Wikipedia:Reference desk/Archives/Science/2014 March 14

= March 14 =

Polyethylene Glycol
After hearing different answers, I wish to ask: Does Polyethylene Glycol contains calories when consumed by humans? thanks. 79.179.193.243 (talk) 03:03, 14 March 2014 (UTC)
 * No. See  and  for a few examples.  No sites I can find note any nutritive value for it at all.  It should also be noted that food does not contain calories.  It provides them.  Calories are a measure of food energy.  Most substances don't provide any food energy; roughly speaking only a few classes of compounds can be broken down by your body to provide you with net energy, the article food energy notes what those are.  Part of the problem is the use of the word polyol which really refers to two (essentially) unrelated classes of compounds.  Polyol can refer to sugar alcohols, which do provide food energy, but it can also refer to polymers made from alcohol monomer units.  Polyethylene glycol is this kind of polyol, which is unrelated to sugar alcohols.  -- Jayron  32  03:15, 14 March 2014 (UTC)


 * It sounds like some unsung heroes of science (I mean, studying diarrhea...) believe that PEG is not metabolized by the human or bacterial components of the digestive system.  I would be suspicious that if someone made a long-term habit of eating large amounts of it that eventually the bacteria would find a way, but that's not discussed here, hopefully due to lack of experimental data! Wnt (talk) 03:20, 14 March 2014 (UTC)


 * There are certainly bacteria that can metabolize it, though not in bacteria you would want to find in your own body (specifically flavobacterium and pseudomonas). Someguy1221 (talk) 03:27, 14 March 2014 (UTC)


 * Regarding that, Wnt, PEG has medicinal use for the purpose of whole bowel irrigation, often in preparation for a colonoscopy. In basic terms, it cleans you out entirely so that they can send cameras up to take a peak.  Diarrhea is basically what it is intended to do to you, "whole bowel irrigation" is a polite term for "medically induced diarrhea".  -- Jayron  32  03:30, 14 March 2014 (UTC)


 * I think that last bit is a little misleading: diarrhea implies watery feces only barely controlled (if you're lucky); PEG is routinely recommended as a simple stool softener. No... explosions or other unpleasantness. Matt Deres (talk) 12:31, 16 March 2014 (UTC)


 * Jayron, sorry, Provides. wrong word usage. Anyways, I understand from you in short that it does not provide calories to humans at all. 79.179.193.243 (talk) 03:23, 14 March 2014 (UTC)


 * My understanding is that polyethylene glycol is not metabolized by the human body, and thus cannot be stored or provide calories. There is research on actually injecting animals with PEG directly into the blood stream or spine, which mention that it "dissolves away". Not sure how that actually happens though . But theory goes it should not enter your circulation from the gastrointestinal tract. So yeah, if your body can't absorb it, and it can't break it down, no calories. Someguy1221 (talk) 03:24, 14 March 2014 (UTC)


 * So far as I can tell, the known means of degrading PEG are very slow, not likely to be too relevant for digestion. The problem is that they are essentially an "exopegylase" rather than an "endopegylase", trimming the molecule with a laborious sequence of reactions at the far end.[  I still bet that if you feed it to an experimental animal or human long enough, eventually something will figure it out - the stuff seems to just beg to be hydrolyzed into ethanol and used for food - maybe this is such an enzyme.  It would only take a little to break up the chains into manageable pieces and then the end-to-end degradation could finish it off. Wnt (talk) 20:34, 14 March 2014 (UTC)


 * Hi Wnt. sorry, but I don't have enough knowledge on the subject to generally understand what you wrote. can you please simplify it? thanks. 79.179.193.243 (talk) 01:33, 15 March 2014 (UTC)
 * There's no known way that humans could get nutrition out of polyethylene glycol - all it does is cause diarrhea and pass out of the body. But it isn't absolutely clear to me that if a person ate some amount of it every day for years, that their intestinal bacteria wouldn't eventually be able to process it into a possible food source (such as ethyl alcohol).  Basically, I am just thinking very hypothetically about how much the intestinal flora (which might spread) can help a population adapt to a new food source. Wnt (talk) 02:07, 15 March 2014 (UTC)
 * Yeah, no. It's basically liquid plastic.  You'd get as much nutrition eating the bottle it comes in.  -- Jayron  32  02:24, 15 March 2014 (UTC)
 * Which one of these possibilities did you mean, Jayron? --   Jack of Oz   [pleasantries]  03:14, 15 March 2014 (UTC)
 * Definition #1 here. -- Jayron  32  03:19, 15 March 2014 (UTC)
 * If it were polyethylene, I'd say that, but this is an ether that, in principle, should be possible to hydrolyze, whether directly (doubtful) or following oxidation of an internal carbon in a manner somewhat analogous to the degradation at the end. But admittedly, ethylene glycol poisoning is more likely than nutritional benefit, come to think of it. Wnt (talk) 03:57, 15 March 2014 (UTC)

