Wikipedia:Reference desk/Archives/Science/2008 September 19

= September 19 =

Sedative Paintballs
Now I know that the police use pepper-spray balls in modified paint ball guns for riot control but I was wondering if sedative versions could be made, possibly containing low levels of Sevoflurane or some other such chemical? Would such a weapon be feasible? Thanks for any response, DTWATKINS (talk) 00:24, 19 September 2008 (UTC).


 * Most anestethics are potentially fatal if you are exposed to too much. Paint ball guns are a pretty imprecise delivery mechanism, and so I'd worry about accidentally overdosing the targets.  You'd need something that knocks people out at relatively low concentrations but doesn't become hazardous at high concentrations.  Maybe such a compound exists, but it would probably require considerable research and experimentation to get it to work.  Dragons flight (talk) 00:54, 19 September 2008 (UTC)


 * Why reinvent Tranquilizer darts? --Dr Dima (talk) 01:03, 19 September 2008 (UTC)
 * To quote the same article: are not included in military or police less-than-lethal arsenals because no drug is yet known that would be quickly and reliably effective on humans without the risks of side effects or an overdose. --Ayacop (talk) 16:19, 19 September 2008 (UTC)

Blood drawing sensation
I had blood drawn today---my question is:

It seemed like I could "feel" the blood flow out of me. Is this merely a mind thing? That is, I know there is blood being taken, so I trick myself into feeling it---

Or is it actually possible to feel that? —Preceding unsigned comment added by NetLace (talk • contribs) 00:57, 19 September 2008 (UTC)


 * can you feel it when you have blood taken? I cant.--GreenSpigot (talk) 01:32, 19 September 2008 (UTC)


 * It leaves your body through a needle which doesn't have any nerves in it, so I think your mind is playing tricks on you.  Plasticup  T / C  04:47, 19 September 2008 (UTC)
 * But the needle passes through the skin, which does have nerves. If you've got a liquid flowing in a pulsed manner through a constriction, you have two sources of "needle motion": wiggling with each pulse (as the flow changes and/or as the blood vessel to which it's attached pulses) and turbulance from the flow. Maybe one could feel that motion, and therefore indirectly be feeling the blood draw? WP:OR: when I had an IV many years ago, I remember noticing some small air bubbles in the line as it was started, and I was able to feel a slight vibration when they passed through the needle.
 * Going a different direction (in terms of sensation, not flow:), when I give blood, I can feel when the line is blocked (due to the bag being filled, while switching among sample tubes, etc.). But the sensation is that of blood not flowing in my arm (cuff blocking normal vein return) and then flowing again, not of the actual blood being drawn. DMacks (talk) 05:11, 19 September 2008 (UTC)
 * There were air bubbles in your IV? Isn't that dangerous? --Tango (talk) 10:49, 19 September 2008 (UTC)
 * Can be, if they're big enough. Avoidable with decent technique. Gwinva (talk) 11:39, 19 September 2008 (UTC)
 * Yeah, there were just a few, only a mm or so long in the line, so probably coupla tens of μL total max. DMacks (talk) 13:07, 19 September 2008 (UTC)
 * I certainly can't feel it when I give blood, the needle feels uncomfortable, but that's it. --Tango (talk) 10:49, 19 September 2008 (UTC)

CO2 production by humans
Do larger people produce more CO2 than smaller ones?--GreenSpigot (talk) 01:34, 19 September 2008 (UTC)


 * On average, yes; see Basal metabolic rate, and note that calories burned increases with body mass. --Allen (talk) 01:44, 19 September 2008 (UTC)
 * Ceteris paribus they might, but weight is negatively correlated with hours of exercise, and exercise produces CO 2 . Michael Phelps, for instance, consumes 10,000 calories per day.  Plasticup  T / C  04:39, 19 September 2008 (UTC)
 * It depends on what you measure, of course. Net biological production is 0 in either case (all the CO2 you exhale comes from your food, which contains carbon that was ultimately fixed by a photosynthesizing plant). The same holds for use of natural fibers in larger clothes. But it takes more energy to support the (on average) larger consumption of larger people. Also, of course, "all else" is rarely equal. Larger people are more likely to live a modern western livestyle, which implies much more use of resources. --Stephan Schulz (talk) 07:28, 19 September 2008 (UTC)
 * I wouldn't say net biological production is 0; most exhaled carbon was originally fixed by a plant, yes, but not nearly all CO2 fixed by plants, even food crops, ends up metabolized by a human. (More importantly, though I know it wasn't your point, the carbon impact of what we eat depends on all sorts of other considerations, like fertilizer use, tilling, transportation, etc.)  --Allen (talk) 14:25, 19 September 2008 (UTC)


