Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

February 27

can hydrostatic testing damage household pipes?

I understand that hydrostatic testing is a method for testing pipes for leaks. There are a number of plumbing companies that offer diagnostic services where they run water into the plumbing system via the sewer line and then monitor the pressure to see whether any leaks could exist underneath the house. My question is whether introducing pressure to a system of pipes (particularly those of an older, 1940's era house) could actually induce a rupture that would then be interpreted as an existing leak -- thus costing money to "repair" the defect. Does anyone have references on such an issue? —Preceding unsigned comment added by 64.91.177.4 (talk) 00:25, 27 February 2009 (UTC)

If there is already a weak spot in the pipes, then hydrostatic testing can convert the weak spot into a leak. However, if the pipes are already that weak, then ordinary events (fluctuations in supply pressure, or water hammer from closing a faucet too quickly) can also cause the weak spot to leak. --Carnildo (talk) 00:59, 27 February 2009 (UTC)

Applying higher than normal presssure to any system of pipes could certainly be the cause of them breaking. A stress test can cause the tested system to break. If if has a leak, the test might help locate it. If it is about to fail, the test could demonstrate that. But a pressure test is not a nondestructive test, since it can cause a marginal system to fail sooner than it would have. I could see hydrostatic testing as a useful acceptance test on a new system. Ask yourself if there is any way that applying high pressure to an aged system could improve it? Edison (talk) 01:55, 27 February 2009 (UTC)

Probably could damage the pipes; if someone wanted to sensibly check I can think of two ways offhand. Attach a pressure meter to an open tap, then close the valve to the mains. Wait and see if the pressure drops due to some leak somewhere. The other method is to close the valve to the mains and lower the pressure at an open tap with a pump, air will invade a leak and become obvious. Polypipe Wrangler (talk) 06:51, 3 March 2009 (UTC)

Macdonald 80 Shopping Center

Can anyone help me find references for Macdonald 80 Shopping Center ?, maybe in the East Bay Express, Contra Costa Times, West County Times, San Francisco Chronicle, Richmond Globe, Richmond Post, KTVU, KRON or any local affiliate of the broadcast channeles, NBC CBS FOX Univisión, etc. Richmond City Council minutes, the developer. Any help would be great!Troyster87 (talk) 02:25, 27 February 2009 (UTC)

Isn;t that a little backwards? Before deciding if the shopping center merited an article, shouldn't you have gathered your sources first? I mean, there is a very good chance that those sources don't exist at all... See WP:YFA for the proper way to build a new article, and notice that the first step, befre writing, is to gather references. Also, what is this doing at the Science Ref Desk???--Jayron32.talk.contribs 02:44, 27 February 2009 (UTC)

Engineering is a science, and this is an engineering project, and article about it, where should i have asked? and the sources exist, i have seen them. i just can't locate them, but it was reported in some of those newspapers and on websites. i am not questioning the notability, as it is a notable place, furthermore there is a precedent for this sort of article and nearly every other shopping center, district, and mall in the bay area has an article. some much smaller and far less notable!Troyster87 (talk) 00:25, 28 February 2009 (UTC)

I don't know about all that. I just know that, before I sit down to write a research-based document, I want to have the sources in front of me before I start writing. It seems a little bass-ackwards to create an article under the "I read this somewhere I think so I'll just go ahead and write all of this down." This has nothing to do with any of the other equally poorly thought out articles you may or may not find at Wikipedia. You wanted to know about your article. What you should have done before creating your article is to gather your sources first, and then used them to write your article. Just diving off the deep end and creating an article on the "maybe I can find something about this later" mentality is the cause of nearly every deleted article. People who do it the right way, by having their sources first, never get their articles deleted. If you contact the news sources you have listed, they likely have archives and concordances and things like that, and should be able to direct you to the right issues where the information is located. Just contact the newspaper and ask for the research department. Then explain that you are looking for articles about this shopping center. They can direct you to the right issues where you can find information. --Jayron32.talk.contribs 03:30, 28 February 2009 (UTC)

Psychological effects of norepinephrine

What are the psychological effects of norepinephrine? NeonMerlin 03:46, 27 February 2009 (UTC)

Did you read Norepinephrine? Or your textbook? --Shaggorama (talk) 04:14, 27 February 2009 (UTC)

I did read Norepinephrine, and it doesn't say anything about psychological effects. NeonMerlin 00:36, 2 March 2009 (UTC)

I hope this Q doesn't put you to sleep...

Is there a device that can detect when a person is asleep ? My Dad seems to have narcolepsy, and falls asleep all the time during a conversation, then wakes up later and continues as if he never dropped off. The issue is with him trying to watch a movie. He is likely to fall asleep several times during the movie, but not realize when, or even that, he fell asleep. At the end he says "that movie was terrible, I couldn't follow the plot at all". It would be nice if there was a device that could detect when he falls asleep, hit the pause button, then unpause when he awakens (although he could do this last part himself, I suppose). He used to enjoy movies, and maybe he could again in this way. StuRat (talk) 04:24, 27 February 2009 (UTC)

I can't think of what it's called, but I remember once seeing a device that kind of hung off your ear and if your head fell to one side it would beep. I think it just had a motion sensor in it, simple, yet probably effective most of the time, as long as your head's not propped up. I don't know if waking him is what you're after, but this is a start at least. I'll post a link if I find it. -Pete5x5 (talk) 05:31, 27 February 2009 (UTC)

This is on the right track. Next I need a variant of this device that can send a signal to a robotic hand that can press a pause button. Any thoughts ? Could I open up the ear device and connect a wire from it to a robotic hand ? StuRat (talk) 14:26, 27 February 2009 (UTC)

Polysomnography --Mdwyer (talk) 06:34, 27 February 2009 (UTC)

Yes, an electroencephalogram (EEG). You probably should read "The Promise of Sleep" by William DeMent, ISBN 0440509017. It discusses the issues you're asking about extensively, mentions treatment options, etc. 207.241.239.70 (talk) 06:48, 27 February 2009 (UTC)

Does his doc know and is/was he taking any medication? Some meds like Zolpidem, Thalidomide, antidepressant (stopping those)etc. can have sleep disorders as side effects. His physician could then send him to a sleep center if necessary. I think this is what Pete was looking for [1]. They tested something similar on truck drivers at a shipping agency I had a project at. They ended up not using it because lots of drivers didn't like it. 76.97.245.5 (talk) 08:36, 27 February 2009 (UTC)

Narcolepsy is a rare cause of excessive daytime somnolence. There are several more likely reasons why your dad is falling asleep. If this is a problem for him, I recommend referral to a sleep specialist. Axl ¤ [Talk] 08:32, 27 February 2009 (UTC)

I thought narcolepsy WAS excessive daytime somnolence. That is, I thought it was a symptom, not a cause. It is most likely a side effect of one of his many medical problems (prostate cancer, kidney failure requiring hemodialysis, diabetes, etc.) and the meds he takes to fight them, but stopping those meds isn't an option in most cases, so we need to find a way to live with this condition, instead. StuRat (talk) 14:26, 27 February 2009 (UTC)

If you believe that your dad has a medical condition such as narcolepsy, you should advise him to seek information from qualified medical professionals, such as a doctor, and not random strangers on teh intrewebz. If he genuinely has a problem, then doctors can prescribe devices or medicine to help him. --Jayron32.talk.contribs 15:32, 27 February 2009 (UTC)

[To StuRat] Narcolepsy is a diagnosis of itself, with specific recommended treatment. It is only one of the causes of excessive daytime sleepiness. Axl ¤ [Talk] 15:40, 27 February 2009 (UTC)

Some cars have been shown (mostly a 'concept cars') with devices that detect when the driver is falling asleep at the wheel. I believe they have cameras that look at your eyes and check things like blink-rate and duration. I have yet to see one sold commercially though. This paper talks of using heart-rate changes to predict when someone is about to fall asleep while driving. Following the references from that paper might yield something useful. SteveBaker (talk) 16:32, 27 February 2009 (UTC)

Going back to the ear device, instead of getting it to activate a robotic arm you could instead get it to send an RF (radio frequency) signal to an RF repeater, changing the signal to IR, and pausing the DVD player. My dad designs and creates custom remote solutions, so I know this is possible, you'd just need to butcher an RF remote and somehow get the device to activate it. Getting the parts shouldn't be hard, but it will be moderately expensive (A good, reliable remote that's RF will run you $200, an RF repeater is about $60, and then the cost of the device (these costs in Canadian dollars)). It'd be really cool if you did it, but it would be a lot of trouble. -Pete5x5 (talk) 19:40, 27 February 2009 (UTC)

That is getting pricey, and I have no problem with wires. Is there a cheaper way to do it with wires ? StuRat (talk) 22:15, 27 February 2009 (UTC)

Well, if you have some kind of device that'll reliably detect when he falls asleep - it should be very simply to modify a 'universal' TV remote to pause the TV. Presumably there is no need to automatically unpause it since when he wakes up - he'll see that the video has paused and realise. He can then un-pause it himself. The only issue is that most DVD/VCR's will drop out of pause and simply stop playing after a couple of minutes. But assuming that's not such a huge deal - you can usually 'train' a universal remote to produce any command on any button. Carefully dismantle the remote - remove all of the buttons - you'll see the two copper 'pads' beneath that the button will connect when you press it. You'd carefully solder a thin wire to each pad and connect them up to either a small relay or an opto-isolator (both parts you can get from RadioShack for a few bucks)...whatever signal comes out of your 'sleep detector' can be used (possibly via a transistor) to drive the relay or opto-isolator to 'connect' the two pads on the remote just like you'd pressed the button yourself. No robots required! However, the means of detecting sleep may be tricky. Does his head change position as he 'nods off'? If so, something as simple as a mercury tilt-switch would work (you find them in old air conditioner thermostats for example). Something like that could be connected directly to the remote's button pads with no other electronics whatever. SteveBaker (talk) 03:26, 28 February 2009 (UTC)

Before you shovel out money on parts for a modification you should first try and see if it works at all. Automatism would have him lose awareness, but the ordinary signs of sleep would not result. A device that reacts to him literally "nodding off" would be useless if his neck muscles didn't get the information that the consciousness was taking a break. I was by no means trying to imply above that he should stop taking his medication. (Some substances can cause sleep disorders when stopped rather than while taken, actually) You should inform his doctor, because he may need to know and apparently your dad's not aware of what's going on. There's an off chance that he could switch your dad from product A to product B, or add pill C to your dad's regimen and things might improve for a bit or at least be kept from deteriorating. Sounds like, in the longer term, you should cast around for things that keep your dad occupied and allow for him to be absent for a bit, or keep his acuity up for the duration. See if he likes puzzles or playing games. --76.97.245.5 (talk) 22:30, 27 February 2009 (UTC)

A doctor can prescribe a sleep study at a hospital. to see if someone has some condition such as Sleep apnea, which is sometimes treated by a CPAP. As for falling asleep during a movie, the proof of it is starting the movie from the beginning when the person is well rested and having him note where material appears that he does not remember from having watched it. One might also sometimes point out the red stain from where the glass of merlot spilled, depending on the cause of the somnolence. The mind is good at filling in when the person sleeps through part of a movie, just as the brain fills in the blind spot in a visual image, and does not see a hole. For people who fall asleep while sitting up, the dropping of the chin on the chest cold be a way to activate a switch which pauses the movie and administers a painful shock to the rear. A Snore detector might also be useful in operating the pause control. Edison (talk) 01:57, 28 February 2009 (UTC)

A cheaper modification to my way still includes the ear thing (as I think that's one of the few, and probably least expensive, reliable methods of detecting when he's asleep. You could just take apart a cheap, Wal Mart style universal remote ($30?), and take out the part that mimic's the IR signal of other remotes. Then 'program' your remote's pause button in (probably just hold it in front of the receiver and press the pause button). Then have an IR transmitter with a wire connected to it ($1.00?) connected to the ear piece and the other end glued to the front of the DVD player, where the sensor is. The wires on the transmitters (at least the ones I have) are 12 ft. long, so that should suffice, or it can be extended. It would be annoying having a thin, black, almost invisible wire going across the room, but other than that it's inexpensive, and overall more reliable than wireless. I'd really like to see you build this contraption, it'd be very cool. I have no doubt that it can be done, you just need to be very good at taking things apart, and have a lot of electrical tape! Alternatively, I just thought that you could tape down the pause button on your remote, then have your dad put his head in the way. If he falls asleep and his head falls, the signal will no longer be blocked and the movie will pause. You'd probably want to get a cheap universal remote for this method too, so that he doesn't have to move the constantly pausing one to un-pause it when he wakes and risk putting in back in the wrong spot. You'd also need rechargeable batteries, or it would get equally costly eventually. -Pete5x5 (talk) 07:22, 28 February 2009 (UTC)

Anybody is answering it?????

What actually are the cyanides? —Preceding unsigned comment added by Achraz (talk • contribs) 05:02, 27 February 2009 (UTC)

Did you read our article on Cyanide? --Jayron32.talk.contribs 05:06, 27 February 2009 (UTC)

That's why I was always afraid to breathe the air in the CN Tower. :-) StuRat (talk) 05:09, 27 February 2009 (UTC)

Possible; his account was just made today and he's already made 3 ref desk posts (even though I don't know who you're talking about when you say Freewayguy). I think we have to assume good faith and try to help unless you KNOW this is someone evading a block. -Pete5x5 (talk) 05:22, 27 February 2009 (UTC)

In fact, the top of this page specifically says "Be polite and assume good faith, especially with users new to Wikipedia."  ;) -Pete5x5 (talk) 05:25, 27 February 2009 (UTC)

For those confused by the above conversation, note a post was removed by the poster [2] Nil Einne (talk) 09:39, 27 February 2009 (UTC)

Doesn't seem like Freewayguy to me. --Tango (talk) 12:20, 27 February 2009 (UTC)

wavefunction in quantum mechanics

we know that not all wave fanction are allowed wave fanction in quantum mechanics only those wave fanction that satisfy schrodinger equation and also they are wellbehaved.But if it is not wellbehaved then what difficultise arise?Supriyochowdhury (talk) 08:18, 27 February 2009 (UTC)

If you expect the wavefunction to be a probability amplitude, you'd hope that it is square integrable and therefore normalizable. Vespertine1215 (talk) 10:14, 27 February 2009 (UTC)

Rear Axle

Which is the most critical part in rear axle ? —Preceding unsigned comment added by 59.98.178.48 (talk) 11:31, 27 February 2009 (UTC)

This looks suspiciously like a homework question. In order to answer this question, we need all the information above the question: Is it a car, wagon, train...? It is a front wheel drive or rear wheel drive? Are there any modifications such as a limited slip differential? -- kainaw™ 14:02, 27 February 2009 (UTC)

If we're talking about rear-wheel drive vehicles - then the most complicated bit is undoubtedly the 'differential'. But the most 'critical' part? Well, I guess it's all pretty critical...you can't really do without any of it. On a front wheel drive vehicle, the rear axle is generally a rather simple affair - and in some there actually is no rear axle at all with the rear wheels mounted directly onto the frame with no connection between them...so in that sense, none of the rear axle is 'critical'. Perhaps you could explain in more detail what exactly it is that you want to know? SteveBaker (talk) 16:24, 27 February 2009 (UTC)

Rear Axle rework

In which section rework is allow ? —Preceding unsigned comment added by 59.98.178.48 (talk) 11:37, 27 February 2009 (UTC)

I'm afraid your question is not understandable. Specifically the word "rework" does not make sense in the context of your question. Your IP address is in India, so I am going to proceed on the assumption that English is not your native language and that you may speak Hindi. If by "rework" you mean गृहकार्य which (I hope) is "homework" in English, there is no section of the Wikipedia reference desk that will answer your homework questions for you. However, the respondents on the reference desk will be glad to help you:

• Interpret your homework questions if you do not understand their meaning
• Help you understand the ideas and concepts
• Attempt to point you to resources that may help you answer them

By the way, I used this Hindi-English dictionary to find the Hindi word for homework. I apologize if I was wrong in assuming you spoke Hindi. I know India has many different languages. Other refdeskers, if I used the wrong Hindi word for homework, please correct it inline. Sifaka ^talk 02:07, 28 February 2009 (UTC)

I think rework means repair, my advice is consult a mechanic.Stevej000 (talk) 17:07, 2 March 2009 (UTC)

Moth question

In the book Silence of the Lambs, a moth species that feeds solely on lachrymal fluid is mentioned. Does such a species of Lepidoptera (spelling?) actually exist? If so, what is its name? 65.167.146.130 (talk) 14:38, 27 February 2009 (UTC)

If I remember correctly, the moth in question was the Death's-head Hawkmoth, which feeds on honey from beehives, according to our article. I am not sure if Thomas Harris conflated the Death's-head moth with another moth, or as is more likely, simply invented the idea out of whole cloth. --Jayron32.talk.contribs 14:59, 27 February 2009 (UTC)

The Asian moth Lobocraspis griseifusa feeds on the tears of water buffalo. Some moths slip their probosces under the eyelids of sleeping birds to feed. It's interesting to note that a character in a sequel drinks the tears of children. --Sean 15:23, 27 February 2009 (UTC)

I guess the question then is "How does the moth make the water buffalo sad?" I got a million like this...--Jayron32.talk.contribs 15:43, 27 February 2009 (UTC)

You need some gnu material. :-) StuRat (talk) 18:10, 27 February 2009 (UTC)

I think Jayron's material is pretty good, especially if the audience has never herd it before. :-) 10draftsdeep (talk) 20:47, 27 February 2009 (UTC)

My aunt never liked that punny sort of humor, but my ungulate it up. --Sean 21:15, 27 February 2009 (UTC)

I wanted to contribute my own bad buffalo pun, but I don't anoa good one to use. --98.217.14.211 (talk) 22:41, 27 February 2009 (UTC)

I suspect that poking the water buffalo in the eye would cause it to water. Thanks for the answer, hopefully an article get created on this moth at some point. 65.167.146.130 (talk) 15:53, 27 February 2009 (UTC)

Shouldn't this question be at the Moth desk :-) Fribbler (talk) 15:59, 27 February 2009 (UTC)

grooooaaannnnnn :) Livewireo (talk) 21:49, 27 February 2009 (UTC)

I strenuously oppose levity on the Ref Desk, and I will not be cowed by anyone. That's no bull. We should not give anyone a bum steer. Edison (talk) 01:49, 28 February 2009 (UTC)

You're just trying to buffalo buffalo off the Science Desk... Nimur (talk) 04:51, 28 February 2009 (UTC)

Glutathione

How can you do to increase glutathione in the cells? It is true that 500 grams of vitamin C increase the glutathione in the cells by 50%? Thank you very much. —Preceding unsigned comment added by 151.65.126.7 (talk) 16:39, 27 February 2009 (UTC)

Our article glutathione mentions methods of supplementation. A google search of Vitamin C and Glutathione turned up this paper which found that mean red blood cell glutathione rose nearly 50% when subjects took doses of 500 milligrams (not grams) for 2-3 weeks. The authors also found that increasing the vitamin C dosage to 2000 milligrams (i.e. 2 grams) did not have a significantly different effect on glutathione levels compared to 500 mg. Sifaka ^talk 00:57, 28 February 2009 (UTC)

How to compare more than 5 products at biocompare.com

I am trying to compare the available unconjugated antibodies to human beta-actin, of rabbit origin for use in Western blots. When I perform a search using these parameters, the results are many. When I attempt to 'select all' and click 'compare', I am confronted with the message 'You are trying to compare more than 5 products. Please log in to add these to your selected products or reduce the number of products selected", or something to that effect. I am signed in, but there is no indication as to how I should "add these to my selected products" nor how this would help me achieve my aim of discerning which source of antibodies is the cheapest. Thanks in advance to anyone who might collaborate with me in elucidating this function of BioCompare. :) --129.125.137.62 (talk) 16:40, 27 February 2009 (UTC)

This is a common problem I have with the Compare function on many consumer websites. Some approaches I've tried:

1) Eliminate some items prior to use of the Compare option. This can be done using those attributes that are listed outside of Compare. In some cases, it's possible to sort by those characteristics, such as price, so you can eliminate some.

2) If you still have too many left, Compare them 5 at a time (or how every many are allowed), and then eliminate all but the best from each batch. Then Compare the best from each previous Compare.

BTW, this would have been an excellent Q for the Computer Ref Desk. StuRat (talk) 18:00, 27 February 2009 (UTC)

Homo sapiens

I know that homo sapiens are the only species within the homo genus still living. I find this curious. How common is it to only have one species within a genus in the animal kingdom? A Quest For Knowledge (talk) 17:56, 27 February 2009 (UTC)

Species and genus is an invention of the people that categorize life based on their own crietria. It is actually mostly arbitrary, and you will not easily find much common agreement between taxonomists on what constitutes distinct species within one genus, subspecies of the same species, different genuses, etc. etc. There's only one "Homo" species because someone decieded there was. You will often hear that breeding compatibility defines a unique species, but there are clear examples of where this falls down; for example what about three animals, A, B and C. Lets say that Animal A & B can breed to produce viable offspring, and B & C can breed to produce viable offspring, but that A & C cannot breed to produce viable offspring. Well, under the standard definition of species, A & B are the same species, B & C are the same species, but A & C are NOT the same species. So how do you classify them??? Depending on whose classification system you use, you will likely find THOUSANDS of single-species genuses. Look at Tuatara for an extreme example. It is an order that consists entirely of two species. --Jayron32.talk.contribs 18:23, 27 February 2009 (UTC)

Yes, but there used to be at least another dozen species under the homo genus. All are extinct except for us. To put it in another and less scientific way, there are lots of dog breeds (Shih Tzu, Pit Bull, German Shephard, etc.) but only one 'breed' of human. How common is this in the animal kingdom? A Quest For Knowledge (talk) 18:49, 27 February 2009 (UTC)

Just to clarify a little bit more, I understand that species can be classified in many ways depending on who is doing the classifying. This has come up before. I guess what I'm getting at is that our closest living relatives are the chimps and they seem to be pretty distant cousins. I'm wondering how unique humans are in not having any other close relatives still alive. I mentioned genus because it seemed the most succinct way of asking it. A Quest For Knowledge (talk) 19:10, 27 February 2009 (UTC)

Weeeeeell, to go back to pedantry and anthropocentrism... :) But seriously, have you seen the discussions on whether chimpanzees and humans should really be in separate genera? 79.66.56.21 (talk) 19:02, 27 February 2009 (UTC)

No, do you have a link you can point me to? A Quest For Knowledge (talk) 19:12, 27 February 2009 (UTC)

Check out The Third Chimpanzee by Jared Diamond. It's been a while since I read it, so I don't recall how serious Diamond was in his assertion or whether it was more or less to make the point that chimps and humans are very closely related indeed. According to the book, the Pan genus was named first, and so would have precedence over Homo, should the two groups be merged. The second chimpanzee, for those not familiar with primates, is the bonobo or "pygmy chimp". Matt Deres (talk) 21:28, 27 February 2009 (UTC)

Also, take a look at the various articles on race.--Shantavira|^{feed me} 19:08, 27 February 2009 (UTC)

To my knowledge no reputable scientist today thinks that the races come from different species of any sort. --98.217.14.211 (talk) 01:38, 28 February 2009 (UTC)

Breeds of dog are different types of the varieties of the same species. They aren't unlike humans of different races, or even just different hair colours/heights/builds. There is more variation between breeds of dog than humans, at least visible variation, but that's only a difference of degree. --Tango (talk) 19:28, 27 February 2009 (UTC)

The question here isn't so much about the vexed question of "What is a species?" - which we've addressed at length many times before (Conclusion: It's a vague term...sorry 'bout that!). This question is "What is a Genus?". If humans are the only species in our genus - what defines that term in such a way as to prevent other species such as the chimpanzee from being a part of our genus - or conversely keeps us out of the same genus as the other great apes? I suspect the answer will boil down to not upsetting the religious nuts...but perhaps there is a better reason.

Our article Genus says:

The rules-of-thumb for delimiting a genus are outlined e.g. in Gill et al. (2005). According to these, a genus should fulfill 3 criteria to be descriptively useful:

• monophyly – all descendants of an ancestral taxon are grouped together;
• reasonable compactness – a genus should not be expanded needlessly; and
• distinctness – in regards of evolutionarily relevant criteria, i.e. ecology, morphology, or biogeography; note that DNA sequences are a consequence rather than a condition of diverging evolutionarily lineages except in cases where they directly inhibit gene flow (e.g. postzygotic barriers).

Sadly, my knowledge of biology fails me at this point. However, I understand there to be a strong case for renaming the Common chimpanzee and the Bonobo 'Homo pan' and 'Homo paniscus' - thereby making them be the second and third extant species in our genus. Then we can arm-wrestle the chimps to see who gets to be type species for the genus....hmmm - maybe we'd better make that 'speed chess' - they'd probably beat us at arm-wrestling.

SteveBaker (talk) 19:50, 27 February 2009 (UTC)

The problem with that definition of Genus is that it is still open to interpretation. What makes two extinct individuals or groups part of the same ancestral taxon? What if new discoveries lead us to want to split a taxon into two new taxons? What happens to the genera below that? What kind of expansion does a genus need? What needless means to one person is different than another. What makes a criteria "evolutionarily relevent" with regards to saying "these two examples are from different genera or from the same genus?" Ultimately, we justinvent these "rules" for classification (which still are themselves open to the subjective interpretation of the individual).

Its not much less arbitrary than how I decide to organize my CD collection. Do I organize it by genre or alphabetically by artist? Do I intermingle Jefferson Starship with Jefferson Airplane or are they seperate? Is Jane's Addiction funk-metal, or alternative-rock? Ultimately, the whole concept of taxonomy is a human invention, created for the convenience of organizing our knowledge of living things. Insofar as it helps us find commonalities and difference among all life, it is a useful thing to classify; but as with ALL classification systems, no set of rules will cover every eventuality, and there will always be a level of arbitrariness to it. Ultimately, "because someone just decided it would be this way" ends up being the biggest justification for deciding how to classify one animal or another into one taxon or another. --Jayron32.talk.contribs 20:47, 27 February 2009 (UTC)

A similar case to humans might be the horseshoe crab, which, despite it's name, is only distantly related to crabs. There are 4 known species of horseshoe crab, but those may be the only species left in their genus, family, or even order. Similarly, the coelacanth, of which there are 2 known remaining species, are the only known survivors of their genus, family, order, and even sub-class. The bowfin appears to be an example where only one species is known to exist in the genus. See living fossil for more examples. StuRat (talk) 21:52, 27 February 2009 (UTC)

Articles more specific to the reduction in the number of Homos walking around at the same time: Neanderthal#Neanderthal_extinction, vs. Multiregional origin of modern humans. Personally I would not have been surprised if Sapiens killed off any others. Our species appears to have never been good with strangers, much less ones who would pose a much more severe threat than many of the animals of the time. --98.217.14.211 (talk) 01:38, 28 February 2009 (UTC)

You also have to be VERY careful if you try to use dogs as an example in any discussion of this sort. Dogs are quite unique in that they are thought to be the oldest domesticated animals and humans have been selectively breeding them for thousands of years, that's why they're called "breeds" of dog. The thing is tho, unlike natural selection, human selection relies purely on traits that we can see, which turn out to be only a superficial fraction of the genetic material that actually "makes" a species. So selective dog breeding has created an incredibly diverse number of physically distinct breeds, much more so then you would find anywhere in nature, especially in the relatively short time, however, genetically the dog "breeds" are still practically identical. Vespine (talk) 12:12, 28 February 2009 (UTC)

Yes, I was afraid my dog breed comparison might derail things a bit. I was just trying to understand how rare it is in the animal kingdom for a species not to have any living close relatives. Koala bears appear to be in similar situation. Part of what was driving my question was me wondering whether homo sapiens intentionally killed off rival homo species. A Quest For Knowledge (talk) 01:41, 1 March 2009 (UTC)

I read a hilarious article a few years ago on how eager people generally are to attribute the Neanderthal extinction to us killing them off, rather than them just not making it. Wish I could find it again :) 79.66.56.21 (talk) 02:01, 1 March 2009 (UTC)

I'm surprised this has not been mentioned yet but we need to remember one of the reasons why there are no seperate humans species is because our migration patterns and high interbreeding has meant few what we can classify as seperate species have been able to develop. In terms of the comment on 12 difference species, what you've missed is that most of these predate Homo sapiens sapiens. In other words, many of them may be just our ancestors. I'm not sure how many are not (Homo neanderthalensis is one) but for example Homo rhodesiensis says it is "it is probable that Homo rhodesiensis was the ancestor of Homo sapiens idaltu (Herto Man), which would be itself at the origin of Homo sapiens sapiens" which is what I would expect for a number of them. Even those which aren't one of our ancestors if they died before we even came into existance, you can't really say 'we' had anything them with their demise per se. And this leads me to my second point, the biggest problem is beyond the already inherent problems in taxonomy, labelling extinct species is even more problematic. While there is still debate over things like punctuated equilibrium I think basically every evolutionary biologist and taxonomist will agree that there is no clear cut line between Homo sapiens sapiens and whatever ancestor we care to name that predated it say Homo sapiens idaltu, the same for idaltu vs Homo rhodesiensis. Given the problems in taxonomic classification that already exist, combined with the problem classifying ancestorial species, you can hopefully easily see why saying that there are other Homo species simply because we have ancestors which we can choose to classify as different species is meaningless. (Some biologists suggest we shouldn't bother to classify historically extinct species or at least we should only view any classification as having any degree of meaning when we are comparing species at a fixed point in time). Leading back to the tuatara, since Sphenodontia once had many different species and this was likely at a distinct point in time (The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago) and "Although tuatara are sometimes called "living fossils", recent taxonomic and molecular work has shown that they have changed significantly since the Mesozoic era" do you see why the idea that Homo sapiens sapiens is unique because we've classified some of our ancestors as difference species is meaningless? Nil Einne (talk) 03:02, 1 March 2009 (UTC)

It's undoubtedly true that there was never a distinct 'break' between the ancestors of modern man and us. If we had always had one decent male and female, adult hominid fossil from every (say) 1000 years from a few million years ago until today - all set out in a neat line - we'd probably never consider an effort to draw a line to distinguish Homo sapiens idaltu from us. However, it is in the nature of archeology that we only find good examples that are widely separated in time - often they are just fragments of bone and we may be uncertain of the age, health or sex of the individual that this represents. These scattered snapshots are clearly and dramatically distinct from each other (although you can still lay them out in a row and see a progression of change). This leads us to want to attach labels to each one - because they ARE quite different and distinct. Identifying them as separate species seems the natural way to do that. However, this tendancy to name things like that in no way alters what we believed happened along the way. SteveBaker (talk) 16:50, 1 March 2009 (UTC)

Maybe this is a fringe theory, but there are people who believe that some cryptids exist, and, in effect, that some of these cryptids are actually other species in the homo genus that had not gone extinct. However, since this is categorised as an "extraordinary claim", scientists will usually reject the possibility. ~AH1^(TCU) 01:36, 2 March 2009 (UTC)

If Homo floresiensis (the "Hobbit") turns out to be a true species then since they were around as recently as 18,000 years ago (and possibly as recently as 12,000 years ago - and according to some reports as recently as the 1800's!) - they would certainly have been an example of a second member of the Homo genus - and one from which modern humans could not have been descended. But the jury still appears to be out on that one. SteveBaker (talk) 05:15, 2 March 2009 (UTC)

Bornholms Disease

Request for medical advice removed

Please note that the Wikipedia Reference Desk cannot provide medical advice. You should speak to a health care provider. - Eron^Talk 22:38, 27 February 2009 (UTC)

We can't but we could at least help the user find related information on wikipedia. (Going with our library analogy, your librarian would also not send you to your doctor if you asked where they have a book on condition XYZ.) The quality and relevance of that information is up to the reader to determine.:

The page you linked has a link to Coxsackie B virus on it. That has a bit more on treatment and a reference to a report on homeopathic treatment. The latter is also only symptom relief, though. A bit on using wikipedia: If you click on a blue word it will get you to a page that is related. To link to a wikipedia page here copy the page name and enclose it in two angled square brackets [[]].76.97.245.5 (talk) 23:01, 27 February 2009 (UTC)

I believe this was incorrectly removed as a request for medical advice (see discussion here: Wikipedia_talk:Reference_desk#.28Possible.29_Medical_advice_question_removed_-_Bornholms_disease) when it's simply a request to improve our article on Bornholm disease. As such, I have added your request to the talk page for that article: Talk:Bornholm disease#Article Improvements Needed. StuRat (talk) 17:55, 28 February 2009 (UTC)

I have done a little work on the Bornholm disease article, more input from others would be welcome. --Scray (talk) 12:07, 2 March 2009 (UTC)

Thanks. It's starting to look a bit better. StuRat (talk) 15:00, 2 March 2009 (UTC)

February 28

Using neutrinos for communication

Glass Earth, Inc. is a science fiction short story by Steven Baxter. The technology part of it hinges on an invention to speed up global communications. Instead of sending signals via surface lines wrapping the globe, or bouncing them to a satellite and back, the company has hit on a way to control how neutrinos change their status, I think in the story it's their "flavor". They use a particle accelerator to produce collisions that send a stream of neutrinos in a straight line through the center of the earth and to the antipodes. Besides the accelerator, the only installation required is the detector at the other end. By modulating the neutrino states as if they were voltages, the information is transported.

