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June 14

Pregnancy

Technically, how long after giving birth can a girl get pregnant again? 2001:B07:6442:8903:D478:83BE:7BFE:74E3 (talk) 16:03, 14 June 2023 (UTC)

Depends on how fertile the father is. Pablothepenguin (talk) 16:20, 14 June 2023 (UTC)

The WP article on superfetation may also be of interest. --Cookatoo.ergo.ZooM (talk) 16:48, 14 June 2023 (UTC)

There are records of intervals of less than 3 months from birth to next pregnancy([1]). However, an interval of less than 18 months is widely accepted as significant health risk for both mother and baby. WHO recommendation is two years interval.

Zarnivop (talk) 19:38, 14 June 2023 (UTC)

See also Postpartum infertility.  --Lambiam 22:21, 14 June 2023 (UTC)

For whatever it's worth, my grandmother (RIP) was born 12 months after my great auntie Jean (RIP) and my great auntie Maureen (still with us) was born 11 months after that. Then my great grandparents didn't have any more children, for whatever reason. This would have been in the 1930s. — Preceding unsigned comment added by 146.200.128.34 (talk) 00:10, 18 June 2023 (UTC)

June 15

Density multiplied by a distance

If I have a density of points per unit volume (P) which varies according to the value of a function y=f(x) in meters, what would the product dP.dy give, a density per unit area or what else? Malypaet (talk) 21:52, 15 June 2023 (UTC)

I'm not able to work out what dP.dy means, in particuler what y=f(x) is supposed to mean. What exactly is the relation between P and f(x)? Perhaps a specific example might help. NadVolum (talk) 22:00, 15 June 2023 (UTC)

Total electron content might be a suitable practical example. catslash (talk) 22:30, 15 June 2023 (UTC)

What is meant is surely $\rho (x)\,\mathrm {d} x$, or better $\int \rho (x)\,\mathrm {d} x$. In astronomy, this is called column density; in general area density in units of number of points per area (according to OP's question) or mass per area if $\rho$ is a mass density. --Wrongfilter (talk) 06:00, 16 June 2023 (UTC)

Are you asking for the dimension of ${\text{d}}P{\text{d}}y$? What does it mean that $P$ "varies according to" the value of $y$? Does it mean $P=y=f(x),$ or $P=g(y)=g(f(x))$ for some unknown function $g$? And what is the role of $x$? Does it represent some physical quantity?  --Lambiam 09:20, 16 June 2023 (UTC)

Yes, for example if "P" is an energy density in joule/m3, a function of wavelength "y" in meter. When you read that "P" (dP ?) is the energy density slice between "y" and "y+dy", represented by the product "P.dy", what does this mean ? And we see here that this product give energy by area in m2, as in column density to area density. Why not represent the energy density slice by "dP(dy)" or some thing else more appropriate, to stay in energy density by volume as a function of "dy" ? Malypaet (talk) 13:36, 16 June 2023 (UTC)

There is no such thing as a "density slice". Density is defined at every point and is a function of position, $\rho (y)$. Writing $\mathrm {d} \rho$ only makes sense if you're talking about the derivative ${\frac {\mathrm {d} \rho }{\mathrm {d} y}}$, the gradient or rate of change of density with position. As far as I can tell this is not what you mean. The product $\rho \,\mathrm {d} y$ has dimensions of energy per area (e.g. J/m²), no way around this. --Wrongfilter (talk) 14:28, 16 June 2023 (UTC)

Sory I wanted to write "energy density of a spectral slice between "y" and "y+dy", but as energy density "P" vary as a function of y, I was considering "dP" as a kind of slice. Malypaet (talk) 15:07, 16 June 2023 (UTC)

"Spectral slice"? Is your "y" supposed to be a frequency $\nu$??? No, probably a typo for "spatial slice"?--Wrongfilter (talk) 15:48, 16 June 2023 (UTC)

