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April 10[edit]

Economic independence of future space colonies[edit]

Assuming that at some point during future space colonization Earth will eventually become uninhabitable for some reason, have there been estimates in what time colonies on Moon, Mars, etc. may become fully independent of Earth supplies and deliveries? Brandmeistertalk 21:37, 10 April 2024 (UTC)[reply]

  • The best research on this can be found in the Mars trilogy by Kim Stanley Robinson. Abductive (reasoning) 22:55, 10 April 2024 (UTC)[reply]
    Let's be careful calling works of fiction "research." Certainly, authors can conduct research while writing their fiction, but there is zero guarantee that they have done so, that they have done rigorous research if it was attempted, nor are they beholden to the results of said research. --OuroborosCobra (talk) 13:51, 11 April 2024 (UTC)[reply]
    Do you seriously think I wasn't sure that Kim Stanely Robinson did a ton of research for his books? Robinson is known for that. Abductive (reasoning) 17:14, 11 April 2024 (UTC)[reply]
    *sigh* Please be careful to not make this personal. I'm commenting on fiction authors, not you or even Robinson specifically. However, that is why I included the clauses "that they have done rigorous research if it was attempted" and "nor are they beholden to the results of said research." In the case of the former, rigorous research usually requires an academic or other functional background relevant to the field. While Robinson has a PhD in English, well deserving of respect, that's not necessarily a background needed for rigorous research (including interpreting/analyzing what they have found) in fields like economics, space travel, aerospace engineering, physics, atmospheric science, terraforming, etc. Nor, as in the latter clause, is an author of fiction, are they beholden to the results of said research should they decide that the narrative needs of their story require some deviation, otherwise known as artistic license. --OuroborosCobra (talk) 19:03, 11 April 2024 (UTC)[reply]
    Robinson assumed vast amounts of subsurface ice, for which (afaik) there is not good evidence. Also he was caught in an engineering blunder (the windmills, whose secret purpose he retconned in the next volume). —Tamfang (talk) 19:39, 11 April 2024 (UTC)[reply]
    ...and still it was the best research on the subject. Abductive (reasoning) 08:13, 12 April 2024 (UTC)[reply]
    What are you basing that belief upon? —OuroborosCobra (talk) 12:00, 12 April 2024 (UTC)[reply]
I doubt that it has been rigourously established that full independence is reachable with currently available technology, not requiring completely untested ideas or hoped-for future inventions.  --Lambiam 14:48, 11 April 2024 (UTC)[reply]
Note that for the scenario to make economic sense, Earth would have to become more uninhabitable than the Moon or Mars, which both are indeed completely uninhabitable with technology prospects in the medium term. The only way this makes sense to me offhand is if Earth becomes completely barren of all life and all water in any form and all convertible energy sources. SamuelRiv (talk) 18:01, 11 April 2024 (UTC)[reply]
Not necessarily. The society, polity, and / or economy of Earth need only to lose interest in extraterrestrial colonies, which might be because there are more pressing matters to attend to, or more profitable ones, or more technologically feasible ones. DOR (ex-HK) (talk) 20:00, 21 April 2024 (UTC)[reply]

April 11[edit]

Gender benders[edit]

Re this comment in an earlier discussion:

...As I understand it, Rishi agreed to ban, for example, mechanical restraints that prevent natural development and cripple young women, and hormone treatments that oppose it. That is because girls of this age are immature and in many cases young women who were crippled in this way later said that their lives had been ruined by what was done to them. So is Stonewall saying that Rishi agreed to the opposite of what he agreed to? 92.10.96.64 (talk) 11:07, 1 November 2023 (UTC)[reply]

Last night's Evening Standard carried this harrowing report:

The most high-profile case of "detransitioning" is that of Keira Bell, who began taking puberty blockers aged 16 before transitioning to a male. She later decided to reverse treatment, claiming she never should have been given the medication and that the Tavistock clinic should have challenged her more.

