Wikipedia:Reference desk/Archives/Science/2007 July 10

Science desk
< July 9	<< Jun | July | Aug >>	July 11 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 10

Question about UV light danger

I was looking at a fume hood today with a germicidal (UV) light on. While the light is concealed from view, the purple light reflects out of the hood. I was wondering, can the UV light reflect off of the walls and floor of the chamber in any sufficient intensity to present a health hazard? The interior of the hood is made of stainless steel. I know that the glass shield will block most UV passing through it, but it is typically half open. And as for a possible health hazard, I am basing this on the possibility of spending anywhere from minutes to hours a day in front of it (I make sure to spend only seconds a day out of paranoia). Everyone who works here, including several doctors, say "Just don't stickaa your hands inside with that light on." But I'm still curious. 151.152.101.44 00:53, 10 July 2007 (UTC)

You can get the bulb's emission spectrum from the manufacturer. You can probably get the reflection characteristics of the stainless steel from the respective manufacturers. In any event, you should have access to a separate instrument that can directly measure the UV spectrum at various locations at your workstation. Until you have these objective measurements, any general advice is meaningless. Nevertheless, here is some general advice: Do not look at the germicidal bulbs directly. To a first approximation, treat the bulbs and their reflections as you would direct solar radiation: do not look at it directly. -Arch dude 02:17, 10 July 2007 (UTC)

How about wearing glasses which block UV, as a first approximation to safety? You can get an anti-UV clear coating on normal glasses. You certainly do not need the UV to see by, because our eyes are insensitive to it (unless the yellowish lens has been removed due to cataracts, in which case the retina can see nicely by UV). Then maybe rub on some UV blocking suntan lotion. (Who needs a melanoma?) Does the school/lab have an industrial hygienist? Measuring UV and checking it against government standards would be his job. Edison 03:24, 10 July 2007 (UTC)

I work with UV lasers. Germicidal mecury lamps emit UV-C, a type of ultraviolet light not found in the sunlight reaching the Earth's surface, and are specifically designed to break down DNA. As a result, for the same amount of energy, the light from germicidal lamps is many many times more carcinogenic than what you will find in sunlight. I would never place exposed skin under a germicidal lamp. Prolonged exposure will also result in sunburn symptoms or eye inflamation. The good news is that UV-C is easy to block. It will be blocked by ordinary glass or plastic. Normal safety glasses are more than adequate at these wavelengths (no need for special "UV" filters, which generally target UV-A/B). Sunscreen is not designed for UV-C and depending on the active ingredients may not offer any protection. For moderate durations, latex gloves plus long sleeves would be adequate if one must work under a germicidal lamp. As for reflections, UV-C will reflect off of many shiny metallic surfaces the same as visible light (though a higher fraction is absorbed than visible light), so if the purple glow is bouncing out under the hood, then so is the UV and it is a potential safety risk. If your hood has a cover/window that can be closed, it really should be when the lamp is on. How large a safety risk will depend on a variety of details of your setup, but I would not want to work in front of it for extended periods. Dragons flight 04:44, 10 July 2007 (UTC)

Dragons flight, if you'll forgive me, I've added a Wikilink to your reply.

Atlant 12:46, 10 July 2007 (UTC)

Somewhat OT but I heard of someone who got sunburnt from the UV light use for visualising a gel electrophoresis (the open one, used for cutting the gel etc). IIRC, he was wearing glasses or a face mask and gloves so those areas were fine but his arms got sunburnt. He was working with a large quantity and didn't take adequete protection. Back on topic, I was thought to always to what Dragons flight said. Close the cover and then turn the light on. Of course, if you need to do some work with it on, this obviously wouldn't be possible Nil Einne 23:03, 10 July 2007 (UTC)

In the UK the public toilets in railway stations or bus stations often have a purple lighting in them in addition to normal lighting which I imagine may be something UV designed to steralise the place when nobody is there. Does anyone know to what extent this is dangerous? Thanks. 80.0.96.159 18:23, 14 July 2007 (UTC)

You'll see "purple lights" in two contexts: Near-UV ("black light") is used to attract bugs to bug zappers. But germicidal lamps were often commonly used in older days; many parochial schools in the US seemed to have the setup you're describing with a G.L. pointing upwards. Clothes dryers also had them to give clothes a fresh, outdoors, ozoney smell. Without a direct view of the lamp (to see if it has a phosphor layer or not), it'd be hard to tell the two apart. A smell of ozone would, of course, be a clear tip-off that it's a G.L. and not a black light.