I found that a fascinating conceit. Is the science simply wrong, as in it violates a fundamental constraint of nature, or could this in principle be done pending future advances?--Goodmorningworld (talk) 03:46, 28 February 2009 (UTC)

Creating neutrinos is relatively easy, although I'm not certain what degree of control one could have over their states. But the problem is that the same thing that makes neutrinos able to pass straight through the Earth with negligable loss make them almost impossible to detect: They almost never interact with anything. Neutrino detectors are notoriously massive, and maybe someone else can answer whether it's even theoretically possible for them to be small. Someguy1221 (talk) 04:56, 28 February 2009 (UTC)

AFAIK Cherenkov radiation offers a nice way of detecting neutrinos. You need a transparent medium (e.g. water) and lots of detection devices. You need that much of your transparent medium because it increases your chances of getting some results. Another way is to count collision products. The Homestake Experiment used a chlorine solution. Again you need lots of it to catch the few reactions. The guys at the Cowan and Reines neutrino experiment created 5×10¹³ neutrinos per second per square centimeter and were able to detect only 3 reactions per hour as a result. Don't know about the "relatively easy" part when it comes to creating neutrinos for a communications device. Neutrino oscillation sends modulating neutrino states to the realm of si-fi. The neutrinos we observe are thought to be mixes of 2 or more states and the mix changes. What might be possible is a digital device that sends digitally encoded messages in the amount of neutrinos you produce during a given period. Message density would be lousy and costs almost certainly prohibitive with current means. E.g. look how long it takes to power up the LHC or an atomic power plant. Just sending "SOS" in morse code could easily take months. There would also be a high error rate due to natural fluctuations.76.97.245.5 (talk) 07:22, 28 February 2009 (UTC)

"Relative" to detecting them, that is ;-) Someguy1221 (talk) 11:10, 28 February 2009 (UTC)

Yeah - it's certainly possible - in principle - to send messages through large, solid objects using some kind of modulated neutrino stream. But the bandwidth of such a link would be of the order of one bit per day - the transmitter would have to be something like a nuclear reactor that could be turned on and off - or perhaps moved from one place to another - and the receiver would be some VAST tank of dry-cleaning fluid buried deep in a mine-shaft, studded with costly electronics. 'possible' and 'practical' are not the same thing. But I don't really see the benefits. A set of satellites in orbit is much cheaper than the gargantuan equipment needed to modulate and detect neutrino flow - the equipment needed to send and receive such signals is small enough to be hand-held and the only real downside is that it takes maybe twice as long for the signal to get there...but compared to the delays inherent in statistical analysis of neutrino detection when just a couple of detections per hour is the maximum rate possible...there is no reason that I could imagine for wanting to use such a device. I have not read "Glass Earth Inc" and our one-line summary ("A policeman must sort through the memories of a murder to find out who the killer is, and in the process, learns more about himself then he ever knew.") is less than revealing about the purpose of this neutrino communication trick. Why was it important to the plot? SteveBaker (talk) 13:27, 28 February 2009 (UTC)

Oh! Now you're putting me on the spot… it's been years since I read the story and unfortunately I am not possessed of a photographic memory… But! The gubmint's on the case already PDF: a project to induce rock deformation processes under the San Andreas fault (p.19) is already well under way. They mention "glass earth" (p.24) and that 1 in 10¹³ particles (p.4) make it all the way through this ole planet… Well that explains that fearsome excavation on Magnolia Boulevard… could I interest you in some prime real estate in the Valley?--Goodmorningworld (talk) 14:55, 28 February 2009 (UTC)

There are many other, less exotic, subatomic particles (like, say photons) which would work much better than neutrinos for the same purposes. Imagine me talking to you on the phone, but you only hear one consonant or vowel per hour. That's the sort of level of reliablity neutrinos provide. I suspect that this is a case of the author picking an exotic sounding real science term and just making up a use for it. Here in the real world, there does not seem to be any compelling reason to use neutrinos for communication; they will still be bound to the speed of light, and so would not be any better than ordinary radio (light) waves/photons, and there are many reasons why they would be WORSE. We already have reliable photon detectors out there which have been working for us for, oh, 100 years or so. If it ain't broke... --Jayron32.talk.contribs 13:31, 28 February 2009 (UTC)

The benefit is that they can get from A to B marginally quicker since going through the Earth is quicker than going round it. So, we have fantastic latency and terrible bandwidth - kind of the opposite of using satellites (although the bandwidth for neutrinos is several orders of magnitude worse than the latency for satellites). --Tango (talk) 14:41, 28 February 2009 (UTC)

Actually I read somewhere (coulda been in the Weekly World News, coulda been SciAm) that data sent over the wires does not in fact propagate at light speed despite them being electromagnetic waves, but only at one-tenth the speed effectively… guess them lil' photons bump into each other like billard balls and there is some friction involved!--Goodmorningworld (talk) 15:02, 28 February 2009 (UTC)

The whole point is that neutrinos are better than photons, albeit in some very specific ways that may not be of use in most situations. Neutrinos are essentially unstoppable and unshieldable; unlike radio or microwave photons, they're not subject to any sort of interference. Lightning and solar storms have no effect. You don't need to have a dish or antenna on the roof to pick them up; they'll get to you in a bunker a mile underground, so you're protected from blizzards, hurricanes, and bombs. Open line of sight isn't required for neutrinos.

Using visible or infrared photons is also inferior over long distances. Either you need line of sight and clear air (for laser communications), or you need waveguides (fiber optics) and lots of repeaters to cover any substantial distance. Long-distance optical fiber is expensive to place, and vulnerable to enemy action, political whims, power failures, ship anchors (quite common), and earthquakes: [3].

In all cases, the time of flight for neutrino communications is shorter. Consider the worst case scenario: two people want to communicate between points on roughly opposite sides of the globe (Perth, Australia and New York, USA, perhaps). The straight-line distance (as the neutrino flies) is about twelve thousand kilometers; going around the surface circumference is about twenty thousand. (The actual distance over the surface will be quite a bit longer, as there aren't any great-circle communications links from Perth to New York.) Communication over fiber will take longer than the distance suggests, as the speed of light is about 30% lower in optical fiber than it is in vacuum; substantial time will also be lost at relay stations where the signal is processed in and out of fibers. Radio is even worse. The distance from ground to geostationary satellite and back is more than seventy thousand kilometers. For a few applications (telepresence for telesurgery, for example) reduction in latency is worth almost any price.

The catch, of course, is that we lack any method to generate and detect powerful, modulated beams of neutrinos in anything approaching an efficient or cost-effective way. With current technology we couldn't send more than a few bits an hour, and we'd have to use billion-dollar particle accelerators and tens-of-millions-of-dollars detectors. For such a system to be viable, you need to make neutrino generation and detection much more efficient; call that the unobtainium problem for this science fiction concept. To the best of my knowledge, the generation problem is not solvable any time soon, and the detection problem is virtually intractable.

Incidentally, the world of science fiction is chock-full of uses for neutrinos. In Larry Niven's Ringworld series, the Ringworld's foundation is made of scrith — a material that stops roughly half of all neutrinos striking it with a layer about 30 meters deep. Greg Egan used neutrinos in Wang's Carpets as a gentle, non-invasive probe of alien life. Dan Simmons uses modulated neutrinos for military communication in the later parts of his Hyperion series. The assorted Star Trek spinoffs can't resist the little neutrino, and – occasionally – they do use it in a way that makes a modicum of sense. (Their favourite particle, though, is most certainly the tachyon. Since it hasn't been observed and its properties are poorly defined, it's much more useful to twenty-fourth century scriptwriters.) TenOfAllTrades(talk) 15:02, 28 February 2009 (UTC)

(unindent) It's crazy to claim that the time of flight of a neutrino makes it superior to a photon. The best neutrino detectors we have can only detect one out of every...uncountably large number...of neutrino's! So sure, the photons get there pretty quickly but all but 0.000000000...lots more zeroes...0000001% of them are completely ignored by the detector! So your transmitter has to transmit the first bit of the message as a gazillion-bazillion neutrons for about 20 minutes in order to be reasonably confident that the detector will pick up one or two of them. The tiny fraction of a second of latency you save by shooting your neutrino's through the earth are completely SWAMPED by the 20 minutes you have to wait in order to detect one of them! There is no object in the universe that's sufficiently transparent to neutrino's - yet opaque to photons that's big enough to save you 20 minutes at the speed of light!

Meanwhile, we've sent a few terabits over good old transatlantic cables, satellites, or carrier pidgeons. No matter the interference - if you could use a piece of equipment the size of a neutrino transmitter/reciever pair and send a few bits per hour we could have error-correcting codes with redundant transmission and enough sheer transmission power that we'd get through ANY amount of interference. Do you SERIOUSLY believe that there are any circumstances whatever in which photons are not at least a million times better? That's just beyond crazy!

Also neutrino's are NOT immune to interference. If your transmitter happens to be between the sun and the receiver then your receiver will be totally swamped with solar neutrino's and you'll get big-time interference from that damned great neutrino source in the sky. This might not be a practical problem for one transmitter and one receiver - but as soon as you get widespread adoption of the technology, those outages and interference between transmitters (which - bear in mind - cannot by any means be directional) would soon be a problem.

This is so far beyond reasonable...I can't believe anyone would even consider a vote in favor of the idea. SteveBaker (talk) 19:24, 28 February 2009 (UTC)

See, I saved you the trouble of brewing a cup of coffee LOL. Actually 1 in 10¹³ neutrinos are detectable with current technology after their trip through Earth (a lump of rock to us, an airy wisp to them). This figure comes from the DUSEL people at Homestake that I linked to above. I admit, I was having a bit of fun with them earlier, as their PDF file looks like something cooked up by a mad scientist gunning for the Ig Nobel prize, but in fact Raymond Davis Jr., who directed the Homestake Experiment, shared the Nobel prize for it in 2002. 10⁶ is a million, 10⁹ a billion, so we need to send ten trillion neutrinos on their way if one of them is to register on the detector. Multiply this by another factor of thousand to get a margin of safety and we're at ten quadrillion. That's only twice as much as the investment banks wrote off last year in dollars :-) How many neutrinos can we transmit per nanosecond, and how quickly can we modulate the stream? How expensive is that and how much do we need to figure for the detector? Suddenly it's beginning to look much more like an engineering and business problem than a physics problem. Which means that Yankee ingenuity will find a way, as it always has…(Probably going to need more orders of magnitude for error correction and a "wrapper" that distinguishes your message neutrinos from other broadcasters, the Sun and cosmic sources…8-) --Goodmorningworld (talk) 19:59, 28 February 2009 (UTC)

Exactly, it's an engineering and business problem. That's what all the responses have said - it's theoretically possible, just overwhelmingly impractical. --Tango (talk) 20:42, 28 February 2009 (UTC)

Steve Baker has it 100% right here (as usual). Lets simplify it. The supposed "benefit" of nutrinos is that they can travel through the Earth. The problem is, your nutrino detector is going to be made out of the same stuff the Earth is. Like atoms and molecules and stuff like that. So you broadcast some information via nutrinos. How do you catch those nutrinos to be able to read what you have broadcast? See the problem here? --Jayron32.talk.contribs 19:50, 28 February 2009 (UTC)

We already have neutrino detectors, I think it's creating the neutrino stream that will be the hard part - creating enough neutrinos quickly enough for the largest imaginable detector to pick up the signal at even a few bits an hour would be next to impossible. Building a slightly smaller detector wouldn't make that big a difference. --Tango (talk) 20:42, 28 February 2009 (UTC)

You may be a bit too pessimistic. I, however, was much too optimistic. The MINOS experiment in Minnesota collects collision events of neutrinos fired off from Chicago.

More than a trillion man-made neutrinos will pass through the MINOS detector each year. Because neutrinos interact so rarely, only about 1,500 of them each year will collide with atoms inside the detector.

— MINOS FAQ

The "trillion" sounds low, could be a dumbed-down figure to signify "very many" for the general public. The 1500 events per year arithmetically come out to a few hours per bit and perhaps give hope for still more in the future. However the 1500 per year is a statistical figure which cannot be taken as "1500 smallest units of information", the number of bits per year would be smaller and availability is capricious.

This is very disheartening, I had no idea that it was so hard to generate neutrinos at a handsome clip.

Maybe we should start thinking out of the box. Pocket supernovas, anyone?--Goodmorningworld (talk) 22:52, 28 February 2009 (UTC)

This confrontation on the Reference Desk a year ago is an interesting and relevant read. --Bowlhover (talk) 19:55, 28 February 2009 (UTC)

Hmm - yeah - this guy "SteveBaker" had the neat idea to point out that if you absolutely had a need to communicate through the solid earth, you'd do better to use high explosives and seismometers. Sure, the speed of sound is kinda slow - but still, you could probably arrange to send one bit per second. Definitely an incentive to keep your emails short though! SteveBaker (talk) 02:03, 1 March 2009 (UTC)

There isn't a need to communicate through the Earth, that just happens to be the quickest way from A to B. Your method would be far worse that existing methods that go around the Earth. --Tango (talk) 11:44, 2 March 2009 (UTC)

There was a semi-serious proposal for this back in the 70's (see abstract here). The actual paper doesn't seem to be online, and I've never read it, but from what I heard the idea was to use neutrinos to send covert messages to Ballistic missile submarines (which would use the surrounding seawater as a detector mass) (I'm not sure how the sub was supposed to detect the interactions — a hull studded with photomultipliers doesn't seem terribly practical). The main advantage over other communications media is the difficulty of intercepting (or even detecting the existence of) the transmission. So it's not as insane as it sounds. Well, not quite, anyway.

Actually, I think the main point of the proposal was that Peter Kotzer thought he could get the Navy to give him some money to look into it further... -- Speaker to Lampposts (talk) 08:32, 1 March 2009 (UTC)

Crazy proposals are made to the Military all the time - that doesn't legitimize them at all! SteveBaker (talk) 16:37, 1 March 2009 (UTC)

You guys are all forgetting that unobtanium is an excellent neutrino detector. --Sean 19:52, 1 March 2009 (UTC)

I see another problem with this whole thing; everyone keeps saying that we need to be able to fire way more neutrinos, but what if we just had a better detector? I haven't really done the reading that everyone's been linking to, so maybe I'm suggesting something more difficult/less efficient than just firing 100 quadrillion neutrinos. But the way I look at it, didn't people once find it impossible to detect other things, like x-rays and such effectively? But we found an efficient way. There's probably a way for neutrino's too. -Pete5x5 18:56, 6 March 2009 (UTC)

Observation of a mysterious psychological phenomenon

How is it that an individual is able to detect when another is staring at him or her even when the starer seems to be beyond even the peripheral vision of the detecter? Furthermore, as the starer, I can usually sense that the other individual can detect my staring insofar as I seem to know when the detecter will return the stare imminently? Is it the case that I was mistaken in the first question and the starer is simply NOT beyond the periphery of the detecter, or is there something more to this apparent example of ESP?Lashyn (talk) 04:54, 28 February 2009 (UTC)

It's likely not ESP. There are several things at work here probably:

1. When someone is very close to you and staring at you, like right behind your back, there are other cues, such as the sound of them breathing or their body heat or smell, which may lie below your conscious perception, but which you clearly are able to detect. Thus, that "creepy" feeling when someone is reading over your shoulder. You can't see them, but you "know" they are there because you can sense them with your other senses.
2. You're eyes are scanning much more than you realize. When you look at something, your eyes don't focus exclusively on that thing, but rather they spend most of the time looking at what you are concentrating on, and the rest of the time scanning your field of vision. If you watch someone's eyes very closely, you will see they are almost never "still", but constantly shifting and moving and refocusing. Thus, while you aren't looking at the guy staring at you, you still "see" him. Also, our minds are atuned to making eye contact; think how disconcerting it is to talk to someone who DOESN'T make it. Our mind automatically notices when someone is making eye contact with us, even from a great distance. These two things make evolutionary sense, as the first thing means that we can reflexly react to a threat even if we aren't focusing on it. The second makes sense because knowing when someone is watching you can be quite important if you need to assess his friend/foe status. Someone looking at you should always be a "person of interest"...
3. A sort of deja vu when you realize that someone IS staring at you. When you notice someone staring at you, you reflexively assume he HAS been staring at you for a while, then you convince yourself that you noticed it earlier. You really didn't, but like all forms of deja vu, your mind creates the memory and so it feels real.

Does this all sound like reasonable explanations besides ESP? --Jayron32.talk.contribs 05:20, 28 February 2009 (UTC)

We have an article for this: The Psychic Staring Effect, but it's not very comprehensive, probably because there doesn't seem to be a lot of convincing scientific data about the thing, despite numerous research efforts. Still, it may give you some pointers on where to look for more information. Personally, I'm extremely skeptical. -- Captain Disdain (talk) 10:16, 28 February 2009 (UTC)

I too am extremely skeptical. I suspect that the 'observer selection' effect is happening. When someone sneaks up and stares at you from behind - but you DON'T notice them - you aren't creeped-out and you never know that you failed to spot them. It's ONLY in those cases when you did eventually spot them that you (perhaps retrospectively) felt that you were 'feeling their presence'. There is strong evidence that our conscious minds operate with a significant delay behind 'real time' events and that our subconsciousnesses 'edit' the perception of the world to make everything self-consistent after the fact. So it could be that we see someone who WAS looking at us - this gives our conscious mind the 'creeped-out' feeling immediately - and then a second or so later, the knowledge that we just saw them hits our conscious brain.

But if it were somehow to be shown to be true aside from all of that - then there are even more subtle cues you could be picking up on - every object in a room reflects light onto every other object - and every object blocks ambient light from every other object. When something as large as a person moves within a reasonably close distance to you, your surroundings change in subtle ways - shadows shift as light that was reflected from the walls behind you is blocked, the color of the person's clothing alters the color of the light being reflected off of things close to you. Similar things happen in the audio domain - ambient sounds such as the whir of the fan in your computer are attenuated by this new, large, soft object in your proximity. This is more than enough for your visual/audio system to realise that there is something large in close proximity that you aren't otherwise aware of. The 'creepy feeling' would be a very useful evolved response to a potential danger. "Warning - Potential sabre-toothed tiger sneaking up behind you - don't move but get ready to move!".

There is certainly no reason to suspect this 'psychic' crap might be true. The idea that this rather simple phenomenon could require most of physics to be rewritten when there are any number of plausible explanations is an exceedingly stupid one. SteveBaker (talk) 13:13, 28 February 2009 (UTC)

My psychic staring perception is absolutely awful. Maybe I'm paranoid (actually, no maybe about it), but I always think people are staring at me, and so I am very self-conscious. I quite often look around to find that people actually aren't staring at me. This whole psychic staring effect to me seems like a load of confirmation bias. --Mark PEA (talk) 14:19, 28 February 2009 (UTC)

As a matter of fact, I and my many fellow sufferers from Human Spontaneous Involuntary Invisibility, or HSII, are afflicted with the opposite condition. There's always people cutting in front of us in line as if we weren't there, and when we get to the counter at the Dept. of Motor Vehicles the lady gets up and puts up the Lunch Break sign because she doesn't see us.--Goodmorningworld (talk) 15:22, 28 February 2009 (UTC)

Heh, I get that even when I'm the only customer. Typically, it's in a cafe where you have to order at the counter. I'm in plain view (and I have a fairly large build, so I'm hardly easy to miss), but sometimes I've stood there for a couple of minutes, just to see how long it takes before one of the up to 6 people behind the counter notices there's someone there. And then one of them finally says "Oh, I didn't see you there. Are you right?" That tempts me to turn and walk out, but that would mean I've wasted my time, so I say "No, not yet" or some equally smart remark, and order what I came for. -- JackofOz (talk) 21:50, 28 February 2009 (UTC)

Rupert Sheldrake's book "The Sense of Being Stared At" covers this. --TammyMoet (talk) 18:01, 28 February 2009 (UTC)

The Sense of Being Stared At#Tests of the staring effect covers the flaws of his experiments. --Mark PEA (talk) 19:18, 28 February 2009 (UTC)

Sheldrake follows the classic path of the failed scientist. He spent an eternity collecting degrees from various colleges - then when he finally has to do 'real' work, he works for nine years as a biochemist trying to figure out some thing or other to do some hormone in plants - then (having utterly failed to do whatever he was supposed to be doing) he claims that it's beyond the ability of biochemistry to do that! This sounds pretty petulant to me! Then he starts writing a bunch of populist crap about all manner of pseudo-science. Who knows whether he really believes it or not - but he's out to parley his qualifications and supposed decade as a working scientist into some kind of credibility for his whack-job ideas and churn that into book revenues. Then he comes out with a bunch of other scientists who supposedly back his theories. At first sight, these look credible - take, for instance, David Bohm - an impressive ex-Manhatten project Physicist who was allegedly impressed with Sheldrakes' work...but Bohm died in 1992 -most of Sheldrake's ravings were published after 1996 - so Bohm can't possibly have seen most of the things the Sheldrake is claiming. Worse still, when Bohm made that comment, he'd been through a couple of years of acute depression and had electroshock therapy...can we really trust this as some kind of peer review?!? I don't think so. This is absolutely typical of this kind of crank stuff...the deeper you look, the crappier and flakier the information becomes. SteveBaker (talk) 01:32, 1 March 2009 (UTC)

I deny the truth of this claimed effect. It has been tested repeatedly by psychologists back to Titchenor, and only chance effects were seen in many opf the experiments. It seems to be purely anecdotal. If the starer's face is visible in peripheral vision, it is very salient, draws your attention, and AHA! You've caught them. If it is out of sight and you happen to turn and catch them, it confirms the myth. But you are utterly unaware of the times when a person out of your visual field stared at you and you failed to catch them. Like other ESP experiments, it is easy to produce positive results. Edison (talk) 21:04, 28 February 2009 (UTC)

Certainly our eyes are EXTREMELY sensitive to subtle motion in our peripheral vision. If you live in the UK where we have 50Hz television - when you look straight at the TV, it looks fine...but if you catch it in your peripheral vision, you can see it flickering. (Some people can see this in US 60Hz television too...but less so). We are SO sensitive to this that even fairly subtle lighting changes in our periphery are noticeable to the point of being distracting. I'm pretty sure that anyone who is moves up behind you (especially indoors) is going to cast a shadow or alter the ambient light levels in your periphery - and it's quite likely that you're noticing that on a subliminal level. SteveBaker (talk) 01:32, 1 March 2009 (UTC)

Intuition, perhaps? ~AH1^(TCU) 01:22, 2 March 2009 (UTC)

contradiction between lorentz transformation and length contraction

the lorentz transformation equation for x' in the coordinate system K' as seen from the other coordinate system K is $x^{'}={\frac {x-vt}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$. But this means that x' should be farther from the origin as seen from K which means that the length will increase. This is contradictory to the length contradiction in special relativity. Please explain if i am wrong--harish (talk) 09:05, 28 February 2009 (UTC)

The length of an object, say $l'\,$, is obtained by simultaneously measuring the position of two extremes, say point 1 and point 2 with coordinates $x_{1}'\,$ and $x_{2}'\,$ and subtracting them. So $l'=x_{1}'-x_{2}'\,$. The condition of simultaneously measuring both ends tells us that $t_{1}'=t_{2}'\,$. If now we apply the Lorentz transformation to both time and space coordinates at both extreme points, we get four equations:

$x_{1}'={\frac {x_{1}-vt_{1}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$,

$x_{2}'={\frac {x_{2}-vt_{2}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$,

$t_{1}'={\frac {t_{1}-{\frac {v}{c^{2}}}x_{1}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$, and

$t_{2}'={\frac {t_{2}-{\frac {v}{c^{2}}}x_{2}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$.

But we've seen that $t_{1}'=t_{2}'\,$ which allows us to obtain

${\frac {t_{1}-{\frac {v}{c^{2}}}x_{1}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}={\frac {t_{2}-{\frac {v}{c^{2}}}x_{2}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$

which simplifys as

$t_{1}-{\frac {v}{c^{2}}}x_{1}=t_{2}-{\frac {v}{c^{2}}}x_{2}$

and

$t_{1}-t_{2}={\frac {v}{c^{2}}}(x_{1}-x_{2})$

The expression for $l'\,$ then becomes

$l'=x_{1}'-x_{2}'={\frac {x_{1}-vt_{1}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}-{\frac {x_{2}-vt_{2}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}={\frac {(x_{1}-x_{2})-v(t_{1}-t_{2})}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}={\frac {(x_{1}-x_{2})-v({\frac {v}{c^{2}}}(x_{1}-x_{2}))}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}={\frac {(x_{1}-x_{2})(1-{\frac {v^{2}}{c^{2}}})}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$

$l'=(x_{1}-x_{2}){\sqrt {1-{\frac {v^{2}}{c^{2}}}}}$

Now, assuming that the object is at rest in the coordinate system K (that's an important point), we must have $l=x_{1}-x_{2}\,$ and we don't care about the simultaneity of those measurements since the object is at rest. Defining $\gamma ={\frac {1}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$, we get

$\gamma l'=l\,$.

Conclusion: the size of the object $l'\,$ measured in a coordinate system K' where it is in motion is smaller then its size $l\,$ measured in a coordinate system K where it is at rest. Dauto (talk) 16:24, 28 February 2009 (UTC)

current even not grounded

Hello,

It seems simpler.

If one is touching a current carrying wire no matter current is A.C. or D.C. should one get a current through its body.I think it should. Consider two points on my finger touching wire they will have some potential difference and ofcourse current will flow .But ya if one was touching ground potential difference will high and got high current so but if only wire is touch P.D. will be there and so current.

Is that concept is right and if not whats wrong with that and how can be improved. —Preceding unsigned comment added by 122.163.42.205 (talk) 12:58, 28 February 2009 (UTC)

If the current in the wires is not enough to overcome the electrical impedance or Electrical resistance of your body, then the current will not flow to any meaningful amount. (the equations imply perfect linearity; that is ANY voltage should always produce a current in any medium; however for practical purposes, extremely high resistances will produce such small currents that they are undetectable, and therefore essentially nil). If you have two wires with a small voltage difference between them, and hold one wire in each hand, likely no measureable current will flow. If the voltage is high enough, then current WILL flow, which can be a dangerous thing, as there's stuff in your body that does not react kindly to having electricty pass through it. Even if it causes no damage, it can create some uncomfortable or painful effects. Now, as to the difference between passing through the two wires OR passing from one wire to the ground; it depends upon which voltage difference is greater. Since the impedence between your outstretched hands and your hands and your feet is likely to be similar, the deciding factor on which path the electrons take will be whichever path will allow the electrons to lose the most energy. If the path to the ground does this, it will take that path rather than the path to the other wire. --Jayron32.talk.contribs 13:24, 28 February 2009 (UTC)

If you touch even one wire with one finger, even while not touching a grounded object, painful or dangerous current can flow, if the wire is at a high enough voltage like a transmission line. It might be due to capacitive current. Edison (talk) 20:48, 28 February 2009 (UTC)

If you're not familiar with capacitive current, I will briefly summarize it. It is possible for current to flow, even though there is no complete circuit, for some amount of time. During this time, electric charge is stored on a capacitor (which may be your body). This current could be sufficiently high to be harmful. Also, remember that you can have a complete-circuit to ground if you are not totally isolated from the environment (a lot of materials act as conductors when a sufficiently high voltage is applied). Nimur (talk) 22:41, 28 February 2009 (UTC)

Diagnosing asthma in children

Hi all the article on asthma does not say why peak expiratory flow rate tests are not used to diagnose asthma in children. I have read elsewhere that they are used in children over 5 and in another source, Clinical Medicine by Kumar and Clark, that excercise tests are mainly used to diagnose asthma in children. Please help - thanks in advance. —Preceding unsigned comment added by 139.222.241.116 (talk) 15:39, 28 February 2009 (UTC)

Peak expiratory flow rate measurement is strongly influenced by effort. It is difficult to get young children to exert a standard amount of effort for what they may see as a pointless exercise. Also, asthma is "reactive" airway disease, and as a rule the lungs of a child with asthma function normally at rest (between exacerbations). Exercise is a common trigger, but is not uniformly so. It's a heterogeneous disease. --Scray (talk) 17:36, 28 February 2009 (UTC)

Many thanks for the reply. But your post made me think - The PEFR test is used commonly in diagnosing asthma in adults but don't the lungs of adults who have asthma function normally at rest as well? So how is the test beneficial? —Preceding unsigned comment added by 139.222.240.115 (talk) 18:36, 28 February 2009 (UTC)

PEFR measurement alone cannot be used to diagnose asthma. The diagnosis is based on history (pattern of symptoms, triggers, etc) supported by testing. Improvement in PEFR after bronchodilator treatment may be suggestive, but more formal (and much more accurate) spirometry is generally used. In many people with true asthma, the spirometry may be normal, but a challenge test can bring out evidence of airway obstruction; common challenges include exercise, cold air, and methacholine. PEFR can be useful in gauging response to treatment, and empowering patients (who have a chronic condition, after all) to assess the severity of exacerbations that might need escalated or more intensive treatment. --Scray (talk) 02:46, 1 March 2009 (UTC)

Why all the various notations for wavelength and frequency?

I hate using (nu) because it looks like a v

Also, there is lamda, and f, and h

Please someone correct me if I'm wrong

(nu) = frequency

f is also frequency

lamda is λ is wavelength

h is also wavelength?

I am learning chemistry and physics at the same time, and I already asked at Yahoo answers. I am OCD, and this multi-naming is really truly frustrating me. I am fixing to start the chapters on waves, and optics (all in physics) but also am doing chemistry review and there is some alternate terminology but the reason is explained well, but I just can't understand it unless someone puts it in laymen's terms. I have tried to read the relevant wikipedia articles, and the gist is something like "chemistry uses lamda, h, and (nu) to highlight the relationship that electromagnetic radiation propogates at a constant phase speed of c = 3*10^8 m/s" whereas "physics takes a holistic approach and analyzes this stuff from looking at everyday wave phenomena like a buoy in the ocean--the waves can be imagined as the buoy oscillating up and down in simple harmonic motion, and its not a physical phenomenon but almost like a mathematical phenomenon governed by a math formula x-doubledot plus cosA(x+phi) = 0"

This my amalgamation of trying to make sense of various online sources with what my book says. My instincts were to ask this on the math refdesk, because I like the style of mathematicians' explanations on stuff like this. I received a very good answer a long time ago about the dx or dt at the end of an integral explanation, and I truly understood the explanation. I don't really understand what I wrote, but I wish to understand why use the various symbols. I really do want to know the reasoning behind keeping around both sets. I personally prefer f for frequency and don't have preference on what to use on the rest.

I am going to print out my responses, because I really need a custom explanation. I like math symbols that make sense, and delving into the science fields of chemistry and physics, they don't have the "purity" that I'm accustomed to from my endeavors in calculus.

If someone else can just write me an explanation that makes sense to me, and won't conflict with my science books, then I can finally just memorize the formulas. Until then, I'm hesitant of memorizing the wrong set of formulas. I am also a perfectionist, as evidenced by how apologetic I am for asking this simple question. Please AGF me, and help me make sense of these two seemingly incompatible reasonings for keeping around both sets of symbols. Thanks very much.

LeeJaedong (talk) 16:42, 28 February 2009 (UTC)

h is Planck's constant. The others are right. It doesn't really matter what you call things, you use whatever symbols aren't already being used for something else, although there are certainly symbols that are generally used for certain things - you should always specify what you mean by each symbol the first time you use it, though. f is often used for a miscellaneous function, so isn't always available for frequency. You may need to alter your handwriting slightly to distinguish all the different symbols. My handwriting changed a lot during my first year of uni - I now cross 7's and z's, I loop ells, I put ticks at the top of 1's, v's, w's and o's, etc., etc.. I write nu's with a straight line down and right, and then a curved line up and out to the right and then back in to the left, whereas v's have a straight line down and right and a straight line up and right, with a horizontal tick at the end - they are easy to distinguish (my u's look more like by v's than my nu's do - that's what the horizontal tick is for, u's don't have them). --Tango (talk) 16:57, 28 February 2009 (UTC)

I also have a pet peeve against the use of the $\nu$ because it looks like a v. But you must be aware that other people like using it and there's nothing you can do about it. There is no other reason for the the multiple notations beyond the fact that different people have different tastes. Get used to it. Just remember that the impostant thing is the physical concept, not the symbol used to describe it. Dauto (talk) 17:05, 28 February 2009 (UTC)

Just consider yourself lucky you're not learning maths too. With German fraktur and Hebrew letters as well. Plus a whole load of invented symbols. On that theme do people have to learn German to do chemistry in your neck of the woods? Anyway its all nothing compared to what the Jpanese do every day of the week Dmcq (talk) 00:15, 1 March 2009 (UTC)

Yeah, some of the symbols in maths are really bad. My handwriting includes 6 different p's. And I still don't know what the symbol that this book I have uses for the residue field of a local field is meant to be - I think it's either a weird I or a weird F... --Tango (talk) 00:18, 1 March 2009 (UTC)

Six? I think I only know 5: lowercase, uppercase, fraktur for ideals, BB for probability and script for powerset. I have recently had to learn to write Thorn, though, which more than makes up for it. Algebraist 00:38, 1 March 2009 (UTC)

Immediately after posting I realized I had forgotten the mysterious Weierstrass p. Algebraist 00:41, 1 March 2009 (UTC)

Yep, those are the 6 (although I use $\mathbb {P}$ for projective space, rather than probability). There is also rho, which you need to be careful to avoid making it look like a p. And you've mentioned thorn (which I've never had to use). I can't think of another letter that's as troublesome as P... --Tango (talk) 01:08, 1 March 2009 (UTC)

Science and math really needs to take a lesson from computer science. We've all learned that using good, clear variable names is one of the most critical things to writing clear, unambiguous code...the same applies to equations. I would NEVER consider using 'f' for 'frequency' - even less, some impossible-to-type wierd-assed v! I can't tell you the number of times I've looked up an equation on Wikipedia and found one or more completely undefined terms! By all means use single-letter variables in informal doodling - but when it comes to publication - the 'hard' sciences should hold to the formal requirements of good programming style! Properly spelled out variable/constant names - in language-independent ASCII - with proper 'declarations':

  equation waveFunction (
     constant  phaseSpeed : units distance time-1,
     parameter frequency  : units time-1,
     parameter wavelength : units distance )
  {
     wavelength = phaseSpeed / frequency ;
  }

SteveBaker (talk) 01:09, 1 March 2009 (UTC)

Do you know how long that would make most formal proofs? Mathematical notation is all about making things concise while still being unambiguous, and for the most part it succeeds. Concise notation, preferably chosen in such a way that the notation mirrors the behaviour of the object it represents (for example, ${\frac {\mathrm {d} y}{\mathrm {d} x}}$ looks like something divided by something else and it behaves like something divided by something else - this makes remembering the chain rule, say, really easy (obviously, you need to be careful to remember that "cancel the dx's" is a mnemonic, not what is actually happening)), makes doing maths easier and quicker. If we had to write out "the derivative of vertical position with respect to horizontal position" (or whatever x and y are representing), nobody would ever bother doing maths and you wouldn't have a computer to program. "Let v_p be the phase speed, ν be frequency and λ wavelength, then λ=v_p/ν." is perfectly clear and is much easier to use than your notation. --Tango (talk) 15:31, 1 March 2009 (UTC)

Yes - and that's exactly what beginning computer programmers say: "Why do I have to say 'numberOfTriangles' instead of 'nt'? They both 'work' - and 'nt' is less typing." However, over the years and with programmers turning out millions of lines of code in their careers - we've learned (typically, the hard way) that the time consumed in entering things in shorthand forms is more than recouped in the clarity of reading it later. The cost of a single error (even more so in math than in computer programs) is so spectacularly high that in the age of the computer and with things like editors that do automatic name completion and such - it's less effort overall to do it right - and the results are clearer and unambiguous for the next generation of readers. SteveBaker (talk) 16:32, 1 March 2009 (UTC)

Ok, that's not at all clear because the default font shows vee and nu identically, but it my handwriting it would be perfectly clear. --Tango (talk) 15:32, 1 March 2009 (UTC)

Aha! Gotcha! My point - precisely. You even found it necessary to say 'vee' and 'nu' in order to disambiguate it. Look at that exact same equation in our Wavelength article:

"Wavelength λ is determined using the formula

$\lambda ={\frac {v}{f}},$

where v is the phase speed of the wave and f is its frequency.

