Wikipedia:Reference desk/Archives/Science/2021 February 18

= February 18 =

Satanic landing gear???
So here I am looking at a schematic for the main landing gear of the Mirage F1 fighter, and two of the parts labels are puzzling to say the least -- one says "Diabolo balance", and the other says "Diabolo pivoting mechanism". My question is, what exactly is it??? 2601:646:8A01:B180:847D:B967:D877:9361 (talk) 02:59, 18 February 2021 (UTC)
 * My guess would be that it is in reference to the juggling/circus prop of the same name. Many terms in aviation do that, where they refer to something else similar in some way. Canards, for example, the foreplanes ahead of the main wings on some aircraft, is the French word for "duck" because one of the first aircraft equipped with them looked to observers similar in appearance to a duck in flight. --OuroborosCobra (talk) 05:05, 18 February 2021 (UTC)
 * Searching the web for "diabolo landing gear" suggests it means two wheels mounted side by side on a common axle, e.g. here. The word is used for various objects that are thin in the middle and surrounded by two wider disks. 85.76.75.69 (talk) 09:34, 18 February 2021 (UTC)
 * That's a devil of a good answer. Richard Avery (talk) 11:15, 18 February 2021 (UTC)
 * This French-English technical dictionary says that diabolo translates to English as "twin-wheeled" but can also mean bobbin, dolly or a waisted slug. This English language article says: "Bogie landing gear has 4 wheels, while the Diabolo has 2 wheels". Alansplodge (talk) 12:50, 18 February 2021 (UTC)
 * Thanks! So the name refers to the dually wheels having a resemblance to the toy, whose own name was in turn derived from its seemingly supernatural properties -- is that correct?  2601:646:8A01:B180:800E:797F:14C2:9143 (talk) 07:59, 19 February 2021 (UTC)
 * The toy was used in a game that was a fad in the first half of the 19th century, known in French as le jeu du diable ("the devil's game"), in which le diable was the term for the object being spun, and in English as "Devil on Two Sticks". It got a boost in the early 20th century in a technically improved embodiment, developed and patented by Belgian automative engineer Gustave Philippart. The idea for the name diabolo came from English cricketer C. B. Fry, who tried to turn the game into one with rules resembling tennis. According to his account, his inspiration was an ancient Greek verb meaning "to throw across". (The account has Diabellein; the verb is actually Diaballein.) Philippart registered that name as a trademark, which however was struck after he lost an infringement suit, with the judge ruling that this was not an "invented word", but (by its similarity to the word ) a word referring to the devil, and thereby to the object used in the game known as "Devil on Two Sticks". Whether Fry was truly not (also) inspired by the sense of Ancient Greek diabolos as translating Biblical Hebrew Satan, I cannot tell. --Lambiam 10:05, 19 February 2021 (UTC)

Medical topic: Technical name for this exercise.
Sit ups with straight legs with head touching to the kneecap. Hand placing backside of the head. I want technical name for this exercise. Rizosome (talk) 13:30, 18 February 2021 (UTC)
 * Sit-ups or Crunch (exercise), depending on the details, perhaps? Mike Turnbull (talk) 13:40, 18 February 2021 (UTC)
 * People don't typically "sit up" all the way like that. The position you describe is common enough in yoga, where it's called (appropriately enough) head to knee or seated head to knee to distinguish it from the standing version. Having one leg crooked inwards is called a "bound angle", but I haven't found a more unique name for the overall pose with both both legs flat and straight out together. Matt Deres (talk) 14:17, 18 February 2021 (UTC)


 * , I'm again asking, is there a goal or point to these random questions? This question certainly isn't about rocketry, and neither was your question about binocular vision. You didn't respond to any of the answers you were given for that question, either. --OuroborosCobra (talk) 16:56, 19 February 2021 (UTC)