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October 4

Lens

Suppose a camera had lenses and one of them was a lens that was flat on one side and convex on the other, and you reversed it so the flat side was in the other direction. What would happen to the focal length? RJFJR (talk) 02:58, 4 October 2024 (UTC)

It would be like a minute change of a zoom objective. The direction of the change depends on the original orientation of the lens. That is because in this case the optical position of the lens is slightly beside the mechanical position. And the shift occurs because the direction of the difference goes to the opposite. 2A02:3032:305:F2EF:616E:4B30:D3CA:B0AE (talk) 09:55, 4 October 2024 (UTC)

Reversing the lens also affects the optical aberrations, which is why we sometimes want an asymmetrical lens. PiusImpavidus (talk) 15:08, 4 October 2024 (UTC)

The OP describes a plano-convex lens. The Focal length of the lens is the distance at which a beam of collimated light will be focused to a single spot and is given exactly by the lensmaker's equation. For most purposes this thin lens approximation can be used: ${\frac {1}{f}}\approx \left(n-1\right)\left[{\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}\right].$. Philvoids (talk) 19:00, 4 October 2024 (UTC)

I have read the article about lenses. The thin approximation is mentioned three times or so. But the real formula is not at all. 176.0.164.84 (talk) 11:28, 7 October 2024 (UTC)

nevermind. Found it. Don't know how I could overlook it. 176.0.164.84 (talk) 11:32, 7 October 2024 (UTC)

Physical Conditions where childhood development is essential to diagnosis

As I understand it, when someone is assessed for autism they are asked questions about their childhood behaviour and development as well as their behaviour now, even if they are well into adult life. This means that two middle-aged men with identical behaviours could receive different diagnoses if one displayed signs of autism as a child and the other didn't.

If that is right, and sorry if it isn't, then are there any examples of physical conditions which are diagnosed the same way? Where displaying symptoms as a child is an essential part of the diagnosis, and two patients displaying identical symptoms in adult life may be diagnosed differently?

81.106.106.219 (talk) 12:43, 4 October 2024 (UTC)

Not an expert by any means, but our autism article says it is a neurodevelopmental disorder that is manifest in early childhood, and therefore a history of the condition is highly pertinent. Alansplodge (talk) 20:16, 6 October 2024 (UTC)

Correct. When even fairly young children are being evaluated, their earlier childhood gets questioned. When I inquired about this, I was told that the reason is to see what the behaviour of the person was like before they starting autistic masking. So, presumably, any other situations where masking (personality) can come into play would also form part of the OP's answer. Matt Deres (talk) 18:37, 10 October 2024 (UTC)

October 5

Polygenism

I can't remember who wrote that Homo sapiens derived from three different apes i.e. Europeans from chimpanzee, Africans from gorilla, and East Asians from orangutan. Thanks in advance.-- Carnby (talk) 07:23, 5 October 2024 (UTC)

Illustration from Winchell's Preadamites, 1888.

The biological racist Alexander Winchell 1824 - 1891 who vaguely states "The doctrine of evolution does not teach that any existing ape is in the direct line of man's ancestry, but that the simian line and the human line are united in remote generalized ancestors common to both groups".[1] is worth further searching in Preadamites Or, a Demonstration of the Existence of Men Before Adam (1888) . Philvoids (talk) 14:02, 5 October 2024 (UTC)

In the US, Samuel George Morton and Louis Agassiz were early exponents of the idea, at least in regard to black Africans. In Europe, Carl Vogt promoted the concept, and the influential Ernst Haeckel also espoused it. Both were German, and evidently the idea persisted well into the 20th century in Germany, because around 1980-ish I bought a UK paperback newly published (by Sphere Books?), translated from a German original, that gave a 'popular' modern account of it (and was of course utter tosh, though amusing): unfortunately I no longer seem to have it (though I collect wacky pseudoscience books) and can't remember the author or title.

[Edited to add] Strike that last, I've recalled (the name is, err, memorable) – it's The Beginning Was the End by Oscar Kiss Maerth, published in Germany in 1971 and in the UK 1973 (Sphere pb 1974, I suspect I bought a reprint). {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 16:49, 5 October 2024 (UTC)

Are any of these three types of apes able to cross-breed? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:30, 5 October 2024 (UTC)

It seems unlikely because of how long ago their lineages diverged: For comparison: chimps and bonobos about 2 million years ago, and can; humans and chimps/bonobos about 5–7 mya, and can't (different chromosome count, other primates 48, humans 46 owing to a post-divergence merger of two chromosomes); gorillas and h/c/b about 8 mya; orangutans and g/h/c/b about 17±2 mya. As far as I'm aware, humans, bonobos, chimps, gorillas or orangutans have never been observed to attempt a mutual intraspecies mating (orangs would never encounter the others in the wild), and it would obviously be unethical to attempt to "assist" such a thing except in vitro (good luck with getting funding). {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 19:36, 5 October 2024 (UTC)

Oh, it was tried by the Soviets, see Humanzee. Abductive (reasoning) 10:51, 6 October 2024 (UTC)

Well, the 46 vs 48 chrmosomes may not completely prohibit chimp-human interbreeding. A similar situation exists with horses and asses, but mules are still a thing. If human-chimp crosses are possible, the resulting "humanzee" would likely be sterile. But if you think chimp-gorilla breeding experiments would be unethical... hooo boy, those ain't got nuthin' on this. --User:Khajidha (talk) (contributions) 21:48, 5 October 2024 (UTC)

Hence, it seems highly unlikely that human descendants of these three species would somehow magically be able to interbreed, yet they can. Humans are a single species. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:43, 5 October 2024 (UTC)

Although somewhat hybridised with Homo neanderthalis, Denisovans, and at least one other as-yet-unidentified archaic human (from genetic evidence).

