Wikipedia talk:WikiProject Physics/Archive October 2009

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Leadership?

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

A bit off-topic -- but -- virtually all of the edits I do at WP are on math articles, with some spill-over to physics and comp-sci. I've not been active for the last few years, because I got tired of the editorial nonsense that goes on. Despite being inactive, I recently was attacked, more or less unprovoked, by a new-age editor who had vandalized an obscure math article I wrote, and someone else reverted. When I told him off, I was promptly piled-on by five admins who blocked me for several weeks. I'm kind of shocked that the power structure here has changed so much that we've got these kinds of nasty, abusive people in admin roles. I complained to the Arb, but they ignored the case. I don't know what to do, other than to complain here, and ask everyone to try to band together, and to figure out how to get the ugly admins and the (incompetent?) leadership out of power, redo Wikipedia leadership, and restore some sanity. linas (talk) 16:42, 13 October 2009 (UTC)

  • Horrible! What Admins tend to do is only focus on the use of "strong words" and not on what people are actually saying to each other in a dispute Modulo any politically incorrect word choice.

    Perhaps we should separate math and science articles from the rest of Wikipedia. The science articles would be subject to different Wiki rules and we would only have Admins selected by editors who have a large number of edits to science articles. Count Iblis (talk) 17:14, 13 October 2009 (UTC)
An editor made an honest mistake accidentally linking to the wrong article. Linas reacted by calling him an idiot. Aboutmovies warned him about the personal attack. Linas responded with "fuck off asshole" and calling him a dick-weed and generally sounding like a Beavis and Butt-head episode. An admin blocked him and Linas responded with with "fuck off" and "get rid of fucking asshole admins like you", etc. How would you have handled that differently? Wknight94 talk 17:34, 13 October 2009 (UTC)
Linas should have assumed good faith in the beginning. He didn't. From his point of view the edit was a deliberate act of vanadalism and he was wrong about that. So, he had to assume good faith, even though from his point of view an act of vandalism has occured. This means that here at wikipedia., even if you feel provoked you have to put aside your feeling atleast for a while and reserve judgment.
But this works both ways. If someone claims that you have vandalized a page then you should also assume good faith and assume that this wrongful judgement was arrived at due to a misunderstanding, even if you are somewhat angry about that accusation. Then, instead of giving a warning on the talk page, it is better to briefly explain that it was a misunderstanding (especially when you're dealing with an established editor).
It seems to have gotten nasty only after that warning was given. I'm not saying that both sides are equally to blame, I think Linas was more hotheaded. But then, we have the WP:AGF policy precisely because even not assuming good faith in a friendly way by one side can cause angry outburst on the other side. Count Iblis (talk) 18:06, 13 October 2009 (UTC)
I couldn't agree more. Linas is trying to appeal to people's anti-authority inclinations with his rants, but when the actual story is laid out, including diffs, most are coming to exactly your conclusion. Facts always win. Wknight94 talk 18:12, 13 October 2009 (UTC)


  • Linas, you dug your own hole. The behaviour you've shown was completely unnacceptable. This is not getting "piled on" by a cabal of admins, this is you behaving inappropriately and getting the routine disciplinary measures. Like it or not WP:CIVIL is policy, and any competent administrator would have banned/blocked you upon reviewing what happened. You will find very few people supporting you if you keep acting the way you did.

    In the future, when you have a problem with an editor, seek dispute resolution (in a calm manner, state the facts and let them speak. If it's vandalism, that will be obvious on its own, etc...), by asking on WP:30, WP:CNB or alternatively asking for input on WP:WPM or WP:PHYS (or a mix of these). You have a head on your shoulder, and it would be a shame to lose your expertise. So please be considerate of others in the future, and don't get yourself banned. If things get heated, go take a walk to calm yourself a bit, then come back and seek dispute resolution, explaining why you think editor X is wrong, possible sources of misconceptions and so on. If Editor X is a vandal, it will be obvious. It will also be more productive, because in the "old behaviour" case, the so-called vandalism doesn't get dealt with, and in the "seek dispute resolution" case, the so-called vandalism does get dealt with. Headbomb {ταλκκοντριβς – WP Physics} 17:15, 13 October 2009 (UTC)
What the heck is going on? Aboutmovies mistakenly added a link to Beyond Words Publishing, and Pohta ce-am pohtit reverted with the summary "Reverted good faith edits by Aboutmovies; That's part of the name of the book, not the publisher." I must be missing something, as the reason why such a minor episode would lead to such an amount of drama is way beyond me. ___A. di M. 19:30, 13 October 2009 (UTC)
Some talk page comments apparently: [1] followed by [2] and so on... --Falcorian (talk) 20:43, 13 October 2009 (UTC)
After carefully following the links and diffs relevant to this unfortunate situation, it seems clear that someone got very angry about a mistaken edit and has attempted to maximize and escalate the conflict in every way possible. The wikipedia policies on civility and assuming good faith are no different than the standard expectations of any real world job or collaborative project. Everyone understands the frustrations of trying to maintain article quality, but continuing to pursue this conflict and involve other editors in the dispute is not improving the encyclopedia. Ben Kidwell (talk) 22:13, 13 October 2009 (UTC)

This has been forum-shopped to Mediation, to the Arbitration Committee, and now to the talk pages of several WikiProjects. Editors coming to this situation with no prior knowledge should read Wikipedia:Administrators' noticeboard/IncidentArchive564#Nuclear meltdown at User talk:Linas, Wikipedia:Administrators' noticeboard/IncidentArchive567#User:Linas again, Wikipedia:Requests for mediation/User:Linas, and this declined ArbCom request to get up to speed. Please place all further discussion at Wikipedia:Administrators' noticeboard/Incidents#Linas, soapboxing on wikiprojects (and userpage), rather than having lots of little disjoint discussions everywhere that this has been shopped around to. Uncle G (talk) 02:05, 14 October 2009 (UTC)

Count Iblis: Wikipedia is never going to adopt different fundamental content or behavioral policies and guidelines for articles about math, science, or knitting. It is contrary to Wikipedia's culture. Further, the policies and guidelines work pretty well even in math and science. Editors in those areas do tend to get away with unsourced calculations, proofs, and "common knowledge", which is OK too. Also, why did you immediately jump to the conclusion that Linas was right and the admins were wrong, without checking? It's obvious that Linas's behavior is unacceptable, as a quick peek at his talk page shows. Finell (Talk) 20:41, 14 October 2009 (UTC)

Linas was wrong in the sense of being rude and not assuming good faith. But the diffs clearly show an ever escalating conflict; banning him for one week only added to that. If Linas comes back a week later and he is still angry, then I don't see how the intervention by the Admins was effective. Count Iblis (talk) 20:57, 14 October 2009 (UTC)
His conduct was wrong in every way possible. Editors who keep telling people to "fuck off" aren't going to be allowed to edit here, nor should they be. Admins have a limited set of tools to deal with bad behavior: they can warn and, if that doesn't work, block. They don't have an analytic couch, can't prescribe meds, and don't have the time or training to coach editors on anger management. If you think that you can do a better job with this particular user, and can turn him into a productive editor here, go ahead and do it. Complaining about admins who are just doing their job isn't helpful, and can be misinterpreted by troublemakers. Finell (Talk) 21:31, 14 October 2009 (UTC)

People! Please! This has nothing to do with physics articles. Please take it to the WP:AN/I section linked-to above. Uncle G (talk) 23:56, 14 October 2009 (UTC)

Agreed. Everyone said their piece anyway. I'm archiving this. If anyone feels that this is not a closed issue, start an WP:RfC/U or ask for WP:MEDIATION or something like it. The project's talk page is not the proper forum of discussion for things like this. Headbomb {ταλκκοντριβς – WP Physics} 04:30, 15 October 2009 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.


No-communication theorem

The article is incomprehensible for a non-expert. Can you please rewrite it such that an ordinary user can understand it? --rtc (talk) 22:38, 3 October 2009 (UTC)

Continuous x-ray

Hi, can someone please have a look at the merits of this article? Looks like a deletion candidate to me, and at least needs a better title. --Pgallert (talk) 15:01, 5 October 2009 (UTC)

I've added mergeto/mergefrom templates, with discussion at Talk:Bremsstrahlung#Merge_from_Continuous_x-ray. --Christopher Thomas (talk) 21:21, 8 October 2009 (UTC)

Physics error in Featured Image for 9/23/2009, Snell's Law !!

The image, in the article at "Explanation#Derivations", is incorrect in the lower part, below the interface. It shows the wavefronts as becoming hyperbolic, so that the portions at large distances from the central axis asymptotically become straight lines. However, the refracted rays below the interface would then not appear to diverge from a point, and that is not the case in reality. The point source position is shifted (upwards, in the figure), but the light source seen from below the interface still appears as a point. This means the wavefronts must continue to diverge from a point, and thus remain segments of a sphere, with only the center of the sphere being shifted. The figure needs to be corrected by someone with a facility in graphics animation. A few other editors should verify and confirm my conclusion, but it is really quite obvious, and easily apparent visually so that it needs to be fixed quickly.

Can some of our project members please verify my reasoning (? on the article talk page I guess, where I have made the same point) ASAP, so the figure can be fixed quickly, as it is embarrassing to the Wikipedia in general, and to the physics project in particular, in my opinion. Thanks! Wwheaton (talk) 16:07, 23 September 2009 (UTC)

I am not 100% certain because the equations are close to impossible to solve, but I think the diagrams are correct. When I solve for the location of the beam that has traveled an arbitrary distance d as a function of the incident angle on a planar surface from a given location at a distance s from the plane then I obtain a plot that is very similar. (The equations are messy but I checked a number of limiting cases and they appeared correct.) I think the problem is that images are formed for planes only in the small angle approximation.
Putting it a different way. Perfect images are formed only for a cartesian ovoid. (See equation 2-7 in Pedrotti, Pedrotti, and Pedrotti on page 27.) I have no clue what a cartesian ovoid is, and I couldn't find any good references to it. I have no clue whether or not a plane is a particular type of 'cartesian ovoid'. It does not appear to be the case, by my rudimentary calculations, though. TStein (talk) 14:43, 12 October 2009 (UTC)

Orthotomic in geometrical optics

Could someone with some knowledge of geometrical optics please look at the Orthotomic article? Right now it's written as a purely mathematical subject and as such it's basically an alternate name for something else and is flagged for a merge. My research has turned up a possibly broader meaning in optics though so I'm raising the issue here to see if anyone wants to expand the article from that perspective.--RDBury (talk) 17:31, 11 October 2009 (UTC)

Here's the optics definition I know of [3]: "A normal ray congruence (also called orthotomic system of rays) is a set of rays whose trajectories are normal to a one-parameter family of surfaces, which are the wavefronts. For instance, the rays issuing from a point form a normal congruence" (with spherical wavefronts). Seems to me that this is totally unrelated to the math definition, so it should be a separate article. Is this the same definition you're thinking of? Is there a relation I don't see? --Steve (talk) 18:39, 11 October 2009 (UTC)
Not totally unrelated, maybe 70%-80% unrelated. As I understand it, if the light from a point source is reflected off a curved surface, then the resulting rays will be an orthotomic (physics) system and the family of surfaces they are normal to are the orthotomic (math) of the surface and the surfaces parallel to the orthotomic. It sounds like the name of the optics article would be orthotomic system of rays and a disambiguation page would be more in order.--RDBury (talk) 19:16, 11 October 2009 (UTC)
FYI, the article is now merged and changed to a redirect.--RDBury (talk) 13:56, 12 October 2009 (UTC)

