Wikipedia:Reference desk/Archives/Science/2007 March 2

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[edit] March 2

[edit] Colours relation to wavelenght

Can I ask another question here? Daniel Dennett mentions that it is studied that each colour does not match with a certain wavelenghts, and so colour does not correlate with wavelenghts, unlike usually people thinks. He says also that certain colour can be produced with very different kinds of light with different wavelenghts. This is against what I have been told on school. Can you explain me how light creates colours according to this what Dennett said. Majji 00:28, 2 March 2007 (UTC)

One important distinction to remember is that between the color(s) of light itself (its wavelength or combination of wavelengths) and the way one perceives that light (its effect on the eye or other receptors). The articles on color and color vision are useful. DMacks 00:39, 2 March 2007 (UTC)
I answered a very similar question a few weeks ago on the Miscellaneous section of the reference desk. What with all the mess with archives recently, I can't figure out how to link to it - so I'll just do a quick copy/paste:
There are certainly things that our senses fool us about. We know for absolute certainty that we don't see "reality". One of my favorite examples is the colour "Yellow". Our eyes only have receptors that are sensitive to colours near red, green and blue. Since pure yellow (such as you might get from a Sodium street lamp) is somewhere between red and green on the spectrum, our red and green receptors are both weakly stimulated and our brains have learned that when this happens, we should label the colour "Yellow" - however, if you mix red and green light (for example on that computer screen you are looking at right now which only has red, green and blue light emitters...no yellow), that also stimulates both red and green sensors in our eyes and we say "Yellow" - despite the fact that there is no yellow light anywhere around. We teach ourselves that (when mixing light) "Red + Green = Yellow" - this is nonsense. Red + Green equals just that - Red plus green. It only looks yellow because our eyes respond to red+green in the same way they do to true yellow light.
This leads us to some interesting observations. There are animals out there (notably some species of shrimp and (oddly) the Goldfish) who have many more colour receptors than we do (some shrimp have twelve, the goldfish has seven, we humans just three). Such a creatures have a sensor that directly percieves true yellow light - so for them, the colour that is a mixture of red and green as seen on a TV screen or computer monitor would not look yellow - but some other colour that we can't even begin to imagine. So there are colours out there - perfectly normal colours within the visible spectrum - that we can't see correctly.
We could get a sense of how dramatic a difference this might be by imagining someone who had a form of colour-blindness that produced no green sensitivity. They would see pure green light as something that would very weakly stimulate their red and blue sensors - which would appear to them to be a darkish shade of purple...but to us "normal" people, it's pure green. So go back to thinking about that goldfish: the yellow on our computer screens and the yellow in a sodium street lamp are as different to them as green and purple are to us! It's exactly like the whole human race were colourblind...compared to the humble goldfish.
If you think about this in terms of sound instead of light, it's as if we heard the note "C" either when someone played a "C" or when someone played a chord containing "B" and "D". Our eyes can't tell the difference between "Yellow" and a "Red/Green" chord.
If you want to get freakier still - there is an interesting genetic condition called tetrachromaticity which can occur very rarely in humans (I believe there is just one known, proven case - an elderly lady in England who was tracked down using genetic testing). Tetrachromats have two different sensors in the green area of the spectrum that work at slightly different frequencies - so the person has FOUR types of colour sensors instead of the usual three. This lady sees colours that (as far as we know) nobody else in the world can see! Many tests have convinced researchers that she can indeed do this and the genetic disposition of colourblindness and other genetic markers in her history explain perfectly how this rare situation came about. Interestingly, she works in a shop selling knitting yarns and she has remarked on how her sensitivity to colour mismatches is significantly better than anyone else she's ever met.
SteveBaker 02:24, 2 March 2007 (UTC)
Tetrachromacy migh benefit from that info, it it can be reliably sourced. Rockpocket 02:38, 2 March 2007 (UTC)
Our perceptions do not map monotonically to physical stimuli. "Color" exists in the eye and brain, not in the physical stimuli. If we stare at a red object for half a minute, then look at the complementary colour, a shade of blue-green, we will perceive a supersaturated blue-green not found in nature, and contrariwise. The Worldbook Encyclopedia of the 1960's had an example of a picture of Abraham Lincoln printed in the complements of natural colors. If you stared at it for half a minute, the color See the American Flag afterimage at [1] If we put a hand in cold water, then put it in warm water, it will feel scalding hot when otherwise it would just feel warm. I heard of a man who was color blind in one eye and had normal color vision in the other. Colors clearly do not correspond linearly and monotinically to wavelengths, since in the CIE colorspace a given color sensation in the interior of the space can be identically created by an infinite number of combinations of two or more discrete wavelengths. This is clearly borne out by a century of color matching experiments. The sensation of white can be created by the admixture of an infinite number of combinations of complementary colors. Freaky: If you look at your image in a mirror in a perfectly dark room and flash a photoflash, a stationary afterimage which looks perfectly natural of yourself is seen, but if you move, the image remains a stationary ghostlike image. Freakier: If you stare at a rotating spiral for half a minute, the movement detection cells in your brain become fatigued. If you then look at another person, their face will appear to flow inward or outward depending on which way the spiral was turning. There is a double spiral demo at the following site, but do not look at it if you are troubled by vertigo or other problems from visual stimuli. [2] Edison 06:15, 2 March 2007 (UTC)
I don't know of any good colour pictures of Lincoln to demonstrate this - so I'll use another of our erstwhile leaders. So stare fixedly at the center of the picture for about 30 seconds - then look at the blank part of the screen next to it. Tadaaaa!

