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June 19

Viscosity from DFT (VASP) using the Green-Kubo relation

Hello! In this paper https://pdfs.semanticscholar.org/e8a2/02f25555cd8c4f947bbbdff5a61a0ea0efd2.pdf the authors use VASP to determine MgSiO3 viscosity using the Green-Kubo relation $\eta ={\frac {V}{3k_{\rm {B}}T}}\int _{0}\left\langle \sum \limits _{i<j}\sigma _{ij}(t+t_{0}).\sigma _{ij}(t_{0})\right\rangle dt$ where $\sigma _{ij}$ (i and j = x, y, z) is the stress tensor, t is time and t0 is the time origin. But I've seen other papers use: $\eta ={\frac {V}{3k_{\rm {B}}T}}\int _{0}^{\infty }dt\left\langle P_{xy}(t)P_{xy}(0)\right\rangle$, where $P_{xy}$ is the off-diagonal component of the stress tensor $P_{\alpha \beta }$ ( α and β are Cartesian components).

OK, so clearly these are essentially exactly the same equation but the second uses only the xy component whereas the first seems to suggest a summation? So which is correct?

Also, VASP outputs the stress tensor components as XX YY ZZ XY YZ ZX. So which of these should I use to input into the Green-Kubo equation? And are there missing components? what about yx, zy, xz?

Thanks in advance. Polyamorph (talk) 15:01, 19 June 2018 (UTC)

• For your second question, per our article Cauchy stress tensor, the stress tensor is symmetric, thus having only six independent stress components, instead of the original nine, see also Stress_(mechanics)#General_stress. For the first question, I am not sure; it could be that only one off-diagonal component is nonzero in the context (for instance in a shear flow where water flows in from (x=±Inf,y=0) and out from (x=0,y=±Inf), and the flow is uniform across z), as is the case in many viscosity-measurement experiments; or it could be the Einstein notation by taking x and y as free variables (but then a factor 1/2 is missing). Tigraan^{Click here to contact me} 16:49, 19 June 2018 (UTC)

I think that in both case sum of off-diagonal components is implied. Ruslik_Zero 20:16, 19 June 2018 (UTC)

Tigraan and Ruslik0 Cool, symmmetry reduces the 9 components to 6, makes sense. But I'm still not sure that the sum is implied in the second equation, only that the xy off-diagonal component of $P_{\alpha \beta }$ should be used, at least that's how I interpret how they've written it. But in any case, to clarify if it is the sum to be taken then should I take the sum of the $P_{xy},P_{yz},P_{zx}$? Many thanks for your help. Polyamorph (talk) 09:59, 21 June 2018 (UTC)

I think that the second equation is just an example, and xy is just one of the components to be used.Polyamorph (talk) 12:35, 21 June 2018 (UTC)

Aerial refueling a commercial jet?

Apparently aerial refueling doesn't make much economic sense for commercial jets. [1] But suppose radar operators were scanning for MH370 on the day of its disappearance and after almost all hope (and fuel) is lost, a passenger had gotten on the radio and said the pilots are dead, but some of us woke up, where are we, all we see down there is water!... Is there any conceivable way that some fast military aircraft swoops up from a carrier and slows down, and we see a boom projecting forward from it or a hose dangling down from in front of the wing, with a hard-bitten soldier or a decently designed robot on the end that can unscrew a gas cap and start pouring gas into the plane's tank so that the passengers don't end their adventure in the Indian Ocean? Or is it completely hopeless? Wnt (talk) 17:38, 19 June 2018 (UTC)

Bear in mind that tanker planes aren't particularly fast; they're primarily freight aircraft. The first picture at aerial refueling shows a Boeing KC-135 Stratotanker, with a cruising speed of 530 mph and a maximum speed of 580 mph, while another picture shows an Ilyushin Il-78, whose maximum speed is similar to the cruising speed of the Stratotanker. If the plane's virtually out of fuel, there's no way you can get a tanker on-site unless it's already really nearby. This assumes that the airliner is comparatively close to land, or that it's not far from a carrier-based tanker. Also see Aerial_refueling#Buddy_store, which notes that carrier groups don't generally have tanker aircraft, so the chance of finding a carrier-based tanker is even tinier. Nyttend (talk) 17:50, 19 June 2018 (UTC)

PS, see Gimli Glider and its paragraph beginning with "On airliners the size of the 767"; a recent commercial airliner without fuel is exceptionally difficult to control, even by professionals, since a Ram air turbine doesn't have much power compared to jet engines. Nyttend (talk) 17:58, 19 June 2018 (UTC)

Modern airlines are set up for single-point refueling, also known as underwing fueling, which requires a fairly complex set of motions when connecting the refueling nozzle. To add another level of complexity, the refueling point is commonly found under an access panel, which will either be held shut by the slipstream or act as a impromptu air brake when opened. So ignoring the logistics of getting the tanker in the right place at the right time... once you have it there, it'll be near impossible to connect and refuel on a commercial airlinger not designed with air-to-air-refueling in mind. WegianWarrior (talk) 18:12, 19 June 2018 (UTC)

Here's a 747 refueling in-flight: [2] —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 21:59, 19 June 2018 (UTC)

Might that be Air Force One? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:10, 19 June 2018 (UTC)

There's a doghouse, so that's a NEACP, not the Trump Tourbus. Some other civilian aircraft in long-duration military service (such as covert ELINT) have been fitted for refuelling too. The current Airforce One was built as a Boeing VC-25, the designed-in Airforce One variant, but the new Airforce Ones are to be recycled from bankrupt Russian oligarchs (seems appropriate), so will require conversion.

Outside the US, there are also Airbus variants, such as the A330 Multi-Role Tanker Transport, which can offer both refuelling supply and consumption. So if you're writing a Dan Brown novel, it's off-the-shelf parts. Andy Dingley (talk) 23:33, 19 June 2018 (UTC)

Unrelated question: At Aviation fuel what does this mean: "Aircraft have a high peak power and thus fuel demand during take-off and landing"? Does that mean that a disproportionate amount of fuel is consumed "during take-off and landing" relative to the rate of fuel consumption at cruising speed and cruising altitude? Bus stop (talk) 23:07, 19 June 2018 (UTC)

Not so much "take off" itself, but the climb to altitude. This is why many military mission profiles involve refuelling very soon after take-off - the aircraft can take off and climb in a much lighter state. Andy Dingley (talk) 23:23, 19 June 2018 (UTC)

"disproportionate amount at take off?" It seems so. According to https://answers.yahoo.com/question/index?qid=20060813151514AAVe8Ms&guccounter=1 a Jumbo Jet consumes 1 gallon per second at cruising regime and 8 gallons per second at take off and climbing. Somewere else it talked of three tons in the first three minutes and eight tons per hour cruising. 194.174.76.21 (talk) 09:54, 20 June 2018 (UTC) Marco Pagliero Berlin

Among other things, you're using a richer mixture at those times. It's vaguely like with a car: you use less fuel when you're cruise-controlling down a straight and flat highway than when you're climbing a hill and accelerating from a stop. Cars don't use much fuel when descending hills, but they don't have to worry about maintaining power in order to avoid stalling too soon and falling out of the sky too fast; the aircraft has to maintain lift until it's ready to stall over the runway, so lots of power has to be used. Nyttend (talk) 00:22, 20 June 2018 (UTC)

Thanks everybody. That is interesting. And I guess the fighter plane has a much further distance on its itinerary than the tanker plane, and that one tanker plane refuels many fighter planes. Bus stop (talk) 01:14, 20 June 2018 (UTC)

Fighters have to be fast and maneuverable, so they can't carry enough fuel relative to their empty weight to provide a long range as well. --76.69.118.94 (talk) 08:36, 20 June 2018 (UTC)

Fighters can, but they do it with drop tanks. Andy Dingley (talk) 10:13, 20 June 2018 (UTC)

Thank you. This is an interesting topic. Bus stop (talk) 12:14, 20 June 2018 (UTC)

June 20

Trumpeter Swan question

Ok, this is kind of a weird one. I was kayaking on one of our local lakes just now and saw that Trumpeter Swans were again present there. They used to only come by during migration but the last few years there has been a pair of them summering there. As I paddled around I came upon what had to be their nest. It was two vegetation-covered rotting logs in shallow water, with lots and lots of shiny white feathers scattered all over. They looked more or less like one expects from a waterfowl nest except for one thing: the poop. I declined to take a picture as I assume words will suffice here. Normally bird excrement is a runny, whitish sort of thing. These two nesting areas each had at the outer corner a pile of very solid turds, as one would expect from a dog or a human. I can’t find anything in our article on these birds about this, but it seems highly unusual to me. Beeblebrox (talk) 01:11, 20 June 2018 (UTC)

Are you asking "what do their feces look like"? Can't speak directly to swans, but if you've ever seen Branta canadensis feces, you'll remember that they're nowhere close to runny or whitish; it's one of the biggest reasons large populations of them are often considered pests in the lower 48. Nyttend (talk) 01:41, 20 June 2018 (UTC)

I used a well known search engine to find images of 'swan faeces' and it provided a few which showed large solid cylindrical motions. For what it's worth it also showed motions from geese and chickens which are solid and shaped, so by no means are all bird faeces liquid. Having kept finches for a while my experience was that liquid faeces usually indicated a digestive problem. Richard Avery (talk) 07:32, 20 June 2018 (UTC)

I guess it’s just something I’ve somehow never run into before, or at least not recognized it for what it was before. Thanks for your replies. Beeblebrox (talk) 17:58, 20 June 2018 (UTC)

FYI, the white part of bird waste is their equivalent of urine (white crystals of uric acid, much more concentrated than our pee); bird feces are typically dark and more or less solid. However, since it all tends to be voided at once from the same fissure (the cloaca), it's easy to conflate the two. Matt Deres (talk) 20:47, 20 June 2018 (UTC)

How to figure out the most energy-efficient way to eat food in an industrialized country?

