Wikipedia:Reference desk/Archives/Science/2013 March 16

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March 16

Jet streams

My geography textbook says- "The movement of the westerly jest stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer affects the monsoons." How? --Yashowardhani (talk) 05:55, 16 March 2013 (UTC)

Read Jet stream, for starters. In general, the jet streams affect weather because they aren't stationary, they shift around and help direct varying weather patterns. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:04, 16 March 2013 (UTC)

I still don't get it. — Preceding unsigned comment added by Yashowardhani (talk • contribs) 06:18, 16 March 2013 (UTC)

I'm more familiar with hurricanes, but presumably the same applies to monsoons. Jet streams serve somewhat like gutter guards in bowling, to corral the big storms between them. A powerful enough hurricane can "win" a fight with a jet stream, though. StuRat (talk) 06:03, 16 March 2013 (UTC)

The Nose Knows?

As a cynophile with a serious interest in criminology, I've read more than a little about cadaver dogs. My understanding is that they are specially trained to detect and respond to extremely minute quantities of cadaverine and/or putrescine. Of cadaverine in particular, I have read that it is nearly impossible to clean up every trace of it from something that has had contact with it, and that it is naturally present in semen and urine (in small quantities, but sufficient to contribute to the way they smell *to humans*). If these two facts are true, wouldn't every bathroom in the world and quite a few bedrooms smell at least as pungent as a well-scrubbed crime scene to one of the canine elite? Perhaps more significantly, I've read that cadaver dogs are trained to respond only to the smell of HUMAN decomposition, but cadaverine and putrescine are chemical compounds with fixed molecular structures, found in all decaying animal tissue. There's no such thing as distinctly "human" cadaverine, so how is the dog able to distinguish a place where a human body lay from a place where there was a dead rat, even after the passage of months or years? I don't doubt the reliability of cadaver dogs; I know they've only been proven wrong in about one percent of cases. I just wonder how it is exactly that they're able to do this, because the way I've read about it seems a little simplistic. — Preceding unsigned comment added by 172.3.129.135 (talk) 05:56, 16 March 2013 (UTC)

I suspect they use the cadaverine and/or putrescine to find the site, then, once close enough, they can detect the other, more subtle chemical odors which distinguish human decomp from other types. I would suspect that chimps would smell the closest to humans, so I wonder if a dead chimp can fool them. StuRat (talk) 06:07, 16 March 2013 (UTC)

They can distinguish a complex array of molecules, analogous to a signature. Some of the chemicals communicate "dead", while others communicate "human". ~:74.60.29.141 (talk):~ —Preceding undated comment added 07:13, 16 March 2013 (UTC)

Double-fuselage aircraft

I think an article about double-fuselage aircraft would be useful, although I have no knowledge of the field. Historical instances could be described along with the recent double-fuselage Airbus patent. Your thoughts? I was searching for this but found that the topic is not covered in Wikipedia.--Anixx1 (talk) 10:17, 16 March 2013 (UTC)

It's interesting we have no such article. But we do have Category:Twin fuselage aircraft for your reading pleasure. Someguy1221 (talk) 10:26, 16 March 2013 (UTC)

Radioactive sound

close request for medical advice
The following discussion has been closed. Please do not modify it.
Hi, I am from Japan, and I used to live in Fukushima Prefecture and moved south to Miyazaki Prefecture out of fears for radiation. I live with my mother and before moving I was wearing a mask and had a thing to detect radiation which I don't know how it's in English and before moving it made lots of sounds, loud sounds meaning that there was huge radiation. My question is whether that radiation stayed with me and If I run any health risk. — Preceding unsigned comment added by Hyerotaku (talk • contribs) 12:41, 16 March 2013 (UTC) Presumably the radiation detector was a Geiger counter of some kind. --Mr.98 (talk) 14:02, 16 March 2013 (UTC) This question is a request for medical advice. Only a medical doctor can determine if you are having health problems due to radiation exposure. Nimur (talk) 15:37, 16 March 2013 (UTC) The map in Fukushima Daiichi nuclear disaster and accompanying map should give a sense of the level of exposure, and Radiation-induced cancer gives some notion of the probability, though the article isn't very good. Wnt (talk) 16:36, 16 March 2013 (UTC)

If you can read and write Japanese, you can ask at the Japanese reference desk: ja:Wikipedia:調べもの案内.

