Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

May 29

Elderly digestion

Older people have more distended intestines due to loss of muscle tone. It also means food is pushed along more slowly along the digestive tract. Does this mean that per ounce of ingested food, elderly people will extract more nutrients?

Of course, if this causes them to eat less, it may not mean more calories absorbed. Imagine Reason (talk) 09:24, 29 May 2024 (UTC)

I don't know if any of the premises of your argument are correct. But consider this; for about half a billion years our ancestors have had a digestive system. Extracting every usable bit of nutrients from our food has been under strong selection the whole time, because starvation kills and food is limited. Why then would a malfunctioning elderly system do better? Abductive (reasoning) 18:54, 29 May 2024 (UTC)

There is an evolutionary pressure to extract every usable bit of nutrients from our food. There's also an evolutionary pressure to keep the power-to-weight ratio of the digestive system high. Wasting some nutrients to keep the digestive system light may be benificial. I'm not suggesting I disagree with your conclusion. PiusImpavidus (talk) 19:54, 29 May 2024 (UTC)

The human digestive system is far from perfect in extracting calories. Imagine Reason (talk) 21:52, 31 May 2024 (UTC)

Elvish astronomy

Considering Legolas' canonical feats, what would be his naked-eye limiting magnitude, assuming seeing conditions in which the average human would get 6.0?

(The main reason for this question is that in Morgoth's Ring an Elvish name for Neptune is given. Though I suppose they might've been using palantíri as telescopes.) Double sharp (talk) 09:36, 29 May 2024 (UTC)

Perhaps elves have eagle eyes; Tolkein is silent on the issue. Alansplodge (talk) 11:15, 29 May 2024 (UTC)

He does kind of imply at least that the naked-eye limiting magnitude is greater for Elves than for Men. In The Nature of Middle-Earth, "Dark and Light" it is written: The Quendian imagination of the shape of Arda and of the visible Heaven (Menel) above it, was due to the acute minds of a people endowed with sight far keener than the human norm. Though this is for the Round World version, in which the Sun and Moon already exist from the beginning. As for quantitative figures, I guess we're stuck with the data point of Legolas counting 105 horsemen from a distance of 24 km.

Actually, it occurs to me that (perhaps more interestingly than limiting magnitudes), Elves really ought to be able to resolve the Galilean moons of Jupiter. This provides an alternate solution to the longitude problem, at least if you take the Round World versions. :) Double sharp (talk) 15:20, 29 May 2024 (UTC)

The Galilean moons would be a cinch for an elf. I had a (human) friend who could do this (he was tested on it several times). Not being particularly interested in astronomy, he only found out in his adult years that this was not usual for most people. {The poster formerly known as 87.81.230.195} 94.2.67.173 (talk) 19:42, 29 May 2024 (UTC)

Hmm, probably also the crescent of Venus should be resolvable for them. This perhaps has implications on the shapes of the Silmarils. (Although in the Round World Version, Venus already exists beforehand, and its identification with Eärendil is said to be mythologising. From the same essay I quoted: Certain stars (no doubt those we call planets) and among them especially Venus, which they called Elmō (and later mythologically Eärendil), they early observed were “wayward” and altered their places with regard to the “farstars” (fixed stars). These they called companions of the Sun and thought them quite small heavenly bodies – derived from the Sun.) Double sharp (talk) 02:31, 30 May 2024 (UTC)

The limiting magnitude can be increased with a sharper view. The sharper the view, the smaller the area of the detector (retina) on which the light falls. The background light is fixed per unit of surface area of the detector, so with the signal on a smaller area, less background competes in this area, increasing signal-to-noise. A sharper view can also help to take a faint object out of the glare of a nearby bright object; relevant to see the Galilean moons.

The other way to increase the limiting magnitude is by increasing sensitivity. No matter how sharp your eyes are, you need a couple of photons before you can see anything. The more photons you detect, the lower the relative Poisson noise. The sensitivity can be increased by (A) a better detector, detecting a larger fraction of the incoming photons; (B) larger aperture, i.e. a bigger pupil; (C) increasing integration time. Many nocturnal animals (and elves may be somewhat nocturnal) have better, more sensitive detectors, although at a price. The tapetum lucidum found in many animals reduces resolution somewhat; some species sacrificed colour vision for better low-light vision. Bigger eyes help to see better, but although Tolkien often writes that Elven eyes are keen and fair, he never writes (AFAIK) that they're big. Maybe elves can at will increase the integration time of their eyes. For humans it's fixed at several centiseconds, but if elves can boost it to a full second (they would largely loose the ability to detect motion), seeing Neptune shouldn't be too hard. Still takes a lot of dedication and patience to find out which of those tens of thousands of faint stars slowly moves, but patience is something you should have if you live forever. Ents might disagree. PiusImpavidus (talk) 20:55, 29 May 2024 (UTC)

Why would Ents disagree? They have loads of patience (though it is unclear if they are immortal or just extremely long-lived). Clarityfiend (talk) 22:23, 29 May 2024 (UTC)

Ents might disagree with the statement that elves have patience. PiusImpavidus (talk) 11:07, 30 May 2024 (UTC)

Thanks for the details! I guess I'm personally more inclined now towards explaining the Neptune thing by an Elvish invention of the telescope.

