Wikipedia:Reference desk/Archives/Science/2011 January 13

= January 13 =

What vehicle is indestructible in any typical commuter's crash?
As a kid, I dreamed of owning a vehicle that couldn't crumple or get disabled in any way through a crash. I wonder what vehicles are indestructible and can put up with such egregious abuse?

I think 5 MPH bumpers aren't enough; how about 95?

So, what vehicles will retain its shapes and remain operable after a crash? --70.179.178.5 (talk) 02:57, 13 January 2011 (UTC)


 * A schoolbus - they are built very strong. Take a look: School vs. Hummer and then you have: Hummer vs Suzuki. I think it may be fun to make a whole chain. But more seriously, the heavier the vehicle the better. Ariel. (talk) 03:24, 13 January 2011 (UTC)
 * Depends what type of vehicle you're talking: do you just mean road-worthy vehicles, or any kind? If you mean the latter, you should consider tanks; pretty much the only way to stop them is explosives or preventing them from getting fuel.  Nyttend (talk) 03:41, 13 January 2011 (UTC)
 * I want a normal commuter's vehicle, so that rules out an Abrams. Besides, I'll probably need a military driving license to drive one anyway. (Moreover, don't they only get 1 MPG?) If 95 is too unreasonable, then 85-MPH bumpers will suffice, because I suppose then, that beyond 85, I'm no longer commuting; I'm racing for recreation. If a schoolbus will give me at least 20 MPG, then I might be up for it. I'd like to rule out the Hummer as well because not only did their division bite the dust, owning and/or driving one could make me look like a douchebag, especially in this environmentally-inclined societal climate!


 * Besides, I might not mind driving a tank as a commuter, but only if they're street-legal, and give me at least 20 MPG. Have you ever heard of a 20 MPG tank? --70.179.178.5 (talk) 04:48, 13 January 2011 (UTC)
 * It's not just your own speed that matters; you also have to consider the speed of the guy you're planning to have a head-on collision with. --Anon, 07:26 UTC, January 13, 2010.
 * Have you considered taking a train? a Solid Diesel locomotive could hit just about any passenger car at 95 mph (if you can get it to go that fast) and only scratch the paint job.  If you have to contend with another locomotive, or a heavily loaded truck, then you are going to not be quite so Unstoppable.  Googlemeister (talk) 19:26, 13 January 2011 (UTC)
 * This is a fantastically bad idea; a vehicle designed to retain its shape perfectly in the event of a crash would be VERY unsafe. When a vehicle crashes, your body is decelerated very rapidly; the effects of this deceleration can be ameliorated if the energy of the crash is dissipated in some way; modern cars are literally designed to crumple in the event of a crash because it is safer for you, the driver, if they do.  If they did not crumple, the full energy of the crash would be felt by the driver and passangers, and could cause much more damage.  To put it in simpler terms: When you crash, something is going to be destroyed: it can either be you or your car.  Which do you choose?  -- Jayron  32  04:54, 13 January 2011 (UTC)


 * There are other options. You can have non-destructive impact absorbers - something as simple as a large spring with a latch/ratchet (the latch to keep the spring from recoiling). Ariel. (talk) 05:54, 13 January 2011 (UTC)


 * The OP seems to be looking for a commercially availible vehicle. A 1970's era Buick would fit the bill; those things were basically as indestructable as a car could get, and much less safe (for the reasons I cite above) than modern cars with crumple zones.  Anyone, I suppose, could invent any number of highly impractical impact absorber which would meet the technical requirements of preserving the car and driver both unscathed; that has to be coupled with the notion of it being a drivable car!  -- Jayron  32  06:00, 13 January 2011 (UTC)

In practical terms, a large, heavy, modern, vehicle that meets Europena crash with 5 stars. I'd have a preference for a unitary body, and a smaller preference for a longitudinal engine. I'd fit a 5 point harness, and do it up tight. Not too sure about wearing a helmet. Greglocock (talk) 06:02, 13 January 2011 (UTC)
 * That protects the driver, but not the vehicle. Every vehicle that passes the Euro NCAP with high marks will have very extensive crumble zones, some of which will even be designed to crumble under fairly low impact forces to protect pedestrians in a collision. What the OP wants is not practically feasible. Kinetic energy grows with the square of the speed. Potential energy of of an elastic medium (as exchanged in a collision) typically is roughly linear with deformation. The energy involved in a 95 mph crash is about 400 times of that in a 5 mph crash. So a bumper that gives only one centimeter on a 5 mph crash would have to give nearly 4 meters to store the energy in a 95 mph collision - that's about the length of a good-size car. And I'm fairly sure that bumpers deform more than a centimeter ("about half an inch" ;-) in a 5 mph collision to begin with. --Stephan Schulz (talk) 09:35, 13 January 2011 (UTC)


