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November 15

Why are Koalas vulnerable to extinction

Hi. I was wondering why Koalas are vulnerable to extinction unlike Kangaroos, which are way more common, and both animals are found in Australia. Please let me know. Thanks. 2605:B100:142:A3B7:1D63:4EBE:694C:7BCA (talk) 04:22, 15 November 2024 (UTC)[reply]

The article has some information on it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:54, 15 November 2024 (UTC)[reply]

Habitat loss, especially lack of connected habitats, chlamidia, overcrowding, dogs. I doubt they are anywhere near extinct. Greglocock (talk) 05:17, 15 November 2024 (UTC)[reply]

It might have been quicker to Google your question - this was one of the first results; Threats To The Koala. Alansplodge (talk) 11:44, 15 November 2024 (UTC)[reply]

Kangaroos are more flexible in what they eat, and can move large distances faster. But koalas are cuter and so have more public awareness and are used as the poster animal, like giant pandas. Graeme Bartlett (talk) 23:52, 15 November 2024 (UTC)[reply]

More generally, the more specialised an organism is, the less likely it is to go extinct as a result of competition from other species but the more likely it is to be affected by environmental changes. So Koalas aren't going to have to worry about some other similar animal taking over its territory and taking all the eucalyptus for themselves. But they would be vulnerable to anything that killed off the eucalyptus. Iapetus (talk) 12:42, 19 November 2024 (UTC)[reply]

Admiral Nakhimov

In the time leading up to the shipwreck in late August 1986, is it known whether Captain Victor Tkachenko of the Petr Vasev had been transferred there from a smaller ship? Because I've read an article a while ago in Science et Vie (the Russian version) about the human factors in that disaster, and this would be the only conclusion which would make any sense! 2601:646:8082:BA0:CD5E:73B7:6DF6:2CF6 (talk) 14:50, 15 November 2024 (UTC)[reply]

I think the question is better suited at WP:RDH. ExclusiveEditor _{Notify Me!} 20:56, 16 November 2024 (UTC)[reply]

Why don't plants photosynthesize efficiently?

Photosynthesis is 6% efficient in green plants, 20% in solar panels. I see hints that it's more efficient in red algae, but I can't find a figure. They need to be efficient because they live in low light environments. There's a note here at Artificial_photosynthesis#Some_advantages,_disadvantages,_and_efficiency which says photosynthesis is typically 1% efficient! What's up with that? Something about not having enough CO2 around in the air to have any use for the energy? I found this article which says For the cell, a steady input of electrical energy coupled to a steady output of chemical energy is best: Too few electrons reaching the reaction center can cause an energy failure, while “too much energy will cause free radicals and all sorts of overcharging effects” that damage tissues, but that seems to boil down to "the cells can't do it". Card Zero (talk) 20:54, 15 November 2024 (UTC)[reply]

Evolution doesn't necessarily aim for perfection, just for survival. If that 6 percent is good enough for survival, there would likely be no evolutionary pressure to do it "better". ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:55, 15 November 2024 (UTC)[reply]

Trees compete for light, so there's some pressure to grow faster, isn't there? Card Zero (talk) 23:15, 15 November 2024 (UTC)[reply]

If you want to compare solar panel effiency, you should compare production of a chemical like glucose from carbon dioxide using electricity. Or should we allow any other reduced and useful carbon compound. As plants do not just produce electricity. Graeme Bartlett (talk) 23:23, 15 November 2024 (UTC)[reply]

Photosynthesis in plants can be very efficient under the right conditions. For instance, from photon to hydrogen/ATP it is nearly 100%,because the difference to really 100% is what destroys the chlorophyll. And replacing destroyed chlorophyll is costly, energywise and sometimes it even costs magnesium. Therefore that part is developed to maximize efficiency. Another goal is in the development of the carbon dioxide capture. For this one must know that chemical reactions with gases are very dependent on the pressure of the gases. Even the direction, that is if it's exothermic or endothermic, depends highly on the pressure. If RuBisCo would be faster the carbon dioxide could not come fast enough onto the site of enzymatic activity and would therefore drop in pressure there. Which in turn would drive the demand for energy up in this pathway. To overcome the RuBisCo-limit the C4 plants were developed. But they have other deficiencies, where they additionally spend energy to capture carbon dioxide for storage, and don't get it back at the RuBisCo.

Generally plants have too much energy for the amount of water and, most important, carbon dioxide, to synthesize sugar. Some hydrogen has to be dumped into the production of Ethen and Latex or other hydrocarbons. Of course, the energy for this is typically not counted towards the efficiency of photosynthesis. Moreover some ATP is simply hydrolysed for heating. Or for regeneration of ADP. Whichever is needed where this takes place.

For comparison there exist bacteria where chemical reactions are driven by 1/16th of a proton, that is 1/64 ATP-Unit. That only works with a large Quantum state in a superposition. If someone would want to maximise the efficiency of the photosynthesis, the recipe is there for the taking. But think of the side effects! 176.2.78.14 (talk) 06:02, 16 November 2024 (UTC)[reply]

For this one must know that chemical reactions with gases are very dependent on the pressure of the gases. Even the direction, that is if it's exothermic or endothermic, depends highly on the pressure. If RuBisCo would be faster the carbon dioxide could not come fast enough onto the site of enzymatic activity and would therefore drop in pressure there.

Does this mean that plants photosynthesize more efficiently in environments with elevated air pressure? Can you recommend any resources for learning more about that? Thank you! -- Avocado (talk) 14:21, 16 November 2024 (UTC)[reply]

@Avocado Not air pressure but partial pressure of carbon dioxide. That's standard in greenhouses. See Greenhouse#Carbon dioxide enrichment for details. Mike Turnbull (talk) 12:57, 20 November 2024 (UTC)[reply]

Thank you! Is there any research about elevated air pressure, too? IIRC, humans absorb oxygen more efficiently at higher air pressures (up to a point), so it seems like it might make sense (based on both that and what little I know about gas exchange across membranes) for plants to absorb CO2 better at higher air pressures as well. -- Avocado (talk) 21:02, 20 November 2024 (UTC)[reply]

humans are developed to an oxygen pressure of 0,22 atm. Over it there are many reactions that disturb the physiology, under it there is to over 0,17 atm no difference as long as no (not the least amount) Carbon monoxide comes into play. But even 0,11 atm is sufficient for up to 2 hours. At this low pressure of oxygen no normal combustion is possible but nobody needs an oxygen mask immediately. In case of a fire that is a great advantage for fire fighting. 176.3.66.65 (talk) 23:04, 22 November 2024 (UTC)[reply]

What about near volcanos?

