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December 1

TV set circuit mystery

What circuit in a TV set goes at (approx) line frequency (and creates bursts of hf radiated noise) but is not locked to it?--TreeSmiler 02:19, 1 December 2007 (UTC)

If you run from a VCR or DVD player the frequency is not locked in precisely and can drift around iwth local oscilators or mechanical speed in the play back. Graeme Bartlett 02:54, 1 December 2007 (UTC)

(edit conflict) Vertical deflection. It goes at exactly line frequency, as I recall, but it syncs on the signal, not the line. I wasn't able to find a Wikilink for it. There doesn't seem to be an article on the innards of a television. --Milkbreath 03:11, 1 December 2007 (UTC)

Ah!. But isnt the vertical sync signal synced to the line freq at the transmitter? Otherwise you would have some bars rolling up or down the screen would you not?--TreeSmiler 03:21, 1 December 2007 (UTC)

I don't think so. You'll see clocks that sync off the line to keep time. The power company tries their best to keep the frequency steady, and they do a darned good job of it, but not perfect. Why would the TV station rely on them when it's a simple matter to generate your own, rock-steady 60 cycles? The vertical oscillator in the set is synchronized by the sync pulses in the signal. Hum bars are a symptom of trouble in the set, like a dry filter cap in the power supply. --Milkbreath 03:55, 1 December 2007 (UTC)

Hmmm! (sorry) That would explain it -- as this article I just found does. Thanks. [1] .Do we have an article on Hum bar Apparently not.--TreeSmiler 04:26, 1 December 2007 (UTC)

I think such a system couldn't have worked in western Europe, because they were using the PAL system which goes 60 Hz, while the power supply goes on 50 Hz. – b_jonas 08:44, 2 December 2007 (UTC)

Wait a minute now. Doesn't PAL use 50 Hz? —Bromskloss 15:50, 4 December 2007 (UTC)

Also the picture is self is strongly modulated by the line frequency as it tends to be similar from line scan to line scan. Then as the whole picture switches scene the noise suddenly stops (or starts). Graeme Bartlett 07:07, 1 December 2007 (UTC)

That seems to be similar what Im picking up on my scope. ie the amplitude of the bursts seems to vary with time (presumably when the scene changes- altho the tv is in another romm so i cant be sure). Do you have any further info on that phenomenon?--TreeSmiler 14:06, 1 December 2007 (UTC)

I expect that "modern" (1941 and after) TV transmitters use a crystal controlled oscillator rather than the utility frequency for the deflection. Early TV systems, such as that of E.F. W. Alexanderson in the 1920s, used mechanical scanning and had a motor synchronized to the power system. The receiver was likely powered by a line locked in synchrony with the power line at the transmitter, so there would be only a slight phase difference between them which was easily adjusted and fairly stable, to prevent the picture rolling. Edison 03:00, 2 December 2007 (UTC)

CD4+CD25bright

Is CD4+CD25bright another way of saying CD4+CD25high? --Seans Potato Business 03:08, 1 December 2007 (UTC)

CD25 bright is CD25 high, and CD4+ is just CD4 positive, in case that wasn't clear also. Someguy1221 00:15, 2 December 2007 (UTC)

Strong Interaction Exploitation for Macro-Engineering Hobby Project

Having nothing else scheduled for the day (the day in question being sometime late in the 100th century AD), I'd like to send a von Neumann machine off into space to have a family and then spend an epoch or two transforming some uninhabited planets into a hybrid Dyson Sphere/Ringworld (which I imagine as an oblong terraced sphere rotating on its long axis to generate artificial gravity on the interior) and am deeply concerned that scrith may not be available on eBay at that time, so I may be at a loss for a material strong enough to make it big enough to also be interesting. I'd like to carry as much of the load as possible under tension, so I'm imagining an innumerable number (which is to say that I have decided not to count them) of spokes that cross the span from one side to another. I need strong wires- much stronger than carbon nanotubes. I guess I have a little while to work out some of the details but here's the best I've come up with. (Here, have a complimentary grain of salt before continuing). By manipulating infinitesimal black holes in ways yet unspecified, confine a stream of protons (or, as long as we're playing around with confined spcaes, super-protons made from decay-proof top and bottom quarks ;-) into the extremely confined space-time geometry of the tiny black hole's interior, and then, taking advantage of very clever timing, trajectories, and an Acme(r) Maximum Luck Field Generator, the black hole's own tendency to evaporate due to Hawking Radiation as a way of opening up an end in another place (white hole? Aaaargh), hope (against hope) to hold the geometry open with the string of protons held inside. Then, inspire the string of protons to behave as a single macro nucleus- only with all its strength focused on a single one-dimensional axis- by providing an appropriately charged negative charge at the ends (simulating the presence of electrons), which also, by the by, provides the means for attaching the ends of the "wire" to the things it needs to hold together. Being particularly naive from this particular technological vantage point, I'm hoping to cheat on the distances required- make the strings short, but connect points that are very distant. Essentially, I think I'm imagining a narrow-throated Einstein-Rosen Bridge held open, not by some exotic anti-energy, but by the presence of the protons themselves. At the end of the day (when it is appropriately dark), my question is singular. How strong could a "confined geometry strong force tension member" be? I'd be happy with anyone's best guess, considering. DeepSkyFrontier 05:51, 1 December 2007 (UTC)

Ringworlds and Dyson spheres have one exceedingly difficult problem. They are unstable. If one part of a ringworld gets a little bit closer to the star than it should be - and (consequently) the part on the opposite side is a bit too far away then because gravity gets stronger as you get closer to the star, the side closest to the star is attracted more strongly than the part on the far side - which serves to accentuate the problem. Hence you have a system that just won't stay put. SteveBaker 06:29, 1 December 2007 (UTC)

I'm sure you could manage some kind of stabilizing propulsion with all that energy you're collecting from the Dyson Sphere ;-) Someguy1221 11:14, 1 December 2007 (UTC)

What are you using for reaction mass? Remember, your sphere weighs at least as much as all of the planets, moons, asteroids and other debris in your solar system. SteveBaker 23:38, 1 December 2007 (UTC)

The step-terrace scheme will fail, I think. How would you prevent each latitude ring from falling toward the equatorial plane? For your strong-force cables, I think we have a little problem with electrical charge. For your proposed schedule, forget it. The universe will have converted itself to pure computronium long before that time. -Arch dude 13:36, 1 December 2007 (UTC)

To actually answer the question, I think you're confusing the nature of these geometric (actually topological) structures, as they do not extend in any spatial dimension. They are, from our perspective, 0-dimensional, and have another dimension in hyperspace. What this means is that you can't use it as a tension or compression member because it doesn't extend out in any real direction - it is just a hole is space. This is if I understand your question correctly.

Furthermore, these holes cannot be stabilized with photons. I'm afraid you need exotic matter - no photon is able to penetrate the hole before it collapses.

And to answer Steve, lots of things are unstable, like Maglevs, LaGrange points, and modern fighter jets. That's why we have corrective feeback loops. SamuelRiv 14:07, 1 December 2007 (UTC)

Yes - but it takes energy (which I'll grant you have plenty of) and reaction mass. As you throw off mass, you have no way to recover it - so gradually, your system 'evaporates'. The mass of a Dyson sphere is immense - it's estimated that you'd need all of the mass of our solar system to form even a skinny ringworld. You aren't talking about pushing a spaceship around - you're talking about pushing the combined masses of Jupiter and Saturn around. For a full 1 AU sphere - thousands of them! A 1 AU sphere would rapidly cook it's inhabitants without some kind of unobtainium heat radiators...so it's gonna be a lot bigger than 1 AU. The power involved in moving this thing is decidedly non-trivial! It's pretty well established that these things are impossible for a bunch of practical reasons...but I find instability to be the biggest. SteveBaker 23:38, 1 December 2007 (UTC)

I answered the question, but asked for clarification. You cannot use such bridges as tension or compression members - the new space that you create will just stay the same as you move your holes closer or farther apart. There is a possibility that you'll lose effective mass due to gravity waves if they are accelerating relative to each other, but I don't see a way for them to act as a tension member in the way you're describing. SamuelRiv 16:29, 2 December 2007 (UTC)

Protons, for one thing. Yes, thank you. You essentially answered the question by saying, "You can't ask this question this way." What I'm asking has, at its root, nothing to do with black hole geometry. I'm asking about how strong the nuclear strong force is. If it could be exploited- by whatever means- what would be the result. Thank you for addressing the question I asked. Your edit interfered with my own restatement of my question that replaced the comment that you responded to. DeepSkyFrontier 16:45, 2 December 2007 (UTC)

Most desirable place to live

Aside from the fact the individuals may have different preferences, where is the most desirable place to live, strictly as an environment and in total if all Friends, possessions, etc. could be relocated there, or is this more a matter of personal history such as where you were born, where you grew up, where you had the most rewarding experiences? Second part of the question is where can I find an online questionnaire that will ask me different questions like "What kind of climate do you prefer: warm, mild, cool, varied...?" and then narrow down the places that meet the criteria I entered? 71.100.1.143 07:02, 1 December 2007 (UTC)

It depends entirely on the criteria you choose to rate. There are plenty of attempts to rank the best places to live, both globally and in specific countries. Here are links to some of them: [2] [3] [4] [5] [6] As for an online questionnaire, try this if you are interested in the USA. Rockpocket 08:11, 1 December 2007 (UTC)

Perhaps it would help to work backward somewhat and decide where the least desirable places to live are and why. For example beyond mere climate considerations, living near an active volcano might not be a good idea. (Also consider places that experience lots of earthquakes, hurricanes, floods, etc.) Besides natural issues there are also man made hazards to consider like areas of high crime, or other armed activity. Along man made lines, also important factors would be local health care and whether or not one could drink the local water without getting sick. Anynobody 08:52, 2 December 2007 (UTC)

The irony of this is that if there is a place that is considered by a large number of people to be "the most desireable place to live", then fairly quickly everyone moves there, and then it becomes not such a desireable place to live. An example of this is Los Angeles, which 100 years ago was pretty close to what most people would consider to be paradise: great climate, layed back attitudes, ocean front, mountains, orange groves stretching as far as the eye could see... But now look at it: traffic congestion, smog, you can't see the mountains most days of the year because of the pollution, very high crime rates, and just too many people. So if your idea of the best place to live includes any of these last things, perhaps Los Angeles WOULD be the perfect place for you to live, otherwise you're going to have to have a compromise. You can't have it all... You should prioritize which things you feel are more important about where you'd want to live, and then look for a place that has those things the most. FOr myself, I highly value low crime, no gangs, few people, lots of trees and wilderness, and lots of water. So I ended up living in a place where there's lots of snow and cold winters, which I don't really like, but that was my trade-off... I just use myself as an illustration. Where I live people never lock their homes or cars, and the biggest crime one hears about is when someone gets a DUI because they've been drinking too much due to all the snow and depressing weather! Saukkomies 05:08, 4 December 2007 (UTC)

Clanks

I just read the Girl Genius series, and there's something I can't help wondering. Just how far can clockwork robotics be pushed? I know some remarkable things were invented in the old days using nothing more than gears and pulleys, up to and including small programmable robots, but just how much is possible? Black Carrot 11:17, 1 December 2007 (UTC)

The non-computer parts of a robot are mostly "clockwork", so you are actually asking about the computer parts. It is theoretically possible to perform any computing task using a mechanical computer, because you can build a mechanical Universal Turing Machine. In practice and using mechanical compones built with today's technologies, an elaborate purely mechanical robot is not feasible. A "mechanical" computer becomes possible with nanotechnology. At that size scale, a mechanical computer may be smaller than an equivalent electronic computer because electrons are hard to confine to small volumes. -Arch dude 13:20, 1 December 2007 (UTC)

If you want to be amazed, look up examples of medieval and Renaissance automata. It's really quite amazing what you can do with the technology; it really just comes down to how many gears you can fit into a given space and how much precision you can have with the gears. I've seen some amazing videos of automatons that could write, play complicated instruments, etc. Obviously they aren't intelligent in any sense but they can fake some pretty fine motor skills. --24.147.86.187 18:08, 1 December 2007 (UTC)

I was too hasty earlier. Sorry. There is a class of non-digital control mechanisms that can be used to create analog robots. You can get really complex behavior from relatively simple analog electronics. A lot of very interesting devices of this type were developed prior to the development of the first digital computers. A famous example was the Nordon bombsight. The mechanical equivalent of an analog circuit is perfectly feasible and easy to implement. By contrast to digital, the analog approach is much more compatible with a Victorian/steampunk worldview. -Arch dude 22:22, 1 December 2007 (UTC)

There is a mathematical theorem called "The Church–Turing thesis". It says that in principle, any minimally capable computer can do anything that any other computer can do - providing it has enough time and memory (and of course the right peripherals - printers, robot motors, whatever). This minimal computer is called a Turing machine. So if you could build a clockwork Turing machine - then it could do anything the PC in front of you right now could do - if there were enough memory and time. Looking at the architecture of the Turing machine, it's quite plausible that someone could make a clockwork machine like that. Here, for example is a "Turing machine" made from toy trains. Well, those could be clockwork trains...so there you are.

OK - so that's the theory...but in practice? Well, no. Turing machines are S-L-O-W - and a clockwork machine would be HIDEOUSLY slow. It would need winding up A LOT! If you look at something like Babbages' Analytical engine, it's full of gears and such - and it's equivelent to a Turing machine - so the Church-Turing thesis says it's a proper computer. It's still pretty slow - and I think a literal clockwork motor might be a little impractical as a power source - but a good sized steam engine would work. It's huge - and still pretty slow. If it had ever been completed (it never was) it would have been able to store 50,000 decimal digits - which is about 200 kbits of memory. That's more than the first computer I used in my first job (an Intel 8008 with 4kbytes of memory). It would have been able to multiply to twenty digit numbers, in three minutes. That would take about a billionth of a second on a modern PC - so this machine would take thousands of years to something as (seemingly) simple as displaying the page you are reading right now.

So - yes, in theory, mechanical computers could work - but they absolutely could not be practically useful.

There is a caveat to that - which is that if nanotechnology lives up to some of it's more extreme promises, we'll be able to make very small mechanical systems that would actually be faster than modern electronics. If we get to that point, then mechanical ("clockwork") computers will be back in vogue.

SteveBaker 22:47, 1 December 2007 (UTC)

(What was I thinking?! No discussion of mechanical computers could be considered complete without mention of the one I happen to own!) Mechanical computers do actually exist - you can buy one called the Digi-Comp I (I own one - it's the one in the photo in that article). This thing is made of plastic (if you have an original one) or cardboard (if you have the modern version). You put it together yourself in about an evening. It's pretty minimal - it has a three bit memory and it's power source is you wiggling a lever back and fourth. It does one 3-bit calculation each time you move the lever across and back - maybe one per second (if you go too fast it jams up)...but it can play the game 'Nim', count and add a 1 bit number to a 2 bit number to produce a 2 or 3 bit result! Yes, it's horribly limited and pretty complicated for a cardboard computer. You program it by moving little bits of drinking straw around - you input data by directly switching it's 3 bit memory - and the output "display" is three little windows that show '1' or '0' depending on ths state of the memory. There was once a Digi-Comp II which used marbles rolling down a pinball-like machine with little plastic levers. It had a dozen or so bits of memory and could do multiplication (eventually) - there was a little electric motor driving the mechanism that recycled the balls to the top of the track. SteveBaker 23:11, 1 December 2007 (UTC)

Ah, yes, the Digi-Comps. The Digi-Comp II my uncle gave me for Christmas when I was 10 years old or so was certainly a formative experience. And I do still have it, somewhere; I'll have to haul it out and take a picture of it for our article.

It's quite an amazing machine. It's got a 7-bit accumulator, a 4-bit addend register, and a 3-bit multiplier register. There was even a way to rig it up to do long division, but it required about a hundred marbles to filter through, all without error, and it was virtually impossible, but fun to try. (And mine had this great bug where a marble would occasionally bounce out of the track it was supposed to be in, roll all the way down to the bottom of the board, bounce back up, fall into an unrelated hole, and start a calculation over again that was supposed to be terminating. Loads of laughs.)

I never heard of an electric motor, though; that may have been some sort of field upgrade. Mine, you had to recycle marbles back up to the top yourself if a long multiplication or division required more marbles than you had. —Steve Summit (talk) 02:01, 2 December 2007 (UTC)

Are you interested in selling it? I've always wanted one and I'm no too fussed about the condition it might be in. I have frequently considered building one out of Lego - but without complete details, it's hard to figure out exactly how it works. Contact me at my talk page if you are interested. You're obviously right about the lack of a motor - I have never actually seen one of these gizmo's actually working. I assumed there must be a motor or something because the description of them always talks about an 'Automatic' mode of operation versus 'Manual' - which I took to mean that there must be some kind of automatic ball feeder...but there was certainly only one version of the Digi-Comp II so if your's has no motor then that's that.

The Digi-Comp I (which I have) was made in polystyrene a year or two before the II came out (around 1963 I think). However, they were flimsy and broke easily - and hence they are much rarer than the Digi-Comp II (in working condition at least). A few years ago an enthusiast made a replica of the Digi-Comp I out of heavy cardboard and is now selling these replicas in kit form. However, so far, nobody has ever built a replica of the Digi-Comp II - and whilst it's mechanically easier to understand than the Digi-Comp I, it's actually the more computationally powerful of the two machines. Of course, neither of them are 'Turing-complete' - so in a sense, they are not true computers. However, they are both programmable and can perform arithmetic, so in another sense, they are computers.

For the technically minded, the Digi-Comp I is essentially just three flip-flops which are clocked synchronously. The "wiring" between them is handled by 'programming' the machine by putting short sections of drinking straws onto the front of the machine where they can block parts of the machine from moving. You can also insert mechanical analogs of "AND" and "OR" gates in front of the inputs to the flip-flops (with certain constraints). Because there is only a three bit memory, if you want a program to actually step through multiple instructions, you have to use one or two of the bits as your "program counter" - which leaves you with very little left for doing actual work! But you can set it up to do things like count from zero to seven (which is an impressive sight actually!) - and it can play a minimal version of the game of Nim using seven objects in one heap...which is actually the only program for it that's actually any use for anything! Programming the thing to do ANYTHING is absolutely mind-bending - you need a very good knowledge of what flip-flops can do. The idea that it might ever have been a kids toy is ridiculous!

SteveBaker 05:52, 2 December 2007 (UTC)

Do you know of any good books on low-tech robotics? Spring-powered, and such? Black Carrot (talk) 03:31, 5 December 2007 (UTC)

Hypothalamus and mammillary body

Reading Hypothalamus#Nuclei gives me the impression that the mammillary nuclei (and thus the mammillary body) are a part of the hypothalamus. Is this true? Lova Falk 14:15, 1 December 2007 (UTC)

Neuroanatomists have often categorized the mammillary bodies as part of the hypothalamus. One anatomy text that does so says, "synthetic descriptions may suggest that all hypothalamic nuclei are well delimited structures" and then it describes how hypothalamic nuclei transition gradually into surrounding brain regions. --JWSchmidt 15:14, 1 December 2007 (UTC)

Thank you! As I usual do with your explanations, I quoted you in mammillary bodies. Could you change the reference to a proper one? Lova Falk 16:34, 1 December 2007 (UTC)

You want me to admit how old my neuroanatomy textbook is? Ow. The quote I gave above is from Human Neuroanatomy (8th edition) by Malcolm B. Carpenter and Jerome Sutin (1983) ISBN 0-683-01461-7.--JWSchmidt 19:50, 1 December 2007 (UTC)

That's almost prehistoric. But it's fine for an uncontroversial question like this one. Maybe I should never have thrown my 1977 book called Psychophysiology... —Preceding unsigned comment added by Lova Falk (talk • contribs) 08:40, 2 December 2007 (UTC)

McDonalds Fries

"because there's too much moisture in the potatoes for them to crisp during baking, I needed to release some of the water first. I ran home at record speed (for me), went directly to the kitchen, and tried parboiling the fries before baking them" - am I not correct in thinking that boiling (par or otherwise) will increase the amount of water in the potato?--Seans Potato Business 19:30, 1 December 2007 (UTC)

What this refers to is commonly called blanching - and is required to make crispy fries. It is the reason that most home-cooked fries aren't as good as fast-food fries. Boiling them makes the water in them expand. They are pulled out and quickly cooled to stop the cooking process. Since the outer layer is mostly cooked - it is no longer very permeable and the cold water has great difficulty soaking back into the potato. The end result is a reduction in water inside the potato and a pre-crisped outer layer. This is highly effective in most "wet" foods that you wish to deep fry. The trick is timing the boiling process so that the cold water won't soak back in. -- kainaw™ 21:14, 1 December 2007 (UTC)

Of course the classical way to make fries is to fry them twice - once to a light brown, then take them out of the oil, reheat it, and do the second stage frying at a somewhat higher temperature until they are golden brown. This should have a similar effect. The result also depends on the kind and age of potato, of course. Very fresh ones are not as good for frying as potatoes that have been stored for a while (in a proper cool, dry environment). --Stephan Schulz 22:35, 1 December 2007 (UTC)

• For a wonderful survey of these sorts of nitty gritty food details, check out On Food and Cooking, by Harold McGee. --Sean 00:03, 2 December 2007 (UTC)

I read a recipe decades ago, by Julia Child, in which she said to cook the fries at the high temperature first rather than second. A home deep fryer usually does this rather automatically, because the initial fat temperature drops shortly after the fries are added, probably because the moisture flashing to steam takes heat from the oil. A restuarant fryer has so much heat capacity in the larger amount of hot oil, as well as a more powerful heating element that the temp stays more constant as things are lowered into the oil. Edison 02:55, 2 December 2007 (UTC)

Some people salt the chopped potato a while before cooking and then dry them with a paper towel just before tossing them into the oil. I presume that the purpose of this is to draw water from the fries via osmosis. SteveBaker 14:49, 2 December 2007 (UTC)

Jesus illusion

What's the general name for optical illusions of the kind of the famous "Jesus illusion"? Icek 20:19, 1 December 2007 (UTC)

I'm still looking, but if you like that, you'll love the lilac chaser. --Milkbreath 20:44, 1 December 2007 (UTC)

It's called an afterimage, explained by Ewald Hering. Sadly, it is not called the Hering illusion, though. This site calls it a "stare negative". --Milkbreath 21:08, 1 December 2007 (UTC)

With a dose of pareidolia thrown in for fun. Matt Deres 02:07, 2 December 2007 (UTC)

Goethe was the first to write about this. That Jesus looked more like Che Guevara to me! Saudade7 03:02, 3 December 2007 (UTC)

Thanks for the answers. Saudade7: Maybe Jesus looked like Che Guevara, I don't know ;-) Icek 02:11, 4 December 2007 (UTC)

All I know is that the Jesus Illusion works in some way similar to that of "photograph negatives"; you'll find that if you stare at anything which contrasts greatly between bright and dark (such as a bright sunny window) for 20 seconds or so and then close your eyes, the same will happen; you'll see a sort of negative photograph effect. Sometimes you don't even need to stare; if you have your eyes shut, and as quickly as you can open and close them, then yet again, an illusion occurs. It seems similar to me as screen burn which can happen with LCD screens, like the light receptors on your retina have been temporarily influenced. Is "temporarily damaged" a good way of explaining it? Adamd1008 18:46, 4 December 2007 (UTC)

snowing

hello im shima ghadiri im from iran and its my first time that i meet your site and now im a new member of your site and i have really strong confidence to be areally active member im 15 years old and i study math in grade two in high school i have alot of question in my mind and i thouth this is a best way to find some one in your sitemaby some abroad iranian at the end my english is not raelly good but i can express my idea thank u alot. my first question is:why when is snowing we dont have any i dont know exact word for example light in sky but when rainig we have alot of light in sky that in persion we say radvabargh?

Do you mean a rainbow? --Reuben 20:54, 1 December 2007 (UTC)

For language questions, try our Wikipedia:Reference desk/Language. Of course we do have a Wikipedia that's written and edited entirely in Persian/Farsi here - it has over 28,000 articles (including one about rainbows [7] !) - but that's only a small number compared to the number we have in English. Perhaps a good way to practice your English would be to translate some articles from the English Wikipedia into Farsi - there are plenty to choose from! SteveBaker 22:12, 1 December 2007 (UTC)

Well, if the question is "why do we see rainbows when it rains, but not when it snows?" that's certainly a science question. The answer is that raindrops are close to spherical in shape while snowflakes are not. This matters because a sphere is very symmetrical and therefore when light from the Sun hits a raindrop at a certain angle it will always emerge at a particular angle (for the same color of light) -- the same angle from one raindrop to the next. What makes a rainbow is the rays of light emerging from different raindrops in the same direction. Snowflakes have complicated shapes and the flakes in a mass of snow are all facing different ways. This means that the light from different snowflakes does not point in the same direction, so it does not form a rainbow.

Another possible form of water in the sky is ice crystals. These have shapes more complicated than raindrops but simpler than snowflakes. In some conditions they become aligned (facing the same way) and then you can get an effect somewhat like a rainbow. There are different types; two of them are called sun dogs and halos.

--Anonymous, edited 22:29 UTC, December 1, 2007.

I just wanted to say that that is a delightful and very informative answer... - Nunh-huh 22:51, 1 December 2007 (UTC)

Nice to meet you Shima! I too am working on the assumption that you are refering to a rainbow. Although I am no meteorologist, I can say that from personal experience I have seen a rainbow while it was snowing, not raining. It was very remarkable and everyone I was with was amazed by it. It occurred during a small snow storm in the state of Idaho in the US, and the sun was low in the sky - it being in the afternoon. --Saukkomies 19:32, 2 Dec 2007 (EST) —Preceding unsigned comment added by Saukkomies (talk • contribs)

Is this the word in Persian: رنگين‌ كمان‌، قوس‌ و قزح‌، بصورت‌ رنگين‌ كمان‌ ? That is the word for Rainbow according to this online dictionary I looked on. I just want to make sure we are answering your question correctly! Saudade7 03:09, 3 December 2007 (UTC)

December 2

High temp superglue

Is there a version of super glue that will withstand soldering temperatures (say 250 C) for a short time without failing?--TreeSmiler 01:30, 2 December 2007 (UTC)

I would try some kind of epoxy instead. —Preceding unsigned comment added by Shniken1 (talk • contribs) 02:09, 2 December 2007 (UTC)

Many electronic components (transistors, capacitors, etc) are sealed in plastic or epoxy of some type and clearly are able to withstand soldering temperatures for a short time. RTV sealants (room temperature vulcanizing, I think, is what the RTV stands for) can withstand high temperatures (used to attach space shuttle tiles, as I recall) and comes out of a tube in liquid form. Edison 02:50, 2 December 2007 (UTC)

Modern printed circuit boards are assembled with components on both sides and use "interesting" mass soldering techniques. In some processes, the components are glued to the board before the actual soldering step. -Arch dude 11:18, 2 December 2007 (UTC)

So what kind of glue is used? That would pretty well answer the question. Edison 21:42, 2 December 2007 (UTC)

Don't know. I was working from a memory of hallway conversations. Look at wave soldering and reflow solder, but they still do not cite the specific glue. -Arch dude 01:01, 3 December 2007 (UTC)

The plant I got a tour of a while back (A Philips TV factory) used a method where components like connectors that have pins that stick into the board were placed by a 'pick and place' robot first. Then solder was flowed over the entire board (There being a 'solder resist' layer silk-screened onto the board beforehand to prevent the solder sticking everywhere. That process filled the 'via' holes between the layers, soldered in the components with pins (via capilliary action) and left little solder 'bumps' on all of the pads where the 'surface mount' components would make contact (the ones that don't have pins that poke into the board). The board was then kept warm (just below the melting point of the solder) with infrared lamps. Then a second 'pick and place' machine placed the components onto the board by blasting the area around each one with hot air as it placed the component onto the (now wet) solder. This was important because the surface tension of the solder was what performed the final, accurate positioning of the component - keeping it in place as the board moved off to be gently cooled. There was no glue involved - yet with careful process control, I don't see any reason why this shouldn't work for double-sided boards as well. I kinda doubt they ever use glue because I've removed components from mass-produced boards (in order to repair or modify them) and I've never seen any kind of residue left behind. I guess it's possible that some companies use something like a wax that would boil away in the end...but I doubt it. SteveBaker 20:54, 3 December 2007 (UTC)

ant trails

Do ants leave trails the same way cats mark boundaries by spraying at certain spots and if so what determines the spot or decision criteria at which to spray? Also is there a die that will reveal the trail chemical and can ant be genetically programmed to release a visible spray? 71.100.1.143 01:39, 2 December 2007 (UTC)

See ant. It clearly states that ants leave a pheromone trail for other ants to follow. They make a trail - not a random spot here and there. As for genetically altering ants to make their pheromones visible, it is possible but not probable. As for being able to see pheromones - I know of nothing in current science that makes pheromones visible (except for Hollywood CGI magic, of course). -- kainaw™ 02:21, 2 December 2007 (UTC)

Ever hear of bread crum trails? Be it bread crumbs or pheromones they are only a mark and a rather scarce mark at that which requires they not be laid end to end but at worst only at decisive intervals. 71.100.1.143 05:07, 2 December 2007 (UTC)

(ec) I think the trail ants leave is formic acid (certainly there's a well-established association between that acid and those insects), but our Ant article just says "pheromones". —Steve Summit (talk) 02:23, 2 December 2007 (UTC)

• I vaguely remember that in one of Richard Feynman's memoirs he describes somehow smearing ant trail stuff in patterns of his choosing, which caused the ants to walk in those squares and circles and things. :) --Sean 03:43, 2 December 2007 (UTC)

Yep - I was going to mention the exact same thing. He found that ants were getting into his larder and rather than killing them or spraying with nasty chemicals, he simply devised a way to have their scent trail lead away from the food and back outside. It's described beautifully in several of his biographies. It's a wonderful example of how you can be an amateur scientist, discover interesting things by yourself and apply them to your own benefit. (Feynman is my personal hero BTW). SteveBaker 05:24, 2 December 2007 (UTC)

Different ant species leave trail pheromones in different ways, but most of them touch the tip of their abdomen to the ground where there is a gland called the sternal gland that contains the trail pheromone. Some, like the African weaver ant, have the ability to rotate their terminal abdominal segment, thereby exposing other glands that contain different signals. The sensitivity of ants to trail pheromones are remarkable. For example, Atta texana trail pheromone is known to be methyl-4-methylpyrrole-2-carboxylate. Only 0.08pg/cm of this is deposited to establish a trail (that is 3.5 x 10⁸ molecules/cm) Scientists have shown that with the amount of trail pheromone in a single Atta texana nest, the ants could leave a trail reaching around the world three times. They don't make a decision to "spray" the chemical, its more likely that the pheromone releasing behaviour is an innate response to the detection of food, thereby forming a trail back to the nest and leading others to the food source.