 * You're essentially looking for some sort of action hero vehicle that can smash through anything and keep on ticking, right?
 * That's going to be a tall order. An HMMWV (A real one. Not an H2 or something) with some of the 'upgrade kits' might be your best street-legal option, but it's not the batmobile. It was really just designed as a jeep replacement.
 * What you really want is some sort of front-line combat vehicle. A MRAP or a M1117. I don't think these are available to civilians, and I doubt you'd be able to get them registered for street use anyway. But if you live the sort of super-hero life where you have to smash through walls in your morning commute, perhaps you don't care if you can get a registration sticker. APL (talk) 17:20, 13 January 2011 (UTC)


 * Indestructibility is a matter of degrees, a school bus would survive most commuter car impacts, but a train would ruin its day severely. Even with military vehicles, they're not designed to be indestructible, they're usually designed to survive a hit from their own main gun, and to survive hits from expected common battlefield dangers (IE the most common weapons of the most probable opponent).  You can buy some British surplus military armor as a civilian, but it is US policy not to sell to civilians but instead sell surplus and replaced armor to allied nations.  You could also buy a used armored car, not the military kind but the kind used by bank cash collection services and retail cash delivery services, there's even a website for it, google turned up a few (would linking a commercial sales list site for what the OP wants be allowed here?) 65.29.47.55 (talk) 22:37, 13 January 2011 (UTC)

When will Harley-Davidson get a hybrid powertrain?
I'm looking to find a hybrid motorcycle someday. Even though the 85-MPG Peirspeed Delivery 150cc is promising as a fuel miser, that might not be enough one day, due to tightening emissions standards and whatever else, that only hybrid powertrains could meet.

Therefore, when will Harley get one on theirs?

And are there other motorcycle manufacturers that already make hybrids?
--70.179.178.5 (talk) 02:57, 13 January 2011 (UTC)


 * The Piaggio HyS is probably the first. Harley will get one a few days after hell freezes over- like BMW and Ducati motorcycles, they are wed to a certain look and a certain engine design. Can-Am was next. I think we'll see more production-ready ebikes before hybrids- it's a packaging issue. tedder (talk) 05:17, 13 January 2011 (UTC)
 * Hell already has. When the EPA keeps tightening their emissions and fuel economy regulations, don't you think Harley will have to comply eventually? Harleys may be wed to a certain look & design, but they have all sorts of new features that they're able to hide under the antiquated-looking chassis. Therefore, they could hide a hybrid drivetrain too, could they? --70.179.178.5 (talk) 05:38, 13 January 2011 (UTC)
 * Eh, they will eventually, or they'll bypass hybrid and go for the electric. Again, it's a packaging issue. BTW, their integration of modern (Bosch) ABS into the current chassis is positively brilliant; research what they did with the wheel position/rotation sensor so they didn't need a toothed hub if you are curious. tedder (talk) 06:06, 13 January 2011 (UTC)
 * A further passing thought- motorcycle efficiency is not constrained by the engine size/efficiency so much as by the aerodynamic efficiency. The biggest wins come from enclosing the vehicle in a fairing. tedder (talk) 17:49, 14 January 2011 (UTC)

Imprinting (biology)
Imprinting is a psychological instance where a sight or a sound is immediately stored into the long-term memory center of an organism either indefinitely or temporarily.

Imprinting is a common occurence in the newborns of many animal species.

Avians Ducks: A Duckling, when it's about to hatch, will visually imprint itself upon the first being that they see and follow it around thereafter as its mother. --Arima (talk) 03:32, 13 January 2011 (UTC)


 * There's already Imprinting (psychology). Clarityfiend (talk) 04:09, 13 January 2011 (UTC)
 * Is there a question? I adjusted the "Avians" subheading. Cuddlyable3 (talk) 00:25, 14 January 2011 (UTC)

Hydrogen fuel cell weight advantages in airplanes
Would an airplane powered by hydrogen fuel cells be significantly lighter than a traditional airplane? ScienceApe (talk) 05:58, 13 January 2011 (UTC)

