Talk:Introduction to quantum mechanics/Archive 3

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This article is intended as an accessible, non-technical introduction to the subject.

Fail. —Preceding unsigned comment added by 173.50.155.230 (talk) 06:42, 17 January 2010 (UTC)

I'm in chemistry I honors, and this article is EXTREMELY useful and detailed - it goes over the parts my teacher skipped for simplicity's sake! As long as you have a little background to quantum mechanics, whether it be from high school or a textbook, this article is an excellent supplement. Also, Physics 2000 is a GREAT website for understanding quantum mechanics.

Easy to understand??

This is supposed to be a "a generally accessible introduction to the subject"? I guess it might be easier to understand than the (non-easy) Quantum Mechanics article, but this is by no means something that the layman could understand. I know this is a complex subject, and that explaining complex things simply is difficult. Still, I hope that this article could be made from "easier quantum mechanics" to "actually easy and fairly simple to understand quantum mechanics". Above all, remember that we don't need to go into that much detail, because this is the "easy" article :). Some suggestions:

-The overview section is really long, maybe we could trim it down?

One of the things that might make the article easier to understand is if we took all the history out of the "Overview" section and put it into a new "History" section that details all the, well, history of QM, like Einstein, Bohr, etc. (see below)

Would it be possible to just put a few simple paragraphs explaining what quantum mechanics is, without going into a lot of detail just yet?

-History

I noticed that there is a TON of historical data floating randomly in this article. I don't know how important this is to quantum mechanics, and of course if it is an important point in the study of quantum mechanics to know who-did-what-when-and-why then of course these little snippets of history should be kept, but if this is not the case, then we have way too much history on our hands here. It seems like what's happening in this article is that instead of explaining QM in an easy-to-understand manner, we are writing about the major "players" in the development of QM. We are going through all these theories and concepts person-by-person, looking at "what Planck did" and then "what Bohr did" etc etc, and not at "what all of this actually is". The history, though an important part of QM as a whole, should not be the focus of the introductory article to the field. Thus, I think that the aforementioned "History" section might be a good idea. That way, we could have a brief discussion of what each genius did, and we can mention their experiments and everything, but we could also try to bring the focus away from the people and towards what QM actually is. Bottom line: what matters more, the who or the what?

Thanks for the time and effort, sorry if I have no idea what I am talking about...I don't know much about QM or even physics for that matter (hah! matter! no pun intended! but how amusing!). About the history, again, if its really important and integral, then I apologize, but it just seems to me, as someone who doesn't know much about the subject, that there is too history for an introductory article. Thanks, 71.178.238.238 (talk) 04:23, 19 May 2008 (UTC)

You might want to look at what some other secondary sources have done with the subject. Brian Greene has written a couple of good books that include chapters on the subject.

Just explaining what classical physics is can be a problem, yet it researches the stuff of everyday life. As soon as you hit Relativity theory, people start making simplistic interpretations that can only mislead others, but at least they are talking about effects that can be observed in things like global positioning satellites. Quantum mechanics deals with things that cannot be seen, and one of the really important lessons tied up with quantum mechanics is that it is essential to keep clear on what is observed vs. what is inferred.

It would be relatively easy to say what quantum mechanics does, i.e., what it explains, what it helps us do, how it directs technological initiatives, etc. But then the question would be, "Well, how does quantum mechanics provide for some of the useful things in our life?" One kind of explanation is like saying that a large box with windows and wheels, you get it, turn a key, and move across the terrain. That kind of explanation would do just as well for Cinderella's magic carriage. The other kind of explanation gets into fuel, pistons, mechanical and electrical connections, tires, etc., and even explaining a relatively stripped-down mechanized vehicle more specifically than saying that you get it and it goes will turn out to involve a long chain of explanations.

I started reading about quantum mechanics sometime before 1958, and my first impression of it was that it had something to do with an "uncertainty principle." For a long time I thought that it was possible that the things in the real world were all at actual points in space and time, and that our knowledge was just limited by the fact that we inevitably mess with these real locations when we try to measure them. It turns out that I had gotten it wrong.

If you don't want people to get misled, then you have to be really careful. You have to include things to head people off from taking some things the wrong way. Furthermore, you can't jump into the middle of the story. You have to provide a road between the things that readers already understand and the new insights you want to teach. P0M (talk) 15:50, 19 May 2008 (UTC)

I've just been through the article again. The intro section gives readers the basic "consumer's view of QM" (equivalent to: Car -- you get in, you get delivered, you get out). Everything else in the article has to do with quantum phenomena, so if the reader wants some flesh on the idea that quantum mechanics deals with how nature works on the very small scale and why that should matter to us then you must work through some concrete examples. But these examples also tell the story, in digestible quantities at each stage, of how the answers to problems that cropped up in the labs each contributed parts to the jigsaw puzzle that was eventually assembled to account for everything except for gravity.

Would a timeline help?P0M (talk) 09:16, 20 May 2008 (UTC)

I agree with both User:71.178.238.238's criticisms. The history is too much, and the overview needs to be simpler. What this introduction to QM needs to address is why QM is so much harder for people to understand than classical mechanics. What about an approach like Richard Feynman uses in his Lectures on Physics? He starts out by saying: "Things on a small scale behave like nothing you have any direct experience with. They don't behave like waves, they don't behave like particles, they don't behave like clouds, or billiard balls, or masses on springs. Even the experts don't understand it the way they would like, because all of our human intuition applies to large objects. But small objects just don't act the same way." Later he goes on to enumerate in simple language how small objects' behavior is different: wave - particle duality, inability to measure variables with arbitrary precision, probabilistic results of measurement, the ability of objects to be in different states simultaneously. These are the things beginners have trouble with in QM, and they should be faced head-on in this article. --Chetvorno^TALK 22:59, 21 May 2008 (UTC)

Your plan sounds good to me. Why don't you write a new front end? P0M (talk) 21:01, 25 May 2008 (UTC)

I warmly applaud the fact that Wikipedia, recognizing the nature of the beast, includes 3 distinct entries seting out quantum mechanics, with this entry intended to be the least technical. That said, this entry leaves something to be desired, if only because many of its sentences and paragraphs are too long. Quantum mechanics and electrodynamics are probably the greatest theoretical achievements of the 20th century. The quantum mechanical theory of the electron orbital grounds all of chemistry. Quantum electrodynamics is the most thoroughly verified scientific theory of all, and is the deep physics behind all information technology. Perhaps the most important fact of the 20th century is the discovery and subjugation of the electron, and the electron is the star of the quantum mechanical play. This story must be told.

