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October 2

List of official lab names

I have been trying for a long time to find a definitive list of all official medical laboratory (pathology) lab names. I have been able to find books containing all labs accepted by certain services, such as LabCorp. I need this to be electronic, not in a book. I also need it to be accurate. For example, "creatinine" is not a valid lab name. It must be "creatninie, serum" or "creatinine, urine" - two very different labs. Does anyone know of a list available online? I'm even happy to screen scrape a website if it actually has all the lab names. Just to note: I did try to use all the pathology items in CPT, but it is missing all incidental labs that you can't bill for. Also, you are supposed to license CPT just to know it exists. I hope everyone here has a license since I just mentioned it! -- kainaw™ 04:16, 2 October 2008 (UTC)

Well hey, if you know about LabCorp, why not call them up? Ask for "customer service, I need a full list of path lab names" - whoever is answering the phone will be confused and impressed enough that they will look at the list of internal numbers and pick one. Then you will get someone who was forwarded an outside call and will get your question answered. If it comes up, don't say "I'm just a student", say "I've just been given this project and I need to gather background information so we can get started". (And if you're not a student, whatever...)

Someone at LabCorp will know where that entire list is - please post it back here and into whichever article is most appropriate! Franamax (talk) 07:20, 2 October 2008 (UTC)

Headache

One thing I think I've noticed is that when you have a headache, if you lie on your back, it tends to get better, if you look downward, it tends to get worse, and if you lie to one side, the pain tends to move to that side. Presumably this would be because some sort of fluid (too high pressure of blood?) is causing the headache, and then it slowly drains certain ways depending on which way your head is aligned. My question is - is there anything to this at all, or is this just a placebo effect and I'm imagining a change in how much the headache hurts that doesn't really exist? And if there is some sort of basis to it, what would be the explanation? (I know you're not supposed to give medical advice, but come on. It's a headache.) zafiroblue05 | Talk 05:32, 2 October 2008 (UTC)

This isn't medical advice - but oohh baby, I know that feeling! I doubt it's blood, but certainly a sinus headache results from inappropriate pressure in the sinuses, and this can move around as you shift your head. There's also the factor of muscle tension, depending on your exact head position, you can build up the tension without knowing it. Depending on the cause of the headache, your balance organs may be affected too. If it's a migraine, all bets are off and it's just a world of pain.

It really comes down to your own particular headaches though, and your own experience. Headaches result from many different causes (including brain tumours, if that makes you feel any better :). If your headaches result from hangovers, the best position is non-bending-elbow the night before. So really, ask your doctor, just like we always say. :) Franamax (talk) 07:06, 2 October 2008 (UTC)

• Might also be blood pressure related. If your lieing down maybe your more relaxed? ---J.S (T/C/WRE) 07:25, 2 October 2008 (UTC)

First, you must find the cause of your headache. It is rather dumb to expect random users on the Internet with no medical experience to diagnose the cause of your headache. That is something a medical professional can do. Once you know the cause, feel free to come back and ask if there is a scientific reason that your specific type of headaches may change based on the position of your head. Anything said here could be based on a terrible misdiagnosis as your headache could be anything from purely imaginary, to simple dehydration (very common), to a brain tumor ... even to having a nail in your brain. In head trauma it is common to forget the incident. So, you could get shot in the head with a nailgun, forget the incident, and walk around not knowing you have a nail in your brain. -- kainaw™ 12:11, 2 October 2008 (UTC)

Before anyone laughs at Kainaw's suggestion, note that it's possible to be shot – in the forehead – and not realize you have a bullet in your skull: [1]. (There are a number of similar cases in the medical literature. While bullets to the head are normally both obvious and rapidly debilitating, there are exceptions.) TenOfAllTrades(talk) 16:24, 2 October 2008 (UTC)

I believe at this point it is traditional to mention Phineas Gage, with a comment such as "Call that a headache ? ...". Gandalf61 (talk) 10:20, 3 October 2008 (UTC)

Name this bug

Locale: Vancouver (actually Surrey) BC, oceanic climate or "inter-coastal Pacific-Northwest" - take your pick.

Diagnostics: body length 20-25mm, diameter 10-12mm. Body with three distinct black/white bands "salient" (45° dorsal leading - like "///"+head ). Four dragonfly-style wings. Distinct proboscis.

Activity: Using long proboscis at multiple flowers.

I've never heard of anything like this. Does anyone have some clues? Franamax (talk) 06:49, 2 October 2008 (UTC)

If it has a long proboscis, and feeds at flowers, it sounds like some sort of moth. If the four wings flap independently (they're probably moving too fast to tell), then it is not a moth. It's difficult to say what it is without a picture.CalamusFortis 15:06, 2 October 2008 (UTC)

Do any of the pictures in Hoverfly look familiar (assuming that you're wrong about the four wings)? Deor (talk) 15:38, 2 October 2008 (UTC)

Hoverfly, specifically Chyrysotoxum intermedium elicited an immediate response on viewing the samples. Mommy doesn't have to go to the home yet, it seems the bug does exist :) The caveats were that the observed head was smaller in relation to body size and the proboscis was significantly more extended. Given the approx. 6000 species involved, I declare a semi-exact match. Deor, keep cleaning that article up if you can, the bottom 5 sections are quite confusing (but it's all good). Thanks! Franamax (talk) 06:57, 5 October 2008 (UTC)

Is this Rose quartz?

Is this really what I think it is?

Is this actually rose quartz? It's my first guess, but I'm not a geologist... so I figure it's time to get a second opinion! ---J.S (T/C/WRE) 07:25, 2 October 2008 (UTC)

The pink parts look like rose quartz, but the yellow bits would be iron staining limonite. Graeme Bartlett (talk) 13:00, 2 October 2008 (UTC)

That would fit. ---J.S (T/C/WRE) 17:50, 2 October 2008 (UTC)

Axully, this looks more like Orthoclase feldspar, but it could be rose quartz. IDing a mineral sample from a photograph is difficult... --Jayron32.talk.contribs 03:42, 3 October 2008 (UTC)

I tried to get a high-quality macro photo of it to help identification. Unfortuantly this stone is under a few feet of water in Folsom Lake. :) ---J.S (T/C/WRE) 01:23, 6 October 2008 (UTC)

Driving a T-72 tank

As we know from the news, Somali pirates have captured a ship with 33 T-72 tanks. Of course, the US, UK and Co. will not let them go away with it, but if they were able to unload the ship, would they also be able to use these tanks? Mr.K. (talk) 08:08, 2 October 2008 (UTC)

Well driving a tank will require knowledge of how to operate the tank. Without knownig about the state of these stolen tanks, I suspect yes...if they could unload them they could maybe 'use' the tanks to some degree (perhaps basic manouvering), but perhaps not all - it depends on how intutitive the tank's controls are (judging from what i've seen on tv - not very at all!!). 194.221.133.226 (talk) 08:51, 2 October 2008 (UTC)

The main thing is, they will be able to sell the tanks farther inland, to people who are able to ask around for someone who knows how to run a T-72. Such operators exist and can be hired. And realistically, a machine is a machine, you can always figure out how it works.

The sea-pirates themselves likely won't try to operate the tanks. The first time they try to take one out to intercept a ship on the high seas, they will see the big flaw in that plan. And anyone who they sell on to will quickly run up against the spare part problem once something breaks. Their rational strategy is to ransom back the tanks and ammunition, same as they do with ships, standard cargo and crew. Franamax (talk) 09:58, 2 October 2008 (UTC)

Yes, and perhaps there are some Russian trained mercenaries deep into Somalia that always wanted to drive such a thing and know more or less how to do it. At least driving the old model doesn't seem to be that difficult, as this BBC articles shows. Mr.K. (talk) 10:28, 2 October 2008 (UTC)

If you look over this page, you'll see that the T-72 and its variants have been used by many countries so there are plenty of people that are fully trained in their operation.--droptone (talk) 11:26, 2 October 2008 (UTC)

When I was in 29 Palms, they would let kids drive around the T-72 and M1A1 tanks on Tankers Day. I'm certain that it is considered a security risk now, but there are plenty of kids who are now adults and know how to, at a minimum, make the tank for forward and turn. -- kainaw™ 12:05, 2 October 2008 (UTC)

The T72 uses standard dual stick controls, with each stick controling its sides engines and brakes, and a single gear lever. Actually driving the tank should be fairly easy, at least if you don't care about running over things. Using the gun might be hard but the gun contains an autoloader, so that is no issue, and moving the turret will be easy too. Hitting things at a distance with such an old tank might be hard as it lacks the fancy laser range finding and targetting kit of a modern tank. The machine guns are standard Russian machine guns that many of them know how to use already I'd wager. I'm sure with a couple of weeks of experimenting they could figure out how to use a tank in some capacity. The main issue is going to be fuel. Tanks use fuel so fast it would make an SUV swoon. 88.211.96.3 (talk) 12:23, 2 October 2008 (UTC)

If you look at news reports, most people aren't particularly worried about the tanks. That's because they are rather large objects which won't easily be offloaded from the ship which is surrounded by several navy vessels as well as under air surveilance. However the other weapons and ammunition, which could more easily be offloaded are of far greater concern. Also, the tanks are worth rather a lot of money meaning that people would like to get them back Nil Einne (talk) 13:06, 2 October 2008 (UTC)

Presumably these tanks come with an owner's manual in the glove compartment? Or, more likely, many thousands of pages of documentation? --Sean 14:33, 2 October 2008 (UTC)

In Somali? Nil Einne (talk) 17:32, 2 October 2008 (UTC)

The interwebs has translators. :) ---J.S (T/C/WRE) 17:53, 2 October 2008 (UTC)

Chinese contributions to engineering

what are the contibutions of the old chineese era in the field of engineering? —Preceding unsigned comment added by Kim014 (talk • contribs) 12:42, 2 October 2008 (UTC)

oil rig wheelbarrow great wall of China, water control. Graeme Bartlett (talk) 13:04, 2 October 2008 (UTC)

Gunpowder,fireworks? 88.211.96.3 (talk) 13:18, 2 October 2008 (UTC)

Blast furnaces, high temperature kilns, ceramics. There's a gigantic list at List of Chinese inventions to look and pick through. Sjschen (talk) 15:45, 2 October 2008 (UTC)

Flight? Plasticup ^T/C 15:55, 3 October 2008 (UTC)

Coloured lights used on CSI

After watching several episodes of CSI, I have seen the characters use several kinds of lights to detect otherwise invisible markings (eg blood which had been cleaned, stains on sheets etc). These lights vary in colour, are always seem to require either a screen to shield the user's eyes from the beam (a coloured screen attached to the light), or for the user to wear coloured goggles. My question: what are these lights (I was going to guess ultraviolet)? Why the need for the coloured screen/glasses? And why do they change colour from episode to episode - are different "colours" used to detect different substances/markings? Thanks very much in advance! — QuantumEleven 12:55, 2 October 2008 (UTC)

This is probably using the same CScIence that allows them to go "Zoom! Now enhance" and make some grainy pixelated CCTV footage show you the face of the killer (I swear to god they rotated the position of the image to show his face once). In other words total rubbish. 88.211.96.3 (talk) 13:17, 2 October 2008 (UTC)

Actually, it's quite reasonable. Skiers tend to prefer amber-colored sunglasses, for instance, to maximize the contrast of their particular environment. Using something similar to highlight a crime scene makes sense. — Lomn 13:30, 2 October 2008 (UTC)

The two specific instances that the original questioner brings up are both indeed ultraviolet light. Semen stains fluoresce under ultraviolet lamps; for fun, bring one to the next hotel you stay in. And cleaned blood stains are detected by spraying the area with a mixture of phenolphthalein and hydrogen peroxide, and then looking at the area with an ultraviolet lamp. This is also called the Kastle-Meyer test. Note that these are presumptive tests only: they can't actually identify the stain as semen or cleaned blood, but they can tip you off that the stain is there so you can perform further testing to actually identify what made the stain. The goggles, as you note, are used to protect the eyes from high-intensity ultraviolet radiation. - Nunh-huh 13:59, 2 October 2008 (UTC)

Thanks for the answers, Lomn and Nunh-huh. The glasses to enhance contrast make sense, and to protect the user's eyes (in which case, the little plastic shield on top of the light probably doesn't do a whole lot of good?). I'm still curious as to the changes in light colour (although that might be down to "it looks cool" on the part of the producers of CSI?) — QuantumEleven 14:51, 2 October 2008 (UTC)

There's a little discussion about potential danger to the eye in the ultraviolet article. You might also be interested in Luminol. --LarryMac | Talk 15:30, 2 October 2008 (UTC)

The change in light colour? Do you mean the fluorescence of whatever UV radi. is being shone on or the result of the light from fluorescence being filtred by the glasses? Sjschen (talk) 15:36, 2 October 2008 (UTC)

I would speculate that since the show is recorded and broadcast electronically, a white balance must be determined for each scene. If the balance is a little in one direction or another, when the image ends up on your TV it may have either a more purple or more blue hue to it, depending on the rest of the scene. --66.195.232.121 (talk) 16:45, 2 October 2008 (UTC)

Have you watched CSI? I don't watch it regularly but caught part of an episode of CSI Vegas while waiting for my take-out food to come in. The whole thing is practically filmed in the dark and every light is tinted. It's "dramatic lighting" taking to the most ridiculous, preposterous extreme (where courts of law look like night clubs). I don't think it's an issue with them adjusting their TV. --98.217.8.46 (talk) 22:25, 2 October 2008 (UTC)

CSI Miami is weird. The sky's green and all the other colours are unnatural. The overly forced, mannered, unnatural acting of David Caruso is in keeping with the unnaturality of the colours. I can't recall him acting that way in other shows I've seen him in, so I guess it's how he or the producers want his character to be. It sure gets my attention every time I watch it. But I thought actors weren't supposed to be drawing attention to their acting; for that hour we're supposed to be believing he really is the person he's playing. -- JackofOz (talk) 00:55, 3 October 2008 (UTC)

It's worth saying one more time. THIS IS FICTION...IT'S NOT REAL! Nothing that happens on these shows has to have any scientific validity whatever. CSI is notorious for performing tests that (in reality) take months in mere seconds - they have rolled every kind of separate lab into a single lab - they've taken away all of the super-careful (and super-tedious) paperwork that has to go on - the control tests - the need to preserve evidence for the defense lawyers to do their own tests on. Long waiting lists for some kinds of test are replaced by someone typing something into a computer and getting an answer in seconds. So the fact that there are some fancy colored lights that show who-knows-what has only coincidental resemblance to what REALLY happens in real forensic labs. SteveBaker (talk) 01:19, 3 October 2008 (UTC)

Yeah. But not everyone realises that, which is why there's the CSI Effect. I wonder how much the technical advisers are being paid for these shows that distort reality so massively. -- JackofOz (talk) 02:22, 3 October 2008 (UTC)

Going back to what 88.211.96.3 touched on; the seemingly crazy enhancement of CCTV and photographs. Obviously you can't tease data out of a picture taken at a low resolution because it just isn't there. What you could do, in principle, is extrapolate from base data. Is that still then admissable as evidence, given that it's effectively "made up" and doesn't exist outside of a (clever) computer algorithm? I guess what you could do is deliberately get some low-res photos of known subjects (i.e. you have higher res copies) and then run your "enhancer" on them, and then compare the results. I'm concentrating on computational examples, but of course the human mind is adept at seeing patterns in this fashion. I've seen tons of episodes where they have a scrap of company headed paper, and manage to work out which firm it is from that. What's the difference? --Rixxin 19:15, 3 October 2008 (UTC)

I certainly wish I had a dollar for every movie/TV show where our hero points at a screen and says "Zoom in there...enhance...now zoom in some more...enhance...enhance some more...AHA! That proves it was Colonel Mustard in the Dining room with the Candlestick!". Well, in truth, there really is only a very limited amount of enhancement you can do - the information simply isn't there - and you can't get information from nowhere. There is a LITTLE that can be done though - if you know a lot about the lens/mirror system that was used to take the original image. There were some algorithms developed on the Hubble telescope that provided modest enhancement when the mirror was discovered to have been ground incorrectly. But if you don't know the exact characteristics of the lens, or if the limiting factor is not the lens but the grain in your film or the resolution of your image sensor - then those "enhancement" tricks are purely cosmetic - to trick the eye into believing the image is sharper without actually revealing any more detail. The "standard" trick is called an "unsharp mask" - what you do (in effect) is to take a copy of the image, deliberately blur it a bit - and then subtract the blurry version from the original. Amazingly, this really does remove some of the blurriness and results in the image looking much crisper. If you overdo it, you end up with the edges in the image standing out and actually obscuring "real" details in the photo. However, this won't help you to solve the murder by reading the date off of that newspaper that some guy in the background of the shot is holding! SteveBaker (talk) 13:09, 6 October 2008 (UTC)

There are also some algorithms that can extract a sharper image from a series of related images - e.g. if you had some grainy video of a UFO flying across the sky, they might be able to give you a single, not-as-grainy photo of a frisbee. It's still got its limitations, though. Confusing Manifestation(Say hi!) 22:54, 6 October 2008 (UTC)

sex change m to f

when a man changes sex. do she get the same fellings as awoman —Preceding unsigned comment added by 86.15.87.151 (talk) 20:26, 2 October 2008 (UTC)

I believe not, although you might like someone to verify this if it is important you are correct. Anonymous101 (talk) 20:37, 2 October 2008 (UTC)

You might be interested in our articles Transwoman and Sex reassignment surgery (male-to-female). --Allen (talk) 21:10, 2 October 2008 (UTC)

Men already have the same feelings as women, however sex hormones do affect the way the two sexes deal with their feelings. Men getting a sex change spend a long time taking women's hormones before the surgery and this could have an effect on the way they experience their emotions. -- Mad031683 (talk) 21:15, 2 October 2008 (UTC)

I suspect that by "feelings" the questioner was referring to "sensations" Plasticup ^T/C 04:34, 3 October 2008 (UTC)

How could she possibly know? --ColinFine (talk) 18:55, 4 October 2008 (UTC)

October 3

Prolonging orgasm

Is there any safe way of prolonging orgasm in men up to, say 10 mins (I think that would be enough). I know that boars (male pigs) can do it for about 20 mins (even with a dummy sow). Lucky boars!--79.74.251.204 (talk) 00:17, 3 October 2008 (UTC)

Umm, you know that? Really? hydnjo talk 00:45, 3 October 2008 (UTC)

[2]

Do you mean delaying orgasm or making it last longer? Some drugs and herbal supplements are availible which claim to increase both semen volume and number of contractions, however I can't imagine that continuous ejaculation for 10 minutes would be all that enjoyable. After a short while, it would probably become more like dry heaving from the penis, which isn't my idea of a good time. --Jayron32.talk.contribs 03:38, 3 October 2008 (UTC)

That may be the ticket for some folks. -hydnjo talk 04:44, 3 October 2008 (UTC)

Some years ago there was experimentation with electrical or chemical stimulation of so-called "pleasure centers" in the brain [3] [4] [5] [6] of rats and humans. Edison (talk) 05:18, 3 October 2008 (UTC)

Yes: ESO: How You and Your Lover Can Give Each Other Hours of Extended Sexual Orgasm. An interesting footnote is that this book was originally co-authored by Pulitzer Prize-winning author Richard Rhodes, though for some reason he's been dropped from the author list in subsequent revisions. I "hear" that the method works. --Sean 14:06, 3 October 2008 (UTC)

To prolong orgasm, you need to be familiar with the sensation prior to ejaculation. As soon as you feel that you're reaching the peak, you need to stop. Otherwise, there's no turning back. Once you're at the peak, orgasm and ejaculation will proceed with or without further stimulation. Once you're done, you'll need a few minutes to recover. The concept is probably the same with females: just take them near the peak and stop when you're almost there; repeat as necessary. Simoncpu (talk)

Who invented the floor buffer?

Question as topic. I'd like to add the info to the article I've been working on. I don't seem to be able to find anything useful using Google. --Kurt Shaped Box (talk) 02:27, 3 October 2008 (UTC)

The first reference to an electric floor buffer I found at Newspaper archive was a classified ad in The Hayward Daily Review, (Newspaper) - April 6, 1942, Hayward California, Classifieds, page 2. It was a floor sanding machine from Montgomery Wards which included tampico scrubbing/polishing brushes, a buffing and polishing wheel and a steel wool floor buffer for $32. Google Books has no view but lists patent 1,468,080, from 1876, for a "floor buffer." No idea how it compares to modern ones, but it would clearly not have an electric motor. Once central station electric power was available in the 1880's the application of connecting an electric motor to a pair of counterrotating brushes would be very obvious and the device should have been commercially available by the 1890's to reduce the labor of polishing floors. Edison (talk) 03:44, 3 October 2008 (UTC)

Did we really not have an article on floor buffers until today? That would make a great DYK. Plasticup ^T/C 15:45, 3 October 2008 (UTC)

What, the article I started - or the fact that WP didn't have an article on floor buffers until yesterday? ;) Yeah, I was surprised to see that was still the case too - I actually mentioned the fact a few months ago (I think when we were discussing floor buffer/MRI interaction). For some reason (don't ask why), I thought about it yesterday. --Kurt Shaped Box (talk) 23:43, 3 October 2008 (UTC)

Thanks - but I'm not quite sure how I'd be able to cite that in the article (if you know better, feel free). Yaknow, I was quite surprised that no-one (apparently) has a website dedicated to floor buffers and the history thereof - considering that lawn mowers and vacuum cleaners seem to have a fair number of fanboys on the net. --Kurt Shaped Box (talk) 23:43, 3 October 2008 (UTC)

US672930 (filed 1901-09-01) is the first one I find for a powered buffer device (appears to rely on external/unspecified rotation power source). It's fixed in place and moves a buffing wheel against a flat surface placed against it (shop machine) rather than being moved against a flat surface (i.e., "the floor"). US871450 (filed 1906-02-24) is the earliest floor buffer, but it's just a block with a a fixed buffer/sander surface (not powered motion). Putting everything together (a electric-motor-powered floor-oriented machine) looks like it starts with US915752 (filed 1906-12-22). Who said Rhode Island was too small to matter or that bowling never led to anything useful? US1468080 was actually filed 1921-03-24...not sure why/where is would be noted as from 1876. DMacks (talk) 14:07, 5 October 2008 (UTC)

So, how would I go about properly citing a patent in an article? I've never done it before... --Kurt Shaped Box (talk) 23:06, 6 October 2008 (UTC)

We have a template for that: {{Cite patent}} Plasticup ^T/C 23:18, 6 October 2008 (UTC)

Note that for research purposes, Google Patents beats the pants off of esp@cenet and USPTO in terms of both the search and display interfaces. DMacks (talk) 01:55, 7 October 2008 (UTC)

Anatomy / behaviour of bullocks etc

Okay, so I hope this isn't too stupid a question (or set of questions). Don't feel you have to answer every single question below in order for your reply to be useful, as any helpful pointers would be great.

I've read that bullocks are castrated bulls, and according to the Ramblers Association in the UK they are exempted from the laws which restrict the keeping of bulls in fields crossed by public rights of way -- they write:

"Although there are specific legislative restrictions on the keeping of bulls, these do not apply to cows and bullocks, which can also be very aggressive." [7]

So presumably then they are less aggressive than "normal" bulls. But just how likely is a bullock to be aggressive? About the same as a cow? Or more so?