I'm no medical expert, so can someone explain what physical (as opposed to intellectual) aspects of adulthood have not been reached by age sixteen? The process begins at age seven. 92.28.114.98 (talk) 10:56, 11 April 2024 (UTC)[reply]

We have an article on Bell v Tavistock. According to this article, the complainant had a double mastectomy at the age of 20, which to me seems a mature age in terms of both physical and mental development, so this would hardly be a relevant case concerning gender-conforming care for children.
An intended effect of the most commonly used puberty blockers is diminished sex-specific physical characteristics, which should no longer be an issue at age sixteen. A potential risk for patients having a change of heart at a later age is compromised fertility; I have not investigated for which age class this may be an issue.  --Lambiam 14:40, 11 April 2024 (UTC)[reply]

Luminosity of air plasma[edit]

Is there some empirical formula or theory that describes the expected (optical) luminosity of a plasma? Say depending on ionization rate and/or ion density. JoJo Eumerus mobile (main talk) 13:43, 11 April 2024 (UTC)[reply]

Are you asking about the black body radiation, atomic emission (or ionic, as it may be), or the combination of both? --OuroborosCobra (talk) 13:48, 11 April 2024 (UTC)[reply]
Both, really - I wonder less about the mechanisms and more about the quantities. JoJo Eumerus mobile (main talk) 15:41, 11 April 2024 (UTC)[reply]
You can't have the quantities without an understanding of the mechanisms. Our article on black body radiation does a good job explaining the necessary mathematics for that aspect. As for atomic emission, that is far less trivial (to the extent that black body radiation can be considered "trivial" to calculate to a given quantitative accuracy). As for atomic emission, that gets far more difficult. For a hydrogen-like atom, i.e. an atom with only one electron, this isn't terribly difficult to solve using the Schrödinger equation. However, once you start having more than one electron, you now have a many-body problem. We do not have exact solutions to the Schrödinger equation for many-body systems. These require approximation methods, such as the Hartree–Fock method, density functional theory, coupled cluster method, etc. That's not even getting into the issue of things like spin–orbit interaction, or relativistic effects that come into play once you start getting to large numbers of electrons around a single nucleus. If we go to molecules, then we may need to consider other effects and make other approximations, such as the Born–Oppenheimer approximation. So... it kind of matters what you are looking at and what you want out of it. --OuroborosCobra (talk) 19:23, 11 April 2024 (UTC)[reply]
The degree to which these issues are relevant depend on the composition of the plasma, density, temperature and the degree of ionisation. Even for astrophysical plasmas (that I am somewhat familiar with) the conditions vary quite a bit. As the intro to bremsstrahlung explains, the emission mechanisms can be classified into free-free, free-bound and bound-bound processes. A very hot plasma, such as the intracluster medium in clusters of galaxies, the free-free process of thermal bremsstrahlung dominates: an electron is scattered, i.e. accelerated, in the electric field of an ion and emits radiation. The resulting spectrum is a continuous spectrum, but not a black-body spectrum (electrons and ions are in thermodynamic equilibrium but the radiation is not). In cooler plasmas, free-bound radiation becomes more important; this is emitted when an ion captures an electron (this is called recombination) and again results in a continuous spectrum. The recombined electron often lands in an excited energy level of the resulting atom (or ion) and can then cascade to lower levels or the ground level. This then leads to bound-bound radiation, which happens in distinct emission lines (for example the reddish glow of an HII region around a hot star is from the Hα line of neutral hydrogen, following recombination of a proton (H+) with an electron). There are computer programmes that can compute the full spectral energy density for a specified plasma; I could dig out some formulas for the luminosity of a cluster of galaxies but I suspect that is not what you're actually after. --Wrongfilter (talk) 21:59, 11 April 2024 (UTC)[reply]
@Wrongfilter and OuroborosCobra: I am mostly looking at air plasma and gas-discharge lamp, not astrophysical things. The plasmas I am interested in have a low ionization fraction and low temperature, and I want to know how bright they would be to the naked eye (or not, if the luminosity is way too low) for a given energy input/ionization rate. I guess that recombination radiation is the most important component. Jo-Jo Eumerus (talk) 07:05, 12 April 2024 (UTC)[reply]

