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March 27

Turtles

When a turtle pulls its head into its shell, does its spine buckle or contract? 70.162.25.53 (talk) 01:11, 27 March 2008 (UTC)

Have you been reading Cat's Cradle? Anyway, the article you linked has the answer: it depends on the turtle. Pleurodira fold their neck to the side, while Cryptodira pull their neck straight back. Algebraist 01:51, 27 March 2008 (UTC)

I disagree. The article does not seem to answer his question. Now that 70.162.25.53 has mentioned it, I'm sort of curious too. How is the spine in the neck constructed so that it can change length so dramatically? APL (talk) 06:37, 27 March 2008 (UTC)

The "spine" of a tortoise is more like part of its shell. See this cutaway section of a tortoise and the mechanics will be obvious.--Shantavira|^{feed me} 15:07, 27 March 2008 (UTC)

Neat! APL (talk) 13:38, 28 March 2008 (UTC)

I think Algebraist is referring to "Turtles are broken down into two groups, according to how they evolved a solution to the problem of withdrawing their neck into their shell (something the ancestral Proganochelys could not do): the Cryptodira, which can draw their neck in while contracting it under their spine; and the Pleurodira, which contract their neck to the side." from the article, which was there at the time you posted from what I can tell [1] Nil Einne (talk) 11:50, 2 April 2008 (UTC)

Why a Horseshoe-shaped Gamut of Visible Colors?

The color space article describes visible colors in the RGB color model, the gamut, represented as a 2-D horseshoe shape. Are all 10 million visible colors found in this (idealized) 2-D image? Why a horseshoe shape? Is the shape a horseshoe on account of the underlying physiology of color reception in humans? Mark465 (talk) 14:52, 27 March 2008 (UTC)

The article on gamut wasn't wikilinked, see specifically Gamut#Representation_of_gamuts. It's really shaped more like a triangle with one rounded side and one rounded corner (the three corners being the three primary colors), than like a horseshoe. I too am interested in understanding the reasons why the range of possible chromaticities has a rounded blue-green side and straight blue-red side. ---Sluzzelin talk 15:11, 27 March 2008 (UTC)

See also CIE 1931 color space. ---Sluzzelin talk 15:17, 27 March 2008 (UTC)

There are three fixed points on these kinds of diagrams representing the three primary colours, which in turn are the wavelength of peak responses of the three kinds of cone detector in the human eye. These three points form the apexes of a triange. The straight line from the Red apex to the Green apex represents a fully saturated mix of the Red and Green wavelengths represented at the apexes. The colour along this line varies continuously from the red through orange and yellow to green. Similarly, the straight line between the Green and Blue apexes represents a fully saturated mix of green and blue light. However, not all light in nature is a mix of these particular three wavelengths, in fact most of it is not. Monachromatic yellow light, for instance, may appear as the same yellow as a mix of red and green light but it has a greater saturation. Since a mix of red and green light with no blue is considered to be 100% saturated, monochromatic yellow must be more than 100% saturated and is described as supersaturated. It must, therefore, lie outside the linear triangle thus accounting for the curves on the diagram. The Red-Blue axis is not curved because mixes of red and blue can only be achieved by mixing two wavelengths and so monochromatic supersaturation cannot occur and the line is therefore straight.

Anticipating the next question - why is monochromatic yellow supersaturated? The reason for this is that red/green mixed yellow obviously has wavelength component of green which is a shorter wavelength than the monochromatic yellow. At this wavelength there is some stimulation of the blue receptor also (mono yellow also stimulates the blue cone but to a much lesser degree). This stimulation of blue means that there is some component of red, green and blue in the eyes response. All three are interpreted as white, so the net result is yellow plus white or in other words desaturated yellow. Since this desaturated yellow has been predefined as 100% saturation, a more saturated yellow must consequently be supersaturated. Luckily for the television companies, supersaturated colours do not occur in nature much, so the fact that RGB television cannot reproduce them is of little consequence. SpinningSpark 16:13, 27 March 2008 (UTC)

It isn't that clear that there are three specified primaries which result from the maxima of cone receptors. The CIE color space isn't set up that way. How about magenta, cyan and yellow as alternative primaries? Edison (talk) 03:53, 28 March 2008 (UTC)

The CIE colour space uses three primaries (called the tristimulus in the article) which are arbitrarily chosen but close to the average human peak cone responses. The difficulty with humans is that they are all different so the human tristimulus is fuzzy, varying from person to person. My post above was really trying to describe the concept of supersaturation in general and was not particulary referring to the CIE colour space (although it does apply). Red-green-blue (RGB) colour spaces are used because light is detected in the human eye in terms of RGB. RGB is also most convenient where colours are being reproduced by an additive process of light such as in television or computer monitors. Where colours are reproduced by a subtractive process such as in printing then it becomes more convenient to use a cyan-magenta-yellow (CMY) colour space. In particular, printers favour the CMYK colour space. It is also worth noting that tristimulus based colour spaces only work for humans and other species with equally useless colour vision. Many species of birds, bees and moths have five colour receptors so RGB colour reproduction would not fool them for one minute. As for species like the pistol shrimp or mantis shrimp, their colour vision is so good that it would be necessary to reproduce a mix of wavelengths near identical to the original scene before they would be satisfied with television pictures. SpinningSpark 10:02, 28 March 2008 (UTC)

See Cone cell for information on the maxima of cone cells Nil Einne (talk) 06:46, 1 April 2008 (UTC)

Alternative medicine

Is there any branch of conventional (western) medicine that would at one time in the past have been considered alternative medicine, or is that by definition impossible?--Shantavira|^{feed me} 14:58, 27 March 2008 (UTC)

I don't know how far back the term "alternative medicine" was used, but there are examples of things that are mainstream thinking now and were not in the past. A great example is the good old germ theory of disease- now accepted by all but the quackiest of quacks, yet it was seen as quite outlandish by the medical establishment when first introduced. "Tiny little bugs made you sick?? Ridiculous. Come on by and I'll fix your humors for you, and you'll be all better." Friday (talk) 15:06, 27 March 2008 (UTC)

Right. Good question. My answer was going to be "Yes, practically all of it", for the reasons Friday mentions. I was thinking of Ambroise Paré and the treatment of battlefield wounds by ligation and clean compress when the rule was cauterize for bleeding and pour hot oil in any holes. (Say what you will about the French, they have produced some bright boys.) --Milkbreath (talk) 15:20, 27 March 2008 (UTC)

Germ Theory is a good answer, but I'm not sure "Practically all of it" works. It seems like there is a lot of modern medicine that never passed through a phase where it was practiced regularly, but not by mainstream doctors. (Though it depends a lot on how narrow you're allowed to define a "branch...of medicine") However, The first paragraph Wikipedia's article on alternative medicine offers a surprisingly broad definition of the term that probably covers even techniques undergoing legitimate clinical trials by mainstream researchers. By that definition "All of it" would be the right answer. APL (talk) 16:14, 27 March 2008 (UTC)

"The Web That Has No Weaver" is a fantastic resource on Chinese Traditional Medicine that may help untangle the philosophical kinks. Western Medicine is evidence-based, and has been for some time, and is largely based upon the principle that different people, with similar medical conditions and similar bodily make-up, should be treated in roughly the same way. TCM is also evidence based, in the sense that it works, but is based upon the principle that every individual must be treated individually based upon their unique energy patterns and fluid movements. That makes it virtually impossible to compare TCM and Western medicine; it is impossible to do a double blind study on a TCM treatment because the practitioner must necessarily know what they are doing. It is also impossible to do a rigorous statistical analysis with statistical significance on TCM treatment for a given condition, because in TCM every patient will be treated differently, and consistency cannot be assured. Western forms of naturopathic medicine follow similar philosophies. So while the treatments themselves may share homology, the philosophies are too divergent for appropriate comparison. Vance.mcpherson (talk) 16:37, 27 March 2008 (UTC)

I'm sorry to derail, but I can't let that pass. Statistical comparisons are ideal for comparing situations with inconsistencies if you use a large enough sample. Are you honestly saying you couldn't do a study that says "Of Ten thousand people with illness X who were treated with western medicine Y% recovered, and of ten thousand other people with illness X who were treated with traditional Chinese medicine Z% recovered." because there's a chance that one of the TCM patients might have gotten lucky and gotten a better treatment? Granted, It may not tell you the scientific validity of TCM,(or western medicine for that matter.) but it would give you an idea which of the two approaches are more likely to work, which is far more useful. APL (talk) 18:00, 27 March 2008 (UTC)

Continuing the derailment... yes. TCM is not disease based, but rather patient based. It is the patient, not the disease, that is treated. Therefore, for example, two people with acute angina, of the same height, weight, race, and sex, may be treated with a completely different set of medications, acupuncture and other regimens, based upon factors like Qi flow, etc. Every patient is different. Further, TCM focusses upon prevention; by the time the disease sets in, it's argued, it's for the most part too late. One could say, for example, that X people with angina were treated with TCM and Z% recovered, as you say, but there would be implied thereby X different treatments. Contrast this to Western Medicine statistics, where one would never say y people were treated for angina in a bunch of different ways, and z% recovered. We'd be insisting on a highly controlled experiment. Sorry to be unclear. Vance.mcpherson (talk) 18:30, 27 March 2008 (UTC)

I'd still say a comparison could be done with a suite a treatments, so "X% recovered using Western treatment A while Y% recovered using TCM treatments B-Z". However, a more useful approach might be to have all patients evaluated for TCM and determine which TCM treatment would be recommended. You could then split each group into two, and conclude "X1% recovered using Western treatment A while Y1% recovered using TCM treatment B", and "X2% recovered using Western treatment A while Y2% recovered using TCM treatment C", etc. You might thus find that some TCM treatments are useless while others are quite effective. As for the preventative aspect of TCM, western medicine also has preventative meds, like those that keep cholesterol or high blood pressure in check. Those could be compared with TCM methods and we could study which prevents a heart attack or other negative health effect the longest. Again, we could break down the study groups based on recommended TCM treatment. Of course, as far as prevention goes, I'd say a healthy diet and lifestyle, exercise, not smoking, avoiding stress, etc., will win every time. Those should ideally be also included in any study, so we don't end up with large numbers of people eating double bacon cheeseburgers every meal and taking drugs to try to prevent the damage, when the far better option is to just eat better. StuRat (talk) 18:59, 27 March 2008 (UTC)

I'm no statistician, but it seems to me that a look at world life expectancies constitutes a very good study of the relative efficacy of the two philosophies, and others, to boot. This is especially true if we're talking about prevention, and the numbers include unweighted infant mortality, which they usually do, I believe. The map I've linked to indicates that Western is better than Chinese, which is better than Indian, and African might just be worse than nothing. --Milkbreath (talk) 19:31, 27 March 2008 (UTC)

I don't think that approach is very useful because there are so many factors which vary from place to place. For example, one of the single most important factors is probably basic sanitation. Do they dump raw sewage into the same rivers from which they drink untreated water ? If so, take 20 years off their life expectancy. So, using such figures to determine which specific medical treatment is best is unlikely to work. StuRat (talk) 20:29, 27 March 2008 (UTC)

The comparison being made is between two schools of thought, two incompatible conceptions of the mechanism of disease. Civilizations that fail to pay due heed to the role of pathogenic organisms in disease will not practice adequate sanitation. That's what I meant by "prevention". --Milkbreath (talk) 21:56, 27 March 2008 (UTC)

The reason they don't have sewage and water treatment plants isn't that they don't believe in germs, it's because they lack the resources to do so. That map seems to correspond very well with per capita income, not philosophy. Haiti, for example, is the one spot of red in the Western Hemisphere. Why ? Not because they have a radical different approach to disease treatment and prevention, but because they are dirt poor. StuRat (talk) 00:05, 28 March 2008 (UTC)

I don't feel qualified to debate world health issues, and this is not the place for that. But I would add that however poor people are, they can choose to reject a religion that makes them ritualistically drink and bathe in some of the most polluted water on earth with dead bodies in it and buffalo dreck, etc. And perhaps per capita income correlates pretty well with the realistic world view and rejection of mysticism that goes along with Western medicine. I'm outta here. --Milkbreath (talk) 00:22, 28 March 2008 (UTC)

I should back up a bit. I was very interested in researching the scientific and medical basis of TCM a few years back, and ultimately in investigating a possibility of the synthesis of TCM and Western medicine. I was told vehemently by some in the TCM community that this could never be done. It's counterintuitive because we're used to Western approaches to thinking about scientific method. Take StuRat's excellent example. "Some TCM treatments are useless while others are quite effective"... this would make sense to the Western scientist, but not in TCM. TCM is predicated upon the idea that the treatment will work if administered in the right context... and if it doesn't work, then there were other factors not considered. For example, if I have anxiety prior to a test, I might take a liver tonic because liver heat results in anxiety. But I couldn't only do this; if I have a weak spleen, for example, (which may predispose me for example to autoimmune disease, allergy, etc., but also governs liver, if memory serves), then it may be more advantageous to achieve spleen yin-yang balance. This may be achieved through a combination of herbs and acupuncture, or medicinal soups, or even a simple diet change. For example, my TCM doctor says that my spleen is cold and damp, which means I should avoid grains except rice and drink warm liquids. This is especially necessary to control insomnia. See, it's really a very different, quite incomparable system. I can't just say "take ginseng to increase your energy" in quite the same way as I can say "take this antibiotic to clear this disease". I highly recommend looking at "The Web That Has No Weaver", ([[2]]) by Ted Kaptchuk for an excellent review of this system. The title of the book is a good analogy -- the human body is "the web that has no weaver" -- there's no beginning or end, and there's not exactly a cause-effect relationship between a pathogen and a disease. Anger could be caused by liver heat or disrupted qi... and on and on like that. Vance.mcpherson (talk) 19:41, 27 March 2008 (UTC)

You're spleen is damp ? LOL. I'd be worried if it wasn't. But seriously, beware that those with a questionable treatment method often come up with some reason to claim it can't possibly be tested, so it can never be shown to be ineffective. A trick chiropractors like to use is to push down on your extended arm before and after a treatment and amaze you by how much better you are able to resist their push, which they swear is just as hard as before the treatment. Of course, this could logically be solved simply be substituting a fixed weight to apply the same force both times, but they aren't interested in doing it that way, for obvious reasons. Another favorite of charlatans is to say "your negative energy (skepticism) is what made the treatment ineffective". Back to the TCM discussion, I'd ignore TCM treatments for "damp spleen" and such. Those people who are concerned that their spleens are damp can go right to the nearest TCM practitioner, as western meds has nothing for this "serious problem". However, I believe TCM does indeed tackle a number of issues which western meds also tackle, such as headaches. And, as I've noted previously, there are ways to design a scientific study to compare the two treatment approaches for such conditions. StuRat (talk) 20:41, 27 March 2008 (UTC)

Actually my chiropractor used an electronic force measuring device. Totally objective measurement. My left arm showed a pronounced difference, right arm was unchanged. There is no need for charlatanry in your example. ~Amatulić (talk) 20:49, 27 March 2008 (UTC)

An "electronic force measuring device" sounds like something that could be tampered with, possibly using a remote control, while a fixed weight could not (unless they can pull a switch on you when your back is turned). A needlessly complex device should be another warning sign that something weird is going on. More generally, the scientific method demands that you not use subjective methods of evaluating effectiveness, which is what TCM will suggest, but instead use objective measures. If they feel people's skin and tell them their "qi" is flowing better, this is of no use in evaluating effectiveness. If, on the other hand, the patient's bad cholesterol level is down in multiple blood tests, this indicates the treatment is doing some good. StuRat (talk) 20:54, 27 March 2008 (UTC)

(Sigh). Some folks just can't let go of preconceived notions. You could do it with a spring scale (which another chiropractor did, with similar result). Using an electronic device doesn't make the chiropractor dishonest; in my case it simply allowed him to record the data more easily in his computer. There was no calibration or adjustment between tests, just comparison of forces each time. If your chiropractor doesn't perform the measurement objectively, that doesn't mean that others don't. ~Amatulić (talk) 21:04, 27 March 2008 (UTC)

You mean you failed to observe any calibration or adjustment between tests. This doesn't mean it didn't happen, just that you didn't see it. It could be as simple as a lever that's pressed or dial that's turned when the device is handled to as complex as a remote control or timer. The only way to be certain it was not changed is to use a device which can't be changed, such as a fixed weight. StuRat (talk) 21:49, 27 March 2008 (UTC)

...or a fixed spring scale, as I already mentioned. Pay attention. ~Amatulić (talk) 22:12, 27 March 2008 (UTC)

I did, and you didn't say "fixed". I have a spring scale at home that is adjustable. Did you examine the scale thoroughly to determine that it can't be adjusted ? StuRat (talk) 23:57, 27 March 2008 (UTC)

Ok, but NONE of that would stop you from treating "traditional Chinese techniques as administered by a well trained doctor" as a single unit and comparing that unit against western medicine in general. To say that the medical techniques are not "disease based" is fine, but presumably, if someone has a disease, their doctor will attempt to either cure it or relieve the symptoms, correct? We could find ten thousand people from each of the two categories that all have disease X, wait a few months, and compare the results. This would provide useful information even if each of the TCM patients received different treatments, so long as those treatments were expertly chosen by whatever rules and criteria TCM doctors normally use.

Statistics could be used even within TCM. You could do a study that says something like "Of the 10,000 TCM patients with disease X, 159 of them recieved treatment Q. Of those 159, a large percentage dropped dead instantly. Treatment Q's effectiveness is therefore in question." I'm exaggerating for comedic effect, but you get my drift. APL (talk) 21:12, 27 March 2008 (UTC)

(outdent)

Derailing further: some aspects of TCM do lend themselves to western-style clinical testing. Regular intake of the herb jiaogulan, for example, has been shown consistently to reduce cholesterol. It's one of the few examples I know of that has solid test results behind it. That's one example where one can use TCM to treat a specific condition rather than adapting a different treatmen to a patient.

Getting back on topic: To answer the OP's question, I'd say one example of conventional medicine that may have once been considered "alternative" is physical therapy. And most herbal treatments are considered "alternative" until some drug company comes along and figures out how to synthesize the active ingredient, as was the case with ephedra, from which pseudoephedrine was derived. ~Amatulić (talk) 20:50, 27 March 2008 (UTC)

...not to mention willow bark. -- Coneslayer (talk) 01:42, 28 March 2008 (UTC)

re: jiaogulan -- yes, but from a TCM perspective, it is warm and it enhances yin while supporting yang, so you wouldn't want to take it if you had excess yin or excess warmth!Vance.mcpherson (talk) 14:26, 28 March 2008 (UTC)

Moon falling into Earth

How close does the moon have to be to fall into Earth's gravity? --Jonasmanohar (talk) 17:38, 27 March 2008 (UTC)

It's already in earth's gravity. We do have an article on the orbit of the Moon. Someguy1221 (talk) 17:46, 27 March 2008 (UTC)

Ok, then I meant crash into earth... --Jonasmanohar (talk) 17:50, 27 March 2008 (UTC)

How close does it have to be to crash? Very close indeed. ;-) As the article linked to above explained, the Moon is (very slowly) getting further from the Earth. Friday (talk) 17:53, 27 March 2008 (UTC)

(Edit conflict) Just to be clear, the moon is already significantly affected by the Earth's gravity. Otherwise it wouldn't orbit the earth. What I presume you really want to know is how close does the moon have to be to the earth such that it will no longer be in a stable orbit around the earth and will eventually crash into the earth. Unfortunately I don't know the answer except that as I expected, the moon isn't actually a truly stable orbit around the earth, see [3]. Not remembering physics well enough, I can't calculate what sort of distance change is necessary. But to bear in mind it's not that the moon is going to suddenly start 'falling' into the earth at high speed. Rather, there will be a distance where the moon is in a truly stable orbit, beyond which the moon will get closer over time. However at first, the distance change will be minimal such that even though the moon will eventually theoretically crash into earth, it will take billions and billions of years for this to actually happen such that the sun will become a red giant before then so presuming the earth and moon even last that long, it will never actually have happened in any case. Of course, the closer the moon gets to the earth, the less time it will take for it to collide with the earth so that at a certain distance, it will possibly have happened were the moon really the close Nil Einne (talk) 17:56, 27 March 2008 (UTC)

You also have to decide at what velocity the moon is traveling in whatever reference frame. You could keep it where it is but just slow it down enough, and it will hit the Earth right quick. But I also forget how to calculate the velocity/distance necessary for crash for an elliptic orbit. Someguy1221 (talk) 18:03, 27 March 2008 (UTC)

(EC again) BTW, do bear in mind this isn't a simple calculation. Both the earth and the moon have a momentum.[4] This momentum was gained during their formation, it's not as if someone simply dumped a planet and a moon in the middle of space and let them start moving. If these momentums had been different, then things would be different. [5] In other words, what I'm trying to say is you can't simply visualise it as a simple system as I have a moon with mass M and a planet with mass E, what will happen when they are distance ME from each other? (Answer I think, many different things could happen including the moon could simply crash into the earth without ever actually orbiting presuming both were simply completely static from the beginning and there was actually no other mass at all [NB this is obviously an impossible system]) Nil Einne (talk) 18:09, 27 March 2008 (UTC)

Final comment: The note on the Orbit of the Moon article about how no one is actually sure what will happen to the earth-moon system after the orbit of the moon reaches 47 days sums up quite well the fact that when you actually start to think about them, these are quite complex systems Nil Einne (talk) 18:16, 27 March 2008 (UTC)

Since we're clearly talking about different things, let's make it clear, there is a distinction between placing the moon in an unstable orbit such that it eventually hits the Earth, and placing the moon in an orbit that actually comes with a moon radius of the Earth's surface (i.e., they will hit during a single orbit). The latter is what could be calculate with relative ease, not that I remember how. Someguy1221 (talk) 18:20, 27 March 2008 (UTC)

I think it's safe to say that if you could place the Moon into any orbit you liked, you would not want to place it close enough that it could hit our atmosphere, because that would cause its orbit to decay and it would almost certainly crash eventually. According to wikipedia The Exosphere ends at about 10,000km from the surface. (for reference, the moon currently does not get close than 363,104km) APL (talk) 18:26, 27 March 2008 (UTC)

OK, placing the moon in an orbit that actually comes with a moon radius of the Earth's surface (i.e., they will hit during a single orbit). --Jonasmanohar (talk) 18:24, 27 March 2008 (UTC)

Actually, the better answer is if the Moon is within the Earth's atmosphere, or closer than 10,000 km, as APL said above. The Moon's radius is only 1,737 km. StuRat (talk) 18:40, 27 March 2008 (UTC)

