Talk:Introduction to quantum mechanics/Archive 1

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Contents 1 my attempt 2 Uses 3 Quantum gets personal 4 This article is w orthless garbage 5 AfD result 6 Suggestions for editing the current version. 7 Completely new article 8 Where do we stop? 9 Illustrations 10 4 decades since I plotted a function, sigh (pi & energy) 11 Question regardin g "packets" 12 Moved 13 PLEASE MOVE AGAIN TO Basic quantum mechanics (not caps) 14 quotation from de Broglie 15 Something missing 16 Regarding the effect of QM on philosophy and its controversies 17 Quantum entanglement 17.1 Classical channel 17.2 3 particle entanglement 18 Quantum entanglement (bis) 19 Uncertainty principle and disturbance of position 20 Any book that says ΔpΔx ≥ h is wrong 21 Uncertainty Principle and Absolute Zero 22 Positives 23 Picture of spectrum has been put in for removal by 24 It appears that in nominating the article it may be deleted 25 Removed one phrase 26 Electron microscopes are not for examining electrons 27 How can energy be caused? 28 images of line spectra 29 electromagnetic waves 30 "mathematical" 31 "Its success is due to its accurate prediction" 32 "inconsistent with the consequences of other successful theories" 33 "This appeared to raise a contradiction when compared to sound waves and ocean waves, where only intensity was needed to predict the energy of the wave." 34 Old quantum theory, and so on. 35 "We cannot see photons" 36 "Fourier series" 37 "standard deviation" 38 "Schrödinger's equation then fails" ? 38.1 Fork 38.2 Spork 39 An unusual teaching experience 40 "physical science" 41 Point by point 41.1 Points corrected 41.2 Points remaining 42 Doesn't make sense 43 Full quantum mechanical theory 44 Odd Sentence? 45 All physics is quantum physics -- true or false 46 Sidebar in drastic need of a re-write 47 Some confusion 48 Wave function collapse (again) 48.1 An additional problem with the paragraph as it was 48.2 What to do about it? 49 AfD raised on Quantum theory 50 History question 51 Introduction!!??!!??

[edit] my attempt

I am trying to expand this article into something fairly thorough, and I welcome comments and suggestions. Of course anyone can contribute directly to the article, but if it helps I'll volunteer to coordinate things; so, maybe we could cont ribute to the discussion before editing the article? For what it's worth, I have no philosophical axe to grind so I will be writing very carefully, neutrally, and simply as much as possible.

I will initially simply try to add structure and clarity.

I in tend eventually to expand this into simplified versions of many major technical articles. Frankly, the quality of most scientific articles I've seen here is VERY poor IMO as encyclopaedia articles. They may be of a "high" standard technically, although th at's open to debate, but they are way below what I would expect as a real explanation of what the subject means to a general audience. Many seem to be written by specialists for specialists without any regard for beginners, children, laymen, non-native En glish speakers, etc.

Paulc1001 06:38, 5 October 2005 (UTC)

[edit] Uses

I think we should illustrate the importance of quantum mechanics by virtue of a list of things that are done with QM, starting with input from the main QM page:

• U sed to help describe everything from the subatomic particle to the universe as a whole.
  • Speculated that QM will help describe black holes, gravity and other mysteries of the universe.
• Help in combining molecules to form chemicals - quantum chemistry.
  • Showing which molecules are energetically favorable to which others, and by approximately how much.
• Modern technology
  • The laser, the transistor, the electron microscope, and magnetic resonance imaging.
• Future research
  • Quantum cryptography, quantum computers and quantum teleportation.

Grika Ⓣ 18:28, 6 October 2005 (UTC)

Someone here told me that black holes abd gravity have unresolved problems with qm. Anyway they are not where it has been most needed. David R. Ingham 06:00, 2 February 2006 (UTC)

[edit] Quantum gets personal

Quantum gets personal I would very much like explore the more personal yet no less fantastic sensory applications of quantum physics. This would include the relationship of the effect of an immediate visual sensory absorption of, let us say, a rainbow in the sky, with the memory of this beautifully natural event. After the rainbow is gone, the memory of the rainbow activates the exact same neurons in the brain as the first observation through sight. Add to this the notion, under quantum theory, that there is no stable "reality" underlining the material world. We relate everyday, as we drive our car, eat, interact and sleep to expected, dependable material objects surrounding our existance. However, are these realities only a manifitestion of an impressionable mind? Is it possible that, given the constant movement of electrons, prot ons and neutrons within the atom, that each one of us determines the possibilitiies of formed matter, at a given time, given our previous relationship with similar observations. Can the same object exist in two places at once? Our world around us is chang ing all the time, and it reacts to our imposition, and creates an impression that is as real tomorrow as it is today. There are no absolutes. We can change the world! --71.12.188.255 22:50, 10 October 2005 (UTC)

This is controversial, at least in Wikipedia, but in my view quantum reality is no less predictable than the 19th century classical view of the world was. The main problem is that the world described by quantum mechanics does not exactly correspond to how we usually talk about it. Your statement asks question also about psychology and philosophy. David R. Ingham 06:11, 2 February 2006 (UTC)

[edit] This article is w orthless garbage

I put delete on the article because as it stands the article is worthless garbage and the contributors do not know what they are talking about. WAS 4.250 22:58, 10 October 2005 (UTC)

I welcome your input but am take n aback but your venom; it seems to be completely incongruous to the quote by Jimbo that you so proudly display on your userpage. Grika Ⓣ 02:05, 11 Octob er 2005 (UTC)

I offer my apologies for my inability to tell the truth as I see it in this matter and not be perceived as being venomous. I don't know how else to say that the article needs to be deleted because it lacks anything worth saving and the co ntributors so far show not a clue as to what they claim to want to write about. Should I say I am sure you are all wonderful human beings in every way but please write about what you know? I certainly wouldn't dare pretend to be a useful editor on an article on tact. WAS 4.250 08:47, 11 October 2005 (UTC)

[edit] AfD result

This article was debated on AfD, with the result of Keep. The closer's comments: "This is a rather tricky one. 19 people expresed definate opnions. Of these 6 or 32% chose a simple keep as their first option, 3 chose a rename (which two others listed as a second choice), and 2 a merge to an existing article, for a total of 11 or just under 58% for keeping on en.wikipedia in some form, with a simple keep the mos t common chice among those 11." The AfD debate may be found at Wikipedia:Articles for deletion/Quantum Mechanics - simplified. DES ^(talk) 18:30, 18 October 2005 (UTC)

Given that in the AfD 8 people at least considered a rename or merge, people here might want to explore those possibilities further. DES ^(talk) 18:34, 18 October 2005 (UTC)

[edit] Suggestions for editing the current version.

I am a little unsure of how to procede to make multiple changes that would not change the meaning of the article as it stands, but only remove some of the language problems. Should we copy the whole article to this discussion page and then mark desired changes on that version? Should we put a separate version in a sort of sandbox file and work on that? If an article gets contentious that might be a good way to preserve "the last version that everybody could basically agree to" while the new issues are fought o ut backstage. That's better than a series of edit wars that make the reader's version dependent on whether s/he looked the article up at 12:00 or at 12:01 or at 12:03. But it hardly seems worth it to change a misused "which" to "that." P0M 05:19, 19 December 2005 (UTC)

[edit] Completely new article

As of December 24, 2005, a completely new article has been presented. The article now has merit. Any input by any persons as to clarity would be appreciated.--Voyajer 17:58, 27 December 2005 (UTC)

I very much appreciate your efforts. I have noticed several things in this article that I have not seen explained anywhere else. It's a little like my experience with reading Greene's recent book -- things that I always felt w ere left hanging in mid-air by other writers turned out really to have been matters of largely unmentioned debate or at least discomfort, rather than just my crazy ideas. I will read through the recent changes. Sometimes things that I write seem clear to me at the time I am writing them because I have some background in mind, but I have forgotten to mention it in the essay I'm writing, and I appreciate help when other people see and fix what I have omitted. So I'm glad to see that you share this welcomin g attitude toward changes. And of course if I twist your intended meaning out of shape, please rephrase or even just revert.

I'm wondering about the title. I think what we are doing here is much more important than just supplying a simplified version. I t may sound to some people as though the treatment is simplistic, and I think it is anything but that. It just takes account of the fact that some people seeking information will not have taken a couple years of 5 classes/week physics courses.

That reminds me of a problem with one of the articles that got me interested in this one. The content may or may not have been correct. I could not tell because the language was so abstract, so disconnected from anything that would even suggest what a relevant lab experiment would be like, that it was essentially meaningless to me. There should always be a bridge from the real world (including the physics lab) to the point where things have to be expressed in mathematical form. One of my favorite physics textbo ok writers is Francis Sears. He has a delightfully lucid way of writing, and he wrote a whole series of physics textbooks. Along came Zemansky, who took out all the useful explanatory stuff to condense three or four normal sized books into one fat first-y ear textbook. Had I realized what was going on in time, I would have bought all of Sears's books and made first-year physics much more productive for myself. P0M 23:57, 27 December 2005 (UTC)

Thanks for your input. I don't like th e title as well. I linked to this article from the main Quantum Mechanics article and called it "Non-mathematical Quantum Mechanics", but I think that is misleading too as if quantum mechanics has a non-mathematical version. I meant "Quantum mechanics explained without the mathematical formulae", but I can't think of a simpler and more incisive title. Can you? ... BTW, your edits were very good. They were precisely what I meant to say, but was thinking faster than I could type.--Voyajer 17:02, 28 December 2005 (UTC)

I think the title should reflect the idea that we always start from human-scale phenomena. If we were to talk about double-slit experiments, for instance, we would give a clear idea of what the actual physical apparatus is, what one actually sees (photos of diffraction phenomena rather than drawings, for instance), etc., rather than jumping into a discussion of £r-functions, etc. It would be too wordy, I guess, but I would favor something like "Quantum Mechanics from the Ground Up." P0M 23:12, 28 December 2005 (UTC)

That sounds good but is it too wordy for an encyclopedia title? Also, I have made many pages including "easy quantum mechanics", "understandable quantum mechanics", and "quantum mechanics simplified" without the hyphen and REDIRECTed to here. They would have to be redirected again to any title change. So let's make sure we like what we come up with. I see this article as the history and development of quantum mechanics, but that is way too long for an article title. Perhaps this should be called Theoretical Quantum Mechanics? Development of Quantum Mechanics? Quantum Mec hanics in a nutshell? Again too long and I think that is a book title anyway. Is anyone else out there following along? Input requested.--Voyajer 23:29, 28 December 2005 (UTC)

O'Reilly has lots of "in a nutshell" books, books with tit les like "Pascal in a Nutshell," "C++ in a Nutshell." I rather like that idea. P0M 02:07, 29 December 2005 (UTC)

There may be a copyright issue. Will "Development of Quantum Mechanics" suffice?--Voyajer 04:20, 29 December 2005 (UTC)

[edit] Where do we stop?

I was considering possibly adding more material, but I don't think this should be a textbook. We haven't covered the tunneling through effect and the definition of a matter-wave, Quarks and Leptons, Bosons and Fermions, Particles and Antiparticles, Symmetry and CP Violation, and atomic forces i.e. weak, strong, electromagnetic. These are part of QM, but I don't want to bog down the article. These could be easily explained in everyday English. The articles in Wikipedia dealing with these subjects amount mostly to mathematical equations and don't explain much. I could start a new section called "Advances in quantum mechanics". But I'm not sure how much to include. Any thoughts? Anyone?--Voyajer 23:29, 28 December 2005 (UTC)

I don't think we should include Quantum Field Theory which is kind of another topic, but I'm open.--Voyajer 23:34, 28 December 2005 (UTC)

I'm thinking this might be too complicated and unnecessary to add: Subatomic particles exist in systems. Mathematics were invented to describe these systems in precise manners. Often one comes across the expression "Hilbert space" in quantum mechanics. Loosely, Hilbert space is used in mathematics to describe systems in motion where every set of points has a distance that is a positive real number and includes characteristics such that the system has symmetry i.e. the mathematical law of commutation applies and the system is usually infinite-dimensional i.e. has limitless possibilities. Because the electron is said to be in a quantum state, mathematics states that a quantum state, describing all we know about a system, can be thought of as a vector in some abstract space called Hilbert space. --Voyajer 05:05, 29 December 2005 (UTC)

[edit] Illustrations

I like all of the illustrations, but I think that Heisenberg's_Uncertainty_Principle_Graph.png is too small. I can barely read the text. Wikipedia was originally a little stingy with file sizes and then about a year ago somebody must have realized that they were tossing away a good bet. Why take a 2x3 picture of a black widow spider if you could get an 8x10 version. Now they don't even want anything with lossy compression. I am sure they have re alized the archival value of good pictures. Diagrams are a little different since one could theoretically scale one up and then edit the image to get rid of the jaggies, etc., but that is a really messy, time-consuming job. (I do the equivalent thing som etimes when I am making special images from photographs.) If I am making an image having no great amount of detail, no need for especially accurate colors, etc., I will sometimes make a large gif image to save file size. Anyway, a larger image would alwa ys be acceptable and you can specify 340px or something like that to get it down to a reasonable size. You can also put in a "magnifying glass" to remind users they can see the full-sized image by just clicking on it.

I hadn't thought of it before, but some Wikipedia readers with poor vision may be using the view menu on their browsers to make the print large enough for them to read. People with limited vision would be especially appreciative of large diagrams. I could easily enlarge the image, but if you have a larger image it might be better to just upload that one. One other thing, are you uploading your images to Wikipedia Commons? If you do it that way, then you will make your stuff available world-wide without the need for somebody in China or w herever to copy your image and then put it on their server. P0M 05:48, 29 December 2005 (UTC)

I agree. It will take a bit of time to re-do. Have you seen the chart on the article Standard model? Even when you magnify it, you can't read it.--Voyajer 21:28, 29 December 2005 (UTC)

If you download the high resolution version you can read it without any problem. It looks like it must be a scanned wall chart. If I were doing it, I would probably just show a "det ail" of the whole chart that people could actually see without blowing it up, and then let them know that they could link to more complete diagrams. As it is, it's kind of like the Lord's Prayer on a grain of rice.

• • Well perhaps we should pray over it t hen? :-) ---Voyajer 02:52, 30 December 2005 (UTC)\

That reminds me of a science fiction story in which somebody discovered that the entire wisdom of a higher intelligence (oh, oh) had been written in coded form in the junk DNA shared by every human. I don't recall that it explained the human appendix and other such mysteries, however. P0M 03:23, 30 December 2005 (UTC)

[edit] 4 decades since I plotted a function, sigh (pi & energy)

I started to try to make the 2 p i factor intuitively more clear, and then reverted it because I'm not sure of the math. I can see the maxima, but doubt that things necessarily work out as conveniently as I would like. See http://en.wikipedia.org/w/index.php?title=Quantum_Mechanics_-_si mplified&diff=33146925&oldid=33126011

I don't have time right at the moment to work it out properly, but seeing the relationship between the length of the line that is a sine curve between x = a and x = b as some function of pi and the distance between a and b will help the average user understand why pi ends up in the middle of some equations involving energy. I also had a couple of other changes that I reverted that probably could go back in without causing any problems.--(written by P0M)

---

Pi ends up in equations involving energy because all energy is oscillations. Heat is an oscillation (excited atoms oscillate). Electricity causes energy and creates magnetism which creates an oscillation called an electromagnetic wave. Work is measured in joules which are the mechanical equivalent of heat. Satellites orbit in circles and conic sections. Angular momentum of charged objects causes magnetic moment. Galaxies rotate. Clusters of galaxies rotate around a common center of mass. E=mc(squared) therefore all mass is energy and mass is made of oscillating atoms because all subatomic particles are also waves. Everything that has energy oscillates in one form or another. All oscillations are cycles. All cycles describe circles. Pi is a circle. The size of the circle depends on a number times pi, but pi describes every circle. Since all energy is movement in the form of oscillations, then pi is always involved. (How is that for a dose of philosophy?)---Voyajer 22:08, 29 Decem ber 2005 (UTC)

There are so many ways to explain this mathematically, that I'm really not trying to.

• There are 6.28 (i.e., 2 Pi) radians in a circle which can be used to express a circle instead of using 360 degrees. When you see 2pi written on an axis, you can read it as 360 degrees. So the standard, sine wave moves from zero to one, back to zero, down to minus one and then to zero again as the angle moves from zero through pi/2 (90degrees), pi (180), 3pi/2 (270) and on to 2pi (360 degrees, the full c ircle).
• 1 degree = Pi/180 radians
• 1 radian = 180 degrees / Pi
• Pi radians = 180 degrees; Pi/2 radians = 90 degree
• There are 2 times pi radians in one complete "cycle" of an oscillation. So if you want to express your frequency variable in terms of osc illations (cycles) per second you have to multiply that value times 2*pi to make it come out right.
• 1 radian equals 360/(2*PI) degrees.
• Cycle = 2*pi*radian so when h is divided by 2pi this leaves radian. h/2pi = h-bar

--Voyajer 19:51, 29 December 2005 (UTC)

What I meant is that we need at least one good example where the general reader can see what is going on to make pi relevant. If your diagram Heisenberg%27s_Uncertainty_Principle_Graph.png is a true sine wave then I think that what I wrote and reverted (see above) is probably valid and if it is it would be helpful to the general reader. P0M 22:40, 29 December 2005 (UTC)

Also, thanks for fixing the units problem I left you last night, I mean early this m orning. I knew it had to include a unit of energy, but I wasn't sure what else might be involved and I didn't have time to look it up.

Have you ever taught physics? You would be much better at it than my teachers at Stanford were. They could do high le vel physics, but they couldn't talk about it very well. You are more like my second trimester calculus teacher, a guy who wrote one blackboardful of neatly written stuff as he explained why things worked the way they worked, and usually finished each lect ure with a problem that you would assume would take you until the next class period to work out -- and then he would show you how to do it in your head. Restrepo was his name. Unfortunately he seems to have disappeared back into S. America, never to be h eard from again. P0M 22:50, 29 December 2005 (UTC)

---

• Thanks for the compliment. No, I'm just a lowly researcher in R&D. I'd rather be teaching though.

• What you wrote and reverted was correct, but I think the distance over time equation would be a little confusing to some. Instead of explaining the relevance of pi, it might make someone not familiar with math simply get distracted by another equation.

• Yes, the graph shows a sine wave. It is actually two sine waves meant to be one sine wave designed to show a standing wave. It is idealized into circles on purpose, but still meets the sine wave requirements.