Corn, wheat, soybeans, cotton, and hay account for 90% of harvested acreage in the United States. Corn, wheat, and soybeans are grown for both animal feed and human consumption. Per 100 grams, cooked yellow corn yields 96 calories. Wheat cannot be eaten directly. It can be turned into bread, noodles, and other wheat-based products, but who has the time to let the bread rise? Home-made bread may be eaten on occasion, but making bread everyday may be tiresome. Also, the inexperienced person who has zero cooking skills may not know how to knead dough. I suppose one can buy dried soybeans and make soymilk, but that's mostly liquid. The okara of the soybeans may be used to make less-filling dishes. Per 100 grams, Russet potatoes yield 97 calories. Per 100 grams, cooked black beans yield 132 calories. Per 100 grams, cooked white rice yields 130 calories. So, judging solely by energy content per weight, cooked black beans and cooked white rice win. However, what about the amount of energy that goes into producing the food or the amount of energy that goes into transporting food from the farm to the supermarket? By taking all things into account, which food would be most economical for a random person in, say, New York City? SSS (talk) 02:38, 20 June 2018 (UTC)

This is why McDonald's was invented. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:31, 20 June 2018 (UTC)

• There are many additional variables here. Take wheat and bread. It is more energy-efficient to make bread in a bakery than at home. This has been true since ancient times. Or look a soy beans in the US: almost all (more than 90%) of the beans and the oil are shipped to China for use as animal feed there. One crude measure of the pre-consumer energy cost is the price per calorie. This works better than you might expect, because it accounts for the energy cost of all of the inputs, including things like marketing, where the money goes to pay the salaries of people who use energy. It does not account for "free" inputs like un-captured environmental costs. You then need to add the consumer's preparation costs and the costs of post-consumer waste handling. -Arch dude (talk) 05:02, 20 June 2018 (UTC)

As an aside, use a no-knead recipe for home made bread. http://www.snk.com.au/html/s01_home/home.asp Makes very good bread. Not, perhaps the best I've ever had, but better than all but the best, and of course we fine tune the recipes to taste, lots of caroway in the dark rye bread for example.Greglocock (talk) 05:50, 20 June 2018 (UTC)

Check out Soylent (meal replacement). Eat it for a week and then watch the movie Soylent Green. --Kharon (talk) 06:15, 20 June 2018 (UTC)

"Soylent Green is ... a brand of meal replacement products !?" Gandalf61 (talk) 08:47, 20 June 2018 (UTC)

It will likely make a difference whether SSS means "most energy efficient for the individual eater" or "most energy efficient for the planet overall". {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 10:29, 21 June 2018 (UTC)

The question title asks about "energy-efficient way to eat" but the question asks about economical food, not exactly the same thing. The human energy and time involved in one person planning, shopping, preparing, cooking, serving, and clearing away meals (for him/herself or for a household) is significant; arguably, the more you care about your health, the more thought and time goes into this. If on the other hand "economical" is used as a synonym for "as cheap as possible, who cares about the externalities", then meal replacements, as pointed out above, are a possibility, as are Pot Noodles. You might want to read Michael Pollan's The Omnivore's Dilemma to give some context to your questions. E.g. "Pollan also accuses large-scale organic agriculture of "floating on a sinking sea of petroleum" by analysing that a one-pound box of California-produced organic lettuce – that contains 80 food calories – requires 4,600 calories of fossil fuel to process and ship to the East Coast." Carbon Caryatid (talk) 11:36, 22 June 2018 (UTC)

Why do small children put stones in their mouth?

Has this behavior evolved to get to a healthy microbiome, or could stones in the stomach work as gastroliths? Count Iblis (talk) 13:27, 20 June 2018 (UTC)

What children do that? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:32, 20 June 2018 (UTC)

[3] Antepenultimate para. —SerialNumber54129 ^{paranoia /cheap sh*t room} 13:58, 20 June 2018 (UTC)

Moonrise Kingdom appears to be fictional. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:33, 20 June 2018 (UTC)

Err. The bloke they were talking to wasnt :D —SerialNumber54129 ^{paranoia /cheap sh*t room} 14:38, 20 June 2018 (UTC)

Typing "Why do small children put stones in their mouth?" into Google produces lots of results such as: "Babies putting things in their mouths, otherwise known as mouthing, is not only normal, but also signals a growing interest in the world around them. In the first year, children explore their surroundings through their senses -- seeing, touching, hearing, smelling, and tasting. The more they explore, the more they learn". [4] Alansplodge (talk) 16:29, 20 June 2018 (UTC)

I've heard that described the same way, as "exploring their world." No indication that they're swallowing them, just tasting them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:35, 20 June 2018 (UTC)

Besides taste, the tongue and lips are also far better at discerning fine texture detail than fingers. Roger (Dodger67) (talk) 10:49, 21 June 2018 (UTC)

Can you provide a cite for that? It appears to be at odds with the various representations at cortical homunculus, though I acknowledge they're not quite mapping the same thing. Matt Deres (talk) 13:51, 21 June 2018 (UTC)

Small children, or babies? The former are more likely to have access to stones. The latter, well, they put everything in their mouths; it's the oral stage, and some never really outgrow it. From that article: "In Freudian psychoanalysis, the term oral stage or hemitaxia denotes the first psychosexual development stage wherein the mouth of the infant is his or her primary erogenous zone. Spanning the life period from birth to the age of 18 months..." Carbon Caryatid (talk) 11:41, 22 June 2018 (UTC)

How many cities have used subway/metro/underground/el/u-bahn/rapid transit cars ≥54 years old for revenue service?

I only know of the R32 and Buenos Aires. Sagittarian Milky Way (talk) 15:15, 20 June 2018 (UTC)

F Market & Wharves in San Francisco uses historical cars, for revenue service, some pre-WWI. --jpgordon^{𝄢𝄆 𝄐𝄇} 15:56, 20 June 2018 (UTC)

But that's streetcar, not subway / rapid transit. --76.69.118.94 (talk) 18:48, 20 June 2018 (UTC)

The Island Line on the Isle of Wight uses refurbished British Rail Class 483 stock. They were built in 1938, and refurbished between 1989 and 1992. They originally worked the London Underground, but the Island Line is a surface service, so I'm not sure that they meet your criteria. TenOfAllTrades(talk) 16:00, 20 June 2018 (UTC)

Apparently the cars for Budapest's line 1 were in use from around 1900 until the 1970s. Rmhermen (talk) 17:23, 20 June 2018 (UTC)

Oh, here's a good one. The Glasgow Subway opened its one and only route in December 1896 with cable-hauled trains, converting to electric motors in 1935. (By the way, they converted the two directions of travel one at a time, so for several months they had electric trains going one way and cable ones the other—which was sensible enough, because the route is a loop and had no connection between the two tracks.) They made the change by modifying the existing trains rather than buying new ones, and many of the subway's original cars remained in revenue service until May 1977 when the line was shut down for modernization. So the oldest cars were then 80 years old. --76.69.118.94 (talk) 08:15, 21 June 2018 (UTC)

The poles and towers for the overhead electric cables of the Gospel Oak to Barking line were constructed by February 2017. The wires were added later. There is still no electric train service. Is this a record? 86.132.186.246 (talk) 10:54, 21 June 2018 (UTC)

Is what a record? Taking a bit over a year for electric trains after finishing the electric cables seems unusual perhaps suggesting poor planning but doesn't seem that likely to be a record. Nil Einne (talk) 10:22, 25 June 2018 (UTC)

The Pyongyang Metro uses ex-german "Dora"-class rolling stock, which is between 53 and 61 years old. WegianWarrior (talk) 20:09, 21 June 2018 (UTC)

Vehicle retroreflectors

In one place, the California vehicle code says "this section applies to the color of lamps and to any reflector exhibiting or reflecting perceptible light of 0.05 candela or more per foot-candle of incident illumination."

Vehicle Code
DIVISION 12. Equipment of Vehicles
CHAPTER 2. Lighting Equipment
ARTICLE 15. Light Restrictions and Mounting
SECTION 25950

I am trying to figure out exactly how to measure this in the context of a plastic retroreflector of the kind normally found on vehicles.

My problem starts with the light source. I can hit it with a foot-candle from a near point source, and the output will be vastly different that if I hit it with a foot candle from a diffuse half sphere. In the former case, the output is much larger at one angle and much smaller at all other angles, and it changes as I tilt the reflector slightly. In the latter case, I get a more even output compared to angle, but it is still a bit "lumpy".