(An aside. I propose that the first "quantum insight" was George Johnstone Stoney's 1881 prediction that electric charge was carried by a tiny particle he named the electrene, and that all electrostatic charge was an integral mutiple of the electrene's charge and hence quantized.)

At the same time, I must admit that it has proved very very difficult to communicate this achievement to educated lay people, and that's not for lack of trying. Many comments on this Talk page reveal that this difficulty extends to this entry. Not that this esoteric topic is lacking in human interest, and dramatic tension and irony. Should anyone doubt this, I refer them to Michael Frayn's play Copenhagen, on the clash between Bohr and Heisenberg. Also to Pascual Jordan's Nazi sympathies, Bohr's presence at Los Alamos, Pauli's intense work with Carl Jung, and Schrodinger's unconventional attitude towards marriage and paternity.123.255.30.126 (talk) 18:59, 14 December 2008 (UTC)

Since the initial criticism was entered above, I've changed the lead. I hope that I've increased the ease of comprehension of the article. It will be a continuing balancing act to avoid short reports that are accurate but so lacking in context as to make them hard to understand on the one hand, and something that grows, topsy-turvy, into something that is too long and contorted. P0M (talk) 00:08, 15 December 2008 (UTC)

Maintenance

I've archived older content to save space here. Old content is available by clicking the archive links at the top of this page. P0M (talk) 00:46, 15 December 2008 (UTC)

Moving new comment to the end of the article. P0M (talk) 21:17, 22 May 2011 (UTC)

Some suggestions for an improved article

One

Rereading the lead and the top parts of the article it occurs to me that some drawings might make the necessarily abstract assertions much clearer to the new student of the subject. For instance, the assertion that electrons and photons do not always show up where everyday experience would anticipate their appearance might be dealt with by a cartoon in which a copyright safe version of Captain Kirk, Captain Quirk, is given a new double-barreled photon rifle for testing. The viewer the looks over his shoulder and sees him drawing a bead on a target directly in front of him. Each time he pulls the trigger a different target is hit, and once somebody behind the bulkhead gets a hole through his chef's tall hat. It should even be possible to do this with GIF images and make it into a little motion picture. The familiar Young's interference pattern emerges, and Quirk returns the rifle with the comment, "Entirely up to specifications Mr. Smock." The cartoon could be linked to a description of how one can actually reproduce much of that scenario with a laser pointer and a few brads fixed into a frame.

Doing things that way should appeal to high school students and other just beginning to understand that physics is mysteriously cool. P0M (talk) 01:10, 15 December 2008 (UTC)

Another cartoon could show a moth flying at a leisurely pace in a large room. Somebody with a butterfly net tries to catch it, but is unsuccessful. To improve her chance of nabbing it, she closes a partition, trapping the moth in half the original space. But that doesn't help because the moth moves more rapidly and erratically. Closing the volume down farther only makes the moth's position more unpredictable.

I think that these two visual analogies would make the main assertions about the weirdness of QM more concrete without being too misleading.P0M (talk) 01:21, 15 December 2008 (UTC)

For the part that introduces the main figures in early QM, how about some pictures, maybe like these? To the new reader, these are just some strange-sounding names. We should select photos that show, e.g., how young Heisenberg was when he figured out his matrix theory. Students probably would otherwise find pictures of these important figures when they were old and famous. P0M (talk) 04:51, 15 December 2008 (UTC)

I made a composite of 10 pictures of individuals who were important in QM. Einstein looks rather older than the rest of the people who were so productive in the early years. I was generally able to find pictures of these individuals that were taken within a few years of their early important discoveries. I put in Feynman just to prevent leaving a blank space. His contributions came much later, but just look at how young he looked when he was working on the fission bomb! No wonder he was always breaking into safes and leaving prank notes. P0M (talk) 03:52, 17 December 2008 (UTC)

Two

I'd like to know what other people feel about the discussion of "h-bar." To me, it is only a computational issue. It may well be worthwhile to direct readers to a discussion elsewhere since the two constants are similarly named and, sometimes, on-line discussions write "h" when the appropriate thing would be "h-bar." But the discussion takes up a huge amount of space and, as far as I can tell, does nothing to elucidate the natural phenomena. P0M (talk) 05:41, 15 December 2008 (UTC)

Three

Is the bit about dimensionality going to be helpful to the beginning student in any way? Is it essential? To me it just seems to be something added in for no good reason. P0M (talk) 05:52, 15 December 2008 (UTC)

The most eminent of physicists have warned...

The most eminent of physicists have warned that if an explanation of quantum physics "makes sense", then that explanation is very likely to be flawed.

Is this intended to be a paraphrase of Bohr's "Those who are not shocked when they first come across quantum theory cannot possibly have understood it" and Feynman's "I think I can safely say that nobody understands quantum mechanics"? If so, I think that we should find a wording which more closely matches the original intent of these. -- Army1987 – Deeds, not words. 16:52, 26 January 2009 (UTC)

In the late 19th century, classical physics appeared to some as nearly complete?!

If I remember my history correctly, in the late 19th century physicists and chemists could not agree on whether atoms were the smallest particle, or if matter was infinitely indivisible. Thermodynamics and statistical mechanics were relative new fields that were developing. No one understood black body radiation or the photoelectric effect. In the last 6 years of the 19th century x-rays, radioactivity and the electron were discovered.

Complete my butt! Technotaoist (talk) 02:18, 23 March 2009 (UTC)

There is no need to be crude.

The statement mentioned above can be substantiated. If I recall correctly it is actually based on a published statement by some eminent figure of the time who said something like, "All that remains is to figure out what is going on with problem x and problem y." The trouble was that x and y were the points where the whole thing was going to come unraveled. It's probably worth digging that quotation out just to demonstrate how successful Newtonian physics and Hamilton's work on electro-magnetics had been.

