Wikipedia talk:WikiProject Physics

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Physics Portal This page is within the scope of WikiProject Physics, which collaborates on articles related to physics.

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Contents 1 Category:Quantum Chromodynamics' physicists 2 Another AfD for OR -- Gravitational attraction 3 Exact solutions in general relativity needs to be more pedagogical 4 Physics Assessments 5 Questions at Talk:Black hole 6 usefulness of physics articles 7 Magnetospheric convection and magnetic storms 8 FTL/time travel animation 9 Please review "Black hole" article 10 Quick check of "Lissajous orbit" article? 11 Three new AfDs 12 The abnormally long name for Planck's law of black body radiation 13 Physical nullification 14 Scientific peer review for "Equipartition theorem" 15 Reverted vandalism unnoticed for more than a year 16 Heat death of the universe

[edit] Category:Quantum Chromodynamics' physicists

Category:Quantum Chromodynamics' physicists has been nominated for deletion. If kept, the bizarre apostrophe should be deleted. Please go express your opinion at WP:CFD. It looks like it's spring cleaning time for physics categories. Dr. Submillimeter 17:28, 16 March 2007 (UTC)

Actually, someone should review Category:Physicists and propose a group nomination that includes Category:Weak Interaction physicists, Category:Electroweak Theory physicists Category:Electromagnetism physicists. Some of the cats I don't mind, but might work better under a better name, e.g. "quantum theorists" instead of "Quantum Theory Physicists", for those who took part in te early-mid 20th-century scene. linas 20:15, 16 March 2007 (UTC)

By the way Wikipedia:Categories for discussion/Log/2007 March 16 has another one, a "quantum gravity physicists" category up for merging. — coelacan — 00:47, 17 March 2007 (UTC)

[edit] Another AfD for OR -- Gravitational attraction

AfD due to OR: Gravitational attraction linas 19:59, 16 March 2007 (UTC)

[edit] Exact solutions in general relativity needs to be more pedagogical

Exact solutions in general relativity needs to be revised so that it is more easily understood by a general audience. At the moment, it is written in language that only some people with advanced physics degrees will understand. At the very least, it needs an introduction written in layman's terms. (I also found a "help" message at Einstein field equation if anyone wants to work on that as well.) Dr. Submillimeter 21:09, 17 March 2007 (UTC)

OK, let's make some distinctions here. More accessible, maybe; more pedagogical, definitely not. WP is a reference work, not a teaching tool. If you want to write a textbook write it at Wikibooks. WP is an encyclopedia, and people use encyclopedias to teach themselves, but they don't and shouldn't expect the encyclopedia to be written like a lesson. --Trovatore 21:22, 17 March 2007 (UTC)

I agree with Dr. Submillimeter to a certain extent. I think pretty much any physicist should be able to read the first paragraph or two and come away with at least the basic idea that finding exact solutions to general relativity is hard and thus such solutions are relatively rare and become fairly well-studied and part of the subject cannon, even if they are not terribly "realistic". So one doesn't have to jump right into the language of manifolds and tensors in the first sentence. On the other hand, I don't think this article has to be written for a very broad audience. It would be better to include a statement early on that directs less specialized readers to the main GR page. I think it's ok for this article to be overall technical and specialized; readers without a specialized background probably won't care that much for this content anyway. —The preceding unsigned comment was added by Joshua Davis (talk • contribs) 21:41, 17 March 2007 (UTC).

That's an orthogonal question. It can (and probably should) be made more accessible to a broader audience, at least in the lede, without devolving into a pedagogical style. --Trovatore 21:49, 17 March 2007 (UTC)

What I meant to emphasize was that the broader audience should basically be physicists, since the topic is already sort of specialized. The intro should be accessible enough for an undergraduate physics student to pick up a main point about why there is such an article and the importance of the subject matter. The content itself can then be pretty specialized. I don't think the intended audience is any broader than those already with some physics knowledge. Those who need it even more accessible should really probably be directed to the main GR page. Joshua Davis 22:55, 17 March 2007 (UTC)