So how do I set up my light source and light meter to measure whether the section in question applies to a reflector? Or do I just forget all that and assume that even the cheapest plastic reflector is good enough that I can assume the law applies? --Guy Macon (talk) 23:54, 20 June 2018 (UTC)

@Guy Macon: The point of a retroreflector is to reflect the light source back to itself. The best retroreflective shape is an orthogonal trihedral surface. I used to teach classes about stealth technology. As a demonstration I had three 1-foot-square mirror tiles taped together forming a corner trihedral. No matter what angle you looked in it, you always saw a reflection of your face looking back at you. That's the worst possible shape for a ship to have on it, and easy to create accidentally, say, by laying a toolbox on the deck next to a bulkhead at right angles. An anti-ship missile will go right for that.

The plastic retroreflectors in cars typically employ an array of little cube-shaped prisms to accomplish the same effect. They are arrays of trihedral prisms In this case the light enters the plastic from flat outer surface and bounces off the surfaces inside the prisms, and comes right back out.

In the case of that spec, the requirement likely applies only to normal incidence to the reflector, from a point source. The intensity of reflection will change because the projected area of the orthogonal surfaces change with angle of incidence. A diffuse half sphere source will illuminate the reflector from a wider range of incident angles. You wouldn't be able to make a valid measurement with a meter the size of a point source.

Your measuring device should be approximately the same location as your light source. In an ideal retroreflector it shouldn't matter how far away your light source is. Distance will only change the illumination incident on the retroreflector. ~Anachronist (talk) 14:05, 21 June 2018 (UTC)

I am well aware of how retroreflectors work and the geometry of corner reflectors in general (years of experience in optical engineering), but I am not convinced that your answer is correct. Yes, that is indeed one way of doing the measurement, but I am asking which of the several ways that I can measure the light is the method that the vehicle code specifies. The requirement "foot-candle of incident illumination" can be satisfied with the light coming in from a point source at any angle or from a uniformly illuminated half sphere. On the output side a candela is the luminous flux per unit solid angle, but which angle? Do I pick the one that has the highest number? I know that averaging the output from all angles is wrong -- if they wanted that they should have specified lux instead of candela.

On a previous project involving lights as opposed to reflectors, I got an answer from the DOT that we should measure what hits a driver's eyes, keeping in mind that some people are driving low-slung sports cars and some are driving tractor trailers. By that standard, an ideal corner reflector sends 100% of its output right back into the headlight of the car behind with 0% hitting the driver's eyes. And indeed if you break open a standard plastic reflector you find that the geometry is not exactly 90 degree corners, but is a bit off (and sometimes the surface isn't quite flat) -- obviously so that the returned beam spreads out some. They also twist some sections compared to others, and in use some sections are much brighter than others, depending on the angle.

Optical engineering is easy. Lawyering (as in "properly interpreting the requirements set forth in government regulations") is hard. --Guy Macon (talk) 15:13, 21 June 2018 (UTC)

@Guy Macon: Hmm. Which angle indeed? Intuitively it seems like an integration problem. Measure the luminous flux in the solid angle emanating from a point on the retroreflector and ending at the pupil of the eye, with the radius of that pupil. Integrate over all points of the reflector. That has to be wrong, because it's too hard and seems backwards.

All I can do is make guesses..... OK, how about defining the beamwidth from the reflector as the solid angle formed by the boundary 3 db from the peak brightness, and that solid angle is large enough to cover sports cars and trucks. Then you can figure out the luminous flux per unit solid angle within that boundary? ~Anachronist (talk) 22:23, 21 June 2018 (UTC)

That has some real promise. It also has the distinct advantage that if someone on the government end thinks that it is the wrong way to do the measurement they would have to tell me what the right way is. I can pretty much set up any measuring geometry in less than an hour on my optical bench. Thanks! --Guy Macon (talk) 22:48, 21 June 2018 (UTC)

Improving one's palate for subtle flavor differences

A Youtube video I saw last year, in which Penn Jillette describes his diet of eating only potatoes for a month, eventually prompted me to write the monotrophic diet stub article. It's a risky and dangerous fad diet. What interested me, however, is a side-effect that Jillette reported: eating nothing but potatoes for a month reset his palate to the point where he can now taste subtle differences in foods that he couldn't taste before, and no longer desires typical American dishes having flavors dominated by salt and sugar.

So this got me to thinking: setting aside the fad mono diet, if I wanted to reset my own palate while consuming nutritionally complete but bland foods, what would I eat? What ingredients would I buy? I do enjoy cooking challenges... Or would it be simplest just to buy a month's supply of unflavored Soylent (meal replacement)? ~Anachronist (talk) 23:58, 20 June 2018 (UTC)

The product you are looking for is unflavored Huel. See [ https://huel.com/ ].

It is well-known that when you reduce salt in your diet, after a while foods that used to taste slightly salty taste very salty. And the opposite effect is well-known with hot peppers; you build up a tolerance to them.

Is this the case with all flavors? I can think of a couple of interesting tests you could do.

One test involves experiments with sugar and purified water. At what concentration can you no longer tell sweetened water from pure water in a blind taste test? Now cut all sugar from your diet for a month and repeat the test.

Or you could pick one of those strongly flavored candies (Jolly Rancher, Jelly Belly) and suck on just one flavor for a month. Can you make it so that, say Apple flavor seems less strong while the others seem normal strength?

Please post a note on my talk page if you do something like this. I usually keep the reference desks unwatched for obvious reasons. --Guy Macon (talk) 01:33, 21 June 2018 (UTC)

@Guy Macon: Thanks, I had never heard of that. I'm not sure how nutritionally complete that is... I don't see any fats, unless the "MCTs from coconut" is a sufficient substitute. No animal protein either, but I guess that's OK for a month. A month's supply (9 pounches) to maintain a 2000 calorie/day diet seems expensive at first but not on a per-meal basis.

Yes, I knew about the peppers. I had read several research articles about how people who regularly eat spicy foods are not sensitive to other flavors. I can also see that in people I know who eat a lot of spicy food and find their sense of taste is not stimulated by subtle flavors that I can distinguish, but my own palate is by no means very sensitive either. ~Anachronist (talk) 13:37, 21 June 2018 (UTC)

4 cups of Unflavored & Unsweetened Huel have 2000 calories, 66 grams of fat, 186 grams of carbs, 148 grams of protein, 9 grams of fiber.

37% of the energy comes from carbohydrate, 30% from fat, 30% from protein and 3% from fiber.

See [ https://huel.com/pages/nutritional-information-and-ingredients ].

Are you under the impression that for humans animal protein is somehow better than plant protein? (Cats, on the other hand, get really sick and eventually die on any vegan diet. Cats need the amino acid Taurine, which plants do not produce. Humans, like most omnivores, can produce taurine from other nutrients.)

I would be interested in reading those research papers about spicy foods. That wasn't my understanding, but I have not studied the question other than running across stuff like this:[5] If only there was some sort of online encyclopedia where we could look this sort of stuff up.... --Guy Macon (talk) 14:13, 21 June 2018 (UTC)

@Guy Macon: I freely admit I have no informed opinion about the value of human protein versus animal protein, other than knowing the human organism is adapted to neither a vegetarian nor carnivorous diet, but rather to an omnivorous diet, which implies we are adapted to require protein from multiple sources, not just from plants. I am skeptical that a vegan diet is healthy over the long term, but there is no harm in it for the purpose for which I started this conversation.

OK, I dug up some searches I had done way back in 2007 about spicy foods and taste desensitization. At the time I was unable to find references indicating that the desensitization is permanent. I concluded that it may seem permanent if a person eats spicy foods on a daily basis. Here are quotes I had found back then. I haven't looked to see if there's been anything more recent.

• "With respect to desensitization following an initial series of stimuli, the present results appear to confirm that, given a particular hiatus in stimulation, the recovery period differs markedly between these irritants. Previous research has shown that the recovery time of capsaicin from desensitization is in the order of hours to days, depending on the concentration (Green, 1989; Karrer and Bartoshuk, 1991),..." [6]
• "Immediately after capsaicin, responses [by rats] to each tastant were in nearly all cases depressed (mean, 61.5% of control), followed by recovery in most cases.... These results support a peripheral site of capsaicin suppression of taste possibly via direct or indirect effects on taste transduction or taste receptor cell excitability. The depressant effect of capsaicin on gustatory transmission might underlie its ability to reduce the perceived intensity of some taste qualities."[7]
• "As to the reason why some people can cheerfully withstand the ravages of irritant-packed food and others bolt for the water fountain at the first nibble on a wayward jalapeno, part of it is no doubt genetic, but there's also a phenomenon known as "transient desensitization." Keep eating chili after chili, and your mouth is going to get hotter and hotter. Take a break, though, maybe two or five minutes, and when you resume your meal, the burning sensation won't be quite so fierce. Desensitization can last hours, and people who make a habit of eating spicy food may be partly desensitized virtually all the time." [8](link is now dead, try http://archive.is/6tDBI instead)

FWIW. ~Anachronist (talk) 22:09, 21 June 2018 (UTC)

Interesting! One thing you wrote caught my eye; "the human organism is adapted to neither a vegetarian nor carnivorous diet, but rather to an omnivorous diet, which implies we are adapted to require protein from multiple sources, not just from plants" I am not sure that it implies that. I think that it implies that we are adapted to thrive on protein any one of multiple sources. We know that this is true of bears; in some seasons they pretty much live on berries, while in other seasons they live on a pure salmon diet. Likewise with humans, some thrive on a vegan diet (if they get enough protein, vitamins, etc), while others thrive on a diet of nothing but meat and seal blubber. Evolution should select against requiring multiple food sources (but could at the same time evolve a preference for them). --Guy Macon (talk) 22:30, 21 June 2018 (UTC)