The ultra-violet catastrophe was probably either x or y, and that was a "little detail" that had to be cleared up in the account of black body radiation. P0M (talk) 05:20, 23 March 2009 (UTC)

Yes, IIRC black body radiation and the associated ultraviolet catastrophe were explicitly flagged up as something they knew they didn't understand -- the surprise was that the can of worms uncovered was just so much bigger than anyone expected. --Michael C. Price ^talk 07:25, 23 March 2009 (UTC)

No, as correctly described in Ultraviolet_catastrophe, the concept of "ultra-violet catastrophe" was recognized in 1905. It played no role in Planck's derivation of the blackbody radiation law.

The "eminent figure" was Lord Kelvin, who, in his lecture presented On 27th April 1900, considered (classical) physics as almost complete, apart from "two clouds", the null result of the Michelson-Morley experiment and the problem of deriving the blackbody radiation law.--Belsazar (talk) 22:19, 24 March 2009 (UTC)

Let's use that quotation. Do you have a citation handy? P0M (talk) 03:29, 25 March 2009 (UTC)

Actually, Belsazar, the equipartition article says that Lord Rayleigh envisaged the need for some new principle to reconcile the equipartition principle with thermal equilibrium in 1900 (which is in the 19th century, and the same year that saw Rayleigh's first derivation the $\lambda ^{-4}$ dependence of the Rayleigh–Jeans law and hence implied the UV catastrophe) he noted the need for a new principle that would provide an "escape from the destructive simplicity" of the equipartition theorem.[29]" The reference is JWS Rayleigh (1900). "The Law of Partition of Kinetic Energy". Philosophical Magazine 49: 98–118." So we have another ref to go with the Lord Kelvin quote.

Re Lord Kelvin, I'm assembling the "two clouds" quote (which may be disputed) over at Lord Kelvin's wikiquote entry. Kelvin is talking about the luminiferous ether (not Michelson Morley directly) and the equipartition of energy (not black body radiation directly). This quote seems to be confused with a similar 1894 statement by Michelson, which would also be relevant to this article. Have a look.

--Michael C. Price ^talk 08:57, 25 March 2009 (UTC)

". . . an accessible, non-technical introduction to the subject . . ."

In accordance with some of the comments on this page, I am submitting to the WP community this revised version of the simplified article concerning quantum mechanics. I have reorganized it and stripped it of its repetition and also placed within it some new links to Main Articles that will be helpful to the advanced reader. I've also deleted almost all the graphics, which are confusing and not at all "accessible and non-technical," in the words of the note at the top of the page (the wp:hatnote). The deleted material can be found at User:GeorgeLouis/QM.Rejects or in past versions of this present article; portions of this material might be added to the "expert" article at Quantum mechanics. As an aside, I note that the supposedly "accessible" article was composed of 82,419 bytes on 27 May 2009, with the "expert" article weighing in at only 51,037. Yours very sincerely, and with great good wishes for a fine Introduction to quantum mechanics (the basic principles of which are not really too hard to understand if presented simply enough), I remain your friend, GeorgeLouis (talk) 07:36, 28 May 2009 (UTC)

Article severely truncated --- opinions?:

A new editor has made some strong comments about the adequacy of the previous version of this attitude and has taken matters into his own hands. Please look at the results and give your opinions. P0M (talk) 16:45, 28 May 2009 (UTC)

I've reverted to the old version. The new version reads more like an account on the historical development of quantum mechanics, which is not the same as an introduction to quantum theory. Now, there already exists an article about the history: History of quantum mechanics, so perhaps the reverted edits can be included in there. Count Iblis (talk) 23:42, 28 May 2009 (UTC)

I am on the verge of being able to finish a re-write of the matrix mechanics part, pursuant to which I have been pestering my colleagues in the physics department. Probably much of that part should go into a sub-article as it takes quite a bit of explication to give a novice reader a clear idea of what caused the breakthrough that ended the "old" quantum mechanics. It was not the matrix idea, but the idea that found clearer expression in matrix form.

I have been hoping to get the Heisenberg part behind me and to go on to clear out some of the excess baggage in later parts of the article. It may be that some things will need to be tucked into sub-articles if they are not deleted. I will bring up major changes on this talk page before I make them. P0M (talk) 00:11, 29 May 2009 (UTC)

(OD) In the spirit of bold, revert, discuss, I suggest that GeorgeLouis now use the Talkpage to propose large scale revisions, perhaps on a section by section basis. This is not to disparage his good faith -- the article was long and somewhat rambling -- but rather an enticement to collaborate with many experienced editors to tighten the existing material.

P0M, when your rewrite is ready, I would be glad to offer feedback. Baccyak4H (Yak!) 03:18, 29 May 2009 (UTC)

I feel that GeorgeLouis's rewrite goes in the wrong direction, but it was at least a start. The previous article had way, way too much baggage. Here's my two cents: (1)I suggest omitting ALL the history. We already have History of quantum mechanics and History of quantum physics and it is clear from comments on this page that people think the article had too much history. (2)I'd also suggest omitting connections to relativity and other advanced topics; we need to keep the article short. (3)It's clear from the comments on this page which direction this article should go. What people want this article to address is why QM is so hard to understand. It should just be a primer, in simple language, of how small-scale (quantum) objects behave differently from large scale objects: wave-particle duality, uncertainty principle, quantum probability and nondeterminism, superpostions, quantized energy levels, interference. Yes, we have articles on these topics, but not in simple language.

I began a rewrite that can be viewed here, although I'm not satisfied the language is simple enough. --Chetvorno^TALK 21:56, 29 May 2009 (UTC)

Baccyak4H, and everybody:

I am stuck on the math, but in general the path up to Heisenberg's breakthrough is clear, and it is easy to explain how everything worked to explain things that had previously been unexplainable:

This is just an outline:

Mystery one: "Every element has its characteristic bright-line spectrum, but how can these irregular sequences be given a theoretical treatment? They don't make any rhyme or reason!" But then:

Balmer: λn=Å•3646•(n2/(n2-4) where (n=3,4,....) and later, in a more productive format:

Rydberg and Ritz: 1/λn = RH(1/4 - 1/n2) where (n = 2, 3, 4...)

Mystery two: "Light waves hit a metal surface but monochromatic light gives the same voltage on the (de facto) light meter. Stronger light gives more amperage, but the same voltage. What the hay?!?" Mystery solved:

E = hf (Planks's constant)

f = c/λ (nothing new here, but novices need to see how to get from frequencies to wavelengths and back.

E_electron = hc/λ

Planck-Einstein relation:

E_photon = E_i - E_j = hf

Mystery three: "The hydrogen spectrum is predictable, for the visible spectrum, but how about ultraviolet and infrared?"

