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

July 12

Scientology, and Mental Health....

....Can the website CCHR.ORG be placed in that, related articles, such as the ones about mental health? This site claims that the mental health system is, among other things, that the whole mental health system is some kind of fraud. I have a Satellite TV system and on it, I have a TV channel that Scientology puts out there, and among other things, says psychiatry has done some really vile things, and mentions the CCHR.ORG website repeatedly. So can this source be useful? Nuclear Sergeant (talk) 08:17, 12 July 2023 (UTC)

The place to propose this is the talk page of the relevant article. It is not clear which article you mean. However, that website would seem to be the very antithesis of a reliable source, and we will not promote Scientology, which, incidentally, is nothing to do with science. Shantavira|^{feed me} 08:39, 12 July 2023 (UTC)

What, next you'll be telling us phrenology is unscientific. —Tamfang (talk) 15:36, 18 July 2023 (UTC)

I've seen some of these documentaries about psychiatry on their Satellite TV channel, incl the CCHR.ORG website. Just looking for a appropriate place for the link. 🥺🥰 Nuclear Sergeant (talk) 08:54, 12 July 2023 (UTC)

Wikipedia links to cchr.org from our article about them. That would seem to be quite sufficient. Shantavira|^{feed me} 10:06, 12 July 2023 (UTC)

Some people in psychiatry have done some afful things. It is a field that deals with really bad and distressing problems and many people are desperate for solutions and frankly there are a number of nutters in the profession. And it costs society a lot of money. It is not hard to find things that have gone badly wrong! However this is an organization devoted to destroying the system and promoting pseudoscience because of something their nutter founder said. It is not there to help and represent people with mental health problems like for instance Mind (charity) does in the UK. Wikipedia does not go in for promoting weird idea, and I especially think we should be careful with things like that where people have mental problems. The article about the organization is quite enough for an encyclopaedia. NadVolum (talk) 12:05, 12 July 2023 (UTC)

Well in fact I don't actually think he was a nutter, just he was good with words and needed money and saw an opportunity and lacked a few morals. NadVolum (talk) 12:14, 12 July 2023 (UTC)

"He" who? --Trovatore (talk) 18:36, 12 July 2023 (UTC)

The founder of scientology, L. Ron Hubbard. He figured out that science fiction sells better when it is turned into a religion. -- Random person no 362478479 (talk) 18:50, 12 July 2023 (UTC)

A Scientologist once tried to recruit me in the street. He did not say that he was with Scientology but tried to get me to sign up for one of those "tests" they do before telling you what's "wrong" with you and which of their extremely expensive courses will help you. I recognized that he was from Scientology because he also carried around copies of Hubbard's book on Dianetics. So I told him that Scientology is a church and that I don't want anything to do with churches. Now in Germany Scientology has for a long time tried to get official recognition as a Church to get all the financial and legal advantages that come with it. So when I called Scientology a church he was so happy that he completely missed the part about me wanting nothing to do with churches. :) -- Random person no 362478479 (talk) 18:56, 12 July 2023 (UTC)

OK. Our article on the organization mentions Thomas Szasz as the first individual named as a founder, so I didn't know for sure who you meant. I tend to think of Hubbard as a con man, but not Szasz. It seems to me Szasz has some very telling criticisms of both the intellectual foundation and the practice of psychiatry, though he probably went overboard in reaction to a technique that can be useful in relieving human suffering. --Trovatore (talk) 19:29, 12 July 2023 (UTC)

I'm assuming that NadVolum meant Hubbard, but of course I may be wrong. -- Random person no 362478479 (talk) 19:45, 12 July 2023 (UTC)

Obviously, "this is an organization devoted to destroying the system and promoting pseudoscience" refers to the Church – psychiatry is not "an organization" – and so "their nutty founder" refers to its founder.  --Lambiam 22:30, 12 July 2023 (UTC)

I meant L Ron Hubbard okay. Thomas Szasz I would count as one of the nutters in the profession I mentioned above. I don't count L Ron Hubbard as nutty, just lacking in morals. NadVolum (talk) 22:37, 12 July 2023 (UTC)

Szasz actually made a lot of good points. --Trovatore (talk) 02:48, 13 July 2023 (UTC)

Agree, Szasz made a lot of good points. But his overall perspective (i.e. mental disorders should not be treated) is wrong.

I mean: it was not his fault that he saw the problems of psychiatry, but he did not really have a solution. tgeorgescu (talk) 03:59, 13 July 2023 (UTC)

I'm not an expert on the man. From my casual perspective, it appears he got a little too absolutist on some things (like an illness not really being an illness if you can't have it when you're dead; that never made much sense). But the established alternative? A bunch of "syndromes" defined by pick-four-of-seven vaguely defined symptoms (presumably you have to have the credential to be able to evaluate them)? Diagnoses that come and go with each rev of the DSM, sometimes based on the political evaluation of the person they're named after? It might be the best thing we have, and that may be better than nothing. But I'm supposed to take it seriously as "science"?

That said, right, to my knowledge he never really came up with anything better. --Trovatore (talk) 05:01, 13 July 2023 (UTC)

It makes me think of:

Doctor doctor, all year long my husband has been thinking he is a chicken.

Why didn't you call me sooner?

I would have done, but we needed the eggs.

Psychiatry exists in this permanent state of it's not good science, but we need the eggs.  Card Zero  (talk) 07:28, 13 July 2023 (UTC)

Bug A Salt

Is there a article on this air rifle that uses SALT as ammo? The ad shows it being used to kill flies, other bugs. I googled this thing after I've seen the ad on late night TV. Nuclear Sergeant (talk) 11:41, 12 July 2023 (UTC)

There is a search icon at the top of every Wikipedia page that enables you to search for articles, such as Bug-A-Salt. Shantavira|^{feed me} 12:13, 12 July 2023 (UTC)

CSF plastics

What is "CSF" in connection with plastics recycling? Facebook just presented me an advertisement (I've tried and failed to link it) for a soft-plastics recycling company, with a link to a fuller description. The advertisement warns me to "Always consider the general CSF risk warning and offer document before investing." What is CSF? The "fuller description" doesn't appear to mention it, none of the items at CSF seems relevant (I assume that plastics aren't made from caesium fluoride, and they're talking about objects already in the household, so Cancer slope factor isn't relevant), and Google searches for <csf plastic> gives only results for Macrophage colony-stimulating factor and Cerebrospinal fluid. Nyttend (talk) 21:58, 12 July 2023 (UTC)

Could it be "crowd-sourced funding"? see Equity crowdfunding AU legislation: [1]. Graeme Bartlett (talk) 00:35, 13 July 2023 (UTC)

https://help.birchal.com/en/articles/1704472-what-is-the-general-csf-risk-warning -- Random person no 362478479 (talk) 07:37, 13 July 2023 (UTC)

July 13

Can I see old aviation maps or airport diagrams for pilots?

