Wikipedia talk:WikiProject Physics/Archive April 2008

Biomechanics of animal locomotion

I'd like help with a bunch of articles on the biomechanics of animal locomotion: Lead change, Lead (leg), Horse gait, Locomotion... See Talk:Horse gait#Group gaits. Thanks. --Una Smith (talk) 16:29, 1 April 2008 (UTC)

I think that you will find that these articles have too much to do with horses and not enough to do with physics to interest the members of this project. Sorry. JRSpriggs (talk) 08:03, 2 April 2008 (UTC)

That narrow POV is exactly why I asked for help. I am into horses myself but apart from Horse gait these articles are too narrowly focussed on horses (and Horse gait is too narrow in another way). --Una Smith (talk) 15:46, 2 April 2008 (UTC)

LaTeX to WikiText Conversion

LaTeX to WikiText Conversion Count Iblis (talk) 21:27, 1 April 2008 (UTC)

Entropy (disambiguation)

I could use some more eyeballs on this page.

In my view, to help people get to the article they want most quickly, it is helpful to include structure in the page to group together meanings primarily related to Entropy in a thermodynamic sense, and those primarily related to Entropy in an Information Theory sense. However, because there is no provision for this is the WP:DAB guidelines, various editors specialising in disambiguation (who may know rather more about disambiguation than they do about entropy), would prefer to see all the links muddled together in a single (IMO much harder to navigate) long alphabetical list. Cf this diff: [1].

Since dab pages are supposed to help readers who do know something about the subject find the article they want, I'd greatly appreciate if members of this project could look at the two versions above, and then leave their thoughts on the talk page.

Thanks, Jheald (talk) 23:23, 23 March 2008 (UTC)

What a fucking failure. I think wikipedia is great for any topic of obscure interest, to small/specialist audience. But once one gets to big-ticket items, such as entropy or black holes or quantum mechanics, the result is almost guaranteed to be a mess. Oh well. I wish that wikipedia's leadership would wake up to the problem, instead of running around in denial. linas (talk) 04:56, 8 April 2008 (UTC)

Black hole related articles

I have been trying to figure out ways to improve the Black holearticle, which has grown to an immense length. In the process I have been looking at related articles and found that they are all over place, having considerable overlap. For example, there are separate articles covering schwarzschild metric and schwarzschild coordinates. These articles (as well as the Black hole article itself) could do with some reorganization (merging, splitting, redirecting where necessary). For convenience, I have made a list of all article I could find on my user page.

Do others feel that this is something worthwhile? And if so are there people willing to help out?

(TimothyRias (talk) 12:58, 2 April 2008 (UTC))

Heh. Try to tackle it as a bit at a time. These articles get many editors over time, and so grow by accretion rather than by planning. The topics draw popular, semi-informed interest, which doesn't help with maintaining their coherency.linas (talk) 04:44, 8 April 2008 (UTC)

vandergraph generator

needs article 58.163.129.146 (talk) 07:52, 5 April 2008 (UTC)

You mean Van de Graaff generator? (TimothyRias (talk) 13:14, 5 April 2008 (UTC))

Fourth dimension article unrelated to physics

Hi, I'm not sure why Fourth dimension was tagged by WikiProject Physics, but I don't think it's relevant to physics. It discusses 4D Euclidean space, a mathematical construct, whereas physics (general relativity) deals with 4D Minkowskian space, which is not an Euclidean space. I recommend that this article be moved under another project (probably Mathematics). Thanks!—Tetracube (talk) 13:58, 5 April 2008 (UTC)

I disagree. Physics often uses a 4D Euclidean space as a mathematical trick to do computations; see for example, Wick rotation. Furthermore, there are physical theories that posit the actual existence of four, or more, spatial dimensions such as Kaluza-Klein theory or string theory. The discussion in Fourth dimension would be equally applicable to questions regarding those theories. Joshua Davis (talk) 20:11, 5 April 2008 (UTC)

Also, the article is "fourth dimension", not "fourth dimension in Euclidean space". And the introduction to the article specifically states that the fourth dimension in Minkowski space is within the scope of the article. Right now, outside the intro, there's a lot of material, some of which is just relevant to Euclidean space, and some of which is relevant to both Euclidean and Minkowski. It could certainly be better differentiated, and also, Minkowski-specific material might be worth adding. But I'd say it's within the scope of this project, even if we were to disregard the possibility of more than three spatial dimensions. --Steve (talk) 21:44, 5 April 2008 (UTC)

Put it another way: if it weren't for Einstein, the "fourth dimension" would not be a part of the popular vocabulary, and there would be no WP article by that name :-) linas (talk) 04:48, 8 April 2008 (UTC)

Template for displaying scientific values

This template is making good progress, the discussion has been moved to Template talk:ScientificValue. Here's some examples of it's use:

6.0221415×10²³ (Avogadro's number)

9.1093826×10⁻³¹ kg (mass of an electron).

