m Changed protection level for "Wikipedia:Reference desk/Science": Vote (X) for Change dodging their ban. ([Edit=Require autoconfirmed or confirmed access] (expires 21:10, 16 January 2018 (UTC)) [Move=Require administrator access] (indefinite))
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Recommendations for non-science books by High Energy physicists
This is a question I could not easily find a good answer to on Google. I am looking for recent books by physicists, in particular physicists who work on fundamental research (as opposed to applied or e.g. condensed matter physics), on topics that range beyond just science to general cultural topics. An example would be Lake Views by Stephen Weinberg, or for older examples, The World as I See It by Albert Einstein or many books by Richard Feynman. Something written since ~2010, and by a well respected physicist, preferably. Any recommendations? 72.221.65.122 (talk) 03:50, 9 January 2018 (UTC)[reply]
Two recent books come to mind:
The Big Picture: On the Origins of Life, Meaning, and the Universe Itself by Sean M. Carroll
John Gribbin has some popular science/history of science books which are easy reads, such as In Search of Schrodinger's Cat and Schrodinger's Kittens. Brian Greene has also written some good, easy reads on similar subjects, such as string theory and the like. --Jayron3220:15, 10 January 2018 (UTC)[reply]
This term has nothing inherently to do with superheating or superheaters (NB the WP article is at superheater, notsuperheating), although it would be unheard of for such a plant to not also use superheating.
WP needs work on the supercritical and steam generator articles. They're mostly not inaccurate (but superheater is), but they aren't complete and they fail badly in explaining why a supercritical steam generator is useful. The term "steam generator" also has several meanings and the articles keep getting messed with and confused.
There is an inherent problem with steam boilers - steam is hard to transfer heat to. It is much easier to transfer heat to water (which is a convenient dense liquid) rather than steam in the low density, high volume, gaseous phase. The goal of any "boiler" is to transfer heat to a mass of water. This is so much easier when that mass of water is dense, i.e. liquid. The transfer can be done with a smaller area of heating surface, and the denser water can be moved around within a smaller boiler. Allowing the water to actually boil, although the ultimate goal of the boiler, is strongly unhelpful!
So a supercritical steam generator keeps the pressure high enough to avoid any boiling. It's arranged as a small number of long water-filled tubes before this (sometimes just one), wherein the water is heated. This hot, high pressure water is then allowed to expand (it may pass through a nozzle) and the drop in pressure allows it to boil immediately, without adding any further heat to it.
Most designs now avoid any single nozzle and instead use a long pipe the steam is allowed to boil gradually over a section of this pipe, but this is after most of the heating has taken place (using the efficient supercritical water phase). Lengthening the pipe after this allows superheating, where more heat is added, raising the temperature of the steam but without increasing its pressure in the normal equilibrium. This is useful because steam engines (steam turbines and a few of the later and more efficient piston steam engines) operate from heat energy within the steam predominantly as temperature, not just as pressure (as is usually thought).
As far as WP goes, WP should not be used as a source for this topic. It's nowhere near good enough, and (like electrical engineering) it keeps getting worse as a target for bad university projects encouraging first year students to trash articles. Andy Dingley (talk) 12:06, 9 January 2018 (UTC)[reply]
To be very basic, this refers to a supercritical fluid, which is denser than a vapor but hotter than a liquid. And typically hotter and more pressurized than the critical point (thermodynamics). That means that above the critical pressure, water can be "boiled" without ever boiling; it is simply heated up until it is a super-dense sort of steam (well, critical fluid) whose pressure could be reduced to form ordinary steam if desired, still without ever boiling. As the article says the lack of boiling means that there is no need to separate the steam from the boiling water with a big chamber prone to explosion; there's only one phase. The previous poster appears to know far more about this than I do, so I'll merely wonder out loud whether supercritical liquid–gas boundaries have any practical effect on the design of these generators. Wnt (talk) 22:10, 9 January 2018 (UTC)[reply]
January 10
Embryo segments (creationist claim)
Biological Anomalies: Humans by William R. Corliss quotes the following from a book called Flaws in the Theory of Evolution by Evan Shute (published 1961):
Homologous structures can arrive fro different segments of the body. In the newt the arm arises from segments 9 to 11, in man from 13 to 18. These "homologies" are not evidence of an ancestral relationship. They are largely accidental-- or artificial!
