Wikipedia:Reference desk/Archives/Science/2009 March 16

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March 16

Turning a clear LED light bulb into a frosted one

Is there an easy DIY method to convert the clear plastic shell of an LED light bulb into a frosted one (without significantly reducing the light output)? —Preceding unsigned comment added by 173.49.9.243 (talk) 02:41, 16 March 2009 (UTC)

It would depend on the type of plastic used. Dipping the bulb quickly in Acetone and letting it air-dry will likely accomplish your goal, though if you're trying to compensate for the extreme directionality of the light from most LED bulbs, a simple bulb frostover isn't going to get the job done. —Scheinwerfermann ^T·_C03:43, 16 March 2009 (UTC)

(ec)I've used various organic solvents (takes some experimentation with solvent and time depending on the plastic) to get frosted effects on clear plastic parts. Could also try sand-paper or steel wool to get a brushed surface effect. Never tried it on LED lightbulbs. DMacks (talk) 03:46, 16 March 2009 (UTC)

OR try little dabs of superglue. Use pin to apply. 76.97.245.5 (talk) 07:33, 16 March 2009 (UTC)

Most people just sand the plastic envelope slightly. It does lose a little light. There are wideangle leds you can buy if that's what you want. 75.62.6.87 (talk) 10:07, 16 March 2009 (UTC)

Optimum sizes/shapes for ice cubes

What would be the best (including practicalities like glass sizes) sizes and shapes for ice cubes to make them melt faster or slower? I'd have thought that a big ice cube would melt more slowly, but would a sphere or cube or any other shape be best? 86.8.176.85 (talk) 03:15, 16 March 2009 (UTC)

My anecdotal observation has been that a long, cylindrical form works better than any of the more traditional cube variants. In my experiments carried out using different rubber ice moulds from IKEA, I found that the cylindrical ices froze fastest and were quickest and most efficient at cooling down drinks. The fast freezing and drink cool-down are probably due to the large surface area of the cylindrical form, while the perceived efficiency is probably because the ice cylinders cool the whole height of the drink. Cubes, on the other hand, float on top and supercool the upper portion of the drink while leaving the lower portion largely uncooled. —Scheinwerfermann ^T·_C03:41, 16 March 2009 (UTC)

The surface area of the ice determine the rate at which heat gets in--the larger the area, the faster the heat transfer. With a certain rate of heat transfer, ice cubes with less volume obviously melt faster. If you want the ice to melt (and cool the surrounding fluid) as quickly as possible, you'd want a high surface-area-to-volume ratio. A sphere has the lowest ratio, so definitely don't use one.

If this is a practical question, I think the best solution is to grind up the ice cubes, whatever shape they happen to be, and dump the pieces into whatever has to be cooled. If you want to have the ice melt faster, just grind it into smaller pieces. Even minimal crushing will increase the surface-area-to-volume ratio to a value much higher than any single ice cube can realistically have. --Bowlhover (talk) 04:58, 16 March 2009 (UTC)

This assumes that the main goal of the ice cubes is to cool the drink quickly. In some circumstances, you might prefer ice cubes that cool slowly, over a long period, in which case spheres might be more desirable. jeffjon (talk) 14:03, 16 March 2009 (UTC)

About the optimality of the spheric shape: it is true that a ball has the surface of minimal area among all bodies with the same volume (that is, solves the three dimensional isoperimetric problem), but, to be precise, what matters here is that a ball has the minimal thermal capacity among all bodies with the same volume; the two variational problems being not directly connected. pma--79.21.30.83 (talk) 16:44, 16 March 2009 (UTC)

Crushing will certainly generate the best surface-area to volume and for practical purposes will undoubtedly cool your drink faster than any other shape. But it's kinda cheating if you're trying to build a single lump of ice. What you need is some kind of fractal surface - a sierpinski sponge perhaps - pleasing because it's so much like a regular ice cube - but able to dissolve in an arbitarily short amount of time. If course constructing such an object in your refrigerator might be a bit of a challenge! SteveBaker (talk) 00:05, 17 March 2009 (UTC)

Having infinite area, the sierpinski sponge would indeed melt instantaneously. Having zero volume, it would do no cooling at all. :) Dauto (talk) 04:39, 17 March 2009 (UTC)

If your point is to cool your beer cooler fast and keep it cold, You might want to try adding some salt to the ice. That will reduce the melting point of the ice several degrees making the ice melt fast. Make sure you wash the beer bottles before opening them. Dauto (talk) 04:45, 17 March 2009 (UTC)

Animal olympics

If there were an animal Olympics, which species would win which events? What would win 100m, weightlifting, any of the events where an animal could sort of compete. 86.8.176.85 (talk) 05:47, 16 March 2009 (UTC)

