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September 29

Oceanic Mammalian Question

I reckon that whales, seals, and dolphins have larger lungs than humans that allow them to dive for such long periods of time. However, they also have larger bodies than humans! Do they also have more efficient lungs which better oxygenate their bloodstream? Is that even a real thing?

Thanks! —Preceding unsigned comment added by 76.24.15.197 (talk) 02:33, 29 September 2008 (UTC)

Our article on whales simply states: "Whales have a unique respiratory system that lets them stay underwater for long periods of time without taking in oxygen." The dolphin article doesn't provide any more insight. -- kainaw™ 02:45, 29 September 2008 (UTC)

Dolphins aren't much bigger than humans - their lungs are probably no bigger. I suspect (without more knowledge) that their metabolism is designed such as to allow the animal to continue to function with much lower blood-oxygen levels than humans. But are dolphins really much better at this than humans? Tom Sietas can hold his breath underwater for over 15 minutes (although he cheats a bit by pre-breathing pure oxygen first - his "fair" record is a little over 10 minutes). One assumes that most humans could come close to that ability if they trained to do it since birth as dolphins are. Bottlenosed dolphins can only hold their breath for 30 minutes. So the disparity isn't as great as you might think. SteveBaker (talk) 02:57, 29 September 2008 (UTC)

I could be wrong, but don't most of the records just involve people holding their breath underwater for long periods of time? They don't involve people actually swimming or otherwise doing stuff underwater for that time and I'm not convinced the record will be as long if it did. With cetaceans though I think they maintain mostly the same level of cognitive/mental and physical functioning throughout the time of holding their breath Nil Einne (talk) 08:52, 29 September 2008 (UTC)

This is probably closest to what we want [1] 244 metres doesn't seem a great distance to me. Since time isn't a concern, it isn't mentioned but if we take double the world record World record progression 200 metres breaststroke that's only about 5 minutes. And even if the time is more then that, it would suggest the person is far from at optimal physical activity level Nil Einne (talk) 09:00, 29 September 2008 (UTC)

Actually the current record is 248m [2]. Also, I just remembered I forgot that was with fins, so they naturally should be faster then the world record set by someone with pseudofins so 5 minutes is definitely probably quite generous. Nil Einne (talk) 09:10, 29 September 2008 (UTC)

The discussion seems to be in the Cetacea article instead. It mentions higher myoglobin concentrations in muscle; myoglobin retaining oxygen better than haemoglobin. And argues that in addition, having more muscle mass (ie from larger body size) increases the oxygen storage capability because muscle stores oxygen, and because larger animals have slower metabolic rates.WikiJedits (talk) 12:54, 29 September 2008 (UTC)

Sperm_Whale#Diving_and_breathing has a bit, too, including some interesting stuff about bone-pitting due to decompression (diving). --Sean 13:57, 29 September 2008 (UTC)

One of the big differences between humans and whales is how much air is exchanged with each breath. A human will only exchange about 10% of the air in their lungs with a deep breath, while a whale will exchange almost 90%. --Carnildo (talk) 20:34, 30 September 2008 (UTC)

MATLAB question

I want to take an arbitrary length array (say, for example, like [1 2 3 4 5]) and convert that into an anonymous function with a function.

So I have a function called any_polynomial which will take an argument of such an array and return the anonymous function, which can be assigned a function handle. This is for an assignment, so I only really want a hint or two. The assignment tells us to use polyval, which is quite useless for this in my opinion, as then the anonymous function will be something like "@(x) polyval(input_array,x)". Thoughts? --M1ss1ontomars2k4 (talk) 03:56, 29 September 2008 (UTC)

I'm not sure if this is an appropriate question for the science reference desk (it being about Matlab and being homework), but I'll try to help a bit. First of all, I wonder if you haven't misinterpreted the assignment - the function polyval(p,x) evaluates a polynomial at x that has the values p(n) as its nth coefficient. I'm not sure what you mean when you say you want to "convert an array into an anonymous function". I guess what I'm saying is...the anonymous function you have described certainly does something, but it's not clear to me why you don't like it. Could you be more specific about what you want the anonymous function to do? --Bmk (talk) 04:58, 29 September 2008 (UTC)

Well, the science ref desk has "engineering" as one of the subjects that fits under it, and this class is taught by the MechE department. It doesn't have much to do with math or actual computer science, so I thought I'd find the best help here. At any rate, the questions asks us to basically take [1 2 3 4 5] and get @(x) x.^4 + 2.*x.^3 + 3.*x.^2 + 4.*x + 5. That's how I interpreted it; it actually asks for the polynomial to be returned, which I assumed meant the actual polynomial. At any rate, I've largely concluded that it would be really not worth the effort or the last whatever percentage of my grade to come up with such a ridiculous bit of code that has almost no real practical usage under any circumstances. Also, the next part of the assignment asks us to use our new function with fzero to find roots, so I explained in the comments for my code that, while the polynomial is not returned, something just as good is--it's a function that represents the polynomial and can be used with fzero. Thanks anyway! --M1ss1ontomars2k4 (talk) 06:01, 29 September 2008 (UTC)

Flatbed scanner covers

Why do flatbed scanners have covers? I have tried scanning with the cover open and with the cover closed, and it seems to make little or no difference in the quality of the scans, even when the document does not cover the entire scanning surface. —Lowellian (reply) 08:50, 29 September 2008 (UTC)

To reduce the light bouncing out and being annoying. If you're sat in a room scanning a document while working on something on your pc the last thing I could imagine wanting is a overly-bright light moving across the room from my scanner. I would have thought it also could make a difference with some documents scanning-quality but if for nothing else I would suspect it is just because the light is quite strong and it's better to try cancel it out with a simple sheet of plastic rather. Oh and it probably acts as a useful guard against damage occuring to the glass plate when the scanner isn't in use. 194.221.133.226 (talk) 08:53, 29 September 2008 (UTC)

On the contrary, I actually find it more annoying to close the cover since by not bothering with opening-and-reclosing the cover between each document, I can scan considerably faster and with more ease. However, the instruction manual seems to stress over and over again how important it is to close the cover. That's what I don't understand: is it somehow harmful in some way not to close the cover? If it isn't, why does the instruction manual stress closing the cover so much? —Lowellian (reply) 09:04, 29 September 2008 (UTC)

Aren't they at least partially there to help squash the document if it isn't flat, e.g. a book? Admitedly most dekstop scanner ones are so flimsy as to be almost worthless in that regard although they may allow you to apply more even pressure if you are holding it down. Also, I think there may be some difference if your scanning a thin single page and the scanner light is very bright Nil Einne (talk) 09:15, 29 September 2008 (UTC)

At least older scanners and copiers would copy any part of the surface not covered by the original or the cover in black, thus wasting a lot of toner. Some of the more modern ones may do some software-based cropping, but manuals change slowly (AFAIK, Apple still sends out battery care instructions that made sense three battery technologies ago). I'd also expect that there is some workplace safety issue with the bright light. It probably does not matter for people who only scan a few pages, but imagine someone doing nothing but scanning day in and day out. --Stephan Schulz (talk) 09:28, 29 September 2008 (UTC)

That doesn't happen for me. The scanner and software I'm using always properly detects the edge of the paper, with or without the cover.

But wait. "Workplace safety issue"? So is the light dangerous in any way, or is it just ordinary light? —Lowellian (reply) 19:19, 29 September 2008 (UTC)

—Lowellian (reply) 19:21, 29 September 2008 (UTC)

As mentioned, the cover holds the paper flat. Also, the cover helps with color/contrast by providing a nice white background. Without the cover closed, everything around the paper is black. Since the software is designed to look for white around the edges, finding black will cause differences in color/contrast. Newer scanners avoid this problem by having a white strip inside the machine that you don't see. I, also, have found it annoying to use the cover before. When I shut it, papers/photos move around. So, I use a small book to hold things down on the scanner. -- kainaw™ 11:13, 29 September 2008 (UTC)

A lot of people are paranoid about that light. Against all logic many people think it's some sort of dangerous radiation and insist on keeping the cover down. ("Better safe than sorry!") I imagine a scanner without a cover would not sell very well because it would make some people so nervous. Even if they knew intellectually that it was an irrational fear they'd find a reason to buy some other scanner.

Also, as everyone else has said, the light can be annoying in a dimly lit room, If you're standing there waiting for it to finish it can dazzle you and irritate your eyes, and the cover keeps things flat and stops them from blowing away if you're next to an AC vent. And finally it stops dust from accumulating on the glass while the scanner is not in use. APL (talk) 13:17, 29 September 2008 (UTC)

See Snow blindness and Over-illumination about having too much light. I had a look at the Interactive whiteboard article because they should have warnings attached about looking at the light, having them too bright and about problems with the eye no adjusting properly if the glare is peripheral giving rise to a temporary tunnel vision or even snow blindness if there is too much UV light. Dmcq (talk) 14:32, 29 September 2008 (UTC)

Copying thin paper with the lid open will make the copy/scan dark, because the light goes through the paper instead of bouncing back into the machine. I belive it will also worsen the problem of the text on the top side of the paper shining through. You might test this with a page from a newspaper. EverGreg (talk) 18:20, 29 September 2008 (UTC)

I have personal experience of someone using a scanner with the cover up, and having the person at the desk next to them get such a surprise from the sudden bright light that they poured hot coffee on their lap. There's a health-and-safety issue for you. :-) ~ mazca ^{t | c} 08:32, 30 September 2008 (UTC)

When blue planet?

Did we all think the planet earth was green until astronauts saw it from outer space? And if so, when did we realise the truth? Alan Rothwell (talk) 11:33, 29 September 2008 (UTC)

We knew that water was blueish and that the sky was blue for a long time before going into space, so it seems pretty reasonable one might have assumed "looks blue from there too". But the second part of your question is confusing: "if so" (i.e., "we all think the planet earth was green until astronauts saw it from outer space") then the answer is right there (when "astronauts saw it from outer space"). DMacks (talk) 13:13, 29 September 2008 (UTC)

Thank you, DMacks. That'll do. Regards Alan Rothwell (talk) 15:45, 29 September 2008 (UTC)

(Of course it wasn't astronauts who first saw the earth from outer space - it was people looking at photos from spy satellites. Before that, high altitude balloons and aircraft could tell that the planet would look pretty much blue from above.)

But anyway: for final proof, if you look back at colored atlasses and globes dating back hundreds of years, they always carefully painted the oceans blue - so I think it's pretty clear we expected them to look that way from a distance. Here, for example is an 1891 globe - and it's blue. SteveBaker (talk) 18:44, 29 September 2008 (UTC)

A child I know heard the rhyme "In 14 hundred and 92, Columbus sailed the ocean blue," and asked "What color was it before that?" Edison (talk) 19:36, 29 September 2008 (UTC)

The OP is quire correct: pre-1957, the general public thought the planet was green. This is clear from reading old science fiction, including thst written by the most scientifically literate writers. "The Green Hills of Earth," by Robert Hienlien, is an example. If nayone had asked one of those guys to analyze the actual color, most of them would have figured it out, but nobody asked. All of us who can remember the first color piictures from space can remember being startled by the fact that our planet is blue. -68.110.230.28 (talk) 02:02, 30 September 2008 (UTC)

That's not true! I vividly recall seeing the first color photos from orbit - and I don't recall anyone being in the slightest bit surprised. I don't think Heilein's title says much - he says the hills are green (which they pretty much are) - but he doesn't say that the entire planet is green - or indeed that his observation of green hills is from orbit. I repeat my earlier "proof" that globes dating back MANY hundreds of years have always had the oceans painted blue...why would they do that if they thought the world would look green from that perspective? SteveBaker (talk) 02:44, 30 September 2008 (UTC)

Please see this page. The first color image was apparently made in 1967. -Arch dude (talk) 04:43, 30 September 2008 (UTC)

I strongly disagree with the claim that people thought the earth was green before the space age. They certainly knew that most of the earth was ocean, and that oceans were blue. They also knew that deserts were not green. Note that Heinlein only referred to green HILLS. The blueness of pictures from space was startling only to the uninformed. Edison (talk) 05:31, 30 September 2008 (UTC)

Star Trek and plenty of other productions had shots of Earth (or Earthlike planets) seen from the Big Black; did they have green oceans? (I didn't have color television until 1981, so have no clear memory on this point.) The strikingly odd thing is that they had no clouds. —Tamfang (talk) 05:33, 30 September 2008 (UTC)

Star Trek started in 1966 - we had color photos from orbit in the late-1950's. I don't know which episode showed the earth from orbit - I'm trying to recall one that did and beginning to suspect that none of them ever did. But I'm not a committed Trekky. The decision to leave out the clouds may well have been an artistic choice. If you can't see the outlines of the continents clearly then you don't know it's earth that they're visiting...and that's a plot point that might well have overturned (ehem) Star Treks' typical "careful adherence to accurate science". :-) SteveBaker (talk) 11:24, 30 September 2008 (UTC)

I can't think of any episodes that did, but some of the films might of done. Films 1 and 4 certainly involved things in Earth orbit. --Tango (talk) 15:10, 3 October 2008 (UTC)

It would have to be "Assignment Earth"; but did I mention earthlike planets and other productions? —Tamfang (talk) 07:46, 4 October 2008 (UTC)

I seem to remember a a C.S. Lewis novel (That Hideous Strength?) in which space looks green when you go up in a rocketship. ike9898 (talk) 15:23, 1 October 2008 (UTC)

Seems to me a better thing to look at would be old coloured globes. For example Mapparium has blue oceans and while the colour of land is not intended to represent the real colour of land, I presume the oceans were made blue because that's the colour the artist felt best represents them. Image:Babsonglobe2008.jpg also has blue oceans and while the it was refurbished in Babson College#Babson Globe in 1993, I strongly suspect more note would have been made if the oceans had been repainted blue and had been green. True it was finished iin 1955 by which time perhaps there were colour photos from space but I strongly suspect it was designed before that and the artist didn't suddenly panic when he? saw photos from space with blue oceans. There's also The Daily News Globe [3]. I believed it was constructed in the 1930s [4] and while I presume it has been repainted several times, I see no evidence it ever had green oceans (although it did rotate the wrong way according to the earlier link). Even the Johannes Schöner globe appears to have blue oceans (albeit a bit light but that might be a matter of fading colours of the availability of pigments). All in all, I don't see any reason to presume that most people would make globes (and of course maps) with blue oceans but everyone thought when you went to space the earth would look green Nil Einne (talk) 12:37, 5 October 2008 (UTC)

Interesting note, related to Ike's comment: I'm reading We (written c. 1920), in which the author speaks of "the blue, silent, interplanetary space". Nyttend (talk) 14:18, 6 October 2008 (UTC)

Long time later I realise SB already said the same thing earlier and I didn't notice, oops Nil Einne (talk) 10:19, 25 December 2009 (UTC)

Digestive System

How does the Digestive system help the circulatory system function properly —Preceding unsigned comment added by 136.229.5.40 (talk) 12:11, 29 September 2008 (UTC)

Sounds like a homework question to me. Ask somewhere else. PS: the heart needs energy to function, so where does the energy come from? Food. :) 31306D696E6E69636B6D (talk) 13:25, 29 September 2008 (UTC)

Well, yes, but it sounds like a really bad homework question. Everyone knows that the rest of the body is just the liver's way of making other livers. - Nunh-huh 13:47, 29 September 2008 (UTC)

this is no place for bilious comments --Scray (talk) 02:59, 30 September 2008 (UTC)

DACs in CD players

I have just bought a new CD player with A delta-sigma converter that uses a switched capacitor DAC. These are sometimes called bit stream or 1 bit DACs.

I found it sounds quite different (warmer, richer etc) from my previous CD player which used the TDA 1514 DAC chip and associated digital filter chip. Can anyone point me to articles discussing why the two types of DAC sound so different?--GreenSpigot (talk) 13:46, 29 September 2008 (UTC)

May I suggest a double blind test to establish that the effect is real? If it is, I would expect differences in the quality and calibration of the pre-amp to affect the the sound much more than the DAC. Can you ensure that all other variables are eliminated? --Stephan Schulz (talk) 14:46, 29 September 2008 (UTC)

I dont think I need to do a DBT to know that the difference is remarkably obvious to my ears. I was totally surprised as I was not expecting to hear any difference whatsoever. So what could the possible reasons be for the unmistakable difference?--GreenSpigot (talk) 17:03, 29 September 2008 (UTC)

You'd be surprised at how easier it is for people to hear a difference that isn't there, even whey they aren't outwardly expecting it. Nil Einne (talk) 18:12, 29 September 2008 (UTC)

Unless one or the other was malfunctioning, there should not be any obvious difference, since it is such high fidelity, with wide frequency response, low noise level, wide dynamic range, and freedom from clicks, rumble, scratches, hiss, wow and flutter which plagued stereo listeners in the analog age. Edison (talk) 19:38, 29 September 2008 (UTC)

I agree. There is a deep problem with serious audiophiles. In the days of analog equipment, they had a lot of fun debating the pro's and cons of various turntables, amps, etc - tricking out turntables with different cartridges, endlessly arguing over the fidelity of vacuum tubes versus transistors. Then we got digital equipment, and now, even a $20 CD player can produce audio significantly better than the human ear can resolve. This has resulted in a lot of people with no hobby. The unfortunate consequence is people spending hundreds of dollars on gold plated nitrogen-injected digital audio cables(!) and other ridiculous junk. This reviewer says that his $300 (!) digital audio cable "The brightness is no longer a problem and now I get the chance to hear the seperation of the instruments and the kind of bass that is tight as a sludge hammer." -- well, I'm surprised he's looking for his audio to sound like a sludge hammer - but for 100% certain, a DIGITAL signal isn't going to sound any different whatever on a $1 cable or on a $300 cable...that's the entire point of digital signals. If someone can convince themselves that a cable (of all things) could possibly make any difference whatever (let alone a $300 difference!) then I'm equally sure that our OP isn't really hearing a difference. An honest double-blind test is undoubtedly called for. SteveBaker (talk) 23:10, 29 September 2008 (UTC)

Ok thanks for the opinion all. Now can someone point me to a site that discusses why there might be a difference?--GreenSpigot (talk) 13:43, 30 September 2008 (UTC)

[5] says a "16-bit/44.1-kHz CD standard" bottleneck is not detectable in double blind testing, compared to higher resolution players. See also High fidelity. Edison (talk) 18:55, 30 September 2008 (UTC)

I think we already have. As remarked above, presuming there is really a difference, it's probably not in the DAC but in something else other the DAC component. You haven't explained whether everything else is the same in your test setup. It seems rather unlikely to me it would be given that it's unlikely everything after the DAC is the same. Even presuming the speakers are the same, there's still the entire analog pathway likely including amplifiers and perhaps equalisers of the CD player you haven't ruled out. And these would be rather difficult to rule out, you'd probably need to modify the player such that you take the signal directly from the DAC output of each player and feed it into a seperate amplifier. To put it a different way, let's say I compare a piece of KFC chicken to a piece of chicken from a gourmet restaurant which is organically raised. It would be silly of me to ask from this "why does organically grown chicken taste better" Nil Einne (talk) 17:44, 2 October 2008 (UTC)

Everything else is exactly the same. I just unplugged my old CD player and inserted the new one. Believe me, Im as skeptical as the next man, but I can definitely hear a (positive) difference! BTW Im a musician also and used to using my ears in a very critical manner.--GreenSpigot (talk) 00:09, 3 October 2008 (UTC)

As I've already said, it's not possible everything else is the same unless you're really trying to convince me that your CD player really feeds the analog output of the DAC directly to your hifi system? which I highly doubt. Both systems almost definitely do some processing to the analog signal before it is output to your hifi system. (I presume your are outputting to your hifi system and not trying to claim everything is the same when you are outputting directly from the CD player to speakers). Heck for all we know, either player may process the signal in the digital stage as well. Have you ruled this out? Nil Einne (talk) 12:43, 5 October 2008 (UTC)

I know on my PS3, switching from Bitstream to LinearPCM output makes music sounds slightly *louder* when using the optical out. Overall loudness can change your perception how the music sounds. (I know in my home theater DTS always sounds "better" than Dolby Digital only because it's louder) How is the signal getting out of your CD player? If it's analog, I'd have a hard time believing there's any difference.

Is a 10% reduction of emissions reasonable?

In Australia, the Federal government's top climate adviser, Ross Garnaut, says that in 2020 a reduction of pollution levels by 10% of 2000 levels is a realistic target. WWF Australia chief executive, Greg Bourne, says that a 20% reduction is better.

http://news.smh.com.au/national/garnaut-wants-10-emissions-cut-by-2020-20080905-4a2d.html

I'm confused. I know little about global warming other than it is real. Does anybody have an argument or some short sharp facts to back up the claim that a larger than 10% reduction in pollution would be better for Australia?

What's a reasonable, realistic, economically responsible target to reduce pollution levels to?

Similarly to the above question, what about targets for the rest of the world? ExitRight (talk) 14:52, 29 September 2008 (UTC)

You may find Kyoto Protocol interesting. The UK has set a target of 60% reduction from 1990 levels by 2050 and seems to be on track, so large reductions are possible. Whether Australia can manage a 20% reduction would depend on what's happened in the last 8 years since we're nearly half way through the given time period. --Tango (talk) 14:59, 29 September 2008 (UTC)

In terms of what's beneficial - a 99.99% reduction would be beneficial from the point of view of avoiding global warming - but the larger the reduction you make, the more it costs the country to do it. Hence there is a balance between benefits to the atmosphere and detriments to the economy. Precisely where that balance is turns out to be almost impossible to calculate. Precisely how much (in monetary terms) is the extinction of the polar bear worth? We can't put a number on that. We can say how much it's going to cost to rebuild cities that get flooded by rising sea levels - and perhaps we can nail an estimate on the cost of crop losses...but because we don't know how much sea level rise there will be - we can't know. The cost to the economy also depends on how you make that reduction. If you buy technology that's already available, it costs some amount - if you throw a lot of cash into research and your country becomes not only a consumer of anti-global-warming technology but also a PRODUCER of it - then it's possible that tougher standards might actually IMPROVE the state of your economy. If you make CO2 reductions by cutting fuel consumption - you'll save money - if you do it by building damned great "carbon sequestration" plants and continue to burn carbon-based fuels - then it's going to cost you a small fortune. A lot depends too on what other countries do. If Australia makes a 20% reduction at huge expense to the taxpayer - but nobody else helps out - and Australian coastal cities get drowned and your fields turn to desert anyway - then that was a waste of money. But if everyone thinks that way - it's a self-fulfilling prophesy.

It's all very difficult - and that's precisely why we have to have the Kyoto accord (or something very much like it) - it's supposed to set standards that we're all going to work hard to meet so that we don't have this kind of debate anymore. However, since the US screwed it up by refusing to ratify it...we're back to arguing about it all over again. SteveBaker (talk) 18:35, 29 September 2008 (UTC)

heating element

what do we mean by buonet heating element. types of heating elements —Preceding unsigned comment added by 117.195.175.156 (talk) 15:08, 29 September 2008 (UTC)

Do you mean bayonet, such as http://www.secowarwick.com/aftermar/RN311-2.pdf? -- SGBailey (talk) 15:26, 29 September 2008 (UTC)

the details of callus formation

How *exactly* do calluses form? The more details the better. Is there some form of callus formation factor that gets released with repeated bruising or pressure that prevents dead skin from shedding and speeds cell death to form that protective layer? Seeing that it often occurs within mere hours of tedious work, it almost seems to me that there are some active factors that get secreted. Googling has been pretty frustrating, because they keep telling you it's the body's natural defence but they tell you nothing about the biology of callus formation. How far back up the phylogenetic tree does this reaction go? I'm also finding it hard to find any useful papers on callus formation, since they all seem to deal with various genetic transformation techniques, etc. John Riemann Soong (talk) 16:10, 29 September 2008 (UTC)

Our Callus article does not answer your question. If you do find the answer, please update the article. -68.110.230.28 (talk) 01:49, 30 September 2008 (UTC)

Also Keratin#Cornification - but it still doesn't elucidate the biomechanism. I would think it is due either to external factors released on death of epithelial (skin) cells, or internal factors generated by deformation of the cytoskeleton in living skin cells. However, searching the pathetically small literature I can access has turned up nothing good. Sorry. Franamax (talk) 08:35, 30 September 2008 (UTC)

reg.heavy duty trailers

dear sir, 'iwish to have the address of an automobile manufacturer in austrlia who r making long and heavy duty trailers containing more than 100 tyres and controlled by electronic sensors and devices. please give information about it.

thanking u, s.r —Preceding unsigned comment added by Rmohan14 (talk • contribs) 16:24, 29 September 2008 (UTC)

Jebus, 100 tyres? that sounds like an awful lot. Not that your question has anything to do with science... Why don't you try contacting the Australian commercial vehicles department or something? Edit: i guess you're looking for something like this [6] (not Australian) although not even all those beasts appear to have 100 tyres Nil Einne (talk) 18:26, 29 September 2008 (UTC)

I believe the concept in Australia is called Road train and according to our article, the world record for the longest road train is held by Marleys Transport with 45 trailers. It does not say how many wheels but its got to be at least 45x4 and probably a lot more. There are lots of links at the bottom of the article which may help you. SpinningSpark 19:04, 29 September 2008 (UTC)

I assumed we were talking about those hydraulic-drive platforms that they use for things like moving entire buildings and such. They do have maybe 100 tyres and are driven using fancy computer stuff to keep them dead level and to allow all 100 wheels to steer. SteveBaker (talk) 21:16, 29 September 2008 (UTC)

High and low biotechnology

What exactly are "high" and "low" biotechnology? I've seen my professor use these words in my biotechnology class, but since I don't have class for a few days, I figured I should ask here instead of looking like a moron in class. Nishkid64 _{(Make articles, not wikidrama)} 16:25, 29 September 2008 (UTC)

I don't know what they mean, and I think we can assume no one else in your class does, either, so far from looking like a moron, you'll look like a hero for being brave enough to ask! --Sean 19:10, 29 September 2008 (UTC)

I would speculate that "high" biotechnology is the cutting-edge stuff where you do precise gene insertions using viral vectors and such-like (ignoring the indiscriminate nature of integrase targeting); and "low" biotechnology is the old-fashioned stuff like using mutagens and plant breeding, then trawling through the results. Let me know if I score better than the moron. :) Franamax (talk) 07:42, 30 September 2008 (UTC)

Or, depending on context, it could be the difference between, say, what we today call genetic engineering and what is usually called selective breeding (e.g. pre-rDNA techniques). --98.217.8.46 (talk) 15:05, 30 September 2008 (UTC)

Lipids

Are lipids considered polymers? Or are they simply a backbone with the "head"? --MrE1 (talk) 21:27, 29 September 2008 (UTC)

Lipid monomers (like palmitate) can be part of polymers, like cutin, cutan, and suberin. These water-insoluble substances are not yet as well characterized as many other more-familiar polymers. --Scray (talk) 02:56, 30 September 2008 (UTC)

Lipids are not polymers because they are not made of a repeating unit cell. And I think you mean "fatty acids" and not necessarily lipids, because lipids refers to all biological material that is soluble in non-polar solvents, and while it does include the "backbone and head" structure you find in a fatty acid, the class of lipids ALSO includes the steroids, like for example cholesterol. Look at the article lipid for some example structures of common lipids. Proteins and nucleic acids could sometimes be considered biological polymers, however not in the strictest sense, since the unit cells are not identical, but merely drawn from a finite set of possible unit cells (about 20 for proteins, and 4 for DNA for example). Polysaccharides are the closest thing to true biological polymers, since they do contain long chains of identical monomers. There are some biological molecules that are made of lipid monomer cells, but that's still not what you are asking above... --Jayron32.talk.contribs 03:00, 30 September 2008 (UTC)

So what would a lipid membrane be called? It's not a polymer, because the units don't form covalent bonds or cross-link, but it does minimize free energy. Is there a generic term for such a self-assembling structure? Franamax (talk) 07:37, 30 September 2008 (UTC)

Interesting question. Does emulsion come close (doesn't seem to require a particular scale)? --Scray (talk) 02:48, 1 October 2008 (UTC)

Yes, that does come close, since an aqeuous (or other polar liquid) phase is required for the membrane to assemble. I'd previously considered and discarded colloid (which is why I asked here) - however looking again, I suppose it would be a colloid, and possibly an emulsion. Thanks! Franamax (talk) 03:53, 1 October 2008 (UTC)

Axully, emulsion doesn't really work either, since an emulsion is just a form of supersaturated solution; the substances want to separate, but the activation energy for the separation is too great. In a membrane, part of the membrane is actually water soluble, and part is not. The actual term for a membrane is an amphiphile or amphipathetic substance. That just means a substance that has different parts which are soluble in different media. Surfactants like soaps and detergents are also amphiphiles. --Jayron32.talk.contribs 04:25, 1 October 2008 (UTC)

I'm pretty sure that amphiphile would refer to the molecule (e.g. a phospholipid), not the structure (i.e. a membrane). So, I don't think that's an improvement on emulsion or colloid. --Scray (talk) 04:45, 1 October 2008 (UTC)

Well, in that case, the structure IS a membrane. There is no finer categorization than that. Emulsions and colloids and suspensions are entirely different organizations of substances. A membrane is, well, a membrane... Its easy to define, and unique from other categories. --Jayron32.talk.contribs 04:59, 1 October 2008 (UTC)

Note Franamax's question above - the question was how to categorize a membrane. I see nothing in the definition of emulsion that excludes a membrane. --Scray (talk) 05:08, 1 October 2008 (UTC)

Calling a membrane an emulsion is kind of like asking what sort of meat an apple is; membranes and emulsions are fundementally different on an organizational level. Membranes are highly organized structures; emulsions, like all suspensions, are essentially random. Once you remove the structure from the membrane, then you don't have a membrane anymore, as you yourself essentially pointed out; you may have a collection of membrane molecules, but that isn't the same thing. --Jayron32.talk.contribs 05:15, 1 October 2008 (UTC)

A cell membrane is a highly-organized structure, but a simple lipid membrane is not highly-organized at all, it spontaneously self-assembles and has a uniform composition. Franamax (talk) 05:22, 1 October 2008 (UTC)

(e/c) Not to categorize a generic "membrane" though - Saran wrap is a membrane (or can be). A lipid membrane has the property that it self-assembles in order to minimize free energy (or at least I think that's what it does). So similar to the way amino acids can polymerize and form a protein which adopts a structural conformation that minimizes free energy, what would be the term for a lipid assembly doing the same thing? A micelle does it too. Franamax (talk) 05:19, 1 October 2008 (UTC)

Yeah, but an emulsion does not self-assemble in that way. The whole point is, that self-assembled "little heads pointing down and little tails pointing up" structure of a lipid membrane is not an emulsion. Its a lipid membrane. I'm not sure you can categorize it as an emulsion, since the emulsion is the exact opposite. In a lipid membrane, you have separation of the lipid molecules from the solvent. In an emulsion, the molecules are dispersed within the solvent. Totally different. --Jayron32.talk.contribs 05:33, 1 October 2008 (UTC)

If the molecules were individually dispersed, they would be in solution. Instead, an emulsion is a dispersion containing aggregates of the dispersed liquid. A lipid membrane could be described as a self-assembling aggregation of lipid molecules. As Franamax pointed out, micelle is very close, too. --Scray (talk) 05:39, 1 October 2008 (UTC)

Yes, but in an emulsion, the aggregates stop aggregating. They are essentially stable aggregates as is, and repain dispersed. Taking the energy arguement; the emulsion remains not because it is a lower energy state than the seperate substances (it isn't; the seperated substances would have a lower free energy), however, the emulsion state is at a local energy minima; sort of like a crater on top of a mountain... But I'm losing track of this arguement. I think I need to get to bed. --Jayron32.talk.contribs 05:46, 1 October 2008 (UTC)

I think we may be stuck with "amphiphilic bilayer aggregate" or something clunky like that. :( Franamax (talk) 19:29, 1 October 2008 (UTC)

Mate selection in gulls

What criteria does a female herring gull (or the male, if he's the one that picks and chooses in this species - I don't actually know which way round it is) use when selecting a desirable mate from a lineup of likely candidates? From my observations of these birds, their mating behaviour in general is very subtle - the male and the female just seem to start 'hanging out' together after no discernible preamble, occasionally calling out or head-flicking in unison. So, does anyone know what physical features and behavioural attributes are considered desirable to the opposite sex in this species? As I say, I've been watching gulls for years and I have absolutely no idea... --Kurt Shaped Box (talk) 21:47, 29 September 2008 (UTC)

I guess it has to be features of their appearance and behaviour that define them as herring gulls within the gull family. If we assume that a while back there was one gull ancestor then successive generations, for reasons unknown to us, started selecting slightly different gulls that further selected these features until eventually a new species developed, much like the development of the various species of birds of paradise. I have no idea what makes a herring gull different from the rest of the gulls, perhaps you can help. Richard Avery (talk) 17:20, 30 September 2008 (UTC)

