Wikipedia:Reference desk/Archives/Science/2009 August 31

= August 31 =

Why do dogs sometimes chase their own tails?
I am not a dog owner, nor have I ever owned a dog - but I have noticed dogs doing the tail chasing thing when I've been out and about. Sometimes I've even seen them manage to successfully bite their own tails - quite hard, if the dog's pained yelp and jump immediately afterwards is anything to go by.

Now, I'd always put it down to dogs not being particularly smart and failing to realize that their tails are part of their own body - but thinking about it now, that doesn't really make any sense at all. Presumably the dog receives sensory feedback from its tail telling the brain where the tail is in relation to the rest of the body, so even if the dog saw its tail in its peripheral vision it would have a good idea that it belonged to its body and wasn't a prey animal/chew toy to pursue and attack...

So, what's really going on here? Some sort of canine body integrity identity disorder or other neurological/psychological issue? Too many recessive genes due to inbreeding? --Kurt Shaped Box (talk) 00:44, 31 August 2009 (UTC)


 * Dogs may not be anywhere close to the intelligence level of humans, but they're much smarter than people often give them credit for. I suspect it's more likely a form of play. – ClockworkSoul 01:00, 31 August 2009 (UTC)


 * I'd say it's exactly that. Cats often do it as well (and they're much smarter than dogs :D).  Next time you see an animal do this, take a look at it - usually, you can tell there's an element of playfulness there as it chases its tail around.  Young cats and dogs will often play fight - it's more common in wild cats like lions - training to hunt and survive on their own.  You might also ask why children play with dolls are pretend to be superheros.  It's creative entertainment. ~ Amory ( user  •  talk  •  contribs ) 01:28, 31 August 2009 (UTC)


 * Don't think that I hadn't considered that myself - but is it really normal to bite one's own body parts hard enough to cause what appears to be significant pain during play activities (excluding certain human sexual practices... ^_^)? --Kurt Shaped Box (talk) 01:33, 31 August 2009 (UTC)


 * One of our cats does it frequently (once a week that we see). Perhaps it is some form of pleasure, sexual or otherwise. -hydnjo (talk) 02:12, 31 August 2009 (UTC)


 * The fundamental error here is to assume that everything an animal does is for a reason. Every action has a cause, but not every action needs to have a reason -- that is, not every action needs to result from a plan formulated with the aim of accomplishing an understood goal.  It seems likely to me that the dog is responding automatically to a certain type of movement, just as you or I automatically look toward a bright light that flashes in front of us. Looie496 (talk) 02:58, 31 August 2009 (UTC)


 * Even if there was no real reason to chase a tail in the first place, a dog may learn that chasing his tail grabs a lot of attention from humans (who usually consider it funny), which may reinforce the behavior. Unilynx (talk) 22:12, 31 August 2009 (UTC)


 * How about drinking? What's the percentage of people that "hurt" themselves while drinking in a "playful" manner?  And how many do it again the next weekend?  Roughly 98.63% of college students, at my last count.  It's a different situation, we could also look at punching a wall or pounding a table in anger or frustration.  I've seen no research on it, but it's probably a feature of highly intelligent creatures to be able to do things that seem to cause themselves immediate pain and harm (mind over matter). ~ Amory ( user  •  talk  •  contribs ) 03:19, 31 August 2009 (UTC)


 * I disagree with the above, i think dogs might not be aware that the tail is their own when they are chasing it. I can't see any reason to doubt it apart from our human interpretation of how "dumb" that would be and how "smart" we think dogs are. Not suggesting it is directly related but most animals, including dogs do not pass the Mirror test. Vespine (talk) 04:02, 31 August 2009 (UTC)


 * OR here, but I always thought that, similar to Looie496's comment, the chasing of tails is related to dogs' built-in chase reaction. Dogs will react to a fleeing squirrel (or dog, or cat, or human) by chasing it, and my belief is that tail chasing is related.  Tempshill (talk) 06:29, 31 August 2009 (UTC)


 * I'd say that they are aware that it's their tail at a certain level, but that's not enough to overcome the instinct to chase and bite at wiggling objects. For a similar example in humans, if I see a bunch of bugs on TV, my skin gets itchy and I just have to scratch, even though I'm fully aware that those bugs aren't actually on me. StuRat (talk) 12:01, 31 August 2009 (UTC)


 * Young dogs almost always do it occasionally - but if your dog does it a lot - or fails to grow out of the habit - then you have a seriously bored dog who needs more stimulation - either from human contact - or perhaps with some chew toys or something. SteveBaker (talk) 18:16, 31 August 2009 (UTC)


 * If your dog need more stimulation, get him a humpy toy. StuRat (talk) 18:54, 31 August 2009 (UTC)

