Wikipedia:Reference desk/Archives/Science/2007 March 5

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March 5

Is it meant to do that?

I shut down my computer and touched the bare metal on the radator and the bare metal on the computer PSU (at the back) and received a quickly-pulsating shock. Am I right in concluding that there is a fault with my computer PSU, leading to mains electricity pulsing through me to the radiator? Should I try it again, just to be sure? :) Is the PSU manufacturer responsible or only while the PSU is under warranty? I'm not paying for a new PSU over a few silly stray electrons... This is really inconvenient, 'cause I was about to open it up to change the fan inside it (the previous one stopped turning before my very eyes (lucky!) and I've since been using a 120mm fan securely taped to the outside. The company, Jeantech, ignored my email regarding the fan breakdown. --Seans Potato Business 00:25, 5 March 2007 (UTC)

It certainly sounds like the PSU has a fault. Don't try it again! PSU faults are not all that unusual - but generally you'd expect the case of the PSU to be grounded - which means if live volts actually contacted it then it should have tripped a circuit breaker or blown a fuse someplace. That suggests that you may have TWO problems - a bad PSU and bad wiring. I wonder whether you have a properly wired power cord with a three pin plug - if you do then I wonder whether your house wiring is wired correctly at that socket. If you have a multimeter, you could measure the voltage between your PSU case and the radiator (or better still, the ground pin of a nearby power outlet). This can be done without you touching the PSU - which might be dangerous. A shock from one hand (on the PSU) to the other (on the radiator) would be especially dangerous because the path of the current travels right across your heart. So you need to fix this - and you must not under any circumstances "try it again"! If the PSU is out of warranty, I doubt the manufacturer will replace it...but it's worth a try. Incidentally, if you are handy with a screwdriver and plan on replacing it, I have found that in many computer stores it is cheaper to buy a PC case (including the powersupply) than it is to buy a new powersupply! Yes, that's ridiculous - but it's happened to me twice and once to a co-worker - so it's not at all uncommon! But before you replace the power supply - you need to be sure you have a good power cord and correctly wired wall socket. SteveBaker 00:36, 5 March 2007 (UTC)

I just took a look at the socket that the printer is plugged into and there's no earth!! I'm living in the Netherlands (I'm here to be a student in September so I only rent this crappy room). First they build a country below sea level, and now this... I'll check the computer socket shortly. Of course if there is a fault, I plug the PC into an earth socket and switch on, wont some components go bad? --Seans Potato Business 01:21, 5 March 2007 (UTC)

Yup, there's no earth. What a backward country... Aren't there laws about this sort of thing?! --Seans Potato Business 01:27, 5 March 2007 (UTC)

It may be loose wiring inside the PSU, but as SteveBaker said, it's not too hard to replace a PSU. They cost about £25 (€40) from a shop - and from about £10 (€15) for cheap ones online - so it's not hugely expensive. Get one of the same wattage (this should be written on the PSU's case). It's not uncommon for PSUs to break, but if they do go, they can sometimes take out some other components too, so it's worth looking into. --h2g2bob 01:59, 5 March 2007 (UTC)

If you're on the cheap side, you can get a wire with alligator clips, and manually connect the case to something else that you know is grounded, and see what happens. That way at least it won't shock you any more if you touch it. On another note, it is also possible that your radiator is not grounded; you might check that too. --Spoon! 03:21, 5 March 2007 (UTC)

Well, if the PSU case is shorted to something - then it's already in deep trouble and fixing the cable isn't going to make things any worse. But it might be that the PSI is fine and the voltage on the PSU's case is just 'floating' compared to the house ground - which would explain a rather weak shock that you got when you briefly become the ground wire. I'm guessing you didn't get the whole 110v (or whatever they have in your part of the world). In which case fixing things just makes everything safe and all is well (except for the fan of course - but a replacement fan should be cheap). I dunno - but it's really dangerous to leave the ground un-fixed - you are just asking for trouble - and the next person who plugs something into that socket could get a fatal dose. This situation could also result in properly grounded peripherals being harmed by the improperly grounded PC (or vice-versa). You don't really have a choice - just fix it and see what happens. I'm not quite sure how wall-socket power works in the Netherlands - but you might also want to check that the other two wires are connected up consistently in all of the wall outlets in your room. Having live and neutral swapped on one socket and correct on another can also produce 'exciting' consequences! If it's crappily wired then who knows what else is screwed up? Whoever you are renting the room from ought to take responsibility for fixing it. Stuff like health and safety standards are almost certainly an EU-specified standard - so I'm sure they're legally required to have safe wall outlet. SteveBaker 03:35, 5 March 2007 (UTC)

