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July 22

vapour adsorption refrigeration system

i want detailed information regarding this non cinventional refrigeration system —Preceding unsigned comment added by 117.98.108.28 (talk) 01:19, 22 July 2008 (UTC)

Try googling "vapor adsorption refrigerator." I found this PDF which seems rather detailed [1] 71.77.4.75 (talk) 01:33, 22 July 2008 (UTC)

We have an article on this: Absorption refrigerator.

Atlant (talk) 12:56, 22 July 2008 (UTC)

The brightest question on the science desk!

One of the joys of having a young child is attempting to field their damnably simple questions. I've gone through the blue sky, the twinkling stars, how tires get made, and what that bug was doing to that other bug, but I'm stumped tonight. What is the most "apparently bright" thing to be seen in the world? We were experimenting with a magnifying glass on a clear sunny day and the question came up if the sun was the brightest thing in the world (yeah, I know, but if it's in the sky, it's part of the world as far as she's concerned...). Now, I don't want to get into quasars and absolute magnitude because that's not what she's looking for. Is there any light she could experience that is brighter than the sun on a clear day? Searches online come up with some interesting homemade flashlights, but they don't specify how bright they are compared to the sun. Matt Deres (talk) 01:26, 22 July 2008 (UTC)

The initial flash of light from a nuclear explosion? You may not want to *actually* show her that one, though... :) --Kurt Shaped Box (talk) 01:35, 22 July 2008 (UTC)

Since people sometimes use welder's helments to view solar eclipses, I'd guess a welding arc and the sun have similar brightness (not that I'd make any recommendations about how to view an eclipse, I'm no expert.) In both cases, UV light is a significant aspect of the problem. --Gerry Ashton (talk) 01:42, 22 July 2008 (UTC)

Some types of arc welding are a good deal brighter than the sun. But that probably doesn't help you, you're not likely to buy an arc welder just for this, and it's not really safe to 'experience' up close anyway.

I think there are some lights designed for film-making that are available pretty cheap that are brighter than the sun at close range. Actually, I'll bet that at close range many photographic flashes appear brighter than the sun. A photographic flash would at least have the virtue be easy and relatively safe to demonstrate. Might be seen as a cop-out, though. APL (talk) 02:20, 22 July 2008 (UTC)

Er, using common sense when it comes to "close range", of course. APL (talk) 02:32, 22 July 2008 (UTC)-

I'd go with a really powerful laser. The amount of light produced isn't all that much, certainly less than a nuclear flash, but if you point it straight at her eye, I imagine far more light would hit her retina than from a nuclear flash. I wouldn't demonstrate that one either, though! --Tango (talk) 01:45, 22 July 2008 (UTC)

Apparent brightness varies dramatically with distance. While our distance to the Sun won't vary all that much, I'd expect any rather bright light to appear brighter than the Sun if you put your eyeball right up to it (not recommended for those who wish to keep their vision). Some particularly bright lights would be search lights. A specific case is the spotlights pointing upwards from the Luxor casino in Las Vegas, which are bright enough to see from 275 miles away. I'd expect that your eyeball would explode from the heat if you put it right up to those lights. StuRat (talk) 01:47, 22 July 2008 (UTC)

Actually, apparent brightness does not vary at all with distance; see my post below. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)

Apparent bightness/apparent luminosity sure does vary with distance, perhaps you were thinking of absolute brightness/absolute luminosity ? The reasons why apparent brightness decreases with distance are that the light spreads out, so that less of it hits your eye at larger distances, and that dust and other particles absorb more light the farther it travels. StuRat (talk) 14:27, 22 July 2008 (UTC)

I was referring to surface brightness, which is what most people mean when they discuss the brightness of a emitter or reflector. --Bowlhover (talk) 08:12, 24 July 2008 (UTC)

Ok, that concept is that the brightness of any given apparent area stays the same, regardless of distance. However, as the total apparent area increases, the total apparent brightness of an object increases (when the distance is reduced). They also seem to have assumed there are no particles to absorb the light, which is a valid approximation in some regions in space, but never valid when looking through the atmosphere (the more atmosphere you look through, the more light will be blocked). So, in short, this method doesn't apply to the question, which was about the total apparent brightness of objects on Earth. StuRat (talk) 13:10, 24 July 2008 (UTC)

All the examples above will suffice as more "apparently bright". Are you just talking visually bright? You might explain spectrum and point out how the sun can burn every part of your body within about 15 minutes - that's pretty hard to beat.

And when you're talking about what's brighter - I hope and am absolutely sure you've explained that we never, never look right at the sun to see how bright it is. The brightness of the sun itself is already past the scale where you only see how bright it is once, so that's the very most important lesson. I'm sure you've explained that, it's worth saying again!

And that said, as far as a light source where you can see ambient light, unlike a laser (any of which can also easily destroy your vision if viewed directly, but cast no ambient light) - an arc-welding flare is a good demonstration of a very bright light cast all around (again, never look at the arc!) and is impressive indoors; a film-projector bulb; a spotlight. Now take anyone of those, look near them in broad daylight - do you see a difference? Likely not. The sun pretty much rules them all.signed byFranamax (talk) 02:56, 22 July 2008 (UTC)

When we were kids, and there were no adults around, we regularly competed to see who could stare at the sun for longest. I have never had any resulting eye problems - I'm already in old age - and wonder whether there is some protective mechanism at work? I think the taboo is wrapped up in a myth that deserves closer scrutiny. 196.2.124.253 (talk) 19:56, 28 July 2008 (UTC)

Lightning flash possibly? I know from experience that burning magnesium wire outdoors (so my eyes were already light adjusted) can be bright enough that I can't look at it directly. 71.77.4.75 (talk) 02:33, 22 July 2008 (UTC)

Those are both good, but if we agree that the sun is bright enough that we can't look at it directly, I interpret this question as "what makes other things look brighter than they do in broad daylight?" Perhaps the best test of this then would be - will this other light source cast a shadow behind something in broad daylight? So if I shine the searchlight or burn the magnesium on one side of a car, without (!) looking at the light source, but just looking at the car, at noon on a clear day, will I see a shadow being cast? Is that a realistic criterion? Franamax (talk) 03:07, 22 July 2008 (UTC)

That makes sense but again distance seems to make it more complicated. I don't remember the shadows clearly but I am pretty sure the light from the burning magnesium was powerful enough at close range to overpower a shadow cast by the sun in broad daylight. I tried to find some videos of burning magnesium in broad daylight. Here is a video of a small ribbon burning (it's enough to cause the auto brightness-senser of the camera to dim). Here is a contains-mild-swearing video of a bunch of adventurous gentlemen burning quite a bit of magnesium in an outdoor oven in midday. 71.77.4.75 (talk) 03:32, 22 July 2008 (UTC)

My thing is not "does it fill in the sun-shadow?", it's more like "does it cast a shadow the other way?" - but we may be talking about the same thing. There's no indication of that in the video by the league of gentleman adventurers, but they missed out on the fact that piping a feed of pure oxygen into the centre of their little pyro-fest would have dramatically enhanced it. If they'd used a little pure O2 in fact, they might have been able to incorporate ambulances into the footage :)

You're right about distance, as are all the above - but the OP is looking for answers for his little girl, and has ruled out distance via quasars not being applicable (and I'd say gamma ray bursters anyway). However I'd say Mg in O2, arc welding and possibly plasma torch welding would be the most accessible real-life demonstrations of comparable light sources. Now compare that with the fact that from 93 million miles away it takes the Sun a half hour to send you to bed feeling bad all over. (Leaving aside nuclear devices, which are best left unexplained until after the talk about sex - at least you can give a realistic reason for the purpose of sex) Franamax (talk) 05:20, 22 July 2008 (UTC)

I don't understand the need to be secretive about the purpose of nuclear weapons. People sometimes don't like each other and they fight to kill. I certainly knew that years before I was taught the details of sex. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)

Just on the surface, that's a difficult subject for a child - 'cause the natural next question is "will someone try to kill me?". But you miss the major benefit of nuclear weapons - it's not to kill, it's to cause massive numbers of hideously wounded casualties, which tie down the resources of the defending power. Sit your young child down and read her Hiroshima by John Hersey. Explain to her how a fallout cloud would make her own hair fall out and how long it would take 'til she started vomiting and trace out on her face where the flesh would be melted to the bone. Were you taught those details when you were seven years old? Franamax (talk) 07:22, 22 July 2008 (UTC)

I never claimed that every single detail about nuclear weapons should be taught to a seven-year-old. In fact, most educated adults don't know how long it would take for nuclear bombs to cause vomiting or exactly where a person's flesh would be melted to the bone. Telling a child that nuclear weapons are used for war, or even that they waste the enemy's resources by killing civilians, requires none of the details you mention. And come on, "will someone try to kill me?" Any form of crime is more of a disconcerting topic than war unless the child's country happens to be in a nuclear war, and you can't possibly say parents don't or shouldn't inform children about crime.

Besides, the major benefit of nuclear weapons isn't forcing the enemy to provide disaster relief. It's either intimidation, or destruction of the enemy's military, economy, AND civilian population, with a focus on the first. --Bowlhover (talk) 08:24, 22 July 2008 (UTC)

Just a note for any casual readers: Do not ever look directly at the Sun; do not ever look directly at a welding arc or plasma arc; do not ever look directly at a projection bulb, especially through a focussing lens; do not ever look at the direct output of a laser of any type; do not ever look at burning magnesium metal. Doing any of these for any significant length of time can cause permanent damage to your vision. In some cases, this can be as little as 1/10th of a second (in some cases less). Use appropriate eye protection. Read instructions, ask experts, take precautions. Don't try to experiment because of something you read on Wikipedia - please! Franamax (talk) 05:33, 22 July 2008 (UTC)

Note that looking at the Sun without optical aid rarely causes permanent eye damage (see Sun#Observation and_eye damage). Burning magnesium is, as I showed below, 1/29th as bright; it is also much smaller than the Sun in angular size. Since burning the metal is a common high school experiment and was done without goggles in my former school, I would be surprised if it's dangerous. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)

It is dangerous, which is why you're told not to look at it directly. The thing is, looking at the sun or a magnesium flare will damage just a part of your retina each time, causing a small permenant area of blindness. Over time you can acquire more of these until it becomes noticable. Don't look directly at the sun, and don't look directly at burning magnesium. 79.66.124.253 (talk) 17:00, 22 July 2008 (UTC)

The brightest light source on Earth or elsewhere is the laser described here, which can output 10^22 watts per square centimetre for a tenth of a trillionth of a second.

The "brightness" of an object, by the most common understanding of the word, is the amount of light emitted per unit of angular area. As distance from a light source increases, both the light's intensity and the source's angular area decrease with the square of the distance. The result is that brightness, termed surface brightness in astronomy, does not depend on the amount of space between the source and the observer. The shadow test is thus inaccurate because it measures irradiation, not the power of light in one unit of angular area.

Burning magnesium is significantly dimmer than the surface of the Sun. According to its article, magnesium's combustion temperature is 2500 K. A calculation using the Stefan-Boltzmann law reveals the Sun's photosphere, at 5778 K, to be 29 times as bright. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)

Part of the lessons of live, i think she was asking for this [2]. Mion (talk) 08:47, 22 July 2008 (UTC)

I guess the article discusss it but looking at the sun directly is usually does not cause permanent damage but can be particularly dangerous during an eclipse where the lack of ambient light means the pupil may not dilate sufficiently. It's also likely to be very dangerous if you have just be given something to dilate the pupil (causing mydriasis), e.g. as part of an eye test or have taken some drug (this includes atropine and amphetamines) or have a disease (e.g. Argyll Robertson pupils, Marcus Gunn pupil, Adie syndrome) or whatever resulting in the condition. All in all, while most people are probably not going to suffer damage from looking at the sun, it's still an incredibly bad idea IMHO. (Note that the reason looking at the sun is not usually dangerous is not because it isn't bright enough to cause damage, it most definitely is, but because your pupils constrict in the bright daylight so don't allow enough light in to cause permanent damage. Also bear in mind that your unlikely to know your eyes are being damaged until it's way too late.) As for burning magnesium, I don't know that much but our own article Magnesium says it's dangerous. My guess is that it can be dangerous particularly if you are close to it, it's a significant amount and lasts a long time. From what I can recall when I was in school, this tended to be a short experiment (under 10 seconds), was usually done by the teahcer (i.e. you were probably resonably far away) and wasn't a great quantity (=smallish flame) likely greatly reducing the risk of harm. I don't see the fact that it's 1/29 as bright as the sun if true as significant as I mentioned already the sun is already way bright enough to damage your eyes. Also from what I can tell the amount of UV light is important too. Nil Einne (talk) 13:29, 22 July 2008 (UTC)

Wow, lots of replies! Thanks guys. Nothing like a six year old's question to get the smart folks thinking. There's a couple of really good suggestions here. The 'cast a shadow' thing sounds like a good one to try, at least to explore the topic (which is probably more important than the answer, even there even is one). The one problem is that I'm not sure it's actually correct. Lots of things can cast opposing shadows on a clear day, even regular flashlights. Maybe I should ignore my own restriction above and try explaining the difference between apparent and absolute magnitude, etc. Less viscerally satisfying, but still good to know. And as for the questions above, she's already aware of her mortality and we've already stayed up a few nights having very impromptu discussions about it. We haven't talked about nuclear war, but she knows about soldiers and war, etc. at least in general, historical sort of sense (Remembrance Day and all). We haven't had an in-depth sex talk yet, but she knows mom and dad somehow put her together inside mom ;-). I try to answer questions on the level they're asked, but I've always felt that if she wants to know, it's my duty to inform her, even if its unpleasant or uncomfortable. Matt Deres (talk) 10:55, 22 July 2008 (UTC)

Going the other way, you can use the shadow trick to show that an incandescent light bulb is less bright than the sun. On a clear day, you can see the shadow of the filament of a (clear) incandescent light bulb even when the bulb is lit. (But a laser still has higher intensity than unfocused sunlght.) Your daughter is already aware that focused sunlight is more intense ("brighter") than unfocused sunlight. -Arch dude (talk) 13:07, 22 July 2008 (UTC)

I have no source for this, but I'd suggest the experience of a strobe light in the dark being the brightest light you could let your daughter safely experience. The contrast from low light to intense flash can be blinding: let her eyes adjust to the dark and give a sudden strobe flash, see what happens. The brightest man made light I can think of (short of a nuke) is the arc on a plasma torch, which can cause severe damage to the retina. --Shaggorama (talk) 14:31, 22 July 2008 (UTC)

Hi. As an aside question, how bright would say, the Hiroshima bomb be in apparent magnitude from say 10km? Thanks. ~AH1^(TCU) 18:34, 22 July 2008 (UTC)

Far too bright. The Trinity test was described as "lighting up the sky like the sun" from a distance of 150 miles. --Carnildo (talk) 21:26, 22 July 2008 (UTC)

Still, you'd probably be close enough to test for yourself whether you really *can* see the bone structure of your hands through your flesh in the light of the flash. In the seconds before your eyes stopped working permanently. --Kurt Shaped Box (talk) 21:32, 22 July 2008 (UTC)

So, how did a butterfly end up being named 'Common Gull'?

Cepora nerissa, FWIW. What's the deal with that, huh? --Kurt Shaped Box (talk) 02:28, 22 July 2008 (UTC)

Quite a few of the butterflies in the genus Cepora seem to include "gull" as part of their common name. [3] I bet the word "Gull" is being used in another sense, perhaps an obsolete definition, place name, or proper name. I tried looking up "cepora" and "nerissa" in latin and greek but came up blank. I thought of the word "Gules" used in heraldry for red but the butterflies of the genus seem to be mostly yellow or white. That still doesn't exclude the possibility of "Gull" being a corruption from another language. I'll think about it some more... 71.77.4.75 (talk) 02:56, 22 July 2008 (UTC)

I got a potential origin idea. From what I can make of using online translators, the word "gul" in Hindi either is or is the first syllable of the word for rose or flower (gulAba?). Someone fluent in Hindi please check me on this. These butterflies seem to be common in India so the connection between the Indian word for flower/rose and the butterfly makes a bit of sense. 71.77.4.75 (talk) 03:08, 22 July 2008 (UTC)

You might have more luck on the language desk, but among the several meanings of gull in the OED is an obsolete adjective meaning "yellow, pale", from the Old Norse (gul-r), Swedish and Danish (gul).--Shantavira|^{feed me} 06:33, 22 July 2008 (UTC)

Do We Reduced Brain Power (Energy Save Mode like a laptop)

When I was struggling to get to sleep last night a thought occured to me. My laptop has 'energy save' mode - and in order to maximise battery-life it does a variety of things, one of which is 'turn-off' some of the processing power (perhaps by only using one of the 'cores') - this prolongs battery-life and allows functioning it a less energy intensive rate. My question is this...Does the human-brain do this ever? Given a time of low-food intake would the brain start 'shutting down' non-essential processing so as to reduce energy use. Would your IQ drop if sufficiently starved of energy (not to the point of no energy of course)? And does the act of thinking consume much more energy than not thinking? E.g. If I sit trying to work out a complicated calculation in my head does it consume more energy than just sitting idly doing nothing? Sorry if this is a daft question but I was struggling to sleep and it then (of course) consumed my thoughts for a while. The thing i'm thinking is they say hunger affects concentration - is this because the brain is working in 'best battery performance' rather than 'best performance' mode (to use my laptop's setting selections)? 194.221.133.226 (talk) 08:07, 22 July 2008 (UTC)

Not knowing exactly how much calories is used by the brain I recall there is no Save Mode for brain activity---it's just that your consciousness varies. We know now better than the Hubbard propaganda that suggested the amount of activity coincides with consciousness or even IQ. Also, the brain gets always the most blood, i.e., when your brain starves the other organs were already starving for some time. Of course I'm simplifying with this but that's the picture. --Ayacop (talk) 09:15, 22 July 2008 (UTC)

Everything you said was correct. The brain does conserve energy during times of starvation (which can include diets), it does use a substantial part of the energy your body uses, and it does use more during mentally challenging activities (like spelling, in my case). StuRat (talk) 13:49, 22 July 2008 (UTC)

Also note that the "nonessential functions" the brain shuts down are sometimes essential after all, such as when operating a vehicle or heavy machinery, where "brain fog" can be fatal. StuRat (talk) 13:53, 22 July 2008 (UTC)

See also Hypoglycemia#Neuroglycopenic_manifestations. --Mark PEA (talk) 14:06, 22 July 2008 (UTC)

I've seen a ref (can't find it now) to the effect that intense mental activity actually increases the carbs burned by the body. I wonder if thermal imaging would show the brain running hotter when doing complicated calculations or memorization, recall, puzzle solving, and such pursuits, compared to just sitting and not thinking about much in particular or in light sleep? Edison (talk) 23:57, 22 July 2008 (UTC)

Not thermal imaging, no, because blood quickly removes the excess heat generated. However, there is a process where radioactive glucose is given to the patient and the more radioactive portions of the brain show where increased brain activity uses more glucose. (I don't think I'll be personally volunteering to have my brain irradiated, however.) StuRat (talk) 07:05, 23 July 2008 (UTC)

When performing a task, more calories are used by people who are less trained or have lower IQs, implying conscious thinking consumes energy. [4] As for energy save mode, metabolism is reduced during starvation, according to this extremely detailed study. --Bowlhover (talk) 08:31, 24 July 2008 (UTC)

I'd conclude from that that learning is what uses the most energy, specifically forming new neural pathways. The "experts" already know how to perform the task, so don't learn anything new by doing so. Those with lower IQ's may learn it, but soon forget and must therefore relearn each time. StuRat (talk) 13:37, 24 July 2008 (UTC)

Doesn't follow. Consider the opposite scenario where pathbuilding cost is much lower than the cost to travel even one 'hop' or a section of path, but costs nonzero time. It need not be that the pathbuilding is expensive: just that the routes *before the direct paths exist* involve more hops, and so are inefficient. DewiMorgan (talk) 16:56, 26 July 2008 (UTC)

Boiling Water at a different tempreture to its boiling point.

Is it possible to boil water at a tempreture of 60 degrees Celcius and if so,why?137.158.152.207 (talk) 08:43, 22 July 2008 (UTC) kirsty

Since I assume this is a homework question, read your textbook or handouts, and if necessary, Boiling_point#Saturation temperature and pressure. If you still don't understand, feel free to ask again and we'll explain. --Bowlhover (talk) 08:55, 22 July 2008 (UTC)

A look at phase diagrams may also be of interest. — Lomn 13:11, 22 July 2008 (UTC)

You can even boil water at room temp by putting it in a sealed syringe and pulling back on the plunger to lower the pressure. StuRat (talk) 13:44, 22 July 2008 (UTC)

I've never seen this demonstration, but I just found this video. It's pretty cool. [5] —Preceding unsigned comment added by APL (talk • contribs) 16:54, 22 July 2008 (UTC)

Is it definitely boiling, as opposed to just having air forced through it (from around the plunger, into the syringe)? --Allen (talk) 17:08, 22 July 2008 (UTC)

Never mind; apparently this works when the syringe is pointed down as well [6]. --Allen (talk) 17:19, 22 July 2008 (UTC)

Also look at how much gas volume is present when the plunger is pushed back in compared to how much gas bubbled when it was pulled back. DMacks (talk) 18:24, 22 July 2008 (UTC)

Good point. So why doesn't the water bubble due to air being forced through it? --Allen (talk) 03:37, 23 July 2008 (UTC)

Er? My observation suggests that air isn't being forced through it (i.e., it's actually boiling). DMacks (talk) 03:54, 23 July 2008 (UTC)

I'm just figuring that a good deal of air has to be getting around the syringe; otherwise they'd be creating a near-perfect vacuum in there, which I'd think one wouldn't be able to pull against so easily. --Allen (talk) 11:49, 23 July 2008 (UTC)

Normal air pressure is around 15 PSI, which would mean only 15 pounds to pull a one inch cross-sectional area syringe (a huge syringe) against a pure vacuum. StuRat (talk) 15:13, 23 July 2008 (UTC)

When the syringe barrel is pushed up, look at how much/little gas space there is: that's exactly how much air has leaked in during the experiment. Note that you cannot (even with a high-vacuum pump) get anything close to a "perfect" vacuum here. You will always have the vapor pressure of the water: as you try to reduce the pressure below the vapor pressure of water, the water vaporizes to keep the pressure at that point. That's exactly what boiling is:) DMacks (talk) 12:51, 23 July 2008 (UTC)

Good points again, both of you. Thanks. --Allen (talk) 15:39, 23 July 2008 (UTC)

You can apply a vacuum pump to a properly constructed container with room temperature water in it and the water boils when the pressure gets low enough. You can even make ice this way. But the oil will need to be changed afterwards. In the 1960's a man testing a prototype American space suit was exposed to near-vacuum in a vacuum chamber when an air hose came loose, and he said the last thing he remembered before blacking out was the strange sensation of the saliva on his tongue boiling. He survived when the chamber was quickly repressurized.(edited to re-add the text the browser windo ate. It oftern happens that I insert text, everything looks fine in the edit window, then when I hit save some of it disappears). Edison (talk) 20:29, 22 July 2008 (UTC)

Edison, your edit seems to be missing some text but I know what your talking about, it can be found in the articleHuman_adaptation_to_space#Unprotected effects. Jdrewitt (talk) 21:50, 22 July 2008 (UTC)

Yes, the article you cited describes the incident. I recently saw a documentary on TV which had the original film or video and audio of the incident. Edison (talk) 23:55, 22 July 2008 (UTC)

We got to see a demonstration of this in my chemistry class. He put a bell jar over a beaker of water and pumped out the air, and the water boiled. It wasn't as cool as the burning methane bubbles, but it was pretty cool. Black Carrot (talk) 05:34, 24 July 2008 (UTC)

Named storm in Atlantic crossing over into Pacific

I am wondering if (a) has the following happened, and (b) if so, how the storm naming has been handled.