Or maybe the Valar told them where to look, noting that Neptune's magnitude is actually brighter than the most extreme reports of naked-eye viewing of stars. It would be a lot easier to find Neptune if you already know where it is, than to find which of those myriad faint stars is slowly moving. In NoME, Elvish Reincarnation implies that the Eldar were informed about isotopes by the Valar, so this isn't unreasonable in-universe. (Though finding that passage makes me amused by the thought of seeing Galadriel's NMR spectra.) Double sharp (talk) 04:23, 30 May 2024 (UTC)

In canon Men are sometimes mistaken for Elves, so there must not be any gross difference in eye size. —Tamfang (talk) 21:37, 30 May 2024 (UTC)

Assuming a comparable physiology, an Elven retina may pack more sensitive photoreceptor cells, while the lens may have better optical qualities.  --Lambiam 06:08, 31 May 2024 (UTC)

I wouldn't take it for granted that the Solar System outside of Middle Earth is the same as the real one. According to The Silmarillion Earth (or "Arda") was explicitly created by God and smaller deities with their omnipotent powers, and so were the peoples of that world (Elves, Men, Dwarves, and surely Hobbits and Ents, too). And the part that would drive mad the astronomers reading that book, the Sun and the Moon were also created by those beings... ages after the creation of Arda, and after life existed on that world. Cambalachero (talk) 13:00, 31 May 2024 (UTC)

Indeed. But Tolkien planned in his later years to make an altered Round World Version in which the Sun and Moon exist from the beginning of Arda. In that case the Two Trees simply preserve their light as it was before they were tainted by Melkor. As I quoted above, these late rewrites imply that the planets in Tolkien's world are the same ones that we have. :) Double sharp (talk) 11:05, 1 June 2024 (UTC)

Hmm, curious where you heard about these supposed intended revisions to create a lore more consistent with actual astral bodies. I'm a little skeptical without seeing a source on this, just because it doesn't seem to add up with other well-established details. Bear in mind that every element of the legendarium that bears light on the creation and cosmology of Eä was published after J.R.R. Tolkien's death. Christopher Tolkien finished The Silmarillion by trying to faithfully patch together the content (and fill in gaps himself) using an express desire to have the final work reflect what his father, the original author, would have intended. Nobody would have been in a better position than the younger Tolkien (who made the completion of the legendarium a substantial part of his own life's work and had the fullest access to the existing materials) to know what the elder intended in this respect, and he would have had every opportunity to cause the final work to reflect it, as he did with countless other details.

Further, thematically it just doesn't seem to fit: the trees are so fundamental to the cosmonogy of the legendarium, as well as its evolution and eschatology. The trees are part of the more gnostically "pure" version of the world after it was sung into existence out of the higher pleroma by the music of Ainur. The fall of the trees, though instigated by the machinations of Melkor and Ungoliant, are thematically (and arguably psuedo-naturally) the result of an inevitable and unarrestable trend of the world trending away from the direct influence of the Valar and towards a world more defined by physicality and all the ills that come with it.

All of this being the result of Melkor's discordant notes, which Eru permitted to remain a part of the song of creation. First the Valar leave Middle Earth and retire to Valinor, and as time wears on, begin making less and less in the way of even indirect influence over it. Next, the Trees are destroyed and the First Age begins. Later the world is reshapped such that Valinor is not even entirely on the same physical plane as the rest of Arda, and reachable only via the Straight Path. The elves diminish and go into the West, returning ultimately to Valinor, the magic and grace of their realms failing and converting them into mundane lands. Meanwhile the light of the trees persists in the silmarils and the phial of Galadriel, bitter sweet echoes of a purer but irretrievable age. Magic fades and Illuvatar's second (and less ethereal) children, humans, inherit the world.

You see what I mean? The idea of the world's inclination to a state defined increasingly more by a base, more purely physical state and away from the direct influence of the spiritual animus that gave birth to it is baked into the narrative and the lore, from start to finish. And the trees are the ultimate symbol of the starting point (or at least the start after the music was finished and the Ainur descended into Arda). Besides, the sun and the moon predating the round world just doesn't make much sense: a flat Arda wouldn't be able to rotate on is axis. Mind you, not to imply that there's in way to get the legendarium's cosmology to work with actual astrophyics. Which Tolkien very well knew: all indications are that this was a part of the point. But introducing the sun and the moon before the First Age just makes the discontinuities more obvious and intrusive.

All that said, very curious to see where this comes from originally. Certainly there is no shortage of matters that Tolkien went back and forth on over his decades of revisions of the relevant works, nor issues where his son had to make best-guess efforts in choosing among the disparate versions of events. But personally, I tend to doubt that Tolkien seriously considered this particular shake-up. Tonally and in terms of continuity, it just doesn't add up. -sighs a sigh of glutted satisfaction, having sucked out all of the fun the subject matter and wrecked it as surely as a giant spider sucking the magic out a world tree and poisoning it.- SnowRise ^{let's rap} 02:51, 3 June 2024 (UTC)

@Snow Rise: There is a good summary here, though the primary sources (JRRT's texts) are still in Morgoth's Ring (ed. Christopher Tolkien) and The Nature of Middle-earth (ed. Carl Hostetter). A scholarly paper about it is here.