I presume they cue into many things. Symmetry is very important as a measure of fitness. And many seabird use voice to judge quality. Sabine's Sunbird talk 21:33, 30 September 2008 (UTC)

Do you have any idea if the female fights with the male as part of courtship in order to test his strength? I remember reading that somewhere (yeah, I know...). --Kurt Shaped Box (talk) 17:41, 1 October 2008 (UTC)

dogs kicking back after defecation

Why do dogs sometimes, after defecation, step aside and kick back scratching the ground, several times? --Halcatalyst (talk) 22:23, 29 September 2008 (UTC)

I suspect they are responding to some ancient wolfish instinct to bury their poop in order to mask their presence when hunting. However, being dogs, they've kinda forgotten why and only half-heartedly bother. SteveBaker (talk) 22:53, 29 September 2008 (UTC)

I know Steve well enough to know what he means (and it isn't what he typed). We can't claim wolves know why they bury their poop (or that they even know they are doing it). It is an evolutionary trait that increases the chance of survival. As such, animals that evolved from wolves carry the same traits - but possibly in a much weaker form. This is just one of those cases where it is easier to say "Wolves do X because of Y" or (worse) "Evolution made wolves do X." Applying human reasoning to animals leads to false statements. Applying human reasoning to evolution (as though it were an intelligent being) leads to false statements. But, it is much easier to treat everything as human (ie: My keyboard is trying to piss me off with this stupid sticky left shift key!) -- kainaw™ 23:17, 29 September 2008 (UTC)

Anthropomorphism Mac Davis (talk) 23:41, 29 September 2008 (UTC)

I've also heard the alternative version that dogs do this to spread their feaces to mark their territory in tyhe same way that they urinate on every tree in sight. 190.244.186.234 (talk) 23:46, 29 September 2008 (UTC)

Well, yes. To phrase it in a more concise manner: It seems likely that wolves have an instinct to bury their poop. Domesticated dogs do not need that evolutionary adaptation and are therefore losing the instinct...but it's not entirely gone yet. It's possible that the original instinct is to spread the stuff rather than bury it. It's hard to know for sure. From what I've observed in my dogs, they are definitely trying to bury it - but they do indeed give up after a couple of half-hearted scrapes. SteveBaker (talk) 02:38, 30 September 2008 (UTC)

Well actually y'all have no idea what goes on in dogs' or wolves' heads - maybe they all deductively reason out the pros and cons of poop-burial, and it's intelligence that was evolved. But that's just me being a trollish animal-rights person. --Bmk (talk) 06:28, 30 September 2008 (UTC)

Cats do carefully bury their poo, or at least try to. That's the whole point of kitty-litter, isn't it? Oop, silly me, carrying a cat into a dog conversation! :) From my observations, dogs pooping in soft soil, and female dogs, will more effectively use the kicking/scraping motion to bury their scat. All this leads me to believe that (well-reasoned or not on the dog's part) it's an action intended to accomplish the purpose of burial. Coyotes however leave their droppings right in the middle of the people-paths in the local (large) parks - again, I believe this action to be quite intentional. Franamax (talk) 07:29, 30 September 2008 (UTC)

It's hard to imagine it's a carefully reasoned behavior. If the dog were carefully considering both the need and it's ability to bury or not depending on soil conditions, terratorial boundary pushing, etc - then why would there be the half-hearted scrape? If this were consciously reasoned behavior then wouldn't it be all-or-nothing? That alone makes me believe it has to be instinctual. SteveBaker (talk) 11:09, 30 September 2008 (UTC)

If a dog/wolf was using rational deduction to decide that it was best to bury or not bury, then a dog in his own backyard wouldn't need to worry about predators or territory. A wolf in a zoo wouldn't need to worry about predators or territory. So, they would decide it was better just to poop in the corner. -- kainaw™ 15:21, 30 September 2008 (UTC)

You're assuming they understand their situation correctly. Rational deduction from an incorrect starting point can result in an incorrect conclusion. --Tango (talk) 00:15, 1 October 2008 (UTC)

• Has anybody noticed whether both males and females do it? Also, how often? My dog is male and does it maybe 10% of the time. --Halcatalyst (talk) 02:48, 2 October 2008 (UTC)

September 30

Photosynthetic Animal

Hey. I'm trying to remember a certain animal that I think I recall seeing on a nature documentary, it was like, some kind of newt or something. But its most remarkable feature was that it shared a symbiotic relationship with algae that lived just underneath its skin, the algae would absorb the sunlight and effectively create food for the newt to live off of. Does anyone have an idea of what animal I'm thinking of? 62.49.131.66 (talk) 00:56, 30 September 2008 (UTC)

Elysia viridis ? It's a sea slug and I don't think it assimilates the intact algae, only chloroplasts. I've never heard of a "solar-powered newt" so to speak, but I'd sure love to know if there exists one :) --Dr Dima (talk) 01:48, 30 September 2008 (UTC)

Or possibly the acoelan flatworm Convoluta roscoffensis. Our article doesn't explain it very well, but one of those other sites mentions symbiotic algae. 'Pedians to the barricades - we need references dammit! Franamax (talk) 06:31, 30 September 2008 (UTC)

Coral, specifically tropical hard corals used to make tropical reefs. I don't know of other animals, but I guess there could be. Sabine's Sunbird talk 19:03, 30 September 2008 (UTC)

Power consumption vs. hour of day

I want to know, in a typical home, what hours of the day tend to show peak electrical power usage, what hours of the day show minimal electrical power usage, and the relative differences throughout the day. Basically, I'd like to see a graph of power consumption vs. hour of day in a typical home in a city. —Lowellian (reply) 02:44, 30 September 2008 (UTC)

It is difficult to have a typical home by hour of day. Most power consumption occurs when people are at home. So, you have to start by generalizing to the point of being incorrect by deciding which hours of the day people are at home (and awake) in a "typical" home. -- kainaw™ 04:43, 30 September 2008 (UTC)

Here's some articles I found through a google search: [7]. About 1/4 of the way down the page is a graph of the power consumption over a single winter day in Humbolt County, California. This one:[8] shows the last 24 hours power consumption in Ontario, Canada. This one: [9] (see figure 2) shows an average graph by season, though I don't see that one's methodology. There's 3 for ya. Good luck! --Jayron32.talk.contribs 04:55, 30 September 2008 (UTC)

The power consumption through the day will vary by season and by region. See Load profile. A Google Book search shows lots of books which discuss such load profiles or load curves. Your own utility doubtless has data on residential load curves which they might provide you. Edison (talk) 05:28, 30 September 2008 (UTC)

(ec)I wrote a paper on the energy saving benefits of daylight savings time (there isn't one, by the way), and the timing of people's power usage was huge part of it. Suffice to say that it varies with climate, season, and culture. Some people need to heat their houses all night and some need to air condition it all day. I don't know what you are using it for, but you might be interested to know that industrial power consumption is more than 3 times larger than domestic consumption. Plasticup ^T/C 05:29, 30 September 2008 (UTC)

Off-topic, but since you mention daylight-saving time - now that the powers-that-be have decided (solely on energy-saving grounds mind you) to extend DST to cover more than half the year, shouldn't we just call it "Time"? The thing we do in winter should now be called "Daylight Deficit Time". Franamax (talk) 06:19, 30 September 2008 (UTC)

While we're discussing it, in 1973 Daylight Savings Time was observed all year! Plasticup ^T/C 14:31, 1 October 2008 (UTC)

Tyvek house wrap

I live in central Ontario, Canada. My house is about 30 years old. It is a two story with brick on the first level and siding on the second. My question is this: is it worth the effort and expense to remove the siding, wrap and seal the second level with Tyvek and then put the siding back on? Modern houses are wraped in Tyvek but I don't believe that they were 30 years ago. Thoughts? —Preceding unsigned comment added by 209.161.212.209 (talk) 04:27, 30 September 2008 (UTC)

If it were my house, I would not do it. I question what the payback period would be for such a retrofit. Edison (talk) 05:23, 30 September 2008 (UTC)

I wonder if there are tax deductions for improving the insulation in your house. That might be something to consider. Plasticup ^T/C 05:30, 30 September 2008 (UTC)

Tyvek (TM) forms an air-tight/water-proof barrier, so the question is whether your existing siding is inadequate to form the air-seal. Call Ontario Hydro (Hydro One now, or your local electric utility) and ask if they still have the cut-rate efficiency assessment programs. Whichever heating supplier you have (such as Enbridge) is a good starting point too. If you're going to pull off the siding, you should also be thinking about putting on 40mm or 50mm of that blue styrofoam insulation. (You'll need 2" corner-caps if you do that though) Franamax (talk) 05:42, 30 September 2008 (UTC)

And rather than strike the above, I'll note instead that if it's an Ontario house, 30 years old, it will already have an air/moisture-seal - that black wax-coated paper you used to always see on houses as they were being built, before Tyvek figured out how to print their brand name in big letters across the whole sheet. If you have no moisture seal at all, you may have a problem - pry up a bit of the siding and look for the black paper. Franamax (talk) 05:51, 30 September 2008 (UTC)

My neighour just added another layer of insulated cladding on the outside of their wall. However they complained about the heat of the sun in summer, so they just altered the west facing wall. Once it was coated and painted it looked just the same as before. Graeme Bartlett (talk) 21:12, 30 September 2008 (UTC)

It can be worth doing the Tyvek if your already planning on replacing the sideing. Otherwise... unless your having water intrusion problems (mold, etc) the cost is not worth it. ---J.S (T/C/WRE) 07:36, 2 October 2008 (UTC)

Charging device: sometimes it works

I have a charging device (for my laptop) that when it's plugged, sometimes works and sometimes not. Chances are 1/10 that it will work. I ruled out a bad contact, since I am not shaking or moving the charging device itself, only plugging the cable to it, and I used two different cables with the same charging device.

Why does it sometimes work?

80.58.205.37 (talk) 10:15, 30 September 2008 (UTC)

It could be that heat, in the cable or the transformer, at some point causes the internal connections to move apart. I had a similar problem with a poorly-connected cable running into the circuit breaker box in my house. Only after a given appliance had been running for a while did heat build up, causing the circuit breaker to trip. The fix involved having an electrician redo the connection. Not that you asked, but with such unreliable performance, I'd be inclined to buy a new charging device. But then, I have two power cord for my laptop -- one stays at my desk, the other stays in the laptop's travel bag, so I don't have to remove and reconnect the desk cord all the time. --- OtherDave (talk) 10:43, 30 September 2008 (UTC)

Oh, that brings me to the idea that perhaps it is the heat in my case. When I connect the power cord a couple of times, the charging device is cold. After it warmed up, it starts to work. I going to test it more thoroughly though. 80.58.205.37 (talk) 10:59, 30 September 2008 (UTC)

And to be thorough, you need to try charging a different laptop with your charger and cables. How do you know yet that it's not a bad connection within the laptop? Franamax (talk) 11:04, 30 September 2008 (UTC)

Because the charger has a led indicating if it is working.80.58.205.37 (talk) 11:21, 30 September 2008 (UTC)

OK, now exactly what do you mean by "it is working"? Do you mean that if the LED is on, it will definitely always charge the laptop? (Sorry, troubleshooting usually has to go one step at a time) Franamax (talk) 12:11, 30 September 2008 (UTC)

Yes, if the LED is on, the charger is charging the battery. Mr.K. (talk) 15:20, 30 September 2008 (UTC)

It could still be in the laptop though. Some batteries have built-in temperature sensors that detect when the battery is overheating and turn off the charging voltage until they cool off a bit. If your battery temperature sensor was intermittant - then that could account for the behaviour. You've really got to do this by a process of elimination. If you know someone with a similar type of laptop the trying the "known good" charger on the "iffy" laptop will either eliminate or implicate the charger. Then, if you establish that the charger is OK (eg, if it successfully charges a different laptop) then you can try exchanging batteries and see whether the fault "follows" the battery or "stays" with the laptop. That'll narrow things down still further. If you can't find someone else with a similar machine then you have to do it the expensive way - buy a new charger - if that doesn't help, buy a new battery - if that doesn't help - junk the laptop or live with the problem! SteveBaker (talk) 19:21, 30 September 2008 (UTC)

In the meantime, I am pretty convinced that the problem lays in the charger. My laptop doesn't receive any power when the LED of the charger is off. It doesn't matter if the battery is being charged or not. I have tested several times, and the charger doesn't work when it is cold. I always have to wait a couple of minutes until it has warmed up a little and is able to deliver power. I am going to live with the problem for a while and buy a new one at the end of the month. Mr.K. (talk) 09:16, 1 October 2008 (UTC)

Methane Clathrates are melting...NOW!

Oh-oh...it looks like the end of the world just started (something to take your mind off of the global economic meltdown at least):

• http://www.independent.co.uk/environment/climate-change/exclusive-the-methane-time-bomb-938932.html
• http://www.independent.co.uk/news/science/hundreds-of-methane-plumes-discovered-941456.html

We've talked about the hypothetical possibility of deep-ocean Methane Clathrates melting being the "tipping point" beyond which it might be impossible to prevent 'runaway' global warming. The two reports above indicate pretty clearly that we just hit that point.

I'm puzzled though - why there? You'd think the arctic waters would be coldest for longest - how come we aren't seeing this happening in more southerly latitudes first? If methane is a 20x worse greenhouse gas than CO2 - should we not set light to these methane plumes? (Is that even possible?)

SteveBaker (talk) 11:02, 30 September 2008 (UTC)

Bah! Peer review? Correlation of atmospheric temperature rise with sea-bottom temperature rise with clathrate release? Causative conclusion or always-been-doing-that? And they're only talking megatonnes of CH4, even at Ce20 - call me when you get a gigatonne. :(

I'll watch my favourite mag closely to see their interpretation. As you say, seems strange to see this. I believe there's an increased flux of freshwater into the Arctic basin, but I would think that would stratify the waters and keep a cold layer below. Regardless of this result, the concerns remain, including potential initiating methane production from soil. Sticking in a big straw and striking a match at the top might not be such a bad idea though... Franamax (talk) 11:27, 30 September 2008 (UTC)

I say we burn it all as it comes out of the ground. 96.242.34.226 (talk) 17:56, 30 September 2008 (UTC)

Well, it's coming out of the deepest parts of the ocean - not the ground. Burning it would convert it to CO2 and water - and the CO2 would still cause an increase in the greenhouse effect - just not as bad as methane. But I'm not sure whether the methane that's appearing in this case is sufficiently concentrated in one place to burn. It could be argued that we should mine the clathrate deposits and use them as fuel as a way to stop the raw methane from making it into the atmosphere - but that's really an admission of defeat, the goal is supposed to be to keep the planet cool enough that they don't melt in the first place. I'm horrified to see that this doomesday scenario already starting to happen. I had imagined that this would be 100 years from now. SteveBaker (talk) 13:08, 1 October 2008 (UTC)

Actually, burning Methane (CH₄) instead of coal (dirty C) or even oil is producing much less carbon dioxide per unit of energy released. So using the clathrates before they melt would be a double gain. Of course, knowing us, we would probably burn both the methane and the coal... --Stephan Schulz (talk) 15:20, 1 October 2008 (UTC)

There is also the teeny-tiny catch in that we have no clue how to mine stuff that's that cold - that deep under the deepest oceans. Learning out how to mine the stuff before it's all gone may be an impossibility anyway. SteveBaker (talk) 01:19, 2 October 2008 (UTC)

Methan Clathrates form under particular conditions, which include "cold enough". But that just means they form deeper in lower latitudes. They will be released not if surface water reaches a certain temperature, but if the water at the reservoir reaches a certain temperature. Arctic waters have warmed most, so the reservoirs in the Arctic melt first. This is, of course, only a first and preliminary popular press report, so it's hard to assess the actual impact. But I'm getting the feeling that we might be on our way to experimentally solve the Fermi paradox. --Stephan Schulz (talk) 18:24, 30 September 2008 (UTC)

Road-safety for trucks

You know the reverse parking sensors you get on some cars? The ones that beep and help you park. I guess they work based on radar on infra-red technology. My question is...Is there anything to stop placing these along the side of trucks trailers and having a light-panel on the dashboard/somewhere that lights-up while vehicles are along-side trucks? This would reduce the risk of side-swiping/trucks pushing vehicles off the road overtaking (or whatever) when not able to see there is a vehicle along-side them? It was just an idea I had when I watched a show about how little visibility there is on trucks and thought...why not employ the same technology but instead of beeping it could light up to show when a vehicle is within X-metres of the side of the truck and thus help prevent accidents. Or is the technology totally unworkable when moving at say 50mph with vehicles alongside that are doing the same? 194.221.133.226 (talk) 11:09, 30 September 2008 (UTC)

Well, in the auto industry, "safety gadgets" have extremely high litigation costs. The first time that one allegedly fails, its a contingency fee lawsuit waiting to happen. Many times, the cost of defending a lawsuit is more expensive than just settling the lawsuit. There are so many car crashes each year, that its a bad business plan thus the entrepreneur would never get venture capital. Sentriclecub (talk) 11:21, 30 September 2008 (UTC)

They'd go off everytime the truck drove close to the concrete barriers at the sides of the road. But I suppose they could be turned on only when the driver switches on his turn signal or something. SteveBaker (talk) 13:18, 30 September 2008 (UTC)

well in my head they would just light-up so if you were driving close to a wall/barrier it would be lit up on the appropriate side. Is there any reason that the technology wouldn't work at the speeds mentioned? —Preceding unsigned comment added by 194.221.133.226 (talk) 13:49, 30 September 2008 (UTC)

So long as it's not using an acoustic (sonar) type of technology, speed ought not to matter - but the idea of having a whole bunch of lights flashing in the cab all the time there is a wall to the side of the truck would drive most people crazy! Also, once a warning light has flashed a few bazillion times, you'd start to ignore it so it wouldn't help when it actually mattered. But as I said - if it only turned on the hazard lights when you hit your turn signal in that direction, then it should be OK. You wouldn't often be indicating (say) a left turn when you're in the left lane on the freeway with concrete lane dividers triggering the sensors. SteveBaker (talk) 19:11, 30 September 2008 (UTC)

This what 194.221.133.226 (talk · contribs) asks about is undergoing very active development, particularly in Europe, for passenger and heavy vehicles. Front, rear, and lateral proximity-alert systems are being tested and implemented, as well as more integrated setups that can actually intervene on the driver's behalf to avoid a collision, lessen the severity of a collision, and/or lessen the consequences of a collision by means of steering assistance, braking assistance, and even acceleration assistance. These systems are variously based on cameras (increasingly using tiny camera-on-chip systems) or on ultrasonic, radar, or lidar sensors. All of these systems fall under the category of driver assistance systems. I haven't (yet) looked to see what articles we might have on related topics, or what condition they're in. —Scheinwerfermann (talk) 13:31, 1 October 2008 (UTC)

This exact sort of product is available on Volvo motorcars (and likely, more brands in the near future).

Atlant (talk) 21:28, 1 October 2008 (UTC)

Is Thrust a usual vector? (i.e. same properties of all vectors I have learned so far?)

I checked on that page, and it is a force. All forces are vectors, thus all white horses are horses right? Also, is this ^{${\overrightarrow {T}}$} the symbol for thrust(in n>1 dimensions)? I'll make some minor improvement to the article asap. Or is ^{${\overrightarrow {F}}_{thr}$}

Secondly, the symbol for impulse. My book says to use J because 'I' stands for electric current, not impulse. (ever heard p=iv? that means power=current times voltage, not impulse times voltage). (source = impulse discussion page) however MIT OCW professor Walter Lewin uses I so I'm curious if the rate at which college students are being taught J is increasing and likely someday to be more popular? Afterall, change is mathematical conventions and symbols are very slow. Sentriclecub (talk) 11:14, 30 September 2008 (UTC)

The choice of symbol depends on what field you're in also. There just aren't enough letters in enough alphabets to cover all of the things we might need to represent mathematically. In aerodynamics, 'I' for electric current is unlikely to be a concern since we're only rarely considering electric current at the same time as the reaction force from a bunch of jet engines - so aerodynamicists may well choose 'I' for impulse. If you design electric cars - maybe it could get confusing - so you use 'J'. <shrug> Not all forces are vectors - some of them are fields...although you may be able to treat them as vectors locally.

My guess is that, if you are starting a garage band, and if if the number "7" is taken, then use "8". That's my creative story of why J=impulse. Also, a lowercase j is resemblant of an i. Sentriclecub (talk) 12:23, 30 September 2008 (UTC)

Or an uppercase J, if your handwriting is as bad as mine. Plasticup ^T/C 14:28, 1 October 2008 (UTC)

Isobaric peptides

In scientific literature, I sometimes see a reference to "isobaric peptides" (meaning peptides of the same mass). As I understand, it "isobaric" is a reference to pressure, not peptide mass, so is it acceptable to use "isobaric" in this way? 11:11, 30 September 2008 (UTC)

I dont know if that is accurate. Is it an online source? Give me the link, i'll take a look. Confirmed, its an accurate way to use the word. As accurate as Pound (mass) guess I'll have to live with another one. Sentriclecub (talk) 11:17, 30 September 2008 (UTC)

This is on the wikipedia page for the term isobaric. A quick search on google also list various research papers that use the word isobaric in this same sense. This link: [10] also cites (from The American Heritage® Medical Dictionary) that the adjective "isobaric" means "Having equal weights or pressures". So this term can definitely be used thus.Leif edling (talk) 11:51, 30 September 2008 (UTC)

What's wrong with Pound (mass)? Its usage predates Newtonian mechanics by centuries. AlmostReadytoFly (talk) 08:01, 1 October 2008 (UTC)

Sunrays and satellites

Why the Sunrays defend th Satelite signals? —Preceding unsigned comment added by 61.2.206.4 (talk) 16:20, 30 September 2008 (UTC)

Your question is unclear, can you re-state it? You may be discussing the ability of solar storms to disrupt electronics (satellites included), however. If so, the phenomenon is well-covered there. — Lomn 19:56, 30 September 2008 (UTC)

Solar outage is due to the sun's radiation overwhelming the satellite signal. It occurs at intervals in October in the northern hemisphere. It happens as the dish pointing at the satellite also points at the sun, which is giving off microwaves too. Graeme Bartlett (talk) 21:31, 30 September 2008 (UTC)

black hole

I appreciate if you could help, i would like to know

1. what is in the black hole
2. what happens if you fall in

thank you —Preceding unsigned comment added by 89.100.97.189 (talk) 17:28, 30 September 2008 (UTC)

See Black hole. Feel free to come back here if you have questions not answered in the article. Algebraist 17:55, 30 September 2008 (UTC)

1. What is in the black hole: A large number of things that fell in, only extremely small and probably warped beyond recognition. 2. What happens if you fall in: You would be extremely small and warped beyond function.--ChokinBako (talk) 22:37, 30 September 2008 (UTC)

It's not so much warped as broken up into tiny pieces by tidal forces. And that's only until you hit the singularity. What happens then is anybody's guess. --Tango (talk) 00:04, 1 October 2008 (UTC)

So what's inside a black hole if atoms and even sub-atomic particles are torn away from each other? Degenerate sub-atomic particles? What kind? --Kjoonlee 03:20, 1 October 2008 (UTC)

What's inside an evaporating micro black hole? --Kjoonlee 03:21, 1 October 2008 (UTC)

Sigh...it's time for a L-O-N-G explanation isn't it.

Ultimately - at the very center of a black hole is a 'singularity' - this is an object with literally zero size. It's not just small - it has no size at all. Within such a thing, all of the mathematics that we might use to analyse it fall apart. Density becomes infinite for example. Gravitation - also, infinite. We really can't say anything about the singularity itself except (oddly) it's mass, it's charge and how it's rotating (I think that's all - someone please correct me if I missed one).

But when we casually talk about black holes, we're usually talking about the region within the so-called "Event horizon" - which is larger. If you think about (say) a planet like the earth, it has an "escape velocity" - if you launch an object into space at a speed lower than the escape velocity then it'll eventually fall back down again. If you launch it at greater than the escape velocity then it'll never quite slow down to a dead stop and fall back - so it has "escaped" the earth's gravity. Well, the escape velocity of a black hole is greater than the speed of light. Since nothing can go faster than light, something that's close enough to the singularity to have an escape velocity that's greater than light is doomed to fall into the singularity and be scrunched up so tight by the infinite gravity at the singularity that it too has zero size. As you get further away from the singularity, the gravity falls to lower values until eventually, the escape velocity is less than the speed of light and fast moving things can (in theory) escape. The distance at which that happens is the "event horizon".

What makes the black hole "black" is that even light can't escape if it starts out inside the event horizon. Hence no light whatever from within the event horizon can ever reach the rest of the universe and the "hole" is black. There are deeper things to consider here. If no light and no matter can escape from within the event horizon, then no information can escape either - since information has to be carried on either light or matter. Hence we can never know what's inside the event horizon - all we can do is predict what happens using math...and since even the math gives up on us at the singluarity - we're going to be somewhat ignorant of the inner workings of these beasts.

The "evaporation" thing is a bit more subtle. All black holes are believed to evaporate - but the big ones do so amazingly slowly and easily make up for that evaporation because their huge gravity is pulling in more and more stuff from the outside universe. The mechanism involved in evaporation is weird. In a pure vacuum, it is believed that fundamental particles (like electrons) spontaneously pop into existance - along with an exactly equal number of anti-particles (positrons, for example). Generally, these "virtual pairs" of particles almost immediately crash back into each other and vanish again...so the vacuum stays empty. But if this happens right next to the event horizon of a black hole, it's possible for one of the pair to accidentally slip across the event horizon and be unable to return to it's partner outside. When that happens, it seems that a particle just suddenly popped into existance AND DIDN'T IMMEDIATELY VANISH AGAIN! So in the region just outside of the event horizon, these particles are popping into existance and (rarely) have enough energy to escape out into the big wide universe without getting 'eaten' by the hole. So if you stand back far enough - it looks like the black hole is slowly emitting particles. Since there has to be an energy balance - this means that the black hole is slowly losing mass. It's "evaporating".

Since all black holes evaporate - there is no special distinction to be made "inside" the ones that are...because they all are.

As for the "tearing up" (spaghettification is the "correct" (if silly) term): Consider the earth and the moon...the moon's gravity causes tides on the earth. That's because on the side of the earth nearest to the moon, the moon's gravity is a bit stronger than on the opposite side. That pulls the ocean towards the moon - which is why we have high tides when the moon is overhead (you also get tides on the opposite side of the earth - but we're not going to get into that right now). When you were falling towards the earth - feet-first let's say - then the gravity of the earth is pulling very slightly more on your feet than it is on your head because your feet are a tiny bit closer. Just as the moon's gravity causes tides on the earth - the earth is causing tides on your body. This "tidal" effect on our bodies is not even slightly noticable because the earth's gravity is pretty feeble and we don't get close enough to the center of the earth to feel their largest effects. But if you were falling feet-first into a black hole - then even if you're outside of the event horizon, the gravity at your feet is a LOT stronger than at your head - to the point that it's going to stretch you out...as you fall closer and closer to the hole, this tidal effect gets worse and worse - you get pulled out into a long, thin streak - like a piece of spaghetti (hence the scientific term "spaghettification"!)...the closer and closer you get, the more this tidal force starts to affect you - until your body is shredded to molecules - then the molecules start to feel different gravity on the atoms at one end of the molecule than at the other - and they too get shredded (into atoms)...then the atoms get shredded and so on all the way down to the most fundamental particles. At the point where the singularity is, this tidal force becomes infinite and we can't even calculate what happens.

Fortunately, black holes are 'cloaked' in this information shield - the event horizon - so no matter how weird and impossible to calculate things get, the bizarre things that happen there can't ever affect the rest of the universe. This has been termed "Cosmic censorship" - and it's almost like the universe doesn't want us to know what's going on in there so it wraps the impossible math in an event horizon to keep the rest of our physics nice and clean and sensible!

SteveBaker (talk) 12:58, 1 October 2008 (UTC)

Infra-Red

On an episode of Mythbusters ages ago, they were testing various movie stories relating to cat burglars getting through various alarm systems, including infra-red lasers. Night-vision goggles did not work on the infra-red lasers, as, apparently, night-vision goggles just intensify remaining light. How would infra-red goggles work in detecting these lasers? Surely they would see them? I assume that the reason they were not used in the episode is because infra-red goggles do not exist....--ChokinBako (talk) 21:39, 30 September 2008 (UTC)

"Active infrared" night vision technology is widely available, though I can't comment on the particulars of the night vision stuff used by MythBusters. The single frequency used by the laser might have been out of the range of what the NVG could detect. — Lomn 21:56, 30 September 2008 (UTC)

Lasers are difficult to see even in visible light - you can only see them if they are either pointed directly at your eye or if the heroine of the story blows her make up into the beam to scatter the light. If you had something to scatter the light then night-vision goggles could well allow you to see them, but you have to bare in mind that the infra-red range is very wide (it goes from around 750nm to around 1mm, whereas visible light is just from roughly 380nm to 750nm - put another way, the wavelength of the top end of visible light is just under twice the wavelength of the bottom end whereas with infra-red it's over 1000 times longer), so just because the night-vision goggles see infra-red and the laser is infra-red doesn't mean they are actually anywhere near each other. --Tango (talk) 22:08, 30 September 2008 (UTC)

So, you would need adjustable goggles so you could set them to the right frequency to see? By the way, the heroine in Mythbusters did blow her make up onto the beams, but this scattered the light so much that it broke the beam and set off the alarm. Wouldn't just blowing cigarette smoke be better? Not very movie-ish and lady-like in these PC times, but, if it works, hey!--ChokinBako (talk) 22:30, 30 September 2008 (UTC)

But risky... cigarette smoke or foundation powder may lower the intensity of the light striking the detector enough to trip the alarm. Anything that scatters the beam to make it visible is likely to also diminish its intensity. --Jayron32.talk.contribs 23:46, 30 September 2008 (UTC)

It's guaranteed to diminish its intensity - conservation of energy, and all that. --Tango (talk) 00:02, 1 October 2008 (UTC)

"If you had something to scatter the light then night-vision goggles could well allow you to see them," Is a key phrase here. You can not ever see the beam of a laser like in star trek unless it's hitting something. (Smoke particles.) Even if you have smoke particles, the laser might be an invisible color of light. It's no use making some smoke light up in infrared if you can't see infrared.

So if you're trying to see an infra-red laser you've got two problems. One is that lasers beams don't show up in air, and the other is that you can't see infrared. The smoke solves the first problem, and the goggles solve the second. With any luck. APL (talk) 00:59, 1 October 2008 (UTC)

Most night vision goggles DO see into the infrared - the only difference between them and the kinds of thermal sensors the fireman and the military use is the range of frequencies within the infrared spectrum that they see. There is a huge variance between the cheap ex-Russian-army goggles a lot of people buy and modern, state-of-the-art US military NVG's. It seems that the more modern the goggles are, the further into the infrared they see. The problem the Mythbusters had was that air is pretty transparent - so not much of the laser light is scattered sideways as the laser crosses the room - that's pretty much as true for IR light as visible light. With that little light being scattered - even a super-sensitive NVG cannot see it. The trick of putting powder into the path of the laser is a good one - because it causes the light to scatter so you can see it - but that also cuts down the amount of light reaching the detector and (as the Mythbusters found) that sets off the alarm. If NVG's did work, the people protecting buildings with IR lasers could simply leave the room lights turned on. Light that bright simply overwhelms the goggles and they can't see a damned thing. SteveBaker (talk) 00:30, 1 October 2008 (UTC)

Sound speed / loudness

When studying the ear, I learned that one of the ways sound is amplified between the environment and the hair cells in your cochlea (the other two being the three ear cells, and the change in area between the eardrum and the oval window) is the vibrations being tranferred from air to a fluid in the cochlea, and since sound waves travel faster in water, this makes the sound louder. But how does travelling faster make a sound louder?

My guess is, if a vibration travels faster, then less energy has time to be lost due to friction. Is that accurate?

