The following is an archived discussion of a featured article nomination. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article candidates. No further edits should be made to this page.

The article was not promoted by SandyGeorgia 21:05, 25 January 2010 [1].

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Speed of light[edit]

Nominator(s): ― A._di_M.^{2nd Dramaout} (formerly Army1987) 16:59, 10 January 2010 (UTC)[reply]

Note: WP:FFA, has already been on main page

• Featured article review/Speed of light/archive1
• Featured article review/Speed of light/archive2

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I am nominating this for featured article because all the controversies which there have been in recent months seem to have settled (no major edit in the last month or so), all of the points in the last peer review were addressed (or made moot by trimming superfluous stuff), and I think the article as it exists now is good enough. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 16:59, 10 January 2010 (UTC)[reply]

• Comment. Alt text done; thanks. Alt text is largely present (thanks), but it is missing for File:Relativity of Simultaneity.svg, File:Stellar aberration.JPG and File:Interferometer.JPG. Most of the existing alt text is good, but I see problems with two images. File:Lorentz factor.svg has alt text that doesn't really capture the graph (the fairly sharp knee and the asymptote); the existing alt text "curved sharply upward and to the right" would describe the sqrt function better than it describes this function. File:Roemer.jpg has alt text that can't be verified from the image itself (see WP:ALT#Verifiability); troublesome phrases include "Io", "Jupiter", and "Earth". Eubulides (talk) 03:43, 11 January 2010 (UTC)[reply]

  Is it better now? A minimum of interpretation is unavoidable, but at least it doesn't mention proper names which aren't found in the picture itself. ("Sun" should be unproblematic, as it's the stereotype depiction which even children use.) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 11:56, 11 January 2010 (UTC)[reply]

  Yes, thanks, it all looks good now. You're right about "Sun" of course. Eubulides (talk) 00:15, 12 January 2010 (UTC)[reply]

• Comments -
  • Current ref 10, the Hall, Hall and McCall ref lacks a page number

    I've asked the user who added this for the page number; meanwhile I'm adding a "page needed" tag. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:41, 11 January 2010 (UTC)[reply]

    She's added it now. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 21:15, 11 January 2010 (UTC)[reply]

  • Please spell out abbreviations in the notes. Yes, they are linked, but you don't want your readers to leave your article, they might never return

    I suppose everyone knows what "US" mean; as for 2p₁₀ and 5d₅, they are de facto no longer abbreviations: many people who use them don't even know that they originally stood for "principal" and "diffuse", and anyway spelling those out isn't going to help the readers who don't know what they mean in that context. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 17:19, 11 January 2010 (UTC)[reply]

    It wasn't those, it's the NIST, etc. type abbreviations I was referring to. Ealdgyth - Talk 17:37, 11 January 2010 (UTC)[reply]

    Ah, you mean the ones in the references. I've fixed them (except NASA which is more widely known by its acronym than by its full name, and FSTC whose expansion on whose website I cannot found). BTW, I'm fixing your indentation mark-up – you have to copy and paste the indentation of the post you're replying to, and add a *, a # or a : at the end, depending on whether you want a bullet, a number or neither at the beginning of your post; otherwise, you can get misplaced bullets and wrong numbers in visual browsers, and even worse things in screen readers. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:30, 11 January 2010 (UTC)[reply]

  • What makes the following reliable sources?
    • http://www.quadibloc.com/other/cnv03.htm

      Personally, I don't think a source is strictly needed for such an unsurprising fact (that if the number of metres in one light-second and the number of metres in one mile/yard/foot/inch are both exactly fixed by definition, then so is the number of miles/yards/feet/inches in a light-second), but there was a discussion about that in November. The source cited here was found by Joe Kress in Talk:Speed of light/Archive 12#Took it out. If we do need a source, I agree that this one isn't the best possible one, but if it's fine for anyone else around here, it's fine for me. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:46, 11 January 2010 (UTC)[reply]

  • Current ref 15 (Gibbs) the publisher is NOT the University of California Riverside, its Gibbs, so what makes him a reliable source?