A slightly shorter summary: pre-ROTK, JRRT produced a version of the Ainulindalë with the changes to the cosmology. Melkor seizes part of the Earth to make the Moon for his stronghold, before the Valar cast him out of it and cleanse it. For the time being, it was only an experiment.

But in the late 1950s, JRRT came to believe that the making of the Sun and Moon was too "astronomically absurd" to write in an age when most people believe that the Earth is spherical and is more or less like an island in space. So he came up with a new concept: the "Flat World Versions" are traditions that were handed down by the Númenoreans and then in Arnor and Gondor, that are inescapably blended and confused with Mannish myths. The Elves had their own lore from Valinor that was astronomically and geologically in accord with what we know instead.

JRRT describes the new cosmology across some essays published in the aforementioned collections and in an interview. The Sun and Moon were created together with the Earth, and originally they had the Primeval Light, and what Melkor did instead was corrupt them. Middle-earth was then twilit, because Morgoth darkened the Earth with clouds, such that the stars and moon were invisible and the Sun was only a dim twilight (something like the real Venus without the greenhouse effect, I might add). The significance of the Two Trees is that only there was the Primeval Light preserved, and Varda domed Valinor over to keep Morgoth's corruption out and have it only be lit by the stars. The world was also round from the beginning, but you could not circumnavigate it before the drowning of Númenor because Aman would block the way. The Númenorean Catastrophe removes the inhabitants of Aman from the physical world, though the landmass remains and becomes America after significant geographical upheaval. Thus JRRT writes in these notes Aman and Eressëa would be the memory of the Valar and Elves of the former land.

Crucially, in 1966 The Hobbit was slightly edited in accordance with this new revision: where once read In the Wide World the Wood-elves lingered in the twilight before the raising of the Sun and Moon (completely correct per the Flat World version), there now read In the Wide World the Wood-elves lingered in the twilight of our Sun and Moon. JRRT's late texts published and edited by Christopher in The Peoples of Middle-earth sometimes also imply this: the new description of Fëanor's burning of the ships specifies that it was done "in the night", and that "In the morning the host was mustered", which makes no sense in the old cosmology because the Sun wouldn't yet have first risen; and Thingol's throne room of Menelrond is supposed to be based on the domes of Varda (which don't exist before the changes). The heraldry JRRT drew in the 1960s for the House of Finwë is a "Winged Sun", which also makes more sense in the new cosmology because Finwë otherwise could not have seen a Sun that only rose after he died. So the evidence is clear that the elder Tolkien really seriously intended this change.

As for why it was not adopted by Christopher: Christopher's commentary on these texts indicates that he seems to have thought it a bad idea on the part of his father. I think Christopher made a sensible call, as going on with the intended changes would require much more editorial intervention than leaving things as they were: it does not seem that JRRT ever finished the planned rewrites. But from my perspective as a fan, the whole idea is fascinating and allows the amusing conceit of trying to figure out what was really going on behind the scenes, which is why I asked the initial question about how astronomically plausible the reworking was in one aspect (the visibility of Neptune). Double sharp (talk) 03:45, 3 June 2024 (UTC)

Fascinating! Just when I thought the paratextual narrative of this particular piece of literature couldn't get more complicated! Personally I like the ultimate approach adopted (even beyond the concern you rightly point out of it requiring more intervention--I still think I prefer the narrative irrespective of whether you hypothesize a scenario in which J.R.R. could make the adjustments himself). The Age of the Trees being treated as literal (or at least facially literal from the perspective of the Silmarillion/legendarium's narrative; all of the books are presented to varying degrees as possibly unreliable ancient historical text, after all) just feels very at home with both the broader cosmogony as well as the thematics of the overall work. But then, I have revisited those books so many times over the years (at least compared to my once, maybe twice and done policy for most literature: soooo many things to read!) that I may have some bias! SnowRise ^{let's rap} 16:54, 3 June 2024 (UTC)

@Snow Rise: I kind of think of JRRT's problem as being that in seeking increased verisimilitude, he'd gone from wanting to write a mythology to wanting to write a science fiction novel. Only, instead of starting a new science fiction novel and leaving the mythology as it was in its almost-complete state, he ended up trying to turn his mythology into a science fiction novel, with predictable results. But I suppose the whole narrative was too dear to his heart for him to come up with another like it, just like the Silmarilli were to Fëanor. Which is understandable: I share your obsession, and how much greater must it have been for the author? :)

With that said: even in this take, the Age of the Trees would still be literal in the sense that there were luminescent trees in Valinor that got killed by a giant spider. They would only not be literal in the sense that the Sun would still be shining (in its form post-tainting by Melkor) over Middle-earth. Only in the northwest (over Beleriand) is there a volcanic winter due to the fumes of Thangorodrim – and from that, we can see where the idea of the Sun first rising later comes from as an in-universe myth. Double sharp (talk) 10:42, 4 June 2024 (UTC)

May 30

Volume of honey in a bee nest

What is the average volume of honey in a bee nest in the wild? I was able to find information on the average volume of a bee nest, but I know that not all of that volume is honey, of course. Thank you! HeyArtemis (talk) 07:49, 30 May 2024 (UTC)

It varies alot. Honey#Production has a number for Apis mellifera. Sean.hoyland (talk) 08:39, 30 May 2024 (UTC)

Does light decay?