—Wavelength (talk) 16:51, 16 March 2013 (UTC)

different sexual responses in women

This is kinda intimate question, but I mean it seriously and not as any kind of joke let alone being smutty or anything. But my boyfriend is interested in psychology, and knows some stuff about Freud, as do I. We both thought that his early material on how clitoral responses to sex are immature forms. But when my boyfriend began fondling me after we became a couple, some really interesting things happened. When it was foreplay and he was feeling my vagina with his fingers, I would become very wet after a while, which is normal of course, and then we would have sex.

But we had another kind of fantasy, which did not really have sex as its end result. You see, we are both very turned on by spanking fantasies. When he fondles me as he tells me how I am going to be turned over his knee and punished, I hardly get wet at all, even though it really makes me hot. On the other hand, my clitoris engorges with blood, and becomes like a stiff little ball, a bit like a penis. They are very different responses, and both of us can feel and attest that this is really happening, but we don't have any idea as to what is going on. It's like TWO different sexual responses based on different fantasies. We haven't asked anybody about it because it is so intimate, but we thought that here in Wikipedia, under the cover of anonymity, there might be some experts who could throw some light on this. Once again, this is real and I hope that no one thinks it is just a dirty joke. It's not. It's our own bodies and feelings, and we are just wondering as to what is going on. Sallysays (talk) 15:11, 16 March 2013 (UTC)

You're not going to get a great deal of 'help' here because many people will regard this as medical advice which we are not allowed to offer. What I would say in a general way is that what you are experiencing is, just as you surmise, different responses from different scenarios. This is widespread among the population and as long as you enjoy what you are doing and are not harming or affronting anyone else enjoy it. Sometimes with sex it is not always helpful to try and analyze everything that is going on. Freud knew little about physical (and probably emotional) sex but he had some theories about how guilty or otherwise some people feel about sex. Don't get hung up on the theory, just enjoy the practical. Caesar's Daddy (talk) 15:52, 16 March 2013 (UTC)

If this is a medical question, then so is a question about how best to roast a duck. :) Unfortunately, I have no idea how to answer it. I strongly suspect that erectile response, though commonly portrayed as all-or-nothing, must be somehow distributed throughout the body, a sort of general sensation/response that is only more prominent in certain familiar places. For example, nipples can become erect - sometimes - and I would suggest that so can the nose, in extreme cases in the form of honeymoon rhinitis. It seems like lots of other parts of the body can become arousable under some circumstances - the feet for example - and I recall reading of a paralyzed person transferring much of his former penile response to his thumb somehow. I personally think that each of these parts is potentially arousable independently of any other. Wnt (talk) 16:16, 16 March 2013 (UTC)

A doctor may have a 'hard' time with this question as I suspect it's not something covered in medical school! Sounds like something for the realm of a sexologist who I'm sure you can find online and anonymously. Sandman30s (talk) 08:10, 17 March 2013 (UTC)