5807.8+3.7
−3.9 MeV/c² (mass of a
Σ⁺
_b bottom Sigma baryon)

-- SkyLined (talk) 10:22, 9 April 2008 (UTC)

Role of special relativity in electromagnetism articles

[note: moved from above into dedicated section Steve (talk) 17:33, 11 April 2008 (UTC)]

Warren Siegel has some good advice for us. It is not a good idea to follow a historical approach to physics. In this case, I would suggest to rewrite all the electromagnetism articles on wikipedia. You just start with Coulomb's law and demand covariance under Lorentz transformation. That then implies the existence of the magnetic field, it yields Maxwell's equations and the equation for the Lorentz force.

This is how Nature works. How all these laws/equations were discovered is a matter of history. The historical approach is necessarily extremely confusing because at the time the laws were discovered we only had a partial understanding of the full theory. Count Iblis (talk) 13:45, 11 April 2008 (UTC)

Count Ibliss, by all means put that in the relativity section. But readers do generally like to see the classical evolution of a topic. George Smyth XI (talk) 14:18, 11 April 2008 (UTC)

My view on this is that the approach of starting with Coulomb's law and getting magnetism through Lorentz invariance is fine pedagogy in a coherent university course, but not appropriate for the primary presentation in an encyclopedia. My main reason is that it's very easy, when you do this, to give readers the false impression that electricity is more fundamental than magnetism. That said, Wikipedia's various electromagnetism articles make all sorts of mutually-contradictory statements about whether and to what extent it's possible to "derive" magnetism from Coulomb's law and special relativity and/or anything else. Accordingly, I recently made a dedicated page where anyone who has an opinion on this can duke it out, hopefully eventually leading to consensus and cross-article consistency. The page is: Classical electromagnetism and special relativity, and the section in question is currently rather sparse, having been simply copied from other articles. (I'm not personally familiar with these arguments.) Also, don't miss the related article Relativistic electromagnetism, which includes some related material, but is more pedagogical than encyclopedic. Thanks! --Steve (talk) 17:33, 11 April 2008 (UTC)

But then should we not start with the Standard Model, and show how classical electromagnetism emerges from that framework? No, we have to choose a more grounded place to start, a place to motivate any more abstract discussion.

Also, be careful! Siegal makes some good points, but Wikipedia isn't a science text-book, it's an encyclopedia. We're not trying to teach, but rather explain all aspects of a subject, including the historical and everyday.

For what it's worth, I've fought this battle before.--Starwed (talk) 09:10, 12 April 2008 (UTC)

On further thoughts, we could indeed start on a clean slate with Count Ibliss's proposal. But I think we would receive objections from a large volume of readers at high school level, and indeed undergraduate university level who are only interested in classical electromagnetism.

The relativistic approach that Count Ibliss suggests in actual fact involves some very difficult mathematics and I don't think it should be used as a substitute for the classical approach. Put yourself in the position of a final year college student wanting to learn more about electromagnetic induction. Will he want to read about Faraday's law or will he want to read about Lorentz covariance?

I think that Count Ibliss's proposals should run in parallel with the classical and historical approach and not as a substitute. I state my own personal opinion that the historical approach is actually very interesting and very important. I always like to know how humans first arrived at these ideas and how they evolved. I don't share the opinion as stated in the web link, that the historical approach is boring or confusing.

To completely erase the historical and classical approach would be getting dangerously close to George Orwellain style revisionism. There may well turn out to be valuable pieces of information in the works of the Great 19th century masters, that have been totally overlooked in more modern approaches. George Smyth XI (talk) 11:32, 12 April 2008 (UTC)

Reply to everyone: Here on wikipedia we don't have to follow precisely the way things are explained in textbooks. If we were to do that then things that are normally first explained at university could never be explained to lay people. Making things accessible to lay people is one thing, the historical approach is something else :) . Count Iblis (talk) 13:54, 12 April 2008 (UTC)

Actually, there is a bit of a policy that has been hashed out on wikiproject mathematics, and this only because of constant, recurring complaints that math articles are too obtuse, too hard to understand. The policy is to state things simply and plainly at first, even if this requires loss of rigor and little white lies. As the article moves on, additional rigor and formalism can be introduced. The goal is that the "average" reader might get half-way through before getting lost -- you don't want to loose them in the first few sentences.

