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August 22

Maxwell's demon

If you explained Maxwell's proposal and told me to suggest a solution, I would imagine that it was the necessity of the demon adding energy to the system by opening and closing the door. However, I see that the actual answer is different, e.g. the necessity of expending energy to learn which molecules were which, or the necessity of erasing one's memory of past molecular movements. So where do I go wrong in suggesting that the energy of moving the door is a possible answer? And has anyone published a WP:RS addressing door-energy requirements and explaining why they don't work? Nyttend (talk) 02:19, 22 August 2018 (UTC)[reply]

It's not about energy, it's about entropy.

Maxwell's demon uses entropy to produce energy. It works within the same simplified world of "light inextensible string" and "frictionless doors" as much conceptual physics. The assumption is that "filtering the entropy" would allow energy to be produced (this is uncontentious) and also that the demon can do this without consuming energy itself (that's a conceptual simplification, but it's valid because if the demon can't do it with this simplification, it certainly can't achieve it without.)

However, even with these advantages over reality, Maxwell's claim is that the demon can't function. Not for lack of energy, but for lack of entropy. Although this didn't really get a theoretical basis until the 1960s. Andy Dingley (talk) 09:48, 22 August 2018 (UTC)[reply]

The assumption is ... that the demon can do this without consuming energy itself (that's a conceptual simplification, but it's valid because if the demon can't do it with this simplification, it certainly can't achieve it without.) Doesn't that just show how meaningless the thought-experiment is? You might as well say "If I use a perpetual-motion machine to operate the door, I can generate free energy!". Iapetus (talk) 09:54, 22 August 2018 (UTC)[reply]

But the demon doesn't say that. It says, "even if I did have a perpetual motion machine, I couldnt generate free energy; so I certainly can't do it without." Andy Dingley (talk) 10:15, 22 August 2018 (UTC)[reply]

Sort-of repeating what AD said: the idea is that Maxwell's demon paradox's standard solution does not involve door-opening costs. It might well be that, if you try to build a Maxwell demon in the lab, the door-opening costs would be prohibitive even with a door in unobtanium; it might even be that matter properties at small scales forbid entirely whatever design you have in mind. However, the crux of the Maxwell demon paradox is in the information/decision part, not in the door design whose refutation will depend on the specifics (for another example of extract-work-from-single-temperature-source design, see Brownian ratchet). Tigraan^{Click here to contact me} 14:27, 22 August 2018 (UTC)[reply]

So in other words, I went wrong because my answer didn't answer the question that Maxwell posed :-) Thanks for the correction. Nyttend backup (talk) 16:20, 22 August 2018 (UTC)[reply]

Just to clarify, the solution to the problem posed by Maxwell's demon is that it is, as originally presented, supposed to violate the second law of thermodynamics by allowing the entropy of the closed system to decrease without itself increasing the entropy of the universe. This was solved by Information Theory's contribution to the idea of entropy, which is that the storage of information always creates entropy. In order to decide when to open and close the door, the demon has to store information in his "mind" (whatever that is) to allow him to decide when to open the door; every new particle creates a new memory location, which creates more entropy. Thus, the second law is still saved. This video, starting at about 7:00 minutes, explains exactly how this works. --Jayron 32 16:33, 22 August 2018 (UTC)[reply]

Why is the letter 'G' used to represent Conductivity ?

This came up on the Sieman's Talk page {1} and it got me curious, so I tried to research it myself briefly to no avail, and thought I would bring it here:
Why was the letter 'G' chosen to represent electrical conductance, the reciprocal of resistivity.
Any insight is appreciated. Cheers! --Elfabet (talk) 14:07, 22 August 2018 (UTC)[reply]

In German one may suggest G stands for Geleitfähigkeit because "Das Formelzeichen des elektrischen Leitwerts ist G (und) seine Maßeinheit Siemens" [1]. Both Georg Ohm and Werner von Siemens were Germans. DroneB (talk) 15:12, 22 August 2018 (UTC)[reply]

(edit conflict) It might not mean anything. There are a limited number of letters one can use, and the obvious letter (C) already is used for electric charge (coulomb charge), so other letters needed to be chosen for other variables; I for current and G for conductance. "G" doesn't have to mean anything per se, it just needed to be an unused letter one could press into service. Notably, G isn't always the symbol used. Sometimes, an inverted omega sign is used, (called the "mho") since the Siemens is an inverse of the Ohm. --Jayron 32 15:14, 22 August 2018 (UTC)[reply]

@DroneB: that technically works, but doesn’t feel natural. I don’t think the term Geleitfähigkeit was ever used (the google results I found are generally typos for Gleitfähigkeit). However, Greek γ is occasionally used for Electrical conductivity, and I could imagine G could be derived from that. Cheers ✦ _hugarheimur 17:02, 22 August 2018 (UTC)[reply]

I lack a reliable relevant source for Geleitfähigkeit ("conduct capacity") because an expression such as "Die Sekretion der Bartholin-Drüsen regt die Geleitfähigkeit des Penis zusätzlich an."[2] gives a wrong (but interesting and useful to know) idea, and is probably a typo of Gleitfähigkeit. So in our fruitless search of the source of G, Geleitfähigkeit fails Wikipedia's WP:SYN and the mho character

\mho

is the unit, not the symbol of conductivity. DroneB (talk) 19:47, 22 August 2018 (UTC)[reply]

It's worse than that: C isn't even the symbol for electric charge. C was already taken for electric capacitance, so the symbol for electric charge is Q and thus conductivity had to settle for G. 97.115.66.87 (talk) 23:43, 22 August 2018 (UTC)[reply]

Really? I thought it was because C already stood for coulomb, and writing C = 0.05 C might be a little bit confusing. 78.0.242.89 (talk) 23:43, 24 August 2018 (UTC)[reply]

There is often no connection with a deeper background or higher meaning. Engineers are traditionally painfully pragmatic in such cases - they pick then "next best" letter and carry on engineering. So the letters "A-F" where already in use and thus they picked "G". --Kharon (talk) 21:24, 25 August 2018 (UTC)[reply]

What's the best estimate for Mauna Kea's all-time high height? How far in the future or past is this?

I'd be interested in any height (from base, from sea level (current or at the time), average pressure altitude..) Sagittarian Milky Way (talk) 19:31, 22 August 2018 (UTC)[reply]

Mauna Kea is towards the end of its growth, although it remains active. It is unlikely to have been higher than it is now and is likely never to get substantially higher. Mikenorton (talk) 05:52, 23 August 2018 (UTC)[reply]

Sapphire

According to sapphire, it's an aluminium oxide Al₂O₃. Does it mean that if I properly oxidize a common alumunium, I can obtain an inexpensive sapphire? 212.180.235.46 (talk) 20:18, 22 August 2018 (UTC)[reply]

Synthetic sapphires are made using the Verneuil process, the Czochralski process, or just by hot isostatic pressing, as explained later in the article. Perhaps someone else can explain how easy or how difficult this is. Dbfirs 20:23, 22 August 2018 (UTC)[reply]

You have three problems to solve:

Grow some corundum. This is fused aluminium oxide. It has been commercially manufactured as an abrasive for about 120 years. It's mostly done by the Verneuil process, which is a fairly simple process using an oxy-hydrogen flame. You now have the sort of thing that looks like a geological sample - chemically it's right, but the structure is amorphous and opaque. If you can see through it at all, that's luck.
Refine the material to make it a single crystal, thus transparent. This might use the Czochralski process. Again, this is much easier than it used to be - induction heater modules are on eBay these days, and they don't catch fire all that quickly.
Change the colour. This is a matter of adding dopants to the aluminium (yes, just like semiconductor manufacturing). Usually chromium. This is very tricky to get the colour right. One of my favourite sapphires are padparadscha sapphires, which have a red colour, somewhere from a salmon pink to an orangey red. If you see one of these for sale today, chances are they're synthetic, grown in Myanmar or Thailand - especially if they're orangey. You can also deepen an existing colour, just by heating them in a controlled manner.

