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January 12[edit]

Bizarre error in official PLU code record?[edit]

If you look up PLU code 3474 on, you see that it's something called "Saffron" sweet potato. If you drill down and look at the whole record, you get this info which says that the botanical name is Escobedia linearis.

Now, I don't know what Escobedia linearis is, but it's in a family of parasitic plants that includes Indian paintbrush and Pedicularis densiflora... and very little that is edible. I would be shocked if E. linearis bears anything that resembles a sweet potato.

It seems much more likely that the species here should be the ordinary sweet potato, Ipomoea batatas. But what does E. linearis have to do with anything, and why is it in the official PLU code data? —Keenan Pepper 01:43, 12 January 2018 (UTC)

The phrase "sweet potato/yam/kumara is used, which seems a tip-off that the common name is not very cladistic in nature. I haven't tried to figure out what this plant is, but I would be prone to suspect it might actually bear something that vaguely resembles a yam or sweet potato, perhaps saffron-colored. As with the common tomato, it is hard to guess whether a plant will bear wholesome fruit by looking at its relatives. Caveat: the image I found doesn't look like much of a potato! [1] (from [2]) Wnt (talk) 02:24, 12 January 2018 (UTC)
So you think E. linearis could actually produce food, and this be known widely enough that it has a standard 4-digit code for use in grocery stores? We should have an article about it! —Keenan Pepper 02:41, 12 January 2018 (UTC)
I don't know, but these PLU codes are published in multiple places; I'd think someone would have noticed. this source says that "azafrancillo" ('saffron', according to Google Translate) variety of sweet potato is indeed this species. Wnt (talk) 02:59, 12 January 2018 (UTC)
That link to kumara that you provided is inappropriate as it links to an article about a South African plant. Kumara (different language entirely) is indeed the Maori word for sweet potato, and in New Zealand it is, to my knowledge, a unique variety of sweet potato. It and its shade of meaning is discussed in the main article you linked to, so there was no need for the South African link. Akld guy (talk) 05:30, 12 January 2018 (UTC)

I agree that the link doesn't relate to what kumara is but I find your clarification equally confusing. Kumara is generally used for any sweet potato, or at least any of the 3 varieties common in NZ i.e. red (also sometimes called Owairaka or sometimes purple although there are also other recent imports often called purple), gold (also sometimes called Toka Toka or sometimes brown) and orange (also sometimes called Beauregard) [3] [4]. As far as I know, all 3 varieties are accepted to be derived from varieties introduced by European settlers or later, and don't share much in common with the varieties grown by Māori pre-contact [5] [6].

They may or may not be unique enough that they could still be called unique to New Zealand. My impression is that for at least one variety, the orange this isn't the case hence the alternative name Beauregard, see List of sweet potato cultivars. It may be what people in NZ sometimes think of when you mention sweet potato, if they don't just automatically translate it to kumara, given it looks similar to what I think is the most common "yam" or sweet potato in the US. (Although I'm not sure how many of those in the US are actually Beauregard even if it came from there. However from my experience, nowadays at least, everyone still just call it kumara or orange kumara or whatever. You sometimes hear sweet potato for very recent imports or those that haven't yet taken any real foothold here, although even then kumara is normally mentioned somewhere e.g. [7].

For further clarity the red variety is the traditional variety (i.e. it's what was probably considered kumara 50 years ago) and remains the most popular. But at least wherever I've been in Auckland, most fruit and vege shops, as well as supermarkets nearly always have all 3, and as said all called kumara. And if anything the gold is less common than orange nowadays. In fact [8] suggests orange could overtake red within 5 years (of 2017) due to changing demands.

There have been some attempts to reintroduce kumara grown pre-contact commercially, but these haven't been particularly successful as yet. As hinted at in the earlier sources and also others like [9] [10] [11], even finding these pre-contact varieties has been difficult.

Now this is English usage, but I'm pretty sure te reo is the same, or probably even more extreme. (I'm not sure if these's any term for sweet potato which isn't kūmara.)

Nil Einne (talk) 09:09, 12 January 2018 (UTC)

[12] has a better image. I do see some tubers. The source is Mexican and in Spanish, but machine translation of the description gives:

This tuber is used as a coloring and flavoring in certain stews; It is scarce, it is only present in one of the municipalities studied, Tacotalpa. It should be mentioned that the information regarding this species is scarce and is commonly confused with turmeric. The cultivation is of easy vegetative propagation due to the existence of abundant buds in the rhizome.

So it seems like the tubers are mostly used for colour and flavour rather than as a food source, which may explain why it's called "azafrancillo" or "saffron". I'm not sure why sweet potato is used, but maybe it is because it's the most commonly consumed tuber by the people who use it so "sweet potato" is something similar to "tuber". (You could probably say there are similarities with the word "yam" in English, and even more so with "corn".)
Nil Einne (talk) 07:05, 12 January 2018 (UTC)
BTW, it's also worth noting that given the large number of varieties, local growing conditions etc, even for something which is Ipomoea batatas people's mental picture is likely to vary. When I was in Malaysia, during Christmas I bought some kumara. The flesh and skin looked like what you'd call orange kumara in NZ but these very tiny, IIRC smaller even than what I'd call small potato. I don't know if I've ever seen a kumara in NZ that small. I think these were very small even by Malaysian standards as e.g. [13] those don't look very small although that's in Sabah no KL or peninsular Malaysia. And these in KL [14] although apparently from a prepared food or drink store rather than a market or supermarket also don't look that small. But even so, the point remains what rural villagers in Tacotalpa think of as a sweet potato may not be that similar to what you and I do even ignoring whatever colloquial usage and language translations issues that arise. Nil Einne (talk) 09:26, 12 January 2018 (UTC)

PID controller[edit]

PID controller uses the standard conventions for the gains, which is well and good:

is the proportional gain, a tuning parameter,
is the integral gain, a tuning parameter,
is the derivative gain, a tuning parameter,

But I'm dealing with a case where the PID controller uses this weird non-conventional notation:

is "Velocity gain" (note capital P)
is "Velocity gain"
is "Distance gain" (note lowercase P)

Since "" looks identical to "", and has the right units (milliseconds), I'm assuming they map to each other. But what about and ? Which one map to the proportional gain and which one map to the derivative gain?

The acceptable range (according to the controller) of is 0 to 10, unit-less. And 1 to 5000 for , also unit-less. Mũeller (talk) 02:25, 12 January 2018 (UTC)

The quoted weird notation strongly suggests a mistake. The name proportional–integral–derivative controller must imply it has three different gain constants which correspond in reality or metaphor to velocity-distance-(de)acceleration respectively. Have you a reference such as a product specification or data sheet that shows this case? SdrawkcaB99 (talk) 10:16, 12 January 2018 (UTC)

Brown crap on people's teeth that doesn't go away[edit]

Sometimes I've seen people with brown who-knows-what on their teeth which stays there day after day. What's that all about? Is it permanent? How did it get there? I'm not talking about a diffuse staining from coffee or nicotine; but it looks like they've eaten recently and got some crap stuck to their otherwise normal teeth. I've seen this several times on different people I've known but I can only dream of the kind of social skill it would take to broach that subject without causing offence. (talk) 17:46, 12 January 2018 (UTC)

Sounds like dental tartar. DuncanHill (talk) 17:48, 12 January 2018 (UTC)
Could also be dental fluorosis, standard tooth decay or celiac disease. Justin15w (talk) 21:28, 12 January 2018 (UTC)
I have brown spots on a couple of my own teeth where the enamel has chipped off, but there is no actual decay. At some point I'll get these covered up, but fortunately they do not show even when I smile. Someguy1221 (talk) 22:55, 12 January 2018 (UTC)


Is it true that orchids were once called bollockwarts as they can resemble testicles? The orchid page does not mention this. (talk) 22:32, 12 January 2018 (UTC)

Orchids are still called testicles, you just don't know it. The word is derived from the Ancient Greek ὄρχις (órkhis), which literally means 'testicle'. Though Google would suggest that no one calls them bollockwarts, now or in the past. Someguy1221 (talk) 22:50, 12 January 2018 (UTC)

Ah no. I its bollockworts . Can I have that as a user name? (talk) 23:52, 12 January 2018 (UTC)

Is "bollock(s)" considered a serious vulgarism in British English? If so, then probably not. ←Baseball Bugs What's up, Doc? carrots→ 00:47, 13 January 2018 (UTC)
Not really. I wouldn't expect to hear it in polite company, but compared with cunt it doesn't really have anything like the same impact. In fact describing something rubbish as "a load of old bollocks" is practically acceptable in many environments short of the vicar's tea party. There again I work with mechanics and engineers, swearing is a fact of life. Greglocock (talk) 02:59, 13 January 2018 (UTC)
Aside from a few comments on internet fora, I cannot find a good source to say that this word was ever used in that manner. One person claims it was once listed in OED, but the 1928 version that's available online doesn't list it. Anyway, it's not the job of Wikipedia to list every word ever used to describe a thing, though if the rumor could be verified, that would be something for Wiktionary. Someguy1221 (talk) 03:05, 13 January 2018 (UTC)
The word bollockwort does appear in the OED Third Edition (Revision of June 2008) as an obsolete word for a kind of orchid, but the two cites are from around 1300 and 1500 (the latter being from "Anglo-Saxon and Old English Vocabulary"). "Bollock grass" is another term for a type of orchid and has more recent usage. The word "bollock" was, according to the OED, "Apparently in standard use until the 17th cent., after which the word is regarded as coarse slang." Dbfirs 08:31, 13 January 2018 (UTC)
There appears to be a German equivalent Hodenkraut. Cheers  hugarheimur 08:51, 13 January 2018 (UTC)
See also our article Bollock dagger for another example of the term being used without contemporary offensiveness. Contrary to some people's hopes, it refers to form rather than function. {The poster formerly known as} (talk) 18:48, 13 January 2018 (UTC)
Our Bollocks article includes some research conducted by the BBC into the 'relative severity of the various profanities, as perceived by the British public'. The results, published in 2000, reported that "bollocks" came in at 'eighth position in terms of its perceived severity, between "prick" (seventh place) and "arsehole" (ninth place)'. So there you have it. Alansplodge (talk) 00:02, 14 January 2018 (UTC)
It's too much of a coincidence that the word bollockwort was mentioned on the BBC2 TV programme "QI XL" 24 hours after the question was asked here, so I wonder if our questioner has some connection with the programme? Dbfirs 07:53, 14 January 2018 (UTC)

