Wikipedia:Reference desk/Archives/Science/2009 September 13

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September 13

Why are prisoners asked to cough during a body cavity search?

This may seem like a silly question at first but I'm being serious. Why are prisoners asked to cough when being strip searched? Specifically, what does the coughing accomplish? I couldn't find this information in the Body cavity search article. I tried googling it and discovered that doctors use the "drop and cough test" to check for hernias or tumors by observing the reflex action that the coughing triggers. But why would prison guards ask prisoners to do this? Are they also checking for hernias or does coughing cause a reflex action that causes any contraband to be dislodged from the rectum? -- œ^™ 00:48, 13 September 2009 (UTC)

Checking for Inguinal hernia. Baseball Bugs ^{What's up, Doc?} carrots 00:54, 13 September 2009 (UTC)

That's coughing during a medical. I can't see prison guards performing that kind of medical test during a strip search. --Tango (talk) 01:44, 13 September 2009 (UTC)

Coughing causes the anal muscles to relax, thereby aiding the insertion of a finger. Hence sometimes the release of flatus on coughing. —Preceding unsigned comment added by 79.75.1.246 (talk) 01:59, 13 September 2009 (UTC)

Perhaps it helps guards find things being smuggled in one's anus. Makes them more visible or susceptible to popping out. DMacks (talk) 03:40, 13 September 2009 (UTC)

This is the most likely explanation of why they're asked to 'bend over, spread their cheeks and cough', during a strip search upon admission intro in prison, however I have yet to find a reliable source that definitively verifies this. -- œ^™ 05:45, 13 September 2009 (UTC)

I recently watched a TV show where the guards were strip searching women. Rather than perform a cavity search they had them squat down and cough. It wasn't explicitly mentioned, but my interpretation was that doing that would expel (or at least shift, so that it became obvious) anything that was concealed in the vagina or anus - without having to do a cavity search. Blu-Ray Betamax (talk) 09:22, 13 September 2009 (UTC)

It would be interesting in an encyclopedic sense to note how and why this would work anatomically. Like maybe a section in the Body cavity search article explaining how coughing causes the pelvic diaphragm to move in such a manner that it dislodges anything inside body cavities. But once again, there's no sources explaining this anywhere and it all amounts to original research. -- œ^™ 18:51, 13 September 2009 (UTC)

Why does the OP think asking to cough is a part of the body cavity search? If this is from own experience, could it be that the searching officer just wanted to establish that they were being understood? Cuddlyable3 (talk) 23:17, 13 September 2009 (UTC)

No idea where OP got the idea, but it's used in "behind the bars"-type documentaries on prison life, and there are court cases that establish how it is (or is not) part of a valid search of a person. DMacks (talk) 00:13, 14 September 2009 (UTC)

Heh. No not from personal experience. Like DMacks said, I've seen it in documentaries and in almost every prison movie I ever saw, and have always been curious as to why. I guess there still ARE some things that you can't discover using the internet. BTW, what's "OP" stand for? -- œ^™ 00:36, 15 September 2009 (UTC)

OP seems to stand for "original poster." A lot of people get stumped by that. I did too. Bus stop (talk) 00:51, 15 September 2009 (UTC)

Phenomenon?

Our house (in northeastern US) has a wooden utility pole diagonally across the street which services us and three other houses. It is only a distribution pole for electricity, telephone and cable for the four houses and doesn't have a transformer or anything else unusual except for a metal junction box. The phenomenon that I notice each year is that a nearby (ten feet away from the pole) deciduous tree begins to lose leaf color and proceeds to drop its leaves about six weeks ahead of schedule. Does the utility pole have an aura of sorts which is screwing around with the tree's expected seasonal leaf cycle? hydnjo (talk) 01:36, 13 September 2009 (UTC)

Unlikely. Where are you getting this "schedule" from? There are lots of factors that determine when a given tree loses its leaves. Are they other trees of the same species nearby that lose their leaves at a different time? If not, it is probably just a type of tree that loses its leaves earlier than other types of tree in your area. --Tango (talk) 01:46, 13 September 2009 (UTC)

The "schedule" is from observing all of the other trees in the neighborhood. The tree is a maple with lots of others nearby which still have green leaves (for a few more weeks anyway) but this particular tree has already lost color and most of its leaves. There are no trees around here that drop their leaves at the end of August - only this one! The reason for asking the question is that this has been "bothering" me for a few years now. BTW, the phenomenon seems to be most intense at the elevation of the top of the utility pole and less so above and below that elevation. hydnjo (talk) 02:09, 13 September 2009 (UTC)

This sounds like some sort of tree disease rather than "aura" (by the way, you might be interested in Tesla's work). Of what species is the tree? Many diseases cause premature loss of leaves, often from the top down. Intelligentsium 02:28, 13 September 2009 (UTC)

You may have missed it - the OP said it was a maple (admittedly, that is a genus, not a species, I don't know if the OP has the expertise necessary to identify the particular species of maple). --Tango (talk) 02:40, 13 September 2009 (UTC)

(after e/c, mostly what Intel said just above) To test the proposed phenomenon, you would either have to cut down the utility pole and watch future year activity, or locate similarly equipped utility poles in your area and observe the surrounding flora. The metal box sounds like a pretty standard distribution box. I'd be looking first for other sources of stress on the particular tree. How well does the ground around it accomodate its root system? For me, that's the single largest source of "early-turning" stress on trees. Also, what do the dropped leaves look like? Do they have evidence of fungus or insect parasite damage? There are lots of reasons that one particular tree will suffer more stress than others, Mithra knows that I suffered much watching some of the trees I planted myself fail to thrive while others did fine. You could always sneak over at night and pump a bit of Miracle-Gro into the root system - in spring / very early summer... Franamax (talk) 02:37, 13 September 2009 (UTC)

Also, it's possible that your tree is just a natural variant, and possibly a successful one. How well does it thrive, and what is it's output of seed? End-of-season activity for a tree is a balance between storing that last bit of sugar down into the root system and the risk of losing valuable organic compounds in an early frost. Maybe this particular tree is just an outlier exploring a particular evolutionary strategy. You will need to enlist your children to check on how well it does for the next hundred years or so. Franamax (talk) 02:50, 13 September 2009 (UTC)