April 13[edit]

Temperature at which dogs stick out tongue[edit]

At what air temperature on average dogs start to stick out their tongues and at what they start to keep them inside mouth? 212.180.235.46 (talk) 18:21, 13 April 2024 (UTC)[reply]

According to this source, the air temperature surrounding the animal must not rise above 29.5°C (85°F). The same article mentions 31°C (87.8°F) as the skin temperature; at higher ambient temperatures panting becomes the only available means by which the dog can cool itself. Normal human skin temperature is a few degrees higher, so you may still be comfortable while your hot dog is not.  --Lambiam 21:15, 13 April 2024 (UTC)[reply]
Long experience tells me it varies a lot by breed and even by individual dogs. I'd be fascinated if anyone has ever worked out an average. HiLo48 (talk) 23:33, 13 April 2024 (UTC)[reply]
I would think it would also depend on the dog's activity level, i.e. whether running around or just setting. ←Baseball Bugs What's up, Doc? carrots→ 00:40, 14 April 2024 (UTC)[reply]
For sure. HiLo48 (talk) 01:21, 14 April 2024 (UTC)[reply]
Hm, I've seen dogs panting during walkout well below 29.5°C which looks quite high (at around 20°C or so). 212.180.235.46 (talk) 11:09, 14 April 2024 (UTC)[reply]
I imagine there are local factors and a lot of diversity. The dog that scammed his way into my house is quite heat intolerant apparently having forgotten his young wild days in a hot eucalyptus forest, whereas the semi-feral street dogs seem unbothered by temperatures like 34C while bathed in IR from concrete etc. Sean.hoyland (talk) 11:30, 14 April 2024 (UTC)[reply]

April 16[edit]

How can some birds have lifelong high core temperatures?[edit]

Understandably they need to be hot to fly well but something must be different. Protein differences? Sagittarian Milky Way (talk) 18:58, 16 April 2024 (UTC)[reply]