Correct my if I'm wrong, but in order to maintain a stable orbit, distance is inversely proportional to velocity. That is, a closer orbit will need to be faster in order to be stable. Now, the moon isn't exactly stable, but it's pretty close. If we were to slow it down substantially or pull it closer to earth without speeding it up, the orbit would begin to decay. How long will it take? Not sure. --uǝʌǝsʎʇɹoɟʇs(st47) 19:50, 27 March 2008 (UTC)

Actually I think if you go faster, you fly away. A closer orbit is slower, but gets round the Earth faster. However, once the Moon comes within the Roche limit, wouldn't it break into pieces anyway? Franamax (talk) 20:10, 27 March 2008 (UTC)

If you can just satisfy yourself that orbital energy for a circular orbit is one half the kinetic energy at escape velocity, it's pretty clear that the minimum velocity for orbit increases as the radius of the orbit decreases. It's thetotal travel time around the Earth that decreases. Someguy1221 (talk) 20:17, 27 March 2008 (UTC)

Huh? The converse of your statement is that as the radius of orbit increases, the minimum velocity decreases, right? I don't think that's correct. The faster you move, the more energy you have, the farther away you fly. Isn't that how the shuttle does it? Franamax (talk) 20:31, 27 March 2008 (UTC)

I take that back. Brain is smoking and making funny noises. Franamax (talk) 20:39, 27 March 2008 (UTC)

Roche Limit. Objects only break up inside the Roche limit if there is nothing other than gravity holding them together. This is sometimes stated as the pile-of-sand model. Crystalline rock, on the other hand, is held together by forces a lot stronger than gravity. There are many examples of objects in the solar system quite happily existing inside the parents Roche limit. SpinningSpark 22:58, 27 March 2008 (UTC)

Yes, some moon-sized objects can exist within the Roche limit, but not by much. At some point, the tidal forces will rip it apart, and I am almost completely certain that this would be well before the moon would impact the atmosphere. Of course, all of this is assuming the moon's orbit is coming closer to the earth; it is actually receding at a few millimeters a year. -RunningOnBrains 23:20, 27 March 2008 (UTC)

True, but even if the Moon did break up, that wouldn't mean that the parts would crash into Earth. They might just form a ring. However, the lack of rings around the terrestrial planets seems to imply that those rings don't last for long. StuRat (talk) 23:52, 27 March 2008 (UTC)

(unindent) The Moon's gravitation produces tides which raise the water level over a meter at numerous locations. Would not a closer Moon produce higher tides, ultimately inundating most of the land mass, even before the Earth was rendered uninhabitable by movement of its crust resulting in earthquakes and volcanoes as the Moon drew nearer, long before there was any contact? Edison (talk) 03:49, 28 March 2008 (UTC)

Yes, the tides would be higher and earthquakes would also be produced. Towards the end the atmosphere would be heated by contact with the Moon, too. StuRat (talk) 14:42, 28 March 2008 (UTC)

A detailed description of this process is to be found at [6]. Edison (talk) 15:49, 28 March 2008 (UTC)

E=MC^2

What is the whole proof to the equation E=MC^2? —Preceding unsigned comment added by 68.252.70.175 (talk) 23:37, 27 March 2008 (UTC)

Mass-energy equivalence might be useful. Algebraist 23:44, 27 March 2008 (UTC)

If you mean the derivation, the original form of it is here. It's a little opaque if you aren't used to the notation and math Einstein is using but if I recall it relates to the energy a photon imparts on the inside of a box in space or something along those lines. --Captain Ref Desk (talk) 23:53, 27 March 2008 (UTC)

One way of checking the equation for reasonableness is by dimensional analysis. The units of energy (on the left side) are kilograms times meters ² per second², by definition. The units of the right side are kilograms times C², which is equivalent to kilograms times meters ² per second², just like the left side. The only thing missing is a constant to allow for the choice of units. The equation would not balance in dimensions if it were E=MC, or E=M²C, or E=MC³, etc. Edison (talk) 03:38, 28 March 2008 (UTC)

Which is fine, but that just says that if there is some kind of mass-energy equivalence, then the constant of proportionality will have dimensions of Length ^ 2 / Time ^ 2. Just through dimensional analysis you will be unable to tell whether that constant was c^2, or something involving the Hubble constant and Planck length. Of course, if you formulated a theory where the constant had dimensions of Length ^ 3 * Time / Mass ^ 4, then yes you might suspect you'd done something wrong. Confusing Manifestation(Say hi!) 15:11, 29 March 2008 (UTC)

March 28

Shape of the Milky Way Galaxy

I remember when I was younger and more interested in astronomy reading that the Milky Way was a spiral galaxy, like the Andromeda galaxy, but while browsing various articles, I came upon the Milky Way article, which said that it was a barred spiral galaxy, which surprised me. When did astronomers figure out that it's a barred spiral galaxy instead of a spiral galaxy? Was there some discovery in the past decade that allowed them to see that it is in fact a barred spiral instead of a spiral galaxy? How do astronomers know what shape the Milky Way is and where the arms are? By judging the distance of tons of stars and laying out a map? How are astronomers able to guess at what lies on the other of the core? Thanks in advance. – Psyche825 _(talk) 04:28, 28 March 2008 (UTC)

Adaptive optics is certainly one breakthrough during the last ten years, that has helped astronomers to dramatically enhance the accuracy and resolution of star charts among other things. I cannot elaborate as I am by no means an expert in astronomical modelling. Sandman30s (talk) 09:36, 28 March 2008 (UTC)

Yes, this conclusion must have been reached by an analysis of the distribution of stars and interstellar gas and dust clouds using observations at various wavelengths. Radio astronomy, for example, allows us to see details of the Galactic Center that are hidden at visible wavelengths. Apparently the crucial evidence that clinched the case for a barred spiral structure were infrared observations made in 2005 using the Spitzer Space Telescope. Gandalf61 (talk) 11:13, 28 March 2008 (UTC)

Ah, thanks. A quick Google search about the Spitzer telescope turns up quite a few articles with more information. – Psyche825 _(talk) 06:09, 29 March 2008 (UTC)

Quantum: Measurement vs. Schrödinger Equation

1. Article Copenhagen interpretation: Each measurement causes a change in the state of the particle, known as wavefunction collapse.

2. Article Schrödinger equation: The Schrödinger equation is commonly written as an operator equation describing how the state vector evolves over time.

Although I don't fully understand quantum mechanics, the two items above seem to be related to each other.

When an observable of a quantum system is measured, the state $|\psi (t)\rangle$ of the system can be expressed as

$|\psi (t)\rangle =\sum _{i}\psi _{i}|i\rangle$ (1)

where $|i\rangle$ is the $i$th eigenfunction, which is associated to eigenvalue $i$, of the observable and

$\psi _{i}=\langle i|\psi (t)\rangle$ (2)

which will "suddenly" or "discretely" collapse from $|\psi \rangle$ to one of terms, say $\psi _{a}|a\rangle$, of the right-hand side of (1). The rest of the terms not associated to eigenvalue $a$ simply vanish after the measurement.

On the other hand, Schrödinger equation

${\hat {H}}(t)\left|\psi \left(t\right)\right\rangle =\mathrm {i} \hbar {\frac {d}{dt}}\left|\psi \left(t\right)\right\rangle$ (3)

where

${\hat {H}}(t)=-{\frac {\hbar ^{2}}{2m}}\nabla ^{2}+V\left(\mathbf {r} ,t\right)$ (4)

describing how the state vector $|\psi (t)\rangle$ evolves over time. When the state $|\psi (t)\rangle$ of the system is measured, the apparatus measuring the system will interact with the system and makes change to the potential field $V\left(\mathbf {r} ,t\right)$. Therefore, the state $|\psi (t)\rangle$ should evolve "smoothly" or "continuously" according to the varying potential $V\left(\mathbf {r} ,t\right)$ during the measurement. According to Schrödinger Equation (3) and (4) together with $V\left(\mathbf {r} ,t\right)$, we should be able to figure out the final state of the system after the measurement.

It seems that the measuring process can be explained by the two ways, wavefunction collapse & Schrödinger equation, above. Do they contradict? Is "wavefunction collapse" compatible with "Schrödinger Equation"? - Justin545 (talk) 08:12, 26 March 2008 (UTC)

Yes, they do contradict. There is no place for a collapse in Schrödinger's Equation, which is one reason why David Bohm concluded that there can be no collapse of a wave function, that it's a figment of the model. — kwami (talk) 08:34, 28 March 2008 (UTC)

Figment of the model? I'm amazed that they do contradict since the two items are considered to be postulate of quantum mechanics in some textbook of quatum mechanics IIRC. It should imply at least one of the two items is wrong. So has David Bohm or some one else solved the contradiction? And how about the experimental evidence? Experimental evidence supports which one? - Justin545 (talk) 08:55, 28 March 2008 (UTC)

The Copenhagen interpretation is just that, an interpretation. It has no empirical support (or at least it didn't some years ago) and is in no way an axiom of QM. I've heard people who use it make the excuse that none of the other interpretations have any empirical support either, even though some of them are less counter-intuitive than Copenhagen. Bohm attempted to create a deterministic hidden-variable QM, but was unable to solve some fundamental problems before he died. One of his students continued with his work, but I don't know if he ever got anywhere. — kwami (talk) 09:04, 28 March 2008 (UTC)

I think neither Schrödinger equation nor wavefunction collapse could be axiom of QM. Therefore, they are considered to be "postulates" of QM. Schrödinger equation seems to correctly predict the spectral lines of each atomic models. On the other hand, wavefunction collapse seems to correctly predict the phenomenon of quantum entanglement. And both of the predictions has been observed by many experiments. The experimental results seem to support both of the two items. But there may be some subtle differences are missing (enough precision? relativity?). When reading the article Copenhagen interpretation, we should also notice the sentence "The Copenhagen interpretation consists of attempts to explain the experiments and their mathematical formulations in ways that do not go beyond the evidence to suggest more (or less) than is actually there." - Justin545 (talk) 09:41, 28 March 2008 (UTC)

>> "There is no place for a collapse in Schrödinger's Equation"

Theoretically, is it possible to build a thought experiment in which the measuring process is simulated and use the Schrödinger equation to find out the result of the experiment? Had some one done this job before? - Justin545 (talk) 10:02, 28 March 2008 (UTC)

As above, it is an open problem. There are ongoing efforts to create "measurement" systems that can be fully modeled quantum mechanically via Schrodinger's equation for all parts of the system. Observationally it is certainly true that wavefunctions "collapse", by which one means that a single particle state interacting with a much larger collection of particles will usually be observed to reside in an eigenstate, however the mechanics of how this occurs is not well understood. The dynamical timescale is apparently quite short, and the systems that need to be modelled fairly large (e.g. 30 or 40 plus particles evolving simultaneously). Dragons flight (talk) 16:02, 28 March 2008 (UTC)

It is likely to get only numerical solution to Schrödinger's equation for so many particles. Finding the solution of exact expression for so many particles seems impossible.

After reviewed the article wavefunction collapse this morning, I noticed this:

By the time John von Neumann wrote his famous treatise Mathematische Grundlagen der Quantenmechanik in 1932, the phenomenon of "wave function collapse" was accommodated into the mathematical formulation of quantum mechanics by postulating that there were two processes of wave function change:

1. The probabilistic, non-unitary, non-local, discontinuous change brought about by observation and measurement, as outlined above.

2. The deterministic, unitary, continuous time evolution of an isolated system that obeys Schrödinger's equation (or nowadays some relativistic, local equivalent).

In general, quantum systems exist in superpositions of those basis states that most closely correspond to classical descriptions, and -- when not being measured or observed, evolve according to the time dependent Schrödinger equation, relativistic quantum field theory or some form of quantum gravity or string theory, which is process (2) mentioned above. However, when the wave function collapses -- process (1) -- from an observer's perspective the state seems to "leap" or "jump" to just one of the basis states and uniquely acquire the value of the property being measured, $e_{i}$, that is associated with that particular basis state. After the collapse, the system begins to evolve again according to the Schrödinger equation or some equivalent wave equation.

It seems that we should treat wave function change as an if-then-else statement in programming. If the change is discrete then use wavefunction collapse method else if the change is continuous then use Schrödinger's method. Not quite a an elegant way in science. - Justin545 (talk) 02:30, 29 March 2008 (UTC)

Any mathematical model that involves "alakazaam!" is obviously fundamentally flawed. However, QM is also the most precisely confirmed theory in human history. As a result, you get the null "Shut up and calculate!" interpretation, which seems to be what most people actually abide by. — kwami (talk) 18:19, 28 March 2008 (UTC)

It sounds like you (kwami) are really sick of quantum theories and those people who are learning it. Unfortunately, I am not here trying to pick a fight with someone over my post. I mean maybe you want to ignore this post and take a rest for a while. - Justin545 (talk) 00:41, 29 March 2008 (UTC)

Nuclear fission

What is the formula for the typ eof Nuclear fission used in power plants? The article has no formulae at all. —Preceding unsigned comment added by Anthrcer (talk • contribs) 09:36, 28 March 2008 (UTC)

The reaction in the top picture is ²³⁵U + n → ²³⁶U → ⁹²Kr + ¹⁴¹Ba + n + n + n. I think that would be fairly typical for anything other than a breeder reactor. The daughter nuclei aren't always the same though. There are a range of possibilities, but the first two steps stay the same. AlmostReadytoFly (talk) 09:48, 28 March 2008 (UTC)

In the case of fission, formulae don't tell you much, as there is a fairly even chance as to what the end-products (the fission products) will be. Pick two arbitrary fission products and you can figure out how many neutrons will be released, and by doing the binding energy calculations, how much energy will be released (in one of a few forms). Power plants don't use a different type of nuclear fission than anything else; where they differ is in the arrangements used to facilitate the fission reactions in different concentrations of uranium, etc. --Captain Ref Desk (talk) 11:18, 28 March 2008 (UTC)

Our article on fission product yield tabulates the most common products of uranium-235 fission, though it doesn't give specific formulae for the fission reaction. In general, the products will be as AlmostReadytoFly says—pick a couple of nuclei from the table that account for all your protons, any 'leftover' neutrons are free neutrons released by the fission. TenOfAllTrades(talk) 13:48, 28 March 2008 (UTC)

STS-123

Why was the hydrazine exhaust more pronounced in this flight than others? Nick (talk) 12:47, 28 March 2008 (UTC)nicholassayshi

I don't know, but here's our article: STS-123. One factor that can make exhaust more visible is humidity in the atmosphere. While on a dry day water vapor will instantly become invisible, on a humid day it can remain indefinitely as an exhaust trail. Under ideal conditions any exhaust particles can also serve as nucleation sites to cause cloud formation. Shock waves can have the same effect. Light conditions will also make the exhaust more or less visible. If it is lit up against a dark sky, that's when it will show up best. This lighting condition is most common before dawn or right after sunset, so the 2:30 AM launch doesn't seem likely to be illuminated by the Sun, but could still be illuminated by the rocket combustion. That seems to be the case in this pic: [7]. StuRat (talk) 16:22, 28 March 2008 (UTC)

doctors whose expertise is diabetics

How do you call a doctor whose expertise is Diabetics ? 'Diabetician' is probably wrong. BentzyCo (talk) 15:55, 28 March 2008 (UTC)

I would think that it's a sub-specialty of endocrinology. -- Coneslayer (talk) 15:56, 28 March 2008 (UTC)

(Which means that the physician's business card may describe him as an endocrinologist.) Individuals interested in a career in endocrinology will first finish a regular medical degree (MD). To become an endocrinologist usually requires at least a two- or three-year fellowship on top of their general training. Many endocrinologists specialize on a specific area within the field (diabetic medicine, reproductive medicine, etc.). TenOfAllTrades(talk) 16:07, 28 March 2008 (UTC)

There are also nutritionists/clinical dieticians who will advise you on a new diet for diabetics. I'm not sure if any handle diabetes alone or if they all handle multiple special diet planning. Also, many may not hold doctorate degrees. StuRat (talk) 16:20, 28 March 2008 (UTC)

It would be a metabolic sub-specialty of endocrinology. Wisdom89 _{(T / ^C)} 18:47, 28 March 2008 (UTC)

I looked up on the internet a doctor (in the US) who is an expert in treating diabetes. The website describes him as "Specialties: Diabetes, Endocrinology & Metabolism, Internal Medicine" and he is Board certified in Internal Medicine and Endocrinology. In the UK I found one who described himself as "Consultant Diabetician and Endocrinologist." So the terminology may vary regionally. Even in the UK "diabetician" seems to be more of an informal usage by patients rather than a professional certification. Edison (talk) 00:15, 29 March 2008 (UTC)

"Diabetologist" has some currency in the U.S. - enough to merit an entry in Merriam-Webster's Dictionary that dates the first use of the term as 1970. - Nunh-huh 01:41, 29 March 2008 (UTC)

That could also refer to a scientist who studies or specializes in or researches diabetes as well - probably why you might find mentions of the term floating around in literature. Wisdom89 _{(T / ^C)} 02:54, 29 March 2008 (UTC)

Well, I suppose it could, but in actual use, it generally doesn't. - Nunh-huh 00:15, 30 March 2008 (UTC)

We call them "Diabetes Specialists." There are CME courses for diabetes specialists and national testing to be officially titled as a diabetes specialist. Right now, I'm beginning a study on how much treatment of diabetes is improved in clinics that employ diabetes specialists. None of them call themselved diabeticians or diabetologists or anything of the sort. -- kainaw™ 03:00, 29 March 2008 (UTC)

Climate change

Given the clearly disturbing events that have just happened a few days ago regarding a 160 km piece of an ice shelf buckling, just how concerned should the world be. Also if the ice shelf does collapse, which areas will most likely be affected, the northern or southern hemisphere? I think we can all agree that we need to start looking for a new planet --77.100.6.191 (talk) 18:37, 28 March 2008 (UTC)

Take it easy. An ice shelf buckling is not going to destroy all life on Earth. Ice floating on water doesn't even increase sea levels when it melts. Ice on land does, but likely only a fraction of an inch worldwide. If all of the ice on Antarctica and Greenland melted, then you would have a significant sea level rise of tens of feet. That would be trouble for some low-lying coastal areas, especially those below sea level. However, as long as this happens slowly enough, we will be able to compensate by moving inland or constructing sea walls. Human life will survive. Now, would it be wise to take some of the resources we would otherwise put into evacuating coastal areas and spend that on slowing global warming, instead ? Sure, that would be a more efficient use of those resources. StuRat (talk) 18:51, 28 March 2008 (UTC)

Okay, this is an excuse to advertise my own work on an interactive tool for seeing regions vulnerable to sea level rise: http://www.globalwarmingart.com/sealevel A complete melt-down would be 65 m (210 feet) and have a dramatic effect, but that is very unlikely and would require a very long time even if it did happen. More likely is somewhere between 0.3 and 2 m (1-6 feet) during the next hundred years, which is important only to isolated regions, like New Orleans and the Netherlands, that are already very close to sea level. Speaking of efficient use of resources, another good one would be to stop building so many beach front properties. Property losses due to hurricanes in the US have increased 10-fold in recent decades, but that is mostly because so much more construction is being built in vulnerable areas. Dragons flight (talk) 21:05, 28 March 2008 (UTC)

Hi. Wow, that looks like a really useful tool, and perhaps just as useful as Flood Maps. The Wilkins Ice Shelf, even if it melts completely, should not be a global catastrophe. However, if Pine Island Bay melts, well, uh, that's another story. Hope this helps. Thanks. ~AH1^(TCU) 21:35, 28 March 2008 (UTC)

Hi. Woah, a mere 25-metre sea level rise would flood large areas around the Caspian sea, acording to that link. Thanks. ~AH1^(TCU) 23:00, 28 March 2008 (UTC)

One problem with these kind of maps is that they usually take into account only elevation, thus showing things like a greatly enlarged Caspian Sea, or a water-filled Death Valley, etc. This one seems a bit better in that its legend is labeled "Elevation Relative to Sea Level" -- which does not necessarily mean "filled with water". Pfly (talk) 18:55, 29 March 2008 (UTC)

Wilkins Ice Shelf

The spectacular series of pictures of a large piece breaking off from the Wilkins Ice Shelf clearly show the broken piece turn from white to blue as the crack progresses through Feb and March. Why is that? Surely it would not have got noticeably thinner in that short space of time. SpinningSpark 18:43, 28 March 2008 (UTC)

I think there was a subtle change in the angle that caused it to reflect light differently (it appears to be higher up on land and lower by the water). In Antarctica the sunlight is coming in at such a shallow angle that any change in the surface angle can put the entire surface in shadow. Shadows on snow and ice often appear blue. StuRat (talk) 18:58, 28 March 2008 (UTC)

Hi. How is it impossible for ice to melt in the space of a month? If it never melted, then it would refreze the next winter, and events like Larsen B would be impossible. Could it be that as the ice became detached from the main shelf, it started to crack, and the colder water, interspersed with large chunks of ice, created a "gel-like" structure overall and became a combination of ice and fresh water? Or, is it really impossible for it to melt that quickly in the space of a month? Didin't Larsen B turn blue when it was melting? How could Arctic ice, similar albeit less thick, melt so quickly if the ice cannot change in thickness? Will the Wilkins Ice shelf, the part that broke off at least, refreze around May and June? Thanks. ~AH1^(TCU) 21:43, 28 March 2008 (UTC)

Earth Hour - feasable or not?

As far as I know about power stations and electricity, it costs more power to halt a power station for an hour and restart it afterwards, than to keep it running. So, what if the Earth Hour succeeds in an impressive way, and everyone turns off everything for an hour. What could possibly happen? Where goes all the generated power? Wouldn't it be dangerous if suddenly everyone turns everything off? Wouldn't all the power stations blow off? with a 10% drop as last year, certainly not, but what about a 95% drop? --V. Szabolcs (talk) 20:04, 28 March 2008 (UTC)

Power networks have pumped-storage hydroelectricity facilities which consume excess electrical power during periods of low demand, using it to pump water from a low reservoir into a high reservoir. The water is then released during periods of high demand, when it generates electricity by driving turbines. In effect, these facilities act as huge rechargeable batteries. This allows the energy company to even out fluctuations in demand on the grid and to run their base load power plants at or near a constant peak efficiency. Gandalf61 (talk) 20:25, 28 March 2008 (UTC)

Thanks for the quick answer. I knew about the water pumping at the hydroelectric stations, but aren't those fluctuations statistical, so they usually never change very much too quick? If everybody at the same time turns everything on or off, wouldn't it cause strange effects? --V. Szabolcs (talk) 21:07, 28 March 2008 (UTC)

(ec) Well that's one solution. Other, not so widespread, options include undergound compressed air storage and NaS batteries (molten sodium batteries have ridiculous capacities, but only operate at high temperatures). For the large part though, much of the power infrastructure is still managed by taking plants on and off-line and allowing voltages to drift by several percent as you do so. Most electronics are tolerant of minor changes in the voltage which gives power suppliers room to adjust the amount of energy they are delivering without having to always react instantly to changes in demand. Dragons flight (talk) 21:16, 28 March 2008 (UTC)

Different types of power plants can be shut down and restarted on different time scales. Base load power plants (conventional coal or nuclear facilities) take hours or days to start up. Peaking power plants (oil-fired and especially gas turbines) can be started or shut down in minutes. The output of most hydroelectric plants can be regulated easily (often in seconds) by adjusting the flow of water through their turbines. Extremely rapid changes in demand (on time scales shorter than a few seconds) will result in brief increases or decreases in the grid's voltage. How easily the power grid can respond to rapid shifts in demand depends on how fast those changes occur, the size of the change, and the makeup of the grid's generating capacity.