How common practice is it to castrate bulls, e.g. would a beef farmer typically castrate most of the bulls and just leave a few for mating? At what age would this normally be done, and for sake of comparison what age is puberty?

Also how do you distinguish bulls from bullocks? Does it require a clear view of the area where the testicles should be (from an angle where this is not obscured by hind legs), or are there other obvious differences which are evident e.g. from the overall build of the animal? I am really after simple guidelines so that when encountering one in a field I make a quick and reasonable decision on how likely it is to be aggressive.

Actually another maybe really stupid question. I'd sort of assumed that the centrally located bulge (i.e. about half way between front and rear legs) is where the penis is -- it would certainly make sense as regards the mating position for it to be further "forward" than in a human -- but it also seems that cows sometimes have a bit of a bulge in this area too. So what am I actually looking at in that case? Do I actually need to see the udders to be confident that it's "only" a cow?

Of course there is also the whole issue of breeds of bull, and if anyone has any good pointers on that, then that would be very useful as well. In principle a dairy bull would be more aggressive by all accounts, but it seems to me that there are so many different breeds that you'd have to be something of an expert to know which is which.

Thanks. Are a wiki (talk) 09:17, 3 October 2008 (UTC)

I can't speak to bullocks, but in capons (castrated roosters), the animal is not only less aggressive, but also has more hen-like physical characteristics (more body fat, etc.). --Sean 14:09, 3 October 2008 (UTC)

See also oxen, which are castrated bulls used in situations where docility is required. There are no "breeds of bulls" but see List of breeds of cattle. Rmhermen (talk) 15:17, 3 October 2008 (UTC)

Castrated male cattle are sometimes also called steers. -- 128.104.112.147 (talk) 15:36, 3 October 2008 (UTC)

Nevermind... --Jayron32.talk.contribs 20:41, 3 October 2008 (UTC)

Bullocks are roughly as aggressive as cows, i.e. not very. If walk through a field with bullocks in, they can be curious and start following you. Not really dangerous; just walk on briskly. The situation that would be most likely to lead to a serious accident is if you were at the bottom of a steep bank and one or more stumbled down on top of you. A beef farmer would typically castrate all the male animals and use artificial insemination for breeding. It's only in traditional farming - for example organic - that bulls are still kept outdoors. I've hardly ever seen a bull when out walking in England, but I've seen them often in parts of France. If the bull is with cows in theory it is docile but I wouldn't risk it. If it is in a field on its own, take the long way round. The males are castrated when they are cute little calves. A bull is quite easy to distinguish: it is massively built and has sizable tackle in the middle of its belly. You'll also learn to distinguish dairy and beef cattle. All cows is a dairy herd, in England usually black and white Friesians. All bullocks is beef cattle. Cows with calves could be either. Advice is to avoid walking between a cow and her calf, which is actually not difficult. Happy rambling!Itsmejudith (talk) 17:23, 5 October 2008 (UTC)

Google Image Search gives an anatomy poster here. BrainyBabe (talk) 17:33, 5 October 2008 (UTC)

Generally per Judith except: AI can be problematic and it is expensive, so it's not that uncommon to select a promising AI-inseminated male calf from your best cow, and use it to naturally inseminate the (non-related) rest of your herd. For high-performance dairy cows, you might want to go AI-only, for beef cows, maybe a different approach - you want a cow that gives good milk but not too much (avoid mastitis), and has a good temperament. You will only want one mature bull, otherwise you will end up with fights and just the smell of the other bull will make the one you're in the pen with impossible to control. Remember that bulls and farmers work on a consensus basis - if the bull is happy, everything is good.

I would not personally recommend walking through any field where a bull is present, unless you are closer to the fence than the herd is to you. Remember too that cows are naturally curious and will come closer to check you out - the bull will eventually notice that and exercise his prerogative to walk out in front of all the girls to check out the new centre of attention - and they're not all that smart.

And I've never known a cow separated from her calf to be aggressive, though she might moo enough to get the calf running. Waving your hands is usually enough in any case. OTOH I usually carried a cane walking through our herd, and I was respectful of the Scottish longhorns - but I've never been charged by a cow, nor a steer. Never been charged by a bull either, but as I said, that was a consensus happy-time decision - I always made sure not to upset the bull, what with the 1000-pound weight differential.

As far as the original anatomy question, all cattle have that distinctive shape on the abdomen, but males have extra longish hair at the pendant point (and pee from that spot), and uncastrated males are distinctively more bulky in general and "well-equipped" at that point. If a significantly larger animal of the herd is approaching you, it's best to rapidly retreat. Threats and appeals to reason are unlikely to help the situation. Franamax (talk) 00:19, 7 October 2008 (UTC)

1)But if you decide that discretion is the better part of valour and retreat, what might trigger it to run after you? 2) Why do females have that shape on the abdomen if it isn't a penis? Is it like the hyena? BrainyBabe (talk) 20:41, 7 October 2008 (UTC)

Misshapen head treatment

What is that treatment called where a baby has a slightly misshapen head and is "corrected" by having the baby wear this head device for several years so that the skull can be shaped to a "normal" form? I read that some native american tribles had done this in reverse decades ago for aesthetic reasons, meaning they deliberately tried to flattened the baby's head....--Anilmanohar (talk) 12:55, 3 October 2008 (UTC)

The Native American tribe you are likely referring to are the Flatheads. Of note, they did not flatten the baby's head. That is folklore. The truth is that a neighboring tribe used head binding to produce pointy heads. So, the normal people were called "flathead." In modern times, a device that it used to change the shape or position of bones (even the skull) is called a brace. There is no specific term for it. It is often termed by the usage, such as dental braces or orthopaedic braces. -- kainaw™ 13:02, 3 October 2008 (UTC)

The technical term for what you are referring to is plagiocephaly (though this entry is pretty much a stub). There is also an entry called positional plagiocephaly which has a tiny bit more discussion of the etiology and treatment. Medical geneticist (talk) 13:27, 3 October 2008 (UTC)

Craniosynostosis. Plasticup ^T/C 14:40, 3 October 2008 (UTC)

It is correct that craniosynostosis is one cause of plagiocephaly (which is simply a technical term for "misshapen head"). The distinction is that craniosynostosis usually requires surgical correction because it involves abnormal premature fusion of the skull bones, while positional plagiocephaly is a deformity that can be corrected by putting a fancy helmet on an infant, which gradually reshapes the bones of the skull while they are still pliable. Medical geneticist (talk) 16:10, 3 October 2008 (UTC)

Someone asked a similar question a couple days ago. -- MacAddct1984 ^{(talk • contribs)} 14:59, 3 October 2008 (UTC)

You may be thinking of the Inca practise of cranial deformation. I haven't studied the topic myself and our article basically just repeats the essence of the blurb here. IOW, yes they did it, but the reasons why are still somewhat unclear. Matt Deres (talk) 16:32, 3 October 2008 (UTC)

Urinary Tract Infection Cause?

From the CNN article: http://www.cnn.com/2008/HEALTH/10/03/bathroom.hygiene/index.html

"It's fine for a woman to hover over the toilet seat if she doesn't want to sit down, but if she doesn't empty her bladder completely, she's at risk for a urinary infection, Bernstein said."

Why is this so? --Anilmanohar (talk) 14:01, 3 October 2008 (UTC)

Because urine acts as a culture medium for bacteria; if the bladder is completely emptied, the urine isn't there to be infected. If the bladder is incompletely emptied, it contains urine that can become infected. The risk is greater for women than men (because women have shorter urethras), but incomplete emptying of the bladder in men (often as a result of protate enlargement) also predisposes to infection. An empty bladder is protected from infection by urothelial surface mucoproteins, but urine has no such defense. - Nunh-huh 21:03, 3 October 2008 (UTC)

"urine acts as a culture medium for bacteria" ??!? Whaaaat? That's not right - Urine (as our article points out) is an antibacterial agent. "Urine has also been historically used as an antiseptic. In times of war, when other antiseptics were unavailable, urine, the darker the better, was utilized on open wounds as an antibacterial.". SteveBaker (talk) 12:38, 6 October 2008 (UTC)

My completely unreferenced understanding of this is that urine remaining in the urinary tract is a source for bacterial accumulation. In other words, for males drinking their own pee (don't laugh, it's both a survival and religious tactic), the first few inches of discharge are un-good, the rest is fine. In the context of the question above, I would interpret this factoid as meaning that premature termination of urination would leave urine in the GU tract, where bacterial proliferation could occur. Franamax (talk) 23:33, 6 October 2008 (UTC)

The reason certain bacteria cause urinary tract infections is precisely because they resist the antibacterial properties of urine. If these antibacterial properties were stronger and controlled all strains of microorganisms, we wouldn't get urinary tract infections. But they're not, they don't, and we do. And all urine is not alike. Any antibacterial effect depends primarily on osmolality, urea concentration, ammonium concentration and pH. And of course urease-producing organisms like Proteus mirabilis love urine. - Nunh-huh 12:01, 7 October 2008 (UTC)

Baby Powder scent?

What's the origin of the "baby powder" scent? What is it supposed to smell like? Why has that scent become associated with all things baby? --70.167.58.6 (talk) 16:54, 3 October 2008 (UTC)

Baby powder (Johnson and Johnson)?--GreenSpigot (talk) 17:28, 3 October 2008 (UTC)

How are these links relevant? --70.167.58.6 (talk) 18:53, 3 October 2008 (UTC)

Most baby powder is made by Johnson and Johnson. So you could ask them--GreenSpigot (talk) 19:52, 3 October 2008 (UTC)

Baby powder is classically made of talcum powder, and I would assume that the particular mineral composition is responsible for the smell. As to why that smell is associated with "all things baby", it probably has to do with the millions of baby bottoms that have had talcum powder applied to them. Medical geneticist (talk) 22:16, 3 October 2008 (UTC)

Poor little buggers. Talcum powder has been the cause of more nappie rashes than babies have had poos. When they wet themselves, the powder turns to a fine grinding agent. Far better to use a little baby oil, and no powder. -- JackofOz (talk) 23:57, 3 October 2008 (UTC)

I don't buy that. Talc is one of the softest substances out there. Check out Mohs scale of mineral hardness - talc is a 1 on Moh's scale - which makes it the least hard substance on the scale. SteveBaker (talk) 12:33, 6 October 2008 (UTC)

I'm sure that's right, Steve. However I was told this when son #2 came along, by senior babycare educator nurses at the hospital, who all agreed that the traditional talcum powder treatment is not only less effective than oil, but causes or at least contributes to nappie rash, so it's actively discouraged these days, certainly in Australia. If the reason for the powder is just make the baby smell nice, that's unnecessary - they smell good naturally. Until the inevitable happens, that is, but talc certainly doesn't mask that smell, and shouldn't be used with purpose in mind. -- JackofOz (talk) 23:57, 6 October 2008 (UTC)

I don't doubt that there are better alternatives to talc. My complaint is only the claim that the stuff is acting as an abrasive - when in fact it's a pretty good lubricant. (Talc is a excellent lubricant for wooden surfaces. If you have a cabinet drawer that's sticking - dust it down with some talc. Our question about sticking piano pedals a couple of weeks ago was answered with "Use talc" for example.) My wife was once a Nurse - and indeed taught nursing for many years (although not in pediatrics). It's clear to me that Nurses become very good at knowing WHAT to do in a vast range of situations - but they don't seem to pass on the knowledge of WHY they do it with any degree of precision. So it would come as no surprise to me to find that talc is bad for some other reason. I could imagine (without evidence) that perhaps talc causes the urine that it absorbs to be retained in contact with the skin where oil (being strongly hydrophobic) repels it. As urine evaporates, the urea concentration rises - and concentrated urine is a skin irritant. But it's really not reasonable for a material that's renowned PARTICULARLY for it's softness to suddenly become an abrasive like that. SteveBaker (talk) 03:08, 9 October 2008 (UTC)

Well they make unscented baby powder, so natural talc doesn't have a smell. It's an added fragrance. --70.167.58.6 (talk) 15:29, 4 October 2008 (UTC)

It doesn't necessarily follow that natural talc doesn't have a smell, just because a version which hasn't had scent added exists. I tend to think of the natural smell of talc as 'chalky', where smell should probably be clarified as the sensation when some of it gets in your nose after a cloud of the stuff has been puffed around you. Whether this is the same smell as you were asking about, I don't know. Maybe you're asking about the smell of the typical added fragrance? 79.66.9.134 (talk) 18:21, 4 October 2008 (UTC)

The talc powder that you scratch off a rock definitely don't have that baby powder smell... --antilived^{T | C | G} 21:56, 4 October 2008 (UTC)

The fragrance is added. Check the ingredients. --Russoc4 (talk) 23:58, 4 October 2008 (UTC)

So back to the original question: what is it supposed to smell like? Is there anything in the world that smells like Baby Powder? --70.167.58.6 (talk) 15:39, 5 October 2008 (UTC)

It seems that Johnson & Johnson created a scent for their talcum powder that they thought help market it to parents, who would have been used to fragrances added to soaps, shampoos, cleaning products etc. Now people associate this scent with babyhood and the company is unlikely to change it. Isn't it the same scent in their baby oil? Itsmejudith (talk) 16:17, 5 October 2008 (UTC)

The J&J babypowder is indeed a perfume, in fact the marketing of this product has been so successful that its perfume scent accord is associated with a baby-hood. As such, any other company in North America producing baby products have to scent their products with similar accords or risk being shut-out. I've heard that associations of baby products with the J&J scent is limited mainly to North America; European baby products are scented primarily with lavender. Demeter fragrance has a pretty similar baby powder perfume. Sjschen (talk) 21:54, 5 October 2008 (UTC)

You don't get out much, do you? When was the last time you had a girlfriend or a female of some sort? Are you gonna write more paragraphs now?--Anilmanohar (talk) 13:21, 7 October 2008 (UTC)

What? Zain Ebrahim (talk) 13:38, 7 October 2008 (UTC)

magnetism

hi .... i have a question that why a magnet only attracts a magnet??? ... why not any other thing??? —Preceding unsigned comment added by 116.71.246.18 (talk) 18:13, 3 October 2008 (UTC)

On a macro scale, magnets do attract things that aren't magnets; see Paramagnetism. On a micro scale, magnetic fields also affect moving electric charges in addition to magnetic dipoles. As for why the electromagnetic force behaves the way it does, check that article, but I think whether an answer exists probably depends on how deep a "why" you're looking for. --Allen (talk) 18:37, 3 October 2008 (UTC)

Huh? --ColinFine (talk) 19:00, 4 October 2008 (UTC)

This is clearly not true! A magnet attracts all sorts of non-magnetic objects. Admittedly, only a few metals respond to magnetism (you can't pick up a chunk of aluminium with a magnet, for example) - but those that do (iron, for example) can be attracted to a magnet even if they are not, themselves magnetized. To convince yourself of this - get a refrigerator magnet. It sticks to the metal of your refrigerator - right? But remember that magnets only attract each other if the north pole of one magnet is close to the south pole of the other - north-to-north or south-to-south, they repel. If the refrigerator door was magnetized then it would have to be exhibiting (say) a south pole on the surface to attract the north pole of the fridge magnet. If you flip the fridge magnet over so the south pole is now facing the door - then it should be repelled...but it's not - it still sticks. Since the refrigerator door can't be presenting both a north pole and a south pole at the same place - you know that it ISN'T magnetized. SteveBaker (talk) 12:26, 6 October 2008 (UTC)

Umm, Steve, the fridge door is an induced magnet isn't it? It is a ferromagnetic material, when another magnet is brought close the unpaired electron spins align (I could be wrong here - is it the atomic spins?) (ferromagnetic domains are coerced into alignment) and it becomes a magnet. Based on my experience with training screwdrivers to pick up metal stuff (like screws), some residual magnetism could be measured in the fridge door after the encounter. In my book, that makes it a magnet. Franamax (talk) 23:20, 6 October 2008 (UTC)

Mules

Mules are F1 hybrids between horse and donkey. Both belong to the genus Equidae in the Biological classification.

There is 94% identical DNA between human beings and chimpanzees. What % of identical DNA does horses and donkeys have? If it is equal or more to humans and chimps, why are there no F1 hybrids (or whatever) between humans and chimps? --Anilmanohar (talk) 19:39, 3 October 2008 (UTC)

See Humanzee for the details. As to why there are none even if it was possible, it's because of the ENOURMOUS social taboo against it. No scientist smart enough to do it would even dare attempt it. 83.250.202.36 (talk) 19:57, 3 October 2008 (UTC)

Sure, but no scientist has to be involved to make a mule. --Sean 11:57, 4 October 2008 (UTC)

Yeah, but I don't think it's likely that any human would naturally have sexual intercourse with a chimpanzee due to the same social taboos. --Tango (talk) 16:59, 4 October 2008 (UTC)

Hmm. --Sean 14:26, 6 October 2008 (UTC)

Actually Equidae is a family, though Equus does appear to be its only surviving genus. But while the question is worth asking, do be cautious about that sort of numerological argument: there is no reason to suppose that there is some particular percentage of common DNA which is the threshold for the possibility of viable offspring.

Note also that all surviving equids are classified as the same genus, whereas no surviving apes are in the same genus (homo) as humans. This is not conclusive - levels of taxonomy are not always self-evident - but it is indicative. --ColinFine (talk) 19:14, 4 October 2008 (UTC)

I'm surprised no one has bothered to read my questions and try to answer them. --Anilmanohar (talk) 13:37, 6 October 2008 (UTC)

That's more than a little unfair. I think we all read your question...but it's probably impossible to answer it. Nobody (as far as I could discover) has yet sequenced Donkey DNA. It's likely that racehorses have been sequenced - there is a lot of money in breeding them - but the people involved do not appear to wish to advertise the results. Hence it's almost certain that the first part of your question is unanswerable - so nobody HAS answered it. User:ColinFine did point out that knowing the percentage of DNA in common doesn't necessarily lead to an explanation of why two different kinds of animal can interbreed - which kinda makes your question moot. And several of us did answer the part about Human/Chimp hybrids - both by explaining why nobody has tried to produce such a hybrid (as if it wasn't bloody obvious already!)...and by pointing you to our article on the subject.

But you can't tell by reading the answers whether anyone tried to find an answer or whether we read the question carefully - and it's quite rude (for someone who is asking for a HUGE favor) to just assume that we didn't. In fact, when we try to find an answer and fail - we don't generally bother to discuss that. But it's quite rude to claim that we didn't read your questions. I certainly did, and I'm sure that at least a dozen other regular contributors did too. Yesterday morning, I searched online for about 15 minutes to try to find out whether Donkey/Horse DNA had yet been sequenced and didn't come up with an answer to that piece of your question - I'd planned to search some likely journal indices at the UTA library today or tomorrow - but since you've been so rude, I don't think I'll bother.

SteveBaker (talk) 14:29, 6 October 2008 (UTC)

Steve, the correct response would be: "The % of identical DNA horses and donkeys have is not known. Thus, your second question is unanswerable." Stop taking things so personal. My original response was not a rude one. It was a true one. Thus my original response still stands as is. --Anilmanohar (talk) 18:21, 6 October 2008 (UTC)

Excuse me? You said that "no one has bothered to read my questions" - which is (a) an accusation of laxity on behalf of those of us who contribute time here for no recompense (b) utterly untrue - at the very least I read every single question that shows up here (and I'm pretty sure most of the other regular contributors did too) and (c) this something you could not possibly know. Hence your accusation is utterly inappropriate. You went on to say that nobody had answered your question - when in fact we had gone a considerable way towards doing so. Now you suggest that we should have said that the "% of identical DNA horses and donkeys is not known" - but I for one won't know that until I've researched it a little further - which is why I didn't answer this before. If you note the Reference Desk guidelines (at the very top of this page) you'll see that it specifically states: "Be patient. Your question probably will not be answered right away (...) A complete answer to your question may be developed over a period of up to four days.". For someone who appears to contribute NOTHING to Wikipedia (yes, I looked at your "Contributions" section - all I see there are RefDesk questions) - I think your gratitude and humility levels could use a little adjustment. SteveBaker (talk) 18:43, 6 October 2008 (UTC)

Helpdesk - It is preferred that SteveBaker not respond to any questions today. Please take the necessary steps to remove him. His responses are accusatory and borderline abusive. --Anilmanohar (talk) 18:49, 6 October 2008 (UTC)

This is not the "helpdesk" it is the Science Reference Desk. People who request answers and then make unfounded accusations about how volunteers are reading and responding really don't get to pick who gets to play. Perhaps Yahoo Answers would be more to your liking. --LarryMac | Talk 20:19, 6 October 2008 (UTC)

Being as said, your "volunteers" need a brush up on reading comprehension... FYI - questions I never asked were answered. Not the orginal question..--Anilmanohar (talk) 20:34, 6 October 2008 (UTC)

Now - you really are doing your very best to make everyone love you aren't you? OK - let's see about this alleged "lack of reading comprehension" were now accused of. Please feel free to award my terribly lame reading comprehension with points out of ten - oh great master of the English language:

You said:

• Mules are F1 hybrids between horse and donkey. - this is a statement, not a question.
• Both belong to the genus Equidae in the Biological classification. - another statement. (It was pointed out that you are in fact incorrect in stating this - but fortunately, that doesn't affect what follows.)
• There is 94% identical DNA between human beings and chimpanzees. - another assertion. (Actually - I believe that if you only count active genes, this number is a little low - between a human and a chimpanzee of the same sex - the number is more like 97% - between human and chimpanzee of different sexes, it's way less than 94%. If you count ALL DNA then 94% is way high - even two non-identical-twin sibling humans of the same sex don't share that much total DNA. But again, this doesn't really affect what follows.)
• What % of identical DNA does horses and donkeys have? - Ah! A question at last. I doubt anyone misunderstood, misread or failed to read this (despite it being a grammatical mess). We simply do not have an answer for you (at least not yet). I have explained why it may not be possible to answer that - and I explained that I intended to look for a better answer - but then you insulted me, so I don't think I'll bother. But at any rate, it's hard to prove a negative, so a good answer might well take longer. It appears likely that the answer is not known.
• If it is equal or more to humans and chimps, why are there no F1 hybrids (or whatever) between humans and chimps? - Since you predicated this with an "if" and the answer to the "if" is unknown, then we must either treat this as a hypothetical or remain silent. So IF humans and chimps (hypothetically) shared more DNA than horses and donkeys do - then what reason might there be for there being no hybrids? Now - if you read the THREE very germane answers we provided - you'll see that we said:
  1. We have an article about this (Humanzee) that you should read.
  2. Your presumption that the amount of shared DNA is a measure of how likely hybridization is possible is incorrect (obviously, IMHO).
  3. That moral and legal constraints make the formation of human/chimp hybrids exceedingly unlikely - biology notwithstanding.

So - every part of your question was read, understood and (as far as can be) comprehensively answered. If you were hoping for lots of exciting details of unusual sexual practices that would help you in your personal life in some way - you're out of luck.

However, you still persist in demanding answers (like it's some kind of legal right or something) from a volunteer-supported service...you do that DESPITE our FAQ at the top of this page clearly telling you that you should be patient and not to expect a full answer for FOUR days. You do it rudely by proclaiming that we somehow aren't reading your question. Now you conclude that our reading comprehension is flawed. I don't know why you put "volunteers" in quotes - they really are volunteers - not one of us is paid or gets recompense in any other form. None of us are under some kind of external compulsion to answer questions...yep - we are actually volunteers.