When I see a discussion about this word, it's hard to resist posting a definition I came across in an old dictionary at the math library at UCLA:

*bollock* _Naut._ Either of two blocks attached to the topsail-yard in a ship, for the topsail-ties to reeve through

— Funk & Wagnalls New "Standard" Dictionary (Reg. U.S. Pat. Off.) of the English Language 1947

--Trovatore (talk) 08:28, 14 January 2018 (UTC)

The same sense of bollocks is recorded in C W T Layton's 1955 Dictionary of Nautical Words: "Blocks in bunt of topsail yards of large ships. Topsail ties are rove through them to increase lifting power"; and in A Ansted's 1898 Dictionary of Sea Terms: "blocks secured to the middle of the topsail yards in large ships; the topsail ties pass through them, and thereby gain an increase of power in lifting the yards." Dbfirs 12:15, 14 January 2018 (UTC)
Looking at a few images of topsail yards suggests that the nautical term may well derive from sailors noting a similarity to the relevant male organs! Wymspen (talk) 16:14, 14 January 2018 (UTC)

In 1977 the Sex Pistols relased an album entitled Never Mind the Bollocks, Here's the Sex Pistols. If you read the article you will find that a record shop manager who displayed posters for the album was prosecuted for displaying an indecent advertisement. During the case evidence was presented that bollocks was an Old English word for a priest and, in the context used on the album cover, meant "nonsense". The judge reluctantly ruled that the shop manager was not guilty saying "Much as my colleagues and I wholeheartedly deplore the vulgar exploitation of the worst instincts of human nature for the purchases of commercial profits by both you and your company, we must reluctantly find you not guilty of each of the four charges." So if you disagree with your priest tell him he's talking bollocks. Richerman (talk) 16:57, 14 January 2018 (UTC)

When I saw the lawyer's argument that "bollocks" is an old term for a priest I immediately thought that this was something he had made up to get his client off the hook. However, the dictionary says that the normal meaning of "bullock" is "castrated bull". Is there some connection given that the priests of the Roman Catholic church (the parish priests of the time) do not have normal sexual relations? Alternatively, is there some connection with the most solemn pronouncements of this church (which the priests circulated to their parishioners) which are known as "bulls"? With the arrival of the Reformation these were treated as nonsense, Latimer commenting in a 1537 sermon "I send you here a bullock which I did find amongst my bulls." (talk) 21:33, 16 January 2018 (UTC)

January 13[edit]

The Muslim Newton[edit]

Is The Book "Musalmano ka Newton" (The Muslim Newton) available in English Version? Danfarid133 (talk) 15:39, 13 January 2018 (UTC)

Musalmano ka Newton :Dr Abdus Salam (2003) مسلمانوں کا نیوٹن ڈاکٹر عبد السلام احمدی سپوت by Muhammad Zakaria Virk in Urdu is available for download here and here. The English Wikipedia article about the Pakistani theoretical physicist Abdus Salam will be of interest. SdrawkcaB99 (talk) 16:15, 13 January 2018 (UTC)
Is this book available in English or French.Danfarid133 (talk) 07:43, 14 January 2018 (UTC)

January 14[edit]

Nannostomus beckfordi in Rio Guapore?[edit]

I am having trouble finding info on whether Nannostomus beckfordi can be found in the Guaporé River. It seems commonly accepted that it inhabits the Madeira River and some of its tributaries, but I could not find a source mentioning the Guaporé River specifically. Surtsicna (talk) 11:01, 14 January 2018 (UTC)

Google suggests:
Nannostomus beckfordi Giinther. 14. Nannostomus ... The Rio Madeira-Rio Guapore collection consists of 31 individuals...
—But I haven't figured out how to find it. —2606:A000:4C0C:E200:1D4C:29E3:6313:60B3 (talk) 23:31, 14 January 2018 (UTC)
There is a PDF version available online but if I understand correctly, it refers to Nannostomus digrammi. Surtsicna (talk) 09:14, 16 January 2018 (UTC)

Accelerating towards the sun[edit]

I was watching this video and it discussed how to hit the sun, and it asserts you have to cancel your orbital velocity in order to fall into the sun. But why can't you just accelerate towards it? Or even just given an initial velocity towards the sun, won't you hit it eventually? The rocket should still have a velocity vector aimed right at the sun correct? And in outerspace there's no friction to slow down your vector towards the sun so I would assume that you can still hit the sun simply by heading towards it. ScienceApe (talk) 13:08, 14 January 2018 (UTC)

Your total velocity vector is relevant, not a possible component you add towards the sun. Note that the Earth is continually accelerated towards the sun (by the gravitational attraction of the sun), yet never hits it (*knocks on wood*). Qualitatively, you can see it this way: If you are in orbit around the sun, you have a significant velocity perpendicular to the line from you to the center of the sun. If you add a small vector along that line, by the time you would have reached the sun, you've moved very much sideways, so you miss. And the added velocity vector is not even pointing towards the sun anymore. On the other hand, if you just cancel your orbital velocity, gravitation alone will accelerate you to the sun, and you will hit it. --Stephan Schulz (talk) 14:49, 14 January 2018 (UTC)
(ec) Orbital mechanics can be counterintuitive sometimes. (If you have the time, money, and inclination, Kerbal Space Program provides a thoroughly frustrating and delightful insight into the problems of manoeuvering in space.)
"The rocket should still have a velocity vector aimed right at the sun...there's no friction to slow down your vector towards the sun..." The problem is that your impulse toward the Sun adds a component to your velocity vector that points towards the Sun at the time that it's applied, but your rocket keeps its original momentum 'sideways' (that is, in the direction of its original orbit, or prograde) as well. That new velocity component that points at the Sun now will be pointing tangentially to it a quarter orbit later, and away from the Sun half an orbit down the road. The overall effect is that you go from your original nearly-circular orbit to one that's more eccentric (more elliptical, or 'squashed' and cigar-shaped), but still stable.
Additional inward burns will change that eccentricity (make the 'cigar' narrower or fatter) and/or rotate the axes of the orbit around the Sun (change the direction the cigar points); the degree to which one or the other occurs depends on where you apply that thrust in the orbit.
In principle, if you apply enough inward thrust over a short enough period of time, you can squeeze that 'cigar' down to be narrow enough that rocket grazes the Sun instead of sliding sideways past—but that's way more expensive than doing a retrograde burn (i.e. 'cancelling' your orbital velocity to fall into the Sun). TenOfAllTrades(talk) 15:16, 14 January 2018 (UTC)
  • Let me just point out the curious fact that it is possible to accelerate constantly toward the Sun (that is, always centripetally) without your orbit changing at all. If the equation a = v2/r holds, with a directed toward the Sun and v at right angles to the Sun, then you will move in an unchanging circular orbit. This actually shouldn't be a surprise, given that gravity creates a constant acceleration that is always directed toward the Sun. Looie496 (talk) 15:41, 14 January 2018 (UTC)
To try to give a more intuitive analogy, imagine you're in a boat in the middle of a river, being pulled by the current. You pick a point on one of the banks, at a ninety-degree angle to your direction of motion, and start moving towards it. By the time you reach the bank, you'll be downriver of the point you selected, because you continued moving with the current while you also moved towards the bank. In this analogy, the point on the river bank is the Sun, and your motion downriver is your previous trajectory relative to the Sun. Things move at high speeds in space, because there's nothing to stop them. It doesn't seem like it because our hard-wired intuition is designed for an Earth-bound environment; because the distances are so big and there's no "fixed" background to easily compare against, it looks like things in space are moving slowly if at all. For some numbers, the International Space Station, and other things in low Earth orbit, are moving at about 8 kilometers per second relative to you and me. That's much faster than a bullet fired here on the ground. They circle the Earth roughly every two hours. Similarly, we're all cruising around the Sun at about 30 kilometers per second. If you point yourself towards the Sun, you're still moving screamingly fast around it, and so (as noted above) you just wind up in a wackier orbit around it (because the Sun's gravity keeps you from flying off into deep space). Although, as TenOfAllTrades said, if you had infinite fuel you could eventually stretch your orbit out so much that you would take a dive into the Sun next time you went past, but there's no real point since that takes more fuel than the "right" way of adjusting your orbit. Also, depending on payload, there's no guarantee (very hot) stuff wouldn't pop back out the other side of the Sun, since you're just grazing the photosphere, which might be a problem if you were trying to get rid of whatever it was. This is one reason why the sometimes-raised idea of launching nuclear waste into the Sun isn't a good idea. This, I think, is good at explaining some more about orbits. -- (talk) 10:24, 15 January 2018 (UTC)

This doesn't really seem very complicated to me. If you made a map of your present orbit, you're moving straight sideways relative to the sun. To hit the sun, the most straightforward way is to have your motion be straight at the sun. I mean, if you picture Captain Kirk on the bridge he wants to see the sun getting bigger and bigger, not moving right or left. And in order to do that, the ship has to counteract its present off-course motion. If your warp engines allow you to accelerate to a much faster speed than your current orbit, you don't even have to aim much to the side of the sun ... just enough to "correct" your course so you're moving right at it. Don't forget the sunblock! Wnt (talk) 20:02, 15 January 2018 (UTC)

Lying to children about science[edit]

When people teach children about complex phenomena like atoms (as composed by little balls orbiting around bigger balls) or DNA (as a building plan for living beings), could it be that we unwillingly making it more difficult to understand the real thing later on? Couldn't it even be that we are making them believe crazy stuff? --Hofhof (talk) 20:33, 14 January 2018 (UTC)