Atlant 23:31, 14 July 2007 (UTC)

The usual delightful reason for having purple light in public toilets in the UK is to make it impossible to see the veins in one's arm, and therefore hard to inject heroin/crack/whatever.

How is the frequency response of an acoustic transducer determined?

How is the frequency response of an acoustic transducer determined? If it is done empirically by measurement, there must be a way to generate an acoustic test signal of precisely known power — without using the transducer under measurement. You could use a pre-calibrated transducer to calibrate the test signal, but that transducer must have undergone calibration before. At some point, you must stop reducing the calibration of one transducer to that of another. How is this problem (meaning frequency response measurement) solved in practice?

See Microphone in the section "Measurement microphones." 2oth century methods included the pistonphone, which mechanically moved a piston a known distance in a known space to create known pressure variations up to 250 Hz. A diaphragm could be electrostatically moved by high frequency alternating current to create pressure variations. AC electrical current could produce pressure variations in the "thermaphone." Certain types of microphones were thus calibrated with the pistonphone and used as lab standards. Now there is the "reciprocity method" which uses microphones which can either receive an acoustic signal and produce an electric signal, or receive an electric signal and produce acoustic waves. This is discussed at [1]. See also [2] and [3]. Edison 05:44, 10 July 2007 (UTC)

Water Retention

My doctor just gave me a medicine and he said it will cause my body to retain water while I am on it (two weeks). I already look fatter in the stomach area with the same diet and exercise. Does water retention look the same as weight gain from fat? If I were to gain 3 pounds of fat on my stomach, would it look the same as retaining the same amount in water?

Firstly we have to say Wikipedia does not give medical advice. If you are concerned about the side-effects of any medicine, talk to your Doctor or pharmacist. That said, in terms of appearence, yes, water-retention can look similar to weight-gain from fat. DuncanHill 09:44, 10 July 2007 (UTC)

induced paranormal experiences

Do we have any articles on the possibility of inducing paranormal experiences by engineering the lighting/dimensions/layout of a room? I remember hearing about a study that showed some kind of link. Also if you know about any other articles that are in the area of the psychology of paranormal experiences, I'd be interested in that too. Capuchin 08:19, 10 July 2007 (UTC)

I don't believe there is scientifically-reproducible evidence that paranormal experiences exist. Therefore, scientifically speaking, the experiences are invariant under room configuration. However some configurations may allow for non-paranormal factors (such as non-verbal communication) to influence the perception of an event. I'm not sure whether there are non-scientific articles on the topic. — RJH (talk) 15:32, 10 July 2007 (UTC)

Possibly Capuchin was asking whether apparent paranormal experiences could be engineered, and if there had been work in this area. That's how it reads to me, anyway. I recall reading very recently (why can I never remember where?) that some percentage of the UK population reported having had a paranormal experience, but that the less educated you were, the more likely you were to claim it was a ghost. The more educated you were, the more likely you were to claim it was a religious experience. I suspect I read it in a printed source. Hmm. Anyway, there are quite a few studies into the psychology of 'paranormal' experiences, but it does seem to be hard to find articles on them here; perhaps I just haven't found the right category yet. Theres Religious and physiological views of near-death experiences, but it doesn't look like a very good article. I'd expected to find stuff in [[Category:Forteana]], but I can't see the sort of thing I think you're looking for. Sorry :-( Skittle 16:27, 10 July 2007 (UTC)

Sorry for misunderstanding then. — RJH (talk) 19:52, 11 July 2007 (UTC)

The acoustics of the room could enable/enhance infrasound, which has been known to make people feel spooked out. --TotoBaggins 16:33, 10 July 2007 (UTC)

It can be done with direct brain stimulation. -Eldereft 03:43, 11 July 2007 (UTC)

See also Angular_gyrus#Out-of-body_experiences. -Eldereft 03:49, 11 July 2007 (UTC)

Skittle, you're quite right about what I am looking for. I remember watching a tv show (or part of a show) where they had set up a room of a specific size/shape at a museum or exibition of some kind. People would go in and sit in there for 5 minutes, and would often come out the other side claiming to have had a paranormal experience in there. I don't think they were providing any kind of stimulus. Looking through the infrasound article, the 18Hz resonant frequency of the room would be a good way to create it. Capuchin 08:13, 11 July 2007 (UTC)

how do you get rid of the smell from dried starfish?