SteveBaker 19:08, 2 March 2007 (UTC)
Image:Wales invert.jpg

[edit] Seeing light while pressing eye

People usually thinks that to see there must be photons. But if you are in totally dark room with no photons there, and you push your eyes outer side, you see round light at inner side of field of vision. This is not hallucination, because hallucinations are created by brain. It is rather experience of something real, perception of pressure on your eye. Somehow vision cells acts like they would receive photons, even though there are none. What it is this experience called then? Is this an instance where you can see touch instead of feeling it? Majji 00:37, 2 March 2007 (UTC)

Sounds like you're seeing phosphenes. DMacks 00:41, 2 March 2007 (UTC)
Yes, phosphenes caused my mechanical stimulation of the retina. It's safe to do. [Mαc Δαvιs] X (How's my driving?) ❖ 03:09, 2 March 2007 (UTC)
I'm not sure it is universally safe. Some people at risk for detached retinas should probably avoid such experiments. Note that if the pressure is toward the bottom of the eyeball, the phosphene is seen at the top, since the retina receives an upside down and backwards version of the world due to the optics of lenses. For me, looking to the extreme left has always caused phosphenes as well as pulsed ringing in the ears, implying involvement of the auditory nerve. No such effect from looking to the extreme right, We are all unique beings. Edison 06:06, 2 March 2007 (UTC)

[edit] straightening light

is there a way to perfectly straighten beams of light using lenses or such ?

the point woult be to straiten the focal point of a parabolic mirror capturing sun light to achieve transmition of all the light to another point

would this be possible? —The preceding unsigned comment was added by 216.113.96.83 (talk) 00:39, 2 March 2007 (UTC).

Perhaps a collimating lens? The question is a bit confusing though...all beams of light are essentially straight to a first approximation, all that changes is the direction they go. So one just needs to design a mirror or lens shape such that each beam coming from "whatever source you're using" gets reflected and/or refracted such that it goes off in "whatever direction you want". DMacks 00:47, 2 March 2007 (UTC)

what experiments ave been done on sun light collimating and what documentation could i see ?(so far i avent found any)

What you are really asking is whether light can be preventing from dispersing as divergent rays. The answer is YES - and you're going to kick yourself when I tell you that it's called a "Laser". Lasers can transmit light over vast distances without losing energy. But you can't make one with a simple mirror because there is no way to make a mirror accurate enough. You also need light all of one frequency to avoid other ikky problems. SteveBaker 01:54, 2 March 2007 (UTC)
Lasers are not perfect rays, though. They have some divergence. 171.64.91.48 04:03, 2 March 2007 (UTC)
Yep they do diverge a little. But they bounced one off a reflector that one of the Apollo crews left on the moon. From a lab on the surface of the earth - out to the moon and back - about 800,000 km, and (if I recall correctly) the beam only diverged to a diameter of a meter or so. Some of that would have to have been due to imperfections in the reflector - so the laser was probably quite a bit better than that. SteveBaker 04:24, 2 March 2007 (UTC)

I think what you are asking is a very common thing. Fiber optics is probably the largest application both for coherent and non-coherent light transfer. It is not collimated in the strictest sense but loss is limited. The article mentions using fiber to transfer sunlight from outside buildings to inside. --Tbeatty 04:57, 2 March 2007 (UTC)

[edit] Flipping turtles/tortoises

Has any predator (besides man) ever grasped the concept of working cooperatively to flip a turtle or tortoise much heavier than any one individual onto its back in order to make a kill? --Kurt Shaped Box 00:55, 2 March 2007 (UTC)

Unless you can break the shell (to get at the yummy turtle meat) it doesn't much matter if you can flip it. I don't see any way reproducible way that a group of animals could cooperatively crack the shell. However, I have heard that single eagles will pick up moderately sized turtles and drop them from altitude in order to break them open. Dragons flight 06:13, 2 March 2007 (UTC)
Hahahah I have an image of tens of meerkats working together to flip a galápagos tortoise. Capubadger 08:15, 2 March 2007 (UTC)
Care to upload it to imageshack[3] or Wikipedia/The Commons? [Mαc Δαvιs] X (How's my driving?) ❖ 18:21, 2 March 2007 (UTC)
This is a thinly veiled seagull question. We should not indulge it any further. Nimur 19:24, 2 March 2007 (UTC)

[edit] Drinking water and losing weight

Does drinking a lot of water cause you to lose weight? PitchBlack 01:03, 2 March 2007 (UTC)

Probably not - but it could very easily kill you. See Water intoxication. If you drink too much water, it can dilute your blood dangerously and kill you. There have been many cases of this happening - so DON'T DO IT! SteveBaker 01:50, 2 March 2007 (UTC)
You will not lose much. It takes one big C Calorie to heat 1 litre of water one degree. SO say if you drank 10 litres of zero degree water, you would only use about 37 * 10 Calories - 370, which is not a huge amount. You could turn down the heat a few degrees to get the same effect. GB 01:56, 2 March 2007 (UTC)
The idea, as I understand it, is that if you drink a fair amount of water, especially before meals, you will get full on it and wont have to eat as much to be sated. Thus, you lose weight. 70.108.199.130 02:10, 2 March 2007 (UTC)
SteveBaker may have over-reacted. It takes quite a bit of water to start feeling the effects of water intoxication (it states how many liters in the article). Drinking water, per conservation of mass, will increase your mass the more you drink it. The ways your body gets rid of it are primarily renal, solid waste, sweat, and exhale. [Mαc Δαvιs] X (How's my driving?) ❖ 03:08, 2 March 2007 (UTC)
According to the article: "Consuming as little as 1.8 litres of water (0.48 gal) in a single sitting may prove fatal for a person adhering to a low-sodium diet, or 3 litres (0.79 gallons) for a person on a normal diet". The questioner is talking about losing weight - and might well be doing some kind of low-sodium diet (either deliberately or inadvertantly) - and I could easily see that a mere 1.8 liters might well fall into their category of "drinking a lot of water" - furthermore - 1.8L is the fatal dose...I would imagine that severe (albeit non-fatal) things could happen with lesser quantities. I'd really like to avoid this reference desk being the first to kill one of it's questioners! SteveBaker 04:13, 2 March 2007 (UTC)
A lot lower than I expected. I'm not sure there are a lot of people that would drink half a gallon or 80% of a gallon in one sitting, but it seems reasonable to say it could happen. [Mαc Δαvιs] X (How's my driving?) ❖ 18:20, 2 March 2007 (UTC)
1.8 liters is only something like 7 eight ounce (250ml) bottles - there are plenty of people who would drink a six pack of beer in one sitting - why not water? If you look at the bottom of the water intoxication article you'll see a list of people who have died from this condition. There was an especially tragic one just a few weeks ago here in the USA where a lady was participating in a radio show contest "Hold your wee for your Wii" where they were offering to give away a Wii game console to the contestant who drank the most water without going to the bathroom. She was the mother of three small boys and did it to try to do something nice for them...stoopid, stoopid, stoopid. People have no clue how dangerous this can be! SteveBaker 18:52, 2 March 2007 (UTC)

How is it then that one (especially me) drink obscene amounts of beer during a night of binge drinking and only wake up with a hangover?