There is some disagreement within anthropology as to whether these are or are not different species, or varieties of the same species (Professor Clive Finlayson, Director of the Gibralter National Museum thinks so, for one) and indeed which of the 30-odd differing definitions of 'species' is applicable. 94.6.86.81 (talk) 18:31, 6 October 2024 (UTC)

Very true. The concept of "species" is highly questionable. For example are Przewalski's horse and domestic horse the same species, despite the fact they have a different number of chromosomes? In the Plant kingdom it is even worse. I suspect that many different species in the well-known genera Quercus and Sorbus are variation of the same species.-- Carnby (talk) 21:01, 6 October 2024 (UTC)

There is only the one human species. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:41, 6 October 2024 (UTC)

There is, now, of course: it even has a lower genetic diversity than all other primate species, and most other mammal species. The question is how many there were 50,000, or 200,000, or 500,000, or 1,500,000 years ago. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 00:50, 7 October 2024 (UTC)

No one doubts it. Except perhaps for some isolated African populations (i.e Khoisan and Pygmies) that could be considered perhaps subspecies, from a merely zoological standpoint. But no matter: a Senegalese, a Korean, and a Norwegian belong to the same species and subspecies.-- Carnby (talk) 09:24, 7 October 2024 (UTC)

October 6

Undissected in Geological Terms

I was looking at the article for Mount Kaimon and noticed the term "undissected" being used as a descriptive for the volcano. I'm unfamiliar with this usage of the term and am having trouble finding a clear explanation elsewhere. What's more, there's already a comment on Talk:Mount_Kaimon asking this same question, so there's surely more than just me who doesn't understand. Is there a clearer way to describe what "undissected" means as a descriptor in this article and the other articles that use the same terminology? Amstrad00 (talk) 00:48, 6 October 2024 (UTC)

It's one that's not dissected. Dissection in this sense means a volcanic cone that's built up by repeated eruptions, but has since been eroded or otherwise affected by processes other than its own eruption (folding, or being cut through by intrusive igneous features). So an undissected volcano is typically a younger one, either still or relatively recently active.

Here's one description of an old, dissected, volcano: Iddings, Joseph P. “The Dissected Volcano of Crandall Basin, Wyoming.” The Journal of Geology 1, no. 6 (1893): 606–11. http://www.jstor.org/stable/30054881. Andy Dingley (talk) 01:12, 6 October 2024 (UTC)

I see you've added a footnote to the article which resolves my issues as far as keeping things understandable for those unfamiliar with the term. Thanks for your explanation and edit to the article, I'll go ahead and add similar footnotes to the other volcano articles I've found with that term in the lead. Amstrad00 (talk) 03:20, 6 October 2024 (UTC)

I have created redirects for Dissected volcano and Undissected volcano (and a redirect target: Volcano#Dissection).  --Lambiam 16:17, 6 October 2024 (UTC)

Watching the gulls eat

I was wondering. Considering that a seagull can swallow a pound of food in about 10 seconds flat and seagulls will fight until bloody over scraps of food - what environment did they evolve into that necessitated this behaviour? Before humans got involved and the gulls came inland and scavenged rubbish and begged for food from people, just how harsh and brutal was their original biome? 146.90.140.43 (talk) 20:30, 6 October 2024 (UTC)

As noted at Gull#Diet_and_feeding, they'll eat just about anything. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:37, 6 October 2024 (UTC)

Indeed. A gull will eat just about anything. But I was thinking about how aggressive gulls are with each other when feeding and how fast they eat when food is available. Did they evolve somewhere that necessitated this behaviour? Out at sea? Because there's lots of available food on the sea shore. Cockles, mussels, limpets, crabs, etc. Or maybe the seagulls can't open the shells. 146.90.140.43 (talk) 20:55, 6 October 2024 (UTC)

The environment could well be our garbage dumps. Evolution can be rapid and in fact usually is. Here are two articles, Metabolic Adaptation of Certain Seagulls to Our Changing World, and Changing gull diet in a changing world: A 150-year stable isotope (δ13C, δ15N) record from feathers collected in the Pacific Northwest of North America. Abductive (reasoning) 22:46, 6 October 2024 (UTC)

In their natural environment, I think gulls mostly catch fish and scavenge carcasses floating in the sea. There is one species that does more than that, but it is quite rare when compared to the others. Iloveparrots (talk) 00:19, 7 October 2024 (UTC)

It's an error to think that Gulls are predominantly sea/ocean dwellers that have "come inland" recently. To quote from that article's lede:

"Gulls are typically coastal or inland species, rarely venturing far out to sea, except for . . .".

And from the Diet and feeding section:

"The food taken by gulls includes fish and marine and freshwater invertebrates, both alive and already dead; terrestrial arthropods and invertebrates such as insects and earthworms; rodents, eggs, carrion, offal, reptiles, amphibians, seeds, fruit, human refuse, and even other birds. No gull species is a single-prey specialist, and no gull species forages using only a single method. The type of food depends on circumstances, and terrestrial prey such as seeds, fruit, and earthworms are more common during the breeding season while marine prey is more common in the nonbreeding season when birds spend more time on large bodies of water."

{The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 01:01, 7 October 2024 (UTC)

Growing up in the English countryside, a flock of gulls following the plough for worms in autumn used to be a common sight. Minimum tillage may have changed that, plus fish and chips. MinorProphet (talk) 09:48, 13 October 2024 (UTC)

Gulls seem to be very fond of school playing fields, regardless of their proximity to the sea. I imagine they find creatures like "leatherjackets" (crane fly larvae) and devil's coach horse beetles. Alansplodge (talk) 16:48, 13 October 2024 (UTC)

"Feeding Frenzy"

We have about 50 images of that on commons.  Card Zero  (talk) 05:46, 14 October 2024 (UTC)

October 7

Naming of gorgonin

I'm trying to write a history section on Gorgonin, a protein found in some corals. Searches for the discoverer turned up a 1939 paper and 2019 book (WP Library link), both of which agree that a specific 1855 paper by Valenciennes was the first to name it "gorgonin". But in the paper itself it appears to name the substance "cornéine". Am I'm missing something? It seems like they can't both have just not read the paper, especially considering the book has a different page range listed than the 1939 paper does.

Basically, I have three questions:

• (The book is unclear on this, and it's hard to understand through the bad English) Is gorgonin a substance (not just made of one protein and no other constituents), a single protein, or does it vary?
• Does anyone know what "iadogorgic acid" is? The book describes its discovery as the beginning of the study of "gorgonin as a substance"
• Am I missing something with regards to the naming situation? It seems confusing.