The other thing to consider is that these chemicals are volatile, (which would make marking them visually a bit of a challenge). Some trail pheromones, such as those from fire ants, last only a few minutes before evaporating away, while other species persist for days. The ants don't detected the trail itself, but the diffusing volatile. Thus they travel through a "vapor tunnel". Finally, its interesting to note that there is no evidence that ant trails are directional (there doesn't appear to be any information in a trail that tells ants which direction to go), instead they rely on visual cues for that. This is in contrast to snails which do produced directional trails, though the exact mechanism is unknown. This information is sourced from Wyatt, Tristram D. (2003). Pheromones and Animal Behaviour: Communication by Smell and Taste. Cambridge: Cambridge University Press. ISBN 0-521-48526-6, and the references therein. Rockpocket 21:38, 3 December 2007 (UTC)

• Wow, great answer! --Sean 13:35, 5 December 2007 (UTC)

Thank you, though this is the area of my professional expertise, so I could waffle on for days about it! Rockpocket 08:09, 6 December 2007 (UTC)

QUESTION ABUOT TEH TERMINATOR LOLZ (seriously!)

"I HAVE BEEN SENT HERE TO DESTROY-- I MEAN, CONFUSE HUMANITY."

Hi wikipeoples! What are the minimum and maximum ground speeds of THE TERMINATOR of Earth??? Kreachure 02:33, 2 December 2007 (UTC)

The max speed would be at the equator - regardless of axial tilt. That is the point with the greatest circumference since the Earth bulges out in the middle. The speed of rotation at the equator is 465.11m/s. The minimum would be when the tip of the terminator hits one of the poles. It stops traveling and becomes 0m/s. -- kainaw™ 02:45, 2 December 2007 (UTC)

...OP says, "of" Earth, not "on" Earth. 71.100.1.143 05:10, 2 December 2007 (UTC)

Yes - but complaining about small grammatical slipups on the part of our questioners is not considered cool. We know what was intended. SteveBaker 05:19, 2 December 2007 (UTC)

Wait, is "of Earth" really ungrammatical? Maximum ground speed of terminator of Earth = maximum speed of Earth's terninator, while maximum ground speed of terminator on Earth = max speed of the terminator that's on Earth or max speed of terminator while on Earth. Both are appropriate, I think. --Bowlhover 16:07, 2 December 2007 (UTC)

Thanks Kainaw. But geez, you guys always find a way to make a questioner feel, um, inadequate about his/her questions, huh? The definition of terminator in the article is, "the line between the illuminated, day side and dark, night side of a planetary body." So, no mistake as far as I'm concerned! Kreachure 16:36, 2 December 2007 (UTC)

Yep, exactly why I complained to 71.100.1.143. SteveBaker 17:37, 2 December 2007 (UTC)

Yeah, don't let Mr. 71 get you down. There's nothing wrong about asking about the "terminator of Earth", as opposed to Venus, the Moon, etc., which also have terminators. -- Coneslayer 00:46, 3 December 2007 (UTC)

HIV (AIDS)

I want to know if a person (girl/boy) willingly or unwillingly drink a person urine, is there any chance of getting HIV infection from the same. —Preceding unsigned comment added by Ashish.k.garg (talk • contribs) 03:35, 2 December 2007 (UTC)

• Didn't you just ask this last week? May I suggest that you stop drinking people's urine until you've discussed this practice with your doctor? --Sean 03:48, 2 December 2007 (UTC)

As for the question of any chance. Blood-to-blood transmission is known to be a method of HIV infection. If there is blood in the urine and open wounds in the mouth, then there is a chance. Of course, you should see a doctor if you are concerned about HIV. The test is simple and rather accurate. -- kainaw™ 03:59, 2 December 2007 (UTC)

• How dare you attempt to trample on this user's inalienable right to engage in Urophagia;-)--Fuhghettaboutit 05:23, 2 December 2007 (UTC)

• S/he can engage in coprophagia for all I care, as long as s/he asks a doctor about it rather than the Wikinerd Collective. --Sean 16:52, 2 December 2007 (UTC)

This was just covered in the Savage Love Column in The Onion a while back (sad that I remember this!): Link to article. Good luck with that. Saudade7 03:19, 3 December 2007 (UTC)

He is asking a question within the guidelines of wikipedia's reference desk. Either answer it, or ignore the question. *talking to sean btw* 64.236.121.129 14:32, 3 December 2007 (UTC)

Chicxulub crater and Plate tectonics

It occurred to me that the theory of an impact event at Chicxulub 65 million years ago should be deformed by continental drift. I was reading up on Pangaea and linked to one of its references, a USGS site. Which discusses its break-up and the formation of the geographic Earth as we know it today. If this image is accurate then there are two plates pushing north, one to the ne and the other nw, south of Chicxulub. Surely I must've missed something, as I'm not a geologist, but I'm just wondering what that is.

This also prompts the question of our ability to accuratly document IEs even earlier. Since Pangaea wasn't the first super continent, just the most recent it seems like craters, mountains, volcanoes, etc. could have been Etch-a-sketched away by continental drift/collision the further in the past they occur. Anynobody 08:31, 2 December 2007 (UTC)

65 million years is not a long time span in the context of plate tectonics. Pangaea was already pretty much split up by the late Cretaceous, and since then its constituent plates have just moved further apart. And remember that the interiors of the plates do not deform - spreading, subduction and mountain building happen at the boundaries between plates. The main reason that it is very difficult to clearly identify craters from older impact events is the removal of surface features by erosion, which happens over shorter timescales - the Grand Canyon, for example, is less than 6 million years old. Gandalf61 11:07, 2 December 2007 (UTC)

And indeed, the two small plates in the image you refer to, the Cocos and Caribbean, are impinging on the southern edge of the formerly isolated Yucatan microcontinent. Where that impinging occurs, largely in southern Guatemala, we would expect features like an impact crater to (eventually) be significantly modified. The north side of Yucatan, where Chicxulub lies, is part of the Yucatan craton that is not being deformed. That side of Yucatan is a passive margin related to the opening of the Gulf of Mexico; the worst that happens there is simple normal faulting, and as Gandalf61 indicates, Chicxulub is actually on the interior of a continental plate. Cheers Geologyguy 17:54, 2 December 2007 (UTC)

This and that book approach

In university, I'm faced with books with titles such as

• Computer Architecture: A Quantitative Approach
• Software Measurement and Estimation: A Practical Approach
• Electromagnetic Field Theory: A Problem-Solving Approach.

I find these approach titles so abstract and, reading in these books, I cannot find any difference in the style of writing among them. Can someone try to come up with definitions or rule of thumbs about what an author wants to tell the readership when he decides on an XYZ Approach title? Thank you, --Abdull 10:10, 2 December 2007 (UTC)

Without actually answering the question, I'll point out that it's the publisher that chooses the title of a book (although normally in consultation with the author). Which means they take marketing into account. --Anon, 10:41 UTC, Dec. 2, 2007.

Gah, edit conflict with Anon, but I'm inclined to agree - here's what I was in the process of posting...

I've always assumed those kinds of books mean the author thinks s/he has a new, useful, or particularly interesting method of approaching the subject. In the examples you gave above, the author of the software measurement book obviously believed that the approach taken was a particularly practical one (therefore implying, I suppose, that other books take a less practical approach). I really think it's mostly down to the author's point of view, and maybe just a little bit of marketing. After all, which would be first to catch your eye in the bookstore - 'Software Measurement and Estimation: A Guide' or 'Software Measurement and Estimation: A Jellybeans-and-donuts approach'? ;) --Monorail Cat 10:48, 2 December 2007 (UTC)

"Computer Architecture: a quantitative approach" was the first mainstream book on the topic that used real measured data (mostly from the VAX) to explain the differences and trade-offs (things like "backward branches are taken 9X% of the time, forward branches 50%", "90% of of the time is spend in 10% of the code", locality of reference). It still is an excellent book by some of the early RISC pioneers. --Stephan Schulz 11:14, 2 December 2007 (UTC)

I may risk soapboxing, but authors of textbooks on the same subject work very hard to differentiate themselves, because much of the material is common between all of the books, and would be obvious to anyone who has already mastered the material. To disguise this effect, an author or publisher may add gimmicks or "twists" on the subject matter - sometimes with valid reason, and sometimes not. If instead of textbooks, we all used wikibooks, the base material in common could be kept in a single place, and additional insights (such as the "practical" or "quantitative" approaches) could be added in separate sections. However, this would make it difficult for an individual author to take credit for an entire body of work. Nimur 21:46, 2 December 2007 (UTC)

Continuing from Stephan Schulz, the "…Approach" tag is usually best for comparing/contrasting within a set of works on the topic. If you want to learn about electromagnetic field theory, you could study the theoretical (quantum mechanics, etc) origins, you could study the applications to other realms of science, you could study the practical aspects for engineering, you could just learn how to solve specific problems related to it without delving deeply into the underlying causes. Different texts for different folks. DMacks 07:04, 3 December 2007 (UTC)

fibre transfer forensics

82.7.252.205 11:36, 2 December 2007 (UTC)Can anyone tell me when the use of fibre transfer forensics was first used and who first used it ?

• Fibres are generally considered trace evidence. That term might give you better search results. Trace evidence is based on Locard's exchange principle, but I wouldn't be surprised if someone used it before he (Edmond Locard) made his postulation. It would be entirely possible for such evidence to have been used a few times in ancient Rome, Greece or Egypt. However, processing of most trace evidence relies on microscopy, so if you go that route, you wouldn't need to go any further back than the 1600s when Antonie van Leeuwenhoek made the first useful microscope. - Mgm|^(talk) 13:57, 2 December 2007 (UTC)

According to Lens, the oldest lens is dated to c.640 BC - so whilst microscopes certainly weren't around in any numbers until the late 1600's - simple magnifying glasses would have been around much earlier. These wouldn't allow you to identify fibres with the exactness demanded by modern judicial standards - but they'd certainly have been enough to give a lynch mob the information they needed to go on if any of them took the time to check. So I don't think this is a matter of when the technology became available so much as when the methodical collection of evidence and control of the crime scene became commonplace. SteveBaker 14:41, 2 December 2007 (UTC)

Forensic science#History of forensic science has some examples of the early use of trace evidence in criminal proceedings. Gdr 15:00, 2 December 2007 (UTC)

Flushing toilet

Hi. I've heard that flushing the toilet can cause fecal coliform bacteria to land on your toothbrush, and even enclosed toothbrushes get exposed to it (MythBusters). However, I know a few people who close the toilet lid when they flush. Does this help keep the toothbrushes free of f. coli bacteria? Or, will peeing and pooing in the toilet cause water torise up, carring fecal germs around the room? To approximately what efficiency (percent) will closing the toilet lid have with preventing contamination of toothbrushes? Thanks. ~AH1^(TCU) 16:23, 2 December 2007 (UTC)

I know I'm supposed to Assume Good Faith, but before I answer, do you mind if I ask: how serious are you in asking this question? Are you truly concerned, or do you just enjoy talking about peeing and pooing, and egging on other people to do the same? (Me, I've never heard of any concerns about flush toilets and toothbrushes, although not being an OCD sufferer, perhaps I've been sheltered.) —Steve Summit (talk) 16:39, 2 December 2007 (UTC)

• If you google "flush toilet spray", you'll see it's not a novel concern. --Sean 16:56, 2 December 2007 (UTC)

Hi. This is intended to be a serious question. I want to know if closing the lid will prevent toothbrush contamination. If yo watched that episode of MythBusters or read the book you will see that they confirmed the presence of f. coli bacterial after a few days of bathroom use. Thanks. ~AH1^(TCU) 17:07, 2 December 2007 (UTC)

Yeah - but they also proved the stuff is EVERYWHERE. it's just a natural part of the habitat in which humans live. The Mythbusters finding was absolutely not that toothbrushes closer to the toilet had a bigger dose - it was that it didn't matter where you put the toothbrushes (including in the kitchen, 50 feet from the bathroom) - the results were substantially the same. However, we humans have perfectly good defenses against these things. You are doing yourself far more damage from stressing out over it. SteveBaker 17:35, 2 December 2007 (UTC)

(ec)

Well, I didn't see that episode, so I don't know what they found, nor can I comment on their methodology.

My own opinion (but please note that this is not even original research, but rather, armchair speculation) is that everybody poops, and fecal coliform is everywhere. Our immune systems can handle reasonable amounts of fecal coliform quite well -- they'd be grossly inadequate immune systems if they couldn't, given how much of the stuff there is guaranteed to be floating around in the environment! As I understand it, it's not the mere presence of fecal coliform that constitutes a public health threat, but rather, elevated levels of fecal coliform. And in fact, coliform isn't dangerous in itself; the only reason we worry about it so much is because it's an indicator bacterium.

I've never noticed my toilet at home spraying anything. I have noticed some spray from the high-pressure (tankless) toilets used in many commercial buildings. I bet there's a significant difference there.

Certainly, if you're worried about spray, closing the lid when you flush can't hurt. If you're male, I would guess that sitting while urinating would help a lot, too, although I gather that this is found unacceptably effeminate by some. Certainly, regular cleaning of any bathroom is indicated, especially if you're worried about germs. —Steve Summit (talk) 17:42, 2 December 2007 (UTC)

So based on SteveBaker's gloss of the Mythbusters episode above, I think we can safely say: yes, closing the lid will absolutely prevent untoward toothbrush contamination. However, it will also prevent Kirlian photography, and if you have any perpetual motion machines in your bathroom or nearby, those are likely to stop working, too. You might also want to consider the effects the lid's position might have on your bathroom's Feng shui. —Steve Summit (talk) 18:10, 2 December 2007 (UTC)

Just about any operation that involves vigorous agitation at a liquid/air interface (as with a stream of urine into the bowl water, or the mixing and agitation that takes place during a flush) will generate aerosols. Aerosols are droplets too small to be seen with the naked eye, that will take seconds, minutes, or hours to settle out of the air under the influence of gravity (larger particles settle faster; droplets are also cleared gradually by air exchange via exhaust fans and such). This is a serious consideration in medical and research settings when individuals work with biohazardous materials—there is often a great deal of careful planning involving in establishing safe protocols for where, when, and how liquids can be handled, mixed, transferred, and dispensed in laboratory environments (Google for 'biohazard' and 'aerosol' for a whole bunch of links). Certainly the violent, vigourous flushing action of tankless institutional toilets is likely to result in greater aerosol generation than a more sedate home toilet, but no toilet will be completely aerosol-free. TenOfAllTrades(talk) 18:20, 2 December 2007 (UTC)

Do people actually pick up tooth brushes and but them in their mouths without even rinsing them first?--Dacium 03:00, 3 December 2007 (UTC)

I did not read all of these responses, but just to say that if you are in the bathroom alive and breathing, anything that could possibly get on your toothbrush is already in your mouth. You can keep your toothbrush in one of those sanitizing things that they sell on TV late night in the United States, but you are still going to be sticking the autoclaved toothbrush into your relatively dirty mouth. That's okay! That's why we have immune systems. It's just life on Earth. Don't worry about it. It is actually unhealthy to be too clean! And let's face it, if the few microbes you are worrying about are going to put you off your toothbrush, you'll have to give up on all but virtual forms of sex. I'm reminded of when Neil deGrasse Tyson gives his lecture on why "intelligent design" is a misnomer, saying that putting sex organs next to the (ends of our digestive tracts) is like putting an amusement park in the middle of a sewage plant! Think about that one! Saudade7 03:37, 3 December 2007 (UTC)

There is certainly evidence that it's bad to be "too clean" - especially when you are very young. We have an article on that (of course!): The Hygiene hypothesis. SteveBaker 20:34, 3 December 2007 (UTC)

isnt there a gum that says Dirty mouth? Clean it up! YA just buy that!!!

Who will die earlier?

Two equally healthy people are put on the test. One is without water and the other is without food. Who will die earlier and why? Also, How long is going to be the difference between their deaths, approximately? DSachan 16:47, 2 December 2007 (UTC)

If the food contains enough fluids, the one without water might die of old age. Lova Falk 17:30, 2 December 2007 (UTC)

You can't survive without water more than a couple of days - you can go without food for weeks. SteveBaker 17:30, 2 December 2007 (UTC)

As Lova said, it is possible to get water from food, but it is not possible to get food from water. So, if given moist foods, it is probable that the person without water will be able to get enough water from the food to easily outlive the person who is only taking water without nutrients. -- kainaw™ 18:12, 2 December 2007 (UTC)

That's ridiculous - there is no way you can get enough water from food. Even if you ate nothing but watermelon. Some animals can do it - but we're not adapted to doing that. Our article on Water says "Also noted is that normally, about 20 percent of water intake comes from food, while the rest comes from drinking water and beverages"...so you'd have to exist on one fifth of the usual amount of water. It also says that you need to drink "1 milliliter for each calorie of food" - so eating five times more (in order to get more water) doesn't help because you need more water in order to digest it. (Of course for the literalist - according to the OP, the one that gets food "is without water" - so they're getting dehydrated food!) SteveBaker 20:09, 2 December 2007 (UTC)

How is it ridiculous? I have known many people who never drink "water". They drink fruit juice, coffee, coke, etc - but not water. So, to use your example - the person has plenty of food, including fruit (ie: watermelon). The person can easily get 8-10 cups of water (with various impurities from the food) per day. The food doesn't have to be eaten in whole. If given a watermelon, the person can opt to only drink the juice. Finally, taking the question literally, the person does not have to survive indefinitely. He only has to outlive the person who does not have any food at all. So, even if the person lacks the daily requirements of water intake, by replacing most of the water needed every day, the person can easily outlive the 3 or 4 days quoted as the limit for living without water. -- kainaw™ 20:24, 2 December 2007 (UTC)

That's a very misleading answer. We can read the OP's question in several ways:

1. Person A gets water and no food, Person B gets food - but dehydrated so he gets no water whatever. Person A definitely outlives person B.
2. Person A is allowed to drink water, Persons B is allowed to eat some kind of a normal diet - but not drink. This is the interesting one. A "normal" food diet doesn't contain enough water. 20% of what you need is what our article says.
3. Person A can drink whatever he wants, Person B can eat whatever he wants. Both of them survive into old age - the first living on a variety of soups and juices, the second living on watermelon and oranges.
4. Person A drinks water, Person B is allowed to consume large amounts of oranges and watermelon (at least five times more than a "normal" diet would contain according to our article). In that case, person B will clearly outlive A.

The only way person B wins is to take the last of these four interpretations - but I maintain that this is a very strange reading of the original question. SteveBaker 01:16, 3 December 2007 (UTC)

I simply took "without water" to mean that the only restriction was no access to plain water and not a restriction to a "normal" diet. I do agree that I don't interpret questions normally. I tend to always look for the loophole. -- kainaw™ 03:14, 3 December 2007 (UTC)

The rule of 4s, that I was taught in a Wilderness First Aid class a few years ago, was: 4 minutes without air, 4 days without water, 4 weeks without food. This is probably a very rough estimate, but should give you an idea. Unfortunately, our articles on fasting related topics don't appear to provide any numbers. (EhJJ) 19:10, 2 December 2007 (UTC)

I actually learned it as the "Rule of Threes" as mentioned in survival skills. Either way, a rough estimate. --Bennybp 19:33, 2 December 2007 (UTC)

Is there a supertough scout troop somewhere who is trained: 6 weeks without food, 6 days without water, 6 minutes without air? As I heard it from someone who had attended "survival school" the three rule also included three hours without shelter (presumably in freezing weather). Edison 21:40, 2 December 2007 (UTC)

Ignore any "rules of threes or fours". People are different. A fatass will obviously live longer without food than some emaciated little girl. As for water, about a week tops, although there are exceptions. 64.236.121.129 14:38, 3 December 2007 (UTC)

Maybe that's why both people stating those rules noted that they are rough estimates. -- Coneslayer 14:47, 3 December 2007 (UTC)

Also, the original question states that "Two equally healthy people are put on the test." (Granted, "equally healthy" doesn't necessarily mean "equal" or "healthy", but it was clearly implied). (EhJJ) 15:48, 3 December 2007 (UTC)

They aren't acurate estimates. People are too different to give a general estimate like that. 64.236.121.129 18:35, 3 December 2007 (UTC)

So why did you give a general estimate of a week? -- Coneslayer 19:06, 3 December 2007 (UTC)

Because it's a more acurate estimate. Being a fatass means you can last longer without food. The same can't be said for water. 64.236.121.129 20:50, 3 December 2007 (UTC)

You actually gave an upper bound, not an estimate. And to give a general estimate is to guess where the mean or median is, which is always valid in this sort of problem. As for how variable the situation is, that's just raising the issue of how large the variance is, which is completely unknown. But the variance does not diminish our ability to provide an estimate of the mean/median, only the likelihood of its being correct for a random individual. Someguy1221 21:01, 3 December 2007 (UTC)

Yes, I gave an upper bound. Coneslayer said I gave an estimate, so blame him for the terminology. An average is fine, unless the variance is too high, and in this case, it is. One guy once went on a hunger strike for over 300 days without food. I don't know if he was a fatass or not, but it gives an idea as to how dispersed these ranges are. Giving an estimate or upper bound for water is a little more consistent from person to person because it doesn't rely on how much blubber you have in your stomach, butt, etc. 64.236.121.129 21:14, 3 December 2007 (UTC)

My point was that the existence of a high variance doesn't make the average any less true. It just needs to be pointed out. Someguy1221 21:49, 3 December 2007 (UTC)

Well, here is one excellent source of data in the 1981 prison hunger strike in Northern Ireland. The variance there is that one person died after as little as 46 days - another survived after 70 days, another died at 73 days. According to Hunger strike "The Guinness Book of Records lists the world record in hunger strike (without forced feeding) as 94 days.". But these were people in prison - they didn't have to exert themselves - they weren't suffering temperature extremes - they were getting plenty to drink (even intravenously after they slipped into coma) and they were getting good medical attention. That means that this is probably close to the maximum possible. If you were in a 'survival' situation where you have to find water, make shelter and at least search for food - you're burning through energy more quickly - so you're not going to survive as long. In light of the Guinness book statement - and the evidence that nobody else seems to have survived to even ONE hundred days - the THREE hundred day number that 64.236.121.129 claims is going to need some kind of a reference (that's a polite way to say bullshit!) - the problem here is that there are variations in what is considered to constitute a hunger strike. Can they drink things other than water? Was force-feeding applied? Was water given intravenously after coma set in? SteveBaker 03:26, 4 December 2007 (UTC)

Continuing: [8] says that one guy survived 123 days on hunger strike - but (a) he occasionally drank coffee and (b) he broke his strike and ate for a few days in the middle - so it wasn't really a continual strike. The trouble is, everything I can find out about him dates from June 2004 and they ALL say "still alive after 123 days so far" - we never seem to find out whether he died or gave it up - and after how many days. But even if he is 64.236.121.129's "300 day" guy - the fact that he "cheated" make him a less than valid scientific test. SteveBaker 03:37, 4 December 2007 (UTC)

OK - nope, he was force-fed after 130 days[9] - then started eating of his own accord - so no 300 days here either. SteveBaker 03:41, 4 December 2007 (UTC)

Easy SteveBaker, I said 300 days, but I might be wrong. 130 days sounds about right. 64.236.121.129 15:21, 4 December 2007 (UTC)

Clearly it depends on things like: the climate, the amount of exertion is required of you, how appropriately clothed and sheltered you are, how much fat deposits you have, how much food/water was in your stomach at the outset, your age, your state of health, what medical facilities there are to help you recover when the ordeal is over...there are bound to be lots of other variables. So any number we tell you here is 100% guaranteed to be wrong for some combination of circumstances. However, "a few days" without water and "a couple of weeks" without food are not bad "rule of thumb" estimates. SteveBaker 20:23, 3 December 2007 (UTC)

Really, it depends on if you are this guy! (Just kidding, don't try this at home!) Saudade7 13:22, 4 December 2007 (UTC)

Camera settings for astrophotography

Hi. Say I wanted to photograph Comet 17/P Holmes sometime in January using a digital camera, a 4 - 6 inch Equatorial Reflector in light-polluted skies (although there are no lights very close to the location of the comet), and Registax. Now, I want to ask approximately what camera settings I should use. I'm thinking of photographing it while it is near either M34 or Algol, under approximately 50x. Which is a better choice for a better image? The camera is capable of up to 10-, 13-, and 15- second exposures. How many images in total should I take, before stacking them? For the aperture, should I use a focal length of 2.8, 3.2, 3.5, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1, 8.0, or should I let the camera set the aperture automaticly? Should I hold the camera using my hands and telephoto, or should I use a special camera adapter to hold the camera steady? Should I use the best resolution and compression avalible? Should I store the images as JPEG or RAW, and what's the difference? Should I leave the focus frame in the centre, or adjust it according to where the comet's nucleus is? Will I be able to visually view the comet's coma in January, using this type of telescope, under light polluted skies, prior to taking the images? Should I zoom in so the FOV of the eyepiece completely fills in the FOV of the camera? What light metering system should I use: evaluative metering, center-weighted averaging, or spot metering? Should I use strong contrast, sharpness, and saturation? What ISO speed should I use: 50, 100, 200, or 400? Thanks. ~AH1^(TCU) 17:02, 2 December 2007 (UTC)

The thing about the night sky is that it is very dark. Even with light pollution. Stars and comets just don't provide much light here on Earth. So, you're going to need a long exposure, which means you definitely can't hold the camera with your hands. The aperture should be wide open, f/2.8 if that's the best you have. There's no reason to stop it down, because everything in the photo is practically at infinite distance, so you don't need any depth of field. The metering systems of everyday digital cameras are not designed for this, so just put the camera in manual mode. If the sensitivity only goes up to ISO 400, then it's probably very noisy at that sensitivity. On the other hand, if you turn the sensitivity down, you need more exposure time, so there's a tradeoff. —Keenan Pepper 19:43, 2 December 2007 (UTC)

I'm pretty sure the OP noted they were using a telescope, so the bit about holding the camera steady probably doesn't really apply. One thing they don't note is whether they have a tracking mount or not; if not, long exposures with high magnification will suffer from motion blurring just from the Earth's rotation. Since they're going to be stacking the images anyway, I'd concentrate on minimizing the exposure time per frame, setting maximum ISO, maximum aperture and an exposure just long enough for some recognizable detail to emerge from the noise for the alignment algorithm to home in on. Oh, and I'd definitely put the camera in fully manual mode for this; you can use the automatic focus and metering to find suitable values, but set them manually before starting the actual shoot. Can't really say much about the zoom, except obviously not to use "digital zoom". I guess if you can zoom the camera in while retaining focus and a reasonable aperture, why not? I'll just give you that much extra magnification. If you can, shooting in RAW mode is probably best. Also disable automatic dark frame subtraction if your camera lets you, and take your own dark frame(s); I believe registax can handle dark frame subtraction during the stacking. Mind you, I've never really more than dabbled in astrophotography myself, so take my advice with a grain of salt. Oh, and you might be interested in our astrophotography article — or at least the links and references at the end. —Ilmari Karonen (talk) 20:26, 2 December 2007 (UTC)

A typical rule of thumb, at least for me, is that the combined image will not look more than 70% better than the original images. So if the details in the original photos are barely louder than noise, the noise will be a huge problem when it comes to combining the photos. --Bowlhover 23:01, 2 December 2007 (UTC)

Oh, I see he did ask about holding the camera in his hands. I suppose, depending on how everything else works out, that it might work if the exposure time per frame is short enough — any shake from his hands will just get added to turbulence and other sources of blurring and hopefully filtered out by registax. But if you have or can reasonably obtain a camera mount, I'd strongly recommend it.