Common sense says use a voltmeter or a test lamp rated for the electrical voltage from the outlet to test for stray voltage on the power supply. If the thing had a third ground prong plugged into a properly wired outlet, then it would have carried the stray voltage back to the ground and you would not have gotten shocked. Was the ground prong cut off, or was an adaptedr used to plug a three prong plug into a 2 prong outlet? That can lead to computer malfunction or electrocution. All the more so if you have 240 outlets instead of the 120 in the U.S. If using a meter or a test lamp, always verify they show voltage correctly before and after checking the thing you are testing. In other words don't let a burned out bulb or malfunctioning meter fool you into thinking a live circuit is dead. Edison 22:26, 5 March 2007 (UTC)

Well, that PSU is gone now. There was a problem where its fan stopped rotating (I saw it happen and shut down) so I improvised with a case fan (58 cfm). I decided that night to finally swap the case fan for the orginal broken fan (which I thought was at fault) and my really good case fan (58 cfm at 11 db is expensive (about 15 pounds)) went exactly the same way! Maybe the two things (my shocking shock and the failed fan) are related. I've ordered a Thermaltake 700W Toughpower so that should be the end of my PSU problems - goed zo!

Edit; Edison, there is no ground at the socket. My plug is a good old-fashioned (and modern) English/British plug; it's the socket that has no ground (apparently common in the Netherlands). --Seans Potato Business 22:20, 6 March 2007 (UTC)

From a standpoint of basic electrical safety, I would find that acceptable only if the outlet were in a room with nothing (like a radiator or sink) which was grounded, or only if used with double insulated (no exposed metal parts) appliances. In the case cited, there was a potentially lethal shock pathway to the radiator, so the electrical code which allowed a 2 prong outlet was shoddy. This was an old style outlet in the U.S., made worse by wiring the house with 2 conductor (no ground) wire. The solution is pulling in a cable with a safety ground conductor. A separate ground is unsafe. Edison 05:27, 7 March 2007 (UTC).

Ice and Fire

I would like to know which one of these two fire or ice can burn you most?

thanks —The preceding unsigned comment was added by 210.1.77.52 (talk) 04:13, 5 March 2007 (UTC).

Fire, both technically and logically. Ice freezes you, regardless of how it may feel in extreme circumstances. 声援 -- The Hybrid 04:16, 5 March 2007 (UTC)

I can only imagine you might be asking about the burn-like symptoms you'd get from handling dry ice with bare skin or maybe liquid nitrogen or something. Frostbite (if left untreated) produces darkening of skin and eventual death of skin - which is somewhat similar to a burn injury. But it's really hard to generalise - how hot is the flame? How long is it held there? Is it a little flame like a candle or a huge inferno? These questions are unanswerable without more information. SteveBaker 04:18, 5 March 2007 (UTC)

Of fire or ice which can burn you more? I would definitely say fire, typically fire is in the order of 500 degrees, ice is usualy zero. The only way i could argue the opposite is if you word the question to say which is more harmful: natural heat or natural cold, in which case I'd say cold, since in the hottest climate: a 50 degree desert you'd last a bit longer then in the coldest: a -50 degree blizzard, but probably not by a whole lot. Vespine 05:36, 5 March 2007 (UTC)

Actually ice would, as it is water and would therefore put the fire out. Also using temperatures equidistant from 0degrees doesn't work, as people are usually a lot hotter than that. However a slight increase in temperature in hyperthermia is as bad as a large decrease in hypothermia.

Ask Robert Frost about Fire and Ice. StuRat 19:13, 5 March 2007 (UTC)

In the book The Alchymists Cat, two characters fight each other, one with ice and one with fire. The one using ice wins.