This source from the American Journal of Physics may be helpful.  Cs32en Talk to me  20:58, 22 January 2010 (UTC)[reply]

• • Current ref 24 Roberts, et al. ... Same deal as above.
  • And the same for Ccurrent ref 29 (Gibbs again) and 38 (Gibbs again) and 44 (Chase)

    I followed the instruction at ((Cite web/doc)), according to which the publisher is the institution hosting the website. If that's not always right, it should be explained there. Anyway, those FAQ were posted on physics newsgroups for years (so they were reviewed quite a lot, I suppose), and were edited by Dr Don Koks of Adelaide University. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 17:19, 11 January 2010 (UTC)[reply]

    Note that WP:SPS says that internet forum postings are not generally reliable, but there are exceptions. For these to work, we'd need to see why the author/etc. meets those exceptions. Ealdgyth - Talk 17:37, 11 January 2010 (UTC)[reply]

    That page suggests "Self-published material may, in some circumstances, be acceptable when produced by an established expert on the topic of the article whose work in the relevant field has previously been published by reliable third-party publications." That is the case for Gibbs,"P+Gibbs"+physics and if we interpret "produced" more broadly than "written" (as in "I produced my ticket to the collector"), the FAQs are on the UCR pages of John C. Baez, probably the best-known living mathematical physicist; they are cited in twenty Wikipedia articles.[2]. Some of them in turn cite a wealth of unquestionably reliable sources. Lastly, the points they support are very uncontroversial and most of them are also supported by other sources, which however aren't freely available on-line (e.g. Sakurai's book). ― A._di_M.^{2nd Dramaout} (formerly Army1987) 21:07, 11 January 2010 (UTC)[reply]

    Not to mention that the Usenet physics FAQ has been read by many other physics experts and has passed their peer review. As such I would consider it much more reliable than for example a text book written by a single author. TimothyRias (talk) 09:11, 12 January 2010 (UTC)[reply]

  • Newspapers titles in the references should be in italics. If you're using ((cite news)), use the work field for the title of the paper, and the publisher field for the name of the actual company that publishes the paper

    Done. (Did I miss any?) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:28, 11 January 2010 (UTC)[reply]

  • Current ref 57 (Egan).. lacks a publisher. What makes this a relaible source?

    Right, that's self-published by a SF writer, and that sentence is already supported by a Nature article. On the other hand, the applet is quite illustrative, so I was going to move it to "External links", but it's already there. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:53, 11 January 2010 (UTC)[reply]

    I've removed it from the citations, only leaving it in the external links. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 22:10, 14 January 2010 (UTC)[reply]

  • Current ref 67 lacks a last accessdate, also what makes this a reliable source? Same for current ref 69...(Both O'Connor)

    These citations are produced by Template:MacTutor; I'm going to ask there. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:57, 11 January 2010 (UTC)[reply]

    Done. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:54, 12 January 2010 (UTC)[reply]

  • Sources that are in languages other than English need to have that language noted in the reference

    Done. (Did I miss any?) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:28, 11 January 2010 (UTC)[reply]

  • Current ref 92 is just a titled link, needs author, publisher, last accessdate, etc.
  • Current ref 99 (IAUWG...) lacks publsiher

    Done both. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:15, 11 January 2010 (UTC)[reply]

Otherwise, sources look okay, links checked out with the link checker tool. Ealdgyth - Talk 16:51, 11 January 2010 (UTC)[reply]

I'm going to address the rest now. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 17:19, 11 January 2010 (UTC)[reply]

Oppose on Image concerns:

• File:PrismAndLight.jpg: Not all images on NASA's website are in public domain (they use a few copyrighted images as well); as such please point this image's source to the NASA page that is displaying it, instead of the link to the image itself (so we can verify if it is NASA authorship).