By the way, if your camera has a video mode, you might want to give it a try; that'll give you a large set of low-resolution frames, exactly what programs like registax are written to work best on. —Ilmari Karonen (talk) 20:37, 2 December 2007 (UTC)

Right, holding the camera simply doesn't work. Neither does touching it during the exposure or less than 3 seconds before the exposure, so I would strongly recommend using the camera's self-timer. I don't think videotaping will work because the minimum exposure time for an adequate-quality photo of the comet, using my Nikon D40x at ISO 1600, was 2 seconds several days ago. Combining the photos is no miracle cure for a low signal-to-noise ratio. --Bowlhover 23:01, 2 December 2007 (UTC)

Hi. Your responses are very helpful, but I still have a few questions and comments. I did say equatorial reflector, which means I will be using sky tracking. However, I'm quite unfamiliar with this, so I'm not sure if I should use an AC/DC adapter and an outdoor AC line, or some kind of battery. Well, If I can get a camera adapter, how much will it cost? Note that my camera lens isn't that long (only about an inch), and actually moves backward and forward again when I zoom it in. Well, I heard using a larger aperture will fade the background, and the stars pretty much are the background, or are they far enough to prevent this? If I use the movie setting, which is avalible on my camera, I will not be able to set such things as the ISO speed. Will it work if I get the final stacked images for both the long-exposure shots and the movie images, and combine them into one final image? Does registax offer image processing? If I am able to use an accurate equatorial mount and camera adapter, can I use longer exposures (eg. 15 secs)? If I do the long exposure times, and take several of these photos, how many will I need? If I use the movie setting, should I use the higher resolution, and how long should the movie be? Can registax cut out undesirable images of a movie sequence, such as if I didn't have a camera adapter and had to occasionally take the camera off the telescope? Does registax give you image processing tools like those in Photoshop? Would digital zoom interfere with my images? How does RAW mode improve the images? If I am to upload the final result onto Wikipedia and/or Commons, what file endings (eg. bmp, gif, jpg) are suitable? What file ending to registax final images come out as? Will using good settings prevent the photo from oranging? What white balance should I use? Thanks. ~AH1^(TCU) 21:20, 2 December 2007 (UTC)

(1) I recommend using the camera's battery if it can last long enough for your photography session, because the wind will blow your DC adapter line around if you use one, moving the camera and blurring the photo. By all means bring extra batteries because long exposure times are very energy-demanding.

(2) Try doing some research on the Internet on adaptors that have the appropriate output voltage. Adaptors should be very cheap, around 4 USD.

(3) Larger apertures fade the background because it leads to a narrow depth of field. This means a small difference between the distance of an object and the distance of the object your camera focused on will cause a large difference in how well-focused the "unfocused" object is. Since both the comet and the stars can be considered to be at the same distance--that is, infinite distance--the aperture has no effect on how well-focused the stars are. They'll be as focused as everything else in the photo.

(4) Registax offers some image processing like rotating and brightness adjustment. Try it out. You'll definitely need another image processing software to edit your photos.

(5) A 15-second exposure time should be no problem. But since I have no experience using your telescope and your equipment, the best way to find out is to try taking astrophotos with varying exposure times, with varying ISOs and the maximum possible apperture. --Bowlhover 23:01, 2 December 2007 (UTC)

(after edit conflict & answering your first set of questions) Since you have a tracked equatorial mount, take as many photos as your computer can combine without running out of RAM. The more the better because the final image's random thermal noise decreases with the square root of the number of photos combined.

Brightness of the comet: according to this graph, Holmes will be magnitude 5.2 on January 1. Extrapolating from this angular size chart, it will be 101 arcminutes on the same day. This gives a surface brightness of 23.9 mag/sq. arcsec. By comparison, the darkest skies have a surface brightness of 23 mag/sq! You may be able to see the inner coma, but I highly doubt you'll manage to see, or even photograph, the outer ring.

When photographing, be sure to zoom in as far as you can without cutting off the comet. Zooming in will give you the same number of pixels for a smaller area of sky, thus increasing the amount of detail in your photos.

Finally, make sure to take the photos in RAW format rather than JPEG. The camera records sensor data directly to the file when shooting in RAW but compresses the image before storing it when shooting in JPEG. The compression involves taking pixels of similar brightness and colour and setting them to the same brightness and colour, creating compression artifacts. JPEG files are around half the size of RAW files but with a lower quality. --Bowlhover 22:20, 2 December 2007 (UTC)

One last thing: The high ISO settings on most cameras are there for marketing purposes only, and the noise you get from them is absolutely unacceptable. Try using the second-highest or third-highest ISO. --Bowlhover 23:01, 2 December 2007 (UTC)

Racing across the universe while sitting on the couch

Hi wikipeoples! I think it's gonna be hard for me to ask this question correctly (even though I saw and successfully passed three "physics for engineers" classes at my university... but that was a long time ago...), and this was probably asked somewhere before, but I'm gonna try anyways, so please don't bite me. In a nutshell, it's this:

What is the absolute velocity of an object resting in place on Earth?

Now that might sound pretty easy or even stupid, but I'm just getting started. Considering a (static) inertial reference frame outside of Earth (I would consider the sun, but maybe I'm complicating myself too much), any object on the surface of the Earth (I like to imagine someone sitting on a couch, for example) would have several velocities, like Earth's rotational speed (so for you picky fellas the guy on the couch would be somewhere on the equator), and the speed given by the orbital rotation of the Earth around the sun. So you got two velocity vectors already; what's the velocity of the object considering these two vectors? (Am I on the right track? Is there something extra I should be considering already?)

So far so obvious, right? Now, I don't know if I should keep going, but, here goes: since according to its article the Sun is moving at 217 km/s around the galactic center, then there's yet another vector to add up. What is, then, the velocity of an object on Earth from the frame of reference of the galactic center of the Milky Way? Is it simply 217 km/s because the other vectors are already negligible? What if I said that this speed isn't considering the bobbing movement of the Sun across the galaxy's disk? What would the speed be with this?

Finally, according to the Milky Way's article, some estimates say that the galaxy is moving at 600km/s from the frame of reference of other galaxies. It also says that the Earth itself would be moving at 51.84 million km/day, but I'm not sure what vectors is it considering. Or, since the magnitude of the galaxy moving would make other vectors negligible, is this 'Earth's speed' all that's needed to consider the velocity of an object on it?

I hope I didn't sound like a moron asking this (though I'm sure my considerations about Earth's speeds around the Sun are wrong somehow). And yes, I'm asking for velocities, not speeds.

So to sum up, I'm asking for three velocities of an object on the surface of the Earth: viewed from the FoR of the Sun, viewed from the FoR of the galactic center (including the bobbing movement if possible), and viewed from outside the galaxy (if the last one isn't already correctly answered). I guess that's it. Thanks in advance! Kreachure 18:13, 2 December 2007 (UTC)

Some of these things are pretty easy to calculate. For example, the average orbital speed of the Earth around the Sun is just 2 pi AU / year in km/s. Similarly, if the circumference of Earth is about 40,000 km, the rotational speed of a point on the equator is 40,000 km / day in m/s. These two vectors don't have a constant angle between them because they rotate at different rates. Earth is a "prograde" planet, which means it rotates in the same direction as it orbits the Sun, so the vectors add at midnight (by some reckoning of time) and subtract at noon. —Keenan Pepper 19:25, 2 December 2007 (UTC)

Unfortunately, your first question is self-defeating, as it asks for the absolute velocity with respect to the "fixed reference frame" of empty space outside our galaxy. No frame is fixed! You can pick any "frame" and call it fixed; then, you can calculate the relative velocity of some other frame. Because of special relativity, the velocities must be less than c, so all you can safely say is this: "on your couch, your relative velocity with respect to any other object in the universe has magnitude between 0 and c." If you want velocity with respect to a specific object, (such as your later questions), then you can of course calculate it as Keenan Pepper explained above. Nimur 21:34, 2 December 2007 (UTC)

Note that you are looking at speeds over a wide range of scales here. Rotational speeds about the centre of the Earth are of the order of 400 m/s, which is very much smaller than the 29.8 km/s orbital speed of the Earth around the Sun. This in turn is an order of magnitude smaller than the 200 km/s orbital speed of the solar system relative to the Milky Way. So if your frame of reference is the Milky Way, you can get a good enough ballpark answer by ignoring the first two components. Gandalf61 10:42, 3 December 2007 (UTC)

There is no fixed reference frame, as others have pointed out, but about the best you can do is use the CMB's frame; see its footnote 2 for a velocity. --Tardis 16:48, 3 December 2007 (UTC)

Name of a medieval herbal medicine manuscript?

Hey I was wondering if anyone could possibly direct me to the page of a certain medical manuscript whose name I cannot currently recall and after searching both Wikipedia and other resources cannot find. It was an illuminated manuscript which, if I recall correctly, mostly dealt with herbal medicine. It was a European manuscript based off of an Islamic one and I believe it was from the 11th or 13th century. Thanks for any possible help.

Cracksells 20:05, 2 December 2007 (UTC)

Herbalism mentions some old manuscripts. --JWSchmidt 21:21, 2 December 2007 (UTC)

Maybe this one? Tacuinum Sanitatis. Saudade7 03:56, 3 December 2007 (UTC)

Strategies for modern cities to become increasingly energy efficient

Can anyone please help me find some strategies for energy efficiency? All I could think of is using alternative sources of energy and using energy efficient products. Please help, I need these for my homework. It would be cool if you provide some links too. Thanks in advance. 202.137.21.176 20:50, 2 December 2007 (UTC)

Alternative energy sources are not necessarily more efficient. In fact, they are often not (solar cells today have a theoretical maximum of about 33% efficiency). Be more creative - look at how much energy we dissipate as heat or friction into the air when we brake, for example - that's the principle behind hybrid cars. SamuelRiv 21:07, 2 December 2007 (UTC)

Thanks for answering. So do you have any suggestions? I'm really in need of help! 202.137.21.176 21:21, 2 December 2007 (UTC)

A modern city with good mass transit would be more energy efficient than one where everyone drives everywhere in a car or SUV. A way for a city to get people to ride buses, subways, trains, or light rail would be to make sure everyone is within walking distance of a transit line, and that the transit runs on a schedule which meets the needs of people needing to get somewherre: the things run frequently and are safe and affordable, and they do not stop running at some inconvenient time like 6 pm. A way to add some 21st century technology would be to use the GPS info the buses and trains often transmit to their control centers to the internet, where a commuter would be able to tell from his home computer or mobile Blackberry just when the bus/train will reach his stop. The same info could allow a display at the train/bus/trolley stop to indicate approximate minutes until the next one arrives, based on GPS info. It is frustrating to reach a bus stop 30 seconds after the bus left with 30 minutes until the next one arrives. Less energy is used per passenger mile on a reasonably well loaded mass transit vehicle than if each person drives. Edison 21:33, 2 December 2007 (UTC)

Relatedly, Geographic information systems (GIS) can be (and are) used for things like route optimization for buses, garbage trucks, etc. There are a huge number of other ways GIS can be used to increase efficiency, especially in combination with technologies with GPS and wireless networks / mobile computing. Pick anything that involves people or goods moving from one place to another and odds are it could be made more energy efficient (and probably cheaper too). It's hard to pick an example because nearly everything a city government does can be improved in this way. So.. say, I don't know, building inspectors going into the field to inspect buildings -- use the above technologies to optimize schedules and driving times, minimize the need to return to the office, etc. Pfly 22:02, 2 December 2007 (UTC)

Thanks for all the suggestions guys! I need at least three strategies and so far I've got two on my hand: utilizing energy efficient products on residential and commercial sites, and improvement on mass transit and other transportations. Anyone has one more idea? Or have resourceful links? Thanks in advance! 202.137.21.176 22:16, 2 December 2007 (UTC)

Also relatedly, mass transit can only work (or can only work efficiently) when people's housing and their workplaces are sufficiently dense and sufficiently close to each other. If everybody wants a house out in the wide-open suburbs, mass transit doesn't work well. If in order to find affordable housing the "wide open suburbs" require a one-hour commute each way, it works even less well. So (just as for any hard problem) some of the solutions for the energy problem will have nothing directly to do with the energy problem. —Steve Summit (talk) 22:19, 2 December 2007 (UTC)

It's a radical one - but population reduction would work too. If there were half the number of people in the world - we'd use half the amount of energy. The problem is: How to get there from here...but that's a problem with many energy reduction strategies. SteveBaker 00:43, 3 December 2007 (UTC)

A city is a system. You need to think in term of the system and not of its separate parts. In a city, you can make efficient use of cogeneration. You can cover a city with a dome. mass transit options are much more economical. Economies of scale change the economics of almost all of energy use. -Arch dude 00:51, 3 December 2007 (UTC)

In a relatively low polution city you could encourage food cultivation inside the city to minimise daily transport from the outside. Keria 10:20, 3 December 2007 (UTC)

This may or may not help. The trouble with such plans is the cost of localised food production can sometimes be vastly more significant then food production in other areas so even with the added cost of transport and perhaps refridgeration, it can still be cheaper to bring food in. However on a related issue, and somewhat radical as well, greatly reducing meat consumption would help. I've seen some studies which suggest some meat consumption may in fact be more environmentally friendly in some areas anyway because the land is not particularly suitable for most crops but even if this is true and it wouldn't in fact be best to just import food the amount most people eat is definitely way too high. Nil Einne (talk) 13:41, 5 December 2007 (UTC)

I've heard of a few interesting systems that use the city's sewage as an alternate fuel source. You treat the water so as to conserve it, and you use bacteria for anaerobic digestion on the leftover sludge which produces heat and methane gas, then you use pyrolysis, gasification, or other methods to turn what's left into solid and gaseous fuels, which can then be burned for more energy. This also has the benefit of reducing the amount of waste material that has to be disposed of. Even if you only break even energy wise, the reduction in waste makes it worth it. Of course, these systems are still being developed, so they can be expensive and experimental right now, and there are a number of different methods being tried. See the biomass and related articles for more information, or some examples like this one in Germany, or this one in Philadelphia, PA USA, or even this system using animal waste parts from food production. Hope that helps! -- HiEv 13:47, 3 December 2007 (UTC)

Not related to cities per se but increasing the energy efficency of homes will obviously help. For example, increasing the usage of energy efficient lighbulbs usually CFL or other flourescent lightbulbs although maybe LED based ones in the future. Increasing thermal insulation of homes and hot water cylinders, particularly in temperate countries. Increasing the usage of solar hot water heaters. Nil Einne (talk) 13:34, 5 December 2007 (UTC)

Electrical Resonance

What would cause the peaks in frequency/current graphs of electrical resonance in an LCR circuit to come out thinner than predicted. with current measured as voltage across the resistor, the peaks have come out much wider and less tight than the peaks predicted by the maths. What could cause this? —Preceding unsigned comment added by 172.203.50.108 (talk) 20:52, 2 December 2007 (UTC)

I'm afraid I don't understand what you've written; you seem to be saying two opposite things. But have you considered Q? Higher frequencies cause a coil to have lower Q because of skin effect. Certain types of capacitor will exhibit very low Q at high frequencies. --Milkbreath 21:22, 2 December 2007 (UTC)

As the resistance in a RLC circuit resonant circuit increases, the peak should broaden. See Q factor. The article LC circuit also says that in a series resonant circuit, a high inductance and low capacitance makes for a narrower peak, while the converse is true for a parallel resonant circuit. Edison 21:27, 2 December 2007 (UTC)

The variations can happen because of stray capacitance, mutual inductance with things that are not inductors, skin effect causing higher resistance than measured at DC. Eddy currents induced due to the magnetic field. Even your measuring equipment could be adding an unexpected load to your circuit. Usually Q gets lower and the peaks broaden. What Frequency are you working with? Graeme Bartlett 01:00, 3 December 2007 (UTC)

You left out the R, or had a much lower value of R in your experiment than you thought.--TreeSmiler 01:13, 3 December 2007 (UTC)

On the other hand, if your peaks are too wide, you have more resistance (or less inductance) in the circuit than you thought. Were you inadvertently putting dc through the inductor as well as ac?--TreeSmiler 02:15, 3 December 2007 (UTC)

I'm not quite as foolish as to have fallen at such basic errors as tree smilers suggestions! But Q factor would seem to account for this, with eddy currents and rogue inductances as such. —Preceding unsigned comment added by Philc 0780 (talk • contribs) 19:49, 3 December 2007 (UTC)

I didnt intend to insult your intelligence, but you left us wondering about the form of circuit (series or parallel)

, frequency of opeation and how much you actually knew about resonant circuits etc. --TreeSmiler 02:48, 4 December 2007 (UTC)

Other responders have asked the frequencies tested. I remember from microwave lab in school how a resistor, inductor or capacitor might change in its characteristic as the frequencies used increased from audio to radio frequency to UHF to microwave. Capacitor or resistor leads can become inductive at high freq, and inductors may have appreciable resistance at any frequency. Edison 03:16, 4 December 2007 (UTC)

electricity consumption of heater

I have an electrical heater. It has a label with 1500W on it. Does this mean it will consume 1.5 KW/h for every hour that I use it?217.168.3.246 22:28, 2 December 2007 (UTC)

Yes, if it is running constantly. -- Coneslayer 22:45, 2 December 2007 (UTC)

It may have a thermostat - which would make it turn off once the temperature gets high enough - then turn on and off as needed to keep the temperature high enough. In that case, the peak usage would be 1.5kW - but the average may be much less depending on how well insulated the room is. If it doesn't have a thermostat and you leave it turned on at its maximum setting - then it'll use 1.5kW all the time. Without more information, it's hard to know which you have. SteveBaker 00:33, 3 December 2007 (UTC)

Nitpick: the second unit in your question should be the KWh (pronounced kilowatt-hour) not the KW/h (kilowatt per hour). Algebraist 02:02, 3 December 2007 (UTC)

Even smaller nitpick: the symbol k for kilo- is not capitalized. You mean kWh. --Anon, 09:35 UTC, Dec. 3.

Thank you for the answers.217.168.3.246 02:54, 3 December 2007 (UTC)

Further, somewhat important nitpick: your heater should have a voltage rating. It will consume 1500 watts only at the specified voltage. If the voltage is increased, a resistive heater will consume more power (and produce more heat) with thc converse true if the voltage is lower than the rating. For instance: a heater rated at 120 volts, but operated on 110 volts (a very realistic scenario), will only consume 1260 watts (assuming the resistance of the heating element remains about the same, a reasonable assumption). If a 1500 watt heater rated at 110 volts were operated at 120 volts, it would consume 1785 watts. Edison 03:11, 4 December 2007 (UTC)

The trouble with that is that ratings like 120 volts and wall-socket power at 110 volts are applicable to AC current, not DC - so these numbers are RMS values, and the math is more complicated. Also, a simple application of Ohms law doesn't work because resistance of most heaters varies with the temperature...it gets ugly, fast! SteveBaker 03:52, 4 December 2007 (UTC)

AC RMS versus DC has no effect on the wattage variation with voltage I stated for a resistive heater. RMS is the heating effect equivalent AC quantity which equals the heating effect of DC. The resistance of the heating element should not vary much over the narrow temperature range involved: not like a light bulb filament going from room temperature to incandescence. As a real-world instance of the variation of heat output with voltage, a kitchen oven was rated for 208 to 240 volt operation, but the designedr told me it was really built for 240. At 208 volts, the element did not get hot enough to broil meat., although eventually it would bake it. Beware of this in any "one size fits all" specification. I have seen electric appliances from India (fans) with a 110 volt nameplate, and wondered the same factory exported heating appliance to the U.S. designed for 110. Edison 05:28, 4 December 2007 (UTC)

December 3

Skin Tightening

I lost about 50 pounds over the last 8 month and I was wondering how long it takes for your intestines to shrink (someone was telling me they shrink after you lose weight) and also for my skin to tighten up. It doesn't look loose, but I heard it tightens up even more. —Preceding unsigned comment added by 76.167.132.90 (talk) 01:36, 3 December 2007 (UTC)

I imagine it would depend on a lot of factors, none of which anyone here could judge from one post on a forum. Skin elasticity varies wildly from person to person, a major factor however would be how old you are, the older you are the more elasticity your skin loses. Also how much sun exposure you have had would be another factor, and for how long and how much larger you were before you lost weight, all these things will vary how much and how quickly your skin will shrink back. Also, i've never heard of intestines shrinking, if they do I doubt you would notice it, you'd probably be better of discussing these things with your GP when you next visit. Vespine 03:03, 3 December 2007 (UTC)

Langmuir adsorption isotherm

Which would obey the Langmuir adsorption isotherm better, metal cations or organic compounds?

Thanks so very much! —Preceding unsigned comment added by 134.82.109.58 (talk) 03:31, 3 December 2007 (UTC)

It would depend greatly on the material its being adsorbed onto so it hard to compare the two. But I suspect it would be organic molecules as the cations (depending on concentration) can create a electrical double layer on the surface thus inhibitng further adsorption. Shniken1 03:54, 3 December 2007 (UTC)

advanced technologies

may i know about some advanced technologies in electrical and electronics for presentation purpose?202.88.234.134 09:03, 3 December 2007 (UTC) —Preceding unsigned comment added by 202.88.234.134 (talk) 08:58, 3 December 2007 (UTC)

You might want to look through the categories at the Electronics Portal and the Technology Portal. --Milkbreath 11:50, 3 December 2007 (UTC)

dreams

may i know whether blinds are able to see dreams?if yes is there any colours in there dreams?what happen to the persons whom became blind during their life..is they saw any dreams?202.88.234.134 09:18, 3 December 2007 (UTC)also can animals are able to see dreams?202.88.234.134 09:18, 3 December 2007 (UTC)

Dreams are based on your memories (real and imagined). People who were born blind won't see in their dreams. People who became blind during their life may see in dreams. Similarly with colors, sounds, and so on. If you remember them, you can dream about them. And yes, animals dream. With a cat, for example, you will see its paws moving as it presumably dreams about fighting. --Anonymous, 09:40 UTC, December 3, 2007.

No, Blinds cannot see dreams, since they are simply inanimate window coverings, with no cognitive functions. -- JSBillings 14:04, 3 December 2007 (UTC)

Making fun of the OP's phrasing of the question is rude and uncool. Please stop doing that. SteveBaker 20:09, 3 December 2007 (UTC)

Here is an academic critique discussing this very question. Rockpocket 18:55, 3 December 2007 (UTC)

Thank you so much for that article link, Rockpocket!! This happens to be something that I've wondered about for many years - apecifically, what people who are completely blind from birth dream about. I thought I'd provide a brief abstract of the article for those who don't wish to wade through it. I found it very interesting to read how people who have been blind from birth have the ability to "see" their surroundings in their minds through other senses (mainly touch) other than sight, and that they then construct three-dimensional imagery in their minds to accompany their perceptions. They also can draw two-dimensional images of a three-dimensional object quite accurately. However, as the article noted, these people have difficulty with being able to perceive that there would be differences in color or brightness levels. The article reported how there is a distinction between a person's visual image (what a blind from birth people "sees") and visual content (what people who can distinguish between color and brightness sees). The article also said that the part of the brain that functions when someone who is sighted is seeing is also the same part of the brain that is functioning when a blind person is "seeing" through touch. So when people who have been blind from birth dream, they do dream in the third dimension about images of things, but they have difficulty with color and brightness of objects. Absolutely fascinating! Saukkomies 14:18, 8 December 2007 (UTC)

Since people are animals it is reasonable to assume that other animals dream. It is not reasonable to supoose that because a cat twitches it is dreaming, unless you also twitch when you dream. I don't (apparently). I would be more convinced by observations of REM in animals.--Shantavira|^{feed me} 19:54, 3 December 2007 (UTC)

If you ever watched a dog sleeping - you can see coordinated twitching of paws plus (sometimes) tiny little yelps of barking, sniffing, ear twitching and small movement of the jaws. You can easily follow the 'plot' of the story they are dreaming out. It's impossible to believe that they aren't dreaming of running and chasing something. I can't say that I've noticed REM - but dogs don't rely on their eyes much - so it's perfectly possible that they don't exhibit this sign - using RPM ('rapid paw movement'!) instead. SteveBaker 20:09, 3 December 2007 (UTC)

Dogs display REM when they dream, just like humans do. Consider poor Dreyfus. Rockpocket 23:57, 3 December 2007 (UTC)

Viruses are all around us?

This is a continuation from a previous question. Are there viruses all around us, even right now? Someone insinuated that the cold virus is one of the viruses all around us constantly, and we can get it from the enviroment without actually being near someone who is already infected. They also insinuated that he reason why we don't get the cold despite it always being around it, is due to our immune system. I find this hard to believe though because the cold virus is an RNA virus, and thus, it would be highly unlikely to be immune to the particular strain that happens to be around us. Can we catch a virus from the enviroment alone, simply by breathing the air, without being near someone who is infected? 64.236.121.129 18:41, 3 December 2007 (UTC)

In principle, yes. In practice, it's fairly unlikely. It's all a matter of probability -- the probability that the virus is sufficiently concentrated, that it's not gone inert/dead/whatever by being outside a host, and so forth. — Lomn 19:14, 3 December 2007 (UTC)

You should be careful when talking about things like "the cold virus". There are hundreds, probably thousands, of different coronaviruses and rhinoviruses that we all describe as causing the "common cold" when we get sick from them. Even if you gain immunity to one of them, there are still plenty of others your immune system will not immediately recognize.

