Wikipedia:Reference desk/Archives/Science/2014 June 19

= June 19 =

Hair growth by weight
How many miligrams of hair (on the head, not including facial hair) does an average man with a full haid of hair grow in a month? Has this ever been measured empircally, rather than calculated? — Preceding unsigned comment added by 24.100.220.34 (talk) 04:39, 19 June 2014 (UTC)
 * L'Oreal did a calculation here that comes out to about .2 grams of hair per day or 6 grams per month. uhhlive (talk) 21:46, 19 June 2014 (UTC)

Geese and the transmission of information
Every spring (starting late May and early June) we get 100's of geese, mainly Canada goose, that congregate on both sides of the airport road (69.11222°N, -105.0875°W) where it is illegal to shoot them. At the same time there are thousands out of town. After a short period they move out onto the tundra to lay eggs and raise their young. Once the gosling's are born there might be one or two families that return to the sides of the road. You can drive by them with a truck or ATV and walk, even with a dog, by them and they don't move. The only way to get them to move is to walk towards them or bend over. However, the geese on the land (this is before the eggs are laid), where you can shoot them, will fly off well before you get into shotgun range. So the question is how do the geese know that being on the side of the road is safe? How do they transmit this information between one another? CBWeather, Talk, Seal meat for supper? 08:08, 19 June 2014 (UTC)


 * Good question. It's kind of the same question as "How do crows know to take off when the farmer walks out the door with his shotgun?" Perhaps it's experience - or lack thereof. ←Baseball Bugs What's up, Doc? carrots→ 09:43, 19 June 2014 (UTC)


 * I don't think it is possible to give any sort of precise answer, but there's little doubt that observational learning plays an important role. There are lots of well-studied examples of it in birds. See for example Observational learning. Looie496 (talk) 12:53, 19 June 2014 (UTC)


 * Crows do seem to be quite intelligent, and do seem to be able to communicate threats to each other. There was a study done where a person wearing a given mask harassed some crows, then later walked by a different group of crows, and they were frightened of him, too.  So, somehow the first group communicated that he was a threat to the second group.  There's also inter-species communication of threats.  Of course a baking dog can communicate a threat to it's owner, but many other species cooperate and share intel like this.  In some cases, the communication even describes the type of threat, like "snake". StuRat (talk) 15:59, 20 June 2014 (UTC)


 * Wait, isn't there a Canadian equivalent of the migratory bird act? I only ask because in USA it is illegal to ever shoot them in many circumstances... Our article says that UK acted "on behalf" of Canada in signing the treaty. Anyway, it's a little unclear from your description, but isn't there a timing difference as well? E.g. parents of young that cannot fly yet will be much less likely to take flight when threatened. Birds in general and fowl in particular behave very differently at different times of the breeding cycle (sorry, that article is terrible). Otherwise I agree with Looie's general comments and links. Finally, if you're interested in controlling them on your property, a pair of mute swans or a border collie usually does the trick. There are even service businesses in the US that come out with dogs and swans to keep geese away from golf courses . SemanticMantis (talk) 14:42, 19 June 2014 (UTC)
 * Canada's version appears to be Migratory Birds Convention Act. According to, Canada geese are considered game birds and may be hunted in Canada under certain circumstances as game birds. Per various links like and  it sounds like migratory Canada geese can generally be hunted in the US during certain seasons that are made on a year by year basis, and resident ones at additional times (when migratory ones are not really present and depending on the area). Nil Einne (talk) 16:10, 19 June 2014 (UTC)
 * Oops, thanks! SemanticMantis (talk) 16:57, 19 June 2014 (UTC)


 * Thanks for the replies. It looks as if Looie's links provide the answer. The parents molt at nesting time so they can't fly until the young are ready. That's why very few return to the road area before migration. They prefer lakes and large ponds where they can escape from foxes. The only problem we have with them is that besides the road they occupy the ponds at both ends of the runway. Thanks. CBWeather, Talk, Seal meat for supper? 09:43, 20 June 2014 (UTC)