Doubt it. Are you hoping the hydrogen would buoy the aircraft? Hydrogen storage may give you a hint why that won't work. Greglocock (talk) 06:06, 13 January 2011 (UTC)


 * Well, it depends. If hydrogen has a significantly higher joules/gram ratio than an equivalent amount of airplane fuel would, for systems of comparable efficiency, you could generate the same range and speed on lower mass.  Likewise, if a fuel cell had a significantly higher efficiency, at a comparable joules/gram ratio, the same would be true.  I have no idea about the actual numbers on these things, but even ignoring the faulty buoyancy arguement, its within the realm of possibility that a hydrogen fuels aircraft would weigh less.  -- Jayron  32  06:11, 13 January 2011 (UTC)


 * If joules/gram is better (which it is for the raw fuel, but may not be once you include the storage system), then simply burning it would work better, and would be just as clean. Unlike cars airplanes don't benefit from the typical advantages of electric motors (high torque, variable speed, regeneration). Ariel. (talk) 07:06, 13 January 2011 (UTC)

Conventional jet fuel is almost 10,000 times as dense as hydrogen gas. On a modern airliner, roughly speaking the fuel tanks are the inside of the wings. To store an equivalent mass of hydrogen gas without pressurization, you would need tanks 10,000 times that size, which would be a little difficult to fit into the airplane. And if you stored it in highly compressed form, then you would need heavy tanks to withstand the high pressures. Today's gas cylinders may support a pressurization of several hundred times normal air pressure, but not several thousand, and they're already pretty heavy. (An alternative is to use liquid hydrogen as was done on the Saturn V rocket, but that requires cryogenic temperatures to be maintained at all times when there is fuel on board; also not very practical today.)

The hydrogen fuel article claims that at pressures typically used, hydrogen occupies 4 times the volume of an amount of gasoline of corresponding energy content, and is 1/3 the weight. But there is a whiff of advocacy about that article and I do not entirely trust it; for one thing, it doesn't even mention the weight of the tanks. --Anonymous, 07:46 UTC, January 13, 2010.
 * There is such a thing as a hybrid airship, which is a not-quite-lighter-than-air vehicle. They don't use their lifting gas as fuel, but perhaps it would be feasible. 81.131.24.134 (talk) 13:13, 13 January 2011 (UTC)

Six Sigma and Human Resources
A few weeks ago some colleagues and I were discussing Six Sigma, Green Belts, and all the trappings of that methodology. Eventually we got around to discussing the applicability of Six Sigma to non-manufacturing areas. The one that stumped us was HR. HR is necessarily quality-focused, but in a far more subjective way. Also, few HR operations approach the scale necessary for Six Sigma statistical analysis. Someone ventured that a theoretically massive company (Walmart? US Federal Government?) could apply Six Sigma methodology to their global training or recruiting programs, assuming they had globally equivalent programs, which is a massive assumption to make. I've been idly considering this for the past 2 weeks and haven't been able to come up with anything any more practical. Can the RefDesk? The Masked Booby (talk) 08:41, 13 January 2011 (UTC)
 * Almost all HR data is subjective, but the six sigma and similar processes need objective measurements to provide useful information. Call center employees' performance is probably measured using objective scales of time, accuracy and/or possibly customer feedback survey scores, so it might work in that context. 71.198.176.22 (talk) 10:51, 13 January 2011 (UTC)

skipped lines in raw Cassini images
In raw Cassini images, such as this one, every other line is typically incomplete on the right side. What causes this? Is it a transmission bandwidth problem, and will the missing data be filled in over time? Or is it a recording bandwidth problem, and is the data lost? — kwami (talk) 09:55, 13 January 2011 (UTC)
 * I'm not sure, but I think it might be an artifact of an automatic contrast adjustment system designed to get the maximum dynamic range out of an image by dynamically stepping the CCD contrast ratio when particularly bright areas unsuitable for the current setting are encountered. The information to adjust for those artifacts is probably sent out of band apart from the raw image data, and they need to be recombined to make a coherent contrast image. 71.198.176.22 (talk) 10:46, 13 January 2011 (UTC)
 * It does seem to occur most often in bright areas when there are also substantial dark areas in the image. But not always: Well, as long as the data hasn't been lost, I suppose it doesn't matter too much. — kwami (talk) 11:13, 13 January 2011 (UTC)


