Wikipedia:Reference desk/Archives/Science/2006 June 28

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Identifying an insect species

Today I saw a flying insect of some kind, bright yellow all over its body (not a single dark spot that I could recall), with bright red eyes. It was about the size of a fly, and this would be in, er, North America. I didn't get a better look than that, though, and I mainly saw it from the anterior end. Anyone know what it could be? –Unint 01:09, 28 June 2006 (UTC)

I thought maybe it could be a whitefly, but only the larvae have white eyes. So I am probably wrong. --Proficient 02:42, 28 June 2006 (UTC)

Yellow Cabs : can they fly ? --DLL 17:56, 28 June 2006 (UTC)

Piaget's Theory of Cognitive Development

What are your views on Piaget's Theory of Cognitive Devopment?

I believe they are wrapped up nicely in the article theory of cognitive development. --Kainaw ^(talk) 01:52, 28 June 2006 (UTC)

The question didn't ask for neutral, verifiable facts; it asked for your views. Personally, I think it's a load of crap, but at least it's a lot better than that nutcase Freud's crazy theories. —Keenan Pepper 02:01, 28 June 2006 (UTC)

Maybe, but when the time comes, I'm totally performing that kind of experiments on my own kids. Melchoir 02:03, 28 June 2006 (UTC)

Why can't my views be a collection of nothing more than neutral, verifiable facts? Can't there be some topic that I'm not obnoxiously opinionated about? --Kainaw ^(talk) 02:26, 28 June 2006 (UTC)

What are your views on whether the Melbourne Demons should arrange to take Jason Akermanis in a trade? How about whether José Ramos Horta or his ex-wife Anna Passoa (no, I'm not making this up, they're both distinct possibilities) should become the interim Prime Minister of Timor Leste? Nothing useful to say about these issues? Well, maybe we have the same problem with your question.

Sorry for the sarcasm, but the personal views of the Wikipedia reference desk dwellers are of little relvance. If you want a relevant survey of expert opinion, go find a group of developmental psychologists and ask them. Otherwise, read our article; it's the best distillation of expert opinion we currently have. --Robert Merkel 02:45, 28 June 2006 (UTC)

But those are easy questions. "Akermanis" looks cool on a jersey, so they should definately take him in a trade. As for Jose and Anna, never trust a politician named Jose. Now, if Anna can sing from her balcony, even better! --Kainaw ^(talk) 02:49, 28 June 2006 (UTC)

Australian Football League jumpers (they're not "jerseys") do not have names on the back. Any other suggestions? --Robert Merkel 02:56, 28 June 2006 (UTC)

East Timor is East Timor in English. Are you starting a campaign to change it, Robert? JackofOz 04:39, 28 June 2006 (UTC)

No names on the "jumpers"? That changes everything. They should dump the yellow-headed freak then. --Kainaw ^(talk) 13:27, 28 June 2006 (UTC)

which school of thought am i closest to?

my philosophy is:

In the beginning there was nothing, over infinite time an impossibility became possible and a certainty. Something was created from nothing. This is the inevitable event. Throughout infinite time and infinite space, endless cycles of the universe our sun was created as was our Earth. The Earth was created by chance, just like the solar system, galaxy and universe. These are all random by products of the aforementioned inevitable event. By coincidence the earth created perfect conditions for our simple organism, which then evolved and here we are.

Nothing matters, because of infinite time and infinite space, we will definitely exist again on the same planet and the same surrounding solar system. We therefore live endless times. No decisions matter because there will always be another opportunity to make them again.

can someone please trundle through this and tell me what i am? I have looked through the wikipedia pages and none of the philosophies seem to fit how i think. Any answers will be much appreciated, and i'm sorry for the long post.--Calcfc 02:37, 28 June 2006 (UTC)

Maybe you are a mixture of several beliefs. It seems so to me, but I may indeed be wrong. --Proficient 02:40, 28 June 2006 (UTC)

thanks for the very quick reply also as a bonus question would anyone agree with my thinking? --Calcfc 02:42, 28 June 2006 (UTC)