Harry Belafonte teaches

Water make the river, river wash the mountain

Fire make the sunlight, turn the world around

But no word on what happens when the river freezes. DMacks 20:22, 5 March 2007 (UTC)

Organic Chemistry Question

Okay, so this is one of my homework questions (the solutions manual is sitting right in front of me, so this is not asking for homework help!):

"Devise a synthetic route that will convert (R)-sec-butyl alcohol into (S)-sec-butyl alcohol."

So I solved it by first changing the alcohol group into a tosylate by adding tosyl chloride (without affecting the butyl alcohol's stereochemistry), then performing an SN2 reaction by adding hydroxide (say, NaOH) which inverts the stereochemistry and gives me the other stereoisomer of butyl alcohol, as I wanted.

This is all well and good, but since hydroxide is a better base than nucleophile, why doesn't it perform an E2 reaction to give me, uh, propene or something? It's a secondary substrate so none of the 4 reactions we've learned so far (SN1, SN2, E1, E2) has an inherent advantage over the other. ugen64 04:46, 5 March 2007 (UTC)

The better choice would be the Mitsunobu reaction I think! The leaving groupe and the solvent influence determins which result you get starting from the same substrate. Tosylates tend to form the alkene if the reaction is done in a protic solvent in basic conditions. Like menthyltosylate forms menthene in glyme with KOH. So you are right and you will end up with pure butane and not with S-sec-butanol.--Stone 18:32, 5 March 2007 (UTC)

The problem is, this is the answer given by the solutions manual so I was wondering if there was something I was missing... guess not. ugen64 21:10, 5 March 2007 (UTC)

The side reaction is always a problem and paper chemistry (it is easy to write stubid things on paper) never gives you all solutions to the problem, but only those you already know. You are on a best way if you question the solutions in the book! --134.76.234.75 08:00, 6 March 2007 (UTC)

As someone who does reactions like this all the time, I can tell you that whoever wrote the solution manual has never actually tried it. You are right that you will get elimination. As Stone suggested, any experienced organic chemist will tell you to use the Mitsunobu reaction. --Ed (Edgar181) 15:10, 6 March 2007 (UTC)

But the really experienced chemist will tell you to buy the other enantiomer ;-) . The Mitsunobu reaction works very well after you have all parameters tuned. Of the shelf, most of the reactions with new substrates have lousy yield.--Stone 16:15, 6 March 2007 (UTC)

Gravity wave generator

We know that antenna produce EMW(photons). Suppose we were to move this generator near the speed of light, then to us, the generator would have infinite mass, but to the generator, it is still the same mass(relativity).So that means we would be sending the relativistically heavy oscillating electrons in the antenna circuit, wont this cause gravity waves?? —The preceding unsigned comment was added by 210.212.194.209 (talk) 08:09, 5 March 2007 (UTC).

Any moving mass causes gravity waves; I'm not sure, though, that moving an antenna quickly would help because while the electrons would register as heavier, they would also be slowed down (time dilation), which would reduce the variation in their gravity fields. Not to mention that the antenna must obviously weigh more than the electrons and is moving near c — which would generate a signifcant gravity "pulse" by itself without any current. --Tardis 15:28, 5 March 2007 (UTC)

In theory, yes. Both gravitational and electromagnetic radiation from sources moving very near the speed of light are emitted in an intense forward beam. See synchrotron for details.

If you are interested in the feasibility of detectable man-made gravitational radiation, you should begin by reading J. Weber's 1960 paper entitled "Detection and Generation of Gravitational Waves". Also try Gertsenshtein's 1962 “Wave resonance of light and gravitational waves”. In fact a long list of such papers, many of which are in peer-reviewed journals, appears at http://www.drrobertbaker.com/biblio.htm . -User: Nightvid

Digital Circuits

Any idea whether we can use an digital logic AND gate to sample the input of an analogue signal, or does the AND gate have an built in square wave generator (which eliminates noise,and whose reference level is at 3v, such that anything below 3V=0 and anything above 3V=5v)which prevents such sort of operation?59.92.247.86

An AND gate will not make a suitable sampler. While it is absolutely true that "digital circuits are built from analog components" and it is also true that you can probably find a very narrow linear range where the AND gate will actually amplify, it really won't be useful. Modern samplers (for sub-megahertz operation) are usually build out of field effect transistors. Faster samplers use exotic techniques like diode bridges. See our pathetic sample and hold article for a few more details or Google up the term for a wealth of info.