 * The raw image pages on the Cassini site all contain a link to the Raw Images FAQ, which seems to describe both of the problems seen in the linked images. The first image, with truncation of alternating rows of pixels, shows an artefact of the image compression algorithm.  When an image is captured in lossless compression mode, the algorithm looks at two rows of the image at a time, and seeks to compress the data down to at most one half of its original size.  If that compression cannot be achieved, the line of pixels is truncated until the desired compression ratio is reached.  This works brilliantly for low-contrast or low-detail subjects (for images containing mostly empty space, for instance, or uniform cloud cover) but gets into trouble with complicated, high-detail subjects filling the full width of the frame (like the densely cratered surface of the moon in the picture).  On the other hand, while the right-hand edge of the image becomes 'tattered', the remainder of the image contains the full detail captured, and won't have any artefacts of lossy compression.
 * The second image looks like it's missing several consecutive rows of data in the upper part of the frame; I would be surprised if it were anything more complicated than a temporary loss of signal. (The ragged edge in the lower-right part of the image is the same lossless compression artefact we saw before.)  The FAQ notes that – due to onboard storage limitations – Cassini only sends most images once; they aren't retained on board, and if part or all of the picture is lost, there's no way to get it back.  Particularly 'important' images are recorded and replayed to ensure successful transmission, but scientists have to select those 'important' exposures in advance.
 * While the speculation about automated contrast adjustment is interesting, the FAQ doesn't mention such a system, and indeed notes that exposure times for images are set by scientists on the ground in advance (which can and does lead to under- and over-exposure, particularly when novel targets are photographed for the first time.) TenOfAllTrades(talk) 13:47, 13 January 2011 (UTC)
 * Good to know, though rather sad. — kwami (talk) 23:16, 13 January 2011 (UTC)
 * The Cassini imaging artefacts are all described here. The raw images can be improved by filling the omitted (black) pieces of alternate lines with an average of the complete lines above and below, effectively halving the vertical resolution in these areas. Cuddlyable3 (talk) 00:20, 14 January 2011 (UTC)

Is vacuum really vacuum or not
Is a vacuum really vacuum or not?

It is impossible to construct a really vacuum space. We all know that electro-magnetic waves can travel through a vacuum. But an electro-magnetic wave is a kind of progressive wave (more specifically transverse wave). As we all know that a wave is caused due to the disturbance of the particles in a medium. So,there must exist some kind of particle in the vacuum which has no mass and charge. The particles are photons. That means a photon does not travel from a place to another to transfer energy. Rather we could say it transfers energy from one point to another point just by transferring the energy to the adjacent photon. That means if we can create a really vacuum space, even the electro-magnetic radiation can not pass it. If this theory could be right then I can assure you that it can be proven that string does not exist. Even the Theory Of Everything can be proven.

(I,being an inhabitant of a third world country could not get the proper opportunity to check it practically due to deficiency of instruments. I could not contact to anyone to verify my thinking as I could not meet to someone who can really guide me to this thing. So,I'm heartily requested to the respectable volunteers of the Wikipedia to help me to find out what is going on actually. Sorry to write this on your page as it is prohibited to write this kind of things. But I could not find any alternative way. Hope that you would be kind enough to help me.) — Preceding unsigned comment added by 61.11.120.66 (talk • contribs) 04:58, January 13, 2011


 * See Luminiferous aether. --Plasmic Physics (talk) 10:15, 13 January 2011 (UTC)


 * You might be interested to read the article on Vacuum energy. Free space does not need to have photons already there for electromagnetic radiation to propagate, but photons (observed as particles) can appear or disappear as required. There are different Quantum vacuum states (see False vacuum), but I have to admit that I don't understand them!    D b f i r s   10:23, 13 January 2011 (UTC)


 * Short answer: a vacuum really is a vacuum. Light does not require any medium apart from space-time itself, any more than gravity does. See also Kaluza–Klein theory. — kwami (talk) 10:26, 13 January 2011 (UTC)


 * There is also Vacuum state discussing this. SmartSE (talk) 10:32, 13 January 2011 (UTC)


 * This: "As we all know that a wave is caused due to the disturbance of the particles in a medium." is not correct. And because it's not correct all the rest of what you wrote is based on a false premise. The links the other editors provided you will explain why it's not correct, but basically photons require no medium in which to travel. Ariel. (talk) 10:48, 13 January 2011 (UTC)


 * Perhaps the OP was thinking of sound waves that do require a medium, but yes, the premise seems to be wrong for E-M radiation. There is also the problem of whether a vacuum is really observed as a vacuum depends on the reference frame (see Unruh effect).    D b f i r s   11:33, 13 January 2011 (UTC)


 * It used to be thought that the luminous aether propagated light (and other e/m radiation) in space. The Michelson-Morley experiment disproved this concept. CS Miller (talk) 11:38, 13 January 2011 (UTC) As noted by PlasmaPhysics above.