Some of that reminds me of existentialism. —Keenan Pepper 03:10, 28 June 2006 (UTC)

Keenan Pepper you make so many posts on this and most of them are helpful. You are a nice person and thank you for your reply.--Calcfc 03:53, 28 June 2006 (UTC)

The Anthropic principle may provide a similar, but slightly alternate, explanation of this coincidence you describe - we are existing now, so it must have happened... Nimur 03:44, 28 June 2006 (UTC)

thanks Nimur, it is similar but my philosophy is slightly different because it is more nihilistic, but the basic idea is there so thank u for ur reply, it was helpful to me. --Calcfc 03:53, 28 June 2006 (UTC)

Partial answer, about cyclicity. See Friedrich Nietzsche, ideas of eternal recurrence, likewise cyclic universe of Hindus, 4 ages, of which we're in the 4th, the Kali Yuga, after which it will start again. They sometimes seem lackidaisical about things mattering. (Note, Hindus have an assortment of docttrines, there is no requirement for uniformity, except acceptance of the Vedas.) --GangofOne 06:04, 28 June 2006 (UTC)

Your philosophy sounds like plain ol' nihilism to me, but you have already identified that. However, I sense some internal contradictions in you position. A true nihilist wouldn't say "sorry" or "thanks" - your actions, like our responses, are entirely random, pointless and without meaning. And a true nihilist wouldn't care whether or not anyone agreed with them. In fact, it is not clear why a true nihilist would even get out of bed in the morning ... Gandalf61 10:44, 28 June 2006 (UTC)

Calcfc, you've posted two quite separate thoughts. This first: The universe arose from nothing, the Earth and life are products of chance, and this occurs cyclically. The second: Nothing matters, no decisions matter, etc. The first is not a philosophy or a school of thought, it is a scientific belief, which is quite different. In this case, most of it is idenitical to the widely-accepted theories of the Big Bang and Evolution, and you've basically made it into the not-widely-accepted Cyclic Universe Theory by saying it repeats itself. The second is a philosophical stance, and is probably closest to nihilism, as others have said. You've made it slightly different because you've said that "nothing mattters because we'll get a chance to do it again." I don't know whether or not this is a named school of thought distinct from nihilism. — Asbestos | Talk (RFC) 17:33, 28 June 2006 (UTC)

Calcfc, your philosophy sounds more like apathy-ism. It cannot be existentialism, as suggested above, since you do not hint of phenomenons. That is, as you describe it, your world follows one course, infinite in duration maybe, but only one course nonetheless. Husserl demonstrated that this is not so: no being, be a table or the whole universe, can be exhausted by experience, not even with infinite ways of experiencing that being. More fundamentally, your world is total, complete, full, and all-encompassing. There is no room for what is missing, that is, the negations (see Being and Nothingness). The ultimate conscequence of your world is that conscious beings cannot exist in it: "Consciousness is a Being that, within itself, is consciousness of the Nothingness of its being." (Sartre).--JLdesAlpins 17:44, 28 June 2006 (UTC)

Image Processing

We want to show a running 3D animation over live video. Pl help me out to find out right solution. I do not want to use ready made packages available with video capture cards. My application is: 1. I want to connect camcoder or colour CCD camera to a personal computer. 2. Frame grabber card or any other external device can be connected to caputer/show live image on computer screen. 3. When the live picture is on the screen, I want to load/call a 3D animation which will run from right to left or left to right on the computer screen. 4. On a single click from mouse or keyboard should store frame of live image and 3D animation(together) on to hard disk of computer. 5. Example: camera is showing live image of Forest, same time I should able to load a 3D animation of a animal from computer hard disk. Now on compter screen one will get a feel that animal is rooming arond in the forest. After clicking frame from live image and animation should get stored on to hard disk. 6. We can do programing in C or VB or any other language suggested. 7. Can you please guide which Frame grabber card and SDK will support for this appication. Thanks Sunil Anaokar; INDIA.