There's nothing particularly surprising in the disparity between your differing responses, really. One scenario involves direct stimulation of the genital region and is more likely to involve parasympathetic nervous pathways which could stimulate lubrication more readily than purely mental/emotional triggers, regardless of overall level of arousal - we are talking about two different types of physical stimuli here, afterall, and it's not surprising that your body would react differently to them, , even though both would borrow upon many of the same physiological mechanisms. Remember also that not every nervous response involves information being passed directly back and forth between the brain (or even the CNS) and the stimulated region of the body; many are partially or completely locally reflexive and some of the former are processes involved in sexual response. In any event, consider that autonomic responses of this nature, including lubrication, sometimes occur during rape, compounding the emotional trauma of victims already struggling with a misplaced sense of shame, and we can make some safe assumptions about how much they enjoyed the stimulation. But even putting those extreme situations aside and looking at arousal in healthy interactions, it's clear that arousal is not one big spectrum of response (zero to a hundred), but a rather a complex composite of interconnected physiological and mental factors (more "a little paprika, a little thyme", and never exactly the same recipe). In fact, you hit upon this a bit in your own question when you noted that sex was not the end result of your fantasy; the fact of the matter is that humans are very lousy at distinguishing between various types of physical arousal (consider for example, the now well-replicated experiment in which men who were asked to meet a female grad student in a dangerous environment later rated her as more attractive than those who met her in a more neutral location; their acute stress response became mingled with their sexual appraisal) let alone distinguishing between different types of specifically sexual arousal. So, yes, not only is it possible to have two very different types of sexual response depending upon stimuli and context, it's a near certainty that you will have many different forms in your life but will be (hopefully blissfully) unaware of the subtleties between them. Snow (talk) 10:45, 17 March 2013 (UTC)

Of course the responses will be different, just as the stimuli are different. In the first instance, your boyfriend was directly stimulating the Bartholin's glands which produce the lubricating fluid. In the second instance, this direct stimulation is absent and, as Snow says, you were getting physically aroused by something different. Don't worry about it, get a copy of The Joy of Sex, and enjoy yourselves! --TammyMoet (talk) 18:21, 18 March 2013 (UTC)

Headphone socket problem

I've got a 3.5mm headphone plug going into (as one might expect) a 3.5mm headphone jack on my hi-fi - but I'm only getting the sound through the left channel. However, I can get stereo again if I only push the plug 3/4 of the way in.

There's nothing wrong with the headphones - I've tried them on a couple of other pieces of equipment and they work fine.

Any suggestions as to how I might be able fix this at home without opening up the stereo (or taking it to someone to fix it for me)? Or is it just the case that the socket needs replacing? I've had this sort of thing happen before on crappy equipment that I was never really bothered about fixing, but this is my main stereo now... --Kurt Shaped Box (talk) 15:22, 16 March 2013 (UTC)

Have you also tried other headphones on the stereo? μηδείς (talk) 16:23, 16 March 2013 (UTC)

Yes. Also with an extension cable. Same thing. --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

The obvious work-around is to jam something into the jack to prevent the plug from going further than 3/4 in. Perhaps tiny balls of aluminum foil ? Be sure to add them slowly, and test after each one, so you don't go past the desired point. StuRat (talk) 16:30, 16 March 2013 (UTC)

When you push the jack in partway are you sure you're really getting stereo sound? Or are you just getting the one working channel in both speakers?

It would be weird it you actually got true stereo with an improperly plugged plug, but getting one channel from both speakers is what normally happens in that situation.

(bearing in mind that this is the final reply I wrote after I went back to check this out) Interestingly, it seems to have started working again now - but I'm aware that electronic equipment rarely fixes itself and it was definitely exhibiting the symptoms I described a few hours ago. Any thoughts... --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

I suspect that your hifi is either broken or misconfigured (Is the balance knob cranked all the way over?) APL (talk) 17:07, 16 March 2013 (UTC)

The balance is fine - that was the first thing that I thought was wrong. --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

My guess is that the hifi jack is either broken, or it isn't made for stereo sound. (They used to have mono headphones at one point, if I remember correctly.) If this is the case, then you only have 2 contacts in the jack, and 3 contacts on the headphones. Perhaps pushing it in 3/4 of the way makes it so the one contact in the jack touches both contacts on the plug. ~Adjwilley (talk) 18:20, 16 March 2013 (UTC)

It's definitely a stereo jack, FWIW. --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

I'd say you have an intermittent open circuit somewhere between the amplifier and the headphone, most likely in the plug or the jack. FWIW 24.23.196.85 (talk) 05:37, 17 March 2013 (UTC)

I have some headphones which include a microphone. The microphone is just a little bulge in one of the wires from the earphone. Because of this, the little plug has one more ring on it than a plain stereo headphone, and if I push it all the way in, I only hear one channel. 99.140.253.109 (talk) 20:31, 16 March 2013 (UTC)