Mrfoogles (talk) 23:09, 7 October 2024 (UTC)

https://archive.org/details/zeitschriftfrbi23unkngoog/page/92/mode/1up had some discussion of the name. Apparently gorgonin and cornein are different? Personally I think both authors you linked must have made a mistake, since gorgonin isn't mentioned in the French paper. HansVonStuttgart (talk) 09:44, 9 October 2024 (UTC)

It seems that gorgonin is collagen-like. There are many collagens, in humans there are now 28 (last I read about this there were 21). In the case of gorgonin (and, like collagen, there has to be more than one, as it is found in 500 species that have had a long time to diverge), it seems that the collagen-like material is secreted (and possibly altered later) to be more resistant to dissolving in water than our collagen. Abductive (reasoning) 20:53, 9 October 2024 (UTC)

Oh, and it's named after the coral, Gorgonia, so named by Linnaeus in 1758, presumably after the Greek mythological Gorgons. Abductive (reasoning) 20:57, 9 October 2024 (UTC)

October 8

What percentage of a ship is under water?

I was wondering how much of a ship is actually under water. Of course we know that weight equals displacement, but what is the relationship between the volumes of the underwater parts to the overall volume of the main hull, and the overall volume of the cubic contents (including superstructure)? For a submerged sub, it's 100% under water - that's easy. But how a about the Japanese battleship Yamato? Or a modern ultra-large crude carrier like the TI-class supertankers? For those we at least get the difference between unloaded and loaded displacement (67,591 tonnes empty - which is still up there with the largest battleships ever built, and 509,484 tonnes fully loaded - which is stupendous). --Stephan Schulz (talk) 11:56, 8 October 2024 (UTC)

The fraction of volume under water is equal to the density of the ship divided by the density of the water. Problem is, how do you define the volume of the above water parts? Volume of the fully enclosed space, volume of the smallest convex surrounding (sorry, forgot the proper maths term), volume of the bounding box? PiusImpavidus (talk) 16:38, 8 October 2024 (UTC)

The mathematical term is "convex hull", but for a ship with a tall mast this is not a reasonable approach. A typical ship design has a relatively small number of relatively small openings, such as hatches and ports, that will be closed under severe storm conditions in order to keep the ship from taking water. This creates a closed surface enclosing the ship; it seems reasonable to me to use the enclosed volume for the total volume, also when the hatches and ports are open. This does not work for an open boat, such as a rowboat, but imagine a custom-made cover of fabric for the boat to keep rainwater out and we have again a closed surface that determines a specific volume.  --Lambiam 20:38, 8 October 2024 (UTC)

Indeed. The background (though not quite scientific) is that I'm currently looking for physics gaffes in ancient German pulp SF novels. One of the problems is that the authors don't quite get the square-cube law, and thus their giant spaceships with (so they think) giant masses turn out to have the density of a puff pastry. I would like to get some comparison data for real ships. So for volume think e.g. Space Battleship Yamato. --Stephan Schulz (talk) 21:06, 8 October 2024 (UTC)

I did calculate an airship. 2500 m high and 1:8:64 aspect ratio. With 10 cm average hull thickness it can lift a whole village into an earthquake area. With 15 cm it doesn't even fly. (There were other assumptions that may modify the numbers slightly) 176.0.162.62 (talk) 21:18, 8 October 2024 (UTC)

Surely it will depend entirely on the architecture and materials of each individual ship design? I don't see how there could be a simple formula or whatever relating to all ships. For example, the same design could be constructed using any one of many woods of different densities, or of various metals, and the percentage would be different for each variant.

Consider also vessels using hydrofoils. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 17:15, 8 October 2024 (UTC)

That's why I listed two concrete examples. --Stephan Schulz (talk) 20:21, 8 October 2024 (UTC)

Titanic = 100%, submarines = 100%, Enterprise = 0%. --217.149.171.88 (talk) 17:18, 8 October 2024 (UTC)

If you exclude your parenthetical (including superstructure) there is a term for this ratio which is reserve buoyancy. That is a redirect and probably a more explanatory article would be freeboard. I've looked for a value for Yamato but just WP's Yamato-class battleship#Armor "...designed with a very large amount of reserve buoyancy..." I don't know what would help for the volume of a superstructure but maybe you could put some limit on it by assuming a cuboidal cow (see block coefficient for different types of ships) and noting that metacentric height must be > 0. fiveby(zero) 00:56, 9 October 2024 (UTC)

Archimedes Principle: buoyant force (upwards) = volume displaced. For a watertight hull with gunwales (outer walls) above the waterline, you draw an imaginary line across the waterline: the volume of non-water-continuous-with-the-sea that's under that line, times weight-density of water (i.e. times density times g), equals the buoyant force. (To set this as an equation, for simple shapes and approximations you can use areas of triangles/prisms, while for more complex shapes you probably want to use integral calculus.)

With no other forces (such as lift from hydrofoils or flat-bottom planing), the boat's waterline is determined where buoyant force = its total weight -- that is, its total mass times g. (This is mass that you would measure by weighing on drydock, for example -- it's independent of how you would think about floating on water.) If your ship's total mass is unknown, but you generally know about stuff like the enclosed volume and what kind of materials are involved, then you would consider the wall thicknesses, enclosed space, etc.

Note that the air inside the enclosed space is often ignored in calculations because there is air outside too -- the air outside provides buoyancy as well, but since an enclosed seagoing ship is mostly filled with air, that cancels out. However, for an airship, the buoyancy of air is the critical consideration. SamuelRiv (talk) 19:16, 9 October 2024 (UTC)

October 9

A spacewalk odyssey

When Alexei Leonov couldn't get back into the airlock at the end of his space walk and had to let the air out of his space suit to get back in, for how long was he without air? Also, was this the inspiration for the decompression scene in Space Odyssey 2001? 2601:646:8082:BA0:2424:470:A683:D4AF (talk) 00:13, 9 October 2024 (UTC)

The article says, "He opened a valve to allow some of the suit's pressure to bleed off..." As to whether that influenced the 2001 scene, I couldn't say. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:10, 9 October 2024 (UTC)

The Voskhod 2 spacewalk was in March 1965; Stanley Kubrick and Arthur C. Clarke drafted the screenplay for 2001: A Space Odyssey in 1964–5, finishing in December, and filming was in 1966–7, during which both screenplay and novel were further amended. (Note that the screenplay was not based on the novel 2001: A Space Odyssey (novel) by Clarke and Kubrick [sic]; instead the two were written in parallel, with many variant scenes proposed and dropped, and the two works ended up with some differences.)