Thanks Jonathan ^talk 22:16, 30 September 2008 (UTC)

The sound is non-existent. Loudness is not about amplitude or pressure or energy. Its about neurons. Loudness is just your brain's way of interpreting simple harmonic oscillations. Sentriclecub (talk) 23:01, 30 September 2008 (UTC)

What he is implying is that the amplitude of the sound waves increase in the ear. While loudness is about perception (after all, one can be exposed to high-frequency sounds which one cannot hear, and thus would not notice the loudness of them, however these sounds can have an amplitude high enough to damage the ear). Its not very helpful to the question asker to play games with semantics. If we replace the word sound with vibration, and the word loudness with amplitude, perhaps someone could answer his question? I'm curious myself... --Jayron32.talk.contribs 23:43, 30 September 2008 (UTC)

I don't think the amplification is due to the liquid. It comes about because a relatively large entrance to the ear is progressively reduced in size through the cochlea. If the amplitude of the sound waves at the entrance to the ear were (say) 1mm and suppose the entrance to the ear was 100mm². The volume of air being moved is therefore 100mm³. Towards the narrow end of the cochlea, it's probably reduced to a cross-sectional area of 10mm² - but more or less the same volume is moving back and forth - so instead of 1mm of amplitude, you have 10mm of amplitude. This increase bends the little hairs more strongly - resulting in a louder sound. It's just like making a cone of paper and sticking the pointy end in your ear - it collects air movement over a large area (at the big end of the cone) and concentrates it to the narrow area at the pointy end. So everything sounds a lot louder. SteveBaker (talk) 00:22, 1 October 2008 (UTC)

When a wave's speed increases its amplitude decreases. When the acoustic energy passes from air to liquid, the energy rate doesn't change (though some energy is lost in the transition). Since the energy/time is constant, a higher speed of sound will cause a lower amplitude. (This parts a guess, but I expect that the liquid will couple with the stereocilia better than air would.) Saintrain (talk) 00:49, 1 October 2008 (UTC)

See Underwater acoustics. Water transmits sound waves faster than air and with lower loss per metre. Therefore sounds carry further than in air (whale song carries hundreds of miles). For scuba divers these two factors also mean that it's a lot harder to locate the source of a given sound. TrulyBlue (talk) 11:35, 1 October 2008 (UTC)

That's true but the losses over the couple of centimeters the sound travels within the ear are truly negligable compared to the losses over many meters before the sound reaches the ear. That can't be the reason the cochlea is filled with liquid. It's much more likely to be that the liquid is incompressible and therefore somehow transmits the vibrations onto the sensing hairs more efficiently...something like that. SteveBaker (talk) 12:22, 1 October 2008 (UTC)

Maybe amplitude is not really the important thing about the fluid in the cochlea... maybe it's more about the clarity of the sound, or maybe it helps keep the cochlea's shape (the same reason the eye is filled with fluid). I bet the stereocilia would vibrate better in a fluid where they're less likely to get randomly squished by outside forces. Jonathan ^talk 15:37, 1 October 2008 (UTC)

The fluid functions as a potassium resevoir for the hair cells to create impulses. Donek (talk) 16:30, 1 October 2008 (UTC)

I believe the shape of the cochlea has evolved to aid the discrimination of different frequencies of sound - as it gets smaller, progressively higher frequencies are detected.

October 1

Sneezing when you look at the sun?

What is the mechanism that causes you to sneeze when you look at the sun? —Preceding unsigned comment added by 69.120.9.204 (talk) 02:17, 1 October 2008 (UTC)

See Photic sneeze reflex. --Tango (talk) 02:21, 1 October 2008 (UTC)

"Autosomal dominant Compelling Helio-Ophthalmic Outburst syndrome" is possibly the most absurd backronym I have ever encountered. Plasticup ^T/C 14:18, 1 October 2008 (UTC)

We seem to have been a bit more comprehensive (chatty?) on this subject a while back ;) hydnjo talk 00:34, 2 October 2008 (UTC)

Anti-Depressants and delayed orgasm

From a scientific/medical standpoint, what is it in the anti-depressants that causes delayed ejaculation? This effect is so strong that I have heard anti-depressants being used to treat premature ejaculation. Thank you. —Preceding unsigned comment added by 68.7.126.152 (talk) 02:33, 1 October 2008 (UTC)

Nobody knows for sure, but it's believed that SSRI's help PE due to increased levels of serotonin. Research into why is ongoing. Fribbler (talk) 11:45, 1 October 2008 (UTC)

I don't know either but I do know my wife is happy! —Preceding unsigned comment added by 69.77.185.91 (talk) 18:04, 3 October 2008 (UTC)

need a reaction

Hi, I need a chemical reaction which can produce opaque compounds from transparent ones by the application of electricity, and is also reversible in nature. That way it might be possible to control light passing through a chemical, I suppose. I am studying electrical engg. and some insight on the concepts of chemistry to be used here would very useful. Cheap chemicals would be nice.117.201.114.27 (talk) 06:43, 1 October 2008 (UTC)

Our article on smart glass touches on a number of approaches to this problem. TenOfAllTrades(talk) 07:00, 1 October 2008 (UTC)

Applying electricity isn't exactly a chemical change is it? Changing things from opaque to transparent and back is how LCDs work. --antilived^{T | C | G} 09:48, 1 October 2008 (UTC)

But in LCDs the change is disdrete, its completely opaque, or trans. I wonder why it can't be made partially transparent ?? 117.201.112.159 (talk) 05:52, 2 October 2008 (UTC)

Your problem there is that all the molecules are the same, so they will all undergo the same change. Maybe you could use a mixture of compounds (with different dipole moments?) that would give a stepwise change? Otherwise you would need a compound where the voltage (or frequency) would cause a uniform partial change - alignment and partial rotation of a dipolar molecule, or partial twisted nematic effect. What would happen if you used a partial voltage on a TN display? That would be easy enough to test - borrow your friend's laptop and sink the voltage going to the non-circuit screen power supply. Franamax (talk) 08:09, 2 October 2008 (UTC)

There are several kinds of LCD mechanism - some of them can do gradual change (the ones in my laptop display, for example, can show at least a couple of hundred gradations of transparency). But even with an on-off effect, you could still achieve what you want with a pulsed voltage. If the material only goes utterly opaque or utterly transparent then you could pulse the voltage on and off a couple of hundred times a second and have a window that APPEARED to be 50% transparent - alter the pulse/space ratio and you can choose any degree of transparency you like. You'd have to do it at least 100 times a second to avoid annoying flicker effects - so there might be a problem with materials that responded to the voltage only very slowly. So if that doesn't work, you could (like an LCD panel) structure the material as a bunch of very small separate cells ("pixels") and turn 50% of them on in a checkerboard pattern when you want 50% transparency - so long as the pixels are small enough - it'll look OK. If that's too difficult to arrange for some reason - then you could arrange for a bunch of thin layers of material to be laminated together - each of which would be thin enough to be less than 100% opaque when turned on - but by turning on several of them, all of them or none of them, have 50% transparency, 0.001% transparency or 100% transparency respectively. There are plenty of ways to do this with an on/off material. SteveBaker (talk) 11:03, 2 October 2008 (UTC)

We have a smart glass article. DMacks (talk) 17:03, 5 October 2008 (UTC)

control systems

Hi, I am learning control systems and have a trivial question in my mind. Is it not possible to create a control system, which can measure performance its own system, and calibrate its parameters (maybe more than one)on its own, so as to reach a desired goal. That way the system would quite easily adapt to changing conditions automatically with no external interference. Obviously, stability should be dealt with, through some algorithms..117.201.114.124 (talk) 07:40, 1 October 2008 (UTC)

What you are describing sounds like an adaptive system - read the article for further details and links. Gandalf61 (talk) 10:09, 1 October 2008 (UTC)

Such systems are not only possible - but used in practice in some very common situations. My car (a MINI Cooper) has an adaptive engine management computer. It "learns" by optimizing the engine parameters and is said to adjust to your driving style, the long-term prevailing weather conditions and the kind of gasoline available in the country you live in. It is noticable that when you get a new or used MINI, it takes a couple of tankfuls of gas for the fuel economy to really get good - and this is the time it takes for the adaptive controller to really settle in on the optimum parameters for the conditions. SteveBaker (talk) 12:18, 1 October 2008 (UTC)

That's interesting, but wouldn't its brains get scrambled by having two different drivers? OTOH, that's a great reason to not let the wife drive the Mini. :) Franamax (talk) 19:10, 1 October 2008 (UTC)

The MINI stores per-driver information in the "key" (which is actually a round plastic thing which talks to the car via a radio link while it's sitting in your pocket!)...of course if you swap keys - then all bets are off. The main reason not to let my wife drive my MINI is my rather clear memory of the cost of replacing the clutch after the last time she drove it. It also stores things like which key was in the car when some fault code occurs - which is apparently used by car rental companies and companies that use them as fleet cars. The key is also logged in the "black box" crash recorder thingy. SteveBaker (talk) 00:26, 2 October 2008 (UTC)

Now that's even more intriguing. If your wife did it right, she could activate her key just before yours when you tried to start the car. Then the stored settings would be going to her chip. If she had more time with the car (perhaps by taking it from your parking lot while you're working), she could train it to be unresponsive to your jabs at the accelerator pedal and aggressive steering inputs. And even if she never drives it, if she has a key, there's probably a way to null the heuristics - so she can probably always prevent you from being sporty. I'm not sayin' she's doin' it - I'm just sayin' :) Franamax (talk) 09:47, 2 October 2008 (UTC)

You misunderstand: The 'learned' settings don't stop you from doing anything - they just alter the fuel-efficiency with which the engine can do it. So (to pick an example that may or may not be true) if you habitually start the car and soon after demand full power then perhaps the idle RPM will be set a little higher so the engine will warm up sooner (using more gas in the process) and the acceleration phase will happen in a warmer engine - and thereby use less gas. If you habitually start the engine and drive slowly for 10 minutes before accelerating hard then the idle can be set lower because typically the engine will warm up enough during the slow driving. In the latter case, you can still turn the car on and immediately go fast - but the heavy acceleration with a cold engine is not so good for wear-and-tear and will consume more gas. SteveBaker (talk) 10:47, 2 October 2008 (UTC)

Permission to Use A Picture

Hello, I am a student in the Anatomy and Physiology Course in the Virtual High School (www.govhs.org) I have been assigned to choose a physiologist and learn more about him/her. I was wondering if I could use the picture of Claude Bernard and post it in my assignment. Acces to the assignment is limited to 24 people. I will cite the source of the picture. Thank you for your time. —Preceding unsigned comment added by 72.25.1.135 (talk) 12:00, 1 October 2008 (UTC)

The image of Claude Bernard at the head of the article is out of copyright and therefore free to use. If you click on the image and then read below the file you will see confirmation of this. 86.4.187.55 (talk) 12:04, 1 October 2008 (UTC)

Be aware that the subject of the photo is likely to retain personality rights. WilyD 12:15, 1 October 2008 (UTC)

Uh, no. Not for someone who died in 1878. And certainly not for a high school assignment. (Personality rights come into play if I were, say, trying to sell mugs with the person's picture on them. And even then it would not be an issue for someone who died over a hundred years ago. Much less a French hero.) --98.217.8.46 (talk) 13:02, 1 October 2008 (UTC)

List of Cathepsins

Where can I get information on all known cathepsins and their structures. I am particularly interested in Fasciola Herpatica cathepsins. Donek (talk) 12:26, 1 October 2008 (UTC)

I can't help much, but you'll find more in search engines if you use the correct spelling: Fasciola hepatica, not herpatica. - Nunh-huh 14:57, 1 October 2008 (UTC)

You're right, you can't help much! Can anyone else? Donek (talk) 16:11, 1 October 2008 (UTC)

Sounds like a job for PubMed. Maybe start at the MeSH for cathepsin. But Nunh-huh is actually right here...why would you respond sarcastically to someone who told you an important reason you may have had trouble searching for this info (you did try to search before asking for help, right)? DMacks (talk) 16:58, 1 October 2008 (UTC)

I did try, with the correct spelling as well. Thank you for your help. Donek (talk) 17:02, 1 October 2008 (UTC)

An article on the two main Fasciola hepatica excretion/secretion products, CL1 & CL2 (potential targets of a fascioliasis vaccine), is at [11] - Nunh-huh 17:10, 1 October 2008 (UTC)

Thank you for your help. Donek (talk) 17:11, 1 October 2008 (UTC)

geophysical and geochemical surveys

what are the basic techniques involved in geophysical and geochemical surveying? Its use in the petroleum sector.

Our article on exploration geophysics has some information that may be of interest. Franamax (talk) 19:07, 1 October 2008 (UTC)

Detergents, chlorine bleach

Hi, i bought some bleach which has detergent in it, but i wanted to add some normal washing powder as well because the water didnt look soapy enough, but i noticed on the washing powder box it says "Do not add chlorine bleach", is this because it'll denature the enzymes in the normal washing powder? —Preceding unsigned comment added by 58.174.201.126 (talk) 13:38, 1 October 2008 (UTC)

What brand is it? It may be a oxygen bleach, not chlorine; mixing the two may not ge a good thing. --—— Gadget850 (Ed) ^talk - 15:33, 1 October 2008 (UTC)

Yeah, depending on the ingredients there are a few reasons not to add chlorine bleach to things - damaging the enzymes is certainly one possibility, but it's more likely to be a safety thing - if you look at the Safety section of our article on Sodium hypochlorite there are various unpleasant chemicals produced if you mix it with acids and/or hydrogen peroxide, both of which may be found in other bleaching/cleaning products. ~ mazca ^{t | c} 18:00, 1 October 2008 (UTC)

Additionally, ammonia and sodium hypochlorite makes a particularly unpleasant combination. Its not unusual for bathroom cleaners, containing ammonia, to mix with those little bleach-containing toilet biscuits, and cause problems... Chlorine bleach is one of the more dangerous chemicals in your house... --Jayron32.talk.contribs 01:36, 2 October 2008 (UTC)

The amount of bubbles does not relate to a detergent's or soaps cleaning power... in fact, when your deal with a mix with chlorine they likely are using one of the low-suds detergents. Please, for your own safety follow the instructions on the packaging. ---J.S (T/C/WRE) 07:32, 2 October 2008 (UTC)

Hyperkalemia

What are causes and consequences of elevated (panic high)potassium levels in the bloodstream? —Preceding unsigned comment added by 98.228.1.6 (talk) 14:51, 1 October 2008 (UTC)

We have an article on hyperkalemia. Please let us know if it leaves your questions unanswered. - Nunh-huh 14:53, 1 October 2008 (UTC)

current density

is current density microscopic or macroscopic? —Preceding unsigned comment added by 117.197.161.250 (talk) 15:23, 1 October 2008 (UTC)

Sounds like this might be a homework question. See Current density, Electron, and Submicroscopic. --Allen (talk) 16:35, 1 October 2008 (UTC)

Current density can be characterized at a microscopic or even submicroscopic level. Edison (talk) 04:51, 2 October 2008 (UTC)

Atmospheric Pressure

I understand that atmospheric pressure near earth's equator exhibits significant diurnal variation due to atmospheric tides, and that this diurnal effect is almost non-existent in more polar regions, but why does atmospheric pressure show so little day to day variation at the equator than in polar regions? This observation was based on a comparison of atmospheric pressure data from Malaysia vs. Alberta, Canada.--216.99.65.64 (talk) 15:30, 1 October 2008 (UTC)

Equatorial climate is relatively more stable (i.e. boring), being in the Intertropical Convergence Zone. The weather in Alberta is much more dynamic, with high- and low-pressure cells moving about constantly, characteristic of continental climate. On any given week in Alberta, several cells could move through, so you would see more variation in atmospheric pressure. Franamax (talk) 19:03, 1 October 2008 (UTC)

So, what is this thing I had when I was a baby called?

First off, this is a question about medicine and about me, but I'm not seeking medical advice or anything :) I feel just fine.

You know how infants don't have a complete skull, but it's divided up into "bits"? (I'm sure there's a medical term for the "bits", but I don't know what it is). Well, I had this thing when I was a baby that the bits were fusing together WAY too fast. So the doctor had to go in and, well, basically saw my skull open to make room for my brain. This left me with a neat scar over my skull and an abnormally large and elongated head (I don't look like a freak, people don't notice it at all, but I've never had the pleasure of wearing a hat or a helmet that fit me well, if at all). I know this syndrome (or whatever) has a name, but I can't think of what it is. So that's my question: what is it called? 90.235.17.83 (talk) 16:29, 1 October 2008 (UTC)

Craniosynostosis (try saying that after a few pints!) if I am not mistaken. Fribbler (talk) 16:33, 1 October 2008 (UTC)

Yes, that's it! That kid in the picture is like me at four months old (except I was much handsomer)! Thank you very much! No wonder I couldn't remember the name, that's an imposing medical term. 90.235.17.83 (talk) 16:45, 1 October 2008 (UTC)

Hmm, I had a teacher at school with an arrestingly bulbous head, it was shaped remarkably like that baby's. Maybe this condition had something to do with it for him too. ~ mazca ^{t | c} 17:56, 1 October 2008 (UTC)

I was reading about craniosynostosis in a textbook the other day, fascinating condition. —Cyclonenim (talk · contribs · email) 20:19, 1 October 2008 (UTC)

Scarlet fever - After Effects?

What if you had Scarlet fever in your childhood but it was not treating properly, could there be any after effects from it in adulthood? --209.0.0.29 (talk) 18:06, 1 October 2008 (UTC)

Fevers in early childhood can cause developmental complications, most often mental retardation. -- MacAddct1984 ^{(talk &#149; contribs)} 19:27, 1 October 2008 (UTC)

Rheumatic fever describes the problems that can occur. Our scarlet fever article includes a list of characters in literature who suffered complications. Fear of this disease (mainly, I think, the heart complications) led to long quarantines of patients and sometimes the destruction of the belongings (Velveteen Rabbit). Rmhermen (talk) 20:50, 1 October 2008 (UTC)

My recollection is that the long-term concerns have to do with joint disease and endocarditis (infection of the heart muscle and valves). In particular, untreated endocarditis can lead to damage/destruction of the heart valves, subsequently causing regurgitation of blood through the incompetent valve, and chronic heart failure. Try this ([12]) for a relatively recent review of the subject. Medical geneticist (talk) 22:03, 1 October 2008 (UTC)

Please be aware that we cannot provide any medical advice at Reference Desk. But heart valves can be damaged by untreated scarlet fever which progresses to rheumatic fever, per the articles linked Edison (talk) 04:49, 2 October 2008 (UTC)

Young's Modulus

Why is the Young's Modulus and other moduli of elasticity known as a modulus? --80.229.152.246 (talk) 18:57, 1 October 2008 (UTC)

The New Shorter Oxford English Dictionary (13th Ed) says a "modulus" (from the diminutive of the Latin word modus meaning measure) in this usage, is a number which combines other numbers (such as stress and strain, at the linear portion of a curve), to characterize the properties of a substance. It is a modulus because it compares a numerical cause to its numerical effect. They had to call it some specific coined term, so that others would know exactly what well defined measurement led to the number. Edison (talk) 20:24, 1 October 2008 (UTC)

Emedicine.com

What is the incentive for the authors of Emedicine.com? Is it that they're paid? If they're paid, how does Emedicine make profits? I haven't seen too many advertisements on their web site. Thanks in advance. —KetanPanchal^taLK 19:22, 1 October 2008 (UTC)

Did you see InfoCenters - Information from Industry? My guess is that "Industry" pays them. Lova Falk (talk) 19:53, 1 October 2008 (UTC)

What is the incentive for any author of any medical publication? Yes, money can be a factor but what's wrong with enjoying research and teaching? —Cyclonenim (talk · contribs · email) 20:18, 1 October 2008 (UTC)

Sorry for the delayed response. Likewise, thanks for your replies. Well, Cyclonenim, you seem to have gotten me wrong here. I was plain curious as the work involved is of quite high quality. And, of course, there's nothing wrong with doing some generous, voluntary work, but the thing with official publications is that they are widely recognized, and improve ones' reputation in ones' chosen field. Although, Emedicine articles are widely accessed, I don't think they add much to a professional's CV. I wouldn't find it wrong, even if the authors are paid for the work--there's nothing wrong in getting paid for writing a good, informative article (IMHO). Take care. —KetanPanchal^taLK 19:49, 6 October 2008 (UTC)

A humanoid changing facing in space

If a person or humanoid machine (mecha) were floating in space, can it change its facing quickly and easily without using thrusters? In other words, just by moving its arms, legs, twisting, shifting mass, etc can it change facing? 98.221.85.188 (talk) 21:01, 1 October 2008 (UTC)

Easily. Just move your arm real fast counter clockwise in circles. You will begin spinning about the line of axial rotation. You will spin this way forever. When you move your arm back to the initial start point, with the same quick motion, you will instantly stop. Sentriclecub (talk) 21:08, 1 October 2008 (UTC)

See reaction wheel. It's how the Hubble Space Telescope points at things without getting "exaust" on the mirror. Saintrain (talk) 21:30, 1 October 2008 (UTC)

It isn't possible to make yourself start spinning continuously from rest because angular momentum is conserved. You can change your orientation this way (since orientation isn't conserved) but I think the details are a bit different. -- BenRG (talk) 22:05, 1 October 2008 (UTC)

Sentriclecub's answer does not make sense to me. Surely stopping the movement of your arm would have and equal but opposite effect of moving it in the first place? Otherwise you'd be creating angular momentum out of the ether. It seems like to have any effect useful effect you would have to cartwheel your arm like you were a windmill until you were in the desired orientation. This would probably take a lot of practice to get right. APL (talk) 22:30, 1 October 2008 (UTC)

A lot of practice, but it can be done - I've seen a video clip of astronauts in space playing around by rotating themselves 90 degrees, saluting, and rotating another 90 degrees, etc., all with military precision (in time with eachother and everything). I don't remember exactly how they did it, but it involved rapidly moving their arms and legs. --Tango (talk) 22:39, 1 October 2008 (UTC)

I don't see how that's possible. (Translation: You are lying to me!) Conservation of angular momentum is a pretty fundamental thing - and those astronauts would certainly NOT be conserving it (at least not as you've described it). Something like the Hubble space telescope can do it because it has onboard gyros (big flywheels) that can be braked and speeded up - in that case, conservation of rotational momentum means that the spacecraft can turn ONLY if the heavy/fast flywheel turns in the opposite direction so that momentum is properly conserved within the entire closed system. External forces such as friction and air resistance allow us to do this down here on earth - but even so, momentum is conserved because if (for example) you are spinning around in your office chair then let friction slow you down to a stop - you are actually applying a torque to the entire planet and speeding it up a tiny bit to compensate. SteveBaker (talk) 23:05, 1 October 2008 (UTC)

::::: You only need to "hit" one atom, to generate yourself an angular velocity. Space is not a vacuum. From wikipedia there are still a few hydrogen atoms per cubic centimeter. Sentriclecub (talk) 00:08, 2 October 2008 (UTC) This is only what I wrote because I was scared (when 3 people disagree with my answer, and I only learned this stuff today, I'll question my accuracy). My original answer is accurate, but not great because it is ambiguous of how to stop your arms. Sentriclecub (talk) 03:01, 2 October 2008 (UTC)

Wait, I want to clarify Sentriclecub's tiny text here. It seems to me that Sentriclecub's original answer is not correct, and is not the consensus that's forming. Sentriclecub's original answer is wrong because of the line "You will spin this way forever." You will not spin forever, you'll "spin" only until you stop moving your arm. This is a very important difference. APL (talk) 13:16, 2 October 2008 (UTC)

Via "cat turns," movements similar to those used by gymnasts, by divers use to change orientation during a dive, or skaters to start or stop a turn (independent of what the skate blades are doing) or that a cat uses to land on its feet, it is possible for a human or a humanoid in orbit to rotate to face upside down, sideways, etc, without thrusters. The movements were described years ago in a science article, probably in Scientific American, called "Cat turns." They were pretty specific and economical and did not involve wildly waving, although that might work.To make one up based on simple physics, if, while floating "weightless" you started with hands at sides and suddenly rotated them upward while keeping them the same distance apart so they were overhead, and left them there, your body would start rotating forward slowly. When your orientation was about what you desired, bringing the arms back down through the same path would tend to cancel the rotation. Other movements should produce rotation in other planes.This was covered in Science 1899, page 933 [13] and in Science 1911 page 844 [14]. A different article discusses this at [15]. This may have been covered in New Scientist 1960 p 559 per the snippet view[16] .Edison (talk) 23:00, 1 October 2008 (UTC)

But only because they have friction and air resistance. I can do that on my office chair. If I twist my body clockwise with arms outstretched and then pull them in and straighten out (counter-clockwise) - then repeat that over and over - I'm not facing the same direction as I started - which appears to be a violation of conservation of angular momentum. However, the reason it works is that I speed up as I pull my arms in (to conserve momentum) - but because the frictional and air resistance forces are higher when you're moving fast compared to moving slowly - you can use that fact to get more frictional force in the clockwise direction than in the anticlockwise - and that gradually rotates you around. But that doesn't work out in space where there is no friction or air resistance. So divers and skaters can do it (and so can geeks in office chairs) - but it doesn't work in space. SteveBaker (talk) 23:12, 1 October 2008 (UTC)

The angular momentum of the whole body cannot change, but that of individual parts can. I think Edison's description is slightly in accurate - your body will move while you move your arms and will stop when you stop moving them (you can get them back to your sides by moving them down via the side of your body, rather than the front, the momentum from each arm will cancel out so you won't move, you can then bring your arms back up via the front if you have moved far enough). You can do the whole thing on a smaller scale with some practice, I imagine. --Tango (talk) 23:46, 1 October 2008 (UTC)

Neither friction nor air resistance are needed. And no change in angular momentum is necessary. Twists and somersaults can be done with zero angular momentum. A person floating in spase who moved a limb so as to create a moment would have to cause a compensating movement of the rest of the body. The old article went through considerable detail, and I wish I had a Scientific American index to track it down. I found an article which has some nice illustrations and explanations of assymettric arm and hip movements used to change orientation during freefall in diving here [17] and here [18]. Edison (talk) 23:24, 1 October 2008 (UTC)

:::Space IS NOT a vacuum. There are atoms which you can accelerate yourself against and have a angular velocity. Sentriclecub (talk) 23:59, 1 October 2008 (UTC) I'll re-update my answer, but this i'm 100% positive--just learned it today and wrote 12 pages of notes. http://www.youtube.com/watch?v=9A1Zb8109fg and the chapter in my book. However, if space were a perfect vacuum, then you cant change the way you face (unless you twist your body, which doesn't count as an angular reorientation which is what the OP is asking) Yeah this was wrong, I was right the first time. Sentriclecub (talk) 02:57, 2 October 2008 (UTC)

Space is close enough to a vacuum as makes no odds for this. The occasional atom of hydrogen isn't going to have any noticeable affect on a person waving their arms around. It's all just conservation of momentum - you move your arms one way, your body will move the other way. --Tango (talk) 00:13, 2 October 2008 (UTC)

That's why I wrote "you'll spin this way forever" and then you can stop. I calculated it out, its extremely small, but if the object is of very small mass, and can morph such a way to reduce its rotational inertia, then using some sample numbers for the density of a few atoms per ml and an object for 10 micrograms that can "pull its arms in" to reduce its effective rotational inertia to almost zero, then a revolution only takes seconds, not hours or days. I can't use higher digits because my calculator only displays 10. But yes for humans, it would take closer to the range of forever for a revolution. However, the effect of friction is even more negligibly small in a near vacuum. Sentriclecub (talk) 00:30, 2 October 2008 (UTC)

When you stop moving your arms, you'll stop spinning, otherwise you would be violating conservation of angular momentum. Friction isn't required. --Tango (talk) 00:35, 2 October 2008 (UTC)

For the human yes, but not my my micro-robot. A human, I can think of an apparatus, similar to a fan with stringlike rubber "paddles". You can spin them, with a hand-crank and then retract them into a tube-like reservoir and similar to a gyroscope you can "pull" yourself linearly wrt the spinning paddles. Pulling the paddles into the reservoir will cause a human to linearly move toward the apparatus. (the center of mass of the human + apparatus system won't change however). Its hard to describe succinctly, but if you think about creating a gyroscope in space, then pulling on it to create a relative linear monentum of the human, then letting go of the spinning apparatus (while it "sits" in space next to you) then you and the apparatus both doing some independent revolutions and you "grab" the apparatus once you are facing whichever way you like. Sorry to be unable to describe the thing in detail, but its real easy to picture. Just start some gyroscopic motion by "cranking it" and then release it from you with an angular velocity, and you will have an angular velocity (3rd law force pair) and voila! Sentriclecub (talk) 00:53, 2 October 2008 (UTC) The micro-robot wouldnt need this device, it could just flap its arms and morph into a nearly zero-inertial shape with just a few nano-radians per second of angular velocity.

If you 'calculated it' then you made a gigantic error someplace! There is about 1 hydrogen atom per cubic centimeter - so in all of the arm-waving and leg flapping - you maybe move a thousand atoms out of the way - at about the speed you move - let's say 1ms^-1 to be generous. There are 6.02214179(30)×10²³ hydrogen atoms per gram of hydrogen - so your thousand atoms weigh about 1/10²⁰ grams. 0.000000000000000000001 grams. Moving that much at 1 meter per second produces an external drag force that's so tiny that it wouldn't be able to accellerate one human chromosome by 1 nanometer per second...let alone your entire body at a noticable rate. So forget the pathetically tiny amounts of gas out in space - in all likelyhood your spacesuit is out-gassing a trillion times that amount - AND IT'S STILL NEGLIGABLE. For your nanorobot, you're statistically so unlikely to hit an atom at all - that it's STILL NEGLIGABLE. This has no bearing on the discussion here. If you can't understand that then you shouldn't be posting answers on the Science ref desk! SteveBaker (talk) 00:59, 2 October 2008 (UTC)

OK - so back to Tango & Edison. Would you guys please explain how come what you are claiming avoids the conservation of rotational inertia? That's a fundamental law - you can't just hand-wave it away. The manouver of (for example) raising your arms from your sides to above your head while keeping your hands together - in a 180 degree forward arc would produce the following effect (let's suppose your arms represent 10% of your total body rotational inertia):

• As you start sweeping your arms upwards at (say) 10 degrees per second, your body will start to rotate in the opposite direction at 1 degree per second.
• When you stop moving your arms upwards, your body stops rotating too.
• When you move your arms back again - your body rotates again at the same rate but in the opposite direction.
• When your arms return to their starting point, your body is back exactly where it was before.