So, not easy. But if you have a glassworking workshop, or even a ceramics workshop, you're halfway there. Or you can grow them directly as crystals, using epitaxial growth. But CVD processes, let alone MO-CVD, tend to involve horribly toxic chemistry. Andy Dingley (talk) 20:51, 22 August 2018 (UTC)[reply]

We have Sapphire § Padparadscha. Might want to make a redirect. --47.146.63.87 (talk) 06:45, 23 August 2018 (UTC)[reply]

Done Tigraan^{Click here to contact me} 07:57, 23 August 2018 (UTC)[reply]

This video may be of interest: https://www.youtube.com/watch?v=a0N4JYN9lFI --Guy Macon (talk) 21:02, 22 August 2018 (UTC)[reply]

Or just buy a synthetic one outright, which will be cheaper than the equipment necessary to make it (as detailed above), unless you're already in the jewelry business. Synthetic gemstones are cheap because gemstones are rocks. They don't involve rare materials. "Natural" gems are only expensive because of a combination of factors that are an object lesson in behavioral economics: the gem mining industry is an oligopoly, and said industry heavily promotes "natural" gems as somehow fundamentally different from "fake" synthetic ones and the only suitable material for demonstrating your love for someone, or from showing off how rich you are, which justifies their exorbitant cost. At least in the Western world the public largely goes along with this because propaganda works. Industrial and scientific use of gemstones is almost universally synthetic stones because in those contexts the people using them aren't trying to impress others; they know the stones are cheaper and just as good. (Sometimes better, because the properties of the stone can be carefully controlled, which is important for some applications.) --47.146.63.87 (talk) 06:35, 23 August 2018 (UTC)[reply]

Nitpick: Synthetic gemstones are cheap because gemstones are rocks. They don't involve rare materials. - Partly true. Ruby and sapphire are waaay cheaper to manufacture (in a marginal cost sense once you have all the equipment) than the natural thing, but synthetic diamonds cost almost as much as natural ones even though it is pure carbon. It depends on the temperatures etc. needed in the production process. Tigraan^{Click here to contact me} 08:03, 23 August 2018 (UTC) [reply]

Are you sure? I thought gem-quality diamonds could be made pretty cheaply (but for the reasons discussed previously people prefer expensive natural ones). The linked article doesn't say anything about the cost to manufacture, just the selling price. Iapetus (talk) 08:14, 23 August 2018 (UTC)[reply]

Hmm, I did base this on the article sentence synthetic diamonds sold as jewelry were typically selling for 15–20% less than natural equivalents, and my knowledge that synthetic rubies are cheap enough that a crazy friend of mine bought some to forge his own proposal ring (here's a retailer at $40 for 200 pieces). However our article also says De Beers started selling synthetic diamonds to the general public at a couple of hundred dollars each, so the manufacturing cost cannot be super high either. Tigraan^{Click here to contact me} 11:03, 24 August 2018 (UTC)[reply]

I've a few 3/4" diameter rubies. One or two I've used, set into sword pommels. I've no real use for 3/4" rubies, but when you see them listed and they're so cheap, it's hard to resist. Much silversmithing I've done has involved padparadscha sapphires, just because I like the colour.

This isn't to say that synthetic means cheap though. Laser rods, or the three foot discs in some of the big lasers, can cost as much as Liz Taylor's diamonds. I've a small piece of a three footer, which one day "just broke". Most of the bigger pieces were worth so much as scrap they were re-ground as rods or discs for smaller lasers. Andy Dingley (talk) 12:03, 24 August 2018 (UTC)[reply]

Isn't the high cost of those laser rods in large part due to their being precision cut to tighter tolerances than jewelry? 202.155.85.18 (talk) 05:57, 28 August 2018 (UTC)[reply]

Certainly in part. The ends have to be polished, and to be both flat and accurately parallel (the sides are less critical). When this comes to a disc laser, the amplifiers are both large and the emitting faces which have to be carefully polished are much bigger. So yes, serious money! Andy Dingley (talk) 00:32, 29 August 2018 (UTC)[reply]

Even for diamonds, it's cheap to make bulk polycrystalline diamonds, and these have been part of the industrial abrasives trade for decades. It's when you need monocrystalline (i.e. transparent) diamonds in large sizes that it gets expensive. Andy Dingley (talk) 08:20, 23 August 2018 (UTC)[reply]

Cheap is relative. The cheapest industrial abrasive is Sand. Compared to Sand, industrial diamonds are still very expensive. The question of worth is nicely pointed out in the article Opal. (cite) The internal structure of precious opal causes it to diffract light, resulting in play-of-color. (citeend) Ofcourse that includes how common these colors are. Thus like the rare pink and blue diamonds are traded highest it seems blue and orange-pink are the most expensive sapphires. Else they become industrial parts like in case of sapphires as bearings in watches or as part of cutting tools in glass works. --Kharon (talk) 21:14, 25 August 2018 (UTC)[reply]

Carborundum abrasives are actually cheaper than abrasive sands. Sand isn't usually very abrasive, so the grades used as abrasives have to come from particular locations. Like building sand (which we're now running short of), the price is going up and poor grades are being passed off as better stuff. Parts of India now have "sand pirates" who are stealing river sandbanks (of good sand) and causing havoc in some deltas.

Sand is also a very poor abrasive (it's both weak at cutting and also hazardous). I have a 17th century book (reprint) which discusses the problem of people selling fake "sandpaper" to woodworkers, instead of the real glasspaper, coated with powdered glass. Andy Dingley (talk) 12:40, 26 August 2018 (UTC)[reply]

I think you confused Carborundum with Corundum aka aluminum oxide or Al₂O₃, which is relative abundant in Nature, used everywhere in industry and manufacturing as main abrasive and only valuable in its rare variations called ruby and sapphire, which of course thus is Al₂O₃ too. So to answer the original question, if you would oxidize Aluminum industrially to Al₂O₃ you would not end up with valuable sapphire but cheap Corundum. But with some advanced tricks you can get sapphires and rubies too. You can read about it under Corundum#Synthetic_corundum --Kharon (talk) 19:26, 26 August 2018 (UTC)[reply]

No, carborundum. Admittedly this is "seconds", and it rather surprised me too, but in fine grits, carborundum grit is available more cheaply than corundum (and normal size carborundum). The grit is manufactured by a different process than for solid pieces and as I understand it from the supplier, this also produces a near-waste stream of undersize particles (they're actually grown as particles in a gas-phase process, so they start out small). Andy Dingley (talk) 20:03, 26 August 2018 (UTC)[reply]