Are there specialized plants growing in carbon dioxide rich environments that photosynthesize faster? Card Zero (talk) 12:42, 16 November 2024 (UTC)[reply]

No. I heard there are only a few places where there is consistent outgassing of CO₂ and yes, plants grow faster there. The thing is, plants are so starved for CO₂ that increasing CO₂ concentration instantaneously leads to increased sugar production. We think that the current photosynthesis evolved in a time when the atmosphere was like Venus's with perhaps 100 times the partial pressure of CO₂. Even now, you can put a houseplant in a pure CO₂ atmosphere in a glass vessel, and it does great. Another way of putting this is that there can be no natural selection for specialization in growing in a "carbon dioxide rich environment" since that would entail getting worse at using CO₂. Abductive (reasoning) 21:07, 16 November 2024 (UTC)[reply]

Thermometer thermal mass

I'd like to measure the air temperature in a room, outdoors, etc. Ideally by bringing the thermometer, turning it on if it is electronic, and looking at it. All thermometers that I've tried take several minutes to settle, which is annoyingly long. Is that inherent? Are there quicker ones? Don't want to spend a fortune, but "premium" is ok. Thanks. 2601:644:8581:75B0:0:0:0:2CDE (talk) 22:12, 15 November 2024 (UTC)[reply]

For an expensive high-tech solution use tunable diode laser absorption spectroscopy which should measure the temperature in the gas, rather than waiting for it to conduct into a detector. see https://www.yokogawa.com/solutions/products-and-services/measurement/analyzers/gas-analyzers/tunable-diode-laser-spectrometer/#Overview for a product. Graeme Bartlett (talk) 23:45, 15 November 2024 (UTC)[reply]

a really cheap way to go at it would be Resistance thermometer of course in Four-wire configuration. If the coil is very short, which is possible in four wires, then it will get the temperature in under a second. 176.2.78.14 (talk) 01:36, 16 November 2024 (UTC)[reply]

Thanks both, the resistance thermometer approach sounds promising. The tunable laser page says "request a quote" which means "too expensive for me to think about". 2601:644:8581:75B0:0:0:0:2CDE (talk) 02:45, 16 November 2024 (UTC)[reply]

An infrared thermometer retails at around USD 10, and reacts in less than a second from when you press the button. It doesn't measure air temperature but if you can assume your walls/floors/furniture/etc are about the same temp, it'll work. 85.76.117.61 (talk) 15:45, 16 November 2024 (UTC)[reply]

I have one but it is not very consistent between surfaces, and the air temperature can change faster than the furniture temperature. I guess it is better than nothing. Thanks. 2601:644:8581:75B0:0:0:0:2CDE (talk) 02:13, 17 November 2024 (UTC)[reply]

November 17

A lead zeppelin is your stairway to heaven?

In terms of fatalities per passenger-mile, and excluding combat losses during World War 1 (but including accidental losses during the same time period), which airships were more dangerous to fly in, those filled with hydrogen or with helium? I'm aware of the argument that helium-filled airships have a narrower flight envelope, which causes them to crash more often -- but, on the other hand, the flammability of hydrogen often had the effect of turning an otherwise survivable crash into one which is fatal for everyone on board, and also created the danger of explosion from lightning strike -- so between these two dangers, which one was the greatest? 2601:646:8082:BA0:CD5E:73B7:6DF6:2CF6 (talk) 03:41, 17 November 2024 (UTC)[reply]

Is there a source for the claimed explosion? It is not plausible, scientifically. --Lambiam 08:48, 17 November 2024 (UTC)[reply]

In what way not plausible? If your objection is to do with needing oxygen, that airship probably leaked: six months previously, "many small tears appeared". Card Zero (talk) 09:39, 17 November 2024 (UTC)[reply]

It would leak hydrogen out, not oxygen in. --Lambiam 10:16, 17 November 2024 (UTC)[reply]

So if a leak of hydrogen into air is hit by lightning, on top of a balloon made from sausage skin that's filled with more hydrogen, how do you imagine events would unfold after that? Hindenburg_disaster#Lightning_hypothesis says that airship fires have been observed under these kind of circumstances. I'm surprised that they were only fires, it makes the outcome sound mild, like lighting a gas stove. Card Zero (talk) 10:52, 17 November 2024 (UTC)[reply]

If there's a leak in the gas bags, it's plausible you may get an explosive mixture in the space between the gas bags and the outer hull. What exactly happened to Dixmude may never be known, but whether it was an explosion or rapid burning, too rapid for an orderly emergency landing (Hindenburg burned all its lifting gas in about half a minute), doesn't matter; all on board would be dead anyway. PiusImpavidus (talk) 14:00, 17 November 2024 (UTC)[reply]

That would indeed explain it. Without prior mixing with oxygen-containing air, hydrogen burns fiercely in a rapidly advancing front, as seen in the Hindenburg disaster, but not so rapid that there is an explosion. --Lambiam 16:46, 17 November 2024 (UTC)[reply]

I found a source, but no explanation. --Lambiam 10:30, 17 November 2024 (UTC)[reply]

According to the footnote in this republished 1923 article, there was an inquiry in January 1924, so maybe there is a report out there somewhere. Sean.hoyland (talk) 10:38, 17 November 2024 (UTC)[reply]

This is hard to say...

A helium-filled airship has less lift for the same volume, so it has to compensate somehow: fewer passengers and passenger-kilometres, giving more accidents per passenger-kilometre, or lighter skin, frame or engines or less fuel, all increasing accident rate.

A helium-filled airship is less likely to burn. The hydrogen fire itself isn't very lethal (except for those sitting high up in the envelope), but it can accelerate the destruction of the airship, leading to a faster crash, and set the skin and fuel on fire, leaving burning wreckage, which can kill passengers.

A third effect, which you didn't mention, is the heat capacity ratio. Helium has a heat capacity ratio of 1.66, hydrogen of 1.41, just like dry air, and moist air has an even lower heat capacity ratio. This means that on descent, helium heats up by adiabatic compression faster than hydrogen or the surrounding air, increasing the stability of the airship. When flying in slightly superadiabatic dry air, a hydrogen-filled airship is unstable in altitude. If it descends, the lifting gas heats up slower than the surrounding air, decreasing lift and accelerating the descent. This is no problem for helium-filled airships. Those have difficulty changing altitude faster than the time needed to equalise inside and outside temperature.