Freezing water
Lets say I have a normal bucket of water and it's lukewarm. I also have an icecube that has been cooled all the way to -100 celsius. Would the bucket freeze if I dropped that icecube into it? What if the icecube is like 200 or 500 degrees negative celsius? — Preceding unsigned comment added by 2001:708:110:1004:CACB:B8FF:FE24:8A97 (talk) 09:45, 14 March 2014 (UTC)


 * The lowest possible temperature is about -273 degrees Celcius. The freezing of water requires the removal of a lot of heat. One icecube is never going to be enough to freeze a bucket of water, no matter how cold the cube is (unless of course the cube is so large that it fills a large portion of the bucket).
 * To put it in more quantitative terms: to freeze 1 kg of water you need to remove about 334 kJ of heat. The heat capacity of ice between - 100 and 0 degrees is roughly 1.7 kJ/kgK on average, so that means that 2 kg of ice of - 100 degrees can freeze about 1 kg of cold water, in other words the icecube would have to fill 2/3 of the bucket. - Lindert (talk) 09:50, 14 March 2014 (UTC)

The question can be answered with a simplifying assumption that the bucket is thermally insulated from the environment; that means we can wait until ice/water/bucket have equalised at temperature T °C. In the process:
 * the ice cube gains

(T - Ti) Mi 2.05 joules

where Ti is the initial temperature of the ice (e.g. -100 °C), Mi is the mass of the ice in gm and 2.05 J/gm °C is the specific heat of ice.
 * the water first loses

( Tw - T) Mw 4.186 joules

where Tw is the initial temperature of the water, Mw is the mass of the water in gm;
 * the water then if T sinks to 0 °C further loses its Latent heat of fusion which is 334 Mw joules;
 * the bucket itself loses

( Tw - T) Mb Sb joules

where Mb is the mass in gm of the bucket and Sb is the Specific heat of the bucket material, possibly steel Ssteel = 0.49 joules/gm °C.

When values are provided for Ti Tw Mb Mi and Sb we have a neat homework question: does T fall below 0 °C i.e. does all the water freeze? However to make a practical experiment the thermal isolation must be very good because ice itself is a poor heat conductor and will tend to float a long time on slightly warmer water. As already noted, Ti cannot be less than -273 °C 84.209.89.214 (talk) 11:38, 14 March 2014 (UTC)


 * Yes it can −273.15° (theoretically) :-)  Richerman    (talk) 19:49, 14 March 2014 (UTC)

Human instinctive behaviour in nightlife
I read an article in a scientific journal recently about how humans tend to most clearly exhibit their natural instincts in clubs, both in terms if survival and finding a mate. But is there any truth to this? I know alcohol lowers inhibitions but surely that only shows the individual's personality more than anything else. Some get angry, some are quiet, some are aggressive. In terms of "finding a mate" some try, some don't in clubs and some are successful and some aren't, but I would have thought this is more to do with personality again more than instincts. — Preceding unsigned comment added by 194.66.246.46 (talk) 09:56, 14 March 2014 (UTC)
 * Which journal was that ? I'm curious how they figured out what a "natural instinct" is in humans.  Sean.hoyland  - talk 10:07, 14 March 2014 (UTC)
 * "Natural instincts" are exhibited in all sorts of ways. There are a lot of "scientific journals" out there, some more reliable than others, so it would help to know which one and exactly what they claim.--Shantavira|feed me 11:27, 14 March 2014 (UTC)
 * Perhaps: (?)
 * Grazian, D. (2007). "The girl hunt: urban nightlife and the performance of masculinity as collective activity". Symbolic Interaction, 30(2), 221-243. DOI: 10.1525/si.2007.30.2.221 (Abstract)  — 71.20.250.51 (talk) 16:01, 14 March 2014 (UTC))
 * Grazian, D. (2007). "The girl hunt: urban nightlife and the performance of masculinity as collective activity". Symbolic Interaction, 30(2), 221-243. DOI: 10.1525/si.2007.30.2.221 (Abstract)  — 71.20.250.51 (talk) 16:01, 14 March 2014 (UTC))