Sagittarian Milky Way (talk) 17:37, 13 July 2023 (UTC)

I've found this to be difficult online. I imagine that a serious library might have them. Abductive (reasoning) 19:13, 13 July 2023 (UTC)

http://www.departedflights.com/airports.html have many airport diagrams. Philvoids (talk) 20:41, 13 July 2023 (UTC)

Any ones from decades ago? Sagittarian Milky Way (talk) 21:07, 13 July 2023 (UTC)

Here's a subject search at archive.org for aeronautical charts. I see a large number of charts from the 1920s ("experimental"!) and several Jeppesen charts for Montana from the 1940s. Some files link to this selection at davidrumsey.com.  Card Zero  (talk) 23:21, 13 July 2023 (UTC)

Energy costs of megalith construction

Was the construction of megaliths energy-consuming to the extent that it required a reliable and stable source of food rather than merely hunting-gathering? The timeline indicates that most such constructions happened after the First Agricultural Revolution, suggesting a supply of cattle meat and plant food may have played a role in feeding all those builders (who possibly spent less efforts and time since then when compared to e.g. a mammoth hunt). Brandmeister^talk 18:44, 13 July 2023 (UTC)

Göbekli Tepe predates agriculture. I think people misunderstand just how productive certain areas can be for hunter-gathers, because current hunter-gathers have been pushed into the marginal lands. In the area that became the cradle of agriculture, there was abundant food. Like, insanely abundant. A Garden of Eden, one might say. Abductive (reasoning) 19:11, 13 July 2023 (UTC)

Actually I do not think that it predated agriculture. Though it may have predated pottery. Ruslik_Zero 20:41, 13 July 2023 (UTC)

Again, this is bias creeping in, from people who can't imagine what the situation was like at the time, or the direction of causality. Abductive (reasoning) 21:15, 13 July 2023 (UTC)

Founder crops is relevant. Einkorn wheat says the process of domestication might have taken only 200 years, 10,000 years ago. There were at some point semi-domesticated grain fields, where the seeds were distributed accidentally on purpose during repeated foraging.  Card Zero  (talk) 23:50, 13 July 2023 (UTC)

I hope that the 200 generations figure is for accidental domestication. Most evolutionary biologists go with 6 generations. Abductive (reasoning) 04:59, 14 July 2023 (UTC)

"20 to 200 years" says the article, I was going with the upper estimate.  Card Zero  (talk) 05:04, 14 July 2023 (UTC)

One of the sections of that Neolithic Revolution page is Diet and health. It mentions risk of famine due to crop failure and the allocation of resources towards reproduction over somatic effort. So stability might be the wrong idea here. There's also the section on Social change which mentions a social elite who [...] monopolized decision-making. Note that compared to hunter gatherer societies, everybody is short, weak, fat, vitamin deficient, sick, and their teeth are falling out, so we're talking quantity over quality. So we have large numbers of somewhat desperate people and a few chiefs or priests, who likely organized the agriculture on which they all depended, with forest clearance, irrigation, and calendars, and notionally protected it in a spiritual capacity. This novel bossiness filled a vacuum left where once people would cooperate to hunt animals, and frequently resulted in the decision that the community should cooperate to put thousands of stones in a big pile, build artificial hills, or move 20-ton megaliths around, often for the purpose of protecting the bodies of the elite after death.  Card Zero  (talk) 00:29, 14 July 2023 (UTC)

The article Einkorn wheat mentions: "One theory by Yuval Noah Harari suggests that the domestication of einkorn was linked to intensive agriculture to support the nearby Göbekli Tepe site.^[12]"  --Lambiam 03:06, 14 July 2023 (UTC)

They needed to support the maintenance budget for Göbekli Tepe, so they invented agriculture. Abductive (reasoning) 04:59, 14 July 2023 (UTC)

Perhaps they also invented entrance fees. Might it be that the chiselled pillars at the site are discarded tickets?  --Lambiam 10:56, 14 July 2023 (UTC)

Why did it take so long to invent pottey? Did no one ever put clay in fire to see what would happen or leave it in the sunny dry season and thought, hey maybe fire can make it even harder and I can make a cup with this? Also why'd it take awhile to invent non-"coil stack" pottery? For something wide-mouthed you could just smoosh the coils smooth on both sides without pottery wheels or tools. Sagittarian Milky Way (talk) 18:07, 14 July 2023 (UTC)

People used containers made of tree bark. You can even boil water in them (not in the way one initially pictures). Pottery wasn't invented until after the invention of the house mouse. Abductive (reasoning) 18:21, 14 July 2023 (UTC)

Physics behind a flying object getting under the wing of another flying object and tipping it over in flight

Something I saw today. There were some very large gulls chasing a grey heron (not sure how it started, but there were about six chasing it - I assume it had messed with their chicks) and one of the gulls was wing-to-wing with the heron and it kinda got to the side and under and used its wing to flip the heron's wing - which sent it spinning out of control for a time. This was down the side of a bridge (railway underneath) and the heron went spinning down, out of control, with the gulls following it. I guess that they were intending to follow it down for the kill (there was another one that made contact and was trying to piledrive it into the ground, it looked like), but the heron managed to recover in flight before it hit the ground and get away - this all happened in about 10 seconds. I'd never seen anything like that from birds before - but it reminded me of World War II stories of British Spitfire pilots flipping the wings of German V1 bombs to crash them. I was just wondering about the physics behind this - can anyone explain how this works? I'm assuming from this that the seagulls have something of an instinctive understanding of how it works, or at least can learn to figure out how to do it. Wish I'd been able to film this, but it all happened so fast. Birds can be brutal, it seems. Iloveparrots (talk) 21:54, 13 July 2023 (UTC)

Possibly the gulls, as habitual formation flyers, had some awareness of the interaction between wingtip vortices and a following wing, and used this to their advantage? The gull species I've observed most closely can be fairly aggressive towards each other, and it may be a familiar harassing tactic for them. Herons tend to be solitary, and thus less familiar with the consequences of close interaction. Whether such interaction between the birds concerned could actually result in a wingtip stall, I don't know, but one can easily imagine it being disorienting to an already-distracted heron, resulting in a momentary 'loss of control' if not an incipient spin. On the other hand, I've seen birds being mobbed use drop-like-a-stone tactics to escape, or at least to signal their compliance with mob rule and their intent to slink away. Mobbing can be brutal, but most of the time it is probably more the threat of violence than the violence itself that resolves the conflict. AndyTheGrump (talk) 22:46, 13 July 2023 (UTC)

I live near the sea and from what I've seen from watching the (sea)gulls they do seem to have some understanding of aerobatics. I've seen them doing Immelmann turns and aileron rolls for sure. They also love ridge lift. They really love ridge lift - and whatever large ship that's going out to sea, they slipstream the hell out of it. Iloveparrots (talk) 23:15, 13 July 2023 (UTC)

This is very common with gulls and birds of prey. See Mobbing (animal behavior). Shantavira|^{feed me} 16:59, 14 July 2023 (UTC)

I've seen them chasing crows and hawks before, but never something as big as a heron and never actually making contact like this. To be honest, I didn't even think that the gulls would think of a heron as a threat, but obviously they know better. Iloveparrots (talk) 18:07, 14 July 2023 (UTC)

Obviously from reading the article, they do eat the chicks of other birds though. I never really thought about herons enough to read up on them until now, to be honest. At one time, I'd just assumed from how they look that they were flightless birds too, lol. Then I saw one flying. Iloveparrots (talk) 18:10, 14 July 2023 (UTC)

Nature's killing machines

I've been reading about giant petrels tonight. I watched a few Youtube videos about their hunting behaviors too. It seems that from a lineage of mostly fish-eaters, somehow an extremely aggressive land predator has emerged, somehow - killing and eating penguins, seals, sheep, etc. (multiple videos of them covered in gore). It looks like the thing is built like a battle tank with a huge reinforced beak, unlike its more slender albatross relatives.