World Drug List
About a year ago, I found a file online that had every prescription drug name (both brand name and generic name) for the entire world. I remember it being hosted by the WHO. However, I simply cannot find it anymore. Can someone provide a link to such a file? I already have the NDC file from the FDA. That file is so full of typos and omissions that it is useless. I'm looking for a file that has all brand names and generic names without typos and without omissions. -- k a i n a w &trade; 01:59, 31 August 2009 (UTC)
 * http://www.who.int/medicines/publications/essentialmedicines/en/ - this one? - use Google with a site limiter e.g. list of drug site:www.who.int  Ron h jones (Talk) 18:39, 31 August 2009 (UTC)


 * Thanks. That is not what I am looking for, but it is a list of medications (a list of what is considered "essential" for a proper health care system).  I meant to use this list for another project and forgot about it.  According to the WHO, these medications are "essential".  I wanted to match them up against what different insurance agencies and drug programs consider to be "essential". --  k a i n a w &trade; 02:05, 1 September 2009 (UTC)
 * Not a file, but Martindale: The complete drug reference is the closest I can think of. It is available online with a subscription. You may be able to find a library with access or a dead tree copy. Fvasconcellos (t·c) 19:53, 5 September 2009 (UTC)

Carl Linnaeus translated to English?
Can anyone point me to some of Linnaeus's scientific writings translated to English please? Thanks Adambrowne666 (talk) 08:05, 31 August 2009 (UTC)
 * The Wikipedia article is Carl Linnaeus. This gives some of his writing in Latin with English translation.Cuddlyable3 (talk) 14:16, 31 August 2009 (UTC)


 * I'd imagine that most of the translations of his major works are in printed form (such as this). Online, things are probably more difficult: There's an old translation of the Ordines et genera insectorum, so disfigured by scanning errors as to be practically unreadable, here; and a few other things are available behind subscription walls. Wikisource has a (very) partial text of an Introduction to Botany that seems to be an exposition in English of Linnaeus' systematic work. Just search for Linnaeus English translation and poke around. Deor (talk) 15:38, 31 August 2009 (UTC)


 * Just a note: there are not a lot of English translations of Linnaeus around. It took me ages to find a good English translation of the first edition of Systema Naturae, ages ago, and I finally did find one as a very rare manuscript. The works are dry and dull; if you are a historian who really wants to know about Linnaeus, you usually already must learn Latin anyway. --98.217.14.211 (talk) 13:23, 1 September 2009 (UTC)


 * Thanks, all - it was just that he's a character in something I'm writing, and was hoping for some characteristic phrases etc - no worries. Adambrowne666 (talk) 01:54, 6 September 2009 (UTC)

Ground
If there is no solid ground on the giant planets, what stops you from going underneath their surfaces? —Preceding unsigned comment added by Jc iindyysgvxc (talk • contribs) 08:21, 31 August 2009 (UTC)


 * At a certain distance, it might be hard to push through the heavily-compressed gas, but otherwise nothing prevents you from going underneath their surface. --99.237.234.104 (talk) 08:30, 31 August 2009 (UTC)


 * Extreme pressures, winds, and, in some cases, temperatures. StuRat (talk) 11:49, 31 August 2009 (UTC)


 * Galileo (spacecraft) sent a probe beneath the atmospheric surface of Jupiter. It certainly vaporized before hitting the metallic hydrogen interior. --  k a i n a w &trade; 11:57, 31 August 2009 (UTC)
 * In my case a lack of transport. Cuddlyable3 (talk) 13:56, 31 August 2009 (UTC)


 * Or, as a linguistic exercise, if there is no solid ground, what does "underneath the surface" even mean? &mdash; Lomn 13:59, 31 August 2009 (UTC)


 * Not a thing. You'd sink right in.  Probably not all the way to the core, but you'd sink for many many miles.  Until you got so deep that the air pressure was high enough to crush you like a tomato. APL (talk) 14:47, 31 August 2009 (UTC)


 * OMG! I had no idea tomatoes were so likely to crush me! I need to be MUCH more careful near my refrigerator. SteveBaker (talk) 18:12, 31 August 2009 (UTC)


 * Yes, that's why they are called "rotten tomatoes" ... those evil fruits masquerading as innocent veggies ! StuRat (talk) 18:40, 31 August 2009 (UTC)


 * No, no, "rot10 tomatoes" would be dywkdyoc, which stands for "Do You Want Ketchup? Do You? Or Catsup?" --Anonymous, 20:08 UTC, August 31, 2009.