Bohr's scheme of energy states predicts many spectral lines:

1/λ = RH( 1/n_f 2 - 1/n_i 2 ) where (n_f = 1,2,3... and n_i > N_f)

Mystery four: "So what is with these bright lines? Why are some brighter than the others? Bet you can't explain that!"

On the existing basis, one could predict the spectral lines for hydrogen, and the energy of the photons associated with each of the lines. The only thing that would not be known on this basis would be the intensities of each of the spectral lines. By studying the best available secondary sources I have realized that the problem for Heisenberg, and the discovery that Heisenberg made to solve it, was how to account for the intensities of the hydrogen bright-line spectrum. Although every step in the math up to this point is almost too simple to believe that it can account for so much, the calculations that he had to perform take him about 16 pages just to sketch out -- and people in the field even complain that they can't understand it. If only he had written in a little more detail it would have been clearer. I say this because some people have since puzzled it out. Right now I'm trying to get a "proof of concept" grasp on the math so that I won't say anything ridiculous on how the matrices are to be written out. What Heisenberg actually wrote and published did not involve a single matrix, but my colleague in the physics department took one look at the equation that a secondary source spotlights as "Heisenberg's law for matrix multiplication," and said that it gave clear directions for how to write a matrix. I do not think that the novice reader is going to object to the article's not giving a clear treatment regarding how the math was worked out. The important thing to see is that once this one step was taken there was a complete quantum theoretical picture of how hydrogen produces light. It also provided the key to the:

Yet another mystery, number five: Heisenberg indeterminacy principle -- discovered when a troublesome bug turned out to be a valuable feature.

Help! Can anybody help with the math given in Heisenberg's 1925 paper and explained (to the satisfaction of people whose math is better than mine) in Ian J. R. Aitchison, David A. MacManus, and Thomas M. Snyder, "Understanding Heisenberg's 'magical' paper of July 1925: a new look at the calculational details. arXiv:quant-ph/0404009v1 1 Apr 2007. Heisenberg figured out a way to compute transition amplitudes from the things already known. He gives a very sketchy treatment.

If I could calculate the transition amplitudes for at least the visual part of the hydrogen spectrum then I could calculate the intensities for the visual part of the spectrum and compare the answers to empirical measurements. It's not that I want to put these results into the article, but that being able to see all of the matrices together I could be more sure of not writing something really ridiculous on the basis of some misunderstanding.

I am less familiar with the developments after that point. The math appears to be more abstract, which may be just the way things are, but some of the discussion like the "h-bar" part clearly do not help novice readers. The math up to the amplitude/intensity part should be stated, but it does not have to do anything other than to give readers the realization that there is nothing mystical or incomprehensible about it. I include them above mainly for concision in showing what needs to be covered.

I plan to finish my rewrite on the basis of what I know now, and keep trying to work through the math so that if I learn anything that contradicts what has been put up then I can correct it -- assuming somebody else has not already caught it. Maybe I can finish up the draft over this weekend. As far as I remember, the material up to Heisenberg is accurate. Historical details can be removed. P0M (talk) 19:30, 30 May 2009 (UTC)

I don't have the early papers you allude to, but trust you to draft something workable. Is it in your userspace?

Anyway, I sympathize with how simple some of the calculations might be and yet when you see where they are going, the mind is fried. I recall a simple work showing how Einstein apparently derived E=mc² and was totally astonished at how easy it was. I cannot remember where it was now, although it predated Larry Gonick's stuff. Baccyak4H (Yak!) 03:32, 31 May 2009 (UTC)

Request for comment

There are two WP articles concerning quantum mechanics. One, Quantum mechanics, is designed to be a full exposition of the subject for those who wish to explore the topic at depth. The other, Introduction to quantum mechanics is, in the words of the WP:Hatnote, designed to "an accessible, non-technical introduction to the subject. For the main encyclopedia article, see Quantum mechanics." The present user, your obedient servant, rewrote the article in what to him was the spirit of its title and introduced it on 27 May 2009. It was reverted with the suggestion WP:BRD. This is the place for that discussion. You can see the difference between the older, longer, article and the new one here. The comments of the entire Wikipedia community, not just physicists, are welcome, and indeed, sought. Yours sincerely, GeorgeLouis (talk) 16:53, 29 May 2009 (UTC)

The current version is similar to History of quantum mechanics. The main article: Quantum mechanics reads a lot like a basic introduction to quantum mechanics, so perhaps an introductory article is redundant. Articles that explain the mathematical formalism of quantum mechanics are spread out over a few wiki articles.

I think we should keep in mind that an introductory text explaining some physics topic and a historical account of how that topic was developed are two entirely different things. If these two things are confused, you get a very bad result.Count Iblis (talk) 17:03, 29 May 2009 (UTC)

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Firstly, this is a noble idea. Difficult, but worthwhile.

The 'see also' is very long. This looks to me like a prime candidate for a navbox - a navigation box. I quickly knocked one up, please see user:chzz/quantum. If you edit it, you'll see that the code is not too complicated. I've made no good attempt at deciding the sections etc, I leave that to the experts, but I feel that if a good, organised navbox could be made about the 'Quantum' topic, this could usefully be used at the bottom of all of those articles. Please feel free to edit it, copy it, play with it, and make a template:navbox quantum.

I think this would be much better than the infobox used at present. For one thing, I'd like to see a more exciting photo at the top; was it Stephen Hawking who was told, every equation he put in his book would halve the readership? If this is an intro for us non-experts, then a nice, impressive picture would be a lot better than an equation which is going to be meaningless to us.

I think that the lede section should be much longer; an overview of the whole article.

I think that a lot of the language used needs work; it often borders on original research, and some of it sounds non-encyclopaedic and perhaps patronising; for example;

The idea of particles and waves is simply a mental model derived from everyday experience. Take, for example, the rainbow of colours reflected from a puddle of water when a thin film of oil rests on its surface. That phenomenon makes sense by thinking of light as waves...

A quick suggested rewrite;

Energy can be thought of as particles or waves; neither is the truth, but both models help us to think of quantum events in every-day terms. The rainbow of colours reflected from a puddle of oily water can be understood by thinking of light as waves...