See what I mean? SteveBaker (talk) 16:32, 1 March 2009 (UTC)

This (in maths, at least) is actually quite a small problem compared to the problem of different definitions. Any sensible author defines the symbols they use (where it's ambiguous), but they don't always bother telling you if rings have 1s, if lattices are bounded, if 0 is a natural number, what locally compact means today, and so on. Algebraist 16:39, 1 March 2009 (UTC)

No mathematician would write up maths in a font where vee and nu look the same. In the default LaTeX font, $v\,\!$ and $\nu \,\!$ look sufficiently different that there is no problem. If you aren't familiar with the default LaTeX font (which won't be the case for any experienced mathematician or scientist, but nevertheless) then you may not know if one of those symbols in isolation is one or the other, but it really doesn't matter. All that matters is that if they both appear in the same bit of maths, you can tell them apart. Not knowing how to pronounce them is a little annoying, but it's not a real problem. --Tango (talk) 16:51, 1 March 2009 (UTC)

There are some formal maths systems around, The Mizar system is about the most readable see Mizar Mini-tutorial but you'd have to be a massochist to do any new maths in it or explain things with it rather than just use it for formal verification. A bit like trying to use COBOL to write a compiler (yes it has been done!, see Micro Focus International). And even with Mizar people tend to use single character names for variables. Try substituting some long names into that tutorial example and see what you get :) Dmcq (talk) 16:17, 1 March 2009 (UTC)

I am very much a fan of Steve's variable-naming. If formal proofs took a few extra pages to print, that would be an acceptable tradeoff to make them comprehensible. This is especially important when you are using a text as a reference rather than a class-aid. When I pull out my physics books to check an equation I haven't used in four years, the last thing I want to do is parse through variable soup - and in this particular author's notation, is $\nu$ with or without the $2\pi$ factor included... if the equations were cleanly printed with unambiguous plaintext names, it would be much simpler. If brevity is that important, then a single, consistent, exact mapping between variable and plaintext name should be included as an appendix. (This is why I love my Thermodynamics book). Nimur (talk) 16:36, 1 March 2009 (UTC)

We're not talking about a few extra pages. We're talking about a 20 page paper taking, maybe, 100 pages. A one blackboard proof taking five blackboards. And it's not just length, it's time - it would take five times as long to write up your papers, you would cover a fifth as much in a lecture, etc. (I'm making a guess at the factor of 5, it could well be quite a bit more, I would be very surprised if it were less.) --Tango (talk) 16:59, 1 March 2009 (UTC)

It's also worth entertaining the possibility that math (and other disciplines) could move to paperless presentation of proofs and other content, in which variables are unambiguously named, and the display could be made compact by wikilinking abbreviations to their definitions and units. Then maybe we would not have to worry so much about killing trees. It's also possible that we waste "paper" (i.e. space) with redundant work made necessary by the confusion we are discussing. --Scray (talk) 18:21, 1 March 2009 (UTC)

A system by which hovering over a variable gives you a tooltip with its definition could be useful. Links would be unnecessary and probably unhelpful. Many variables don't really have a definition, though (although it might be useful if hovering over it told you its domain). --Tango (talk) 20:03, 1 March 2009 (UTC)

That seems like the perfect oportunity for me to voice my rant about how much I hate WP's defaulf font. Dauto (talk) 21:16, 1 March 2009 (UTC)

Not sure what that rant's about, but on the business of long names can I point to Chunking (psychology) and to how much more efficient people are coding in less verbose and more high-level programming languages. Dmcq (talk) 21:26, 1 March 2009 (UTC)

I really don't give a damn about some psychological theory. Practical computer programmers have learned the hard way how important this is to clarity. The temptation to brevity is always there - and good programmers resist it strongly because they know the consequences. To pick an example out of the air - let's take a look at the very first piece of PHP code wikipedia runs when you start it up:

# Initialise common code
require_once( './includes/WebStart.php' );

# Initialize MediaWiki base class
require_once( "includes/Wiki.php" );
$mediaWiki = new MediaWiki();

wfProfileIn( 'main-misc-setup' );
OutputPage::setEncodings(); # Not really used yet

$maxLag = $wgRequest->getVal( 'maxlag' );
if ( !is_null( $maxLag ) ) {
        if ( !$mediaWiki->checkMaxLag( $maxLag ) ) {
                exit;
        }
}

# Query string fields
$action = $wgRequest->getVal( 'action', 'view' );
$title = $wgRequest->getVal( 'title' );

We don't write long names like 'MediaWiki', 'OutputPage' and 'maxLag' for fun! The program would have worked just as well if the code was written with 'M', 'O' and 'L', and there would have been less typing and a much more compact representation - but programmers coming fresh to the code (or even the person who wrote it coming back to it years later) would have a much harder time finding problems and fixing them. Wikipedia has about 300,000 lines of this stuff (that's maybe 5,000 pages). It's not a matter of a mere 20 page proof! The extra effort to expand a mere 20 pages into a more readable form would be negligable compared to the intellectual effort required to figure out the proof in the first place. Programmers are very practical people - we don't lift a finger if we don't have to. We've arrived at the benefits of long variable names through the totally pragmatic process of suffering develoment hell with short variable names back in the 1960's and 70's and gradually coming to the realization that a little more typing and perhaps a doubling in the amount of stuff we carry around is more than worthwhile. A programmer who habitually used small variables names would be unlikely to keep a job in any kind of large scale programming effort. That's not to say that we don't seek brevity - we certainly do, where it's appropriate. We don't write "integer", "character", "floating point" or "double precision floating point" - we say "int", "char", "float" and "double". Most modern programming languages use every single character in the ASCII character set for something (except, perhaps '@' - for historical reasons). SteveBaker (talk) 01:35, 2 March 2009 (UTC)

Mathematicians have been around far long than computer programmers and have been using modern notation for hundreds of years (if memory serves, the Ancient Greeks were a little more verbose). It seems to work well for us. I rarely have any problem remembering what a variable means (it often doesn't matter - we try to keep things general as much as possible, so all you need to know is what type of object it is and we use various conventions for that, which, along with context, tend to work - it might be a little more useful in the sciences, or applied maths, to be more verbose, but it tends to work anyway).

Perhaps the difference is in the number of times a variable is used. In maths, a given variable will probably be written dozens if not hundreds of times in a few pages. When programming you tend not to use the same variable more than a handful of times during any given part of the code (except for things like iterators which are often given single character names). This means that when programming it is often easier to use a long name and let your code be self-documenting as much as possible, rather than using a short name and defining what it is with a comment in every subroutine. Whereas in maths, it is easier to write a sentence at the beginning of each theorem or lemma explaining precisely what "x" means and then just write "x" the next hundred times. --Tango (talk) 11:57, 2 March 2009 (UTC)

Then this is a perfect opportunity for me to point out that Wikipedia doesn't have a default font. Your problem is with your browser's default sanserif font (I know IE's is vile, for instance), not with WP. Algebraist 00:33, 2 March 2009 (UTC)

IE's default/generic CSS sans-serif font appears to usually be Arial, which is the same as Firefox 3's default CSS sans-serif font. (At least it is on my computer and other people have also mentioned it.) However IE does sometimes pick another default font (why I'm not sure and as you can't change the default CSS sans-serif font on IE unlike you can with Firefox, you're SOL if it does (well there are ways to convince it to change the default but it's not easy). [4] [5] [6] So I guess if you consider Arial vile then it is, as is Firefox. If not, then it's not unless your unlucky. IE7 does use Cleartype by default regardless of your OS settings which is annoying if you don't have an LCD monitor. Nil Einne (talk) 11:15, 2 March 2009 (UTC)

SteveBaker, your idea of replacing mathematical symbols with something more descriptive would make sense if, as you said, the extra effort at writing time payed off with extra clarity at reading time. But it doesn't. In fact, it makes it harder to read. With fully descriptive symbols any equation with more then a few terms or factors wouldn't fit the page and would require a lot of effort to parse it properly. The one letter per concept standard used allows people to (with no more then a glance) comprehend long complex equations, as long as some reasonable formatting has been performed by the author. Programs such as Latex do most of the hard work of properly formatting equations automatically. Dauto (talk) 21:39, 1 March 2009 (UTC)

Wow, thanks so much guys. I have really enjoyed reading this conversation; I have learned a lot, and feel a lot better now. Thanks a ton! LeeJaedong (talk) 01:40, 2 March 2009 (UTC)

Characteristic time scale for rotational motion.

I am interested in knowing the time scale on which a molecule rotates in free space. I have estimates for the three principal moments of inertia. I know that this time would depend on the particular J state involved, so perhaps we can assume that the molecule is in the ground rotational state. I have looked at Rotational spectroscopy and Moment of inertia but neither seem to address this issue. Thanks in advance Man It's So Loud In Here (talk) 16:55, 28 February 2009 (UTC)

Use the formula $L=I\omega \,$ and the eigenvalue relations $L^{2}|l>=\hbar ^{2}l(l+1)|l>$. Dauto (talk) 17:38, 28 February 2009 (UTC)

Is this material covered in a WP article, for those who would like to understand more? --Scray (talk) 17:46, 28 February 2009 (UTC)

From infrared spectroscopy, you will notice that most molecular vibrations and rotations occur at infrared frequencies, while atomic vibrations and rotations often occur at optical frequencies. Larger molecules will have resonances at lower frequencies (due to larger mass), but their spectra may be dominated by functional groups, (small, tightly-coupled sub-molecule atom-groups). Do you need help converting infrared frequency to time scales? These should be on the order of 10x10^-15 seconds, or ~ millionths of nanoseconds. Nimur (talk) 22:46, 28 February 2009 (UTC)

For molecular vibrations, each [normal mode] has a characteristic frequency at which it oscillates. When more energy is put into the system the range of motion is increased but the frequency, and therefore the time period, doesn't change. The article here on the quantum harmonic oscillator has been very helpful. I am confused about rotations though and think the page on the rigid rotor is not very helpful. First off things are different because when you pump more energy into a rotational mode the frequency of rotation increases by some (quantized) amount. Let's say I have a molecule, and I've calculated the three principal moments of inertia and therefore have $I$ as a diagonal matrix. How would I go about finding the rotational frequency for the ground state? (this is not a homework question I assure you, although it sounds like a good one). Man It's So Loud In Here (talk) 02:18, 1 March 2009 (UTC)

Dauto Should I take from your formula that for a rotational eigenstate with $l$ quanta in the $i$ direction the angular velocity is $\omega _{i}={\frac {\hbar }{I_{i}}}{\sqrt {l(l+1)}}$? Then the period is just ${\frac {2\pi }{\omega }}$. Man It's So Loud In Here (talk) 02:51, 1 March 2009 (UTC)

Also with no characteristic frequency, is there no zero-point energy in rotations?Man It's So Loud In Here (talk) 21:15, 1 March 2009 (UTC)

Yes and no. A rigid rotator has no zero-point energy. In reality, vibrational and rotational terms aren't separable, so it does. But it's small enough to be neglected in most cases. --Pykk (talk) 00:21, 2 March 2009 (UTC)

Hormones and neurotransmitters

As I understand, the same chemical can be a hormone and a neurotransmitter, but when is it a hormone and when is it a neurotransmitter? Do I understand correctly that both chemicals influence other cells, but if it is produced by a nerve cell, we call it neurotransmitter, and when it is produced by any other cell, we call it a hormone? Or is there more to it? Lova Falk (talk) 17:14, 28 February 2009 (UTC)

A hormone is released in the bloodstream. A neurotransmitter is released into the synapse cleft. Dauto (talk) 17:25, 28 February 2009 (UTC)

Ah! It is as simple as this. Thank you! Lova Falk (talk) 17:37, 28 February 2009 (UTC)

PS Maybe not quite as simple. My textbook says: "There are axosecretory synapses, in which an axon terminal synapses with a tiny blood vessel called a capillary and secretes its transmitter directly into the blood." Do the authors of this book just express themselves in a sloppy way or are there exceptions to the rule? Lova Falk (talk) 17:49, 28 February 2009 (UTC)

The difference between hormone and neutransmitter is in scope of action. When the trasmitter is released in the bloodstream (using an axosecretory synapses, for instance) it may act on all the body cells that happen to have detectors for that substance (provided that enough of the transmitter was released to begin with).When the transmitter is released in a synapses cleft (acting on another neuron, for istance) the action may be restricted to just one cell at a time and will act on a much shorter timeframe. Dauto (talk) 18:49, 28 February 2009 (UTC)

soda ash clairification

Is soda ash used in swimming pool treatment the samae thing as soda ash used in well water treatment. We lost our supplier for the soda ash we used in our water system and can see there is what is called soda ash in both swimming pool sites and water sites. Thank you Marilyn —Preceding unsigned comment added by 63.46.128.40 (talk) 18:26, 28 February 2009 (UTC)

Soda ash is the old-fashioned name for Sodium carbonate - and sodium-carbonate is sodium-carbonate is sodium-carbonate. So if what you have is pure soda ash with no other ingredients - and what you need is pure soda ash with no other ingredients - then it should be just fine. Since both swimming pools and drinking water need similar properties - I (personally) would feel perfectly OK with stuffing the pool stuff into my well. SteveBaker (talk) 18:57, 28 February 2009 (UTC)

Difficult to know, because nonstandard nomenclature is, well... nonstandard. Do you have any old buckets which state definitively whether it's sodium carbonate? Additionally, please note that different formulations can make a lot of difference - for one easy example, it would be a horrible idea to use 80% Na2CO3 in the same amount that you would use 10%. (Not to mention that you wouldn't know what's in the remaining 20% or 90% composition.)

Even with a chemistry degree, I would be extremely hesitant to use something meant for one purpose for another in this manner. arimareiji (talk) 19:03, 28 February 2009 (UTC)

You REALLY must be careful, because like other terms such as Lime (material) or Potash, there are actually many compounds that fall under the "soda ash" label. Soda ash (unqualified) is usually used to mean sodium carbonate, but "caustic soda ash" is sodium hydroxide and there are other variations. The problem is that, in the 19th century world, "Soda ash" meant "a melange of sodium containing compounds" while "potash" meant the same for potassium and "lime" meant the same for calcium. These compounds could be seperated or treated to form new compounds, but the entire class is still known as "soda ash"; just different kinds of soda ash. The convention has just hung around for 150 years or so. As noted, what is called "soda ash" for one application may be very different than what is "soda ash" for another. You would need to know the assay of the soda ash in the water treatment application, and obtain something which was the same stuff. Just being called "soda ash" makes no guarantee that it will be... --Jayron32.talk.contribs 19:14, 28 February 2009 (UTC)

What Jayron said. One other thing which might help explain why we're advising such strong caution... drinking genuinely strongly-alkaline water is a really good way to wind up in the hospital or dead, health food gurus' claims notwithstanding. Underdoing the amount (and alkalinity) could be dangerous if it means bacteria don't get zapped, but overdoing it can easily be just as dangerous. If you ever saw a skull and crossbones on a sign in a really old Western that warned "ALKALI WATER" - well, alkalosis can kill you a lot faster than dehydration. arimareiji (talk) 19:40, 28 February 2009 (UTC)

This is all very interesting and all - but nobody has yet said why putting soda-ash-designed-for-swimming-pools into drinking water would be such a terrible idea. You typically ending up ingesting a fair amount of pool water - and when you add soda-ash to your well, you obviously have to take precautions to use appropriate amounts - perhaps to check pH and such. People who get their water supplies from their own wells know how to deal with the water not becoming too alkaline. People outside of big cities live from well water throughout Texas - it's not at all an uncommon thing. Why is this so terrifyingly different for 'pool soda ash' than 'well soda ash'? SteveBaker (talk) 00:55, 2 March 2009 (UTC)

You drink far more water from a well than you do a swimming pool, that makes a big difference. Swimming-pool-soda-ash might not be purified as much as drinking-water-soda-ash, since there is no need to and it save money, and those impurities will become a problem when you drink several litres of well-water. --Tango (talk) 12:00, 2 March 2009 (UTC)

In the water supply here the water companies uses slaked lime to achieve correct pH that stoppes pipes from being dissolved. I hope you are testing the water before drinking it! Graeme Bartlett (talk) 20:21, 1 March 2009 (UTC)

Why Are People So Stupid?

Why do people take a health class, learn about the germ theory of disease, and yet still think that going outside in the cold is what causes their illnesses. I thought we were out of the dark ages, but I guess not. Why do you think people think this? 169.229.75.128 (talk) 19:24, 28 February 2009 (UTC)

Because there is a correlation between low temperatures and people getting ill, and people often misunderstand the natures of causation and correlation. See Common cold#Exposure to cold weather for details. --Tango (talk) 19:30, 28 February 2009 (UTC)

That, and people have forgotten about the importance of handwashing in disease prevention. It's nasty to think about, but 1) cold weather -> runny nose 2) runny nose gets wiped by hand 3) hand touches object (i.e. door handles) 4) other hand acquires infectious mucus from object 5) repeat steps 1 and 2. arimareiji (talk) 19:44, 28 February 2009 (UTC)

But the cold weather doesn't CAUSE the runny nose. 169.229.75.128 (talk) 19:55, 28 February 2009 (UTC)

My nose and the weather outside beg to differ. ;-) But more importantly, so does wisegeek.arimareiji (talk) 20:12, 28 February 2009 (UTC)

I concur. We now have two anecdotes, thus data, QED. :) --Tango (talk) 20:33, 28 February 2009 (UTC)

Germs may be the cause of a particular disease, but dried out sinuses due to low humidity inside in the winter might lessen the bodies resistance, as could stress or other effects of extreme cold. Cold weather might increase to chances of exposure to a germ resulting in the full-blown infeection. Edison (talk) 20:45, 28 February 2009 (UTC)

Cold weather does too cause runny nose. When you inhale, the cold air cools the internal surfaces of you nose cavity. Then when you exale warm and humid air, the vapor condenses on these cold surfaces and the now liquid water runs down your nose, hence a runny nose. Dauto (talk) 20:48, 28 February 2009 (UTC)

The problem is that the average person in the street is continuously bombarded with false information. We're told that herbal remedies will cure medical conditions by 'boosting your immune system' (these statements have not been verified by the FDA, this food supplement is not designed to diagnose or treat any medical condition) and that you can lose (up to) 30lbs (results not typical) just by taking this pill without exercising - and eating all you want!! (results obtained along with diet and exercise). We find 'dianetics' filed in amongst 'diabetics' in book stores - we have homeopathic remedies (ie pure water) in amongst actual real treatments in pharmacies. We have adverts on TV telling you that "it's now well accepted that male enhancement really works" - and that "we couldn't say this was true if we didn't have TWO!!! US patents for our product!!!" (sadly, yes you could - and a patent proves nothing). We have 'energy drinks' in the 'health food' aisles in supermarkets and yoghurt that makes you shit at "more regular" intervals (Why is that important?). I especially liked the product that contains as it's "active ingredient" something described as "a tiny relative of the mushroom" (they mean it has fungus in it). Even fully trained doctors are prescribing antibiotics for viral diseases such as the common cold because people who've sat around for an hour with a whiny sick kid don't want to leave the office without a prescription for SOMETHING in their hands. No wonder people are confused! Who should they believe? SteveBaker (talk) 20:49, 28 February 2009 (UTC)

We don't need no education? But seriously, the United States has mandatory free public education and in many places it's all-year long. If this kind of exposure to scientific fact is not able to eliminate misinformation, I can only conclude that in some statistical sense, much of the population will never be able to distinguish fact-based reality from fiction. Calling them "stupid" is just a pejorative label of their alternative viewpoint about reality. Nimur (talk) 22:50, 28 February 2009 (UTC)

Well -- just to pick what may be one of the most obvious examples here -- if one authority tells you that the Earth is 4.5 billion years old, and another tells you that it's 6,000 years old, and you're in an environment where a lot of the people you know will insist on the latter being the truth, no matter how much that violates logic or what scientists say, it's not that surprising that a lot of people get confused about a lot of things. It's not just a question of providing people with education, because not all of that education is good or provided in the interests of expanding the recipient's knowledge and understanding. -- Captain Disdain (talk) 23:20, 28 February 2009 (UTC)

The average person in a US street is bombarded with the kind of information you refer to. The UK does not have such bad advertising (it doesn't have good advertising, but everything's relative), yet people here still have many of the same misconceptions. I think it's word of mouth that spreads the kind of nonsense we're talking about, not TV. --Tango (talk) 23:49, 28 February 2009 (UTC)

Many schools teach their pupils to be stupid - they actively discourage questioning attitudes & encourage the thoughtless acceptance of "authority". In the world of employment, again, stupidity can be advantageous - after all, pointing out one's boss's errors is unfortunately not a good carreer move in many companies. DuncanHill (talk) 23:53, 28 February 2009 (UTC)

And hence, we don't need no education -Pete5x5 (talk) 05:12, 2 March 2009 (UTC)

Schools generally teach fact learning because it is easier to test than understanding and governments want statistics they can misrepresent during elections. --Tango (talk) 00:03, 1 March 2009 (UTC)

Cold weather doesn't cause a cold, but it can decrease blood flow to the head, weakening the immune system in that area. For example, I find that I most often experience colds and diarrhea (AKA stomach flu, a misnomer) in the wintertime, although this isn't always the case. As for education, North America probably has quite poor mathematics curriculums in elementary school, I remember people in my class struggling with problems which, I know in some other countries, is taught, say, five years earlier. As for misconceptions, there are plenty of them. In fact, I wouldn't be surprised if most people "know" more misconceptions and myths than they do facts. For example, I know this is OR, but I've often noticed people misidentifying "power" as the most important aspect of a telescope or misidentifying Venus as an airplane.

It's strange, that people who don't care about nearly anything, can suddenly defend to death a misinformation what they have heard from a friend who heard form another friend who read it in a magazine. "It's absolutely true that yoga can change your bioenergy flux and cure cancer if you concentrate enough". --131.188.3.20 (talk) 13:53, 2 March 2009 (UTC)

Stone-age axe-head factory.

I recently listened to the audio book of Bill Bryson's A Short History of Nearly Everything. Near the end he speaks of a place in Africa (Rift Valley?) where there are remains of a massive stone-age axe-head factory. He describes how hundreds of people must have been employed in the production of stone tools for some time at this one location. Because I only have the audio book, I don't know how he is spelling the name of this place, but it sounds like Olega Sally, although that's not how it's spelt so I can't find out any further info on it. Can anyone give me the actual name of this place please? Thanks.91.111.64.177 (talk) 23:04, 28 February 2009 (UTC)

Are you sure it wasn't Olduvai Gorge? That's sort of the best known rift valley site. --Jayron32.talk.contribs 23:30, 28 February 2009 (UTC)

It's Olorgesailie (no idea if that will be blue!) DuncanHill (talk) 23:42, 28 February 2009 (UTC)

Here's a blue link [7], though not one of WP's. // BL \\ (talk) 00:16, 1 March 2009 (UTC)

Olorgesailie is on the WikiProject Missing encyclopedic articles list of important/missing articles - so hopefully someone will fix that. SteveBaker (talk) 00:52, 1 March 2009 (UTC)

Not exactly my cup of tea, but I dug up what I could. Clarityfiend (talk) 06:06, 1 March 2009 (UTC)

Thank you! That's great! This is the Ref Desk at it's best - feeding consumer demand back into the encyclopedia. With a new article like that (and one so well referenced) - you should probably shoot a line to the Template_talk:Did_you_know folks - they'll put a line from the article onto Wikipedia's "Did You Know" box on the front page and within days roughly a gazillion^* avid Wiki-acheologists will have edited the heck out of it and you'll have a proper article. (^* five)SteveBaker (talk) 15:55, 1 March 2009 (UTC)

Alas, it isn't long enough (1500 words) for DYK. Too bad, because the Italian POWs would have made a nice hook. Clarityfiend (talk) 21:02, 1 March 2009 (UTC)

No, no, no! 1500 CHARACTERS - not words! You have over 2600. You need to get a move on though - once the article is more than 5 days old, it no longer qualifies. SteveBaker (talk) 23:23, 1 March 2009 (UTC)

Actually, its 1500 characters of main-body text, not counting references, infoboxes, hidden comments, categories, templates, etc. Ran the main text thru Word, and it's only 819 non-space characters. It would need to be about twice as long to qualify. And he has 4 more days (March 5th) to get it in under the next update. --Jayron32.talk.contribs 01:17, 2 March 2009 (UTC)

Julia Rossi has gone ahead and nominated it. I've expanded it a bit, but it's still rather marginal, especially since DYK doesn't use stub articles. Well, we'll see. Clarityfiend (talk) 07:56, 2 March 2009 (UTC)

Another collection of stone age tools was recently found in Colorado. It consisted of 83 Clovis-style tools. I wonder if it was the stock of a stone age merchant. The find is described at http://news.yahoo.com/s/ap/20090226/ap_on_sc/ancient_tools

GlowWorm. —Preceding unsigned comment added by 98.17.40.185 (talk) 02:08, 1 March 2009 (UTC)

Thanks guys, good work. I'd stick a 'resolved' thingie on this if I knew how.91.111.64.177 (talk) 18:43, 1 March 2009 (UTC)

Easy! You just say {{resolved}} (things inside doubled curly braces are 'TEMPLATES')...although I generally advise against doing that because other editors may yet have more information (or, more importantly, corrections to existing responses) - and I always feel that the big RESOLVED check mark dissuades people who come along later from reading the question and it's responses so far because they suspect that the OP (that's you) won't be coming back to read more. That's sad because very often the most interesting and perceptive answers come along later because not everyone patrols the RD every day (especially over the weekend). But if you feel the need - go ahead and stick a {{resolved}} on it. SteveBaker (talk) 23:45, 1 March 2009 (UTC)

Isn't there a template for articles that says something like "This article brought to you by the fabulous people at the RefDesks"? DuncanHill (talk) 12:09, 2 March 2009 (UTC)

This article brought to you by the fabulous people at the RefDesks.

No, there isn't. SteveBaker (talk) 20:15, 2 March 2009 (UTC)

March 1

Lineage dna testing

I've been thinking about getting some DNA testing done to learn a little bit more about my family's past. What are some of the most reputable companies. I'm on a budget, so I don't want to be spending my payckeck to get this done either. --Ghostexorcist (talk) 17:39, 1 March 2009 (UTC)

What kind of testing do you mean, particularly? I mean, are you looking to see, say, if you and your siblings come from the same biological parents (for example), or are you looking for, say, one of those "how many racial groups am I made of" sort of tests (which are extremely problematic, it must be said), or, are you looking to compare some old lock of hair found with other DNA, or what? I imagine all of these would require somewhat different labwork, probably are done by different companies. --98.217.14.211 (talk) 18:02, 1 March 2009 (UTC)

(ec - I'm assuming the 2nd of the anon's options) You'll probably learn more by tracing your family free the old fashioned way - go through censuses, birth, marriage and death certificates as the local records office (and other records offices wherever your family have lived), baptism records at churches, etc., etc.. There are people (and websites) that can help you with such things. DNA testing will only give you very vague information, if anything. --Tango (talk) 18:05, 1 March 2009 (UTC)

We would be able to tell you more if you were more specific about exactly what you want to accomplish by DNA testing. One of the best known companies is Family Tree DNA [8], which has a large associated database due to its (comparatively long, for a DNA company) history. It performs Y-DNA and mtDNA testing. Another more recent entry is 23andme, [9] which tests autosomal markers as well as Y-DNA snps and mtDNA, though less extensively than FTDNA. There are other comments which I would make about companies to avoid that are more suited for a less public forum; feel free to e-mail me at the "E-mail this user" link on my talk page -Nunh-huh 18:09, 1 March 2009 (UTC)

You also may be interested in the International Society of Genetic Genealogy (ISOGG) y-DNA testing comparison chart. the ISOGG mtDNA testing comparison chart, and other information at the ISOGG site. - Nunh-huh 18:15, 1 March 2009 (UTC)

If you are thinking about these "what races am I made of" tests, you should really be aware that the methodology is very problematic and the information they give you (in terms of the % black, % white, etc.) is often scientifically quite meaningless. --98.217.14.211 (talk) 19:20, 1 March 2009 (UTC)

Unless you have a specific question (e.g. which allele do I have at a specific locus), you would be better off putting the money you intend to spend on this in a high interest savings account for 5-15 years. In that time, both sequencing technology and our knowledge of DNA sequence variation will have advanced significantly, so you can get a lot more bang for your buck. Currently, genome sequencing is expensive and the genealogy information they can provide is limited to say the least. Rockpocket 19:34, 1 March 2009 (UTC)

Well, yes and no. Some considerations include the likelihood that the person you want to test will die before the test reaches your desired price; one alternative to testing now is DNA storage. - Nunh-huh 19:59, 1 March 2009 (UTC)

Fair point. But even if time is an issue (unless you have some particularly unusual or rare genetic features or know nothing about your biological family) you would likely infer, with similar confidence, as much about your ancestry with a little old fashioned genealogy as you would from any commercially available DNA testing. DNA storage is a good idea, though. I have mine cryopreserved in a number of places (I used to use it as a control for various DNA testing I used to do!). Rockpocket 21:21, 1 March 2009 (UTC)

Like I previously stated, I want to learn a little more about my family's past, so it would be one of those "how many racial groups am I made of". --Ghostexorcist (talk) 02:04, 2 March 2009 (UTC)

Tests that come back with results like "70% European, 20% East Asian, 10% African" are really more or less a waste of money. (See our Genealogical_DNA_test#Geographic_origin_tests ). They're inadequately validated and provide very little information for the money provided. Have a look at what 23andme is offering: they test your genotype via a DNA chip rather than by sequencing. The ethnicity portions of the test don't claim to provide more information than they actually do, and in addition to the ethnicity portion you are likely to find interesting genetic information. - Nunh-huh 05:48, 2 March 2009 (UTC)

voice on the moon

I have reed that when Neil Armstrong go to Cairo ,where he herd a voice of Azan (Muslim calling before prayer) ,he mentioned that I have herd this voice on moon.I think this event is not happened.But I want to know your opinion —Preceding unsigned comment added by True path finder (talk • contribs) 19:41, 1 March 2009 (UTC)

Later, Muslims were elated with the baseless rumour that Neil Armstrong had converted to Islam as he had heard the call to prayer (azan) on the moon. Another version attributed his conversion to his having seen signs of the ‘parting of the moon’ as believed by Muslims. [10] This rumour is also revealed as untrue in numerous biographies of Armstrong, e.g. [11] and books about Islam, e.g. [12] Rockpocket 19:48, 1 March 2009 (UTC)

I'm sure he didn't say that (of if he did - then I'm certain it was a remark made out of courtesy that was misinterpreted)...and Rockpocket's references confirm that. But in any case - there is no air on the moon. There is no sound there. If he had truly heard something it would have had to come over his radio - and that could just as easily have come from earth as from the moon. He would certainly know this! Hence, he would have known that he either imagined the whole thing - or heard some sound from mission control. It's really an impossible story. SteveBaker (talk) 23:18, 1 March 2009 (UTC)

Shows what you know! God is everywhere, which obviously includes Neil Armstrong's inner ear. --Sean 15:32, 2 March 2009 (UTC)

I don't know about that - but the Azan is a very human human standing at the top of a tower yelling REALLY loud. I don't think god or gods are very much involved in that bit. SteveBaker (talk) 20:12, 2 March 2009 (UTC)

Every place I have ever been has always used a loudspeaker with electronic amplification to replace the "really loud yelling". Most of them used pre-recorded versions, typically MP3 recordings of famous Azans such as those of Haram Ash-Sharif, or famous poetic recitations recorded in the 1950s and 1970s. I've also seen phonograph records and audio-cassettes used in places where iBooks don't penetrate the market so thoroughly. I would hope that this demonstrates that the majority of mainstream Muslims can adapt and adopt science and technology to the culture, without spewing out mindless fringe pseudo-scientifico-theologicial nonsense. Nimur (talk) 21:43, 2 March 2009 (UTC)

Presumably on the Moon the 'loudspeaker' would be arranged so that the sound is conducted through the ground. —Tamfang (talk) 03:06, 3 March 2009 (UTC)

I believe that at least one pair of moon-walkers tried that experiment. Turning off their radios and yelling really loud to see if the other person could hear them from a foot or two away...without luck apparently. SteveBaker (talk) 00:15, 4 March 2009 (UTC)

Did they try it with helmets touching? That ought to work reasonably well. --Tango (talk) 00:25, 4 March 2009 (UTC)

Do Homophobic Men Harbor Secret Homosexual Desires?