Fact checking and correcting my list

Hi all! I just completed a major rewrite and expansion of the list of elementary physics formulae. I'm just a student myself so I feel it would be smart to have someone check my work. The list attempts to be a complete 'cheat-sheet' or list of theorems for a first year two-semester college course or for non-specialists who need to keep the basics handy. I've tried to keep the theorems as unit-system agnostic as possible while avoiding changes which would render the material into an unrecognisable form to students (IE I've kept the SI magnetic and electric constants). I would be overjoyed if anyone would like to take a look and offer advice or corrections. Also I've lost the fluid dynamics section of my notes, so that still needs to be filled in. Stuff needs DABed too but I'm working on it. Regards, -Craig Pemberton (talk) 22:46, 12 October 2009 (UTC)

Article status challenge

Here's a challenge: by the end of the year, let's try to get all of our top-importance articles up to at least C class and our high-importance articles up to at least start class. We currently have 35 start-class/top-importance articles and 54 stub-class/high-importance articles. With 3 months to go in the year (decade...) then if a few people join in, we should be able to get both of these numbers down to 0 with a bit of effort! Djr32 (talk) 22:05, 2 October 2009 (UTC)

(To find the articles in question, go to Wikipedia:WikiProject Physics/Quality Control#Table of articles by quality and importance and click "show" on the green bar, and then click any of the numbers in the table that appears.) :-) --Steve (talk) 22:32, 2 October 2009 (UTC)
Good point Steve! I've edited my original post to add links directly to the relevant categories. Djr32 (talk) 09:28, 3 October 2009 (UTC)
Good idea, although I think that more than 10% of these articles should be merged into their "parents". ___A. di M. 18:12, 11 October 2009 (UTC)
I agree that some articles are likely to be merged - I've done one or two of these already, and proposed a few more. Progress so far: we now have 31 start-class/top-importance articles, 48 stub-class/high-importance articles, but unfortunately we've gained 1 stub-class/top-importance article. Djr32 (talk) 20:17, 11 October 2009 (UTC)
Should that one article be merged into physical quantity? (Or can "physical property" also refer to non-quantitative properties?) ___A. di M. 21:41, 12 October 2009 (UTC)
Apparently it can, at least according to the first sentence of Physical quantity: "Informally, a physical quantity is a physical property that can be quantified." I'm not sure there's much to be added to Physical property, or indeed much to be said about non-quantitative physical properties (but then I am a physicist...) Perhaps the two articles could be merged but under the heading Physical property?
Progress after 2 weeks: 29 start-class/top-importance articles, 39 stub-class/high-importance articles, 1 stub-class/top-importance article, 1 long-running row kicked back into life. Djr32 (talk) 22:15, 18 October 2009 (UTC)

IP creating questionable articles, part II

We had a discussion in August (link) about 195.47.212.108 (talk · contribs · WHOIS), who has created 11+ dubious physics-y articles. Nothing seems to have happened since then. So I figure I'll get the ball rolling...I proposed deletion for one of those articles, selfconsistent electromagnetic constants. Please contribute to the AfD discussion. --Steve (talk) 20:50, 8 October 2009 (UTC)

We need more science-types taking a look at this AfD, especially if it's intended to be a trial balloon for the rest of the IP's articles. So far only two people from WT:PHYS posted (along with the IP and one self-stated non-expert). --Christopher Thomas (talk) 21:28, 11 October 2009 (UTC)
All articles created by this editor need to be looked at. If it doesn't yet exist, why don't you create a page for physics AfDs like this one Wikipedia:WikiProject Deletion sorting/Academics and educators? Interested people could then put it on their watch list. Xxanthippe (talk) 01:22, 12 October 2009 (UTC).
There was at one point a "Wikipedia:Pages needing attention/Physics" index page, but that's been unmaintained for years now. Problematic articles mostly just get flagged here, as far as I know. Article improvements, as opposed to problems, do get handled by a centralized system of some kind (the article sorting/classification mentioned in another thread), but I haven't worked with it.
Regarding the "walled garden" of synthesis works this used appears to be creating, if people feel they should be deleted, they can probably be flagged in one omnibus AfD. These are usually titled "(Article), and related (Article), (Article), (Article), ...", and listed only under the first article. This only actually simplifies the process if the articles are similar enough that people vote the same way for all of the ones named. May be worth a try, if the present AfD results in a deletion consensus. --Christopher Thomas (talk) 01:40, 12 October 2009 (UTC)
Also, we now have the Article Alerts system going on (see WP:PHYS, on the right) as do most active projects. Simply tag the talk page with the relevant projects' banner and they'll be notified in the next 24 hours. Headbomb {ταλκκοντριβς – WP Physics} 06:02, 12 October 2009 (UTC)
The closest delsort is Wikipedia:WikiProject Deletion sorting/Science, which has five articles listed at the moment. - 2/0 (cont.) 02:54, 13 October 2009 (UTC)
I supported deletion of the above article, but in studying these interrelated articles, there does seem to be more substance than I would expect from standard fringe/original research contributions. Are participants in this discussion knowledgeable enough in current research in gravitation and electromagnetism to verify that these are not legitimate attempts to summarize notable research topics? The topic of mathematical connections between general relativity and maxwell's equations goes back a long way (Kaluza-Klein_theory) and I'm not familiar with all the contemporary approaches. Perhaps some dialogue with the author might be attempted? Ben Kidwell (talk) 02:38, 12 October 2009 (UTC)
The content of most of these articles looks valid, actually. The problem is not WP:FRINGE, but WP:SYN: Anon seems to be trying to write a book about the topic, not an encyclopedia article. They're also completely ignoring the content that already exists (duplicating material rather than improving existing articles). --Christopher Thomas (talk) 02:47, 12 October 2009 (UTC)
I agree that these articles, even if accurate, do not correctly present and integrate their material with the rest of the enyclopedia. I also think that only someone who already understands all of the content is going to be able to parse any of it! At the same time the contributor seems to be working in good faith and has the knowledge to be a useful editor, so hopefully their energies can be directed to improving articles and creating new ones that fit with the current organization of content. Quite a bit of time and effort seems to have been invested and I'm concerned that wholesale deletion without trying to engage the editor may seem like an unfriendly community reaction to good faith contributions. Ben Kidwell (talk) 03:16, 12 October 2009 (UTC)
Feel free to mentor them if you want. I'm mostly returning to wiki-sabbatical, and so am not in a position to do so. They also didn't display much comprehension of the issues involved in their comments on the AfD, so I'd expect this to be an uphill struggle. Arguably worthwhile, still, but I'm not going to be the one doing it. --Christopher Thomas (talk) 03:21, 12 October 2009 (UTC)
Thanks for the perspective and information. I will try to stay engaged in a constructive way but without the expertise to differentiate between what is well-established consensus in the field and what is an original synthesis I don't feel very confident in engaging with this material in the detail which it demands. (Later) After seeing some additional comments of this user at the AfD discussion which seem to indicate that he thinks his work stands in contrast to conventional field theory, I'm inclined to think the fringe issue is real and en-masse deletion is probably the necessary solution. Ben Kidwell (talk) 15:44, 12 October 2009 (UTC)

See Here...there's some idea that modern quantum mechanics doesn't discuss capacitances and inductances enough, and is overly-focused on electric and magnetic fields. (That's what he or she may have meant by "feeld theory" at the AfD discussion.) That whole article is very strange, by the way. In reality, the quantum treatment of an electromagnetic cavity is very well known: The classical electromagnetic standing waves get quantized into photons, etc. This article does it differently, creates a nonsense Hamiltonian in "charge space", and calls the result "nonrelativistic quantum electrodynamics, which considers elementary particles from the intrinsic point of view. Note that, the standard quantum electrodynamics conciders elementary particles from the external point of view." It infers that the electron isn't a point charge but has a uniform mass distribution over a sphere of a certain radius, and that the electron mass comes from these quantum electromagnetic resonator oscillations or something.

OK, I found how to AfD multiple articles at once. I'll wait for this AfD discussion end first though. --Steve (talk) 17:10, 12 October 2009 (UTC)

Do you think there is anything that can be salvaged from all this work? For instance, we have an LC_circuit article and I do find a fairly significant amount of published research about the Quantum_LC_Circuit. I tried to compare the IPs treatment of the topic with this and it seemed like they were at least starting out from roughly the same place - but then the article moves to the concluding sections such as "photon as LC circuit" that are non-standard. Would it be possible to prune the OR material and leave anything meaningful? Ben Kidwell (talk) 19:17, 12 October 2009 (UTC)

Well...

In general, I haven't seen any valuable discussion or derivation of standard physics anywhere here. There's a tiny little bit, but all the "meat" of the articles is weird OR, in my opinion. Quantum capacitance is marginally better than the others, it has some sentences and equations and references that might be kept during a rewrite.
By the way, the same IP is putting nonsense into other articles, like Quantum harmonic oscillator and Planck mass. Worse, the nonsense doesn't get deleted very quickly, since it's so technical-looking. --Steve (talk) 00:28, 13 October 2009 (UTC)
Maxwell-like gravitational equations seems to be about the same topic as gravitomagnetism; while not something of top importance, that's not fringe nor too obscure for Wikipedia. Stoney units are units in which c = G = e = 4πε0 = 1 and ħ = 1/α; they might not be commonly used today, but they are of historical interest as the first system of natural units ever used. Not sure of whether they deserve their own article or it should be merged into Natural units; the Stoney mass itself clearly doesn't deserve its own article. (Of course, OR-y stuff should go away.) ___A. di M. 01:12, 13 October 2009 (UTC)
Would you be willing to give them a formal request to stop adding non-mainstream material? I don't have a strong enough QM background to be able to state what material was objectionable. If they've been warned, and continue putting in material that's demonstrably bogus, then further steps in WP:DR can be taken, but we should be trying to talk to them first. --Christopher Thomas (talk) 01:06, 13 October 2009 (UTC)
Thanks for taking the time to wade through all that. Hopefully the cleanup process won't be too difficult. Ben Kidwell (talk) 01:18, 13 October 2009 (UTC)

The IP is active on the AfD again. I've reached my "dealing with this crud" limit, and I think they'll only accept responses from someone who can critique the math. I'm bowing out. --Christopher Thomas (talk) 06:55, 13 October 2009 (UTC)

The first AfD passed. Now eight more articles are listed for another AfD. Please contribute at Wikipedia:Articles for deletion/Selfconsistent gravidynamic constants. --Steve (talk) 22:30, 15 October 2009 (UTC)

Emission Spectrum Lines Images Proposal

Suggestions for pictures of emission spectra

I am learning about emission lines in physics right now, and I noticed that we don't have very many diagrams of them, and that it would be nice if they were standardized. So I am proposing that we make standard images for them according to the following plan:

  • Make it in SVG format. This is a vector format, and so the lines can be placed with arbitrary precision, and the image can be scaled as much as necessary without losing any information.
  • Use the same color scheme for all of them. I'm not sure what would be best as there are several problems in displaying the spectrum on a RGB monitor. See [4] and also the discussion at the visible spectrum talk page.
  • Use the same reliable source for each image. I don't really know enough about this yet to know what a good source would be, so some suggestions here would be appreciated.