Rice foamed after being soaked for a couple of days, probably less

I put the rice in the rice cooker but never got to cooking it. It's summer, and after more than a day, the water had quite some foam on the top with a hint of fermentation. Is the rice still safe for cooking? 104.162.197.70 (talk) 21:44, 22 August 2018 (UTC)[reply]

see Rice wine which is what is forming. Rice is quite cheap, chuck out, wash it out and start again. Graeme Bartlett (talk) 21:58, 22 August 2018 (UTC)[reply]
Going by this NHS page, I'd strongly suggest not eating it. As Graeme says, even if it is actually safe, why risk it? › Mortee _talk 22:36, 22 August 2018 (UTC)[reply]
- Could be Bacillus cereus which can survive boiling and is a known pathogen of cooked rice. Heaviside glow (talk) 22:40, 22 August 2018 (UTC)[reply]
  - Yes but the OP isn't referring to cooked rice. There are significant differences between cooked rice and uncooked rice, especially regarding nutrient availability. Germinated brown rice is a common thing, and while it's generally suggested to change the water after a while, there doesn't seem to be great concern over food illnesses from Bacillus cereus. Of course nutrient availability is likely to be reduced further with brown rice although interestingly this [3] mentions that brown rice has higher Bacillus cereus load in the first place. Germinated brown rice seems to end up with an overall load of a bit over 1 order of magnitude higher load although they didn't test enterotoxin levels. Nil Einne (talk) 01:21, 23 August 2018 (UTC)[reply]
    - All true, and I'm interested in the white vs brown rice distinction you raised. Still, given that the bugs are there and inclined to grow in a damp environment at room temperature, unless OP fancies experimenting on themselves, it's probably best that they just get some new rice. Per our article, germinated brown rice is left for 4–20 hours, not "a couple of days". At a guess, brown rice is also more resilient to soaking because its husk is intact, so I'd expect B. cereus to get started rather faster with white rice, regardless of the initial load (not that we know what colour OP's rice is). I don't have any expertise here at all, but I'm still very much inclined towards caution. › Mortee _talk 01:35, 23 August 2018 (UTC)[reply]
      - No that's for 30-40 degrees C water. The OP appears to come from New York, and while a lot of the northern hemisphere is having hot summers, i find it unlikely that water sitting there. Most sources including our article recommend longer for lower temperatures although I can't find good sources discussing recommended times for more reasonable temperate country room temperatures (say 20 degrees C). Although this source mentions one commercial processor using 72 hours at 30 degrees C [4]. Various sources e.g. [5] [6] mention GABA or other levels peak at 48 hours, so they seemingly didn't think these such dangerous levels to be not worth testing. This isn't exactly surprising since as the sources also mentioned, soaking grains and other seeds for such periods isn't exactly uncommon. This source actually suggests up to 72 hours may be best [7]. (As an aside it also hints at as do other sources another thing namely that you probably also get better results at higher temperatures (well the 30-40 degrees) than you do at lower temperatures.)
        I'm not suggesting there is no risk or the OP does it, but we also have to be realistic here that there's very limited evidence either way. The risks with cooked rice have very little relation to the risks with cooked rice.
        BTW an an interesting point, some sources recommend soaking rice overnight to reduce arsenic levels and I'm pretty sure this includes white rice which I assume is what the OP is referring to. Unfortunately the best source I could find is some BBC show [8]. (Since it's just a summary from the show, it doesn't say if this soaking was at room temperature or in the fridge or what.) This source which is discussing the results of the show includes a quote from an epidemiologist endorsing soaking [9]. While it's impossible to know if she gave some dire warnings the source neglected to mention, none are mentioned there.
        Weirdly this group carried out fancy percolator tests for cooking but didn't seem to test such a basic step. However I don't believe this is likely to be due to health concerns from soaking rice overnight. More likely that percolator makes for a more popular paper than simple soaking and also as fancy as it sounds, it's probably a more cost effective method for industrial and commercial kitchen usage. Of course 48 hours is quite a bit longer than overnight, however I don't think sources are going to recommend leaving cooked rice out overnight or even for 4 hours. (This is of course a common problem. Simple solutions which have the potential to work well in lesser developing countries where the problems may be significant are not well considered.)
        Nil Einne (talk) 04:25, 23 August 2018 (UTC)[reply]
        
        P.S. I initially gave Bangladesh as an example in my last sentence but removed it as in retrospect it may be a poor one give the frequently high arsenic levels in their water levels meaning that you could perhaps make the problem worse or at least get a lot less improvement than may be observed in countries with better water supplies. Nil Einne (talk) 04:33, 23 August 2018 (UTC)[reply]
        
        Interesting, I'd never heard the arsenic advice. › Mortee _talk 09:30, 23 August 2018 (UTC)[reply]
        Personally, I think there's far too much personal speculation going on here, and I wish this matter had been left at the initial advice of Graeme and Mortee. This is an inquiry that is close enough to a request for medical advice (it is, afterall, an inquiry about the safety and health implications of a course of action) that the editors here should have refused to answer this question outright, and if any answer were put forth, it should be the one which clearly endorses precaution and safety. A protracted discussion about whether or not food poisoning is actually likely to occur only creates the possibility that the OP may decide to consume something at least potentially dangerous on the basis of opinions (or a sense of doubt among them) here. That is exactly the kind of outcome our no medical advice rule was established to guard against. Frankly, some of the laissez-faire opinions above display a marked lack of understanding of the topic and a pretty free-wheeling willingness to discount the risk of contamination. For starters, one doesn't just have to consider common pathogens associated with under-prepared foodstock of this sort; so long as there is standing water involved, the question of what was in that water initially, what was on the surface of the cooker, and in the immediate environment (in the addition to heat and other factors) all create risk of bacterial and/or fungal growth after that period of time, with potential toxicological consequences. Indeed, the fact that the OP mentioned the heat and apparent fermentation are additional signs of why it is imprudent to say anything tot he OP which might induce them to have doubt as to whether to pursue the more cautious course (in the present case or in the future). And even if I were not familiar with these basics microbial concerns, I'd still be saying as a matter of policy that opining on this topic is not appropriate use of the desk. The OP should be advised to seek their health and safety advice from appropriate sources, and this discussion should be closed. Props to Mortee, however, for maintaining a consistent tone of discouragement to the notion of reheating already fermenting food. Snow ^{let's rap} 06:18, 24 August 2018 (UTC)[reply]
        Some medical advice ("don't risk it. Throw it out and thoroughly clean the cooker") is OK, and is vastly preferable to "ask your doctor if eating rotten food is OK", Other medical advice ("go ahead and eat rotten food") is definitely not OK. --Guy Macon (talk) 07:38, 24 August 2018 (UTC)[reply]
        More on this in the section below. --Guy Macon (talk) 10:39, 26 August 2018 (UTC)[reply]

WP:LOCALCON and WP:TPOC

Please folks... You know fully well that's the kind of things that goes on the talk page, not on the main refdesk page. Move it there, if you really want to rehash it. Tigraan^{Click here to contact me} 16:19, 26 August 2018 (UTC)[reply]

There are some who believe that Wikipedia has a policy against giving medical, legal, and business advice, but no such policy or guideline exists. (If you are about to cite the reference desk guidelines, please read WP:LOCALCON and then show me where the Wikipedia community approved them).

Here is some medical advice: Don't do crystal meth. It will screw up your health. Don't bother asking a doctor if crystal meth is good for you. It isn't. Here is some legal advice: Don't do crystal meth. It is likely to get you arrested. Don't bother asking a lawyer if crystal meth is illegal. It is. Here is some professional advice: Don't do crystal meth. It will use up all of your money and is likely to get you fired. Don't bother asking a certified financial planner if becoming a meth addict is good for your finances. It isn't. (general disclaimer, medical disclaimer. legal disclaimer, risk disclaimer.)