This is a common problem with wear and corrosion in the jack socket. If you are able to take your hi-fi apart (having unplugged it first, of course) to gain access to the socket, just gently clean the spring contacts with emery paper and very gently bend them in slightly towards the centre, but not too far or your headphone plug will not go in. If you plug in your headphones with the hi-fi opened up, then you will be able to see where there is a bad contact. Dbfirs 09:00, 17 March 2013 (UTC)

Alternatively, the contacts may be aligned properly but the slot itself malformed, such that the plug is skewed or leveraged at an inappropriate angle, forcing only one contact. I once had a device with a hard plastic o-ring on the outer surface of the socket of the jack, which was meant to grip the plug at its thickest point and hold it in place such that it made firm connection with the contacts inside. When the o-ring cracked, it released tension on the plug, allowing the weight of the cord to skew the angle of the plug such that only the one contact was made and it produced exactly the type of issue the OP is describing as a result. 108.248.176.172 (talk) 14:04, 17 March 2013 (UTC)

One thing I've seen on more than one piece of equipment is cracks in the solder joint between the jack and the circuit board, where there is typically not a great physical connection. The joint is typically subject to a lot of stress due to the cord leaning on the lever arm of the piece of the plug which protrudes, and one or more of the contacts breaks or gets loose and intermittent. Gzuckier (talk) 01:32, 18 March 2013 (UTC)

Runny nose / stuffy nose

When people get sick, they often experience either a runny nose or a stuffy nose. While we have article on both, neither seems to address the issue I am wondering about. When we get a runny nose or a stuffy nose in association with an illness is that because A) the illness / infection is directly causing problems with the nose, or B) the body is intentionally adjusting mucous production in an attempt to fight the illness / infection (i.e. its a natural response to infection)? I would assume that changes in nasal mucous composition might offer some protective benefit against certain nasal infections / irritants, so it seems plausible that it might be part of the body's natural response. However, I haven't seen anything that provides a detailed explanation of how and why people develop runny / stuffy noses. Dragons flight (talk) 16:56, 16 March 2013 (UTC)

It's actually both. Mucus production is a physiological response to agents that infect cells in the mucous membranes. Its function is to flush the agent out of the membranes. For viruses, for example, they infect cells, replicate massively, and then burst the cells and diffuse away to infect other cells. Flushing the membranes reduces the density of virus there. Looie496 (talk) 17:45, 16 March 2013 (UTC)

(ec) I believe it is an immune response designed to wash bacteria and viruses out of the nasal cavities. It might seem like this immune response is too late, but, once you are infected, that leaves you even more open to reinfection or additional infections, so keeping out additional microorganisms is important. Unfortunately, this is also a method to spread the disease to others, and some of the diseases may specifically trigger our immune response, in order to achieve this goal. StuRat (talk) 17:47, 16 March 2013 (UTC)

Hmmm, according to [1] it looks like the people getting placebo medications after laboratory infection with rhinovirus type 39 had the lower virus titer, but the difference wasn't significant. They had substantially fewer symptoms, however. Of course, this doesn't measure many things, including longer term effects, secondary infections, or antibody titer years later... I'm still not going to call the response worthless without more data than this. But it should be clear enough that if the virus is doing it "intentionally", it's doing it to spread, not to replicate. Wnt (talk) 18:10, 16 March 2013 (UTC)

Thinking back to AP biology (ugh, over a decade ago), a lot of the stuffy runny nose problems are actually caused by the immune system's response. That's why you still get stuffy when you have allergic reactions (i.e. when the immune system mistakes something harmless like pollen for a virus.) Unfortunately I don't remember any of the names of the cells that do the fighting (other than antibodies). ~Adjwilley (talk) 18:24, 16 March 2013 (UTC)

Histamine#Effects on nasal mucous membrane has a little bit, as does mast cell. --Jayron32 03:13, 17 March 2013 (UTC)

Thick rotor blades

Could the rotor of a helicopter be thicker, more resembling of aircraft wings? OsmanRF34 (talk) 19:53, 16 March 2013 (UTC)

Just over a week ago, I wrote a response to a similar question, comparing wings and rotors.