• I was considering less why pi is relevant and more why h-bar is used more often than h. h-bar is divided by 2pi, so I was wondering what the significance would be in using a radian or dividing by 2pi instead of using the energy of the full cycle. I came up with:

• • Angular velocity or angular frequency is measured in radians per second. Also, EM waves are sine wav es. The harmonic of a wave is the frequency times an integer which forms basic waves. Fourier series is a mathematical analysis of basic sine waves. Loosely, Fourier series is a mathematical technique that provides a way to average out randomly shaped wav es to define them into a quantifiable single sine wave. In Fourier series if a function f is periodic with period 2Pi, then any interval of length 2Pi will be good for computing the Fourier coefficients. The fourier transform and its inverse differ by a f actor of 2π. Also, the phase of a wave is given in either radians, degrees, or fractions of a wavelength.--Voyajer 03:21, 30 December 2005 (UTC)

I read what you had written in the article after I finished yesterday and before I wrote the above stuff today, and was just going to ask what you have already answered. I wonder what the most transparent example of measuring angular velocity in quantum mechanics would be. I am hampered in my thinking by trying to go from an abstract formula t o understand how it was derived in the process of solving some practical (lab) task. That reminds me, have you ever come across a book by an early Gestalt psychologist, Max Wertheimer? The book is entitled Productive Thinking and is outstanding in the way it gives models for teaching about math -- not as some abstract rigamarole involving mysterious formulae but as sensible procedures that students can learn to work out for themselves. When you teach like that, students are not left to sink or swim. P0M 03:35, 30 December 2005 (UTC)

• • Another thought: the spin of an electron (its integral rotation) creates a moving circle so that if one chooses a point on the spinning electron as it moves through space and draws its three-dim ensional motion, it would look like a coil made of circles like a "slinky" toy. If you ran it over with a steam roller, it would be a sine wave. The spin of all subatomic particles including the electron is a multiple of h-bar (h/2pi). (Pi has to do with circular motion and sine waves.)--Voyajer 03:40, 30 December 2005 (UTC) --Sorry, haven't read Wertheimer.

I think the radian came about something like this: On the practical lab task that produced the use of radians. Lab worker did not want to use degrees. Any circle is 360 degrees. Any circle is pi. Then why not divide circle into segments of pi? But how? Well, let's divide 180 degrees by pi and call it a radian. That will make 2 pi radians per circle. However, since pi is 3.1415... that makes a weird number of radians per circle when you multiply pi x 2 you get approx. 6.28 radians per circle, but who cares? At least we don't have to use degrees. (Strange story but probably true.)--Voyajer 03:57, 30 December 2005 (UTC)

A revealing picture of Schroedinger's understanding of waves is this document in his own writing:

Schroedinger original documents

Thank you. I really like Schroding, somehow, just from looking at those few shards of his real life. P0M

--Voyajer 05:34, 30 December 2005 (UTC)

Once I figured out what the question I was trying to ask myself was, and then poked around some more, I found the answer I was looking for. It's , angular velocity.

One of the Wikipedia articles has

is the quantized energy of the photons of radiation having frequency (Hz) of or angular frequency of (radian/sec).

is angular frequency and is measured in joules per (radian per second).

Since h-bar is jus t a convenience for calculation, and I suspect that there are enough truly mystifying things in QM without bringing it in. If at some point there is a natural reason for using it, e.g., a formula in with pi factors will cancel out and simplify calculation, then we could introduce it at that point. I found out that there is a list of math symbols, but not a list of physics symbols on Wikipedia. I found the definition I quoted above in one of the books I bought recently. The definition was on page 4, b ut was not explained. If the general reader comes to a formula like PD = ir, it can be daunting and off-putting if the person who learned the formula as a 18 year old doesn't bother to explain it. As for titles, how about "Basic Quantum Mechanics" or "The ABCs of Quantum Mechanics"? (One of my most useful books, now lost, was The ABC and XYZ of Beekeeping.) Never fear that the title would be too long. We could shorten it to ABCs of QM and follow it with ABCs of QED ;-) P0M 17:30, 30 December 2005 (UTC)

• Oh, I didn't see this before I answered below. Yes. I had realized this about angular velocity and convenient calculation as described below. Basic Quantum Mechanics is good. However, how does one go about changing the name of the page? Does one start a new page and move the info over? Wouldn't all the history be lost?--Voyajer 18:32, 30 December 2005 (UTC)

It's easy. You just hit "move" in the top bar, if I remember correctly.

The quantum of energy is not h. In fact, if we weren't committed to ergs and joules we could divide one of those units by h, make a new unit of energy measurement called the "jerg" (well, maybe that's not a good idea), and a u nit of frequency would equal an amount of energy. I hope I've said that correctly. (It's called making natural units, I think.) Anyway, h is the ratio between energy and frequency. The quanta of energy delivered are not divisible. One photon o f ultraviolet delivers one quantum of energy. One photon of infrared delivers one quantum of energy. But they are different in "size." If you are dealing with photoelectric effects of ordinary metals, it doesn't matter how many photons of ir radiation yo u pile on, you won't get a photoelectric effect. If you fire one photon of uv you'll pop an electron out of a lower orbital and create an electrical potential. I was thinking about this very question, and I think I have save a quotationf rom Reichenback or somebody like that, somebody who writes very clearly and leaves no loose ends. I've got to go buy some uv LEDs now (for security, not for science). More later. P0M 19:20, 30 December 2005 (UTC)

• I'm terrible with word shortcut s at times. Yes, the quantum of energy is "not" h. And I cannot do the "move" thing you are saying. (learning how to manipulate Wikipedia is like learning html all over again)--Voyajer 19:24, 30 December 2005 (UTC)

[edit] Question regardin g "packets"

In the current version of the article it says: "So the reduced Planck's constant gives the energy of a wave in packets per radian instead of packets per cycle." I think one could speak of "conventional units of energy" where you have "pa ckets," but could not substitute "quanta" for "packets," which is what I suspect you mean to do.

My understanding is that when a photon (quantum of light energy) strikes an electron it will either be reflected in a perfectly elastic way or else the photon will be absorbed and the electron will jump to a higher orbital. If the electron falls to a lower orbital, the energy differential will appear as a photon. If conditions are right, the electron could immediately accept another energy boost, jump to a higher orbital, shed its energy as a photon, and in this way a "train" of waves would Each cycle is a kind of mapping of the rise and fall of one electron one time. So each cycle can carry only one quantum of energy, and the color of the light is an indication of the amount of energy characteristic of that frequence of light.P0M 08:09, 30 December 2005 (UTC)

• • Okay, I've been researching the same thing since yesterday. I've been trying to decide if dividing the energy into radian was making a smaller packet and if that meant that a photon wasn't the fundamental size of energy but rather energy could come in whatever size packets scientists proposed or not? I've read conflicting arguments, saying that h-bar is more fundamental, but I'm inclined to believe that Einstein felt h was more fundamental. h is a photon or one quantum of energy. h-bar is a reduced quantum of energy, but it is more like taking pizza pie slices out of a single quantum of energy. I've been trying to decide since yesterday whether to explain it this way or not. I think that h is the only form of a quanta of energy. I believe in all sincerity that h-bar was simply invented because it is easier to do the math if you divide it by 2pi. Fourier series is wave analysis. The Fourier transform is an algorithm. It was used by Heisenberg in matrix mechanics. The only way to make the algorithm manageable is to have a periodic of 2pi. Since there were no computers and even no calculators and the math was probably done with an abacus or by hand, I think it was convenient to divide h into apple pie slices of radians to do the calculations. It appears to be so, but I'm looking for more confirmation. I've been researching for several hours and have not been able to pinpoint a reliable source though other than every source says the photon (meaning h and the entire cycle) is the quantum of energy.--Voyajer 18:24, 30 December 2005 (UTC)

[edit] Moved

I just moved the article. The change didn't show up in my watchlist, so I will notify you individually. Things may be a little slow in the system. Have you been getting lots of "session info lost" errors? P0M 20:06, 30 December 2005 (UTC)

[edit] PLEASE MOVE AGAIN TO Basic quantum mechanics (not caps)

I just changed twenty or so links. Please rename as Basic quantum mechanics. Thank you. Also, parentheses in an encyclopedia title are incongruent with major encyclopedia.---Voyajer 21:35, 30 December 2005 (UTC)

Ambush Commander. I'm sure your heart is in the right place, but where were you when we were considering a consensus name for this article? I do not see your title here nor the pros and cons against it. If you can come up with a valid reason for your title, the n let everyone agree on it. I've browsed every article on Encyclopedia Britannica and none have parentheses in the title. At worst there is a colon or a comma. ---Voyajer 21:52, 30 December 2005 (UTC)

Hello, I was being bold. Hopefully I was not reckless by fixing all the links, but let's see...

I was vaguely aware about the discussion about the naming of the article. One particular point you offered stuck out to me: They would have to be redirected again to any title change. Fixing double redirects is not an extremely big issue, and I cleaned them up completely (as opposed to your move back, which left about seven double redirects... if it's clear that we're definitely not going to use Quantum mechanics (basic), I'll fi x them.)

In truth, the change from Basic Quantum Mechanics to Quantum mechanics (basic) was concentrated on the basic being kicked to the end, but rather, uncapitalizing the "quantum mechanics." So some good came out of the page move I guess, but I felt that "Basic Quantum Mechanics" was unsatisfactory, and moved the basic qualifier to the end in parentheses.

While Encyclopedia Britannica may not have parentheses in names, it is a common practice in Wikipedia, especially for disambiguation, see: Wikipedia:Manual of Style (disambiguation pages).

Basic quantum mechanics, in my humble opinion, is ambiguous because it implies there is a field called "basic quantum mechanics", (like Basic English) as opposed to an article that talks ab out quantum mechanics in a basic manner. Both talk about Quantum Mechanics though: remember that.

So this makes titles like "Quantum mechanics in a nutshell" out of question: perhaps the reader thinks, "Hmm... is that the name of a book?" The classic method of disambiguating with parentheses, however, works perfectly. An Interval (mathematics) is not called an "interval (mathematics)", but the (mathematics) offers crucial information as to what the topic is on.

Alternatively, we could try Basics of quantum mechanics.

Your last suggestion is interesting: Development of quantum mechanics. Is this article a basic overview of quantum mechanics (as the current title implies), or does it deal with the development of quantum mechanics? Hmmm...

I'm off to fix the double redirects now.— Ambush Commander^(Talk) 23:21, 30 December 2005 (UTC)

I would not characterize the article as either an overview or as a history of its development, although it contains elements of both kinds. Take a look at the main QM article. Unless you already know a great deal of the kind of college ph ysics that physics majors learn (and not the 3 hour course for BA students), it is going to be pretty much useless. The need of someone who has not studied physics at this level, perhaps a high school student that has studied physics without the benefit of having learned calculus, is to get an accurate picture of what is studied in this field, what some of the main accomplishments are, etc. Many times if you base yourself clearly on what the student already knows you can create an understanding of that is valid, whereas if you just throw a number at somebody it becomes the mystery. So one anchor is to start from what is known, both as empirical experience, and also as math concepts that anybody who is old enough to be interested in quantum m echanics would be expected to know. Then, it may be possible to find examples or applications that can be used to fill-out the picture of quantum mechanics without the need to go through all the historical twists and turns that explain how the examples o r applications came into existence.

Take a look at an old book, George Gamow's One, Two, Three ... Infinity. Gamow said he wrote it for his own son. I think his son was a little young for the book when Gamow wrote it so he probably really said that he wrote it with his son in mind. It's a great book. It does not use any higher math, but it does open the minds of its readers to dozens of leading edge questions, and, since he was a leading physicist and not somebody getting paid a penny a word, it i s an accurate and responsible book.

"Basics of quantum mechanics" sounds o.k. to me. "ABCs of quantum mechanics," which I proposed earlier, would mean about the same thing, so how could I object.

Thanks for help with the capitalization and the re directs. P0M 00:45, 31 December 2005 (UTC)

On second thought, I like Basics of quantum mechanics more than the place I moved it to. I'm opposed to ABCs because: one, the meaning is a bit roundabout (colloquial language), a nd two: it implies juvenile, simplistic content. — Ambush Commander^(Talk) 04:32, 31 D ecember 2005 (UTC)

I am not at all opposed to "Basics of quantum mechanics", but I don't feel like fixing any redirects if no one else minds doing it.--Voyajer 05:14, 31 December 2005 (UTC)

Done. — Ambush Commander^(Talk) 06:13, 31 December 2005 (UTC)

[edit] quotation from de Broglie

Here is a quotation that may provide some back-up. It comes from Louis de Broglie's Revolution in Physics, p. 244: "In quantum theory, atomic electrons in their quantized states possess an orbital kinetic moment whose value is always a whole multiple of Planck's constant divided by 2 π: This is the result of quantization itself." P0M 08:29, 31 December 2005 (UTC)

• Actually, de Broglie wrote this after Bohr had made his assumptions and de Broglie was merely stating them as if they were now fact. It was discussed between De Broglie, Schroedinger, Bore and Einstein what model of the atom was best suited to describe it and Bohr's model was universally accepted as the only viable solution. Bohr however was making an assumption that since the first orbit K was found to have an angular momentum of 1/2r that all consecutive orbits should be multiplied by the first orbit, first by h, then 2h, then 3h, and so on. This was assumed without proof. The only circumstantial evidence was that the lines in the atomic spectrum only appeared in certain discrete places for each element, therefore, the orbits were in discrete places. Bohr assumed they were multiples of h because h was how wave energy had been quantized. If you read the external link in the article entitled [1], you will see that this was all kind of arbitrary with 4 basic unprovable assumptions. However, if the assumptions were true, then the electron wouldn't fall into the nucleus of every atom. So it was liking creating a theory to fit nature, not much di fferent than when Aristotle said that the "natural place" for all objects on earth was to come to rest in its own "natural place". In Bohr's time and even now, we have to believe that the orbits are quantized by h or else the electron would fall into the nucleus. We don't have any other explanation. In the case of outer electrons, the dividing by 2pi is not a result of mathematical ease, but rather the result of the first orbit being 1/2pi so all the other orbits were multiplied by integers of h and the first orbit of 1/2pi. There were other theories floating around. After all, some force could be counter-balancing the electron away from the nucleus, but then electrons were counter-balanced away from each other in their orbits, so there would have to be two new kinds of forces added. Choosing Bohr's atom became a matter of Ockham's Razor. Least amount of new assumptions. h was already known.--Voyajer 17:43, 31 December 2005 (UTC)

It all boils down to integrity, doesn't it.

T o me, a more natural example of a standing wave would be a standing wave in a cup of coffee. P0M 19:40, 31 December 2005 (UTC)

[edit] Something missing

The Bohr atom section currently says: An orbital with the same value of n is c alled an electron shell." Shouldn't that be An orbital with the same value of n as has ____________ is called an electron shell.?? P0M 01:17, 1 January 2006 (UTC)

Happy New Year!

It was supposed to say "any" and I'll fix it in a sec. For values of n2, n3, n4, etc. there are suborbitals, but any having the same n-value are in the same electron shell.--Voyajer 01:54, 1 January 2006 (UTC)

Do you happen to have any good photographs of standing waves in cups of cof fee or the like? I'm trying to remember where I've accidentally produced these, and I suspect that it was in a car on a rough road -- not a very good photography studio. P0M 01:17, 1 January 2006 (UTC)

Well, I kind of made a standing wave Bohr atom. It's not quite correct in that each electron itself is a standing wave, but the idea is that there is a probability distribution related to each electron that goes to zero in between electrons. Hope it helps.--Voyajer 01:54, 1 January 2006 (UTC)

Another question, the article currently says, "If a string is made to form a circle in the same way that the wave of an electron forms a circle in its orbit in the Bohr atom, then a standing wave is formed when the wave fits the available space around the circle." To me, that verbal picture suggests a solitron that is somehow guided in a circular path. It is my impression that standing circular waves are normally constrained by the rim of the container, which acts in the same way as the two fixed support at the ends of a plucked string in which standing waves can be excited. I seem to recall some physicists saying that the idea of an electron actually "orbiting" the nucleus is an idea carried over from the Bohr atom model. P0M 01:35, 1 January 2006 (UTC)

Orbits are from Bohr. Standing waves were later added to Bohr's model (see [1]) because it is not so easy to draw a three-dimensional standing wav e in the shape of a sphere for H. "Schrodinger's Wave Equations of Quantum Physics describe real Standing Waves of Matter in Physical Space" see [2].--Voyajer 01:54, 1 January 2006 (UTC)

I didn't express myself clearly enough. The idea that the electron is a "something" that moves around "in the form of a circle" is not really part of the new QM. So using the string analogy is not perhaps as good as using the coffee cup analogy. The orbitals locations in atoms of different elements are greatly influenced by the nucleus, and its attractive force on the electron would seem to me to be, like the clay in the cup, what the wave is reflecting against. Of course both ways of talking a re using macro world experiences to try to describe the quantum domain.

I may have produced a good enough picture of a standing wave. Strangely, there are hardly any pictures of them on the WWW. What is there are mostly simulations. Years ago there were some beautiful pictures made by somebody studying standing waves by using a sand table and a vibrator. Anyway, my idea is that standing waves are things that we have experience of in our own lives if we are at all observant. So that is a tie-in for the general reader to the world of QM. Its obvious that you can't have half of a standing wave going on at the surface of the left half of your coffee cup, and nothing going on in the right half. You either have a standing wave or you don't. It would be fascinating to see what happens on the sand table when the vibrator is set a notch higher and one standing wave is replaced by another, not that it would prove anything about what happens when an electron gets bumped into a higher orbital. But, anyway, if readers can understand that a given kind of atom can have only certain kinds of standing waves, and that when the electron drops down an orbital it has to go from definite energy to definite energy, then that makes it clear why you get atomic spectra that are "diagnostic."