My question - can you think of examples of other lineages of animals that are generally non-predatory that have an occasional member that has become a killing machine? I'm quite familiar with birds and parrots (as my name suggests!) and I can think of the Antipodes parakeet, which often eats seabirds and their chicks. But apart from that, I'm not sure. Iloveparrots (talk) 22:35, 13 July 2023 (UTC)

Further to that, I was going to suggest the ferret, but then from reading the article I see that it's not actually a rodent. So, never mind. :) Iloveparrots (talk) 22:46, 13 July 2023 (UTC)

Vampire ground finch? Not exactly a killer, but a fine example of natural selection finding a way to exploit a new niche while working from an unlikely starting point. AndyTheGrump (talk) 23:02, 13 July 2023 (UTC)

Just thinking. The opposite way around is the giant panda. Well, now it's been established that it's a bear. When I was at school it was something like "an herbivorous mammal that resembles a bear". Iloveparrots (talk) 23:30, 13 July 2023 (UTC)

Rats are definitely an omnivorous rodent. Pigs among ungulates, maybe? -- Avocado (talk) 02:46, 14 July 2023 (UTC)

My great uncle used to have a farm - "don't feel bad about eating a pig - he wouldn't feel bad about eating you, if he only thought of it first" he'd say, probably rightly. Iloveparrots (talk) 18:16, 14 July 2023 (UTC)

There are apparently 137 kinds of carnivorous sponge. Also the Dayak hunters of Borneo say that the tufted ground squirrel will jump from low branches to ambush deer, bite them in the jugular and then disembowel them (a story for which the world is not yet prepared).  Card Zero  (talk) 05:26, 14 July 2023 (UTC)

My first thought was Homo sapiens, which is far more aggressive and carnivorous than other primates. The most extreme example though is probably from the Unglates: the group that includes sheep, pigs, horses, giraffes ... and killer whales. Iapetus (talk) 10:13, 17 July 2023 (UTC)

Mock turtles

Is there actually an animal called the mock turtle? As in something that resembles a turtle but technically isn't related to turtles? Google is useless as it throws up Alice in Wonderland references or references to the band. 146.200.127.4 (talk) 23:55, 13 July 2023 (UTC)

See mock turtle soup. Not a turtle, but an imitation of a product made from turtles. Lewis Carrol then created the obvious parody. AndyTheGrump (talk) 00:00, 14 July 2023 (UTC)

The body of a turtle with a cow's head and hooves. Perfect. :) (And standing on hind feet, a la Gary Larson's typical cow.) ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:20, 14 July 2023 (UTC)

July 14

Beginning of the Cambrian Period: which is it, 538.8, 539, or 541 years ago?

The article on the Cambrian Period, https://en.wikipedia.org/wiki/Cambrian, says that it lasted "from the end of the preceding Ediacaran Period 541 million years ago (mya)"

This disagrees with the Ediacaran article, https://en.wikipedia.org/wiki/Ediacaran which says it lasted "to the beginning of the Cambrian Period 538.8 Mya."

Also note that the end of the Ediacaran Period "marks the end of the Proterozoic Eon" However the Proterozoic Eon, https://en.wikipedia.org/wiki/Proterozoic, "is a geological eon spanning the time interval from 2500 to 538.8 million years ago."

Note that the Cambrian Period is the earliest period of the Paleozoic Era, which is the "longest of the Phanerozoic eras, lasting from 538.8 to 251.902 million years ago." Sadly, within the Proterozoic Era article, it is in disagreement with itself when it says that "The Cambrian spanned from 539–485 million years ago and is the first period of the Paleozoic Era of the Phanerozoic. "

OK, so which is it, 538.8, 539, or 541 years ago? PaulChouinard (talk) 03:19, 14 July 2023 (UTC)

I especially like the "251.902 million years ago" one. Must be a floating pimp error made when correcting from Charlemagnean time to Metric time. Abductive (reasoning) 04:53, 14 July 2023 (UTC)

Gotta watch out for them floating pimps. —Tamfang (talk) 15:18, 14 July 2023 (UTC)

These geological periods tend to be defined by particular features in the rocks that can be reliably identified in many places. Actually dating these features is another matter. So all sources may agree that the Cambrian started at one particular layer of rock, but may not agree on the exact time. Consider the end of the Cretaceous. For decades everybody has agreed that it happened at a particular iridium and soot rich layer, but estimates for the age of this layer have varied over more than a million years. PiusImpavidus (talk) 08:21, 14 July 2023 (UTC)

• There's probably some false precision in dating methods shown above, making all three numbers functionally equivalent. The range of difference between your three numbers is 0.4%, which is likely smaller than the precision with which we can actually date rocks that old. --Jayron32 12:22, 14 July 2023 (UTC)
• Did you read the obvious section Cambrian#Dating the Cambrian? This explicitly notes that "A more precise date using modern radiometric dating yield a date of 538.8 ± 0.2 million years ago." supporting the view that 539 and 538.8 are functionally equivalent and just depend on the level of precision you want, although 538.8 isn't really false precision assuming you trust the dating method and its error estimate. While it doesn't specifically comment on a 541 figure, it does mention "Nevertheless, there are arguments that the dated horizon in Oman does not correspond to the Ediacaran-Cambrian boundary, but represents a facies change from marine to evaporite-dominated strata – which would mean that dates from other sections, ranging from 544 or 542 Ma, are more suitable. Nil Einne (talk) 15:08, 14 July 2023 (UTC)
• I want to note that our article Cambrian references the 541 Ma claim with International Commission on Stratigraphy's chronostratigraphic chart. The older version of that chart indeed says that the Cambrian period began 541.0 Ma ago, but since February 2022, the chart has used 538.8 Ma as the beginning of the Cambrian. Valtaisa varpunen (talk) 15:46, 19 July 2023 (UTC)

Collocyte, collencyte, collenocyte

Hello, I'm a boring bastard from Wiktionary (the free dictionary project, defining words), and I would like some expertise from biologists. Look at our entry for collocyte. You can also see the etymology (word origin) there, meaning basically "glue cell".

So: it seems that there might be three words: collocyte (see above), collencyte and collenocyte. I am personally sceptical about the middle one because it doesn't sound like a typical formation: these Latin and Greek words would not usually allow something like ..nc.. in the middle. HOWEVER...

We have this interesting slice of pie: Collocyte#Confusion_between_collocytes_and_collencytes Is that really correct? Is anybody experienced and confident enough to help our little dictionary project with these words?

Thanks, from your word nerd, Equinox ◑ 11:02, 14 July 2023 (UTC)

They all seem to be words relating to slightly different things, sometimes coined for very niche subjects. "The problem is so marked that to avoid confusion many workers are abandoning traditional terms in favour of new words."

A treatise on zoology, Vol 2, p. 52, as cited in the Collocyte#Confusion_between_collocytes_and_collencytes section on collencytes seems to be relatively authoritative on sponges, if a century out of date. The article says the term was borrowed from Collenchyma. My Shorter Oxford English Dictionary 3rd ed., only lists collenchyma and none of the words you are asking about. Britannica has its own section on collencytes in the Sponges article (subscription or UK Public Library membership needed.)