You're right of course, evolution shouldn't require multiple sources of protein, but simply allow for multiple sources. However, surviving isn't equivalent to thriving. In my view, the best diet includes both animal and vegetable protein, assuming that no protein is "complete" and that "thriving" requires completeness. I would argue that the human body has features, such as a long intestinal tract, that makes it hard to "thrive" on a carnivorous diet. Digesting meat produces toxins that are best evacuated quickly, which is why carnivores tend to have short intestinal tracts compared to vegetarian animals. Meat-eating cultures do have a higher incidence of colon cancer too. This would qualify as a MEDRS-compliant source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3108955/ ~Anachronist (talk) 22:50, 21 June 2018 (UTC)

By the way, back on the original topic, here's the original video of Penn that I saw: https://www.youtube.com/watch?v=NelIXCuuSZ0 — the relevant part that struck me starts near the end, at 7:35. ~Anachronist (talk) 22:58, 21 June 2018 (UTC)

June 21

Please Help me find a botanical term and an existing page

Originally published in Teahouse (https://en.wikipedia.org/wiki/Wikipedia:Teahouse#Please_Help_me_find_a_botanical_term_and_an_existing_page) and I was guided to reference desk.

There is a terminology for when due to secondary growth a tree engulfs surrounding foreign objects . But I forgot the term and can't recall it back. There was an Wikipedia page about the term; which contained an image of a tree engulfing a barbed wire fence; upto best of my recall. (The image was from side view, and not from oblique view). Today I searched a lot of page; but could not find the page. Please help me to find the term and the page. Thanks in advance.

If I've asked the question in an inappropriate location or formatting then please do necessary guide/correction.

RIT RAJARSHI (talk) 04:38, 21 June 2018 (UTC)

• This is the right place, but I haven't found it yet. In the mean time, look at these: [[9]]. -Arch dude (talk) 05:08, 21 June 2018 (UTC)

That site asks at one point: "Is it possible there are items entirely consumed by trees that we don't know about?" I can confirm from personal experience (yeah, OR) that this is so. About 5 months ago I had a tree felled at the bottom of my garden which had grown too large (approaching a yard/metre thick at the bole) for its surroundings. The fellers discovered that it had entirely engulfed at least one metal fence post that had originally marked the garden boundary – they broke some chainsaw teeth when they unexpectedly hit the metal. Outside of the tree so few remnants of the fence remained that I (resident 27 years) had no idea it had once been there. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 10:44, 21 June 2018 (UTC)

I've found a few words, but none that are quite as specific or correct for "engulfment of foreign object". For example, burl (found where this question was asked at Talk:Tree archives and did not receive an answer), engulfment, inosculation, espalier, pooktre, edaphoecotropism. DMacks (talk) 05:18, 21 June 2018 (UTC)

There is such an image here but it doesn't seem to be used in any other articles.--Shantavira|^{feed me} 14:50, 21 June 2018 (UTC)

Plenty more pictures at commons:Category:Ingrown things in trees. DuncanHill (talk) 14:56, 21 June 2018 (UTC)

Spiders looking like ants

I've heard some spiders and other bugs appear like ants so they can sneak around among them and then eat them. That's right, isn't it? I've actually seen some bugs like that.

So, if ants cannot see well, why is looking like an ant so important? Anna Frodesiak (talk) 06:58, 21 June 2018 (UTC)

• Ant mimicry#Spiders says there are over 300 species of spider that have evolved Batesian mimicry of (or for?) ants. Just because ants can't see well doesn't mean that they can't recognize a typical spider shape. Abductive (reasoning) 07:08, 21 June 2018 (UTC)

• Batesian mimicry seems to be more about evolving to protect yourself not infiltrating other species communities. Ants rely very heavily on pheromones for communication (as stated in Ant) It would seem unlikely that looking like an ant but not smelling like an ant would be a successful strategy. And remember there are hundreds of ant species and most of these do not rub along too well together. So the answer to the original question is - no, that's not right. Richard Avery (talk) 07:47, 21 June 2018 (UTC)

• So, you think maybe the article is (partly) wrong? Abductive (reasoning) 16:03, 22 June 2018 (UTC)

In the case of the Large blue butterfly, the caterpillars are mimicking the ant larvae rather than the adult ants, but this broadly fits your scenario. The first article Richard Avery linked says, in the lede: "Some arthropods mimic ants to escape predation (protective mimicry), while others mimic ants anatomically and behaviourally to hunt ants (aggressive mimicry)" [my italics], and cites a paper. In all such cases physical resemblance will be necessary but not sufficient – the mimics will have to smell and move similarly to the ants as well, which means they will have to be mimicking a specific ant species and perhaps even a specific colony population. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 11:03, 21 June 2018 (UTC)

That makes sense. Thank you for clearing that up. And thank you for taking the time. It is appreciated. Anna Frodesiak (talk) 19:43, 21 June 2018 (UTC)

Mandatory swim caps

Is the mandatory swim cap thing baloney? So what if hair gets into filters? Isn't that what filters are for? Anna Frodesiak (talk) 06:58, 21 June 2018 (UTC)

Where is this rule in place. It's not in my little corner of the world - Australia. HiLo48 (talk) 07:16, 21 June 2018 (UTC)

The idea would be to prevent too much hair from getting in the filter and clogging things. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:47, 21 June 2018 (UTC)

This is probably a health and safety issue [10], [11], [12]. In one case, a young woman was only saved when a bystander who had been in the bar the previous evening when a huge knife was delivered for cutting ice cubes rushed to get it. He handed it to the father (who had been attempting to cut her loose with a penknife) and with one slice she was free. 86.132.186.246 (talk) 10:35, 21 June 2018 (UTC)

It's also quite unpleasant while swimming to suddenly get a faceful of floating hair that has been shed by others and has then clumped together. I myself tend to gag if I unexpectedly get one of my own hairs in my mouth. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 11:17, 21 June 2018 (UTC)

Thank you all. Good points. Anna Frodesiak (talk) 19:43, 21 June 2018 (UTC)

@Anna Frodesiak: Having worked extensively with swimming pool filtration in my younger days, I'll say that pool filters are best at removing particulates (dirt, bugs, leaves, and other solid materials). Hair, on the other hand, isn't friendly. It's like trying to suck a string through a pump. What gets through the first stage basket gets tangled around the pump impeller and shaft, and accumulates. Short hair doesn't present a problem. But long hair (or thread or string) doesn't just get caught in the first stage basket or the final stage filter, it gets caught in the machinery. And if there's enough of it, the only way to get it out is to take apart the machinery, which is a lot harder than simply backwashing the filter or cleaning the removable components.

The UK Health and Safety Executive lists compulsory swimming caps amongst Health and safety myths; "There is no health and safety regulation which requires people to wear hats in swimming pools". I recall caps being compulsory in some public pools in France and Luxembourg a few decades ago, on the stated grounds of hygiene. Alansplodge (talk) 09:14, 22 June 2018 (UTC)

I agree, I see no hygiene reason to require swimming caps. I think the reason is more practical: Keep hair out of the machinery. Also there may be an added benefit to keep hair oil (if people use it) from scumming up the tiles on the pool walls. And to make the overall swimming experience more pleasant for everyone by keeping long floating hairs out of the pool. A good hair-band to tie back long hair, or wearing the hair in braids, would be just as effective, though. ~Anachronist (talk) 17:59, 22 June 2018 (UTC)

Ah, mainly hair in the works, understood. Still, I'd say tying one's hair back plus better filters would be better than requiring everyone to wear those daft caps. They're uncomfortable and rather spoil the experience. I do miss Canadian lakes. Thank you all again. Anna Frodesiak (talk) 23:21, 22 June 2018 (UTC)

Japan Meteorological Agency

Is there any reason why in Japan the Meteorological Agency handles the earthquakes instead of dedicated seismological authority, given the frequency of their earthquakes? Brandmeister^talk 08:48, 21 June 2018 (UTC)

It also covers volcanoes and tsunamis. Given that these as well as extreme weather, floods and earthquakes all require a warning network as well as sometimes being causationally linked, it makes sense to group them under the same umbrella rather than having separate agencies trying to co-ordinate. The article's reference 7 links to a 32-page PDF here which may shed light on the historical reasons for this arrangement having come about. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 11:12, 21 June 2018 (UTC)

The Philippines' hurricane warning center (PAGASA) is even broader. It handles meteorology, geophysics and astronomy (!) Sagittarian Milky Way (talk) 18:19, 22 June 2018 (UTC)

Australia, where I am, is at the other end of the seismological activity scale from Japan. Earthquakes are very much rarer and less extreme here. We don't have a "dedicated seismological authority". (Or if we do, it's low profile enough for me not to have noticed it.) I do know though than when earthquakes do occur (usually small tremors by global standards) people tend to phone up the local weather service to ask/tell them about it. I guess there's something in human nature that lumps these physical environmental things together. HiLo48 (talk) 22:42, 22 June 2018 (UTC)