Also, although not as aesthetically pleasing, it might be useful to include a "ruler" next to the spectrum like in this one File:Helium_spectrum.jpg. Additionally, to make these images easily created and edited by others, I was thinking that I (or someone) could create a continuous spectrum, and then black out the unseen parts in each specific picture. This method could work for the absorption lines as well. I'm not sure that we really need an image like this for every element, but it would be nice on ones named after their emission lines like Indium and Thallium. Any suggestions welcome. Jkasd 09:14, 9 October 2009 (UTC)

It's an interesting suggestion, and I've posted a link to WT:CHEMISTRY in case any other chemists want to come through and give their opinions.
We currently have three types of images of atomic emission spectra.
  1. This image of the iron spectrum was created roughly in the way you suggest. For me it has two main problems:
  • It is not a good representation of the differences in intensities of the different lines. Some spectral lines are brighter than others, but it is very difficult to express this by the simple method that is proposed here.
  • Related to the above, the image is a poor representation of what you would actually see looking through a spectroscope – we have better, but not for all the elements by any means.
  1. We also have 19th-century artists impressions of spectra, such as this and this. The spectra of thallium and indium are the fourth and fifth from the top (respectively) on the right-hand side of the second image.
  2. We also have a small set of images which appear to have been taken directly through a spectroscope, such as this helium spectrum. I'd say that we're lucky to have them, as they must have taken a great deal of work to obtain. I'm not sure if this caesium spectrum was taken from a photograph or created from data, but it is a very good image all the same.
I am hesitent as to the utility of spectral diagrams such as the iron spectrum – they seem to given a certain "false impression" to me – but I look forward to other comments. Physchim62 (talk) 12:12, 9 October 2009 (UTC)
Well due to the limitations of the average monitor color space, there will be a trade-off between color and intensity. We could either accurately depict the brightness of each line, or the color of each line, but not both. Figuring out a good compromise is probably the hardest part of this project. Jkasd 22:19, 9 October 2009 (UTC)
I think it'd be more useful to accurately depict brightness than to depict colour. The human eye more readily distinguishes brightness, so a tradeoff that favours brightness will give the reader a closer impression to what the spectrum actually looks like. Regarding thickening lines to give the impression of brightness, I'd caution against doing this excessively; in the photographs of spectra linked from this discussion, you can see a few places where a spectrum has double lines, which would be more difficult to distinguish if lines were too thick. Thick lines might also falsely give the impression of a wider or doubled spectral line, so I'd argue for a consistent width (not necessarily single-pixel, but used for all lines).--Christopher Thomas (talk) 18:10, 17 October 2009 (UTC)
That's a good point. The image is in svg format, so the width would not be "single-pixel" but would be some proportion of the spectrum, for example, in my image below, the width of each line as approximately 1 nm. Do you know how close the closest double lines are, so I can make sure I don't make them too thick? —Jkasd 23:29, 17 October 2009 (UTC)
Based on the conversation at Talk:Hydrogen#Emission Spectra, it seems that finding good data for intensity values would be difficult, and approximate at best. —Jkasd 02:18, 18 October 2009 (UTC)
Among other things, I'd expect the strengths of lines in the emission spectrum to vary depending on how the gas was excited, so there may not even be one universally accepted set of line strengths. The data tables on the web site linked from that thread should be sufficiently reliable to use (they're cited as being from NIST). NIST may also have data for other gases and substances available. Regarding linewidths and double lines, I'm not sure where you'd find data (though NIST would be a good starting point). For purposes of pictures, looking through the data tables should tell you how close lines can be spaced. I hope this helps! --Christopher Thomas (talk) 06:35, 18 October 2009 (UTC)

Generating new pictures, take 1

Perhaps a better question to ask is: "What purpose would such pictures have and what information would we like them to convey?" Then we could have some sort of guiding principle for deciding on the details. Jkasd 05:18, 10 October 2009 (UTC)

Hydrogen Emission Spectrum.svg

Visible spectrum of hydrogen.jpg

The top picture is a new one that I created using this method, while the bottom one is an actual photograph of it. I made the bottom half of the red line a little brighter by increasing the saturation, but I think to accurately depict the brightness, we would have to have a gradient from red to white to red, depending on the brightness. I think that since when we have an actual photograph we should use that, but since these photographs seem to be rare, I think it would be good if we had a way to create an accurate diagram. An additional way to convey brightness, also seen in the photo, is to increase the width. A combination of these methods may yield a tolerable result. The color spectrum I used was the one from here. (Note: I did not take much effort ensuring the accuracy of my top picture, it is merely a proof of concept.) Jkasd 09:42, 17 October 2009 (UTC)

I have now changed the H-alpha line by making it slightly thicker and by overlaying a gradient on it to look brighter. The top half is at half brightness and the lower half is at full brightness. —Jkasd 23:31, 17 October 2009 (UTC)
I have changed it to a new version now, no attempts to convey brightness have been made, but the data is from NIST. The lines have been colored according to the algorithm here. —Jkasd 09:58, 18 October 2009 (UTC)
The second column in the NIST data seems to be intensity, though it looks like http://astro.u-strasbg.fr/~koppen/discharge/ used a log scale when turning this into colour information (probably a good idea, if we're keeping the lines with intensity less than 10, but it'd have to be noted somewhere in the figure). From a scan of the data table and detailed figure for magnesium, it looks like the closest pairs of lines are 0.5 nm, but that 5 nm and larger is more typical of spacing. It's much worse for things like xenon, of course.
Would it help if I wrote a script to crunch the NIST data into SVG spectrum graphics for evaluation (and hopefully eventual use)? --Christopher Thomas (talk) 16:38, 18 October 2009 (UTC)
Well actually the current version of the picture was created by a python program I wrote. But I don't know how to write a script that would go through the NIST data (I had to input the data by hand). So a script that does that or pointers on how to write one would be helpful. About the intensity, I agree that a logarithmic scale would probably be best. I'm still not sure how I'm going to depict it though. —Jkasd 22:14, 18 October 2009 (UTC)
I was going to put together a Perl script, that would use file I/O to read the data tables and write the SVG files (they're text/XML; very convenient). Perl has string-processing operators that make it very easy to parse data out of files like this. My understanding is that Python is just as good for all of these tasks.
Should I put together the script, or would you prefer to modify yours? My default plan would be to make a picture with two spectra (top linear intensity, bottom log) so as to both show the perceived intensities, and show the fainter lines, without sacrificing either one. In between I'd put a small colour strip to give the reader a better idea of the part of the visible/near-visible spectrum they were looking at (near-IR/UV would be illustrated with red/violet lines, but indicated as non-visible in the colour strip). Let me know if I should put this together (I have a bit of free time this afternoon, and it should take at most an hour or two). --Christopher Thomas (talk) 22:51, 18 October 2009 (UTC)
Whatever way is easier for you is fine by me. Here is the code that I've been using:
As you can see, it is not very well written yet, and could use some major improvements, especially the part where I convert from RGB to hex. Also, the "wav2RGB" function was slightly modified from here. (Are there any copyright issues I should be aware of?) The "H.esl" file is simply a list of all the wavelengths (in nanometers) of Hydrogen, one per line. —Jkasd 23:24, 18 October 2009 (UTC)
I'll probably write my own version using yours as a reference implementation, then. Thanks for the link to the RGB conversion information, also! --Christopher Thomas (talk) 23:55, 18 October 2009 (UTC)
Also, in the current version, the width of each line is slightly larger than 0.1 nm. —Jkasd 22:18, 18 October 2009 (UTC)

NIST data and Ritz wavelength

(Outdented; this was a reply to the previous section's thread.)

Also (again), could someone please explain the difference between the "Observed Wavelength" and the ""Ritz Wavelength" to me? —Jkasd 22:23, 18 October 2009 (UTC)

I'm having trouble finding references to "Ritz wavelength". The closest I can find is Rydberg–Ritz combination principle, which says that if two wavelengths A and B are in the spectrum of an atom, lines with wavelengths (A+B) and (A-B) may be present too. I'm glossing over a large amount of detail (didn't read the article giving the detailed derivation), but it sounds like this is just a logical consequence of any given line representing a transition between two levels (level x->y gives line A, level y->z gives line B, and x->z gives line (A+B), for example, if all of the transitions are ones that are allowed). Because the angular momentum will differ between levels, the formula won't quite hold (angular momentum changes the energy level slightly if there's a magnetic field or if the atom has a significant magnetic moment). This may or may not be the difference you're asking about.
Further context might help pin this down. Where did the question come up? --Christopher Thomas (talk) 22:51, 18 October 2009 (UTC)
Those are the first two columns in the NIST data. It offers this as an explanation, but I'm afraid I don't quite understand it. —Jkasd 23:06, 18 October 2009 (UTC)
Ok, according to the documentation, the Ritz wavelength is the calculation of what the wavelength should be, given the starting and ending energy levels for that transition, and the observed wavelength is what the spectrograph measured the wavelength as. The Ritz value is treated as more accurate for most cases, because the energy levels have (usually) been measured very precisely, and the spectrograph used for any given plot may not have been calibrated quite as precisely.
The documentation also confirms that relative intensities of the lines vary considerably depending on how the equipment is set up. I still think it's useful to have them, but this is also a good reason to keep the log-intensity plot as well (lines won't quite be constant-intensity, but will be a lot closer).
Mining the NIST database should be straightforward. I think it counts as a US government work and so public domain, and the spectrum values themselves aren't possible to copyright, so this should be compatible with Wikipedia's policies (especially since we'd be producing derived diagrams, not copying the data tables verbatim). Others' thoughts on whether this is appropriate? It's a pretty important consideration. --Christopher Thomas (talk) 23:35, 18 October 2009 (UTC)

Generating new pictures, take 2

(Outdented; this was a reply to the previous section's thread.)

I would expect using the information from NIST to be fine. (I actually was concerned about my use of the code from the blog). About the Ritz values, should I use those instead? Also, I have found that repeating a line increases the perceived brightness, to about 10 repetitions. I think that a combination of increasing the width (very slightly) and repeating a line could be used to achieve the desired effect. —Jkasd 00:05, 19 October 2009 (UTC)

I'm using my own variant of the RGB code, better-suited to Perl (a piecewise-linear list of transfer functions stored in a hash, roughly matching the curves given in Dan Bruton's code, with a bit of magnitude normalization thrown in to remove the bright yellow/cyan bands in the continuous spectrum). I'm really leery of making lines with different widths. It'll increase the apparent brightness as long as they're smaller than about 1 milliradian to the viewer, but beyond that will increase both apparent brightness and width, which would lead to confusion with closely-spaced groups of lines. I'll run a few test images and see how they look.
I'm going offline for a while, but should post an update tonight or Monday night. I'll provide the code when I'm finished, so anyone who wants to tweak it can. --Christopher Thomas (talk) 00:19, 19 October 2009 (UTC)
I understand your concern about increasing the width, but I have found that starting with a width of .01 nm, which is barely visible at "normal" scaling, and multiplying this by the square root of the relative intensity increases the perceived brightness noticeably, and at the maximum relative intensity I could find (500), the width of the line is only .22 nm, which I think is acceptable. —Jkasd 00:36, 19 October 2009 (UTC)

Here are images made using the first-pass version of my script. Top spectrum has linear intensity, bottom spectrum has logarithmic. So far, I have to download NIST data manually (though the script will parse it without me having to do data entry). I'm using lines instead of rectangles, and parameters like the visible range are hardcoded (though set up in a way that makes it easy to make them command-line parameters). If the displayed range extends into IR or UV, "IR" and "UV" labels are added at appropriate ends of the display (including the same one at both ends, if you're doing a close-up of a non-visible part of the spectrum). Everything including text scales to the correct size when a sub-range is being plotted. The aspect ratio of the image stays the same.