 * If you have a way to slow down (e.g. re-entry shield and then a parachute. You will eventually begin descending slowly and approximately vertically. Your descent will stop at the point where the density of your spacecraft equals the density of the gas, assumiig that your spacecraft is strong enough to resist crushing. You can go deeperby usig power or by increasing your denisty (e.g., by compressing some of your internal atmosphere) similar to the way a submarine operates. -Arch dude (talk) 15:24, 31 August 2009 (UTC)


 * You must be using an ablative shield, as atmospheric pressure has apparently blown away the closing parenthesis for that first sentence, the "n" in "assuming" (where the existing "i" was also split into two), the space between "deeper" and "by", and the "n" in "using". The letters in "density" were apparently also shaken out of position. I'm just glad that any of your paragraph managed to survive at all. :-) StuRat (talk) 18:51, 31 August 2009 (UTC)
 * This is what happens when every component of your paragraph lander has been made by the lowest bidder. ;) Franamax (talk) 20:07, 31 August 2009 (UTC)


 * It would be a straightforward engineering exercise to calculate how large a gas bag would support a small pressure cabin, so that a vessel could descend in the atmosphere of a gas giant to a level where the pressure would not crush the pressure cabin and the gas bag would give the entire craft neutral bouyancy. For extra credit, could it jettiston ballast, expand the gas bag and ascend to a higher altitude, then launch a rocket to escape the planet? Edison (talk) 18:40, 31 August 2009 (UTC)


 * Isn't Jupiter also highly radioactive? Googlemeister (talk) 20:09, 31 August 2009 (UTC)
 * not especially so radioactive in the body of the planet, it is the magnetosphere of Jupiter that is full of radiation. Graeme Bartlett (talk) 21:41, 31 August 2009 (UTC)

Moon
Why doesn't the Moon have an official name? Jc iindyysgvxc (talk) 08:50, 31 August 2009 (UTC)
 * What about Luna? -- Aeluwas (talk) 10:48, 31 August 2009 (UTC)
 * The other earth moon is called Cruithne —Preceding unsigned comment added by 79.75.25.53 (talk) 10:57, 31 August 2009 (UTC)


 * The Moon does have an official name. According to the IAU, it is called "Moon", alternatively "Earth I". Perhaps you are thinking of other natural satellites, which are commonly called moons, with a lower-case "m"? There is only one Moon, the one in our sky. Sorry I can't pop up the link just now, this is my last post before bed. Franamax (talk) 11:47, 31 August 2009 (UTC)
 * Nahh, I lied, I have one more post in me. From the IAU page, you go to the link they supply and voila - it's called "Moon"! Franamax (talk) 11:56, 31 August 2009 (UTC)
 * An etymological dictionary implies that until 1665 the only moon to consider was the Moon. The first non-earth moon identified as such was Titan in 1655. (Galileo saw 4 of Jupiter's moons in 1610 but called them the Medician Stars.)Cuddlyable3 (talk) 13:53, 31 August 2009 (UTC)
 * This is going to get confusing if we ever start communicating with other civilisations. I'll bet everyone calls their moon "Moon". APL (talk) 14:44, 31 August 2009 (UTC)
 * And I bet everyone also calls their own planet some variation of the theme of "Earth." Thankfully, they probably won't speak English, so we can just call their moon "J'klorb" or whatever their word is. ~ Amory ( user  •  talk  •  contribs ) 15:42, 31 August 2009 (UTC)
 * It works for countries here. There are several countries or ethnic groups whose names mean "the people" or "people who can talk" (i.e. in a comprehensible language), but we just use their words for that, or a form of them.  Two examples that come to mind are the Slavs and the Inuit. --Anonymous, 20:17 UTC, August 31, 2009.
 * "They" will probably communicate in high frequency, highly directional pure sound tones that cause your eyeballs to burst when spoken to...83.100.250.79 (talk) 18:35, 31 August 2009 (UTC)
 * Similar question came up before http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2007_September_5#Names_of_Sun_and_Moon
 * 83.100.250.79 (talk) 14:52, 31 August 2009 (UTC)


 * To sum it up, "There's a moon in the sky; it's called the Moon." --98.217.14.211 (talk) 15:11, 1 September 2009 (UTC)


 * In English the Earth's natural satellite's name is 'The Moon.' Although Gallleo tried sucking up to the Medicis, Johannes Kepler denominated all secondary objects as 'satellites,' from the Latin for the hangers-on of a famous man (ie the "posse").


 * "Luna" is incorrect, as it is Latin, not English. Calling the satellites of other planets "moons," while nor absolutely right, only bothers the very pickiest folk.