Oh, thanks Franamax! A bit of context: I'm sitting on my deck with my wife enjoying the afternoon sun and have noticed this happening for several years now. My wife who thinks that I know everything asked me "why does this happen to that tree every year?" So, I take another sip and tell her that I'll get back to her on that one and change the subject. The proximity of the pole and the tree piqued my curiosity an so I probably made an unwarranted connection that might support my infallibility (with support from y'all). Oh well - maybe a tinfoil shield... awh screw it! hydnjo (talk) 02:56, 13 September 2009 (UTC)

Be very careful. I have reliable evidence that certain tinfoil manufacturers are in fact front companies for the NSA. In fact I'll tell you who they are: Al&cg%, RusQvW59* and Chni7&dfR43. I hope that information is of help. Also, it's often useful to punch holes in the tinfoil to allow breathing, although the CIA controls most of the pokey-instrument makers. Sigh. Franamax (talk) 03:10, 13 September 2009 (UTC)

OK - I'll walk (drive) around the neighborhood to see if my "pole/tree" connection is unique. Stay tuned :( hydnjo (talk) 03:09, 13 September 2009 (UTC)

Actually, I was suggesting first to look for unique conditions associated with the particular tree (other than utility poles). That would involve walking over to inspect the particular environment of that one unique living thing, and the dropped leaves which may give clues to its' own circumstances. But you can look for wider correlations first if you want! Another thing to check is whether your tree has bugs in the bark or excessive cracking of the bark that might expose it to excessive stress. Franamax (talk) 03:19, 13 September 2009 (UTC)

And apropos of recent off-desk discussions, this is an area where I couldn't pull out any great source to help, but I do feel that my own speculations and personal experience are helpful contributions worthy of inclusion here. Franamax (talk) 03:19, 13 September 2009 (UTC)

I remember seeing a while ago that there was some evidence the branches of trees very close to high power lines grow slightly faster and have more leaves, but that's the exact opposite of what the OP is talking about if anything. The lines near your house would have undetectable effects. Dmcq (talk) 07:40, 13 September 2009 (UTC)

A random wild guess: the magnetic field generated by the powerline affects pollinators and seed dispersers. John Riemann Soong (talk) 14:41, 13 September 2009 (UTC)

So this tree has this condition - and there happens to be a power pole nearby - but correlation does not imply causation. There could be something in the soil beneath the roots of the tree that causes this - a greater or lesser degree of soil nutrients perhaps. Or perhaps it's in a more exposed position than the other trees. Maybe the tree has some kind of infection. Perhaps utility pole is a wooden one that's coated with some kind of wood preservative that leaches into the soil in wetter weather towards the end of summer? Perhaps the tree is a lot older (or a lot younger) than the others in the area? Maybe it simply has some different genetic makeup than the others? You can come up with dozens and dozens of possible reasons - but until you do some actual experiments - you really can't come to any really solid conclusions. What you CERTAINLY can't do is to start assuming that some pseudo-scientific clap-trap about auras has anything to do with it. Occam's razor says that this is the least likely explanation - so it should be the last one to consider after you've ruled out every other cause. It's up there with "Maybe God doesn't love this tree as much as the others?" SteveBaker (talk) 17:17, 13 September 2009 (UTC)

Clearly, this is a medical question requiring diagnosis and treatment. As you should know, with requests for medical advice you are barking up the wrong tree on this RD. URGENTLY suggest to the prematurely denuded maple in question to see a tree surgeon ASAP! I believe there is one just 100 metres down the road form the power pole. --Cookatoo.ergo.ZooM (talk) 20:11, 13 September 2009 (UTC)

Forests Vrs. Deserts

Why is it that some regions are deserts while others are tropical rain forests? I understand that rain shadow is a consideration, but I am guessing there is a lot more to ecological development than just mountain placement.Nkot (talk) 02:52, 13 September 2009 (UTC)

I think that ecological is an afterthought to precipitation. I would imagine in a hand-wavey sort of way that something in atmospheric circulation would be important in regulating some deserts (e.g., the Sahara), while others (e.g., Atacama) would be a rain shadow. Arctic deserts might be because of the relationship between temperature and precipitation (harder to get much precip in very cold places). But hopefully someone who knows more than me responds. Awickert (talk) 02:58, 13 September 2009 (UTC)

The most important factor is atmospheric circulation, particularly the Hadley cell mechanism, which produces rising air near the equator and falling air in the subtropics. It causes the air over the tropics to be mainly moist, producing wet environments, and the air over the subtropics to be dry, producing mainly deserts and semideserts. Looie496 (talk) 03:10, 13 September 2009 (UTC)

The great deserts of the world typically have a large land mass between them and the potential moisture toward the equator. The Sahara and the Gobi are obvious examples. In the USA, you can practically draw a straight line north, tangent to the west edge of the Gulf of Mexico, as a separator between the moist and the dry areas of the USA. Baseball Bugs ^{What's up, Doc?} carrots 03:18, 13 September 2009 (UTC)

And yet none of what I've seen yet here seems to explain the vast expanse of the boreal forest, which occurs on large continental land masses. Unfortunately I have no good explanation for that either. :( Franamax (talk) 03:27, 13 September 2009 (UTC)

Franamax, Looie expained it above. It is due to atmospheric planetary circulation. The southward moving airmass from the polar cell joins the northward moving airmass from the mid-latitude cell around 60 degrees and the general upwards motion caused by that leads to generous rain fall. Dauto (talk) 06:55, 13 September 2009 (UTC)

See also desertification. --Sean 13:54, 13 September 2009 (UTC)

Well ecology can affect climate too, what with transpiration, Rnet and whatnot. Forests retain topsoil... water doesn't evaporate as quickly, and in a controlled manner (through transpiration, controlled by stomata). Destroy the forest, erosion destroys the topsoil, and suddenly the thing does become a desert even though the area was once very rainy. John Riemann Soong (talk) 14:37, 13 September 2009 (UTC)

Becauae there's land, the ideal Hadley cell is distorted so there's no desert on the east sides of continents. What J. R. Soong said is already happening in cities in Indonesia or Malaysia or something. The city is getting dry heat waves (which were almost unheard of 20 years ago). The rainforest's existance itself produces it's own existance. Sagittarian Milky Way (talk) 16:00, 13 September 2009 (UTC)