The condition you're describing – where a power plant running at full output faces a sudden sharp drop in demand – is called load rejection. Power plants are designed to shut down safely when this occurs (as can happen during a major transmission line failure, for example—see Northeast Blackout of 2003), though restarting tripped plants can take hours or days. TenOfAllTrades(talk) 21:25, 28 March 2008 (UTC)

Hi. Should someone add Earth Hour to the on this day for the main page March 29, as well as edit the article on March 29 to mention Earth Hour, or should I do that myself? Thanks. ~AH1^(TCU) 21:46, 28 March 2008 (UTC)

I've mentioned Earth Hour in the March 29 artcle. --Bowlhover (talk) 04:37, 29 March 2008 (UTC)

Sounds like an interesting experiment, and I plan to do my part. An imbalance between generation and load due to everyone turning off lights at the same instant would cause the power frequency in the affected region to increase a bit above the normal 60 Hz until the steam valves could react by decreasing the input power to the generators. Most people will not alter their usage during the appointed hour. Other load which will not be affected includes electricity used to operate in full or in part the heating plants, refrigeration systems,stores, electricity used in industry, that used to operate electric trains,for operating elevators, restaurants, streetlights, sewage plants, hospitals, broadcasting operations, and many other portions of the load. The baseload plants will be dispatched according to the expected load. Baseload plants could be tripped offline if the load dropped too abruptly, and they would takw a while to restart. Peakers are smaller units designed to start rapidly and to change their output rapidly to follow loadswings. If folks in each timezone turned off their lights frop 8 to 9 pm local, there would be interesting swings in the powerflow on the tielines between utilities on either side of the time zone boundary. The US is connected a grid,(or rather grids) with large areas interconnected to allow one area to back up the next when load is added or when generation drops. It sounds like a field day for burglars, if residential security lights are turned off. Edison (talk) 22:28, 28 March 2008 (UTC)

I suspect it's a truism in control theory (and if someone can confirm this, I'd be grateful) that the best regulation can be achieved only with anticipation of future events. Machines aren't good at predicting unpredictable events in the future, but people can be. I suspect that, as the publicity surrounding Earth Hour has increased, the word has gone out to all the power plant operators everywhere (via whatever bulletin-board or chat system they use) that they'd be well-advised to have their finger closely on the throttle at 8:00 tonight.

I wonder, too, how far this observation goes in explaining what I hear has recently been discovered to be the inherent instability of large-scale electric power generation and transmission networks. We'd like to think that those networks, and all their regulation and protection mechanisms, are fully automated, removing us unreliable people from the loop. But if the systems are operating close enough to the edge (of capacity or stability or any other factor) that the best possible regulation is absolutely required, and if the best possible regulation requires more anticipation than "dumb" machines can possibly handle, then humans may be unavoidably part of the system, meaning that the possibility of human error (with arbitrarily catastrophic results) can't ever be entirely eliminated. —Steve Summit (talk) 18:50, 29 March 2008 (UTC)

"People can be good at predicting unpredictable events"?!?!? Would you, ah, care to rephrase that? --Anon, 21:45 UTC, March 29, 2008.

Well, okay, if you want to be pedantic about it, would you settle for "People can be good at reading the newspaper and anticipating events that couldn't have been predicted when the power grid management system was designed N years ago"? :-) —Steve Summit (talk) 22:52, 29 March 2008 (UTC)

How about Earth Away From Home? I now have my breaker box wired with contactor relays for each and every circuit and the contactor relays setup for remote control so that instead of shutting everything down for just an hour I can shut everything down including such electric appliances as the electric water heater when I leave for work. Except for the security system my house is dead until I return. That's everything off for at least eight hours a day. 71.100.15.236 (talk) 00:06, 29 March 2008 (UTC)

Well, I killed the main breaker in my home at 8 and restored power at 9. I did not see much of a blackout at neighbors' homes. During the hour I had a battery radio on, a fire in the fireplace, and a few battery lights, candles and kerosene lamps burning. It was a pleasant interlude, for what it's worth. It will be interesting to see if the experiment caused a measurable change in power demand. Edison (talk) 02:19, 30 March 2008 (UTC)

what causes water drops to join up?

I'm not talking about condensation, or the formation of water drops. I'm asking what is the name (if one exists) of the phenomenon of water drops clumping up to join a larger mass.

There are two scenarios in which i've seen this: first, when it's raining outside, and water drops slide down my car window, as they travel, they absorb more drops, gaining in mass and velocity. Second, if given enough time, and the frequency is right, free falling water drops will seem to clump up and form larger clumps.

I heard this refered to as the 'Moydo (Moydow?) Effect' but can't find any reference to it. Does anyone have a clue if this phenomenon has a name (other than water clumping, of course)204.154.43.244 (talk) 21:53, 28 March 2008 (UTC)

It's largely a function of surface tension. The most volume enclosed by a given surface area (or the least surface area required to enclose a given volume) is a sphere, and water tends to sit as spherically as possible given the constraints of gravity, intervening surfaces, and so forth. — Lomn 21:57, 28 March 2008 (UTC)

Do you mean the Marangoni effect ? SpinningSpark 22:16, 28 March 2008 (UTC)

More generally, perhaps coalescence? Sadly we don't seem to have much info on that, although it can be fascinating. 81.157.46.230 (talk) 01:44, 29 March 2008 (UTC)

Also, capillary action might be at work here, although this is related to/involves surface tension effects, in addition to intermolecular forces. Wisdom89 _{(T / ^C)} 03:03, 29 March 2008 (UTC)

Thermal ballast

Is it more energy efficient to keep a freezer and a refrigerator as empty as possible or to keep them loaded to the max.? —Preceding unsigned comment added by 71.100.15.236 (talk) 23:35, 28 March 2008 (UTC)

Personally, I believe it makes little difference, although having it fuller will probably make it slightly more efficient. And my hero agrees with me. —Steve Summit (talk) 00:49, 29 March 2008 (UTC)

I would define efficiency in terms of how much food is kept cold per dollar. In that case, an empty freezer is running at 0% efficiency. StuRat (talk) 04:02, 29 March 2008 (UTC)

If you have the type of freezer with a front-opening door and shelves, then every time you open the door the cold air flows out and it replaced by warm air from the room, which then has to be cooled again. In that situation it's more efficient to keep it full, since frozen food doesn't convect! I did see a suggestion somewhere though that you could reduce that problem by filling excess freezer space with empty cereal boxes to hold the cold air in place. Freezers with drawers also solve the problem. Eve (talk) 13:26, 29 March 2008 (UTC)

However, when you do put food in, you would then need to remove a cereal box full of cold air, and that won't help efficiency. StuRat (talk) 14:21, 29 March 2008 (UTC)

If it was a cereal-box-sized piece of food you put in, it would have displaced the equivalent volume of cold air anyway. —Steve Summit (talk) 14:54, 29 March 2008 (UTC)

Talking Budgerigars - sex difference

Why is it (usually) easier to teach a male Budgerigar to talk than a female? Why do male birds usually develop a larger overall vocabulary than females? --90.242.159.224 (talk) 23:45, 28 March 2008 (UTC)

Probably to impress the females. Male birds usually have many distinguishing features, like more colorful feathers, for the same purpose. --V. Szabolcs (talk) 08:28, 29 March 2008 (UTC)

Puck of the most words made the Guiness Book of Records in 1995[8] – he was a bloke, too. Julia Rossi (talk) 08:49, 29 March 2008 (UTC)

See sexual selection. --Captain Ref Desk (talk) 20:04, 29 March 2008 (UTC)

March 29

Canned tuna

Is canned tuna cooked? 71.100.15.236 (talk) 01:02, 29 March 2008 (UTC)

In short: yes. There's some information about it at Tuna#Canned tuna. --Masamage ♫ 01:14, 29 March 2008 (UTC)

Okay, cooked but a couple of other questions... it looks like there is no minimum amount of tuna per can to call it tuna. 90% water or oil and 10% tuna and its tuna. No one would probably buy it again but what about 10% tuna, 41% catfish and 49% water? 71.100.15.236 (talk) 02:31, 29 March 2008 (UTC)

The cans have to contain a certain weight of tuna after the liquid in the can is drained. See here for the FDA regulations on canned tuna, specifically part c. Someguy1221 (talk) 11:07, 29 March 2008 (UTC)

cd recycling

Can cd's be recycled? If so, do you put them in with normal municipal recycling? I know the procedure might vary from place to place, so fyi, in my city of Perth, my local council (Claremont) uses mixed recycling, ie. without source separation. thanx in advance, 130.95.106.128 (talk) 07:10, 29 March 2008 (UTC)

I recycle mine as coffee cup coasters. Seriously, they can be recycled. Try this [9] google search string. You will also see that there are a lot of charities that will take them to make interesting products. SpinningSpark 13:12, 29 March 2008 (UTC)

Sodium Bicarbonate Vs Constipation?

Why does Sodium Bicarbonate help in going to the toilet? I know it is an has a much higher ph than the stomach but why does this result in the need to visit the toiler 5 mins after drinking it mixed with warm water? Is it bad for the stomach to use on a regular basis?

Lopex —Preceding unsigned comment added by 86.4.182.208 (talk) 08:42, 29 March 2008 (UTC)

When you mix Sodium bicarbonate with stomach juice it foams up making carbon dioxide gas, which build up pressure in the digestive tract, that pushes the contents out. Too much will give you pH imbalance, and also too much sodium. Graeme Bartlett (talk) 22:18, 29 March 2008 (UTC)

I am not convinced that a pressure build up in the stomach will have a direct pressure-based effect on the lower bowel. They are separated by several metres of soft small bowel which would absorb the pressure and apart from that, if there is that much pressure build up (again, questionable) surely it would escape upwards through the gullet, giving a vomiting effect. Bowel movements are associated with psychological stimuli in some people and the thought that something will effect the bowels does just that. An alternative explanation may be related to the gastrocolic reflex, even so five minutes seems a bit quick. Richard Avery (talk) 07:19, 31 March 2008 (UTC)

As for regular basis, once things are back to normal, probably no need. Julia Rossi (talk) 07:53, 31 March 2008 (UTC)

I would think the more likely explanation of any laxative effect of sodium bicarbonate is induction of hyperosmotic diarrhea. On the other hand (or on the other end), sodium bicarbonate's "fizzy" effect is used in suppositories, and acts by inducing a feeling of rectal "fullness", with the expected reflex action. Bicarbonate isn't really a popular laxative - it's used more as an antacid - and of course, it's considered bad form to use any laxative regularly without consulting a physician to see if there is an underlying problem that need to be addressed.- Nunh-huh 09:53, 31 March 2008 (UTC)

What is the difference between a UPS and a inverter ?

—Preceding unsigned comment added by 124.124.1.131 (talk) 12:17, 29 March 2008 (UTC)

An inverter is a device for converting dc power to ac power. An Uninterruptable power supply (UPS) stores energy it obtains form its input (often in a battery, but it could be something else, eg a flywheel) which it applies to its output if the primary source fails. A UPS will often contain an inverter because its output may be ac while it has stored power as dc. However, in principle, a UPS might not have an inverter if its output was required to be dc. SpinningSpark 12:29, 29 March 2008 (UTC)

SpinningSpark is right. Also, sometimes people may say "inverter" when they mean UPS. I knew someone who had a home-built UPS system, basically a inverter, a charger, and a big battery. They called it an inverter even though that was just one part of the system. -- 71.91.127.85 (talk) 16:25, 30 March 2008 (UTC)

If you remove the DC input to an inverter, the AC output will immediately go to 0VAC. If you remove the (usually AC) input to a UPS, the AC output will not change (much). A UPS includes an inverter, a battery, and a battery charging system. -Arch dude (talk) 23:41, 30 March 2008 (UTC)

blackout --- caused by global warming?

I would like to know if I got it right that global warming also has something to do in any way with having power/electrical loss or blackout. Thank you in advance for the reply. —Preceding unsigned comment added by 119.93.229.75 (talk) 12:30, 29 March 2008 (UTC)

In general no, but the drought in Australia, which could have been global warming related, nearly lead to blackouts becuase of lack of water to hydro-electric plants [10] -- Q Chris (talk) 13:11, 29 March 2008 (UTC)

Indirectly, I suppose you could say that global warming leads to more use of air conditioning leads to higher electricity usage leads to more risk of brown- or blackouts. (Contrariwise, of course, more electrical usage for air conditioning leads to more global warming...) —Steve Summit (talk) 13:43, 29 March 2008 (UTC)

Hi. I just thought of something, could the 2003 European heat wave somehow been related to the 2003 Italy blackout, even if indirectly? Thanks. ~AH1^(TCU) 13:56, 29 March 2008 (UTC)

The electric company here in our city has announced a citywide blackout and giving "global warming" as a reason. —Preceding unsigned comment added by 119.93.229.75 (talk) 14:35, 29 March 2008 (UTC)

Wild guess - is this perhaps something to do with Earth Hour ? Although I thought that was supposed to be a voluntary initiative, so I don't see why a power company would announce a blackout. Anyway, there is a list of participating cities in our Earth Hour article. Gandalf61 (talk) 15:01, 29 March 2008 (UTC)

Rules for making Baryons

I'm trying to understand what are the rules for making baryons. I know baryons are made from 3 quarks (screw pentaquarks for now), any quarks. Since there are 6 different quarks, then we have 6^3 combinations of 3 quarks. However, from the Δ⁺ and the proton, each with quark composition u/u/d, it looks like the spin orientation has to be taken into account. Since each quark can be in +1/2 or -1/2 spin state, then we have 12 different quarks/quarkstates possible for each of the three quarks, which gives us 12^3 different combinations of three quarks. If we remove the degeneracies (such as ssd (3/2),sds(3/2),dss(3/2)), then we have 364 (12+11+10...+11+10+9...+10+9+8+...3+2+1+2+1+1) distinct combination of quarks/quarkstates.

Now I'm not sure of this, but I think that it is the modulus of the spin that is important, so particles with spin -3/2 and -1/2 really are the same than the particles with spin 3/2 and spin 1/2. Removing these degeneracies leaves us with half the particles, and thus we have 182 distinct baryons that can be made from three quarks.

Also, there seems to be some states that are forbidden - the Δ⁺⁺ cannot be in spin 1/2 configuration, and there are some duplicate combinations &Lamba;⁰ is uds (1/2) and so is Σ⁰. Headbomb (talk) 16:18, 29 March 2008 (UTC)

The top quark does not form baryons, according to our article, because its lifetime is too short. Apart from that, I think any combination of three quarks gives a baryon (and the corresponding three anti-quarks gives the baryon's anti-particle). If the three quarks all have the same flavour then their spins must align (because of the symmetry of the state) and you get a spin 3/2 baryon. If the quarks do not all have the same flavour then their spins may align to give a spin 3/2 baryon, or their spins may not align, which gives a spin 1/2 baryon. Quarks can also exist in excited states within a baryon - so the spin 1/2 Σ⁰ is an excited state of the Λ⁰. See list of baryons and particle zoo. Gandalf61 (talk) 13:12, 30 March 2008 (UTC)

Top Ten Chemicals Produced

I need to find the top ten chemicals produced in any given year from 1973 to the present. I have done some online searches but have found very little data. Please help.Jdbauman283 (talk) 19:06, 29 March 2008 (UTC)

Do you mean chemicals deliberately produced by humans on the earth in a manufacturing chimcal industry process? (ass opposed to naturally produced, in space, a waste product, or grown or quarried). Graeme Bartlett (talk) 22:21, 29 March 2008 (UTC)

Obviously they meant man-made. Is that obvious? that's what I'm answering anyway - see below

Sulphuric acid is always a big one. Also see Chemical industry . " Polymers and plastics, especially polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polystyrene and polycarbonate comprise about 80% of the industry’s output worldwide."

Also ammonia, fertilzers.

plus liquid nitrogen/oxygen

Here's a very out of date list http://pubs.acs.org/hotartcl/cenear/960624/prod.html 87.102.16.238 (talk) 11:14, 30 March 2008 (UTC)

I recall from the sulfuric acid article once, that sulfuric acid was actually the number one highest purposefully produced industrial chemical in terms of mass. Mac Davis (talk) 17:52, 30 March 2008 (UTC)

Do residential security lights reduce burglary?

In the Earth Night thread above I saw this comment: sounds like a field day for burglars, if residential security lights are turned off. And wondered whether such lights actually deter burglary. My understanding was that it is usually easier to see a person in the dark outside without lights than it is to see a person lurking behind a bright light. In other words, a smart burglar would use security lights to advantage. Am I misinformed? Pfly (talk) 19:12, 29 March 2008 (UTC)

I'd suspect you're mis-reasoning. If it is non-lighted at night it can be hard to see anything, something we forget in our current constantly-lit existence. Yes, standing behind a bright light can make it hard to be seen, but that requires 1. being able to get "behind" the light in the first place, and 2. knowing exactly whom you are hiding "behind" the light from (hence the quotation marks around "behind"—to someone on the other side of you, you're in front of the light!). I don't honestly see how even a smart burglar, much less the normal variety (which any public defender can tell you are not usually the best and the brightest), would use basic security lights to their advantage in a practical way. In any case, it's also a psychological case: someone under spotlights is probably more likely to feel like they are being seen, or at least could be seen, that someone without them, regardless of whether anyone is looking at them or whether they might also be able to be seen at night. --Captain Ref Desk (talk) 19:56, 29 March 2008 (UTC)

According to the article on light pollution, the International Dark-Sky Association (which is honestly a biased source) says that there's apparently no current scientific research supporting (or opposing) the idea that lighting increases security. And there's plenty of anecdotal evidence out there. I personally think most people overdo it. (The light pollution haze from the city actually does a better, more uniform job lighting my place than having proper security lights would). -- Consumed Crustacean (talk) 22:06, 29 March 2008 (UTC)

Hi. Security lights are so annoying because their glare prevents good observation of the night sky. Besides with all these street lights around it would already be bright enough. A good security system shoul only activate when the burgler is detected trying to enter the house and not up all night (most burgleries happen during the day). Thanks. ~AH1^(TCU) 23:50, 29 March 2008 (UTC)

Ah ha, I believe I did hear this idea from someone from the International Dark-Sky Association on the radio. Biased, of course. And certainly it is easy to think up examples (and places) that are obviously one way or the other. I can imagine it would be difficult to do a good scientific study of the matter. Then again, I know certain towns and suburban areas have had "dark sky" programs for years. I'd think there would be studies of those kind of places and crime rates over time. Not that it would show causality, and would be limited to the kind of neighborhoods that would actually implement such programs. Still, I wonder.. Pfly (talk) 01:28, 30 March 2008 (UTC)

When Los Angeles had a big earthquake about a decade or two ago, the power went out and the milky way was visible. People rushed outside during the earthquake, and most have never seen the real milky way before. The reason? The Los Angeles city lights have been washing out the stars for all this time. In the past 50 years or so, stereotypes have developed about what the night sky really looks like, because most urbanites have never seen the real night sky. So, a lot of people called to ask the observatory if a sudden brightening of the milky way had caused the earthquake. The observatory workers tried to explain that this is how the night sky is supposed to look. The L.A. residents didn't believe them. Pfft. ~AH1^(TCU) 21:12, 30 March 2008 (UTC)

efficiency question .

what portion of energy is wasted as a result of friction of an automobile ? how efficient will maglev train be compare to conventional vehicle ? —Preceding unsigned comment added by Shamiul (talk • contribs) 20:37, 29 March 2008 (UTC)

Pretty much all of the inefficiency in an electric car is a result of some type of friction. There is friction in the engine and transmission, rolling friction in the wheels, air resistance is a type of friction, and brakes use friction. If all friction could be eliminated, say by traveling in a vacuum, using regenerative braking, etc., then the only energy used would be in raising the elevation of the car, providing heat and A/C, running the lights, and maybe the radio. Internal combustion engines also suffer major inefficiencies due to incomplete combustion and heat bled off to the environment from the radiator. Electric cars also suffer inefficiency due to battery leakage. StuRat (talk) 21:42, 29 March 2008 (UTC)

Have you seen our engine article?. And does this answer your question? 81.93.102.185 (talk) 21:50, 29 March 2008 (UTC)

What do you see?