Happty New Year. P0M 06:33, 1 January 2006 (UTC)

Actually, the standing wave formed in a cup is not like the picture given by de Broglie of a standing wave of the electron. The standing wave of the electron does not vibrate outward away from the nucleus. The standing wave vibrates on the flat surface of the sphere of the orbit perpendicular to the nucleus. The nodes appear on the surface of the orbital. There can be many cycles of the wave appearing at a si ngle distance from the nucleus. It is as the picture of the Schroedinger atom in the article. The two electrons are standing waves on the flat spherical surface of the orbital. Therefore, circular rings appearing in a liquid are not a good analogy as the standing wave does not radiate from the nucleus of the atom in quantum mechanics. However, there are many non-mainstream fringe theories floating around that say that it should be as you propose. There is a lot of controversy over quantum mechanics, historically, by physicists involved in the theory themselves. It is because the theory was sort of an ad hoc theory to make mathematics that fit the measurements of the atomic spectrum. It was a shot in the dark similar to the Ptolemian earth-centered solar system. The system of Ptolemy was a great theory with the earth at the center. It worked very well to predict all the movements of the planets with great accuracy even retrograde motion. In fact, when Copernicus came up with his sun-centered sola r system model, it didn't predict the position of the planets nearly as well as the earth-centered system because Copernicus still used absolutely circular orbits. It wasn't until Galileo saw through the telescope that Venus went through all its phases t hat it could be proven beyond a doubt that the sun was at the center. Today Quantum Mechanics works like Ptolemy's earth-centered solar system. It may not be reality, but it sure predicts things very well. Once a better microscope (analogous to Galileo's telescope) is invented that can actually see the atomic structure, QM will probably be overturned. There is so much information on the controversy over QM that it would make an interesting article just quoting the physicists who invented it and Einstein who rejected many of its principles. However, QM is so extremely useful in predicting outcomes at the atomic level in our present state of technology that it probably won't be revised for some time to come. --Voyajer 07:39, 1 January 2006 (UTC)

What is your citation for de Broglie's picture of the electrons in their orbits? I can't find it. Thanks. P0M 08:43, 1 January 2006 (UTC)

There are so many: [3], and "An answer to these questions was offered by Prince Louis de Broglie in 1923 with the theory that, as Einstein had introduced the idea that light could behave like both waves and particles, perhaps particles of matter could also behave like waves. Thus, electrons in an atom were not moving in orbits but filled an orbit as standing waves. Familiar electromagnetic radiation, like light, exists as traveling waves, moving through space at the velocity of light. A standing wave does not move, but vibrates between fixed points, like the string on a violin. The sine wave at right represents a whole wavelength. It has a portion with a positive magnitude, a portion with a negative magnitude, and a node, which has zero magnitude. The ends of the wave, which also have zero magnitude, are usually not considered to be nodes. Half a wavelength would have no nodes; one and a half wavelengths, two nodes; and two whole wavelengths, three nodes. A one dimensional wave has nodes that are points, and it vibrates into two dimensions. Similarly, a two dimensional wave, like a wave of water on the ocean, has nodes that are lines, and it vibrates into three dimensions. A three dimensional wave, which is what electrons in an atom would be, has nodes that are surfaces. Such surfaces can be planes, cones, or spheres. By analogy, we might want to say that a three dimensional wave would vibrate into four dimensions, but this aspect of the matter does not seem have been much discussed or explored. In electron waves, each non-spherical node represents a quantum of angular momentum. Thus, a half wavelength, with no non-spherical nodes, is 0 angular momentum; a full wavelength, with one non-spherical node, is angular momentum; a wavelength and a half, with two non-spherical nodes, is 2 angular momentum; etc." [4]

but possibly the best explanation is shown in the illustration at [5] which shows the waves perpendicular to the nucleus.--Voyajer 14:05, 1 January 2006 (UTC)

[edit] Regarding the effect of QM on philosophy and its controversies

To those interested (and certainly there are many following this article who are) QM has had many detractors including Albert Einstein and Erwin Schroedinger. QM has had a profound affect on philosophy. Immanual Kant wrote about the philosophy of determinism derived from the ability to predict future outcomes in the universe (such as future position of planets) by science. QM took away predictability and therefore was a blow to philosophy. THEREFORE, without going into religious philosophy, I will be beginning an article entitled Quantum mechanics, philosophy and controversy within the week. It should be an interesting study and I welcome contributors. Of course, however, with the usual caveat as with all physics articles, please restrict links and contributions to science and philosophy disregarding any religious implications. The freedom of religion act show allow each individual to draw their own religious implications from science and none should be thrust upon them by implying any particular religious view can be drawn from them. I say this in advance knowing the impact on religion that science has always had and the impact that QM had on believers in fate. I look forward to beginning the article and to your contributions.--Voyajer 18:53, 1 January 2006 (UTC)

[edit] Quantum entanglement

I'm going to quote a Nasa article so I don't get accused of personal interpretation, because I'm going to say that the paragraph added by Ancheta Wis that quantum entanglement follows classical laws at 10 KM with a "finite speed" is wrong. I'm going to argue that "instantaneously" by definition is infinite and faster than the speed of light.

NASA article: Particles entwined

Einstein never liked entanglement. It seemed to run counter to a central tenet of his theory of relativity: nothing, not even information, can travel faster than the speed of light. In quantum mechanics, all the forces of nature are mediated by the exchange of particles such as photons, and these particles must obey this cosmic speed limit. So an action "here" can cause no effect "over there" any sooner than it would take light to travel there in a vacuum.

But two entangled particles can appear to influence one another instantaneously, whether they're in the same room or at opposite ends of the Universe. Pretty spooky indeed.

Quantum entanglement occurs when two or more particles interact in a way that causes their fates to become linked: It becomes impossible to consider (or mathematically describe) each particle's condition independently of the others'. Collectively they constitute a single quantum state.

Left: Making a measurement on one entangled particle affects the properties of the other instantaneously. Image by Patrick L. Barry.

Two entangled particles often must have opposite values for a property -- for example, if one is spinning in "up" direction, the other must be spinning in the "down" direction. Suppose you measure one of the entangled particles and, by doing so, you nudge it "up." This causes the entangled partner to spin "down." Making the measurement "here" affected the other particle "over there" instantaneously, even if the other particle was a million miles away. [Bold added for emphasis] http://science.nasa.gov/headlines/y2004/23jan_entangled.htm

end article: Most explanations for quantum entanglement after years of research say that instantaneous effects over millions of miles faster than the speed of light are okay because no information is sent faster than the speed of light. This is the current understanding. So I will be changing this paragraph.--Voyajer 19:04, 2 January 2006 (UTC)

I looked at the NASA article, just to be sure. It's not clearly stated. I would not necessarily read it to affirm that one can choose whether to "nudge it up" or "nudge it down" by the way the measurement is made. Unless you can do that, all you know is that, e.g., you have spin up, and therefore the other guy must have spin-down. The same for the other guy. But he doesn't derive any "yes" or "no" or binary 1 or binary 0 from that information. P0M 01:27, 3 January 2006 (UTC)

For the uninitiated (meaning those out there who don't have a clue what I just said):

Once two particles interact, they become a system. It is as if a long string is attached between them that can never break. They exist as one although they are two. It's as if they now sit on the same teeter-totter seesaw. No matter how long the seesaw is, even if it is one million miles long, you push one end down and the other end goes up instantaneously. This is not due to one particle sending a message to the other particle saying, "I'm going down, therefore, you must go up" and waiting for the particle to receive the message, but the particles are always connected and do not have to send signals to each other, they always react to each other instantaneously because they are part of the same system called "the same quantum state".--Voyajer 19:44, 2 January 2006 (UTC)

FWIW, I think Voyajer is correct in what he says above. The problem may come about because in our macro perspective we typically investigate things that occur by means of operations that do not involve "action at a distance." It may appear to the uninitiated that when a highway construction worker pushes a plunger "over here" an explosion occurs "over there," much as when a Kung-fu adept makes a pushing motion with his hands "over here" somebody drops dead "over there." ;-) But the initiated know that there are wires or radio links between the highway engineer's plunger and the explosives implanted into the shelf of rock. Everything we do suggests that there has to be some kind of a connection by way of direct physical contact, poking something with a stick, blowing something over with a puff of breath, horn here and electrical servo-mechanism over there, or, at the fastest, a light going off here and a photoelectric switch goingg off over there. For a long time people imagined that light moved from signal beacon to signal beacon instantaneously, and then it was discover that light is fast but finite.

We are also well conditioned to believe that "an entity" must be physically connected. If it is my hand, it cannot continue to function as part of this organism if somebody cuts it off. But the Harvard logician/philosopher Quine long ago pointed out that this view is conditioned by our everyday thought. In the QM world, the issue of what "one thing" or "an entity" is usually gets tagged as "non-locality". This "one thing" is also perfectly elastic (rigid), unlike a teeter-totter. Even though separated by a distance, "they" are in fact one thing.

To make communications possible using this kind of two-in-one, (1) You'd have to make lots of them, since they can only be used once. (2) You'd have to transport one face of each Janus by sub-C drive to wherever you wanted to use it.

I think the article currently may be a little unclear to the average well-informed user. The understanding we currently have on the mmovement of anything by a chain of physical causation is that such actions cannot occur at a speed faster than c. That conclusion follows because all physical operations proceed by exchanges on energy, i.e., exchanges of photons. Photons cannot go faster than they can go. But the entanglement phenomenon is not mediated by photon transmission. It is something entirely different. Do photons have location while they are in travel between emitter and detector? Not by the kind of definition that the word "location" is ordinarily attached to. If two things do not have location, then they do not have any "distance" between them. Experience on the macro level makes us inclined to say, "But they must have distance between them." Experience with entanglement makes us unwillingly admit, "They at least act like there is no distance between them." P0M 21:25, 2 January 2006 (UTC)

---

Popular article. 2 edit conflicts, so far.

[edit] Classical channel

I made no claim that quantum entanglement follows classical laws at 10 Km with a "finite speed". It is true that verification of an entanglement result would have to be made using a classical channel for the information.

The disclaimer was merely to stop thoughts that entanglement allowed communication faster than light. In order to verify the entanglement, classical communication channels are needed. That was what I was trying to state in the prose. But my phraseology is immaterial. The disclaimer is the important thing -- no results that break the speed limit. No free lunch. The classical channels are necessary for the rest of us, even if A B were entangled. The rest of us wouldn't know it until we could perform a classical verification.

I don't follow this argument. Before I forget about it, let me say that the difficulty with communicating as proposed is that (as far as I know) there is no way to set the photon. It makes a difference whether one can set the state of one of two entangled protons, or whether one mere discovers the state of one of the protons. Measurement involves a physical operation that changes things, but maybe there is indeed some way to coerce the appearance of one state or another in the local particle. Assuming this to be the case, and assuming that one could transport one half of a Janus pair at sub-C velocity, then one could use a simple code system. Once humans get to the remote star, if they need to warn earth of an approaching attack fleet by aliens who now know where we are, then we'll send one signal, and if nothing is threatening, we'll send the other signal. You couldn't do that with a photon unless you established a communications system midway and beamed pairs ahead toward the new colony and back toward earth. The new colony could then "flip" the arriving photon, assuming it could somehow be distinguished from all the other photons, and the other half of the pair could be examined on Earth. This method strikes me as being about as primitive as the early system of signal beacons used in China to warn the capital of trouble on the frontier.

Anyway, back to the argument above. Why would one need to "verify the entanglement"? If the method works reliably in the laboratory, it should be possible to scale it up. Then if a few pairs could be employed, one could simply check for a consistent message on most or all of these "channels." P0M 01:15, 3 January 2006 (UTC)

[edit] 3 particle entanglement

I have just seen the analogy to a see-saw. That explains a previous statement in the article, but there doesn't need to be a compensating up/down for a down/up. It is more like up/up followed by down/down. I quote from Aczel's restatement ^[6] (p.226) of 3 entangled particles. The formulas are the same whether the particles are photons with +1, -1 polarization, or particles with +1, -1 spin. The following experiment was designed by Michael Horne using polarization as the entangled property^[7]:

A source emits 3 entangled particles A B C simultaneously. A B C pass simultaneously through three sets of two slits a,a'     b,b'     c,c' at the same time. Each part of slits are given a set of beamsplitter settings (Left or Right =L or R). A precise set of QM predictions exists: Up or Down = +1, -1 in detectors D_a,D_a'    D_b,D_b'     D_c,D_c' for 3 entangled particles A B C. All the particles can be in the same state +1 or -1 after the detection. Given specific outcomes for B C, then A is known with certainty. (Aczel p227.)

Condition and Predicted state.

A B C Settings.	n particles in -1 state.
R L L	0 or 2
L R L	0 or 2
L L R	0 or 2
R R R	1 or 3

The end result, which has been clearly stated in the Entanglement article, is that locality is violated. A B C are entangled at a distance from each other. But that was not the point of this note; the point was that the entanglement doesn't have to be a seesaw up/down for down/up. It is more like the '0 or 2' versus '1 or 3' particle outcomes as stated in the table above. Which outcome? -- we don't know until the experiment is performed.

^  Greenberger, Horne, Shimony and Zeilinger (Dec. 1990) "Bell's Theorem without inequalities" American Journal of Physics 58.12 pp1131-43, appendix as referenced by Amir Aczel (2003), Entanglement p.222

^  Michael Horne (2001) "Quantum Mechanics for Everyone" Third Stonehill College Distinguished Scholar Lecture May 1, 2001 p.4. as referenced by Amir Aczel (2003), Entanglement p.224

--Ancheta Wis 22:03, 2 January 2006 (UTC)

[edit] Quantum entanglement (bis)

I have made a lot of changes on the entanglement section in order to reflect what I think is correct and verifiable and uncontroversial. It will be interesting to see whether people largely agree with me. I plan to refine my edits by addition of references and wikipedia links, in the near future. Underlying my edits is my knowledge of Bell's theorem which derives a contradiction between quantum theory and classical theory, using entanglement, by making at least three assumptions: unmeasured variables can be thought of as taking values; influences between these variables and others cannot spread faster than the speed of light; experimenters do have freedom to measure what they like without this changing the values that they would see if they make any particular choice. The conditions are usually called Realism, Locality and Freedom, respectively. The conclusion is that (if QM is true) nature is non-classical. It could then simply be that we must abandon realism (Bohr would say: "I told you so"), but if you want to have realism -- it certainly has been an uncontroversial implicit or explicit feature of all physics for about 2000 years -- you have to abandon locality (this seems to have been Bell's inclination) or freedom (this is what Gerard 't Hooft seems to prefer). Gill110951 11:07, 6 December 2006 (UTC)

[edit] Uncertainty principle and disturbance of position

I do not believe that the uncertainty principle teaches that the position is "disturbed" by measurement. I believe this is a throwback to the Heisenberg microscope thought experiment which is not a correct image of Uncertainty. I give a rather brutal debate on the Uncertainty Principle talk section because I'm battling strong supporters of the Heisenberg microscope. I do not mean to be unkind just strong in my arguments.

The Heisenberg microscope was a kind of reductio ad adsurdum argument, no? We start with the everyday view that says that electrons are little spheres circling the nucleus of some atom. We would like to know not only where it is, but where it is going and how fast it is headed there. So we can try to look at it with a microscope. The problem is that visible light has a large wavelength relative to the size of the electron, so we would not get a clear image. We would like a clearer image, so we try for gamma radiation. But one hit of gamma will give the electron the energy of ionization. So the second "frame in our movie" shows nothing because the electron is gone. If we back off on the energy, then we get more of an idea of momentum but we lose the exactness of

One of the things that most people seem to agree upon is that when a photon is absorbed by an electron then the electron changes its orbital or is ionized.P0M

Niels Bohr is actually said in some sources to have originated the thought experiment of a gamma-ray microscope which suggests that, since a microscope's light “disturbs” the motion of small objects under observation in an intractable way, exact simultaneous knowledge of the position and momentum of elementary particles is impossible. This thought experiment has repeatedly been deemed a poor proof of the uncertainty principle because

• 1. Heisenberg's microscope is stating that uncertainty is an error in measurement, when the uncertainty principle itself is not about there being an error in measurement due to the instrument or type of measuring procedure, but about there being a fundamental deviation between position and momentum of observables.

Please define "deviation." P0M

and

• 2. Heisenberg's microscope suffers from the same problematic assumptions about locality as Einstein's analysis of the EPR experiment.

Once this thought experiment has gotten you thinking about what you can really mean by "position" and by "momentum," then further thought exposes the problem of "location" to be deeper than everyday thought would lead one to believe. We assume that when Superboy leaves home moving so fast that nobody can see him and arrives at school a second later we would nonetheless have found his image on a sufficiently fast motion picture camera. He had a location whenever we might have opened the shutter of that incredibly rapid camera. In that sense of "location," I think you are right. When a photon or an electron is emitted in a double slit apparatus, we can know about it in two ways. (1) We fed the device enough juice to stimulate the emission of one particle. (2) Something showed up at an appropriate amount of time thereafter on the detection screen. We know nothing about position between those points in time. So if an electron in orbit is like a photon in passage, then it doesn't have a position in the sense we give "position" in everyday language. P0M 02:11, 3 January 2006 (UTC)

Thirdly, the uncertainty principle did not arise from observations of a single particle. The uncertainty principle arose from spectroscopy. In spectroscopy, no one is looking at subatomic particles through a microscope. In spectroscopy a single light source is illuminating an element. Therefore that single light source is disturbing all the particles to the same degree and the spectrum created is therefore all disturbed to the same degree so no particle is more or less disturbed than another. Yet, even in this case, Heisenberg is saying that there is still a deviation in measurement between position and momentum of a moving particle. This therefore cannot be due to a collision of a photon under a microscope, but is inherent in nature. Therefore, it is a fallacy to say that the act of measurement disturbs the particle. This is a leftover from the HM thought experiment. Nothing disturbs the particle. Heisenberg's uncertainty principle arose from inaccuracy in measurement where there was nothing to disturb the measurement. He saw this as not the fault of the spectroscope, but an inherent characteristic of the universe.--Voyajer 00:56, 3 January 2006 (UTC)

It's certainly true that the uncertainty principle did not arise from observations of single particles. A thought experiment is just that.

Spectroscopy can also be pursued by heating a sample of some material to incandescence. What one sees then are a few characteristic bright lines in the spectrum produced, and nothing in between. These characteristics were observed and used for a long time without there being any explanation for them. It turned out that these bright lines are related to the orbitals that are proper to the element under investigation, and the orbitals are in turn related to Planck's constant.

Shining a white light on a sample of a gas will result in the negative of the above situation, since certain wavelengths will be absorbed by the electrons in the gas, causing them to jump up a level rather than passing through to the observer.

So what in all of the above regarding spectroscopy has anything to do with uncertainty? The uncertainty in any measurement of atomic particles turns out to involve Planck's constant because the energy proper to any photon is a function of its frequency. Higher frequency gives clearer image but also delivers more energy to the thing you are trying to measure. P0M 02:11, 3 January 2006 (UTC)

Heisenberg derived the Uncertainty Principle from actual deviations in measurement using spectroscopy. He just didn't come up with it in a void. Sorry but you are about to get more than you asked for, but I find the different views on Heisenberg's microscope fascinating so I'm going to post them here (those I haven't posted to other talk). But first, the origin of the Uncertainty Principle is from measurements made in spectroscopy for matrix mechanics using in all probability the Fourier Transform Spectroscope invented in 1911.

Quote from origins of Uncertainty Principle:

"After Schrödinger showed the equivalence of the matrix and wave versions of quantum mechanics, and Born presented a statistical interpretation of the wave function, Jordan in Göttingen and Paul Dirac in Cambridge, England, created unified equations known as "transformation theory." These formed the basis of what is now regarded as quantum mechanics. The task then became a search for the physical meaning of these equations in actual situations showing the nature of physical objects in terms of waves or particles, or both. As Bohr later explained it, events in tiny atoms are subject to quantum mechanics, yet people deal with larger objects in the laboratory, where the "classical" physics of Newton prevails. What was needed was an "interpretation" of the Dirac-Jordan quantum equations that would allow physicists to connect observations in the everyday world of the laboratory with events and processes in the quantum world of the atom.

"Studying the papers of Dirac and Jordan, while in frequent correspondence with Wolfgang Pauli, Heisenberg discovered a problem in the way one could measure basic physical variables appearing in the equations. His analysis showed that uncertainties, or imprecisions, always turned up if one tried to measure the position and the momentum of a particle at the same time. (Similar uncertainties occurred when measuring the energy and the time variables of the particle simultaneously.) These uncertainties or imprecisions in the measurements were not the fault of the experimenter, said Heisenberg, they were inherent in quantum mechanics. Heisenberg presented his discovery and its consequences in a 14-page letter to Pauli in February 1927. The letter evolved into a published paper in which Heisenberg presented to the world for the first time what became known as the uncertainty principle."--[8]

"In 1927 Heisenberg tried to show the impossibility of quantum trajectory by the use of his microscope thought experiment. And in 1928 Bohr added that what can never be empirically decided should be left outside science for good. Yet Heisenberg's microscope thought experiment employed not quantum electrons but the arbitrary mixture of classical wave and particle presentations of it. And Bohr confused what is outside the domain of quantum mechanics with what is outside science at large -- a confusion known in the philosophical jargon as hypostatization. Clearly von Neumann tried to prove the impossibility of hidden variables in 1932 because he was not fully satisfied with Heisenberg's and Bohr's discussions. Yet hidden variables proved possible even if admittedly hideous. Meanwhile, heavy beam microscopes either had the Heisenberg-Bohr claim that we can never see atoms refuted, or shown it too vague for a proper debate. With this, much of the force of Bohr's thought experiments was gone." Quanta in Context, Joseph Agassi, Boston University, USA, and Tel-Aviv University, Israelin Einstein Symposion. Lecture Notes in Physics,Berlin: Springer, Vol. 100, 1979, pp. 180-203.