There. I just provided medical, legal, and professional advice, and while I did make a point, I did so without being disruptive.

Feel free to report my behavior at WP:ANI if you believe that I have violated any Wikipedia policy or guideline.

BTW, here is some more free advice: In my opinion both terminal cancer and AIDS are even more effective methods of weight loss than food poisoning or crystal meth, so if you really want to shed those pounds why not try all four at the same time? More advice: don't get your medical advice from an electronics engineer. ^{In case anyone missed it, that was a joke.} --Guy Macon (talk) 07:38, 24 August 2018 (UTC)[reply]

_{Re. the above, see WP:SOAPBOX. The Wikipedia article about Methamphetamine gives referenced information about the illicit use of methamphetamine hydrochloride as a recreational drug and its less common legally controlled medical prescription as a second-line treatment for attention deficit hyperactivity disorder and obesity. DroneB (talk) 13:03, 24 August 2018 (UTC)}[reply]

In order to properly evaluate your assertion, would you be so kind as to tell us which of the five numbered entries on the WP:SOAPBOX page you believe forbids the above? --Guy Macon (talk) 13:57, 24 August 2018 (UTC)[reply]

_{No. DroneB (talk) 23:52, 24 August 2018 (UTC)}[reply]

I will take that as an admission that you don't actually believe that I have violated any part of WP:SOAPBOX with my comments above. --Guy Macon (talk) 10:39, 26 August 2018 (UTC)[reply]

I'm not sure what to make of your post, because you seem to frame it as if in counterpoint to my own, and yet much of your perspective seems similar to my own assertions. However, a few important caveats:

No, it's is not really appropriate (let alone "vastly preferable") to answer even simple questions where they have potential medical or legal consequences. The best course of action there is -always- to point the individual in question to a qualified professional, no matter how obvious the answer may seem, because the devil is very much in the detail when it comes to risks in this area. I agree with you insofar as there is a world of difference between the inappropriateness of telling someone not to take a risk and the inappropriateness of encouraging them to do so; the latter is clearly much more unacceptable. But neither form of speculation should be engaged with by amateurs. The irony is, some of us certainly are qualified to provide medical or legal advice, but it is exactly those individuals who would never do so in this highly problematic forum (for both professional and ethical reasons). Which means by definition the people providing advice of that sort here are those who are not qualified to be doing so. Shutting down inquiries that can lead to poor advice that may affect another's well-being is such a substantial way is manifestly the appropriate thing to do in such situations; engaging with such questions just so one can scratch the itch of playing expert is irresponsible in the extreme.

And as to your closing comment there, I presume that the electrical engineer in question is yourself, in a quasi-self-effacing jib. Here's the problem with that: the person requesting that information probably doesn't know your background (I didn't, and we've been editing alongside eachother in multiple spaces for years) and they may be foolish enough to assume anyone answering a question knows their stuff, which is...not likely, to put it mildly, when it comes to the RefDesks. Meaning no disrespect to the present OP, but many of the people who will come here seeking guidance on a question with medical implications may not be exactly flush with good common sense, or they probably would not be making such an inquiry here to begin with. We have a moral obligation not to facilitate their reliance on advice about such issues, by closing down such conversations. With certainty, nobody should be spitballing answers to such questions here. We should especially never be telling them "don't bother to check with a professional, just trust me."

I think you may want to review WP:LOCALCONSENSUS yourself, because you've nearly completely inverted the policy with your presentation of it there. Here's the very first sentence from that section of WP:CONSENSUS: "Consensus among a limited group of editors, at one place and time, cannot override community consensus on a wider scale." (emphasis added). Nothing in that subsection remotely implies that local groups of editors cannot come to their own conclusions about the best way forward on an issue, be it content or process. And indeed, obviously this is so, because the entirety of that policy is about how one goes about doing exactly that. LOCALCON only tells us that broader approaches already adopted cannot be put aside by local editors.

And dearth of guidelines or not, this is a topic the community (here at the RefDesks and elsewhere) have grappled with, and shown a great deal of concern about. I guarantee you that anyone making a habit of providing medical or legal advice (even if the answers seem entirely straightforward in every instances) would eventually be removed from this space. Indeed, I'm not sure how heavily involved you have been here recently, but in the event you missed the actions, we have recently topic banned an editor (and warned others) who have a habit of offering fly-by responses, and most of their offenses didn't even rise to the level of importance of medical or legal advice. Partly this was done out of a concern with the quality of our responses, but also because acting with impunity in this regard has been increasingly bringing the broader community's scrutiny upon this corner of the project (for entirely legitimate reasons, in my opinion). There was even a VPP discussion six months ago that sought to close the desks altogether because of the problems wrought by our most free-wheeling "contributors"--and potentially dangerous advice was one of the issues raised there. I guarantee the regular and semi-regular contributors to this space are not going to allow the people who think they are a qualified expert on everything get the RefDesks (a valuable part of our educational exercise) shutdown over such nonsense.

Beyond that, you've been around long enough that you surely know that there are higher authorities on this project than even community consensus. For example, the WMF, which (in the strict legal sense anyway) owns this project and its assets. The WMF imposes many rules that put limitations upon what our policies can or cannot say, and provide guidance that is in effect regardless of whether or not the community has yet arrived at the same conclusions. Shall we ping WMF legal here and ask them if we are allowed to provide medical or legal advice in direct response to explicit inquiries? Because I feel I can tell you with some certainty that the standard they will require of us will not map very well to the one you're suggesting. And indeed, they have very compelling reason for requiring that we err on the side of caution; as the entity hosting this space, they have substantial vicarious liability for any ill-advised (read: dumbarse) medical or legal (or otherwise dangerous) advice provided here. Such considerations being in addition to any previously mentioned moral restraints that we ought to be applying in such cases.

Sorry, but all said, I strongly disagree with you. Would I call an editor out for telling someone to do the cautious thing with regard to consuming something potentially toxic? No--in fact, the above discussion demonstrates as much, so it would be foolish for me to claim otherwise. But do I think that is the ideal solution? No, I do not, because to encourage such an approach is to open up the door to someone pressing the matter too far on an issue they feel is "obvious", and potentially causing real harm as a consequence. The appropriate response is to close down all such threads on sight and encourage the individual to seek the professional advice they need. Not the random best guesswork of the Reference Desk regulars--no matter the fact that we are a generally knowledgeable group whom I am happy to count myself amongst. Snow ^{let's rap} 04:57, 25 August 2018 (UTC)[reply]

Thank you for the thoughtful response. Alas, I believe that you have a few things wrong and that it may be worth appealing to a higher authority by asking WMF legal or the community (in the form of an RfC) in order to resolve which of us is mistaken.

The first thing that I believe that you have wrong is WP:LOCALCON. You say

"I think you may want to review WP:LOCALCONSENSUS yourself, because you've nearly completely inverted the policy with your presentation of it there. Here's the very first sentence from that section of WP:CONSENSUS: "Consensus among a limited group of editors, at one place and time, cannot override community consensus on a wider scale." (emphasis added). Nothing in that subsection remotely implies that local groups of editors cannot come to their own conclusions about the best way forward on an issue, be it content or process. And indeed, obviously this is so, because the entirety of that policy is about how one goes about doing exactly that. LOCALCON only tells us that broader approaches already adopted cannot be put aside by local editors."