Anyway - I can prove that I'm a volunteer. I believe that you are exhibiting unacceptable behavior - and since I'm just a volunteer - I have decided that I will not knowingly answer any more of your questions until you apologize to the volunteers who worked hard to help you out here. If I am not in fact a volunteer, my boss will probably tell me to get back to work and answer your questions...let's see what happens shall we?

SteveBaker (talk) 23:22, 6 October 2008 (UTC)

<Redacted personal attack --Stephan Schulz (talk) 15:28, 7 October 2008 (UTC)> --Anilmanohar (talk) 15:05, 7 October 2008 (UTC)

Nobody "erased your response," although anybody would have been right to do so; you put it in wrong section. Your continued uncivil posts can and most likely will result in at least a temporary block from Wikipedia. --LarryMac | Talk 15:30, 7 October 2008 (UTC)

Indeed - I did not erase anything (as is easily demonstrated by checking the "history" tab). As for obtaining an additional female companion (per Anilmanohar's recommendation) - I suggested this to my wife - but sadly, she was not keen on the idea. SteveBaker (talk) 02:50, 9 October 2008 (UTC)

Hi, after reading the above content, in Anil's defense, it seems that the volunteer did hastily respond back with negative undertones. I understand that Anil has not contributed to Wikipedia, but that shouldn't be an excuse to verbally attack him in this forum. Not to say that English is a second language to him but it is possible, and to send a response that Steve sent is not only discouraging to Anil, but to the rest of the population (like me) who use Wikipedia.org. I have worked as an ESL tutor for quite some time and in many cases, my students have been misjudged or misterpreted for their lack of understanding certain nuances in the English language. That is just my personal opinion.....--Emyn ned (talk) 14:47, 9 October 2008 (UTC)

How exactly would you construct an "unfair" coin?

When you're learning about probablity theory, there's always discussions of "unfair" coins (i.e. "How many coin-flips do you have to do to find out if a coin is fair" or "What's the probability distribution for a certain unfair coin"). The idea is of course a supposed coin that when you flip it, it comes up with one side more often than the other.

My question is this: is it even physically possible to construct such a coin? Or is this a completely fictional concept? I mean, it's easy constructing an unfair die, if you just weight the "1" side a little heavier than the others, it will more often come up "6". But that wouldn't work on a coin, would it? I mean, if you weighted the "heads" side heavier, it would come up "tails" more often if you just threw the thing up in the air, but that's not what you're doing. When you flip a coin, you spin it in the air. For the tails-side to come up more often, the coin would have to spend more time with the heads-side down while it is flying through the air. That means, if it is spinning, the coin would have to decelerate while the heads side is down, and accelerate when the tails-side is down. But that's not what it's doing, even if it is weighted, it's just spinning the at the same angular velocity all the time. The time it spends with the heads-side up is exactly the same as the time it spends with the tails-side up.

I'm willing to concede that if you let the coin bounce on the floor once, then it could have an effect (as the coin then is just basically flying randomly through the air). But if you cought it in your hand, this wouldn't happen. So, is it possible to construct an unfair coin, and how would you do it (without putting teeny-tiny engines on the thing, that is :)? 83.250.202.36 (talk) 19:52, 3 October 2008 (UTC)

You could cast the coin to have two faces. You could use a coin where one side was notably distinct from the other, perhaps to the point where a keen-eyed "flipper" could know when to grab it in flight. You could have a noticeably different texture on one side, so the flipper knew to either slap the coin onto his other hand "honestly" (reversing it) or attempt to manipulate the coin while it is still unseen so the other side comes up. Matt Deres (talk) 20:03, 3 October 2008 (UTC)

These are all true, but it's not exactly what I'm looking for. I'm thinking of something analougous to an unfair die, where it really looks like a regular coin, but when you flip it, one side comes up more often. So someone could give it to you and say "Find out (with X percent probability) if this is an unfair coin by flipping it as many times as you need" 83.250.202.36 (talk) 20:06, 3 October 2008 (UTC)

Its not hard. You construct the coin so that the one side is made of a denser metal than the other, for example make the tails half lead and the heads half aluminum. Then clad the whole thing in whatever a coin of that type is clad in (for example, if a penny you'd clad the off-balance coin in copper). The result is that, over many flips, the tails side will be favored to land down, being denser... It wouldn't work every time, but even loaded dice don't work everytime... --Jayron32.talk.contribs 20:19, 3 October 2008 (UTC)

The original poster is specifically asking about a coin that is unfair when it is spun and caught while in the air, so all that matters is its position when you grab it while it's rotating at a constant speed. I suppose an uneven weighting or a beveled edge might have some tiny effect by introducing a slight asymmetry in the situation where its position is right on the cusp between coming out heads and tails, but it sure won't be much. Of course you could make a coin with both sides the same and have 100% chance of it coming out the way you expect, but people might notice that!

For coins spun to land on a table, I have heard that with some ordinary coins there can be noticeable "unfairness" due to the image on one side having higher relief than the other. But I don't have a cite for that. --Anonymous, 04:48 UTC, October 4, 2008.

Actually it's even easier. You take a fair coin and hit it with a hammer. It will then be slightly u-shaped and thus be heavier on one side. This also solves the problem of spinning while being in the air. The hollow side will be more unstable in flight thus will end on top. - Dammit (talk) 20:29, 3 October 2008 (UTC)

A coin badly dented with a hammer would have visible damage and be suspect.

It would be easier to take a normal coin and bevel the edges slightly. Normally a coin can stand on its edge. Beveling the edge, even a small amount, would bias the coin to falling over on one side when bouncing or spinning on a hard surface. This wouldn't guarantee the same result every time, but the coin would be biased to one result. ~Amatulić (talk) 20:56, 3 October 2008 (UTC)

Actually, all coins are unfair. 51% of the time—not 50%—a coin will land on the same face it started out on. zafiroblue05 | Talk 22:40, 3 October 2008 (UTC)

If you want to be technical, it isn't the coins that are unfair, it is the "flip". Much of the time, the "flip" doesn't cause the coins to flip at all. They wobble in the air and come down without turning over at all. -- kainaw™ 23:42, 3 October 2008 (UTC)

I read somewhere that the American penny is an unfair coin. I don't remember which side shows up more often, but it's only like 1 more in every 1000 or so. --M1ss1ontomars2k4 (talk) 21:15, 5 October 2008 (UTC)

You don't need to construct one - get yourself a Belgian 1-Euro coin. There was a significant study into the fairness of the various 1 Euro coins out there (every country got to put it's own design onto their version of the coin) - the differences were pretty dramatic: This New Scientist article says that the Belgian 1 Euro coin (for example) comes up heads 56% of the time! So I would imagine that lots of other coins in common circulation would be unfair too. SteveBaker (talk) 12:13, 6 October 2008 (UTC)

A very tiny effect would be caused by the fact that the density of air decreases with height. The lower edge experiences larger air resistance, having a similar (but of course smaller) effect as the edge hitting the ground. Another small effect of this kind occurs if the coin comes close to a stationary surface: The viscosity of air will decelerate the edge closer to the surface. Icek (talk) 20:50, 8 October 2008 (UTC)

"Simplicity" of scientific/mathematical problems

It strikes me that something like Fermat's Last Theorem or e=mc^2 is relatively easy to understand, the former (not the solution by the hypothesis) to anyone that's taken middle-school algebra, and the latter to anyone who knows that c is the speed of light. But when I look at something like Millennium Prize Problems, all the problems listed are little more than nonsense to someone without the requisite mathematical knowledge, and physics questions such as string theory or higgs bosons are based on complex mathematics that can't really be explained to the average person without bastardizing them. I'm wondering if there's anything to this - that science and math have advanced beyond the understanding (not just understanding the recognizability, really) of the average person, and why this would be, and also if there are any standing problems in either area that appear as basic as, say, Fermat's last theorem. zafiroblue05 | Talk 20:30, 3 October 2008 (UTC)

Actually, e=mc^2 is so simple that dozens of people observed it before Einstein. It's not really that big of a deal. Einsteins real genius, mathematically speaking, comes from his explanations of General Relativity, vis-a-vis such phenomena as the effect of gravitation on light, and on his calculations tied to quantum theory. The math in those is WELL beyond most laypeople. Quite honestly, most fields are beyond the average person who does not have adequate training. Anyone could probably be taught to handle the math required to "get" advanced physics, its just that most people aren't interested. The inner workings of my car are a complete mystery to me, and that's why I pay someone to take care of it. Other people have expertise where I don't. This is just as true for auto mechanics as for mathematicians... --Jayron32.talk.contribs 20:38, 3 October 2008 (UTC)

That's no excuse for failing to write articles in layman's terms. United States jury trials do similar things all the time. I get depressed when I see a once-decent article such as linear regression, which once contained practical and useful information that a layman with some college math could put to use, turned into a jargon-filled theoretical treatise (at least that article now contains a practical example to clarify things). That isn't encyclopedic, that's merely obfuscation. Experts in the field don't need to go to Wikipedia for this sort of thing, so the articles don't need to be written for experts only. ~Amatulić (talk) 20:51, 3 October 2008 (UTC)

Um, you'll get no arguement from me. I don't think that answers the question from the original OP or even comments on it... It's merely diatribe... If you don't like an article, take care of it. --Jayron32.talk.contribs 20:58, 3 October 2008 (UTC)

I thought I did address the OP's comment, which seemed to comment on the level of expertise needed to understand the meaning of millenium prize problems. As for articles like linear regression that got converted to jargon, I have tried to "take care of it" as you suggest, but after a point I got tired of my attempts being reverted, and moved on. ~Amatulić (talk) 23:40, 3 October 2008 (UTC)

If the article is too technical, perhaps you could dumb down a version for the Simple English Wikipedia? Isn't that what the project is for? Plasticup ^T/C 01:38, 4 October 2008 (UTC)

No it's not, we are supposed to be building an encyclopedia here not a technical reference book. Equendil Talk 07:28, 4 October 2008 (UTC)

We should be doing both here. Articles should explain the concepts or have links to simplified explanations; and they should lay out the whole difficult field in all its technical glory. Our problem is simply to properly explain. When a user searches for quantum mechanics, do they want an overview, a basic understanding, a confusing in-depth glimpse, or the specific underlying equations? Wikipedia is big enough to do all of these. Franamax (talk) 05:57, 5 October 2008 (UTC)

I agree with what Jayron wrote above, but with a small addendum that, media portrayals of what life, the universe, and everything should be like aside, the real world has no obligation to be either simple and beautiful or complex and murky; it just is. Some parts will be explained neatly, some parts will not. Some parts can be summarized into very basic steps (evolution by natural selection), yet are still wonderfully complicated and nuanced when you try to understand how the theory applies mechanically. How complicated something appears to be can depend greatly on how in-depth you want your knowledge to be and also what aspect you want to understand. Cars seem to have changed a great deal over the last century, but you can still get a great deal of insight in how they work by understanding such basic concepts as the four-stroke engine, the carburetor, and differential gearing - the same concepts you'd have needed 100 years ago. Seen that way, they're still pretty simple, but seen from the POV of the computer systems designed to regulate all that simple stuff they seem horribly complex. Matt Deres (talk) 13:28, 4 October 2008 (UTC)

In answer to the OP's actual question, yes there are still some simple problems left. The twin prime conjecture springs to mind. However, modern mathematics has been being built up for thousands of years so a lot of problems have already been solved. Everything builds on what went before so you generally need a good understanding of what went before in order to understand the new stuff. It's not quite so bad in science since sometimes theories are proved to be complete nonsense and you can just forget about them, but in maths everything that's been proven once is still true now and always will be. Every now and then mathematicians will find a new branch of mathematics or a new approach to an existing branch that hasn't been done before and they get to find out new maths which can actually be understood without knowing lots of existing maths, but it doesn't happen very often. --Tango (talk) 15:55, 4 October 2008 (UTC)

In terms of problems that are very simple to understand, but as of yet unproven, I'd think Goldbach's conjecture would top the list (that is, "every even integer greater than 2 can be written as the sum of two primes"). There are a bunch of other ones, though, like the existance of an odd perfect number or whether there are an infinite number of Fibonacci primes. And if you have a nice person explaining it to you, P vs. NP isn't all that hard to understand, at least not conceptually. 83.250.202.36 (talk) 20:10, 5 October 2008 (UTC)

Yes - P vs. NP is pretty simple. The question is this: If you have some problem to solve and you have some easy way to determine whether the answer you get is correct or not - then is there always an easy way to find that answer in the first place? Are there any problems where finding the answer can be amazingly difficult - but checking it is amazingly easy? Suppose, for example, that you have a list of a million random numbers, each between 1 and 1,000,000 - and someone asks you whether there is an '84' anywhere in the list. If I asked you to find that out, you might have to look through all million numbers. But if you tell me that the answer is "Yes" then I can verify that this answer is true merely by having you show me the '84' that you found...which is very easy to do. Of course if the answer is "No" then it's just as hard to prove that your answer is correct as it was to find the answer in the first place because to convince myself that you were right - I'd also have to look through all million numbers. So in this (very simple) case, it is certainly true that we have a easy check that a "yes" answer is correct for a problem that requires hard work to solve.

In P vs. NP, the definition of 'easy' and 'hard' is rather more formal than that and the example problem I just gave doesn't count as "hard"...but that's essentially the issue here. The commonest example of a 'hard' problem (in this context) is the travelling salesman problem. Given a list of cities and the distances between them, what is the shortest route that will allow someone to visit each of the cities at least once? For a large number of cities, the answer is very hard to find - and proving that it is indeed the shortest route is also hard to do...so this example doesn't help us to answer P vs NP. SteveBaker (talk) 14:04, 6 October 2008 (UTC)

Everything about P vs NP is easy to understand except the definition of "easy" (although even that isn't too hard). I think the whole thing needs to be easy to understand to qualify, personally, but that's just me. --Tango (talk) 15:32, 6 October 2008 (UTC)

To take another example from the Millenium Prize Problems, there are equivalent formulations of the Riemann hypothesis which are easier to understand. In response to a comment by Tango on the certainty of mathematical proofs, in the 19th century there was a proof of the four color theorem which was shown to contain errors only 11 years after publication! Icek (talk) 21:12, 8 October 2008 (UTC)

"Hologram" mirrors illusion??

Hi all, sorry if this question sounds a little bit silly. During a guided tour of a jewelry factory, we came up to a hexagon(I think)-shaped 'table', with a hexagon-shaped hollow space on its center which seemed to be covered in mirrors. Over the hole was a 'hologram' of a watch, but the thing is that the "hologram" had real colors, not those silly greenish-reddish colors holograms usually have! It genuinely looked like a real watch floating in place. We were able to see the watch from all around as if the watch was actually standing right there! They even allowed us to pass our hand through it (which made your eyes a little woozy somehow, focus-wise I guess). I'm sure the table itself wasn't a 'machine' of any sort, and that it must have been some weird illusion with mirrors (a real watch probably being inside the table thing), but I haven't seen that sort of thing anywhere else. My question is, how is that done? That's pretty much what I remember, and I'm still amazed at what I saw back then. I would love to know how they did that! Thanks in advance, Kreachure (talk) 21:33, 3 October 2008 (UTC)

This is an example of a real image. What you saw sounds like the "Mirage" toy mentioned/advertised in the article, though I don't know where to find a diagram of this particular case. You can buy them at places like museum gift shops. --Allen (talk) 22:54, 3 October 2008 (UTC)

Here, this website seems to have a good explanation. --Allen (talk) 22:57, 3 October 2008 (UTC)

(Edit Conflict) I'm not sure what these things are called, they seem to sell under the name "3d mirascope". (Google Search) There doesn't seem to be an article. Essentially there was a real watch inside the table, and through a clever arrangement of curved mirrors the reflection actually appears to be hovering above the hole in the mirrors. I've got one of these right here. The illusion is quite convincing. APL (talk) 23:01, 3 October 2008 (UTC)

Yeah, it's definitely that one, thanks, all! What I'm wondering now is why aren't they popular, because the illusion seems incredibly cool to me, even if it's (as I suspected) such a simple trick... I want one of those right now!!! :) Kreachure (talk) 23:13, 3 October 2008 (UTC)

They were popular as a novelty item, but they've been around for several decades. I remember seeing them advertised in the back of comic books in the 1960s and 1970s. ~Amatulić (talk) 23:36, 3 October 2008 (UTC)

There was even a very bad video game based on them back in the 80s. I don't remember what the purpose of the game was. It was the first 3-quarter game I ever saw, so I just watched a couple other kids waste some time on it and went to play other games. -- kainaw™ 23:38, 3 October 2008 (UTC)

Found the game - and it was 1991, not the 80s. Man, I am getting senile. -- kainaw™ 01:29, 4 October 2008 (UTC)

Reminds me of a gadget I saw in 1981 which used an oscillating mirror to build 3d images – wireframe only. —Tamfang (talk) 07:51, 4 October 2008 (UTC)

They sooo need to bring that style of game display back. :) ---J.S (T/C/WRE) 01:38, 6 October 2008 (UTC)

Mirage Mirror Musings

If you're able to create this kind of image with curved mirrors, is it possible to alter the image of the original to change its size? Maybe make it bigger? Maybe displaying the image a little higher instead of on the edge of the hole? Cause that would be even cooler! Kreachure (talk) 00:00, 4 October 2008 (UTC)

Science museums I've visited have had vertical versions set up that you can put your hand in to 'shake hands with yourself'. The image of your hand was flipped, if I recall, and the size depended on where you positioned your real hand - like with a normal mirror. So I imagine you could create a convincing larger image just by playing with distances. 79.66.115.246 (talk) 01:11, 4 October 2008 (UTC)

I have one of the toy ones. It makes the items inside of it appear noticeably larger. Also, telescopes have long used curved mirrors to make objects look larger. I suspect using mirrors to make objects look both larger and closer would be simple, though I'm not certain. — DanielLC 15:22, 5 October 2008 (UTC)

Water on Mars

Do Mars still have liquid water lye anywherr on crust? From what I learnt is Mars is a very cold planet. Do Mars even get to 25 Celsuis over summer equator. If it gets this warm then Mars might have some pink-orange oceans flown on it's surface. Usually tropical avg. on Mars surface is like below 0 Celsius, and the mid-lattitude on Mars surface si -53 Celsius, this is colder than Alaska over summer. Since Mars atmosp is alot thinner than Earth would it's 25 Celsius feel like 0 Celsius. The simple study is Mars is a very cold planet.--SCFReeways 22:26, 3 October 2008 (UTC)

There is no standing liquid water on Mars' surface due to the low atmospheric pressure, as discussed at Mars#Hydrology. Lower atmospheric pressure wouldn't cause Mars to feel "colder" so much as it would feel "less". There's less opportunity for conductive or convective heat transfer. — Lomn 23:14, 3 October 2008 (UTC)

• This site say mars low is -125 F and high is 23 F, and rf#4 on Mars say the vg. surface temp. is -81 F. I thought Mars have greater surface range. The ext low I thought is like -180 F, and what about the extr high? Is the extr high like +50 F? The short answer is Mars is a very cold planet.--SCFReeways 23:57, 3 October 2008 (UTC)

Certainly small amounts of liquid water couldn't hang around for very long on the surface. Between the cold causing it to freeze and the low pressure causing it to boil - it's really not able to stay liquid for long. However, there have been discussions of underground liquid water possibly still existing - and there are suggestions that periodically, a large volume of liquid water may appear - flow for a while and then either boil away - or freeze and then sublimate. The Phoenix lander has observed ice sublimating into water vapor without ever becoming a liquid along the way. There is ample evidence that there HAS been liquid water there in the past - but the martian atmosphere may have been very different back then. SteveBaker (talk) 13:36, 6 October 2008 (UTC)

October 4

Seeing bullets (with no tracers) streak through the air using IR goggles

Would bullets (with no tracers) be very visible if you were to observe them using IR goggles? —Preceding unsigned comment added by ScienceApe (talk • contribs) 16:38, 4 October 2008 (UTC)

There are two main types of IR goggles and cameras. There are night vision ones that work user near-IR (nearer to visible light, that is) which work by capturing the reflected IR in the same way that visible light is used. They often come with an IR light that illuminates the area with IR so it can be seen (if you watch night vision video you can often see that there's a light shining on the middle of the image and around the edge is much darker). There is then thermal imaging which uses far-IR and captures IR emitted directly by the objects before of their heat. I believe bullets are fairly warm, so would show up well on thermal imaging, but I see no reason why they would show up any better than anything else under night vision. --Tango (talk) 16:57, 4 October 2008 (UTC)

Yes, very visible. Well, the thermal imaging ones at least, as Tango said.

edit: You may want to consider these things though:

• A bullet is small and fast, so seeing it will be really hard using goggles, a camera will have a better chance.
• As noted in the link, the bullet will cool down in flight.

- Dammit (talk) 22:17, 4 October 2008 (UTC)

The night vision goggle (NVG) type can see emitted IR as well as reflected - but the higher frequencies that NVG's are sensitive to are not normally emitted in much quantity by things that are merely warm. However, a piece of "red hot" steel is obvious even to the naked eye (that's why we call it "red" hot). Hence, something that's just a little cooler than red hot would be highly visible by radiated IR in NVG's. The lower frequency detectors in InfraRed cameras (such as you might find on a combat helicopter, drone or fighter/bomber) are able to see radiated IR across a wider range and are sensitive enough to see things that are just a fraction of a degree above their environment - you can see warm 'tracks' left by a vehicle driving by for example! I've worked a lot with both kinds of sensor - you can't see regular bullets in flight with either of them - there just isn't enough light (IR or otherwise) and it's not there for long enough. Also, the resolution of both NVG's and IR cameras is nowhere near fine enough to pick up something that small at a distance. But tracer is highly visible to both because it produces a lot of visible light (which the NVG can see) and the cloud of combustion products is large enough and hot enough for the IR camera to pick up. The 'rangerats' stuff that User:Dammit provided is deceptive. Firstly they aren't using regular NVG's or military IR - they are using some kind of very fancy IR camera that's specifically designed for measuring temperature rather than for seeing well at night (this is obvious from the 'false color' images on their site - military stuff doesn't use false color - the images are invariably monochromatic, and typically green). Secondly they say that the bullet was only visible fairly briefly just as it left the barrel of the gun - a fraction of a second later, it was too cool to register on their equipment. SteveBaker (talk) 11:56, 6 October 2008 (UTC)

Please read better before of calling something deceptive. The only thing fancy about the camera used is that it is a high speed one, other than that it's not all that different from thermal imaging goggles. Also they don't write that the bullet was only visible briefly, in fact they could have followed it right to the target if the camera could pan fast enough (see the link to the shot apple on the article). They just used a static camera pointed at the muzzle and selected the first image where the bullet came out of the gas cloud (before that bullet it was not visible). - Dammit (talk) 23:40, 8 October 2008 (UTC)

Is this understandable?

Quite confusing IMO.

Our sail car is trapezoidal with two horizontal extensions, one on each side of the car in the back. The extensions are created using four straws. Two are linked together to form what appears to be one long straw in the very back (creating the rear base of the trapezoid as well), so that only very ends of the 'straw' are part of the extension. It holds two wheels on each extension, both (wheels) kept from sliding by two pins placed beside each wheel, the pins being stuck into the straw. The other two straws are on opposite sides of the car and in front of the rear straw. They support the wheels as well (the support pins are stuck through them after being stuck through the rear straw), but they bend towards the front of the car upon clearing the extensions. These straws bend upon reaching the front, creating the smaller (shorter) top (front) base of the trapezoid by connecting at the center of the front base. The front ends of the straws then hold two more wheels near the bent area. Right at the bend of each of the two front straws are two more straws are pinned to each one of the straws just aforementioned. These two straws converge and meet at the midpoint of the rear straw.