As for your main question, yes, there are viruses around us constantly, but that's because all life can be infected by viruses, even bacteria (see Bacteriophage). This means that the wind blowing past your home carries viruses from all sorts of organisms, though in very tiny quantities, and smaller quantities means a smaller risk of infection. Also, the innate immune system can sometimes deal with viruses never encountered before, so if there are only a few viruses they may not survive long enough to become a full-blown infection. Besides that, most viruses can only flourish in a few specific genera, which means that you're probably safe from most viruses you encounter. Also, those viruses in the environment tend not to live very long, especially in sunlight, because UV light, oxygen, and other such things kill most viruses rather quickly. All of that means that, yes, you can get infected with a virus when "isolated" from other people because you're not actually totally isolated (unless you're somewhere like Antarctica), but your odds of infection are extremely small. Also, you never get a virus "from the environment alone", you're getting it from some other organism who was infected with it and spread it into the environment fairly recently. So, if you see someone who is sick from a virus, the odds are way more likely that they got it from close contact with someone (or something) else that was infected, and not from long-distance "environmental" contact. -- HiEv 21:04, 3 December 2007 (UTC)

There's some new research about the persistence of influenza virus in the environment. -- Coneslayer (talk) 12:16, 5 December 2007 (UTC)

Here's a version of that link so you won't have to login to read it: "Study shows why the flu likes winter". The short version is that the flu viruses survive longer outside of the body in cold, dry air, and the body also releases viruses longer in a lower temperature environment. Increasing the temperature or the humidity reduces the odds of transmission, with 30°C (86°F) or 80% humidity being about the limit the viruses can function in. The optimal environment for the viruses was about 5°C (41°F) and 20% humidity. So, in cold, dry environments you're likely to be exposed to more viruses at once, which increases your odds of getting sick, and more people getting sick increases the odds of other people getting sick. However, I was kind of disappointed that the article didn't mention the lengths of time the viruses survive outside the body in the different environments. -- HiEv 15:46, 5 December 2007 (UTC)

So it is a fact that viruses can exist outside of an organism, and in cold temperature, the flu virus can exist outside of an organism for longer periods of time. But what about the common cold? Does it also live longer outside of an organism for a longer period of time in cold temperature? 64.236.121.129 (talk) 17:26, 5 December 2007 (UTC)

giardia/mitochondria

Given that Giardia lack mitochondria, how and where do they create energy/ATP?75.42.65.119 19:20, 3 December 2007 (UTC)

Like most protozoans (all of which lack mitochondia), Giardia can produce ATP by glycolysis. I'm not an expert, but one will probably come by in the next hour eventually. Nevertheless, our article on glycolysis should get you started and feel free to ask additional questions if you have any. (EhJJ) 19:35, 3 December 2007 (UTC)

Actually, only a few protozoa lack mitochondria. According to eukaryote, The few protozoa that lack mitochondria have been found to contain mitochondrion-derived organelles, such as hydrogenosomes and mitosomes. These mitochondrion-derived organelles do some of the work normally performed by mitochondria. --mglg_(talk) 00:02, 4 December 2007 (UTC)

I need to make sure I drink coffee before posting to the Ref Desk. In any case, prokaryotes do not have mitochondria and survive just fine. Although Giardia is not a prokaryote, it could use similar mechanisms if it lacks mitochondria. Sorry for the confusion. (EhJJ) 15:34, 4 December 2007 (UTC)

Keep in mind that mitochondria were most likely once separate organisms. In the beginning, no life used mitochondria, but some organisms developed a symbiotic relationship that evolved into the cell+mitochondria system we see in most life today. See the Endosymbiotic theory article for details. However, just because that system is common today doesn't mean that it's the only way life can survive. -- HiEv 04:11, 4 December 2007 (UTC)

The main ATP producing process comes from the electron transport chain. For eukaryotes, the process occurs in the mitochondria. For prokaryotes, it occurs in the cytosol.128.163.224.222 (talk) 21:50, 4 December 2007 (UTC)

Dry hands, lips

I just moved into a place and at night time I have very dry hands (put cream on it a couple times until I fall asleep), I wake up from having a dry throat and I am thirsty, and my lips are chapped. Would a humidifier help with these symptoms? Any suggestions? Thanks

There is probably no connection between your symptoms and the move. Please consult a doctor.--Shantavira|^{feed me} 19:57, 3 December 2007 (UTC)

I would not entirely discount the effect of the move. If the move was to a new, drier climate, it could have such effects. Also, differences in the HVAC system could also affect the indoor humidity (for example, some furnaces have humidifiers, and others don't). -- Coneslayer 19:59, 3 December 2007 (UTC)

To add to what Coneslayer said - simple, inexpensive hygrometers exist which will measure the humidity in the air. Taking a reading would show if your environment falls outside the "normal" zone. A humidifier would help put that back into the normal humidity region. We can't say if that would help your chapped hands/lips/throat, as there may be an underlying medical condition behind it. To rule that out, you would need to see a doctor. -- 20:09, 3 December 2007 (UTC) —Preceding unsigned comment added by 128.104.112.21 (talk)

Yes, a new place is very likely to be less humid, and if so a humidifier will help. Since you might have a medical condition, we are required by our policy to recommend that you consult your doctor: Please do so, because there are all sorts of nasty thinks with thees symptoms. Furthermore, even if the problem is actually a humidity problem, the dryness may have caused a medical problem that will require treatment DO this even thoug you may end up getting advice from your doctor to install a humidifier. OK, If you decide to add a humidifier, do some quick research first. If your dwelling has forced-air heat, a plenum humidifier is a good choice, but if you live in a "hard-water" area, do not add a pulse humidifier, as it will generate what is effectively chalk dust. However, a plenum wick humidifier should be periodically cleaned to avoid nasty things growing in your air handler. -Arch dude 00:53, 4 December 2007 (UTC)

Products such as Chapstick or other lip balms can reduce the unpleasantness of chapped lips. Humidifiers of various sorts add moisture to the air. See also Consumer Reports for discussion of humidifiers. A forced air furnace humidifier may stop working for a variety of reasons, such as a blockage in the water supply tube or an electrical problem, or simply a turned off supply valve or a humidity control set too low. Cheap hygrometers may be more decorative than informative. Accurate ones such as art conservators or heating repairmen use are fairly expensive. A science buff can use dew point measurement combined with temperature measurement, or wetbulb/dry bulb measurement to determine relative humidity. I concur that the sudden onset of recurring thirst and other symptoms listed is better discussed with your doctor than with contributors to Wikipedia. Edison 02:56, 4 December 2007 (UTC)

If your old home used radiators, and your new home uses forced air heating, that would cause a major decrease in the humidity of the air you're exposed to. Unlike with radiators, forced air heating is known to produce often uncomfortably low humidity. I guess we're probably supposed to say "consult with a doctor" in this case, but to me, getting typical symptoms of exposure to low humidity at the exact same time as a move seems unlikely to just be a coincidence. Yes, humidifiers relieve the symptoms due to the low humidity caused by forced air heating. Getting the humidity back up to a more moderate level is also easier on any wood furniture like a piano that you may have. MrRedact 04:59, 4 December 2007 (UTC)

I'm very skeptical about the statement that forced-air heating produces lower humidity. The relative humidity is a function of the temperature and the absolute humidity. Presumably the selected temperature will be the same in either case and the heating process will not affect the absolute humidity, so why would there be a difference? --Anon, 05:11 UTC, December 4, 2007.

The difference is due to imbalances and leaky ducts in forced air systems causing negative air pressure in the house, which causes outside air to get sucked into the house.[10] Although the relative humidity of outside air in the winter is comparable to that in the summer, it has a low absolute humidity due to the cold temperature. When that outside air gets sucked into the house and then heated up, that results in a low relative humidity indoors. Radiators don't have that problem, because they don't affect the air pressure inside the house, and hence don't cause outside air to get sucked inside. MrRedact (talk) 23:42, 4 December 2007 (UTC)

"But only if they are improperly installed in leaky homes", says your link. Okay, that way it makes sense. Thanks. --Anon, 06:17 UTC, Dec. 5.

Also be careful with humidifiers. If you don't get it right they can cause condensation and destroy electronics and cause electrical fires.--Dacium 03:56, 4 December 2007 (UTC)

Warm air heating (along with many other types of mechanical ventilation systems) are often noted for causing dry air. This can be overcome by installing a humidifier, however a lot of systems were either designed without humidification equipment or had that equipment turned off or removed because of fears about leigonella bacteria which thrive in warm conditions where there is standing water. The risk of this can be eliminated by heating the water to above 60c or treating it with an antibacterial agent. A Steam Humidifier boils the water which effectively prevents any bacteria from breeding, however these solutions are all expensive and may not be applicable for your individual situation. 62.249.220.179 16:53, 4 December 2007 (UTC)

Assuming that you live in the Northern Hemisphere, the air might just be less humid everywhere due to colder temperatures. sh¤y 21:53, 4 December 2007 (UTC)

Sugar in Soft Drinks

Hello I was just wondering what would be the best chemical indicator for testing the amount of sugar in soda the result only needs to be a qualitative measurement i have thought of using Glucose oxidase, (the chemical used in glucose meters that changes color depending on the amount of glucose present.) or a isotope of Potassium. Any and all thoughts on this subject are welcome. thank you —Preceding unsigned comment added by 76.100.154.203 (talk) 20:28, 3 December 2007 (UTC)

Since soft drinks are mostly sugar and water and you only need a rough estimate ("qualitative"?), evaporating the water would show the amount of sugar. Icek 02:17, 4 December 2007 (UTC)

Sugar is both hygroscopic (adsorbs water) and polymerizes with heat (turns into caramel), so I'd guess that evaporation would be a very inaccurate way to determine sugar concentration. Delmlsfan 02:49, 4 December 2007 (UTC)

All advice which follows is anecdotal and should not be depended on if economic, safety, or health consequenses attend. Soft drinks sweetened with sugar are denser than soft drinks of the same manufacturer and flavor sweetened with Nutrasweet or other artificial sweeteners, in general. Thus density is a physical (sorry, you asked for chemical) measure of whether the pop is sugar or artificially sweetened. Freezing point is another physical measure: in my experience, artificially sweetened pop freezes at a higher temperature than similar sugar pop. Sugar pop is said (note the weasel words) to test higher with strips and meters used by diabetics for determining blood sugar. Strips useed for testing for sugar in urine are a closely related possibility for "qualitatitive" analysis of sugar in soda pop. Edison 02:44, 4 December 2007 (UTC)

To get around both of those problems, you could evaporate most of the liquid off, then treat it with strong sulfuric acid (we're talking the concentrated laboratory kind here), which converts carbohydrates to water and pure carbon. Let the carbon dry and take the mass, and you should be able to calculate the amount of sugar you had. (This is based on a fairly well-known chemistry demonstration.) sh¤y 21:56, 4 December 2007 (UTC)

One difficulty you would have is that soft drinks are usually sweetened with high-fructose corn syrup. Although partly glucose, there is also a large amount of fructose, which will be poorly oxidized by glucose oxidase (more properly an enzyme, rather than a "chemical"). Note that glucose oxidase, by itself, won't produce any sort of visible color. It produces hydrogen peroxide, a colorless chemical which can be detected by another enzyme (horseradish peroxidase) and a colorimetric reagent. To detect the fructose in addition to glucose, you can also add in a glucose-fructose isomerase, but the only one I'm aware of that might help is Glucose-6-phosphate isomerase, which requires fructose-6-phosphate, not just fructose. You would have to add in Fructokinase and ATP to the reaction mix as well. Also be aware that some soft drinks (particularly those made outside the US) contain sucrose (table sugar) as a sweetening agent, rather than HFCS. To use glucose oxidase on those, you would need to add Sucrase to the reaction to break the sucrose to glucose and fructose.

As an alternative, you can look for alternative sugar assays. Tollens' test, Benedict's test, Fehling's test, the Nelson-Somogyi assay, and the DNS assay are popular choices, but there are dozens in the scientific literature. These tests can detect both glucose and fructose without enzymatic conversion. One problem with these assays is that they tend to have different responses to the different sugars, so you would need to know the approximate ratio of glucose to fructose. Also, they tend to be unresponsive to non-reducing sugars, so they may not detect sucrose without prior hydrolysis.

Probably the best way to determine the sugar composition of an unknown sample is using chromatographic techniques like HPLC. They sell special columns specially designed for carbohydrate analysis [11].

Regarding the evaporation-then-weigh, note that carmelization tends not to happen until over 100 C, so if you heat gently, you may be able to drive off water, and avoid decomposition of the sugar. If you have access to a lyophilizer, that would work even better. Note that both glucose and fructose have the same molecular weight. - I'm not sure what you thought of doing with the potassium isotope, but I doubt that it would work. -- 21:44, 5 December 2007 (UTC)

list of various maps per country

I came across a list of all the countries of the world and it included many various types of maps. But, I lost the link and have looked and looked and cannot find it again. Does anyone know the link? —Preceding unsigned comment added by 66.136.99.246 (talk) 21:09, 3 December 2007 (UTC)

I don't know specifically which list you are referring to, but I bet it can be found in Lists of countries. Rockpocket 21:45, 3 December 2007 (UTC)

Perhaps you are referring to the CIA Factbook maps? (EhJJ) 22:30, 3 December 2007 (UTC)

For almost any kind of map, my first stop is the University of Texas' Perry-Castaneda collection at http://www.lib.utexas.edu/maps/ -SandyJax 19:13, 4 December 2007 (UTC)

There are a lot of map collections linked from our Map article. 152.16.59.190 (talk) 04:38, 6 December 2007 (UTC)

Salt Water Pool Levels

In a salt water pool it is typically 3,000ppm salt, which enables the chlorination to typically produce about 3ppm chlorine. As the salt level drops, the water conducts less and electricity does not flow across the cell as well and less chlorine is produced. Is this likely to be a linear or exponential decay? My pool has dropped to 0.5ppm chlorine, I was wondering if there is anyway to know the salt level? Would it be 500ppm? Or is there a salt level where conduction stops and there is a dramatic drop in the chlorine production, such that my salt may still be quite high, such as 2000ppm. We do not have a test kit for salt and don't have a shop within reasonable distance to take the water to for testing because we are in remote Australia. I can test for free chlorine, ph, akalinity. Is there any easy way to get figure out a salt level?--Dacium 22:27, 3 December 2007 (UTC)

is 3000ppm equivalent to 3 grams of salt per liter? If so and if you have the patience, you may be able to boil a liter of water and and then weigh the salt. This may require several steps of boiling in progressively smaller containers and carefully washing down the container walls with pure water to recover any salt that dries onto the walls. presumably you can zero out the empty weight of the final small container, so you need not actually scrape all the salt out of that last container. -Arch dude 00:39, 4 December 2007 (UTC)

I'm not much of an expert on this subject, but it seems to me like the chlorination cell is going bad. A pool will generally not decrease in salinity unless you are continually pumping in fresh water. In fact, salinity should go up due to evaporation. The chlorination cell (as I understand it from your question) will produce chlorine from the dissolved chloride ions in your pool, but the counterions (likely Na+) should remain. This would mean that you might see the pH of the water go up over time, which is arguably of greater immediate concern. 142.103.207.10 02:16, 4 December 2007 (UTC)

I am pretty sure then it is a problem with the cell like you said, particularly a bad wire that might not be making any contact. I can't figure out anyway how salt would disappear otherwise. The pool has been filled about 5 to 10% with rain water, but not enough that the salt level should be any less than 3,000ppm. I know it was 3,500ppm almost constantly for over a year without having to add any salt, and like you said the only problem I have ever had is the ph slowly goes up and I just add a little acid every weekend. It must be a dirty or dead cell.--Dacium 03:51, 4 December 2007 (UTC)

Well, if any water splashes or drains out of the pool that is not recirculated back in, and is replaced with fresh water, then you could lose salt that way. -- HiEv 04:36, 4 December 2007 (UTC)

The chlorine level however is a more than jsut a function of the generator and salinity. Temperature, sunlight and other chemicals are more likely culprits. Doesn't your chlorine generator tell you the current that is going through the cell? That is probably a good gauge of whether the salinity is correct. Also the generator may need to be cleaned. --DHeyward 07:26, 4 December 2007 (UTC)

Junk DNA

Seeing as most everybody's DNA (regular genes) are so similar is it the differences in our junk DNA which control when things get turned on (I can't remember the ACTG code for the on and off) and how much to be allowed, for instance how much height one person would grow how much to use of this gene or that gen to determine eye color? So would we basically all have the same genes/cells it is just the amount of the genes used that causes our variatioons. —Preceding unsigned comment added by 67.127.165.154 (talk) 22:33, 3 December 2007 (UTC)

Short answer is no. Quantitative traits are due to the different alleles for the various genes in a population. A small base subsitution may have a large difference in phenotype if it is a missense or nonesense mutation. Mutations in the regulatory sequences out side coding DNA can also have phenotype consequences (change gene expression) but these would never be regard as junk DNA. David D. (Talk) 22:46, 3 December 2007 (UTC)

To add to the above, the short answer is still no. However, there's still a lot we don't know about how genes are regulated. While known regulatory sequences wouldn't be considered "Junk DNA," that's not to say that we may find in the future that something we believed to be junk turns out to be important. I wouldn't be surprised if we learned one day that some of this "junk DNA" actually did play some role. What kind of role and how important it is remains to be seen. 142.103.207.10 02:06, 4 December 2007 (UTC)

I agree that some of the current junk DNA may well have important roles in regulation and potentially have non coding transcripts. When/If such discoveries are made will those specific sequences still be termed junk? I doubt it, so in a way the junk will always have no function, but we may see less junk in the future. David D. (Talk) 03:34, 4 December 2007 (UTC)

FYI, some noncoding/junk DNA is already known to have a purpose, like introns, for example. -- HiEv 04:48, 4 December 2007 (UTC)

It depends, many model organisms have quite small genomes, with equally small introns, are they classified as junk in those? Certainly there are some very large introns in humans so I could see some maybe most of those sequences, especially the repeats, being classified as junk, but it was known there were many regulatory sequences within the introns not to mention the sequences necessary for splicing. In general, I would not classify all intron sequences as junk and those who defined the term were specific in saying "without a function" because they were very aware that some of the intron sequences (and those between genes) were functional. So I'm not sure it is valid to consider introns enmasse as an example of junk DNA with a function. David D. (Talk) 04:54, 4 December 2007 (UTC)

Well, it kind of depends on your definition of "junk DNA". It was commonly believed that all noncoding DNA was unused at one point, thus was called "junk DNA". However, introns and other discoveries led them to discover that some of that "junk DNA" actually had functions, and other hypotheses have been made suggesting more possible uses for it. This is why many people are shifting to the term "noncoding DNA" instead, because calling it "junk" includes an inbuilt assumption of uselessness that isn't always correct. So, introns were considered "junk DNA" before people discovered that they had a purpose, and if you take a look at the junk DNA article you'll see that most sequences within introns are still considered "junk". -- HiEv 16:04, 5 December 2007 (UTC)

After go through the Wikipedia articles it sounded like the phenotype (aside from environment) were based on the genes or position on the chromosomes. If that is the case is the same gene like the one for hair and hair color in a different location for each person, won't be found in the same spot? AND is the on and off genes the same or in the junk genes cateogry?

No gene, even when "off", is in the junk category. On or off is related to development while some genes have no function in some cells all genes have a function in some cells of an organism. Junk is defined as having no function at all. Genes are in the same spot, but there are many flavors (alleles) of the same gene. The diferences you see are to the various flavours. David D. (Talk) 16:07, 4 December 2007 (UTC)

Proper interval locality theory

Yo, physicisterns, I stumbled across this (rather hastily thrown-together) site in the innertubules: [12]. After a precursory, half a cursory and three fifths of a postcursory examination, it seems like the guy is on to some pretty deep stuffs. Does anyone know:

• (1) if this is an entirely novel perspective on the various problems he purports to solve or demystify (entanglement, quantum gravity, etc.), and
• (2) if there might be any problems with the approach (of defining locality by null intervals in minkowski spacetime)

Your assistance is my subsistence, Rupert Barnswobble Sardinian, esq. 217.43.117.20 23:55, 3 December 2007 (UTC)

At a glance, it looks exactly like an introduction to quantum electrodynamics. I think that's the intention. It's certainly nothing new: electromagnetism and quantum mechanics have been jointly described since the 30s. Nothing of consequence is said about gravity, and QFT cannot support gravity anyway for fundamental reasons. SamuelRiv 00:32, 4 December 2007 (UTC)

I don't remember anything about minkowski spacetimes in Feynman's book on QED... Are you sure you didn't glance too glancingly? 217.43.117.20 01:46, 4 December 2007 (UTC)

Minkowski space is just flat space (equivalent to the Lorentz space of Maxwell's equations). They don't seem to change the curvature. Therefore there is no gravity (hence talking about special relativity instead of general relativity). SamuelRiv 08:29, 4 December 2007 (UTC)

According to proper interval locality the propagation of electromagnetism is facilitated by the signature of the space-time metric. Since the metric signature is common to both flat and curved space-time then the theory is valid in space-time as defined by both special and general relativity. I would suggest a glance is inadequate if you wish to understand proper interval locality, however here are some of the salient points.

1. The wave particle duality of matter results from the geometry associated with our inertial reference frames and is an inevitable consequence of the constancy of the speed of light relative to those frames.

2. The theory distinguishes between observable events that can be assigned precise and accurate locality relative to our inertial reference grids and quantum events that do not have exact locality relative to our inertial grids. (Where a quantum event is considered to be a point in the history of a quantum object relative to itself).

3. The metric associated with our inertial reference grids, precludes the possibility of quantum events being assigned a unique set of coordinates relative to our reference grids, instead quantum events are projected onto our reference as event surfaces.

4. The light cones illustrated in the website are quantum event surfaces. In free space the apex of the light cone is the proper interval locality of the quantum event.

5. Pairs of quantum objects are likely to interact if the apexes of their light cones are spatially close. (The likelihood of interaction falling off with the inverse of the square of the spatial separation)

6. Every point on the primary light cone is projected onto our reference grids as a secondary light cone. This mechanism results in an infinite succession of event surface projections that fill the whole of space-time. (It is this secondary quantum event surface projection that is responsible for the interference effects in experiments such a Young's double slit.)

7. In Aspect's experiment the quantum event surface associated with the cascade of the calcium atom intercepts the detectors at the moments the detections occur. The calcium atom relative to itself interacts with both detectors immediately and simultaneously, therefore, the result must be inherently correlated regardless of when the polarizers are set.

8. Proper interval locality is a self-consistent theory which is also wholly consistent with both relativity and quantum mechanics (That is the mathematics of quantum mechanics, clearly it deviates metaphysically in that it does not accept that light is required to be mediated by a particle.)User talk:WROBO 1 July 2008

December 4

Guppy

My guppy that i think is a female has a pointy think sticking out of its but lol and i know its not poop because its been there a long time what is it? thanks --Sivad4991 03:37, 4 December 2007 (UTC)

Can you describe this "pointy thing" with more detail? It would cut down on guessing and specious answers. 70.57.229.74 04:43, 4 December 2007 (UTC)

Have a look at this [13] page and see if it helps. Richard Avery 15:20, 4 December 2007 (UTC)

Processor Cooling

My heatsink has a fan on its right side, would it be beneficial to put a fan on the left side also (mounted onto the heatsink) or would it be better to put it on one of the other sides or top? Thanks —Preceding unsigned comment added by 76.167.132.90 (talk) 05:13, 4 December 2007 (UTC)

I would be most efficient if the airflow goes in the same direction, so put one on the other side with the same orientation as the original. However, are you sure that your processor need an extra fan? --antilived^{T | C | G} 09:47, 4 December 2007 (UTC)

Trying to overclock the processor as high as it goes, so I want to keep it as cool as possible without spending a lot of money on a cooling solution (like water cooling). Thanks for the reply —Preceding unsigned comment added by 71.106.34.15 (talk) 16:12, 6 December 2007 (UTC)

Little fishes

What kind of little fishes school at the surface of the water near the bank in a river in subtropical brackish water and appear to breath air? (At a distance of 10 feet or so this activity appears to be bubbles coming from the bottom.) Is this behavior because the water does not have enough oxygen or is this some type of social or other natural behavior of the fish? —Preceding unsigned comment added by 71.100.1.143 (talk) 05:31, 4 December 2007 (UTC)

Bubbles? Schooling in a single place? Sounds like they're spawning. SamuelRiv 08:27, 4 December 2007 (UTC)

Individual fishes remain separated by 4 to 6 inches. Stop at the slightest move I make although I'm a tremendous 20 feet away.

Many fish feed on insects at or just above the surface of the water. Shooting on along that thought, you might want to see our article about archerfish.

Atlant 14:08, 4 December 2007 (UTC)

They are not archering.

Some extra information would be helpful. How big are these 'little fishes', one or two centimetres? or smaller. Where, geographically, are you talking about? In the meanwhile, subtropical brackish water is likely to be low in oxygen if the water is warm. In these circumstances some species of fish do come to the surface to try and augment their blood oxygen level. This may account for the disturbance you have seen. Richard Avery 15:15, 4 December 2007 (UTC)

Lat. 27. Water Temp. 72 Air temp 82. They are 1 to 2 inches long.

A picture is worth a thousand words. Someguy1221 20:17, 4 December 2007 (UTC)

The wiki did not come to mind until I was home. I shall return to the spot when it warms up (has dropped to the low fourties over night) and take pictures galore.

one scientist's take on evolution

I just spent another useless hour googling for this: I remember once reading in an interview with some brain/intelligence researcher where he stated a piece of opinion that went something close to "The biggest evolutionary leap lies within mankind". He was talking about differences in intelligence and illustrating his opinion that the difference between the most gifted humans and averagely gifted humans is far greater than that between the average human and other primates. I have googled off my finger-tips several times over now, but I just can't seem to find it online who that researcher may have been? I dorftrottel I talk I 10:17, December 4, 2007

I remember hearing something about this on a science podcast once, maybe in relation to Artificial Intelligence (and the singularity) too in a Raymond Kurzweil kind of way, but it isn't him...I even tried to Google search your problem myself, as everyone tells me that I seem to be able to find out anything, but alas it is a real stumper! I will be interested to see if someone has the answer. Maybe when people in North America wake up. I keep thinking of James D. Watson! So sad. There was just that report in the news the other day about Chimpanzees beating college students at short-term memory tests too. Good luck! P.S. Not that people in North America are smarter, just that a majority of them read English and like to come to the the Wiki! Saudade7 13:02, 4 December 2007 (UTC)

Here's the short-term memory story. And an important note to that study was that the chimps were faster in their recall abilities, but no more accurate. So saying "they had better short-term memory" isn't precise enough to say exactly what the study concluded. And I highly doubt it was Watson. He usually just makes controversial claims about race and intelligence.--droptone 13:28, 4 December 2007 (UTC)

The chimps were faster at entering their responses - but no more accurate. That could be that the humans were being overly cautious or something. What was impressive was further down that article where they started to reduce the amount of time for which the numbers were flashed onto the screen. At four tenths of a second, the chimps were still doing quite well when the humans were failing utterly. That might mean that their visual system is more acute. I don't think these tests show anything about intelligence. SteveBaker 13:34, 4 December 2007 (UTC)

Just to say that I was just kind of throwing out ideas...I didn't read that chimp story very carefully, I just read the headline and skimmed. And I don't actually think that Watson said it, I was just saying that it made me think of him given his recent public comments when I was in London. I'm sorry if what I said sounded purposefully misleading or wrong. I really hope you find out. Take care. Saudade7 19:37, 4 December 2007 (UTC)

The BBC TV news showed some video of the chimps performing - DAMN! - they were fast! It was quite utterly amazing that such a complex task could be done that fast. They started off teaching the chimps the numbers 1..9 and scattering the numbers at random across a computer screen. The game was for the chimp to use a touch-screen to touch the numbers in ascending order (as each one is touched, it disappears). Then they'd flash the numbers up - for some amount of time - then write white squares over where the numbers had been. The game is the same, touch the white squares in the order of the (now concealed) numbers. Finally, they'd leave out some of the numbers - so you might have 1,2,4,6,7,8 and 9. That's quite a hard task when you only see the numbers up there for less than half a second. It was easy to see that the chimps were both faster (MUCH faster) and more accurate than the humans. (What's more, they were doing this for treats - and the chimp was casually eating with one hand and playing the game with the other!) But I'm still not convinced that this is a demonstration of intelligence - dexterity and 'photographic' memory - yes, but IQ, no. I could easily program a dumb old robot arm with a webcam to beat both chimps and humans...and such a machine would have no intelligence whatever. SteveBaker (talk) 01:55, 5 December 2007 (UTC)

I don't think it was supposed to be about IQ (nebulous as that is), what was supposed to be amazing was that Chimps outperformed humans in an area of cognition (is this the word I want or is it too specific? 'using their brains' is what I mean) and that this could happen was pretty dismissable until now. After all, you can program a computer to calculate arithmetic considerably faster than chimps and humans, but it would still be amazing if young chimps were faster and more accurate at arithmetic than humans. Skittle (talk) 09:57, 5 December 2007 (UTC)

Yeah - I agree. I think it would be surprising if there weren't quite a few mental skills that Chimps have that can beat us. I'm just dubious about attaching this "intelligence" tag to what they do. After all, what they are doing isn't so different than (say) dogs doing scent tracking - but we don't put that down to intelligence because it's clearly sensory and motor skills...well, so was the chimp test. SteveBaker (talk) 04:39, 6 December 2007 (UTC)

Thanks for the replies, will keep looking then. ¶ dorftrottel ¶ talk ¶ 07:48, December 5, 2007

Iranian nuclear video

In reports about Iran's nuclear program, the TV news often shows a clip where there's some sort of large ductwork on a floor with a gap where you can see an orange flame moving right-to-left. What is that apparatus doing? --Milkbreath 12:03, 4 December 2007 (UTC)

Can you find a link to a video on YouTube or YahooNews or something that shows this object? Saudade7 13:11, 4 December 2007 (UTC)

I found one on BBC World News, but it's not a direct link. You have to go here and click on "Pictures from inside an Iranian nuclear facility". The apparatus appears at 35 seconds in. --Milkbreath 14:54, 4 December 2007 (UTC)

Here's an attempt at a direct link:

mms://a113.v373744.c37374.g.vm.akamaistream.net/7/113/37374/1.0/clipdownloads.bbc.co.uk/realmedia/news/media/avdb/news/world/video/134000/nb/134442_16x9_nb.wmv

Thanks goes to Firefox plugin UnPlug. How do I make it an ordinary link, btw? —Bromskloss 15:40, 4 December 2007 (UTC)

I don't think you can make a direct link with something that doesn't start with "http://" etc. - this link has to have another program open to view it. It is kooky but it worked! I don't know what that thing is however. Good luck. Saudade7 19:32, 4 December 2007 (UTC)

They are using gas centrifuge technologies for doing the separation of the necessary isotopes. One assumes that this entails vaporizing the uranium and keeping it gaseous as it passes through successive enrichment stages. The boiling point of Uranium is around 4100 degrees C. So I guess that could easily be one of the centrifuge heaters...but who knows? Maybe the factory just gets kinda chilly in the winter? SteveBaker 15:54, 4 December 2007 (UTC)

I don't think so: The gas centrifugation is done with uranium hexafluoride which has a boiling point lower than water. 193.171.121.30 19:05, 4 December 2007 (UTC)

Emotional music

I'm trying to understand why most people have such a strong emotional response to film music (the kind you get in blockbusters and Disney movies). Why do we loose control of our emotions when hearing overwhelming violins and a few timbals? Not sparing myself for scientific experimentation, I rented a Hans Zimmer CD and I'm getting the expanding lungs, tingely heart thing as I type this so the film is not needed for the music to work. Why is it so effective? Keria 15:26, 4 December 2007 (UTC) and I have to add insistant wind instruments to the list.

