Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

December 5

Polymers and viruses classifications.

Weird, I been waiting almost 24 hours for SCSBot to add Dec. 4. So polymers have like a 3 by 2 classification. Polymers can be thermplastics, thermosets, and somewhat overlap elastomers. Polymers can also be amorphous or crystalline. However, elastomers are amorphous-only. But I'd like some crystalline examples.

Amorphous thermoplastics: Glue.

Amorphous thermosets: epoxy resins, polyurethanes.

Amorphous-elastomers: rubber bands, tires, and contact lens.

But what are crystalline examples, for thermoplastics and thermosets? The only 1 I have is glass. But is that a thermoplastic or thermoset? Elastomers can also sometimes be a thermoplastic or thermoset. Thermoplastics I believe have no cross-linking, thermosets high-cross linking, and elastomers low-cross linking.

I'm also looking for a categorical classification for viruses. The only 1 I can think of is enveloped viruses vs. non-enveloped viruses. Are there any others? Thanks. 67.165.185.178 (talk) 00:57, 5 December 2021 (UTC).

Virus classification Sagittarian Milky Way (talk) 01:50, 5 December 2021 (UTC)

Not a chemist, but since nobody else is replying, I'll mention that I looked at the articles liquid crystals, kevlar and spider silk, which sound to my naive mind like possible examples of crystalline polymers. The article on glass begins "Glass is a non-crystalline ...", which throws me off, but I don't want to tell you you're wrong, since words can have two meanings.  Card Zero  (talk) 16:29, 5 December 2021 (UTC)

Bird rabies?

Are birds susceptible to rabies (or any other transmissible neurological disease which causes aggression)? If so, can they transmit it to other birds and/or to people? (No, I have NOT been bitten by a bird -- I've watched a film where lots of people were!) 2601:646:8A81:6070:E03D:3B7A:ECA5:DA02 (talk) 06:28, 5 December 2021 (UTC)

From our article on rabies transmission: "Birds were first artificially infected with rabies in 1884; however, infected birds are largely, if not wholly, asymptomatic, and recover." Source. For this to occur naturally, a bird would have to either be bitten by or eat a rabid mammal first; in many cases of the former I suspect the bird would die from the wound before any viral CNS involvement (I'm guessing this is also why rabies in small terrestrial mammals is virtually never found). As for the latter, antibodies to the virus have been recorded in predatory and scavenger birds, but they seem to be clinically asymptomatic.

Neuroinflammation and/or neurodegeneration from any cause is capable of producing behavioral changes, including aggression, but these can vary significantly between individuals. Even rabies has multiple disparate outward presentations. The same is true for BSE and sad horse disease. So a particular disease would have to have a pretty specific mechanism to produce consistent behavioral results. I did find some reports of Mycoplasma gallisepticum infection decreasing aggression in male finches, but then this illness also causes lethargy so it's more likely these sick birds just didn't have the energy to get in fights. My brief search didn't return anything else documenting a neurological infection inducing aggression in birds. JoelleJay (talk) 08:11, 5 December 2021 (UTC)

If you've only seen the movie and not read the article you may not be aware that The Birds was inspired by real life events. The real life birds went crazy due to algae poisoning, though, which is not transmissible, and they didn't organize themselves into planned attacks like in the movie. Matt Deres (talk) 15:20, 5 December 2021 (UTC)

There are several behavior-altering parasites with birds as hosts: however, they all alter the behavior of the birds' prey rather than that of the bird itself. The default bird activity of flying around eating stuff, and depositing it again in random places, serves parasites very well without the need for any alterations such as aggression. The evolutionary pressure might be different if birds were large and durable, had teeth and were bitey. Rabid pterosaurs are a plausible concept. One might also wonder about ostriches, but I think they tend to kick rather than peck, which removes the transmission vector through saliva.  Card Zero  (talk) 16:09, 5 December 2021 (UTC)

Russian nuclear missiles

In the early 1960s, were the warheads on Russian sub-launched nuclear missiles single-point safe? In other words, might an on-board reactor explosion have set off the warheads and caused a full-scale nuclear explosion, as Captain Vostrikov claimed? 2601:646:8A81:6070:E03D:3B7A:ECA5:DA02 (talk) 06:43, 5 December 2021 (UTC)

I think the design of the nuclear warheads that were the payload of the R-13 missiles aboard the K-19 is still a guarded secret. No nuclear reactor has ever "exploded", other than steam explosions; the worst accidents have been meltdowns. A nuclear explosion close to a fission weapon is – I think – more likely to destroy it before it can go off than to set it off, regardless of its design. In either case, the resulting contamination is disastrous.  --Lambiam 08:55, 5 December 2021 (UTC)

BTW, the captain at the time of the incident was Nikolai Vladimirovich Zateyev. "Captain Alexei Vostrikov" is a pseudonym of Indiana Jones, an infamous archaeologist who claims to have made the Kessel Run in less than twelve parsecs – thereby establishing a lack of scientific credentials.  --Lambiam 09:03, 5 December 2021 (UTC)

What I meant is a steam and/or hydrogen explosion in the reactor (like at Chernobyl) setting off the warheads. 2601:646:8A81:6070:E03D:3B7A:ECA5:DA02 (talk) 10:22, 5 December 2021 (UTC)

So where exactly DO we go one and all?

In a sailing vessel with a hybrid (both square and fore-and-aft) sail plan (such as a brigantine), if a white squall (or any other squall, for that matter) approaches from abeam without warning, which way should the helmsman turn her if her square sails are set -- upwind or downwind? How about if only the fore-and-aft sails are set? 2601:646:8A81:6070:E03D:3B7A:ECA5:DA02 (talk) 06:54, 5 December 2021 (UTC)

I think the general advice is to turn into the wind and confront any approaching high waves from the bow, but immediate reefing or even dropping the sails, especially those more to the fore, is also important to avoid the vessel capsizing or a mast breaking; the direction of the wind may vary abruptly during a squall.  --Lambiam 08:25, 5 December 2021 (UTC)

Unlike the days of wooden ships, it is rarely feasible to send down steel topmasts and yards to reduce overpowering windage, nor to cut away a mast to relieve a ship on its beam ends. The master must rely on situational awareness of a thousand factors to avoid or find a way through mayhem... The practice in square-rigged ships encountering squalls is to bear away, ensuring that the load remains abaft the rig. Sheeting of fore-and-aft sails or the setting of an autopilot can frustrate this... From Sailing ships: a catalogue of disasters. Alansplodge (talk) 15:31, 5 December 2021 (UTC)

So, bear away = turn downwind? 69.181.91.208 (talk) 07:50, 6 December 2021 (UTC)

In this case, yes.[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:31, 6 December 2021 (UTC)

Thanks! So, the guys who made the movie were right for once! 2601:646:8A81:6070:C5F1:8E3E:7A99:E108 (talk) 04:37, 7 December 2021 (UTC)

