Talk:Quantum mechanics/Archive 3

Image Excellence
Just wanted to mention that the image (the red and black one on top) is excellent! However, is there a source for it? I highly doubt that that picture was taken by a home camera. :D
 * If you click on the image you can see the image description page. This particular image was uploaded by User:FlorianMarquardt, who I'm sure used some software to create the image rather than a camera.  His user page says he mostly uses Yorick (I would've guessed Matlab), but if you want to know for sure how they're done, you can always ask him on his talk page.  &mdash; Laura Scudder | Talk 15:58, 18 October 2005 (UTC)

Experimental confirmation of predictions
As it stands, experimental confirmation of the theory seems to be mentioned only within the "philosophical consequences" section, where it crops up in relation to the Bell tests and entanglement. Perhaps "Experimental confirmation" should be a section of its own? Caroline Thompson 17:14, 14 Jan 2005 (UTC)
 * I suggest a separate article; otherwise, too much in one article.

wording quibble
"Quantum mechanics is a physical theory which, for very small objects such as atoms, produces results that are very different and much more accurate than those of classical mechanic" First, it's not just small things, there are macroscopic q. phenomena, eg superconductivity/fluidity/lasers blackbody radiation spectra, heat content of solids, etc ; and it's not that for atoms it provides a more accurate theroy than classical mech, it's that classical mech. doesn't provide ANY theory that's EVEN CLOSE to the facts, for atoms, and those other things I just mentioned. Needs rewriting.67.118.116.145 04:38, 21 Jan 2005 (UTC)
 * I agree with your points. I made an attempt to address them.  Tell me what you think.  -Lethe | Talk 05:14, Jan 21, 2005 (UTC)

Gnome!?
In a recent edit, someone added a picture of a garden gnome and nothing else. I could just be missing some obvious connection between gnomes and quantum mechanics, but I doubt it. I'm removing it for the moment.

Feynman
Richard Feynman was not among the founding fathers of QM. I added Pauli's name there instead.--Ashujo Feb 11, 2005

More founding experiments?
Doesn't the line spectra of atomic hydrogen hold its place among the ones mentioned? I am from Sweden so I might be biase to Rydberg, but I guess Bohr migh side with me on this...

Maybe also the photo-ekectric effect - connecting Plank's constant with something else than the black-bodies?
 * I tried to add the citation to Rydberg, but it would take the addition of Fraunhofer lines etc. etc. So perhaps the citation should go into History of Physics with a link to QM? Ancheta Wis 14:49, 28 August 2005 (UTC)

more fundamental theory
CYD, I noticed that you removed my remark about quantum mechanics being suitable a more fundamental theory. Didn't you like it? Basically, I have in mind that any theory with the larger domain of applicability should be said to be more fundamental. -Lethe | Talk 08:00, Mar 3, 2005 (UTC)


 * Okay, now I see what you are getting at. I put it back in a slightly different form. -- CYD

new intro
"It is believed to be a more fundamental theory than Newtonian mechanics, because it provides accurate and precise descriptions for many phenomena where Newtonian mechanics drastically fails. Such phenomena include the behavior of systems at atomic length scales and below (in fact, Newtonian mechanics is unable to account for the existence of stable atoms), as well as special macroscopic systems such as superconductors and superfluids."

Many of these failures are more accurately attributed to the failure of Maxwellian electromagnetism.

Also, there needs to be mention of the discovery of the photoelectric effect by Hertz.

I disagree with the above. ""Believed" is superfuous—This fact is more certain than almost anything else in this encyclopedea. Whether something is mechanical or electromagnetic is not a matter of accuracy. Einstein explained the photoelectric effect. I have not seen it mentiond who observed it first. Heinrich Hertz varified Maxwell's equations by inventing radio.  I do find a refference to the Frank/Gustav Hertz experiment http://hyperphysics.phy-astr.gsu.edu/hbase/FrHz.html#FH, but that is not exactly the photoelectric effect. --David R. Ingham 15:42, 27 July 2005 (UTC)

I have some comments about the new intro:

-Lethe | Talk 23:40, Apr 13, 2005 (UTC)
 * 1) I like the idea of the new intro.  It would be useful to put quantum mechanics into the larger context of other kinds of mechanics.
 * 2) but don't just insert a new intro in front of the existing intro
 * 3) respect the conventions of the article.  For example, this article uses the phrase "quantum mechanics" to mean any theory that is quantized.  Therefore, to distinguish quantum mechanics from relativistic quantum mechanics is confusing.
 * 4) furthermore, I would not seperate relativistic quantum mechanics from nonrelativistic quantum mechanics.  The only difference between the two is basically a choice of Hamiltonian.
 * 5) quantum field theory, on the other hand, is the true marriage of quantum mechanics and relativity.  And it is a qualitatively different theory from quantum mechanics (single particle).
 * 6) what you consider to be a significant fraction of the speed of light depends of course on your needs.  GPS satellites probably don't even go 0.1% the speed of light, but still the engineers use relativistic mechanics with them.  Because they require great accuracy.
 * 7) we changed in the old intro some wording to make clear that it's not the smallness that makes quantum mechanics apply.  Some atoms are classical, and some macroscopic systems are quantum.  So it's inaccurate to just say "small things like atoms" are quantum systems.  and again, it depends on the level of accuracy.
 * 8) Classical mechanics includes many things besides Newtonian mechanics. I would distinguish Hamiltonian and Lagrangian mechanics from Newtonian mechanics.  I might also distinguish fluid mechanics, statistical mechanics.
 * 9) what about general relativity?  Shouldn't it fit in some where?
 * To make the article less tedious, how about moving the first five paragraphs elsewhere to other articles in the physics category? This preliminary non-quantum prose might even be a welcome addition to a section of the major physics article. The state of the article when it had just become featured was pretty good. Right now, a re-run of other topics makes for tedious reading. There isn't an equation in sight, for some reason. Ancheta Wis 00:38, 14 Apr 2005 (UTC) My thanks to LauraScudder for the improvements as I was typing this.
 * As of 08:36, 14 Apr 2005 (UTC), the first paragraph belongs to a parent article. My vote is to move it to physics or mechanics. Ancheta Wis 08:36, 14 Apr 2005 (UTC)
 * As of 08:36, 14 Apr 2005 (UTC), the first paragraph belongs to a parent article. My vote is to move it to physics or mechanics. Ancheta Wis 08:36, 14 Apr 2005 (UTC)


 * The new intro has got us arguing over whether Newtonian mechanics is all there is to classical mechanics and I've been editing such things too until I realized that the subfields of classical mechanics have nothing to do with quantum mechanics and just distract and confuse the unintiated while boring the others. I shortened that segment to:


 * ''Most physicists would divide mechanics into four major areas: classical mechanics, relativistic mechanics, and quantum mechanics.


 * But in physics, quantum mechanics can be regarded as the fundamental theory. ''


 * I think it simplifies the intro significantly and takes it back to the spirit of the first featured version while still putting the field into context for those who want to clicky clicky like mad. The distinction between nonrelativistic quantum mechanics and relativistic quantum field theory is made on the appropriate quantum field theory pages.--Laura Scudder 18:28, 14 Apr 2005 (UTC)

Introduction
You are losing our reader with this introduction, although the worst was taken care of during the last few days. Please consider the frame-of-mind of someone seeking info on "quantum mechanics" as a fairly unfamiliar topic. This reader does not want to hear about Newtonian mechanics, or relativity, or any number of other fancy classifications, at least not until later. Give the reader a break, at plainly start by telling what it is about. And why anyone should take an interest, besides the specialists. April 15, 2005 - Guest


 * I agree, in making the introduction more "accessible", we have severely bogged it down. Also doesn't really match the Wikiproject science guidelines now either.  I'll be bold and if people disagree, edit away and/or discuss here. --Laura Scudder 18:13, 14 Apr 2005 (UTC)


 * Yes, much nicer. However, I have to say that "relativistic" should not be extracted from either classical or quantum mechanics. Both include relativity (special, of course), and one takes a non-relativistic limit as the need arises. I know that most university course plans start out non-relativistically, and this should of course be mentioned, and is quite reasonable, but it is not really fundamental. We don't hit students with relativity on day one, of course (we wait a couple of months:-). Also, something must be done for the general readers, there has got to be many at this place, and they should be able to come away with something too. -Guest April 15, 2005