Are you looking for absolute numbers or would you figure in relative body sizes. Have a look, we probably have a couple of lists somewhere. (Sorry but I got to turn in so can't/ won't be more help. Speed record's a start.76.97.245.5 (talk) 07:32, 16 March 2009 (UTC)

I think what you really want to know is which of the animals is the strongest, fastest, etc... right? Or maybe you just dig crazy animal Olympics. Hell, why not! But honestly, that's a problematic theme, because it's kind of hard to figure out how to measure or even compare these animals. In a lot of cases, this would involve guesswork: for example, gorillas are really, really strong, but it's hard to make them do bench presses, so the scientific data on how strong they precisely are tends to be sketchy. In fact, the definition of strength can also be iffy: an elephant can haul amazing loads, but I'd bet that a blue whale is still stronger. So how do you measure that? And then again, surely proportion has to count for something: all of these animals are pretty much lightweights compared to ants, which can lift many times their own body weight... To switch tracks a little, speedwise, a cheetah can pretty much beat anything on land on a 100m sprint -- they can sprint at up to 120 km/h. And yet a peregrine falcon will leave it in the dust; they've been clocked at 250 km/h when diving. We'd definitely need some ground rules here -- in addition to ridiculously cooperative animals... -- Captain Disdain (talk) 10:41, 16 March 2009 (UTC)

I think the animal Olympics would need to borrow a page from the Paralympic Games and institute a classification system, where the various animal athletes would be grouped for competition according to their physical function. So we could have the 100m for biped, quadruped, avian, aquatic (mammal), aquatic (non-mammal), invertebrate, etc. - Eron^Talk 14:31, 16 March 2009 (UTC)

Solar cooker

why is glass plane/cover used in a solar cooker? —Preceding unsigned comment added by Pratimap (talk • contribs) 07:39, 16 March 2009 (UTC)

The glass cover allows sunlight to enter the device unimpeded, but upon entering, some of the sunlight's energy is converted into heat within the cooker. The cover then traps the heat by blocking the escape of hot air. This is the "heat trapping" type of solar cooker, and other types exist as well. Read more at Solar cooker. Someguy1221 (talk) 08:32, 16 March 2009 (UTC)

Glass is also pretty opaque to infrared, so it stops heat escaping as radiation, as well. (This is how the greenhouse effect works in the case of actual greenhouses.) --Tango (talk) 15:22, 16 March 2009 (UTC)

Glass is transparent to IR, or else thermographic cameras won't work. Greenhouses trap heat by preventing warmed air from mixing with the surrounding atmosphere or rising to high altitudes, as explained by Greenhouse effect#Real greenhouses. --Bowlhover (talk) 21:06, 16 March 2009 (UTC)

You really can't lump the entire IR spectrum together like that. Glass has transmission/absorption peaks and valleys throughout the IR range, which is why, simultaneously, 1) IR cameras can use glass lenses, and 2) glass bending and laminating operations can use IR to heat the glass efficiently. jeffjon (talk) 13:12, 17 March 2009 (UTC)

Watch one of those police programs on TV where they have thermal imaging - the windows of houses look like solid white squares, you can't see inside the houses through them. That's because IR is pretty much opaque at the relevant wavelengths. I'm not sure how the glass lenses in such cameras work - perhaps it's a different type of glass? --Tango (talk) 14:29, 17 March 2009 (UTC)

Yes it's some kind of quartz-like stuff. IR does go through glass - just not very efficiently. One of the major reasons you don't see thermal signatures through house glass is that we go to a lot of trouble (with double-glazing, IR-reflective coatings and such) to insulate them, SteveBaker (talk) 02:07, 18 March 2009 (UTC)

Killer cancer

I'm not seeing this in our articles. What are the most common proximal causes of death associated with cancer? Metastatic growths in the brain or heart would obviously be good candidates, but probably not the only major ones. What do tumors typically do to people that cause the body to cease functioning? Obviously with a group of diseases as diverse as cancer there are probably many possible ways it can kill you, but I just looking for the common ones. Dragons flight (talk) 08:18, 16 March 2009 (UTC)

It varies significantly between types of cancer. I found a number of reviews of the precise question on PubMed: [1] [2] [3] [4] [5]. I recall from some or another doctor that infection is in general the single most common cause of death amongst cancer patients. Someguy1221 (talk) 08:48, 16 March 2009 (UTC)

Measurement of breast size by water displacement

Hi I was wondering if anyone had any idea where I could find some information regarding this please:
Basically sometime around 1985-1990, James Owen Drife led a study where they measured women's breast size through submersion in water, (and presumably its displacement), which caused a far bit of newspaper controversary, at least in the UK.
Does anyone know where this was published? Or even in which newspapers it was reported? Or just some more information on it??
Many thanks Duke Of Wessex (talk) 08:45, 16 March 2009 (UTC)

