Talk:3176: Inverted Catenaries

Hoookay ... am I nutz, or shouldn't a physical object with the shape of an inverted catenary (2D or 3D) fall and land with the rounded side down? And shouldn't such a "catenary fall" (if 3D objects) produce a flat-ish, unstable surface that would be [ahem] very interesting to drive (or walk or yada) on, and on which square tires would be useless? 2605:59C8:160:DB08:216D:5149:ACEB:AD1C 03:42, 4 December 2025 (UTC)

Not necessarily. Depends on how catenary is weighted, it doesn't have to be of uniform density.--Trimutius (talk) 04:23, 4 December 2025 (UTC)

If inverted catenaries flip, during their fall, then they become "inverted inverted catenaries", instead, which some might say are 'just catenaries' (or, indeed, be best observed as the catenary-chord, utmost). So, by definition, they don't. ;) 82.132.239.140 13:03, 4 December 2025 (UTC)

The comic itself is 2D, so if this were a 3D scenario it might be that the inverted catenaries are actually extended, like a series of speed bumps aligned with roads. That may be likely since I'm pretty sure xkcd has more 3D cars than 2D throughout the comics R128 (talk) 14:14, 4 December 2025 (UTC)

A caternary curve is that of a tethered chain hanging loose in gravity, so defined as one with the curve pointed downward. this requires its inversion to curve up. Semantics, but in this case important ones. 50.37.102.15 (talk) 07:24, 4 December 2025 (UTC) (please sign your comments with ~~~~)

Coming from a snowy country, we don't use all-season tyres. We have summer tyres (useless on snow and ice, very well suited for dry and wet surfaces) and winter tyres. Winter tyres without studs can legally be used all year round, but are ill-suited for summer conditions. 109.247.36.180 08:32, 4 December 2025 (UTC)

Well in Canada many people never use summer tires at all. They would drive all-season and then switch to winter tires. Cold snaps are sometimes so sudden in Canada, that many people don't want to risk driving on summer tires as it can come to bite you in Spring or Fall.--Trimutius (talk) 15:31, 4 December 2025 (UTC)

Although square wheels on inverted catenaries have no practical use, non-circular wheels on non-smooth tracks are used in rack railways, which are an application of a rack-and-pinion mechanism. 85.228.125.118 (talk) 11:41, 4 December 2025 (UTC) (please sign your comments with ~~~~)

Did Randall move to canada? 206.193.5.5 16:40, 4 December 2025 (UTC)

I reckon he's been tempted, like many of us. But if we tried it, all we'd be likely to find was Randy Bachman singing his new song "The Ghost of Stephen Harper". We have all been here before ... 205.175.118.102 20:20, 4 December 2025 (UTC)

Northern parts of USA get a lot of snow too. Some select cities in the North of US might even get more snow than southern Canadian cities.--Trimutius (talk) 16:48, 4 December 2025

Pretty sure Randall lives near Boston MA (https://xkcd.com/3081/), and we had a significant storm on Tuesday (the day before this was posted). Plenty of people here (myself included) switch to snow tires around this time. 130.64.22.2 17:30, 4 December 2025 (UTC)

I was referring to South Park featuring Canadian vehicles having square tires, not anything related to climate. 206.193.5.5 20:38, 4 December 2025 (UTC)

Has there actually been any research into a wheel shape that’s the best on average over any given terrain pattern, or is that just Randall having a laugh? KelOfTheStars! (talk) 21:37, 4 December 2025 (UTC)