You did not explain the meaning and significance of the variable $x.$ Also, what is the dimension of $P$ (or is it the Greek upper-case letter $\mathrm {P}$ or lower-case letter $\rho$?)? First you said a density of points per unit volume, but now you have switched to energy density. Which is it?  --Lambiam 18:12, 16 June 2023 (UTC)

The name of the letter does not matter, here the point or energy density is the same. With this exchange I found the solution to my problem which was to know how to pose it. "x" doesn't matter, "P" is a function of "y" expressed in meters, but in a fourth dimension. In this case it is necessary to use the integral calculus for "y" varying from 0 to infinity, as that one remains in a density of volume with "P" .

Thank you all Malypaet (talk) 08:01, 17 June 2023 (UTC)

June 16

Identify species in photos in c:Category:Macropodidae at Kangaroo Creek Farm

c:Commons:Village_pump#Animal_identification_requested asks to identify the species of Macropodiae deipcted in those photos. I'm forwarding that request because this reference desk has editors competent in animal identification. – b_jonas 10:10, 16 June 2023 (UTC)

To me, they look like red kangaroos - Osphranter rufus. HiLo48 (talk) 10:41, 16 June 2023 (UTC)

Some may be, but most definitely are not. Some of the ones I could identify myself were clearly wallabies! - Jmabel | Talk 15:27, 16 June 2023 (UTC)

They are all apparently taken at Kangaroo Creek Farm. The red ones are kangaroos. The gray and the brown ones are wallabies. They also have an albino wallaby. 97.82.165.112 (talk) 18:47, 16 June 2023 (UTC)

Yes. All of that is in the captions I wrote. The problem is that there are 20-odd species of wallaby (for example) and in most cases I don't know which is which. - Jmabel | Talk 16:41, 17 June 2023 (UTC)

Well, maybe someone at Kangaroo Creek Farm would be willing to look at them and help you? --142.112.221.43 (talk) 18:58, 17 June 2023 (UTC)

Their website lists the animals that they have and identify them as Red Kangaroo, Wallaroo, Bennet Wallaby, and Albino Wallaby. 97.82.165.112 (talk) 11:53, 19 June 2023 (UTC)

Name for this type of cloud?

Rows

Is there a name for this type of cloud? Bubba73 ^{You talkin' to me?} 20:11, 16 June 2023 (UTC)

It looks like cirrostratus undulatus.  --Lambiam 20:53, 16 June 2023 (UTC)

June 17

Planck's law simplification

On "On the Law of Distribution of Energy in the Normal Spectrum", chapter "Introduction of Wien’s Displacement Law" , §7, Planck made a simplification from :

u.dv=ϑ...(...).dv

to:

u=ϑ...(...)

am I to understand that u.dv is a product and it simplifies equality by dividing by dv, or is it another operation? Malypaet (talk) 13:51, 17 June 2023 (UTC)

Yes, that's essentially correct. --Wrongfilter (talk) 17:10, 17 June 2023 (UTC)

This simplification is allowed when the relation between the two differentials is an identity. Let $f$ and $g$ be two functions with primitives $F$ and $G$, so $\textstyle {\int f(x)dx=F(x)+C_{1}}$ and $\textstyle {\int g(x)dx=G(x)+C_{2}}.$ The differential identity $f(x)dx=g(x)dx$ only implies the identity of their primitives up to an additive constant of integration. But this does not matter; we have

$f(x)-g(x)={\frac {d}{dx}}F(x)-{\frac {d}{dx}}G(x)=$ ${\frac {d}{dx}}(F(x)-G(x))=$ ${\frac {d}{dx}}(C_{2}-C_{1})=0.$

So we may conclude that $f(x)=g(x).$  --Lambiam 18:25, 17 June 2023 (UTC)