Why is Somalia the only place on the equator with desert (!)? And why does the Peru Current penetrate so far? It brings bone-chilling water more equatorward than any other place in the world. Sagittarian Milky Way (talk) 16:00, 13 September 2009 (UTC)

The Humboldt Current (what you call the Peru Current) brings cold water up from the depths of the ocean near Antarctica, playing an important role in the global climate system. A displacement of this current, which occurs when trade winds weaken and warm water starts blowing westward toward South America thereby cutting off the upwelling of cold water, causes the devastating El Niño. Also, the Atacama Desert extends approximately to the equator due to the effects of this current, the Desert of Somalia occupies some of Kenya at the equator, and depending on your definition, the Andes mountains and highlands of Africa could count as desert as well. Also, there are some studies that suggest global warming could result in the Amazon Rainforest turning into desert (which is on the Equator), thereby turning the American Midwest into desert as well. Much of this connection also has to do with Atmospheric wind patterns. Wind blowing off the Sahara Desert produces the Saharan Air Layer. ~AH1^(TCU) 20:20, 13 September 2009 (UTC)

• You're right. (Wikipedia's Koppen map makes my book's look like a crude drawing). The high altitude thing is pretty much a given and the low precipitation in alpine climates are also characteristic of tundra, some ocean and icecap, but it's more useful to have those seperate terms.

• Yes, I know El Niño's bad. Even though there's one now, [www.wunderground.com/tropical] shows unswimmable SSTs at latitudes usually considered immune to coldness (near sea level anyway). South America sticking out further toward the poles than any other eastern boundary current bordering landmass probably helps. Sagittarian Milky Way (talk) 18:39, 16 September 2009 (UTC)

Virtual Work (again!)

This is basically a follow up to my original question here. I just had my exam on the said topic, and I really have solved sums involving indeterminate systems using the principle of Virtual Work, albeit not really understanding the concept behind it. For example, consider this book, our textbook for the course, which has a few worked out examples on the topic. Figure 10.8 shows a system with two pin joints, ie, which is indeterminate. However, it is solved, along with a few other such systems... I need somebody to tell me if I've grossly misunderstood something, or if Virtual Work really is that powerful... Rkr1991 ^{(Wanna chat?)} 07:29, 13 September 2009 (UTC)

You could find all the forces just by treating each rigid piece separately, requiring that the net force and net torque on each piece is zero, but that's sort of a pain. I'm not sure if this is the source of the confusion, but the angles involved here are fixed, so the joints don't add a degree of freedom. In general if a method for solving the mechanics of a system is fully derived from Newtonian mechanics then it's impossible for it to tell you anything more than Newtonian mechanics does. Rckrone (talk) 17:03, 13 September 2009 (UTC)

The pin joint gives two reaction forces. Two pin joints give four. With only three equations (in 2D), how do you solve that usong Newton's Laws ??Rkr1991 ^{(Wanna chat?)} 07:30, 14 September 2009 (UTC)

There are a bunch of ways to formulate the equations so I don't know specifically which ones you're referring to, but here's how I would do it with forces.

For rod B, call the magnitudes of the components of the force acting on the bottom end B_1x and B_1y and the magnitudes of the components acting on the top end B_2x and B_2y, and use the same labeling for rod A. Since the torque and net force on each rod are zero, A_2x/A_2y = B_2x/B_2y = tanθ. A_2x = B_2x by Newton's third law, and P = A_2y + B_2y. From these relations, B_2y = P/2, so B_2x = (P/2)tanθ. Since net force on B is zero, B_1x = B_2x = (P/2)tanθ. Rckrone (talk) 20:31, 14 September 2009 (UTC)

Beer traps

How to beer traps work? This web page suggests what I had assumed, which is that the slugs become intoxicated, so they drown, but I recently bought some new traps which came with a yeast sachet which you are supposed to mix water as bait. Obviously they are attracted by the yeasty smell but I wouldn't have expected them to be poisoned by the yeast, or to willingly and soberly drown in the solution.--Shantavira|^{feed me} 08:13, 13 September 2009 (UTC)

Maybe the yeast satchet contains glucose so when you combine it with water it's sufficiently fermented to intoxicate the slugs? Are you sure the slugs don't just get stuck in the traps? Nil Einne (talk) 11:35, 13 September 2009 (UTC)

They drown in any liquid! Water works fine as a slug trap, but you need some smell of decay (beer, yeast etc) to atract the slugs. I don't think they are intelligent enough to avoid drowning if the attraction of food is strong enough. Dbfirs 11:47, 13 September 2009 (UTC)

If too much of this kind of thing is done, it could result in artificial selection of those slugs that are smart enough to avoid drowning. Assuming there are any. Baseball Bugs ^{What's up, Doc?} carrots 11:52, 13 September 2009 (UTC)

Evolution is efficient but lazy. It's more likely to drive an aversion for beer than the development of intelligence (maybe this explains my mother in law?) Anyway, the mechanism of attraction this guy gives is questionable at best. First, he says it's the yeast smell that attracts the snails, though most commercial brews are filtered to remove any yeast that may offend the literal consumer with a clouded beer. Second he says that lagers don't work because they're fermented with sugar. I'm an avid brewer, and without going into detailed explanation, I'll just say "bullshit". Ales (as opposed to lagers), are more flavorful due to the esters (and various other chemicals) produced at higher fermentation temperatures (around 70F as opposed to 55F), and often (but not always) have more residual sugars as well. This is probably what attracts our little friends. – ClockworkSoul 12:58, 13 September 2009 (UTC)

"Smart enough" in a broad sense, i.e. inclined to avoid it for whatever reason, as per your explanation. Unintended artificial selection is a major consequential risk of trying to wipe out populations of critters that can evolve quickly, such as insects and microbes. Practically speaking, a few beer traps wouldn't have such impact - except maybe locally. Baseball Bugs ^{What's up, Doc?} carrots 13:07, 13 September 2009 (UTC)

I really doubt that the critters get "drunk" before they drown - they are air breathers - I'm pretty sure they just drown. SteveBaker (talk) 17:04, 13 September 2009 (UTC)