Because beer is nnot water. -Nunh-huh 03:44, 3 March 2007 (UTC)
Yep - exactly. Alcohol is a diuretic - it makes you pee - also, it takes quite a bit of water to metabolise alcohol - so the alcohol "consumes" some of the water and makes you get rid of the rest a lot sooner. In fact, the one utterly solid way to minimise the effects of a hangover is to drink two glasses of water before you go to bed because dehydration is the major cause of the symptoms of a hangover! My main problem with that idea is that if I get too drunk, I forget to drink the water! The fix for this (which I have learned after many years of experience) is to place two full glasses of water beside my bed before I go out drinking - this helps my memory as I come back! SteveBaker 16:31, 3 March 2007 (UTC)

[edit] Oscillation

Is there a name for something (if something exists) that oscillates between being matter and energy according the Einstein’s equation such as the oscillation of energy between electrostatic and electromagnetic fields and how fast would this oscillation be? 71.100.171.80 01:34, 2 March 2007 (UTC)

Most matter is stable and does not convert into energy. Unstable matter such as the neutral pion can decay into electromagentic gamma rays, but then it does not oscillate and reform pions, as the chance of the two photons colliding is very low in the present universe. In the first microseconds after the big bang the background radiation may have been high enough to recreate matter, but it would be formed chaotically, not oscillating. However you may be thinking of the wave nature of matter, matter wave. GB 02:01, 2 March 2007 (UTC)

No, I'm thinking of oscillation or perhaps a stable form of energy we only call matter in the form of various atomic particles which may actually be a self-captured wave of energy (oscillating electromagnetic and electrostatic fields) where the path of propogation through space is merely diverted from straight to a circular path by the electromagnetic phase being 180 degrees out of phase with the electrostatic phase such that they become "locked" together at certain diameters as what we call a "particle" of matter. Something troubles me about not being able to describe matter as a "captured" form (wave) of energy and to describe the mechanism of its capture if Einstein's equation is true. (Which I don't doubt it is.) 71.100.171.80 02:29, 2 March 2007 (UTC)
No - nothing gets turned around in a circle to make a nice spherical particle - it's not like that at all. The wave that corresponds to a particle is a Wave packet. SteveBaker 04:06, 2 March 2007 (UTC)
Take a look at virtual particle. Particle/anti-particle pairs appear for short periods, then annihilate each other. These virtual interactions are important in analysis of particle interactions using Feynmann diagrams. Gandalf61 10:41, 2 March 2007 (UTC)
Yes, as for the concept of oscillation that came to mind virtual particles are essentially only different in that they represent a single rather than a cyclic existance, if my understanding is correct. As for describing particles in a more intuitive way the term that pops into mind to describe this concept of matter (particles) being merely variable duration spheres of energy formed by the interaction of energy's counterparts of electromagnetic and electromagnetic fields from their interaction at a frequency that jumps to near infinity resulting in spherical particle formation: a particle thus being described as perhaps as virtual energy; if you will. 71.100.171.80 12:21, 2 March 2007 (UTC)

[edit] Hair Growth Question

This is pretty plebian for the fairly technical Science desk, but I don't know where better to ask. I'm a highschooler who goes to a school with a no-facial-hair policy. This hasn't been much of a problem for me because all I've got in the way of facial hair is a slow-growing faint mustache, which is easy enough to shave, and a little hair in what might be called the goatee area (chinnish) that, if left unhindered, would probably grow out into a bizarre and conspicuous chin patch. Nothing really between the sideburns and goatee. I figure that'll come in in a year or two. The thing is, I just tried out, and have been given reason to believe I might have been accepted, for a school play where the characters are supposed to be sporting Miami-Vice style two-day growth. The question was whether anti-balding products, such as Rogaine etc, might be an ok idea if I wanted to stimulate hair growth around the regular beard area? My face isn't completely hairless there, just not enough to grow a legit beard, and I'm guessing that if I did this play half a year to a year from now, this wouldn't be a problem at all. So is that a good or bad idea? Any other suggestions?

Probably a bad idea, as Minoxidil should only be used on the scalp (see more details here) and it would take many months to show any effect anyway. There is little one can do to increase facial hair (short of injecting hormones). I would suggest you use makeup to generate stubble for your role. Rockpocket 02:32, 2 March 2007 (UTC)
Hope you don't feel embarrassed! I could imagine it, but, eh, you should be fine. [Mαc Δαvιs] X (How's my driving?) ❖ 03:03, 2 March 2007 (UTC)
I agree - makeup for stage needs to be somewhat exaggerated anyway - so even a real stubble might not be enough to look good. Also, unless you have very dark hair, your growth could be fair-coloured anyway. But it's stupid to mess with treatments like that unless you have to - there are health risks and side-effects with these things. Just so you think carefully about that - look at the list of side-effects for Minoxidil:
  • acne on the area where it is being used as a topical solution
Yeah - that's gonna look real good for Miami Vice!
  • headaches and/or lightheadedness
  • very low blood pressure
  • irregular or fast heart beat
  • blurred vision
  • chest pain
I don't think it's worth the risk just for a play!
SteveBaker 03:49, 2 March 2007 (UTC)
Googling theatrical makeup "beard stubble" led to a sponge for applying makeup to create such an effect at [4] Crepe wool and spirit gum are also classic standbys. Remember that it only has to look good from 20 feet and farther (or whatever your staging implies). Edison 05:59, 2 March 2007 (UTC)
Wait, you're doing Miami Vice for a high school production? [Mαc Δαvιs] X (How's my driving?) ❖ 06:24, 2 March 2007 (UTC)

[edit] Amiodarone and D5W

I am an instructor who helps teach paramedic students. We teach our students to mix amiodarone in D5W -- one student wants to know why D5W and is it OK to mix with normal saline? I've looked all over wikipedia and also at the manufacturer's website but can't find the answer. Futrmd2009 03:00, 2 March 2007 (UTC)