Squashed molecules

A few years ago there was a new Wikipedia article on a kind of molecule where the two atoms were abnormally close to each other and electrons were pushed up to higher energy levels to accommodate. This type of molecule was very unstable emitting X-rays to drop energy and push the two atoms apart. I cannot find the article though. What is this kind of molecule called? It's not in Category:Chemical bonding. Graeme Bartlett (talk) 12:28, 21 June 2018 (UTC)

I can't remember that WP article--do you remember if the two atoms were bonded or nonbonded? In the mean time, here is an item describing pushing the limits of nonbonded close contacts.[13] Perhaps WP:CHEM could help--lots of active editors there with diverse interests. For a newer ref that includes intermolecular not just intramolecular-cage, see doi:10.1021/jacs.7b01879. DMacks (talk) 12:49, 21 June 2018 (UTC)

The molecules were much more compressed than in the blog, so much so that one atom appeared to be embedded in the other. The repulsion was much stronger than the bond due to the closeness, but I would guess that the bond would be much stronger than a normal bond. However they still had defined quantum states. (They may form inside white dwarfs for example of the pressure needed). Graeme Bartlett (talk) 22:52, 21 June 2018 (UTC)

By chance, was it related to Rydberg polarons? Those allow you to put atoms inside another atom. 209.149.113.5 (talk) 11:27, 22 June 2018 (UTC)

That is a good suggestion, and the atom combination is like that but at much higher energy. So it was actually another article. I think they needed particle accelerators to get an ion with enough energy to penetrate into another atom. (I should have put the page on my watch list!). Graeme Bartlett (talk) 02:39, 23 June 2018 (UTC)

Diet pills

For me, any 'fat burning' claim of diet pills is automatically suspicious. However, some diet pills claim to block the absorption of fat, something that, at a first glance, seems possible. Could indeed something as small as a pill make our bodies extract less calories from fatty food? I assume ingesting some substances with more volume than a mere pill, like lots of fiber, would have it easier. But still, a pill could de/activate some mechanism, resulting in blocking fat digestion.--Doroletho (talk) 13:03, 21 June 2018 (UTC)

Eating fats don't make you fat, so blocking absorption of fats just seems counterproductive to health. Eating excessive carbohydrates make you fat. If there's a pill that is proven to block absorption of starches and sugars, I don't know what it is. ~Anachronist (talk) 13:48, 21 June 2018 (UTC)

You just haven't looked in the right places. http://media.philly.com/images/1200*800/TapewormDietPills.jpg

And please don't tell people that "Eating fats don't make you fat". Eating more calories than your body burns makes you fat. It matters little what form the calories take. See Healthy diet#Obesity. --Guy Macon (talk) 15:29, 21 June 2018 (UTC)

Beware of Products Promising Miracle Weight Loss, from the FDA, the agency responsible for regulating drugs and medical products, and making sure the advertisements do not make unscientific claims.

In particular:

• "Dietary Supplements are not FDA-Approved" - this means that if a product "isn't technically" a drug, the FDA will not validate the claims they make - even if the seller wraps the product up in a pill shape and puts it in pill-bottles for retail sales... as long as they technically make no medical claims
• Any products that make medical claims - including drugs and things that technically aren't drugs - are still subject to regulation
• A huge variety of products are sold in stores, and are not approved by the FDA. Such products were not put through rigorous independent scientific testing - but you can buy them and eat/drink them anyway (at your own risk of harm, let alone risk of being cheated by the merchant)
• A huge variety of products, including drugs, are approved for treating obesity, or otherwise assisting with weight loss, but those products must be subjected to intense scrutiny - especially about the way they are advertised to consumers
• Widespread efforts by scammy companies to circumvent that scrutiny are the reason why FDA publishes consumer protection messages, like this video: Health Fraud Scams - Weight Loss

I can't find a short statement by FDA that clearly specifies whether the words "weight loss" or "diet pill" are categorically regulated as "medical claims," which probably means that they evaluate each product or situation on an individual basis. Egregious violaters who get caught lying about their unregulated medical products can be subject to civil or criminal action.

Nimur (talk) 16:16, 21 June 2018 (UTC)

Excellent post. I would add that if you sell a pill with nothing in it but inert filler, the FDA will approve it as being safe without approving it as being effective, then the ads scream "FDA Approved!". Homeopathic quackery does this all of the time. --Guy Macon (talk) 18:20, 21 June 2018 (UTC)

Wouldn't a hoemopathic pill that contained nothing kill you from an overdose? (slightly labored reworking of an excellent joke) Greglocock (talk) 22:36, 21 June 2018 (UTC)

The Amazing Randi regularly starts out lectures by sending someone to the local drug store to purchase homeopathic sleeping pills and then when they arrive he "overdoses" on stage. I think that CVS, Walgreens, etc. should stop selling things that they know don't work.

BTW, I created 37 new homeopathic articles on Wikipedia this week. no, not articles on homeopathy; I wrote an article, diluted it a million times, and posted the result. --Guy Macon (talk) 22:55, 21 June 2018 (UTC)

Don't underestimate the power of such pills. And they can do harm. Count Iblis (talk) 23:13, 21 June 2018 (UTC)

Some of the stuff sold over-the-counter can be actually harmful. "And if you’re about to take what you think of as “natural” dietary supplements, ...be aware that FDA has found some of these products also contain hidden active ingredients contained in prescription drugs.", In general, it is not safe to assume that a material is inert, let alone safe in large quantity, simply because it's a "homeopathic" remedy. Worse still, some of these products are (accidentally or intentionally) mislabeled, tainted, or contain active substances that can cause serious harm.

Here is a list of a few hundred products including "herbal remedies" and "natural bee pollen pills" that were found to be illegally tainted with hidden ingredients, often including active drug ingredients that would normally be prescribed by a real medical doctor for totally different medical purposes. Selling a controlled substance and calling it a natural remedy is not only bad, it is actually the most prevalent and widespread drug crime in the United States. Real actual drug crime! The very stuff they don't turn into big-budget Hollywood action movies! In 2016, deaths related to illegal use of controlled prescription drugs exceeded deaths from cocaine and heroin combined.

Even if we know or suspect that a product's claims are pure "quackery," we would be wise not to automatically conclude that the product itself is a totally safe and inert substance - especially in large doses. Nimur (talk) 05:39, 22 June 2018 (UTC)

Do you have a citation that shows that any FDA-approved (for safety, not effectiveness) homeopathic medicine has ever been been tainted in this way? "Since 1988, it has been the de facto policy of the FDA to treat homeopathic remedies listed in the Homeopathic Pharmacopeia of the United States (a collection of homeopathic ingredients and practices continually updated since 1897), as safe and legal to market — so long as that marketing does not meet the FDA’s definition of making fraudulent claims."[14] --Guy Macon (talk) 05:57, 22 June 2018 (UTC)

• Homeopathic Products: "Examples of FDA’s concerns, include:"
  • Pleo Homeopathic Drug Products by Terra-Medica: Recall - Potential for Undeclared Penicillin...

...so, yes. There are just so many more - hundreds of cases each year - and this one example is simply the very first instance I found, after a very cursory reading through the FDA informational page.

In fact, just this week: June 18, 2018, "A 35-year-old Corpus Christi woman has pleaded guilty to one count of possessing a controlled substance with the intent to distribute and one count of receiving a misbranded drug in interstate commerce..." "The FDA found a number of the products X2Zero sold as “herbal weight loss supplements” to contain misbranded or unapproved foreign drugs." The defendant "knowingly possessed and sold diet drugs containing sibutramine," a drug illegal to sell in the United States because it "increased risk of heart attack, stroke and death."

Point being, we don't have to look hard for examples of herbal diet remedies with nasty, often illegal, contaminants.

Nimur (talk) 06:06, 22 June 2018 (UTC)

The pill that blocks fat absorption is orlistat, which is, in fact, FDA approved. I have never personally seen a plausible explanation for the "fat burning" pills, and honestly, that sounds like a really dangerous thing to do, just messing with your metabolism. Someguy1221 (talk) 01:47, 22 June 2018 (UTC)

I do NOT recommend this, but can't Amphetamines speed up your metabolism, and suppress your apetite? @Guy Macon:, can you please enlighten us about the exact nature of fat-burning potential of Crystal Meth, and why it is not a good idea to use it for this? Eliyohub (talk) 17:29, 25 June 2018 (UTC)

Glad to! Turns out that the following is some of the most popular advice I have ever given...

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. 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).

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

BTW, in my opinion both terminal cancer and AIDS are even more effective methods of weight loss than meth, so why not try all three at the same time? Also, don't get your medical advice from an electronics engineer. --Guy Macon (talk) 01:17, 26 June 2018 (UTC)

June 22

Ecoregions follow-up

OK, here's Part 2 of the question I asked earlier about ecoregions of North America (and the real reason why I asked in the first place): Which ecoregions of the United States do not have any native Papilionidae (swallowtail butterfly) species, except maybe near boundaries with other ecoregions, or as very rare vagrants? (NO PHOTOS OF SWALLOWTAIL BUTTERFLIES PLEASE, but maps of their native range are always welcome, especially if these have state lines, major cities and/or ecoregion boundaries shown for reference!) Oh, and I'm asking only about the continental USA -- I know that these critters are found pretty much everywhere in Hawaii, but you won't find them at all in Alaska! 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 03:04, 22 June 2018 (UTC)

No swallowtail butterflies here
The Imperial Dunes in the Yuma Desert

See distribution map: [15]

Note: Canadian tiger swallowtail (Papilio canadensis) is indeed distributed in Alaska.