Leonov's difficulties and the necessity of depressurising his spacesuit were not immediately revealed by the Soviet authorities, and only emerged "later" (though I haven't discovered exactly when), so it's unlikely that Kubrick & Clarke knew about them when writing. Clarke doesn't mention the event in The Lost Worlds of 2001.

Yes, the Soviets were not terribly good at admitting their space programme cock-ups; both the 1960 Nedelin catastrophe and the 1980 Plesetsk launch pad disaster weren't publicly acknowledged until 1989. Alansplodge (talk) 11:54, 10 October 2024 (UTC)

An answer might be found in Michael Benson's 2018 book Space Odyssey: Stanley Kubrick, Arthur C. Clarke, and the Making of a Masterpiece, which unfortunately I don't have. Anyone? {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 18:52, 9 October 2024 (UTC)

Thanks! So, the answer to the second question is that Clarke didn't know -- right? So that leaves the first question: for how long was Leonov without air? 2601:646:8082:BA0:98A8:D148:F8F4:4270 (talk) 02:25, 12 October 2024 (UTC)

Leonov was never without air because the decompression was partial. And what Clarke did know or not is pure speculation because Clarke was able to look into the future. Clarke did know about satellite tv before it was invented, to use a well known example. 176.0.154.204 (talk) 04:54, 12 October 2024 (UTC)

Your second question was, Was Leonov's having to let some air out of his space suit the inspiration for the decompression scene in 2001: A Space Odyssey? If Clarke, who co-wrote the screenplay, didn't know of the Leonov incident, the answer can only be "no". Leonov takes about the incident in an episode of the PBS special "The Russian Right Stuff", which aired in 1991. However, even if Clarke somehow already knew all about this when the screenplay was written, I see no reason to think that it might have been a source of inspiration for which in the film is a completely different scene.  --Lambiam 08:11, 12 October 2024 (UTC)

October 12

Space iceberg?

On average, what's more massive: an iceberg or a comet? 2601:646:8082:BA0:98A8:D148:F8F4:4270 (talk) 02:26, 12 October 2024 (UTC)

Google is your friend. "Density of a comet" gives 0.5-1.0 g/cm³[2] or a mean value of 0.52 ± .01 according to this 2022 paper, while "density of an iceberg" spits out 0.92. Clarityfiend (talk) 07:15, 12 October 2024 (UTC)

You answer on density, not on mass. To convert this info, we would also need the volume distributions of icebergs and comets. I don't think we even have good definitions of how small an iceberg can be and still be a berg ;-). The largest iceberg we have reliable data on is Iceberg B-15, with a surface area of 11007km². I could not find the height, but Ross estimated the depth of the ice shelf as a bit under 300m on the edge (where the berg would have broken off), so that would make it a volume of about 3700km³ corresponding, at the density given above, to 3400 million tons. NASA says comets are "from a few miles to a few tens of miles wide". Let's call it 30km for a biggish one, which makes it about 13500km³. That makes it significantly heavier than B-15, mo matter which density of the given range we use. And, of course, Pluto, at 1.3025e16t, would be a comet if it ever came to the inner solar system. So I would think that on average comets are bigger, but it depends on what you define as iceberg and comet. --Stephan Schulz (talk) 07:51, 12 October 2024 (UTC)

Unless you're asking about the average mass, in which case (ballpark numbers) 10¹⁴ kg vs 10¹⁰, respectively. Clarityfiend (talk) 07:28, 12 October 2024 (UTC)

• The largest known comet is called C/2014 UN271 (Bernardinelli–Bernstein) whic has an ice core "approximately 80 miles across, making it larger than the state of Rhode Island... Its mass is estimated to be a staggering 500 trillion tons". NASA article.
• The largest known iceberg was Iceberg B-15, which " measured around 295 km × 37 km (159 nmi × 20 nmi)". You can do the maths. Alansplodge (talk) 16:59, 13 October 2024 (UTC)

"Respectively" needs clarification, as a commentator reversed the order already. I believe from google that you mean to say that the average mass for comets is 10¹⁴kg, while the average for icebergs is 10¹⁰kg.

Of course the internet loves to not give citations for raw numbers, and as both icebergs and comets span an enormous range of sizes they are difficult to get a representative sample for which the "average" is meaningful (and I would guess a more meaningful average would have to be something like RMS instead of an arithmetic mean.)

To get to the sources, I actually think Google's AI-aided results have gotten better. The text is still wrong, but they do provide the principal source for the text, which the other results do not; and for comet size it's space.com which cites ESA's article on comets, which says that the nucleus is "usually several kilometers across" based on observation data (space.com says 10km or less). This will be biased to more massive comets, based on the visibility of passing objects, but no matter, because the only way we get to the 10¹⁴kg number for a comet (density 0.6) is by calculating from the maximum nucleus volume, not the average. As for icebergs, I think I can get the 10¹⁰kg number by taking the antarctic iceberg tracking data (a selection of the very largest icebergs visible by satellite), multiplied by the thickness of antarctic sea ice (1--2 meters) and sea ice density, which gives 6x10¹¹kg, which is ballpark. So I think these numbers looking at something closer to the very largest icebergs vs the very largest comets, instead of the averages.

I have not been able to find ready sources attempting to systematically find average masses. I found one taking a random survey of sea ice of all types, but nothing to compare it to, and it's difficult to convert the measured areas to full masses given the varieties of sea ice involved.

To conclude, an "average" is undetermined until we get a survey that gives some landscape of small-sized comets and icebergs. Every example given so far only measures the largest examples. SamuelRiv (talk) 17:57, 13 October 2024 (UTC)

Sea ice is frozen sea water, which can be a few metres thick. Icebergs are pieces that have broken away from glaciers and can be several hundred metres thick. For the largest icebergs, that gives 4000 km² times 300 m times 920 kg/m³ is about 10¹⁵ kg. The range in size is very wide. A small iceberg could have a 20 by 20 by 6 metre pyramid above the surface, giving a mass around $6\cdot 10^{6}$ kg. Looks like a very large iceberg is more massive than a big comet, but most icebergs are less massive than a small comet. PiusImpavidus (talk) 08:47, 14 October 2024 (UTC)

Thanks for catching this. Yeah, the table of iceberg sizes with heights is in the article (and Universal Compendium has similar table that includes mass estimates).