When looking at fatalities per passenger-kilometre, it's best to look only at passenger flights. Including military flights, test flights and accidents on the ground will increase the number of accidents without adding passenger-kilometres, making the airship appear more dangerous. Worse, those were the most dangerous occasions for airships. Ground accidents happened when the airship was grounded for bad weather, test flights were obviously more dangerous than regular flights and even when excluding combat damage, military flights were more dangerous as the airship was flown in weather and through manoeuvres that no captain would attempt on a civilian flight. However, excluding all military flights will exclude all helium-filled rigid airships, so no useful statistics are left. The safety record of those four helium-filled rigid airships of the US Navy doesn't appear too good though: three fatal crashes in only a third of the flight hours of Graf Zeppelin. PiusImpavidus (talk) 16:50, 17 November 2024 (UTC)[reply]

As noted in List of airship accidents, there is a variety of causes, a number of them being weather-related. The most successful airship was the Graf Zeppelin, which was filled with hydrogen, but never burned up or crashed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:55, 17 November 2024 (UTC)[reply]

There were no helium-filled passenger airships - they were all operated for naval reconnaisance. Alansplodge (talk) 15:56, 19 November 2024 (UTC)[reply]

There are some modern helium-filled non-rigid or semi-rigid passenger airships, used for sightseeing, but there are no hydrogen-filled modern airships, so there's no useful comparison possible. There are both helium-filled and hydrogen-filled gas balloons, but that isn't really the same thing. PiusImpavidus (talk) 09:57, 21 November 2024 (UTC)[reply]

Land surveying

Does modern land surveying (such as placement of streets after another, width of roads and blocks etc.) in take place using metric units in countries such as Canada, Australia and New Zealand, which have used metric distances for many decades now? Is there any English-speaking country that had already metricated when first surveys for 19th-century cities were done? Are there any downtown grids in English-speaking areas where streets are placed exactly 100 metres apart, and there are ten streets per one kilometre? In grids that place 16 streets per mile, the number of metres passed eventually deviates from number of 100 metres (hectometres) passed, since one mile is not exactly 1,600 metres. Placing ten streets per mile indicates number of miles passed by fourth-to last digit of house numbers, but does not indicate number of feet (or any other imperial unit) passed by whole number. By contrast, placing ten streets per kilometre indicates both number of kilometres passed by fourt-to last digit of house numbers and number of metres passed by whole house numbers. This placing is common in Argentina, but does it occur in any English-speaking country? --40bus (talk) 16:01, 17 November 2024 (UTC)[reply]

There are 100 meter blocks in Melbourne, Australia if I remember correctly. Mile/km/block-based addresses is not the original England way which was to count plots or buildings and call an unexpected new building in between the address of its neighbor suffixed with a letter or fraction. Manhattan's a hybrid: 1 address pair per 20ft plot of ownable (non-street) distance except 1 axis is 100 per block causing gaps like 153, 155, 201 except 3LPM5's 100 per 2 blocks cause Lex+Mad are new. Sagittarian Milky Way (talk) 05:48, 18 November 2024 (UTC)[reply]

The Melbourne blocks are 200 metres and then only by a coincidence; they are actually 10 chains or 660 feet, which happily converts to 201.17 metres. See Hoddle Grid for the details. Alansplodge (talk) 15:38, 19 November 2024 (UTC)[reply]

This is a new South Australian development near to where I live and the blocks are measured in metres, but not in nice whole metres. Zoom in and move the map to see details of the blocks. https://villawoodproperties.com.au/community/oakden-rise/find-buy/interactive-masterplan/ TrogWoolley (talk) 09:41, 18 November 2024 (UTC)[reply]

The same inaccuracy as 16 per mile then. Sagittarian Milky Way (talk) 01:29, 20 November 2024 (UTC)[reply]

Just to note that Australia, South Africa, New Zealand and Canada all began metrication in the 1960s or very early 1970s, so using metric measurements for any official purposes in the 19th-century would be highly improbable. Alansplodge (talk) 15:54, 19 November 2024 (UTC)[reply]

Is the any English-speaking country that already used metric measurement for official purposes in the 19th century? Was there anything that was measured in metric during Victorian times in the UK? --40bus (talk) 21:20, 19 November 2024 (UTC)[reply]

There was apparently a 6 mm government cartridge specification, the 6mm Lee Navy. I haven't dug up a contemporary source using mm, but it looks like it was so named even in 1895. (Note though the alternate .236 name.) Card Zero (talk) 06:26, 20 November 2024 (UTC)[reply]

The Abridgment: Containing Messages of the President of the United States to the Two Houses of Congress (1898) p. 480:

"Ten thousand 6 mm. Lee straight pull rifles have been supplied..." Alansplodge (talk) 12:44, 20 November 2024 (UTC)[reply]

On the subject of weapons, the QF 2-pounder naval gun of 1915 was made by the very British firm of Vickers and had a calibre of exactly 40 mm, but was known in British service by the weight of its shell in Imperial measure. The use of metric units here may be connected with the acquisition by Vickers of the Maxim Nordenfelt Guns and Ammunition Company in 1897, which although a British company, had its origin in the company owned by Thorsten Nordenfelt, a Swedish inventor. Alansplodge (talk) 12:33, 20 November 2024 (UTC)[reply]

A near miss though. Québec was a French colony using French units until 1763, switched to Imperial units after that, which was only 32 years before France metricated.

South Africa is an even nearer miss. It (or at least, the Cape Colony) was a Dutch colony until 1795, which is the year when the Netherlands metricated. The British then introduced Imperial units as they took over. Dutch rule was briefly restored in 1803–1806, but it appears this was too short to make the switch to metric. The Boers went their own way, continuing the use of traditional Dutch units (no longer used in the Netherlands) until Imperial units were made the standard in 1922: one of the last countries to switch to Imperial units. PiusImpavidus (talk) 19:31, 19 November 2024 (UTC)[reply]

How sampling rate in ADC adjusted or set ?