In the case of music-for-film, it's easy to explain. Human memories are stored 'holistically' - we don't remember things the way a computer does by tucking one memory away in a little box with a label on it. Instead we remember by connecting every little bit of information with every other little bit. This makes it impossible to hear the music without (possibly subconsciously) recalling the movie it was attached to. This is sometimes very annoying...but it's how our brains work. Consequently, I cannot listen to the "Dance of the Sugar Plum Fairy" without thinking of chocolate with nuts and raisins in it because the tune was used for a particularly memorable series of UK television adverts a few decades ago. So I presume, the music is evoking the memory of (and emotions relating to) the movie. SteveBaker 15:47, 4 December 2007 (UTC)

By "film music" I only meant the type of music. I guess you could call it a certain type of classical music (the only example I can think of would be Carmina Burana). In the example of Zimmer, I haven't seen any of the films yet the music as a strong emotional impact. I'm pretty sure, for example, that it increases my heart rate, which feels like it's being crushed yet is all tingely at the same time; eyes go moist etc. This doesn't happen with most music. I can be excited and appreciate a good rock record but it hasn't the same direct emotional impact (maybe I'm wrong in calling it emotional). I guess this might happen with martial music too. Keria 15:59, 4 December 2007 (UTC)

This is a phenomenon that a lot of composers use, not just Hollywood composers. It is created by playing a chord of three notes (a triad), and then playing some other chords and notes that are dissonant to the original chord (called the root). This dissonance creates an uncomfortable feeling among the listeners. Eventually the composer then inserts a chord that will resolve or complete the root chord. This resolving chord may be a fifth or a seventh usually. This resolution to the dissonance creates a feeling of satisfaction and even euphoria for the listeners. For a more complete explanation of this, look at the wiki article called Seventh chord, with special attention to the section entitled "Dominant seventh". Saukkomies 16:09, 4 December 2007 (UTC)

It's not necessarily the music per se. You can listen to the same music on CD, radio or in a concert hall and not be affected by it to the same degree, or at all (although you might). It's the combination of the on-screen action with exactly the right music at exactly the right moment, that does the trick. This is not a new idea; for centuries, composers have been commissioned to write incidental music to plays (such as Grieg's music for Ibsen's Peer Gynt, Bizet's music for Alphonse Daudet's L'Arlésienne, Mendelssohn's music for A Midsummer Night's Dream, and hundreds of other examples). Stage managers cottoned on very early in the piece to the fact that audiences had a greater emotional reaction to the play when music appeared at judicious intervals to counterpoint the action; which would encourage patrons to come back and back, ie. put bums on seats. And of course, it's the entire basis of opera and modern day musicals, and try to imagine Swan Lake with dancing but no music. This doesn't help explain why it's so effective, but to show the idea has been around a lot longer than the movies. -- JackofOz (talk) 22:52, 4 December 2007 (UTC)

Level of inflammation determines speed of healing process?

Hi. Generally speaking, as an exercise question only. Suppose someone has a sprained foot. The body's natural healing process is to make the tissue surrounding the injury site inflamed. Thats called Inflammation. So, the patient takes Ibuprofen, a non-steroidal anti-inflammation drug. As I understand it, the body's purpose in making inflammation is to generate the replacement of injured tissue. The inflammation triggers this process, right? So, suppose patient A does take ibuprofen, and patient B doesn't (assuming the same kind of injury) I would imagine patient A will take longer to heal than patient B. Because patient A's inflammation will be less, and so the molecular replacement mechanism will be less intense, and stretch out over a longer period of time. Patient B will experience more pain, the inflammation will be more, but the injury will heal faster, because the repair signals are stronger. Right?

Thanks! —Preceding unsigned comment added by InverseSubstance (talk • contribs) 17:01, 4 December 2007 (UTC)

As noted at Inflammation#Inflammatory_disorders, not all inflammation is beneficial. Whether inflammation will help or hinder healing in any particular case is a medical question which should be directed to your doctor. The reference desk does not give medical advice. Dragons flight 19:47, 4 December 2007 (UTC)

There have actually been a number of studies on this, like this one, which found no significant increase in post-operative recovery with increasing dosages of anti-inflammatory drugs. Of course, these studies were operating only on approved dosage levels. Someguy1221 20:06, 4 December 2007 (UTC)

compass needle

what is the meaning of the phrase "needle point north to south" although a needle has two ends, how would we know which end is towards north and which is towards south?193.251.135.124 17:12, 4 December 2007 (UTC)

By convention, compasses are constructed such that the end that points north is marked in some way, often by being painted red. MrRedact 17:37, 4 December 2007 (UTC)

If I had to guess, I suspect that compasses were invented by people who lived in the Northern hemisphere and who didn't know that the South Pole even existed. For them, it pointed toward the North Pole - the back end pointed towards nothing in particular. SteveBaker 21:17, 4 December 2007 (UTC)

The compass was available well before most people had a concept of a globe in mind, and so it is doubtful whether those people even concieved of a "Pole" at all. I suspect there was a time when it was seen more as "one end points towards the cold lands and the other end points at the hot lands", at least in the early times. Dragons flight (talk) 21:25, 4 December 2007 (UTC)

For what it's worth, the compass was invented around 1000 and reached Europe around 1300. The idea of a Spherical Earth goes back to ancient times. More info on the general topic at History of navigation. The page on Christopher Columbus puts it, "the Earth had generally been believed to be spherical since the 4th century BCE by most scholars and almost all navigators". Pfly (talk) 21:59, 4 December 2007 (UTC)

Indeed. It's in our article, but in the interest of it becoming more widely known: Columbus' great idea was not that the world was round. His great idea was that the world was significantly smaller than it was then thought to be, and that he could thus sail all the way to Asia by going west. In this he was entirely mistaken, and was saved from mid-ocean starvation by running into the New World. Algebraist 22:26, 4 December 2007 (UTC)

{fact} Known certainly. Widely known and accepted by most scholars? I'd question the reality of that during the say the 12th century. Pre-renaissance there was a lot of old wisdom that wasn't exactly well known. Dragons flight (talk) 23:21, 4 December 2007 (UTC)

I too thought that statement was probably going too far -- but in a hurry I used it anyway -- the basic idea I was aiming for was that as the use of the compass spread through Europe, circa 1300-1400 or so, the people most likely to find them useful and practical would be navigators of the open seas (perhaps a rare breed at the time), who would probably already be familiar with celestrial navigation and methods of determining location that presumed a spherical planet. Just a minor tangent to the OP's question. Also, it amazes me that exploration voyages such as the Norse to Greenland and North America were done without the aid of compasses, relying on dead reckoning, measurements of latitude, and celestrial navigation. In any case, it may be difficult to determine how widespread the idea of a spherical Earth was in the late Middle Ages. The people most likely to make practical use the concept, sailors and navigators, tended to leave very little written record back then. Another grey area is in the three centuries between the compass's invention in China and its introduction to Europe. I know very little about what the Chinese and Muslim sailors of the Indian Ocean thought about the sphericity of the world -- though Medieval Muslim scholars were world's ahead, so to speak, than their European contemporaries on such things. But if we're talking about Europe, we're looking more at the 1300s and 1400s, by which time I think even among scholars -- at least scholars who cared to swell upon such topics -- the sphericity was becoming well established. Still I agree the statement on the Columbus fact was rather sweeping. Pfly (talk) 03:43, 5 December 2007 (UTC)

See Flat Earth. The early Christians were (as ever) dubious scholars, and no-one knows what the common people thought, but a recent study of medieval concepts of the sphericity of the Earth noted that "since the eighth century, no cosmographer worthy of note has called into question the sphericity of the Earth." And don't forget that the Polynesians achieved far greater (and much earlier) navigational feats than the Norse. Algebraist 16:55, 5 December 2007 (UTC)

ammonia

why ammonia is a gas even though it has three polar bonds? 122.163.139.129 19:12, 4 December 2007 (UTC)

One reason (or at least a devil's-advocate for your idea) is that the bond dipoles somewhat cancel each other, making the molecule as a whole less polar than "lots of N–H bonds" would suggest. DMacks 19:40, 4 December 2007 (UTC)

(ec) The polar bonding between ammonia is not nearly as strong as between water molecules. Firstly, oxygen is a much more electronegative than nitrogen, so the bonds are much more polar. Secondly, a water molecule has two lone pairs and two partially positively charged hydrogen atoms, whereas an ammonia molecule has one lone pair and three such hydrogens. Now, consider that a hydrogen bond can only be made between a lone pair on a partially negative atom (such as oxygen or nitrogen in these molecules), and a partially positive hydrogen. Since water has two pairs and two hydrogens, each water molecule can hydrogen bond to four other water molecules, and form a very strong nearly continuous lattice. (Indeed, at room temperature a water molecule is bonded to 3.6 other water molecules, on average.) An ammonia molecule can also make four hydrogen bonds, but the average over a large group cannot be four, as they contain disproportionately many hydrogen atoms to lone pairs. At best, a volume of pure ammonia could have each molecule make only one two hydrogen bonds. Combine this with that afformentioned weaker polarity, and the cohesive force holding ammonia molecules together is much weaker than in water. Someguy1221 19:42, 4 December 2007 (UTC)

The ammonia molecule is also closer to planar than a water molecule, which weakens its polarity further, thus weakening simple dipole-dipole interactions. I'll spare you the quantum mechanical reasoning for this. Someguy1221 19:47, 4 December 2007 (UTC)

Uhh, if I remember correctly, isn't ammonia sometimes a liquid? I remember, when we did experiments at my school, the ammonia was in the form of a liquid, at room temperature. Thanks. ~AH1^(TCU) 23:02, 4 December 2007 (UTC)

It can be liquid if stored at low temperatures and/or high pressures. It can also be dissolved in solution (ammonia is quite soluble in water), or dissolved as ammonium salts. It is also a product of many common chemical reactions. Someguy1221 (talk) 23:08, 4 December 2007 (UTC)

The "liquid ammonia" you used at school was almost certainly a solution of ammonia in water. You'll probably recall that the stuff smelled pretty strongly — that was the ammonia gas gradually evaporating out of the solution. —Ilmari Karonen (talk) 01:15, 8 December 2007 (UTC)

Gasoline-methanol blends?

From methanol:

The use of methanol as a motor fuel received attention during the oil crises of the 1970s due to its availability and low cost. ... As a result of its low price, some gasoline marketers over-blended.

How inexpensive can methanol be? How much would a gas station profit from over-blending? I mean, methanol has to be synthesized from simple organic molecules. The prices of these materials would also rise during an oil crisis because they are also fuels. Chemical synthesis adds to the costs of methanol. How could an over-blender profit from over-blending? If methanol is so cheap and abundant, why don't big companies build methanol burners to power their big factories? -- Toytoy 19:50, 4 December 2007 (UTC)

As of 2002 it cost 50 cents a gallon. However, this is the cost at very low levels of production (relative to global oil consumption). Someguy1221 19:56, 4 December 2007 (UTC)

The subsections on "production" and "automotive fuel" may also be enlightening. Methanol is not (primarily) derived from crude oil, and so its price isn't really tied to the 1970s oil crises. Over-blending builds the profit margin by substituting additional cheap materials for expensive ones. The section on "automotive fuel" (among other places in the article) notes that methanol is corrosive, damaging both metal parts and rubber seals. I'd think this a major reason that methanol burners aren't in vogue, and Someguy's note about production level's impact on cost is worth noting, too. Methanol may not be economically feasible if scaled up to crude oil demand levels.

As for profits, I'll pull numbers out of a hat for example purposes. I'll use $3/gal gasoline and $1/gal methanol. Pure gas costs $3/gal. The gas station decides that no one will notice their little "this gas contains methanol" sticker and substitutes 5% methanol without adjusting the sale price. They're now charging $3/gal for what's only worth $2.90/gal, pocketing the extra 10 cents on every gallon. Unscrupulous Gas Station X then decided to overblend to 10% methanol, charging $3/gal for $2.80/gal product. UGSX can even drop their sale price below the regular blenders (to, say, $2.95/gal) and still haul in a higher profit margin -- at the expense of their customers' engines. — Lomn 20:08, 4 December 2007 (UTC)

I wasn't aware of methanol as a gasoline additive, but we do have an article on Methanol_fuel. If it's like ethanol, my understanding of it being bad for engines is that this is merely a myth. You'll still find plenty of old timers who're convinced it's harmful to the engine, but I don't think this is really true today, if it ever was. Friday (talk) 21:21, 4 December 2007 (UTC)

Methanol/ethanol are solvents the designers of 1970's and 1960's engines did not plan for, and in a vehicle of mine, the blended alcohol destroyed the plastic float in the carburetor. Myth? I don't think so. Edison (talk) 22:47, 4 December 2007 (UTC)

Ethanol most certainly does destroy some OLD engines. It has three properties that are bad:

1. It dissolves rubber. So any car older than about 25 years that still has it's original rubber seals in the fuel path is in trouble. Even 10% ethanol ("E10") is enough to do this - and I can tell you that the classic car club I run has seen a MASSIVE increase in problems with various rubber seals since E10 was introduced into Texas. Retrofitting with modern seals fixes the problem - but for those who absolutely must keep their cars completely original, this is a major blow.
2. Ethanol conducts electricity - gasoline doesn't. At 10% (E10) it doesn't seem to be a problem - but it's anticipated that if/when we go to E20 or E25 in a few years time, then some gas gauge 'sender units' will misread or fail completely - as will some electric fuel pumps that are cooled by the gasoline. Again - not a problem for modern cars - bad news for classics and clunkers.
3. The combustion by products of high-ethanol mixtures are pretty acidic and will attack non-synthetic engine oil. So switch to synthetic and your problems are over - except that a very few old cars (of which my '62 Mini is one) use engine oil to lubricate the gearbox and synthetic oils aren't so good at that job. How big a problem that will be - I have no clue.

So yeah - it's mostly not a big deal - but the dissolving of rubber seals is absolutely real - and I have the rotted out 2 year-old seals to prove it.

I haven't heard of polythene parts in carb floats being destroyed yet - and I'm inclined to think this is a myth - but since my Mini has one - I'm going to keep a close eye on it! The '62 Mini has a float chamber that regulates the flow into the carb with a plastic float. If it jams in one direction, the engine is starved of fuel and stops. If it jams in the other direction the gasoline is over-pressurised and squirts out of an overflow hole in the float chamber - landing on all sorts of hot engine parts...it's quite exciting really!

SteveBaker (talk) 01:38, 5 December 2007 (UTC)

For anyone interested in ethanol-petrol blends, there's been a lot of hype and controversy about this recently with the recent launch of a 10% blend combined with the governments plans to mandate the introductions of such blends. New Zealand has a large number of used import cars, largely from Japan (which is rather late to the ethanol blend 'party' and isn't going to require all new cars to be compatible with E10 until 2010 and I think doesn't have much or any use of ethanol blends at the moment [14]) and the average age of the vehicle fleet is something like 12 years. Most imports are not carried out by the manufacturers so there are complicated liabity and COI (it's obviously in the manufacturers interest to claim most imports are unsuitable) issues etc. In any case, most manufacturers are reluctant to certify many of their imported cars as being suitable for anything greater then E3 (3% ethanol) while the government wants E5 and E10 and believes many vehicles should be fine. Some links which may be of interest [15], [16] & [17], [18], [19], [20] & [21] Nil Einne (talk) 11:05, 5 December 2007 (UTC)

Is it safe to say that gasoline blends with 10% methanol OR ethanol are not harmful to modern cars? Friday (talk) 15:26, 5 December 2007 (UTC)

I would say that 10% ethanol is OK for any car made in the last 20 years. Given the potential liability issues, it's hard to imagine how E10 could be sold in the USA if that were not the case. Here in Texas, ALL gasoline is E10 these days. But Nil Einne's evidence says otherwise. 'Harmful' is a tough word to use here...if E10 were to cause your oil seals to degrade after (say) 200,000 miles - is that "harmful"? I have less confidence with saying that is the case for Methanol. Switching to sythetic motor oil (which is a good idea anyway) is a wise thing to do - but it doesn't seem to be 100% necessary. It'll be a few years before we know for sure. SteveBaker (talk) 04:34, 6 December 2007 (UTC)

telescope type

Hi. I saw a telescope in the glass display case facing outside a store window. I want to know what type of telescope it is: refractor, reflector, or catadioptric. Sorry, I don't have an image, but if you want I might be able to upload one taken earlier. This telescope is about 4 inches in objective diameter, although the tube is about half an inch thick. It seems to have an objective lens, although it is about a centimetre behind the front of the telescope. The eyepiece is at the back of the tube, but sticks out of the tube vertically, sort of like in a Newtonian, further in front than the back of the telescope, but at the back. The finder seems to be a red-dot or reflex, but I'm not sure. It is computer-controlled, and has no counterweight. It's a Celestron. I estimate the focal length at f/5, but I'm not sure. I'm usually sort of a telescope "expert", but now this one confuses me. This is why:

refractor characteristics

• objective lens
• eyepiece at the back of telescope
• relatively small total size

reflector characteristics

• eyepiece jutting perpendicular from main tube
• relatively short focal length
• in-tube mirror may be needed to place the eyepiece there

So, any ideas to what type it might be? About how much would it cost if it were new and regular price? Thanks. ~AH1^(TCU) 22:57, 4 December 2007.

The people at the store ought to at least know what model number is written on the thing, if not the detailed specification. If you can't go back there and ask them, why not telephone them and ask? --Anonymous, 23:10 UTC, December 4, 2007. (UTC)

Possibly a Maksutov-Cassegrain or similar design? They are relatively short for their aperture. (Because the light path is folded, the real focal ratio is slower than the length would suggest, i.e. slower than the f/5 you estimate.) -- Coneslayer (talk) 00:36, 5 December 2007 (UTC)

It is probably a four inch Matsukov or Schmidt-Cassegrain. Those are about 300-400 dollars. You should go to the Celetron website and look up the pictures Website or on the Meade site. Saudade7 00:49, 5 December 2007 (UTC)

To tell what sort it is, look at the front of the scope. If there's a plain sheet of glass, it's a reflector. If there's a round object supported by a sheet of glass, it's a catadioptric of some sort. If there's a round or rectangular object supported by one or more wires, it's a reflector. --Carnildo (talk) 01:11, 5 December 2007 (UTC)

I think it's their 4" Maksutov-Cassegrain (NexStar 4SE). The eyepiece and prism looks like it's built into the rear plate which hides the actual path out the center of the rear mirror. It's actually an f/13 scope. --DHeyward (talk) 17:56, 5 December 2007 (UTC)

Hi. Uhh, how could you try to find out what is is if you don't know what it looks like? First of all, the telescope actually isn't for sale, and it's more of a used items store than a telescope or department store. Well, I only know the telescope by looking at the images, and there is a lens visible but even when photographed head-on, it's hard to see anything other than the lens. I don't think it is a NexStar 4SE, for many reasons. First, the telescope tube is much closer to the mount than that. Second, the eyepiece doesn't just look close to the tube, the hole for the eyepiece atcually juts perpendicularly through the top of the tube, closer to the back than the front. Also, It was impossible to see someting that resembled that white circle in the centre of the lens, as only the front lens was visible at all when the telescope was photographed head-on. If you want, I could probably upload a photo sometime later today. Oh, and the photo might suit the article for Celestron, Telescope, and the one for whatever classification it is. Thanks. ~AH1^(TCU) 18:36, 5 December 2007 (UTC)

Hi. I uploaded the image so hopefully you might be able to tell what type it is.

Here's the image! There's a lens at the front. If you look closely the eyepiece juts from the tube.

Thanks. ~AH1^(TCU) 23:23, 5 December 2007 (UTC)

Okay, look at the end of the tube nearest the camera and you'll see a brand name: it appears to be NexStar. Look on the Celestron website and you'll see that they have two NexStar lines. The telescope in the photo looks very similar to the NexStar 114 SLT or the slightly larger NexStar 130 SLT. Presumably the telescope in the window is an older model that was replaced by one of these; of course the differences might be enough to significantly affect the price.

I note also that the telescope in the window is pointed the wrong way! That's the mirror end nearest the camera. --Anonymous, 00:14 UTC, December 6, 2007.

Hi. Um, the end nearest the camera actually has a hole, and a lens behind it. I know it's hard to see on this image, but my other images show that there is glass at the end of the tube closest to the camera. I can't see where it says NexStar, and I know that if it were a reflector, the end nearest the camera would be closed, but actually that end has glass, and you could see to the other end of the telescope if you looked at it head-on. Thanks. ~AH1^(TCU) 01:05, 6 December 2007 (UTC)

The lettering is at the top of the tube, above the double wavy line. As to the construction, obviously I haven't seen the actual thing, but that looks like a mirror mount, and the layout looks reversed compared to the images on the Celestron site and I cited. --Anon, 01:55 UTC, Dec. 6.

Hi. Actually, nevermind. I checked the Celestron's site using the Internet Archive's wayback machine. The telescope seems to be a model from about 5 years ago, a NexStar 114. The new telescope doesn't really look like this, but the NexStar 114 from back then looks almost identical, although I can't tell if it's a GT or an HC. The new version sells for over $450, but the old one was probably cheaper, although I can't tell because the old version didn't have its price listed. Well, thank you all for helping me solve this mystery. Thanks. ~AH1^(TCU) 00:22, 7 December 2007 (UTC)

Mystery Vegetable

I bought some interesting produce from a stall outside a little shop, and I've worked out what everything was except for one root vegetable (my favourite was realising that the weird knobbly black things were chestnuts with complete outers). This root vegetable is white and about 30 cm long, 10 cm in diameter (with little tapering until the very end where it has a root which was not included in the measurements I gave). When cut it smelled like radish, and when nibbled it tasted like radish and had the same texture. I assume it's in the same family as radish, possibly it's just called 'giant white radish'?

Anyway, does anyone have any idea what this vegetable is? Thanks. Skittle (talk) 23:09, 4 December 2007 (UTC)

Could it be a Daikon? --TeaDrinker (talk) 23:13, 4 December 2007 (UTC)

Fantastic! (The introduction actually uses the phrase giant white radish :P If I hadn't thought I was suggesting something ridiculous, I could have searched the phrase) Hooray! Thanks TeaDrinker. Now, to learn! Skittle (talk) 00:18, 5 December 2007 (UTC)

Redirects are cheap. Giant white radish.  ;-) Dragons flight (talk) 00:23, 5 December 2007 (UTC)

Yes, but alas, the poor mangel-wurtzel has to make do with beet.... - Nunh-huh 00:28, 5 December 2007 (UTC)

Maybe you mean a Mangelwurzel? DuncanHill (talk) 01:25, 5 December 2007 (UTC)

No, I meant mangel-wurzel, the spelling which actually appears in my dictionary. Unfortunately a "t" got caught up in it. It's nice to know we have an article on my favorite strange vegetable, but it would be nicer if the redirect went from the wrong spelling to the correct one, rather than vice versa. :) - Nunh-huh 01:49, 5 December 2007 (UTC)

Those chestnuts did not have "complete" outers. When the chestnut falls off of the tree, it has a prickly husk about the size of a baseball ( about 100mm in diameter.) This husk is so prickly that you must be quite careful when you pick it up from the ground. The husk contains several of the covered nuts that you found in the market. You should use those nuts immediately instead of keeping them. roast them or boil them, or eat them raw. They may (and probably do) have insect eggs that will hatch into larvae that become evident if you keep them for more than about two weeks. This is not a health problem, but it is an aesthetic issue. take a look at this:

those nuts came from several of those prickly things. When they are still green the husks can be picked up carefully with your bare hands. They turn brown after about three days. At that point you will need either some good garden gloves or a high pain tolerance. -Arch dude (talk) 01:38, 5 December 2007 (UTC)

Whenever I see discussion of chestnuts, and eating them, I feel inclined to remind American readers that the tree and nut commonly called "chestnut" in the US is actually Aesculus hippocastanum, "horse-chestnut" or "buckeye", and can make you sick if eaten. I for one believed for years that the "chestnuts" we collected as kids were the same things one could "roast over an open fire". Essentially all the American Chestnut trees were killed by the Chestnut blight of the early 20th century. Just a friendly word of warning. Pfly (talk) 04:01, 5 December 2007 (UTC)

Yes, do not under any circumstances eat a buckeye. My comments were with respect to the Chinese chestnut which is now grown in many places in the United States. I have personally encountered trees planted in about 1945 in Tennessee and in about 1960 in Virginia. if you encounter a "chestnut" in the wild in North America, do not eat it. -Arch dude (talk) 02:25, 6 December 2007 (UTC)

I've actually been puzzling over this. When I said 'complete outers' I meant it; the shiny brown things were inside a shrivelled black layer, but the shrivelled black layer contained only one of them. I'm now wondering if they were water chestnuts, but I don't have much experience with water chestnuts except in certain take-away meals. I tend to think of water chestnuts as having a different texture and flavour, but perhaps that is only in the preparation? I boiled these and they tasted like chestnuts and had the same texture as roast chestnuts. Skittle (talk) 09:42, 5 December 2007 (UTC)

How can this thread POSSIBLY be complete without mention of the noble 'Conker'?!

British schoolboys have been using horse chestnuts (aka conkers) to play the game of Conkers since time immemorial. There is something wonderful about opening that shrivelled spikey green/brown husk and finding a beautiful, shiney smooth conker inside. Conkers were played obsessively when I was a kid in the 1960's. Truly great conkers (six'ers and better) were traded and competed in exactly the way the Pokemon cards are - the difference being that you could find your conkers lying in the street. Truly great, legendary twenty'er conkers were practically worshipped. People would give their lunch money just to be allowed some practice swings with such heroic nuts. The dozens of arcane and mysterious techniques for hardening conkers were passed on from father to son, from elder brother to younger. Debate over which techniques were fair - which acceptable - which worked and which didn't would consume all of our waking hours! The string could be improvised from a shoelace in an emergency - but the perfect, softest sting and the exact way to knot it was another subject for endless debate. People perfected their swings, complete with follow-through - with the verve of pro-golfers. SteveBaker (talk) 04:23, 6 December 2007 (UTC)

Um, I'd rather you'd passed on any experience you had of water chestnuts and chestnuts, how they are different from a culinary point of view and whether what I bought more closely resembles one or the other. I was not buying conkers. Skittle (talk) 18:55, 6 December 2007 (UTC)

Good, it would be immoral to buy conkers, totally contrary to the spirit of the game. DuncanHill (talk) 01:20, 8 December 2007 (UTC)

December 5

Company

What is the worlds largest company?thanks --Sivad4991 (talk) 00:14, 5 December 2007 (UTC)

Exxon Mobil is the largest by revenue, PetroChina is the largest by market capitalization. MrRedact (talk) 00:28, 5 December 2007 (UTC)

Walmart by revenue (among public companies) and by number of employees. Dragons flight (talk) 00:28, 5 December 2007 (UTC)

• This page says it's Exxon this year, with Wal-Mart at #2. I believe Wal-Mart is usually #1, but the oil biz is having a great time lately. I find the distribution of industries in the top ten interesting/depressing:

1. OIL: Exxon Mobil
2. Wal-Mart
3. OIL: Royal Dutch Shell
4. OIL: BP
5. CARS: General Motors
6. OIL: Chevron
7. CARS: DaimlerChrysler
8. CARS: Toyota Motor
9. CARS: Ford Motor
10. OIL: ConocoPhillips

--Sean 14:03, 5 December 2007 (UTC)

What's so interesting and or depressing about it? I would fully expect the top companies to be those with scalable advantage and wide appeal. Since car mfg, retail, and energy fall nicely into those two categories, it's natural that they top the list. What would be depressing is if the list were topped by Halliburton... --Jmeden2000 (talk) 17:32, 5 December 2007 (UTC)

Dear Sean, I too thought that the list you provided was self-evidently depressing. Our planet is (and we are) doomed! Saudade7 23:25, 5 December 2007 (UTC)

downhill,luge weight balance

i have a heated battle going on with a friend of mine on how to make our street luges faster.I,being slightly smarter than him had the idea of using physics to my advantage.I was wondering what would be the optimum center of gravity point. i was thinking about a 70-30 ration with the 70 being towords the nose. or maybe a 80-20? —Preceding unsigned comment added by 67.8.167.136 (talk) 00:25, 5 December 2007 (UTC)

If you're trying to reduce friction, I don't think the weight distribution would matter much. The resistant force of rolling friction is proportional to the normal force, so the total rolling friction is going to be pretty much the same, regardless of how the weight is distributed. Stability considerations would probably outweigh any slight difference in rolling friction. And off the top of my head, I can't think of any other reason why a change in weight distribution would affect your speed. Certainly the force of gravity is the same regardless of where you are on the luge. Why do you think putting more of the weight toward the nose will make the luge faster? MrRedact (talk) 00:42, 5 December 2007 (UTC)

because of those little wooden race cars that i made in the boy scouts that went down a sloping track and when i put more weight in the front it went faster. —Preceding unsigned comment added by Gotnse (talk • contribs) 21:13, 5 December 2007 (UTC)

Conventional wisdom is to put the weight as far back as possible, so the weight will stay on the sloped part of the track for a fraction of a second longer. --Carnildo (talk) 22:49, 5 December 2007 (UTC)

I thought the reason was to grab additional gravitational potential energy by starting off with the weight being higher up the track so the heaviest part of the car falls a greater vertical distance. But for a street luge this doesn't seem terribly relevent since the shape of the track is unknown. Some of the other techniques used by Pinewood derby cars might be relevent. But in the end, I can't imagine that anything other than reducing the friction of the wheel bearings would have much effect. SteveBaker (talk) 04:01, 6 December 2007 (UTC)

Those are the same idea. While a car with its weight in rear and a car with its weight forward are both on the slope, each's center of mass will fall the same distance over time. When the cars hit the flats is when you notice that the one with its weight in rear is still accelerating. That is, it had more GPE to convert to KE. — gogobera (talk) 08:06, 6 December 2007 (UTC)

Grab a heavy dumbell, and go do a couple of runs! Of course, you'll want to do several with the weight in each position, so you can average your results to reduce your uncertainty. My guess, for the record, is in consensus with the above: it shouldn't matter where the center of mass is. — gogobera (talk) 07:04, 6 December 2007 (UTC)

In fact, if you've had a course in physics (mechanics), you can draw up a simplified cart with wheels and a center of mass between them. You'll find that the normal force on the front wheel is proportional to (1-l/L), where L is the distance between the wheels and l is the distance from the front wheel to the center of mass. The normal force on the rear wheel is proportional to (l/L). Therefore, the frictional force, f, which is the sum of the frictional forces on the two wheels, doesn't change with respect to where the center of mass is. That is, (1 - l/L + l/L) = 1. If your two axels are the same, that is. I'd concentrate on reducing friction (good lubricant?) and drag (streamlined profile).