Land between two tributaries/rivers

Overall, the land drained by a river is called a drainage basin or watershed (or a bunch of other names listed there), but is there a more specific name for the localized space between two tributaries? For example, if a city was built at the place where two tributaries met, how would we describe its placement? It feels like there would be a name for that. When I search online for land between two rivers it leads me to Mesopotamia which is cool, but not really what I'm after. Matt Deres (talk) 15:27, 5 December 2021 (UTC)

The place where two rivers join is called the confluence. Cities built there are often described as "located at the confluence of the ___________ and _________." See: https://ludwig.guru/s/located+at+the+confluence --Khajidha (talk) 15:32, 5 December 2021 (UTC)

And our confluence article. Alansplodge (talk) 15:35, 5 December 2021 (UTC)

Aha! I knew there was a word; it just wouldn't come to mind. Thank you both! Matt Deres (talk) 16:30, 5 December 2021 (UTC)

But it's only part of what you asked for. Is there a word for the zone between two tributaries? --184.144.99.241 (talk) 22:27, 5 December 2021 (UTC)

I also want to know if there's a word for this except any combination of rivers, seas etc, not just tributaries. Sagittarian Milky Way (talk) 22:41, 5 December 2021 (UTC)

Tolkien[2] invented the Elvish (Sindarin) word 'naith', as a translation of the common word 'gore', for such a feature.--Verbarson (talk) 14:31, 6 December 2021 (UTC)

According to our own article, the word for any such combination is the same: confluence. --Khajidha (talk) 14:45, 6 December 2021 (UTC)

A search for "confluence of the Mediterranean" seems to confirm that: https://www.google.com/search?q=%22confluence+of+the+mediterranian%22&client=firefox-b-1-d&sxsrf=AOaemvIYUEgZ1a5Yp-lc-zJVUcKWLuk0SA%3A1638801990167&ei=RiKuYcDFCd-NwbkPnISy8As&ved=0ahUKEwjAgOyTtc_0AhXfRjABHRyCDL4Q4dUDCA4&uact=5&oq=%22confluence+of+the+mediterranian%22&gs_lcp=Cgdnd3Mtd2l6EAMyBwghEAoQoAEyBwghEAoQqwIyBwghEAoQqwI6BwgjELACECdKBAhBGAFKBAhGGABQ0ARY3RpgyBxoAXAAeACAAdQBiAH7ApIBBTIuMC4xmAEAoAEBwAEB&sclient=gws-wiz --Khajidha (talk) 14:48, 6 December 2021 (UTC)

• Sensu stricto, land between two rivers (or tributaries) almost never belongs to both, all land is in one river basin or the other. The boundary between river basins is called a drainage divide, and represents a putative boundary that separates all water that may flow into one river or the other. Land that does not drain to the ocean is called an Endorheic basin, all other land belongs to a specific drainage basin, by which water reaches the ocean through a series of tributary basins. --Jayron32 16:13, 6 December 2021 (UTC)

Mesopotamia (the part literally between the rivers) would technically be a peninsula (whether they have a confluence with each other or reach the Gulf without merging like in the past) but I don't think Mesopotamia if often called a peninsula. There's probably at least a thin strip of Mesopotamian farms outside the between the river area but the river would slow down invasions from Persia and Egypt so maybe that's why it was called Mesopotamia instead of Peripotamia. Sagittarian Milky Way (talk) 17:45, 6 December 2021 (UTC)

I know of literally zero people in the history of the world before you typed the above sentences that would consider Mesopotamia a peninsula. Please stop. --Jayron32 13:20, 7 December 2021 (UTC)

Okay great, so no one considers the Tigris wide enough to cause a peninsula. I haven't heard it either. Sagittarian Milky Way (talk) 15:06, 7 December 2021 (UTC)

I doubt there will be a word for the zone between two tributaries - for example the distance from the Amazon's confluences with the Madeira (near Manaus) and the Tapajós (at Santarém) is about 400 miles. Tributaries can enter from either side. 87.75.36.211 (talk) 12:02, 7 December 2021 (UTC)

Impact of tobacco toxins on plant itself

Cigarette#Health_effects says there are "many toxic chemicals in the natural tobacco leaf" that are already there before smoking. Why they don't harm or damage plant's own DNA? 212.180.235.46 (talk) 16:57, 5 December 2021 (UTC)

How do you know they don't? ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:33, 5 December 2021 (UTC)

Many plants have toxic chemicals that act as insecticides and/or fungicides. Tobacco used to be (and still can be) used as an insecticide: "Tobacco and its evil cousin nicotine are good as a pesticide". American Chemical Society. -- 2603:6081:1C00:1187:C0D8:D7A:7996:A83B (talk) 20:48, 5 December 2021 (UTC)

Well, the DNA is contained in the nucleus, with the nuclear membrane forming the barrier. Just like the cell membrane, the nuclear membrane lets some things cross and keeps other things on one side of itself. The toxic chemicals may also be further segregated by being contained in their own membranes (think of the hydrogen peroxide in the lysosome). --Khajidha (talk) 14:50, 7 December 2021 (UTC)

"Toxic" does not necessarily mean "damages DNA" (genotoxic). "Toxic" is a polysemous word, and the core principle of toxicology is "the dose makes the poison". Nicotine itself, as mentioned, is very toxic to invertebrates, and is toxic to humans in sufficient doses—in fact it's been used in poisonings. I note that table a little ways down proceeds to list toxic compounds in cigarette smoke. Some of these are combustion products, not present in the tobacco leaf until burnt. And some of these are widespread in small quantities. Formaldehyde is produced by the body as an intermediate in amino acid catabolism. Acetaldehyde is produced in the liver by alcohol dehydrogenase metabolizing ethanol, which is present in small amounts in the blood even if you don't consume alcoholic beverages. But your body is adapted to the everyday amounts of these it's exposed to, and has mechanisms for detoxifying them. It's when exposed to much greater amounts that these mechanisms become overwhelmed and problems start. --47.155.96.47 (talk) 08:25, 10 December 2021 (UTC)

Would non-binary mammals be more efficient?