I am interested to learn how sampling rate in Analog-to-digital converter adjusted or set ? This page: Sampling (signal processing) didn't explain how it was adjusted. HarryOrange (talk) 18:36, 17 November 2024 (UTC)[reply]

Do you mean on a black box ADC (the sort of thing you have in a lab), or do you mean on an adc chip? Greglocock (talk) 22:00, 17 November 2024 (UTC)[reply]

@Greglocock I mean any typical ADC chip. How Sampling rate is adjusted? HarryOrange (talk) 05:03, 18 November 2024 (UTC)[reply]

I guess you read the data sheet for the chip. eg p41 and 42 here https://www.analog.com/media/en/technical-documentation/data-sheets/ad7768-7768-4.pdf Greglocock (talk) 06:04, 18 November 2024 (UTC)[reply]

An ADC sampling rate is determined by the data rate of the desired digital audio format. This article gives many examples of which 44.1 kHz, 48 kHz, 88.2 kHz and 96 kHz are typical. A designer simply ensures that an ADC chip receives a digital clock signal at appropriate frequency. Philvoids (talk) 20:17, 19 November 2024 (UTC)[reply]

Which is almost irrelevant to the question. An ADC chip or lab instrument can sample at many different rates. Greglocock (talk) 21:55, 19 November 2024 (UTC)[reply]

November 18

Open-air dust explosions

Dust explosion#Conditions required says There are five necessary conditions for a dust explosion. It even has a pointless diagram that arranges the five conditions in a pentagon with "dust explosion" in the middle. Condition 5 is confinement. But further down the page, Dust_explosion#Mechanism has a series of photographs demonstrating a dust explosion in open air. And thermobaric weapons, although more effective at killing people in confined spaces, seem to explode just fine in the open. So is condition 5, as a "necessary condition", plain wrong, perhaps an exaggeration of the fact that confinement makes a dust explosion more likely?

Supplementary question: I hear residents of Lahore and Delhi are wondering if their very sooty smog might one day explode. Is this at all plausible? Card Zero (talk) 00:09, 18 November 2024 (UTC)[reply]

Pointless? It is a five-pointed diagram. --Lambiam 06:53, 18 November 2024 (UTC)[reply]

In general, not only for dust, for detonation to occur, a mix of fuel and oxygen within the explosive limits has to be present in a compact largish volume. Upon detonation, the pressure in this volume will rapidly increase tremendously within (typically) microseconds. If the volume is not confined by an enclosure, the gases resulting from the combustion will expand supersonically with a shock wave that may or may not cause damage, depending on the power released and the environment. If the volume is confined by an enclosure, the enclosure may be able to withstand the pressure and contain the gases – possibly with controlled release through safety valves. (See e.g. Pyréolophore.) Otherwise, if the enclosure is broached, the gases will also expand explosively.

The OSHA fact sheet that is the source of our five-pointed list of conditions is actually about another scenario. It considers the case in which ignition merely leads to deflagration, which is much more likely to occur – the mix only has to be within inflammability limits. The combustion is much slower and does by itself not cause a shock wave. However, although the pressure rises less rapidly, the rise is still dramatic, especially if the volume is contained by an enclosure. If the enclosure cannot withstand the pressure, the gases will also expand explosively, as before.

So I think a fuel–oxygen explosion can occur in open air, but for this to be an explosion in the strict sense of causing shock waves, the right conditions will only very rarely be fulfilled accidentally. (In thermobaric weapons, they are fulfilled by design.) --Lambiam 09:05, 18 November 2024 (UTC)[reply]

But in the conditions there is no requirement of an accidental event?! 176.3.66.65 (talk) 15:10, 22 November 2024 (UTC)[reply]

The OSHA fact sheet does not deal with ways to mitigate the risk of intentional explosions, such as may be caused by weapons. You are free to see this as an omission; I doubt though they will agree. --Lambiam 12:00, 23 November 2024 (UTC)[reply]

Delayed onset muscle soreness

How long does it last and how to recover from it? CometVolcano (talk) 16:53, 18 November 2024 (UTC)[reply]

According to the article: "It peaks from 24 to 72 hours, then subsides and disappears up to seven days after exercise." --Amble (talk) 17:11, 18 November 2024 (UTC)[reply]

From the top of this page: We don't answer (and may remove) questions that require medical diagnosis... AndrewWTaylor (talk) 14:15, 19 November 2024 (UTC)[reply]

It is said that the soreness is helped by consuming protein. Abductive (reasoning) 10:27, 20 November 2024 (UTC)[reply]

November 20

John Balbus and Steven Balbus

Are Steven Balbus (Oxford University astrophysicist) and John Balbus (Head of Office of Climate Change and Health Equity in Biden's HHS) related? 178.51.16.158 (talk) 19:43, 20 November 2024 (UTC)[reply]

Given their mutual association with Philadelphia and their strong physical resemblance, it seems very likely, but I haven't been able to find any source confirming it with a cursory web search, so this might take some deep digging (better suited to someone in the USA, not Europe). John Balbus, incidentally, seems to me to be a good candidate for a Wikipedia article. {The poster formerly known as 87.812.230.195} 94.1.211.243 (talk) 02:13, 21 November 2024 (UTC)[reply]

They are brothers, with a third brother named Peter.^[1] Here on p. 33 is a photo of Steven en John side by side. Their father was Theodore G. Balbus,^[2] a radiologist, and their mother Rita S. Frucht.^[3] A bio of the father is found here, where you can also find that Peter runs a consulting firm called Pragmaxis. --Lambiam 10:09, 21 November 2024 (UTC)[reply]

November 21

Griffiths in math and physics

There's something called the Griffiths phase. If you search for griffiths phase activity so, you'll find things with similar names. A Griffiths singularity, Griffiths effects, there's probably more than one thing people call Griffiths' formula since there's a physicist called Phillip and two named David J. Griffiths. How many things are we dealing with under this name? Is there a book where they're all listed right next to each other? Gongula Spring (talk) 19:37, 21 November 2024 (UTC)[reply]

The concept of a Griffiths phase is named after theoretical physicist Robert B. Griffiths, who was the first to describe the appearance of such phases in an Ising model of ferromagnetism.^[4] He is also the eponym of the Griffiths inequality. Most uses of Griffiths singularity and Griffiths effect appear to be related. "Griffiths' formula" is a very general name that may refer to various formulas found by mathematicians with the surname Griffiths, such as Griffiths' integral formula for the Milnor number of an isolated hypersurface singularity, found by pure mathematician Philip A. Griffiths, also the eponym of the Griffiths group. See also Griffiths' theorem, named after yet another Griffiths. --Lambiam 23:43, 21 November 2024 (UTC)[reply]