It appears you are advocating the position of a reader who has not yet considered the microcosm. This suggests that the article might start off with the atomic hypothesis, then radioactive decay, or perhaps cosmic rays (leakage from a Leyden jar, etc.). ... This approach might then culminate with the statement about general applicability of QM as a fundamental theory, and the current non-relationship to GR. A complete rewrite or new article history of quantum mechanics. Ancheta Wis 10:32, 15 Apr 2005 (UTC) ( By the way, you can date-time-stamp your posts with the 5-tilde notation: )


 * Well, yes and no, advocating "the position of a reader that has not yet considered the microcosm". Of course, the large scale history as you describe it belongs elsewhere. However, as anyone who teaches (science not least) will confirm, it is very easy to assume too much pre-knowledge, and not advisable. In a *pedia one really should be forthcoming towards uninitiated readers, at least when dealing with a difficult topic (if ever there was one) which receives much public attention. For instance, consider the general use of the term "theory" as some sort of idle speculation, while quantum theory is often presented in the media as a collection of "puzzles and paradoxes". It ought to be clearly stated up front how most serious an enterprise it really is.


 * Here is what I had in mind - hope I managed to incorporate your latest contributions. It would perhaps be fair of me to let you know a little of my background, but on the other hand, it's the words that count, so maybe better to do without. -Guest April 15, 2005

Umm, no. An introduction has to introduce the topic clearly and concisely. Quantum mechanics is regarded by virtually all physicists as the most fundamental framework currently available for understanding physical nature (but it is not the only one in use) is a terrible way to start an article. -- CYD


 * I can assure it is true, and what people want to be sure of when paying tuition - but suit yourself. -Guest April 15, 2005


 * Let me elaborate on that sentiment. I think, Guest, that you're trying to do an admirable thing by making this article more accessible to the unititiated, especially since it has become featured, but are going about it the wrong way.  For someone who doesn't understand the distinctions between fields of physics well, the most important thing to know right off the bat is that quantum mechanics means quantization and that it's the best theory we've got right now (argue that one with the string theorists).


 * According to Wikiproject science guidelines, we do need to put it into context, but too much context is just making distinctions the newcomer doesn't understand (quantum physics versus quantum mechanics versus quantum field theory - not to mention that I disagree that studying fields is outside of mechanics) while boring the experienced. I think saying its the best theory we've got and has some mindbending consequences (wave-particle duality) is a pretty good motivation take an interest in it. --Laura Scudder | Talk 16:42, 15 Apr 2005 (UTC)


 * It's the centuries-old question: my kid would do well to become a lawyer or a doctor, but he/she wants to be a physicist (it used to be astronomer) - but that's all up-in-the-air, or isn't it? When coming to an article like this, the reader is entitled to a clear and unambigous statement, of what this subject means in the world, and not to go directly into some jargon for the initiated. As a professional physicst, who has taught quantum mechanics to those kids for a long time, I know very well that the point is quantization, but that makes no sense at all outside of physics. First question to answer: is it any good?

And by the way, from your quotes it seems like you're not looking at my version - which was the "soft learning curve" one. -Guest April 15, 2005


 * Thank you for your thoughts on the intro. Here is my take on your 4-paragraph precis of QM:


 * 1) QM is a fundamental framework for understanding Nature. It has withstood a century of experimentation, and therefore is worth your intellectual investment required to learn it (as the student).
 * 2) QM applications and successes.
 * 3) QM has some surprises for anyone wishing to invest time learning it.
 * 4) as for QM vs GR, the story is not complete yet; there is hope that you (the student) can add to the physics, should you care to accept the challenge.
 * I do not disagree that the 4-part story is intriguing. The English is immaterial and can be word-smithed if everyone is agreeable that the 4-part structure (+the 5th para. of names) makes a good intro. I like what I see. Ancheta Wis 02:25, 16 Apr 2005 (UTC)
 * Now if I may, Prof. G., ask you some questions: The Schrödinger picture is really how I think of the topic, based on my brainwashed view of the flow of time, but I am told that Dirac espoused the Heisenberg picture; it takes an odd frame of mind to view the system using time as an independent variable upon which we can travel at will. I have to admit difficulty visualizing such a system. But if we take a GR POV, and view the cosmos as evolving in time and space, much like a tree growing, I can visualize that. Might it be possible that the Heisenberg picture is more like GR (or statistical mechanics) that way? That would give me more of a feel for the evolution operator. So right away, the framework aspect of QM comes up for explication and evaluation. (Your paragraph 1 of the intro) It's difficult, in another way. Unless the student can take that on faith, somehow. It's like the student has to start all over again, on another kind of kinematics. I would imagine that the dropout rate would be high, to get through the framework part. That implies that the successes (paragraph 2) are what sustains the student. Ancheta Wis 02:25, 16 Apr 2005 (UTC) Yet upon reflection, to state that the framework is the general entry point for learning QM, has to be a conclusion based on the century of development and experimentation; QM certainly didn't start out with that status at all. So the 4 part intro can't be the TOC for an article or course, it would have to start with experiment, perhaps a failed hypothesis or two, and then the string of successes.
 * Another line of questioning: QM is the basis for computational chemistry, which takes up a ton of computing power. Yet we do not hear much about the codes currently in use by Peter Coveney et. al. I would think that your students could gain some significant experience if they got some background for that area. I still am unclear on how much the QM computer codes compare in processing load, compared say to Earth Simulator.
 * I recognize that the questions are unfair, but it doesn't hurt to ask. Maybe we can find some answers. Ancheta Wis 02:25, 16 Apr 2005 (UTC)

Umm, most of this is dealt with in the rest of the article, if one bothers to read anything apart from the introduction. See, in particular, the section Interactions with other scientific theories. See also Manual of Style. -- CYD

Reply to Ancheta Wis: Thanks for taking time with my suggested intro (which is at "intro with softer learning curve" here>; it was immediately thrown out by CYD).

Just passing by as a guest, I got somewhat disturbed at the impression an uninitiated reader of this featured article would get. Science is not faring too well among young people, and I find that it is partly due to the way it gets represented in the media: too much nerdy whizzkid, too little serious business. Choosing a line of study, we all need to see the long professional aspect, not just the instant gratification entertainment value. Therefore I find it important to provide a readable and understandable intro, where the reader can hang on as long as possible. I'm pleased to see that you recognize this.

My contribution is/was an attempt to simplify the flow of ideas, which seemed to me to have gotten rather entangled (with all due respect, probably an artefact of the editing procedure). As we all know, of course, to start a fresh version can often help.

Here are my answers to your (welcome) questions (and some thoughts while we're at it):

> QM is a fundamental framework for understanding Nature. It has withstood a century of experimentation, and therefore is worth your intellectual investment required to learn it (as the student).

Indeed, and your financial investment too (as a parent). As a community, physicists can assert this in absolute honesty, and with complete confidence. The scientific test procedures involved in that so many physicists have worked on this, everywhere, every day, for a hundred years, is so tremendous that it needs to be asserted explicitly. No one outside science or technology can possibly have any realistic idea of the degree of certainty that has been achieved here. Now, I am well aware, of course, that as an academic one tends to shy away from making such blunt statements - and that's why it's not well understood outside of science. Now, since practically every professional physicist (and chemist as well, I suppose) agrees, I believe it should be said here, in this article, in an unambigous statement, that, this is what most of us find, and that many of us use quantum mechanics day in and day out (except, of course, ... you know). It does not have to be presented as an absolute and final truth (which no physicist of course would subscribe to), but the strong confidence must come through. It is justified.

> QM applications and successes.

Yes, most readers will appreciate this when listed in general terms. And I linked to the quantum specific pages.

> QM has some surprises for anyone wishing to invest time learning it.

Now that we have said that quantum mechanics is serious, and works, it's motivating to know this.

> as for QM vs GR, the story is not complete yet; there is hope that you (the student) can add to the physics, should you care to accept the challenge.

Yes, we really hope that one of you (students) will be the one to make a discovery, like what Planck did, to find the more fundamental framework of the future.

> I do not disagree that the 4-part story is intriguing. The English is immaterial and can be word-smithed if everyone is agreeable that the 4-part structure (+the 5th para. of names) makes a good intro. I like what I see. Ancheta Wis 02:25, 16 Apr 2005 (UTC)

Thanks.

