Wikipedia:Featured article review/Speed of light/archive2


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

The article was kept by Nikkimaria via FACBot (talk) 3:02, 19 March 2022 (UTC).

Speed of light

 * Notified: TimothyRias, A. di M., DVdm, Headbomb, Vsmith, Physics Wikiproject, talk page notification diffs: November 2020 & January 2022 unarchived

While the articles has good bones, concerns with citations are have not been addressed since they were mentioned in 2020. The most modern 'modern reference' is from 2004, and it would be good if an expert could go over the text to see where more modern sources are needed. There are likely too many external links. I hope a FAR will bring more eyes to this important article. Femke (talk) 19:40, 5 February 2022 (UTC)
 * Comment Many of the citation needed tags seem to have been added without care, e.g., not considering what is a routine calculation or when a sentence merely summarizes the paragraphs that follow it. XOR&#39;easter (talk) 02:14, 6 February 2022 (UTC)
 * We're down to 3 citation needed tags, all of which look fairly easily fixable (either by finding/reusing references or by trimming the text). The intro might be somewhat overlong, and the "External links" probably need pruning, but overall, I don't think much work needs to be done. XOR&#39;easter (talk) 12:20, 6 February 2022 (UTC)
 * - my instinct on the ELs would be to remove the University of Colorado Department of Physics link as not including much information, the Usenet page, and De Mora Luminis as the latter appears to be part of a 1985 work and if it was copyrighted, would be a WP:ELNEVER situation. Hog Farm Talk 19:21, 6 February 2022 (UTC)
 * , that sounds good to me. Done. Thanks! I've now addressed all the citation needed tags and caught the text/references up to date where I noticed they had gotten a little stale. I have not tried to shorten the intro. XOR&#39;easter (talk) 19:55, 6 February 2022 (UTC)

Examples of citation overkill: Similar questions apply here: Please review throughout for same. The last paragraph of the lead repeats info already in the first paragraph of the lead. Sandy Georgia (Talk)  18:20, 8 February 2022 (UTC)
 * A pulse with different group and phase velocities (which occurs if the phase velocity is not the same for all the frequencies of the pulse) smears out over time, a process known as dispersion. Certain materials have an exceptionally low (or even zero) group velocity for light waves, a phenomenon called slow light, which has been confirmed in various experiments.[76][77][78][79]
 * What cites the first sentence, versus the second sentence?
 * IF this has been "confirmed in various experiments" (four of them), why is there not one definitive more modern source that can be used, rather than four citations?
 * And if there isn't, is that original research?
 * And if not, can the citations be bundled?
 * No variation of the speed of light with frequency has been observed in rigorous testing,[60][61][62]
 * Thanks for the feedback! I have trimmed and reorganized the lead to avoid redundancy. In going through the page, I did not find any instances of synthesis, i.e., advancing a conclusion not itself present in the sources. Stacks of three or four footnotes in a row are typical for scientific writing, and thus probably inevitable given the background of the editors who would have worked on this page. Often, there is no single definitive reference for an important fact, but many references that are roughly equally good. This applies to secondary sources, particularly when it comes to broad, important and much-covered topics like speed of light: for a given claim in such an article, many textbooks and review articles will likely cover it, and there is no solid reason to prefer one over another.
 * In the first example given above, the two sentences function as a unit and the references pertain to both. I wouldn't mind bundling them for cosmetic purposes. The same goes for a few other triple-citation clusters that I noticed. XOR&#39;easter (talk) 20:20, 8 February 2022 (UTC)
 * Nice improvements to the lead. If bundling of those citations work, I say go for it.  The word various is a pet peeve; maybe that can be improved. Sandy Georgia  (Talk)  20:29, 8 February 2022 (UTC)

Keep Featured Article. I think the article is clear and easy to read.ScientistBuilder (talk) 19:19, 9 February 2022 (UTC)
 * Please see the FAR instructions; subheads are discouraged, and Keep/Delist are not declared in the FAR phase, which is for identifying issues and hopefully rectifying them. Sandy Georgia (Talk)  19:21, 9 February 2022 (UTC)


 * Could we get an update on status here? Nikkimaria (talk) 03:49, 12 March 2022 (UTC)
 * I ran out of things I could find that needed fixing, and nobody (other than InternetArchiveBot) has touched the article since then. XOR&#39;easter (talk) 04:09, 12 March 2022 (UTC)