...the above is by no means perfect - a rough draft. The idea is to present the facts, and let the reader draw their own conclusion. Avoid saying "this is simple" and "makes sense by..." (maybe to you, maybe not to the reader), and "Take, for example" (not very encyclopaedic language).

I think that the article should focus more on an explanation of Quantum mechanics, and less on the history. If the history can still be covered whilst explaining the theory, then all the better.

All of the above - as everything I write - is IMHO. Explaining Quantum mechanics to non-experts is not easy, but exactly the sort of thing that Wikipedia can strive to do. I wish you the very best of luck with it.  Chzz  ►  05:26, 31 May 2009 (UTC)

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I don't know how to insert the Navigation Template. Could you do it in lieu of the See Also section? The principal discussion of the Request for Comment is going on at http://en.wikipedia.org/wiki/Talk:Introduction_to_quantum_mechanics#Request_for_comment. I copied your lengthy message over there. Sincerely, GeorgeLouis (talk) 06:02, 31 May 2009 (UTC)

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I am not sure why certain folks are taking exception to the simplification of this article. Could it be an example of WP:Ownership? I am willing to discuss any changes, but we should really start and end up with a simple, nontechnical article, as is promised in the title. It doesn't make any sense to add stuff that is totally incomprehensible to the layman and then insist on keeping it there. Remember, there is already a very complete article on Quantum mechanics and many other articles dealing with allied subjects in Wikipedia. This one is supposed to be nontechnical. Yours sincerely, GeorgeLouis (talk) 02:01, 1 June 2009 (UTC)

I like George's lead, which has been reverted. The old lead was looking too much like a history of quantum mechanics, which is of no relevance to the non-specialist and of doubtful pedagogical value. George's lead, by contrast, says the essential thing clearly: that particles are waves and waves are particles. --Michael C. Price ^talk 08:26, 2 June 2009 (UTC)

Michael, please check through the sequence of events. The whole article was replaced. Some of the material had serious problems. I attempted to adapt to the abrupt and unresponsive behavior of Mr. Louis by working on the text he had provided. But when I critiqued a section of the replacement text (see above), that critique was received with gracious words by Mr. Louis -- and then altered to a very great extent without any discussion whatsoever. When I complained about the lack of due process Mr. Lous did not make a responsive answer. He merely complained that my remarks about his behavior did not belong where I had put them but somewhere else.

I am not opposed to changes, and suggested many (see up near the top) to which nobody has responded as yet. I am opposed to a process of "communication" that consists of pronouncements from Mr. Louis but no responses to attempts at rational discussion.

The old lead had problems and will be changed. What needs to be done now is to make something that is not misleading and also not so free of real content that it does not serve the needs of a novice reader. It should be possible to arrive at changes by a collaborative process. Doing so means discussing large-scale changes beforehand, and giving responsive answers to criticisms. P0M (talk) 15:19, 2 June 2009 (UTC)

It's true I haven't followed the history of these changes, and didn't read past the lead. But I did think the revised lead had some very positive aspects. Can't speak for the other changes without looking further, of course. --Michael C. Price ^talk 18:16, 2 June 2009 (UTC)

Mr. Louis gutted the corrections he had just thanked me for and replaced one paragraph with:

The idea of particles and waves is simply a mental model derived from everyday experience. Take, for example, the rainbow of colours seen on a puddle of water when a thin film of oil rests on its surface. The different wavelengths of light reflected from the two layers of liquid are perceived as different colors. That phenomenon makes sense by thinking of light as waves.[5] Other phenomena, like the working of light meters in cameras, can be explained by thinking in terms of particles of light (called photons).

What it boils down to is saying that light is perceived as having different colors when it has (a range of) different wavelenths. But that fact has nothing to do with the oil slick, and it does not explain why a wave explanation seems necessary to account for ambient light not being reflected in all its wavelengths. It's because he hsa cut out the explanation of the interactions of light "waves" coming off two surfaces of a very thin film. Similarly, he replaced an example of a phenomenon that cannot be explained on the assumption that light is a wave with a phenomenon that can be explained on the assumption is a wave. The light meter example is only relevant if one specifies that a wave explanation cannot account for why the intensity of the light does not increase the voltage but only increases the amperage.

We cannot make progress with this article if changes that matter are not discussed beforehand. I tried to fix the even worse misinformation provided by Mr. Louis, but his reaction was not constructive.P0M (talk) 19:35, 2 June 2009 (UTC)

Yes, the paragraph you quoted is basically a non-sequitur. And an over-eager editor is a pain. --82.31.28.46 (talk) 04:21, 3 June 2009 (UTC)

Article has been "unreverted"

I would not like to see progress on this article made by way of an edit war.

The change was made and then covered up by a minor edit with a notation appropriate to that minor edit. P0M (talk) 06:49, 31 May 2009 (UTC)

Point by point

(1) The current text has:

Take, for example, the rainbow of colours reflected from a puddle of water when a thin film of oil rests on its surface. That phenomenon can be understood by thinking of light as waves, the length of which results in different colours. Other phenomena, like the working of light meters in cameras, can be explained by thinking in terms of particles of light (called photons) colliding with the detection screen inside the meter, the force of which is registered mechanically by a pointer or needle.

This is just plain wrong. The length of waves does not "result in different colours." The different wavelengths of light are perceived as different colors. And the fact that the waves of light have different lengths does not explain the "rainbow of colours" either. If the editor had bothered to read Sears he would have an understanding that would allow a correct explanation, not an exercise in the mystification of the novice reader.

Second, the description of the light meter suggests a device like the carnival strength meter in which a contestant strikes a lever using a sledge hammer and the other end of the lever hits a ball that then moves vertically alongside a measuring stick of some kind. Nothing could be farther from the truth. Even if the crude analogy of an electron as a bullet that strikes electrons and knocks them out of their original planetary orbits be accepted, the electrons do not then physically strike the end of a needle that then moves along a dial face. T

If this article is to be radically rewritten, it should be done so with both a clear understanding of what the true facts are and also with an eye to presenting those facts in a way that will not cause very damaging preconceptions to form in the mind of the novice reader.

It is the differences in phases between the light waves reflected by the air/oil surface vs. the phases in the light waves reflected by the oil/water interface that effectively "cancels" light of some wavelengths and permits light of some wavelengths to reach the eye of the observer from each different region of thickness of the oil film. You criticized the original diagram that clearly shows how interference occurs as "off-putting." But what have you put in its place?