I found in Sulak et al 2017 a distribution and model for Arctic icebergs (sampled from a few Nordic fjords), including volume calculation. This and other studies show that the distribution of iceberg area follows a power law with some head and tail divergence. (They also model apparent breadth, surface area, and total volume of icebergs as a power law with a rather good fit.) Among three fjords studied, they report mean volumes (excluding largest and smallest sizes), with an average between them of about 40x10⁴ m³ (average area about 40x10² m²), which gives an average mass of 3.7x10⁸ kg.

They also gave an average for the "maximum"-sized icebergs they found (not sure on the methodology with that number), which is 1.8x10⁸ m³ among the fjords, giving 1.7x10¹¹ kg.

Arctic ice is considered much thicker than Antarctic ice (which is what my numbers in the previous comment were, that User:PiusImpavidus used). I believe I looked up the Antarctic tabular icebergs as having average thicknesses closer to 30 m rather than 300 m. I'm not sure where their number comes from still: a tracking survey of "the largest icebergs" in the Antarctic is what I had originally used, so I'm guessing they are using the largest iceberg, A23a, at 3672 sq km. I'm not sure if the absolute maximum sizes are illustrative of anything here. You can find a continental-sized iceberg in Earth's history, or you can find a comet the size of Pluto (which of course is another debate). SamuelRiv (talk) 14:42, 14 October 2024 (UTC)

As an interesting aside, your question's wording is vulnerable to a variant of Simpson's paradox: In a hypothetical scenario, let's say every day for a year, you see one comet and one iceberg pass. In this hypothetical, on the vast majority of days, the comet you see that day is much bigger than the iceberg, while on only a couple days you had an enormous iceberg be bigger than the passing comet. Then if you total up the day-by-day as like a win-to-loss record for the year, one can accurately say that "on average, a comet is bigger than an iceberg".

Alternatively, you can total all icebergs for all the days over the entire year and find the average iceberg size, and all the comets and find the average comet size, and then compare the average iceberg to the average comet in that sense (even if that might not be representative of they type of iceberg and comet that pass by each other on the same day). If there are many small icebergs that are smaller than most comets, but then only a handful of totally gargantuan ones that skew the average size to be larger than the average comet, then you can accurately say that "an average iceberg is bigger than an average comet".

My previous response ended with a caution about comparing maximum sizes, that the largest comet is (arguably) the size of Pluto, and discounting unobserved minimum sizes. The paper I linked mitigates this by truncating the size bounds in its analysis. SamuelRiv (talk) 15:36, 15 October 2024 (UTC)

Pollen mites

Pollen mite is a redlink, so if there's an existing article, I'd like to create it as a redirect. Would it be a good redirect to the article about the genus Chaetodactylus? At least some members of the genus are pollen mites — I first encountered the concept a few minutes ago when Special:Random showed me Chaetodactylus krombeini — and the genus article says These mites usually kill young bee larvae and feed on provisioned pollen and nectar, but it's quite possible that some pollen mites are members of other genera. Google finds references to a pollen mite Mellitiphis alvearius, but Special:Search finds zero references to a genus Mellitiphis, so I'm wondering if it's just an alternate name. Nyttend (talk) 20:24, 12 October 2024 (UTC)

What I discovered by searching for pollen+mite:

• Things that eat pollen are called palynivores. The article lacks a section on mites.
• Varroa jacobsoni#Evolution says Cleptophagous mites eat pollen and other nutrients stored by bees, but it's unclear what that has to do with that kind of Varroa mite, and I think the whole section has been directly copied from the source.
• One of these kleptoparasites is Parasitellus. It inhabits bumblebees, but steals their pollen.
• Phytoseiidae#Lifestyles says that "type 4" (did we get tired of naming species?) feed primarily on pollen.
• Hummingbird flowers Lobelia laxiflora have a mite that lives inside them eating nectar and pollen.
• Typhlodromips swirskii is cool because it eats pests until all the pests are gone, then survives on pollen until they come back.
• Generalists like Euseius concordis are similar, and eat some pollen sometimes.

The C. krombeini article strongly implies that "pollen mite" is the common name (if a misnomer) of the genus Chaetodactylus. I guess I should have been searching for evidence of that instead of finding all this other stuff.

OK, now I've found a site that says "the scientific name is Melittiphis alvearlus", and a forum that says "pollen mites are usually Carpoglyphus lactis". This may be a situation where asking three beekeepers will produce three different answers.

From those names, I found the very specific and practical site Bee Mite ID.  Card Zero  (talk) 04:05, 13 October 2024 (UTC)

I have not checked all of it, but at least substantial parts of the text of Varroa jacobsoni echo, with minor variations, text found in

Oldroyd, B. P. (1999). "Coevolution while you wait: Varroa jacobsoni, a new parasite of western honeybees". Trends in Ecology & Evolution, 14(8), 312–315. doi:10.1016/s0169-5347(99)01613-4.

V. jacobsoni, as described there, is parasitic, feeding on bee larvae, and not cleptophagous.  --Lambiam 14:20, 13 October 2024 (UTC)

Bee Mite ID mentions only Melittiphis and Chaetodactylus as "pollen mites", so a disambiguation page linking to those two (with a redlink for the first) seems like a good start.  Card Zero  (talk) 18:58, 13 October 2024 (UTC)

aren't redlinks forbidden on disambiguation pages? Won't be a stub article a better idea? 176.0.148.153 (talk) 19:57, 13 October 2024 (UTC)

Yes. I thought vaguely the redlink would cause somebody to make the article, didn't know about this rule.  Card Zero  (talk) 20:31, 13 October 2024 (UTC)

See MOS:DABRED. They're allowed if there's an article that mentions them (and is also redlinked). Clarityfiend (talk) 21:05, 13 October 2024 (UTC)

a redlinked article can mention something? 2A02:3032:302:3F8E:5531:CB3D:1EB2:F4FC (talk) 02:34, 15 October 2024 (UTC)