A source-book of biological names and terms, p. 63 (free registration needed, 1 hour borrow) gives the etymology of collenocyte, kolla, glue, + engchyma, something poured in, calling it a "poorly-formed word". So there would appear to be three separate words with separate individual meanings and etymologies. MinorProphet (talk) 12:29, 14 July 2023 (UTC)

Spectroscopic electron configurations

The NIST Basic Atomic Spectroscopic Date pages give the following ground states for thulium, ytterbium, lutetium, and hafnium:

69 Tm	(1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2  5p6) 4f13 6s2 
70 Yb	(1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2  5p6) 4f14 6s2
71 Lu	(1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2  5p6) 5d1 6s2
72 Hf	 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2  5p6  5d2 6s2 

The bold text and irregular spacing is mine.

Why is it that for Lu and Hf the 4f14 orbital is demoted so that it appears after the 4d10 orbital rather than after the 5p6 orbital as in Tm and Yb? Sandbh (talk) 12:44, 14 July 2023 (UTC)

So, there's a LOT of conflicting conventions when writing electron configurations. It appears from my quick looking over that NIST website is that everything in the parenthesis are "non-valence" electrons; i.e. sublevels from which electrons are NOT normally lost during normal chemical reactions. Lutetium, for example, has a maximum oxidation state of 3+; Lu³⁺ is presumably /1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6/ By contrast, Thulium also has a 3+ oxidation state, and that means that once the two 6s2 electrons are removed, a third electron has to come from somewhere, Th³⁺ must therefore be /1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f12 5s2 5p6/ (bold for highlight), implying that the 4f sublevel is acting as a valence level, given that electrons can easily be removed from hit. Basically, for Tm and Yb, the valence electrons are 4f and 6s, while in Lu and Hf the valence electrons are 6s and 5d, with 4f electrons not participating in bonding. This is common among both transition (d block) and post-transition (f block) elements, where the d and/or f sublevels function as valence levels. This sort of thing is known as "pseudo-octet" configurations, see here for some examples.--Jayron32 18:09, 14 July 2023 (UTC)

Thank you @Jayron32:

There may be an explanation that I hadn't appreciated. This is that the spectroscopic configuration of e.g. neutral Lu does not necessarily denote the order in which electrons leave. That is to say, as electrons leave or are ionized away the remaining sub-orbitals may change their order. Continuing the example, it is known that Lu⁴⁺ is [Xe]4f13. IOW, the electrons that have left appear to be 4f, 5d and 6s. OTOH, looking at the spectroscopic configuration of Lu as (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6) 5d1 6s2 it appears that the leaving order should be two s, one d, and then (presumably) a 5p electron. Whereas in actuality, a 4f electron appears to leave.

The Tm example is a good one. Spectroscopically it is (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6) 4f13 6s2. Tm3+ would be (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6) 4f12, as you suggest but for the position of the 4f12 sub-orbital.

Does the above seem plausible?

I don't yet know if it's right (I could be wrong) but it appears to do the least amount of injury to the known experimental facts. Sandbh (talk) 05:15, 15 July 2023 (UTC)

I am not aware of a Lutetium 4+ being a common oxidation state; according to Lutetium, the maximum common chemically stable oxidation state is Lu³⁺. This only lists 3+, I'm not sure where you are seeing data showing a Lu⁴⁺ state, so I can't comment on your proposed configuration. If you could provide a source for that information, it may help someone answer your question. --Jayron32 10:49, 17 July 2023 (UTC)

July 15

Sky curvature at ground level

It seems that, alongside usual horizon curvature of the Earth, I also perceive sky curvature at ground level through distribution of clouds that, when looked wider, appear to be scattered in an arched pattern (as opposed to notorious flat Earth where clouds would be distributed flatly). Is it sort of a horizon curvature or another manifestation of Earth curvature? 212.180.235.46 (talk) 19:15, 15 July 2023 (UTC)

See Celestial sphere. If the coordinate lines of the celestial sphere were visibly painted somewhere up there (they aren't) then we would notice their arched pattern. My clouds may be more random than yours because I don't see that pattern. Philvoids (talk) 09:28, 16 July 2023 (UTC)

Imagine a very long straight line in front of you, higher than your point of view, say the overhead wire over a straight train track. In front of you, you have to look up. When you follow it in the distance to your left, it goes down to the horizon. But it also goes down when you follow it in the distance to your right. So if you try to capture this in a picture on a possibly panoramic flat canvas (something you can do with a fisheye lens), you get a curved line. In this fisheye photo of stair steps, you can see whether they are above or below the camera's pov by the way they are curved.  --Lambiam 07:16, 17 July 2023 (UTC)

July 16

to every deer there is a season

In my town one often sees mule deer going about their errands. Today I saw a doe and fawn, hardly worth even a Tweet, but the fawn was much smaller than I expect at this time of year.

Could the fawn have been born a couple of months later than normal? Is that, as the young people say, a thing that happens? —Tamfang (talk) 06:25, 16 July 2023 (UTC)

I live in a city and occasionally deer cross my garden, apparently they are trying to follow an old migration path in spite of modern roads and buildings. These skittish deer are clearly ill at ease, frightened by people and traffic. I have been warned never to pet a fawn no matter how sweet the little "Bambi" seems because the mother will reject a fawn that carries human scent. These are wild animals whose milieu is disrupted by humanity so their pasture and growth cycle are both stunted. Philvoids (talk) 09:39, 16 July 2023 (UTC)

The "rejecting human scent" is hooey, though it's of some antiquity. (Though with fawns, it's possible the human scent might attract predators.) But yes, it's a thing that happens. We have a lot of mule deer here. I've seen fawns in the autumn. A friend had a couple dropped in her yard just a week ago. --jpgordon^{𝄢𝄆𝄐𝄇} 15:04, 16 July 2023 (UTC)

Heat wave

In school, it is taught that countries near the equator will face more heat from sun, but in news more heatwaves are in India, Pakistan, Europe, Canada than Indonesia, Sri Lanka, Brazil? Nasterg (talk) 11:21, 16 July 2023 (UTC)

Conditions in the equatorial area are more constant. They are hot all the time. The weather is less variable. Where I live a heat wave happens when the air gets baked over the desert in the center of the continent, and then a wind blows the heat away from the equator (to the south in my case) and brings abnormal heat. But for the dessert area, that heat is normal, so its not a heat wave there. Graeme Bartlett (talk) 11:35, 16 July 2023 (UTC)

A heat wave is relative. In much of Canada, a week of 85-degree weather would be a heat wave, whereas in some parts of the globe, that might constitute cool weather.

All parts of the globe are expected to see more extreme weather due to climate change than we did in previous centuries. Because there's little cold weather in equatorial regions, the increased heat there will be more remarkable than increased incidence of cooler weather. In middle latitudes, we're seeing more extremes of both heat and cold. And in all areas we're seeing more extremes of both drought and precipitation. -- Avocado (talk) 14:34, 16 July 2023 (UTC)

At NYC weather stations a week of 85.0 highs in the hottest part of the year would be calendar day averages, maybe even slightly below. It's not considered a heatwave till 90F highs for 3 days in a row. At the north tip of Canada all-time high is 21 (69.8°F), previous record was ~20 (68), room temperature would be a heat wave. Everywhere on Greenland had melted by now but 32F is still a heat wave in parts of Greenland. At the South Pole -12.3C/9.86F is the hottest in the station's over 66.5 year history. Sagittarian Milky Way (talk) 15:35, 16 July 2023 (UTC)

Here are the hottest temperatures ever recorded at each latitude band:

90°N to 89.9°N: 13C/55.40F NORTH POLE

89.9°N to 80°N: 21.0C/69.80F CANADA

80°N to 70°N: 36.7C/98.06F ASIAN RUSSIA

70°N to Arctic Circle (~66.56°N): 38.0C/100.40F ASIAN RUSSIA

Arctic Circle (~66.56°N) to 60°N: 39.9C/103.82F CANADA

60°N to 50°N: 49.6C/121.28F CANADA

50.24°N to 45°N: 49.6C/121.28F CANADA 2021

45°N to 40°N: 52.2C/125.96F CHINA. The record was 50.7C/123.26F from 1986 to about half day ago!