As to textbooks: unlike most other subjects, physics seems to have a very highly standardized presentation style. The article on Maxwell's is a case in point. That article bears little to no resemblance to how most theoretical physicists understand Maxwell's eqns. today. These days, they are understood to be geometrical in nature, either as a fiber bundle, or in reference to adjoint 2-forms, or along those lines. God-help you tried to explain that in that article: a bevy of students would promptly revert it to the way its done in undergrad textbooks, and you will *never* win that argument against the students, there are too many of them, and they are too interested in passing mid-term exams to give a bleep that the "modern" way of writing maxwells eqns might be [d,F]=0. Don't fool yourself, WP is very highly textbook-oriented precisely because the students outnumber/outvote the professors on the basic articles. linas (talk) 23:46, 12 April 2008 (UTC)

I don't think that it is only students who would dislike the presentation of Maxwell's equations which you call "modern". Ask a random experimental physics professor about Maxwell's equations and I seriously doubt they would start talking about fibre bundles or differential forms. They just don't have a great need to think in those terms(depending of course on their specialty; experimental particle physicists will probably be more likely to use a more "high-brow" language). Given that theoretical physicists are a clear minority in the field, it hardly seems reasonable that topics with very broad interest, like classical E&M, should be written exclusively in their language. Joshua Davis (talk) 00:21, 13 April 2008 (UTC)

Single observer

I was thinking about the anime Noein, and it occurred to me that it might be implicitly based on the philosophical idea (akin to solipsism) that there is only one observer (in this case, Haruka Kaminogi) whose consciousness causes collapse of the quantum state (wave function) of the universe. This is kind of like the idea of the Hindu god Brahma who makes the world come into existence by looking at it. Do any of you know what this doctrine is called? Do we have an article on it? JRSpriggs (talk) 06:51, 11 April 2008 (UTC)

Heh. Hell of a question. Simulation hypothesis is not what you want, but is what comes to mind. linas (talk) 16:01, 11 April 2008 (UTC)

To Linas: Thanks, that sounds like The Matrix (film). Unfortunately, it is not quite that for which I was looking.

Does anyone else know anything about the (ridiculous) hypothesis that all wave function collapse is caused exclusively by the observations of a single consciousness? JRSpriggs (talk) 07:19, 12 April 2008 (UTC)

All wavefunction collapse is caused by me making observations. Clearly if you observe something then that's simply an interaction between you and the observed system, which is described by the Schrödinger equation. So, we have a unitary time evolution. No matter how much the system decohers by interactions with the environment, time evolution is unitarity. At least, we don't have any evidence that compels us to believe otherwise.

But if I observe something then the other sectors of the Hilbert space in which I saw something else have become irrelevant to me. So, there can only be an effective collapse of the wavefunction if I observe something, not if someone else makes an observation. Count Iblis (talk) 18:13, 12 April 2008 (UTC)

Roger Penrose had an idea similar to this hypothesis, the Penrose interpretation, except the role of the single observer was taken by the gravitational field (assumed to be non-quantum) instead of a consciousness. Personally, I lean towards the Many-worlds interpretation. But it can be objected that the state of system is really relative not just to the system but the observer as well because it is defined by measurements (interactions between the system and the observer). So that if there were no outside observer (as would happen if the system were the universe), then there would be no Hilbert space of states, i.e. nothing. JRSpriggs (talk) 10:51, 13 April 2008 (UTC)

Thermoelectric cooling: Just how does it work, anyway?

Can anybody please add a simple lay-comprehensible explanation to Thermoelectric cooling on just how it works?
The workings of conventional electric heating -- "pump electricity in, get heat" -- seem obvious enough, but "pump electricity in, get cooling" is puzzlingly counter-intuitive -- the thing is making some sort of tricky end run around the usual workings of the laws of thermodynamics. Where does the energy of the heat in the material being cooled go, and why?
Thanks for assistance. -- 201.37.229.117 (talk) 02:07, 14 April 2008 (UTC)

I am not an expert on this, but I believe that it just reverses the action of a thermocouple. By sending electric current in a loop through two different metals, heat is driven from one junction between the metals to the other junction. It does not disappear. Although some heat is in the form of vibration and twisting of the metal crystal, another part is in the form of pairs of electrons (with energy above the Fermi level) and holes (the absence of an electron below the Fermi level). At the junction being cooled, the heat energy is consumed by lifting the electrons from the lower Fermi level of one metal to the higher Fermi level of the other metal. Only the hottest (most energetic compared to the Fermi level) electrons cross the junction (becoming cool in the process) and then absorb heat from vibrations. At the junction being heated, the electrons fall back to the lower Fermi level and release heat. I hope that helps. JRSpriggs (talk) 03:43, 14 April 2008 (UTC)

I added a little pathetic stub of a section directing curious readers to the article Peltier effect, which seems to be the proper place for a reader to go to find information on this. --Steve (talk) 04:20, 14 April 2008 (UTC)

Wanted: Theoretical physicists

Hello physics people. I have been working to reconstruct the article about Emmy Noether on my drawing board. I have completed her biography and have now come to the part where I must explain (briefly, but in some detail) her contributions to mathematics and theoretical physics.