The main problem I've found so far is that the browsers I've tested don't like me trying to specify a rendering size for an SVG image. So, even though a picture of, say, the 500-600 nm range of the Magnesium spectrum can be scaled to arbitrary size, it renders as a nearly-unreadable thumbnail. I can kludge a solution by introducing a "preferred size" into the script, and wrapping everything in an object-group box and scaling it to the preferred size. Not tonight, though.

Comments about what works well and what could be changed are appreciated. Not sure when I'll next have time to modify the script (this weekend was semi-vacation, but next weekend is very busy).

(I know the Xenon spectrum looks dim; near as I can tell, there's a very strong line in near-IR that's messing with my autoscaling.) --Christopher Thomas (talk) 06:50, 19 October 2009 (UTC)

Emission spectrum of helium (from NIST data).
Emission spectrum of xenon (from NIST data).
So what difference does having lines instead of rectangles make? I checked and it seems like you still have to have a width for them. It would be nice if there was a way to make the lines have the same width regardless of the scaling factor, but I doubt it is possible. Also, inspired by the note by the relative intensity in the NIST data that said the intensity was shared by several lines, I made a new image using only the Ritz wavelengths. Here is the one for Helium:

Helium Emission Spectrum.svg

At least on my browser (firefox) the intensities look about the same as yours on the logarithmic scaling. All the widths are the same, no effort was made to depict intensity at all, so this might yield a better way to do this. Some of the lines are missing because no Ritz wavelengths were given for them. Jkasd 07:18, 19 October 2009 (UTC)
Lines in SVG have a consistent width regardless of scale (one pixel by default, I think). You can override this by specifying a stroke width; not sure if that stays consistent or not (haven't tried it).
Re. missing lines, I hadn't noticed that Ritz data was sometimes missing (the NIST site said this happened when measured data was more precise, but I hadn't seen it in other spectra). It's easy enough for me to update my script to parse that too.
Re. logarithmic vs. constant, I'm concerned about what happens with things like Image:Emission_spectrum-Fe.png, where you lose enough information for the spectrum to be not terribly informative. The best way to handle this is probably to have several rendering options, make a big table of specrta rendered the default way (whichever that ends up being), and ask everyone to go through the table flagging images that should be rendered a different way. Nothing says we can't fine-tune rendering on a per-image basis as long as they look consistent. --Christopher Thomas (talk) 16:41, 19 October 2009 (UTC)
I changed my program to lines to see if this works, but the lines definitely got thicker as I zoomed in, even though I didn't define a stroke width. However, I found that adding this "shape-rendering:crispEdges" to the lines' style gave the desired effect. That is, the lines can be extremely thin, say .001 nm, but they will be clearly visible even on a thumbnail sized picture. It basically forces the lines to be one pixel despite the magnification. Jkasd 22:36, 19 October 2009 (UTC)

Christopher those images look nice, but I'm having some trouble. Some comments:

  • The images are very dim, or at least there is very little contrast making them almost impossible to see. I would suggest doing something to make the lines stand out more overall. Maybe just increase the default width for the lines a little bit.
  • The letters "IR" and "UV" at the ends of the spectrum bar are illegible (at least to me.) I suggest putting the letters inside the relevant parts of the spectrum bar and making them a color which contrast with the color of the bar. You might also want to specify a font family for the letters to make them render more uniform among platforms.
  • I'm not sure what your issue was with passing a render size through the SVG, but remember that by default wikipedia will render SVGs at 180px width when rendering thumbnails. You can scale this by including the "upright=" parameter with each picture. (Also not that the wikipedia servers will serve SVG to the user but instead first renders them to PNG using the RSVG renderer. (which is a bit quirky at times.))

(TimothyRias (talk) 12:23, 19 October 2009 (UTC))

Render size isn't an issue on Wikipedia (it makes rescaled PNGs as you point out), but it's a royal pain when testing (default images are too big for my browser window, and trying to render small sections of the spectrum makes a very-detailed unreadable thumbnail).
Regarding IR/UV labels, do you mean that they're illegible on the thumbnail, or in the full-sized images? I agree that contrast could be improved. White letters in the same locations would be my first solution approach, and white letters with black outlines inside the bars would be my second approach. I'm leery of putting them inside the bars because certain choices of spectrum range would produce very short stretches of UV or IR spectrum on the edge of the image, which would make the labels overlap the visible portion, but I can check for those as special cases to avoid the problem.
Regarding dim lines, this is deliberate for the linear-mapped case (the point of having both is to underscore for the reader that only a few of the lines are readily visible). I agree that the current presentation may be sub-optimal (especially for the xenon spectrum). My preferred solutions would be to increase the stroke width of all lines to three pixels, and to tweak my intensity-mapping functions to have a floor at 25% intensity, so that all lines are always (dimly) visible. Another potentially useful option would be to add a roundoff at high intensity, though this would mostly be a xenon kludge (is the IR line really that strong, or is this a data-table artifact?).
Would these approaches address your concerns with the images? --Christopher Thomas (talk) 16:41, 19 October 2009 (UTC)
About the IR/UV labels, they are (for me) hard to read on full size and impossible to read for the thumbnails.I would suggest using white or gray letters.
Regarding dim lines, at a first glance (when looking from the text to the picture) I can hardly see even the brightest lines in the linear portion, especially in the thumbnails. Tripling the stroke widths should help with this though. (TimothyRias (talk) 20:14, 19 October 2009 (UTC))
PS. I've taking the liberty of increasing the size of the thumbnails a bit. (maybe too much) (TimothyRias (talk) 20:14, 19 October 2009 (UTC))
I agree about the brightness thing: thin coloured lines against a black background with a white coloured screen behind that… they just don't look very bright. It's almost too realistic! (it's not always easy to see spectral lines with the naked eye through a spectroscope either :P)
I think it would be best not to include IR and UV lines at all. The human eye can't see them… it might be interesting for cases like magnesium, which is notorious for it's large number of UV lines, but in general I'd just stick to the visible region.
Otherwise, the pics look great, thanks a million to everyone whose been working on them. Physchim62 (talk) 12:42, 19 October 2009 (UTC)
The wavelength range is tailorable (and will be even more tailorable when command-line arguments are implemented), so it's easy enough to exclude IR and UV if desired. I'll add samples with just-visible in the next batch of test images. I can also produce spectra of narrow regions, if there are any cases where that would be useful (requests?). --Christopher Thomas (talk) 16:41, 19 October 2009 (UTC)

Cool! Non-black background. As this suggests, it allows to show realistically both colour and intensity. Essentially, you map the interval [min, max] to [0, 1] before applying the gamma correction. This is my take, for a constant-intensity spectrum:

Spectrum (gray background).png

If you drop the requirement that the same mapping should be used for each channel, you get this:

Spectrum (brown background).png

Actually, I didn't expect such good results for the latter. Apparently, the eye adapts to the environment's colours so well that not only colours don't move significantly (i.e. yellow appears to be around 580 nm, where it's supposed to be, etc.), but it's not even that evident that the legend (representing white light after rescaling) is coloured. (Anyway, using brown only in the horizontal zone of the spectrum itself and black above and below it, as NIST do, defeat the purpose.) The only problems with such an approach are 1) that it looks unusual, and 2) that very weak lines would be hardly visible. ___A. di M. 14:58, 19 October 2009 (UTC)

This is an interesting suggestion (and the link you provided was very interesting reading), but I'm not sure it's a good idea if we're trying to show dim lines (which is one of the things that kicked off this discussion in the first place, if memory serves). Per this image's grey tracks, I'm pretty sure it only works well if the spectrum strip is very narrow (so that you have strong contrast between it and the background), also. This might or might not be an issue (wouldn't be for the lines themselves except in very dense spectra). Thoughts on this? --Christopher Thomas (talk) 16:41, 19 October 2009 (UTC)
I haven't tried to make a spectrum with that brown background yet. This might or might not turn out to be not such a great idea as it originally seemed to me. I'm going to give it a try and to upload the results. ___A. di M. 16:54, 19 October 2009 (UTC)
OK, this is the hydrogen spectrum:
Hydrogen spectrum (green background).png
And this is the helium spectrum:
Helium spectrum (teal background).png
They are "too realistic" in the sense Physchim62 mentions, in that lines which are hard to see in real life are also harder to see in the pictures, and vice versa; IOW, they remind me too much of the days when I was swearing against an early 20th-century prism spectroscope in my "Laboratory of Electromagnetism" class. Hey, I've also reproduced the effect that if I stare at the "black" until I get used to it and move my eyes around a little, I can see the red line of helium which I couldn't see at a first glance. (Maybe making them less realistic by using the square root of NIST's relative intensity might be an idea.) Also, the coloured backgrounds look funny. (BTW, I was going to upload the OpenOffice spreadsheet I used to get the numbers for a PPM image, but the Wikipedia software doesn't let me to.) ___A. di M. 18:57, 19 October 2009 (UTC)

Metamaterial

Would someone with a background in physics please run through this article once and correct the most glaring factual inaccuracies and edit what you can? I don't know what is going on with the article, other than severe ownership issues, but it has sentences like, "A recurrent issue with either naturally occurring, or conventional materials, is the lack of magnetic response." --69.225.5.183 (talk) 19:36, 14 October 2009 (UTC)

I do not know enough to edit the article, but I am fairly sure that a negative refractive index can only be achieved for a limited frequency range. This fact does not seem (at first glance) to be mentioned in the article. JRSpriggs (talk) 10:30, 15 October 2009 (UTC)
There's been talk of wideband materials if memory serves, but most of the ones so far have indeed been narrow-band. The only exception I can think of is the silver film superlens construct (though it's possible I'm misremembering and they too have a narrow frequency response).
Re. content concerns and ownership, I agree to some extent, but I think the best thing to do now is to wait until User:Ti-30X (and to a lesser extent User:Materialscientist) are done with it, and then post a wider call for reviews. The users involved have responded well to discussion in the past, so I don't expect any fireworks as long as everyone takes care to avoid stepping on each others' toes.
Speaking of which, Ti-/M, how are you guys doing with this article? Still undergoing a rewrite, or is it at the point where the rest of us should take a look at it? --Christopher Thomas (talk) 01:22, 16 October 2009 (UTC)
Christopher - the article is still being re-written. The particular issue which the anonymous IP brings up regarding "magnetic response" has been addressed on the Metamaterial discussion page. Ti-30X (talk) 10:59, 16 October 2009 (UTC)
One more thing - this forum may or may not be aware that the Metamaterial article is currently undergoing a major re-write, and has been for some time. It is not helpful to read comments like "yikes" or "yaw, this article needs some work". That is stating the obvious, for no valid reason, other than to be critical. The article is under construction, and as far as I can see it will be under construction for awhile longer. There is so much research that has been done on metamaterials, and is being done that it boils down to a day to day, week to week process of obtaining and reading the material. This article is not complete. Believe me, when I started this project I thought I would be in and out. But I am happy to say trying to organize all this material has kept me working on this article.
I guess I can inform this forum when the article appears to be completed and to go have a look. Of course anyone is welcome to take a gander at anytime. It appears to me that the anonymous IP is mistakenly viewing the article as though it is completed. It is not completed.
Also, this is not my full time job, and I am a volunteer, so I normally can't spend 40 hours per week on this article. I do enjoy it though. Ti-30X (talk) 12:07, 16 October 2009 (UTC)


The article is being copied into cyberspace as is. If it's inaccurate, it needs to be worked on outside of article space. I've learned from Ti-30X that magnetic response has nothing to do with magnetism, that "lack of" is quantitatively the same as "lack of large," and that even if a research group's name isn't on their page or anywhere else in cyberspace besides that article, it's still a verified name and acronym for the research group.