You need to use the program you produced the 3D animation in to output the animation as a video overlay. Then you need to apply the animation to the live video using video editing software. Something like Adobe Premiere, Adobe After Effects, Ulead Media Studio Pro on the PC or Final Cut Pro on the Mac. If you cannot afford or find this software, you could try using the free Windows XP Movie Maker or iMovie but I'm not sure if they can overlay. You will need a IEEE 1394 card in your computer to capture the DV from the camcorder. If your camcorder is not a DV format (such as 8mm, Hi–8, VHS, or S-VHS) you can use any analog video capture card. --Canley 07:34, 28 June 2006 (UTC)

I can tell you that one problem you will run into is the way live video works on many video cards. With your eyes, you see live video on the screen. You do a screen capture and the area of live video shows up as a block box. It is because the operating system only knows that there is a black box there - so that is what it captures. The video card knows that it is supposed to draw live video in the black box. But, to save on time, it doesn't send any info back to the operating system. Put those together and you may end up with your final product being a 3D model superimposed on a black box in your screen capture. If that is the case, you now know why that happened. --Kainaw ^(talk) 14:44, 28 June 2006 (UTC)

What you are trying to do seems extremely complicated and technically difficult. I would personally be wary of actually trying to pull it off, given that you have to ask on the internet how it would work. If it were something within your current project resources, you would probably already have a good idea of how to accomplish it. I don't mean this to be negative, but in my experience if one has absolutely no idea how to accomplish something technically difficult, or even where else to really look for information on the subject, then it is probably not worth trying to do unless you are willing to hire someone who is an expert in the subject. You will end up spending a lot of time and resources just trying to learn the technology you need for the project, probably two to three times as much time and resources as the actually project would need by itself. Just my two cents (from someone who has been involved with a few over-ambitious projects which did not pan out). --Fastfission 17:52, 28 June 2006 (UTC)

Calculating rate of osmosis

How do I calculate the rate of diffusion of distilled water through a semi-pearmeable membrane (potato cylinders)?

• Make up your mind. Your title and question state two different things. Osmosis and diffusion are not the same. Seeing as you're talking about a membrane, take a look at the equations in Osmosis. -- Mgm|^(talk) 12:33, 28 June 2006 (UTC)
  • Isn't osmosis diffusion of water through a semipermiable membrane? Theresa Knott | Taste the Korn 14:23, 28 June 2006 (UTC)

Yes Mgm, even though my title doesn't match my question, you know they are equivalent. The diffusion of water IS osmosis!

• Yes but: Osmosis is the diffusion of a liquid (most often assumed to be water, but it can be any liquid solvent) through a partially-permeable membrane from a region of low solvent potential to a region of high solvent potential. Diffussion normally goes from a high to a low concentration to even them out. - Mgm|^(talk) 08:07, 29 June 2006 (UTC)

• Osmosis is the diffusion of solvent across a semi-permeable barrier from a region of low solute concentration to a region of high solute concentration. Lower concentration of solute molecules means higher concentration of solvent molecules, and vice versa. Solvent molecules do in fact diffuse from a region of high concentration to a region of low concentration in osmosis.--72.78.101.61 03:28, 30 June 2006 (UTC)

Looking for the Right Material

What are the materials that can resist Ammonium Fluoborate solution?

Glass --mboverload@ 12:41, 28 June 2006 (UTC)

Cooking query

Hello; last night I cooked myself some broad beans (shelled). While I was cooking them I noticed the water turning a pale green colour, which became a murky grey once they were cooked. I didn't throw the water out immediately and noticed that over a couple of hours it turned bright red in colour. Why did this happen if there is no red pigment in the beans? What is the chemical process that occured here? Many thanks. --russ 14:56, 28 June 2006 (UTC)

I'm not sure if this answers your question, but try this link [1]. --hello, i'm a member | talk to me! 17:38, 28 June 2006 (UTC)

My guess (and I may be way off here) is oxidation. Like when you leave an apple wedge out for a couple of hours, it will turn from that "white" inner color to a dark brown.