 * So does fat people create more global warming than thin ones? —Preceding unsigned comment added by 79.76.233.214 (talk) 00:12, 20 September 2008 (UTC)

Fat woman
The usual rule of thumb to know if a woman will become fat is "take a look at her mom!". Is this rule accurate? Mr.K. (talk) 08:24, 19 September 2008 (UTC)
 * Hardly, body weight is more a matter of nutrition and exercising than genetics, though the latter can contribute. Equendil Talk 08:50, 19 September 2008 (UTC)


 * As Equendi notes the reality is that (for most people) weight is at least as much based on individual actions as it is on genetics. Also...what difference does it make even if the rule were true? You'd have to be a pretty despicable person to not enter a relationship with someone today because you think that in 10 years that person may be fat. What if in 10 years you're fat, or bald, or lose your looks or whatever? Would you want someone to not date you based on what 'might' occur in the future? 194.221.133.226 (talk) 09:30, 19 September 2008 (UTC)


 * Am I too shallow or even despicable as you said? I think that any male (is being male despicable?) interested in a long-term relationship (and yet? is that despicable?) will ask (is asking questions acceptable?) himself questions like that. Mr.K. (talk) 10:52, 19 September 2008 (UTC)


 * If the query was merely 'is there a genetic link to obesity?' then I guess looking at Obesity would be a start - and if that was purely the reason then i am sorry I jumped to a conclusion about why this would be of interest to someone. I got the impression from the way the question was asked that such a thing was going to be used as a criteria for whether or not to date someone - which would be to me (a male too) shallow. 194.221.133.226 (talk) 13:20, 19 September 2008 (UTC)


 * I think that I am the Galactic Emperor, but that doesn't mean I am. --- OtherDave (talk) 11:11, 19 September 2008 (UTC)


 * If you wanna be happy.......--Shantavira|feed me 12:41, 19 September 2008 (UTC)
 * It makes a whole hell lot of difference. People of both sexes want an attractive partner who will sexually satisfy them - a recipe for success in a relationship. --mboverload @  22:53, 21 September 2008 (UTC)

My mom is rather slender.--The Fat Man Who Never Came Back (talk) 12:54, 19 September 2008 (UTC)


 * Can I suggest that the question might be referring to more than genetics? If your mother is overweight it can (but not necessarily) also point to poor eating habits or a poor relationship with food. Something like that can influence the habits of the child just as much as a recessive gene. Poverty generally follows family lines, but because of shared environments, not genetics. --98.217.8.46 (talk) 13:43, 19 September 2008 (UTC)


 * What about children with one large parent and one small one?!  Plasticup  T / C  17:19, 20 September 2008 (UTC)


 * It seems a highly valid predictor, but clearly there are exceptions.Edison (talk) 22:49, 21 September 2008 (UTC)

DNA of monozygotic twins
Is there any genetic difference (something like a minor mutation), even small, to tell apart two monozygotic twins? Would a paternity test be able to prove that a child is of twin A or twin B?Mr.K. (talk) 08:56, 19 September 2008 (UTC)


 * Our twin article has a useful discussion, and mentions a number of times that monozygotic twins' DNA will be nearly identical.  That's because mutations can occur early in development that could enter the germline and be carried on to offspring.  The challenge is the needle-in-the-haystack issue: there's no guarantee that the mutation(s) is/are there in the germline, nor where it/they will occur.  There's also the possibility of epigenetic differences, a slightly diffent issue, and we don't know exactly how heritable they are. --Scray (talk) 10:05, 19 September 2008 (UTC)

How much of the population uses medicine?
How much of the population of the Western world uses at least one prescription medicine? Seans Potato Business 08:58, 19 September 2008 (UTC)
 * American stats are easy to find: This says 45%. Don't know how this would translate to other "Western" nations, though. Fribbler (talk) 09:51, 19 September 2008 (UTC)
 * Uses at any given time? Uses at some point in their lives? Uses on a continuous basis? --Tango (talk) 11:00, 19 September 2008 (UTC)


 * You are getting into one of my areas of study... By defining a person as a "user", you are implying that the person actually puts the medicine in or on his or her body. Most statistical information is based on prescriptions.  Those prescriptions may or may not be filled.  If filled, they may or may not be taken.  So, counting prescriptions will give you a high percentage that isn't accurate.  Then, there are the samples.  Doctors often give samples of medications without prescribing them.  So, if you are counting prescriptions, you have a lower number.  Which is further off - those getting prescriptions without taking them or those taking meds without a prescription.  Now, what do you do about the illegal trade of prescription drugs? --  k a i n a w &trade; 02:49, 20 September 2008 (UTC)