If the group is so unheard of, Ti-30X, that it isn't on a single google page, not even on the group's page, you've either made up the name (yes, you have!), or it's not noteworthy enough to be in the article (it's not because it only exists in your head, not in verifiable secondary sources, 'cause it doesn't exist).

I think that wikipedia has a responsibility to readers to not create articles in article space that are full of nonsense.

Wiki project physics members disagree with me.

Support for your local Essjay wins. I can't do anything but alert people who should be concerned. I don't have a week or two for every physics error, when there was no way to even show this user that

the reason the group name you made up isn't anywhere but your article, not even on the page you made it up for, is that you read the page wrong, and the name doesn't exist anywhere but where you made it up: in your head and in wikipedia article space.

And, you've read incorrectly almost everything you've added to the article. It's a randomized assortment of half pieces of information copied in strange orders from a number of good sources whose authors would be surprised to see what they say according to you.

This article is a serious problem. There are some excellent physics articles on wikipedia, written by people who not only have a grasp of physics at a high level, but are able to transfer that knowledge clearly, concisely, and accurately to a general audience. Given this, I thought WP:physics members would be concerned to be represented by garbage. I'm wrong.

Enjoy. --69.225.5.183 (talk) 16:08, 17 October 2009 (UTC)

Discussing editor conduct and disciplinary actions on project talk page.

Do we have a policy against using the project board in lieu of or along side of the arbitration, Administrative notice of incident, or the other arbitration processes available. I am thinking about both the post by Linas and the previous posts about Brews which caused all kinds of problems on this board, but did not lead to a solution.

In situations where discussion on the project talk page degenerates to the point that some sort of arbitration beyond the board is needed and/or when there is already such an arbitration already in place, I would like to either move, scratch, or put in a collapsed box, all material pertaining to that case. The material would be replaced by a carefully worded neutral statement pointing out the contention with a link to where the arbitration is at. (Possibly similar to UncleG's last post but in a neutral fashion; not discussing forum shopping for instance. It should also include the fact that Linas requests that..)

The board has a large and important role in deciding whether or not something should be sent to mediation, and on settling small grievances. We simply don't have the resources to arbitrate or mediate conflicts that are larger.

Having a consistent and neutral policy that everyone could agree on like this would discourage people from 'forum shopping'. More importantly it might keep the board from degenerating into a futile chaos and help to keep the inevitable frustrations contained.

As a side note, I would like to see the same policy for the discussion of material on the project page that is more appropriate to an article talk page.

I don't mean any of this as an attack on anybody involved in any of these cases. This policy will not work unless it is enforced with consistency and neutrality.

TStein (talk) 20:56, 14 October 2009 (UTC)

Any content questions should probably stay here, but I would say everything else has priority for conduct disputes. You might try putting a little remember to stay focused note at the top of this page, but if we are a little more aggressive with archiving and redirecting off-topic discussions, that should suffice. - 2/0 (cont.) 01:18, 15 October 2009 (UTC)
The project can be used as the main discussion space to solve some content-related disputes that can be solved in a few backs and forth, or ask for third opinions. Behaviour problems can be reported here, but such reports should be kept short and to the point (such as An editor keeps making weird edits against consensus at Article X. I have requested for comments at WP:RFC/U/Editor X, and the input of the physics project would be appreciated. I also asked the Mathematics and Astronomy projects for input. Thanks.), and link towards the proper forums for behaviour problems. That is: user talk pages, article talk pages, administrator noticeboards, request for comments, arbcoms, and so on. This keeps a low-drama atmosphere on the project, which is essential to its health, and does not flood the Project's talk page with extremely long sections. Headbomb {ταλκκοντριβς – WP Physics} 04:40, 15 October 2009 (UTC)

Vacuum permeability and vacuum permittivity

While looking at the lists in "Article status challenge" above, I've encountered the articles vacuum permeability and vacuum permittivity, which, IMO, focus way too much on the fact that these constants depend on the system of measurement (something which, to a larger or smaller extent, is true of any dimensionful quantity), and too little about what they serve for. They even state that the view that ε0 and μ0 are physical constant is "incorrect", but I can't see why they are any less of a physical constant than, say, the speed of light is, or than the Boltzmann constant would be if the kelvin was redefined in terms of it. (Imagine, for the sake of argument, that the kelvin were redefined so that the numerical value of kB became a defined constant. We wouldn't edit the Boltzmann constant article so that 75% of it is about the fact that it's only a measurement system-dependent constant with no physical significance, would we?) Also, some paragraphs in vacuum permeability seem to suggest that free space refers to an ideal medium with permittivity equal to 8.854...×10−12 farads per metre by definition. That's as backwards as claiming that water refers to an ideal medium with a triple point temperature of 273.16 K by definition.

What do you others think? --___A. di M. 09:42, 15 October 2009 (UTC)

While I entirely agree with you, that's something related to the speed of light ARBCOM case, and I'm not touching anything SoL-related until the case is closed. Otherwise it'll just grow into the same mess that has happened/is happening at the speed of light talk page. Feel free to start the WP:BRD cycle, but be prepared to face some big frustrations. Headbomb {ταλκκοντριβς – WP Physics} 11:33, 15 October 2009 (UTC)
The claim that "free space" is defined by ε0 = 8.854…×10−12 F/m is a misconception which has been expounded at great length by one of the participants at the current speed of light arbitration. The electric constant has a defined value in SI units, agreed, but that doesn't dictate anything at all to Mother Nature. It is simply a test of the theories which lie behind the SI system: if the theories are wrong, equations in SI units will no longer add up. As equations in SI units add up (to within the limits of experimental uncertainty), there is no problem at the moment, and we should not pretend that there is a problem where none is apparent. Physchim62 (talk) 12:03, 15 October 2009 (UTC)

My view is that the parameters called the electric constant and the magnetic constant do not refer to any realizable, real medium, but only to a reference state commonly called classical vacuum that is not found in the Universe. Of course, one can compare the behavior of real media with the predicted behavior of classical vacuum and determine how well or how poorly the real medium is modeled by classical vacuum; that is what a "reference state" means. There is no sense in which classical vacuum "dictates" to nature; one simply compares nature to the predictions for classical vacuum to see how they compare. There may be a notion above that "vacuum permeability" (aka magnetic constant) refers to the permeability of some real medium called "vacuum", but that is erroneous. It is a defined, not a measured number, as is the vacuum permittivity (aka electric constant). Brews ohare (talk) 13:00, 15 October 2009 (UTC)

I quite realise that that's your view, but you don't seem to have any support for it. In particular, you don't have any support that the macroscopic effects of light passing through a quantum vacuum are any different from the asymptopically observed effects in a practical vacuum. Physchim62 (talk) 13:50, 15 October 2009 (UTC)
Again Brews, read WP:OR and WP:SYNTH. Headbomb {ταλκκοντριβς – WP Physics} 13:52, 15 October 2009 (UTC)
OK guys, why are you right? I have NIST and BIPM on my side as well as a number of texts. Read classical vacuum. What have you got?? The issue of macroscopic effects of light passing through a quantum vacuum are any different from the asymptotically observed effects in a practical vacuum is a non-starter: it simply has no relevance to free space what the comparisons of two real media might be. Waving WP:OR and WP:SYNTH around like flags has no merit without some backup indicating just what particular statement is questioned and has to be supported by sources. Let's get real: pick up some statements from classical vacuum that you feel are unsupported, and let's start there. Brews ohare (talk) 14:11, 15 October 2009 (UTC)
Headbomb's answer to technical engagement is to apply for Admin intervention. Brews ohare (talk) 16:17, 15 October 2009 (UTC)
No, that's my answer to your (and Tombe's) refusal to stop repeating the same thing over and over again. My answer to these "technical arguments" can be found in the who-knows-how-many archives resulting from your obstinate behaviour. Your views are are completely idiosyncratic (see triple point of water analogy), and when they are not they are at best WP:UNDUE. Headbomb {ταλκκοντριβς – WP Physics} 16:45, 15 October 2009 (UTC)
Headbomb: My behavior is simply to respond to a reopening of these issues that was not begun by myself. If the issues are to be rehashed, why should I be obliged to sit it out? IMO you do not understand my position, but only assume what it is, and the matter needs to be fully aired and everything put on the table. A discussion among a few of you that are blind to some aspects of the issues is not a discussion but a social event. Incidentally, I don't think it is D Tombe that you differ with here; it is just me. Brews ohare (talk) 17:26, 15 October 2009 (UTC)

I do more or less agree with Brews here. But I would suggest discussing concrete examples and discussing them in detail from first principles. Otherwise it is not clear how relevant this all is. In QED you can integrate out the electrons and then you can obtain the effective Euler-Heisenberg lagrangian. You can then derive expressions for the permittivity and permeability tensors, see e.g. here. There are also nontrivial effects due to boundary conditions, e.g. the Scharnhorst effect etc. Count Iblis (talk) 16:13, 15 October 2009 (UTC)

OK, OK, let's stick to what everyone agrees with. Are ε0 and μ0 physical constants? Yes, at least to the extent that c, NA and kB are. Are their numerical values in SI units fixed by definition? Yes, they are 1/(4π × 299,792,4582×10−7) and 4π×10−7, due to the definition of the units. Can you measure them in SI units? No, or more precisely, you can but it'd be pointless: assuming that classical electromagnetism and special relativity work and that your measuring instruments are correctly calibrated, you already know what you're going to get. Are they properties of a material medium? No, unless you consider empty space to be a material medium. I think everybody agrees about that, no? (Headbomb, maybe you're right. I shouldn't have started a thread with two things in the title whose product is the inverse square of the nominal subject of a pending arbitration. But I feel reckless. <g,d&rVF!>) ___A. di M. 20:26, 15 October 2009 (UTC)