However, I – as an English teacher who failed astronomy in college because there were too many evil numbers – can't understand very much of the science behind Noether's theorem. I'm hoping one of you is willing (or can recommend someone) to help me write this final section about Ms. Noether's work in the areas of symmetry and conservation laws. If so, please leave a note here (I'll watch the page) or – preferably – on my talk page. I thank you in advance and will now recede to my lair of Balzac and Achebe. – Scartol • Tok 00:20, 14 April 2008 (UTC)

Note: We've filled in this information with the help of TimothyRias, but of course others are invited to review and make sure there's nothing horribly wrong. If anyone has source(s) for the "citation needed" second paragraph, those would be handy as well. – Scartol • Tok 19:32, 14 April 2008 (UTC)

A note for the project

Introduction to M-theory was completely rewritten in 2004 by an editor who included large swaths of text copied verbatim from the book Turn of the Century. The article was brought up for concerns about no references being cited in such a large article and the general format of 'introduction to...' articles when the copying was noticed (see Wikipedia:Administrators' noticeboard/Incidents#X for Dummies fork). Due to the volume of the material copied, and subsequent wording changes being derivatives of the copyrighted text, all revisions of the article since January 2004 were deleted. Since this was a lengthy article, I would appreciate it if members of this wikiproject could get it back up to speed. Four years is a long time to miss things in most theoretical science fields :) -M^ask? 09:00, 14 April 2008 (UTC)

Notice that this article has been nominated for deletion by Gwen Gale (talk · contribs) and Morven (talk · contribs). See Wikipedia:Articles for deletion/Introduction to M-theory. JRSpriggs (talk) 06:11, 15 April 2008 (UTC)

Update on Afd: "The result was nomination withdrawn.". Thus we should proceed with improving the article. JRSpriggs (talk) 06:38, 16 April 2008 (UTC)

Dispute at Faraday's law of induction

Hi everybody,

I just posted a "request for comment" in reference to an ongoing revert-war at Faraday's law of induction. Despite having better things to do with my time, I'm now having four simultaneous disputes with User:George Smyth XI -- at Talk:Maxwell's equations, Talk:Faraday's law of induction, Talk:Lorentz force, and Talk:Biot-Savart law.

Here are some of George's priceless quotes from the past week or two:

• "There is something seriously wrong with the Biot-Savart law"
• "Faraday's law and the Lorentz force contain exactly the same physics"
• "div B = 0 follows from curl A = B, but not vica versa".
• "Griffiths is totally confused"

Has anyone had success dealing with situations/people like this? I'm at my wit's end. :-) --Steve (talk) 06:37, 11 April 2008 (UTC)

Steve, at least tell them all what the argumnet is really about. It stems from the fact that originally you couldn't see that the Lorentz force is the equation for electromotive force that plays the role of Faraday's law in Maxwell's original eight equations by virtue of giving an equation for EMF.

In the modern Maxwell's equations we use a limited version of Faraday's law that is a partial time dervivative and hence doesn't cater for the convective vXB aspect of Faraday's law. As such, we need to compliment the modern Maxwell's equations with the Lorentz force in order to supply the vXB effect that is missing.

You somehow read into all this that there are two Faraday's laws. In actual fact, there are two aspects to a single Faraday's law.

You now want to cloud the introduction to the Faraday's law page by making the misleading claim that there are two Faraday's laws and discussing these fine details, when in fact they are dealt with in the main body of the article.

If Griffiths decides, as you say, that the EMF induced in a loop that is being pulled through a time-constant magnetic field, is not Faraday's law, then Griffiths is clearly wrong and confused. We cannot have the article on Faraday's law dictated by Griffiths. We need to adopt a broad approach based on all modern texbooks and all modern encyclopaedia.

The fact is that there is one single Faraday's law which was discovered in 1831 and described in the version of the introduction that you keep deleting.George Smyth XI (talk) 10:27, 11 April 2008 (UTC)

I'm with George on this; there really is only one "standard" Faraday's law; the fact that there's another, related Maxwell-Faraday law shouldn't cloud the issue. By analogy: imagine an article on Newton's laws of gravitation, wherein the very first few sentences claim that there are actually two such laws: the Newton laws, and the Newton-Einstein laws, which are almost the same except for a general theory which introduces a corrective term to Newton's laws ... Yuck! While this is true at some level, it completely plays havoc with trying to convey what Newton's laws are about, what one does with them, not to mention thier historical and cultural status. I don't think anyone would want to edit the article on Newton's gravitation in this way, and I don't think we should edit Faraday's law in this way either.