I answered this question 23 days ago... Possibly an Fe(II) Fe(III), porphyrin ligand substitution from green (Mg(II)) (i.e. the porphyrin part of chlorophyll) to red (Fe) (i.e. the Haem part of haemoglobin) and subsequent oxidation... The question is, are the beans rich in Iron?

The answer is yes. The green Fe (II) is oxidised in air, coordinated with the porphyrin, making a bright red solution. --Eh-Steve 21:17, 29 June 2006 (UT)

Oops, sorry - am new to this so didn't check for a previous query. Thanks for the help though. I am tempted to retake my A-level chemistry --russ 20:34, 30 June 2006 (UTC)

SLAX problem

i'm running slax in paralles workstation for win

after i type in the root password i get the text in the root@slax:~#

what do i type (do) --hello, i'm a member | talk to me! 17:06, 28 June 2006 (UTC)

You would type 'startx' to start up a GUI similar to what you are used to with Windows. The SLAX distribution starts the X Window system with the KDE interface. More information is available on the Slax website including a FAQ and user forums.

consuming about 5 to 10 liters of water a day

I have developed a habit of consuming about 5 to 10 liters (or more) of water a day. Can't I just add a lite salt substitute, saccharin and aspartame (the combo removes the metallic taste of saccharin and ends up being a lot sweeter) and make up a homemade drink of my own instead of spending $20 a day on Gatorade?

Here are the serving sizes I have to work with…

Saccharin 1 gram

Aspartame 1 gram

Lite salt 1.2 grams (290 mg sodium & 340 mg potassium)

How many grams of each do I need per liter of water (plus a packet of kool aid – got to have a little flavor plus it has vitamin C)

What is the maximum amount of each per liter? ...IMHO (Talk) 17:43, 28 June 2006 (UTC)

This doesn't answer your question, but it's possible to buy powdered gatorade mix in big cans. It's probably not as cheap as mixing your own ingredients, but it'll be easier, and still cheaper than buying the drink. Melchoir 17:58, 28 June 2006 (UTC)

I'll have to do a new total price comparison for Gatorade powedered Gatorade but if my recollection is correct then it came out to $0.60 to $0.90 per liter whereas a certain store brand of powdered kool type aid with Vitamin C is only $0.10 per 1.9 liters plus $0.02 or less for the electrolytes. ...IMHO (Talk) 09:09, 29 June 2006 (UTC)

See above for a detailed discussion about this. I'm not sure how you are going about this, but I do know that you can pick up electrolyte tablets from your drug store. They are meant to better hydrate people suffering from dehydration. This article might be of use. As for the aspartamte, I don't recommend it. Though it is used in sport drinks like Gatorade and Powerade is small amounts, if you plan on consuming a lot of it, you might want to consider sucralose instead, which is "better" for you, but this has neither been substantially proven nor disproven as of yet. Pure sucrose would be the best to use. --Russoc4 18:01, 28 June 2006 (UTC)

Although I would prefer to use Splenda it still has a heafty price penalty and is cut down to be equal in sweetness to cane sugar. Food grade sucralose can not be purchased from the manufacture except in pallets. Want to form a corporation to manufacture an even lower cost and sweetened kool aid substitute than is available on the market now? You know my email address. ...IMHO (Talk) 09:09, 29 June 2006 (UTC)

What's wrong with plain old water? I drink about as much of the stuff (well, maybe not that much, but at least 5 litres) and I feel no need for extra ingredients. Anyway, in case I didn't convert you, this might also help: Oral_rehydration_therapy#Recipe. :) DirkvdM 19:20, 28 June 2006 (UTC)

Plain Old Water (POW) is like (POT) Plain Old Telephone. Move up to fancy dancy vidio image projection cell phone or forever be unable to find a date. ...IMHO (Talk) 09:09, 29 June 2006 (UTC)

Isn't there a serious ilnness you can get from drinking to much. I knew someone who followed the government campaign on 8 pints a day or more or whatever it was, he always had a bottle with him, and beside the fact he couldn't spend more than half an hour without going to the toilet, he is now in a home and seriously ill. The disease name has hydro in it, but I cant remeber what it was called. The closest I could find on wikipedia was Polydipsia. Philc _T^E_C^I 19:44, 28 June 2006 (UTC)