Literally Original Research: I once divided an aquarium in half, and in half I placed 12 slugs and a dish of beer. In the other half, I placed 12 slugs with a dish of the same volume of water. There was mostly dry area in each half, and no other food. Slugs were randomly assigned to conditions. The number of slugs per condition was recorded over time. In the beer half, as in the water half, slugs crawled into the liquid, stayed a while, and crawled out seemingly none the worse. The number of living slugs in each half decreased as time passed for several days. There was no apparent difference in the survival rates, with 1 or 2 alive in each half at the end of data collection. The lucky survivors were released.The important observation is that the beer dish did not fill up with slugs who died the first time they crawled into it. Edison (talk) 20:18, 13 September 2009 (UTC)

Was there any difference at all in their behaviour? Frequency of visits to the liquids, duration of visits etc. Martlet1215 (talk) 21:15, 13 September 2009 (UTC)

Or state of inebriation? Baseball Bugs ^{What's up, Doc?} carrots 07:25, 14 September 2009 (UTC)

Slugs are hermaphrodites - after a few beers EVERYONE starts to look gorgeous! SteveBaker (talk) 17:15, 14 September 2009 (UTC)

growth of a cell membrane

How exactly does a cell grow? Okay sure it metabolises, takes in nutrients, synthesises membrane proteins and whatnot and some enzymes are probably producing those fun phospholipids, but how do you add those units to the existing membrane without disrupting it? Do phospholipid molecules and proteins just migrate there and wait for a small "hole" to open up? (In a sort of weird cell bio equivalent of a vacancy defect?) Does an enzyme make a hole in a membrane and then some other helper enzyme insert the phospholipid/protein into the membrane?

Are their enzymes that make temporary holes (not permanent channels) that allow say, enzymes to pass through? How do you catalyse the formation of an extracellular matrix outside of the cytosol? John Riemann Soong (talk) 14:30, 13 September 2009 (UTC)

There are very complex mechanisms for cells to insert proteins/lipids into the membrane and to deliver components into the extracellular matrix. Mostly it occurs through fusion of vesicles containing lipids and proteins. Have a look at endocytosis and exocytosis. You could also read secretory pathway. Of course, the next question you'll want to ask is "how are vesicles formed?" For that, you'll want to read vesicle (Biology), endoplasmic reticulum, and Golgi apparatus. Ok, that should be a good start. --- Medical geneticist (talk) 17:26, 13 September 2009 (UTC)

Okay, I have some vague introductory conception of those from ap bio... well admittedly I guess proteins / phospholipids would be transported along vesicles or via the cytoskeleton. How does vesicle fusion occur? On the macroscopic scale, don't two bubbles normally repel each other? John Riemann Soong (talk) 17:35, 13 September 2009 (UTC)

See clathrin and dynamin for details on how vesicles are "pinched" off of a membrane. See SNARE (protein) for details on vesicle fusion. There are still details to be ironed out, but that's the basics of it. --- Medical geneticist (talk) 02:13, 15 September 2009 (UTC)

Is this correct?

Can you please check over this work. It took me a very long time to re-type everything again, but I know there are a lot of smart people on WP. The bullet which speaks about dissolving is about solubility in water. After seeing the facts stated below, what would the answer to this question be : 1. How does the range in properties of salts compare molecular compounds? Would somebody please put a talkback on my talk, when this has been answered. warrior4321 15:40, 13 September 2009 (UTC)

Steel

• solid
• gray/silver
• conductive
• does not dissolve
• no crystal structure
• metallic bond

Gel

• liquid
• blue
• not conductive
• dissolves
• conductive when solution
• no crystal strcture
• polar covalent bond

Copper

• solid
• red/copper
• conductive
• does not dissolve
• no crystal structure
• metallic bond

Wood

• solid
• brown
• not conductive
• does not dissolve
• no crystal structure
• polar covalent

Marble (calcium carbonate, not toy marble)

• solid
• brown
• gray/white
• not conductive
• does not dissolve
• has a crystal structure
• ionic bond

Sugar

• solid
• white
• not conductive
• dissolves
• crystal structure
• ionic bond

Salt (sodium chlroide NaCl) (not ionic salts)

• solid
• white
• not conductive
• dissolves
• crystal structure
• ionic bond

Copper (II) Sulfate

• solid
• blue
• not conductive
• dissolves
• conductive in a solution
• crystal structure
• polar covalent bond

Air (Nitrogen)

• gas
• transparent
• not conductive
• does not dissolve
• no crystal structure
• polar covalent bond

All correct except:

Steel has a crystal structure.

A gel is not a liquid or a solid - they're in between. Also a lot of intermolecular bonds in a gel. Also might not be conductive in solution - it depends on the gel.

Copper (same as steel) - has a crystal structure.

Wood - lots of colours including brown, ebony, beech etc , also has a composite (material) structure if that matters.

Marble - yes - but also polar covalent bond in carbonate.

Sugar sucrose - NOT ionic. bonds are covalent, plus intermolecular forces between the molecules - hydrogen bonding.

Salt - all ok except what does "not ionic salts mean?" - NaCl only?

Copper Sulphate - polar covalent bonds and ionic bonds.

Nitrogen - the covalent bond is non-polar. Dissolves a very small amount in water.

Also you missed conductivity in water for salt, sugar

As for your question - I suggest make a table of list of properties in two columns, with mostly covalent in one column, and mostly ionic in the other and compare. However it's already half done for you at Ionic compound77.86.47.174 (talk) 17:33, 13 September 2009 (UTC)

The properties you described for copper(II) sulfate are for the hydrated version. I'm not sure whether it's asking about that or about the anhydrous version. Also nitrogen dissolves a little. I don't know if that counts or not. Rckrone (talk) 17:28, 13 September 2009 (UTC)

Many crystals, especially ionic crystals, conduct electricity when they dissolve. That's actually because they're good charge carriers. (They're ions). They're just not very mobile in the solid state. If you melt salt, it becomes highly conductive. (The reason why solid metal can be conductive is because of this thing that gets formed called a valence band.)

