Wikipedia:Reference desk/headercfg

September 28

Subway menu

What does BMT stand for? —Preceding unsigned comment added by 84.64.122.81 (talk) 03:50, 28 September 2007 (UTC)[reply]

"Biggest, Meatiest, Tastiest", with a nod towards "Brooklyn-Manhattan Transit." --Mdwyer 04:07, 28 September 2007 (UTC)[reply]

Back when the names of the sandwiches were taken from subway lines, it did stand for Brooklyn Manhattan Transit. They moved away from the naming scheme but that one stuck. At least that's what the Subway manager I spoke to told me when I asked this years ago. Dismas|^(talk) 15:47, 28 September 2007 (UTC)[reply]

Subway's own website plays coy:

"Italian B.M.T.® An old-world favorite. Sliced Genoa salami, pepperoni and ham and your choice of fresh vegetables and condiments served on freshly baked bread. Some say BMT stands for biggest, meatiest, tastiest. We wouldn’t disagree."

I've also seen "Bigger, meatier, tastier" on in-store posters, though not recently. TenOfAllTrades(talk) 16:00, 28 September 2007 (UTC)[reply]

Transverse Doppler effect

I've been reading the Transverse Doppler effect article, and I just don't get what it's saying. If the redshift factor is ${\frac {1}{\gamma }}$ , then does that mean that the factor is less than one and an object moving laterally appears redshifted to the observer? 18.238.6.77 04:06, 28 September 2007 (UTC)[reply]

Have you noticed that there is an article on the relativistic Doppler effect, and it even has colourful figures and animations. Looking a bit at these will show you that, yes, an object moving laterally gets redhsifted a bit, too. See relativistic beaming for something even stranger. 138.232.67.15 12:17, 28 September 2007 (UTC)[reply]

Fibreglass for oven insulation

This probably isn't the best place to ask but what the heck... After my stupid cat brought in and lost one (or more) mice in my house, it evidentally took up nest in the oven. Today when I turned it on (mostly use the elements), the heat and/or air movement because of the heat caused the outside to stink terribly (inside it smelled fine). After finally working out how to take the damn thing apart I decided the fibreglass insulation which had some holes in some places had probably been contaminated and it was unlikely I could get the smell off so I removed it. I now of course have to replace the insulation if I don't want to waste a lot of electricity.

Does anyone know if you need special high temperature fibreglass or most stuff will be fine (obviously wool or something is a bad idea). I have some left over from a water heater job but which looks more or less the same but of course that only needs to work at 100 C whereas this will in theory get close to 250C in some cases.

N.B. The often is fairly old so if worse comes to worse it can be replaced. Hopefully I can put I back together okay

Nil Einne 15:09, 28 September 2007 (UTC)[reply]

YIKES! Are you sure that's fibreglass and not some kind of asbestos wool? The latter is not stuff you'd want to be messing with! Asbestos fibre looks almost identical to fibreglass - it's much more temperature-resistant and if your oven is old then it may well have been made before the stuff was banned. Asbestos is a nasty health hazard. I don't know if that's what you have here (obviously) - but then, neither do you - so for sure wear a mask and (even if it's only fibreglass), you should certainly wear gloves! SteveBaker 15:33, 28 September 2007 (UTC)[reply]

Asbestos thermal insulation really doesn't look much like the fiberglass used in ovens, but your suggestion of caution is still welcomed. Having said that, I'll make three observations and a suggestion:

The insulation may not be just for efficiency. It may be for safety, as in keeping the exterior of the oven at a low-enough temperature so as not to cause thermal burns and light the kitchen cabinets, floors, etc. on fire. Don't omit it!
For a self-cleaning oven that uses pyrolytic decomposition, you need insulation that will go a lot higher than 250C, more like 500-560C.
I personally wouldn't trust "improvised" insulation so I'd go to my nearest appliance parts dealer and try to buy replacement appropriate insulation board which you could then cut to shape.

Atlant 15:51, 28 September 2007 (UTC)[reply]

I'm pretty sure it's not asbestos because amongst other things asbestos has been more or less completely banned in NZ since 1987 AFAIK, altho the regulations were fairly strict before then anyway (since the early 80s or so I think). And the oven is old but I don't think it's that old. Also as Atlant said (although I've no experience in recognising asbestos) I don't think it looks like fibreglass. It's not a Self-cleaning oven BTW, it's not that fancy although it did seem to be quite well insulated (from experience of how well it kept the heat when off). Nil Einne 16:55, 28 September 2007 (UTC)[reply]

You're probably right - you said the oven was old...but not how old...and I felt it better to be "safe, quickly" than to do a whole lot of research. Anyway, I strongly disagree about asbestos and fibreglass looking different - check out the two photos from our asbestos and fibreglass articles respectively. I couldn't tell the difference. SteveBaker 18:16, 28 September 2007 (UTC)[reply]

Perhaps in their "raw" form, but as a final product, I still think they're pretty unmistakable. For example, I've never seen pink asbestos ;-), and even the more-common fiberglass "yellow" color is pretty unique to fiberglass. Asbestos and rock wool tended to be used in their natural colors.

Atlant 19:14, 28 September 2007 (UTC)[reply]

Insect identification

Can anyone identify this... thing? It was seen in Vermont. It's about 3-4" long and about 3/4" in diameter. Sorry for the crappy cell phone pics... [1] [2] [3] [4] Thanks, Dismas|^(talk) 16:57, 28 September 2007 (UTC)[reply]

I'm no bugologist, but it looks like a Sphinx Moth caterpillar, perhaps a Eumorpha pandorus. Was he by any chance munching on a grape vine? There are some nice pics of them here. Some Eumorpha do an absurdly good job of tricking birds into thinking they're snakes: [5], [6] (!). --Sean 18:09, 28 September 2007 (UTC)[reply]
- Kind of close but I don't recall the one I saw having that horn on the head. Oh, and a "bugologist" would be an entomologist. Dismas|^(talk) 22:21, 28 September 2007 (UTC)[reply]
  - Kind of close, but an entomologist studies insects, which are a subset or superset of bugs depending on your vantage point. There are many bugs which aren't insects and true bugs are studied by hemipterologists. --Rajah 01:33, 29 September 2007 (UTC)[reply]

preproprotein

Can you please add a definition for preproprotein and examples? thanks208.146.45.110 17:46, 28 September 2007 (UTC)[reply]

Wikipedia has a fairly long article on insulin, but does not do a very good job of explaining the preproinsulin molecule. Most peptide hormones and neuropeptides are derived from preproproteins that use a signal peptide to interact with signal recognition particles and gain entry into the endoplasmic reticulum. After the signal peptide is cleaved from the preproproteins, the prohormone must be further processed to produce a functioning signal molecule that can bind to its receptor. Proopiomelanocortin is derived from preproopiomelanocortin. The articles on oxytocin and cholecystokinin also indicate that they are produced from a larger preproproteins. --JWSchmidt 19:55, 28 September 2007 (UTC)[reply]

Proprotein is also currently without an article. The Transhumanist 20:31, 28 September 2007 (UTC)[reply]

I just added redirects for proprotein and preproprotein to protein precursor. I also described prepropeptides there. The pre- prefix should be elaborated upon at either signal peptide or protein targeting, in my opinion. --David Iberri (talk) 01:25, 29 September 2007 (UTC)[reply]

Hunger and grumpiness

Howdy, does anyone know why huger leads to being grumpy, irritable, or otherwise tetchy? I'm curious about both the biochemical cause (is there some hormone release?) or evolutionary (ultimate) cause would be greatly appreciated. Thanks, --TeaDrinker 20:31, 28 September 2007 (UTC)[reply]

I’ll go out on a limb and hypothesize that it may be caused by very mild hypoglycemia (low blood sugar) due to not eating for an unusual stretch of time. Although the article points out that blood plasma glucose levels are usually maintained at about 70-140 mg/dL throughout the day in healthy humans, if a person breaks from their routine (skips a meal for instance) the unaccustomed fasting could cause the blood sugar level to dip. --S.dedalus 23:51, 28 September 2007 (UTC)[reply]

Geos

Hi. The article, Geo (landscape) states that the term is only used in Shetland and Orkney Islands but Im quite sure that the term can also be used to refer to similar features in England. For example clefts formed when chalk caves on the coast collapse in. An example being on Flamborough head, Yorkshire. Could someone help me out here? Tbo ¹⁵⁷(talk) (review) 22:03, 28 September 2007 (UTC)[reply]

The OED says "In Orkney and Shetland: A gully, a creek. Also, in wider use: a long, narrow, steep-sided cleft or inlet formed by erosion in coastal cliffs, and typically represented by the geos of Orkney." I haven't found an example applied to Flamborough, though. --ColinFine 19:43, 6 October 2007 (UTC)[reply]

September 29

Venusian atmospheric pressure

The earth and venus have aprroximately the same size, but venus has about 90 times the atmospheric pressure of earth, why's that? —Preceding unsigned comment added by 88.203.105.128 (talk) 00:14, 29 September 2007 (UTC)[reply]

There is 90 times as much gas in the atmosphere - which makes it push down 90 times harder. Venus' gravity is a little less than Earths - but that's made up for by the fact of much the atmosphere being almost entirely CO2 - and CO2 is heavier than Oxygen and Nitrogen. SteveBaker 00:40, 29 September 2007 (UTC)[reply]

Best place to start...Atmosphere of Venus. It has a history section, bits that suggest that it may have been more earth-like in the past. ny156uk 00:41, 29 September 2007 (UTC)[reply]

using electrical appliances in Israel

Please help me. What kind of plug or adaptor do O ineed on appliances to use in Israel? And does Israel use 240 or 120v?… Bonnie Ralph bonnie.ralph@btinternet.com —Preceding unsigned comment added by 86.142.73.24 (talk) 07:33, 29 September 2007 (UTC)[reply]

Looks like you need a "European" adapter, as Israeli sockets take type H or type C plugs. See our article domestic AC power plugs and sockets. Hopefully someone else here will have hands-on experience and can tell you more.--Shantavira|^{feed me} 07:52, 29 September 2007 (UTC)[reply]

Mains power systems has some info also.

Penny battery - another wild and sovereign funded idea

The penny is no longer made of solid copper but of zinc encased in a copper foil. Would the savings in material cost of recyclable copper and zinc oxide justify the energy that could be produced (for powering personal electronic devices, etc.) by using a redesigned coin with one side made of zinc at 90% total coin thickness and the other side made of copper at 10% total coin thickness so the end user could stack the coins between pieces of blotter paper saturated baking soda solution? Clem 10:27, 29 September 2007 (UTC)[reply]

The biggest and best savings would be to stop making the damned things. ~~Your information is outdated, there is now less than 2.5% copper in a penny - the rest is zinc.~~ The trouble with making batteries out of them is that it's a lot of hassle to mess around with blotting paper and baking soda - and the resulting battery wouldn't fit in anything that takes regular batteries. But worst of all - your pennies would have to be zinc on one side and copper on the other. If the mint believed that people would accept such a coin, they'd make them zinc on both sides - 100% zinc - and save more money. Since a penny costs a lot more than a penny to make - that's an important thing! But the best reform of all would be to simply stop making them. SteveBaker 16:00, 29 September 2007 (UTC)[reply]

(Actually - you might be right about the 10% copper thing - I was assuming you were talking about US 1c coins - you probably mean a UK 1p coin or something.) SteveBaker 16:04, 29 September 2007 (UTC)[reply]

The OP is presumably not referring to the British one penny coin, which is of copper-plated steel. Algebraist 19:23, 29 September 2007 (UTC)[reply]

Yes, I am referring to the US penny. At 1.5 volts per coin I could stack 9 (8 blotter inserts) and get 12 volts. ...Just thought of something. You can cause a piece of steel wool to ignite by using it to short a 9 volt battery. So if you fell out of a plane and landed safely near some salt water and had some pieces of cloth to use as a blotter substitute and had a pocket full of the new, lets call them energy pennies, and had a piece of steel wool then you could make a fire and stay warm until a spotter plane saw the smoke - all because the government invested in energy pennies. Cool. Clem 01:17, 30 September 2007 (UTC)[reply]

And if you had some ham, you could have ham and eggs, if you had some eggs. --Sean 15:47, 30 September 2007 (UTC)[reply]

(outdent):::::A pocket full U.S. one cent coins in the possession of a McGyver quality artificer on a desert island could be made into a battery of respectable voltage and of very modest current output. By using a flat rock to grind away the copper coating from the edges and one face, a stack of these separated by paper or thin pasteboard soaked in a conductive solution (brine, etc) could be assembled to produce the required voltage (say 12 volts to power a small radio transmitter whose battery is dead, lost, or unsalvageable). But the output current would be very small due to the small area of a cent. Early 19th century batteries used zinc and copper, but the pieces were typically many times the area of a U.S. cent, like several square inches. Several penny voltaic piles could be paralled to increase the current output. I built such a penny battery, after reading this question, using 100 grit sandpaper as a surrogate for a flat stone, to expose the zinc on 2 pennies, leaving the copper on the head side (obverse). With a piece of paper soaked in lemon juice between them, I saw an open circuit voltage of about 0.4 volts and a short circuit current of about 25 microamperes (this was an old crappy analog multimeter, so the numbers are approximate). I checked the current draw of a small instrument powered by 2 AAA batteries, and it was 2 milliamperes, so it would have taken about 8 of these units to get the voltage and about 80 in parallel to get the current to run even a low power instrument that doesn't light up, move, or transmit messages. Various alternatives for such Galvanic cells might just use aluminum (such as from a boat or plane) as one electrode, covered by cardboard or paper soaked in a conductive liquid, with a number of intact pennies covering the top of the cardboard, to increase the area, then a piece of aluminum on that followed by the cardboard, pennies, etc to get both the current and voltage needed. Sand could be used to remove any paint, etc., from the aluminum. Edison 20:11, 30 September 2007 (UTC)[reply]

Has somebody access to this article on Earthdoc?

Hi, I hope this is the right place to ask (please forgive me if it isn't): Can someone with access to Earthdoc (meaning someone who is member of the European Association of Geoscientists & Engineers) please send me an article (PDF 2,13MB)? The text Geophysical Investigation of the Nasca Lines by A. Weller, K. Hartsch, S. Rosas, G. Reppchen (2006) seems to published nowhere else. Concerning its content, the website says: "The content on this site is provided without charge as a service to members, to be used for information and educational purposes only." So, I would welcome a EAGE member willing to inform and educate me in this respect :-) Yours, --Jonas kork 12:28, 29 September 2007 (UTC)[reply]

Buffers

What shifts in the following reactions may occur in the event of addition of a) H+ ions and b) OH- ions.

NaHCO3 ↔ Na+ (+) HCO3-

H2O ↔ H+ (+) OH-

H+ (+) HCO3- ↔ H2CO3 —Preceding unsigned comment added by 89.242.33.223 (talk) 12:44, 29 September 2007 (UTC)[reply]

Maybe look at Le Chatelier's principle. Someguy1221 17:27, 29 September 2007 (UTC)[reply]

Human eye frames per second

Just as video cameras have a certain number of frames per second that they can record, does our eye have a certain number of frames per second that we can process? I'm assuming this must be true because if we see something going very fast we see it as a blur. If it is true, than about how many do we see per second? Would this number change throughout our life? One of the reasons I find this so interesting is because if our FPS is lower, we can comprehend less things per second, and therefore our perception of time might seem to go faster, and vice versa. Imaninjapirate^{talk to me} 14:47, 29 September 2007 (UTC)[reply]

This question seems to get asked every few months. See for example Wikipedia:Reference desk/Archives/Science/2007 January 16 and persistence of vision.--Shantavira|^{feed me} 14:56, 29 September 2007 (UTC)[reply]

Certainly check the archives - we've discussed this to death in the past. The short answer is "No, the human eye doesn't have a 'frame rate'". It just doesn't work like that. Using our peripheral vision (which is most sensitive to time-varying information) we can see things flickering at maybe between 30 to 100 Hz - it depends a lot on the individual and on the ambient lighting conditions. I know that in an otherwise utterly dark room I can reliably see flicker at 72Hz and I can reliably NOT see it at 76Hz - but other people have different limits a few don't see flicker at 30Hz and I met an unfortunate chap who can't watch TV or operate a normal computer because he can see flicker directly in front of him at over 100Hz! That indicates some limits on minimum 'response time' - but that's not at all the same thing as 'frame rate'. SteveBaker 15:37, 29 September 2007 (UTC)[reply]

Does anyone else see flicker after the source is removed? It's sort of like a dynamic version of staring at a yellow and green picture and then switching to a white background and seeing blue and red. If I turn off a tube TV in a dark room, I will see a flickering image that is square and TV sized that persists in my main field of vision for quite a while longer. It's not a definable image, just a flickering rectangle. Chemical persistence doesn't seem to explain this. --DHeyward 08:37, 1 October 2007 (UTC)[reply]

I can only see flicker while it's present, but I haven't actively tested my "persistence of flicker". BTW, I can see flicker of 70Hz, but not 75Hz in peripheral. —Preceding unsigned comment added by 203.22.236.14 (talk) 09:25, 1 October 2007 (UTC)[reply]

I think it's very possible that you still "see" flicker after it's gone away. Our brains are good at cancelling out unchanging distractions. So you stop 'hearing' the 'shhhhhh' noise of the fan of your computer and only notice that it was ever there when you turn it off. For a moment, the silence seems somehow more silent than a mere absence of sound - it's almost like there was 'anti-sound' (bear with me here!). There are also those 'illusions' where you stare for 30 seconds directly at a US or UK flag that's painted in cyan, black and orange instead of red, white and blue - then you look at a blank page and see the flag mysteriously floating there in it's normal red/white/blue colours...those work the same way. Your eyes get bored with looking at orange and cyan and 'cancel them out' - so when you look at a white sheet - you see the complements of those colours ("anti-colours") for a few seconds until your eyes adapt to the change. I think it's possible you could be doing the same thing with the flicker - except that when the flicker goes away you are seeing 'anti-flicker'. Dunno - but it seems plausible. SteveBaker 14:33, 1 October 2007 (UTC)[reply]

Renaming proteins after discovery of function(s)

Does anyone else feel that scientific things and processes should be named according to what they do? I note that people refer to such names as unimaginative but as a student, I find them so much easier to remember. I hold the highest respect for scientists who name their discoveries after their function etc, instead of slapping their name or something on it. I know that a protein's function isn't always known at the time of discovery but is it unfeasible to rename proteins as their functions are established? Sonic hedgehog is probably characterised well enough to rename it, right? Am I the only one that gets fustrated? I envision some organisation like IUPAC, renaming proteins for the common good... IUPAC did it with chemicals, and we all survived. This isn't just a rant; ideally someone would say "yes, we all agree and <<acronym>> is already making progress in doing exactly as you describe". It's probably just me... —Preceding unsigned comment added by 201.220.222.140 (talk) 20:22, 29 September 2007 (UTC)[reply]

I suspect that at some point most proteins will exist within a standardization system such as the one for enzymes. There are some relatively young efforts to categorize all proteins (see List of types of proteins, Gene Ontology) that should eventually lead to ways to develop standardized names....hopefully names that will reflect function. In the case of enzymes, it is often possible to identify a single active site that defines the function of the enzyme. However, in the case of many other proteins there are multiple binding sites on the protein and it is often not a trivial matter to define "the" function of the protein. For some types of non-enzymatic proteins, groups of scientists sometimes get together and propose a standard nomenclature, but so far it is not unusual for the proposed standard nomenclature to be ignored by other scientists. It might be educators who have to step in and push for sensible names rather than wait for working scientists to do it. (external links: a wiki thesaurus for gene and protein names, Gene and protein nomenclature in public databases). --JWSchmidt 17:26, 29 September 2007 (UTC)[reply]

As a student, you are frustrated by this, but as a reasearcher, you will soon find the opposite source of frustration: After some lengthy discussion, some phenomenon has been finally named somehow but for some reasons you want to study the discussion that ed to this naming and locate the research papers involved in it. What do you use as search term if you look for old articles from a time when a name was not yet established and everybody just wrote "that strange phenomenon that occurs in X, Y and Z, and hes been described by, among others A, C, D, and F? Then, you'll be happy if the name that the first researcher proposed simply stuck. But you might be pleased to hear that recently on a conference of geneticists, a resolution was passed urging scientists to stop using too flamboyant gene names, because --so they argues-- that may be funny with fruit flies but becomes embarassing with the equivalent human genes. No doctor would want to have to say: "I am so sorry, but your baby seems to suffer from a sonic hedgehog mutation." Simon A. 18:06, 29 September 2007 (UTC)[reply]

The problem with this suggestion is that proteins do not have a single function. For example, what should one call Adrenocorticotropic hormone? It can act through a number of different receptors to influence many different biological processes. As it happens, it was named after the process that was first discovered. In addition, protein families to provide information about their phylogenetic relationship. Consider the 800+ olfactory receptors in mice. Each one will bind a number of different odorants with higher or lower affinity. Currently a numerical nomenclature is used based on chromosome cluster (and hence phylogeny) and order. Even if we knew all the odorants that even one receptor can bind (and we don't) exactly what would we call it? This is one example, but the principle hold true for pretty much all proteins. At very best all we could do is name than after one of the functions we happen to know they have. Rockpocket 04:32, 30 September 2007 (UTC)[reply]

Nitrogenous polysaccharide

What elements, other than nitrogen, make up the nitrogenous polysaccharide capsule of prokaryotik cells? Thanks alot 88.110.203.63 16:31, 29 September 2007 (UTC)[reply]

see polysaccharide -- Flyguy649 ^talk _contribs 16:36, 29 September 2007 (UTC)[reply]

Thanks alot, thats just great, i got mixed up with amino acids, and started thinking there may be an 'r' (variable) group, wich can contain sulphur as well, but im just dumb, your not :) thanks again, 88.110.203.63 16:48, 29 September 2007 (UTC)[reply]

(me again, wow i just read your user page flyguy, and read you are studying amino acids, and i dont think its geeky at all) —Preceding unsigned comment added by 88.110.203.63 (talk) 16:50, 29 September 2007 (UTC)[reply]

Pupil size

Is pupil size a genetic trait? I know some people whose pupils are like pinheads in sunlight and other people whose pupils are like planets at night time. Are there any advantages/disadvantages to having smaller/larger than average pupils? --Candy-Panda 16:49, 29 September 2007 (UTC)[reply]

First of all, the pupil size of a single healthy individual has a wide range (about a factor of 4 in diameter, or 4 stops in photography jargon). Therefore it doesn't make sense to talk about "pupil size" itself as a genetic trait, but it does make sense to ask about the heritability of minimum or maximum pupil size. This study found that maximum pupil size after mydriasis has a heritability of up to 80%, so it has a strong genetic component. Here's an important quote:

This study only examined final pupil size, and so it cannot be certain whether the strong genetic influence is on actual maximum pupil size or on the response to mydriatics. Bertler and Smith's previous twin study found a high MZ [monozygotic] correlation for initial pupil size and no difference in the rate of dilatation between MZ and DZ [dizygotic] twins, suggesting that the genes determine mydriasis not in response to drug or dose, but determine the maximal possible size of the pupil.

I couldn't find an analogous study for the minimum size of the pupil.

The advantages of small and large pupils are exactly the same as those of large and small f-numbers in a camera, with the additional consideration that if you're in bright sunlight too often and your pupils aren't small enough, the ultraviolet does long-term damage to your eyes. —Keenan Pepper 18:06, 29 September 2007 (UTC)[reply]

I knew this girl who's pupils were always dilated - had to wear sunglasses when out Think outside the box 12:12, 4 October 2007 (UTC)[reply]

As far as advantages and disadvantages go, smaller size makes you more suitable for laser vision correction and less prone to halos.

STOP YOUR BODY'S MELANIN PRODUCTION

is there something that can stop your body from producing melanin in hair —Preceding unsigned comment added by 81.99.212.22 (talk) 18:34, 29 September 2007 (UTC)[reply]

The short answer is no. -- Flyguy649 ^talk _contribs 20:26, 29 September 2007 (UTC)[reply]

With all respect, no matter how many times you ask the same question, albeit phrased slightly differently, you are going to get the same answer. There is no safe way one can change one's hair colour permanently. Rockpocket 04:17, 30 September 2007 (UTC)[reply]

Come now. Surely it's well known that aging or stress can stop melanin production in hair. —Tamfang 08:08, 30 September 2007 (UTC)[reply]

Aging and stress are not safe, though. And I think it would be nice if someone produced a post regarding the reason why the original poster would like to know that, which seems to be to become a white person. It is not healthy for one to wish to become a white person, since this is impossible. I believe that, if the original poster wants to become a white person, they ought to look for a psychologist. A.Z. 08:16, 30 September 2007 (UTC)[reply]

I don't see anything about safety in the OP, do you? If I asked "is there something that can cause skin to become red and itchy" would you say "No" because poison oak is unhealthy? Tsk. —Tamfang 16:09, 30 September 2007 (UTC)[reply]

The poster didn't make it explicit that they want something safe. No, I wouldn't say no to that question about the red and itchy skin. A.Z. 19:25, 30 September 2007 (UTC)[reply]

?Stress, Tamfang are you sure about that. I know it's a popular myth that stress turns your hair grey or white but is there any scientific evidence? I have serious doubts that stress can affect your hair colour although this idea has been perpetuated in many films. As the colour is dictated by the growth of the hair in the follicle it is likely to take many weeks to change the colour of a sizeable strand. I will accept that nutritional stress may cause a change in hair colouration , as seen in pellagra or beri-beri.Richard Avery 13:17, 30 September 2007 (UTC)[reply]

Yes, we all know that any change in your metabolism won't be visible in your hair until it has time to grow out, nobody here implied otherwise. —Tamfang 16:09, 30 September 2007 (UTC)[reply]

Ok, for the sake of hypotheticals, it may be possible using genetic tricks. This is not possible currently in humans. Disrupting the melanin biosynthetic pathway throughout the body would likely not be good for you, since many other molecules your body needs, such as some neurotransmitters, are produced by the same (or related) pathways. Also, melanin is really important in the eye to prevent excess light reaching the retina. Albinos have poor vision in part because of a lack of melanin. And remember that melanin is important for the protection from UV damage in the skin. Back to the question. The trick is to block the creation of melanin only in hair; this could be done using a virus that would deliver DNA coding for small interfering RNA sequences that would disrupt the production of melanin synthesis enzyme or enzymes. If such DNA was under the control of a hair-specific promoter, it would only disrupt melanin production in hair follicle cells. I don't think it's likely that you'd be able to "hit" all the cells in all the hair follicles, so you'd still likely end up with some coloured hair. Also, even if all hair melanin production were stopped immediately, that would only affect new hair; existing hair would still be coloured until it grew out. You'd need to bleach it to remove the colour in older hair. -- Flyguy649 ^talk _contribs 15:44, 30 September 2007 (UTC)[reply]

There seems to be an ever-increasing amount of money being spent by cosmetics companies in an attempt to find ways to alter melanin production and storage. Such efforts are of interest to the US government because there are important health implications of research aimed at providing tools that could be used to change to melanin production and storage. Here is a recent article that mentions some existing melanin research directions: Regulation of Skin Pigmentation via Modification of Tyrosinase Function. --JWSchmidt 17:21, 30 September 2007 (UTC)[reply]

Funny, I want to darken my skin. I live in Australia and of Irish ancestory, so every summer it takes a couple of months to tan sufficiently to avoid quick sunburn. I envy a darker skinned Sri Lanken person I work with who has never suffered sunburn. Wouldn't it be nice to be able to adjust one's skin colour to the environment in which they live. --203.22.236.14 09:19, 1 October 2007 (UTC)[reply]

A recent study from Australia: Nle4-D-Phe7-alpha-melanocyte-stimulating hormone significantly increased pigmentation and decreased UV damage in fair-skinned Caucasian volunteers.
--JWSchmidt 21:14, 1 October 2007 (UTC)[reply]

Swappin' spit reagents

Frequently in journal articles, I read about experiments being performed with reagents sent as gifts from other researchers. I was wondering what limitations there are in this practise? If I buy mice, I'm allowed to breed them for my own use but not allowed to send them to other researchers. What about expression vector plasmids for example? Are some unpatented? Perhaps the research community would benefit from some sort of network/website through which scientists could swap reagents more easily. I suppose some big companies might oppose this... --Seans Potato Business 18:53, 29 September 2007 (UTC)[reply]

As a condition of publishing in peer reviewed journals, one usually has to agree to make one's reagents available for other scientists. There are limits to this, obviously, when the materials are very expensive or rare or commercially available for purchase. That said, some scientists will resolutely ignore any requests for materials (not that I'm bitter or anything...) but most will make an effort to provide materials at no cost when asked. Since many novel materials may have commercial, value most institutes, universities and companies will make your sign a material transfer agreement, which can limit your use of the gift. The most common limit is that you will not pass the material on to anyone else and that your relinquish the rights to any commercial application you may stumble upon. MTAs have to go through the legal and/or technology transfer department of your institution, so an online swap-meet would probably not work.

When you purchase plasmids from companies, you usually agree to a limited license of use, which restricts you from copying the plasmid and giving it to others for free. Like in the computer software industry, this is the way producers ensure they recoup profit from their work. Rockpocket 04:08, 30 September 2007 (UTC)[reply]

"...And the clueless newb was enlightened" :) Do you say that I can't take my plasmid and copy it so that I never have to buy more of it or just that I can't copy and give to someone else? --Seans Potato Business 17:55, 30 September 2007 (UTC)[reply]

You can amplify plasmids as much as you want, they would not be of much use otherwise. This right could probably be restricted for commercial applications, but I doubt that this happens a lot. As long as you don't make money out of selling the plasmid directly you are by all means on the safe side. Cacycle 19:10, 30 September 2007 (UTC)[reply]

Andrew Ryan would disagree. -Wooty [Woot?] [Spam! Spam! Wonderful spam!] 08:16, 1 October 2007 (UTC)[reply]

How to choose best undergraduate school for best mcat scores

Hello, I am going to attend undergraduate university next year. I searched for statistics of students who take the MCAT from certain undergraduate schools to compare undergraduate programs, but could not find any results. Is there a site/listing of the best programs that prepare students to take the MCAT exam?

Thanks, Robert —Preceding unsigned comment added by 71.56.231.40 (talk) 20:27, 29 September 2007 (UTC)[reply]

Honestly, I'm a little dubious about the idea of picking your undergrad location based on average standardized testing scores of graduates. I think as a metric that is likely to be highly unreliable, and will have little guarantee of giving you, the individual, high MCAT scores. --24.147.86.187 21:35, 29 September 2007 (UTC)[reply]

If your goal is to do well on the MCAT, start experiencing what you need to know now. Go to a hospital and volunteer (especially in the emergency room). Classes and studying are necessary, but they don't replace experience. -- kainaw ™ 00:19, 30 September 2007 (UTC)[reply]

Pick a university where you think you will be happy. If you are happy, it will be easier to put you best efforts into your studies. ike9898 17:29, 30 September 2007 (UTC)[reply]

Resistor capacitance

Any estimates for the capacitance of a metal film resistor with a body length of 6mm? —Preceding unsigned comment added by 88.110.150.148 (talk) 21:32, 29 September 2007 (UTC)[reply]

Is there anything written on it? --Mdwyer 23:05, 29 September 2007 (UTC)[reply]

A 1/4 watt resistor has about 1/2 pF of residual capacitance according to the first link in this search. - hydnjo talk 23:07, 29 September 2007 (UTC) Amended to fix link. - hydnjo talk 23:22, 29 September 2007 (UTC)[reply]

For a specific inidivual resistor, you should measure the capacitance. If you are designing for production, you should use the manufacturer's spec sheet. Resistors are typically manufactured for a specific tolerance in resistance, so the tolerance in capacitance will typically be much larger. Your circuit design should therefore accommodate the entire range of possible capacitance values from the manufacturer's spec sheet. -Arch dude 23:44, 29 September 2007 (UTC)[reply]

130.15.208.183 08:32, 30 September 2007 (UTC)[reply]

Contact Lenses and Frothy Solution

I have begun to notice that whenever I apply solution to my contact lenses, (for example after removing them from the case, just before I would put them in my eyes) the solution frothes up and many small bubbles form. Does this indicate some sort of reaction taking place, or that the lenses are very dirty?

The good sign is I haven't gone blind, even if this does indicate something, since I still put them in. But, I was just wondering, since it only started happening recently...

Thanks, Eclipse45 22:01, 29 September 2007 (UTC)[reply]

They, I mean we, don't do medical advice here. The reason is obvious when you think about it. Sorry. --Milkbreath 22:50, 29 September 2007 (UTC)[reply]

Most contact lens solutions have a consumer help telephone number on the label. You should immediately call this number for an answer to your question. If you are not completely satisfied by the information you get over the phone, you should immediately contact your eye-care professional. Do this now. Do not delay. -Arch dude 23:33, 29 September 2007 (UTC)[reply]

(In response to the comment of Milkbreath) The way I read it, the question is about chemistry, not health. --71.175.68.224 02:31, 30 September 2007 (UTC)[reply]

It's borderline; that's why it's still here. She mentions going blind from a chemical reaction on her contact lenses, however facetiously. That's medical in addition to chemical. Suppose someone here tells her not to worry about it, and she actually does go blind from it. Don't say it can't happen; you're not an eye doctor, and neither am I. I'm tempted to remove it even now, but her intent clearly was not to ask a medical question, and, to judge by her user page, she's at least relatively sane. --Milkbreath 03:19, 30 September 2007 (UTC)[reply]

Contact lens mentions cleaning and disinfecting fluids. Then look up Hydrogen peroxide.Polypipe Wrangler 02:52, 30 September 2007 (UTC)[reply]

Ok, first of all, DID I say I was a she? Where did you get that from? And second of all, you can notice I said the good thing was I DIDN'T GO BLIND, AS IN A JOKE, that nothing did happen to me even when I still put the contacts on afterwards, after noticing the froth.

And yes, for the record I asked about the chemistry involved. Maybe the 2nd part of the last sentence was unclear, but, the rest I think is fine. Learn to read. And yes, I know it says not to ask medical advice.

Thanks for the whole fiasco. If I was blind, could I see the screen to type that question? Think about it. 130.15.208.183 08:32, 30 September 2007 (UTC)[reply]

We are supposed to assume good faith in Wikipedia. I did. And all caps is considered shouting. Don't shout. I haven't. Flinging insults invites a flame war. We don't do that here (though I, personally, think they're tons of fun). We have to be nice, dammit. So. I had a fifty-fifty chance with the sex. Why should there be a problem with a gender-neutral "she", anyway? As for the going blind, you haven't gone blind, yet. But that isn't the issue. I don't know how to put it any clearer than I have. There was a medical aspect to your question. You expressed concern for your safety. If the froth had appeared on your car instead of on something you put in your eyes, that would be different. Blindness is no joking matter, by the way. We couldn't tell whether you were joking or whether you had any sense at all because we don't know you, but we're learning fast. --Milkbreath 14:28, 30 September 2007 (UTC)[reply]

The chemical reaction is the decomposition of hydrogen peroxide into water and oxygen:

2 H₂O₂ -> 2 H₂O + O₂

I believe this reaction occurs quite slowly spontaneously, but quite quickly in the presence of the catalyst catalase, contained in protein deposits on your contact lenses.