I bought some dried starfish from a tourist shop to use as decoration, but the smell coming off them is so repulsive. how can i get rid of it, will it fade with time? and could i use sodium bicarbonate, as this is reknown for neutralising bad odors? has any one ever solved this problem?

I would suggest making sure that it is thouroughly dry should help - leave it in the sun outdoors for a few hours. Don't get it wet - they can go mushy, and will start to decompose, smelling even worse. I have seen a suggestion online that you soak it in 70% isopropyl alcohol, but have no experience of this. DuncanHill 10:08, 10 July 2007 (UTC)

70% isopropyl alcohol is 30% water, so presumably would wet it. --TotoBaggins 19:48, 10 July 2007 (UTC)

I'd have thought that would depend on whether the starfish is more or less than 30% water. I'd imagine (though I do not have a source) that an undried starfish would be much more than 30% water. What percent of this particular dried starfish is water, I do not know. Skittle 18:20, 11 July 2007 (UTC)

"Your Face Will Stick Like That!"

If someone continuously wipes their nose so that it is mushed into a "pig nose" shape... or holds it that way to make a stupid face... is it possible for the nose's shape to be altered (permanently or short-term?

• Yes. --jpgordon^∇∆∇∆ 14:37, 10 July 2007 (UTC)

Not sure. I do know that extremely vigorous laughing can cause your face to temporarily be stuck in a smile , I'd assume due to contractions of the muscles. I imagine long term damage nearly impossible though, unless, say, your process scrunching up your nose also includes a sledgehammer to the face, or you bind your nose to grow like that from a young age, such as the old feet binding practices in asia --L^augh! 14:45, 10 July 2007 (UTC)

Possibly, but my intuition says you will have better luck with continuous pressure, an ill-fitting muzzle or somesuch. See lip plate and body modification for some other ideas. -Eldereft 04:33, 11 July 2007 (UTC)

• Artificial cranial deformation allowed for reshaping of the skull, so I'd imagine it's possible with the softer nose cartilage. — RJH (talk) 19:52, 11 July 2007 (UTC)

Question, re: Archaea taxonomy

A few questions, please!

1.) If Archaea is a domain (or sometimes a superkingdom), then why do so many systems refer to Crenarchaeota as a phylum (though some do refer to it as a kingdom)? I personally don't like skipping levels, but maybe there's a good reason to skip over Kingdom.

2.) Some references list the phyla (or kingdoms) of Archaea as: Crenarchaeota and Euryarchaeota; some also include Nanoarchaeota and/or Korarchaeota. Would you think that, if Nano and Korar are not listed as phyla/kingdoms, then their species are currently included in Cren or Eury?

3.) Isn't there some organization that "decides" taxonomy? If not, how is it taught in schools? Just depends on the textbooks' POV?

(Please forgive if my questions are lame, I'm a tech writer, not a biologist.)

Reenie15:12, 10 July 2007 (UTC)

PS, I clicked on a link to ask a question; now it looks like I'm making a comment. I have a reference question!

I'm no biologist - but isn't it the case that Archaea have been moved around in the taxonomy over the last few years (decades)? Maybe you are just comparing sources that are current with books that are somewhat out of date? SteveBaker 23:37, 10 July 2007 (UTC)

Steve: the domain/kingdoms have changed much in thepast 30 years. I'm interested in how to find a consensus on this, if there is one!

There is no one organisation, but taxonomist follow strict Nomenclature Codes. Cladistics have come a long way and is now a more exact science thanks to molecular techniques. I know little about the archaea, but if Nano and Kor are omitted, everything under them is omitted: unless included in the other phyla (probably the case as they couldn't be placed anywhere else). This is a part of the age old lumpers and splitters debate and is very tiresome. Bendž|Ť 09:53, 11 July 2007 (UTC)

Communication in Behavioural Science

Can you critically analyse the place of silence in communication. Mabel

Yes, but your teacher probably wants you to do it. alteripse 15:21, 10 July 2007 (UTC)

Certainly. ... ... ... ... ... ... Clarityfiend 15:58, 10 July 2007 (UTC)

I certainly can. I might use Calvin Coolidge as an example. Edison 18:08, 10 July 2007 (UTC)

Depending on your particular "take" on things, you might want to see our articles on either dead air, Morse code, or 4′33″. The fortress of the Soundkeeper in The Phantom Tollbooth might also prove interesting to you.