Do they? Or is it just a strategy of the gay community to strike back?--83.59.239.32 (talk) 19:51, 1 March 2009 (UTC)

Some probably do, I very much doubt all do. I doubt there are any real studies on the subject - I'm not sure homosexual homophobes would describe themselves as such on a questionnaire (even an anonymous one). Am I the only one that hates the word "homophobe"? The word should mean "one who is afraid of things that are the same". --Tango (talk) 19:55, 1 March 2009 (UTC)

And pontiffs should build bridges. LANTZY^TALK 04:49, 2 March 2009 (UTC)

It is better to pontificate than to curse the river! —Tamfang (talk) 03:02, 3 March 2009 (UTC)

Of course, we have an article (well, a section): Homophobia#Internalized homophobia. --Tango (talk) 19:57, 1 March 2009 (UTC)

I would kinda think this belongs at a culture/sociology desk... but I don't know if we have one. You could make a good case for projection out of many incidences of fanatical hatred. But that's gay-bashing rather than homophobia - IMO, two very different critters. I don't really care who does or doesn't like my sexuality, as long as they leave me alone about it.

(Nonetheless, $20 says Fred Phelps is gayer than a mauve flamingo in buttless chaps.) arimareiji (talk) 20:13, 1 March 2009 (UTC)

I guess they would come under the Humanities desk. There is always a lot of overlap between the desks, though. --Tango (talk) 20:29, 1 March 2009 (UTC)

Reaction formation also touches on the subject. But I doubt ALL homophobic men are actually gay. Then again, some say that most people aren't 100% homosexual or 100% heterosexual. --Bennybp (talk) 20:38, 1 March 2009 (UTC)

Some men certainly do: just take a look at Ted Haggard, whose anti-gay rhetoric got a delicious end when the male prostitute he'd been banging for three years outed him. (Generally speaking, I'm not a big fan of outing people, but Haggard certainly had it coming.) Or Senator Larry Craig, whose legislative career was far from gay-friendly, but who still felt the urge to cruise airport bathroom stalls for a little man-on-man action. There are plenty of other examples. But does that mean that all homophobes are closeted homosexuals? Of course not. You don't need to have complex psychological self-image issues for that. You can just be an asshole. -- Captain Disdain (talk) 20:39, 1 March 2009 (UTC)

I nominate the last two sentences for Comment of the Day. Thanks for the laugh. ^_^ arimareiji (talk) 21:51, 1 March 2009 (UTC)

In there interests of WP:BLP, we should note that Larry Craig does not self identify as homosexual and he says that the bathroom stall incident(s) were misunderstandings. [13] Rockpocket 00:13, 3 March 2009 (UTC)

Also, Ted Haggard only shared unspecified "sexual immorality", with the admission only of massages, with his motel-mate. So there's hope for these heterosexuals yet! --Sean 02:04, 3 March 2009 (UTC)

Why do all these homosexuals keep sucking his cock? LANTZY^TALK 05:42, 3 March 2009 (UTC)

That was definitely the Link of the Week. XD And could be a great Kids in the Hall skit. arimareiji (talk) 05:58, 3 March 2009 (UTC)

Pfft. WP:BLP doesn't apply; this is not a biography, this is a conversation, and obviously my personal opinion. In fact, I'll grant you that it's possible that Craig, an unmarried man, is completely heterosexual, and this is all just a big misunderstanding, just like it was when it was rumored that he was involved in the sex scandal that involved congressional male pages, back in the 80s. And perhaps he was indeed just in the bathroom minding his own business, when a terrible misunderstanding occurred. And all those other allegations may be nothing but lies. It's possible. -- Captain Disdain (talk) 07:01, 3 March 2009 (UTC)

How long would my body take to realize I'm healthy again?

I'm sneezing, my muscles are aching, I'm coughing and it tastes of blood. Suddenly an alien from outer space appears in my bedroom, pointing its mobile at me. It does a quick scan, then presses a button. A little flash of light, and all DNA and RNA of any microbes, is teleported away. The alien, too, vanishes.

Given the above scenario would be true, how long would my immune system take to realize there's nothing more to do than to bail out the now defunct cells (or hulls, if viruses) of the invaders and go back from war to healthy, watchful sentry? Would that be minutes, seconds, hours or days?

Same question the other way round: say that alien bastard appears again, putting everything back in place, muttering something about misspelled names and how we earthlings all look alike, how long would it take to start the immune reaction up again? 93.132.153.222 (talk) 20:14, 1 March 2009 (UTC)

Getting rid of all microbes would be a bad idea - you would get terrible stomach cramps, at the very least (maybe worse). There are lots of bacteria in the gut that are very important. If you revise your question to just disease causing microbes, then I don't know! --Tango (talk) 20:36, 1 March 2009 (UTC)

I'm not a ruminant feeding on grass, why should I get stomach cramps? 93.132.153.222 (talk) 20:55, 1 March 2009 (UTC)

Although you're not a cow, what Tango said is still true. Check out Human flora. Also, I think it's debatable whether or not you would still call yourself "healthy" if your body doesn't "recognize" that you are. There's lots of shit that your body can do to you to make you feel like shit without the help of microbes, like autoimmune disorders, degenerative muscle diseases, and endocrine issues (like diabetes). If you feel like shit, you're still not "healthy."--Shaggorama (talk) 21:06, 1 March 2009 (UTC)

I wrote realize, not recognize. I'm not a native speaker and may have a false concept about some words, if so, please correct me. The human flora article doesn't really tell me why I should get stomach cramps. The normal flora can act as opportunistic pathogens, cause acne, dissolve tooth enamel and assist global warming by producing methane. On the pro, it prevents the really bad microbes from growing, produce some vitamins and help digest some of the complex sugars. (In case I'd have lactose intolerance that would really give me stomach cramps, I know people who have.) 93.132.153.222 (talk) 21:49, 1 March 2009 (UTC)

I think, in this context, 'realise' and 'recognise' mean the same thing. As you say, one of the things the bacteria in your gut do is aid digestion - without them, you can't digest food properly and that gives you stomach cramps. It's a fairly common side effect of taking lots of antibiotics. --Tango (talk) 21:55, 1 March 2009 (UTC)

Thank you for the realise/recognise help. As for the food digestion, I think this is only a problem when other bacteria digest what the good ones would, but to different end products. If there are no (no, none at all) bacteria around that would not happen. Otherwise stomach cramps from taking antibiotics would be quite common. In the above scenario there wouldn't even be yeasts to do a maldigestion. 93.132.153.222 (talk) 22:10, 1 March 2009 (UTC)

Actually, I've had stomach trouble most of the times I've taken antibiotics... but I see what you mean. No cramps from gas, but it might still cause trouble from osmotic issues. arimareiji (talk) 22:30, 1 March 2009 (UTC)

I'm not sure about the removal of DNA/RNA from microbes, but a complete lack of exposure to "germs" in general can act to weaken the immune system (and usually at a bad time)! For example, if you were subject to using hospital pillows for a number of days, your immune system may be weakened to the pillow fungi in ordinary pillows. ~AH1^(TCU) 00:26, 2 March 2009 (UTC)

In an attempt to answer the question... The amount of time it took to get your body back to healthy would vary from symptom to symptom and person to person. A rough analog might be found in the case of allergies, where the ingestion of antihistamines can get you back on your feet in anything from a few minutes to a few hours, depending on how inflamed your tissues are, etc. The allergen doesn't actually do any damage (almost by definition), so the issue is just about calming your system down and then letting your body get back to normal. In a similar vein, a persistent symptom can keep going indefinitely even after the disease is finished. On a couple of occasions I've gotten over a cold, but been unable to shake a cough that the doctors said was simply due to the irritation of coughing... which made me cough - and onwards into a vicious cycle. The alien could have cured me an an instant, but I would have kept coughing regardless. Your second question probably relies most heavily on the incubation time of the particular bug. Matt Deres (talk) 17:51, 3 March 2009 (UTC)

Psychology: why is working on computer dull, but computer games fun?

Doing administrative work of some kind using a computer may require the same amount of decision making, intellect, and time, as playing a computer game. But one is dull, the other fun. What are the differences between the two that make it either fun or work? NB:- this is not a homework question. I'm wondering how I can make my own work more interesting, and motivate myself to do more of it more avidly. Thanks. 89.241.154.51 (talk) 21:59, 1 March 2009 (UTC)

I don't think the computer part is relevant - work is (or can be) dull, games are fun, regardless of the medium. I'm not sure there is much you can do to make work interesting - either you're doing work you find interesting, or you aren't. You could try getting a different job. I think the key difference is that you choose what games to play, so you choose games that you find interesting. You generally have less choice about what work you do. --Tango (talk) 22:06, 1 March 2009 (UTC)

I think it's the liberty to do it or leave it. If you would be forced to play computer games (say you have a payed job as tester that your income depends on) there would be no fun in it. 93.132.153.222 (talk) 22:14, 1 March 2009 (UTC)

Some people could call it the perfect combination of skill level + job + fun. Julia Rossi (talk) 22:29, 1 March 2009 (UTC)

Annoyingly, a lot of people think that - and it's a myth that's fed by the colleges that offer courses in game technology. In truth it's boring, repetitive, exacting work. They don't just play the finished game for a week or two - they play the exact same game over and over for YEARS. To start with the game is utterly bug-ridden - it'll crash at the most annoying moments. You'll get halfway through some interesting new part - and find that the rest of the 'quest' or whatever hasn't been written yet. They have to push it in every way - go everywhere in the game levels - try to do things as stupidly as possible as well as with the most skill possible. And they have to log what goes wrong (and in the early days, LOTS of things go wrong) - there are daily reports to be made. They find a bug and report it - then every day from then until it's fixed, they have to try the same complicated thing and report on whether the latest code release from the programming/art/level/audio teams fixed it. Even after it's fixed - they have to recheck it periodically to ensure that it didn't 'come back' later. Trust me - it's about as far from playing an enjoyable game as you can imagine. Job prospects as a game tester are pretty limited - there is a team leader job to aspire to - but there aren't lots of grades of play tester that you can progress through. It's also pretty low paid because of the supply-and-demand thing. So many kids think (as you evidently do) that this would be the most fun thing in the world - that the supply of willing workers is high - so the pay is low. Trust me - this is NOT a great job. SteveBaker (talk) 23:05, 1 March 2009 (UTC)

Yet, for some reason, people still recommend game testing as a good way to get into the games industry on your way to becoming a developer. I've never understood where people get that idea... --Tango (talk) 23:34, 1 March 2009 (UTC)

Not really - I mean, it's possible I suppose - but I don't see hoards of people who came at it that way. There are no skills you learn as a play tester that are of much use through the rest of the development chain. I suspect that those who do make it are taking community college classes in something relevent. The best way in is to take a proper college course. Someplace like Full Sail University in Florida which seems to provide a lot of the talent that feeds into the business. Alternatively, a solid, proven background in 3D art, programming or the technical side of music/audio recording. I had been a 3D graphics programmer for a gazillion years before I got into the biz. SteveBaker (talk) 00:38, 2 March 2009 (UTC)

I'm a game developer - we have people within our team who's job it is to play games all day - they are in our quality assurance group. I think pretty much everyone agrees that it's the least exciting job in the company. The reason is because when you play a game for the first time, it's new - it's different - and game designers work hard to keep the experience changing from start to finish by adjusting the play difficulty upwards as you progress through the levels - and making the levels fairly diverse - adding new abilities for your avatar to use - then (perhaps) horribly limiting them to make a new challenge. That simply doesn't happen with administrative work, spreadsheets, word processors - what you have on the first day you use WORD you have on the last day. Our play-testers get just as bored as you do because they play the same game over and over - literally thousands of times each over periods of one to two years. It's a job...it's not "fun" most of the time. But you'll only play our games a few times...you won't (hopefully!) get bored with it before the next game comes along.

Having said that - I don't entirely agree with your premise. Not all non-game-things one does at a computer are boring and repetitive. My specialty is programming - and I LOVE to program. When the difficulty of what I'm doing at work isn't challenging enough, I spend my off hours writing OpenSource software...sometimes my own games..just to keep my skills sharp. I love working at the computer.

SteveBaker (talk) 22:55, 1 March 2009 (UTC)

What you need is, as Steve makes clear, a job that does for you what the games do: gives you interesting, changing problems. There are many jobs that can do that. If you aren't in one, figure out what you need to do to get into one. Life's too short to do incredibly dull, repetitive work all day long. --98.217.14.211 (talk) 01:36, 2 March 2009 (UTC)

Unfortunately, for 90% of the people, life becomes shorter when you choose not to do dull, repetitive work all day. In an ideal world, everyone would be able to support themselves with jobs that meet their skill set and interests. In the real world, people often take whatever job they can get in order to survive. Sometimes, if they don't like it, they can find another job they don't like just as much as the last one. And then they can either stick with that job they don't like, or find yet another unfulfilling job. Either that, or live on the street and panhandle. --Jayron32.talk.contribs 02:41, 2 March 2009 (UTC)

Obviously we don't live an ideal world—certainly not at the moment—but the idea that people get into their heads that their only two options are shitty job they don't like or panhandling is usually quite false. From what I can tell most people end up becoming quite fatalistic quite quickly. There are some people who are in exceptionally bad circumstances and are lucky to get whatever they can find. But there are quite a lot of people in a more middling category. I don't deny though that making radical changes means making radical choices—one has to figure out one's priorities, because not all situations are mutually reinforcing. --140.247.253.176 (talk) 19:36, 2 March 2009 (UTC)

I want to fly over the program to spot anything awry. Neaaaagh I push my joystick forward and dive down to see what's happening. It's a horrid great big bug. I press the button and dat dat dat I've blasted it. It dies with a shriek and explodes. I splat a sticker on the side of my cockpit with the others. Yeah another one bites the dust. There, you jus need the right atttude to software. Dmcq (talk) 01:04, 2 March 2009 (UTC)

Zackly. An that's just the spreadsheet! :)) Julia Rossi (talk) 01:34, 2 March 2009 (UTC)

There you go! Like increasing numbers of games companies, we use the SCRUM development method - and the morning scrum meetings (when things are going well) has a lot of that feel to it. Lots of energy - lots of good feelings about nailing problems. When you nail a bug that's been annoying everyone or show off a new feature - expect applause...cheers...tons of energy. On Friday - late afternoon, we all show off our latest stuff, the company pays for beer, food - we play RockBand...etc. It's not a 'normal' job - work hard, play hard, be a real team - never leave a buddy behind...that kind of thing. SteveBaker (talk) 02:39, 2 March 2009 (UTC)

Looks good. I like in particular the work had not long bit. I've always wanted to work into the rules that it is the teams that get the job done without fuss and in time get extra resources and are kept together and used as a group to fix problems rather than being split up and used as resources where things are failing. Too often it is the person who is late and then works hard fixing a mess that gets the praise and promotion. A moderate amount is fine but more should be given for doing it without going into headless chicken mode. Dmcq (talk) 09:03, 2 March 2009 (UTC)

Seems like games testing is not much different then testing any other software, except games are at least fun the first couple of weeks. 65.167.146.130 (talk) 16:27, 2 March 2009 (UTC)

Playing a game constantly for two weeks in which only half a level is written and even that doesn't work properly doesn't sound like much fun to me... --Tango (talk) 17:43, 2 March 2009 (UTC)

Yes, exactly. On week 1: The 'world' is four large white cubes sitting on a checkerboard. Your character is borrowed from the last game you wrote - you can walk and run but not jump, climb or crawl and none of the weapons are implemented yet...the first 'enemy' or 'puzzle' is about six months away. Enjoy! (Actually, we usually don't start using play-testers in any great numbers until we're further along than that - but at worst, it can be that bad.) SteveBaker (talk) 20:09, 2 March 2009 (UTC)

Responding to the title question rather than to the discussion: You need to consult that great scientist Mark Twain, who wrote up the definitive answer to this quandary in one of his paradigm-changing papers, entitled The Adventures of Tom Sawyer. --Trovatore (talk) 20:11, 2 March 2009 (UTC)

March 2

Egyptian Goose?

Egyptian Goose?

I saw two of these birds in a park in Southern California. I hadn't seen this type before, so I took a picture and did some searching. It appears to resemble an Egyptian Goose, although from what I can tell that bird isn't usually found in the U.S. Any ideas of other similar-looking birds or might the two birds I saw have been a little far from home? --Nick—^Contact/_Contribs 01:12, 2 March 2009 (UTC)

Maybe they are continent hopping – how far from home is Britain to Southern California? Julia Rossi (talk) 01:39, 2 March 2009 (UTC)

Could it possibly have been an escapee from someone's collection? In the UK, there are loads of touristy-type places that have fancy geese and peafowl wandering around the place, looking pretty... --Kurt Shaped Box (talk) 01:42, 2 March 2009 (UTC)

Certainly the top-left photo here looks identical to your photo...so I think we can be sure it's an Egyptian Goose. Is it possible that the park keeps these exotics (perhaps with clipped wings to keep them there) as a part of the attraction of the place? Could you tell us the name of the park and it's location? Perhaps there is information to be found about that someplace online. SteveBaker (talk) 01:45, 2 March 2009 (UTC)

Doh! Yeah, the bird may very well belong to the park (sorry, I didn't fully read the question). It may even have been pinioned to stop it from flying away... --Kurt Shaped Box (talk) 01:53, 2 March 2009 (UTC)

Nah, it's a small neighborhood park with a lake maintained by the city. It must just be feral or an escapee or something. Thanks though, I appreciate the confirmation of my suspicions of the type of goose. --Nick—^Contact/_Contribs 02:30, 2 March 2009 (UTC)

[14] says that there are feral Egyptian Geese in SoCal. [15] says that there are small 'escapee' colonies in many US states. In comments attached here it's clear that sightings in California certainly happen...it's hard to say how common they are. SteveBaker (talk) 02:03, 2 March 2009 (UTC)

It could also be someone's fancy lawnmower service. Don't know whether they still do it, but back in the 70s a couple of people rented out geese as environmentally friendly alternative to keep people's lawns short. They had clipped wings and their owner would come back after they had spent the allotted time grazing to collect them. This ghit seems to indicate they're still doing that [16] 76.97.245.5 (talk) 09:14, 2 March 2009 (UTC)

You might want to go with a mushroom/chestnut stuffing with appleauce over long-grain and wild rice. B00P (talk) 10:58, 2 March 2009 (UTC)

Is there a psychological reason why...

...certain people get *really* offended and/or angry if one is to in any way criticize their favourite fictional character in the context of discussing say, a TV show or a movie? I don't know for certain if it's just a web forum thing - but I don't personally know any people like that in real life. It's (very) easy to think of them as 'insane fanboys', or even 'idiots' - but is there any deeper psychology at work here? --Kurt Shaped Box (talk) 03:24, 2 March 2009 (UTC)

There's a concept in psychoanalysis: Identification (psychodynamic). It seems to be a defense mechanism and about lacking awareness at least. From experience, it's subjective, about lacking boundaries, and it's like an opinion is not an opinion it's a personal extension of the self. When you try talking about things people are heavily invested in for whatever ego-reasons, there's really no way around it. You might find Boundaries of the Mind: The Individual in the Fragile Sciences interesting though it needs cleanup. Julia Rossi (talk) 04:00, 2 March 2009 (UTC)

Can you point me to an example? I'm not familiar with this phenomenon. LANTZY^TALK 04:53, 2 March 2009 (UTC)

The classic example would be this exchange between Tuvok01 and SithLord12. Be sure to read Ms. Keavney's commentary, too, about SithLord12's good intentions. (Any resemblance to WP:AGF is of course purely accidental.)--Goodmorningworld (talk) 12:54, 2 March 2009 (UTC)

Heh, yeah. I can't actually find any bona-fide examples of precisely what I was talking about in my OP offhand. I don't make a habit of bookmarking them and those kind of threads usually get deleted by the mods/admins for being 'very silly indeed' at whatever board they happen to occur at. FWIW, it seems to get nastiest when people are discussing whom <character> should choose as his/her 'one true love' out of two of more possibles. It often (usually?) leads to fictional characters being insulted and fans of those characters jumping in to defend their fictional honour like a pack of rabid dogs... --Kurt Shaped Box (talk) 00:03, 3 March 2009 (UTC)

That probably points toward identification, as another poster said, then, becuase the person has chosen to...for lack of a better word...model their lives on that character, and feel insulted when it is stated that what they think is true of a character cannot occur. Sort of like when people choose to walk around speaking Klingon and dressing like one all the time. So, if person x thinks character A would hook up with character B, they are really saying, "if I were A, I would like B," because they might actually be putting some of their own personality into person A. Thus, when another comes along and says, "But, A would never like B, they are incompatible because..." the original person gets all offended becuase in their minds, A is hooked up with B, because they have become A int heir minds,a nd chosen B.

I think that makes sense, anyway.Somebody or his brother (talk) 17:01, 3 March 2009 (UTC)

Nonstick coatings

Would diamond make a good nonstick coating for things? Like teflon, it's extremely low-friction, but unlike teflon, it's extremely hard (and presumably wear-resistant). --Carnildo (talk) 05:21, 2 March 2009 (UTC)

This company makes cookware using a composite containing diamond crystals. You might also find this link interesting. LANTZY^TALK 05:33, 2 March 2009 (UTC)

You might have the reverse problem here. That is, instead of the utensils scratching the pan, the pan would scratch the utensils. Also, the mechanism you use to adhere the diamond dust to the pan might not be able to hold up to the stresses of cooking, meaning it would eventually come loose and be eaten. I'm not sure if diamond dust would be harmful if swallowed. I imagine it would be biologically inert, but might scratch up your teeth or intestines going through. See diamond tool for some of the other issues with using diamond powder. StuRat (talk) 14:39, 2 March 2009 (UTC)

If my diamond-coated frying pan scratches my stainless-steel spatula, it's a much smaller deal than if my spatula scratches a teflon-coated frying pan. --Carnildo (talk) 01:57, 3 March 2009 (UTC)

There are wooden and nylon spatulas especially made for teflon (certainly cheaper than diamond coated cookware). Why use stainless on the teflon?63.88.67.230 (talk) 05:37, 3 March 2009 (UTC)

Because roughly 99% of the items in my kitchen are steel: everything from whisks to knives to the uncoated sides of pans. I'd rather have a coating that I don't have to keep away from everything else. --Carnildo (talk) 01:25, 4 March 2009 (UTC)

The answer is no, (probably) - diamond has a three dimension lattice (unlike slippery graphite which is two dimensional) and teflon which is linear chains (probably) - so the surface of the three dimensional lattice will have reactive sites (unlike graphite and teflon) - usually these sites have -OH functional groups (hydroxyl) which is definiately sticky...

However 'fluorinated diamond coating' would not have this problem, and would be a much more scratch resistant coating than teflon - so such a coating could be a better replacement for teflon. —Preceding unsigned comment added by FengRail (talk • contribs) 15:06, 2 March 2009 (UTC)

Established biological basis for neuroses and biological therapy!

By now it is well established that psychoses have a biological basis and respond to biological treatments.Is there similar evidence for biological basis for neuroses as well?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 12:18, 2 March 2009 (UTC)

Our article on Neurosis notes that they can be treated by drugs. Since drugs have to act on the physical body, it seems rather simple that yes, neurosis are sometimes treated "biologically". --Jayron32.talk.contribs 12:28, 2 March 2009 (UTC)

Hardness of teeth

What is the approximate hardness of human teeth on Mohs scale? DuncanHill (talk) 14:44, 2 March 2009 (UTC)

Hydroxylapatite 5, or even Tooth enamel: second paragraph. —Preceding unsigned comment added by FengRail (talk • contribs) 15:10, 2 March 2009 (UTC)

Thanks - I didn't think to look under tooth enamel! DuncanHill (talk) 15:40, 2 March 2009 (UTC)

Blow it out your hole...

Why is it that more volume of a gas can pass through a given hole in a given time period than a liquid ? I know this is the case because the air hole on the far side of a can of juice doesn't need to be anywhere near the size of the liquid hole. I would guess it's because gases are far more compressible. So, this would mean the air compresses as it goes through the hole and decompresses on the other side, right ? Is this what's happening ? Also, what is the ratio, 10:1 ? That is, can ten times the volume of air pass through a given hole over a given time period as the volume of water which can pass ? Assume that the pressure differential is the same for both fluids (air and water). StuRat (talk) 15:16, 2 March 2009 (UTC)

Compression is probably indeed a factor, but I'd imagine that the fact that air suffers much less from drag than water does also plays a part in this. -- Captain Disdain (talk) 16:02, 2 March 2009 (UTC)

I agree with the Cap'n that it's drag/viscosity. A (thought) experiment to rule out compressibility would be to have a high-viscosity liquid in the jar, and a reservoir of low-viscosity liquid connected to the "air" hole. The limiting action is how fast the partial vacuum inside the jar can suck a fluid (gas or liquid) in through the pinhole in order to equalize the pressure of the outgoing thick stuff. I know intuitively that I could suck water through a pinhole more easily than I could suck cold honey through that same hole. --Sean 16:21, 2 March 2009 (UTC)

The different viscosities is the answer. The air compresibility plays very little role here. Dauto (talk) 17:13, 2 March 2009 (UTC)

As an alternate perspective (it's the same reason, just a different way of looking at it) gases have about 1/1000 the molecule density of liquids. As a liquid passes through a hole, more molecules are dragging against the edge of the hole, and against each other, than with a gas. More of these unproductive collisions is essentially greater friction, slowing the motion of the bulk fluid. With a gas, you have about 1/1000 of these frictional interactions, so it flows much faster. --Jayron32.talk.contribs 18:39, 2 March 2009 (UTC)

Im not sure the original claim is true. You say "more" like "more volume" - but I'd go by the mass. I'd be surprised if more MASS of gas could pass through a typical sized hole at soda-can-like pressures than mass of liquid. Remember one 240mL can of coke would produce 660 liters of steam if you turned it into gas. Could a can of liquid drain out of a quarter inch hole faster than telephone booth of gas under similar pressure? I think so. SteveBaker (talk) 19:02, 2 March 2009 (UTC)

The example given was a carton refilling with air after the liquid is poured out - that's clearly a matter of volume, not mass. --Tango (talk) 19:24, 2 March 2009 (UTC)

No - quite the opposite - my point is that the air hole can be much smaller because only a VERY tiny amount ("mass") of air is required to replace quite a lot of liquid. The volume is the same - but the number of molecules per second going through the two holes is vastly different. SteveBaker (talk) 20:57, 2 March 2009 (UTC)

Yes, but the OP's statement is still correct. You have equal volume going through both holes (otherwise the carton would collapse), yet the air hole is smaller. That corresponds to a greater volume of air going through a given hole than water could fit through that hole. The difference in mass may well be the explanation for that, but that doesn't make the statement incorrect. --Tango (talk) 21:15, 2 March 2009 (UTC)

True - but I'm trying to point out that 'equal amounts' shouldn't mean 'equal volumes' - and if you consider the number of molecules having to make it through the two holes - the entire question is moot because the amount of liquid and the amount of air are vastly unequal. So the ability of some amount of liquid/gas to flow through a hole may not be all that different. When you look at it like that, any mystery and suspense in the original question kinda goes away. SteveBaker (talk) 00:10, 4 March 2009 (UTC)

The Hagen-Poiseuille equation models laminar flow through a straight tube.

$\Phi ={\frac {|\Delta P|\pi R^{4}}{8\eta \Delta x}}$

$\Phi$ is flow

$|\Delta P|$ is change in pressure

$R$ is the radius of the tube

$\eta$ is dynamic viscosity

$\Delta x$ is the length of the tube

The dynamic viscosity of water is 1 centipoise, while that of air is about 0.017 centipoise. Axl ¤ [Talk] 19:31, 2 March 2009 (UTC)

OK, so that would mean that the air hole can be 1/59th the size of the water hole. With a rather thick juice, even more of a difference would work. I didn't know the difference was that much. Thanks. StuRat (talk) 15:00, 3 March 2009 (UTC)

Just to clarify the answer to the original question: yes, more volume of gas can flow than liquid (per unit time), because of the difference in viscosity. To Steve: The original claim certainly is true. The question explicitly asks about volume. If you are considering "mass" (not "volume"), that's an entirely different question. Axl ¤ [Talk] 19:36, 2 March 2009 (UTC)

Above, the incorrect statement was made, "You have equal volume going through both holes (otherwise the carton would collapse)" - it is certainly possible that the liquid drains out sufficiently fast that the gas pressure will drop (unable to be replenished by enough room air to maintain atmospheric pressure). The only hard requirement is that the pressure maintain high enough that there is a net flow of liquid out the other port (remember, though, that the liquid is acted on by air pressure inside the can AND by its own weight). After the liquid flow is done pouring, there may still be gas flow continuing to repressurize the can interior. In some extreme examples (say, dumping out an entire gallon of water from a "milk-jug" sized container) you can actually hear the container depressurize and repressurize. In cases where the liquid pressure is sufficiently high, (lots of mass in a tall-shaped container, e.g.) the internal gas pressure can drop significantly. Nimur (talk) 22:05, 2 March 2009 (UTC)

There are three possibilities - equal volume going in and out, the container collapsing (or, more likely, being squeezed) or the liquid "glugging" out as you describe. My statement was slightly incorrect in that I missed out the final option (and, I guess, there is a special case where it would glug but you finish pouring before the first cycle is complete). --Tango (talk) 16:38, 3 March 2009 (UTC)

OK, so that would mean that the air hole can be 1/59th the size of the water hole.

— StuRat

No, that not correct. The dynamic viscosity of water is about 59 times that of air. However flow is proportionate to the radius raised to the power four. Thus the radius of the water hole needs to be about 2.8 times that of the air hole for equal laminar flow through both holes (if the holes are the same length and the pressure gradient is the same). Axl ¤ [Talk] 18:27, 3 March 2009 (UTC)

I see. That's a bit closer to my estimate of 10:1. Thanks. StuRat (talk) 19:50, 3 March 2009 (UTC)

Chloroplasts and mitochondria

Hi,

Hopefully a very easy question - is there a word for chloroplasts AND mitochondria collectively? I thought plastid meant this, but apparently that's only chloroplasts (and related) organelles. Is there a better word than "DNA-containing(-but-not-the-nucleus-)organelles"? Symbiotic organelles? Any ideas?

Thanks

141.14.245.244 (talk) 16:04, 2 March 2009 (UTC)

"Obligate endosymbionts" was my first thought, since Endosymbiotic theory is the theory that deals with the origin of such organelles, but the term is a bit more inclusive than you're thinking of. You may not be able to find a term that neatly excludes the nucleus: see Viral eukaryogenesis.-gadfium 20:02, 2 March 2009 (UTC)

Eggs or secretion by unknown Animal/Creature ?