 * Don't feel bad, of course, This question puzzled great minds for hundreds of years, until Einstein (among others) solved it. APL (talk) 17:03, 13 January 2011 (UTC)
 * I'd attribute the discovery of the ability of electromagnetic waves to propagate in a vacuum to James Clerk Maxwell or maybe to Heinrich Hertz. Einstein studied photons and electromagnetic waves, but I don't think his triumphant works were related to discovering that electromagnetic wave propagation can occur in free space.  Nimur (talk) 19:44, 13 January 2011 (UTC)


 * The "vacuum" is basically what's left when we remove everything that we know how to remove. It is possible that what we think of as the vacuum has additional structure that can be removed in some way unknown to us. That would be what's called a false vacuum. If it is possible, though, it's ridiculously far beyond our current capabilities as a species, because we know from astronomy that events far more energetic than anything we can create have failed to make a dent in the vacuum. -- BenRG (talk) 01:44, 14 January 2011 (UTC)

Also, with respect to the original poster: Satyendra Nath Bose was a native of Kolkata, yet he managed to not only rise through the local education system, but to eventually develop some of the most earth-shattering theories of our century about the behavior of matter in unusual circumstances. I can't know what opportunities or challenges you may face, but "being an inhabitant of a third world country" is not, in and of itself, necessarily a barrier to becoming a physicist. It may be much more difficult, but it is still possible. Nimur (talk) 19:52, 13 January 2011 (UTC)

Snow glow
On the night of a snowstorm, the entire sky remains bright overnight with an orangish glow: it seems to occur even in rural areas. I surmise this is the town's lights reflecting off the snow and back into the atmosphere. However, even one night later, this glow disappears. It's a pattern that's remained consistent (in my observation) throughout my lifetime. The only explanations I can think of:


 * 1) The snowplowing of the roads diminishes the light
 * 2) The cloud cover dissipates, diminishing the reflection.
 * 3) The structure of the snow crystallizes after sublimating in the sun.
 * 4) The snow disappears out of the trees via wind and sublimation.

None of these explanations immediately strikes me as the main culprit. Respectively:
 * 1) I note that streets are most likely located in the same location as street lights. However, snowplowing still only covers a minor part of the surface area of a town, and the diminishment of light strikes me as disproportional.
 * 2) Even with cloud covers on subsequent nights, the light is less clear.
 * 3) Does sublimation really change the reflective properties of the top of the snow so much that it reflects less?
 * 4) This immediately strikes me as a stretch, unless we maintain that only a little snow can stay in the trees overnight (the rest falls off), all of which sublimates/blows off by the next night.

Any thoughts? Magog the Ogre (talk) 11:54, 13 January 2011 (UTC)


 * Assuming your observation is accurate, the only possibility that comes quickly to mind for me is that during the interval the surfaces of the snow deposits change, lowering their albedo. The hypothesis would thus be that newly-fallen snow arranges in such a way that the reflectivity is maximized, and environmental factors (temperature, wind, vibration, physical contact) degrade this reflectivity over time. I look forward to reading other answers! The Masked Booby (talk) 12:24, 13 January 2011 (UTC)


 * Maybe the falling snow intercepts and scatters the light before it reaches the ground? Or perhaps the worst light pollution in the area isn't actually from streetlights but a commercial or industrial parking lot that is normally kept clean from end to end? Wnt (talk) 13:55, 13 January 2011 (UTC)


 * Just to chime in — though two anecdotes are not data — I have noticed the exact same thing, and in fact noticed it against last night and thought about posting a question about it on here myself. --Mr.98 (talk) 14:44, 13 January 2011 (UTC)
 * Me too 82.44.55.25 (talk) 16:50, 13 January 2011 (UTC)


 * I'll bet that #1 is a much bigger part of it than you think. The yellow glow comes from those sodium vapor lights that are pointing almost exclusively at the road. (And at parking lots!)  Sure, this is a small fraction of the town's total area, but no one is shining floodlights on empty fields. APL (talk) 16:45, 13 January 2011 (UTC)