 * {{B00P (talk) 01:25, 2 September 2009 (UTC)

Genetic modification of pubic hair for transplant?
Could pubic or body hair be modified by genetic or chemical methods to permanently resemble head hair, and then be transplanted on to balding mans scalps?80.2.197.71 (talk) 10:54, 31 August 2009 (UTC)


 * Pubic hair (and armpit hair) is about as far from head hair as you can get, but arm hair and leg hair is a bit closer. However, if we could do that level of genetic manipulation, we could convince the hair follicles on the head to produce more hair.  StuRat (talk) 11:47, 31 August 2009 (UTC)
 * The Wikipedia article Hair transplantation reports that transplanted hairs grow and last just as they would have at their original home. It mentions that donor hairs may be extracted from the chest, legs or beard. It does not mention Pubic hair that is often closer in colour to the eyebrows than to scalp hair, but I find no suggestion that genetic modification would be needed to transplant them.Cuddlyable3 (talk) 13:29, 31 August 2009 (UTC)

Spider identification
I don't think I've ever seen a green spider, much less one that was pale and translucent. Anybody know what species this thing is? -- ErgoSum • talk • trib  14:11, 31 August 2009 (UTC)


 * Hmmm, so far it looks like a close match to the green lynx spider, perhaps a juvenile? I'm not an expert on spiders. -- ErgoSum • talk • trib  15:02, 31 August 2009 (UTC)


 * Where (geographically speaking) was this taken? What region/country/state/etc.? Might help narrow down the species. The   Seeker 4   Talk  17:44, 31 August 2009 (UTC)


 * Arkansas. I think the photo of the green lynx spider in the article closely resembles my photo. I'll probably just delete the picture since there is already a better quality photo of the spider in place. I was under the assumption that all spiders were black or brown, so I was quite surprised to see a green spider. Thanks anyway! -- ErgoSum • talk • trib  22:33, 31 August 2009 (UTC)


 * I think your photograph is great. It very clearly shows in detail the structure of the legs. Beautiful. Bus stop (talk) 22:43, 31 August 2009 (UTC)
 * Yup. I voted keep on Ergo talk page, and have boldly added the image to the article's gallery. --Tagishsimon (talk) 22:49, 31 August 2009 (UTC)


 * Thanks guys, this is why I love this place! I'll leave the photo uploaded. Happy editing. -- ErgoSum • talk • trib  00:19, 1 September 2009 (UTC)


 * I'm wondering whether the three photographs taken in India oughtn't be removed from that gallery. According to the article, the Indian critter is a different species, P. viridana, which has its own article (albeit a one-sentence substub); and according to the descrptions on the image pages, they are purported to depict still another species, Oxyopes viridanus (which does not appear in List of Oxyopidae species). Deor (talk) 14:17, 1 September 2009 (UTC)


 * I was wondering the same thing, the spiders in those photos look much larger than the one I saw, which made me think it was a juvenile. I see what you are saying though, the other images are obviously of a different species so I have boldly removed them for now, until somone can confirm they are the same species. -- ErgoSum • talk • trib  22:10, 1 September 2009 (UTC)

Swine flu - dead birds
Anyone know of a link between "swine flu", and large apparently healthy looking birds dropping out of trees stone dead - I ask because swine flu has recently been identified in my area, and I have recently noticed an unusually large number of dead birds on the grass verges near to where I live, seemingly not the victims of "road kill" ?
 * thanks.83.100.250.79 (talk) 15:36, 31 August 2009 (UTC)
 * I don't think Swine flu infects birds. Here in central California the West Nile virus (carried by mosquitoes) has kille a lot of birds that way, but I don't know whether that could happen in the Sheffield area. Looie496 (talk) 15:41, 31 August 2009 (UTC)
 * Looie is right. Birds cannot catch swine flus (although pigs can be infected with avian flus, potentially making them very dangerous) so you don't have to worry about that. ~ Amory ( user  •  talk  •  contribs ) 16:33, 31 August 2009 (UTC)
 * A little followup research shows that there have been reports of West Nile in British birds this year. In California corvids such as crows and magpies have been most strongly affected -- do you know what types of dead birds you are seeing? Looie496 (talk) 16:52, 31 August 2009 (UTC)
 * All pigeon type birds, probably Wood Pigeons rather than "town pigeons". No dead crows as yet.83.100.250.79 (talk) 18:11, 31 August 2009 (UTC)
 * If H1N1 ("Swine flu") had indeed crossed over to birds, that would be a rather worrying thing because that would increase the chances of a gene exchange with H5N1 ("Bird flu") resulting in H5N1 variants being able to be passed from human to human rather than only from birds to humans as currently is the case. SteveBaker (talk) 18:10, 31 August 2009 (UTC)
 * Of course there a numerous other explanations which don't involve a global human catastrophe, I'm still panicking though, just to be on the safe side...83.100.250.79 (talk) 19:20, 31 August 2009 (UTC)
 * You could always call your local health authority and ask. When West Nile first came to my region, the public was asked to report any dead crows, jays, other large birds. They might be interested in getting a recent corpse for testing. (And we were told not to handle them ourselves) Franamax (talk) 20:25, 31 August 2009 (UTC)
 * Yes, already e-mailed local "enviromental health department" as they are called here.83.100.250.79 (talk) 20:34, 31 August 2009 (UTC)
 * Well, H5N1 had been found in pigs years ago, and while it may not be perceived as as big of a threat as it once was, H5N1 is definitely still around so the possibility certainly exists. ~ Amory ( user •  talk  •  contribs ) 19:54, 31 August 2009 (UTC)
 * H1N1 is not synonymous with "Swine flu". There are loads of strains of H1N1, some of which are probably definitely (Avian flu) already in birds. The current outbreak is just one strain of H1N1. --Tango (talk) 20:21, 31 August 2009 (UTC)
 * This year's pandemic novel swine flu H1N1 virus has indeed been detected in turkeys at a farm in Chile and in pigs in several countries. 75.41.110.200 (talk) 03:26, 1 September 2009 (UTC)