So, if "u.dv" is a volume density of a spectral slice between v and v+dv, what does "u" represent once dv removed? Malypaet (talk) 19:34, 17 June 2023 (UTC)

u is called "spectral energy density" (at least where I come from, i.e. astrophysics; I'm not linking because that would lead to an article that discusses a somewhat different concept of "spectral"), it has dimensions of energy per volume per frequency interval (units e.g. ${\frac {\mathrm {J} }{\mathrm {m} ^{3}\,\mathrm {Hz} }}$). By contrast, $u\,\mathrm {d} \nu$ is an energy density (${\frac {\mathrm {J} }{\mathrm {m} ^{3}}}$) but only the density of photons with frequency between $\nu$ and $\nu +\mathrm {d} \nu$. The total energy density is the integral of that expression over all photons. --Wrongfilter (talk) 19:56, 17 June 2023 (UTC)

So going back to E, we have a spectral energy density in J/m3.wavelength. That is to say that in the black body we measure the power/m2 for a wavelength, power divided by this wavelength and the speed of light to obtain a spectral energy density, or is it different? Malypaet (talk) 06:11, 18 June 2023 (UTC)

In detail it's more complicated (and a hell of a confusing subject with varying nomenclature in different fields; look at the bewildering variety of quantities in radiometry) but you're partially on the right track. Note that E is not the usual notation that we would use nowadays; I'd write it as $u_{\lambda }$ (as opposed to what we had before, which would be $u_{\nu }$). You're right with the division by c (physical reason is that photons passing through a given area in the time interval $\mathrm {d} t$ come from a maximum distance $c\,\mathrm {d} t$. You're wrong about the division "by this wavelength". In fact it's impossible to go from bolometric power to spectral density. Working forward from spectral density, you need to integrate over all wavelengths such that power is proportional to $\int _{0}^{\infty }u_{\lambda }\,\mathrm {d} \lambda$. You're really better off trying to find a modern text book where this is explained systematically and in a clearer and more didactic way that in Planck's original paper. --Wrongfilter (talk) 08:07, 18 June 2023 (UTC)

Sorry, but I always prefer the original to a copy, here with you and the original I got the answer I was looking for. Malypaet (talk) 22:14, 18 June 2023 (UTC)

So when you write "spectral energy density" , as you don't divise by frequency or wavelength, how can you have a dimension by hertz for example ? Do you use a vector with 2 attribut (energy density, frequency), a matrice with 2 élément (energy density, frequency) or what else ? Malypaet (talk) 05:03, 19 June 2023 (UTC)

For the bolometer, it seem that in experiment, in front of it you can apply a filter (a crystal) to select a very fine slice of wavelenth, isn't it ? So Why don't divise by wavelength ? Malypaet (talk) 05:09, 19 June 2023 (UTC)

You don't divide by wavelength but by a wavelength interval. For "bolometric" look at, I don't know, it just means "integrated over all wavelengths". You can always observe through a filter, than you only measure radiation within some wavelength window of some width Δλ. And so on. We'd have to write a text book for you to explain all this. I'm not going to do this. --Wrongfilter (talk) 14:17, 19 June 2023 (UTC)

Once you succeed in understanding the derivation of Planck's law as presented in a modern textbook, you'll probably have a much easier time following Planck's original paper.  --Lambiam 19:32, 19 June 2023 (UTC)

Escaped genetic experiment

Read something years ago about this but I can't remember all the details. Apparently some geneticists in South Africa were messing around with locusts back in the day, splicing their genes with god knows what in an attempt to create a less aggressive, less voracious, less swarmy version. But someone screwed up and the resulting organisms escaped into the wild. These organisms are huge, slow, placid bugs, the size of mice, flightless and seem to enjoy eating human garbage, but are otherwise harmless, except that they look scary and are a minor annoyance to people. So the government just left them alone. Does this sound familiar to anyone? I remember a South African person online telling me that the District 9 movie was kinda based on the premise of "what if these things were sentient?". — Preceding unsigned comment added by 146.200.128.34 (talk) 22:20, 17 June 2023 (UTC)