I believe that your interpetation of WP:LOCALCON is incorrect. You seem to be saying that a local consensus (such as a handful of editors making some local rules and never bothering to post an RfC to see if the community approves those rules) is binding on all Wikipedia editors unless it conflicts with a policy or guideline that has been approved by the community. I say that no such local consensus is binding on all Wikipedia editors.

In this particular case we do have an existing policy or guideline that the local consensus is attempting to override. That guideline is WP:TPOC. And none of the editors who have come to the local consensus that it is OK to remove medical or legal advice have attempted to add medical or legal advice to the list of posts that are allowed to be removed per TPOC.

So far the administrators at WP:AN and WP:ANI have consistently refused to enforce any local consensus. If every case that I am aware of they have asked the person reporting the violation of a "rule" supported only by a local consensus to post an RfC and see if the community agrees to make the rule part of our global consensus (in other words, a policy or guideline).

I can see one way that we could resolve this difference of opinion. You (as the person advocating violating WP:TPOC by removing posts) could post an RfC at Wikipedia:Village pump (policy) asking the community whether a local consensus is binding on all Wikipedia editors unless it conflicts with a policy or guideline that has been approved by the community. Or you could post an RfC at Wikipedia talk:Talk page guidelines asking them to add asking and/or answering requests for medical and legal advice to be added to WP:TPOC.

Until an RfC says otherwise, we already have the answer when the local consensus attempts to override WP:TPOC: As it says in WP:LOCALCON, such rules "have not formally been approved by the community through the policy and guideline proposal process, [and] thus have no more status than an essay".

Another possibility is that I am misinterpreting your response and that you are not advocating removing posts that ask for or give medical or legal advice in violation of WP:TPOC but rather are advocating reporting them at WP:ANI. Is so, we agree. While I have never seen ANI enforce any rule that is supported only by a local consensus, they can and do enforce our global-consensus-approved rule against being disruptive, and WP:TPOC does allow removal of harmful posts. That is why my advice about crystal meth above would be a good test case. It clearly contains medical, legal, and professional advice, but it is neither disruptive or harmful. In other words some (I can see a strong argument for "most") medical, legal, and professional advice is disruptive (and should be reported) or harmful (and should be removed). So, is anyone here willing to report me to WP:ANI for posting medical, legal, and professional advice without being disruptive? Or is anyone here willing to delete my advice about crystal meth and thus volunteer to be reported at WP:ANI for violating WP:TPOC?

The other area where I believe that you got it wrong is when you write

"The WMF imposes many rules that put limitations upon what our policies can or cannot say, and provide guidance that is in effect regardless of whether or not the community has yet arrived at the same conclusions. Shall we ping WMF legal here and ask them if we are allowed to provide medical or legal advice in direct response to explicit inquiries? Because I feel I can tell you with some certainty that the standard they will require of us will not map very well to the one you're suggesting."

You can ask them if you wish, but be aware that dozens of editors have asked them already and that they have steadfastly refused to endorse the removal of medical or legal advice by non-administrators. They either ignore the query or tell the person asking to go to ANI or Arbcom with the specific post. And the disclaimers (general disclaimer, medical disclaimer. legal disclaimer, risk disclaimer) also lack any wording that implies that local consensus overrides WP:TPOC or in any way hints that non-administrators are allowed to delete non-harmful posts such as my advice on crystal meth. --Guy Macon (talk) 10:39, 26 August 2018 (UTC)[reply]

Thank you for your thoughtful response as well. To answer your implied inquiry, I personally don't advocate for removing the posts of others. Even though the reference desks are unique amongst Wikipedia spaces in combining aspects of content and process pages--and correspondingly, the question of how much our content policies govern (vs. TPG) is an open one--I personally don't think it's a good solution to encourage our contributors to go around reverting one-another's comments off the page. It just has too much potential for disruption and edit warring. Probably if someone was encouraging a course of action that was manifestly dangerous and/or illegal, I'd have to reconsider that stance, but it would have to be a pretty explicit and non-ambiguous case. Likewise, I don't view ANI as an ideal solution, partly for some of the reasons you mention above and for others beside. Here too, there may be exceptions where I'd support taking this action, but only with regard to someone who makes a habit of providing this kind of advice; the noticeboards are just not a well-suited (or in-proportion) solution to isolated incidents--not even ANI. Rather, the solution I advocate for is shutting down any discussion that has significant medical or legal implications for the OP (or any others which are blatantly straying into such advice at the direction of overzealous contributors), instead directing the OP to seek their advice from professionals, and creating a culture of making this the default approach. Of course, that's largely the case already, so what I am really advocating for, I suppose, is the reinforcement and codification of that approach--the latter being, as you point out, a very much unresolved matter.

Regarding another of your points: are you saying that you know of instances where the WMF legal has weighed in on the RefDesks? I'm aware of instances where WMF personnel have tangentially addressed the matter of the limits of our medical or legal content, but I am not familiar with any occasion where they have commented upon (or been asked to comment upon) whether direct medical or legal advice on the reference desks is permissible. The disclaimers are meant to express lack of warranty on our article content, as a source of abstract, objective, and generalized knowledge. That is a very, very different context from individualized, specific advice, provided to someone in a direct exchange of comments. The implications for liability (and for the potential for harm generally) are different between those acitvies/forms of content in key respects. To the extent the WMF legal team has not put a moratorium on the latter activity, I can only assume it is because much of what happens here flies under their radar. But if I'm mistaken and they have been asked about the specific activity of direct medical/legal advice at the desks (as opposed to the more general variety implicit in encyclopedia content), I'd be in the debt of anyone who can direct me towards it, because I missed the discussion, whenever it was.

I have some further thoughts as the LOCALCON issue, but I'm just out the door in minutes here, so they will have to wait (and it may be worth moving further discussion to the talk page if we want to discuss further, so as not to clog the front page further). I will say that I think your proposed solution (an RfC at VPP) probably has some merit, though I think may make more sense to make the question even more specific and ask the broader community to simply validate or reject the "no medical or legal advice" rules. Indeed, that's pretty much the standard process we ask other sub-communities to utilize when the want to turn WP:advice page/WP:LOCALCON "best practice" suggestions into a firm rule and principle of community consensus. Snow ^{let's rap} 12:14, 26 August 2018 (UTC)[reply]

I have no objection to moving this entire section to the talk page, leaving a link here.

As for WMF legal, I also am not familiar with any occasion where they have commented upon whether medical or legal advice on the reference desks is allowed. But I do recall (I would have to search to find examples, and memory can be tricky) them being asked. Anyone reading this is free to ask them and see what the response is.

When I read your

"shutting down any discussion that has significant medical or legal implications for the OP (or any others which are blatantly straying into such advice at the direction of overzealous contributors), instead directing the OP to seek their advice from professionals, and creating a culture of making this the default approach."

I realized that I had neglected the option of shutting down the discussion with Template:Hidden archive top. This does appear to be a much better solution than deletion in violation of TPOC or an ANI report of a first time offender. I have a minor disagreement with the bit about directing the OP to seek their advice from professionals; I think that a simple link to Wikipedia:Medical disclaimer is a better choice and a better fit for the limited space of a hat comment. Also, asking someone to make an appointment with an M.D. to ask whether eating rotten food and using crystal meth are healthy is just plain silly. They aren't, and there is nothing wrong with saying so.