Bug control with garlic water?
Is this advice (found on the Internet) useful or merely wishful thinking? Thanks. Wanderer57 (talk)

"Get rid of bugs on plants by spraying them with garlic water. Peel and chop three garlic cloves, put them in a mason jar and fill 3/4 full with water. Put on the lid and shake then let soak for a week or two.  Place water in a spray bottle and spray directly onto your plants. Do not soak, just mist. Do this for a few days in a row and this should get rid of your problem. Repeat as needed. "


 * It sounds like a harmless experiment. Why not do it yourself and report the results?  It should be a fairly easy thing to check out.  It is at least possible that chemicals in the garlic may act as a natural deterrant to some insects.  But if you actually do them experiment, you may find out yourself... -- Jayron  32  18:12, 31 August 2009 (UTC)


 * And, if it does work, it's possible that garlic developed those strong smelling chemicals exactly because they kept bugs from eating it. I believe many spices developed their flavors that way.  While those spices might taste nice when properly diluted, mixed with sugar, etc., the straight plants would also seem noxious to us, in many cases. StuRat (talk) 18:31, 31 August 2009 (UTC)


 * I will try a experiment at the next opportunity. My sense if that this method actually worked it would be well known that it works and I would not have to ask. Thanks Wanderer57 (talk)

Do snakes has vision
Yes it is true that snakes has eyes but can they see. Or they sence through there toung. —Preceding unsigned comment added by 125.18.239.135 (talk) 18:06, 31 August 2009 (UTC)


 * See Snake. -- Coneslayer (talk) 18:07, 31 August 2009 (UTC)


 * (edit conflict)Sure they can see. Some snakes may not be able to see well, or may use other senses more to help them navigate, but I am fairly certain that nearly all snakes have some sense of vision of some sort. -- Jayron  32  18:10, 31 August 2009 (UTC)


 * Many snakes (like rattlesnakes) can also see in infrared... 98.234.126.251 (talk) 05:37, 2 September 2009 (UTC)

The smallest hole water can penetrate
How can I calculate the minimal diameter of hole in flat surface water can penetrate in standart conditions? Renaldas Kanarskas (talk) 20:48, 31 August 2009 (UTC)


 * You would need to more clearly define what standard conditions are. Water that is under pressure can go through a smaller hole because surface tension is less of an impact, and your pressure is going to probably be determined by how deep the water is at the level of your hole.  Shape would also play a part, however, the use of the word diameter would indicate a circular hole?  Googlemeister (talk) 21:15, 31 August 2009 (UTC)
 * 20C temperature, 1 atm. pressure. Lets take the heigth of water in, e.g., cylinder, as variable, which we will use in formula. As I understand, it will depend not only on water surface tension but also on contact angle with the the material where the hole is made. Renaldas Kanarskas (talk) 22:17, 31 August 2009 (UTC)
 * Do you know the relationship between contact angle and 'surface energy'? There is one, but I don't have it to hand - it can be derived however. You can use the surface energy of water/hole material to work out how much energy the H2O will need to leave the bulk water, and enter the hole.
 * Using an energy distribution equation you can work out what percentage of water molecules have enough energy to enter the hole.
 * The height of water converts to increased pressure - which gives a change in relative energies on either side of the hole. I'm not sure how to directly relate this to rate of reaction - though it will obviously favour an equilibrium in one direction through the hole.
 * Is that the sort of calculations you were thinking of making.?83.100.250.79 (talk) 22:43, 31 August 2009 (UTC)


 * For diffusion of water molecules you need is the molecular size, though the diffusion will be affected by the interaction of the substance the material that contains the hole is made of with water. ie the hydrophobicity of the hole material.
 * You are looking for the minimum swept area for motion of a H2O molecule.
 * See Water (data page) - I would estimate somwhere between 10^-10 to 2x10^-10 meter for the minimum size (this is a hole that would only allow 1 molecule through at a time). This is assuming that the material is hydrophilic.
 * 83.100.250.79 (talk) 21:55, 31 August 2009 (UTC)


 * You seem to be interpreting the Q in a completely different way than I did. I thought the Q was about what size hole would allow drops of water to drip thru, in which case the answer is likely in the millimeter to centimeter range, depending on the material. StuRat (talk) 00:06, 1 September 2009 (UTC)


