Wikipedia:Reference desk/Archives/Science/2022 September 20

= September 20 =

Onions
Onions famously come in layers, with the outermost layers being a dry, papery consistency, while the inner layers are fleshy (and delicious). Now I believe I've seen layers in-between these two states, so I assume they start out basically the same. Is that correct? If so, what process is turning the thick layer into the papery state? It's apparently not simple desiccation, as the thin versions seem to be largely immune to water, and cannot be re-hydrated... --Stephan Schulz (talk) 12:12, 20 September 2022 (UTC)
 * What onions have you found that are "delicious"? ←Baseball Bugs What's up, Doc? carrots→ 13:27, 20 September 2022 (UTC)
 * Obviously all of them. Shallots, red onions, yellow onions, white onions, spring onions. Not to mention onion rings, onion soup, pickled onions, and The Onion. --Stephan Schulz (talk) 14:30, 20 September 2022 (UTC)
 * I love how every one picks the key portion of an asker's question to refer to... brill... --Ouro (blah blah) 19:17, 20 September 2022 (UTC)
 * How does Charlie Brill figure into it? ←Baseball Bugs What's up, Doc? carrots→ 19:32, 20 September 2022 (UTC)
 * I wouldn't know that he does, I meant it as a contraction of 'brilliant'. --Ouro (blah blah) 20:40, 23 September 2022 (UTC)
 * I Love Onions. They are "very, very tasty". Mitch Ames (talk) 08:36, 22 September 2022 (UTC)
 * Here you can read a highly technical description of the biochemical changes that accompany the drying of the outer scales – which already begins in a relatively early stage of bulb growth. I don't know what sometimes triggers more inner scales' going down the same path; perhaps some disease that leads to premature cell senescence. --Lambiam 15:22, 20 September 2022 (UTC)
 * Thanks! It seems to be indeed a more complex chemical/biological process. --Stephan Schulz (talk) Stephan Schulz (talk) 19:21, 20 September 2022 (UTC)

How deep would Challenger Deep have to be for the silica floor ooze to dissolve?
I found graphs for boilers and extremely hot pressurized water underground but not for 4°C or whatever the water temperature would be.

2. If you dug a perfect cone extremely steep in a rocky seabed point side down is the bottom pressure not higher than if you dug a cylinder? Why does that happen? Sagittarian Milky Way (talk) 14:18, 20 September 2022 (UTC)


 * With respect to 2, no it would not be higher, and hence there is no reason why it happens ;-). --Stephan Schulz (talk) 14:35, 20 September 2022 (UTC)
 * Why is it not higher? Probably the seafloor area increasing with steepness perfectly balances it becoming less and less like a floor and more and more like a wall? Sagittarian Milky Way (talk) 16:03, 20 September 2022 (UTC)
 * The pressure depends only on the weight of the water column (and atmospheric column, if you are particular) directly above any particular parcel of water. If you find that hard to imagine, consider a plexiglass cone, open in the bottom, in a bath tub. If there was a pressure differential at the bottom of the cone, there would be a continuous flow, and you'd have a nice perpetuum mobile. This is physically somewhat unlikely ;-). So there is no differential. And why should that change if you close off the bottom? --Stephan Schulz (talk) 16:28, 20 September 2022 (UTC)
 * The effect of a narrowing cone-shaped restriction on a pressure wave travelling in a fluid is to increase its pressure so adding a cone can usefully increase the sensitivity of a hydrophone. However the presence of a rigid cone anywhere in a fluid Pressure gradient that gravity has established makes no difference to the vertical pressure distribution. The pressure at the bottom of the cone described by the OP depends only on the depth of communicating layers of sea water above. The geometry of connections between the layers is actually irrelevant so there can be convoluted horizontal channels and not all water need be directly above.


 * Hydrostatic pressure is a scalar quantity calculable by Stevin's law
 * $$p = \rho g H + p_\mathrm{atm},$$
 * where $ρ$ is the fluid density (kg/m3), $g$ is gravitational acceleration (m/s2), $H$ is the total height of the liquid column and $p_{atm}$ is the atmospheric pressure. This can be visualized as a pressure prism. The only difference between the forces exerted by fluid pressure on unit areas of a vertical wall, a sloping wall, floor or submerged ledge is the direction of the force vectors. Philvoids (talk) 18:38, 22 September 2022 (UTC)


 * The Challenger Deep south of Japan extends as deep as 10,920 ± 10 m (35,827 ± 33 ft). The ROV Kaikō measured temperature (water temperature increases at great depth due to adiabatic compression), salinity and pressure values 2.6 °C (36.7 °F), 34.7‰ and 1,113 bar (111.3 MPa; 16,140 psi). I find no data to suggest that strongly covalent silicon dioxide SiO2 the constituent of silica sand and quartz is soluble in those conditions. However silica might dissolve, possibly to Silicic acid, in these cases:


 * hydrothermal vents raising superheated water that is known to dissolve quartz. That is the basis of a useful industrial process to obtain pure quartz crystal that forms when the solution cools.
 * unspecified organic process(es) in the organisms that live in the mud sea floor. Philvoids (talk) 20:40, 22 September 2022 (UTC)