It is the (mechanical analogy) pressure of the dislodged electrons that moves them off of the surface of the metal plate and through a wire to an electromagnet that attracts the spring-balanced needle which then moves in a way proportional to the induced amperage. Then they go through another wire back to the "low pressure" region of the metal plate. Even in modern light meters, it is all a matter of electrons moving in electrical circuits, not electrons pushing on lever arms.

Please be careful to give the most useful citations. I have discovered one citation that is a circular reference to a Wikipedia article by way of an external "encyclopedia." Also, the expression "Trojan wave packet" will not mean anything to the average well informed reader, hence serving only to create an air of mystery and incomprehensibility. I have already supplied a reference that distinguishes Trojan wave packets from other wave packets.P0M (talk) 18:02, 31 May 2009 (UTC)

Thanks for the fine corrections and the explanations therefor. We are all relying upon people with scientific expertise to make this the best article possible. (What a way to spend a Sunday!) Sincerely, your friend. GeorgeLouis (talk) 19:44, 31 May 2009 (UTC)

I object to the change that you just made. Can you please give evidence of good faith by discussing changes before you make them? P0M (talk) 21:29, 31 May 2009 (UTC)

Uh, the place to discuss all this is above, where it says "Request for comment." Sincerely, GeorgeLouis (talk) 01:49, 1 June 2009 (UTC)

Rewrite

While it's definitely possible to trim this article down significantly, doing it in one swell foop, without discussion, is not likely to be productive. I've reverted to the long version, and I'll put subheadings here to discuss the issues with the various sections.--SarekOfVulcan (talk) 23:42, 31 May 2009 (UTC)

One of the complaints about this article was the length. As of today the lengths of the two articles are approximately the same, and I still intend to cut more.P0M (talk) 06:42, 23 June 2009 (UTC)

Lede

Ok, for one thing, the lede on this article is longer than the lede in the QM article. :-) What can we do about this?--SarekOfVulcan (talk) 23:52, 31 May 2009 (UTC)

One thing to keep in mind is that Einstein's whole paper on Special Relativity was only 26 pages long (I think it was). His introduction might have been a couple of equations. Density is possible if people already know a great deal, and density is aided if a symbolic mechanism exists for cramming layers of meaning into simple symbolic representations. But when the reader is unfamiar with material then one thing left unsaid can stymie the whole process or at least slow it down greatly. P0M (talk) 01:34, 22 June 2009 (UTC)

Chetvorno had some useful ideas, which I quote from the material above:

The history is too much, and the overview needs to be simpler. What this introduction to QM needs to address is why QM is so much harder for people to understand than classical mechanics. What about an approach like Richard Feynman uses in his Lectures on Physics? He starts out by saying: "Things on a small scale behave like nothing you have any direct experience with. They don't behave like waves, they don't behave like particles, they don't behave like clouds, or billiard balls, or masses on springs. Even the experts don't understand it the way they would like, because all of our human intuition applies to large objects. But small objects just don't act the same way." Later he goes on to enumerate in simple language how small objects' behavior is different: wave - particle duality, inability to measure variables with arbitrary precision, probabilistic results of measurement, the ability of objects to be in different states simultaneously. These are the things beginners have trouble with in QM, and they should be faced head-on in this article.

I still think his would be the best approach. Above I listed around 5 mysteries that might be listed with brief statements of what they are as the second paragraph of the lead. P0M (talk) 00:34, 1 June 2009 (UTC)

Draft, 325 words:
Life gives humans preconceptions that fail drastically when experience is extended to the very massive and the very fast, and that also fail drastically when experience is extended to the very small and the very cold. On the large scale humans need relativity theory, and on the small scale humans need quantum mechanics.

Quantum physics deals with the unexpected realities of "neither-nor." Photons and other very small things are neither waves nor particles. They have spectrums, but the spectrums are chopped up instead of being continuums. The energies carried by particles are discontinuous and color coded. The energies, the colors, and the spectral intensities of electromagnetic radiation produced by something like a neon light bulb, are all interconnected by laws. But the same laws ordain that the more closely one pins down one measure the more wildly another measure relating to the same thing must fluctuate. Even more disconcerting, particles can be created as twins and therefore as entangled entities -- which means that doing something that pins down one characteristic of one particle will determine something about its entangled twin even if it is millions and millions of miles away.

The most elegant character on the quantum stage is the double-slit experiment. A single photon emitted by a laser or an electron emitted by a cathode will behave differently depending on whether one or two slits lie in its path. With two slits present, the particle that arrives at a remote detection screen will be a superposition of two wave functions. Where a photon or electron shows up on the detection screen will show the resolution of those wave functions, sometimes called the "collapse" of the wave functions, and the location where this "collapse" occurs will be absolute in that it must appear in one of the bright "fringes" that will show up when many photons are run through the apparatus, but entirely unpredictable as to which of the fringes it contributes to.P0M (talk) 14:57, 2 June 2009 (UTC)

I'm not sure that we should follow the old section headings. I request feedback on the above. In the meanwhile, I have taken the suggestions given above, particularly from Chetvorno, and have drafted new text for the "old" quantum physics at: User:Patrick0Moran/Rewrite_QM

Thanks.P0M (talk) 18:11, 2 June 2009 (UTC)

I have started to pare the article down, starting at the top. If I have taken out things that others regard as crucial, please let me know. (It may be that I have it in mind to put some things later, but one way or another we should be able to agree on what needs to stay and what can go.) Please be aware that there will be a ripple effect. P0M (talk) 01:29, 22 June 2009 (UTC)

Overview

See "General trends of development"P0M (talk) 06:27, 22 June 2009 (UTC)

An elegant example

I added this section to get readers to jump into the cold pool.P0M (talk) 06:27, 22 June 2009 (UTC)

The unexpected

Combined with the following. P0M (talk) 06:27, 22 June 2009 (UTC)

How the unexpected came to light

Rewritten.P0M (talk) 06:27, 22 June 2009 (UTC)

Planck

I just added a brief section. Keep first things first. Cut some stuff that would have been duplications below. May still need to tidy up, but don't want to leave readers with any big holes to try to cope with. P0M (talk) 06:27, 22 June 2009 (UTC)

Spectroscopy and onward

So far I have just put in a diagram. This one equation gets reformulated a few times, and so it is made to mirror and explicate the structure of the atom (as regards its function of emitting photons) more and more closely.