 * There are going to be a couple of "knee point" diameters, at which the mass flux per unit-area will dramatically change. Between these "knee points", a continually decreasing diameter will result in slower fluid flow, probably along a rough 1/r^2 law; at the knee-points, this law will probably change.  (I don't claim the following analysis to be complete or authoritative, but I think the proper methodology is to consider all the relevant physical effects that impede water flow, and start listing the characteristic length scales that they occur on).  Starting with a large hole, the first impediment to flow will be the cavitation limit, which probably occurs around a few centimeters diameter, depending on the fluid head.  Above this diameter, the water will exhibit laminar flow down the drain; below that limit, it will start to be predominantly turbulent (and spinning on its way).  The next critical point, probably on the order of a few millimeters, is when the capillary action force is going to become critical - the adhesion of water to the wall orifice will approximately equal the force of gravity, and so the flow will be impaired (but not stopped).  This rate will be highly dependent on the material the water is flowing through (as mentioned above, with hydrophilic and hydrophobic materials at the extrema).  The next limits are going to be permeability limits, dictated by the porosity of the material.  Now, the fluid will still flow, but it will do so in a slow, meandering style.  This is the regime of reservoir engineering in the parlance of petroleum engineering (or aquifer/water engineering); it is an active area of research, as the presence of fluid inside a porous medium changes the medium's properties - the result is a very nonlinear fluid flow.  Assuming a subsonic fluid, I think these are the primary physical scenarios which can occur; if, for some reason, the water is sufficiently pressurized or accelerated, it may also have a sonic-shock crossover, (again resulting in a nonlinear flow analysis).  It should be noted that fluid mechanics is one of the most complicated areas of classical physics, and empirical observations often contradict theoretical predictions for even complex models; probably, the best way to get an answer suitable for your needs is to define the regime of interest and experimentally test a few conditions.  Nimur (talk) 00:28, 1 September 2009 (UTC)
 * Masterful analysis Nimur. I recall doing a level-test on a low flowrate liquid distributor in a distillation column once, with 3 mm diameter drip points punched through 3 mm thick steel. I couldn't help but notice that there was no actual water flowing through the holes. As the manufacturer rep, this was a little awkward - but I was the only one in the column, hydrocarbon service has lower surface tension, we needed to complete the job, and it wasn't near as bad as the other liquid distributor which you could tell by eye would definitely overflow. Me keeps mouth shut - but you are absolutely right about boundary conditions where the expected equations break down. The flow regime determines the equations you use, and the knee points are critical. Oh yes, also the OP left out the liquid head/kinetic energy in defining the problem.Franamax (talk) 02:33, 2 September 2009 (UTC)
 * I can't help wondering if this condition is meant, in which any further increase in height causes the droplet to burst - ie the contact angle is "90 degrees" ? HappyUR (talk) 12:51, 1 September 2009 (UTC)Drophole.jpg
 * Ok, imagine the hole is made in the material thickness value of which we can neglect. Will it be possible to express a hole diameter only in values of pressure of water, surface tension of water and contact angle?Renaldas Kanarskas (talk) 17:20, 2 September 2009 (UTC)

Cockroaches
Do they live in herds? If they do, how big are those herds? --Soppaluu (talk) 21:57, 31 August 2009 (UTC)
 * See Cockroach for some information. In short, they aggregate into complex social groups and display emergent behavior. By the way, the collective noun for cockroaches is unlikely to be "herd"., According to List of collective nouns for fish, invertebrates, and plants (unsourced), it is an "intrusion of cockroaches", though various academic studies seem to prefer the term "group". As for the size of these groups, it seems to depend on resources available. According to Cockroaches: ecology, behavior, and natural history by William J. Bell, Louis Marcus Roth, Christine A. Nalepa, up to 100,000 have been observed in a single apartment (nice!), however in general most species live in much smaller groups: on average 2-8 adults and 5-8 nymphs. Rockpock  e  t  22:28, 31 August 2009 (UTC)

Would New York City's subway be designed any differently now?
Sagittarian Milky Way (talk) 23:01, 31 August 2009 (UTC)


 * If someone were building a subway now, in a dense city like New York (and you wouldn't build a subway elsewhere) then the cut-and-cover method used to build the new york subway would probably antagonise too many people. The advent of tunnel boring machines makes a deeper bore a more affordable option than it was when the NY subway was built. Other than that, electric light rail is much the same world over, and new underground systems are built with mostly off-the-shelf components, and one is much like the others. -- Finlay McWalter • Talk 23:07, 31 August 2009 (UTC)