Wikipedia and the persons who answer questions here cannot give any medical adice, because the person giving the advice might be a physician, or he might be a teenage prankster. They might give well-meaning but incorrect advice, or they might give malicious advice. You will have to determine for yourself the reliability and validity and verifiability of the information there. The life of a patient might depend on getting medical advice only from qualified health practitioners. Edison 05:51, 2 March 2007 (UTC)
The questioner isn't asking for advice, he's asking for information. The reason amiodarone is given in D5W is simply tradition; that's the way the protocols were developed. As you know, amiodarone dosing is critical as to speed and concentration as well as in its interactions with various drugs and intravenous tubings. Because some drugs given in emergency situations are incompatible with (precipitate out in) normal saline, it's easier to use D5W. But even though amiodarone and NS are not incompatible per se, D5W is used in the manufacturer's literature and in ACLS protocols, and you really need to follow these rather than improvise. By the way, the manufacturer, like all U.S. pharmaceutical companies, has people whose only job is to answer these questions, and you can rely on the information being correct, so you should shoot off an e-mail to them. -Nunh-huh 13:58, 2 March 2007 (UTC)

Here's a good start. Skip to the background section where they talk about amiodarone. Dextrose is an osmotic agent. --Tbeatty 06:22, 2 March 2007 (UTC)

"is it OK to mix with normal saline?" sure sounded like asking for advice which might be implemented by health care personnel. Edison 16:13, 2 March 2007 (UTC)
Most information can be acted upon. That doesn't make it advice. The information being asked for was "is it contraindicated to administer amiodarone in Normal Saline, and if not, why do most people administer it in D5W?" - Nunh-huh 17:08, 2 March 2007 (UTC)
We hope a trained paramedic or medical professional will not use Wikipedia as the guideline for safety, regardless of what is posted here (advice, information, articles, or otherwise). Nimur 21:08, 2 March 2007 (UTC)
The paramedic instructor who asked the question was asking why it is that one mixes amiodarone with D5W. He was asking why it was a guideline, not for permission to ignore it. - Nunh-huh 21:28, 2 March 2007 (UTC)
Yes, I agree with you, Nunh-huh. I have no problem giving information out. It is the responsibility of whomever uses the information to ensure that it is correct; and that they are doing so in a safe, legal, and intelligent way, whether the information is about health, legal issues, etc. Nimur 23:17, 2 March 2007 (UTC)
We're in complete accord then, but I'd add that the original questioner did nothing and asked nothing that should make us suspect he's going to do anything remotely irresponsible with any information provided. - Nunh-huh 00:05, 3 March 2007 (UTC)

[edit] email

How can I email a page from Wikipedia. There seems to be no link to "email this page". I found some info that I wanted to share with family, and when I saved it to a document file it broke it into numerous files and I was unable to find the text. Help. Anjie

Why not email your friends the Wikipedia page's URL? Alternatively, you can save the webpage and email the .html file (forget about the folder with the same name), if you don't need any pictures.
Another option is to save the webpage, compress the numerous files you were talking about into one file, and then send the one file. To open the webpage, click on the file ending in .html. --Bowlhover 05:40, 2 March 2007 (UTC)
Email them the URL - cut/paste it from the bar at the top of your browser window directly into the email text. That way they have a link to the latest version of the page so if we fix things in the future, they'll see the fixed version. Worse still, links within the article are relative - not absolute - so if you send them the HTML from Wikipedia, links and images won't work for them - if they go directly to the Wikipedia site via the URL, they will. Not only that but you won't be filling their in-box with junk. If you did succeed in actually sending them everything, you'd be sending them a copy of the Wikipedia logo - which is illegal because the logo is copyrighted (although the body of the encyclopedia is free to be copied - the logo isn't) SteveBaker 11:54, 2 March 2007 (UTC)

[edit] solar furnaces

i`ve benn reading on solar furnaces and i was wondering and i was wondering how, since they produce such high temperature they are not the proposed way of producing energy oposed to other types of solar gathering divices ?

also i was wondering what is the size of the area requiered to gather so much light ?

Well, I'm not entirely sure what your first question is getting at, but there is actually a lot of solar energy that hits the earth, and that energy can be turned into heat in many ways (okay, not "a lot" in the cosmic sense, but allow me this liberty). The rule of thumb is that roughly 1 kW/m2 of solar power is incident on the Earth's surface on a sunny day. Of course, there is no way to convert that to your favored energy form with 100% effiency, but even with conversion (in)efficiency, there's enough there to work with for many purposes (photovoltaics, direct solar heating, etc). -- mattb @ 2007-03-02T07:26Z

i was talking about high flux solar furnaces like this one http://www.nrel.gov/csp/lab_capabilities.html?print

theyr talking about heat high enough to vaporise carbon coming from sunlight alone, isnt that more eficient than plants like the solar one tower ?

It depends on what you want to do with the energy. If you want to focus it all into a small area and make something really hot, it's great, because you're making direct use of sunlight (as opposed to letting it be used in photosynthesis, compressed for millions of years, and then set fire to, wastefully releasing the heat in all directions). Solar power towers actually do work like this, but they collect the heat in another object, where it can be drawn off and used at a later time; but there must surely be additional losses involved. Given that most current solar farms focus on collecting solar energy directly (solar to electrical), rather than these two or three intermediate steps, I'd assume that that's a more efficient process (just as not relying on plants to turn it into coal first is), else we wouldn't be doing it. Solar panels do keep jumping up in efficiency. (And please sign your posts with four tildes, ~~~~) Spiral Wave 17:47, 2 March 2007 (UTC)
The best efficiency I've seen in a solar cell is tandem cell with about 31% quantum efficiency (for all intents and purposes, this means 31% of the solar power falling on its surface is turned into electrical power). However, tandem cells are expensive compared to ultra-cheap multicrystaline and polycrystaline silicon cells. The best poly-Si cells I've seen to date have about 16% efficiency... And time marches on... When compared to other forms of energy conversion, photovoltaics aren't to bad on the efficiency scale. Then again, they really must have high efficiency since it's so easy to release massive amounts of energy by breaking chemical bonds in hydrocarbons and collecting a few measily percent of that energy. -- mattb @ 2007-03-03T00:17Z

[edit] Unknown military device?

I don't know is it illegal for me to tell about this. Therefore I am not revealing where this happened. This was not long ago.

While I was camping during my compulsory military service our group saw a ground-colored truck with had tall thing totally covered with "curtain" at its back. Then at night while I had to patrol the area with one other person we saw that thing without curtain. There was like a thick pillar attached at the back of tuck. At the top of it there was like two "horns", resembling gigantic U-letter. It did not rotate like radars but it changed its direction once.