I can't find any discussion of this claim online, nor any explanation of the embryo segment numbers (which don't seem to be used anymore in embryology). Is this claim accurate in any way, and if so, what explains the apparent discrepancy? 169.228.152.135 (talk) 02:48, 10 January 2018 (UTC)[reply]
What explains the apparent discrepency is bullshit. You can safely ignore such arguments without giving them further consideration, they are generally some combination of outright lies and cherry picking specific things (usually not-as-yet explained things) rather than anything that resembles reasonable science. The proper response to such arguments is "..." --Jayron3211:43, 10 January 2018 (UTC)[reply]
Let's not be so touchy. There may be a difference, because the location of Hox gene activity (gene expression) varies a little between tetrapods; it is also possible that the response to it is different. In sort, evolution doesn't mean things stay the same - they can make use of the underlying genetic framework to move by making little tweaks here and there. The idea of paralogs is essential to this: one gene gets duplicated many times, resulting in genes that are similar but not the same, so that changing one of them just changes a few things, or so that becoming regulated by one rather than another with a small change in the DNA doesn't cause a drastic deformity. I don't have time presently to find the specifics of where newt limbs and Hox genes are; they're not in this review but you might find it helpful for general concepts.
The war between creationism and evolutionism is futile. You don't expect the text of a book and the author's notes on the book liner to agree about how characters in it came to exist. Wnt (talk) 15:18, 10 January 2018 (UTC)[reply]
This sort of thing is silly given our modern knowledge of genetics and embryology. An easy analog for non-biologists to understand is the turtle. Turtle evolution. The upper shell of the turtle is comprised of the back of the ribcage. In all other vertebrates with limbs, the limbs lie outside the ribcage, assuming the ribcage extends down as far as the hind limbs, which it often doesn't. In any case, think of your shoulderblades. They lie outside the ribs, not inside them. So God must have created the turtle especially, since its entire set of limbs lies within the ribcage. The limbs can't move through the ribcage during development, can they?
Well, the problem has been solved with clever study of embryology and the discovery of fossils which were unknown back when Jerry Fallwell was running the Moral Majority. The problem has been solved; science moves on; embryology is plastic; organisms evolve. It is human minds which sometimes do and sometimes don't catch up. μηδείς (talk) 18:27, 10 January 2018 (UTC)[reply]
Wnt, please look up projection (psychology). You call one editor touchy, then you "correct" (?) me by saying the issue has been addressed more recently? The time stamp I gave was Jerry Fallwell. He died in 2007, so was there actually any point in the "more recently" non-sequitur? Do us a favor, and apply your ample time and wisdom to making turtle evolution a bluelink. μηδείς (talk) 02:21, 11 January 2018 (UTC)[reply]
You said "back when Jerry Falwelll was running the Moral Majority" -- which was disbanded in 1987, according to our article. And you miss the point that as far as I could tell from the coverage I cited, we still don't have convincing fossils to illustrate how turtles altered the relations of ribs and pectoral girdle -- instead, we have an inference (a strong one) from observation of embryological development. Wnt (talk) 22:13, 11 January 2018 (UTC)[reply]
Does normal salt intake cause cardiovascular disease and high blood pressure by depressing the renin–angiotensin system?