Do the eyes of all mammals see the same spectrum of what we call "visible light"? Seems like they do.. any particular reason? Seems like a predator who developed eyes that could react to infrared radiation would quickly dominate their environment. :D\=< (talk) 20:38, 29 March 2008 (UTC)

A very similar question was asked last December and got a lot of responses. (Just putting that out there, not trying to discourage more answers, thoughts.) --Captain Ref Desk (talk) 21:10, 29 March 2008 (UTC)

See our article on the eye and retina. It has to do with the physiology of the cells in the latter. rods and cones. Wisdom89 _{(T / ^C)} 21:55, 29 March 2008 (UTC)

Let me quote Richard Dawkins in the ancestor's tale page 147. "All eyes on our planet are set up in such a way as to exploit the wavelengths of electromagnetic radiation in which our local star shines ... For an eye that has commited itself to biochemical techniques suitable for this loosely bounded range of wavelengths, the laws of physics impose sharper bounds to the portion of the electro-magnetic spectrum that can be seen using those techniques. No animal can see far into the infrared. Those that come closest are pit vipers, who have pits in the head which, while in no sense focusing a proper image with infrared rays, allow these snakes to achieve some directional sensitivity to the heat generated by their prey. And no animal can see far into the ultraviolet although some, bees for instance, can see a bit further than we can. But, on the other hand, bees can't see our red: for them it is infrared. All animals agree that 'light' is a narrow band of electormagnetic wavelengths lying somewhere between ultraviolet at the short end and infrared at the long end. Bees, people and snakes differ only slightly in where they draw the lines at each end of 'light'" emphasis and typos added by me. -- 71.91.127.85 (talk) 19:21, 30 March 2008 (UTC)

I assume its because water is only transparent within a narrow range of frequencies.Em3ryguy (talk) 21:13, 30 March 2008 (UTC)

March 30

Tongue rolling genes

From Mendel's list I've looked at that section in the Tongue article and it mentions curling the tongue lengthwise. I know someone who can flex the tongue muscle in three different ways: curling lengthwise, turn it over and fold the tip back flat on itself like folding a piece of paper – all without help from fingers. How common is this – is it genetic and how is it passed along? His parents don't seem to have the knack, but his grandfather could touch the tip of his own nose. Julia Rossi (talk) 02:13, 30 March 2008 (UTC)

I don't know much about genes, but I know from Wikipedia that as soon as people discovered genes, they said that genes were responsible for just about every single behavior of the body that was unexplainable. I would personally not believe that being able to move your tongue in certain ways does not come from your genes, but rather something else. Mac Davis (talk) 17:47, 30 March 2008 (UTC)

While it is right to criticise a naive view of absoulte genetic determinism, building bodies is an area where genes obviously play a huge role. I probably wouldn't be able to fold my tongue back as described no matter how much I tried, just like I cant change my eye color, my genes just built my body not to be able to do those things. -- 71.91.127.85 (talk) 19:33, 30 March 2008 (UTC)

I believe that certain tongue-rolling abilities are genetic. Edison (talk) 20:23, 30 March 2008 (UTC)

I've always believed that tongue (lengthwise) curling was indeed a simple dominant-recessive (it's a common example in text books), well established and understood trait. Evidentally it's not. [11], [12], [13], [14] & [15]. Eye colour is mostly genetic, and reasonably well understood but it also not a simple genetic trait (the article has more info). Nil Einne (talk) 18:12, 2 April 2008 (UTC)

gas molecule unpredictability

If you set up a barometer in a controlled environment with perfectly stable 1 atm air pressure, would you ever see any sort of noticable fluctuation? Would the heat death of the universe occur before you even had a billionth of a percent chance of seeing a 1-second millimeter rise/drop in the mercury, or is it actually quite likely? I'm just looking for very round answers here :D\=< (talk) 02:59, 30 March 2008 (UTC)

I just realized how absurd that question is.. the part about the perfectly stable air pressure pretty much makes no sense! Let's say the number of gas molecules in the chamber is stable, there's no external influences like heat causing convection, and the average air pressure is 1 atmosphere. :D\=< (talk) 03:03, 30 March 2008 (UTC)

Wind or pressure/temp changes would cause fluctuations. If there is no wind or pressure/temp change, I wouldn't expect any fluctuations until the mercury evaporation has a noticeable effect. StuRat (talk) 03:07, 30 March 2008 (UTC)

Well I just mean from gas molecules not hitting the surface. Like how if every air molecule happened to be bouncing exactly away from your mouth, then your lungs would collapse from lack of air pressure.. except with the surface of the mercury :D\=< (talk) 06:49, 30 March 2008 (UTC)

Consider a simple approximation: If each particle is approximately independent, then we can pretend that the direction it is moving (e.g. up-down, left-right, etc.) is random. Pressure is created by particles bouncing off a surface. Under normal conditions ~50% of the particles in any given volume will have a downward component to their motion. Let's consider, what is the probability that only 45% or less of particles have a downward motion. This would correspond to a 10% reduction in the downward flux and hence the instanteous pressure.

If the motion is random, then the number moving down is governed by combinatorics. Specifically, the probability of $N_{down}<=\alpha *N$ is

${1 \over 2^{N}}{\sum _{i=1}^{\alpha N}{N \choose i}}$

$={1 \over 2^{N}}{\sum _{i=1}^{\alpha N}{N! \over {i!(N-i)!}}}$

$\approx {1 \over 2^{N}}{\sum _{i=1}^{\alpha N}{N^{N} \over {i^{i}(N-i)^{N-i}}}}$

$\approx {1 \over 2^{N}}{N^{N} \over {{(\alpha N)}^{\alpha N}{((1-\alpha )N)}^{(1-\alpha )N}}}$

$={1 \over 2^{N}}{1 \over {{\alpha }^{\alpha N}{(1-\alpha )}^{(1-\alpha )N}}}$

$=({0.5 \over {\alpha }^{\alpha }{(1-\alpha )}^{1-\alpha }})^{N}$

Where I have used approximations appropriate for large N. If α = 0.45, then this reduces to $0.995^{N}$. So with a hundred particles, a 10% fluctuation occurs ≈0.995¹⁰⁰ = 60% of the time. For 2000 particles this reduces to 4 in 10⁵. For macroscopic ensembles, e.g. 10²³ particles, the odds of 10% fluctuation at random is essentially 0 for all practical timescales. Dragons flight (talk) 08:27, 30 March 2008 (UTC)

Simplify your gedankenexperiment by using a J-shaped tube with a vacuum at the tall end and a gas (at one ATM0 at the other. Replace the "mercury" with a perfect theoretical fluid that cannot react with or absorb gas. Now do the math again. -Arch dude (talk) 23:29, 30 March 2008 (UTC)

"japanese algae" keychain

My friend has this keychain, which is a sealed plastic container filled with a liquid and two green spherical puffs which she says are marimo. The liquid looks like green-colored water with oil floating in a layer on top. Could marimo actually survive in this kind of environment, or are they probably just green pom-poms? --Anakata (talk) 03:24, 30 March 2008 (UTC)

Another possibility is that it's real, but not alive. It could be preserved in some liquid like formaldehyde. StuRat (talk) 13:45, 30 March 2008 (UTC)

Sure its possible, with the right mix of microorganisms, but I am very skeptical. I'd imagine that the smaller the ecosystem, the harder it is to balance and keep healthy. I was poking around for info about ecospheres and people say that they are highly sensitive to changes in light and temperature. Being repeatedly stuffed into a warm dark pocket does not sound conducive to a stable ecosystem. -- 71.91.127.85 (talk) 19:39, 30 March 2008 (UTC)

Wow. Marimo sound cool - thanks to WP, I've learned something else new. Are there any legitimate sports-based applications for these green balls? --Kurt Shaped Box (talk) 19:50, 30 March 2008 (UTC)

Hawaii up from Alaska...?

If you look at Google maps you can see a line of submarine mountains that runs South from Achayvayam, Russia off a jetty, past the West side of Attu Island to a point about 1,800 miles East of Tokyo and then runs South East about 500 miles to Midway Island and then another 1,500 miles or so where it terminates at Hawaii. Does this mean that the hot spot that is still creating Hawaii actually originated in Russia and if so how long ago? —Preceding unsigned comment added by 71.100.0.187 (talk) 05:30, 30 March 2008 (UTC)

It looks that way (well, the hotspot stays fixed and the tectonic plates move over it, but same difference). About 80 million years. See Hawaii hotspot and Hawaiian-Emperor seamount chain.

Hi. Well, The plate that Hawai'i is situated over is constantly moving northeast, so the islands eventually move, then a new island is remade in its place. The old islands eventually erode and sink underwater. This creates a chain, and it is eventually eaten by the North American place at the destructive boundary. I think I've heard from various places that the Hawai'i chain was nonexistant during the Cretaceous. A new volcano is being created off the coast of the Big Island, and will soon replace it, but it's still got many kilometres and hundreds of thousands of years to go. Hope this helps. Thanks. ~AH1^(TCU) 21:19, 30 March 2008 (UTC)

Reversing the effect of Sun tanning on skin colour.

Is it possible to reverse the effect of sun tanning on skin colour ? Does sun tanning permanently change skin colour ? —Preceding unsigned comment added by Shamiul (talk • contribs) 08:33, 30 March 2008 (UTC)

Yes, if you stay out of the sun, your skin will eventually return to its original paler colour. However, you may tan more quickly next time you are in the sun. Also note that persistent overexposure to the sun can permanently damage your skin in a number of ways. See the article Sun tanning. SpinningSpark 12:30, 30 March 2008 (UTC)

Hi. I the summertime, I often get a "sandal tan" from wearing sandals. This usually lasts for several months, then fades away around wintertime. It usually redevelopes around late spring. I think it takes about a week to develop, and a few months to fade, although a remnant can still be seen that persists until next summer. Since it becomes darker than usual the next summer, it is often easier to get it again. Hope this helps. Thanks. ~AH1^(TCU) 21:23, 30 March 2008 (UTC)

MA and VR Can Opener

How do you calculate how much effort you put on a can opener?

Bzinc (talk) 12:40, 30 March 2008 (UTC)

Would that be Mechanical advantage and Velocity Ratio you would be after? And would this be a homework question? The Lever article might help you. SpinningSpark 12:54, 30 March 2008 (UTC)

What do t hese mean?

I love science, and a lot of the articles have images like on them. I was wondering if anyone would tel me what they mean, because someone (we're brothers) doesn't like me. Thanks! Yamakiri ^T_C § 03-30-2008 • 14:32:00

Ribbon diagram. TenOfAllTrades(talk) 14:59, 30 March 2008 (UTC)

Ahhh! My attention span! It's average! Nooooooooo! Yamakiri ^T_C § 03-30-2008 • 17:14:05

OK, we'll try to go easy. Ribbon Diagrams in fifteen sentences or less. Proteins are special chemicals that exist in all living things. Every gene is (basically) the set of instructions for building one protein. So if you've heard of different genes doing different things, it really means that different genes make different proteins that have different functions. So, it's really, really important, if we're to understand the molecular basis for biology at all, to understand just what those proteins are doing, and how they work.

It turns out that you can tell a lot about what a protein does (its function) by looking at its shape (its structure). Imagine that you had to make a chain, the kind you might attach to an anchor or a locked gate. But imagine that, to make the chain, instead of being given one type of link, you were given twenty similar-looking, but different, links. That's basically what a protein looks like if you stretch it end-to-end -- a long chain of molecular "links" (called amino acids), twenty different amino acids in all.

But a protein isn't very happy stretched end-to-end. It folds in on itself. Actually, the twenty different links control how it folds. Let's not worry about that just now. The important thing is that the folds of that protein determine all of its properties -- whether it will attach to other proteins, whether it will speed up chemical reactions, whether it will make your eyes blue, whatever. So to really understand what a protein, and therefore what a gene, is doing, you have to look at how it folds.

A ribbon diagram is a way of diagramming how a protein chain folds. Each protein gets its own diagram, because it's got its own shape.Vance.mcpherson (talk) 16:22, 1 April 2008 (UTC)

add milk now or later?

I'm about to take a shower and so made an extra-hot coffee to drink when I'm done. I'm going to put some room-temperature milk in it, but should I do so now or when I'm back?

If I do it "now" then the very hot coffee will not have a chance to retain its heat while I shower, since it will be brought a bit right away.

If I do it "later" then the very hot coffee can hold onto its heat a bit, although of course losing some while I shower, only to be brought down a bit later.

It seems the two choices should be identical, but in fact, does heat follow a curve, where the farther from room temperature something is, the faster it loses heat? In this case, I'd better add the milk now, since it will save 15 minutes of heat loss. —Preceding unsigned comment added by 79.122.31.17 (talk) 15:39, 30 March 2008 (UTC)

That's correct. Heat flow is proportional to the temperature difference between the two reservoirs (in this case your cup of coffee and the surrounding air). So if your coffee is hotter, it will loose more heat. Of course, other things may come into play - putting milk into very hot coffee may scald the milk, putting the taste off. --Stephan Schulz (talk) 15:51, 30 March 2008 (UTC)

Thank you. —Preceding unsigned comment added by 79.122.31.17 (talk) 15:54, 30 March 2008 (UTC)

I dispute Stephan Schulz's explanation: If the initial temperature difference (coffee - ambient/milk) is X, and you want to have a fraction p of coffee and a fraction 1-p of milk in what you're going to drink, then you could mix the two now: The temperature difference drops to X*p, and if the heat flow is proportional to the temperature difference, then it will decrease exponentially with some factor a: ΔT = X*p*exp(-a*t)

where t is the time. If you do it the other way around, it will fall off exponentially to X*exp(-a*t), and then you add the milk, and the outcome is again X*p*exp(-a*t).

However, heat transfer by thermal radiation increases with the difference of the fourth powers of the temperatures, and this will make adding the milk "now" superior. Icek (talk) 17:10, 30 March 2008 (UTC)

That's strange. You have me completely baffled. Sticking just with Newtons law of cooling for the moment and ignoring the Stefan-Boltzmann radiation law to keep it simple. The black coffee at every moment up to when the milk was put in is losing heat at a faster rate than the white cup. After the milk is put in, the two cups are identical composition. How can the (ex) black cup be at the same temperture when it has lsot more heat. SpinningSpark 18:27, 30 March 2008 (UTC)

Icek is computing with both milk and environment at 0K, I think. --Stephan Schulz (talk) 18:28, 30 March 2008 (UTC)

I don't think so, he has used ΔT throughout. SpinningSpark 18:48, 30 March 2008 (UTC)

Don't forget that coffee with milk has a lower heat transfer coefficient than black coffee. --Allen (talk) 20:12, 30 March 2008 (UTC)

Well that was exactly my point. The white cup is losing heat more slowly so it should end up at a higher temperature. Anyway, after a monumental struggle with the maths (for me anyway), I've worked out what the difficulty is. There is a hidden assumption in the Icek analysis that each gram of coffee is losing heat at the same rate (per ^oC of course). Since the white cup has more grams of liquid it is losing heat at a faster rate than the black cup at the same temperature. This precisely cancels the faster rate of heat loss of the black cup. Happily for the laws of thermodynamics, conservation of energy has been restored and we can all rest easy again. In a real world cup, the heat loss is not proportional to the mass of coffee, but rather to the surface area of the cup since the internal masses are insulated from the surface. So I would still go with the white cup, entirely based on Newtons law of cooling, without having to invoke black-body radiation or crackpot ice cream manufactures (and yes, I do know it does work despite sounding crackpot). SpinningSpark 21:04, 30 March 2008 (UTC)

You're right - the constant a will not be the same for both cases in reality. For a cylindrical cup the heat loss should be something like dQ/dt = -(b*m + c)*ΔT, the constant c representing the heat loss due to the the nonchanging top and bottom surfaces, the constant b representing the heat loss due to the changing side area, and m being the mass (ignoring different heat capacities and densities). And for the temperature difference it's dΔT/dt = k/m dQ/dt. That makes the final temperature differences for "adding now" p*ΔT_initial*exp(-k*(b + c/(m_coffee + m_milk))*t) which is larger than for adding later: p*ΔT_initial*exp(-k*(b + c/m_coffee)*t). Icek (talk) 12:29, 1 April 2008 (UTC)

See Mpemba effect. Gandalf61 (talk) 20:14, 30 March 2008 (UTC)

The discussion page there is most interesting, but not that informative!Snorgle (talk) 11:42, 1 April 2008 (UTC)

Isaac Asimov wrote that adding the milk early is the best choice if you want the coffee to be hotter later. Edison (talk) 20:21, 30 March 2008 (UTC)

North American bird ID, complex song, PBS "life of birds"

I was just out in my back yard (North Texas, suburban) and noticed some birds presumably doing courtship behavior. The males were dark/black colored, slighlty irridescent and the females more drab and lighter brown. They were approximately the size of a mocking bird. The reason they caught my attention was the complex but short song the males (presumably) would sing. It is a song I remembered from The Life of Birds TV series. It was extremely short, maybe .5 to 1 seconds long but it contained many notes. If I recall, the TV series showed a sonagram of the song and maybe said that it was the fastest (in notes per time unit) song in the bird world. The male would sit next to the female, when she was looking at him he would puff up his feathers and start the song, as he sang he would bow his head down, finishing the song with his head far down. I'm just curious to get an ID of the bird so I can do some more research about it. I have read through the PBS website on the series and tried to do some flowchart-style identification I found on the web but have been unsuccesful. Thanks. -- 71.91.127.85 (talk) 16:44, 30 March 2008 (UTC)

I'm looking at the Rusty Blackbird. The song can be heard here at Cornell's excellent site. --Milkbreath (talk) 17:15, 30 March 2008 (UTC)

Yeah thats the one, and thanks for the link. -- 71.91.127.85 (talk) 19:03, 30 March 2008 (UTC)

Calculating Mechanical Advantage

How do I know how much force I put on a can opener? and how much force is then put on the can? Bzinc (talk) 16:58, 30 March 2008 (UTC)

MA = Output

  Input

but IDK how to find out the can opener thing. Yamakiri ^T_C § 03-30-2008 • 17:18:07

The fulcrum of the lever is where the can-opener rests on the edge of the tin. Measure the distance from the fulcrum to the pointy end of the can-opener where the force is applied to the tin. Measure the distance from the fulcrum to the end of the handle where you apply the force. You now have enough data to calculate mechanical advantage. Work out for yourself how to calculate the MA - I am not going to do ALL your homework for you. The force applied depends on how much force your arm provides and the mechanical advantage - again, work out for yourself how that would be calculated. SpinningSpark 18:45, 30 March 2008 (UTC)

a can opener is a type of lever. But both the force you apply and the force the can applies to the blade, are on the same side of the "fulcrum" (the hinge). On my can opener, the blade is about one inch from the hinge, and my hand grip applies force at about five inches from the hinge. You must measure your own can opener, and then apply the correct math. If you cannot figure it out, then please come back and ask another question: we will not do your homework, but we will certainly help you with your homework. Here is a bonus question: How is force actually applied to the top of the can, and what is the correct unit of measurement? You know that you cannot push your thumb through the can top, so why does a can opener work? -Arch dude (talk) 23:11, 30 March 2008 (UTC)

Friction

if you wanted to reduce the friction between two objects what would you do —Preceding unsigned comment added by Caseywirth (talk • contribs) 17:58, 30 March 2008 (UTC)

Add a lubricant like grease, cooking fats, or graphite etc. Yamakiri ^T_C § 03-30-2008 • 18:18:11

Invent something round which rotates in between the two objects. Let´s call it a wheel? --Cookatoo.ergo.ZooM (talk) 22:43, 30 March 2008 (UTC)

Or possibly a ball bearing. Algebraist 23:07, 30 March 2008 (UTC)

Or maybe reduce the force holding them together, such as a partial lift on the upper object, loostening screws, expanding a screw top through heat. For example when openeing a jam jar lid, it is easier if you don't force it down as you turn. Graeme Bartlett (talk) 02:37, 31 March 2008 (UTC)

That point about jam jars is not necessarily true. If the lid is quite tight (as opposed to, say, glued on by dried jam), each of its screw threads is pressed against the corresponding thread on the jar — from below, as that is how the lid is drawn against the jar. Then applying a compressive force may loosen the contact and reduce the friction. However, in practice one may instead simply deform the lid without the desired effect. --Tardis (talk) 01:19, 1 April 2008 (UTC)

And don't forget sonic lubrication. StuRat (talk) 02:58, 31 March 2008 (UTC)

Would a radio work under 1 foot of water?

Would a radio work under 1 foot of water? Obviously we're assuming its in a waterproof container or something, but would the radio waves penetrate the water? —Preceding unsigned comment added by 79.75.132.81 (talk) 19:06, 30 March 2008 (UTC)

Short answer is no. It might be possible to design something that works in only one foot of water but I doubt it. If it were possible the military would have it already. Submarines need to surface to use their radio. Submerged, they use acoustic systems usually. They can use VLF up to 20 metres in depth but you need something large like a submarine to contain the equipment. ELF can be used even deeper, but only for reception. The transmitter would be impractically large for any existing vessel. There are other problems as well, see Communications with submarines.

Devices fitted to animals for scientific tracking only work while the animal is on the surface, or else they are designed to float on the end of a tether - see this picture of a manatee being tracked. SpinningSpark 19:32, 30 March 2008 (UTC)

I would expect a radio to be able to receive signals under one foot of water. The dropoff of signal strength with depth would depend on the frequency. Why not put an expendable cheap am/fm radio in a well sealed widemouth gallon jug and push it under the surface of the water for a test, at the beach or in a swimming pool? If your head is under water you can listen for the strength of the sound from the radio. Having headphone leads or a speaker or microphone cord stick up out of the water would invalidate the test. Edison (talk) 20:19, 30 March 2008 (UTC)

The attenuation is very severe because of the conductivity of the water. Where ground-penetrating radar is used in geophysics, they can only manage a couple of inches if the soil is wet. And that is with the antennae right above the surface being surveyed. If you want to put the remote station some distance away you haven't got a hope of getting it to work at all. Yes, it does depend on frequency - penetration improves with decreasing frequency (or increasing wavelength). That is why submarines use VLF. The wavelength of this band is 10 to 100 km. You need a big antenna - not suitable for the swimming pool. With ELF the situation is astronomically worse, a geophysical feature (such as the Rocky Mountains) needs to be used for the antenna. Even the connection "leads" are around 30 km long. SpinningSpark 22:14, 30 March 2008 (UTC)

Radios work much better in fresh water than in salt water because the salt water is a lot more conductive. This is why remote control submarines always come with warnings not to use them in salt water. Anecdotally, I've read that R/C model submarines that can go four or five (or more) feet down in lakes, lose their signal under only a foot of ocean water. I have no idea how accurate those numbers are, I've never tried it myself. APL (talk) 13:27, 31 March 2008 (UTC)

The article on Evanescent_waves gives the basics. Although its examples are oriented towards optical waves (light), the basic physics is the same for radio waves. The article points out that the rate of exponential decay (as a function of distance from the surface) depends on wavelength; that is part of the explanation of why ELF can be used by submarines. JohnAspinall (talk) 13:31, 31 March 2008 (UTC)

Drinking water

Some time in the late '70's or early '80's my grandfather showed me a magazine article (I think it was in national geographic but not sure) that refrenced a study concerning drinking water quality. In it, the author stated that "Polar, Wisconsin has the worlds best drinking water." I am doing some research and am having trouble locating this article. I have had other peop[le tell me they remember seeing this article, but no-one can tell me what magazine or exactly when it was published. I would greatly appreciate any help in locating this information. I have tried researching National Geographic archives, Guiness book of records, our local library, and internet searches all with no results, It may be that it is old enough that it isn't cataloged anymore, but someone, somewhere must know where I can find this. Please help! steveg-1960 —Preceding unsigned comment added by Steveg-1960 (talk • contribs) 19:34, 30 March 2008 (UTC)

In that same time period Consumer Reports (headquartered in New York City) did a taste test on samples of tap water from different cities around the US. Not surprisingly, they concluded that their local tap water tasted best. Edison (talk) 20:51, 2 April 2008 (UTC)

Slowpitched softball

If I slowpitch a softball with good backspin, does that encourage a ground ball or a fly ball, and why? What are the physics (for dummies) involved? Thanks if you can explain.