October 13

Chicken's ancestors vs. ours

I have heard it claimed that at some point in prehistory, the chicken's ancestors ate our ancestors. Is that actually true? Animal lover |666| 17:20, 13 October 2024 (UTC)

My ancestors weren't eaten by prehistoric chickens 🏃‍♀️🏃‍♂️🐤 - well at least not until after they'd had eggs/babies :-) NadVolum (talk) 17:38, 13 October 2024 (UTC)

It's likely true. Chickens are Birds, which are surviving therepod dinosaurs, which originated around 230 million years ago and (it is thought) were originally mostly carnivorous or omnivorous. Avialae, the clade including bird ancestors, became distinct from other Theropods perhaps around 160 million years ago. We are primate mammals, whose ancestors the Mammaliformes evolved some time between 200 and 150 million years ago, were mostly small, and were undoubtably predated by many dinosaurs, including some Avialae. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 20:41, 13 October 2024 (UTC)

Astonishingly, this question is an existing Google search term: "common ancestor of chickens and humans". The top result, from Nature, a reputable scientific journal, says:

The most recent common ancestor for humans and chickens is thought to have been some kind of primitive reptile that lived more than 310 million years ago. [3]

Alansplodge (talk) 11:49, 14 October 2024 (UTC)

But unless it was cannibalistic, this common ancestor is not an example of an ancestor of the birds eating an ancestor of the primates.  --Lambiam 17:22, 14 October 2024 (UTC)

Ah yes, misread the question (again). Alansplodge (talk) 08:54, 15 October 2024 (UTC)

The split between the clades Sauropsida (which includes chickens) and Synapsida (which includes us) took place about 312 million years ago.^[4] There was ample opportunity for the carnivorous theropods in the ancestral line of today's chickens, which appeared 231 million years ago, to snack on contemporaneous siblings of some of our ancestors.  --Lambiam 17:56, 14 October 2024 (UTC)

October 14

Does the Minkowski space (or the Min. metric) add, any empirically verifiable information, to Einstein's original Special Relativity theory?

Just as Einstein's Special Relativity theory added some empirically verifiable information, to what scientists had known about physics. HOTmag (talk) 08:01, 14 October 2024 (UTC)

No it doesn't. It is a name for the mathematical structure of the space described in Special Relativity. If you take it away you just make things cumbersome and can't talk properly to physicists. It would be like taking complex numbers away from electronics - it would make formulae bigger and annoy people. NadVolum (talk) 09:06, 14 October 2024 (UTC)

That's what I think as well, but surprisingly, your first sentence is not mentioned (nor hinted) in our article Minkowski space, although it's a very important point that should have been pointed out, IMO. HOTmag (talk) 09:47, 14 October 2024 (UTC)

The earliest empirical confirmations of special relativity announced by Einstein in 1905 included Arthur Eddington's photographic record of the Solar eclipse of May 29, 1919. I expect that Eddington was aware of Minkowski's lecture that presented his Spacetime diagram in 1908. Philvoids (talk) 09:17, 14 October 2024 (UTC)

AFAIK, this solar eclipse has nothing to do with special relativity. HOTmag (talk) 09:43, 14 October 2024 (UTC)

The very first sentence of Minkowski space says "In physics, Minkowski space (or Minkowski spacetime) is the main mathematical description of spacetime in the absence of gravitation", and later in the lead "Minkowski space is closely associated with Einstein's theories of special relativity and general relativity and is the most common mathematical structure by which special relativity is formalized". It says it is used in formalizing special relativity, it does not say it is a theory or anything like that. That's straight in your face! No extra 'hinting' is needed! NadVolum (talk) 11:10, 14 October 2024 (UTC)

In physics, Minkowski space (or Minkowski spacetime) is the main mathematical description of spacetime in the absence of gravitation. Yes, but I can't see any relation between this fact and my question in the title.

Minkowski space is closely associated with Einstein's theories of special relativity. Of course, just as the electric force - actually expressed by Coulomb's law, is closely associated with the magnetic force - actually expressed by the Lorentz force law. Yet, the Lorentz force law, does add some empirically verifiable information to Coulomb's law. For the same reason, the sentence you've quoted from our article Minkowski space, doesn't rule out the possibility that the Minkowski space adds some empirically verifiable information to Einstein's theory of special relativity.

Minkowski space...is the most common mathematical structure by which special relativity is formalized. Of course. That's because the Minkowski space is an integral part of Special relativity. However, my question in the title didn't ask whether the Minkowski space added new information to "Special relativity", but rather whether the Minkowski space added new information to "Einstein's original Special Relativity theory".

That's why I'm still asking, if you think the article should have pointed out the very important fact (IMO), that the Minkowski space added no new information to "Einstein's original Special Relativity theory. HOTmag (talk) 11:54, 14 October 2024 (UTC)

No I see no good reason for thinking the article should say irrelevant things like that. Find a reliable source if you want to add it. NadVolum (talk) 13:20, 14 October 2024 (UTC)

Isn't your first sentence (in your first response) based on a reliable source? If it is, then what does your last sentence (in your last response) mean? HOTmag (talk) 13:24, 14 October 2024 (UTC)

No what I said is not based on a reliable source. This discussion is not an article. NadVolum (talk) 13:46, 14 October 2024 (UTC)

I'm quite surprised. You are calling - the relation between the Minkowski space and Einstein's theory of Special relativity - "irrelevant things", but you admit that your own opinion (about this relation) - that the Minkowski space adds no empirically verifiable information to Einstein's original Special Relativity theory - "is not based on a reliable source".