Perhaps "pedagogical" was the incorrect term to use. Nonetheless, the page still needs to contain at least an introdcutory paragraph in non-technical terms (so that the average person from the general public will understand what physicisists do and why they should continue to receive government funding) and more information at a level that undergraduates would understand. I also like the suggestion of referring the average reader to an introductory article on general relativity. Dr. Submillimeter 07:26, 18 March 2007 (UTC)

[edit] Physics Assessments

I don't think the following scale is useful for classifying the importance of articles "within physics":

Astigmatism for example, is a must-have for a print encyclopaedia, but it's definately not "top-class" in physics. How about we link to something like the following instead:

Flying fish 22:16, 17 March 2007 (UTC)

I don't agree with the equation of "low importance" with "specialist interest". Some of the stuff that popularizers like is often of low importance within the field. The math project describes "low importance" as "peripheral knowledge, possibly trivial"; you might consider adopting that formulation. --Trovatore 06:03, 18 March 2007 (UTC)

so what is the purpose of these tags? Does importance refer to how important a topic is to physicists or does it refer to how important it is that we work to write a good article about it? The current scale seems to imply the latter. I would say that it is also the more useful to have for people involved in 'project physics'. --V. 07:30, 18 March 2007 (UTC)

Good question. Here's a possible testcase: Which is the more important topic from the point of view of the WikiProject, Schrödinger's cat, or the Copenhagen interpretation? I would say surely the latter, even though it's arguably the more "specialist" topic; the shockingly mistreated feline is just an illustration of some ideas from the more general concept. On the other hand, while it might not be terribly important to make sure the article on the kitty is complete or inclusive, it's probably very important to patrol it for the nonsense that it's likely to attract from half-informed editors that have heard of it somewhere. So it's a tricky issue. Maybe there's more than one dimension to importance -- important to have good coverage, versus important to make sure it doesn't mislead. --Trovatore 08:06, 18 March 2007 (UTC)

I had sort of considered "specialist interest" to mean that it's probably only interesting to a small number of people, whether inside or outside the field. Something a random person might read if she sees a link to it, but that she'd only search for if she already know something about it. How about something like this:

I agree with you that Copenhagen interpretation is more important than Schrodinger's cat, interesting point. I think that if something that is definately a "physics" subject is likely to draw a lot of readers it should be at least Mid-Class rather than Low-Class. Flying fish 15:47, 18 March 2007 (UTC)

Before we get too excited about changing the importance-scale, lets decide what we want to do with it. Making a ranking of physics topics by how often they are used by contemporary physicists is an interesting exercise, but one that will no doubt be subject to controversy and one that is not very useful to the wikipedia. as I have said before, it would be more useful to have a ranking by how important it would be to have a good article on this topic in an encyclopedia. I do not think that 'project physics' is 'physicists for physicists', I think physics here for everyone else too. And to the world at large, a topic like 'refraction' or 'newtons laws' are probably of more interest than 'bosons' or 'neutrino mass problem' whereas the first two have no conferences devoted to them the later two actually do.

Perhaps this is a part of a more fundamental discussion: what do we want the wikipedia to be? Do we want it to be the ultimate textbook for physicists or do we want it to be an accessible reference for all those with a passing interest in science? --V. 21:30, 18 March 2007 (UTC)

Ok, I think this is a discussion we should have. What was the point of creating the physics project tag in the first place? The reason I brought this up was because I think the current "importance" guidelines don't make any sense, I'm very open to suggestions regarding what they should be. I tend to agree with you that we should be ranking articles in order to focus on what it's most important to have correct. I would expect (I haven't checked) that "Newton's Laws" would be Top ranked, and that refraction would be High-Class. Identical particle statistics is one of the most important (and at first confusing) things you learn about in undergrad, so I think it's very important that the page be developed. My other thought is that subjects that are related to very expensive experiments (Fermilab, ATLAS, WMAP, Kamioka Observatory) should have very good pages. Wikipedia should be able to help people to understand why they were worth the effort.