If everything had a wang and a womb and reluctance to being inseminated was the sexual minority instead of the other way around then the gene pool would be pregnant almost 24/7. Though if it were possible for that to be good enough to outcompete what we have now (?) and also to arise from random mutations in the first place (??) then sex may become more and more flatworm-like and evil over time with less of the gene pool pregnant at any given time. Sagittarian Milky Way (talk) 17:58, 5 December 2021 (UTC)

It would help if "efficient" was clarified for this context. However, there are reasons why flatworms do not rule the planet, or even fill all that many niches that other organisms haven't evolved to better fill. In terms of mammals doing this, I'd suggest that it would be inefficient from a resource perspective. Remember that any structures and organs within a given organism require both raw materials and energy (LOTS of energy) to produce, grow, and maintain. Let's just say that 50% of the time, half of those reproductive organs end up not being used during reproduction... that's an enormous waste of resources and energy. At least among chordates (as far as I am aware), hermaphroditism is very much the exception, not the rule, and usually only occurs under extreme stresses (such as an isolated population that almost entirely lacks one gender, and so needs to spontaneously get some of that gender or reproductive capability or die off). Additionally, what you are calling "reluctance to being inseminated" would be more properly called sexual selection, which is a tremendous driving force of natural selection and fitness of future generations. Given that, I doubt that removing sexual selection would be any more "efficient" at anything other than producing a ton of offspring, but those offspring have just lost benefit to one of the major factors in determining fitness. That's not very efficient, at least not in my book. Lastly, what do you mean by "evil" in this context? I have absolutely not idea. --OuroborosCobra (talk) 18:35, 5 December 2021 (UTC)

Perhaps the drawbacks of each organism having a half-system on each side would overwhelm the ability to outreproduce then. At least for "complex" or locomoting life. Well if everything was enough like the flatworms that make the news then Earth would be like a planet of sex predators and there may not be enough inter-individual cooperation for technology to ever get very high, though what does and doesn't seem evil is fuzzy and inconsistent within one human much less one culture. Spiders and parasitic wasps seem evil to me but flesh-eating bacteriums and Guinea worms don't have enough anthropomorphicizability-to-cruelty ratio. If I saw flatworms trying to stab each others' skin with their penes I wouldn't stomp them but if I saw a spider being as unoffensive as possible I stomp even though another will quickly take it's place but if it's too inconvenient I'm not bugged that bugs will be eaten alive for my convenience. Sagittarian Milky Way (talk) 22:05, 5 December 2021 (UTC)

"Anthropomorphicizability-to-cruelty ratio" - we really need this in {{subspeciesbox}}--Verbarson (talk) 14:23, 6 December 2021 (UTC)

Anthropomorphicizability^xcruelty^y product or sum. Sagittarian Milky Way (talk) 19:42, 6 December 2021 (UTC)

Pregnancy is hardly free to the organism. In fact in humans lactation tends to suppress the menstrual cycle and therefore the ability to become pregnant—lactational amenorrhea—which implies some selection pressure, at least in humans, against the ability to be "constantly pregnant". The general question of why sexual reproduction is the norm for multicellular life, I thought, was called the "problem of sex", which shows up red, but you can read about the evolution of sexual reproduction. --47.155.96.47 (talk) 08:34, 10 December 2021 (UTC)

A tyrannosaurus by any other name

Ever since their discovery and modern interpretation, dinosaurs and other prehistoric animals have captured the popular imagination and, since they were not given "everyday" names, the public knows them solely by their genus names with one exception - the T. rex. Is there a specific (pun not intended) reason why it's the only prehistoric animal for which people know the species name? Or is it random happenstance? I'd wager almost nobody outside of paleontology could even hazard a guess of any other dino's species name, yet every 8-year-old in the world knows rex. I'd even wager that, outside of H. sapiens, Tyrannosaurus rex is likely the best-known species binomial, period. Is there a reason why? Matt Deres (talk) 20:49, 5 December 2021 (UTC)

Probably just happenstance. The meanings of the two parts of the binomial add up to "king of the tyrant lizards", and that has a sort of poetic feel that resonates, but it would not guarantee the widespread knowledge. Boa constrictor might be even more well known. Possibly even more well known than Homo sapiens, but most people may not realize that the "common name" there actually is the scientific name. --Khajidha (talk) 20:58, 5 December 2021 (UTC)

The Western gorilla is Gorilla gorilla, but that's not quite what you were asking about.--Khajidha (talk) 21:01, 5 December 2021 (UTC)

I'll see your Gorilla gorilla and raise you Bison bison bison.  Card Zero  (talk) 02:37, 6 December 2021 (UTC)

There's also a gorillier gorilla (Gorilla gorilla gorilla). Of tribe gorillini. Sagittarian Milky Way (talk) 03:13, 6 December 2021 (UTC)

The expression E. coli is pretty well known, but the full genus-name Escherichia, not so much. --184.144.99.241 (talk) 22:30, 5 December 2021 (UTC)

Heck, I deal with cultures of E. coli at work, and still keep misspelling it as"Escherischia". --Khajidha (talk) 23:56, 5 December 2021 (UTC)

So did I when I first typed my comment. I was saved because no one's made that misspelling a link. --184.144.99.241 (talk) 04:22, 6 December 2021 (UTC)

C elegans is also well known to most people interested in science, though few of them could spell out its genus. {The poster formerly known as 87.81.230.195} 90.208.90.66 (talk) 10:43, 6 December 2021 (UTC)

This question reminds me of the "Did You Know" segment from the main page on April 1 2010. Wikipedia:Recent_additions/2010/April#1_April_2010

ApLundell (talk) 02:45, 6 December 2021 (UTC)

The single-syllable specific name makes it catchy and easy to remember. How many others are there? Crex crex, Lynx lynx. Not many.  Card Zero  (talk) 03:14, 6 December 2021 (UTC)

Aha ha. Sagittarian Milky Way (talk) 03:23, 6 December 2021 (UTC)

Nice, and there's the list. That T.L. Erwin's taxonomy is out of control. Agra dax, Agra max, Agra nex, Agra nox...  Card Zero  (talk) 03:40, 6 December 2021 (UTC)

This RefDesk thread from a year ago mentions some of the above as Latin binomials in common usage, but also boa constrictor and glis glis. Alansplodge (talk) 00:19, 7 December 2021 (UTC)

I'm not sure how old the use of the "T. rex" abbreviation is, but I wonder if its adoption was influenced by the popularity of T. Rex (band) in the 1970s? Alansplodge (talk) 13:49, 6 December 2021 (UTC)

www.etymonline.com agrees: Abbreviated name T. rex attested by 1970 (apparently first as the band name). Alansplodge (talk) 14:02, 6 December 2021 (UTC)

"Tony Visconti (their producer for several albums) claimed in a documentary on the band that he had taken to using the abbreviated term "T. Rex" as a shorthand, something that initially irritated Bolan, who gradually came around to the idea and officially shortened the band's name to "T. Rex" at roughly the same time they started having big hits (shortly after going electric)." The single "Ride a White Swan" was the first release credited to the abbreviated "T. Rex", in October 1970, released on the band's new Fly Records label. Ghmyrtle (talk) 14:48, 6 December 2021 (UTC)

The band may have been where most people first encountered the abbreviation, but it was used in E. A. Maleev's 1955 paper on Tyrranosaurus bataar. As is usual in papers such as this, he used T. rex and T. bataar for the two species to save time. The band's choosing the shorter form was probably influenced by this standard practice in scientific writing. --Khajidha (talk) 14:55, 6 December 2021 (UTC)