Roughly halfway between the extensions and the midpoint of the rear straw are straws extending vertically upwards. These straws are connected to a sail. The sails is bent inwards and is supported by a crossbeam at the top.

Rest assured, for the prototype actually worked.

--hello, i'm a member | talk to me! 22:21, 4 October 2008 (UTC)

Clarification is needed here. Is this native English language or a translation? (For that matter, please provide proper attribution when quoting extensive text on a GFDL site such as Wikipedia - who said that, where?)

And in particular, what does "straw" mean in context? Drinking straw, wheat straw, something else? Once you attribute that quote, we may be able to shed some light. Franamax (talk) 05:11, 5 October 2008 (UTC)

It seems to be some kind of little toy made with drinking straws. To answer the question: yes, this text is confusing. I got lost in the first sentence because I could not visualise the "sides" and the "back" of the trapezoid. A diagram would help. Itsmejudith (talk) 15:44, 5 October 2008 (UTC)

Is there any way I can clarify the passage? 'Front' and 'back' are arbitrary positions (they were defined on a whim...doesn't really matter too much) and yes, those straws are drinking ones. --hello, i'm a member | talk to me! 15:57, 5 October 2008 (UTC)

I second Itsmejudith...a diagram would help immensely. Even a very simple sketch would clarify what is where relative to what else. Alternately, a more technical diagram could have labeled parts replace this entire paragraph! DMacks (talk) 16:09, 5 October 2008 (UTC)

Assuming that I have a diagram, would this passage still be confusing? I know my question isn't all that answerable... --hello, i'm a member | talk to me! 16:28, 5 October 2008 (UTC)

The description is confusing and ungrammatical in places. It sounds like a first draft. In the fourth sentence, it's not clear what the pronoun "It" refers to. Perhaps if the text said "The rear axle," with that axle defined by what straws it was made of, all would be clearer. In the fifth sentence, instead of "in front of the rear straw" it should say "at the front of the trapezoid" to give a point of reference. In the sixth sentence replace "they" with an explicit declaration of what is referred to. In the 7th sentence, it is not clear in what direction the front straws bend: is the outside end of a front straw closer to the rear, or farther from the rear than the center of the front line of the trapezoid? In the 8th sentence, "the bent area" is undefined. The 9th sentence is vague and confusing, and contains an extra "are." If the front 2 wheels are on straws which are bent, then are their axes not parallel to the axes of the rear wheels? It sounds like the front wheels point at an angle, which would make it difficult for the device to move forward without dragging the front wheels, which would want to roll in different directions from the back wheels and each other. Sentence 11 does not specify which straws are "the extensions" it refers to: front, back, or all four? How many straws point upwards in sentence 11, and where are they located in the trapezoid? Sentence 12: Specify the arrangement of the sail. Sentence 13: "Bent inwards" is vague. To move forward in a wind, the sail would need to be parallel to the rear axle to maximize thrust from wind coming from the rear, or at some lesser angle such as 45 degrees to take advantage of side winds and produce forward movement. Sentence 14: It "worked?" Even a crackerbox would move in a strong wind. How fast did it move in what speed of a wind coming from what direction? Edison (talk) 20:44, 5 October 2008 (UTC)

October 5

How to Get Gray Hair

I understand there is a multitude of products in current circulation designed to rid people of gray hair, which is a process that I am not in the market for. I actually want the exact opposite. My hair is a dark brown/black, and I want it to have a nice Andy Warhol/Randy Newman gray tone. What should I look into regarding this? Is it even possible? Thank you folks. Kenjibeast (talk) 02:36, 5 October 2008 (UTC)

Hydrogen peroxide and ammonia will strip the color out of your hair, but it will leave it a whitish blonde, not gray. :( --Russoc4 (talk) 03:11, 5 October 2008 (UTC)

Keep in mind that Warhol wore a wig. Dying your hair to that level of white is possible but it's not easy and it's not very good for the hair. I don't know how you'd get it gray rather than white, though. --98.217.8.46 (talk) 04:01, 5 October 2008 (UTC)

Get a stressful job or go to graduate school in some crazy competitive field like biochem. It's guaranteed to work though it does take some time. Comes with free wrinkles too ;) Sjschen (talk) 04:20, 5 October 2008 (UTC)

Just wait: time has a tendency to take care of such things. ៛ Bielle (talk) 04:31, 5 October 2008 (UTC)

This evidence is anecdotal, but ever notice how all the US presidents look so old after just 4-8 years? Stress does seem to assist with the graying. This does pose the question, does stress induced graying recover with the relief of stress? Sjschen (talk) 04:49, 5 October 2008 (UTC)

That's not just anecdotal, plenty of others have noticed it too. I've read articles on it, but I can't find any now. It looks like ABC had a slideshow on it, but has since taken it offline. Plasticup ^T/C 15:45, 5 October 2008 (UTC)

Playing devil's advocate for a moment, I think it's worth noting that most new Presidents are into what might be charitably described as 'late middle age' by the time that they take office. According to List of United States Presidents by age, the average age of a new President is 55 years. Add four or eight years on to that, and and they're eligible for senior's discounts at a lot of retailers. In other words, they look so old because they've gotten so old. Compare photographs of the average non-President at ages 55 and 63, and you might notice that they've aged, too. TenOfAllTrades(talk) 19:42, 5 October 2008 (UTC)

I considered that, yes. I think it would be interesting to test it. Plasticup ^T/C 19:53, 5 October 2008 (UTC)

Even the young presidents (Clinton, Kennedy) look much older after a few years in office. --Carnildo (talk) 22:24, 5 October 2008 (UTC)

In that case, how does stress induce greying? How does melanine production get turned off in such a manner? Sjschen (talk) 21:04, 5 October 2008 (UTC)

Exactly. ---J.S (T/C/WRE) 01:31, 6 October 2008 (UTC)

This sounds like a problem that actors would be faced with, as they may have to play the same character at different ages. I suggest trying a supplier of theatrical cosmetics. --Anonymous, 04:44 UTC, October 5, 2008.

Having teenage children is a tried and true method for getting gray hair. You also might ask to borrow some teenagers if the time constraints of raising your own are a problem. Edison (talk) 20:22, 5 October 2008 (UTC)

Scientific American took up the question of stress and gray hair. There are some other interesting notes there, too. Keep in mind the hair isn't just one shade of gray -- as the melanocyte cells fail, there's less and less pigment; when there's none, the hair appears white. Also, blondes seem to turn gray later, because the white doesn't stand out as much against the blonde. --- OtherDave (talk) 00:59, 7 October 2008 (UTC)

Alright, apart from getting a wig, looking for theatrical cosmetics, and applications of constant stress, are there any permanent methods to grey my hair out? By permanent I don't mean forever, I just mean it won't wash out, dig? Thanks folks, you've been a great help so far. Kenjibeast (talk) 05:59, 7 October 2008 (UTC)

Nomex

How fire/heat resistant is Nomex? I can find all sorts of words like "very" and "extremely", but no hard numbers. --67.185.172.158 (talk) 09:12, 5 October 2008 (UTC)

Nomex is meant to save you from flash injury, it's not really made for running into fires. As such, you won't necessarily find "hard" numbers. Suffice to say, if a pool of flammable liquid ignites 20 feet away, you're better off wearing Nomex. The ejected flammable liquid won't hit your skin and the flames will bounce. If you end up lying in a pool of burning hydrocarbons, you will still have to get up and run. Franamax (talk) 09:39, 5 October 2008 (UTC)

[8] "The rate of material decomposition and charring rate is high only after the temperature greatly exceeds 350°С; however, the material does not melt." Also a bunch of other figures not related to using it for protection (e.g. [The unique combination of electrical and mechanical strength, heat resistance (temperature rating of 220°С]). Perhaps you can find some graphs showing decomposition and stuff, but I don't really see how you can get any 'harder' then that. I presume precisely what it does will depend on the temperature and time period of exposure and whether it's a naked flame. As Franamax says I think the primary point of Nomex is that it stops flames from hitting your skin and it doesn't itself catch fire in most situations you'd expect to encounter. It's not some sort of extrme insulator so you've still going to get burnt if you stay in a fire/hot temperature for too long Nil Einne (talk) 10:24, 5 October 2008 (UTC)

I smell an experiment! Plasticup ^T/C 15:42, 5 October 2008 (UTC)

We'd better hope that the experiment doesn't lead to our smelling a burnt body. --M1ss1ontomars2k4 (talk) 21:17, 5 October 2008 (UTC)

Fire-suite manufactures do internal testing and are loathe to share their results. It's the same in any very specialized industry... the research is just too expensive to share with their competitors. ---J.S (T/C/WRE) 01:35, 6 October 2008 (UTC)

Nomex coveralls are also horribly uncomfortable, since they retain your sweat. I always used Proban^TM, which was treated cotton, and I got away with it 'cause I was the manufacturer's rep and could explain that I threw them away after ten washings. In any of my safety-trainings (one per chemical plant) I was told the rule that no sleeves could be rolled up, and that Nomex was the just-in-case for "uncontrolled ignitions" and that all normal evacuation procedures must be followed. Ironically, the protection of the coveralls would mean that only your hands and face would be hideously burnt, but you'd still be alive. I've since eased out of that field of work... Franamax (talk) 23:01, 6 October 2008 (UTC)

Err...franamax, as a firefighter, allow me to advise you to qualify your first statement. Nomex hoods are standard issue for firefighters in the united states and therefore are literally made for running into fires. Granted, the protection the hood gives is limited and the first area that usually gets burned (the ears) is under the hood's jurisdiction. NFPA standard 1971 probably has something to say about them if you can find a copy. --Shaggorama (talk) 07:27, 7 October 2008 (UTC)

Hyperthyroidism and the risks of general asesthesia/surgery

I was recently scheduled for a hysterectomy and the Surgeon cancelled the surgery because of the TSH result from my pre-op blood test. If the T3 & T4 results are in the reference range is there a risk of going under general anesthesia? If so, are they and what are the statistics? —Preceding unsigned comment added by Istaffordcomcastnet (talk • contribs) 17:04, 5 October 2008 (UTC)

Your surgeon, your consultant and other doctors involved in your treatment know your medical history and your test results and are obviously a much more reliable source of information than random strangers on the internet. So ... wouldn't it be better to put your questions to them ? Gandalf61 (talk) 17:26, 5 October 2008 (UTC)

There does appear to be an interaction between thyroid horormones and some specific anesthetics and/or major surgery. Googling for t3 t4 tsh anesthesia finds some refs. Even though this isn't (to my reading) a request for medical advice, your doctor could at least tell you the specific guidelines he's following. That would be a great starting point to finding out the basis for those guidelines and the risks that specific deviations would entail. DMacks (talk) 17:31, 5 October 2008 (UTC)

Reasons people mumble - hearing loss, etc.

I'm curious as to the physical reasons people mumble. Specifically, I heard someone say recently that some older people start talking lower because of hearing loss. That sounded strange, because I would think, instinctively, one would speak louder with a hearing loss. I supose the issue could be the "internal volume control," so to speak, where the person just *thinks* they're speaking normally because they're used to not hearing much, anyway. It just seems so counter-intuitive.; it seems that once you get that volume down when you're a child, it stays, unless you think you have to speak louder.

Also, considering the person mentioned older people, I wonder if mumbling could be due to a heart problem, with not enough oxygen coming to the person. Although, I always though those weak voices of dying people in movies and TV were just dramatized; sure, my grandparents' voices sounded a little weaker toward the end, but not *that* weak. Thanks.Somebody or his brother (talk) 19:33, 5 October 2008 (UTC)

In my experience, some muttering is passive aggression. Mumble first, then when someone asks for clarification shout "I SAID...." Other mumbling may reflect shyness or a defense mechanism for fear of being attacked for saying something. Also consider that when it seems like other people are mumbling, it might actually reflect a hearing loss on the part of the listener. Edison (talk) 20:51, 5 October 2008 (UTC)

Much of our speech habits is controlled/re-enforced by hearing our own voice or the voice of others. If we lose our hearing we lose that reference and the habits can slip. Ever notice how weird it is to talk with really good sound protection on?

Speculation... If an older person is losing their hearing then it's possible they are told a few times too many that they are talking loud... and then they over-compensate in response. ---J.S (T/C/WRE) 01:29, 6 October 2008 (UTC)

A rather simplistic explanation: Humans are inherently designed to put forth the least amount of energy required to complete a given task. If that task is communicating a message, there is not point in speaking in a loud, clear voice when a soft mumble will likely work just fine. I ride the bus most days. I hear conversations that sound like, "Isa you gur edda sto." "Mudu?" "Yaw." "Aw, shu gedda da mun etta." It may sound like nonsense, but it is the minimum effort required for the two to converse. Sometimes it fails. I was one of my favorite Chinese food restaurants and the lady in front of me ordered "frump fry fie". The guy at the register didn't understand. She asked again for "frump fry fie". He didn't understand. After going back and forth a large number of times, a cop behind me asked her if she wanted "shrimp fried rice." She replied "Fu!" -- kainaw™ 03:34, 6 October 2008 (UTC)

I agree with these answers. In addition, though, think about a feedback loop. Will the person get positively or negatively reinforced when they begin to dabble in mumbling behavior. The answer is positive reinforcement, so they will keep winding down the slippery slope. Plus, you gave stated information that it is about older people. Society has norms for providing people these unfortunate feedbacks. Its just an interesting theory, not quite yet a paradox. It was good though, I liked reading and answering your question. Thanks Sentriclecub (talk) 18:39, 6 October 2008 (UTC)

Loss of hearing acuity would sever the feedback link between spoken volume and perceived volume. Also, the volume of your own speaking is largely transmitted through your own skull, so problems at the eardrum mechanism would cause other people's voices to decrease in perceived volume more than your own. It is only the younger cellphone generation who have decided that the solution to poor audio is to SPEAK LOUDER into their own phone. (Incidentally people, you don't have to face outwards on your balcony to get better reception, although it does let everyone know how cool you are. And ain't it strange how all the phones work so well indoors in wintertime, but in summer you suddenly need to give me all the details of your life?) If you can't accurately assess your own relative vocal loudness, it's hard to say whether your own loudness would increase or decrease.

That said, I am well-known in various workplaces as "talks to himself" - so to some extent, mumbling is also a vocalized internal conversation. Franamax (talk) 22:37, 6 October 2008 (UTC)

I'm the same, Franamax. One of my kids once mentioned in passing how I was talking to myself when I was typing something on my computer. I said I wasn't aware of it, but if it was true, I must have had something on my mind and it would have been a one-off experience. I was humbled when he said "Dad, you do it all the time". Others have since commented on this. Maybe I'm the Glenn Gould of Wikipedia. My experience of increasing deafness is that I'm more and more often asked to speak up. Apparently, to my interlocutors I'm mumbling, but to me I'm speaking at what I think is a normal volume. What people hear in their own heads when they're speaking is not the same as others hear them. I'm reminded of this whenever I'm watching TV and munching on a snack. Whenever I take a bite, I momentarily lose what I'm listening to, and I've learned to do most of my munching during the ad breaks. -- JackofOz (talk) 23:45, 6 October 2008 (UTC)

Well luckily I'm showing no signs whatsoever of aging. There is an increasing trend to smaller font sizes and lower light levels in general, but I'm sure that will change back in time. I too have noticed the new more loudly-crunching snacks that prevent one from hearing the program. This will all doubtless be fixed when the US Democrats come to power. Or was it the Republicans? I'll consider this when I've finished my nap. :) Franamax (talk) 01:09, 7 October 2008 (UTC)

"When in doubt, mumble" -- James H. Boren. I know I do that a lot. — DanielLC 23:50, 6 October 2008 (UTC)

On a related "what you hear in your head and what others hear is not the same" topic... I very much like to sing when I program. In my head, I hear a voice somewhat in tune with what is coming out of my speakers. To everyone else, my voice is monotone, nasal, and very annoying. Hence, I do most of my programming at home, at night, after the family is asleep. -- kainaw™ 01:21, 7 October 2008 (UTC)

You should probably get a small headset-microphone and plug that into your sound-card so you can mix a little of your voice into whatever it is you are singing along to so you can hear yourself as others do. SteveBaker (talk) 11:35, 7 October 2008 (UTC)

Blindness and visual artefacts

Do people who are blind from birth 'see' visual phenomenons, artefacts or hallucinations, perhaps due to the lack of stimulation of the visual cortex? Has anyone got links or refs on that subject. Thank you. 190.244.186.234 (talk) 21:38, 5 October 2008 (UTC)

Ah, I already found this: Charles_Bonnet_syndrome. 190.244.186.234 (talk) 21:43, 5 October 2008 (UTC)

That article doesn't mention persons who are blind from birth. That syndrome seems to afflict persons who lose their sight later in life. Plasticup ^T/C 04:10, 6 October 2008 (UTC)

Almost the exact same question was asked about a month ago and given (in my opinion) thorough treatment. Check out the response here. --Shaggorama (talk) 06:13, 7 October 2008 (UTC)

Hurray! Fanx. OP. 190.220.104.35 (talk) 15:38, 7 October 2008 (UTC)

extrusion of rock

What do the extrusion of rock form? Thanks, from my son - for his Science homework. —Preceding unsigned comment added by 76.69.48.237 (talk) 22:12, 5 October 2008 (UTC)

All kinds of neat stuff. Extrusive article is a good place to start. -- Finlay McWalter | Talk 22:14, 5 October 2008 (UTC)

October 6

Sleep Noises

As people fall asleep I've noticed (through my limited experience) they make some sighs/moans/grunts/little noises. Is there a cause, or reason for this?207.172.71.243 (talk) 00:14, 6 October 2008 (UTC)

According to our articles on sleep stages and myoclonus, these seem to result from normal involuntary muscle movements when entering the "N1" stage of sleep. Claiming my unsigned edit from 22:21 06Oct08. Franamax (talk) 01:49, 8 October 2008 (UTC)

See hypnagogia and hypnic jerk for related subjects, although I don't see anything specifically about making noises. --Anonymous, 22:24 UTC, October 6, 2008.

Volume of human voice

Is an increase in the volume of a human voice, be it shouting, talking louder, or full-on-screaming--mostly created through the larynx, or lungs?

I'm really just wondering about the ability for humans to raise and lower the volume of their voices, how is that controlled?207.172.71.243 (talk) 00:19, 6 October 2008 (UTC)

I do not know for sure, but I think it's controlled by the volume of air permitted to pass over the lungs... much in the same way that a whistle gets louder as you blow harder into it. ---J.S (T/C/WRE) 01:24, 6 October 2008 (UTC)

Today is a bad day for people NOT doing experiments here on the science desk! Put your hand just in front of your mouth...whisper something...did you feel any air flow? Probably not. Now yell as loud as you can...do you feel air flow now? I guess so...hence a greater volume of air is being moved when you shout. Now - how on earth could your larynx cause air to flow? Just feel what happens to your lungs when you shout - it's really obvious. The larynx controls the pitch (frequency) of the sound - not the volume. SteveBaker (talk) 13:26, 6 October 2008 (UTC)

Well, the larynx certainly enters into the picture. When you produce a soft sound at a given frequency, your vocal cords open and close at that frequency. When you shout at the same frequency, your vocal cords open and close at the very same frequency. When a greater volume of air passes, the vocal cords must open more widely, i.e. they vibrate with a greater amplitude. To achieve that requires that the laryngeal muscles be kept tighter. Amplitude corresponds to volume. The increased amplitude of the vocal cords is transmitted to the resonant cavities (chest, sinuses) resulting in the louder sound. By the way, to be precise, it isn't your lungs that cause the increased air flow, it's the diaphragm and chest muscles. --NorwegianBlue ^talk 19:05, 6 October 2008 (UTC)

That's right. Trained singers (and speakers) keep good control of their diaphragm so that they can control the amount of air (well, CO2 to be precise) they expel. That way they can sing a long phrase, in which the volume might vary from soft to loud and back again, without needing to take a breath and in the process interrupt the musical phrasing. If they try to do it by just allowing their lungs to deflate, they'll run out of breath too quickly. Far better to use a taut diaphragm to push the air out in a controlled way. -- JackofOz (talk) 23:33, 6 October 2008 (UTC)

Jack, not to be a stickler or anything, it's actually air (N, O2, CO2, etc) your exhaling... with co2 being only a minority part of it. ---J.S (T/C/WRE) 03:39, 7 October 2008 (UTC)

Thanks, J.S. I'll remember that. Also not to be a stickler, but let me repay the kindness by alerting you that it's "you're exhaling"  :) -- JackofOz (talk) 01:22, 8 October 2008 (UTC)

What Jack is referring to is commonly known as the rule, "Sing/Speak from your stomach, not your chest." Some people naturally use their diaphragm. Others use their chest. The voice produced usually sounds very different. -- kainaw™ 03:45, 7 October 2008 (UTC)

Hypnic jerk

Is there a way to decrease the strength and frequency of hypnic jerks? Plasticup ^T/C 02:22, 6 October 2008 (UTC)

Not medically speaking mind you but it seems to occur more when I'm sleep deprived so in my case I'd say to me-self "get more sleep"  ;) -hydnjo talk 03:09, 6 October 2008 (UTC)

Are they, neurologically speaking, similar to seizures? Have they ever been treated with anti-seizure medications? Plasticup ^T/C 03:37, 6 October 2008 (UTC)

Now that is seeking medical advice and therefor we'all must resist the temptation to further diagnose or offer treatment suggestions for the affliction of which you speak - seriously. -hydnjo talk 03:56, 6 October 2008 (UTC)

Oh darn, because I really was going to walk down to my local pharmacy and buy some anti-seizure meds. I just want to know where the science stands. Humor me, I promise I won't sue. Plasticup ^T/C 04:05, 6 October 2008 (UTC)

If you wanted to know where the science stands, you would search medical journals for "hypnic jerk" and "seizure". Instead, you are asking random strangers who likely have no medical experience of any kind. It shouldn't be too difficult to understand how stupid that appears. A proper question would something like, "Does anyone have any links to medical studies on hypnic jerk?" For, you see, this is a reference desk, not a "does anyone have any medical opinions based on years of watching the Simpsons and Family Guy that I can use to try and diagnose and treat an annoying problem that I think I might have" desk. -- kainaw™ 04:09, 6 October 2008 (UTC)

Don't be facetious. A link to a medical journal is exactly what I am looking for. If you cannot answer without referring to the Simpsons then don't answer. Leave it for someone else. Plasticup ^T/C 04:13, 6 October 2008 (UTC)

C'mon now Plas, no one is being a dick here, we're just trying to comply with the arduously arrived at guidelines with regard to the phrasing of your question. Of course a different phrasing would bring a different response. -hydnjo talk 04:26, 6 October 2008 (UTC)

That is more or less the definition of facetious. Why should the wording matter? If someone is aware of an article in a medical journal on this subject they will share it no matter how I word the question. Besides, where did I ask for advice? I have only asked for information. Plasticup ^T/C 04:39, 6 October 2008 (UTC)

Unfortunately, the result of being stepped upon by the "community" in these matters has left the desks with an uneasy feeling about all things that could be interpreted as "medical advice". I agree with you but past experiences have left us impotent. So, careful wording is more important than you could imagine but please try:

I'm seeking information beyond what is cited in the Hypnic jerk article. Specifically, and in neurological terms is that jerk similar to a seizure and has it ever been treated with anti-seizure medications such as gabapentin or the like? Any links besides those available when I googled "hypnic jerk"would be appreciated. Thank you (wimp-ally ), (say), - hydnjo talk 05:18, 6 October 2008 (UTC)

Yes but it falls into personal experience which I don't want to publish here. If you wish I would be glad to share my experiences via email. (say), - hydnjo talk 05:41, 6 October 2008 (UTC)

I'm glad to see that nobody's succumbed to the temptation of calling you a "hydnjic jerk" just because they disagree with you, Hydnjo.  :) -- JackofOz (talk) 23:23, 6 October 2008 (UTC)

At the risk of stepping into the discussion, here is a reference that appears to be freely available in PubMed. It appears to be a general review about sleep disorders but has a small section on "Sleep Starts (Hypnic Jerks)". There seems to be a dearth of medical research into this subject, but according to this reference there are no known treatments. Perhaps someone interested in the subject could improve the Hypnic jerk article? —Preceding unsigned comment added by Medical geneticist (talk • contribs) 13:59, 6 October 2008 (UTC)

Hypnic jerks are at one end of a spectrum leading up to periodic limb movement disorder (nocturnal myoclonus). Hypnic jerks are usually regarded as a trivial normal phenomenon. If your patient's hypnic jerks are so disruptive that he/she is considering taking medication, it is more likely to represent periodic limb movement disorder. I recommend referral to a sleep specialist (in the UK a subspecialty among pulmonologists) for a sleep study. Treatment options for PLMD are the dopamine agonists ropinirole and pramipexole. Axl ¤ [Talk] 19:23, 6 October 2008 (UTC)

multinucleate cells

What's the difference between a syncytium and a coenocyte? --Anakata (talk) 03:03, 6 October 2008 (UTC)

The articles say a syncytium is "cell-like" (but, presumably, not a cell) with multiple nucleii, while a coenocyte is a "cell" with multiple nucleii. And that's as far as I can go. ៛ Bielle (talk) 04:46, 6 October 2008 (UTC)

Maroon Clowns

Transferred from Miscellaneous desk Gwinva (talk)

Can a Gold-stripe maroon clown fish and a normal Maroon clown mate together?--Pufferfish4 (talk) 20:19, 5 October 2008 (UTC)

I couldn't find anything, but I bet the folks at http://www.fishforums.net/ would be able to help you. Alternatively, you could ask some of the contributors at Wikipedia:WikiProject Fishes. If they don't know the answer offhand I bet they would know where to look. Plasticup ^T/C 03:52, 6 October 2008 (UTC)

Languages in dreams

Has anyone ever researched languages in dreams? I was speaking with a couple of friends (both Greek Cypriots who are fluent in English), both of whom said that they dream both in English and in Greek. Any idea if such is common? I looked at dream, and I couldn't find anything even about speaking in dreams in general, let alone the language in which the speech is conducted. Nyttend (talk) 04:49, 6 October 2008 (UTC)

Well, speaking for myself, I certainly dream both in English and Finnish, absolutely. I think someone brought this up here before, but I can't seem to find that discussion now. -- Captain Disdain (talk) 07:30, 6 October 2008 (UTC)

In contrast, I'm fluent in Hindi, English and Bengali but have never had a dream in any language apart from hindi, which is my native language.Leif edling (talk) 11:37, 6 October 2008 (UTC)

I don't remember my dreams but in waking life I don't think in language much anyway except when thinking about communicating with other people. It's more about connections and movement and probabilities - gut feel but structured if you like. Dmcq (talk) 12:17, 6 October 2008 (UTC)

I used to dream in broken Spanish. It was horribly frustrating, because my limited language skills would impede the progress of my dream. Apparently this book discusses a "pidgin Malayalam used by Todas in trance states", but I couldn't find the passage. Plasticup ^T/C 15:57, 6 October 2008 (UTC)

I've always thought that the assumption that most people experience the world in generally the same way was a particularly limiting facet of contemporary psychology. How most people see the world is often confused with how everyone sees the world. --Shaggorama (talk) 05:58, 7 October 2008 (UTC)

marine engineering

ship is using heavy oil during sailing in sea.But in port it is using diesel oil why —Preceding unsigned comment added by Rajulramachandran (talk • contribs) 07:35, 6 October 2008 (UTC)

I presume that the heavy oil is used for running the main engines - but in port they only need smaller diesel generators to produce electricity. But that's just speculation. SteveBaker (talk) 11:33, 6 October 2008 (UTC)

Ships at sea use bunker oil, pretty much the worst and dirtiest petroleum-based product there is. The lower parts of an oil refinery fractionator produce a very low quality type of oil, and in particular, the wash zone just above the inlet feed is used to remove heavy metals from the stream. This is the most worthless of crap in the petroleum (NB asphalt is even worse, but it goes out the bottom and gets put on roads, also vast effort is expended on getting anything good out by means of the vacuum fractionator). All the junk that can still flow gets sold somewhere, and that somewhere is ships at sea, where no-one can hear you scream. No right thinking harbourmaster would allow such junk to be burnt anywhere near people - so ships switch over to half-decent fuel when they come into port. Out on the ocean, they use the really cheap and nasty stuff. Franamax (talk) 22:02, 6 October 2008 (UTC)

SOUND

WILL SOUND PASS THROUG SOLIDS —Preceding unsigned comment added by 59.93.6.27 (talk) 11:49, 6 October 2008 (UTC)

Yes, see the article named sound. It normally goes very well through solids and liquids as well as the air, the only problem it has is going between different mediums - that's why soundproofing is made of mixtures of odd shaped materials and air. Dmcq (talk) 12:22, 6 October 2008 (UTC)

This being the science desk - I recommend an experiment (actually, a "thought experiment" should do here). Sit inside a car on busy road - shut all the doors and windows and turn the engine and radio off. Can you hear the other cars on the road? Yes? Then sound passed through the solid surface of the car. Sound is just a vibration. The air vibrates - your ears pick up that vibration. In the case of our experiment, vibrations in the air outside of the window caused the glass to vibrate. On the inside of the car, the vibration of the glass started the air inside the car vibrating - and that's what you could hear. If you gently touch the glass with your fingertip as a big truck goes by - you can feel the glass vibrating. SteveBaker (talk) 13:19, 6 October 2008 (UTC)

I think that is wrong. it could it ber comming from throught the air conditioning pipe from outside and not throught the solids? —Preceding unsigned comment added by 194.80.240.66 (talk) 14:27, 6 October 2008 (UTC)

Have you ever heard a sound? If so, it's because it went right through your solid eardrum. --Sean 14:41, 6 October 2008 (UTC)

Even those not blessed with the faculty of sound can feel low tones resonating in their chest cavity. Plasticup ^T/C 15:50, 6 October 2008 (UTC)

Sound actually travels *faster* through most (all?) solid objects than air. In steel, sound travels at 5,100 m·s^-1, about 15 times faster than in air. If you yell at your friend underwater, it will get to them about 4 times faster than having a conversation above ground. -- MacAddct1984 ^{(talk &#149; contribs)} 18:57, 6 October 2008 (UTC)

It should be possible to demonstrate this if you have access to a straight metal bar at least 100 feet (30 meters) long and preferably somewhat more (an abandoned railway track would be ideal, but please don't try it on a working railway, where you might get run over by a train!). Perhaps you can find a long, continuous metal railing somewhere in a public park or plaza. Okay, now you need a friend to assist you, or maybe you can trick an enemy into doing it, if you don't have any friends. :-)

Have your assistant bang on the bar every few seconds with something hard like a rock or a small hammer (if the bar has a decorative finish, it would be safer to stand a flat piece of metal on top of it and bang on that, to avoid damage). If you stand far enough away along the bar, you will hear the sound lagging behind the your assistant's motions. 100 feet will give a lag of about 1/10 second; at 200 feet the lag is 1/5 second and will be more obvious. Now put one ear against the bar and you should hear the tapping in that ear ahead of the other ear. That proves that the sound is traveling through the solid bar faster than the air, and therefore that the sound is traveling through the solid. --Anonymous, 22:39 UTC, October 6, 2008.

Light from the remote visible in the video image?

when i has my video camera and my tv remote i can sees the light from the remote in the video camera but not irl, so what is the thing thats happerning here? why is this? —Preceding unsigned comment added by 194.80.240.66 (talk) 12:19, 6 October 2008 (UTC)

I moved the question from the Miscellaneous dek, as this is really a Science question. (Also retitled it.)

It's pretty simple: your eyes can only see light within a certain visual spectrum. The infrared light your remote emits is outside that spectrum, and thus it isn't visible to the naked eye. The video camera, however, detects it. (Not all cameras do this; it's a question of filtering the light properly, and cheaper or older models in particular don't necessarily do it very well.) Therefore, when you look at the video image, it looks as if there's a light shining from the remote. (And there is, you just don't normally see it.) -- Captain Disdain (talk) 13:24, 6 October 2008 (UTC)

Ah, thank you. Also i has another question = with thr remote when i use it near an readio on fm or longwave i head a buzzing noise from the radio. but only when the remote was in useing. again, how would light be affecting my radio? —Preceding unsigned comment added by 194.80.240.66 (talk) 14:25, 6 October 2008 (UTC)

While I'm not sure of exactly what frequencies would be responsible, it's worth remembering that light and radio waves are both forms of electromagnetic radiation -- they're just at different frequencies. Infrared and radio are far enough off, though, that I don't think this is necessarily what's responsible. If you use the remote next to the radio, you get interference, right? But I bet if you back 10 feet away and just point the remote at the radio (and then press buttons), nothing happens. That would suggest that it's not the IR light but rather the circuitry internal to the remote that's responsible. Circuits tend to leak EM radiation as well, and remotes aren't likely to be shielded to prevent interference at close range. Electronic circuits are also more likely to operate at frequencies near common radio bands. — Lomn 14:43, 6 October 2008 (UTC)

(ec) That's nothing to do with the IR light - it's because the remote contains a small computer. Computers do their calculations at rates that vary a lot from machine to machine. Your PC probably has a processor that runs between 1GHz and 3GHz - but the small computer inside the remote has to operate for long periods on one tiny battery and it doesn't have much work to do to figure out what IR light pulses to send when you push a particular button - so it's pretty slow...perhaps below 1MHz. At those sorts of frequency, the speed that the computer works at is close to the frequencies that your radio is designed to pick out of the air and amplify. The radio has to be sensitive enough to pick up very faint radio signals from a transmitter 20 miles away - so if the computer circuitry in your remote is leaking even a tiny amount of radio waves and you hold it close enough to the radio - then the radio will pick up the signal and you'll hear it. Back in the early days of home computers, I had a TRS-80 computer - which didn't have a sound chip inside. Some enterprising programmers figured out how to make the computer play music by running certain program sequences that could be picked up by holding a radio close to the computer chip! SteveBaker (talk) 14:46, 6 October 2008 (UTC)

Biology word

I'm having trouble recalling a word that began with the letter "A", having something to do with organs becoming unimportant / unused over time, like the appendix, or tonsils. —Preceding unsigned comment added by 69.16.88.147 (talk) 15:18, 6 October 2008 (UTC)

It doesn't begin with "A", but I have heard the term vestigial structure used to describe those phenomenon. Plasticup ^T/C 15:24, 6 October 2008 (UTC)

(edit conflict) Such organs are called vestigial. The only word beginning with 'A' that I can think of that could be relevant is atrophy, which could be used to describe an organ shrinking down to a small remnant of what it was when it was being used, however I don't think that would be a strictly correct use of the word. --Tango (talk) 15:25, 6 October 2008 (UTC)

Adventitious? "Developing in an unusual place or from an unusual source", though that may be even further afield. -- 128.104.112.147 (talk) 23:03, 6 October 2008 (UTC)

Atrophy? — DanielLC 23:42, 6 October 2008 (UTC)

Atrophy doesn't seem quite right - that suggests a single creature losing an organ during it's lifetime. Here we're presumably talking in an evolutionary sense - like creatures who spend their entire lives in caves gradually evolve into a form that has no eyes (see: troglobite). Adaptation would perhaps be an appropriate term - but it means a lot more than just losing organs. Regressive evolution is another term that you see a lot. SteveBaker (talk) 11:28, 7 October 2008 (UTC)

Atavism? -- Ferkelparade π 15:33, 7 October 2008 (UTC)

Debunking Ghosts

They say that ghosts are not real and that most scientists say they truly don't exist and have proven so. Exactly what scientists are they referring to? I am looking to get specific branches of science that these scientists are from. --Anilmanohar (talk) 15:38, 6 October 2008 (UTC)

See Princeton Engineering Anomalies Research Lab and everyone who criticized their poorly designed experiments. That would be physicists, psychologists, chemists, economists, and statisticians. That lab, by the way, was eventually closed as an embarrassment to the good name of Princeton University. Plasticup ^T/C 15:46, 6 October 2008 (UTC)

It's not really possible to prove something like "ghosts don't exist", and no reputable scientist is likely to claim to have done so. What they can confidently say is more along the lines of "there is no evidence that ghosts exist", and then it's up to you to decide whether you believe in things for which there is no evidence. --Sean 15:58, 6 October 2008 (UTC)

I don't think anyone believes in things for which they think there's no evidence. Some people just think that there is evidence that ghosts exist, in the form of bright spots in photographs or mysteriously moving objects or what have you. So I think the operative question is, who scientifically investigates the evidence proffered by such people? I don't think the answer is CSICOP, in spite of its name. They have on occasion scientifically investigated a claim of the paranormal, but mostly they seem to report the claims and scoff at them without any substantial investigation. -- BenRG (talk) 17:02, 6 October 2008 (UTC)

It's notable that the claims of the existence of a hypothetical or doubtful entity cannot be refuted by experiments. There is only scope for affirming the existence of such entities (eg the case of the mountain gorilla). So long as there is no experiment affirming the existence of such entities (especially something as preposterous as ghosts) I think it would be safe to presume there aren't any. As far as branches of science go, parapsychology is a field of related research.Leif edling (talk) 16:56, 6 October 2008 (UTC)

In such cases where proving a negative is impossible, we have to fall back on a scientific principle called Occam's razor. This isn't a law of science - but it's a good principle to live by. It says that if all else is equal and there are multiple explanations for a phenomenon, you should pick the simplest - the one that requires least change to established science. In the case of ghosts - where there is absolutely zero solid evidence for them, we're left with two possibilities: (a) that there is an entire range of common, complex phenomena that science has somehow completely and utterly missed or (b) that some idiots are lying to us. Guess which we pick? SteveBaker (talk) 18:19, 6 October 2008 (UTC)

I choose (b), but how did the Bush administration creep into this discussion? (Hey, I gotta get my shots in while I still can.) If somebody from the Secret Service is reading this, I mean it figuratively. Clarityfiend (talk) 22:37, 6 October 2008 (UTC)

What about the coelacanth? Scientists regarded it as having been extinct for millions of years, based on the fossil record and the utter absence of any evidence - known to them - that it had survived. Then they discovered it had indeed survived, and had been regularly if infrequently caught by islanders since time immemorial. It was certainly no stranger to the people of the Comoros. It all depends on who you talk to and where you look when you're gathering your evidence. Not having looked in all possible places does not equal "it does not exist". -- JackofOz (talk) 23:18, 6 October 2008 (UTC)

There are innumerably many things that exist that we haven't discovered. As much as it is, it doesn't compare to the number of things that don't exist that we haven't discovered. Nobody claims that everything that we don't have evidence for is false. Quite the contrary, any scientist will tell you that we have no evidence for almost everything that's true. We also have no evidence for almost everything that's false. Because the number of things that we have no evidence for that are false astronomically exceeds the number that are true, it is reasonable to suppose that a given thing that we have no evidence for is false. For example: it is generally believed that the number of living species exceeds the number we have discovered by several orders of magnitude. Despite this, if you just made up a species, you could safely say it doesn't exist. By the way, the coelacanth is a bad example, as we at least knew it existed at one time. Every time we discover a new species of fish, until that point we had no reason whatsoever to believe that it existed. — DanielLC 23:41, 6 October 2008 (UTC)

Oh, I don't know. I agree with your last point, but in relation to the coelacanth, scientists confidently claimed "it no longer exists", when that was not true. They didn't just say "we know of no evidence that it has survived". -- JackofOz (talk) 00:03, 7 October 2008 (UTC)

Actually, the coelacanth is always a bad example, because its an aquatic species, and there are such vast areas of the earth;s oceans that have gone unstudied. Were scientists mildly intrigued to find one alive? Certainly, but its not like finding an extinct land-based animal alive. If someone found a live T. Rex, for example, it would be far more shocking... --Jayron32.talk.contribs 03:27, 7 October 2008 (UTC)

Mildly intrigued? That would be rather an understatement. This gets back to Steve Baker's options (a) and (b) above. They chose option (b) with the coelacanth, as they do with ghosts and other claimed phenomena - but option (a) turned out to be the one they should have chosen. It wasn't as if the evidence wasn't there for those with eyes to see it, but they based all their findings of non-existence on published research papers etc, none of which had ever looked in the numerous places where the coelacanth is now known to have thrived for millions of years after it supposedly became extinct. -- JackofOz (talk) 06:03, 7 October 2008 (UTC)

Before the discovery of a modern coelecanth, we have these two competing hypotheses:

1. The coelecanth is extinct.
2. Nobody has happened to catch one recently (or nobody who had ever caught one has ever come forward to mention it).

Using Occam's razor to choose between these two options is dubious at best. Neither of them breaks any extant scientific laws or principles or requires any rewriting of the rest of science. The existance or non-existance of this fish doesn't really change much of what we know about the remainder of the universe. Perhaps our notion of cuttlefish population densities and breeding rates off the coast of one small stretch of South African coastline may need tweaking - but that's hardly a big deal! This is a case where archeologists and marine biologists simply made an overly hasty assessment due to an understandable lack of evidence - science is not infallible and we can easily be wrong about the small details. But for ghosts to exist, huge swaths of biology, physics and chemistry would need to be rewritten - things that we've carefully measured and graphed and calculated for two hundred years or more would have to be proven wrong. The chances of that being the case (versus "a few idiots are lying to us") is close to zero. Hence the use of Occam's razor in that case is entirely appropriate. SteveBaker (talk) 11:06, 7 October 2008 (UTC)

And back to the original question; the reason scientists don't reliably believe that ghosts exist is that all paranormal experimentation lacks the one property that all true scientific proof requires: repeatability. In every case, independent verification of the results fails; it always depends on the the individual performing the experiment. That is why there is no scientific proof of ghosts; and why it is assumed they don't exist; any "proof" of their existance falls apart under controlled conditions... --Jayron32.talk.contribs 03:30, 7 October 2008 (UTC)

It's useful to understand the argument from ignorance fallacy (aka: lack of proof is not proof of lack) in any discussion of paranormal proof like this. --Shaggorama (talk) 05:48, 7 October 2008 (UTC)

"Proof" is too strong a term here. Let me state this very clearly and carefully: We do not have proof that ghosts don't exist. But proof isn't everything. What we must have (for sanity's sake) is the general principle that we don't go around believing in things just because there is no proof to the contrary. I don't believe that the Invisible pink unicorn (mhhnbs) exists - but I don't have a shred of proof for that non-belief (although the otherwise inexplicable existance of pineapple and ham pizza could certainly use some in-depth research). So, yes, User:Shaggorama is right: Absence of evidence is certainly not evidence of absence (ie it is not proof that something doesn't exist). But it is quite solid grounds for the only-slightly-weaker statement that we do not believe in something. The absence of evidence for ghosts is more than enough reason to disbelieve in them. There are quite literally an infinite number of things that we cannot prove do not exist. Does that mean that we should go around with the default hypothesis that those things do exist? Certainly not! That way lies madness. If you have to believe in a literally infinite number of improbable things until you have solid proof that they do not exist then your life becomes quite impossible to live. You can't get up in the morning for fear that an previously undiscovered species of mothball-scented purple velociraptor has been nesting in back of your sock drawer for the last 100 million years and is about to pounce...you can't prove that it hasn't, and this certainly explains all of those odd socks! SteveBaker (talk) 11:06, 7 October 2008 (UTC)

Just to clarify, I wasn't trying to say I beleive in ghosts :) --Shaggorama (talk) 20:36, 7 October 2008 (UTC)

I'm going to start checking for those mothball-scented purple velociraptors though. That provides an ideal explanation for my unmatched socks. The evidence is compelling - the only question now is whether those sock-eaters evolved or were created by God on Oct. 23, 4004 BC. Thanks Steve, for clearing that up! Franamax (talk) 02:17, 8 October 2008 (UTC)

LCD Spectral Lines

I was curious one day so i got a pocket spectroscope and looked at my LCD monitor with it. Curiously, very defined spectral lines appeared. I can't find anything on this and i want to know why this happens. Can someone help? PS I don't know how to take a picture of these lines, sorry guys :) 31306D696E6E69636B6D (talk) 16:26, 6 October 2008 (UTC)

I think the backlight is a kind of fluorescent lamp. These can have sharp lines, depending on the design. See the article for examples. -- Coneslayer (talk) 16:48, 6 October 2008 (UTC)

The backlight is designed to produce pure colors when filtered through the LCD panel - so ideally it needs one spectral line at the center of each of the red, green and blue filters - putting out frequencies between those three colors would produce a 'muddy' display with all sorts of nasty colors and no decent, solid black. I don't know how they get it that good - but evidently, they do. SteveBaker (talk) 18:22, 6 October 2008 (UTC)

Fatigue relief

Is there any method whereby one may be relieved of fatigue and pain due to lactic acid deposition? Could ice packs be of any help?Leif edling (talk) 16:45, 6 October 2008 (UTC)

Rest would be best way to treat fatigue. If you want more of an answer than that, you'll need to ask a doctor, we can't medical advice here. (Ice could numb the area and reduce the pain, but then again it could give you frostbite or hypothermia or both, hence the need to ask someone more reliable than a random guy on the internet.) --Tango (talk) 17:00, 6 October 2008 (UTC)

Never place ice packs directly on the skin, no matter what you're trying to alleviate. Always put a towel or bandages between your skin and the ice. -- MacAddct1984 ^{(talk &#149; contribs)} 18:44, 6 October 2008 (UTC)

We do have an article on Fatigue (medical), but it has no discussion on relief. --—— Gadget850 (Ed) ^talk - 18:54, 6 October 2008 (UTC)

Ice packs do help with pain caused by exercise, as do warm baths. Other than that, rest is your only other option without seeing a doctor. —Cyclonenim (talk · contribs · email) 23:02, 6 October 2008 (UTC)

Sounds like you're talking about post-exercise cramps. If so, check out Delayed onset muscle soreness. Being proactive with a warm-up, cool-down and stretching is believed to help alot. Also, cramping is usually the worst when beginning an exercise regimen: after a few weeks, your muscles become acclimated to the workout and your metabolism adjusts appropriately. --Shaggorama (talk) 05:42, 7 October 2008 (UTC)

Gauge>Alum foil?