 * For your specific example, here are some ways they could know the difference between areas where they might be shot and areas where they won't be:


 * 1) Their own experience. If somebody shot at them or another bird in sight in one area, they will tend to think of that area as dangerous.  This may not apply to other areas.  Being migratory birds, they would need to understand that threats vary by location.  For example, bears might be malnourished in one area and try to catch them, but may be well fed in another location and leave them alone for easier prey.  Knowing this would be important to their survival.  Also, they may remember a threat from previous years.


 * 2) Another bird could communicate the threat level to them simply by flying away, or not, for a given stimulus. If all other birds fly away, they may do so too, even if they aren't directly aware of a threat. This can include birds of other species and non-birds that run away.  A forest fire is a good example of this, when all species of animals can be seen flying and running away.  I don't think they all directly detect the fire, but many just "go with the crowd" and follow where they are going.  (Of course, this type of group behavior can lead to problems, too, like when one whale beaches itself and all the other whales follow it and beach themselves, too.)


 * 3) Birds may also make warning calls telling others of the threat. This can include birds of other species and non-birds, too.


 * And a note on evolution here. While it wouldn't do a bird much good to understand the Theory of Relativity, knowing what is and isn't a threat is critical to their survival and thus passing down their genes, so a large portion of their rather limited brain capacity is devoted to this task.  Therefore, they seem to be able to figure out threats in ways that require more intelligence than we credit them with possessing. StuRat (talk) 16:14, 20 June 2014 (UTC)

Synthesis of
What solvent would be useful for the titular synthesis, using dichloridomercury and lithium tetrahydridogallate, the temperature must be kept below 149 K? Plasmic Physics (talk) 11:42, 19 June 2014 (UTC)
 * Ethereal solvents are commonly used for metal-hydride reactions, but I don't know specifically about gallates. Diethyl ether melts at 157 °C, so having some reactants/products dissolved it it (or adding a small amount of some other cosolvent) would probably drop the mp 8 K or or more, enough to keep it liquid at your target temperature. Dimethyl ether would be a liquid at that temperature range, but you'd have to condense it to use it...a practical annoyance. If you don't need an ether, alkanes C5 and smaller have low enough mp. DMacks (talk) 18:08, 19 June 2014 (UTC)
 * Erm, you mean 157 K! Wnt (talk) 22:32, 19 June 2014 (UTC)


 * I don't think that alkanes are good solvents for salts (lithium tetrahydridogallanate), or is this particular salt an exception to rule? Plasmic Physics (talk) 03:25, 20 June 2014 (UTC)


 * Why in God's name would you want to make mercury(II) hydride in the first place? TenOfAllTrades(talk) 18:04, 19 June 2014 (UTC)
 * As the article states, it has no economic uses, and is made only as an academic curiosity. Like all mercury compounds, it is toxic.  If you aren't a chemistry professor planning to publish a paper for research, it is best avoided.  (If you were a chemistry professor, you probably wouldn't ask here because you would have done a literature search.)  Robert McClenon (talk) 18:09, 19 June 2014 (UTC)
 * As a starting point, one would have found a ref for using lithium gallanate in this type of reaction it and start with that solvent. DMacks (talk) 18:18, 19 June 2014 (UTC)
 * No need for him to apologize for curiosity - it is indeed interesting to find out about solvents that are good for crazy cryogenic reactions! Wnt (talk) 22:32, 19 June 2014 (UTC)


 * It is probably toxic, but since it rapidly decomposes above 149 K, the only likely hazard is by contact, and even then, cryogenic burns are the biggest issue. Plasmic Physics (talk) 00:19, 20 June 2014 (UTC)