Presume a named Tropical Storm or Hurricane has formed in the Atlantic Ocean and is either large enough in either strength or size to cross over the relatively small land mass of Central America and either stay a TS or re-form back into a TS once in the waters of the Pacific Ocean -- would it be given a new name? Thanks. --Jordan 1972 (talk) 18:11, 22 July 2008 (UTC)

Hi. Yes, it has happened. See List of Atlantic hurricanes#Atlantic-Eastern Pacific crossover storms. Sometimes they lose their old name if the old system dissapated, as with Hurricane Dean or Tropical Storm Arthur (2008), but sometimes hyphenation is the answer, for example Hurricane Fifi-Orlene. Thanks. ~AH1^(TCU) 18:29, 22 July 2008 (UTC)

Some say that Hurricane Hattie and Tropical Storms Simone, and Inga were all the same storm that moved from the Atlantic to the Pacific and back to the Atlantic. [7] In 1961 they didn't have the fancy sateliite images that we would like to confirm it, but it is possible. Our article on Hurricane Hattie-Simone is rather confused about the issue, and there don't seem to be any reliable sources confirming that the storm maintained its circulation. The WP:WikiProject Tropical cyclones is actually discussing that storm right now. Plasticup ^T/C 19:42, 24 July 2008 (UTC)

Aphasia only when alone? Or just refusing to talk to oneself?

If a person wants to say a sentence, but can't get the words out, when alone, but can when there is another person providing a stimulus, would this be aphasia, or would it just be a mental block against talking to oneself? In looking at the article on aphasia, it sounds like the disorder is mroe than just the ability to get words out, but on the other hand, intrapersonal communication implies that everyone talks to themselves - or at least has the physical capability to.

So, I guess what I'm getting at is, is aphasia only consistent speechlessness? Or, does there have to be more of a general language problem? Is it possible for a person to develop such a persistent mental block agsinst talking to oneself that they can't speak unless someone else is int he room? (It's just nice to know that it is normal to talk to myself :-) 209.244.187.155 (talk) 18:34, 22 July 2008 (UTC)

According to the article, aphasia is caused by brain damage, so it likely to be consistent. There are other conditions which may be relevant - for example there are children that will only talk to close family and friends and will go completely silent in public. I don't know what that's called, though. What you describe seems to be the opposite of that. --Tango (talk) 20:23, 22 July 2008 (UTC)

Reply to Tango: Selective mutism. --Mark PEA (talk) 23:07, 22 July 2008 (UTC)

Sorry, but we cannot speculate about medical diagnoses here at the Reference Desk, per the guidelines posted at the top of the page. You might wish to discuss this with your physician. Edison (talk) 20:25, 22 July 2008 (UTC)

Find me Alexander Selkirk's physician and I'll ask him. :-) I had read where this real life castaway, who inspired somewhat the story of Robinson Crusoe, had mostly lost the ability to speak after being stranded for 4 years with no human companionship, and wondered if this would have been possible because he simply didn't exercise that while alone. That's where this question came from.

Although, ironically, I found the man's name in the Crusoe article, and read that a fall from a cliff is mentioned (fromt he talk section), which implies if he did lose it, it may have been because of a physical injury after all, and not because of some inhibition agains ttalking to himself that had grown into an inhibition agaisnt speaking, period, unless in the presence of others.

I thought my query would be a little less convoluted without throwing the stuff about Selkirk in there, and Crusoe - especially since I mention I can talk to myself so don't have this problem - but I guess not. And who knows, maybe what I read about Selkirk having lost the ability to speak was wrong, anyway.

Though, now that I look at your answer, Edison, you probably *did* understand it wasn't my problem and that I can talk to myselrf (and do). And, I can understand, perhaps it is best you don't speculate on anyone's medical condition. I imagine the condition of someone 300 years ago would lead to a much higher degree of speculation than you'd ever want to do Wikipedia, even without the legal ramifications. :-)

(And, I should add, now looking at the article on Selkirk that is cited, what I'd heard about his losing his ability to talk may have been quite incorrect anyway.)209.244.30.221 (talk) 21:18, 22 July 2008 (UTC)

Rodent identification

I'm trying to figure out what rodent I just saw in our garage. It was likely a chipmunk, but it looked too large to be so (though the light was off, so it's difficult to tell). Does anyone know how I can find out what rodent species are native to Manitoba? 24.76.161.28 (talk) 19:39, 22 July 2008 (UTC)

http://canadianbiodiversity.mcgill.ca/english/species/mammals/rodentia.htm is a list of rodents found in Canada. Note that clicking on the name of a species usually gives you its distribution map. --Bowlhover (talk) 20:36, 22 July 2008 (UTC)

Heat and tiredness

Why does hot weather and high humidity always tire me out and make me irratable? —Preceding unsigned comment added by 79.76.157.37 (talk) 23:34, 22 July 2008 (UTC)

See Humidity#Effects on human body. PrimeHunter (talk) 23:46, 22 July 2008 (UTC)

I believe this is a protective mechanism. Your body detects that it's overheating, and lowers your metabolic rate to limit heat production to fight this. Lowering your metabolic rate will result in you being sluggish and tired. StuRat (talk) 06:52, 23 July 2008 (UTC)

Shouldn't it rather sweat than make tired? --Ayacop (talk) 16:14, 23 July 2008 (UTC)

Hi. No, that doesn't work when it's humid, as shown by the above link. Sweating usually cools you down by evaporating, but when it's that humid, the sweat can't eveporate, so it just sits there, making you feel hotter. Hope this helps. Thanks. ~AH1^(TCU) 16:34, 23 July 2008 (UTC)

You'll also sweat. Our bodies have multiple cooling methods. In an "emergency situation", it will use every mechanism at it's disposal to cool you down quickly. StuRat (talk) 01:26, 24 July 2008 (UTC)

July 23

Theory of subspace model

Search for help on theory of subspace model!

'System identification: theory for the user'(2nd edition, 1999) had introduced such theory about subspace model in section 10.4. However, I cannot get that book. If possiable, please help me in finding some materials about that. Your kind help will be appreciated sincerely. —Preceding unsigned comment added by Cjt1982818 (talk • contribs) 01:44, 23 July 2008 (UTC)

In the case of system identification, I'm guessing that a "subspace model" would refer to Dimensionality reduction. One example is Principal components analysis which projects experimental data onto a subspace of the "parameter space", making for simpler analysis. EverGreg (talk) 09:43, 23 July 2008 (UTC)

hamburger

Ground beef is called hamburger. What do you call ground horse meat, ground ham and all of the other ground meats? -- adaptron (talk) 04:19, 23 July 2008 (UTC)

Just ground meat or mince (outside North America). 81.174.226.229 (talk) 09:03, 23 July 2008 (UTC)

Isn't 'hamburger something to do with the German city/town of Hamburg? If I wasn't at work i'd research and get a definitive answer - as it stands I hope one of the two articles references it... 194.221.133.226 (talk) 09:28, 23 July 2008 (UTC)

Just checked the Hamburg article - it is to do with the place - see the 'cuisine' section (http://en.wikipedia.org/wiki/Hamburg#Cuisine) 194.221.133.226 (talk) 09:29, 23 July 2008 (UTC)

This is also mentioned in the article Hamburger, which you have already linked to, under Definition. Jdrewitt (talk) 11:59, 23 July 2008 (UTC)

Not everyone calls ground beef hamburger, though, as it can be used for other purposes, especially meatloaf and meatballs. --Russoc4 (talk) 13:09, 23 July 2008 (UTC)

I'd go further and ask: does anyone call ground/minced beef "Hamburger"? Fribbler (talk) 13:12, 23 July 2008 (UTC)

My mom calls it "hamburg" (Western Pennsylvania, USA). -- Coneslayer (talk) 13:13, 23 July 2008 (UTC)

I've never even known it could be a synonym. A hamburger for me is most likely the premade burger or perhaps the pattie but defintely not ground/mince meat. BTW, is ground ham actually common? Ground pork is but I've never heard of ground ham. Nil Einne (talk) 13:38, 23 July 2008 (UTC)

Presumably the people who named Hamburger Helper? AlmostReadytoFly (talk) 13:50, 23 July 2008 (UTC)

I believe they call it either hamburg or hamburger in Maine. Not in NY/NJ/CT though.--Russoc4 (talk) 13:56, 23 July 2008 (UTC)

"Hamburger" has no etymological connection to "ham". It was originally a "hamburger steak", i.e. a steak made the way people in Hamburg make them. Similarly a "frankfurter" is a sausage of the kind they make in Frankfurt. I suppose "hamburger" can then by extension mean meat sold as suitable for making a hamburger. Minced (ground) pork is called "sausagemeat" in the UK; if you wanted to make sausages at home it would be the thing to choose. Itsmejudith (talk) 14:00, 23 July 2008 (UTC)

Pork mince is available labelled as such in every supermarket I've seen. Sausagemeat contains other ingredients such as rusk. It's not easy to link products, but you can browse here to see. AlmostReadytoFly (talk) 14:08, 23 July 2008 (UTC)

"Two great nations separated by a common language?" It's hard to imagine sausage made of rusk. On the U.S. side of the pond it is "ground beef" in the store, and might become a hamburger, meatloaf, meatballs, sloppy joe, tacos, or lasagna. One would not list "hamburger" as an ingredient in any of these foods. The repeated findings of E coli or other pathogens in groundbeef made in giant meat processing plants, where intestine contents from one processing mishap may be mixed in with hundreds of other cows in a given serving of ground beef, makes me avoid steak tartare, which was quite tasty back in the day of beef being locally ground. Ive never heard "minced" applied to meat. "Mincemeat" in the U.S usually contains no meat, except perhaps for fat. Edison (talk) 16:20, 23 July 2008 (UTC)

Mincemeat in the UK no longer contains meat either (though it used to), but minced meat does since mincing = grinding AlmostReadytoFly (talk) 07:54, 24 July 2008 (UTC)

N.B. In case it wasn't obvious, I was refering to adaptron who asked about ground ham whice I've never heard of before Nil Einne (talk) 17:11, 23 July 2008 (UTC)

Unindent. Google finds thousands of entries for "ground ham". The few I checked were recipes using both ground ham and ground pork. Perhaps people grind their own ham at home - I can't remember ever seeing ground ham in the meat section. Although there is deviled ham. Rmhermen (talk) 18:05, 23 July 2008 (UTC)

Apparently it's used industrially [8] Nil Einne (talk) 18:46, 23 July 2008 (UTC)

And in ham salad (ground at home, in my experience). -- Coneslayer (talk) 19:02, 23 July 2008 (UTC)

Actually, AlmostReadyToFly, to me mincing certainly does not = grinding. In my idiolect, 'grinding' is pulverisation by crushing or friction, and not by cutting or tearing; something squashy like meat cannot be ground. I am of course aware that Americans talk of 'ground beef' but to me it can only be 'minced'. --ColinFine (talk) 18:52, 26 July 2008 (UTC)

Ground meat is "pulverized by crushing" through the use of a meat grinder. Mincing meat using some cutting instrument such as a food processor has a different result. Grinding is superior to mincing for most culinary applications such as making hamburger, meatballs, or meatloaf. —D. Monack ^talk 07:42, 28 July 2008 (UTC)

science

What is the graph called that has all the scientific symbols on it?— —Preceding unsigned comment added by 203.202.70.133 (talk) 05:12, 23 July 2008 (UTC)

You'll have to be much more specific than that. What do the scientific symbols look like? Can you post a sample of the graph? What's the title? Where did you see it? --Bowlhover (talk) 05:43, 23 July 2008 (UTC)

(Winging it here) Periodic table? --Kurt Shaped Box (talk) 06:55, 23 July 2008 (UTC)

That was gonna be my guess also. I don't know why, but many of my students call any sort of organized display of information a "graph". DMacks (talk) 07:04, 23 July 2008 (UTC)

They're certainly graphics. I imagine many people either confuse the two words or treat them as synonyms. -- BenRG (talk) 10:51, 23 July 2008 (UTC)

Technically they're right to call it a graph (ie not incorrect).. if the answer was the periodic table..?87.102.86.73 (talk) 12:18, 23 July 2008 (UTC)

I suppose it's a bit like how if all you knew were horses, you'd refer to a Frisian cow as 'a fat, funny-shaped, black and white horse'. Or something. :) --Kurt Shaped Box (talk) 18:08, 23 July 2008 (UTC)

repetitive behavior

Is there any disorder besides autism or other disorders in the autism spectrum (like Asperger syndrome where the affected person exhibits a pattern of repetitive behavior, specially repetitive verbal behavior? —Preceding unsigned comment added by Mr.K. (talk • contribs) 09:30, 23 July 2008 (UTC)

OCD? Usually not verbal, though. -- Aeluwas (talk) 09:34, 23 July 2008 (UTC)

(ec) Schizophrenia can involve stereotyped speech patterns, as can Tourette Syndrome. Also see Echolalia for one specific type of verbal repetition. 12:53, 23 July 2008 (UTC)

Tourette syndrome? -- Coneslayer (talk) 12:51, 23 July 2008 (UTC)

Then there are those who repeatedly ask the same questions here, I wonder what medical disorder they have ? StuRat (talk) 15:06, 23 July 2008 (UTC)

(from Forgetfulness#Organic_causes - Alzheimer's, Amnesia, Dementia ?)87.102.86.73 (talk) 15:57, 23 July 2008 (UTC)

Concusion, and if you want to call it a condition, Nagging. --Shaggorama (talk) 06:23, 24 July 2008 (UTC)

Methotrexate in use for RA

Can it please be explained to me why Methotrexate is used alongside Folic Acid. My boyfriend has been prescribed 5mg of Methotrexate once per week, with 5mg of Folice Acid every other day of the week. How does the Folic Acid react with Methotrexate. What exactly does it do to help RA? thank you

Dawn Gardiner 88.109.199.248 (talk) 09:46, 23 July 2008 (UTC)

For those (like me) who couldn't guess what "RA" might be, it's rheumatoid arthritis. --Sean 13:07, 23 July 2008 (UTC)

Methotrexate is an antifolate drug. (I recommend reading these links) Reducing the amount of available folic acid is beneficial to patients with autoimmune diseases such as RA. However, we don't want to eliminate all folic acid as it is needed for cell division. So a supplement is given. This is a bit of a rushed introduction to a relatively complex topic but I hope it helps! Fribbler (talk) 14:06, 23 July 2008 (UTC)

Folic acid (or folinic acid) is commonly given with methotrexate to decrease methotrexate's gastrointestinal side effects. As Fribbler described above, one of methotrexate's actions is to impair the synthesis of folic acid, an important vitamin in DNA synthesis and cell division. The gastrointestinal side effects presumably result from methotrexate inhibiting cell division in the GI system, leading to irritation, burning, etc. Adding folic acid back into the system restores the ability of the stomach and intestines to regenerate cells efficiently, thus improving the side effect profile of the drug. --David Iberri (talk) 02:50, 26 July 2008 (UTC)

mostly water

Since the human body is made mostly of water, is it possible for one to melt, and how would this be achieved? 'cause I know this one girl and I swear when ever she phones me or touches me I start to melt. —Preceding unsigned comment added by 193.115.175.247 (talk) 12:28, 23 July 2008 (UTC)

You know that ice (solid water) melts at 0 °C and that your body is much warmer than that. Therefore, any water in your body is already "melted". Physically anyway:) DMacks (talk) 12:48, 23 July 2008 (UTC)

(Insert voice of favorite American sitcom dad.) Awww, how cute. You're not melting; I think you've got puppy love. Known in American slang as a "crush" nowadays. Probably among your first; or, at least you feel different about this girl than any other you've felt; hence you're unsure what that feeling of "melting" is.

While we can't give medical advice, I will say this - if my theory is correct, then the first thing you should do is ask how she feels when she talks to you. It's okay if one feels something and the other doesn't right away, because those feelings aren't what's going to last; feelings come and go. Keep maintaining the friendship, and remember that that friendship should be the key to your relationship. Find out what she likes, and do fun stuff together. Maybe it'll last,a nd maybe it won't. But, I know one thing. That feeling can be pretty intense. But, it's fun, too. Just don't go too fast with any girl, okay? The key to a girl you like is, would you still like her if you were both really old, bald, and incontinent. but, it's okay to have fun and think about this situation now; because those feelings are real. It's part of gorwing up.

Boy, that *did* sound like a sitcom, huh? :-) Yes, that's the way I talk, too.

Oh, and to the original question, for something to melt it has to be at a very high heating point. So, for skin and bones to literally melt, you'd have to be in a blast furnace or something. Yes, the body is mostly water, but the part that isn't is very solid and rugged.Somebody or his brother (talk) 12:56, 23 July 2008 (UTC)

P.S.: Feel free to show her this response if you struggle for a topic of conversation, or how to approach your puppy love. It may help you talk about and emphasize the friendship part and also be good for a laugh, perhaps. Good luck.Somebody or his brother (talk) 13:20, 23 July 2008 (UTC)

Rather, the proteins will denaturate on heating which won't make you very attractive. --Ayacop (talk) 16:09, 23 July 2008 (UTC)

The fat will melt. Wick effect has some interesting if potentially grusome discussion of the potential effects of such Nil Einne (talk) 16:47, 23 July 2008 (UTC)

It might be best to avoid being quite so poetic until after the first date - this isn't the renaissance, you might just scare her off! If the first date goes well, though, then go for it! --Tango (talk) 21:35, 23 July 2008 (UTC)

The human body is made mostly of water in the same general way as a water balloon is. Ever seen a water balloon melt? — DanielLC 17:10, 23 July 2008 (UTC)

"When your heart's on fire, you must realize, smoke gets in your eyes." Itsmejudith (talk) 17:11, 23 July 2008 (UTC)

Yes. Just this morning I took a water balloon out from the freezer and watched it melt. Nil Einne (talk) 18:44, 23 July 2008 (UTC)

Wht did you put a water balloon into your freezer, may I ask? --Bowlhover (talk) 01:49, 24 July 2008 (UTC)

Nil, clearly that was an ice balloon that melted into a water balloon. :) — Scientizzle 18:50, 23 July 2008 (UTC)

By the way, when all the water is removed, the human body turns into a cuboctahedron made of some sort of crumbly foam rubber or something. Then the aliens take over your ship and try to fly it back to their own galaxy. --Trovatore (talk) 02:01, 24 July 2008 (UTC)

Not so! You turn into a small pile of white powder, but adding water will make you OK again. And I have a reference to prove it! [9] 17:31, 26 July 2008 (UTC) —Preceding unsigned comment added by DewiMorgan (talk • contribs)

When in doubt, always seduce the best-looking alien. And speak ... quickly with ... odd pauses. Franamax (talk) 17:44, 26 July 2008 (UTC)

biochar

Is there a Wikipedia article or other online reference that shows the yield of biochar, bio-oil and syngas from various types of municipal organic waste such as sludge and bio-mass? —Preceding unsigned comment added by Adaptron (talk • contribs) 15:59, 23 July 2008 (UTC)

The relevant articles are gasification and pyrolysis though I can't find any figures there - it probably also depends on the exact process used - which you could be more specific about.

I'd recommend trying searching for 'waste gasification' or 'waste pyrolysis' as a start.87.102.86.73 (talk) 16:44, 23 July 2008 (UTC)

Temperature scales

What temperature scales other than Fahrenheit were in common use in what countries before adoption of celsius? --Random832 (contribs) 16:10, 23 July 2008 (UTC)

The Réaumur scale. Itsmejudith (talk) 16:17, 23 July 2008 (UTC)

I guess this isn't what you mean but Centigrade. You might also be interested in Temperature conversion Nil Einne (talk) 16:41, 23 July 2008 (UTC)

No temperature scale was in widespread use before the seventeenth century, but according to the thermometer article:

"In 1665 Christian Huygens suggested using the melting and boiling points of water as standards, and in 1694 Carlo Renaldini proposed using them as fixed points on a universal scale. In 1701 Isaac Newton proposed a scale of 12 degrees between the melting point of ice and body temperature. Finally in 1724 Daniel Gabriel Fahrenheit produced a temperature scale which now (slightly adjusted) bears his name."

A more detailed history can be found here. As for the countries that adopted these scales, the Delisle scale was used in Russia from 1738 on and the Reaumur scale was widely used in Europe, particularly in France, Germany, and Russia. --Bowlhover (talk) 22:12, 23 July 2008 (UTC)

physiology of respiratory system

How long humans can stay under water holding their breath? How long perl-collectors in Tahiti can hold their breath under water? What is the world record of holding the breath? Dimitar (medical student) —Preceding unsigned comment added by Velimir14 (talk • contribs) 16:40, 23 July 2008 (UTC)

According to this article the world record is 10 minutes 12 seconds. -- Mad031683 (talk) 17:10, 23 July 2008 (UTC)

Hi. Remember however, that techniques such as hyperventilation before diving can cause drowning, see shallow water blackout. Thanks. ~AH1^(TCU) 22:19, 23 July 2008 (UTC)

According to this Reuters article, the record for underwater breath holding, set by David Blaine, is 17 minutes and 4 seconds. The average time is 1 minute, according to http://www.news.harvard.edu/gazette/2005/10.13/01-divers.html. --Bowlhover (talk) 01:40, 24 July 2008 (UTC)

Water turns cloudy after boiling

Please help solve this mystery: water from a water filter turns slightly cloudy after boiling. The water is somewhat high in dissolved minerals. The filter is supposed to reduce a variety contaminants in the water, including lead. Before boiling, the filtered water is clear.