Atlant 19:49, 10 July 2007 (UTC)

Nil Einne 22:35, 10 July 2007 (UTC) (sic)

Sure you can. If I tell the following joke:

Knock knock. Who's there? The interrupting sheep. The interrupting sh Baaaaaaa!

I must be careful not to leave too much silence in my performance or the joke falls flat. Timing is critical to much of humor and drama alike. Timing is merely the presence, absence or duration of silences. A poor performer might have silences of the wrong duration or clever use of an appropriate pause can stretch the humor or the drama of the moment. That's certainly a topic for critical analysis. SteveBaker 23:35, 10 July 2007 (UTC)

I'm sure you could refer to the 18 1/2 minute silence in the Watergate tapes for something. Maybe as a "silence for lying by omission"? _{Escape Artist Swyer} ^{Talk to me} _{Articles touched by my noodly appendage} 13:12, 13 July 2007 (UTC)

old dog dilemma

My old Irish setter is 15 which makes her venerable.Her original vet(now retired)administered seven years of delvesteron heat suppresants before retiring,and earlier this year the dog had three mammary tumours removed.She recovered amazingly well,but the new young vets refuse to give delvesteron.Trouble is,dog's now in season(over a month),lovesick and pining for a mate. Vet says hysterectomy. I say how can more hormones hurt now?She surely doesn't have much more than a year to live-however dirty the drug,can it matter now?usually she is happy,lively,sociable,no joint problems.This is an ethical problem.Help!

We can't give medical advice, so I'll just say "go see a different vet". --TotoBaggins 19:51, 10 July 2007 (UTC)

Did you speak to your vet about why he or she refused to give the drug? I see from the factsheet that delvosteron is associated with mammary hypertrophy. This would likely be the cause. Given your dog has already had mammary tumours, it would seem a bad idea to prescribe such a drug. If the tumours were removed and your dog recovered well, why do you assume she only has a year to live? Somewhat OT, but why didn't you spay her rather then take the risk and expense of an unspayed dog with hormone treatement? Nil Einne 22:23, 10 July 2007 (UTC)

Dog#Lifespan_and_old_age says midsize dogs live (on average) 13 or 14 years - it's reasonable to assume that a 15 year old Setter might not live much longer - especially if her health is already on the decline. SteveBaker 23:25, 10 July 2007 (UTC)

But that's average. Admitedly the dog was not spayed so it's lifespan may be below average since I presume the average is for all dogs and sterilised animals tend to live longer (I presume the hormone therapy helps but it not as beneficial as complete sterilisation). Nevertheless while I'm not going to say you shouldn't expect the dog might not last much longer, I don't think you should expect the dog to die in a year or less either especially when it's in apparently good health. IMHO, it would still be better for the poster to at least talk to their vet first, with an open mind and try and get an understanding of why the vet recommends his/her current course of action. If after doing so, and having carefully considered what's been said, you still feel your course is best, think carefully why and try to explain to the vet in these terms. You may find he or she will be much more receptive when you have carefully considered the recommendations and explain why you want to take a different course. Indeed, you may find in doing so you'll be able to convince the vet. If not, he or she may at least recommend you seek a second opinion. If none of this works, you can obviously still seek a second opinion even without your vet recommending it. Perhaps you've already done or this but from the way you phrased the question it just sounds to me like you've made up your mind without really bothering to consider what's been suggested and have just tried to convince the vet to do it, I apologise if I'm wrong. This is likely to be a problem since if the vet, as is hopefully the case has strong ethical reasons based on his/her medical knowledge for feeling his/her course is the best course then when you don't bother to consider the recommended course and instead try and convinice your vet without having considered the course and perhaps without even sufficiently explaining why you feel your course is best (which may be difficult if you haven't heard properly thought about the vet's recommendation) then the vet is understandably going to be concerned and may be unwilling to go against what he/she feels is best. I'm not saying the vet has to be right, simply that IMHO it's wise to properly consider what the vet recommends and why first if you haven't already since there's a good chance he or she has reasons you aren't aware of. Nil Einne 00:31, 11 July 2007 (UTC)

