Talk:Introduction to quantum mechanics/Archive 2

message: Here is an example of the kind of writing that I rather hate: "Amplitudes of position and momentum that have a period of 2 π like a cycle in a wave are called Fourier series variables. Heisenberg described the particle-like properties of the electron in a wave as having position and momentum in his matrix mechanics."
The writer presumably knew what s/he intended to convey. I can guess that there has to be some connection between Fourier series variables that are chosen to represent positions and momentums and the matrices that are alluded to in the next sentence. Of course the claim is uncited, so I'll have to go rooting through my old books until I find something that I can cite. I think maybe the author was trying to say that Heisenberg believed the electrons in their orbits are in an oscillation that could be graphed as angular position set against time, and that it was convenient for him to describe the position and momentum of the electron as Fourier variables and then put those expressions into his matrices. (What the heck is an "amplitude of position" anyway?) P0M 04:29, 8 February 2007 (UTC)
replies: text: \lambda=\frac{h}{p} or p=\frac{h}{\lambda}
but then a reasonable question would be, "Where did that dogmatic statement come from?"
If you know that E = h v (i.e., that energy is related to frequency times Planck's constant), and that E/c = p (i.e., that energy divided by the speed of light is related to momentum), and you know the general relationship between wavelength, speed of the wavefront, and frequency, then you can get the interesting results given above. Planck's constant is at the heart of quantum theory, so that is something to learn about. The idea of the relationship between energy and momentum has something to do with the speed of light is a little unexpected, but that the momentum of something is related to a speed is a little closer to home. So with a little algebra we can demystify. With no math at all we could just say, "Wavelength is equal to Planck's constant divided by momentum."  How is that related to the fact that the energy photons carry is a function of their wavelength? We wouldn't explain because explaining would amount to writing out all of the equations in plain English and that would be tedious to do and actually harder for the reader to follow.
The one "formulaic" part of the article that I have a little question about is the long discussion of why physicists like to use "h-bar" rather than just using "h/2π". It doesn't do anything to the real math, so in a sense it's an unneeded complication. On the other hand "h-bar" is a mysterious new symbol meaning who knows what when you first stumble upon it, so perhaps it is worth demystifying it up front.P0M 06:04, 8 February 2007 (UTC)

text: Do you mean the one that looks a little like 入 ?  That's a lower-case (Greek letter) lambda, and is used for wavelength.  P0M 01:07, 9 February 2007 (UTC)
thread_title:  Fixes for some fuzzy points? 

message: Perhaps articles like this would have a better place as part of a Wikibook rather than an encyclopedia entry. Fyorl (talk) 09:19, 14 February 2008 (UTC)
thread_title:  Use in Wikibooks? 

message: This is in response to a recent edit by Cmeyer1969.  You say you "Removed confusing joke and added informative reference."  I appreciate the reference to the Westmoreland and Schumacher paper; I will read it.  Shimony's idea of "passion at a distance," however poorly it may be named, is not a joke.  See Abner Shimony and the reference to Sandu Popescu's essay in this article.  If you are under the impression that someone added the sentence you removed as a joke or as vandalism, you are mistaken.  By the way, I have no personal stake and I did not write that sentence; someone called for a citation to back up the sentence and I found one. — SWWrightTalk 03:20, 8 March 2007 (UTC)
thread_title:  Shimony and "passion at a distance"? 

message: The text currently says: "In May 1926 Schrödinger published a proof that Heisenberg's matrix mechanics and his own wave mechanics gave equivalent results: mathematically they were the same theory. Both men claimed to have the superior theory." Somebody has put a "fact" tag on this claim. It is true that Schrödinger published such a proof.  If one theory can be derived from another theory, i.e., if they are "mathematically the same theory," then one cannot be superior to the other. About the only thing one of them might claim would be that his way for formulating the mathicatical relationships is easier to compute under certain conditions. I would be in favor of deleting the claim. It does not help the reader to understand quantum physics. P0M 21:13, 30 April 2007 (UTC)
replies: text: * I put that tag there, not doubting that Schroedinger gave the proof (Eckart did too), but doubting that both men claimed their own theory to be superior. I have never before read that. As far as I am aware Heisenberg understood immediately the equivalence proved by Sch. Equivalent theories rank equally as you, H., and Sch.  know, but not the author of the sentence. So, I am in favor of deleting the sentence + tag, too. --P.wormer 15:26, 16 May 2007 (UTC)
thread_title:  fact? 