A. di M.: You're off to a good start except for Are they properties of a material medium? No, unless you consider empty space to be a material medium. The problem with these sentences are: (i) "empty space" is a nightmare. It might mean classical vacuum, good terrestrial vacuum, quantum vacuum or QCD vacuum, or maybe something else. (ii) It suggests that if I think my version of "empty space" is a material medium, then ε0 and μ0 are the properties of a material medium. That is not so, ε0 and μ0 are properties of classical vacuum, which is a reference state, not a material medium, whatever my opinion might be about how closely "empty space" (in any of its embodiments) resembles classical vacuum. I believe the initial few references in classical vacuum support this viewpoint.Brews ohare (talk) 22:24, 15 October 2009 (UTC)
Of course, the extent to which ε0 and μ0 are physical constants can be somewhat debated. They are no more physical (or fundamental) then for example kC and αB defined in the cgs units article. (which of course can be considered physical constants under some definition). They are not really properties of anything physical though, in the sense that a parallel universe in which they take different values is not distinguishable from ours. (but that is an objection to all dimensional physical constants). Personally, I would consider them the results of our conventions of how we define objects like the electric and magnetic field charge, etc.
In the end the discussion is mostly a philosophical one. And one that IMO is getting way too much weight in the speed of light, the vacuum permittivity, and the vacuum permeability articles. These article should put much more focus on how these constants are used and where they appear in physics, and much less on their "physical interpretation", of course the latter should be covered in a good article on any of these subjects, but this can probably be done with a single section and at most a single paragraph in the lead. It is not what a reader coming to these articles are looking for. (TimothyRias (talk) 09:48, 16 October 2009 (UTC))
What are these stupid constants "ε0" and "μ0"?)  :) Count Iblis (talk) 14:46, 16 October 2009 (UTC)
Timothy: Are you suggesting that the electric constant and the magnetic constant have some role outside the SI units? ?? Or, are you suggesting that the role of SI units in electric permittivity and magnetic permeability should be augmented by more discussion of other systems of units? Or what?? It seems to me that if we are talking about the electric permittivity and magnetic permeability of real materials, which actually should be the focus of these articles, a discussion of their "physical interpretation" is basically what condensed matter physics and solid state physics is all about, and it should not be downplayed. Also, that topic really is about relative constants and has little to do with ε0 and μ0. Is that where you are going? Brews ohare (talk) 16:20, 16 October 2009 (UTC)
I think he meant "vacuum permittivity" not "electric permittivity" etc. ___A. di M. 20:10, 16 October 2009 (UTC)
Obviously, ;). Not sure what happened there, lets call it dyslexia. (TimothyRias (talk) 20:18, 19 October 2009 (UTC))
TimothyRias, that's my view too, but then the article about kB doesn't say that it's just a conversion factor needed because a brain-dead system of units treats energy and temperature as different quantities. ___A. di M. 20:10, 16 October 2009 (UTC)
It wouldn't hurt if the article about K_b did say that. It would save people who teach statistical physics/thermodynamics some work if this were common knowledge. This doesn't mean that the article should be a one line stub saying only this. Count Iblis (talk) 20:27, 16 October 2009 (UTC)
Reply to A. di M.: If Timothy is saying that too much emphasis is placed upon the "physical interpretation " of the electric constant and magnetic constant because "They are not really properties of anything physical", he may be right. They are constants peculiar to the SI Units' reference state classical vacuum, which is not extant, but an ideal limiting case not found in the universe. Brews ohare (talk) 16:00, 17 October 2009 (UTC)
They are also not properties of the classical vacuum. They are just historical accidents, that are about as fundamental as the yard to metre ratio. (i.e. they are conversion ratios for quantities that should in all right be measured in the same units.)(TimothyRias (talk) 20:25, 19 October 2009 (UTC))


Comments by David Tombe

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

One of the reasons why the speed of light, the electric permittivity, and the magnetic permeability, and the inter-relationship between the three, so easily stirs up a hornet's nest, is because there are many opinions going around as to the physical significance of these quantities and their inter-relationship to each other. As we speak, an article on this very topic is being nominated for deletion because it contains points of view. Whatever one's opinions are, the facts are that the established opinion has changed drastically since the time of James Clerk-Maxwell in the early 1860's. In 120 years, we changed from a state of affairs in which the speed of light was the speed of a wave in an elastic medium, with the density and the elasticity of that medium being related to the speed of light through Newton's famous equation. Maxwell used his own vortex sea model to link density to the magnetic permeability, and elasticity to the dielectric constant, and he obtained the relevant numerical ratio from the 1856 leyden jar experiment of Weber and Kohlrausch. In the 20th century however, the luminiferous medium disappeared, and magnetic permeability became a defined constant. Then in 1983, the speed of light became a defined constant and so the electric permittivity was compelled to follow suit. Hence, what was once Newton's equation relating the density and elasticity to the speed of wave propagation, as adapted by Maxwell to the luminiferous medium, ended up becoming a mathematical equation relating three defined numbers without any physical significance.

It's not surprising that A. di M. is somewhat perplexed by the emphasis that is being put on the significance of permittivity and permeability in the wikipedia articles. The points of view being expressed in those articles will almost certainly be influenced by the thinking that came about in the wake of the 1983 SI definition of the metre. Such thinking is unlikely to entertain any physical significance to these quantities. And in particular, it is highly unlikely that any modern article will entertain the Maxwellian viewpoint that permeability is a density, and that permittivity is an elastic constant. David Tombe (talk) 14:18, 15 October 2009 (UTC)

I haven't seen any discussion of how the switch to times-of-transit as length measurement plays into other quantities like the electric constant and the magnetic constant. Most probably it just shows up in the metre again as an empirically determined length instead of a defined length. David, I think that Maxwell was thinking about real media; what was called vacuum at that time is probably the role of, say, QCD vacuum today. He was not thinking about some idealized reference state with defined properties. Brews ohare (talk) 14:26, 15 October 2009 (UTC)

Brews, There was a discussion about that issue here at WT:PHYS in August. It'll be in the archives. That discussion led to the thorny issue of how can we measure the distance between the plates of a capacitor in the new SI system. And yes, Maxwell was indeed thinking about a real medium made of part aether and part ordinary matter. David Tombe (talk) 14:34, 15 October 2009 (UTC)

I'd guess that in some interpretation of the math the permittivity of QCD vacuum will still have some connection to charge separation and how much separation depends upon the "elastic constant". My feel for the magnetic behavior is that it is related to density of microscopic angular momentum, so maybe that would fit with Maxwell too. Brews ohare (talk) 14:38, 15 October 2009 (UTC)
If the plate separation is determined by the time it takes light to transit between the plates, and C = ε/d or ε=Cd =C c0 t, how does that affect ε0 ? Brews ohare (talk) 14:53, 15 October 2009 (UTC)

Brews, I didn't follow their argument at all. Steven G. Johnson simply told me that we can't measure ε0 experimentally in SI units. I couldn't see why not. All we need to do is measure the distance between the capacitor plates and apply the C = ε/d formula. David Tombe (talk) 14:58, 15 October 2009 (UTC)

Well, it's another one of those apparently simple matters that can tie us all up for months, I guess. We have ε=Cd =C c0 t = κ ε0. In free space κ=1. And ε0 =1/(c02 μ0) so ε0=C t /√(μ0 ε0). So we can solve for ε0 in terms of C t. Now t is measured. The determination of C is the problem; that may reduce this equation to ε0 =8.8541878176 pF/m when we include how the charge and voltage are found. For example, the voltage is field (basically charge) times length, so the time t is going to divide out. Maybe you can help me with this? Brews ohare (talk) 15:20, 15 October 2009 (UTC)
Unfortunately we can't, sorry, you'll have to help yourself. Physchim62 (talk) 16:18, 15 October 2009 (UTC)
A little sarcasm, perhaps, or is it really an admission of incapacity?? Can't you engage in discussion without incivility and irrelevancies? Brews ohare (talk) 17:02, 15 October 2009 (UTC)

I think that we need to get the facts straight here. This thread was begun by A. di M. with a perfectly legitimate query. He was asking why there has been so much emphasis on 'systems of units' on the electric permeability and the electric permittivity articles. I had noticed the same thing myself about two months ago. I had noticed that 'electric permittivity' had totally sold out to the modern SI system of units.

In response to A. di M. I was very careful not to state my own opinions on the matter. I merely charted the historical evolution of these two parameters from being 'elastic constant' and 'density' in the time of Maxwell, to being defined numbers with no physical significance post-1983.

We then see the same old hysteria erupting. My comments get archived, and the allegations of disruptive behaviour start to fly from the same two sources, which are Headbomb and Physchim62. David Tombe (talk) 01:36, 16 October 2009 (UTC)

This is nonsense. Physics has not changed as a result of the 26-year-old definition of the metre. There is no change in the physical meaning of physical constants as a result of that definition. There is no conspiracy to hide anything. Editors are merely trying to keep Wikipedia accurate and free of unverifiable non-scientific, or anti-scientific, notions about these subjects. I thought this topic was closed. Finell (Talk) 02:31, 16 October 2009 (UTC)

No Finell, It wasn't closed. I doubt if it will be closed for hundreds of years. It is only closed in the minds of certain people. David Tombe (talk) 02:52, 16 October 2009 (UTC)

Finell: This discussion could be kept on track with more precise wording. No-one is saying that physics changed because of a change of units or the definitions of the SI units. We have to be clear about which physical constants are being discussed. Perhaps the word "conspiracy" is better avoided: the presentation of matters has changed. The WP articles on magnetic constant and electric constant and classical vacuum are accurate, and this accuracy will not be threatened if we can keep discourse calm and open and avoid too much excited speech. Brews ohare (talk) 04:49, 16 October 2009 (UTC)
Brews, I know you don't say it changed physics, but I believe Tombe does. For example, Tombe claims that a physics experiment has been "purged from the textbooks since 1983" in order to "preserve this new physics in which three previously measured physical quantities have now all been consumed in a definition", and was "sacrificed in order to preserve the new 1983 definition of the metre" which he calls "a foolish mistake which took place at a conference in 1983". He continued, "This most important chapter of scientific history has now degenerated into the abominable post-1983 new physics that is summed up in the lead to the vacuum permittivity article." These quotations all come from this archived "discussion": Wikipedia talk:WikiProject Physics/Archive August 2009#Experimental determination of the electric permittivity. And, aside from his arguments with everyone else in that thread, Tombe claims to know better than the world's leading experts. Again, that is Tombe, not Brews. Finell (Talk) 22:10, 16 October 2009 (UTC)
Finell: You have a point that David goes overboard at times. However, I'm prepared to live with that for two big reasons. One is David himself can be very cogent and worth listening to, and I think that's valuable. Second, the example we have seen of late of extremely sarcastic and even vicious behavior affects everybody and makes editing disagreeable. Contrariwise, an open stance even in the face of what seems a bit off leads on occasion to discovery that what looked unpromising actually was great. It is like a walk in the sun to be in an atmosphere like that. So I really think the behavior of Headbomb, Physchim62, and sometimes others based upon putting people down and scoring great caustic aphorisms, or even just being a snoot, is detestable and ultimately destructive of much more than the few that get beaten down. I suspect you agree, and I hope that you can assist in making a more open, relaxed and tolerant atmosphere. I know, I could take the same advice. Brews ohare (talk) 00:18, 17 October 2009 (UTC)

Finell, I don't quite see what the problem is here. You seem to hold up everything that I say as a being a crime as a matter of course, rather than actually examining the contents and making a rational assessment, based on that examination. If you would do that, you might learn something. You will have to snap out of this habbit of holding up every edit of mine as constituting evidence of wrongdoing.

