Wikipedia:Reference desk/Archives/Science/2021 August 25

= August 25 =

I saw a gull swallow a fried chicken leg whole
Just made me wonder what happens next. Does the bone digest entirely, or will the bird regurgitate it from the mouth? I'm not sure if it isn't the case that the gull wouldn't just fly somewhere quiet, cough up the bone and then pick the meat off. — Preceding unsigned comment added by 146.90.140.25 (talk • contribs) 00:52, 25 August 2021 (UTC)
 * Well, a seagull can swallow a fish about that size, but fish bones are smaller and digestible. Personally, I don't expect that gull would survive a chicken leg bone. ~Anachronist (talk) 02:07, 25 August 2021 (UTC)
 * I know an old lady who swallowed a horse. She's dead, of course. Gulls lack the pouches in their bills which pelicans have. Regurgitating would be a potential strategy? Or maybe it could just stay there, like the stones that birds are known to eat? ←Baseball Bugs What's up, Doc? carrots→ 03:14, 25 August 2021 (UTC)
 * I googled "gull swallowing chicken leg", and many entries turned up - including at least one that says gulls typically swallow small animals whole, and that they can, in fact, digest bones. ←Baseball Bugs What's up, Doc? carrots→ 03:17, 25 August 2021 (UTC)
 * How about giving a link to said entry? I mean, you already did 90% of the work towards providing a reference... Tigraan Click here for my talk page ("private" contact) 11:35, 25 August 2021 (UTC)
 * The OP most likely won't be back. Here's the one I was looking at. But it's more instructive to do the google search, as there are several videos of gulls swallowing various things - including a chicken leg. ←Baseball Bugs What's up, Doc? carrots→ 13:20, 25 August 2021 (UTC)
 * See Pellet (ornithology). Andy Mabbett ( Pigsonthewing ); Talk to Andy; Andy's edits 10:11, 25 August 2021 (UTC)
 * Yes, Gull says: "Looking at the effect of humans on gull diet, overfishing of target prey such as sardines have caused a shift in diet and behavior. Analysis of yellow-legged gull's (Larus michahellis) pellets off the northwest coast of Spain revealed a shift from a sardine to crustacean-based diet," But nothing about whole chicken legs, alas. Martinevans123 (talk) 11:43, 25 August 2021 (UTC)
 * At about 6 minutes into this youtube video a lesser black-backed gull can be seen eating a whole pigeon head. It isn't possible to see what happens subsequently (i.e. whether regurgitaion occurs), but seeing as the video is about this particular gull that regularly kills and eats pigeons, it obviously doesn't suffer ill-effect from consuming avian bones of reasonable size. PaleCloudedWhite (talk) 21:24, 25 August 2021 (UTC)
 * Just a pigeon head? Meh. --Floquenbeam (talk) 21:32, 25 August 2021 (UTC)


 * Gulls consume vertebrate prey whole but, like most avian predators, are unable to digest bone. Pellets containing feathers, bone and other hard parts are regurgitated 24-48 hours after consumption and may include parts of more than one meal. Gulls also have an expanded esophageal sac (crop) in which food is stored and then regurgitated to feed chicks, mates, or to break apart and reconsume. Relatively large prey items can be stored in this sac...
 * Pellet and Bone Accumulation at a Colony of Western Gulls (Larus occidentalis), Journal of Vertebrate Paleontology, 1991.
 * Alansplodge (talk) 22:10, 25 August 2021 (UTC)

Shampoo types
For any given brand of shampoo, are the formulae for dry, normal, and greasy hair significantly different? How so, and how does it work? Or do manufacturers just put the same stuff in different bottles? Andy Mabbett ( Pigsonthewing ); Talk to Andy; Andy's edits 10:10, 25 August 2021 (UTC)
 * This article discusses some of the differences between different types of shampoo. I know from experience that different brands of shampoo have different formulations that produce different results.  Some brands will over-dry my hair, while others leave it still feeling greasy.  -- Jayron 32 11:54, 25 August 2021 (UTC)