I haven't been able to check H. F. Osborn's earliest paper on the animal, but his second communication to the American Museum of Natural History on the subject (1906) used the abbreviated form. This is absolutely standard practice when mentioning a binomial multiple times in one paper or when mentioning multiple species in the same genus. --Khajidha (talk) 18:08, 6 December 2021 (UTC)

Thank you for the insights, though the bit about T. Rex is maybe a secondary part of the question. As a fan of the group, it's awesome to think that they played a part in popularizing the short form. However, the basic part of my question is why the rex part became so widely known in the first place. Every eight year old kid in the world for the last century could tell you Stegosaurus, Triceratops, and Tyrannosaurus... rex. I guess it's a nice short name, but kids have little trouble with pronouncing Pachycephalosaurus. I guess what I'm getting at is: was there perhaps a very influential book or display that chose to include the T. species name but not others? Matt Deres (talk) 14:55, 11 December 2021 (UTC)

December 6

Protons and neutrons in Atomic nucleus

Atomic nucleus has diagrams of nuclei with the protons and neutrons as spheres. For a given isotope with a large number of nucleons (e.g. lead-208), do the protons and neutrons in the nucleus always have the same arrangement?

(Or are those images an oversimplification?) Bubba73 ^{You talkin' to me?} 03:33, 6 December 2021 (UTC)

Technetium 99m is a different arrangement and half-life and is ellipsoidal I think. There are many such nuclear isomers, some are numbered things like m2 cause an isotope has more than one "imperfect form". Nuclei also have nuclear shells. Sagittarian Milky Way (talk) 03:53, 6 December 2021 (UTC)

There is a section for Atomic nucleus#Composition and shape that has some details and refs (and the surprising detail that some of the nuclear particles might exist at the exact same location as each other). Searching for "shape isomer" in the the nuclear isomer article finds some additional relevant info. The Nilsson model is some complex math, but it makes the point that some observed nuclear properties contradict a perfect spherical shape. DMacks (talk) 04:16, 6 December 2021 (UTC)

These images are an oversimplification. As the caption of the image with red and blue balls states: "In this diagram, protons and neutrons look like little balls stuck together, but an actual nucleus (as understood by modern nuclear physics) cannot be explained like this, but only by using quantum mechanics." The "balls" do not occupy definable locations; they may apparate as suddenly and silently as Dumbledore where the observer happens to be looking, but also somewhere else. Also, as long as we use models from the macroscopic world, the protons and neutrons are more like bean bags with jumping beans.  --Lambiam 04:24, 6 December 2021 (UTC)

Thanks, I read most of the article, but I didn't read that important caption. Bubba73 ^{You talkin' to me?} 04:47, 6 December 2021 (UTC)

At the scale of subatomic particles, location is not defined well enough for things to have a "shape" in a traditional sense. For the purpose of visual representation, we often draw protons, neutrons, and electrons as little circles on paper (or represent them with physical spheres), the real particles are not well modeled in that way. They are likely point particles, and we have what might be thought of as "regions of probability" for those point particles to most likely be (in the case of electrons, those would be in various electron orbitals, while for protons and neutrons, that region would be the atomic nucleus. It's important not to think of these places as well-defined objects on their own, but rather regions where something is most likely to be found; however we can't get more finely tuned than that: we can't (for example) say where within an atomic orbital an electron is located, or where within a nucleus a particular proton is located, just that it is most likely located in that region. The modern quantum theory explaining the nucleus is known as quantum chromodynamics. --Jayron32 13:14, 6 December 2021 (UTC)

Our various articles are consistent that protons and neutrons have a spacial extent in some sense, measured variously to be a little less than a femptometer. Charge radius in particular even notes distinct radial probability regions of a neutron for its different constituent quarks. DMacks (talk) 13:27, 6 December 2021 (UTC)

How do you convert the mass of an object to the radius of the smallest sphere that contains it 1-standard deviation of the time (~68%)? It's probably in the article's alienese somewhere but not in a form of math that I can do. I would like to see a line graph with the size of this sphere on one axis and the particle's mass on the other. Sagittarian Milky Way (talk) 15:16, 6 December 2021 (UTC)

The charge radius, or any of various other size measures, does not define a hard bound but is based on the average value of something that has a considerable variation, each time an observer measures it, possibly even depending on the specific measuring setup. Just look at the range of values given in the lead section of our article Proton, and compare these with the 2014 CODATA recommended value given in Charge radius § Modern measurements. The individual measurements have values with a probability density that decreases exponentially with increasing radii.  --Lambiam 18:15, 6 December 2021 (UTC)

Yeah that's what I mean, where is this 1-sigma radius? ~68% of the time you measure the position to a few attometers (do you need future technology?) it will be inside but you'll have circa no fucking clue of its velocity and every so often it will be on Mars but less once per 10^many measurements. Sagittarian Milky Way (talk) 19:12, 6 December 2021 (UTC)

December 7

Nuclear Winter vs. Climate Change

Could a purposefully-created nuclear winter viably be created in order to offset the warming effects of climate change? Would it work in dampening the effects of global warming going forward, or cause more problems than it's worth? Tyrone Madera (talk) 01:23, 7 December 2021 (UTC)

It would cause way more problems than it is worth. --OuroborosCobra (talk) 02:23, 7 December 2021 (UTC)

So, even if undesirable, it could theoretically be done, say to offset global temperatures after they've risen drastically? I read that it would cause something equivalent to the Little Ice Age, but that is with current global climactic conditions. If the earth heats by 3.3 °C to 5.7 °C, would a nuclear winter just bring temperatures back down to what they are now, or would it still be a "winter" of sorts? Tyrone Madera (talk) 03:28, 7 December 2021 (UTC)

Whether it would have that effect or not is not really all that important given that we would all die of radiation poisoning and other long-term radiation exposure effects. Hence why I linked you to nuclear fallout. The cure would be far, faaaaaar worse than the disease, assuming it would even have the desired cooling effect at all. It's not worth really spending CPU hours on a climate model of this when, even if it had the cooling effect, we'd all die. --OuroborosCobra (talk) 03:32, 7 December 2021 (UTC)

Fair enough. This was more out of interest in the effects on climate than on humans or ecology.

For example, if a massive volcanic eruption brought down temperatures in the future, would that be offset by elevated climate temperatures due to global warming to make them more like temperatures now, or would it be the same as if that eruption had happened now because it would block so much solar radiation that the greenhouse effect would be negligible?