Also, I'm not sure that "importance" rankings need be any more controversial than the pages themselves. Surely we can come to consensus in the same ways as usual. I do think that pages are sometimes overly technical. It makes me wonder sometimes whether it would make sense to split pages into technical and lay versions? I haven't been looking around Project:physics for long, so it wouldn't surprise me if this debate has already been resolved multiple times...Flying fish 02:03, 19 March 2007 (UTC)

importance ranking indeed need not be controversial, but ranking by importance to physicists is more controversial than ranking by importance to an encyclopedia. I agree that all the topics that you mention are important and as far as I am concerned they are all must-haves for a written encyclopedia. So lets make great articles about all of them. The current standard seems to do a great job classifying articles within the bigger picture of creating an encyclopedia. Do we really need more classification? if so, to what practical purpose? --V. 04:58, 19 March 2007 (UTC)

Some people have been discussing a very similar system for astronomy articles, but people still see it suffering from POV problems. I inadvertently came up with a good example of one type of article that would cause problems. Arp 220, a relatively nearby ultraluminous infrared galaxy is the subject of intense scientific study, yet the galaxy is hardly ever mentioned in any material that would be read by the general public or amateur astronomers. If I were ranking the article, I would list it as having "top" priority, but if other people were ranking it, it would be listed as "low". I would guess that similar examples can be identified for other branches of physics.

While I would guess that the prioritization of Arp 220 can be discussed in a civil manner, I do see problems with articles about fringe science or pseudoscience. Someone writing about their favorite wacko alternate physics theory (free energy, alternatives to the Big Bang, etc) may identify their article as a "top" priority, whereas most other physicists would label the article as "low". This could spur a useless yet lengthy debate about prioritization that has nothing to do with writing material for the articles. Dr. Submillimeter 08:29, 19 March 2007 (UTC)

I agree with Dr. Submillimeter here. Would there be any objections to simply getting rid of the importance/priority tag all together? Mike Peel 09:57, 19 March 2007 (UTC)

Wait ... I thought the point of prioritization was to determine what articles would go into a printed version of he encyclopedia (a printed version aimed at non-physicists). (See Wikipedia:Version 1.0 Editorial Team/Release Version Criteria) Thus, we shouldn't get rid of that tag, since it negates the whole purpose of the thing. However, I do agree w/ flying fish that something other than a ham-handed importance should be used. Renaming to need with the definition of needed for non-physicists is a lot less inflammatory than "importance". linas 23:49, 20 March 2007 (UTC)

I agree with linas' comment (23:49, 20 March 2007), especially "needed for non-physicists". There's no point in trying to produce an importance / need scale that's more sophisticated than "must / should / could be included", and these are just rough guides for the compilers of the CD if they find they're hitting some sort of limit on content. And in assessing importance / need, the "hotness" of the topic should get higher weight than its intellectual significance.
Despite the uncertainties mentioned below (are there real constraints on quantity of content? how easy is it to assemble the CD?), I'm not sure that "importance" is terribly important. Wikipedia:Release Version says of Version 0.7 test release, "This CD contains a collection of 2800 articles ..." To me that implies a single CD, i.e. maximum capacity 650MB. I just checked a fat 1-volume text-only encyclopedia and estimated that it contains about 6MB of text. Does anyone know how much pure text the online English version of WP contains, counting only latest versions of all articles? And the size of images used in these articles, allowing for the fact that some images are re-used? I'd guess an illustrated encyclopedia like WP would be about 50% text, after making allowances for images and and for layout and mark-up overheads. So the CD can accommodate about 325MB of text, i.e. over 50 volumes of my printed encyclopedia. That suggests space is not a strong constraint. The only other constraint I can think of is the time required to ensure that what is published is good and is internally consistent, e.g. if article A is included and relies on article B, article B should be included. I don't know sophisticated the assembly process is - ideally it should be largely automated by software e.g. changing links to included articles so they point to the CD and leaving other links (including excluded WP articles) pointing to the Web.
I think the key sentences in Wikipedia:Version_1.0_Editorial_Team/Release_Version_Criteria are "An article judged to be 'Top-Class' in one context may be only 'Mid-Class' in another. By 'priority' or 'importance' of topics for a static version of the encyclopedia, we generally mean to indicate the level of expectation or desire that the topic would be covered in a traditional encyclopedia." The second sentence implies that importance should be judged from a reader's point of view. The problem is, what type of reader? Undergraduate and higher-level students of physics are unlikely to use WP, except to find out what's happening on the periphery of the subject (e.g. "... in popular culture"). So I think the target readers should be non-specialists, especially early to mid teens (if WP motivated a teenager to become the next Einstein, WP would have achieved more than a bookcase full of academic papers). That suggests to me that "hot topics", "junk science" and scientifically minor but attention-grabbing examples may sometimes be more "important" than intellectually significant scientific content, and I think the first sentence I quoted from Wikipedia:Version_1.0_Editorial_Team/Release_Version_Criteria supports this idea.Philcha 09:56, 23 March 2007 (UTC)