That formulation seems at least superficially be leading to references to Alan Arnold Griffith. Formulas like ohmic or non ohmic dissipation in metallic griffiths phases used at the National High Magnetic Field Laboratory then tend to appear ambiguous to that effect too. Most other examples are deeply plunging into statistical quanta states thus unambiguously associated with Robert B. Griffiths instead. --Askedonty (talk) 00:13, 22 November 2024 (UTC)[reply]

The bracketing is not as in ((Griffith phase) field theory) but like (Griffith ((phase field) theory)), a theory of fracture, based on a phase-field model, developed by Griffith. --Lambiam 08:47, 22 November 2024 (UTC)[reply]

The interesting thing is that those approaches are leading us very near of a (a least to me ) finally rather satisfying view of the problematics induced by the idea of Action at a distance. --Askedonty (talk) 10:51, 22 November 2024 (UTC)[reply]

So much that you only have to think about it and what do you get? Long distances in apparent contradiction to.. --Askedonty (talk) 11:00, 22 November 2024 (UTC)[reply]

I'm not sure if these long distances anticipate my next question, which is what does "long-range" mean in the search results above?

Gongula Spring (talk) 15:54, 22 November 2024 (UTC)[reply]

Perhaps, as in #16 from that request as I get it "Temporal disorder in discontinuous non-equilibrium phase transitions: general results". The "long distances" discussion above being from 2002 by contrast. --Askedonty (talk) 16:39, 22 November 2024 (UTC)[reply]

Number 16 uses "temporal" and "critical" terms, are we getting toward ideas about long-range temporal correlations in critical brain dynamics? Are they spooky?

Gongula Spring (talk) 17:05, 22 November 2024 (UTC)[reply]

I don't think so. Or not so directly anyway. Number 16 seem to be about logic and geometry: distance in that context is fact, and can also be manipulated. Relevant quote if there was one regarding our subject - but their process define a temporal Griffiths inactive phase some time - relevant would be (see their pdf):

Disorder due to spatial or temporal inhomogeneities is almost an unavoidable ingredient in many real systems, it is then desirable to understand their effects on these phase transitions. For continuous phase transitions, it was earlier recognized that spatial and temporal disorder changes the critical behavior whenever the generalized Harris criterion is violated [11, 12]: quenched spatial disorder is relevant whenever dν⊥ > 2 is violated while temporal disorder is relevant when νk = zν⊥ > 2 is violated; with ν⊥, νk and z being critical exponents of the clean phase transition and d being the number of spatial dimensions. Since the critical exponents of the directed percolation universality class violate the Harris criterion, it was then argued that this was the reason why it was never seen in experiments [13] (see however Ref. 14).

(They describe their purpose as: Non-equilibrium phase transitions have constituted a rich and lively topic of research for many years. They occur in a wide variety of models in ecology [1], epidemic spreading [2], sociophysics [3], catalytic reactions [4], depinning interface growth [5, 6], turbulent flow [7], among other fields [8–10].) [8–10] refer to Nonequilibrium Phase Transitions in Lattice Models. Sociophysics is a product of Positivism#Logical positivism ( perhaps note there a spooky "component not derived from observation" ) --Askedonty (talk) 21:03, 23 November 2024 (UTC)[reply]

November 22

Heat of chillies

How hot, in terms of Scovilles, does a chilli need to be before a parrot can feel the burn? I just saw a video on Facebook of a macaw eating a ghost pepper without the slightest care. From what I read, parrots are extremely resistant to the capsicum from chillies. Or is it because we have thousands of taste buds and parrots have tens, which is also true. 146.90.140.99 (talk) 01:27, 22 November 2024 (UTC)[reply]

“The seeds of Capsicum plants are dispersed predominantly by birds. In birds, the TRPV1 channel does not respond to capsaicin or related chemicals but mammalian TRPV1 is very sensitive to it. This is advantageous to the plant, as chili pepper seeds consumed by birds pass through the digestive tract and can germinate later, whereas mammals have molar teeth which destroy such seeds and prevent them from germinating.” Card Zero (talk) 03:22, 22 November 2024 (UTC)[reply]

Yes, as Card Zero says, birds have different TRPV receptors (for vanilloids like capsaicin) than mammals. I guess chillis want their seeds distributed far and wide by birds. On the other hand, I've never seen anything eat the chillis that accidentally grow in my garden. Interestingly, my dog appears to have different TRPV receptors than me as they don't seem to notice very spicy chilli seeds on food and they won't be damaging the seeds. Sean.hoyland (talk) 03:32, 22 November 2024 (UTC)[reply]

Indeed, one of the most effective ways to keep squirrels off my bird feeder is to sprinkle the birdseed with chilli powder. Shantavira|^{feed me} 09:23, 22 November 2024 (UTC)[reply]

My entire home crop of capsicums (bell peppers to Americans), and some chillis disappeared in one night last summer right after a colony of fruit bats arrived in my local park. Fruit bats, of course, are mammals. HiLo48 (talk) 10:08, 22 November 2024 (UTC)[reply]

That's interesting because there are many bats here. They often sleep individually or in small groups inside young banana leaves that haven't unfurled yet. They sometimes crash into me at night if I'm moving. I guess in bat-world tree-like things don't move. They seem to have a chilli-free diet but might eat some of the other fruit. Plenty of insects to eat. Bat teeth seem to be quite diverse molar-wise. Chilli is the only thing that survives the wildlife. It's a multi-belligerent fruit-based forever war over resources with the birds, squirrels, rats, countless insects, fungi, bacteria and viruses. Sean.hoyland (talk) 15:50, 22 November 2024 (UTC)[reply]

Insect eating bats are very different from the fruit bats. There's a theory that peppers have the same sort of relation to fruit bats as chillis do to birds so I can easily imagine a fruit bat being partial to a couple of chillis even if it does find them rather hot. NadVolum (talk) 21:23, 25 November 2024 (UTC)[reply]

November 23

Before Puberty, sex organs are not functional?