The main blank area in the map roughly corresponds with the Yuma Desert section of the Colorado Desert region of the Sonoran Desert.—2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 17:43, 22 June 2018 (UTC)

Thanks... for the bad news! :-( So, how big can each of these critters grow (maximum size)? 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 02:44, 23 June 2018 (UTC)

The largest butterfly that can be found naturally in the United States is the Giant Swallowtail (Papilio cresphontes) with a wing span of 4-6 inches.[16] —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 03:47, 23 June 2018 (UTC)

And the ones which are shown on the map? How big can they grow? (BTW, I was pretty sure P. rutulus could grow to 6 inches or more -- but maybe that's just me being too frightened to estimate size accurately! Or maybe it was P. cresphontes I saw on all those occasions -- is it native to California and/or Oregon?) 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 06:38, 23 June 2018 (UTC)

Trademark symbols in academic writing

In academic writing is there any point in putting trademark symbols for company names and products like Thermo Fischer Scientific or SYBR Safe? — Preceding unsigned comment added by 129.215.47.59 (talk) 17:53, 22 June 2018 (UTC)

For company names, probably not, unless confusion is likely for some reason without it. For products, it may sometimes be useful. I have seen quite a number of papers using a trademark symbol when giving the proprietary name of a drug. For example, even doctors seeing the names diltiazem and Cardizem might not be certain which is the generic name and which is the proprietary name. Looie496 (talk) 18:04, 22 June 2018 (UTC)

I've never used or seen it in published academic writing. I wouldn't. If it was a requirement, the author guidelines for your journal of choice would say to do it. In my experience. none do. Fgf10 (talk) 08:12, 23 June 2018 (UTC)

Here's one 185.230.100.66 (talk) 00:17, 24 June 2018 (UTC)

I'd say omit ™ (and the related ® too) in general, if possible. Just use consistent and proper capitalization and spelling. From the Chicago Manual of Style: "Although the symbols ® and ™ often accompany trademark names on product packaging and in promotional material, there is no legal requirement to use these symbols, and they should be omitted wherever possible." source

--Doroletho (talk) 12:05, 23 June 2018 (UTC)

Estimating tree mass: is height and species enough?

How accurately can a tree's mass be estimated, given only its height and species? NeonMerlin 22:33, 22 June 2018 (UTC)

Try GlobAllomeTree. Alansplodge (talk) 22:58, 22 June 2018 (UTC)

June 23

Where is the south pole of a power meter's north pole?

I've read that a magnetic monopole has never been observed. In Toronto in the early 2000s, I used a magnetic compass for some science-class work and noticed that when close enough to a power meter, it would always mark the meter as the magnetic north pole. (My neighborhood was of older semidetached houses; I was told my home at the time had been built in the 1950s.) Where is the south pole of a magnet, whose north pole is a power meter of the type I would have observed? NeonMerlin 03:31, 23 June 2018 (UTC)

If I understand your question properly, the "north pole" would be the compass needle's attraction to the meter's electromagnetic field (EMF) -- and in effect, the "south pole" would be, in this case, "ground". 2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 07:09, 23 June 2018 (UTC)

No. The compass needle aligns itself along a Field line that emerges from a south magnetic pole and curves through space to return to a north magnetic pole. Both these magnetic poles are located inside the electric power meter and produce an external Magnetic field. This could be prevented by shielding the meter with an iron case. DroneB (talk) 11:40, 23 June 2018 (UTC)

June 24

looking for news about some guy who dies due to using deodorant or perfume

I'm looking for news from many years ago (maybe 10-15 years ago) about a guy that died due to using of deodorant or perfume. In this news they explain that it's not healthy to use them because of that. I don't have any lead for these news. 93.126.116.89 (talk) 07:35, 24 June 2018 (UTC)

Jonathan Capewell or Daniel Huxley, mentioned in our List_of_unusual_deaths#1990s. Brandmeister^talk 09:42, 24 June 2018 (UTC)

No Huxley on that page. --76.69.47.228 (talk) 21:14, 24 June 2018 (UTC)

Because he was the second to die in that manner, so only the first is included. Brandmeister^talk 07:13, 25 June 2018 (UTC)

Remark that Capewell was not killed by the deodorant or perfume itself, but instead by the propellant (butane and propane) in the spray can. 194.174.76.21 (talk) 11:47, 25 June 2018 (UTC) Marco Pagliero Berlin

Yeah, hydrocarbon propellants are flammable, and cans using them usually contain warnings to this effect. Bach in the old days, they used Chlorofluorocarbon propellants, which I think are not flammable, (Halomethane was actually used as a fire-fighting agent) but these were phased out due to damaging the ozone layer Eliyohub (talk) 17:34, 25 June 2018 (UTC)

Highest possible limit in nature

What accelerates the fastest particles in nature? Something that's moving below that speed?

And what is the highest possible frequency of an electromagnetic wave? Can a process cause a frequency higher than its own frequency? --Doroletho (talk) 12:24, 24 June 2018 (UTC)

Have you reviewed Electromagnetic radiation? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:58, 24 June 2018 (UTC)

Yep, but there's no hint of a frequency limit. --Doroletho (talk) 13:19, 24 June 2018 (UTC)

I'm not sure I understand your question. The sun gives off sunlight, which moves at, well, the speed of light while the sun itself moves at a much lower pace (it will depend on which POV you measure from, but it's much less than the speed of light). The highest frequency electromagnetic waves are classified as gamma rays; the article lists some sources, including thunderstorms here on earth. Matt Deres (talk) 13:32, 24 June 2018 (UTC)

The Speed of light 299,792,458 metres per second is a limit that particles cannot exceed so a particle's acceleration is described in terms of its energy or momentum, usually measured in electron volts (eV). Among Particle accelerators the Large Hadron Collider located underground near Geneva reaches a record 6.5 teraelectronvolts (TeV) per beam. Higher energy accelerators will require even larger curved tunnels due to the increased beam rigidity, see Particle accelerator#Higher energies.

The highest possible frequency of an electromagnetic wave is when its wavelength is in the vicinity of the Planck length, such as a Gamma ray of frequency 10²⁰ Hz.

Can a process cause a frequency higher than its own frequency? Yes, when a single frequency (sinusoidal) signal is distorted by a non-linearity then harmonic component frequencies are produced at integer multiples of the input frequency, see Frequency multiplier. DroneB (talk) 13:35, 24 June 2018 (UTC)

Plank frequency is actually about 3×10⁴² Hz, not 10²⁰ Hz. Ruslik_Zero 20:59, 24 June 2018 (UTC)

The OP may find information, and further links of interest, in our article on the Oh-My-God particle. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 21:11, 24 June 2018 (UTC)

Particles with rest mass not only can't exceed c, they can't even attain c, the speed of light in a vacuum, though they can get arbitrarily close. Photons always travel at c in a vacuum, and moreover all observers agree that they travel at c. This is one of the two fundamental premises of special relativity. There isn't anything that "accelerates" photons, because they always travel at c or, if traveling through a medium, slower. --47.146.63.87 (talk) 07:24, 26 June 2018 (UTC)

How fast would a lineac have to accelerate protons and nuclei to disintegrate them without collision?

The neutrons and down quarks would be left behind if the electromagnetic field was strong enough to overcome the strong force right? How hard would it be to actually build a lineac that can make an electromagnetic field strong enough to break nuclei or protons? Is it like something we could build (in space?) with $100 billion or $10 trillion or is it forbidden by the known laws of physics or somewhere in between? Sagittarian Milky Way (talk) 16:17, 24 June 2018 (UTC)

The process of accelerating a particle is inherently a type of collision, insofar as momentum and energy are imparted to the particle. A good article to start at would be scattering theory, which introduces some pretty heavy concepts.

The original question - "how fast ... could a particle accelerate ...without a collision..." is almost as meaningless as asking "how fast could a particle move if it wasn't moving?"

Sometimes, it's hard to put ideas about physics into words of the English language; but this is why physicists spend so many years in formal study, so that their terminology is standardized and so they can encapsulate complicated ideas in mathematical formulations that concisely and precisely summarize the statement. A really good introductory physics textbook might be worth your time, before you dive headfirst into theoretical limits that take a toll on simplification.

If you're looking for more palatable fare, here's last week's SLAC public lecture: The End of Spacetime

Nimur (talk) 19:27, 24 June 2018 (UTC)

The electromagnetic force must become larger than the QCD string tension. A charge particle that enters a strong electromagnetic field will accelerate, emit bremsstrahlung, and lose energy. This will happen long before the field has had a chance to build up to the required strength. So, you must consider a neutron which enters a region where there exists a strong field. You can e.g. consider an ultra high energy cosmic ray with a kinetic energy of, say ,$10^{20}$ eV in the form of a neutron that enters the magnetic field of a magnetar, see this article for details. Because the neutron has net zero charge, it won't get deflected by the magnetic field. However, the Lorentz force on the quarks becomes extremely large, so large that this will overcome the QCD string tension. This causes quark anti-quark pairs to be created forming pions, and these pions are ten subject to the extremely strong fields, causing more pions to be formed. Count Iblis (talk) 19:55, 24 June 2018 (UTC)

Neutron has a magnetic moment. So, it is deflected by an inhomogeneous magnetic field. Ruslik_Zero 20:56, 24 June 2018 (UTC)

June 25

Tokamaks and actual fusion

Having looked over the tokamak article, I find myself still in doubt about a pretty central point: Have tokamaks, thus far, achieved actual fusion, at a measurable level?