In air - or in water, the resistance of the medium has an effect - your arms (because they are moving faster) create more drag than your body does (or maybe the body is bigger so it causes more drag than your arms) - either way - that differential of drag is enough to allow you to come up with complex sets of manouvers that produce more drag in one direction than in the other and that asymmetry in drag force allows that EXTERNAL force to appear to violate the conservation principle. But in space - no such luck (except to an entirely negligable degree that does not suffice to explain the phenomena described above). SteveBaker (talk) 00:59, 2 October 2008 (UTC)

The key thing is not to move your arms back by the same route. Start with your hands by your sides, lift them up above your head via holding them out in front of you and then move them back to your sides via holding them out to the side. --Tango (talk) 01:08, 2 October 2008 (UTC)

I didn't calculate it for a human, but for the microrobot. Sentriclecub (talk) 01:08, 2 October 2008 (UTC)

I dont know how you could have came to the conclusion that I was referring to both the human and the micro-robot. I thought I explained very well, that a human can only do it with the described apparatus. The microrobot could do it by "flapping its arms". I even wrote that it "would take forever" for the human to do a revolution. If I don't belong at the science desk, then read the answer below this one about hydrophobic properties of the GI tract and fat solubility in water. Then again maybe you can't read? I think there's clear straw man here if you thought I said a human can make a revolution in a few seconds. If you re-read what I wrote, or I can post it to your user:talk page. Done--its at your talkpage. Sentriclecub (talk) 01:15, 2 October 2008 (UTC)

It doesn't matter, we're not talking about nano-robots, we're talking about people. Using drag isn't feasible for a person, we're all agreed on that, so let's move on. --Tango (talk) 01:37, 2 October 2008 (UTC)

Yes tango, I agree, I am interested in reading the response that you and Edison raised. I read the links provided and it seems that doing a certain sequence of moves will cause rotation in one plane, even without air resistance because of the mathematical properties of Pseudovectors do not apply to normal vector addition and subtraction. I told Steve B. that I'll refrain from further posts, since I want to hear him address the points you and Edison raised here[19] [20] [21] [22] [23] [24] I'm also interested in this seeming contradiction of conservation. Sentriclecub (talk) 01:55, 2 October 2008 (UTC)

There is no contradiction - at all times the net angular momentum is zero, and that's all the matters (the individual parts of your body aren't a closed system, so there are no conservation laws for them individually). --Tango (talk) 02:16, 2 October 2008 (UTC)

There is an easy way to explain this. Suppose you want to face 'downward' from the direction you are currently facing. Assume you start with your hands at your sides and with zero rotation. You lift them up in front of you, then over your head, then wheel them back behind you ("doing windmills"). As you apply a torque to your arms, so do your arms apply a torque to you. Your arms are spinning upward (at the front) so you will spin downward at the front. Your arms are spinning one direction and you are spinning in the other, so the net angular momentum of the system is zero. When you are facing down, you stop moving your arms in circles. This requires you to apply a 'braking' torque to your arms, and so they will apply a 'braking' torque to you. When your hands stop moving, so do you. Now the system has reoriented itself (you are facing downward) but its total angular momentum is still zero. Drag and air resistance has nothing to do with it. Maelin (Talk | Contribs) 01:49, 2 October 2008 (UTC)

I agree with the correction that you would raise your arms from your sides to above the head, keeping them equidistant. This should result ins a forward rotation of the body, which I suppose would cease when you stopped the arm movement. If you then returned them to down by the sides by rotating them outwards, this would not negate the initial rotation. Repeat as needed to rotate the body so the head is where the feet were, facing the opposite way. Not even the slightest violation of any law of conservation. I wish to hell they would send a cat to the space station and record how he changed his orientation, as he sprung from surface to surface. It would be a good project to do just before the decommissioning, since there would be dander, hairballs, and other cat ick. My cat can reverse from feet-in-the-air to feet-on-the ground in a drop of one half foot, and he is quite old. I just tested it. The cat did not use thrusters, or a gyroscope. Marey, who invented the motion picture camera, filmed cat turns in the 1890's and wrote up the findings in Science. Edison (talk) 04:35, 2 October 2008 (UTC)

So you're saying that other animal forms may be able to change facing in a zero G environment even better than the humanoid form? 98.221.85.188 (talk) 05:48, 2 October 2008 (UTC)

I dunno about real animals, but cats are pretty twisty! If I and a cat were falling upside-down, my money would be on the cat landing right side up. I'd extend the bet to zero-g too - I have no idea how to twist around in free-fall, whereas a cat evidently does. But cats are gods, not mere mortals. Franamax (talk) 07:30, 2 October 2008 (UTC)

You tested it? Does that mean you held your cat upside down and dropped it? That sounds like animal cruelty to me... --Tango (talk) 18:06, 2 October 2008 (UTC)

I'm sure Edison meant that they merely altered space-time around the cat, whilst the cat itself remained unharmed. Franamax (talk) 07:52, 5 October 2008 (UTC)

Probably one of those kittens that Schrodinger was trying to give away after his experiment failed and the other cat got into the box. :) Franamax (talk) 07:55, 5 October 2008 (UTC)

I'm continually amazed--but I know I shouldn't be any more--that "Wikipedia has an article about that": Cat righting reflex. And even a secondary page: High-rise syndrome. DMacks (talk) 18:38, 2 October 2008 (UTC)

GI Tract

When the intestines absorb fat, some of the fat can permeate through the intestinal wall and the fat will conglomerate in to plaque. Why doesn't calcium or magnesium or proteins do this when the intestines absorb these chemicals?24.65.69.8 (talk) 23:35, 1 October 2008 (UTC)

Fats are hydrophobic and in water, they will get forced into a small group since the hydrogen bonding between interbonding water molecules will "squeeze out" the non-ploar molecules like fat. Fat isn't water soluble. Calcium and magnesium and about 75% of the proteins are hydrophilic and even the non-polar proteins usually have a polar region or a couple polar regions, so they are at least slightly water soluble. Sentriclecub (talk) 00:18, 2 October 2008 (UTC)

As a followup, its not really specific the the transportation process accross membranes, its just a property of lipids in an aqueous environment. Think of it like this way. Its not that the fat molecules are "actively" trying to amalgamate, but its just the fact that the water is the one actually trying to make as many bonds with other water molecules as possible. Then one hydrogen is near 18 other water molecules and near 3 lipid molecules, it will try to "improve" by surrounding itself with only other water molecules. Thus the observation of seeing fat molecules clump together, is actually through the water molecules "preference" to only surround itself with other water molecules. Sentriclecub (talk) 02:07, 2 October 2008 (UTC)

Likewise, before we anthropomorphise the world, there is no "trying" effort involved. Water is a polar molecule, with a net dipole moment. That means that water is a molecule with oppositely charged sides, or "poles". These charges assert an attractive force on opposite charges (like ALL electric charge). Since fat molecules are essentially non-polar, water molecules exert more force pulling on each other than they exert on the fat molecules, and so they sqeeze the fat molecules out of the way. Interestingly, due to the inductive effect, water molecules are actually MORE attracted to fat molecules than the fat molecules are to each other. This effect is overtaken by water molecule's attraction to other water molecules, which is why fats don't desolve. In fact, fats lack of attraction towards each other is why they tend to spread out so thin on the surface of the water; they are more attracted to the water than to each other, so they tend, if given the space, spread out into very thin layers, sometimes as thin as a single molecule. As to the mechanics of artierial plaque formation, I'm not sure I can be much help, and our Wikipedia article on the subject Atheroma, lacks any such info. --Jayron32.talk.contribs 04:58, 2 October 2008 (UTC)

I only provided the followup to make it easier to understand. I gave a think of it this way explanation just in case he or she is a high school student. I think your explanation about a dipole moment is over the person's head. The OP does not likely know about charges, or the F=kq1q2r^-2 formula. Sentriclecub (talk) 07:26, 2 October 2008 (UTC)

Tru dat. Your probably right... --Jayron32.talk.contribs 03:47, 3 October 2008 (UTC)

^{[citation needed]}. Does fat actually escape through the lining of the intestine to form plaques? I've not heard of this process before, and I'm not sure if it's an accurate representation of something which really happens to any significant extent.

There might be some confusion with visceral fat deposits, which is fat which accumulates around the abdominal organs (including the intestines). While these deposits aren't generally associated with good health or good diet (they're responsible for the 'beer belly' look), they're composed of ordinary fat cells (adipocytes), not 'free' fat in plaques.

Another possible confusion is with atherosclerotic plaques—extracellular fatty deposits which form inside blood vessels (not around the intestinal walls) and which are again related to poor diet. These plaques can form throughout the body, and include fats, calcium, and connective tissue. Their formation is rather complicated, and is not simply the result of poorly-water-soluble fats precipitating or coalescing. TenOfAllTrades(talk) 04:32, 3 October 2008 (UTC)

What will happen to planets when sun finally elapse to a white dwarf

What will happen to Jupiter, Saturn, uranus, and Neptune after when the sun collapse into white dwarf. What will happen to it's gaseous layers. Will it evaporate, strip away leaving a solid core? Will Earth survive or be deceaseb? Alot of new search say Earth will unable to escape su's engulfment. I say Earth is 70% chance to be decase when sun becoems a giant star.--SCFReeways 23:53, 1 October 2008 (UTC)

What will happen to the Earth is still very uncertain, while the Sun will probably expand to engulf the Earth's current orbit it may shed enough mass beforehand for the Earth's orbit to be enlarged enough for the Earth to escape. It's also possible that the Earth will survive being engulfed - the Sun won't be that big for long on an astronomical scale. Whatever happens, it certainly won't be inhabitable! The outer planets will continue in their (possibly slightly larger) orbits, although they'll now be in the cold and dark (Jupiter and Saturn are large enough that they may be able to keep themselves warm for a while). Eventually, due to passing stars, etc., the planets will be flung out of their orbits, but you could be talking quadrillions (10¹⁵) of years for that. --Tango (talk) 00:33, 2 October 2008 (UTC)

What about Venus' fate. I've elarnt Venus can also escape, but even if Venus escapes I thgoht the planet condition will just be worse. Venus' fate is not quite certain yet I thought. What you menat by eventually all planets will be flung out orbits. Will they drift away? So when sun becomes a white dwarf, it's gas will stay?--SCFReeways 00:41, 2 October 2008 (UTC)

• What happen to Venus I thoguht have some questions. I thoguht Venus may also widen orbits. I seen few sources say Venus will actually survvie over white dwarf. Even if Venus still exist over white dwarf, I thought Venus will just be frozen, dark, and deep cold.--SCFReeways 00:52, 2 October 2008 (UTC)
• Am I right saying this? Veuns fate is not that certain yet. If Venus still exist over sun's giant stage then it's surface will be total molten, all the atmospher' will totally been gone.--SCFReeways 00:57, 2 October 2008 (UTC)

I think there is a chance Venus' orbit could expand enough for it to escape, but it's less likely that for the Earth. When the Sun collapses to a white dwarf it's outer layers will be shed and will become a planetary nebula, which will quickly dissipate. The remaining planets (whichever ones survive) will become cold and dead (except maybe Jupiter and Saturn which may be able to generate their own heat for a while longer, I'm not sure how much longer they will generate heat for, they may have already stopped by then). --Tango (talk) 01:36, 2 October 2008 (UTC)

I saw on a documentary-style TV program that Jupiter and Saturn would be stripped of their gaseous layers. Remember that the sun shedding its outer layers is nothing compared to a supernova, but it'll still be very powerful (and fast-moving and hot). I don't know how to calculate something like that but maybe it's possible to, although there's probably a lot of uncertainty. ~AH1^(TCU) 21:37, 3 October 2008 (UTC)

Also, see formation and evolution of the solar system. New orbital calculations show that the Earth will probably be pulled into the sun. ~AH1^(TCU) 21:42, 3 October 2008 (UTC)

Was the theory that the exploding outer layers would strip the gas giants of their gas or that the increased energy from the sun during the red giant phase would strip them. The latter seems more likely to me. --Tango (talk) 23:21, 3 October 2008 (UTC)

By the time sun becomes a white dwarf, all gas giants could strip away gaseous envelopes leaving the core. For Earth, it seems to have greater chance to be engulf by 65%chance,then to survive at 35%chance about. Even if Venus and Earth survives over sun's white dwarf, it will just be total uninhabitatable. It will just change from surface fo molten rocks into a planet black, and bleak, and frozen cold. We do have questions to whether Venus will survive, it just don't have as many chance to survive than Earth does.--SCFReeways 23:32, 3 October 2008 (UTC)

October 2

List of official lab names

I have been trying for a long time to find a definitive list of all official medical laboratory (pathology) lab names. I have been able to find books containing all labs accepted by certain services, such as LabCorp. I need this to be electronic, not in a book. I also need it to be accurate. For example, "creatinine" is not a valid lab name. It must be "creatninie, serum" or "creatinine, urine" - two very different labs. Does anyone know of a list available online? I'm even happy to screen scrape a website if it actually has all the lab names. Just to note: I did try to use all the pathology items in CPT, but it is missing all incidental labs that you can't bill for. Also, you are supposed to license CPT just to know it exists. I hope everyone here has a license since I just mentioned it! -- kainaw™ 04:16, 2 October 2008 (UTC)

Well hey, if you know about LabCorp, why not call them up? Ask for "customer service, I need a full list of path lab names" - whoever is answering the phone will be confused and impressed enough that they will look at the list of internal numbers and pick one. Then you will get someone who was forwarded an outside call and will get your question answered. If it comes up, don't say "I'm just a student", say "I've just been given this project and I need to gather background information so we can get started". (And if you're not a student, whatever...)

Someone at LabCorp will know where that entire list is - please post it back here and into whichever article is most appropriate! Franamax (talk) 07:20, 2 October 2008 (UTC)

Headache

One thing I think I've noticed is that when you have a headache, if you lie on your back, it tends to get better, if you look downward, it tends to get worse, and if you lie to one side, the pain tends to move to that side. Presumably this would be because some sort of fluid (too high pressure of blood?) is causing the headache, and then it slowly drains certain ways depending on which way your head is aligned. My question is - is there anything to this at all, or is this just a placebo effect and I'm imagining a change in how much the headache hurts that doesn't really exist? And if there is some sort of basis to it, what would be the explanation? (I know you're not supposed to give medical advice, but come on. It's a headache.) zafiroblue05 | Talk 05:32, 2 October 2008 (UTC)

This isn't medical advice - but oohh baby, I know that feeling! I doubt it's blood, but certainly a sinus headache results from inappropriate pressure in the sinuses, and this can move around as you shift your head. There's also the factor of muscle tension, depending on your exact head position, you can build up the tension without knowing it. Depending on the cause of the headache, your balance organs may be affected too. If it's a migraine, all bets are off and it's just a world of pain.

It really comes down to your own particular headaches though, and your own experience. Headaches result from many different causes (including brain tumours, if that makes you feel any better :). If your headaches result from hangovers, the best position is non-bending-elbow the night before. So really, ask your doctor, just like we always say. :) Franamax (talk) 07:06, 2 October 2008 (UTC)

• Might also be blood pressure related. If your lieing down maybe your more relaxed? ---J.S (T/C/WRE) 07:25, 2 October 2008 (UTC)

First, you must find the cause of your headache. It is rather dumb to expect random users on the Internet with no medical experience to diagnose the cause of your headache. That is something a medical professional can do. Once you know the cause, feel free to come back and ask if there is a scientific reason that your specific type of headaches may change based on the position of your head. Anything said here could be based on a terrible misdiagnosis as your headache could be anything from purely imaginary, to simple dehydration (very common), to a brain tumor ... even to having a nail in your brain. In head trauma it is common to forget the incident. So, you could get shot in the head with a nailgun, forget the incident, and walk around not knowing you have a nail in your brain. -- kainaw™ 12:11, 2 October 2008 (UTC)

Before anyone laughs at Kainaw's suggestion, note that it's possible to be shot – in the forehead – and not realize you have a bullet in your skull: [25]. (There are a number of similar cases in the medical literature. While bullets to the head are normally both obvious and rapidly debilitating, there are exceptions.) TenOfAllTrades(talk) 16:24, 2 October 2008 (UTC)

I believe at this point it is traditional to mention Phineas Gage, with a comment such as "Call that a headache ? ...". Gandalf61 (talk) 10:20, 3 October 2008 (UTC)

Name this bug

Locale: Vancouver (actually Surrey) BC, oceanic climate or "inter-coastal Pacific-Northwest" - take your pick.

Diagnostics: body length 20-25mm, diameter 10-12mm. Body with three distinct black/white bands "salient" (45° dorsal leading - like "///"+head ). Four dragonfly-style wings. Distinct proboscis.

Activity: Using long proboscis at multiple flowers.

I've never heard of anything like this. Does anyone have some clues? Franamax (talk) 06:49, 2 October 2008 (UTC)

If it has a long proboscis, and feeds at flowers, it sounds like some sort of moth. If the four wings flap independently (they're probably moving too fast to tell), then it is not a moth. It's difficult to say what it is without a picture.CalamusFortis 15:06, 2 October 2008 (UTC)

Do any of the pictures in Hoverfly look familiar (assuming that you're wrong about the four wings)? Deor (talk) 15:38, 2 October 2008 (UTC)

Hoverfly, specifically Chyrysotoxum intermedium elicited an immediate response on viewing the samples. Mommy doesn't have to go to the home yet, it seems the bug does exist :) The caveats were that the observed head was smaller in relation to body size and the proboscis was significantly more extended. Given the approx. 6000 species involved, I declare a semi-exact match. Deor, keep cleaning that article up if you can, the bottom 5 sections are quite confusing (but it's all good). Thanks! Franamax (talk) 06:57, 5 October 2008 (UTC)

Is this Rose quartz?

Is this really what I think it is?

Is this actually rose quartz? It's my first guess, but I'm not a geologist... so I figure it's time to get a second opinion! ---J.S (T/C/WRE) 07:25, 2 October 2008 (UTC)

The pink parts look like rose quartz, but the yellow bits would be iron staining limonite. Graeme Bartlett (talk) 13:00, 2 October 2008 (UTC)

That would fit. ---J.S (T/C/WRE) 17:50, 2 October 2008 (UTC)

Axully, this looks more like Orthoclase feldspar, but it could be rose quartz. IDing a mineral sample from a photograph is difficult... --Jayron32.talk.contribs 03:42, 3 October 2008 (UTC)

I tried to get a high-quality macro photo of it to help identification. Unfortuantly this stone is under a few feet of water in Folsom Lake. :) ---J.S (T/C/WRE) 01:23, 6 October 2008 (UTC)

Driving a T-72 tank

As we know from the news, Somali pirates have captured a ship with 33 T-72 tanks. Of course, the US, UK and Co. will not let them go away with it, but if they were able to unload the ship, would they also be able to use these tanks? Mr.K. (talk) 08:08, 2 October 2008 (UTC)

Well driving a tank will require knowledge of how to operate the tank. Without knownig about the state of these stolen tanks, I suspect yes...if they could unload them they could maybe 'use' the tanks to some degree (perhaps basic manouvering), but perhaps not all - it depends on how intutitive the tank's controls are (judging from what i've seen on tv - not very at all!!). 194.221.133.226 (talk) 08:51, 2 October 2008 (UTC)

The main thing is, they will be able to sell the tanks farther inland, to people who are able to ask around for someone who knows how to run a T-72. Such operators exist and can be hired. And realistically, a machine is a machine, you can always figure out how it works.

The sea-pirates themselves likely won't try to operate the tanks. The first time they try to take one out to intercept a ship on the high seas, they will see the big flaw in that plan. And anyone who they sell on to will quickly run up against the spare part problem once something breaks. Their rational strategy is to ransom back the tanks and ammunition, same as they do with ships, standard cargo and crew. Franamax (talk) 09:58, 2 October 2008 (UTC)

Yes, and perhaps there are some Russian trained mercenaries deep into Somalia that always wanted to drive such a thing and know more or less how to do it. At least driving the old model doesn't seem to be that difficult, as this BBC articles shows. Mr.K. (talk) 10:28, 2 October 2008 (UTC)

If you look over this page, you'll see that the T-72 and its variants have been used by many countries so there are plenty of people that are fully trained in their operation.--droptone (talk) 11:26, 2 October 2008 (UTC)

When I was in 29 Palms, they would let kids drive around the T-72 and M1A1 tanks on Tankers Day. I'm certain that it is considered a security risk now, but there are plenty of kids who are now adults and know how to, at a minimum, make the tank for forward and turn. -- kainaw™ 12:05, 2 October 2008 (UTC)

The T72 uses standard dual stick controls, with each stick controling its sides engines and brakes, and a single gear lever. Actually driving the tank should be fairly easy, at least if you don't care about running over things. Using the gun might be hard but the gun contains an autoloader, so that is no issue, and moving the turret will be easy too. Hitting things at a distance with such an old tank might be hard as it lacks the fancy laser range finding and targetting kit of a modern tank. The machine guns are standard Russian machine guns that many of them know how to use already I'd wager. I'm sure with a couple of weeks of experimenting they could figure out how to use a tank in some capacity. The main issue is going to be fuel. Tanks use fuel so fast it would make an SUV swoon. 88.211.96.3 (talk) 12:23, 2 October 2008 (UTC)

If you look at news reports, most people aren't particularly worried about the tanks. That's because they are rather large objects which won't easily be offloaded from the ship which is surrounded by several navy vessels as well as under air surveilance. However the other weapons and ammunition, which could more easily be offloaded are of far greater concern. Also, the tanks are worth rather a lot of money meaning that people would like to get them back Nil Einne (talk) 13:06, 2 October 2008 (UTC)

Presumably these tanks come with an owner's manual in the glove compartment? Or, more likely, many thousands of pages of documentation? --Sean 14:33, 2 October 2008 (UTC)

In Somali? Nil Einne (talk) 17:32, 2 October 2008 (UTC)

The interwebs has translators. :) ---J.S (T/C/WRE) 17:53, 2 October 2008 (UTC)

Chinese contributions to engineering

what are the contibutions of the old chineese era in the field of engineering? —Preceding unsigned comment added by Kim014 (talk • contribs) 12:42, 2 October 2008 (UTC)

oil rig wheelbarrow great wall of China, water control. Graeme Bartlett (talk) 13:04, 2 October 2008 (UTC)

Gunpowder,fireworks? 88.211.96.3 (talk) 13:18, 2 October 2008 (UTC)

Blast furnaces, high temperature kilns, ceramics. There's a gigantic list at List of Chinese inventions to look and pick through. Sjschen (talk) 15:45, 2 October 2008 (UTC)

Flight? Plasticup ^T/C 15:55, 3 October 2008 (UTC)

Coloured lights used on CSI

After watching several episodes of CSI, I have seen the characters use several kinds of lights to detect otherwise invisible markings (eg blood which had been cleaned, stains on sheets etc). These lights vary in colour, are always seem to require either a screen to shield the user's eyes from the beam (a coloured screen attached to the light), or for the user to wear coloured goggles. My question: what are these lights (I was going to guess ultraviolet)? Why the need for the coloured screen/glasses? And why do they change colour from episode to episode - are different "colours" used to detect different substances/markings? Thanks very much in advance! — QuantumEleven 12:55, 2 October 2008 (UTC)

This is probably using the same CScIence that allows them to go "Zoom! Now enhance" and make some grainy pixelated CCTV footage show you the face of the killer (I swear to god they rotated the position of the image to show his face once). In other words total rubbish. 88.211.96.3 (talk) 13:17, 2 October 2008 (UTC)

Actually, it's quite reasonable. Skiers tend to prefer amber-colored sunglasses, for instance, to maximize the contrast of their particular environment. Using something similar to highlight a crime scene makes sense. — Lomn 13:30, 2 October 2008 (UTC)

The two specific instances that the original questioner brings up are both indeed ultraviolet light. Semen stains fluoresce under ultraviolet lamps; for fun, bring one to the next hotel you stay in. And cleaned blood stains are detected by spraying the area with a mixture of phenolphthalein and hydrogen peroxide, and then looking at the area with an ultraviolet lamp. This is also called the Kastle-Meyer test. Note that these are presumptive tests only: they can't actually identify the stain as semen or cleaned blood, but they can tip you off that the stain is there so you can perform further testing to actually identify what made the stain. The goggles, as you note, are used to protect the eyes from high-intensity ultraviolet radiation. - Nunh-huh 13:59, 2 October 2008 (UTC)

Thanks for the answers, Lomn and Nunh-huh. The glasses to enhance contrast make sense, and to protect the user's eyes (in which case, the little plastic shield on top of the light probably doesn't do a whole lot of good?). I'm still curious as to the changes in light colour (although that might be down to "it looks cool" on the part of the producers of CSI?) — QuantumEleven 14:51, 2 October 2008 (UTC)

There's a little discussion about potential danger to the eye in the ultraviolet article. You might also be interested in Luminol. --LarryMac | Talk 15:30, 2 October 2008 (UTC)

The change in light colour? Do you mean the fluorescence of whatever UV radi. is being shone on or the result of the light from fluorescence being filtred by the glasses? Sjschen (talk) 15:36, 2 October 2008 (UTC)

I would speculate that since the show is recorded and broadcast electronically, a white balance must be determined for each scene. If the balance is a little in one direction or another, when the image ends up on your TV it may have either a more purple or more blue hue to it, depending on the rest of the scene. --66.195.232.121 (talk) 16:45, 2 October 2008 (UTC)

Have you watched CSI? I don't watch it regularly but caught part of an episode of CSI Vegas while waiting for my take-out food to come in. The whole thing is practically filmed in the dark and every light is tinted. It's "dramatic lighting" taking to the most ridiculous, preposterous extreme (where courts of law look like night clubs). I don't think it's an issue with them adjusting their TV. --98.217.8.46 (talk) 22:25, 2 October 2008 (UTC)

CSI Miami is weird. The sky's green and all the other colours are unnatural. The overly forced, mannered, unnatural acting of David Caruso is in keeping with the unnaturality of the colours. I can't recall him acting that way in other shows I've seen him in, so I guess it's how he or the producers want his character to be. It sure gets my attention every time I watch it. But I thought actors weren't supposed to be drawing attention to their acting; for that hour we're supposed to be believing he really is the person he's playing. -- JackofOz (talk) 00:55, 3 October 2008 (UTC)

It's worth saying one more time. THIS IS FICTION...IT'S NOT REAL! Nothing that happens on these shows has to have any scientific validity whatever. CSI is notorious for performing tests that (in reality) take months in mere seconds - they have rolled every kind of separate lab into a single lab - they've taken away all of the super-careful (and super-tedious) paperwork that has to go on - the control tests - the need to preserve evidence for the defense lawyers to do their own tests on. Long waiting lists for some kinds of test are replaced by someone typing something into a computer and getting an answer in seconds. So the fact that there are some fancy colored lights that show who-knows-what has only coincidental resemblance to what REALLY happens in real forensic labs. SteveBaker (talk) 01:19, 3 October 2008 (UTC)

Yeah. But not everyone realises that, which is why there's the CSI Effect. I wonder how much the technical advisers are being paid for these shows that distort reality so massively. -- JackofOz (talk) 02:22, 3 October 2008 (UTC)

Going back to what 88.211.96.3 touched on; the seemingly crazy enhancement of CCTV and photographs. Obviously you can't tease data out of a picture taken at a low resolution because it just isn't there. What you could do, in principle, is extrapolate from base data. Is that still then admissable as evidence, given that it's effectively "made up" and doesn't exist outside of a (clever) computer algorithm? I guess what you could do is deliberately get some low-res photos of known subjects (i.e. you have higher res copies) and then run your "enhancer" on them, and then compare the results. I'm concentrating on computational examples, but of course the human mind is adept at seeing patterns in this fashion. I've seen tons of episodes where they have a scrap of company headed paper, and manage to work out which firm it is from that. What's the difference? --Rixxin 19:15, 3 October 2008 (UTC)

I certainly wish I had a dollar for every movie/TV show where our hero points at a screen and says "Zoom in there...enhance...now zoom in some more...enhance...enhance some more...AHA! That proves it was Colonel Mustard in the Dining room with the Candlestick!". Well, in truth, there really is only a very limited amount of enhancement you can do - the information simply isn't there - and you can't get information from nowhere. There is a LITTLE that can be done though - if you know a lot about the lens/mirror system that was used to take the original image. There were some algorithms developed on the Hubble telescope that provided modest enhancement when the mirror was discovered to have been ground incorrectly. But if you don't know the exact characteristics of the lens, or if the limiting factor is not the lens but the grain in your film or the resolution of your image sensor - then those "enhancement" tricks are purely cosmetic - to trick the eye into believing the image is sharper without actually revealing any more detail. The "standard" trick is called an "unsharp mask" - what you do (in effect) is to take a copy of the image, deliberately blur it a bit - and then subtract the blurry version from the original. Amazingly, this really does remove some of the blurriness and results in the image looking much crisper. If you overdo it, you end up with the edges in the image standing out and actually obscuring "real" details in the photo. However, this won't help you to solve the murder by reading the date off of that newspaper that some guy in the background of the shot is holding! SteveBaker (talk) 13:09, 6 October 2008 (UTC)

There are also some algorithms that can extract a sharper image from a series of related images - e.g. if you had some grainy video of a UFO flying across the sky, they might be able to give you a single, not-as-grainy photo of a frisbee. It's still got its limitations, though. Confusing Manifestation(Say hi!) 22:54, 6 October 2008 (UTC)

sex change m to f

when a man changes sex. do she get the same fellings as awoman —Preceding unsigned comment added by 86.15.87.151 (talk) 20:26, 2 October 2008 (UTC)

I believe not, although you might like someone to verify this if it is important you are correct. Anonymous101 (talk) 20:37, 2 October 2008 (UTC)

You might be interested in our articles Transwoman and Sex reassignment surgery (male-to-female). --Allen (talk) 21:10, 2 October 2008 (UTC)

Men already have the same feelings as women, however sex hormones do affect the way the two sexes deal with their feelings. Men getting a sex change spend a long time taking women's hormones before the surgery and this could have an effect on the way they experience their emotions. -- Mad031683 (talk) 21:15, 2 October 2008 (UTC)

I suspect that by "feelings" the questioner was referring to "sensations" Plasticup ^T/C 04:34, 3 October 2008 (UTC)

How could she possibly know? --ColinFine (talk) 18:55, 4 October 2008 (UTC)

October 3

Prolonging orgasm

Is there any safe way of prolonging orgasm in men up to, say 10 mins (I think that would be enough). I know that boars (male pigs) can do it for about 20 mins (even with a dummy sow). Lucky boars!--79.74.251.204 (talk) 00:17, 3 October 2008 (UTC)

Umm, you know that? Really? hydnjo talk 00:45, 3 October 2008 (UTC)

[26]

Do you mean delaying orgasm or making it last longer? Some drugs and herbal supplements are availible which claim to increase both semen volume and number of contractions, however I can't imagine that continuous ejaculation for 10 minutes would be all that enjoyable. After a short while, it would probably become more like dry heaving from the penis, which isn't my idea of a good time. --Jayron32.talk.contribs 03:38, 3 October 2008 (UTC)

That may be the ticket for some folks. -hydnjo talk 04:44, 3 October 2008 (UTC)

Some years ago there was experimentation with electrical or chemical stimulation of so-called "pleasure centers" in the brain [27] [28] [29] [30] of rats and humans. Edison (talk) 05:18, 3 October 2008 (UTC)

Yes: ESO: How You and Your Lover Can Give Each Other Hours of Extended Sexual Orgasm. An interesting footnote is that this book was originally co-authored by Pulitzer Prize-winning author Richard Rhodes, though for some reason he's been dropped from the author list in subsequent revisions. I "hear" that the method works. --Sean 14:06, 3 October 2008 (UTC)

Who invented the floor buffer?

Question as topic. I'd like to add the info to the article I've been working on. I don't seem to be able to find anything useful using Google. --Kurt Shaped Box (talk) 02:27, 3 October 2008 (UTC)

The first reference to an electric floor buffer I found at Newspaper archive was a classified ad in The Hayward Daily Review, (Newspaper) - April 6, 1942, Hayward California, Classifieds, page 2. It was a floor sanding machine from Montgomery Wards which included tampico scrubbing/polishing brushes, a buffing and polishing wheel and a steel wool floor buffer for $32. Google Books has no view but lists patent 1,468,080, from 1876, for a "floor buffer." No idea how it compares to modern ones, but it would clearly not have an electric motor. Once central station electric power was available in the 1880's the application of connecting an electric motor to a pair of counterrotating brushes would be very obvious and the device should have been commercially available by the 1890's to reduce the labor of polishing floors. Edison (talk) 03:44, 3 October 2008 (UTC)

Did we really not have an article on floor buffers until today? That would make a great DYK. Plasticup ^T/C 15:45, 3 October 2008 (UTC)

What, the article I started - or the fact that WP didn't have an article on floor buffers until yesterday? ;) Yeah, I was surprised to see that was still the case too - I actually mentioned the fact a few months ago (I think when we were discussing floor buffer/MRI interaction). For some reason (don't ask why), I thought about it yesterday. --Kurt Shaped Box (talk) 23:43, 3 October 2008 (UTC)

Thanks - but I'm not quite sure how I'd be able to cite that in the article (if you know better, feel free). Yaknow, I was quite surprised that no-one (apparently) has a website dedicated to floor buffers and the history thereof - considering that lawn mowers and vacuum cleaners seem to have a fair number of fanboys on the net. --Kurt Shaped Box (talk) 23:43, 3 October 2008 (UTC)

US672930 (filed 1901-09-01) is the first one I find for a powered buffer device (appears to rely on external/unspecified rotation power source). It's fixed in place and moves a buffing wheel against a flat surface placed against it (shop machine) rather than being moved against a flat surface (i.e., "the floor"). US871450 (filed 1906-02-24) is the earliest floor buffer, but it's just a block with a a fixed buffer/sander surface (not powered motion). Putting everything together (a electric-motor-powered floor-oriented machine) looks like it starts with US915752 (filed 1906-12-22). Who said Rhode Island was too small to matter or that bowling never led to anything useful? US1468080 was actually filed 1921-03-24...not sure why/where is would be noted as from 1876. DMacks (talk) 14:07, 5 October 2008 (UTC)

So, how would I go about properly citing a patent in an article? I've never done it before... --Kurt Shaped Box (talk) 23:06, 6 October 2008 (UTC)

We have a template for that: {{Cite patent}} Plasticup ^T/C 23:18, 6 October 2008 (UTC)

Note that for research purposes, Google Patents beats the pants off of esp@cenet and USPTO in terms of both the search and display interfaces. DMacks (talk) 01:55, 7 October 2008 (UTC)

Anatomy / behaviour of bullocks etc

Okay, so I hope this isn't too stupid a question (or set of questions). Don't feel you have to answer every single question below in order for your reply to be useful, as any helpful pointers would be great.

I've read that bullocks are castrated bulls, and according to the Ramblers Association in the UK they are exempted from the laws which restrict the keeping of bulls in fields crossed by public rights of way -- they write:

"Although there are specific legislative restrictions on the keeping of bulls, these do not apply to cows and bullocks, which can also be very aggressive." [31]

So presumably then they are less aggressive than "normal" bulls. But just how likely is a bullock to be aggressive? About the same as a cow? Or more so?

How common practice is it to castrate bulls, e.g. would a beef farmer typically castrate most of the bulls and just leave a few for mating? At what age would this normally be done, and for sake of comparison what age is puberty?

Also how do you distinguish bulls from bullocks? Does it require a clear view of the area where the testicles should be (from an angle where this is not obscured by hind legs), or are there other obvious differences which are evident e.g. from the overall build of the animal? I am really after simple guidelines so that when encountering one in a field I make a quick and reasonable decision on how likely it is to be aggressive.

Actually another maybe really stupid question. I'd sort of assumed that the centrally located bulge (i.e. about half way between front and rear legs) is where the penis is -- it would certainly make sense as regards the mating position for it to be further "forward" than in a human -- but it also seems that cows sometimes have a bit of a bulge in this area too. So what am I actually looking at in that case? Do I actually need to see the udders to be confident that it's "only" a cow?

Of course there is also the whole issue of breeds of bull, and if anyone has any good pointers on that, then that would be very useful as well. In principle a dairy bull would be more aggressive by all accounts, but it seems to me that there are so many different breeds that you'd have to be something of an expert to know which is which.