Please could you identify what has laid a amound of very very small black balls held together with a very gluey subtance on my garden lawn?. I do have a garden ornamental raised pond.It is not frogspawn or toads which are laid in bead like strands. No these black balls are completly joined together in a formation similar to a blackberry, but minute.The mound measured about 3inches in width and bound together with a subtance not visible.I have never seen anything like it before. Supersaddlers (talk) 16:08, 2 March 2009 (UTC)

Could it be frogspawn? DuncanHill (talk) 16:36, 2 March 2009 (UTC)

• 
  Is this something like it? (pic added by DuncanHill, before the question was amended to say it wasn't frogspawn)
• 
  Or this? (pic added by DuncanHill, before the question was amended to say it wasn't frogspawn)

My guess would also be frogspawn -- you say that it's not that, because frogspawn looks like "beadlike strands", but I believe that's only true for toadspawn! Frogspawn looks like clusters, as you describe (and as is pictured above). -- Captain Disdain (talk) 17:03, 2 March 2009 (UTC)

Looks like frogspawn to me, but why not in the pond? Perhaps they need your assistance there. Julia Rossi (talk) 21:33, 2 March 2009 (UTC)

Not necessarily. Ponds and streams are dangerous places for frog eggs, so many frogs lay their eggs out of the water, but in such a place that the lil tadpoles will fall into the water upon exiting the egg mass. Leave 'em where they are! Matt Deres (talk) 19:30, 3 March 2009 (UTC)

Where are you in the world? Snails lay egg clusters of differing colours. Salamandars spawn are in a lump.91.111.64.177 (talk) 22:51, 2 March 2009 (UTC)

About miracles

Most religious people try to prove some scientific facts from their religious books and present them as a miracle of their religious books .Most of them (may be all) are the wrong uses of words . My question is ," Is their any miracle which is free from doubt, can be proved from these books ".Any one know about such miracle which we all can understand

A miracle is something that happened through divine intervention. If there were miracles that were free from doubt, that would be a proof of some kind of god. If there were a conclusive proof of a god, I'm pretty sure I would have heard about it, so I'm going to say "no". --Tango (talk) 17:42, 2 March 2009 (UTC)

Actually, most religious people make no attempt to disprove what their senses tell them about God's creation, and happly allow God to make his creation however he sees fit, with evolution and the Big Bang and all that. There are a few vocal crackpots who do what you are describing, but they are simply heavily reported on because they are so vocal and such huge crackpots. The rest of the religious people are happy not trying to tell God how he should operate, and just accept him and his creation for what it is. --Jayron32.talk.contribs 18:10, 2 March 2009 (UTC)

It's a mistake to claim that science proves that miracles could not have happened; if a creator God exists it's surely possible that he could override his own created physical laws. It's silly to try to prove God exists by finding an explanation for miracles within scientific law, for exactly the same reason. DJ Clayworth (talk) 18:30, 2 March 2009 (UTC)

If there were something that one could describe as a 'miracle' - it would have to be a solidly demonstrable thing with tons of evidence that everyone could look at and agree upon - otherwise it's just going to be dismissed along with UFO sightings and the Loch Ness Monster. So if this is something that's free from doubt - then the world of science would be most unlikely to say "Wow! A miracle - there must be a God." - we'd be much more likely to say "Wow! An event happened in the world that disproves one or more 'laws' of science. Let's study it carefully and amend our laws accordingly." - let's think of an actual example...everyone thought that the Coelacanth (a fish) was long extinct. We had fossils of it - but no biologist had ever suspected that they still existed. Then, in 1938 someone caught one, had it stuffed by a taxidermist and sent it to a biologist. So - did we fall on our knees and say "Lo! A miracle hast been wrought by a divine being - yeah this long dead fish has been brought to life by His divine will. Let us abandon our crappy science and go hence to the nearest Mosque/Church/Synagogue and praise Him."...no - we crossed out the bit in the Biology textbook that said "The Coelacanth was a prehistoric fish living in the Middle Devonian, Late Paleozoic and Mesozoic." and wrote "The Coelacanth is a fish which has been around since the Middle Devonian and can still be found off the coast of South Africa."...problem solved. The only way that a 'miracle' (that is to say - an undeniable event that does not fit into the present laws of science) would result in all of this religious stuff being considered "true" would be if careful study of the event somehow showed the definite presence of a "God" as the only way it could have come about. But most of these events don't come close to that. Looking at the christian miracles - we have stuff like "A Virgin Birth"...yeah - right. I wish I had a dollar for every teenage girl who got 'knocked up' after an illicit fling who then claimed she'd never had sex in her life...sure - that's a miracle...NOT! The 'water into wine' - meh - I bet that any decent member of the Magic Circle could pull that one off easily enough. The story of the loaves and fishes - well, that sounds a lot like some kind of a spontaneous block party we had when I lived. I had some food - some neighbours came over - we decided to make a party of it - more people came over - but we didn't have enough food - so people disappeared and came back with whatever leftovers they had in the fridge - before you know it we had a 100 people and more food and drink than we could possibly get through. Was it such an amazing party that you'd want to write about it...sure! Was is 'magic'...no. We have 'raising the dead' - well, where are the medical records to prove that the guy was actually dead. There are plenty of documented cases of people being thought to be dead - then waking up in the morgue some hours later. The problem with most of these things is that they aren't written with a scientist's skepticism. SteveBaker (talk) 18:50, 2 March 2009 (UTC)

This priest held that a belief in miracles was atheistic. DuncanHill (talk) 18:56, 2 March 2009 (UTC)

You might check out Hume's famous piece, Of Miracles. --140.247.253.176 (talk) 19:33, 2 March 2009 (UTC)

"Most religious people" of my acquaintance do nothing like what the original questioner claims. Maybe he ran into a zealot or crackpot somewhere, or tuned into a TV religionist from an extreme faction. There is no "Journal of Repeatable and Well Proven Miracles" describing phenomena inexplicable by the laws and generally accepted theories of science. "Now watch me turn this wine and bread into flesh and blood!" A miracle performed at every Mass, when the Priest says the words of institution, but the transubstantiation cannot be proven by DNA or mass spectrometer analysis, since the "essence" changes while leaving the "accident" the same. Edison (talk) 19:43, 2 March 2009 (UTC)

I guess the whole point of miracles is that they stand outside science: if proven by science, they are not miracles, but natural (if rare) occurrences. How do you prove something that doesn't conform to scientific laws? With great difficulty! Hence miracles are always very firmly tied up with faith. That they cannot be proved does not automatically or reasonably mean they cannot exist. That some claims to the miraculous are disproved does not mean all miracles are false claims; nor does it mean that if (somehow) one miracle could be "proved", then all miracles exist. Philosophers and theologians have pondered these things for generations. Miracle offers various views on the subject. You might also consider looking at Miracles by C.S. Lewis. Also, look at Epistemic theory of miracles, which considers "miracles" to be events outside our understanding, rather than outside science. Which is quite plausible. Many things we consider normal and logical today would seem miraculous to our ancestors. Only arrogance holds that our modern scientific understanding is complete. We cannot possibly be able to explain everything correctly; there must be things we don't understand, or that are beyond our comprehension. And thus it is impossible to either prove or disprove God, or to prove or disprove miracles, until we have reached the knowledge of all things. Gwinva (talk) 04:47, 3 March 2009 (UTC)

You said "I guess the whole point of miracles is that they stand outside science:" - but the problem is that science is about explaining absolutely everything (or at least that is the goal). So if a 'miracle' happens (something that science cannot yet adequately explain) then our job as scientists is to get on with explaining it. If necessary we'll change our laws to incorporate the new phenomenon...and as soon as we do that, it's a part of science and (as you said: "if proven by science, they are not miracles") that removes the 'miracle' status. At the time that the Coelacanth was discovered, a superstitious person with a familiarity with fossil Coelacanths might well attribute the 'magical' resurrection of an entire species to be a miracle. But scientists don't do that - we merely go and revise our laws to compensate. Since you can now look up "Coelacanth" in an encyclopedia and it says "Not Extinct" - we can hardly regard it's discovery as a miracle anymore. This means that there cannot (by definition) be miracles which can be solidly proven to exist - because the moment you have that proof, science adapts to it - and then (by YOUR definition) it's no longer a miracle. Hence, if we follow your reasoning - the only "miracles" left in the world are the flakey 'unfalsifiable' ones that can't be properly shown to have happened. As usual in religion - as soon as you point out an unfalsifiable element of their belief - you're told that this is a part of the 'faith'...in otherwords "it's like that because we say so". SteveBaker (talk) 18:26, 3 March 2009 (UTC)

You could have falsifiable miracles, but only by completely destroying science. Science is based on the assumption that things are inherently predictable and explainable and are governed by set laws (even if we don't know what those laws are). The existence of a god (Level 2 or higher) would render that assumption false, and would allow miracles that cannot be explained by science - you just have to say "God did it" and get a new job. --Tango (talk) 18:31, 3 March 2009 (UTC)

Ah - but the moment a god shows his hand by doing things that science can examine - he ceases to be unfalsifiable and thus can be the subject of study. We could look carefully at what happens when these miracles happen and perhaps start to make deductions, new laws of the universe. By becoming detectable, god becomes merely another part of the universe for us to study - just like a black hole or a higgs boson. God with unlimited powers (level 2 and up on the increasingly useful 'Baker Scale of Omnipotence') are tricky because they could be messing with the brains of the researchers - but if that is possible then all of the science that we already "know" has to be flushed down the toilet because we have no experiment that can confirm it. In a sense, any proposition (including science itself) becomes unfalsifiable. SteveBaker (talk) 23:59, 3 March 2009 (UTC)

I guess the most easy way to call it is, miracles are supernatural claims, supernatural as in, unnatural and not possible. If a miracle happens, it automatically becomes a non-miracle. ch¹⁰ · 18:37, 3 March 2009 (UTC)

The 68 allegedly miraculous cures at Lourdes present an interesting case. Many thousands of people have claimed to have been miraculously cured this way, but only 68 cases have ever been accepted as miraculous by the Catholic Church. There are 2 parts to this process: the International Lourdes Medical Committee (CMIL) must first decide the case is "medically inexplicable". CMIL is an international panel of about twenty experts in various medical disciplines, and of different religious beliefs. They conduct rigorous and searching examinations over a long time, and certain criteria must be met, before any cure can be declared as "medically inexplicable". The Catholic Church can then go the next step and accept the cure as "miraculous". That is, not only can it not be explained by medical science, but it is, they say, evidence that the hand of God is at work. What the CMIL does, and the conclusions it comes to, would be fully acceptable to science, because the members of CMIL are themselves scientists. What the Church does would not, because they can never provide any proof that would satisfy a scientist that the cure is evidence of the work of a supernatural being. And that's the sticking point. Whether such a case is merely medically inexplicable, or crosses over into a miracle, comes down to a matter of personal belief. Looking at some of the prominent Lourdes cases, I guess if I were the patient, I wouldn't spend any time arguing the toss. I’d just be happy to have been cured after all reasonable hope of a cure had long since faded. -- JackofOz (talk) 19:38, 3 March 2009 (UTC)

Well the catholic church don't seem to have high standards, trying to claim that mother Teresa has preformed miracles, presumably just because a woman touched a locket she'd owned or something like that... ch¹⁰ · 19:44, 3 March 2009 (UTC)

I'm no supporter of the RC Church, but the record shows they are extraordinarily reticent about ever regarding any claimed apparition, cure or whatever to be of supernatural origin. They insist on evidence that goes way beyond what any court of law would require, and they generally take decades or even centuries before declaring that a dead person has intervened in some living person's life and can now be regarded as a saint. There's a lot of crap written about Mother Teresa and her claimed intercession and miracles after she died. I don't know what episode you're referring to, but the vagueness of your language makes it sound like it's in that category. -- JackofOz (talk) 22:18, 3 March 2009 (UTC)

There are some severe problems with the way these 'miracles' are handled:

• While they say that the board who votes on these events contains both believers from the catholic church, believers from other religions and non-believers, the fraction of the latter groups amongst the voting body is small (I don't have the numbers to hand but it's below 10%).
• They only require a 2/3rds majority in order to pronounce the case as 'medically inexplicable' - so it's easily possible for a catholic-only vote to proclaim this. Sadly, the voting is not carried out openly - so we have no way to check.
• The criterion is "medically inexplicable" - only the church itself can proclaim a 'miracle' - and that process is not related to science at all.
• There is a LOT of money spent by tourists and pilgrims at Lourdes - and they get a big spike in revenue when one of these 'official' miracles happens. It's perfectly possible that all manner of skulduggery is going on behind the scenes here. We all know the ways in which the Catholic church covers up inconvenient misdeeds - even when they are of a serious criminal nature. How much does it cost to get fake diagnoses, doctor reports and so forth? Not a fraction of what a decent sized gift-shop makes in a year...and Lourdes has PLENTY of gift shops!

So all we really know is that a bunch of doctors (possibly all catholics and possibly all believers in the 'Lourdes miracle') couldn't figure it out - and there are strong motives for all concerned to find more miracles. That's not a standard by which modern science works. Furthermore - nobody looks to see why so few people pass this criteria. If there was something miraculous going on - why are so few people truly getting better? Nobody studies them to discover whether they've been more pious or led a more virtuous existence than the others. There is no element of prediction here...proper scientific method would require them to seek out cases that are as close as possible to the 'miracle' cases and ask why these other people didn't also get better. Out of 5 million visitors each year - and over the course of 150 years since the place was 'discovered' to be miraculous - we only have 68 successes?! That's beyond "not statistically significant"!! The extenuating circumstances of someone who is literally one in a million can be quite extreme...who knows what medical mixups and confusions may have gone on to make just one in a million cases turn out to be "medically inexplicable"? Where is the study comparing them to the 'control group' who didn't go to Lourdes - or the 'double-blind group' who were taken to the next village along from Lourdes? I wouldn't be at all surprised to hear that ANY group of 5 million sick people wouldn't have a couple of 'inexplicable' cures.

Extraordinary claims require extraordinary evidence...and we don't come close to that standard here.

SteveBaker (talk) 04:53, 4 March 2009 (UTC)

Good points, Steve. All I'll say is that there are a large number of scientists who happen to also be devout Catholics (or Jews, Muslims, whatever), who would never for a second allow their religious beliefs to ever influence the way they go about their scientific work. It might in some cases influence their choice of projects, but not how they do their scientific/medical investigations or what conclusions they come to. It's possible, of course, that there are some who do let their religious beliefs get in the way, but would they retain their scientific standing for very long? I doubt it. As for the voting procedure, non-unanimous but majority votes are the norm, most everywhere. That applies in most legislatures, whose decisions affect entire countries. It applies in the Australian High Court, whose decisions on constitutional issues affect the entire country. It probably applies in the US Supreme Court and similar bodies. A 2/3 vote is more stringent than a simple majority. Even if a particular CMIL vote happened to be unanimous, that in itself wouldn't "prove" that the case in question was any more "inexplicable" than another case, because if there had been 20 different people on the panel, it may well have come out as a lower vote for "inexplicable", or maybe even not inexplicable at all. -- JackofOz (talk) 21:13, 4 March 2009 (UTC)

A Priest can say "..This is my body given for you. Do this in remembrance of me" and bread miraculously becomes Jesus' flesh, in its essence. The physicallly testable "accident" remains bread. If the Priest could say "Lord, please make a kilogram of gold appear on the altar," and a kilogram of gold magically popped into existence on the altar, remaining there for chemical analysis, that would be a repeatable miracle, suitable for the confounding of any doubter. However, a competent magician could make comparable phenomena occur via apparatus, trickery and distraction. Magicians have sawn ladies in half, without any enduring ill effects, and have made elephants appear and disappear, without any real miracle. Edison (talk) 05:00, 4 March 2009 (UTC)

the question will be ... will you believe if god perform a miracle if you saw a man came down from the sky , its easy to say this an alien if you read any book talking about scientific facts , its easy to say Avery advanced civilization had lived in the past .

the problem is what is a miracle to you ... and did you think that god will perform a miracle to each one of us , according to his own standards.

i think you should believe in a religion if your convinced with it. i think the best thing to do is to ask god if he exist to show you the way ...

Its easy to disprove god existence , and its easy to prove it but i think is not every thing is meant to deal with using your solid mind , you should follow your heart a little.

That's a little silly. If you could prove God exists, then you could not prove he didn't exist - or vice versa - because those two "proofs" would conflict with each other. The truth is that God's existence can neither be proven nor disproven, in a way that would satisfy scientific criteria. It can be proven or disproven according to some people's personal subjective criteria, however. For others, it's simply unknowable. I agree with your last statement. -- JackofOz (talk) 06:18, 5 March 2009 (UTC)

Creating New Land

Would it ever be possible to pump desalinated sea water from the Atlantic/Mediterranean into the Sahara and create plains and forests? What would the energy requirements be and could they be met through massive nuclear or fusion power plants? Would the sand/soil need to be treated in some manner besides the addition of water? What about other inhospitable biomes; with enough investment (orbital mirrors, cloud seeding, etc?) could we make Greenland green?

Thanks for your thoughts! —Preceding unsigned comment added by TheFutureAwaits (talk • contribs) 19:42, 2 March 2009 (UTC)

Well your first big problem is that desalination is very expensive. It's barely economical as a source of drinking water. (Or rather, it _isn't_ economical, except in countries with expensive tap water and the resources to manage the heavy capital investments required) --Pykk (talk) 19:44, 2 March 2009 (UTC)

Have you read Land reclamation? I don't think it answers your specific question, but it's a good place to start. Desalination requires very large amounts of energy. If someone invents a viable method of fusion, then that wouldn't be a problem, but there are no signs of getting that worked out any time soon. If you want to warm up Greenland, it might be best to wait and let global warming do the job. --Tango (talk) 19:46, 2 March 2009 (UTC)

Well I guess I'm thinking more in terms of theory than real cost (whether or not it's economical is a lesser issue). The heart of my question is really if it could one day be possible to make most of the Earth's land area verdant through the directed use of technology and what steps would need to be taken? For example, do we have enough water to irrigate the continents? Thanks again! TheFutureAwaits (talk) 20:05, 2 March 2009 (UTC)

You may need to breed plants that like to grow in salt water, even so you may need to keep that water circulating to stop salinity getting too high. Then desalination is not required. Graeme Bartlett (talk) 20:26, 2 March 2009 (UTC)

If you have unlimited budget and unlimited energy to throw at desalinization - then certainly there is enough water in the ocean to do the job. Without desalinisation though - definitely not. There is a world-wide shortage of fresh water as it it - this would make things a LOT worse!! But with unlimited energy/money - that's not an obstacle. Fertiliser can be made from air and water if you have enough energy. The soil would initially be pretty poor - but I'm sure you could find something that would grow. After enough years - you could make 'ordinary' crops grow...but depending on how you got your energy, the consequences for the ecosystem - global warming and all that kind of think might be somewhat horrific. SteveBaker (talk) 20:53, 2 March 2009 (UTC)

Going back to Graeme's point, I don't think it would prohibitively hard to de-desertify at least part of the Sahara. The Qattara Depression is up to 133 metres (436 ft) below sea level, and its northern extent is only about 80 kilometres (50 mi) south of the Mediterranean Sea. It certainly isn't inconceivable that one could build a wide canal which would deliver a constant supply of salt water to the depression, eventually filling it, which would provide a source of moisture for eastern parts of the Sahara. The environmental/climatological impact would be incalculable however, so I don't think it would be worth the expense.-RunningOnBrains 21:41, 2 March 2009 (UTC)

You don't really need a canal. A large siphon should do. --164.67.100.97 (talk) 00:32, 3 March 2009 (UTC)

How high is the ridge between them? A siphon can only lift 30 feet or so above the starting point. --Carnildo (talk) 01:31, 4 March 2009 (UTC)

Even if it was possible, I seriously doubt it would have a good effect. If anything it would probably just ruin the worlds balance and screw up our weather horribly. If you've ever seen An Inconvenient Truth, Al Gore talks about how when huge frozen masses melt (such as Greenland) the sea level rises significantly around the world. Not only would it would be difficult, but once it was done millions of people would be dead. It's probably better we can't do it. -Pete5x5 (talk) 21:56, 2 March 2009 (UTC)

I'm not sure what your point is. I've never been, but I'm pretty sure that you don't see a lot of "huge frozen masses" in the Mediterranean Sea. APL (talk) 01:00, 3 March 2009 (UTC)

There's been lots of plans like that. See Sahara Forest Project for instance. Dmcq (talk) 22:52, 2 March 2009 (UTC)

Interesting points Pete5x5, though if we were to melt Greenland while pumping massive amounts of water into the world's deserts we could possibly do both at a pace that would keep world sea level at an equilibrium. I'm not saying it would be practical, but it's possible in theory. In regards to global warming, I know it's an issue we're all familiar with and this topic somewhat lends itself to an al gore discussion, but given enough energy, capital and technology it seems like any unwanted ecological consequences could be negated. Or are there some fundamental limits when geoengineering the planet? Oh and dmcq thanks for the link, this discussion has been very interesting so far. TheFutureAwaits (talk) 23:27, 2 March 2009 (UTC)

The Quattara Depression thing is mentioned in a book from the fifties, called "Engineers' Dreams" [17], that also has a discussion about Atlantropa (mentioned a few questions down). You could also generate quite a bit of power this way, by controlling the inflow of water so that evaporation made sure the depression did not fill, water would always flow in, excellent for hydroelectric power (a similar scheme has been proposed for the Dead Sea). However, I expect the salinity would then always increase, so habitability might not improve much (unless the output from the hydroelectric plants was sufficient to extract the salt with conventional methods). Jørgen (talk) 01:38, 3 March 2009 (UTC)

Link for Atlantropa, mentioned above. Pfly (talk) 08:59, 3 March 2009 (UTC)

Peachy, and the new land can then be settled by all the people who lose their homes to Tropical cyclones because the Saharan Air Layer is no longer what it used to be. I bet inhabitants of Bangladesh and Southern Louisiana are just waiting to move to Darfur. In Israel they do use desalinated water in agriculture [18]. 76.97.245.5 (talk) 11:28, 3 March 2009 (UTC)

Besides - it would certainly hasten global warming. Water is dark - it absorbs heat - ditto plants which are evolved specifically to absorb sunlight rather than reflecting it. Bright white desert sand is highly reflective. So - you replace the sand with plant cover and irrigation water - the planet's net albedo drops a notch further - and the planet gets hotter...doubly so if you go around deliberately melting that nice shiney-white snow and ice to do it! SteveBaker (talk) 04:35, 5 March 2009 (UTC)

Death by bloating

Are there any documented cases of intestinal gas buildups leading to a ruptured intestine? I realize flatus is generally harmless, but bloating can be unpleasant. If carried to an extreme, can enough gas be produced in situ to cause actual harm? Perhaps if part of the intestine was also blocked up for some reason leading to a pocket of trapped gas? (For the record, I'm not looking for personal medical advice. I'm just curious if gas buildup has ever been documented to cause more serious problems. Physically, it seems like it probably could, but I'm not sure.) Dragons flight (talk) 19:48, 2 March 2009 (UTC)

Bowel obstruction can certainly be a serious condition. I don't know if the gas is generally a significant factor or not. --Tango (talk) 19:52, 2 March 2009 (UTC)

The Mythbusters 'pop-rocks and soda' experiment suggests not...but that's not really much to go on. SteveBaker (talk) 20:18, 2 March 2009 (UTC)

It however does happen in ruminants and other animals that subsist on high-fiber diets (sheep, goats, cows, horses). There's a scene in Tess of the D'urbervilles (or was it Return of the Native? Some Hardy novel) where they have to go around puncturing the sheep to prevent flatulence from rupturing their intenstines. this text (page down and do a search for "Colic") describes the treatment of "wind (flatulent) colic" where it says "Wind colic may need prompt use of the trocar and cannula to puncture high up in the right flank for liberation of gas" Basically, you drive a metal straw into the horses flank to relieve the pressure from unpassed farts. So, it does happen that bloating can be more than unpleasant, and must be relieved by drastic measures, at least for some farm animals. --Jayron32.talk.contribs 21:23, 2 March 2009 (UTC)

I think it was Far From the Madding Crowd, which I had the misfortune to read for O-level. DuncanHill (talk) 21:44, 2 March 2009 (UTC)

Mr Creosote SpinningSpark 22:27, 2 March 2009 (UTC)

Yes, Duncan, it was Far from the Madding Crowd. The scene in the film version, with Alan Bates puncturing the sheep, has remained with me since my adolescence. Deor (talk) 23:12, 2 March 2009 (UTC)

Yes, Alan Bates, that was it. The film was better than the book, by several hours. Still, at least I learnt how to deal with exploding sheep. DuncanHill (talk) 23:23, 2 March 2009 (UTC)

Your wording made me realize it... it never occurred to me that there could be a basis in reality for that particular Warcraft item. And apparently use of that concept isn't limited to Warcraft, either. You learn something new every day. ^_~ arimareiji (talk) 00:11, 3 March 2009 (UTC)

We do not give veterinary advice, but if horses consume too much green corn/Maize, they can die unless veterinary surgical or other intervention occurs to deal with the resulting colic. Edison (talk) 03:25, 3 March 2009 (UTC)

Toxic megacolon is the article you're looking for. Mattopaedia ^{Have a yarn} 04:07, 3 March 2009 (UTC)

Though the article isn't that clear, the references in it seems to be referring to an enlarged colon as a result of infection or inflammation. I'm not sure if an enlarged colon due to gas buildup would be described the same way. Dragons flight (talk) 06:23, 3 March 2009 (UTC)

Amazed no-one has linked bloat yet. DuncanHill (talk) 13:44, 3 March 2009 (UTC)

The OP linked to bloating. I'm surprised to discover that they are different articles... --Tango (talk) 13:53, 3 March 2009 (UTC)

Sorry Dragons flight, I only glanced at the article to convince myself it was there - I didn't look long enough to see if it connected the dots. As a result of infection, inflammation, infarction or some mechanical cause like volvulus, you get a segmental obstruction of the colon somewhere. Many of the native gut bacteria are gas producers (mostly CO₂, and some aromatic amines with wonderful names like cadaverine and putrescine) - these little dudes go on producing gas & it's got nowhere to go. The internal pressure increases beyond capillary venous pressure resulting in no venous (or lymphatic) drainage from the segment, but blood keeps flowing in. This builds up gut wall pressure and also causes an accumulation of toxic metabolites. Eventually the gut wall becomes ischaemic. The resultant increase in migration of cellular inflammatory mediators, particulary neutrophils, release a whole bunch of lytic enzymes in an attempt to mop up this mess. The combination of necrosis from the ischaemia and (largely) proteolysis from neutrophil granules weakens the gut wall, leading to perforation, septicaemia, peritonitis and septic shock. Untreated, this is uniformly fatal. Hope that makes things clearer! Mattopaedia ^{Have a yarn} 12:56, 4 March 2009 (UTC)

Damming the Strait of Gibraltar

My friend (who comes up with these sort of mad-but-close-to-genius ideas) suggested that you could dam the Strait of Gibraltar, opening up trade routes, generating electricity, immunising the Med from sea-level rises and looking impressive. The possibility comes from Strait of Gibraltar#Inflow and outflow that stats there is a net inflow to the Med, so you build the dam, wait a couple of years for the waterlevel to lower slightly (hopefully avoiding the effect on people's coastlines) and then run turbines. I've posted it here because I want to know if there are any scientific reasons why this can't happen. As I see it, there may be salinity questions; also effects on the environment. Secondly, how much would the sea level need to drop, and would this mean coastal settlements a long way away from the coast? Thanks, - Jarry1250 ^{(t, c)} 20:03, 2 March 2009 (UTC)

In the geological past this has happened, the Mediterranean was reduced to some salt lakes more than a thousand meters below sea level. These have formed thick salt deposits. The area was a desert, this would affect the climate of the surrounding countries with reduced rain and more extreme temperatures. Graeme Bartlett (talk) 20:19, 2 March 2009 (UTC)

Your friend is not really original. See Atlantropa. --Stephan Schulz (talk) 21:13, 2 March 2009 (UTC)

Trust me, he is. Replacing all cars with tanks to save on military budgets. Has anyone had that one before? - Jarry1250 ^{(t, c)} 21:45, 2 March 2009 (UTC)

Wouldn't such high tank availability drastically increase the need for military hardware? Perhaps most of that expense would be pushed off to local law enforcement. APL (talk) 01:13, 3 March 2009 (UTC)

Opening up the med to development, tanks on the streets – I think this guy's in the pay of the road-building industry. Algebraist 09:12, 3 March 2009 (UTC)

(ec)I highly doubt that your friend's benefits of "opening up trade routes, generating electricity, immunising the Med from sea-level rises and looking impressive" would outweigh the "catastrophic drought and death of thousands or millions from heat and famine". That may be an over-statement, but I can't see a reduction in the size of the Mediterranean doing anything good for the European/North African climate.-RunningOnBrains 21:52, 2 March 2009 (UTC)

Well the map for Atlantropa shows the effect of over a 100m drop; I'm no expert in dams, but you could build a far more modest one with less of a drop, which would mean very little reduction in the size of the Med itself. I can't help but think my own question was actually a bit silly, because what I really need is an investigation into that exact proposal, which has not happened. I can't even imagine we'd be able to model the climatic changes (and there'll be some) until the thing actually happens. - Jarry1250 ^{(t, c)} 22:02, 2 March 2009 (UTC)

Geo politically it might turn out to be a very bad idea. Neither the British nor the Spanish would likely be too happy to move closer to invading hungry refugees of the next conflict in Africa. Even if you could keep climate change at bay, lots of countries around the Mediterranean depend on tourism. They bank on their beaches, reefs and waterways being just the way they are now. The archeologists who found the remnants of the library in Alexandria might have an easier job with a lower water level, though :-) 76.97.245.5 (talk) 10:50, 3 March 2009 (UTC)

You could probably get benefit from tidal flow by installing a bank of turbines in the waters around the island without resorting to damming it. The trouble with a dam is that it relies on the height difference between the two sides - which is bad because it entails raising the height of the dammed-up water - with consequences for fish migration, flooding in coastal areas, etc. However, a gigantic, slow-turning turbine could capture the flow both into and out of the 'med without making any difference to those kinds of thing. SteveBaker (talk) 15:51, 3 March 2009 (UTC)

Gardening: Are hardy annuals usually or always self-seeding?

In Britain the term hardy annual is used a lot by gardeners. Being only a beginner gardener, I found out recently that hardy annual plants can be sown outdoors in situ without having to begin their life in a greenhouse, as is required with half hardy annuals. Another category is hardy perennial. I like self-seeding flowers as they save you the trouble of planting them again next year, and they can build up into large dense masses of hundreds of flowers which out-compete the weeds and look nice as a solid block of colour. Unfortunately seed packets never, and gardening books rarely, tell you if a flower is self-seeding or not. Does a flower being a hardy annual imply that it is self-seeding? 89.240.206.134 (talk) 22:08, 2 March 2009 (UTC)

Another question is why are all those links red? Wikipedia should have those articles. There is annual plant which implies, but does not specifically answer your question. SpinningSpark 22:20, 2 March 2009 (UTC)

Yet another question, apropos of little, would be... how did the less hardy plants ever survive to the present day? Would the answer be the same as in When Did Wild Poodles Roam the Earth?, i.e. those plants have been inbred far beyond the traits of their original ancestors? arimareiji (talk) 00:16, 3 March 2009 (UTC)

A classic example is Maize/Corn, which thousands of years ago became dependant on humans to reproduce. There can be no feral maize, because it simply cannot reproduce on its own. --Jayron32.talk.contribs 00:23, 3 March 2009 (UTC)

The Mexican plant teosinte is thought to be the ancestor to modern corn/maize and still grows wild in Mexico. Edison (talk) 03:19, 3 March 2009 (UTC)

Indeed, but it appears to be quite a distinct, distant relative to modern Maize. It is to Maize what the Chihuahua is to the Great Dane... --Jayron32.talk.contribs 04:42, 3 March 2009 (UTC)

Maybe more like the wolf is to the chihuahua? Sorry, I'm an analogy geek. arimareiji (talk) 05:01, 3 March 2009 (UTC)

Back to the original questions. Hardiness describes the tolerance of cold weather. Both hardy and half-hardy annuals do not need warm soil temperatures to germinate, i.e. in principle they can self-seed. Hardy annuals will also tolerate frost (i.e. they can be sown in late summer/autumn, will overwinter as small plants and generally flower early the following year). In my experience, whether plant will in practice self-seed or not, depends more on their hardiness with regards to slug attacks. By and large mainstream british gardening culture dislikes self-seeding annuals, I think "self-seeding" and "weed" are pretty much used as synonyms (a view that I don't subscribe to). Get some stuff and try it out, the things that are likely to succeed fortunately tend to be cheap to buy. I've had success with Calendula (pretty much indestructible), Ox-eye daisies, Wallflower, Nasturtium (you need a critical mass here, but once established they come back on their own) and Cornflowers (they need a bit of help against slugs). 195.128.250.230 (talk) 22:33, 4 March 2009 (UTC)

March 3

do indoor roses need a night phase?

I notice my indoor miniature rose has a tendency to bloom during my sleep (while the lights are dimmer) and sprout new leaves yet remain static while I'm awake. (Maybe this is a watching the kettle boil thing.) It occurred to me that I don't know what type of photosynthesis a rose would carry out. I suspect C3 (why it needs so much water) -- but if not, does it need a minimum amount of dark per day in order to optimise its growth? I'm not sure if it would schedule some growing phases during the dark.

I know indoor roses often suffer from lack of light. But provided adequate water and fresh, cool air, is it possible to give rose too much light (I'm using purely fluorescent light). The new leaves are remaining yellower longer than expected. I'm growing this in a pot in my dorm until it warms up -- I've basically it elevated the plant until the topmost leaves are barely an inch away from the in-built desk fluorescent light, and I've got another study lamp (fluorescent) with a flexible stem shining on it at the side just centimetres away from the leaves. John Riemann Soong (talk) 03:24, 3 March 2009 (UTC)

Sorry, I don't know a lot about plants and next to nothing about roses. Fluorescent lamps come in many different types and generate various spectra. Plants usually need special grow lamp bulbs for optimum growth. Putting your pot near a window might get you better results. 76.97.245.5 (talk) 09:48, 3 March 2009 (UTC)

Three thoughts: [1] could the yellow leaves be a sign of overwatering? [2] indoor roses have a tendency to not do very well after the initial blooms, unless you let them go through a period of dormancy somewhere cool (like a garage). Are you doing this? [3] Roses require 5 hours of direct sunlight per day. I don't know how many hours of grow-light that translates into. - Nunh-huh 10:13, 3 March 2009 (UTC)

How bad are shrooms for you?

Really...how bad are they for you? I have tried doing research, but I've discovered NOTHING. I can't find anything! Everywhere I go they just talk about the immediate, post-consumption effects of shrooms. Nothing on effects on cognitive ability, memory, recognition of simple shapes/colors..etc. I haven't been able to find a source that describes any sort of long term health issues with chronic mushroom use. This has given me the impression that they aren't bad for you. Am I right? --71.117.36.86 (talk) 03:35, 3 March 2009 (UTC)

Thanks for posting your question. Your question seems to be a request for medical advice. It is against our guidelines to provide medical advice. You might like to re-phrase your question. You may also find it helpful to read the article: Psilocybin, and form your own opinion from the information there. Specific advice below pertaining to the consumption of hallucinogens has been removed. Note to editors: Any response containing prescriptive information or medical advice will be removed. Please ensure your responses are constructed so as not to be construed as medical advice! If you remove a response, please paste it and your reason for removal on the Reference Desk Discussion page If you feel a response you have given has been removed in error, please discuss it at the Reference Desk Discussion page before restoring it.