Some possible answers here. Mikenorton (talk) 19:21, 16 April 2024 (UTC)[reply]
How do chickens live for 5-10 years with average body temperatures of 105-107? With smaller breeds over 106. Sagittarian Milky Way (talk) 00:51, 17 April 2024 (UTC)[reply]
That article says a lot about how active birds are, but some are not terribly active at all. Eagles glide and soar with seemingly minimal energy input. Unless under threat (which is rare), Australia's large ratites spend the day strolling around or just sitting. Other Australian birds just seem to sit on tree branches all day, only very occasionally making a very short foray for food. HiLo48 (talk) 03:18, 17 April 2024 (UTC)[reply]
Their defense against pathogens is presumably dependent to some extent on maintaining high core body temperatures, or having very elevated temperatures in bursts like bats. Is a temperature difference of a few Celsius between us and chickens that much of a challenge for biological systems? Many social insects operate at much higher temperatures. Sean.hoyland (talk) 04:29, 17 April 2024 (UTC)[reply]
It depends on a lot of factors, but probably the biggest one is just whether enzymatic function can happen well enough at those temperatures. Not only is temperature an important factor in any equilibria or reaction rates (see reaction rate, Arrhenius equation, equilibrium constant, Van 't Hoff equation and Van 't Hoff plots, etc.) and are enzymes often quite pH dependent, which itself changes as a result of temperature, but at different temperatures the physical structure of enzymes, i.e. how they are folded and other structural issues, can change. This will denature the enzymes, potentially permanently, and a denatured enzyme either has incredibly reduced function or total even loss of function. That said, there isn't some magic one temperature that is best for all enzymes in nature. Rather, as a result of evolution and natural selection, the enzymes of a particular organism will be at their optimal temperature and pH range (or close enough to it for organism survival) for the given conditions of that organism. If you try to put human lysozyme in a chicken or a cat, it likely will not function. However, chickens and cats have their own versions of lysozyme which do work at their operating temperatures. Put chicken or cat enzymes in us, and they might not thermally denature, but they might not be at an optimal temperature for enzymatic activity (or worse, the direction of the equilibrium could even shift, depending on the thermodynamics involved). The adaptations needed to adjust enzymatic optimal temperature ranges often (but not always) aren't very complicated, to the point that a few degrees Celsius adaptation might only require a single point mutation changing one codon/one amino acid. However, even that can become a problem when you have a lot of enzymes needing to adapt to a very quickly changing temperature condition. Thus the problem with coral bleaching, for example. Not having a lot of temperature regulation and being dependent on external temperature, if a temperature shock happens too rapidly for generational/evolutionary adaptation, you start seeing bleaching and eventually extinction events (we have extensive fossil records of other temperature shocks that wiped out the vast majority of marine corals). --OuroborosCobra (talk) 14:53, 18 April 2024 (UTC)[reply]
An intelligent bird might just as easily ask "How can some mammals have lifelong low core temperatures?"
Everything is relative, and birds have been around something like 160 million years longer than H. sapiens, so their 'normality' is more established than ours. {The poster formerly known as 87.81.230.195} 151.227.134.31 (talk) 16:08, 17 April 2024 (UTC)[reply]
Their biochemical and enzymatic activity is optimized enough to that temperature for function. Same as any other living thing. --OuroborosCobra (talk) 17:26, 17 April 2024 (UTC)[reply]

April 17[edit]

pouch delivery[edit]

Hi. The medical field has been using Modified-release dosage tablets/pills/capsules for decades.

Today, I heard about Nicotine pouch on the news. I have never came across this delivery method before, so it got me curious. Nicotine pouch slowly release Nicotine over time, in an analogous way as modified-release dosage tablets/pills/capsules slowly release medication over time.

1. Are there any medication that is delivered via the pouch method?

2. There are Nicotine pouch, Nicotine patch, Nicotine gum, and Nicotine Lozenges[1] that is kept in the mouth but must not be swallowed. There are probably many other nicotine delivery methods that I am not aware of. Are there any Modified-release dosage nicotine tablets/pills/capsules that you swallow?

3. To the best of my knowledge, it seems like almost every nicotine delivery method that goes in the mouth is kept in the mouth, and must not be swallowed. Is there a reason for this?

OptoFidelty (talk) 05:28, 17 April 2024 (UTC)[reply]

  • It seems that nicotine causes nausea and vomiting when it hits the stomach. Also, the stomach acids destroy it, according to Quora. This article says that a time release pill for treating ulcerative colitis with nicotine gets a lot of nicotine where it's needed in the colon, but not so much in the bloodstream. The nicotine in the pouches and other delivery methods needs to travel across the mucous membranes, skin, or lungs to get people feeling good. Abductive (reasoning) 10:37, 17 April 2024 (UTC)[reply]
Thank you! OptoFidelty (talk) 18:53, 17 April 2024 (UTC)[reply]
Some medications (and foods) besides nicotine are being packaged in edible film pouches or capsules. [2] It's been studied for new methods of drug delivery [3] but I haven't personally seen anything other than self-medications taken with these kinds of pouches. Reconrabbit 01:42, 19 April 2024 (UTC)[reply]

April 20[edit]

Xia's five-body configuration[edit]

One of my favorite webcomics, Saturday Morning Breakfast Cereal, once made a joke about Xia's five-body configuration (comic here). I went looking for what it was talking about and found our article on the Painlevé conjecture, to which I added a redirect-with-possibilities. As an aside, the article could use some TLC; the most glaring problem is that it introduces variables without saying what they represent.