  TimothyRias has done that. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:54, 12 January 2010 (UTC)[reply]

  Unfortunately, this turns out to be a copyviolation (sneaky NASA!!). The image is copyrighted to Exploratorium. Originally, NASA used it as is, with Exploratorium's watermark (see here). Other sites used it with an explicit statement of permission.[3][4][5] NASA simply cropped off the watermark and displayed it on their StarGazerz site. Exploratorium's materials are copyrighted.[6] Jappalang (talk) 12:11, 13 January 2010 (UTC)[reply]

  I've replaced it with a drawing. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:38, 13 January 2010 (UTC)[reply]

  And I see that the album which inevitably springs to mind when seeing that picture is featured on the Main Page today. (Incidentally, it happens to be one of my favourite albums.) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 12:56, 14 January 2010 (UTC)[reply]

  Replacement image File:Prism-rainbow-black.svg checks out fine. Jappalang (talk) 02:45, 15 January 2010 (UTC)[reply]

• File:Stellar aberration.JPG: labels and explanation of the symbols would help in the Description.
• File:Fizeau.JPG: reference for the design (i.e. is this how Fizeau notched wheel is set up)?
• File:Interferometer.JPG: labels and explanation of the symbols would help in the Description.

Something bothers me about this image. The light sources are shown as light bulbs, but light bulbs emit incoherent light and thus cannot produce interference.TimothyRias (talk) 10:46, 13 January 2010 (UTC)[reply]

Some of the images here, in particular this one, are the work of User:Brews ohare, who is technically is unable participate in the discussion here because of his topic ban, as mentioned here. As I see it this doesn't prevent him modifying the image on commons, or the ban could be adjusted to let him participate more fully. --JohnBlackburne^words_deeds 19:28, 13 January 2010 (UTC)[reply]

I've asked that he be temporarily unbanned. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:38, 13 January 2010 (UTC)[reply]

Otherwise, images are verifiably in the public domain or appropriately licensed. Jappalang (talk) 13:54, 12 January 2010 (UTC)[reply]

On another note (not of copyright but aesthetics), File:Speed of light from Earth to Moon.gif, an animated GIF, shows a beam of light travelling between the two bodies. However displayed at a width of 360px, the beam is not rendered; it simply becomes a black bar with two very small circles at either end. Not a good choice image. Jappalang (talk) 13:54, 12 January 2010 (UTC)[reply]

Weird, I'm somewhat sure it used to work. Maybe the switching from |upright to a fixed size had something to do with it. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:54, 12 January 2010 (UTC)[reply]

Yeah, apparently it's a new bug. There are two WP:VPT threads about that. I'll try to make a smaller version of the picture myself; meanwhile I've shown it at full size using ((wide image)). ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:06, 12 January 2010 (UTC)[reply]

Done. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:34, 12 January 2010 (UTC)[reply]

Support—all significant issues addressed. Article appears to be FA quality.—RJH (talk) 19:25, 18 January 2010 (UTC)[reply]

Comment – Overall the article is in pretty good shape, and is close to FA quality. Here's a few issues that I'd like to see addressed:

• You have "group velocity" linked twice in the same section.

  Unlinked the second one. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:11, 12 January 2010 (UTC)[reply]

• The jargon term "group index" is not explained.

  Removed. "High group index" is completely equivalent to "low group velocity", so that was redundant. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:11, 12 January 2010 (UTC)[reply]

• Common terms like air, water and glass usually don't need to be linked.

  I've removed some. The one to "matter" was particularly unhelpful, as it suggested that there is an accepted technical definition of matter relevant to this article, whereas in that sentence "other types of matter" could be replaced with "other stuff" and the denotation would stay the same. On the other hand, I seem to recall there were pages or sections specifically about the indices of refraction of air, glass and water, and I'll somehow link to them if I find them. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:11, 12 January 2010 (UTC)[reply]

• The paragraph that begins with the sentence, "The finite speed of light is particularly important in astronomy", seems too opinionated. It would be more encyclopedic if written without the "particularly important" and "crucial".