How do sex organs function in both genders before puberty in humans? Not after Puberty. HarryOrange (talk) 07:24, 23 November 2024 (UTC)[reply]

Sexual maturity is only reached during puberty. Before it is reached, the sex organs are not (or not yet fully) functional. See also Sex organ § Development and Precocious puberty. --Lambiam 11:51, 23 November 2024 (UTC)[reply]

They're functional. It's just that their functions are generally under the headings of "basic maintenance" and "not atrophying". Abductive (reasoning) 09:39, 24 November 2024 (UTC)[reply]

To my understanding (which may be deficient), testicles prior to puberty are secreting some levels of androgens (including testosterone) and estrogens, which contribute to the male body's normal development, even though these levels are well below what they become during and after puberty. I imagine (perhaps wrongly) that similar considerations apply to the ovaries.

Our immediately relevant articles seem not very informative about pre-pubertal operations of the sex organs. Perhaps someone more knowlegable could take a look at them. 94.1.211.243 (talk) 09:46, 24 November 2024 (UTC)[reply]

I did take a look, I always do before answering a question. Here is a representative article; The immature human ovary shows loss of abnormal follicles and increasing follicle developmental competence through childhood and adolescence. The word "competence" means that in vitro the ovary tissue does a better job of taking on adult functionality the older the girl, but in vivo such activity is suppressed. Abductive (reasoning) 10:08, 24 November 2024 (UTC)[reply]

Nevertheless, if I've understood the peripheral hints I've encountered, those pre-pubertal levels of androgen and estrogen (and steroid, etc.) secretions are necessary at the time (the pre-pubertal period) for ongoing normal development, which is kinda what the OP asked about. Of course, all this is well above my pay grade. {The poster formerly known as 87.81 230.195} 94.1.211.243 (talk) 13:36, 24 November 2024 (UTC)[reply]

This discussion seems to have focused on the testicles and ovaries but the penis is also a sex organ and is capable of an erection before puberty. This is mentioned in our erection article in a sort of weird way given the flow on sentence. Ejaculation however only happens after puberty. I assume there is similarly some level of function in female sex organs. As mentioned in our masturbation article it's normal in children even in infancy and may even happen in the womb and is only a concern when there are indications it may relate to sexual abuse. Nil Einne (talk) 20:46, 24 November 2024 (UTC)[reply]

The penis as such is able to "ejaculate" well before puberty (somewhat dependent on definition) but because the prostata doesn't produce anything, there is nothing to ejaculate. So it's going through the motions way before the other organs are functional. 176.0.132.86 (talk) 05:20, 29 November 2024 (UTC)[reply]

November 25

Is there a cryonic company that will freeze me while I'm still alive and healthy, and reanimate me 15 years later? If I arrest the aging process for 15 years this way, could I then pass for a Gen Z?

Could I have myself cryofrozen (without dying of another reason first) in 2025 with instructions to reanimate me in 2040 so that I could more convincingly pass for and live like someone born in the Gen Z generation?

What companies cryofreeze people who ask for it while still alive and healthy?

Or does such a cryonic plan and company exist anywhere in the world?

I wanted to be born in 2000, not the year I was actually born in. So if I get cryofrozen for enough years, I'll look as young as a Gen Z when I'm reanimated.

Lastly, Reddit's r/Cryonics subreddit's automoderator keeps glitching out because it keeps autoremoving any content of mine from there. I tried posting this question and above summary to other subreddits but their automod keeps autoremoving it too. Their persistent glitches kept bugging me enough to dust off the Wikipedian reference desk and post here again for the first time in many years. I used to be a regular on the refdesk, then moved to Reddit, and now I'm back. --2600:100A:B005:AFD5:B08A:71E6:8521:5D8E (talk) 01:48, 25 November 2024 (UTC)[reply]

Short answer: No. As currently freezing a human adult, results in their death, as no resuscitation is possible. It would be some kind of murder to perform this, so only a crime syndicate would be willing. And then could you trust them for 15 years? Graeme Bartlett (talk) 01:59, 25 November 2024 (UTC)[reply]

In 15 years, you'd be just as deceased, pushing up daisies, no more, pining for the fjords. So what's trust got to do with it? Clarityfiend (talk) 08:34, 25 November 2024 (UTC)[reply]

At this point I feel bound to recommend that you watch Sleeper.Shantavira

Terraforming a planet around some distant star and setting up a population there sounds far easier and actually doable to me. Perhaps in the far future it'll be possible to create a new body and copy the brain fom one of those frozen blocks for it, or maybe set up an android with an artificial copied brain - but why would any people who could do that bother with anyone from this time, would it be ethical for us to try and make a Neanderthal clone? NadVolum (talk) 21:15, 25 November 2024 (UTC)[reply]

By way of a reference, try 'We don't yet have the know-how to properly maintain a corpse brain': Why cryonics is a non-starter in our quest for immortality. Alansplodge (talk) 11:53, 26 November 2024 (UTC)[reply]

Can any insurance company make a cryonics bankruptcy insurance policy for companies that preserve bodies in cryogenic preservation vats so that even when the company goes bankrupt, their insurance policies will keep these vats running and bodies preserved?

...So that we can continue the hope and possibility of reanimating these bodies back to life when medical science advances and finds cures to reverse whatever they died from?

This topic was also autoremoved from r/Cryonics so that's why I'm bringing it here too. Thanks in advance. --2600:100A:B005:AFD5:B08A:71E6:8521:5D8E (talk) 01:48, 25 November 2024 (UTC)[reply]

An insurance policy defines the amount of money to be paid to the holder of the policy when a specified contingency occurs. If the contingency is bankruptcy and the idea is to keep the company running, the amount should be larger than the prospectively unknowable debt to preferential creditors. It should be obvious that no insurance company can offer a policy with an unlimited payout. Apart from this, even an insurance for a sufficiently large amount cannot guarantee that the company or trustee will use the money paid out for the intended purpose. --Lambiam 02:53, 25 November 2024 (UTC)[reply]

Who would be a creditor? They're all dead and have no rights. NadVolum (talk) 21:00, 25 November 2024 (UTC)[reply]

Creditors of Instant Immortality (the bankrupt cryonics company, for short II) could be: (1) the tax office; (2) II's bank; (3) the company from which II hired its cryogenic equipment; (4) II's provider of liquid nitrogen; (5) II's lawyers; (6) scores of estates of frozen clients, legally presumed dead, who won a class action lawsuit against II. --Lambiam 11:43, 26 November 2024 (UTC)[reply]

Wow, is it April 1 already? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:00, 26 November 2024 (UTC)[reply]

Cryonics is such a blatant scam I don't understand how it is legal. Shantavira|^{feed me} 09:33, 26 November 2024 (UTC)[reply]

More blatant than (also legal) homeopathy? Clarityfiend (talk) 10:06, 26 November 2024 (UTC)[reply]

A marginally better idea might be to create a testamentary trust fund, if you could find a willing trustee. I'm not sure how far into the future you might want this to extend (do frozen corpses have a "best before" date?) but a legal expert might advise on how to extend the trust beyond the lifetime of the trustee, and what incentives might be required for another person to accept that role. Alansplodge (talk) 11:45, 26 November 2024 (UTC)[reply]

Where to verify a chemical compund name synonyms?