Let's say that an object, such as a star, emits a beam of light and it moves across the space. It goes at the speed of light and, unless it reaches an opaque object, it would keep going... for how much time? Forever? Or is there a point when light would simply dimish and disappear? Cambalachero (talk) 19:53, 30 May 2024 (UTC)

No.

It may react with matter, if it encounters any. A flux of many photons will spread out to a larger volume and so the intensity (number of photons passing through an area) will diminish in accord with the inverse square law. But light passing through a vacuum does not 'decay' or have a limit on its range.

BTW, this theory that light can only travel a few thousand miles before 'running out' is part of flat earther canon for some models, as an explanation of how nighttime happens. But then they're flat earthers. Andy Dingley (talk) 20:11, 30 May 2024 (UTC)

The idea of tired light used to be somewhat popular but has been entirely discarded by now. --Wrongfilter (talk) 20:22, 30 May 2024 (UTC)

I'm afraid it is a zombie idea.^[1]  --Lambiam 05:58, 31 May 2024 (UTC)

I guess the apparent reality that things in motion continue in motion forever by default, if unperturbed, seems a bit unnatural when you live in a macroscopic world. Sean.hoyland (talk) 07:32, 31 May 2024 (UTC)

Correct. If that wasn't the case, we wouldn't be able to see stars that are too far away. We are currently seeing stars so far away that they aren't just stars. They are galaxy or similar objects so far away that they show up as one little blob of light. The limit is not how far light can travel before pooping out. It is how old the stars are. For example, a 100 year old star that is 90 light years away would not be visible becuase the original light hasn't reached us yet (ignoring the complication of direction of relative movement). So, the argument is that the night sky should be flooded with light from all directions. And, it is. It only looks black in a relative sense. 12.116.29.106 (talk) 14:51, 4 June 2024 (UTC)

I imagine it would be much worse than not being able to see stars. If excitations of quantum fields got tired we would be in big trouble. Sean.hoyland (talk) 15:05, 4 June 2024 (UTC)

May 31

Is redshift calculated differently for different spectra?

I ask because I came across an article, TXS 1545-234, in the course of regular gnoming. The article claims this radio galaxy to be one of the most distant known objects, but its redshift is only around z = 2.754 (which I take to be measured from radio emissions). It does appear in this source (|date= at least 2006), and I'm wondering whence the claim of such great distance paired with such pedestrian redshift. I'm not able to understand our article Redshift. Also, if anyone has any ideas about how to de-orphan the article linked, please do have at. Folly Mox (talk) 11:31, 31 May 2024 (UTC) edited 11:52, 31 May 2024 (UTC)

It is certainly not one of the most distant galaxies known. The author of the article, @Galaxybeing:, should explain why they think it is. --Wrongfilter (talk) 12:12, 31 May 2024 (UTC)

They appear to have made a similar claim at MRC 0406-244 (z = 2.44) although thankfully not at another recent creation, QSO J0100-2708 (z = 3.52). Folly Mox (talk) 12:57, 31 May 2024 (UTC)

The redshift, a dimensionless quantity, is the same for the whole spectrum emitted by an object. Compared to TXS 1545-234, JADES-GS-z13-0 is thought to be more than three times as far away from us.  --Lambiam 12:37, 31 May 2024 (UTC)

Thanks both for your answers, and confirming my suspicion that the claim was merely incorrect. Folly Mox (talk) 13:00, 31 May 2024 (UTC)

A redshift of 2.754 is pretty far away, but stating it's one of the most distant known objects is overstating it a bit. Distances to far-away galaxies are normally expressed in redshift, as redshift is directly observable, in contrast to distance, which depends on a model of the expansion of the universe. But when using redshift as a distance measure, one has to keep in mind that it's highly non-linear. Also, distance is a bit of a strange concept when dealing with these cosmologically distant objects. Are we talking about the distance today, or at the time the light was emitted, or the distance travelled by the light? That last at least has some relevance as it translates to the time that the light has travelled and therefore when it was emitted. JADES-GS-z13-0 may be several times farther away today than TXS 1545-234, but most of that is thanks to the expansion of the universe after the light was emitted. When the universe was young and small (although still infinite), it expanded fast in absolute numbers (percentage per year). In light travel distance, the difference isn't so much.

These objects can be studied to learn more about the early universe. For that, knowing the distance to us is not so important; we want to know about the distance (or time) to the Big Bang. At some point, distances (times) to the Big Bang are known more accurately than distances (times) to us. In any case, the redshift tells us immediately that the universe expanded by a factor of five between the times when the light of JADES-GS-z13-0 was emitted and when the light of TXS 1545-234 was emitted. That puts JADES-GS-z13-0 a lot closer to the Big Bang, although only a small fraction farther from us. PiusImpavidus (talk) 11:05, 1 June 2024 (UTC)

On a tangent but an amusing use (abuse?) of "red shift": chemists use red shift generically to mean "moves to lower energy". Even in the IR part of the spectrum, the term red shift would be used to describe the shift of a band to lower E, say 2000 to 1950 cm-1. This language is of course strange because, formally speaking, a shift toward red for an IR band would mean a shift to higher E. Just sayin'.--Smokefoot (talk) 17:11, 1 June 2024 (UTC)

