Template:Did you know nominations/Reuleaux triangle


 * The following is an archived discussion of the DYK nomination of the article below. Please do not modify this page. Subsequent comments should be made on the appropriate discussion page (such as |this nomination's talk page, the article's talk page or Wikipedia talk:Did you know), unless there is consensus to re-open the discussion at this page. No further edits should be made to this page.

The result was: promoted by Yoninah (talk) 20:25, 24 June 2015 (UTC)

Reuleaux triangle

 * ... that a manhole cover in the shape of a Reuleaux triangle (pictured) can't fall into its hole?
 * Reviewed: R136a1
 * Comment: Many other hooks are possible but I chose this one because it has a good image to go with it

5x expanded by David Eppstein (talk). Self-nominated at 22:15, 24 May 2015 (UTC).


 * Symbol voting keep.svg on the source for the proffered hook, which I also like for the photograph. Symbol voting keep.svg on the expansion (the prose size tool is down at the moment or otherwise not working to count text beyond the first ) and Symbol confirmed.svg on the other factors for promotion.  Imzadi 1979  →   02:22, 25 May 2015 (UTC)
 * Symbol confirmed.svg Update, I got the expansion size verified as 3197 words / 450 words = 7.10x or 19 kB / 2682 B ≈ 7.08x expansion. Either way, that's sufficient expansion for DYK purposes.  Imzadi 1979  →   02:27, 25 May 2015 (UTC)


 * Can you find an image that doesn't have a normal triangle withing the R.T.? I think it's confusing to the reader. EEng (talk) 05:00, 30 May 2015 (UTC)
 * Maybe it's an electronics cover? Martinevans123 (talk) 20:26, 30 May 2015 (UTC)
 * My shadow, ladies and gentlemen! EEng (talk) 21:41, 30 May 2015 (UTC)
 * "Everyone carries a shadow". Martinevans123 (talk) 22:00, 30 May 2015 (UTC)
 * Shame we couldn't have worked out a joint hook with Dr. Young's Ideal Rectal Dilators... EEng (talk) 02:13, 31 May 2015 (UTC)
 * A manhole cover means something quite different in women's cricket. Martinevans123 (talk) 11:42, 31 May 2015 (UTC)


 * The San Francisco ones are the only instance I know of where someone actually used this shape for manholes rather than just treating it as a hypothetical mathematical conundrum, and other images of their manhole covers would have the same issue. In any case I don't think there's another image like this to replace it with on commons. I tried doing a few general Google image searches but didn't turn up anything even among non-free images. I did find a few other designs in the same shape, but all with the central triangle-in-triangle. —David Eppstein (talk) 05:15, 30 May 2015 (UTC)
 * Oh, it's you! It's weird, because it actually doesn't look like the R.T. comes out -- looks like it's set in the cement, and the inner triangle comes out of it. If so, what was the point? EEng (talk) 05:38, 30 May 2015 (UTC)
 * I'm not really sure. I tried and failed to find sources on why SFWD chose this design (although "to amuse nerds in the city" is pretty high on my list of hypotheses). —David Eppstein (talk) 05:43, 30 May 2015 (UTC)
 * I had precisely the same idea. Hey, this isn't really a manhole, is it? It's just a handhole or valve cover, right? EEng (talk) 05:58, 30 May 2015 (UTC)
 * Maybe. The image name has "manhole" in it but that's no proof of anything. A commenter here has the same valve cover theory but again it's not much of a source. Part of my cleanups to the article involved removing an unsourced sentence about SFWD's use of this shape, because it was unsourced. I think in colloquial English most readers wouldn't make much of a distinction between manhole covers and valve covers. —David Eppstein (talk) 06:02, 30 May 2015 (UTC)
 * Consider the size of the leaves... EEng (talk) 06:18, 30 May 2015 (UTC)
 * Well, do you think the hook should be amended to "manhole cover or valve cover (pictured)" for greater accuracy? It's not as crisp that way. And the actual source for the hook doesn't talk about valve covers, I think. (Also valve cover is the wrong wikilink but I'm not sure what the right one should be.) —David Eppstein (talk) 06:25, 30 May 2015 (UTC)

I know you share my pedagogical concern re the distraction of the inscribed triangle, but I've looked around as well and can't find a better image either. I guess we'll just have to make the best of the one we have. EEng (talk) 15:22, 30 May 2015 (UTC)
 * ALT1 ... that a lid in the shape of a Reuleaux triangle (pictured) can't fall into its hole?
 * The thing is, this (the hook claim) really is a classical example in mathematical exposition, repeated by many sources and in all cases used with "manhole cover". So changing it to "lid" just makes it feel flat. —David Eppstein (talk) 16:24, 30 May 2015 (UTC)
 * Well, lids and manhole covers are both flat, so what do you expect?? But I think you're right. EEng (talk) 19:18, 30 May 2015 (UTC)


 * It turns out that I was mistaken about San Francisco being the only place with these things. There are some mere feet from the building I work in. So obtaining different photos of these objects would be very easy. But as before, they're clearly valve covers, with the actual cover being a straight-sided triangle set into a Reuleaux-triangle base. Given that these are not really Reuleaux triangle manhole covers, maybe we should consider some alternative hooks?
 * ALT2 ... that Gothic churches from the 13th and 14th centuries used the Reuleaux triangle for the shape of some windows (pictured) and window tracery?
 * ALT3 ... that Leonardo da Vinci published a world map (pictured) in which eight octants of the earth were projected onto eight Reuleaux triangles?
 * Personally I'd go with Leonardo. EEng (talk) 01:45, 2 June 2015 (UTC)
 * Symbol voting keep.svg This article is a fivefold expansion. It is new enough and long enough. The ALT2 and ALT3 hooks have inline citations and their images are suitably licensed. The article is neutral and I did not detect any copyright issues. Cwmhiraeth (talk) 05:59, 4 June 2015 (UTC)