Incidentally, blind people can use computers, via screen readers and other technologies. StuRat 11:46, 30 September 2007 (UTC)[reply]

Indeed, Jack Vance (for example) has cranked out a handful of novels since he lost his sight. —Tamfang 16:14, 30 September 2007 (UTC)[reply]

Ok, so then, as you put it milkbreath, there does seem to be a medical aspect to my question (i swear i never thought of it like that when I typed it), but just the same, i wanted to know about the chemical aspect, which others have answered. as for insults, no I didn't want to cause anything, nor am i particularly nuts. I just got a bit angry to see that instead of answers I got a bunch of 'don't seek medical advice' - which in retrospect follows with wikipedia policy if you saw my question in a medical light. in any case, i'm sorry for anything that did happen: heat of the moment thing? but i did get an answer so i'm still content. 130.15.208.183 17:49, 30 September 2007 (UTC)[reply]

Sorry for the slow response; I missed your reply. No hard feelings. I know only too well how easy it is to get, or make someone, exasperated in this medium. My rule is "Shit is a dish that is best served cold", if you'll pardon my French. That applies literally, too, come to think of it. --Milkbreath 15:40, 1 October 2007 (UTC)[reply]

Who, me? :o --⁪froth^t 06:23, 4 October 2007 (UTC)[reply]

September 30

Hydrocloride vs Dihydrochloride

Whats the different between dihydrochloride and hydrochloride? I was looking at betahistine and found both versions, the HCL was used in a study and I found the dihydrochloride version online. Are they much different? —Preceding unsigned comment added by 76.167.139.80 (talk) 02:22, 30 September 2007 (UTC)[reply]

No - it dissociates anyway. Icek 03:08, 30 September 2007 (UTC)[reply]

See betahistine The hydrochloride has formula C8H12N2 HCl, the dihydrochloride has formula C8H12N2 2HCl A dihydrochloride can exist because it has two basic sites - the amine and the nitrogen in the benzene ring pyridine - they are different salts of betahistine87.102.11.118 12:22, 30 September 2007 (UTC)[reply]

solar wind hydro and geothermal energies

how can i get the questions where does the resource come from how its obtained for usage what are its uses what are some of the advantages of it and what are some of the disadvantages of it —Preceding unsigned comment added by 67.60.91.27 (talk) 03:15, 30 September 2007 (UTC)[reply]

Solar power, hydroelectric power, geothermal power. When you're looking for general information, you can just type the term of interest into the search bar on the left of this window. Please come back if you have questions not answered in the articles. Someguy1221 03:30, 30 September 2007 (UTC)[reply]

Diagnostic and Statistical Manual

I have read the artical on the DSM but am not clear: is the DSM considered "evidence-based" and, if so, how is the research to establish this conducted? —Preceding unsigned comment added by 209.161.212.229 (talk) 04:42, 30 September 2007 (UTC)[reply]

It depends on what you mean by "evidence-based". A DSM practitioner would probably say that the descriptive approach which leads to a DSM classification is "evidence-based" in that it is based on clinical or analytical experience and is often culled from a larger body of work in psychology. However a skeptic of the DSM, of which there are many, would likely argue that it was not "evidence-based" as the categorizations are not established by rigorous empirical standards, and the differentiations between categories are meant to be simply recognized by an experienced professional rather than being testable in a standard empirical sense. That is my understanding of it, anyway, but I am not a huge expert in such things. --24.147.86.187 10:50, 30 September 2007 (UTC)[reply]

Life!...

When will MAN 'give up' religion, and start relying on FACT!? Just been watching too much news. Dave 64.230.233.222 05:23, 30 September 2007 (UTC)[reply]

Because humans need something to believe in. If "MAN" gives up religion then he would need to believe in something else.

It's easy to believe in religion because it's requirements are so low. Compare that to quantum physics where you literally need to spend years studying before you can even do the basic problems. 220.239.107.201 06:26, 30 September 2007 (UTC)[reply]

Perfect answer, I think. Reminds me of when I asked a certain person, "What would happen if it were PROVED/PROVEN that God didn`t/doesn`t exist?" This person mentioned , and I`m paraphrasing, something that Voltaire once said, "If God died, 'man' would just invent another God."!!! Dave 64.230.233.222 07:35, 30 September 2007 (UTC)[reply]

Believing and relying on facts isn't exclusive. – b_jonas 13:24, 30 September 2007 (UTC)[reply]

To attempt a proper answer to this question: The fact is that religion appears to have sprung up independently in many (if not all) civilisations suggests that at some time in the past it served an important function. In an era before modern science, perhaps it produced answers to difficult questions and allowed important men to make themselves more important by claiming to be speakers for and interpreters of the greatest possible power in the universe. Nowadays we're able to use the tools of mathematics, astronomy, geology, paleontology, cosmology, physics, chemistry and biology that humanity has worked so hard over centuries to perfect - and over just the last 50 or so years have we produced more straight, clear-cut answers to the difficult questions of life than any of the previous millenia. We don't have to guess anymore - we finally know. The first black hole was found just three years ago - over the last decade, the results of quantum theory are so well understood that we use them to make mundane things like MP3 players. We've only been able to do detailed DNA analysis for a dozen years - but now we have the human genome laid out in detail before us. Those of us who are alive today are the first in all of human history to be able to deal with these questions of "how did we get here" without the need for ancient pseudo-science and myth - we don't have to guess how the universe was formed - we have proof. We don't have to wonder which animals descended from which - we can see it clearly in the DNA. I think it'll take a few more generations for the consequences to fully play out - but I honestly believe that we have no further need for religion - and the terrible wars and apalling deeds that are done in religion's name are things we are definitely better off without. SteveBaker 19:52, 30 September 2007 (UTC)[reply]

Another thing that IMHO religion often provided was a resonably simplistic sense of right and wrong and rules to live by guided by other people who help you understand the 'rules'. It also provided a sense of justice and a reason to live by these rules. Note that even nowadays, some religious people opposed to atheism say that without religion/God, people don't have to be 'good'. It is perhaps easier for people to be willing to do good when they believe those that don't will ultimately be punished. Nil Einne 03:29, 1 October 2007 (UTC)[reply]

Given the Crusades and recent Islamic extremist terrorism, I reckon that (organised) religion is also good at excusing or encouraging rather immoral behaviour. --203.22.236.14 04:45, 1 October 2007 (UTC)[reply]

Organised religion has a lot to answer for in terms of the troubles of the world - but small-scale religion is no better (Branch Davidians, Jonestown, Heaven's Gate, etc). SteveBaker 19:44, 1 October 2007 (UTC)[reply]

SUCH ANSWERS SHOWS ME THAT YOU GUYS DONT HAVE A LIFE WELL IF GOD DIDNOT EXSIST WHO CREATED THE WORLD? WHO CREATED THE UNIVERSE? WHO CREATED HUMANS,ANIMALS,AND LIVING THINGS? CAN YOU ANSWER THESE QUESTIONS? I AM COMPLETLY POSTIVE THAT GOD EXSIST AND HE IS THE ONLY ONE WHO GOT ANSWERS TO THESE QUESTIONS AND SOON WE WILL SEE —Preceding unsigned comment added by 212.71.37.107 (talk) 14:50, 30 September 2007 (UTC)[reply]

To 64.230.233.222: you might be interested in the book Consilience: The Unity of Knowledge by E. O. Wilson. Wilson mentions the idea that given the realities of human nature, it might be useful to create new religions that incorporate scientific facts.
To 212.71.37.107: Since this is the science desk I'll provide a reply that is found in many scientific publications. If there is a God of the type you mention, then where did that God come from? Most scientists are not satisfied by taking a mystery, putting a name on it and pretending that you are done. --JWSchmidt 15:12, 30 September 2007 (UTC)[reply]

I`m gonna read that book JWS. Thank you. I have no reply for 212. Dave 64.230.233.222 15:30, 30 September 2007 (UTC)[reply]

212.71.37.107, if you reject the hypothesis that the answer to WHO could be "nobody, no more than someone makes water run off a boulder," there's not much we can say to you. But I'm curious as to what makes you think THAT YOU GUYS DONT HAVE A LIFE. If you think only losers ponder such questions, rather than accepting what someone told them in childhood and never seriously considering them again, I reckon that tells us something about you and I wonder why you're even looking at the Science Desk. (But please note that I'm only making a guess here about what you think, based on the limited evidence available; the Voices haven't spoken up yet on this subject.) —Tamfang 16:22, 30 September 2007 (UTC)[reply]

Smart Question JWSchmidt .... but that is why we call him god we humans are not supposed to prove god presence or not god created us to worship him and if you look deep you will find the one true religion in the world that will help us find our way through life why was there prophets remember something god is going to judje us cause god created us look deep and you will find the truth as we know from physics ....everything is there for a reason and i beleive god created these reasons

I have an excellent life without any sign of belief in any god or gods - it's very possible to have a full and satisfying life without religion. No gods were required to make the universe - the Big Bang Theory has the creation of the universe explained down to a fairly exacting degree. Therefore there is no "WHO" in "who created the universe"...and even if there was, that would only push the question back to "How did your god/gods get created?" - adding another step doesn't in any way help you find the answer. Humans, animals and living things come about through evolution from a single random coincidence that caused the first self-replicating molecule to appear (probably in the primordial earth - but perhaps elsewhere if panspermia turns out to be true). Can I answer these questions? Yes, easily - anyone who goes around with their eyes wide open can find these answers. Since you have absolutely no evidence or proof of any kind that your idea of god exists - your belief is merely an act of faith (as I recall your religion teaches you). Blind faith is a risky business - without evidence, how do you know that you are worshipping the correct god. I'm pretty sure the devil worshippers will also tell their supporters to have faith. Anyway, if god is the only one who can answer these questions - and I can certainly answer these questions then I am your god and "SOON YOU WILL SEE" - because I just told you. The only question I find tough to answer is WHY THE HECK YOU CAN"T FIND YOUR CAPS LOCK KEY. SteveBaker 16:44, 30 September 2007 (UTC)[reply]

To begin with , we are just discussing so it would be nice to respect each other. i want to ask you a question did u read about old times , and the real prophets that once was present and if you read about them , i suppose you heard about their miracles . what makes you think that god is made or created , then how on earth is he called god. let me go back to miracles of the prophets that was once there and the fact that alot of people beleived in them because they found the truth. another thing how do you explain that everything that consider life science and everything was mentioned either directly or indirect in the holy books of god if you think that someone wrote them then how do expect him to find out about all this so early ,,(was he a genius!!!)

Actually, if you believe in god (or gods) I honestly don't respect you. It's hard to respect someone who bases his or her entire life on something that's exactly as believable to me as Santa Claus or the Tooth Fairy...respect has to be earned and claiming that everything about science is in this one skinny 2,000 year old book does nothing to help you here. Did I read about the old times? Sure - I've read the bible from cover to cover - I have a passing knowledge of world history. The miracles the bible describes would indeed be fairly impressive if they were true - but there is really no evidence that they ever happened. Someone wrote it down in a book - and the book has been repeatedly retranslated from a source language that's confusing as all hell because the written form contains no vowels. How do we know it's true? It could just as easily be a work of fiction. Since it contradicts itself in many, MANY places - it certainly can't all be true.

You say that all of the answers are there. OK - let's try a nice simple test. Let's look at the creation of life itself. What does the bible say in answer to the question "Which came first - animals or people?" - do me a favor. Look it up in your bible and post the answer here - tell me simply and clearly: "Animals came before people" or "People came before animals". It's right there in Genesis - I'd like you to tell everyone here what it says - post your answer here. I want to know what your holy book - on whose teachings you base your entire life - tells you about this very basic question.

SteveBaker 21:00, 30 September 2007 (UTC)[reply]

They way "I" understand God and the various religions is that they were invented to give people guidance. Perhaps even to encourage people to behave. Offer them an incredible reward, Heaven, if they behaved and of course, the most hedious of punishments if they didn`t. Almost sounds sane, until you really think about it though. I very much tend to agree along the same lines as SteveBaker, only problem is, how does one change all that brainwashing that has been around for so long? One cannot stop believers from believing. And to force them to not believe, if possible, would surely be unethical/immoral, to say the least. I too, have a very difficult time showing respect towards a person who follows the BOOK err, religiously. I think I`d better stop else this could turn ugly. Thanks for all your thoughts. Dave 64.230.233.222 21:48, 30 September 2007 (UTC)[reply]

Reluctantly, I'm increasingly agreeing with Richard Dawkins - atheists have to take off the kid gloves and stop treating religion and the religious with respect. This is not a popular point of view in the middle of Bible-belt America - but that's where I happen to live. The people who believe in this pile of nonsense don't deserve my respect. I now feel very confident about calling them idiots - mocking their beliefs - disbelieving their sincerity because not a one of them is consistent about their beliefs. I intend to continue pointing out the ridiculousness of the crap they are espousing. It's easy to focus on this way of thinking - try my recipe: Whenever they say "God", think "Tooth Fairy" and whenever they say "Heaven" think "Santa's grotto". After all, if you are an atheist, those terms are equally believable - and switching them around enables us to rid ourselves of thousands of years of brainwashing. It's very hard not to giggle when a priest in his silly costume starts telling us (in all seriousness) that if we believe in the Tooth Fairy, we'll end up spending eternity in Santa's grotto...but that's exactly as believable to me as what he's actually saying. SteveBaker 03:12, 1 October 2007 (UTC)[reply]

Very few, if any, people entirely rely on 'fact' alone; almost everyone has things that they think or do which are not supported by facts. If you look at populations where few people practise religion, you do not tend to see the majority of the population building their lives on facts; rather, these people practise feng shui, read their horoscopes, mutter phrases to magpies, repeat 'please please please' under their breath after bowling and before the ball hits the pins. They buy lottery tickets, they believe that they have paranormal abilities, or that someone else who wants their money does, they see ghosts, they see UFOs, they press the button at the pelican crossing again when the lights take a long time to change, they think that their loved ones are looking down on them, or have gone on to a better place, or are waiting for them, or have come back to guard them. For whatever reason, most people do not really want to live lives based on fact alone; they get something out of religion and supernatural beliefs that they do not get elsewhere. If you do not, that's fine, but please do not assume that people believe these things just because they are ignorant or stupid, or that they would be happier without them. Oh, and if it's just brainwashing, why so many converts to so many religions and beliefs? 79.65.119.193 22:53, 30 September 2007 (UTC)[reply]

Oh, and if it's just brainwashing, why so many converts to so many religions and beliefs? People do "irrational" things because it brings meaning to their lives. Before you jump on that let me tell you that:

People do hobbyX not because hobbyX is rational but because hobbyX bring meaning to their lives. hobbyX can be {swiming, jogging, horseridding, mountain climbinb, sking, dancing}. Now no one suggest that hobbyX is rational or that hobbyX is TRUE or that if anyone insults hobbyX that they should have their head chopped off. No one gets angry if you suggest that hobbyX is a social construct or if you choose to join hobbyX and hobbyY at the same time.

Compare that with religionX. People do religionX not because religionX is rational but because religionX bring meaning to their lives. People gets very angry if you suggest that religionX is NOT TRUE or if you suggest that religionX is a social construct. And people get angry if you choose to join religionX and religionY at the same time.

Religions are just like hobbies, except that it is a philosophical hobby that insists on it's own validity and rejects any other philosophies that suggests that itself is FALSE.202.168.50.40 23:26, 30 September 2007 (UTC)[reply]

I understand why many people 'need' religion. They would feel that life was unimportant, for some reason, without it. I just feel that any sort of unsubstantiated belief system is a little silly, that`s all. Humans are so knowledgeable now. Way back when, when just about everything was mysterious, even the wind was a 'god', then I can see how people needed religion. It helped 'explain' such mysteries. The fact that almost everything is fairly easily explainable now makes me wonder how ANYONE can still 'believe'. Dang, I`ve said too much already. I really didn`t want to start anything here. Sorry if I offended anyone. Dave 64.230.233.222 23:52, 30 September 2007 (UTC)[reply]

Exactly! The point of religion isn't really to explain things that science explains, it's because it gives people something they cannot get anywhere else. If you see why people need religion, why talk about changing 'brainwashing'? Most people need religion or supernatural beliefs, and it is not to explain the things which are explained. People who read their horoscopes (and many people really, truly believe them, and some even become quite aggressive when you suggest horoscopes are silly) do not do so because they require an explanation for the movements of the planets. People who pray to a god don't generally do so because they want an explanation for why wind blows. With very few exceptions (if even those) people do not want to live only with verified facts. "I understand why many people 'need' religion. They would feel that life was unimportant, for some reason, without it." Does this mean that you feel life is important? Do you have any way of backing that up; is it supported by facts? Does believing it matter to you? :) 79.65.119.193 00:20, 1 October 2007 (UTC)[reply]

Very good questions 79.65.119.193. If I`m forced to think about it long enough, I would have to conclude that life is more or less meaningless. It`s neat though. It`s quite a curiosity. But heck, everyone dies. How cruel is THAT? Life can still be important though. Just skip a couple of car or house payments to quickly find out just HOW important a life is, especially to a banker. As for astrology, sheesh! That`s not even worth a comment. I am utterly amazed at all the crap people can be made to believe in. My original question merely wanted to get some sort of 'blanket' answer as to why, or how people can still believe, given all the knowledge at hand. Wouldn`t you agree that religion has caused more harm than good? Just think about all the wars based on it. Thanks for listening. CHEERS! Dave 64.230.233.222 00:50, 1 October 2007 (UTC)[reply]

:) I think you're starting to feel what I'm trying to show. Logically, when you think about it, you can see there is nothing to support the belief that life matters. But, it feels better to believe that life matters. If someone offered to prove to you that life didn't matter, would you welcome it? Equally, if thinking logically, people know that there is nothing supporting the belief that any gods exist. Nonetheless, it feels better (to them) to believe that a god, or gods, exist, so they do. Thinking logically, people know that pressing the button again at the pelican crossing doesn't speed up the change, but they won't welcome you explaining this to them when they do it; it feels good to do it and to believe, at some level, that you have affected the process. No, I wouldn't agree that religion has done more harm than good, any more than I believe that politics has done more harm than good. I have never seen a war that was fought because religion existed; religion is an excuse and a marker, it is useful in propaganda and in countering it, but it is not the cause of the wars. Since religion and politics seem to be pretty much hardwired into humans and their interactions, it's sadly not really possible to do a control study :P Who knows what the human race would be like without them, but they wouldn't be the human race. 79.65.119.193 01:04, 1 October 2007 (UTC)[reply]

You have quite a way with words 79. Your points are well taken. Just a quick guess at your last comment: Without religion and politics, I think we`d still be savages. I think humans NEED rules and regulations to live in a civilized sort of way. Thanks for your fine points. I know Wikipedia is important. I love this place. lol Dave 64.230.233.222 01:21, 1 October 2007 (UTC)[reply]

I love this place too. Happy thinking :) 79.65.119.193 07:02, 1 October 2007 (UTC)[reply]

first , you don't deserve to be respected if you dont respect others whatever their belief is. next the bible is not my book. and if this makes you feel better the bible was changed with by people over time and that's why you cant beleive in it , next do you actually beleive in the bigbang theory if you do so then who created what's before bigbang or was it a coincedince that earth was formed and we were created . no reason just like that , that is impossible —Preceding unsigned comment added by 212.71.37.73 (talk) 08:20, 1 October 2007 (UTC)[reply]

To address your points one by one: Respect is indeed a bi-directional thing. It's not just that withhold my respect from people with crazy beliefs - I also don't give a damn whether they respect me or not. Truly - why would I care about the opinions of someone who runs his/her life on a rock-solid belief in the tooth-fairy? That person is a nut-job and I no more care how they feel about me than how they feel about the tooth-fairy. I would be more upset if someone with opinions I can understand (if not agree with) didn't respect me...but those are people I can respect.

So - I can well understand why you wouldn't believe in the things written in the bible - that's a good thing! But without that - what do you know about this "god"? How do you know what she/he/it demands of you? So you are just making up your entire personal cosmology as you go along without any evidence whatever? Don't you think that's a dangerous viewpoint? If you are going to go around just believing in anything on a whim without evidence, what's to stop you suddenly believing that your god wants you to blow up tall buildings with airplanes...or poisoning the Kool-Aid and waiting for the aliens to come and resurrect you? Those who believe in random things without proof or reason are dangerous, scary people!

I do believe that there is strong evidence for the big bang theory - cosmic background radiation measurements pretty much clinched that debate. But this continual demand for "What created the ultimate thing" - then when I tell you, you demand the thing that created the ultimate thing, then the thing that created that. It might make you happier to believe that some god or other created the big bang - but that raises an even nastier question: "How did the god get there?". Most religious people simply say that their god has always been there because god is outside of time - and they are happy with that answer. But why is that a better answer than "The singularity that was the source of the big bang was always there and is 'outside' of time". I don't see how a complex thing like a god (with thoughts and powers and strong opinions and all of these abilities) is a more probable starting point than a simple 'dot' of infinite density.

Describing the formation of the earth as a 'coincidence' is missing the point that science is making. Science says that the universe is VAST - the number of planets that have formed is hugely greater than the number of grains of sand on a beach. The formation of the earth was no coincidence - it seems that there are billions and billions of planets out there, they are formed from simple physical processes that are exceedingly common in our galaxy. Perhaps the only oddity is that this particular planet has all of this complex life on it (although we don't really know whether that's an oddity or not - maybe all planets have complex life on them but we just haven't found them yet). But even if we are alone in the universe, that's not a 'coincidence'. Beings that are capable of asking the question "How did I get here" can only arise on those planets which have exactly the right conditions - so it is inevitable that we live on a planet like this one that is exactly suited to us. If only one planet in the entire universe happens to have those exact conditions - then it is certain that the beings asking the question must be living on it. SteveBaker 14:17, 1 October 2007 (UTC)[reply]

Anyone (especially atheists like me) who wants to understand religion, its evolutionary fitness, and its appeal to adherents must watch the PBS Frontline expisode "The Mormons" (available online). This documentary was extremely enlightening to me even though I had already read some books on the subject. Just watch how the young woman's eyes light-up when she describes the mormon concept of marriage in the section "The Family" in part 2 and you will understand how religion is a natural outgrowth (exploitation?) of human evolutionary desires. -- Diletante 15:54, 1 October 2007 (UTC)[reply]

I think it's the height of stupidity, and perhaps arrogance, to not believe there is an intelligent Uncaused Cause. There is no logical reason for existence, and to chalk it up to the argument, "Well, who created God?" is tiresome. Believe in the Darwinian goop-to-human theory, and make it your god, fine, but please don't try to explain away the existence of the Universe through nonsensical, essentially nihilistic arguments. --68.63.11.221 15:18, 5 October 2007 (UTC)[reply]

how to test caffeine content??

please suggest a possible experiment(home test) to find caffeine content in common drinks an coffee and tea -sumit —Preceding unsigned comment added by 59.94.140.159 (talk) 06:47, 30 September 2007 (UTC)[reply]

Try searching the internet for the two keywords Daphnia and caffeine. You might be able to use the heart rate of Daphnia as a bioassay for the concentration of caffeine. --JWSchmidt 14:57, 30 September 2007 (UTC)[reply]

This question came up a few months ago - we concluded that there was no easy test that could be done in the home. But using Daphnia could maybe work with appropriate calibration of the method against samples with a known content. SteveBaker 15:21, 30 September 2007 (UTC)[reply]

Here's that thread, easily found by googling 'spider web cafeine site:http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives'. I rather liked my suggestion of using a spider. :) DirkvdM 18:24, 30 September 2007 (UTC)[reply]

thanks sir, but i had asked this qn on 30 or 29 sep not a month ago--59.94.146.227 12:59, 1 October 2007 (UTC)[reply]

Yeah - we know that - it's just that it's a surprisingly common question and it's easier to point you to the replies that were given last time than to answer it all over again. SteveBaker 13:38, 1 October 2007 (UTC)[reply]

FIRE FIGHTING ROBOT

My question regarding the above topic is

I wanted to know how does the software part has to be explored as on case of fire fighting robot which is basically dependent on the temperature sensors used(LM315). Wanted to know how the KEIL software come into play with the following project. my query was how is the programming going to be used in the above project fire fighting robot. Miki619 09:38, 30 September 2007 (UTC)[reply]

OK - back up a bit here. Which fire-fighting robot are you talking about? Do you have link to it? Your question is a bit confusing - so let's take this slowly. The robot uses some temperature sensing mechanism - using LM313 chips maybe - and you want to know what the software does with the data that comes out of those chips? This doesn't sound like a 'real' project. Is it some school project with a home-made robot or something? If so, and if I were programming it for a competition, and assuming the robot has just one temperature sensor pointing forwards, I'd write something like this:

Make the the software turn the robot slowly around in a full circle taking temperature readings all the while and noting the highest reading and the direction we were pointing in when that reading was taken.
Rotate back to the direction where we got the highest reading (so, hopefully we're pointing towards the hottest part of the fire).
Then, I'd look at the actual temperature we detected in that direction and say:
- If the temperature is lower than a certain threshold, drive forwards for a few seconds.
- Else, if the temperature is high enough that we believe the fire is immediately in front of the robot we squirt water/foam/CO2 at the fire until the temperature drops below the pre-programmed threshold - or some short time limit is reached (10 seconds maybe).
Then, go back to step (1) and look for a new direction to drive in.

Hopefully, this would cause the robot to drive towards the hottest part of the fire that it can see - put it out - then go looking for the next most hot part - put that out and so on. At the end, when there are no more heat sources hot enough to be fires, the robot will drive towards the next hottest thing it can see - which is probably the sun - which would probably cause it to triumphantly leave the building. Of course in the real world, things would be vastly, insanely, more complicated than that - but for some kind of school robotics class, that would do the job quite nicely.

But we have no way to know whether the robot you are thinking of is at all like that - there are other ways to program the thing. Maybe it has cameras - maybe it has a map of the room - maybe it has temperature sensors pointing in all directions, an infra-red camera. Maybe it has to ration it's water/CO2/foam supplies, maybe it has to distinguish between different kinds of fire so it knows whether it's safe to use water or not. Maybe it has to climb staircases - to put out fires up high on a rooftop or down low on the floor. Maybe it has to be able to smash down doors to get into a room - or avoid fallen debris. Perhaps it has to check that the floor is still strong enough to support it. Maybe it has to give a higher priority to saving lives than to putting out the fire.

You really didn't give us enough information! SteveBaker 15:17, 30 September 2007 (UTC)[reply]

Possible amnesia question.

Is there a certain type of amnesia to where a person only remembers things for as long as they stay conscious? So basically, after they fall asleep, they forget everything they learned when they wake up.--SeizureDog 10:12, 30 September 2007 (UTC)[reply]

Anterograde amnesia? --71.175.68.224 14:20, 30 September 2007 (UTC)[reply]

You don't have to fall asleep to forget with Anterograde amnesia though - it's a failure of the mechanism that transfers data from short term to long term memory - so memories fade after 20 to 30 minutes because short-term memory can't hold them any longer and long term memory can't kick in. I can't imagine a mechanism that would cause you to forget things only when you fell asleep - so I think the answer to the question is "No". The opposite can happen though - if someone is deprived of REM sleep for too many nights, they become forgetful. SteveBaker 14:54, 30 September 2007 (UTC)[reply]

50 First Dates is, I assume, the source of this musing? 79.65.119.193 22:22, 30 September 2007 (UTC)[reply]

Could be. The real-world cases are a lot sadder than that. There was a story on the radio about a guy who has this terrible condition - every time his wife steps into the room he greets her like he's been separated from her for years - since the time he suffered the injury that caused the disease. He says that he's "waking up for the very first time" - and the poor woman has to explain to him what the problem is and that this happens all the time to him - dozens of times per day. 50 First Dates sugar-coats it to hell and back! SteveBaker 13:36, 1 October 2007 (UTC)[reply]

At least he can hide his own Easter eggs. --Sean 18:12, 1 October 2007 (UTC)[reply]

Amiodarone

Many sources refer to the chemists Tondeur and Binon as the original discoverers of amiodarone, working for the Belgian company Labaz. Despite this, I could not find a reference to their original publications even in the 1985 Cordarone FDA approval documents[7]. Anyone? (Reply on my talkpage please, or on Talk:Amiodarone.) JFW | T@lk 10:16, 30 September 2007 (UTC)[reply]

It's allright - PubMed worked. How odd that Google does not index all pubmed abstracts?? JFW | T@lk 10:28, 30 September 2007 (UTC)[reply]

Mitochondria

How would you count the number of mitochondria within a liver cell? Using a series of images from a transmission electon microscope, or could a image from a scanning microscope be used,( or does a scanner produce an image of the exterior of the cell?) 88.110.203.63 11:11, 30 September 2007 (UTC)[reply]

If you search PubMed here you might be able to find the full text of articles that describe how to use either transmission electron microscopy or confocal microscopy to estimate the number of mitochondria in cells. --JWSchmidt 14:46, 30 September 2007 (UTC)[reply]

(Carbon) Emissions Data

I am looking for comprehensive, standardised, reliable emissions data please —Preceding unsigned comment added by Canuinti (talk • contribs) 13:58, 30 September 2007 (UTC)[reply]

Emissions from what? SteveBaker 14:48, 30 September 2007 (UTC)[reply]

And where and over what period. I assume you mean antrhopogenic emissions of CO2, probably in connection with global warming. Is that correct? Googling 'co2 emissions' gives loads of results on that, so you'd have to narrow it down a bit. If you mean worldwide, then the IPCC might be a reliable source for that, such as the fourth assessment report]. Alas, they're bloody pdf's and I don't know how to search through those. DirkvdM 18:36, 30 September 2007 (UTC)[reply]

DNA

can DNA be manupilated to add or remove certain characteristics ? can this possibly be true ? i mean as a good mutation!! —Preceding unsigned comment added by 212.71.37.108 (talk) 14:53, 30 September 2007 (UTC)[reply]

Try reading Genetic engineering. --JWSchmidt 15:54, 30 September 2007 (UTC)[reply]

Yes, and we're getting better at it all the time. It does bring up many moral issues, however, like stem-cell research. StuRat 22:32, 30 September 2007 (UTC)[reply]

Calculus needed?

Hello. I am just a high school student. I am considering studying thermodynamics as well as the methods used to date geological strata and the age of the Earth. I want to know about these things so I can evaluate claims in the creationism vs. evolution debate. Is it necessary to know calculus to have an adequate grasp of these subjects? Thanks. 68.77.186.32 16:23, 30 September 2007 (UTC)[reply]

I linked a couple of the keywords in your question.

You might find some useful info in http://www.talkorigins.org/origins/faqs-youngearth.html

As a layman I can think of a couple of points where differential equations are relevant, but they seem to be simple ones requiring only the basics of calculus – or you could use a "cookbook" approach, i.e. plug in numbers to a formula without needing to understand the formula. —Tamfang 16:33, 30 September 2007 (UTC)[reply]

I would say it depends on how deeply you want to go into these subjects. Calculus turns up in many, many areas of science when they are studied at a deep level. However, I think you could get a good overall understanding of both these subjects with only basic math. ike9898 17:25, 30 September 2007 (UTC)[reply]

Common sense and simple arithmetic should suffice, butif during your research you run into the need for higher math, please come back and ask for help. Someone here may be able to either help you with the math or direct you to a simpler way to handle the particular problem. You will need higher math if you proceed to University-level thermodynamics, of course. -Arch dude 17:30, 30 September 2007 (UTC)[reply]

If you're doing 'real' thermodynamics using numbers and energies and things, rather than just vaguely talking about the rules of thermodynamics, then you definitely need calculus; there's a lot of integrating and differentiating. So it depends how much thermodynamics you want to understand. I'd recommend you study calculus if you get the chance, if you're interested in science at all; it isn't as hard as cartoons would have you believe, and it lets you learn at lot of other things. 79.65.119.193 22:21, 30 September 2007 (UTC)[reply]

I'd say you would need to use logarithms for calculating ages based on decay of radioactive isotopes. That's the most complex math that comes to mind. StuRat 22:28, 30 September 2007 (UTC)[reply]

I would also like to point out that calculus is very useful for the lifetime of thinking you have ahead of you, even if you only have a qualitative ("calculus for poets") understanding of it. You should definitely learn it if you're curious about the world around you. --Sean 18:16, 1 October 2007 (UTC)[reply]

Slightly off-topic, but regarding thermodynamics (specifically entropy and the Second Law) and creationism vs evolution, and claims about entropy and disorder from order being a natural consequence of systems (and therefore, supposedly, of evolution being "false") I was reminded of the following point (thanks to M.C. Hawking):

"Creationists always try to use the second law, to disprove evolution, but their theory has a flaw. The second law is quite precise about where it applies, only in a closed system must the entropy count rise. The earth's not a closed system; it's powered by the sun, so **** the damn creationists, Doomsday get my gun!"

Hope this helps in your evaluations :) -Wooty [Woot?] [Spam! Spam! Wonderful spam!] 23:25, 1 October 2007 (UTC)[reply]

Hey, thanks for your help everyone, and sorry for the late thank-you. 69.218.205.188 00:25, 5 October 2007 (UTC)[reply]

Graphics of a X-box 360 to graphics of a ps3

Can I get a website that shows a comparison of the graphics for the x-box 360 and ps3. It would be nice if it would be a same game comparison. Thank you in advance for your help. (Wookiemaster 17:35, 30 September 2007 (UTC))[reply]

It's a really complicated trade-off. I can't reveal what I know because I've signed non-disclosure agreements (I'm an Xbox360/PS-3 game designer - and my job is the graphics). I would say this though. There isn't that much to choose between them. The horrific cost of designing video games these days means that most (if not all) games that come out on both platforms will have pretty much the same graphic design for both of them. The result is the games looks pretty much identical - no matter whether one is better than the other or not - it's a compromise between what the two machines can do. If you want to choose which one to buy - look only at whether the games you want are available on the console you want and ignore the millions of fanboi sites because not a single one of them know all of the facts (because to find them out you'd be under NDA and unable to write about them) - and for sure none of them are unbiassed. SteveBaker 21:50, 30 September 2007 (UTC)[reply]

You may have already said too much! Anyway, there's been an awful lot of computer-related questions on the science desk. I'm not sure how video-game graphics are a good fit for the Science Reference Desk... Nimur 04:20, 2 October 2007 (UTC)[reply]

Search for "xbox ps3 graphics comparison" like this http://ww.google.co.uk/search?hl=en&q=xbox+ps3+graphics+comparison&meta= and as the above says - mostly the stills look exactly the same - though sometimes the dynamic range or brightness differs...87.102.19.191 21:56, 30 September 2007 (UTC)[reply]

ionosing gas

i would like to know about the best ionising gas121.246.251.238 17:43, 30 September 2007 (UTC)[reply]

Best for what? Best at what? --Mdwyer 17:55, 30 September 2007 (UTC)[reply]

A gas with low ionisation energy is good - such as Xenon, ~~or maybe sulphur hexafluoride~~.. Radon is a good ionising gas as it is radioactive and a such self ionises.87.102.19.191 21:58, 30 September 2007 (UTC)[reply]

Physics Phenomena i don't understand

1) If a plane with two jet engines has the left one fail, the plane will deccelerate, and rotate left, is this correct?

2) Why does your reflection run at you twice your speed

3) i understand circular motion, so why do the planets move ellipcically?

4) if i shot a bullet out of a gun pointed in the opposite direction to my motion in a car that is travelling say 50 m/s and the bullet also travels at this speed what wil happen, does the bullet just stay in the gun?

5) I'm sitting here trying to figure out this damn questions, its not homework i promise, in fact i've changed the numbers. ok so lets say there are 40 chlorine particles per 10^7 air particle (made that up), and your lungs together can take 1 litre of air, atmospheric pressure is 1.0x10^5 Pa, how many chlorine molecules would you breath in?

78.146.4.0 18:10, 30 September 2007 (UTC)[reply]

1) Thankfully, all planes have some form of yaw control, usually a rudder. 2) If you are running towards a mirror that is facing you, from the perspective of someone standing next to the mirror, you are both running towards eachother at the same speed. Therefore, the distance between you two is closing at twice whatever that speed is, so from your perspective your reflection is approaching you twice as fast as you are running (assuming you're not running near the speed of light). 3) A circular orbit is merely the perfect orbital situation, where an orbiting object has the exact right velocity and altitude that gravity cannot pull it any closer, or let it go any further away. As you can imagine, in the chaos that was our early solar system, the chance of a planet forming in such a perfect situation was about nil. You might want to check out orbit. 4) No, the bullet exits the gun at 50m/s with respect to the gun. Anyone standing on the road sees the bullet plop out of the gun and fall harmlessly to the ground with no horizontal motion. According to the laws of special relativity, there is no preferred frame of reference. I am sitting still in my chair typing at my computer, but i'm on a spinning globe, which is hurtling around the sun, which is hurtling around the milky way galaxy, which is hurtling in some direction I don't know with respect to nearby galaxies. So what makes the road any better a frame from which to measure velocities than any other frame i can think of? Any inertial reference frame (a frame with constant velocity) is a valid one from which to draw physical conclusions. So as long as your car is moving with constant velocity, you can say that, from the car's perspective, the bullet will leave the gun with the same velocity that it would if the car were stopped. This is actually a better reference frame to use than the road because with the road you have to deal with a bullet from a moving gun, which is more complex. 5) One liter of gas at that pressure contains about 0.045 moles of particles. Someguy1221 18:35, 30 September 2007 (UTC)[reply]

1) If a plane with two jet engines has the left one fail, the plane will deccelerate, and rotate left, is this correct? -- Well, it would - but such aircraft are designed to still be flyable under those circumstances - so generally one has to throttle back the one remaining engine and apply rudder to keep it flying straight. In some kinds of aircraft you get other ikky problems due to the flow of the exhaust gasses over the tail plane being asymmetrical so that when you climb or dive, the plane wants to roll slowly to one side or the other. But again, the remaining controls are designed to be sufficient to keep the plane flyable.