Also, I think you're wrongly assuming that crystals have to be ionic. Polar substances form crystals (and in fact, so do heavy nonpolar substances). Look at all those OH groups on sugar, plus some hydrogen bond acceptors (the ethoxy group). As you can see, ethanol has a very low melting point, only because it forms a fragile crystal structure that can be broken easily at higher temperatures. John Riemann Soong (talk) 19:51, 14 September 2009 (UTC)

In addition, the majority of wood is made of lignin. Look at all that cross-linking! John Riemann Soong (talk) 04:42, 15 September 2009 (UTC)

Real time (or time based) public transport information on maps

Time Based maps of Public Transport has 2 links to time based public transport maps - that is it can tell you right now where many transport units, such as buses or trains, are actually or scheduled to be on a map.

Are there any other websites like that - and even websites which have animations about where a public transport unit has been in the past? 118.208.97.169 (talk) 16:23, 13 September 2009 (UTC)

Yes, there are loads but I don't think the urls are easily available. My flatmate is a bus driver and he tells me that National Express West Midlands has a control room where they can see the location of all their buses. He doesn't know the wesite address but it is likely to be accessible. www.livebus.org has something similar to what you want.--Shantavira|^{feed me} 16:43, 13 September 2009 (UTC)

If ferry boats count there are a number of real-time GPS-based maps of the Washington State Ferry vessels here. For example, this page shows the current locations of the two ferries on the Edmonds-Kingston run. Pfly (talk) 07:32, 14 September 2009 (UTC)

Thanks for that. I tried looking at livebus but I couldn't work out the interface. Also the Midlands one I did a google search and went to the web page but couldn't see anything. I'm mostly looking at animated ones where you can see it move so that counts out the last one as it's a static display. —Preceding unsigned comment added by 118.208.97.169 (talk) 16:03, 15 September 2009 (UTC)

I've found this link mashups directory. Go there and click on real time. I think those are most of em. But I would love to see more. 118.208.97.169 (talk) 17:36, 17 September 2009 (UTC)

Time freezing

One of Don Rosa's pseudo-scientific Donald Duck comics involves Gyro Gearloose's new invention, which freezes time everywhere outside a small sphere outside the point where the invention was activated, and on further request, reactivates time everywhere. The Beagle Boys steal the invention and use it to steal Scrooge McDuck's money. Now, for the sake of suspension of disbelief, let's ignore that it's just a faerytale and such an invention can never be invented in real life. The point of my question is, wouldn't such an invention also freeze the air steadily in place outside the sphere of activation? What happens if someone runs against air that refuses to so much as budge a molecule? Will it become an impenetrable wall, will the air molecules rip through the intruder's body, or what? JIP | Talk 18:32, 13 September 2009 (UTC)

As you say, it's a fairytale. We can't ignore that. It is impossible, so what happens will be whatever the person making it up says will happen. To say what would happen we would have to know how it was done, which we can't know because it can't be done. --Tango (talk) 18:43, 13 September 2009 (UTC)

Well that answer was entirely worthless. What I only wanted to know is, if there somehow is a mass of air that just won't move, not even a single molecule, can such a mass of air be penetrated at all? It's the same bloody thing every time I ask about a scientific detail about a fictional story. The first reply is always "it's fictional, so anything what-so-bloody-ever goes". JIP | Talk 18:50, 13 September 2009 (UTC)

It wasn't worthless at all, in fact it was right on the money. You're asking us to fill in the gaps in a fictional and impossible scenario posed by someone else's imagination, so it's not absolutely answerable by anyone except (possibly) its author. I could see at least a couple of scenarios, and there could be dozens more: (1) All the molecules in the universe could be frozen in place, and unmovable, in which case the answer obviously is no, nothing would budge, including the air molecules, in which case you would be stuck inside that "bubble" until you turned the machine off. (2) They might be frozen in place, but movable. For example, a frozen person (as per that Twilight Zone episode and similar fanciful scenarios) might still be able to be nudged aside. But those are large objects. As noted by an editor below, the writer would have to answer the question of what would happen at the molecular level. Even if you could push the air molecules aside, what would happen if you inhaled them? Would they regain their motion because they're in your "sphere"? Or would they remain motionless, and suffocate you? Baseball Bugs ^{What's up, Doc?} carrots 19:35, 13 September 2009 (UTC)

Like, say, Maxwell's demon ... fictional and impossible. Nobody could extrapolate any useful information from conjectures about that. 81.131.38.252 (talk) 19:49, 13 September 2009 (UTC)

There is a difference between a well-defined thought experiment and a work of fiction. Maxwell's demon explains precisely what happens, it just has one simple (but impossible) assumption - that you can have something that lets things through or not depending on their speed. --Tango (talk) 20:00, 13 September 2009 (UTC)

I would guess that the 'frozen time air' would cease movement as long as the machine was in operation, but a non 'time frozen agent' would be able to brush the air aside - like walking against the wind - however this would technically leave a vacuum behind them, and a region of highly compressed air in the region of the envolope of motion. Obviously if the 'frozen time' region can not be altered the machine is worthless..

This would mean that once time was restarted there would be loud bang, as the air pressure differences created by motion through the air re-organised to equalise pressure.

There would be other problems such as breathing - ie does time start again once the air is inside the body - if so where - can the oxgygen be allowed to diffuse into the lungs - technically this requires time to be in motion..77.86.47.174 (talk) 19:15, 13 September 2009 (UTC)

This is a much better answer, thanks. AFAIK, "time frozen" air means air that literally can't be moved, so it can't even be brushed aside. Is air dense enough so that if it literally can't move, not even a single molecule, it's impenetrable? I also understand the breathing problem. If air can't move, it can't enter someone's lungs either, so once the person leaves the sphere of the device's initial activation, he/she will eventually suffocate. JIP | Talk 19:23, 13 September 2009 (UTC)

How is that answer better? The answer is as fictional and nonsensical as the question. Movement means a change of position over time, you can't have movement if you don't have a passage of time, it makes no sense. --Tango (talk) 19:28, 13 September 2009 (UTC)

Tango is right. There can't be a mass of air (in the gaseous state) that won't move; that's not permitted by the laws of physics, so there's no sense in asking what the laws of physics say about that situation. All that 77.86.47.174 did was invent further fantasy on top of Don Rosa's. -- BenRG (talk) 19:36, 13 September 2009 (UTC)