On the other hand, if George really said something like "div B = 0 follows from curl A = B, but not vica versa". -- well, yeah, that's the scent of blood in the water for sharks; which puts George at a serious disadvantage when negotiating. (disclaimer: I frequently make inane posts on topics I don't understand; and I frequently suffer the consequences). George needs to brush up on the hard math basics. linas (talk) 15:56, 11 April 2008 (UTC)

Linas, the difference is that there are a mountain of reliable sources that refer to the equation curl E = -partial B/partial t as "Faraday's law of induction". In fact, when you see "Faraday's law of induction" in a book or paper, it's about equally likely to refer to the "curl-of-E-and-partial-derivative-of-B" version as the "flux-and-EMF" version. There are not a mountain of reliable sources that write Newton's law with Einstein's correction and say "This is Newton's law of universal gravitation." Instead, they'll say, this the "Newton-Einstein law", or "Newton's law with Einstein's correction". When you see "Here is Newton's law of universal gravitation" written in a book or article, you can be almost 100% sure that the equation following does not have Einstein's correction. This is clear-cut WP:NPOV: The two different laws are equally represented as "Faraday's law" in the physics literature, so it would be wrong to completely privilege one over the other in the article. --Steve (talk) 16:49, 11 April 2008 (UTC)

Linas, I was misrepresented by Steve on the issue of "div B = 0 follows from curl A = B, but not vica-versa". I merely pointed out that curl A = B is a less ambiguous equation because div B = 0 might also be interpreted as referring to an inverse square law.

We know of course that in the case of the inverse square law solution that the divergence will not be zero at the origin and so in the case of the magnetic B field, it is important that we emphasize that the divergence is zero everywhere.

In the case of curl A = B, the equation is unambiguous. My ultimate point was that the equation div B = 0 is really referring to curl A = B and as such, the term 'Gauss's law for magnetism', while techniccally correct, is not the best name to use in the circumstance.George Smyth XI (talk) 00:10, 12 April 2008 (UTC)

OK. And there's a subtle point here: curl A=B is in a certain sense "more strictly correct", because it is a statement about local properties. By contrast, div B=0 is a global property, it states that there are no magnetic monopoles anywhere in the universe. Global properties have much more subtle , more advanced mathematics behind them than local properties. linas (talk) 22:45, 12 April 2008 (UTC)

I should know better than to get in the middle of this, but I was wondering how Jackson defines Faraday's Law. In the above argument and the talk pages that I visited there were some quotes from Griffiths which said one thing and also claims that Griffiths is wrong. So what do other books, like Jackson, say? I'd check myself but my copy is in my office. Joshua Davis (talk) 05:48, 12 April 2008 (UTC)

Jackson has a whole section on this (5.15). He states the integral form of Faraday's law as:

$\oint _{C}\mathbf {E'} \cdot d\mathbf {l} =-\ {d \over {dt}}\int _{S}\mathbf {B} \cdot \mathbf {n} \,da$

where E' is the electric field at dl in its rest frame of coordinates.

He also states the differential form as:

$\nabla \times \mathbf {E} +{\frac {\partial \mathbf {B} }{\partial t}}=0$

Hope that helps. --Starwed (talk) 09:27, 12 April 2008 (UTC)

Starwed, In all fairness to Steve, he did notice something that I don't think many people have noticed. The integral version of Faraday's law that you cite above is a full version of Faraday's law. It involves total time derivatives and as such it caters for motion dependent EMF.

The differential version below it only caters for time varying magnetic field dependent EMF, as it is a partial time derivative equation.

Unfortunately however, this whole dispute has come about because Steve has read into this the idea that there are two Faraday's laws. While there is certainly a matter which needs to be explained, I believe that Steve is over reacting in his assertion that there are two Faraday's laws.

My objective in all this was to begin the Faraday's law introduction in the normal manner explaining what Faraday's law is. Further down in the main body of the article, I would have mentioned the fact that the version of Faraday's law as it appears in Maxwell's equations, does not cater for motion dependent EMF and that it is an incomplete version.

Steve however wants to make a big issue of this in the introduction of the article. The result is a very unprofessional and misleading introduction. It begins by stating that Faraday's law is a term ambiguously applied two two different but related laws in EM.

That is not a professional way to write the introduction. The alternative version which Steve keeps deleting is much more in line with standard encyclopaedia and textbook introductions.

Steve has insisted in having his version of the introduction in place despite the fact that it is essentially wrong when the situation is viewed from the general perspective. There is only one Faraday's law.

Unfortunately, without giving any reason whatsoever, PhySusie has intervened to ensure that Steve's amateurish version remains in place. George Smyth XI (talk) 11:17, 12 April 2008 (UTC)

For what it's worth, Feynman's Lectures on physics uses essentially the same terminology as Griffiths. The flux one is called the "Flux rule", and the partial-derivative-and-curl one is called "Faraday's law". He's quite clear in differentiating the two. See page II-17-3 and thereabouts. --Steve (talk) 16:46, 12 April 2008 (UTC)

