Of course there must be current philosophical discussion of physics, but I can't see how that can be interesting until we already know enough physics to understand entanglement and quantum computing. From what I am reading in Physics Today, that will not reach an encyclopedia soon.

If I find some historical evidence, I would like to include that Einstein's failure to "understand" quantum mechanics was caused by people putting things too conservatively for him to see the leap. I don't remember much talk about the "interpretation of curved space". He simply said that was how it is and the experiments confirmed it. There was no putting it softly to keep from disturbing people. David R. Ingham 03:24, 31 October 2005 (UTC)

Physics and the Real World (is that a tv show?)

I looked this up :"Physics and the Real World" by George F. R. Ellis, Physics Today, July, 2005 I don't see what the error you refer to is. Maybe you could write one of your essays and post it to your personal website , or to wikinfo.org where original research is ALLOWED (along with an unmangled version of this Phil Interp. of Cl Phys. page while you're at it.) GangofOne 03:14, 3 November 2005 (UTC)

Point by point (6)

The current text says:

The Copenhagen interpretation was formulated while quantum mechanics was new and no one was used to it, so it describes quantum mechanics in terms of classical physics in a way that is adequate for practical purposes. The Copenhagen interpretation holds back from declaring quantum mechanics primary and from downgrading classical physics to the status of an approximation that uses terms for which there are no true referents at the micro scale. That is, it still spoke as though the uncertainty principle were a part the the quantum theory itself rather than part of nature.

After reviewing Heisenberg's Physics and Philosophy, among other early works, I believe the above statement does not correctly reflect the facts. Note that no citations have been provided. The passage consists of groundless assertions made in support of one point of view. P0M 08:10, 3 November 2005 (UTC)

Point by point (3)

Failing to find any place in Messiah's book that actually fits the statement that "One of Messiah's examples involves measuring the position of an electron with light. If the light's wave function is not known and hence cannot be included in the system wave function, then the predictions of the electron's position can only be stated in terms of probabilities, because the light photons exchange amounts of momentum with the electron which would then be unknown," I have decided to track through the literature in more-or-less historical sequence to discover where there might be an actual assertion that is at least close to what has been claimed in the article.

• The Revolution in Physics, Louis de Broglie. Nothing even close.
• Atomic Physics and Human Knowledge, Niels Bohr. Chapter on "Discussion with Einstein on Epistemological Problems in Atomic Physics." This article is very well written, but difficult to comprehend unless one has thoroughly learned the exact definitions of many terms. It does not appear to support David's specific contentions, however.
• The Nature of the Chemical Bond, Linus Pauling, pp. 10-11:

The stationary quantum states of a molecule or other system are states that are characterized by definite values of the total energy of the system. These states are designated by a quantum number, represented by the number n, say, or by a set of two or more quantum numbers, each of which can assume any one of certain integral values. The system in the nth stationary quantum state has the definite energy value W[n] and is represented by the wave function ψ[n]. Predictions can be made about the behavior of the system known to be in the nth quantum state by use of the wave function. These predictions, which relate to the expected results of experiments to be carried out on the system, are in general not unique, but instead statistical in nature. For example, it is not possible to made a definite prediction of the position of the electron relative to the nucleus of a normal hydrogen atom; instead, a corresponding probability distribution function can be found.

