Wikipedia:Reference desk/Archives/Science/2008 July 20

= July 20 =

Sildenafyl Citrate
What (if anything) would happen if a woman takes a Viagra tablet? —Preceding unsigned comment added by 99.240.186.7 (talk) 01:45, 20 July 2008 (UTC)


 * Sildenafil might be of some interest. --Tango (talk) 02:11, 20 July 2008 (UTC)


 * I would expect it to have a similar effect on the analagous structure in the female anatomy (you can decide whether to take clitorally all the things I say). StuRat (talk) 20:21, 20 July 2008 (UTC)
 * GROAN, that's a horrible pun! Exxolon (talk) 20:14, 21 July 2008 (UTC)

gas flaring
what is the natural consequence of gas flaring on both plants and inhabitants41.219.197.37 (talk) 09:10, 20 July 2008 (UTC)


 * See Environmental issues in the Niger Delta. --Bowlhover (talk) 09:35, 20 July 2008 (UTC)

Universe Expansion
Is the universe's expansion speeding up or slowing down? I always thought it was slowing down but now someone has confidently asserted to me the opposite. I have looked at the wiki page on Expansion of the Universe but I don't think it says there (a lot of it was quite technical).

Thanks! 91.84.178.119 (talk) 12:05, 20 July 2008 (UTC)


 * The universe's expansion is currently accelerating, as far as we can tell, something thought due to dark energy.--Fangz (talk) 13:15, 20 July 2008 (UTC)

Thanks a lot, that's perfect.91.84.178.119 (talk) 13:40, 20 July 2008 (UTC)

Salt in medicine
Is salt (Natrium cloride) ever used for the treatment of any disease? (Like for example low blood pressure). —Preceding unsigned comment added by Mr.K. (talk • contribs) 12:45, 20 July 2008 (UTC)


 * Hyponatremia would be the obvious one. DMacks (talk) 13:40, 20 July 2008 (UTC)


 * For future reference, "natrium" is called Sodium in English. --Tango (talk) 17:18, 20 July 2008 (UTC)


 * And yes, it is used to raise blood pressure in patients with dangerously low levels, either as an IV or given orally (say as a broth). Low blood pressure is a common result of dialysis, for example, and this is a common treatment. StuRat (talk) 20:10, 20 July 2008 (UTC)
 * For more, see Saline (medicine). --Shaggorama (talk) 14:47, 21 July 2008 (UTC)

Olive oil in medicine
Is any serious study about the medicine use of olive oil in the treatment of any disease (like depression, for example)? —Preceding unsigned comment added by Mr.K. (talk • contribs) 12:47, 20 July 2008 (UTC)
 * There are some unsourced medical uses mentioned at Olive oil. Zain Ebrahim (talk) 12:55, 20 July 2008 (UTC)
 * One of the main components of olive oil comprises the majority of Lorenzo's oil, a substance which is used in conjunction with a controlled diet to treat adrenoleukodystrophy. The oil is still being evaluated by the FDA, but it's discovery was impressive and effective enough to merit the production of an academy award nominated film. --Shaggorama (talk) 06:09, 21 July 2008 (UTC)

Disadvantages of cholesterol drugs
What could possibly be the disadvantages of taking cholesterol reducing drugs? —Preceding unsigned comment added by 89.242.157.92 (talk) 12:49, 20 July 2008 (UTC)


 * Most drugs have side effects. It might be a good idea to look at the article for the specific drug you are interested in. Or consulting a doctor, if this relates to a specific medical concern.--Fangz (talk) 13:17, 20 July 2008 (UTC)


 * You may also want to read Statins. While not without side-effects you'll probably come across a lot of talk discussing statins as a sort of wonder drug given their general relatively high safety while having a relatively high success in lowering cholesterol. One concern, as is not uncommon in treating any condition diet related is that it's generally far better to modify/improve one's diet rather then to go on drugs, not just to avoid side effects of drugs, but also because of the other likely benefits of an improved diet Nil Einne (talk) 18:10, 20 July 2008 (UTC)