"Furthermore, Heisenberg's microscope is today seen as naive. It is based upon the idea that the wavelength of the probe in a scattering is the ultimate lower limit of resolution. Nuclear magnetic resonance imaging medical machines show that is false." Nature 242, 190–191 (1973)

"Readers are warned that Heisenberg's microscope experiment can be misleading. In particular, students should resist the temptation to believe that a particle can really have definite position and momentum, which, because of the clumsy nature of the observation, cannot be measured. In fact, there is no evidence for the existence of particles with definite position and momentum. This concept is an unobservable idealization or a figment of the imagination of classical physicists. Indeed, the Heisenberg uncertainty principle can be considered as a danger signal which tells us how far we can go in the using of the classical concepts of position and momentum without getting into trouble with reality." -A.C. Phillips

There is more, but then this talk section would be entirely too long.--Voyajer 02:40, 3 January 2006 (UTC)

Well, I can't resist one more:

Book:

"The Disappearance of Quantum Reality

"There the matter stood until Niels Bohr stepped in. While physicists such as Werner Heisenberg, Wolfgang Pauli, Erwin Schroedinger, and Max Born were working at the mathematical formulation of the new theory, Niels Bohr was thinking about what the theory actually meant. For this reason he summoned Heisenberg to Copenhagen and confronted him about the deeper significance of his "microscope experiment."

"Bohr argued that Heisenberg's explanation began by assuming the electron actually has a position and a speed and that the act of measuring one of these properties disturbs the other. In other words, Bohr claimed that Heisenberg was assuming the existence of a fixed underlying reality; that quantum objects possess properties-just like everyday objects in our own world-and that each act of observation interferes with one of these properties.

"He went on to argue that Heisenberg's very starting point was wrong in assuming that the electron has intrinsic properties. To say that an electron has a position and has a speed only makes sense in our large-scale world. Indeed, concepts like causality, spatial position, speed, and path only apply in the physics of the large scale. They cannot be imported into the world of the quantum.

"Bohr's argument was so forceful that he actually reduced Heisenberg to tears. Whereas Heisenberg had argued that the act of looking at the universe disturbs quantum properties, Bohr's position was far subtler. Every act of making a measurement, he said, is an act of interrogating the universe. The answer one receives to this interrogation depends on how the question is framed-that is, how the measurement is made. Rather than trying to unveil an underlying quantum property, the properties we observe are in a certain sense the product of the act of measurement itself. Ask a question one way and Nature has been framed into giving a certain answer. Pose the question in another way and the answer will be different. Rather than disturbing the universe, the answer to a quantum measurement is a form of co-creation between observer and observed.

"Take, for example, the path of a rocket in the large-scale world. You observe the rocket at point A. Now look away and a moment later glance back and see it at point B. Although you were not looking at the rocket as it sped between A and B, it still makes perfect sense to assume that the rocket was actually somewhere between the two points. You assume that at each instant of time it had a well-defined position and path through space irrespective of the fact that you were not looking at it!

"Things are different in the quantum world. An electron can also be observed at point A and then, later, at point B. But in the quantum case one cannot speak of it having a path from A to B, nor can one say that when it was not being observed it still had a speed and position." F. David Peat, FROM CERTAINTY TO UNCERTAINTY: THE STORY OF SCIENCE AND

IDEAS IN THE TWENTY-FIRST CENTURY, (Joseph Henry Press, 2002).

Here is Neils Bohr's take on things, from his 1949 "Discussion with Einstein." (Atomic Physics and Human Knowledge, p. 38f.

This phase of the development [of the observational problem] was, as is well known, initiated in 1927 by Heisenberg, who pointed out that the knowledge obtainable of the state of an atomic system will always involve a peculiar 'indeterminancy.' Thus, any measurement of the position of an electron by means of some device, like a microscope, making use of high-frequency rdiation, will, according to the fundamental relations (1) [E=hv and P =hσ ], be connected with a momentum exchange between the electron and the measuring agency, which is the greater the more accurate a position measurement is attempted. In comparing such considerations with the exigencies of the quantum-mechanical formalism, Heisenberg called attention to the fact that the commutation rule (2) [qp - pq = (-1)^-2 h/2π)] imposes a reciprocal limitation on the fixation of two conjugate variables, q and p, expressed by the relation

Δq×Δp≈h,

where Δq and Δp are suitably defined latitudes in the determination of these variables.

P0M 03:06, 3 January 2006 (UTC)

And from later in the same article:

As stressed in the lecture, an adequate tool for a complementary way of description is offered precisely by the quantum-mechanical formalism which represents a purely symbolic scheme permitting only predictions, on lines of the correspondence principle, as to results obtainable under conditions specified by means of classical concepts. It must her be remembered that even in the indeterminacy relation (3) we are dealing with an implication of the formalism which defies unambiguous expression in words suited to describe classical physical pictures. Thus, a sentence like 'we cannot know both the momentuum and the position of an atomic object' raises at once questions as to the physical reality of two such attributes of the object, which can be answered only by referring to the cnditions for the unambiguous use of space-time concepts, one the one hand, and dynamical conservational laws, on the other hand. While the combination of these concepts into a single picture of a causal chain of events is the essence of classical mechanics, room for regularities beyond the grasp of such a description is just afforded by the circumstance that the study of the complementary phenomena demands mutually exclusive experimental arrangements.

P0M 03:36, 3 January 2006 (UTC)

There are a couple of good examples in de Broglie's The Revolution in Physics, (check the index for uncertainty). I don't have the time to copy them over here. They indicate that there are more general ways to look at indeterminancy, ways that do not involve the same measurement contingencies that would occur in the microscope problem. P0M 04:00, 3 January 2006 (UTC)

Now I have found again what Heisenberg said in 1958. Somewhat surprisisngly, in view of what Voyajer has said, he still uses the microscope example, or, I should say, he uses a microscope example. Before I quote what he says, I think I should attempt to explicate something that I think may be a confusing factor. There are several sources of uncertainty regarding the position of an electron. One factor pertains to larger objects as well -- the experimenter has to judge pointers on scales, etc. The scales may not be perfect, the experimenter's vision may not be perfect. His judgment of a fractional position between two marks on a scale may not be so hot. The second kind of uncertainty is what Voyajer has been talking about, an uncertainty that is due to our imagining that if only we had a small enough needle we could pin an electron down or follow it along like a parent holding the hand of a child on a ferris wheel. But the "child" is more like an ill-defined, not really discrete, puff of water vapor. It doesn't have "a real position", it has whatever the fuzzy quantum domain equivalent is. The third kind of uncertainty involves exchanges of momentum that must occur in some measurement procedures. If we try to locate even the position of some macro objects by shining light on them, we can cause them to move. (I think the little windmill in a vacuum flask are called radiometers or something like that.) Whatever an electron is, if we keep zapping around with gamma photons we may eventually get a reflection, in which case we will know where the electron was at a certain time -- but it will be gone.

Physics and Philosophy, p. 47f.

Is the first step, the translation of the result of the observation into a probability function, possible? It is possible only if the uncertainty relation is fulfilled after the observation. The position of hte electron will be known with an accuracy given by the wave length of the γ-ray. The electron may have been practically at rest before the observation. But in the act of observation at least one light quantum of the γ-ray must have passed the microscope and must first have been deflected by the electron. Therefore, the electron has been pushed by the light quantum, it has changed its momentum and its velocity, and one can show that the uncertainty of this change is just big enough to guarantee the validity of the uncertainty relations. Therefore, there is no difficulty with the first step. At the same time one can easily see that there is no way of observing the orbit of the electron around the nucleus. The second step shows a wave pocket moving not around the nucleus but away from the atom, because the first light quantum will have knocked the electron out from the atom. The momentum of light quantum of the γ-ray is much bigger than the original momentum of the electron if the wve length of the γ-ray is much smaller than the size of the atom. Therefore, the first light quantum is sufficient to knock the electron out of the atom and one can never observe more than one point in the orbit of the electron; therefore, there is no orbit in the ordinary sense.... Actually we need not speak of particles at all. For many experiments it is more convenient to speak of matter waves; for instance, of stationary matter waves around the atomic nucleus.

If it was not already clear, the mention of the possibility of describing the electron as a standing wave both makes it clear that the electron has no point location, and the fact that this "wave pocket" leaves orbit and becomes ionized makes it clear that the incoming gamma photon does something to the position and momentum of the electron. P0M 05:05, 3 January 2006 (UTC)

---

Okay, Patrick, don't get offended but I'm going to get black-and-white about this.

There is one, and only one, kind of uncertainty in the uncertainty principle.

True uncertainty is described here from article on the Uncertainty Principle: "Consider an experiment in which a particle is prepared in a definite state and two successive measurements are performed on the particle. The first one measures the particle's position and the second immediately after measures its momentum. Each time the experiment is performed, some value x is obtained for position and some value p is obtained for momentum. Depending upon the precision of the instrument taking the measurements, the measurements should be extremely close, however, they are usually off by a small fraction. If the experiments are repeated over and over and the results are plotted on a graph with a dot for every measurement, the graph will display a high density of dots for each measurement of position and another high density of dots for each measurement of momentum showing an inverse relation between the two measurements. However, the dots indicating each measurement will not all be plotted on top of each other because they would have to have infinite precision to be precise in each repeated experiment. In other words, there is an uncertainty in the outcome of the measurements. One might suggest that the instrument itself is flawed, but that with an infinitely accurate instrument, each measurement would indeed be infinitely precise. However, Heisenberg postulated in his principle that, even in theory, with a hypothetical infinitely precise instrument, that even in such a case, no infinitely precise measurement could be made of both the position and the momentum of observables at the same time and one must still provide for a dispersion, a standard deviation, a give-and-take (also called slop in engineering)."

• 1. What this means is that fundamentally in the universe there is a displacement between the position and momentum of a moving particle. It doesn't matter how you measure it, it exists. This and only this is uncertainty.
• 2. Uncertainty as a displacement is not caused by the instrument.
• 3. Uncertainty as a displacement is not the result of the measurement causing a disturbance.
• 4. Uncertainty as a displacement is not the result of a photon of any wavelength moving or "disturbing" the particle while measuring.
• 5. Uncertainty as a displacement is not caused by a collision between a photon (of any wavelength) colliding with the particle and disturbing it.
• 6. Quantum entanglement says that you can measure the position and momentum of an entangled particle by measuring one of its partners, therefore the partner particle being measured is not being pushed by a photon (of any wavelength whether a gamma ray from a microscope or visual light) because we are observing one partner particle in order to get the position and momentum of another partner particle, therefore, there is no disturbance to the partner particle not being measured, however, we know its momentum and location. Yet, even then without a disturbance of any kind, through measurement of other particles in an entangled state by measuring one particle in the state and therefore not "disturbing" the other particles, still, even then, there is an uncertainty or displacement between position and momentum.
• 7. So saying that uncertainty or displacement of position and momentum is caused by the photon of a microscope disturbing the position and momentum of a particle is absolutely dead wrong. (Can I be more clear?) Bohr said this to Heisenberg above. Bohr told Heisenberg that "your so-called Heisenberg microscope is stupid" in so many words as shown above from the book quotation because it means that there is some instrument error.
• 8. Uncertainty does not involve instrument error. Uncertainty exists even when in theory one has a hypothetical infinitely precise instrument and even if one isn't even measuring the particle in question but only its partner particle, even then, there is a displacement of measurement in a moving particle.
• 9. All books and textbooks that say that measuring a particle disturbs its position are dead wrong. They are relying on the Heisenberg microscope analogy which is dead wrong.
• 10. Heisenberg's microscope analogy was used mainly before 1935. After 1935 and the discovery by Einstein of quantum entanglement it became wrong to say that in a microscope, a photon could collide with the particle and disturb it. In quantum entanglement, one can measure a moving particle without looking at it directly.
• 11. The Heisenberg microscope analogy was trying to make uncertainty understandable. But it merely complicated uncertainty. It introduced the concept of a collision between a photon and the particle disturbing the particle. This is fundamentally wrong as Bohr told Heisenberg above. This is in effect saying that there is some error in the way things are measured that causes the Uncertainty Principle. There is not. Uncertainty still holds no matter how you measure it, no matter whatever indirect means you use that will not disturb the particle, the measurement is still displaced by the amount of the Uncertainty Principle.
• 12. Anyone that anyone quotes as saying uncertainty is caused by the disturbance of the particle by the measurement is dead wrong and does not understand the Uncertainty Principle EVEN Heisenberg as Bohr clearly showed above in his conversation with Heisenberg.
• 13. Uncertainty arose from data derived from measurements using spectroscopy. Heisenberg did not think the displacement of a moving particle being measured was the fault of the instrument but intrinsic to the universe. Therefore, as Bohr pointed out to Heisenberg, it was wrong to use an instrument model to try to prove the uncertainty principle because the analogy is false.
• 14. The website [9] describes the Heisenberg microscope and says, "Looking closer at this picture, modern physicists warn that it only hides an imaginary classical mechanical interaction one step deeper, in the collision between the photon and the electron. In fact Heisenberg's microscope, although it was a big help in developing and teaching the quantum theory, is not itself part of current understanding. The true quantum interaction, and the true uncertainty associated with it, cannot be demonstrated with any kind of picture that looks like everyday colliding objects. To get the actual result you must work through the formal mathematics that calculates probabilities for abstract quantum states. Clever experiments on such interactions are still being done today. So far the experiments all confirm Heisenberg's conviction that there is no "real" microscopic classical collision at the bottom."
• 15. "Readers are warned that Heisenberg's microscope experiment can be misleading. In particular, students should resist the temptation to believe that a particle can really have definite position and momentum, which, because of the clumsy nature of the observation [as Hiesenberg's microscope suggests that a microscope itself is just a clumsy way to measure things], cannot be measured. In fact, there is no evidence for the existence of particles with definite position and momentum. This concept is an unobservable idealization or a figment of the imagination of classical physicists. ..." -A.C. Phillips. In other words, you can't use Heisenberg's microscope and measure a moving particle and say, "Oops, if I just hadn't knocked that moving particle with a gamma ray photon, I'd know where it is this very minute." The uncertainty principle says you wouldn't know anyway. That's why Heisenberg's microscope is a horrible analogy. AND you can't say, "Well, if I just calculate the exact amount that a gamma ray photon will knock the moving particle, if I just know all there is to know about what a gamma ray photon will do to a particle, then I can just subtract out the amount of disturbance that the gamma ray caused and I will get the exact position of the moving particle before I disturbed it by measuring it with my Heisenberg microscope." NOPE. False. No way. Bad analogy. You can't ever know the position not even if you subtract out the result of hitting the particle with a gamma ray photon. In other words, the Heisenberg microscope analogy is wrong, wrong, wrong.
• 16. Many textbooks and authors misunderstand uncertainty due to the widespread use of the Heisenberg microscope analogy which is dead wrong. Quantum entanglement shows it is dead wrong. There is still uncertainty or displacement in the measurement no matter the method being used to measure. Even if there were such a measuring device as one that could measure a moving particle without using light or wavelengths, say a futuristic device that could measure a moving particle in some other fashion, still the Uncertainty Principle says that the measurement would show a displacement or uncertainty in position meaning a deviation between position and momentum even if no photon hits the particle.

17. Any book or textbook that says that the Uncertainty Principle "distorts" measurement is correct. Any book or textbook that says that the Uncertainty Principle "disturbs" measurement is incorrect. --Voyajer 21:25, 3 January 2006 (UTC)

This boils down to the definition of Uncertainty: "The position and the velocity of an object cannot both be measured exactly, at the same time, even in theory." If I can in theory visualize an instrument that can measure a moving particle without using a photon or wavelength to disturb it, then the uncertainty principle says even then, even in theory, I cannot overturn the uncertainty principle and will still get a deviation of measurement, a displacement, at the minimum of the uncertainty principle deviation of h-bar/2. The key words are "even in theory".--Voyajer 22:31, 3 January 2006 (UTC)

I'm not at all offended by your taking the time to explicate these matters. As I said above, there are at least three different things being called by the same name, and that is always a problematical situation. Two things seem important to me now. One is from a heuristic point of view: Since there is confusion, even among people who should not be confused, it is important for the beginning reader that the distinction between these three be made clearly at the very beginning. I have an idea of one way to make the consequences of quantum uncertainty clear even to the beginner, but I will hold off on that for the time being. The second important thing relates to "politics," i.e., to what one really has to deal with. You mentioned a stiff debate with editors on some discussion pages for other QM articles. Two Wikipedia policies are going to come into play. One is "neutral point of view." When there are several points of view on a subject, the encyclopedia writer may not say, e.g., "Mao's policy and plan for change in China was right. He was a veritable Abraham Lincoln to his people." Nor may one say, e.g., 'Chiang Kai-shek's continuation of the republican revolution would have ended the war with Japan quicker if the CCP had not interfered, and would have brought China out of its little dark ages period more quickly and humanely than ever the CCP could have done. Unfortunately, he was betrayed and reduced almost to insignificance." All the encyclopedia writer can do in the face of strong points of view is to say that Able, Baker, and Carter favor Mao, etc., etc. Dent, Fenton, and Garbo support Chiang, etc., etc. The other policy is "No original research." So you've got to be able to argue from authority, just to get the second point of view into the article. The artful way to achieve an objective account that still manages to make clear what the truth is would be to show the evolution of ideas, criticisms by people of stellar importance of the inconsistencies of lesser lights -- criticisms where they really nail them, and perhaps very nuanced explications by writers such as Messiah who mention "uncertainty of the first type, "uncertainty of the second kind," and "real uncertainty," start out from a position that brings in situations analogous to the Heisenbergs microscope situation and then cast it in light of the third kind of undertainty and thereafter continue to write about the third kind of uncertainty. P0M 01:22, 4 January 2006 (UTC)

• • You should understand that Messiah in saying "uncertainty of the first type" and "uncertainty of the second kind" and "real uncertainty" was not saying that Heisenberg's Uncertainty Principle could be divided into different types of uncertainty. Rather, Heisenberg's Uncertainty Principle can only be explained in one way. And Heisenberg's microscope is not the way. I have quoted several sources that show this very point, all of the highest caliber. However, I could quote hundreds more. I am a researcher and the best sources always say the same thing: Heisenberg's microscope is not a good analogy, presents a wrong viewpoint, and this was argued by Bohr. Messiah is speaking of something very, very, very different. I can't stress that enough. He was speaking about Immanual Kant's views of reality. There is what the universe is and there is what we say it is through our theories. When does a theory become the reality of the universe? When does "uncertainty" become real in this sense? This does not change the definition of the Uncertainty Principle which has only one definition as explained by Bohr to Heisenberg above. Messiah's work is merely a philosophical treatise on whether HUP is real in the Immanuel Kant sense.

