Wikipedia talk:WikiProject Physics/Archive February 2017

Bouncing ball
I have just created this. I've looked at it for too long, and can't find any more issues with it due to being too familiar with the words I wrote. Feedback is appreciated (as would a GA review, which I've nominated it for). I'm also citing my own work for a few things. While I don't believe this is very controversial given the statements it supports, a second set of eyes wouldn't hurt either.. Headbomb {talk / contribs / physics / books} 21:11, 3 February 2017 (UTC)

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Missing topics lists
My lists of missing topics about physics, part 1 & part are updated - Skysmith (talk) 15:41, 8 January 2017 (UTC)


 * I'm not sure how this list was generated, but a lot of these pages exist under a slightly different name. e.g. 750 GeV diphoton resonance exists as 750 GeV diphoton excess and eta-meson exists as eta meson. Dukwon (talk) 16:36, 10 February 2017 (UTC)
 * I have created redirect pages for both of these. Absolutelypuremilk (talk) 17:56, 10 February 2017 (UTC)

Wikipedia talk:WikiProject Chemistry
There is currently an RFC on what do do with the shortcuts used for the chemistry-related projects. Please comment. Headbomb {talk / contribs / physics / books} 16:15, 14 February 2017 (UTC)

New(ish) user being slightly too BOLD
I came across some edits made by today, and I'm not entirely sure they're constructive. They've been creating a whole ton of random redirects (most of which I've deleted) and created General relativity and quantum mechanics (which at the very least probably needs to be renamed). A second or third set of eyes on this would be appreciated. Primefac (talk) 15:04, 30 January 2017 (UTC)
 * I undid quite a few of their edits today. As the subject is treated in Quantum gravity already, I have db-a10-ed General relativity and quantum mechanics. - DVdm (talk) 15:52, 30 January 2017 (UTC)
 * I need to bump this post. has created a stupid number of rather implausible redirects, basically turning phrases into wikilinks. Basically, they're trying to avoid the pipe trick by making redirects. I could use some help looking through them all. Primefac (talk) 16:54, 13 February 2017 (UTC)
 * Just as a note, I call this a "stupid" number because they've made over 200 redirects in the last three weeks. Primefac (talk) 17:00, 13 February 2017 (UTC)
 * Why would you object to this? I dont know when I create a redirect where else it is used (because I haven't read the whole of wikipedia yet!!!), or where it might be used in future. Often the links ARE applicable in multiple places. The redirects make it easier to FIND links, because you dont always know what to search for (if you dont already know what something is called). Every link increases the knowledge encoded in the system. If you think this is a problem in any way, why dont you get on the suggestions box and come up with improvements to the platform ('overlinking'? NONSENSE, there should be a way to prioritize the links, rather than having to make a binary choice 'link or no link'. Look at the new hovercards feature, it's great having definitions pop up below things. The physics articles are full of jargon that isn't at all obvious. and so on.Fmadd (talk) 17:09, 13 February 2017 (UTC)


 * At any rate, you should slow down since people object – not only here, but at your talk page too, and it is not entirely new. Please sort this out before proceeding in the same manner. Otherwise, if it turns out to be "bad" (or if community consensus has it that it is bad, whether actually good or bad), it will be a too massive job for anyone to rectify. YohanN7 (talk) 17:16, 13 February 2017 (UTC)
 * I have also not been happy with some of the edits made by this editor. Xxanthippe (talk) 21:38, 13 February 2017 (UTC).
 * What gets me are things that are self-explanatory, like particle–antiparticle pair in the antiparticle article (which inexplicably links to pair production) and combinations of two concepts, like scattering event (which links to event (particle physics) but not scattering). These edits often demonstrate a lack of understanding of the terms being wikilinked, and sometimes they end up pointing to a misleading or confusing target. Dukwon (talk) 13:45, 14 February 2017 (UTC)
 * Great, and now lots of non-particle-physics articles containing the two-word phrase "scattering event" are linking to event (particle physics). Now I have to fix these mistakes. These sorts of edits are not helping. Dukwon (talk) 13:57, 14 February 2017 (UTC)
 * Many of the redirects are sensible, though don't create a redirect if you don't know where to point it. Also don't point mainspace redirects at categories. Also a disambig page does not have one entry only. Graeme Bartlett (talk) 00:39, 14 February 2017 (UTC)
 * Some are not. Also, this editor has a habit of bolding some words in a haphazard way, inconsistent with Wikipedia style MOS:NOBOLD.Xxanthippe (talk) 01:31, 14 February 2017 (UTC).
 * The lack of edit summaries, and inappropriate markings of non-minor edits as minor, is also a problem. Not all of these supposedly minor edits are good, and they should be carefully reviewed.   Sławomir Biały  (talk) 01:43, 14 February 2017 (UTC)