2) Why does your reflection run at you twice your speed - you run towards the mirror as speed X, your reflection runs towards the mirror at speed X. Relative to you, you are stationary and the mirror is moving towards you at X - so your reflection is moving towards you at X+X = 2X.

3) i understand circular motion, so why do the planets move ellipcically? - To move in a circular orbit, you'd have to be moving with a velocity that's exactly at right angles to the line between you and the star/sun. If your initial velocity is pointing at some other angle (inwards towards the star, for example) then you are going to start moving closer to it instead of staying at the exact same distance. Because you are moving closer, you start going faster and faster - but this increases the amount of centrifugal force - which eventually pushes you away from the star. So now you are moving further away from it, you will gradually slow down and then move back towards it again. If the speeds are just right, you remain in a stable - but elliptical - orbit forever. Another way to look at it is that all orbits are 'elliptical' but a circle is just a special case of an ellipse.

4) if i shot a bullet out of a gun pointed in the opposite direction to my motion in a car that is travelling say 50 m/s and the bullet also travels at this speed what wil happen, does the bullet just stay in the gun? -- We have to be very careful about what you mean by the speed of the bullet. If you mean that if you were standing still (in a vacuum) and you fired the gun then the bullet would come out of the barrel at 50 ms^-1 - then when you fire it from the car (still in a vacuum), the speed imparted to the bullet by the propellant in the barrel will be added to the speed of the car - so someone beside the road would say that the bullet was travelling at 0 ms^-1 - the bullet would come out of the gun and fall to the ground. In reality, things will be much more complicated because of air resistance. The pressure of the air in the barrel of the gun will be lower because the speed of the car is pulling air out of the barrel creating a partial vacuum. So the pressure of the explosive propellant behind the bullet minus the air pressure in front of the bullet will be more than it would be if you were firing the gun in still air. In the case of a real gun, the difference would be almost negligable - but your gun is an AMAZINGLY slow one - so it might not be so negligable. Certainly, the bullet would come out of the barrel - but nowhere near as fast as it 'should'.

5) I'm sitting here trying to figure out this damn questions, its not homework i promise, in fact i've changed the numbers. ok so lets say there are 40 chlorine particles per 10^7 air particle (made that up), and your lungs together can take 1 litre of air, atmospheric pressure is 1.0x10^5 Pa, how many chlorine molecules would you breath in? -- Well, I'm not doing this one for you - check out Gas laws to figure out the number of molecules in the air from the pressure and volume - divide by ten to the seven and multiply by 40 - but it's made very messy by the fact that air is a mixture of lots of gasses. SteveBaker 21:32, 30 September 2007 (UTC)[reply]

for 1), see ETOPS. -Arch dude 02:33, 1 October 2007 (UTC)[reply]

THANKS guys! for question 5, can i use pV=nrT, but i do not have a value of temperature, what do i do? 89.240.40.152 17:08, 1 October 2007 (UTC)[reply]

When unspecified, you normally use either STP (273K) or room temperature (293K). Since you're talking about breathing, I'd imagine it would be the latter. Someguy1221 17:24, 1 October 2007 (UTC)[reply]

Perhaps a more practical example than the bullet one, since gas pressures and high muzzle velocities would not play a role, and you could titrate the amount of force used, would be to shoot an arrow backwards from a car. It's interesting (and counterintuitive to many) that the bullet or arrow would not hang suspended in the air at all, but would fall at the same rate as if you just dropped it by hand. --Sean 18:23, 1 October 2007 (UTC)[reply]

People are not good at those kinds of thought experiment. We used to ask job candidates: "If you are driving along in a car at constant speed with a ball in your hand. There is a bucket beside the road. You need to drop the ball into the bucket. Should you drop the ball (A) just before you reach the bucket, (B) exactly as you pass it, or a (C) little while after you pass it?" - an amazing number of people answer "as you pass it" or "after you pass it" - the latter group usually tell you "because of air resistance" and the middle group often say "assuming we can neglect air resistance" (which is a shame because they are closer to having the right answer if we take air resistance into account). It's very sad. SteveBaker 19:27, 1 October 2007 (UTC)[reply]

Hmm. Are you sure the question was stated the same way you posed it here? If so, it's difficult to comprehend how the incorrect answers could be appealing even in an intuitive sense. Even if you were sitting in a stationary chair with a stationary bucket in a total vacuum, the ball is still going to take time T > 0 to reach the bucket, so (C) doesn't even seem to make sense. My guess: there were other considerations (such as time pressure) you haven't mentioned here. dr.ef.tymac 21:45, 1 October 2007 (UTC)[reply]

Still dr., talk about a simple problem. I`m guessing your candidates are college graduates? Sheesh! That is VERY sad. Dave 64.230.233.209 21:54, 1 October 2007 (UTC)[reply]

Yep - college grads. Their thinking goes like this: When I stick my hand out of the window of the car - there is a really strong wind blowing. Balls aren't very heavy so they're going to be blown backwards really fast. So I need to let go of the ball after we've passed the bucket so that the ball gets blown backwards into the bucket. Yeah - I'm well aware of all of the fatal flaws in that logic - but that's what they say. I'm not putting them under time pressure - but then they never seem to take time to come to their conclusions - they always think it's so "obvious". In fact, I prefer that they take time and think - because I wasn't in the business of needing people who could come to a snap decision - I wanted people who'd take the time to get the right answer. The nastier question we used was "If you are in a boat on small 10' deep pond with a large, heavy, iron anvil on board - if you chuck the anvil over the side, will the water level in the pond go up, down or stay the same?" It's not a trick question. SteveBaker 22:54, 1 October 2007 (UTC)[reply]

I know you`re not asking me, per se, but I believe the water level would drop some. Briefly: With the anvil in the boat, being so much more dense than water, it would displace its whole 'mass worth' of water. Once completely submerged, it will only displace its equivalent volume of water. This would be much less water than it would displace while in the boat. Of course, the water would be at its lowest level while the anvil was in the air, before submerging. Do I get the job? lol Dave 64.230.233.209 01:15, 2 October 2007 (UTC)[reply]

Yep - that's it exactly. When it's in the boat, the anvil displaces it's own weight of water - when it's in the pond it displaces it's own volume of water. Since water is less dense than iron, it displaced more volume when in the boat than it did when it sank - so the water level goes down. It's a great question because the answer is the opposite of intuition - and most people who think scientifically but don't take the time to reason it out will guess "no change". Good candidates are the ones who stop to think about it - and even if they get the answer wrong, the point is that they didn't jump to a conclusion. I'd give you the job - but I don't work there anymore! SteveBaker 14:47, 2 October 2007 (UTC)[reply]

Aw shucks! May I get a recommendation at least? lol Dave 64.230.233.209 15:01, 2 October 2007 (UTC)[reply]

Perfect sharpness?

Is it possible to achieve a nearly perfect sharp blade by making it as much thin as possible (about 1 micron or something like that, assuming that the blade is of very firm material), so one would be able to cut up a considerable parts of nearly every material even by a slight strike? --85.132.14.38 18:43, 30 September 2007 (UTC)[reply]

See Monomolecular wire and Monofilament (science fiction) for some idea. Basically this is science fiction. Exxolon 20:54, 30 September 2007 (UTC)[reply]

some diamond knives can do close to this (can cut apart a cell) read "The Hot Zone" —Preceding unsigned comment added by 12.217.195.89 (talk) 00:00, 1 October 2007 (UTC)[reply]

Considering we can move separate atoms these days (can someone provide a link?) it may be becoming more science than fiction. However, when you use such a blade, it will become blunt again, so it's a one-off thing. Unless it's extremely tough material, like diamond. But then I suppose one cannot make diamond with the method I cannot find a link to. So maybe more fiction than science after all. DirkvdM 08:15, 1 October 2007 (UTC)[reply]

Hold on, what about this? Cover a knife in some insulating material, then use a laser (how thin can that be?) to cut out a strip right at the edge. Then put it in a galvanising bath and a perfectly sharp edge will form. Of course, this will still suffer the problem that it will go 'blunt' very fast. It might help if this was done in several stages, ever narrower, so the edge will be wedge-shaped. DirkvdM 08:23, 1 October 2007 (UTC)[reply]

I always wondered whether you could do this by electro-plating ultra-thin layers of progressively harder metals onto some kind of substate - ending with the hardest metal you can find - then adding more layers of progressively softer metals. Remove the substrate and you have a sandwich of a spectacularly thin layer of hard metal encased in softer metals on both sides. Sharpen it so the hard metal is the cutting edge of the V-cross-section blade. Now, as you use the knife, the softer metals will wear away faster than the hard one - leaving a perpetually ultra-sharp knife that maintains it's own sharpness as you use it. I imagine there must be a terrible problem with this idea because nobody seems to be doing it already - but if we're postulating nanotech solutions - that's the way to go. SteveBaker 15:41, 1 October 2007 (UTC)[reply]

That sounds a bit like the Dayak method of machete-making taken several steps further. See the last paragraph of the Dayak people#Society section. I wrote that. :) (how does one make a proud emoticon?) DirkvdM 18:57, 1 October 2007 (UTC)[reply]

1 micron is pretty achievable. Obsidian-bladed surgical tools can get as sharp as 3 nm (well, according to our article, anyway.) GeeJo ^(t)⁄_(c) • 19:56, 3 October 2007 (UTC)[reply]

What is the whitest substance ?

I recently read an article on research to create the whitest substance using nanotechnology, but I can't find it anymore. I looked at wikipedia hoping to find a definition of what being "whitest" means, and a list of very white natural substances (such as the foam of a breaking ocean wave). Any information on these subjects ? Pcarbonn 20:09, 30 September 2007 (UTC)[reply]

Well, I suppose 'whitest' would mean 'reflecting all of the visible wavelengths of light equally' - but a mirror does that pretty well and it's not what we'd call 'white'. So I suppose it also has to be a diffuse reflector. Most tests that are done where a perfectly white diffuse reflector is required (eg in calibrating a camera or something) use very pure calcium carbonate blocks - but I guess it's not perfectly white or the question would never have arisen. SteveBaker 21:09, 30 September 2007 (UTC)[reply]

Are you sure it was a substance and not a light? There have been many advances towards producing pure white LEDs using nanotechnology. -- kainaw ™ 21:45, 30 September 2007 (UTC)[reply]

Titanium dioxide seems to be claimed to be the whitest, but I recall hearing that there are coatings used on the fibres of white clothes which absorb UV light and re-emit it in the visible spectrum to make the clothes look whiter (or at least brighter). —Preceding unsigned comment added by 203.22.236.14 (talk) 04:17, 1 October 2007 (UTC)[reply]

UV dyes are mixed in with your detergents for exactly that reason. Look at your washing detergent under black-light for a fun time. --Mdwyer 05:07, 1 October 2007 (UTC)[reply]

Thanks for the answer. I guess 'white' is a mix of reflection and scattering, and nanostructures can contribute to building a good diffuse reflector. The article I mentioned was not about LED. Pcarbonn 07:16, 1 October 2007 (UTC)[reply]

There was an article a while back on an extremely white beetle. http://news.bbc.co.uk/2/hi/science/nature/6272485.stm 71.226.56.79 02:01, 2 October 2007 (UTC)[reply]

Wow! That's amazingly cool! SteveBaker 14:40, 2 October 2007 (UTC)[reply]

Spectralon bills itself as having the highest diffuse reflectance of any known material or coating over the UV-VIS-NIR region. It's mostly used for spectrophotometry.146.139.76.94 17:12, 4 October 2007 (UTC)[reply]

Calories in alcohol

Does alcohol have any calrories? If so, how many (per ounce or what have you)? Please do not respond by telling me how many calories alcoholic drinks have; I'm only interested in how many calories are found in ethyl alcohol itself.--The Fat Man Who Never Came Back 20:19, 30 September 2007 (UTC)[reply]

7 calories per gram. More than portein and carbohydrates, less than lipids. I imagine that that number is just an average though, and that specific types of alcohols will yhave different energy densities based on their chemical structure. --Ybbor ^Talk 20:47, 30 September 2007 (UTC)[reply]

The question was about ethyl alcohol, which is the only alcohol used in beverages, so the "specific types of alcohols" bit is irrelevant. --Anonymous, 21:23 UTC, September 30, 2007.

There's plenty of different types of alcohols.--Ybbor ^Talk 21:59, 30 September 2007 (UTC)[reply]

It is however true that ethyl alcohol/ethanol is the only one that really matters when it comes to alcoholic beverage. While other alcohols are consumed like sugar alcohol & propylene glycol, this is usually only im minor quantities. Also, as anon said, fat man did specify ethanol in particular near the end of his question Nil Einne 03:08, 1 October 2007 (UTC)[reply]

Perfect, thanks. Now how many grams are in an a shot of alcohol... maybe an ounce or so? Not that I'm going around doing everclear shots... I'm just curious.--The Fat Man Who Never Came Back 21:14, 30 September 2007 (UTC)[reply]

Well, a US fluid ounce is about 29.57 ml, and ethyl alcohol has a density of 0.789 g/ml, so one US fluid ounce of pure ethyl alcohol would be 23.33 g or about 160 calories worth. --Anonymous, 21:23 UTC, September 30, 2007.

I suspected as much.... more calories than bread, less than butter. Thanks, folks.--The Fat Man Who Never Came Back 21:47, 30 September 2007 (UTC)[reply]

Also bear in mind that most alcoholic drinks will also contain calories in the form of carbs and some will also contain calories from protein and fats (such as those with milk in them). StuRat 22:07, 30 September 2007 (UTC)[reply]

big bang theory

although there are many explanations given as to how earth came about from the "big bang" theory, i wanted to no how the material and atoms actually got there in the first place to create this big bang? how was this material invented from nothing?

thanks liam —Preceding unsigned comment added by 86.4.197.35 (talk) 22:23, 30 September 2007 (UTC)[reply]

I don't think anyone really knows the answer to that. —Preceding unsigned comment added by 12.217.195.89 (talk) 23:57, 30 September 2007 (UTC)[reply]

Timeline of the Big Bang#The very early universe lists links to some proposals. It is important to note that the big bang theory is actually entirely meant to describe what happened right after the universe started existing. For the actual moment of the big bang itself, or what, if anything, came before it, there is no accepted theory. Someguy1221 00:05, 1 October 2007 (UTC)[reply]

The big bang supposes that an infinitely small 'dot' of infinite density is the start of it all. In a sense, that is nothing - it's zero sized - but space itself is also scrunched up to zero size, also time, information - everything that ever was or ever will be is in this infinitesimal dot. Like the singularity at the center of a black hole perhaps. Since no information can pass through a singularity - it would be impossible to know what (if anything) created the singularity. One popular suggestion it that it arises from a 'big crunch' of some previous universe. But we can never know. It has also been suggested that time itself would be crunched up in the singularity - so that time would be kick-started up by the same process. In that sense, the singularity would have created time too. Without a 'before' - there can be no thing that 'created' it because the thing that created it would have to have been around before...no before - no creator.

There is a serious problem with asking the question "What was the ultimate cause of everything?" - and when you get the answer 'X' (a space-time singularity in this case) - going on to ask what caused 'X'? When someone provides the answer 'Y' - you're just going to ask "What caused 'Y'?" - if there is some kind of ultimate answer - then that something pretty much has to have no cause - to have been around for infinite time or to have created time. A zero sized, infinitely dense dot that's crunched up time too - through which no information can pass...that's a pretty definite "ultimate" beginning.

SteveBaker 02:36, 1 October 2007 (UTC)[reply]

The big bang theory is based on the FLRW solution to general relativity, which has a singularity at the beginning, but physicists do not give this mathematical singularity a physical interpretation. It's just a sign that the theory doesn't work there. Big bang cosmology is about the evolution of the universe, not how it began. The name "big bang" is very unfortunate. It was, as you might know, originally invented as an insult (by Fred Hoyle). Imagine the confusion if the theory of natural selection were known as the tornado-in-a-junkyard theory, after his (senseless) criticism of it. -- BenRG 11:00, 1 October 2007 (UTC)[reply]

Stephen Hawkins writings indicate that he is talking about a literal singularity with scrunched up time. It's explained reasonably well in 'A brief history of time' - although you need to read his published papers to get a proper mathematical grasp of the idea...of course he could be wrong, there isn't any actual evidence until a fair amount of time after the actual start of the universe. SteveBaker 13:25, 1 October 2007 (UTC)[reply]

Ok, I`m going out on a limb here. This might very possibly be complete rubbish, but this idea came to me not very long ago while trying to explain, to my own satisfaction, if nothing else, to attempt an explaination to how 'our' Universe began. Here goes...please don`t laugh TOO hard!
While reading-up on the possibility(ies) of there being multiple universes, I thought, "What happens when a black hole is 'created' in another 'neighbouring' universe? Where does the matter go?" I`ve coined the term 'white-burster'. This white-burster is what 'could be' the beginning of OUR universe, as we know it. Of course, I coined to term to make reference to its connection with the 'other side' of a black hole. I know, this is totally unfalsefiable, so therefore not science, but I think it 'could' work. One of course, would have to presume that that 'other' universe, if it exists, would be many magnitudes bigger than the one we presently know. Carl Sagan's most famous, I think, quote obviously comes to mind right now: "Extraordinary claims require extraordinary evidence." Of which of course I have none. Sorry if this just wasted everyone`s time. But, if I may just add: Despite being impossible, I think, to prove true, I think it may be just as impossible to prove untrue, which is, of course, nearly assinine as an argument. I`m very afraid to click on "Save page". lol CHEERS! Dave 64.230.233.209 14:29, 1 October 2007 (UTC)[reply]

See White hole and White holes in fiction - it's hard to come up with something we don't already have an article about! SteveBaker 15:34, 1 October 2007 (UTC)[reply]

I don't know about that; Wikipedia has some hefty gaps in its coverage. A search for slightly obscure items turned up these redlinks: biopsy punch (or punch biopsy if you prefer), pin joint, drip mat, bar runner, and the humble ice bucket (the fact I'm posting this from a pub may've influenced my search terms :P ). Even concepts like the dancing bear and the pauper's funeral, with which most will have at least a passing acquantaince, come up blank. Still, nice to know that there's still so much more out there to write about :) GeeJo ^(t)⁄_(c) • 19:01, 3 October 2007 (UTC)[reply]

Simply amazing! I swear I hadn`t heard of any such thing before. Only reason being, I refused to call 'my' white-bursters 'holes'. Maybe I could get the name changed to bursters. I DID however read Hawking`s Black Holes and Baby Universes, but I did not think of each Black Hole being a White Hole someplace else. "MY" white-burster was coined to 'explain' OUR Universe, not other baby ones. So, a little bit of a twist there. Perhaps WE are one of those huge universe`s babies! Thanks for finding that for me. QI! Dave 64.230.233.209 15:57, 1 October 2007 (UTC)[reply]

For the record though - I don't think the material that falls into a black hole goes anywhere - it stays right where it is - in the middle of the black hole. That's why these things get gradually bigger. As more material falls in and is compressed down into the singularity, the mass of the hole increases - an the event horizon gradually increases in diameter. If the material somehow fell through and popped out of someplace else (either in our universe - or in another) then the black hole would presumably be unable to grow - and therefore no black hole would ever be any bigger than the star that formed it. Since we know there are 'supermassive' black holes (like the one in the center of our very own Milky Way) - there must be some way for them to grow. Hence, no white holes of the kind you are thinking of. SteveBaker 19:15, 1 October 2007 (UTC)[reply]

Yes, I know that Steve. I didn`t get 'into it' as deeply as I could have, just for clarity and conciseness sake. I`m thinknig that maybe there`s some sort of theoretical limit to just how massive a black hole can get, or maybe even a finite age for a huge black hole, then BOOM!...it 'disappears' from huge universe, to create a baby. Maybe once it gets to a certain theoretical limit, the 'dimensions' can no longer hold onto it, and it disappears, creating said 'new' universe. I know, still totally unfalsifiable. This will be my last post right here. Thanks all. Dave 64.230.233.209 20:47, 1 October 2007 (UTC)[reply]

What is meg

Look at this picture. http://www.theoildrum.com/files/Slide7_0.png

At the bottom half, it says "O2/N2 (per meg)", can anyone explain what meg is? Thank you. 202.168.50.40 23:18, 30 September 2007 (UTC)[reply]

this site www.eol.ucar.edu/~stephens/talks/stephens_occc0508.ppt claims it is mol/m^2/year —Preceding unsigned comment added by 12.217.195.89 (talk) 23:50, 30 September 2007 (UTC)[reply]

I would think megaliter as a volumetric measure of atmosphere.
However, I'm not sure where you got that from, but it looks fishy all around. I wouldn't source it or anything.
Mrdeath5493 03:50, 1 October 2007 (UTC)[reply]

Well "per mille" (also "per mil") means thousandths (i.e. 5 per mille = 0.005) in the same way "percent" means hundredths (5% = 0.05). Maybe "per meg" is meant to convey millionths or something like that but its terminology I've never seen before. I dislike 12.217...'s answer because O2/N2 (i.e. a ratio of concentrations) should be a number and hence dimensionless. 76.240.228.205 03:58, 1 October 2007 (UTC)[reply]

If you look at the original graph the O2/N2 (per meg) axis has a numeric scale going from 0 down to -500 - so it can't be anything like a percent/per mil/per million thing because those numbers can't be negative. Also the top graph does everything in ppm (parts per million) and if per-meg were a per-million thing then surely that would have been a 'ppm' scale too. At least 12.217.195.89's suggestion of mol/m^2/year would be a negative number - as CO2 builds up, oxygen declines and the ratio of oxygen to nitrogen would decrease. But a rate of decrease of a few hundred moles per meter cubed per year would have us all gasping for breath a long time ago!

This article [8] has a definition of 'per meg' that says:

per meg = ((O2/N2)/(O2/N2)^ref - 1} x 10⁶ - in other words the ratio of present-day oxygen levels to the oxygen level at some reference date - messed around until it's some kind of reasonable number scale that looks good on a graph.

This graph [9] in that same article appears to be presenting the same data as the bottom half of the graph that our OP posted - except that there is a 'delta' symbol in front of the "02/N2 per meg" axis - indicating that this is the rate of change of oxygen nitrogen as expressed in this peculiar 'per meg' notation. Both graphs are attributed to 'R. Keeling' - I suspect they are intended to represent the same underlying data - but the version our OP found has been 'messed about with' by people who didn't know what they were doing. I wouldn't pay too much attention to a graph that spells 'dioxide' with a 'y'. Without that delta symbol (and especially without telling us what reference date is being talked about), the numbers don't make much sense. Urgh. SteveBaker 13:21, 1 October 2007 (UTC)[reply]

I was skeptical of the dioxide with a 'y' too, but I guess some Euro languages do that. —Preceding unsigned comment added by 12.217.195.89 (talk) 08:53, 2 October 2007 (UTC)[reply]

tick + blade of grass

why is it recommended that when you submit a tick to a lab for analysis you put it in a plastic bag with a blade of grass?

Here is a guess: The grass is a plant, taking in carbon dioxide and giving off Oxygen. That way the tick can continue to breathe and it will stay alive and retain all the diseases so they can be detected. John 03:57, 1 October 2007 (UTC)[reply]

Is it even possible to get a tick off you without killing it? I thought that the things have to be dead before you can safely twist them out of your skin? --Kurt Shaped Box 09:14, 1 October 2007 (UTC)[reply]

No, you're supposed to twist them off alive with tweezers (preferably ones specially designed for the purpose). If you kill them first (how?), they're more likely to spit some possibly infected fluids back into you as they die. —Ilmari Karonen (talk) 09:58, 1 October 2007 (UTC)[reply]

Whenever I've had a tick, I've doused it with isopropyl alcohol (or vodka) until it stops moving, *then* twisted it out with tweezers. A doctor once told me to do that! I had no idea! I have also burned them (and the surrounding area) away with a cigarette when nothing alcoholic was available. I was under the impression that if you tried to remove the tick whilst still alive, then the head would 'lock', snap off and stay firmly attached to your flesh (ticks being tenacious little buggers) and cause an abscess. It's probably lucky that I haven't had a lot of ticks! F-ck me!

How do the 'tick tweezers' work, as a matter of interest, then? At the end of the day, it's a smallish bug - how can you apply enough pressure to the thing to get a grip on it without squashing it flat? --Kurt Shaped Box 13:30, 1 October 2007 (UTC)[reply]

When "in their shells", They are extremely hard, almost like an unpopped popcorn kernel. 86.153.44.115 20:28, 1 October 2007 (UTC)[reply]

Cool. How are they 'constructed'? Any idea? --Kurt Shaped Box 22:46, 1 October 2007 (UTC)[reply]

There are a number of different types of tick tweezers, but a general trait they all seem to share is fairly sharp tips shaped so that they go around the tick's body and only grab the head. The kind I have here (and of which I'll upload a picture of as soon as my camera battery is charged) also have a spring-loaded mechanism which keeps the tips closed unless actively pulled apart: you pull the tweezers open, position them around the tick and let them close. Once you've got a good grip on the tick's head, you can then twist it off without having to worry about the tweezers slipping. (By the way, the second link above has some pretty firm but good advice on the hows and whys of tick removal.) —Ilmari Karonen (talk) 21:12, 2 October 2007 (UTC)[reply]

U.S. patent 5002323 seems to describe exactly the type I have here. Click on "images" to see some illustrations. —Ilmari Karonen (talk) 21:25, 2 October 2007 (UTC)[reply]

I have also heard the “burn or douse in pesticide first, then remove” advise about leeches. In both cases it was ostensibly to prevent bits of the mouth parts from remaining in the wound. I saw both bits of advice in first aid books. Not sure what is the right answer though. --S.dedalus 00:22, 2 October 2007 (UTC)[reply]

Thinking about it, I suppose the advice given might depend on what sort of diseases the local parasites are likely to be carrying - whether the risk of an infection from leaving the head/mouth stuck in your flesh is worse than the risk of the dying critter vomiting god-knows-what into your bloodstream. --Kurt Shaped Box —Preceding signed but undated comment was added at 00:27, 2 October 2007 (UTC)[reply]

That’s a pretty picture. :) --S.dedalus 00:51, 2 October 2007 (UTC)[reply]

The ideal method of tick removal is with a biopsy punch. You'll get the entire tick out without encouraging it to discharge anything into your bloodstream -- but on the downside, it also removes a chunk of your skin. --Carnildo 00:07, 3 October 2007 (UTC)[reply]

Would a blade of grass, presumably snapped off near the base, continue to provide gas exchange? I learned the hard way what happens if you burn a tick before removing it. I had always been taught to heat up a needle and apply that to the tick to convince it to back out of its own volition. One day I didn't have a needle so I heated up the tip of my knife and applied the blade tip to the tick. Too much heat. The tick died in place, vomited into the skin and caused cellulitis which persisted for months. That was the last time I applied heat to a tick. 152.16.59.190 04:07, 6 October 2007 (UTC)[reply]

DEET

what is the metabolic pathway (if there is any) that makes DEET effective at preventing insects from attacking me?

From DEET:

DEET is believed to work by blocking insect receptors (notably those which detect carbon dioxide and lactic acid) which are used to locate hosts. DEET effectively "blinds" the insect's senses so that the biting/feeding instinct is not triggered by humans or animals which produce these chemicals.

Someguy1221 00:10, 1 October 2007 (UTC)[reply]

Deserts

Hi

I've had a look at deserts, but surprisingly it's a little scarce on this topic. My question is: what's the biodiversity really like in deserts in general? I want to say that there are few animals but more insects/microorganism/plants than you'd expect. Would I be right? Comments appreciated. Aaadddaaammm 23:54, 30 September 2007 (UTC)[reply]

Sounds about right. Even though there are more than you'd expect, there are fewer than in most other land types (arctic tundra may be an exception). StuRat 01:49, 1 October 2007 (UTC)[reply]

Comment: an insect is an animal Nil Einne 02:57, 1 October 2007 (UTC)[reply]

I wonder if he appreciated that one. :) DirkvdM 09:11, 1 October 2007 (UTC)[reply]

Thanks for your input, guys! Helpful comments (yes, even Nil Einne's - I'll have to specify vertebrates). Aaadddaaammm 23:06, 1 October 2007 (UTC)[reply]

BTW, believe it or not I didn't actually purposely include the comment: part because of the 'comments appreciated' part of the qunestion. I had that style of answer on my mind since I'd been discussing stuff at other places and because my comment was unrelated directly to the question I answered like that. The comments appreciated part may have had a subconscious influence obviously. The 'insect is an animal' part was a bit tongue in check since I suspected Aaadddaaammm was probably aware of that (and it seemed a harmless jibe if he/she was) although it was also serious since it was possible he/she didn't. Just saying this to remind everyone including myself that sometimes things come out in strange ways quite by accident :-P Nil Einne 19:12, 2 October 2007 (UTC)[reply]

October 1

Lightning as source of electricity

Is it possible to harvest the electricity from lightning strikes? If it is, then we can put an end to burning fossil fuel for electricity. Oidia (talk) 04:41, 1 October 2007 (UTC)[reply]

Electricity doesn't store all that well, sadly. So, if you're intending to use it all up at once -- say, launching your Delorean through time or jump-starting your monster, the I suppose lightning would work. It practice, humans just don't have a way to convert and store that much energy in that little time. Besides, you've also got to be in the right place at the right time to collect it! --Mdwyer 05:04, 1 October 2007 (UTC)[reply]

Electricity can be used for the electrolysis of water, which will produce Hydrogen, which is handy stuff to store and use energy (see Hydrogen economy). However, as Mdwyer pointed out, lightning comes in extreme bolts and it is hard to predict where it will strike, so you'd have to 'harness' it somehow. The latter can be solved by using a good lightning conductor. But then you'd have to convert all that energy into hydrogen in a split second (or could it be delayed somehow?) and for that you'd need a pretty big installation, I suppose (how big?), so that would have to be stationary, so it had better be in a place where there is a lot of lightning to be economically viable.

Btw, suppose we could somehow (by my method or otherwise) harvest all the energy in electricity. How much would that amount to? Would it be enough to fulfill all our energy needs if it were all 'harvested'? I heard on QI the other day that worldwide, there are about 200 lightning strikes per second. Stephen Fry did not say if this included minor strikes, if there are such things. The lightning article says an average lightning bolt has an energy of 500 MJ. Times 200 per second is 100 GW. Energy consumption says we use up 15 TW (2004, so probably 20 TW now). So even if we could harvest all lightning energy in the world (including in very remote places) at 100% efficiency, that would only contribute 0.5 % of our energy demand. This surprises me. I thought it would be much more. Did I make a mistake somewhere? DirkvdM 08:32, 1 October 2007 (UTC)[reply]

Apparently the idea of using lightning as an energy source is not quite as flaky as it sounds. There is a detailed discussion here and an overview article here. A company called Alternative Energy Holdings, Inc.] produced a press release last year claiming it had developed a prototype "lightning farm", but the company's website does not give an update, so practical results may not have lived up to expectations. Gandalf61 09:40, 1 October 2007 (UTC)[reply]

The real problem is that any plant that took advantage of a lightning strike - capturing and storing the energy and pushing it out onto the electrical grid - would be quite large and expensive. But how many times a year would it get struck? Even in places where the most storms are found, a handful of times at most, I'd guess. That's hardly going to be worthwhile as an investment because it's sitting idle 360 days of the year. I'm also a little skeptical about that figure of 500MJ - sure, that's the total energy of the lightning bolt - but isn't most of that consumed in ionising the air to allow the strike to reach the ground - and producing all of that light and sound energy. I always assumed that only relatively little of that actually hit the ground. SteveBaker 12:55, 1 October 2007 (UTC)[reply]

Isn't it a question of ease of collection / cost really? Surely alternatives such as solar power or wind farming would be much more economical? It does however sound like a very macho way of harvesting electricty. "We shall gather it from The Gods themselves - plucked from the heavens in my lightning-dirigible!" Don your flying goggles and scarves. Lanfear's Bane 14:06, 1 October 2007 (UTC)[reply]

I believe some places, like radio towers on top of mountains, are struck by lightning quite often, perhaps many times a month. I would expect the key would be harvesting the electrical potential before it becomes an unmanageable lightning bolt. This could perhaps be done using thin wires hanging from weather balloons, launched from mountaintops. These would pose an obvious hazard to navigation, however, so any area where this was done would have to be off-limits to airplanes. StuRat 15:03, 1 October 2007 (UTC)[reply]

Update on my calculation. The lightning article says that lightning strikes the earth only about 100 times per second (or might that difference be explained by only counting lightning striking ground, so not over sea?). But lightning between clouds is more common (doesn't say how much, nor how powerful they are). And there is also upper-atmospheric lightning. To harvest those, a solution along the lines of what StuRat says might be needed. (Possibly above the cruise altitude? Hmm, that's about 10 km I understand). But unless that lightning is much more powerful (and assuming my calculation was correct) this will even under ideal circumstances only supply a fraction of our energy needs. So unless it's real simple to develop (there is always that option, so give it some more thought), we'd better put our effort into other energy-sources. DirkvdM 07:20, 2 October 2007 (UTC)[reply]

Using airplanes isn't really going to work. Remember there is no such thing as something having a voltage - there is only 'potential difference'. It's the difference in voltage between one thing and some other thing. Unless the airplane can touch both the cloud and the ground - or one cloud and another - it can't take advantage of any difference in potential between two things. So you need a very large craft - or something trailing long cables or something. Also, lightning mostly happens in stormy weather...the very worst time to be flying! I just don't think this is a feasible idea. SteveBaker 14:33, 2 October 2007 (UTC)[reply]

I think it would fall into the same category as wind, water, and solar power, each of which are only feasible in certain places with consistently high winds, flowing water, or bright sunlight. Therefore, each can only provide a fraction of our total energy needs, but this is a good thing. We don't want to go from being overly dependent on one single energy source (fossil fuels) to another. If we used 100% solar power and the climate shifted, causing cloudier weather, for example, we would be in big trouble.

So, I think the long, thin wires trailing from weather balloons could provide some power, in certain locations (like mountaintops). Perhaps they could also be strung between mountain tops, for a system that would last a bit longer. We might even be able to adapt existing wires, like phone lines and cable-car wires, to extract some electricity. StuRat 14:47, 2 October 2007 (UTC)[reply]

Overcast skies don't affect insolation as badly as people think. It's an important factor, but not all-important. This is why solar power is even a good option in countries like the Netherlands.