Please relax. I am basically agreeing with you, and also to help you deal with any difficulty you may be having getting this matter straightened out in the course of editing other articles. Do you have access to Messiah's two volume Quantum Mechanics? He taught for several years at the French Atomic Energy Commission’s Center of Nuclear Studies at Saclay. He does not mention Kant. Amazon in Great Britain has a brief review of his book: " The books resulted from courses given at the Center of Nuclear Studies at Saclay during the 1950s, and they are esteemed for the clarity and coherence of their presentation." The ISBN is 0486409244. Vol. I, p 142 has some material that supports your position and may add the weight of authority if such is needed.

• • Major attacks on QM have come from Heisenberg's microscope such as Gong's essay. This is rebutted at http://physics.about.com/library/weekly/aa122202e.htm where a Cambridge physicist answers: "This misunderstanding is common, and is unfortunately made worse by the common use of the Gamma ray microscope thought experiment to motivate it to undergraduate students."

• • The Heisenberg microscope is ruthlessly destroyed by Henry Margenau and Leon Cohen. http://etext.lib.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv2-65

Doubtless true. However, Margenau is not above exploring a similar situation and clarifying the components of such an experiment, much as Messiah does. See Robert Bruce Lindsay and Henry Margenau, Foundations of Physics, p. 420ff. I won't quote the entire thing, just enough to let you see that he is taking account of the effects of measurement. (N.B. To say that some meaurement difficulties involve quantum mechanical momentum interactions is not the same as saying that all quantum mechanical uncertainties are caused by momentum exchanges.) He goes on to give those effects of measurement their proper position in the context of general QM theory.

An inequality similar to (9.3-8) was first discovered by Heisenberg, and has been made the basis of a far-reaching and fruitful system of analogies, known as indeterminacy relations...Let it be required, for instance, to determine the coordinates and the momentum of an electron...The electron will, by virtue of the great momentum of short-wave-length radiation, experience a recoil which changes completely its initial state of motion and therefore precludes every possibility of determining it....Is the uncertainty attending the measurement of q conditioned by the destruction of the "state" through a measurement of p? ....In the foregoing statements we have placed the word state in quotation marks, fore clearly we were using the term in its classical sense. Quantum mechanically, coordinates and momentum of an electron do not define its state....Nevertheless it is possible to restate the matter using the correct definition of states in terms of ɸ functions. We shall then have to answer the question: will measurements change the state-function of the system? ....The answer cannot be derived from the postulates given so far, for we have not yet considered the manner in which ɸ functions change in time.....Later (Sec. 9.11) we shall learn how, in interactions where the energy operator involves the time, ɸ functions are modified in time. The answer to our query will then be in the affirmative: quantum mechanical states will change upon interaction with measuring devices.... (I'm leaving out quite a bit here.)....We therefore conclude that the scattering of measurements has its roots in a fact more fundamental than the destruction of states by interaction with measuring devices, namely, in the definition of states peculiar to quantum mechanics.

Margenau is not using Heisenberg's microscope "disturbance" here, but is in fact saying that it is not valid. When he says the "scattering of measurements", he means the distortion of measurements, not the "disturbance by being measured" (which is Heisenberg's microscope) He says the "scattering of measurements" meaning the distortion of measurement, the indeterminacy of measurement, the uncertainty of measurements, is "more fundamental" than Heisenberg's microscope i.e. "the destruction of states by interaction with measuring devices" which is what Heisenberg's microscope describes. Margenau is here saying that "the definition of states" as being "scatter[ed] in measurements" is "peculiar" meaning a singular attribute, a unique characteristic of "quantum mechanics". This quote is still quite a blow to Heisenberg's microscope as a definition of Uncertainty. It is saying that uncertainty is not described by "interactions with measuring devices" which is the very way that Heisenberg's microscope describes them.--Voyajer 17:09, 5 January 2006 (UTC)

• • The destruction of Heisenberg's microscope has come way before me. Detractors use it to show uncertainty doesn't exist because it is such a weak argument and as I have quoted above many articles show Heisenberg's microscope is is not itself part of current understanding. This has been shown over and over again in many forms. My discussions on other talk pages especially with a quantum field physicist did not take long before it was agreed that it is not a part of current understanding. It is know accepted common knowledge among physicists that Heisenberg's microscope is not a correct model of HUP. This is found in several old journals such as ROYCHOUDHURI C 1978 FOUNDATIONS OF PHYSICS 8 (11-1): 845-849: "HEISENBERG MICROSCOPE - MISLEADING ILLUSTRATION". And it doesn't really need to spelt out again and again by me.

One approach would be to ignore the existence of this argument. Unfortunately, probably every high school student has heard some version of the general idea even though the term "Heisenberg's microscope" may never have been encountered. The other approach would be to do as Margenau et al. have done and show it for what it really is.

• • Bottom line: Who needs me to go on quoting reliable sources to believe me that Heisenberg's microscope is not a good analogy? Did everyone see below on "Absolute Zero"? Are there still people out there convinced that my arguments need reinforcing? Because I'm willing to go on debating this until the point is made. What is the point? The Uncertainty Principle is not about disturbing a particle. It exists when a particle is NOT disturbed. --Voyajer 01:50, 4 January 2006 (UTC)

I prefer to discuss rather than to debate. This discussion began with your statement: "I do not believe that the uncertainty principle teaches that the position is 'disturbed' by measurement." The uncertainty principle is just ΔpΔx ≥ h. It comes into play whenever there is a change of momentum or a change of position on the quantum scale. It has application to "cases where quantum mechanical states change upon interaction with measuring devices," and it also has application to "the definition of states peculiar to quantum mechanics." Heisenberg's microscope is not an analogy. It is a thought experiment. It appears, however, to function for many people as a red herring, leading them away from a deeper understanding of QM. It would also seem to serve as a straw man for some people interested in "defeating" QM. I think we should be open to discussing how to head off the objections of people who come to QM-related articles with at least the idea that "quantum mechanics means that measurements always distort what is being measured." I don't intend to find any more historical passages. We probably already have plenty of those. P0M 06:43, 4 January 2006 (UTC)

Distorting measurement and disturbing measurement are two different things. That is what I have been trying to say.--Voyajer 15:52, 4 January 2006 (UTC)

A thought experiment is "an imagined scenario. Our intuitions about the scenario may be incompatible, with what a theory claims about the scenario, forcing us to decide between the theory and our intuitions." A thought experiment example: If you lift a mountain it will take more force than if you lift a pebble. A mathematical equation: F=ma. Which is science? Certainty cavemen could have figured out that lifting a mountain even in thought would be harder than lifting a pebble. Did they have science then? Did they have Newton's laws of motion? Is a "thought experiment" in and of itself a scientific theory? What is science? The uncertainty principle has one formula, therefore, it has one scientific definition. The formula shows that measurement does not commute by h/2pi. There is a measurement error. (THIS IS NOT A DISTURBANCE, but a mathematical deviation in measurement i.e. a standard deviation.) The formula came years before Heisenberg's microscope. Which is science? The thought experiment or the formula? --15:52, 4 January 2006 (UTC)

Heisenberg "He attempted to explain this novel feature through a gedanken or thought experiment, which uses a hypothetical gamma-ray microscope to observe electrons. His original argument, however, is not part of our current understanding of the actual Uncertainty Principle, for it treats interactions between quantum objects somewhat unrealistically, analogous to mechanical collisions of classical particles."--theoretical physicist S Lakshmibala http://www.iisc.ernet.in/academy/resonance/Aug2004/pdf/Aug2004p46-56.pdf --Voyajer 16:28, 4 January 2006 (UTC)

[edit] Any book that says ΔpΔx ≥ h is wrong

The correct formula is ΔpΔx ≥ h-bar and where measurements are made once on each copy of an ensemble the formula is ΔpΔx ≥ h-bar/2. http://www.iisc.ernet.in/academy/resonance/Aug2004/pdf/Aug2004p46-56.pdf page 8 --Voyajer 16:28, 4 January 2006 (UTC)

I believe the problem stems back all the way to 1928 when Dirac's constant (called the reduced Planck's constant) was not signified by h-bar, but was simply written in formulas as h. The writer was obligated to state unequivocally that h in this particular case was not the regular Planck's constant but Dirac's constant. Such a paper exists from 1928 on the web where although all the formulas include simply an h for Planck's constant in the Uncertainty relations, the following stipulation is made:

"We use Dirac's notation in the main, except that we do not designate numerical quantities by primes, and the reader is referred to his paper if desirous of more background for the present article. In particular we use Dirac's h, which is l/2π times the usual Planck's constant 6.55 X 10-27." THE CORRESPONDENCE PRINCIPLE IN THE STATISTICAL INTERPRETATION OF QUANTUM MECHANICS BY J. H. VAN VLECK January 16, 1928-- http://www.pubmedcentral.gov/picrender.fcgi?tool=pmcentrez&blobtype=pdf&artid=1085402

I do not know when h-bar began to be used to signify the reduced Planck's constant, but evidentally in the early years of physics, use of h for Planck's constant and Dirac's constant evidently led to a great deal of confusion and this confusion still holds today as still many scientists themselves confuse h-bar for h in the Uncertainty Principle.--Voyajer 05:04, 5 January 2006 (UTC)

It is comforting to see papers from 1929 on the Uncertainty Principle showing the correct equation. Instead of using h, it uses c so as not to be confused with Planck's constant in its full form. This article is called ON COMMUTATION RULES IN THE ALGEBRA OF QUANTUM MECHANICS By NZAL H. McCoy February 7, 1929 which reads:

"The algebra of the new quantum mechanics is a special form of the algebra of matrices. For one pair of canonically conjugate variables its properties are determined by the assumption

pq - qp = c

, (1) where q and p are matrices which represent the coordinate and momentum, respectively. The value of the constant c plays no part in the development of the algebra although in the quantum mechanics it is assigned the value h/2π. http://www.pubmedcentral.gov/picrender.fcgi?tool=pmcentrez&blobtype=pdf&artid=522434 also correct at http://www.pubmedcentral.gov/picrender.fcgi?tool=pmcentrez&blobtype=pdf&artid=1076216 --Voyajer 05:23, 5 January 2006 (UTC)

[edit] Uncertainty Principle and Absolute Zero

"The temperature at which all classical molecular motion stops, equal to 0 Kelvin or -273.15° Celsius. However, quantum mechanically, molecules cannot cease all motion (as this would violate the Heisenberg uncertainty principle), so at 0 K they still vibrate with a certain small but nonzero energy known as the zero-point energy." http://scienceworld.wolfram.com/physics/AbsoluteZero.html

Okay, this is another example where Heisenberg's microscope does not apply. Is anyone measuring all the atoms in the universe at the same time so that a photon of light is hitting them so that they have an uncertainty of position and cannot reach absolute zero?

In other words, the Uncertainty Principle is applied to the universe even when no measurements are being taken. Therefore, no disturbance is being made to the measurements. The Uncertainty Principle is taken to be fundamental. It says that fundamentally no moving particle can ever have an exact position. Therefore, no moving particle can ever be said to stop its motion. Therefore, no atom can cease motion at absolute zero. This is without measurements being taken to "disturb" the particles. Therefore, Heisenberg's microscope is wrong.

Now, I want to mention this caveat. Heisenberg's Uncertainty Principle will in the near future be either proven or disproved. In creating BECs (Bose-Einstein Condensate) scientists are building better and better instruments to reach absolute zero. When they build one that reaches absolute zero, HUP will either be debunked or raised to the status of absolute law.--Voyajer 00:28, 4 January 2006 (UTC)

• "Heisenberg's microscope is. . . a misleading attempt to “explain” the concept behind a purely quantum mechanical theorem . . . " Chandrasekhar Roychoudhuri. Heisenberg’s microscope—a misleading illustration. Foundations of Physics, 8:845–849, 1978.

• ". . . the consideration of optical analogies — such as . . . Heisenberg’s gamma ray microscope, are mistaken. Indeed, the reasoning in these cases is fallacious because it employs propositions belonging to optics, not to quantum mechanics — e.g. the formula for the resolving power of a lens . . ." Mario Bunge. The interpretation of Heisenberg’s inequalities. In Heinrich Pfei®er, editor, Denken und Umdenken. Zu Werk und Wirkung von Werner Heisenberg, pages 146–156. R. Piper & Co. Verlag, M¨unchen Z¨urich, 1977.

• In their (Mara Beller and Arthur Fine.) Bohr’s response to EPR. (In Jan Faye and Henry Folse, editors, Niels Bohr and contemporary philosophy, pages 1–31. Kluwer, Dordrecht, 1994,) Beller and Fine convincingly show the difficulties one runs into if one tries to salvage the idea of disturbance causing the validity of the uncertainty relations. "The concept of disturbance, inaugurated in Heisenberg’s uncertainty paper, is an ill-fated and inconsistent one..." Mara Beller, Quantum Dialogue. The Making of a Revolution. University of Chicago Press, Chicago, 1999.

• The greatest most profound proof that uncertainty is not the result of a disturbance is from Einstein, himself, who inadvertently invented quantum entanglement for quantum mechanics. The idea of disturbance causing the uncertainties is not only incoherent, in 1935 it was also shown to be false, on the supposition that all disturbances propagate locally, in the famous EPR thought experiment. "Rosen , Einstein and Podolsky imagined two particles S and T that had spent some time in close interaction, so much so that they became thoroughly causally entangled: knowing the behavior of S would give complete information about the behavior of T, provided that the state of S could be measured without disturbing the state of T." No disturbance, yet measurement = uncertainty principle (is not equal to) Heisenberg microscope.

--Voyajer 04:47, 4 January 2006 (UTC)

In conclusion, Heisenberg's microscope was invented as allegory, not as a real interpretation of Uncertainty. It was a device subtlely trying to discredit Schroedinger's wave equation. It's use is not to define Uncertainty but to make it visual in an imaginary classical sense, but loses all real meaning of Uncertainty. The Uncertainty principle is defined by the formula. The formula came in the form of Matrix mechanics in 1925. In 1927, Heisenberg showed that matrix mechanics formulae describe the Uncertainty Principle. Matrix mechanics had been attacked by Schroedinger as being unable to visualize. Heisenberg countered with Heisenberg's microscope, but the analogy was not meant to be a real picture of the formula. The formula is real Uncertainty. Heisenberg's microscope is not. The formula is not about disturbance. The end.--Voyajer 04:53, 4 January 2006 (UTC)

Aaah, Patrick, I see why you won't budge. You wrote the article Heisenberg's microscope as if it is truly scientific and truly represents the Uncertainty Principle and is truly part of current understanding. It has been known to be incorrect since 1935 from a scientific standpoint. It is fine as far as metaphysics go. It is even good to look at to show Heisenberg's frame of mind when he wrote it since he was clearly trying to attack Schroedinger's wave mechanics. It is however not a scientific explanation of Uncertainty since it does not describe the formula. You should say so in your article perhaps quoting theoretical physicist, S Lakshmibala, at http://www.iisc.ernet.in/academy/resonance/Aug2004/pdf/Aug2004p46-56.pdf -- It is important not to be misleading in encyclopedia articles. It is important to show integrity. The Uncertainty Principle is about a distortion in measurement not about a disturbance in measurement.

You write in your Heisenberg microscope article: "The result of this thought experiment has been formalized as Heisenberg's Uncertainty Principle." Horrible, horrible. The Uncertainty Principle was not the result of some thought experiment. It was the result of mathematics. The formula came first. The thought experiment was "an after-thought". --Voyajer 16:40, 4 January 2006 (UTC)

[edit] Positives

Voyajer and company, I like the article I see. Congratulations to all of you. --Ancheta Wis 21:01, 8 January 2006 (UTC)

Thank you, Ancheta Wis, but could you put this on the "leave feedback" for the nomination? I think it would help.--Voyajer 05:16, 9 January 2006 (UTC)

[edit] Picture of spectrum has been put in for removal by

Please also note I have listed the spectrum image for deletion for being Education license. (I don't see it justify FU either.) -- KTC 22:41, 8 January 2006 (UTC)

This is from "leave comments" on nomination.

Any who believe that this is a quality article please help me object to opposition to the nomination by clicking on "leave comments" in the above gold box.--Voyajer 05:55, 9 January 2006 (UTC)

Actually, while the spectrum image is pretty it is too small to be helpful. It is a constructed image, which makes it a little dubious as well, i.e., I would rather see the real absorption lines, not a picture that somebody has made to show me where they ought to be. That being said, I don't see why the permissions on the original image would prevent its being used in Wikipedia. If we can't get a better image maybe we need to communicate with the creators and get them to put it on the Commons. P0M 21:02, 9 January 2006 (UTC)

[edit] It appears that in nominating the article it may be deleted

There appears to be strong opinion that the article is a fork. I am arguing that it is a completely separate article from Quantum Mechanics main article. --Voyajer 17:03, 9 January 2006 (UTC)

[edit] Removed one phrase

In the section on h-bar, there was a sentence comparing circles, which have 2 pi radians, with cycles "each having 180 degrees." I think originally it must have been intended to say that each half of a sine curve has 180 degrees. Anyway, I couldn't figure out exactly what was going on so I tried to rephrase it. Please put it back right if I misinterpreted something. P0M 06:59, 16 January 2006 (UTC)

[edit] Electron microscopes are not for examining electrons

The text currently says:

Bohr basically theorized that electrons can only inhabit certain orbits around the atom. These orbits could be derived even before the 1931 development of the electron microscope by looking at the spectral lines produced by atoms.

Is the electron microscope in any way relevant to knowledge about orbits of electrons? Unless there is some devious way that this works out, the above sentence will need to be removed. P0M 18:09, 16 January 2006 (UTC)

[edit] How can energy be caused?

The text currently mentions "the magnetic moment of the orbital, which is a type of energy caused by the charge of the electron as it rotates around the nucleus." Energy is not caused. Do you mean to speak of "force exerted"? P0M 07:57, 20 January 2006 (UTC)

[edit] images of line spectra

Will this work? Except that I should change "spectra" to "spectrum" and re-upload. P0M 01:34, 21 January 2006 (UTC)

[edit] electromagnetic waves

I am happy to see "electromagnetic waves" so near the start. In the Feynman Lectures, he brings up, at the start, that what one (the student) gains at the cost of complex wave functions and other difficulties is that the same principles now apply to "electrons and to light". This not only motivates the student, it also automatically doubles (at least) his learning rate, because he is learning the same things about what he perviously thought were two different subjects. David R. Ingham 06:29, 1 February 2006 (UTC)

The change you created from electromagnetic_waves to waves had consequences that may be problematical. Did you intend to produce these changes in what the user would see when s/he clicks on the link? Please be careful. P0M 07:03, 1 February 2006 (UTC)

Because my strong point is technical depth, I am being careful not to make this article, also, too technical. I don't think this change did that. If my change conflict with some other part, then I suppose that part will need changing also. Since this article does not refer in the first paragraph to electromagnetism as the quantum mechanics article does, the word electromagnetic seems unnecessary. I think I changed it to be both briefer and more general. (Messiah makes the point that quantum mechanics wouldn't make sense if there were anything that was not quantum mechanical in the world.) This prepares them to learn that waves and particles are not two different things, but aspect of the same things.

I took the liberty of generalizing one more step to waves, but the concept "everything" is not esoteric. I put it to my bright 10 year old niece (and her mother) when she asked what an atom was: "When you keep looking through stronger and stronger microscopes, you don't keep on seeing more and more detail forever. Matter is composed of units called atoms and motion is composed of units called quanta." ("Units" may not be the best word.) Of course one can not be so ambitious talking to students or writing an encyclopedia as when talking to one's own family because they are less likely to pay close attention. Also "motion" doesn't go very far, either, toward explaining what quantum mechanics is about. It is about everything.