message: Spin was  discovered by Uhlenbeck and Goudsmit in 1925 as stated in most textbooks of QM. Not by Kronig as  myth has it. See http://www.lorentz.leidenuniv.nl/history/spin/goudsmit.html
--P.wormer 15:10, 16 May 2007 (UTC)
replies: text: This problem seems to have been fixed. P0M (talk) 17:05, 20 December 2007 (UTC)
thread_title:  spin 

message: "These ideas [waves and particles] seem mutually contradictory, because neither idea by itself can explain electromagnetic radiation".
This doesn't make sense. It's like saying wheels and engines are contradictory because neither alone can explain vehicle motion.
Should the two parts of this sentence instead be separated by but?
--217.18.21.2 14:30, 29 May 2007 (UTC)
replies: text: * I agree, but couldn't find the sentence--P.wormer 14:41, 29 May 2007 (UTC)

text: * Right next to the constructive and destructive interference image. Note that when quoting the sentence, I added the portion in square brackets to make it easier for people to follow the point I was making.--217.18.21.2 15:07, 29 May 2007 (UTC)
replies: text: * OK I found it. I would write something like: In classical physics these ideas are mutually contradictory. Ever since the early days of quantum mechanics we know that neither idea by itself can explain electromagnetic radiation. --P.wormer 15:26, 29 May 2007 (UTC)
thread_title:  contradictory? 

message: I see that this has already been reverted 3 times in few days - so, before it becomes an edit war, let's spell it out clearly: Planck constant is 6.6260693 × 10E-34 joule seconds; light's frequency is  hertz =  1/seconds; the resulting unit for h * \nu is joule seconds / seconds = joules, so the result is in joules, a unit of energy like the electronvolt, ok ? :-) -- Sergio Ballestrero 17:55, 30 June 2007 (UTC)
replies: text: Paul, you're right that the only SI energy unit is the Joule, and that you can use other units; but unlike the others you mentioned, eV is a proper energy unit, with no "hidden constant", because the "e" in eV stands for "electron charge with unit": 1 Coulomb * 1 Volt = 1 Joule -> 1e * 1V= 1.602 ×10E−19 C * 1 V = 1.602 ×10E−19 J , so there is only a (quite explicit) numeric factor, the electron charge in Coulombs, not a constant with units. If you use eV for momentum, mass etc then yes, you have implicit, hidden factors and, more important, hidden units, but that's not the case for energy. Aside from this, my main point was that the corrections were replacing Joules with Hertz without adjusting the numerical value, which is incorrect no matter what! -- Sergio Ballestrero 10:32, 1 July 2007 (UTC)
replies: text: Sergio, I agree with your main point, but only partially with with your first point. If one goes from joule to any other "energy unit", one has to multiply with one or more natural constants. This is also true for the eV, as you say yourself: you multiplied with the charge e of the electron. I call e a natural constant with SI unit coulomb. However, I grant you that the eV is special among the "energy units" in the sense that it has  the dimension of energy (as does the hartree), while  most of the other "energy units" do not even have the dimension energy (for instance Hz has the the dimension 1/second).  --P.wormer 13:24, 1 July 2007 (UTC)
thread_title:  h*hertz=joules 

message: I saw the following sentences in this article:
:Therefore, an electron in a certain n-sphere had to be within a certain range from the nucleus depending upon its energy. This restricts its location. Also, the number of places an electron can be is also called "the number of cells in its phase space". The Uncertainty Principle set a lower limit to how finely one can chop up classical phase space, so the number of places that an electron can be in its orbital becomes finite. An electron's location in an atom is defined to be in its orbital, but stops at the nucleus and before the next n-sphere orbital begins.
Is this understandable for the proverbial "average reader"? I, for one, don't know what an n-sphere is, and why the phase space [for one particle a 6-dimensional space of points (q,p)] enters here.--P.wormer 14:53, 24 July 2007 (UTC)
replies: text: Valid criticism to be sure. Can somebody put in explanations and links to make this stuff more accessible? Otherwise it can only be read by the people who already know about it. P0M (talk) 18:07, 19 December 2007 (UTC)
replies: text: While fixing something else I noticed that n-sphere is defined at its first occurrence in the article. I'm not sure but what its use (or its reuse) serves a valid function. Maybe some diagrams would help? P0M (talk) 07:39, 20 December 2007 (UTC)
thread_title:  accessible discussion? 