  I've tried to use a more neutral wording, but I fear I might have overdone that; after all, we're not writing about a living person or a commercial product, and it'd be ridiculous to accuse us of being biased towards the speed of light. :-) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:38, 13 January 2010 (UTC)[reply]

I restored "important", but "particularly" and "crucial" are (still) out. Please let us know if you think that "important" is a problem. If anything, "important" is an understatement, but I agree that a gushing tone is not encyclopedic.—Finell 01:53, 14 January 2010 (UTC)[reply]

• "Until relatively recent times" is a tad vague. The seventeenth century doesn't seem like recent times. Instead, I'd say something like "Prior to the seventeenth century,"

  Is "Until the early modern period" better? ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:11, 12 January 2010 (UTC)[reply]

• The first paragraph of the "Earth-bound techniques" section needs a cite.

  Added. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:38, 13 January 2010 (UTC)[reply]

• The Cavity resonance section needs citing.

  I can find a lot of cites for the 299,792.5±1.0 km/s, but none mentions the controversy or the 12th URSI General Assembly. The proceedings of that assembly seem not to be not available on-line, so I asked the editor who added that section in the first place. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:38, 13 January 2010 (UTC)[reply]

  Unfortunately that user, User:Robma, according to his own user page, has retired from Wikipedia. What Wikiprojects could I ask for such a citation? ― A._di_M.^{2nd Dramaout} (formerly Army1987) 16:48, 14 January 2010 (UTC)[reply]

  I'm not sure. My experiences with most wikiprojects hasn't been impressive.—RJH (talk) 00:03, 15 January 2010 (UTC)[reply]

  I've added a cite for the values, but I can't find anyone on the Web (except for WP mirrors) mentioning that the 1950 value was adopted by the 1957 12th URSI GA, so I've removed that part. (The source gives errors three times as large as the one we had, but maybe that's because they use 3σ rather than 1σ; when I get back to the university, where (IIRC) I can access to the full text of JSTOR entries, I'll read it.) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 20:57, 15 January 2010 (UTC)[reply]

  Nope. My "institution participates in JSTOR, but doesn't have access to this article." Not a vital point, though. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 13:10, 18 January 2010 (UTC)[reply]

  Yes, I wish we all had easier access to JSTOR. There's a lot of useful material in that archive.—RJH (talk)

• "The main problem with interferometry is to measure the frequency of light in or near the optical region." I think this needs some clarification. Why is it a problem?

  I'll take a look at the Evenson et al. 1972 article when I'm back to the university (presumably Monday).

  I've tried to clarify that. Is it OK now? ― A._di_M.^{2nd Dramaout} (formerly Army1987) 12:34, 18 January 2010 (UTC)[reply]

  Much better. Thanks.—RJH (talk) 18:59, 18 January 2010 (UTC)[reply]

• Why does the "Laboratory demonstration" section matter? Is there a benefit to that capability?

  I think there was a discussion about that on the talk page, but the archives have such a low signal-to-noise ratio that finding that discussion is going to be an awful task. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 16:34, 14 January 2010 (UTC)[reply]

  I've tried to resurrect that discussion. See Talk:Speed of light#Laboratory demonstration section. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 19:48, 17 January 2010 (UTC)[reply]

• Did you want to mention the GRB 090510 result?[7]

  Done. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 23:38, 13 January 2010 (UTC)[reply]

Thanks.—RJH (talk) 18:55, 12 January 2010 (UTC)[reply]

• Dabs; please check the disambiguation links identified in the toolbox. Dabomb87 (talk) 15:33, 23 January 2010 (UTC)[reply]

  Fixed (one of them by changing the target of a redirect!). ― A._di_M.^{2nd Dramaout} (formerly Army1987) 17:09, 23 January 2010 (UTC)[reply]

The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.