 * Are there studies on what percentage of prescriptions are not filled, and what amount of drugs are dispensed but not used? Also, what happens to all the drugs that are unused? (I'm guessing that the unused portion adds up to a large weight of drugs.) Wanderer57 (talk) 05:07, 20 September 2008 (UTC)


 * There are limited studies on prescriptions at this time. The VA is doing a rather large-scale study, but it will be skewed since the VA often has the pharmacy inside the VA or mails refills directly to the patient's home.  A true study would require checking patient's blood and urine every week to ensure that the proper drug levels are present.  As House says, patients lie.  So, you can't depend on any study which simply asks them if the prescriptions were filled or if they took the drugs properly. --  k a i n a w &trade; 00:51, 22 September 2008 (UTC)

Rats vs Mice for public health
Hello,

I've recently discovered that i live with some mice. I called the council who are prepared to get rid of rats for free because they are a danger for public health, but for mice they'll charge me through the nose. anyway, why is this? i mean, i can understand that rats are less cute, but significntly less hygenic? How come? (p.s. how do i know they're not rats... its obvious right?)217.169.40.194 (talk) 09:20, 19 September 2008 (UTC)
 * Yes, it's obvious: rats are big and unmistakeable; mice are fairly small. Mice are quite easy to catch using baited mouse traps: found in any hardware shop, and many supermarkets.  Plenty of styles to choose from, to suit your budget and/or ethical stance.  Gwinva (talk) 09:25, 19 September 2008 (UTC)
 * This will not only catch your mice, but provide companionship as well. DuncanHill (talk) 12:09, 19 September 2008 (UTC)


 * Mice don't live in the sewers, but see Brown Rat.--Shantavira|feed me 12:49, 19 September 2008 (UTC)


 * Do you really know the difference between closely related rodents? You're not the Pied Piper! Just tell them you think you have rats and they might not charge you for it.  Plasticup  T / C  17:15, 20 September 2008 (UTC)

Smallest eye
How small is the smallest known eye of adult animal? I dont mean patch of photosentive cells but a real complex eye. 193.65.112.51 (talk) 12:04, 19 September 2008 (UTC)


 * If you include all animals, I imagine the eye of a flea is quite small. If you exclude compound eyes, then I suppose mice or hummingbirds have rather small eyes. Scorpions and spiders too, but I'm not sure if they're compound or not. Calamus Fortis  16:14, 19 September 2008 (UTC)


 * Erythropsidium, a dinoflagellate. Axl  ¤  [Talk]  17:35, 19 September 2008 (UTC)


 * Thanks! Wow, that is incredible! Single cell organism having an eyeball! 193.65.112.51 (talk) 23:25, 19 September 2008 (UTC)

Animals rejected by their mothers
In the news, I keep coming across cute pictures of baby zoo animals that were "rejected" by their mothers. See this gallery for some examples.

Is there a WP article or offwiki resource that discusses this aspect of animal behavior? Other than, say, obvious physical defects or mental retardation, why might a mother reject her offspring? Is this a bestial analogue to postpartum depression. Have zoologists studied this phenomenon? Can a baby animal ever survive in the wild without a mother? Are they ever adopted by other mothers? Any information on this topic would be appreciated.--The Fat Man Who Never Came Back (talk) 12:47, 19 September 2008 (UTC)
 * I recall some documentary (March of the Penguins?) discussing it. Parents in large breeding colonies often lose track of their own offspring, so they adopt/steal others. It is speculated that near neighbors are likely to be genetically related, so it makes Darwinian sense. Clarityfiend (talk) 20:18, 19 September 2008 (UTC)
 * Also, every so often, we're subjected to news filler about cross-species adoption, lionesses adopting antelopes, cats adopting dogs, Republicans adopting Democrats (well, maybe not that)... Clarityfiend (talk) 20:29, 19 September 2008 (UTC)
 * Here's a Discover Magazine article, The Adoption Paradox. Birds do it involuntarily; fish do it. Clarityfiend (talk) 04:00, 20 September 2008 (UTC)

Ear and Collarbone
I have heard that only seven pounds of pressure are required to fracture a clavicle or tear off an ear. It seems like those two parts of the body are absurdly fragile. Is there any truth to this? Calamus Fortis  16:04, 19 September 2008 (UTC)