Thanks. Are a wiki (talk) 09:17, 3 October 2008 (UTC)

I can't speak to bullocks, but in capons (castrated roosters), the animal is not only less aggressive, but also has more hen-like physical characteristics (more body fat, etc.). --Sean 14:09, 3 October 2008 (UTC)

See also oxen, which are castrated bulls used in situations where docility is required. There are no "breeds of bulls" but see List of breeds of cattle. Rmhermen (talk) 15:17, 3 October 2008 (UTC)

Castrated male cattle are sometimes also called steers. -- 128.104.112.147 (talk) 15:36, 3 October 2008 (UTC)

Nevermind... --Jayron32.talk.contribs 20:41, 3 October 2008 (UTC)

Bullocks are roughly as aggressive as cows, i.e. not very. If walk through a field with bullocks in, they can be curious and start following you. Not really dangerous; just walk on briskly. The situation that would be most likely to lead to a serious accident is if you were at the bottom of a steep bank and one or more stumbled down on top of you. A beef farmer would typically castrate all the male animals and use artificial insemination for breeding. It's only in traditional farming - for example organic - that bulls are still kept outdoors. I've hardly ever seen a bull when out walking in England, but I've seen them often in parts of France. If the bull is with cows in theory it is docile but I wouldn't risk it. If it is in a field on its own, take the long way round. The males are castrated when they are cute little calves. A bull is quite easy to distinguish: it is massively built and has sizable tackle in the middle of its belly. You'll also learn to distinguish dairy and beef cattle. All cows is a dairy herd, in England usually black and white Friesians. All bullocks is beef cattle. Cows with calves could be either. Advice is to avoid walking between a cow and her calf, which is actually not difficult. Happy rambling!Itsmejudith (talk) 17:23, 5 October 2008 (UTC)

Google Image Search gives an anatomy poster here. BrainyBabe (talk) 17:33, 5 October 2008 (UTC)

Generally per Judith except: AI can be problematic and it is expensive, so it's not that uncommon to select a promising AI-inseminated male calf from your best cow, and use it to naturally inseminate the (non-related) rest of your herd. For high-performance dairy cows, you might want to go AI-only, for beef cows, maybe a different approach - you want a cow that gives good milk but not too much (avoid mastitis), and has a good temperament. You will only want one mature bull, otherwise you will end up with fights and just the smell of the other bull will make the one you're in the pen with impossible to control. Remember that bulls and farmers work on a consensus basis - if the bull is happy, everything is good.

I would not personally recommend walking through any field where a bull is present, unless you are closer to the fence than the herd is to you. Remember too that cows are naturally curious and will come closer to check you out - the bull will eventually notice that and exercise his prerogative to walk out in front of all the girls to check out the new centre of attention - and they're not all that smart.

And I've never known a cow separated from her calf to be aggressive, though she might moo enough to get the calf running. Waving your hands is usually enough in any case. OTOH I usually carried a cane walking through our herd, and I was respectful of the Scottish longhorns - but I've never been charged by a cow, nor a steer. Never been charged by a bull either, but as I said, that was a consensus happy-time decision - I always made sure not to upset the bull, what with the 1000-pound weight differential.

As far as the original anatomy question, all cattle have that distinctive shape on the abdomen, but males have extra longish hair at the pendant point (and pee from that spot), and uncastrated males are distinctively more bulky in general and "well-equipped" at that point. If a significantly larger animal of the herd is approaching you, it's best to rapidly retreat. Threats and appeals to reason are unlikely to help the situation. Franamax (talk) 00:19, 7 October 2008 (UTC)

1)But if you decide that discretion is the better part of valour and retreat, what might trigger it to run after you? 2) Why do females have that shape on the abdomen if it isn't a penis? Is it like the hyena? BrainyBabe (talk) 20:41, 7 October 2008 (UTC)

Misshapen head treatment

What is that treatment called where a baby has a slightly misshapen head and is "corrected" by having the baby wear this head device for several years so that the skull can be shaped to a "normal" form? I read that some native american tribles had done this in reverse decades ago for aesthetic reasons, meaning they deliberately tried to flattened the baby's head....--Anilmanohar (talk) 12:55, 3 October 2008 (UTC)

The Native American tribe you are likely referring to are the Flatheads. Of note, they did not flatten the baby's head. That is folklore. The truth is that a neighboring tribe used head binding to produce pointy heads. So, the normal people were called "flathead." In modern times, a device that it used to change the shape or position of bones (even the skull) is called a brace. There is no specific term for it. It is often termed by the usage, such as dental braces or orthopaedic braces. -- kainaw™ 13:02, 3 October 2008 (UTC)

The technical term for what you are referring to is plagiocephaly (though this entry is pretty much a stub). There is also an entry called positional plagiocephaly which has a tiny bit more discussion of the etiology and treatment. Medical geneticist (talk) 13:27, 3 October 2008 (UTC)

Craniosynostosis. Plasticup ^T/C 14:40, 3 October 2008 (UTC)

It is correct that craniosynostosis is one cause of plagiocephaly (which is simply a technical term for "misshapen head"). The distinction is that craniosynostosis usually requires surgical correction because it involves abnormal premature fusion of the skull bones, while positional plagiocephaly is a deformity that can be corrected by putting a fancy helmet on an infant, which gradually reshapes the bones of the skull while they are still pliable. Medical geneticist (talk) 16:10, 3 October 2008 (UTC)

Someone asked a similar question a couple days ago. -- MacAddct1984 ^{(talk &#149; contribs)} 14:59, 3 October 2008 (UTC)

You may be thinking of the Inca practise of cranial deformation. I haven't studied the topic myself and our article basically just repeats the essence of the blurb here. IOW, yes they did it, but the reasons why are still somewhat unclear. Matt Deres (talk) 16:32, 3 October 2008 (UTC)

Urinary Tract Infection Cause?

From the CNN article: http://www.cnn.com/2008/HEALTH/10/03/bathroom.hygiene/index.html

"It's fine for a woman to hover over the toilet seat if she doesn't want to sit down, but if she doesn't empty her bladder completely, she's at risk for a urinary infection, Bernstein said."

Why is this so? --Anilmanohar (talk) 14:01, 3 October 2008 (UTC)

Because urine acts as a culture medium for bacteria; if the bladder is completely emptied, the urine isn't there to be infected. If the bladder is incompletely emptied, it contains urine that can become infected. The risk is greater for women than men (because women have shorter urethras), but incomplete emptying of the bladder in men (often as a result of protate enlargement) also predisposes to infection. An empty bladder is protected from infection by urothelial surface mucoproteins, but urine has no such defense. - Nunh-huh 21:03, 3 October 2008 (UTC)

"urine acts as a culture medium for bacteria" ??!? Whaaaat? That's not right - Urine (as our article points out) is an antibacterial agent. "Urine has also been historically used as an antiseptic. In times of war, when other antiseptics were unavailable, urine, the darker the better, was utilized on open wounds as an antibacterial.". SteveBaker (talk) 12:38, 6 October 2008 (UTC)

My completely unreferenced understanding of this is that urine remaining in the urinary tract is a source for bacterial accumulation. In other words, for males drinking their own pee (don't laugh, it's both a survival and religious tactic), the first few inches of discharge are un-good, the rest is fine. In the context of the question above, I would interpret this factoid as meaning that premature termination of urination would leave urine in the GU tract, where bacterial proliferation could occur. Franamax (talk) 23:33, 6 October 2008 (UTC)

The reason certain bacteria cause urinary tract infections is precisely because they resist the antibacterial properties of urine. If these antibacterial properties were stronger and controlled all strains of microorganisms, we wouldn't get urinary tract infections. But they're not, they don't, and we do. And all urine is not alike. Any antibacterial effect depends primarily on osmolality, urea concentration, ammonium concentration and pH. And of course urease-producing organisms like Proteus mirabilis love urine. - Nunh-huh 12:01, 7 October 2008 (UTC)

Baby Powder scent?

What's the origin of the "baby powder" scent? What is it supposed to smell like? Why has that scent become associated with all things baby? --70.167.58.6 (talk) 16:54, 3 October 2008 (UTC)

Baby powder (Johnson and Johnson)?--GreenSpigot (talk) 17:28, 3 October 2008 (UTC)

How are these links relevant? --70.167.58.6 (talk) 18:53, 3 October 2008 (UTC)

Most baby powder is made by Johnson and Johnson. So you could ask them--GreenSpigot (talk) 19:52, 3 October 2008 (UTC)

Baby powder is classically made of talcum powder, and I would assume that the particular mineral composition is responsible for the smell. As to why that smell is associated with "all things baby", it probably has to do with the millions of baby bottoms that have had talcum powder applied to them. Medical geneticist (talk) 22:16, 3 October 2008 (UTC)

Poor little buggers. Talcum powder has been the cause of more nappie rashes than babies have had poos. When they wet themselves, the powder turns to a fine grinding agent. Far better to use a little baby oil, and no powder. -- JackofOz (talk) 23:57, 3 October 2008 (UTC)

I don't buy that. Talc is one of the softest substances out there. Check out Mohs scale of mineral hardness - talc is a 1 on Moh's scale - which makes it the least hard substance on the scale. SteveBaker (talk) 12:33, 6 October 2008 (UTC)

I'm sure that's right, Steve. However I was told this when son #2 came along, by senior babycare educator nurses at the hospital, who all agreed that the traditional talcum powder treatment is not only less effective than oil, but causes or at least contributes to nappie rash, so it's actively discouraged these days, certainly in Australia. If the reason for the powder is just make the baby smell nice, that's unnecessary - they smell good naturally. Until the inevitable happens, that is, but talc certainly doesn't mask that smell, and shouldn't be used with purpose in mind. -- JackofOz (talk) 23:57, 6 October 2008 (UTC)

Well they make unscented baby powder, so natural talc doesn't have a smell. It's an added fragrance. --70.167.58.6 (talk) 15:29, 4 October 2008 (UTC)

It doesn't necessarily follow that natural talc doesn't have a smell, just because a version which hasn't had scent added exists. I tend to think of the natural smell of talc as 'chalky', where smell should probably be clarified as the sensation when some of it gets in your nose after a cloud of the stuff has been puffed around you. Whether this is the same smell as you were asking about, I don't know. Maybe you're asking about the smell of the typical added fragrance? 79.66.9.134 (talk) 18:21, 4 October 2008 (UTC)

The talc powder that you scratch off a rock definitely don't have that baby powder smell... --antilived^{T | C | G} 21:56, 4 October 2008 (UTC)

The fragrance is added. Check the ingredients. --Russoc4 (talk) 23:58, 4 October 2008 (UTC)

So back to the original question: what is it supposed to smell like? Is there anything in the world that smells like Baby Powder? --70.167.58.6 (talk) 15:39, 5 October 2008 (UTC)

It seems that Johnson & Johnson created a scent for their talcum powder that they thought help market it to parents, who would have been used to fragrances added to soaps, shampoos, cleaning products etc. Now people associate this scent with babyhood and the company is unlikely to change it. Isn't it the same scent in their baby oil? Itsmejudith (talk) 16:17, 5 October 2008 (UTC)

The J&J babypowder is indeed a perfume, in fact the marketing of this product has been so successful that its perfume scent accord is associated with a baby-hood. As such, any other company in North America producing baby products have to scent their products with similar accords or risk being shut-out. I've heard that associations of baby products with the J&J scent is limited mainly to North America; European baby products are scented primarily with lavender. Demeter fragrance has a pretty similar baby powder perfume. Sjschen (talk) 21:54, 5 October 2008 (UTC)

You don't get out much, do you? When was the last time you had a girlfriend or a female of some sort? Are you gonna write more paragraphs now?--Anilmanohar (talk) 13:21, 7 October 2008 (UTC)

What? Zain Ebrahim (talk) 13:38, 7 October 2008 (UTC)

magnetism

hi .... i have a question that why a magnet only attracts a magnet??? ... why not any other thing??? —Preceding unsigned comment added by 116.71.246.18 (talk) 18:13, 3 October 2008 (UTC)

On a macro scale, magnets do attract things that aren't magnets; see Paramagnetism. On a micro scale, magnetic fields also affect moving electric charges in addition to magnetic dipoles. As for why the electromagnetic force behaves the way it does, check that article, but I think whether an answer exists probably depends on how deep a "why" you're looking for. --Allen (talk) 18:37, 3 October 2008 (UTC)

Huh? --ColinFine (talk) 19:00, 4 October 2008 (UTC)

This is clearly not true! A magnet attracts all sorts of non-magnetic objects. Admittedly, only a few metals respond to magnetism (you can't pick up a chunk of aluminium with a magnet, for example) - but those that do (iron, for example) can be attracted to a magnet even if they are not, themselves magnetized. To convince yourself of this - get a refrigerator magnet. It sticks to the metal of your refrigerator - right? But remember that magnets only attract each other if the north pole of one magnet is close to the south pole of the other - north-to-north or south-to-south, they repel. If the refrigerator door was magnetized then it would have to be exhibiting (say) a south pole on the surface to attract the north pole of the fridge magnet. If you flip the fridge magnet over so the south pole is now facing the door - then it should be repelled...but it's not - it still sticks. Since the refrigerator door can't be presenting both a north pole and a south pole at the same place - you know that it ISN'T magnetized. SteveBaker (talk) 12:26, 6 October 2008 (UTC)

Umm, Steve, the fridge door is an induced magnet isn't it? It is a ferromagnetic material, when another magnet is brought close the unpaired electron spins align (I could be wrong here - is it the atomic spins?) (ferromagnetic domains are coerced into alignment) and it becomes a magnet. Based on my experience with training screwdrivers to pick up metal stuff (like screws), some residual magnetism could be measured in the fridge door after the encounter. In my book, that makes it a magnet. Franamax (talk) 23:20, 6 October 2008 (UTC)

Mules

Mules are F1 hybrids between horse and donkey. Both belong to the genus Equidae in the Biological classification.

There is 94% identical DNA between human beings and chimpanzees. What % of identical DNA does horses and donkeys have? If it is equal or more to humans and chimps, why are there no F1 hybrids (or whatever) between humans and chimps? --Anilmanohar (talk) 19:39, 3 October 2008 (UTC)

See Humanzee for the details. As to why there are none even if it was possible, it's because of the ENOURMOUS social taboo against it. No scientist smart enough to do it would even dare attempt it. 83.250.202.36 (talk) 19:57, 3 October 2008 (UTC)

Sure, but no scientist has to be involved to make a mule. --Sean 11:57, 4 October 2008 (UTC)

Yeah, but I don't think it's likely that any human would naturally have sexual intercourse with a chimpanzee due to the same social taboos. --Tango (talk) 16:59, 4 October 2008 (UTC)

Hmm. --Sean 14:26, 6 October 2008 (UTC)

Actually Equidae is a family, though Equus does appear to be its only surviving genus. But while the question is worth asking, do be cautious about that sort of numerological argument: there is no reason to suppose that there is some particular percentage of common DNA which is the threshold for the possibility of viable offspring.

Note also that all surviving equids are classified as the same genus, whereas no surviving apes are in the same genus (homo) as humans. This is not conclusive - levels of taxonomy are not always self-evident - but it is indicative. --ColinFine (talk) 19:14, 4 October 2008 (UTC)

I'm surprised no one has bothered to read my questions and try to answer them. --Anilmanohar (talk) 13:37, 6 October 2008 (UTC)

That's more than a little unfair. I think we all read your question...but it's probably impossible to answer it. Nobody (as far as I could discover) has yet sequenced Donkey DNA. It's likely that racehorses have been sequenced - there is a lot of money in breeding them - but the people involved do not appear to wish to advertise the results. Hence it's almost certain that the first part of your question is unanswerable - so nobody HAS answered it. User:ColinFine did point out that knowing the percentage of DNA in common doesn't necessarily lead to an explanation of why two different kinds of animal can interbreed - which kinda makes your question moot. And several of us did answer the part about Human/Chimp hybrids - both by explaining why nobody has tried to produce such a hybrid (as if it wasn't bloody obvious already!)...and by pointing you to our article on the subject.

But you can't tell by reading the answers whether anyone tried to find an answer or whether we read the question carefully - and it's quite rude (for someone who is asking for a HUGE favor) to just assume that we didn't. In fact, when we try to find an answer and fail - we don't generally bother to discuss that. But it's quite rude to claim that we didn't read your questions. I certainly did, and I'm sure that at least a dozen other regular contributors did too. Yesterday morning, I searched online for about 15 minutes to try to find out whether Donkey/Horse DNA had yet been sequenced and didn't come up with an answer to that piece of your question - I'd planned to search some likely journal indices at the UTA library today or tomorrow - but since you've been so rude, I don't think I'll bother.

SteveBaker (talk) 14:29, 6 October 2008 (UTC)

Steve, the correct response would be: "The % of identical DNA horses and donkeys have is not known. Thus, your second question is unanswerable." Stop taking things so personal. My original response was not a rude one. It was a true one. Thus my original response still stands as is. --Anilmanohar (talk) 18:21, 6 October 2008 (UTC)

Excuse me? You said that "no one has bothered to read my questions" - which is (a) an accusation of laxity on behalf of those of us who contribute time here for no recompense (b) utterly untrue - at the very least I read every single question that shows up here (and I'm pretty sure most of the other regular contributors did too) and (c) this something you could not possibly know. Hence your accusation is utterly inappropriate. You went on to say that nobody had answered your question - when in fact we had gone a considerable way towards doing so. Now you suggest that we should have said that the "% of identical DNA horses and donkeys is not known" - but I for one won't know that until I've researched it a little further - which is why I didn't answer this before. If you note the Reference Desk guidelines (at the very top of this page) you'll see that it specifically states: "Be patient. Your question probably will not be answered right away (...) A complete answer to your question may be developed over a period of up to four days.". For someone who appears to contribute NOTHING to Wikipedia (yes, I looked at your "Contributions" section - all I see there are RefDesk questions) - I think your gratitude and humility levels could use a little adjustment. SteveBaker (talk) 18:43, 6 October 2008 (UTC)

Helpdesk - It is preferred that SteveBaker not respond to any questions today. Please take the necessary steps to remove him. His responses are accusatory and borderline abusive. --Anilmanohar (talk) 18:49, 6 October 2008 (UTC)

This is not the "helpdesk" it is the Science Reference Desk. People who request answers and then make unfounded accusations about how volunteers are reading and responding really don't get to pick who gets to play. Perhaps Yahoo Answers would be more to your liking. --LarryMac | Talk 20:19, 6 October 2008 (UTC)

Being as said, your "volunteers" need a brush up on reading comprehension... FYI - questions I never asked were answered. Not the orginal question..--Anilmanohar (talk) 20:34, 6 October 2008 (UTC)

Now - you really are doing your very best to make everyone love you aren't you? OK - let's see about this alleged "lack of reading comprehension" were now accused of. Please feel free to award my terribly lame reading comprehension with points out of ten - oh great master of the English language:

You said:

• Mules are F1 hybrids between horse and donkey. - this is a statement, not a question.
• Both belong to the genus Equidae in the Biological classification. - another statement. (It was pointed out that you are in fact incorrect in stating this - but fortunately, that doesn't affect what follows.)
• There is 94% identical DNA between human beings and chimpanzees. - another assertion. (Actually - I believe that if you only count active genes, this number is a little low - between a human and a chimpanzee of the same sex - the number is more like 97% - between human and chimpanzee of different sexes, it's way less than 94%. If you count ALL DNA then 94% is way high - even two non-identical-twin sibling humans of the same sex don't share that much total DNA. But again, this doesn't really affect what follows.)
• What % of identical DNA does horses and donkeys have? - Ah! A question at last. I doubt anyone misunderstood, misread or failed to read this (despite it being a grammatical mess). We simply do not have an answer for you (at least not yet). I have explained why it may not be possible to answer that - and I explained that I intended to look for a better answer - but then you insulted me, so I don't think I'll bother. But at any rate, it's hard to prove a negative, so a good answer might well take longer. It appears likely that the answer is not known.
• If it is equal or more to humans and chimps, why are there no F1 hybrids (or whatever) between humans and chimps? - Since you predicated this with an "if" and the answer to the "if" is unknown, then we must either treat this as a hypothetical or remain silent. So IF humans and chimps (hypothetically) shared more DNA than horses and donkeys do - then what reason might there be for there being no hybrids? Now - if you read the THREE very germane answers we provided - you'll see that we said:
  1. We have an article about this (Humanzee) that you should read.
  2. Your presumption that the amount of shared DNA is a measure of how likely hybridization is possible is incorrect (obviously, IMHO).
  3. That moral and legal constraints make the formation of human/chimp hybrids exceedingly unlikely - biology notwithstanding.

So - every part of your question was read, understood and (as far as can be) comprehensively answered. If you were hoping for lots of exciting details of unusual sexual practices that would help you in your personal life in some way - you're out of luck.

However, you still persist in demanding answers (like it's some kind of legal right or something) from a volunteer-supported service...you do that DESPITE our FAQ at the top of this page clearly telling you that you should be patient and not to expect a full answer for FOUR days. You do it rudely by proclaiming that we somehow aren't reading your question. Now you conclude that our reading comprehension is flawed. I don't know why you put "volunteers" in quotes - they really are volunteers - not one of us is paid or gets recompense in any other form. None of us are under some kind of external compulsion to answer questions...yep - we are actually volunteers.

Anyway - I can prove that I'm a volunteer. I believe that you are exhibiting unacceptable behavior - and since I'm just a volunteer - I have decided that I will not knowingly answer any more of your questions until you apologize to the volunteers who worked hard to help you out here. If I am not in fact a volunteer, my boss will probably tell me to get back to work and answer your questions...let's see what happens shall we?

SteveBaker (talk) 23:22, 6 October 2008 (UTC)

<Redacted personal attack --Stephan Schulz (talk) 15:28, 7 October 2008 (UTC)> --Anilmanohar (talk) 15:05, 7 October 2008 (UTC)

Nobody "erased your response," although anybody would have been right to do so; you put it in wrong section. Your continued uncivil posts can and most likely will result in at least a temporary block from Wikipedia. --LarryMac | Talk 15:30, 7 October 2008 (UTC)

How exactly would you construct an "unfair" coin?

When you're learning about probablity theory, there's always discussions of "unfair" coins (i.e. "How many coin-flips do you have to do to find out if a coin is fair" or "What's the probability distribution for a certain unfair coin"). The idea is of course a supposed coin that when you flip it, it comes up with one side more often than the other.

My question is this: is it even physically possible to construct such a coin? Or is this a completely fictional concept? I mean, it's easy constructing an unfair die, if you just weight the "1" side a little heavier than the others, it will more often come up "6". But that wouldn't work on a coin, would it? I mean, if you weighted the "heads" side heavier, it would come up "tails" more often if you just threw the thing up in the air, but that's not what you're doing. When you flip a coin, you spin it in the air. For the tails-side to come up more often, the coin would have to spend more time with the heads-side down while it is flying through the air. That means, if it is spinning, the coin would have to decelerate while the heads side is down, and accelerate when the tails-side is down. But that's not what it's doing, even if it is weighted, it's just spinning the at the same angular velocity all the time. The time it spends with the heads-side up is exactly the same as the time it spends with the tails-side up.

I'm willing to concede that if you let the coin bounce on the floor once, then it could have an effect (as the coin then is just basically flying randomly through the air). But if you cought it in your hand, this wouldn't happen. So, is it possible to construct an unfair coin, and how would you do it (without putting teeny-tiny engines on the thing, that is :)? 83.250.202.36 (talk) 19:52, 3 October 2008 (UTC)

You could cast the coin to have two faces. You could use a coin where one side was notably distinct from the other, perhaps to the point where a keen-eyed "flipper" could know when to grab it in flight. You could have a noticeably different texture on one side, so the flipper knew to either slap the coin onto his other hand "honestly" (reversing it) or attempt to manipulate the coin while it is still unseen so the other side comes up. Matt Deres (talk) 20:03, 3 October 2008 (UTC)

These are all true, but it's not exactly what I'm looking for. I'm thinking of something analougous to an unfair die, where it really looks like a regular coin, but when you flip it, one side comes up more often. So someone could give it to you and say "Find out (with X percent probability) if this is an unfair coin by flipping it as many times as you need" 83.250.202.36 (talk) 20:06, 3 October 2008 (UTC)

Its not hard. You construct the coin so that the one side is made of a denser metal than the other, for example make the tails half lead and the heads half aluminum. Then clad the whole thing in whatever a coin of that type is clad in (for example, if a penny you'd clad the off-balance coin in copper). The result is that, over many flips, the tails side will be favored to land down, being denser... It wouldn't work every time, but even loaded dice don't work everytime... --Jayron32.talk.contribs 20:19, 3 October 2008 (UTC)

The original poster is specifically asking about a coin that is unfair when it is spun and caught while in the air, so all that matters is its position when you grab it while it's rotating at a constant speed. I suppose an uneven weighting or a beveled edge might have some tiny effect by introducing a slight asymmetry in the situation where its position is right on the cusp between coming out heads and tails, but it sure won't be much. Of course you could make a coin with both sides the same and have 100% chance of it coming out the way you expect, but people might notice that!

For coins spun to land on a table, I have heard that with some ordinary coins there can be noticeable "unfairness" due to the image on one side having higher relief than the other. But I don't have a cite for that. --Anonymous, 04:48 UTC, October 4, 2008.

Actually it's even easier. You take a fair coin and hit it with a hammer. It will then be slightly u-shaped and thus be heavier on one side. This also solves the problem of spinning while being in the air. The hollow side will be more unstable in flight thus will end on top. - Dammit (talk) 20:29, 3 October 2008 (UTC)

A coin badly dented with a hammer would have visible damage and be suspect.

It would be easier to take a normal coin and bevel the edges slightly. Normally a coin can stand on its edge. Beveling the edge, even a small amount, would bias the coin to falling over on one side when bouncing or spinning on a hard surface. This wouldn't guarantee the same result every time, but the coin would be biased to one result. ~Amatulić (talk) 20:56, 3 October 2008 (UTC)

Actually, all coins are unfair. 51% of the time—not 50%—a coin will land on the same face it started out on. zafiroblue05 | Talk 22:40, 3 October 2008 (UTC)

If you want to be technical, it isn't the coins that are unfair, it is the "flip". Much of the time, the "flip" doesn't cause the coins to flip at all. They wobble in the air and come down without turning over at all. -- kainaw™ 23:42, 3 October 2008 (UTC)

I read somewhere that the American penny is an unfair coin. I don't remember which side shows up more often, but it's only like 1 more in every 1000 or so. --M1ss1ontomars2k4 (talk) 21:15, 5 October 2008 (UTC)

You don't need to construct one - get yourself a Belgian 1-Euro coin. There was a significant study into the fairness of the various 1 Euro coins out there (every country got to put it's own design onto their version of the coin) - the differences were pretty dramatic: This New Scientist article says that the Belgian 1 Euro coin (for example) comes up heads 56% of the time! So I would imagine that lots of other coins in common circulation would be unfair too. SteveBaker (talk) 12:13, 6 October 2008 (UTC)

"Simplicity" of scientific/mathematical problems

It strikes me that something like Fermat's Last Theorem or e=mc^2 is relatively easy to understand, the former (not the solution by the hypothesis) to anyone that's taken middle-school algebra, and the latter to anyone who knows that c is the speed of light. But when I look at something like Millennium Prize Problems, all the problems listed are little more than nonsense to someone without the requisite mathematical knowledge, and physics questions such as string theory or higgs bosons are based on complex mathematics that can't really be explained to the average person without bastardizing them. I'm wondering if there's anything to this - that science and math have advanced beyond the understanding (not just understanding the recognizability, really) of the average person, and why this would be, and also if there are any standing problems in either area that appear as basic as, say, Fermat's last theorem. zafiroblue05 | Talk 20:30, 3 October 2008 (UTC)

Actually, e=mc^2 is so simple that dozens of people observed it before Einstein. It's not really that big of a deal. Einsteins real genius, mathematically speaking, comes from his explanations of General Relativity, vis-a-vis such phenomena as the effect of gravitation on light, and on his calculations tied to quantum theory. The math in those is WELL beyond most laypeople. Quite honestly, most fields are beyond the average person who does not have adequate training. Anyone could probably be taught to handle the math required to "get" advanced physics, its just that most people aren't interested. The inner workings of my car are a complete mystery to me, and that's why I pay someone to take care of it. Other people have expertise where I don't. This is just as true for auto mechanics as for mathematicians... --Jayron32.talk.contribs 20:38, 3 October 2008 (UTC)

That's no excuse for failing to write articles in layman's terms. United States jury trials do similar things all the time. I get depressed when I see a once-decent article such as linear regression, which once contained practical and useful information that a layman with some college math could put to use, turned into a jargon-filled theoretical treatise (at least that article now contains a practical example to clarify things). That isn't encyclopedic, that's merely obfuscation. Experts in the field don't need to go to Wikipedia for this sort of thing, so the articles don't need to be written for experts only. ~Amatulić (talk) 20:51, 3 October 2008 (UTC)

Um, you'll get no arguement from me. I don't think that answers the question from the original OP or even comments on it... It's merely diatribe... If you don't like an article, take care of it. --Jayron32.talk.contribs 20:58, 3 October 2008 (UTC)

I thought I did address the OP's comment, which seemed to comment on the level of expertise needed to understand the meaning of millenium prize problems. As for articles like linear regression that got converted to jargon, I have tried to "take care of it" as you suggest, but after a point I got tired of my attempts being reverted, and moved on. ~Amatulić (talk) 23:40, 3 October 2008 (UTC)

If the article is too technical, perhaps you could dumb down a version for the Simple English Wikipedia? Isn't that what the project is for? Plasticup ^T/C 01:38, 4 October 2008 (UTC)

No it's not, we are supposed to be building an encyclopedia here not a technical reference book. Equendil Talk 07:28, 4 October 2008 (UTC)

We should be doing both here. Articles should explain the concepts or have links to simplified explanations; and they should lay out the whole difficult field in all its technical glory. Our problem is simply to properly explain. When a user searches for quantum mechanics, do they want an overview, a basic understanding, a confusing in-depth glimpse, or the specific underlying equations? Wikipedia is big enough to do all of these. Franamax (talk) 05:57, 5 October 2008 (UTC)

I agree with what Jayron wrote above, but with a small addendum that, media portrayals of what life, the universe, and everything should be like aside, the real world has no obligation to be either simple and beautiful or complex and murky; it just is. Some parts will be explained neatly, some parts will not. Some parts can be summarized into very basic steps (evolution by natural selection), yet are still wonderfully complicated and nuanced when you try to understand how the theory applies mechanically. How complicated something appears to be can depend greatly on how in-depth you want your knowledge to be and also what aspect you want to understand. Cars seem to have changed a great deal over the last century, but you can still get a great deal of insight in how they work by understanding such basic concepts as the four-stroke engine, the carburetor, and differential gearing - the same concepts you'd have needed 100 years ago. Seen that way, they're still pretty simple, but seen from the POV of the computer systems designed to regulate all that simple stuff they seem horribly complex. Matt Deres (talk) 13:28, 4 October 2008 (UTC)

In answer to the OP's actual question, yes there are still some simple problems left. The twin prime conjecture springs to mind. However, modern mathematics has been being built up for thousands of years so a lot of problems have already been solved. Everything builds on what went before so you generally need a good understanding of what went before in order to understand the new stuff. It's not quite so bad in science since sometimes theories are proved to be complete nonsense and you can just forget about them, but in maths everything that's been proven once is still true now and always will be. Every now and then mathematicians will find a new branch of mathematics or a new approach to an existing branch that hasn't been done before and they get to find out new maths which can actually be understood without knowing lots of existing maths, but it doesn't happen very often. --Tango (talk) 15:55, 4 October 2008 (UTC)

In terms of problems that are very simple to understand, but as of yet unproven, I'd think Goldbach's conjecture would top the list (that is, "every even integer greater than 2 can be written as the sum of two primes"). There are a bunch of other ones, though, like the existance of an odd perfect number or whether there are an infinite number of Fibonacci primes. And if you have a nice person explaining it to you, P vs. NP isn't all that hard to understand, at least not conceptually. 83.250.202.36 (talk) 20:10, 5 October 2008 (UTC)

Yes - P vs. NP is pretty simple. The question is this: If you have some problem to solve and you have some easy way to determine whether the answer you get is correct or not - then is there always an easy way to find that answer in the first place? Are there any problems where finding the answer can be amazingly difficult - but checking it is amazingly easy? Suppose, for example, that you have a list of a million random numbers, each between 1 and 1,000,000 - and someone asks you whether there is an '84' anywhere in the list. If I asked you to find that out, you might have to look through all million numbers. But if you tell me that the answer is "Yes" then I can verify that this answer is true merely by having you show me the '84' that you found...which is very easy to do. Of course if the answer is "No" then it's just as hard to prove that your answer is correct as it was to find the answer in the first place because to convince myself that you were right - I'd also have to look through all million numbers. So in this (very simple) case, it is certainly true that we have a easy check that a "yes" answer is correct for a problem that requires hard work to solve.