There's hyperhydration and hyponatremia, but those have pretty immediate symptoms, and clear themselves up once you solve the electrolyte deficit. (Of course, if you don't solve the deficit, you keel over dead.) Drinking a great deal of water may also be a symptom of any of a number of problems, ranging from type 1 or type 2 diabetes to kidney disorders, but drinking water doesn't cause the problems, it's the body's reaction to an existing problem. --Serie 22:40, 28 June 2006 (UTC)

But with both of those, if I am not mistaken (which I might be) once they become noticable, they can rapidly deteriorate to death, within hours. Also, is there an electrolyte deficit, of has it just been diluted to an unsafe low level. And just adding to my original point, drinking 1.8 litres in an hour can lead to water intoxication and possibly death, which you may be at risk of if you are drinking over 10 litres in a waking day, assuming you do not drink evenly of course, but naturally you take a predominant amount of your liquid intake around meals and excercise. Philc _T^E_C^I 23:56, 28 June 2006 (UTC)

I suspect you are thinking that the water must have the proper balance of electrolytes. This would only be true if you didn't eat anything. Anyone with a typical Western diet will get far more salt and sugar in their diet than they need, anyway. If you just want to make the water more palatable, try just adding a few drops of lemon juice. It masks the taste of hard water and chlorine, some of which can also be removed by filtering the water and letting it sit until the chlorine outgasses away. StuRat 01:47, 29 June 2006 (UTC)

Before I go to bed, I drink over 1 litre and sometimes over 1,5 litre in just a few minutes. It hasn't killed me yet. :) DirkvdM 07:27, 29 June 2006 (UTC)

What's going to kill you is tripping over your slippers on the way to the head. I've solved both the daytime sitting-at-the-computer-all-day and the nightime oh-do-I-have-to-get-up-and-go-again problems with pee cups and am seriously considering hooking up my wet & dry vac so I won't have to dump anything more than once a day. ...IMHO (Talk) 09:15, 29 June 2006 (UTC)

When you develop something that works, you might sell it to some spave agency for astronaut suits. Alternatively, you could buy a used suit. Walk around in that. Cool. Might become a trend. :) DirkvdM 10:43, 29 June 2006 (UTC)

Naw I think I'll pass. Someone just told me that if I hit the wrong button or unzipped the wrong fly I could be accidently sucked into outer space. ...IMHO (Talk) 13:04, 29 June 2006 (UTC)

Timeline from death to skeletal

I have searched everywhere, maybe I am using the wrong search terms?

I volunteer for a website that tries to match unidentified Does with the missing.....I can't find anywhere something like a timeline to explain what happens to the body after it is deceased...leading up to skeletal...this would help greatly in my research and matching up does with unidentifieds.

I also believe that a lot things could alter this timeline, that info would be helpful too, like weather, climate, etc...

Thank you in advance and kindest regards, Christine

I don't know of a timeline, but Decomposition has some background info. Perhaps the books listed at the end of the article will be more helpful? Melchoir 18:31, 28 June 2006 (UTC)

Thank you Melchoir, that is exactly what I was looking for! The info in that article is great and there are many links, references, books, etc that will take me along on my research. Thanks again! And thank you everyone who works on the website...it is truly AMAZING!

• The investigators at the Body Farm at the University of Tennessee may be able to provide you with further resources. - Mgm|^(talk) 08:02, 29 June 2006 (UTC)

would putting a powerful magnet on your head alter your thoughts?

If you put a magnet on your head do electrons rush over to that area of the brain and stimulate it? Could you set up a current? Would it alter thoughts?