(Vetinary advice != Medical advice : the Wikipedia rules don't apply here) I'd agree that this is a case of 'doing the least harm'. Find another vet who will do what you want. One of our dogs has bad arthritis in all four limbs (he's a VERY large dog) and he finds it hard to walk. The vet pointed out that in the absence of a cure, we must either euthenise the dog or manage his pain - but the continuous dosage of painkillers it takes to get a 150lb dog over this much pain is going to damage his kidneys within a year. Well, they get him up and about and chasing squirrels again - better a year of that followed by death from kidney failure than death now - and better that than years of pain. Losing a dog is a horrible thing - do whatever it takes to make it easier. SteveBaker 23:25, 10 July 2007 (UTC)

Never harms to get a second opinion in any case. I had a budgie with a massive tumour in his abdomen - the first vet I saw said that it was inoperable and that euthanasia was the only option. Not happy with this, I went to another vet who examined him and said that he was prepared to perform the (albeit very high risk of death on the table) op. I figured that if the bird was going to die anyway, then it might as well be during an attempt to fix him that just *might* work. As it turned out, he was pretty much back to normal a couple of days after the op and he lived for another six years. --Kurt Shaped Box 23:34, 10 July 2007 (UTC)

I agree with Steve that keeping a dog comfortable at that age is the most important thing, and if the choice is between putting a very old dog through a fairly major surgery and giving a shot that may or may not cause problems in the future, then ethically a vet has some leeway. I assume you are in Europe since delvosteron is not available in the U.S., and I don't know if they have different laws pertaining to drug use than we do here, but it is much different for a vet than an M.D.: a vet can ethically do something that may sacrifice the patient's health in order to keep it comfortable (euthanasia being an extreme example). However, I will say that I disagree with Steve's assessment of Wikipedia:Medical disclaimer. I don't see why that wouldn't apply to veterinary medicine just as much as human medicine (well, maybe not just as much, but still we shouldn't say "do this to your dog", or "give this medication to your goat"). --Joelmills 23:40, 10 July 2007 (UTC)

Agreed. Don't want anyone coming back at us with lawyers in tow, angry that "WP told me to give this to my expensive pedigree dog and now my dog is dead!". --Kurt Shaped Box 23:48, 10 July 2007 (UTC)

The medical rule is primarily because it's illegal to practice human medicine without a license in most jurisdictions. There is no defense against bad advice causing people harm - we're certainly allowed to give car maintenance advice - "WP told me to put this in the tank of my $100,000 BMW and now my car is broken!". Offering vetenary advice is far less likely to be injurious to our readership. If we omit to tell someone to tighten up the wheel nuts after changing a tyre (or if there were just merely a typo in the torque wrench setting we advised them to use) then they may well die as a result. If we had to protect against all of these things, we'd be unable to give any advice whatever. SteveBaker 05:08, 11 July 2007 (UTC)

Well, we have whatever protection is provided by the various disclaimer notices linked from every page. These include both a Medical disclaimer and a more general Risk disclaimer that says "None of the authors, contributors, sponsors, administrators, vandals, or anyone else connected with Wikipedia, in any way whatsoever, can be responsible for your use of the information contained in or linked from these web pages". The guideline that prohibits medical advice on the RDs is an additional (and sensible) prevention measure around the most potentially dangerous area of advice. Gandalf61 07:36, 11 July 2007 (UTC)

As I understand it, disclaimers are not legally binding in all circumstances. After reading about some of the insane lawsuits that people bring that actually make it to court, I don't doubt that someone will eventually try to sue WP (or a particular user thereof) over a broken car, or suchlike. --Kurt Shaped Box 09:24, 11 July 2007 (UTC)

On further consideration and reading, I agree that veterinary advice should be OK here, since pets are essentially seen as property by the law. My advice is to see a different vet until you're satisfied with either the treatment or the explanation of why the treatment is not possible. I definitely agree with SteveBaker that it's better to potentially shorten the life of the animal in order to avoid having it live with pain. Dogs live in the now. Disclaimer: I have 4 dogs, but have not yet had to deal with any end-of-life issues; I'm still in denial that they'll die at all. :( --TotoBaggins 14:05, 11 July 2007 (UTC)