 * Yes, the lack of a good diet is a concern. I'd even go further and argue that some people may allow their diets to significantly worsen if they think some "miracle drug" will solve all their health problems for them.  StuRat (talk) 20:02, 20 July 2008 (UTC)

asteroid - earth impact
How precisely can we detect in advance menacing asteroids that might crash on earth? How do the predictions improve as the object approaches? At what moment are we able to pinpoint an area where it will crash? Is there a range of speeds asteroids find themselves in, do different speeds change the force or probability of an impact? Could one bounce off the atmosphere if it arrived a low angle? I read Asteroid impact but couldn't find the answers. Thank you. 190.190.224.115 (talk) 14:10, 20 July 2008 (UTC)


 * Different speeds, angles, locations, and the impactor's composition greatly affect the damage - see http://www.lpl.arizona.edu/impacteffects/ -- Finlay McWalter | Talk 16:05, 20 July 2008 (UTC)


 * Using radar, we can get extremely precise measurements, often a long time in advance. I think the asteroid needs to be quite close to get such measurements, but there are often close approaches to Earth before the one that could result in a collision, so we can take the measurements then and project the path forwards. Where it will hit depends on the exact time of the collision. Working out the thin path that the asteroid could hit is quite easy, since it just depends on the direction the asteroid is coming from, working out where on that path it will hit requires exact timing, and that requires much more accurate measurements. We would probably still get that some time in advance. I would expect asteroids can bounce off the atmosphere, although I'm not sure it's very likely - there's probably a very narrow range between where it becomes shallow enough to bounce and where it misses entirely. --Tango (talk) 17:28, 20 July 2008 (UTC)


 * The difficulty isn't just in taking precise measurements of location, direction, and velocity, but is complicated by the fact that asteroids can change direction. This change, while slight, can significantly affect whether one will hit the Earth several passes later.  Changes in direction are often due to interaction with other objects, but not always in a predictable manner.  For example, while passing a planet or the Sun, tidal forces or sunlight can melt ices, which can then be vented.  Those can change both the mass and trajectory slightly. StuRat (talk) 19:58, 20 July 2008 (UTC)

Midget sub in Birkenhead
Please see this request for info. &mdash; RHaworth (Talk | contribs) 15:41, 20 July 2008 (UTC)

Can someone help me in my own noble pursuit of all the world's (scientific) knowledge?
What would be the proper order to read your science articles so I can become a scientific personality with a steel trap mind? I mean someone says " .... my milkman, 1846, berylium, and the tenth law of thermodynamics?" I would immediately reply "My good man, your statement about the nonexistant 10th law of thermodynamics strikes I, a well known intellectual powerhouse in the esteemed scientific community, as peplexing and oddly prophetic. For it has been determined, by a barrage of outside the box labrotory research, that the math, using a newly, sometimes controversial property discovered by a still top secret learning facility, is indeed correct. Your milkman will discover 6 more laws of thermodynamics! ]:)

It would sound rediculous to the layman, but that's just the point, I want to be resprected by scientists, not necessarily people in general. --Hey, I&#39;m Just Curious (talk) 19:03, 20 July 2008 (UTC)


 * You can read them in any order. Science does not have a starting point.  You study.  If you find something that you do not understand, you study that.  If that leads to something you do not understand, you study that.  You continue until you understand the first thing you were reading.  As for being respected... you will need a PhD.  Make a list of the top 100 scientists of all time.  You will have a handful that lived before the invention of the PhD (so they don't have one).  You will have a couple that didn't get a PhD for one reason or another.  Then, the majority will have a PhD.  Why?  If you are too stuck up or lazy to get a PhD, why should all those who got theirs want to spend their time listening to you? --  k a i n a w &trade; 19:34, 20 July 2008 (UTC)
 * PhD is certainly the qualifier. All those man-hours put into achieving a doctorate, shows that you are a dedicated scientist in your field, and worth listening to. No one would care about what Miss Teen South Carolina thinks of blackholes or general relativity, but lots of people listen when Carl Sagan or Michio Kaku talk about them, because they know what they are talking about. ScienceApe (talk) 20:38, 20 July 2008 (UTC)
 * I don't think that's true at all. A PhD is nearly a requirement if you want a career in academia, but respect in academia is almost entirely a function of what you publish. Anyone who does look at your educational history will be more interested in the schools—a BA from Berkeley is worth a lot more than a PhD from Columbia Pacific University. I think professional astronomers appreciate Sagan's popularization of astronomy, but I don't think they'd rate his scientific work as especially memorable. Kaku I think is little short of a crackpot. Jack Sarfatti is an outright crackpot, and he has a PhD in theoretical physics from UC Riverside. There's a popular perception that anyone who can get a PhD must know what they're talking about, but sadly it isn't true. Anyone can get a PhD if they try hard enough; most people are just smart enough not to bother. -- BenRG (talk) 12:37, 21 July 2008 (UTC)
 * It strikes me that brushing up on grammar would enhance your intellectual powerhouse reputation (even among scientists). Clarityfiend (talk) 21:50, 20 July 2008 (UTC)