 * ... and, of course, it doesn't happen in truly rural areas that are far from street lighting. We don't see "tangerine trees and marmalade skies" here.    D b f i r s   18:01, 13 January 2011 (UTC)

It sounds like we're informally agreeing that #1 plays a large part. As baffling as this sounds, it may be the reason - as huge a difference as the lighting makes. I can tell you two things about where I've lived: 1) never a huge city (which would render it moot), and 2) I've lived fairly rural, but I don't remember what happened there to be honest. Magog the Ogre (talk) 18:52, 13 January 2011 (UTC)


 * I don't know what you consider a "huge city" but it happens in Boston very plainly. --Mr.98 (talk) 23:27, 13 January 2011 (UTC)


 * If you're talking about the night during the snow, then of course the air is full of scatterers (snowflakes) and you would expect the city glow to be much enhanced. Even if it's not appreciably snowing at the ground, I would guess it possible for many snowflakes to stay suspended in moving air beneath the clouds for some time.  --Tardis (talk) 01:22, 14 January 2011 (UTC)


 * Incoherent scatter is the process by which electromagnetic signals (usually radio) bounce off a huge ensemble of individual tiny scatterers (usually ions). However, the principle applies equally well to light scattering off of optical scatterers (snowflakes).  It should be noted that the radar equation, adjusted for incoherent ensemble scatterers, computes a signal return orders of magnitude larger than for a single point scatterer.  (In plain English: lots of tiny snowflakes, each oriented randomly/independently, are sufficient to make one really bright non-specular reflection).  Nimur (talk) 19:58, 14 January 2011 (UTC)


 * The light itself should be the result of light domes in rural locations which are more visible when the cloud ceiling (cloud) is lower. ~ A H  1 (TCU) 02:57, 18 January 2011 (UTC)

Do vaginas scale?
Vagina is unclear on whether the dimensions of a human's vagina correlate with their height. Is this the case or are they more or less unrelated? 83.70.228.170 (talk) 13:38, 13 January 2011 (UTC)
 * Vagina dimensions correlate no more to a woman's height than a man's penis length or, say, the size of one's earlobes or nose. They are indepedent genes (French and Jewish noses aside... OK bad joke... take whatever potshot you'd like at me, I'm American and we take our fair share). Mind you I'm not a medical expert (and neither have I slept with tons of women so as to get a scientific sample size... a number that would need to be quite large anyway), but this is what I've heard. Magog the Ogre (talk) 18:47, 13 January 2011 (UTC)
 * Only female humans have vaginas. Obviously there is a correlation between vaginal dimension and the height of the female because the vagina of a child is smaller than an adult. The vagina is very flexible and able to expand to pass a baby. Tall slim women are not known (OR) to have larger vaginas than short women, hence there is no obvious correlation among adults. Vaginismus is the condition where a vagina is abnormally restricted due to a muscle reflex. Episiotomy is an operation to enlarge the vagina to ease childbirth. After giving birth vaginally, it's normal for the vagina to be larger than it was before. Whether one recovers the pre-birth size is uncertain but may be helped by doing Kegel exercise. Cuddlyable3 (talk) 00:03, 14 January 2011 (UTC)
 * If "Only female humans have vaginas," then how do females of all other, nonhuman, vaginaless, species copulate? Edison (talk) 05:35, 14 January 2011 (UTC)
 * I agree with Edison; I don't have any idea why you've said that Cuddlyable. Also, puberty can change all sorts of characteristics which have nothing to do with height. Magog the Ogre (talk) 06:25, 14 January 2011 (UTC)
 * I'm guessing Cuddlyable3 meant pedantically to say that among humans, only females have a vagina – presumably because the OP refers to "a human's vagina" instead of either "the human vagina" or else "a woman's vagina". WikiDao    &#9775;  07:09, 14 January 2011 (UTC)
 * I'm guessing Cuddlyable3 subscribes to a particularly binary view of gender, which is dependent entirely and only on the genitals. This would classify all those with vaginas and without penises as female, and all those without vaginas and with penises as male. Quite how Cuddlyable3 would then classify those with ambiguous genitalia I don't know, but this classification would certainly imply classifying all transgender people as being whatever Cuddlyable3 thought their genitalia looked like, rather than what they say they are. All in all, an odd thing to say.  86.164.67.42 (talk) 12:45, 14 January 2011 (UTC)
 * Note the use of indent. The set "human" was established by the OP. A subset of that set is "female human". Another subset is "nervous american who weighs quantities of women in tons". Gender is a classification like that of a lens "concave or convex is what defines sex" and a penis is a vagina that got made inside out. We are not so ogreish as to assume that everyone has found out what should happen at Puberty. Those still in doubt need the WP:DUCK test. Cuddlyable3 (talk) 13:20, 14 January 2011 (UTC)
 * Just as a technical reminder, the penis corresponds to the clitoris. It is not "a vagina that got made inside out." I'm sure you knew that. :) Regarding ducks, the Ireland-based IP hadn't been used in over 3 years until today, so who knows. ←Baseball Bugs What's up, Doc? carrots→ 17:19, 14 January 2011 (UTC)
 * Oh! Human females! Of course! It's all so obvious now. That certainly explains a lot.  Thanks Cuddlyable. APL (talk) 17:59, 14 January 2011 (UTC)
 * When I first read the statement, I thought that maybe the term "vagina" was reserved for the human part, with some other term for animals. Humans sometimes use different words for their body parts compared to the equivalent parts on animals. Humans (both male and female, generally) have "nipples," cows have "teats," for instance. A dead human may get an "autopsy," but a dead animal only gets a "necropsy."  Edison (talk) 18:36, 14 January 2011 (UTC)