(Edited to add:) A simple experiment reveals that water from the source turns cloudy after boiling, filtered or not. —Preceding unsigned comment added by 96.245.76.192 (talk) 17:44, 23 July 2008 (UTC)

Could this not merely be lots and lots of tiny air bubbles? I know that the water from my hot tap sometimes comes out milky-white due to this. If I put some in a glass and leave it to settle, I can see the bubbles (quite slowly) rising to the top, with the water below clearing. --Kurt Shaped Box (talk) 18:44, 23 July 2008 (UTC)

I'm aware of that possibility, but this is not a case of it. Water from the tap is initially clear. It only turns slightly cloudy after boiling. Giving things time to settle doesn't change the cloudiness. --96.245.76.192 (talk) 23:31, 23 July 2008 (UTC)

Could it be water hardness coming out as a fine suspension after boiling - some sorts of hard water do this. Also are you sure it's not your heating device - have you tried boiling in a different thing - eg a very clean pan or dish?87.102.86.73 (talk) 19:05, 23 July 2008 (UTC)

Not likely to be the "heating device"—the cloudiness is observed after the water has been boiled in a glass kettle, which seems clean. Your hardness explanation seems more plausible. --96.245.76.192 (talk) 23:31, 23 July 2008 (UTC)

Sounds like carbonate hardness. If you have high levels of carbonate minerals in your water, boiling the water causes a portion of them to precipitate. My guess is that your water comes from a limestone aquifer. -- 128.104.112.147 (talk) 21:14, 23 July 2008 (UTC)

That seems plausible. So the cloudiness is dissolved calcium bicarbonate turning into calcium carbonate? --96.245.76.192 (talk) 23:31, 23 July 2008 (UTC)

Yes exactly, and if you live in a hard water area it's probably the answer. Wait a minute - your filter should remove this I think?87.102.86.73 (talk) 00:07, 24 July 2008 (UTC)

Salmons - polyphyletic or paraphyletic?

Given that the common name "salmon" does not correspond exactly with any taxonomical group, and that some "salmon" species are closer to trouts than to other "salmons", should the term "salmon" be considered as:

• a) a paraphyletic grouping
• b) a polyphiletic grouping
• c) a vernacular name with no corresponding taxonomical group (or groups)

Which of these would fit best? Thanks. Leptictidium (mt) 19:32, 23 July 2008 (UTC)

I believe that C is correct. "A" might be correct if it was determined that the common ancestor to the group was a salmon and that trout form a monophyetic group that could be pruned from the tree (see paraphyly). "B" would only be correct if the term salmon included multiple monophyletic groups separated by other groups and I don't think that's the case (hence my qualifier at the beginning). Matt Deres (talk) 20:01, 23 July 2008 (UTC)

[edit conflict] I'd say C. To determine whether the group was paraphyletic or polyphyletic, you'd have to know whether the most recent common ancestor of all salmon was called a salmon. My guess would be that we don't know exactly what fish that was, and that we certainly haven't thought to decide whether it was a "salmon" or a "trout". --Allen (talk) 20:08, 23 July 2008 (UTC)

I don't think that really makes sense <quote> It was shown, however, that the inclusion of ancestors in the classification leads to unavoidable logical inconsistencies</quote>

You should ignore that inconsistency.87.102.86.73 (talk) 20:22, 23 July 2008 (UTC)

(edit conflict) A:

I'd assume 'A' in the absense of contrary data.

In the absence of contrary data I'd assume salmon ie Salmonidae subfamily Salmoninae to be paraphyletic

Assuming all 'salmon' (Salmonidae) Salmoninae have a common ancestor (why not?) (additional - common ancestor should not have any descendants outside salmoninae prefereably) then the salmon are paraphyletic, if you describe a group 'salmon' minus trout etc then that group would be monophyletic - but there is no name for such a grouping currently.

In phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all the descendants of that ancestor.

B is wrong because all salmon are found in the same subfamily - if there were 'salmon' in a different family as well then B would be right.

C is wrong because all salmon are found in the group Salmoninae therefor there is a corresponding taxo-group (that is fairly narrow in its spread). —Preceding unsigned comment added by 87.102.86.73 (talk) 20:19, 23 July 2008 (UTC)

CORRECTION B could be right as well if the subfamilies Oncorhynchus and Salmo each have a common ancestor, and there is a common ancestor of the common ancestors which has descendants outside these two subfamilies..

How are we supposed to know? is there any 'educational material' associated with this question which may contain answers to this problem?

The question is unanswerable as is.87.102.86.73 (talk) 20:45, 23 July 2008 (UTC)

I don't follow you. What doesn't make sense? What are you quoting from? Why would I want to ignore an inconsistency? What do you mean by asking whether two groups have a common ancestor? (Any two cellular life forms on Earth have a common ancestor.) It seems like you might be assuming that "salmon" = Salmonidae, but I think the OP was referring to fish called salmon, not all members of Salmonidae. --Allen (talk) 22:12, 23 July 2008 (UTC)

Oops sorry - mistake I've corrected that (see above)

As to the other bit - what I'm saying is that the question doesn't give enough information for us to decide? even though it says

Quote: some "salmon" species are closer to trouts than to other "salmons"

I can't read enough into that to make a decision either way. I quoted from the articles Paraphyly and Paraphyly as well for the second quote. You might want to ignore an inconsistency if it's of the kind described by yourself above, since the question is not of an (possibly extinct) ancestors 'name'.

The paraphyly/polyphyly question is answer by finding the ancestors (A and B) of both groups (that's two ancestors) and seeing if those two ancestors are either

One or the other is an ancestor of the other (A of B , or , B of A), or their common ancestor (C) has no descendants (along a branch not going through A or B) that are separate from the two groups

Or that the two ancestors of the two branches of 'salmon' (A and B again) have an ancestor themselves (C) that has descendants that have evolved into a set of species going through a branch not including A or B.

Did I get that right after the correction to the name? Maybe I'm not reading enough into the statement at the beginning - if so what is it?87.102.86.73 (talk) 22:59, 23 July 2008 (UTC)

(obviously common ancestor means 'most recent common ancestor')87.102.86.73 (talk) 23:41, 23 July 2008 (UTC)

My interpretation was that the OP, by the word "salmon", meant neither Salmonidae nor Salmoninae. Rather, they just meant all those species that have the English word "salmon" in their common name. E.g. Chinook salmon would be a "salmon", while Biwa trout would be a "trout", even though they're both in the same genus of Salmoninae. That's why I said the answer was C: the common word "salmon" does not correspond to any taxonomic group. --Allen (talk) 23:48, 23 July 2008 (UTC)

I made that assumption too. I suppose it must be C then since I can't show either A or B from the info given, and it states something very similar in the question - I must have been trying to be 'too clever' - C.87.102.86.73 (talk) 07:17, 24 July 2008 (UTC)

I still don't see how C follows though: "Salmon" could have (from the information given) corresponded to say, a family of 'salmon' and another sub-family of 'salmon' (not closely related or necessarily in the same order etc),but with a 'sister' group consisting of 'trout' in the same family. This would have made C wrong as it did say 'corresponding group or groups'. Thank god it's not my exam.!87.102.86.73 (talk) 07:22, 24 July 2008 (UTC)

As far as I can see you'd need a time machine to answer this, or more information.87.102.86.73 (talk) 23:43, 23 July 2008 (UTC)

Nuclear Physics

Kindly please answer me why don't Bosons obey the 'Pauli Exclusion Principle'?Asim Chatterjee (talk) 20:04, 23 July 2008 (UTC)

Did you read the Pauli Exclusion Principle article? DMacks (talk) 20:08, 23 July 2008 (UTC)

Yes —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 20:10, 23 July 2008 (UTC)

Did its many paragraphs explaining the answer to your question in several different ways not suffice? DMacks (talk) 20:14, 23 July 2008 (UTC)

HEY! It didn't explain why - It just said they don't obey..87.102.86.73 (talk) 20:25, 23 July 2008 (UTC)

Sorry but it did not.I'll be immensely thankful to anyone who would like explain to me the answer in brief. —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 20:18, 23 July 2008 (UTC)

It is not perfectly explained therein. —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 20:51, 23 July 2008 (UTC)

In brief, the exclusion principle is a result of particles having anti-symmetric wave-functions. That means only fermions, not bosons, are subject to it.

Let's look at the PEP article: "According to the spin-statistics theorem, particles with integer spin occupy symmetric quantum states, and particles with half-integer spin occupy antisymmetric states". The math in the "Connection to quantum state symmetry" section starts from the antisymmetry property and leads to exclusion. You asked about bosons, which by definition are integer-spin particles, and therefore have symmetric wavefunctions. I'll try the same math, but with a symmetric wave-function: if there is symmetry, A(x,y) = A(y,x), which does not lead to a conclusion of A(x,x)=0. Therefore, there can be a non-zero chance that two such particles could both be in state x. DMacks (talk) 20:56, 23 July 2008 (UTC)

So why are The wave functions of a system of identical half-integer-spin .. (are)... anti-symmetric under exchange - what does this mean, are the 'particles' (fermions) distinguishable then? Is there a simple way to understand this?87.102.86.73 (talk) 21:05, 23 July 2008 (UTC) fuck it - i remembered I don't care87.102.86.73 (talk) 21:09, 23 July 2008 (UTC)

I'm not a quantum physicist, but I'll give you a stab at it, given my The Elegant Universe/A Brief History of Time/etc. inspired understanding. (With the hope that more knowledgeable people will correct/expand upon my misstatements.) The key point is that, if they have the same quantum numbers, particles are indistinguishable. An electron is an electron is an electron, and a photon is a photon is a photon (assuming identical energy, momentum, etc.). Given this, when you do all the fancy quantum mechanical calculations you have to take into account the possibility of exchange. That is, if we have electron 'A' over here and electron 'B' over there (metaphorically speaking), we have to write all the equations such that the equations still work if we'd have electron 'B' over here and electron 'A' over there (since the electrons aren't carrying little 'A' and 'B' labels). So why does this matter? Well, since electrons are Fermions, and thus carry spin 1/2, their wavefunctions are anti-symmetrical. This means that you can't write quantum mechanical equations where two electrons have the same quantum state - if you did, you'd find out that once you include the exchange terms, the terms cancel out and your probability density goes to zero, violating a whole slew of conservation laws. Bosons, on the other hand, have symmetric wavefunctions, on account of having integer spins. This means that the probability densities don't cancel when you include all the exchange terms, leaving you with a non-zero (i.e. possible) probability density. This means that almost an infinite number of bosons can have identical quantum numbers. (The articles Bose–Einstein statistics and Fermi–Dirac statistics may help to clarify.) So the surprising result is not that Bosons don't obey the exclusion principle, but that the equations for Fermions work out such that they do. (Again, not an expert - please correct where needed.) -- 128.104.112.147 (talk) 21:09, 23 July 2008 (UTC)

Yes -you didn't explain anything - ie you didn't answer the question at all- you just restated the result, and quoted some books. That is not an explanation.

Your explanation "..the terms cancel out and your probability density goes to zero..." may well be true when the two particles have spin +1/2 and -1/2 but what about the same situation with particles spin +1 and -1 ... as far as I can see the situation is the same.. maybe there is an explanation for this?87.102.86.73 (talk) —Preceding undated comment was added at 21:18, 23 July 2008 (UTC)

So what do I read to find out why W(x,y)=-W(y,x) (W represents wavefunction?) for fermions (I see that this can explain the exclusion principle).87.102.86.73 (talk) 21:37, 23 July 2008 (UTC)

That's the definition of antisymmetry. The spin statistics theorem article is pretty technical, but it links this site that might be more understandable.

It's just a technical way of saying that the wave-function (the mathematical description of a thing) of a half-integer-spin particle is antisymmetric ("half integer spin means that the phase change for a 360 degree rotation is -1") whereas an integer-spin particle's is symmetric ("[i]nteger spin means that the phase change for a 360 degree rotation is 1").

Consider the difference between a half-wave and a full-wave of the sine function: going from the start to the end of each of these shapes begins at zero and ends at zero and both start out by going "up" (increasing y values). However, one comes back to zero by going down whereas the other comes back to zero by going up. You wind up back where you started, but in one case you're now there going the same way you started and the other you're now going in the opposite direction from how you started. Thus, the symmetry of these two cases is different. These two cases are similar to integer vs half-integer spins: the number of half-waves corresponding to the particle.

Now, if two things are symmetric, you can exchange them easily, like the you and your reflection in a mirror (you and your reflection could swap places and nobody could detect that). If two things are anti-symmetric, the mirror image is not the same (it's the opposite, like a trick mirror or a simple microscope). You and the image are now distinguishable because you go in opposite ways (move a microscope slide to the left, and you see the image through the eyepiece move right, etc.).

Two things that are antisymmetric are always distinguishable (they never exist in completely the same state) because something about them is noticeably different. Two things that are completely the not distinguishable are symmetric (could be secretly swapped for one another).

So there we have it: antisymmetry implies distinguishability, which is the Pauli Exclusion Principle. Multiple bosons indeed can exist in identical states (Bose–Einstein condensates). DMacks (talk) 21:40, 23 July 2008 (UTC)

When you quote "..half integer spin means that the phase change for a 360 degree rotation is -1 .. [i]nteger spin means that the phase change for a 360 degree rotation is 1..." is that any more than restatement of

W(x,y)=-W(y,x) for half integer spin

W(x,y)=W(y,x) for integer spin

?

Also "360 rotation" - what is that - is it another way of saying swapping, or is there more to it? If so where can I read about the properties of things that change on undergoing a "360 rotation" and why they do it. Specifically those whose 'phase' changes sign upon 360 rotation (since the other seems trivial)? 87.102.86.73 (talk) 22:02, 23 July 2008 (UTC)

I thank you both whole-heartedly for helping me.Dmacks, I'll be ever grateful to you for answering me.Now it does not appear to me tough indeed to find out the reason.Thank you once again.117.201.97.128 (talk) 05:54, 24 July 2008 (UTC)

Thanks to yuu both.Both of you have done an immense favour to me.117.201.97.128 (talk) 05:56, 24 July 2008 (UTC)

is cortisone synthetic cortisol?

Is cortisone a patented form of cortisol? I understand the drug companies pushed cortisone because of that, is that true? Thanks Mathityahu (talk) 20:08, 23 July 2008 (UTC)

No. see cortisone and cortisol - the chemical structures and formulae are different.87.102.86.73 (talk) 20:28, 23 July 2008 (UTC)

I assume by 'patented' you mean 'trade name for' - perhaps you didn't - if so please expand.87.102.86.73 (talk) 20:29, 23 July 2008 (UTC)

You may be confusing cortisone with hydrocortisone; the latter is the name commonly given to synthetic cortisol. --David Iberri (talk) 02:40, 26 July 2008 (UTC)

July 24

Arctic flora?

Is rock samphire found anywhere in the Canadian Arctic, e.g. Nunavut?

Also, is there an English umbrella term or descriptor for plants like rock samphire and purple saxifrage, i.e. plants whose roots seem to grow through rock?

--Sonjaaa (talk) 04:29, 24 July 2008 (UTC)

Here[10] talks about survival food in parts of Canada including Nunavut. Part 2, found they are "seaside plants" (somewhere said related to carrots but can't find it again). Rock samphire includes culinary uses and it was known as "Crest Marine". Some common names could turn up here[11]. Julia Rossi (talk) 06:46, 24 July 2008 (UTC)

Sunglasses

When I wear my sunglasses, I notice two interesting effects. The first is that when I look at either the sky or my laptop screen, tipping my head to the side makes it brighter or darker. I know why that is--because my lenses are polarized, only waves at a certain angle get through. The second effect, though, is a mystery. Certain screens (calculators, parking meters, some cell phones, some iPods, etc.) appear all rainbow-y and the rear window of my car appears to be covered in dark splotches (not the other windows, though). I don't see how this could be a result of the polarization (though it may be and I'm just missing something), but I don't know what other property of my sunglasses could alter light in such strange ways. Explanations? Cherry Red Toenails (talk) 05:40, 24 July 2008 (UTC)

Read Polarized light#Polarization effects in everyday life. The effect you saw in your rear window should be present in all windows except the front windshield (polarized light reveals the stress pattern in tempered glass). Perhaps you're not looking at the proper angle. --Shaggorama (talk) 06:15, 24 July 2008 (UTC)

This is somewhat off the topic, but polarization + tipping your head while looking at your laptop and the sky, made me think of Haidinger's brush. Jkasd 06:32, 24 July 2008 (UTC)

As for the screens; LCD screens use polarized light as part of how they work. See Liquid crystal display. --Random832 (contribs) 13:15, 24 July 2008 (UTC)

I know LCD screens are polarized, but why rainbows? It's like it's bending and separating the light instead of just filtering it. How does that happen? Cherry Red Toenails (talk) 06:51, 27 July 2008 (UTC)

BTW, have you noticed that if you look at a rainbow with polarized glasses at a certain angle it disappears? --Itub (talk) 17:30, 30 July 2008 (UTC)

Nano water

There is some product on the market called "nano water",claiming that it is made of "smaller water molecules" which can be more easily absorbed by human body. Well, aren't all molecules of some kind have excatly the same size? How come nano tech can change this without changing the chemical property of water?--218.103.243.132 (talk) 07:25, 24 July 2008 (UTC)

Bunk. Pure bunk. Don't even think of spending your hard-earned money even just to try it out. Have a read of this - more than you probably ever wanted to know about pseudoscientific water-related products. --Kurt Shaped Box (talk) 07:58, 24 July 2008 (UTC)

How would being more easily absorbed be beneficial anyhow? --Bowlhover (talk) 08:10, 24 July 2008 (UTC)

O₂ enriched water, tachion absorbing mouse pads, the pyramide effect and many other things are invented to earn money not to have an effect. If the water molecules would be 10% smaller than usual you would die very soon, because the folding of proteins is vitaly conected to hydrogen bridge bonds mediated by water molecules and the equilibrium constants for all reactions including this water would be significantly different. You have a similar effect if you drink heavy water upto a certain percentage no big problem, but than......--Stone (talk) 08:47, 24 July 2008 (UTC)

To be completely fair, from what I can find online, they're not saying they restructure or alter the molecules, but rather are [supposedly] breaking up "clusters" of molecules. --Random832 (contribs) 13:24, 24 July 2008 (UTC)

Nano water is one of the most shameful marketing idea. They just flush water pass through strong magnetic, neodymium type. The water will be ionized a little, which can reduce some scale problem in the hard water. Or some even believe the germs can be killed by that ions. And the ions in the water may make someone feel refreshment like some electric fan claimed the anion wind blow. But to say changing molecular shape of water is no science intelligent wording. And H2O is smallest unit of water which has been nano unit already. Always remind yourself one thing when talking about nano technology, most of them is related to solid matter, liquid may be emulsion only.......NINJAW —Preceding unsigned comment added by 124.120.205.180 (talk) 17:05, 24 July 2008 (UTC)

You may be interested in Penta Water. 81.132.215.251 (talk) 20:26, 24 July 2008 (UTC)

Can hydrogen peroxide destroy a man?

The other week someone told me of an industrial accident that one of their friends had witnessed a few years ago. Supposedly, a man at wherever this was meant to have happened was sprayed from head to toe with concentrated hydrogen peroxide from a leaky thingamajig. Within seconds, he 'simultaneously ignited, dissolved and exploded', leaving only his boots, a few unidentifiable chunks of flesh/bone and a pool of sizzling goop behind.

Tall tale, or a possible, genuine risk when handling H2O2? --Kurt Shaped Box (talk) 08:14, 24 July 2008 (UTC)

If you jump into a tank of H₂O₂ the organics are converted to CO₂ and the carbonate of the bones and all inorganic salts are oxidized but most of them are not very volatile, so you will have a layer of salts on the bttom of the container. This will take a little while to disolve the whole man, and the iron salts catalyse the destruction of H₂O₂. This is basically a good thing for a mythbusters test, because theoretically it is possible.--Stone (talk) 08:21, 24 July 2008 (UTC)

Thew youtube video Wasserstoffperoxid in Schweineblut gives a impression on how H₂O₂ reacts with the blood of a pig.--Stone (talk) 08:33, 24 July 2008 (UTC)

The hydrogen peroxide you buy in a drug store is only 3% concentration, and can still bubble when applied to a wound, so it's easy to see how 100% concentration would dissolve flesh entirely. StuRat (talk) 11:59, 24 July 2008 (UTC)

I'm skeptical about the speed of the process. Also don't forget that it's probably just the oxygen bubbling out of the H2O2 on the wound (catalyzed by substances on the wound) not the products of dissolving the body. Finally, expect bones to not react at all with H2O2. --Ayacop (talk) 14:13, 24 July 2008 (UTC)

Ayacop beat me to it. H2O2 sizzles on a wound because of the catalytic effect of hemoglobin, which is the same reason H2O2 is used in forensics to find blood. And the visible bubbles isn't any evidence of solvency as StuRat suggested, the H2O2 is just being broken down into water and oxygen gas. On unbroken skin, store concentration H2O2 does zilch. I can believe getting burns from the stuff though if a high concentration was sprayed on you: H2O2 is relatively unstable, so if a high concentration was sprayed out at a high pressure, O2 might rapidly evolve and if there was an ignition source nearby, could cause a fire. If the H2O2 was on someone, then the fire could be localized to the surface of their body. I vote for calling mythbusters. --Shaggorama (talk) 14:22, 24 July 2008 (UTC)

Not quite zilch (3% H2O2 on unbroken skin); if you get it on your skin and leave it there you're likely to get a little white spot, sort of a burn I guess you'd say, but it doesn't usually hurt. With 30% the burn looks the same, but does hurt. --Trovatore (talk) 17:58, 24 July 2008 (UTC)

I once soaked my feet in some 3% H₂0₂, and I only felt a slight tingle at first. Then a type of slow burn set in, and they were in pain for days afterwards. The stuff's a lot nastier than it would seem. StuRat (talk) 02:59, 25 July 2008 (UTC)

I agree with the above. Oxygen fires can be pretty nasty things. shoy (reactions) 16:05, 24 July 2008 (UTC)

Why would it leave his boots, but not his skin, which are both made of the same stuff? Also, anything you hear that your friend's friend saw is probably wrong. — DanielLC 15:08, 24 July 2008 (UTC)

Concentration of H2O2 in industrial application is about 35%only, there is a note that if more than 65%concentration will be dangerous for fire and explosion matter (but never found in industry). It also dosed with some kind of retarder to slow down its O2 releasing. To activate it, staffs in factory may adjust pH. U can see details of danger from website link below:

http://www.h2o2.com/intro/MSDS_35_Arkema.pdf

If someone got spraying of concentrated H2O2 (which available in the market) on him, the problems occured with him will be as below cautions:-

DANGER!CAUSES EYE BURNS. MAY CAUSE BLINDNESS.CAUSES SKIN BURNS.CAUSES RESPIRATORY TRACT BURNS.HARMFUL IF SWALLOWED.STRONG OXIDIZER.