Steve, of course this should not be done with airplanes. Those are real 'gas-guzzlers' that would use up way more energy than they'd collect. Balloons and electrolysis are simple enough that it might be possible to develop a cheap method of hydrogen-production that is a matter of 'let it fly and forget about it until there's enough to collect'. One problem might be that uncompressed hydrogen will make the balloon go up even further, but maybe that could be used to some advantage. Also, unattached balloons will fly off in all directions, so someone else might collect your hydrogen unless international agreements are made. DirkvdM 19:04, 2 October 2007 (UTC)[reply]

This is not a way to capture lightning, but if you're still interested in creative ways to store electricity, see Pumped-storage hydroelectricity. --M @r ē ino 15:04, 4 October 2007 (UTC)[reply]

Hall of mirrors

Just curious, but has anyone ever tested the hall of mirrors in Versailles for mercury vapor? —Preceding unsigned comment added by KeeganB (talk • contribs) 15:12, 1 October 2007 (UTC)[reply]

Why? We know that mercury is used in the manufacture of mirrors. Do you think there is a problem because of the age of the mirrors - or because there are so many of them? If it's the former, I doubt that the mirrors are the original ones - when I visited there a couple of years ago, they certainly didn't have the tarnished yellowish look of very old mirrors. If it's the latter, then there are lots of places in the world with many more mirrors than that. SteveBaker 15:29, 1 October 2007 (UTC)[reply]

I haven't looked at a lot of old mirrors to be familiar with the tarnished look Steve has in mind, but I would have thought that a "yellowish look" in an old mirror was due to the use of a cheaper reflecting metal that was yellowish to begin with. (Why would the reflecting metal tarnish if it's covered with glass?) But I was in the Hall of Mirrors last week, and what I noticed was that a lot of the mirrors have a gray or cloudy appearance. I didn't take too close a look (the place was chock-full with other tourists), but I certainly assumed that they were the originals, and this coloring was introduced during manufacture. --Anonymous, 16:26 UTC, October 1, 2007.

(The reflecting metal tarnishes because only the front face of the metal is covered with glass - the back is not. SteveBaker 19:07, 1 October 2007 (UTC)[reply]

But it's the front of the metal you look at. Are you saying the metal is then enough that the tarnish penetrates its entire thickness? I didn't think of that. --Anon, 13:25 UTC, October 2.

Yep. They paint the back of the metal on modern mirrors for precisely that reason...but many antique mirrors don't have that - or the paint cracked or whatever. I just didn't recall seeing any of that kind of damage at Versailles - so I presumed that the mirrors had been replaced at some time. However, I could easily be wrong. SteveBaker 14:28, 2 October 2007 (UTC)[reply]

Don't get your panties in a wad, Stevie. I was just wondering if the possibility of dangerous levels of mercury vapor in the hall has ever been considered. —Preceding unsigned comment added by KeeganB (talk • contribs) 02:09, 2 October 2007 (UTC)[reply]

Oh - I wasn't upset. I was just wondering why you thought there might be a problem. Modern mirrors aren't a source of mercury poisoning - so I wondered whether you were concerned because of some ancient manufacturing process that I might be able to search for - or whether it was just the large number of them that might make you worry. I genuinely wanted to know the reason for your concerns in order to better answer your question. SteveBaker 14:28, 2 October 2007 (UTC)[reply]

Penis question

Is there any way of decreasing the time it takes for my penis to beome hard again after ejaculating? Thanks. —Preceding unsigned comment added by 90.240.244.96 (talk) 16:32, 1 October 2007 (UTC)[reply]

Well viagra is a popular 'hardening' drug, similar to starch but for people... ny156uk 16:35, 1 October 2007 (UTC)[reply]

First off, slow down and don't stress over it. I don't know that you are but I do know that stress is the anti-viagra. Slow down, and be intimate following ejaculation; touch, rub, fondle, do whatever turns you and your partner on. Based on my original research I'd say the erection is 80% in your mind. It comes when you are aroused, assuming you do not have a medical condition. Also it takes longer the older you get. I could keep going here but I'm not Dr. Ruth. Man It's So Loud In Here 17:20, 1 October 2007 (UTC)[reply]

Women. DirkvdM 07:31, 2 October 2007 (UTC)[reply]

Plural? SteveBaker 14:24, 2 October 2007 (UTC)[reply]

Or men or both, whatever you fancy Nil Einne 19:25, 2 October 2007 (UTC)[reply]

Hey, I see nobody has any scruples here about giving medical advice... ;-)) —Preceding unsigned comment added by 86.17.50.12 (talk) 18:39, 2 October 2007 (UTC)[reply]

I was asking a new question. It's only medical advice if they are wearing nurse uniforms. :-P SteveBaker 19:17, 2 October 2007 (UTC)[reply]

BTW, what you're asking about is Refractory period (sex) although I couldn't find anything specificically about suppressing or reducing it. Personally I think a MISLIH's advice is the best if you have a partner. Especially if you intend the relationship to be medium to long term, you may find it better for the relationship in the long run to take the time doing other things rather then trying to have the shorts refractory period possible. And if you aren't talking about a situation involving a partner well then DirkvdM's advice may be the best (reducing the time spent in one area may enable you to focus on another area). Nil Einne 19:25, 2 October 2007 (UTC)[reply]

There's a story that President Calvin Coolidge visited a farm with his wife. She nudged him and said "Cal, I hear that a rooster can do his male duty many times a day". The President said "But it is not with the same hen each time, is it?" So see the Coolidge effect, and consider the effect of changing partners, as in an orgy. Edison 05:20, 3 October 2007 (UTC)[reply]

Iridescence

Why does iridescence occur only in very thin surfaces such as soap bubbles and not in, e.g. 5 mm-thick glass? Goodgerster 18:04, 1 October 2007 (UTC)[reply]

If you have a soap bubble that's one micron thick, then 2.5 wavelengths of 400 nm blue light can fit within it, and 1.4 wavelengths of 700 nm red light can fit within it. If you have two wavelengths that are close together, like 500 nm green and 501 nm green, then the number of wavelengths will be very close (2 versus 1.996). The point is, the accumulated phase difference changes slowly with wavelength.

In contrast, if you have a 5 mm thick piece of glass, then 10,000 wavelengths of 500 nm green light fit inside, but 9980 wavelengths of 501 nm light fit inside. The difference is more than one whole wavelength, so the phase is very sensitive to the wavelength and in practice that just means it's unpredictable. The thick film has totally different effects on very close wavelengths, so they appear to average out over the whole spectrum (because your eye isn't sensitive to such tiny changes in wavelength).

In other words, a thin film modulates the spectrum by a slowly varying function (for example, stopping blue and passing red), and a thick film modulates it by a rapidly varying function that's impossible to perceive. —Keenan Pepper 18:24, 1 October 2007 (UTC)[reply]

Nice explanation. – b_jonas 09:08, 2 October 2007 (UTC)[reply]

What are the isomers for C7H16 (isomeric heptanes)?

What are the isomers for C7H16 (isomeric heptanes)? —Preceding unsigned comment added by 69.179.253.76 (talk) 19:03, 1 October 2007 (UTC)[reply]

The isomers of C7H16 are the different structures that have that formula.

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. DMacks 19:35, 1 October 2007 (UTC)[reply]

Heptane may be of use. Algebraist 19:38, 1 October 2007 (UTC)[reply]

C7H16 is an alkane because it fits the CnH(nx2)+2 definition. So all you have to do is figure out how many structures you can create with 7 carbon atoms. Remember to look out for structures that look different on paper but bond can be rotated to give the same structure. Don't forget a linear molecule, and make sure that no C has more than 4 carbons attached to it! Good luck, have fun - I used to love these kind of questions! Aaadddaaammm 23:04, 1 October 2007 (UTC)[reply]

I could find 8, fyi. I could have missed some, though. Aaadddaaammm 00:29, 3 October 2007 (UTC)[reply]

Trust me, you don't want to know how many isomers it has. You want to know how many constitutional isomers it has. There is a big difference.
Mrdeath5493 05:30, 3 October 2007 (UTC)[reply]

"God initiated the Big Bang and then burned and died in the flames of his own creation..."

Would this statement be any less wrong than any of the other current theories about what happened just before and just after the Big Bang? --Kurt Shaped Box 19:18, 1 October 2007 (UTC)[reply]

Well, most theories of God suggest he is all-powerful and omni-present, do they not. So He should not be able to be killed, surely? I much prefer the simpler and more logical explanation: God doesn't exist. --80.229.152.246 19:45, 1 October 2007 (UTC)[reply]

There is currently no scientific theory describing anything "before" the Big Bang, so this is purely a philosophical question. The general idea behind objection to your theory is that the only reason to include God in the picture is that no one likes the idea of something coming from nothing. Unfortunately, you still have that problem because you start the story with God already existing; anything you can say about His provenance, one could also say about the universe's provenance, so it really doesn't buy you anything. The only reason it sounds nicer to do an end run with "God created Himself" than "the universe created itself" is that people who believe in the supernatural are sometimes willing to accept lower evidentiary standards than those who do not. --Sean 20:20, 1 October 2007 (UTC)[reply]

Speaking about something "before" the Big Bang is absurd, since current theories consider that time was created with the Big Bang. And I'd say your statement is somewhat more wrong than the other one, since yours includes God, who is completely unnecessary for the consistence of the theory. The addition of God only adds complication, making the theory, therefore, more improbable. --Taraborn 20:31, 1 October 2007 (UTC)[reply]

If time was created by the big bang, where did all the matter that is the universe come from? And if you think it came from God, what created God? —Preceding unsigned comment added by 128.101.53.147 (talk) 20:43, 1 October 2007 (UTC)[reply]

I believe the comforting part of the Judeo-Christian God is that he doesn't require a creator of his own. Someguy1221 20:49, 1 October 2007 (UTC)[reply]

How convenient! Dave 64.230.233.209 21:02, 1 October 2007 (UTC)[reply]

That's not comforting. That's infuriatingly absurd. Beekone 21:03, 1 October 2007 (UTC)[reply]

Did you miss the hint of sarcasm in there? Dave 64.230.233.209 21:09, 1 October 2007 (UTC)[reply]

It would be impossible to prove it either true or false - because no information can pass through a singularity. This makes it 'unfalsifiable' - which is a huge red flag for any theory you want science to take seriously.

It would also be impossible to disprove the statement "The tooth-fairy did it" or "Kurt the Almighty caused the initial singularity to be pooped out by his 'seagull of eternal light'" - or "A pink and purple striped hamster named Norbert created the initial singularity by running too fast on his 'hamster wheel of ultimate destiny'"...there are an infinite number of such possible statements and all of them are impossible to either prove or disprove. Why would we believe one over the other? The probability that the Christian God did it is no greater than that a Hindu god or a Roman god or a Greek god or "The Devil" or the Tooth Fairy or Norbert the ethereal hamster did it.

Worse still, all of those kinds of statement just force you to ask things like "What created Norbert?"...and when someone randomly (and without proof) says "Norbert was created by a small yellow teacup", we simply MUST ask "What created the teacup?" and when we find out who/what created THAT, we simply have another unanswerable riddle to solve. None of these complicated (and unfounded) claims are ever "final" - none has any measurable reason for being more true than the infinity of other possible creation stories. It's possible to suppose that "Norbert created the universe - and Norbert lives 'outside of time'" (whatever that means) - thereby making moot the question of what created Norbert...but why not simply say that the singularity is 'outside of time' - that's a much simpler answer.

We are typically left with two options in the case of unfalsifiable claims: Occams' Razor - which may be roughly stated as: "The simplest explanation is usually the best" and Carl Sagan's: "Extraordinary claims require extraordinary evidence" - since we have none of the latter - we'd best rule out extraordinary claims and stick with the Occam - ruling out all but the simplest explanation - which is that no weird god-like thing did the job and a simple physical explanation for the beginning of the universe is much more likely to be true.

Right now, I think the best is the one that Stephen Hawkins seems to promote - that time itself came out of the big bang, so there was no "before". Without a "before", nothing can have created the big bang - it is the first thing. To ask "what came before the beginning of time" is about as meaningful as asking what number comes after infinity. Mathematically, he could certainly be correct. But not everyone agrees with that point of view.

Another plausible suggestion is that the universe ends with a 'big crunch' as gravity pulls everything back into one gigantic black hole...the singularity of which then explodes to form the big bang of the 'next' universe. This is simple - but it's starting to look like our universe doesn't have enough dark energy/matter/whatever in it to halt the expansion - so no convenient 'big crunch' will ever happen. However, the 'previous' universes could all have had more matter/energy in them and ended in a crunch - with ours being the first to last forever.

We'll never know though.

SteveBaker 21:06, 1 October 2007 (UTC)[reply]

Be careful, Steve, or Norbert will condemn you to an eternity of hamster racing. Gandalf61 10:23, 2 October 2007 (UTC)[reply]

Trust me, I lie awake at nights fearing that very thing. :-) SteveBaker 14:23, 2 October 2007 (UTC)[reply]

In reference to God being invincible because he is all powerful: it should be noted that a necessary property of an all-powerful being would be the power of removing that power from himself. So, an all powerful being could technically commit suicide. If not, then there would be one thing which he could not do and thus he would not be all powerful. I believe the Zoroastrians had a dialog about this. I didn't see it in the article, but I'm sure they challenged several apparent properties of God.
Mrdeath5493 05:27, 3 October 2007 (UTC)[reply]

And you're assuming the concept of non-existence has any meaning to an all-powerful being. I believe, as the famously nonsensical quote goes, "There definately exists something, namely, nothing." You might say that we, in our universe, have a concept of nonexistence, but what if the entirety of the universe is the functional equivalent of a passing thought in the mind of an all powerful entity? And so our apparent concepts of existence may have no real meaning. Although, if the all powerful being can imagine it, then can't he make it...really real? I have one answer to all of this: meh. Someguy1221 06:24, 3 October 2007 (UTC)[reply]

Alright, there is a big difference between non-existence and intangibility. I think you might be equivocating the two. The phrase "nothing exists" has two meanings.

1. Either there is nothing whatsoever in existence. (Which can't be true if you are discussing it), OR
2. The concept of "nothing" exists.

Even if we are a passing thought in the mind of an all powerful being, there is one necessary condition of that situation: An all powerful being must exist. Otherwise we couldn't be a passing thought in his head; and, the rules still apply there too. Now, an all powerful being can do anything. So he could definitely exist while being intangible (i.e. the Christian God). However, he can't both 'not exist' and 'be all powerful'. This is because for something to have any property whatsoever, it must exist.
I believe a main theme of your statement though was how can we draw conclusions like this based on our perceptions and definitions if we have no way of verifying their ultimate truth and reliability? The answer is: it is the best we can do. Unless one of us is going to pass out of this dimension to a theoretically unquestionable position of ultimate understanding of everything, and then come back and let us know if our unique conception is reliable, then we will never know whether or not it is. Also, we can never escape the way our brains organize and conceive. So, we can never change it and can't verify it (ultimately). If you want to take the position that our perceptions might be unreliable go ahead, but then you'll never actually 'know' anything. However, most people value the type of knowledge we can arrive at through our unique understanding, so we might as well trust it until there is a reason not to. (Big correlation: this is the goal of science. We want to come as close to the perceivable truth as possible.)Mrdeath5493 18:06, 5 October 2007 (UTC)[reply]

Mix dogs

Aside from the obvious physical difficulties, is it possible to get puppies from dogs of very different sizes? Are there examples of puppies from say a great dane and a chiwawa? If it doesn't work what other characteristic would it need for them to be different species? 80.200.230.7 21:49, 1 October 2007 (UTC)[reply]

Yes - all dogs can interbreed between breeds. SteveBaker 23:05, 1 October 2007 (UTC)[reply]

Dogs are in fact all of one species, and they can therefore breed and produce fertile offspring whether they are poodles or Mexican rat terriers. In fact, the subspecies of dogs, Canis lupus familiaris falls into the same species as wolves, so dogs and wolves can actually interbreed. - Nunh-huh 23:09, 1 October 2007 (UTC)[reply]

You might find reading Poodle hybrid interesting (though as far as I know poodles can be of various sizes) ---- Xil...sist! 23:16, 1 October 2007 (UTC)[reply]

(I think this user is talking more about the obvious physical differences.) Probably only if the chiwawa is the male. . . --S.dedalus 00:10, 2 October 2007 (UTC)[reply]

There can be a problem of, well, "mechanics" when two dogs of very different sizes attempt to mate. But, I once saw a video of a small dog trying to mate with a rather annoyed-looking lioness, so anything is possible. StuRat 00:12, 2 October 2007 (UTC)[reply]

I've often wondered what the offspring of a chihuahua and a Great Dane would look like. -- JackofOz 01:05, 2 October 2007 (UTC)[reply]

Apparently others have wondered before me - Wikipedia:Reference desk/Archives/Science/2007 February 5#Dog breeds -- Help! -- JackofOz 05:53, 4 October 2007 (UTC)[reply]

The whole idea that you can divide the world's population of animals into different species, such that healthy adult individuals of appropriate sex can produce fertile offspring if and only if they are of the same species, is only an approximation. Species like dogs with a wide range of sizes are one exception. For another class of exceptions, see ring species.

Incidentally, there is an analogous problem with the idea that the different ways of speaking in the world can be divided into different languages: see dialect continuum. --Anonymous Homo sapiens speaking some sort of English, 13:37 UTC, October 2, 2007.

Artificial insemination could be used to bypass the physical problems. — Daniel 22:35, 2 October 2007 (UTC)[reply]

Only the first one. There's also the matter of the size of the puppies. Although I must admit to having no experience with how the sizes of different breeds' puppies vary. --Anon, 00:54 UTC, October 4.

Is this a new question?

If there is so many breeds of dogs, why aint there more breeds of humans? Is this a new question? —Preceding unsigned comment added by 88.109.239.189 (talk) 00:14, 2 October 2007 (UTC)[reply]

See Selective breeding --S.dedalus 00:24, 2 October 2007 (UTC)[reply]

On the first part, you've made it so, so yes it is now.

On the second part, humans almost went extinct a few million years ago (when was that again), so they started off with a very narrow gene pool. As for dedalus' answer, he means humans have pushed the limits of what one could squeeze out of the canine gene pool. Natural selection doesn't work like that. It only creates the useful varieties. DirkvdM 07:40, 2 October 2007 (UTC)[reply]

There are plenty of breeds of humans. I see groups of people at least as different from one another as, say, a German shepherd is from a Rhodesian ridgeback, and that's without even looking at different races. We're all the same species, genetically speaking, but if you ask me we're not by the taxonomical definition: Organisms are said to be of the same species if they normally interbreed. There are plenty of girls who wouldn't normally interbreed with me, and that's a fact (for the humor-impaired, that was a joke with a germ of truth in it). And I have to say that I don't think natural selection applies to humans the same way it does to the other animals. "Usefulness" of traits in humans depends on more than a trait's contribution to mere physical survival; a person's accidental resemblance to a famous person can confer advantage, for instance. Humans can alter their environment, too, allowing even those who made no contribution to altering it to survive, and we help one another survive things that would kill any animal no matter how social it was. --Milkbreath 12:37, 2 October 2007 (UTC)[reply]

I disagree - there are strong evolutionary pressures on humans - we are most definitely still evolving - check out lactose tolerance for example - we've evolved that trick over just the last few thousand years. With dogs, we intervened and things are different. There are two ways to look at what happened:

We deliberately bred them in ways that are contrary to evolution - often looking after dogs that could never survive in the wild in order to prevent evolution from culling the 'useless' ones that we happen to like.

...OR...

Dogs (like all animals) evolve to exploit the prevailing environment. In a world full of humans - with food, health-care and all other needs fully taken care of if you are a pet - it makes sense that dogs would evolve to fill the niche of being a 'pet'. If a particular kind of 'look' or temperament pleased humans then those breeds of dog got to breed on into the next generation. Breeds of dog that look terrible or bite their owners generally don't get to breed - (or at least they don't get kept as pets - so they are tossed out into a hostile environment that they aren't evolved to cope with) so they die out. In a sense, dogs are evolving to suite humans.

There is no similar pressure on humans - we evolve to suite our environment - at the same time as we are changing our environment, that's true. For there to be more than one species of human, there would have to be two different environments and very little gene interchange between the populations in those environments. With the prevelence of international travel - it's hard to imagine a population getting cut off from the rest of the world for tens of thousands of years with no genetic interchange. Sure, we're evolving - but without prolonged separate gene pools, we can't become different enough from each other to form separate species because any new gene gets stirred into the pot almost as soon as it appears. We can't build up enough genetic differences to get to the point where we can split. It's worth pointing out though - that even the more extreme differences between dogs don't yet qualify them as separate species - they can all still interbreed. SteveBaker 14:13, 2 October 2007 (UTC)[reply]

There are human gene pools that have been cut off from each other for tens of thousands of years, and birds of a feather still tend to flock together. (I'm deliberately avoiding giving examples to avoid this discussion becoming what such discussions too often do.) I'm not really saying that there are different species among humans, but only because I consider species to be defined genetically and not "culturally". Our minds can completely override any of our instincts, if instinct can indeed be said to come into play at all, and people of the most disparate genetic makeups imaginable will marry and have children, and no big deal. Certain monkeys, however, who live not far from each other, will not breed because of a slight difference in the patterns of their markings. This amounts to cultural selection. We humans have that, too, to the point where traits are selected for that confer no direct survival or reproductive benefit. If a culture selects for the ability to grow a good moustache, for instance, that culture is playing the same role in molding humans as humans do in molding dogs. --Milkbreath 16:52, 2 October 2007 (UTC)[reply]

Either I don't understand what you're saying or I don't agree. Artificial selection is different from sexual selection... Sexual selection is part of natural selection, artifical selection is not. Artifical selection is one species specifically breeding another species often without any real regard other then their what suits their requirements based on conscious thought. It means amongst other things that, artificial selection is still usually a lot faster and is goal directed. Sexual selection as it occurs in many animals including humans is only occuring within one species and is part of evolution. While it's true that sexual selection can similarly result in traits which are not directly an advantage evolutionary wise the two still aren't the same thing. Even taking into account cultural influences on sexual selection including the fact that individuals not involved directly in the reproductive event have an influence IMHO it's still useful to have the distinction (in humans obviously people like priests, leaders etc; in other animals there is probably also some influence e.g. the matriach in elephants). I guess at the extreme of eugenics especially for example those advocates by the Nazis, it get's very hazy although even in this case, it's still within one species. (Of course if you believe some conspiracy theorists, aliens may be artificially selecting humans and some religious people who accept evolution believe God/gods are influencing us so could be said to be involved in artificial selection) Artificial selection may also have some similarities with co-evolution (although the selective pressure on humans is IMHO usually very limited) but there are still many differences IMHO Nil Einne 18:59, 2 October 2007 (UTC)[reply]

(edit conflict) My theoretical "moustache" example was not intended to be sexual selection. I didn't mean that women like the tickle, I meant that both sexes would perceive a good moustache as a desireable trait. The magnificently moustachioed would enjoy material and social advantage in additon to sexual. The male body is thus modified by selection in the same way we modifiy dogs for inessential physical characteristics. I think this would be a form of artificial selection, with culture as the agent. This is not deliberate, granted, but the result is the same. I don't want to put too fine a point on it, but I'm contending that humans have undergone a kind of de facto artificial selection within cultures, and that we have, especially recently, thwarted natural selection both positively and negatively with modern medicine and modern warfare. We're talking about breeds, not species, remember. The original question was why there aren't many breeds of human. I say there are. (And, in case you're wondering, my moustache looks like a pair of eyebrows, so I don't grow it.) --Milkbreath 19:36, 2 October 2007 (UTC)[reply]

What you are saying is of course true - but you can look at it from another direction.

From a human perspective: You breed a new kind of dog by getting a few litters of puppies from a different breed (or breeds) of dog - and you pick the ones that are most like what you want - and breeding from those while you neuter the others to prevent them from reproducing. From the human perspective, we artificially selected the right puppy - so this is 'artificial selection'.
From the dog/dog-gene's perspective: The environment the dog is evolving to fit is an unusual ecological niche where it is a parasite (or at least a symbiote) of a human family. In order to engage in this parasitic behaviour, it must not displease the humans by biting their kids - and it must meet various other arbitary criteria. Those animals that pass the test are those most likely to have offspring - classic 'survival of the fittest' where 'fittest' is defined as 'most able to reproduce in their environment'. But in the end, from a gene's point of view, this is no different to evolving to suite a new food source or to being able to hunt in a different set of weather conditions...it's just an environment that it's optimising itself to fit. The genes that most suited that environment were the ones that survived into the next generation - which is natural selection. The only unusual part is that the survival/not-survival rate is an unusually hard cut-off, so evolution happens fast. SteveBaker 19:14, 2 October 2007 (UTC)[reply]

My opinion is it's best to look at it from neither perspective. From an external perspective, one species is consciously selecting another species to achieve an outcome they desire. The second species may be 'evolving' within the environment provided by the first species but the fact that this first species has a conscious goal directed selection role is IMHO an important distinction from natural selection to most extents. The mechanisms may be the same, the outcomes may be somewhat similar to possibilies but the process has an important distinction Nil Einne 19:33, 2 October 2007 (UTC)[reply]

First, there can never be a "breed" of human because the word "breed" simply means a domesticated subspecies. So we are talking about subspecies here. In that case, there possibly has been subspecies of Homo Sapiens, including Homo Sapiens Neanderthals. As for existing subspecies, there are none that currently exist. The "races" are mostly social constructs, but there are certainly differences in skin color and facial features (like eyes) that are due to geographic distance and evolution. However these differences are not considered to be significant enough to be classified as different subspecies of Homo Sapiens. In addition to that there is a significant amount of gene flow which inhibits speciation. With airplanes, ships, etc, one can travel to the other side of the world in a short period of time. Because of this, there are no isolated groups of humans anymore, and people are free to travel and mate with anyone from any other culture if they so choose. This inhibits speciation, and thus the likely hood of subspecies arising is diminished. Malamockq 01:21, 4 October 2007 (UTC)[reply]

I highly recommend reading "Why We Should Not Name Human Races - A Biological View" by Stephen Jay Gould. It does an excellent job of explaining how "breeds", "races", and other terms simply make no sense for species like humans where the differences between organisms are on a continuum, as opposed to being separated by some major gap that implies a new species is about to emerge. Since written history began, no group of humans has ever been so isolated for a long enough amount of time for speciation to be a realistic possibility. --M @r ē ino 17:42, 5 October 2007 (UTC)[reply]

Locust flying speed

What is it? page does not say —Preceding unsigned comment added by 88.109.239.189 (talk) 23:38, 1 October 2007 (UTC)[reply]

~3.5 m/s or about 7.8 mph. [10]. Someguy1221 23:48, 1 October 2007 (UTC)[reply]

Note, however, that the flight speed of an individual locust is much higher than the rate of progression of a locust swarm. Each individual locust flies and then stops, and each flight is at some angle with respect to the average vector of the swarm. for example, assume that on average an individual locust spends 10% of its time flying and flies on average at an angle of 45 degrees to the average direction of the swarm. Then, the rate of progression of the swarm would be 0.1/root 2 of the flight speed of the average locust. -Arch dude 01:59, 2 October 2007 (UTC)[reply]

Swarm mechanics are much more complicated, though. Each individual's path can be thought of as a diffusion problem with a random walk. This results in a spreading swarm of ever-decreasing density. To counter that phenomenon, a "swarm" mentality exists which causes locusts to fly towards other locusts. The net motion of the swarm is a product of the random motion, as well as external stimuli such as a wind or light gradient, or the scent of food, etc. See boids for some simulations! Nimur 04:45, 2 October 2007 (UTC)[reply]

October 2

Weighty of charge

I think about charge and current. what is weight of charge and current plese? —Preceding unsigned comment added by 88.109.239.189 (talk) 00:17, 2 October 2007 (UTC)[reply]

An electron has a mass of 9.109 382 15(45) × 10^–31 kg, but I'm unsure if charge has mass. Does the negative electrode of a capacitor gain mass when charged? anonymous6494 02:47, 2 October 2007 (UTC)[reply]

Along the lines of a capacitor gaining mass, I`ve wondered if a rechargeable battery is just a teeny bit more massive when fully charged compared to when it`s exhausted. I would have to guess yes. Is that correct? I suppose any kind of battery could also apply. Thanks, Dave 64.230.233.209 03:33, 2 October 2007 (UTC)[reply]

The electrons may be on the negative electrode, but they have been taken away from the positive electrode, so the net change in mass of a capacitor is nothing. However there will be some relativistic mass (E=mc²) due to the energy stored. The same will apply to the battery. Electrons are just mvoed from one place to another, so the mass of electrons in the battery is the same when it's charged as when it is empty. Graeme Bartlett 04:06, 2 October 2007 (UTC)[reply]

Could you not use a static-discharge to transfer electrons to one plate of a capacitor without having electrons drained from the other plate? Something like the active part of an electroscope. I don't think net total charge (i.e., electron count) needs to be conserved in a non-closed system, so how about looking at mass change in only one part of a closed system before/after creating electron imbalance of that part with respect to some other part. DMacks 04:27, 2 October 2007 (UTC)[reply]

Static charge capacitors with the other plate at infinity (or earth) have a low capacitance and cannot store much charge. You will be working hard to get a nanofarad of capacitance, and if you combine that with the mass of the electrons involved - you will get very little mass. Graeme Bartlett 00:11, 3 October 2007 (UTC)[reply]

Charge itself has no mass. Charge is a fundamental property of a particle, just like rest mass is. Asking what the mass is on charge is as meaningless a concept as asking what the mass of a velocity or the charge of a temperature is. They simply have no such inherent relationship. Someguy1221 04:49, 2 October 2007 (UTC)[reply]

According to our electron article, each electron has a mass of 9.109 382 15(45) × 10^–31 kg and a charge of –1.602 176 487(40) × 10^–19 C. This gives us a mass per charge of -5.7 x 10^-12 kg/C or -5.7 x 10^-9 g/C. The negative value means that you will subtract some mass for objects with a positive charge and add some mass for objects with a negative charge. This all assumes that the charge is in the form of ionized atoms, and/or free electrons. Free protons have a positive charge and are much heavier. StuRat 14:24, 2 October 2007 (UTC)[reply]

If you took an uncharged capacitor of huge capacitance, say of 1 farad and, and charged it with electricity, the energy stored in it would increase by 1/2*(capacitance)*(voltage)² Joules. The equation for mass and energy says E= mass*c² (where c is the velocity of light, approx 3 x 10⁸m/sec. If it were charged to 100 volts (a very high voltage rating for such a large capacitor), the increase in energy would be 5000 Joules, indicating a mass increase of 5.6 x 10^-14 kilograms, probably not detectable by any existing means, especially considering the mass of such a large capacitor. If it were charged to 1000 volts, the mass increase would be still only 5.6 x 10^-12 kg or a thousandth of a microgram, still unmeasurable in a capacitor probably weighing over a kilogram. (Please check the math, formulas, and analysis). Edison 14:39, 2 October 2007 (UTC)[reply]

I don't think that formula is applicable here. That only applies when mass is converted to energy (as in a nuclear reaction) or vice-versa. That doesn't happen in a capacitor. StuRat 14:54, 2 October 2007 (UTC)[reply]

It applies to everything. E=mc^2 is right no matter where the energy came from. Someguy1221 16:38, 2 October 2007 (UTC)[reply]

In a completely unrelated question, would that mean that a warm cup of coffee has a very slightly higher mass than a cold one? —Preceding unsigned comment added by 66.28.242.74 (talk) 17:40, 2 October 2007 (UTC)[reply]

Much higher since the cold one has already lost a lot of steam while it was hot and the hot one is still losing steam :D --⁪froth^t 18:00, 2 October 2007 (UTC)[reply]

Yes. Ignoring evaporation, the hot cup of coffee will be very slightly heavier. If you want to think in terms of exactly where the mass is, the particles in the hot coffee will be moving faster, and therefore possess more relativistic mass. Someguy1221 00:23, 3 October 2007 (UTC)[reply]

If you wind as alarm clock, it gets heavier (by a tiny undetectable amount). If you accelerate a subatomic particle in a cyclotron, to an appreciable fraction of the speed of light, and fail to allow for the mass increase, your results will not be as anticipated (per old cyclotronists). The meaning of the "weight of current" is harder to interpret. Current into a conductor equals current out, so at first blush current would seem to have no weight. Edison 05:15, 3 October 2007 (UTC)[reply]

Another tick question I just thought of...

Is it possible for a tick to transmit HIV from one human to another? --Kurt Shaped Box 00:28, 2 October 2007 (UTC)[reply]

theoretically yes, practically no. Each individual tick (or mosquito or other arthropod vector) almost never attacks more than one human. Ticks in particular usually attack an animal host and then a human host. The chances of a particular human being attacked by a tick that had previously attacked a HIV-infected human are vanishingly small. A flea is theoretically more likely, but I have not seen any reports in the literature. -Arch dude 01:42, 2 October 2007 (UTC)[reply]

But leeches are another matter. Our article states that blood borne illnesses can be spread through a leech biting an infected person. --S.dedalus 01:45, 2 October 2007 (UTC)[reply]

Does water expand when heated?

If a glass of water is heated from 20 Celsius to 80 celsius, does the water expand and become less concentrated? Acceptable 01:28, 2 October 2007 (UTC)[reply]

Yes the water will expand a very small amount and become less dense, if that is what you mean by concentrated. See the section on water density. Sifaka ^talk 02:05, 2 October 2007 (UTC)[reply]

The table in that article stops at 30°C, but I have here the CRC Handbook, 67th edition. It gives the density at 20°C as 0.99823 g/ml and at 80°C as 0.97183, so the "very small" increase in volume is more than you might think -- a bit over 2.7%. At the boiling point the density is 0.95838, so from room temperature to boiling, water expands by over 4%. This relatively large expansion is why it was possible for some early thermometers to use water as a working fluid; but of course they would not be usable with temperatures close to freezing, where water stops contracting as it gets colder and starts expanding again. --Anonymous, 13:48 UTC, October 2, 2007.

This is also (at the moment) the major contributor to sea level rise, not melting ice, as most people think, although that might become the major factor in the future. DirkvdM 07:42, 2 October 2007 (UTC)[reply]

This business of water expanding as it gets close to freezing is an extremely rare thing - there are only a handful of substances that do this. It's also the reason why your water pipes can split if they come close to freezing. The metal of the pipe is contracting with the cold - but the water expands and something has to give! But above those low temperatures water behaves like almost every other substance and expands as it gets warmer. SteveBaker 13:55, 2 October 2007 (UTC)[reply]

The water expands when heated alright, look at the overpressure valves dribble on hot water systems; or have a long, hot shower so the hot water system has only cold water in it, wait until the water is fully hot again then open a tap. The pressure is noticeably greater (the water spurts out at higher pressure than usual). This is particularly noticeably where the water pressure is normally fairly low.Polypipe Wrangler 06:50, 6 October 2007 (UTC)[reply]

FYI, I think some people may be confused about water expanding as it cools, and also expanding as it is heated. The most dense water (at least at normal atmospheric pressure) is I believe 4 Celsius. Many lakes are permanently 4 C at the bottom because it is heaviest and sinks. —Preceding unsigned comment added by 99.233.83.143 (talk) 16:19, 6 October 2007 (UTC)[reply]

Atoms

How can one determine the number of neutrons in an isotope. Marlith ^T/C 02:54, 2 October 2007 (UTC)[reply]

See mass number. --24.147.86.187 02:57, 2 October 2007 (UTC)[reply]

Wow, that page is amazingly verbose for such a simple concept. Let me summarize that page for you: atomic mass = protons + neutrons. DONE. Assuming you know the number of protons and the atomic mass, you should be in good shape. --Ybbor^Talk 03:01, 2 October 2007 (UTC)[reply]

Except that's not 100% true, especially for isotopes. Atomic mass is not the same thing as the mass number, which is simply a total of neutrons plus protons; atomic mass also has electrons involved, and the mass of isotopes can be slightly different than the mass number, and can deviate from their mass numbers based on their mass defect. So you have to make sure you are always rounding atomic masses, essentially, before you try to use them to calculate neutrons. --24.147.86.187 12:36, 2 October 2007 (UTC)[reply]

Yes - but the error is truly microscopic in all but the most exotic elements. We have:

'atomic number' -- the number of protons - which determines what we name the atoms and how many electrons they have when they are electrically neutral - which in turn determines most of their chemical properties).
'mass number' -- the number of protons+neutrons - which determines which isotope you have. Two atoms with the same mass number may have a different number of protons, so they may have wildly different chemical properties.
'atomic mass' -- the actual mass of an atom. The mass includes protons, neutrons and electrons. Since a proton weighs 1.007276 atomic mass units and a neutron is a little more at 1.008665 units and the electron is 0.000548 units - you can see that roughly, protons and neutrons have masses of almost exactly 1 and the electron weighs almost nothing - so the atomic mass is going to be almost exactly the same as the mass number but with a few extra digits after the decimal point.