It's because of Coriolis effect. Basically if you spin a ball a layer of air on the surface of the ball will also spin with it. Say the ball spins clockwise and is traveling to the left. The top of the ball will be going at the same direction as the airflow, while the bottom goes in the opposite direction. When it goes in the same direction, it has very little drag, because the speed difference between the ball's surface and the surrounding air is small, whereas if it goes in the opposite direction it has lots of drag, because the speed difference is much higher. When one side has very little drag while another has lots of drag, it will start to change its trajectory (like when you walk into a pole, if you hit it with your left shoulder you will turn left after you hit the pole, because there's lots of drag on your left side). --antilived^{T | C | G} 05:08, 31 March 2008 (UTC)

It's the Magnus effect, not the Coriolis effect, and the direction of the resulting force for a ball with backspin is upwards. Gandalf61 (talk) 12:18, 31 March 2008 (UTC)

I would expect that the main effect of strong backspin, at the speed of a softball, would not be anything to do with coreolis but simply the friction when the spinning ball contacts the bat. Which would tend to make the ball fly downwards off the bat. DJ Clayworth (talk) 14:34, 31 March 2008 (UTC)

Where are all the physicists? Anyone who has ever played ping-pong knows that a backspin volley makes your opponent hit it off the end of the table, and a topspin volley makes him hit it into the net. This is the way the ball will come off his paddle due to your spin. The mechanics of this are counter-intuitive, them being the same as the motion of the ball in the air. A topspin pitch makes for grounders, and a backspin pitch makes for fly balls, if you only count the movement of the ball off a bat swung along the ball's predicted pitched path in the air and striking the ball in the center when perpendicular to its path. --Milkbreath (talk) 15:00, 31 March 2008 (UTC)

Agreed. What happens is that when the spinning ball hits the bat, the friction between ball and bat converts some of the spin into upwards velocity. You can test the phenomenon yourself by spinning a ball on a table and then barely touching its side with your flat palm. — Laura Scudder ☎ 22:22, 31 March 2008 (UTC)

Global warming

In the last few years, global warming has become an often-discussed issue not only in scientific circles, but also in everyday life. We are warned against it, we have been told about the terrible consequences it could potentially have, and there are groups dedicated to fight climate change. So, I wonder, why is global warming actually so bad?

We are told that mankind is altering Earth's natural state, but our knowledge of the geological history tells us that in fact ice caps are a rare event in our planet's history, happening only in a handful of ice ages. Not only was the Earth devoid of ice caps during most of its history, but also the temperatures in the geologic past were almost always higher. During periods such as the Carboniferous, the Mesozoic and the Eocene, global temperatures were much higher than they currently are, and all of these times were periods in which life thrived and many species radiated – amphibians, dinosaurs and mammals, most notably. On the other hand, since the Azolla event and the break-up of Antarctica and Australia started cooling the planet, the climate has steadily deteriorated and with it, biodiversity has steadily become smaller, especially since the Miocene.

People also seem to equate a hotter climate with a drier climate. Yet the tropical rainforests show that is not (necessarily) true. A huge part of the Earth's species live in the Amazon rainforest, and African and south Asian rainforests are also blooming with life despite their tropical latitudes. The Eocene, with its PETM, was a period in which the Earth was covered in rainforests and other vegetation, showing that there is no necessary correlation between a warmer climate and a drier climate. Rather, the rise of grasses since the Miocene seems to indicate that cooler periods are drier periods.

Let's move to another oft-cited problem of climate change: freak climate episodes become less rare. Hurricanes become more common and heat waves become a greater problem. The sea level rises. Well, IPCC estimates that the current trend of ice melting in the Greenland ice sheet can cause a rise in sea levels of one metre during the next millenium. 1.000 years is more than enough for human civilisation to adapt, and even taking into account other ice sheets around the world, the sea level rise is still far from not being manageable. Adaptations can be made to protect coastal cities, and even paying for developing countries to get those adaptations ready would be costlier than the economic cost of fighting global warming. The fact that heat waves may become more common is compensated for by the fact that cold waves will become rarer: scores of people died in Uzbekistan last winter when temperatures dropped below -40º C, and many people – and animals – have a harsh time in winter.

On the other hand, the benefits would be many: the Northwestern passage open to ships all year long and ice-free; availability of mineral resources currently buried under tons of snow in the poles; an increase in biodiversity... Believing that, without human intervention, the Earth's climate will remain stable is a naive phantasy. We're currently in an interglacial period, so things should be colder in the future – how will we feel when polar caps cover Stockholm, Moscow, Montréal or London? How will we feel when hundreds of tropical species become extinct because cold destroyed their ecosystems? Fighting global warming is like leaping out of the frying pan into the fire: we have a choic between an icehouse world or a greenhouse world, and we are much more suited to the latter.

If the so-called ecological dangers of global warming aren't really dangers (biodiversity thrives in the heat!), and the economic cost of fighting it is higher than what it would cost to adapt, why is there so much insistence on global warming being bad? Aren't we against it because we're told it's bad, without even knowing what it means? Aren't we just afraid of changes, even though we're now in a "freak" period of Earth's history and warming would just bring everything back to normal?

So, wouldn't humanity – and life on Earth as a whole – be better off if all the money which is invested in fighting global warming were invested in more urgent and real problems such as desertisation, pollution of water, deforestation, protection of endangered species, etc.?

88.1.139.15 (talk) 22:10, 30 March 2008 (UTC)

This very much looks like WP:SOAP, not a question. Anyways, there is quite a number of unjustified assumptions in your "question", the major one being that not the absolute temperature is a problem, but the change in temperature. The climate has been quite stable for the last few 1000 years, and human populations and ecosystems are adapted to this stable state. Oak forests will not move North at kilometers per decade (even if there are no humans in the way). For a farmer in Mali whose fields dry up it's little use to know that the season for growing rye has increased by two days in Siberia. Indeed, in the long term the climate will change anyways. But humans live in the short term. The best assessment of the effects of global warming we have is the IPCC Working Group II report.[16]. From the Summary for Policy Makers: "Impacts of climate change will vary regionally but, aggregated and discounted to the present, they are very likely to impose net annual costs which will increase over time as global temperatures increase." --Stephan Schulz (talk) 22:32, 30 March 2008 (UTC)

Also, if I'm not mistaken, isn't the main problem with CO_2 not the warming that it has already caused, but the potential future warming. Complex systems take a while to reach a steady state; I have read that if humans stopped emitting all greenhouse gases today, the global temperature would continue to rise (by a few degrees a century) for a few hundred years, to well beyond what has occurred in the past few million years. Life thrived in periods of warmth because these earth warmed over many many millenia, allowing natural selection to take its course. Evolution cannot occur fast enough to adapt to the current warming properly. -RunningOnBrains 22:47, 30 March 2008 (UTC)

(ec) Please re-read the instructions at the top of this page. The reference desk is here to respond to questions of fact. It is not here to "start debates or to post diatribes." In my opinion, the only further responses to this post will be suggestions of where (other than here) this issue should be discussed. -Arch dude (talk) 22:38, 30 March 2008 (UTC)

Agreed, unless the poster has an actual question for the Reference Desk in amongst that rant, in which case could he/she please delete the rant from around the question so we can read it. SpinningSpark 22:49, 30 March 2008 (UTC)

(edit conflict)Hi. Well, it's a very complicated issue. True, the climate is rarely stable for very long periods. However, most of us, if we found out that we are living on this borrowed time, would like to prolong this time as much as possible. Now, with sea level rise, the only way I can think of to protect cities all around the world, is to build a massive seawall, along every single coastline around the world, leaving no gaps, and stretching 50 metres high and 100 metres deep. Why? Well, let's say that you build a wall around a coastal megacity. However, if this wall is breached by a major storm or earthquake, or if sea levels rise, say, 5 metres and the highest part of the base of the seawall is 5 metres, the water would flood from the other side.

Global warming would also produce environmental disasters that could destroy cities. How would you feel, if your city became too dry, or under water, and forced to evacuate? We would have to make domed cities, live underground, or in space. Why is hot associated with dry? Well, it's not really. Global warming could make coastal reigons flood, and coastal deserts flood too. However, inland, even in rainforests, places could turn to desert. According to a book I'm reading, "With Speed and Violence: Why scientists fear tipping points in climate change", tropical rainforests, like massive ice sheets, are usually stable but can suddenly collapse. Fires can destroy rainforests, allow billions of tons of methane to be released (like Borneo in that huge El Nino a decade ago), and our deforestation of rainforests is not helping.

Also, global warming will not prevent another ice age. In fact, it can trigger one. Remember the Younger Dryas era? The ice age was in full melt, when suddenly, freshwater was released into the ocean, and boom, ice age for another 1,300 years. Also, although not as quickly as depicted in The Day After Tomorrow, melting water can trigger a disruption in the ocean currents. I suggest you read that book I'm reading. It's up-to-date, too. Some say this could cause a mass extinction worse than the K-T one. Would we want that? I think not. Also, the Greenland ice sheet, as well as the West Antarctic Ice sheet, and perhaps even the East Antarctic ice sheet, are unstable, and can be lubricated from the bottom. Pine Island Bay, for example.

Also, nature prefers slow changes. Also, the statement about "biodiversity thrives in the heat" is not nessicarily true. In the ocean, most plakton, as well as coral, thrive in current temperatures. Turn it up a few degrees, and they die. During El Nino, it becomes overheated off the coast of Peru, plankton die, and so do fish. When you change the sea pressure, temperature, salinity, etc, by a miniscule amount, many species of jellyfish suddenly bloom by the billions, killing off other lifeforms in the ocean and inhabit dead zones (especially the Nomura's jellyfish). Also, some periods, like the late Permian, were hot as well as dry.

Also, have you read about global dimming? This isn't really fighting against climate change, but masking its effects. For 3 days after 9/11, air traffic was grounded. Suddenly, the US experienced unusually sunny and warm conditions. Also, as the Himalayan glaciers melt, and this could happen by midcentury, there will no longer be a constant supply of water, threatening water supplies for 500 million people. The monsoon? It has become erratic and unpredictable over the years. Already, lakes in Nepal and Bhutan are filling with water. Hence: without water, we'd all drown. Also, more flooded areas means hurricanes can travel farther inland. At this rate, even with the melting arctic, oil will likely run out in a few decades and peak immediately. If sea levels rise, Tuvalu will likely be history by midcentury. Also, many species, as well as people, thrive in the arctic.

Global warming is not nessecarily good news for food production. Many species of plants, such as rice, fail to produce good results if you turn up the temperature 1 or 2 degrees. Forests could even go form a carbon sink to a carbon source, with the sun being blocked more often, more trees being pushed into unsuitable territory, and more fires. Also, the forest pine bark beetle is eating many trees in Canada and the United States. If this continues, over half of the pine trees could be damaged or destroyed by midcentury. Also, the dangerous and urgent global warming is already here. Already, towns are drowning below sea level. Have you read a list of possible doomsday scenarios? True, we all choose to deny the truth and live on with our lives, going business-as usual and hoping the worst will never happen in our lifetimes. Yet, it already has, for millions worldwide. So why do we choose to do something? Well, because we can at least do something to delay the parts of climate change caused by our own actions, and hopefully our children will not suffer. That's the reason for many people to help fight climate change, think of the children.

In fact, at this rate the truly poor countries will never be developed. Yet, fighting climate change would only push us back a mere 2 years by 2100, if we start now, that is. Why don't we help more urgent issues? This is an urgent issue, and its long-term implications will be even worse. Also, global warming has been listed as the #2 urgent threat to humanity, second only to a nuclear war, but this is far more likely. Also, global warming might trigger wars as economic instability is pushed to the brink. If we did nothing, civilization would collapse, simple as that. However, although it would probably collapse anyway, don't we at least want a future, for civilization to exist as long as possible, and to help ourselves continue to exist for the time being? Nobody can predict what will happen 1000 or a million years from now. However, this issue is happening right now, and yes we can make a differnece, and it'll be a difference for the better because civilization, the economy, and the environment all prefer stability, even if we can just prolong that stability a little bit.

I already know that climate change will be a reality we will have to face, but if we do something now, then we won't have to face as many horrors later. Also, have you noticed a lot of these urgent issues are somewhat related to global warming? Even disease is spreading, killing off many humans as well as animals, partly owing to global warming. So, it's a very complicated issue, but yes, action on it does help somewhat. Hope this helps. Thanks. ~AH1^(TCU) 23:10, 30 March 2008 (UTC)

<my2cents> Over geological time scales Human induced global warming could be seen as insignificant as life will adapt to it. Over the period of a human generation the effects of gloabl warming could be seen as nothing short of apocaliptic. </my2cents>

--Shniken1 (talk) 00:41, 31 March 2008 (UTC)

If as you claim, pumping out carbon dioxide to produce global warming may be necessary to avert an 'icehouse world' there is a simple solution, start doing that when we need it. As it stands, there is no evidence we need it at the current time, all the evidence suggests it's harmful and will result in an increase in temperatures, not a stabilisation. Sure once the earth starts to cool, we can consider it. It's not as if it's hard to do. The problem is that the reverse, removing the carbon dioxide that we've already put there, is a lot harder to do therefore it's exceptionally dumb to do it when we don't need it for the sole purpose of preventing a long time in the future 'icehouse world' or ice age Nil Einne (talk) 17:32, 31 March 2008 (UTC)

Mirror, Mirror

If I have room with four walls, floor and ceiling, all made out mirrors--and one wall is a two-way mirror, the material that's a mirror on one side, but see through glass on the other--what would I see if I looked into the room?

I guess my question is--what does a mirror reflect if there is nothing in the room to reflect?NetLace (talk) 22:17, 30 March 2008 (UTC)

Assuming that the mirrors aside from the two-way allow no transmission of light, I would think that such an apparatus would act as a blackbody. Unless the room were a few hundred degrees Celsius, you would see nothing. -RunningOnBrains 22:28, 30 March 2008 (UTC)

Well, there's no person or thing in it, but that doesn't mean there's nothing at all. Assuming there's a light source, the mirrors would reflect each other as they reflect the corners and joins in the mirror room until you've got that labyrinth or hall of mirrors thing happening. Without a light source there'd be no reflection to track anyway. You could try it on a small scale model to test it. Julia Rossi (talk) 22:33, 30 March 2008 (UTC)

Hi. Well, if I understood your question correctly, and there is a light source, it will appear like an endless tunnel. If you have a webcam, for example, and turn on a program that displays what the webcam sees, and the image is inside a rectangular box, then try pointin gthe webcam at that box. What happens is, the box appears like an endless tunnel, and if you shake the webcam, the tunnel shakes. Also, if you could stand between two mirrors, held facing each other, and looked at one of them face-on, yet you are small enough not to be blocking anything yet large enough to see the whole mirror, you'd see an endless tunnel, and maybe endless images of yourself inside it. The tunnel doesn't really appear endless, however, because as you look farther inwards, the deeper frames are not bright enough to be shown. Hence, if you take two mirrors, and put them at an angle to each other, and shrink the angle, you get more images. Thus, if you turn them towards each other, there should (theoreticly) be an infinity of images. However, many factors prevent us from actually seeing into infinity. Hope this helps. Thanks. ~AH1^(TCU) 23:23, 30 March 2008 (UTC)

That's right, you'll see an endless tunnel of mirrors, one copy of the room after the next, and getting darker as they are farther away. Just one point needs to be added and that's that the conditions described in the original posting require a light source to be in the room. A two-way mirror, also called a one-way mirror, is simply a partially silvered mirror that you look through from a darker room into a lighter one. You can see through it into the light room because there's enough light in there for you to be able to see by even when only a fraction of it gets through the mirror. In the setup described, you will see a copy of the lamp in each copy of the room. But because the two-way mirror is partially silvered, the more times the light reflects, the less there is of it, and so the "farther" copies of the room look dark. --Anonymous, 09:50 UTC, March 31, 2008.

The semi-silvered mirror is symmetric, except that one side is subject to higher ambient light, so it's harder to see through from that side. Tangential question- do anisotropic "two-way mirrors" exist? Specifically, do materials exist with higher reflectivity coefficient in one direction than the other? (Surely there are materials with variable reflectivity based on the incident angle, but are any known with directionality? Nimur (talk) 19:24, 31 March 2008 (UTC)

I doubt it — at a glance such a mirror would seem to violate the second law of thermodynamics, as it would essentially constitute a Maxwell's demon operating on photons. —Ilmari Karonen (talk) 22:10, 31 March 2008 (UTC)

Optical isolator. Someguy1221 (talk) 22:26, 31 March 2008 (UTC)

Yes, the Faraday isolator is the interesting answer, for which transmission is asymmetric. But the question as worded was about asymmetric reflectivity, and that can occur in much more mundane circumstances. For instance, consider a symmetric, lossless 50% mirror with an anti-reflection-coated 90% absorber glued to one side. From the mirror side, this device would have a 50% reflectivity, but seen from the absorber side the reflected light would have to travel through the absorber twice, being attenuated by a factor of 10 each way, resulting in a reflectivity of 0.1*0.5*0.1=0.005=0.5%. Transmission on the other hand would be symmetric, at 5% in either direction. --mglg_(talk) 02:38, 1 April 2008 (UTC)

Interesting. But, this is a composition of different materials. I guess I was curious if any single material (e.g. unusual crystal structure, or something) could generate that effect. Thanks for the insights! Nimur (talk) 14:47, 1 April 2008 (UTC)

March 31

Something semi-interesting about Cockatiels...

Anyone here have experience with keeping large numbers of Cockatiels? I was told today by someone who does that in aviary conditions, the birds form a loose social hierarchy based upon how 'natural' their plumage appears. In other words, the birds with wild-type plumage tend to dominate birds of alternate colour mutations when it comes to feeding, mate selection, choice of nest box, etc.. Apparently, the more grey feathers and the closer its resemblance to a wild 'tiel, the more 'respect' the bird gets from its flockmates. Pieds/whitefaces/pearls are somewhere in the middle and the lutinos and albinos are at the very bottom of the pile.

I'd never heard of this before (I've never noticed anything similar with the various shades of budgie I own) but it sounds absolutely fascinating (to me, at least - maybe not to you). Does this sound familiar to anyone? Any link to writings on the subject? Thanks. --Kurt Shaped Box (talk) 00:41, 31 March 2008 (UTC)

In support of what you were told, there's cockatiels and pecking order here[17]. Male vocals or "song" count for something, apparently even more than colouring. Females can mate downwards and out of the family until they have chicks. Complicated little network, aren't they. Budgie pecking order would be an interesting search. Julia Rossi (talk) 22:41, 31 March 2008 (UTC)

Thanks for that. When I hear about bird breeders who place a particular chosen genetically suitable male and a particular chosen genetically suitable female together in an artificial environment and just expect them to reproduce, it makes me of the opinion that sometimes we, as humans just don't 'get it'. I just leave my birdies to as they wish. When it comes to my flock, I can't say that I've noticed a particular pecking order forming, unless the dominance of adults over recently-fledged youngsters counts. The hens can get a bit snippy with each other in the spring when it comes to nesting box selection but that seems to be first come, first served (as long as there are sufficient boxes for all). --Kurt Shaped Box (talk) 21:43, 1 April 2008 (UTC)

You're welcome. Breeders just don't 'get it' because they have market priorities as in the article. Maybe pecking order is more obvious when there's a limit at stake. Nests (and other things such as space, roosts etc) for all would take the pressure off probably. A spider person told me about the pecking order of daddy long legs spiders. The important thing was once the webs are set up, the pressure is gone and they become very tolerant. Julia Rossi (talk) 00:49, 2 April 2008 (UTC)

Sharing genes with bacteria

What percentage of our genes, approximately, do we share with bacteria? And what other species do we have such information for? Is there a table I could see somewhere? Thanks!

James 01:12, 31 March 2008 (UTC)

For the second part of your question, the chimp is the best example for genetic similarity - about 95%. See here. Wisdom89 _{(T / ^C)} 01:26, 31 March 2008 (UTC)

The human genome consists of about 30,000 human genes; about 1,000 of these are nearly identical to analogous genes in bacteria. I don't know of a table; as far as I know you'd have to look at each organism's genome individually. - Nunh-huh 01:34, 31 March 2008 (UTC)

Be mindful though, that there isn't really a true consensus on the actual number of human genes (protein encoding). I've seen estimates range from 25,000 to 80,000. This is a good link [18]. Wisdom89 _{(T / ^C)} 01:45, 31 March 2008 (UTC)

Thanks for the interesting replies. I'm surprised by Nunh-huh's reply that we share about 1/30th of our genes with bacteria. After writing this question, I was able to come up with a little more research, and found that we have about 3 billion base pairs, while many bacteria have only a few million base pairs, which would put the upper-bounds of our similarity at under 1%, but I guess there is probably large variation in the size of bacteria DNA. — James 13:18, 31 March 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

There's a difference between the number of base pairs and the amount of genes that are expressed (or at least, are currently known to be expressed). Bacterial DNA tends to have a lot less non-coding DNA in it than humans. The important point here is that a while humans differ a lot from, say, yeast, we both need to be able to convert sugar to energy and perform other metabolic functions, and those genes are highly conserved. -- JSBillings 15:24, 31 March 2008 (UTC)

There used to be such a table in WP. After a bit of guesswork and searching through page histories I found it in this old version of Genomics. It was deleted on 10th October 2006. --Heron (talk) 20:52, 31 March 2008 (UTC)

DIY Lab hood

I am trying to make a DIY laminar flow hood. I have already built the the hood and have used a plenum coupled with a furnace blower and HEPA filter to create the laminar flow stream. I would like to add a UV light for sterilization. I want to just buy a UV bulb and put it in a standard fixture (Like so: Fixture and Light but none of these lights appear long enough! Am I going about this improperly? Is there a special fixture I need to use a UV light?

Thank you!