I can't remember which of my professors told me that students without "flexible minds" do not like quantum mechanics "because they have already learned much classical physics". This was a surprise to me, because I had been exposed to quantum concepts early and had always thought of classical physics as an approximation. Even so, I was somewhat surprised to hear of phonons. David R. Ingham 18:01, 1 February 2006 (UTC)

When you destroy one link and create a new link, please be sure that the new link goes somewhere useful. Did you try your new link yet? P0M 21:49, 1 February 2006 (UTC)

Thanks, POM. I fixed it. I don't know why it was "electromagnetic waves" but the more general article is called "wave". David R. Ingham 04:16, 2 February 2006 (UTC)

Speaking of what would be good for a viewer to see when they first visit this article, could we do something with the caption of the top image? "Quantum Mechanics" may have something to do with each of the parts of that collage, but it seems like this image will do more to confuse than clarify. I was confused, and I'm a physics grad student! My vote is replace it with something simple; perhaps a picture that shows some quantum mechanical behavior that can be summarized in a short caption. If I had no background in physics, this image wouldn't give me any reason to read on except dispell the confusion it creates. JonPaul 06:00, 2 February 2006 (UTC)

Anything--as long as it is not a smeared cat! ;-) P0M 08:52, 2 February 2006 (UTC)

[edit] "mathematical"

I think that is the wrong term for that other article. The Born approximation article is mathematical. How about "deeper" or "more technical". I think "advanced" would also be too strong. David R. Ingham 18:06, 1 February 2006 (UTC)

[edit] "Its success is due to its accurate prediction"

There is something wrong with this choice of words. "Measured by"? David R. Ingham 05:48, 2 February 2006 (UTC)

The problem derives from anthropomorphizing a theory. How about, "Its widespread acceptance is due to its accurate prediction..."? P0M 09:05, 2 February 2006 (UTC)

The two things are the same. It is a succes means it makes accurate predictions which means it is a success. String theory is not a success, even though it is very popular. The solution is to remove one of the repetitions. --MarSch 11:12, 2 May 2006 (UTC)

[edit] "inconsistent with the consequences of other successful theories"

There may be difficulties with general relativity, but does this belong in a discussion of the basics? Are people reading this assumed to be versed in the subtleties of general relativity? Should not they be told that it agrees with every test to at least the precision of usual floating point computer arithmetic first? David R. Ingham 07:01, 2 February 2006 (UTC)

I will await news from Voyajer about what he was really trying to say. I doubt he was referring to difficulties with general relativity, which would indeed be irrelevant here. Instead, I this maybe that vague sentence had something to do with places where relativistic factors have application to atomic scale events and the consequences for QM have not been worked out. P0M 09:17, 2 February 2006 (UTC)

[edit] "This appeared to raise a contradiction when compared to sound waves and ocean waves, where only intensity was needed to predict the energy of the wave."

This may be historically correct but it is misleading to a student, because it implies that sound waves are not compose of phonons, which they actually are. David R. Ingham 07:11, 2 February 2006 (UTC)

Otherwise, the discussion of the history of the understanding of light seems very good to me. David R. Ingham 07:22, 2 February 2006 (UTC)

"not, however, speaking of sound waves," repeats this pedagogical error. David R. Ingham 07:55, 2 February 2006 (UTC)

The same objection can be made to the use of the word "particle". David R. Ingham 08:01, 2 February 2006 (UTC)

Are you saying that frequency of sound waves determines the force with which they strike solid objects? A photon either does or does not dislodge an electron depending on its frequency. Does a sound wave either displace or not displace an eardrum depending on whether its frequency is high enough?

There is indeed a problem with both the terms "wave" and "particle." They are both macro-world terms imported to refer analogically to things that happen at the atomic scale, and they encourage us to mis-think things. If a bobber jiggles up and down in a pond, then a series of circular waves will radiate out from the location of the bobber. It never happens, as far as I know, that a sort of solitron makes its way across the pond in a straight line and disturbs only things along that line. But electrons make a single track across a cloud chamber. They don't ripple through all the fog in an expanding circle. P0M 09:35, 2 February 2006 (UTC)

[edit] Old quantum theory, and so on.

One thing about which I disagreed with my thesis advisor was the historical approach in his text books. I have later become more interested in the history of physics, but it seemed a bother to an enthusiastic student who wanted to know about nature and not about human history.

With the exception I wrote above, I think the history of light is fine. But let us work towards having most of the history on one section and the rest pure physics. That may be quite hard, but there is no schedule of budget to meet. David R. Ingham 07:48, 2 February 2006 (UTC)

In fact, I see so much history, that I suggest that this article be re-named "Early history of quantum mechanics" and a new article be started entitled "Basics of quantum mechanics", with some rule limiting use of history. It need not be more than a few sentences at first. That is all that most readers will read, anyway, or will remember, even if they try to persist. David R. Ingham 08:41, 2 February 2006 (UTC)

IMHO there's too much history in this article. For newbies to the subject the historical development is completely irrelevant and may actually hinder comprehension. It should placed in an entirely separate article. --Michael C. Price ^talk 22:48, 15 October 2006 (UTC)

[edit] "We cannot see photons"

This may be OK, but the dark sensetivity of the eye is not so much less that one photon. David R. Ingham 08:17, 2 February 2006 (UTC)

We have a physiological reaction to the impact of light quanta. We "see" the burning match, however, not the photon. What would a photon look like? We have even less possibility of seeing a photon than we have of seeing an electron. If I have a camera with an ultra-fast shutter and very sensitive film I may be able to photograph a bullet from the side as it travels from a gun to a target, but that's because light strikes the bullet and gets reflected into my camera lense. I can't shine light on a photon travelling from a laser pointer to a movie screen. As far as our experience of photons goes, we are more like the shooter who pulls the trigger and then sees a hole appear in the target. P0M 09:43, 2 February 2006 (UTC)

[edit] "Fourier series"

If the version called "mathematical" above does not have to introduce Fourier series, why do so here? David R. Ingham 08:21, 2 February 2006 (UTC)

I'm not sure of this, but I think it may have been an attempt to explain the prevalent use of h-bar (Dirak's constant) instead of h. To me it seems to be a mistake because both h and h-bar are conversion factors. The salient facts are that energy and frequency are proportional, and that they can only come in integer units. P0M 10:07, 2 February 2006 (UTC)

[edit] "standard deviation"

I don't like introducing this statistical concept. As far as I know, it is not really mathematics or statistical mechanics. It is not a basic concept. If it is really needed, how about speaking in terms of the Gaussian function and some simplified version of Fourier transforms (which I objected to above). David R. Ingham 08:52, 2 February 2006 (UTC)

[edit] "Schrödinger's equation then fails" ?

Quantum mechanics has never failed when a full quantum mechanical calculation has been possible. There may still be meaningful discussions but they are not "basic" in the sense of elementary. An article with this title must accept quantum mechanics as a fact or be counted with the "intelligent design" nuts. David R. Ingham 09:09, 2 February 2006 (UTC)

I agree that this formulation is unsatisfactory. It's like the "success" mentioned above, an example of anthropomorphizing that is asking for trouble. The problem is the old one of how to describe the so-called "waveform collapse." Between the time the "photon cannon" is fired, and the time that a "hole" appears in the target somewhere, if we are talking about a double-slit experiment for instance, the equation tells us what it tells us between times, and then we get a "hole" at a location that we can predict with high statistical success. Afterwards, people try to figure out ways that some additional factors could act to determine at which point on the target the hole will appear. The "materialization" of a hole in the wall is not a failure of Schrödinger's equation, it's just what happens when we've ridden that horse as far as it will go. P0M 09:59, 2 February 2006 (UTC)

Let us not discuss the subtleties of the relationship between qm and its classical approximations here. That is part of the reason that I am for taking almost all of the history out. For a basic understanding and for many applications these subtleties are not necessary or useful. That subject isn't even covered well in the main qm article yet, and is much too advanced for here. We should stick to explaining how quantum mechanics itself describes the world. As long as one sticks to simple systems that can be calculated purely in quantum mechanics, there is no "waveform collapse." David R. Ingham 21:16, 2 February 2006 (UTC)

Please try to work on the article and straighten out as many miswordings as possible. I do not agree with your point of view, and you do not agree with mine. Voyajer has a third point of view that has to be taken into account. Trying to lay out fiats about what can and cannot go into an article is not going to be helpful, in my opinion. P0M 21:46, 2 February 2006 (UTC)

I still think that we should rename this article "Early history of quantum mechanics" and start over, talking mainly about physics instead of about history, and glossing over the difficulties involving classical physics and ordinary language. These are in no way central to quantum mechanics. I suggest starting by trying to simplify early parts of the third volume of the The Feynman Lectures on Physics. He was an awesome teacher. I heard him when I was in high school and was amazed to learn so much so quickly. I think this is consistent with Carl Wieman and Katherine Perkins, "Transforming Physics Education" - Physics Today, November 2005.

After reading Feynman give educational research as his first example of "Cargo cult science" in Surely You are Joking Mister Feynman, I was hesitant to take the above reference seriously until I noticed that one of the authors was, like Feynman, a co-recipient of a Nobel prize. Their simplest lesson is not to grade students on applying formulas in the same way that the formulas were taught, because that makes them think that physics is plugging numbers into formulas. We don't have exactly that problem here, because there are no formulas. Their spirit is to make physics education have the same flavor, on a smaller scale, as research, that is intuitive and creative.

Then there is the question of, aside from the lack of homework and tests, how an encyclopedia should differ from a text book. In my opinion, the first goal is to help someone who does not already know qm to learn enough to use it in a simple way, or to see whether it is relevant to his problem. I don't see how history contributes much to that. For example the optical communications engineer who is working on quantum noise and needs to understand it better, or an electron device engineer who is reaching the scale where electron transfer across P-n junctions is beginning to be coherent. David R. Ingham 07:08, 3 February 2006 (UTC)

I will think about your idea of splitting the article. We are already accused of being a "fork" of the main article. On the other hand, this article is getting long.

There are many more statements like the one that says that the "equation fails." I usually can understand what Voyajer was trying to say, but I do not like to guess. When I have complained about some of these things on this discussion page he has not responded, and, so far, when I have changed things he has not reverted. I don't have time to list more problems at this moment, but I'll come back to the problem later today. We can surely make progress on improving the present version to the point that it is clear, and then decide (or discover in the process) what to do about the slant of the article. One place, off the top of my head, where we could make things easier both for the beginner and the mathematically inclined, is to make it clear that the numerical value of Planck's constant could be 1 if we did not restrict ourselves to arbitrarily determined units such as the foot and the meter. There is a long section on h and h-bar that is intended to immunize readers against psychological trauma upon seeing these two "crazy and mysterious" numbers. P0M 16:07, 3 February 2006 (UTC)

[edit] Fork

One criticism I do not agree with is that this is "a 'fork' of the main article". In school, qm is taught on many levels. It is too complicated and too important to be covered, even in a fairly elementary way, in a single article. I believe that some of the basic concepts, like a foreign language, are most easily absorbed at an early age. David R. Ingham 17:53, 3 February 2006 (UTC)

[edit] Spork

What would this article look like if we not only took the history part out but also avoided the seemingly mysterious h and h-bar? They are just conversion factors anyway. Has anybody actually figured out the wavelength corresponding to the lowest possible frequency? I suspect I've been indoctrinated by reading too many secondary sources that say that the energy of a photon has to be some multiple of h. That never seemed right to me. First, it does not seem to have any connection to experimental determinations of energies. Energies and frequencies are found, and then h is computed. Second, I can't think of any reason why there should be any limit on wavelength -- although there might be practical difficulties in creating or finding radiators beyond a certain length. ELF seems to have been detected down to a few hertz on earth, but Earth is a relatively small place.

You mentioned Fourier expansions above. I don't think you can get rid of them so easily. In Physics and Philosophy, p. 38f, Heisenberg says:

p. 38: “The precise mathematical formulation of quantum theory finally emerged from two different developments. The one started from Bohr’s principle of correspondence. One had to give up the concept of the electronic orbit but still had to maintain it in the limit of high quantum numbers, i.e., for the large orbits. In this latter case the emitted radiation, by means of its frequencies and intensities, gives a picture of the electronic orbit; it represents what the mathematicians call a Fourier expansion of the orbit. The idea suggested itself that one should write down the mechanical laws not as equations for the positions and velocities of the electrons but as equations for the frequencies and amplitudes of their Fourier expansion. Starting from such equations and changing them very little one could hope to come to relations for these quantities which correspond to the frequencies and intensities of the emitted radiation, even for the small orbits and the ground state of the atom. This plan could actually be carried out; in the summer of 1925 it led to a mathematical formalism called matrix mechanics or, more generally, quantum mechanics. The equations of motion in Newtonian mechanics were replaced by similar equations between matrices; it was a strange experience to find that many of the old results of Newtonian mechanics, like conservation of energy, etc., could be derived also in the new scheme. Later the investigations of Born, Jordan and Dirac showed that the matrices representing position and momentum of the electron do not commute. This latter fact demonstrated clearly the essential difference between quantum mechanics and classical mechanics.

If we are going to keep everything neat and consistent, shouldn't we go with the Dirak formulation that folds Heisenberg and Schrõdinger together? We would in any event need a clear example of matrix multiplication and how it can work out to be non-commutive. P0M 22:32, 4 February 2006 (UTC)

[edit] An unusual teaching experience

I once had the privilege, with another physicist, of explaining quantum mechanics to a mathematician. (We were working on radar but had time to talk.) We started in the usual qualitative way that it is taught, in ordinary language, but he didn't seem to comprehend. Then we started to remember how to express it in terms of Hilbert spaces, and it quickly became clear to him. David R. Ingham 07:30, 3 February 2006 (UTC)

I suspect that one of the reasons that this and similar articles are hard to formulate and hard to agree upon is that our verbal formulations of "wave" are tied too much to the everyday world. Heisenberg, op. cit., p. 39, says that Schrödinger "succeeded in deriving the energy values of the stationary states of the hydrogen atom as 'Eigenvalues' of his wave equation and could give a more general prescription for transforming a given set of classical equations of motion into a corresponding wave equation in a space of many dimensions." I have another mention somewhere, in one of Sears's physics texts I believe, that specifies that these waves are not in normal 3-D space. I think Sears uses the expression "configuration space." P0M 22:43, 4 February 2006 (UTC)

[edit] "physical science"

I changed "mathematical". (See above.) That was a poor word to describe the quantum mechanics article, which suffers greatly from being written in ordinary language, rather than in linear algebra.

"Physical science" isn't right either. It could be called a theory or a branch of physics. Early in the 20th century, the word would surely have been "theory", but now qm is more like a "cornerstone" that underlies most of physics. David R. Ingham 17:31, 3 February 2006 (UTC)

[edit] Point by point

It is important that the individual sentences in an article actually mean what they were intended to convey. The following sentences are problematical: (P0M 23:40, 3 February 2006 (UTC))

[edit] Points corrected

• By means of the gold foil experiment physicists discovered that the nucleus was at the center of the atom.

The nucleus was not previously imagined to be at the periphery of the atom. What the experiment discovered was that matter is, volume for volume, largely space. Once that was clear, it was hypothesized that negative charge entities called electrons surround nuclei with positive charges.

Old "plum pudding" view vs. new view of small-volume positive charge surrounded largely by space.

• The way that Bohr quantized the orbits of the electrons was by assuming that the angular momentum of each of the orbits was derived from the value of h, Planck's constant.

This odd way of conceptualizing things makes it seem that a mathematical operation determines the path that an electron takes. That formulation is flawed. Orbits go wherever orbits go, and humans come along later and use math to explain why they go there. Bohr explained the orbits that electrons can take by relating the angular momentum of each "permitted" orbit to the value of h. The ground state, i.e., n = 1, has a theoretical angular momentum = h/2π.

• Specifying that the frequency of each orbit must be an integer multiple of Planck's constant h would only XXX certain orbits, and would also fix their size.

Obviously something has been omitted from this sentence. I assume it is "permit." This sentence, too, seems to put the physicist in the position of God, determining what electrons should do in their flights by the mathematical magic of science.

• Therefore, the number of orbits per second of the electron around its nucleus would create a frequency.

Literally, this sentence says that a number creates a frequency in nature. That explanation is almost solipcistic in character. The intent behind the sentence would seem to be to say that the number of revolutions per second is (or defines) what we call the frequency of that electron or that orbital.

• In Heisenberg's matrix mechanics, the sets of numbers were infinite representing all possible positions of the electron and those sets when multiplied together could not be multiplied in reverse order and equate.

I think that this sentence is probably o.k. except that it is not correctly punctuated.

• Bohr found that the first allowed orbit, called K, was equal to 1/2π.

That's totally wrong. The problem is that in the article this statement was based on, "K" means two things. It's a constant that turns a proportion into an equation at one point, and it is the name of the K orbit.

• In accord with de Broglie's conclusions, in Bohr's atom the orbit is only stable if it meets the condition for a standing wave.

Once again the writer phrases things as though theory determines reality. This psychological condition is akin to solipcism. Bohr theorized that electrons can only appear under conditions that permit a standing wave.

• Angular momentum measures an object's tendency to continue to spin.

Wrong. The rate of change of the angular momentum of any system is equal to the resultant external torque acting on that system. If there is no external torque, the object will continue to spin.

• He came up with a wave equation that describes each electron as having a wavefunction. He thus showed that the atom was not at all like a miniature solar system, but that the electron in a hydrogen atom was more like a wave that covered the entire sphere of its orbital all at once meaning it was three-dimensional.

Again, which comes first, the model or the phenomena in nature that are being modeled? "He came up with a wave equation" describes finding one way of modelling what happens in nature. Coming up with a model does not establish what nature has to be like, but the text says that "He thus showed that the atom was not like a miniature solar system..." Sorry, but the empirical facts do not follow from the model that we create. What it is, in nature, that indicates that an electron is not restricted to an orbit that resembles the orbit of a planet around a sun is not stated.

• However, Einstein's challenge brought along with it decades of substantial research into this quantum mechanical phenomenon of quantum entanglement.

Following the above, the "however" part is confusing and misleading. And "brought along with it" suggests to somebody who does not know the history that Einstein (metaphorically) carried onto the debate stage years and years of prior research on entanglement. What the sentence should say is not that it "brought along with it" but that it "led to" decades of research.

• In Heisenberg's quantum mechanical mathematics, the normal multiplication law of commutation where A x B = B x A does not apply for matrices A, B; in this case, the commutator AB-BA is not zero.

I don't see any problem with this statement, at least not as long as I have on heavy enough glasses to see the semicolon. But for people who do not know what matrix notation is all about it is not going to be meaningful, and for people who are familiar with matrices it probably isn't going to provide any new information. We should be able to come up with a concrete example whereby the average reader could see and understand the operations behind the symbolism and understand why doing operation X and then doing operation Y produces a different result from doing operation Y and then doing operation X.

I think this sentence has been ironed out now.

• However, the fundamental packet of energy in a photon is some multiple of h describing a vibration having one quantum of energy.