The more "practical" scenario, the one seemingly posed by The Twilight Zone and by Gyro Gearloose and some recent film on the subject whose name escapes me, is for large objects to freeze while air continues to flow freely so that you don't suffocate. Another factor: The world would probably have to keep turning also. In either the book or film version of H.G. Wells' The Man Who Could Work Miracles, he wished the world to stop. It did, and then everything and everyone went flying off of it. At that point he asked for his last wish - to put everything back and take his power away. Baseball Bugs ^{What's up, Doc?} carrots 19:40, 13 September 2009 (UTC)

The physics paradox posed by this idea was addressed, at least in part, by a Star Trek episode in which certain humans were living at an "accelerated" pace, such that the humans around them appeared to be frozen but in fact were moving, only extremely slowly by their reckoning, and were unaware of those who were living at the accelerated pace because they moved too fast, by our reckoning, to register on the senses. That approach could have a much better chance of success than literally freezing everything in place. It also sounds likely to be impossible, but not necessarily absolutely impossible. Baseball Bugs ^{What's up, Doc?} carrots 19:49, 13 September 2009 (UTC)

I frequently dream about time-stopping devices. Besides the problem of breathing, there are also questions like: do electrons stop holding things together? (What are things like to touch?) Does gravity stop happening? Does light stop moving? And a particularly interesting one, I think, is: when time is restarted again, where has the information about the momentum of objects been stored, so that they can continue to move as they were moving before? Which is also a question that applies to ordinary life. Maybe it has an obvious answer that I don't know about. 81.131.38.252 (talk) 19:44, 13 September 2009 (UTC)

The basic problem with these scenarios is the same one that arises with backwards time travel: They just plain don't make sense, because they postulate unworkable paradoxes. "When you start with invalid assumptions, you're liable to get interesting results." An even more practical (well, not practical, but theoretically possible) approach would be not to literally stop time, but simply to render everyone unconscious (i.e. asleep) for some stretch of time. Baseball Bugs ^{What's up, Doc?} carrots 19:51, 13 September 2009 (UTC)

Yes, that would be much less interesting. 81.131.38.252 (talk) 19:57, 13 September 2009 (UTC)

The possible is often much less "interesting" than is the imaginary. It's a nice fantasy, to imagine backwards time travel or putting a stopwatch on time for everyone except yourself (Groundhog Day is another variant on these ideas). You can fantasize about forward time travel, but that's much less "interesting" since it's what we're doing anyway. But it's also much more interesting, if you want to actually do something, as opposed to fantasizing about something that's impossible. Baseball Bugs ^{What's up, Doc?} carrots 20:14, 13 September 2009 (UTC)

The premise may or may not be interesting, but how interesting the resultant story is is entirely in the hands of the author. A world where everyone has suddenly fallen asleep? You could make a great story out of that. Vimescarrot (talk) 20:16, 13 September 2009 (UTC)

As, for example, Nicholson Baker did in The Firmata. Also, who else here remembers that old Australian TV show The Magic Boomerang? 87.81.230.195 (talk) 20:25, 13 September 2009 (UTC)

That show was about stopping time, which is much less interesting than a bunch of people falling asleep, and so must be very dull indeed. Andy Warhol's Sleep is a superior work. 81.131.38.252 (talk) 20:49, 13 September 2009 (UTC)

The OP has received extensive answers. It would be appropriate for the OP who is supposed to be an admin here to reconsider the unpleasant tone of their 2nd post above. Cuddlyable3 (talk) 22:54, 13 September 2009 (UTC)

It truly is a meaningless question - the laws of physics are tightly intertwined - you can't yank one of them out, rewrite it and wedge it back in again without creating meaningless contradictions in the other laws. Hence the question is meaningless - as are ALL of the above answers that attempt to make sense of it. Our OP should realise that the questions he/she "likes" are in no way better answers than "The universe explodes" or "Everything turns bright pink - but otherwise behaves normally"...it's a meaningless question. Without meaning in the question, the "answers" have no meaning. You might as well make up any random fiction that makes you happy - really. So if it makes you happy for me to say "no, the sphere of time wouldn't be able to move" - then fine - take away that answer and enjoy the thought of it - but don't think for one moment that there is any rational scientific truth behind that statement. The amount and quality of meaning is PRECISELY the same as if I said "yes, the time frozen air molecules would just be wafted gently away" - or "The time-frozen atoms would be forced to undergo a fusion reaction with the moving molecules and the whole thing would blow up like a fission bomb" - or "14 green aardvarks would materialise from thin air and ask you nicely if you would please turn off that damned annoying time gizmo."...all of those are equally good answers if the laws of physics are all completely turned around compared to reality. So - yeah - it's a meaningless question. Sorry if that doesn't fit into your world-view. SteveBaker (talk) 23:21, 13 September 2009 (UTC)

What we're getting into here is some interesting meta-issues about the proper way to answer counterfactual questions. I learned a lot about the difficulties they raise from Douglas Hofstadter's book "Goedel, Escher, Bach" -- but unfortunately I don't think I could reduce it to a summary. The gist of the problem is that counterfactuals are senseless from a purely logical point of view, yet somehow we humans frequently manage to extract information from them. Looie496 (talk) 23:50, 13 September 2009 (UTC)

Indeed. The problem is with the degree and nature of the counter-factual. If I were to ask "If my car could go 1 mph faster than it really can - what would it's gas consumption be?" - then no really fundamental laws of physics are violated - and perhaps some sort of a reasonable stab at an answer could be found. But if I ask "What would the volume of a one meter sphere be if Pi was exactly 3 ?" - then absolutely no reasonable answer answer is possible. The universe would simply not function in such a situation - we don't know whether there would be "spheres" or the concept of "volume" at all - and if there was, what the equation for their volumes might be is impossible to fathom. The question we're given here (arguably) falls between those two extremes...but closer to the Pi=3 end of the scale IMHO. SteveBaker (talk) 01:40, 14 September 2009 (UTC)