Would you start elementary reading classes by having them read Shakespeare? Or would you go for simpler stuff that they can more easily grasp? ←Baseball Bugs What's up, Doc? carrots→ 20:42, 14 January 2018 (UTC)
Don't "people" teach children that this was what was once believed, or that this is a first approximation? All scientific models eventually turn out to be approximations[1]. This doesn't make them lies. Dbfirs 20:48, 14 January 2018 (UTC)
The aricle you linked in the header discusses at length the value of the method, the risks, and the importance of choosing the correct lie to help learners get started but not get too misled for later learning. It even uses DNA as a specific example. DMacks (talk) 20:53, 14 January 2018 (UTC)
Maybe. As our article you linked to states, however, 'Worstall stressed that this form of educational methodology was ubiquitous across multiple academic disciplines: "This is true of any form of education by the way. We don’t start music classes with atonality, we start with simple scales. We don’t do syncopation until we’ve mastered 2/4 and 4/4. Einstein’s corrections at the margin to Newton come quite late in a physics education."' In other words, whether it leads to wrong-thinking or not, it is pretty much the standard way to teach everything... everywhere. Reality is horribly complicated; people would get lost if you started the ABCs with discussions about phonetics. Matt Deres (talk) 22:11, 14 January 2018 (UTC)
On the contrary, teaching a simple model can make it easier, not more difficult, to understand a more complex model later. If we don't teach simple models, then the human brain makes its own model, and can often get it even more wrong. Dbfirs 22:20, 14 January 2018 (UTC)
This is the right way. 00:16, 15 January 2018 (UTC) — Preceding unsigned comment added by Count Iblis (talkcontribs)
I would start by teaching scientific method, for young children just hypothesis and test (salt will dissolve in water but sand won't, maybe asking them about some less familiar substances). Then as they get older teach them about hypotheses, laws, and theories. That way, when you teach simplifications they will realise that these are not "lies" but hypotheses and laws that have actually been refined. I think a great example is Newtonian physics, and how it can be used to land a man on the moon, but not explain things like gravitational lensing. -- Q Chris (talk) 08:58, 15 January 2018 (UTC)
Thanks, Count Iblis! Joepnl (talk) 00:47, 18 January 2018 (UTC)
  • Well, the word "like" exists. Children have no problem understanding that chocolate is like hard cheese or butter in a way that it is not like broccoli or spinach. They can understand at about age 6-7 that there are difficult ideas that you have to learn first before you can understand even more complex ideas.
I remember being annoyed that the only thing adults would tell me about Watergate was that I would understand when I was older, and I remember being told the basics of stoichiometry and algebra at age 8 with the ability to see it worked, even if I hadn't automated the more basic concepts yet that you needed to master to move on to those harder ones.
There is absolutely no a priori reason to believe that scientists believe that particles are billiard balls. Billiard balls are both mechanically disruptible and exist on a hugely different scale. Some people do get English degrees and become science journalists, but there's no reason to believe we are all confused as they are. I suggest Ayn Rand's Introduction to Objectivist Epistemology, especially the chapter on "Abstractions from Abstractions". μηδείς (talk) 03:18, 16 January 2018 (UTC)
When I was in primary school the music teacher told us that a crotchet was one beat. Some time later she said that the beat depended on the music (this is discussed in the second sentence of the article lead). I said she must have got it wrong, because we had always been told it was one beat. She then said that she had only told us this initially because it was simpler to understand. I asked her if this was explained in a book anywhere and she showed me a copy of Rudiments of Music which appeared to cover the theory in great detail, and sure enough it was as she said. (talk) 21:11, 16 January 2018 (UTC)
It is important to develop trust with students, and I make it a point always to explain when I am using simple examples, analogies, rules of thumbs, when exceptions are known, that an idea is heuristic, etc. One of my favorite legal writers is absolutely brilliant as both a legal writer and thinker and extemporaneous speaker, and her knowledge is so broad that I find it absolutely incredible that she neither believes in nor can explain evolution, although she graduated from a well-regarded secular secondary school and has a JD.
I suspect that at some point she was told a falsehood--maybe something like "monkeys eveolved into people"--as a fact when it is shorthand for saying that monkeys and humans have the same ancestors. This same problem makes it impossible for my otherwise quite intelligent mother to understand why the rest of the monkeys aren't currently also evolving into people, if monkeys really do "evolve into people". Pedagogy is much too dangerous to be left to the professionals. μηδείς (talk) 21:51, 16 January 2018 (UTC)
Recommending Ayn Rand is one of those ref desk jokes, right? - (talk) 19:29, 17 January 2018 (UTC)
No more of a joke than the original premise of this section. ←Baseball Bugs What's up, Doc? carrots→ 22:15, 17 January 2018 (UTC)
So if DNA is not a building plan, what's the use? Even scientists at the very edge of science need to have some sort of model. Science didn't skip Atomism to reach the current state of quantum mechanics, and we probably wouldn't get much further without studying the current model even when we know that we're still looking at a model that can't possibly be describing the full truth. I think kids follow the same path. Joepnl (talk) 22:38, 17 January 2018 (UTC)


  1. ^ "truth … is much too complicated to allow anything but approximations".von Neumann, J. (1947), "The Mathematician", in Haywood, R. B., Works of the Mind, University of Chicago Press, pp. 180–196 .

January 15[edit]

How much care is exercised in naming new concepts in quantum physics? (e.g. "wave function collapse")[edit]

I understand naming standards like ISO for computer science and IUPAC for organic chemistry, but I don't know any details about the process of naming terms & concepts in quantum physics. Those I've asked in discord/reddit have said quantum physicists have bigger egos than computer scientists or chemists, which I find irrelevant. Hoping to find a more helpful answer here... Thanks, (talk) 16:15, 15 January 2018 (UTC)

The basic answer is that the person who invents a concept has the right to name it, and often exercises little care in doing so, because people don't usually realize that their new concepts will turn out to be important. The result is that lots of things get poorly named. One of the most egregious examples is theory of mind, which is not actually a theory. Computer science is not by any means immune to this. Standardized naming only applies to things that fall into recognized groups, such as file formats. New concepts, such as agile testing, are named by whoever thinks they are worth naming. The history of the word interface -- as central a concept to computer science as you can find -- is particularly interesting: it came into use because some engineer back in the 1950s couldn't think of anything better. Looie496 (talk) 17:09, 15 January 2018 (UTC)
It is also worth considering that much of quantum mechanics was originally developed in languages other than English. Important concepts are embodied with non-English words like eigenfunction, ansatz; and even words like the photon and the action and even the quantum are at best "technically" part of the English language, though they all derive their modern application in physics by way of other modern languages, followed by subequent retranslation into our own English-like technical jargon.
When you read about wave function decomposition in German, it reads a lot more like plain language. I frequently wonder if American students of physics would have an easier time if we never used the word-fragment "eigen" for any purpose; many modern math curricula use the word "characteristic" in its place.
The jury is still out on how effective any of this stuff is. Some research implies that students learn better if we vary the vocabulary while teaching the concept. Contrarily, some research implies that students learn worse if we vary the vocabulary while teaching the concept. Here's a research brief from a group recommending that we make introductory-level students write essays about physics vocabulary: The vocabulary of physics and its impact on student learning.
In my experience, I have found that the pioneer researchers do not automatically obtain the privilege of naming the concepts: on the contrary, they reap fame and credit, but it is the forgotten, nigh-anonymous authors of the best textbooks who actually get to name the concepts.
Though you surely believe that Newton and Leibniz invented calculus, you almost certainly recognize the mathematical vocabulary and the symbolic equation conventions used by Stewart. I challenge any novice to read Principia Mathematica and make a concerted effort to recognize when and where our esteemed author applies u-substition! And the very same applies to more advanced physics: just a few weeks ago, here on Wikipedia, we did an etymological dive into the etymological history of quantum mechanics: Who first analyzed the 'particle in a box' model? Again, most readers of Schrodinger's actual writing will not recognize the Schrodinger equation that we all know from our textbooks. Which author actually came up with that name?
And if you read that paper, why, it's right there in plain German, with no bizarre or fancy techno-babble jargon! There is no "quantization," and the author takes pains to avoid the word "whole," explaining in his opening that the quantization is the natural consequence of the system. Now! This is troublesome, because in the English language, a whole number is a mathematical word for a natural number (or integer); how can we possibly translate this concept into our language, in which the natural number occurs naturally without a priori requiring it to be a whole number? The trick is to first learn German, and then to learn quantum physics, and it will save you a lot of conceptual headaches - especially when you study translational invariance.
Nimur (talk) 23:48, 15 January 2018 (UTC)

trying to identify a plant by pictures[edit]

unidentified plant from Caesarea, Israel
unidentified plant from Caesarea, Israel

I'm trying to identify a plant, shown in the following pictures, which resembles arecaceae, but it isn't a member of this family. The pictures were taken somewhere in ancient Caesarea in Israel, in October 2017. Also the purple cluster shown doesn't look familiar, at least to me. I'll be glad to get clear & professional identification. Some Yucca, may be ? Not sure. בנצי (talk) 15:12, 15 January 2018 (UTC)

Not identical, but Yucca baccata leaves and fruit have a similarity (but a long way from home). Alansplodge (talk) 19:38, 15 January 2018 (UTC)
The fruit look like those of Yucca aloifolia - not native to the Middle East, but widely planted and naturalised in some Mediterranean countries. Wymspen (talk) 21:57, 15 January 2018 (UTC)
a. I don't know who aligned the pictures - thank you (you saved me another question, a technical one, regarding this).
b. I tend to agree with the 2nd identification - Yucca aloifolia. It seems the only Yucca bearing such fruit cluster, in shape & color as well. Also the comment you make regarding acclimatizing the plant to the region sounds true to me.
c. In Yucca appears the following wonderful Yucca species, but with no name - who knows which one is this (see below) ?
בנצי (talk) 17:57, 16 January 2018 (UTC)
Could be Yucca neomexicana - right colour, and right location. Wymspen (talk) 21:45, 16 January 2018 (UTC)

Fire containment calculations[edit]

I was reading our article about the Thomas Fire and I'm curious about some of the statements made regarding fire containment. How is it calculated? Is it a measure of the active perimeter under control? I understand there's a technical definition being met, but to the layperson saying that a fire is 10% contained is a bit like being 10% pregnant. I assume we have an article about it, but I can't seem to find it, having gone through glossary of wildfire terms, wildfire, fire control, and fire suppression. Fire containment just redirects to firefighting. Matt Deres (talk) 17:27, 15 January 2018 (UTC)