> Now if I may, Prof. G., ask you some questions: The Schrödinger picture is really how I think of the topic, based on my brainwashed view of the flow of time, but I am told that Dirac espoused the Heisenberg picture; it takes an odd frame of mind to view the system using time as an independent variable upon which we can travel at will. I have to admit difficulty visualizing such a system. But if we take a GR POV, and view the cosmos as evolving in time and space, much like a tree growing, I can visualize that. Might it be possible that the Heisenberg picture is more like GR (or statistical mechanics) that way? That would give me more of a feel for the evolution operator. So right away, the framework aspect of QM comes up for explication and evaluation. (Your paragraph 1 of the intro)

As you know, the Heisenberg picture is mathematically and physically equivalent to the Schrödinger picture, by unitary transformation. It is good for theoretical work, and is quite widely used. For visualization, I recommend using the H picture with the Ehrenfest procedure, to recover the Newton equations of motion, where the time dependence nicely associates with the observables, as we are used to. Indeed, in this way I derive classical relativistic electrodynamics, for the (graduate) students in relativistic quantum mechanics, so it is basically all there.

> It's difficult, in another way. Unless the student can take that on faith, somehow. It's like the student has to start all over again, on another kind of kinematics. I would imagine that the dropout rate would be high, to get through the framework part. That implies that the successes (paragraph 2) are what sustains the student. Ancheta Wis 02:25, 16 Apr 2005 (UTC)

Yes, we wait until the second year to do q.m., but in principle one could start with it, in principle. If systematically presented it is not hard to understand, but the mathematical framework must be taught in mathematics beforehand. Many students, of course, are more interested in other things, and just need to see a bit of it, at some stage, to be convinced that it works, and understand how material properties get deduced in q.m. Some day we may even be able to compute masses, some day...

> Yet upon reflection, to state that the framework is the general entry point for learning QM, has to be a conclusion based on the century of development and experimentation; QM certainly didn't start out with that status at all. So the 4 part intro can't be the TOC for an article or course, it would have to start with experiment, perhaps a failed hypothesis or two, and then the string of successes.

Indeed, so we should imply these empirical foundations via the Part 2. Anyhow, It still helps to know that there is a reliable mathematical framework, even if you do not intend to become a specialist in it. So the general framework part is important for building confidence, although the learning is done via more specialized calculus formulations. Hope I understood your question here.

> Another line of questioning: QM is the basis for computational chemistry, which takes up a ton of computing power. Yet we do not hear much about the codes currently in use by Peter Coveney et. al. I would think that your students could gain some significant experience if they got some background for that area. I still am unclear on how much the QM computer codes compare in processing load, compared say to Earth Simulator.

This topic is beyond my scope, so I have to pass on that.

> I recognize that the questions are unfair, but it doesn't hurt to ask. Maybe we can find some answers. Ancheta Wis 02:25, 16 Apr 2005 (UTC)

Not at all. Let's hope it becomes possible to have an introduction that part of the way, at least, makes sense to all readers. -Guest April 16, 2005

Dear writers. Quantum Mechanics is a difficult and confusing subject. What is the essence ? How can it be explained shortly and understandably ? To me it is the following. "Quantum Mechanics identifies energy and frequency. The unit of frequency, the hertz, is also a unit of energy. The number of joules per hertz is Planck's constant. As energy is a property of particles and frequency is a property of waves, quantum mechanics identifies particles and waves. When the frequency is low, the particle aspect fades away and it looks like 'classical' waves like those on the sea. When the energy is high, the wave aspect fades away and it looks like 'classical' particles like grains of sand. So Quantum Mechanics merges two distinct classical theories into one. It is actually a conceptual simplification". Bo Jacoby 09:49, 13 September 2005 (UTC)

Yes, that's why I added electromagnetism in the first paragraph, but I am not sure "unifies" is the best word. I think "Quantum mechanics is a theory of mechanics, a branch of physics that deals with the motion of bodies" is wrong. It is not a theory, it is the theory, and as above it is not just about mechanics, or at least that implies lack of generality. I'll see if I can find an improvement. --David R. Ingham 16:30, 13 September 2005 (UTC)

Needs a more simplified definition for the lay person
"Quantum mechanics is a fundamental physical theory that extends, corrects and unifies Newtonian mechanics and Maxwellian electromagnetism, at the atomic and subatomic levels." is going to tell a person SQUAT unless they already know what newtonian mechanics and maxwellian electromagnetism is. A more simplified basic definition is needed before expounding in the excellent detail this article gives.

well i am a layman (high school student infact) and i dont find the introduction difficult

-protecter

I wouldn't have had any problem understanding that when I was in high school either, because I had already read a lot of physics and astronomy, but not everyone is so interested in science.