To clarify Starwed: the chapter in Jackson is titled "time varying fields, maxwell equations, conservation laws". Jackson starts with the integral form of Faraday's law, and then spends 3+1/2 pages on it. Then he spends a paragraph where he says (paraphrasing) "oh by the way, here's the differential form, its a trivial rewrite from Stokes thm". A section later, (after a 4 page interlude on Ampere's law), he introduces Maxwell's laws. The presentation implies, to me, a historical flow: (to paraphrase) "Here's that complicated Faraday's law which needs 3-4 pages of articulation and discussion, but it can be recognized as just one little piece of that grand unification, Maxwell's laws." As an aid to the student, he then writes "Faraday's law" next to one of Maxwell's laws. So what I get from Jackson is that he is assuming that students have seen the integral form first, earlier in their career, he takes to be the primary form of Faraday's law, and is using it to illustrate Maxwell's law. He's right to do so, the integral form is simpler to understand, and so is presented earlier in curricula. Yet, at the same token, by the time most grown men write about this, they've pretty much forgotten that there might ever have been a difference between the integral and the differential forms; its just six vs. half a dozen by that point in life. And Feynmann ... jeez, Feynman breaks the mold. He provides greater and deeper insight into everything, often by turning it upside-down and backwards. He does that on purpose.

I think there's yet another subtle point, really, and thats about the mutability of labels. I don't know, but I've been told, that Maxwell's original formulation of his laws used quaternions, and, as such, bore strong resemblance to modern-day spinor-type equations you might see in e.g. susy. Apparently he spent years working on it in this form, apparently preferring it (?) and that the div-curl form we know today didn't really become popular until after his death. Or at least, so I've been told. So that's the funny thing about equations, they're rather mutable, and the labels attached to them mutate as well. linas (talk) 23:20, 12 April 2008 (UTC)

Hi everybody! There's been little progress on this front in the past few days, except that George's series of priceless quotes continues to grow:

• "I can assure you that [an equation straight out of Jackson is wrong]. In fact, the correct equation is...." (See this edit, referring to this equation, the formula for the classical electromagnetic force on a magnetic monopole.)
• "Feynman didn't understand classical electromagnetism" (see here)

The conversation threads are all probably way too long, at this point, for anyone else to want to read. I sure wouldn't. :-) Oh well, no one ever promised me that Wikipedia would be a flawless system. To George's credit, most of the disputes have been restricted to the talk pages, apart from at Faraday's law of induction where it's also associated with a revert-war over the introductory section (subject of the still-pending "Request for Comment"). Hope all is well, --Steve (talk) 18:39, 15 April 2008 (UTC)

Steve, try and keep your arguments to physics.

Chapter 20, “Solutions of Maxwell’s Equations in Free Space”-

“I’ll tell you what I see. I see some kind of vague, shadowy, wiggling lines- here and there is an *E* and *B* written on them somehow, and perhaps some of the lines have arrows on them- an arrow that disappears when I look to closely at it. When I talk about the fields swishing through space, I have a terrible confusion between the symbols I use to describe the objects and the objects themselves…” p 20-10, vol II

Feynman, Richard Phillips, *The Feynman Lectures on Physics*, Vol I-III, (Commemorative Issue), (1989, 1964), Addison-Wesley Publishing Co., ISBN 0-201-5104-9 (v. 2)

Is that the writings of a man who understands classical electromagnetism?

No. But it's a great consolation to those others amongst us who don't understand classical electromagnetism even if they pretend to do so. As a last resort, they can always duck behind the line "Well if Feynman couldn't understand it, then nobody can, and so that excuses us'.

Feynman is also on record as saying that anybody who claims to understand quantum mechanics is either lying or stupid. So which category did he believe himself to fall into?

And clearly, Feynman had failed to see that very simple mathematical link between the vXB force and the partial time dependent version of Faraday's law. The relationship is a simple partial and convective derivative summation into a total derivative.

But you would rather dwell on the confusions of Feynman when it comes to a classical law such as Faraday's law, than listen to what Faraday and Maxwell have told you. You are on record as having ruled Maxwell's papers invalid as regards matters relating to electromagnetism.

I think that you are the one that needs to open your eyes a bit more to what is going on around you.

For Faraday's law, listen to what Faraday says. Not to what Feynman says. George Smyth XI (talk) 08:31, 16 April 2008 (UTC)

Hi George: It isn't unknown for Nobel Prize winners to be nuts, but usually it shows up outside their domain of expertise. I'd say that the Feynman quotes you make are more intended as expository devices to encourage some intuitive thinking than a sign of incompetence. In any case, I'd like you to look at the Faraday paradox, which might soften your view of Feynman. Brews ohare (talk) 15:16, 16 April 2008 (UTC)

Brews, Regarding the Faraday paradox, Feynman completely overlooked the fact that if he had used a total time derivative version of the Maxwell-Faraday law, then the vXB effect would have been catered for by the convective (v.grad)B term. Take the curl of vXB and you get (v.grad)B.

The maths is very basic. Total time derivative = Partial Time derivative + Convective derivative.