This is well beyond the accuracy (or is it precision?) of Pi somehow being exactly 3. It's more on the order of "what would happen if a circle's diameter and circumference were identical?" That can only happen if the universe shrinks down to a singularity - which is what I was thinking might happen with gyro gearloose's instrument. All molecular motion ceases. The temperature is not "near" absolute zero it's exactly at absolute zero. And maybe, just maybe, everything collapses into a singularity. Then we start over again, with a big bang. Baseball Bugs ^{What's up, Doc?} carrots 02:01, 14 September 2009 (UTC)

Obviously the volume would be 4 cubic meters. Har har har harumph. (I did not miss the point, I'm making a meta-point about the way the human mind works.) Looie496 (talk) 02:22, 14 September 2009 (UTC)

So the universe might shrink down to a cube. That would be interesting. I knew this discussion seemed vaguely deja vu.[1] Baseball Bugs ^{What's up, Doc?} carrots 07:35, 14 September 2009 (UTC)

Okay, ignoring the context that's getting people het up, here's how I'd go about thinking about it. What would happen if you try to push something with the area of the molecules in a layer of air, that was firmly fixed in place?

First, what is that area? Well the number density of dry air is about 2.5*10²⁵ m^-3. Assuming a Van der Waals radius of about 1.6*10^-10m as air is mostly Nitrogen, consider a layer of air one VdW radius thick* and equal to the cross sectional area of a human. For an order of magnitude estimate, let's say 1m². Thus we get the number of molecules N = n * V ~ 2.5*10²⁵ * 1.6*10^-10 ~ 4*10¹⁵. The area of these, again using VdW radii, would be A ~ N * π r². This comes out to A ~ 3*10^-4 m².

A sensible next step is to compare this number to the area of a bed of nails. Most of the articles I find are woefully lacking in numbers, but maybe someone else knows this?

* This is a major simplification. Since skin bends, it seems reasonable to suggest that the relevant layer could be thicker. AlmostReadytoFly (talk) 09:57, 14 September 2009 (UTC)

There is nothing wrong with your internet. Do not attempt to adjust the picture. We are controlling packet protocol. If we wish to make the font larger, we will bring in the <big> tags. If we wish to make it smaller, we will tune it to a <small>whisper</small>. We will control the <hr>. We will control the scroll-bar. We can source the <image>, make it <blink>. We can change the link to a soft redirect or sharpen it to a hard link. For the next hour, sit quietly and we will control all that you see and hear. We repeat: there is nothing wrong with your internet. You are about to participate in a great adventure. You are about to experience the awe and mystery which reaches from the inner mind to... The Outer RefDesk. SteveBaker (talk) 17:11, 14 September 2009 (UTC)

I release the following tale under GFDL.

It was a dark and stormy night. Working alone in the physics laboratory of the University the Professor peered through the microscope at the tiny green crystal that had been brought back from the crashed UFO discovered on the Moon. How they had laughed at his theories, those professors who thought they knew all there was to know about the semiconductor crystals that make transistors work. But now he would show them all. Now he would show those know-it-alls who had the temerity to reject his original research from Wikididdlypedia. He had waited for this moment, waited for a day when the University would be empty, waited for a day when the giant megafusion project would be down for maintenance so that he could draw power unnoticed from its mighty banks of polychromatic condensifiers. Taking a deep breath, he moved his radar solenoid lever a notch forward. An almost imperceptible glow arose in the crystal. Yes yes! he gasped, this was the time dislocation that his calculations had predicted! Those fools. Those moribund simpletons. Of course they had analysed the crystal looking for any tiny dislocation in the crystal lattice, such as could be found in a silicon crystal to which has been added a tiny impurity that would make it a semiconductor. And what had they found? Why, nothing. Indeed the crystal had an unfamiliar lattice structure but nothing about it supported the idea that the unknown designers of the crashed UFO had used transistor technology. But what of his theory that the lattice of the alien crystal contained a time dislocation? What if he took this theory further to say that the crystal could be used to amplify its time dislocation? That was no less logical than saying a tiny transistor can control a huge machine, if enough power is provided. He advanced the solenoid lever another notch. The crystal began to sparkle with tiny lightning flashes inside. In fact the flashes began a millisecond before the lever reached its notch. This was the time dislocation in action, thrusting the crystal lattice into the future when the solenoid power would be increased. Impatiently he swung the lever to maximum. The ceiling lights in the laboratory dimmed as megagigawatts of power were directed into the time crystal. An outside observer would have heard a muffled implosion as air rushed in to the spherical vacuum that arose at the instant that the Professor, his apparatus and the laboratory ceased to exist. Everything in a sphere of pi squared yards radius from the crystal had departed from normal time. This was how the civilisation of Atlantis had vanished in ancient time. Among their inhabitants had been alchemists who in their search for the philosopher's stone had stumbled on the time crystal. The UFO that crashed on the Moon had carried the last refugees from Atlantis. The Professor lived. Inside the sphere nothing seemed changed, except that the wind and rain of the storm outside were suddenly silent. The surface of the sphere was a transparent, slightly cloudy, membrane that marked the boundary of the time dislocation that had spread from the time crystal. To the Professor sitting inside the sphere the outside world seemed frozen in time. Even the raindrops hung like beads in the air. Nothing moved, nothing changed and the Sun would not rise. THe spaces inside and outside the sphere were universes apart; in each the laws of physics were obeyed but there could be no communication between them. Hardly believing the magnitude of his triumph the Professor turned to the portable radio he had brought with him. Normally there should be a multitude of broadcasting stations to hear. He brought the volume to maximum and tuned across the waveband. There was nothing to hear but the hiss of the radio's own circuits. The Professor laughed as he thought of how his successful experiment would be his triumph over his sceptical peers and not least an article that Wikididdlypedia would not dare refuse. But wait, could there be an Internet

Vernor Vinge's novels "The Peace War" and "Marooned in Real Time" are written around the notion of a gadget that makes spherical fields for which time stops inside. That includes stuff like air molecules and in those stories the OP's question is resolved by the observation that inside the field, nothing moves. 70.90.174.101 (talk) 04:25, 15 September 2009 (UTC)

For a taste of a world where people take Donald Duck physics literally, here is a thread where people debate with great sincerity how God managed to put a time-freeze on the Sun that one time. --Sean 08:26, 15 September 2009 (UTC)