The ARM390 compound has multiple IDs, (some of?) which can be found at PubChem here:

https://pubchem.ncbi.nlm.nih.gov/compound/9841259#section=Synonyms

There are two among them, which differ with one zero only: AR-M1000390 and AR-M100390. The difference seems too small to be just a coincidence, it looks like one must be a typo modification of the other.

Is there any way for a non-chemistry/medicine-professional to trace the origin of those specific symbols and learn whether they are actually the same, or genuinely different? --CiaPan (talk) 08:09, 25 November 2024 (UTC)[reply]

PS. The motivation for publishing this question here is it's not only me in doubt – another user called for discussion at Redirect discussion: AR-M100390. The sources refer to both names, so from the Wikpedia point of view both are valid, but... Out of curiosity, I just would like to know: are they independent, truly different? CiaPan (talk)

Usually, I would trust ChemSpider to validate such synonyms and that's where I'd send a non-expert. In this particular case, Chemspider seems to prefer AR-M1000390 but one possible source of misinformation/typo is this paper, which consistently uses AR-M100390 in the text but AR-M1000390 in the citation #23, which is correct at doi:10.1016/S0024-3205(03)00489-2. Mike Turnbull (talk) 12:14, 25 November 2024 (UTC)[reply]

The earliest use of the name AR-M1000390 seems to be in a PhD thesis from 2003.^[5] The same name was used in a 2003 journal article in Life Sciences describing the results of this PhD thesis.^[6] The substance was synthesized by researchers from AstraZeneca R&D; their paper describing the design, synthesis, and pharmacological evaluation of the drug, published in 2000, does not use this name, but only the systemic name N,N-diethyl-4-(phenylpiperidin-4-ylidenemethyl)benzamide.^[7] Plausibly, the "AR" bit is short for "AstraZeneca R&D" and the whole was originally a code for internal use in the AstraZeneca lab. Subsequently:

AR-M1000390 was deposited on 2016-02-05; the source was the IUPHAR/BPS Guide to PHARMACOLOGY,^[8] which references the 2003 Life Sciences article.^[9]
The synonym ar-m100390 was deposited on 2017-09-13 by Springer Nature.^[10]
Yet another synonym: AR-M 1000390, deposited on 2024-11-14 by a chemical vendor.^[11]

--Lambiam 20:02, 25 November 2024 (UTC)[reply]

Thank you both, Mike Turnbull and Lambiam, for detailed info.

CiaPan (talk) 07:24, 26 November 2024 (UTC)[reply]

November 27

Right whales and Left whales

Why are there right whales, but not left whales? Someone who's wrong on the internet (talk) 09:05, 27 November 2024 (UTC)[reply]

Perhaps there's a naming dispute in the whale courts over brand names, a left vs wrong case. Sean.hoyland (talk) 09:32, 27 November 2024 (UTC)[reply]

You're thinking of the Narwhal. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:00, 27 November 2024 (UTC)[reply]

Not right versus left, but right versus wrong. This was the right species to catch. PiusImpavidus (talk) 10:10, 27 November 2024 (UTC)[reply]

Th answer is in the article you linked: Right_whale#Naming. Shantavira|^{feed me} 11:27, 27 November 2024 (UTC)[reply]

If a member of a group of whales manages to beach itself, and the others swim on, then the one on the beach would be a left whale. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:11, 27 November 2024 (UTC)[reply]

What is a wrong whale exactly? Someone who's wrong on the internet (talk) 23:19, 27 November 2024 (UTC)[reply]

The ones that don't fit the definition given in the article. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:42, 27 November 2024 (UTC)[reply]

There's also this:[12] ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:45, 27 November 2024 (UTC)[reply]

Maybe Gregory and Syme got to them. Iapetus (talk) 12:01, 28 November 2024 (UTC)[reply]

Lawson Criterion: calculating energy density W

Lawson Criterion

The article states:

Ion density then equals electron density and the energy density of both electrons and ions together is given by
$W=3nT$
where $T$ is the temperature in electronvolt (eV) and $n$ is the particle density.

However, there is no clear explanation given as to why the energy density equals 3nT, rather than 2nT or just nT. If the electrons and ions are in equal parts within the plasma, shouldn't it equal 2nT?

Is there any source that clears this up? — Preceding unsigned comment added by Shouldputsomethinginterestinghere (talk • contribs) 11:28, 27 November 2024 (UTC) Shouldputsomethinginterestinghere (talk) 11:27, 27 November 2024 (UTC)[reply]

The energy density of a monoatomic gas is

E={\frac {3}{2}}nT

. Both electrons and ions can be considered monoatomic gases, so the total energy density is double of that value. Ruslik_Zero 20:56, 27 November 2024 (UTC)[reply]

Depends on what n is precisely. If n is the ion density (equal to the electron density), then

2\cdot {\frac {3}{2}}nT

is correct. If taken literally as "particle density" (i.e. ions and electrons combined), then it should still be

{\frac {3}{2}}nT

. I assume that the former is meant, but the formulation seems ambiguous. --Wrongfilter (talk) 21:39, 27 November 2024 (UTC)[reply]

stage 4 breast cancer

I'm not seeking medical advice, but stage 4 cancer means you're gonna die from it imminently, can someone confirm? Or is it wait, what?? Maybe I'm confused. Thanks. 2601:644:8581:75B0:0:0:0:6B00 (talk) 22:22, 27 November 2024 (UTC)[reply]

According to breast cancer classification, Stage IV means the cancer has metastasized, that is, tumors that have "broken off" of the original tumor have appeared elsewhere in the body. "Metastatic breast cancer has a less favorable prognosis." Abductive (reasoning) 06:52, 28 November 2024 (UTC)[reply]
"While there is no cure for metastatic breast cancer, it is possible to control it with treatment for a number of years. The cancer can also go into remission."^[13] So "imminently" is not generally correct. --Lambiam 15:17, 28 November 2024 (UTC)[reply]

November 28

Are there any volatile gold compounds?