So if you have the mass number and that atomic number, subtract them to get the number of neutrons. If you only have the atomic mass and the atomic number, then chop off all of the digits after the decimal point of the atomic mass to get the mass number and then subtract the atomic number. (This rule breaks for the very heaviest atoms - Darmstadtium for example has a mass number is 281 but it's atomic mass is 282 - but I think the rule works OK up to maybe Dubnium - you'll never care about this fact!)

SteveBaker 13:50, 2 October 2007 (UTC)[reply]

Also, in reference to the second answer, the mass number changes with each isotope. The atomic mass for any element is an average of all the possible isotopes' masses in relation to their abundance.Mrdeath5493 05:14, 3 October 2007 (UTC)[reply]

Foucault Pendulum Animation

I can't seem to wrap my mind around what this animation is trying to do. I think I understand foucault pendulums (it goes back and forth in the same plane relative to the stars, but since the earth is moving, the ground turns under it. Also the whole apperatus is moving around the earth's axis) but this image seems to contradict it. Shouldn't the the pendulum's swing be the same from the star's point of view? The animation is from the star's point of view so why does it spin? The spin would only be accurate if the earth were moving under it and the image was relative to the pendulum. Or is this only valid if the pendulum's on the north pole? Even so the image seems wrong. Aargh, it's hard to visualize things spinning while stuck on the surface of a rotating sphere.. can anyone help? --⁪froth^t 04:33, 2 October 2007 (UTC)[reply]

I also wonder about the accuracy of that image. It's sort of hurting my head right now, so I'll think about it some more and report back. Nimur 04:49, 2 October 2007 (UTC)[reply]

I'm not going to view the image right now, but it's not correct in general that a Foucault pendulum goes back and forth in the same plane relative to the stars. Its initial plane of motion is determined by three points: the fulcrum F, the center of the Earth E, and the location B where the bob is released. As the Earth rotates, points E and F must remain in the pendulum's plane of motion, but point F is moving and will not (in general) remain in the original plane. The plane of motion thus rotates with respect to the stars as well as with respect to the Earth. --Anonymous, not moving right now with respect to the Earth, 14:00 UTC, October 2, 2007.

*explodes* x_x I see how this is possible and I can look at the animation and imagine it making sense at the north pole where the earth is spinning under it and the fulcrum is stationary, but at an angle when the fulcrum is moving too, it... zomg I see it, it's working hah! thanks --⁪froth^t 17:58, 2 October 2007 (UTC)[reply]

The surface of the Earth has intrinsic Gaussian curvature, so parallel transport of a vector around a closed curve may result in a net change in direction. See also Geometric phase#The Foucault Pendulum. —Keenan Pepper 02:45, 3 October 2007 (UTC)[reply]

Dimensions in a World

04:47, 2 October 2007 (UTC)210.0.136.138AHow many dimensions exist in the real world? And, how does this really mean to human beings? Can a specific person exist in a separte world of different dimensions, if that exists. Is it true that Eistein has already affirmed this?04:47, 2 October 2007 (UTC)210.0.136.138Allen Chau, from Hong Kong[reply]

There are as many dimensions as we define to exist. See degrees of freedom. One might say that the number of dimensions is equal to the rank of the system matrix. Alternatively, one might choose to describe the spatial extent of an object, which would only include three dimensions. One might also choose to represent system space in terms of phase or velocity - so we could easily have six dimensions. These concepts are quite complicated, but in short summary for layman's purposes, there are as many dimensions as we feel like adding to describe the situation at hand. Most systems can be easily described with three spatial dimensions (and often time as an additional dimension). Nimur 04:53, 2 October 2007 (UTC)[reply]

I think the OP was referring only to the commonsense meaning of "Dimension" as in space and time dimensions. We can plainly see three dimensions in space, and only three. As Einstein explained, time can be thought of as a fourth, somewhat wierd dimension. This gives our world four dimensions that we can observe. No higher dimensions have ever been observed, ever. Now, if a person were to exist in an "alternate set of dimensions" he'd better damn well be in another universe in the greater multiverse, or one of the many-worlds, because if he isn't, there's pretty much nothing but speculation to explain it (er, those first two were also speculation, but they've been floating around for quite a while). Now, the only remotely close to accepted theory that allows alternate dimensions to exist in our own universe without our observing them is string theory and its variants, but absolutely nothing can occupy these unobservable dimensions (except for strings themselves, which can sort of wiggle around in them). Everything you've seen on Sci-Fi shows about a person entering an "alternate phase" or something like that, and suddenly no one can see him, is entirely bullshit. Someguy1221 05:01, 2 October 2007 (UTC)[reply]

Mathematicians and scientists often deal in higher dimensions and calculate things using them. They can be assumed to exist on a theoretical level, in the same way that the square roots of negative numbers are assumed to exist on a theoretical level. These assumptions are useful in such contexts. But whether any human mind can actually visualise or even comprehend what they mean, outside of such theoretical considerations, is a moot point. -- JackofOz 13:05, 2 October 2007 (UTC)[reply]

Why do you say that? Have you ever read Flatland? The 2 dimensional people would have had 2 dimensional physics and called time the 3rd, and told their ref desk OPs that it's nonsense to think that you can just poof out into the 3rd dimension.. which of course the sphere does in the story, baffling their scientists --⁪froth^t 18:05, 2 October 2007 (UTC)[reply]

Erm, what? Flatland is fiction, by the way. In modern physics, if a spatial dimension exists, there is utterly nothing to prevent any particle from moving through it. And so there would be some quite severe consequences. For example, chirality could not exist in three dimensional objects, which would conflict quite severely with many observations in chemistry. That's just the simplest to imagine example (in my opinion) of where the existence of a fourth spatial dimension would alter the laws of physics (er, chemistry, whatever). Now, string theory does allow wierdness like the existence of extra dimensions that are unobservable to only some observers. For example, every particle on in the universe could be bound to a "three dimensional surface" of a higher dimensional object. Thus, as if flatland were on the surface of a sphere, we would exist in a higher dimensional universe we could not observe. And this does not necessarily prohibit other objects, universes, whatever, from not being bound and limited by this three dimensional surface we are bound to. The problem is that string theory is presently unverifiable. So it is quite correct to say that there is no accepted theory in physics that would allow the existence of unobservable spatial dimensions. Someguy1221 20:08, 2 October 2007 (UTC)[reply]

You can define any point in space relative to some fixed coordinate system using three distances. This makes it a three-dimensional world. If you follow Einstein and wish to employ the mathematical convenience of talking about 'space-time' then you need to add one time measurement. This makes three or four dimensions depending on what you are trying to measure. Nimur's degrees of freedom argument is wrong because that's an argument about measuring things other than space itself. You can choose to measure space with things other than three distances - but no matter what, you always need just three numbers...so for example, you can measure every point in space using two angles and one distance ('spherical polar coordinates') or one angle and two distances ('cylindrical polar'). In space/time, you always need four numbers. The exact formulation doesn't matter - the dimensionality of space (or space/time) doesn't change depending on how you measure it.

The extra dimensions that string theory predicts are claimed to be 'very small'. Understanding what this means is tricky - we have do take it in small steps:

Suppose for a moment that we were observing some two-dimensional creatures - living on the surface of a flat piece of paper. In our present world view, the paper is flat and infinitely large. There is no 'up/down' dimension for them because they are 2D creatures - they only have left/right and forwards/backwards.
But suppose one of those two spatial dimension (let's pick the left/right dimension) was 'small' - just a 10 miles across say. The universe can't have 'edges' - it has to 'wrap around'. By this, I mean that moving in the left/right dimension for exactly 10 miles would take you all the way around that dimension and back to where you started - for a 2D creature this would be a bit strange - but for us 3D creatures watching them, it would be like they were living on the surface of an infinitely long cylinder of paper that's just one mile in diameter. They could move as far as they wanted along the length of the cylinder - but if they moved a long distance in the other direction, they'd go all around the cylinder and back to the start. Because their 2D light beams are stuck in the 2D surface, if they looked off to the left or right using a pair of decent binoculars, they'd be able to see themselves 10 miles away.
In a three dimensional universe like ours, if our up/down dimension was only 10 miles across then you'd be able to travel as far as you wanted left/right or forwards/backwards - but if you moved upwards by 10 miles (or downwards by the same amount), you'd be back where you started. Also, if you were out in space and looked up using a pair of binoculars, you'd be able to see your own feet, just 10 miles away. Looking left or right or forwards or backwards - and everything looks kinda normal.
Now - imagine that third dimension isn't 10 miles across - but just one millimeter across. We would be almost like 2D beings - almost all of our existance would be in two dimensions since nothing in the universe could be more than a millimeter in height - and moving up or down would have almost no effect on your life. That third dimension exists - but it's hardly any use at all. We would have to be almost perfectly flat creatures - it would be ALMOST a 2D world...but not quite.
Now imagine that instead of the up/down dimension being a millimeter across, it's much MUCH smaller than the diameter of an atom...in that case we'd have no way to know that there even was a third dimension - it would seem exactly like being in a flat, 2D world since any motion at all in the 3rd dimension would have no effect and no object could be as tall as even an atom...atoms themselves would have to be almost exactly 2D objects. We wouldn't even know that the up/down direction existed at all. It the third dimension were that small, we might as well be living in a 2D world for all that it would matter to us.
OK - so back to a normal 3D world. What would happen if there were a 4th dimension? Well - we can't see it, measure it...it's not in any way detectable...so we might jump to the conclusion that there isn't one. But if the 4th dimension existed but was very small (much less than the diameter of an atom) - then it could very well be there but we'd be totally unaware of it...unable to detect it. It would SEEM like we were living in a 3D world.

The string theorists claim that there are DOZENS of extra dimensions beyond the three we can normally experience - but all but the first three are so small that we can't tell that they are there - even with the most sophisticated equipment we have. I've heard these extra dimensions described as being 'rolled up'. They might very well be correct - but we have no way to know.

SteveBaker 13:16, 2 October 2007 (UTC)[reply]

Just to note: dimensions aren't like they appear in cartoons. They aren't alternative worlds somehow layered on top of ours where aliens live (though note that in the many-worlds interpretation of quantum mechanics—something entirely distinct from the idea of "dimensions" in science—there can in fact be multiple layered realities). They aren't ways to conduct psychic or supernatural phenomena. They are different ways in which geometry can be expressed in the world in which we live, basically. The dimension of time can be as mundane as noting that things change — the apple disintegrates on your table as it moves through the time dimension. Dimensions are not all that exciting, from a science fiction point of view.

Einstein's work, via Minkowskii's interpretations of it, basically reduced discussions of time and space to questions of geometry, and emphasized that time has a geometrical, spatial component to it. This is why he is often credited with introducing the idea of time as a fourth dimension, though he was not really the first person to introduce such an idea and in fact most of our understanding of "Einstein's work" in this regard is through the filter of Minkowskii, who "geometricized" Einstein in really wonderful ways. --24.147.86.187 13:50, 2 October 2007 (UTC)[reply]

I'm not sure that I'd say that extra dimensions are not exciting in a science-fiction kind of way. If there are more than three spatial dimensions and they are 'small' (per string theory) then, indeed, they aren't much fun. But if there were a fourth dimension - but something about our minds/bodies/physics meant that we somehow couldn't percieve it - then indeed there would be sci-fi possibilities. An ability to move in that fourth dimension would allow you to do some pretty incredible tricks. Escaping from a locked (3-dimensional) room might be as simple as taking a step in the 'other' dimension, walking past the room then taking a step back again into our normal world. It would be like trying to imprison a 3D person in a 2D rectangle - they'd just step out of it using the 3rd dimension. You'd be able to tie knots that would be impossible to untie...all sorts of weird stuff. A lot of people worry about what the 4th dimension would look like - but that doesn't bother me at all - we can use computer graphics to simulate exactly how a 4D world would project onto 2D retinas just as we understand how a 3D world projects onto a 2D retina. The ikkier thing to contemplate is that some of the string theorists want more than one time dimension - and that's really hard to get one's head around. We can guess what 4D space would be like to 3D beings by analogy with how 3D space would seem to 2D beings. But we only percieve 1D time - and we can't use analogies to extrapolate out to 2D time...it's a real head-spinner. SteveBaker 15:19, 2 October 2007 (UTC)[reply]

There's a very clever little story along these lines by Heinlein, called ...and He Built a Crooked House. The opening half-page alone is worth the price of the anthology you get the story in. An LA architect builds a house in the shape of a tesseract, but cut open and unfolded into three dimensions, as you might cut a 3-d cube and unfold it into a 2-d shape. Then there's an earthquake....

The story is very carefully constructed to be geometrically accurate and it's an interesting exercise to verify that. A few details, like what happened to certain walls, are sloughed over, but after all it's just a story. --Trovatore 17:34, 2 October 2007 (UTC)[reply]

As I linked above, you might too enjoy Flatland. Many people (including myself) report it being much easier to visualize and work in additional spatial dimensions after reading flatland. I disagree with 24.147 and the other guy that extra dimensions aren't like cartoons- stevebaker's got the right idea from a common sense approach, which is what I'm inclined to believe since string theory isn't really demonstrated by anything in our real world -⁪froth^t 18:10, 2 October 2007 (UTC)[reply]

Yep - I agree, I'm quite doubtful that String Theory will ever be shown to be correct. It's a shame because it's very elegant - and correct things are usually elegant! But a theory that's unfalsifiable is not acceptable - so unless there is some kind of major new breakthrough, I think we have to put string theory back on the shelf and go back to looking for something else. SteveBaker 18:34, 2 October 2007 (UTC)[reply]

Despite all this talk of "rolling up" and string theory, I stand by my original assessment - there are exactly as many dimensions as we choose to model. I have worked physics problems which are not "wacky" (String Theory), but still imply high dimensionality - for example, a triple-pendulum can be described with six or 12 dimensions (perhaps each joint has a displacement, a momentum, and an acceleration; and maybe we want to throw in a nonlinear potential such as a magnetic attraction at each joint to an external magnet). Each one of these dimensions is a physical parameter where motion, displacement, energy, and other physical quantities can "go." We might start calling the dimensions (θ₁, θ₂, ...), (p₁, p₂...) and so forth. Dimensions can interact via the governing equations, derived from fundamental physical laws. We might take care to set up dimensions which are linearly independent and orthogonal, or we might not choose to do so. The system equations would be straightforward, and the dimensions would be quite complex.

I could just as well model the system in three dimensions of an absolute fixed frame, (X, Y, Z) and time (T). These dimensions are very straightforward, but the system equations would become much nastier, since the relationships would become very highly coupled. But, I could never reduce the complexity to fewer than the total number of variables in the system to begin with.

The same can be said of String Theory and any other "magic" theory which introduces a new variable. Decoupling complex interactions into "separate" dimensions is an operation on a mathematical model and does not change the system in any way. Simple transforms are heavily detailed in linear transform. More sophisticated decouplings are the crux of a lot of modern research topics. Nimur 17:34, 2 October 2007 (UTC)[reply]

There is a big difference between using multidimensional mathematics to solve a problem and saying that this many dimensions exist in space. It's not at all the same thing. I too have used as many as 14 dimensions to solve work-related problems in computer graphics...but the world still only has 3 dimensions.

Example: Computer graphics hardware really only draws triangles. If you want to draw a quadrilateral, it is usually split into two triangles. If you have two triangles that you think may originally have made up a quadrilateral - but you really wish (for various arcane reasons) that you could have split the quad along the OTHER diagonal, then you need to check that the two triangles lie in the same plane (if they don't then they didn't come from a quad and swapping the diagonal will do weird things to the graphics). This is a simple 3D problem as you might expect. However, if the triangles have (for example) smoothly varying colours that are linearly interpolated between their vertices - then swapping the diagonal can change the look of the final quad (imagine one triangle has three red vertices and the other has two red and one green - as is, the center of the line between the two triangles is red - but if you swap the diagonal, you get an orange colour in the middle - not at all the same thing). To check that it's safe to re-split it, you also need to check for "planarity in colour space" (Red/Green/Blue space) - so now you are doing a six-dimensional check in X/Y/Z/R/G/B space. But there are other parameters of a triangle in a graphics system such as texture coordinates, surface normal, transparency and so on - and to do a proper job, you need to know that ALL of them are 'planar'. I ended up with 14 per-vertex parameters - so I had to check for planarity in 14-dimensional space!

So yeah - it's easy to end up using math in higher dimensions as a convenient way of solving real-world problems - but that doesn't tell you anything about the number of dimensions of 'space'...which is still (seemingly) three. SteveBaker 18:31, 2 October 2007 (UTC)[reply]

Note that when I said extra dimensions weren't exciting, all I meant is "the current theories of extra dimensions are not that interesting when compared with the way that the idea of extra dimensions is invoked in popular fiction." You know, dimensional gateways, portals of alien worlds, etc. That's all. Sure, sure, Flatland, but that's not what most people have in mind when they talk about "dimensions". --65.112.10.56 20:41, 2 October 2007 (UTC)[reply]

I think we're largely in agreement, SteveBaker. Whether we are doing graphics or physics or string theory, adding new variables to the mathematics does not actually change the real system's dimensionality. It's only our model that changes. Nimur 16:01, 3 October 2007 (UTC)[reply]

Yeah - largely. I believe the string theorists claim that all of their extra dimensions are real, actual spatial dimensions - but 'curled up'. So small that we can never detect them. But they need the extra dimensions to give their strings the ability to vibrate in enough different modes to fulfill all of the things that are demanded of them in the theory. Super-strings are very tiny indeed - vastly smaller than an atom - so even the very tiny extra dimensions are large enough to let them vibrate in those directions as well as the usual three. SteveBaker 02:28, 4 October 2007 (UTC)[reply]

To Sweep Mercury

If a little mercury poured on ground and scattered, how can we completely remove it(in a normal condition and out of lab)?Flakture 13:20, 2 October 2007 (UTC)[reply]

http://www.epa.gov/mercury/spills/index.htm, from the article on, you guessed it, mercury. Lanfear's Bane 13:48, 2 October 2007 (UTC)[reply]

If you don't live in the US, you might also want to consult with your local authority or at least check out their website or other documents provided. There may be additional legal requirements or expectations. According to the EPA website, in the US you only have to report a spill of 1 pound/2 tablespoons or more. The minimum could easily be less in other countries and/or could vary depending on where it occurs. You probably should do this for anything more then a thermometer. Also in a lab in particular, there may be additional requirements imposed by whoever owns or is in charge of the lab. You should check with the lab's safety officer if that's not you (if it is you, it is doubly important you make sure you are aware of all legal requirements and check any existing in-lab regulations) Nil Einne 18:07, 2 October 2007 (UTC)[reply]

Check page 23 of Princo's mercury barometer guide. It says to NEVER sweep mercury, and not to use a vacuum. In general, use disposable paper, tape, droppers, etc to collect. --Mdwyer 19:50, 2 October 2007 (UTC)[reply]

calcium phosphate

what is the molecular formula (empirical would work as well) of the above compound? Our own wikipedia entry is kinda confusing. Am I supposed to combine the molecules it lists? --MKnight9989 14:02, 2 October 2007 (UTC)[reply]

The Oxford Concise Science Dictionary OUP, 1984, has the following:- "Calcium phosphate (V) A white insoluble powder, Ca₃(PO₄)₂; r.d. 3.14 It is found naturally in the mineral apatite, Ca₅(PO₄)₃(OH,F,Cl), and as rock phosphate ... The compound was formerly known as calcium orthophosphate." DuncanHill 14:09, 2 October 2007 (UTC)[reply]

Thanks mate. --MKnight9989 14:23, 2 October 2007 (UTC)[reply]

Which we have as tricalcium phosphate while calcium phosphate refers to a group of related compounds. Rmhermen 14:42, 2 October 2007 (UTC)[reply]

Propidium iodide stains only necrotic cells?

According to WP: "Propidium iodide (or PI) ...can be used to differentiate necrotic, apoptotic and normal cells." According to my understanding, PI stains necrotic but not apoptotic and normal cells. Can someone corroborate this? --137.120.3.217 16:46, 2 October 2007 (UTC)[reply]

My first Google hit.....there are others. --JWSchmidt 17:01, 2 October 2007 (UTC)[reply]

patents::??

hey friends i have thought of a completely new way of ignition in ic engine.i am sure that it would increase the efficiency and would be able to every problem related to spark plugs.but i cant experiment on it since it require quite costly trials,what should i do.how/which company.how to get a patent .please help.

regards Reveal.mystery —Preceding signed but undated comment was added at 17:04, 2 October 2007 (UTC)[reply]

Contact a Patent attorney in your area. -- JSBillings 17:26, 2 October 2007 (UTC)[reply]

Or, you might just choose to put this detail on your resume and apply for a job in research as a mechanical engineer. If your system is truly innovative, you should have no trouble finding employ as an engineer. You will probably have an easier time funding your idea if you are part of a corporate, academic, or institutional research group. Most importantly, you will gain the insights of expert peers who can examine your system and help you improve it. Science and engineering, especially in the 21st century, is a collaborative effort. Nimur 17:43, 2 October 2007 (UTC)[reply]

"Science and engineering, especially in the 21st century, is a collaborative effort." — what planet are you living on? Science and engineering in the 20th century is marked by increasing patents, defensive monopolies, and a total fear of litigation. Universities push researchers to patent anything and to patent broadly. True collaboration and free IP sharing on profitable technologies takes place only in fields heavily influenced by the ideology of the open source movement (basically fields with close connections to computer science) and even then they wring their hands constantly about whether or not they should patent or how they are going to avoid patent wars and the like. Whether you think science and engineering should be collaborative in this economic sense does not have any bearing on whether it really is collaborative in this sense. --65.112.10.56 20:37, 2 October 2007 (UTC)[reply]

You can patent it yourself - you don't need a company to do it for you. However, it can be a little tricky to get the language right when you write your patent - it's very easy to not quite patent enough, so that someone can come along with a small variation of your idea and dodge the patent, rendering it useless...or to somehow misword it in some other way that allows a loophole to be exploited. If you are really convinced that this is something special - then certainly you should consult a patent lawyer. I strongly disagree with User:Nimur. Once you have presented your idea in public - without the protection of a patent - they can just take your idea and use it without paying you a cent. So for chrissakes don't put it into a resume or send it to anyone else without having at least applied for a patent. Note that it's enough to have applied for one - it doesn't have to have been granted yet. You can wait YEARS between applying and completing the process. Personally, I would be quite surprised if you could improve on a simple spark gap as an ignition source - and if I were you, I'd DEFINITELY want to do some basic experiments just to prove that it works at all. You ought to be able to do that with something like a small motorbike engine that you could pick up on the cheap. Just to prove that it works - not that it's efficient or better or anything - just to convince yourself that it'll work. If necessary, find someone you trust with the right skills to help you do this. If your idea is truly better/cheaper than spark ignition, you'll make enough millions from it that splitting the rewards with a close collaborator won't be so terrible. The process of patenting something in a bullet-proof manner with lawyers and such isn't cheap - and you wouldn't want to waste that money on an idea that has a fatal flaw. SteveBaker 18:08, 2 October 2007 (UTC)[reply]

The premise of course, is that owning a patent provides legal protection. Gauging the cynicism which pervades the above posts, what makes you think a well-worded patent will protect you from large corporations? You must understand that to defend a patent requires a lengthy legal battle with a very high budget. Even if you are completely legally protected by your fully-encompassing patent, a large legal team may still beat you in court or bankrupt you through legal process. Sometimes that may even be part of the strategy - large legal firms do not have to win, they just have to out-live your budget. A patent is among the most exposing ways to demonstrate your technology - you must carefully detail every mechanism of your system, explaining to the whole world how your system works, and hoping that infringers will be prosecutable. Alternatively, by engaging work as a researcher, you can build up a trusted network of colleagues who will support you, and gain the business infrastructure of a larger organization. These people will be on your side, collaborating with you, you make your product more successful.

When I say "collaborative," I do not mean "open-source" at all. I mean that large engineering projects cannot be operated by a single person. You need a team of engineers, a legal team, a finance team - there are so many tasks, one person cannot make it all happen alone. Competition is certainly a key element of the modern technology economy. But when you face the whole world alone, you are competing with everyone. Nimur 16:09, 3 October 2007 (UTC)[reply]

The usual trick if a large, rich company infringes on your patent is to let them get away with it until a year before the patent is due to expire - and then sell it to their biggest competitor. Patent law is nasty. SteveBaker 19:15, 3 October 2007 (UTC)[reply]

Laches? TenOfAllTrades(talk) 12:27, 5 October 2007 (UTC)[reply]

I am doing some reading on patents, so I'll tell you some of what I've learned so far. But if you're not exaggerating about your idea you should indeed consult a patent consultant, because the wording in the patent is very essential to the protection you get. It's a legal thing, so there are loads of loopholes for others to legally steal your idea. This is the reason to patent broadly, as the anon pointed out.

Firstly, laws differ from country to country, but in general they work roughly the same. The most important deviation is (again) the US, where patents are given out more liberally. There, 'anything under the sun made by man' is supposedly patentable. You could go for a national patent (not necessarily in your own country and possibly in several countries) or a PCT patent, which is a wider international patent (there is as yet no such thing as a worldwide patent). In Europe you could also go for a European patent. In that case, the more countries you want to cover, the more it will cost of course. Per country, count on a few thousand euro, more if you want it properly done (researched well and written by an expert). But if in Europe you want a patent in at least 3 or 4 countries, then it is cheaper to get a 'European patent', which is basically a collection of national patents. But the research into patentability only needs to be done once, which saves money.

As I understand it, it makes sense to apply for a patent in one country first to have it researched by the patent bureau. It might turn out to have been thought of before, in which case there is no point in taking it any further. But it may also turn out not to be patentable for various other reasons, such as it following logically from the state of technology; if for an expert in the field, it is a logical solution to a problem then it is not patentable. Then again, if that has been the case for several decades and no-one has patented it yet, then it apparently breaks with some rusty line of thinking and it is patentable again. The loopholes can work both ways, so to say. After you have applied for a patent, it will be kept secret for one year, to give you time to decide on further patents and maybe start setting up your business. Also because any competitors might violate the patent, hoping you won't have the time or money to sue them, as Nimur pointed out. Not uncommon, as I understand it, so even if you have a patent, you're still not in the clear. But that year might give you a decisive head start if you use it wisely.

About getting a job through your idea, keep in mind that if you're hired for the specific purpose of being inventive then your employer gets the patent - all you get is the bone he throws you. Speaking of which ... if you happen to live in the Netherlands, drop me a note. I'm trying to get together some inventive minds with the idea to make money out of patents. Don't worry, I wont' hire you. :) It'll be a joint venture of sorts, something along the lines of what Nimur was talking about (still working on the legal aspects of that - damn, I just want to be an inventor).

But like I and others said already, get professional advise. This is a tricky business (which sort of takes the fun out of inventing if you want to make money out of it). Btw, this is a legal question, so count yourself lucky no-one has bitched about that yet. :) (Damn, now I just did.) DirkvdM 18:45, 3 October 2007 (UTC)[reply]

It's certainly no fun being the lone inventor in the face of gigantic multinational corporations and truly pathetic patent offices. You spend a fortune on getting your patent through the process - but yet the patent office probably didn't spend more than a couple of minutes looking at your patent - just barely enough to read through it. So there is no guarantee that your patent is meaningful - or that it'll stand up in court. You won't know that until someone infringes on it and you have to get big expensive law firms on your side to defend it with no real guarantee of winning. SteveBaker 19:15, 3 October 2007 (UTC)[reply]

Update on defending the patent before court: for a European patent that only happens in 10% of the cases. The explanation for this is probably that for a European patent an extensive research is required. In the US, a different system is used. Like I said, patents are given out much more liberally. This is possibly the 'declaratory system' (literal translation from Dutch), in which one only needs to apply and pay a sum. The European ('attributive') patenting system gives much more legal certainty. But of course the extra research means it's more expensive. Too bad one doesn't always have a choice between the two. In the Netherlands, one can also apply for a 'small patent', which is cheaper and faster and more appropriate for small inventions that might not be worthwhile for potential competitors to go to court for. This doesn't appear to apply to your invention, so a European or PCT patent (the latter of which leads to an 'International Search Report') might make more sense for you. DirkvdM 11:45, 5 October 2007 (UTC)[reply]

Carbonated Water

Is drinking carbonated water (as in, just plain seltzer water) bad for you? The articles on it and soda seem kind of fuzzy on this, and one of my friends claims that the acid they use to carbonate water leeches calcium from bones. 66.28.242.74 17:38, 2 October 2007 (UTC)[reply]

Osteoporosis lists the risk factors for calcium loss - it does mention soft drinks as one of the possible causes - but in the context of phosphoric acid - which isn't present in plain carbonated water. Your friend is probably thinking about Carbonic acid - which is certainly present in plain seltzer water because it's formed whenever you dissolve CO₂ in water. However, carbonic acid is floating around in your blood quite naturally - it's the way that CO₂ gets carried from the cells that produce it back to your lungs. Transporting the stuff around is an important blood function - just as carting loads of oxygen around is - so it's hard to imagine it would be a problem. The osteoporosis article also says (in effect) that if you drink lots of soft drinks (with no calcium in them) then maybe you are drinking less of things that provide calcium (milk for example) - but you'd have the same problem if you drank un-carbonated water. It doesn't mention carbonation as being a specific problem though. The article gives some useful links - you should probably read those too. If you are concerned about a health risk - or if you have any symptoms - you should (of course) consult a doctor. SteveBaker 17:56, 2 October 2007 (UTC)[reply]

The acidity of carbonated beverages has been implicated in some tooth decay as it may contribute to erosion of tooth enamel. — Scientizzle 19:28, 2 October 2007 (UTC)[reply]

The acidity may lower the pH of your blood, eventually leading to metabolic acidosis. In reality, the body's Bicarbonate buffering system is more than sufficient to handle soda water... or lemons... --Mdwyer 19:41, 2 October 2007 (UTC)[reply]

Michoud Fault article

http://en.wikipedia.org/wiki/Michoud_fault

I know enough about geology to know that there are not two tectonic plates involved in this fault as it states in the article. I don't know enough to rewrite it. I put a link to a good paper in the external links section. Dansample 18:53, 2 October 2007 (UTC)[reply]

You should leave a note on the 'discussion' page relating to that article. List your concerns there. Someone will come along and take note of it. SteveBaker 19:24, 2 October 2007 (UTC)[reply]

And you might tag the article as needing expert attention, using {{expert}} . --Anonymous, 21:48 UTC, October 2.

The Michoud fault is a normal fault. DuncanHill 23:36, 2 October 2007 (UTC)[reply]

Fungus fungus

Can a fungus get a fungus infection? --Milkbreath 21:49, 2 October 2007 (UTC)[reply]

Interesting question. Can whatever 'drug' utilized to treat first infection be considered a fungus on the fungus? Sorry if that`s just stupid. Dave 64.230.233.209 22:11, 2 October 2007 (UTC)[reply]

Only if that drug was a fungus which lived on the fungus. I doubt that it was :) 79.65.119.193 22:46, 2 October 2007 (UTC)[reply]

Hi again 79.65.119.193. Just as I thought, hence I wrote 'drug' as I did. I didn`t think that answer was very smart. Not my forte. I should stick to high-school-level physics' problems. lol Dave 64.230.233.209 22:58, 2 October 2007 (UTC)[reply]

Mushrooms can go mouldy. DuncanHill 23:37, 2 October 2007 (UTC)[reply]

Ah. Good. That's what got me wondering in the first place; I don't remember ever seeing that in my fridge, and there's ample reason to suppose I would have. --Milkbreath 00:27, 3 October 2007 (UTC)[reply]

Yay, a mycology question, I'm so happy! Absolutely, it happens all the time although the parasitism may be out of sight underground. Most of the species in the genus Hypomyces participate in some form of fungus on fungus action. Hypomyces includes the tasty lobster mushroom (Hypomyces lactifluorum) which basically takes over its host fungus's mushroom and replaces all its tissue with its own. Asterophora lycoperdoides actually grows mushrooms out of other mushrooms, especially the Russulas. (more pictures of this here and here.) The fungal world is full of strange surprises. Sifaka ^talk 01:04, 3 October 2007 (UTC)[reply]

Excellent. Thanks. So nobody's safe. Cool links. I'll have to try that microphotography trick. --Milkbreath 01:18, 3 October 2007 (UTC)[reply]

This process helps get rid of that fungus among us. Edison 05:08, 3 October 2007 (UTC)[reply]

Even better, the fungal fungal infection could be treated with an antifungal medication isolated from a fungus. Most of the antifungal drugs were isolated from bacteria, and others are synthetic, but some, such as griseofulvin, were originally isolated from specific fungal microorganisms (in this case, Penicillium griseofulvum. - Nunh-huh 05:28, 3 October 2007 (UTC)[reply]

Do "voices in one's head" ever engage one in normal "small talk"

Are "voices in one's head" seen as negative just becasue a person decided, say, to go around shooting because of them, and the times people hallucinate innocent things don't get attention? Do voices in one's head ever engage in small talk. You know, "Hey, Jim, how are you doing? Nice day, huh? How 'bout that game last night? Our quarterback stunk." I suppose it's possible that such a hallunciation could come from an imaginary friend, but from the article, I don't thikn so, because my understanding of imaginary friends is that they're always internal - i.e.: The person knows they're an imaginary friend, even if it's an adult who has adopted one for some reason, such as Asperger's Syndrome. I could be wrong on that, though. I also am not talking about hypnogogia, as from what I read that usually isn't understandable, it sounds more like mumbling if it's audible. It does seem strange, though, that the only thing one hears about hallucinations is bad stuff, though, never just innocent stuff like, "The voices in my head and I are discussing what we want for lunch." Something which sounds very normal for a young child with an imaginary friend, which as I say, I suppose to be internal, even if the child talks as thought it's external.209.244.187.155 23:24, 2 October 2007 (UTC)[reply]

There was a rather long feature article in the New York Times not too long ago about the Hearing Voices Movement, which was basically people arguing that hearing voices is not necessarily something that needs to be medicalized or medicated or something like that. I seem to recall some of the people in the article saying that the voices weren't always abusive or malevolent though I also got the impression that most of the time they were, that something about whatever it is that creates the voices seems to make them focus on the negative. But that was just my impression. Here's the article, in any case, though I last read it last March so my memory of the details might be foggy. --24.147.86.187 02:16, 3 October 2007 (UTC)[reply]

(Also, I had never heard of hypnogogia before—how interesting. I've had the "tripping" feeling many times while waking up, and was always shocked by how violent it felt in comparison with other dream-like sensations, but never realized there it was a general phenomena by the name and that it was basically the strange border line between being awake and asleep. How interesting.) --24.147.86.187 02:19, 3 October 2007 (UTC)[reply]

It gets better. "Hypnogogia" is specifically the strange border line between being awake and asleep when falling asleep. "Hypnopompia" is specifically the strange border line between being awake and asleep when waking up. - Nunh-huh 05:24, 3 October 2007 (UTC)[reply]

Have anyone ever subjected those "voices" to an IQ test? or get the "voices" to write up a scientific paper on Quantum Physics? After all if God is speaking to you, he must know some serious shit. 202.168.50.40 04:21, 3 October 2007 (UTC)[reply]

If voices in one's head say innocuous things like "Looks like it might rain today" they probably get little noted nor long remembered. Edison 05:07, 3 October 2007 (UTC)[reply]

Thanks, all; especially for the article. I'm trying to do research into a possible novel idea I have, a pitcher with mental challenges who makes the majors, sort of a modern day Rube Waddell but without the alcoholism; so any eccentric behavior is straight mental condition. In a way, one might say it's a cross between Rube Waddell and Harvey (film) —Preceding unsigned comment added by 209.244.187.155 (talk) 12:38, 3 October 2007 (UTC)[reply]

Richard Rhodes' fascinating book Why They Kill, while not addressing mental illness as such, spends on a good deal of time on Lonnie Athens' research into violent criminals' "internal community" of voices. --Sean 13:20, 3 October 2007 (UTC)[reply]