I don't know. Do you get where I'm coming from? I am not legitimately proposing that we deliberately irradiate ourselves back into the stone age. Tyrone Madera (talk) 03:43, 7 December 2021 (UTC)

Conventional means can be used to produce firestorms in a sufficient number to set of the effect; see Nuclear winter § Mechanism. The amount of greenhouse gases emitted by these firestorms, whether ignited by nuclear bombs or otherwise, will have a countereffect and may in the end make a dire situation worse; see Nuclear winter § Nuclear summer.  --Lambiam 08:45, 7 December 2021 (UTC)

Ah, that makes sense. Nuclear winter caused by nuclear devices was the only form I was familiar with, so it's good to know that it can be done through conventional means. I didn't know if Nuclear summer was a guaranteed thing or not, so that's nice to know as well. Thank you for your help!

Would the massive volcanic eruption take on similar effects? Best, Tyrone Madera (talk) 17:20, 7 December 2021 (UTC)

There are ways of doing this that don't involve nuclear bombs, this is known as Stratospheric aerosol injection. The youtube channel Kurzgesagt had an interesting episode ("Geoengineering") about this that I can recommend. El sjaako (talk) 10:36, 7 December 2021 (UTC)

The article Milankovitch cycles is well worth reading. The idea is that ice ages occur in predictable ways and that the Earth is well past the peak of the Holocene interglacial. Hence we might well be worrying about global cooling if we weren't worrying about global warming! Mike Turnbull (talk) 11:29, 7 December 2021 (UTC)

If those snowy Elizabethan-Victorian winters didn't do it then then nothing could till half a thousand centuries AD. Hudson Bay, Canada has to avoid melting completely for a year (maybe more if hotter summer(s) happen soon enough after) for an ice cap to start covering North North America in a feedback loop. Sagittarian Milky Way (talk) 16:43, 7 December 2021 (UTC)

Like, a glacial feedback loop? How would it loop? Tyrone Madera (talk) 17:10, 7 December 2021 (UTC)

Hudson Bay melts completely for a few months a year on average. Around 100,000BC the melting seasons stopped obliterating the ice completely so the ice accumulation seasons started having head starts. Sagittarian Milky Way (talk) 17:47, 7 December 2021 (UTC)

Ah, that's a neat tidbit of information that I was unaware of. The more you know :) Tyrone Madera (talk) 18:49, 7 December 2021 (UTC)

Ice age § Feedback processes: Ice caps and sheets grow by positive feedback mechanisms. One of these is that ice has a high albedo, reflecting more sunlight back into space, that in the absence of ice would be instead absorbed by the land and water. --47.155.96.47 (talk) 08:10, 10 December 2021 (UTC)

Thanks for pointing this out to me! I was not aware of the article on Milankovitch cycles, so I'm grateful that you've brought it to my attention. Tyrone Madera (talk) 17:12, 7 December 2021 (UTC)

That's super cool! For those interested, here is the video mentioned: Geoengineering: A Horrible Idea We Might Have to Do. I'll be sure to give both the video and the article a look. Tyrone Madera (talk) 17:15, 7 December 2021 (UTC)

Mask effectiveness vs Covid

Hi. Have any reliable scientists/journals etc published data on effectiveness of masks on preventing transfer of Covid, either focused on protecting the wearer or protecting those the wearer mixes with?

Particularly keen to see information about the kind of home-made cloth masks people tend to wear, rather than 'proper' PPE.

Thanks --Dweller (talk) Old fashioned is the new thing! 10:15, 7 December 2021 (UTC)

There's quite a lot of reliable WP:MEDRS-compliant information at COVID-19 masks. Mike Turnbull (talk) 11:32, 7 December 2021 (UTC)

Thanks. Is there anything on cloth masks? --Dweller (talk) Old fashioned is the new thing! 11:58, 7 December 2021 (UTC)

Literally the first section of the article. --Jayron32 12:05, 7 December 2021 (UTC)

That section has a vague part sentence of text on effectiveness. The effectiveness section (which is really good) doesn't seem to relate to cloth masks. --Dweller (talk) Old fashioned is the new thing! 13:07, 7 December 2021 (UTC)

The article I linked points out that there is a more detailed account at Cloth face mask. Enjoy! Mike Turnbull (talk) 13:10, 7 December 2021 (UTC)

You could also try a search on Google Scholar like this.

Evaluation of Cloth Masks and Modified Procedure Masks as Personal Protective Equipment for the Public During the COVID-19 Pandemic is about the newest I could see at a quick glance. Alansplodge (talk) 16:49, 7 December 2021 (UTC)

Thanks all --Dweller (talk) Old fashioned is the new thing! 18:04, 7 December 2021 (UTC)

Suggest Wikipedians good in writing lead definitions

Greetings,

I am looking for suggestions for (not retired/ still active) Wikipedians in writing comprehensive and good Wikipedia article lead definitions (from available multiple definitions) for articles related to Sciences and Humanities (preferable at least five from each segment, and expecting users names suggestions other than one's own :))

Thanks

Bookku, 'Encyclopedias = expanding information & knowledge' (talk) 16:18, 7 December 2021 (UTC)

December 8

CiteSeerX and DOI

CiteSeerX and DOI:

• https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.533.6677 . . . . REAL
• https://doi.org/10.1.1.533.6677 . . . . 404
• https://dx.doi.org/10.1.1.533.6677 . . . . 404

what the heck ?

.... 0mtwb9gd5wx (talk) 01:44, 8 December 2021 (UTC)

That's not a properly formatted DOI. DOIs should take the form of "10.1000/xyz123," but there is no forward slash in the DOI you've given. --OuroborosCobra (talk) 02:08, 8 December 2021 (UTC)

Can ammonia be used instead of natural gas in gas stoves and home heating systems?

Ammonia can be produced from hydrogen, it's easier to transport and store than hydrogen itself. However, can ammonia then be directly combusted in the systems that are designed to combust natural gas? Count Iblis (talk) 07:39, 8 December 2021 (UTC)

First, natural gas isn't just hydrogen. People don't burn hydrogen gas in gas stoves. Also, natural gas doesn't have to be produced, just extracted. Clarityfiend (talk) 09:21, 8 December 2021 (UTC)

As implied below, natural gas is not even mostly hydrogen, but rather methane, see for instance that source. Article improvement suggestion: put typical compositions somewhere in the article natural gas. Tigraan^{Click here for my talk page ("private" contact)} 16:00, 8 December 2021 (UTC)

AFAICT there's nothing in the OP's question suggesting natural gas contains significant amounts of hydrogen. Instead the OP seems to be asking whether ammonia produced from hydrogen, probably blue, turquoise or green hydrogen, can be used as a direct substitute for natural gas perhaps aware that hydrogen can not be or maybe they consider it unimportant since the main issue is whether hydrogen converted to ammonia for reasons of transport, storage etc can be used as a direct natural gas substitute (since if it can then whether hydrogen can be might be irrelevant if ammonia is overall a better option). The ultimately goal we can assume is likely to come up with a more climate friendly substitute for natural gas hence why the hydrogen being considered here would likely be blue, turquoise or green. Nil Einne (talk) 02:49, 9 December 2021 (UTC)

I agree. Must be old age creeping up on me. Clarityfiend (talk) 05:00, 9 December 2021 (UTC)

Per our article on the Haber process, a significant fraction of the world's energy (article says 1% to 2%) goes into reacting hydrogen with nitrogen to make ammonia. It would be pretty odd, I think, to do that just to burn the ammonia, especially from a "green" point of view (not sure what "blue" and "turquoise" refer to here). --Trovatore (talk) 03:30, 9 December 2021 (UTC)

See [3] for discussion of the various "colors" of hydrogen. DMacks (talk) 06:07, 9 December 2021 (UTC)

Odd perhaps but seems to be under active consideration. Well not in the form the OP suggests but Japan in particular (and to a much lesser extent South Korea) seems to have a lot of interest in using ammonia to supplement and eventually replace coal in their power stations [4] [5] [6] [7] [8]. (The last link also has discussion about the colours BTW.)