Atlant 13:43, 5 March 2007 (UTC)

Addressing the "built in square wave generator" comment. Well, I really wouldn't call it a square wave generator at all, but it is correct to say that CMOS (well, digital logic in general) is designed to be as resistant to noise problems as possible. CMOS power rail voltage will usually be at least twice the actual transistor threshold voltage in order to ensure that gates are well into the saturation region of operation and therefore can drive enough current to quickly charge the next logic stages (this is touching on a concept called fan out). However, as Atlant alluded to, a CMOS logic gate is intended to provide output levels at the high voltage rail and the low voltage rail and nowhere in between--this is fundamentally what "digital binary logic" implies (okay, full disclosure: there's a high impedance "state" that is considered a valid output of transmission gates, but that's irrelevant here). Anyway, the device you are looking for is called an analog-to-digital converter, and there are many approaches to building one depending on your exact functional and performance requirements. -- mattb @ 2007-03-05T22:34Z

Your second idea about the squaring off of the wave is correct. However it is possible to digitise the analog signal by adding it to a ramp of comtinuously changing voltage. The time that the gate switches on will be the level of the analog signal. If you supply a sawtooth wave you will get a periodically sampled analog signal. The and part of the gate is not used in this case - you can tie the two inputs together and and or gate could do the same trick. Alternately you could add in random white noise at a high enough level to the analog signal. This will sample at random times and will not suffer from nyquist frequency artifacts. GB 22:38, 5 March 2007 (UTC)

analog---/\/\/\/\--+
                   |    +\
                   +-+--| \
                   | |  |  \
noise----/\/\/\/\--+ +--|and>---out
OR RAMP                 |  /
                        | /
                        +/

There's another issue that comes into play when you try to feed an analog signal into a digital input -- transition time. There's an obscure spec which governs how much time you're allowed to spend transitioning from a low to a high or a high to a low state. If you spend too much time in the "forbidden zone" between the two states, the circuit you're feeding may oscillate. I learned this when I tried to build a simple digital clock by feeding a low-voltage, 60Hz sine wave (the output of a step-down transformer driven by my AC house current) into a series of ÷60 digital counters I'd assembled. At first my clock ran randomly fast, because it turned out it was counting two or three pulses for each of the comparatively slow transitions of the sine wave. Inserting a 7414 Schmitt trigger solved the problem. —Steve Summit (talk) 01:18, 6 March 2007 (UTC)

Super Shock Absorbing material

I saw in the discovery channel that a certain Japanese running footwear company used a particular shock absorbing material in their shoes, and to prove its effectiveness they dropped eggs from a height of 2-floors on to the material, and the eggs survived( RAW, Not boiled). Any idea about the mystery material??59.92.247.86

It's not that hard to keep eggs from breaking over a two-story drop; it's a common practical science problem set before kids. Eggs are stronger than you think so long as the load on their shells is evenly distributed.

Atlant 13:45, 5 March 2007 (UTC)

It's so common a project we even have a page for egg drop competition. DMacks 20:45, 5 March 2007 (UTC)

It could be sorbothane, which is apparently used commonly in shoes, as well as some more exotic applications. I've used it to eliminate any possible vibrations of a laser while I did some holographic photography... Wintermut3 20:11, 8 March 2007 (UTC)

Colorblindness.

Over this last weekend, we discovered that my son (aged 16) is colorblind. It's amazing that we've gone so long without noticing - but he was messing around with his Wii game console - which has an On/Off LED that is green when it's on and orange when it's off. He remarked that he couldn't tell whether the darned thing is on or off because the LED stays lit! So I had him do the standard [1] color-blindness test - and lo and behold, he's a textbook case of someone who is red/green colorblind. OK - so that fits the facts, it's very common (1 in 12 men have it) and there is no cure for it. It's AMAZING he's gone 16 years without either him or us noticing and without a school doing a colorblindness test...but that's what happened!

However, accordint to the Wikipedia article and everything else I can find online, there seem to be four variations on the basic red/green problem - and the standard test doesn't distinguish between them.