In P vs. NP, the definition of 'easy' and 'hard' is rather more formal than that and the example problem I just gave doesn't count as "hard"...but that's essentially the issue here. The commonest example of a 'hard' problem (in this context) is the travelling salesman problem. Given a list of cities and the distances between them, what is the shortest route that will allow someone to visit each of the cities at least once? For a large number of cities, the answer is very hard to find - and proving that it is indeed the shortest route is also hard to do...so this example doesn't help us to answer P vs NP. SteveBaker (talk) 14:04, 6 October 2008 (UTC)

Everything about P vs NP is easy to understand except the definition of "easy" (although even that isn't too hard). I think the whole thing needs to be easy to understand to qualify, personally, but that's just me. --Tango (talk) 15:32, 6 October 2008 (UTC)

"Hologram" mirrors illusion??

Hi all, sorry if this question sounds a little bit silly. During a guided tour of a jewelry factory, we came up to a hexagon(I think)-shaped 'table', with a hexagon-shaped hollow space on its center which seemed to be covered in mirrors. Over the hole was a 'hologram' of a watch, but the thing is that the "hologram" had real colors, not those silly greenish-reddish colors holograms usually have! It genuinely looked like a real watch floating in place. We were able to see the watch from all around as if the watch was actually standing right there! They even allowed us to pass our hand through it (which made your eyes a little woozy somehow, focus-wise I guess). I'm sure the table itself wasn't a 'machine' of any sort, and that it must have been some weird illusion with mirrors (a real watch probably being inside the table thing), but I haven't seen that sort of thing anywhere else. My question is, how is that done? That's pretty much what I remember, and I'm still amazed at what I saw back then. I would love to know how they did that! Thanks in advance, Kreachure (talk) 21:33, 3 October 2008 (UTC)

This is an example of a real image. What you saw sounds like the "Mirage" toy mentioned/advertised in the article, though I don't know where to find a diagram of this particular case. You can buy them at places like museum gift shops. --Allen (talk) 22:54, 3 October 2008 (UTC)

Here, this website seems to have a good explanation. --Allen (talk) 22:57, 3 October 2008 (UTC)

(Edit Conflict) I'm not sure what these things are called, they seem to sell under the name "3d mirascope". (Google Search) There doesn't seem to be an article. Essentially there was a real watch inside the table, and through a clever arrangement of curved mirrors the reflection actually appears to be hovering above the hole in the mirrors. I've got one of these right here. The illusion is quite convincing. APL (talk) 23:01, 3 October 2008 (UTC)

Yeah, it's definitely that one, thanks, all! What I'm wondering now is why aren't they popular, because the illusion seems incredibly cool to me, even if it's (as I suspected) such a simple trick... I want one of those right now!!! :) Kreachure (talk) 23:13, 3 October 2008 (UTC)

They were popular as a novelty item, but they've been around for several decades. I remember seeing them advertised in the back of comic books in the 1960s and 1970s. ~Amatulić (talk) 23:36, 3 October 2008 (UTC)

There was even a very bad video game based on them back in the 80s. I don't remember what the purpose of the game was. It was the first 3-quarter game I ever saw, so I just watched a couple other kids waste some time on it and went to play other games. -- kainaw™ 23:38, 3 October 2008 (UTC)

Found the game - and it was 1991, not the 80s. Man, I am getting senile. -- kainaw™ 01:29, 4 October 2008 (UTC)

Reminds me of a gadget I saw in 1981 which used an oscillating mirror to build 3d images – wireframe only. —Tamfang (talk) 07:51, 4 October 2008 (UTC)

They sooo need to bring that style of game display back. :) ---J.S (T/C/WRE) 01:38, 6 October 2008 (UTC)

Mirage Mirror Musings

If you're able to create this kind of image with curved mirrors, is it possible to alter the image of the original to change its size? Maybe make it bigger? Maybe displaying the image a little higher instead of on the edge of the hole? Cause that would be even cooler! Kreachure (talk) 00:00, 4 October 2008 (UTC)

Science museums I've visited have had vertical versions set up that you can put your hand in to 'shake hands with yourself'. The image of your hand was flipped, if I recall, and the size depended on where you positioned your real hand - like with a normal mirror. So I imagine you could create a convincing larger image just by playing with distances. 79.66.115.246 (talk) 01:11, 4 October 2008 (UTC)

I have one of the toy ones. It makes the items inside of it appear noticeably larger. Also, telescopes have long used curved mirrors to make objects look larger. I suspect using mirrors to make objects look both larger and closer would be simple, though I'm not certain. — DanielLC 15:22, 5 October 2008 (UTC)

October 4

Water on Mars

Do Mars still have liquid water lye anywherr on crust? From what I learnt is Mars is a very cold planet. Do Mars even get to 25 Celsuis over summer equator. If it gets this warm then Mars might have some pink-orange oceans flown on it's surface. Usually tropical avg. on Mars surface is like below 0 Celsius, and the mid-lattitude on Mars surface si -53 Celsius, this is colder than Alaska over summer. Since Mars atmosp is alot thinner than Earth would it's 25 Celsius feel like 0 Celsius. The simple study is Mars is a very cold planet.--SCFReeways 22:26, 3 October 2008 (UTC)

There is no standing liquid water on Mars' surface due to the low atmospheric pressure, as discussed at Mars#Hydrology. Lower atmospheric pressure wouldn't cause Mars to feel "colder" so much as it would feel "less". There's less opportunity for conductive or convective heat transfer. — Lomn 23:14, 3 October 2008 (UTC)

• This site say mars low is -125 F and high is 23 F, and rf#4 on Mars say the vg. surface temp. is -81 F. I thought Mars have greater surface range. The ext low I thought is like -180 F, and what about the extr high? Is the extr high like +50 F? The short answer is Mars is a very cold planet.--SCFReeways 23:57, 3 October 2008 (UTC)

Certainly small amounts of liquid water couldn't hang around for very long on the surface. Between the cold causing it to freeze and the low pressure causing it to boil - it's really not able to stay liquid for long. However, there have been discussions of underground liquid water possibly still existing - and there are suggestions that periodically, a large volume of liquid water may appear - flow for a while and then either boil away - or freeze and then sublimate. The Phoenix lander has observed ice sublimating into water vapor without ever becoming a liquid along the way. There is ample evidence that there HAS been liquid water there in the past - but the martian atmosphere may have been very different back then. SteveBaker (talk) 13:36, 6 October 2008 (UTC)

Seeing bullets (with no tracers) streak through the air using IR goggles

Would bullets (with no tracers) be very visible if you were to observe them using IR goggles? —Preceding unsigned comment added by ScienceApe (talk • contribs) 16:38, 4 October 2008 (UTC)

There are two main types of IR goggles and cameras. There are night vision ones that work user near-IR (nearer to visible light, that is) which work by capturing the reflected IR in the same way that visible light is used. They often come with an IR light that illuminates the area with IR so it can be seen (if you watch night vision video you can often see that there's a light shining on the middle of the image and around the edge is much darker). There is then thermal imaging which uses far-IR and captures IR emitted directly by the objects before of their heat. I believe bullets are fairly warm, so would show up well on thermal imaging, but I see no reason why they would show up any better than anything else under night vision. --Tango (talk) 16:57, 4 October 2008 (UTC)

Yes, very visible. Well, the thermal imaging ones at least, as Tango said.

edit: You may want to consider these things though:

• A bullet is small and fast, so seeing it will be really hard using goggles, a camera will have a better chance.
• As noted in the link, the bullet will cool down in flight.

- Dammit (talk) 22:17, 4 October 2008 (UTC)

The night vision goggle (NVG) type can see emitted IR as well as reflected - but the higher frequencies that NVG's are sensitive to are not normally emitted in much quantity by things that are merely warm. However, a piece of "red hot" steel is obvious even to the naked eye (that's why we call it "red" hot). Hence, something that's just a little cooler than red hot would be highly visible by radiated IR in NVG's. The lower frequency detectors in InfraRed cameras (such as you might find on a combat helicopter, drone or fighter/bomber) are able to see radiated IR across a wider range and are sensitive enough to see things that are just a fraction of a degree above their environment - you can see warm 'tracks' left by a vehicle driving by for example! I've worked a lot with both kinds of sensor - you can't see regular bullets in flight with either of them - there just isn't enough light (IR or otherwise) and it's not there for long enough. Also, the resolution of both NVG's and IR cameras is nowhere near fine enough to pick up something that small at a distance. But tracer is highly visible to both because it produces a lot of visible light (which the NVG can see) and the cloud of combustion products is large enough and hot enough for the IR camera to pick up. The 'rangerats' stuff that User:Dammit provided is deceptive. Firstly they aren't using regular NVG's or military IR - they are using some kind of very fancy IR camera that's specifically designed for measuring temperature rather than for seeing well at night (this is obvious from the 'false color' images on their site - military stuff doesn't use false color - the images are invariably monochromatic, and typically green). Secondly they say that the bullet was only visible fairly briefly just as it left the barrel of the gun - a fraction of a second later, it was too cool to register on their equipment. SteveBaker (talk) 11:56, 6 October 2008 (UTC)

Is this understandable?

Quite confusing IMO.

Our sail car is trapezoidal with two horizontal extensions, one on each side of the car in the back. The extensions are created using four straws. Two are linked together to form what appears to be one long straw in the very back (creating the rear base of the trapezoid as well), so that only very ends of the 'straw' are part of the extension. It holds two wheels on each extension, both (wheels) kept from sliding by two pins placed beside each wheel, the pins being stuck into the straw. The other two straws are on opposite sides of the car and in front of the rear straw. They support the wheels as well (the support pins are stuck through them after being stuck through the rear straw), but they bend towards the front of the car upon clearing the extensions. These straws bend upon reaching the front, creating the smaller (shorter) top (front) base of the trapezoid by connecting at the center of the front base. The front ends of the straws then hold two more wheels near the bent area. Right at the bend of each of the two front straws are two more straws are pinned to each one of the straws just aforementioned. These two straws converge and meet at the midpoint of the rear straw.

Roughly halfway between the extensions and the midpoint of the rear straw are straws extending vertically upwards. These straws are connected to a sail. The sails is bent inwards and is supported by a crossbeam at the top.

Rest assured, for the prototype actually worked.

--hello, i'm a member | talk to me! 22:21, 4 October 2008 (UTC)

Clarification is needed here. Is this native English language or a translation? (For that matter, please provide proper attribution when quoting extensive text on a GFDL site such as Wikipedia - who said that, where?)

And in particular, what does "straw" mean in context? Drinking straw, wheat straw, something else? Once you attribute that quote, we may be able to shed some light. Franamax (talk) 05:11, 5 October 2008 (UTC)

It seems to be some kind of little toy made with drinking straws. To answer the question: yes, this text is confusing. I got lost in the first sentence because I could not visualise the "sides" and the "back" of the trapezoid. A diagram would help. Itsmejudith (talk) 15:44, 5 October 2008 (UTC)

Is there any way I can clarify the passage? 'Front' and 'back' are arbitrary positions (they were defined on a whim...doesn't really matter too much) and yes, those straws are drinking ones. --hello, i'm a member | talk to me! 15:57, 5 October 2008 (UTC)

I second Itsmejudith...a diagram would help immensely. Even a very simple sketch would clarify what is where relative to what else. Alternately, a more technical diagram could have labeled parts replace this entire paragraph! DMacks (talk) 16:09, 5 October 2008 (UTC)

Assuming that I have a diagram, would this passage still be confusing? I know my question isn't all that answerable... --hello, i'm a member | talk to me! 16:28, 5 October 2008 (UTC)

The description is confusing and ungrammatical in places. It sounds like a first draft. In the fourth sentence, it's not clear what the pronoun "It" refers to. Perhaps if the text said "The rear axle," with that axle defined by what straws it was made of, all would be clearer. In the fifth sentence, instead of "in front of the rear straw" it should say "at the front of the trapezoid" to give a point of reference. In the sixth sentence replace "they" with an explicit declaration of what is referred to. In the 7th sentence, it is not clear in what direction the front straws bend: is the outside end of a front straw closer to the rear, or farther from the rear than the center of the front line of the trapezoid? In the 8th sentence, "the bent area" is undefined. The 9th sentence is vague and confusing, and contains an extra "are." If the front 2 wheels are on straws which are bent, then are their axes not parallel to the axes of the rear wheels? It sounds like the front wheels point at an angle, which would make it difficult for the device to move forward without dragging the front wheels, which would want to roll in different directions from the back wheels and each other. Sentence 11 does not specify which straws are "the extensions" it refers to: front, back, or all four? How many straws point upwards in sentence 11, and where are they located in the trapezoid? Sentence 12: Specify the arrangement of the sail. Sentence 13: "Bent inwards" is vague. To move forward in a wind, the sail would need to be parallel to the rear axle to maximize thrust from wind coming from the rear, or at some lesser angle such as 45 degrees to take advantage of side winds and produce forward movement. Sentence 14: It "worked?" Even a crackerbox would move in a strong wind. How fast did it move in what speed of a wind coming from what direction? Edison (talk) 20:44, 5 October 2008 (UTC)

October 5

How to Get Gray Hair

I understand there is a multitude of products in current circulation designed to rid people of gray hair, which is a process that I am not in the market for. I actually want the exact opposite. My hair is a dark brown/black, and I want it to have a nice Andy Warhol/Randy Newman gray tone. What should I look into regarding this? Is it even possible? Thank you folks. Kenjibeast (talk) 02:36, 5 October 2008 (UTC)

Hydrogen peroxide and ammonia will strip the color out of your hair, but it will leave it a whitish blonde, not gray. :( --Russoc4 (talk) 03:11, 5 October 2008 (UTC)

Keep in mind that Warhol wore a wig. Dying your hair to that level of white is possible but it's not easy and it's not very good for the hair. I don't know how you'd get it gray rather than white, though. --98.217.8.46 (talk) 04:01, 5 October 2008 (UTC)

Get a stressful job or go to graduate school in some crazy competitive field like biochem. It's guaranteed to work though it does take some time. Comes with free wrinkles too ;) Sjschen (talk) 04:20, 5 October 2008 (UTC)

Just wait: time has a tendency to take care of such things. ៛ Bielle (talk) 04:31, 5 October 2008 (UTC)

This evidence is anecdotal, but ever notice how all the US presidents look so old after just 4-8 years? Stress does seem to assist with the graying. This does pose the question, does stress induced graying recover with the relief of stress? Sjschen (talk) 04:49, 5 October 2008 (UTC)

That's not just anecdotal, plenty of others have noticed it too. I've read articles on it, but I can't find any now. It looks like ABC had a slideshow on it, but has since taken it offline. Plasticup ^T/C 15:45, 5 October 2008 (UTC)

Playing devil's advocate for a moment, I think it's worth noting that most new Presidents are into what might be charitably described as 'late middle age' by the time that they take office. According to List of United States Presidents by age, the average age of a new President is 55 years. Add four or eight years on to that, and and they're eligible for senior's discounts at a lot of retailers. In other words, they look so old because they've gotten so old. Compare photographs of the average non-President at ages 55 and 63, and you might notice that they've aged, too. TenOfAllTrades(talk) 19:42, 5 October 2008 (UTC)

I considered that, yes. I think it would be interesting to test it. Plasticup ^T/C 19:53, 5 October 2008 (UTC)

Even the young presidents (Clinton, Kennedy) look much older after a few years in office. --Carnildo (talk) 22:24, 5 October 2008 (UTC)

In that case, how does stress induce greying? How does melanine production get turned off in such a manner? Sjschen (talk) 21:04, 5 October 2008 (UTC)

Exactly. ---J.S (T/C/WRE) 01:31, 6 October 2008 (UTC)

This sounds like a problem that actors would be faced with, as they may have to play the same character at different ages. I suggest trying a supplier of theatrical cosmetics. --Anonymous, 04:44 UTC, October 5, 2008.

Having teenage children is a tried and true method for getting gray hair. You also might ask to borrow some teenagers if the time constraints of raising your own are a problem. Edison (talk) 20:22, 5 October 2008 (UTC)

Scientific American took up the question of stress and gray hair. There are some other interesting notes there, too. Keep in mind the hair isn't just one shade of gray -- as the melanocyte cells fail, there's less and less pigment; when there's none, the hair appears white. Also, blondes seem to turn gray later, because the white doesn't stand out as much against the blonde. --- OtherDave (talk) 00:59, 7 October 2008 (UTC)

Alright, apart from getting a wig, looking for theatrical cosmetics, and applications of constant stress, are there any permanent methods to grey my hair out? By permanent I don't mean forever, I just mean it won't wash out, dig? Thanks folks, you've been a great help so far. Kenjibeast (talk) 05:59, 7 October 2008 (UTC)

Nomex

How fire/heat resistant is Nomex? I can find all sorts of words like "very" and "extremely", but no hard numbers. --67.185.172.158 (talk) 09:12, 5 October 2008 (UTC)

Nomex is meant to save you from flash injury, it's not really made for running into fires. As such, you won't necessarily find "hard" numbers. Suffice to say, if a pool of flammable liquid ignites 20 feet away, you're better off wearing Nomex. The ejected flammable liquid won't hit your skin and the flames will bounce. If you end up lying in a pool of burning hydrocarbons, you will still have to get up and run. Franamax (talk) 09:39, 5 October 2008 (UTC)

[32] "The rate of material decomposition and charring rate is high only after the temperature greatly exceeds 350°С; however, the material does not melt." Also a bunch of other figures not related to using it for protection (e.g. [The unique combination of electrical and mechanical strength, heat resistance (temperature rating of 220°С]). Perhaps you can find some graphs showing decomposition and stuff, but I don't really see how you can get any 'harder' then that. I presume precisely what it does will depend on the temperature and time period of exposure and whether it's a naked flame. As Franamax says I think the primary point of Nomex is that it stops flames from hitting your skin and it doesn't itself catch fire in most situations you'd expect to encounter. It's not some sort of extrme insulator so you've still going to get burnt if you stay in a fire/hot temperature for too long Nil Einne (talk) 10:24, 5 October 2008 (UTC)

I smell an experiment! Plasticup ^T/C 15:42, 5 October 2008 (UTC)

We'd better hope that the experiment doesn't lead to our smelling a burnt body. --M1ss1ontomars2k4 (talk) 21:17, 5 October 2008 (UTC)

Fire-suite manufactures do internal testing and are loathe to share their results. It's the same in any very specialized industry... the research is just too expensive to share with their competitors. ---J.S (T/C/WRE) 01:35, 6 October 2008 (UTC)

Nomex coveralls are also horribly uncomfortable, since they retain your sweat. I always used Proban^TM, which was treated cotton, and I got away with it 'cause I was the manufacturer's rep and could explain that I threw them away after ten washings. In any of my safety-trainings (one per chemical plant) I was told the rule that no sleeves could be rolled up, and that Nomex was the just-in-case for "uncontrolled ignitions" and that all normal evacuation procedures must be followed. Ironically, the protection of the coveralls would mean that only your hands and face would be hideously burnt, but you'd still be alive. I've since eased out of that field of work... Franamax (talk) 23:01, 6 October 2008 (UTC)

Err...franamax, as a firefighter, allow me to advise you to qualify your first statement. Nomex hoods are standard issue for firefighters in the united states and therefore are literally made for running into fires. Granted, the protection the hood gives is limited and the first area that usually gets burned (the ears) is under the hood's jurisdiction. NFPA standard 1971 probably has something to say about them if you can find a copy. --Shaggorama (talk) 07:27, 7 October 2008 (UTC)

Hyperthyroidism and the risks of general asesthesia/surgery

I was recently scheduled for a hysterectomy and the Surgeon cancelled the surgery because of the TSH result from my pre-op blood test. If the T3 & T4 results are in the reference range is there a risk of going under general anesthesia? If so, are they and what are the statistics? —Preceding unsigned comment added by Istaffordcomcastnet (talk • contribs) 17:04, 5 October 2008 (UTC)

Your surgeon, your consultant and other doctors involved in your treatment know your medical history and your test results and are obviously a much more reliable source of information than random strangers on the internet. So ... wouldn't it be better to put your questions to them ? Gandalf61 (talk) 17:26, 5 October 2008 (UTC)

There does appear to be an interaction between thyroid horormones and some specific anesthetics and/or major surgery. Googling for t3 t4 tsh anesthesia finds some refs. Even though this isn't (to my reading) a request for medical advice, your doctor could at least tell you the specific guidelines he's following. That would be a great starting point to finding out the basis for those guidelines and the risks that specific deviations would entail. DMacks (talk) 17:31, 5 October 2008 (UTC)

Reasons people mumble - hearing loss, etc.

I'm curious as to the physical reasons people mumble. Specifically, I heard someone say recently that some older people start talking lower because of hearing loss. That sounded strange, because I would think, instinctively, one would speak louder with a hearing loss. I supose the issue could be the "internal volume control," so to speak, where the person just *thinks* they're speaking normally because they're used to not hearing much, anyway. It just seems so counter-intuitive.; it seems that once you get that volume down when you're a child, it stays, unless you think you have to speak louder.

Also, considering the person mentioned older people, I wonder if mumbling could be due to a heart problem, with not enough oxygen coming to the person. Although, I always though those weak voices of dying people in movies and TV were just dramatized; sure, my grandparents' voices sounded a little weaker toward the end, but not *that* weak. Thanks.Somebody or his brother (talk) 19:33, 5 October 2008 (UTC)

In my experience, some muttering is passive aggression. Mumble first, then when someone asks for clarification shout "I SAID...." Other mumbling may reflect shyness or a defense mechanism for fear of being attacked for saying something. Also consider that when it seems like other people are mumbling, it might actually reflect a hearing loss on the part of the listener. Edison (talk) 20:51, 5 October 2008 (UTC)

Much of our speech habits is controlled/re-enforced by hearing our own voice or the voice of others. If we lose our hearing we lose that reference and the habits can slip. Ever notice how weird it is to talk with really good sound protection on?

Speculation... If an older person is losing their hearing then it's possible they are told a few times too many that they are talking loud... and then they over-compensate in response. ---J.S (T/C/WRE) 01:29, 6 October 2008 (UTC)

A rather simplistic explanation: Humans are inherently designed to put forth the least amount of energy required to complete a given task. If that task is communicating a message, there is not point in speaking in a loud, clear voice when a soft mumble will likely work just fine. I ride the bus most days. I hear conversations that sound like, "Isa you gur edda sto." "Mudu?" "Yaw." "Aw, shu gedda da mun etta." It may sound like nonsense, but it is the minimum effort required for the two to converse. Sometimes it fails. I was one of my favorite Chinese food restaurants and the lady in front of me ordered "frump fry fie". The guy at the register didn't understand. She asked again for "frump fry fie". He didn't understand. After going back and forth a large number of times, a cop behind me asked her if she wanted "shrimp fried rice." She replied "Fu!" -- kainaw™ 03:34, 6 October 2008 (UTC)

I agree with these answers. In addition, though, think about a feedback loop. Will the person get positively or negatively reinforced when they begin to dabble in mumbling behavior. The answer is positive reinforcement, so they will keep winding down the slippery slope. Plus, you gave stated information that it is about older people. Society has norms for providing people these unfortunate feedbacks. Its just an interesting theory, not quite yet a paradox. It was good though, I liked reading and answering your question. Thanks Sentriclecub (talk) 18:39, 6 October 2008 (UTC)

Loss of hearing acuity would sever the feedback link between spoken volume and perceived volume. Also, the volume of your own speaking is largely transmitted through your own skull, so problems at the eardrum mechanism would cause other people's voices to decrease in perceived volume more than your own. It is only the younger cellphone generation who have decided that the solution to poor audio is to SPEAK LOUDER into their own phone. (Incidentally people, you don't have to face outwards on your balcony to get better reception, although it does let everyone know how cool you are. And ain't it strange how all the phones work so well indoors in wintertime, but in summer you suddenly need to give me all the details of your life?) If you can't accurately assess your own relative vocal loudness, it's hard to say whether your own loudness would increase or decrease.

That said, I am well-known in various workplaces as "talks to himself" - so to some extent, mumbling is also a vocalized internal conversation. Franamax (talk) 22:37, 6 October 2008 (UTC)

I'm the same, Franamax. One of my kids once mentioned in passing how I was talking to myself when I was typing something on my computer. I said I wasn't aware of it, but if it was true, I must have had something on my mind and it would have been a one-off experience. I was humbled when he said "Dad, you do it all the time". Others have since commented on this. Maybe I'm the Glenn Gould of Wikipedia. My experience of increasing deafness is that I'm more and more often asked to speak up. Apparently, to my interlocutors I'm mumbling, but to me I'm speaking at what I think is a normal volume. What people hear in their own heads when they're speaking is not the same as others hear them. I'm reminded of this whenever I'm watching TV and munching on a snack. Whenever I take a bite, I momentarily lose what I'm listening to, and I've learned to do most of my munching during the ad breaks. -- JackofOz (talk) 23:45, 6 October 2008 (UTC)

Well luckily I'm showing no signs whatsoever of aging. There is an increasing trend to smaller font sizes and lower light levels in general, but I'm sure that will change back in time. I too have noticed the new more loudly-crunching snacks that prevent one from hearing the program. This will all doubtless be fixed when the US Democrats come to power. Or was it the Republicans? I'll consider this when I've finished my nap. :) Franamax (talk) 01:09, 7 October 2008 (UTC)

"When in doubt, mumble" -- James H. Boren. I know I do that a lot. — DanielLC 23:50, 6 October 2008 (UTC)

On a related "what you hear in your head and what others hear is not the same" topic... I very much like to sing when I program. In my head, I hear a voice somewhat in tune with what is coming out of my speakers. To everyone else, my voice is monotone, nasal, and very annoying. Hence, I do most of my programming at home, at night, after the family is asleep. -- kainaw™ 01:21, 7 October 2008 (UTC)

You should probably get a small headset-microphone and plug that into your sound-card so you can mix a little of your voice into whatever it is you are singing along to so you can hear yourself as others do. SteveBaker (talk) 11:35, 7 October 2008 (UTC)

Blindness and visual artefacts

Do people who are blind from birth 'see' visual phenomenons, artefacts or hallucinations, perhaps due to the lack of stimulation of the visual cortex? Has anyone got links or refs on that subject. Thank you. 190.244.186.234 (talk) 21:38, 5 October 2008 (UTC)

Ah, I already found this: Charles_Bonnet_syndrome. 190.244.186.234 (talk) 21:43, 5 October 2008 (UTC)

That article doesn't mention persons who are blind from birth. That syndrome seems to afflict persons who lose their sight later in life. Plasticup ^T/C 04:10, 6 October 2008 (UTC)

Almost the exact same question was asked about a month ago and given (in my opinion) thorough treatment. Check out the response here. --Shaggorama (talk) 06:13, 7 October 2008 (UTC)

Hurray! Fanx. OP. 190.220.104.35 (talk) 15:38, 7 October 2008 (UTC)

extrusion of rock

What do the extrusion of rock form? Thanks, from my son - for his Science homework. —Preceding unsigned comment added by 76.69.48.237 (talk) 22:12, 5 October 2008 (UTC)

All kinds of neat stuff. Extrusive article is a good place to start. -- Finlay McWalter | Talk 22:14, 5 October 2008 (UTC)

October 6

Sleep Noises

As people fall asleep I've noticed (through my limited experience) they make some sighs/moans/grunts/little noises. Is there a cause, or reason for this?207.172.71.243 (talk) 00:14, 6 October 2008 (UTC)

According to our articles on sleep stages and myoclonus, these seem to result from normal involuntary muscle movements when entering the "N1" stage of sleep.

See hypnagogia and hypnic jerk for related subjects, although I don't see anything specifically about making noises. --Anonymous, 22:24 UTC, October 6, 2008.

Volume of human voice

Is an increase in the volume of a human voice, be it shouting, talking louder, or full-on-screaming--mostly created through the larynx, or lungs?

I'm really just wondering about the ability for humans to raise and lower the volume of their voices, how is that controlled?207.172.71.243 (talk) 00:19, 6 October 2008 (UTC)

I do not know for sure, but I think it's controlled by the volume of air permitted to pass over the lungs... much in the same way that a whistle gets louder as you blow harder into it. ---J.S (T/C/WRE) 01:24, 6 October 2008 (UTC)

Today is a bad day for people NOT doing experiments here on the science desk! Put your hand just in front of your mouth...whisper something...did you feel any air flow? Probably not. Now yell as loud as you can...do you feel air flow now? I guess so...hence a greater volume of air is being moved when you shout. Now - how on earth could your larynx cause air to flow? Just feel what happens to your lungs when you shout - it's really obvious. The larynx controls the pitch (frequency) of the sound - not the volume. SteveBaker (talk) 13:26, 6 October 2008 (UTC)

Well, the larynx certainly enters into the picture. When you produce a soft sound at a given frequency, your vocal cords open and close at that frequency. When you shout at the same frequency, your vocal cords open and close at the very same frequency. When a greater volume of air passes, the vocal cords must open more widely, i.e. they vibrate with a greater amplitude. To achieve that requires that the laryngeal muscles be kept tighter. Amplitude corresponds to volume. The increased amplitude of the vocal cords is transmitted to the resonant cavities (chest, sinuses) resulting in the louder sound. By the way, to be precise, it isn't your lungs that cause the increased air flow, it's the diaphragm and chest muscles. --NorwegianBlue ^talk 19:05, 6 October 2008 (UTC)

That's right. Trained singers (and speakers) keep good control of their diaphragm so that they can control the amount of air (well, CO2 to be precise) they expel. That way they can sing a long phrase, in which the volume might vary from soft to loud and back again, without needing to take a breath and in the process interrupt the musical phrasing. If they try to do it by just allowing their lungs to deflate, they'll run out of breath too quickly. Far better to use a taut diaphragm to push the air out in a controlled way. -- JackofOz (talk) 23:33, 6 October 2008 (UTC)

Jack, not to be a stickler or anything, it's actually air (N, O2, CO2, etc) your exhaling... with co2 being only a minority part of it. ---J.S (T/C/WRE) 03:39, 7 October 2008 (UTC)

What Jack is referring to is commonly known as the rule, "Sing/Speak from your stomach, not your chest." Some people naturally use their diaphragm. Others use their chest. The voice produced usually sounds very different. -- kainaw™ 03:45, 7 October 2008 (UTC)

Hypnic jerk

Is there a way to decrease the strength and frequency of hypnic jerks? Plasticup ^T/C 02:22, 6 October 2008 (UTC)

Not medically speaking mind you but it seems to occur more when I'm sleep deprived so in my case I'd say to me-self "get more sleep"  ;) -hydnjo talk 03:09, 6 October 2008 (UTC)

Are they, neurologically speaking, similar to seizures? Have they ever been treated with anti-seizure medications? Plasticup ^T/C 03:37, 6 October 2008 (UTC)

Now that is seeking medical advice and therefor we'all must resist the temptation to further diagnose or offer treatment suggestions for the affliction of which you speak - seriously. -hydnjo talk 03:56, 6 October 2008 (UTC)

Oh darn, because I really was going to walk down to my local pharmacy and buy some anti-seizure meds. I just want to know where the science stands. Humor me, I promise I won't sue. Plasticup ^T/C 04:05, 6 October 2008 (UTC)

If you wanted to know where the science stands, you would search medical journals for "hypnic jerk" and "seizure". Instead, you are asking random strangers who likely have no medical experience of any kind. It shouldn't be too difficult to understand how stupid that appears. A proper question would something like, "Does anyone have any links to medical studies on hypnic jerk?" For, you see, this is a reference desk, not a "does anyone have any medical opinions based on years of watching the Simpsons and Family Guy that I can use to try and diagnose and treat an annoying problem that I think I might have" desk. -- kainaw™ 04:09, 6 October 2008 (UTC)

Don't be facetious. A link to a medical journal is exactly what I am looking for. If you cannot answer without referring to the Simpsons then don't answer. Leave it for someone else. Plasticup ^T/C 04:13, 6 October 2008 (UTC)

C'mon now Plas, no one is being a dick here, we're just trying to comply with the arduously arrived at guidelines with regard to the phrasing of your question. Of course a different phrasing would bring a different response. -hydnjo talk 04:26, 6 October 2008 (UTC)

That is more or less the definition of facetious. Why should the wording matter? If someone is aware of an article in a medical journal on this subject they will share it no matter how I word the question. Besides, where did I ask for advice? I have only asked for information. Plasticup ^T/C 04:39, 6 October 2008 (UTC)

Unfortunately, the result of being stepped upon by the "community" in these matters has left the desks with an uneasy feeling about all things that could be interpreted as "medical advice". I agree with you but past experiences have left us impotent. So, careful wording is more important than you could imagine but please try:

I'm seeking information beyond what is cited in the Hypnic jerk article. Specifically, and in neurological terms is that jerk similar to a seizure and has it ever been treated with anti-seizure medications such as gabapentin or the like? Any links besides those available when I googled "hypnic jerk"would be appreciated. Thank you (wimp-ally ), (say), - hydnjo talk 05:18, 6 October 2008 (UTC)