Anyway, we will probably remain in disagreement, about whether this relation is "irrelevant" (as you claim) or "very important" (as I claim). I wonder what other users think about this controversy between us. HOTmag (talk) 15:26, 14 October 2024 (UTC)

There are experimentally verifiable geographic facts, such as that Europa and Asia are part of a connected landmass that is not connected to the Americas. There are many ways to create flat two-dimensional maps of the surface Earth, such as the Mercator projection and the Mollweide projection. The maps are alternative ways of describing the same geographic reality; obviously, they cannot produce new verifiable geographic facts. Likewise, Minkowski space is an alternative way of mathematically describing the same physical reality; it cannot produce new verifiable physical facts.  --Lambiam 17:18, 14 October 2024 (UTC)

Yes, that's what I think as well, as I have already responded to the user above you, but then I asked them a follow-up question, as you can see above. HOTmag (talk) 07:08, 15 October 2024 (UTC)

I'm not sure what the follow-up question is. In my opinion, it would be curious, to say the least, to see some statement in Wikipedia to the effect that the Molweide projection did not add any empirically verifiable information to geography. It is not different for Minkowski space and physics.  --Lambiam 15:26, 16 October 2024 (UTC)

Violation of the conservation of energy by virtual particles, vs violation of the formula E=mc^2

Virtual particles, appearing out of the cacuum, are known to be a (theoretical) instance violating the conservation of energy.

Is there also any instance (even a theoretical one only), violating the formula $E_{0}=m_{0}c^{2}$ (while $E_{0}$ denotes a given body's rest energy and $m_{0}$ denotes the body's rest mass)? HOTmag (talk) 12:56, 14 October 2024 (UTC)

Theory says they don't. However they can for instance have negative kinetic energy which balances the equation. NadVolum (talk) 13:25, 14 October 2024 (UTC)

What do you mean by "they"? Do you mean virtual particles?

Additionally, what do you mean by "don't"? Do you mean they don't [violate the conservation of energy]? Or don't [violate the equation $E_{0}=m_{0}c^{2}]?$

Additionally, could you elaborate on your second sentence? HOTmag (talk) 13:35, 14 October 2024 (UTC)

Yes they refers to a virtual particle, but really since one never comes across an actual isolated virtual particle one should be considering the whole configuration, see On shell and off shell. NadVolum (talk) 13:42, 14 October 2024 (UTC)

Thank you. HOTmag (talk) 15:28, 14 October 2024 (UTC)

I don't think they're violating conservation of energy. Yes, they "exist" and would have mass. At the same time they're entangled to have a zero sum of mass. That means, if you observe one of the particles into existence, the other particle automatically achieves negative mass equivalent to the observed particle. Such a "negative" particle is for all intents and purposes like an anti particle,but with one exception. If it encounters it's partner (entangled or not) it doesn't annihilate, it merely nihilates. That is like annihilation but without releasing energy. 2A02:3032:302:3F8E:5531:CB3D:1EB2:F4FC (talk) 02:30, 15 October 2024 (UTC)

October 15

Audio Engineer vs. Music Engineer

Are these two things interchangeable? Or is there a meaningful difference? Trade (talk) 01:44, 15 October 2024 (UTC)

Audio is reciting too. 2A02:3032:302:3F8E:5531:CB3D:1EB2:F4FC (talk) 02:09, 15 October 2024 (UTC)

Neither are engineers, but we let them bask in reflected glory. Greglocock (talk) 04:18, 15 October 2024 (UTC)

Seriously tho both audio engineer and music engineer are sharing the same Wikidata item and i need to figure out if i should split them Trade (talk) 05:13, 15 October 2024 (UTC)

Is a music engineer the same as a music producer? Some random website about careers thinks audio and music engineers are different, although it implausibly claims that the primary skill for an audio engineer is video, and I don't know why music engineers need to know R.  Card Zero  (talk) 05:27, 15 October 2024 (UTC)

Engineering in the recording industry can be very well defined. There are engineers who focus solely on drum kits and nothing else. There are engineers who focus solely on microphone gear and placement and nothing else. If you ask them for their title, they might say they are a sound engineer or recording engineer or audio engineer or music engineer. The title isn't important. The skill being implemented during the production of a recording is what is important. My short experience (installing Sony hardware in one studio) involved working with engineers in front of and behind the glass. The ones in front of the glass set up mics, cables, etc... The ones behind the glass worked on the audio levels, mixes, and such. They worked together, but did not do each other's jobs. Then, when finished, more engineers came in and worked on optimizing the mix for CD compression (this was pre-MP3 days). So, in summary, the title means whatever they want it to mean because the title is not directly related to the job performed. 12.116.29.106 (talk) 13:09, 15 October 2024 (UTC)

The behind glass people can also be called "sound desk operators", if you want a less vain designation. Graeme Bartlett (talk) 05:12, 16 October 2024 (UTC)

I’ve been practising audio engineering at my college. When I’m in the studio, I would call myself a recording engineer or mixing engineer. Pablothepenguin (talk) 16:56, 16 October 2024 (UTC)

Electron energy level in atoms

Depending on the excited state of the atoms, some electrons are in a higher energy state than in their ground state. But what is the distance from the nucleus of an electron when its energy level increases, does it move away or does it move closer? Does its angular velocity increase or decrease? Malypaet (talk) 11:36, 15 October 2024 (UTC)

The usual type of excitation is that that electron moves into a different atomic orbital. The mathematical definition of an electron's state does include among other things both angular-momentum details and something similar to the average distance from the nucleus. The exact types of change depend on which orbitals are involved. But remember that electrons are not objects that "orbit", so the idea of simple closer vs further or faster vs slower, as one might visualize planetary motion, is an incorrect model that leads to many incorrect thoughts. DMacks (talk) 11:52, 15 October 2024 (UTC)

As in the naive Bohr model, the expected distance of an electron to the nucleus of an atom, given its orbital, is determined by the principal quantum number n of that orbital. Here, "expected distance" means the mean distance obtained by experimental measurements, which make the orbital wave function collapse. There is a relationship between the energy and this expected distance, although the precise picture is complicated; see Electron shell § Subshell energies and filling order.  --Lambiam 06:02, 16 October 2024 (UTC)

For the naive person that I am, I understand that the electron is a particle with a mass and moves in a particular probabilistic way around an atomic nucleus having a kinetic energy (${\frac {1}{2}}mv^{2}?$). So, if the most energetic electrons are the furthest away, what is the force that keeps them with the nucleus, an increase in their electric charge in relation to their energy level, , or whatever else? (I understand that with a soup of electrons rotating around a nucleus we are in a world of probability.) Malypaet (talk) 13:18, 16 October 2024 (UTC)

It is a vibrating cloud of excitations to which you cannot assign a velocity. Perhaps the answers given here will help you.  --Lambiam 15:38, 16 October 2024 (UTC)

Thanks Malypaet (talk) 21:41, 16 October 2024 (UTC)

Another way to think about the energy of an electron in an orbital is by considering its ionization energy - the energy it would take to remove it. For hydrogen atoms, the energy needed to remove a ground state electron is 13.6 MeV, so we say the n=1 energy level has energy -13.6 MeV.