After we went to the tents we heard two times terrible very high pitch noise that made many people to put fingers on their ears. I don't know does it have anything to do with the truck we saw. Could you have any idea what we saw? Radar jammer perhaps? Akrieria 06:52, 2 March 2007 (UTC)

Radar dishes only go round and round when they are sweeping the area looking for something. A targetting system that has found it's target and locked onto it may stay pointed at it tracking small movements. So if it was a targetting system then it might well sweep rapidly then stop when it's locked onto something. Is it possible that those two 'horns' were actually short missiles? That might well be what the radar was aiming. I suppose a high pitched noise could be a missile launch even - but there are other possibilities - it's hard to know without hearing the noise. Was it the sort of exercise where live fire might have taken place? Personally, I would have asked my superior officer - if you were training then learning what these other things are is just a part of the learning process. SteveBaker 12:04, 2 March 2007 (UTC)
I thought that one of the fundamental rules of being a soldier was "don't ask, don't tell"? ;) --Kurt Shaped Box 17:09, 2 March 2007 (UTC)
its fun to know what the military is up to though wouldnt you agree kurt? Maverick423 17:11, 2 March 2007 (UTC)
If I asked, they wouldn't tell me. --Kurt Shaped Box 17:28, 2 March 2007 (UTC)

Sounds like a tuning fork but in a large size. i acctually heard that the military was wanting to use sound weapons to suppress resistance and minimize casulaltys. i dont see the point to this though since if your in a war with someone else you should kill them not give them mercy. NO MERCY GET BACK TO WORK SOLDIER AND KILL!! =P JK or am i?? Maverick423 17:06, 2 March 2007 (UTC)

I think you're right about it being an experimental non-lethal sonic weapon. There are many cases where non-lethal weapons are needed. Take the case of the "students" who overran the Iranian US embassy in 1979. Mowing them down with machine guns would have resulted in war between the US and Iran, but a piercing noise could have driven the "students" away before they captured the entire embassy staff leading to the Iranian Hostage Crisis. There are many current cases of "protests" in Iraq and elsewhere that aren't yet violent, but need to be dispersed before they become violent. StuRat 17:33, 2 March 2007 (UTC)
Great idea Maverick, it seems like an excellent candidate! [Mαc Δαvιs] X (How's my driving?) ❖ 18:17, 2 March 2007 (UTC)
Active Denial System
Active Denial System
It probably wasn't this, since these non-lethal microwave weapons haven't been deployed yet. Nimur 19:34, 2 March 2007 (UTC)

[edit] Coloured fire preparing safety

I am planning to make logs that burns with green coloured fire. Internet pages tells that I should do it by putting logs in water with copper sulfate until they are completely wet, and then dry them until they are completely dry. But can I do this at home? Is it safe to breath inside if I do it? Or should I do it outside? The problem is that I live in high house and have no own yard. I will burn the logs while I go to forest 193.167.45.242 09:04, 2 March 2007 (UTC)

Copper sulfate is not very good for you at all. It's poisonous. That being said, I've never come across copper sulfate fumes, despite handling copper sulfate solution a number of times, so you might be safe. I'm not entirely sure how healthy burning logs coated in copper sulfate would be for people around the fire, either. Maybe someone a little less rusty with chemistry can chime in :) Capubadger 09:38, 2 March 2007 (UTC)
Borate is the better choice. (For indoor use borate or boric acid are mixed with alcohol and a drop of sulfuric acid and this mixture burns than with a green flame.) Soaking a log with boric acid or borate dissolved in water should work, but a test with a pice of paper would help. --Stone 10:09, 2 March 2007 (UTC)
I have to try that. Why is sulfuric acid needed to be mixed there? Alchemal 11:56, 2 March 2007 (UTC)
The triethylboric ester does not form spontanious, it needs acid catalysis. The methylester forms without acid catalysis, but methylalcohol is very toxic. --Stone 15:57, 2 March 2007 (UTC)

[edit] Electrically Charging a liquid

My question is that is it possible to electrically charge a liquid or even a drop of liquid ... ??

Yes, see Oil-drop experiment for a famous example. In fact, drops of liquid we encounter in everyday life are usually charged to some degree: by interaction with the nozzle, by air friction, or by some other mechanism. The excess charge, by the way, is practically always found on the droplet surface. Cheers, Dr_Dima
A glass or plastic container partially filled with water becomes a Leyden jar and electric charge was stored in it (probably in the surface lining the container) with the experimenter's hand outside as the other conductor comprising the capacitor. Note that a dangerous electrical shock can be the result of charging such a capacitor to high voltage, so don't try this without proper supervision and knowledge of and observance of all safety precautions.Edison 16:09, 2 March 2007 (UTC)
Early inkjet printers used electrostatic deflection of ink droplets.
Atlant 18:02, 2 March 2007 (UTC)

Powder coating? --Tbeatty 06:11, 3 March 2007 (UTC)

[edit] bluetooth

sir i want to know that can bluetooth be used in tv . by the help of microcontrller. if it is yes then tell me what kind of microcontrller i w'd have to design ? thanks

A complicated one. You can buy commercial microcontrollers that already support Bluetooth. Here]'s an evaluation board from Analog Devices; you can use Google or search major manufacturers' web sites. Nimur 19:37, 2 March 2007 (UTC)

[edit] Holding Your Breath

Why is it that I find it must easier to hold my breath for an extended period of time under warmer water compared to that of cold water? For example, I can stay under in a hot tub longer than a cold swimming pool. --Russoc4 16:43, 2 March 2007 (UTC)

not exactly sure about this as i too have that same prob heh. i think it has to do with the lungs contracting more in cold water then in warm water.Maverick423 17:09, 2 March 2007 (UTC)

How about it taking more energy to keep you warm, energy which comes from "burning" calories with oxygen from the air ? StuRat 17:24, 2 March 2007 (UTC)
This is probably a psychological effect more than physiological. Cold water should slow your metabolism, hypothetically enabling you to stay submerged longer. When training for SCUBA, we were always instructed to begin our dive by taking our diving mask down, allowing cold water to hit our face for up to 60 seconds. This was supposed to relax us, equalize our temperature perception (preventing panic if we should get cold water on our face later), and slow our breathing. Nimur 19:54, 2 March 2007 (UTC)
The slowing of the metabolism only kicks in with hypothermia, I was assuming we weren't taking it to that extreme. StuRat 00:18, 3 March 2007 (UTC)