He wrote an article on what you describe in 1975 (available free here) in the British Medical Journal. Drife has published 20 articles on various issues relating to breasts, but I'm not sure any of the ones contain what you described based on their titles. But they are available for free from pubmed, except for one which I have read but is a review and not a research paper. Someguy1221 (talk) 09:02, 16 March 2009 (UTC)

Thanks for those links, (and in super-fast time!), I think the 1975 one is what I'm after, but have you (or anyone) any idea if it was mentioned in the newspapers at the time? Or more recently? Thanks! Duke Of Wessex (talk) 16:11, 16 March 2009 (UTC)

The obvious problem with this method is that breasts are generally attached to someone, so you can't determine the displacement of the breasts alone. Deciding where the breasts end and the rest of the person begins is not an easy or precise task. StuRat (talk) 02:22, 17 March 2009 (UTC)

Haha, I can just imagine a Loki's Wager coming up... bibliomaniac15 02:56, 18 March 2009 (UTC)

Why doesn't clingfilm / plastic wrap cling to Parmesan?

In my fridge, once opened, all the cheese are covered in clingfilm. For the vast majority of the cheese the film does what it's supposed to and clings tightly to the cheese, wrapping it up. With parmesan, however, it doesn't - it's almost as though it loses its static, and instead of clinging to it, simply covers it loosely. Why? It's not a case of the same piece of film being opened and closed multiple times, as it will happen with a fresh piece of film - after a certain period of time, when I go back to the fridge to get it out, it's given up the ghost and gone all loose... pushthebutton | go on... | push it! 09:55, 16 March 2009 (UTC)

Parmesan cheese (Parmigiano-Reggiano to purists) has a slightly oily surface; you can feel the difference when you pick up a wedge of the stuff. The film just slides off. (The fats in most other cheeses tend to stay quite solid at refrigerator temperature, so there's less sliding.) TenOfAllTrades(talk) 13:56, 16 March 2009 (UTC)

I put a section in Plastic wrap on how it works. To elaborate a bit on Ten of all Trade's "oily" explanation: the wrap will bond lightly with the fat molecules on the cheesy surface, but those molecules are not tightly bonded to the cheese. In butter or American cheese there is enough of a smooth surface that is tightly bonded to the rest of the block so the wrap will stick. 76.97.245.5 (talk) 14:15, 16 March 2009 (UTC)

Transmission line simple problem

Hi, I'm trying to solve Problem 1 at [6], but I'm not sure, any help will be appreciated. What I do is apply Ohm's law at t=0, so that the voltage wave is -1 volts towards de open circuit. That way I'll get a series of -1 and 0 voltage levels at the short circuit and 1,0,1,0 at the open circuit. Is this correct? Thanks! --62.57.238.224 (talk) 10:49, 16 March 2009 (UTC)

I think you're forgetting a few things, mainly the reflection off the short. Draw a diagram and follow along:

• The initial -1V wave travels to the right and reduces the voltage on the line to 0.
• The initial wave (-1V) is reflected with coefficient 1.
  • Note that the open end is now at -1.
• The first reflected wave (-1V) travels left, reducing the voltage on the line to -1.
• The first reflection is reflected from the short, with coefficient -1.
  • Note that the reflection instantly cancels the incoming wave, so the short is always at 0.
• The second reflection (+1V) travels right, raising the voltage on the line to 0.
• The second reflection is reflected with coefficient 1.
  • The open end is now at +1.
• The third reflection travels left and raises the voltage on the line to 1V.
• The third reflection is reflected with coefficient -1.
• Repeat.

--mako 03:43, 18 March 2009 (UTC)

error in lorentz transformation

I think there is a contradiction between the formula of the lorentz transformation and the length contraction in special relativity. In the formula $\mathbf {x={\frac {x'+vt'}{\sqrt[{}]{1-{\frac {v^{2}}{c^{2}}}}}}}$, suppose a coordinate system K' is moving with a relative velocity to K equal to v. Then if we solve the formula for t' = 0, x' = 0 and a v less than c, we will surely get a value greater than 1. So what will happen is that a rod measuring 1m in K' will appear to be longer as seen from K. But this is in contradiction with the length contradiction formula, $L'={\frac {L}{\gamma (v)}}=L\,{\sqrt {1-v^{2}/c^{2}}}$ which states that the length will decrease. Please explain. (if this is really a discovery, please guide me to get a patent for it because i don't know the procedure as i am only 14).--harish (talk) 11:57, 16 March 2009 (UTC)

If you put t’=0 and x’=0 in the formula for the Lorentz transformation, according to me the result would be x=0. This just means that the origin of both systems K and K' (i.e. the points x and x’) are coincident at the moment t=0 (i.e. before the system K' has moved relative to K at all). This is just a trivial result, really... Or are you doing something else? MuDavid 12:17, 16 March 2009 (UTC)