Sounds like an article I should think about drafting...
You are correct in saying that wildfire containment is calculated as a percentage of the active fire perimeter which has, in the view of the incident commander, sufficient fire control line around it. (Note that this does not always mean that line will hold up under any conditions.) These are always somewhat rough calculations, but they are aided by GIS, satellite and aerial tracking methods; major wildfires in the United States are mapped nightly by United States Forest Service infrared scanning aircraft when available and there are several NASA satellite programs which aid in remote sensing of wildfire, including the Moderate-resolution Imaging Spectroradiometer and the Visible Infrared Imaging Radiometer Suite. Note that the definition of "active fire perimeter" we use might be different than the one laypeople expect — while the TV cameras might have moved on from an area because the fire has burned through, we still consider that area "active" until there is a control line around it. Just because there aren't big photogenic flames anymore doesn't mean there isn't still enough residual heat to reignite under the right conditions. NorthBySouthBaranof (talk) 18:08, 15 January 2018 (UTC)

Nuclear Propulsion Technology (Ships)[edit]

How long would it take us to create the infrastructure for nuclear propulsion technology for cargo ships on a massive scale? Please direct me to sources showing why or why not we would be able to achieve this goal within the next 20 years or so. Thanks! HarryOtter (talk) 22:30, 15 January 2018 (UTC)

Four nuclear-powered cargo ships have been built, starting in the 1950s: Nuclear marine propulsion#Civilian nuclear ships, plus some icebreakers. One of the cargo ships is still puttering around today. Another is moored in Baltimore if you want to go take a look at it. Abductive (reasoning) 22:36, 15 January 2018 (UTC)
(edit conflict)You mean like, ocean-bound cargo ships, but nuclear powered as with aircraft carriers and submarines? Also, do you mean massive scale as in the ships are massive, or the fleet of ships is massive? We have an article Nuclear marine propulsion, that includes a section on civilian use. Experimental nuclear-powered cargo ships have already been built, but it has apparently been repeatedly determined that the infrastructure costs of nuclear power as compared to fossil fuel use are prohibitive, and not offset by how much cheaper uranium is on a per-energy-unit basis. It is also speculated, as described in the article, that a large fleet of nuclear cargo ships could share some of the infrastructure costs and make this less of an issue, but there simply isn't any motivation to do that. Someguy1221 (talk) 22:41, 15 January 2018 (UTC)
Here is a 1999 report from RAND on the implications to the nationwide industrial base, to help the Navy decide whether to build non-nuclear or nuclear versions of what are now the USS Ronald Reagan and the USS George H.W. Bush: Industrial Base Implications of Nuclear and Non-Nuclear Options.
Those are just two vessels. However, the report explains that building merely two vessels will have strategic impact on the entire industrial base. In particular, it impacts things like the total number of nuclear engineers needed in the entire world. Where will you buy your fuel? "I'm sure that in 1985, plutonium is available in every corner drugstore, but in 2018, it's a little hard to come by." For example, did you consider than in 1999, almost all of BWXT's work force was due for retirement? Unless somebody starts getting the young kids to start taking degrees in nuclear engineering, who will design, build, and sell fuel rods to your fleet of ships? (It sure is a bummer that our society pays engineers more money to build software toys than to make nuclear reactors - one of many flaws of a western-style capitalist economy. What smart young whippersnappers are going to want to take on a difficult, high-risk, hazardous, low-transferrible skillset, when they can get paid 500% more money to spread Russian propaganda? Besides, nuclear physics is hard, even if you're ... like, really smart!)
So, unless the Government steps in to ...ahem, "reequilibrate" the invisible free hand of the economy - you know, all Reagan-style, like they did in the 1980s, back when the Government didn't interfere with the economy - our best and brightest just don't want to do the jobs that our world requires to sustain a nuclear-powered economy.
With a twenty year lead time, we could probably train a new cohort of nuclear scientists and engineers... so don't worry, it isn't like we have a twenty-year backlog of crushing the hopes and dreams of aspiring nuclear scientists. We've only been doing that for, um, darn it, thirty years? Man, I'm getting old and crochety!
Nimur (talk) 23:46, 15 January 2018 (UTC)
When we learn to manage stable Nuclear fusion there will be a good chance for broad civil use. Current nuclear technology is to dangerous, regulated and complicated for civil use, with a few exceptions where it has so huge benefit that it makes sense again, like in nuclear medicine, large scale electrical power generation and as capital icebreaker propulsion. --Kharon (talk) 02:34, 16 January 2018 (UTC)
"Dangerous" my ass -- just compare how many nuclear meltdowns there have been (only THREE so far -- Three Mile Island, Chernobyl and Fukushima, and ONLY Chernobyl caused any loss of life) versus how many refinery fires happen each year, and see for yourself! 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 06:01, 16 January 2018 (UTC)
Three? You mean 20? Nuclear meltdown#Nuclear meltdown events. The meltdown at the military's Stationary Low-Power Reactor Number One (SL-1) in 1961 was the first time a nuclear meltdown proved unambiguously fatal, killing three operators. Generally most people only talk about the meltdown events that breach the containment vessel and spread radiation into the general population, but reactor failures resulting in partial or total meltdown have happened more often than just the three you mention. Dragons flight (talk) 08:06, 16 January 2018 (UTC)
No matter -- compare the miniscule loss of life in nuclear accidents vs. the thousands who die in accidents involving oil production and refining, and see for yourself that nuclear power is NOT dangerous! 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 10:36, 16 January 2018 (UTC)
Keep telling yourself that. ←Baseball Bugs What's up, Doc? carrots→ 14:07, 16 January 2018 (UTC)
The biggest problem with nuclear incidents is that Futaba still has a population of zero, just like Chernobyl. It is one thing to have an accident that kills a few people, even a few hundreds of people, but it is something else again to draw a circle around a 24-mile diameter chunk of a country and say nobody can live there any more. Nobody wanted those nuclear cargo ships in their docks -- that was one of the main obstacles to their service. Also, remember the Fukushima disaster was really pretty moderate, only a "level 7 nuclear disaster" or so with multiple reactors leaking. Had they failed to prevent the vast numbers of stored waste fuel rods on site from catching on fire and burning, I'd call it more like a "level 8". (They don't actually have that ... our article International Nuclear Event Scale claims numerically it would be more like 10 or 11 even as it was) Wnt (talk) 16:44, 16 January 2018 (UTC)
The earth's surface in on the order of hundreds of millions of km2. I'd say a few thousand km2 lost in learning mistakes are vastly preferable to systematically destroying the whole ecosystem. (different IP) (talk) 03:35, 17 January 2018 (UTC)
Rather than participating in the infighting, here's a link to the MIT Reactor public tours website. Act now! Tours re-open in February. It's one of the largest reactors that you can visit. Be sure to pick up some souvenier alternate-periodic-table-of-the-elements wall posters while you're there, arranged by radiochemistry instead of electron configuration (like this digital copy from BNL). Those posters are hard to find outside of the private collections of the ever-so-small cabal of esoteric nucleon science enthusiasts!
And if you, like I, should have the opportunity to take a ski vacation to the Rockies, don't forget your geiger counter. In all seriousness, pick up (and study) a geology field guide and be careful what you carry home - thar be real radioisotope in them hills! Many rock-collectors have accidentally obtained concentrated uranium in their collections; and while sporadic exposure is probably okay, keeping a source of ionizing radiation in your house leads to all sorts of problems - especially that most invisible foe, carcinogenesis by chronic inhalation and bioconcentration of radiogenic radon. It's never the obvious hazards that get you!
Nimur (talk) 16:22, 16 January 2018 (UTC)
My landlord placed several sources of ionizing radiation in my house, americium to be precise, hidden in plastic containers. He claimed that the state ordered him to do it. He calls them "smoke detectors". -Arch dude (talk) 17:08, 16 January 2018 (UTC)
It's not a technology issue, rather a security, economic and risk issue. Warships are heavily guarded and overmanned. Container ships are lightly guarded and lightly manned. In general, efficiency for economic reasons tends to move towards less manpower which nuclear does not do at the ship level (even in the Navy, only the largest aircraft carriers are nuclear powered). Economy of scale is limited to propelling a single ship and no shipping vessel will want a crew complement equivalent to the security and engineering on an aircraft carrier. The holy grail of course is batteries with the energy density of fuel oil that could be recharged by nuclear power at a port. --DHeyward (talk) 00:47, 17 January 2018 (UTC)
Actually the main issue would be general maintenance and regular checks that puts these vessels into the docks for weeks or even months on a regular interval, similar as its done at nuclear powerstations. That is no problem for military vessels or icebreakers, which are expected to come back home frequently or on a seasonal basis.
But cargo ships are generally expected to never stop. Especially the big ones, which would make most sense to equip with nuclear propulsion, need to make their Return on Invested Capital in competition to any other investment. You can not send such a big ship to the docks for one month every year for mentioned and revision while cheaper build big ships in competition, with usual diesel engines, just keep making money. Better fuel economy can not make up the difference. Unless you are the CEO of your privately owned shipping company you will be in huge trouble with all the extra costs. --Kharon (talk) 03:11, 17 January 2018 (UTC)

More advanced reactors that are more than twice as efficient as current designs could make civil nuclear ships feasible. See Fission fragment reactor ScienceApe (talk) 20:26, 17 January 2018 (UTC)

January 16[edit]

Stirling single[edit]

Is it possible for a Stirling Single to use anthracite or coke for fuel instead of bituminous (usually Welsh) coal (as was done, although with engines of a very different design, on the Lackawanna line)? How would this affect performance? Would this completely eliminate particulate emissions, or would these still happen at some point (e.g. smoke emissions during starting and acceleration, due to fire-throwing)? 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 06:07, 16 January 2018 (UTC)