[edit] Questions at Talk:Black hole

Many questions have been posted to Talk:Black hole, mostly to do with rotating black holes. Any of the GR-types who are active might want to take a stab at answering this, as it's out of my league. --Christopher Thomas 06:35, 18 March 2007 (UTC)

[edit] usefulness of physics articles

while reading Quantum mechanics I came across the following passage

"In the mathematically rigorous formulation of quantum mechanics, developed by Paul Dirac and John von Neumann, the possible states of a quantum mechanical system are represented by unit vectors (called "state vectors") residing in a complex separable Hilbert space (variously called the "state space" or the "associated Hilbert space" of the system) well defined up to a complex number of norm 1 (the phase factor). In other words, the possible states are points in the projectivization of a Hilbert space. The exact nature of this Hilbert space is dependent on the system; for example, the state space for position and momentum states is the space of square-integrable functions, while the state space for the spin of a single proton is just the product of two complex planes. Each observable is represented by a densely defined Hermitian (or self-adjoint) linear operator acting on the state space. Each eigenstate of an observable corresponds to an eigenvector of the operator, and the associated eigenvalue corresponds to the value of the observable in that eigenstate. If the operator's spectrum is discrete, the observable can only attain those discrete eigenvalues."

Makes perfect sense, right? My compliments to the writer of this passage for coming up with such a compact description of the formalism of quantum mechanics. it is indeed nicely densely defined. My question is, can some one who does not already know this, possibly understand any of this? And if only some one who already knows this is can understand this, does this passage still contain any new information? Sure, WP is a reference work not a teaching tool, but where do we draw the line? is there even a line at this point, specific to science articles? --V. 21:45, 18 March 2007 (UTC)

See the short discussion on exact solutions in general relativity up above. This is a general problem for physics articles. I would suggest that these articles contain at least some basic background information that the average reader understands. (I myself attempt to write astronomy articles so that they can be understood by laypeople but so that they do not lose scientific information. For example, see NGC 3031 or NGC 4594.) Dr. Submillimeter 08:13, 19 March 2007 (UTC)

[edit] Magnetospheric convection and magnetic storms

I wikified the above article - somebody had to - but I really didn't know what I was doing. I would guess that it is quite an important topic and wondered if someone here could have a look. I have put this project as the one best suited for finding an expert to look at the article. Thanks. Itsmejudith 22:38, 18 March 2007 (UTC)

[edit] FTL/time travel animation

In case anyone finds it useful for time travel or other articles, I've produced an animation showing how one would navigate a path that ends up in the past light-cone of the departure event, with diagrams and appropriate subtitles. Drawback: the animated .gif is huge (6.8 megabytes), even with all appropriate tricks applied (line art and very small palette).

Mostly this was a "because I don't want to go to bed yet" project, but it may still serve some useful purpose. --Christopher Thomas 06:12, 22 March 2007 (UTC)

[edit] Please review "Black hole" article

I've completed pass 1 of the edit of Black hole discussed in Talk:Black_hole#Possible_restructure? Please check it for errors, inconsistencies and serious omissions. For comparison, the previous version of the article is at [1]Philcha. Talk:Black_hole#Please_review_the_recent_edits states the objectives of the edit. 10:12, 23 March 2007 (UTC)

Dr. Submillimeter suggested I also ask Wikipedia:WikiProject Astronomy and Wikipedia:WikiProject Astronomical objects to review Black hole, and I'm informing these projects that I've asked Wikipedia:WikiProject Physics to review Black hole.
Dr. Submillimeter commented that Black hole is too long, and I think that for each major "entry point" article WP needs a plan which defines how much detail goes where Talk:Black_hole#Please_review_the_recent_edits.Philcha 22:47, 23 March 2007 (UTC)

[edit] Quick check of "Lissajous orbit" article?