Yes but it falls into personal experience which I don't want to publish here. If you wish I would be glad to share my experiences via email. (say), - hydnjo talk 05:41, 6 October 2008 (UTC)

I'm glad to see that nobody's succumbed to the temptation of calling you a "hydnjic jerk" just because they disagree with you, Hydnjo.  :) -- JackofOz (talk) 23:23, 6 October 2008 (UTC)

At the risk of stepping into the discussion, here is a reference that appears to be freely available in PubMed. It appears to be a general review about sleep disorders but has a small section on "Sleep Starts (Hypnic Jerks)". There seems to be a dearth of medical research into this subject, but according to this reference there are no known treatments. Perhaps someone interested in the subject could improve the Hypnic jerk article? —Preceding unsigned comment added by Medical geneticist (talk • contribs) 13:59, 6 October 2008 (UTC)

Hypnic jerks are at one end of a spectrum leading up to periodic limb movement disorder (nocturnal myoclonus). Hypnic jerks are usually regarded as a trivial normal phenomenon. If your patient's hypnic jerks are so disruptive that he/she is considering taking medication, it is more likely to represent periodic limb movement disorder. I recommend referral to a sleep specialist (in the UK a subspecialty among pulmonologists) for a sleep study. Treatment options for PLMD are the dopamine agonists ropinirole and pramipexole. Axl ¤ [Talk] 19:23, 6 October 2008 (UTC)

multinucleate cells

What's the difference between a syncytium and a coenocyte? --Anakata (talk) 03:03, 6 October 2008 (UTC)

The articles say a syncytium is "cell-like" (but, presumably, not a cell) with multiple nucleii, while a coenocyte is a "cell" with multiple nucleii. And that's as far as I can go. ៛ Bielle (talk) 04:46, 6 October 2008 (UTC)

Maroon Clowns

Transferred from Miscellaneous desk Gwinva (talk)

Can a Gold-stripe maroon clown fish and a normal Maroon clown mate together?--Pufferfish4 (talk) 20:19, 5 October 2008 (UTC)

I couldn't find anything, but I bet the folks at http://www.fishforums.net/ would be able to help you. Alternatively, you could ask some of the contributors at Wikipedia:WikiProject Fishes. If they don't know the answer offhand I bet they would know where to look. Plasticup ^T/C 03:52, 6 October 2008 (UTC)

Languages in dreams

Has anyone ever researched languages in dreams? I was speaking with a couple of friends (both Greek Cypriots who are fluent in English), both of whom said that they dream both in English and in Greek. Any idea if such is common? I looked at dream, and I couldn't find anything even about speaking in dreams in general, let alone the language in which the speech is conducted. Nyttend (talk) 04:49, 6 October 2008 (UTC)

Well, speaking for myself, I certainly dream both in English and Finnish, absolutely. I think someone brought this up here before, but I can't seem to find that discussion now. -- Captain Disdain (talk) 07:30, 6 October 2008 (UTC)

In contrast, I'm fluent in Hindi, English and Bengali but have never had a dream in any language apart from hindi, which is my native language.Leif edling (talk) 11:37, 6 October 2008 (UTC)

I don't remember my dreams but in waking life I don't think in language much anyway except when thinking about communicating with other people. It's more about connections and movement and probabilities - gut feel but structured if you like. Dmcq (talk) 12:17, 6 October 2008 (UTC)

I used to dream in broken Spanish. It was horribly frustrating, because my limited language skills would impede the progress of my dream. Apparently this book discusses a "pidgin Malayalam used by Todas in trance states", but I couldn't find the passage. Plasticup ^T/C 15:57, 6 October 2008 (UTC)

I've always thought that the assumption that most people experience the world in generally the same way was a particularly limiting facet of contemporary psychology. How most people see the world is often confused with how everyone sees the world. --Shaggorama (talk) 05:58, 7 October 2008 (UTC)

marine engineering

ship is using heavy oil during sailing in sea.But in port it is using diesel oil why —Preceding unsigned comment added by Rajulramachandran (talk • contribs) 07:35, 6 October 2008 (UTC)

I presume that the heavy oil is used for running the main engines - but in port they only need smaller diesel generators to produce electricity. But that's just speculation. SteveBaker (talk) 11:33, 6 October 2008 (UTC)

Ships at sea use bunker oil, pretty much the worst and dirtiest petroleum-based product there is. The lower parts of an oil refinery fractionator produce a very low quality type of oil, and in particular, the wash zone just above the inlet feed is used to remove heavy metals from the stream. This is the most worthless of crap in the petroleum (NB asphalt is even worse, but it goes out the bottom and gets put on roads, also vast effort is expended on getting anything good out by means of the vacuum fractionator). All the junk that can still flow gets sold somewhere, and that somewhere is ships at sea, where no-one can hear you scream. No right thinking harbourmaster would allow such junk to be burnt anywhere near people - so ships switch over to half-decent fuel when they come into port. Out on the ocean, they use the really cheap and nasty stuff. Franamax (talk) 22:02, 6 October 2008 (UTC)

SOUND

WILL SOUND PASS THROUG SOLIDS —Preceding unsigned comment added by 59.93.6.27 (talk) 11:49, 6 October 2008 (UTC)

Yes, see the article named sound. It normally goes very well through solids and liquids as well as the air, the only problem it has is going between different mediums - that's why soundproofing is made of mixtures of odd shaped materials and air. Dmcq (talk) 12:22, 6 October 2008 (UTC)

This being the science desk - I recommend an experiment (actually, a "thought experiment" should do here). Sit inside a car on busy road - shut all the doors and windows and turn the engine and radio off. Can you hear the other cars on the road? Yes? Then sound passed through the solid surface of the car. Sound is just a vibration. The air vibrates - your ears pick up that vibration. In the case of our experiment, vibrations in the air outside of the window caused the glass to vibrate. On the inside of the car, the vibration of the glass started the air inside the car vibrating - and that's what you could hear. If you gently touch the glass with your fingertip as a big truck goes by - you can feel the glass vibrating. SteveBaker (talk) 13:19, 6 October 2008 (UTC)

I think that is wrong. it could it ber comming from throught the air conditioning pipe from outside and not throught the solids? —Preceding unsigned comment added by 194.80.240.66 (talk) 14:27, 6 October 2008 (UTC)

Have you ever heard a sound? If so, it's because it went right through your solid eardrum. --Sean 14:41, 6 October 2008 (UTC)

Even those not blessed with the faculty of sound can feel low tones resonating in their chest cavity. Plasticup ^T/C 15:50, 6 October 2008 (UTC)

Sound actually travels *faster* through most (all?) solid objects than air. In steel, sound travels at 5,100 m·s^-1, about 15 times faster than in air. If you yell at your friend underwater, it will get to them about 4 times faster than having a conversation above ground. -- MacAddct1984 ^{(talk &#149; contribs)} 18:57, 6 October 2008 (UTC)

It should be possible to demonstrate this if you have access to a straight metal bar at least 100 feet (30 meters) long and preferably somewhat more (an abandoned railway track would be ideal, but please don't try it on a working railway, where you might get run over by a train!). Perhaps you can find a long, continuous metal railing somewhere in a public park or plaza. Okay, now you need a friend to assist you, or maybe you can trick an enemy into doing it, if you don't have any friends. :-)

Have your assistant bang on the bar every few seconds with something hard like a rock or a small hammer (if the bar has a decorative finish, it would be safer to stand a flat piece of metal on top of it and bang on that, to avoid damage). If you stand far enough away along the bar, you will hear the sound lagging behind the your assistant's motions. 100 feet will give a lag of about 1/10 second; at 200 feet the lag is 1/5 second and will be more obvious. Now put one ear against the bar and you should hear the tapping in that ear ahead of the other ear. That proves that the sound is traveling through the solid bar faster than the air, and therefore that the sound is traveling through the solid. --Anonymous, 22:39 UTC, October 6, 2008.

Light from the remote visible in the video image?

when i has my video camera and my tv remote i can sees the light from the remote in the video camera but not irl, so what is the thing thats happerning here? why is this? —Preceding unsigned comment added by 194.80.240.66 (talk) 12:19, 6 October 2008 (UTC)

I moved the question from the Miscellaneous dek, as this is really a Science question. (Also retitled it.)

It's pretty simple: your eyes can only see light within a certain visual spectrum. The infrared light your remote emits is outside that spectrum, and thus it isn't visible to the naked eye. The video camera, however, detects it. (Not all cameras do this; it's a question of filtering the light properly, and cheaper or older models in particular don't necessarily do it very well.) Therefore, when you look at the video image, it looks as if there's a light shining from the remote. (And there is, you just don't normally see it.) -- Captain Disdain (talk) 13:24, 6 October 2008 (UTC)

Ah, thank you. Also i has another question = with thr remote when i use it near an readio on fm or longwave i head a buzzing noise from the radio. but only when the remote was in useing. again, how would light be affecting my radio? —Preceding unsigned comment added by 194.80.240.66 (talk) 14:25, 6 October 2008 (UTC)

While I'm not sure of exactly what frequencies would be responsible, it's worth remembering that light and radio waves are both forms of electromagnetic radiation -- they're just at different frequencies. Infrared and radio are far enough off, though, that I don't think this is necessarily what's responsible. If you use the remote next to the radio, you get interference, right? But I bet if you back 10 feet away and just point the remote at the radio (and then press buttons), nothing happens. That would suggest that it's not the IR light but rather the circuitry internal to the remote that's responsible. Circuits tend to leak EM radiation as well, and remotes aren't likely to be shielded to prevent interference at close range. Electronic circuits are also more likely to operate at frequencies near common radio bands. — Lomn 14:43, 6 October 2008 (UTC)

(ec) That's nothing to do with the IR light - it's because the remote contains a small computer. Computers do their calculations at rates that vary a lot from machine to machine. Your PC probably has a processor that runs between 1GHz and 3GHz - but the small computer inside the remote has to operate for long periods on one tiny battery and it doesn't have much work to do to figure out what IR light pulses to send when you push a particular button - so it's pretty slow...perhaps below 1MHz. At those sorts of frequency, the speed that the computer works at is close to the frequencies that your radio is designed to pick out of the air and amplify. The radio has to be sensitive enough to pick up very faint radio signals from a transmitter 20 miles away - so if the computer circuitry in your remote is leaking even a tiny amount of radio waves and you hold it close enough to the radio - then the radio will pick up the signal and you'll hear it. Back in the early days of home computers, I had a TRS-80 computer - which didn't have a sound chip inside. Some enterprising programmers figured out how to make the computer play music by running certain program sequences that could be picked up by holding a radio close to the computer chip! SteveBaker (talk) 14:46, 6 October 2008 (UTC)

Biology word

I'm having trouble recalling a word that began with the letter "A", having something to do with organs becoming unimportant / unused over time, like the appendix, or tonsils. —Preceding unsigned comment added by 69.16.88.147 (talk) 15:18, 6 October 2008 (UTC)

It doesn't begin with "A", but I have heard the term vestigial structure used to describe those phenomenon. Plasticup ^T/C 15:24, 6 October 2008 (UTC)

(edit conflict) Such organs are called vestigial. The only word beginning with 'A' that I can think of that could be relevant is atrophy, which could be used to describe an organ shrinking down to a small remnant of what it was when it was being used, however I don't think that would be a strictly correct use of the word. --Tango (talk) 15:25, 6 October 2008 (UTC)

Adventitious? "Developing in an unusual place or from an unusual source", though that may be even further afield. -- 128.104.112.147 (talk) 23:03, 6 October 2008 (UTC)

Atrophy? — DanielLC 23:42, 6 October 2008 (UTC)

Atrophy doesn't seem quite right - that suggests a single creature losing an organ during it's lifetime. Here we're presumably talking in an evolutionary sense - like creatures who spend their entire lives in caves gradually evolve into a form that has no eyes (see: troglobite). Adaptation would perhaps be an appropriate term - but it means a lot more than just losing organs. Regressive evolution is another term that you see a lot. SteveBaker (talk) 11:28, 7 October 2008 (UTC)

Atavism? -- Ferkelparade π 15:33, 7 October 2008 (UTC)

Debunking Ghosts

They say that ghosts are not real and that most scientists say they truly don't exist and have proven so. Exactly what scientists are they referring to? I am looking to get specific branches of science that these scientists are from. --Anilmanohar (talk) 15:38, 6 October 2008 (UTC)

See Princeton Engineering Anomalies Research Lab and everyone who criticized their poorly designed experiments. That would be physicists, psychologists, chemists, economists, and statisticians. That lab, by the way, was eventually closed as an embarrassment to the good name of Princeton University. Plasticup ^T/C 15:46, 6 October 2008 (UTC)

It's not really possible to prove something like "ghosts don't exist", and no reputable scientist is likely to claim to have done so. What they can confidently say is more along the lines of "there is no evidence that ghosts exist", and then it's up to you to decide whether you believe in things for which there is no evidence. --Sean 15:58, 6 October 2008 (UTC)

I don't think anyone believes in things for which they think there's no evidence. Some people just think that there is evidence that ghosts exist, in the form of bright spots in photographs or mysteriously moving objects or what have you. So I think the operative question is, who scientifically investigates the evidence proffered by such people? I don't think the answer is CSICOP, in spite of its name. They have on occasion scientifically investigated a claim of the paranormal, but mostly they seem to report the claims and scoff at them without any substantial investigation. -- BenRG (talk) 17:02, 6 October 2008 (UTC)

It's notable that the claims of the existence of a hypothetical or doubtful entity cannot be refuted by experiments. There is only scope for affirming the existence of such entities (eg the case of the mountain gorilla). So long as there is no experiment affirming the existence of such entities (especially something as preposterous as ghosts) I think it would be safe to presume there aren't any. As far as branches of science go, parapsychology is a field of related research.Leif edling (talk) 16:56, 6 October 2008 (UTC)

In such cases where proving a negative is impossible, we have to fall back on a scientific principle called Occam's razor. This isn't a law of science - but it's a good principle to live by. It says that if all else is equal and there are multiple explanations for a phenomenon, you should pick the simplest - the one that requires least change to established science. In the case of ghosts - where there is absolutely zero solid evidence for them, we're left with two possibilities: (a) that there is an entire range of common, complex phenomena that science has somehow completely and utterly missed or (b) that some idiots are lying to us. Guess which we pick? SteveBaker (talk) 18:19, 6 October 2008 (UTC)

I choose (b), but how did the Bush administration creep into this discussion? (Hey, I gotta get my shots in while I still can.) If somebody from the Secret Service is reading this, I mean it figuratively. Clarityfiend (talk) 22:37, 6 October 2008 (UTC)

What about the coelacanth? Scientists regarded it as having been extinct for millions of years, based on the fossil record and the utter absence of any evidence - known to them - that it had survived. Then they discovered it had indeed survived, and had been regularly if infrequently caught by islanders since time immemorial. It was certainly no stranger to the people of the Comoros. It all depends on who you talk to and where you look when you're gathering your evidence. Not having looked in all possible places does not equal "it does not exist". -- JackofOz (talk) 23:18, 6 October 2008 (UTC)

There are innumerably many things that exist that we haven't discovered. As much as it is, it doesn't compare to the number of things that don't exist that we haven't discovered. Nobody claims that everything that we don't have evidence for is false. Quite the contrary, any scientist will tell you that we have no evidence for almost everything that's true. We also have no evidence for almost everything that's false. Because the number of things that we have no evidence for that are false astronomically exceeds the number that are true, it is reasonable to suppose that a given thing that we have no evidence for is false. For example: it is generally believed that the number of living species exceeds the number we have discovered by several orders of magnitude. Despite this, if you just made up a species, you could safely say it doesn't exist. By the way, the coelacanth is a bad example, as we at least knew it existed at one time. Every time we discover a new species of fish, until that point we had no reason whatsoever to believe that it existed. — DanielLC 23:41, 6 October 2008 (UTC)

Oh, I don't know. I agree with your last point, but in relation to the coelacanth, scientists confidently claimed "it no longer exists", when that was not true. They didn't just say "we know of no evidence that it has survived". -- JackofOz (talk) 00:03, 7 October 2008 (UTC)

Actually, the coelacanth is always a bad example, because its an aquatic species, and there are such vast areas of the earth;s oceans that have gone unstudied. Were scientists mildly intrigued to find one alive? Certainly, but its not like finding an extinct land-based animal alive. If someone found a live T. Rex, for example, it would be far more shocking... --Jayron32.talk.contribs 03:27, 7 October 2008 (UTC)

Mildly intrigued? That would be rather an understatement. This gets back to Steve Baker's options (a) and (b) above. They chose option (b) with the coelacanth, as they do with ghosts and other claimed phenomena - but option (a) turned out to be the one they should have chosen. It wasn't as if the evidence wasn't there for those with eyes to see it, but they based all their findings of non-existence on published research papers etc, none of which had ever looked in the numerous places where the coelacanth is now known to have thrived for millions of years after it supposedly became extinct. -- JackofOz (talk) 06:03, 7 October 2008 (UTC)

Before the discovery of a modern coelecanth, we have these two competing hypotheses:

1. The coelecanth is extinct.
2. Nobody has happened to catch one recently (or nobody who had ever caught one has ever come forward to mention it).

Using Occam's razor to choose between these two options is dubious at best. Neither of them breaks any extant scientific laws or principles or requires any rewriting of the rest of science. The existance or non-existance of this fish doesn't really change much of what we know about the remainder of the universe. Perhaps our notion of cuttlefish population densities and breeding rates off the coast of one small stretch of South African coastline may need tweaking - but that's hardly a big deal! This is a case where archeologists and marine biologists simply made an overly hasty assessment due to an understandable lack of evidence - science is not infallible and we can easily be wrong about the small details. But for ghosts to exist, huge swaths of biology, physics and chemistry would need to be rewritten - things that we've carefully measured and graphed and calculated for two hundred years or more would have to be proven wrong. The chances of that being the case (versus "a few idiots are lying to us") is close to zero. Hence the use of Occam's razor in that case is entirely appropriate. SteveBaker (talk) 11:06, 7 October 2008 (UTC)

And back to the original question; the reason scientists don't reliably believe that ghosts exist is that all paranormal experimentation lacks the one property that all true scientific proof requires: repeatability. In every case, independent verification of the results fails; it always depends on the the individual performing the experiment. That is why there is no scientific proof of ghosts; and why it is assumed they don't exist; any "proof" of their existance falls apart under controlled conditions... --Jayron32.talk.contribs 03:30, 7 October 2008 (UTC)

It's useful to understand the argument from ignorance fallacy (aka: lack of proof is not proof of lack) in any discussion of paranormal proof like this. --Shaggorama (talk) 05:48, 7 October 2008 (UTC)

"Proof" is too strong a term here. Let me state this very clearly and carefully: We do not have proof that ghosts don't exist. But proof isn't everything. What we must have (for sanity's sake) is the general principle that we don't go around believing in things just because there is no proof to the contrary. I don't believe that the Invisible pink unicorn (mhhnbs) exists - but I don't have a shred of proof for that non-belief (although the otherwise inexplicable existance of pineapple and ham pizza could certainly use some in-depth research). So, yes, User:Shaggorama is right: Absence of evidence is certainly not evidence of absence (ie it is not proof that something doesn't exist). But it is quite solid grounds for the only-slightly-weaker statement that we do not believe in something. The absence of evidence for ghosts is more than enough reason to disbelieve in them. There are quite literally an infinite number of things that we cannot prove do not exist. Does that mean that we should go around with the default hypothesis that those things do exist? Certainly not! That way lies madness. If you have to believe in a literally infinite number of improbable things until you have solid proof that they do not exist then your life becomes quite impossible to live. You can't get up in the morning for fear that an previously undiscovered species of mothball-scented purple velociraptor has been nesting in back of your sock drawer for the last 100 million years and is about to pounce...you can't prove that it hasn't, and this certainly explains all of those odd socks! SteveBaker (talk) 11:06, 7 October 2008 (UTC)

Just to clarify, I wasn't trying to say I beleive in ghosts :) --Shaggorama (talk) 20:36, 7 October 2008 (UTC)

LCD Spectral Lines

I was curious one day so i got a pocket spectroscope and looked at my LCD monitor with it. Curiously, very defined spectral lines appeared. I can't find anything on this and i want to know why this happens. Can someone help? PS I don't know how to take a picture of these lines, sorry guys :) 31306D696E6E69636B6D (talk) 16:26, 6 October 2008 (UTC)

I think the backlight is a kind of fluorescent lamp. These can have sharp lines, depending on the design. See the article for examples. -- Coneslayer (talk) 16:48, 6 October 2008 (UTC)

The backlight is designed to produce pure colors when filtered through the LCD panel - so ideally it needs one spectral line at the center of each of the red, green and blue filters - putting out frequencies between those three colors would produce a 'muddy' display with all sorts of nasty colors and no decent, solid black. I don't know how they get it that good - but evidently, they do. SteveBaker (talk) 18:22, 6 October 2008 (UTC)

Fatigue relief

Is there any method whereby one may be relieved of fatigue and pain due to lactic acid deposition? Could ice packs be of any help?Leif edling (talk) 16:45, 6 October 2008 (UTC)

Rest would be best way to treat fatigue. If you want more of an answer than that, you'll need to ask a doctor, we can't medical advice here. (Ice could numb the area and reduce the pain, but then again it could give you frostbite or hypothermia or both, hence the need to ask someone more reliable than a random guy on the internet.) --Tango (talk) 17:00, 6 October 2008 (UTC)

Never place ice packs directly on the skin, no matter what you're trying to alleviate. Always put a towel or bandages between your skin and the ice. -- MacAddct1984 ^{(talk &#149; contribs)} 18:44, 6 October 2008 (UTC)

We do have an article on Fatigue (medical), but it has no discussion on relief. --—— Gadget850 (Ed) ^talk - 18:54, 6 October 2008 (UTC)

Ice packs do help with pain caused by exercise, as do warm baths. Other than that, rest is your only other option without seeing a doctor. —Cyclonenim (talk · contribs · email) 23:02, 6 October 2008 (UTC)

Sounds like you're talking about post-exercise cramps. If so, check out Delayed onset muscle soreness. Being proactive with a warm-up, cool-down and stretching is believed to help alot. Also, cramping is usually the worst when beginning an exercise regimen: after a few weeks, your muscles become acclimated to the workout and your metabolism adjusts appropriately. --Shaggorama (talk) 05:42, 7 October 2008 (UTC)

Gauge>Alum foil?

The metallic scale GAUGE? 75.60.90.25 (talk) 16:58, 6 October 2008 (UTC)

The "gauge" of some aluminium foil is its thickness, is that what you wanted to know? According to Aluminium foil, it's usually between around 0.006mm and 0.2mm. --Tango (talk) 17:03, 6 October 2008 (UTC)

If you are wondering why metal thickness is measured in "gauge" units, this is a shorthand notation to make it easy for people in the metal industries to refer to their products. The development of the gauge system is rooted in the history of metalworking and lets everyone produce a series of standard products. For instance, 24-gauge mild steel is .024" thick and weighs 1 lb/sq.ft. Going by our Sheet metal gauge (redirected) article, aluminum foil thicknesses fall below the established "gauge" range - but the thickness is still referred to as the "gauge", even though it should be called "thickness". One reason might be that thicknesses are measured with a gauge instrument; another might be that the term "thickness" implies a definite number, whereas a metal "gauge" incorporates variations in thickness produced by the rolling mill, for instance 10-gauge mild steel has a "thickness" of .1345" but this can vary between .1285" and .1405".[33] Short answer: when we talk about metal thickness, we speak in terms of its "gauge". Don't know if that helps at all :) Franamax (talk) 21:45, 6 October 2008 (UTC)

finger print sensors

just like other sensors ,are there some finger print sensors that could be interfaced with some microcontrollers(like 8051).plz tell me the sources of information about it as well. 116.71.187.243 (talk) 19:25, 6 October 2008 (UTC)

Most seem to offer a Serial Peripheral Interface Bus interface, which can be spoken to as described here. Search for Template:Websearch to see a bunch of them. --Sean 20:26, 6 October 2008 (UTC)

Zombie Newton is haunting me

I'm trying to understand how any why momentum, kinetic energy and mechanical work ... well, work in classical mechanics. I took a few courses of physics and mechanics years ago, but they all skirted the deep questions about exactly why they take the forms they do. Why should work be the dot product of displacement and force? Why is the first integral of mass relative to velicity momentum, and then why is the second integral kinetic energy? Is that something to do with the conservation of {energy, momentum, mass}, but why velocity?

I know these are rather open questions, but my curiosity keeps nagging away at me, and I don't seem to be able to find the answers without taking a physics degree myself. 79.72.138.94 (talk) 19:30, 6 October 2008 (UTC)

Also, I realise full well that the answer might be 'because it is, and that's just how it works', which would leave me feeling rather unfulfilled but sated. 79.72.138.94 (talk) 19:31, 6 October 2008 (UTC)

Actually, the answer is the exact opposite of what you expect. It is because that's the way we as people have organized our thinking. There's nothing fundemental about the concepts of "force" or "work" or "velocity". They are just convenient ways for us to organize our observations of motion. When we push something harder, it moves faster, so the concept of "force" was invented to explain this observation. When an effort is used to move something, that effort can no longer be used to move something else; thus the concept of energy is created. If you want to get beyond classical mechanics, physicists have been working on explaining it all, indeed a few different times but there are some fundemental flaws in all of these. Some show promise, others have run into dead ends. Maybe someone else wants to take a crack at this, but that's the best explanation I can come up with... --Jayron32.talk.contribs 19:41, 6 October 2008 (UTC)

Good point. I probably should have included that disclaimer as well, that it might just be an artifact of the analysis. I can accept the definition of force, velocity or acceleration as arbitrary artifacts, but energy and momentum seem to be more fundamental, because of the laws of conservation. Even if this is just the way they are organised, I still can't see the reaoning behind the patterns that form, so there is still something I'm missing. And GUTs and TOEs are altogether to visceral for me :) 79.72.138.94 (talk) 19:54, 6 October 2008 (UTC)

Noether's theorem (warning: article is extremely equation-heavy) basically boils down to "where you have symmetries, you have conserved quantities". As such, once you've defined positions, velocities and forces, under Newtonian mechanics you find that there are symmetries (e.g. time reversibility of a system) that are then associated with conserved quantities that happen to correspond to energy and momentum. Confusing Manifestation(Say hi!) 22:36, 6 October 2008 (UTC)

I have "answers" in some sense for you, as I've thought about these points myself.

1. Your question about work can be answered in two ways. You can identify force with the negative gradient of potential energy, which makes intuitive sense because we expect things on hills to be gravitationally accelerated down them and more quickly for steeper hills; then, using the chain rule, $dU=\sum _{i}dx_{i}{\frac {\partial U}{\partial x_{i}}}=d{\vec {x}}\cdot {\vec {\nabla }}U=-d{\vec {x}}\cdot {\vec {F}}$, and then (by conservation of energy) $U+E=C\Rightarrow dU+dE=0\Rightarrow dE=d{\vec {x}}\cdot {\vec {F}}$. (Note that nonconservative forces are a simplification of conservative ones; we need not treat them separately.) Alternatively, take the derivative of kinetic energy with respect to time: ${\frac {dE}{dt}}=m{\vec {v}}\cdot {\frac {d{\vec {v}}}{dt}}=m{\vec {a}}\cdot {\frac {d{\vec {x}}}{dt}}={\vec {F}}\cdot {\frac {d{\vec {x}}}{dt}}$ and $dE={\vec {F}}\cdot d{\vec {x}}$ immediately: in other words, when you apply a force in the opposite direction of displacement, you're slowing the object down, and when you apply it in the same direction, you're speeding it up, so the dot product is natural.
2. Momentum must be linear in velocity for the simple reason that otherwise small internal motions (like those due to heat) would affect the collective answer. But if heating (or cooling) an object reduces its momentum, what happens to a stationary object? Momentum must also be linear in mass so that inconsequential gossamer connections between objects sharing a velocity do not change their dynamics.
3. Energy's quadratic nature is the interesting part, and derives from the fact that it and momentum are conserved are a scalar and a vector respectively. Thus a change of frame of reference changes velocity but not energy (in Galilean relativity). (The reason for this is that any such changes must be linear functions of observer velocity, so that we can compose frame shifts without changing the answer. For changes in (measured) velocity, the identity function serves the purpose well, but the only isotropic scalar function is the zero function.) Now consider two observers who place a compressed (massless) spring between a pair of identical objects. Then one of the observers starts moving along the direction of the spring, and it fires. Choosing convenient numbers ($m=1,|v|=1$) and coordinates, the stationary observer records velocities of $({\vec {0}},{\vec {0}})$ and $(-{\hat {x}},{\hat {x}})$, for a total momentum before and after of $({\vec {0}},{\vec {0}})$ and a total energy before and after of $(0,2E(1))$. (I'm writing $E(v)$ for the "unknown" function that gives the energy per mass associated and speed v; we know it's linear in mass by the same argument as for momentum, and we know it's just speed because it has to be independent of direction.) The moving observer instead records $({\hat {x}},{\hat {x}})$ before and $({\vec {0}},2{\hat {x}})$ after, for a total momentum of $(2{\hat {x}},2{\hat {x}})$ before and after. This is good; our linear transform of velocity has preserved the conservation. But what of energy? In the moving frame, the construct already had $2E(1)$ kinetic energy, and the spring must still have added its own $2E(1)$; the one moving object must have kinetic energy $E(2)=2E(1)+2E(1)=4E(1)$; evidently it is quadratic. (The ½ is arbitrary; we could just as easily define ${\vec {F}}=-2{\vec {\nabla }}U$, for instance.)
4. Other arguments about energy include that it should be a smooth function of velocity (since observers with slightly different velocities should see much the same thing), and yet it must be a function only of speed. This rules out $E({\vec {v}})=f(|{\vec {v}}|)$, because the magnitude of a vector is only continuous and not smooth at 0. (Consider the plot of $f(x,y)={\sqrt {x^{2}+y^{2}}}$; it's a cone and is sharp at the origin.) $E({\vec {v}})=f(v^{2})$ is the obvious choice. Finally, consider throwing an object into a potential energy barrier (like gravity): if the force is uniform, the object will slow down uniformly. Then throw it twice as fast: it takes it twice as long to stop, and was making twice as much progress per time all the while, so it made it four times as far into the barrier. The force being uniform means that, were we to push the object in rather than throwing it, we would certainly expect the effort involved to be linear in the distance, so kinetic energy is again quadratic in speed since it only took twice as much speed to affect four times as much progress.

There's a certain mathematical circularity that's inevitable here, and even appeals to intuition are subject to the objection that they are merely descriptions of our intuition's basis in physics rather than explanations of physics based in intuition. But I find it helpful to understand better the connection between the mathematics and my intuition even if neither has any external justification. Hope this helps. --Tardis (talk) 17:34, 7 October 2008 (UTC)

False or true?

The keratitis that can occur in a contact lens wearer caused by Pseudomonas aeruginosa is an ocular emergency, as if left untreated it could destroy an eye within 24 hours(four tildes). —Preceding unsigned comment added by 79.97.241.246 (talk) 20:03, 6 October 2008 (UTC)

We're not allowed to give medical advice here. The article on keratitis says that it can scar the eye and permanently damage vision. (Or worse : "loss of the eye"! ) If this question is more than hypothetical I strongly recommend that you get to a doctor or E.R. right away. Don't trust your eyesight to strangers on the internet. APL (talk) 20:13, 6 October 2008 (UTC)

I can't tell you how disturbed I am when a single question falls foul of both "we can't give medical advice" and "we won't do your homework for you". --Sean 20:30, 6 October 2008 (UTC)

At least we didn't have to explain how to sue the contact lens manufacturer! SteveBaker (talk) 22:39, 6 October 2008 (UTC)

Just using the information you gave in your question, "is an ocular emergency as if left untreated it could destroy an eye within 24 hours". If that's true, you're damn right it's an emergency. —Cyclonenim (talk · contribs · email) 23:07, 6 October 2008 (UTC)

We have an article on keratitis, which mentions "pseudomonas aeruginosa", "contact lens" and "loss of the eye". It also says that "[o]ne should consult a qualified Ophthalmologist or Optometrist for treatment of an eye condition". Take from that what you will. Plasticup ^T/C 02:04, 7 October 2008 (UTC)

BTW, your supposed to type out four tildes like this ~~~~ not type out the words four tildes. The tilde key would usyally be besides the 1 key on your keyboard. You probably have to hold down shift to get the tilde Nil Einne (talk) 15:34, 7 October 2008 (UTC)

Electricity and magnetism

Is it possible to relate the positive and negative charges of protons and electrons and such to the north and south poles of a magnet? For example, does the north pole of a magnet act in a way that implies that it is positively (or possibly negatively) charged? Or are the similarities between electricity and magnetism, such as like repels like and opposites attract, explained in fundamentally different ways? Thank you. 86.74.122.84 (talk) 21:47, 6 October 2008 (UTC)

Magnetism is caused by a changing electric field, such as a moving charge. As such, two particles of opposite charge moving in the same direction will have opposite magnetic fields, so in that sense there is some similarity between north and south poles and positive and negative charges, but it's a little more complicated than that. Confusing Manifestation(Say hi!) 22:30, 6 October 2008 (UTC)

Umm, magnetism is an inherent property of matter, a changing electric field is not required. Variations in the electric field can induce a magnetic field perpendicular to the direction of charge motion, but you don't need current to have a magnet. Or at least, the electric field doesn't have to be changing. See magnetism. Franamax (talk) 00:40, 7 October 2008 (UTC)

Indeed, nuclei of atoms (which are for all intents and purposes "motionless") can display magnetic properties. Generally, the nucleons (protons and/or neutrons) will "match" magnetic poles so as to cancel out, but in nuclei with odd numbers of them (such as C-13) there is a net magnetic moment. Nuclear magnetic resonance and Magnetic resonance imaging use this property of the atomic nuclei. --Jayron32.talk.contribs 03:13, 7 October 2008 (UTC)

You may be interested in the "Gilbert Model" of magnetic behavior; just remember that it's not really physically accurate. --Tardis (talk) 15:43, 7 October 2008 (UTC)

Is THIS version understandable?