40°N to 30°N: 130.0F/54.444C FURNACE CREEK (DEATH VALLEY, CALIFORNIA)

30°N to Tropic of Cancer (~23.44°N): 54.0C/129.20F KUWAIT

Tropic of Cancer (~23.44°N) to 20°N: 52.0C/125.60F SAUDI ARABIA

20°N to 10°N: 50.0C/122.00F MAURITANIA

10°N to 0°N: 46.4C/115.52F NIGERIA

0°S to 10°S: 42.7C/108.86F BRAZIL

10°S to 20°S: 48.4C/119.12F AUSTRALIA

20°S to Tropic of Capricorn (~23.44°S): 50.7C/123.26F AUSTRALIA

Tropic of Capricorn (~23.44°S) to 30°S: 50.7C/123.26F AUSTRALIA

30°S to 40°S: 50.0C/122.00F AUSTRALIA

40°S to 45°S: 44.6C/112.28F ARGENTINA

45°S to 50°S: 40.2C/104.36F ARGENTINA

50°S to 60°S: 37.0C/98.60F ARGENTINA

60°S to Antarctic Circle (~66.56°S): 19.8C/67.64F OBSCURE ISLAND

Antarctic Circle (~66.56°S) to 80°S: 15.0C/59.00F ANTARCTICA

70°S to 80°S: 15.0C/59.00F ANTARCTICA

80°S to 89.9°S: 5.9C/42.62F ANTARCTICA

89.9°S to 90°S: -12.3C/9.86F SOUTH POLE WEATHER STATION

That's just how the Earth works, hot air rises the most in an intertropical convergence that follows where the Sun is overhead at noon but delayed so it never gets >23° from the equator everywhere cause 365 days is too short, this makes that zone humid and cloudy as f**k, not a dry heat at all. The air goes miles high then migrates to about 30 degrees from the equator (this moves a bit with the seasons too) where it sinks. Can't have all the latitudes going up and none going down. The high altitude air of the mid-latitudes also ends up in this band around 30 degrees from the equator and sinks. This downdraft makes this latitude band have less clouds than low or medium latitudes and also being on land, north of equator, on a continent not an island, west side of the continent, at low altitude and upwind of mountain range(s) all increase the heat, cloud rarity, humidity lowness and record highs of parts of the band with these feature(s). Then the wind returns to the equator and roughly 60 north completing the cycle. 3 cell-pair convection! Sagittarian Milky Way (talk) 19:03, 16 July 2023 (UTC)

(edit conflict)In some places in the mid latitudes, most notably central and eastern North America in winter, we see an increase in cold extremes. This is quite exceptional. Here in western Europe, both the 10 coldest days of the year and the 10 hottest days have become 5°C warmer over the past 40 years, while the average day has only become 2.5°C warmer (already twice the worldwide average), so the hot extremes increase and the cold extremes decrease. PiusImpavidus (talk) 19:16, 16 July 2023 (UTC)

(edit conflict)Near the equator, the sun is on average higher in the sky, giving more incoming radiation, but there are a few factors to complicate matters. At the equator, the air generally rises, giving much cloud cover. In the desert bands (20–35 degrees latitude), the air sinks, reducing cloud cover. That makes the subtropical latitudes hotter. Also, the lack of moisture available for evaporation allows the temperature to rise much faster during the day in such arid areas. And when you're at the tropic circle at midsummer, the sun gets as high in the sky as on the equator at the equinox (i.e. in the zenith), but the day lasts longer.

As mentioned above, heat waves are somewhat relative. They get in the news when it's much hotter than what people (and nature) are used to. The higher your latitude, the faster the temperature rise due to anthropogenic global warming, so this is mostly a problem of the mid and high latitudes. Not entirely though: when the dew point gets close to body temperature, you've an absolute problem. PiusImpavidus (talk) 19:16, 16 July 2023 (UTC)

Another factor is proximity to the sea and the temperature of the currents within it. Alansplodge (talk) 16:24, 18 July 2023 (UTC)

July 17

Lorentz transformation vs Galileo

In special relativity, Einstein in a thought of mind shows that the time measured using a light pulse reflection between 2 points A and B in the same moving reference frame is not the same for an observer at rest and an observer in this mobile reference frame. In this case the speed of light is not taken into account, it is its constant value whatever the frame of reference which requires a Lorentz transformation. However, in another thought of mind, if I replace the reflection of a light pulse between the points A and B by an object in movement starting from A at constant speed and going to rebound on B by an elastic shock to return in A , that in A, then B, then A it emits a light pulse, in this case do we always use a Lorentz or Galileo transformation? Why would this variant of the mind's thought not be valid? Malypaet (talk) 03:53, 17 July 2023 (UTC)

What do you mean by "valid"? In one thought experiment, we flip a pancake and it falls flat on the floor. In another thought experiment, we flip a pancake and it gets stuck to the ceiling. Both are valid thought experiments.  --Lambiam 06:57, 17 July 2023 (UTC)

Your answer begs the question. Because if the second experiment is valid with Galileo's transformation, then it shows that the first is invalid for measuring time, that as a measuring instrument it has a bias due to the use of reflection on a mirror with speed referential independent, right? Do you have another interpretation? Malypaet (talk) 08:21, 17 July 2023 (UTC)

Lorentz transformations are always more accurate than Galileo transformations, but the errors introduced by using a Galileo transformation may be too small to matter. In the typical scenario with bouncing balls, using Galileo instead of Lorentz transformations gives you an error on the order of one in a billion. That's much smaller than your other sources of uncertainty and not worth the mathematical complexity of Lorentz transformations. PiusImpavidus (talk) 09:34, 17 July 2023 (UTC)

When a thought experiment is used, it is theoretically perfect and no accuracy errors occur. So can you explain to me your one in a billion error rate with the bouncing object? Malypaet (talk) 14:24, 17 July 2023 (UTC)

Your first thought experiment requires measurement of time between two flashes observed at one point, with no assumption of c. But your second thought experiment requires measurement of time between flashes emitted at A then at B. Can you tell us how fast the light travels to a common observing point for the time measurement? Philvoids (talk) 15:24, 17 July 2023 (UTC)

On the Electrodynamics of moving bodies extract:

"a ray of light proceeds from A at A-time tA towards B, arrives and is reflected from B at B-time tB, and returns to A at A-time t'A."

In my thought experiment:

"a ray of light proceeds from A synchronously with an object at A-time tA towards B, all 2 arrives at B that is a black body walls with perfect elastic properties so only the object is bounced from B at B-time tB and simultaneously proceeds a Ray of light, returns to A at A-time t'A and simultaneously proceeds a Ray of light."

In the 2 thought experiment, the observers read there clocks to get tA , tB and t'A.

The difference is that in the first case you need Lorentz transformation between observer at rest and the mobile one. In the second experiment as you have Galileo transformation, the clocks of the 2 observers are always synchronised, confirming Newton's absolute time.