 * Also bear in mind that it grew organically (see History of the New York City Subway), and that if starting from scratch now the designers would be able to optimise for current population and travel patterns.
 * Did you have a specific aspect of design you had in mind - there are many - architecture, route, technology used, track geometry, construction methods and materials, etc
 * Have you considered any of these or were wondering about a specific area?83.100.250.79 (talk) 23:37, 31 August 2009 (UTC)
 * Also please try to think a little for yourself, or at least show that you have attempted to consider some part of your own question.83.100.250.79 (talk) 23:38, 31 August 2009 (UTC)
 * I was thinking of locally specific, mostly routing, there's not much to be said in the ways of tech that's either not obvious (use fluorescent tunnel lighting), or didn't change) Unless you're a real subway buff, you won't be familiar with every line, so someone might notice something I haven't. Here's what I noticed: In Manhattan, there's a bias of service to the West Side. The D and the 4 run like 500 feet apart for miles in Bronx, a seeming lack of desire to go turn from Manhattan early to go into Queens. The 42 St Shuttle saves only one stop over the 7, the PATH and MTA duplicate service in Manhattan. Many PATH stations are very close to sea level. and their tunnels are below it (tropical cyclone storm surge + high tide + 21st century sea level rise). Queensboro Plaza and Queens Plaza not having transfers. A small stretch of Flatbush Avenue in Brooklyn with two lines whose stations seem to be avoiding each other. Incompatible car widths and platform clearances might prevent certain better routings. All because the system was built by 3 differant companies competing for riders. Sagittarian Milky Way (talk) 06:57, 1 September 2009 (UTC) edited 21:08, 2 September 2009 (UTC)
 * Routing is the most difficult of all the questions you could have asked :)
 * It would probably be easier to rebuild the entire city from scratch :)
 * One suggestion I'd make lightly is to have entirely parallel N/S tracks (under manhattan) turning east at S end (no crossing points) - with a series (about 6) of shorter high capacity crossing routes (again starting at the west end under manhattan) connecting 'at right angles' (topologically speaking) all the N/S tracks - this would have the effect of meaning that no subway journey would require more than 2 changes.
 * Where meaninful the e/w tracks could be extended east, and fanned out to form full length lines
 * Basically a grid system with dangling ends going into the subburbs.
 * It's not based on any knowldege of new york...83.100.250.79 (talk) 12:22, 1 September 2009 (UTC)
 * That's all my guess, and I am breaking my own rules by posting it, there's no reason I've got to suggest that it would be any better than any other sensible suggestion, OR, better than the current system that has grown and been modified 'organically'... 83.100.250.79 (talk) 14:27, 1 September 2009 (UTC)
 * Novel idea. Like a street grid or Interstate made out of railroads. Somehow, I'm wondering if this would help the most unlucky station pairs and commutes at the expense of the city having slightly longer morning commutes on average (the time when people probably care most about shaving minutes) Because the current like for Midtown- and Downtown-favored glancing angle crossing and merging lines would be shorter than doing everything at right angles. Thankfully, the presence of Central Park allows some of the trunk lines to be peeled off in the current system without causing a shortage of lines in the Upper Central Side (as you can't annoy the commutes of people who don't exist) Sagittarian Milky Way (talk) 21:08, 2 September 2009 (UTC)
 * They would likely build it deeper down, as there's more stuff in the way at shallow depths now due to all the construction since then. StuRat (talk) 00:00, 1 September 2009 (UTC)


 * If you're interested specifically in how a new line would be constructed today see Second Avenue Subway. That doesn't say much about how the overall system would be designed if it were built today, but it provides some insight into things like construction methods. Rckrone (talk) 00:04, 1 September 2009 (UTC)
 * I don't know about the state of the NY subway now, but when I was there in 1996, I was negatively surprised by the construction quality, poor station layout, and state of the rolling stock. The noise was unbelievable compared to the more modern designs I was used to from e.g. Munich (essentially all remodeled for the 1976 Olympic games and kept reasonably up to date since). I think a new system would probably be somewhat deeper, more level along the tracks, and the stations designed more generously, and much higher (for improved lighting, better ventilation, and less claustrophobia). I also suspect new routes would be found to correspond to current and anticipated commuting patterns. Again, in Munich distances from the city center influence housing prices, but "distance" is not measured in meter or miles, but in minutes, usually walking to the next light rail station and riding into the city. As a result, housing prices essentially follow the star shaped layout of the light rail network. --Stephan Schulz (talk) 07:45, 1 September 2009 (UTC)
 * Claustrophobic, lol. It seems like a normal interior room to me. Now the huge barrel vaults (a la Washington Metro) seem grandiose and done for the sole purpose of showing off how much volume they can excavate! I suppose it could be cheaper than building all those columns? I never much noticed the noise much, but I see some conductors wearing earmuffs cause they stay there longer than the users. A rubber tyre metro would definately help the people living feet from the elevated tracks sleep much easier.
 * I agree, stations like Times Square are way too complicated for what should essentially be a T-junction.
 * There are many new cars now, but much the rolling stock was and is from the 60s. Sagittarian Milky Way (talk) 22:21, 2 September 2009 (UTC)

