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September 11

Firearms design / "free-floating rails"

Is Free-floating barrel synonymous with "free-floating rail / handguard"?

Note: related edit is . Was considering making a new redirect. 海盐沙冰 _{/ aka irisChronomia / Talk / Uploads} 13:42, 11 September 2026 (UTC)

They are related, not synymous. A free-floating barrel only attaches at the receiver end. A free-floating rail (or handguard) does not attach to the barrel. It is necessary to have a free-floating rail/handguard to achieve a free-floating barrel. But, technically, you can attach the barrel to something other than the reciever end, rail, or handguard such that it isn't free-floating while still having a free-floating rail. An example is a rifle with a bipod attachment. A gray area is the gas block, which is attached to the barrel. Because you can't grab the gas block, making it a source of variable pressure, it is usually considered a fixed part of the barrel and the barrel remains free-floating. ~2026-38520-51 (talk) 12:19, 12 September 2026 (UTC)

Light Emitting Plastic

Our local variety shop has a cheap gimmick driven by two AA cells which dimly illuminates a colored plastic line maybe 1.0 ~ 1.5 mm thick and 3m long, very much resembling a heavy gauge fishing line. The battery box is connected to the line via a miniature 2-pin connector. When switched on, the line glows evenly along its full length, so it's not just fluorescent. What's the technology? Doug butler (talk) 15:34, 11 September 2026 (UTC)

It sounds like Electroluminescent wire. ~2026-46630-01 (talk) 16:19, 11 September 2026 (UTC)

Great answer, thanks. A remarkable technology at a nugatory price. Doug butler (talk) 21:45, 11 September 2026 (UTC)

Resolved

September 16

Statistical probability vs. biological bias in skewed offspring sex ratios (e.g., Peter I, Duke of Bourbon)

Hello. I am looking into the genealogy of Peter I, Duke of Bourbon (1311–1356), who famously fathered one son followed by seven daughters in a row with his wife, Isabella of Valois.From a purely mathematical standpoint, if we assume a roughly 50/50 chance for each birth, the probability of a specific sequence of seven children of the same sex in a row is quite low (1 in 128, or about 0.78%).My question is whether modern evolutionary biology or reproductive medicine views extreme family sex-ratio imbalances like this as purely a matter of random chance (the gambler's fallacy in action over a small sample size), or if there is evidence that certain men are genetically or physiologically inclined to produce one sex over the other?Specifically:Is there any known genetic mechanism in human spermatogenesis (such as an allele that affects the ratio of X-bearing vs. Y-bearing sperm, or the motility/survival of Y-sperm) that can inherently bias a father toward producing daughters?Alternatively, could maternal factors (such as uterine environment or selective spontaneous abortion of male fetuses) cause a consistent skew across eight pregnancies with the same partner?Do modern population studies show that men who father many daughters are statistically more likely to continue having daughters, or does the probability always reset to the population baseline (~105 males to 100 females) for each subsequent child?I would love to read any academic papers, statistical studies, or medical literature addressing familial sex-ratio deviations. Thank you! ~2026-50008-57 (talk) 00:45, 16 September 2026 (UTC)

It does not require any hypothesis other than what is necessary to bring it to your attention. If after you start observing it, the sequence continues to say 40 children in a row of the same sex, then you may assume that there is some causal mechanism in operation. JRSpriggs (talk) 01:42, 16 September 2026 (UTC)

40 kids is extremely unrealistic other than for sperm and egg donors! But there was a couple in Michigan that kept having sons (14 sons in total!) until they finally had a daughter and declared their family complete after a grand total of 15 children: https://www.npr.org/2020/11/06/932185995/after-14-boys-michigan-couple-welcomes-first-baby-girl-to-the-family ~2026-50008-57 (talk) 03:43, 16 September 2026 (UTC)

There is a lady in Africa at the present time who has given birth to 40-something kids (and has recently gotten her tubes tied because she's had enough). She has some kind of hyperactive ova producing condition (plus she was 12 when she married). So it's extremely rare, but not outside the realm of possibility. I do not know the sex ratio of her children, though. (Although she herself was the only girl out of seven children). HierophantOfOmens (talk) 18:23, 22 September 2026 (UTC)

How many multiples? —Antonissimo (talk) 20:46, 22 September 2026 (UTC)

The probability of having at least one run of 7 of the same outcomes in a sequence of 8 coin flips is 6/256, more than 2%.  ​‑‑Lambiam 05:49, 16 September 2026 (UTC)

2.34%, which technically rounds down to 2% or down to 2.3%. ~2026-50008-57 (talk) 07:12, 16 September 2026 (UTC)

From Sex ratio:

A large 2025 epidemiological study of American nurses found the chances of a specific couple giving birth to a boy or girl are not always 50-50, and the overall pattern follows a beta-binomial distribution. The number of families with three or more children that have all boys or all girls is higher than would be expected by random chance. Families with three girls had a 58% chance of having a fourth, and families with three boys had a 61% chance of having a fourth.