[edit] Warning i am Bored

Ok guys i am bored. im thinking about removing the lid of a microwave and using it like a gun or something. what am i getting into if i do this? Maverick423 17:22, 2 March 2007 (UTC)

Do not do this. Hipocrite - «Talk» 18:02, 2 March 2007 (UTC)
This is called a microwave gun. Rather unstandard and always improvised. They are occasionally made for a portable controlled source of microwaves, and are rarely used. I've seen scientists trying to reproduce "higher electromagnetic field strengths" around crop circles with this. Because there needs to be a nozzle mechanism on it, they attempted to make one and there ended up being holes in it, and areas of space with massive heat energy, and one of them got burned. Powerlabs gives as good a disclaimer as any: WARNING: Attempting to operate a magnetron outside its designed cavity is VERY dangerous and will not only decrease its useful life, but will also pose a serious threat to the operator of the device. Microwaves can cause cataracts and deep thermal burns. Any electronic equipment within range of the magnetron will be instantly destroyed. Please do not tamper with your microwave oven. [Mαc Δαvιs] X (How's my driving?) ❖ 18:14, 2 March 2007 (UTC)
Active Denial System
Active Denial System
It probably won't be as powerful as this, since these microwave weapons operate at 95 GHz and are ... very ... large. Perhaps if you are seriously interested in microwaves, you should study Electrical Engineering (instead of harming yourself and others by taking apart an oven). This solves your boredom problem, too! You will find that microwaves have huge utility outside of the realm of weaponry. Did you know your cell phone operates at microwave frequencies? (*depending on type, carrier, geography, etc). Did you know that your computer's wireless network uses microwave? So do missile-trackers, point-to-point communication systems, weather satellite and deep-space-probe communications systems, and plenty of other neat stuff. Nimur 19:41, 2 March 2007 (UTC)
Or, get a job working with radars. Basically the same theory as what you want to do: Throw a lot of electromagnetic radiation into the air and see what comes back. They make great microwave ovens - just toss your dinner in front of one while it fires. Make sure you don't try to catch it on the way down. Also, make sure you aren't standing on something that melts (like an iced over lake). I lost a lunch that way. --Kainaw (talk) 19:54, 2 March 2007 (UTC)
I am trying to interpret your statement about the lunch. A few possible interpretations: 1) The lunch was sitting on the ice, which melted, and then fell into the lake. 2) You were standing on ice, which melted, and then you vomited. 3) You bet your friend that you would stand on a block of ice in front of a powerful RADAR without dying; you lost the bet and had to pay for his lunch. Are any of these close? Nimur 19:58, 2 March 2007 (UTC)
To make it clearer: To use a radar as a quick food heating unit, hold your meal in front of you. Stand in front of the radar unit (they are normally safe to stand around up to 15 feet in the air). Moving your arm in a quick upward motion, release the meal and let it fight against gravity to a height of 20-30 feet. As the radar fires, it will irradiate the meal, filling with a lot of energy. Most food will radiate the absorbed energy as heat (I know that rice cakes do not). When the food returns to your elevation above the ground, it will be very hot. Do not attempt to catch it. Let it hit the ground and it will cool rather quickly as it releases the energy it was just forced to absorb. If, however, you are standing on an iced over lake as you do this, the heat released by the food will quickly melt the ice. Then, your meal will go through the ice and into the lake below. --Kainaw (talk) 20:08, 2 March 2007 (UTC)
How can you lose a bet about standing in front of a active radar transmitter without dying and still pay off?! Clarityfiend 20:46, 2 March 2007 (UTC)

wow the conversation sure did change since i been gone. well that ADS looks cool and the experiment didnt work =( i dont know why but when i opened the electrical area where all the resistors and stuff is at i found some burned =( im not ganna waste a new micro (the old one was one i found that still kinda worked) =( Maverick423 21:45, 2 March 2007 (UTC)

Please seek immediate medical attention. Thank you. Hipocrite - «Talk» 21:46, 2 March 2007 (UTC)

Or please find out if the uncyclopedia has a reference desk and if so take this nonsense there. Nocternal 19:49, 3 March 2007 (UTC)

[edit] Alcohol

Hey guys, i understand that alcohol is considered a drug, but is it a stimulant or depressant? I cant seem to find it anywhere and it intrigues me because it has different affects on different people. Any other advice/info/links on alcohol for a teenager would be appreciated, thanks alot Dave 17:47, 2 March 2007 (UTC)

Alcohol is a depressant. It slows reaction time, metabolic activities, etc. Nimur 19:42, 2 March 2007 (UTC)
Advice. Don't drink and drive. Whatever else you do, understand and be prepared for the consequences. In some places, it is illegal to purchase or consume alcohol if you are under certain age. Realize that even small amounts of liquid can contain lots of concentrated alcohol and may affect you seriously. If you're bored, consider studying Electrical Engineering instead of drinking alcohol. Nimur 19:50, 2 March 2007 (UTC)
Surely our article on alcohol contains this information. Better idea, Ethanol metabolism. Oh nevermind, both articles seem to be written at the near graduate level, so I'll just answer it here, it's a depressant. No, wait, here's one: Try Effects of alcohol on the body--VectorPotentialTalk 17:48, 2 March 2007 (UTC)
Advice for a teenager? White cider is bad - very, very bad. No not drink it, even though it is very, very cheap. It causes the worst hangovers imaginable and makes you chunder very quickly. --Kurt Shaped Box 17:52, 2 March 2007 (UTC)
In the U.S., advice for a teeanger is: Don't drink because it's against the law. And there are very good reasons for it being so. --Tbeatty 06:06, 3 March 2007 (UTC)
In the UK, theres a more relaxed attitude to drinking, as long as it's not in public. Drink Aware has a lot of good, sensible advice on alcohol.
My advice is only get drunk with people you trust. This is really important, as when you're drunk these are the people who will (or won't) help you back home and make sure you're safe.
Finally, read up on hangover cures - h2g2 has some good cures. Drinking "spacers" of soft drinks will also help prevent a hangover. --h2g2bob 22:04, 3 March 2007 (UTC)

[edit] Raw Eggs

How does the nutrition of a raw egg compare to a cooked one, if i put a whole raw egg (white and yolk) into a milkshake? would it be any different than a hard boiled egg or an egg scrambled with no margarine/butter in a non-stick pan? is there any harm in consuming to many raw eggs? i dont mean in terms of fat/cholestrol or other concerns, i mean just in comparison to cooked eggs. e.g., if its healthy for an active person to eat X number of eggs a day, would it be ok to eat them all raw?