The metallic scale GAUGE? 75.60.90.25 (talk) 16:58, 6 October 2008 (UTC)

The "gauge" of some aluminium foil is its thickness, is that what you wanted to know? According to Aluminium foil, it's usually between around 0.006mm and 0.2mm. --Tango (talk) 17:03, 6 October 2008 (UTC)

If you are wondering why metal thickness is measured in "gauge" units, this is a shorthand notation to make it easy for people in the metal industries to refer to their products. The development of the gauge system is rooted in the history of metalworking and lets everyone produce a series of standard products. For instance, 24-gauge mild steel is .024" thick and weighs 1 lb/sq.ft. Going by our Sheet metal gauge (redirected) article, aluminum foil thicknesses fall below the established "gauge" range - but the thickness is still referred to as the "gauge", even though it should be called "thickness". One reason might be that thicknesses are measured with a gauge instrument; another might be that the term "thickness" implies a definite number, whereas a metal "gauge" incorporates variations in thickness produced by the rolling mill, for instance 10-gauge mild steel has a "thickness" of .1345" but this can vary between .1285" and .1405".[9] Short answer: when we talk about metal thickness, we speak in terms of its "gauge". Don't know if that helps at all :) Franamax (talk) 21:45, 6 October 2008 (UTC)

finger print sensors

just like other sensors ,are there some finger print sensors that could be interfaced with some microcontrollers(like 8051).plz tell me the sources of information about it as well. 116.71.187.243 (talk) 19:25, 6 October 2008 (UTC)

Most seem to offer a Serial Peripheral Interface Bus interface, which can be spoken to as described here. Search for Template:Websearch to see a bunch of them. --Sean 20:26, 6 October 2008 (UTC)

Zombie Newton is haunting me

I'm trying to understand how any why momentum, kinetic energy and mechanical work ... well, work in classical mechanics. I took a few courses of physics and mechanics years ago, but they all skirted the deep questions about exactly why they take the forms they do. Why should work be the dot product of displacement and force? Why is the first integral of mass relative to velicity momentum, and then why is the second integral kinetic energy? Is that something to do with the conservation of {energy, momentum, mass}, but why velocity?

I know these are rather open questions, but my curiosity keeps nagging away at me, and I don't seem to be able to find the answers without taking a physics degree myself. 79.72.138.94 (talk) 19:30, 6 October 2008 (UTC)

Also, I realise full well that the answer might be 'because it is, and that's just how it works', which would leave me feeling rather unfulfilled but sated. 79.72.138.94 (talk) 19:31, 6 October 2008 (UTC)

Actually, the answer is the exact opposite of what you expect. It is because that's the way we as people have organized our thinking. There's nothing fundemental about the concepts of "force" or "work" or "velocity". They are just convenient ways for us to organize our observations of motion. When we push something harder, it moves faster, so the concept of "force" was invented to explain this observation. When an effort is used to move something, that effort can no longer be used to move something else; thus the concept of energy is created. If you want to get beyond classical mechanics, physicists have been working on explaining it all, indeed a few different times but there are some fundemental flaws in all of these. Some show promise, others have run into dead ends. Maybe someone else wants to take a crack at this, but that's the best explanation I can come up with... --Jayron32.talk.contribs 19:41, 6 October 2008 (UTC)

Good point. I probably should have included that disclaimer as well, that it might just be an artifact of the analysis. I can accept the definition of force, velocity or acceleration as arbitrary artifacts, but energy and momentum seem to be more fundamental, because of the laws of conservation. Even if this is just the way they are organised, I still can't see the reaoning behind the patterns that form, so there is still something I'm missing. And GUTs and TOEs are altogether to visceral for me :) 79.72.138.94 (talk) 19:54, 6 October 2008 (UTC)

Noether's theorem (warning: article is extremely equation-heavy) basically boils down to "where you have symmetries, you have conserved quantities". As such, once you've defined positions, velocities and forces, under Newtonian mechanics you find that there are symmetries (e.g. time reversibility of a system) that are then associated with conserved quantities that happen to correspond to energy and momentum. Confusing Manifestation(Say hi!) 22:36, 6 October 2008 (UTC)

I have "answers" in some sense for you, as I've thought about these points myself.

1. Your question about work can be answered in two ways. You can identify force with the negative gradient of potential energy, which makes intuitive sense because we expect things on hills to be gravitationally accelerated down them and more quickly for steeper hills; then, using the chain rule, $dU=\sum _{i}dx_{i}{\frac {\partial U}{\partial x_{i}}}=d{\vec {x}}\cdot {\vec {\nabla }}U=-d{\vec {x}}\cdot {\vec {F}}$, and then (by conservation of energy) $U+E=C\Rightarrow dU+dE=0\Rightarrow dE=d{\vec {x}}\cdot {\vec {F}}$. (Note that nonconservative forces are a simplification of conservative ones; we need not treat them separately.) Alternatively, take the derivative of kinetic energy with respect to time: ${\frac {dE}{dt}}=m{\vec {v}}\cdot {\frac {d{\vec {v}}}{dt}}=m{\vec {a}}\cdot {\frac {d{\vec {x}}}{dt}}={\vec {F}}\cdot {\frac {d{\vec {x}}}{dt}}$ and $dE={\vec {F}}\cdot d{\vec {x}}$ immediately: in other words, when you apply a force in the opposite direction of displacement, you're slowing the object down, and when you apply it in the same direction, you're speeding it up, so the dot product is natural.
2. Momentum must be linear in velocity for the simple reason that otherwise small internal motions (like those due to heat) would affect the collective answer. But if heating (or cooling) an object reduces its momentum, what happens to a stationary object? Momentum must also be linear in mass so that inconsequential gossamer connections between objects sharing a velocity do not change their dynamics.
3. Energy's quadratic nature is the interesting part, and derives from the fact that it and momentum are conserved are a scalar and a vector respectively. Thus a change of frame of reference changes velocity but not energy (in Galilean relativity). (The reason for this is that any such changes must be linear functions of observer velocity, so that we can compose frame shifts without changing the answer. For changes in (measured) velocity, the identity function serves the purpose well, but the only isotropic scalar function is the zero function.) Now consider two observers who place a compressed (massless) spring between a pair of identical objects. Then one of the observers starts moving along the direction of the spring, and it fires. Choosing convenient numbers ($m=1,|v|=1$) and coordinates, the stationary observer records velocities of $({\vec {0}},{\vec {0}})$ and $(-{\hat {x}},{\hat {x}})$, for a total momentum before and after of $({\vec {0}},{\vec {0}})$ and a total energy before and after of $(0,2E(1))$. (I'm writing $E(v)$ for the "unknown" function that gives the energy per mass associated with speed v; we know it's linear in mass by the same argument as for momentum, and we know it's just speed because it has to be independent of direction.) The moving observer instead records $({\hat {x}},{\hat {x}})$ before and $({\vec {0}},2{\hat {x}})$ after, for a total momentum of $(2{\hat {x}},2{\hat {x}})$ before and after. This is good; our linear transform of velocity has preserved the conservation. But what of energy? In the moving frame, the construct already had $2E(1)$ kinetic energy, and the spring must still have added its own $2E(1)$; the one moving object must have kinetic energy $E(2)=2E(1)+2E(1)=4E(1)$; evidently it is quadratic. (The ½ is arbitrary; we could just as easily define ${\vec {F}}=-2{\vec {\nabla }}U$, for instance.)
4. Other arguments about energy include that it should be a smooth function of velocity (since observers with slightly different velocities should see much the same thing), and yet it must be a function only of speed. This rules out $E({\vec {v}})\propto |{\vec {v}}|$, because the magnitude of a vector is only continuous and not smooth at 0. (Consider the plot of $f(x,y)={\sqrt {x^{2}+y^{2}}}$; it's a cone and is sharp at the origin.) $E({\vec {v}})\propto v^{2}$ is the obvious choice. Finally, consider throwing an object into a potential energy barrier (like gravity): if the force is uniform, the object will slow down uniformly. Then throw it twice as fast: it takes it twice as long to stop, and was making twice as much progress per time all the while, so it made it four times as far into the barrier. The force being uniform means that, were we to push the object in rather than throwing it, we would certainly expect the effort involved to be linear in the distance, so kinetic energy is again quadratic in speed since it only took twice as much speed to effect four times as much progress.

There's a certain mathematical circularity that's inevitable here, and even appeals to intuition are subject to the objection that they are merely descriptions of our intuition's basis in physics rather than explanations of physics based in intuition. But I find it helpful to understand better the connection between the mathematics and my intuition even if neither has any external justification. Hope this helps. --Tardis (talk) 17:34, 7 October 2008 (UTC)

False or true?

The keratitis that can occur in a contact lens wearer caused by Pseudomonas aeruginosa is an ocular emergency, as if left untreated it could destroy an eye within 24 hours(four tildes). —Preceding unsigned comment added by 79.97.241.246 (talk) 20:03, 6 October 2008 (UTC)

We're not allowed to give medical advice here. The article on keratitis says that it can scar the eye and permanently damage vision. (Or worse : "loss of the eye"! ) If this question is more than hypothetical I strongly recommend that you get to a doctor or E.R. right away. Don't trust your eyesight to strangers on the internet. APL (talk) 20:13, 6 October 2008 (UTC)

I can't tell you how disturbed I am when a single question falls foul of both "we can't give medical advice" and "we won't do your homework for you". --Sean 20:30, 6 October 2008 (UTC)

At least we didn't have to explain how to sue the contact lens manufacturer! SteveBaker (talk) 22:39, 6 October 2008 (UTC)

Just using the information you gave in your question, "is an ocular emergency as if left untreated it could destroy an eye within 24 hours". If that's true, you're damn right it's an emergency. —Cyclonenim (talk · contribs · email) 23:07, 6 October 2008 (UTC)

We have an article on keratitis, which mentions "pseudomonas aeruginosa", "contact lens" and "loss of the eye". It also says that "[o]ne should consult a qualified Ophthalmologist or Optometrist for treatment of an eye condition". Take from that what you will. Plasticup ^T/C 02:04, 7 October 2008 (UTC)

BTW, your supposed to type out four tildes like this ~~~~ not type out the words four tildes. The tilde key would usyally be besides the 1 key on your keyboard. You probably have to hold down shift to get the tilde Nil Einne (talk) 15:34, 7 October 2008 (UTC)

Ha, I'm tempted to create a sockpuppet named User:Four Tildes! (But I won't.) —Tamfang (talk) 15:38, 8 October 2008 (UTC)

Electricity and magnetism

Is it possible to relate the positive and negative charges of protons and electrons and such to the north and south poles of a magnet? For example, does the north pole of a magnet act in a way that implies that it is positively (or possibly negatively) charged? Or are the similarities between electricity and magnetism, such as like repels like and opposites attract, explained in fundamentally different ways? Thank you. 86.74.122.84 (talk) 21:47, 6 October 2008 (UTC)

Magnetism is caused by a changing electric field, such as a moving charge. As such, two particles of opposite charge moving in the same direction will have opposite magnetic fields, so in that sense there is some similarity between north and south poles and positive and negative charges, but it's a little more complicated than that. Confusing Manifestation(Say hi!) 22:30, 6 October 2008 (UTC)

Umm, magnetism is an inherent property of matter, a changing electric field is not required. Variations in the electric field can induce a magnetic field perpendicular to the direction of charge motion, but you don't need current to have a magnet. Or at least, the electric field doesn't have to be changing. See magnetism. Franamax (talk) 00:40, 7 October 2008 (UTC)

Indeed, nuclei of atoms (which are for all intents and purposes "motionless") can display magnetic properties. Generally, the nucleons (protons and/or neutrons) will "match" magnetic poles so as to cancel out, but in nuclei with odd numbers of them (such as C-13) there is a net magnetic moment. Nuclear magnetic resonance and Magnetic resonance imaging use this property of the atomic nuclei. --Jayron32.talk.contribs 03:13, 7 October 2008 (UTC)

You may be interested in the "Gilbert Model" of magnetic behavior; just remember that it's not really physically accurate. --Tardis (talk) 15:43, 7 October 2008 (UTC)

Is THIS version understandable?

Still confusing, but a lot better IMRHO.

Sail Car Preliminary Description Our sail car is a trapezoid with two parallel sides, front and back. One side, the back, is longer than the other (hence a trapezoid), requiring two straws linked together (for the purposes of this description, they will be referred to as one straw). Two hypotenuses lie on the side of the trapezoid. They extend from the back to the front, where they bend and then meet to form the front side. They bend out on the back, creating two extensions outside of the trapezoid. These extensions are two straws deep with the back side straw in the rear and the hypotenuse straws immediately in front. On these extensions are two wheels. They are supported by two pins on each side of each wheel. On the front, there are two wheels as well. They lie near the bends of the front side.

At the midpoint of the back side, two straws extend diagonally frontwards towards the bends of the hypotenuse straws to give the frame extra support. Roughly halfway between the hypotenuse straws and the midpoint of the back side are two straws extending vertically upwards. Between the two straws is a sail. The sails is pinned to the straws for support. The sail is bent inwards and is thus also supported by a crossbeam at the top.

--hello, i'm a member | talk to me! 23:38, 6 October 2008 (UTC)

Member, a simple diagram would really help you out in this. Maybe the better strategy would be (assuming you want to create a new article) for you to start a page in your own user-space, let's say by clicking here: User:Member/Sailcar. You could put some external references in there for us to click on, so we could better understand what you are describing. You (or us others) could then have a shot at creating graphics to better describe your concept. Franamax (talk) 00:29, 7 October 2008 (UTC)

And as you can maybe see from Edison's comments below, put your text into the wiki-space and we will all slice-and-dice it into an encyclopedia article. The safest place is your own user-space per the redlink I gave above. Give us a link to an image or site that describes your concept, we can work with you to make it all work. Honest! Franamax (talk) 01:38, 7 October 2008 (UTC)

I will count the title as a sentence. In sentence 3, why not call the rear "straw" the rear axle? Your use of "hypotenuse" in the paragraph is inconsistent with Trapezoid and with Hypotenuse. Call them the "nonparallel sides of the trapezoid." In sentence 5 you refer to the "front" where the straws bend, and to a different "front side" which is formed by the meeting of the side straws. Eliminate the ambiguity. Sentence 6: Replace "They" with a more explicit description of the members you refer to. How about eliminating pronouns in such a terse yet confusing description? No idea what sentence 6 refers to. Sentence 7 is obscure and confusing. Sentence 8:Which extensions? Sentence 9: What does "They" refer to? Sentence 11: What is the "back line?" The "rear straw," which should probably be called the "rear axle?" Sentence 14 and 15: No idea of the shape or orientation of the sail. Edison (talk) 01:21, 7 October 2008 (UTC)

A diagram - or a photo - is needed here. There are some things that just don't work when put into words. It's possible we could come up with some better words - but because the words you have aren't working, we need the diagram/photo in order to understand what we're writing about! SteveBaker (talk) 10:16, 7 October 2008 (UTC)

I'm still stuck right at the start. A trapezoid is a 2D shape. Is your car a trapezoid cut out of cardboard and held vertical? Or is it a 3D solid shape, like a prism of a trapezoid? You need to make that clear before you start talking of front and back. Itsmejudith (talk) 11:07, 7 October 2008 (UTC)

There are lots of patented mechanical devices far more complex than this thing which have clear and unambiguous descriptions in the patent specifications. Instead of "two straws which will be called one straw" call it a freakin' "rear axle," for instance. From the description, it could be a structure made only of straws, or it could have a trapezoidal planar body made of some unspecified substance. It does not say what the vertical straws are attached to. Edison (talk) 18:18, 7 October 2008 (UTC)

Here is a (eui) sketch of what I see this thing as. Heaviest lines are the wheels, lightest are the pins, in the middle are the stiffeners and sail assembly. All are in the same plane except the cirlces and curved line representing the vertical sail. Franamax (talk) 02:44, 8 October 2008 (UTC)

And here is the elevation view. The U-shaped sail-straw is pinned through the two stiffener straws near the midpoint of the vehicle. Franamax (talk) 02:57, 8 October 2008 (UTC)

Momentum and photons

Gah such a simple question I've forgotten the answer to. How the hell do photons have momentum when they have no mass? Is it due to rest mass? Cheers! —Cyclonenim (talk · contribs · email) 23:05, 6 October 2008 (UTC)

They have no rest mass, but due to E=mc² they have mass which gives them momentum (m=E/c² so p=mv=E/c - there is a lot of hand waving required for that derivation, but it gets the right answer!). --Tango (talk) 23:15, 6 October 2008 (UTC)

Likewise, Electrons are dimensionless (they have no volume), yet they have a "spin". Try to figure that out using classical mechanics... --Jayron32.talk.contribs 03:07, 7 October 2008 (UTC)

How do you know that an electron has no volume? Ohanian (talk) 06:22, 7 October 2008 (UTC)

See Electron#Fundamental properties. Axl ¤ [Talk] 08:29, 7 October 2008 (UTC)

...which is not very helpful, because it says "for convenience, <the electron> is usually defined or assumed to be a point charge with no spatial extent; a point particle", and a point particle is "an idealized object". We know that the "point particle" model cannot be the whole story, because then the electron would be a singularity. In quantum field theory fundamental "particles" like the electron are not really particles at all - they are excitations of a quantum field, and they don't have a volume because the "volume" concept just doesn't apply to such things - any more than the colour red or the number seven has a volume. Fundamental particles might have some multi-dimensional equivalent of "spatial extent" in string theory, but I am not sure whether that could be made to correspond in any reasonable way to our macroscopic concept of "volume". So in simple terms, we might say that we don't think that an electron has a property that we could interpret as a volume - which is not the same as saying it has zero volume. Gandalf61 (talk) 09:30, 7 October 2008 (UTC)

Gandalf, your response is one interpretation. Axl ¤ [Talk] 10:31, 7 October 2008 (UTC)

If I understood (and/or remember) my Feynman, he described the paradox of infinite charge given zero volume for the electron vs. the impossibility of making accurate calculations without assuming zero volume. As I recall, he advised the whole matter was best swept under the desk. Franamax (talk) 03:06, 8 October 2008 (UTC)

They just do. We cannot demand that the universe conforms to our everyday notions, which require an object to have a non-zero rest mass in order to have momentum. Note also that photons are never at rest in any inertial frame.Martin Hogbin (talk) 09:44, 8 October 2008 (UTC)

Mars and Jupiter and Saturn's moon over sun's RGiant Stage

If Mars still exist, does anybody know what Mars surface will be like over sun's R Giant? Will it be yellow-orange molten lava like Earth was 4.6 billion years ago? What about Europa-Jupiter's moon. Europa's tan-gray ice will melt into water, then what will ahppen next. Will it scorch like Mercury. Titan's orange smog might bluen out. By 6 to 7 years from now, it is learnt Titan is the only place going to habitat for life. I wonder what will happen to Uranus' moon when sun enters a R Giant.--SCFReeways 23:44, 6 October 2008 (UTC)

• Will somebody be able to answer it?--SCFReeways 01:04, 7 October 2008 (UTC)

• Come on, do anybody know this?--SCFReeways 01:43, 7 October 2008 (UTC)

Have some patience, we don't know this off the top of our heads. Plasticup ^T/C 02:07, 7 October 2008 (UTC)

And we live in a variety of time zones... (yawwn) --140.247.11.55 (talk) 02:29, 7 October 2008 (UTC)

And it says at the top of this page that we may need as much as four days to fully develop an answer. Anything that might be needed in less than four days is probably homework - which we don't do. The sun isn't going to do this for another 7 billion years - so this is hardly a time-critical answer. SteveBaker (talk) 09:58, 7 October 2008 (UTC)

It's tough to be patient though.--SCFReeways 02:48, 7 October 2008 (UTC)

The primary difficulty in answering your question is your poor grammar. Your first question appears to be "Does anybody know what will happen to Mars when the Sun turns into a red giant? It is not known. Mars may become superheated. It may escape the Sun since it will enlarge its orbit. So, no, nobody knows. Your next "questions" have leading assumptions that do not appear to be based on popular scientific evidence. Why do you assume Europa's surface will melt? Why do you believe that Titan will be the only habitat for life in 6 or 7 years? Uranus is very far from the Sun, why do you assume it will be heavily affected? Is this all based on an assumption that, as a red giant, the Sun will suddenly start producing so much heat that it burns up the Solar System? You must take into account how little heat reaches the outer planets right now and that they will move further from the sun when it loses mass. -- kainaw™ 03:34, 7 October 2008 (UTC)

They will move further out. Alot of sources said Titan might be habitatable at this time. I wonder about Uranus moon. Whole solar ssytem will heat up at this time. Mercury and possibly Venus and Earth will be engulf and destroy, then Mars will be the only inenr planets left. About Europa, after ice melt, even escaption Europa can be a little too hot. Uranus moon could get beenfit from sun's heating too.--SCFReeways 03:52, 7 October 2008 (UTC)

What about this?--SCFReeways 04:35, 7 October 2008 (UTC)

My understanding is that Titan may heat up to habitable temperature but it will lose its atmosphere so won't be habitable. The reason it can maintain such a dense atmosphere with its low mass is because it is very cold (cold gasses don't move around as much so are less likely to randomly achieve escape velocity). Once it warms up, the atmosphere will leak away into space pretty quickly. (That's just the theory I've heard, there are so many variables we can't pin down that it's difficult to say for sure.) --Tango (talk) 14:39, 7 October 2008 (UTC)

When you say "6 to 7 years" do you mean "6 to 7 billion years"? Plasticup ^T/C 15:19, 7 October 2008 (UTC)

I would guess so. It's still wrong, though, since by then the Sun will have gone past being a red giant and will be a white dwarf giving off very little heat. The red giant phase only lasts for a few million years, if that. --Tango (talk) 16:09, 7 October 2008 (UTC)

• This site said the tan-gray ice on Europa might melt into water, and possibly be warm enough.--SCFReeways 22:08, 7 October 2008 (UTC)

• THis site shows in 7 billion years, Europa's thick ice can melt into globe of liquid ocean, but artist say it's sky will still be black in 6 to 7 Gyrs when sun turns into giant star.--SCFReeways 22:15, 7 October 2008 (UTC)

  I question the reliability of those sites. For a start, it's 5 billion years, not 7. Secondly, Europa doesn't have the atmospheric pressure required for an ocean - the water would just boil away. --Tango (talk) 23:44, 7 October 2008 (UTC)

• you menat the ice will just boil away right? One source said only surface temperatu will be habitable. In about 1 to 2 billion year-time Mars can get bluer, possibly as the planet warm up the greenhouse effect will start to incrase, but after few billion year later, Mars could just black out right airless.--SCFReeways 00:17, 8 October 2008 (UTC)

  I'm afraid I don't understand. Mars is essentially airless now (from the point of view of liquids boiling and habitability) and I don't think it will get more air as it warms up. Likely less, in fact, since warm air escapes into space faster. --Tango (talk) 00:23, 8 October 2008 (UTC)

Mars has no magnetic field to speak of, so holding in an atmosphere is very difficult. Gasses need to increase in the atmosphere faster than they are lost into space. There is a theory that if it warms up enough a magnetic field will build up. Of course, this is all just theory. Give me any theory and it is trivial to find someone who disagrees. -- kainaw™ 00:22, 8 October 2008 (UTC)

I theorise that when I hold a pen about a metre off the ground away from any other objects and let go, it will fall. --Tango (talk) 00:25, 8 October 2008 (UTC)

I theorise that someone will come along and explain the difference between a validation experiment and a theory :) -- kainaw™ 00:27, 8 October 2008 (UTC)

It was a very restricted theory, but a theory nonetheless (ok, perhaps it was a law and I should have added some explanation to make it a theory). --Tango (talk) 14:16, 8 October 2008 (UTC)

This said Mars was once a blue planet, it just got too cold. In fact right now Mars is very cold. in about 1 to 2 Gyrs Mars might attain to the Earth surface temp today.--SCFReeways 00:39, 8 October 2008 (UTC)

At this time, Earth may be a greenhouse planet like Venus today.--SCFReeways 00:40, 8 October 2008 (UTC)

I think you are missing the point. It might turn blue again. It might not. It might get destroyed by a Vogon fleet to make way for an interstellar bypass. Whatever answer you want to get, there's a reference for it. That is why I stated that it is all theories. It is even possible that the sun may not turn into a red giant (though unlikely). -- kainaw™ 00:46, 8 October 2008 (UTC)

While it will probably heat up again that doesn't mean it will become Earth-like. It's already lost its atmosphere and warming up isn't going to bring it back. Without an atmosphere (and a significant one, not the few wisps of CO2 Mars has) you can't have liquids on the surface. Mars lost its atmosphere over millions, possibly billions of years due to its low mass and lack of an magnetic field (which allows solar wind to erode the atmosphere). --Tango (talk) 14:16, 8 October 2008 (UTC)

October 7

Quantum: Difference between an operator and a measurement

Suppose there is a qubit whose state is

$|\psi \rangle ={\frac {1}{\sqrt {3}}}|0\rangle +{\frac {\sqrt {2}}{\sqrt {3}}}|1\rangle ={\begin{bmatrix}{\tfrac {1}{\sqrt {3}}}\\{\tfrac {\sqrt {2}}{\sqrt {3}}}\end{bmatrix}}$

After we measure the qubit, the state of the qubit will change from $|\psi \rangle$ to $|1\rangle$ with probability

${\big |}\langle 1|\psi \rangle {\big |}^{2}=\left({\frac {\sqrt {2}}{\sqrt {3}}}\right)^{2}={\frac {2}{3}}\approx 0.666\dots$.