This is really the first difference equation and they are key to switching from classical physics that operated on the basis of infinite numbers of geometrical points (calculate the frequency associated with point 3384) to quantum physics that asks not what electron was doing in such and such an "orbit" or while it was in such and such an energy state, but where it started from and where it jumped to (energy state n - energy state m).

This equation, which started out like an NPR puzzle from Will Shorts, was the next major step after Planck's constant. The next building block will be the rule for multiplying grids filled with numbers arrived at on this basis or derived from numbers gotten this way. The third thing happened when Born realized that the rules of matrix multiplication were going to make pq - qp be something other than zero.

It's too late to do anything more. I'm keeping vampire hours already. ;-) P0M (talk) 06:27, 22 June 2009 (UTC)

Old quantum theory

I feel this whole section should be omitted, in compliance with the desire expressed by many people on this page for less history. There is already a History of quantum mechanics. This article should omit the history. --Chetvorno^TALK 21:59, 6 June 2009 (UTC)

As far as the history items, such as the (to me) interesting fact that Balmer was a pioneer who had no great status, a sort of one-hit wonder, I agree. On the other hand, the discovery he made is about as concrete as you can get. It's something that the average well-informed reader can understand. If you don't take the approach of showing the pathway in physics then you jump right into Schrödinger. Take a look at the Hyperphysics site (http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html) and how they introduce quantum physics. The minute you get into Schrödinger it is entirely abstract, and terms such as "Hamiltonian" and "Hermitian" are used without definition. The full Wikipedia article starts with high level math. So in both those approaches the reader who doesn't know the math has to either work out the math or take conclusions on faith.

I haven't even edited the article form Schrödinger on, but I think that it is possible, on the basis of one of the graphs in the Hyperphysics (?) site, to show how the discontinuous picture of something like the hydrogen bright-line spectrum, which is sort of like a bar graph in appearance, can be converted into a continuous picture by means of Schrödinger's math. That way the reader gets an intelligible bridge from a Will Shorts kind of math puzzle to a higher math picture that really requires professional training to understand. The alternative is a "OU! AH!" kind of mystification.P0M (talk) 15:39, 10 June 2009 (UTC)

Planck's constant

needed: Einstein

photoelectric effect

needed:Balmer

breakthrough equation, had more refined versions later

Reduced Planck's (or Dirac's) constant

As discussed above, several months ago, this section is rather pointless. The reduced Planck's constant is just the Planck's constant divided by another constant. So all the reader needs to know is about that much. I therefore will delete it if I do not hear arguments to the contrary. P0M (talk) 06:28, 4 June 2009 (UTC)

doneP0M (talk) 20:21, 6 June 2009 (UTC)

After I cut down earlier sections, the little paragraph on h-bar seemed totally out of place, so I have cut it.P0M (talk) 04:33, 23 June 2009 (UTC)

Bohr atom

It's pretty hard to talk about "orbitals" without a minimal understanding of "orbit."P0M (talk) 15:39, 10 June 2009 (UTC)

DeBroglie: Wave-particle duality

This part is central. I do not see how we could possibly leave this idea out.P0M (talk) 15:39, 10 June 2009 (UTC)

Development of modern quantum mechanics

Full quantum mechanical theory (Heisenberg and Born)

I will replace the currently incorrect matrices with reduced size versions that are formulated in accord with Heisenberg's paper of 1925. If there is no objection to the draft at User:Patrick0Moran/Rewrite_QM#The_new_quantum_mechanics I will make a full replacement in a couple of days. P0M (talk) 21:16, 6 June 2009 (UTC)

I feel the mathematics in your rewrite, although important, is just far beyond what should be in an "introduction". I think this article should have almost no mathematics, except possibly simple things like the Uncertainty principle and E = hν. --Chetvorno^TALK 22:54, 6 June 2009 (UTC)

Sometimes not having important content is more confusing than something that looks intimidating. The article could just say that Balmer had come out of obscurity to hand scientists the answer that they could not find, and the reader might carry away the impression that Balmer's formula must be something very difficult. When readers go to the advanced articles on quantum physics they are likely to be introduced to daunting equations in high math. In this article the only equations that would be that intimidating are those concerned with calculating transition amplitudes, and they clearly would not be suitable.

Fortunately not only are the equations that predict the bright-line spectrum simple, but there is a website that lets visitors plug in numbers and get back frequencies, wavelengths, etc. Readers do not even have to look at the equations to understand the text, but they are there if the reader wants them.

There is so much mystification involved with the matrices that readers deserve to have a demystified way into the subject. Heisenberg's "multiplication law" looks complicated, but it really is not. It explains in operational terms what a matrix does. And the matrix multiplications demonstrate why there is a difference when the complex thing called "p" and the complex thing called "q" are multiplied the results are going to be different. That in turn explains where the indeterminacy principle comes from.

Ideas like chain reactions in nuclear physics can be very abstract and mystifying unless they are made concrete to average people with demonstrations like the roomful of mousetraps functioning as catapults for ping-pong balls.

Take a look at Introducing Quantum Theory by McEvoy and Zarate, p. 127. It is a good example of how an over-simplification is a disservice to the reader.P0M (talk) 16:21, 8 June 2009 (UTC)

Seeing no further comment, let me suggest three equations, all of them first-year algebra. One gives the structure of the hydrogen atom, one relates frequency to energy, and one is just a schema for dealing with the fact that as far as radiation goes, it is not important what the electron is doing but what orbitals its transits between. P0M (talk) 12:08, 19 June 2009 (UTC)

I put up a diagram that indicates in a structural way how just the difference between energy levels (orbits in old QM) determines frequencies and wavelengths. The equation is absolutely central even though the math is so simple that you can see how it works without having to work out any examples unless you want to.

I replaced the discussion about Heisenberg because as I have chipped away at the layers of misunderstanding created in the secondary sources that are simplistic I have had to rely on the treatments by Van der Waerden, Aitchison et al., and the three volume series of the history of QM. I am taking the word of Aitchison et al. that Heisenberg actually computed amplitudes and thereby got quantum theoretical predictions that matched observed intensities, but frankly I can't find where or how he did it. Other than that, I think it states everything clearly and is or can be validated by citations to reputable studies. At least I trust it much more than what I wrote before.

Some things that come before this section in the article need to be changed next to accomodate these changes.