Anyway I was trying to figure out where this infinite energy was supposed to be coming from. My best guess so far is that the five bodies are idealized as point masses, which means that the gravitational energy released as you let two of them approach one another grows without bound. This of course would make them black holes in our actual universe, so that energy wouldn't be available, but in the universe of the comic, I guess this wouldn't be a problem (I've never thought very deeply about what happens to general relativity as c approaches ∞, so I'm not sure about that). But in any case there's no new energy appearing that wasn't there before, so the comic's claim that "the universe collapses" seems wrong.

No, really, I actually do have a sense of humor. I just want to know if I've understood this correctly. Does anyone have a different understanding? --Trovatore (talk) 19:50, 20 April 2024 (UTC)[reply]

O/T That article rather overeggs the pudding. The various proofs are for the 2d case ie planar. Perhaps it is obvious that if it works in 2d it'll work in 3d. Greglocock (talk) 21:22, 22 April 2024 (UTC)[reply]
I'm not too sure what it means to "overegg the pudding" but I was not interpreting the configuration as planar; if that's correct then I've misunderstood the drawing. Can you point me to why you say that? --Trovatore (talk) 21:43, 22 April 2024 (UTC)[reply]
It means exaggerating the utility of . The repeated use of the word planar is what I was getting at.Greglocock (talk) 05:45, 23 April 2024 (UTC)[reply]
The last section of the AMS article by Saari and Xia has this: "While we now know that noncollision singularities exist, several mysteries remain. Any partial listing has to include whether n = 5 is the cut-off for this surprising behavior, or whether the four-body problem can propel particles to infinity in a finite time. Can, for instance, Anosov’s suggestion be carried out? Are there planar examples with small n values?" This implies IMO that Xia's construction is non-planar. I think the sketch of the construction also implies this: the orbits of the pair of point masses m1 and m2 are said to be parallel to the x-y plane and highly elliptical, while m3 moves along the z-axis. The orbits of the pair m4 and m5 are also orthogonal to the z-axis, with their major axes shown at an angle to those of m1 and m2 in the accompanying figure.  --Lambiam 12:52, 23 April 2024 (UTC)[reply]
Energy borrowed from the potential energy shed by point masses approaching each other closely but not, in the finite time, "arbitrarily closely", can only be finite. To reach infinity their distance has to become less than any positive number, which means it is zero. Doesn't that qualify as a collision? What is worse, in Jinxin Xue's 4-body solution all four bodies are said to escape to infinity in a finite time. Do they scoot off in four different directions?  --Lambiam 13:18, 23 April 2024 (UTC)[reply]
I believe the idea is this: as you approach the time of the singularity, the separation between some pairs of masses approaches zero, but the positions of those masses diverge to infinity. If you consider a collision to be when two masses have identical, finite coordinates, then that never happens in this scenario. --Amble (talk) 22:59, 23 April 2024 (UTC)[reply]

April 23[edit]

Fulgurite: vandalism or proper fixings?[edit]

While adding a brief historical context section to that lemma I noticed some former changes of another IP which I doubt to be correct. Please could somebody countercheck, since I have no access to the referenced Elsevier source documents from which the data has been obviously originally taken. Here the difflinks in question:

I would tend to revert these unverified changes, they look illogicaly to me, but wanted to ask here first.

Many thanks! --92.117.130.94 (talk) 05:06, 23 April 2024 (UTC)[reply]

P.S.: Maybe there is a need to improve my wording or grammar in the historical section I have added, since I'm not an English language native speaker, sorry if I've used unusual or strange wording. --92.117.130.94 (talk) 05:12, 23 April 2024 (UTC)[reply]

Thanks for noticing. I've reverted these edits because they look like vandalism to me. HansVonStuttgart (talk) 08:13, 23 April 2024 (UTC)[reply]

April 24[edit]

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