Radioastronomers apply the same "abusive" terminology. We see this linguistic phenomenon also in uses of the verb "to dial", as in the advise to "dial 9-1-1 for any emergency" given to users of smartphones with touch screens. (Using the original rotary sense of the verb in connection with the casual parlance of "butt dial" results in the unfortunate mental image of Giuliani twerking.) Other examples are referring to cotton bed sheets as "linens", or (in the US) to stainless-steel knives, forks and spoons as "silverware", and the computer-graphics terminology calling a screen region a "canvas". I think there is a learned term for this phenomenon if the sense of a word getting abstracted from the physical embodiment after which it was originally named.  --Lambiam 05:29, 2 June 2024 (UTC)

JADES-GS-z13-0

Astronomers talk about redshift if it goes to longer wavelengths, in radio, IR, UV etc., and about blueshift if it goes to shorter wavelengths, in radio, IR, UV etc. Things can also redshift past red. See how red that distant object in this picture is? It's a feature coming from UV, shifted to IR. The Lyman-alpha absorption line is at 121.6 nm, here broadened into a Gunn–Peterson trough, redshifted to 1.6 μm, between the F150W and F200W filters of the camera in JWST. It's how they make a first estimate of the redshift, based on broadband images. A precise number follows later from spectroscopy, but takes far more observing time, so this is only done for the most promising targets. PiusImpavidus (talk) 10:18, 2 June 2024 (UTC)

Physics problem

A shop sign is made of a panel that protrudes slightly from the wall on which it is hung, forming an angle of 5° with it. It is 0.74 m tall and has a mass of 8.9 kg. The upper side of the panel is attached to the wall by two cables, one from the right side and one from the left side. Find the tension of the 2 cables 78.211.54.11 (talk) 19:40, 31 May 2024 (UTC)

Original in Italian, now edited by IP to English.Translates as: "A shop sign consists of a panel that protrudes slightly from the wall on which it hangs, forming an angle of 5° with it. It is 0.74 m high and has a mass of 8.9 kg. The upper end is attached to the wall by two cables, one on the right side and one on the left side. Find the tension in the 2 cables."

IP editor: as it says at the top of this page, we don't answer homework questions and what we do answer should preferably be asked in English. Mike Turnbull (talk) 19:46, 31 May 2024 (UTC)

Asking homework questions also causes tension. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:15, 1 June 2024 (UTC)

Doesn't the tension depend on the angle the cables (idealized as straight line segments) make with the panel?  --Lambiam 02:53, 1 June 2024 (UTC)

Correct. The answer to the question as asked is a curve of tension vs cable length or vertical location. Greglocock (talk) 22:56, 1 June 2024 (UTC)

Is it like this? Graeme Bartlett (talk) 22:42, 1 June 2024 (UTC)

or is it like this? Graeme Bartlett (talk) 22:22, 1 June 2024 (UTC)

like this but not equilateral

In my interpretation of the problem – which is not necessarily the intended one – the lower edge of the panel is attached to the wall and the panel can rotate along that edge, like in the "or is it like this?" diagram, which has an exaggerated thickness for the panel. Unlike that diagram, the panel does not stick out at a 90° angle but is standing almost upright. Also, the cables are attached to the upper edge. So it is more like the situation here to the right, but instead of a bottom 60° angle we have a 5° angle. Not enough info has been given to determine the other angles.  --Lambiam 04:45, 2 June 2024 (UTC)
P.S. Another way to frame the problem could have been in terms of a drawbridge.  --Lambiam 04:53, 2 June 2024 (UTC)

The answer is 42 (glorps). I'll leave it to you to figure out the conversion factor to mks. Clarityfiend (talk) 12:06, 3 June 2024 (UTC)

                |
      		|'.
		|  '.
		|    '.
		|      '.   
		|        '.
		|          ::
		|         ::
		|< 5deg >::
		|       ::
		|      ::
		|     ::.
		|    :: .
		|   ::  .
		|  ::   .
		| ::    .
		|::     V
		|*      8.9kg

Equate turning moments at *
                      clockwise  =  anticlockwise
 8.9 kg x sin(5 deg) x 0.74m / 2 = t/2 x 0.74m
                         where t = tension in each of 2 cables
                                 = 8.9 sin(5 deg)
                                 = 0.775686... kg

Philvoids (talk) 13:16, 3 June 2024 (UTC)

Shouldn't there be a sine or cosine factor in the anticlockwise term? Imagine the cables being attached to the wall very close to the *. Consider dU/dL, where U is potential energy of the panel and L is the length of the cables.  --Lambiam 15:27, 3 June 2024 (UTC)

Although not accurately shown in the ASCII sketch my calculation presumes that the two cables are at right angles to the sign, are parallel and are fastened to the wall separately at two points. This minimises the cable lengths and tensions. Philvoids (talk) 10:28, 4 June 2024 (UTC)

The homework problem did not specify where the cables are attached or that the tension should be minimized, making it unsolvable for the average student. For an old-fashioned drawbridge over a castle moat, as in the animation, a better choice is to place the attachment point of the cables at a distance from the hinge equal to the length of the bridge, making the triangle isosceles. Otherwise, the tension grows without bounds as the bridge near a vertical position.  --Lambiam 15:37, 4 June 2024 (UTC)