Another area to research might be Dissociative identity disorder, previously known as "Multiple Personality Disorder." It is a controversial diagnosis, but I am just offering it as another topic that might have some relevance. While fictional, Matt Ruff's excellent novel Set This House In Order contains a protagonist who is a "multiple" and there are depictions of two or more of his "alters" in conversation. Finally, I feel the need to mention that Elwood P. Dowd was a bit of souse, if not an alcoholic himself. --LarryMac | Talk 20:02, 3 October 2007 (UTC)[reply]

Thanks.209.244.30.221 13:55, 4 October 2007 (UTC)[reply]

First missile guidance system

After reading the article on missile guidance I started wondering what guidance method the first guided missile had. I have tried searching a bit, but so far I haven't been able to find it. - Dammit 00:23, 3 October 2007 (UTC)[reply]

As I recall, and as Anti-ship missile suggests (but does not source!), these first appeared in WW2. I think they were radio guided, as certainly some "plane bombs" were (haven't uncovered the link for that one yet). Someguy1221 00:30, 3 October 2007 (UTC)[reply]

Ah, Operation Aphrodite. Someguy1221 00:33, 3 October 2007 (UTC)[reply]

Maybe the Henschel Hs 293 radio-controlled anti-ship missle? --Milkbreath 00:37, 3 October 2007 (UTC)[reply]

IMO the V1 was the first guided missile. —Preceding unsigned comment added by 88.111.81.231 (talk) 01:02, 3 October 2007 (UTC)[reply]

I wouldn't call the V-1 flying bomb "guided." It could only be guided to the extent that the operators could control roughly how far it travelled before it landed, and you can do the same with an artillery shell. Someguy1221 01:55, 3 October 2007 (UTC)[reply]

The definition of "guided" in this case is whether the projectile's path can be changed in flight. Which you can't do with an artillery shell. The V-1 could do this in about the bare minimum sense of the word, since its "autopilot" would make adjustments based on the conditions the V-1 encountered. --24.147.86.187 02:31, 3 October 2007 (UTC)[reply]

The V1 was more of an unmanned airplane than a missile. It flew at a controlled altitude in a selected direction until the fuel ran out, then it fell and exploded. The V2 was a ballistic missile with a guidance system which operated during the boost phase. —Preceding unsigned comment added by Edison (talk •

contribs) 05:05, 3 October 2007 (UTC)[reply]

Come on, the very 1st paragraph of the V1 article contradicts precisely what you are saying. It was NOT simply an unmanned airplane, it was the 1st guided missile as it did have a dedicated albeit rudimentary guidance mechanism. The engine cutting out for lack of fuel was a design flaw and was rectified, the control mechanism caused a powered dive onto the selected target area, it was not simply a "run out of fuel" process. Vespine 05:47, 3 October 2007 (UTC)[reply]

My mother was living in London throughout the time of the V1 attacks (and twice came close to being a victim of them). She told me many, many times that her most vivid memory of the V1 (she calls them 'doodlebugs') was that the distinctive sound of their pulse-jet engines going overhead was actually rather comforting because it was only when the engine stopped that the weapon would glide down and explode. She told me this often and explained the terror that everyone felt when the engine sound cut off and there was that awful silence that would end in an explosion - I simply do not believe that they were ever powered into the ground. They may not have run out of fuel - but the engine was definitely not running when the things actually smacked into the ground. SteveBaker 12:50, 3 October 2007 (UTC)[reply]

There are details on it in the article. The early ones did not have powered dives but later ones did. And they certainly did not just run out of fuel—they had their distance "programmed" into them and that would make it dive at a steep angle. I mean, we all could just talk about stuff without checking, but it seems so easy to just check, right?)--24.147.86.187 13:10, 3 October 2007 (UTC)[reply]

While I also first thought of the V1, as the first one I've found that there already were some before the V1, but I have no idea if one of these is considered the first:

The US Navy's N-9 Curtis-Sperry Flying Bomb, might not even be considered a missile although NASA states it to be the "Navy's first guided misile effort" (1917)
The German A3, test rocket with inertial guidance (1937)

As I've said, I've already consulted a few sources, but none that claims to describe the first. - Dammit 10:37, 3 October 2007 (UTC)[reply]

If it has to, like, work, I'm pretty sure the Henschel was the first, unless you count the falcon with its biological navigation, acquisition, and terminal homing. --Milkbreath 16:14, 3 October 2007 (UTC)[reply]

The dictionary definition of a "missile" is "something that is thrown." A V2 clearly is a missile. It is loose terminology to call any "cruise missile" a missile, when they are sustained in flight by their engine, like the V1. The V1 was a pilotless jet, but it also had a kamikaze style piloted version which the Germans may not have actually deployed. If a WW2 B17 bomber had an autopilot to fly it as an unmanned drone into a populated area of Germany, would that have made it a "guided missile?" I think not. Sure the V1 is a guided missile, like a whale is a fish. Edison 04:24, 4 October 2007 (UTC)[reply]

Yeah but a V1 weighs a lot less than whale, doesnt it? —Preceding unsigned comment added by 88.109.121.209 (talk) 20:06, 5 October 2007 (UTC)[reply]

"Missile" = "something that is thrown." Hmm... okay, the guidance method for the first guided missile would be tugging on the rope. :-) 152.16.59.190 08:51, 6 October 2007 (UTC)[reply]

joints in the human body

What is a joint in the cranium? —Preceding unsigned comment added by 68.248.145.158 (talk) 01:28, 3 October 2007 (UTC)[reply]

From Human skull: "Except for the mandible, all of the bones of the skull are joined together by sutures, synarthrodial (immovable) joints formed by bony ossification, with Sharpey's fibres permitting some flexibility." The term you're probably looking for is suture. --Ybbor^Talk 02:04, 3 October 2007 (UTC)[reply]

Household electroplating

I have some small objects that I would like to coat in copper. They are very small, and I believe they are zinc. What would be an effective way to plate them? HYENASTE 02:03, 3 October 2007 (UTC)[reply]

Spray the surface with small balls of copper, when the balls hit they heat up and melt forming a thin layer.

In theory, just stick them in a copper sulfate solution. In practice, that will produce a mess of little flakes or feathers, which will be oxidized, so it will be reddish brown and not shiny. If you want a nice and even, permanent, shiny coating, it will take a lot more effort. This classroom lab manual seems reasonable. —Keenan Pepper 03:02, 3 October 2007 (UTC)[reply]

Thanks for providing an easy setup. I assume a lantern battery and some wire will work for electrodes. Now, where do I find sulphuric acid, soda lye, and copper (II) sulphate? HYENASTE 01:56, 4 October 2007 (UTC)[reply]

Copper sulphate can be found in garden supply stores - it's an old-fashioned herbicide, fungicide and pesticide. I believe tropical fish fanatics use the stuff too - so you could try a pet store if you don't need much of the stuff. If you only need rough-and-ready plating, you can skip the acid and lye. "Soda Lye" is an old-fashioned name for Sodium Hydroxide - it's also called "caustic soda". I've seen it in swimming pool supply stores. You might maybe find it sold as a drain cleaner - but probably it would be mixed with a bunch of other junk. Sulphuric acid used to be easily available for topping up car batteries - but with the advent of sealed-for-life batteries, it may be hard to find. Maybe a car parts store might stock it...I suppose you could get some out of an old car battery - but it's about 30% concentrated in a car battery - so please be VERY careful! Wear gloves, mask, goggles...also, remember - always add acid to water - NEVER add water to acid. SteveBaker 02:19, 4 October 2007 (UTC)[reply]

Why so much effort? There's many simpler ways. Here's one that I've personally used. It recommended for home plating enthusiasts by a professional metalworker on finishing.com (an answers forum for the industry).

Strip the insulation from about 2 feet of copper wire. Clean with toothpaste and a sponge or brush. Coil this up and place in a beaker or bowl. Wear gloves so you don't recontaminate the wire with oil from your fingers.
Add 100 cc of white vinegar
Add 1 heaping teaspoon of salt or preferably baking soda. (baking soda is safer, as using salt will produce chlorine gas)
Add 3-6 cc of ethylene glycol antifreeze, if you have it. It'll still work without.
Use a spare copper coin or piece of copper wire for a temporary cathode. This is to dissolve enough copper into solution so it can be available for plating. The temporary cathode also keeps you from dirtying the item you want to plate.
Give the temporary cathode a quick rinse with alcohol and water to remove surface dirt & oil.
Next, rig a 1.5 volt battery, optionally with a 30 to 200 ohm resistor in series.
Attach the positive terminal to the anode (your copper wire).
Attach the negative terminal to the cathode (the temporary copper object).
If using alligator clips, make sure they grip the very edge. The less space covered, the better.
Electrolyze the plating solution for 10-15 minutes.
Replace your original cathode with the item you want to plate. A faint copper color should appear after 60-120 seconds. Occasionally jiggle the cathode a bit during plating.
Move the clip around the coin a few times while plating to plate the bare spots where the clip was.

Plating brightness, depth and coverage will steadily improve over 20-90 minutes. You can plate pieces for longer periods to get a thicker plate. The color will eventually turn black after plating more than an hour or so. You can wipe this off with a damp cloth, or gently polish to an antique copper finish using toothpaste when you finish. This method of plating will produce a reasonably durable and attractive, but not quite as good as a pro job. Simple as that, and no lye or sulfuric acid needed. Kel - Ex-web.god 02:44, 4 October 2007 (UTC)[reply]

Hominin evolution

What is the most recent common ancestor of humans and bonobos? Would it be Australopithecus, or not necessarily?--Sonjaaa 02:30, 3 October 2007 (UTC)[reply]

I've only seen the term "Australopithecus" applied to bipedal Hominina. See: Image:Hominintree4.gif. According to Hominini, "both Orrorin and Sahelanthropus existed around the time of the split, and so may be ancestral to both humans and chimpanzees". --JWSchmidt 04:03, 3 October 2007 (UTC)[reply]

Building 140 decibel or higher system at 25KHZ (ultrasonic)

I'm wanting to build a 140 decibel or higher system at 25KHZ (ultrasonic). Amazing1.com has something like it, but it's huge. I'm looking for something that'll do it but be really tiny. Anyone have any ideas where I can start? William Ortiz 03:33, 3 October 2007 (UTC)[reply]

140dB is a horribly high noise level, which could harm the listener. What is the goal? Deafening mice? Edison 04:50, 3 October 2007 (UTC)[reply]

Driving certain animals away. I have something at 130DB and in the most obvious example, birds will still hang out all the time 20 centimeters (less than a foot) away so clearly more decibels are needed. William Ortiz 05:44, 3 October 2007 (UTC)[reply]

This seems like a really bad idea - 25kHz isn't much above the level of human hearing (lots of people can hear 20kHz - and young people may hear 22kHz and higher) - and 130dB is quite capable of damaging your ears - 140dB is above the pain threshold! I would certainly not want to be around this thing when it's turned on. If you really need such high amplitudes you should certainly be using a higher frequency to be really sure that humans aren't going to be harmed. Are you even sure that the species of bird you are trying to repel can hear 25kHz? If they could, there is no doubt that 130dB would be enough to scare them off. SteveBaker 12:36, 3 October 2007 (UTC)[reply]

Look into hydrophones. These are bidirectional transducers (speakers AND microphones) and are most often used for underwater applications. Next you'll need a signal generator (any standard electronics lab will have a function generator suitable for 25 kHz, or you can build your own oscillator). Finally, you need a power amplifier of a considerable size (unfortunately, there are physical limitations on power densities, and 140 dB is a lot of power). Also, it is more difficult to miniaturize components for such low frequencies (in the electromagnetic spectrum sense). Are you building a sonar or are you trying to make a sonic weapon? Please do not use the reference desk for destructive purposes. Nimur 16:50, 3 October 2007 (UTC)[reply]

Reaction to frankincense?

Whenever I smell frankincense resin (in essential oil blends), especially if I am exposed to the scent for a longer period of time, I get a dry, scratchy feeling in the back of my throat. It's like a need to cough that is not satisfied by coughing. It is slightly irritating but doesn't feel like a serious or life-threatening reaction; it never occurred to me before to wonder what it was. I know I can't ask for medical advice here, and I'm sure that my doctor would only tell me to stop exposing myself to frankincense, which I've already figured out. I am really more curious about whether anyone else experiences the same thing, or whether there is a name for that symptom. --Grace 05:31, 3 October 2007 (UTC)[reply]

It's possible you are slightly allergic to it, or something else in the oil. Stick go gold and myrrh. Lanfear's Bane 09:42, 3 October 2007 (UTC)[reply]

Perhaps you went to too many requiem masses as a kid, and developed a sub-conscious aversion to the stuff?

Atlant 12:05, 3 October 2007 (UTC)[reply]

It's the sort of thing that's definitely worth asking a doctor about, as they are going to know about this sort of thing. They might have rather more to tell you than just avoiding frankincense, which may not always be possible; since nobody with medical training will answer this question in this sort of forum, it's really rather hard to tell. On another note, I tend to find many people's throats are irritated by various incenses. —Preceding unsigned comment added by 79.65.119.193 (talk) 22:51, 3 October 2007 (UTC)[reply]

Couple of Questions on Acids

pH of HCl, Citric and Acetic Acid

I've read over their articles, but I only have a basic understanding of chemistry so I don't get the kP_a1 things, is someone able to give me the pH and % dissociation of hydrogen molecules of:

HCl
Acetic acid (CH₃COOH)
Citric acid

under standard conditions. Thankyou

Have you taken a look at Acid dissociation constant yet. The first two are monoprotic acids, whereas citric acid is triprotic. Graeme Bartlett 12:55, 3 October 2007 (UTC)[reply]

Acidity of Salts

I'm sort of having a little bit of trouble understanding this, so would someone be able to tell me if this is correct:

Some salts are acidic/basic as their ions are derrived from weak bases/acids. They can undergo a hydrolysis reaction with water to reform the original base/acid

For example consider ammonia chloride (NH₄Cl). When it dissolves it dissociates to form NH₄⁺ and Cl^-. The chloride is the conjugate base of a strong acid (HCl), and hence is neutral and will not react with water. The ammonia is the conjugate acid of a weak base (NH₃) and hence will react with water such that NH₄⁺ + H₂O -> NH₃ + H₃⁺. Hence it is an acidic salt derrived from a weak base.

Similarly consider sodium acetate (NaCH₃COO^2-). When it dissolves it dissociates to form Na^- and CH₃COO^-. The sodium ion is derrived from a strong base and hence is neutral and will not react with water. The acetate ion is the conjugate base of a weak acid, and hence will react with water to reform the original acid, such that CH₃COO^- + H₂O -> CH₃COOH + OH^-. Hence it is a basic salt derrived from a weak acid.

On the other hand, consider sodium chloride (NaCl). When it dissolves it dissociates to form Na⁺ and Cl^-. The sodium ion is derrived from a strong base (NaOH), and hence is neutral and won't react with the water. Similarly the chloride ion is derrived from a strong acid (HCl) and hence is neutral and won't react with the water. Therefore it is a neutral salt derrived from a strong base and a strong acid.

That's the pinnacle of my understanding so far, I just have three big biffs with it

Why don't the ions from strong acids/bases react with water to reform the original acid/base (someone said this was something to do with the conjugate of a strong thing being weak and vice versa but I'm not sure)

The ions such as Cl^- does not react much with water, and the same with Na⁺, so their presence does not alter the pH. You need something that will react with H⁺ or OH^- to change pH. So if you dissolved a salt of a strong acid and a strong base in the water you just get the ions from the salt hydrated in solution. Any H⁺ or OH^- reacts with each other to leave a very small remainder, with the product of their concentrations being about 10^-14. Graeme Bartlett 12:41, 3 October 2007 (UTC)[reply]

What about Fe(OH)₂, it's a weak base but then how does the ionic component of the salt derrived from it act as an acid in water (it has no proton to give up)? This sorta follows for a lot of other weak bases.

The weak acid is actually Fe²⁺ it reacts with water taking away OH^- to form FeOH⁺, and a H⁺ ion in solution. Graeme Bartlett 12:41, 3 October 2007 (UTC)[reply]

Is the reaction between HCl and NH₃ even a proper neutralisation reaction? I thought the formula was acid + base = salt + water, but there's no water involved

Yes - water does not have to be formed. A base can also work by removing H⁺ instead of supplying OH^-. Graeme Bartlett 12:41, 3 October 2007 (UTC)[reply]

I have a test on this coming up, and this is the only thing I don't understand. If the question was say, explain the acidic, basic and neutral nature of salts do you think my explanation would be adequate, and if not what can I add in to complete it?

Thankyou very much in advance 124.183.13.48 09:29, 3 October 2007 (UTC)[reply]

Balancing equations

--Mostargue 18:05, 3 October 2007 (UTC)[reply]

Hi all, thanks in advance.

1. When the question below is balanced correctly, what is the co-efficient for O₂

C₄H₁₀ + O₂→ CO₂ + H₂0

Is the answer:

A: 9

B: 13

C: 18

D: 24

2. Consider the composition of the particle, W, X, Y and Z below.

W: Protons: 11, Neutrons: 12, Electons: 10

X: protons: 12, Neutrons: 12, Electrons: 12

Y: Protons: 12, Neutrons: 13, Electrons: 12

Z: Protons: 13, Neutrons: 14, Electrons: 10

Which two particles are isotopes of the same element.

Once again thanks guys. --Andrew Hadland 2007 07:55, 3 October 2007 (UTC)[reply]

1) b - 2C₄H₁₀ + 13O₂→ 8CO₂ + 10H₂0

2) W and Y, they both contain the same number of protons, hence have the same atomic number hence are the same element —Preceding unsigned comment added by 121.217.13.71 (talk) 08:02, 3 October 2007 (UTC)[reply]

This looks an awful lot like homework - I don't think we should be answering with exact answers - broad brush explanations please! SteveBaker 12:26, 3 October 2007 (UTC)[reply]

And multiple choice, at that! Nimur 16:46, 3 October 2007 (UTC)[reply]

For the first problem, put coefficients in front of the CO₂ and H₂0 first, making sure that each side of the equation has the same number of carbon and hydrogen atoms. Once you have the carbon and hydrogen balanced then you move on to the oxygen, count the number of O atoms taking account of the coefficients you already added. For the second question, the article on Isotopes answers your question in the first paragraph. Man It's So Loud In Here 16:43, 3 October 2007 (UTC)[reply]

Another way to do the first one is to put coefficients in front of the substances with Hydrogen in them, because on each side there is exactly one substance containing hydrogen.--Mostargue 18:05, 3 October 2007 (UTC)[reply]

Electron arrangement

Sorry for the sloppy formatting, the 16 and the eight are supposed to be directly above and underneath each other. What is the electron arrangement of the ion ^16₈O2-. Is it:

A: 2, 6

B: 2, 8

C: 2, 8, 6

D: 2, 8, 8

Thanks --Hadseys 08:42, 3 October 2007 (UTC)[reply]

Uh, you've asked for the electron configuration of an ion of oxygen, and then the electron configuration for the diatomic oxygen gas molecule. What I think you're after is the electron configuration of a single oxygen atom which is 2.6 or 1s²2s²2p⁴ (the easy way to see this is that the number of protons in oxygen is 8, and 2+6=8 since the charge is (I think) neutral). So the answer is a UNLESS you are after the electron configuration of the O^2- ion which would be 2,8 which would be b. 124.183.13.48 09:06, 3 October 2007 (UTC) Nevermind, I misread the question (it should be O^2-, not O_2-). In this case the atom has a charge of 2-, so it has two more electrons than protons (10 electrons). The only answer which fits this is b, 2.8 124.183.13.48 09:09, 3 October 2007 (UTC)[reply]

HCl vapor from Na2CO3 + H2SO4?!

A friend's sister was working on her upcoming science project, part of which required producing (I think) sodium sulfate by neutralizing sodium carbonate with 97% sulfuric acid. She didn't have any Na2CO3 available, so made some with Arm & Hammer baking soda, which, according to their literature is 99.995% pure. She did this by heating the NaHCO3 at ~200 °C until it (presumably) thoroughly dehydrated into Na2CO3, which she then let cool. However, when she later pipetted H2SO4 onto the Na2CO3, she noticed a bit of white, sharp-smelling fumes being produced which she said smelled "just like HCl fumes". She didn't think this should be possible, so she freaked out and dumped the experiment. She wants to know what this vapor was. She's still too embarrassed about making such a huge mess in the lab that she won't ask her chem teacher. :) My guess was that Arm & Hammer's purity claims aren't as accurate as they'd like to believe, and the product contains small amounts of one or more chloride salts -which would explain HCl vapor. But I could be wrong, and I'm pretty curious myself about what could have caused this. Any ideas? Thanks in advance. Kel - Ex-web.god 08:53, 3 October 2007 (UTC)[reply]

Is it possible that she used hydrochloric acid instead of sulphuric? Or that the acid was labeled incorrectly? Lanfear's Bane 09:36, 3 October 2007 (UTC)[reply]

Well she would have produced CO₂ gas and some spray consisting of sulphuric acid. A fair bit of heat would be released also. It is quite likely that this would smell like hydrochloric acid. 97% sulphuric acid is pretty nasty, so it is not a good idea to sniff it. One test is to see if it really is sulphuric is if it carbonizes sugar. HCl would not do this. Food products should be quite pure. But I could imagine that NaCl could be a contaminant. Graeme Bartlett 12:30, 3 October 2007 (UTC)[reply]

Well, I've seen the lab, and it's definitely reagent-grade sulfuric acid (still in the original dispenser from the supplier). To further clarify, she noticed the fumes from 2-3 feet away, so she didn't exactly stuff her nose into her Erlenmeyer flask. Also, the vapor was wispy and white, just like fuming HCl. It wasn't a spray. Again, I may be wrong, but I'd assume a mist of H2SO4 being released from bubbles of bursting CO2 wouldn't form a visible wispy strand that rises out of the flask. :)

Also, assuming she did somehow accidentally use HCl, (see above, she didn't.) That still doesn't explain the fumes, as if I'm not mistaken: 2HCl + Na2CO3 ---> CO2 +H2O +2NaCl. I also thought there might have been a little carbonic acid that hadn't completely broken down yet, but she says an indicator strip placed at the top of the flask showed a pH of around 1, which that acid wouldn't do. So, any other ideas? Kel - Ex-web.god 21:28, 3 October 2007 (UTC)[reply]

I'm rather nonplussed about her being ashamed to tell her teacher. I think a student with her sort of curiosity about an unexpected result would delight most teachers. As they say, the productive moment in science is not "eureka!", but "that's funny ...". --Sean 21:58, 3 October 2007 (UTC)[reply]

I agree, but it's a teenage girl, so what do you expect? :) She apparently made a pretty big mess when she knocked over her entire apparatus. Kel - Ex-web.god 23:50, 3 October 2007 (UTC)[reply]

Wonder if she got exothermic and vaporization enough to create substantial H₂SO₄ vapor. Lots of acids smell similarly "sharp" to me, not sure what specific part of "the HCl smell" was noticed. That's a pretty hydroscopic acid, maybe the visible vapor trail was from it absorbing humidity? Or maybe she drove off some SO₃, which would be another sharp/acid-smelling thing, and would maybe also leave a visible vapor trail as it absorbed humidity to become or H₂SO₄ droplets (a la "fuming sulfuric acid"). DMacks 01:56, 4 October 2007 (UTC)[reply]

Possibly, but according to her, she had only combined ~100mg of sodium carbonate and 5-6 drops of sulfuric acid when she noticed the fumes. As for the "HCL smell", I can tell a slight difference between HCl and SO₃. Not sure if she can, but that was what seemed the most familiar to her, I guess. Given that she was freaked out about getting an unexpected result, it's possible she was mistaken, hence the question. :) Kel - Ex-web.god 02:49, 4 October 2007 (UTC)[reply]

Basically you don't mix 97& sulphuric acid with any base - it is too concentrated and will give out so much it it will volatalise. 10% acid would be safer - usually at school all experiments need to be supervised - for safety - in most places it's the law - however this dosen't seem to have been the case here - this was a dangerous and stupid experiment.87.102.94.194 15:09, 4 October 2007 (UTC)[reply]

That answer was incredibly presumptuous and generally unhelpful, not to mention the part about never mixing concentrated acid with any base. I guess the all those college labs that required I do exactly that (on countless occasions) was also stupid? I think not. For the record, the experiment she attempted was taken directly from her textbook, was pre-approved by her teacher, used less than 10 drops of acid, and of course there was an adult supervisor present. She also wore appropriate lab gear. No, stupid are those kids that somehow managed to steal 70% HNO3 and used it to dissolve pennies in the bathroom sink while standing around gloveless in short-sleeve shirts giggling and poking their fingers in that cool cloud of brown smoke. Kel - Ex-web.god 00:59, 5 October 2007 (UTC)[reply]

Where exactly does a text book say to mix conc acid with base - maybe america hey - fuck you I cant wait for the next fucking 9/1183.100.250.154 13:14, 5 October 2007 (UTC)[reply]

Um, how about any reaction where excess water isn't wanted? Normally, I'd remind you of the minuscule scale of the experiment in an attempt to appeal to your sense of reason, but your last post proves that would be a colossal waste of time. If you can't be helpful, kindly spew your venom elsewhere. Not only does it discourage potentially useful and rational responses, it gives those people with a rational anti-American sentiment a bad name. Kel - Ex-web.god 20:32, 5 October 2007 (UTC)[reply]

Marfan Syndrome

How is Marfan Syndrome diagnosed? Is it done solely by physical examination, or is there more to it than that? --MKnight9989 12:09, 3 October 2007 (UTC)[reply]

Our article on Marfan syndrome says There are no signs or symptoms that are unique to Marfan syndrome. It is usually a single apparent sign or symptom that leads doctors to look for others and eventually to diagnose the syndrome. So evidently each symptom has to be tested for separately since no single test would be conclusive. From what the article describes, some of the symptoms might require X-ray or MRI exams - there is also an eye test. Since the disease is genetic and the defective gene is dominant, a detailed family history might be a useful aid to diagnosis. SteveBaker 12:23, 3 October 2007 (UTC)[reply]

The British Medical Association Complete Family Health Encyclopedia, 2nd ed., 1995, states "There are no specific diagnostic tests for Marfan's syndrome. Echocardiography may be used to investigate heart abnormalities, and an eye exam may be performed." DuncanHill 13:34, 3 October 2007 (UTC)[reply]

I can tell you from experience that many American doctors are eager to diagnose Marfan's when a patient with the usual connective tissue symptoms also has a high palate. In the case of one hapless patient that I know of, though, each of the doctors ultimately found that the diagnosis was non-productive. --M @r ē ino 17:53, 5 October 2007 (UTC)[reply]

Possible to create an aircraft supported by magnetic levitation alone?

Is it possible? 64.236.121.129 15:59, 3 October 2007 (UTC)[reply]

Did you read Magnetic levitation? An airplane flies anywhere- magnetic levitation requires that you are directly above the other part of the system. Also, the distances between the objects are typically quite small, whereas an airplane flies pretty high. Friday (talk) 16:02, 3 October 2007 (UTC)[reply]

I guess I should have clarified the idea, and yes I did read it obviously, but I don't think you understand what I'm asking. If the aircraft is generating the magnetic field, can it repel the ground with it. 64.236.121.129 16:58, 3 October 2007 (UTC)[reply]

In general, the ground is uncharged/unpolarised, and thus won't be affected by a magnetic field. Also, given the relative masses of the Earth and the aircraft, it'd be a tad silly to say that the Earth is being repelled. GeeJo ^(t)⁄_(c) • 17:23, 3 October 2007 (UTC)[reply]

The ground is still diamagnetic I believe. I guess this question is directed towards people who are familar with how things can be levitated with diamagnetism. With sufficient energy in the magnetic field generated (by the aircraft), is it possible? Btw, as for your last point, the object of less mass would be the one which is "repelled", in other words, ideally the aircraft would be floating due to it's magnetic repullsion from the ground. 64.236.121.129 17:35, 3 October 2007 (UTC)[reply]

Only if the ground was also made of something magnetic. But the problem with using magnetism (Magnetic levitation) is that the force it exerts drops off with the square of the range. So if there was enough force to lift to the aircraft a foot off the ground, it would take a magnet 100 million times more powerful to fly at 10,000 feet. (10,000 squared is 100 million) If you think of the size of magnet you'd need to lift an entire airplane...then imagine one 100,000,000 times bigger! We do use magnetic levitation for trains (Maglev train) - they move on special tracks (unlike a plane - which you'd like to fly everywhere in!) - and they only hover a 15 millimeters above the track! (Remember - the SQUARE of the range!) —Preceding unsigned comment added by SteveBaker (talk • contribs) 17:26, 3 October 2007 (UTC)[reply]

Technically you could run a very powerful current through an aircraft, parallel to the Earth's surface and perpendicular to its magnetic field to generate magnetic lift. However, you would need current in one direction to not be going through the aircraft, or else this would generate a counterforce that would exactly cancel out your lift. You could theoretically accomplish this by ionizing a region of air outside the aircraft and sending the current through that (and have the aircraft appropriately insulated so that the current only goes through that. However, needing to constantly ionize the air around the aircraft, as well as needing some rediculous current to levitate on the Earth's oh so weak magnetic field would be quite energy consuming. Disclaimer: This idea I have just described is certifiably rediculous and will probably never work except as an amusement. Someguy1221 17:40, 3 October 2007 (UTC)[reply]

Yeah but then you might as well build an Ionocraft - at least those things actually work. SteveBaker 19:19, 3 October 2007 (UTC)[reply]

My magnetic hovercraft is full of electric eels. --M @r ē ino 17:55, 5 October 2007 (UTC)[reply]

A version of a maglev train could be created with wings, however, to create something similar to a ground effects airplane. This would, though, mean it could only travel a few feet above the ground and only on top of energized tracks. Such a vehicle might be useful for low cost (lower than normal aircraft), high speed transport, along a few busy routes, over flat terrain. StuRat 18:10, 5 October 2007 (UTC)[reply]

The earth's magnetic field is about .06milliTesla. At various locations, the field lines go vertically downward, vertically upward, or parallel to the ground. If our magnetic aeronaut had a magnetic monpole, how powerful would it have to be to support, say, 1000 kilograms at a point where the field lines were vertical? If magnetic monopoles do not exist (no one has ever found one), then aren't there stable configuration of normal magnets or solenoids producing a magnetic field which could in principle hover in a magnetic field with vertical field lines, and with field lines horizontal or at any arbitrary intermediate angle? (Talking theory, not practicality here). Edison 18:32, 5 October 2007 (UTC)[reply]

October 3

Human Spine

Do all the bones move?

What is the function of the discs?

In which area of the spine do most people get back ache?

This is not for homework, as some of you might think. - 81.158.75.136 16:05, 3 October 2007 (UTC)[reply]

Nothing triggers my "homework" RADAR like an assertion that questions are "not homework." In any case, here's some links which will help:

Many of the bones are fused; so these bones do not articulate with respect to each other.

The discs are part of the joint, and serve as a soft cartilaginous material to allow for slight movement.

Of course you can have an ache in any part of your back, depending on the source of the pain. Poor posture may result in lumbar pain. Nervous system problems, such as a pinched nerve, can be very serious. If you are seeking medical advice, see a doctor.

Hope this helps, Nimur 16:43, 3 October 2007 (UTC)[reply]

Quantum physics (I think). Confused. Deuterium is a wave?

According to deuterium, deuterium is a boson and according to boson, this makes it a "force carrier" particle like a photon? Does this mean that deuterium is as intangible as light? --Seans Potato Business 16:54, 3 October 2007 (UTC)[reply]

Deuterium is a "composite boson" (it's a boson because its spin is an integer: +1), but it acts as a boson only at long distances. In high energy interactions it acts as an assemble of two fermions (a proton and a neutron). Thus it is in a sense as "solid" as any fermion. See under the heading "Composite bosons" in our article boson.--Eriastrum 17:17, 3 October 2007 (UTC)[reply]

It's an isotope of hydrogen - one proton, one neutron. In bulk, it's a gas...just like hydrogen - but heavier. SteveBaker 17:18, 3 October 2007 (UTC)[reply]

However, at very low temperatures composite bosons can do wierd things, or yet wierder things. Someguy1221 17:34, 3 October 2007 (UTC)[reply]

All matter have waves. See matter wave.--Mostargue 17:36, 3 October 2007 (UTC) ~~Oh dear, Wikipedia has no article on that??~~--Mostargue 17:38, 3 October 2007 (UTC)[reply]

There, redirected to de Broglie hypothesis.--Mostargue 17:40, 3 October 2007 (UTC)[reply]

Confirm vs define

Mendeleev's_predicted_elements says, in the last paragraph, that hydrogen was confirmed to be the first element. I don't understand what that means. Wouldn't it be better to say that hydrogen was defined to be the first element? How has the definition of "element" changed over time? Of course, the classical elements are no longer considered elements, but I mean from Mendeleev to now.--Mostargue 18:24, 3 October 2007 (UTC)[reply]

Mendeleev sorted elements in terms of weight. Therefore, to say that hydrogen is the "first" element is to say that it is the lightest, which can certainly be confirmed. The modern periodic table sorts elements by atomic number, and it can again be confirmed that hydrogen has the lowest atomic number (one), making it first. So, what we are truly saying here is that hydrogen can be scientifically "confirmed" to be the first element, within the confines of a particular definition of "element." Someguy1221 18:30, 3 October 2007 (UTC)[reply]

Well I've heard of a single Neutron be called the element neutronium, with atomic number zero.--Mostargue 19:02, 3 October 2007 (UTC)[reply]

An isotope of which would be neutronium⁰ I suppose? SteveBaker 19:24, 3 October 2007 (UTC)[reply]

I've also heard of positronium, which only has an electron and a positron. — Daniel 22:17, 3 October 2007 (UTC)[reply]

speed

Does a car speedometer measure speed,velocity or both? —Preceding unsigned comment added by Ekumak (talk • contribs) 19:21, 3 October 2007 (UTC)[reply]

Only speed. Velocity is a measure of speed AND direction. So "20mph, heading North" is a velocity, "20mph" by itself is a speed. SteveBaker 19:26, 3 October 2007 (UTC)[reply]

Though I wouldn't be surprised if there were a dashboard out there with a built-in compass. GeeJo ^(t)⁄_(c) • 20:40, 3 October 2007 (UTC)[reply]

Maybe if it had an inclinometer too... SteveBaker 18:26, 4 October 2007 (UTC)[reply]

The surface of a sphere can be treated as a two-dimensional geometry, in which case a compass and speed indicator are enough to give you the velocity. --Carnildo 21:56, 4 October 2007 (UTC)[reply]

Well, this "velocity is a vector; speed is a scalar" stuff is convenient for high school physics teachers, but it doesn't necessarily reflect real-world usage. Plenty of times "velocity" is used to mean just the magnitude, and this usage isn't wrong. Similar considerations apply to "weight" and "mass" -- historically, there are lots of contexts in which "weight" means "quantity of matter" rather than "gravitational force". When teaching the subject to students who aren't used to making the distinction, it no doubt helps to have different words, even if you have to be a bit arbitrary about which word to use for which concept. Unfortunately sometimes the students don't realize that the particular semantic assignments made to these terms in a scholastic context don't necessarily apply outside that context. --Trovatore 21:20, 3 October 2007 (UTC)[reply]

Well, yes, but the questioner specifically asked about the two as separate terms, so e is clearly aware that there's a difference between the two. It'd be silly to pretend there's another difference between them other than the scalar/vector "stuff" when answering. GeeJo ^(t)⁄_(c) • 22:15, 3 October 2007 (UTC)[reply]

My point was precisely that, depending on context, there may not be a difference between the two. Some people have so rigidly internalized what they were taught in freshman physics that they're not aware of that. --Trovatore 22:29, 3 October 2007 (UTC)[reply]

Nonsense - there is always a difference between the two words. In some contexts the difference may not matter - but that's not the same thing. A lot of people mis-use these two words - but their meanings are clear and quite distinct. If someone misuses the terms - then please correct them - and if (as in this case) someone asks about the distinction - then we should explain it clearly and without cluttering up the explanation with this kind of misdirection. Some serious errors can be made by people misusing words - so let's not condone it. When we say "The velocity of an object remains constant unless an external force is applied to it" - we mean that neither the speed NOR the direction of motion changed. When we say that "an object cannot exceed the speed of light" - we mean that the direction doesn't matter. It's an exceedingly precise distinction and you make life harder by screwing the terms up. Ditto mass and weight. They are as different as "time" and "thyme". SteveBaker 02:01, 4 October 2007 (UTC)[reply]

No, Steve, you're making the mistake I outlined; over-rigidly internalizing a distinction that someone found convenient to make. "Velocity" is simply the Latinate word for "speed" (must be late Latin; I think classical Latin for "fast" is celerus, not velox). Somewhere along the line someone got the bright idea to use the fancier word distinctively for the vector quantity, and that's fine in context, but it's not wrong not to.