A similar question was asked last month (but with the co-ordinate systems swapped). See Wikipedia:Reference_desk/Archives/Science/2009_February_28#contradiction_between_lorentz_transformation_and_length_contraction. The core of these sorts of problems are that, even though the Lorentz transform is symmetric, observers in different reference frames will disagree on lengths and times. Remember that you have to account for relative lengths as well as times and that length measurements are presumably made at simultaneous times, where Relativity_of_simultaneity needs to be accounted for. Someone42 (talk) 12:37, 16 March 2009 (UTC)

The question was asked by the same person, which means he reamains unconvinced. Dauto (talk) 13:10, 16 March 2009 (UTC)

Simple explanation is that if you measure the distance between two space-time events that are simultaneous in K' (i.e. have the same value of t') then you are measuring length from the point of view of K'. And from the point if view of the K' frame of reference, L' is indeed greater than L. But if you want to measure length in the K frame of reference then you need to measure the distance between two space-time events that are simultaneous in K (i.e. have the same value of t), in which case in turns out the L is greater than L'. As a general principle, the difference between the space co-ordinates of two points in space-time that are separated by a space-like interval is maximised in the frame of reference in which they are simultaneous. Gandalf61 (talk) 14:21, 16 March 2009 (UTC)

Gandalf, from the expression for the invariant 'distance' $(dS)^{2}=(dl)^{2}-(dt)^{2}=(dl')^{2}-(dt')^{2}\,$ (where $dl\,$ and $dl'\,$ are the space coordinate distances between the two events and $dt\,$ and $dt'\,$ are the time differences between the two events) we see that if the primeless frame is the one where the two events are simultaneous $(dt=0)\,$, then $(dl')^{2}=(dl)^{2}+(dt')^{2}>(dl)^{2}\,$, which makes $dl\,$ minimal (not maximal as you stated). —Preceding unsigned comment added by Dauto (talk • contribs) 19:27, 16 March 2009 (UTC)

Yes, indeed. And, now I think again, my final point was not relevant to the original question anyway. Gandalf61 (talk) 13:17, 17 March 2009 (UTC)

Yes, I agree - for the second time around, our OP is incorrect. ...And as for a patent...it varies under the laws of different countries - but in most places, you can't patent an equation - even if it's correct. SteveBaker (talk) 23:36, 16 March 2009 (UTC)

I've always thought patents were for commercially useful inventions, and that scientific and mathematical discoveries go in academic journals. --Bowlhover (talk) 14:40, 17 March 2009 (UTC)

Thank you someone42 and dauto. I have now understood that i ahve done a fundamental error. yl' = l was the thing i already knew. But I confused l' and l. Now i have understood that l' will be smaller than l. So when we want to find l', we take y(the constant) to the other side so now we have to solve l' = l/y which will give a value smaller than l. Thanks again. Actually I wasn't able to see the answers for the archived question a few days after.--harish (talk) 17:02, 18 March 2009 (UTC)

Perchloric acid

What is the oxidation state of Cl in Perchloric acid?--Abhishek Jacob (talk) 12:47, 16 March 2009 (UTC)

+7, i.e. chlorine(VII).

Ben (talk) 13:01, 16 March 2009 (UTC)

Just in case this was a homework question, please keep in mind that the guidelines suggest that we should try to avoid answering homework questions (though we're happy to give a helpful nudge in the right direction if the OP shows that an effort has already been made. --Scray (talk) 23:09, 16 March 2009 (UTC)

nutrition

at what temperature a body starts to feel in coldness and a temperature out side his body is 22???thank you —Preceding unsigned comment added by Nisreen mansour (talk • contribs) 14:26, 16 March 2009 (UTC)

Moving the following from the mathematics desk, posted by the same user under an identical header. —JAO • T • C 14:29, 16 March 2009 (UTC)

how can i organize my food per a day? how many calories i'm suposed to include in my daily meals?? what are the most important kinds os food i may eat in order to make a 'diet'? i'm 12 years old and am 72kg that is so bad:S

please help me by answering i need it!! —Preceding unsigned comment added by Nisreen mansour (talk • contribs) 14:22, 16 March 2009 (UTC)

Specific advice should be provided by a medical professional. We have an article on the US Dietary Reference Intake, but that's provided for adults aged 40-50. As our dieting article notes, dieting in youth can be extremely hazardous. Consult a professional to develop a plan that is safe and healthy. — Lomn 14:49, 16 March 2009 (UTC)

If your school has a School nurse she can help answer your questions. She's there for students' health and should have relevant information available. 76.97.245.5 (talk) 15:07, 16 March 2009 (UTC)

why?who?when?what? (questions)

why do a person cry? why do a person cough? why do a person laugh? why do a person shout? how do a person feels when he sneeze ?why? who can help by answering these questions?ineed them am doing a project just any umm inf.about it i hope findung please help !! without details!!bye —Preceding unsigned comment added by Nisreen mansour (talk • contribs) 10:35, 16 March 2009

Onion or Emotion, Cough,Laughter, Vociferation, Sneeze. There's a search window in your side bar. Type in your word and click on "Search". 76.97.245.5 (talk) 15:01, 16 March 2009 (UTC)

Supermassive black hole collisions...again.