Besides using ammonia directly in power stations, there is also a suggestion it could be used for transportation, either directly with ammonia fuel cells [9], but more likely indirectly i.e. being used to make hydrogen. [10]

If using hydrogen to make ammonia to use as a fuel sounds silly, using hydrogen to make ammonia to make hydrogen seems even sillier. But as the Science news article says the problem is that transporting and storing hydrogen in bulk effectively is still something we don't have good solutions for. But transporting and storing ammonia in bulk is something we have a lot of experience with and a lot of existing facilities for. The Science article claims currently (well in 2018 I guess), the energy loss from the roundtrip conversion is similar to liquifying hydrogen. So it seems some have decided ammonia as an intermediary is the best solution.

Beyond Japan apparently deciding to go big on hydrogen and ammonia although this isn't directly stated in any source I've read so is OR, I suspect another reason why this is recently such a big thing is precisely because of what we're already doing. I suspect those investing in it in from Japan etc figure that even if it completely fails as a fuel, low carbon ammonia is of interest due to the need to fill the world's existing demand for ammonia mostly for fertiliser. So if they can "crack" (pun not really intended) the market for low carbon ammonia, they'll still be successful even if it never becomes a fuel. And likewise there's also interest, investment, research etc from those who think the idea of using is as a fuel is odd but are looking for a solution for our existing demand. Interesting enough although only relevant in a very limited way, there's recently been a lot of noise about a shortage of urea [11] [12]

Nil Einne (talk) 10:27, 10 December 2021 (UTC)

To be clear, I'm not saying Japan's plans make sense. As the BBC article says it sort of seems like they're stuck in a sunk cost situation. Fukushima meant they made a lot of new coal power stations at a time when most of the developed world was starting to turn off them. But this happened just around the time renewables were starting to be cost effective. Now they're trying to find a way to keep them going since they don't want to decommission power plants they just built. Nil Einne (talk) 10:44, 10 December 2021 (UTC)

At the very least you have to adjust the device to change the fuel to air ratio. Ammonia reacts with oxygen in a 4:3 ratio, methane in a 1:2 ratio (and hydrogen in a 2:1 ratio). You even have to adjust a British gas stove when moving it to the Netherlands, as the composition of the natural gas is different. But a bigger problem is that ammonia is rather toxic. 300 ppm is the limit of what's considered immediate danger. For methane, the main danger is getting an explosive mixture with air at about 50000 ppm, so an ammonia leak is far more dangerous than a methane leak. PiusImpavidus (talk) 09:28, 8 December 2021 (UTC)

You can read this article. Ruslik_Zero 20:15, 8 December 2021 (UTC)

When ammonia is burnt it is much more likely to produce nitrogen oxides, which is not generally a good idea for pollution or climate reasons. If using blue hydrogen, you may as well have just burnt the methane. Or for fuel transform the methane into bigger hydrocarbons. Graeme Bartlett (talk) 21:58, 9 December 2021 (UTC)

Yes you can, but ammonia is pretty nasty stuff. If given the choice, for most uses, I'd reformulate the H2 from pV electrolysis into methane, a fuel we are used to handling and that is somewhat less obnoxious. The obvious use for ammonia is fertiliser. Greglocock (talk) 23:48, 9 December 2021 (UTC)

To echo others, ammonia is poisonous. It may be technically feasible, but probably not a very wise idea. Ammonia is in wide use industrially as a refrigerant, and places that use it need leak detection systems, evacuation procedures, hazardous materials training for people on-site, you get the picture. Natural gas is not toxic, merely flammable and a possible asphyxiant in confined spaces—as is any gas not oxygen. All the work that would be required to do such a thing might as well be invested in replacing natural gas appliances with electric ones. --47.155.96.47 (talk) 08:07, 10 December 2021 (UTC)

"Places that use it need leak detection..." On the other hand, many, if not most, RV refrigerators are ammonia systems, and have no special leak detection or other such things. --jpgordon^{𝄢𝄆𝄐𝄇} 15:27, 11 December 2021 (UTC)

Correct. These are absorption refrigerators (explicit link for readers). But the amount of ammonia is limited to what's contained in the fridge's refrigerant loop. Converting a natural gas distribution system to distribute ammonia would produce the possibility of large, dangerous ammonia leaks. --47.155.96.47 (talk) 11:16, 12 December 2021 (UTC)

Bug species

Could someone identify this bug or beetle species, please? Length is slightly less than half of the index finger, sitting calmly in a living room in Poland. 212.180.235.46 (talk) 12:54, 8 December 2021 (UTC)

It's a shield bug, but not sure which one. Mikenorton (talk) 13:22, 8 December 2021 (UTC)

It could be a Brown marmorated stink bug, which has been reported from Poland. Mikenorton (talk) 13:28, 8 December 2021 (UTC)

Thanks all. 212.180.235.46 (talk) 18:07, 8 December 2021 (UTC)

December 10

Mammals that sexually mature more slowly than Humans?

I was looking at the wikipedia page on Gorillas and the physical/sexual maturity time period seems pretty close to that of humans, humans may physically mature slightly faster (with the (relatively) easy access to food) but of course socially we delay that. Are there any animals that have a *clearly* slower sexual maturity than humans (no female in captivity has shown interest in mating prior to age 20, etc.)— Preceding unsigned comment added by naraht (talk • contribs)

The answer seems to be "none". Humans reach physical sexual maturity at puberty (i.e. the physical ability to have children), and social sexual maturity at their late teens. I can find no other mammals that have anywhere near that slow development. This article seems salient; it's a study of the relationship between age of sexual maturity and brain complexity; it seems to indicate that there's a close correlation between the size and neuron density of an animal's cerebral cortex and how long they spend in childhood. Under that concept, it is pretty easy to see how humans (and other animals with well-developed cerebral cortexes like the great apes and certain marine mammals) have the slowest rate of childhood development. --Jayron32 16:54, 10 December 2021 (UTC)

You're looking for animals which are K-selected, and basically it's whales. The male sperm whale sexually matures at 18, apparently. If you'll allow non-mammals, the greenland shark reaches sexual maturity at age 150.  Card Zero  (talk) 17:28, 10 December 2021 (UTC)

The way I also see this question, is which mammals have a longer lifespan than humans? Cuz if there were, those can be correlated with puberty ages. 67.165.185.178 (talk) 10:31, 11 December 2021 (UTC).