Salmonella is the first concern that comes to mind. But it's a statistical thing. Some eggs are perfectly free of salmonella and are safe to eat raw; some are not, and must be cooked to be safe. There is no easy way to know whether a particular egg is safe or not, so it should be cooked (ensuring that all salmonella is destroyed). The symptoms of Salmonellosis are vomiting, diarrhea, and other illness, so you probably want to err on the side of caution. Nimur 20:58, 2 March 2007 (UTC)
Raw eggs contain avidin, a protein which binds to biotin. It's inactivated by cooking. The concern is that if you eat a lot of avidin, you'll eventually become biotin deficient. - Nunh-huh 00:56, 3 March 2007 (UTC)

[edit] Microwaved Egg

Does the nutrition of a scramble microwaved egg (no margarine/butter) differ at all from one thats scrambled in a non-stick pan on the stove (also no margarine/butter)?

Probably not in any significant way. There might be stretch-cases where the pan leeches metal ions into the egg, but I doubt it's significant. Nimur 20:55, 2 March 2007 (UTC)

[edit] Microwaved Egg--part 2

is it possible to cook an egg by putting it it alone in the in the microwave without breaking its shell, such that it would turn out just like if it was boiled? it seems to me that should be possible because it contains plenty of water to absorb the waves and heat up. but how long would i have to microwave it?

if not, can u do the same but actually boil it in a microwavble dish

and once again, would the nutrition content vary between a microwaved one (either of the two methotds explained above) or a stove boiled egg?

The egg may burst, since the insides would be heating up very rapidly (as compared to boiling), and there would not be time for vapors to permeate through the shell. I haven't tested this hypothesis. Other than that effect, I don't see why you couldn't. Try it, put the egg in a bowl or on a plate to catch any mess if it does break. Nimur 20:57, 2 March 2007 (UTC)
Nimur is right, eggs explode in the microwave quite readily. I wouldnt do it unless you want to spend a long time cleaning up :) Capubadger 22:26, 2 March 2007 (UTC)
I've tried it, and the egg exploded, blew the door open, and splattered all over the kitchen. You could be severely burned if you were standing in front when this happened. Don't try this at home, kids. StuRat 00:14, 3 March 2007 (UTC)

[edit] science and technology dvd player

what is the difference between a 5.1 channel dvd player and a 4.1 channel dvd player —The preceding unsigned comment was added by 216.239.52.136 (talk) 21:13, 2 March 2007 (UTC).

Presumably the audio output for Surround sound. We have a good overview at this section. Nimur 21:41, 2 March 2007 (UTC)

i think its the number of speaker/sub 4.1 = 4 speakers 1 sub 5.1 5 speaker 1 sub i am not sure about this tough

You're right. Most commercial DVDs use 5.1 surround sound. This is encoded on the DVD using AC3 (also known as "Dolby Digital" or "a52"). The 5 refers to 5 normal speakers placed in different positions around the room. These are front-left, front-right, (in front of you) back-left, back-right (behind you), and center (in front of you). The 1 refers to a single subwoofer. 4.1 would presumably miss the center speaker. If you don't have a surround sound system, the output will simply be stereo through your TV speakers in either case. --h2g2bob 21:34, 3 March 2007 (UTC)

[edit] Health and safety when casting steel

Hi! Does anyone know anything about the production of steel? I need to research what health and safety methods need to be put into place in the standard steel factory. So far, the risks I've come up with are:

  1. Extreme heat from molten metal
  2. Hot gases
  3. Fumes from melting process
  4. Danger of spillage from molten metal - apparently when molten metal comes into contact with water there's a big explosion or something, a bit like pouring water onto a chip pan fire.

To counteract these:

  1. The workers should wear thick leather overalls and gloves as well as boots and masks.
  2. Possible ventilation systems?
  3. Same as 2.
  4. Dry dirt or sand floor with no moisture

Can anyone think of other risks and how to counteract them? I've probably missed some really obvious ones! Thanks, Bioarchie1234 21:28, 2 March 2007 (UTC)

A few come to mind...
  1. Metal is heavy, and the containers needed to hold and move melted metal are large and ever heavier...standard dangers of things falling, body parts getting crushed or caught in machinery, etc.
  2. It takes a lot of energy to melt metal, so there's lots of flammable gas or high-voltage/current electrical power.
  3. Chemicals used to clean metal or as additives to alter the composition may be toxic and/or flammable.
How to counteract them? Well that's why you pay an engineer (if this is a real-world problem) or use your brain to figure it out (if this is an academic exercise). DMacks 21:37, 2 March 2007 (UTC)
Never underestimate the importance of steel-toed boots in a factory. Nimur 21:42, 2 March 2007 (UTC)
Thanks, DMacks. I've been working for a while and I'm not really thinking of obvious things like metal being heavy! (By the way, this is an academic problem.) I'll work out solutions for them in the morning when I'm more awake! Thanks for your help. Also, thanks for the steel-toed boots mention, Nimur. Although it's a bit of a unfulfillable cycle - you need steel to make the steel-toed boots, and to make steel it's good to have steel toed boots!Bioarchie1234 21:46, 2 March 2007 (UTC)
OSHA has some suggestions which are legally mandatory in the United States. Nimur 21:53, 2 March 2007 (UTC)

[edit] heart

the heart pumps approximately how many liters of blood each dayCharity rob 21:50, 2 March 2007 (UTC)

I always hated these statistics in biology. The terms are so vaguely defined that almost any answer is permissible. If the pioneers of human anatomy were electrical engineers instead of biologists, they would never have allowed such ambiguity - especially in the way that the material is taught. Furthermore, when anatomical terms ARE precisely defined, they are usually in Latin (presumably to obfuscate things). Instead, I will post these questions and hope somebody else answers them.