Does anyone know of an online test that can distinguish:

• Protanopia is a severe type of color vision deficiency caused by the complete absence of red retinal photoreceptors. It is a form of dichromatism in which red appears dark. It is congenital, sex-linked, and present in 1% of all males.
• Deuteranopia is a color vision deficiency, moderately affecting red-green hue discrimination in 1% of all males. It is hereditary and sex-linked form of dichromatism in which there are only two cone pigments present.
• Protanomaly is a mild color vision defect in which a deficiency of red retinal receptors results in poor red-green hue discrimination. It is congenital, sex-linked, and present in 1% of all males.
• Deuteranomaly is the most common type of color vision deficiency, mildly affecting red-green hue discrimination in 5% of all males. It is hereditary and sex-linked.

I don't think he has protanopia or deuteranopia because he can distinguish strong shades of red/green/yellow - so I'm thinking that it's either protanomaly or deuteranomaly. Both he and I would like to know which.

Does anyone here with either of those conditions have any good advice for him that they may have learned over the years? SteveBaker 20:20, 5 March 2007 (UTC)

I have the same thing and can't tell whether the ps3 is on or off! Never affected my life much, except you have to write off jet-fighter pilot, and electronics technician! None of my kids have it, and they greatly enjoy laughing at my struggles. --Zeizmic 21:30, 5 March 2007 (UTC)

Assuming you are male (most r/g colorblind people are), your kids won't inherit from you - they got it from their mother. It's passed down the female line - but only expressed in males. SteveBaker 02:44, 6 March 2007 (UTC)

A woman can have a sex-linked recessive trait, like (the most common forms of) colorblindness or hemophilia, if she got the defective gene from both parents — or, I imagine, if the "good" X chromosome happens to be inactive in the retina. —Tamfang 01:20, 8 March 2007 (UTC)

This is completely useless as regards the actual question goes... but when it comes to distinguishing between consoles that are on/off/standby, etc, you can stick a bit of coloured cellophane over the LED so that it only appears lit at the appropriate moments. For example, I know someone with R/G colourblindness who has a small red strip over the power LED on their DS, so when it lights up they know the battery is almost gone. It's a small trick, but it might not have occurred to some folk reading this. Spiral Wave 21:51, 5 March 2007 (UTC)

Advice? Give up any dreams of being an electrician (advise him to be a EE; much more fun anyway). Wiring telephone is hell when you're red/green colorblind. Other than that I wouldn't worry much; it's hardly a debilitating condition. Actually the most trouble it has ever caused me is mild annoyance with people who, upon learning that you're colorblind, start asking you to identify various colors. I like the term "color-confused" as a more apt description of the problem. :) -- mattb @ 2007-03-05T22:21Z

I'd heard that one should give up on being in electronics too (because the resistor color codes would be a pain). I'm not convinced that it's insurmountable. SteveBaker 02:51, 6 March 2007 (UTC)

Haha, yeah those things suck. I keep resistors in little labeled bins. I don't think its a huge deal, but my area of expertise is semiconductor devices and analog ICs... You don't really have to worry about color codes when you're creating schematics and doing IC layout. I guess it might be an annouance as a hobbiest or electronics repair tech, but in a design capacity I've never found it to be a hinderance. Just get some little bins and labels and a multimeter. :) -- mattb @ 2007-03-06T03:42Z

Yes - exactly. I do that too - and I'm not colourblind! SteveBaker 18:57, 6 March 2007 (UTC)

Perhaps he can be a fashion designer, many of them appear to be color-blind. :-) StuRat 00:27, 6 March 2007 (UTC)

Black, brown, red, orange, yellow, green, blue, violet, gray, white is the resistor code, memorized via a naughty mnemonic abut "bad boys," representiong the digits 0 through 9. So he would randomly confuse what? 2,3, and 5? That could result in some smoking circuits. Seems like also it should be a simple project these days to build a color identifying probe which would say the color name when you moved it across the color bands on a resistor or across a color coded wire, or even socks or neckties. It was an amazing experience to see a color blind guy hold red and green socks or skeins of yarn up to the light and study them and eventually come up with correct or incorrect color names. It was as if he was matching two dark blue socks, when one had gone through the washer a couple more times than the other and had faded a bit. Edison 05:21, 7 March 2007 (UTC)