Hi. OK, so I remember asking a question about the merger between Andromeda, the Milky Way, and Triangulum a while back, and whether their black holes might collide. They might miss, but now it looks like collisions between supermassive black holes as a result of galaxy mergers might not be so rare after all: [7][8][9]. If two black holes collide in this manner, could the ensuing explosion have effects on Earth? Remember that explosions such as this may travel at close to the speed of light, so the explosion itself would not take much longer to reach us after the light from the explosion has reached us. Could a similar scenario occur between Milky Way, Andromeda, Triangulum, and possibly a few other galaxies? Thanks. ~AH1^(TCU) 15:54, 16 March 2009 (UTC)

As far as I know, the details of black hole mergers is still an open question. However, I don't know of any reason for a massive explosion. There would be lots of gravity waves gravitational waves oops! emitted, but they would have to be really powerful to cause any harm to Earth from such a big distance - I would be surprised if they were that powerful. --Tango (talk) 16:10, 16 March 2009 (UTC)

Well, you'd get a big mess from the black holes becoming active feeders, and their accretion discs interacting would likely result in a big mess. As I recall, Death from the Skies discusses this in one chapter. I believe the odds tend to favor minimal effect on the solar system (there's a good chance it gets ejected from the galaxy entirely) unless it happens to be along the polar axes of the SMBHs, which is fairly unlikely. — Lomn 16:17, 16 March 2009 (UTC)

See gravitational wave (not gravity wave!), which says "even waves from extreme systems like merging binary black holes die out to very small amplitude by the time they reach the Earth". Presumably if we were in the line of fire for any resulting relativistic jet it would be a lot more noticeable. --Sean 17:01, 16 March 2009 (UTC)

Oops! Fixed. --Tango (talk) 17:06, 16 March 2009 (UTC)

VERNIER CALLIPER

HOW TO MEASURE WITH DIAL VERNIER —Preceding unsigned comment added by VIVEK MENON89 (talk • contribs) 16:33, 16 March 2009 (UTC)

See Caliper scroll down to dial caliper. Be sure your dial is set to zero before you start and don't forget to add the readings from the slide. 76.97.245.5 (talk) 17:25, 16 March 2009 (UTC)

With proper care, such a measurement is very near accurate. Edison (talk) 14:17, 17 March 2009 (UTC)

German toilet

Why do German toilets have a little shelf?--80.58.205.37 (talk) 17:47, 16 March 2009 (UTC)

Far greater minds than mine have pondered (and probably solved) this question, but I think it is simply an excuse for German women to insist that men sit down to pee, because (with the shelf) they argue that pee splashes out of the toilet creating a mess worse than death. Why they need to emasculate men so badly they have redesigned the toilet, I do not know. 77.12.50.107 (talk) 19:15, 16 March 2009 (UTC)

Apparently it's designed to facilitate examination of one's feces. --Sean 21:52, 16 March 2009 (UTC)

For those like me who had no idea what this was talking about but are curious, here's a helpful link. Maybe I'm just being culturally insensitive, but ew. arimareiji (talk) 22:11, 16 March 2009 (UTC)

The last Vespasienne in Paris

I have observed similar - but much smaller - shelves in French toilets. Fortunately, us boys are able to negotiate these smaller devices from our lofty peeing posture...and of course there is always the pissoir or vespasienne (WHAT! We have no articles on these magnificent monuments to male urination?)... But sadly, I have yet to visit any country (the US included) who have reached the pinnacle of success of The Great British Loo. US toilets come close - but the failure to master the simple concept of the siphon dooms them to dribble and leak and need all manner of careful tweaks and adjustments. The worst I've encountered is certainly on some of the Greek islands where the diameter of their sewer pipes are mathematically guaranteed to block for any human of normal 'caliber'. They insist that you deposit used toilet paper in a small basket provided for this very purpose (cue ungodly smells and health hazards). One 'safari lodge' in Kenya was particularly lacking. "Where is the toilet?"..."Everywhere" (accompanied by a sweeping gesture across the entire landscape outside the hut). Sigh. SteveBaker (talk) 23:22, 16 March 2009 (UTC)

The original reason had more to do with flushing. 2 Systems used to be common in Germany: a thing called "Druckspüler" which basically produced a high pressure jet of water. The second is a cistern mounted near the ceiling. (About 2 yds. above the commode.) Both created a significant amount of water pressure when flushing. Reportedly an American style flushing toilet then could create a whirlpool effect that let the "item to be flushed" stay in the bowl. Most Germans answering to online questions stated that they preferred the German system (called Flachspüler), because with the flush toilet water from the bowl may spray up onto one's butt (following the equal but opposite reaction principle). (If you can read German google the topic. Lots of toilet humor.:-) 76.97.245.5 (talk) 23:31, 16 March 2009 (UTC)