Mosquitoes

Hey there! Would like to know what role do mosquitoes play in the food web.If anyone could help me out.Thanks. --Lightfreak (talk) 19:55, 13 September 2009 (UTC)

Mosquitoes eat nectar, etc. and occasionally blood. They are eaten by the various things mentioned here. --Tango (talk) 20:03, 13 September 2009 (UTC)

Insects in general are an important part of the food chain. Baseball Bugs ^{What's up, Doc?} carrots 20:11, 13 September 2009 (UTC)

Mosquito larvae are a very important food source for some types of fish, especially trout. That's the only important role I know. Looie496 (talk) 23:52, 13 September 2009 (UTC)

A citation is needed for that. Mosquito larvae are predominantly found in stagnant or still water, trout require moving well oxygenated water. Trout eat various insects and their larvae found in cold-water environments. 86.4.181.14 (talk) 06:18, 14 September 2009 (UTC)

Mosquito larvae indeed are one of the most important links in the aquatic food chain. They consume microscopic algae (and generally all sorts of microscopic gunk present in the water) and are consumed by fish, aquatic invertebrates, and some wading birds. Adult mosquitoes are consumed by predatory insects (mostly by dragonflies AFAIK), spiders, birds, etc., but the larvae are indeed more abundant and more important in the food-chain. Adult mosquitoes are also important pollinators and important disease vectors. They also play a significant role in the biomagnification of pollutants and pesticides. --Dr Dima (talk) 01:29, 14 September 2009 (UTC)

Regarding the trout (freshwater salmonids): the young are insectivorous but the older, larger trout feed mostly on fish. I would suspect that young trout are far more likely to feed on midge larvae than on mosquito larvae, for the reasons 86.4.181.14 has noted. --Dr Dima (talk) 07:18, 14 September 2009 (UTC)

I've done a little search and it looks like young trout actually feed both on midge larvae directly and on the larger insects that feed on midge larvae, so that introduction of trout or increase in trout population does not necessarily reduce the midge larva abundance :) --Dr Dima (talk) 07:30, 14 September 2009 (UTC)

But this is their significance in forest and wild life.Actually, I was looking for domestic ones. Thanks still.--Lightfreak (talk) 18:45, 14 September 2009 (UTC)

To the best of my knowledge mosquitoes have never been successfully domesticated ;) . A "domestic mosquito" is a mosquito, any species belonging to family Culicidae such where adult females feed on blood. Not to be confused with midges (Chironomidae, Chaoboridae, etc.), as explained above. --Dr Dima (talk) 01:59, 15 September 2009 (UTC)

accuracy and precision

what is the difference between accuracy and precision? arent they both basically the same thing? —Preceding unsigned comment added by 174.6.144.211 (talk) 23:57, 13 September 2009 (UTC)

Nope. See Accuracy and precision. --Tagishsimon (talk) 23:59, 13 September 2009 (UTC)

If you have a robot and you tell it to drive 3 meters forwards and it ends up at 3.03 meters because (say) it's wheels are a bit bigger than they should be - then that's a problem of accuracy. If you repeat the experiment ten times and if it ALWAYS goes 3.03 meters - then that's amazingly good precision. If sometimes it goes 3.02 meters, sometimes 3.01 meters, sometimes 3.04 meters because the wheels sometimes slip on odd rocks and pebbles along the way - then that's not so good precision. Generally, issues of poor accuracy can be compensated for - in this case, we could program the computer to always drive 1% less distance than we ask it to - and it would then be pretty much spot on. But the lack of precision is hard to engineer out. SteveBaker (talk) 01:07, 14 September 2009 (UTC)

1% --Tagishsimon (talk) 01:10, 14 September 2009 (UTC)

1 percent, actually. And the question of "calibration" would seem to come into it also. Baseball Bugs ^{What's up, Doc?} carrots 01:11, 14 September 2009 (UTC)

Jeez - you guys are too quick off the mark! I couldn't fix it because of the edit conflicts! SteveBaker (talk) 01:15, 14 September 2009 (UTC)

Complicating matters is that 1 percent off would leave you at 3.03 - .0303 = 2.9997. Depending on the precision (or is it accuracy?) of your measuring tools and how much accuracy (or precision?) you're looking for. If you want 3.0300 - x = 3.0000, then x = .0300. Then the multiplier is more like .00990009... instead of .01. Baseball Bugs ^{What's up, Doc?} carrots 01:56, 14 September 2009 (UTC)

How exactly does this complicated effort to prove your mental superiority over the rest of us help the OP through the discussion of accuracy and precision? Meanwhile - may I suggest you consider reading significant figures and perhaps you would note my careful use of the phrase "pretty much spot on" rather than "exactly correct". K'thanks. SteveBaker (talk) 03:04, 14 September 2009 (UTC)

I've never been so insulted. But it's early yet. Baseball Bugs ^{What's up, Doc?} carrots 07:23, 14 September 2009 (UTC)

These same terms were used regularly when I went to rifle school. Accuracy is your ability to hit the bullseye. Precision is how close each shot is to the previous shot. If you put 10 shots right on the same spot, but it is not in the bullseye, you have high precision and bad accuracy. If you get all shots in the bullseye, but they are all over the place inside of it, you have high accuracy but bad precision. -- kainaw™ 03:14, 14 September 2009 (UTC)

This also gives another example of the point above SB was making. If you get 10 shots right on the same spot every time say 5 centimetres to the left of the bulls eyes, you just have to learn to aim for 5 centimetres to the right of the bulls eye. If your shots are all over the place, you can't easily improve that other then to practice more Nil Einne (talk) 11:39, 14 September 2009 (UTC)

What you're calling "precision" is more like "consistency". A pitcher learns the mechanics that will make the ball go where he wants it to go. But consistency isn't everything. I once heard a comment about a pitcher, I forget which one, that "he would have been a Hall of Famer if the strike zone were high and outside." Baseball Bugs ^{What's up, Doc?} carrots 15:53, 14 September 2009 (UTC)

Yes - precision is indeed more like consistency. So if this pitcher could have been pursuaded to aim low and inside - he'd be a household name and you wouldn't have forgotten the poor fellow already? SteveBaker (talk) 16:58, 14 September 2009 (UTC)