I could not find an ASCII symbol for a hinge but installing one at the base of the sign is a well thought mechanical improvement that can stop the thing flapping about in a wind. This reference desk cannot grant permission to construct a drawbridge with walkway at this location and the shop owner of the wall would likely protest at your plan to cut a hole for passage. Unless he is a herder of sheep or other small animals and himself less than 74cm tall and sees some advantage. The OP doesn't ask for the cable tension when the sign/bridge is vertical but we can say there are two cases: Case #1: The hinge is broken or absent. t = 8.9/2 = 4.45 kg plus distributed weight of the cable itself; Case #2: The hinge takes the weight, t = 8.9 sin (0) so both cable lengths and tensions are zero. In that case it would be simpler just to nail the sign to the wall. Or put out a call to Banksy who can save us the cost of the sign, usually upset someone and greatly increase the value of the wall. Philvoids (talk) 18:39, 4 June 2024 (UTC)

For all we know, there is already an opening behind the sign for letting the proprietor's homing pigeons in. If they are equipped with an RFID chip, the sign can be let down automatically on their arrival.  --Lambiam 05:39, 5 June 2024 (UTC)

Pigeon RFIDs can be compromised by malicious Yinpterochiroptera and Yangochiroptera. Members of this notorious "YinYangBat Gang" equipped with ultrasound-to-UHF converters can mount Spoofing attacks on the shared ID frequency. An ad hoc aposematic remedy such as a wall painting of a cat with the sign text "I EAT BATS" does not alone give security. To this end all pigeons must be urged to register a pass-coo that is less obvious than the too common "Coo Coo". Philvoids (talk) 10:28, 5 June 2024 (UTC)

June 2

Why females produce androgens

If human embryons of both sexes start off from a female blueprint and given that females lack the male Y chromosome, how it came that women also produce androgens (even if in small quantity), with related limb and facial hair? 212.180.235.46 (talk) 19:59, 2 June 2024 (UTC)

The article you linked says that the ovaries also produce androgens. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:33, 2 June 2024 (UTC)

Biological systems weren't built by any sort of logical designer. They in no way resemble a computer program, a computer, or, for that matter, anything else in the universe. In the case of androgens, the article mentions that androgens are the precursors to estrogens. Males need estrogens too, btw. All these are steroids, which are fundamental to life and are derived from cholesterol. Abductive (reasoning) 23:18, 2 June 2024 (UTC)

"Biological systems weren't built by any sort of logical designer." Which is why so-called "intelligent design" is just nonsense. The "design" is emphatically not "intelligent". --User:Khajidha (talk) (contributions) 12:07, 3 June 2024 (UTC)

I'm not sure biology and computing are as far apart as they used to be now that systems essentially create the gigantic opaque function that transforms input to output themselves in response to their environment/what they have seen and the objectives. Generative adversarial networks for example seem a bit closer to biology than systems used to be. Sean.hoyland (talk) 13:06, 3 June 2024 (UTC)

Not in a billion years. Abductive (reasoning) 17:51, 3 June 2024 (UTC)

The technology for synthetic biology, still in its infancy, is advancing with large strides. Whether you like it or not, sooner rather than later it will become possible to design and create complete viable and functioning biological organisms.  --Lambiam 06:40, 4 June 2024 (UTC)

Further, the idea that it is so complicated that nobody understands what it does because it thinks for itself is a farce. No matter what is being used for the computing hardware, be it electronic or biological, the mechanism of operation is very well understood by the engineers who developed it. It just sounds cool to say that it is beyond comprehension. It doesn't sound cool to say that the engineers understand it very well and could trace input through to the output if they wanted to, but simply don't care to do because they have other things to work on. 12.116.29.106 (talk) 14:42, 4 June 2024 (UTC)

Tracing the input through to the output is IMO not a helpful concept. Not only do we not know why the most advanced chess or go playing programs make certain surprising moves, but it is not even clear what it means to "understand" why they did this. The computing platform performs a calculation with a certain outcome. The engineers can perform the same calculation by hand, or using abaci, and if they make no mistake they may arrive at the same result in a few billion years: 42. But can they say more than that the answer is 42 because this is the consequence of the rules applied to the input? They knew that already. If someone wants to know why it is the consequence, they can tell them to repeat the calculation.  --Lambiam 15:51, 4 June 2024 (UTC)

IP, LLMs for example involve activations in very high dimensional spaces. Trying to map those activation patterns to things we can understand, like concepts etc., is the whole field of interpretability, and it is in its infancy (and safety critical). Engineers are still far from understanding why input A to a model is transformed into output B. If this is something that interests you, have a look at the work being done in Anthropic's lab. Sean.hoyland (talk) 17:16, 4 June 2024 (UTC)

Overgrown Markov Chain models are pretty much useless in any technical field. BTDT Greglocock (talk) 04:48, 5 June 2024 (UTC)

I guess that's one of the reasons why "Attention Is All You Need" turned out to be such a great title for a paper. Sean.hoyland (talk) 08:39, 5 June 2024 (UTC)

June 5

Prostheses

what are the matrials uesed in implantable artificial prostheses, such as artificial hearts and small-diameter blood vessels; in the engineering of living tissues ? -- 196.153.184.240