How about adding, at the very top, something like "Quantum mechanics is based on the observation that, on a very small scale, waves and particles are not different sorts of object but complementary properties of all objects." --David R. Ingham 20:29, 19 September 2005 (UTC)

Or how about, at the very top, "Quantum mechanics accounts for the fact that motion, as well as matter, does not have unlimited detail, but is built up of tiny elements. The tiney elements of matter are called atoms.  The tiney elements of motion are called quanta." This is the way I started to introduce the idea to a smart ten year old (and her mother). (This omits optics, but, at this level, that is appropriate.) David R. Ingham 17:57, 28 September 2005 (UTC)

I have to agree with David. Having a good basic layman's knowledge of the subject, I found the intro overwelming. There is no mention of what makes Quantum mechanics so exciting, a simple explaination of wave/partical duality. Maybe an early reference to the "double slit" experiment to give the newer readers an idea what it's all about. Everything in the intro is needed, but maybe not all of it in the intro. Intro should be shorter, more attention grabbing. Just a thought. 12.218.132.240 13:17, 7 December 2005 (UTC) S. O'Reilly 12/7/2005

generality
People took out my generalization of the introduction. Please read The Feynman Lectures on Physics, vol. 3 first. He words it much differently, but he does explain the generality when he introcuces the subject. So what I said is not only true, but it is the best known way to teach quantum mechanics. If this makes it too hard to read, then re-word it or add something more basic, as my suggestions in the previous sub-heading, above it. David R. Ingham 17:57, 28 September 2005 (UTC)

Navbox
In order to make the quantum-theory Navbox more accessible in the other articles, I propose that it move up just under a heading, such as Quantum mechanics. Thus by inserting a parenthetical link ([other articles on QM]) in the child articles, the Navbox becomes more accessible other places. Is that alright with everyone? Alternatively, smaller versions of the quantum-theory Navbox might be placed in the child articles; as its transclusion would overwhelm many of them, currently. Ancheta Wis 08:25, 19 Apr 2005 (UTC)

As it turns out, the first article I had chosen, on the commutation relation, did not have a link back to QM, so I inserted a small version of the Navbox there. The other articles appear to at least mention this page, so the need for a link to the Navbox is partially answered already. The little navbox is titled

Minor edit
I removed this paragraph, which can't be understood (to put it nicely):


 * Another difficulty with quantum mechanics is that the nature of an object isn't known, in the sense that an object's position, or the shape of the spatial distribution of the probability of presence, is only known by the properties (charge for example) and the environment (presence of an electric potential).

-Guest April 19, 2005

I am reading a book "Quantum Generations: The History of Physics in the Twentieth Century" by Helge Kraugh that details all the inaccuracies and crises in quantum theory as it developed over the past century. The statement: "The predictions of quantum mechanics have never been disproved after a century of experiments." (introduction, 7th paragraph) is completely false and I removed the sentence. It had repeatedly been contradicted and the science has very clumsily evolved due to all these contradictions.

-Brian, February 5th, 2006

You know, how do you reconcile the predictions of Quantum Electrodynamics with your categorical statement? Are you in fact talking about the shift from the Classical to a QM viewpoint? Are you disagreeing with the QM framework? The QM framework is very broad. Curious to hear more critique by Helge Kraugh. --Ancheta Wis 22:21, 5 February 2006 (UTC)

I am not talking about Quantum Electrodynamics specifically but about QM as a whole. Each major experimental or theoretical development (discovery of new particles, uncertainty/complimentary theory, properties of high energy cosmic particles, etc) was argued and often rejected or ignored among the leading physicians at the time it was concieved. While many of these were wrong, the ones that were right often conflicted directly with the current theories and provoked serious modifications. Some of these (that are currently accepted) weren't taken seriously until decades after they were formulated.