Could someone please do a quick check of the newly created Lissajous orbit article? Can anything be added about e.g. the source of the name, or how Lissajous orbits are related to Lissajous curves? Thanks! Sdsds 01:37, 24 March 2007 (UTC)

[edit] Three new AfDs

Physics folk may be interested in these:

• 25 March – Physical economics (discussion)
• 26 March – Tom Van Flandern (discussion)
• 27 March – SklogWiki (discussion)

Anville 14:41, 28 March 2007 (UTC)

[edit] The abnormally long name for Planck's law of black body radiation

Does anyone know why the article named Planck's law of black body radiation? Could we move it to Planck's law? Nothing else is apparently referred to as Planck's law, which is just a redirect to Planck's law of black body radiation. If no one objects, I will request a move on 31 Mar 2007. Dr. Submillimeter 22:01, 28 March 2007 (UTC)

I'd be minded to Keep. I like the long title which explains exactly what area of Physics the law relates to. I think that's helpful for Newbies. It doesn't prejudice Planck's law also being there as an alternative link, and being used from then on through the article. Jheald 23:22, 28 March 2007 (UTC)

I think the move is obvious. See WP:COMMONNAME. It would be a simple thing except for some history at Planck's law where someone had put the wrong content there. --Trovatore 23:35, 28 March 2007 (UTC)

[edit] Physical nullification

Hello. Could someone competent look at Physical nullification. I know about the article because it's uncategorized but that appears to be the least of its problems. Thanks for your help. Pascal.Tesson 02:49, 29 March 2007 (UTC)

The positive energy of matter and radiation is balanced by the gravitational potential energy which is negative. There is no basis for believing that any other kind of negative energy is possible. The article is pure speculation. JRSpriggs 09:10, 29 March 2007 (UTC)

Without a source indicating that Robert Forward's idea was directly based on Isaac Asimov's, then collecting them together is Original Research. The same goes for this part:

It mght be noted that there are places in General Relativity where the existence of negative mass/energy would allow things like time travel and faster than light travel to exist (it can stabilize the mouth of a wormhole, for example).

This is OR because we have no evidence that Forward said any of it, and it probably just stems from the imagination of whoever wrote the article, trying to connect an old SF idea with something more modern.

If you cut out the stuff from Asimov's essays, which are forty years out of date anyway, there's not enough left to merit an article. WP:AFD, anyone? Anville 13:54, 29 March 2007 (UTC)

Update Suiting the action to the words, I went ahead and began AfD proceedings. Anville 20:36, 29 March 2007 (UTC)

[edit] Scientific peer review for "Equipartition theorem"

Hi, I just added Equipartition theorem for scientific peer review. I'd like to bring the article to FA status in the near future. Please give me your thoughts and suggestions — thanks muchly! :) Willow 20:19, 29 March 2007 (UTC)

Any help you can give at the FAC review of the Encyclopædia Britannica would be most welcome as well; thanks! :) Willow 23:04, 30 March 2007 (UTC)

[edit] Reverted vandalism unnoticed for more than a year

I've just reverted a sneaky piece of vandalism in Quark model unnoticed for more than a year (introduced [2], reverted [3]). In the meanwhile it has propagated to countless Wikipedia mirrors and clones. So much for reliability of Wikipedia. 131.111.8.104 13:57, 30 March 2007 (UTC)

[edit] Heat death of the universe

At the request of another user, I've tweaked the "current status" section in Heat death of the universe (edit|talk|history|links|watch|logs) to improve clarity (and remove flagged weaselling). If any of the cosmology-types lurking here are bored, it would be nice if someone could vet it for accuracy and fill in the "citation needed" points. I am not an expert on physical cosmology. --Christopher Thomas 04:55, 31 March 2007 (UTC)