A popular urban legend, propagated by April Fools' Day articles published by the Johannesburg newspaper The Star, claims that the Parktown prawn was the result of a genetic experiment by students from the University of the Witwatersrand in the 1960s ...  Card Zero  (talk) 23:52, 17 June 2023 (UTC)

Thank you. So this creature is entirely a creation of nature? 146.200.128.34 (talk) 00:40, 18 June 2023 (UTC)

Well yes. Myths have arisen regarding this species: some people feel it is an alien invader or the result of a freak mutation. But it's just one of the Anostostomatidae.  Card Zero  (talk) 12:03, 18 June 2023 (UTC)

Sounds like a mixed up version of the real origin of Africanized bees. Matt Deres (talk) 20:43, 18 June 2023 (UTC)

June 18

Non human animals that are considered sentient beings?

Does anyone have a current list of which non human species which are now considered by scientists to be sentient? Last I heard it was the gorilla, chimpanzee, the two African grey parrots, the European magpie and perhaps some octopuses. Has there been any more recent additions? — Preceding unsigned comment added by 146.200.128.34 (talk) 00:56, 18 June 2023 (UTC)

I just did a search. In the UK, octopi, lobsters and crabs in addition to ALL vertebrates are considered sentient beings. Wow. I always thought that intelligence was a factor (edit: are cows/sheep/pigs considered sentient?). I read Professor Pepperberg's books about her studies on parrots and even though she spent 30 years with ONE African grey parrot (Alex) who appeared to demonstrate sentience - looking in a mirror and asking "what colour am I?" (first animal that ever asked an existential question???), she wasn't sure, even now, whether Alex was a one-off unique mind or not. She hasn't found another one as of now, but apparently Alex was utterly furious that the other parrots in Pepperberg's lab were responding inadequately to the same experiments he'd been involved with. Anyway from Psittacus - Birds appear to offer, in their behavior, neurophysiology, and neuroanatomy a striking case of parallel evolution of consciousness. Evidence of near human-like levels of consciousness has been most dramatically observed in African grey parrots., so there you go. Iloveparrots (talk) 02:43, 18 June 2023 (UTC)

Octopi are definitely smart. They have problem-solving intelligence. Sadly, they have not yet solved the problem of why their lifespans are so short. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:41, 18 June 2023 (UTC)

The popular meaning of "sentient" seems to have shifted over the years. 'When I were a lad' it was often used (particularly in the Science Fiction I read copiously) to mean something like 'conscious and reasoning', with the implication of having human-comparable intelligence; this popular meaning seems latterly to have been replaced by "sapient", with sentient reverting to its original meaning as detailed in the linked article, implying a capacity to suffer. {The poster formerly known as 87.81.230.195} 46.65.228.117 (talk) 04:28, 18 June 2023 (UTC)

What is "sentient"? Do we have a stable, widely agreed upon and testable definition? In any case, such a list of sentient (or sapient) animals suggests that somebody devised a test that's supposed to demonstrate sentience (or sapience), then subjected a random sample of animals to the test. Those listed passed, some others failed, most were never tested. Obviously, animal rights activists will assume every animal is sentient unless proven otherwise; hunters and fishermen will assume no animal is sentient unless proven otherwise:

Fisherman: ‘It's OK if we catch grey mullet. They aren't sentient, so they can't suffer.’

Scientist: ‘We've just proven that grey mullets can feel pain.’

Fisherman: ‘OK, I'm sorry. I'll switch to red mullet. They can't feel pain.’

(One year later)

Scientist: ‘We've just proven that red mullets can feel pain.’

Fisherman: ‘OK, I'm sorry. I'll switch to black mullet. They can't feel pain.’

(One year later)

Scientist: ‘We've just proven that black mullets can feel pain.’

Fisherman: ‘OK, I'm sorry. I'll switch to striped mullet. They can't feel pain.’