An electron in a higher level requires less work to knock it off. For n=2, the required energy is only 3.4 MeV, meaning an electron at the n=2 level is 10.2 MeV MORE energetic than n=1, at -3.4 MeV. PianoDan (talk) 22:46, 16 October 2024 (UTC)

This is similar to a gravitational orbital system, in which a body in a more distant orbit needs less energy to extract itself from the system. Malypaet (talk) 09:28, 17 October 2024 (UTC)

Did you confuse electrons with neutrons? MeV are nuclear, electrons are in the range eV to keV. 176.0.163.195 (talk) 13:58, 17 October 2024 (UTC)

October 16

Total global river discharge rate

Is there an estimate for the total global discharge rate of surface / ground water to the sea? It would be nice to state e.g. the Amazon as a percentage of the global total, just as we do for areas and populations of large countries. — kwami (talk) 06:23, 16 October 2024 (UTC)

I googled "amazon river total discharge rate" and it led me back to Amazon River, which says "The Amazon River has an average discharge of about 215,000–230,000 m3/s (7,600,000–8,100,000 cu ft/s)—approximately 6,591–7,570 km3 (1,581–1,816 cu mi) per year, greater than the next seven largest independent rivers combined." ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:25, 16 October 2024 (UTC)

Yes, rather amazing. We used to have a circle graph in that article that gave percentages, but the numbers were bullshit so I removed it. It would be nice to have an accurate graph, though: the full circle would be the global total, with pie slices for individual rivers. — kwami (talk) 07:55, 16 October 2024 (UTC)

Daylight saving time - why change on different dates?

In the UK & Europe, daylight saving time this year runs from 31 Mar – 27 Oct.

In the USA & Canada, it's 10 Mar – 3 Nov.

In Australia, the opposite changes are 7 Apl – 6 Oct.

Why not make them coincide? Surely there would be cost savings on all sides? Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 15:12, 16 October 2024 (UTC)

Why have DST at all? :D

Speaking a bit more seriously: isn't the debate more about abolishing DST than making it consistent across countries? According to this Bloomberg article from 2021, there are moves to do so in the US and the EU. Double sharp (talk) 15:20, 16 October 2024 (UTC)

There is also discussion in America of making DST permanent. But nothing ever gets done. America and Europe's dates used to be pretty close to coinciding, but America expanded it some years back. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:17, 16 October 2024 (UTC)

In Australia it's determined on a state-by-state basis. It's settled down now to a consistent set of dates, but Queensland and Western Australia both adopted and abandoned it more than once. For some decades now neither state has had DST, which makes it fun and games when working out times in the eastern states, and when travelling east-west or reverse, during the summer period. This is all because our Constitution makes no mention of time as a Commonwealth responsibility, which means it's automatically a state matter. -- Jack of Oz ^{[pleasantries]} 17:07, 16 October 2024 (UTC)

Also state-by-state in America: Daylight saving time in the United States. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:15, 17 October 2024 (UTC)

Well, sort of. As I understand it, states have the option to observe DST or not, but they do not have the option to choose their own starting/ending dates. I'm not really convinced that this restriction is constitutional (I have a fairly narrow view of the Commerce Clause) but there doesn't seem to be any great advantage for a state to challenge it. --Trovatore (talk) 00:21, 17 October 2024 (UTC)

Yes, that's what I was trying to say. And presumably interstate commerce is the justification for the federal law. If I remember correctly, the need for standard time was driven by the railroads, in place of a myriad of local times. And also, if I recall correctly, it used to be that the railroads worked strictly within standard time, even during DST, as DST was only sporadically used until 1967. Once DST became standardized, the railroads could change to DST also. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:15, 17 October 2024 (UTC)

While we have an article on Summer time in Europe, it is not very detailed. I found what appears at glance to be a reliable and well-researched article on the history of European time zones at "When Did DST Start in Europe?" via timeanddate, which suggests that Central European Standard Time as we know it (with its onset date) really began its continuity and spread from the Nazi conquests. (Other countries had been experimenting with daylight saving, but inconsistently, as the article explains.) The incongruity in clock-switch dates would be due to the haphazard nature of daylight saving being adopted in various countries, where countries tend to only finally decide to align their clocks with some treaty or conquest or absolute trade necessity. (Of course there are famous exceptions: the U.S. state of Indiana only adopted daylight saving in 2005, despite the rest of the continental U.S., including the entire surrounding time zone, having uniform daylight saving dates.) SamuelRiv (talk) 01:56, 17 October 2024 (UTC)

Be careful — CEST does not stand for "Central European Standard Time" (easy mistake to make as a North American) but for "Central European Summer Time". It's the opposite of what you would expect from PST / PDT. CET is UTC+1; CEST is UTC+2. --Trovatore (talk) 06:08, 17 October 2024 (UTC)

As for Indiana, I assume that's because they're so far west in their time zone, making DST a double misery for night owls and farmers. They really should be on Central Time and then it would be much less of a problem. --Trovatore (talk) 06:18, 17 October 2024 (UTC)

Oh, and not quite true about "the rest of the Continental US" -- Arizona, except for the Navajo Nation, does not observe DST. I expect that's because they're far enough south that the difference between summer and winter times doesn't justify it. Not sure why other southern states don't do the same thing. --Trovatore (talk) 06:21, 17 October 2024 (UTC)

My nerdy brain tells me that, logically, daylight saving should run for the same amount of time either side of the summer solstice. It doesn't in my state of Australia. My ageing memory tells me that the finishing date was extended further into autumn by a populist state premier who wanted more people to go to the Formula 1 Grand Prix. HiLo48 (talk) 02:16, 17 October 2024 (UTC)

Your logic may fail to take into account that the Equation of time is not symmetrical, owing to that pesky 0.0167 eccentricity of the Earth's orbit: see the end of the Practical use section. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 03:47, 17 October 2024 (UTC)

What difference would it make? HiLo48 (talk) 03:53, 17 October 2024 (UTC)