This process is called wave function collapse. If $|1\rangle$ is observed after the measurement, the qubit becomes

$|\psi \rangle =|1\rangle$

Instead of measuring the qubit, a Hadamard gate

$H={\frac {1}{\sqrt {2}}}{\begin{bmatrix}1&1\\1&-1\end{bmatrix}}$

operates on the qubit will be

$H|\psi \rangle ={\frac {1}{\sqrt {2}}}{\begin{bmatrix}1&1\\1&-1\end{bmatrix}}{\begin{bmatrix}{\tfrac {1}{\sqrt {3}}}\\{\tfrac {\sqrt {2}}{\sqrt {3}}}\end{bmatrix}}={\frac {1}{\sqrt {2}}}{\begin{bmatrix}{\tfrac {1+{\sqrt {2}}}{\sqrt {3}}}\\{\tfrac {1-{\sqrt {2}}}{\sqrt {3}}}\end{bmatrix}}={\frac {1+{\sqrt {2}}}{\sqrt {6}}}|0\rangle +{\frac {1-{\sqrt {2}}}{\sqrt {6}}}|1\rangle$

as I know, the process of the operation is 'not' a wave function collapse.

My problem is why an operator acts on a qubit doesn't cause a wave function collapse? As I know, any subtle interaction with the qubit will cause the wave function to collapse. The Hadamard gate operator, which should be an apparatus, when acts on the qubit should also interact with the qubit. So how an operator can circumvent the wave function collapse? - Justin545 (talk) 05:28, 7 October 2008 (UTC)

I'm a little rusty in my quantum theory, but if I remember correctly, it's not all interactions that cause wave-form collapse, only those actions that generate information. It is entirely possible to transform a wave-function without actually observing (i.e. gaining information from) said wave function. Take for example the most basic quantum experiment, the double-slit experiment. The slit certainly interacts with the beam of particles; as the beam hits the slits, an interference pattern immerges, this is a result of the slits "transforming" the beam of particles via interaction. The wave function collapse occurs only when you try to gain information about the particle's location, for example, by placing a charge detector at one of the slits. As long as no information is obtained on the system, it goes on behaving as an uncollapsed wave function. Once the detector is placed, information is extracted, and the wave function collapses, resulting in an uninterferred double beam... The Hadamard gate must operate in the same way; it performs a transformation on the qubit blindly (that is, without observing the state of the qubit). Such an action is not philosophically that hard to understand. Imagine a blind man turning coins over. You hand the man a coin, and he simply reverses the face of the coin. He can perform the operation (turning heads to tails and tails to heads) perfectly every time, even if he doesn't know which states the coins are in before he flips them. To take this on a quantum scale, he's able to perform a transformation on the wave function, without causing any waveform collapse. He's made no observations of the bits of information he's transforming, he's just doing the transformation. A Hadamard gate must work on this level. --Jayron32.talk.contribs 05:47, 7 October 2008 (UTC)

It could be difficult to define the term 'gaining information from'. Cite form the article Quantum computer:

One major problem is keeping the components of the computer in a coherent state, as the slightest interaction with the external world would cause the system to decohere. This effect causes the unitary character (and more specifically, the invertibility) of quantum computational steps to be violated. Decoherence times for candidate systems, in particular the transverse relaxation time T2 (terminology used in NMR and MRI technology, also called the dephasing time), typically range between nanoseconds and seconds at low temperature.

I think the 'decohere' is actually the wave function collapse. It seems that even the 'temperature' is also a way to interact with the qubit and it is not clear to me how an environmental temperature makes information gaining... maybe what you mean is that a measurement is an irreversible operation whereas a gate operation is a reversible operation. Indeed, the action of a Hadamard gate is a reversible operation since there is no information lost during the operation of the Hadamard gate. And saying that a measurement is an irreversible operation is just my suspicion since some information is lost and gained by the observer during a measurement. By thinking the gate operation as a transform as you said make it more understandable to me. And now I know there are some interactions don't collapse the wave function. - Justin545 (talk) 07:23, 7 October 2008 (UTC)

Unless the qubit is lost due to interaction with other particles; at high temperatures there are bound to be more particles moving faster and thus more interference on the qubit; there may be some threshold temperature where the system becomes so inefficient due to losses that it stops "working." --Jayron32.talk.contribs 11:29, 7 October 2008 (UTC)

Definitely some interactions don't collapse the wave function, otherwise a proton, for example, couldn't be a quantum particle since it consists of more fundamental particles constantly interacting with each other.

See quantum decoherence for more on that subject. It is effectively the same thing as wavefunction collapse and people are likely to use the terms interchangeably.

Measurement/decoherence is all about copying. An example of copying is a transition from $\alpha |0\rangle +\beta |1\rangle$ to $\alpha |0\rangle |0\rangle +\beta |1\rangle |1\rangle$. This is different from cloning, which would take $\psi$ to $\psi ^{2}$, e.g. $(\alpha |0\rangle +\beta |1\rangle )^{2}=\alpha ^{2}|0\rangle |0\rangle +\cdots$. Cloning isn't possible, but copying is possible. The key difference between them is that copying is basis-dependent. The example I gave above was copying with respect to the computational basis $\{|0\rangle ,|1\rangle \}$. Copying with respect to the dual basis $|{\pm }\rangle ={\tfrac {1}{\sqrt {2}}}(|0\rangle \pm |1\rangle )$ takes

$\alpha |{+}\rangle +\beta |{-}\rangle$ to $\alpha |{+}\rangle |{+}\rangle +\beta |{-}\rangle |{-}\rangle$,

which is the same as taking

$\alpha |{0}\rangle +\beta |{1}\rangle$ to ${\tfrac {\alpha }{\sqrt {2}}}(|00\rangle +|11\rangle )+{\tfrac {\beta }{\sqrt {2}}}(|01\rangle +|10\rangle )$,

if I calculated right—at any rate it's a different operation. If you copy a qubit (with respect to a basis) and put the copy somewhere where it's unavailable to you, the effect on the original qubit is exactly as though you'd measured it (with respect to that basis). But if the copy ever becomes accessible to you again, you can use it to "undo the measurement," so it's not a real measurement. Measurements only become definite when they can no longer be undone, e.g. because the copy has been amplified into a macroscopic thermodynamically irreversible state change like a flash from an LED.

Reply composed in a hurry and I may not be able to reply again for a few days. -- BenRG (talk) 11:44, 7 October 2008 (UTC)

Noisy laptop fan

Why do they (fans) do it (noise)? Is a silent laptop fan possible?Mr.K. (talk) 11:06, 7 October 2008 (UTC)

A (laptop) fan moves air, using an electric engine. Air flow creates sound, and the engine can't be perfectly silent either, so: no, a silent laptop fan isn't possible. There are however some new, interesting ways of cooling coming about, some of which may be silent. Someone please fill me in here :) -- Aeluwas (talk) 11:08, 7 October 2008 (UTC)

Actually, there are ways of generating air flow without any moving parts, for example see Air ionizer; it operates similar to a mass spectrometer; air molecules can be ionized via say, a negatively charged plate, and accelerated via a pair of positively charged plates. Many air molecules will simply gain electrons at one plate and lose them back at the other (or visa-versa; I am not positive on the specific mechanics of the situation), however, some will "overshoot" the second plate, and also drag many "non-charged" molecules with them, resulting in net air flow. However, the method is quite innefficient, especially on a scale small enough to fit into a laptop, and I suspect that in terms of net air flow for, for both its size and wattage, a simple mechanical fan is far more efficient. --Jayron32.talk.contribs 11:24, 7 October 2008 (UTC)

The engine could be so silent like the HDD. Moving air doesn't have to be noisy. I suppose it is noisy only if it generates turbulence right? So, a silent laptop fan should be possible... Mr.K. (talk) 11:38, 7 October 2008 (UTC)

But laminar airflow may not be terribly efficient at moving heat around, as it may not move all the air and probably wouldn't move fast enough. 130.88.64.189 (talk) 12:29, 7 October 2008 (UTC)

The other common means of making a fan quieter is to spin it at a lower RPM. Of course, the direct consequence is that you move less air, reducing the cooling effectiveness. In a desktop system, that just means that you make the fan larger to compensate. With space at a premium in laptops, this solution is less effective. — Lomn 12:59, 7 October 2008 (UTC)

A related option is to reduce your CPU usage, which reduces the laptop's need for cooling, which should let the fan run slower and less frequently. Plasticup ^T/C 15:15, 7 October 2008 (UTC)

Often, reducing the CPU usage is not an option, since I use the laptop with a purpose. Mr.K. (talk) 15:24, 7 October 2008 (UTC)

Amen to that! Plasticup ^T/C 00:28, 8 October 2008 (UTC)

To remove a particular amount of heat per minute, you must move a particular amount of air per minute, often measured in CFM. A fan with a smaller diameter must spin faster for the same CFM. The higher speed results in a higher amount of vorticity at the blade ends, and this is where most of the noise is generated. A laptop cannot accomodate a large-diameter fan, so the fan must spin very fast and is therefore very noisy. The same is true for 1U rack-mount servers. As an example of the difference diameter makes, consider the difference between a 20" diameter window fan and a 3" diameter "muffin" fan in a desktop computer. The window fan at its lowest speed moves much more air than the muffin fan at its normal niosy speed, but is virtually silent.The motor contributes very little noise in either case. -Arch dude (talk) 00:41, 8 October 2008 (UTC)

Question (Goliath Beetle)

What is the main predator to the Goliath Beetle? —Preceding unsigned comment added by 204.210.238.42 (talk) 11:54, 7 October 2008 (UTC)

I'm not sure it has a main predator. There are more than enough predators and omnivores in tropical Africa that would not think twice before dining on a huge delicious beetle larva. Mandrill comes to mind as a very likely predator, but I couldn't find any specific data. Besides, Mandrill habitat extent is much smaller than that of Goliathus sp. . Sorry. --Dr Dima (talk) 17:13, 7 October 2008 (UTC)

How does fruit get "bruised"?

Just curious how fruits like apples and bananas get "bruised"? Aren't they dead? How does impact against the surface affect the fruit below the skin? --70.167.58.6 (talk) 16:00, 7 October 2008 (UTC)

I'm not sure it's accurate to say they're dead. They are still chemically active, otherwise they wouldn't be able to ripen after being picked. I think the bruising is caused by breaking the cell walls so the individual cells die, but I can't guarantee it. I'm sure a botanist will be along shortly. --Tango (talk) 16:07, 7 October 2008 (UTC)

Not a botanist, but Tango has the right idea. Inside of plant cells are chemicals which oxidize upon exposure to air. If the cell remains intact, nothing happens. However, cutting the fruit or striking it can cause the cell walls of the cells to break, exposing the chemicals to air, and causeing a change in both color and texture. Incidentally, bruised fruit is perfectly healthy and there's nothing at all wrong with eating it. You abuse the fruit much more when you chew and swallow the fruit anyways; the color change is not a sign of bacterial growth in any way, its merely a sign of physical damage. --Jayron32.talk.contribs 16:47, 7 October 2008 (UTC)

You may want to look at this. --Dr Dima (talk) 19:18, 7 October 2008 (UTC)

Fresh animal products consists of all dead cells when you buy them but fruits fruits and vegetables are all alive. The "bruise" consists of plant cells that are dead. Sjschen (talk) 03:51, 8 October 2008 (UTC)

So is it possible for bruises to grow? Will a bruise "infect" undamaged cells making it more unattractive? Do bruised areas rot faster? --71.158.222.207 (talk) 03:59, 8 October 2008 (UTC)

Yes, bruises will grow - the lysed cells burst in the original insult will release oxidizing enzymes which will continue to degrade the contents of the fruit, in part by lysing more cell membranes. And yes, as more cells contents are spilled out, they will be more susceptible to bacterial invasion. This is why the little bruise spot on your tomato when you bought it gets bigger and gets a grey mold at the centre. Franamax (talk) 05:54, 8 October 2008 (UTC)

Unquestionably the best resource on this is On Food and Cooking: The Science and Lore of the Kitchen H. McGee ISBN 978-0-684-80001-1.[10] It explains all this stuff and tells you how to get your eggs right! :) Franamax (talk) 06:18, 8 October 2008 (UTC)

Grass Seed Lifespan

I have had a bag of lawn grass seed in my garage for over 4 years. Over that time it has been exposed to -20C to +35C degrees. Would it still be alive and able to grow after all? —Preceding unsigned comment added by 151.123.128.250 (talk) 16:40, 7 October 2008 (UTC)

Quite possibly. Many kinds of seeds are quite resilient. There are some seeds that have been shown to germinate after hundreds of years of dormancy. The best thing to do is to run a little experiment. Take a cup of dirt, put a small pinch of seeds in it, keep it moist and in direct sunlight (like the windowsill) and see what happens. The seeds, if still viable, should germinate within a few days. If they do, you probably have good seed. If it just sits there for a week and nothing happens, then you probably need to pitch them. --Jayron32.talk.contribs 16:44, 7 October 2008 (UTC)

The normal rule is: If at least 75% of the seeds germinate, use as directed. If 50%-75% germinate, use double the normal amount. If less than 50% germinate, toss it and get a new bag. --Stephan Schulz (talk) 17:41, 7 October 2008 (UTC)

calorie consumption per hour/ mile (cycling)

Hello Everyone,

i've been trying to work out how many calories I burn on my cycle to work but i'm struggling to get some relevant info (i've been on a few forums but they use 40 year olds as reference points -i'm not even sure if one burns more or less calories as one ages so this is less than helpful.) Anyway, i'd be grateful if any one has any ideas - its about 4.7 miles (according to google maps anyway) each way, along reasonably flat terrain -stopping and starting for traffic lights often. It takes me about 30 minutes on average. Also i'm a (reasonably fit) 24 year old man... Any help, or even some starting data, would be great...

Thanks, 82.22.4.63 (talk) 19:09, 7 October 2008 (UTC)

While caloric intake is relatively easy to calculate, based on the nutritional content of the food in terms of ammounts of proteins, fats, and carbohydrates, its a different story for caloric output, in terms of exercise. Its going to vary WILDLY depending on how hard you are pedaling, your current body weight, your personal body chemistry and metabolism, the ambient temperature that day, your muscle mass, yada yada yada. The variables are almost too great to even think of all of them. Calculators that purport to determine how many calories you burn (for example, those found on treadmills or stationary bikes) are likely just WAGs. They may be based on, for example, the 50th percentile human, but variation from that ideal is likely so large that there is no way to assure they will be accurate for you. The easiest way to tell is to see if it has an effect on your own body: If you are losing body fat over time, you are likely burning more calories than you take in. If you are gaining body fat over time, you are likely consuming more than you burn. Take Michael Phelps for example. It is widely reported that he consumes 10,000 calories per day. That's roughly the amount of food 4 people would eat. And yet, he has almost no body fat, which means his level of activity has him burning at least that much. The funny thing is, another person, performing the same workout regimen as he does, may find himself gaining fat at that level of intake. Isolating WHICH activities are burning which calories is entirely a guessing game. The best thing that can be said is more activity always burns more calories, so more is always better. --Jayron32.talk.contribs 20:21, 7 October 2008 (UTC)

Human feet vs. Chimp feet

Chimps' feet have thumb like digits on them so they can grab objects with their feet in a similar way to how we can grab things with our hands correct? So I was curious if our feet which do not have that ability, have any advantages over their feet. 98.221.85.188 (talk) 19:51, 7 October 2008 (UTC)

Chimp feet are great for walking on branches, too. But they're lousy for running. (See achilles tendon not what I expected.) See Persistence hunting. Saintrain (talk) 20:07, 7 October 2008 (UTC)

Chimps are also not bipedal like humans. Like some other animals (bears, for example) they can, relatively easily walk on two legs, but their preferred method of ground locomotion is "knuckle walking" on all fours, generally as a sort of side-shuffle. Chimps are not very efficient at walking flat footed, however, as noted above, they are VERY efficient at traveling in trees, having evolved in a forested habitat. Modern humans largely evolved in a savannah habitat, with few trees, and thus flat-footed walking gave them an advantage in that environment. Thumbs are an impediment to flat-footed walking, and so proto-humans with "modern human" style feet tended to predominate in that environment. --Jayron32.talk.contribs 20:26, 7 October 2008 (UTC)

To expand on Jayron32, the human foot is specifically adapted to walking upright. The big advantage we have over chimps (for the bipedal environment) are the two arches of the foot which act --like springs-- as shock absorbers, distributing weight and allowing us to easily run upright. --Shaggorama (talk) 20:56, 7 October 2008 (UTC)

I was talking a while back to someone who lost their big toe in a lawnmower accident and they said the loss of the toe made walking quite bit more difficult. So it looks like the toe might have been actively evolved to help with walking. Dmcq (talk) 00:30, 8 October 2008 (UTC)

Fizzy drinks.

The aqueous carbon dioxide in fizzy drinks makes the drinks acidic (for some reason that I have forgotten), couldn't you just add an alkaline solution to the drink to neutralise it. Fizzy drinks are critisised for being bad for your teeth because they're acidic, this would get rid of that problem. Thanks.92.2.212.124 (talk) 20:02, 7 October 2008 (UTC)

Except that acidic compounds have a generally pleasant "sour" flavor. Alkali compounds have a bitter, soapy flavor. Eat a bar of soap, or drink some lemonade. Which do YOU prefer? --Jayron32.talk.contribs 20:31, 7 October 2008 (UTC)

Also, its not the acid in sodas that is damaging to your teeth per se since it does not remain in contact with your teeth for very long. However, bacteria, which DO remain in contact with your teeth for a long time, will feed on the sugar in the soda, and produce an acidic waste product. Since these bacteria are essentially always there, the more sugar you give them, the more acid they make. Its this acid, which is held directly against the tooth for a long period of time, and not the acid that washes over the tooth which causes decay. Its the sugars in the soda that cause the decay, not the acid inherent in the carbonic acid. --Jayron32.talk.contribs 20:31, 7 October 2008 (UTC)

Thanks92.2.212.124 (talk) 20:43, 7 October 2008 (UTC)

It is not carbonic acid that is responsible for the sour taste and the tooth weakening, it is phosphoric acid (Cola) or citric acid. Cacycle (talk) 03:28, 8 October 2008 (UTC)

From this article, it's due to a combination of acidity, buffering capacity (titratable acidity) and sugar content. Axl ¤ [Talk] 17:40, 8 October 2008 (UTC)

The grayed tip of a banana

As a child I was told to bite off the usually grayed tip of a banana before eating it. What is it, though? Thanks. Imagine Reason (talk) 20:03, 7 October 2008 (UTC)

Greyed tip? I assume this means pre-peeled bananas, but i wouldn't bite the peel of a banana. If this means a peeled banana, what grey tip? Anyway, I've never heard that.92.2.212.124 (talk) 20:30, 7 October 2008 (UTC)

I'm pretty sure it's banana. --Shaggorama (talk) 20:38, 7 October 2008 (UTC)

Yes, it's the tip of a just-peeled banana. It's usually not white. C'mon, I thought that were the common experience. Imagine Reason (talk) 21:19, 7 October 2008 (UTC)

See vascular bundle and, specifically for bananas, phloem bundle (What!? No article!?). What you are referring to is the part of the banana where the bundles (strings) join and invert into the center of the fruit. -- kainaw™ 21:49, 7 October 2008 (UTC)

You mean the dark bit at the far end from where you open it? I don't bite it off, it comes off very cleanly on its own if you push it sideways slightly. --Tango (talk) 23:17, 7 October 2008 (UTC)

This sounds like bruising as described not far above. When the cells are damaged, they release enyzmes which oxidize the surrounding tissue. Damage could occur at the stalk end due to wrenching when the banana bunch is pulled of the stem, at the bottom end when the bunch hits the container, and anywhere else the bananas get bumped in transit. If you're getting bananas with brown on them, consider yourself lucky, the only bananas I ever see are very far from ripe - thank you very much, modern commercial food distribution system. Franamax (talk) 03:33, 8 October 2008 (UTC)

My dad used to bite out the bruised bits of bananas before slicing them onto his breakfast cereal. (I don't know whether he still eats breakfast cereal.) The texture may be icky to some, but it won't hurt you, if that's what you're asking. —Tamfang (talk) 06:44, 8 October 2008 (UTC)

Nobel Prize winners

Have there been any Nobel Prize winners whose work has since been completely discredited or otherwise found to be useless/incorrect? -Elmer Clark (talk) 20:41, 7 October 2008 (UTC)

Interesting question! Since you posted in Science, I assume you're less interested in the Nobel Peace Prize, where Rigoberta_Menchú and Henry Kissinger come to mind. --Sean 21:45, 7 October 2008 (UTC)

If this were about Nobel laureates generally, I'd mention Paul Heyse, who won the 1910 Literature prize. One of the judges said "Germany has not had a greater literary genius since Goethe" - but history has been rather less kind to Heyse. -- JackofOz (talk) 01:12, 8 October 2008 (UTC)

Off the top of my head, the closest I could come up with is Neils Bohr, who won the Nobel Prize in Physics for devising the Bohr model of the atom. Its not that the Bohr model was wrong, in fact it is perfectly accurate for any two particle system. The problem is, in practical terms it means it predicts the electronic structure of the Hydrogen atom (which has an electron and the nucleus) and nothing else. The Bohr model breaks down for any atom with more than one electron in it; so while it works for the He⁺¹ ion, it doesn't work for the He atom. It was an important step in the modern understanding of the electronic structure of the atom, but other more recent models, such as the wave mechanical model of the atom as derived by Erwin Schrödinger, Paul Dirac, Louis de Broglie, and others is far more useful, and as a model it contains the Bohr model as a special case. Still, Bohr is important as a key step in our understanding of the atom, and his contributions should not be deminished merely because better models came along later. --Jayron32.talk.contribs 21:37, 7 October 2008 (UTC)

Bohr's idea of quantization of angular momentum also inspired de Broglie whose's work latter inspired Erwin Schrödinger so that he came up with Schrödinger equation. I believe that the modern quantum theory couldn't exist without Bohr's breakthrough. - Justin545 (talk) 00:35, 8 October 2008 (UTC)

Johannes Andreas Grib Fibiger is an interesting case, especially in light of this week's award to Harald zur Hausen. --Arcadian (talk) 09:47, 8 October 2008 (UTC)

Argh - the guy's name escapes me for the moment. There is at least one case where someone made a seemingly great discovery - and it was disproven shortly before the Nobel was awarded - so they gave him the prize anyway but changed the citation from that very specific discovery to some kind of vague lifetime-achievement award...but the guy's name escapes me right now. SteveBaker (talk) 13:55, 8 October 2008 (UTC)

honey locust spines: poisonous?