 * If you want my, totally biased advice: a great way to get a very generalist understanding of science is not to study science itself, but to study the history of science. If you read through the article on History of physics and took the time to look into the sub-articles linked to there, you'd have a great, great understanding of physics for practical, conversational purposes. Could you set up an experiment yourself? No. That takes formal training for the most part. Could you carry on a conversation about the relevance of the expanding universe? Yes indeed. Could you probably find yourself with a lot to say on the topic of string theory, relativity, and the philosophical implications of quantum mechanics? Yes you could—and frankly, if you aren't actually going to be whipping out your calculator right there, I'm not sure trying to parse through all the equations is going to get you very far anyway. Just my two cents. --98.217.8.46 (talk) 00:29, 21 July 2008 (UTC)


 * Having a PhD is not a requirement for being smart, or a good scientist. To be a good scientist, it is all about the mindset and philosophy you are in. A PhD is merely a good sign of one. Freeman Dyson is a famous physicist and Planck Medal winner who hates PhDs. Just wanted to get that in there. Mac Davis (talk) 03:43, 21 July 2008 (UTC)


 * You're only going to read (with dedication) if you're interested, and you'll talk more about subjects you're interested in as well. I'd suggest focusing your study on areas that fascinate you and follow tangents as they arise. You might also want to start brushing up on lay-science magazines; it sounds like you're interested in physics, so I'd suggest something like Scientific American or Popular Mechanics. --Shaggorama (talk) 06:24, 21 July 2008 (UTC)


 * I for one don't like popular science magazines at all. They just leave you "OK, black holes are like vacuum cleaners of space, but how does it really work.". Reading Wikipedia, for example, is much better. —Bromskloss (talk) 15:02, 21 July 2008 (UTC)

Don't forget to regularly read the Wikipedia Science reference desk (like you are now), I learn lots of new things everyday in just a 5 minute visit to this place. --Mark PEA (talk) 15:12, 21 July 2008 (UTC)

How does the odor of rotten food make us gag?
I suppose the "why" is a survival mechanism, so that we won't ingest foods that have been taken over by possibly noxious or even toxic bacteria. (Please correct me if I'm wrong.) What I don't understand is how this works. I had to get within arm's length of some overage potatoes today, last week it was a (refrigerated) leftover portion of baked tilapia. My few experiences with natto also made me gag almost to the point of retching. The pharyngeal reflex page wasn't much help, though I've also had this difficulty when clenching my teeth around those cardboard-covered dental X-ray film holders. Advice on avoiding this reaction would be helpful, but I'll settle for understanding it better. -- Thanks, Deborahjay (talk) 19:30, 20 July 2008 (UTC)


 * Yes, evolution is certainly why. As for how, I don't think it's anything mysterious.  Your nose detects various chemicals in the smell and sends the signals to the part of your brain that analyzes the info.  It compares it to a list of chemical combinations it recognizes as "rotten food" and sends the appropriate response to your body.  That list of chemical combinations recognized as rotten food is somewhat interesting, though.  It's partly inherited, but also partly learned.  If you've ever eaten a food that had gone bad and then made you violently ill, let's say eggs, that may very well cause all eggs, fresh or not, to be recognized, from then on, as "rotten food". StuRat (talk) 19:49, 20 July 2008 (UTC)