It would help to begin with, if you would reply to issues that have been raised in the actual thread itself, rather than digging up old edits from the past to respond to. David Tombe (talk) 14:14, 17 October 2009 (UTC)


The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.


Potential energy

A quick skim of Potential energy (edit | talk | history | protect | delete | links | watch | logs | views) shows that it now has the same issue that gravitational potential did a while back: An unusual choice for sign convention (opposite the one used at scalar potential and in my textbooks). There's also an overly-complicated distinction made in potential energy between "potential" (a scalar field) and "potential energy" (energy required to bring a test particle in the field to a fixed reference location); for the types of potential being discussed, potential energy is just potential times the test particle's charge associated with that field (electric charge, mass, etc). For reference, see the discussion at Talk:Gravitational potential#sign (+ or -) of the gravitational potential P, from when this came up at the previous article.

It's possible that I'm off-base and that the majority of sources use the positive rather than the negative sign for things like gravitational potential, but I'd appreciate it if a few people with wider literature exposure than I have could take a look at Potential energy (edit | talk | history | protect | delete | links | watch | logs | views) and comment as appropriate. --Christopher Thomas (talk) 18:28, 17 October 2009 (UTC)

Huh? Right now, it appears to have the "right" sign (where by "right" I mean that F = −U and that the total mechanical energy, conserved by conservative forces, is E = K + U). Maybe somebody's fixed it meanwhile? BTW, I've seldom seen the other convention for the potential (i.e. V = −U/q rather than U/q), but AFAICR not for the potential energy. (Having the total energy being the difference between two types of energy would sound quite weird to me.) ___A. di M. 19:30, 17 October 2009 (UTC)
I think you (and Steve who has now fixed it) are entirely right - I moved the equation for gravitational potential from lower down in the section, and didn't notice that the sign convention was, er, unconventional. (I also changed the symbol from the equally unconventional P.) Djr32 (talk) 19:37, 17 October 2009 (UTC)

Need help at Electromotive force

At Talk:Electromotive_force#Introduction_Should_Include_More_Casual_Language, a user has complained about the uninterpretable lead here; I agree it's a problem, but not just a language problem. The lead says things that don't appear to make sense, citing sources that don't come close to supporting it. I learned a lot about emf and the confusion around it in my previous attempt to work on this article, but I'm no expert, so I'd like to get some help or suggestions before I dive in to try to fix it. Please come to the talk page there or here. Dicklyon (talk) 01:46, 18 October 2009 (UTC)

I'll ask Jorge Hirsch if he can spare the time to contribute to this article. Count Iblis (talk) 02:07, 18 October 2009 (UTC)
Great idea! Dicklyon (talk) 20:57, 18 October 2009 (UTC)

Messy

Please see Talk:Alternatives_to_general_relativity#Why_is_this_article_such_a_mess.3F. Michael Hardy (talk) 20:14, 18 October 2009 (UTC)

Gravitational induction?

Can someone have a look at the new article Gravitational induction, a page created and maintained by Fedosin only, and entirely based on his own work. Is this appropriate? DVdm (talk) 15:35, 21 October 2009 (UTC)

While AFAICT the effect it's talking about theoretically exists, I guess it'd be so ridiculously small that no-one will ever measure it before my death. Probably, no-one's ever bothered to describe it, either, in which case it fails WP:N and doesn't belong here. ___A. di M. 15:50, 21 October 2009 (UTC)
If it's based on work that he published, then WP:COI strongly discourages him writing articles about it (it'd be considered self-promotion). A quick skim suggests that it could also use considerable cleanup (particularly to clearly spell out what scenarios it's analyzing before beginning the analyses, but also to add a lede that properly summarizes its content). It doesn't look incorrect (to my untrained eye); just like it violates WP:UNDUE (the bit about "giving undue weight to any aspect of a subject", not about fringe views) unless this effect is a common textbook example or is otherwise in use outside of this author's work. --Christopher Thomas (talk) 17:03, 21 October 2009 (UTC)
Thanks AdM and CT. As I have no expertise in this, I'm not going to make a remark on the article, but feel free to do so. Cheers, DVdm (talk) 17:07, 21 October 2009 (UTC)

Caveat: In the interests of keeping a constructive atmosphere, I'd suggest proposing a merge to somewhere appropriate rather than an AfD. Surely this could be incorporated as a one-line reference to higher-order effects at gravitomagnetism or similar, once it's been vetted. --Christopher Thomas (talk) 17:20, 21 October 2009 (UTC)

BTW, many of the Google Scholar hits for "Gravitational inductance" obviously refer to something else, but some might refer to the same concept as the WP article (I didn't bother to read them). ___A. di M. 17:24, 21 October 2009 (UTC)
That's the problem with original research on this level. In order for it to be verified, someone must go to work, and perhaps work hard. It should be the other way around. Get rid of the article asap and warn the author not to come back unless he can properly source it. Let him do the work.
I know... I'm not really contributing to a constructive atmosphere here, but I'm sure the author is not going to settle with an obscure one-line reference :-|
Anyway, I'm not going to intervene. Cheers, DVdm (talk)
Personally, I don't really have a problem with this article content wise, since the article is pretty straightforwards physics. Is it COI? Yes, but not in a harming way. It needs more references, which shouldn't be all that hard to find. I doubt there's only one person in the world who ever thought "Hey, let's apply Maxwell's equation to gravity". But it could probably be merged with Gravitomagnetism. Headbomb {ταλκκοντριβς – WP Physics} 18:05, 21 October 2009 (UTC)

Synchrotron radiation and synchrotron light source

I've taken a glance at these articles, and they both seem to contain some rather odd text describing the mechanism of light generation. The relevant text describes electrons moving in a circular path as generating EM radiation in the same manner as a dipole antenna, except with a frequency boost of \gamma^2. I'm almost positive that this description is incorrect with regards to the emission mechanism, though the frequency boost sounds reasonable. Could one of the resident EM-types take a look at this and adjust or clarify as-necessary? I've seen the proper derivation off-wiki, but I don't feel that I have enough expertise to adapt it to these articles --Christopher Thomas (talk) 06:31, 22 October 2009 (UTC)

I think I've figured out the line of reasoning that led to the "dipole antenna" comparison (consider the acceleration of an electron within a hollow antenna during half of an oscillation), but it seems like it would only make sense as a comparision to people who already know how the emission occurs (in addition to being confusingly-phrased). Or, I could be misreading the relevant sections. --Christopher Thomas (talk) 06:34, 22 October 2009 (UTC)
I've come across the dipole antenna analogy before. It's just a phenomenological analogy: accelerating charged particles leads to the emission of EM radiation. If someone is going to put some more details in there, there's cyclotron radiation to look at as well. Physchim62 (talk) 07:39, 22 October 2009 (UTC)
Cyclotron radiation is a very close analogy to an antenna, as in both cases you have (more or less) steady-state oscillation of charges. My understanding is that synchrotron radiation a lot closer to bremsstrahlung, in that it's caused by a one-time deflection (or can be; I realize that in a synchrotron you're looping through the system many times, but you'd get the same result aiming a linear accelerator at a bending magnet and deflecting only once). Rather than having an oscillating system driving EM emission at the period of oscillation, you have a non-oscillating deflection imposed that causes EM emission through a more general process (of which oscillating motion is a special case). --Christopher Thomas (talk) 08:04, 22 October 2009 (UTC)
I should know the answer to that question, as there's a synchrotron opening just down the road at the moment! On their helpful page What is a synchrotron?, it seems that both analogies (antenna and bremsstrahlung) are valid. You can see it as lots of linear accelerators each deflecting only once but linked together so that they form a circuit. Or you can see it as an oscillating system with a superposition of several fundamental frequencies (after all, the electrons stay in the ring for several hours at a time). However, the linear accelerator + bending magnet model allows you to explain the existence of dedicated beam lines for different types of investigation (ie, different X-ray frequencies and intensities), so that is probably more helpful. Physchim62 (talk) 08:51, 22 October 2009 (UTC)
My understanding was that periodicity of the path only makes a difference in devices like free electron lasers, where you're trying to phase-match emissions from several magnets. Your link describes a source that seems to be a hybrid of synchrotron and FEL, in that it uses a FEL-type "undulator" that presumably is phase-matched. I agree that they use the same mechanism of emission (synchrotron radiation, in both cases), but was unaware of FELs being described as synchrotron light sources. I'll dig through the reference material a bit more before making any changes, to make sure I'm getting the terminology and the math right.
I think I'm finally starting to wrap my head around a) how this works and b) how to express it in terms someone unfamiliar with the subject would understand. I'll try to produce a suggested replacement and maybe a figure or two in my Copious Free Time(tm) (along with a revised version of the spectrum-plot program). --Christopher Thomas (talk) 02:10, 23 October 2009 (UTC)

IP creating questionable articles, part III

It appears that the second RfD will pass, as soon as someone gets around to closing it (we'll know when the links turn red). All of these articles passed WikiProject Articles for Creation. Should this project be playing more of a role in that project? Also, 3 of the 8 articles now up for deletion have templates on their talk pages:

Finell (Talk) 03:09, 23 October 2009 (UTC)
QHCR was classified by Tnxman307 (talk · contribs), QI was classified by Akradecki (talk · contribs), and QER was classified by SharkxFanSJ (talk · contribs). These appear to be the AfC workers who moved the articles from the anon scratchpad to article-space (category templates are added during this process).
My impression is that AfC is mostly a rubber-stamp process, filtering out only blatant abuse. That said, there's quite a lot of blatant abuse that they're successfully filtering. If the "declined submissions" list is any indication, they're doing an admirable job (nothing but spam/promotion pages as far as the eye can see in there).
The best approach that I can see offhand would be to find an automated way of maintaining a list of recently-created physics articles (including, but not limited to, those from AfC). WP:PHYS members (and anyone else who felt like it) could then vet them as time allowed, flagging problematic ones for merge or AfD. Trying to jump into AfC itself seems like a recipe for burnout, if the spam queue is any guide (your mileage may vary). --Christopher Thomas (talk) 03:33, 23 October 2009 (UTC)
Thanks for the explanation. I meant to say Project Physics templates on their talk pages. I assumed that these were put there, and graded, by someone who does this for Project Physics. I wonder, then, why these three had Project Physics templates and not the others. I don't think I will be volunteering for AfC anytime soon, based on your description. —Finell (Talk) 04:00, 23 October 2009 (UTC)
As near as I can tell from skimming the "how to review" guide, reviewers processing the AfC queue are encouraged to add appropriate stub and classification templates if they feel able to do so. That'd be my first guess as to what happened with these three. My second guess would be that the anon added them themselves while working in scratch-space, but the fact that it was done inconsistently argues against that. Going to be a moot point shortly, so I'm not worrying. --Christopher Thomas (talk) 04:07, 23 October 2009 (UTC)

3rd opinion at Journal of Optics

I say this version is superior. An IP claim this one is. Please leave comments and opinion at Talk:Journal of Optics. Headbomb {ταλκκοντριβς – WP Physics} 05:17, 23 October 2009 (UTC)