Nimur 21:56, 2 March 2007 (UTC)

  • How much blood is in the human body at one instant?
Blood says "about 5 litres" for an adult human. Nimur 22:05, 2 March 2007 (UTC)
  • What is the average linear-flow rate of pumping of the human heart?
This is called stroke volume (per heartbeat) and has a huge variance. Nimur 22:11, 2 March 2007 (UTC)
Linear flow is about 5l/mintucker/rekcut 18:04, 3 March 2007 (UTC)
  • What is the surge flow-rate of the human heart as a pump?
Blood pressure varies between 120 (systolic) and 80 (diastolic) mmHg for a healthy human (with great variation due to hypertension, level of hydration, health, etc. This pressure can only be converted to a linear flow rate via some nasty physics and some approximations of blood vessel size. Nimur 22:07, 2 March 2007 (UTC)
Surge flow is given by 70mL/stroke divided by the average time per ventricular contraction, approximately equal to the ST interval (from the end of the S wave to the end of the T wave, not the same as the ST segment) of about .3sec. This gives 70mL/.3sec or 235mL/sec.tucker/rekcut 18:04, 3 March 2007 (UTC)
  • What percentage of time is the heart actively pumping?
Systole (medicine) is the best place to look. Blood is pressurized (and flowing) even when not being pumped. But the pressure, flow-rate, and other parameters will vary throughout the body. The actual heart valves will be opening and closing between diastole and systole as the pressure in each chamber changes. Nimur 22:05, 2 March 2007 (UTC)
Not if you're using aortic stroke volume. Nimur 22:18, 2 March 2007 (UTC)


Multiplying stroke volume (70 mL / beat) by heart-rate (85 beats / min) by 1440 minutes/day gives me 8568 Liters per Day. This means each iota of blood goes through the heart about 1700 times per day. I would not recommend taking these number at face value; it's clearly much more complicated. Nimur 22:14, 2 March 2007 (UTC)
Hmmm - so at 70mL per beat and with 5L of blood in your body, we'd have to say that it takes 71 beats of your heart to circulate your entire blood volume - so it only takes a little under a minute for the blood to head out, get where it's going, back to the heart, out to the lungs and back to the other side of the heart! Wow! It's moving pretty fast! SteveBaker 16:24, 3 March 2007 (UTC)
Though 70mL/beat is a commonly cited value, 5L/min is too, and has less error associated with it. This gives about 7.2 kL / day. Cardiac output has more info. Your heart rate above, 85Hz, is a little fast. Circulation time for a given bolus to go all the way around the circulatory circuit is about 21-24 sec, so a bit faster than your math gives above. tucker/rekcut 18:04, 3 March 2007 (UTC)

[edit] RADAR blips from throwing food

Kainaw claims that you can cook food[5] by throwing it in front of an operating RADAR transmitter.

Question: Does the radar operator know about it? If he doesn't, can he see it on the scope? I imagine that the food absorbs a lot of energy, but probably reflects enough back (given the close range) that it might actually form a blip on the radar console. It might be confused with a UFO. What else should we know before throwing food at an active RADAR transmitter? Nimur 23:13, 2 March 2007 (UTC)

I hope not, otherwise one good food fight and NORAD will think we're under attack. StuRat 00:42, 3 March 2007 (UTC)
To answer the question exactly: No. The radar operator does not see what the radar sees. In the old (very old) radars, they saw green (or amber) blurs and tried to make sense of them. Now, a group of complimentary radars in different areas, of different frequencies, pointing at different elevations, all send data into a computer. The computer analyzes the signals and creates "tracks". A track the location, history, and estimated trajectory of a moving object "of interest". Normally, these are aircraft of some sort, but radars can track boats (including subs that aren't too deep due to the bulge they make in the water), tanks, and even large groups of armed military (because they have so much metal on them). The operator only sees what the computer is programmed to display. So, the computer would temporarily see a huge blur in front of the radar. That blur does not fit the signal for any known aircraft, so it is ignored. Now, if you want to have fun, get on the computer and zoom in real tight on a location. Drop a bunch of waypoints there to write out a nasty message or draw something obscene. The operator will see a pile of dots. If they zoom in close enough on it, they'll see your message. Then the Gunny will be asking why you have so much time to waste writing nasty messages over the southern tip of Florida. But it's America's wang! --Kainaw (talk) 00:50, 3 March 2007 (UTC)
The Mythbusters tackled cooking food with a radar dish, I believe the verdict was that it is just a myth. Cyraan 01:20, 3 March 2007 (UTC)
I never saw that episode, though it may confirm a belief that I had. I found that some items did not heat up: a plastic bag of rice cakes, a plastic bag of beef jerky, a banana, and plain toast. However, an MRE, which comes in a wierd thick brown bag full of little bags, heats up well. A metal foil bag of Doritos heats up. A can of Coke heats up. A regular screwdriver heats up. It was my theory that metal objects heat up, but nonmetal ones do not. The reason I kept it as a theory was that it didn't explain why potatoes and shrimp in a plastic bag with butter would heat up well. --Kainaw (talk) 01:50, 3 March 2007 (UTC)
I have never really linked up theoretical understanding to observations on this subject. Ideally, metal objects should reflect microwave radiation, not absorb it. Yet, foil in the microwave oven (specifically, foil-on-one-side, paper-on-the-other-side wrapper for a fast-food hamburger) combusted when I put it in the oven. Clearly metal objects are heating up somehow. This seems to corroborate Kainaw's experiment. 128.12.131.62 03:38, 3 March 2007 (UTC)
I was mistaken slightly, the episode was a holiday special, so it was only a turkey they tried to cook using a radar unit on the SS Jeremiah O'Brien without success, they didn't try any other foods. Deserves a myths revisited episode methinks. Cyraan 02:02, 3 March 2007 (UTC)

Microwave cooking was discovered as the result of a chocolate bar melting, getting soft or warm that was in the front vest lab coat or shirt pocket of one of the original radar scientists, inventors, workers or technicians as they worked in front of the radar antenna but I've forgotten where I saw this information. Nocternal 19:37, 3 March 2007 (UTC)

Obliquely related- The mythbusters were unable to cook a chicken with a radio antenna. Would it be possible to actually cook the chicken with an x-ray machine, which is of higher energy? -- Sturgeonman 16:30, 4 March 2007 (UTC)

No. Microwaves work by operating at the resonant frequency of water, and certain microwave radio applications do too (they operate in a freely-licensed ISM band). X-ray machines operate at a completely different frequency. —The preceding unsigned comment was added by 203.49.242.20 (talk) 08:58, 5 March 2007 (UTC).