 * The "how" is a involuntary muscle spasm and an emotional reaction. As with many involuntary reactions you can learn to suppress it, if you for some reason have a need.  Garbage men learn that trick fairly quickly, I'd bet. ---J.S  (T/C/WRE) 00:09, 21 July 2008 (UTC)


 * Actually despite what StuRat might think, the mechanism behind the gag reflex in response to certain odors is mysterious. The reason is that it appears to be largely innate, and not learned. That means that there is some genetically hard-wired neural network that encodes the odor-to-behavioral response. This type of innate response to odors is not unusual in animals, but they typically detect such odors with their vomeronasal organ which projects neurons directly to regions of the brain that mediate innate responses. The problem is, humans do not have a vomeronasal organ. Which means we detect the odors through or main olfactory system or one of the mysterious olfactory sub-system such as the septal organ or the Grüneberg ganglion (these are so mysterious, in fact, we don't have an article on them). Yet the neurons in the these systems project to cortical regions and don't appear to mediate innate responses. So the answer is that no-one really knows how certain smells appear to be innately aversive in humans. Rockpock  e  t  01:42, 21 July 2008 (UTC)


 * This isn't sourced, but I don't think I agree that it's not learned. Have you seen game shows like Fear Factor where the contestants have to eat century egg? I enjoy an occasional one "fresh" (haha, fresh century egg) out of the shell, as do many Chinese, but the people on the shows always gag. So in some ways, it has to be at least partially learned. --Wirbelwind ヴィルヴェルヴィント (talk) 14:54, 21 July 2008 (UTC)


 * Like anything in the nature vs nurture debate, the truth is likely to lie somewhere between. Also, like I said before, it's possible to "learn" to suppress some types of involuntary reactions. ---J.S (T/C/WRE) 18:05, 21 July 2008 (UTC)

Blowing up nuclear powered vehicles
Lets say a nuclear powered vehicle like an aircraft carrier or a nuclear sub is attacked and destroyed with conventional weapons. Would the vehicle explode in a nuclear explosion, or would the explosion be no different than a similar conventional vehicle blowing up? Would there be radioactive contamination? ScienceApe (talk) 20:33, 20 July 2008 (UTC)


 * It's very hard to start a nuclear explosion (fission or fusion), and virtually impossible to do so with reactor that is designed specifically to avoid that occurrence. You'd get somthing like a dirty bomb, just dispersing all that nuclear material as a contaminant not trigger any further nuclear reaction. DMacks (talk) 20:36, 20 July 2008 (UTC)


 * (ec) There would certainly not be a nuclear explosion -- the fuels in such a vehicle are not weapons-grade in the first place, and even if they were, making a nuclear explosion is difficult; it requires very fussy design. Not gonna happen by accident. Radioactive contamination is certainly plausible -- I don't know what if any steps have been taken to prevent that in a war scenario and would be interested in finding out from someone who know --Trovatore (talk) 20:37, 20 July 2008 (UTC)


 * Actually US nuclear subs run on 93% enriched uranium, I do believe (and this article seems to claim such as well). It's not uncommon for small propulsion reactors to run on HEU—you get a lot more energy out of a lot less material that way (most research reactors used to run on HEU until somebody figured out that was a very bad idea). But no, you wouldn't get a real nuclear explosion, even with that fact being true, though you could get secondary explosions—e.g. inadvertent generation of hydrogen gas, that mixes with oxygen, that ignites, and spreads a lot of nasty stuff all over the place. You could imagine the fuel melting and forming a critical mass or two on the bottom of the reactor, which would result in neutron fluxes and maybe very tiny explosions but that's about it. --98.217.8.46 (talk) 21:40, 20 July 2008 (UTC)


 * If the reactor were a pure fusion reactor using maybe inertial confinement fusion, (I realize they aren't practical at the moment but for argument's sake) would the radioactive contamination be far less severe? ScienceApe (talk) 20:42, 20 July 2008 (UTC)