If the course levels out at some point before the end, placing the CM as far to the rear as possible (as high above that level point) might let you squeeze out a couple more meters/sec. — gogobera (talk) 08:06, 6 December 2007 (UTC)

I get very nervous about applying the standard "laws" of friction in these kinds of practical situation - the real-world situation rarely matches the "high-school" friction law that says that the frictional force is proportional to the mass and that's all. We had a thread about this a while back and I ended up going to a lot of trouble to show skeptics that this 'law' is only an approximation of the truth (and in many cases, a TERRIBLE approximation).

So if (to pick a purely hypothetical example) you had soft rubber tyres on these things - then changing the weight over the wheel alters how much the tyre deforms under the weight - and the continual flexing and unflexing of the tyre as it rotates eats energy and slows you down (this is one reason why you get worse gas mileage in your car with under-inflated tyres). If that were the case here (and this is only an example) - then moving the weight to the center of the luge might eliminate the flexing (a net win) - or distribute it more equally so that more tyres flex (making matters worse). If this 'flexional' loss were not a linear function of the weight over the wheel, there could very well be a reason to move the weight for or aft. Now, I may well be completely wrong - since probably street-luges use hard nylon wheels - but all sorts of parts of the luge might flex like that - you may have much more complex things going on than we can easily imagine. That's not to say that I know the answer - only that an over-simplistic treatment of the problem may produce seriously incorrect conclusions. I think our OP needs to do some controlled tests. SteveBaker (talk) 18:26, 6 December 2007 (UTC)

The factors that I remember being decisive from my days in the Cub Scouts: 1) Lubricate axles. 2) Streamline the shape. 3) Even more than the above, make sure the axles are perfectly straight & perpendicular to the direction of travel. Anything else will have the wheels dragging against the ends of the axle. Of course, I'm not sure how much of the above is applicable to downhill luge. jeffjon (talk) 14:56, 6 December 2007 (UTC)

Cold Chills

I have been trying to start the page for Cold Chills Does anyone know why we get chills when we listen to music that affects us deeply or when we have certain thoughts? Thanks,--DatDoo (talk) 02:06, 5 December 2007 (UTC)

We already have a shiver page; we probably don't need one for cold chills. We certainly don't want one called "Cold Chills", because that's incorrectly capitalized. - Nunh-huh 04:01, 5 December 2007 (UTC)

My bad brah...I wasn't really sure how to CAPTALIZE it. do you know how to change??? The shivers page has no info on getting chills from music or inspiration or anything like that.--DatDoo (talk) 04:26, 5 December 2007 (UTC)

The solution would be to add that information to that page, not start another page! Yes, Cold Chills could easily be moved to cold chills, or if you want, I'll delete it at your request and you can add any information you want to shiver. - Nunh-huh 04:30, 5 December 2007 (UTC)

I think the OP is not talking about the medical condition but about what the German Romantics (poets, philosophers, biologists etc.) called the "Heilige Schauer" or "Holy Shiver". I wonder if we already have a page on it...Nope - so it is free for you to build/write! Immanuel Kant, Johann Gottfried Herder, Friedrich Schiller, Johann Gottlieb Fichte, Friedrich Wilhelm Joseph Schelling, Johann Wolfgang von Goethe, Wilhelm von Humboldt, even Georg Wilhelm Friedrich Hegel all wrote things but you will probably need to read some German. Good luck. (By the way, if you Google it, the first hit where the guy is relating it to only courage in battle and sports...he's wrong. It's more subtle that that. It's about the Sublime). Saudade7 23:45, 5 December 2007 (UTC)

The OP isn't describing the reflex response of shivering which "is a bodily function in response to early hypothermia in warm-blooded animals". DatDoo is instead referring to that emotionally triggered response which also results in goose bumps but without the cold stuff. hydnjo talk 05:20, 6 December 2007 (UTC) addendum: Accordingly, the cold chill article has been started to address this difference. hydnjo talk 05:29, 6 December 2007 (UTC)

Poorly Defined Triple/Critical Points?

I have seen a number of examples on wikipedia and even in journals of triple points given as "triple point temperature" as in Tetrafluoromethane. What use is this without the pressure of the triple point? Shniken1 (talk) 03:47, 5 December 2007 (UTC)

...left as an exercise to the reader? ;-) Someguy1221 (talk) 04:21, 5 December 2007 (UTC)

Unconscious sleep?

Are we unconscious when we are asleep? —Preceding unsigned comment added by Cockysht (talk • contribs) 11:38, 5 December 2007 (UTC)

Is there any reason why Unconsciousness which is a link from Unconscious doesn't help? Seems pretty straightforward to me... Nil Einne (talk) 12:22, 5 December 2007 (UTC)

I'd have to say no. They're two different things. To be unconscious means that you can't be roused. --Milkbreath (talk) 12:31, 5 December 2007 (UTC)

Not necessarily. A person who faints is unconscious but can usually be aroused pretty quickly. Being asleep (which sometimes happens involuntarily, like when watching TV) and being unconscious for other reasons (eg. fainting) are two different ways of being non-conscious. -- JackofOz (talk) 13:41, 5 December 2007 (UTC)

(after e/c) I'd have to say yes. You are not conscious when asleep so.... But (like so many questions) it's probably just a question of definition. The OED doesn't say anything about "can't be roused" for "unconscious", indeed it defines sleep as "The unconscious state or condition regularly and naturally assumed by man and animals, during which the activity of the nervous system is almost or entirely suspended". But the OED is not a medical dictionary, which would no doubt be much more specific.--Shantavira|^{feed me} 13:44, 5 December 2007 (UTC)

"Unconsciousness" / "being unconscious" is a physical state e.g. being in a coma. The "Unconscious", on the otherhand, is an area of one's psyche that is not directly accessible to thought or introspection...e.g. in Freud's psychoanalytical theories. One is physiological; the other is psychical. (Which is not to say that Freud and I aren't materialists). Saudade7 23:57, 5 December 2007 (UTC)

Yes because we are 'not knowing' (the meaning of unconscious)--TreeSmiler (talk) 02:23, 6 December 2007 (UTC)

Ah, but do you not know, or do you just not remember? Hard to be sure. I'm fairly certain there have been times I have been asleep, but still able to think and be aware that I'm thinking (not dreaming), and even remember what I was thinking about when awakened shortly afterwards. --Trovatore (talk) 02:27, 6 December 2007 (UTC)

You are not aware of the outside world: therefore you are 'unconscious'--TreeSmiler (talk) 02:29, 6 December 2007 (UTC)

That's a rather restrictive interpretation. If you're aware of anything, external or not, that constitutes consciousness, in the sense that we're most interested in (for example, in the question of whether a machine can be conscious, we don't really care whether the machine's perceptions correspond to any external reality, but only whether the machine has perceptions of any sort). Anyway I strongly suspect that's what the original poster was asking: Are we aware while sleeping? --Trovatore (talk) 02:35, 6 December 2007 (UTC)

I quote from our article:

Consciousness is a characteristic of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment. It is a subject of much research in philosophy of mind, psychology, neuroscience, and cognitive science.--TreeSmiler (talk) 02:42, 6 December 2007 (UTC)

Do you disagree with this definition?

Note that it's not, strictly speaking, a definition; it tells you something about consciousness, but does not precisely demarcate what is and what is not consciousness. Nevertheless, it's pretty accurate -- it's a list of a bunch of things that can be called consciousness. It doesn't imply that they all have to be present for a state of mind to be considered conscious -- any one of them is sufficient. --Trovatore (talk) 02:46, 6 December 2007 (UTC)

Is DNA unique to Earth?

What the arguments (or evidence if it exists), for and against the idea that extra-terrestrial life will be made up of DNA os we know it? Do we expect some variance, or a completely new system of life? What are the scientific implications of being able to interact with life not made up of DNA? Fenton Bailey (talk) 12:54, 5 December 2007 (UTC)

Today, no one can say for sure. If the panspermia theory is true, DNA arrived here from "out there" already in operational condition, so we may eventually find DNA other places as well. If DNA evolved here on earth, it may still exist in other places if it is a "pretty-good" encoding scheme (as it seems to be); in this situation, it (or something very much like it) may have independently evolved on other life-bearing planets as well. It's also possible life elsewhere evolved other, completely-different coding schemes for their equivalent of a genome that doesn't involve anything like a four-base double helix. For example, if we are eventually replaced on this planet by self-replicating artificial intelligences, they are unlikely to use DNA as a storage medium.

Atlant (talk) 13:21, 5 December 2007 (UTC)

I am afraid this calls for speculation. In anycase would the basic building blocks / storage of alien life even have any greater impact when it came down to interaction or communiction? You require sapience for communication anyway, as for interaction it very much depends on exactly what you intend to interact with. It is a very open set of questions with very speculative answers. Lanfear's Bane | t 13:23, 5 December 2007 (UTC)

• It would be interesting to know if anyone has developed a theoretical genome encoding not based on DNA or RNA (which works, chemically). Such an alternative would answer the question of whether DNA/RNA are the only way to do it. The fact that all the diverse life on Earth is DNA/RNA-based makes me wonder whether it's unique in some way. --Sean 13:49, 5 December 2007 (UTC)

There have been theories about using proteins for storing information.--Stone (talk) 13:58, 5 December 2007 (UTC)

Looking back on the history of mankind the most important consequence of an alternative biochemistry of aliens would be that you can't eat them! Humans are only able to do a limited set of transformations in organic molecules and therfore digestion and reusing the molecules of aliens will not work. Bacteria are by far more capable and the would recycle the organic molecules.--Stone (talk) 13:56, 5 December 2007 (UTC)

We have no good reason to expect that extra-terrestrial life will be based on DNA. Jack Cohen and Ian Stewart warn against this sort of restrictive and unimaginative thinking in their book Evolving the Alien. We don't even have a good reason to expect that extra-terrestrial life will be made of matter. However, there is a point beyond which extra-terrestrial life-forms may be so "alien" that we cannot meaningfully interact with them or even recognise them as living beings at all. Gandalf61 (talk) 16:23, 5 December 2007 (UTC)

Keep in mind that even if aliens do have DNA, it may be in a different form than is commonly found on Earth. See DNA#Alternative double-helical structures for other ways DNA can be structured other than the familiar double-helix. Also, some organic molecules tend to be left- or right-handed for life formed on Earth. For example, sugars tend to be right-handed, and proteins and amino acids tend to be left-handed. But alien life may have the opposite handedness for some or all of those things, which could make it hard for us to get nutrition from each other's foods. See Chirality (chemistry)#Chirality in biology. So, even if the aliens have DNA, they may still be rather unlike us in other details.

But, regarding your main question, it wouldn't surprise me at all if advanced aliens had transfered their minds from organic brains into mechanical/electronic devices. It would allow them to survive without aging and they could "sleep" during the long interstellar voyages to other worlds. As for interacting with them, well, it might take some time, but some form of communication should be possible, though we may never totally understand each other. -- HiEv 18:47, 5 December 2007 (UTC)

It's also interesting that adenine, a precursor to the nucleoside adenosine, is found all over the solar system and is feasibly created in widespread interstellar dust clouds. It's cool to learn that the buidling blocks of known life can be found well outside planet Earth... — Scientizzle 21:34, 5 December 2007 (UTC)

There are several reasons for suspecting alien life to be chemically similar to life on Earth, and it mostly revolves around what is easiest to do, chemically. Amino acids, nucleic acids, and other simple organic molecules are "easy" to make in many anoxic environments, and some have even been found naturally in space. Further, any presently plausible life form has to compartmentalize itself to confine chemicals inside or outside, and in Eukaryotes, in different intracellular compartments as well. The "easy" way to do this is with water and an amphipathic lipid. This can be done outside of water, but not with anything that's remotely likely to form in an Earthlike environment. So with all of this, it's not to say that alien life is necessarily similar, or even that it's likely to be, but rather that on the conditions of planet earth, our current almost certainly the easiest way for life as we know it to happen. Someguy1221 (talk) 19:05, 5 December 2007 (UTC)

• I recommend this recent article in Scientific American. In addition to chirality (noted above), and changes in amino acids (which could be done with DNA, just not the sort of DNA that we have), this is the proposal that I find the most intriguing: arsenic instead of phosphorus. The result would be stunningly similar to DNA, except that the creatures would find phosphorus to be just as poisonous as we find arsenic. --M@rēino 19:21, 5 December 2007 (UTC)

Taxonomy

Is there a classification of animals and plants strictly according to the chemicals and the amounts their body can produce? —Preceding unsigned comment added by 71.100.1.143 (talk) 14:13, 5 December 2007 (UTC)

I'm not aware of such. It may not be a very useful way to classify- down at the molecular level, a lot of what's going on inside you, and inside, say, corn, is the same. Friday (talk) 16:05, 5 December 2007 (UTC)

On the other hand it may render relationships such a predator and prey more obvious.

It would be too hard to classify like that too. How could we classify dinosaurs with this system? Our classification system is based on common ancestry, which provides insight to how the animals evolved, and how recent a common ancestor existed between two or more living beings. 64.236.121.129 (talk) 18:22, 5 December 2007 (UTC)

Certainly to hard for manual classification. Automated techniques on the other hand such as Optimal classification need only a list of entities and their chemicals.

Junk DNA Part 2

I was wondering if the what's referred to as junk DNA could be the coding for genes that we carry but do not express? Could they be for example some of the genes that your great grandmother maybe had green eyes or your grandfather was really good in math and science, but these traits were not expressed in you, however, they are carried and could be expressed in your child? —Preceding unsigned comment added by 68.120.83.149 (talk) 15:22, 5 December 2007 (UTC)

Yes and no. So-called Junk DNA is not usually in a form which translates to protein. DNA which codes for a protein has three base pair combinations called codons which code for specific amino acids (which combine in folded chains to form protein). So while much of the junk DNA used to code for something, mutations have accumulated in it so it no longer works (in the sense there are no recognizable codons anymore). The term "junk" however should not be taken to mean it is useless. There is also some reason to think the non-coding sections alter the expression of genes. Other hypotheses have suggested it acts as spacers or buffers to add robustness to mutation. There is more extensive discussion on the junk DNA article. --TeaDrinker (talk) 17:43, 5 December 2007 (UTC)

Might I ask a question to the answer; with such variation in sheer size between DNA between different species, how does Evolution treat and discuss this? 81.93.102.185 (talk) 18:15, 5 December 2007 (UTC)

Four paragraph discussion in an online book, with some references. Some interesting articles: Cell size as a link between noncoding DNA and metabolic rate scaling, Economy, speed and size matter: evolutionary forces driving nuclear genome miniaturization and expansion.
--JWSchmidt (talk) 19:53, 5 December 2007 (UTC)

Do you mean the article Evolution, or the field of evolution? Assuming you mean the latter, there are various theories based in evolution regarding the existence and utility of junk/noncoding DNA (see those articles for many of them.) It is also known that birds, for example, tend to have less noncoding DNA than most mammals and reptiles. For example, chickens have about as many genes as humans, however the human genome is nearly three times the size of the chicken genome (see here). It was thought that evolutionary pressure is stronger on birds to lose any unimportant noncoding DNA because evolution strongly favors lighter designs for flight, but more recent research suggests that the reduction in genome size may have happened during dinosaur evolution because smaller genomes meant smaller cells and an elevated metabolism. See JWSchmidt's comment above and Dinosaurs provide clues about the shrunken genomes of birds". It could be that a smaller genome in dinosaurs created the possibility of bird evolution. Also, as the article notes, non-flying birds today have more noncoding DNA than flying birds, so having more noncoding DNA probably has benefits too (as I mentioned above). Does that answer your question? -- HiEv 20:07, 5 December 2007 (UTC)

Human eye size

I have studies many people's faces, including my own, and one eye is always bigger than the other. In certain people this feature is more visible than in others. I want to know what causes this irregularity or asymmetry. I know that when I was little, I used to lay on my side while watching TV. Obviously this would have an effect on what eye the body considers more important, and then would adjust its size or position? Also, could it be that if you see closely the whole time (like reading, computer, etc.), the one eye might go back into the cage, and the other might become more pop-eyed? And that if you see far the whole time (like on farms or the countryside) that your eyes might be more equal in size? Just like a binoculars? Please tell me a) what you think subjectively about this, b) what scientific research was done about this and what science says about this, and c) what you think objectively about this (ie give your unbiased opinion based on the facts). — Adriaan (T★C) 15:38, 5 December 2007 (UTC)

If you are concerned about buphthalmos, please seek professional medical advice. As for body symmetry, human bodies are not normally symmetrical. There are many studies that have shown better symmetry is linked to attractiveness. That implies that a lack of symmetry is common. -- kainaw™ 16:00, 5 December 2007 (UTC)

An interesting exercise that is very easy for those with Photoshop or equivalent is to take a photo of oneself (or anyone) where the subject is looking straight at the camera, and to create 2 faces: one with the left half mirrored, and one with the right half mirrored. The hair can be cropped or masked so it looks like the normal hairdo. The two faces often look like utterly different people. Edison (talk) 20:26, 5 December 2007 (UTC)

This is also the reason people find photos of themselves to be such terrible likenesses (NOBODY thinks their drivers license photo looks like them). We are used to seeing ourselves in the mirror - but that produces an image that's flipped left/right compared to a photograph. Just as mirroring a face renders it less recognisable - failing to mirror it when you're used to seeing it mirrored is also every-so-slightly "wrong".

Many years ago, before there were PC's, I was writing a paint program for television studios and we had a very early colour document scanner. We had great fun stealing photographs of people's families from their offices, scanning them and very-subtly "damaging" them to make the people look every so slightly wrong. Since we had no colour printers back then, we had to use a hideously expensive gadget we had for taking large-format polaroid photos of a special CRT - but we could then re-insert the 'damaged' versions back into their frames. The trick was to 'damage' them just enough so they didn't look quite like the real person - but not so much that their owner could tell what we'd done. Mirroring the face was one trick we discovered - and moving one eye or one ear just a tiny fraction away from it's original position such as to make the faces just a little bit less symmetrical. Rotating the nose just a few degrees clockwise or anticlockwise, repositioning the hair out a quarter inch further down to create a 'low-brow' forehead also has a dramatic effect. Since the technology to scan, edit and print photos was unheard of back then, none of the victims could quite believe what had happened. Anyway - you can do very subtle things to a human face and make it wildly ugly or completely unrecognisable...it's another one of those ways in which humans see things in a manner that is completely unexpected.

SteveBaker (talk) 20:57, 5 December 2007 (UTC)

Interestingly, there has been some genuine peer-reviewed research into the effect of facial and body symmetry – or asymmetry – on perceived health and attractiveness. A number of researchers have found evidence that we find more symmetric faces more attractive. Our article on symmetry (physical attractiveness) has a number of interesting links. TenOfAllTrades(talk) 21:57, 5 December 2007 (UTC)

Something odd I saw on Discovery Channel

I'm hoping somebody can refresh my memory on this. I saw something on the Discovery Channel about 6 years ago about somebody working at Princeton who conducted this odd study where he placed analogue random number generator devices around various parts of the world that reported their histograms on an hourly basis; and he found that whenever there were catastrophic world events (such as 9/11), the histograms indicated that the random number generators were not being as equiprobable as you would expect from a random number generator. I think the point of the study was to investigate the claim that human moods could alter technology. It struck me as rather "out there", but since it was a peer-reviewable, falsifiable study that anyone could reproduce, I don't think it was unscientific per se. Anyway, I hope someone can refresh my memory as to the details; all I remember is that it was conducted by someone at Princeton. Is there an entire community of people who study this phenomenon in a scientific approach? --75.165.55.66 (talk) 16:57, 5 December 2007 (UTC)

Sounds like Global Consciousness Project. -- Finlay McWalter | Talk 17:00, 5 December 2007 (UTC)

Maybe this is it. (Actually, Princeton Engineering Anomalies Research Lab.) --Milkbreath (talk) 17:09, 5 December 2007 (UTC)

Not to be confused with the (interesting but fictitious) Hundredth Monkey Effect.--Shantavira|^{feed me} 18:08, 5 December 2007 (UTC)

If it's true - and if it can be reliably demonstrated then it's a little surprising that they haven't claimed their million dollars yet. SteveBaker (talk) 20:41, 5 December 2007 (UTC)

The Princeton Engineering Anomalies Research (PEAR) lab and the Global Consciousness Project (GCP) are actually somewhat related, though the PEAR lab has since shut down. Also, there are many criticisms of the methodology used, questions about some of the results, and attempts to reproduce some of the results have had a tendency to fail. While the research is interesting, and has claimed some results, the overall results have generally been overstated in the media and public discussions. The PEAR researchers have been offered the James Randi Educational Foundation $1 million prize if they could reproduce their results twice under controlled conditions (as SteveBaker mentioned above), and they have repeatedly refused to even attempt it (see here for example). All of this makes me doubt the results they have claimed.

Regarding the GCP, they claim that "global consciousness" somehow affects their randomly generated numbers, but instead it looks to me like they are cherry picking their data. For example, during the 2004 Indian Ocean earthquake that caused tsunami damage in 20 countries and cost over 200,000 lives, the CGP didn't show any significant difference (see the mean composite of all eggs graph here). In their own analysis of the event (seen here) they show almost nothing during that time of statistical significance (which they show as the blue line with "P=0.05" (5%) on their graphs; note also the arbitrary selection of where they start and end showing data, which affects significance). The only graph on that page that shows a significant change on the day of and following the quake is the final one, but that is merely a chart of the number of hits on their website. However, with things like this, it's usually the case that the hits are remembered and the misses are forgotten, which makes the evidence seem stronger than it really is. -- HiEv 21:03, 5 December 2007 (UTC)

Yes, I heard these guys (The Princeton Engineering Anomalies Research (PEAR) lab and the Global Consciousness Project (GCP)) on a few old Art Bell shows maybe a year or two ago (while I was doing dishes - always a good crazy show to clean house to); I think you'd have to subscribe to their show-downloads (like 6 bucks a month) on Coast to Coast but then you could download all 8-12 hours of the interviews. I am pretty sure they were on with Art and not the new guy George Noory who, as an interviewer, is a tad too fluffy, ADHD, and religious for my tastes. Saudade7 00:10, 6 December 2007 (UTC)

The existance of the Randi's $1 million prize is a great way to debunk a wide range of paranormal claims. Few people can come up with a believable reason to turn down a million dollars for a couple of day's work - and an underfunded college research group certainly cannot. So as long as the prize is still on offer, we may be reasonably confident that not one of these paranormal claims can be trusted. People who refuse to even try the test must not only be unable to demonstrate their effect - but also KNOW that they can't...nobody turns down a million dollars. SteveBaker (talk) 03:45, 6 December 2007 (UTC)

Buddha did :D -Shniken1 (talk) 04:06, 6 December 2007 (UTC)

Well, the issue with the Randi challenge (and the reason I guess he's so sure he'll never pay it off) is that as soon as something is provable and repeatable, it's not 'paranormal' in any real sense anymore. Personally, I agree with Randi that self-professed psychics and healers, etc. are either charlatans or deluded individuals, but anyone looking for the million bucks should accept the fact that they're just not going to "beat the system", because the system always moves. It reminds me of an essay by Bertrand Russell where he mentions that the reason many philosophers seem so weird and nonsensical is because as soon as something is proved empirically it becomes science and if it is proved theoretically it becomes mathematics. All that can be left has to be a little wacky. Matt Deres (talk) 18:16, 7 December 2007 (UTC)

December 6

F-35 questions

Looking at the recently released information of the F-35 engine failure in May, is it possible to install a ram air turbine on the F-35? Also, why is there no trainer version? And why no two-seat version? --Blue387 (talk) 01:10, 6 December 2007 (UTC)

You would probably do better asking over at the F-35 talk page, but if I was to guess I would say "weight concerns". Astronaut (talk) 01:59, 6 December 2007 (UTC)

I would actually say the science desk is the better place to ask, as it's much more heavily trafficked than most talk pages. Someguy1221 (talk) 04:06, 6 December 2007 (UTC)

Agreed. Talk pages are for discussing the article, not the topic of the article. -- HiEv 12:11, 6 December 2007 (UTC)

I don't think it's weight. They could quite easily take out a few hundred pounds of fuel to compensate - you don't need long range capability for training missions. No - the real reason is that it costs a lot of money to design, build and certify a two-seat version of a plane that's intended to be single-seat-only in actual mission usage. They might only ever make a dozen of the two seat version - which means there is no economy of scale. In the past, there was little choice in the matter since you had to have some way to teach people to fly the darned thing. On the F22 program, they planned some two seat varients - but cut them from the program to save money. For both the F22 and F35, it was decided that flight simulator technology was sufficiently good that pilots could go straight from other aircraft types (F16, F18) for which two-seat variants exist to flying solo in an F35 - with only simulator time used for the transition. Since they need good simulators anyway - it's much cheaper to do that than to design and build two-seaters that are effectively useless for actual missions. I was the lead graphics engineer for the F22 and F35 simulators - and it was quite a proud moment to understand the that simulators have attained to become so well accepted by the military. Incidentally, civil airlines are routinely allowed to have pilots transition from one aircraft type to another using "zero flight time training" (ie simulation) - and they've been doing that for at least 20 years. So the pilot on your next flight could easily be on his first ever trip in that kind of an aircraft! SteveBaker (talk) 03:30, 6 December 2007 (UTC)

I believe it's possible to get a complete type rating from simulator time alone. In a recent "Flying" magazine article, one of the regular contributors (a surgeon by trade) who only flies a twin engine Beechcraft, received his Boeing 737 type rating without leaving the ground. (Type ratings are all that is required for turbine and airplanes greater than 12,500 lbs beyond the "Airplane, multi-engine, land" rating. So to go from a twin engine, six seat, propeller Beechraft to a 4 engine boeing 747 is a type rating. No airline would let you fly it, but you can get the legal ability to do it and all you need is sim time). --DHeyward (talk) 04:14, 6 December 2007 (UTC)

Yes - from a multi-engine rating, I think it's possible. It's been a long time since I last did civilian simulation - but that's a much easier job than simulating a modern fighter. The fidelity of even a 20 year old 737 simulator is really close to 100% and training on a simulator is so much cheaper and safer than flying a real plane that flight hours logged in a sim are actually more valuable than on the actual aircraft. In the simulator you can toss up fault conditions, singly and in combination, fly at night and in fog, you can bring in other aircraft on converging or colliding courses and practice at airports from all around the world without going there...all manner of things that you can't possibly do in a real plane. SteveBaker (talk) 04:55, 6 December 2007 (UTC)

No two seat version, because that's what the F-22 is for. The F-35 is a smaller, STOVL version of the F-22 essentially. The F-35 is a smaller, navy fighter, while the F-22 is a larger airforce fighter. 64.236.121.129 (talk) 14:32, 6 December 2007 (UTC)

But there isn't a two seat version of the F22 either - that was to have been the F22B but it was cancelled in 1996 or so (probably when they saw how good our simulator was!) SteveBaker (talk) 18:08, 6 December 2007 (UTC)

Actually, the F-35 is a multi-service fighter (with distinct Air Force, Marine, and Navy versions) intended to fill a role separate from that of the F-22. For the Air Force, the F-35 fills a role akin to that of the F-16, while the Navy and Marines will use it to replace F-18s (though not the E/F Super Hornets). Only the Marine variant has STOVL capability. — Lomn 15:48, 6 December 2007 (UTC)