Feynman seems to have missed this basic fact. On the Physics forum web link which I supplied above, somebody called "Obsessive Maths Freak" points this very basic point out, but nobody seems to be paying any attention to him. They are all running around confused like headless chickens because of Feynman. It seems that if Feynman is confused, then everybody has to be confused and nobody wants to listen to the solution.George Smyth XI (talk) 02:05, 17 April 2008 (UTC)

To George: I have not been following this dispute in detail, so please forgive me if my question has already been answered. How can you talk about "the curl of vXB" when the very fact that v appears in it means that you are talking about a particle which has a single location, but curl is talking about a field defined over a volume? Which is it — a single location or a volume? JRSpriggs (talk) 04:02, 17 April 2008 (UTC)

JRSpriggs, it's only in recent times that a vector field has been restricted to referring to fixed points in space. Maxwell gave the full expression for electromotive force in an equation which is essentially the Lorentz force. It applies at points in space that are coincident with a moving charged particle. After all, an electric field only has any meaning when a particle is actually being accelerated.

Maxwell did however drop the vXB term when it came to deriving the EM wave equation for that very reason. He wanted to consider the wave equation with reference to a stationary point in space.

The fact is that if you take the curl of vXB, you get the exact result that makes the partial time derivative Faraday's law into the total time derivative version.

Feynman failed to see that vXB was in fact the convective term in Faraday's law.

Unless you are prepared to expand your understanding of vector fields to include moving points, then you will forever remain as confused as Feynman. George Smyth XI (talk) 09:59, 17 April 2008 (UTC)

Survey: bit/s/Hz, (bit/s)/Hz or bit·s⁻¹·Hz⁻¹ as Spectral efficiency unit?

Please vote at Talk:Eb/N0#Survey on which unit that should be used at Wikipedia for measuring Spectral efficiency. For a background discussion, see Talk:Spectral_efficiency#Bit/s/Hz and Talk:Eb/N0#Bit/s/Hz. Mange01 (talk) 07:21, 16 April 2008 (UTC)

I would guess that bits/cycle would be appropriate. JRSpriggs (talk) 10:40, 16 April 2008 (UTC)

Physics Portal Idea

I have this great insight: A subject as large as physics cannot have only one "Table Of Contents". It needs multiple TOCs, each organized in different ways. kinda like Yahoo shopping results sorted by different criteria. The sorts for physics: --by history --by "subject" [problem: what's a "subject"??] --by "Foundation".

Details on "Foundations" order: Crucial experiments/observations together with their related theory, in order by date of theory publication. An ultra primitive startup list:

PRIMARY OBSERVATIONS/EXPERIMENTS - [THEORY] --Observations of The Almagest; Copernicus; Galileo; Kepler et al-[Newtonian Mechanics] --Experiments of Faraday & others-[Maxwell's Equations] --Experiments of Planck, Debye, et al-[Quantum Mechanics] --Michelson-Morley experiment-[Special Relativity] --Precession of Mercury [General Relativity} --DeBroglie waves &??-[Shrodinger equation] --Electron/electron scattering [QFT & Dirac] --Face of Alfred E.Neuman-[String theory]

Ultra primitive list above needs a lot of work. Just a start.

Further thoughts: One index - by history - should include all people, great and small[er], experimentalists and theorists. The "Foundations Index" should only cover the most prominent observations, tied to most significant theories, like precession of Mercury and general relativity. I just realized I omitted thermodynamics cause I know no thermodynamics. I can see how debating what is most "Foundational" would lead to endless debate and strain Wikipedia. But it does seem like a great idea to try to create some kind of better ordered, briefer summary of physics. It is such a pivotal science but like David Letterman said "Its just so BIG". HarryWertM (talk) 16:38, 19 April 2008 (UTC)

"Featured" status of two pictures of waves

References for "Shallow water equations"

Shallow water equations includes a striking picture that has "featured" status, but the article has a "no references" tag. Does someone know what the most suitable references are? Michael Hardy (talk) 20:53, 21 April 2008 (UTC)

Another "wave"-topic featured image question

Frequency dispersion in bichromatic groups of gravity waves on the surface of deep water. The red dot moves with the phase velocity, and the green dots propagate with the group velocity. In this deep-water case, the phase velocity is twice the group velocity. The red dot overtakes two green dots, when moving from the left to the right of the figure.
New waves seem to emerge at the back of a wave group, grow in amplitude until they are at the center of the group, and vanish at the wave group front.
For gravity surface-waves, the water particle velocities are much smaller than the phase velocity, in most cases.

Here's an image found in group velocity. It's not visually stunning like some "Featured" images, but its purpose is to make a concept clear rather than to hit you between the eyes before you've read anything. This seems like a perfect example of a well-explained picture being worth a very large number of words. Should this one have "Featured" status? Michael Hardy (talk) 20:53, 21 April 2008 (UTC)

List of physics journals?