Interestingly, I see that the reference desk header now says "Do not request medical, veterinary or legal advice. Ask a doctor, veterinarian or lawyer instead." Has it always said that, or did that somehow come out of this discussion? Either way, I don't think that anything that has been mentioned in this discussion really constitutes veterinary advice. Nobody is giving dosage information or offering to write a prescription. --Joelmills 03:16, 12 July 2007 (UTC)

Never mind, I saw the answer over at Wikipedia:Reference desk/Miscellaneous#Why cant medical advice be given here?. --Joelmills 03:28, 12 July 2007 (UTC)

Just to clarify for those using the archives, it's always said medical or legal, but the veterinary was added in response to this [4] and this was later changed to don't ask for profesional advice. Anyway I thought of a better way to explain my earlier thoughts a few days ago but forgot to post. Here goes. If an otherwise healthy 80 year old women from the UK who's only recent health problems were some tumours which successfull removed and which she's managed to recover well from, would you say she probably only has 5 years to live? I wouldn't. We might say she's lived a resonable lifespan and it would surely surprise no onw if she dies within 5 years. But this is different from saying she only has 5 years to live. It's not a perfect comparison obviously, the level of detail about her health condition and how successful the removal of the tumours was would probably be known in far greater then with a dog. And the level of health care available would also be far greater. Nevertheless, I think it does illustrate why it's a bit of a fallacy to say average lifespace = X, therefore A would probably die within Z years. Now I'm not saying we shouldn't do something to the dog because we wouldn't do the same thing to an old woman, that's stupid. I'm simply using it to explain why I think it's a mistake to say the dog probably only has a year to live based on averages Nil Einne 19:47, 15 July 2007 (UTC)

Microwave of Doom

How dangerous is the radation inside of a microwave after the signal has gone off that you can take your food or whatever out? How long after the microwave stops doing it's thing is it dangerous to be exposed to it (i.e. opening the door and sticking your arm in..or putting your face really close)? If someone is in the habit of opening the microwave door during operation, could the amount of radiation from that eventually be damaging?

Microwaves are a form of light. As such they move at the Speed_of_Light. Therefore it doesnt take very long for them to bounce around inside the microwave oven before they are absorbed by the food you are heating. Since the Magnetron automatically turns off when you open the door, an insignificant amount of radiation would be able to reach you. Also understand, the all microwaves do is heat things up, so even if you could get your arm into a microwave and turn it on, it would burn you due to heating the water in your body, as opposed to damaging your DNA which would happen if you were exposed to higher energy light radiation, X_rays or neutron radiation, Gamma_rays. -Czmtzc 17:14, 10 July 2007 (UTC)

Things being heated = higher rate of molecule movement... if this is going on inside your body, would that be an issue?

Yes - look at what happens to a piece of meat when you put it into an oven. That is heating - and that is bad for a live human. Batmanand | Talk 17:28, 10 July 2007 (UTC)

The Microwave oven#Controversial_hazards article has more information about some of these hazards. In summary, you've got more to worry about radiation from your cell phone than a standard microwave. -- JSBillings 19:04, 10 July 2007 (UTC)

Note that that cell phone you hold next to your head puts out 300X the permissible leakage of a microwave oven. I'm not saying it's dangerous, I'm just saying if I were to get worried about microwave radiation, I'd start with the big end and work down.Gzuckier 15:27, 11 July 2007 (UTC)

Body composition

A general ball-park figure is fine. What percent of the human body is water? Thanks. (JosephASpadaro 17:27, 10 July 2007 (UTC))

60-78% Batmanand | Talk 17:29, 10 July 2007 (UTC)

Also, check out this page: Body water. Hope that all helps. Batmanand | Talk 17:30, 10 July 2007 (UTC)

Thanks. You gotta be kidding me? So, if a person weighs 200 pounds, up to 160 pounds of that is merely water? And there is only 40 pounds "left over" for organs, bones, tissue, muscle, fat, etc.? (JosephASpadaro 20:34, 10 July 2007 (UTC))

Bear in mind that a large part of the weight of tissue, organs, muscle, fat, etc (perhaps not bones) is itself water, so "water vs everything else" isn't really a list as you describe it. — Lomn 21:06, 10 July 2007 (UTC)

Not quite. Consider that the individual cells that make up your organs are much like water filled sacks of protein, lipids, and other biomolecules (some arranged into neat little organelles, of course). 151.152.101.44 21:09, 10 July 2007 (UTC)