 * Well, I thought since this compound has been identified for a while, it is about time that it is isolated also. So, I'm just working through a method to see how it could be done. Plasmic Physics (talk) 00:02, 20 June 2014 (UTC)
 * One of the refs in the article (the one that discusses the magic temperature of decomposition) mentions making it and isolating it on a cold plate. Heck, they make it at what, 4 K, and then warm it enough to remove the unreacted reactants, matrix, etc. DMacks (talk) 02:23, 20 June 2014 (UTC)


 * That is not what I meant. I meant a reaction which is not photocatalytic. Plasmic Physics (talk) 03:25, 20 June 2014 (UTC)

How well can temperature be controlled in cryogenic syntheses? Plasmic Physics (talk) 00:02, 20 June 2014 (UTC)


 * Very well on small scale. Baths can easily be controlled to a degree or tenth or even better at some ranges. But getting that equilibrated throughout a reaction medium becomes harder as scale increases as the reaction becomes more exothermic. Endothermic often less of a problem because "a bit too cold" for an already very cold reaction just means the reaction slows down until the temperature re-rises to match bath (negative feedback that does not usually damage the product, etc.) See Cryocooler and Cooling bath (I remember being surprised at first how predictable those were once I managed to avoid freezing them outright). Or can just use a liquid+solid bath of some material whose melting point is the temp you want. DMacks (talk) 02:20, 20 June 2014 (UTC)

Parallel plate transmission line
I looked in the transmission line article but it does not describe this version. I want to know if parallel plate transmission lines are always balanced, or can they be operated unbalanced?--86.180.143.223 (talk) 17:33, 19 June 2014 (UTC)
 * A Microstrip line consisting of a thin flat conductor which is parallel to a ground plane is an example of an unbalanced parallel plate transmission line. One can model a balanced parallel plate transmission line as two microstrip lines back-to-back with a common ground plane that can be removed since, by symmetry, it carries no current. 84.209.89.214 (talk) 19:55, 19 June 2014 (UTC)
 * I should have made it clear that what I meant by a parallel plate transmission line is one where the conductors each have the same width. This is therefore different from the microstrip arrangement which is operated in unbalaced mode. Is there any advantage to a symmetrical parallel plate line being operated balanced or unbalanced? --86.180.143.223 (talk) 11:11, 20 June 2014 (UTC)
 * The unbalanced parallel plate line is not as well isolated from the surroundings as when balanced, since its fields do not cancel at a distance. Therefore unbalanced lines are more susceptible to interference or to causing interference...unless you wrap the ground plane around to change the line to a Coaxial cable. Balanced lines are easy to set up for a desired impedance, such as when matching to a Dipole antenna. See Dipole antenna. 84.209.89.214 (talk) 19:14, 20 June 2014 (UTC)

Wheat in Stilton
Our article on Stilton cheese makes no mention of its wheat content, but it's an allegation -- for want of a better term -- that's consistently made online. Could anyone point me in the direction of a WP:RS that states that Stilton contains wheat so that I can add it to the article (or not, as the case may be)? I don't eat wheat but used to be damned fond of a tasty piece of Stilton and would like to be sure one way or another. Thanks, Ericoides (talk) 18:25, 19 June 2014 (UTC)


 * Hope this article and the links contained therein helps you make your mind up. --TammyMoet (talk) 18:32, 19 June 2014 (UTC)


 * Thanks very much for that, interesting. I was looking more for a book or journal article on Stilton rather than web/blog links. The material also seems rather US-centric, not much on Stilton per se. But thanks again. Ericoides (talk) 18:55, 22 June 2014 (UTC)


 * The most official thing I can find is, the British gov’s product specification for Stilton. Unfortunately, it simply refers to penicillium roqueforti without specifying how this mould is grown (as I understand it, the worries are if the mould is grown on bread, some wheat could be transferred to the cheese). However, it also contains contact info for the official makers’ organization, if you wanted to follow up.
 * The only promising scholarly reference I found doesn’t make the crucial page available (for me, perhaps you will have better luck). 184.147.135.33 (talk) 21:48, 22 June 2014 (UTC)


 * Thanks for that, appreciated. Ericoides (talk) 07:00, 23 June 2014 (UTC)

Islands with largest highest-point-to-area ratio
I'm interested making relief maps of islands with large highest points relative to their area, so that they look more interesting. Taking islands over 10000 km² in area from List of islands by area and over 2000 m high from List of islands by highest point, I compiled this list:

However, Penang Island, at 833 km² and 295 m has a ratio of 2.824, much larger than any of the above.