Primitive extant members of Carnivora
Based on a recent question about the most-recent common ancestor of cats and dogs, I'd like to see some candidates for the most primitive living Carnivoran. By primitive I mean possessing a smaller number of derived characteristics. It may be hard to compare primitiveness between felids and canids, so perhaps finding a primitive member of each would be enlightening. Thanks, SemanticMantis (talk) 15:06, 13 January 2011 (UTC)
 * There do not seem to be definitive answers to this question, perhaps because the Order underwent a good deal of rapid evolution soon after its appearance. Googling "Basal living carnivore" finds a good many sites discussing matters surrounding the topic: one, a Powerpoint presentation appearing under the heading "Fissipedia and Pinnipedia_Pailinrut - Slide 1" (which I lack the interweb-fu to link directly) has some particularly relevant slides. My impression is that, of extant Carnivora, the African palm civet is a good candidate for the most basal of the Feliformia, but I'm unsure whether this is borne out by genetic analyses. 87.81.230.195 (talk) 17:16, 13 January 2011 (UTC)
 * Thanks, the slide set you mention is here: . The palm civet is a good example. Still interested in other candidates, or examples from Caniformia. SemanticMantis (talk) 18:07, 13 January 2011 (UTC)

wha t happens to the body after death?
Hi, I was thinking that if we take a dead body, and instead of burying it under the ground, we put it in some place hard to penetrate, what will it become after a long time? will it turn into soil? or petroleum? i'm asking this because I see some creationist say that "we are made of soil, because we will turn into soil after being buried." the soil itself isn't mainly made up of organic compounds and is mostly made up of mineral ones, so where doall the organic compounds in our body go? — Preceding unsigned comment added by Sina-chemo (talk • contribs) 18:33, 13 January 2011 (UTC)
 * In the short term, it will blow up. In the long term it will dry out and turn to dust as long as there is air to wick off moisture. Anything that can sublimate/evaporate will. I'm sure there will be folks who provide more accurate answers. (!) P ЄTЄRS J V ЄСRUМВА  ►TALK 18:39, 13 January 2011 (UTC)
 * Assuming the container is sealed, even from water, most likely you'd end up with a damp sludge containing the mineral and organic compounds that the gut flora couldn't digest along with their waste. I wouldn't call it soil, although it'd probably be something that'd be good on your rosebed.  Check out the Decomposition article. --  JSBillings  18:50, 13 January 2011 (UTC)
 * And about Sina-chemo comment about soil, it depends which soil you are talking about. O horizon soil is almost all organic matter, whereas the B-horizon is mostly mineral matter. --  T H F S W  (T · C · E) 18:59, 13 January 2011 (UTC)
 * Body farm isn't exactly what you mean, but might be of interest. --198.178.232.2 (talk) 20:45, 13 January 2011 (UTC)
 * Judaism, Christianity, Islam and Zoroastrianism all variously describe a Resurrection of the dead, usually referring to a regeneration of all people to face God on Judgment Day. Cuddlyable3 (talk) 01:03, 14 January 2011 (UTC)
 * Actually Judaism doesn't believe in a Judgment day. Rather the resurrection of the dead is a reward - basically heaven on earth. Ariel. (talk) 01:35, 14 January 2011 (UTC)
 * You might be interested in reading about bog people, who are essentially preserved in an almost pristine state for thousands of years, due to the presence of tannins in their environment. It's almost a natural mummification.  The exact outcome in the long-term is highly dependent on environmental conditions - in very hot, dry areas, bodies will dessicate; in very cold areas, they will freeze and preserve.  In a temperate area, they will engorge (bloat) and then proceed to rot.  If bacteria, fungi, insects, and large predators have access, the soft tissues are stripped.  And given a long enough time and proper geological and environmental conditions, the bones and some other parts can fossilize, meaning that certain minerals will be chemically replaced by more permanent minerals - petrification. Nimur (talk) 01:06, 14 January 2011 (UTC)