(etc.)

For the plural of octopus, see the usage notes at wikt:octopus. PiusImpavidus (talk) 09:29, 18 June 2023 (UTC)

Douglas Hofstadter discusses Thomas Nagel's What Is It Like to Be a Bat? in The Mind's I:

The image conjured up by the phrase "What is it like to be A"? is so seductive and tempting. . . . Our minds are so flexible, so willing to accept this notion, this idea that there is "something it is like to be a bat." Furthermore, we also willingly buy the idea that there are certain things that it is "like something to be" — "be-able things," or "BATs" for short — such as bats, cows, people; and other things for which this doesn't hold — such as balls, steaks, galaxies (even though a galaxy may contain innumerable be-able things). What is the criterion for "BAT-itude"?

In philosophical literature, many phrases have been used to try to evoke the right flavors for what being sentient really is (“being sentient” is one of them). Two old terms are “soul” and “anima.” These days, an “in” word is “intentionality.” There is the old standby, “consciousness.” Then there is “being a subject,” “having an inner life,” “having experience,” “having a point of view,” having “perceptual aboutness” or “personhood” or a “self” or “free will.” In some people’s eyes, “having a mind,” “being intelligent,” and just plain old “thinking” have the right flavors. In Searle’s article (selection 22), the contrast was drawn between “form” (hollow and mechanical) and “content” (alive and intentional); the words “syntactic” and “semantic” (or “meaningless” and “meaningful”) were also used to characterize this distinction. All of the terms in this huge showcase are nearly synonymous. They all have to do with the emotional issue of whether it makes sense to project ourselves onto the object in question: “Is this object a BAT, or not?” But is there really some thing to which they refer?

Meanwhile (admittedly almost 40 years later, but are we really any clearer?) the UK has the Animal Welfare (Sentience) Act 2022, and Wikipedia has an article on Animal consciousness (beset with a number of difficulties).  Card Zero  (talk) 10:58, 18 June 2023 (UTC)

June 19

What are the c. 1 millimeter long pale bugs on indoor paint?

In NYC. What do they eat? Sagittarian Milky Way (talk) 12:51, 19 June 2023 (UTC)

They could be Silverfish. They primarily eat paper, decaying wood, and pantry items like flour. They are commonly seen out out in the open during the humid summer as the dry air during winter keeps them hidden in places where there is moisture. Thriley (talk) 13:25, 19 June 2023 (UTC)

Way too small to be adult silverfish. I've killed them but luckily there aren't enough to cause noticeable book damage. Sagittarian Milky Way (talk) 13:40, 19 June 2023 (UTC)

Could they not be nymphs? They can be quite small. Are you able to see how many legs they have? Thriley (talk) 13:44, 19 June 2023 (UTC)

If I see one again I'll try to count them. Sagittarian Milky Way (talk) 13:46, 19 June 2023 (UTC)

Actually those were centipedes, not silverfish. Which explains the lack of book damage. I wonder why I saw centipedes in at least 3 different neighborhoods but even when I didn't kill them cause someone said they were book-eating silverfish they never seemed to reproduce. Usually when you see even one roach if you don't do anything (i.e. poison, squishing, food reduction) you'll eventually have many, why don't the centipedes ever have a population explosion? Sagittarian Milky Way (talk) 14:09, 19 June 2023 (UTC)

If they are that small, they are nymphs and unable to reproduce till they mature.  --Lambiam 19:02, 19 June 2023 (UTC)

I've seen both adult and juvenile centipedes, maybe that species only eats outdoor stuff and doesn't stay long enough to find opposite sex adult(s) and bang. They're a bit darker than these extremely tiny things but not very dark. Come to think of it I think I've seen them (maybe neither centipedes or silverfish nor aphids) in books too but maybe that's just a "hide when not hungry/thirsty" instinct? Sagittarian Milky Way (talk) 19:37, 19 June 2023 (UTC)