I am not rejecting quantum mechanics. What I am rejecting is a theory of quantum mechanics that was developed in the early 1900's and remained unchanged and accounted for everything. Quantum mechanics evolved as scientists gathered more experimental evidence and dispelled groundless theories. Even the basics of quantum theory (such as the existance of the nucleus, the proton and the neutron) wasn't even accepted or confirmed by experiment until less than 100 years ago. The neutron wasn't confirmed until 1932.

The statement "The predictions of quantum mechanics have never been disproved after a century of experiments." is false not because quantum mechanics is entirely wrong (it is not) but because quantum mechanics has historically been a very unstable field. Disproofs and contradictions have been a major force driving its development throughout its history.

-Brian, February 5th
 * The 6th Solvay Conference (1930) is the one where Einstein decisively lost his debate with Bohr; thereafter Einstein refrained from direct attacks and instead used philosophical arguments against QM. Using the QM machinery, he formulated the EPR paradox, leading to Schrödinger's cat etc. I am curious what Helge Kraugh has to say about this; we, as a civilization, have not yet come to terms with what QM has to say about this. The QM framework includes definite predictions, some of which have subsequently been observed. Those observations have to be counted as successes for the framework (i.e., Schrödinger equation etc.). --Ancheta Wis 03:23, 6 February 2006 (UTC)
 * BTW we need an article on Théophile De Donder (he wrote on relativistic QM and was a supporter of Einstein). De Donder was a major influence on Ilya Prigogine. Does Kraugh mention De Donder? Ancheta Wis

Hmmm, we might be arguing along different lines. Kraugh repeats exactly what you said above.

I just read the history section and I see where a problem could arise: between old quantum theory and new quantum theory. Since the wording was "a century" I intepreted the meaning to be "since 1900". But it is probably since the mid to late 30's, which I have little knowledge of. The 1920's and early 30's were full of the crises, dead ends, the freak discoveries and ignorance to correct theories that I was talking about. Specifically, Helge Kraugh mentions that high energy particles, available at that time only from cosmic rays, did not fit the mathematical model used for lower energy particles. The problems with the 1929 Heisenberg-Pauli theory of QED was emphasized. She states: "In spite of promising features, it was infected with paradoxes and divergent quantities. In particular, the self-energy of the electron (the energy of an electron in its own electromagnetic field) turned out to be infinate, which was, of course, an unacceptable result." She also includes a 1933 letter from Robert Oppenheimer to his brother: "As you undoubtedly know, theoretical physics- what with the haunting ghosts of neutrinos, the Copenhagen conviction, against all evidence, that cosmic rays are protons, Born's absolutely unquantizable field theory, the divergent difficulties with the positron, and the utter impossibility of making a rigorous calculation at all- is in a hell of a way" The Einstein-Bohr arguments, as well as other examples (the faulty early atomic models; the electromagnetic view of the early 1900's; the often rejected theories of relativity; and the problems that erupted when antiparticles and other non-fundamental particles were discovered) are some examples of how the physics community was not all on the same page. Helge Kraugh continually depicts the early years of quantum physics (atleast till the mid 30's) as a period where quantum physics confused the most brilliant minds and divided the whole community over a number of issues. She details many theories of quantum physics which couldn't be agreed upon unless proven or disproven through experiments. Are you referring to the QEM models from the late 30's?

I have been looking for references to De Donder but have not been able to find any yet. Sorry about that. I'll let you know if I do.