I guess there are two different sorts of "measurable" that could be of interest here. More academically, one could look for the neutrons and other particles that would be emitted from a fusion reaction, and say whether they have been detected and whether other explanations have been ruled out.

Somewhat more practically, there's a metric called Q that indicates the amount of power produced by the reaction, divided by the power needed to keep the reaction mixture at the indicated temperature and pressure. Is it possible to measure this Q and give a confidence interval for it that does not include zero?

And for both questions, if so, then how long has this been so? --Trovatore (talk) 03:14, 25 June 2018 (UTC)

It's not technically a Tokamak, but the Wendelstein 7X has achieved fusion. It's always been a net power consuming process though, and the experiment was never expected to generate net energy. 202.155.85.18 (talk) 04:07, 25 June 2018 (UTC)

Our Fusion energy gain factor article (the Q factor) says: "As of 2017, the record for scientific breakeven is held by the JET tokamak in the UK, at Q = (16 MW)/(24 MW) ≈ 0.67, first attained in 1997." DMacks (talk) 04:10, 25 June 2018 (UTC)

Thanks (both)!

I think this should be covered in the main tokamak article. As it stands, you can read the whole thing without learning whether they've achieved fusion with the things or not. --Trovatore (talk) 05:48, 25 June 2018 (UTC)

Technically, fusion occurs at all temperatures all the time, just at a very slow rate. Any amount of heating and compression of a gas will increase the rate of fusion. So all fusion experiments achieve fusion in a sense, even Martin Fleischmann's. The question is when you would consider the border to be crossed between a trivial increase in the rate of fusion and one with significant implications for a useful reaction. 202.155.85.18 (talk) 06:28, 25 June 2018 (UTC)

Well, sure, in a "what is not forbidden is required" sense (I'm sure we have an article on that but I can't find it). That's why I specified "measurable". --Trovatore (talk) 19:11, 25 June 2018 (UTC)

The early uses I can find of it are in religious-law practices, such as Thomas Smyth (note none of these DAB entries is the right person?) in 1858 (Complete Works, Volume 9 at Google Books, page 482). DMacks (talk) 19:28, 25 June 2018 (UTC)

I'm talking about the QM concept, not the phrase in general. --Trovatore (talk) 19:29, 25 June 2018 (UTC)

I know that:) But it's a general logical concern too. In physics, it seems to be called "Gell-Mann's Law" (or ...Dictum), for Murray Gell-Mann. DMacks (talk) 19:33, 25 June 2018 (UTC)

Ah, that helps. Our article is at totalitarian principle. --Trovatore (talk) 20:11, 25 June 2018 (UTC)

I could be wrong, but it was my understanding that the rate at which fusion happens "all the time" is not particularly meaningful. Say, could it turn out to be one fusion reaction in a trillion years per ton of deuterium-tritium mixture at standard temperature and pressure? In any case it would have to be something you would detect, if at all, only by detecting the high-energy reaction products escaping, and not by measuring the power output of the reaction. --Trovatore (talk) 19:11, 25 June 2018 (UTC)

Muons catalyse fusion reactions and they are constantly incident on the earth from cosmic sources. About 10,000 impact per square meter of earth every second. Under laboratory conditions each muon can catalyse up to 150 fusion events before they decay or bind thus ending the catalytic cycle. Deuterium molecules confined to a lattice at room temperature can undergo fusion at a rate of around 3000 events per second per mole [17]. I don't know the exact measurements for background fusion rates, but they're reasonably frequent and definitely within the range of measurability. 202.155.85.18 (talk) 00:06, 26 June 2018 (UTC)

Ah, interesting. I wasn't considering muon-catalyzed fusion. But since the tokamak concept is not relying on muon catalysis, it seems like a bit of a distraction.

My vague thoughts on the subject are that a tokamak has to create an environment where D-D and D-T collision events greater than the energy barrier for fusion are common. If you're below the temperature where a typical deuteron/triton has kinetic energy of that order, then you can still get a fusion event if (a) just by luck you get a couple of nuclei colliding that happen to be on the far-right tail of the energy distribution, or (b) the energies aren't that high, but they tunnel over the barrier.

And I think both of those possibilities go down at least exponentially with the energy deficit, correct?

So would it be fair to say there is no measurable non-muon-catalyzed fusion at room temperature? --Trovatore (talk) 00:17, 26 June 2018 (UTC)

The linked article claims ~3000 events per second per mole for deuterium. While any given experiment might not being specifically trying to use muon catalysis, if muons are present, it will benefit from them anyway (they may not be present if the magnetic confinement that keeps the plasma in also keeps the negatively charged muons out...not sure). Without a catalyst of some kind the energy required to overcome the coulomb barrier between two nuclei is prohibitively high. Without it, the sun wouldn't achieve it's large fusion rates (the nuclear fusion inside stars is catalysed via the CNO cycle, positron catalysis and probably also a fair bit of muon catalysis, and possibly also quarks and other poorly understood, speculative processes). You could crunch the numbers and determine the fusion rate at room temperature excluding all catalysis if you really wanted to, but I'm not sure it would be very relevant for a comparison to real systems that have all kinds of catalysis happening all the time. 202.155.85.18 (talk) 00:38, 26 June 2018 (UTC)

"[I]f muons are present it will benefit them anyway" -- sure, but not proportionally. You have muons creating those catalyzed events. You increase the temperature and pressure to the levels of a tokamak that's actually generating power, you don't get any more muons, so who knows, maybe they catalyze a few more events, but presumably not enough to be noticed compared to the the thermally generated ones.

That's why I think it's a distraction to talk about muons. OK, I hadn't thought of them, and it's an interesting point, so thank you for raising it. But I don't think it's really relevant to my question. I was talking about events created by the mechanism the tokamak relies on, and I think muon catalysis is completely irrelevant to that. --Trovatore (talk) 00:47, 26 June 2018 (UTC)

Well, ok then. Here's another irrelevant fact that you might nonetheless find interesting, and it also highlights the banality and commonness of fusion reactions. Commercially available neutron generators for industrial applications like moisture detection use D-T fusion reactions to generate their neutrons. 202.155.85.18 (talk) 04:09, 26 June 2018 (UTC)

That is indeed interesting, thanks! Following on that link, I also found the fascinating fusor article, which seems more "thermal". --Trovatore (talk) 05:06, 26 June 2018 (UTC)

Yes, it's not hard to get nuclei to fuse: just accelerate them to high enough speeds to overcome the Coulomb barrier. This can be done with a fusor you can build yourself that fits on a table, as noted. The thing is, this takes more energy than is released by the fusion reactions. No big deal if what you want is, for instance, a neutron source. Projects like the tokamak are trying to accomplish fusion that gives a net energy release, for generating power. Stars accomplish this because of their enormous mass that compresses the nuclei in the core. The problem is we can't fit a star inside the building next door, so we instead have to use extremely strong magnetic fields that take a lot of energy to produce. --47.146.63.87 (talk) 07:16, 26 June 2018 (UTC)

Moment of Inertia, Torque and Angular Momentum

This excerpt from my textbook appears to contradict itself. It seems to give two different definitions for torque: one being the first derivative of the moment of inertia with respect to time, the other being the first derivative of angular momentum with respect to time (both circled in red). I can't see how it's possible for both to be true. In a normal circumstance we wouldn't expect the moment of inertia to change with respect to time anyway during the course of applying a torque (maybe orbits are a different story where accelerating a body will cause the radius of its orbit to increase, but simple, classical systems like a spinning disc or whatever wouldn't see a change). By the analogy implied by the textbook itself, force is not the first derivative of mass in linear kinematics either. Is this a mistake in the text, or am I missing something? 202.155.85.18 (talk) 04:06, 25 June 2018 (UTC)

Lousy textbook. T=I*d(omega)/dt , or as they also say T=dJ/dt. Typo maybe. Greglocock (talk) 05:02, 25 June 2018 (UTC)

Yes, probably the printers mixing up Is and Js, and not knowing any mathematics or physics. This is the sort of error that a good specialist proof-reader should have corrected. Dbfirs 06:29, 25 June 2018 (UTC)

It's possible it's a typo... or, it's an advanced physics book, and they're analytically decomposing the formula for torque by applying the product rule to calculate it for a nonrigid object. Conceptually: if the object is deforming inelastically, there can be a torque that relates to the change in shape, hence change in the moment of inertia. Which textbook are you using?

Torque is the derivative of angular momentum; so it is ${\frac {d(I\omega )}{dt}}=I{\frac {\partial \omega }{\partial t}}+\omega {\frac {\partial I}{\partial t}}$. It is very rare - in textbooks, at least - for the partial of the moment of inertia to be non-zero. A non-zero rate of change in the moment of inertia means that mass is moving in the object; a classical case would be a complex pendulum, which is invariably the pedagogical instrument that is specifically used to knock physics students out of Newtonian mechanics and into advanced dynamical analytic tools, mostly by shaking a lot of time-varying force equations at them.