And of course hatting should never be automatic, but should be applied wisely. If, for example the section that started this only contained a short question about whether to eat rotten rice and a brief reply advising the OP to throw it out and clean the container thoroughly, I don't see that as being a good candidate for hatting. (Which would likely result in another long pointless debate about whether "don't eat rotten food" is medical advice.) I have seen some real stretches by editors who want to delete what other editors write, calling almost everything they don't like "medical or legal advice".

So it looks like we are in broad agreement about how the refdesks should handle requests for legal or medical advice. That being said, I still contend that Wikipedia:Reference desk/Guidelines directly contradicts WP:TPOC. In particular the words "For removing a question seeking medical advice, you can make use of the boilerplate text..." are advising editors to violate WP:TPOC, which does not allow such a removal.

I still contend that WP:TPOC overrules WP:RD/G where they disagree and that WP:RD/G never overrules WP:TPOC.

And I still stand by the statement at the top of this section:

"There are some who believe that Wikipedia has a policy against giving medical, legal, and business advice, but no such policy or guideline exists. (If you are about to cite the reference desk guidelines, please read WP:LOCALCON and then show me where the Wikipedia community approved them)."

--Guy Macon (talk) 16:04, 26 August 2018 (UTC)[reply]

Methamphetamine salts are effective in the treatment of attention deficit hyperactivity disorder and narcolepsy. Discuss with your doctor. 151.227.20.35 (talk) 16:06, 27 August 2018 (UTC)[reply]

August 23

Varicoceles

Would a varicocele show up on a conventional (black and white) ultrasound, or would it only show using Doppler ultrasonography? I'm reading conflicting information. Thanks Uhooep (talk) 13:18, 23 August 2018 (UTC)[reply]

Ultrasound with color Doppler is diagnostic in nearly all cases of varicocele and is the imaging technique of choice. The linked article shows images with and without Doppler. DroneB (talk) 16:00, 23 August 2018 (UTC)[reply]

August 24

Fertility question

If one gets one's entire epididymis (on both sides) surgically removed and one's vas deferens grows and attaches itself to the the spot on the testicles to which the epididymis was previously connected, would you once again begin ejaculating sperm--but with the sperm being undeveloped this time around (since it won't have an epididymis to go through)--thus ensuring that you'd remain infertile? 68.96.95.13 (talk) 21:58, 24 August 2018 (UTC)[reply]

Just use spermicide condoms and the calendar method. Sagittarian Milky Way (talk) 23:00, 24 August 2018 (UTC)[reply]

That doesn't answer my question here, though. 68.96.95.13 (talk) 02:18, 25 August 2018 (UTC)[reply]

Who was it that asked this question a few months ago? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:34, 24 August 2018 (UTC)[reply]

I did--though I don't think that it was quite the same question. Futurist110 (talk) 19:09, 25 August 2018 (UTC)[reply]

Thanks for giving us your IP address. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:37, 25 August 2018 (UTC)[reply]

What use would it give you? Futurist110 (talk) 20:50, 25 August 2018 (UTC)[reply]

So that we'll know not to block the IP for trolling. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:03, 25 August 2018 (UTC):::[reply]

"07:04, 25 August 2018 Mz7 blocked 68.96.95.13 with an expiration time of 36 hours (anon. only, account creation blocked) (ref desk trolling)" --Guy Macon (talk) 21:12, 25 August 2018 (UTC)[reply]

Who is Mz7, though? Futurist110 (talk) 21:56, 25 August 2018 (UTC)[reply]

That would be the admin that blocked the IP after I reported it to AIV. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:09, 25 August 2018 (UTC)[reply]

Oh. Futurist110 (talk) 22:26, 25 August 2018 (UTC)[reply]

Also, for the record, my question here was actually meant to be completely serious. Futurist110 (talk) 21:56, 25 August 2018 (UTC)[reply]

Especially the joke about my mother, eh? That's what led me to assume it was just a troll. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:09, 25 August 2018 (UTC)[reply]

Yeah, I'm sorry about that. I went too far with that comment of mine. However, you weren't answering my question and thus I got a bit sassy. Futurist110 (talk) 22:26, 25 August 2018 (UTC)[reply]

I thought the IP was mocking the original questioner from some months back (you), and the personal attack on me cemented it. Henceforth, either log in or explain, and you shouldn't get blocked. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:51, 25 August 2018 (UTC)[reply]

Yeah, the reason that I asked this question anonymously is that I was hoping not to get future employers of mine to notice this question. I don't know if this is a good idea, but I want to describe my work on Wikipedia on my resume (along with my work verifying supercentenarian cases) since I don't have much else to brag about. I mean, I've recently (two months ago) got a bachelor's degree from a good university, but I don't have much else to write about on my resume. Futurist110 (talk) 00:23, 26 August 2018 (UTC)[reply]

That is allowed, but it is best to do it right. See WP:VALIDALT and WP:ALTACCN. Be aware that there are amateur sleuths who love to figure out who is using the legitimate alternate account, so it is best to avoid asking the same question, editing the same page, using characteristic language (one person was outed after calling two different politicians on two different pages "asshat"), etc. And never respond to the amateur sleuths. That's why I will neither confirm or deny that my alternate account (if I have one, which I also do not admit) is User:Jimbo Wales... :) --Guy Macon (talk) 18:02, 26 August 2018 (UTC)[reply]

Also, I really do hope that someone here is actually going to answer this question. Futurist110 (talk) 00:25, 26 August 2018 (UTC)[reply]

I wouldn't know where to start looking for the answer. Perhaps there is something in the medical literature concerning vas deferens reattachment? --Guy Macon (talk) 18:02, 26 August 2018 (UTC)[reply]

August 25

Source of a basemap

Greetings, does someone have an idea where the underlying information of File:Peru physical map.svg might come from? Jo-Jo Eumerus (talk, contributions) 07:30, 25 August 2018 (UTC)[reply]

According to the file description (on commons), it is the "author's own work"; you can contact the author here: https://commons.wikimedia.org/wiki/User:Urutseg —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 01:23, 27 August 2018 (UTC)[reply]

Range of Likely Rise in GMST

The second paragraph of the global warming article reports "Climate model projections summarized in the report indicated that during the 21st century, the global surface temperature is likely to rise a further 0.3 to 1.7 °C to 2.6 to 4.8 °C depending on the rate of greenhouse gas emissions." What is the significance of four temperatures in defining this range? Shouldn't a range be defined by two temperatures and a confidence level? Also, where do theese numbers come from in the source? --Tag (talk) 15:35, 25 August 2018 (UTC)[reply]

It has to be 4 because how much of the 2001 carbon humans decide to burn by 2101 and how front-loaded or back-loaded and how much they slash-and-burn, desertify and plant trees and stuff is hard to pin down. Sagittarian Milky Way (talk) 17:32, 25 August 2018 (UTC)[reply]

I don't think this answers my question. Can you elaborate specifically on what each of the four numbers means and where I can find them in the source? --Tag (talk) 18:01, 25 August 2018 (UTC)[reply]

The first number is fast emissions cutting timeline, low estimate; second is fast emissions cutting timeline, high estimate; third is humans treat the Earth like crap timeline, low estimate; fourth is humans treat the Earth like crap timeline, high estimate. Probably. This is useful because it provides more information than just 2 numbers, it shows what's scientific uncertainty and what's "we don't know what humans will do in the future". Sagittarian Milky Way (talk) 20:00, 25 August 2018 (UTC)[reply]