The bold print is mine. --P0M

I believe that the above quotation is illustrative of a more general characteristic of the problems involved in locating an electron or other quantum domain entity by causing a second quantum domain entity to impinge upon it, and, subsequently, determining the location at impact of the second object on a detection screen. Neither the electron nor the photon has a location or a trajectory in the sense of the words as used in macro-scale discourse. Each has its ψ function. When the photon and the electron interact with each other, their ψ functions are both changed in some way. The energy of the light can be known because we can arrange an experimental apparatus that reliably emits light of a certain frequency. The direction of the line between the light source and the target can only be determined (when there is no intervening electron or other light blocker) by observing its point of arrival on the target. So if it hits the electron we can only be approximately aware of its "line of flight" because we do not know where the electron is except in a general way. Then the electron will strike the detection screen at some point at some verifiable point. That means that we have only two points out of three defined clearly. The "orbit" (to once again use figurative language from the macro world) of the electron will be changed by the impact of the photon. That is to say, its ψ function will be changed. So the ψ function of the electron, which originally had to have been unknown, has now been changed by the impact of the photon, which originally had an unknown ψ function. The resultant ψ function now has two unknown components. If we haven't hit it too hard with the photon, then we know what its orbital is, so we know what its frequency and energy are, but we do not know its position. Its position was precisely what we were trying to determine in the first place, and it seems that the one thing we can know for sure is that we have jarred it to someplace it wouldn't be if we had left it alone. I'm doing this in first-draft mode, thinking at the keyboard. Please correct what I have written if needed. P0M

Failure to give a citation may necessitate removing the statement quoted above. Emended,P0M 00:28, 17 October 2005 (UTC)

I know that I am not following my sources closely, but that is all in there somewhere. Just worry about making it correct and clear.

I cannot help make it correct and clear unless you will tell me the source in Messiah or somebody who writes equally clearly like Francis Sears. I have scanned the two volumes of this text and looked in the obvious places. I have looked through the index. I have searched the other physics texts that I have on hand. Nowhere do I find a trace of the kind of discussion you mention. P0M 02:46, 20 October 2005 (UTC)

I think your paragraph above is correct but don't see how to use it yet. The uncertainty principle garantees that one must make enough random phase approximations for the unspecified phases to supply the extra information for the classical description.

Incidentally, Linus Pauling said that his appointment was as professor of physics as well as of chemistry but the chemistry department head was his boss and wouldn't let him teach the nature of the chemical bond in a physics class. David R. Ingham 23:33, 19 October 2005 (UTC)

One note: the statement above: "Neither the electron nor the photon has a location or a trajectory in the sense of the words as used in macro-scale discourse. Each has its ψ function. When the photon and the electron interact with each other, their ψ functions are both changed in some way." is not the way QM works. To understand how two particles interact, one generally must construct a single wave function that describes both. There are special situations where one can simplify things. For example in solving the hydrogen atom, one normally ignores interactions with the proton and just calculates a single electron moving in the proton's static coulomb field. In general, however, you can't do that. For two entangled photons you need a wave function that includes both. The case of an electron and a photon gets even messier because photons can be created and destroyed in the process. --agr 10:56, 6 November 2005 (UTC)

Thank you very, very much. At last some light on this subject. P0M 16:22, 6 November 2005 (UTC)

Afd failed

Per Wikipedia:Articles_for_deletion/Philosophical_interpretation_of_classical_physics. Most were for delete, but could not agree on what form of deletion. --Woohookitty^{(cat scratches)} 11:42, 5 November 2005 (UTC)

So what now?Karol 09:05, 28 November 2005 (UTC)

We need to decide what the article is intended to explain, and then we need to find a title that is clear.P0M 15:06, 28 November 2005 (UTC)

New material

I have not had new sources to add recently, but here is a very good one.

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."

In principle the answer is given by the correspondence principle, but the details are very complicated, so there is not a clear derivation of "the usual probabilistic rules". Theorists tend to be more often quoted than experimentalist and less involved with this issue. David R. Ingham 05:57, 10 May 2006 (UTC)

This quote clearly supports the thesis of this article, that it is classical physics that requires explanation in terms of quantum physics. David R. Ingham 06:26, 10 May 2006 (UTC)

Entangled cat

To avoid repeating the same text again, I am putting a link to my comment about Schrödinger's cat: [[6]].

This is another example of how it is dangerous to think of our classical picture as real. It is only an approximation to QM, and the rules about when it is valid can be subtle. David R. Ingham 20:49, 23 August 2006 (UTC)