By analogy to linear dynamics - it is rare but not impossible to impart momentum by changing an object's mass with respect to time: ${\frac {dp}{dt}}={\frac {d(mv)}{dt}}=m{\frac {\partial v}{\partial t}}+v{\frac {\partial m}{\partial t}}$. Although it is rare in elementary physics to change mass with respect to time, it is a critical element in non-rigid body analysis. This full expansion, it turns out, is the foundation of the rocket equation. The other textbook example cases are a heavy chain falling off a table, or a massive train derailing, changing the mass of its cars. If we zero out that second term, we get our familiar "F=m a" formulation, which is the kind of ancient, centuries-old Newtonian physics they teach to teenagers in schools.

My copy of Marion & Thornton - which is now apparently available online at Archive.org - introduces torque in a few important places - notably, in the chapter on, ahem, "rocket dynamics," where a younger version of myself penciled in the margins: "very horrible algebra." Every physicist should read this book, and real physicists should own a copy so they can pencil in their own commentaries.

Sadly, in the case brought by our OP, it looks like it's just an unfortunate typographical error, and not a foray into exciting nuances of physics. But why waste a learning opportunity?

Nimur (talk) 14:39, 25 June 2018 (UTC)

The textbook is ATKINS, P. W., & DE PAULA, J. (2006). Atkins' Physical chemistry. Oxford, Oxford University Press. The probable typo is from page 11 in the "Foundations" section; essentially a review of basic chemistry and physics that is assumed knowledge for the rest of text. 202.155.85.18 (talk) 00:17, 26 June 2018 (UTC)

I agree that formula (B.6) contains a typo but still the partial derivative of I by time is quite often non-zero when, for instance, a non-spherical body rotates. This of course depends on choice of the reference frame. Ruslik_Zero 18:25, 25 June 2018 (UTC)

In such cases, it's more common to expand the scalar moment of inertia into an inertia tensor so that it is non-time-variant, irrespective of the axis of rotation. (...grumble, grumble, something about why this is always guaranteed to be possible). But you could, of course, use a wacky coordinate system and encapsulate the object's apparent change in moment-of-inertia by writing it as a time-varying scalar property, functionally coupled to the rate and axis of rotation. I'm not sure that would be easier... but hey, it presents an awesome opportunity to conduct some fun with equations! Nimur (talk) 20:49, 25 June 2018 (UTC)

Swallowtails follow-up (last question on this subject, I hope)

Hello again, since it was shown to me a few days ago that swallowtail butterflies are found pretty much everywhere in North America and I can never be sure to avoid them completely (unless I move to the western half of Alaska, or to the Yuma Desert), I've decided to see if I can overcome my fear of them instead -- and I'm trying to think of a strategy to do that. But for this, I'll absolutely need the following info:

• 1) What is the native range of Papilio cresphontes (the biggest of all, and therefore the one which would scare me the most)?
• 2) How large (in terms of wingspan) are each of the most common North American swallowtail species, P. appalachiensis, P. canadensis, P. eurimedon (sp.?), P. glaucus, P. multicaudata and P. rutulus? (I need either the range of wingspans, or the maximum wingspan, in either inches or centimeters.)
• 3) Excluding the above-named species, I need the following info on any and all swallowtail species which are found in the USA and which can reach a size (in terms of wingspan) of more than 3 inches (excluding Battus philenor, because I have already looked up the info for that one and discovered that photos of it do not scare me): species name, native range, wingspan (either maximum wingspan or range of wingspans), and whether or not the species is tiger-striped (i.e. has any pattern of contrasting dark stripes or veins on a bright background, like the above-named species, or vice versa -- this is a major factor in my phobia of them).
  

As before, NO PICTURES PLEASE (but maps are welcome) -- I don't want to get an anxiety-induced heart attack from seeing close-ups of those critters, seeing them every summer IRL is bad enough! 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 08:14, 25 June 2018 (UTC)

A tentative suggestion: in the UK we have recreational Butterfly farms (as I am accustomed to calling them, but our article is at Butterfly house – NB: one photo of NOT-Swallowtail butterflies lower down in the article), where one can visit hothouses containing (in both senses of the word) native and exotic butterflies that one can walk amongst – if one so wishes. (Understandably, this might not be something you've previously sought out in your locality.) At such a venue one could, perhaps, arrange to observe the problematic butterflies from the other side of glass or mesh barriers without immediate "danger" of physical contact. I will not presume to discuss the details of what amounts to medical treatment (as I suppose you have already given this topic much thought), but our articles Specific phobia and Exposure therapy might be of broad interest.

That first article has a link to List of butterfly houses (NB: photos of large butterfly-shaped billboards, though none clearly showing actual butterflies), which contains a lengthy list of such venues in the USA. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 15:40, 25 June 2018 (UTC)

Yeah, in fact the strategy I have in mind is a sort of impromptu DIY exposure therapy (in fact, I've been doing this since early childhood and this has helped me to overcome my fear of many other butterfly species, from cabbage whites to monarchs) -- I just want to take this to the next level, now that I've narrowed down the problem species to only tiger-striped swallowtails, I think that if I deliberately occasionally expose myself to the smaller-sized species in this category (while avoiding the big ones, at least until my fear has faded significantly), my fear will fade over time. The only problem is, this takes time (several years for each "kind", as defined by wing shape and coloration), and my place of residence is within the native range of some VERY large swallowtails (including, possibly, P. cresphontes, the worst offender of them all) -- so every spring and summer, I see the really big ones and it traumatizes me all over again and undoes any kind of exposure therapy I might have done, and in fact leaves me worse off than before. So tell me, where can I go to see the smaller ones while avoiding the bigger ones? And, once again, what is the size of the common North American species listed above (P. canadensis, P. glaucus, P. multicaudata, etc.) -- would they be too big for me, or not? 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 09:19, 26 June 2018 (UTC)

Reducing neutronium

Is it possible in theory form a BCS pair from two disimiliar fermions, namely the neutron and electron? If so, can this be considered to be analoguous to reduction in the chemical sense; can one then consider a BCS paired, neutron infused electride to be a neutronide compound, even though it would only be stable at nano-Kelvin temperatures? Plasmic Physics (talk) 13:10, 25 June 2018 (UTC)

These usually requires identical particles as their Fermi energy should be the same. Ruslik_Zero 18:43, 25 June 2018 (UTC)

'Usually' or 'absolutely'? I thought that it would be determined by the common denominator. Plasmic Physics (talk) 19:43, 25 June 2018 (UTC)

Radiation Symbol T-Shirts

Are there any efforts to ban this (or similar uses) type of use of the radiation icon? Wouldn't that dilute the powerful message the icon is meant to conceive? --Doroletho (talk) 17:24, 25 June 2018 (UTC)

To my knowledge, there are many regulations and laws in the United States that require markings and placards for certain hazardous materials - (e.g. for purposes of transportation, 49 C.F.R. §172.300 and onward); but I am not aware of any American laws that prohibit incorrect or unauthorized use of markings or placards in cases where a real hazard does not actually exist. On a technicality, you could probably find some regulation or local law that prohibits these types of unauthorized markings... or if you can technically classify wearing the t-shirt as "transportation" then you could cite §172.303 or §172.401 or §172.502, but those are DOT rules and probably do not apply to a t-shirt.

Generally, especially when I'm around lab newbies, I try very hard to indoctrinate that warning-signs are not "cool-looking decorations." They are actual, functional warning signs, and should be used correctly.

Nimur (talk) 20:43, 25 June 2018 (UTC)

• The first amendment of the constitution of the US protects freedom of speech, which includes display of icons. In theory, no law can prohibit the display of these symbols. However, if such display results in actual harm, then the person who displayed it can be prosecuted for causing that harm: the "don't yell fire in a crowded theater" scenario. -Arch dude (talk)

Technically, people are radioactive, so the shirt isn't even wrong. I am a radiation safety officer in Australia, and the regulations require us to affix radiation warnings if certain criteria are met, but do not prevent us from using the signage just to be safe in cases that may fall short of the criteria. 61.247.39.121 (talk) 23:27, 25 June 2018 (UTC)

If you're in a counting lab, it's not so unusual to see things warning stickered (bananas?) if they merely have a high background count (far from a hazardous one), and so shouldn't be left near or in the shielded counting chambers. I've even seen this on packets of welding rod - specially prepared low-background rods were to be used, not the standard grade stuff. Some scrap armour from the German fleet was spray-stencilled with a green logo when it was recovered in the 1980s to distinguish it. Andy Dingley (talk) 09:15, 26 June 2018 (UTC)

June 26

Could all diesel engines use pure cetane if it's warm enough?

Are there cons besides wasting money and freezing at 18 Celsius? Sagittarian Milky Way (talk) 00:27, 26 June 2018 (UTC)

All "regular" fuel contains various fuel additives to impair engine wear and tear. So if you were to use pure anything as fuel, you'd beat up the engine. Apart from that, I believe you can use just about anything in a diesel engine as long as it will ignite under the conditions in the engine. --47.146.63.87 (talk) 07:05, 26 June 2018 (UTC)