We can read here that taking in very low amounts of salt (less than 0.1 grams a day) leads to elevated levels of aldosterone and renin and on the long term you then don't see the usual rise in blood pressure with age. So, could it be that by adding salt to our diets at the RDA levels (note that a few grams of salt is already 50 times the natural amount), we achieve a normal blood pressure but in the wrong way, and that this causes the blood pressure regulation to not work as well causing damage to the arteries on the long term that in turn causes arterial calcification which leads to hardened arteries and blood pressure rise? Count Iblis (talk) 00:36, 11 January 2018 (UTC)[reply]
The ones that say we're not supposed to speculate here. We're supposed to provide reading material (references) in the form of reliable sources. Since you, yourself, just provided your own reference, and then ask us to speculate on it, Medeis is just noting that that sort of thing is not what we do here. It is explicitly written in the guidance at the top of this very page. --Jayron3215:28, 11 January 2018 (UTC)[reply]
Yes, Medeis is right, of course. It's entirely logical that a 42 year old suggestion in the literature would be taken to be the last word in the scientific community. Without even searching the literature, we can be 100% sure that there is nothing more to be found in the literature, therefore anything anyone could possibly have to say must be pure speculation, so let's hat this question! Count Iblis (talk) 15:45, 11 January 2018 (UTC)[reply]
I never said any of that. I'm not sure why you would want to hat the question now. Here is an overview of more recent studies about heart health and salt intake. Here are the most recent recommendations of the American Heart Association. The problem is that the phrasing of your question "could it be that..." is leading and an invitation to speculation. If you had phrased it "what is the current research on..." then you would have gotten a different response. --Jayron3215:52, 11 January 2018 (UTC)[reply]
Titanic
If they knew then what we know now about hypothermia, would it have been possible to save at least some of the people who died on the Titanic (I don't mean those who went down with the ship, but specifically the ones who jumped into the water)? Because the Carpathia arrived on the scene only a couple of hours after the great ship went down, and it's not exactly unknown for a hypothermic victim to be revived after such a time, right? 2601:646:8E01:7E0B:1DAB:D57B:F9C8:4AE0 (talk) 05:16, 11 January 2018 (UTC)[reply]
(Fixed your link.)
In the article you linked, the section Hypothermia#Prognosis suggests an answer of "maybe yes". Of course the number of victims who could be intensively treated would have been limited by the number on board the Carpathia who were qualified to do so. The best chance of revival would have been with children. Beyond these points we get into speculation, which we should not do here. --70.29.13.251 (talk) 06:56, 11 January 2018 (UTC)[reply]
According to our article Lifeboats of the RMS Titanic the Saveguard planning was insufficient and what was available was badly organized on top. Of course they already knew then that humans dont survive in ice cold water. The Titanic was not the first ship in history that sank in bad weather. Shurely with more Precaution almost everyone could have been saved. You can even argue if the captain had known a little more about Icebergs - but the big surprise is that everyone already knew back then everything important to know about icebergs. --Kharon (talk) 07:22, 11 January 2018 (UTC)[reply]
What I meant, though, was that we now know (but they didn't know then) that people sometimes DO survive in ice-cold water despite being mostly dead to all appearances (as the article on hypothermia points out) -- so my question was, with this knowledge alone, could they have saved more people even with all the other factors remaining the same? 2601:646:8E01:7E0B:1DAB:D57B:F9C8:4AE0 (talk) 09:45, 11 January 2018 (UTC)[reply]
How many extra lives could have been saved depends on what alternative history one cares to speculate. With the knowledge at the time of Titanic's sinking April 1912 it would seem obvious that earlier rescue with treatments such as a hot bath, massaging arms and legs, using a heating pad, and possibly giving alcohol could have saved more from death by Hypothermia. Today it is known that such treatments risk causing blood to be directed away from vital organs to the skin, see Hypothermia#Management. Modern recovery treatments for severe hypothermia such as extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass, including cardiopulmonary resuscitation (CPR) for those without a pulse are most effective but they would have required a well equipped Hospital ship to be present at the scene. SdrawkcaB99 (talk) 11:50, 11 January 2018 (UTC)[reply]
Review of probable survival times for immersion in the North Sea from the UK Health and Safety Executive, on p. 22 points to the example of the Ocean Ranger, a mobile offshore drilling unit that sank in Canadian waters on 15 February 1982. The standby vessel arrived within 20 minutes of the sinking, but capsized a lifeboat while trying to rescue survivors. Those that fell into the sea could not hold on to the lifeboat or rescue lines and died. "It is apparent that in cold water sea conditions, the survivors who were not equipped with immersion suits succumbed within minutes to cold shock and hypothermia". I'll leave you to read through the rest of the data and evidence, but it's clear that two hours in the winter sea in your dinner suit is not survivable. Alansplodge (talk) 12:03, 11 January 2018 (UTC)[reply]
How did Sir Humphry Davy discover cool flame? Our article mentions that he produced the flame and accidentally noticed its coolness, but it doesn't mention what he did to produce it in the first place. All I'm finding with Google is numerous references to the fact of discovery, with (again) no mention of the process. Here's a good candidate for article expansion, if we can get a source. Nyttend (talk) 12:51, 11 January 2018 (UTC)[reply]