Is there a quick way of get a list of islands with the largest ratios?

Thanks! cm&#610;&#671;ee&#9094;&#964;a&#671;&#954; 19:25, 19 June 2014 (UTC)


 * Can't help with a general list, but I bet Ball's_Pyramid has a high ratio. It made some news recently when this critter Dryococelus_australis was recently re-discovered there. Stack_(geology) will have some other very tall "islands" with small areas. Also, your ratio is effectively getting at rugosity, though that ratio is unitless, while yours comes out to the slightly-weird 1/m. SemanticMantis (talk) 20:18, 19 June 2014 (UTC)
 * The smaller the islands in your list are, the bigger the numbers you will get, so for a 1 km2 island peaking at 1m you will get 1.0, but really that is not very impressive at all. You should use something more like a height to width ratio. Graeme Bartlett (talk) 21:13, 19 June 2014 (UTC)
 * Good point. Rugosity is similarly not biased by area. But computing rugosity for an island probably can't be done without very good topographic maps or lidar imaging (and some decent effort on top of that). SemanticMantis (talk) 21:29, 19 June 2014 (UTC)
 * Try height divided by the square root of area. It's dimensionless and doesn't depend on the island being round or long. Oh, and do compute it for SemanticMantis' example, and for the Old Man of Hoy. AlexTiefling (talk) 21:35, 19 June 2014 (UTC)
 * (ec) Exactly. To some approximation, you will have the steepest average slope from shoreline to peak on the island with the greatest ratio of highest point to 'width'.  Of course, since islands aren't necessarily square or circular, that concept of 'width' is a bit fuzzy.  For a 'scale' term, you could just use the square root of area, and take the ratio of height to that scale length to get a 'steepness' score.  (Incidentally, Hawaii tops that list too.  Penang Island, meanwhile, ends up around the middle of the new list.)  TenOfAllTrades(talk) 21:39, 19 June 2014 (UTC)


 * Many thanks, SemanticMantis, Graeme, Alex and TenOfAllTrades. You're right, this gives prominence (mind the pun!) to small islands. Perhaps even more extreme than Ball's Pyramid is Ko Tapu, assuming its area is a circle of 4m diameter at sea level. I couldn't find the area of Old Man of Hoy, but estimate a width of 35 m from photos. Dividing by square root of area gave:


 * {| class="wikitable sortable"