Heterologous prime-boost vaccination

need plain english definition from a reliable source of "Heterologous prime-boost vaccination", "Homologous prime-boost vaccination", "Heterologous prime-boost immunization", "Homologous prime-boost immunization",

For: Heterologous vaccine = Heterologous prime-boost vaccination

.... 0mtwb9gd5wx (talk) 22:08, 10 December 2021 (UTC)

OK, here's one: using a third dose of a different COVID-19 vaccine as a booster 3 to 6 months after a primary vaccination course (heterologous boosting). This ECDC news item also defines hetrologous primary vaccination and homologous vaccination.

Here's another: A homologous booster dose means an individual will be inoculated with the same vaccine brand used in their primary series while a heterologous booster dose means an individual will be vaccinated with a different brand. This news item is written in English that lapses in places into Filipino, but it seems to be a reliable source (msn.com / GMA News).  Card Zero  (talk) 22:49, 10 December 2021 (UTC)

"Heterologous vaccine" is a case of false rebracketing. What is heterologous is not the vaccine, but the vaccine regimen (also called vaccine schedule). It is like defining "intensive dairy" as the yield of intensive dairy farming.  --Lambiam 08:19, 11 December 2021 (UTC)

December 11

Physics: which materials reflect light the most?

If you have a room where you replaced material that reflect (absorb) light from 99%, to 98%, then your room is 1% brighter. What materials reflect light the most / absorb the least? And what is this property called? 67.165.185.178 (talk) 11:04, 11 December 2021 (UTC).

See reflectance. Mikenorton (talk) 11:47, 11 December 2021 (UTC)

If the reflectance goes down from 0.99 to 0.98, the room becomes less bright. Shiny metals, such as used for the reflective layer of mirrors, have a vert high reflectance. A layer of deposited soot has very low reflectance. For the "blackest black" yet developed, see here. See also the runner-up, Vantablack.  --Lambiam 17:25, 11 December 2021 (UTC)

Weird, metals are conductors, they allow for electron to flow. Insulators block electron flow. I would expect metals to absorb electrons more, but it seems the opposite is true, metals reflect photons the most. 67.165.185.178 (talk) 19:18, 11 December 2021 (UTC).

Photons and electrons are very different kinds of particles. Photons can be absorbed by donating their energy to an electron, allowing it to jump to a (higher energy) excited state. What makes a metal electrically conduct is the presence of free electrons, which can occupy a continuous spectrum of energies without jumping between states. That is also why they can collectively respond to the incoming electromagnetic wave to form a counter wave that materializes as an emitted photon – just as if the incoming photon bounces back. Or is the emitted photon another photon?... in the quantum world, the distinction between it being the same or a newly created photon loses its meaning.  --Lambiam 22:16, 11 December 2021 (UTC)

I'm wondering how the fuck anything is transparent. If electron clouds block, reflect, absorb and scatter visible light so much and make the universe opaque before 380,000 years old then how is everything not opaque with the exception of things thin enough that some rays do not have to penetrate many electron clouds. Are the electron clouds transparent if you are not trying to penetrat with a spectral line? Then why can't I see the broad-spectrum sunlight through a graphite brick? Why do some substances block a broadband part of the spectrum seemingly for no reason but transmit nearby ones well? Why is crystal glass colorless when it has such a high percentage of orange lead oxide? Sagittarian Milky Way (talk) 21:04, 11 December 2021 (UTC)

See Transparency and translucency - transparent materials such as glass lack internal defects, like grain boundaries. Mikenorton (talk) 21:16, 11 December 2021 (UTC)

So the magic electrons = transparency obliterating thing of early universe must not be some inherent "photon bothering property" of electrons then (presumably enhanced by Heisenberg or something but maybe space clearing up didn't have much to do with that). The ability to see through quadrillions of fiber optic atoms in a row had been confusing me for well over a decade. Why is hematite opaque? It has an index of refraction higher than diamonds and silicon carbide gems but no one can make a crystal flawless enough. Sagittarian Milky Way (talk) 01:25, 12 December 2021 (UTC)

I remembered that clouds and especially snow are big reflectors of IR, forgot what are big reflectors of UV, but that does not necessarily mean they are good reflectors of regular light? 67.165.185.178 (talk) 14:28, 12 December 2021 (UTC).

Temperature of black and white cars in winter.

So we know that black color cars absorb heat the most, white the least. In the summer times, the temperature inside a black car could be 10 to 17 F more hotter than inside a white car. But what I'm trying to find is, winter examples. A Google search of "temperature of black and white cars winter" still shows nothing but summer results. Even adding the word "cold" before winter, still shows summertime results. However, I have a feeling, that the disparity, is going to be less than summertime results? Making a black car in the cold winter, no real applications for warmer temperatures? 67.165.185.178 (talk) 12:44, 11 December 2021 (UTC).

Heat is going into the car at one rate, and going out of the car at another rate, and there's a bunch of heat equations for dealing with different situations, which might fill an engineer with joy. Point is, anyway, the car is not only getting more radiation in sunny weather, it's also heating up because the heat can't leave very fast, because the outside air is also warm. If the outside air is extremely cold, the rate of heat loss (assuming it's at least a bit warm inside) is much higher than the rate of heat gained from the thermal radiation of the sun - even if it's sunny and cold at the same time. That article has a nice graph from NASA (twice over!) showing that white paint actually absorbs heat radiation at an unexpectedly high percentage (but a mirror doesn't).

For every situation (a white car on a sunny day in the arctic, a black car on a cloudy day in the tropics) there will be a thermodynamic equilibrium, the temperature inside the car the system eventually settles on. I think that's the right term, anyway. I can't actually read the article to find out because I don't have all day to figure out what it really says, so I'm not even sure what the point of linking you to it is. I hate the inaccessibility of mathematics.

Edit: I found a calculator for temperature of a car in sunlight at different outside temperatures, over time. The foot of the page has "The color of a car does not have a significant impact ...".  Card Zero  (talk) 15:08, 11 December 2021 (UTC)

There is something incongruent about that calculator. I enter in temperatures of below freezing, and it still shows getting marginally warmer over time. But there should be a point where the longer you leave your car outside, the colder it gets inside. 67.165.185.178 (talk) 17:23, 11 December 2021 (UTC).