thanks. tha t helped alot. so is this finally right to say that we turn nto soil(even if we are not buried in it)? — Preceding unsigned comment added by Sina-chemo (talk • contribs) 13:55, 14 January 2011 (UTC)
 * Depends how you define "soil". Most people want some sand (dare I say "dust"?) in it, which a body will never produce. --Sean 16:33, 14 January 2011 (UTC)
 * Generally, bodies already are put in containers that are relatively hard to penetrate: sealed coffins, and the coffins placed inside concrete vaults, be they above or below ground. Surely not a truly airtight environment, but the body should stay relatively intact much longer than if buried in a shallow grave in a forest or some such. ←Baseball Bugs What's up, Doc? carrots→ 17:09, 14 January 2011 (UTC)
 * The term 'soil' usually includes a mineral component, the 'parent material', although peats can be almost entirely organic. Given enough time, most of the human body will decay and can be metabolised to carbon dioxide and water. Depending on the conditions, the nitrogen compounds (mostly from proteins) will end up as ammonium, nitrate or nitrogen compounds - soluble organic or inorganic material. In a sealed environment, the process may not run completely due to a lack of oxygen (with anaerobes you may end up with methane instead of carbon dioxide) and a lack of carbon sources to convert the nitrogen compounds to nitrogen gas. Bones have a lot of calcium - decay would leave bones brittle, but I think it would still take some force (if only being touched) to make them crumble to dust. Teeth last a really long time. Guettarda (talk) 20:02, 16 January 2011 (UTC)
 * Interstellar dust, over billion-year time scales? ~ A H  1 (TCU) 02:46, 18 January 2011 (UTC)

Medical Doctors in Canada
How many medical doctors, NOT including dentists, are there in Canada99.232.23.179 (talk) 19:04, 13 January 2011 (UTC)
 * The Canadian Medical Association provides some statistical information on Canadian physicians. –Henning Makholm (talk) 19:25, 13 January 2011 (UTC)
 * http://www.wolframalpha.com/input/?i=canada+physicians Bo Jacoby (talk) 08:52, 14 January 2011 (UTC).

The origin of the term "HVAC"
Who is the first people to use the term "HVAC" to refer system with Heating, Ventilating, and Air Conditioning ? Thanks--Wolfch (talk) 22:36, 13 January 2011 (UTC)
 * It's an acronym. --Sean 16:34, 14 January 2011 (UTC)
 * Which does not answer the question of who brought it into use. I found nothing with a quick search, but would suggest checking with a large dictionary, such as the OED, that provides a date of first reference.  It may not tell you who, but it will at least narrow down when. &mdash; Lomn 18:38, 14 January 2011 (UTC)
 * It would be a good idea to ask on the Language RD, and some of the regulars there have OED subs, plus those who don't may be taking advantage of the current free access offer that was noted on that desk. -- LarryMac  | Talk  18:51, 14 January 2011 (UTC)
 * I took advantage of the OED offer, which is nothing more than a username and password, and HVAC does not show up at all (which surprised me). I also checked google books, but there was too much. I will point out that A/C was invented by Willis Carrier of the Carrier Corporation in 1902, so maybe ask them. Ariel. (talk) 19:21, 14 January 2011 (UTC)
 * I think the OED is more interested in words than acronyms. Is HVAC common as a term?  I've never met it in the UK, but air conditioning is less common here.    D b f i r s   13:25, 16 January 2011 (UTC)
 * Maybe the "VAC" in HVAC was chosen to be part of the acronym because it functions in a similar way to a vacuum cleaner (by circulating air)? ~ A H  1 (TCU) 02:37, 18 January 2011 (UTC)