Ebenbayer (talk) 02:08, 31 March 2008 (UTC)

I'm fairly certainly that any UV fixture you purchase does not have to extend the entire length of the laminar cabinet. My experience with such hoods is 1.) The UV light isn't really that effective at sterilization when the hood is not in use and 2.) A small fixture is enough to illuminate everything behind the UV protective shield. You might want to try contacting NuAire, which is where my laboratory purchased their flow hood. I'm sure they sell accessories for them. Wisdom89 _{(T / ^C)} 02:19, 31 March 2008 (UTC)

Thank you for the response, the problem I am having is that the light bulb length appears to short for the fixture, not that the fixture is to short for the hood (sorry to not be more clear). I just seem unable to find a site that sells a fixture that would interface with the germicidal bulbs I referenced. —Preceding unsigned comment added by 128.113.36.116 (talk) 12:57, 31 March 2008 (UTC)

You can get away without one if the hood is used a lot. I have two commercial ones in my lab and neither have a UV light fixture. Just clean everything regularly with >70% ethanol. —Preceding unsigned comment added by 82.36.27.228 (talk) 17:38, 31 March 2008 (UTC)

I'd just like to point out that "laminar" does not really mean clean or sterile. When used in this sense, laminar flow is in contrast to turbulent flow. This is important for hood design in that if you have turbulent flow, there is a higher likelyhood that dust and bacteria will make their way in from the outside. Having a laminar, nonturbulent flow means that all the air passing over the samples has passed over the HEPA filter. So while the HEPA filter will make the airflow clean, it will not make it "laminar". (Although how necessary a truly "laminar" airflow is depends on your application. You may not need it.) -- 128.104.112.85 (talk) 18:21, 2 April 2008 (UTC)

Dosage of medication

What's the term for giving someone a larger dose of a medication when starting them on the drug and then cutting it back to a smaller dose once they've ramped up the dosage in their body? I'd like to read the article on it so that I can understand why this needs to be done with some meds but I don't know the term. Thanks, Dismas|^(talk) 02:58, 31 March 2008 (UTC)

Loading dose. The article needs expansion and probably won't be of much help. - Nunh-huh 09:42, 31 March 2008 (UTC)

Yeah, thanks. That took me less than a minute to read and I'm still not any closer to knowing why a loading dose is necessary. At least now I have a term for it though. Thanks! Dismas|^(talk) 09:53, 31 March 2008 (UTC)

It depends on the pharmacokinetics of the drug in question. Some drugs are cleared from the body relatively slowly. In order to maintain a constant concentration of these drugs within the body, only small doses need to be taken—but if one only administers small doses, it can take a long time for the drug to reach a useful concentration in the body after starting therapy.

Consider the hypothetical drug foosporin. Suppose it has a long lifetime in the body, and only ten percent of it is cleared from the blood each day by the liver and kidneys. Suppose also that the drug works best when the total amount in the body is exactly one gram. So, your maintenance dose of foosporin is 100 milligrams (100 mg) per day—just enough to offset the amount cleared.

Suppose you just started taking 100 mg of foosporin every day. On the first day you'd have 100 mg in your system; your body would clear 10, leaving 90 mg. On the second day you'd have 190 mg in total; your body would clear 19 mg, leaving 171 mg. On the third day, you'd be up to 271 mg total; your body would clear 27 mg, leaving 244 mg. As you can see, it will take many days for the total amount of drug within the body to come close to 1 gram (1000 mg) and achieve its full therapeutic effect.

For a drug such as this, a doctor might prescribe a loading dose of one gram to be taken on the first day. That immediately gets the drug's concentration in the body up to the therapeutically-useful level. First day: 1000 mg; the body clears 100 mg, leaving 900 mg. On the second day, the patient takes 100 mg, bringing the level back to 1000 mg; the body clears 100 mg overnight, still leaving 900 mg...and so forth. TenOfAllTrades(talk) 19:00, 31 March 2008 (UTC)

I've taken the liberty of incorporating your example above into the article. Thanks! —Ilmari Karonen (talk) 21:54, 31 March 2008 (UTC)

Cool! Thanks for that! Dismas|^(talk) 22:08, 31 March 2008 (UTC)

Nanoparticles

Size (nm)	Number of atoms	Fraction on surface (%)
0.5	1	-
1	8	100
2	64	99
5	1000	50
10	8,000	25
20	64,000	12
40	512,000	6
80	4,000,000	3

Is the above table (approximately) accurate? I extrapolated (and rounded) the last few entries. It is for spherical particles isn't it? (I may insert this into nanoparticles) Cheers, Shniken1 (talk) 04:01, 31 March 2008 (UTC)

The percentage on the surface doesn't appear to be quite correct. Using a cubic structure, you could use the formula 100-[100(N^1/3-2)³/N] to find the percentage given N atoms. This gives me the following results:

Number of atoms...	Fraction on surface (%)
8	100
64	88
1000	49
8,000	27
64,000	14
512,000	7
4,096,000	4

StuRat (talk) 05:04, 31 March 2008 (UTC)

hair loss

hi, it is said that it is normal to lose 50-100 hairs a day, but how come we don't go bald as i am quite convinced that the rate of hair growth is much slower than the rate of loss. thanks :) —Preceding unsigned comment added by 218.250.158.232 (talk) 10:39, 31 March 2008 (UTC)

If the rate of hair growth were much slower than the rate of loss, we would all go bald. Perhaps you are going bald, if this is the case for you? For those of us who are not going bald, the rate of hair growth cannot be much slower than the rate of loss and you shall just have to unconvince yourself :) Skittle (talk) 11:51, 31 March 2008 (UTC)

Another way to look at it: On average, people have about 100,000 hairs on their head.[19] Each hair grows at a rate of about 1/2 inch per month. So your total hair growth is 50,000 inches per month, or 1643 inches per day. As long as your total hair loss (including haircuts) is less than 1643 inches (or 136 feet) per day on average, you should be holding steady against balding. jeffjon (talk) 12:47, 31 March 2008 (UTC)

Buffer solutions

Hello. Do you think you could offer a brief explanation of how buffer solutions work? I (think) I get what they are, as in what they're overall effect is, but how they work has never made sense to me. For example, if you add HCl to water, the water molecule splits into H+ and OH- (or really into H3O+ and OH-, if I recall?) and the OH- accepts the H+ from the HCl, neutralising it. But surely just as many protons are donated by the water as are accepted, so why would this have a neutralising effect? What have I misunderstood? Skittle (talk) 12:00, 31 March 2008 (UTC)

Water isn't a buffer solution, so yes, if you add HCl to water you get an acid. Algebraist 13:36, 31 March 2008 (UTC)

Really? It was always used as an example of a buffer solution that could buffer both acids and alkalis, at A level. Skittle (talk) 16:05, 31 March 2008 (UTC)

Water can act as an acid or a base, as it is amphoteric. It's a relatively poor buffer. Wisdom89 _{(T / ^C)} 17:48, 31 March 2008 (UTC)

For water alone, there exists an equilibrium between three species:

2H₂O ←→ H₃O⁺ + OH^-, often written in simplified form as

H₂O ←→ H⁺ + OH^-

This dissociation is spontaneous, but tends to sit well to the left—at room temperature only about 1 of every ten million water molecules is dissociated into charged species. When hydrogen chloride gas dissolves in water, it dissociates as well:

HCl ←→ H⁺ + Cl^-

This reaction proceeds essentially to completion, elevating the concentration of hydrogen ions (H⁺) in solution. By Le Chatelier's principle, this pushes the equilibrium from the first two equations back to the left—some of the excess hydrogen ion in solution reacts with hydroxide (OH^-) to re-form water. This still leaves a surplus of hydrogen ions, rendering the final solution acidic. TenOfAllTrades(talk) 18:19, 31 March 2008 (UTC)

It's not 1 in 10 million molecules, but one ten millionth mole per liter - about 1 in 555 million molecules. Icek (talk) 12:03, 1 April 2008 (UTC)

Buffers work by soaking up the excess proton (hydroxide) ions. Buffers are weak acids (weak bases) - this means that they can exist in both the acid form and the conjugate base forms in significant amounts. Now, if you look at the chemical equation for the reaction, you'll notice that where the equilibrium lies is affected by the pH (i.e. the amount of protons):

Acetate buffer: CH₃COOH <=> CH₃COO^- + H⁺

When you add in H⁺ ions to the solution (say from dissociated HCl) you add to the right hand side. By Le Chatelier's principle, that means that the reaction moves to the left, removing free hydrogen ions from solution. If there is a drop in the number of protons (say from adding base), the equilibrium then moves to the right, and the acid form of the buffer dissociates into conjugate base and hydrogen ions, reducing or "buffering" the loss of protons. The pH stays stable with large perturbations because buffers usually are used in large concentrations (milimolar), as compared to the amounts of free hydrogen and hydroxide (picomolar at pH 7). Now, this only works when there are significant amounts of both the acid and base forms of the buffer. The pH at where both forms are equal is called the pKa, and this is where the buffer is most effective. Now away from the pKa (about 1 pH unit in either direction), there is not much of the other form, and the buffer doesn't work too well. This is just a consequence of simple equilibrium principles - the Henderson-Hasselbalch equation may look magical, but it's just the K_eq equation rewritten. Now for water, one may be tempted to think that the pKa of water is 7, but that's not quite right. Remember that pKa is where the concentration of the two forms are equal. At pH 7, there is 10^-7 M H⁺, but ~55 M H₂O - You need to get well above pH 14 or below pH 1 before water even begins to become a decent buffer. -- 128.104.112.85 (talk) 18:13, 2 April 2008 (UTC)

Pain of death

Do people dying of congenital heart desease experience unbearable pain and if so what is the cause of the pain? 71.100.4.126 (talk) 13:05, 31 March 2008 (UTC)

Have you read Congenital heart disease? I'm not quite sure if you have the right disease. Are you sure you don't mean Coronary heart disease or Congestive heart failure? Nil Einne (talk) 17:23, 31 March 2008 (UTC)

Commercial aviation \ Airports: Penalty box

ORD airport layout.

What is it for? It is provided at O'Hare International Airport nearby A 5 (around 87° 55' W 51° 59' N). Thanks, --Scriberius (talk) 17:46, 31 March 2008 (UTC)

The 'penalty box' is just a (somewhat whimsical) name given to an area in which aircraft can be temporarily parked, usually either while waiting for a gate to open up, or after boarding to free up a gate for another aircraft. (Notes: [20], [21].) TenOfAllTrades(talk) 18:25, 31 March 2008 (UTC)

OK thanks. Looks like this parking space is a unique word just justed in Chicago. --Scriberius (talk) 20:31, 2 April 2008 (UTC)

I notice they also have a "Scenic Hold Pad". --LarryMac | Talk 20:46, 2 April 2008 (UTC)

Thermoregulation

A mother complains that her 3year old child's head is hot while the extremeties are cold. What are the physiological mechanisms responsible for this symptoms--82.128.29.40 (talk) 20:55, 31 March 2008 (UTC)Oyinmart

A doctor's primary concern would be to determine whether the temp difference is noteworthy. It's quite common for someone's head to feel warm relative to hands or feet (irrespective of age); I would hazard a guess that the distinction is a function of blood flow (heat in) versus surface area (heat out). — Lomn 21:08, 31 March 2008 (UTC)

Architects in construction project

Are architects in most major "design and build" construction projects appointed by the client or by the main contractor? Thanks in advance. Clover345 (talk) 21:09, 31 March 2008 (UTC)

Fancy buildings will have the arcitect employed by the client, and then give the concept to the construction company. Graeme Bartlett (talk) 05:33, 1 April 2008 (UTC)

My wife is an architect and this is what I have gleaned. Normally the client hires an 'architect of record'. These guys do the 'big picture design'. If the architect of record doesn't have the capacity to handle all the work, they will get a 'design architect' firm to help do the mountains of detail, documentation and project management. I believe the client separately gets the contractor to build the thing. From what I understand, this is the normal set up in big commercial projects in the US, but there are many variations. ike9898 (talk) 16:42, 1 April 2008 (UTC)

Radio waves, microwaves, cancer

Just today on MSNBC there was a story about some Australian neurosurgeon claiming that mobile phones are more likely than cigarettes to give you cancer - similar to claims we've seen countless times in the past. But how could radio waves and microwaves give you cancer when they are less energetic than visible light - that is, not nearly energetic enough to ionize, like UV light, X-rays or gamma rays - and when there are so many studies like the ones here that show no link? And yet how do you explain studies like the ones cited here that do purport to show a link? I'm not a high-frequency cell phone user, but I still need to know if my wireless MacBook is going to kill me. --Lazar Taxon (talk) 21:10, 31 March 2008 (UTC)

We have an article on Electromagnetic radiation and health. Basically, there have been studies that purport to show a link and many that don't, but there is also a weighty little pile of organizations that don't believe in a link, such as the WHO, the American Medical Association, and the NIH. Someguy1221 (talk)

Regardless of the merit of the claims, it is not sufficient to rule out all health effects just because the emissions do not cause ionization. Ionization is only one form of energy transfer from electromagnetic waves - there are many potential effects of radiation at various wavelengths. For example, microwave heating does not occur by ionization; instead it excites a molecular resonance. Undoubtedly, dielectric heating can occur at mobile-phone frequencies, but as Someguy1221 mentioned, many reputable institutions do not consider this to be a health hazard at the power levels in use. Nimur (talk) 14:59, 1 April 2008 (UTC)

Nitpick: it's not molecular resonance, it's just plain old dielectric absorption. It says so in microwave heating.

Anyway, if anybody here is worried by Dr Khurana's findings, then at least take a look at denialism blog, which picks a few holes in his research. I particularly liked the bit about hot water bottles. --Heron (talk) 12:21, 2 April 2008 (UTC)

Bekenstein Bound

How would the Bekenstein bound work in a universe without a surface, such as a 3-sphere? Thanks *Max* (talk) 21:32, 31 March 2008 (UTC).

The Bekenstein bound should still work as you will have volumes of space that you can surround with a surface, and the bound will apply to that surface and volume. You can expect that the volume will be a blackhole if you reach the bound! Graeme Bartlett (talk) 00:53, 1 April 2008 (UTC)

But bekenstein bounds are proportional to surface area, not volume, so they don't add (except in the special case when the regions are disconnected and at least a certain distance apart). *Max* (talk) 01:09, 1 April 2008 (UTC).

Smelly puddle

<moved from misc desk> While the snowbanks from winter are melting away in spring, puddles of water will form on the roads and streets. Occasionally, the water in these puddles will give off a very nasty, stinky odour. I can't really think of a comparison with the smell, but it is a sharp, repulsive smell. However, the smell does go almost completely away after a while. What describes this phenomenal? Is it some sort of bacteria in the water? Thanks. Acceptable (talk) 20:57, 30 March 2008 (UTC)

One guess, an animal (hopefully) has defecated in the snow, it froze into a nice little popsicle, and then, when it warmed up, it melted into a nice bit of "mud". This will be quite fragrant until the bacteria break it down in a few days. StuRat 00:47, 1 April 2008 (UTC)

April 1

Apparent multiplying of mercury in body

A friend was telling me of how much his wife suffers from mercury poisoning,and one odd thing stoof out - it's taken years for it to get out of her system. Does it multiply by forming compounds with other things in the bloodstream or something? Does the mercury alter other cells? Or what? When he talks about how she has to swear it out, how the smell is on her clothes & such, and other things, it seems like the small amount of mercury she has shouldn't take tht long to get out.209.244.187.155 (talk) 00:05, 1 April 2008 (UTC)

Smell? SMELL? What does it smell like?

When liquid mercury is spilled, it forms droplets that can accumulate in the tiniest places; these droplets can emit vapors into the air that we cannot see or smell. —Preceding unsigned comment added by 79.76.208.103 (talk) 00:15, 1 April 2008 (UTC)

It's not that it smells, sorry; I just associate that witht he fact she has to take two long showers a day, soak in a sauna, etc. - there are other reasons for showering besides smell. :-) But, the main question is, what does the mercry do in the body that causes it to take so long to get out?209.244.187.155 (talk) 00:28, 1 April 2008 (UTC)

Which oaths does she use when swearing out mercury? Is it like "Out, damned spot!"? Edison (talk) 00:29, 1 April 2008 (UTC)

I wonder why she would have guilt over the mercury. Did she steal it? --Bowlhover (talk) 03:23, 1 April 2008 (UTC)

Without treatment for mercury poisoning, namely chelation therapy, the mercury will, indeed, take a very long time to leave the body. This is true of all heavy metals. The kidneys don't filter them from the body, so not much is removed in urine. I also don't believe a significant amount exits in respiration or sweat. This leaves things like skin flakes, hair, and fingernail clippings as the rather slow way to remove mercury from the body. StuRat 01:03, 1 April 2008 (UTC)

I once heard of a case where someone swalled metallic mercury and for some reason it stayed in their stomach and did not pass through to the intestines. This person was slowly being poisoned, not by the metallic mercury but by the vapours that came up from his stomach and then went into his lungs. I'm not sure but I think he survived.--Shniken1 (talk) 01:40, 1 April 2008 (UTC)

As for whether mercury can multiply over time, the answer is a definite no. Chemical reactions can only change the arrangements of atoms inside a compound, not the identity of the atoms. Iron, for example, cannot change into mercury. Unless your friend's wife absorbed additional mercury, the amount of mercury inside her body will decrease by the same amount that was expelled from her body. --Bowlhover (talk) 03:23, 1 April 2008 (UTC)

I assumed the questioner was asking if it can accumulate over time, which does happen if there is a continual source of mercury. StuRat (talk) 15:38, 1 April 2008 (UTC)

One of the more bizarre radiographs I've ever come across involved an individual who had – for no good reason and presumably while under the influence of intoxicating substances – injected himself intravenously with liquid metallic mercury. He had presented to the emergency room with persistent cough and a chest x-ray was ordered. His lungs were speckled throughout with bright, x-ray opaque spots. Here's a similar image: [22]. Google for 'mercury embolism' or 'mercury emboli' to find more case reports. TenOfAllTrades(talk) 14:57, 1 April 2008 (UTC)

A few years ago, I remember reading a news story about a mentally-ill man who had some sort of obsession with mercury and wound up in hospital after swallowing and skin-popping vast amounts of the stuff over a long period of time. IIRC, the hospital had to close down a whole ward for decontamination afterwards. --Kurt Shaped Box (talk) 22:20, 1 April 2008 (UTC)

chelation therapy is unproven science, the evidence of it's effectiveness is tenuous at best, you hear about it mostly along side other "alternative" medicines. -- JSBillings 11:21, 1 April 2008 (UTC)

I was under the impression that it is proven for certain limited uses (the article says it's licensed by the FDA), but that it's touted for uses where it's not proven (e.g. in autism). 81.174.226.229 (talk) 11:48, 1 April 2008 (UTC)

Both of the above responses are correct—chelation therapy is an appropriate, approved, and demonstrated effective treatment for certain types of metal poisoning (especially the heavy metals lead, arsenic, and mercury). It is also promoted by quacks for a range of other conditions for which it has no demonstable efficacy, including (and especially) autism spectrum disorders. TenOfAllTrades(talk) 14:57, 1 April 2008 (UTC)

Cassette speed

I've just bought Who's Next through the iTunes store and for whatever reason, I decided to compare it with my old cassette tape recording. I started to play both recordings at the same time. The first thing I noticed was that it sounded awful. The cassette was very noticeably higher than the aac. Then, it began to sound worse—the cassette was going much faster than the iPod. The two together made me suspect that my stereo is perhaps playing the cassette a bit fast, so I was wondering, is this normal? Are recordings sped up/slowed down from the originals, perhaps to fit more music on a smaller space? Or is it just my stereo? 66.21.215.126 (talk) 00:33, 1 April 2008 (UTC)

Cassette players can easily go the wrong speed. You could check the belts to see if they are on the wheels properly and are not loose. Graeme Bartlett (talk) 00:58, 1 April 2008 (UTC)

Or, the recordings could be different. Sometimes, for obscure marketing reasons, record labels will release different versions of the same album via different mediums (CD, cassette, vinyl, etc). Nimur (talk) 15:04, 1 April 2008 (UTC)

Turning a frog into a prince

Okay, say I had a frog and I wanted to make him a prince with *no* magic. In other words, say the technology existed to re-configure the cells changing frog organs into human ones, though not instantly like when a fairy godmother waves her magic wand. What would be the most difficult organ to change, assuming the frog had to be opened up to do this with? I'm guessing the stomach, so the guy wouldn't have to eat flies all his life, but I'm not sure. Would anything need added, or could something in the frog be used? Finally, how tall would this guy be when it was all said and done? Would he be tall enough to be a match for Thumbelina, anyway? (My question for April Fools' Day - but I am curious, too. Just don't say you can't give out medical advice :-)Somebody or his brother (talk) 02:35, 1 April 2008 (UTC)

Biggest problem I see with your plan is finding a country willing to have an ex-frog as regent.--Shniken1 (talk) 05:22, 1 April 2008 (UTC)

I'm not an expert in frog physiology, but I'd say the brain would be the most difficult organ to change. Not only would the physiological changes have to occur, but the learning necessary to have even a physically functioning individual would take decades. This won't be a problem if you don't mind having a brainless prince, which wouldn't be much different than we've got now in the States *rimshot*. — Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 05:35, 1 April 2008 (UTC)

Agree, I don't think you can stuff that much neurons in such a small space to reproduce human intelligence--Lenticel ^(talk) 05:54, 1 April 2008 (UTC)

I may have misunderstood the question, but I think the question asker is wanting to change a frog into a normal sized and I guess fairly normal looking human. While the brain would indeed be a big problem, I have to say the whole thing sounds fairly unlikely to me. For starters, where would all the mass come from? It sounds to me like you're planning to more or less create a human out of thin air, the existing frog is most irrelevant Nil Einne (talk) 06:36, 1 April 2008 (UTC)

The user wanted a thumbelina escort so I think he/she means a frog-sized prince. Anyways there are lots of problems to where the mass could come from. The ideal mass would come from a fresh male human body with princely qualities. Note that neurons don't divide so we can't expand the frog's brain into the human skull housing.--Lenticel ^(talk) 07:01, 1 April 2008 (UTC)

Perhaps the frog's brain could be removed and replaced with technology. I suppose an AI could be used, but I prefer a wireless link to an existing human brain in a jar. If the brain previously belonged to a prince you may have also solved the royalty problem. APL (talk) 22:23, 1 April 2008 (UTC)

I suspect the easiest way to turn a frog into a prince is to feed the frog to a pregnant queen. -- JSBillings 11:12, 1 April 2008 (UTC)

There is, just, the technology now to reengineer living organisms in vivo, although changing a few proteins is the very limit of that right now. Recombinant DNA technologies, the mechanisms used in gene therapy, and in particular viral vectors allow you to alter the DNA of a living, mature organism. But doing this to affect wholesale change is a mammoth task (it's unfeasably huge, really), as you need to change every adult stem cell, and with a genetic payload vastly greater than a virus can carry. Even if you could jump that huge hurdle, you'd find the design of the intermediate forms of the frog-man would have to be very carefully done, so that each form was viable (just changing frog heart cells in to human heart cells won't make it grow a human heart). And even if you can do that, these genetic changes only apply when the cells are renewed. Nerve cells generally aren't, so your completed frog-man would still have the brain and nervous-system of a frog (it couldn't regulate its blood pressure, never mind move or think). You could engineer your organism to grow a fresh new CNS in parallel, a human one that the prince could use. But this transformation is so fundamental that you really can't say that the frog has turned into a prince, but rather that you've spent (wasted) a trillion dollars growing a human on the back of a frog. As you totally control the cell divsion, you can make frogPrince any size you want; as he's not much use to a princess unless he's normal size (or a big bigger, if you know what I mean) then he'd probably be a regular guy, except with the remnant of a little frog on his back. -- Finlay McWalter | Talk 12:42, 1 April 2008 (UTC)

Oh, I forgot. You also need to worry about telomere length, genetic damage, and other gene-level aging and cancer-causing problems. Really it's much more efficient for the princess to shop for a regular prince on the internet (Horsefacebook.com)' then she'll have a prince and a frog. -- Finlay McWalter | Talk 13:00, 1 April 2008 (UTC)

Once you turn your frog into a man, you still have the problem that he's not a prince. You would have to find a font of honour to do that job - a reigning King or Queen, for example, and persuade them to do the deed. Good luck! - Nunh-huh 21:49, 1 April 2008 (UTC)

I thought of another good way to turn a frog into a prince: Crown the frog's father King. -- JSBillings 23:38, 1 April 2008 (UTC)

The problem remains though that you're going to have to convince someone to take a frog or a frog-human (presuming you did the same for the father or mother) as king or queen. Given that on the whole, the monarchies of this world seem to be being reduced, not increased, I don't think it would be a simple matter even without the complexity of your candidate being a frog/frog-human Nil Einne (talk) 11:45, 2 April 2008 (UTC)

Did excess water intake leads to kidney troubles?