I degaussed my head. Does that count? --Kainaw ^(talk) 19:29, 28 June 2006 (UTC)

Since MRIs - some of the most ******-******** insanely powerful magnets on earth - are used to see how the brain responds to different stimuli, no. --mboverload@ 19:40, 28 June 2006 (UTC)

Actually, magnetic stimulation may affect the firing of synapses and things like that, but not in the way you are talking about. A number of studies have used transcranial magnetic stimulation as a way of trying to see if quick little electric bursts get people do make different decisions (i.e. blasting certain regions of the motor cortext to see if you end up, in an ambiguous situation, preferring your right hand over your left). I have no idea what the results of the research are, though, but I know such tests have taken place (I volunteered for one years ago—it was awful. Your brain doesn't feel anything from TMS but all of the skin in between the top of your head and your brain certainly does, and it feels like getting a heavy tap to the head). --Fastfission 19:55, 28 June 2006 (UTC)

Somewhere on the web (I can't find it now) there is a "How" to build your own TMS device. Its basically some supermagnets on the a pole that spins around so the magnets come close to your head. I've forgotten results but heard then it was only a few seconds and most of the time where but okay when memory comes back to me. If I where was not will come back to me. ...IMHO (Talk) 20:48, 28 June 2006 (UTC)

Everytime I walk into the NMR room, I get the uncontrolable urge to sing "The Michigan Rag", it could very well be the magnets doing it--152.163.100.74 21:25, 28 June 2006 (UTC)

Electrons are not drawn to magnets. Instead, moving electrons in a magnetic field experience a lateral (sideways) force that causes their paths to curve—this is how CRTs work. The Hall effect is another example of this. And, mboverload is right that the magnet you press against your head is magnitudes less powerful than the magnetic field generated by the super-conducting magnets in an MRI and as no effect is seen there, there will be effect by pressing a rare-earth magnet to your head. —Bradley 21:47, 28 June 2006 (UTC)

If you scroll waaaaaay down in this article, you'll find a quick summary of the effects of intense static and changing magnetic fields. Briefly, any static field that you're likely to be able to create with a portable device isn't going to do anything. With rapidly changing fields, you can do some rather funky things. At a minimum rate of change of two to five telsa per second (T/s) you can generate magnetic phosphenes by directly stimulating the optic nerve. Peripheral nerve stimulation can occur at 60 T/s, stimulation of the respiratory system at 900 T/s, and cardiac stimulation at 3600 T/s. TenOfAllTrades(talk) 21:56, 28 June 2006 (UTC)

You can make your own TMS unit, or perhaps use a simpler brute force method using a twist drill and a large neodymium magnet. I haven't dared to try either of these myself. --Wjbeaty 01:43, 29 June 2006 (UTC)

I wonder if any terrorists have experimented with such a device as the SHAKTI to render Brain fingerprinting usless or invalid through very thin conductors surgically implanted under their scalps? ...IMHO (Talk) 09:40, 29 June 2006 (UTC)

Of course putting a powerful magnet on your head would alter your thoughts. You would be continually aware of its presence and others would be constantly asking you why you have a magnet on your head. Simple question, simple answer. alteripse 09:47, 29 June 2006 (UTC)

(edit conflict) Darn, alteripse beat me to it. I was going to say: I suspect a powerful magnet could definitely alter your thoughts. Just prior to putting it on your head, you would likely be thinking, "I am about to put a powerful magnet on my head." Just after doing so, you'll likely be thinking, "Why in the world do I have a powerful magnet on my head?" This transition from stating the obvious to rhetorical questions and talking to yourself is obviously a side effect of the magnetic field. EWS23 (Leave me a message!) 09:51, 29 June 2006 (UTC)

I've heard that (according to the Red Green Show) you can go down to the electical supply store and buy one of those hundred foot coils of house wiring and a male and female socket for each end a one of those light bulb to socket adapters plus a light bulb and some electical tape and then come home and take the wire out of the box (oh by the way don't do this if you have been drinking or snorting crack) and then secure the coil so it doesn't uncoil and then fix up the ends of the house wiring with the male and female sockets and then plug in the socket adapter and screw in the light bulb and then test it to make sure it won't shock anything and then put your head in the coil to melt the snow off of your head after a shobbgan ride in the Wintertime or to dry your hair in the summer after a swim. Oh yes did I mention you have to plug in the thing? I've never tried I don't remeber ever tryin' this unless it was that time when the house burn't down. Anyway you are still on your own. ...IMHO (Talk) 12:29, 29 June 2006 (UTC)