. Mattopaedia ^{Have a yarn} 06:06, 3 March 2009 (UTC)

Psilocybin#Toxicity is one relevant link. Friday (talk) 03:37, 3 March 2009 (UTC)

No, if you find long-term studies concluding it's safe, then it's safe. If you can't find any such studies because none have been done, then the best answer would be 'We don't know'. Given the track record of the vast majority of hallucinogens I sure wouldn't default towards 'safe'. --Pykk (talk) 03:53, 3 March 2009 (UTC)

There's no clear physiological damage of the kind that you might see with alcohol or cocaine, or with any kind of smoking. On the other hand, changes in cognitive abilities might be difficult to recognize and detect - I don't think anyone's done a controlled study. It seems that it would be difficult to organize one. -GTBacchus^(talk) 04:18, 3 March 2009 (UTC)

Response removed. See discussion page

Please note that this is dangerously close to a medical question, if not over the border. arimareiji (talk) 05:03, 3 March 2009 (UTC)

There are case reports in the scientific literature of Hallucinogen persisting perception disorder as a consequence of psilocybin abuse. HPPD is listed in the Diagnostic and Statistical Manual of Mental Disorders. See for example, PMID 15963699. Rockpocket 07:03, 3 March 2009 (UTC)

Erowid is a good souce for this kind of thing. This is their main mushroom page. Pfly (talk) 09:06, 3 March 2009 (UTC)

That is one big template! --Tango (talk) 13:51, 3 March 2009 (UTC)

To our OP: Absence of information most certainly DOES NOT indicate that there are no problems. There is probably no good online information on the consequences of hitting yourself on the head with the pointy and of an icepick either...but it's not generally recommended. SteveBaker (talk) 15:46, 3 March 2009 (UTC)

Thank you guys for your responses so far, I've got some interesting reading to do. Firstly, I was most certainly not requesting medical advice. I have never experimented with shrooms, but rather I inquiring about studies or general information regarding and demonstrating the long term effects of mushroom use. And yes, you guys who said that just because there is no definitive information about the negative effects of something doesn't mean it isn't harmful are absolutely right...I just found it unusual that I could not find much info on how horrible they are for you, considering how (esp. the government) publishes and propagandizes studies showing how terrible illicit drugs are for the body. I just figured if they didn't go on a huge crusade about the evils of mushrooms, then they might not actually be THAT bad for you. Certainly there is the more obvious reason of no credible or viable studies being undertaken..and @Steve--Just because there is an absence of information (and the lack of any information regarding negative long term effects) does not indicate that there are problems. Obviously, one can see how hitting oneself in the head with a heavy, metal object may be detrimental to one's health. Drugs, on the other hand, are not so easily categorized as some are beneficial and have no negative side effects in moderate doses. --71.117.38.74 (talk) 01:27, 4 March 2009 (UTC)

Yeah - well, everyone who I ever knew who messed with drugs in the 1970's and onwards either ended up in a very bad way for one reason or another (mostly because they escalated to worse and worse things) - or they got out of it eventually - but still come over as slow, dull intellects who have lost that sparkle they had when I knew them beforehand in college. When I go to college reunions - you can instantly tell who was in which crowd. The people who didn't touch the stuff are much more interesting to work with and talk to - and 99% of the time, they are earning more money for less work and are VASTLY happier in later life. That's anecdotal evidence - but it's over a fairly wide sample from the tail end of the hippie era when that stuff was pretty rampant. It's pretty clear that the effects these things have on your brain are the biochemical equivalent of that ice-pick. Every time you do it you get more stupid and you notice it less and less - it's amazing to me that every time a pro-drug-legalization person comes on TV or the radio, they come over as amazingly slow and stupid...but they don't seem to realize it. But do it over enough years - you'll wind up dull and stupid too - so perhaps you won't care anymore. My brain matters to me - it's where I spend most of my time! I intend to look after it and not hit it with random concoctions and just hope that because I couldn't find any mention of problems, that there are no problems. Modern medicine can do a lot to fix up abuse of your body - but to date there is hardly anything they can do if you screw with your brain. SteveBaker (talk) 04:22, 4 March 2009 (UTC)

Steve, you misunderstood the point of my question. It was in no way intended to push a pro-drug agenda or try to rationalize the use of mushrooms by myself. I don't plan on getting mixed up with illicit substances or abusing them. I was simply curious, however odd that may be, and was playing devil's advocate earlier (in regards to the fact that there is no evidence that it is very harmful over long term use). I don't doubt for a second though that any form of drug abuse will not have adverse effects if used long enough or in high enough doses. I appreciate the impassioned censure of abusing illegal drugs...largely in part because it's common knowledge that 99% of those substances will mess up your brain and its neurochemistry! Which leads me to why I originally asked the question in the first place...cocaine, marijuana, ecstasy, heroin, meth, etc., all have terrible long term side effects that are quite noticeable and dangerous, while mushrooms, on the other hand, apparently have no known long term use side effects which I thought was unusual. Hence my curiosity. So please do not misinterpret this as I was saying earlier as a rationalization for drug abuse- it's not. All it is, is simple curiosity. --71.117.38.74 (talk) 05:58, 4 March 2009 (UTC)

Steve, although I have much respect for you, I think your anecdotes aren't necessary here. Many people turn "slow and dull" after college. Correlation-causation problems also arise in that people who take recreational drugs may be predisposed to, and may also be predisposed to being slow and dull people (risk-seeking people are quite biochemically different to risk-averse people). Also, in order to get hold of recreational drugs, people will often start to hang around with those they can get them from (dealers). In order to befriend a dealer (usually someone lacking success in life and of a low intellect), they must start to behave differently, to be accepted in that group (peer pressure). Eventually people adapt to that lifestyle, a sort of "being dumb is cool" attitude, and the self-fulfilling prophecy comes true (acting dumb turns into being dumb). As for 5-HT_2A agonists being "biochemical icepicks", well, I don't quite understand what you are trying to say. They cause lesions? Or they just destroy one's intellect? I have found a review study (free, full text) which should be of much interest: "Role of the Serotonin 5-HT_2A Receptor in Learning". [19] To quote the abstract:

Agonists at the 5-HT2A receptor including LSD (d-lysergic acid diethylamide) enhanced associative learning at doses that produce cognitive effects in humans.

I'm not saying that we should take psychedelics whilst reading through a ton of papers, of course they produce many other effects. What I am saying is that there is no solid evidence that consuming a psychedelic drug will cause you to be "dumb". Unless Albert Hofmann, Alexander Shulgin and probably thousands of other scientists are dumb as well. --Mark PEA (talk) 13:34, 4 March 2009 (UTC)

I'm not sure I would characterize Carl Sagan as being stupid or dull-witted. Matt Deres (talk) 14:48, 4 March 2009 (UTC)

Another of the reasons I suspect there aren't very many studies of long-term shroom use is that, in my limited experience, it's not a drug that is regularly used over an extended period. While there are certainly some people that are sufficiently enamoured with it that they do it regularly, everyone I know that has taken shrooms has done it as a very occasional thing: they seem to be used far more for occasional fun trips rather than as a daily/weekly habit. It may well be that for most people the effect, while generally pleasant, is not something you actually want to do that often - I've heard the same about LSD. This is in contrast to drugs like marijuana, where studies of the long-term effects are most important as it is often used regularly (in some cases multiple times daily) over a long time. ~ mazca ^t|c 08:54, 4 March 2009 (UTC)

To OP, the original question is quite ambiguous. Asking if water is safe can be ambiguous (hyponatraemia). Due to ethical and legal reasons, psychedelic drugs are very poorly researched in humans (and you can't get solid evidence without placebo-controlled studies). As far as I'm aware, there are no "psychedelic models" in animals either. We can see if their 5-HT2a receptors are up/downregulated, but that is about it. As already mentioned, HPPD is a reported problem in some users. There is also some anecdotal evidence of "flashbacks", and a "bad trip" may lead to some form of PTSD. As for the government, don't they normally say that psilocybes are dangerous because they can change your behaviour and make you jump out of a window? (as for ketamine, you might walk into a road, not that anyone under the influence of ethanol has ever done that). --Mark PEA (talk) 13:34, 4 March 2009 (UTC)

Yeah, that dihydrogen monoxide is dangerous stuff. Inhaling a small quantity can kill. Axl ¤ [Talk] 18:06, 4 March 2009 (UTC)

LOL. Thank you for your comments everyone, especially Mark. --71.98.15.188 (talk) 00:54, 5 March 2009 (UTC)

I don't think chronic consumption of magic shroom is widespread and that would make another reason (beyond ethical and legal reasons) why you can't find much of a study out there regarding long term health effects. Besides, health issues related to psychedelic drugs being largely psychological in nature, a study about drugs with similar effects such as LSD or mescaline would likely be just as relevant. Equendil Talk 17:25, 5 March 2009 (UTC)

Are chard and beets the same plant? "beta vulgaris"

If so, is there a link to the USDA or a Dept. of Agriculture website that states this so I can be sure?Troyster87 (talk) 05:00, 3 March 2009 (UTC)

I think this site provides what you want - the family tree of chard, showing it's a member of the beet family. Our page on Chard essentially states this, but provides no references (eww!). --Scray (talk) 06:02, 3 March 2009 (UTC)

This link from our beet article provides very thorough scientific/taxonomic names and multi-lingual common names. It is from The University of Melbourne (article), may also be reliable for academic/citation purposes. Note that beets are classified into a large number of subspecies. "Swiss chard" is a type of beet, but it may be a different breed or cultivar, depending on your classification scheme. As this topic comes up often, classifying things as the "same species" is entirely a matter of your taxonomy preference. Nimur (talk) 07:08, 3 March 2009 (UTC)

When it comes to plant relatedness, agriculture has often created widely different cultivars or breeds of plants which are essentially genetically the same "species", but have been bred to force certain traits to express themselves in an "unnatural" way, i.e. in ways that they could never do in the wild. There are wildly different members of the cabbage family, for example Kale. Brussel Sprouts, and Broccoli which are all essentially descend from the same wild "proto-cabbage". See also the relationship between Teosinte and Maize. --Jayron32.talk.contribs 13:07, 3 March 2009 (UTC)

To make a analogy to something people may be a little more familiar with, a chihuahua, a poodle, a St. Bernard, a German Shepherd(Alsatian), and a wolf are all the same animal/species (a "dog"), but are vary different in their characteristics and their use due to selective breeding. -- 128.104.112.117 (talk) 19:06, 3 March 2009 (UTC)

okay so my question is a little more specific than perceived, i would like to know if beats and chard can be harvested from the same plant, i.e. i plant some beta vulgaris seeds, could i eat the root (beet) and the leaves (chard) and if so would they be the same i find in the supermarket or would they be the leaves that grow on beets that are not commonly eaten and the chard root that is not commonly eaten?

In a word, no. The plants grown for chard and the plants grown for beetroots, while the same species, are different varieties (see Beet#Taxonomy). That said, you can probably use the tops of garden beets as a leafy vegetable. Doing an internet search on "beet greens" reveals a lot of hits. (Although I can't be sure if they're all talking about the leaves of garden beets, or might instead be referring to the spinach beet, which is grown especially for its leaves.) -- 128.104.112.117 (talk) 00:37, 5 March 2009 (UTC)

sub : Quantum mechanics

The wave funtion corresponding to np hydrogenic orbital are imaginary the howI conceive of np orbitals in reality.Supriyochowdhury (talk) 06:06, 3 March 2009 (UTC)
I have edited this into a format that I believe was intended Mattopaedia ^{Have a yarn} 06:21, 3 March 2009 (UTC)

It's not clear exactly what your asking here, but perhaps you could first look at our article on quantum mechanics then direct any further questions here. Mattopaedia ^{Have a yarn} 06:21, 3 March 2009 (UTC)

If I understand S's question, the square of the wave function gives the probability of an electron "being" at a specified position at a specified time. You should try reading that article; it also has some nifty orbital diagrams. Clarityfiend (talk) 07:48, 3 March 2009 (UTC)

While the wave equations may be imaginary, certain sums and differences of wave equations can also valid solutions (a general property of solutions to differential equations). The imaginary terms can be made to cancel out, allowing three completely "real" p orbitals to exist on any energy level. Someguy1221 (talk) 08:36, 3 March 2009 (UTC)

More specifically, the square of an imaginary number is always real, which is why Ψ² is the relevent function here, not Ψ. --Jayron32.talk.contribs 12:59, 3 March 2009 (UTC)

It's not the square, it's the square of the absolute value. This is always a positive real number, as expected of probabilities. Algebraist 13:04, 3 March 2009 (UTC)

Is Ψ imaginary? I thought it was complex (ie. can contain both real and imaginary parts). While the square of a strictly imaginary number is always real (a negative real number, in fact), the square of a complex number can be absolutely anything. That's why, as Algebraist says, you take the the square of the absolute value, or equivalently the product of Ψ and its complex conjugate. --Tango (talk) 13:49, 3 March 2009 (UTC)

Tango is correct. Ψ is properly treated as a complex value, though for some special circumstances it only has a real or an imaginary component. For probability calculations, we use the square of the absolute value: |ψ|². Conveniently, one can calculate this value by multiplying ψ by its complex conjugate, often denoted ψ^*. So |ψ|² = ψ^*ψ. TenOfAllTrades(talk) 14:30, 3 March 2009 (UTC)

I do not understand Faster-Than-Light( physics, relativity) article

B and E fields travel faster than light but energy travels at the speed of light? How is it possible? How we know that magnetic and electric fields travel faster? By Maxwell's equations? Is the photon speed constant and it is 3*10^8 m/s? —Preceding unsigned comment added by Logicman112 (talk • contribs) 12:26, 3 March 2009 (UTC)

B and E fields propagate at the speed of light. What made you think they go faster? Dragons flight (talk) 12:28, 3 March 2009 (UTC)

Is there some confusion involving group velocity and phase velocity? --Tango (talk) 13:40, 3 March 2009 (UTC)

What article are you reading? I can't find B and E fields mentioned in Faster-than-light, although it does cover phase and group velocities which, as Tango suggests, might be the root of your problem. SpinningSpark 17:57, 3 March 2009 (UTC)

Could it be that OP fell into the "in a vacuum" trap? Light propagates through different media at different speeds. It is possible to exceed the speed of light in a given medium. (See Čerenkov radiation.) It's one of my pet peeves that last bit of the saying usually gets left out. 76.97.245.5 (talk) 21:26, 3 March 2009 (UTC)

This part of physics is really a horrible mess because of the choices people have made for the names of things.

• The speed of light IN A VACUUM ('c') is unchanging...and it's the cosmic speed limit beyond which energy, mass and information cannot travel.
• Photons always move at 'c' - even when they are travelling through (for example) water.
• The speed of light in a material like water (which is about 75% of 'c') is not the speed that the photons travel - for they HAVE to travel at 'c', no matter what. But if you take a flashlight and a large tank of water with a mirror at the other end - turn on the flashlight and start your stopwatch, then when you see the light bouncing back at you through the water - you'll notice that it took longer to do it than if the light was moving at 'c'.
• This ought to be obvious because from the perspective of a photon, most of what's in a glass of water is vacuum...the spaces between the molecules and between electron clouds and nucleus is all big open space as far as the photon is concerned.

The reason that the photons can be moving at 'c' but your light beam is only moving at 75% of 'c' is because the photons aren't able to make a simple straight-line trip through the water. They are being bounced around by the water molecules - absorbed and re-emitted and all sorts of other exciting things - which means it takes them longer to get from A to B - even through they are going at 'c' all the time. Personally - I thing physicist should stick with 'c' as "The Speed of Light" and explain that the water merely makes it travel further some factor due to all of these interactions. Talking about "The Speed of Light in Water" is a stupid and meaningless confusion.

So: that said - if the B and E fields carry energy, mass or information - they can't go faster than 'c' - but they may possibly be able to take a shorter route through water than a photon of visible light can - and thereby get there first. That's not the same thing as "Travelling faster than 'c'" - it's only "taking a short cut" - which is much less exciting.

SteveBaker (talk) 23:40, 3 March 2009 (UTC)

SteveBaker, the reason physicists don't stick with 'c' as "The Speed of Light" and then explain things the way you explained is because your explanation is wrong. If it was true that the bouncing of photons off other particles inside the material were slowing them down, you would get light scattering as well as dispertion (even for photons with identical frequencies). In fact that happens (see Rayleigh scattering), but that is another matter and is not the cause of the photon slowing down. Dauto (talk) 01:40, 4 March 2009 (UTC)

You aren't telling me that the photon slows down are you? Relativity applies equally in water and in vacuum - and the 'c' it uses is the speed of light in a vacuum - not the speed of light in water. Photons can't literally slow down because in order to have non-infinite mass when travelling at lightspeed in a vacuum - they would have to have zero mass when they slowed down in water...and that doesn't make sense. So while the photon is in the water - it has to be travelling (over short distances) at 'c' - and to be interfered with in some manner in order for it to take longer to travel over a given distance.

Our article: Čerenkov radiation says: "It is important to note, however, that the speed at which the photons travel is always the same. That is, the speed of light, commonly designated as c, does not change. The light appears to travel more slowly while traversing a medium due to the frequent interactions of the photons with matter. This is similar to a train that, while moving, travels at a constant velocity. If such a train were to travel on a set of tracks with many stops it would appear to be moving more slowly overall; i.e., have a lower average velocity, despite having a constant higher velocity while moving.".

In Speed of light we have: "In passing through materials, the observed speed of light differs from c. When light enters materials its energy is absorbed. In the case of transparent materials (dielectrics) this energy is quickly re-radiated. However, this absorption and re-radiation introduces a delay. As light propagates through dielectric material it undergoes continuous absorption and re-radiation. Therefore when the speed of light in a medium is said to be less than c, this should be read as the speed of energy propagation at the macroscopic level. At the microscopic level electromagnetic waves always travel at c."

Which is what I endeavored to convey...perhaps badly! SteveBaker (talk) 04:06, 4 March 2009 (UTC)

I find the second quotation to be misleading the point of being partially wrong. The delayed speed of light can be understood entirely classically (one doesn't need to introduce photons at all). The propagation of an electromagnetic wave into a dielectric excites a polarization wave in the medium of opposite sign (i.e. locally charges move to partially cancel the external excitation). In the continuum approximation of matter (useful since EM waves are useful much larger than atoms), the superposition of the excitation wave and polarization wave is a new wavefront of the same frequency but slower velocity. The net result is that the electromagnetic wave, expressed as changes in the E and B field, is honestly propagating at less than the speed of light and one doesn't need to invoke any silliness about macro vs. micro waves to get that. At a quantum level the wave is generated by (usually) a very large number of photons. The excitation of the polarization wave is caused by photons being absorbed by the medium. As the polarization wave collapses, new photons are coherently re-emitted in the same direction of travel, after some effective retardation in time. So, yes, the net flow of photons is delayed by interacting with the medium, but the physics of wave propagation in dielectric medium and the consequent delay is better understood by the reaction that retards the purely classical evolution of the wavefront. Dragons flight (talk) 09:46, 4 March 2009 (UTC)

SteveBaker, both your quotations from the Čerenkov radiation and Speed of light articles are rubbish. If I were in a particularly generous mood, I would say that the first one isn't entirely wrong, but needs clarification. I don't think I'm feeling that generous though. The second one really is wrong. Dragons flight already explained what's really going on. In short: Light in vacuum consists of oscillations on the electromagnetic field. Light in a medium consists of oscillations of the electromagnetic field plus oscillations of the charged constituents of the medium (mainly electrons). A different kind of animal entirely. Dauto (talk) 14:25, 4 March 2009 (UTC)

For what my opinion is worth, I don't think SteveBaker (or his quotations) said anything incorrect. It is worth bearing in mind that although you can consider wave propogation in a dielectric as a classical phenomenon, we understand that the world acutally behaves in a quantum manner. Any such classical model must be acknowledged as simply a model which is ony valid if it correctly describes the limiting quantum behaviour. So it's not silly to look at the interactions on a micro- level just because one can find a model which gives the same answers as the quantum case. I agree that the slowing of electromagnetic waves can be 'explained' by the classical continuum model but really we should try to understand this at a quantum level where all quanta of the electromagnetic field necessarily travel at c.

Dragons flight, It seems to me that (ignoring any classical model) your description actually agrees with the second quotation. You say that there are a large number of photons entering the material, this causes some kind of excitation of the material due to photon absorption which in turn leads to re-emitted photons after some delay. Could you elucidate your disagreement? Vespertine1215 (talk) 10:45, 5 March 2009 (UTC)

Unpleasant screeching noises

Why is it that humans find it difficult to stand certain screeching noises like the one produced on scratching one's nails against a granite board, or steal, or even rubbing two metals against each other. What is the scientific and evolutionary reason for humans (like me) find such noises so unpleasant and anxiety producing? Thanks. --ReluctantPhilosopher (talk) 14:08, 3 March 2009 (UTC)

I'd say it's because the sounds resemble screams people (and before them, other animals) gave out as a warning of danger, causing us to flee immediately. Those who ran immediately when hearing such sounds are more likely to have survived and passed on their genes. StuRat (talk) 14:47, 3 March 2009 (UTC)

Equal loudness curve, with "perceived loudness" plotted vs. frequency. Nimur (talk) 15:33, 3 March 2009 (UTC)

Also, you may find phon interesting. A human's sensitivity to loudness is not "flat" - certain tones which contain the same total sound energy (or same sound pressure level) seem louder or quieter depending on their frequency. (This should be no surprise to any engineer who's worked with complex frequency-responses - we see poles and nulls of frequency response in all kinds of mechanical and electronic systems). Anyway, it's possible that your ear/brain audio perception pathway is "amplifying" the specific frequency of the screeching noise to a much higher level than equivalent non-screech-sounds. Nimur (talk) 15:31, 3 March 2009 (UTC)

The question you are asking has been researched rather extensively. The research culminated in the 2006 IgNobel Prize being awarded to people researching Sound of fingernails scraping chalkboard. The latter article lists a few ideas as to why the said sound is so disagreeable. --Dr Dima (talk) 18:44, 3 March 2009 (UTC)

dual exhaust and fuel efficiency

My buddy and I are debating the merits of having dual exhaust. I have a 2000 F-150 with a single exhaust. Would having a dual exhaust improve the mileage? If so, what are the physics behind this? —Preceding unsigned comment added by 216.154.22.180 (talk) 14:40, 3 March 2009 (UTC)

I'd say probably not on mileage. Dual exhaust is normally used to make a car faster, not to improve mileage. By reducing back pressure, dual exhaust can allow for slightly more horsepower, but the added weight of the dual exhaust system will also reduce the mileage slightly. StuRat (talk) 14:43, 3 March 2009 (UTC)

No, actually, a less-restrictive exhaust system tends to improve engine efficiency by dint of reduced pumping losses. Depending on how restrictive the baseline (single) system was, the gain may be small or large. If the driver operates the vehicle so as to produce the same performance level as before, then fuel economy will improve on account of the increased efficiency. If the driver routinely takes advantage of the increased efficiency to accelerate faster, then fuel economy will not improve. Unless the original system is extremely restrictive — generally not the case — the efficiency gains are rather trivial at low, normal engine speeds. On anything but a vehicle specifically designed for minimal weight, and especially on a very heavy vehicle like the pickup truck under discussion, the weight of a dual vs. single exhaust system is insignificant with respect to the vehicle's overall weight and will therefore not materially affect fuel economy. It can be difficult and costly to retrofit a dual exhaust system while remaining in compliance with applicable emissions regulations, unless the vehicle was originally offered by the manufacturer with dual exhaust, in which case it is merely costly — the expense of doing so must be figured into the reckoning of whether it makes financial sense to proceed. Unfortunately, our exhaust system article is presently of low quality and in need of much work. —Scheinwerfermann ^T·_C15:07, 3 March 2009 (UTC)

Thanks. So, technically: we both win . . . and we both lose! Being a gentleman, I'll buy the beer as a gesture of good sportsmanship! —Preceding unsigned comment added by 216.154.22.180 (talk) 15:32, 3 March 2009 (UTC)

Maybe. The amount of 'back pressure' exerted on the engine is a rather important tuning parameter - and changing it has implications for engine power - which may or may not require it to burn more fuel. On a turbocharged car - where the exhaust is fed through the turbocharger's turbine to spin it up and allow better air compression, adding a more freely flowing exhaust will generally give you a few more horsepower because it allows more pressure to build up between engine and turbo. This improved efficiency might cut gas consumption - but if you actually DEMAND that extra horsepower, you'll burn more fuel doing it. On a normally aspirated engine (no turbo) you might not improve things at all - and you could make matters worse. But going from a single to a dual exhaust on most cars is nothing more than a decorative feature - since most of them feed all of the exhaust gasses through a single catalytic converter and silencer (aka muffler) before splitting the exhaust in two. In such cases, the effect is most likely to be zero - no matter what technology is used in the engine - because the limiting factor on flow rate is the catalytic converter and muffler. Doubling up on the catalytic converter and muffer gets around that - but it does add weight - and that might adversely affect your fuel consumption if the original single pipe was already perfectly adequate. SteveBaker (talk) 15:41, 3 March 2009 (UTC)

Angular momentum

http://img183.imageshack.us/img183/887/habitat.png
Say you constructed a Stanford torus, spun it, and climbed up to the exact center. You're just spinning in place, so if you let go your angular momentum is conserved and you continue spinning about your navel and stay perfectly still relative to the supports you were just holding. The article says you're probably spinning about one revolution per minute. But say you were down on the habitat level, facing forward, and you fell through a trap door out into space. Yes you fly off tangentially but do you additionally spin once per minute head over heels? Or do you spin a fraction of that depending on how far you were from the center? Or do you not spin at all? If the last case, where does angular momentum cease to be conserved? Is it when your axis of rotation is no longer inside your body and becomes kind of an axis of revolution?

http://img410.imageshack.us/img410/113/earth.png
Also, say you had a device, gyroscopically stabilized against any change in rotation from outside wind forces. It's on the north pole and it's lifted up and dropped. During the short free-fall the Earth didn't rotate below it because it spun at the same speed. But what if the device is on the equator, tipped over horizontally? It is spinning one rotation per day relative to the stars, same as on the north pole, as you make it around the globe, but is this really the type of rotation that's conserved or just a side effect of the centripetal force? Will the cylindrical device shown over the equator land on a different number than was pointing down when it was picked up? .froth. (talk) 19:23, 3 March 2009 (UTC)

When talking about angular momentum, you have to specify the point you are taking as the centre. In this case, that's the centre of the torus. When you move off tangentially, your angle to that centre will still be changing, since the point isn't on your line of travel. That means you still have angular momentum and, if there aren't any external influences (like the Earth's gravity) that angular momentum will remain constant. --Tango (talk) 19:52, 3 March 2009 (UTC)

Interesting.. but that angle-changing isn't constant. The rate of change of the angle is ${\frac {30\Pi }{t^{2}+900}}$ radians/second at t seconds, given the figures in the article. It starts out at the point of release to be equal to the rate of angle change of the wheel, but then rapidly decreases. In fact, the angle relative to the point of release will never be greater than 90 degrees. So how can you say that you still have the same angular momentum, when before it was whipping around at a steady π/30 radians per second? .froth. (talk) 20:32, 3 March 2009 (UTC)

With respect to your original question, the angular speed $\omega$ will indeed be the same, no matter where you are inside the space torus. With respect to your follow up question, The angular momentum $L\,$ will be conserved and from the formula $L=I\omega \,$ you can se that if your moment of inertial with respect to the center of coordinates $I=mr^{2}\,$ varies, so will your angular velocity around that center $\omega ={\frac {d\theta }{dt}}$, $r\,$ is the distance to the center of coordinates. As you pointed out, once you "fall" off the torus, $r\,$ will increase over time and $d\theta ={\frac {L}{I}}dt={\frac {L}{mr^{2}}}dt$ will decrease over time (for fixed $dt\,$). Do not confuse the angular velocity around the center (which is in fact decreasing over time) with the angular velocity that the poor fellow will have around himself (rotation). That last one will be constant. Dauto (talk) 21:47, 3 March 2009 (UTC)

But the angular velocity he will have about himself (rotation).. if he falls out of the bottom, will he have the same angular velocity about himself as the fellow standing at the hub of the wheel? I think you're saying No but it's hard to decipher .froth. (talk) 21:54, 3 March 2009 (UTC)

He may be spinning around his own centre of gravity, he may not, it's irrelevant. It will depend on exacting how he leaves the station - if he pushes off with just one arm, that would provide a torque that sets him spinning. That won't affect his angular momentum around the centre of the station, though. --Tango (talk) 22:15, 3 March 2009 (UTC)

Tango is right that any torque at the moment he leaves the station will afect his angular velocity around himself. But assuming that there was no torque, it is safe to say that his angular velocity around himself will be the same as the fellow standing at the hub. Dauto (talk) 22:22, 3 March 2009 (UTC)

I don't think that's true. The angular velocity of someone at the hub around their centre of gravity is the same as that around the centre of the station, since that is where their centre of gravity is. Assuming there is no ground underneath them and they just fall away from the centre unhindered then their angular momentum around that centre will remain constant, their angular momentum around their centre of gravity will not since their centre of gravity is moving (obviously, I'm working in an inertial, non-rotating reference frame, if you do it in terms of the person's inherent reference frame you will get different results - you'll have centrifugal force and things to contend with). I can't see anything that would set the person spinning. --Tango (talk) 22:46, 3 March 2009 (UTC)

His angular momentum relative to the hub will be unchanged from what it was just before he left the station. It will be much larger than that of the dude at the hub, because he was further from the hub to begin with. He may or may not be rotating about his navel depending on how cleanly he left the station, but that's irrelevant when it comes to computing his angular momentum relative to the hub.

A curious thing about angular momentum is that you can take an object undergoing linear motion, select a point, and compute the angular momentum of the object relative to the point. And as the object moves along, the angular momentum will remain constant. --Carnildo (talk) 01:52, 4 March 2009 (UTC)

For the first part of your question: If the floor of the space station beneath your feet simply vanishes - you'll proceed in a straight line at a tangent to your former circular motion - which will seem to you like you fell through the floor. You'll continue to rotate at 1 rpm about your center of mass. If you were to rotate about any other point, that would be a net acceleration - and there is no longer a force present to provide that. Rotational and translational inertia are both preserved and all is well with the universe...until your air supply runs out.

If that's hard to imagine - separate out the rotational motion from the translational. Firstly, while you're inside the space station, you are translating around in a circle, secondly you are spinning about your center of gravity at exactly the right rate to keep your feet on the floor and your head up by the ceiling - which is 1rpm. When you take away the floor - you take away the force that's making you translate in a circle - but your 1rpm rotation remains.

For the second part: This is really the same thing - the object is rotating about it's center of gravity at one rotation per day - and travelling around in a circle at one rotation per day. When your "device" (it's really a kind of dice) is tossed upwards (let's do the experiment someplace where there is no atmosphere), it'll continue to rotate at one revolution per day - so when it comes back down again, it'll land on the exact same number. The result is the same no matter where you are on the earth because you are rotating about an axis that's parallel to the axis of the earth,

SteveBaker (talk) 23:23, 3 March 2009 (UTC)

Tango, nothing sets the person spinning. He is already spinning to begin with, along with everything else inside the station. Dauto (talk) 01:14, 4 March 2009 (UTC)

Yes, I missed the fact that his feet always point away from the centre, which requires a rotation around his centre of mass in addition to the rotation around the hub. --Tango (talk) 12:31, 4 March 2009 (UTC)

March 4

Creation (and use) of mass alternative fuel based cars would solve the petroleum Environmental effects?

So much has been talked nowadays about electric cars, hydrogen cars.... Because of petroleum problems and other things... My question is, would the used of alternative fuel only (or almost only) cars would solve the Environmental effects of petroleum?? I mean, petroleum is used to another things also. 201.79.81.7 (talk) 01:41, 4 March 2009 (UTC)

Hidrogen and electricity are means of distribution of energy. They are not sources of energy and cannot in themselves be a solution to the energy problem. But they can be important links in the distribution of other sources of energy. Dauto (talk) 02:23, 4 March 2009 (UTC)

No - without doubt. Solving the car problem completely with some kind of magical 100% renewable-energy, non-CO2-producing fuel would not be enough to fix the global warming or energy shortage crises. But on the other hand - neither would solving any one of the other problems either. In order for us and our planet to get through the mess we've created, we have to agressively attack all sources of greenhouse gas emission and all source of energy consumption. In truth, the "energy crisis" isn't a problem at all because if we burned all of the oil, coal and gas we know that we have - we'd have made the planet unlivable long before we ran out. Whatever solution we come up with for fixing global warming will (by necessity) result in us not having a shortage of coal, oil or gas.

As you can see from the diagram, transportations (which includes trucks, trains, planes and shipping) is only 28% of our energy consumption. To limit global warming to 2 degrees C worldwide (which is a HELL of a lot of temperature increase), we need to get back to 1990 consumption levels by 2020 and to between 40% and 95% BELOW 1990 levels by 2050...clearly cutting 28% off our consumption won't do that.

I think we could fairly easily halve our domestic energy consumption - using better insulation and energy-efficient appliances, I've managed to get my house down to about one third of my neighbours...and I paid for it using the electricity savings I made amortized over about 5 years. With fairly modest government help - all new homes could EASILY do that with the government paying the difference in price for us and collecting that back from fuel taxation equal to the savings you'd make over those 5 years. The result would be that for new home owners, there would be no cost to building an energy efficient home - and after 5 years, they'd make a huge profit on the savings when the fuel tax would go away. For the government/tax payer, it would be a zero-sum game. For energy producers, they'd win because they'd need fewer new power plants. I would assume that commercial users (office buildings, stores, etc) could make similar savings. The two tough ones are industry and transport. Personally, I drive a 40mpg car (a MINI Cooper'S) - the average fuel consumption of a car in the USA is 19mpg - so without electric/hydrogen/hybrid technology - we could probably halve our consumption in the USA...in Europe it's going to be tougher because everyone is already driving tiny cars...but there are other ways to squeeze more out of less.

I'd like to telecommute - that would cut the energy consumed by my 'commercial' contribution to zero at work. I think we could do more shopping online and such like to cut the need for so many 'big box' stores...but for that we need a more efficient delivery system...electric postal delivery vehicles would make a TON of sense for that.

So it's basically do-able (at some cost) for everything EXCEPT industry...hence the pressure for 'cap and trade' systems to put pressure on the big energy consumers in factories. If more people recycled - and if the recycling system were more streamlined, we could make some significant savings there...but it's tough.

Some of the savings can be had without cutting consumption by using windmills (which seem very popular right now) and solar power (less so)...and I'd really hope to see more nuclear power - but there is no way to get the nuclear industry back up and running in as little as 10 years. It takes longer than that to get through the regulatory hurdles - let alone building the darned things.

However, to hit that 2020 target (WORLDWIDE!!) we have to start now. Houses last a lot longer than 10 years - we're still building energy inefficient homes! Even if a super-efficient-home law were to pass today, we wouldn't have more than maybe a quarter of our houses replaced by the deadline. Cars also last 5 to 10 years - getting the old gas-guzzlers off the streets would be very hard - even if we sold no cars that did less than 40mpg starting today! The longer we leave it - the tougher it becomes. We wasted 8 years with that idiot Bush...let's hope we can kick things into high gear now.

There are also huge problems in the developing world. It's going to be very hard indeed to get China and India to follow the 40% to 95% cut by 2050...especially if the cost of oil and gas drop precipitously as the western world starts to use less of it.