Cardboard
If a human tried to digest a small piece of corrugated cardboard, what would happen? --Bnā We must Eashgf (talk) 13:38, 14 March 2014 (UTC)


 * Cardboard is made of cellulose and glue. Humans can't efficiently digest cellulose, so the cardboard would pass through, acting as sort of a rough fiber.  Generally speaking, small quantities of cardboard would not be harmful to your health; however, it may have toxic glue or other additives. Justin15w (talk) 13:46, 14 March 2014 (UTC)


 * Glad you qualified that. See Kraft process - doesn't sound tasty. Wnt (talk) 14:50, 14 March 2014 (UTC)


 * So that's the process they use to make Kraft American "cheese" slices ! :-) StuRat (talk) 18:51, 14 March 2014 (UTC)

Metals Fusing in Space
I read something a few days ago which I find very difficult to believe. It said that if two identical metals touched in space, they would fuse together - like cold fusion. The author said something to the effect that as there were no other particles to keep the two metals apart, they would automatically fuse together. Is this true, or is this an early April Fool's joke? KägeTorä - (影虎) ( TALK )  15:21, 14 March 2014 (UTC)


 * Two unoxidised metals will indeed fuse together. On Earth, the oxygen in the air stops this from happening. It has nothing to do with cold fusion though.217.158.236.14 (talk) 15:25, 14 March 2014 (UTC)


 * Yup - I think you mean 'like welding' Cold fusion is (or would be) something else entirely. AndyTheGrump (talk) 15:27, 14 March 2014 (UTC)


 * Cold welding.--Shantavira|feed me 15:54, 14 March 2014 (UTC)


 * You might also be interested by the wringing together of gauge blocks, smooth blocks used in tool shops. μηδείς (talk) 17:03, 14 March 2014 (UTC)


 * And we need consider what "touch" means. If one hits another at high speed (the most common type of contact in space), they won't fuse, and may each break up if the speed is high enough.  They need to be still or almost still relative to one another to fuse (does anybody know exactly how still ?).  At some point the relative velocities will be low enough that gravitational attraction should held them together long enough to fuse. StuRat (talk) 18:21, 14 March 2014 (UTC)
 * How still? Enough that motion doesn't overcome Intermolecular force (presumably). ~: 71.20.250.51 (talk) 18:37, 14 March 2014 (UTC)


 * Note that metal objects made on Earth will be surrounded by an oxide layer. I'd assume that metal oxides, just like the oxides of lunar regolith, would fail to fuse because of the more covalent and localized nature of the metal-oxygen bonds? Wnt (talk) 20:15, 14 March 2014 (UTC)


 * Gauge blocks are made of special alloys and kept oiled to help prevent this. μηδείς (talk) 20:34, 14 March 2014 (UTC)


 * With metals, the electrons bind the metal atoms closer, but the atoms are still separate. In Cold Fusion, hydrogen (isotope) nuclei are fused to form a new type of atom, Helium, and this requires a lot of energy. Star Lord -   星王 (talk) 15:02, 15 March 2014 (UTC)

If the surfaces are perfectly smooth then the atoms from the different parts will fit into the crystal structure of the merged metal. You can also consider the fact that the laws of physics imply invariance under time reversal. So, if we break a metal into two parts, the time reversal of that act would merge the two metals back together without any need to glue or weld them together. In that case the two parts fit exactly toghether. If we are given two pieces that were not created from a single piece, then they would not fit toghether unless the surfaces of the two parts are perfectly smooth.Count Iblis (talk) 15:25, 15 March 2014 (UTC)

Plurals of Abbreviated Words
[Moved to language desk]

Hot water
What's the highest temperature of water (or other liquid) that's tolerable for (a) drinking, (b) being immersed in? --rossb (talk) 16:20, 14 March 2014 (UTC)


 * In case of b) this is slightly above 40 C. The body then cannot keep its body temperature from rising to the water temperature which will eventually be fatal. Count Iblis (talk) 16:26, 14 March 2014 (UTC)


 * That depends on how much of the body is immersed in the water and if cooling methods like fans and drinking cold fluids can be used. And much hotter water would be needed to kill you quickly. StuRat (talk) 18:36, 14 March 2014 (UTC)


 * ... and for a) I would guess around 80 C, but it seems to vary between individuals and depends on how carefully and how fast they drink. I suspect that people who consume drinks at this high temperature have some trick for reducing the temperature in the mouth to below 70C within a very short time.  I burn my tongue and top lip!  For most people, the temperature will drop to below 50C as the liquid goes down the gullet, and will fall to below 40C in the stomach.    D b f i r s   22:13, 14 March 2014 (UTC)