At least one researcher believes that magnetic fields can affect your thoughts. See the article on Michael Persinger for more information. Matt Deres 21:18, 8 July 2006 (UTC)

My Physics teacher did once mention that when he was a student he and a few others had access to a very large and powerful ring magnet. By putting your head inside this magnet, and then rotating your head, hallucinogenic effects can apparantly experienced. This was apparantly due to inducing a current in your brain, which played havok with it for some time...the teacher described it as "typical of the wacky things you get up to when you're a student". Not to be recommended though, I don't want to think about the long term effects of such an act. ('Don't try this at home folks!'). Chrisd87 21:59, 10 July 2006 (UTC)

Snapping neck

Having just watched The Descent (and jibbering somewhat), I was wondering: is it actually possible for a human with their bare hands to twist someone else's head hard enough to break their neck and kill them? It was done several times in the film, and I have seen it done on fantasy TV series (well, specifically, Buffy the Vampire Slayer), but was wondering if it was actually possible. Note: I'm not looking for original research here! — QuantumEleven 20:42, 28 June 2006 (UTC)

• so, does that mean you don't want us to go out and try it for ourselves? darn--152.163.100.74 21:21, 28 June 2006 (UTC)

Probably is, it would just be a question of getting the twist right. It wouldn't be easy though, a more convinient method is to break the collarbone (takes around 4-8 lbs of pressure), then stamp down on the neck while the victime is writhing in pain. (This was not original research, just memories of theatrical fighting techniques). Emmett5 21:40, 28 June 2006 (UTC)

This is relying on fiction, but I remember seeing a film about Nancy Wake where Special Operations Executive training on how to break people's necks by hand was depicted. Wake did indeed kill a German sentry with her bare hands on one occasion, but I don't know whether she actually used the technique depicted. --Robert Merkel 01:17, 29 June 2006 (UTC)

Based on the total lack of murders done this way, I would say it must be extremely difficult or impossible. StuRat 01:36, 29 June 2006 (UTC)

The problem is that the method shown on TV will not work. If you put one hand on top of a person's head, grab their chin, and whip their head around, they will just turn. The strength of the spine is far more than the sitting inertia of the shoulders. The proper way to do it is to keep the shoulders from spinning. So, you need to get the person chest down on the ground, sit on their back, turn their head so they are facing to your right (make all 'rights' into 'lefts' if you are left handed), place your left hand on the side of the head just above the right ear, grab the mouth and left cheekbone firmly, and finally pull with all your strength. From there it is just physics. If you don't have enough weight on their back, they will roll over. If you don't push down above the ear, the head will just lift up. If you do it all correctly, the twisting motion will sever the spine due to the fact that it is stronger against bending motions than twisting ones. --Kainaw ^(talk) 02:14, 29 June 2006 (UTC)

Probably a good thing that there's an ineffective yet dramatic looking method, since you know there will be someone out there who just has to try something he sees on TV.... Peter Grey 17:37, 29 June 2006 (UTC)

Wouldn't just a choke hold be better? I mean you have to be strong enough to get the person on the ground, etc. with the neck snapping technique whereas with the choke hold you can probably do it even if you are a child. ...IMHO (Talk) 13:31, 29 June 2006 (UTC)

Yes. Neck snapping is a difficult and useless technique. In the Marines we weren't trained on choke holds either. The standard training was to hyperflex the elbow, pull the arm out of socket, and then force the guy to the ground. If that doesn't work, grab his balls and pull upward with all your strength. That usually gets a guy to the ground. Yes - it is dirty fighting, but the rule was that if a fight takes longer than 3 seconds then you don't know what you are doing. --Kainaw ^(talk) 14:44, 29 June 2006 (UTC)