I used to drink more & more water since long time. seeing this my mom is claiming that excess water intake leads to kidney truble as the water u drink will undergo filteration by them. may be she's true to some extent b'coz i used to urinate more frequently than any other else. that shows that my kidneys are working more as i'm drinking more water. so now should i stop taking that much water in order to safegaurd my kidneys. or is it just our hype? Temuzion (talk) 04:58, 1 April 2008 (UTC)

You might want to read our article on water toxicity. Wisdom89 _{(T / ^C)} 05:04, 1 April 2008 (UTC)

Note that the amount listed in the above article is more than 10 liters (around 2½ gallons) in a few minutes. You probably don't drink nearly as much water so quickly. The kidneys do process the water, true, but processing large amounts of water doesn't damage them. To the contrary, this may help to prevent kidney stones, which can indeed damage the kidneys, by diluting the materials from which kidney stones form to below the concentration where they come out of solution and form stones. Numerous studies have recommended drinking large quantities of water, on the order of 10 cups a day, for this and other reasons. The downside, of course, is that you will need to urinate more often. If you "hold it in", that could potentially cause a problem. So, assuming you drink around 10 cups a day and urinate as needed, you are correct and your mom is wrong. Go ahead and keep drinking water. StuRat (talk) 15:46, 1 April 2008 (UTC)

Please note that unusual thirst can be a sign of diabetes, so it is very important that you discuss this question with a doctor. The same is true for all other health matters – reference desk volunteers cannot give medical advice. --169.230.94.28 (talk) —Preceding comment was added at 16:00, 1 April 2008 (UTC)

U should know a point that this water drinking is not because of thrist but it was because i want to look attractive. I got many pimples on my face when i don't have the habit of taking so much water. But after starting intake of water in this way my pimples reduced & the face indeed becoming smooth. This was encouraging me to take more & more water. So r u sure that "over" processing of water won't lead to any kidney trouble. If u confidently say 'yes', I'll continue the habit. No question of diabetes once again I'm saying this because our family has a habit of consuming very less oil in our daily intake. My grand father has diabetes. So my father is taking all the measures he know in order to reduce the diabetic attack. Still at this 50+ age my father is very relaxed regarding sugar levels & we all are following that measures too. So now plz after considering all these situations suggest me the way I should go...whether to carry on or to stop? Temuzion (talk) 04:33, 2 April 2008 (UTC)

We can’t give you medical advice here. Talk to a doctor. --S.dedalus (talk) 05:31, 2 April 2008 (UTC)

How much water to drink each day isn't medical advice, it's dietary advice. With that in mind, go ahead and drink up to 10 glasses of water each day. It's good for you. Also, to help reduce pimples avoid fatty foods, especially trans fats, which can clog pores. StuRat (talk) 13:08, 2 April 2008 (UTC)

What animals have adrenaline?

Is there some equivalent for insects, reptiles, etc? Mr.K. (talk) 08:56, 1 April 2008 (UTC)

I would imagine reptiles have adrenaline, along with any other vertebrates. You should read into the autonomic nervous system. —Preceding unsigned comment added by Mark PEA (talk • contribs) 17:12, 1 April 2008 (UTC)

Adrenaline (or epinephrine) is part of the monoamine neurotransmitter family. Animals throughout metazoa have various combinations of these. Some, for example octopamine, are neurotransmitters in invertebrates but only a trace amine in mammals. PMID 17142674 ←This paper interestingly discusses the genetic diversity and phylogeny of monoamine transporters throughout metazoa. If you're looking for the non-mammalian equivalent of the fight-or-flight hormonal action of adrenaline, PMID 17874113 deals with the "Evolutionary origin of autonomic regulation of physiological activities in vertebrate phyla". According to that paper, 5-HT plays the role in Aplysia that norepinephrine plays in mammals, for example. — Scientizzle 18:52, 1 April 2008 (UTC)

High output renal failure

Do we have an article on this ? It's a form of renal/kidney failure my Dad had. If I understand it correctly the kidneys first remove just about everything from the bloodstream, then put the water back in. In normal kidney failure the first step doesn't work, while in high output kidney failure the second step fails, leading to consumption of large quantities of water and production of large amounts of dilute urine. This condition is less serious than low output kidney failure because the toxins and wastes are still removed. StuRat (talk) 16:01, 1 April 2008 (UTC)

We don't have a separate article on it, but it's mentioned in the acute renal failure article (as nonoliguric renal failure). - Nunh-huh 22:03, 1 April 2008 (UTC)

All I see there is the phrase "although nonoliguric ARF may occur", is that all we have on Wikipedia ? StuRat (talk) 03:17, 2 April 2008 (UTC)

SDS-PAGE and Size Exclusion Chromatography

Before running a protein sample on an SDS-PAGE gel, you mix the sample with SDS and the SDS "binds" to the protein. There is also SDS in the gel I believe. My question is -- Let's say you mix a protein with SDS as above, but instead of running this sample on a gel, you run it through an SEC column -- Would the SDS stay associated with the protein or get separated from it? ike9898 (talk) 16:51, 1 April 2008 (UTC)

Ok, well, what you describe is never really done - and I think the reason is because the SDS will bind/coat the protein (I think in a 4:1 ratio if I remember correctly) and force the protein to extend into a linear rod like configuration. If you ran the sample over a gel filtration column using an inert buffer like HEPES pH 7.4, the SDS would remain with the protein, but the protein would probably run slower than the folded globular configuration since it would remain outside the pores. So, it might work, but you wouldn't know where the protein would come out - perhaps in the void volume. Wisdom89 _{(T / ^C)} 17:35, 1 April 2008 (UTC)

To clarify, I am asking because we have a sample that is giving us trouble with our SEC method. It is a sample of gelatin and a lot of the sample is coming off the column at a retention time that would indicate a MW of greater than 500 kDa. I think that this represents multiple peptides of less than 100kDa associated non-covalently. I'd like get the MW distribution of peptides when they are not associated like this. ike9898 (talk) 19:19, 1 April 2008 (UTC)

Gotcha, in that case I would use an non-ionic detergent such as Triton X-100 in your buffer. Also, you could trying using a high sodium chloride concentration along with beta-mercaptoethanol to disrupt the aggregation. Wisdom89 _{(T / ^C)} 19:24, 1 April 2008 (UTC)

How is DNA an acid?

Doesn't the phosphate make it a base? 128.163.170.163 (talk) 17:12, 1 April 2008 (UTC)

Phosphate is the ionized form of phosphoric acid, if you look at the DNA molecule and see the negatively charged oxygens in the phosphate group, you might think of it as a base, but the oxygen is negatively charged because the hydrogen (H⁺) has dissociated. --Mark PEA (talk) 17:24, 1 April 2008 (UTC)

Yes, since the proton in the phosphate dissociated, doesn't it make the DNA the conjugate base?128.163.170.163 (talk) 17:35, 1 April 2008 (UTC)

Yup, pretty sure that's the definition of a conjugate base. Wisdom89 _{(T / ^C)} 17:38, 1 April 2008 (UTC)

To the annoyance of biochemistry students everywhere, the convention for diagramming biochemical acids is to show the proton already dissociated, and bases showing an extra proton, often signified by a H⁺. When I angrily asked my professor about this during my undergrad years, he told me that this is because at physiological pH, DNA (being acidic) has given up its proton. It makes some sense, because the conjugate base isn't really all that basic, so it sort of shows that the acid has taken action. Of course, realistically, the acid and conjugate base form of DNA are in constant equilibrium, with the balance being in favour of the conjugate base. And from an organic chemistry context, being able to see the conjugate base sure is helpful in drawing resonance structures that explain the molecule's acidity in the first place!Vance.mcpherson (talk) 00:10, 2 April 2008 (UTC)

Pulmonary artery

On an episode of Dexter, Rudy has a girl in a headlock and squeezes a her neck with his arm, claiming that he is blocking her pulmonary artery, cutting oxygen from her brain and that she will be unconscious in a matter of seconds. I know its a TV show, but is this at all true? If so, how long would a subject stay unconscious for? This is purely out of curiosity I might add; I'm not planning to kill anyone just yet ;) —Preceding unsigned comment added by Crazy joke (talk • contribs) 18:59, 1 April 2008 (UTC)

The carotid arteries are those vessels which supply blood to the brain. Wisdom89 _{(T / ^C)} 19:20, 1 April 2008 (UTC)

The Pulmonary arteries are in the thorax near the lungs, so Rudy is way off. Yes, this WILL knock you out if your brain doesn't get oxygen. I'm sure if he held her long enough, he could cause permanent brain damage or death. However, I don't know how long it would take for the victim to recover. Paragon12321 (talk) 19:29, 1 April 2008 (UTC)

How long would it take to recover from death? I would say an infinite amount of time. —Preceding unsigned comment added by 79.76.250.241 (talk) 00:48, 2 April 2008 (UTC)

(edit conflict) If he really said "pulmonary", we have one more reason to support the writer's union. It's the carotid arteries that when occluded will cause unconsciousness. Some people never wake up from that, but almost everybody comes to in seconds with no lasting effects if the choke is maintained only briefly. Our article says that unconsciousness lasts for double the time the choke is held after the person passes out, unless they die, of course, or suffer permanent brain damage from ischemia. Other risks include physical damage to the neck itself, plaques in the arteries leading to stroke, and lung damage if you do it wrong. The guy's a serial killer, for cryin' out loud. Don't listen to him. --Milkbreath (talk) 19:31, 1 April 2008 (UTC)

Yeah, I think it was the carotid arteries he said. To be honest I just remember the arteries bit. BTW, thanks Wisdom89, Paragon12321 and especally Milkbreath. All you guys on the ref desk are the best! Crazy joke (talk) 19:38, 1 April 2008 (UTC)

I saw that episode, and I think you were right the first time, he did say "pulmonary". I remember thinking "don't they mean carotid" ? StuRat (talk) 20:29, 1 April 2008 (UTC)

I just checked StuRat, and he does say carotid artery. Looks like they did their research. Anyway, thanks everyone. Crazy joke (talk) 20:52, 1 April 2008 (UTC)

Where did you check ? Sometimes the script says one thing but the actors say another. StuRat (talk) 03:06, 2 April 2008 (UTC)

I'd downloaded the episode a while back. Its episode 11 of season 1. Crazy joke (talk) 19:17, 2 April 2008 (UTC)

alternative to chloroform

Another question, again out of curiosity. I'm writing a short story, actually. What would be an alternative to chloroform? It has to be something that could be used to knock someone out, but that is undetectable and non lethal? I found this yahoo answers question which suggested something that is detectable, but that is not unexpected, like opiates in a heroin user, benzodiazepines in a benzo addict, GHB in a GHB abuser or alcohol in an alcoholic. The problem with these, in the context of my short story, is that they are not readily available chemicals, except for the alcohol which would be pretty hard to get into someone quickly and stealthily. Any suggestions? It doesn't have to be a chemical, it just has to get them unconscious Crazy joke (talk) 19:38, 1 April 2008 (UTC)

Nitrogen. They'll pass out without knowing anything's wrong. — kwami (talk) 19:45, 1 April 2008 (UTC)

Anything that goes under the "instead of oxygen" category is going to fail "non-lethal". Wholesale replacement of a room's atmosphere? Not very likely. — Lomn 21:43, 1 April 2008 (UTC)

Who said anything about likely? It's happened, though as you say, with lethal results. But chloroform would be lethal too in excess - question's in the timing. — kwami (talk) 00:08, 2 April 2008 (UTC)

If there were easily available substances that could reliably be used to knock people out non-lethally, they would be used by criminals. (There is a myth that this actually happens on sleeping-car trains, but if you look for specifics, nobody has any. It doesn't happen. See this message board thread for an example of such a discussion. Apparently it's easier for people to believe that they fell victim to a chemically-armed crook than to a quiet one.)

Of course a gaseous anesthetic will make someone unconscious, and so will replacement of oxygen in the air with something else; but, as already stated, it'd be very easy to kill the victim doing that unless you were very careful. --Anonymous, 00:33 UTC, April 2, 2008.

Is there a particular reason you eliminate chloroform? (Might help with suggestions if you told us.) Pretty much any general anesthetic will knock someone out. The two "classics" are chloroform and (diethyl) ether. Note, however, that "non-lethal" is dependant on dose - one reason chloroform and ether aren't used as anesthetics anymore is that the amount needed to knock someone out is very close to the amount needed to kill them. If you let your characters have access to medical equipment, your best bet would likely be some medical anesthetic. (If it's rare enough, it would be "undetectable" in the fact that no one would likely test for it.)-- 128.104.112.85 (talk) 17:05, 2 April 2008 (UTC)

Thanks all you guys! Yeah, I eliminated chloroform because its hard to come by and a bit old school. Saying that though, there are sites out there that tell you make your own chloroform. As Lomn and others pointed out, replacing all the air in a room is not practical, especially on a low budget. And chloroform risks killing the victim. Its important they don't die. If it helps the character is a teenager seeking revenge. She's a bit of a psycho and decides the best way to humiliate her cheating boyfriend is to knock him out and set him up. It has to be something believable though, as she later confesses to the police, so no Vulcan neck pinches! Unless of course that would work? Would it? BTW, (again from Dexter) would injecting something into the victim work? Dexter seems to have the nack of it. Anyway, a big thank you to everyone who contributed! You've given me some great ideas! Crazy joke (talk) 19:34, 2 April 2008 (UTC)

Gas mileage

I'm trying to determine my minivan's gas consumption under various conditions. I have a 6 cylinder, 3.8L engine which idles at about 600 rpm. I need to know volume of vaporized gasoline is injected into each cylinder during the intake stroke. Does it vary among different engines? So far I have determined that the van will travel about 30 ft per mL. I want to know how fast it is using gas when I am stopped. —Preceding unsigned comment added by 66.120.95.34 (talk) 20:04, 1 April 2008 (UTC)

You want to know gas mileage while idling? The only way I can think of to measure this would be to fill up, let it idle for a few hours (so that a measurable amount of gas was used), then fill up again to measure. Then you can figure how much gas per hour is used while idling. Most people don't really care, tho. Why not just measure the mileage you get while driving? Friday (talk) 20:08, 1 April 2008 (UTC)

Isn't the answer obviously 0 miles per gallon when idling? Nimur (talk) 21:56, 1 April 2008 (UTC)

Well, yes. I should have said "usage" or something. Friday (talk) 21:57, 1 April 2008 (UTC)

The magic of google suggests a number between 0.5 and 1 gallon per hour while idling. Dragons flight (talk) 20:18, 1 April 2008 (UTC)

It's clearly a pretty small number. A couple of winters ago, when our house was without power for several days, we hooked up a big (750W) inverter to our Dodge Caravan (with the 3.3L V6) and set it "fast idling" in the driveway. It ran for hours and hours with what I thought was a surprisingly small consumption of gas. (1/4 of a tank?)

And I've thought about exactly the question posed here; I decided that if I were ever really interested, I'd wire into the solenoid valve on one of the fuel injectors and integrate the pulses. I'm pretty sure that modern electronic fuel injection systems run at a constant fuel pressure (unlike older mechanical fuel injection systems) so the integral of the injector's pulses should directly translate to fuel consumed. You could take a short-term moving average and display instantaneous fuel consumption or integrate over time and come up with total volume consumed. You'd have to wire-in carefully, though, lest you cause severe, expensive damage to your car's engine management computer. That's why I haven't performed the experiment yet.

Atlant (talk) 00:05, 2 April 2008 (UTC)

Something else you could try is to install a flow meter into the pipe between the gas tank and the engine (this is how the Mythbusters calculated their gas mileage). That way, you can get a direct measurement of how much gas you're using, without having to do any fancy math. — QuantumEleven 14:24, 2 April 2008 (UTC)

Depending on how the car is designed, that may or may not work. Some cars have the mechanical equivalent of a shunt regulator to regulate the pressure so they pump more gas than they need and dump the excess back into the tank (via a 'return" line). And cobbling a flow meter into the high-pressure gasoline line sounds like a much more dangerous experiment than tapping onto a 12V solenoid wire.

Atlant (talk) 15:40, 2 April 2008 (UTC)

Hedgehogs and breeding

In hedgehogs, who takes care of the young, the female, the male or both? Leptictidium (mammal talk!) 20:25, 1 April 2008 (UTC)

Yes but, first, you have to ask how hedgehogs make love! —Preceding unsigned comment added by 79.76.250.241 (talk) 01:05, 2 April 2008 (UTC)

I used to think they were silent creatures, but then I realized that they were affected by Sonic interactions. DMacks (talk) 03:01, 2 April 2008 (UTC)

Refdesk regular Kainaw's user page asserts "when it comes to hedgehogs, there are few people who know more than I do", so you might ask him/her if you don't get a good answer here. --Sean 13:40, 2 April 2008 (UTC)

Spider eyes

Do spiders have eyelids? If not how do they keep them their eyes moist or protected? 200.127.59.151 (talk) 22:16, 1 April 2008 (UTC)

Well, some have no eyes, others have Compound eyes that don't have any eyelids. --Lenticel ^(talk) 22:26, 1 April 2008 (UTC)

Spiders have compound eyes? They don't look like compound eyes. Is there an anatomy drawing of spider eyes somewhere? 200.127.59.151 (talk) 22:51, 1 April 2008 (UTC)

If you shine a laser at a big wolf spider you only see a pair of eyes in front but almost to the sides. The reflected light is fairly intense and this is how I find spiders at night and other little creatures. 71.100.173.69 (talk) 23:19, 1 April 2008 (UTC)

I believe some spiders only have simple eyes, but some have both. — kwami (talk) 00:09, 2 April 2008 (UTC)

I'm sorry but this needs investigation. I can't find a reference that says spiders have compound eyes unless you take compound as meaning multiple individual eyes but that doesn't seem to fit our article's definition (or am I mistaken?). And it leaves the question of how the eyes are cleaned or moistened. 200.127.59.151 (talk) 01:44, 2 April 2008 (UTC)

I retracted the compound eye part, it seems that spiders evolved simple eyes per [23]. Somebody should fix the Spider anatomy article.--Lenticel ^(talk) 04:06, 2 April 2008 (UTC)

Do eyes necessarily need to be moist in order to function (ours do - but our eyes are not representative of all eyes)? I *think* I've seen spiders cleaning their eyes with their forelimbs - flies certainly do that. --Kurt Shaped Box (talk) 01:50, 2 April 2008 (UTC)

Another question about spider eyes

How and why did spiders wind up possessing six-to-eight eyes when most (all the rest of the?) creatures with what we would recognize as a face have only two? I'm looking for a slightly more in-depth answer than "they just evolved that way", if you please. :) --Kurt Shaped Box (talk) 22:44, 1 April 2008 (UTC)

This site [24] explains that in most species the eyes have different sizes and are thus able to focus at different distances and have different fields of view. The Daylight hunters sections says:

When hunting, the eyes of jumping spiders see in three different ways, using three different sets of eyes:

• The spider first senses movement of distant prey with the side eyes (PLE), which provide a blurry wide-angle image.
• Once movement is detected, the spider turns in that direction and locks onto the moving prey with the large, middle front eyes (AME). These eyes provide a clear, focussed telephoto image, probably in colour. The spider can track moving prey both by body movements and by using muscles to internally swivel the elongated eye capsules so that the light sensitive retina of each eye remains locked on the prey.
• While the spider stalks closer, it uses the side front eyes (ALE) judge the distance to the prey. When it judges the prey to be close enough (about 2 - 3 cm), the spider leaps.

200.127.59.151 (talk) 23:04, 1 April 2008 (UTC)

And this seems to show that the eyes are organised in formations of three pairs (the side eyes as a double pair). 200.127.59.151 (talk) 23:10, 1 April 2008 (UTC)

Cool about how jumping spiders use their eyes.

I guess the question is, Why do arthropods have multiple eyes, and why have spiders (other than jumping spiders) retained them? I imagine it has something to do with peripheral vision when your eyes (except for jumping spiders) are immobile. Crustaceans have mobile eyes, and AFAIK only two of them. — kwami (talk) 00:12, 2 April 2008 (UTC)

Can spiders turn their heads independently of their bodies to look at objects, as a matter of interest? If not, this could be another reason for requiring the expanded peripheral vision provided by multiple eyes... --Kurt Shaped Box (talk) 01:33, 2 April 2008 (UTC)

Unless I misread them, the links say that the spiders only have two body segments and so have to move their body to follow a prey that might leave their field of vision. It also says that appart from rare species, the majority have very poor eyesight relying much more on the vibration in their legs and hair to locate potential preys and threats. Like you said, it does make sense that the distribution of their eyes work as a way of expanding their basic field of view. Add to that the specialisation of each pair of eyes it seems to make a pretty efficient tracking device. Now thinking about how and why their multiple eyes developed in the first place sends my head into a spin. Maybe a good soul could provide us with the name of that spider that manages to scan very complicated paths in space and retain them all in memory before engaging on her journey. 200.127.59.151 (talk) 01:56, 2 April 2008 (UTC)

Portia. I think I saw the trait that you mentioned in the National Geographic Channel.--Lenticel ^(talk) 06:50, 2 April 2008 (UTC)

Multiple eyes

I seeeee youuuu with my little blue eyes...

