Wikipedia:Reference desk/Archives/Science/2018 June 20

Science desk
< June 19	<< May | June | Jul >>	June 21 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

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)

[1] 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". [2] 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:[3] 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),..." [4]
• "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."[5]
• "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." [6](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)