What is false there ? Malypaet (talk) 19:32, 17 July 2023 (UTC)

I don't fully understand the thought experiment you propose. It seems that you assume that when moving objects are involved, you have to use Galileo transformations instead of Lorentz transformations. That's incorrect. You always use Lorentz transformations when the relative velocity of your frames of reference is a significant fraction of the speed of light. When dealing with electrodynamics, you may need Lorentz too. When playing a game of billiards, Galileo is good enough. PiusImpavidus (talk) 08:28, 18 July 2023 (UTC)

There's no explanation in your answer, just assertions based on articles I'm familiar with, but which don't address the case of the thought experiment I proposed. Lorentz transformations apply when using echoes of electromagnetic waves to measure the times of moving objects between different frames of reference. But, even if it is the most practical and precise method, it is theoretically not the only one available. If you are blind, time still passes and objects also move. Why don't you analyze my thought experiment in detail, contradicting it on every point or not? Malypaet (talk) 13:21, 18 July 2023 (UTC)

An object moves at constant speed from A to B to A, at each of these points emitting a light pulse. OK, but how is this a thought experiment? What is there to be analyzed?  --Lambiam 05:54, 19 July 2023 (UTC)

Based "On the Electrodynamics of moving bodies".

A thought experiment is an experiment that we imagine to validate a hypothesis and that we put in the form of a mathematical exercise, while waiting to be able to see it validated or not by a physics experiment or an observation in physics . For Einstein it came with Edington's observation and Pound and Rebka's experiment.

Here, in both cases, the times tA, tB and t'A are measured by a light pulse. On the other hand in the 1st case the object moving on a rod and reflected by a mirror is a light pulse with constant speed c whatever the referential, whereas in the second case the object which bounces on the mirror has a speed constant v1 only on the rod.

With the rod stationary, we have (tB - tA) = (t'A - tB) for all observers and in both cases, either (2 AB)/(t'A -tA)=c or (2 AB)/(t'A -tA)=v1 .

Now we consider the rod at speed v2.

In the 1st case for observer at rest we obtain:

(tB-tA)=rAB/(c-v2) and (t'A-tB)=rAB/(c+v2) => (tB-tA) # (t'A-tB)

Therefore, a Lorentz transformation is necessary between the observer at rest and the moving one.

In the second case for observer at rest we obtain:

(tB-tA)=rAB/(v1+v2) and (t'A-tB)=rAB/(v1-v2) => (tB-tA) = (t'A-tB)

Here just a Galilean transformation.

Voilà. Malypaet (talk) 13:01, 19 July 2023 (UTC)

Still not sure about the part thought experiment here. In both your functions, (tB-tA) = (t'A-tB) *(U+v2)/(U-v2), where U is either v1 or c. Rmvandijk (talk) 06:30, 20 July 2023 (UTC)

Well done for the illusionist trick with your U like a hat, but:

(tB-tA) = (t'A-tB) *(c+v2)/(c-v2)

&

(tB-tA) = (t'A-tB) *(v1-v2)/(v1+v2) Malypaet (talk) 20:34, 20 July 2023 (UTC)

However, I also made a mistake. In fact when my object goes from A to B, for the observer at rest it has the speed (v1+v2) and on the way back the speed (v1-v2), but on the way out point B moves away at the speed v2 and on the way back approaches at the speed v2.

So we get

tB-tA=rAB/((v1+v2)-v2) =rAB/v1

t'A-tB=rAB/((v1-v2) +v2) =rAB/v1

To resume your U, going U=v1+v2 and returning U=v1-v2 Malypaet (talk) 04:25, 21 July 2023 (UTC)

I correct by taking up Rmvandijk's idea. With for the observer at rest, going to B a speed of the object v'=v1+v2 and on the return v''=v1-v2, we obtain:

(tB-tA)=rAB/(v' -v2) and (t'A-tB)=rAB/(v''+v2) => (tB-tA) = (t'A-tB) Malypaet (talk) 04:44, 21 July 2023 (UTC)

Has there ever been a documented example of an animal using a weapon?

I don't know if you ever seen this, but this video has been doing the rounds for years online. Some soldiers were goofing around and gave an AK-47 to a monkey, which then proceeded to shoot at them and make them run away. It might be fake (I don't know), but I first saw it like 10 years ago. It turned up on my Youtube recs again tonight. Made me wonder - have there been any 100% confirmed, real examples of animals using weapons? For example, if a monkey picked up a thigh bone (as in 2001: A Space Odyssey), or a block of wood, or a rock, or whatever and bludgeoned another monkey to death in a fight. I know for sure that monkeys watch what people do and will do things like pick up smouldering dogends and smoke them, or drink the dregs out of people's beer bottles. How far does this go? Iloveparrots (talk) 23:58, 17 July 2023 (UTC)

As noted in Tool use by non-humans (WP:WHAAOE strikes again), it was discovered in 2007 that chimps use sharpened sticks while hunting. There's an unsourced claim there that "This is considered the first evidence of systematic use of weapons in a species other than humans." Sea otters routinely use rocks to smash open their food/prey. Clarityfiend (talk) 00:23, 18 July 2023 (UTC)

"Research in 2007 showed that common chimpanzees sharpen sticks to use as weapons when hunting mammals. This is considered the first evidence of systematic use of weapons in a species other than humans" - I see, thank you.

Another thing I was wondering from watching the breeding birds around here, and I'm not sure if this has ever happened. Although birds often work together to chase away hawks from their breeding colonies when the hawk appears - have the birds (crows for example) ever thought, after that, to figure out where the hawk lives and then send (say) 20 of the strongest males from the colony to take it out while it was least expecting it? Iloveparrots (talk) 01:07, 18 July 2023 (UTC)

While I am not an expert ornithologist (so am very open to correction), not only have I never heard of such a thing (in over half a century of reading about natural history), but everything I (think I) know about avian cognition suggests such high-level reasoning, communication and co-operation would be considerably above even the most intelligent birds' capabilities.

Obviously, finding a reliable reference that a thing that has never been observed has not, in fact, ever been observed is problematical. {The poster formerly known as 87.81.230.195} 51.198.140.169 (talk) 05:34, 18 July 2023 (UTC)

George Orwell composed an anthem "Beasts of England" to incite animals on a farm including hens, ducks, roosters and geese to revolution. Philvoids (talk) 10:49, 18 July 2023 (UTC)

He did, but the work clearly falls into the genre of Fable, so is not a reliable reflection of real-world natural behavior. (Taking off my pedant hat, I am a lifelong fan of non-realistic genres.) {The poster formerly known as 87.81.230.195} 51.198.140.169 (talk) 00:44, 19 July 2023 (UTC)

I think, from reading about corvids that this is the case: individual corvids sometimes collect food items (nuts and seeds, for example) and store them by burying them in the ground or hiding them in tree hollows with the expectation that they will be able to collect them later, say in winter, when food is scarce. Some do it, some don't - but they are at least somewhat capable of realizing that actions committed today may influence future events (but it doesn't happen that often). But it is never the case that the entire flock works together to gather and store food and (say) keeps it in one place which is then guarded by the entire flock, in order that they all may benefit from the food in winter. Iloveparrots (talk) 19:24, 19 July 2023 (UTC)

Well, many animals cache food but I don't think we can assume that the behavior is indicative of planning rather than instinct. My pet rats, when offered food, will usually grab it and immediately run and hide it. I don't think it indicates planning or a deliberative thought process, it's just an instinct to hide food that one is not going to eat right now. Some individual rats seems to have a stronger caching instinct than others though. CodeTalker (talk) 20:55, 19 July 2023 (UTC)

