Talk:Philosophical interpretation of classical physics/Archive 1)

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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.

Contents

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)