To get splashed on the butt while flushing, you'd need to flush while seated. I always stand up before flushing; doesn't everyone else ? StuRat (talk) 01:44, 17 March 2009 (UTC)

Nope, they're talking about water splashing back up when solid feces drop into the bowl. Not while flushing. People did say it was easier to get a stool sample with a "Flachspüler" but that was not cited as the major advantage. It seems merely a side benefit. There seem to be quite a number of well established urban myths circulating. 76.97.245.5 (talk) 14:16, 17 March 2009 (UTC)

Wait, you just said "with the flush toilet water from the bowl may spray up onto one's butt". StuRat (talk) 19:08, 19 March 2009 (UTC)

Long time later, but it seem obvious there was simply a missing coma. The OP mean with the flush toilet, water... Nil Einne (talk) 09:05, 14 July 2011 (UTC)

Of course Wikipedia also writes about German toilets. See Flush toilet#Cultural variations. PrimeHunter (talk) 04:11, 17 March 2009 (UTC)

This topic is very interesting but does it really belong in the "Science" desk? :) --Taraborn (talk) 17:27, 17 March 2009 (UTC)

The OP probably didn't know why German toilets are like that and speculated that it has to have some scientific explanation. --Mr.K. (talk) 20:12, 17 March 2009 (UTC)

I've been building up pressure ever since I've read Tarborn's comment, but I'll try not to do a dragon flaming here. If the topic didn't develop into something "scientific" enough for some posters, how is this in the nature of the question? I apologize for not giving sufficient fluid dynamic background for my response, but that's not an area I'm comfortable in. Most reliable information being only available in German and buried in a deluge of urban myth and humorous ghits surely doesn't help us answer. I don't find Taraborn's comment appropriate in the least, though. We are already so firmly sticking to our "no medical advice" rule that people need to add grovelling disclaimers to any question even remotely connected to the human body or (heaven forbid!) diseases. Now we ridicule OPs for daring to ask whether there's a scientific background for a certain engineering feature? The fact that the answer in this case is more rooted in marketing, patent rights and consumer preference should not be taken as an excuse to discourage questions. I probably wouldn't have wasted a minute of thought on this if the above post weren't symptomatic of a sentiment I increasingly encounter to discourage asking questions in favor of regurgitating memorized "established facts". Engineering may not be quantum physics but pondering questions is what elevates it above assembly line work. I would wish people who are unwilling or unable to answer questions would take their posts elsewhere. Even wikipedia provides ample room for that on other pages. BTW: I was told the ref. desks were supposed to work as wikipedia's librarians. Any librarian who put that much effort into determining whether or not to answer a question instead of pointing the person at least toward the right aisle or shelf would deserve to be let go. 76.97.245.5 (talk) 15:27, 18 March 2009 (UTC)

While I agree with your sentiments, in general, in this case I interpreted Taraborn's comment as just meaning it would be better to post this on the Misc Ref Desk. I don't happen to agree, as there is definitely science and engineering involved in any answer to this Q, but I'm not mad at Taraborn for making the comment. StuRat (talk) 16:56, 18 March 2009 (UTC)

Yes, I was thinking what StuRat said, just that... And if you get that angry so easily my advice is that you should stay away from internet conversations, but I don't know if this is medical advice. --Taraborn (talk) 20:18, 18 March 2009 (UTC)

That seems like an over-reaction, they just misinterpreted a comment, as we all have, no big deal. StuRat (talk) 04:59, 22 March 2009 (UTC)

bladder removal

Does bladder removal surgery effect male verility and what other side effects 66.53.123.127 (talk) 18:29, 16 March 2009 (UTC)

Bladder removal? Is that even possible? The bladder is a vital organ. Do you mean gall bladder? --Tango (talk) 18:39, 16 March 2009 (UTC)

cystectomy 77.12.50.107 (talk) 20:24, 16 March 2009 (UTC)

The bladder isn't a vital organ, perhaps you're thinking of the kidneys, which filter waste from the blood and produce urine. The bladder only stores urine. As long as a path exists from the kidneys to the outside of the body, the waste can still be eliminated. Of course, without either an internal or external bag of some sort, urine will just drip out continuously, which is a major quality of life issue, though not fatal (unless it leads to death by suicide or some other cause). StuRat (talk) 01:16, 17 March 2009 (UTC)

Bladder removal surgery (cystectomy) has a number of complications, including a small number of men who require an inflatable penis prosthesis. Axl ¤ [Talk] 10:18, 17 March 2009 (UTC)