The source is likely to be IPCC5. I'm not going to bother to look through it to find out. As SMW says, the 4 numbers encapsulate different CO2 emissions rates, and different estimates of the sensitivity of GMST to CO2 concentration. Specifically the higher numbers are based on RCP 8.5 which the frauds called 'business as usual'. Among other assumptions is that the population of Nigeria will grow to 1.5 billion (one eighth of the then predicted population) , giving the same population density for the entire country as the Vatican City is at the moment https://link.springer.com/article/10.1007%2Fs10584-011-0148-z. Really? Here's an article with a graph that agrees with the numbers in question. Overplotting the actual data would be an interesting exercise. https://medium.com/@davidfurphy/what-on-earth-is-an-rcp-bbb206ddee26 Greglocock (talk) 21:16, 25 August 2018 (UTC)[reply]

The abbreviation "GMST" means "Greenwich Mean Sidereal Time". It obviously doesn't mean that here. What does it mean? 151.227.20.35 (talk) 07:08, 26 August 2018 (UTC)[reply]

Global Mean Surface Temperature. Mikenorton (talk) 07:21, 26 August 2018 (UTC)[reply]

The figures are on p. 89: Under the assumptions of the concentration-driven RCPs, GMSTs for 2081–2100, relative to 1986–2005 will likely be in the 5 to 95% range of the CMIP5 models; 0.3°C to 1.7°C (RCP2.6), 1.1 to 2.6°C (RCP4.5), 1.4°C to 3.1°C (RCP6.0), 2.6°C to 4.8°C (RCP8.5) (see Table TS.1). With high confidence, the 5 to 95% range of CMIP5 is assessed as likely rather than very likely based on the assessment of TCR (see TFE.6).

Incidentally, the word "Nigeria" does not appear in the reference Greg gives, so I'd take his answer with a barrel of salt. Henry ^Flower 21:55, 28 August 2018 (UTC)[reply]

August 26

Feynman Lectures. Exercises. Exercise 27-8 PNG

...

27-8. Two thin lenses L and L', of focal lengths f and f', are separated by a distance D. Find the equivalent focal length F of the combination, and the distances Δ, Δ' of the principal planes from the respective lenses L and L'.

— R. B. Leighton , Feynman Lectures on Physics. Exercises

The Solutions give next explanation:

...
27.8. From the definition of the main planes of the optical system follows their important property: if the point is in the main plane at a distance y from the optical axis, then its image is obtained in the other principal plane at the same distance from the optical axis. We use this property of the principal planes to solve the problem. The image of the point located in the main plane is shown in the figure. The following relations are obvious:

$y=f\tan(\varphi )=F\tan(\Phi )$
$y'=(D-f)\tan(\varphi )=(f'+x')\tan(\Phi )$ .

It follows from the lens equation for $L'$ also

$f'^{2}=x'(D-f-f')$ .

Eliminating from this the angles $\varphi$ and $\Phi$ , as well as the distance $x'$ , we obtain

$F={\tfrac {ff'}{D-f-f'}}$
$\Delta '=f'+x'+F={\tfrac {f'D}{D-f-f'}}$ .

From a similar consideration for the lens $L$ :

$\Delta ={\tfrac {fD}{D-f-f'}}$ .

— MEPhI , Solutions (Google Translate)

But I don't understand why does MEPhI use both -- principal planes and lenses -- simultaneously . The principal planes are only for replacing the lens system, not for using simultaneously . Username160611000000 (talk) 06:02, 26 August 2018 (UTC)[reply]

If we draw the rays correctly PNG , we see that the ray will go through the path BNE'S' if the principal planes are used , or the path BEE'S' if the lenses are used. From this correct image I write down:
Consider light path BEE'S'.
for lens L':

{\tfrac {1}{s'}}+{\tfrac {1}{s''}}={\tfrac {1}{f'}}

{\tfrac {1}{s'}}+{\tfrac {1}{\infty }}={\tfrac {1}{f'}}

{\tfrac {1}{s'}}={\tfrac {1}{f'}}

for lens L :

{\tfrac {1}{F-\Delta }}+{\tfrac {1}{s'}}={\tfrac {1}{f}}

{\tfrac {1}{F-\Delta }}+{\tfrac {1}{f'}}={\tfrac {1}{f}}

By analogy consider the light path B'G'GS:

{\tfrac {1}{F-\Delta '}}+{\tfrac {1}{f}}={\tfrac {1}{f'}}

.
Now we see

{\tfrac {1}{F-\Delta '}}=-{\tfrac {1}{F-\Delta }}

2F=\Delta +\Delta '

, which absolutely doesn't coincide with The Exercises answer and The Solution answer. Where is my mistake???
Username160611000000 (talk) 07:00, 26 August 2018 (UTC)[reply]

Lines of magnetic flux

Magbetic flux density is quoted as nunber of lines per unit area coning our of the magnet. So how do these lines actually originate and is there flux between the lines? Is not the fkux equalky distivuted icer the surface of the poke?.80.2.20.210 (talk) 21:18, 26 August 2018 (UTC)[reply]

Here line is the old name for the Maxwell (unit), equal to 10^-8 Wb. Think of the lines, not as discrete curves with no cross-sectional area, but rather as fat bundles packed together and each carrying this much flux. --catslash (talk) 21:46, 26 August 2018 (UTC)[reply]

Wikipedia has an article titled Field line which may be useful here. --Jayron 32 17:28, 27 August 2018 (UTC)[reply]

The lines of magnetic flux form closed loops. The path of a 'line' leaves the magnet at one pole, passes through the air to the other pole where it re-enters the magnet and passes through the metal back to the first pole (I assume that originate asks for a starting-point rather than for a reason for existing).

According to classical physics the flux is distributed smoothly (if not quite equally) over the surface of the pole, and not in discrete lines with gaps between them. In quantum physics the flux can be quantized (see magnetic flux quantum), but the quantum of flux is far smaller than one 'line' --catslash (talk) 23:01, 27 August 2018 (UTC)[reply]

Leccy dlux

Wht they call th leccye field effect flux,? I thot flux id sonthin flowing.. but leccy fields Dolby fliw anywhere. Tbe jyst exist?80.2.20.210 (talk) 21:22, 26 August 2018 (UTC)[reply]

It's just an analogy which -for the reason you mention- is less than perfect. See flux and the section Flux#Flux_as_a_surface_integral. --catslash (talk) 22:11, 26 August 2018 (UTC)[reply]

shoulda be called effective ekectic or magnetic field.as the permirtivity or permeability affwcts the field strength. Yes? 80.2.20.210 (talk) 23:57, 26 August 2018 (UTC)[reply]

August 27

Why do ants avoid salt? How does salt affect ants?