Yes, it would be possible. It would work fine on anthracite, as that's what the GNR used to fuel it. This fuel (hard coal from NE England) was used by the GNR, then LNER, and was why they adopted those wide Wootten fireboxes, as are so distinctive on Flying Scotsman today. It's good coal, but it needs a wide fire.
It wouldn't work so well on coke. Coke provides less specific heat by volume, but also has a higher burning temperature on the firebars. If you build a typical fire, you run out of steam. If you build a thicker fire, and force it, you can melt or clinker the firebars. Coke is sometimes used today on preserved lines, because it can be obtained cheaply from old filter beds. Horrid stuff though!
The question of appropriate coal is an important one in the UK. The GWR in particular relied on Welsh steam coal (the world's finest quality coal for this) and designed their fireboxes to be narrow and deep accordingly. One reason why they kept 4-6-0 rather than 4-6-2 Pacifics was that they didn't need to carry such a big heavy firebox. Similarly for the LMS under Stanier (GWR V2.0). In the 1948 Locomotive Exchange Trials, the locos of the different companies were swapped around and compared on local workings. It was found that all the locos of this generation were well designed and performed well, but that firing techniques needed to follow the locomotive and that some coals didn't work well on some locos - mostly the King running on the East Coast line.
UK locos weren't noted for fire throwing. It's too urban a country, with too good a supply of coal, so throwing smoke or sparks was quickly noticed and heavily frowned upon. It did happen during WWII when coal quality fell (small coal), but not in peacetime. The BR Standard classes did have self-cleaning smokeboxes though, which operated by breaking the smokebox char down into small enough pieces to be thrown out through the chimney.
The leading work here was the Gas Producer Combustion System, based on the work of L.D. Porta and later David Wardale. This allowed low quality small coal, usually of the higher chemical grades, to be burned more efficiently (it wasn't much use for coke). This was adopted by the NCB as it allowed them to burn waste coal from the pithead. However the development of pulverised fuel for power stations gave a better market for that. Andy Dingley (talk) 14:04, 16 January 2018 (UTC)
So, by using anthracite, would it be possible to achieve completely smokeless operation (as in, zero visible smoke or soot under all normal driving conditions, even in tunnels and when starting on steep grades) specifically with a Stirling Single? (Or, for that matter, with a Black Five or the Flying Scotsman you mentioned?) 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 07:27, 17 January 2018 (UTC)
Well, what's "normal"? How exceptional is it allowed to get before it's not?
British steam locos, in normal operation during the "golden years" (i.e. not clapped out or wartime austerity) had clean exhaust. This was a legal requirement since the Stephenson era, and meant coal couldn't be used before the 1860s and the development of the firebox brick arch. It was also a pretty carefully enforced rule within companies, and a fireman who couldn't manage it would find themselves carpeted by the inspector. Of course it wasn't perfect. Of course some lines were careless, or just uninterested. But if you look at photos of the period, a well-run loco in a city would have a clean exhaust - at least to the level where any dark smoke was hidden by the steam. Wartime and post-war austerity - different story. Mostly owing to poor coal, even more so than lack of maintenance.
Tunnels, in particular, would require clean exhaust. No footplate crew wants to get kippered. Inclines were avoided in tunnels, for just that reason. Some city station approaches had infamous tunnel gradients, and these often required locos to be in good condition to work them - and it's recorded (particularly for Kings Cross) that a worn loco which couldn't manage this would be rapidly moved off that roster. The UK just didn't go in for those long "rolling coal" hillclimbs beloved of US photographers, or the lignite coals of Eastern Europe where nothing could make it burn cleanly.
One exception to this was around coal mines themselves. The lure of cheap (or even free) small coal meant that these were a lot sootier and ashier. With the gradients of South Wales, you do see some locos making a lot of smoke - but in the Welsh Valleys, few would notice a bit more. Also the prevailing gradients there were mostly downhill. Most Welsh coal came out via the GWR coast route, not northwards and up over the LNWR. Andy Dingley (talk) 10:36, 17 January 2018 (UTC)
Well, "normal" means a well-maintained locomotive with an experienced crew starting a train of up to maximum rated weight for that locomotive (in case of the Stirling Single, up to 26 lightweight coaches or 6 heavyweight ones), accelerating up to maximum speed (again in the case of the Stirling Single, 85 mph with 6 lightweight coaches or about 60 mph with 26 lightweight coaches), hauling it up and down a 1-in-75 grade (AFAIK the maximum allowed on British mainlines), and then stopping at the next station. With good-quality anthracite fuel, would it be possible to achieve completely smokeless operation (meaning no particulate emissions at all, not just smoke being hidden by the steam)? I.e. if, say, some patriotic passenger decided to wave the Union Jack out the window of the first coach the whole way between stations, would the flag remain clean, or would it get dirty from the cinders and ashes thrown out from the engine's smokestack? 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 11:10, 17 January 2018 (UTC)
There's a difference between throwing out some collectable solids, and visible exhaust. "No particulate emissions at all" just isn't going to happen. After all, where would Brief Encounter be without the odd cinder? If you wave something out of the window, it will collect particles (it has some time to do so, and they're collected). If you look at the smoke, you may yet not see any - there's nothing there visible right at that one moment. Andy Dingley (talk) 00:23, 18 January 2018 (UTC)
So, just like I thought -- the amount of smoke would be negligible for environmental purposes, yet it would not be entirely smoke-free (so it would be more accurately described as "low-smoke operation" rather than "smoke-free operation"). Is that correct? 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 06:05, 18 January 2018 (UTC)
"Smoke" has changed over the years, as a legal definition. The notion is quite old - Elizabeth I had laws banning the burning of sea coal within London, to stop it. From the beginning of steam locos, they were required "to consume their own smoke". The Lancashire boiler was developed partly to reduce this (by alternate firing of the two flues). Stephenson used two similar flue boilers for his Lancashire Witch. In recent years (I worked on this for big diesels around 1990) we've gained the technical ability to measure smoke automatically, much more sensitively than by eye. Particulate emissions, particularly diesel particulates, are now a huge issue for diesel cars in Europe - to the point when the efficient, modern diesel car might disappear altogether within a couple of years! Andy Dingley (talk) 09:26, 18 January 2018 (UTC)
Actually, I didn't tell you, but this question had nothing to do with any legalistic folderol -- it was inspired by "Pingy Pongy Pick Up" (a particularly cringe-worthy episode of Thomas & Friends), where near the end they dry out the wet laundry by hanging it on a line behind Emily's smokestack (where it's practically guaranteed to get dirty again from her cinders and ashes!) So this was only a fact-check -- I wanted to double-check whether the laundry would in fact get dirty even if Emily uses anthracite (which it appears would be the case). Anyway, thanks for the info! 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 11:24, 18 January 2018 (UTC)
Thomas the Tank Engine is an excellent series of small books (I have still have mine). There is no TV series. There is certainly no "movie". No such things exist. None at all. Andy Dingley (talk) 14:56, 18 January 2018 (UTC)

Physics Question[edit]

All the Matter in our universe is made of atoms but all these Atoms, which consist of subatomic particles such as electron, neutrons, protons, quarks, gluons etc, do not constitute matter. Right! - WHY? (talk) 06:35, 16 January 2018 (UTC)EEK

What gave you the idea that atoms don't constitute matter? They have mass and volume, don't they? Double sharp (talk) 07:33, 16 January 2018 (UTC)
As discussed at matter, there is no universally agreed definition of what it means to be "matter". Historically, "things made from atoms" was one way of describing matter. Another was anything that "has mass and takes up space". Another, more modern definition, is any particle with a "non-zero rest mass". Depending on the definition one chooses, subatomic particles may or may not be a form of "matter". It's complicated, and for the most part not very interesting since it is just a question of how we define our labels. Dragons flight (talk) 07:45, 16 January 2018 (UTC)
(e/c) You nearly answered your own question. Subatomic "particles" (which might be somewhat of a misnomer) are constituent to atoms; atoms are matter. Bricks and mortar are constituent to buildings, but do not constitute buildings. — (talk) 07:53, 16 January 2018 (UTC)
Yeah, except as noted, there is non-atomic matter. See Degenerate matter, etc. --Jayron32 13:32, 16 January 2018 (UTC)
Another functional definition of matter (besides those mentioned above, which are all fine, and perfectly workable) is matter is anything that interacts with the Higgs field. But that's the point, really, defining "matter" is a human problem; its about setting up what kind of categories we decide to organize our experiences, and how to fit things into those categories. The category definitions are purely up to us based on what is most useful to us. If a particular application seems to need us to define matter as "made up of atoms", then we use that definition. If a different application seems to find "has a mass and a volume" as a more useful definition, then we use that one. These are all purely linguistic concerns, and language serves only to be useful to us in communication. Whatever the situation needs, we do that. --Jayron32 15:26, 16 January 2018 (UTC)

They (subatomic particles such as electron, neutrons, protons, quarks, gluons etc,) do have masses but they must be composed of something (which we don’t) but not matter. They have no constituents in simple words.

An atom of a specific element can be distinguished from its atomic number however I have no idea how do these numbers distinguish one element from another and why but since subatomic particles (electrons, protons and neutrons etc.) of all the elements are exactly alike and hence an element is indistinguishable at the individual subatomic particle level therefore an individual subatomic particle say electron can be associated with any atom irrespective of the type of element due to nature of its unknown composition or one can't tell the atoms with which the electron is associated. The same is applied to all the individual subatomic particle.

For Example:If the electron of an Aluminum and Zinc are not made up of Al and Zn respectively then how do we differentiate between the electron of Al and Zn if analyzed separately? Further, At what minimum size of any element say Zn started showing up its physical appearance as a substance of Zn if we zoom out slowly from the nucleus of its any atom. (talk) 05:32, 17 January 2018 (UTC)EEK

The difference between the electrons does not matter, but we need to count the electrons. Just as you can count the people in identical twins, you can count electrons. Perhaps you could do this by successive ionization, or by observing the energy needed to extract the innermost electron, or by measuring the charge on the nucleus. One atom of zinc will be nothing like the bulk material, it will be more like a gas. Dizinc, Zn2 will have different properties again, and larger clusters will be different again. Different properties will emerge at different numbers of atoms. Density, crystal structure, melting point (when the structure is disorganised) or boiling, when atoms escape from the surface, hardness, strength will all vary depending on the particle size when there are few atoms in the cluster. Graeme Bartlett (talk) 11:36, 17 January 2018 (UTC)
References for those that care: and where you can find out for small clusters zinc will form an icosahedron, but with enough atoms it will have hexagonal close packed structure as in the metal. Graeme Bartlett (talk) 11:46, 17 January 2018 (UTC)


I'm dimly aware that NSAIDs reduce inflammation, which in turn helps reduce pain.