Heart valves usually made from pyrolytic carbon. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10034107/#:~:text=Mechanical%20valves%2C%20usually%20made%20from,stroke%20(3%2C%204). 41.23.55.195 (talk) 06:13, 5 June 2024 (UTC)

Many different materials are used depending on requirements. For details see prosthesis and the many links therefrom.Shantavira|^{feed me} 15:30, 5 June 2024 (UTC)

June 6

Health risk of taurine consumption

Realistically, how worried should people be about the health risks of consuming taurine as a supplement? I only ask because half the literature says they find it helpful and beneficial at some unknown dosage, while the other half says it is potentially carcinogenic and could contribute to colon cancer. As a layperson, I find this very confusing. Some of the literature says it could be simply a matter of dosage, but nobody seems to know what the safe or harmful limits are. Can anyone offer some risk analysis devoid of emotion? Should we avoid anything with taurine in it, or not worry at all about it? Viriditas (talk) 01:27, 6 June 2024 (UTC)

As far as Wikipedia is concerned, WP:MEDRS applies. That means that the minimum quality level for WP:RS making medical claims are systematic reviews indexed for MEDLINE (there are some exceptions from this indexation, but generally speaking MEDLINE is the gold standard). tgeorgescu (talk) 03:29, 6 June 2024 (UTC)

Our article states that there is no good clinical evidence that taurine supplements provide any benefit to human health, Why pay for useless supplements? The human body naturally produces a large amount of taurine, far more than one can reasonably take in as a supplement. There is increasing evidence that taurine actually plays a role in preventing cancer.^[2] Any carcinogenicity of supplements can only be due to their being fake, or a lack of quality control in their production.  --Lambiam 07:23, 6 June 2024 (UTC)

The underlying issue is that large doses of taurine are added to energy drinks. Nobody seems to know why. A current study is looking at an association between energy drink consumption and the rise in colon cancer in young adults.[3] Viriditas (talk) 08:23, 6 June 2024 (UTC)

Even disregarding any potential carcinogenic risks, there are enough studies that show damaging health effects of high consumption levels of energy drinks.^[4][5]  --Lambiam 18:28, 6 June 2024 (UTC)

¼ liter of my favorite energy drink has 80 mg caffeine, while adults usually consume up to 400 mg caffeine per day. And I use the energy drink totally without sugar. tgeorgescu (talk) 18:59, 6 June 2024 (UTC)

The energy drink thing may be related; most energy drinks contain vitamin B12. There is a concern that (mega)dosing B12 in excess of daily requirements carries with it a slight increase in risk of cancer due to B12 containing cobalt, which is both a heavy metal and has a trace of radioactive cobalt-60. Abductive (reasoning) 20:25, 6 June 2024 (UTC)

Thank you, that's helpful. I just read the comments by the epidemiologist on that topic, and while my reading might be flawed, they seemed to indicate that dosage and tobacco smoking played a significant role in the risk. Viriditas (talk) 22:02, 6 June 2024 (UTC)

Real skepticism cuts both ways. Taurine is in human breast milk, evidence of benefit of at least one energy drink exceeding risk. :-) But our article has imho excessive, even dubious doubt in that section on its conditional essentiality or benefit for infants, and thus its common use in another energy drink. Doubt that appears to stem from OR or opinion rather than the source, which says e.g. "Thus the new data provide further support for the view that taurine is a conditionally essential nutrient for the preterm infant" & that ethical considerations seem to prevent further research.John Z (talk) 03:57, 7 June 2024 (UTC)

June 9

Weigeltisaurus species clarification

Is this Weigeltisaurus reptile in this family Rhynchocephalia. Would that statement be true to say. Its for this article Johannes Weigelt. There is source that states it but I don't know how accurate it is. scope_creep^Talk 21:23, 9 June 2024 (UTC)

While Weigeltisaurus flourished in the Late Permian, our article on the order Rhynchocephalia states that the oldest record of the group is dated to the Middle Triassic. According to this chronology, a gap of several million years separates them.  --Lambiam 07:21, 10 June 2024 (UTC)

Right. I'll leave the Rhynchocephalia bit out and only mention the Weigeltisaurus bit, since I don't understand it. Thanks @Lambiam: scope_creep^Talk 08:52, 10 June 2024 (UTC)

June 11

Can we agree on what the rule of the Council of Nicaea actually was?

• Transferred from Humanities desk

Let me highlight Jack's comment above:

...What is or is not legal is a matter for courts or legislatures to determine. Not the media, not individual partisan politicians, not the man in the street, not the reasonable man, and not random commentators (on Wikipedia or anywhere else). -- 22:23, 6 June 2024

So why is Wikipedia still saying Wedding of Prince Harry and Meghan Markle#Preceding private ceremony "The Church of England sources commented that this was not a legally recognised marriage ceremony, which requires two witnesses", citing journalist and radio commentator Camilla Tominey, who screamed down the telephone I WILL NEVER WRITE THE STORY that Camilla and Charles' wedding ceremony was a "non-qualifying ceremony" (i.e. void), following up with a stream of invective which only ended when she was cut off? And as the words "Registrar General" are eiusdum generis with the list of occupations provided by Jack, why is the linked article still saying "the Registrar General, Len Cook, determined that a civil marriage would in fact be valid"? The articles are so full of editorialising that it is best not to read them and go to [6] and [7] instead. Needless to say the "impediments to marriage" listed in the licence do not apply to the marriages of non-royals, because they were abolished by the Marriage Act which specifically states that its provisions have no applicability whatsoever to royal marriages. 92.25.129.245 (talk) 16:45, 8 June 2024 (UTC)