This seems surprising in part because it's hard to believe that something that's 70% water is anything other than a puddle on the ground! But consider this - a cucumber is 96% water. This large and very solid seeming object is basically just slightly impure water! One of our regular help desk contributors has the Wiki username 'Ugly bag of mostly water'...which is a fair description of most of us. SteveBaker 23:08, 10 July 2007 (UTC)

... sans the "ugly"? (JosephASpadaro 23:16, 10 July 2007 (UTC))

The mythical beautiful wikipedian exists? Nil Einne 00:45, 11 July 2007 (UTC)

Every Wikipedian is beautiful, in his or her own way ........ -- JackofOz 01:40, 11 July 2007 (UTC)

A human body is just a big concentrated jello mold, on one level of abstraction. That's one reason they use gelatin for ballistics testing, for instance.Gzuckier 15:25, 11 July 2007 (UTC)

How to Make Someone Feel Something Without Touching Them

Can anyone explain why this trick works?-How to Make Someone Feel Something Without Touching Them--Foljiny 17:53, 10 July 2007 (UTC)

No evidence was provided that it does work. Edison 18:05, 10 July 2007 (UTC)

I'm sure it'd make me feel annoyed. -- JSBillings 18:39, 10 July 2007 (UTC)

It looks (at first glance) like a combination of at least two factors... the expectation of contact and the movement of eye muscles as the subject tries to focus on the object almost-touching them on the forehead. If this works with the individual's eyes closed, then something else is going on :) ◄Zahakiel► 19:53, 10 July 2007 (UTC)

It probably touches the small hairs on their foreheads, which would cause them to feel a sensation without anything touching their skin.

My brother hates it when I do this to him. I don't think I'm touching any hairs on his forehead. I think it's mostly what Zahakiel says, that there's an expectation of contact. If my brother closes his eyes, he feels nothing. —Bkell (talk) 00:13, 11 July 2007 (UTC)

I haven't got past Step 1: "Retrieve a pencil or use your own finger and retrieve another person". What does that mean in English? -- JackofOz 01:33, 11 July 2007 (UTC)

Obtain a pencil *and* a human for the experiment? --Kurt Shaped Box 01:40, 11 July 2007 (UTC)

This trick does not work. As Bkell mentioned, if the subject closes his eyes, either he will not feel the effect or he may feel that tingling sensation even if there is no pencil near his forehead. It is the expectation. -- WikiCheng | Talk 05:45, 11 July 2007 (UTC)

Step 4 says to "Gently shake, vibrate the pencil back and forth and the person should feel a strange sensation." I would think that the person/victim is feeling little air currents in front of those sensitive little hairs. --JDitto 02:52, 12 July 2007 (UTC)

Noon and the middle of the day

Is there a day (= one of the 365 or 366 slices of the year) where noon falls exactly in the middle of the day (= the period of time between sunrise and sunset)? For example and hypothetically speaking, if the sun rises at 0700h and sets at 1700h then noon (1200h) falls in the middle. Is this possible concerning midnight (0000h) too, ie falling at exactly the time between sunset and sunrise? (cubic[*]star(Talk(Email))) 18:16, 10 July 2007 (UTC)

The article Noon explains this pretty well. Noon is the middle of the day, when the sun is highest. Due to Standard time (Time zones), Daylight saving time, and other things, "clock noon and solar noon hardly ever coincide", but they can and do. If one lives close to one's time zone's central meridian and it isn't currently daylight saving time, solar noon and clock noon should be about the same, if I understand it right. Pfly 18:30, 10 July 2007 (UTC)

You might also enjoy our article on the Analemma (which shows the oscillation of the sun in the sky vis-a-vis a fixed clock-time of day).

Atlant 19:57, 10 July 2007 (UTC)

Yes, four times a year. The article you want to read is Equation of time. The equation of time (which is not an equation but a function) is the difference between true local time and mean local time, and the article explains the rest nicely. Simon A. 19:59, 10 July 2007 (UTC)

I think you mean up to four times a year, depending on location. If you are more than a degree and a bit from your time zone's central meridian, then you probably won't get any. More than a third to a half of a degree away and you might get this happening twice a year. But these might only be approximately in the middle of the day, i.e. on the time zone's central meridian, you might not get the equation of time exactly equal to zero at precisely noon, but that could be being pedantic?