Anyway, not having seen a discussion of the RAT specifically, here's what I've dug up: The F-35 uses an IPP, or Integrated Power Package for auxiliary and emergency power, which seems to negate the need for a RAT. The article linked notes that the F-35 is moving towards "more-electrical" components like this one to save weight, improve reliability, and improve packing efficiency (that is, you don't have to put it where it can deploy into the airstream). I haven't run across the details of the May engine failure, though, so I can't offer much as to the specific implications for that incident. — Lomn 16:04, 6 December 2007 (UTC)

atomic number

how do they know how many protons are in an atom? How did Mendeleev know the atomic masses of the elements in his periodic table?70.171.229.76 (talk) 03:00, 6 December 2007 (UTC)

They have little teeny eyes

For seeing little teeny things

Like you need little teeny license plates for bees

With apologies to whoever it was that Larry Niven copied it from. --Trovatore (talk) 02:54, 6 December 2007 (UTC)

...oh, by the way, it actually is a good question, and I don't know the answer off the top of my head. It just made me think of the song. --Trovatore (talk) 03:03, 6 December 2007 (UTC)

The number of protons has to equal the number of electrons in an electrically neutral atom. So the question is really "how do they know how many electrons there are in an atom". Sadly, I don't know the answer to that either - but I bet it's a lot easier to answer! SteveBaker (talk) 03:05, 6 December 2007 (UTC)

Mass is easy. They used scales! They do a titration or something to know how much stuff there is and then weigh it. That mass divided by number molecules is the mass of the molecule. The number of protons would have been determined first ionising the atoms completely and finding their mass/charge ratio in a mass spectrometer Shniken1 (talk) 03:35, 6 December 2007 (UTC)

The periodic table was invented before the concept of an electron as a discrete particle. They didn't have mass spec or the ability to fully ionize heavy atoms. The original periodic table was based on shared chemical properties and increasing mass, not number of protons. For example, unreactive gases (e.g. noble gases) formed one column. They did have a rudimentary concept of valence based on how chemicals combined, so they could place alkali metals and halogens in their columns, etc. But the largest determining factor in the overall ordering of the original table was mass. Dragons flight (talk) 05:12, 6 December 2007 (UTC)

My point is that you can't use mass alone because you can't tell the difference between the mass of a proton and a neutron with any degree of precision. So if they had been using mass alone, they wouldn't have been able to tell the difference between (say) Pb²⁰⁵ and Tl²⁰⁵ (that's a bad example because lead-205 is very rare - I'm sure there are better examples) - and they'd have been unable to set things out neatly using mass alone. You need to look at how the elements react together to get an idea for valences - which in turn relates to the number of electrons/protons. However, you can almost guess where each element belongs in the table by examining it's properties - metals on the right, non-metals on the left. Reactivity rates increasing across the rows, similar chemistry down the columns... that's the kind of thing that would let you know if you had two elements in the wrong order...not mass. SteveBaker (talk) 17:57, 6 December 2007 (UTC)

Perhaps a better example would be tellurium and iodine, which have atomic masses 127.6 and 126.9, respectively. Sorting by mass puts them in the wrong order (compared to atomic number) due to a high natural abundance of the heavier tellurium isotopes, and indeed I believe they were originally switched on early attempts at periodic tables. However, examining their chemistry clearly shows that iodine is a halogen and belongs in group 7. --Bob Mellish (talk) 19:07, 6 December 2007 (UTC)

Mendeleev would have had no notion of isotopes or anyway to get elements in any masses other than the naturally occuring mixture. Natural masses gives you the right ordering for all but 3 naturally occuring elements. His insight was actually to arrange groups and predict gaps where elements hadn't been discovered based on chemical properties, but figuring out the overall ordering is easy on the basis of mass alone. Dragons flight (talk) 19:03, 6 December 2007 (UTC)

According the Wikipedia's article on Dmitri Mendeleev, he created the table from known atomic masses and properties (discovered by other scientists). In fact, his table was capable of predicting the masses of not yet discovered elements. You can read more about Mendeleev's Periodic Table. (EhJJ) 03:46, 6 December 2007 (UTC)

By shooting electrons onto a sample of the element in question, one obtains x-rays. The spectrum of these x-rays is composed of a continuous portion (bremsstrahlung) and characteristic lines. By measuring the characteristic lines the effective nuclear charge can be determined (the charge affecting the innermost (1s) electrons, generating energy levels similar as in the hydrogen atom, but at higher energies). The effective nuclear charge is approximately Z-1, where Z is the number of protons (and if this is not accurate enough, neighboring elements in the periodic system have always an effective nuclear charge differing by approximately 1, so you can make the measurements for many elements until you have a complete series up to the element in question). Icek (talk) 05:07, 6 December 2007 (UTC)

Another method is using the Geiger-Marsden experiment: The number of deflected particles from a "monochromatic" (all particles have got the same energy) alpha source is proportional to the nuclear charge if everything else (like the thickness of the foil in atomic layers) is equal. Icek (talk) 05:20, 6 December 2007 (UTC)

To determine relative atomic masses you make careful measurements of the relative masses of different elements as they participate in a range of different chemical reactions, then you apply the law of multiple proportions (that's not a great WP article, because it reads like a chunk from a textbook, but it does illustrate the law with various numerical examples). Chemists like John Dalton were determining relative atomic masses at the beginning of the 19th century, many years before anyone even postulated the existence of protons, neutrons or electrons. Gandalf61 (talk) 13:43, 6 December 2007 (UTC)

I'd like to draw attention to the fact that this edit providing the majority of the multiple proportions article appears to have copied it from this book, which is under cc-by. I'm not an expert at how to give the appropriate attribution, but something clearly needs to be done about it. --Tardis (talk) 16:41, 6 December 2007 (UTC)

How does the nuclear binding energy (mass defect) compare to the difference between proton and neutron masses? HRMS can pretty easily distinguish between different element combinations that have the same integral mass ("number of nucleons"), so given a nuclear mass with enough precision, could one determine what specific combination of protons and neutrons gives it? DMacks (talk) 18:29, 7 December 2007 (UTC)

For ²H, nuclear binding energy is about twice the ¹p⁺ vs ¹n⁰ mass difference, I guess this isn't gonna work in many cases:( Yup, two minutes in the library saves a lot longer and megabucks of lab-work. DMacks (talk) 18:33, 7 December 2007 (UTC)

ring finger

Why is it hard to stick only your ring figer up. or to do that thing from star trek where your fingers look like \\// .thanks--Sivad4991 (talk) 03:02, 6 December 2007 (UTC)

It's odd - but some people have problems with that and some don't. I can do both of those very easily. Another one is the ability to raise one eyebrow and not the other. Yet another is to have one big toe point upwards and the other downwards - then to switch them both - then to alternate rapidly between the two such that one toe is always up and the other down. I think it's simply that these are things that we never normally need to do - and therefore get very little practice at. I kinda suspect that if you don't do them as a kid, some neural pathways don't form - then it's very tough to learn how to do it as an adult. I know my son couldn't do the "Live long and prosper" Vulcan salute thing when he was 10 years old - but managed to learn how to do it. There are some of these things (like rolling your tongue into a tube) that have actually been studied rather carefully - but I have to say that the results aren't exactly convincing. SteveBaker (talk) 03:14, 6 December 2007 (UTC)

Another one, most people can pat their head and rub their stomach, but can't do the opposite. —Preceding unsigned comment added by Shniken1 (talk • contribs) 03:30, 6 December 2007 (UTC)

From ring finger, "It is the weakest of the fingers on the hand, as it shares a flexor muscle with the middle and little fingers. It is the only finger that cannot be fully extended by itself separately." This is as much as I suspected, "something wierd about muscles." Someguy1221 (talk) 04:08, 6 December 2007 (UTC)

fully extend - no but 'stick it up' - yes. SteveBaker (talk) 04:43, 6 December 2007 (UTC)

Place one hand on the underside of your forearm about 60% of the way toward the hand. Now open and close your other hand. You should feel the muscle base pulling the tendons that go up through your hand to manipulate your figures. (Your fingers are essentially moved by wires anchored in your forearm.) The muscles that move adjacent fingers are partly connected so when you attempt to close or extend one finger you often end up manipulating adjacent fingers. It is possible with training to significantly increase the degree of independent movement. Such training is a common element of some dance styles, particularly those from the Indian subcontinent. Dragons flight (talk) 05:22, 6 December 2007 (UTC)

I used to have problems moving my fingers independently but playing the piano helped me to 'train them to move independently although my ring finger and little finger still want to move together a bit. The same goes for playing a different tune with the right and left hands, it's very difficult but practice makes perfect. As for the patting your head and rubbing your stomach, I can do it both ways round although it takes some practice and coordination! Some people can also wiggle their ears but I've never been able to do that. I think a lot of the reason is that muscles are very weak unless they actually get used, as most people have no need to wiggle their ears or precisely control their little finger, we perhaps 'forget' or don't learn how to use them in the first place? GaryReggae (talk) 11:59, 6 December 2007 (UTC)

variable frequency drive

at the inverter section, what will happen if one of the igbt's component short out or opens? —Preceding unsigned comment added by 70.251.116.191 (talk) 04:08, 6 December 2007 (UTC)

What exactly are you talking about? Power supplies? Amplifiers maybe? It's hard to tell! SteveBaker (talk) 04:41, 6 December 2007 (UTC)

Any short in a transistor in the bridge circuits of a variable-frequency drive will usually blow a fuse (and maybe the "other" transistor in that half-bridge). It's harder to assess what will happen for an "open"; an already-running motor may keep running, but will commonly overheat. A stopped motor probably won't start on the remaining two phases. In either case, a good VFD will recognize that something is wrong and shut down.

Atlant (talk) 13:15, 6 December 2007 (UTC)

Overloading an IGBT is very likely to vaporise it and the surrounding circuitry, so that you will not be able to determine what caused the failure. Good luck if you are operating without protection. Graeme Bartlett (talk) 20:32, 6 December 2007 (UTC)

Vaporize? Not if it's fused properly. And I speak from direct experience here.

Atlant (talk) 23:49, 6 December 2007 (UTC)

cosmic microwave background radiation

Are the photons of CMBR gravitationally lensed? —Preceding unsigned comment added by 203.192.230.107 (talk) 08:39, 6 December 2007 (UTC)

Cosmic microwave background radiation mentions this and cites a published article from 2006. --JWSchmidt (talk) 14:17, 6 December 2007 (UTC)

Faraday cages

I've read some Wikipedia articles related to Faraday cages. I'm not sure if I have understood correctly but, do they mean it is impossible to build a Faraday cage that cancels every incoming electromagnetic wave (because each skin depth nullifies a definite range of frequencies)? --Taraborn (talk) 11:57, 6 December 2007 (UTC)

A given Faraday cage is effective over a range of frequencies. At the high frequency end, it's (usually) pretty simple: the size of the openings, if any, must be quite small compared to the wavelength you're trying to exclude; the rule of thumb is to keep openings smaller than a quarter wavelength. At the low frequency end, I'm not quite sure, but it seems to me that there's no problem excluding the electric field but that the exclusion of the magnetic field requires increasingly good conductivity as the frequency goes lower and lower (because the Faraday cage must conduct an opposing current, creating an opposing magnetic field). A superconductive Faraday cage would probably exclude the magnetic field right down to DC (see the Meissner effect), but non-superconductors must have a practical lower limit (combined with an attenuation factor).

I'm not sure "skin depth" comes into play directly, though.

Obviously, I hope someone comes along who can offer a more-concrete answer to your question.

Atlant (talk) 13:24, 6 December 2007 (UTC)

Thank you for your response. Let's see if somebody else has something to add. --Taraborn (talk) 14:52, 6 December 2007 (UTC)

Skin depth comes into play with the low frequency end. If your shield has only a few skin depths of thickness then some fields will penetrate, so for audio frequencies you may have to use thick layers of metal. Graeme Bartlett (talk) 20:38, 6 December 2007 (UTC)

Plasmon frequency again?--TreeSmiler (talk) 02:37, 7 December 2007 (UTC)

Purple sky

A few days ago, the sky turned purple, during the day. Why is this? It was not sunset.

(Sorry to link to this place but it was exactly what was seen). Photo from flickr 147.197.229.134 (talk) 14:36, 6 December 2007 (UTC)

Purple is a mixture of red and blue. Towards dawn or dusk, the sunlight is red but the sky away from where the sun is shining is blue. Generally, these colours stay in their own parts of the sky and don't bother each other - but just the right kind of a layer of thick cloud between you and the sunset can diffract and mix the light together - resulting in reddish sunlight and blue from the sky being mixed into this purplish colour. SteveBaker (talk) 16:54, 6 December 2007 (UTC)

This photo was quite obviously taken at night (buildings are dark with indoor lights coming through the windows). My guess is that it's a photograph of lightning. (EhJJ) 20:26, 6 December 2007 (UTC)

I'm the photographer of that photo (my site logs pointed me here!), and I can tell you it was taken at 4pm on the 4th December, in mid-Norfolk, UK. It was dusk at the time - and certainly no lightning! I took a similar photo at a similar time almost a year ago too: link to more purple sky.--DeKay01 (talk) 22:07, 6 December 2007 (UTC)

So why did our questioner say "It was not sunset"?? On December 4th in London, sunset time is 3:58pm and the photo was taken at 4pm. At sunset, no other explanation is needed than the one I gave above - red+blue=purple. QED. SteveBaker (talk) 23:42, 6 December 2007 (UTC)

I interpreted the questioner to mean that the photo is an example of what he saw, but perhaps not exactly what he saw. The IP seems to come from the Univerity of Hertfordshire and my UK geography is woefully lacking - is that near mid-Norfolk, where our photographer was? --LarryMac | Talk 23:52, 6 December 2007 (UTC)

A similar picture taken of a lightning strike. (EhJJ) 01:28, 7 December 2007 (UTC)

Seems to me like SteveBaker is probably right about the reason. Sorry if it seemed like I was jumping to a conclusion, but it looks a lot like this photograph (right) that I took a few months ago; the image the OP linked is in no way taken in the middle of the day. (EhJJ) 01:28, 7 December 2007 (UTC)

The photo the OP linked to was mine, taken at 4pm on the 4th December. However, the OP seems to be using it as an example of what he saw - so he may well have seen the same sort of thing earlier in the day. Mid-Norfolk is about 100 miles N/NE of Hertfordshire. --DeKay01 (talk) 07:40, 7 December 2007 (UTC)

Obviously, the further north you go, the earlier sunset will be - and the longer it will last. The 3:58pm sunset time on Dec 4th was what I looked up for London. Also, sunset is defined as the time the upper rim of the sun drops below the horizon - there will be a lot of red light in the sky for a long period before that. The amount of cloud cover serves to diffuse the light - so it might not be obvious to people observing the effect that they are actually looking at the consequences of the sun starting to set. I think the OP may merely be surprised that the sky was actually turning red (behind the clouds) so early in the day. SteveBaker (talk) 16:33, 7 December 2007 (UTC)

How well do battery electric cars perform under cold and hot temperatures?

Topic says it all. 64.236.121.129 (talk) 15:56, 6 December 2007 (UTC)

I find very little discussion of significant problems with nominal temperature extremes. I would hypothesize that, should efficiency problems be severe enough, it would be no big deal to heat or cool the battery compartment along with the passenger compartment. — Lomn 16:14, 6 December 2007 (UTC)

My understanding of lead-acid batteries is that they have trouble delivering a large current in cold temperatures (think of starting your car on a cold day), but the cold temperatures do not cause permanent damage. Hot temperatures, on the other hand, do not cause immediate problems, but do shorten the lifetime of the battery. I don't know about other battery types in this regard. -- Coneslayer (talk) 16:39, 6 December 2007 (UTC)

(old answer deleted - I didn't notice "electric cars"!) SteveBaker (talk) 16:57, 6 December 2007 (UTC)

As far as cold temperatures are concerned, you get mixed messages. This page claims that there are no problems and quotes a study done by REV Consultants. The REV Consultants page explains that the test was on a battery heating system to keep the battery from getting too cold. So, you have one person saying that batteries work just fine in the cold and another marketing a battery heating system so they don't get too cold. -- kainaw™ 17:20, 6 December 2007 (UTC)

If you'll accept a practical example, the battery pack in the Toyota Prius hybrid car is air-cooled using a fan. So Toyota's designers clearly considered that higher temperatures were bad for the long-term health of the battery. The problem on the cold side is that aqueous electrolytes all have some freezing point and the amount of charge in a battery can affect that; for a lead-acid battery, the electrolyte becomes more- and more-pure water as the battery is discharged, leading to the possibility of the battery freezing at a mere 0°C if the battery is dead flat.

Atlant (talk) 17:28, 6 December 2007 (UTC)

Floppy McDonald's Fries

How can one make fries floppy like at McDonalds? I know they're supposed to be crispy or whatever, but I like them when they're floppy. What goes "wrong" to make 'em good 'n' floppy? --Seans Potato Business 16:18, 6 December 2007 (UTC)

Less frying time gets you softer fries. More time makes em cripsy. Friday (talk) 16:24, 6 December 2007 (UTC)

For home fryer use, a single fry is a good way to make floppy fries. For crispy-but-not-burned, a double fry is advocated -- once to cook, and once at a higher temp to crisp. Professional jobs use a different method, but I forget what it is offhand. — Lomn 16:32, 6 December 2007 (UTC)

I suspect that some floppy fast-food fries are the result of them sitting under a heat lamp for a while before they are served. -- Coneslayer (talk) 16:37, 6 December 2007 (UTC)

Does Ball Lightning have an charge?

Can it be affected by magnetic fields? 64.236.121.129 (talk) 18:32, 6 December 2007 (UTC)

Since the nature of ball lightning remains unknown, no definitive answer can be given to these questions. — Lomn 19:00, 6 December 2007 (UTC)

It's not at all clear that ball lightning is in fact a real phenomenon. They have not been produced artificially - and the conditions under which they are supposed to have arrived in nature is poorly described. There is no reasonable way in which a ball of electrical charge could be stable for seconds to minutes as claimed. I'm utterly horrified at our article Ball lightning which shows a short movie clip of "Ball lightning seen here following a car" which is quite obviously a reflection of the sun on a wet road that appears to be chasing the car because the camera is in a moving helicopter. If they were indeed real (and I'd put the probability down at one in a hundred that they are) then if they are (as claimed) electrical in nature - then magnetic fields ought to affect them...but as I said...they are about as real as UFO's aren't. SteveBaker (talk) 19:03, 6 December 2007 (UTC)

The article seems to indicate that they are real, and the skeptics are in the minority now. Maybe they just aren't completely understood yet. 64.236.121.129 (talk) 19:10, 6 December 2007 (UTC)

I think there's room for discussion as to what constitutes "real". Are there some phenomena that are real? Absolutely. Is there any one phenomenon that we can identify as "ball lightning" to the exclusion of all others, apart from arbitrarily saying "This is 'ball lightning'"? Perhaps not. If the latter holds, then I think it's fair to say "Ball lightning isn't real", even if there are phenomena that partially resemble descriptions of ball lightning. — Lomn 19:41, 6 December 2007 (UTC)

A load of ball (lightning) or not? [22]--TreeSmiler (talk) 03:13, 7 December 2007 (UTC)

There is a lot of difference between that (which is a ball of burning silicon gas/particles) and ball lightning. Sure, you can get small balls of burning gas under rather special laboratory conditions...nothing too remarkable about that. It's the claims for electrical effects that are dubious. SteveBaker (talk) 16:27, 7 December 2007 (UTC)

I just remembered the name of the phenomenon of burning gas balls that I've been wracking my brain trying to remember since the start of this thread! See Will-o'-the-wisp - little balls of methane that spontaneously ignite after bubbling up from rotting vegetation in marshland. The reason for ignition of the gas is poorly-understood - but once ignited, there is not much mystery. I strongly suspect that something like Bubble fusion is involved - not necessarily actual fusion but a dramatic increase in temperature as bubbles collapse. Since the methane is very unstable in air, it wouldn't take much of a spark to set it off. But it's still not ball lightning - just a more reasonable phenomenon that might explain many of the supposed sightings. SteveBaker (talk) 16:47, 7 December 2007 (UTC)

Ah, and that's where we differ. I'd say it is ball lightning, since that is the term used to describe it. That this term includes the word 'lightning' which implies it has a lot in common with normal lightning is just an historical accident, revealing what people used to think they were. After all, we can talk about Will-o'-the-wisps being 'real' without implying there's any 'will' behind them or that there are little people with lamps guiding travellers to their doom. It's the old thing of not discarding data points that don't fit, but also not necessarily buying the explanations people offer for them. If a lot of people report seeing ball lightning which appears to respond to electrical fields, then that needs to be noted. It might be that it's all an illusion, in which case learning that is good. It might be that it's something else, in which case you've avoided throwing knowledge away. After all, rains of fish were once dismissed as fanciful. Skittle (talk) 18:39, 7 December 2007 (UTC)

Can palms grow in Switzerland and the UK?

Cabbage trees (aka "Torbay Palms") growing in Torquay, England

Hi! I once read that palms can naturally occur in the southernmost parts of Switzerland and in south of England. Is that true? --escondites 18:37, 6 December 2007 (UTC)

From the article Arecaceae (you can find the link in Palm): "The northernmost palm is Chamaerops humilis, which reaches 44°N latitude in southern France, where the local Mediterranean climate is milder than other places as far north." -- kainaw™ 18:48, 6 December 2007 (UTC)

Well, yes...and no. So-called "Cabbage trees" are reasonably cold-tolerant and can be grown in the south-west of England in places with an especially good microclimate such as Torquay. They look an awful lot like palm trees and are sometimes called "Torbay Palms" (although technically, they are not palms at all). Switzerland is considerably further south - so in low-lying areas, it ought to be possible to grow them there too. I don't think true, honest-to-goodness palms do actually grow in England though - but I can't speak for Switzerland. SteveBaker (talk) 18:56, 6 December 2007 (UTC)

Here (http://www.thepalmcentre.co.uk/palms.htm) suggests yes some forms of palm can. Is true ny156uk (talk) 22:44, 6 December 2007 (UTC)

Trachycarpus fortunei has been cultivated in gardens and parks of the Swiss canton of Ticino for hundreds of years - the ones skirting the promenade along the Lago Maggiore, for example, belong to Locarno's touristic trademark. For the past 30 years or so, they have started to grow wild and naturally as an introduced species in the Ticino too. Biologists have studied this trend and linked it to climate change. I remember reading about it in Swiss papers a couple of years ago. International press centre biodiversity research has some information in English. ---Sluzzelin talk 00:50, 7 December 2007 (UTC)

Palms do grow in parts of Cornwall. Bananas can be grown there too, and indeed were in the war. DuncanHill (talk) 00:55, 7 December 2007 (UTC)

Trebah has palms, see [23] for some pics and binomials. DuncanHill (talk) 00:57, 7 December 2007 (UTC)

But can they grow "naturally", i.e. in competition with native species, in southern England? ---Sluzzelin talk 01:03, 7 December 2007 (UTC)

England I dunno, Cornwall I'd say yes, in some places. DuncanHill (talk) 01:06, 7 December 2007 (UTC)

Please forgive me, I meant Great Britain. ---Sluzzelin talk 01:10, 7 December 2007 (UTC)

You are forgiven (on production of one saffron cake), tho' I'm still not happy with your spelling preferences in -ise/-ize :)DuncanHill (talk) 01:20, 7 December 2007 (UTC)

Uh, what are you guys apologizing and forgiving about? Cornwall is in southern England, which is part of England, which is part of Great Britain. --Anon, 01:27 UTC, December 7, 2007.

There's a bit of a 'Free Cornwall' movement. Maybe we should just all split into subcountries and see how that improves things... Free Cotswolds! 79.69.14.132 (talk) 02:08, 7 December 2007 (UTC)

Scilly Isles Also Scotland [24]

—Preceding unsigned comment added by TreeSmiler (talk • contribs) 02:26, 7 December 2007 (UTC)

What's the largest supermassive black hole that we know of?

^Topic 64.236.121.129 (talk) 18:57, 6 December 2007 (UTC)

http://www.google.com/search?q=largest+black+hole suggests the core of galaxy M87, at 3 billion solar masses. — Lomn 19:49, 6 December 2007 (UTC)

Hmm, that's not the largest. Q0906+6930 is larger at 16 billion solar masses, but I don't think it's the largest we know of. 64.236.121.129 (talk) 20:54, 6 December 2007 (UTC)

Mosquitoes the size of birds

Most places with significant numbers of mosquitoes also have tall tales of the exploits of their extra-large mosquitoes -- carrying off small dogs, biting people through the walls of houses, and the like. Which area really has the world's largest mosquitoes? --67.185.172.158 (talk) 19:50, 6 December 2007 (UTC)

A number of references cite mosquitoes of the Toxorhynchites genus as the largest mosquitoes. Toxorhynchites larvae are known to feed on the larvae of other mosquito species. The adults are gentle and peace-loving (well, for mosquitoes)—they don't suck blood, but rather live on plant nectar. I don't know what the full range of all Toxorhynchites species might be – our article lists at least forty or fifty species – but Toxorhynchites rajah comes from East Malaysia. This page has pictures of this mosquito in various stages of development. TenOfAllTrades(talk) 20:03, 6 December 2007 (UTC)

Ah—the Walter Reed Biosystems Unit indicates that the genus Toxorhynchites is very widespread: [25]. (There's also a great picture there—note the bent proboscis and long legs.) —Preceding unsigned comment added by TenOfAllTrades (talk • contribs) 20:12, 6 December 2007 (UTC)

Isn't the daddy long legs (UK edition) technically a mosquito? It's certainly fairly large for an insect and I know that some people are terrified of them. Makes a fairly loud (for an insect) thudding noise when it collides with windows and walls too. --Kurt Shaped Box (talk) 22:50, 6 December 2007 (UTC)

You can hear stag beetles flying towards you in the dusk before you can see them. I guess they would make a fair noise hitting glass. Lanfear's Bane | t 23:41, 6 December 2007 (UTC)

A friend of mine discovered that with the (very large) cockroaches in North Africa, much to his terror one night. English 'roaches just skitter around, you see... --Kurt Shaped Box (talk) 19:20, 7 December 2007 (UTC)

I don't think so. The article includes the phrase Unlike mosquitoes..., and lists mosquito eater as one of their alternative names. Skittle (talk) 00:21, 7 December 2007 (UTC)

Hmmm. Yes, you are correct. Same order, not the same family. Sorry about that. --Kurt Shaped Box (talk) 19:20, 7 December 2007 (UTC)

The so-called "Hexham Grey" seems to be in the running if we're talking about mozzies (Ozzies call them "mozzies", it seems) that bite people. --Milkbreath (talk) 20:03, 7 December 2007 (UTC)

Mammal lips

What is the purpose of the split in the top lips of many mammals? —Preceding unsigned comment added by 84.66.155.90 (talk) 20:46, 6 December 2007 (UTC)

There is cartilage there that allows muscles to have good control of the upper lip. It is called the philtrum. -- kainaw™ 21:26, 6 December 2007 (UTC)

Presumably it is so there is enough skin to stretch when you perform certain mouth movements? Like all the lines in your hand that just seem (to me at least) to be crease-lines because you don't always have your hands in such a way that maximises the amount of surface-area the skin needs to cover. I'm sure someone will confirm this is just gibberish if indeed it is. ny156uk (talk) 22:43, 6 December 2007 (UTC)

The heart

I was reading my bodybuilding magazine and I read that aerobic exercise strengthens the heart and makes the left ventricle thicker, I had previously thought that they said steroids was bad because steroids do that also, so is it really that bad? —Preceding unsigned comment added by 76.167.132.90 (talk) 23:56, 6 December 2007 (UTC)

We actually have a short article just on this (Left ventricular hypertrophy). Muscles naturally enlarge when they strengthen (see Muscle hypertrophy). Anabolic steroids, which are taken illicitly to this effect, are dangerous for their other influences on the human body (see Anabolic steroids#Adverse effects). Someguy1221 (talk) 00:18, 7 December 2007 (UTC)

Actually, I take that partially back. Our own articles disagree over whether LVH is a "bad thing." I'll be researching it now...Someguy1221 (talk) 00:30, 7 December 2007 (UTC)

Ok, I think I have it now. This paper shows that steroid-free exercise-induced LVH is accompanied by a clear increase in cardiac performance, one that is not seen in LVH caused by hypertension (the only alternate cause of LVH discussed in that article). Further, this paper indicates that LVH caused by steroid use is accompanied by decreases in certain aspects of cardiac performance. So LVH itself is not inherently good or bad, as our LVH article suggests, but the impact of LVH plus other, possibly unidentified changes in the heart, is very dependent on the cause of LVH. I hope this answers your question. Someguy1221 (talk) 00:44, 7 December 2007 (UTC)

One (somewhat comic) side-effect of exercise-induced LVH is that it causes you to have a different cardiac rhythm to normal people, which makes jittery paramedics fear something very nasty has happened to your heart. It's not unheard of for marathon runners (who encounter a paramedic for minor stuff like treating cuts and abrasions from a fall) to be whisked off to a cardiac care unit, while loudly protesting that they feel fine and really would rather carry on with the race. -- Finlay McWalter | Talk 01:01, 7 December 2007 (UTC)

December 7

Need to burp!