 * "Pound" is a unit of force, not pressure (although "pound" is also used as a unit of mass). It is actually the pressure applied (and direction of pressure) and the duration (see "Impulse") that determine risk of injury. Axl  ¤  [Talk]  17:39, 19 September 2008 (UTC)


 * The OP probably is referring to pounds per square inch. -- MacAddct1984 (talk &#149; contribs) 18:37, 19 September 2008 (UTC)


 * I'm not exactly sure whether it's seven pounds of force or seven psi. Either way, it seems like a small value to cause injury to the ear or collarbone. Can anyone answer the question I originally posed? Calamus Fortis  19:44, 19 September 2008 (UTC)


 * 7 psi seems extremely low to break any kind of bone, or tear off an ear, for that matter. It is probably enough to pull an earring out though... -- MacAddct1984 (talk &#149; contribs) 19:45, 19 September 2008 (UTC)


 * Your clavicle is essentially designed to break. When you fall onto your hands (as when you trip over your feet to the ground), there are a limited number of places for the shock of the impact to go. One of the "popular" ones is your clavicle, which, if you've seen one, is pretty flimsy and twisted looking. A broken clavicle is no fun, but it's probably less dangerous for you than a dislocated shoulder or a broken arm. Matt Deres (talk) 20:28, 19 September 2008 (UTC)

Bridging the pond
It would surely be uneconomical, but how might one best go about building a bridge across the Atlantic &mdash; presumably from St John's to Belmullet? The 3034 km route would be ideal for a high-speed train: it's a 7h35 trip at 400 kph, which ought to be achievable on the flattest and straightest line ever. Most of the run would be over depths of about 4 km (I think), and the geological activity of the Mid-Atlantic Ridge would further trouble support from the seabed. Floating bridge supports come to mind, but I don't know how troublesome ocean currents would be. Such a line would probably be threatened by icebergs; how might it be made to survive them? Would, perhaps, wave power be enough to make the line (significantly) self-powering? --Tardis (talk) 16:15, 19 September 2008 (UTC)
 * See Transatlantic tunnel. Saintrain (talk) 19:17, 19 September 2008 (UTC)
 * There already is a Bridge over the Atlantic... Gwinva (talk) 03:33, 20 September 2008 (UTC)


 * For Pacific Ocean bridges, see this page:


 * http://www.connexin.net/humor-genie-wish-understand-man-woman.html


 * Wanderer57 (talk) 05:36, 20 September 2008 (UTC)

Doppler effect
If a sound source came directly towards me at Mach 2, playing a piece of music backwards, would I eventually hear the piece of music forwards? Rawling 4851 17:24, 19 September 2008 (UTC)


 * The only thing the doppler effect effects is the lengthening/shortening of frequency/wavelength. So you'd hear a higher pitched backwards music coming toward you and then a lower pitched piece of music being played backward when it passes by you. (Followup) If you were in the air, the sound couldn't travel at Mach 2. You'd need to be in some other medium, such as being underwater, to achieve that speed. -- MacAddct1984 (talk &#149; contribs) 17:38, 19 September 2008 (UTC)


 * (e/c) Doppler effect wouldn't cover it, though.  The end of the song would be emmited when the supersonic phonograph was right next to you so you'd hear it instantly. Assuming that the song traveled at the speed of sound, the begining of the song would not have arrived yet. In that ideal case you would hear the song exactly backwards.
 * But that's a big assumption. Wouldn't a supersonic anything cause a massive wake that would screw up the local speed of sound? In that case probably all you'd hear is a distorted mess. Hopefully someone will come along who knows about this sort of thing and product a better answer. APL (talk) 17:47, 19 September 2008 (UTC)
 * (after e/c) He's not talking about sound traveling at Mach2, he's talking about sound traveling at the normal speed, and the player going so fast that it passes through the beginning of the song so that it can deliver the end of song before the beginning arrives at the listener.