The third "equation" that I proposed above has also been included, but it is really only a "recipe" for writing a matrix. It just amounts to saying that you should multiply X × Y, X' × Y', and so forth, and then add them all up and store the results in the right slot.P0M (talk) 18:02, 20 June 2009 (UTC)

It is beginning to look like I may be able to off-load the more technical part of this section into a sub-article.P0M (talk) 20:20, 20 June 2009 (UTC)

Bad idea. In a recently purchased book I found assurance that the indeterminacy relationship comes out of the math. The math comes out of the matrices. The matrices come out of the weird C(n,n-b) = Σ A(n,n-a)B(n-a,n-b) business, and that in turn comes out of the 1/λ=R((1/m^2)-(1/n^2)) business. On the surface the whole structure is clear. (Why don't people supply the parts in order and context?) But the details quickly start to involve matrices each "cell" of which is itself a matrix, and the details get so intense that one has to have the "rules" of matrix math on the tip of one's tongue. That level of complexity can be glossed over with matrix mechanics, but the Schrödnger equations can't be handled that way. I think it is better to do all that we can dowith high school math.P0M (talk) 04:47, 23 June 2009 (UTC)

Schrödinger wave equation

• The current section is an abstraction about an abstraction. There are easy ways to make equations such as f=ma concrete. With Heisenberg's matrix mechanics one can give readers the information that it allows the prediction of the amplitudes corresponding to each of the energy levels of the hydrogen atoms, and from them it allows the prediction of the intensities of the lines in the bright-line spectrum.

Since the Schrödinger model of the quantum world produces the same predictions as the Heisenberg model, it may be useful to point out that many models may equally serve human purposes.P0M (talk) 19:16, 5 June 2009 (UTC)

I've looked at several secondary sources and so far none of them have been able to say anything sensible about the Schrödinger equation without going off the deep end of the math pool. The math behind the relatively simple stuff that Heisenberg ended up with was already extremely difficult. So it may be that the novice is lucky that there is anything at all that does not have to be accepted on faith absent of a couple years of university physics and higher math. Introducing Quantum Theory doesn't spare the magic wand and fairy dust. I wonder if there is a way to make it clear to readers why the level of mathematical complexity gets so intense. P0M (talk) 19:12, 20 June 2009 (UTC)

Uncertainty principle

This is one of the main pillars of quantum mechanics. You can't even begin to explain it without the matrix picture or high level calculus. I think anybody can understand that if prices per gallon of gasoline vary by city, and city to city the distances are different, then if you top your gas tank of at each stop it may make a difference which way you travel between a series of cities.

Heisenberg's microscope is a reductio ad absurdum that depends on classical physics to defeat classical physics, so it is not ideal, but it does make part of the nature of the problem intuitively accessible to readers. Gamow used it in his One, Two, Three... Infinity.P0M (talk) 12:42, 19 June 2009 (UTC)

The indeterminacy relationship was not an empirical discovery. It came out of the numbers. I found Born's own words from his Nobel lecture. So there is an organic connection among the main equations I have included, and at least up to this point they are simple. In Born's formula that gives the Uncertainty Principle, the "i" factor has to come out of the math somehow, and I suspect it either has to do with using an exponential i in phase relationship factors to some of the classical equations Heisenberg was taking inspiration from, or (more likely) it is something about matrix math that was already common knowledge, i.e., part of a regular formula, in use by clued-in mathematicians of Heisenberg's time.

There is no reason to dig out the origin of the use of "i" in this equation. But without the basic and simple math up to this point we would have the equivalent of a detective story that just said, "Someone was murdered. The butler did it."

It's late. I'll put the reference to the quotation from Born in tomorrow. P0M (talk) 07:20, 21 June 2009 (UTC)

Actually, both i and h come out of the math. The whole thing is derived in an appendix to Aitchison, et al. P0M (talk) 02:33, 28 June 2009 (UTC)

Wavefunction collapse

This topic has to be described in conjunction with superposition. The only situation wherein superposition is going to be clear to most people is the way a single wave function is divided in the double-slit experiment and arrives at the detection screen by paths of different lengths so that the waves are out of phase. While it is true that some readers may not be visual thinkers, it will be helpful to must people to have a drawing to show how waves may reinforce each other if in phase or cancel each other if out of phase. Such a drawing literally shows one wave superimposed over the other. How to explain the "collapse" is more difficult. It is possible that a "colllapse" occurs, potentially at least, at each point from the double slits to the detection screen, but for a photon to actually manifest its presence by boosting an electron in orbit there has to be an electron available. Occasionally, a photon may cause a scintillation on a dust particle flying in the beam, but most of the time photons will show up on the plentiful electrons of the detection screen. There seems to be a sort of cosmic roulette wheel that determines which of the bright fringes a photon will contribute to, but my understanding is that there is no mechanism proposed.P0M (talk) 19:11, 19 June 2009 (UTC)

This section starts out treating an electron but in the last sentence it seems to have changed to a photon. WmMBoyce (talk) 15:50, 24 January 2010 (UTC)

Eigenstates and eigenvalues

• Is there any need for this section in an introductory article? I think readers who go beyond the scope of the article might encounter it, but their need would only occur at that point. Perhaps a very brief paragraph and then a sub-article? If I hear no objection I will reduce or delete this section in the next few days. P0M (talk) 18:16, 5 June 2009 (UTC)

I agree. --Chetvorno^TALK 21:53, 6 June 2009 (UTC)

I moved most of the content to a sub-article. P0M (talk) 18:05, 8 June 2009 (UTC)

The Pauli exclusion principle

This section is poorly written. It involves circular reasoning and/or the use of undefined terms, e.g., fermion. P0M (talk) 12:35, 19 June 2009 (UTC)

I don't see 'fermion', so I guess it's had rewriting. Should clarify that it's an electron 'within an atom' that has the orbital numbers, not an electron in a beam or otherwise unattached. WmMBoyce (talk) 16:06, 24 January 2010 (UTC)

Dirac wave equation

I think this section can be drastically pruned. The last paragraph is redundant. The rest of it includes details for which the average well-informed reader will have insufficient background to understand.

If we are going to eliminate history from this article, then not much is left to talk about in regard to Dirac. Unless I hear otherwise within a day or two I will prune this part and then we can discuss reactions to the changes. P0M (talk) 10:18, 19 June 2009 (UTC)