! Island || Highest point (m) || Area (km²) || m/&#8730;km²
 * Ko Tapu || 20 || 0.000016 || 5000
 * Old Man of Hoy || 137 || 0.01 || 1370
 * Penang Island || 833 || 295 || 48
 * Hawaii || 4205 || 10434 || 41
 * Mindoro || 2582 || 10572 || 25
 * Seram || 3027 || 17454 || 23
 * Sumbawa || 2722 || 14386 || 23
 * Jamaica || 2256 || 11190 || 21
 * Negros || 2435 || 13074 || 21
 * Taiwan || 3952 || 35883 || 21
 * Sicily || 3326 || 25662 || 21
 * Flores || 2370 || 14154 || 20
 * Panay || 2117 || 12011 || 19
 * Palawan Island || 2085 || 12189 || 19
 * Timor || 2963 || 28418 || 18
 * Alexander Island || 2987 || 49070 || 13
 * New Britain || 2334 || 35145 || 12
 * Vancouver Island || 2195 || 31285 || 12
 * Hispaniola || 3098 || 76480 || 11
 * Axel Heiberg Island || 2210 || 43178 || 11
 * Sri Lanka || 2524 || 65268 || 10
 * Java || 3676 || 138794 || 10
 * South Island || 3724 || 145836 || 10
 * Mindanao || 2954 || 97530 || 9
 * Luzon || 2922 || 109965 || 9
 * North Island || 2797 || 111583 || 8
 * Sulawesi || 3478 || 180681 || 8
 * Hokkaido || 2290 || 78719 || 8
 * Honshu || 3776 || 225800 || 8
 * Iceland || 2110 || 101826 || 7
 * Ellesmere Island || 2616 || 196236 || 6
 * Sumatra || 3805 || 473481 || 6
 * New Guinea || 4884 || 785753 || 6
 * Borneo || 4095 || 748168 || 5
 * Madagascar || 2876 || 587713 || 4
 * Baffin Island || 2147 || 507451 || 3
 * Greenland || 3694 || 2130800 || 3
 * }
 * Axel Heiberg Island || 2210 || 43178 || 11
 * Sri Lanka || 2524 || 65268 || 10
 * Java || 3676 || 138794 || 10
 * South Island || 3724 || 145836 || 10
 * Mindanao || 2954 || 97530 || 9
 * Luzon || 2922 || 109965 || 9
 * North Island || 2797 || 111583 || 8
 * Sulawesi || 3478 || 180681 || 8
 * Hokkaido || 2290 || 78719 || 8
 * Honshu || 3776 || 225800 || 8
 * Iceland || 2110 || 101826 || 7
 * Ellesmere Island || 2616 || 196236 || 6
 * Sumatra || 3805 || 473481 || 6
 * New Guinea || 4884 || 785753 || 6
 * Borneo || 4095 || 748168 || 5
 * Madagascar || 2876 || 587713 || 4
 * Baffin Island || 2147 || 507451 || 3
 * Greenland || 3694 || 2130800 || 3
 * }
 * Honshu || 3776 || 225800 || 8
 * Iceland || 2110 || 101826 || 7
 * Ellesmere Island || 2616 || 196236 || 6
 * Sumatra || 3805 || 473481 || 6
 * New Guinea || 4884 || 785753 || 6
 * Borneo || 4095 || 748168 || 5
 * Madagascar || 2876 || 587713 || 4
 * Baffin Island || 2147 || 507451 || 3
 * Greenland || 3694 || 2130800 || 3
 * }
 * Borneo || 4095 || 748168 || 5
 * Madagascar || 2876 || 587713 || 4
 * Baffin Island || 2147 || 507451 || 3
 * Greenland || 3694 || 2130800 || 3
 * }
 * Greenland || 3694 || 2130800 || 3
 * }
 * }


 * (For comparison, Burj Khalifa at 830 m and 0.008 km² has a value of 9300 and the Dushanbe Flagpole at 165 m and 0.00002 km² (estimate) has a value of 37000!)


 * Guess the problem now becomes subjective, as to how small an island to accept while it still being relatively well-known. Thanks for all your help! cm&#610;&#671;ee&#9094;&#964;a&#671;&#954; 13:15, 20 June 2014 (UTC)


 * If anyone's curious, approximating the basal area of Ball's Pyramid by an ellipse, we get an area of ~1.036 km^2. This gives the ratio as 563m/&#8730;(1.036)km² ~= 552, making it third on the list above. Also I think the arithmetic on Ko Tapu is wrong. For a 4m diameter I get area= 4pi m2=1.25664e-5 km^2. Then 20m/&#8730;(1.25664e-5)km² ~= 5642. Using the top diameter of 8m I get a ratio of ~2821. So barring any other arithmetic errors, Ko Tapu is the clear 'winner'! SemanticMantis (talk) 15:37, 20 June 2014 (UTC)
 * For comparison, a perfect hemisphere would score one tenth of that, 564.2, as would a cone when its height is half the width of its base. A pyramid (45° slope) would score 500. - ¡Ouch! (hurt me / more pain) 06:37, 23 June 2014 (UTC)