Something, which may cause body dissolving, should be strong acid or base most likely...........NINJAW —Preceding unsigned comment added by 124.120.205.180 (talk) 16:49, 24 July 2008 (UTC)

Can someone search the MythBusters forum? When I get back to a computer with Flash I plan on submitting this. Those guys are geeky enough that they might like the Wikipedia angle. Plasticup ^T/C 17:51, 24 July 2008 (UTC)

ANNOUNCEMENT: I now have further clarification from my associate. The substance in question was apparently High test peroxide for military use and the accident occurred while the stuff was being transferred from a tanker. --Kurt Shaped Box (talk) 00:19, 25 July 2008 (UTC)

Helicopter: blades vs. turbine

Why do all helicopter (at least the ones that I have seen so far) have blades? Couldn"t we build a helicopter with a turbine in the middle? (and perhaps some other minor turbines for controlling the balance). —Preceding unsigned comment added by Mr.K. (talk • contribs) 10:32, 24 July 2008 (UTC)

Are you talking about blowing the air through the center of the helicopter instead of around the sides ? If so, that sounds like a less useful design in that the space for passengers and cargo would be reduced and in a weird hollow cylinder shape. You could also put two turbines on opposite sides, mounted on wings, to get something like the V-22 Osprey. StuRat (talk) 11:46, 24 July 2008 (UTC)

I think he means that blades vs turbine so to say V-22 Osprey vs Dornier Do 31. And he is right if you substitute the blades by a jet engine and make them turnable you get a Vertical Take-Off and Landing aircraft. I do not recognize any jet engine driven Helicopter which neglegted the posibility to turn the exhaust of the jet around to convert itself to a jet airplane.--Stone (talk) 12:22, 24 July 2008 (UTC)

Ultimately, the "why" is a matter of efficiency. As noted near the top of our helicopter article, "The lift from the rotor also allows the helicopter to hover... more efficiently than other forms of vertical takeoff and landing (VTOL) aircraft." The advantages posed by VTOL turbines do not offset this fundamental deficiency for the roles that helicopters fill. There was a related discussion about why we don't make similar aircraft designs some time ago. — Lomn 13:59, 24 July 2008 (UTC)

Lunar Landing Research Vehicle sounds like an example of what you're talking about. There are a number of problems with this arrangement, the big ones being safety (a helicopter can autorotate if the engine fails, while an LLRV can't) and fuel consumption (the LLRV can fly for ten minutes on a thousand pounds of fuel). --Carnildo (talk) 22:04, 24 July 2008 (UTC)

The efficiency problem is due to the size of the turbofans. They are naturally smaller than a big rotor, and a big rotor is more efficient. The turbofans do have advantages over rotors though. They have a higher thrust to weight ratio than a rotor of the same size. They can be vectored easily so they can turn the VTOL into a jet airplane which means much higher velocities compared to helicopters. Since the fans can be vectored, it also means greater manuverability than either a helicopter or airplane. Eliminates the exposed rotor which can accidentally strike something when landing. It means you can land in less open areas than a helicopter. You basically get the best of both airplanes and helicopters, and even some additional advantages depending on the design. But until there are some major innovatinos in energy sources, main rotors will be used because fuel efficiency is a priority. ScienceApe (talk) 19:34, 25 July 2008 (UTC)

Several dozen at least ?

how many atoms are there in the universe? —Preceding unsigned comment added by 218.186.12.11 (talk) 12:58, 24 July 2008 (UTC)

You may be interested in Observable_universe#Matter_content. -- Coneslayer (talk) 13:25, 24 July 2008 (UTC)

Hi. On the other hand, if you want to know how many elements there are in the universe, see periodic table, but note that only 94 are found to be naturally occuring, of which 10 occur only from radioactive decay, and 118 in total if you count the synthetic elements up to ununoctium, some of the higher elements have never been sucesfully produced, and more than that if the purely theoretical elements (beyond ununoctium) are counted. Thanks. ~AH1^(TCU) 18:20, 24 July 2008 (UTC)

Whew AH, thanks indeed!  ;-) -hydnjo talk 02:36, 25 July 2008 (UTC)

Seeing colours where there are none

Sometimes when I stare at objects which have a high degree of repetitiveness I will soon start to see a rainbow of sparkling colours. This quickly gives me a headache. The objects involved are almost always white. A good example would be a very fine white mesh net. Or a piece of paper with many alternating thin black on white stripes. Is there a name for this optical illusion? PvT (talk) 14:28, 24 July 2008 (UTC)

It may be related to Fechner color; that requires motion, but perhaps the natural motions of your head are enough. -- Coneslayer (talk) 14:30, 24 July 2008 (UTC)

I don't think fechner colors explains this, although i'm not sure what does. My guesses are more along the lines of lateral inhibition, in which case you should take a look at the grid illusion and mach bands articles. You might also want to read McCollough effect. Another idea I had is that you might be staring so fixedly as to effectively kill the capacity of your eyes' saccadic motion to copmensate for hyperpolarization of cone cells. --Shaggorama (talk) 15:47, 24 July 2008 (UTC)

Well one thing is for sure that figure in the top right of the McCollough effect article sure induces rainbow fireworks in my brain. It almost becomes wavelike and the aftereffect lasts quite long. PvT (talk) 19:52, 24 July 2008 (UTC)

Quasers

According to the latest developments in the field of Radioastronomy, Quasers have been discovered. But along with their discovery, a question arises in my mind. It is well-known that light emitted from them is a bit reddish in colour. There can be two possible reasons for this, namely:-\ 1)The Doppler Effect 2)The Einstein-Shift Principle But if the first concept is right, then the Quasers must be very far away. Hence they are not present in our locality. This proves 'Steady-State Theory' wrong. But if the second concept is correct, then light from Quasers appear to be reddish because of being released from very powerful gravitational fields. This on the other side proves the Steady-State Theory right. Which is the more probable cause of this event, the Doppler effect or the Einstein-Shift? —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 14:42, 24 July 2008 (UTC)

You may want to read quasar (note spelling). Their discovery is hardly a new development, and it is well-established by this point that their redshift is cosmological in origin. -- Coneslayer (talk) 14:52, 24 July 2008 (UTC)

The lack of quasars "locally" is because their formation is a less common phenomenon than other stellar processes. In any given region of space, the chance of finding a quasar is low. Superpositioned with the weak anthropic principle, it's even less likely to have intelligent-life-sustaining planets near them. I don't see how the absence of a quasar "in our locality" proves or disproves a steady-state universe hypothesis. Nimur (talk) 15:05, 24 July 2008 (UTC)

The OP is saying that the existence of a cosmological redshift is incompatible with a steady-state theory of the universe. This is true, but it's also old news, and nobody has believed in a steady-state universe for decades. But in response to your statement, note also that the peak of quasar activity was a long time ago, at redshift 2.5–3. They really are much less common in the modern era (which is synonymous with the local universe, due to the finite speed of light) than they used to be. -- Coneslayer (talk) 15:15, 24 July 2008 (UTC)

You'll have redshift in any expanding universe and you can have an expanding steady state universe, it just requires the constant creation of matter (to fill in the gaps, so to speak). The lack of nearby quasars could disprove steady state if it was due to quasars only existing in the early universe (when we look far away we see the universe as it was long ago) - the early universe being different from the current universe is the exact opposite of what steady state is all about. I'm not sure that is the case with quasars, though, although I'm sure it has been theorised at some point. --Tango (talk) 01:41, 25 July 2008 (UTC)

I took "steady state universe" to mean non-expanding, as in Einstein's universe. Apparently, that's not what it means—I apologize for mixing up the names of discredited theories. Anyway, as I wrote above, the quasar population absolutely shows time evolution; there were more of them, and they were more luminous, at earlier redshifts. This has been known for decades, and is not merely something that people have theorized about. My PhD thesis involved measuring the faint end of the QSO luminosity function at redshift 3, so this is a topic with which I have some familiarity. -- Coneslayer (talk) 02:10, 25 July 2008 (UTC)

Building projects

Are systems engineers involved in large scale building projects along with civil engineers? If so, what do they do in such projects? Clover345 (talk) 17:46, 24 July 2008 (UTC)

Ah another Systems engineering question.. The answer is yes, thought they may not call themselves/be called 'systems engineers'.

More likely is this in large/very large projects such as building the channel tunnel or making a airport terminal, but also in design of warehousing etc - in fact anywhere where the building/construction is built for a specific purpose and needs to be designed to operate efficiently when built and also when the project is complex and requires a lot of management to be done safely/on time/etc...

So they may be managers or designers or both.87.102.86.73 (talk) 18:02, 24 July 2008 (UTC)

I find it difficult to understand the concept of systems engineering. To me it seems simply to be project management, which is an already well established field. Many engineers claim they have never heard of such a field as systems engineering. Clover345 (talk) 18:47, 24 July 2008 (UTC)

No, project management (as typically intended) is quite distinct. Management is the high-level application of administrative skills to a given project. Systems engineering is better described as the high-level application of technical skills. That said, I find that it's often an appendage of another engineering discipline. SE on a large construction project is likely better filled by someone with a civil or industrial engineering background as opposed to an electrical or computer engineering background. SE on a highly electronic project would reverse the preference. In any event the systems engineer is likely to be treating many highly-technical portions of the program, themselves complex programs in their own right, as something approaching black boxes that must themselves be engineered to function together. — Lomn 19:18, 24 July 2008 (UTC)

Yes, and No. I tend to feel that 'systems engineering' is/was just a new buzzword. It does include project management, as well as ... well , basically everything else. (I bit like how 'bin men' or 'garbage collectors' are now called 'waste management logistics operatives'.) - now everyone is a systems engineer.

Oh and a systems engineer could also be a 'designer' or just a truck driver .. at the basic level getting your truck into a depot without blocking all deliveries for the rest of the day or running anyone over, or not demolishing one of the supporting structures of the delivery bay can be described as a 'successful systems engineering procedure'.. (I might be exaggerating)

You could describe 'systems engineering' as a field of bullshit, nevertheless it is being beginning to be taught at some levels as a concept - so I might as well be respectful.87.102.86.73 (talk) 21:17, 24 July 2008 (UTC)

The above wasn't intended to be overly negative, systems engineering does give a framework to systematically study the behavior of complex multi-part things, especially useful to spot potential problems that might (in a less systematic study) only become apparent 'in the field' - nevertheless it does tend to result in a hell of a lot of paperwork, eg Systems_engineering_process,System of systems,System of systems engineering,Enterprise systems engineering, Systems thinking etc etc. which makes many people sigh at the vast number of fields that now have 'system' inserted into their name..87.102.86.73 (talk) 11:52, 25 July 2008 (UTC)

Pre Bigbang Theory

In the Pre Bigbang theory, it has been said that at the beggining of the creation of the Universe,only one superforce was there, which later split up into two forms i.e the Electronuclear force and the Gravitational Interaction. But the Electronuclear force also split up to form Electroweak force and Strong Interaction, the former of which further fragmented to generate Electromagnetic Force and the Weak Interaction. But even the Theory of Relativity can not answer what was before 10^-43 seconds of creations of the Universe, as we then need to face the Unexplainable Singularity. It is also said by Stefen W. Hawking that Bigbang will be followed by Bigcrunch, which will be the contraction of the universe to an unimaginably dense and small ball of energy floating in space. But this process will start only when the value of Ά (the Relative Density of the Universe) exceeds 1. But at the end of this process of contraction, will all the forces meet up to form the Cosmic Superforce again? And if they combine, will the unification of the forces take place just before 10^-43 seconds of the Bigcrunch? —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 19:04, 24 July 2008 (UTC)

Yes. I mean, you are missing some details and assuming certain theories to be true, but if there is a Big Crunch the Universe will experience conditions similar to those 10^-43 seconds after the Big Bang. Plasticup ^T/C 19:26, 24 July 2008 (UTC)

As noted at our Big Bang article, generally-accepted scientific theory does not reach as far as the singularity, much less prior to it. No real consensus about a theory of everything and a resultant "superforce" exists. As for Stephen Hawking's putative support of a Big Crunch, I find little evidence -- the Big Crunch is thought unlikely based on present understanding, though virtually all cosmologists acknowledge it as a possibility. Given all of this, no meaningful answer can be given to your questions. We don't know (or have significant confidence in a guess) if your scenario will occur at all, much less whether it will play out as you've indicated.

ec with User:Plasticup -- As noted at Big Crunch, a crunch is not a "bang-in-reverse". Additionally, even if final conditions closely resemble the initial conditions of the Bang, we don't know if said initial conditions are what Asim suggests above. — Lomn 19:32, 24 July 2008 (UTC)

Apothecary symbols

I am reading some early 19th century apothecary recipes and am stuck on one of the symbols. There are two consecutive underlined letter a's followed by the sign for one ounce. What do the underlined a's stand for? —Preceding unsigned comment added by Wityoungbod (talk • contribs) 19:28, 24 July 2008 (UTC)

Could it be referring to an Apothecaries' system Ounce. The symbol doesn't look the same, but I suspect things weren't particularly standard at the time Nil Einne (talk) 21:16, 24 July 2008 (UTC)

An image would help - or a link to the book? - could those a's be two s instead ? meaning half?87.102.86.73 (talk) 11:00, 25 July 2008 (UTC)

Is there any drug that does this?

Is there any drug that produces a feeling anything like orgasm or 'sexual pleasure'? 199.133.19.254 (talk) 19:50, 24 July 2008 (UTC)

Normally only orgasm is the result of genital excitement. However, there are many drugs that produce euphoria, but taking them would probably be illegal as you can't go to the doctor and say you want medicine for "euphoria". Such illegal drugs include opiates, amphetamines, cocaine, methamphetamine and MDMA (see Euphoria_(emotion)). 81.132.215.251 (talk) 20:22, 24 July 2008 (UTC)

Sure. Some anti-depressants, at least, have been known to produce spontaneous orgasms in women. There may well be other drugs that have similar effects, though I can't think of any off the top of my head. Also note that numerous recreational -- both legal and illegal -- drugs have an effect of increasing sexual desire and/or making sex more pleasurable; while they don't really produce orgasms in themselves, a bit of physical stimulation can go a long way while under their influence. -- Captain Disdain (talk) 20:32, 24 July 2008 (UTC)

Aphrodisiacs. Surprisingly, despite the commercials, Viagra has no effect on the brain. --Bowlhover (talk) 20:36, 24 July 2008 (UTC)

Clomipramine#Side_effects. --Allen (talk) 21:53, 24 July 2008 (UTC)

You don't need drugs to do this. Self hypnosis can make you fell exactly the way you want to feel. But I'm not sure it can induce orgasm. Any way, the feeling you get is better than orgasm and lasts longer! —Preceding unsigned comment added by 79.76.239.220 (talk) 02:35, 25 July 2008 (UTC)

Wow Allen, good find! That's ::yawn:: crazy! --Shaggorama (talk) 20:11, 26 July 2008 (UTC)

July 25

Intellegent design...

Just looking at the human body alone, how much of it has evolved and how much was designed?I'm assuming the more complex organs like the eye and the brain were designed, and simpler ones like finger nails and the nose evolved naturally.... but I just dont get how a simple life form can have coplex organs like the aforementioned eye before the foot has had the time to evolve, or is it a case that an organism evolves to a certain level and then carefully designed components are added at different stages... I'm probably missing something obvious but your help would be appriciated, :)165.228.176.26 (talk) 06:49, 25 July 2008 (UTC)

As far as I can tell, you're the first to come up with the idea that some components are evolved and others designed. I think everyone else pretty much says either it's all evolved, or all designed. The empirical evidence supports the former view, with the latter simply being a strongly-held religious belief. - Nunh-huh 06:56, 25 July 2008 (UTC)

Well, fish have eyes (What do you call a fish with no eyes? a fsh), but they haven't evolved feet. Current consensus on the Timeline of evolution has it that animals in general have been around for much much longer than those with mammal-like feet. You don't exactly start from nothing and try to achieve feet and eyes at the same time.

Even if the eye couldn't evolve in the time for feet to evolve, would that matter? You would have blind things walking around for a while, while eyes gradually evolved. (N.B. This is not how it happened)

You might be interested in evolution of the eye, which explains how such a complex organ could evolve. The short answer is "from simpler ones", and this applies to all of the other organs too. AlmostReadytoFly (talk) 08:21, 25 July 2008 (UTC)

The problem of how the eye could develop through evolution is debated and explained by many evolutionary biologists, so there should be several texts on this online in addition to wikipedia, if you'r interested. The basic approach is to show that each step towards an eye increases evolutionary fitness. then one document through fossils or contemporary simple organisms that the intermediate steps indeed happened.

For instance, just being able to distinguish light from dark or the general direction of light would be an advantage for an organism and is indeed found in many of today's microscopic creatures.

As an apropos, Nunh-huh is wrong to say that you'r alone with the evolution+creation idea. Some creationists accept evolution-like phenomena within a species but denies that new species are ever created from old ones. EverGreg (talk) 08:30, 25 July 2008 (UTC)

Of course, that's not at all what I said. -Nunh-huh 09:17, 25 July 2008 (UTC)

Just greated an acount:) I was just using the foot as an example of something of a body part simple enough as to not necessatate design... I'll try to rephrase the question, basically I understand that parts of us evolve naturally but other parts are for to complex not to have had a designer, I'm just wondering at what stage the designed components were added? For example, back when we were just a basic blob of flesh eyes wouldn't have been much use without a brain to process the information, they would have been largely pointlessHypervalve (talk) 08:45, 25 July 2008 (UTC)

Well, first of all, a foot is a pretty complex body part. You've got circulation that brings in oxygen to the muscles, you've got the muscles themselves which make it move, you've got bones that support the foot (and the rest of the body) and cartilage that ties them together and allows them to move, you've got tendon that connects the muscles to the bones, you've got (in the cases of humans and many other, but not all species) toes that help with balancing yourself, you've got a lot of useful nerve endings that help you feel your way when you're barefoot, you've got skin that keeps out germs and regulates your body temperature by sweating... I mean, there's a lot of stuff down there that works together. It's not at all "simple". An eye does a lot of cool stuff too, but they're not that different in terms of complexity. It's not as if some simple organism in the primordial slime suddenly grew up, noticed that it had feet and then started walking around on land (presumably bumping into things a lot if it didn't have eyes yet). It doesn't work that way.

Secondly, I don't think we know exactly at what stage the various components were "added". We weren't around to observe, after all, though we can certainly make some educated guesses. You should bear in mind, though, that none of this happened overnight, and a lot of it happened "simultaneously", if you can use such a term when discussing events that took millions and millions of years. -- Captain Disdain (talk) 09:11, 25 July 2008 (UTC)

I'd recommend perusal of Evolutionary developmental biology, not just evolution. A very enlightening book 'Endless forms most beautiful' is referenced there. You'll be lead to understand homeoboxes, why they are important for development of limbs etc. and how and when they evolved (which can be measured exactly). None of these facts can be explained by intelligent design. --Ayacop (talk) 09:13, 25 July 2008 (UTC)

Is it the same as saying the body is a self-designing organism? Julia Rossi (talk) 09:38, 25 July 2008 (UTC)

As the body is 'just' the means of the DNA to survive, I'd rather say 'the DNA designs itself and the body to cope with and survive in the changing environment'. However, the process is influenced by random events (changing environment, mutation), and if you want to see this, too, as design, then there is no single design but the two mentioned, survival and chance (the latter of which you may want to connect to a god of your liking). --Ayacop (talk) 09:58, 25 July 2008 (UTC)

Hi, you wrote: "basically I understand that parts of us evolve naturally but other parts are for to complex not to have had a designer", which is based on the idea of irreducible complexity. This idea is not one which is accepted by most scientists working in the field of evolution. They would probably state "All parts of us evolved and continue to evolve naturally". AlmostReadytoFly (talk) 09:48, 25 July 2008 (UTC)

Evolving anatomical structures such as eyes, brains and feet is child's play compared to the biochemical processes such as the metabolic pathways, DNA replication and photosynthesis. The first half of the timeline of evolution is taken up with evolving these well adapted fundamental mechanisms. This is where the true complexity and wonder of life lies - compared to these processes, eyes, brains and feet are just the blinkenlights. Gandalf61 (talk) 09:42, 25 July 2008 (UTC)

Hi, you wrote: "parts are far too complex not to have had a designer", which leaves you with 3 choices for how such a designer was created:

1. He evolved from simpler forms
2. Another designer designed him
3. He's always been here

I suspect you might choose #3, but if you can accept that, why not just accept the simpler idea that eyes and feet have always been here? That's certainly more believable, since we can at least all agree that they're here now. --Sean 12:59, 25 July 2008 (UTC)

As has been pointed out above, all parts of the human body, and every living organism, has evolved, and has not been "designed" in any way or part. A good introduction to this topic if you're happy to read a book is The Blind Watchmaker which explains how the eye may have piecemeal evolved. The book may be tainted in your eyes by the author "coming out" as an atheist and practically starting the neo-atheist movement, but long before all that happened, and still, this book was considered a great neo-darwinistic introduction to evolutionary thinking. —Pengo 12:29, 26 July 2008 (UTC)

Evolution of dogs

Since many dog owners prefer dogs that react to them, including when they talk to their pets, or dogs that are more intelligent than their peers, is it too crazy to suppose than someday dogs will evolve into speaking beings?Mr.K. (talk) 08:45, 25 July 2008 (UTC)

Of course not -- provided that when you say "some day" you mean that you'd be willing to wait millions of years. (I'm sure you could shave some time off that figure by aggressively breeding for intelligence, which of course didn't happen to humans in nature.) There's no reason to believe that they couldn't evolve that way. Then again, that doesn't mean that they necessarily would. Intelligence is by no means a guaranteed result of evolution. But is it too crazy to think it might happen? Nah. (Oh, and speaking would also require some considerable changes in the shapes of their mouths, of course, but what the hell, that wouldn't be impossible either.) -- Captain Disdain (talk) 08:56, 25 July 2008 (UTC)

What about greyhounds? Since they're aggressively bred for speed is it reasonable to assume that on a long enough time line the would be able to travel at a rate approaching the speed of light? Hypervalve (talk) 09:00, 25 July 2008 (UTC)

Traveling at a rate approaching the speed of light is not possible on earth. Speaking mammals, on the other hand, do exit. Mr.K. (talk) 09:22, 25 July 2008 (UTC)

...but "thinking mammals" is an open-ended research problem ;-) --Stephan Schulz (talk)

Excuse me while I pull myself together after taking that the dogs are more intelligent that the owners' peers, but dogs do speak -- it's that we can't understand them. The question of whether they learn sign language like lab chimps, or articulate verbally so they sound like Prince Charles is another issue... I personally haven't learned to do either. Julia Rossi (talk) 09:30, 25 July 2008 (UTC)

Uh, no. No. There are all sorts of problems here. If we did have a super-evolved and super-fast greyhound that could go that fast, it would need tremendous amounts of energy in order to reach and maintain such a speed... and I don't mean an extra helping of Alpo, either. The dog would also pretty much explode right away; at speeds like that, hitting the atmosphere would be like hitting a wall. The dog would be a spectacular ball of fire that would cause horrible destruction. The sonic booms, from breaking the sound barrier, alone would wreak havoc. At those speeds, the kinetic energy from each paw hitting the ground alone would destroy both the dog and the ground. I mean, overall, the energies involved in something like that would be utterly ridiculous. (Let me put it this way: a Greyhound jumping up and running full tilt to the door to do some energetic barking when the doorbell rings would make Hiroshima look like a walk in the park...) -- Captain Disdain (talk) 09:39, 25 July 2008 (UTC)

So, if we scale things back a bit - would breeding a greyhound or whippet that could run faster than the speed of sound be in any way feasible in the extreme long term? --Kurt Shaped Box (talk) 09:57, 25 July 2008 (UTC)

Well -- if you'll allow me to wax pedantic for a moment -- in that case you wouldn't scale things back a bit, you would scale things back a lot. It's comparable the difference between a single drop of water and the Atlantic, kinda. But to answer the question... uh, I dunno. I don't think so. I can think of all sorts of problems with that, one of the key ones being the greyhound's method of propulsion -- that is to say, running. Running isn't terribly efficient at high speeds. A supersonic jet fighter has a jet engine, which doesn't require any friction with the ground; it just sucks in air and spits it out. Running, on the other hand, does; the dog needs to constantly be able to hit the ground with its legs in order to maintain or increase speed. There comes a point where it's no longer a question of whether the dog can move its legs fast enough, but whether any such movement is enough to counter air resistance instead of, say, just propelling the dog into the air. (This would be comparable to what can happen to high-powered F1 boats, for example.) I guess, if the dog were to evolve some kind of claws or something that could grab the ground and keep it anchored, that would help. Also, the mechanical stress of pumping its legs that fast would be tremendous; I think more likely than not, it'd start damaging itself pretty quickly, if not immediately. And, of course, that air resistance is no joke at those speeds: pushing through the sound barrier can be pretty harsh on the body. But, you know, given enough time? I guess a dog might -- I don't really believe this could happen, you understand, but hypothetically speaking, might -- evolve muscles and joints and bone and the claws and whatnot that could somehow support this sort of activity so the animal wouldn't just shake itself apart. (The paws would take an incredible beating. Each step would send a powerful physical shock through the animal's body; I'd guess it'd get a series of concussions when running. And the physical stress directed at an object moving that fast through the air is tremendous anyway. Falling in mid-run would be like being pummeled by fifty sledgehammers... but, you know, for the sake of argument, let's assume that somehow this amazing dog can take all this.)