Still confusing, but a lot better IMRHO.

Sail Car Preliminary Description Our sail car is a trapezoid with two parallel sides, front and back. One side, the back, is longer than the other (hence a trapezoid), requiring two straws linked together (for the purposes of this description, they will be referred to as one straw). Two hypotenuses lie on the side of the trapezoid. They extend from the back to the front, where they bend and then meet to form the front side. They bend out on the back, creating two extensions outside of the trapezoid. These extensions are two straws deep with the back side straw in the rear and the hypotenuse straws immediately in front. On these extensions are two wheels. They are supported by two pins on each side of each wheel. On the front, there are two wheels as well. They lie near the bends of the front side.

At the midpoint of the back side, two straws extend diagonally frontwards towards the bends of the hypotenuse straws to give the frame extra support. Roughly halfway between the hypotenuse straws and the midpoint of the back side are two straws extending vertically upwards. Between the two straws is a sail. The sails is pinned to the straws for support. The sail is bent inwards and is thus also supported by a crossbeam at the top.

--hello, i'm a member | talk to me! 23:38, 6 October 2008 (UTC)

Member, a simple diagram would really help you out in this. Maybe the better strategy would be (assuming you want to create a new article) for you to start a page in your own user-space, let's say by clicking here: User:Member/Sailcar. You could put some external references in there for us to click on, so we could better understand what you are describing. You (or us others) could then have a shot at creating graphics to better describe your concept. Franamax (talk) 00:29, 7 October 2008 (UTC)

And as you can maybe see from Edison's comments below, put your text into the wiki-space and we will all slice-and-dice it into an encyclopedia article. The safest place is your own user-space per the redlink I gave above. Give us a link to an image or site that describes your concept, we can work with you to make it all work. Honest! Franamax (talk) 01:38, 7 October 2008 (UTC)

I will count the title as a sentence. In sentence 3, why not call the rear "straw" the rear axle? Your use of "hypotenuse" in the paragraph is inconsistent with Trapezoid and with Hypotenuse. Call them the "nonparallel sides of the trapezoid." In sentence 5 you refer to the "front" where the straws bend, and to a different "front side" which is formed by the meeting of the side straws. Eliminate the ambiguity. Sentence 6: Replace "They" with a more explicit description of the members you refer to. How about eliminating pronouns in such a terse yet confusing description? No idea what sentence 6 refers to. Sentence 7 is obscure and confusing. Sentence 8:Which extensions? Sentence 9: What does "They" refer to? Sentence 11: What is the "back line?" The "rear straw," which should probably be called the "rear axle?" Sentence 14 and 15: No idea of the shape or orientation of the sail. Edison (talk) 01:21, 7 October 2008 (UTC)

A diagram - or a photo - is needed here. There are some things that just don't work when put into words. It's possible we could come up with some better words - but because the words you have aren't working, we need the diagram/photo in order to understand what we're writing about! SteveBaker (talk) 10:16, 7 October 2008 (UTC)

I'm still stuck right at the start. A trapezoid is a 2D shape. Is your car a trapezoid cut out of cardboard and held vertical? Or is it a 3D solid shape, like a prism of a trapezoid? You need to make that clear before you start talking of front and back. Itsmejudith (talk) 11:07, 7 October 2008 (UTC)

There are lots of patented mechanical devices far more complex than this thing which have clear and unambiguous descriptions in the patent specifications. Instead of "two straws which will be called one straw" call it a freakin' "rear axle," for instance. From the description, it could be a structure made only of straws, or it could have a trapezoidal planar body made of some unspecified substance. It does not say what the vertical straws are attached to. Edison (talk) 18:18, 7 October 2008 (UTC)

Momentum and photons

Gah such a simple question I've forgotten the answer to. How the hell do photons have momentum when they have no mass? Is it due to rest mass? Cheers! —Cyclonenim (talk · contribs · email) 23:05, 6 October 2008 (UTC)

They have no rest mass, but due to E=mc² they have mass which gives them momentum (m=E/c² so p=mv=E/c - there is a lot of hand waving required for that derivation, but it gets the right answer!). --Tango (talk) 23:15, 6 October 2008 (UTC)

Likewise, Electrons are dimensionless (they have no volume), yet they have a "spin". Try to figure that out using classical mechanics... --Jayron32.talk.contribs 03:07, 7 October 2008 (UTC)

How do you know that an electron has no volume? Ohanian (talk) 06:22, 7 October 2008 (UTC)

See Electron#Fundamental properties. Axl ¤ [Talk] 08:29, 7 October 2008 (UTC)

...which is not very helpful, because it says "for convenience, <the electron> is usually defined or assumed to be a point charge with no spatial extent; a point particle", and a point particle is "an idealized object". We know that the "point particle" model cannot be the whole story, because then the electron would be a singularity. In quantum field theory fundamental "particles" like the electron are not really particles at all - they are excitations of a quantum field, and they don't have a volume because the "volume" concept just doesn't apply to such things - any more than the colour red or the number seven has a volume. Fundamental particles might have some multi-dimensional equivalent of "spatial extent" in string theory, but I am not sure whether that could be made to correspond in any reasonable way to our macroscopic concept of "volume". So in simple terms, we might say that we don't think that an electron has a property that we could interpret as a volume - which is not the same as saying it has zero volume. Gandalf61 (talk) 09:30, 7 October 2008 (UTC)

Gandalf, your response is one interpretation. Axl ¤ [Talk] 10:31, 7 October 2008 (UTC)

Mars and Jupiter and Saturn's moon over sun's RGiant Stage

If Mars still exist, does anybody know what Mars surface will be like over sun's R Giant? Will it be yellow-orange molten lava like Earth was 4.6 billion years ago? What about Europa-Jupiter's moon. Europa's tan-gray ice will melt into water, then what will ahppen next. Will it scorch like Mercury. Titan's orange smog might bluen out. By 6 to 7 years from now, it is learnt Titan is the only place going to habitat for life. I wonder what will happen to Uranus' moon when sun enters a R Giant.--SCFReeways 23:44, 6 October 2008 (UTC)

• Will somebody be able to answer it?--SCFReeways 01:04, 7 October 2008 (UTC)

• Come on, do anybody know this?--SCFReeways 01:43, 7 October 2008 (UTC)

Have some patience, we don't know this off the top of our heads. Plasticup ^T/C 02:07, 7 October 2008 (UTC)

And we live in a variety of time zones... (yawwn) --140.247.11.55 (talk) 02:29, 7 October 2008 (UTC)

And it says at the top of this page that we may need as much as four days to fully develop an answer. Anything that might be needed in less than four days is probably homework - which we don't do. The sun isn't going to do this for another 7 billion years - so this is hardly a time-critical answer. SteveBaker (talk) 09:58, 7 October 2008 (UTC)

It's tough to be patient though.--SCFReeways 02:48, 7 October 2008 (UTC)

The primary difficulty in answering your question is your poor grammar. Your first question appears to be "Does anybody know what will happen to Mars when the Sun turns into a red giant? It is not known. Mars may become superheated. It may escape the Sun since it will enlarge its orbit. So, no, nobody knows. Your next "questions" have leading assumptions that do not appear to be based on popular scientific evidence. Why do you assume Europa's surface will melt? Why do you believe that Titan will be the only habitat for life in 6 or 7 years? Uranus is very far from the Sun, why do you assume it will be heavily affected? Is this all based on an assumption that, as a red giant, the Sun will suddenly start producing so much heat that it burns up the Solar System? You must take into account how little heat reaches the outer planets right now and that they will move further from the sun when it loses mass. -- kainaw™ 03:34, 7 October 2008 (UTC)

They will move further out. Alot of sources said Titan might be habitatable at this time. I wonder about Uranus moon. Whole solar ssytem will heat up at this time. Mercury and possibly Venus and Earth will be engulf and destroy, then Mars will be the only inenr planets left. About Europa, after ice melt, even escaption Europa can be a little too hot. Uranus moon could get beenfit from sun's heating too.--SCFReeways 03:52, 7 October 2008 (UTC)

What about this?--SCFReeways 04:35, 7 October 2008 (UTC)

My understanding is that Titan may heat up to habitable temperature but it will lose its atmosphere so won't be habitable. The reason it can maintain such a dense atmosphere with its low mass is because it is very cold (cold gasses don't move around as much so are less likely to randomly achieve escape velocity). Once it warms up, the atmosphere will leak away into space pretty quickly. (That's just the theory I've heard, there are so many variables we can't pin down that it's difficult to say for sure.) --Tango (talk) 14:39, 7 October 2008 (UTC)

When you say "6 to 7 years" do you mean "6 to 7 billion years"? Plasticup ^T/C 15:19, 7 October 2008 (UTC)

I would guess so. It's still wrong, though, since by then the Sun will have gone past being a red giant and will be a white dwarf giving off very little heat. The red giant phase only lasts for a few million years, if that. --Tango (talk) 16:09, 7 October 2008 (UTC)

• This site said the tan-gray ice on Europa might melt into water, and possibly be warm enough.--SCFReeways 22:08, 7 October 2008 (UTC)

• THis site shows in 7 billion years, Europa's thick ice can melt into globe of liquid ocean, but artist say it's sky will still be black in 6 to 7 Gyrs when sun turns into giant star.--SCFReeways 22:15, 7 October 2008 (UTC)

October 7

Quantum: Difference between an operator and a measurement

Suppose there is a qubit whose state is

$|\psi \rangle ={\frac {1}{\sqrt {3}}}|0\rangle +{\frac {\sqrt {2}}{\sqrt {3}}}|1\rangle ={\begin{bmatrix}{\tfrac {1}{\sqrt {3}}}\\{\tfrac {\sqrt {2}}{\sqrt {3}}}\end{bmatrix}}$

After we measure the qubit, the state of the qubit will change from $|\psi \rangle$ to $|1\rangle$ with probability

${\big |}\langle 1|\psi \rangle {\big |}^{2}=\left({\frac {\sqrt {2}}{\sqrt {3}}}\right)^{2}={\frac {2}{3}}\approx 0.666\dots$.

This process is called wave function collapse. If $|1\rangle$ is observed after the measurement, the qubit becomes

$|\psi \rangle =|1\rangle$

Instead of measuring the qubit, a Hadamard gate

$H={\frac {1}{\sqrt {2}}}{\begin{bmatrix}1&1\\1&-1\end{bmatrix}}$

operates on the qubit will be

$H|\psi \rangle ={\frac {1}{\sqrt {2}}}{\begin{bmatrix}1&1\\1&-1\end{bmatrix}}{\begin{bmatrix}{\tfrac {1}{\sqrt {3}}}\\{\tfrac {\sqrt {2}}{\sqrt {3}}}\end{bmatrix}}={\frac {1}{\sqrt {2}}}{\begin{bmatrix}{\tfrac {1+{\sqrt {2}}}{\sqrt {3}}}\\{\tfrac {1-{\sqrt {2}}}{\sqrt {3}}}\end{bmatrix}}={\frac {1+{\sqrt {2}}}{\sqrt {6}}}|0\rangle +{\frac {1-{\sqrt {2}}}{\sqrt {6}}}|1\rangle$

as I know, the process of the operation is 'not' a wave function collapse.

My problem is why an operator acts on a qubit doesn't cause a wave function collapse? As I know, any subtle interaction with the qubit will cause the wave function to collapse. The Hadamard gate operator, which should be an apparatus, when acts on the qubit should also interact with the qubit. So how an operator can circumvent the wave function collapse? - Justin545 (talk) 05:28, 7 October 2008 (UTC)

I'm a little rusty in my quantum theory, but if I remember correctly, it's not all interactions that cause wave-form collapse, only those actions that generate information. It is entirely possible to transform a wave-function without actually observing (i.e. gaining information from) said wave function. Take for example the most basic quantum experiment, the double-slit experiment. The slit certainly interacts with the beam of particles; as the beam hits the slits, an interference pattern immerges, this is a result of the slits "transforming" the beam of particles via interaction. The wave function collapse occurs only when you try to gain information about the particle's location, for example, by placing a charge detector at one of the slits. As long as no information is obtained on the system, it goes on behaving as an uncollapsed wave function. Once the detector is placed, information is extracted, and the wave function collapses, resulting in an uninterferred double beam... The Hadamard gate must operate in the same way; it performs a transformation on the qubit blindly (that is, without observing the state of the qubit). Such an action is not philosophically that hard to understand. Imagine a blind man turning coins over. You hand the man a coin, and he simply reverses the face of the coin. He can perform the operation (turning heads to tails and tails to heads) perfectly every time, even if he doesn't know which states the coins are in before he flips them. To take this on a quantum scale, he's able to perform a transformation on the wave function, without causing any waveform collapse. He's made no observations of the bits of information he's transforming, he's just doing the transformation. A Hadamard gate must work on this level. --Jayron32.talk.contribs 05:47, 7 October 2008 (UTC)

It could be difficult to define the term 'gaining information from'. Cite form the article Quantum computer:

One major problem is keeping the components of the computer in a coherent state, as the slightest interaction with the external world would cause the system to decohere. This effect causes the unitary character (and more specifically, the invertibility) of quantum computational steps to be violated. Decoherence times for candidate systems, in particular the transverse relaxation time T2 (terminology used in NMR and MRI technology, also called the dephasing time), typically range between nanoseconds and seconds at low temperature.

I think the 'decohere' is actually the wave function collapse. It seems that even the 'temperature' is also a way to interact with the qubit and it is not clear to me how an environmental temperature makes information gaining... maybe what you mean is that a measurement is an irreversible operation whereas a gate operation is a reversible operation. Indeed, the action of a Hadamard gate is a reversible operation since there is no information lost during the operation of the Hadamard gate. And saying that a measurement is an irreversible operation is just my suspicion since some information is lost and gained by the observer during a measurement. By thinking the gate operation as a transform as you said make it more understandable to me. And now I know there are some interactions don't collapse the wave function. - Justin545 (talk) 07:23, 7 October 2008 (UTC)

Unless the qubit is lost due to interaction with other particles; at high temperatures there are bound to be more particles moving faster and thus more interference on the qubit; there may be some threshold temperature where the system becomes so inefficient due to losses that it stops "working." --Jayron32.talk.contribs 11:29, 7 October 2008 (UTC)

Definitely some interactions don't collapse the wave function, otherwise a proton, for example, couldn't be a quantum particle since it consists of more fundamental particles constantly interacting with each other.

See quantum decoherence for more on that subject. It is effectively the same thing as wavefunction collapse and people are likely to use the terms interchangeably.

Measurement/decoherence is all about copying. An example of copying is a transition from $\alpha |0\rangle +\beta |1\rangle$ to $\alpha |0\rangle |0\rangle +\beta |1\rangle |1\rangle$. This is different from cloning, which would take $\psi$ to $\psi ^{2}$, e.g. $(\alpha |0\rangle +\beta |1\rangle )^{2}=\alpha ^{2}|0\rangle |0\rangle +\cdots$. Cloning isn't possible, but copying is possible. The key difference between them is that copying is basis-dependent. The example I gave above was copying with respect to the computational basis $\{|0\rangle ,|1\rangle \}$. Copying with respect to the dual basis $|{\pm }\rangle ={\tfrac {1}{\sqrt {2}}}(|0\rangle \pm |1\rangle )$ takes

$\alpha |{+}\rangle +\beta |{-}\rangle$ to $\alpha |{+}\rangle |{+}\rangle +\beta |{-}\rangle |{-}\rangle$,

which is the same as taking

$\alpha |{0}\rangle +\beta |{1}\rangle$ to ${\tfrac {\alpha }{\sqrt {2}}}(|00\rangle +|11\rangle )+{\tfrac {\beta }{\sqrt {2}}}(|01\rangle +|10\rangle )$,

if I calculated right—at any rate it's a different operation. If you copy a qubit (with respect to a basis) and put the copy somewhere where it's unavailable to you, the effect on the original qubit is exactly as though you'd measured it (with respect to that basis). But if the copy ever becomes accessible to you again, you can use it to "undo the measurement," so it's not a real measurement. Measurements only become definite when they can no longer be undone, e.g. because the copy has been amplified into a macroscopic thermodynamically irreversible state change like a flash from an LED.

Reply composed in a hurry and I may not be able to reply again for a few days. -- BenRG (talk) 11:44, 7 October 2008 (UTC)

Noisy laptop fan

Why do they (fans) do it (noise)? Is a silent laptop fan possible?Mr.K. (talk) 11:06, 7 October 2008 (UTC)

A (laptop) fan moves air, using an electric engine. Air flow creates sound, and the engine can't be perfectly silent either, so: no, a silent laptop fan isn't possible. There are however some new, interesting ways of cooling coming about, some of which may be silent. Someone please fill me in here :) -- Aeluwas (talk) 11:08, 7 October 2008 (UTC)

Actually, there are ways of generating air flow without any moving parts, for example see Air ionizer; it operates similar to a mass spectrometer; air molecules can be ionized via say, a negatively charged plate, and accelerated via a pair of positively charged plates. Many air molecules will simply gain electrons at one plate and lose them back at the other (or visa-versa; I am not positive on the specific mechanics of the situation), however, some will "overshoot" the second plate, and also drag many "non-charged" molecules with them, resulting in net air flow. However, the method is quite innefficient, especially on a scale small enough to fit into a laptop, and I suspect that in terms of net air flow for, for both its size and wattage, a simple mechanical fan is far more efficient. --Jayron32.talk.contribs 11:24, 7 October 2008 (UTC)

The engine could be so silent like the HDD. Moving air doesn't have to be noisy. I suppose it is noisy only if it generates turbulence right? So, a silent laptop fan should be possible... Mr.K. (talk) 11:38, 7 October 2008 (UTC)

But laminar airflow may not be terribly efficient at moving heat around, as it may not move all the air and probably wouldn't move fast enough. 130.88.64.189 (talk) 12:29, 7 October 2008 (UTC)

The other common means of making a fan quieter is to spin it at a lower RPM. Of course, the direct consequence is that you move less air, reducing the cooling effectiveness. In a desktop system, that just means that you make the fan larger to compensate. With space at a premium in laptops, this solution is less effective. — Lomn 12:59, 7 October 2008 (UTC)

A related option is to reduce your CPU usage, which reduces the laptop's need for cooling, which should let the fan run slower and less frequently. Plasticup ^T/C 15:15, 7 October 2008 (UTC)

Often, reducing the CPU usage is not an option, since I use the laptop with a purpose. Mr.K. (talk) 15:24, 7 October 2008 (UTC)

Question (Goliath Beetle)

What is the main predator to the Goliath Beetle? —Preceding unsigned comment added by 204.210.238.42 (talk) 11:54, 7 October 2008 (UTC)

I'm not sure it has a main predator. There are more than enough predators and omnivores in tropical Africa that would not think twice before dining on a huge delicious beetle larva. Mandrill comes to mind as a very likely predator, but I couldn't find any specific data. Besides, Mandrill habitat extent is much smaller than that of Goliathus sp. . Sorry. --Dr Dima (talk) 17:13, 7 October 2008 (UTC)

How does fruit get "bruised"?

Just curious how fruits like apples and bananas get "bruised"? Aren't they dead? How does impact against the surface affect the fruit below the skin? --70.167.58.6 (talk) 16:00, 7 October 2008 (UTC)

I'm not sure it's accurate to say they're dead. They are still chemically active, otherwise they wouldn't be able to ripen after being picked. I think the bruising is caused by breaking the cell walls so the individual cells die, but I can't guarantee it. I'm sure a botanist will be along shortly. --Tango (talk) 16:07, 7 October 2008 (UTC)

Not a botanist, but Tango has the right idea. Inside of plant cells are chemicals which oxidize upon exposure to air. If the cell remains intact, nothing happens. However, cutting the fruit or striking it can cause the cell walls of the cells to break, exposing the chemicals to air, and causeing a change in both color and texture. Incidentally, bruised fruit is perfectly healthy and there's nothing at all wrong with eating it. You abuse the fruit much more when you chew and swallow the fruit anyways; the color change is not a sign of bacterial growth in any way, its merely a sign of physical damage. --Jayron32.talk.contribs 16:47, 7 October 2008 (UTC)

You may want to look at this. --Dr Dima (talk) 19:18, 7 October 2008 (UTC)

Grass Seed Lifespan

I have had a bag of lawn grass seed in my garage for over 4 years. Over that time it has been exposed to -20C to +35C degrees. Would it still be alive and able to grow after all? —Preceding unsigned comment added by 151.123.128.250 (talk) 16:40, 7 October 2008 (UTC)

Quite possibly. Many kinds of seeds are quite resilient. There are some seeds that have been shown to germinate after hundreds of years of dormancy. The best thing to do is to run a little experiment. Take a cup of dirt, put a small pinch of seeds in it, keep it moist and in direct sunlight (like the windowsill) and see what happens. The seeds, if still viable, should germinate within a few days. If they do, you probably have good seed. If it just sits there for a week and nothing happens, then you probably need to pitch them. --Jayron32.talk.contribs 16:44, 7 October 2008 (UTC)

The normal rule is: If at least 75% of the seeds germinate, use as directed. If 50%-75% germinate, use double the normal amount. If less than 50% germinate, toss it and get a new bag. --Stephan Schulz (talk) 17:41, 7 October 2008 (UTC)

calorie consumption per hour/ mile (cycling)

Hello Everyone,

i've been trying to work out how many calories I burn on my cycle to work but i'm struggling to get some relevant info (i've been on a few forums but they use 40 year olds as reference points -i'm not even sure if one burns more or less calories as one ages so this is less than helpful.) Anyway, i'd be grateful if any one has any ideas - its about 4.7 miles (according to google maps anyway) each way, along reasonably flat terrain -stopping and starting for traffic lights often. It takes me about 30 minutes on average. Also i'm a (reasonably fit) 24 year old man... Any help, or even some starting data, would be great...

Thanks, 82.22.4.63 (talk) 19:09, 7 October 2008 (UTC)

While caloric intake is relatively easy to calculate, based on the nutritional content of the food in terms of ammounts of proteins, fats, and carbohydrates, its a different story for caloric output, in terms of exercise. Its going to vary WILDLY depending on how hard you are pedaling, your current body weight, your personal body chemistry and metabolism, the ambient temperature that day, your muscle mass, yada yada yada. The variables are almost too great to even think of all of them. Calculators that purport to determine how many calories you burn (for example, those found on treadmills or stationary bikes) are likely just WAGs. They may be based on, for example, the 50th percentile human, but variation from that ideal is likely so large that there is no way to assure they will be accurate for you. The easiest way to tell is to see if it has an effect on your own body: If you are losing body fat over time, you are likely burning more calories than you take in. If you are gaining body fat over time, you are likely consuming more than you burn. Take Michael Phelps for example. It is widely reported that he consumes 10,000 calories per day. That's roughly the amount of food 4 people would eat. And yet, he has almost no body fat, which means his level of activity has him burning at least that much. The funny thing is, another person, performing the same workout regimen as he does, may find himself gaining fat at that level of intake. Isolating WHICH activities are burning which calories is entirely a guessing game. The best thing that can be said is more activity always burns more calories, so more is always better. --Jayron32.talk.contribs 20:21, 7 October 2008 (UTC)

Human feet vs. Chimp feet

Chimps' feet have thumb like digits on them so they can grab objects with their feet in a similar way to how we can grab things with our hands correct? So I was curious if our feet which do not have that ability, have any advantages over their feet. 98.221.85.188 (talk) 19:51, 7 October 2008 (UTC)

Chimp feet are great for walking on branches, too. But they're lousy for running. (See achilles tendon not what I expected.) See Persistence hunting. Saintrain (talk) 20:07, 7 October 2008 (UTC)

Chimps are also not bipedal like humans. Like some other animals (bears, for example) they can, relatively easily walk on two legs, but their preferred method of ground locomotion is "knuckle walking" on all fours, generally as a sort of side-shuffle. Chimps are not very efficient at walking flat footed, however, as noted above, they are VERY efficient at traveling in trees, having evolved in a forested habitat. Modern humans largely evolved in a savannah habitat, with few trees, and thus flat-footed walking gave them an advantage in that environment. Thumbs are an impediment to flat-footed walking, and so proto-humans with "modern human" style feet tended to predominate in that environment. --Jayron32.talk.contribs 20:26, 7 October 2008 (UTC)

To expand on Jayron32, the human foot is specifically adapted to walking upright. The big advantage we have over chimps (for the bipedal environment) are the two arches of the foot which act --like springs-- as shock absorbers, distributing weight and allowing us to easily run upright. --Shaggorama (talk) 20:56, 7 October 2008 (UTC)

Fizzy drinks.

The aqueous carbon dioxide in fizzy drinks makes the drinks acidic (for some reason that I have forgotten), couldn't you just add an alkaline solution to the drink to neutralise it. Fizzy drinks are critisised for being bad for your teeth because they're acidic, this would get rid of that problem. Thanks.92.2.212.124 (talk) 20:02, 7 October 2008 (UTC)

Except that acidic compounds have a generally pleasant "sour" flavor. Alkali compounds have a bitter, soapy flavor. Eat a bar of soap, or drink some lemonade. Which do YOU prefer? --Jayron32.talk.contribs 20:31, 7 October 2008 (UTC)

Also, its not the acid in sodas that is damaging to your teeth per se since it does not remain in contact with your teeth for very long. However, bacteria, which DO remain in contact with your teeth for a long time, will feed on the sugar in the soda, and produce an acidic waste product. Since these bacteria are essentially always there, the more sugar you give them, the more acid they make. Its this acid, which is held directly against the tooth for a long period of time, and not the acid that washes over the tooth which causes decay. Its the sugars in the soda that cause the decay, not the acid inherent in the carbonic acid. --Jayron32.talk.contribs 20:31, 7 October 2008 (UTC)

Thanks92.2.212.124 (talk) 20:43, 7 October 2008 (UTC)

The grayed tip of a banana

As a child I was told to bite off the usually grayed tip of a banana before eating it. What is it, though? Thanks. Imagine Reason (talk) 20:03, 7 October 2008 (UTC)

Greyed tip? I assume this means pre-peeled bananas, but i wouldn't bite the peel of a banana. If this means a peeled banana, what grey tip? Anyway, I've never heard that.92.2.212.124 (talk) 20:30, 7 October 2008 (UTC)

I'm pretty sure it's banana. --Shaggorama (talk) 20:38, 7 October 2008 (UTC)

Yes, it's the tip of a just-peeled banana. It's usually not white. C'mon, I thought that were the common experience. Imagine Reason (talk) 21:19, 7 October 2008 (UTC)

See vascular bundle and, specifically for bananas, phloem bundle (What!? No article!?). What you are referring to is the part of the banana where the bundles (strings) join and invert into the center of the fruit. -- kainaw™ 21:49, 7 October 2008 (UTC)

Nobel Prize winners

Have there been any Nobel Prize winners whose work has since been completely discredited or otherwise found to be useless/incorrect? -Elmer Clark (talk) 20:41, 7 October 2008 (UTC)

Interesting question! Since you posted in Science, I assume you're less interested in the Nobel Peace Prize, where Rigoberta_Menchú and Henry Kissinger come to mind. --Sean 21:45, 7 October 2008 (UTC)

Off the top of my head, the closest I could come up with is Neils Bohr, who won the Nobel Prize in Physics for devising the Bohr model of the atom. Its not that the Bohr model was wrong, in fact it is perfectly accurate for any two particle system. The problem is, in practical terms it means it predicts the electronic structure of the Hydrogen atom (which has an electron and the nucleus) and nothing else. The Bohr model breaks down for any atom with more than one electron in it; so while it works for the He⁺¹ ion, it doesn't work for the He atom. It was an important step in the modern understanding of the electronic structure of the atom, but other more recent models, such as the wave mechanical model of the atom as derived by Erwin Schrödinger, Paul Dirac, Louis de Broglie, and others is far more useful, and as a model it contains the Bohr model as a special case. Still, Bohr is important as a key step in our understanding of the atom, and his contributions should not be deminished merely because better models came along later. --Jayron32.talk.contribs 21:37, 7 October 2008 (UTC)

honey locust spines: poisonous?

I just tore an enormous (23 centimeter long) spine off of a honey locust near here and in the process my left hand got jabbed. It didn't break the skin or draw any blood, but there's a small, red raised bump there like an insect bite that itches a little and the area around it is somewhat red and feels sore. I heard that honey locusts have some sort of toxin in their thorns that can be dangerous, but I can't find any information on it at all. Is this true? If so, do I need to seek medical attention? Can this get infected?

Any help is appreciated. Thanks. 63.245.144.77 (talk) 20:44, 7 October 2008 (UTC)

UPDATE: I think I'm having some sort of allergic reaction. My face is all swollen up and I'm about to stop breathing. Should I seek medical attention?wq —Preceding unsigned comment added by 63.245.144.77 (talk) 22:18, 7 October 2008 (UTC)

Ah, sorry. Disregard that last message. My brother was messing around. I'm fine. —Preceding unsigned comment added by 63.245.144.77 (talk) 22:18, 7 October 2008 (UTC)

Holt Biology

What is a phospholipid layer that covers a cell`s surface and acts as a barrier between the inside of a cell and the cell`s environment? —Preceding unsigned comment added by 75.68.106.206 (talk) 21:14, 7 October 2008 (UTC)

Your Holt Biology book should have the answer. Please post all your homework questions at once so we don't have to repeat multiple times that we are not here to do your homework. -- kainaw™ 21:22, 7 October 2008 (UTC)

See comments below on the plant cells. Be aware that while Wikipedia has an article on Cells, which I recommend that you read, your Holt Biology book is likely much easier to follow, and if you read it, it will give you the answer. --Jayron32.talk.contribs 21:23, 7 October 2008 (UTC)

Hearing

Hi all,

Hypothetically, and I do mean hypothetically because I’m not asking for medical advice, how does one increase the results of a hearing test (only a temporary basis, not permanently).

I’ve heard that: 1. One’s hearing is better in the morning (so take the hearing test in the morning) – there will be a slight benefit. 2. Wear headphones (like the headphones for ear protection with firearms) prior to the hearing test. This will allow one to “rest” the ear drums so they’ll be more “sensitive” during the hearing test.

Any other thoughts (again, not seeking medical advice). Thx! Rangermike (talk) 21:15, 7 October 2008 (UTC)

Holt Biology

what is an organelle found in plant and algae cells where photosynthesis occurs? —Preceding unsigned comment added by 75.68.106.206 (talk) 21:17, 7 October 2008 (UTC)

You know, if you read your Holt Biology book, you may find the answer very easily. I bet you wouldn't have to look for more than 2 or 3 minutes. As an aside, you should also read the disclaimer at the top of this page, where it mentions that we aren't here to answer your homework questions. If reading your textbook is too much, you may want to read the Wikipedia article on Plant cells. Toodles. --Jayron32.talk.contribs 21:20, 7 October 2008 (UTC)

Really you'd get a much faster answer by typing photosynthesis into the search box than we could ever provide, I just don't get it. -- Mad031683 (talk) 22:07, 7 October 2008 (UTC)

steam rockets

I am interested in steam rockets. What can you tell me about them? I specifically wanted to know about heating the steam. The small steam rockets I've seen are preheated with a torch and then released. Is it possible to have an onboard heating system on a relatively small rocket? What would that be? Any additional information would be very helpful. Thank you.Wizardh2o (talk) 22:43, 7 October 2008 (UTC)

We have an article on hot water rockets. While it's possible to do an onboard heating device, it's inefficient -- you're burning fuel to heat water not just to "steam" but to "very hot steam" (to ensure sufficient pressure) when you could just be burning fuel for the pressure of the initial combustion and leaving the weight of the water out. So while it's possible, it's going to be rare. — Lomn 23:09, 7 October 2008 (UTC)

Putting car in park

Is it a good idea to shift my car (a 2004 automatic) into park when I'm at a long light or waiting for a left turn? Can doing this alot damage my car? Does it save any gas?97.118.170.250 (talk) 23:08, 7 October 2008 (UTC)