However, I was of the impression that inflammation was a biological process that aided healing and/or reduced susceptibility to infection. If this is true (I may be totally wrong), it seems plausible that NSAIDs might inhibit healing. Is this true?--Leon (talk) 08:11, 16 January 2018 (UTC)

There is evidence (often from animal models) that prolonged use of NSAIDs may impair healing from certain kinds of bone, muscle, and connective tissue injuries. [17][18][19] Short-term and low dose use of NSAIDs is usually considered to be of minimal concern. Contrariwise, it is also worth noting that pain management may aid recovery in some circumstances by allowing people to be more active and/or participate in physiotherapy more eagerly, etc. [20] Pain management may also allow a faster return to a normal lifestyle. Finding a balance between beneficial pain management and potential risks is something that needs to be considered on a case-by-case basis. If you have specific concerns about your own treatment, you should consult a doctor. Dragons flight (talk) 08:37, 16 January 2018 (UTC)

Side note here — you seem to be under the impression that the pain relief from NSAIDs is a result of their anti-inflammatory effect. I don't think that's correct. NSAIDs interfere with the production of prostaglandins, which are part of the causal chain in both inflammation and pain.
Of course, if you bring down inflammation, then you may also prevent pain that would have been caused by that inflammation, but that takes longer. I'm pretty sure the analgesic effect of NSAIDs works faster than that. --Trovatore (talk) 21:05, 16 January 2018 (UTC)
Actually I'm not sure now. I can't find "prostaglandin" mentioned at either pain or nociception. "Pain" is mentioned at prostaglandin once, in a fairly offhand way, saying that one function is to "sensitize spinal neurons to pain". I don't find anything in the NSAID article that specifically explains the mechanism(s) of analgesia (though there's an intriguing sentence about how acetaminophen (paracetamol), which is not normally considered an NSAID, interferes with COX in the nervous system specifically rather than in the body generally).
So I think there's an opportunity for someone to improve at least three articles (NSAID, prostaglandin, and pain) with some details on the mechanism or mechanisms by which NSAIDs reduce pain. Assuming, of course, that such details are known. Does anyone here know? --Trovatore (talk) 21:53, 16 January 2018 (UTC)
The details are not really well known, prostaglandins do sensitize nociception (see so at least some of NSAIDs analgeisc properties are due to COX inhibition. Some NSAIDs also inhibit the lipoxygenase pathway which is involved in inflammation and sensitizing nociceptors. This paper goes into more detail on possible mechanisms 2600:1700:A460:5060:9C44:6B42:8646:43CF (talk) 06:28, 19 January 2018 (UTC)

How long have zoologists known that animals don't have four legs + wings?[edit]

I was looking at commons:Category:Obsolete dinosaur restorations for a larf, and this image struck me, but "Proportions and poses are wrong in all the animals" seemed a bit simple, and I noticed that the creature on the far right appears to be (the image is a little blurry) some kind of four-legged, winged "dragon"-type creature. Would an up-to-date scholarly work from Princeton University in 1877 portray such an animal? Or are my eyes just failing me and it's just a pterodactyl in the wrong pose? Either way, I'm kinda curious when scientists figured out about the four legs and wings thing. Hijiri 88 (やや) 09:01, 16 January 2018 (UTC)

This one does. But it depends on how one defines "wings". — (talk) 09:20, 16 January 2018 (UTC)
I'm not sure I really understand the question. Yes, I think it's a pterosaur of some kind (probably a pterodactyl), but it's probably the only animal on there that's pictured correctly (we have it on all- fours in our size chart at Pterodactylus, for example), though the proportions are a little off. The dinosaurs pictured are much too up-right and their tails should not be all wavy like a cat's. Likewise, the plesiosaur-ish beasties would not have such wavy necks. I'm not quite sure what those two squat aquatic beasties are meant to be. Matt Deres (talk) 15:07, 16 January 2018 (UTC)
Further to the pterosaur on all fours reconstruction, see this image of Dimorphodon Matt Deres (talk) 16:55, 16 January 2018 (UTC):
Reconstructed skeleton, Rainbow Forest Museum

To my eye the limbs seem relatively accurate -- the folded wings appear to have multiple fingers pointing forward, as best as I can see, as pterosaurs did, rather than only a single free thumb as in bats. I don't see four legs. The remarkably rigid groundplan of tetrapods is certainly not something that could have been predicted a priori - for example, the number of legs and wings in various insects is prone to considerable variation, though they don't typically add much to the primitive groundplan but only take away in varying degree (compare Nymphalid butterflies with two wing and two leg pairs, flies with one wing and three leg pairs, and other butterflies with two wing and three leg pairs). Of course, before awareness consolidated of evolutionary and developmental principles, even the framework to assemble such knowledge would not have existed. If the gods want to make a pegasus, why not? Wnt (talk) 16:31, 16 January 2018 (UTC)
Since it hasn't happened with vertebrates, I think that if the gods made a pegasus, they would demonstrating that they were gods. Robert McClenon (talk) 04:45, 17 January 2018 (UTC)
The evolution of the insect body plan is really fascinating. Most extant insects, including all winged insects, are in the subclass pterygota. The ancestral pterygotan is believed to have had an odonatan body plan, with six legs (three pairs) and four independently-articulated wings (two pairs). It's actually more common for a pair to be modified than deleted. Dipterans have evolved the hind pair of wings into halteres, and beetles have evolved the fore pair of wings to serve as protective organs when folded, and balancing organs in flight. How fascinating is it that for hundreds of millions of years, millions of species simply worked on this one body plan with really only marginal changes to it? Really cool! Also, to the original question, I agree with others that the animal on the far right of that picture does not look like a dragon, it looks like its wings are part of its forearms. Someguy1221 (talk) 23:37, 16 January 2018 (UTC)
As no-one has never found an animal with four legs and also wings, the assumption is that such an animal doers not exist. Logically, however, zoologists still do not "know" that such an animal does not exist - because it is impossible to prove the negative. Wymspen (talk) 17:05, 16 January 2018 (UTC)
True, but, since the evolution of wings in addition to four legs would provide an evolutionary advantage, and hasn't happened, we can conclude that the most likely reason it hasn't happened is that there is a reason why it doesn't happen. Robert McClenon (talk) 04:45, 17 January 2018 (UTC)
Some poor animals have been born with six legs instead of four so yes it isn't entirely impossible that for instance a bat like that might arise. Dmcq (talk) 18:22, 16 January 2018 (UTC)
That's one of the big mysteries though. Lots of people have hexadactyly, and polydactyl cats occur much more commonly in certain breeds, and the fossil record shows polydactyly in early tetrapods before five became the standard ... yet there are no polydactyl species now that I know of! There are a lot of spectacular things like asexual reproduction that can evolve very fast in multiple populations of modern origin ... yet they always lose out in the long term. (Well, except in rotifers...) This gives me a sense that there is a kind of "temporary" evolution where radical variants are selected for in the short term, and can become prevalent under extraordinary conditions (such as artificial selection) yet be utterly doomed on a longer time scale. Indeed, I have a creeping suspicion that there may be a distinction between "stem species" and "terminally differentiated species" that remains to be made. In the case of six-limbed mutant animals though, the point is not so subtle - so far as I know these are almost always freakishly impractical. (Please correct me if I'm wrong; I'm going by recollection) Wnt (talk) 22:35, 17 January 2018 (UTC)

All Chordates Are Tetrapod[edit]

It appears that the chordate body plan is inherently tetrapod. The arthropod body plan, which involves a variable number of segments, each of which can have appendages, is an entirely different scheme. The only vertebrates (and therefore the only chordates) that have evolved the capability of flight paid the price of repurposing their front limbs as wings, rather than evolving wings as additional appendages. There is every reason to believe that the chordate body plan doesn't support a hexapodal anatomy. Of course, the original question was how long this has been known. That is, how long has it been known that the hexapodal vertebrates of folklore, such as winged horses and winged humans, are only found in folklore and not just "not yet found" (cryptids)? Robert McClenon (talk) 04:15, 17 January 2018 (UTC)

Sharovipteryx is a chordate which repurposed its hind legs as wings!-gadfium 08:26, 17 January 2018 (UTC)
All tetrapods are chordates, but not all chordates are tetrapods. Good luck finding the four legs on a sea squirt or an acorn worm! Wnt (talk) 22:41, 17 January 2018 (UTC)

Well, it seems everyone else is seeing the image differently from me. I can see, having read the rest of yer comments, that it probably is not a creature with wings and four other, separate limbs extending from its torso. And I had always thought there was some reason scientists had established why real animals (as opposed to dragons, pegasuses and angels) tend not to have four legs and wings. Granted, I'm a total layman and I heard this fairly recently from another layman (an interview with George R. R. Martin where he explained why the dragons in his A Song of Ice and Fire books do not have four legs like the ones in Dungeons & Dragons). Hijiri 88 (やや) 05:23, 17 January 2018 (UTC)

For the record, I wasn't aware of the two most recent comments when I wrote the above (check my edit summary -- I edited the main heading). I was responding to the discussion as I had read it a few hours earlier. Hijiri 88 (やや) 09:15, 17 January 2018 (UTC)

January 17[edit]

Taxonomic History of Mollusca[edit]

When were the very diverse Mollusca identified as a phylum? Our article on mollusca identifies them as having been identified in 1758, in the great 1758 edition of Systema Natura, but I further see that Linnaeus had identified the Mollusca as an order in the class Vermes. The phylum, as the highest-level division within the kingdom Animalia or Metazoa, wasn't defined by Linnaeus, only by Haeckel. (Linnaeus defined kingdom, class, order, genus, species. Family also came later.) So my question is when were the Mollusca defined as a distinct phylum? Also, were they always recognized as a distinct phylum? The various classes of molluscs are not obviously related except to a zoologist who is familiar with the mantle and mantle cavity. A clam, a snail, and an octopus certainly don't look alike. I see that Linnaeus evidently did recognize that they were a single taxon (but he saw almost everything). So what is the taxonomic history of the category of Mollusca? Robert McClenon (talk) 04:25, 17 January 2018 (UTC)

Why is pittsburgh pa so cold?[edit]

In Pittsburgh today it is 11 degrees F. That's way colder than Boston, Bangor, Ithaca NY, and Burlington today, but it's way farther south. Is it random or does it happen a lot? Thanks. (talk) 04:49, 17 January 2018 (UTC)