But even then, there's the question of energy for this kind of activity: that dog would have to have an incredibly efficient metabolism. Kibbles and bits wouldn't do the trick; it'd be burning some serious calories at those speeds, tens of thousands of them at the very least, so it would have to eat something that contained pretty serious energy -- I don't think there would be nothing in nature to fulfill that need. (And it couldn't just make up for it by having a large stomach and eating more; it'd be crucial for the dog to be as streamlined as possible.) I mean, I guess it could have some sort of a hyper metabolism and the ability to effectively store energy for future use and depend entirely on some sort of human-created ridiculously high-energy meals, but... also, the dog would have to breathe, which is just about impossible at those speeds, and in any case the demand for oxygen would be incredible when the body is working that hard, much greater than lungs could be expected to efficiently provide, and...

...nah. I really don't think so. -- Captain Disdain (talk) 10:52, 25 July 2008 (UTC)

Man. That was a good answer. :) --Kurt Shaped Box (talk) 23:24, 25 July 2008 (UTC)

I'd expect the max speed a highly evolved dog could reach to be on order with that of a highly evolved cat, namely the cheetah, which reaches 75 mph/120 kph. That's only around a tenth of the speed of sound, however. As for intelligence, I see no inherent reason why dogs couldn't eventually evolve the same intelligence and talking abilities as people, but we are talking millions of years here, even with selective breeding, as entirly new structures (like vocal cords) need to develop. Its not just a matter of varying the size and shape of the existing range of structures, which is all dog breeding so far has accomplished. However, we might be able to speed this up using recombinant DNA technology, and end up with The Island of Dr. Moreau. StuRat (talk) 16:01, 25 July 2008 (UTC)

It's not just that, it's unlikely we're even trying to make talking dogs, whatever features are being selected for it's unlikely to be those which could eventually lead to vocal chords capable of human like speech Nil Einne (talk) 17:33, 25 July 2008 (UTC)

A highly evolved dog (millions of years of successful adaptation) named Laika achieved earth orbit in 1957. Does that count as "faster than the speed of sound?" Or did you mean "without human intervention?" A dog which went over a cliff under its own power might also exceed the hypothesized 75 mph, especially if it adopted a streamlined Underdog flight posture during the fall. Edison (talk) 16:27, 25 July 2008 (UTC)

Well, going by this logic, you might put a small radio in the dog's mouth and claim that it talks, but it's pretty obvious that it's really got nothing to do with the dog's evolution. =) -- Captain Disdain (talk) 18:50, 25 July 2008 (UTC)

Yes. Dogs may some day evolve speech. But it seems unlikely to happen in our life time, if at all. While there is evolutionary pressure for dogs to be able to communicate with humans, the type of communication will likely stay non-grammatical (you could argue that there is already 'verbal' communication between humans and dogs). What has happened already is that dogs have become very good at reading human emotions and faces -- better so than even chimps (our closest relatives in the animal world). What will happen in the future is always speculation of course -- but if dogs do start to talk, will they still want to be mere pets? —Pengo 12:38, 26 July 2008 (UTC)

Good question. When I had two dogs, I was their slave (play, walk me, feed me, let me in, let me out, wash, dry... you-know-the-routine). Where is it says that dogs could talk but their vocal chords are not the right length? Julia Rossi (talk) 04:46, 28 July 2008 (UTC)

Captain Disdain said "nah. I really don't think so." I would have imagined that if the only criteria for selection is speed.... wouldn't it keep increasing incementaly... couldn't alot the constraints you've mentioned be eventually overcome if the fastest and fastest alone are always the most successful, could it really reach a point where the greyhound reaches its top average speed and cannot possibly improve? I mean there are many obvious restraints but hasn't nature come up with some pretty cool stuff in the past? 203.59.254.122 (talk) 14:21, 28 July 2008 (UTC)

The mechanics of graden furniture (AKA "garden furniture")

I'm visiting my folks at their summer-place this week, and me and my dad (well, mostly him, I'm basically the muscle of this operation) are making a large table for the garden out of concrete. It's going to be a slab that's 220cm x 90cm big, resting on three pillars in an isoceles triangle, with two pillars at the corners on one of the 90cm side and the other about 120 cm's into the table (see diagram). The slab weighs about 182 kg. This design is for two reasons, the first being that it is going to make the slab very stable. If there was four pillars and one was slightly shorter, the table might wobble depending on where the weight is (the slab is just going to be laid on top of the pillars, not screwed to it or anything). Second, my father wants to acheieve an effect that makes it appear like the table is "floating". I had some doubts about this design, mostly because I figured that if you put enough weight on one of the corners, the hole thing would flip over and fall off. To back up my assertion, I wanted to calculate how much weight would make the table flip over. And that's where I need you guys' help :)

Here's a diagram of the table, on a coordinate system with (0,0) at the bottom left corner of the table. The green squares are the pillars (which are 10cm x 10cm).

So, here's the problem: how much weight can you put on the bottom right corner (at (220,0), in other words) before the whole table flips over? I'm not really very good at this, but I tried calculating it and I got about 35 kgs (which, if true, is far to little, and I'll have to dig up one of the pillars and move it :( ). I would really appriciate if I could get someone to verify that I'm using the right method and that my calculations are correct.

The way I did it was to figure the table as just one big lever, with the red line as the fulcrum. Then I used the lever principle to figure out how much each part of the table pushes down, and how much force at the bottom right corner would make that side "heavier". The red line meets the edge of the table at approximately (0,0) and (220,65). I figured out the center of gravity for both parts of the table, which I got to be (89,58) and (149,22). To get the distance between the centers of gravity and the fulcrum-line, I used this neat formula. The distances are about 30cm and 20cm respectively (30.16 and 20.36 to be specific). The product between the distance and the weight (in newtons) of the top part of the table is 34050.64 Nm and the bottom part is 12989.68 Nm, according to my calculations (this is where the lever principle comes in). That means that the top part is 21060.96 Nm "heavier" than the bottom part. Since the distance from the bottom right corner to the red line is 62.2cm (again, using the formula mentioned above), to flip the table over it, you would have to apply 21060.96/62.2 = 338.6 newtons of force, or about 35 kilogram in earth gravity.

As I said, I really just want someone to tell me that this is the right way to do it. If someone could check on the actual calculations, I'd be hugely grateful, but that isn't necessary. Just a confirmation of the method would make me a very grateful man. Or not so much, if I have to spend most of the afternoon digging the damn thing up :) ADFSGL (talk) 11:28, 25 July 2008 (UTC)

Small correction: replace all occurances of Nm with Newton-centimetres :) —Preceding unsigned comment added by ADFSGL (talk • contribs) 12:11, 25 July 2008 (UTC)

I can't resist linking this dolmen.

I haven't checked it - but you could just use the centre of gravity for the whole table at (110,45) which should give you exactly the same result. Your reasoning seems correct otherwise.

I'd guess that 35kg is borderline unsafe.. (if I sat on the corner..)

if you want to have 4 legs - I recommend using lead/rubber/plastic spacers between table and legs to prevent wobbling - anything that can deform under weight - lead is a particularly good choice as it doesn't look out of place with concrete - just use some roofing lead folded over...87.102.86.73 (talk) 12:17, 25 July 2008 (UTC)

Out of curiosity, is there some reason to have the slab of concrete just be there instead of anchoring it to the pillars with... uh, crap, my vocabulary fails me here. I don't know what they're called, but one of those steel plate things, bent at a 90 degree angle? A couple of those would probably be quite enough to keep the slab from flipping even if someone were to sit on the other edge or something. -- Captain Disdain (talk) 12:44, 25 July 2008 (UTC)

Because the table isn't all that thick, only 4 or 5 cm. You could screw it down, but my father intends it to stay there for 15-20 years, and he doesn't want cracks to be formed. And 182 kg is a lot, so if you can eliminate the flipping risk, it'll stay there forever. ADFSGL (talk) 12:58, 25 July 2008 (UTC)

Well, you could probably get around the cracks by simply inserting steel rods or something into the concrete before it hardens and then hooking the metal plate thing into them, for example. That'd probably be easier on the concrete than drilling holes into it. (Well, maybe not; your father may well be more familiar with concrete than I am. It wouldn't take that.) In any case, if he's not willing to anchor it, you're probably going to just have to move that pillar. Or put some kind of a counter weight on top of the slab, but that'd take up table space and look less than charming. Another option that occurs: perhaps you could hook some kind of a weighted clamp on the other end of the table; done right, it would probably be pretty hard to spot. Still, not exactly the most elegant solution imaginable... -- Captain Disdain (talk) 14:10, 25 July 2008 (UTC)

In case you need a nudge towards being extra-cautious, here's a video demonstrating that concrete is heavy. --Sean 13:13, 25 July 2008 (UTC)

Hmmm ... 220 cm x 90cm x 5cm - I make that about 0.1 m³. Unless you are using pumice to make lightweight concrete, your weight calculations are on the low side - should be more like 230 to 240 kg [12]. That improves your stability, but unless you are an Olympic weightlifer, you will need a block and tackle or similar. Gandalf61 (talk) 13:28, 25 July 2008 (UTC)

I just checked with my dear old father, and he measured the thing to be 220cm x 90cm x 4cm. According to the manufacturer, the concrete has a density of 2300 kg/m^3, thus 182.16 kg. It's not lightweight concrete, but it is extremely fine-grained (the most fine-grained we could find). We did a test-table, and not only is it in a very nice eggshell-white, it's smooth as a cue-ball. ADFSGL (talk) 13:36, 25 July 2008 (UTC)

And you're right, there's no way we can lift it on our own, but we have recruited a merry band of assorted neighbours and relatives to lift it when it is dry enough tomorrow. We're going to be around six people. ADFSGL (talk) 13:38, 25 July 2008 (UTC)

I see I'm about to ask an entirely theoretical question: how come concrete? I've seen attractive cast-aluminum outdoor furniture. It doesn't rust, it's easy to move, and it doesn't look like it came from Joe Stalin's House of Outdoor Design. OtherDave (talk) 13:42, 25 July 2008 (UTC)

I had the same doubts as you, but it's actually very nice. The concrete isn't rough building-concrete, it's extremely smooth and very white, much prettier than metal. It's almost like marble, only not glossy and slightly more gray. It's also (very!) sturdy, it's not rickety or anything. It feels much more like a real table. ADFSGL (talk) 13:52, 25 July 2008 (UTC)

...unless it falls on you. A la the stability issue, why not replace that one pillar in the middle of the table with two pillars spread slightly apart? They don't have to be all the way to the edge, but spreading them a little will shift your fulcrum further from the center of gravity. Plasticup ^T/C 14:10, 25 July 2008 (UTC)

The design proposed seems unsafe to me, because it will cause the concrete beyond the pillars to be under a bending and sheering load, and concrete is quite weak under that type of load. Since concrete is best under compression, it would be better to use it, say, for the pillars themselves, and use some other material for the table surface. Also note that square, non-attached pillars will tend to concentrate forces on the table at the corners of the pillars, causing crack propagation and eventual fracture. Circular pillars would be better. If your dad insists on going with a concrete table surface, I suggest a thick steel "tray" (coated with weather-proofing material) underneath the concrete, capable of supporting the concrete and anything on the table, along with circular pillars. Here's a pic of a cantilevered concrete diving platform, which is similar to your table: [13]. Note the tapered side supports and lack of a center pillar (to prevent force concentratations). You can't see it, but I believe this design uses steel-reinforced concrete, with rebar inside the concrete. StuRat (talk) 15:25, 25 July 2008 (UTC)

Had you condsidered casting 'dumbell' shaped legs for a more organic feel:Organic architecture

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87.102.86.73 (talk) 19:56, 25 July 2008 (UTC)

Just to be clear: if I'm not paying for the table, your dad can make it out of whatever he likes. The sturdy part I had no doubt about. OtherDave (talk) 01:42, 26 July 2008 (UTC)

I am not a structural engineer, but I rather share StuRat's concern about the bending strength of the concrete. Actually, you didn't specify whether you put any rebar in it; I'd suggest you do, but that may be too late if, as you imply, it's already cast and curing. Even with rebar, I think something like circular steel plates at the tops of the legs would be useful to spread the load, and coincidentally to expand the support a bit around the middle leg. I'd also be worried about the tabletop possibly sliding off the legs when pushed if it isn't attached to them, especially when the "floating" end is loaded (which reduces the load, and thus the friction, on the corner legs). —Ilmari Karonen (talk) 13:39, 26 July 2008 (UTC)

The concrete is indeed full of rebar, for exactly this reason. Anyway, I dug up the pillar (it's a wood pillar that's screwed to a cement plinth dug down about half a meter, btw) and moved it to about 35 cm from the edge of the table. We assembled the neighborhood strong-men and we lifted it on. It's steady as a rock now, nothing short of a 8.0 earthquake is going to move it, and there's absolutely no chance of sliding. It's just far to heavy for that. Anyway, thanks everyone for all your helpful tips and nice conversation! Me and pops are grateful. Here's a picture of the finished table:

It's slightly wet because we're using soap to create a smooth surface. Oh, and in the image, it looks like right pillar is a crooked, but that's 100% illusion, it's completely straight, so don't worry :) Cheers! ADFSGL (talk) 14:33, 26 July 2008 (UTC)

Your argument that it won't slide at all due to the weight isn't correct. I'd expect it to move over time, so you will have to occasionally reposition it. After all, glaciers and continents are a lot more massive, yet still slide over time. Incidentally, this table would represent an extreme risk to anyone sitting there during an earthquake, so I hope you're in a geologically stable area. StuRat (talk) 15:27, 26 July 2008 (UTC)

I'm in a very geologically stable area, so that's not a problem. As for the sliding, I tried with all my might to push it from the side so that it would slide and it wouldn't budge a millimeter. I think it'll stay where it is (friction does increase with the weight of the object, and this is a very heavy object. It might slide a little, but that's nothing that two strong men can fix in a minute) 83.188.214.253 (talk) 21:59, 26 July 2008 (UTC)

You probably can't break a hole in a cement sidewalk with just your hands, either, but a lowly weed can do it, given enough time. Many things that are difficult to move quickly are quite easy to move a little bit at a time. For example, it may vibrate a thousandth of an inch out of position each time a car drives by. StuRat (talk) 01:08, 27 July 2008 (UTC)

Well, if that happens, we'll notice it, and as I said, it only takes two strong men to lift it back into place. 83.188.214.253 (talk) 10:20, 27 July 2008 (UTC)

High Fructose corn syrup

I have been reading quite a few health articles about the ill affects of high fructose corn syrup (or corn syrup) and the bodies inability to process it. High Fructose Corn Syrup is an extremely sweet and cheap sugar altenative but it has very bad effects on the human body. It has been looked at quite a few times but always from the perspective of a user. Is there any other studies that have fully looked at the ill affects caused by corn syrup.

P.S It is used in almost everything we eat since the 1980s and the obesity rate has risen 37% since.

Rocco F Gervasi

Well, okay. Did you have a question about it, or...? -- Captain Disdain (talk) 14:00, 25 July 2008 (UTC)

Oh, geez, I must be going blind or something; I somehow completely missed the last sentence there. I'm sorry. -- Captain Disdain (talk) 14:01, 25 July 2008 (UTC)

I need a clarification myself. It sounds like you want to know about studies of the bad effects of corn syrup, but "not from the user perspective", which I suppose means "not from the consumer perspective". What perspective do you want ? Are you talking about people who come in contact with it during processing ? As far as I know, it doesn't cause any negative health consequences from touching it or inhaling fumes, if that's what you're after. Here's the Material Safety Data Sheet for corn syrup solids (powder): [14]. It looks like the two dangers identified are getting it in your eyes and a corn syrup dust and air mixture being explosive. StuRat (talk) 14:47, 25 July 2008 (UTC)

"User" could very well refer to the industrial users (the food companies). -- Coneslayer (talk) 14:50, 25 July 2008 (UTC)

Now I'm thinking you meant to ask "rather than look at nonrigorous studies by consumer organizations, I'd like to see some hard scientific data on the health consequences of consuming corn syrup, particularly it's relationship to obesity". Is this what you're asking ? If so, I'll let others answer, but would like to comment that having cheap, sweet goods available, in and of itself, may tend to cause obesity. StuRat (talk) 14:59, 25 July 2008 (UTC)

Not just that but there are many other things that happened in the 1980s, e.g. I was born then. I don't think anyone is going to say I'm the cause of the rising obesity rate. Nil Einne (talk) 17:29, 25 July 2008 (UTC)

• Well, I start with a search for HFCS negative effects, and the first thing that comes up is "The Negative Effects of High Fructose Corn Syrup on the Human Body". Google is your friend! --jpgordon^∇∆∇∆ 14:55, 25 July 2008 (UTC)

• Doesn't turning corn into syrup start with a smelly fermentation process, which is quite noticeable when driving by one of the factories? Could such manufacturing externalities have "ill effects" on neighbors? Edison (talk) 16:11, 25 July 2008 (UTC)

If you are looking for academic studies rather than general health articles you could also try a search at pubmed. "High fructose corn syrup" gave 97 hits, including this overview editorial from the American Journal of Clinical Nutrition which might be a good place to start. best luck, WikiJedits (talk) 20:09, 25 July 2008 (UTC)

For the record, Australia has similar rates of obesity to the US, but high fructose corn syrup is hardly used here. Personally I blame cars (lack of exercise) and the meat-sweet diet of the Western world. —Pengo 12:44, 26 July 2008 (UTC)

I blame the Internet. Apparently there are some people out there who spend a good portion of their free time editing online wikis instead of exercising. StuRat (talk) 06:03, 27 July 2008 (UTC)

Antimatter and matter

Why isn't there a perfect symmetry between antimatter and matter in the universe if they were formed from energy? Particles and antiparticles are produced in pairs, aren't they? —Preceding unsigned comment added by 116.68.79.122 (talk) 15:18, 25 July 2008 (UTC)

You are talking about CP-violation. As for why is exists, that is one of the biggest questions in particle physics. Hopefully the Large Hadron Collider will shed some light on that for us. Plasticup ^T/C 15:22, 25 July 2008 (UTC)

(edit conflict) Our relevant article is baryogenesis (and see also baryon asymmetry, CP violation). The question you ask is among the most important unsolved problems in physics. -- Coneslayer (talk) 15:25, 25 July 2008 (UTC)

Although the matter and antimatter are opposite to each other, but they actually do not follow the similar processes of integration and fragmentation.

To examplify, let us take the example of Proton and antiproton. Proton disintegrated to form electron and antineutrino during bigbang. But there can never be the breakdown of Antiproton to Positon and neutrino. Hence, there is no perfect symmetry between antimatter and matter. You may read the Book 'A brief History of Time by Stephen W. Hawking' as it provides a vivid description of answer of your questions.Asim Chatterjee (talk) 19:42, 25 July 2008 (UTC)

What in the world are you talking about? There is no evidence for proton decay, and there is also no proof that antiproton decay is impossible. I'm pretty sure they're on equal footing at the moment. Anyway, what you say would predict an imbalance towards more antiprotons and fewer protons, which is the opposite of what we observe! —Keenan Pepper 19:55, 25 July 2008 (UTC)

Pepper, you must know it that the total energy of the universe is zero. And according to the latest developments in quarks and quantum mechanics, proton decay can obviously take place. It has been shown in Fermi Lab that as a result of collison of proton and antiproton, top quark is evolved, which has anatural capacity to breakdown protons(and not antiprotons). But the idea of Roger Penrose regarding this is that the rate of antiproton decay, if it takes place at all, is obviously not comparable to that of proton decay. If you take into account the second step ionization equation of 'Saha Equation', you will no doubt find a possiblity leading to my statement being correct. Although we may see the positive universe, but it arose from a negative C-field as predicted by Hoyle. Even the General Theory of Relativity supports this statement.117.201.97.131 (talk) 21:04, 25 July 2008 (UTC)

Last I heard, there was no empirical evidence that proton decay could occur. Could you provide a link to something discussing these developments? --Tango (talk) 21:13, 25 July 2008 (UTC)

If proton decay occurred, it would still have to conserve baryon number and charge surely, which is totally at odds with what Chatterjee is saying. Philc 0780 17:58, 28 July 2008 (UTC)

I'm sorry, I can't as I am not yet too much familier with Internet because of being a new user. But you may consult the Book 'Meghnad Saha & Developments in Science'. There, in the middle of the third chapter, a set of ionization equations are there, derived from Dirac Equation which will help you to understand proton-decay.117.201.97.131 (talk) 21:24, 25 July 2008 (UTC)

Sign of the wavefunction

Hi! When I was learning atomic structure, the diagrams of orbitals had '+' or '-' signs marked on it(For eg., each lobe of a p-orbital had '+' on one lobe and '-' on the other). My teacher mentioned something about it relating to the wavefunction and addition/ subtraction interference or something like that, but I didn't get the point completely(I'm only in high school) I believe the wavefunction is a complex no., the square of whose magnitude gave the probability density. I don't understand what the sign means. Does it imply that the value of the wavefunction in one region is the conjugate of another?? Can anyone explain to me?? 116.68.79.122 (talk) 15:29, 25 July 2008 (UTC) A 15-year-old.