 * I imagined this like... picture the sound source "writing" the piece of music on a piece of paper. The paper is travelling towards you at Mach 1, but as the source is travelling towards you at Mach 2, it is "writing" on the paper at Mach 1, but backwards... or something. Rawling 4851 17:53, 19 September 2008 (UTC)


 * I expect you'll hear a sonic boom first, followed by heavily distorted backwards music (probably not recognizable as music). Axl  ¤  [Talk]  18:45, 19 September 2008 (UTC)


 * That's a fun question. The moving strip of paper is a good analogy.  After the boom you'll hear the last note that was played (the first note of the song) then the second-to-last note played (the 2nd note of the song) etc.  So, yes, you'd hear the song played in the correct order.  You'll have to play the farther note louder, though.  Saintrain (talk) 19:12, 19 September 2008 (UTC)


 * Er, yes, that's what I meant. ;) By "backwards music", I meant the music originally played backwards, would be heard forwards (albeit distorted). Axl  ¤  [Talk]  19:24, 19 September 2008 (UTC)
 * And the music would have to be slowed down by a factor of two to compensate for the Doppler shift. Saintrain (talk) 00:35, 20 September 2008 (UTC)
 * No, the point of going at Mach 2 is that an emitter approaching at that speed will produce sounds with the same apparent wavelength only recieved in reverse order. Dragons flight (talk) 00:46, 20 September 2008 (UTC)


 * If the source went silent, or stopped, before it reached you, would you even hear a sonic boom? Rawling 4851 12:21, 20 September 2008 (UTC)

Live food
The somewhat disturbing Live food doesn't explain if it is necessary. Will certain species only eat live prey? Clarityfiend (talk) 18:43, 19 September 2008 (UTC)


 * I would say most animals only eat live prey, otherwise they'd be considered scavengers, no? As for pets, while anecdotal, our snake (a Columbian red-tailed boa constrictor) only ate live animals otherwise she'd have no interest in it. -- MacAddct1984 (talk &#149; contribs) 19:09, 19 September 2008 (UTC)


 * There is an old wives' tale that if confronted with a bear, you should lie down and pretend to be dead. I think the idea here is that, if it is dead it must have died of something, and you don't want to catch what it died of by eating it, or it may have been dead for a while, so for the same reason, you wouldn't want to be chomping on something with flies and bacteria all over it, even though animals that do eat dead things don't seem to have this preconception about dead things. For us, it is common sense. I hunt rabbits from time to time with the purpose of putting them in a casserole, but I would never touch a rabbit I saw dead already, and not from one of my bullets.--ChokinBako (talk) 19:50, 19 September 2008 (UTC)


 * I think the idea with the bear is that by playing dead you will no longer be perceived as a threat. Most bears (except the polar variety) have no interest in people as food; they just want to make sure you're no threat to their cubs or themselves. Once the bear sees you're not a danger (so the thinking goes), they'll give you a sniff and leave you alone. Not recommended for OR! Matt Deres (talk) 20:34, 19 September 2008 (UTC)


 * Well, a large number of animals are probably herbivores, so the live food/non-live food distinction probably isn't relevant. Secondly, the phrase "live food" is usually applied for captive animals only. While in the wild carnivores may only eat food they killed themselves, in captivity a large number of animals (including lions and bears) are perfectly content to eat dead stuff - just look at feeding time at the zoo. Also, I think you underestimate the prevalence of scavengering-like behavior. While they may not eat meat that's gone rancid, lions and bears are not above picking over a fresh corpse, and a number of carnivores aren't shy about stealing an already-dead kill from another hunter. However, there are a number of animals, like some snakes and lizards, which either will only eat still-living prey, or whose appetite is stimulated by the sight of living prey. -- 128.104.112.147 (talk) 00:17, 20 September 2008 (UTC)
 * I meant prey being eaten while still alive. AFAIK, lions and such kill their prey, then eat it. 128 has answered my question. However, that raises another. What possible advantage would there be in restricting oneself to live vs. freshly killed food? Clarityfiend (talk) 01:38, 20 September 2008 (UTC)


 * Many animals eat live prey. Consider big fish eating little fish.  How about frogs eating bugs.  The main advantage is that there is much of a less consideration for infection in live animals compared to dead ones.  Some animals, such as crabs, are very quick to spoil.  That is why you boil them live. --  k a i n a w &trade; 02:43, 20 September 2008 (UTC)
 * I think the main advantage is just that it's easier. Killing the animal takes effort, if it's not necessary, why both? A lion needs to kill its prey because otherwise it will run off before it can be eaten, food which is eaten live is eaten in one mouthful, so that isn't an issue. --Tango (talk) 19:54, 20 September 2008 (UTC)
 * I have seen a family of lions (ok, it was TV, but it was very clear) eat an antelop or similar prey (I can't remember the exact species) while it was still clearly moving and trying to escape, although badly injured. One of the bigger lions was holding it down while all the other ones where happily extracting flesh and chewing. It took several minutes for the prey to die in this manner. The images were clear, so even if the commentator didn't know what he was talking about, I think the images alone were compelling evidence that lions eat living prey when it is easy to do so. --Lgriot (talk) 06:43, 25 September 2008 (UTC)