Does somebody know of a list (as complete as possible) of physics journals, including their ISSN? I'm currently working on extending a reference database, currently used in the Math WP, to physics, as well. I'd like to incorporate the journals into this database, as well. Thanks, Jakob.scholbach (talk) 09:25, 17 April 2008 (UTC)

according to Utrecht University (TimothyRias (talk) 11:39, 17 April 2008 (UTC))

Thank you. In the list provided above I would have to click at every single item. For the purposes of zeteo (see below) I need something which is computer readable without much clicking etc. Is there something in this manner, too? Jakob.scholbach (talk) 19:49, 22 April 2008 (UTC)

reference tool available for physics

There is now a database containing the references of all WP physics articles (as of April 08). This tool has been used by the Wikiproject Math community since about half a year and, according to the feedback I get, is a valuable tool for simple and quick referencing.

In total, there are 10500 references. You can access the database at http://zeteo.info. The references are linked to their corresponding authors, publishers, and journals respectively. An author/publisher/journal is a separate database entity, thus providing the correct structure to uniformly host additional information like wikilink of an author, issn of a journal etc.

More or less manually I fed the data into the database. It was quite a bit of work to do this. I haven't attempted to verify the information which is now in the database. An in-depth check of a small sample of templates showed, that the stuff is generally pretty well-done, though.

Several options are available; for example it is easy to let it put out something like

<ref>{{citation|...}}</ref>

for those who prefer footnote-style referencing. For your commodity, there is a little search engine template similar to the google toolbar etc., which can be integrated in the browser's menu. So, no excuses anymore :-) for not referencing an article when you actually know a reference off your head.

Anybody can add/update database items. It is possible to import bibtex files and also wikipedia source code (containing reference templates such as {{cite}} and {{citation}}) and let the database parse them, so you can relatively comfortably add the items of your personal bibtex file. A brief documentation can be found here, bugs and questions etc. can be reported at my talk page. Also, if you have ideas how to improve the database, let me know. I'm myself not into physics, so I don't know your guys' needs.

Enjoy! Jakob.scholbach (talk) 19:24, 22 April 2008 (UTC)

Crank posts

An IP user who has posted as 200.97.93.67 and 189.48.105.246, among others, has been adding stuff about his personal theory to talk pages, including an advertisement for his book, along with stuff on the main pages referencing the talk pages (these have been reverted).

He does this presumably since he knows his essays won't be accepted in the articles. I have deleted all his edits except those that have been replied to, which are on Talk:Wave-particle duality and Talk:Bohr model. Other pages he has edited can be seen in the histories posted above. The way, the truth, and the light (talk) 07:04, 21 April 2008 (UTC)

Yes, deletion is a good way to deal with this problem. It does, however, increase the entropy of the universe :) Count Iblis (talk) 14:15, 21 April 2008 (UTC)

Apparently this is banned W.GUGLINSKI. But WHY couldn't anyone tell me here? Why the hell did I have to find out by looking through Talk:Bohr model, AfDs, and a post at AN/I? The way, the truth, and the light (talk) 18:18, 22 April 2008 (UTC)

And apparently almost no one reads this page, where one would think information about physics articles might be found. The way, the truth, and the light (talk) 18:35, 22 April 2008 (UTC)

Good catch. Guglinski made a number of AfD edits under 200.X and 189.48.X IPs; I checked all of the IPs he used, but these two specific ones never popped up there. Bm gub (talk) 20:46, 22 April 2008 (UTC)

And yet again, see Wikipedia:Administrators'_noticeboard/Incidents#Fringe_pusher_block_evasion. The way, the truth, and the light (talk) 05:02, 29 April 2008 (UTC)

List of Baryons

I have been updating the list of baryons extensively in the last few days. However, I am not a particle physicist and it would be peachy if one (or twenty hundreds) could visit the List of baryons page and the Talk:List of baryons page to give some feedback and check if explanations given for different stuff makes sense. If you aren't a particle physicist, that's cool too. You could give general feedback about the page and if things were presented clearly. Headbomb (talk) 20:08, 22 April 2008 (UTC)

Major rework has been done, sections clarified, improved flow... so if you took a drive by a few days ago, you might want to take another one again. I'm trying to push this list to featured list status and help would really be appreciated.Headbomb (talk · contribs) 13:27, 28 April 2008 (UTC)

New article : Spin multiplicity

Over the past few days there's been a poster using IPs 87.194.39.42 and 84.56.74.246, reverting the redirects at singlet state and triplet state to point at the quantum-mechanical meanings instead of diradical. I didn't want to respond to him directly as he's used vulgar insults, but he does have a point. Therefore, I created the new article spin multiplicity to unify the physics and chemistry links here. I propose that singlet and spin triplet be moved over those redirects, for consistency - I just moved doublet (physics) (yet a third naming convention!) to doublet state, the only one I could do myself. The way, the truth, and the light (talk) 08:11, 25 April 2008 (UTC)

I think, in cases like this (overriding redirects with a history), it is best to address your request for assistance to a specific administrator. If you do not know who they are, see Category:Wikipedia administrators. JRSpriggs (talk) 13:28, 25 April 2008 (UTC)