I'll throw in a third. What other animals have more than two eyes? 200.127.59.151 (talk) 22:55, 1 April 2008 (UTC)

Depends on your definition of eye (any old photoreceptor cell?), but jellyfish have multiple ways of processing light information, sea stars have little eyes on their end of their stalks, clams have tons of eyes, as do scallops. But these are all pretty simple "eyes", save the scallop, who have lens-bearing eyes. --Captain Ref Desk (talk) 23:46, 1 April 2008 (UTC)

Ophiocoma wendtii is all eyes, so to speak. Cool, huh? --Kurt Shaped Box (talk) 01:38, 2 April 2008 (UTC)

Very simple eyes (small, lensless, and immobile) are only going to be of use on that part of the body, so you'd need a lot of them to see very much. The question really is, why have so many animal lineages reduced the number of eyes to just two? — kwami (talk) 00:14, 2 April 2008 (UTC)

My guess would be that eyes are "expensive" from an evolutionary point of view, though I recognize that is something of a tautological statement (durr, they didn't evolve because they didn't evolve). If binocular vision evolved first, then it would make a lot of sense that two eyes was the template on which other eyes were based. Binocular vision is common to most predators, so that wouldn't be too unexpected, and it makes for relatively easy 3-D imaging (not sure how well the brain handles multiple eyes in that respect; even spiders usually have two main, front-facing eyes for that reason). But obviously I'm not speaking with any real knowledge here, just speculation. --Captain Ref Desk (talk) 01:09, 2 April 2008 (UTC)

Hi. Some jellyfish have "eyes" across their body, but no brain. They will bump into white poles, turn around black poles, and avoid red poles. Don't try picking up even a dead jellyfish, they can still sting, but if you do make sure you pick it up by its bell and not its tenticles (especially if it's a box or irikanji jellyfish), and even if you don't feel anything, they can still be dangerous. Box jellyfish are perhaps one of the most poisonous creatures on Earth (if not the most venomous). They sting with millions of Gs (how do they do that?!). So, anyway, if I remember correctly some have around two dozen "eyes". Source: National Geographic on TVO. Hope this helps. Thanks. ~AH1^(TCU) 20:20, 2 April 2008 (UTC)

"Pins and Needles"

I'm not asking for medical advice, just to be clear. I'm wondering about something I've noticed since I was a child: when one of my legs "falls asleep", part of it "waking up" involves excruciating pain. It's kind of like a paralytic numbness, which apparently is typical, but what's different with me is that that is accompanied by this sort of unbelievably sharp tingling that subsides after a few minutes. I can avoid feeling it very much if I manage to keep my leg perfectly still for a few minutes as its waking up; the slightest shiver or pressure is crippling, though. I'm not at all worried about it, but I'm wondering because I've tried to explain this to friends and no one has ever known what I'm talking about. Any one? Thanks! —Preceding unsigned comment added by 96.232.160.116 (talk) 23:10, 1 April 2008 (UTC)

Well, "pins and needles" is apparently called paresthesia. It's not abnormal. I suspect the reason your friends don't know about it is because they don't suffer as many "asleep" limbs as you? My legs fall asleep very easily just from sitting in certain positions (my entire butt can even fall asleep), so I am very very familiar with what you describe (it's awful), whereas my wife can count on one hand the amount of times parts of her limbs have fallen asleep, and as a consequence has a much harder time talking about the experience. The page on it says that there are all sorts of horrible conditions that can be associated with but if one just has bad circulation you'd get the same thing (I'm pretty sure mine is just bad circulation, it's been like that since I was a child, and my doctor's tests always come back fine). Anyway, if it helps, I know exactly what you are talking about, I get it all the time, and I too have trouble explaining it to people who don't experience it, as it must be hard to imagine what it's like to have your whole leg (or both legs) feel like they are being jabbed with little sharp implements if you haven't felt it before. --Captain Ref Desk (talk) 23:39, 1 April 2008 (UTC)

Ah, interesting. I looked at the paresthesia page; I should have mentioned that. My friends get "pins and needles" (apparently, that's just the little numbness/tingling everyone gets when a limb falls asleep). The painful pins and needles is either something different, or we're just too sensitive! Knives and daggers maybe... —Preceding unsigned comment added by 96.232.160.116 (talk) 01:02, 2 April 2008 (UTC)

I notice a distinct difference depending on how "asleep" my leg is. For example, just a minute ago, I had my laptop on my crossed legs for a bit too long and my feet fell asleep. But they weren't very asleep, and "woke up" pretty quickly, and I only had very mild, non-objectionable pins and needles. However when my entire leg falls asleep for some time, usually because I'm cutting off some circulation via my rear (the toilet seat, I must admit, is the most common culprit of this for me—it's almost ideally designed to make my legs fall asleep), then I really get painful pins-and-needles.

All of which is to say that with my easy-to-fall-asleep legs, I notice lots of variations in how intense the pins and needles are, and it seems to matter (for me) exactly how much circulation I'm cutting off. --Captain Ref Desk (talk) 01:12, 2 April 2008 (UTC)

Earth's magnetic field

If you loaded a big boat up with permanent magnets or a giant magnetic coil would the boat begin heading for the closest magnetic pole? 71.100.173.69 (talk) 23:12, 1 April 2008 (UTC)

In theory, yes. In practice, I suspect that even the proverbial boatload of magnets would exert an extremely small pull. Here's why. Once the boat has turned to line up the magnets with the Earth's field, the remaining force will be proportional to the difference in the value of the Earth's field at the two ends of the magnet. A magnet in a uniform field won't feel a force; any force is from the gradient (change) in the field. JohnAspinall (talk) 00:44, 2 April 2008 (UTC)

Hi. Well, there's also the problem of sinking if the boat gets too heavy, and bumping into land or ice is also a possibility. However, if you magnetise a steel needle, place it into a cork, and float the cork on a tub of water, it will start pointing towards the north pole. Metal objects in water can do some amazing things (besides sink). For example, if I put some paper clips containing metal in water and let the surface tension to float them, they sometimes become attracted to each other, stick together, and even sink to the bottom together. Also, there may be areas in the water in the ocean where methane is released, and causes boats to sink, and people that jump out sink too because the water itself has lost its bouyancy. Hope this helps. Thanks. ~AH1^(TCU) 20:27, 2 April 2008 (UTC)

A floating magnet on Earth would experience Torque which would tend to cause it to rotate to align with the Earth'sd magnetic field. It would not move toward the magnet because the repulsion would counteract the attraction. If you could find or create a Magnetic monopole, which no one to date has done, then it would move. Edison (talk) 21:02, 2 April 2008 (UTC)

effect of sugar water

Q What is the effect of sugar water on a plants growth? Bailey504 (talk) 23:15, 1 April 2008 (UTC)

Glycolysis. -- JSBillings 23:26, 1 April 2008 (UTC)

Might attract hummingbirds for pollination too. --Kurt Shaped Box (talk) 23:27, 1 April 2008 (UTC)

Program to create legal and medical troubleshooting charts

Not really sure where to put this question since it involves mathematics, science, humanities and business. Anyway here goes... I have written a computer program to apply the method described in Optimal classification for identifying flags to identifying actions. The program can handle a large number of actions, conditions and multiple states, which makes it suitable for use in creating legal and medical troubleshooting charts. All I need to publish such troubleshooting charts are legal and medical logic tables. I could in the alternative publish just the program. How would I go about doing this in the shortest amount of time while preserving my rights to the program? 71.100.173.69 (talk) 23:56, 1 April 2008 (UTC)

I have no idea what a lot of that means, but a trick for retaining a copyright (besides simply declaring the copyright) that was shared with me by an author some years ago is this: Print a hard copy, and send it by registered mail to yourself. Don't open it. That way, in the event of dispute, a court of law has a federally attested post-mark date by which it can determine the document's correct age. I've never done it, but it sounds reasonable... Vance.mcpherson (talk) 00:16, 2 April 2008 (UTC)

See Poor man's copyright for why it isn't reasonable. As to the original question, this is basically asking for legal advice, which we aren't allowed to give here. --Anonymous,00:18 UTC, April 2, 2008.

Since you have not charged me any money I do not think anyone can claim it as legal advice, which would otherwise be a fruadulent claim since clarification of the law is simply not. 71.100.173.69 (talk) 05:51, 2 April 2008 (UTC)

Clarification - The reference desk will not provide legal advice. This has nothing to do with charging for services. See Wikipedia:Legal disclaimer for further information and explanation. Nimur (talk) 13:56, 2 April 2008 (UTC)

There are ups and downs to either business model; the one that will likely get you the most profit is also, non-coincidentally, the one that will cost you the most in terms of time and personal investment.

I deplore software patents (because I think they stifle creativity and are used maliciously) but that's the strongest way to preserve your rights. As for copyrighting the program, that's not hard to do; the hard part about copyrighting is enforcement (that is, it'll be up to YOU to take offenders to court and to prove that they are infringing on your specific code). --Captain Ref Desk (talk) 01:41, 2 April 2008 (UTC)

Since my objective is to see that both medicine and law are published in the form of a troubleshooting chart the program is only incidental as a means of optimizing the charts. I love free software as well but the reality is that I have worked long and hard to create it at my own expense and without any compensation so I can not in all due respect to myself release it free of charge.

While software patents may stifle creativity for the end user they may provide incentive and promote creativity for the author. I have copyrighted and published the program and required the user to obtain a key but have since withdrawn the demo and limited versions from publication. Now I'm thinking of using it only as an in house tool and merely offering the service of optimizing any troubleshooting chart. 71.100.173.69 (talk) 05:51, 2 April 2008 (UTC)

April 2

Angle

What angle does water make with a capillary tube? —Preceding unsigned comment added by 71.175.123.209 (talk) 00:21, 2 April 2008 (UTC)

See Contact angle my friend. Any trouble understanding, please come back here. —Preceding unsigned comment added by 79.76.250.241 (talk) 00:37, 2 April 2008 (UTC)

Killer strangelets

What the problem with so-called "killer" strangelets here[25]? Julia Rossi (talk) 01:14, 2 April 2008 (UTC)

It has been suggested that strange matter could convert all normal matter on the Earth into strange matter in a chain reaction, something like Ice-nine. See Strangelet#Dangers. Someguy1221 (talk) 01:22, 2 April 2008 (UTC)

Well, that certainly does sound unpleasant. :-/ --Captain Ref Desk (talk) 01:47, 2 April 2008 (UTC)

I'll really start to worry when 'they' decide to start exploring the potential military applications of strange matter chain reactions... --Kurt Shaped Box (talk) 01:53, 2 April 2008 (UTC)

Before you panic, see Safety at the LHC — Kieff | Talk 02:29, 2 April 2008 (UTC)

Can I get a shout of "Well, they would say that, wouldn't they?"? ;) --Kurt Shaped Box (talk) 02:43, 2 April 2008 (UTC)

Well, and that's really what the lawsuit is (ostensibly) about—not so much saying it will happen as it is saying that "they said it won't happen, but we think they should take a more thorough look at it." (One could argue, as the CERN people no doubt do, that the lawsuit is just nonsense, and it may be. All I'm saying is, that's what they're saying on the face of it.) The basic argument of CERN is, "if it could have happened, it already would have happened", which is in some ways comforting and some ways not, though for my money I don't think there's going to be a problem. But I am not a physicist. --Captain Ref Desk (talk) 02:48, 2 April 2008 (UTC)

"I get drunk every night and walk home down the white line in the middle of the road at night whilst wearing black - if I was going to get hit by a car, it would've happened by now". ;) --Kurt Shaped Box (talk) 14:13, 2 April 2008 (UTC)

I see two solutions - (1) slap a warning label on it: "Caution: Use of this device may result in the destruction of the universe. Handle with care." or (2) Let them run the damn thing, and if it does kill us all then hit them with a class action. Confusing Manifestation(Say hi!) 05:20, 2 April 2008 (UTC)

Who needs government think tanks when there's you guys, the think tins. I thank you.  : ) Julia Rossi (talk) 06:26, 2 April 2008 (UTC)

The last report I saw quoted the odds as 1 in 10,000,000,000,000,000,000,000,000,000,000,000,000,000. Unfortunately I can't link because it's from a now-defunct article in the NZ Herald. AlmostReadytoFly (talk) 08:49, 2 April 2008 (UTC)

So, if someone has demonstrated that there *is* a chance that 'Something Very Bad That Cannot Be Undone' might happen when the machine is started up - then why are they still planning to do it? Will this experiment benefit humanity in any real sense - or does it basically boil down to "We want to poke it with a stick and see what it does"? --Kurt Shaped Box (talk) 14:06, 2 April 2008 (UTC)

Please take a careful look at that figure. Consider Orders of magnitude. Note that it is greater that the number of microseconds since the Big Bang. Assume that physicists would not spend billions of Euros on a whim and consider that they might have a reason, rather than giving a knee-jerk anti-science reaction. Consider reading about the Higgs boson and the LHC and the Standard Model. Think about the size of the number again. It's longer than the odds of winning the lottery jackpot five times out of five. I don't think you grasp how vanishingly small the chance is. AlmostReadytoFly (talk) 14:49, 2 April 2008 (UTC)

It wasn't my intention to sound 'anti-science'. I know very little of particle physics and my eyes tend to glaze over whenever I attempt to learn more about particle physics - even the links you have provided are scarily complex (heh, they should publish a 'Particle Physics for Dummies' book). I was attempting to question the practical benefits of these experiments - I personally don't believe that a risk (even an infinitesimally tiny risk) to all life on this planet can be justified for the sake of an experiment, if the end result will only be of interest to the practitioners of particle physics experiments themselves and people who read books about particle physics. My question, from a position of ignorance - if they carry this out and it works, what will the new knowledge enable us to do (in a real world sense) that we couldn't do before? --Kurt Shaped Box (talk) 20:18, 2 April 2008 (UTC)

It's a reasonable question. According to the laws of physics as we currently understand them, nothing bad will happen. Even if the LHC uncovers some new and unexpected physics, it is only creating events in a controlled way that happen naturally through cosmic ray interactions anyway, so it is still very unikely that anything bad will happen. However, the LHC will be operating at the boundary of known physics, so there is a very, very, very small chance that something bad will happen. But you can balance this very, very, very small risk against the possibility that a better and more complete understanding of particle physics could eventually lead to solutions to the very much greater dangers of global warming, destroying the ozone layer, running our of fossil fuels or being wiped out by a dinosaur killer. Poking things with sticks is what makes us human. Gandalf61 (talk) 15:01, 2 April 2008 (UTC)

To be a bit more polite than I was above... The UK regulatory body for nuclear power plants sets a limit of <10^-4 public deaths per year for one plant, and a target of 10^-6 (I believe these numbers are "handed down" from IAEA). Assuming 10^10 (10 billion) people on Earth and that the risk of 10^-40 applies for the first year of operation, that's a risk of 10^-30, a factor of 10^24 less than a roughly equivalent target. AlmostReadytoFly (talk) 15:16, 2 April 2008 (UTC)

The anthropic principle basically says "the universe had to work out well for creating intelligent life; otherwise we wouldn't be here to discuss it". I hereby proclaim the misanthropic principle: "it doesn't matter if we wipe out all intelligent life, because we won't be here here to discuss it". :) --Sean 13:50, 2 April 2008 (UTC)

Low-gravity humans?

I'm reminded of this question by the recent news about the Virgle Project: Supposing that Mars is terraformed and permanent human settlements are established, what would be the physiological effect of the planet's low gravity on the generations of humans living there, having been gestated and raised there? Would they become taller and more gracile, as I read in some science fiction book? Would they be unable to walk on Earth? --Lazar Taxon (talk) 02:27, 2 April 2008 (UTC)

Probably yes to all your theories. The effects of microgravity on physiology are quite real and detrimental to any return to full Earth gravity. Mars' .38g will, naturally, have less impact, but the impact will be nonetheless real. Note, however, that training could probably overcome the last (walk on Earth). — Lomn 03:08, 2 April 2008 (UTC)

The colonists would certainly need to exercise more than those remained on Earth, to have the same physical strength. --V. Szabolcs (talk) 09:27, 2 April 2008 (UTC)

What is the Fabric named "armalith" made from (or how its made), and what are the benefits of its use?

I saw a website that showed a video of some pants made from it with a person sliding on pavement and the "armalith" was very resistant to damage. The website is www.esquad.fr

My google search had very little information and wiki had nothing.Nusaince (talk) 03:19, 2 April 2008 (UTC)

"The jeans are made entirely from a fabric called Armalith, which is claimed to be “the most resistant of all textiles” and is blend of cotton and high-tech fiber. The website doesn’t disclose the “high-tech fiber,” but the tag inside the jeans says its polyethylene -- yep, plastic. Probably an ultra-high molecular weight polyethylene (known as UHMWPE) that is so strong and elastic it has replaced Kevlar in bulletproof vests."[26] DMacks (talk) 03:28, 2 April 2008 (UTC)

Acetone combustion

What is the combustion equation for acetone in air? 71.100.173.69 (talk) 05:10, 2 April 2008 (UTC)

Is this a homework question? The burning of a hydrocarbon or a compound containing only hydrogen, carbon, and oxygen will always produce carbon dioxide and water. [27] The chemical formula of acetone is CH₃COCH₃ and combustion in air always involves oxygen, so finding the equation should be easy. --Bowlhover (talk) 05:45, 2 April 2008 (UTC)

No not homework, just curious about whether or not it could be used as a camp stove fuel or for that matter as an ICE fuel. 71.100.173.69 (talk) 21:49, 2 April 2008 (UTC)

Well, complete combustion will always produce... But incomplete combustion can produce all sorts of weird things (most notably including carbon monoxide).

Atlant (talk) 15:44, 2 April 2008 (UTC)

Pipe - Solar Heating System - for homes

I want to make a cheap solar heating system for homes using pipes only and a pump motor that circulates the water which is all connected to a geyser. The pipes will be connected in parallel like a big web and sit on the roof. What kind of pipe would be suitable, what kind of plastic? Does it have to be weather proof and high pressure and able to take high temperatures? Is copper pipe better, maybe with a black plastic coating on the outside? What length of pipe would be effective? I want to help the poor who cant afford normal solar panel or tube heating systems and I also want to help combat global warming. Any advice or help would be greatly appreciated. Thanks so much.

--CrypticApple (talk) 09:15, 2 April 2008 (UTC)

You confused me when you mentioned a "geyser", so I'll ignore that. I would think clear plastic pipes would be most effective, with some dye added to the water to make it absorb heat from sunlight. You would want the pipes to be flattened so they can absorb as much sunlight as possible. Special outdoor plastic must be used so it won't deteriorate when exposed to UV light. One potential problem is that the water could freeze in cold weather and burst the pipes. Some type of antifreeze would need to be added to prevent this. Since you're concerned about the environment, I'd suggest a nontoxic antifreeze. You still have the problem of how to power the pump. Solar panels could work for this. Another approach is to make the pump child-powered. In Africa they have child-powered water pumps that are hooked up to merry-go-rounds. This allows the excess energy children have to be put to good use. I wouldn't expect the pipes to get to boiling temperature, and there are many plastics that can take those temps and pressures. Copper would be a poor choice on the roof because it would radiate heat. However, it might be a good inside choice, although it's relatively expensive. Some type of sealed radiators could also be used. (They must be sealed as you wouldn't want the antifreeze leaking inside the house.) One big flaw is that there is no sunlight at night when the heat is needed the most, especially in winter. This would require a storage tank to store the heated water until night. The children's merry-go-round could lift the heated water into a water tower at night, then gravity could allow it to flow through the house into a lower tank at night. StuRat (talk) 12:44, 2 April 2008 (UTC)

One of the key characteristics I'd look for in my piping is the ability to resist solar radiation over the years. For example, in the US, "Schedule 40" PVC piping would be an awful choice because it rapidly becomes brittle when exposed to the sun. (Plus, of course, it's white, so maybe if it were painted black...) Clear piping sounds like a poor idea to me as well because clear liquid in clear piping wouldn't absorb much heat. You might want to see our article on solar collectors (although it's pretty scant).

Atlant (talk) 15:50, 2 April 2008 (UTC)

...and that would be why I suggesting adding dye to the water. That way all the heat is generated directly in the water, versus on the outside surface of the pipe, from which only a portion would find it's way inside the pipe, while most would radiate back into the air. This is especially true of plastic pipes, since they don't transfer heat well. That's a good quality once the heat is inside the pipe and you want to keep it there, but it's a bad thing if the heat is outside and you want to let it in. StuRat (talk) 16:59, 2 April 2008 (UTC)

It's probably worth reading Solar hot water. -- Coneslayer (talk) 17:06, 2 April 2008 (UTC)

Though water is mostly transparent to visible light, it's a pretty good absorber in the medium-wavelength infrared range, which is where much of the sun's energy lies. I don't expect that dye would have much of an effect. jeffjon (talk) 20:18, 2 April 2008 (UTC)

I've read somwhere that in places like Isreal they use ponds with a freah water layer and a salt water layer beneath. The reash water layer acts as insulation while the salt water absorbs heat. Salt might work in place of a die. I know for sure that chromium oxide will. 71.100.173.69 (talk) 22:05, 2 April 2008 (UTC)

Exercising while taking human growth hormone supplements

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, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

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, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

You should speak to your pharmacist or the prescribing physician about the effects of any medication or supplement on your health and activities. TenOfAllTrades(talk) 17:23, 2 April 2008 (UTC)

Heartbreak

My heart is completely broken and I cannot function because my other half does not want to be with me anymore. We have been together for several years. It feels like I am dying inside and food tastes like sawdust. What, if any at all, are there any benefits for a human to endure this? Is there some sort of biological benefit to this?--Jonasmanohar (talk) 18:35, 2 April 2008 (UTC)

If all food tastes like sawdust, then it becomes easier to eat more healthy-yet-tasteless food instead of delicious-yet-nutritionally-vapid food. I'd call that a biological benefit. — Lomn 18:47, 2 April 2008 (UTC)

No obvious evolutionary advantage occurs to me for the downside of intimate relationships. However you probably can't have the good without putting up with the bad, and the usefulness of a pair bond should be fairly apparent from a biological perspective. Friday (talk) 18:53, 2 April 2008 (UTC)

If your other half is in fact your conjoined twin, we can't give you medical advice beyond saying that you should see a doctor immediately. Ben Carson's good. --Sean 69.134.209.199 (talk) 19:22, 2 April 2008 (UTC)

There are several evolutionary approaches to depression, not that I'm diagnosing you or anything...That page gives a few theories as to why it's not easy to be happy. Someguy1221 (talk) 19:28, 2 April 2008 (UTC)

analysis of acidic and basic radicals

i am a student of chemical engineering... is wanted to ask what should be the correct procedure to carry out analysis of acidic and basic radicals???