Reference no 5 in the cool flame article provides the answer - "H. Davy (1817) "Some new experiments and observations on the combustion of gaseous mixtures, with an account of a method of preserving a continued light in mixtures of inflammable gases and air without flame," Philosophical Transactions of the Royal Society of London, 107 : 77-86. On p. 79, Davy inserted a hot platinum wire into a mixture of air and diethyl ether vapor: "When the experiment in the slow combustion of ether is made in the dark, a pale phosphorescent light is perceived above the wire, which is most distinct when the wire ceases to be ignited. This appearance is connected with the formation of a peculiar acrid volatile substance possessed of acid properties." (though I do wonder if he really wrote vapor rather than vapour). Wymspen (talk) 13:09, 11 January 2018 (UTC)[reply]
Ah, sorry, I failed to check the references; I figured that whoever added the sources would have added the "how" if the sources supported it. Nyttend (talk) 13:14, 11 January 2018 (UTC)[reply]
January 12
Bizarre error in official PLU code record?
If you look up PLU code 3474 on plucodes.com, 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 Pepper01:43, 12 January 2018 (UTC)[reply]
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! [3] (from [4]) Wnt (talk) 02:24, 12 January 2018 (UTC)[reply]
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 Pepper02:41, 12 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
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) [5][6]. 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 [7][8].
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. [9].
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 [10] 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 [11][12][13], 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.)
[14] 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".)
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. [15] those don't look very small although that's in Sabah no KL or peninsular Malaysia. And these in KL [16] 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)[reply]
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 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)[reply]
Brown crap on people's teeth that doesn't go away
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. 129.215.47.59 (talk) 17:46, 12 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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."Dbfirs08:31, 13 January 2018 (UTC)[reply]
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 87.81.230.195} 90.200.41.3 (talk) 18:48, 13 January 2018 (UTC)[reply]
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)[reply]
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? Dbfirs07:53, 14 January 2018 (UTC)[reply]
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
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."Dbfirs12:15, 14 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
(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)[reply]
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)[reply]
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. --47.157.122.192 (talk) 10:24, 15 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
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. Dbfirs20:48, 14 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
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. Dbfirs22:20, 14 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
References
^"truth … is much too complicated to allow anything but approximations".von Neumann, J. (1947), "The Mathematician", in Haywood, R. B. (ed.), Works of the Mind, University of Chicago Press, pp. 180–196.
January 15
How much care is exercised in naming new concepts in quantum physics? (e.g. "wave function collapse")
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, 67.233.34.199 (talk) 16:15, 15 January 2018 (UTC)[reply]
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)[reply]
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.
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)[reply]
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) ?
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)[reply]
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)[reply]
Nuclear Propulsion Technology (Ships)
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)[reply]
(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)[reply]
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!
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)[reply]
"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)[reply]
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)[reply]
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)[reply]
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!
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)[reply]
January 16
Stirling single
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)[reply]
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)[reply]
Physics Question
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? 50.66.1.32 (talk) 06:35, 16 January 2018 (UTC)EEK[reply]
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)[reply]
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. --Jayron3215:26, 16 January 2018 (UTC)[reply]
NSAIDs
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)[reply]
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. [19][20][21] 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. [22] 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)[reply]
How long have zoologists known that animals don't have four legs + wings?
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 (聖やや) 09:01, 16 January 2018 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
,20.10.17.jpg)