As a general rule, areas close to ocean coasts like Boston, and to a lesser extent, Bangor, Burlington and Ithaca have more moderate temperatures with fewer extremes, than inland areas like Pittsburgh. Ocean waters change temperature very slowly, whereas the land and the air can change temperature much more readily. So, nearby ocean waters act as a buffer to rapid changes in temperature. Please read this for more information. Cullen328 Let's discuss it 05:06, 17 January 2018 (UTC)
Ithaca isn't at all close to sea. (talk) 05:16, 17 January 2018 (UTC)
That is exactly why I said "to a lesser extent". Pittsburgh is roughly twice as far from the Atlantic Ocean than Ithaca is. And individual temperature readings on one day mean very little. If you take a look at historical average temperatures by month in that region, you will find that, in general, inland areas have more extreme variations than coastal areas. Cullen328 Let's discuss it 05:24, 17 January 2018 (UTC)
I suspect that when you compare Pittsburgh to Boston, the most salient factor explaining the difference in climate is each city's proximity to the ocean.
I suspect that when you compare Pittsburgh to Ithaca, the most salient factor explaining that difference in climate comes down to prevailing winds.
But in any given instance, we need to get some more details to understand what makes your town colder than the town 200 miles northeast.
If I was in a hurry, I'd just blast through the METAR:
KPIT ... 3045 ... T11441167
... and so on. That's quite compact, and I already know what I think is keeping you below freezing... but I'm heavily trained in interpreting weather, and the Government actually measures how rapidly I can spit back those weather-numbers! To the untrained eye, that number-soup carries very little information! Besides, we're in no hurry now - I've got a lot of spare time to think about weather at the moment!
As an avid enthusiast of the weather, I always start with the prog charts and surface analysis, and then I read the Forecast Discussion. In these special technical weather service products, the chief meteorologist on duty in your area will explain in great detail what they're observing, why they think it's happening, and how their analysis is informed by technology, including computer climate models. It tells you not only what the weather's doing, but why it's doing it, and how we know.
For example, today in Central New York:
And in Pittsburgh:
And Boston:
Wow, that's a lot of atmospheric science, delivered straight up from a real actual atmospheric scientist!
When you get into the Forecast Discussions, you start to recognize that the air and atmosphere are a giant system, and when it's cold on the ground in Pittsburgh, it's because Earth's atmosphere is doing something special somewhere else. At this very moment, Pittsburgh is colder than the cities north of it because you're behind the front. Your cold air is too low-pressure to blast into Ithaca; for now, a slug of cold air is trapped near the ground in western Pennsylvania, even though it looks like in the next few days, your cold air is going to ride over the top of their airmass. In the short term, their cloud cover is going to hold in some thermal energy, and they'll soon be mixing in more heat out of the Atlantic over the next few days. But, it's the Northeast - it's really dynamic and anything could change! I spent the first few days of 2018 travelling the Eastern seaboard, convinced that the giant high pressure slug three thousand miles wide was totally impenetrable, and ... whack! A surprise hundred knot high level wind killed our blue skies from totally the opposite direction!
If you love weather, and need more than just the conditions forecast, learn to know and use the Area Forecast Discussion!
Nimur (talk) 05:54, 17 January 2018 (UTC)
It's west of most Appalachiany stuff, not all. I've been there and there's freaking cliffs/near cliffs everywhere. Okay not everywhere but the Greyhound goes through a tunnel through the cliff right outside downtown just to get in and there's many bridges over valleys or inclined rail-like things (see image) from the steep(ish) elevation drops of hundreds of feet impeding metro area connectivity so much. Sagittarian Milky Way (talk) 06:32, 18 January 2018 (UTC)
Elevation profiles of Pittsburgh inclines.svg
Yes, it's just barely southeast of the line between the glaciated and unglaciated sections of the Allegheny Plateau. There's virtually nothing to obstruct the passage of weather from the northwest. Nyttend (talk) 13:36, 18 January 2018 (UTC)
I didn't say hundreds of feet of relief was enough to obstruct the weather, I just expected the site to be less hilly and have wider riverplains since it's so west and big. Perhaps Philly had a financial interest to make it bigger while trying to copy the Erie Canal? Perhaps the hilliness was a benefit since it meant nearby fossil fuels for the factories? I wonder if Burlington would've been at least a degree Fahrenheit warmer that day if the gaps in the Appalachians at the Burlington to Montreal and Mohawk River routes didn't exist. Sagittarian Milky Way (talk) 01:39, 19 January 2018 (UTC)
Here's an archived map showing the cold front Nimur mentioned. Sagittarian Milky Way (talk) 01:39, 19 January 2018 (UTC)

Chemistry question.[edit]

Is it a contradiction to be a strong Lewis acid (receive electrons) and a strong reducing agent (loses electrons) at the same time? And is it a contradiction to be a strong Lewis base (loses electrons) and a strong oxidizing agent (causes others to lose electrons) at the same time? Can anyone list any molecular examples? Thanks. (talk) 15:33, 17 January 2018 (UTC).

Hydrogen iodide is a strong acid and a strong reducing agent. This Chemistry Stack Exchange question and answer may be of interest. Double sharp (talk) 15:50, 17 January 2018 (UTC)
Okay here's my list.
Strong acids and strong oxidizing: HNO3, H2SeO4, CrO3, H2SO4, HMnO4, HClO4, OsO4, RuO4.
Strong acids and strong reducing: HI.
Strong bases and strong oxidizing: none.
Strong bases and strong reducing: LiH, NaH, CaH2, MgH2. (talk) 14:38, 18 January 2018 (UTC).
Various iron(II) compounds are a prototypical example of a metal cation that is in the lower of several common oxidiation states for that metal. It is a fairly good reducing agent, becoming the more stable iron(III) species (see iron(II) sulfate), and it is a Lewis acid because it is cationic with many open coordination sites (notice the many Coordination complex of it; doi:10.1021/cr040664h has many examples of reactions involving Lewis aciditity anddoi:10.1002/cctc.201402029 is an interesting recent example). DMacks (talk) 16:01, 17 January 2018 (UTC)
Then if I follow the pattern, can I generalize, metal ions in their lowest oxidation state? (talk) 14:38, 18 January 2018 (UTC).
doi:10.1021/ed019p24 is a J. Chem. Educ. article discussing the parallels of the two concepts from first principles. DMacks (talk) 18:18, 18 January 2018 (UTC)

Accelerating radioactivity naturally decay[edit]

Can you accelerate radioactivity naturally decay of atomic waste, instead of waiting millennia until it's harmless? --Hofhof (talk) 19:41, 17 January 2018 (UTC)

No, see Radioactive_decay#Radioactive_decay_rates - for any one isotope of any particular element, the equations are governed by constants. Mikenorton (talk) 20:05, 17 January 2018 (UTC)
Well, Radioactive_decay#Changing_decay_rates. But not really practical. DMacks (talk) 20:07, 17 January 2018 (UTC)
Besides, decay rates only change noticeably with environment for 7Be (an L-capturer where the captured electrons are also the valence electrons) and some cases where the decay energy is tiny (for example, nuclides in this position cannot undergo internal conversion with the inner electrons, but only on the outer valence electrons). Most fission products and actinides don't fall into either of these groups; actually I am not sure if any do, since fission products are neutron-rich, and electron capturers must perforce by neutron-poor, so you'd mostly have to look for gamma emitters. (Is 99mTc a significant fission product? Its ground state certainly is, but I don't know about the metastable state. If so it would be an example, but note that the decay rate changes produced by such means don't usually even get close to 1%.) Double sharp (talk) 08:23, 18 January 2018 (UTC)
You can't really change the decay rate of any particular type of nuclear waste, but you can (sometimes) bombard it with neutrons to convert the waste into different isotopes, which may have a faster decay rate. See Nuclear transmutation#Artificial transmutation of nuclear waste. PiusImpavidus (talk) 20:22, 17 January 2018 (UTC)
Also Radioactive waste#Transmutation. - (talk) 20:24, 17 January 2018 (UTC)
A Breeder reactor creates less waste because it burns up some of what would otherwise be waste. You might also be interested in the rather strange Quantum Zeno effect which does the opposite - though it is not practical as a way of stoping radioactivity. Dmcq (talk) 23:10, 17 January 2018 (UTC)

January 18[edit]

Coherent or highly monochromatic terahertz[edit]

Brain fart corrected in title, sorry

I was looking at a paper about imaging cancer with terahertz that is monochromatic, but I'm not sure how monochromatic:

Measurements were performed using a THz time-domain spectroscopy (THz-TDS) system based on a Ti:sapphire femtosecond oscillator (Synergy; Spectra-Physics) pumped by a 10-W diode laser, Verdi. The laser delivered 10-fs pulses at a wavelength of 800 nm with an 80-MHz repetition rate. The laser beam was separated by a polarizing beam-splitter and turned towards the emitter and the detector separately. The emitter was a p-InAs crystal that utilized the photo-Dember effect, and the laser beam was incident at 78° on the surface of the crystal for high THz intensity51. The THz beam that radiated from the emitter was gathered by a parabolic mirror and focused onto the sample holder by a pair of THz focusing lenses

My assumption is that this generates noncoherent light with a narrow range of frequencies. But I don't see how narrow.

The issue here is that they detect methylated DNA in cancer cells as a little bump, maybe a bit more than a tenth of the total signal present. Most of the signal is from a smooth curve of absorption by ice. The thing I'm getting at is that if they had a tighter range of frequencies, they might get a higher signal if they tune precisely right. I also don't know whether the absorption by ice might break up at a very fine scale, with bands where there is no absorption, if you had truly monochromatic terahertz waves to test with???

Obviously what I want to do is find something only the cancer absorbs and turn it up to MICROWAVE HIGH setting until every last tumor cooks through and through, while normal tissue with just a little methylated DNA gets toasty warm but not damaged. Wnt (talk) 01:24, 18 January 2018 (UTC)

Looking at graphs in this doi=10.1088/0022-3727/47/37/374002 paper, you only get about one full cycle of the THz radiation, and it drops off exponentially with time on the scale of 1ps. So it is actually hardly monochromatic, and would have a bandwidth of 100s of GHz. This would depend on the duration of the laser pulse. If you could pulse your laser every 2 ps perhaps you could get it as coherent as the pulse rate, but then you would have a near THz generator driving your laser anyway! On the topic of selecting DNA methylation, it is found in all kinds of cells, so perhaps it is not targetable. A vibration of a methyl group in a liquid environment may have a band, but it would not break down into fine lines due to the varying environment of the liquid. Graeme Bartlett (talk) 05:26, 18 January 2018 (UTC)
So is there any known way to make more monochromatic THz radiation? I would think this should be the hottest topic in weapons work right now (to DNA-identify people from space or displace specific binding factors and cause a different syndrome in every member of the political opposition), but all I want to kill this time is cancer. Wnt (talk) 14:55, 18 January 2018 (UTC)
You should read Terahertz_time-domain_spectroscopy. Ruslik_Zero 20:32, 18 January 2018 (UTC)

Canon de 75 modèle 1897: The Italian Response[edit]

I need help finding an artillery gun based on this information.