@Sagittarian Milky Way Centipedes are predators, consequently they cannot experience a "population explosion" on the scale that cockroaches do. Roger (Dodger67) (talk) 20:27, 19 June 2023 (UTC)

Could also be Planococcus citri or an aphid of some sort. A picture would help. 41.23.55.195 (talk) 13:35, 19 June 2023 (UTC)

Smaller than adult P. citri, and not as pale as and more slender than the Planococcus citri article photo. Sagittarian Milky Way (talk) 13:44, 19 June 2023 (UTC)

Finding Accepted Sources Of Info

I need to find more information about Soviet’s Turbojet Train, also known as “High-speed Laboratory Railcar” or “SVL”. Thanks, Brevqvist (talk) 12:51, 19 June 2023 (UTC)

Have you already read Turbojet_train#SVL and references 6–9? Shantavira|^{feed me} 15:51, 19 June 2023 (UTC)

I used 8 and 9 but the rest 6 and 7 were unfortunately in Russian. Thanks, Brevqvist Brevqvist (talk) 15:55, 19 June 2023 (UTC)

Enter the URL into Google translate and it will give you a link to a translated version of the page. catslash (talk) 23:04, 20 June 2023 (UTC)

June 20

COVID and the brain

Rong et al., 2023 observed COVID spike protein in the skull marrow, brain meninges, and brain parenchyma of adults who had died from COVID. Are there any other examples of predominantly respiratorily transmitted viruses expressing in the brain this way (I.e. excluding HIV/Ebola/HSV)? Uhooep (talk) 15:45, 20 June 2023 (UTC)

I question the characterisation of COVID-19 as a "predominantly respiratory virus". I am no more than an interested observer (and recoveree), but from my popular science media reading it seems to me that Covid-19 infects many different organs and tissues, perhaps most significantly the nervous system, and that its effects manifesting in the lungs just happen to be more noticeable in many, but by no means all, victims.

In my own case (2 months ago), my respiratory system seemed entirely unaffected bar a couple of days of mild dry cough, but the effects on my lower alimentary canal were severe. {The poster formerly known as 87.81.230.195} 46.65.228.117 (talk) 18:17, 20 June 2023 (UTC)

The original post said "predominantly respiratorily transmitted viruses", not "predominantly respiratory viruses". --User:Khajidha (talk) (contributions) 20:58, 20 June 2023 (UTC)

You are correct, and I apologise for my mis-reading of the question. {The poster formerly known as 87.81.230.195} 46.65.228.117 (talk) 07:32, 21 June 2023 (UTC)

June 21

Lost submersible at the Titanic site

Something I heard on a radio phone-in tonight, and I wondered if it was true. There was someone who said he had expertise in this area called up and pointed out that if (specifically) those guys were stuck at the bottom of that particular area of ocean in their sub, then they were pretty much screwed. Said something about how they might as well be stuck on the moon for all their chances of rescue, that you can count on one hand the number of vessels in the world capable of reaching that depth and that none of them would be capable of performing deep sea rescue operations. Also that the US and Canadian navies don't have any such vessels anyway and it would take too long to transport anything else in place before the lost peoples' oxygen supplies ran out. Basically that it wasn't looking good at all. Any thoughts? Iloveparrots (talk) 01:09, 21 June 2023 (UTC)

DSRV is a good lead article for information about who has what capabilities (as publicly known). DMacks (talk) 01:53, 21 June 2023 (UTC)

And 2023 Titan submersible incident is what Wikipedia has about this accident so far. (Side comment: I'm somewhat amazed that they gave the vehicle that name. Anyone interested in the Titanic should know about the novel The Wreck of the Titan.) --142.112.221.43 (talk) 04:42, 21 June 2023 (UTC)

An example of Nemesis clobbering Hubris, as somebody once said. {The poster formerly known as 87.81.230.195} 46.65.228.117 (talk) 07:35, 21 June 2023 (UTC)