“ ...the thing to remember is that helicopter blades, fan blades, propeller blades, and fixed wings are all just airfoils. ...A helicopter rotor is different from (fixed-wing) airfoils; it is designed to provide lift and remain stable while the helicopter is operating in its normal flight envelope. ”

For good measure, here's The Helicopter Flying Handbook from the FAA, with all you need to know to start learning to fly helicopters. Nimur (talk) 20:21, 16 March 2013 (UTC)

And here's an easily-digestible quick read from NASA's technical archive, Desgn and Analytical Study of a Rotor Airfoil, and it's sibling-report, ...for an Advanced Rotor Airfoil (both produced for NASA out of Lockheed from 1980). As I summarized previously, and as both these reports clearly state, the primary design objectives (item number one, in fact) are limited by practical concerns like weight, manufacturability, and safety/reliability/durability. Table III in the first report lists dozens of airfoils tested and analyzed (including several NACA airfoils with various cambre). It even has a cartoon "design decisions flow-chart" on Page 64, indicating a few conditions that would encourage engineers to choose a thicker or thinner airfoil - with particular emphasis on the relationship between thickness and the drag divergence parameter. Nimur (talk) 20:46, 16 March 2013 (UTC)

See Sikorsky S-72 ScienceApe (talk) 22:13, 16 March 2013 (UTC)

Helicopter rotors and aircraft wings already resemble each other - but the chosen airfoils differ because the speed and AoA differs. It is also considered beneficial for a rotor blade to have a symmetrical airfoil, since it reduces the movement of the centre of pressure, whereas for fixed wing aircraft an asymmetrical airfoil is often preferred since it can provide more lift for less dreag. As a sidenote, the thickness of an airfoil is usually expressed as a percentage of the chord. Thus a wing for a passenger jet can be said to be just as thick as the rotorblade for a helicopter - but since the chord of the jet is longer, the measured thickness of the wing is several inches - or even feet - more. WegianWarrior (talk) 08:30, 17 March 2013 (UTC)

Aircraft wings are hollow! Rotor blades are usual not because they not only have to take up with much more than typical wing-forces (like vibration from switching airspeeds) but also with significant centrifugal force. So every extension of blade surface will get you a heavy extra weight for the hole rotor construction likely outweighing most or all gain in lift. --Kharon (talk) 12:09, 17 March 2013 (UTC)

One big problem is that when the helicopter is pitching or rolling, the swash plate is tilted and each rotor blade will change pitch twice in each revolution of the rotors. If the blades were wider, the rotational inertia about their long axis would be higher and it would be harder to get them to change pitch like that. This would, in turn, result in the helicopter being harder to control. This is enough of a problem in fixed wing aircraft so we (mostly) have ailerons, flaps and elevators rather than altering the pitch of the entire wing. Getting controls and actuators to do that inside a helicopter rotor would be really tough! Also, if the rotors are heavier, then the tendency of the body of the craft to rotate in the opposite direction of the rotors would be far greater - and since that force is controlled by the tail rotor, you'd need that to be MUCH bigger too. SteveBaker (talk) 19:28, 19 March 2013 (UTC)

Line of sight to the sun

Let's say you're naked in outerspace, and for some reason you don't die (just for the purposes of this question). If you have a direct line of sight to the sun (without anything else in the way), how hot will the side of your body facing the sun be compared to the side that isn't? ScienceApe (talk) 23:54, 16 March 2013 (UTC)

The answer depends on how far from the sun you are. Spectral_flux_density might be interesting. SemanticMantis (talk) 00:04, 17 March 2013 (UTC)

This third question from the last may be helpful. --PlanetEditor (talk) 01:20, 17 March 2013 (UTC)