Yes, yiu caught me. I first wanted to write: True local time equals mean local time four times a year but then realized that the questioner asked about zone time, not mean local time. To lazy to dive into this subtlty I decided that the Equation of Time article explains this well enough. Simon A. 07:09, 11 July 2007 (UTC)

To be really picky, at every point in time, the day is either getting longer (if we're between the winter solstice and the summer solstice) or shorter (if we're between the summer solstice and the winter solstice). Hence, if 1200h falls exactly halfway between sunrise and sunset, then it will not correspond precisely to solar noon, the point in time when the sun is highest in the sky! For example, if the day is getting longer, then the period from sunrise to solar noon will be slightly shorter than the period from solar noon to sunset. Someone with an actual background in astronomy should either agree or disagree with me. —Bkell (talk) 00:10, 11 July 2007 (UTC)

That's true, but I'll talk about "local solar noon" here for convenience. Everything I say is true both for local solar noon and for the midpoint between sunrise and sunset, although those do not exactly coincide.

The thing is that at some particular location, the clock time of local solar noon time on successive days might be 11:59:25, 11:59:39, 11:59:54, 12:00:09, 12:00:24, for example. So it does hit 12:00 if you only measure time to the minute, but not exactly 12:00:00 -- but how close it comes is essentially random. It might exactly hit 12:00:00 once ever few years. But if you measure time to the millisecond, you might have to wait a few thousand years before local solar noon was exactly at 12:00:00.000. And if you measure to the microsecond, a few million years.

But all that's for a specific location. If you move west a mile or so (assuming mid-latitudes; the exact distance depends on your latitude), you're still in the same time zone, and now the local solar noon is 6 seconds later. So in this example you do get 12:00:00. And if you want to measure the time to the millisecond and get 12:00:00.000, you just have to measure the distance with corresponding accuracy. So it is true that there are places where the local solar noon occurs at noon by the clock, if you measure to the second: they just aren't the same places each time it happens. And if you measure to the minute, then it happens in lots of places.

There are also places where it never happens, because their local zone clock time the clock time in their particular zone is based on a longitude meridian too far from the place. For example, some decades ago France switched to using time zone UTC 1 (which is local mean time for longitude 15°E) in winter and UTC 2 (30°E) in summer (daylight saving time). But France actually extends from about longitude 5.25°W to about 8.25°E. 15 minus 8.25 is 6.75 degrees, which corresponds to 27 minutes of time, and the equation of time never gets to values that large. So in France they never have local solar noon at noon by the clock. There are several other parts of the world where the same thing is true (they choose to use the same zone time as another place, or a zone time closer to that of another place than they might, for political/economic reasons), notably including large parts of China and Alaska. And daylight saving time can also make it impossible for clock noon to be local solar noon during that part of the year. --Anonymous, July 11, 2007, 00:12 (UTC).

A note on terminology. When discussing time, the word 'local' indicates that we are talking about the time as specified by the sun viewed from the current place. 'Zone time' is the time we usually use. 'Local zone time' is hence a confusing oxymoron even though 'local time zone' sound reasonable. Furthermore, true local time is defined as the time given by a sun dial, i.e. whenever the sun passes through the meridian (in astonomy, the meridian is the thought line from the south point on the horizon through the zenith to the north point), it is by definition 12:00 h true local time. The time from true noon to true noon is not exactly 24:00:00 h (i.e. sundials are clock with varying speed), and this is why we define a mean local time to allow clocks run at constant speed. The mean local time a zero longitude is defines as GMT. Simon A. 07:09, 11 July 2007 (UTC)

On the first point, thanks; I've corrected my wording above to avoid the confusion. As to "true local time", I don't think this is a commonly used name for this concept. I think "local solar time" is what I usually see for it, although Wikipedia's Solar time article goes with "apparent solar time". --Anon, July 11. 22:30 (UTC).

Stomatal Density and Transpiration

Is it correct to assume that the relationship between stomatal density and the rate of transpiration is such that as the stomatal dessity increases, the rate of transpiration also increases. How is this explained, and is this true for all species of leaf? Thanks, 86.142.230.63 20:59, 10 July 2007 (UTC)

astronomical device

I am trying to find the name of a divice thats similar to a mobile with planets on but mimicks the position and rotation of the in relation ot the sun the name of the developer and its modern nameor the device if possible.

An Orrery is what you are looking for. DuncanHill 21:45, 10 July 2007 (UTC)