Readers may be interested in a dream I just had. Following the inception of the discussion (Wikipedia:Reference desk/Humanities#June 7) about al-Biruni and the Byzantine calendar, before I went to bed last night (30 James, the day before the date marked with this year's "golden number" (11), 1 Eloise), I looked for the new moon and saw a very slender crescent low in the north-west. In the dream, I was at work and was told that Camilla Tominey and another presenter had arrived to interview me. The male presenter remained outside and Camilla came in. She was aggressive and incoherent, and after a while an aide entered and bundled her out. I heard him say as he took her away "You're not on the programme any more. We're changing the presenter." Then the other presenter came in and said "You're going to be on the programme - ATV." As we left, he commented "You're casually dressed." I said "Shall I go home and change into something more formal?" and he said "We'll dress you at the studio." Then he asked an assistant "She's carrying a handbag, take it from her." I thought "This is for the general election." Outside there were a number of vehicles. Beside one of them a woman staff member was restraining a short man with his hands behind his back. I woke up at this point and went downstairs. It was 1:30 AM. I switched on the radio and this song began playing: [8]. 92.12.79.187 (talk) 15:42, 9 June 2024 (UTC)

As a matter of historical interest, one grouse the Muslims had about the imposition by the Caliphs of the new, unintercalated Islamic year for administrative purposes to replace the 365-day Zoroastrian year previously used in Persia was that it was shorter, which meant that the land tax would come round before the harvest had been collected! The Caliphs relented and reinstated the araji (land-tax) year for fiscal purposes.

But then another problem presented itself. The Muslim era began in AD 622 with the Hegira (flight) - the Persians later fixed the beginning of this era on Friday, 19 March. The Zoroastrian year needed periodic readjustment because it was itself on average six hours shorter than the Julian. Al-Biruni notes that there was a double adjustment of the start of the araji year during the reign of Yazdegerd I (AD 399-420). An araji era was introduced dating from AD 621. In a further recalibration, the Yazdegerdi era, still used by the Zoroastrians (Parsees), dates from the accession of Yazdegerd III on 16 June AD 632, so the Yazdegerdi era is eleven years behind the araji. In AD 895 there was another double readjustment of the start of the araji year. It moved from 1 Frawardin (12 April) to 1 Khordad (11 June), referred to as 11 Haziran (I think the Turks call June by this name to this day).

Today's Byzantine date (Monday, 2 Eloise), marks the imminent arrival of the Jewish Feast of Weeks (Pentecost), observed on the 6th of the corresponding Jewish month. It is barred from falling on Tuesday, Thursday or Saturday, and slots in this year this coming Wednesday (4 Eloise). Orthodox Whitsun is not till Sunday, 23 June (15 Eloise), because of the rule that Orthodox Easter falls on the Sunday after the Wednesday after the date of the Paschal Full Moon (14 Miri) between 1800 and 2099 inclusive, a sharp contrast with the Roman Catholic Church (but not it's Byzantine arm), which likes to time its Easter festivities to fall in the week after the "Purim Full Moon". The Orthodox consider the Catholics to be in error and they are right - the Council's direction was that the Easter full moon must not precede the equinox, but in 1582 Gregory XIII directed that it must be the first after the equinox. This led to his calendar being banned in Orthodoxy. 2.30.124.132 (talk) 15:43, 10 June 2024 (UTC)

Some common Serbian names feature in the story. This article includes the following points:

• In addition to the issue of calendar reform, the Council of Constantinople (1923) also discussed possible union with the Anglican church and second marriage for priests

• Vladimir Dimitrijevic, a conservative author, said the Council of Constantinople was among the greatest mistakes of the Orthodox Church in the 20th century

The author is Jovan Trpkovic. An article by M S Dimitrijevic and others includes these points:

• The Serbian delegation came to the Congress with a proposition for calendar reform authored by Maksim Trpovic. He proposed the intercalation rule that the secular years in centuries which when divided by 9 have remainders of 0 or 4 will be leap years

• The general opinion of the participants was that the better solution was to retain the Julian calendar and only delete thirteen days...

The information was duly sourced and added to Julian calendar. This led to one editor demanding that the contributor be banned from Wikipedia for "inserting false information into articles" because "if thirteen days are excised from the Julian calendar it is no longer Julian." He further demanded that articles be pre-emptively semi-protected to prevent editors removing any unsourced falsehoods added by others. His campaign was successful and false information, for example that the Greek government introduced the Gregorian calendar in 1923, is embedded in articles all over Wikipedia. The original Serbian proposal was in fact a proposal that the calendar already legislated by the Greek government should now be adopted by the Orthodox Church. As to where the Greek government got its calendar from, it's described here although Trpkovic (who proposed it in 1900) denied all knowledge of Barnaba Oriani's calendar. Another example is the claim that "The reform of the calendar was authorised by a canon of the Council of Trent in 15.." (the last two digits of the date of the alleged canon are something of a movable feast, since they change periodically). 92.19.71.221 (talk) 15:14, 11 June 2024 (UTC)

References