I don't know much about specific techniques, but my dad's a martial arts teacher (Wing Chun), and has occasionally mentioned things that, given the force a strong man can put into something, are guaranteed to at least damage the spine or, failing that, hurt like hell. What I'm thinking of right now of one that involves holding his arm and jamming your hand up under his chin. Black Carrot 15:45, 29 June 2006 (UTC)

Correct. The method taught in the marines is to grab the wrist, twist the person down to their knees, and then stomp into the armpit while pulling on the wrist to separate the shoulder socket. --Kainaw ^(talk) 16:57, 29 June 2006 (UTC)

Or better yet, just take a knife and slit the poor bastard's throat or stab him in the lungs through the ribs, instead of foolishly trying to break his neck with your bare hands or get him in some Judo armlock/armbar. 69.138.62.148 05:48, 30 June 2006 (UTC)

Better yet?? Why can't we all just get along?? --Username132 (talk) 23:10, 30 June 2006 (UTC)

Why can a black hole not explode

If a Black hole is held together by the infinate mass it contains wich is why its escape velocity is faster than the speed of light so no light escapses. Surely if eventually one sucked in enough matter would the pressure it exerts outwards not be greater than the gravitational force therefore making it expand so exploding. I think i have seen an example of this in stars and am wondering why the same does not happen with black holes.

if eventually one sucked in enough matter would the pressure it exerts outwards not be greater than the gravitational force - once a star passes the chandrasekhar limit, the outward pressure (a combination of the neutron degeneracy pressure and the electron degeneracy pressure) of the matter can no longer overcome gravity and it collapes into a black hole. Raul654 22:12, 28 June 2006 (UTC)

Also, black holes do not have infinite mass. Melchoir 22:48, 28 June 2006 (UTC)

True, but they may have an infinite density at the singularity. StuRat 01:30, 29 June 2006 (UTC)

Due to the curvature of spacetime, even infinite pressure/force can't hold things from falling to the center of a black hole. Interestingly, though, black holes are believed to slowly radiate, and the process gets much faster as they become very small—so in a sense little black holes do explode. See Hawking radiation. -- SCZenz 22:51, 28 June 2006 (UTC)

Like Beakman once said: an explosion is something that get really big, really fast, so black holes do NOT explode. They may, let's say, "waste away" over a very long period of time. --Quase 03:25, 29 June 2006 (UTC)

Let me clarify what I wrote. The rate of Hawking radiation "gets much faster as they become very small," more specifically the rate of radiation goes as some inverse power of the surface area. Thus when the black hole is "little" its rate of radiation has become enormous and it does effectively explode. You can see, for example, the introduction to Black Holes and Time Warps by Kip Thorne. -- SCZenz 09:10, 29 June 2006 (UTC)

StuRat+Melchior= A black hole may have infinite density, so only an infinite mass could cause it any trouble (I always have difficulty weighing infinities against each other, but luckily that doesn't come in here because.... ). But they have no infinite mass. So no problem, they can hold it all without any urge to throw up. Right? DirkvdM 07:41, 29 June 2006 (UTC)

Well, it's true that there aren't any infinite masses, but even if there were, I don't see why a black hole couldn't contain them. That is, unless you consider that an infinite mass outside a black hole would also have an infinite volume and thus take an infinite time to be consumed by the hole. StuRat 18:27, 29 June 2006 (UTC)

chemistry

How could you separate barium sulfate from ammonium schloride? (filtration, decantation, extraction, sublimation?)

Barium sulfate is a solid precipitate in solution. Ammonium chloride in solution breaks up. Decant the solution of ammonium chloride, or filter out the barium sulfate. do....your....own....homework..? ~Peter

I suspect we send a mixed message when we tell him to do his own homework—then go ahead and do it for him anyway.... TenOfAllTrades(talk) 01:06, 29 June 2006 (UTC)

these kids've gotta learn the hard way like I did that BaSO4 just ain't gonna dissociate! ~Peter

I don't think I ever learned that. Should I go back to being a kid then? DirkvdM 07:42, 29 June 2006 (UTC)

Rediscovering your inner child can be fun, Dirk. JackofOz 03:12, 30 June 2006 (UTC)