"Examples of complications include cardiovascular (myocardial infarction, bradycardia, atrial flutter, congestive heart failure), diversion-related (urinary leak, afferent/efferent limb malfunction or stenosis, stomal stenosis, urinary fistula, ureteroenteric anastomotic stricture), gastrointestinal (small bowel obstruction, gastrointestinal bleed, enteric fistula, hepatic failure, diarrhea), infectious disease (sepsis, pneumonia, pyelonephritis, abscess, urinary tract infection, clostridium colitis), lymphatic (lymphedema, lymphocele), neurologic (cerebrovascular accident, seizure, nerve palsy, psychosis), pulmonary (respiratory failure, pneumothorax, asthma exacerbation), renal (calculous disease, hyperchloremic metabolic acidosis, renal failure), vascular/thrombosis (deep venous thrombosis, pulmonary embolus, mesenteric thrombosis), wound/incision/hernia (superficial wound infection, incisional hernia, fascial dehiscence, parastomal hernia) or other (gout, drain migration, hydrocele)."

— Clark et al.

Axl ¤ [Talk] 10:32, 17 March 2009 (UTC)

Lice

Do lice have parasites that live on them? Thanks for info. --AlexSuricata (talk) 21:06, 16 March 2009 (UTC)

I'm not sure about on them (ectoparasites), but a few Rickettsia and Anaplasma species exist as parasites in lice (intracellular parasites). If lice have not yet been shown to carry Wolbachia (endosymbionts), they probably will. --Scray (talk) 22:49, 16 March 2009 (UTC)

Yeah - and if you're ever inclined not to panic over a few lice - check out the impressive list of human diseases that are attributed to Rickettsia's. Our article lists: typhus, rickettsialpox, Boutonneuse fever, African Tick Bite Fever, Rocky Mountain spotted fever, Australian Tick Typhus, Flinders Island Spotted Fever and Queensland Tick Typhus!! Sadly the ticks don't seem to mind them at all. Yikes! SteveBaker (talk) 23:05, 16 March 2009 (UTC)

C'mon now Steve, be fair. I've voted for a few lice, and some companies give 'em big bonuses. --Scray (talk) 23:12, 16 March 2009 (UTC)

Don't you mean you've voted for ticks ? "Politics" = poly + ticks, meaning many blood-sucking parasites. StuRat (talk) 01:02, 17 March 2009 (UTC)

No - you have the wrong derivation of the term. Politician is a mispronounciation of the french polyteteian - specifically a person with two or more faces. Traditionally, most politicians are, to this day, two-faced. SteveBaker (talk) 01:38, 17 March 2009 (UTC)

Hmm... perhaps it's the invertebrate parasites that we're treating unfairly. --Scray (talk) 02:13, 17 March 2009 (UTC)

Glad you provided the link, because otherwise I wouldn't have known which set of spineless bloodsuckers you meant. arimareiji (talk) 04:28, 17 March 2009 (UTC)

That was vicious. Nice one! --Scray (talk) 04:35, 17 March 2009 (UTC)

...here they are! --pma (talk) 18:37, 17 March 2009 (UTC)

Some little parasites suffer from smaller parasites: "Great fleas have lesser fleas upon their backs to bite'em, and little fleas have lesser fleas, and so ad infinitum." Edison (talk) 14:15, 17 March 2009 (UTC)

By the way, Edison's quotation is from A. de Morgan, who quoted Swift, and I wonder if Swift was quoting some other source (suddenly an horrific idea: is this a never ending chain of quotations?) --pma (talk) 11:08, 18 March 2009 (UTC)

It's described in "Ad infinitum". Axl ¤ [Talk] 13:33, 18 March 2009 (UTC)

Note that there is another version: "So naturalists observe, the flea hath little fleas upon his back to bite'em. And little fleas hath lesser fleas, and so proceeds, ad infinitem." To whom is that one credited? Edison (talk) 23:29, 18 March 2009 (UTC)

That looks like a conflation of the two verses. Axl ¤ [Talk] 08:08, 19 March 2009 (UTC)

Anticonflationally speaking, the verse "So Naturalists observe the flea, Have other fleas that on him prey, And these have others still that bite'em, and so proceed ad infinitum." was attributed in 1868 to "Hudibras." Apologies for slight variation in mu second quotation of the verse. There is some satisfaction in imagining the bedbug suffering from the bite of a still smaller parasite. Disappointingly, no reference to this appears in Hudibras or the 17th century poem about that character. Edison (talk) 01:36, 23 March 2009 (UTC)