I've added a section at Talk:Journal_of_Optics#Straw_poll for this. Per WP:POLLING, this should be considered a starting point for discussion or a tool to judge pre-existing consensus, not a binding vote. --Christopher Thomas (talk) 05:30, 23 October 2009 (UTC)
The question is: Are the Journal of Modern Optics and the two Journals of the Optical Society of America referred to as "Journal of Optics"? If so, the anonymous version is better. If not, Headbomb's version is better. ___A. di M. 13:30, 23 October 2009 (UTC)

Gibbs paradox

The Gibbs paradox article probably needs the attention of someone from this Wikiproject. There have been two RfCs, but not a great deal of response, though what there has been seems to suggest that the article's current content is somewhat dubious. Could someone take a look? Thanks, Miremare 17:48, 23 October 2009 (UTC)

Proposed article "SlipString Drive" for deletion

I have proposed SlipString Drive for deletion. I requested acceptable sources months ago, and none have been forthcoming. No serious (in my opinion) defense has been mounted on the article talk page. If anyone believes it should be saved, please open a discussion and make your case. (This is the first time I have done this, and I am not sure I know how the process should be carried out; apologies if I have goofed it up.) Thanks, Wwheaton (talk) 05:35, 25 October 2009 (UTC)

You did good. Bringing it up here was a nice courtesy, but not necessary. Dicklyon (talk) 05:44, 25 October 2009 (UTC)
Nah it's a good thing to bring it up here. This way people know about the dicsussion. An easier way even if to simply tag the talk page of the article with the {{physics}} banner, and it will show up in the Article Alerts (which can be found here Wikipedia:WikiProject Physics/Article alerts and on WP:PHYS (right panel)). Headbomb {ταλκκοντριβς – WP Physics} 04:38, 26 October 2009 (UTC)

Focus Fusion?

There is disagreement on whether Focus fusion should redirect to Eric Lerner or Dense plasma focus, or be its own separate article. See Talk:Focus fusion. YellowFives (talk) 23:37, 25 October 2009 (UTC)

Peer review for Speed of light

Here it is. I'd particularly appreciate feedback from people who hadn't significantly contributed to the article (or to the surrounding disputes) before. I feel it's quite close to FA status, but I guess it's too soon to nominate it right now, just two days after an ArbCom case about it was closed. ___A. di M. 15:36, 22 October 2009 (UTC)

It's indeed too close to the closing of the ARBCOM case. FAs needs to be stable. At the very least, I would wait one month before going to FA, just to see if it's indeed stable. Headbomb {ταλκκοντριβς – WP Physics} 15:43, 22 October 2009 (UTC)
Yeah; one month is also listed as the typical duration of a peer review. (More specifically, it says that peer review should be closed after 14 days of inactivity, or after 2 days of inactivity if they are more than one month old.) ___A. di M. 15:55, 22 October 2009 (UTC)

Perhaps we should directly contact some suitable people for this peer review, as many of them are not very active on Wikipedia. E.g., I think that User:Joke137 would be a good reviewer. Count Iblis (talk) 16:36, 22 October 2009 (UTC)

Tombe and Brews both proposed turning the article over to Sbyrnes321 to rewrite. While I would never appoint one person to rewrite any article on Wikipedia, his participation in a peer review would be very welcome. Finell (Talk) 21:47, 22 October 2009 (UTC)
Good idea, Count Iblis. I don't know Joke137, but I've sent an email to John Baez; he had participated in a discussion which was somewhat close to the dispute which led to the ArbReq. Do you know anyone else we could contact? ___A. di M. 23:13, 22 October 2009 (UTC)
It would be great to have John Baez' input! User:SCZenz may also be a good Referee. Both User:Joke137 and User:SCZenz have experience in bringing articles to FA standard. User:Sbyrnes321 or any other editor with a good knowledge of physics who has not frequently visited this page lately can be of help. Count Iblis (talk) 00:57, 23 October 2009 (UTC)
Thanks for the shout-outs :-) But I have been involved in the article and disputes. For what it's worth, I think the article is perfectly fine as it stands right now.
Maybe someone should go through this list and make sure that all the old complaints (from the last FA review) have been fixed, before re-nominating. --Steve (talk) 01:02, 23 October 2009 (UTC)
Good idea. ___A. di M. 09:52, 23 October 2009 (UTC)
I've also advertised this PR on sci.physics and some of its subgroups.[5] ___A. di M. 22:29, 26 October 2009 (UTC)

Overview and differences of 1964 PRL symmetry breaking papers

This is a pretty interesting article, but the name could use some work IMO.

I was thinking 1964 PRL symmetry breaking papers, or 1964 Physical Review Letters symmetry breaking papers, or even 1964 PRL papers on symmetry breaking or 1964 Physics Review Letters papers on symmetry breaking or something along those line.

Comments/ideas/suggestions? Headbomb {ταλκκοντριβς – WP Physics} 14:14, 26 October 2009 (UTC)

I remember thinking this was a weird name a few months ago, but hoping that someone else would figure out what to do about it! Clearly odd to have Overview and differences of 1964 PRL symmetry breaking papers but not 1964 PRL symmetry breaking papers, and especially given that Symmetry breaking refers to lots of non-Higgs symmetry breakings. I agree with dropping the "Overview and differences", and with expanding PRL, but it still seems strange. This sort of fits off Higgs mechanism#History and naming, so another approach would be something like History of the Higgs mechanism. (History of the Higgs–Brout–Englert–Guralnik–Hagen–Kibble mechanism? It's not my field so I don't know what the politics of this is!) Djr32 (talk) 20:14, 26 October 2009 (UTC)

Generalized Maxwell Model

According to The Phenomenological Theory of Linear Viscoelastic Behavior by Tschoeogl NW, the Weichert/Wiechert model is named after Johann Emil Wiechert and not Dieter Weichert (named referred to originally, now changed). Which is right? Unfortunately, all other web sources were identical to (copied from) this wiki page. Zachareth (talk) 10:52, 25 October 2009 (UTC)

Which of what is right? You've only mentioned one source. Dicklyon (talk) 03:15, 25 October 2009 (UTC)

The original name on the page with the title Generalized Maxwell Model was Dieter Weichert but it has now been changed to Emil Wiechert as quoted by several textbooks including The Phenomenological Theory of Linear Viscoelastic Behavior. Emil Wiechert (listed on Wiki) seems to be correct as he lived between about 1850 to 1930 which is when all the viscoelastic theory research was done. On the other hand, Dieter Weichert who is also listed on Wiki, was born in the 1950s and is still alive. 121.7.101.86 (talk) 11:54, 25 October 2009 (UTC)

Re Generalized Maxwell model, yes, the oldest sources, before 1940, all point to E. Wiechert; see [6]. Dicklyon (talk) 22:57, 25 October 2009 (UTC)

Found several scientific journal papers which state that Emil Wiechert worked closely with Voigt, Maxwell, Thomson, Kelvin, Poynting, etc. who pioneered viscoelastic theorem (Kelvin-Voigt, Maxwell-Wiechert, Poynting-Thomson, Zener models, etc.). So the Maxwell-Wiechert model is indeed named in part after Emil Wiechert. It's funny how the wrong facts can end up being copied from Wiki to everywhere else. Zachareth (talk) 23:05, 25 October 2009 (UTC)

It's not funny; it's a tragedy that we'll be seeing increasingly in coming years, and one that Wikipedia better figure out how to deal with. See for example Talk:Cardboard_box#another_non-source_for_Malcolm_Thornhill, where the so-called inventor Sir Malcolm Thornhill is now verifiable in a 2009 book. Dicklyon (talk) 23:15, 25 October 2009 (UTC)
The Phenomenological Theory of Linear Viscoelastic Behavior appears to have been published in 1989, so it can't have got the wrong info from Wiki. Disinformation spread by people who take their sources at face value has existed long before Wikipedia. ___A. di M. 19:51, 28 October 2009 (UTC)

E-mailed question re: accuracy in Neutron moderator

The Wikimedia Foundation received a note (Ticket:2009102810027125 viewable to OTRS volunteers) suggesting that a piece of information in Neutron moderator is wrong. According to our correspondent, the sentence reading "The free neutrons are emitted with a kinetic energy of ~2 MeV each." should read "The free neutrons are emitted with a kinetic energy of 200 MeV each." (Actually, I can't tell if he believes we should be omitting the ~)

I have no idea if he's right, but it seems like either we or he are way off base.

Help would be much appreciated. :) --Moonriddengirl (talk) 11:29, 28 October 2009 (UTC)

In the page on Uranium-235, the energy details are given in a fair amount of detail. 200 MeV seems to be the energy released in fission on one atom. Most of this is attributed to kinetic energy of the fission fragments, with about 5 MeV going into "prompt neutrons". It seems like your correspondent is mixing up the total energy released with the energy of the emitted neutrons. I believe the page is correct as given. By the way... what does it take to be an OTRS volunteer? Duae Quartunciae (talk · cont) 13:01, 28 October 2009 (UTC)
Thank you very much. I'll let him know and also alert him how to discuss the matter further on the article's talk page, if needed. :) The OTRS admins evaluate volunteers, and I'm not sure entirely what they're looking for, but I know it is some combination of time in saddle, basic (calm) temperament and interest in needed areas. Oh, being multilingual is also a plus, though not essential. We typically deal with copyright permissions for images & text and basic "quality" concerns for articles. Those quality concerns typically break down into pointing out vandalism, pointing out mistakes, complaining about BLP issues, etc. We get a fair amount of letters from people who want us to write articles about them. Oh, and lots of spam. :D We've recently changed our designation on Wikipedia from WP:OTRS to WP:Volunteer response team (which sounds to me like a t.v. show about citizens who collect in times of natural disaster). Anyway, the "official" job description is at meta:OTRS/info-en recruiting, and the page for raising your hand is at meta:OTRS/volunteering. :) --Moonriddengirl (talk) 13:17, 28 October 2009 (UTC)
OK... I thought it might have been physics specific. By the way, you can also refer your correspondent to pages at the hyperphysics website. See Moderation of Fast Neutrons, and also Energy from Uranium Fission. Duae Quartunciae (talk · cont) 13:58, 28 October 2009 (UTC)
Thanks. :) In the time I've been doing OTRS (4 or 5 months, I think), I've only seen a couple of science-related letters, though we do get the spectrum. --Moonriddengirl (talk) 14:03, 28 October 2009 (UTC)

Carbon burning process

Don't have ref for the temp and density figures typical of carbon burning inherited with the article. Similar problem with the (stub) articles on neon burning process etc. Would like feedback about my mention of stellar models, in particular can references be improved. From the stellar models article, I noticed only description of the 1D models with r as ind. var., yet the refs only appear to refer to 1D models with mass m as ind. var.. I understand the latter are helpful for isochrones of groups of stars of the same age evolving in the HR diagram. But for my article would like to illustrate more elementary concepts in models of individual stars, as well as comparing how the features change with mass. For example, would like to illustrate how the total mass of core nuclear fuel burnt increases during different stages of evolution. Is this related to shell-burning? Puzl bustr (talk) 12:59, 29 October 2009 (UTC)