SteveBaker (talk) 03:30, 4 March 2009 (UTC)

The major reason why transport is considered a particular problem is because most moving vehicles are inherently "off the grid". Solar, wind, water, tides, nuclear (fission or fusion) can be used to generate electricity, and electricity is extremely versatile, i.e. it can easily be used for most stationary energy needs. So solving this is a problem of scale, economics, and policy. But Hydrocarbons are extremely attractive as energy sources for mobile needs - they have comparatively high energy density, and they have reasonably benevolent handling properties. And we have the infrastructure for their use in place. So changing transportation to other energy sources is much harder - its an unsolved research problem. Cars can go electric, but with reduced range and/or performance. I don't know of any serious attempts for ship or aircraft that do not involve hydrocarbons in some form (although possibly as biofuels). Well, ships can sail - not quite a stupid idea for bulk goods with modern weather satellites and predictions supporting route planning. --Stephan Schulz (talk) 10:12, 4 March 2009 (UTC)

SteveBaker and Stephan Schulz already covered that one pretty well. I would like to point out that Global Warming may make lieving on earth more unpleasant, but it will not be "unlievable". Even with full blown Global Warming humans will survive to see another day (and do some more enviromental damage). Dauto (talk) 14:04, 4 March 2009 (UTC)

One question for Steve Baker here. Does the average of 19 MPG only cover passenger cars, or does it also include tractor trailers? Because it would appear to me that a significant percentage of the transportation energy would originate from them, and there is absolutely no way that you can get one of those as a hybrid without major sacrifices to pulling power using current technology. 65.167.146.130 (talk) 15:08, 4 March 2009 (UTC)

Yeah - that figure is for passenger vehicles - I'm not sure where the cutoff is for trucks and pickups and such. Also, that's the figure for what vehicles are actually achieving in practice - not the EPA numbers (which tend to be pessimistic for new gasoline vehicles but wildly optimistic for hybrids and old, poorly-maintained vehicles) which I vaguely recall says that the average mpg for passenger vehicles is something like 25 mpg. I agree that work is also needed on tractor-trailers...but there is no reason in principle why a similar application of high-technology shouldn't help them too. You can absolutely build a hybrid-technology truck and it would make perfect sense because truck engines are even more sensitive to the RPM you drive them at than car engines (that's why trucks have so many gears!). The single biggest reason that true hybrids like the Prius produce the benefits they do is that they run the engine ONLY at it's most fuel-efficient RPM level.

But in case you doubt the degree to which these things are being agressively pursued - check out Big-Rig trucks, this...um...hybrid truck, er, pusher, Hybrid-engine tug-boats, of course most submarines and diesel/electric railroad locomotives have been using 'hybrid' technologies since before the name was invented. SteveBaker (talk) 04:17, 5 March 2009 (UTC)

You might want to visit here (http://withouthotair.com/) - it's a very interesting book and is available to be read online for free. The section on cars is here (http://www.inference.phy.cam.ac.uk/withouthotair/c3/page_29.shtml) - the book explores simplified calculations to consider whether or not we can maintain our current way of life and reduce our energy consumption as required based on using different technology etc. It's really rather an interesting read, made me much more appreciative of the scale of the issue at hand. ny156uk (talk) 21:01, 4 March 2009 (UTC)

Density

What are the primary factors that make substances as dense as they are? Say, at STP, why is hydrogen less dense than Iron? Does this correlate at all with Atomic size? Is there any pattern in the density of the elements in the table? 99.226.138.202 (talk) 01:49, 4 March 2009 (UTC)

It really is "how much mass is crammed in a certain volume", just like the definition says:) What are the things that compose a substance? "How much they weigh" and "how close they are together" is what gives density. What gives an atom its weight? What controls how closely you can pack atoms together? What pattern(s) do these properties follow? DMacks (talk) 02:15, 4 March 2009 (UTC)

So I understand that Atomic weight is determined by the number of protons and neutrons in an atom, but what determines how closely they can be packed together? Does this have to do how easily atoms are excited? If so, what determines how easily atoms are excited? If the answer to the previous question was atomic mass, why do noble gases stay gases? —Preceding unsigned comment added by 99.226.138.202 (talk) 02:24, 4 March 2009 (UTC) Well, I was going to sign that, but signbot got there ahead of me. XD 99.226.138.202 (talk) 02:26, 4 March 2009 (UTC)

Well, for gases, the controling factor is simply pressure and temperature, as explained by the Ideal Gas Law. Density of different gases at the same set of pressure and temperature conditions is controled entirely by the atomic mass of the gases. (Well, a real gas differs slightly from an ideal gas due mostly to Van der Waals forces, but these effects are negligible at room conditions). In condensed phases (solids and liquids), the volume is controlled by such things as atomic radius and ionic radius and Intermolecular forces which are all a function of the electrostatics going on at the atomic level. --Jayron32.talk.contribs 02:39, 4 March 2009 (UTC)

edit conflict

Mass is pretty well understood at the atomic level - roughly speaking, "count the number of protons and neutrons and ignore everything else." Volume is a lot more complicated, and it depends entirely on packing density. Atomic packing density is an extremely complicated field and an active area of research. While some simple atomic and molecule packing arrangements (particularly, gases and solid-state crystal structures) can be derived from fundamental atomic physics, most of the more complex substances are too complicated to describe their molecular packing analytically (with equations) at present. (Note that "density" is less useful than "pressure" for a gas, although they will be related by the ideal gas law and its experimental variants. Those variants are exactly meant to account for the "unexpected" volume errors due to atomic spacing, atomic bonding, etc.). For most substances, the density is measured macroscopically as the mass per volume at a large scale. Scientists are developing new techniques, and already have a repertoire of long-existing techniques like x-ray diffraction to probe atomic arrangements at the molecular scale. Nimur (talk) 02:40, 4 March 2009 (UTC)

It's a tricky subject - as others have pointed out, the packing of complex compounds is too complex to easily explain. But broadly speaking - the atomic radius of atoms increases fairly slowly as they go up the periodic table. That's because all of the mass is in protons and neutrons the very center of the atom - packed into 1/100,000th of its total size. Adding more neutrons to an atom doesn't change it's size - adding more protons only increases the size because more electrons are required to neutralize the atom - and the number of electrons alters the size of the entire atom. But if you look at Atomic radius#Empirically measured atomic radius - you'll see a table of atomic radii plotted onto the periodic table. Compare some of the lighter elements: eg Lithium with a radius of 145pm - that's picometers - and an atomic mass of around 7...to and the some of the heavier: eg Lead at 180pm and an atomic mass of 207) only differ by a small factor in radius - but the atomic masses are different by a factor of around 30! Now, admittedly, the 'atomic radius' is a slippery term - and it doesn't directly predict density - but you can see that the size of the atom doesn't get much bigger when you add protons and neutrons to it's nucleus. So the higher numbers in the periodic table tend to be the most dense. SteveBaker (talk) 03:00, 4 March 2009 (UTC)

That's just wrong. The size and weight of the nucleus is wholly irrelevant to the atomic radius, which is entirely dependent on the nuclear charge. Comparing Lithium to Lead is ridiculous. Lithium has a relatively large radius due to its 1s¹ configuration and Lead has a relatively small radius due to the lanthanide contraction and relativistic effects which are entirely insignificant in Lithium's case. It's actually fairly predictable that the densest elements will be the heaviest non-lanthanide/actinide ones. --Pykk (talk) 05:35, 4 March 2009 (UTC)

No, Pykk, you just missed entirely what Steve was saying. First: Steve gives effective atomic radii, not nuclear radii; so he is right. And he clearly says that nucleus size is much smaller, hence irrelevant. Second: Lithium atom has ground state configuration 1s² 2s and not 1s¹. That, however, is again entirely beyond the point, as solid Li is a metal and 2s electron is free (what used to be the 2s orbital becomes a part of the conductivity band). Third, it is quite fair to compare Lithium to Lead; differences in electronic structure don't make them any less comparable. Now, to the original question. H, F, Cl, N, O, and noble gases are in gaseous state at STP. All the other elements are solid or liquid. Now, if you are asking "why H₂ is a gas and Fe is a metal", the answer is "because H₂ molecules don't attract each other strongly enough to keep them together at STP; but Fe atoms do". If you are asking "why all noble gases (Group 18) are gases, but all alkali metals (Group 1) are metals", the answer is "because noble gases have an electronic structure such that makes the attraction between their atoms very weak, and the atoms do not stay together; but alkali metals have electronic structure such that atoms attract more strongly, and furthermore one electron per atom is collectivized, which makes them metals". You surely know that the periodic table arrangement into groups mirrors the regularities of the electronic structure of the atoms of chemical elements. Finally, if you are asking "what determines how closely the atoms are packed in a solid" - that was answered already. --Dr Dima (talk) 06:45, 4 March 2009 (UTC)

A chart of density versus atomic number. Actually I'm a little disappointed that Wikipedia does not appear to already have such a graph. Dragons flight (talk) 03:06, 4 March 2009 (UTC)

Aha! Thanks to all the people who helped. 99.226.138.202 (talk) 23:23, 4 March 2009 (UTC)

Length of one second in meters

As is well know, time is the fourth dimension of the space-time continuum. This means that, fundamentally, duration and physical length are simply two forms of the same thing. What then is the equivalent of one second in meters? If this is not a valid question, why not? —WikiMarshall (talk) 01:50, 4 March 2009 (UTC)

299,792,458 meters? :) Arakunem^Talk 01:54, 4 March 2009 (UTC)

Arakunem's got it right. for some reason he worded it as a question? Dauto (talk) 02:15, 4 March 2009 (UTC)

It is not useful in all physical contexts to treat time duration and spatial extent as equivalent or interchangeable quantities. "One second" and "2.99e8 meters" are not as interchangeable as, for example, one gram and 1000 milligrams. Nimur (talk) 02:22, 4 March 2009 (UTC)

I don't think this is a valid question - we casually talk about time as "the fourth dimension" - and lots of really annoying high school text books say it - but time is so different from spatial distances that this really doesn't make much sense. To the extent you can express something I suppose it's most natural to use the speed of light as the 'conversion factor'...so one nanosecond is a foot...but I really don't think that works. Time is SO different from the three spatial dimensions that it hardly bears comparison - why would we arbitrarily lump them all together? So I'd prefer to answer: "Time is NOT the fourth dimension" and "The space-time continuum comprises three spatial and one temporal dimension". It really goes deeper than that - there are "three spatial dimensions"...OK - so point to one of them! The fact is that you can pick any three 'axes' in space to use as your three dimensions - or you can pick an angle and two distances or two angles and one distance. Certainly it's OK to say that "space is three dimensional"...but there aren't three specific dimensions out there. On the other hand, time just "is" - we can't really swap it with the other axes...and it behaves differently from them too. There are lots of equations where you can't use spatial dimensions instead of temporal ones and vice-versa. SteveBaker (talk) 02:43, 4 March 2009 (UTC)

Time isn't just time, you can change your coordinates to combine space dimensions and time dimensions. When you do so you will always end up with one timelike dimension and three spacelike dimensions, but they can be completely different from the one timelike and three spacelike dimensions you started with. Time dilation and related concepts can be viewed as a change in coordinates. For example, if your coordinates start off as (t,x,y,z) you could change that to (t-x,t+x,y,z) and still have a perfectly valid description of spacetime, just with two of your axes "rotated" 45 degrees. In general relativity, spacetime is modelled as a four-dimensional pseudo-Riemannian manifold, it really is four-dimensional and "time" can be considered as one of those dimensions (for varying definitions of "time").--Tango (talk) 13:24, 4 March 2009 (UTC)

Yes - but that's just a mathematical convenience. I often (in computer graphics) treat (X,Y,Z)-space and (R,G,B)-color as a uniform six-dimensional (X,Y,Z,R,G,B)-space. It doesn't mean that space-color is a meaningful concept - it's just easier to do some math operations that way. Some of the things I do have extended up to 14-dimensional "spaces" - but I certainly don't "see the world" as a 14-dimensional place. Doubtless some calculations could usefully be done with three spatial coordinates and one 'mass' coordinate - that would make things like 'density' fall out with greater elegance - just as 'c' falls out when you consider space and time together. We shouldn't confuse a mathematical convenience for "how things are". SteveBaker (talk) 15:08, 4 March 2009 (UTC)

SteveBaker, what universal constant do you suggest we should use to convert color to distance? Or to convert mass to distance. (Hint:there there is an right answer to the second question). Dauto (talk) 16:10, 4 March 2009 (UTC)

You couldn't meaningfully change your (X,Y,Z,R,G,B) coordinates to anything else (at least, not anything that would mix locations and colours in one coordinate), though. (You could do it, mathematically, but it wouldn't have a real world interpretation. Coordinate transforms of space-time do have real world interpretations.) --Tango (talk) 19:39, 4 March 2009 (UTC)

Why the need for a 'universal' constant? As it happens, we typically scale colors either 0..1 and distances at some points in the 3D calculations are scaled 0..1 in screen X/Y and in depth into the screen (Z) - but in other places we have X,Y,Z in meters or something and R,G,B on a 0..255 scale...and in high dynamic range rendering situations, we may toss in another constant ('S') to allow brighter colors than the 0..255 or 0..1 scale would allow. But we're not arrogant enough to claim that there is "one true way" - it's all just a matter of convenience. It's the same in physics - for some fields, using so-called natural units in which 'c' is 1.0 - and in other fields that's a crazy choice and meters per second makes more sense. It's ridiculous arrogance to claim that there is "one true way". If I have to use a conversion constant of e or pi or c or 7 - then that's what I'll use. So long as you make it clear - everything works out just fine. For example, I've used 14-dimensional math to determine whether a particular pair of triangles with a shared edge form a quadrilateral that is "convex" and "planar" in 14-space...if it is then I can dissect the quadrilateral along the opposite diagonal to form two different triangles without messing up the appearance when I draw them. The fourteen (or so) "dimensions" are things like color, translucency, gloss, lighting and shading 'pseudo-curvatures' (normal, tangent and binormal), texture 'grain'...as well as the traditional (x,y,z). Now - in practical work, the precision of the computer isn't infinite - so hardly any quadrilaterals actually turn out to be perfectly planar - so I need to assess the amount of non-planarity and decide whether it's small enough that we don't care. Now I'm measuring this non-planarity in 14-space and coming out with a 'distance' that's in 14 dimensions. Now - the relative scaling of all of these bizarro 'dimensions' suddenly matters. So the 'natural' units for things like color and texture grain are chosen such that a minimally acceptable visual error is the same amount in all 14 dimensions. Are these now in "natural" units? Well, yes...no...who knows?! The fact is that this is what makes things work. In this application, scaling gloss from 0..0.1 while color goes from 0..1 turns out to make pragmatic sense. Would I claim some 'fundamental' connection between color and gloss and distance? Certainly not! It's merely a notational and computational convenience. What physicists do when they drop out 'c' is exactly the same deal. SteveBaker (talk) 03:53, 5 March 2009 (UTC)

Spacetime is not about saying time = length. It's about saying that time and length are deeply connected. So there isn't "one second in meters"—you don't convert time into length. Spacetime, as Einstein formulated it, is about saying that you can't make a length measurement without a time measurement, and you can't make a time measurement without a length measurement. So instead of saying, "this bus is one meter long," you recognize that what you are really saying is, "I measured the position of the front of the bus at time t, and I measured the position of the back of the bus at time t', and now I can express the length of the bus as the difference between these two points." Which in most cases is pretty trivial and it hardly matters, but when the bus as the person measuring it are moving at different speeds, it becomes more problematic, ergo special relativity. --98.217.14.211 (talk) 02:58, 4 March 2009 (UTC)

WikiMarshall, don't pay attention to the nay sayers. Time is indeed the fourth dimension of spacetime and c=299,792,458 m/s is indeed the conversion factor. This is as much true as, for instance, the conversion factor between calories and joules is 1 cal = 4.18 J (approximately). Dauto (talk) 03:35, 4 March 2009 (UTC)

Okay, so if a car is driving at 60 miles per hour, it is moving at 8.97x10^-8? Your assertion of absolute interchangeability of time and space holds no water in virtually all standard physics contexts. Nimur (talk) 08:45, 4 March 2009 (UTC)

Actually, special relativity tells us that all world lines have a four-velocity whose magnitude is fixed at the speed of light. If you are locally at rest, one could say you are moving through time at the speed of light. As your velocity in purely spatial coordinates increases, then your velocity in time coordinate must decrease by a compensating amount. This is another way of looking at the result that highly relativistic objects experience an apparent decrease in the flow of time (i.e. their velocity in the time dimension is decreased). Also, contrary to what Steve says above, there is not one fixed time dimension, but rather the "direction of time" is also a property of the local reference frame. Lorentz transformations are formally coordinate rotations that partially interchange spatial and time dimensions. In order to fully interchange space and time dimensions (so that the time dimensions behaved in a space-like manner, and vice versa) would require traveling faster than the speed of light and so as a practical matter this is forbidden under our existing understanding. Nonetheless, the perception of the spatial distance and time difference between events will vary significantly depending on the local reference frame of the observer, and one can add apparent distance by subtracting apparent time, and vice versa. Dragons flight (talk) 09:19, 4 March 2009 (UTC)

To Nimur, Yes! a speed of 60 miles per hour is (approximately) equivalent to a speed of 8.947x10^-8 (no units). No problem there. Dauto (talk) 13:42, 4 March 2009 (UTC)

While we're throwing caution to the wind, and canceling units for no good reason, I also found the speed of the 60 mph car to be equal to 3.99x10^-4 ... (no units).

(60 miles per hour)/ sqrt(Boltzmann constant * room temperature/electron mass).

But, in real physics..., there has to be a better reason to multiply a quantity by a physical constant. "Just because" doesn't cut it, even if the units work. Nimur (talk) 14:46, 4 March 2009 (UTC)

Nimur, "room temperature" ain't a physical constant. Dauto (talk) 15:05, 4 March 2009 (UTC)

Yes - exactly. As I said above - don't confuse a mathematical convenience with "how things are". SteveBaker (talk) 15:08, 4 March 2009 (UTC)

Lets make things a little more clear. 'c' is indeed a universal physical constant that can be used to convert distance units into time units. The Boltzmann constant is indeed a universal physical constant that can be used convert temperature units into Energy units. Electron mass is a physical constant but it is not a universal physical constant (You had to specify a particle, making it non-universal) so it cannot be used to convert units. Room temperature isn't a physical constant at all. SteveBaker, that is "how things are". Dauto (talk) 15:59, 4 March 2009 (UTC)

My point was that canceling units is not acceptable justification for a physical operation. Pick the mass of the car and the temperature of the car, and you will get a different value, and the units will still cancel, but it has no physical meaning. Why would you be willing to multiply by the speed of an electromagnetic wave, but unwilling to multiply by the temperature of an electron? Why would either of those operations ever make physical sense when calculating a car's speed? Nimur (talk) 16:04, 4 March 2009 (UTC)

And if I wanted to play with fundamental constants long enough, I can create a "universal mass", let's say (ħ/c^2)/t_planck; and a temperature constant... Still, random changing of variables and units does not make physical sense. Nimur (talk) 16:09, 4 March 2009 (UTC)

The car temperature and mass are not universal physical constants. Yes!! use Plank's mass and Plank's temperature in your expression (those are universal constants). See what you get. It won't be random, I promiss. Dauto (talk) 16:23, 4 March 2009 (UTC)

Clearly you are missing my point; maybe my example is distracting from the main issue here. Take a look at The Application of Dimensional Analysis to Cosmology, by Prof. P.S. Wesson of Harvard. He's got a whole book on the subject! Regarding dimensional transformations resulting in unit cancellation: "Physically, it represents a loss of information and can lead to confusion, as a little thought will reveal." Nimur (talk) 16:31, 4 March 2009 (UTC)

The 3+1 dimensions of space and time are not euclidean. If they were, distance would be ${\sqrt {x^{2}+y^{2}+z^{2}+t^{2}}}$. In special relativity, it's ${\sqrt {x^{2}+y^{2}+z^{2}-t^{2}}}$. This makes rotation work different. For the specifics, see Lorentz transformation. Rotations involving time are really just changing to a moving point of reference. Where in euclidean geometry, you could just rotate <0,0,0,1> (one second) by 90 degrees to get <1,0,0,0> (one light-second), in special relativity, rotating it would increase the time component. You could say that one second is two seconds and, I'm not sure, ${\sqrt {2}}$ light-seconds? Anyway, there's no way to rotate it to get zero seconds, or for that matter, anything less than one second, for the time component. — DanielLC 16:32, 4 March 2009 (UTC) [edit] Come to think of it, you could say that one second is i light-seconds, because if you put them both in that equation for distance I mentioned, they would get the same value. — DanielLC 22:03, 4 March 2009 (UTC)

Nimur, I've seen Paul Wesson's quotation before. He is simply wrong. There's no loss of information. We would still be able to apply dimensional analysis even if we use plank's units.

See the last section of dimensional analysis article. Dauto (talk) 17:39, 4 March 2009 (UTC)

There is a loss of information - you don't know how many factors of pi are floating around. You can deal with all the dimensionfull (is that a word?) constants, but once you introduce dimensionless constants it starts to get confusing. That section talks about using h-bar as a conversion factor, it could just as well talk about using h as the conversion factor, it's an arbitrary choice. --Tango (talk) 19:46, 4 March 2009 (UTC)

Tango, some people use degrees to measure angles, some people use radians. It's an arbitrary choice. Both units are adimensional. Yet there is no loss of information (as long as you tell people what units you are using). What was your point again? Dauto (talk) 20:52, 4 March 2009 (UTC)

Mathematicians always use radians, anything else is just radians multiplied by an arbitrary number. An angle is defined as the ratio of the radius and the arc length, there is no reason to multiply that by anything. But that's beside the point - as you say, you need to tell people what units you are using. If you were working dimensionlessly, then there aren't any units, so it doesn't work. --Tango (talk) 21:16, 4 March 2009 (UTC)

Tango, you are right. angles are defined as the ratio between an arc and an radius which comes out naturally in radians but some people chose to arbitrarily multiply that by a constant for tradition's sake and use degrees instead. hence it is necessary to specify which units you are using (radians or degrees) in order to avoid confusion. Notice that angles are dimensionless but it is still possible to use different units, contrary to your point that when working dimensiolessly there aren't any units, so it doesn't work. You just didn't think it through. The same thing is true about the definition of the speed of an object. it is defined as the ratio between two components of the quadrivector $ds^{\mu }\,$ along the direction of the particle's trajectory (world line) through spacetime. These components must have the same units, since they are components of a single object. Therefore velocity is an adimensional quantity. c=1 comes out of this definition naturally but some people chose to arbitrarily mutiply that by a constant for tradition's sake and use m/s instead. hence it is necessary to specify which units you are using (m/s or natural units) in order to avoid confusion. No loss of information as long as you tell people which units you are using. Dauto (talk) 22:26, 4 March 2009 (UTC)

Mathematicians never use degrees (in any real work, anyway - they might come up in casual conversation) and very rarely use the word "radian". Angles are dimensionless, there are no units, we don't use units. A right angle is "pi-by-2" not "pi-by-2 radians". Using degrees is simply wrong from a mathematical perspective. Any comparison between radians vs degrees and ft/ns vs m/s is misconceived. The four vector you mention is defined in terms of c, you need the c in there otherwise it is wrong (you can, of course, define c=1 and then not worry about it until you get to the end of your calculation and plug in the appropriate constants to get the units to balance). When you work out the velocity as you were doing, you do get a dimensionless quantity, but that quantity isn't velocity, it's velocity/c. c has dimensions, so so does velocity. --Tango (talk) 22:41, 4 March 2009 (UTC)

Mathematicians can get away with skipping mentioning the fact that they are using radians because they know that their audience knows that they are using radians. It goes without saying because, as you said, radians come naturally and any other units would in a sense be wrong. Guess what, quantum field theorist and relativists also get away with skipping mentioning the fact that they are using natural units because they know that their audience knows that they are using natural units. It goes without saying because natural units come naturally (hence the name) and any other units would in a sense be wrong (to use your words). c=1(no units) is more than a mathematical convenience. It is the right way to think about it. In fact, Those physicists I talked about never (to use another of your words) use 'c' in their equations. Think about it. Why should two different components of a single physical object (a quadrivector) be measured using different units? You said I have to stick a 'c' in there in order to make it right. I say you are the one sticking 'c' in there when you arbitrarily chose to use different units to measure time and space. Dauto (talk) 23:50, 4 March 2009 (UTC)

It's not even true that radians are somehow 'natural' units for angles. There are engineering applications where 'grads' are used (100 grads = 90 degrees). There are plenty of situations where a full 360 degrees is more usefully and 'naturally' scaled to a 0..1 or -1..1 scale. There are times in computer-based applications when it's more natural to use 1/256th of a circle. If you ever played a computer game that used the "Unreal Engine", all of your angles are in 1/65536ths of a circle. Math isn't just for mathematicians - we normal people get to use and adapt it too! SteveBaker (talk) 03:27, 5 March 2009 (UTC)

SteveBaker, radians are the natural units for angles. But you are free to introduce arbitrary constants in your choice of units if that is somehow convenient. As you said yourself, "don't confuse a mathematical convenience with 'how things are'". Dauto (talk) 03:54, 5 March 2009 (UTC)

No! That's bullshit. Having 2.pi units in a full circle is undoubtedly convenient in situations where pi is involved for some other reasons (eg when working with sines and cosines) but in other situations where pi is NOT involved, a 0..1 scale is vastly more 'natural'. You have a prediliction for having 2.pi units because that's the kind of field you happen to be working in - but in areas I happen to work in (some of the time), having an irrational number of angle units in a full rotation is not merely inconvenient - it's utterly untenable! There are things you literally cannot do with radians. For example - I have two objects that are spinning - adding some amount of rotation per time-step...and I want to know on any given time-step whether they are pointing in the same direction. Using radians I have to divide their total accumulated rotation by 2.pi and take the remainder and compare the two results. However because pi is irrational - I can't make such a comparison in finite precision. In that case using radians is not only unnatural - its downright useless! So - I store rotations such that a full rotation is 1 unit. This is beautifully natural - I simply compare the fractional parts of the numbers and I'm done...what could be more natural? Radians are also useless for people who have to do actual numerical calculations rapidly in their heads - using degrees is incredibly useful in that situation because you can do exact division by 2,3,4,5,6,8,9,10,12...and so on...jut try calculating the numerical value of a third of two-pi in your head so you can mark it using your (non-existant) radians-scale-protractor!!! One man's "natural" is another man's "completely and utterly impractical". So your 'natural' units are only natural for your applications - and this pigheaded insistence that your way is right and everything else is somehow wrong is just phreaking crazy! We can do calculations using angles using any damned units we like. Get out here in the real world where math is actually used for practical purposes and you'll soon find that what is 'natural' or 'convenient' changes from one day to the next. The sooner you get your head out of the clouds (or wherever it's currently stuck) and into the real world the sooner your contribution to the world will be of practical relevance. SteveBaker (talk) 05:22, 5 March 2009 (UTC)

"Natural" has a very precise meaning in this context, it doesn't just mean "the most obvious/useful". There are plenty of situation where it is best to use unnatural units and conventions, but that doesn't make them natural. --Tango (talk) 15:41, 5 March 2009 (UTC)

SteveBaker, I don't dispute that other angle units can be more useful or practical then radians. I myself find it more practical to use degrees in many situations, and I understand why a computer programmer would prefer to use some power of 2 such as 256 for 360 degrees. That does not change the fact that an angle is defined as the ratio between two lengths (a radius and an arch) and the natural thing to do is to use the same units to measure both lengths. Guess what angle units turn up when you do that? Dauto (talk) 19:27, 5 March 2009 (UTC)

Physicists never use c in their equations? I can't tell if you're just making stuff up here or are somehow totally confused. Show me some of this physics that somehow never uses natural units and implies multiplying things by c but doesn't say it. I call foul—you're spouting nonsense. --98.217.14.211 (talk) 01:00, 5 March 2009 (UTC)

May be I didn't make my self clear enough. What I meant to say was that whenever using natural units $(c=\hbar =1\,)$ 'c' or '$\hbar \,$' don't appear in the equations. What would be the point of multiplying by powers of c=1(no units)? That's why c never apears in the equations when natural units are being used. Dauto (talk) 03:29, 5 March 2009 (UTC)

Look at the rightmost column of the table atPlanck units#Planck units simplify key equations. See any physical constants there? That's what I'm talking about. Dauto (talk) 03:47, 5 March 2009 (UTC)

Plumbide

I just created an article called Plumbide and was told to come here for help expanding it. Chlorine Trifluoride (talk) 02:07, 4 March 2009 (UTC)

It would help if your footnotes actually explained the reference - WP:CITATIONS will help you with the formatting. From what I see at present, it is not possible for a reader to track your sources down. I've done one as an example for you... (it's not a perfect cite template, but it's at least possible to track down the article without a lot of effort). Nimur (talk) 02:25, 4 March 2009 (UTC)

Well, there are quite a few things here:

• Your 'references' aren't references, they're footnotes. References are links to documents outside of Wikipedia that specifically back up what you are saying - scientific journals, chemistry books for example. You could start by doing a Google search on your subject and see what decent articles have been written about it.
• Your link to rare earth links to a 'disambiguation' page - that's bad because the poor person who follows your link doesn't know which meaning of the term you are referring to. Link instead to rare earth element.
• The article is very short - it'll definitely need some expansion. I recommend you look at other articles on similar topics - phosphite for example. It has diagrams of the structures it's talking about, a 'See Also' section - which you should use to link to other Wikipedia articles that talk about related topics.
• You should do a 'search' on the word 'plumbide' using the regular Wiki search box and see what other articles mention the word - this may give you more ideas for things to write about - and you can edit those articles to link to yours on the first occasion they mention the word.
• If you have a copywrite-free photo of some samples of these materials - add it into your article.
• There are lots of other categories you could add your article to - there are categories "Inorganic compound stubs" and "Lead compounds" that seem reasonable.
• You could try joining the Wikipedia:WikiProject Chemistry - they have MANY resources for people writing on chemistry-related subjects. There are entire specialised manuals-of-style for writing these kinds of article.

I hope that helps! SteveBaker (talk) 02:29, 4 March 2009 (UTC)

Damn, I saw the link to Rare Earth and thought I was gonna get a 22 minute version of Get Ready... --Jayron32.talk.contribs 02:42, 4 March 2009 (UTC)

Well you've definately got a good name for this type of work CF₃.

For some reason you put the page in the category 'plumbates', I changed that to 'lead compounds' - as phosphide is not a phospate etc.

Beyond that I can't see so much wrong with it. Why not go and make another article. It's perfectly acceptable to me after I made tiny changes to it. Keep up the good work, wikipedia needs more articles like this.FengRail (talk) 04:23, 4 March 2009 (UTC)

medium oil

what is the composition of medium oil? —Preceding unsigned comment added by 119.154.9.144 (talk) 03:42, 4 March 2009 (UTC)

It depends on the brand and where you bought it. Megilp is a painting medium consisting of a mixture of mastic varnish and linseed oil. Most will be similar, combining a thickener with linseed or synthetic oil. Nimur (talk) 08:48, 4 March 2009 (UTC)

Legal "uppers"

Caffeine and sugar are legal "uppers": something you can take that gives you some more energy for some hours. Are there more "things" a normal healthy person can take to get some more energy? I'm not interested to read about illegal drugs or about stuff that is detrimental for your body, just something comparable to coffee (but that I don't know of). Lova Falk (talk) 07:27, 4 March 2009 (UTC)

Some people find coffee or tea stimulating even if it is decaffeinated. This may be a psychological response, but it's possible there are other compounds in the drink that are also categorically stimulants. Nimur (talk) 08:50, 4 March 2009 (UTC)

Indeed, I am one of those people. —Cyclonenim (talk · contribs · email) 23:22, 4 March 2009 (UTC)

See energy drink and energy bar. Those articles contain a number of links to other compounds people ingest to get some "energy", ranging from outright stimulants like ephedra to Calorie rich food products like starches. Dragons flight (talk) 08:56, 4 March 2009 (UTC)

Starches are converted to sugar by the saliva in your mouth...(try chewing a piece of bread and notice how it gets sweeter as you chew)...so for our purposes, starches ARE sugars. SteveBaker (talk) 14:59, 4 March 2009 (UTC)

If you chew long enough, yes. Saliva isn't the only source of amylase, some starch is broken down later, so it does take longer to get energy from starch than sugar. See glycemic index. --Tango (talk) 19:36, 4 March 2009 (UTC)

Laws vary from country to country. Kava seems to be legal in most places, although perhaps hard to come by other than in the South Pacific. It's also not very pleasant to drink - like mud, but perhaps it's an aquired taste.-gadfium 09:17, 4 March 2009 (UTC)

Hmm, Kava as an "upper"?

Kava is a tranquilizer primarily consumed to relax without disrupting mental clarity. Its active ingredients are called kavalactones. In some parts of the Western World, kava extract is marketed as herbal medicine against stress, insomnia, and anxiety.