Title. Let's say "boiling point under 500°C" counts (as long as it actually boils and doesn't decompose). :) Double sharp (talk) 03:11, 28 November 2024 (UTC)[reply]

Gold(III) fluoride apparently undergoes "sublimation above 300 °C". Tracing the dewiki article's data suggests this comes from CRC 10th ed. doi:10.1016/0022-328X(87)80355-8 is a lead article about volatile gold compounds, but these (and others I found) are generally about transferring as a vapor for CVD, nanoparticle formation, or other short-timeframe processes, so probably low pressure and maybe not highly stable in the vapor phase. DMacks (talk) 03:58, 28 November 2024 (UTC)[reply]

The compound [Me₂AuOSiMe₃]₂ sublimes at 40 °C (0.001 mmHg) without decomposition. (doi:10.1002/anie.196706831) --Leiem (talk) 04:24, 28 November 2024 (UTC)[reply]

Closure, does it exist in physics?

In mathematics, closures are pretty common, e.g. a sum of positive/negative numbers is a positive/negative sum - respectively, and a space of two/three dimensional bodies is a two/three dimensional space - respectively, and so forth.

I wonder if closures also exist in physics, i.e. when the closed properties are physical rather than mathematical, i.e. I'm not interested in applying mathematical properties - like a sum or a space - in physics: e.g. when we say that "a sum of two electric forces is an electric force": It's a bad example for closures in physics, because a "sum" is a methematical property, whereas I'm only interested in purely physical examples.

The above-mentioned example for closures in physics is bad also for another reason: Whereas there is a concrete difference between an electric field and a magnetic field (e.g. by how they influence a stationary body), there is no concrete difference between an electric force and a magnetic force: They influence a given body by the same way, e.g. if their value is 1 kg N they will accelerate a given body by the same acceleration, so the only difference (if at all) between an electric force and a magnetic force and a gravitaional force is "historical", i.e. it only tells us whether the source of that force, was an electric field or a magnetic field or a gravitational field.

HOTmag (talk) 08:35, 28 November 2024 (UTC)[reply]

1 kg is the unit of mass and not of force for which physicists have another unit Newton (the force to accelerate 1 kg at 1 m/s²⁾ and your Greengrocer uses a scale that displays W(kg)=mg. Mathematical Addition (or summation), whether of scalar or vector quantities, is defined in abstract symbols. Those symbols may represent any physically real quantities and the summation result is equally real. That is no set-limited exercise or example-setting in Set theory and physical science is well enough aware that that there can be four (not just 3) fundamental forces viz. gravity, electromagnetism, weak interaction and strong interaction that act in combination and cease to be explicitly separable in the result. Philvoids (talk) 13:40, 28 November 2024 (UTC)[reply]

Yes, I really meant Newton (sometimes people tend to replace weight by mass, but this mistake is so widespread - mainly in daily life, that it should be forgiven when readers understand what the speaker meant). Additionally I didn't want to mention the other forces becuase they are not useful in daily life.

As for your main response, I didn't fully understand the bottom lime: Do you eventually claim that there don't exist purley physical closures (although there are purely mathematical closures)? HOTmag (talk) 14:08, 28 November 2024 (UTC)[reply]

Are Symmetry (physics) and Conservation law what you're after?

Not necessarily, but could you give a concrete example? HOTmag (talk) 14:27, 28 November 2024 (UTC)[reply]

In mathematics, a closure is always the closure if a set. The set of positive numbers is closed under addition. The concept of closure requires the notion of an operation such as addition that can be performed on elements of the set. What is closed is not a property but a set. --Lambiam 15:08, 28 November 2024 (UTC)[reply]

A property is usually interpreted as a set. E.g. the property "Asian" is the set of all Asian objects, and when we say that a given object is Asian we only mean that it belongs to that set.

Here is a surprising example of closure: "a space of two/three dimensional objects is a two/three dimensional space - respectively". It really points at a closure because: on one hand, the operation is "to collect objects in a space": the result of this operation is the space in which those object are collected. On the other hand, the property is "two/three dimensional" (choose one option): this property is represented by the set of all two/three dimensional objects (respectively).

My original question was, if there was any physical property (i.e. a set of physical objects sharing an indentical physical property), closed under a physical operation. HOTmag (talk) 17:59, 28 November 2024 (UTC)[reply]

Do you mean, in lay terms, 'is there any physical property of a physical object that can never be changed?' (I assume by a physical process – I don't think changing the host's accident by transubstantiation counts.)

I'd guess that Dark matter can't be changed into Baryonic matter and vice versa, but I might well be wrong. {The poster formerly known as 87.81.230.195} 94.1.211.243 (talk) 10:01, 29 November 2024 (UTC)[reply]

Active galaxys

What are active galaxies? NoBrainFound (talk) 17:29, 28 November 2024 (UTC)[reply]

See Active galactic nucleus, first paragraph. Perhaps there should be a redirect for this topic. -- Verbarson ^talk_edits 18:11, 28 November 2024 (UTC)[reply]

Oh. There is one: Active galaxy. It's a bit annoying that the search bar does the redirect invisibly. -- Verbarson ^talk_edits 19:10, 28 November 2024 (UTC)[reply]

November 29

Where can I find counterintuitive phenomenons list in Science?

Examples:

Asymptotic freedom - We'd normally expect forces to increase as objects get closer, but surprisingly, the strong nuclear force between quarks decreases as they get closer together.

Mpemba effect - The phenomenon where hot water can sometimes cool and freeze faster than cold water

Ultraviolet catastrophe

Pioneer anomaly HarryOrange (talk) 16:19, 29 November 2024 (UTC)[reply]

The ultraviolet catastrophe is not actually a phenomenon (that's the point). 19th-century classical physics theories predicted it should happen and, because it doesn't, were superceded by improved, quantum theories. {The poster formerly known as 87.81.230.195} 94.1.211.243 (talk) 18:45, 29 November 2024 (UTC)[reply]

There are some examples at List_of_paradoxes#Physics AndrewWTaylor (talk) 19:12, 29 November 2024 (UTC)[reply]

November 30