I thought that as well, but deleted my objection, because the calculator starts with the inside of the car at the same temperature as outside, then of course it increases under sunlight like the temperature in any greenhouse, and (presumably) levels off at a temperature which is warmer inside than outside, but still potentially horribly cold.  Card Zero  (talk) 17:31, 11 December 2021 (UTC)

The color of the interior of a given car might be more important than what color the body is painted. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:40, 11 December 2021 (UTC)

Four heat transfer processes can be distinguished (if the car windows are closed and the AC is not running), each of which involves predominantly one type of transfer. (1) Heat captured from incoming radiation. (2) Heat exchanged by convection between the outside surface of the car and the outside air. (3) Heat exchanged by conduction between the outside and inside surfaces of the car body. (4) Heat exchanged by convection between the inside surface of the car body and the interior air. The car colour is only important for (1). In equilibrium, process (4) stops exchanging heat: the temperature of the interior air has become the same as that of the inside surface of the car body. This simplifies the equations. The radiation emitted by a hot car is not entirely negligible, but of minor importance compared to the heat loss by convection.  --Lambiam 17:07, 11 December 2021 (UTC)

Okay, a separate question, and this can be applied to clothing/coats. After black and white, the next colors are the Roy G. Biv spectrum. So wearing red is the best color to remain cool in the hot summer, and violet to remain warm in the cold winter. But what if you were to compare dark red, with light violet? Would that make it the same temperature effect? Gray is not a color in the spectrum, but I presume wearing gray is like the halfway point from wearing black vs. white, I wonder if wearing dark red and light violet is the same point? 67.165.185.178 (talk) 17:27, 11 December 2021 (UTC).

In cold weather, the effects of clothing colour will be orders of magnitude less that the effects of the clothing's material, thickness, and insulation (within and between layers) that shed water from precipitation, prevent external air penetration, and trap and retain body heat.

In hot (and presumably sunny) weather the most important colour effect would be reflectance of infra-red light. A garment red to the eye might still absorb greatly in infra-red; conversely a garment violet to the eye might also reflect infra-red well: the reflectance spectra of materials is not necessarily the same shape as an ideal black-body radiation curve. {The poster formerly known as 87.81.230.195} 90.205.227.133 (talk) 12:03, 12 December 2021 (UTC)

Objects at around room temperature emit radiation in the infrared band, but the sun is not such an object, so maybe visible light energy is significant when it comes to staying warm/cool under sunlight? "In terms of energy, sunlight at Earth's surface is around 52 to 55 percent infrared ... 42 to 43 percent visible". Then, from Infrared#Heat, "Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths."  Card Zero  (talk) 13:51, 12 December 2021 (UTC)

You say the sun is no such IR object, but then say it emits 52-55% infrared? 67.165.185.178 (talk) 14:15, 12 December 2021 (UTC).

I mean they emit all, or nearly all, or most, of their energy in IR. Except, say, in a steelworks, where objects are hot enough to glow brightly. Even so, IR probably still accounts for most of the energy. It's just that with the sun, it seems that the visible component of the energy starts to be a significant proportion.  Card Zero  (talk) 14:39, 12 December 2021 (UTC)

So there is no UV-light affect for colors of clothing? Compared to IR? (In terms of temperature?). And in winters, there is still a difference between cloudy vs. sunny-days, right? 67.165.185.178 (talk) 13:54, 12 December 2021 (UTC).

Sunlight says only 3% to 4% of the energy reaching a person on Earth is UV. However, if your clothing is a pure spectral color, that means it's absorbing only a very narrow band (which is why it will look bright), and might be absorbing an even lower percentage of the available energy. (By the way, don't confuse UV with visible violet, if you were about to.) What you want is to absorb as wide a band of the spectrum as possible: so if the resulting clothing color isn't black, it will be dark, and probably some kind of brown - but perception can be deceptive. Pointillism mixes colors using adjacent bright dots, meaning that "bright brown" is possible. (Come to think of it, so does any computer screen, so you can experiment in a good graphics editor: I think the brown turns into purple or orange usually, so perhaps darkness is part of our definition of brown.) Best just to pay attention to brightness/darkness as an indicator of reflected/absorbed (visible) energy.  Card Zero  (talk) 14:30, 12 December 2021 (UTC)

" so perhaps darkness is part of our definition of brown" Yep. One common phrasing is that "brown is dark orange" (see our own article on brown). --Khajidha (talk) 15:01, 12 December 2021 (UTC)

Okay, back to clothing again, I did a Google "what colors absorb IR the most" and got into a clutter. Some do not necessarily say the Roy G Biv, but they all agree about black and white as the most opposites. Then, I found this on a physics stack exchange comment from a physics PhD: "People wearing dark clothing then wasn't an accidental cultural thing. Heat does not just come onto us from the sun. It also comes off our warm bodies. When all that body heat hits the white clothing we might be wearing, it also gets reflected right back into our bodies. So when we wear white, we are actually heating our bodies. This means that the best color to keep cool, is black. Black does absorb all wavelengths coming from the sun, but black also absorbs energy leaving our bodies, instead of reflecting it back into our bodies."

So, intuitively, this is the opposite, but, if you combine these 2, then, the best way to keep warm, from wearing 2 layers of clothing, would be, wear white on the inside, and black on the outer layer. 67.165.185.178 (talk) 15:05, 12 December 2021 (UTC).

But, if asking what's the best color to wear in the summer weather to keep cool, you got contradicting factors. If you're only in the shade, black is the coolest, but if you're under sunlight, then whether wearing white or black, you got contradicting factors. 67.165.185.178 (talk) 15:37, 12 December 2021 (UTC).

Organs of tinned fish

If I consume sardines or pilchards out of a can, I have so far always found that inside each fish, apart from the backbone and spinal cord, there is usually also either one of two things: eggs (i.e. roe) or what I assume is the liver, the latter of which I don't consume for reasons of accumulation of toxins. However I cannot recall finding both of these (i.e. liver and roe) together in any one fish. Is this a known 'thing'? Do female fish absorb their own livers while eggs develop within them? Am I misidentifying the liver (sometimes there appear to be two of these)? Why are other organs not apparent (e.g. heart, intestines etc.)? PaleCloudedWhite (talk) 16:49, 11 December 2021 (UTC)

Could be milt rather than liver. Delicious. Bazza (talk) 19:16, 11 December 2021 (UTC)

December 12

What does "impresses information" mean?

Sentence from Transmitter: The transmitter also impresses information such as an audio or video signal onto the radio frequency current to be carried by the radio waves. Rizosome (talk) 09:21, 12 December 2021 (UTC)

Impressive

To mark or stamp (sense 4). Basically, to press.  Card Zero  (talk) 10:43, 12 December 2021 (UTC)

See also Carrier wave.--Shantavira|^{feed me} 13:13, 12 December 2021 (UTC)