After taking notice of the success of the Famous French 75, Italy manufactured their own, indigenous design of the artillery piece. Although it had the same rate of fire as the Canon de 75 modèle 1897, it was more mechanically complex and was not as successful. Arima (talk) 04:42, 18 January 2018 (UTC)

Cannone da 75/27 modello 11 seems a possible candidate. The main italian field gun in WWI, the Cannone da 75/27 modello 06, was a licence-built Krupp design. Try List of artillery by country#Italy. Alansplodge (talk) 11:07, 18 January 2018 (UTC)

Cold desert at night[edit]

So if rock holds heat so well, why does the desert get freezing cold at night? Rock does hold heat well, right? Anna Frodesiak (talk) 09:12, 18 January 2018 (UTC)

Not as well as bodies of water. Also deserts have low precipitation, so often clear skies, thus the optimum for radiative losses.
It's a delusion amongst the flat earth people that "Moonlight radiates cold". Indeed, moonlit rocks are often colder than those which aren't. However the reason is that days are hotter than nights, and so night temperatures depend on how fast things are cooling, not how well they're being heated. An area exposed to clear moonlight is the same area that's losing the most by radiation. Andy Dingley (talk) 09:29, 18 January 2018 (UTC)
Thank you, Andy. So this is about very clear air above allowing heat to escape, and about lack of moisture within the ground, which holds more heat than dry sand? (I've slept on both sun-baked earth and desert, and wow, that sand and air gets cold.) Anna Frodesiak (talk) 11:22, 18 January 2018 (UTC)
Yes. We have an article: Radiative cooling. "The exact process by which the earth loses heat is rather more complex than often portrayed..."
Here's a great free textbook on weather: Aviation Weather. I actually like the old version - I keep a link to it on my user-page - the AC 00-6A version - it still has the original cartoons from 1943's Meteorology for Pilots!
If you like math, you can use the Stefan-Boltzmann law to study why deserts get cold. Here's some science from Arizona State University - a world-reknowned center for excellence in both deserts and planetary science: Stefan-Boltzmann law for radiative cooling. In my old planetary science class, we were taught by a radioscientist, so he made sure we corrected for the non-zero cold sink of the cosmic microwave background radiation: on a clear night with no clouds, your desert ground is essentially losing heat to a cold-sink that's only a few kelvins! This is why it is possible to use a clear desert night to produce ice, even if the air temperature is above freezing! If you're really smart, you can make the physicists mad by pretending to violate the second law of thermodynamics, like this Nature letter demonstrates! Hey, I recognize that photograph - I've spent a lot of time on that roof looking skyward!
Nimur (talk) 17:18, 18 January 2018 (UTC)
The theoretical Volumetric heat capacity of Silica (Sand, Sandstone, Glass) is 1.5, of Water 4.18 and of Air 0.0013 J⋅cm³⋅K−1 (Joule per cubic centimeter per temperature difference of 1 Kelvin). So Sand, which always contains some air is not a good material to store heat. Like a battery that can store 1 Kw/h compared to one that stores 4 Kw/h. The volumetric heat capacity of Sand is actually only around 0.8 tho there are many different "mixtures" of minerals called Sand and thus it can be a bit higher or lower. Additionally by definition deserts contain the least amounts of water. Thus a desert is physically less able to store the heat from sunlight and it gets hotter with less "energy efford" aswell as cold faster when the heat disperses. --Kharon (talk) 13:59, 18 January 2018 (UTC)

Thank you, especially Nimur for the really good pdf. Weather has always mystified me and this is really interesting. And no, anything about maths goes way above my head. :) Anna Frodesiak (talk) 22:10, 18 January 2018 (UTC)

One reason for the "Moonlight radiates cold" adage is that moonlight indicates a lack of clouds, and clouds act like a blanket to hold in some of the radiant heat. —2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 05:40, 19 January 2018 (UTC)
If the daily temperature range's x tens of degrees in Atacama-grade air will it be at least 1°F less if there was more water vapor? (but not so much that condensation wets the ground at dawn or causes cloud) Sagittarian Milky Way (talk) 07:15, 19 January 2018 (UTC)

Carbon fibre[edit]

How much weight can a carbon fibre sheet hold, in:

1) 1 inch thick sheet.

2) 1 feet long stand, filled round stick or non-filled round stick.


I require a calculating method or so, to calculate weight vs. height, length, filled/non-filled carbon fibre base. (talk) 15:45, 18 January 2018 (UTC)

There are enough varieties in construction of such materials that you would need to be much more specific if you want quantitative results.
Typically, material properties can be found from whomever sells such materials. For example, here is one vendor listing, technical data sheets from PlastiComp. You can use standard-form equations from our article on flexural modulus to model the material. Beware that fibers and textiles are not always well-modeled by simple equations! In such a case, you'll need to track down data from an empirical test.
Nimur (talk) 16:41, 18 January 2018 (UTC)
Isn't pure carbon fibre better than mixed with plastic? What is used in formula 1 Cars? What material would you say is solid and light? (talk) 16:55, 18 January 2018 (UTC)
Have you read Carbon fibres and Carbon fibre reinforced polymer? Also do you know what fibre means? Nil Einne (talk) 17:08, 18 January 2018 (UTC)

MPG - casues of significant improvement?[edit]

I have recently noticed a significant improvement in the mpg I get from my Fiat Punto Mk2 1.2l 8 valve. In the past I have usually got about 40-45 mpg, but the last two fills I have got 50 mpg. The types of journeys and loads have not changed. What could cause such an improvement? DuncanHill (talk) 19:40, 18 January 2018 (UTC)

Setting aside that fascination of such minutia is possibly a sign of a mental disorder ; -) It may be that DH lives in the northern hemisphere where it is currently winter. Cold air is denser. Thus the compression ratio is slightly raised thus increasing engine efficiency. 10-20 % seems a lot however. Is this metered fuel from the pump or what appears on the gauge or a mixture of both? As you may be aware, gasoline/petrol and diesel have large coefficient of heat expansion. This is why aircraft are fuelled by weight and not volume. Therefore, volumetric gauges can easily be out by 10-15% over the course of a year. RH can affect MPG as well. Oh, and of course, have you recently inflated the tyres/tires ? That can reduce the rolling friction too. So that dispenses with the most obvious. Back to you to add more info. Aspro (talk) 20:25, 18 January 2018 (UTC)
Metered from the pump, Northern Hemisphere, no change to tyre pressures. Nothing mentally disordered about noticing that you're saving money! DuncanHill (talk) 20:54, 18 January 2018 (UTC)
Perhaps you are just driving more efficiently since you have become interested in mpg. Dmcq (talk) 23:36, 18 January 2018 (UTC)
I don't think we have "boutique fuels" in the UK. DuncanHill (talk) 00:26, 19 January 2018 (UTC)
I haven't done an exhaustive search, but its possible that your fuel provider changes blend seasonally; cf:[24]2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 01:29, 19 January 2018 (UTC)
If there's a way to get 11-20% better fuel efficiency from a car (similar to my own), I'd really like to know about it! The only possible factor I can think of in this instance, Duncan, is that it's been somewhat windy in the UK of late – is it possible that by lucky chance your recent journeys have experienced more favourable wind assistance (and less wind resistance) than average? {The poster formerly known as} (talk) 00:45, 19 January 2018 (UTC)
Or, he drives downhill -- both ways. —2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 01:14, 19 January 2018 (UTC)
Gasoline is denser at cold temperatures, so you get more kgs per gallon. Add to that that maybe you took an extra motorway trip or avoided some traffic jams (maybe roads were quieter because of holidays), and 10-20% is certainly possible, especeially if you have a 30-40 L tank. — Preceding unsigned comment added by (talk) 02:23, 19 January 2018 (UTC)

Physics Question (one more)[edit]

Are the standard sizes and masses of a proton, neutron, electron etc. are naturally selected and why do they not change over time?

Similarly, nature has the ability of random selection too, therefore, we can't neglect completely the chances of varying masses of subatomic particles instead of standard as a proton is approx. 1850 times’ massive/heavier than an electron so it means the chances of the diversity in the masses of subatomic particles in the random selection are more than the chances of the standard masses of subatomic particles. Please disregard if not interested (talk) 21:04, 18 January 2018 (UTC)EEK

Relevant articles include Proton-to-electron mass ratio, Time-variation of fundamental constants, and perhaps Fine-tuned Universe. -- ToE 22:12, 18 January 2018 (UTC)
Natural selection in the usual scientific sense requires the populations of entities being selected producing similar but not identical progeny with slightly varying characteristics due to occasional errors in the functioning of a genetic code. Since particular kinds of subatomic particles do not have a genetic code (or any analogue to it) and do not reproduce their own kind (though they can give rise to different kinds by decaying or combining) the concept is not applicable. The OP's second sentence ("Similarly [. . .] particles.") does not appear to be meaningful English in any of its clauses. {The poster formerly known as} (talk) 00:41, 19 January 2018 (UTC)
The anthropic principle, while not selection, is a selection bias relevant to this question. -- ToE 02:36, 19 January 2018 (UTC)

January 19[edit]

What's a cryogel?[edit]

Hi. The word "cryogel" appears in various WP articles but doesn't have its own article or redirect. There's also no Wiktionary entry, and I ask as someone who works on Wiktionary. Could someone give us a quick but clear definition we can use, that distinguishes a cryogel from other things (gel, aerogel, xerogel, whatever)? Thanks! Equinox 06:56, 19 January 2018 (UTC)

I can't seem to find an explicit definition of the word, but the various things I find that are referred to as "cryogels" have in common that they are made by first dissolving something in a solvent, and then freezing and thawing until it polymerizes. Someguy1221 (talk) 07:19, 19 January 2018 (UTC)