 * The British Health & Safety Executive require that bathing water for vulnerable people should not exceed 44C (110F), or 46C if supervised. Water just five degrees hotter than this (49C, 120F) can cause minor damage to the outer layer of skin in 90 seconds, and a serious scald in ten minutes.  Immersion in water at 71C (160F) can result in serious scalds (third-degree burns) in as little as one second.  Don't try it!    D b f i r s   14:07, 15 March 2014 (UTC)


 * 44 or 46C seems like it would cause overheating of the core body temp, since that should be around 37C. How is this prevented ? StuRat (talk) 15:13, 15 March 2014 (UTC)


 * By sipping slowly. ←Baseball Bugs What's up, Doc? carrots→ 17:00, 15 March 2014 (UTC)


 * Sipping bathwater ? Ewwww ! StuRat (talk) 19:05, 15 March 2014 (UTC)


 * Ha. Mixed up Dbfirs and yourself while in edit mode. :( ←Baseball Bugs What's up, Doc? carrots→ 07:40, 16 March 2014 (UTC)


 * By not submerging the head. You lose an immense amount of head through the head. 86.152.129.197 (talk) 02:47, 16 March 2014 (UTC)


 * Especially if you are Marie Antionette. StuRat (talk) 15:29, 16 March 2014 (UTC)


 * Given the modern habit of labelling disposable coffee cups with warnings that the contents may be hot, I'm wondering if there are official rulings in various places as to what temperature requires such a helpful warning. HiLo48 (talk) 22:00, 15 March 2014 (UTC)


 * Here in the USA, water heaters are required to display a table of time-to-scald vs. water temperature (mine sure does, and I know from personal experience that the times in the table are calculated with quite a safety margin too). 24.5.122.13 (talk) 08:45, 16 March 2014 (UTC)


 * In the UK, hygiene regulations require reheated food to be reheated to at least 82°, which is too hot for most people to eat. --ColinFine (talk) 12:29, 16 March 2014 (UTC)


 * Slurping involves taking in a bit of hot liquid while bringing in sufficient cool air to rapidly reduce the temperature of the liquid while preventing prolonged contact with the lips, and other mouthparts. (It's amazing Wikipedia lacks an article on this notable, useful, and annoying practice). I am able to slurp coffee at a temperature which would certainly cause second degree burns if I simply sipped it. Edison (talk) 22:53, 16 March 2014 (UTC)

Body painted blindness
Would a color blind person (Monochromacy type) perceive a body painted person as naked?--85.52.89.152 (talk) 20:41, 14 March 2014 (UTC)


 * That would depend on the darkness of the paint. If it was just as dark as the person's skin, then it wouldn't be visible to the colorblind person.  If it was significantly lighter or darker, then it would be visible.


 * Also note that normal vision individuals would see the same thing in dim light, where color vision is absent. StuRat (talk) 21:35, 14 March 2014 (UTC)


 * Would we perceive a body painted person in a black and white picture as naked? OsmanRF34 (talk) 23:19, 14 March 2014 (UTC)


 * Also note that color blindness rarely leads to completely monochromatic vision -- the vast majority of colorblind people can in fact perceive some colors, just not very well. 24.5.122.13 (talk) 01:19, 15 March 2014 (UTC)
 * Agreed - see Types of Colour Blindness which explains what colour blind people actually see. Alansplodge (talk) 13:05, 15 March 2014 (UTC)
 * First riddle me whether a non color blind person would see a person painted in "flesh tones" (their own, or those of any race?) as being naked. For that matter, whether the titlillation of the art form is based primarily on us seeing body paint of any color as not quite nakedness.  Bonus points: whether women coerced into wearing ugly Western style cosmetics should be counted as wearing a hijab for legal purposes. Wnt (talk) 15:39, 16 March 2014 (UTC)

What is this
One of those animated gifs of a reaction in a beaker (erlenmeyer flask?) I'm curious what it is. What the reacting chemicals are, not the flask. -71.238.189.52 (talk) 23:35, 14 March 2014 (UTC)
 * It looks like elephant toothpaste. Red Act (talk) 23:58, 14 March 2014 (UTC)
 * Thanks! -71.238.189.52 (talk) 00:18, 15 March 2014 (UTC)
 * Not Erlenmeyer flask, probably volumetric. Rmhermen (talk) 02:02, 15 March 2014 (UTC)
 * Volumetric flask indeed. DMacks (talk) 07:43, 16 March 2014 (UTC)