The simplest 'probe' to determine which resistor you have is an ohmmeter! Personally, I can never remember which end of the resistor the colours should be read from - so I always double-check with a meter anyway. But as for red and green socks - you'd have to have one of the two '-anopia' types rather than the '-anomaly' versions of the syndrome in order to be unable to tell red from green. The lesser (and vastly more common) '-anomaly' versions don't stop you distinguishing red from green - only greenish-yellows and orangey-reds - so the green/orange power LED on the Wii is hard for him to see - but he can easily tell the difference between pure reds and greens. But certainly there are people who aren't so lucky. Oliver now uses a red-tinted plastic filter - holding that over the Wii's power LED produces a very dim green when it's turned on and pure red when it's really orange. That's enough for him to easily be able to tell whether it's on or off. SteveBaker 20:49, 7 March 2007 (UTC)

Yes, I always wanted to meat Violet. Just don't ever ask how I memorized the organic acids for chemistry (formic acid, ethanoic acid, propanoic acid, butanoic acid, valeric acid). StuRat 18:46, 7 March 2007 (UTC)

Voltages in countries

Why do different countries follow different standards? There seems to be 110 V, 115 V, 220 V, and 230 V. Why aren't they all just say, 110 like America, or 230 like the EU? Why these specific numbers? Thanks! [Mαc Δαvιs] X (How's my driving?) ❖ 21:21, 5 March 2007 (UTC)

110 volts was selected by Thomas Edison when he built the first electric utility for power and incandescent lighting , Pearl Street Station in New York City in 1882. The voltage was high enough to work with affordably small mains, but low enough that a shock was judged survivable and the insulation of the day could prevent shorts. Other countries who got electricity later had the benefit of improved insulation in appliance cords and perhaps less concern for electrocution hazards, so they saved even more on copper and gained electric kettles which could boil water with satisfying speed. In much of the U.S., the nominal AC voltage standard is for the utility to deliver 120 volts (RMS) at the customer's meter. In many states, this has a 5% allowable variation for highs or lows over 1 minute long. Greater variations are allowed for less than a minute as transformer tap changers operate to regulate voltage, or generator governors adjust, or faults are cleared, or switching is done. This means they can deliver between 114 and 126 phase to ground long term and be legal. On hot days, the utility may be running all available generators and have all transformer tap changers boosting the voltage as high as possible, and still have the supply drop below 114. I have seen 110 at my home at the supply and less at the appliances. They may also intentionally reduce the voltage on some lines by 5% to preserve more voltage for downtown business districts (a "brownout"). Your air conditioner will then draw excess current and shorten its life, or it might trip your circuit breaker, or your gas oven may fail to light, or the edges of the TV picture may pull in. This same 5% percent limit applies to the nominal 240 volt supply between the two hot wires coming in. This is termed "lighting" load.(For larger U.S. "power" customers, getting 480 volts or more, the allowable variation is genereally plus or minus 10%.) But the electricity might easily have to go 50 feet or 100 feet through the house, to some load like an air conditioner at the other end of the house. The voltage drop in that wiring will reduce the voltage further. Many appliances are designed to work well down to 110 volts, which is a nominal voltage at the appliance. So the short answer is your "110" motor wants a 120 volt service. Some ovens, air conditioners receive their supply from 120/208 three phase supply, so they must be designed to work on 208 rather than 240. Edison 22:15, 5 March 2007 (UTC)

I cannot find an article about a hydraulic car hopper.

You've probably heard of and/or seen cars that have a hydraulic aftermarket accessory that allows it to "hop" (or "jump") when you press a button. Sometimes, these hoppers, usually installed on "low riders", are specially configured to raise as little as one wheel at a time, like when you make the low-rider "dance" to some hip-hop beats.

Needless to say, there's not an article about a car hopper nor a hydraulic car hopper. What article am I looking for? --129.130.38.99 21:44, 5 March 2007 (UTC)

Have you tried lowrider ? That directed me to height adjustable suspension#Aftermarket Systems. StuRat 21:55, 5 March 2007 (UTC)

Dangers of deep throat

I read up your article on deep throat and saw that it involved dismissing the gag reflex, I was wondering if this brought about a greater risk of choking —The preceding unsigned comment was added by 213.217.212.29 (talk) 22:28, 5 March 2007 (UTC).