It's the sign of the real part of the wavefunction. (or if the wavefunction is not complex - just the sign)87.102.86.73 (talk) 15:44, 25 July 2008 (UTC)

" Does it imply that the value of the wavefunction in one region is the conjugate of another?? " - no, don't think that..87.102.86.73 (talk) 16:05, 25 July 2008 (UTC)

In general, the wavefunction is complex, but in the case of atomic orbitals, the eigenfunctions of the hamiltonian all happen to be real (or more correctly, you can multiply them by some complex constant to make them real). (I'm sure there's a good reason for this, but for now you can think of it as a mathematical accident.) The sign is simply the sign of the (real) wavefunction. 128.165.101.105 (talk) 19:51, 25 July 2008 (UTC)

But what does the sign physically mean?? 116.68.79.122 (talk) 07:52, 27 July 2008 (UTC) A 15-year-old.

For a single orbital in isolation, it has no physical meaning. It only means something when different orbitals combine, for example when two atomic orbitals combine to form a molecular orbital. If parts of the orbitals have the same sign, they fuse together, allow the electron to delocalize more, and lower the energy. If they have opposite signs a node forms between them and it raises the energy. See Linear combination of atomic orbitals and MO diagram. 128.165.101.105 (talk) 14:33, 28 July 2008 (UTC)

Neonatal Circumcision as a preventative measure against HIV...

Does neonatal circumcision help prevent the possibility of contracting HIV? Unfortunetly much of the research on the subject is highly biased either in favor for or against circumcision. I understand there is much debate on the subject and a list of medical journals or articles explaining the medical aspect of the procedure as a preventative measure without bias would be greatly appreciated. 65.9.252.237 (talk) 17:46, 25 July 2008 (UTC)

I don't know about neonatal circumcision specifically, but I remember reading a study conducted by a UN group that ended early because the results were so heavily in favor of circumcision reducing HIV transmition that they deemed it unethical to continue keeping a control group of uncircumcised men. Plasticup ^T/C 17:56, 25 July 2008 (UTC)

Does it really matter? I never understood what the point of the study was. Just wearing a condom or even better, not having sex with HIV infected women seems to be a better option than circumcision. The simplest solution is always the best solution. ScienceApe (talk) 18:57, 25 July 2008 (UTC)

The studies are all a little dicey as circumsized/uncircumsized men tend to represent different cultural samples and all this so take some salt, but yeah, circumcision reduces the transmition rate of HIV. It also reduces the occurances of trench foot in your penis if you're drafted to fight in World War I. WilyD 19:08, 25 July 2008 (UTC)

To be specific about the question though, neonatal circumcision is not shown to affect HIV transmission rates. Being circumcised has been shown effective in some populations where the males are non-monogamous and unprotected during sex (per ScienceApe) - neither of these criteria apply to a 4-year-old boy. The difference between circumcision and neonatal circumcision is that the neonate is not given a choice. Franamax (talk) 19:38, 25 July 2008 (UTC)

Err, as long as it's not so recent that you're not completely healed, the exact time of circumcision doesn't matter. It's probably not effective against many methods of HIV transmission, such as blood transfusions and sharing needles. WilyD 16:37, 26 July 2008 (UTC)

Catalyst?

In the reaction '2SO₂+O₂=2SO₃', the required conditions are 1:Presence of 450^oC temperature and 2:A catalyst Now this catalyst can be either Vanadium Pentoxide or Platinum in general. But among these two, which catalyst pprovides a better speed of reaction?Asim Chatterjee (talk) 19:33, 25 July 2008 (UTC)

According to Contact process platinum is the better catalyst.87.102.86.73 (talk) 20:14, 25 July 2008 (UTC)

Yes, I think platinum is much more expensive, so why would anyone use it unless it worked better? —Keenan Pepper 20:48, 25 July 2008 (UTC)

It is, they don't, it does... but the platinum is more easily poisoned according to reports. Otherwise they would use it if it allows the reaction to occur at a lower temperature (which is almost the same as having faster reaction rates - one follows the other..)87.102.86.73 (talk) 21:04, 25 July 2008 (UTC)

You are most welcome for having me helped,User-87.102.86.73.You are truely among the most brilliant persons I've ever talked to.Thank you. —Preceding unsigned comment added by 117.201.97.131 (talk) 21:19, 25 July 2008 (UTC)

Thank you very much, but please don't thank me, thank those who wrote the articles and did the research in the first place, and of course thank wikipedia..87.102.86.73 (talk) 21:23, 25 July 2008 (UTC)

Yeah, I'll surely do the same.But I can't ignore your efforts. I shall be ever grateful to Wikipedia.117.201.97.131 (talk) 21:27, 25 July 2008 (UTC)

Collisional quenching rate constants for some excited states of N₂ and N₂⁺ in helium

I don't really expect this to be answered here, but I figure it's worth a shot. The RD has surprised me before!

I'm interested in the C³Π_u state of the N₂ molecule, and the B²Σ_u⁺ state of the N₂⁺ molecular ion. I need to know the reaction rate constants for the collisional quenching reactions of these species when they collide with ground-state helium atoms. If experimental data are not available, I need some theory that will allow me to estimate these rate constants to at least order-of-magnitude accuracy. All responses appreciated. —Keenan Pepper 20:07, 25 July 2008 (UTC)

This pdf http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740002549_1974002549.pdf mentions in the references "reaction rates for collisional de-excitation of B²Σ⁺_u states of N₂⁺..." see Ref 4. but doesn't mention what in.. The article itself also mentions measurements in helium, but I didn't read it all to check it..87.102.86.73 (talk) 21:01, 25 July 2008 (UTC)

Insect Survival

How long can insects survive in a vacuum? Does their exoskeleton help protect them? Just curious. Horselover Frost (talk) 22:03, 25 July 2008 (UTC)

You'll find several papers with Google Scholar and the keywords insects vacuum. However, you'll need a library visit if you want to know the complete picture, as some abstracts aren't online. What I could gather was that insect eggs aren't affected by low pressure plus low temperatures, but are vulnerable with longer exposure or higher temperature (Mbata et al., Mortality of Eggs of Stored-Product Insects Held Under Vacuum: Effects of Pressure, Temperature, and Exposure Time) and that At 50±5 mmHg, the egg stage was the most resistant in all three species, times needed to obtain 99% mortality being 45, 49 and 22 h, respectively. (Finkelman et al., Effect of low pressures on the survival of three cocoa pests at 30°C) which would give an upper bound to the answer to your first question. --Ayacop (talk) 05:57, 26 July 2008 (UTC)

Shark vs. Crocodile. Who is stronger?

In a confrontation between both. 190.49.102.65 (talk) 22:04, 25 July 2008 (UTC)

Well ignoring the fact that a shark is a blue water animal while the crocodile is a brown water animal... Actually it's almost impossible to answer because the environment would dictate who would win. A shark is not "designed" to swim in shallow brown water, where a croc lurks. Likewise, a croc can't swim forever, and would drown in open blue water. So in brown water, the croc, in blue water, the shark. Probably. ScienceApe (talk) 22:17, 25 July 2008 (UTC)

Animal Face-Off says it all - shark is the winner.87.102.86.73 (talk) 22:33, 25 July 2008 (UTC)

Those face-offs are pretty ridiculous. Incidentally they also said a lion would win in a fight against a tiger. This match-up has actually occurred a few times in captivity, and the tiger almost always wins. ScienceApe (talk) 00:47, 26 July 2008 (UTC)

Which would seem obvious from their respective sizes (tigers are HUGE). --Ayacop (talk) 06:02, 26 July 2008 (UTC)

Actually the Saltwater crocodile does at times swim in the open ocean, according to our article. Considering the fact that "Salties" can be 20 feet long and weigh more than a ton, a shark might come out second best. Consider also that crocodiles are well armored over much of their body. --Eriastrum (talk) 19:33, 26 July 2008 (UTC)

Alligators are seen rarely in the ocean[15] while bull sharks are occassionally found hundreds of miles up freshwater rivers. Rmhermen (talk) 20:40, 26 July 2008 (UTC)

Don't confuse alligators (Family Alligatoridae) with crocodiles (Family Crocodylidae). They are very different animals. Alligators (genus Alligator, found only in southeastern United States and in China's Yangtze River) are almost always found in fresh water. The Crocodile I was referring to is the Saltwater Crocodile (Crocodylus porosus) that is very definitely found in salt water, including ocean far from land. It is native to Southeast Asia and Australia. --Eriastrum (talk) 21:57, 26 July 2008 (UTC)

Electronic interference on airplanes

Hello. Does leaving on your "portable electronic devices" prior to take off/landing on an airplane really have any interfering effect in the cockpit? It just seems to me that even if everyone on a plane had a CD player with headsets on, there could not possibly be enough interference to inhibit cockpit communication with the airport, or to distort the autopilot. Also, would cell phones in operation during flight cause a technical problem either? I've seen a stewardess use a credit-card scanner during flight that sends a signal to accept the charge, which to me would seem to have the same interfering effect as a cell phone, yet the scanner is allowed to be used. It makes me think that cell phones are prohibited just for the sake of passenger comfort (no one wants to sit next to someone who yells on their cell phone the whole flight). Comments? Answers? Thanks!--El aprendelenguas (talk) 22:05, 25 July 2008 (UTC)

On more thing: After the plane has landed, why is it okay to use cell phones at that point but "all other electronic devices should remain off"? Thanks!--El aprendelenguas (talk) 22:12, 25 July 2008 (UTC)

See Mobile_phones_on_aircraft#Current_status. The gist of it is the FCC forbids the use of cell phones on planes in flight (based on some evidence that they can interfere with navigational equipment), while the use of cell phones on the ground is up to the FAA, who may permit or forbid cell phone use as they see fit. Horselover Frost (talk) 22:22, 25 July 2008 (UTC)

Mythbusters aired an episode where it tested the claim. The answer was no, it doesn't effect the airplane's electronics, they just ask people to turn them off just to be safe, because there might one day be an electronic device that might have unforeseen effects on instrumentation. ScienceApe (talk) 22:25, 25 July 2008 (UTC)

The UK Civil Aviation Authority did a study in 2003 that determined that interference from cell phones may disrupt the functioning of the electric compass used in airplanes. (study and results here) Horselover Frost (talk) 22:36, 25 July 2008 (UTC)

The irony is that the alternative, the in-flight entertainment system, has already caused at least one crash, while there's no record of CD players, cell phones, etc., causing a crash. Therefore, I'd prefer if they kept all that unneeded hidden wiring off the plane and let people use their own, much safer, devices. StuRat (talk) 23:28, 25 July 2008 (UTC)

Personally I'm glad from a personal standpoint that cell phones aren't operated on planes. Businessmen on planes are irritating enough ("So I SAID to the GUY, buy LOW, sell HIGH, ya'know what I'm SAYIN'?") without being able to communicate with people outside of their seats. But the other electronics—totally silly to have them switched off for takeoff and landing, but whatever. --98.217.8.46 (talk) 03:27, 26 July 2008 (UTC)

(As an aside, this is my favorite comic on the subject.) --98.217.8.46 (talk) 03:27, 26 July 2008 (UTC)

I liked the Simpson's episode where the stewardess made Bart turn off his game. Then the plane's engines quit and it went into a dive. Next the stewardess said "turn it back on !", and the problem was fixed once Bart did. StuRat (talk) 04:44, 26 July 2008 (UTC)

Bear in mind that for large items like laptops, one of the reasons your supposed to switch them off is because you're also supposed to put them away so they don't become dangerous flying objects in an emergency. As for devices like CD players etc, I suspect one of the reasons why your supposed to switch them off is so you're not listening to them and can actually hear any annoucements and instructions in an emergency (supported by this reference [16]) Nil Einne (talk) 20:15, 26 July 2008 (UTC)

EMP against guns

If an E-bomb or EMP weapon was used against soldiers armed with guns, would it ignite the smokeless powder, and cause the guns to explode? ScienceApe (talk) 22:23, 25 July 2008 (UTC)

Do you mean conventional mechanical guns, or electrically operated guns? Horselover Frost (talk) 22:28, 25 July 2008 (UTC)

Mechanical guns like M16 or AK47. ScienceApe (talk) 00:44, 26 July 2008 (UTC)

Then no, or at least it didn't happen when the U.S. Military tested EMFCGs back in the late 70s. And I don't see how it could happen, since the effects of an electromagnetic pulse on a conventional firearm would be roughly the same as a shock from static electricity. Horselover Frost (talk) 04:21, 26 July 2008 (UTC)

Possibly not - if the gun is metal and the cartridges inside the gun the metal of the gun might absorb most of the EMP.87.102.86.73 (talk) 22:35, 25 July 2008 (UTC)

Metal doesn't absorb though, it's a conductor. ScienceApe (talk) 00:45, 26 July 2008 (UTC)

A conductor will reflect em radiation —Preceding unsigned comment added by 79.76.216.89 (talk) 02:03, 26 July 2008 (UTC)

Also, if you try to argue that it may conduct or reflect and, as a result, produce heat... The heat of the Mojave (and Iraqi) desert hasn't caused round to explode. -- kainaw™ 18:15, 26 July 2008 (UTC)

Why do some birds have long tails?

Why exactly is it that some bird species have evolved long tails whilst other species in the same family with broadly similar behaviour have not?

Compare the European Magpie and the Carrion Crow, or the Peach-faced Lovebird and the Budgerigar, for example. What exactly are the benefits to a bird of having a long tail anyway? --Kurt Shaped Box (talk) 23:30, 25 July 2008 (UTC)

Good question. A common answer to "what is a long tail good for?" is either "balance" or "showing off". The latter normally implies a pronounced sexual dimorphism, which for the birds you mention is not the case; so balance (in flight, perched, or on the ground) would be the first thing that comes to mind. However, I have found this abstract, which suggests that the long tail serves for the potential mates as an indicator of overall physical condition of the bird (and therefore its reproductive potential). The suggestion is very interesting, but not necessarily correct. Another thing that can not be ruled out is that a long tail is meant to confuse predators, either by increasing the perceived size of the bird or by moving the potential point of attack away from the vital areas. The tail is graded, so it is not very bulky for its length; but a magpie really looks bigger than it really is: a typical magpie weights 200-240 gram, a typical carrion crow about 500. Hope this helps (I doubt it though...). Best regards, --Dr Dima (talk) 01:13, 26 July 2008 (UTC)

One factor is manuverability. For example, raptors that are soaring birds that largely fly in wide open areas have short, broad tails (example, golden eagle shown here [17]). However, raptors such as accipitors that hunt their prey in wooded areas have distinctly longer and narrower tails (for example, see this Sharp-shined Hawk here [18]). And then there are forest birds, like ant pittas [19] that spend almost all their time on the forest floor and have almost no tail at all--presumably because they don't need it. However, when it comes to the more extreme examples of long tails it is probably related to sexual selection. For example, motmots [20] or squirrel cuckoos [21]. This is certainly the case in the the longest tails of all, the lyrebird [22], for example.--Eriastrum (talk) 22:28, 26 July 2008 (UTC)

Thanks very much for the thoughtful answers, folks. On the 'confusing predators' angle - is it the case that the tail feathers of long-tailed birds will generally come out at the root quite easily if something catches ahold of them? I've found myself wondering this whenever I've been trying to pick up one of my (very quick, very manoeuvrable - even in a cage) budgies. On more than one occasion now, I have ended up with a fistful of tailfeathers but no bird in the hand (man, I feel so guilty whenever that happens). It wouldn't surprise me one bit if a magpie couldn't just leap away from its tail if a cat had it's jaws around the other end. --Kurt Shaped Box (talk) 07:15, 27 July 2008 (UTC)

July 26

Brain development

Which is better for improving your brain, listening to music or watching TV? —Preceding unsigned comment added by 79.76.216.89 (talk) 02:00, 26 July 2008 (UTC)

I'd say it depends on the shows. Listening to Howard Stern has got to be worse for your brain than watching Charlie Rose, while listening to NPR has got to be better for your brain than watching Jerry Springer. StuRat (talk) 04:24, 26 July 2008 (UTC)

Reading, playing games, problem solving, doing puzzles, exercising and eating well are better than music or tv. That said, music is better than tv because it takes more imagination to experience it. -LambaJan (talk) 04:45, 26 July 2008 (UTC)

"I like radio better than TV...because the pictures are better." StuRat (talk) 04:50, 26 July 2008 (UTC)

Actually, music is said to give patience to mind. It increases mental concentration according to Sigmund Fraud because of its rhythemic sequences of audible frequences. Brain is linked to ears through auditory nerves. The music produces periodic vibrations in our eardrum and drags our concentrations more towards it. But if you say frankly, no such effect is produced by TV. TV combines both sound and video (and many a times the sound is not in a singsong manner,i.e periodic).Electromagnetic Transverse light waves from TV entering our eyes and longitudinal sound waves dilate each other's effects.Hence, no net development is caused. In my words, frequent adds in the TV often carry away our minds by making us impatient.So, music is better than TV. Thanks for asking such a realistic question. Best Regards.117.201.96.242 (talk) 19:42, 26 July 2008 (UTC)

Was that a Freudian slip when you misspelled Sigmund Freud? ;-) AlmostReadytoFly (talk) 20:48, 26 July 2008 (UTC)

Yes, it was indeed. I'm sorry. I'm not a good typist.117.201.96.242 (talk) 21:22, 26 July 2008 (UTC)

Treated or untreated lumber?

Is it possible to tell, based on visual inspection, whether an existing wood structure was built with treated or untreated lumber? If so, how do you do it? —Preceding unsigned comment added by 71.162.242.76 (talk) 02:23, 26 July 2008 (UTC)

Treated wood often has a stamp indicating what kind of treatment it's had. Also, older treatment methods tended to turn the wood green. Also, if the structure's been there for a while, and it's touching the ground, and there's no rot where it's touching the ground, and it's not cedar or one of the other naturally resistant species, it's a good bet that it's treated. --Sean 69.134.125.191 (talk) 04:23, 26 July 2008 (UTC)

Anti-Light

Is it possible for there to be anti-light which when shined on a surface gives the opposite colors to what light would have given? —Preceding unsigned comment added by Jamesernator (talk • contribs) 02:27, 26 July 2008 (UTC)

Mmm, I'm thinking no. Think about how "light" works—"white light" is a broad spectrum of frequencies, most of which are absorbed by the surface you are shining them on except for a few that scatter off and produce what we consider to be the "color" of something. (This is a very rough approximation, I know.) So what you're asking for is a way to shine frequencies of light at something in a way that will instead reflect back different frequencies than they normally would. If something appears red, it's because it absorbs all frequencies except red. So how are you going to make that possible reflect back green? It's not going to happen. It doesn't have to do with the light. (If you shined light at it that didn't contain any red, you'd get something that looked blackish and washed out, like what happens when you drive through tunnels with very narrow frequency lighting and all the cars look greyish.) --98.217.8.46 (talk) 03:23, 26 July 2008 (UTC)

What is the opposite of red? Colors don't have opposites. Plasticup ^T/C 03:41, 26 July 2008 (UTC)

Yes they do (after a fashion). Cyan (a combination of blue and green) is the opposite of red. Since people percieve color using three kinds of color receptors in their eyes that roughly correspond to red, blue, and green, then every color can be approximately represented as a combination of red, blue, and green where each component has an intensity between 0 (absent) and 1 (fully saturated). This RGB color scale thus gives rise to natural opposites, where if a color has RGB components (r,g,b) then it's complement is the color represented by (1-r,1-g,1-b). Dragons flight (talk) 05:01, 26 July 2008 (UTC)

Right, but the RGB scale is more an artifact of our vision hardware than the physical aspects of the colors themselves, I do believe. There's no physical reason that a 700nm frequency is the "opposite" of 500nm (or thereabouts). As far as physics is concerned they are just lines on a scale, if that. --98.217.8.46 (talk) 05:42, 26 July 2008 (UTC)

Of course there are opposite colors: if you shine a white light on a surface that absorbes everything but colors in the red spectrum, then the surface will be red. However, if you shine a white light on a surface that does the opposite, it reflects everything except colors in the red spectrum, then you get cyan. They are opposite, complementary colors. Mix them together, and you get black, white or some sort of gray. See also Negative (photography). As for the original question, no, there is no such light. Shine a cyan light on a red surface, and the surface is going to appear black. It's never going to emit cyan because the surface absorbes those wave lengths. An even more clear example is black: a black shirt is going to stay black, no matter how much light you shine on it. It's never going to appear white under any sorts of light. ADFSGL (talk) 14:52, 26 July 2008 (UTC)

Again, the color wheel and all is just an artifact of our visual system. You could imagine visual systems that do not have the same "opposites". Physically there is nothing as an "opposite" of a color—that is just a physiological artifact of how our brains deal with color vision. --98.217.8.46 (talk) 23:33, 26 July 2008 (UTC)

I believe what ADFSGL is trying to point out is that, while complementary colors, like all colors, are indeed artifacts of the human visual apparatus, complementary electromagnetic spectra are well defined (up to a constant) by objective physical laws (specifically, the additivity of electromagnetic waves) and do, indeed, give rise to complementary colors when perceived by the human eye (assuming that both the original spectrum and its complement have intensities within the range of photopic vision, which tends to imply a lack of sharp peaks). Of course, your point that the crudity of human color perception causes some non-complementary spectra (such as your monochromatic examples) to also be perceived as complementary colors is also true. —Ilmari Karonen (talk) 23:54, 26 July 2008 (UTC)

Exactly! Any perceptible color has a clearly defined opposite: its inversion in the visible spectrum. Just because we restrict the wavelengths doesn't mean that we can't have a strict definition for "oppositeness". ADFSGL (talk) 10:29, 27 July 2008 (UTC)

Well what do you mean, that you look at the histogram for the prevalence of every wavelength in a light source and then invert all of the values? But for every wavelength where there is zero prevalence in the initial source would have to have infinite luminosity in the anti-equivalent? If how ever you just mean invert of the RGB scale, whereas you may argue that each colour does have an opposite, it is true that this is just an artifact of our perception, and also that in this case (as in all others) the answer to the original question is no, there is no antilight, it violates conservation of energy and momentum. Philc 0780 17:52, 28 July 2008 (UTC)

Ahem in the olden days of film photgraphy, colour negatives showed the opposites (as did b/w negs). Also remembering something about colours are one thing (such as trees really being red) but we perceive the opposite though have no ref for it. Julia Rossi (talk) 05:26, 28 July 2008 (UTC)

A question on civilization and cooling

How could a pre-electricity, pre-electronics people from the desert adapt their empire to stay cool in rain-forest climes? Could they build windmill fans, or would water mills or water-based turbines work without electricity? Would windmills work even if they didn't have a constant flow of wind going for them? Wiwaxia (talk) 08:12, 26 July 2008 (UTC)