Carbonatite magma phase separation
Carbonatite lavas are very unusual in appearance and composition, and apparently result from the separation of phases in magma. See for some video well worth watching. A question they raise in my mind, though: does the separation of phases here have anything to do with the hydrophilic aqueous phase and hydrophobic organic phase that typically dominate a smaller and cooler separatory funnel than the ones here delivering different flavors of magma to the Earth's surface over spans of (only) thousands of years? Does the partition of various minerals to these phases align with an analysis of how polar they are expected to be in a magma setting? Can you say that a carbonatite or silicate phase mixes with X mixes with Y mixes with... until you have a series that relates it in hypothetical miscibility directly to oil or water? If not, can you find a direct analogy from liquids at STP for this kind of phase separation? Wnt (talk) 22:40, 19 June 2014 (UTC)
 * WE have an article on this volcano, Ol Doinyo Lengai. μηδείς (talk) 17:27, 21 June 2014 (UTC)
 * In magma, hydrophilic/hydrophobic properties are irrelevant because the system does not include liquid water (only water vapor, if any); a more relevant classification is into lithophile, chalcophile and siderophile minerals (which has more to do with electronegativity and polarisibility polarisability, not dipole moment). That said, since the elements found in carbonatites are extreme lithophiles, this kind of differentiation may indeed take place (although there are other hypotheses as well).  Bottom line is, we don't know enough yet to tell for sure. 24.5.122.13 (talk) 00:40, 20 June 2014 (UTC)
 * Perhaps there should be a redirect: polarisibility → Polarizability   71.20.250.51 (talk) 03:19, 20 June 2014 (UTC)
 * polarisability?
 * In any case, how can things be separated based on electronegativity? I thought things with different electronegativity tend to like each other, like sodium and chloride?
 * As for polarisability, is that more important in magma because so many ions are present in that environment, or some other reason? Is there any example of phase separation on this basis at STP?
 * Oh, also: under Goldschmidt classification all the rare earths are listed as "lithophiles". But the article I linked at top says that the only rare earth mines are in these abnormal carbonatite deposits... Wnt (talk) 05:43, 20 June 2014 (UTC)
 * OK, one thing at a time:
 * (1) Thanks for correcting my spelling -- that's precisely what I meant.
 * (2) In magma, precisely such a separation is believed to take place: siderophile (electronegative) cations remain in their reduced (metallic) state, chalcophile (electropositive, polarizable) cations combine with sulfur anions (one of the two major anions in magma) to form sulfides, and lithophile (electropositive, non-polarizable) cations combine with oxygen anions (the other major anion) to form oxides (which may react further to form hydroxides or carbonates).
 * (3) In magma, polarisability is important because oxygen and sulfur are the major anions, and polarisability determines a cation's affinity to each -- high polarisability will favor combining with sulfur (which is also polarizable), and low polarisability will favor combining with oxygen (which is also nearly non-polarizable).
 * (4) The carbonatite deposits preferentially include lithophilic minerals, and exclude siderophilic and chalcophilic minerals -- so there's no contradiction re. rare earths. 24.5.122.13 (talk) 07:50, 20 June 2014 (UTC)
 * Thanks! You're being very helpful.  I hope you'll consider starting an account and contributing to our articles.
 * Come to think of it, would a mixture of metallic mercury and carbon tetrachloride provide an example of this sort of phase separation? Wnt (talk) 14:03, 20 June 2014 (UTC)
 * Perhaps, if they're mixed and then allowed to stand for a few days (or maybe a couple weeks or more). Why don't you try and see?  (I don't need to remind you to do it in a well-ventilated area -- both substances give off toxic vapors.) 24.5.122.13 (talk) 06:02, 21 June 2014 (UTC)