I don't really think that animals really have much of an understanding that actions committed in the past may have consequences in the present, or that actions committed in the present may influence the future. There have been occasional studies, like with the Tanimbar corella that demonstrated that they can reject food items if they are aware that they will be awarded with superior food items in the future - but that is literally talking about minutes later, not weeks or months. I'm well aware that punishing a pet dog for something like damaging furniture, ripping up the wallpaper, or peeing on the carpet by yelling at it, cuffing it upside the head or sticking a boot up its ass (please don't do this - but people do, talking from personal experience) doesn't work at all because they are literally unable to make the connection between something that happened a couple of hours ago and now. Iloveparrots (talk) 21:21, 19 July 2023 (UTC)

I didn't find a source, so take it with a grain of salt: A group of baboons attacked a leopard using rocks. Zarnivop (talk) 08:25, 18 July 2023 (UTC)

Orcas use directed waves to dislodge prey from icebergs. BBC Earth, via Youtube Bazza (talk) 08:33, 18 July 2023 (UTC)

If the future's dystopic enough someone will invent gorilla guerillas. Driving the cyborg body like a video game or gene editing it to the intelligence, fine motor skills and brainwashability of a child soldier without loss of muscularity or possibly just extremely good selective breeding and training. And AK-style rifles with giant levers or whatever's the easiest trigger for gorillas to use. Also someone will invent 2 millimeter spy roaches. With cameras in shop ceiling-like fake eye globes and Wifi for brain-interface and live video. Sagittarian Milky Way (talk) 18:42, 18 July 2023 (UTC)

I don't know if you ever seen this, but this video has been doing the rounds for years online. Some soldiers were goofing around and gave an AK-47 to a monkey, which then proceeded to shoot at them and make them run away. It might be fake (I don't know), but I first saw it like 10 years ago.

It's 100% fake. The video you refer to, "Ape with AK-47", is a viral video campaign created by ad agency Mekanism on behalf of their client 20th Century Fox to promote the 2011 film Rise of the Planet of the Apes. Viriditas (talk) 23:38, 18 July 2023 (UTC)

There was an ISIS video where they had a chimpanzee execute a hostage with an SKS. McAynus (talk) 02:24, 19 July 2023 (UTC)

Google says nary a word about it. Viriditas (talk) 02:31, 19 July 2023 (UTC)

I suspect that any extended searching of ISIS videos might bring you to the attention of the security services. Alansplodge (talk) 11:44, 19 July 2023 (UTC)

Well, if you consider Homo sapiens being a species in the animal kingdom... --CiaPan (talk) 20:16, 19 July 2023 (UTC)

July 19

Magnesium Sulphate

Last year, I bought some magnesium sulphate paste for removing splinters. Now it has separated into a hard, crystalline, mass and some clear liquid resembling glycerine. Is there any way of returning it to a paste or do I have to buy some more? Alansplodge (talk) 10:52, 19 July 2023 (UTC)

Magnesium Sulphate Paste is literally just magnesium sulphate and glycerine, with a small amount of phenol. Here is a typical ingredient list, but I've checked several others, and that's what it is. It hasn't "gone off" or anything, the magnesium sulphate has just settled out of the suspension (which is what a "paste" generally is, from a chemistry point of view). Depending on how much effort you want to put in (vis a vis the cost of just buying more) you should be able to just remix the ingredients. --Jayron32 11:36, 19 July 2023 (UTC)

Thanks Jayron. The problem is that the solid part has the consistency of concrete and has so far resisted my remixing efforts. Would heating it help? Alansplodge (talk) 11:42, 19 July 2023 (UTC)

Possibly, gentle heating would help. IIRC, magnesium sulphate is usually a fairly well-hydrated crystal, and gentle heating may help release some of the "waters of hydration", possibly enough to dissolve it slightly and help break it up (see Epsom salt). If that doesn't work, perhaps something like a kitchen blender or food processor may help? If you don't have anything like that, I'm at a loss. --Jayron32 11:48, 19 July 2023 (UTC)

Bingo! I pinged it in the microwave - worked like a charm. Many thanks. Alansplodge (talk) 12:50, 19 July 2023 (UTC)

Resolved

Evolution of birds from dinosaurs

As far as I'm aware, the current scientific consensus is that modern birds evolved from the tiny number of dinosaurs that survived the Chicxulub impact. However, it is somewhat unclear to me - did birds, as we know them now exist *before* the meteorite hit, or did they emerge later? At school, I was taught that all mammals evolved from a small number of tiny rat-like creatures (in terms of body form) that somehow survived the apocalypse - and that all birds evolved from a small number of tiny velociraptor-like creatures (in terms of body form) that somehow survived the apocalypse - but I think from my readings that this is inaccurate now? Iloveparrots (talk) 21:50, 19 July 2023 (UTC)

See the related articles Origin of birds and Evolution of birds. The evolutionary events that gave rise to the early birds within maniraptoran theropods and the origin of bird flight are disputed questions. Philvoids (talk) 22:35, 19 July 2023 (UTC)

Today's birds form the class Aves, which is a subset of the clade Ornithurae. This clade also includes two extinct genera of bird-like reptilians.  --Lambiam 22:39, 19 July 2023 (UTC)

Birds evolved before the end-Cretaceous extinction event, although exactly how much before depends on how you define "birds". If "birds" means "the most recent common ancestor of all living birds and all of it descendants", then birds first appeared some time in the Cretaceous. If "bird" is defined more broadly to include Archaeopteryx, then they evolved in the Jurassic. Iapetus (talk) 12:30, 20 July 2023 (UTC)

(edit conflict) To build on the excellent answers above, and to directly answer the question "did birds, as we know them now exist *before* the meteorite hit, or did they emerge later?" four clades of birds are believed to have existed prior to the Cretaceous–Paleogene extinction event that killed off the non-avian dinosaurs, which is to say that the "most recent common ancestor" of all modern birds predates the extinction event by some time. Roughly speaking, those clades are the "big fat running birds" of the ostrich-emu-cassowary type, "waterfowl" like ducks and geese, "groundfowl" like chickens and turkeys and peafowl, and "everything else". It is thought that these divisions among birds (or bird-like dinosaurs or whatever term you wish to use) existed prior to the extinction event. You can find a partial list of such birds at Category:Mesozoic birds. Also as noted, the exact nature of mesozoic bird evolution is unresolved; there are several competing theories, but all we do know is that whatever happened to give us birds, it certainly happened prior to the extinction event that took out the rest of the dinosaurs. --Jayron32 12:31, 20 July 2023 (UTC)

GF's question:

My girlfriend wants to know what is the world's largest penis, and I'm NOT talking about porn. (She caught me editing on Wikipedia and got curious about Wikipedia as well ) I'm talking about human penises. 😺😘🥰 Nuclear Sergeant (talk) 22:57, 19 July 2023 (UTC)

See the article Human penis size and a claim of Jonah Falcon. Philvoids (talk) 01:46, 20 July 2023 (UTC)

Or this:[2] ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:59, 20 July 2023 (UTC)

According to Wikipedia, the penis on a right whale can be up to 2.7 m (8.9 ft) Shantavira|^{feed me} 07:59, 20 July 2023 (UTC)

July 20

Blackbody emission questions.

1. Almost everything with heat emits IR. Humans, animals, water. The biggest source is the sun and fire. But I'm trying to find out who doesn't emit IR in darkness. I suppose humans and animals emit IR in darkness, but not water?