I'm not sure I understand the question. Should the windmill fan create electricity or create wind? If a wind is going, you don't need a fan. Historically, there are some techniques for cooling, the most widely used ones probably evaporative cooling (humans have that build-in ;-) and manually operated fans (e.g. the slave with the palm frond). Good building construction helps (use of thermal mass and good ventilation), and so do lifestyle change. See Siesta. --Stephan Schulz (talk) 08:37, 26 July 2008 (UTC)

Bedouins wear white for a reason. --antilived^{T | C | G} 12:11, 26 July 2008 (UTC)

Rain forests tend to be quite humid, so evaporative cooling doesn't work well, and sweating therefore doesn't cool people down much. It tends to be cooler under the tree canopy just because no sunlight makes it near the ground, however. People in rain forests typically wore minimal clothing, perhaps just a loin cloth, as sunburns aren't an issue and overheating can be. As mentioned previously, resting during the hottest parts of the day can help, as can using a hand fan or taking a swim. StuRat (talk) 13:34, 26 July 2008 (UTC)

Yakhchal are mighty impressive to say they're two-and-a-half thousand year old technology. — Jack (talk) 20:53, 26 July 2008 (UTC)

Underground living. 152.16.59.190 (talk) 10:19, 27 July 2008 (UTC)

I don't believe that's an option in the rain forest, as any underground area is likely to flood. Indeed, many homes in the Amazon are built on stilts because of the risk of flooding. StuRat (talk) 14:30, 27 July 2008 (UTC)

Rashes from insect bites

Insect bites sometimes produce rashes that last several days. I'm talking about the kind that is red, raised, itchy, and lumpy(?). Physiologically, what's happening at the affected sites that makes them "lumpy"? —Preceding unsigned comment added by 71.162.242.76 (talk) 13:10, 26 July 2008 (UTC)

I think it's a histamine reaction. That article may help. --Tango (talk) 17:06, 26 July 2008 (UTC)

Most of it is already answered by Tango, but I want to add something. Some insects also have greater adenine concentration in their DNA. They produce a mixture of citric acid (note the formulae HOOCCH₂COHCOOHCH₂COOH) and histamine. The -COOH carboxyl group, being acidic, facilitates the action of histamine reaction. You can jump to the link for more information. Thank you, for asking such an interesting question.117.201.96.242 (talk) 19:08, 26 July 2008 (UTC)

Getting Punched in the Stomach And Its Effects On The Digestive System

When a person gets hit in the stomach, what are the effects of the force of the body blow to the stomach on the digestive system? Ericthebrainiac (talk) 15:19, 26 July 2008 (UTC)

The immidiete effect will be the initialization of the process of regurgitation. The blood will rush out from the mouth (due to wave of antiperistalsis) if the hurt is dangerous. It may also cause vomiting. If the hit is due to some metal piercing through then peptic infections may aslo occur. These infections can last for several days, often causing peptic ulcer. More details can be found from the thorough study of functions ofstomach.117.201.96.242 (talk) 19:31, 26 July 2008 (UTC)

Hi. If a person gets hit in the diaphram, however, this may cause impact to the solar plexus, which knocks the wind out of the person. By the way, I have a feeling this is related to the "getting kicked in the testicles" question, which by the way is often illegal. Hope this helps. Thanks. ~AH1^(TCU) 16:34, 27 July 2008 (UTC)

FYI, I think you have diaphragm and solar plexus reversed. Illegal? It's rarely permitted in contact sports if that's what you mean, but I don't think a kick to someone's balls is any less legal than other forms of unarmed aggravated assualt. --Shaggorama (talk) 20:06, 27 July 2008 (UTC)

biology

Who coined the term tissue? ```` —Preceding unsigned comment added by 61.1.236.70 (talk) 16:31, 26 July 2008 (UTC)

It's an old word, apparently originating from the Middle English word "tissu", meaning "a rich kind of cloth", according to the American Heritage Dictionary. Nobody just suddenly looked at tissue and decided to call it "tissue" out of the blue. -- Captain Disdain (talk) 16:51, 26 July 2008 (UTC)

bacteria longevity

How long would (harmful) bacteria live on a dry smooth surface, such as a plate? A women's mag I like recently had a rant about bacteria collecting on dishcloths. But if I wash a plate, let it dry in the rack overnight, and use it for breakfast or lunch the next day, does anything harmful from the dishcloth still remain? I did read the bacteria article, but couldn't find the answer. Thank you.64.231.9.30 (talk) 17:21, 26 July 2008 (UTC)

The answer is "it depends". Clean, dry surfaces like porcelain or glass are not friendly for bacteria. So while your plate may have some bacteria, the chance that there are enough to cause trouble is minimal. More importantly, fear of harmful bacteria is often much out of proportion (very much aided by advertising from detergent companies with disinfectants to sell). A normal household is never sterile, and probably never will be. Normal hygiene is sufficient in nearly all cases, and overly aggressive use of disinfectants is likely to be worse that the occasional microorganism. Just wash your utensils, hands, and towels occasionally (especially after handling risky food like chicken). --Stephan Schulz (talk) 17:58, 26 July 2008 (UTC)

Thanks!64.231.9.30 (talk) 18:24, 26 July 2008 (UTC)

And note that if you somehow did get rid of all of the bacteria in your life your immune system would probably suffer. The most low-level exposure you have to things like that, the better your immune responses are to larger attacks. A truly sterile household would be a recipe for disaster. --98.217.8.46 (talk) 23:28, 26 July 2008 (UTC)

two basic kinds of bacteria, either of which can be harmful or benign (or even good for the body). your normal bodily residents are fairly well protected against your body's constant attacks, but in the process have lost the ability to form spores and when conditions get unhealthy for them, they just die. (gram negative) overnight drying out on something nonporous like a counter or a plate would certainly do them in. they might survive in a damp sponge or some such, though. nasty varieties would include salmonella, or the toxic strains of e. coli. bear in mind that they don't come out of nowhere; they need to come from a source, like raw poultry, or an infected person, or food which has been contaminated by an infected person in the process before it got to your kitchen.

the other kind of bacteria, gram positive, are evolved to live out in the wild rather than in your body; since conditions are much more variable, they have the ability to sporulate whenever conditions get tough, like drying out. and the spores are damn near unkillable under normal conditions (that's kind of what they evolved to be); the standard sterilization procedure is typically 15 lbs pressure (above atmospheric) of live steam for 15 minutes, for instance, which is something typically not found in the home. concentrated bleach or various high powered acids would do it, but you probably don't want to mop your kitchen with them. in fact you're probably more at risk from routine exposure to them than any of the bacteria in question. the side effect of being able to sporulate is that their surface is more susceptible to things like your immune system, the opposite of the gram negative described above; this is why you don't rapidly die from the uncountable bacteria all around you all the time. but the few who have discovered how to make an attack on the human body are, logically, pretty brutal in order to knock out your defenses. anyway they would include things like anthrax; but nobody gets anthrax from a kitchen counter.

mostly, it's not a question of eliminating all bacteria, just being aware of what possible harmful bacteria are and where they are and concentrating on them; so clean up thoroughly around where raw chicken has been, for instance, or raw vegetables; but you don't have to worry that a placemat which has seen only cooked food is going to be a problem if it isn't sterilized. Gzuckier (talk) 06:42, 27 July 2008 (UTC)

Antlions and Rain

How do antlions avoid drowning in the rain? The article says that they usually build a pit where they are sheltered from direct sunlight and rain, but there are some in my yard that are out in the open lawn, and I don't know how they don't drown.CalamusFortis 20:13, 26 July 2008 (UTC)

Antlions probably do drown sometimes if rain is very heavy. However, they normally build their pits in sandy soil or just plain sand that drains very well. So most rain would just seep away and not accumulate enough to drown the antlion. Also, most antlions live only in arid areas where there is very little rain in the first place.--Eriastrum (talk) 22:02, 26 July 2008 (UTC)

What is this plant?

What is this plant? (Flower inset)

Hi folks, I was wondering if you could help me identify this plant that's been growing in my garden? I live in Nottinghamshire, England. The plant in question is a small herbaceous angiosperm with branched green leaves and blood-red stems. The flowers are small and pink. It seems to be perennial and spreads like wildfire, thriving even in very rocky soil. It was pretty at first, but is starting to create monocultures, so I assume its alien to Britain. Any takers? — Jack (talk) 20:30, 26 July 2008 (UTC)

I don't recognize the species, but it is obviously a plant in the Geranium Family (Geraniaceae). The unequal petals (three smaller and a different color than the other two) indicates it is not an Erodium (Cranesbill), which was my first impression. This also rules out the genus Geranium. So it must be one of the many species of Pelargonium. Take a look at this link [23] to get an idea of how many species there are in this genus. The trifoliately compound leaves and bright red stems are a bit unusual, however. I'm sure that you are right that it is a weed. Most species are native to south Africa; certainly none are native to England. I live in California where we have a number of weeds that belong to the Geranium family, but not this one.--Eriastrum (talk) 21:43, 26 July 2008 (UTC)

Ah, I think I've found it! Herb Robert, I believe it's called. Thanks for pointing me in the right direction (the flower was viewed from an angle and slightly overexposed). Thanks again — Jack (talk) 00:14, 27 July 2008 (UTC)

Yes, definitely [[Herb Robert]. Richard Avery (talk) 07:02, 27 July 2008 (UTC)

Can that triffic pic go in the article or in the article Rosette? Julia Rossi (talk) 05:21, 28 July 2008 (UTC)

black hole theories

hi, i am doing a study on different aspects of black holes. i am trying to find a range of theories on how they are formed, how long they exist etc. if anybody knows any theories, that would be a great help.

p.s. couldnt find any info about it in the article.

thanks, Missy315 (talk) 23:01, 26 July 2008 (UTC)

Black holes are formed when a massive star dies, and collapses into itself. If it's not massive enough, it will collapse into a neutron star, or a white dwarf. But if the star is massive enough, it will become a black hole. How long they exist depends on the size of the bh, and if it's "eating" any matter. A black hole will eventually evaporate into hawkings radiation, which I believe is just photons. The rate that it evaporates also depends on its size. The more massive the bh, the slower the rate of evaporation. So not only is a small black hole going to evaporate faster because it has less mass to evaporate, but the rate is also faster. To give an idea of how long massive black holes will last, according to the heat death article, they will be the last vestiges of our universe before they evaporate, meaning everything else will be gone before they are.ScienceApe (talk) 23:09, 26 July 2008 (UTC)

Did you read Black hole#Formation and evolution? PrimeHunter (talk) 23:11, 26 July 2008 (UTC)

umm...i dont think so, im only thirteen by the way. i was having lots of trouble finding theories on it and somebody directed me to here. thanks, anyway. Missy315 (talk) 07:04, 27 July 2008 (UTC)

To understand the formation of black holes, you must know about the life-cycle of stars. The stars of central masses more than 3.2 times the Solar mass end their life cycles through a severe SUPERNOVA explosion. This explosion causes the outer parts of the star to be ejected out into space.As a result, tremendous force of gravitation collapses the centre of the star. When the centre collapses to an extent that its radius becomes less than Scwzerchild Radius, the star gets transformed to a Black Hole. A black hole always spins about itself. It is said to be "A fourth dimensonal Gateway". The black hole slowly emits Hawking radiation and in fact gets evaporated or vapourised. If you are interested in more details, should I provide you with the steps of formation of black holes?117.201.97.83 (talk) 18:56, 27 July 2008 (UTC)

July 27

Where is you stomach?

sorry to be so stupid, but can anyone say whether thestomach is above or below the diaphragm in human. —Preceding unsigned comment added by 79.76.140.78 (talk) 00:57, 27 July 2008 (UTC)

Below, definitely below. The diaphragm acts as a barrier between the upper Thoracic cavity (containing the heart and lungs) and the lower Abdominal cavity (containing the stomach, liver, intestines etc.) — Jack (talk) 01:07, 27 July 2008 (UTC)

This image is way simplified, but it should be good enough for your needs. --Shaggorama (talk) 01:23, 27 July 2008 (UTC)

The stomach is actually located at the level of our belly-button or navel.It is located in our abdominal cavity, which is obviously below the Diaphragm.117.201.97.83 (talk) 19:00, 27 July 2008 (UTC)

A better description would be that your stomach is on the left side of your abdomen, extending up from the belly button to the diaphragm (bottom of rib cage). Make a fst with your left hand, put your thumb on top of your bottom rib with your knuckles roughly in line with your left nipple, and that's about where you're stomach is. Here's a better image for you --Shaggorama (talk) 08:02, 28 July 2008 (UTC)

Polycarbonate against glass causes oily looking adhesions

I recently bought a case for my iPhone. The case has a thin polycarbonate protective screen that sits on against the iPhone's glass screen. I notice that there are areas where the glass and polycarbonate rest against each other. In bright light, these areas look dark and oily with a rainbow refraction around the perimeter. If I squeeze the case, I can get the polycarb to lift away from the glass and these areas disappear. What causes this weird oily/wet areas and rainbow refraction? How can I prevent it? --70.167.58.6 (talk) 01:20, 27 July 2008 (UTC)

Did you clean your screen before putting it on? It may simply be moisture or grease from your fingers. --antilived^{T | C | G} 02:08, 27 July 2008 (UTC)

It sounds like a interference pattern like newtons rings. Ask for more details.87.102.86.73 (talk) 10:13, 27 July 2008 (UTC)

Yes, Newton Rings! Here's a photo [24] (sorry, I don't know how to post to Wiki commons). Both surfaces have been cleaned over and over with lens cleaner and microfiber cloth. --70.167.58.6 (talk) 22:30, 27 July 2008 (UTC)

yep, thin film interference, unless if you find a way to suck out all the air at the interface, then I don't know how you'll be able to fix it. Coolotter88 (talk) 18:53, 28 July 2008 (UTC)

The insecure narcissist?

Are there any psychological terms that would describe someone as being both a narcissist and having low self esteem (two seemingly antithetical personalities)? --70.167.58.6 (talk) 01:24, 27 July 2008 (UTC)

You might throw anorexia or other eating disorders up there, at least maybe as a consequence of the above combination. I hesitate to suggest that though because as I understand it, narcissism is more than self-obsession: it's self-love. That kind of egoism would presumably be wrapped in strong self-esteem, so what you are suggesting may be an analytic impossibility (like a square circle). --Shaggorama (talk) 04:08, 27 July 2008 (UTC)

Many personality disorders are often attributed to the opposite being true - hence the term 'disorder' - as such and analytical impossibility is (irrelevent) and actually is indicative of the disorder itself...

There is an article Narcissistic personality disorder

NPD is considered to result from a person's belief that he or she is flawed in a way that makes the person fundamentally unacceptable to others [5]. This belief is held below the person's conscious awareness; such a person would typically deny thinking such a thing, if questioned. In order to protect themselves against the intolerably painful rejection and isolation that (they imagine) would follow if others recognised their supposedly defective nature, such people make strong attempts to control others’ view of them and behaviour towards them.

also common in teenagers and by no means necessarily a personality disorder, (unless you're still acting like that when you're 37...)87.102.86.73 (talk) 15:31, 27 July 2008 (UTC)

g-force

From my calculations I figured this out:

333 m/s (334)
333 * 60 (334 * 60) = 19,890 (20,040) m/min
19,890 * 60 (20,040 * 60) = 1,193,400 (1,202,400) m/hr
1,193,400 / 1,000 (1,202,400 / 1,000) = 1,193.4 (1,202.4) km/h

741.5443808156358 (747.1367215457689) mi/h

I want to figure out the g-force for the above mentioned data, I looked over the g-force article, but couldn't figure out how to get the value. 76.29.116.172 (talk) 02:34, 27 July 2008 (UTC)

g-force measures acceleration, the rate of change in velocity. It is impossible to calculate acceleration unless, in addition to the velocity you gave, you have the time in which it was attained. --Bowlhover (talk) 03:29, 27 July 2008 (UTC)

yup. it doesn't matter how fast you're going: if you're going 741 mi/h but at a constant speed, then you're going 0 g's. Out of curiosity, where did you pull your original velocity from? --Shaggorama (talk) 04:03, 27 July 2008 (UTC)

At a guess, the speed of sound at sea level. —Preceding unsigned comment added by 121.72.174.226 (talk) 04:19, 27 July 2008 (UTC)

Just as an example, say it takes you exactly one minute (I completely random number that I pulled out of my ass) to accelarate to Mach 1, the speed of sound in air. The acceleration is then 333 m/s divided by 60 s, which is 5.55 m/s^2. Since the earth's gravitational acceleration is about 9.8 m/s^2, this accelration would give about half a g-force. ADFSGL (talk) 10:36, 27 July 2008 (UTC)

Removal of spleen, lymphnode and thymus

What are the effects of removal of spleen, lymphnode and thymus in new borns? —Preceding unsigned comment added by 59.92.122.159 (talk) 04:28, 27 July 2008 (UTC)

A weak immune system, at the very least. Have you read spleen, lymph node, thymus? --Ayacop (talk) 06:00, 27 July 2008 (UTC)

In addition to that, the lympathic system will also get weakened. You should know that spleen acts as a blood-reservoir. In case of emergency, such as excessive bleeding, spleen releases its extra blood for replenishing the loss. If the spleen is removed, this mechanism will not work. In addition to that, spleen produces new leucocytes in new borns. So, the leucocyte no. in their bodies will also fall, making them more prone to pathogens. If we remove the thymus, some thymus related hormones will not be formed in the later age. For the removal of lymphnodes, the deamination rate in the liver may decrease.117.201.97.83 (talk) 18:40, 27 July 2008 (UTC)

We have an article specifically on asplenia, the condition of being without a spleen. -- Coneslayer (talk) 16:58, 28 July 2008 (UTC)

"the button"

What is the physiology behind the syncope that often results from a strong punch to the jaw or chin? --Shaggorama (talk) 04:38, 27 July 2008 (UTC)

Head gets punched, head snaps backwards, brain bangs against back wall of skull, brain doesn't like this, brain goes bye-bye for a while. I think. --Kurt Shaped Box (talk) 07:40, 27 July 2008 (UTC)

Due to inertia it first bangs against the front, after gaining momentum it bangs against the back. Then it may wobble around a bit, but by then you are likely to have lost a few of your wits. Traumatic brain injury has some data on this. --Cookatoo.ergo.ZooM (talk) 11:20, 27 July 2008 (UTC)

Then what's so special about the chin? There are loads of ways to get hit in the face, but for some reason getting a solid knock right on the kisser seems to make people's knees more rubbery than other spots on the head. Besides, I don't think all KO's are concusions, otherwise we'd be seeing alot more permanent brain damage cropping up faster from boxers. I'd heard some rumor that the mandibular nerve has something to do with it (hence having a solid chin helps counter this effect because the nerve doesn't get stimulated when the button is "pushed"), but I don't know what that's all about. --Shaggorama (talk) 15:51, 27 July 2008 (UTC)

Could it be because the chin is further away from the brain and is forward of the neck so you get more leverage? If you hit someone above the ear, say, their head will just move sideways, you hit them in the chin and it rotates as well. --Tango (talk) 17:27, 27 July 2008 (UTC)

My father was a professional boxer at one time and he said that to knock someone out you have to hit them on the side of the head and make the head whip round. SpinningSpark 17:36, 27 July 2008 (UTC)

I remember a show (probably the Discovery Channel) that discussed the "side of the head" vs. "face" angle in boxing and car crashes. They said it had something to do with the hemispheres of the brain spreading apart due to a blow to the side of the head. This would cause the connecting tissues (axon?) between the hemispheres to swell up, causing passing out, or worse, coma and death. I suppose hitting on the side of the chin might be worse as it is farther away, as Tango said, increasing torque. --Bennybp (talk) 18:45, 27 July 2008 (UTC)

I think the tissue you meant is the Corpus callosum. I still don't believe that getting KOed means you necessarily underwent brain trauma (not that it's great for the brain), although there certainly seems to be some consensus here. Speaking of the temporal vs facial angle, I also read that a blow to the temple can take a person down because it disrupts the equilibrioception of the semicircular canals. Thoughts? --Shaggorama (talk) 19:59, 27 July 2008 (UTC)

I think I found what I was talking about: Diffuse axonal injury (although not necessarily about spreading of the hemispheres, it's close). When not a direct hit (ie a hit on the chin, causing rotation, etc) it can sometimes cause more damage. --Bennybp (talk) 23:50, 27 July 2008 (UTC)

There's also the Glass Jaw. Julia Rossi (talk) 00:53, 28 July 2008 (UTC)

Is Purell safe to drink?

Everyone's sort of paranoid about security where I live right now; I've seen security guards ask people to take a drink of every liquid they're carrying to make sure they're not trying to bring harmful chemicals into museums and stuff. My question is: if someone had to drink some Purell for security reasons, would it be safe, and how much would be the maximum amount someone could drink safely? Thanks in advance. —Preceding unsigned comment added by 58.35.41.223 (talk) 11:14, 27 July 2008 (UTC)

"if someone had to drink some Purell for security reasons" ?? what?