Is this statement really correct? The original observation was that E is proportional to v (frequency). H is a conversion factor. Why does a conversion factor become a fundamental unit of energy? Why would there be a longest possible wavelength (for other than practical reasons)? Are there tiny black lines between permitted frequencies in a white-light spectrum? If a frequency of 3+ 10¹⁸ hertz is permissible, but 3.0001 + 10¹⁸ hertz is not permissible, what happens when light of 3+ 10¹⁸ hertz is red-shifted? Are the orbitals for atoms of different elements entirely dependent on the charge of the nucleus? Or does the mass of the nucleus have an effect? If mass has an effect, then it matters that the mass of atoms high on the periodic table is not a simple multiple of the masses of single protons and single neutrons because of the so-called "packing effect." P0M 09:05, 5 February 2006 (UTC)

The granularity of radiation appears to depend on the found nature of the orbitals. The angular momentum of the lowest energy electron is a kind of natural constant. Electrons "jumping" from higher orbitals to lower orbitals will emit photons depending on the difference in energy of the two orbits. But how about the photons emitted by an electron fired at a target from a remote source? Is the spectra of these photons continuous or discontinuous? P0M 15:17, 6 February 2006 (UTC)

When a metal target is bombarded with electrons that have been accelerated through some considerable potential (say 5-50 kV), one obtains what is called bremsstrahlung (German for "deceleration radiation'). The spectrum of this radiation is continuous and covers a wide reange of wave-lengths.

-- An Introduction to Quantum Physics, French and Taylor, MIT intro physics series, Norton. p. 21

The statement in the article is a good example of mistaking the map for the territory. It must be changed.

[edit] Points remaining

• Bohr considered one revolution in orbit to be equivalent to one cycle in an oscillator (as in Planck's initial measurements to define the constant h) which is in turn similar to one cycle in a wave.

The part in parentheses is not well stated. I suspect it was intended to convey the idea that Bohr conceived of one revolution of an electron as equivalent to one cycle in the operation of a mechanical oscillator, and that this conceptualization is analogous to the way Planck conceptualized atomic processes and then calculated the value of h on that conceptual basis.

• Full quantum mechanical theory (section)

This entire section needs to be rewritten. It starts out talking in terms of matrices, jumps back without warning to a description of what Heisenberg was supposedly doing and thinking (with giving citations), and then explains that Heisenberg was put onto matrix mathematics. The usual "solipcism" seems to be present here too. What is possible or common in matrix math does not determine what nature does.

I've made some progress with the "mystifying" nature of matrix mathematics. Unfortunately, I don't seem to have the right books to locate the actual matrix formulation that Heisenberg made, so getting it right is going to be difficult. The section still needs to be reorganized so that the timeline doesn't double back upon itself. P0M 08:24, 11 February 2006 (UTC)

• However, the spectral lines of the atom reveal the orbits of electrons and the energy that can be expected.

False and misleading to the general reader. We can draw conclusions from the spectral lines because we can use them to compute the frequencies of the light that is emitted by excited electrons of some elemenet. Given the frequencies we can make models that would account for the observed frequencies. We have reason to be quite confident about the model we have produced. The theory has been validated time and again, and nothing suggests that our model is inappropriate. But we have never had the orbits revealed to us. The text above almost makes it seem like the spectral lines are some kind of projection of the orbits themselves. Who knows what false conclusions the average well-informed reader will draw when given a badly worded account?

• Albert Einstein rejected Heisenberg's Uncertainty Principle. Heisenberg's quantum mechanics based on Bohr's initial explanation became known as the Copenhagen Interpretation of quantum mechanics. Both Bohr and Einstein spent many years defending and attacking this interpretation. After the 1930 Solvay conference, Einstein never again challenged the Copenhagen interpretation on technical points, but did not cease a philosophical attack on the interpretation, on the grounds of realism and locality.

This passage is misleading. First, it creates the impression of there being an argument from authority against Heisenberg's Uncertainty Principle. The great Albert Einstein rejected it. Then there is a rather vague depiction of the Copenhagen Interpretation. Then it says that after the Solvay conference stopped attacking it "on technical points." I suppose that this phrasing is intended to indicate that Einstein accepted the math and the experimental results that corresponded to it -- the inability of humans to pin down both position and velocity for instance, but that he continued to attack it on "philosophical" grounds. What troubled Einstein was the possibility that it wasn't just that humans could not simultaneously pin down velocity and position, but that there might not actually be a position and velocity for something like an electron the way there is for a golf ball being whacked down the fairway. What troubled Einstein was the possibility that it wasn't just that humans did not have access to hidden variables that determine at which point a photon in a dual-slit experiment will hit a target, but that there are no hidden variables and it really is a matter of "chance" at which point the photon will show up.

Saying that Einstein objected "on the grounds of realism and locality" is going to be totally meaningless to the average well-informed reader. Was Heisenberg in the wrong country? What was wrong with his locality?

• Bohr's original response to Einstein was that the particles were in a system.

What is that statement intended to convey? So what if entangled particles are "in a system"? Bohr surely had good reason for whatever he said, but the person who has not read Bohr's original words will not have a clue.

• This research clarified by Yanhua Shih points out that the two entangled particles can be viewed as somehow not separate, which removes the locality objection[20].

No. The problem is that everything we know about from macro-world experience tell us that things either influence each other by "direct" contact (you shove my shoulder and I bounce off the wall) or by delivery of energy by ordinary physical processes -- you shoot me with a .45 slug or vaporize me with a military laser. Either way, I have a brief grace period before I die. "There is no action at a distance" -- in the sense that what I do here has to be transmitted by movement of energy across space-time, I can't click my fingers here and have somebody near Alpha Centauri die of a deadly hex at that very instant. So we expect that changing something "here" takes some time to affect something "there." That is what everything in our human experience tells us is true.

Of course, if we want to make the above statement "correct" then we can change the meaning of the word "separate," which, I guess, is what "somehow not separate" is intended to do. One entangled electron is in a vial in my pocket and the other entangled electron has been travelling for all the hundred years of my lifetime at a hefty fraction of c, but... they are not "separate" and when I measure some characteristic of the electron I can be sure that the corresponding characteristic of the other electron will be found to be its counterpart. (Of course I'll have to stay alive long enough for the remote space ship to send back a message at light speed confirming the "hit.") Word play aside, the experiment fact appears to be that doing something to one electron is also doing something to its counterpart and no part of that action is mediated by physical processes of the ordinary sort. So it doesn't take a time interval of d/c to have something happen.

Having looked at the paper by Shih, I was unable to find a clear statement that the locality objection is removed. The entangled photons are justifiably considered as one "biphoton", but I cannot find an instance of this strong statement in the paper. If Shih ever made it, I believe he would have highlighted a conclusion such as this! Zaiken 05:02, 4 December 2006 (UTC)

I did not look at the Shik paper but what was reported in the article was merely that Bohr was right all the time, so I've removed that reference.Gill110951 11:35, 6 December 2006 (UTC)

• This means that no matter the distance between the entangled particles, they remain in the same quantum state so that one particle is not sending information to another particle faster than the speed of light, but rather a change to one particle is a change to the entire system or quantum state of the entangled particles and therefore changes the state of the system without information transference.

Right -- if by "information transfer" you mean information carried by physical processes like light propagation.

• In May 1926 Schrödinger published a proof that Heisenberg's matrix mechanics and Shroedinger's wave mechanics gave equivalent results: mathematically they were the same theory. Both men claimed to have the superior theory. Heisenberg insisted on the existence of discontinuous quantum jumps in his particle-like examination of the oscillation of a charged electron giving more precise definitions and Schroedinger insisted that a theory based on continuous wave-like properties which he called "matter-waves" was better.

This part might represent the facts of an irrational belief, but on the surface it is nonsense. If the two theories are the same then how could one theory be superior to the other? The assertions about what Heisenberg thought and what Schrodinger thought are not properly supported by citations.

I understand that it was von Neumann (a mathematician) who succesfully merged (and showed compatible) Heisenberg's (a physicist) matrix mechanics and Schroedinger's (a physicist) wave-mechanics; moreover the Schroedinger-picture and the Heisenberg picture are also mathematically equivalent (does the state change and the observables remain fixed or vice-versa?). In order to complete his program von Neumann single handedly discovered/invented most of the modern spectral theory of (possibly unbounded) self-adjoint operators. His results finally put both Heisenberg's and Schroedinger's approaches on firm and compatible footings and moreover legitimized a lot of till then heuristic physicst's notations, arguments and computations. His work was summarized in his magisterial book of 1932.Gill110951 11:35, 6 December 2006 (UTC)

I've had these problems up for several days now, with no comment from other editors. I will continue to try to (a) figure out what the original intent was and (b) check and correct what I can. P0M 16:36, 9 February 2006 (UTC)

[edit] Doesn't make sense

Planck's Constant "which predicted that radiation emitted by a heated object should theoretically be infinite, he started with a completely different basic premise: What if energy is not infinitely divisible?"

Coudn't the radiation emitted by heated object be infinite and the energy emitted be not infinitely divisible. There could be infinite packets of energy.

The problem was to make a theory that would predict the correct, moderate, amount of radiant energy output. Maybe what you are complaining about is another instance of a kind of "solipcistic" account that seems to say that theory determines reality. I'll check the remark you quoted in context.

Reduced Planck's constant Error : "So, dividing h by 2 π describes a constant that, when multiplied by the frequency of a wave, gives the energy in joules per radian per second. And h/2 π is h-bar or \hbar = \frac{h}{2 \pi} \."

Unit of hbar is Joule second per radian and unit of \hbar multiplied by frequency is Joule per radian.

Let's see. What is w/(y/z)? Isn't it wz/y? The units for h should be Jouleˑsec,

h-bar = h Jouleˑsec/2π = h Jouleˑsec/radian -- But isn't that = h Joule/(radian/sec)? P0M 06:47, 21 February 2006 (UTC)

Since the meaning is the same and the Jouleˑsec/radian formulation is a bit cleaner, I have changed that part. P0M 04:02, 23 February 2006 (UTC)

Uncertainty Principle "measurement of uncertainty as to the position of a moving particle is one-half the width from the crest to the trough or one-half of one radian of a cycle in a wave."

Isn't the width from crest to the next trough \pi radians. So one half of the width is \pi/2 radians and not one radian of a cycle in a wave. OR does the 'or' mean 'either of'

[edit] Full quantum mechanical theory

The writers who originally structured this section put things in what to me seems a strange order. The article has been essentially untouched for a long time while I have been researching some of the many problems left outstanding. Dipping back into the "full qm theory" section, it seems clear that it needs some structural changes. The primary problem seems to be how to insert the material about matrix math at the most appropriate point. Originally it was made to seem almost as though matrix math was some kind of geni who popped up to make truth out of the incomprehensible, so it got mentioned before it should have been. Bohr had things figured out. His math was correct, but apparently it went with directions for what had to be computed first and what had to be computed next. (Wish I had the original document.) Then somebody saw how to express in in a relatively familiar, and mathematically "respectable" way, matrix mathematics. Having a neat symbolism that helps you keep track of data and operations to be performed on that data may not make things as much more convenient as "self evident" than did the invention of zero, but it must have come close to that. P0M 00:47, 29 March 2006 (UTC)

A month later I am much clearer on the matrix stuff. I've found enough early information to begin straightening this mess out. So much of the secondary material has been written on the basis of the writers' memories (or imaginations) that all sorts of misinformation has creapt in. Many writers have tried to make things easier for the average reader by saying things that amount to "the number of beans in a can times the number of cans is not equal to the number of cans times the number of beans in a can," when in fact that are being multiplied are matrices, not integers. When I've got the math figured out (not easy when writers use their own symbols without defining them, assuming "they'll know what I mean"), I'll rewrite this section and provide good references. P0M 18:11, 7 May 2006 (UTC)

[edit] Odd Sentence?

original:

"However, strange and counter-intuitive this may seem, quantum mechanics however does tell us the location of the electron's orbital, its probability cloud."

I fixed some grammar and made it sound better into:

"How ever strange and counter-intuitive this may seem, quantum mechanics does still tell us the location of the electron's orbital, its probability cloud."

But it still sounds a little bit odd with the part after the second comma. I don't know enough of quantum mechanics to try to change it without changing the meanings. Maybe someone can, if they agree with me that it does sound off. Janechii 00:48, 7 May 2006 (UTC)

It's got a couple of obvious problems" "How_ever" instead of "However," and a naked "this" (which the reader is free to fill out in whatever way his/her reading of the passages prior to it may suggest). It doesn't help to have a "however...however..." construction either. I'll try to intuit what the original writer meant and then try to fix it.P0M 17:49, 7 May 2006 (UTC)

I think it had already been changed a little. I fixed the "how ever", but (see above) the whole section needs to be rewritten so there is little point in fixing small problems. P0M 18:25, 7 May 2006 (UTC)

[edit] All physics is quantum physics -- true or false

I'm puzzled as to why the sentence "All modern physical theories are quantum theories." was deemed to strong?--Michael C Price 21:34, 12 June 2006 (UTC)

How about Chaos theory? Most physicist are working with QM, but not all. Zarniwoot 21:50, 12 June 2006 (UTC)

OK, so perhaps "All modern fundamental physical theories are quantum theories." would be acceptable? --Michael C Price 22:34, 12 June 2006 (UTC)

Usually, modern, as opposed to classical, includes the theory of relativity. I would say it depends on what is meant by "modern" and also by "fundamental". It may be diffecult to describe the importence of QM in one sentence. (I know I'm not helping here :( ) Zarniwoot 00:43, 13 June 2006 (UTC)

True, relativity is a not a quantum theory itself, but all fundamental theories are relativised, just as they are all quantised. What I really mean is that today a credible fundamental theory would have to be a relativistic quantum field/string/M- theory.--Michael C Price 01:01, 13 June 2006 (UTC)

The current version is: "all modern fundamental physical theories are quantum theories." I am not sure where this "true of false" discussion originated; I guess I was tuned out at some crucial time period. Anyway, I think the way it is now the average reader is likely to get a little confused or misled. I think maybe what needs to be made clear is that everybody is aware of the points at which quantum mechanical considerations come into play. How about: "All modern physics must appropriately reflect quantum mechanical interactions." When a "grand unified theory" is achieved there will be a clear connection between QM and everything else. On the other hand, if one restricts the scope of some division or field of physics narrowly enough there would be wide ranges of "QM-irrelevant" studies. Doing so is arbitrary, of course. The instance mentioned above, "chaos theory," could be one such restrictive field where one could do lots of work and never touch a QM-sensitive interaction. On the other hand, an understanding of chaos theory is really the understanding of how a slight difference between two measurements can predict two greatly different outcomes at some time in the future, and marginal QM effects could produce one kind of such small variations. P0M 05:02, 13 June 2006 (UTC)

Good points all, but even chaos theory is based on classical mechanics, which we now know emerges from QM via Ehrenfest's theorem and the correspondence principle (shouldn't this be mentioned in the article, rather than just a reference?); in that sense therefore chaos theory based on quantum theory -- although many of its insights would be applicable even if classical mechanics were absolutely true. --Michael C Price 11:39, 13 June 2006 (UTC)

If memory serves, "chaos theory" got its name because it was a discovery about the unexpected consequences of working out certain kinds of equations reiteratively that helped us to understand what appear to be chaotic phenomena. So it is not a theory in the sense that thermodynamics is a theory. It's a kind of meta-theory in the sense that it explains not phenomena but the illusion of chaos in the working out of explanations of phenomena. The appearance of "chaos" may be a consequence of working out some equations associated with QM, but that's not quite the same as QM being the basis of chaos theory. P0M 15:32, 13 June 2006 (UTC)

I agree with all you've said, except the last half of the last sentence, which is just a disgrement about style, I think. I'll reread the article and think about adding a ref' to the correspondence principle.... --Michael C Price 16:44, 13 June 2006 (UTC)

All physics is quantum physics, in the sense that at the fundamental level everything is quantum mechanical may not be true. Some notable physicists as e.g. 't Hooft, disagree see e.g. here and here. Count Iblis 01:06, 17 June 2006 (UTC)

The term "physics theories" is conceptually a little slippery, no? The question is whether we have a number of apparently competing theories that turn out to be either the same thing (i.e., one formulation can be converted into the other) or are linked at a more general level of organization, or whether there are two or more theories that are "modern" but unconnected. In The Elegant Universe,p. 3, Greene says: "As they are currently formulated, general relativity and quantum mechanics cannot both be right." The quest now is for a theory that will unite the two somehow, which will mean finding a more basic level of generality. When and if such a theory is successfully produced, it will have to account for the same things that QM does, just as QM has to account for all the things that classical physics predicts. P0M 17:25, 19 June 2006 (UTC)

[edit] Sidebar in drastic need of a re-write

This sidebar is, I believe, comprehensible only to people who already know what the writer was trying to convey. Would someone like to try to fix it up? Here are some of the problems I see:

"Bohr's analysis of electron orbits as circular"

The unsuspecting reader could guess either that Bohr analyzed the orbits of electrons and concluded that they are circular, or that Bohr assumed that the orbits are circular and attempted to draw theoretical consequences on that basis.

"A little math on circular orbits."

It is a minor quibble, but the above collection of words is not a sentence. If you are Frank Lloyd Wright you can write that way. Mere mortals ought to stick to true sentences in deference to other mere mortals.

"Bohr was very familiar with the dynamics of simple circular orbits in an inverse square field as described in classical mechanics."

At the bare minimum this sentence needs a wiki link to "inverse-square field". The average well-informed reader might even read this sentence as referring to a square field that is in some sense inverted.

"Simply explained: "

This phrase gives a promise that is not needed and is not fulfilled.

"To find the acceleration of a circle, place it inside the shape of a square where tangents meet, then find the linear speed along one side of the square, then square the speed of one side to complete the speed of the entire square, then divide by the radius of the circle placed in the square to get the speed around the circle."

Circles cannot accelerate.

What is the difference between putting a circle inside a square (by which I am guessing the author meant to say: construct a circle within a square) and putting a circle inside a shape?

"Where tangents meet" -- meet what? It looks like the author is trying to describe a circle that has been fitted within a square so that it meets at four points -- no more and no less.

"Then find the linear speed ..." The linear speed of what? Is the author trying to say that one should use the orbital speed of an electron travelling in the orbit diagrammed by the circle to calculate the speed of a point mathematically projected onto one side of the square?

"square the speed of one side" The circle does not accelerate and the side does not move. If we are talking about the metaphorical speed of the shadow of an electron as it is projected on a wall perpendicular to the plane of the orbit, then it is clear that the speed of movement of that shadow will go from zero to some maximum and back to zero. So we are dealing with a function and not a constant when we talk about "the speed."

"then square the speed of one side to complete the speed of the entire square" -- Really? Going across the top of the square, the point has an average speed of 500 zonks/hour. So going around all four sides of the square the point has an average speed of 2500 zonks/hour? What?!

"then divide by the radius of the circle ... to get the speed around the circle." Arggh. The author didn't mean for us to start with the "speed around the circle." So what were we supposed to be starting with? And what does any of the above gobblydegook have to do with the following?

The equation for the centripetal acceleration is a = v² / r. That is, acceleration is inversely proportional to the radius of the circle.

Hmmm. We had something divided by the radius of the circle above. If we denote "the speed of one side" by s, then the "speed of the entire square", S = s² / r. Then in the following part the writer seems to equate "speed" with acceleration.