After reading the NASA link above, I'd say that you would be pretty hot overall (over 100 C), but that there wouldn't be a huge temperature difference between the two sides of your body. I say this because I believe the rate of heat flowing from one side of your body to the other would be fairly large, especially if you're alive and your circulatory system is still going. But then you'd dehydrate pretty fast, being above the boiling point of water and in a vacuum. As a side note, I hope you're wearing sun screen, especially if you plan on performing this experiment naked. ~Adjwilley (talk) 01:32, 17 March 2013 (UTC)

What sunscreen is going to do when his body temperature is above 100 C? --PlanetEditor (talk) 02:05, 17 March 2013 (UTC)

If you were as far away as the Earth and rotating wouldn't you be about the same average temperature as the Earth? μηδείς (talk) 02:44, 17 March 2013 (UTC)

Approximately, yes; although some models also account for albedo or use a "gray-body" instead of black-body Stefan-Boltzmann law. This question is a typical homework problem in an astronomy class; apply your favorite variation of the equation for planetary surface temperature, accounting for as many non-idealities as necessary. Unlike planets and cows, a person might not be well-modeled as a sphere... If the question really is asking about the difference in temperature between illuminated and dark sides of an object, we must stop approximating the object as a sphere, and apply Fourier's law with an appropriate choice for heat capacity and thermal conductivity. Nimur (talk) 02:48, 17 March 2013 (UTC)

A bit hotter, since you don't have clouds to reflect some of the sunlight before it hits you. Sunlight can still reflect directly off you, but that's similar to it reflecting off the surface of the Earth. StuRat (talk) 02:50, 17 March 2013 (UTC)

Great thanks, that's exactly what I was looking for. I recall there being a huge disparity between something in the shade vs. in direct sunlight in space. That leads to my second question, why is it that night time (the side of the planet not facing the sun) doesn't freeze to those cold temperatures? Obviously nighttime is colder but if it's summer time, or near the equator, you can have a very very hot night, but that part of the planet is in the shade. Is it because of the retention of heat in the atmosphere? ScienceApe (talk) 08:09, 17 March 2013 (UTC)

Clouds in the atmosphere help to retain heat, so rapid cooling and frost is more likely with a clear sky, but the main effect preventing frost in summer is the thermal retention of the earth and oceans. Dbfirs 08:52, 17 March 2013 (UTC)

Agreed. Places without bodies of water or clouds (that is, deserts) do have temperatures drop dramatically at night. StuRat (talk) 08:56, 17 March 2013 (UTC)

Larry Niven's first story "The Coldest Place" (spoiler alert) Gzuckier (talk) 01:45, 18 March 2013 (UTC)

Your skin color might make a rather noticeable difference in how hot you get. Of course, once we turn into jerky, we'll probably all have similar coloration. StuRat (talk) 02:50, 17 March 2013 (UTC)

Here, Ice on the Moon... one of the greatest unresolved questions about lunar geology is exactly what thermal capacity and conductivity does the lunar substrata have? Though Apollo brought back lots and lots of surface material for study, we have never been able to directly study the geological properties of the subsurface. NASA's academic research consortium called this among the highest-priority unresolved scientific facts about the moon. Why does it matter? Because we're looking for icy permafrost in permanently shadowed areas of the moon, hoping these areas are cold enough to keep ice frozen - but that assumes that the thermal input comes from the sun - and we know that there is some thermal flux through the substrata. (Even shady regions will get some solar energy input that flows through the ground!) So, if we want to estimate how much ice there can possibly be, we need better thermal models for heat flow in the subsurface. In other words, how cold are the shadowed areas of the lunar polar regions? Are they cold enough for ice? To some extent, the LCROSS water vapor plume provided some new information. As we look for more water ice in more places around the solar system, we need all the information we can get to complete the picture - particularly when it comes to setting bounds on possible temperatures. Moral of the story: learn Fourier's law early, learn it well, apply it frequently; simulate your coffee thermal performance every morning,... because you never know when NASA will need to call you up to exercise those skills. Nimur (talk) 03:08, 17 March 2013 (UTC)