 * Close without FARC. Brilliant work, thanks :). A few things you still may want to tackle
 * The first image is not of a very high quality. It's difficult to read the text. Do we have higher-quality images?
 * The external link section is on the long side. Some of the links go to very old websites (f.i. http://www.ertin.com/sloan_on_speed_of_light.html). Are they necessary, and is there is more modern equivalent?
 * Similarly, Modern references contains only old references. Are there older sources that can be replaced by higher-quality modern references? Femke (talk) 08:09, 12 March 2022 (UTC)

I did not make it out of the first paragraph of the lead: The lead could use some trimming and bringing down a notch for the layreader. Sandy Georgia (Talk)  17:18, 16 March 2022 (UTC)
 * It is exact because, by a 1983 international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time interval of 1⁄299792458 second.[Note 3]
 * Why do I have to hit this kind of detail in the third sentence? First, it may leave the reader confused about why the metre was defined in 1983, and second, they will wonder where the heck the fraction of a second came from.  This is a concept/article a non-physicist will access; this is overload at the third sentence.
 * According to special relativity, c is the upper limit for the speed at which conventional matter, energy or any signal carrying information can travel through space. A light-year is a distance unit, defined as the distance travelled by light in one Julian year. The speed of light is sometimes referred to as lightspeed, especially in science fiction.
 * And right after that sentence, the lead paragraph switches topic, and suddenly, the lay reader is in to special relativity by sentence four. Besides needing to bring this down a notch for the layreader, why is this not the start of a new paragraph?
 * The reason for that particular fraction was to make the new definition agree as closely as possible with the old. This is a point that is hard to convey without building a whole narrative that wouldn't fit into the lead and would itself be demanding upon the reader no matter how much we simplified. I'll do what I can, particularly in regard to the ordering and organization of the sentences; the line about "lightspeed" can probably be removed entirely, since the rest of the article doesn't use it, and the intro is supposed to summarize what will be found later. At some point, though, simultaneously satisfying the goals of "accurately summarize the scientific contents of a science article" and "being instantly comprehensible to a lay reader" is ... well, I hesitate to say "asking for a miracle", but that's about the size of it. XOR&#39;easter (talk) 18:43, 16 March 2022 (UTC)
 * Let's just not have them hit jargon/terminology so soon, and clear up the wording somehow to make it not seem like the metre didn't exist before 1983 :) Sandy Georgia (Talk)  19:03, 16 March 2022 (UTC)
 * Also, Julian might be linked and spelled out as Julian calendar. Sandy Georgia (Talk)  19:05, 16 March 2022 (UTC)
 * A better link is Julian year (astronomy). -- 20:12, 16 March 2022 (UTC)
 * I removed the sentence which referred to the Julian year, because the main text of the article doesn't say much on the topic, and any lay reader who wants the definition of "light-year" will be directed by Google/Alexa to light-year. XOR&#39;easter (talk) 20:26, 16 March 2022 (UTC)

Can we spell out kilometres per second and miles per second on the first occurrence (as metres per second is spelled out)? Why do we give the precise measurement in metres per second, yet round the others ? Also, can this: ... become this or similar ... That will make it clearer to the layreader that special relativity is a theory, so they don't have to click out to understand the context of the sentence, and simplified "upper limit". CPU needs a link or to be spelled out. Should inertial frame be linked to inertial reference frame when used in the third paragraph (it is now linked in the fourth paragraph). Why do we need to introduce refractive index in the lead? Can instead a sentence that c stands for 'constant' be added to the first para ? That should make the first paragraph sufficient for the layreader. Sandy Georgia (Talk)  03:22, 17 March 2022 (UTC)
 * According to special relativity, $c$ is the upper limit for the speed at which conventional matter, ... All forms of electromagnetic radiation travel at the speed of light, not just visible light.
 * According to the special theory of relativity, $c$ is the highest speed at which conventional matter, ... All forms of electromagnetic radiation – not just visible light – travel at the speed of light.
 * Close without FARC; looks good. All done by User:XOR'easter alone! Sandy Georgia  (Talk)  03:29, 17 March 2022 (UTC)

Nikkimaria (talk) 03:02, 19 March 2022 (UTC)
 * The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.