Alien878 (talk) 10:28, 16 September 2026 (UTC)

At all developmental stages from conception to infancy, males are less likely to survive. --User:Khajidha (talk) (contributions) 14:23, 16 September 2026 (UTC)

That's what I'm looking for! It seems that there might've been something in Peter's sperm that made girls more likely! ~2026-50008-57 (talk) 00:51, 17 September 2026 (UTC)

The likelihood of Peter I, Duke of Bourbon (1311–1356), fathering seven daughters on the trot is exactly 1. You can't lay your bets after the race is run. Doug butler (talk) 02:49, 17 September 2026 (UTC)

The odds of this were less than 1 in 100 by conventional odds in 1335, before he began breeding, unless his sperm were stacked a certain way to favor daughters. ~2026-50008-57 (talk) 04:02, 17 September 2026 (UTC)

That's one explanation. Another is that he's the one French aristocrat (of how many?) that happened to, which made him memorable. Other factors can come into play: males have a much higher rate of birth deformities (something to do with unpaired chromosomes), so baby boys who are less than perfect are susceptible to misadventure. Doug butler (talk) 07:48, 17 September 2026 (UTC)

We should not overlook the fact that while the odds against a particular couple having such a run were, let us say, 100 to 1, there were many, many more that 100 couples around having children in that milieu, so one or more of them actually having it was close to a certainty. It just happened to have been that couple who, being aristocratic, were recorded as so doing, but doubtless there were other 'ordinary' families who also did but went unremarked because, y'know, peasants. {The poster formerly known as 87.81.230.195} ~2026-43920-01 (talk) 13:08, 17 September 2026 (UTC)

I would direct all in this subthread's attentions to the comment above by Alien878: apparently some couples actually are predisposed to producing offspring of one sex or the other. If a couple has had 3 girls, their fourth is more likely than not to be a girl also, and apparently even slightly more so with boys. HierophantOfOmens (talk) 18:37, 22 September 2026 (UTC)

More likely that his wife's immune system reacted more strongly to male embryos than to female ones. --User:Khajidha (talk) (contributions) 18:57, 17 September 2026 (UTC)

Spider webs

I have seen that if spider are of different species then their web designs also changes.

But these spiders of same types, who never meet each, but for decades and centuries they know that their species will have to make web of this particular design? ~2026-49993-89 (talk) 02:30, 16 September 2026 (UTC)

It's how the various species evolved. I recommend that you read Spider web. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:51, 16 September 2026 (UTC)

• "Because different species have characteristic web shapes and young spiders make them without training, the capacity to build webs must be genetically encoded, hard-wired in their nervous systems."
• "The orb spider’s set of web-construction rules has been fixed in its genome by past selection; this is witnessed not least by the fact that it is often as easy to distinguish spiders by features of their webs as by their morphology."

 ​‑‑Lambiam 05:18, 16 September 2026 (UTC)

Josino Levino Ferreira's cause of death details

I am looking for additional biographical or journalistic details regarding the passing of the Brazilian supercentenarian Josino Levino Ferreira (April 3, 1913 – October 5, 2025). At the time of his death at age 112, he was recognized as the world's second-oldest living man. [1] (https://ru.wikipedia.org/wiki/%D0%9B%D0%B5%D0%B2%D0%B8%D0%BD%D1%83_%D0%A4%D0%B5%D1%80%D1%80%D0%B5%D0%B9%D1%80%D0%B0,_%D0%96%D0%BE%D0%B7%D0%B8%D0%BD%D1%83), [2] (https://longeviquest.com/2025/10/josino-levino-ferreira-worlds-second-oldest-man-dies-at-112/) Public statements from his family and groups like LongeviQuest confirmed that his cause of death was due to "complications from aspiration". [1]I am trying to find out if there are any specific local Brazilian news reports or medical disclosures that detail:

• The specific trigger: What exactly triggered or caused the initial episode of pulmonary aspiration (e.g., dysphagia, a specific meal, or an underlying acute illness)?
• The clinical progression: What did the subsequent "downhill spiral" look like physiologically (such as the onset of aspiration pneumonia or acute respiratory distress) in the days leading up to his morning passing on October 5? [1] (https://ru.wikipedia.org/wiki/%D0%9B%D0%B5%D0%B2%D0%B8%D0%BD%D1%83_%D0%A4%D0%B5%D1%80%D1%80%D0%B5%D0%B9%D1%80%D0%B0,_%D0%96%D0%BE%D0%B7%D0%B8%D0%BD%D1%83)

If anyone with access to regional media archives from Rio Grande do Norte (where he resided in Coronel Ezequiel) can provide reliable sources or deeper insight into these final circumstances, it would be greatly appreciated. Thank you! ~2026-50008-57 (talk) 07:21, 16 September 2026 (UTC)

The Russian Wikipedia states that he died "от аспирации вызванной пневмонией", which means, "from aspiration caused by pneumonia". This does not make much sense; the intention is, presumably, from aspiration pneumonia, that is, pneumonia caused by pulmonary aspiration. The statement carries a reference, which, however, does not discuss a cause of death.

The Portuguese Wikipedia does not cite any Portuguese sources.  ​‑‑Lambiam 18:43, 16 September 2026 (UTC)

Are there more details anywhere about how and when he experienced aspiration? ~2026-50008-57 (talk) 22:33, 16 September 2026 (UTC)

Even if there are contemporary accounts in regional media archives, one should not expect to find a mention of the specific proximate cause of the occurrence of pulmonary aspiration. It would be nice, though, to have a more reliable source for the cause of death than a report by the family.  ​‑‑Lambiam 08:32, 19 September 2026 (UTC)

more legible link: ru:Левину Феррейра, Жозину —Antonissimo (talk) 00:47, 19 September 2026 (UTC)

September 17

Sending matter (micro-drones vs. humans) to specific coordinates in past or future spacetime

I am looking for a rigorous, physics-based breakdown regarding the theoretical feasibility of time travel for physical matter to a specific, pre-determined destination in the spacetime continuum. Most popular discussions focus on the grand energy requirements of moving a human, but I want to look at this from a scale and control perspective.

Assuming a future civilization possesses arbitrary engineering capabilities, does the math behind general relativity or quantum field theory allow for targeted macroscopic breakthroughs? Specifically:

1. Past vs. Future Asymmetry: We know time dilation allows a one-way trip into the future (e.g., traveling at relativistic speeds). However, does general relativity permit navigating to a specific, chosen day in the future without just guessing the speed and duration? Conversely, assuming closed timelike curves (CTCs) or wormholes are stable, is there any mathematical framework that allows targeting a specific coordinate in the past, or would it be inherently unpredictable/restricted to the moment the machine was built?

2. The "Size" Constraint (Drone vs. Human): From a fundamental physics standpoint, does the mass or quantum complexity of the object matter? Would sending a microscopic, solid-state drone (e.g., a few grams of silicon) bypass certain quantum decoherence or energy-density restrictions that would otherwise tear apart a biologically complex, multi-kilogram human? Or do the field equations treat a gram of matter and a human identically?

3. The Spatial Displacement Problem: Because the Earth, solar system, and galaxy are in constant motion, moving through time requires drastically moving through space to avoid materializing in a vacuum. Does any serious theoretical model automatically couple chronological targeting with spatial tracking, or does the math treat them as completely decoupled variables?

4. The Information-Entropy and Interference Problem: If sending a tiny drone to a specific historical coordinate is theoretically possible, how do quantum mechanics and causality handle the drone's interaction with the environment? For example, if a micro-drone were sent to a precise coordinate in the early 20th century to passively film or record an event involving historical figures (such as Lenin, Trotsky, or Hitler), would the mere displacement of air or the scattering of photons trigger a macro-scale causal divergence? Or does the physics demand a strictly non-interactive, "ghost-like" observation state to prevent paradoxes?