message: I'm new on here, but I found a source to the Heisenberg qoute in 3.3 Uncertainty Principle in the Intro. to QM but am not sure how to go about adding it, if someone else will or give me more specific instructions that would help.
The html is http://www.aip.org/history/heisenberg/voice1.htm, and they have it cited as "From "The Development of the Uncertainty Principle", an audiotape produced by Spring Green Multimedia in the UniConcept Scientist Tapes series, © 1974."
Thanks
RangerA 04:55, 31 October 2007 (UTC)
replies: text: Done. The original also cleared up some misreading in the quotation. Thanks. P0M (talk) 07:40, 20 December 2007 (UTC)
thread_title:  Citation 

message: Where would I find an explanation of the quantum-mechanical understanding of absorption, for example, the absorption of a photon by an atom? Thinking of a photon as a particle, I can imagine it "hitting" an atom and transferring energy, but as a big wave, I don't see it. —Ben FrantzDale 04:07, 6 November 2007 (UTC)
replies: text: See Absorption cross section? 155.212.242.34 (talk) 13:45, 19 November 2007 (UTC)
thread_title:  Absorption? 

message: I'm moving on through the article now that I've finally figured out something to say about the matrix math rationale.
The first paragraph of the section called "Uncertainty principle" is terribly muddy. Does anyone understand what the original writer of this part was trying to say well enough to make to both clear and correct? P0M (talk) 18:55, 20 December 2007 (UTC)
thread_title:  Writing needs to be improved 

message: The text currently claims that:
*A wave is also a moving stream of particles.
It is not clear whether the writer was confusing light "waves" with water waves, talking about light "waves", or talking about water molecules.
A "photon" is a shorthand way to refer to something that is not a classical particle and is not a classical wave. It is an individually created disturbance that has wave characteristics and particle characteristics.  The wave that is named in the definition of a photon is not "a moving stream of particles."
If the writer was talking about water waves, the statement is misleading because the water involved in a wave doesn't move across the surface of the body of water that is disturbed by waves. The molecules in a wave are moved up and down. The particles do not "stream" anywhere.
If one were forced to make a physical analogy, the "particle part" of a light wave could be imagined to be a surfer riding a wave in toward the beach. But there isn't any reason to claim that this surfer is different in kind from the wave that it rides.  Analogies are risky, but the passage of a photon would be more like a water wave that moves smoothly across the water surface but, upon hitting the beach, delivers all of its force at a very small volume of space. 
Does anyone follow what the original writer was trying to say well enough to clarify this point?  P0M (talk) 19:28, 24 December 2007 (UTC)
replies: text: Someone else marked the above-mentioned section for clarification, and, seeing no way to clarify it I have removed it. The idea of reinterpreting a particle-like description in wave terms and thereby rationalizing the uncertainty factor is interesting but highly technical. If it is going to be in the article it needs to be put in a very cogent way. Otherwise it is a hindrance to the reader who is not already very familiar with the subject. P0M (talk) 23:05, 31 December 2007 (UTC)
thread_title:  A questionable assertion 

message: The actual development of matrix mechanics has been made the subject of mystery and even mystification (or maybe it's obfuscation). I've at least found outline information on what went into Heisenberg's original calculations and have added two charts that show the kind of information he was working with and, also, give an indication of how suggestive of matrix math this information becomes when so organized.
Does anyone have access to the actual charts or data sets? P0M (talk) 23:10, 31 December 2007 (UTC)
thread_title:  added tables 

message: Someone has tagged a statement for lack of a citation:
The statement is problematical for another reason: it uses theory to attempt to predetermine an empirical observation. At most, one could argue that information transfer using quantum entanglement would be inconsistent with Special Relativity. That's why Einstein et al. thought that quantum mechanics could not be a valid theory, which brings the argument full circle.
There is at least one serious proposal that would have to be given "equal time" if a cleaned up version of the quoted assertion is to be retained.P0M (talk) 17:20, 12 January 2008 (UTC)
thread_title:  Dogmatic assertion 

message: I think that this article should be moved to Wikibooks... any suggestions?  CJ Miller. (That's my name.Don't wear it out.) 01:33, 9 February 2008 (UTC)
replies: text: Why? P0M (talk) 02:36, 9 February 2008 (UTC)
thread_title:  Transwiki?