— Kava

I have never tried Kava, but its mechanism of action appears similar to benzodiazepines, and they sure don't make me feel "up" (since I take them for sleep!). -- Aeluwas (talk) 11:27, 4 March 2009 (UTC)

Beware of Kava, I don't have a reference right now, but remember reading that one particular part of the plant contains some hepatotoxic compounds. --Mark PEA (talk) 12:41, 4 March 2009 (UTC)

If this piece is to be believed, consuming bicarbonate of soda before exertion leads to amazing increases in performance.[ http://ironpower.biz/sup/sup_energy2.htm] --TammyMoet (talk) 11:57, 4 March 2009 (UTC)

I was expecting that to be a typical pseudoscience piece by some uninformed layperson, but was pleasantly surprised. However, it still isn't peer reviewed (I can't access full studies of 30+ years ago) and if the OP is asking for an alternative to caffeine for mental stimulation, sodium bicarbonate is not going to help. --Mark PEA (talk) 12:41, 4 March 2009 (UTC)

Contrary to popular belief, increased concentration of lactate does not directly cause acidosis, nor is it responsible for delayed onset muscle soreness. Noodle snacks (talk) 06:09, 5 March 2009 (UTC)

Native peoples in Bolivia and similar places chew coca leaves for energy, and it's legal for them to do so. I personally take pseudoephedrine for chronic sinus headaches, and I've noticed that it gives me a big energy and concentration boost. Other stimulants, such as Ritalin, have a similar effect. --Sean 14:00, 4 March 2009 (UTC)

In Brazil it is common to use guarana as an energy boost. It contais more caffaine then coffe as well as Theophylline plus other components. Dauto (talk) 14:49, 4 March 2009 (UTC)

I've seen guarana listed in some energy 'uppers' commonly sold in gas stations in the USA. SteveBaker (talk) 15:00, 4 March 2009 (UTC)

I used to have a friend who ate supari, but the taste is pretty awful (at least to my taste buds). You can check out our articles under the Herbal and fungal stimulants category [20]. If you consult a doctor, there's Adderall. A Quest For Knowledge (talk) 16:03, 4 March 2009 (UTC)

Khat may or may not be legal depending on where you are (legal in UK, not in USA); it contains the stimulant cathinone. --Maltelauridsbrigge (talk) 18:37, 4 March 2009 (UTC)

Something else that hasn't been mentioned: modafinil, piracetam and the various other racetams. Please also see this template: Template:Psychostimulants, agents used for ADHD and nootropics. --Mark PEA (talk) 21:07, 4 March 2009 (UTC)

Abstinence from sexual activity will allow you more energy than its opposite. Cuddlyable3 (talk) 14:17, 5 March 2009 (UTC)

Thank you all for answering! I'll check everyone of them, to see if I'll use it, but the side effects scare me.Lova Falk (talk) 17:18, 5 March 2009 (UTC)

Fluid therapy

Explain the difference between "maintenance" volume, "replacement" volume and "ongoing losses" in fluid therapy? —Preceding unsigned comment added by 124.178.147.147 (talk) 09:10, 4 March 2009 (UTC)

Or article on fluid balance may provide some useful background information for you. As for your questions:
Maintenance = the volume of intravenous fluid required to maintain a neutral (no net loss or gain) fluid balance (so input matches output).
Replacement = the amount of fluid required to correct a negative fluid balance to neutral (so input = fluid volume deficit + ongoing losses).
Ongoing losses = fluid losses through all means, both sensible ( or quantifiable, including urinary output, faecal/diarrhoeal, wound drainage, bleeding) and insensible (or non-quantifiable, including evaporative losses to respiration, perspiration and open wounds, especially burns and other large surface area wounds). Hope that helps. Mattopaedia ^{Have a yarn} 13:17, 4 March 2009 (UTC)

The Rust Process

I need a few minutes of the right person's time and his/her expert opinion on how fast rust can appear on newly exposed steel following removal of paint on a car part - the frame of a door open to the weather. (I'm in dispute with a body shop as to how some damage was caused.) The car was parked outside for ten days in cold, wet conditions. How quickly would a visible layer of rust appear? A few days? A week? Would much more than ten days be needed?

Many thanks

FrancisMacFrancisMac (talk) 09:23, 4 March 2009 (UTC)

This is original research so not actually permissible in the World of Wikipedia, but steel body work can rust in a couple of days in wet conditions, a couple of years ago I was making a steel framed table and this rusted within 36 hours after a shower of rain. Richard Avery (talk) 10:12, 4 March 2009 (UTC)

Original research is not allowed in articles. I don't see how knowledge of rust constitutes original research

However we are not here to give legal advice, and any information given here can't be relied on in a legal dispute at all.

It also depends on the depth of rust. Exposed steel can get a thin layer of rust in seconds213.249.232.187 (talk) 12:13, 4 March 2009 (UTC)

Sorry 187 I missed out a ;-) Richard Avery (talk) 15:03, 4 March 2009 (UTC)

Indeed. High quality knives, such as Honyaki and other Japanese cutlery require constant vigilant maintenance. They must be wiped dry immediately after use, lest moisture rust the blade and ruin the edge. Visible rust and pitting can occur within minutes if the blade is left damp. --Jayron32.talk.contribs 14:43, 4 March 2009 (UTC)

I also agree that exposed steel will start to rust immediately. In my case, I polished steel samples for microscopic viewing, and it was necessary to repolish them the next day because of surface rust. However, the serious type of rust that causes pieces of the metal to flake off will take longer. Also note that the car steel may have had some protective coating underneath the paint. Whether this coating was also stripped off with the paint, I do not know. Salt will greatly speed up the rusting process, so, if they splashed saltwater on it while moving it through an icy lot, that would also have an effect. StuRat (talk) 14:50, 4 March 2009 (UTC)

It's vastly variable.

When I lived on the south coast of the UK, my wife reversed one of our cars into the other (doh!) scraping a 6" swath of metal on one car down to the bare metal. Two days later, it had a patina of rust on it - the metal was no longer shiney and it had little orange splotches. By the time we got it to the body shop, maybe a week later, it was orange-colored all over, rough to the touch and there was no shiney metal visible anywhere.

Here in central Texas, I was rear-ended in my old pickup truck and lost about the same amount of paint in roughly the same area. Since the truck was old and crappy - I pocketed the insurance money and didn't bother to get it repaired and I never did get around to painting the 'ding'. Four years later, when I sold the truck, that patch of metal was still as shiney as the day the accident happened.

The difference was:

• The car in the UK was a Morris Marina - notorious for being built from low-grade steel. The truck in Texas was a Ford Explorer. Made from pretty decent steel.
• The weather in the UK is damp and rainy - the humidity is often high. The weather in Texas is hot and dry - and in central Texas, the humidity is typically close to zero.
• In the UK, it snows and gets icy in the winter and they used to spread a lot of salt onto the roads to melt it. Here in Texas, it only rarely gets icy - and when it does they use grit from inland quarries - not salty beach sand. When the ice melts and the road dries out - the salt stays there. UK roads are salty even in the summertime - and it's well known that salt+water+steel=rust.
• In the UK, we lived in Brighton - close to the sea - lots of salt is in the air. Here in Texas, we're 300 miles inland...so not.
• Although the annual rainfall in this part of Texas is comparable to the southern counties of the UK, the rain happens in a few torrential downpours a few times a year. Cars get wet - but they dry out pretty quickly. In the UK, it drizzles just enough rain to get things wet - then stops for a while - then does it again - and it does that through most of the year. It often doesn't get dry enough or warm enough for things to properly dry out for weeks or even months at a time.
• Even in the winter, in Texas there are cold days (below freezing sometimes) - but they are mixed in with hot days - so again, things don't stay wet for long. (There is a saying here that in the winter: "If you don't like the weather today - wait until tomorrow - it'll be different.")...sometimes we have snow on Xmas day - but other times we can eat our Xmas dinner out in the open air...it's random.

I also have a 1973 VW Bug that spent most of it's life in Arizona (hot, dry, no humidity) and the rest in Texas - despite its age and a total lack of rustproofing, it has zero rust.

Somewhere between two days and 35 years is where your answer lies!

SteveBaker (talk) 14:56, 4 March 2009 (UTC)

(Are very expensive cars ever made of stainless steel?)FengRail (talk) 17:42, 4 March 2009 (UTC)

The added cost and difficulty of working with stainless steel mean that it is seldom used unless absolutely necessary. (Stainless steel is harder than most other steels, and it's a bloody nuisance to work with.) The DeLorean DMC-12 – the car featured in the Back to the Future films – is a famous exception, being equipped with stainless steel body panels. DeLoreans were left unpainted, as their fiberglass and stainless-steel bodies were not vulnerable to rust. A few other vehicles have also been built with stainless steel finish, usually for promotional or demonstration purposes: [21]. TenOfAllTrades(talk) 22:39, 4 March 2009 (UTC)

Thanks.FengRail (talk) 22:52, 4 March 2009 (UTC)

I believe that the DeLorean was the only mass-production car ever to use stainless steel. They don't make regular cars out of the stuff because it doesn't take paint very well - you can have it any color you want so long as it's dull-silver. (Hence the "natural metal" finish on the Deloreans). Sure, DeLorean's don't rust (and because the stainless steel body panels are essentially just decorative - it would still work just fine if it did). But it was far from an easy car to maintain - there were problems with hard-to-remove marks from fingerprints and bird poop and such. You had to clean it with some fairly exotic cleaning agents that you had to get from the DeLorean factory. Without a protective paint finish, fine scratches were more noticable because you couldn't just wax the car to get rid of them - and because you can't use paint and bondo and the body has a 'brushed' finish - you can't either hammer out or fill and paint a ding. SO any kind of minor body damage pretty much requires replacing the entire body panel. SteveBaker (talk) 03:01, 5 March 2009 (UTC)

It would be a lot easier? to make them out of normal steel, polished and then clear lacquered. (by the sounds of it) Such as is found on many shiny steel tools.FengRail (talk) 13:52, 5 March 2009 (UTC)

Birds and sex

Sorry if this is a bit of a vulgar question, but I saw two pigeons having sex outside my window this morning and it got me thinking. How exactly does the male bird manage to get his cum into the female and avoid getting it plastered all over her rump feathers, or his own feathers when he ejacultates, seeing as though he doesn't actually have anything he can 'stick inside'? There seems to be an awful lot of feathers to get in the way of a successfull mating. --81.77.40.134 (talk) 14:19, 4 March 2009 (UTC)

Well, they must work it out somehow, since there do seem to be an awful lot of little pigeons running around. Seriously though, you should read Cloaca, and especially the paragraph on the "Cloacal kiss". It's enlightening. --Jayron32.talk.contribs 14:40, 4 March 2009 (UTC)

I would guess that a lot does miss the target, but enough hits to cause pregnancy, and that's what's important. StuRat (talk) 14:44, 4 March 2009 (UTC)

The cloaca is colloquially known as a "vent", presumably because "cloaca" sounds vulgar. Nimur (talk) 14:56, 4 March 2009 (UTC)

I seem to remember someone mentioning something on here once about how the mating method used by birds is not particularly efficient, compared to the way that most mammals go about it. As someone who's bred birds, I suppose the fact that sometimes you'll get a hen laying an entire clutch of unfertilized eggs, despite being 'serviced' repeatedly by her mate (or only ending up with one or two eggs that develop - out of six) is testament to its (literally!) hit-and-miss nature. As Jayron32 said, I suppose that it works as well as the species needs it to work in order to keep the numbers up. --Kurt Shaped Box (talk) 19:29, 4 March 2009 (UTC)

Ask the quelea how it works, they seem to have got the hang of it! Richard Avery (talk) 07:23, 5 March 2009 (UTC)

There must be more chickens than quelea? Kittybrewster ☎ 07:39, 5 March 2009 (UTC)

Expected decline of the Earth biosphere

Hello. I'm looking for an article about this subject. But I cant find one. Is there one? (Specifically, an article which describes the predicted decay of the biosphere due to the growth of the sun. How and when different aspects of the biosphere would be expected to decline and dissappear. When would the oceans become shallow seas? When would the disappear altogether? When would life begin to decline? When would it dissappear? And so on). Thanks in advance for pointing me in the right direction! —Preceding unsigned comment added by 81.233.212.12 (talk) 15:19, 4 March 2009 (UTC)

According to our article on the Sun, we have about a billion years. A Quest For Knowledge (talk) 16:34, 4 March 2009 (UTC)

I see it. I've no plans to still be here by then, so I should be OK. But is there a full article on the subject? If not, can I request the creation of one? 81.233.212.12 (talk) 16:38, 4 March 2009 (UTC)

Be bold and make it yourself. Just make sure you follow all notability and referral guidelines or you risk having your article deleted. Livewireo (talk) 16:55, 4 March 2009 (UTC)

We have an article, Risks to civilization, humans and planet Earth, if that helps. --Tango (talk) 00:01, 5 March 2009 (UTC)

There is no way to realistically predict that. We have no clue how life would evolve in the presence of gradually increasing heat - and we really don't know precisely what will happen to the sun and when. This would be approximation layered on guesswork layered on wild supposition. SteveBaker (talk) 02:33, 5 March 2009 (UTC)

We can put upper bounds on it, though. Once the average temperature gets above the boiling point of water, life as we know it is going to struggle. That's where the 1 billion years prediction comes from. --Tango (talk) 13:47, 5 March 2009 (UTC)

That's a bold supposition. Evolution has produced some rather impressive extremophiles. It's not beyond the realms of possibility for a creature to be able to operate at those temperatures. Hyperthermophiles are around today that can survive well above boiling point (see Methanopyrus Strain 116...happily living their boring, hot little lives at 122 degrees centigrade...well beyond boiling point. As temperatures rise - those critters will become more prevalent as their competitors are wiped out - evolution will allow some of them to survive at higher and higher temperatures and in increasing salinity...perhaps multicelled hyperthermophiles will evolve? As the oceans boil, the cloud cover over the planet will increase - pushing up our Albedo and reflecting more sunlight away - that'll slow things down somewhat...but precisely how much is a relative unknown because we don't know the geography of that future era. Will the oceans be deep or shallow when they start to boil? Will ocean current mix up the cold, deep layers and the hot top layers or not? We can't predict ocean currents a billion years from now! Heck we can't even predict the effects of global warming to that kind of degree over even 50 to 100 years! But until the oceans are literally boiled dry - I think we'll see life clinging on in some niche environments - because that's what evolution does. However, once all the water has gone - it's certainly gonna be tough. But predicting that with the kind of specificity and precision that our OP demands does not seem likely. Will we have extremophiles above the size of a bacterium? Will there be extremophile Lions and Giraffes? Will they learn to live in the air like birds and insects in clouds of live steam? Due to the random nature of evolution - we can't know - we can't even sensibly speculate. SteveBaker (talk) 14:09, 5 March 2009 (UTC)

Those examples you mention live at above 100C, they don't live at above the boiling point of water, since they are deep underwater where the high pressure increases the boiling point. The Earth may have to heat to somewhere above 100C in order for all the water to boil (especially since the atmospheric pressure would presumably increase will all the extra water vapour), but sooner or later the temperature will reach the boiling point of water even at the bottom of the oceans. Some life may be able to survive after that, but it wouldn't be life as we know it. --Tango (talk) 15:36, 5 March 2009 (UTC)

Does anyone happen to know how warm Mars will be and how habitable it will be by then? A Quest For Knowledge (talk) 17:08, 5 March 2009 (UTC)

While it is possible Mars would warm up to a habitable temperature for a time (probably a fairly short time, geologically speaking), it still wouldn't have much of an atmosphere. The ice caps would sublime, providing some more atmosphere, but probably not enough to support humans without protect (and there certainly wouldn't be any free oxygen without active terraforming). It might make terraforming an easier job, but it would still take a lot of work. --Tango (talk) 18:02, 5 March 2009 (UTC)

looking for a photo

I am looking for a photo of the earth from space at night, however there is a catch. I want one during a large widespread power outage, so I can see how much light there is on emergency power only. Anyone able to help? 65.167.146.130 (talk) 16:31, 4 March 2009 (UTC)

List of power outages is a first place to look. You should be very careful that you are comparing "apples-to-apples" images - with modern processing techniques like image compositing, multispectral cameras, gain adjustment and auto-leveling of brightness and intensity in both acquisition and post-production, it may be hard to tell exactly how much light you are actually receiving (typically, I think Earth at night as viewed from orbit looks pretty dark when viewed with the naked eye). Next, take a look at NASA's Science on a Sphere Night Lights data sets. They specifically mention techniques to display power outages by comparing average data to single-night data. Again, note that these are false-color (enhanced) images. Alternatively, you can look at this Columbia University Earth Institute press release, which has a few low-resolution images, and references further research. Here's a blog which makes a vague citation to "NASA" but no real information on the image processing techniques. Nimur (talk) 16:38, 4 March 2009 (UTC)

After a major outage in the northeast USA a few years back, such a picture made the rounds, but was said to be phony. —Tamfang (talk) 18:37, 4 March 2009 (UTC)

Here are the real images of the 2003 blackout. They're not as impressive as the fake ones, but still pretty neat. APL (talk) 18:55, 4 March 2009 (UTC)

Surely there has never been a world-wide outage? Kittybrewster ☎ 07:36, 5 March 2009 (UTC)

no. an outage can only go as far as the power systems are linked. --98.217.14.211 (talk) 12:55, 5 March 2009 (UTC)

Hypothetically speaking, an external event (like an extraordinarily strong geomagnetic storm) could affect multiple power grids simultaneously. It would take a heck of a solar storm to bring down all the electric grids in the world (or even in just one hemisphere), though. TenOfAllTrades(talk) 18:09, 5 March 2009 (UTC)

Comparing the nightime views from space of the North and South Koreas supports the contention that the South may suffer an occasional power outage but the North never enjoys a power inage. Cuddlyable3 (talk) 14:25, 5 March 2009 (UTC)

Osseous structures and soft tissue uptake in L3 vertebra

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

--Milkbreath (talk) 17:46, 5 March 2009 (UTC)

The discussion about whether this is a request for medical advice is here. StuRat (talk) 05:18, 5 March 2009 (UTC)

This question may be a request for medical advice. It is against our guidelines to provide medical advice. You might like to re-phrase your question. You may also find it helpful to read the article: Positron emission tomography, osteoblasts, and osseous tissue, and form your own opinion from the information there. Thank you. StuRat (talk) 19:25, 5 March 2009 (UTC)

.

March 5

magnatizing a charged body

some one has told me that we can magnatized a uncharged body but charged body can not be magnatized.I could not understand this.Is it true ,plz explain —Preceding unsigned comment added by 119.154.28.19 (talk) 01:06, 5 March 2009 (UTC)

Not true, a magnet can be charged. Graeme Bartlett (talk) 05:14, 5 March 2009 (UTC)

There might be a misunderstanding here - in general permanent magnets cannot be made from good conductors. But being a poor conductor does not mean the material will make a good magnet. (Before anyone says - Iron which can be magnetised contains a lot of ceramic paricles in the matrix - which are respondsible for it's ability to be magnetised as well as its brittleness - any conduction of electricity is around the particles held in the matrix - pure iron which does not contain any ceramic particles does not make a permanent magnet)FengRail (talk) 13:49, 5 March 2009 (UTC)

The OP may also be confused because electric charge does exist, while magnetic charge does not. Magnetism in materials is not caused by a (magnetic) charge, but it can co-exist with an electric charge and will certainly interact with moving electric charge. It sounds like you misinterpreted someone explaining: there is no way to put a magnetic charge on an object; but it is definitely possible to put an electric charge on a magnet.. Nimur (talk) 15:34, 5 March 2009 (UTC)

It is also possible to magnetize a piece of iron after an electric charge is placed on it. Edison (talk) 19:36, 5 March 2009 (UTC)

How do we know how high the sea level was 500 million years ago?

I heard that the last time we had the same level of greenhouse gases was some 500 million years ago, and the sea level was then several hundred feet above what it is now. I checked the sea level article, which led me to sequence stratigraphy, but I must admit, I don’t understand that article well enough to get that information. The whole earth crust is continuously in motion, and some of the highest mountains contain sediments from the bottom of the sea. What does it tell us about the sea level 500 million years ago if we find sediments from what was 10,000 feet below sea level then 10,000 feet above sea level now? Mary Moor (talk) 02:03, 5 March 2009 (UTC)

That article makes precious little sense to me as well, but it appears to be mostly about methods for oil prospecting. I'm also not an expert (sad but true, I'm related to a sad number of them and they would all laugh at my pathetic attempt at a response), but rocks that are under water for extended periods are different than those that are above water. Fossils are the obvious difference (very few cnidarians on land, for example), but there are chemical and physical features as well. If you have a network of points, you can create a map from dot to dot and from known rates of continental drift, and you can give an estimate of where the land was and where the sea was. Just a guess. SDY (talk) 03:25, 5 March 2009 (UTC)

True - but the OP's question is an entirely valid one - we know that over geological timescales, mountain ranges may be formed by upward buckling of the crust as two plates are forced together (kinda like you can create an upwards ruck in a rug by sliding one end of it towards the other). So just because you find fossils 10,000 feet up a mountain - even if they were fossils of horseshoe crabs or something that could only have formed at close to sea level - that doesn't prove that the ocean was once 10,000 feet deeper than it is now. The problem here is that you should be asking: "Sea level was then several hundred feet above what it is now...relative to what??" You can't just put a mark on the side of a mountain where the sea level was then - and take a tape measure and measure down to where sea level is now - because the mountain itself has moved up or down in the meantime. The only MEANINGFUL measure would be if you could say that "The radius of the earth measured to the surface of the ocean was several hundred feet greater than it is now"...but I very much doubt that's what's being measured here. So I don't know that this measurement is terribly meaningful when you are comparing ocean levels over geological timescales. BUT when we say that global warming might raise ocean levels by 7 meters (or whatever the current estimate is) - we're talking about this happening on timescales of perhaps just 50 years - and the continents, mountains and everything else won't have moved noticiably over that amount of time. So this measure of sea level rise is entirely meaningful...it tells us how many major cities - and even entire nations will vanish beneath the waves. SteveBaker (talk) 04:52, 5 March 2009 (UTC)

I wasn't clear. Something can be 10,000 feet up or down because the plates and rocks that make up the plates are moving. If you're talking 500mya, the world looks rather different (the map is a little ways down the page). If we assume that the mountains aren't drastically steeper (et cetera), if there is FOO% less dry land then there must be BAR% more ocean therefore there must be BAZ% more water and BAZ% more water equals QUX% feet deeper. SDY (talk) 05:54, 5 March 2009 (UTC)

No - you were perfectly clear - but I don't see how you can make that equation without also knowing things like how the continents are depressed by the weight of the oceans on top of them (a not inconsiderable matter) - and also the extent of water locked up in the ice caps. I think these claims from so far in the past would be tough to substantiate. SteveBaker (talk) 13:52, 5 March 2009 (UTC)

I would say that the answer is that while some of the Earth's surface is uplifted or subsides, this is not true of all of the surface, at least over a time scale of 500 million years. So, the goal would then be to find a geologically stable area and measure historic sea levels there. StuRat (talk) 05:13, 5 March 2009 (UTC)

There is so much assumptions one is making when looking at sea level 500,000,000 years ago relative to today. Lets look at how these interfere with making a meaningful comparison.

1. There was the same amount of water (including ice and atmospheric water) on earth 500m years ago... Possibly not true. Water comes and goes as it evaporates into space (slowly) and also as more water lands on earth on meteorites, and is released from volcanic activity. On human timescales (measured in the thousands or tens of thousands of years) such effects may not be noticable, but on the multi-million-year timescale, there is likely to be marked differences in the total amount of availible water on Earth.
2. There was the same amount of availible space for that water to take up... Also possibly not true. The level of the oceans is due not only to the amount of water in them, but also their shape. Plate tectonics is a complex process, and depending on what the surface of the earth looked like; even assuming we had the same amount of total water to deal with (see above, we may not) then differences in sea level could be due almost entirely to differences in the shape of the surface of the earth; i.e. where the continents were, how low the ocean floors were in comparison to this, yada yada yada.
3. That the level of greenhouse gases is the ONLY controling factor in the Earth's temperature... Also not true. The earth's temperature can also be affected by solar output, by surface albedo, by surface area of the oceans vs. land, by overall volcanic activity, etc. etc. These factors remain relatively constant on the short term, which is why measureing greenhouse gases and their effect on climate, say over the past 10,000 years, may be useful, it isn't going to be terribly useful over 500,000,000 years, since so many other parts of the system are changing that we can't necessarily say "The temperature the earth was 500,000,000 years ago should be the same as it is today solely because the greenhouse gases are at comparible levels"...

Throw all of this stuff in, and even if we COULD actually tell what the greenhouse gas levels and the climate of earth was really like to any detail (and I am not sure we can); it still doesn't mean we can make meaningful statements about sea level based on those statements. --Jayron32.talk.contribs 06:14, 5 March 2009 (UTC)

The existence of one REALLY deep/wide ocean trench at one period in time - and it closing up or filling in some other period in time would erase any hope of appealing to any idea of the total volume of water remaining constant - and therefore the ratio of dry land to ocean surface giving you this answer. If you don't know how deep the ocean went below (or above) present day levels - you can't use the constant volume argument to say very much about overall levels. But unless you're talking about knowing the average radius of the earth measured at "sea level" half a billion years ago - to a rather impressive precision of a couple of hundred feet...you can't make this kind of statement in any meaningful way - no matter what fossil or geological evidence you have. SteveBaker (talk) 13:52, 5 March 2009 (UTC)

Global sea levels changing by hundreds of feet is not very precise at all, we're talking a couple percent change or so in average ocean depth (current average is about 10k ft/3km). Not a huge change, but not impossible precision either. SDY (talk) 16:14, 5 March 2009 (UTC)

It's much easier to find out if the sea-level was LOWER than present levels, because the evidence will exist in sedimentary rocks. But, it's complicated - the current height of the shoreline in the rock layer is not necessarily the original height of the water, because on geological timescales, rocks don't stay in the same place. The crust sort of flows and moves, and float up or down, convecting like a very very slow fluid, and occasionally collide catastrophically. Geologists can estimate how fast a vertical upwelling occurs by a number of techniques, ranging from physics-based modeling of material densities, to observations of broken layers and index fossils.

Old shore-lines and rivers still exist in geological strata and are often CLEARLY visible. In some cases, they can be exposed by erosion, like the amazing canyons carved through the American west. We can also find old geological strata by digging (impractical but possible), or by subsurface imaging. This excerpt, from Geophysical Estimation by Example, shows a marine sounding sonar used to survey the Sea of Galilee, and a bit of signal processing theory to help view what's happening: "The output of the roughening operator is an image, a filtered version of the depth, a filtered version of something real. Such filtering can enhance the appearance of interesting features. For example, scanning the shoreline of the roughened image (after missing data was filled), we see several ancient shorelines, now submerged." Nimur (talk) 15:46, 5 March 2009 (UTC)

At any rate, I'm not an expert, I'm just speculating on how it might have been done and I'm probably wrong. Note that the CO2 level was not claimed to be the cause of high sea levels, simply that it was associated with high sea levels. Chicken and egg possibilities abound, as does pure coincidence. I am, however, almost certain that it has nothing to do with sea level compared with radius of the earth, since that's such a tiny percentage (The stupendously deep Mariana trench is ~10k, radius of the earth is ~6,370 km) that I don't see how it could have been meaningfully measured, and the variability in shape of the earth's crust is such that not only is Kansas flatter than a pancake, but so is Mount Everest. Improbable research is your friend. SDY (talk) 15:55, 5 March 2009 (UTC)

In a recent paper (October 2008) Haq & Schutter [22] describe evidence for a major but gradual sea level rise throughout the Cambrian, culminating in the late Ordovician about 450 million years ago, also shown in this diagram [23]. This rise is recorded by marine transgressions across previously non-marine strata in stable cratonic areas (much as suggested by StuRat above). How accurate such estimates are compared to present day values, that's another issue. Note that 500 million years ago is not associated with an unusually high sea level on these estimates, it happens to be about half way through a 100 Ma period of gradual rise. Mikenorton (talk) 16:04, 5 March 2009 (UTC)

To go back to the original question: As far as I know nobody seriously claims that "the last time we had the same level of greenhouse gases was some 500 million years ago". This seems to be a case of Chinese whispers. We have good evidence that CO2 is higher than during the last 800000 years, and we believe it to be higher than during the last 20 million years. Not a short while, but very different from 500 million years. James Hansen's somewhat famous quote is "The last time the world was three degrees warmer than today - which is what we expect later this century - sea levels were 25m higher." Hansen was talking about a period about 3 million years ago. --Stephan Schulz (talk) 16:34, 5 March 2009 (UTC)

Thank you; it was indeed Chinese whispers. I think it originally comes from Field Notes from a Catastrophe, and I would have to get the book to see the actual numbers. But that was only the background for my question. I wanted to know how we even know how high the sea level was many years ago. The beautiful diagram Mikenorton showed us has three very different curves for the sea level, which could indicate that there is so little consensus among scientists as to render it practically useless. But then again, the diagram was funded by the oil industry, which has used precisely this argument of "there's no consensus among scientists" to persuade the last administration to do nothing about climate change. Mary Moor (talk) 17:55, 5 March 2009 (UTC)

Chlorine in tap water

How poisonous is Chlorine in tap water?--Mr.K. (talk) 13:06, 5 March 2009 (UTC)

To you or the bacteria? 76.97.245.5 (talk) 13:58, 5 March 2009 (UTC)

Sufficiently poisonous to kill the things it's supposed to kill, particularly E. coli, which, believe me, is good news for all of us. There isn't enough of it to be harmful to humans, though. -- Captain Disdain (talk) 14:05, 5 March 2009 (UTC)

Some reading material [24] - 76.97.245.5 (talk) 14:34, 5 March 2009 (UTC)

This one's better [25] and also see Risk assessment. To reduce health risks you would do better giving up commuting than water chlorination. Living is detrimental to one's health, but beats the alternative :-)76.97.245.5 (talk) 16:56, 5 March 2009 (UTC)

Interchangeable left and right hand driving

Is there a car where you can interchange the wheel from left to right and back? At least, was any car designed so that this is easier to accomplish?--Mr.K. (talk) 13:12, 5 March 2009 (UTC)

There are a few cars out there that have a center steering wheel - exotic three seaters sports cars and concept cars, typically[26]. The Toyota Alessandro Volta has three seats in the front - and because it's completely drive by wire, any one of the three people can drive! But sadly, it's just another concept car. Of course there are also driving instruction cars fitted with steering wheels and pedals in both front seats...although these days those are very rare and most instructors have just a set of pedals on the passenger side. Many years ago, BMW ran a newspaper ad showing how their cars could be easily switched from left to right hand drive...and later advertised a car with no steering wheel and center console...but alas, both were just an April Fools pranks. [27]

My classic 1963 Mini has a steering wheel and pedals that can be switched sides in perhaps 4 hours with the right tools...but I suspect you're looking for something a lot more convenient than that. SteveBaker (talk) 13:42, 5 March 2009 (UTC)

Yes, 4 hours would be too much. I was thinking about something more convenient for casual drivers in Europe. The strange thing is that the auto industry doesn't offer this extra. Thousands of vehicles cross the Channel everyday and some drivers would be clearly happy of being able to drive on the proper side of the road. --Mr.K. (talk) 16:48, 5 March 2009 (UTC)

Systemic Beta Hemolysis Infection

Is it possible that one can get systemic Beta hemolysis (Beta Strep) infection? I know that some women can get a Beta Strep infection vaginally but it possible that it could spread throughout the body? Also, does anyone know why more research hasn't been done on this? --Emyn ned (talk) 14:19, 5 March 2009 (UTC)

Well, yes, it's possible. Streptococcus agalactiae is an important cause of neonatal sepsis, especially effecting premature babies. Less commonly, it can effect pregnant women or non-pregnant adults. [28] - Nunh-huh 14:24, 5 March 2009 (UTC)

Woman with 3 breasts

Warning: The video linked hereunder is sexually explicit.

The specific link is www.redtube.com/21290 Does the this unusual thoracic development shown in the linked video seem credible or faked?

I remember seeing cases of people having an extra nipple or two that are located under the standard two, and underdeveloped. I presume these are so easily removed surgically that their actual rate of occurrence is unrecorded - or does anyone know about these? Can anyone add any knowledge about the fully formed triplet exhibited by the actress in the video? Is it practical to "build" such a chest by cosmetic surgery? If her triple breasts are a genuine mutation are other internal abnormalities likely, and should all 3 breasts lactate? What can one say about human breast number and evolution? Is there evidence that human mutation is increasing? Cuddlyable3 (talk) 14:38, 5 March 2009 (UTC)

We have an article, Accessory breast, that would be a good place to start. --Tango (talk) 15:13, 5 March 2009 (UTC)

Milk lines extend from the axilla to the groin, both on the left and the right frontal side of the body (see the teats of cats or pigs). It would seem to be anatomically impossible for a mammary gland to develop in the centre. --Cookatoo.ergo.ZooM (talk) 16:53, 5 March 2009 (UTC)

The article I linked to describes cases of extra breasts growing on the feet, so I guess it is possible for them to grow pretty much anywhere. I do think the case shown in the video is rather unlikely, though - the three breasts are very symmetrical and equal in size, which I think would be extremely rare. --Tango (talk) 17:01, 5 March 2009 (UTC)

The only way I can imagine a third breast between the other two is in the case of conjoined twins, in particular, the parapagus type. However, they would likely have other duplicated body parts, as well, such as heads. StuRat (talk) 19:35, 5 March 2009 (UTC)

LC/NE system and the ascending activating systems

Sometimes it is hard to connect information from different sources. In the article on stress, the "LC/NE system" is mentioned. In my textbook on neuropsychology, the authors mention "the four ascending activating systems, classified by the dominant transmitter and their neurons: the cholinergic, noradrenergic, dopaminergic and serotonergic systems". My question: is the LC/NE system the same as the noradrenergic system? And if not, what is the difference? Lova Falk (talk) 17:27, 5 March 2009 (UTC)

This [29] source has: "The principal components of the stress response consist of the hypothalamic-pituitary-adrenal (HPA) system (most commonly known as the HPA axis), the locus coeruleus-norepinephrine (LC-NE) system, and the extrahypothalamic corticotropin releasing hormone (CRH) system." --Cookatoo.ergo.ZooM (talk) 18:04, 5 March 2009 (UTC)

Question on mag fields and EMF

A magnetic field is perpendicular to the plane of a single-turn circular coil. The magnitude of the field is changing, so that an emf of 0.70 V and a current of 3.5 A are induced in the coil. The wire is the re-formed into a single-turn square coil, which is used in the same magnetic field (again perpendicular to the plane of the coil and with a magnitude changing at the same rate). What emf and current are induced in the square coil?

So I have no idea how to get the EMF without the area of the circle which the coil creates. I'm assuming the EMF changes due to the area of the coil. I'm also assuming that if you shape a circular coil into a square the area should be the same anyway... I know that the EMF and the current can give me the resistance of the wire. I got .2 ohms of resistance. With this, if I get the EMF of the square coil, I can get the current (I think). But I don't know how to get the EMF of the square coil. I'm really confused as to how to go about this... 98.221.85.188 (talk) 19:34, 5 March 2009 (UTC)

If you are forming it out of the same wire then the perimeter will be the same, not the area. If you know how to calculate EMF given area (unfortunately, I don't!), then do it in reverse to get the area and perimeter. You should then be able to use that, together with the formulae for area and perimeters of circles and squares to get the answer. --Tango (talk) 19:39, 5 March 2009 (UTC)

The magnetic field is changing... EMF= -(number of turns in coil)*[(change in Mag Flux)/(change in time)]. I know Magnetic flux = (Mag field) * (Area of the coil). The magnetic field is changing though, so I'm not sure how to get the Magnetic flux... 98.221.85.188 (talk) 19:45, 5 March 2009 (UTC)