I am looking for insights grounded in established physics (e.g., Kip Thorne's wormhole physics, Novikov self-consistency, Alcubierre metrics, or quantum gravity hypotheses) rather than science fiction tropes. Citations to relevant peer-reviewed papers or physics textbooks are highly appreciated. ~2026-50008-57 (talk) 05:45, 17 September 2026 (UTC)

What system do you envisage a sender to use for specifying the destination in the spacetime continuum? Like "Stardate 7541.4, Delta Quadrant, a bit to the left of these merging black holes over there"?  ​‑‑Lambiam 04:33, 18 September 2026 (UTC)

Taking these in order. Short version first: the future side is ordinary physics with a precision-engineering problem; the past side is blocked less by gross energy than by energy conditions, stability, and reach.

1a. Targeting a future date. Time dilation forward is a solved design problem, not a guess. The elapsed proper time along your worldline is an integral you choose through your trajectory, so for a desired offset you solve for a speed or gravitational-potential profile that produces it, and you can measure and correct en route. The cheapest machine for reaching a specific future day remains patience; the interesting case, arriving with less elapsed time, is the twin paradox, whose small-speed version was measured by the Hafele–Keating experiment (1971). No fundamental obstruction, only a delta-v budget.

1b. Targeting a past date. General relativity does contain closed timelike curves in idealizations: the Gödel metric (1949), the Tipler cylinder (1974), the interior of an idealized rotating black hole, and traversable wormholes (Morris & Thorne 1988). For wormhole time machines (Morris, Thorne & Yurtsever 1988) the standard result is a reach limit: you cannot go back earlier than the moment the machine was assembled, because the moved mouth is younger by exactly the dilation its history accumulated (Thorne 1994, ch. 14; Everett & Roman 2012). Within that reach, targeting is set by the machine's actual history; it does not dial arbitrary coordinates.

Two further obstacles. Construction requires violation of the energy conditions ("exotic matter") at the throat (Morris & Thorne 1988). Quantum fields do permit small, localized violations (the Casimir effect; the Ford–Roman quantum inequalities bound how much, for how long), and later constructions need arbitrarily small violations (Visser, Kar & Dadhich 2003), but a persistent macroscopic machine is another matter. And even granting a stable wormhole, it tends to destroy itself once the time difference becomes usable: vacuum fluctuations pile up at the Cauchy horizon (Hawking 1992; Kim & Thorne 1991), semiclassical back-reaction either collapses the wormhole or makes the mouths repel (Visser 1993), and each classical traversal shifts the wormhole's parameters (Echeverria, Klinkhammer & Thorne 1991). These are semiclassical arguments, so the conclusion is stated as a conjecture, but it is the mainstream expectation: standard physics appears to prevent macroscopic CTCs.

2. Size: drone vs. human. The field equations make no distinction: everything enters as stress-energy, so a few grams of silicon and a person are governed by the same equations; the difference is in the numbers, not the rules. What mass and size change is engineering: tidal tolerance (a throat tight enough to spaghettify a person can pass a chip intact), the exotic-matter and mass scales set by the throat size, and stability margins. A drone does not bypass any rule-level constraint; it needs a smaller, cheaper machine. Quantum decoherence is not an issue for sending a classical object; it matters in the quantum versions where qubits traverse CTCs, where the standard treatment (Deutsch 1991) makes evolution nonlinear. That is a separate physics problem, not a loophole.

3. Space and the "vacuum" problem. This is an artifact of treating space and time as independent variables. In general relativity a time machine connects events, points of four-dimensional spacetime, along physical worldlines, so "which place" and "which time" are not separately dialable: the metric couples them, and the output mouth must be carried along a history to the target event. (You do not feel the Earth's orbital motion while in free fall; a carried mouth shares your local frame.) The "you'd materialize in vacuum because the Earth moved" picture assumes absolute space. The actual restriction is again the worldline one: the output event must lie on the history the machine really has.

4. Interaction and observation. There is no non-interactive observation in physics: recording is coupling (photons scattered, air displaced, entropy written), and the drone's passage is itself an interaction. But nothing in the formalism "notices" changes or punishes small ones; chaotic dynamics can amplify tiny perturbations (Lyapunov growth), which makes prediction hard, not forbidden. What replaces the paradox worry is consistency. Either Novikov self-consistency: only globally self-consistent histories occur, so local interactions are permitted only insofar as the loop closes (Friedman et al. 1990; the billiard-ball example in Echeverria et al. 1991). Or, on the chronology-protection side, the loop never forms. Neither introduces a "ghost observer" mode. And targets like Lenin or Hitler are ruled out in the standard models for a simpler reason: no wormhole reaches a time before it was built.