-Brian, February 6
 * QM arose historically from spectroscopy, cosmic rays, and radioactivity (called 'modern physics' -- the physics after Newton and Maxwell's pictures of the world). At the beginning of the twentieth century, there was still the concept that the atom was the ultimate Platonic object, indivisible and immortal (or 'hard spheres', in physics-talk). Statistical mechanics can be formulated from this mental picture, which can be used to derive thermodynamics. But in 'reality' the hard spheres are in flux - the neutron decays into its constituent parts in 15 minutes. Our very bodies are in flux. QM takes this as a given. It has taken a century (loosely speaking) to renounce the little spheres and replace them with jello -- a world of approximate objects with finite lifetimes. (Now I admit that protons have very long lifetimes.) Even in the realm of very low temperatures, the objects are still jello-like; they jiggle. Eric Cornell has illustrated this very well in his public lectures. The pictures of Newton and Maxwell are still valuable, of course; the engineered objects we use today were built from this worldview, but there are more POV's out there, resting on QM, like lasers. --Ancheta Wis 11:14, 8 February 2006 (UTC)

From up top of this section, "difficulty with quantum mechanics" is entirely wrong. The "difficulty" is with ordinary language, which is not intended to deal with the microscopic world. David R. Ingham 09:45, 12 February 2006 (UTC)

From the bottom paragraph, "Statistical mechanics can be formulated from this mental picture" is not correct. First, one cannot directly formulate equations from mental pictures, in the sense of pictures that can be expressed easily in words. Historically, part of the origin of qm was that the statistical mechanics that was formulated from the classical view of nature, that it had unlimited detail like the Mandelrot set, was inconsistent or gave unrealistic results.
 * David R. Ingham, I appreciate your comment; the hard sphere approach is the program of Kerson Huang's Statistical Mechanics. Huang was a collaborator with Max Born, as well. Michael Faraday formulated the picture which Maxwell proceeded to express in his equations. --Ancheta Wis 11:54, 12 February 2006 (UTC)

"engineered objects we use today were built from this worldview" is not exactly correct. Did you mean the simpler objects like floor mops and earth dams? Qm has been used to understand semiconductors since at least the time Bell Labs invented the transistor. Chemistry has depended heavily on qm, at least since Linus Pauling explained the chemical bond. Lasers, though in principle a classical phenomenon, have always been understood using quantum mechanics. As an engineer as well as a physicist, I feel slighted by that remark.
 * David R. Ingham 10:30, 12 February 2006 (UTC)
 * David R. Ingham, I do not disagree, and actually believe that lasers are squarely in the QM world because lasers use QM phenomena for the laser action. My personal belief is that QM's most useful contribution is the solid explanation of the periodic table. But even a transistor can be understood, from an engineering POV, without QM. 'Guest' is the one who removed the sentence in the 'minor edit'; Guest mentioned that the Ehrenfest procedure can be used to map a QM description (in the Heisenberg picture) to a time-averaged description which seems somehow less abstract to me. So I admit that the Schrödinger picture feels more real to me. But I am trying to formulation a question for you. Something seems entangled here (pun intended). If a macroscopic-scale observer, who seems to get time from his scale, were to shrink down to electron-sized scale, would time flow equally for him? I am not trying to trip you up. I am honestly trying to get an insight here. If the Ehrenfest procedure is an important-enough process to give us time, then it ought to be possible to come up with a phenomenon which transcends time, just as  q. entanglement transcends space. From a macroscopic perspective, that seems to contradict my prejudices. If we somehow could define simultaneity using some natural feature like polarization or spin, we could define some pretty good clocks, etc. --Ancheta Wis 11:54, 12 February 2006 (UTC)
 * I can sharpen my question -- QM applies even at regions of low temperature, where the celebrated BEC phenomena occur, and which show QM up at macroscopic scale. Obviously QM applies to the very small, with apparent applications at macroscopic scale (lasers, transistors, etc.). There are other continuous parameters out there; mass is one example. If we could shrink the quantity of mass for an object, what would happen? Would time flow equally for two synchronized objects, one of which was subject to decay in mass? Conversely, what would remain invariant? --Ancheta Wis 12:16, 12 February 2006 (UTC)

Ancheta Wis, I think I finally understand your intepretation of that sentence. You meant "Quantum mechanics as a worldview has never been discredited by experimentation during its century long development. Experiments support this jello-like existance of the atom." I completely agree with that intepretation. As you have probably guessed, I derived a very literal meaning of the sentence: "The sole Quantum mechanical theory, proposed around 1900, has predicted a whole bunch of stuff that can't be disproven by experiments." You can see why this bothered me.

"The predictions of quantum mechanics have never been disproved after a century of experiments." may need to be reworded before it is reinserted.

-Brian, February 13