For the mass/weight thing, do a "Google Groups" search on Garry Vass's postings on the subject in alt.usage.english; he makes the point quite convincingly. --Trovatore 02:24, 4 October 2007 (UTC)[reply]

The word "velocity" has two meanings- a more precise one, used within certain fields (science and engineering) and also a less precise common meaning. When in doubt, consult a dictionary- mine shows both meanings, so I'd say this means they're both considered correct. Yes, unfortunate confusion can happen (the word "theory" is notorious for this), but I don't see that it's terribly bad in this case. If someone uses "velocity" to mean "speed" in physic class, yes they should be corrected, but I don't think it's fair to say the usage is always wrong. Friday (talk) 02:31, 4 October 2007 (UTC)[reply]

Exactly -- in physics class, not in physics generally. In class, the assignment speed/scalar, velocity/vector, is observed scrupulously, not at all for linguistic reasons, but as an aid to help students remember that the scalar quantity and the vector quantity are not the same thing (whatever you call them). Once you're past the point where you might confuse the two concepts, there's no longer any great necessity to follow this rather arbitrary naming convention (how would you do a similar thing in Italian, where there's only one word, velocità?). I imagine you wouldn't have to look very hard to find plenty of formal research papers in physics using the word "velocity" for the scalar quantity -- it's hard to imagine a context where this would result in confusion among trained physicists; it will generally be obvious whether the scalar or the vector is intended. --Trovatore 03:09, 4 October 2007 (UTC)[reply]

From our Muzzle velocity article: A gun's muzzle velocity is the speed at which the projectile leaves the muzzle ... (emphasis added) - hydnjo talk 03:49, 4 October 2007 (UTC)[reply]

But surely that is a vector? The muzzle velocity is the speed in the direction out of the muzzle. The distinction still seems apparent :) I'm not saying people don't use one for the other, just that this is perhaps not an example of it. 79.65.119.193 10:01, 4 October 2007 (UTC)[reply]

Maybe the distinction seems apparent because you just happen to know that when a bullet leaves a gun, it travels in the same direction as the muzzle. And, I must say, that would seem pretty obvious to most people, I imagine. I think the purpose of that definition was to talk about the speed/velocity of the bullet without regard to whatever direction it happens to be travelling in relative to the muzzle. Which would explain why the direction isn't referred to. -- JackofOz 10:24, 4 October 2007 (UTC)[reply]

Toe Nail

What might make a human toe nail discolor, like to an ugly brown or black? I was assuming that the toe nail was "dead" -- but, on second thought, isn't every toe nail already "dead" (that is, some form of dead skin)? If a toe nail were to become dead/discolored, would it just remain there or would it fall off? And, what type of doctor handles this? Would it be a dermotologist ... or something else? Thanks. (Joseph A. Spadaro 19:41, 3 October 2007 (UTC))[reply]

We aren't allowed to offer medical diagnoses. See a doctor...a podiatrist perhaps. SteveBaker 19:48, 3 October 2007 (UTC)[reply]

He's asking a question. What makes a toe nail discolor. That's not a medical diagnoses. 64.236.121.129 20:42, 3 October 2007 (UTC)[reply]

It can go black when there is blood underneath it. This could happen if a bruise happens to the nail - eg hit with a hammer. If the nail bed is damaged then a new nail may grow out. Eventually the black will disappear. The nail itself is not living cells, but underneath the skin is alive. Graeme Bartlett 21:06, 3 October 2007 (UTC)[reply]

I agree. It's a question, not a diagnosis. With that said: The toenail is "dead", but there is a living layer of cells underneath called the nail bed. The most common causes are damage to the nail bed, which can occur from dropping something heavy on your toe or kicking something (or someone!). Also very common are dermatophytic fungal infections of the nail bed. Minor damage from blunt-force trauma will usually heals naturally over a few weeks, however, fungal infections usually persist and may worsen over time. This can result in the nail completely falling off, and even spreading to other toes. Any licensed general/family practice doctor is able to diagnose and treat the problem. If it's a fungal infection, there are prescriptions available (Lamisil). If the problem is due to a less-common problem (skin condition, immunological problem, adverse drug reaction, diabetes, gangrene) or the toe is damaged to the extent that it requires surgery, the family doctor will usually refer the patient out to an appropriate specialist, which may be a dermatologist or even a podiatrist. Kel - Ex-web.god 21:04, 3 October 2007 (UTC)[reply]

Apropos of nothing, bruises under nails are subungual hæmatomae GeeJo ^(t)⁄_(c) • 22:00, 3 October 2007 (UTC)[reply]

Another common source of blackened and/or falling-off nails is running marathon distances, as I can currently -- and grotesquely -- attest. --Sean 22:05, 3 October 2007 (UTC)[reply]

Another couple causes of this are frostbite and lead poisoning. StuRat 06:23, 5 October 2007 (UTC)[reply]

Tattoos, Moles and Fat

I'm wondering whether moles can have an impact on tattoos. For instance, is it at all possible to tattoo a mole? What happens if you get a tattoo, and some time later you develop a mole where the tattoo is?

And while I'm at it, what happens to a tattoo if you get fatter/more muscular?

Thanks, 81.165.126.252 20:17, 3 October 2007 (UTC)[reply]

The Tattoo FAQ on About.com may be of some use. In short: moles, acne, and other skin blemishes while you are getting a tattoo aren't going to make the artist's job any easier, and if the mole(s) are particularly prominent, you'd probably be better off getting them removed. As for weight change, provided it's fairly slow, you should be alright. Pregnancy or other rapid changes to the area the tattoo is covering are less forgiving, though. GeeJo ^(t)⁄_(c) • 20:56, 3 October 2007 (UTC)[reply]

No reputable tattooist will tattoo over a mole because occasionally they can develop into skin cancer and a possible warning sign is changes in shape & size of the mole. Covering one with a tattoo would make it harder or impossible to spot changes in the mole. Exxolon 01:05, 4 October 2007 (UTC)[reply]

Doppler Effect

If there were two torches, one stationary and one moving towards a stationary observer, the photons from the torch moving towards the observer would have a higher frequency than the other torch. This means that they have a higher energy. Where does this energy come from? (I think I have a basic misunderstanding of the doppler effect, as applied to electromagnetism, but I couldn't decipher most of the article on the Relativistic Doppler effect ). Thanks a lot for your time.86.150.251.208 21:59, 3 October 2007 (UTC)[reply]

Before the moving torch is moving fast enough for this effect to be noticeable, the wind will blow out the flame.

But if you had something other than a torch, say a flashlight for example, then to trace where the extra energy was coming from in your frame of reference, you'd have to trace back to the battery, consider time dilation, consider the changes to the electromagnetic fields within the battery, etc. It would be a tricky accounting problem, but all the books balance in the end. Maybe someone else can break it into a manageable number of accounting steps. --Trovatore 22:42, 3 October 2007 (UTC)[reply]

A torch can mean a flash light in some parts of the world. --antilived^{T | C | G} 00:57, 4 October 2007 (UTC)[reply]

UK IP address generally means UK terms. Torch = electric torch. I hope someone with a better knowledge of relativity than me can answer this question. In my ignorance, I would assume that the energy came from the movement, or something. Hmm, that doesn't really make sense. Skittle 01:00, 4 October 2007 (UTC)[reply]

It's ordinary kinetic energy. In the rest frame of the observer, the moving torch has more kinetic energy than the stationary one, and it also loses more due to radiation pressure (it slows down more than the stationary torch accelerates backwards). —Keenan Pepper 01:10, 4 October 2007 (UTC)[reply]

Don't say I am spoiling all the fun but since Kinetic energy is half mass times velocity squared, where will you fit this extra energy in the equation? A photon has no mass and it has a specific velocity. Oh, I am falling into my own trap ... --Kushal^{Click me!} write to me 03:18, 4 October 2007 (UTC)[reply]

A photon doesn´t have rest mass, but it still has relativistic mass. But does that formula actually work in special relativity? --antilived^{T | C | G} 04:01, 4 October 2007 (UTC)[reply]

Of course the kinetic energy of the source (the flashlight, not the photons!) can be non-relativistic. This effectively provides more energy to the photons, even if the total Doppler effect is treated non-relativistically. Nimur 16:22, 4 October 2007 (UTC)[reply]

Kinetic energy is the difference between rest mass and relativistic mass. If that formula is applied to photons, the result is that they are pure kinetic energy. — Daniel 23:40, 4 October 2007 (UTC)[reply]

normal variation sample #

I've heard more than one stats person say that you need 30 samples to be able to describe a normal variation. Why is this? How do they get 30? I think I once heard 34 too, why would this be? Thanks . —Preceding unsigned comment added by 12.217.195.89 (talk) 22:30, 3 October 2007 (UTC)[reply]

Start by reading Sample size and the links within. --Cody Pope 23:47, 3 October 2007 (UTC)[reply]

In elementary statistics (professional statisticians look away now !) 30 is traditionally given as a heuristic minimum sample size for applying the central limit theorem - see this Yahoo!Answers link. Gandalf61 08:59, 4 October 2007 (UTC)[reply]

October 4

How come cigarrettes don't have nutrition facts?

--Mostargue 01:43, 4 October 2007 (UTC)[reply]

Because you're not supposed to eat them? Because they have no nutritional value? Because there is no legislation requiring it? - Nunh-huh 01:46, 4 October 2007 (UTC)[reply]

Yeh, I think you have to ingest something for it to have nutritional value? HYENASTE 01:52, 4 October 2007 (UTC)[reply]

For the Language Desk I suppose but why does "how come" translate to "why" (or the other way around)? - hydnjo talk 02:01, 4 October 2007 (UTC)[reply]

Supposedly, as a locution for "how comes it that..." or "how did it come about that..." The Random House Dictionary gives a list of similar phrases in noted works: ""How comes it then that he is prince of devils?" (Marlowe, Doctor Faustus); "How comes it that they travel?" (Shakespeare, Hamlet); "How comes it thus?" (Milton, Paradise Lost); "How comes any particular thing to be of this or that sort?" (John Locke, An Essay Concerning Human Understanding); "How comes it to be any concern of yours?" (Fielding, Tom Jones); "How comes this about; there must be some mistake" (Jane Austen, Mansfield Park); "How comes it that we whalemen of America now outnumber all the rest of the banded whalemen in the world?" (Melville, Moby-Dick); and "Then if it's so precious how comes it to be cheap?" (Henry James, The Golden Bowl)." -Nunh-huh 02:10, 4 October 2007 (UTC)[reply]

Holy cow! Thanks ;-) - hydnjo talk 02:23, 4 October 2007 (UTC)[reply]

Thanks ... --Kushal^{Click me!} write to me 03:15, 4 October 2007 (UTC)[reply]

What about chewing tobacco then?--Mostargue 05:27, 4 October 2007 (UTC)[reply]

The same answer would hold -- not ingested / not required by legislation. — Lomn 12:58, 4 October 2007 (UTC)[reply]

It often is ingested; but not normally in quantities that would have any significant effect on your nutrition. You don't usually have nutrition labeling on cayenne pepper, either, and that clearly is ingested by many people. Gene Nygaard 13:10, 4 October 2007 (UTC)[reply]

The short answer is, 'because they're not required to'. Depending on your jurisdiction, different products will fall under different legislation and have different labeling requirements. Beer, wine, and liquor; vitamins, over-the-counter medications, and prescription drugs; cigarettes, cigars, and chewing tobacco—these are all things that you put in your mouth, but in most places they tend not to carry nutritional information on their labels. These products all are regulated in one way or another, though, and all will carry some sort of specific information detailed in whatever local laws are appropriate. TenOfAllTrades(talk) 13:25, 4 October 2007 (UTC)[reply]

Thanks. Now here's my science question: if Cigarettes DID have a nutrition facts label, what would it list?--Mostargue 14:06, 4 October 2007 (UTC)[reply]

According to TheTruth.com there are over 4000 'ingredients' in tobacco smoke. You're going to need a big label if you are going to list the things that come OUT of a cigarette when it's burned. Listing what goes into one is not so useful since you really don't eat them. Mostly, it's leaves and paper...but that's not the problem - it's what happens to those things when you burn them. SteveBaker 15:48, 4 October 2007 (UTC)[reply]

That's 4000 chemical compounds that can be found in tobacco smoke, but ingredient labels list actual ingredients, not the chemical constituents of those ingredients, nor the things they become through combustion. The same source suggests that there are about 600 possible ingredients that are used by at least one cigarette manufacturer, with no indication of how many might be in any one particular cigarette. In any case, it's a bit moot. Cigarettes get warning labels, not nutrition facts labels; there's no nutrition involved, so there can be no meaningful answer to the hypothetical. - Nunh-huh 16:01, 4 October 2007 (UTC)[reply]

But I've seen stuff like mouthwash, which clearly shouldn't be ingested, have nutrition facts. Certainly tobacco companies are required to list the ingredients of their product? I'm sure they could fit a small folded into the carton listing all the ingredients. If not, is this a result of the tobacco lobby?--Mostargue 16:06, 4 October 2007 (UTC)[reply]

I think you are thinking of an ingredient list: certainly mouthwashes have that. I've never seen mouthwash with a nutritional facts label. for, say, a pizza, the ingredients would be Enriched flour, water, mozzarella cheese, pepperoni, tomato puree, asiago cheese, parmesan cheese, yeast, maltodextrin, Salt, Garlic Basil, etc., but the nutritional label would be more like this: File:Pizzalabel.png. Cigarettes (or mouthwash) don't have the fat, carbohydrate or protein content that would make such a label meaningful or useful. - Nunh-huh 16:25, 4 October 2007 (UTC)[reply]

In the USA, alcohol and cigarettes are not managed by the Food and Drug Administration, so both are exempt from the FDA's nutritional information labeling requirements. (Mouthwash usually has an antibacterial agent, so it is regulated as a drug, not as an alcohol... isn't bureaucracy amazing!) We have an entire Bureau of Alcohol, Tobacco, Firearms and Explosives, a federal agency responsible for regulating these items. In addition, individual states may have further requirements regarding distribution (though this probably does not affect labeling and packaging). Nimur 16:24, 4 October 2007 (UTC)[reply]

Lungs vs stomach

In response to previous question:

Would it be possible to gain nutrients from an aerosol or powdered spray vitamin? It would be administered like an inhaler. Or are the lungs unsuitable to distribute nutrition to the body? HYENASTE 01:52, 4 October 2007 (UTC)[reply]

You can administer certain drugs (such as insulin) through the lungs, but these are drugs, rather than nutritional substances. This in essence is exploiting the highly vascular lung structure as a drug delivery system. A cigarette is a means of getting a drug, nicotine, into the blood stream. You can't eat with your lungs; unlike the G.I. tract, no digestion occurs there. . - Nunh-huh 02:06, 4 October 2007 (UTC)[reply]

I understand, but what is the difference between insulin and, for example, vitamin A? And on a tangent, could you create an insulin cigarette? :P HYENASTE 02:40, 4 October 2007 (UTC)[reply]

By "cigarette" do you intend a delivery system that "burns" something to deliver useful insulin as a vapor or gas? - hydnjo talk 02:51, 4 October 2007 (UTC)[reply]

No, a cigarette is made of tobacco. Inhaled insulin is delivered as a powder. See this page if you are interested in inhaled insulin. - Nunh-huh 04:12, 4 October 2007 (UTC)[reply]

There may not be any digestion in the lungs, but digestion is a means to break down food to get the nutrients out, which go into the blood. Lungs are also designed to get stuff into (and out of) the blood (oxygen and carbondioxide, resp). But other substances can also be absorbed, such as several drugs. One could also ask this the other way around; which gases would the lungs not let through? DirkvdM 06:41, 4 October 2007 (UTC)[reply]

The lungs let all gasses through (useful in the delivery of anaesthetic gasses, for example), but the drugs so far alluded to are either solid or liquid; the question to be asked in regard to drug delivery is whether enough of the drug can be administered via this route to have the desired effect. - Nunh-huh 15:15, 4 October 2007 (UTC)[reply]

For large molecules (sugar, most proteins, etc) you generally need an active cellular pump to move the molecules into and out of the bloodstream. These are present in the digestive system, but not in the lungs. --Carnildo 22:02, 4 October 2007 (UTC)[reply]

When do pipes freeze?

How cold does it need to be to freeze pipes. Specifically, at what temperature will pipes freeze where a water faucet that extends from the outside of the house connects to a drip watering system that primarily lays on or just under the ground.

Thanks! —Preceding unsigned comment added by Prplflwr1 (talk • contribs) 02:30, 4 October 2007 (UTC)[reply]

Given enough time (this is important) and if the drip is slow enough (also important) and if the water is reasonably free of minerals (again important), slightly below 0ºC should do it. If the ground/soil is colder than 0ºC then things should freeze up faster but remember that the "drip" or flow rate and the temperature of the flowing water and the length of piping etc. could prevent or encourage freezing. So, we need more data to give you even a ballpark estimate. - hydnjo talk 02:59, 4 October 2007 (UTC)[reply]

At my place the hose will freeze up easily if temperature is below -1°C and it lies on top of the ground, but the water supply pipe very rearly freezes, it will have to be below -5° for quite a while to go solid. I have never had temperatures below -10° where I live. Graeme Bartlett 06:42, 4 October 2007 (UTC)[reply]

Per Hydnjo, there are a lot of factors to consider. Ordinary tap water will freeze at close enough to 0°C so as to make pretty much no difference. While the pressure in the pipe will depress the freezing point very slightly, it's not going to help appreciably—for a single degree drop in freezing point, one would need to elevate the pressure by about 140 atmospheres.

More important is the flow rate in the pipe and its amount of insulation. In order for water to freeze solid, two things must happen. First, it has to get cooled down to 0°C for the freezing process to start. Then you need to remove additional heat – the latent heat of fusion – to actually convert the liquid water into solid ice. It turns out that this second step actually involves quite a bit more energy than the first step. (The specific heat capacity of water is about 4 joules per gram per degree Celsius; to take a gram of cold tap water from 8°C to 0°C one must extract 32 joules of heat. The latent heat of fusion of water is 334 joules per gram—ten times as much.)

So the question becomes, for the flow rate, level of insulation, length of pipe run, and exterior temperature, will a gram of water be able to shed 300 or so joules between the point where it leaves the insulated home and where it exits the pipe? TenOfAllTrades(talk) 13:05, 4 October 2007 (UTC)[reply]

Beyond what TenOfAllTrades said, there's also the question of how much heat is getting into the water piping from inside the house. When we had a spate of very, very cold weather, within the house, we deliberately removed some of the thermal insulation that was covering the copper pipe leading to the sill cock/bib cock. This allowed more of the heat from the house to reach the "freezable" part of the pipe, keeping it from freezing. Alternatively, you could wrap the pipe in electric heating tape; these tapes often come with an automatic thermostat so they only switch on as the pipe approaches freezing temperature. All in all, it's a fine dance between wasting energy and frozen pipes!

Atlant 13:23, 4 October 2007 (UTC)[reply]

There are way too many variables. In Texas, when the weather gets below freezing, it only ever does it for a couple of days each year. So at the depth below ground of the water main coming into the house, it's still well above freezing - so relatively warm water is feeding the drip and keeping the pipe warm. It's unlikely ever to freeze. However, if you're in a part of the world where there is snow/ice on the ground for many months then the water main itself is only just above freezing (maybe it even runs through permafrost!) - so you are dripping very nearly freezing water - and your outside pipes could very easily freeze. Another variable to consider is where the faucet is plumbed into the house. At our home in England (where it does get cold enough for long enough), we have one outside faucet on the side of the (unheated) garage and another coming out of the wall next to the downstairs bathroom. The former freezes up alarmingly often (and even split once) because the water comes out of the cold ground, through the cold garage and then outside. The outlet next to the bathroom never froze because the air inside the bathroom is nice and toasty - and the pipe T's off of the bathroom plumbing and then heats through the wall to the garden. Only a few inches of pipe are exposed to the cold - so it never freezes even without letting the faucet drip. So it's not enough to say what outside temperature makes things freeze. You need to know the deep underground temperature, the amount of pipe that runs through heated parts of the building, you need to know for how long the outside temperature is that cold...insulation...just too many things. SteveBaker 15:40, 4 October 2007 (UTC)[reply]

Is it liquid mercury?

A liquid which produces a convex surface in a graduate cylinder. —Preceding unsigned comment added by Popbet (talk • contribs) 02:46, 4 October 2007 (UTC)[reply]

This sounds an awful lot like a homework question. The concavity of a liquid in a graduated cylinder is dependent on the cohesion of the liquid, and its adhesion to the material of the cylinder (with complications that don't matter for your question). From reading those links, you should be able to figure out whether mercury is a candidate. Someguy1221 04:59, 4 October 2007 (UTC)[reply]

(EC) It depends what the cylinder is made of. For glass, mercury will indeed be convex. See meniscus. --Sean 05:01, 4 October 2007 (UTC)[reply]

That's what all the books say about mercury, but if you look at a real mercury thermometer, the surface looks flat. Why? Do those not use a glass tube? The article about mercury has an image of a mercury barometer which shows the same. – b_jonas 16:48, 4 October 2007 (UTC)[reply]

Thermometers and barometers use very small tubes where the capillary effect is the dominant feature. In other words, the tube is too small for a visible meniscus. Nimur 16:53, 4 October 2007 (UTC)[reply]

Ice cubes and the family jewels

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis.

(EC) You should consult a medical professional. If nothing, it will give them a good laugh too. Lanfear's Bane 15:42, 4 October 2007 (UTC)[reply]

You know, I'm not sure it's fair to the rest of us Reference Desk Regulars to hide questions like these. We could have at least linked the poor questioner to the Darwin Awards article or made some sort of awful "frozen stiff" joke.

Atlant 13:27, 4 October 2007 (UTC)[reply]

That's what edit histories are for :-) SteveBaker 14:35, 4 October 2007 (UTC)[reply]

That's pretty lame. Who would look something up if they don't know what it is? And especially if they have to go through that trouble (the history page is of course quite huge here), assuming they know how to do that in the first place. In this case the header might be interesting enough, but that is not normally the case. DirkvdM 18:17, 4 October 2007 (UTC)[reply]

Yeah, it wasted 2 minutes of my life to look that up in the history page... --antilived^{T | C | G} 21:05, 4 October 2007 (UTC)[reply]

Thank you, Antilived. Personally I can't get up enough enthusiasm to go through all that stuff on the history page.--Eriastrum 22:38, 4 October 2007 (UTC)[reply]

Unplugging electronic devices

My router at home doesn't have a power button and, whenever I need a new IP address, I have to unplug it. For some reason I feel suddenly unplugging an electronic device, such as my router, can damage it. On the other hand, there are many computer peripherals which simply don't have a power button, so it mustn't be crucial for the survival of the device. Additionally, what a power button does is to (suddenly) interrupt the flow of electrons into the device, isn't it? So, is it unsafe or not? --Taraborn 13:24, 4 October 2007 (UTC)[reply]

Unplug the AC (mains) side of the power brick/wall wart, not the DC connector side. You'll be fine. After all, the router must be designed to survive power failure]s undamaged, right?

Atlant 13:29, 4 October 2007 (UTC)[reply]

Could you briefly explain why I should unplug the AC side instead of the DC one, please? Thanks for your answer. --Taraborn 13:51, 4 October 2007 (UTC)[reply]

Unplugging the mains side ensures that power goes away monotonically, whereas pulling the DC power connector may lead to a series of brief power interruptions and restorals that might wreak havoc with the electronics of the device. You may even get arcing. Also, if the DC power connector has more than one power rail, who knows what the removal and re-application sequence of the voltages will be? As I said, the device is clearly designed to withstand interruptions of mains power, but it's not nearly so clear that it's designed to withstand (many) cycles of DC power via the DC power connector. But its' your device so you obviously don't have to take my advice ;-).

Atlant 16:34, 4 October 2007 (UTC)[reply]

I'd say unplug the DC (almost entirely for convenience' sake, though the paranoid can also take comfort in staying further from mains power). As a practical rule-of-thumb, sudden shutdowns will not break electronic devices. You should avoid sudden shutdowns of data storage devices (USB drives, hard drives, etc) while they're doing stuff to prevent data corruption, but yanking the plug on a router is fine. — Lomn 14:41, 4 October 2007 (UTC)[reply]

I can't think of a reason to prefer the AC side. But to answer the original question - with things like this, you only have to worry about unplugging them 'suddenly' if they have data in volatile memory (RAM) that has not been saved out to a more permenant form of storage like a hard disk. For PC's, shutting them down by yanking out the power cord or pushing the OFF switch isn't good for them - but for something like a router that stores things in flash memory, you should be OK to turn it off providing you wait just a few seconds since the last operation. I'm a little concerned that you have to unplug it at all however. Are you doing this so that your computer gets a new IP address when the router comes back up again? Or is it that when you shut down your computer and bring it back up again, the router doesn't give you a new address properly? If it's the latter, then your router is set up incorrectly...which would be a good question for our Computer reference desk. If it's the former...why? SteveBaker 14:41, 4 October 2007 (UTC)[reply]

Thanks to all. My reason for needing a new IP address is that one-click hosts impose a download limit for non-premium users. --Taraborn 15:13, 4 October 2007 (UTC)[reply]

The flaw in your logic is assuming that the power button does something more than break the power rail circuit. In some sophisticated devices, the power switch may trigger a software or hardware shutdown routine, but most small appliances just power down. In that case, unplugging a cord or pressing a button is technically equivalent. Nimur 16:30, 4 October 2007 (UTC)[reply]

I know, I know that my logic isn't the law of gravity, just a general thought for the most common devices. --Taraborn 07:49, 5 October 2007 (UTC)[reply]

As a rule, you want to use the power switch if there is one. Among other reasons, any time you make or break a circuit you get an arc. In low-power devices, the arc is a teensy one. Down at the power station, it's a big, nasty, Frankenstein one. A switch is physically and electrically designed to take that. I have to unplug my router once in a while when it gets confused, and I always just yank the DC. But if you're worried about it, put the router on its own little power strip, and use the switch on that. One reason it's better to cut the power at the wall is that the doodads in the pack help soak up whatever spike happens. If you want it more technical, let me know. --Milkbreath 17:50, 4 October 2007 (UTC)[reply]

I do not think you should even need to power down your router to get a new IP. There should be a reset button that you can use a paperclip to activate. Alternatively you should also be able to reboot the router or have it release/renew the WAN IP from the router's interface. Try plugging 192.168.1.1 into the adress bar of your web browser (other common router LAN IPs are 192.168.0.1, 192.168.123.254, and 192.168.2.1). If you can access the interface you can get a new IP wothout even getting out of your chair! 161.222.160.8 22:27, 4 October 2007 (UTC)[reply]

Pressing the reset button will return the router to factory settings in addition to restarting it, which a lot of people probably don't want to do. Someguy1221 23:28, 4 October 2007 (UTC)[reply]

Hmmm... Not for me. I have used it many times. All settings stay the same (ports, DHCP, static vs. dynamic). Come to think of it, on my particualr model I think the only way to restore defaults is through the console. Good point though, reset switch is prob not the best idea unless you know what will happen. 161.222.160.8 00:41, 5 October 2007 (UTC)[reply]

I would disagree with Atlant that interrupting the mains by withdrawing the plug would result in a monotonic decay of the output voltage. Any voltage above ~~about 70v~~ a few hundred in air at atmospheric pressure is likely to produce arcing. See Paschen's Law. This will give nothing like a monotonic decease in the output voltage, but a series of surges. I would recommend unplugging at the low voltage or dc section of the power supply.--88.109.121.209 01:36, 5 October 2007 (UTC)[reply]

Yeah, but the bulk storage capacitors in the power supply unit will mitigate this; they've already got enough charge in them to ride through at least a half-cycle of the power waveform so introducing small pulses of the (current value of the) power waveform won't affect their charge level much. As I said, one can take my advice or not; it has no impact on me; my networking gear is all powered from a single (common) wall switch so when it needs to be reset (and it does occasionally), I just flip the switch down and back up again.

Atlant 13:27, 5 October 2007 (UTC)[reply]

Bear in mind that large electrolytics have quite a high impedance at rf frequencies, so unless there is proper surge protection, these spikes are going to get through your power supply. I surmise that it all depends upon the current one is trying to break, whether there is enough inductance in that circuit to cause arcing, whether that arcing can be supressed by any filtering you have, and whether the residual surges can damage any components. Its not really a simple question. My advice would be; break the circuit at the lowest voltage/current that you can and make sure the switch dosent cause more bouncing than your filters/suppressors can handle.--88.109.121.209 15:12, 5 October 2007 (UTC)[reply]

Identifying an insect

I don't have a photo, I'm afraid, but it had noticeable orange legs with a browny-orange body, and on the end of the body it had a black patch. It had reasonably long orange antennae and had two points on its 'shoulders' like shoulder blades. Does anyone know what it could be? I'm in the south of England. Thanks. —Preceding unsigned comment added by 84.68.35.79 (talk) 13:28, 4 October 2007 (UTC)[reply]

Your description of "shoulder blades" suggests the Shield Bugs, Pentatomoidea. However, I can't after a quick look find one that has orange antennae. Try doing a google image search of these names and see if they are similar. How big was the insect? What was it doing? What kind of environment did you find it? Did it have wings?--Eriastrum 15:47, 4 October 2007 (UTC)[reply]

Does it match the pics at shield bug ? StuRat 06:11, 5 October 2007 (UTC)[reply]

Peri-synaptic

What does peri-synaptic mean? Lova Falk 14:17, 4 October 2007 (UTC)[reply]

Just as "perinatal" means "the time before and after a birth" or "the time around birth", so "perisynaptic" means "the area before and after a synapse" or "the area around a synapse". -- Nunh-huh 15:09, 4 October 2007 (UTC)[reply]

Thank you! I didn't know what perinatal meant either. :) Lova Falk 15:31, 4 October 2007 (UTC)[reply]

Maybe "periscope" would have been a better explanation...it lets you look all around..... :) - Nunh-huh 15:53, 4 October 2007 (UTC)[reply]

When I think of the meaning of peri-, I always think first of periokoi, but I may be non-typical here. Algebraist 17:20, 4 October 2007 (UTC)[reply]

Within this small period of time, several perilous suggestions almost made me perish... Lova Falk 18:31, 4 October 2007 (UTC)[reply]

Well then have a look a the Peripatetics walking around. The word gave the now disused french "péripatéticienne" for ... hooker! Keria 21:39, 4 October 2007 (UTC)[reply]

You got one out of three. Period does come from Greek peri- "around", but peril comes from Latin periculum "danger", and perish comes from Latin per- "thoroughly, completely", neither of which is related to peri-. —Keenan Pepper 04:47, 5 October 2007 (UTC)[reply]

It makes me think of chicken... — Matt Eason ^{(Talk  Contribs)} 23:30, 4 October 2007 (UTC)[reply]

about optical microscope

can we start the design of microscope with objective using ZEMAX.If i start like that what happens regarding aberrations.which type of objective i can use to get 100x magnification. —Preceding unsigned comment added by Mahendarkumbham (talk • contribs) 15:13, 4 October 2007 (UTC)[reply]

Jack plug

When cutting the wire of a three connector jack plug I can see 3 wires. From the outside it looks like 2 wires running alongside but when i cut them: one in its own plastic insulation and in the second i find a wire wrapped around a smaller third inside a white plastic insulation. Which is left, which right and which is ground? Thank you. Keria 17:34, 4 October 2007 (UTC)[reply]

Sorry my mistake it's actually two pairs of wires and the solution is there http://forum.ecoustics.com/bbs/messages/15118/14935.html . Keria 17:48, 4 October 2007 (UTC)[reply]

Definition of a Human

What do people think of this definition? An embryo must have both brain and heart cells present (happens three weeks after conception) to be considered a human or must have at least one cell from each organ that a healthy adult cannot live more than a 24 hour period without. I have also heard that a human is composed of three parts: body, soul and spirit. If this is true, is there a way of detecting this and if so would this change the definition of a human to be: have both heart and brain cells present and have a detectable soul/spirit? —Preceding unsigned comment added by Rsdetsch (talk • contribs) 17:38, 4 October 2007 (UTC)[reply]

You may define a human however you like for any given argument. Definition of terms is really a matter of choice, not science. As far as detecting a soul, there is no scientific evidence that any detectable item which you might call a soul exists. We do, however, usually have an easily detectable brain. Nimur 17:41, 4 October 2007 (UTC)[reply]

One might argue that someone doesn't have a "soul" until well after birth, maybe even back it up with various religious references. As Rsdetsch (actually Nimur) says, there's no empirical evidence of a soul, only religious or non-scientific theories. -- JSBillings 17:46, 4 October 2007 (UTC)[reply]

I said that, not Rsdetsch! Nimur 17:48, 4 October 2007 (UTC)[reply]

Whoops, sorry. I picked the wrong name out of the earlier wikitext. -- JSBillings 17:51, 4 October 2007 (UTC)[reply]

Thanks for your comment(Nimur), but is there an indirect way of detecting a Soul and/or a relational dependence we can associate with its existence. Like a Soul cannot exist without a brain? —Preceding unsigned comment added by Rsdetsch (talk • contribs) 17:49, 4 October 2007 (UTC) [reply]

It depends on your definition of Soul. Check out the Science and the soul section, to see some attempts of defining "soul" scientifically. You'll see a later discredited attempt to discover the weight of the soul by measuring the weight of the body before and after death. -- JSBillings 17:55, 4 October 2007 (UTC)[reply]

That is an interesting point (JBillings), if one was able to come up with a unique weight of a human soul then one can come up with a necessary (not sufficient) condition of being human e.g. if the embryo weights less than that unique weight it is not a human. —Preceding unsigned comment added by Rsdetsch (talk • contribs) 18:14, 4 October 2007 (UTC)[reply]

No - that truly wouldn't help. If you could come up with some bizarro experiment that measured the weight of a soul - I guarantee that you'd be able to do the same experiment on a Chimpanzee - get more or less the same result - then have to fight tooth-and-nail with the religious loonies who claim that "animals don't go to heaven because they don't have souls" - so now you have to label this thing that your experiment showed up with some other name - and now you are no closer to proving the moment of humanity. SteveBaker 18:18, 4 October 2007 (UTC)[reply]

Besides, you'd have to prove that souls have constant weight. If not, the weight of a fullgrown one would not help. 69.95.50.15 20:10, 4 October 2007 (UTC)[reply]

It doesn't really matter how you make your definition - it's just a word after all. What matters is what you intend to use the definition FOR. If (to take an obvious example) you are talking about the abortion debate - then one bunch of people are going to complain bitterly about your definition because it de-humanises the very young and "permits people to murder them" - and another bunch are going to complain just as much because it implies that the termination of a fetus beyond a certain (fairly early) age is "killing a human" and that would effectively remove "the right to choose". So, by all means, define the word however you like - but don't expect many people to agree with you! There is no "right" definition from a scientific perspective - there is a continuous process from the instant of conception, through birth and into adulthood - and we could pick any one of a bazillion events along the way to label as "the transition to humanity". Personally, I would prefer to use the word 'human' throughout the process - the label says what kind of cells this fetus is made of - as in: "This is a human egg/fetus/baby/child/adult as distinct from a chimpanzee egg/fetus/baby/child/adult." SteveBaker 18:15, 4 October 2007 (UTC)[reply]

Well said, SteveBaker. I have to wonder why having a brain, heart or soul matters for the definition of Human. Does having an artificial heart make one less human? What about an artificial brain? One could go as far as defining Human as the common genetic sequences all humans share. I think the OP really was trying to define what makes someone a conscious entity (although the heart is no more important than the lungs when it comes to cognition). -- JSBillings 20:02, 4 October 2007 (UTC)[reply]

Typically these debates focus on "personhood" rather than humanity. My own simple test -- equally unsatisfactory as a universal one, no doubt -- is "if it looks like a person, it is". I could quibble about when that happens, but I'll never be convinced that some "persons" look like this (actual size) ---> • --Sean 20:12, 4 October 2007 (UTC)[reply]

Just don't try to use that to advocate abortion. The question isn't about whether or not it's killing something that looks like a person. The question is about whether or not killing a fetus, whether or not it matches any definition of a person, is wrong. — Daniel 23:29, 4 October 2007 (UTC)[reply]

I like to look at the implication of a proposed rigorous definition of what is a human. If heart tissue must be present to qualify, then during a heart transplant, the recipient ceases being human for a while once his old hear has been removed and before his new heart in installed. He was human when they began the operation, then he was not human for a while, then he was human again. The notion just doesn't work for me. Edison 02:26, 5 October 2007 (UTC)[reply]

We have an article on that effect and several variations (all stem from a continuum fallacy. It's come up on the desk a few times. As I mentioned, you can play whatever games you want with your definitions. Consistency becomes very difficult when you take a large number of scenarios into account. Nimur 03:08, 5 October 2007 (UTC)[reply]

The problem is that it's OK (useful, valuable, reasonable) to give a name to some region of a continuum - so to say "This is a fast car" because it can go 200mph is not disputed by anyone and to say "This is a slow car" when it has a top speed of 20mph would not be disputed. The problem comes when you get into the grey area between those two terms. Is a car that can only go 70mph fast or slow? But this doesn't matter so long as you don't use these vague 'partial-continuum' names to force a binary yes/no decision. We don't try to pass laws that say "You aren't allowed to drive fast down this road" - we say "You aren't allowed to drive at more than 40mph down this road".