If the radius is doubled, then the acceleration is halved.Also, Kepler's Third Law is that the radius cubed equals the circumference of the orbit squared. It immediately follows that the radius of any n orbit is proportional to the orbit n squared, and the speed in that orbit is proportional to 1/n. Speed times radius gives angular momentum. That leaves n-squared over n. It then follows that the angular momentum for any orbit n is just proportional to n. Bohr argued then that the angular momentum in any orbit n was nKh, where h is Planck's constant and K is some multiplying factor, the same for all the orbits, which was later determined to be 1/2π.

Linear acceleration, a, is defined as the rate of change of velocity, and in orbital mechanics it isn't the speed of the orbiting object that changes, it is the velocity that changes -- or to put it in other words it is not the absolute value of the velocity that changes but its direction.

Let's either scrap this sidebar, scrap it and write a new one, or fix it so that a bright high school student interested in going into a physics major in university can see physics as a comprehensible activity. P0M 02:03, 22 July 2006 (UTC)

I just had a look at the Kepler's law stuff. It's wrong. I checked Kepler's Third Law, and that's not it. (r²= (2 π r)³?!) I'm going to delete the sidebar but leave it here (in the form above) for anybody who wants to try to make it a useful aid to the person who lacks a basic college physics book and a semester or two of calculus. P0M 19:55, 22 July 2006 (UTC)

I think you did right by deletion. It was godawful mess. --Michael C. Price ^talk 21:02, 22 July 2006 (UTC)

[edit] Some confusion

The explaination on the background page doesn't make much sense. Especially this part...

in 1873 James Clerk Maxwell showed that by making an electrical circuit oscillate it should be possible to produce electromagnetic waves. His theory made it possible to compute the speed of electromagnetic radiation purely on the basis of electrical and magnetic measurements, and the computed value corresponded very closely to the empirically measured speed of light.

How did he do this? It is not clear how he did this. The page makes perfect, perfect, perfect sense and is wonderful up til this point, then I became confused. I speak as an ignoramus on quantum physics. I love the idea of this page, and it is otherwise very good.

69.174.134.56 19:54, 6 August 2006 (UTC)

I've linked in Maxwell's equations to "His theory" -- not ideal I'm sure, but better I hope. --Michael C. Price ^talk 22:17, 6 August 2006 (UTC)

Thank you for the very useful feedback. I've worked hard to make things comprehensible, but I haven't made it all the way through yet. (I've been stuck on one point...) I'm not familiar with Maxwell's methods, but I'll see what I can do. P0M 22:22, 6 August 2006 (UTC)

O.K. I think I have a line on the operations involved. The passage to which you refer is from the excellent series of textbooks by Francis Weston Sears. I basically paraphrased what he said. (See the footnote.) He's one of the best textbook authors I've ever found, and in this case he mentions a historical fact. Being able to calculate the speed of light in a new way didn't have any practical consequences since it had already been measured very accurately. The development of the theory that churned out this result was primarily important because it showed how certain things were related, and the speed of light sort of popped out as a consequence of figuring these other things out. So a straight-line explanation of Maxwell's equations might pass over this tid-bit to get to the stuff that the physics textbook writer is trying to get students to understand and to be able to calculate. A real explanation looks like it will take about a 10k article, and I sort of doubt that it would be an encyclopedia article. It really belongs in a physics textbook. If Sears mentioned the matter again (and I haven't found any such mention), he may have done what he frequently does and that is to tell the student to start with certain given information and derive the speed of light.

All that being said, I think I can explain by way of an analogy what was going on.

Suppose that somebody wants to measure the speed of some wave phenomenon. Maybe the person wants to measure the speed of sound. One way to do it is to get two very accurate clocks, a starter's pistol, and two mountain peaks so far apart that one can barely hear a gunshot from one to the other. Then you measure the distance from peak to peak, fire the gun on top of one peak at a pre-determined time, and somebody on the other side hits a button when the gunshot is heard. You do this a whole bunch of times to try to even out any experimental error, and if you're really slick you measure the reporter's reaction speed. You grind all the numbers together and come out with the speed of sound. (Of course you have to do the measurements when the air pressure is the same, etc.)

How else could you measure the speed of sound? Well, it turns out that the loudness of the sound doesn't have anything to do with its speed (as long as you don't get really energetic and produce a shock wave). What does matter is the elasticity of the vibrating medium. (Here I am using the physics definition of "elastic", the idea that steel is very elastic and rubber bands are not very elastic because steel snaps back much more quickly and powerfully.) Sound travels faster is a steel railway track than it does in the air above the track.

We don't have to use sound transmission to figure out the elasticity of various substances. Once we have that kind of a measurement, we can start thinking about how long it takes a displaced atom in a bar of steel to reach the point where it will impact on another atom You've probably seen the office toy that consists of a bunch of big ball bearings hung from a wooden rack. If you pull one on the end and let it fall back down and smack its neighbor, it stops dead in place and the ball on the opposite end (almost) instantaneously jumps out. Then it falls back after a short time, and the original ball is thrown into the air. This back-and-forth can go on for a few seconds, long enough for heat losses to siphon off the energy originally provided by the person who moved the ball bearing in the first place. The time delay turns out to be a function of the length of the strings and the acceleration of gravity -- as with any pendulum. Neither of those quantities has anything obvious to do with the speed of waves passing through a medium, but if you string a bunch of balls from a bar on equal lengths of string and equal distances from each other, you can pretty easily figure out how long it will take motion to propagate from one end to the other. I think that's a pretty fair analogy for how wave motion passes through a bar of steel, a tube of water, etc. This is all off the top of my head, so let me know if my powers of visualization are failing me at some point. (By the way, one of the neat things about the simple toy mentioned is that you could arrange to keep a trickle of energy flowing into the system so that you could keep things bouncing for minutes or hours, count the number of "ticks" for a long period of time and figure out very accurately how long a single tick is.)

Meanwhile, I'll try to digest Maxwell a bit. It may require a pot or two of appropriately branded coffee. P0M 01:24, 7 August 2006 (UTC)

Still with us? Maxwell House coffee didn't help much, but if I am right, here is the deal. The article on Maxwell's equations has the key:

In the late 19th century, because of the appearance of a velocity,

in the equations, Maxwell's equations were only thought to express electromagnetism in the rest frame of the luminiferous aether (the postulated medium for light, whose interpretation was considerably debated). The symbols represent the permittivity and permeability of free space.

What is not clear from that discussion is that Maxwell did not start with the idea of the speed of light. He developed an equation in which a constant (which he might have call "a," "b,"...or whatever) "which represents the ratio of the units of charge or of field in the system of electromagnetic units and in the system of electrostatic units." (Lous de Broglie, The Revolution in Physics, p. 53. De Broglie continues:

By combining the fundamental equations, it is easily shown that electromagnetic field are propagated in a vacuum in accordance with the wave equation and with a phase velocity equal to the constant in question. Therefore, if one wishes with Maxwell to interpret light waves as being electromagnetic disturbance, one is led to predict that the velocity of propagation of light in vacuo ought to have the same value, [now] generally represented by the letter c, as the ratio of these units.

The permittivity and permeability mentioned above are factors that are analogous to the inverse of the atomic forces that create the rigidity of substances that relates to their speed of sound transmission. So just as you can figure out the speed of sound in steel and the speed of sound in water, you can figure out the speed of light in a vacuum or in glass or some other substance if you know the factors that are analogous to rigidity or elasticity (both are different ways of talking about the same kinds of physical interactions from different points of view).

How's that? Clear? Or murkier than bad coffee? One of the problems with understanding things like this is that we often lack the experience of dealing with real world systems that are the same as or analogous to what the physicists are talking about. If you had two steel block joined by a spring in the middle, how long would you predict that it would take a whack on block A to appear as a movement in block B? If the spring were so stiff that it behaved as though it were a simple steel rod, then the movement of block B would appear simultaneous to observers. (Actually it wouldn't be, but you'd need a very fast clock to measure the time gap.) If you replaced it with a weaker spring, what do you think would happen? An analogous physical situation is produced when you measure the speed of sound at various altitudes. So if you can see this qualitatively then maybe that will help you see how somebody could start out with measurements about the force required to compress a medium and come up with a speed of sound for that medium. P0M 18:40, 8 August 2006 (UTC)

[edit] Wave function collapse (again)

In general, I am happily surprised by the present state of this article, but somehow "Schrödinger's equation then fails" has come back. As he said in his "Cat" article in 1935, what happens is that the system needs to be described by the many-body form of the equation. I will try a simple fix, but others also should work on making it both correct and understandable. David R. Ingham 01:23, 15 October 2006 (UTC)

Two points:

1) Wavefunction collapse does not mean that the entity becomes "particle-like", as is currently implied. If you are measuring wavelength then the reverse occurs, namely a particular frequency is selected (as happens when a radio detector is tuned to a single frequency).

2) Where does Schrödinger's 1935 "Cat" article state that wavefunction collapse is successfully modelled by the many-particle picture? I can't find such a statement.

--Michael C. Price ^talk 08:06, 15 October 2006 (UTC)

He didn't say one can calculate an observation purely with QM. There are too many variables. But he anticipated, as has since been observed, that when you "shut up and calculate" QM never "fails". The problems like EPR only arise when classical intuition is involved. Any useful "interpretation" must deal with this. David R. Ingham 15:38, 16 October 2006 (UTC)

But what section of the article does he say this in? --Michael C. Price ^talk 16:34, 16 October 2006 (UTC)

I will look back if I have time. The article is worth re-reading. He does say that the only discontinuity is a mental one, but I don't remember the words. This is not really the place to discuss this because the fact that we disagree shows that it is an advanced topic. To make sense of the old paragraph, I had to bring in many body wave functions and the infinite energy of a zero length wave packet. I think my change made it correct, but it also shows that it doesn't belong in an introduction. When people are introduced to classical mechanics, they should be warned that it does not include relativity or QM. There is, as yet, no known such caveat that must be made for QM. Quantum gravity is only speculative. Mentioning the measurement problem does not hurt, but I think it is a mistake to try to explain it here. David R. Ingham 22:16, 16 October 2006 (UTC)

Classical mechanics often includes relativity. --Michael C. Price ^talk 02:23, 17 October 2006 (UTC)

[edit] An additional problem with the paragraph as it was

From the article "Improving Student's Understanding of Quantum Mechanics" in the August 2006 Physics Today:

A related false belief is that measurement of any physical observable causes the system to get "stuck" in the measured eigenstate forever unless an external perturbation is applied. Again, the statement is true only for observables whose operators commute with the Hamiltonian, but students seem to generalize that property of measurement to include all observables.

The old paragraph would seem to encourage this error. David R. Ingham 21:12, 21 October 2006 (UTC)

[edit] What to do about it?

I was thinking of taking (my altered version of) the paragraph out of the article until someone finds a more elementary way to address Wave function collapse, or perhaps better Measurement, but it does not look quite that bad to me as it now stands.

What about summarizing how typical experiments are done on time dependent cases (such as scattering) and (nearly) time independent quantum systems (such as atomic and nuclear spectroscopy) and then mentioning that these approaches do not cover all cases? David R. Ingham 22:48, 21 October 2006 (UTC)

[edit] AfD raised on Quantum theory

If you have view on this please go to Wikipedia:Articles_for_deletion/Quantum_theory and cast your vote. --Michael C. Price ^talk 06:02, 20 October 2006 (UTC)

Note that this is related to a controversy here about the change [10], that re-reverted a previous revert of the first paragraph to Revision as of 19:55, 15 October 2006, MichaelCPrice, without calling attention in the edit summary that a contested change was being insisted on. David R. Ingham 13:58, 22 October 2006 (UTC)

I.e. a content dispute, not a reason for an AfD. --Michael C. Price ^talk 14:24, 22 October 2006 (UTC)

Perhaps it was rude of me to put it thay way. No, it is not a reason for deletion, it is just a related subject.

I have said about all I have to say on this and trust that you and others will resolve the issues, if my perception that there were issue is correct. It is really a matter or semantics and organization, which are not my strongest points. David R. Ingham 19:36, 22 October 2006 (UTC)

As AfD nominator you may withdraw the AfD. --Michael C. Price ^talk 20:16, 22 October 2006 (UTC)

[edit] History question

(Both 50 and 60 years seem too small to me.) David R. Ingham 03:40, 22 October 2006 (UTC)

I am assuming that this comment is irrelevant to the AFD. The question of how long quantum physics has been important to consumer life seems to be what this comment was directed to. The transistor has been around since sometime around 1948, so what earlier technological innovation do you have in mind? P0M 05:37, 22 October 2006 (UTC)

As far as I, know the back and forth changes between 50 and 60 years are only incidental to the questions about "quantum theory" discussed above. I don't recall now who favored which number. David R. Ingham 13:55, 22 October 2006 (UTC)

[edit] Introduction!!??!!??

I am studying A-level physics, and do not understand much of this page...

is it basic enough, or am i just being thick? Roband 20:45, 1 November 2006 (UTC)

If you had a full year of college physics intended for physics majors, then you might have a good enough idea of what classical physics says about the world to be able to understand the article easily.

One could do damage to the students' understanding of the true nature of science by claiming certain statements to be "the truth about sub-atomic events," and, once given these statements as premises one could "prove" and explicate some of the consequences of the models that we use to think about sub-atomic events.

If you want an account of quantum mechanics that does not deal with abstractions and that has no mathematical complexities, then you could observe an experiment wherein the voltage (not the amperage) of a photoelectric light meter is compared to the frequency (not the intensity) of monochromatic light that falls on the light meter. You could try to understand that the frequency of the light determines the velocity with which electrons are expelled from the photoelectric detector. That kind of result is already counter-intuitive to most people. If you try to go any deeper you will enter a world in which many of the usual expectations of daily life have to be torn down, and a world whose description in other than qualitative ways requires something beyond high school math.

You shouldn't be surprised or disheartened by the difficulty. Consider the the man who made the basic solution to the problems involved despaired of ever being able to figure out how to describe and predict the seemingly perverse twists and turns of sub-atomic interactions.

You could have a look at Introducing Quantum Theory, by J.P. McEvoy and Oscar Zarate, ISBN 1-84046-577-8. To me it seems just a little bit too simple in some respects. You could also have a look at the relevant parts of George Gamow's One, Two, Three...Infinity. It's an old book by a real physicist who made a strong attempt to write simply without falsifying anything. P0M 22:01, 2 November 2006 (UTC)

This seems as good a place as any to comment :) I can't get the idea of this Wikipedia thing! anyway . . . I think the stuff on the page is great. I have no idea about it's accuracy but it "sounds" good to me. HOWEVER . . . the structure of it doesn't work for me at all. Currently it falls half way between a rambling encyclopedic entry and a collection of information for a text book. My view is that the whole page should be radically edited. I suggest two methods to accomplish this. The first is to rely far more heavily upon links to other pages in Wikipedia. This would obviate a considerable amount of text. Then I would suggest that a more basic and easily understood structure is applied to the page, in line with the aim of it. The evolution of the concept, those that contributed to it etc should be extracted into a History section for instance. The overall structure of the page should be explained in an introduction. The summary at the head of the page should be a complete summary only and not include any such level of detail as it does at present. Etc. My own case is that I needed to get some information relatively quickly. I found the page (and links fascinating) but in the end gave up because I didn't have time to read all the detail. Furthermore the conversational almost anecdotal writing style was difficult. Sorry. It's great stuff but IMHO needs a really hard pruning and then a robust and clear structure applying to what remains. The pruned material would then either go to other pages, create new pages or be deleted.

A random example for instance: ". . . produced what we would now call microwaves — essentially radiation at a lower frequency than visible light . . ." could be replaced by the word "microwaves" and a hyperlink. Although there is additional information in the extra 15 words, is it really that valuable or even decipherable? Microwaves may not have been called microwaves then but is such an aside fitting here? There is no hyperlink and I don't know if the fact has relevance or not really. Or again ". . . For example, the behaviour of microscopic objects described in quantum mechanics is very different from our everyday experience, which may provoke an incredulous reaction. . . ." There is no benefit to this passage at all that I can see. A stream of questions are aroused and never (?) answered: "What experiences?", "Why don't they?" etc. Would it not be better to refer to this by saying something like: "Quantum mechanics describes behaviour of . . . in a counter-intuitive way. [see . . . below]".

I hope this comment is welcome, constructive and helps. I would really like to know if it is (or if it is not) or if I could help with the work you outline at the top of this discussion page in any way.

LookingGlass 22:06, 14 December 2006 (UTC)

It is always useful to have an outside eye on an article like this one. When I get my final grades in I will take a closer look at what you suggest.

One problem with an article like this one can be that the author knows the subject but cannot explain it to people who do not know the subject.

Another kind of problem can occur when someone thinks s/he knows but in fact has gotten things wrong.

Assuming that one is not creating those kinds of problems, then the next issue insolves how to present something totally outside of one's everyday experience to the non-expert. (See Quantum mechanics]] for the way physicists talk to physicists about this subject.) One could try to turn the equations of quantum mechanics into a very abstract kind of English. But then one would have a logical system of propositions involving words that have no referents in the reader's experience. To the extent that the reader makes any sense out of this logical system of propositions that s/he can apply to the real world it is likely to be misleading.

Rather than plunge in with new vocabulary words like "orbitals," it is better to start with the experiences we have in our daily lives that are the consequences of the quantum nature of reality, e.g., "Why does the color of the flame of a bunsen burner change if one sprinkles salt into it?" That experiment is one that anybody can do. But to explain it in quantum terms involes building up a complex system of observations and ideas, i.e., a theory.

The reaction to the "bare facts" of quantum mechanics is frequently something like, "How can you justify that nutty idea?" So just stating the "bare facts" will not be satisfactory to those who do not easily submit to authority. (And if everybody just accepted authority we would probably still be Platonists.)

I don't know of anyone who has gotten the dope on QM quickly. If you are interested in a series of things that can reliably be memorized and repeated, then I would suggest 'Introducing Quantum Theory, by J.P. McEvoy and Oscar Zarate, ISBN 1-84046-577-8. If you were to get rid of the illustrations (pictures of Neils Bohr, et al. for instance) you would only have a few pages of text.

As an undergraduate in the physics department of a good univsity I had a very uneven experience during the three trimesters. The first trimester was mechanics, and a bit difficult for me because mechanics involved calculus, and calculus was new for me. The second trimester was on electricity, and I got an A. The reason wasn't because the instructor's ability to teach had improved. It was because I had accidentally provided myself with a very thorough grounding in electricity through all of the gadgets, crystal radios, home-made telegraph sets, etc., etc. that I had made going back to my days in primary school. I already knew in very practical terms what happens when two resistors are connected in series and two are connected in parallel, so I didn't have to memorize the information at exam time. And all the way along I had attempted to understand in terms of the "lives of electrons" what was really going on in the interactions expressed in the formulae of physics that were pertinent to my little projects. So what was to others abstract and counter-intuitive (how can two resistors working together give less resistance than one resistor working alone?) was to me concrete and natural.

Failing to understand the physical systems that are being described by the useful fictions that we call theories can lead to some strange mistakes. One of my lab instructors poked one probe of a volt meter into one side of a 60 VDC electrical socket and wondered why the needle didn't move. "The socket must not be connected to the power supply. I measure no potential." One finger in each side of the outlet would have convinced him otherwise. P0M 23:26, 14 December 2006 (UTC)