 * Yes. ICF contamination is just from the material holding the reactor together, mostly. An actual fission reactor is constantly producing highly radioactive substances in great quantity. ICF has very mild contamination risk compared to fission. --98.217.8.46 (talk) 21:40, 20 July 2008 (UTC)


 * I question the "great quantities" part. Certainly the quantity is less than or equal to the mass of nuclear fuel lost during the reaction, which is quite low. StuRat (talk) 03:39, 21 July 2008 (UTC)
 * Yes, but the reaction products typically have much shorter half-lives, and therefore are much more radioactive, than the fuel. So while the quantity might not be large as measured in kilograms, it's a lot as measured in curies (or, more modernly, Bequerels oops, I guess it's becquerels, but who really knows what those are?). --Trovatore (talk) 03:51, 21 July 2008 (UTC)
 * And I was referring to it relative to the ICF as well. A fission reactor contains far greater quantities of far nastier poisons than something that is only getting somewhat irradiated by a bunch of neutrons would. I am not trying to be anti-fission here, just pointing out that the production of rather nasty waste is an inevitable side-effect. ICF will irradiate its containment structure with neutrons which should induce some radioactivity but it's not going to be anything as bad as actual fission products. --98.217.8.46 (talk) 17:08, 21 July 2008 (UTC)
 * Depending on the details of the attack, it's quite possible that the reactor would survive intact (probably not watertight, but recoverable intact). Large metal objects have survived remarkably close to nuclear explosions.  If the explosion was some distance away from the vessel, and ideally with the large bulk of the vessel between it and the reactor, then you might well expect the reactor (which is very heavily constructed indeed) to be ejected intact and deposited on the sea floor as a (warped, leaky) whole. -- Finlay McWalter | Talk 20:53, 20 July 2008 (UTC)
 * It might also depend on the specifics of the reactor. I recall a number of scares (though only over contamination rather than nuclear explosion) involving nuclear reactors on submarines during the cold war. (E.g. Soviet submarine K-19) What almost happened by accident can happen also by malice. See for a list of such accidents.--Fangz (talk) 22:37, 21 July 2008 (UTC)

Seagull dawn chorus of squawks
Why do they make so much noise as soon as it starts getting light in the morning? I looked out of my window today after they woke me up and saw them just flying around squawking loudly at each other. —Preceding unsigned comment added by 90.242.57.76 (talk) 20:51, 20 July 2008 (UTC)


 * Our dawn chorus article says that songbirds start to sing at dawn, often for territorial reasons. Less melodious, but the seagulls are doing the same. If you're in the UK/Europe, the seagulls have young in their nests at the moment so the parents are defensive. Watch out, because they sometimes circle and threaten to dive-bomb you. Itsmejudith (talk) 22:34, 20 July 2008 (UTC)


 * There is a Herring Gull nest on my roof this year. When it gets to about 4am, the chick is all "cheep! cheep! cheep! cheep! cheep!" whilst the mother (or father) gabbles/clucks away softly. It goes on all day - unless the chick is napping. The early-morning squawking gulls may also be on the look out for anything edible that has found its way onto the street overnight. When a gull spies food, it generally loudly announces the fact - which starts off a chain reaction of squawking amongst any other nearby gulls. --Kurt Shaped Box (talk) 23:26, 20 July 2008 (UTC)


 * Why would they announce it, knowing that this causes all the other gulls to try to steal their food ? Not the brightest, are they ? StuRat (talk) 15:34, 21 July 2008 (UTC)


 * I don't know for certain - but I suspect that any gull discovered feeding at a significant find without first notifying the rest of the flock will be on the receiving end of some heavy 'social pressure'. OTOH, the gull that spots the food might merely be giving a (fruitless) warning to the rest of the flock to stay away from his find... --Kurt Shaped Box (talk) 16:30, 21 July 2008 (UTC)


 * Or it may be that the script writers for the film Finding Nemo actually translated gull-speak correctly. They're all sqwawking "mine!" "mine!" "mine!" ~Amatulić (talk) 20:15, 21 July 2008 (UTC)