One normally assumes that the penis leaves the airway before somebody could get hurt. I do not see why it would not restrict airflow when in place, and I suppose there could be a potential hazard. [Mαc Δαvιs] X (How's my driving?) ❖ 08:05, 6 March 2007 (UTC)

Deep Throat is the pseudonym that was given to William Mark Felt, Sr., the secret source who leaked information about the involvement of U.S. President Richard Nixon's administration in the Watergate first break-in and subsequent events that came to be known as the Watergate scandal. Where did you get the information regarding gag reflex? :) --Parker007 08:06, 6 March 2007 (UTC)

Haha. − Twas Now ( talk • contribs • e-mail ) 17:11, 6 March 2007 (UTC)

Downregulating the gag reflex can have bad consequences. During everyday life, this reflex is not so important, but it can be a life saving reaction during unconsciousness. The gag reflex can help reduce the likelihood of aspiration of foreign matter (usually vomited stomach contents) into the lungs, which can cause blockage or infection. Alcohol (or other drug/toxin) intoxication and anorexia bulimia can turn this mechanism off (either acutely and temporarily, as with intoxication, or chronically, as with bulimia). If one was so adept at deep throating that he or she lost this reflex, there could be negative consequences. Since one would be less likely to gag when something was introduced to a potentially occlusive position in the airway while eating, it is possible that the likelihood of choking would be increased. But as I said, it is during unconsciousness that this is most important. ^tucker/_rekcut 18:40, 6 March 2007 (UTC)

Yawning as a defense mechanism?

Is it possible that yawning evolved as an aggressive expression (display of teeth etc.) to protect the animal when they are most at risk from attack, such as when tired?

There is anecdotal evidence that a group of humans will all yawn when they are about to change what they are doing - eg getting up to go out. It has been speculated that the meaning of a yawn is approximately "I agree" - but not at a conscious level. SteveBaker 02:42, 6 March 2007 (UTC)

I must agree a lot then. Capubadger 07:39, 6 March 2007 (UTC)

Goddamn, can you believe I yawned while reading SteveBaker's answer? I must agree then too :D --Taraborn 11:13, 6 March 2007 (UTC)

It's very common for people to start yawning during a discussion on yawning. Same for coughing. Victor Borge had a great routine in which he would announce "The next piece is one during which most people cough". There would immediately be paroxysms of coughing from various members of the previously quiet audience. People who suffer from intermittent tinnitus are only too aware that as soon as the subject of tinnitus is mentioned, they suddenly become aware of it inside their heads. There must be a name for this type of inductive phenomenon. JackofOz 04:07, 8 March 2007 (UTC)

Air Pressure

What sort of units do weather people measure air pressure in? (like in the news)... I have researched and all I am coming up with are mathematical equations that are not giving me the answer I need. Thank you-

The bar and the torr (mm Hg) come immediately to mind. The SI unit of pressure is the Pascal (atmospheric pressure will be around 101 kilopascals). There's also the atmosphere and a few others. See atmospheric pressure. -- mattb @ 2007-03-05T22:54Z

Inches of mercury are also sometimes used in the US. StuRat 00:21, 6 March 2007 (UTC)

As is the good old psi ($\mathrm {lb} /\mathrm {in} ^{2}$). Feel free to fix notation, I do not know how. Oh, and with psi it is useful to know if the number includes the base atmospheric pressure. Tire gauges do not, so the reading is pressure above atmospheric pressure. 161.222.160.8 01:47, 6 March 2007 (UTC)

I believe "in HG" is the ICAO standard for aviation altimeter setting as well. 29.92 "in Hg" is a standard day and is also the altimeter setting for Flight Level altitudes (~ > 18,000' MSL). --Tbeatty 06:18, 6 March 2007 (UTC)

In Europe/metricated countries it's usually given as millibar/hectopascal, 1013 mBar being the reference point for sea level Galf 09:35, 6 March 2007 (UTC)