Bottom line: future targeting, solvable within known physics; past targeting, idealizations of general relativity admit CTCs, but buildable models cap reach at the machine's creation and quantum effects plausibly prevent stability; small probes relax engineering, not rules; "purely passive" observation is not a physical category, and self-consistency is what does the work. For depth: Thorne, Black Holes and Time Warps (1994), ch. 14; Everett & Roman, Time Travel and Warp Drives (2012); Visser, Lorentzian Wormholes (1996).

~2026-50160-80 (talk) 12:43, 17 September 2026 (UTC)

Paging Gregory Benford, a Physics professor emeritus who has speculated and written about such matters. {The poster formerly known as 87.81.230.195} ~2026-43920-01 (talk) 13:14, 17 September 2026 (UTC)

September 19

Does the Southern black rhinoceros still exist?

While reverting an IP who has removed the infobox image from Southern black rhinoceros twice now, I realized this second time that the image was taken in 2022, despite the page saying Diceros bicornis ssp. bicornis went extinct in 1850. The image is sourced to iNaturalist, which has many more recent photos and sightings.

IUCN lists it as near threatened, not extinct, and this 2011 paper indicates it is still extant. From a quick skim, the citation at the end of "This former species was brought to extinction ..." in the introduction says, "The genus contains one extant species, D. bicornis", with nothing specific about the subspecies.

However, there is an "IUCN status" section on this page (as well as South-western black rhinoceros), added by @J. J. Hornung in 2012, that claims the IUCN confused it with D. bicornis occidentalis. Neither the IUCN nor Pachyderm journals cited mention such a subspecies, but I know very little about biology, so I don't feel qualified to definitively change the article. Can someone help clarify what's going on here? Iiii I I I (talk) 17:53, 19 September 2026 (UTC)

The article states "Zoos, animal sanctuaries and conservation centers use this same scientific name as an indicating reference to the surviving south-central black rhinoceros." Which means the website is referencing the wrong Wikipedia page... assuming our articles are accurate. There should be no photo. Modocc (talk) 00:38, 20 September 2026 (UTC)

Thanks for taking a look. Which article are you referring to with that quote? Iiii I I I (talk) 18:29, 20 September 2026 (UTC)

South-central black rhinoceros. Modocc (talk) 18:36, 20 September 2026 (UTC)

Ah okay, I thought you meant one of the journal articles cited on the page. How do you know this is correct, though? It was added by an IP without a reference, and it contradicts the IUCN status section, which mentions D. bicornis occidentalis, not D. bicornis minor. Iiii I I I (talk) 18:42, 20 September 2026 (UTC)

I don't know if it is correct or the only one. However, black rhinoceros lists the extant subspecies and the extinct southern black rhinoceros which this article covers in detail. Modocc (talk) 19:08, 20 September 2026 (UTC)

Also the south-western black rhinoceros article asserts: "This subspecies is often mistaken for either the extinct southern black rhinoceros (D. b. bicornis) or the southeastern subspecies (D. b. minor)." Modocc (talk) 01:35, 21 September 2026 (UTC)

We can't say that a subspecies "went extinct in 1850" when we do not even have one source that says it is extinct at all. Unless there are sources that says they went extinct that information should be removed. And to avoid citogenesis danger it must be an RS dated before that was put in the WP article. HierophantOfOmens (talk) 18:12, 22 September 2026 (UTC)

I've removed the photo that was recently added about three weeks ago. Modocc (talk) 00:57, 20 September 2026 (UTC)

September 20

Extraterrestrial ice halos

What would ice halos around the sun look like from other planets? Mars’ would presumably look similar if not exactly the same as ours, but outer planets like Jupiter, Saturn, Uranus, et cetera, have atmospheres with ice crystals of far more interesting compounds than oxygen and CO2; stuff like ammonia and methane. How would that affect the appearance of ice halos? Would there be different arcs? Are there hypothetical images (like ray traced simulations) of these arcs? Do they have names (or would the individual arcs each be analogous to one of our Earth arcs and thus take their names)? Cheers, 𝔰𝔥𝔞𝔡𝔢𝔰𝔱𝔞𝔯 ^{(𝔱𝔞𝔩𝔨)} (any/all) In solidarity. 09:55, 20 September 2026 (UTC)