 * Likewise personal experience, from one with somewhat oily hair: I used to use a shampoo for oily hair, but it had the countereffect of making my hair too dry. As I recall, the amount of alcohol in it can be a factor. ←Baseball Bugs What's up, Doc? carrots→ 22:12, 25 August 2021 (UTC)
 * Alcohol can be pretty dehydrating. Sagittarian Milky Way (talk) 03:25, 26 August 2021 (UTC)
 * The easiest way to find out is to check for differences between the ingredients lists of variants within a given brand.
 * Based on my experience as a former employee of a private-label toiletry manufacturer, the main difference between the three is the level of surfactant, which is highest for greasy and lowest for dry. Depending on the brand and the price point, there may also be specific additives for specific types of hair, e.g. gentler surfactants and/or polymeric quaternary ammonium salts (conditioning agents) for dry hair, or niacinamide for oily hair. Rhythdybiau (talk) 13:29, 26 August 2021 (UTC)
 * Is shaving cream bad for some hair types? It seems to work if you're out of shampoo. Sagittarian Milky Way (talk) 15:36, 26 August 2021 (UTC)
 * It also works if you're not out of shampoo. (When shaving, shaving cream is good too for the stubble you shave off, but unfortunately it can enjoy this goodness only briefly.) --Lambiam 06:58, 27 August 2021 (UTC)
 * Traditional soap-based shaving cream is very alkaline, and can potentially dry out/damage your hair, but non soap-based shaving cream is much more benign.
 * Shower gel, handwash and bubble bath are functionally very similar products to shampoo, albeit with different fragrances - if you're out of shampoo, they'll do the job, though maybe not as well. Rhythdybiau (talk) 01:00, 29 August 2021 (UTC)

Is this beyond current material science or not?
Manufacture a not very stretchy overhead projector sheet of normal dimensions that no human can damage with only their body, where damage is defined as "any change detectable to the naked eye or touch senses which persists ~1+ second after ceasing the damage attempt" and not very stretchy is defined as "a human cannot increase its length more than 1% by pulling".

So a human would probably have be able to break their canine teeth by biting it without causing a bump you can feel, it'd have to withstand simultaneous biting and pulling at the limit of teeth strength, if it can bend to a tight curve it'd have to withstand attempting to fold with the fingernails or front teeth at their strength limit, if bendable it should flop back to flat when left on a flat surface and should not be damaged by twisting or unusually corrosive vomit or any other body fluids. Sagittarian Milky Way (talk) 20:02, 25 August 2021 (UTC)
 * What problem are you trying to solve? And when have you ever bitten an overhead projector? ←Baseball Bugs What's up, Doc? carrots→ 22:14, 25 August 2021 (UTC)
 * No problem, just wondering if an indestructible* transparency (the transparent "paper", not the machine) would be science fiction or if you could make one from some exotic substance. Also if you can roll it into a tube try to do things to the tube like repetitive bending, folding and biting/chewing, more ideas for how to damage a thin resilient sheet without tools or fire. Presumably Mohs hardness would have to exceed tooth enamel or they'd be scratchable (people used to saw prison bars with muddy or toothpaste-coated strings and patience) Sagittarian Milky Way (talk) 23:17, 25 August 2021 (UTC)
 * I'm reminded of a plastic men's hair comb which literally said unbreakable and while it'd likely always spring back from sane bends it could be repeatedly squeeze-bent back and forth as hard as I could, then twisted back and forth, then finished off without changing twist direction. Behold, bisected comb halves. Sagittarian Milky Way (talk) 02:54, 26 August 2021 (UTC)
 * You need to set a time limit, one that is probably less than a second of eternity (see "The Shepherd Boy"). --Lambiam 05:44, 26 August 2021 (UTC)
 * All possible materials would eventually have repetitive stress failure? Sagittarian Milky Way (talk) 15:11, 26 August 2021 (UTC)
 * Some are self-healing but need a refractory period to repair the mini cracks that lead to stress failure. But repeatedly rubbing a plate will, with each stroke, take some atoms, making it thinner and thinner. --Lambiam 21:53, 26 August 2021 (UTC)


 * With a creative interpretation of "normal dimensions" to mean only width and length, not thickness, then a standard 4mm sheet of tempered glass fits the bill. However, the thickness of a standard projector sheet seems to be about 0.1mm. I have a feeling that anything of that thickness should be bendable. I have no time to do the math right now but I would look up the transparent material with the highest yield stress possible, what maximal force a human can apply, and the formula for beam deflection with a bending load. Tigraan Click here for my talk page ("private" contact) 08:25, 27 August 2021 (UTC)