I just tore an enormous (23 centimeter long) spine off of a honey locust near here and in the process my left hand got jabbed. It didn't break the skin or draw any blood, but there's a small, red raised bump there like an insect bite that itches a little and the area around it is somewhat red and feels sore. I heard that honey locusts have some sort of toxin in their thorns that can be dangerous, but I can't find any information on it at all. Is this true? If so, do I need to seek medical attention? Can this get infected?

Any help is appreciated. Thanks. 63.245.144.77 (talk) 20:44, 7 October 2008 (UTC)

Sorry, we can't give medical advice. Please contact your doctor's office. The nurses there will be able to tell you what sort of medical attention (if any) you need. Also, note that some locations have a poison control telephone number - they are usually staffed with medically trained people, and are very helpful with "is this plant poisonous" type questions. -- 128.104.112.147 (talk) 23:39, 7 October 2008 (UTC)

Holt Biology

What is a phospholipid layer that covers a cell`s surface and acts as a barrier between the inside of a cell and the cell`s environment? —Preceding unsigned comment added by 75.68.106.206 (talk) 21:14, 7 October 2008 (UTC)

Your Holt Biology book should have the answer. Please post all your homework questions at once so we don't have to repeat multiple times that we are not here to do your homework. -- kainaw™ 21:22, 7 October 2008 (UTC)

See comments below on the plant cells. Be aware that while Wikipedia has an article on Cells, which I recommend that you read, your Holt Biology book is likely much easier to follow, and if you read it, it will give you the answer. --Jayron32.talk.contribs 21:23, 7 October 2008 (UTC)

Hearing

Hi all,

Hypothetically, and I do mean hypothetically because I’m not asking for medical advice, how does one increase the results of a hearing test (only a temporary basis, not permanently).

I’ve heard that: 1. One’s hearing is better in the morning (so take the hearing test in the morning) – there will be a slight benefit. 2. Wear headphones (like the headphones for ear protection with firearms) prior to the hearing test. This will allow one to “rest” the ear drums so they’ll be more “sensitive” during the hearing test.

Any other thoughts (again, not seeking medical advice). Thx! Rangermike (talk) 21:15, 7 October 2008 (UTC)

I had an uncle (until my aunt divorced him) who was practically deaf from working on jet aircraft. He needed to pass a hearing test to stay in the Navy Reserve or National Guard (don't remember which). What he did was wear ear plugs for a week or two before the test. Then, he would barely pass. He never tried it without the earplugs before the test, so I can't make a claim that it actually helped. -- kainaw™ 23:39, 7 October 2008 (UTC)

Fully off-topic - what is that guy called now? Ex-uncle? Uncle infinitely-removed? Former uncle (is this one best)? And for that matter, how do I refer to events that occured when my ex-wife was still just my girlfriend? SciRefDesk is probably not the best place to ask, I suppose... Franamax (talk) 05:45, 8 October 2008 (UTC)

Um - he is called "the ass who tried to stay in the reserves so he could spend one weekend a month in another city where he married another woman and, eventually, couldn't keep the two wives apart, got caught, and got dumped by both of them", or "the ass" for short. -- kainaw™ 13:16, 8 October 2008 (UTC)

Holt Biology

what is an organelle found in plant and algae cells where photosynthesis occurs? —Preceding unsigned comment added by 75.68.106.206 (talk) 21:17, 7 October 2008 (UTC)

You know, if you read your Holt Biology book, you may find the answer very easily. I bet you wouldn't have to look for more than 2 or 3 minutes. As an aside, you should also read the disclaimer at the top of this page, where it mentions that we aren't here to answer your homework questions. If reading your textbook is too much, you may want to read the Wikipedia article on Plant cells. Toodles. --Jayron32.talk.contribs 21:20, 7 October 2008 (UTC)

Really you'd get a much faster answer by typing photosynthesis into the search box than we could ever provide, I just don't get it. -- Mad031683 (talk) 22:07, 7 October 2008 (UTC)

What is, "I'll take chloroplast for 200, Alex"? - Nunh-huh 06:47, 8 October 2008 (UTC)

steam rockets

I am interested in steam rockets. What can you tell me about them? I specifically wanted to know about heating the steam. The small steam rockets I've seen are preheated with a torch and then released. Is it possible to have an onboard heating system on a relatively small rocket? What would that be? Any additional information would be very helpful. Thank you.Wizardh2o (talk) 22:43, 7 October 2008 (UTC)

We have an article on hot water rockets. While it's possible to do an onboard heating device, it's inefficient -- you're burning fuel to heat water not just to "steam" but to "very hot steam" (to ensure sufficient pressure) when you could just be burning fuel for the pressure of the initial combustion and leaving the weight of the water out. So while it's possible, it's going to be rare. — Lomn 23:09, 7 October 2008 (UTC)

Putting car in park

Is it a good idea to shift my car (a 2004 automatic) into park when I'm at a long light or waiting for a left turn? Can doing this alot damage my car? Does it save any gas?97.118.170.250 (talk) 23:08, 7 October 2008 (UTC)

For an automatic? It's not likely to affect the car negatively, though in many cases it'll burn more gas -- my auto, and most I've driven, idle faster in park/neutral than in drive. There's an advantage to shifting to neutral in a stick shift so as to reduce wear on the clutch. — Lomn 23:11, 7 October 2008 (UTC)

Is there much wear on a clutch when it's fully disengaged? --Tango (talk) 23:19, 7 October 2008 (UTC)

According to the Car Talk guys, keeping the clutch pedal fully in causes wear on the throw-out bearing. They recommend shifting to neutral. — Lomn 00:02, 8 October 2008 (UTC)

The only advantage of shifting to park that I can think of is to avoid putting your foot on the brake. The disadvantage is that you'll need to ensure you shift into drive (not neutral and definitely not reverse) when the light turns green. As for the transmission (it's automatic, so you aren't manually messing with the clutch), each car I've owned has run just fine for at least 10 years without transmission problems. From my experience, people I know with automatic transmission problems are those who gun it and race from light to light - which has nothing to do with sitting at a light. My sister-in-law has two foot settings: all the way down or all the way up. She goes through a transmission a year. -- kainaw™ 23:36, 7 October 2008 (UTC)

But will it save me any gas?97.118.170.250 (talk) 23:41, 7 October 2008 (UTC)

Did you read Lomn's response above? He states that his experience is that it will burn more gas, not less. -- kainaw™ 23:45, 7 October 2008 (UTC)

Re Lomm's observation: isn't the idling speedup due to removing the transmission load from the engine rather than increasing the fuel supply? -hydnjo talk 00:40, 8 October 2008 (UTC)

It is difficult to say in modern vehicles where a computer controls the fuel supply. In the good old days, shortly after we had to use our feet to make the car move, the gas pedal actually increased/decreased the amount of fuel to the engine. So, regardless of what else was happening, not having your foot on the pedal would make it consume fuel at the idling rate at all times. The OP said this was a 2004 car, so it is one of those newfangled computer-controlled ones. -- kainaw™ 01:53, 8 October 2008 (UTC)

In re the above:

• Switching an automatic transmission into Park should alert the computer to select the most economical fuel mode possible. At certain times, it could select "curb idle", which is a higher idle rate to maintain alternator output. If you aren't running your A/C, there's no particular reason I can think of that the computer would choose to send more fuel to the engine. However, given the same amount of fuel, shifting to Park would stop your motor from pumping liquid around the transmission torque converter, so I'd expect the engine to rev a little higher without that load.
• And for a manual transmission, shifting to neutral is always good, not least because your leg doesn't get tired. However, I think Lomn's Car Guys link is a piece of semi-crap. Their piece ends with an appeal to send them $3 to find out the rest of the mysteries, which is a little suspicious. Keeping your clutch depressed means there is a constant load on the throw-out bearing, but there is no other load - the bearing is not rotating, it's just sitting there with the incredibly hard steel of the bearing-balls and bearing-races subject to the pressure of - your foot! Contrast keeping the clutch fully disengaged though with riding the clutch, or keeping your foot lazily off the floor, so that the throw-out bearing is under pedal pressure and is rotating the partially-engaged clutch - that's definitely not good! But I've gotten 14 years and 440,001 km out of a single clutch (1992 VW Golf), and I never worried that much about shifting to neutral. The Car Guys might be right though, maybe the clutch would have blown at 600,000 km... :) Franamax (talk) 04:08, 8 October 2008 (UTC)

Keeping your foot on the clutch in a stick-shift car does indeed wear out that bearing prematurely (it's sometimes called the "thrust washer"...same thing). But in a modern car, with a typical driver, it's pretty unlikely that that'll wear out before the clutch itself - so while it's a good idea to shift into neutral and take your foot off the clutch when stopped - it's not a really critical thing. On an automatic, it's irrelevant because there is a fluid coupling clutch. There are many cases though where it's DANGEROUS to leave the car in gear with your foot on the clutch - for example, if you are stopped at a junction and you get rear-ended, your foot will almost certainly slip off of the clutch and you'll be launched forward into oncoming traffic - turning a minor fender-bender into a life-threatening situation. If you are in neutral with your foot on the brake (either in an automatic or a manual, then if your foot should happen to slip (eg as a result of a rear-ending or wet shoes or something) then at least you'll only roll rather gently forwards. Best of all is to put the car in neutral and put on the parking brake. In an automatic, putting it in park should have the same effect - but I have heard that the pin that slips into the transmission when you put the car in park can get worn out from excessive use...so I'm still going to say "Neutral with the parking brake on" is the best option and "In park" as the second best. I would be very surprised indeed to discover any difference whatever in gas consumption with any of the above techniques so long as you aren't revving your engine to keep your turbo spooled up in preparation for an impending burn-out when the light turns green!

October 8

Headset to hear dictations

What are the technical specifications that we have to look in a head phone to get maximum efficiency to hear dictations and comfort for wearing long hours?

As far as comfort goes, that's not likely to be a question of technical specifications. Your head and ears are pretty unique in their shape, and what is comfortable for one person may not be comfortable for you, and vice versa. -- Captain Disdain (talk) 01:17, 8 October 2008 (UTC)

For example, I switched from earmuffs (which I otherwise prefer) to plugs after I got new glasses whose shafts stand out further from my head than before. —Tamfang (talk) 05:34, 8 October 2008 (UTC)

Sensory Integration Disorder and its Impact on Potty Training

I have a 4 yr old daughter who has SID and is very hypersensitive. She has been working with OT and PT since she was 5 mths old. No one has any clear information to give me on how to potty train! The developmental specialist states to give her time- the uroligists states she must get it done b/c of the severe negative side effects it has had on her (kidney infections that have led to hospitalizations). She is very fearful of even sitting on the toilet much less wanting to be in the bathroom when it flushes! I have read all I can find on SID and own numerous books on potty training. Are there methods used for children with SID to help with this issue??

Thank you- —Preceding unsigned comment added by 12.202.108.191 (talk) 03:25, 8 October 2008 (UTC)

Have you asked the medical professionals for locations of appropriate support groups? Have you tried searching on the web for support groups that address this specific issue? There are lots of parents here, but we're really not allowed to give medical advice on specific issues. Franamax (talk) 05:01, 8 October 2008 (UTC)

And there's no particular reason the child must be in the bathroom when the toilet flushes. She can be standing just outside the door watching when you flush the toilet, and then she can hold a long stick to help you flush the toilet, and then she can use the stick herself. But that's starting to be medical advice... Franamax (talk) 05:07, 8 October 2008 (UTC)

Strange gender inequality in the dental industry

I've been to numerous dentists. Why are the dentists always only men and the assistants always only women? Are you ready for IPv6? (talk) 03:49, 8 October 2008 (UTC)

That's an interesting question. Have you tried to seek out dental clinics where the dentists are female? As far as the gender split goes:

• Dentist does seem to be a male-dominated field. A discussion on possible gender-bias can be found here. Stand-alone professional fields such as dentistry would seem good ground for women to avoid gender bias, since they have only to fulfill the qualifications. I would speculate that those women so inclined might gravitate instead to pharmacology or in particular physiology (M.D.-type doctor rather than D.D.S-doctor). Perhaps those women inclined to a medical field either go big or go home (pace to any dentists who might think I denigrate their important field - but it does rank just a little under M.D.).
• As far as dental assistants or dental hygienists, I would speculate that the field offers a good way for women of child-bearing age to acquire a valuable transferable skill that offers them maximum flexibility as to hours worked, balanced with a good income. Also, women are probably just better as dental assistants, since they're more empathetic, interact naturally with children, etc. You can read that as a sexist statement, but I mean it as a statement of great admiration.
• And the factor of bearing and caring for children must always be considered in choice of training and work for women - they're the ones making them after all. :) In the case you question though, the balance does seem somewhat skewed. Franamax (talk) 04:55, 8 October 2008 (UTC)

My current dentist is female, my former dentist was female. Of the 4 dentists over my life-time 2 have been female. Of course that's my perspective and so statistics might not back this up. Just throwing that in there. 194.221.133.226 (talk) 10:32, 8 October 2008 (UTC)

Could it be the case that greater (on average) physical strength and large hands are an advantage when pulling teeth? Or that the general wisdom is such - thus discouraging some women from taking up dentistry? A personal observation - the only time a female dentist tried to remove one of my teeth (I've had a lot of teeth removed), she wasn't strong enough to budge it and had to go fetch a male colleague. --Kurt Shaped Box (talk) 10:59, 8 October 2008 (UTC)

This site has some numbers. It says there is an 83%/17% male/female split among all private practice dentists in the US. It's interesting to note that at a prestigious veterinarian school in my area there is a similar split in the other direction. --Sean 14:51, 8 October 2008 (UTC)

It's probably the same reason that most Doctors (traditionally) have been male, and most Nurses female. "Dentist is to Doctor as Dental hygienist is to Nurse" (FWIW, my current dentist is female, and I know of male hygienists, just like I know female doctors and male nurses) -- 128.104.112.147 (talk) 15:40, 8 October 2008 (UTC)

immume system

types of immumoglobine —Preceding unsigned comment added by Ksneyhaa (talk • contribs) 06:37, 8 October 2008 (UTC)

WIth regard to the immune system, we discuss immunoglobulins IgA, IgD, IgE, IgG, and IgM. - Nunh-huh 06:43, 8 October 2008 (UTC)

chemistry

two flasks A & B have equal volumes .flask A contains Hydrogen maintained at 300K while B contains methane gas maintained at 600K. 1.which flask contain greater number of molecules & hwmany times more —Preceding unsigned comment added by Bhuwanntl (talk • contribs) 07:55, 8 October 2008 (UTC)

"Do your own homework. The reference desk will not give you answers for your homework, although we will try to help you out if there is a specific part of your homework you do not understand. Make an effort to show that you have tried solving it first." -- Aeluwas (talk) 08:53, 8 October 2008 (UTC)

Your question is unanswerable, because you have not specified whether the two flasks have equal pressures. Take a look at combined gas laws. If we specify that pressure is equal, you're looking at Charles's law. - Nunh-huh 09:00, 8 October 2008 (UTC)

Aflatoxin in raw peeled peanuts

How can I know if raw peeled peanuts are contaminated by Aspergillus flavus and Aspergillus parasiticus? Is it possible to see it like mold on bread? Mr.K. (talk) 12:14, 8 October 2008 (UTC)

Peanuts in general are susceptible to aflatoxin contamination. You wouldn't see the aflatoxin itself (except under blacklight), but you might see the fungus that produces it. Cooking doesn't really affect it, since the toxins are heat stable (the fungus that produces them, however, is not). Fungus doesn't imply aflatoxin (not all fungi produce it), but lack of fungus doesn't guarantee safety. Like most toxins, a really small dose (i.e. one dubious peanut eaten per year) isn't going to kill you. If in doubt, don't eat it (no surprise there), but probably best to avoid the whole group if you see some fungus growing on anything in it. SDY (talk) 13:01, 8 October 2008 (UTC)

Sleep injuries

I'm failing to find the medical term for injuries that occur while sleeping, such as pulling a muscle or separating a joint. Is there a term to classify those injuries? -- kainaw™ 13:18, 8 October 2008 (UTC)

They don't happen often enough, and aren't intrinsically different from similar injuries occurring while awake, for there to be a common medical name for them. - Nunh-huh 15:22, 8 October 2008 (UTC)

Semen and Enzymes

Do the enzymes in washing detergent break down the proteins ect, that are in semen? i always wash my underwear seperately, because i worry that im simply spreading it all evenly on my clothes, and that microscopic amounts will rub off on where i sit ect. Zakbrak341 (talk) 13:56, 8 October 2008 (UTC)

If they're only microscopic amounts, what difference does it make? Also, why do you have so much semen in your underwear? You're meant to remove your clothes for that kind of thing... --Tango (talk) 14:10, 8 October 2008 (UTC)

Its not loads, just very small amounts of precum before i take them off ect, if got lots on them i'd just throw them away, but the thought of any amount of semen on anything bothers me, for a while i was doing a hot wash, so it would denature the protiens but then i worried that the heat would denature the enzymes in the powder, and if the enzymes break down the protiens into amino acids, then thats better than simply unfolding the protien into its secondary of primary structure, then i started worrying, what if these enzymes in the washing powder are specfic to protiens in common food stains only and have no effect on the protiens in semen, so now im just wash them in serveral changes on water with lots of detergent. —Preceding unsigned comment added by Zakbrak341 (talk • contribs) 14:31, 8 October 2008 (UTC)

Tango, two things. First, some people are kinda clean freaks when it comes to everything, so it's not really unusual to be concerned over whether semen is contaminating other clothes in the washing machine. Secondly, it's not really your place to ask him why he has semen in his underwear, you should only address his questions. 98.221.85.188 (talk) 14:35, 8 October 2008 (UTC)

Your detergent should emulsify fats, which means that it wraps little bubbles of detergent around your semen and stops it from sticking to any of your clothes. Plasticup ^T/C 15:08, 8 October 2008 (UTC)

Except that semen is essentially fat-free. No emulsification. For the original questioner: the enzymes in washing detergents are designed to be as non-specific as possible in breaking down proteins, and should have no trouble with semen. - Nunh-huh 15:19, 8 October 2008 (UTC)

Even if someone can get something which is soiled physically clean, meaning that the offending sunstance cannot be seen or even detected by CSI, they still remember it was once there. It can get more into ritual purification, like the concept of a ritual bath removing some iniquity or moral stain. I read a housewife's complaint to an advice column that her husband had soaked his sore toe in warm salt water (at the doctor's advice) in one of her expensive gourmet cooking pots, and that she had to throw the pot away because she would never afterward feel that it was "clean" regardless of scrubbing or dishwasher cleansing. If the questioner gets a reference to an authoritative laundering site which says a wash of some temperature on some cycle with certain cleaning products will render the garment as clean as it was when it came out of the package, then he might be saved the expense of frequently throwing garments away and buying replacements. Some people, even in this era of "cold water" energy-saving detergents wash a load of white cotton washcloths, towels, and underwear in the "hot" wash cycle with detergent and chlorine bleach, with an extra rinse, Not saying this is the authoritative answer to the original question, and there is also the question of enzymes versus bleach and hot versus cold water to eliminate biological stains. Interestingly there are loads of book references dealing with semen stains[[11]] though few specifically address their removal. (Not to be confused with the mythical character "Seaman Staines" on the Captain Pugwash children's program). Edison (talk) 15:23, 8 October 2008 (UTC)

E=mc^2...Whatever that means.

Hey...what unit is the E in $E=mc^{2}$? Is it calories, Joules, tons, or what? I have been wondering about this for a while and saw the article on E=mc^2 with its handy list of how much energy is contained in a dollar bill. It lists several units of measuring energy, which got me confused. When you convert mass to energy, is the mass converted to Joules or calories or another type of energy? 31306D696E6E69636B6D (talk) 16:36, 8 October 2008 (UTC)

Well, it defaults to kg·m²/s² (Joules), which it does say in the intro :)

In the formula, c2 is the conversion factor required to convert from units of mass to units of energy. The formula does not depend on a specific system of units. In the International System of Units, the unit for energy is the joule, for mass the kilogram, and for speed meters per second. Note that 1 joule equals 1 . In unit-specific terms, E (in joules) = m (in kilograms) multiplied by (299,792,458 m/s)2.

-- MacAddct1984 ^{(talk &#149; contribs)} 16:42, 8 October 2008 (UTC)

(ec) :Joules and calories are units of measurement, not different "type[s] of energy". Just like you can measure speed as miles per hour or kilometers per hour or feet per second and can convert a speed from one to the other but it's still the "same speed". So whatever units you use for c and for m determines the units of E. If that's not the unit you want, you can convert. Or you can choose what units of energy you want and then convert the mass and speed of light to use them. DMacks (talk) 16:43, 8 October 2008 (UTC)

As long as you're consistent, you can use any unit system (for example, you could use ergs, but then you would have to measure the mass in grams and the speed of light in cm/s - see cgs). Usually scientists use SI units, where energy is measured in joules. It's also common to see energy measured in electron volts. --Tango (talk) 16:46, 8 October 2008 (UTC)

yeah, just remember that the CONSTANT in the equation, C, isn't just a number, like a million. Instead, it's a "million miles per hour" (for example). So, if you take a pound, or a kilogram, or any unit of mass you want, and mulitply it by a million miles per hour squared, you get a certain amount of energy. I don't have an intuitive conception for why a million miles per hour squared times 1 pound should be an amount of energy though...

safe dough?

I live with an Italian, and she's making pizza in four days -- but she's started today. She mixed a spoonful of honey with oil into flour and water and is letting it rise at room temperature, keeping it moist under a moist cloth (which she will keep remoistening over the next four days). This "mother" dough she will use over the course of several pizzas, the first one Saturday, until she's done with it.

My question is: how does this work? I'm not sure what role the "mother" dough has, is it like yeast?

In fact I heard that "sourdough" was created by accident more than a hundred years ago, and since then they have alwyas been reusing the same starter -- they always saved a little to make more. But she's not adding a "starting" piece, she's just starting from honey and oil! So, isn't it just a random toss-up what microbes will start growing? Why is it even safe?

Obviously I'm not asking for any medical or legal advice... —Preceding unsigned comment added by 82.120.232.170 (talk) 17:14, 8 October 2008 (UTC)