No it's not safe to drink in general it's amongst other things 62% alcohol - that's almost twice that of vodka.87.102.86.73 (talk) 11:25, 27 July 2008 (UTC)

Heh, like I said, people here are crazy. —Preceding unsigned comment added by 58.35.41.223 (talk) 11:29, 27 July 2008 (UTC)

Well, that alcohol content certainly wouldn't make it unsafe to drink, it just means it gets you drunk pretty easily. Looking at the article, there doesn't seem to be anything particularly toxic in Purell. That doesn't mean it's good for you, but taking a sip of it wouldn't do you any actual harm. Presuming, of course, that the article lists the ingredients correctly, which may or may not be the case. (That said, the bit about the maximum amount someone could drink safely kind of activates my "suspicious bastard" cycle and makes me wonder if the part about museum guards and whatnot is made up and you'd just like to use Purell as a substitute for an actual alcoholic beverage, perhaps because those bastards at the store want to see some proof of age. Should this be the case, I'd recommend against it. Not only is it not made for drinking and probably isn't good for you, it's downright pathetic. I mean, we're talking bum pathetic; that's like one step away from drinking anti-freeze. It's just a dumb idea.) -- Captain Disdain (talk) 12:49, 27 July 2008 (UTC)

The maximum amount part does seem funny. Why does it matter what the maximum amount you can drink is. All that matters is whether you can drink the small amount a security guard is likely to request of you. Nil Einne (talk) 15:23, 27 July 2008 (UTC)

I think the security guard would not let you take it in, or a bottle of wine, or crate of beer either.. They tend to discourage museums being used as a drinking pit in general...87.102.86.73 (talk) 15:25, 27 July 2008 (UTC)

Given that the manufacturers of Purell themselves advise against its ingestion, I think you have good grounds to tell this security guard he can drink it himself if he wants. This is really strange. Even airport TSA guards don't make you drink your liquids, nor do guards at the Smithsonian. What museum is doing this? --Shaggorama (talk) 15:56, 27 July 2008 (UTC)

Nothing to do with museums, I know, but I've definitely heard of it happening on some train networks when there's a security alert. 91.143.188.103 (talk) 18:36, 27 July 2008 (UTC)

I've heard it happening with security in airports too at least in the immediate post 2006 transatlantic aircraft plot world. I suspect any security in such a world won't allow you to bring in anything with that high a alcohol content anyway. See [25] for example which suggests in 2006 when the liquid ban in the US was initially relaxed liquor still had to be checked-in. I don't know what conditions are like now but again, I suspect if anyone is that paranoid about liquids whether in airports, museums or train stations, they're not going to allow anything with a 62% alcohol content no matter whether you drink it or not. For that matter, I doubt any security guard is going to ask you to open your bottle of liquor or any other alcoholic beverage and take a sip so I would suspect they're automatically out. If they are going to ask you to drink all liquids, Purell is likely to go with them simply because no security guard is likely to ask you to drink it and if that's their only option, they'll just ask you to chuck it... (Indeed I suspect if you did volunteer to drink Purell the guards would be even more concerned) Nil Einne (talk) 18:55, 27 July 2008 (UTC)

I remember when the only liquids you were allowed on planes were things like baby's milk they made you take a sip. The only reason for requiring people to take a sip of any liquid is if you want to verify the liquid is a drink. Purell is not a drink, so it's a pretty pointless test. --Tango (talk) 19:15, 27 July 2008 (UTC)

Forgive my lateness, but doesn't Purell contain toxic *denatured* alcohol? --70.167.58.6 (talk) 22:31, 27 July 2008 (UTC)

Makes no difference, god bless them! -hydnjo talk 23:42, 27 July 2008 (UTC)

Why would a product like that be misleadingly named Purell? It sounds like spring water - unless it's pronounced pure-'ell. Julia Rossi (talk) 03:24, 28 July 2008 (UTC)

there's actually a problem in prisons with people drinking hand sanitizer. http://www.webmd.com/content/article/131/118125.htm hey everybody, purell coladas!Gzuckier (talk) 03:47, 28 July 2008 (UTC)

Hmm, interesting. The OP appears to be in China. If this is the case, then it might make his story slightly more plausible.--Anakata (talk) 09:53, 28 July 2008 (UTC)

Funny story. I was traveling with a swim team several years ago and the airport security guards made one of my team mates take a drink from the bottle he was carrying, but this joker had a water bottle full of 151 proof vodka. He did a great job of drinking deeply, smiling politely, walking away quickly, and vomiting in the bathroom. Plasticup ^T/C 12:26, 28 July 2008 (UTC)

Suicide thoughts sympton or illness

Are suicide thoughts always a sympton of an illness (like depression) or can they be a illness on their own? —Preceding unsigned comment added by Mr.K. (talk • contribs) 17:28, 27 July 2008 (UTC)

Question moved from:http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Miscellaneous#Suicide_thoughts_sympton_or_illness

Suicide crisis says it is usually caused by depression or some other psychiatric illness, I don't know if it always is. It's probably just a matter of definition. If you or someone you know is having suicidal thoughts, there are phonelines you can call for advise (I don't know where you are, so I don't know any specific ones). They'll be more help than us. --Tango (talk) 19:19, 27 July 2008 (UTC)

Foam on the beach

If I find some foam/spum on the beach, floating everywhere, kind of green/brown, what is it supposed to be? —Preceding unsigned comment added by Mr.K. (talk • contribs) 17:41, 27 July 2008 (UTC)

Take saltwater. Add various proteins. Swish it up. You'll get foam. If it comes out of the sea, it is called sea foam. -- kainaw™ 19:51, 27 July 2008 (UTC)

Oooh! Here's a nice picture. -hydnjo talk 23:36, 27 July 2008 (UTC)

It's extraordinary and beautiful with every bubble about to give birth to a human! Julia Rossi (talk) 00:44, 28 July 2008 (UTC)

And, every human is ... a photographer!  ;-) hydnjo talk 00:51, 28 July 2008 (UTC)

Is it me, or is every human a photograph in a space suit? --Tango (talk) 01:43, 28 July 2008 (UTC)

ET alert. It gives "pond life" another illustration. Julia Rossi (talk) 03:10, 28 July 2008 (UTC)

And the reason why salt water does this and plain water doesn't (so why you get seafoam and not riverfoam) is to do with ions and some ionic behaviour that, rather excitingly, was only really noticed a few years ago. That salt water foams was obviously noticed ages ago, but it's only recently that we've got close to understanding why. Even in apparently simple areas, there is still a lot to be studied :D 79.66.124.253 (talk) 20:48, 28 July 2008 (UTC)

Collection of gas over water

If one collects a gas, say hydrogen gas, over water, I know that one must subtract a constant based on the temperature to find the pressure of the gas to account for the water vapor present. What if the same operation is performed over a solution? For example, if you react perchloric acid solution and magnesium, producing magnesium perchlorate and hydrogen gas, and collect the hydrogen gas, do you have to factor in the water vapor coming off from the solution in determining the pressure, and hence the molarity or mass of hydrogen? FlamingSilmaril (talk) 20:04, 27 July 2008 (UTC)

Yup, you still need to account for vapor pressure. The vapor pressure of a solvent over a solution will always be less than the solvent as a pure liquid, but its' still there. Use Raoult's law. BUT, in the specific example you gave, if you use an excess of acid, the magnesium should react completely allowing you to produce a good estimate of the mass of product by using stoichiometry. This all mainly depends on how accurate you need to be and whether we're talking ideals on paper or laboratory products. --Shaggorama (talk) 20:23, 27 July 2008 (UTC)

Actually, it's dealing with an excess of magnesium. What we're given is: you react a certain volume of the perchloric acid solution and excess magnesium, and a certain volume of gas is produced at a certain temp and pressure. Then you have to find the molarity of the solution. I'm fairly sure I know how to do it; I was just wondering whether the vapor would be a factor. And this is all on paper, not actually in the lab. Thanks very much! FlamingSilmaril (talk) 20:45, 27 July 2008 (UTC)

Wow, i can't believe I gave you teh wrong limiting reagent! Thanks for the correction, I've gotta stop doing this tired... I haven't done the math yet myself, but my guess is that the vapor pressure will be a very small contributor to the product. If you're actually given the temperature and pressure of the gas produced, then I would suggest assuming that the vapor pressure contribution is negligible: find theoretical moles of hydrogen produced via stoichiometry, then compare the pressure given by PV = nRT with the experimental pressure given by the problem. It's an estimate, sure, but if it matches up, you're set; if not then backtrack to considering vapor pressure. --Shaggorama (talk) 07:47, 28 July 2008 (UTC)

Information!

Can anyone suggest me a link from which I can download all Scientific Laws, effects and principles in one complete .pdf or .doc form?117.201.97.83 (talk) 20:49, 27 July 2008 (UTC)

ALL? -hydnjo talk 23:27, 27 July 2008 (UTC)

That's what the OP said. I don't think we're going to be able to help with this one. Algebraist 23:29, 27 July 2008 (UTC)

How about $R_{ab}-{1 \over 2}Rg_{ab}={8\pi }T_{ab}-\Lambda g_{ab}$

${\frac {\partial \langle H\rangle }{\partial \pi _{n}}}={\frac {\partial a_{n}}{\partial t}}\quad ,\quad {\frac {\partial \langle H\rangle }{\partial a_{n}}}=-{\frac {\partial \pi _{n}}{\partial t}}$

and the QM Hamiltonian (anyone know it?). *Max* (talk) 03:04, 28 July 2008 (UTC).

I was going to suggest downloading Science for Dummies from the library shelf, but I changed my mind. Julia Rossi (talk) 03:21, 28 July 2008 (UTC)

I can't imagine you would find them all in one place. Try starting with our laws of science and physical law articles.--Shantavira|^{feed me} 06:24, 28 July 2008 (UTC)

More than half of those are approximations and the rest can be derived from my four. *Max* (talk) 15:04, 28 July 2008 (UTC)

New surgical procedure

A female doctor from Michigan devised and conducted a new heart repair surgical procedure (along with a team of other surgeons) on a man about 26 years old who resided in San Diego. The surgery was performed sometime in November 2007. It was even rumored that the new procedure might be named after her. Does anyone out there know the name of this doctor and the name and/or type of procedure she performed?

71.191.91.20 (talk) 21:02, 27 July 2008 (UTC)

Quality of medical reliable sources

I am wondering how to evaluate the quality (reliability, impact factor) of medical sources when using them as references on Wikipedia. Since I am not experienced in reading or evaluating studies directly, my focus is more on articles that interpret study results. I would like to learn how to research the journal and the author(s).

Specific journals:

• Emergency Medicine News, indexed/distributed online by Lippincott Williams & Wilkins
• Canadian Medical Association Journal, prestigious, but recent decline mentioned at Talk:Canadian Medical Association Journal

Thanks. Flatscan (talk) 22:26, 27 July 2008 (UTC)

Let me get this straight; are you asking us on the Reference desk how you should evaluate the references that you may find in articles relating to medicine. Is that your question? -hydnjo talk 22:53, 27 July 2008 (UTC)

That's about right, although these references may not be in the Wikipedia article yet – I would be considering whether to add them and how to present them. Would Wikipedia:WikiProject Medicine be a better place for this question, or would you suggest another place? Flatscan (talk) 23:07, 27 July 2008 (UTC)

Before asking elsewhere please read and understand our article about citing sources. -hydnjo talk 23:26, 27 July 2008 (UTC)

Thank you for the link. I navigated through Wikipedia:Scientific citation guidelines to Wikipedia:Manual of Style (medicine-related articles)#Citing medical sources and Wikipedia:WikiProject Medicine/Reliable sources. CMAJ is listed there as a core journal. Flatscan (talk) 23:52, 27 July 2008 (UTC)

For all of that, "You're a better man than I am..."! -hydnjo talk 00:00, 28 July 2008 (UTC)

July 28

Is there a combination of foods that can explode in a peron's stomache?

Are there any combinations of foods that, although each is individually tasty, eaten succession would explode? —Preceding unsigned comment added by 79.122.77.196 (talk) 04:42, 28 July 2008 (UTC)

I'm going to make a giant leap of faith here and assume that you mean stomach when you ask about "stomache" and by "peron's" you mean person's. These spelling errors aside, there may indeed be some combination of foods that meet your requirements but you'll not likely find help at Wikipedia unless you provide some context that shows your intentions to be benign. Otherwise, find another site to screw around with. -hydnjo talk 05:08, 28 July 2008 (UTC)

Unless you develop a taste for something exotic, I really doubt it. And hydnjo, let's assume good faith. 79.122 is probably refering to the urban legend that soda a "pop rocks" can make your stomach explode. The RefDesk gets much stranger questions that this. Plasticup ^T/C 12:10, 28 July 2008 (UTC)

To explode would require your stomach to be sealed off from the outside atmosphere, but it's not (see belching). --Sean 14:00, 28 July 2008 (UTC)

The stomach's venting doesn't always work (see "torsion" in dogs, cows, humans and presumably all mammals). This happens when the stomach twists and cuts off the normal intake or exit routes - like bending a garden hose sharply to cut off the flow. The condition can prove to be fatal within the hour. 196.2.124.253 (talk) 19:34, 28 July 2008 (UTC)

With the right preparation just "one wafer-thin mint" should do it. Richard Avery (talk) 15:53, 28 July 2008 (UTC)

I doubt there's an explosive combination, but I'm sure you could get something poisonous. Salt is the exact opposite: It's made from chlorine, a poisonous gas, and sodium, which would explode if you ate it. — DanielLC 16:47, 28 July 2008 (UTC)

Perhaps Evita Peron's and/or Juan Peron's stomach would explode if they took enough nitroglycerin pills ? StuRat (talk) 16:48, 28 July 2008 (UTC)

Hi. This doesn't make your stomach explode, but certain combinations of foods will cause food poisoning. For example, I don't have a source for this, but it is a widely known fact (in some countries) that eating persimmons and crab meat together will lead to severe food poisoning. There are also claims that other foods together will cause ill effects, like beef with chestnuts or carrots with turnips, but it's more likely that those might be made up. Thanks. ~AH1^(TCU) 17:59, 28 July 2008 (UTC)

Hi. Here is an example of ill-matched foods (but will not make your stomach explode). Thanks. ~AH1^(TCU) 18:05, 28 July 2008 (UTC)

Are we getting into Culturally specific illnesses like Fan death? 79.66.124.253 (talk) 20:41, 28 July 2008 (UTC)

A confusing post

(header added by hydnjo)

why does compensation point occurs onlu twice a day? —Preceding unsigned comment added by 219.90.105.176 (talk) 04:58, 28 July 2008 (UTC)

Is the teeny article compensation point any guide? Julia Rossi (talk) 05:41, 28 July 2008 (UTC)

Hint: photosynthesis is driven by sunlight - is there more sunlight at noon or at midnight? Franamax (talk) 08:52, 28 July 2008 (UTC)

Well the rate of photosynthesis will increase from zero at night to a maximum in the day, before returning to zero at night. Intersecting the rate of respiration once on the up and once on the down, these two points are the compensation points. Philc 0780 17:42, 28 July 2008 (UTC)

"Compensation"? Why not equilibrium point? 196.2.124.253 (talk) 19:38, 28 July 2008 (UTC)

Dolmen construction

Is this the right desk, but after looking at the article refd above Dolmen and finding a topstone that weighed 150 tonnes (I take it the article may mean 1.5 tonnes), how were they lifted into place? Julia Rossi (talk) 05:38, 28 July 2008 (UTC)

In colder climates, one way to do that would be through frost heave. Get the soil at the centre wet, when it freezes, it will lift the stone a little bit - then brace at the outside to keep it elevated. Next summer, pack more earth underneath and get it wet again. I have no idea if they did it that way, but maybe the aliens gave them some tips. Franamax (talk) 07:57, 28 July 2008 (UTC)

And I agree 150 tonnes is a little much. Switching units, rock is 160-190 lb/ft3, so a 20' x 8' by 1' slab would be around 12 tons. To get 150 tons, you need 50' x 9' x 4' - none of the pics look to be quite that impressive. Franamax (talk) 08:12, 28 July 2008 (UTC)

Agreed. Maybe the detail needs a point in the article. Will take it to the talk page. Julia Rossi (talk) 08:58, 28 July 2008 (UTC)

Hi! The article says The largest dolmen in Europe is the Brownshill Dolmen in County Carlow, Ireland.[citation needed] Its capstone weighs about 150 tonnes where as Brownshill Dolmen says The capstone at Brownshill, weighing an estimated 100 metric tons - so there is definately some error there. (though link 2 from that article gives a 'reputed 150 tonnes'.

Well granite weighs more than water and 1cubic meter weighs ~3 ton so 150 ton would be 50 cubic metre (100 tonn 33 cubic metre) giving 5x5x2m (or 3x2x5.5m) both of which seem optimistic estimates. Tens of tonnes seems more likely87.102.86.73 (talk) 11:18, 28 July 2008 (UTC)

If you expand this image then you can see that the stone is ~2x5m on the front face - so maybe the figure is correct.87.102.86.73 (talk) 11:41, 28 July 2008 (UTC)

Following up a bit, the 150-tonne figure seems not unreasonable for the biggest stone pictured in the article. A general method of construction would be to build a long slope to the desired height and drag or use rollers to move stones into place. Vertical stones can be emplaced by digging a pit and tipping the stone in (some crushing of workers may occur, don't try this at home). The cap stone can be simply dragged over top, clear away all the dirt, bob's yer uncle - standing stones. Considering that these were for ritual/religious purposes, it's not unreasonable to think that this vast an effort would be expended over a period of years. Franamax (talk) 10:24, 28 July 2008 (UTC)

More likely method is to use a lever or wooden wedges to raise one end of the capstone by a few inches, then secure this end with wooden blocks and repeat at the other end, thus raising the stone incrementally on a wooden platform. An article on Megalithic tombs built by small teams in British Archaeology suggests this could be done with surprisingly small amounts of manpower - it says a team of 8 could have raised the capstones of the Stonehenge trilithons, weighing 40 tons each. But earthen ramps are also possible - I think there is a theory that many dolmens were originally buried in earth mounds, like passage graves. Gandalf61 (talk) 10:38, 28 July 2008 (UTC)

One theory (for specific dolmens) is that they weren't raised at all - but were dug into below, smaller stones inserted and the rest of the soil removed. This requires the capstones to be already there - erratics.87.102.86.73 (talk) 11:30, 28 July 2008 (UTC)

which kidney works first?

As we all know, most humans have two kidneys. i want to know that which kidney (left or right one)starts to work first & which remains in stand by.Alok2n 00 (talk) 08:04, 28 July 2008 (UTC)

I don't think it works quite like that. Unless I'm mistaken, they both work simultaneously -- it's just that they're efficient enough that we can get by with only one of them if the other one is removed or stops working for some reason. -- Captain Disdain (talk) 09:54, 28 July 2008 (UTC)

Wait, you guys don't consciously choose? Plasticup ^T/C 12:13, 28 July 2008 (UTC)

Well, y'know, kidneys these days. They never do as I say. -- Captain Disdain (talk) 12:41, 28 July 2008 (UTC)

Have a look at Development of the urinary and reproductive organs#Metanephros and definitive kidney and Kidney#Embryology for more information. Zain Ebrahim (talk) 14:05, 28 July 2008 (UTC)

Refridgerators

what are the gases that used in refrigerators?what are they used for? —Preceding unsigned comment added by 117.196.134.20 (talk) 15:55, 28 July 2008 (UTC)

See refrigerant and list of refrigerants.--Shantavira|^{feed me} 16:11, 28 July 2008 (UTC)

That list is free/on us. StuRat (talk) 16:36, 28 July 2008 (UTC)

Groannnnn. 128.165.101.105 (talk) 19:27, 28 July 2008 (UTC)

Energy efficiency of a human compared to a robot

If we were to compare Asimo with a human, which is more energy efficient? Like if a human ate two burgers in the morning and Asimo had his batteries charged, then both go for a walk, which one uses their energy more efficiently? ScienceApe (talk) 16:03, 28 July 2008 (UTC)

The average person uses about 2000 Calories per day. That's about 100 watts. This is average, including sleeping. Asimo uses about 25 watts while walking,[26] so he's more than four times as efficient. Sorry, didn't read the article. It's a different robot that they were comparing to Asimo. Asimo uses 1200 watts,[27] so people are about twelve times as efficient. — DanielLC 16:27, 28 July 2008 (UTC)

I'd say the person is more energy efficient in most situations. This is because machinery often wastes so much energy, in the form of heat, that it gets too hot to touch, while people don't. However, machines have an "off" position, where they use little or no energy, while people don't. So, the robot is more efficient when off than the person when not working. If the machinery is electric, there is also the inefficiency of converting some other form of energy into electricity, delivering it, and storing it. Although, in this case, I suppose the inefficiency of human digestion must also be addressed. StuRat (talk) 16:32, 28 July 2008 (UTC)

Stu's comment about digestion makes me think the question is not completely answerable unless the Humans and Robots share a common fuel source, otherwise it's hard to contemplate overall efficiency. For example, the robot might be charged by a solar panel of certain dimensions. Could a human be sustained by food grown on farm land of that same dimensions? Probably not if the human's preferred fuel is hamburgers, but probably so if the human can be fueled by blue-green algae or some other such horrible food. APL (talk) 18:16, 28 July 2008 (UTC)

Perhaps alcohol and/or some organic oils can be used as fuel for both. StuRat (talk) 18:23, 28 July 2008 (UTC)

Haha alcohol! I'd like to see a workforce powered by that, but more importantly when a human digests alcohol, dont they only oxidise it to a ketone or carboxylic acid, and not fully, like in a combustion engine, to CO2 and water. Gving a much smaller energy release. Philc 0780 18:26, 28 July 2008 (UTC)

I'd say the robot because the robot is just walking, the human is walking, thinking, digesting, pumping blood round the body, processing waste, etc. You design a robot to do one task and it will generally do that one task far better than a human ever could. The good thing about humans is that we are extremely multi-purpose. --Tango (talk) 16:38, 28 July 2008 (UTC)

Would that mean it is foolish to design a robot in the image of a human, as it will only fail to be as versatile, however well it performs at individual tasks. Philc 0780 17:39, 28 July 2008 (UTC)

Humans (and other organisms) do have an "off" switch. It only gets used once. Recycling organic matter is a technology predating Homo Sapiens. Humans (and other...) are self replicating, whilst the production cost of robots is significant. Humans (and other...) are sustained by solar enery. Mind you, this is the Science Desk... --Cookatoo.ergo.ZooM (talk) 18:41, 28 July 2008 (UTC)

Production costs of humans are significant - I'm sure you've seen the statistics for the cost of bringing up a child. Humans work indirectly from solar energy, just like pretty much everything else. Where do you think the energy in oil comes from? --Tango (talk) 19:09, 28 July 2008 (UTC)

I pointed out that humans (and other organisms) are sustained by solar energy, implying that heat, food, fossil fuels (and pretty much everything else) is the result of the proximity of a star. I fail to see your point, Tango. --Cookatoo.ergo.ZooM (talk) 20:00, 28 July 2008 (UTC)

Common cold and sense of smell

Hi, sometimes when I catch a cold, my sense of smell gets altered in a strange way. In such cases, I always sense a characteristic smell which reminds me of pills or medicine, but I can't put my finger on what specific drug it might be. The smell gets stronger as the cold progresses, and I've never had the same sensation when I didn't have a cold.

Is there a place where I can read how the common cold affects the sense of smell? I want to see if other people experience the same thing too. (As a side note, when I get that smell, I almost always find that my nasal mucus gets dry and flaky easily as well.) --Kjoonlee 18:59, 28 July 2008 (UTC)

Panadol and fever

My question is, does panadol help cure fever or does it simply relieve the sensations of the patient while the body heals it's self?Bastard Soap (talk) 19:56, 28 July 2008 (UTC)

It relieves symptoms. This can be a benefit because sleeping helps the body heal itself, and can sleep easier when you aren't being kept awake by coughing and difficulty breathing. ~Amatulić (talk) 20:00, 28 July 2008 (UTC)

How to answer this child's question

"Why does a mirror reverse only right and left, but not up and down?"

I have an answer inadequate for a child about how reflectance works, but I want to know what others would say. ~Amatulić (talk) 20:00, 28 July 2008 (UTC)

Basically, the mirror doesn't reverse anything. It only appears to reverse left/right because your hands are mirror images of each other. Looking at the mirror and moving your right hand, the hand on the right from your point of view moves. If you move your head, your head moves toward the top of the mirror. Your right hand only looks like your left hand because of your own internal symmetry. We don't have top/bottom symmetry, so it doesn't appear to flip that. (I'm sure there are probably better explanations out there, probably with pictures, too). --Bennybp (talk) 20:38, 28 July 2008 (UTC)

It exchanges back and front, not up and down. It's like looking at your twin, reaching the right hand to shake it. 93.132.186.140 (talk) 20:44, 28 July 2008 (UTC)

Respiration

Is it fair to say that the primary function of respiration is to regulate PCO2 within narrow limits ~40mmHg? That oxygen isn't because under normal circumstances, O2 capacity of blood is surplus to requirements.