You may also be interested in the Jubilee Line and the major new addition to the London Underground it added quite recently. Some of the stations are very different to 'normal' London undeground stations. The line in the Paris Metro, France one of the lines is entirely automated. I can't remember which but there's basically no driver which makes for an enjoyable view from the front/back of the train. ny156uk (talk) 16:05, 1 September 2009 (UTC)

Ahh it's Paris Métro Line 14 apparently. ny156uk (talk) 16:08, 1 September 2009 (UTC)


 * The most significant difference we can be certain of would be that the whole system would be wheelchair-accessible.
 * As to technical changes, quite possibly the trains would use an AC power supply, as the technical advantages that DC had 100 years ago no longer exist. Very likely the trains would have either cab signaling or full automatic driving (with or without a human driver), rather than lineside signaling.  Certainly there would be a greater ability to control and monitor the trains from a central location.  A single width of train would be used for all lines rather than needing to have two separate fleets as now.
 * Different widths and lengths, that's caused by the competing companies. Stupid, isn't it? Sagittarian Milky Way (talk) 21:08, 2 September 2009 (UTC)


 * Subway planners today tend to like to keep the operational patterns as simple as possible, so New York's many junctions where trains cross over from one line to another would be looked on with disfavor. Similarly, 4-track lines with express and local trains are rare in other cities: planners prefer to provide two separate lines instead.  So some might argue for avoiding that design in a New York subway built from scratch; however, with the strong north-south traffic in the narrow island of Manhattan, they might find it worth doing there after all.


 * New construction probably would not include the elevated sections over streets that are still common outside Manhattan today. (However, going underground adds cost, which leads to the point that any sensible speculation is conditional on the amount of money presumed to be available.)  Similarly, we can expect that the airports would be served (if politics and funding permitted). Interchange stations would be planned as interchanges, without the awkward layouts you get when one line is built and another that was never thought of is added later.


 * Finally, the system would never be given a prosaic name like "the subway"; there would have to be a political or marketing spin put on it, like "Metrorail" or "Metrolinx" or "The Alfred Beach Memorial - Michael Bloomberg City of New York Underground Transportation System".

--Anonymous, 20:28 UTC, September 1, 2009.
 * That's an uncannily accurate description of the RAV Line (oops, I mean the "Canada Line") opened a few weeks ago in Vancouver, including the Cambie Street switchover to cut-and-cover to save money, with the minor result of absolutely devasting the local mechants. Automation, central operation, airport access - all there. I do like the idea of express lines though. Is the existing NY metro quad-tracked? Franamax (talk) 02:56, 2 September 2009 (UTC)
 * In much of the system, it is. The 2 platforms are usually between the tracks in express stations. Sagittarian Milky Way (talk) 21:08, 2 September 2009 (UTC)


 * The provision of express trains on separate tracks is one of the most distinctive characteristics of the New York system. It generally isn't done over the full length of each line, but is done over the busiest section of many lines.  On the outer portions often one 2-track branch feeds the express tracks and another feeds the local tracks.  A few secondary lines are entirely 2-track.  There are also a few lines with 3 tracks, allowing for express trains in the rush-hour direction only.  --Anon, 03:55 UTC, September 2/009.


 * Some other details nobody has mentioned yet: First of all, the stations would prolly be built with vaulted ceilings, which would eliminate the need for columns (like many stations on the Washington DC subway). The ventilation system would incorporate air filters to remove car exhaust gases from the air before admitting it into the subway tunnels, and prolly some kind of air conditioning system as well.  The tracks would be laid on concrete slabs to reduce maintenance expenses, with rubber pads under the rails to reduce noise.  (Welded track might be a possibility too.)  The trains would incorporate full rheostatic braking in addition to the normal air brakes.  Finally, platform barrier gates might be a good option to prevent people from falling onto the tracks (which is a common type of accident on many subway systems). 98.234.126.251 (talk) 05:59, 2 September 2009 (UTC)


 * The newer cars (the ones that are brighter) use regenerative braking. It's amazing they didn't do that earlier, considering how much momentum they bleed. Sagittarian Milky Way (talk) 21:08, 2 September 2009 (UTC)


 * Also, train protection system and electronic track monitoring are recent inventions; earlier rail systems had more clumsy electric or mechanical monitoring, or none at all. Everything's digital now.  Nimur (talk) 23:22, 3 September 2009 (UTC)


 * The New York subway actually has mechanical train stops that trip the train's brake valve if it runs a red light. But you're right, if the subway was built today, it'd prob'ly incorporate an inductive Automatic Train Protection system that uses track circuits to send electronic signals to the train. 98.234.126.251 (talk) 04:52, 5 September 2009 (UTC)