I wonder if this counts as a medical question. Whenever I have a stomach full of gas, I have a hard time burping it out, so it ends up being very uncomfortable and painful until it finally happens.

What are best ways to stimulate burping? — Kieff | Talk 00:57, 7 December 2007 (UTC)

With babies you pat them on the back for a while, maybe it can have the same effect on you? —Preceding unsigned comment added by 128.101.53.177 (talk) 01:08, 7 December 2007 (UTC)

Eno's Fruit Salts. DuncanHill (talk) 01:25, 7 December 2007 (UTC)

Yes it does. This could actually be a medical condition (a feind of mine had similar condition). Please see a doctor.--TreeSmiler (talk) 03:17, 7 December 2007 (UTC)

As far as my understanding of our policies is concerned: a) we can tell you how to induce burping, but b) we can't tell you if it's healthy to do so in your case. If this (epigastric discomfort) is a problem for you, you should see a physician or other health care worker, as it may be a sign of a serious condition (or it could just be gas, but since it's causing you grief, why not look into a solution with a doctor that will stop the gas from forming, rather than finding ways of relieving it?) (EhJJ) 04:15, 7 December 2007 (UTC)

Just as with the question "How do you get to Carnegie Hall?", the answer is "Practice!". Drink something highly carbonated such as seltzer. Learn to relax the muscles in your throat and contract the muscles in your abdomen. Seriously. You can train yourself. People who have had their larynx surgically removed learn to swallow air and burp it out to simulate the buzzing of their now-missing vocal cords; you can probably Google up more info regarding how they train themselves. And then there's the contest in Revenge of the Nerds...

Atlant (talk) 14:08, 7 December 2007 (UTC)

Dear Reference Desk: Does telling someone how to make it worse count as medical advice? I'm uncertain. SteveBaker (talk) 16:16, 7 December 2007 (UTC)

Questioner: Remove the opening sentences and just leave your question. "What are best ways to stimulate burping?" is in no way a request for medical advice. Adding personal history confuses some people and makes it difficult for them to see the question. As with any abnormality, you should seek professional medical advice to ensure that you are healthy. Answering the question - as with babies, patting someone on the back and rubbing the center of the back in circles helps with burping. -- kainaw™ 17:28, 7 December 2007 (UTC)

Wikipedia talk:Reference desk

Hydrogen Peroxide

Does anyone know what the heck is that white gunk you get from hydrogen peroxide you put on any unsterile surface (i.e. sink, tub, bathroom floor), or on raw meat? --Agester (talk) 01:19, 7 December 2007 (UTC)

Beyond "white", tell us something about this "gunk". Is it a solid, liquid? Does it dissolve if you pour some water on it? Does it disappear after sitting for a while? Is it foamy (H₂O₂ decomposes to H₂O and O₂ and this reaction is strongly catalyzed by several common biological materials). DMacks (talk) 02:41, 7 December 2007 (UTC)

It sounds like bleached scum. Graeme Bartlett (talk) 21:22, 7 December 2007 (UTC)

Not quite too sure what it is. But it seems very similar to the foamy stuff if you put hydrogen peroxide in a open cut / wound. I figured it might be the dead bacteria, because when i put it in a clean bowl that i just washed it doesn't build up that foamy stuff, but if i accidentally drip some in my sink it'll foam up similar to it being applied to a cut. And if it isn't assumed I'm talking about the hydrogen peroxide you can get in your local pharmacy for antiseptic uses. --Agester (talk) 01:09, 8 December 2007 (UTC)

Malt liquor

Is malt liquor sweet? Heegoop, 7 December 2007 (UTC)

Our article on malt liquor doesn't really answer the question, aside from mentioning that sugar is sometimes added. I would guess that it would depend on the particular brew, as it is essentially beer with a little more alcohol (like they sell in Canada and Europe). As a scientist, I'd like to suggest a simple experiment :P (EhJJ) 04:20, 7 December 2007 (UTC)

The article says sugar is sometimes added before fermentation, "to boost the beverage's alcoholic strength". Adding sugar before fermentation has somewhat the opposite effect to adding it afterward, because the yeast use up all the sugar present and turn it into alcohol. —Keenan Pepper 06:17, 7 December 2007 (UTC)

Malt liquor is really little other than distilled beer, and as a brewer I can tell you that beer can be made sweet or not so. Depending on mash temperatures (the temperatures at which the malt is steeped), sugars in the grain are broken down to various degrees. At some temperatures you end up with much of the sugar of the kind yeast likes, and little of the stuff yeast can't easily digest; and at other temperatures, the opposite. Any sugars the yeast doesn't digest to ethanol+CO₂ increase the sweetness of the finished product. Psud (talk) 10:09, 7 December 2007 (UTC)

What?!? Maybe this is a difference in terminology between different places, but around here, what we call "malt liquor" is beer that's a bit stronger than typical beers. It is most emphatically not distilled! It's still just beer. The article Malt liquor also does not mention distillation. If it's distilled, it's not beer. Friday (talk) 16:38, 7 December 2007 (UTC)

As with anything that's brewed, the amount of sugar left at the end of fermentation depends on how much you put in at the outset and how long the fermentation went on. Fermentation stops when either the yeast runs out of sugar to convert - or it poisons itself with it's own alcohol production (or maybe if someone stops it prematurely by messing up the temperature or something). So there are a range of possible outcomes here. Obviously, the manufacturers can also alter the final sweetness by adding more sugar after fermentation is complete. So it's not true to say that because something sweet went in at the outset, that the result will be sweet...but "it depends". SteveBaker (talk) 16:11, 7 December 2007 (UTC)

• You might be thinking of Malt beverage, which is a little different from malt liquor. In the United States, makers of Alcopops such as Mike's Hard, Zima, etc. refer to the drinks as "flavored malt beverage" or "premium malt beverage". These drinks are very different from malt liquors, which more often taste like smooth beers, as Steel Reserve and Hurricane High Gravity Lager do. Also, don't forget Low-end fortified wine like Mad Dog and Thunderbird -- these are often sold in the same section as the malt liquor, and most of them are very sweet to cut the harsh taste. --M@rēino 19:01, 7 December 2007 (UTC)

Gene transfer a mutation?

Would horizontal gene transfer be considered a mutation for the organism that receives the transferred gene? I'm confused. I stumbled across a PNAS article which seemed to refer to it as a "mutational process," [26] but sometimes the two terms may be observed contrasting with eachother (e.g., [27] , scroll down to the section that says "evolutionary genetics in bacteria"). Thanks! Schmitty120 (talk) 01:33, 7 December 2007 (UTC)

One could argue the semantics of describing the effect of horizontal gene transfer as a mutation. From a strictly technical point of view, it could be considered mutational. For instance, if the gene integrated into the recipient genome it would result in a "mutation" of the genetic insertion site. Likewise, of you wish to use the term to describe the phenotype affected then the recepient could be described as having a "mutant phenotype" and it follows that must have occured by a mutational process. In the link where you suggest it is used in a contrasting manner, I think the use of the term "mutational process" is really a shorthand for "classical mutational processes in vertical gene transfer" (meaning indels and point mutations) in contrast to horizontal gene transfer and recombination. I don't think in calling them "mutations" (or not) the author is attempting to make a point about whether they are involved in the evolutionary process (or not). It is fairly well established that both types of genetic changes have driven evolution (at least in bacteria, see Horizontal gene transfer#Evolutionary theory). Rockpocket 08:15, 7 December 2007 (UTC)

Neurobiology: Effects of decreased membrane capacitance

My script says that Myelination reduces the leakage current and decreases the axon's membrane capacitance. By this the speed of signal propagation is increased. However, I do not see which effect decreasing the membrane capacitance has on the speed of signal propagation in addition to reducing the leakage current. Can somebody please explain this to me? Falk (talk) 08:27, 7 December 2007 (UTC)

We are propagating a potential difference up the axon. By $Q=CV$, we see that for this potential to stay constant, there must be a buildup of charge difference on each side of the membrane, and to get this charge difference there must be an ion flow toward the membrane, which takes time. By reducing capacitance, the necessary charge difference becomes lower. Otherwise, we could say $I=CdV/dt$, in which case reducing the capacitance for a given ion current (the rate of flow of ions we'll assume is constant) increases our voltage propagation speed $dV/dt$. SamuelRiv (talk) 13:27, 7 December 2007 (UTC)

Cold Car Experiment

Two identical cars are started, and their heaters turned on, on a cold wintry morning. One car is encased in half an inch of ice; the other car was covered and is clean. In which car will the internal air temperature rise faster? We've come up with several hypotheses:

a) The icy car will warm faster, because it is insulated with an extra layer of ice.

b) The clean car will warm faster, because the ice on the icy car conducts heat away from the windows faster than air could, due to ice's higher thermal conductivity.

c) It depends on how close the ice is to the freezing/melting point, since

d) It depends on the air temperature or velocity outside -- if the air is significantly colder than the freezing point of water, it will cool the windows faster than melting water.

e) More than one of the above are true, and the problem is too complex to definitively answer.

Your thoughts? jeffjon (talk) 14:07, 7 December 2007 (UTC)

Assuming the outside air temperature is the same as the temperature of the ice (which is reasonable) and that it's a lot colder than zero centigrade (ie well below freezing): I think the one covered in ice will win - ice is a reasonably good insulator - but not as good as air. However, with air, as soon as you heat it up just a bit, it drifts upwards to be replaced with new, cold air. Hence any heat that leaks out of the second car is lost immediately. With first car, with an icy jacket, the heat you radiate goes into warming up the ice - at least until it reaches it's melting point - and that warmth is retained close to the surface of the car. Since the rate of heat loss is proportional to the square of the temperature difference (Newtons law of cooling), the ice-encased car will do better.

If the air around the second car was retained close to the car though (eg if it had a loose car-cover thrown over it) then the superior insulation value of air would win out.

SteveBaker (talk) 15:55, 7 December 2007 (UTC)

I agree with Steve. There would be several minutes of ambient temperature air coming out of the vents until the engine warmed up, then the ice-encased car would have less heat loss due to convection, leading to a faster rise from the assumed below zero C interior temp and temp of the ice. Of course if it were warm outside, then the ice-free car would warm up faster. Edison (talk) 23:55, 7 December 2007 (UTC)

Hovercar?

Think these would ever be viable? How would one break or slow down in one? 64.236.121.129 (talk) 14:19, 7 December 2007 (UTC)

Presumably by reversing the means of propulsion (a fan or whatever). If you can figure out how to make it go forward, you can figure out how to make it slow down. And I would think they would break the same way regular cars do—when it's least convenient, and at great expense. -- Coneslayer (talk) 14:23, 7 December 2007 (UTC)

I reckon they'd be too expensive in fuel. Hovering is very energy intensive, especially when compared to rolling. As to braking, consider an already existing vehicle that can hover - the helicopter. Helicopters brake by vectoring their thrust forward, a hover car would presumably do the same. --Psud (talk) 14:39, 7 December 2007 (UTC)

I think by the time the technology is good enough and reliable enough and they are cheap enough to be somewhat popular, there will be other, far better forms of transportation people will use instead. Recury (talk) 14:41, 7 December 2007 (UTC)

Actually, I like the idea of travel by rocket - a short high acceleration burn; a ballistic arc; a short high acceleration burn to stop. Fun and quick whether across town or across continents! --Psud (talk) 14:45, 7 December 2007 (UTC)

Hovering as in hovercraft? The trouble with hovercraft is that they are very unmanouverable - you don't have friction with the ground - hence you have no brakes. Redirecting thrust to slow you down means that you can't slow down any faster than you can accellerate and if there is even the slightest deviation from aiming the thrust dead straight, there is a tendency for the craft to spin or slip sideways. Stopping at traffic signals would be tough. Energy-efficiency-wise, they aren't so good either. The lack of friction with the ground is a net win - but it's very expensive to maintain the hover thrust - so you end up needing more power than with a car. It's nice to be able to travel over water and to not need paved roads (it would be nice if all of our roads could be turned into lawns - or farmed for grain!). Hovercraft are impractical for other reasons: If your lift motor fails, you can't push the vehicle off the road - if your thrust motor (which is also doing the braking remember!) fails then you have a dangerously uncontrolled vehicle on the streets. At stop lights, or in heavy traffic, everyone has to land and lift off again because, again, there is no way to keep a hovercraft stationary. Even the slightest breeze would be enough to blow you onto the sidewalk if you continued to hover.

Using propellors to direct thrust has another set of problems in that the 'blow back' from the rear of the craft will tend to knock pedestrians off their feet and blow out windows! Also, if two or more hovercraft are manouvering close together (again, think busy city streets with people turning, parking, stopping and starting) - then there are lots of dangerous cross-winds induced by one craft turning that would tend to blow other craft sideways.

All in all, hovercraft just aren't really practical in tight areas. Great for lakes and open grassland and such though. SteveBaker (talk) 15:43, 7 December 2007 (UTC)

• my hovercraft is full of eels --M@rēino 19:07, 7 December 2007 (UTC)

You can buy a hovercar today: the M200G Volantor or the Moller Skycar M400. Rockpocket 19:19, 7 December 2007 (UTC)

That's not really true. They are offered to sell one of their prototypes - on the condition that you basically use it as a museum piece and promise not to fly it - but the price was so high, I don't think they actually managed to find a buyer. You can't actually buy a working, flyable, usable flying/hovering car from them - it's always "a few years away"...which is why Moller are being dragged through the courts over it by their investors. SteveBaker (talk) 19:48, 7 December 2007 (UTC)

Also those are flying cars. That's a bit different. A hovercar doesn't lift off the ground by too much, while a flying car can fly very high. 64.236.121.129 (talk) 19:57, 7 December 2007 (UTC)

"The computer system also prevents the machine from flying higher than 10 feet (3 m) above the ground." - sounds like a hover car to me. I didn't say you should buy one, just that could could buy either of those functional prototypes if you had enough money. It would then be up to you to find somewhere to use it legally. ;) Rockpocket 01:14, 8 December 2007 (UTC)

Chemical(s) responsible for Pine/Christmas Tree Scent

Can anybody inform me of the name(s) of the chemical(s) responsible for the fragrance associated with Christmas/Pine trees? --Mark PEA (talk) 16:00, 7 December 2007 (UTC)

I presume pine oil. Someguy1221 (talk) 17:54, 7 December 2007 (UTC)

Most fragrances are very complex mixtures of chemicals - I doubt there is one particular one that produces the "Pine tree" smell. SteveBaker (talk) 19:44, 7 December 2007 (UTC)

Okay, thanks for the answers. I thought maybe there would be some research into the constiuents of pine oil but I can't seem to find any without digging deep. --Mark PEA (talk) 23:51, 7 December 2007 (UTC)

Testosterone Question

I read something about testosterone and how bodybuilders have to keep using more and more each time they use it to get the same effect. Does that mean, that when your off of synthetic testosterone, the testosterone that is body makes is less effective then it used to be before you started using synthetic testosterone? (assuming your body is making the same amount of testosterone as it did before you started using synthetic testosterone) —Preceding unsigned comment added by 71.106.34.15 (talk) 17:18, 7 December 2007 (UTC)

This is a phenomenon known as downregulation, which occurs when any receptor is overstimulated by a ligand. I've never answered a question here before, so maybe someone else can put more effort into it and explain it better. See also: Desensitization (medicine), Drug tolerance, Physical dependence. --Mark PEA (talk) 23:49, 7 December 2007 (UTC)

With testosterone it's more complex than mere downregulation. In fact, when you massively flood your system with artificial testosterone, your endogenous production is completely knocked out. This is what causes rather extreme withdrawl symtoms for several weeks after going cold turkey from steroids, as your body takes that long to regain normal production levels. Additionally, your body will initiate processes to convert excess testosterone into other hormones, including estrogen (if I recall correctly). I'm not sure if these two processes in combination are the complete reason for any apparent drug resistance seen in steroid abusers. Someguy1221 (talk) 23:57, 7 December 2007 (UTC)

Autothermal Reforming and Modelling Software

Okay, this is possibly a little specialised but I'm losing track of what reasonable values are for things and nobody else around me seems to be doing better with the software. I'm modelling autothermal reforming of methane with oxygen and steam using PRO/II (pro2), which has to be the most irritating piece of software ever coded. Putting 16152.7060 kmol/hr of my reactants into a Gibbs reactor, at some temperatures the reactor is giving out 3,000 million kJ/hr in heat. At some lower temperatures it requires nearly 300 million kJ/hr heat to be put in. Now, pro2 being as erratic as it is (and given the weird way the duty is varying with the pressure), I'm suspicious of these values. Are they, in fact, reasonable?

Thanks for any help. I've just reached the stage where I'm so frustrated with the software I can't think clearly about the actual process. Skittle (talk) 17:31, 7 December 2007 (UTC)

I really have no knowledge whatsoever of your problem domain. So I'll respond anyway (that's what teh Intarweb is for!). 3,000 million kJ/hr is 833 megawatts, which is pretty close to the electrical output of Three Mile Island's remaining nuclear reactor. Do you anticipate that what you're trying to do should have energetics on the same scale as a power plant? -- Coneslayer (talk) 17:44, 7 December 2007 (UTC)

Hmm, thanks. I wasn't really expecting to get nuclear power plant levels of heat :) Although, it would provide excellent heat integration opportunities. That was the sort of reality check I needed; I was starting to doubt the size of a kilojoule. So, pro2 screws up again. Hooray! Skittle (talk) 18:05, 7 December 2007 (UTC)

BTW, Google is good for quick unit conversions... 3000 million kJ/hour in watts is what I used. -- Coneslayer (talk) 18:29, 7 December 2007 (UTC)

Yes, but without someone who isn't me to tell me 'that's like a power plant', I couldn't be sure I wasn't just being stupid :) Skittle (talk) 18:31, 7 December 2007 (UTC)

We all came from the sun?

Would it be a fair statement to say that we all came from the sun? The matter in our bodies came from the sun, and the energy that sustains us also came from the sun in one form or another. 64.236.121.129 (talk) 19:37, 7 December 2007 (UTC)

That assumes (incorrectly in my opinion) that absolutely no matter from outside the solar system or matter that existed in the ooze that became the solar system made it to Earth. -- kainaw™ 19:44, 7 December 2007 (UTC)

That's true, but how much matter from outside the solar system contributed to the ooze? 64.236.121.129 (talk) 19:47, 7 December 2007 (UTC)

The matter in our bodies did not come from the sun. It came from the Earth (and the stuff on the Earth's surface) and thus (ignoring meteorites and so on as negligable), it came from the cloud of gas and dust that collapsed into the solar system. Some or all (not sure which) of this cloud came from a previous supernova, so we come from a star, but not from the sun in any literal sense. See formation and evolution of the solar system. Algebraist 20:16, 7 December 2007 (UTC)

No, little of you came from the Sun. Much of your body consists of hydrogen (either in the water that comprises much of your body, or in the many compounds that comprise the solid bits), which was formed in the aftermath of the big bang. Almost all of the remaining atoms were made in a sun, but not our Sun. Right now the Sun is turning hydrogen into helium; much later in its life it'll make a few heavier elements. The atoms that comprise your body (bar the aforementioned hydrogen) were made by old suns that have since exploded, the wreckage of which condensed to form the planetary nebula from which the Sun, the Earth, and the rest of our solar system formed. Our Nucleosynthesis article is a good place to start. -- Finlay McWalter | Talk 20:12, 7 December 2007 (UTC)

"Us from the sun"? No way…planets and sun all came from a common origin, not one from the other. See Solar System#Formation. DMacks (talk) 20:14, 7 December 2007 (UTC)

As for the energy that sustains us, virtually all of this comes from the sun. The energy contribution of extra-solar sources is truly negligable in comparison. Some primitive organisms, however, obtain their energy from geothermal sources, which certainly didn't originate from the sun. Someguy1221 (talk) 20:17, 7 December 2007 (UTC)

Gravity fields, mass, volume, density

Lets say we have two objects. Jupiter, and Mini Jupiter. Jupiter, is the planet Jupiter. Both have exactly the same mass. However, Mini Jupiter has a radius of only 500 miles. As such, Mini Jupiter has less volume, but is much more dense. How do their gravity fields compare? Which is stronger? Which is larger? 64.236.121.129 (talk) 19:45, 7 December 2007 (UTC)

You can use simple Newtonian gravity and the shell theorem to figure this out. Outside the radius of Jupiter, the gravitational fields are identical. Inside the radius of Jupiter, Jupiter's own field weakens, its strength now directly proportional to the radius (if you assume Jupiter's density is irrespective of radius, so this is a very very bad assumption. It's assumed for simple physics problems, and I don't know the actual density vs. radius of Jupiter). MiniJupiter's gravity, on the other hand, keeps getting stronger right up until you reach it's edge. Inside of here, it also decreases as you approach the center, under the same bad assumption for density. So MiniJupiter will have stronger gravity inside Jupiter's outer radius, and outside of that radius, they will have equal gravity. Someguy1221 (talk) 19:59, 7 December 2007 (UTC)

Are living beings mostly comprised of water and carbon?

^Topic 64.236.121.129 (talk) 19:49, 7 December 2007 (UTC)

The average organism is said to be about 70% water. In a sense, living organisms are just aqueous chemical reactors. There are some insects that are considerably less that 70% water (as low as 15% if I recall correctly) as an adaptations for dry environments. There are also plants that contain significantly higher than 70% water. As for carbon, well, carbon is a main constituent of every major chemical group in a living organism. Reading from my years old biochemistry notes, living organisms are 1-3% carbohydrates (made mostly of carbon, oxygen, and hydrogen), 2-3% lipids (mostly carbon and hydrogen), 15% protein (mostly carbon, nitrogen, hydrogen, and oxygen), and 7% nucleic acids (mostly carbon, oxygen, nitrogen, hydrogen, and phosphorus). Carbon, oxygen, hydrogen, and nitrogen constitute 96% of living matter (I believe this number is by mass). Someguy1221 (talk) 20:08, 7 December 2007 (UTC)

The Carbon page tells us that that element "is ubiquitous in all known lifeforms, and in the human body it is the second most abundant element by mass (about 18.5%) after oxygen." DMacks (talk) 20:11, 7 December 2007 (UTC)

See also an elemental breakdown at: [28]. Maybe someone who remembers their chemistry class a little better could figure out how much water might be present based on the H & O content. jeffjon (talk) 21:19, 7 December 2007 (UTC)

Large trees have more carbon than water. Inside the tree is dead wood which contains a massive amount fo carbon but no water. David D. (Talk) 23:41, 7 December 2007 (UTC)

I call that cheating. Someguy1221 (talk) 23:54, 7 December 2007 (UTC)

UK telephone extension wiring

I bought a standard UK telephone extension kit (Homebase), wired it up according to the simple instructions, and plugged it into the master socket. (There are no other extensions.) I have two handsets, an old one (maybe ten years old or more) and a new one. Plugging either handset into either socket on its own works just fine: both handsets will ring and give me a dialtone. Plugging the new handset into the master socket and the old one into the extension works just fine too. However, when I set up the configuration I want, with the old one in the master socket and the new one on the extension, the old handset works but the new one is dead. The old handset seems to be somehow blocking the extension. Any ideas how to solve this? Will I have to get another new handset or can the old one be fixed?--Shantavira|^{feed me} 20:10, 7 December 2007 (UTC)

The description you have given of the problem seems to mean that there is a difference between the two sockets. They should be the same. Me, I would double-check my wiring job, with reference to this site and this one. --Milkbreath (talk) 00:12, 8 December 2007 (UTC)

See Ringer equivalence number. This may ring some bells (or not)--TreeSmiler (talk) 01:11, 8 December 2007 (UTC)

Maternal depressions effects on the Family

What are the effects of maternal depression on the spouse and children, especially teenagers? —Preceding unsigned comment added by 75.131.194.201 (talk) 21:24, 7 December 2007 (UTC)

Wikipedia has postnatal depression. A starting point in the research literature: Do Parenting and the Home Environment, Maternal Depression, Neighborhood, and Chronic Poverty Affect Child Behavioral Problems Differently in Different Racial-Ethnic Groups?
--JWSchmidt (talk) 00:49, 8 December 2007 (UTC)

Photographs

If I point a camera at a brick wall, I see straight lines of bricks running left and right. I really don't understand how this is possible. Since the far corners of the wall are farther away from the camera than the brick directly in front of the camera, they should logically be both out of focus and smaller than the center. I believe our eye corrects for this because it projects the image on a curved surface, but the film in a camera is flat, so this shouldn't affect it. How does this work? 72.155.209.101 (talk) 21:44, 7 December 2007 (UTC)

The focus is due to the depth of focus (dependant on the aperture). In short there can potentially be a wide range of distance that remains in focus. David D. (Talk) 23:38, 7 December 2007 (UTC)

It does get out of focus, if you're shooting with 85mm f/1.2 at 1m away from the wall, or try some macro photography. Point and shoot cameras usually has enough DOF (which is also dependant on the focal length is well) to get pretty much everything in focus. --antilived^{T | C | G} 01:41, 8 December 2007 (UTC)

That's not what I am saying. There is a focal plane, here represented by the wall - DOF does not factor in if the object is flat. Try shooting a grid; if I'm right, the corners squares will be smaller than the center squares and not on the focal "plane" (since they are farther away from the lens). Even if I have your 85mm f/1.2 pointed at this hypothetical wall, the wall would all be in focus, since it is flat. However, the far corners of the wall are farther away from the lens than the part directly in front of the camera. Thus, rather than a focal plane, should we not be seeing a focal sphere, where the points in focus lie at equal distance from the camera? And since the points farther away from the camera are, well, farther away, should they not be rendered smaller? 72.155.209.101 (talk) 02:32, 8 December 2007 (UTC)

(edit conflict) It all depends on the projection. Normal camera lenses are designed to give a rectilinear projection, which has the desirable property that the resulting image looks "right" (as in undistorted) when displayed on a flat surface (such as a piece of paper or a computer screen) — assuming the viewing distance and angle are correct. (Fortunately, our brains also tend to mostly ignore the small distortions that result from viewing such images from a wrong distance or angle, as long as the mismatch isn't too severe.) Essentially, this is because the rectilinear projection is exactly what you'd get if you, say, held up a flat transparent sheet in front of your face and traced the scene onto it as you saw it.

However, the rectilinear projection does have some disadvantages, particularly in wide-angle photography. One is that it can't possibly produce a field of view wider than 180°, and even at much lower fields of view (say, anything over 60°) it tends to look distorted unless projected on a very large canvas and/or viewed from a very close distance. Another problem is that, contrary to what you might expect, if you rotate the camera the image will not simply scroll left or right — rather, horizontal lines will appear to rotate. This is the price one has to pay for keeping straight lines straight, and is related to the effect known as the corner illusion (or I thought it was, but I can't find an article on it — perhaps I'm misremembering the name). There are alternative projections, commonly used in panoramic photography, which avoid this at the cost of making some straight lines appear curved. —Ilmari Karonen (talk) 02:38, 8 December 2007 (UTC)

Molecular solution

From [29], a distinction is made between a solution and a molecular solution. I have never heard of this before, but I am not a chemist. Can anyone clarify this? If this is important, maybe we should have an article on molecular solution ?--Filll (talk) 23:12, 7 December 2007 (UTC)

They seem to be referring to ionic organometallic compounds. Unlike an inorganic salt, these compounds don't fully dissociate in solution, and instead form complexes of several carbanions and metallic ions. However, I've never heard this term used to describe it. Someguy1221 (talk) 23:27, 7 December 2007 (UTC)

Final cause of death in cancer

I never understood why cancer was so deadly. Yes, you do have an abnormal growth/tumor growing somewhere in your body, but I don't see why that would eventually cause death. If there was a tumor within a blood vessel that directly caused a stroke or heart attack, then the cause of death in that case is quite obvious. But in "normal cancer" (if such a thing exists), what is usually the final cause of death?

I asked myself that same question a year or two ago, and the answer I came up with after a bit of research is nobody really knows. They don't do autopsies on cancer deaths, and the oncology community seems to be concentrating on getting rid of the cancer to the exclusion of finding out exactly how it kills. Some ideas are that the tumor sometimes, of course, impinges on something vital like the pancreas and you die from the trauma to the vital part. Brain tumors are obviously going to kill you by compressing the brain. But the main deadly effect of a tumor seems to be that it disrupts your chemistry. Tumors produce all sorts of nasty chemicals as though they were a gland, which accounts for the weight loss that accompanies them. But nobody as far as I could find out has determined exactly which chemicals do what when. I remember thinking at the time that there might be a way to live with cancer if we could counteract that process, but what do I know? --Milkbreath (talk) 01:54, 8 December 2007 (UTC)