Euclid's Elements

At the end of the opening of the article Euclid's_Elements it states "Not until the 20th century, by which time its content was universally taught through school books, did it cease to be considered something all educated people had read." Who/what/why/where/when did this happen? I find it interesting and perplexing to note the swift roundhouse kick delivered by Euclid_and_his_Modern_Rivals to its competitors in the late 19th century, and also Einstein's first words in his book on special relativity: "In your schooldays most of you who read this book made acquaintance with the noble building of Euclid's geometry, ..." If the Elements was so deeply entrenched in most education systems, what or who was the driving force behind getting rid of it? —Preceding unsigned comment added by 99.255.228.5 (talk) 21:46, 16 March 2009 (UTC)

We haven't gotten rid of it - we teach the same principles - just without the archaic language and old-fashioned terminology. I was certainly taught geometry from the axioms and theorems of Euclid...just not from that exact book. As a work, it's really remarkable in being probably the first book to approach mathematics methodically. Define some "obvious" axioms - then use the axioms to prove some simple stuff - then build proof on proof until you have things coming out of the system that are truly NOT obvious. It's what mathematics is all about. It's almost incidental that it teaches us the basics of geometry - although that's why most people would have been taught it. Furthermore, huge, interesting and (above all) useful areas of mathematics have been opened up by methodically pursuing what happens if you deny one or more of Euclid's axioms and follow where that leads you. Non-Euclidean geometry has come about (ironically) because of Euclid - where the Euclidean stuff was pretty much already known - but just not proven so rigorously. SteveBaker (talk) 22:59, 16 March 2009 (UTC)

I had a reasonably good math education in high school in Ontario, Canada, in the late 1960s / early 1970s, and we certainly did not learn Euclid's axioms. I never learned them in school, although I did read the Elements for fun later. We learned how to do formal proofs in geometry in high school, I think in grade 10, but they were not founded on an explicit set of axioms. On the other hand, in grade 13 we did some group theory on abstract operations, and that involved what amounted to reasoning from axioms. --Anonymous, 03:45 UTC, March 17, 2009.

This is the OP. I fully agree with both responses but also assert that there has been a major paradigm shift in math education. If you compare learning from a standard, universally agreed upon, axiomatic curriculum, like with the Elements, with the ever-changing, ad-hoc curriculum we have today (here in Canada at least), you have to admit something has changed. I was hoping for some literature on the subject but it's probably not that simple. —Preceding unsigned comment added by 207.245.46.74 (talk) 18:57, 17 March 2009 (UTC)

I believe it would be wrong to go back to Euclid's book for modern teaching. It truly is tough to read - even with a pretty good translator - because the language and the form of stating things is just so stilted. We do need to teach our kids to be able to discuss things with other MODERN mathematicians - so Euclid has to go. Now, the question of whether something modern should be taken as an alternative standard becomes just another debate about textbook A versus textbook B...which is a much more difficult debate. SteveBaker (talk) 21:18, 17 March 2009 (UTC)

Google: "Association for the Improvement of Geometrical Teaching".—eric 22:18, 17 March 2009 (UTC)

One reason is perhaps that mathematical arguments no longer use geometry as their foundation, as they once did. Nowadays mathematical concepts are built up from sets and some axioms about how to manipulate them. Also, as some other responses have mentioned, Euclid lacks a lot of the formal language that makes today's mathematics more rigorous. A line is breadthless length (book 1, definition 2) is fine to intuit but it needs formalization in order to be something you can work with mathematically. Strad (talk) 00:43, 18 March 2009 (UTC)

Actually, the most obvious way to modernize Euclid (and that taken by Hilbert) is not to rigorize the definitions of points and lines, but to avoid defining them at all. Algebraist 00:47, 18 March 2009 (UTC)

Painful bumps in Inner Lip

About four days ago, I started feeling a tiny bump on my bottom inner lip and in a matter of hours, it got bigger and painful (about the size of a bell pepper seed). It was flesh-coloured and had a little red dot. I went to bed that night and by the next day, it had disappeared. Today, I'm feeling the little tiny bump again and I'm afraid it's going to happen all over again. I'm freaked out because I don't know what it is. Has anyone experieced anything like this or have any information that might help? Many thanks. AC —Preceding unsigned comment added by 189.216.26.199 (talk) 22:44, 16 March 2009 (UTC)

I'm sorry but we are not allowed to answer this sort of medical question here on the reference desk. If you are concerned - you should consult a doctor. Sorry. SteveBaker (talk) 22:49, 16 March 2009 (UTC)

To expand on that, anonymous advice from random people on the internet is worse than useless when it comes to your health. Go see a doctor, tell them what you told us, show them, etc. 79.74.9.81 (talk) 22:54, 16 March 2009 (UTC)

Sorry, I didn't know that. Thanks to both. AC —Preceding unsigned comment added by 189.216.26.199 (talk) 22:57, 16 March 2009 (UTC)

This question's medical advice request status is being discussed here: Wikipedia talk:Reference desk#Possible medical advice question: "Painful_bumps_in_Inner_Lip". StuRat (talk) 15:08, 17 March 2009 (UTC)