The editor has now been indefinitely blocked. Now the mess he made has to be cleaned up. Is there a bot for that? Xxanthippe (talk) 00:29, 17 February 2017 (UTC).
 * , I've rolled back all of their "current" edits (though there is some pushback about my actions). That was about as "bot-like" as it's going to get. I started User:Primefac/Fmadd, which looks at the redirects they've created, so that's another starting point for cleaning things up. You're welcome to join in the discussion. Primefac (talk) 02:01, 17 February 2017 (UTC)

Two forms of Ampere's force law - looking for citation for proof of equivalence
Ampere's force law can be written in two ways:
 * $$ \vec{F}_{12} = \frac {\mu_0} {4 \pi} \int_{L_1} \int_{L_2} \frac {I_1 d \vec{\ell}_1\ \mathbf{ \times} \ (I_2 d  \vec{\ell}_2 \ \mathbf{ \times } \ \hat{\mathbf{r}}_{21} )} {|r|^2}$$,
 * $$ \vec{F}_{12} = -\frac {\mu_0} {4 \pi} \int_{L_1} \int_{L_2} \frac {( I_1 d \vec{\ell}_1\ \mathbf{ \cdot} \ I_2 d  \vec{\ell}_2 ) \ \hat{\mathbf{r}}_{21} } {|r|^2}.$$

There's a proof that the two forms are equivalent (expand the vector triple product then use Stokes theorem), but it's hard to find online or in textbooks. I could only find it at citizendium. So I cited citizendium, but then someone deleted that citation - I guess they think that citizendium is never a reliable source. (I disagree, but that's an issue for a different forum.) My question for y'all is: Has anyone seen the proof of equivalence in any textbook, online lecture notes, or somewhere else I can cite other than citizendium? Thanks in advance! --Steve (talk) 17:18, 4 February 2017 (UTC)


 * I think the issue is that this particular Citizendium article has yet to be approved (i.e. be peer-reviewed). It's an interesting (and certainly valid) proof. I've never seen this version of the law before. I wonder why, since dot products tend to be much easier to understand, and a geometric proof showing that $$d \vec{\ell}_1 \times \left(d  \vec{\ell}_2 \times \hat{\mathbf{r}}_{21} \right) = -d \vec{\ell}_1  \cdot d  \vec{\ell}_2  \hat{\mathbf{r}}_{21}$$ should be fairly straightforward to have (unless this doesn't hold true, of course). Headbomb {talk / contribs / physics / books} 11:55, 5 February 2017 (UTC)
 * It's not true that $$d \vec{\ell}_1 \times \left(d  \vec{\ell}_2 \times \hat{\mathbf{r}}_{21} \right) = -d \vec{\ell}_1  \cdot d  \vec{\ell}_2  \hat{\mathbf{r}}_{21}$$. The integral is the same, but the integrands are different.   :-D --Steve (talk) 16:23, 5 February 2017 (UTC)
 * Yeah, I tried it at home, and it's almost the same, but not quite. If you call &theta;1, &theta;1, and &theta;12 the angles between dl1 and r21, dl2 and r21, and between dl1 and dl2, you end up with dl1 dl2 sin &theta;2 = - dl1 dl2cos &theta;12. Those must be equivalent under integration, but not before. And at this point, attempting that proof would be no simpler than expanding the vector triple product and doing the Stokes' thing. Headbomb {talk / contribs / physics / books} 17:14, 5 February 2017 (UTC)


 * UPDATE: I found it, I'm all set now. The proof is briefly summarized (in passing) in an American Journal of Physics article from 1988. Apparently Maxwell himself knew that these forms were equivalent! --Steve (talk) 16:56, 5 February 2017 (UTC)


 * I am 64.76% sure this is thoroughly proved in Roald K. Wangsness' Electromagnetic Fields. I'll check when I get home. YohanN7 (talk) 09:22, 17 February 2017 (UTC)

Value of Chandrasekhar limit, is it 1.39 solar masses or 1.4?
Came here after seeing a discussion in StackExchange Astronomy questioning the value given by Wikipedia. Sure, the article is cited multiple (three) and reliable sources. I am afraid, though, one has to accept the value in GF as the sources cannot refer online. What scared me was, the google information card gives the value as 1.4 and was able find a couple of sources, here and here agreeing with it. Has Wikipedia got it wrong while the rest of the internet agreeing the limit to be 1.4 solar masses? -- Chanaka L  ( talk ) 09:27, 20 February 2017 (UTC)
 * Just as a thought, 1.39, 1.4, and 1.44 (gleaned from the StackExchange post) all round to 1.4, so technically speaking (unless the uncertainty is very small) those values are all pretty much the same. Research changes and improves over time (and scientists get different values all the time), so I think finding research that shows both might be the best course of action. This would allow us to say "the limit has been found to be between 1.39-1.4X " or something similar. Primefac (talk) 13:02, 20 February 2017 (UTC)
 * The three sources currently cited give the value as 1.4, 1.44, and 1.38, respectively, so for now I've rounded it to 1.4. If you have a source with an explicitly up to date value or want to give a range of values or whatever, you should certainly feel free to change it. 786b6364 (talk) 01:00, 23 February 2017 (UTC)