2. As sunlight is 52-55% IR and causes water to emit IR, I'm also curious to know how we draw the line between Blackbody radiation, and fluorescence/phosphorescence, of IR. Things that absorb IR, and emit in deep-IR. The thing is, if water stops emitting IR as soon as darkness, then that is equivalent to fluorescence, and if water emits for another 10 seconds after darkness, that's equivalent to phosphorescence.

3. They say most things that Blackbody IR at room temperature, will emit light, starting at red light, at 500 C. But what material is that, I've never found a chart for different materials such as steel, plastic, water (albeit some will turn liquid or gas 1st). What are some Blackbodys that have the lowest temperature to emit visible light? Thanks. 170.76.231.162 (talk) 16:17, 20 July 2023 (UTC).

The maximum wavelength of emission depends on the temperature

All objects emit light, so long as they have a temperature, so ANY thing with a higher temperature than absolute zero will emit light. The specific spectrum of light that object emits is basically dependent only on the temperature, so long as the only source of light is from thermal radiation (there are OTHER processes that will emit light as well; the point of a blackbody is that it is an idealized object that can only emit thermal radiation. Simply put, all objects with any temperature at all emit thermal radiation; that thermal radiation (light wavelengths) fill follow a type of normal distribution whose central limit is dependent on the temperature. In simple terms, the frequency distribution of the light will have the shape of a curve shown at right, with frequency on the X axis and intensity on the Y axis; the peak of the curve will be shifted further right for hotter objects and left for cooler objects. As some examples of this temperature dependence, humans have a temperature on order of about 300ish K, which corresponds to a frequency distribution whose peak is in the infrared. However, something like a lightbulb filament has a temperature on order of about 5000 K, which corresponds to an peak frequency somewhere near the middle of the visible range. If you look at the cosmic microwave background, which is basically the "temperature of space", it's about 3 K, which corresponds to a frequency peak in the (you guessed it) microwave range. However, it's important to note that this is a distribution and not a singular monochromatic light. The exact distribution (from which you could work out the relative amounts of each frequency of emitted light) is given by Planck's law. --Jayron32 16:35, 20 July 2023 (UTC)

I have no idea how to calculate this, but there must be a minimum yet greater than zero Kelvin temperature which under it no light will be emitted. A single photon of the longest wave light (deep red) has a fixed energy. When the energy of light is under that threshold, no light will be emitted. Zarnivop (talk) 17:21, 20 July 2023 (UTC)

Not necessarily. The limit is set by Planck's constant, which merely states that the smallest unit of light is the photon, but a single photon can have any arbitrarily small frequency of light. E = hν, so for any frequency of light, the smallest amount of energy for that frequency is just Planck's constant times the frequency, but there is no lower limit on frequency. "Deep red" is still very high frequency light, with wavelengths on the order of a micrometer (1 millionth of a meter) or so. The CMB light has wavelengths of cm scale, however meter-length wavelengths or longer are perfectly common. VHF frequency radio waves have wavelengths in the meter-to-tens of meters range, while light with wavelengths as long as hundreds of thousands of kilometers (see ELF) which have been used to practical effect by humans. There is no functional "longest wavelength of light". There is a functional "Smallest quantum of energy for a given wavelength" (the photon) but that's not the same thing. --Jayron32 17:37, 20 July 2023 (UTC)

Also, the light is emitted by a system of atoms, not by a single atom. If you've got 10²³ atoms forming a solid with a temperature of a few kelvin, there's more than enough thermal energy to emit a single visible photon. It's not very likely to happen though. PiusImpavidus (talk) 19:33, 20 July 2023 (UTC)

Light is by definition is bound between red (or at most IR) and purple (or at most UV). Radio frequencies are not light. Both are EM radiation, but you stated that anything above absolute 0 emits light. This is not true. EDIT: Anything above absolute zero emits photons, but not every photon is light - that depends on its energy. Zarnivop (talk) 22:27, 20 July 2023 (UTC)

I took upon myself to replace the image given here with the actual graph. The old graph accurately depicted that the maximum-emission wavelength changed with temperature, but (wrongly) implied that for a given wavelength, an increase of temperature could decrease the emission. That is not true - for all wavelengths, spectral emissivity increases with temperature. Tigraan^{Click here for my talk page ("private" contact)} 08:44, 21 July 2023 (UTC)

July 21

In two bottles of different volume, both emptied up to a vacuum, is the pressure on the seal of each the same?

In two bottles of different volume, both emptied up to a vacuum, is the pressure on the seal of each the same? Bumptump (talk) 01:00, 21 July 2023 (UTC)

I'd think so. Thought experiment: what causes the presssure? What mechanism would increase or decrease said pressure based upon the contents (or absence thereof) of the bottles? --jpgordon^{𝄢𝄆𝄐𝄇} 01:34, 21 July 2023 (UTC)

Assuming they're sitting next to each other, presumably each would experience the same air pressure. Are you thinking that the larger bottle would have more "suction" than the smaller one? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:15, 21 July 2023 (UTC)

I assume "emptied up to a vacuum" means that the sealed bottles each contain vacuum, and you're asking about the pressure exerted by the surrounding atmosphere. Then there are a couple of things to consider. First, since the atmosphere has weight, the atmospheric pressure varies according to altitude, so if one of the bottles is placed higher, then the pressure on it will be reduced. And second, it's not clear whether the original poster was asking about "pressure" in its proper technical sense (referring to the amount of force per unit area), or in the informal English sense where it just means a force that presses. If the pressure in the technical sense is the same on both bottles (the air is at the same altitude and temperature), then the force on the larger seal will be larger in proportion to its area.

In any case, the volume of the bottles is irrelevant. --142.112.221.64 (talk) 05:19, 21 July 2023 (UTC)

Why does electrocution stop after a few seconds in a bug zapper?

I have observed that when an insect is electrocuted in a bug zapper, there are typically a few sparks or flashes of light. Sometimes the insect will catch on flame in a tiny fire, and the body will burn for a few seconds before stopping burning. The lights and flames stop after a few seconds, but the insect body often, instead of falling, remains in position still connecting two wires.

Given that the body is still in position connecting two wires, why is it that after a few seconds, sparks or flashes of light stop appearing, and any fire is extinguished? Does that mean that electricity is no longer flowing through the insect's body, and if so, why does the electricity stop flowing if the body is still connecting the two wires?

—SeekingAnswers (reply) 05:48, 21 July 2023 (UTC)

Maybe once their little carcasses are dried up, they can't conduct electricity? Abductive (reasoning) 06:55, 21 July 2023 (UTC)

That is very likely the main cause - the corpse becomes non-conductive because it dries and burns up.

Another possibility (which, again, is less likely in my semi-informed opinion) is that the bug zapper needs time to recharge. A bug zapper is a discharge circuit where a capacitor is slowly charged when the circuit is open and then quickly discharged when the circuit is closed (by the poor insect). The charge time can be a couple of seconds while the discharge is much quicker (millisecond or lower) - but it’s hard to tell without a spec sheet of the electrical circuit, which I did not find in a quick online search.

Yes, discharge circuit is a redlink. Wikipedia does not have an article about everything, apparently. We have articles about Capacitor discharge ignition, cattle prod, bug zapper etc. but none of those give an electrical diagram. Tigraan^{Click here for my talk page ("private" contact)} 09:24, 21 July 2023 (UTC)