--إلياس الجزائري^Elias 14:30, 27 August 2018 (UTC)[reply]

This article has some interesting info. MarnetteD|Talk 14:35, 27 August 2018 (UTC)[reply]

@MarnetteD:, I only have access to Wikipedia at the moment. Could you give me the gist of it? Or refer me to some related articles? --إلياس الجزائري^Elias 14:55, 27 August 2018 (UTC)[reply]

That article, titled Does Salt Kill Ants? What Really Happens When Salt Touches Ants? -- mentions various methods for controlling ants. The salt method references a 1937 study (relating to beetles and epsom salt), but suggests ant/salt control methods are mostly anecdotal and sketchy, adding: "Some theories claim that salt penetrates ant exoskeletons and wreaks havoc inside"; and concluding with: "Take this with a grain of salt." More recent studies suggest that ants might be more attracted to salt than sugar (especially in non-coastal areas where salt is scarce): [10], [11]. —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 17:33, 27 August 2018 (UTC)[reply]

Thank you 2606. I have been out running errands and only just saw the OPs request. I appreciate you taking the time to summarize the info at the link I provided and for adding the info about recent studies. MarnetteD|Talk 17:51, 27 August 2018 (UTC)[reply]

August 28

Nomenclature for Vitellaria paradoxa

My questions in the first section of Talk:Vitellaria, about how the shea tree came by its different scientific names, have been unanswered for a little while which means in my experience they may go unanswered for years. If anyone here can point me to where I might be able to research the story (out of a rural home, with the Internet as my research library) I will try to find it out myself, or I'll be delighted if someone can add to the discussion on that Talk page. - Egmonster (talk) 01:56, 28 August 2018 (UTC)[reply]

A copy of my answer on the article talk page - "The book "100 Top Food Plants" has some information on the naming see page 474. According to that, Vitellaria derives from vitellus (yolk in latin) and aria meaning 'like', a reference to the valuable kernel, and the paradoxa specific name (meaning strange or contrary to expectation) is from its ability to grow in extremely dry regions. The Hall 1996 monograph probably goes into a lot more detail." Mikenorton (talk) 08:40, 28 August 2018 (UTC)[reply]

Thank you very much, Mikenorton. Now I have some reading to do! It would be nice if I could understand that timeline. - Egmonster (talk) 16:20, 28 August 2018 (UTC)[reply]

Cations and HDPE

do cations adsorb to plastics (Ca2+, Na+, K+), possibly reducing the concentrations of cations in a water sample? — Preceding unsigned comment added by 184.167.211.134 (talk) 03:54, 28 August 2018 (UTC)[reply]

For most plastics no, but you may be interested n ion exchange resin. Most plastics with a hydrocarbon backbone (polythene, HDPE polypropylene) do not interact with metal ions in solution, and the ions will prefer the company of water. Graeme Bartlett (talk) 22:11, 28 August 2018 (UTC)[reply]

Autonomic block

Pharmacology: When a first generation H1 blocker like Diphenhydramine causes as a side effect an "autonomic block" what does that exactly (Which functions of the body are impaired) mean? --2003:C3:EF0F:CF43:9D84:42D3:4E4A:2A20 (talk) 09:18, 28 August 2018 (UTC)[reply]

Read autonomic nervous system. Graeme Bartlett (talk) 22:14, 28 August 2018 (UTC)[reply]

More specifically: first-generation H-1 antagonists tend to be "dirty" and have, in addition to their desired antihistamine effect, activity at other receptors, which can produce side effects. --47.146.63.87 (talk) 07:04, 29 August 2018 (UTC)[reply]

minnesota starvation experiment

the minnesota starvation experiment mentions people eating 10,000 calories a day. what causes that extreme hunger and how does the body know when they have eaten enough?

See Hunger (motivational state). And the correct number is 1,560 kilocalories per day. --Guy Macon (talk) 15:42, 28 August 2018 (UTC)[reply]

The OP may be confused by the difference between a calory with a small "c" (also known as a small calory or gram calory) and a Calory with a capital "C" (aka a large calory, food calory or kilocalory). The latter is equal to 1000 of the former, and is usually the unit discussed in dietary contexts, but many non-scientific writers are careless about defining their terms and/or about using the capital.

1,560 kilocalories, equal to 1,560,000 small/gram calories, is a fairly frugal daily diet. 10,000 (small) calories is equal to 10 large/food/kilocalaries and is equivalent to about one tenth of a slice of bread. {The poster formerly known as 87.81.230.195} 90.208.127.181 (talk) 16:19, 28 August 2018 (UTC)[reply]

I'm not sure what this discussion about kilocalories means. I was reading the book "The Great Starvation Experiment" which is about the minnesota starvation experiment. In chapter 10 it says; "They each consumed on average 5,219 calories per day. Most commented that even when they were stuffed to the point that they couldn’t eat any more, they still felt hungry. There was a seldom-verbalized irrational fear among them that food might be again taken away. Periodic uncontrolled gorging was common. The doctors noted with awe that Richard Mundy, on one Saturday in November, managed to consume 11,500 calories." I just wanted to know what bodily process causes such hunger in a person. The book doesn't say. Thanks 77.101.141.178 (talk) 18:34, 28 August 2018 (UTC)[reply]

Ancel Keys involvement means the results can't be trusted. Abductive (reasoning) 18:57, 28 August 2018 (UTC)[reply]

OK.

Resolved

I don't know what "resolved" means: the original question states something not true (our article never mentions people eating 10,000 or more calories a day) and the book The Great Starvation Experiment was not written by A. Keys, so his credibility is here irrelevant. What about the credibility of Todd Tucker? 194.174.76.21 (talk) 12:06, 29 August 2018 (UTC) Marco Pagliero Berlin[reply]

August 29

what makes atoms bond

does anyone know what makes atoms bond — Preceding unsigned comment added by 69.14.221.97 (talk) 02:28, 29 August 2018 (UTC)[reply]

Yes, some people do. -- Because they read Wikipedia's Chemical bond article.

—2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 05:07, 29 August 2018 (UTC)[reply]

You see, when two atoms love each other very very much, sometimes they... --Guy Macon (talk) 07:55, 29 August 2018 (UTC)[reply]

Fields of study whose mere existence offend a certain group(s) of people

Rationale for this question (why it belongs here): I am not asking for opinions, I am just asking for names of the fields; Quora has eliminated the ability to provide question details (making many questions impossible to ask on that website); I do not want to see responses which contain more things (such as criticism of those fields) than the ones I asked for (I think that Refdesk regulars are less likely to do such a thing than Quora users are).

My question: What are some fields of study or sub-fields (not counting fields regarded as pseudoscientific) whose mere existence offend a certain group(s) of people, other than evolutionary biology?

VarunSoon (talk) 10:47, 29 August 2018 (UTC)[reply]

It likely depends who and when, but aspects of geology and physics (in relation to dating and assessing major past events as well as discovery of how energy/matter works), neurology (mind having a lot to do, if not entirely, with physical/electro-chemical processes), astronomy (contesting geocentrism and flat earth), other aspects of biology than evolution that contest racism or sexism, come to mind. —Paleo Neonate – 11:22, 29 August 2018 (UTC)[reply]

(edit conflict) A lot of groups of people exist who are "offended" by various kinds of human activity. I doubt there is any area of research that is not controversial in the eyes of at least a couple of crazy lunatics. This being said, prominent examples include:

Stem cell research are considered unethical by some, roughly for the same reasons as abortion
The whole of psychiatry has been opposed, notably by the church of scientology (for reasons ranging from the reasonable to the batshit crazy)
Any sociology/economics research about intergroup differences, when groups are made by religion, race, or the like, "offends" certain people. That is not really a homogeneous "field of research" in itself, though.

Tigraan^{Click here to contact me} 11:25, 29 August 2018 (UTC)[reply]

Good points; this reminds me that other aspects of medicine are also sensitive like vaccination (conspiracy theories in relation to autism for instance) and blood transfusions (i.e. opposed by the Jehovah's Witnesses). Organ transplant used to be considered cannibalism by the same group. —Paleo Neonate – 11:31, 29 August 2018 (UTC)[reply]