The same exact problem bedevils the abortion debate. We mostly agree that you shouldn't be allowed to kill a "person" - but almost all of us agree that a single cell is not a "person". If I cut my finger and it bleeds - we don't rush the droplets of blood to the hospital and attempt to keep them alive - yet they are just as 'alive' and 'human' as a newly fertilised human egg cell. So here we have a continuum - yet people are talking about it as if it was not a continuum. This forces some people to have to take an extremist attitude that goes something like "Because we don't argue about whether a two-week premature baby is a person - and we have a continuum from there all the way back to the instant of fertilisation of egg by sperm - then we must declare that one is a full person with all rights that this entails from the moment of fertilisation."...but in reality, that's as dumb as saying "Driving at 200mph is obviously dangerous and should be disallowed - but because there is a continuum between that and 0.001mph, then it follows that all cars must be banned." SteveBaker 14:51, 5 October 2007 (UTC)[reply]

Moon Rise and Set

I watch the moon quite frequently when out walking my dogs. Although I know there are phases to the moon and how long it takes for that whole cycle to occur. I haven't seen anything that tells how to tell what time the moon will rise and when it will set. Is there a specific way to know that?206.17.145.132 20:32, 4 October 2007 (UTC)beth[reply]

Some newspapers print sunrise, sunset, moonrise, and moonset times; otherwise you need to consult an almanac or its equivalent. It obviously depends on your specific location. One that's online is <http://www.skyandtelescope.com/observing/objects/javascript/3305541.html#> - Nunh-huh 21:33, 4 October 2007 (UTC)[reply]

A full Moon is opposite the Sun, so it rises when the Sun sets (roughly at the other side of the horizon) and vice versa. A new Moon is at the same side as the Sun, so it rises and sets together with the Sun, at roughly the same spot. You figure out the middle parts. :) (Sorry, a bit tired now, should be going to bed). DirkvdM 18:50, 5 October 2007 (UTC)[reply]

Awake again now. See lunar phase. In the first quarter, the Moon is straight overhead at sunset (where it says 6 pm) and then follows the Sun and sets in the west at around midnight (depending on how your timezone differs from solar time). And in the third quarter (when it forms a 'C' in the Northern Hemisphere), it rises at midnight and is overhead when the Sun rises. DirkvdM 08:55, 6 October 2007 (UTC)[reply]

Thirst for knowledge and the human condition

Okay, so this is more of a philosophical question than an actual scientific one; but what if one day we reach the limit of miniturisation and computational power and still the technology we have has not unlocked the secrets of the universe and the human condition. What happens next? Are there enough 'clever people' to be able to think our way to the answers we are looking for? Do we simply give up on certain questions? What if locked within our own experience is the inherant inablility to understand even the questions to ask, let alone the answers we find? --russ 22:55, 4 October 2007 (UTC)[reply]

You are asking the wrong question. We will never the unlock all the secrets of the universe because we only have 80 years of thinking life. Just look at what it takes to do orignal research nowadays, you need to study for 25 years before you can reach a point where you know the known science.

If we ever reach a point where we need to study 80 years before we can do original research then we have hit our thinking limit and humankind cannot progress further scientificly. 202.168.50.40 23:16, 4 October 2007 (UTC)[reply]

Yes, I agree with your perspective, but I meant generally, rather than personally - could one individual not continue another's work until we find the answers we are looking for, much in the same way that that for instance our understanding of 'gravity' continues to develop, even though it takes centuries to build up that knowledge? I am making the assumption that we are able to build upon our understanding, otherwise fields that took Newton and Einsein a lifetime of calculation to grapple with would not have progressed, surely? --russ 23:26, 4 October 2007 (UTC)[reply]

John Horgan wrote a book called "The End of Science" and suggested that we are passing out of the golden age of science. My personal view is that there is still a large amount of interesting science to be done, and it seems far to early to put much effort into worrying about "the end of science". --JWSchmidt 02:12, 5 October 2007 (UTC)[reply]

It seems to have been a general feature throughout the history of the sciences that as soon as people start making comments about having "discovered nearly everything", "just need to get the constants down to a couple more decimal places and fill in a couple of holes", "solve some minor problems", etc. - that's when someone makes some startling discovery that turns all of our current knowledge on its head. I'd even be willing to guess that we're approaching such a time soon. Confusing Manifestation 04:10, 5 October 2007 (UTC)[reply]

What I'm trying to say is that all the easy fruits have already been picked. The fruits of science still left hanging on the tree of knowledge are the really hard ones, ones that needs years of study before you can even begin to try picking them.

But you can't go from this to say that we have picked all the fruits of science. There will always be fruits of science so high up the tree of knowledge that we can never pick them. 202.168.50.40 04:47, 5 October 2007 (UTC)[reply]

Science as we know it today is not the right method to unlock the secrets of the universe and the human condition. Lova Falk 09:13, 5 October 2007 (UTC)[reply]

People thought we had discovered everything useful in physics in 1905. The only things left were blackbody radiation and the nature of light, but it was thought those things would be solved soon under classical physics. They couldn't be more wrong.--Mostargue 11:20, 5 October 2007 (UTC)[reply]

There's no reason to be sure that we will be *able* to understand everything that we can observe. There's no more evolutionary requirement for us to be able to, say, come up with a grand unification theory than there is for a dog to be able to set the time on a VCR. --Sean 12:34, 5 October 2007 (UTC)[reply]

Are we close to knowing everything? The claim that we're close to having learned all that there is to know comes up at least once a century - and every time (so far) it's been proven wrong. To be sure, the rate of new discovery is increasing exponentially - but there are two ways to look at that. One is that at this prodigious rate we'll very soon have discovered everything we're capable of - but the other is that we are opening up lines of new enquiry at an exponential rate too. So I doubt we'll ever know everything - but I'm optimistic that during the last 50 years we've answered a lot of the really big questions to a reasonable degree of accuracy. The very large, the very small and the very old were shut out of our knowledge until quite recently but now we can answer "Where did we come from", "What makes the sun shine", "What is the smallest indivisible object"...many of those things were still completely uncertain even 50 years ago - yet nowadays, even my teenage son has a pretty good shot at giving a good answer.

Are there things that we cannot ever solve? Yes - we know that there are mathematical theorems can be neither proved nor disproved, we know that some measurements are strictly limited in precision, we know that some calculations will take longer than the life of the universe to perform so we cannot calculate an answer, we know that 'sensitive dependence on initial conditions' (chaos theory) puts sharp limits on our ability to do even seemingly easy things like predicting the weather that we once thought we'd have solved within 50 years.

Are there are things we can't ever do because we aren't smart enough?...that's a tough one. Humans have several unique abilities that mitigate the limits of the sizes of our brains. We have computers - it's pretty clear that we can make a computer that's faster than we are and which has a better memory - we're fairly sure that a computer that's generally more intelligent than us is possible (although efforts to actually build one have been frustratingly difficult). But if such a computer existed, it could probably be used to make another computer yet faster and smarter still - and so on to the limits of practical technology. (Let's face it - there is absolutely no way we can design a computer even now without using another computer to do the bulk of the work.) We have writing and speech which lets us communicate ideas so that one person doesn't have to solve a problem alone - we network our brains and our increasing population is making us collectively smarter. We can also spread the work of making a discovery over many generations - breaking problems into sub-problems and sub-sub-problems until we have small enough pieces to be tractable to a single person within their lifetime.

Is there an issue with it taking longer and longer to learn what you need to know to get started on a problem? This is something that we've always solved by specialising. As subjects get too large for one person to fully understand, we split them into specialities. So in the time of Newton, one person could be fairly conversant will all of science and mathematics. Nowadays there are dozens of branches of mathematics and hundreds of sub-specialities within science because even knowing everything there is to know about (say) cosmology is more than one person can handle.

SteveBaker 14:23, 5 October 2007 (UTC)[reply]

Level of fossilization in T.Rex Tissue?

I'm reading a paper published in Science magazine two years ago [11]. It documents a famous finding of soft tissue in T.Rex fossil bone. I'm trying to figure out to what extent the tissue recovered from the bone was fossilized, but I'm just a half-educated layman and I get lost easily in all the big words. First, what precisely is the definition of "fossilization" that a scientist would use? To what extent must the remains of the organism be changed (or do they have to be changed at all)? Second, the paper refers to the tissue having to be "demineralized" before analysis. Does this imply that the tissue had been fossilized, or is it something that you would have to do to any bone to get at the tissue? Thanks! 69.218.205.188 00:23, 5 October 2007 (UTC)[reply]

FWIW, bone specimens usually are decalcified before attempting DNA extraction, as it greatly increased the yield, even in fresh bone. - Nunh-huh 00:42, 5 October 2007 (UTC)[reply]

I was about to say "that's impossible", but then I read this section in our T. Rex article. The term "fossilisation" usually means that the original tissue has been replaced by minerals. So if soft tissue was found inside a fossilised bone then it would be more correct to say it has been "preserved" rather than "fossilised" - indeed the title of the Science paper, which is cited as a reference in our article, is Soft Tissue Vessels and Cellular Preservation in Tyrannosaurus rex. The "demineralisation" process uses weak acid to dissolve the fossilised bone, and so presumably leave the soft tissue remains behind. The researchers claim to have found blood vessels, tissue that is still flexible, and possibly even blood cells. If this find is confirmed by other researchers then it is a truly astonishing discovery. Gandalf61 09:02, 5 October 2007 (UTC)[reply]

Macaroni and cheese mystery

Say I pour a packet of cheese powder on my macaroni, then I pour a cup of milk onto the powder. But instead of soaking into the powder, the milk just beads up and rolls right off down to the bottom of the bowl. The powder stays totally dry! What's going on? This has bugged me for years. 154.5.195.217 01:20, 5 October 2007 (UTC)[reply]

The cheese is greasy and contains fat that repells water in the way you say. If you can melt the cheese you find that the fat is actually in very small droplets and can disperse in the milk if it is mixed. Graeme Bartlett 01:30, 5 October 2007 (UTC)[reply]

I had no idea that cheese came in powdered form. Is it dehydrated? Nimur 02:51, 5 October 2007 (UTC)[reply]

Yes, in a little packet that comes in the Kraft Macaroni and Cheese package (or several other brands). You must not be from the US if you don't know about powdered cheese. I don't think the earlier explanation is correct, however, as the cheese packet does not contain much fat. That is supplied by milk and butter which are added to the mix. StuRat 04:17, 5 October 2007 (UTC)[reply]

I'm not sure of the cause, but chocolate powder in milk does the same thing. A boundary layer seems to form between the milk and powder which can only be broken up by vigorous stirring. StuRat 04:23, 5 October 2007 (UTC)[reply]

The best plan is to add a small amount of milk to the powder in a cup, mix it well into a half-runny paste, add enough more milk to enable it to coat the macaroni, mix it again, pour it onto the macaroni, and pour the remaining milk on top. -- JackofOz 04:59, 5 October 2007 (UTC)[reply]

Right, but I think the original poster was looking for an explanation of why the powder won't dissolve more easily. StuRat 06:03, 5 October 2007 (UTC)[reply]

It's certainly not due to any fat content, because talcum powder behaves in the exact same way. I think it has to do with wetting and hydrophobicity. Here are the ingredients of the "cheese" packet: Whey, Milkfat, Milk Protein Concentrate, Salt, Calcium Carbonate, Sodium Tripolyphosphate, Contains Less than 2% of: Citric Acid, Sodium Phosphate, Lactic Acid, Milk, Yellow 5, Yellow 6, Enzymes, Cheese Culture. --Sean 12:47, 5 October 2007 (UTC)[reply]

General rule: Any product that contains the word "American" and "Cheese" in it should be avoided at all cost. American cheese is bland beyond belief - the only difference between the different kinds is the colour. Somehow they've even found a way to pursuade the French to make stuff that looks just like Brie and even comes in one of those little round wooden boxes - but which tastes of exactly nothing and goes hard as it 'matures' instead of turning into a pungent creamy liquid as should be the case. I don't know how they do this...or why...but it's a fact. I bought some 'Munster' in the supermarket the other day - this is one of the strongest smelliest cheeses you can find in a French supermarket - and this stuff smells and tastes of precisely nothing. As far as I can tell is exactly the same stuff as their "Sharp cheddar" - but without the orange food colouring. "Sharp cheddar" has definitely not been within several thousand miles of Cheddar gorge - and is only sharp in the sense that a marshmallow is. My wife (who is French) found an interesting little cheese shop in Dallas - it turns out that the cheeses they keep are exactly the same as the ones in WalMart except that some have little bits of nuts in them. Hence we may deduce that the strange orange powder that comes with Mac'N'Cheez is some fascinating chemical substance with all sorts of interesting properties...none of which should encourage you to actually eat the stuff. SteveBaker 13:44, 5 October 2007 (UTC)[reply]

What you describe is processed cheese. The main ingredient is soybean oil, versus milk/cream for real cheese. Note, though that real cheeses are also made in the US. I do, however, agree that "American cheese" seems to be a keyword for processed cheese. I would expect that if you bought "sharp cheddar" in the US, it would indeed be real cheddar, unless it had some disclaimer on the label like "processed", "cheese food", "cheese product", or "artificial".

Another hint, any cheese that comes sliced in tiny plastic wrappers is also likely to be "processed cheese". (Cheeses sliced with tiny pieces of waxed paper between them tend to be real, however.) Most Americans are rather disgusted by smelly cheeses, however, so you will find a rather small market for limberger, etc.StuRat 17:38, 5 October 2007 (UTC)[reply]

It's not cheese if you can't smell it from three counties away! DuncanHill 18:59, 5 October 2007 (UTC)[reply]

digestive tract

05:02, 5 October 2007 (UTC)05:02, 5 October 2007 (UTC)~~m4.239.243.165 05:02, 5 October 2007 (UTC)Is it neccessary to have a bowel movement everyday? And is there a certain number of bowel movements a person should have per day?4.239.243.165 05:02, 5 October 2007 (UTC)[reply]

From 3 a day to once every 3 days is the guideline I heard, and that's the latest poop. StuRat 05:51, 5 October 2007 (UTC)[reply]

Quite. I once heard that nothing varied so much between humans as much as this statistic. It depends a lot on what you eat. Once every three days was normal for me as a kid, because I was fed hardly any roughage.--Shantavira|^{feed me} 17:37, 5 October 2007 (UTC)[reply]

In Western societies, people generally defecate two or three times a day, but it’s an individual matter. All the advice about the importance of regular bowel movements notwithstanding, some people defecate just once a week and are perfectly healthy. Constipation isn’t defined by the frequency of bowel movements, but by whether someone has difficulty when they have one. —Preceding unsigned comment added by 88.109.121.209 (talk) 19:53, 5 October 2007 (UTC)[reply]

It's my understanding that keeping feces in the bowel for long periods is associated with higher colon cancer rates. --Sean 14:19, 6 October 2007 (UTC)[reply]

Klebsiella Infection

What is the acceptable colony count of Klebsiella per Milligram?

Diya Mukherjee —Preceding unsigned comment added by Diya2710 (talk • contribs) 07:38, 5 October 2007 (UTC)[reply]

It's impossible to answer the question for at least two reasons. First, you haven't specifed what is being counted (though I suspect you're talking about urine). Second, colony counts alone are not diagnostic of anything: a colony count has to be considered in light of actual clinical conditions (symptoms of the person, reason for the testing, the presence or absence of instrumentation). As such, a colony count really needs to be evaluated by the treating physician or other medical practitioner. For example, if a patient has an indwelling urinary catheter and a colony count of 10,000, it might be considered a colonization requiring no treatment (in the absence of symptoms), and it might also be considered an infection requiring treatment (in the presence of fever or other symptoms). Similarly, the significance of the presence of Klebsiella in sputum would depend on the clinical setting in order to distinguish between colonization and infection. - Nunh-huh 17:37, 5 October 2007 (UTC)[reply]

This sounds like either a homework question or medical advice. The Reference Desk has a policy of not answering either. If homework, look it up yourself (e.g. in your textbook or class material). If medical advice, talk to a licensed medical professional. -- 72.33.121.200 18:58, 5 October 2007 (UTC)[reply]

It sounds like neither. A homework question would be more exactly phrased, and medical advice would pertain to a clinical question rather than an abstract one about lab values. - Nunh-huh 20:02, 5 October 2007 (UTC)[reply]

What kind of lock / key combination is this?

I need access to this common type of lock to open a panel but I don't know the name of the lock / key I need to get hold of to open it. These things open pretty easily and I have a feeling some thin pliers might do the job, but is there a particular name? Thanks.

http://img515.imageshack.us/img515/862/lockfh6.png

Looks like a meter cabinet - I think (in the UK) you should be able to get one from Screwfix, B&Q, Homebase etc. They are just called "meter cabinet keys". DuncanHill 08:48, 5 October 2007 (UTC)[reply]

aids

why aids donot spread by mosquito bite? —Preceding unsigned comment added by 202.177.155.94 (talk) 10:45, 5 October 2007 (UTC)[reply]

HIV_and_AIDS_misconceptions#HIV_is_transmitted_by_mosquitoes--Mostargue 11:13, 5 October 2007 (UTC)[reply]

unlitateral carotid ligation

What is unlitateral carotid ligation? Does it just mean that the two carotid arteries are connected? What would serve as the conduit? It's used or was used, as part of an animal model for cerebral ischemia. --Seans Potato Business 13:43, 5 October 2007 (UTC)[reply]

Here's a partial answer. Unlitateral carotid ligation is the tying off of one of the two carotid arteries, which supply the head and (most importantly) the brain. Normally, this should not cause problems because of the Circle of Willis, which is a circular arterial loop fed by both internal carotid arteries. However, if one of the carotids is partially or completely occluded (e.g. with atherosclerotic plaques), it would be dangerous to ligate the carotid on the other side. -- Flyguy649 ^talk _contribs 15:43, 5 October 2007 (UTC)[reply]

(after edit conflict) Unilateral carotid artery ligation is the closure of the carotid artery on one side. The artery is not rerouted or attached anywhere else; it's just closed. It is indeed used in animal cerebral ischemia studies. See for example Guri Bronner, Kendall Mitchell and Frank A Welsh "Cerebrovascular Adaptation After Unilateral Carotid Artery Ligation in the Rat: Preservation of Blood Flow and ATP During Forebrain Ischemia" in the Journal of Cerebral Blood Flow & Metabolism (1998) 18: 118–121 [12].

It turns out that closure of one carotid artery doesn't typically have any serious effects in an otherwise healthy rat's brain. There's sufficient redundancy in the blood vessels of the rat's brain to maintain an adequate supply of blood to the affected hemisphere of the brain. However, combining this closure with other stresses (hypoxia, closure of additional vessels, etc.) will cause damage—there's not as much 'reserve capacity' in the system. Some researchers have looked at the ability of the rat's brain to adapt to closure of one or more major vessels to model chronic disease in humans; the paper I linked above showed that closing one carotid artery results in adaptive vascular changes in as little as three days. (This can happen in humans as well; there are cases of patients with both of their carotid arteries completely closed—their brains get sufficient blood through vertebral arteries that have expanded to take up the slack.) TenOfAllTrades(talk) 15:47, 5 October 2007 (UTC)[reply]

Thank you both. I see how "unilateral" was pointing in this direction, and checking that article, I gather "ligation" refers to the closure of the vessel ends created by cutting through it. --Seans Potato Business 18:25, 5 October 2007 (UTC)[reply]

"Ligature" refers to closing it by tying (see wiktionary:ligature; compare to ligature strangulation). However, practically , it doesn't matter how one of the carotids is blocked. -- Flyguy649 ^talk _contribs 21:05, 5 October 2007 (UTC)[reply]

Petroleum jelly

Is there a silicon based equivalent for Petroleum jelly? 71.100.9.205 17:36, 5 October 2007 (UTC)[reply]

For what use? Shoe shine? Lip moistener? Spitball doctoring? Personal lubricant? People use petroleum jelly for many different things, so you'll have to clarify what you want the silicone equivalent for. Note also that silicon is a chemical element, while silicone is the slippery rubbery stuff. --Sean 17:56, 5 October 2007 (UTC)[reply]

To compare its physical, mechanical and thermal properties for a school project? —Preceding unsigned comment added by 71.100.9.205 (talk) 18:07, 5 October 2007 (UTC)[reply]

Silicone grease probably. You should be able to get some at a car parts store. (Note that's silicone - although it contains silicon). SteveBaker 18:32, 5 October 2007 (UTC)[reply]

Is there any real difference between generic silicone O-ring sealing greases and a specialized silicone grease like Dow Molykote 55? Kel - Ex-web.god 20:37, 5 October 2007 (UTC)[reply]

Modulation techniques book

Can someone give me the name of some good books on modulation techniques for wireless communication systems? I'm particularly interested in information about QAM and the various forms of PSK, which I think are the most used modulation formats and also OFDM. I would appreciate your help, thanks! 217.129.207.58 21:28, 5 October 2007 (UTC)[reply]

Look for Signal processing, modulation and noise by J.A.Betts (Dept Electronics Univ of Southampton). Published by Hodder and Stoughton 1970 (reprinted 1975 and maybe later) ISBN N0: 340 09895 3 (paperback) or 0 340 05212 0 (Case bound) —Preceding unsigned comment added by 88.109.121.209 (talk) 22:22, 5 October 2007 (UTC)[reply]

Proakis and Manolakis Digital Signal Processing is a good start, and though it's not extremely thorough in the actual modulation architecture, it will provide the processing techniques you need to use, which will assist your understanding. Nimur 22:51, 5 October 2007 (UTC)[reply]

Preferential Solubility?

Assume I have two substances of differing solubility in water: A=250mg/mL and B=50mg/mL. Excluding any temperature and pressure variables, what happens when I add 250mg of A and 50mg of B in 1mL of water concurrently? I assume both substances partially dissolve, but in roughly what amount or ratio? Also, what happens when A and B are added to the water consecutively? Last question: what's the name of the rule/law/effect/whatever that governs this effect? Kel - Ex-web.god 23:07, 5 October 2007 (UTC)[reply]

I think you are likely looking for the common ion effect. We would need to know more information to tell you specifically what would happen, but this has hints of a homework problem. Someguy1221 00:15, 6 October 2007 (UTC)[reply]

Hmm. I never would have guessed my writing style could be confused with that of a 12-year-old. Regardless, were this a homework problem, I'd have asked it a decade ago, when I was still in college. :) This is for my own education. Anyway, what further information do you need that would make any difference? The solubility figures above weren't from any specific substances, but if it makes a difference, I'd say any random hydrochloride (or sulfate) salts. Kel - Ex-web.god 00:39, 6 October 2007 (UTC)[reply]

To a first approximation, this turns out not to be the case: the basic rule is that the concentration of one substance in a solution will not affect the solubility of another. This is because the solubility of a substance is not determined by "the amount of dissolved stuff the water can hold", but by a chemical equilibrium at the interface between the solution and the solid substance. Basically, the substance dissolves at a constant rate (per unit area), but also precipitates back at a rate proportional to its concentration (again per unit area). In a saturated solution these two rates will be equal, and no more of the substance can dissolve.

Of course, these rules do have exceptions. One is the "common ion effect" already mentioned above: if the substance split into multiple components when dissolving, the concentrations of all those components will affect the precipitation rate. Another is that, to be precise, the word "concentration" in all of the above really needs to be replaced with chemical activity, a more complicated measure that tends to be proportional to the concentration in dilute solutions but deviates from it in more concentrated ones. The activity can also depend on the general ionic strength of the solution: essentially, as the solution gets concentrated enough, the different dissolved substances start interacting with one another. Our article on the solubility equilibrium lists several more such effects, and also describes the matter in general. —Ilmari Karonen (talk) 15:33, 6 October 2007 (UTC)[reply]

Scarlet Macaw

Should his claws cut into and hurt my shoulders like that? I only got him recently and he seems to really dig in and hold on when he sits up there. —Preceding unsigned comment added by 81.79.213.158 (talk) 23:45, 5 October 2007 (UTC)[reply]

Excluding the possibility that he really dislikes you, I'd say it's because his claws are designed to grab a branch. Your shoulder is too big, so he needs to squeeze harder to get a good grip. It might help if you wore a strong (for you), yet thin (for him), shirt. And preferably just one (so not a shirt and a t-shirt). DirkvdM 09:01, 6 October 2007 (UTC)[reply]

Glucose in benedict's solution

When one puts glucose into a dialysis tubing and into a test tube of Benedict's Solution and heats it in a water bath, the Benedict's solution inside the test tube turns an opaque yellow. But does the glucose inside the dialysis tubing (which is inside the test tube) also turn yellow? I guess in short, will the Benedict's solution diffuse into the dialysis tubing? Thanks. Acceptable 23:46, 5 October 2007 (UTC)[reply]

Try Benedict's reagent. --JWSchmidt 15:28, 6 October 2007 (UTC)[reply]

Self sufficient communities

This is a follow up question to Planning for a bleak future on the Miscellaneous reference desk. I have two questions about closed communities:

What is the smallest possible genetically self sufficient community? (In other words, how big does an isolated community have to be so it will not die off through inbreeding?) 500? 1,000? 2,000?
How many acres of arable land/pasture is necessary to support an adult person year round? (x acres of land divided by x number of people in community). How would this differ between Subtropics, Humid continental and Temperate climates?

Thanks for your help! --S.dedalus 00:28, 6 October 2007 (UTC)[reply]

To answer the first question our article on a generation ship says about 500 people. However, there's no citation. And remember you won't necessarily need that many people, just that much genetic material. So a good cryofreezer and a lot of frozen eggs/sperm etc could do the trick with a very small population (assuming the stuff stays fresh for a very long time). Not sure about the second part though. --Cody Pope 01:15, 6 October 2007 (UTC)[reply]

For the first question, ask a hillbilly.

For the second question it would matter a lot on how much meat you want, because that takes up a lot more land, it is said. Also, you seem to assume a purely cultivation-based food supply. For the bleak future scenario, it makes more sense to rely on hunting/gathering because that way you won't have much stock that can be stolen. Of course, a combination of the two might be best - under uncertain circumstances, it's always best to put your eggs in as many baskets as possible. And a crossover might also be a good idea - plant the food, but not all in one spot, but spread out over different areas under different conditions, so a failed harvest will be limited and you won't run the risk of being completely out of food.

So there are many variables, but a good indication might be found in mediaeval subsistence farming. Open field system says each villager got 30 strips of 2000 m², so that's 60,000 m² per person, roughly 250 x 250 m (assuming that's really per person, not per family, which I rather expected to find). So a community of 500 would require about 100 km² or 10 km x 10 km. That's about the size of Amsterdam for a small village, which sounds like a lot. But farming was probably much less efficient in those days (as it is likely to be under the survival conditions we're talking about), and there were nowhere near as many people then, so it might still be fairly accurate. I guess most mediaeval villages were about that size and about 10 km apart. Of course, that may also be an explanation. Maybe they used that much space simply because that's what was available. DirkvdM 09:25, 6 October 2007 (UTC)[reply]

The Bible says two people are enough. I seem to remember Guns, Germs and Steel giving a figure for how much acreage is needed to support one person's foraging, but I can't recall the number. --Sean 14:00, 6 October 2007 (UTC)[reply]

Spider ID

This spider jumps. Seen at Dennis railway station, Melbourne. Can anyone name the species? —Pengo 02:56, 6 October 2007 (UTC)[reply]

Well, it's clearly of the family Salticidae (jumping spider), but I'm not sure from that angle it will be easy to distinguish it from many of the very similar looking jumping spiders (many of which are generally brown, have large forward-facing eyes, and make that little sort of face). --24.147.86.187 04:09, 6 October 2007 (UTC)[reply]

How about this angle? —Pengo 04:29, 6 October 2007 (UTC)[reply]

There are over 5000 jumping spider species. I doubt it would be possible to find the exact species of the spider in your picture. The only way would be if a life specimen crawled through the series of tubes on the Internet for me to perform DNA testing, and then search for the sequence on PubMed. But if you'd be satisfied with just a genus or a family, I'd recommend using this site--Mostargue 12:39, 6 October 2007 (UTC)[reply]

There is a "find-a-spider" site for Australian spiders here. I went through all of the pictures for that particular family but didn't see any obvious 100% matches. --24.147.86.187 14:53, 6 October 2007 (UTC)[reply]

Killing with sound

Is it possible to generate a sound that can kill a human? Either by the sheer power of it or by creating some kind of harmonic vibration that will shake the body apart? Exxolon 03:30, 6 October 2007 (UTC)[reply]

Massive ordnance air blast over-pressures the human with a pressure wave. It might be considered "killing with sound" but it's really more of a supersonic over-pressure. Nimur 04:27, 6 October 2007 (UTC)[reply]

See our article on sonic weaponry. General consensus seems to be that lethal sonic weapons are only possible underwater. Gandalf61 08:00, 6 October 2007 (UTC)[reply]

Monty Python had a suggestion for this - a joke that is so funny that the enemy will laugh themselves to death. Of course it can't be told by one single person, or they would themselves die. See the episode for solutions. DirkvdM 09:34, 6 October 2007 (UTC)[reply]

That would be The Funniest Joke in the World. DuncanHill 12:43, 6 October 2007 (UTC)[reply]

On a more serious note, one torturing method (which appears to be used in Guantanamo Bay, or that's where I think I got this from) is to expose people to white noise. Don't know if that could be lethal if used in excessive amounts. Can madness kill? DirkvdM 09:35, 6 October 2007 (UTC)[reply]

For a smaller scale version of a similar phenomenon, check out the pistol shrimp. Capuchin 10:28, 6 October 2007 (UTC)[reply]

microbiological test

1. what are the Cleaning procedures in food production site? 2.what are the decision can be taken by quality assurance representative when the products are affected by microbiological problem? —Preceding unsigned comment added by 60.53.109.73 (talk) 04:49, 6 October 2007 (UTC)[reply]

These will differ according to site, the food being produced, and the regulations on the industry in the specific jurisdiction. You might want to take a look at this U.S. F.D.A. site which discusses Hazard Analysis and Critical Control Point procedures. - Nunh-huh 05:02, 6 October 2007 (UTC)[reply]

Spinal cord, ventral and dorsal tracts

In Kolb & Whishaw, Fundamentals of Human Neuropsychology (2003) is the following sentence: "In the spinal cord itself, the outer part consists of white matter or tracts, arranged so that with a few exceptions the dorsally located tracts are motor and the ventrally located tracts are sensory."
Is this correct? If I compare with pictures, for instance this one: http://faculty.etsu.edu/currie/images/neuro2.jpg, it seems to me that most dorsally located tracts are sensory and most ventrally located tracts are motor. Lova Falk 09:02, 6 October 2007 (UTC)[reply]

Spinal cord provides a description of the major tracts. I wonder if "Fundamentals of Human Neuropsychology" just makes that statement in passing or if they have a supporting figure or cited references. Here is another figure similar to those found in many textbooks. --JWSchmidt 15:25, 6 October 2007 (UTC)[reply]

Physics???

If we want to become a doctor when we grow up, is it necessary for us to take Physics, Chemistry and Biology in our secondary education?? Or will it be sufficient if we simply take Biology and Chemistry? —Preceding unsigned comment added by 219.74.132.62 (talk) 09:43, 6 October 2007 (UTC)[reply]

It varies significatly depending on which institution you choose to seek your degrees from. If you are beginning to plan what colleges you would like to attend, you should look on said colleges' websites for their admission and graduation requirements for their premed programs. My own university's premed program entails what some would consider a surprising amount of physics and mathematics, but I've seen others that require almost none, comparatively. Someguy1221 09:52, 6 October 2007 (UTC)[reply]

Basic physics will help you to understand the advanced chemistry and biology which you'll need to be a doctor. Additionally, the way things are approached in physics classes will give you a slightly different set of problem solving skills which may be of use in any profession. Finally, if you are going into certain specialties like orthopedics or radiology, you'll need to have a solid background in physics to understand the principles behind what you are doing. In short, it might not be necessary, but it'll be a good idea. -- 72.33.121.200 16:51, 6 October 2007 (UTC)[reply]

RE: helium

as it is a natural resource how many years do we on earth have with the resource of helium, before it is gone? —Preceding unsigned comment added by 12.217.132.163 (talk) 15:02, 6 October 2007 (UTC)[reply]

You may find this article of interest. Cheers Geologyguy 15:11, 6 October 2007 (UTC)[reply]

Helium is a byproduct of nuclear fusion, so if that ever becomes a major power source, we probably won't run out of it. Assuming it doesn't, as the amount of helium left decreases, it will get more expensive and be used less. Mathematically, it should never run out completely. The same goes for deuterium if nuclear fusion does. — Daniel 15:34, 6 October 2007 (UTC)[reply]

Harvard Chart Method

This was a method presumably developed at Harvard University which was used to both replace Boolean Algebra and to automate the process of reducing logical equations to minimum form. Yet, I can find no reference to this method either at Harvard or at MIT. It was suggested that the method was developed by Howard Aiken preliminary to development of Aiken's Harvard Mark II. Does anyone have reference to the method or any other information regarding it? Clem 15:31, 6 October 2007 (UTC)[reply]

beams that reflect from bones

for long i'm looking for some rays or beams that can be transmitted and then sensed back as reflection of the same from bones. may be the rays are not reflecting merely from bones but it gets special deflection after reflecting from bones that can be sensed and hence can be concluded that the object from which the reflection has occured is bone. if some one could help... —Preceding unsigned comment added by Neel shah556 (talk • contribs) 16:09, 6 October 2007 (UTC)[reply]

Lethal acceleration/jerk

How much acceleration or jerk would kill a human being? --Anakata 16:25, 6 October 2007 (UTC)[reply]

Our article on g-force says that an unaided human (say, in a plane) will black out at 50m/s² (5 g) in the vertical direction, but can stand 12-17 g in the horizontal direction. "Any exposure to around 100 g or more, even if momentary, is likely to be lethal, although the record is 179 g." More facts and figures can be found in the article. -- 72.33.121.200 16:44, 6 October 2007 (UTC)[reply]