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June 24

What kind of clothing do workers wear when doing work on power lines?

To protect themselves from electricity I mean. Do they wear rubber boots? ScienceApe (talk) 01:01, 24 June 2011 (UTC)

Most Linemen were standard personal safety equipment: gloves, safety hat, etc. For linemen that work on the sort of very high tension wires where they need protection from the electricty itself, they wear a sort of chain mail suit which acts as a personal Faraday cage. See this video. But most linemen don't need that sort of protection. The guys working in the cherry picker working on the lines running next to the road usually just wear a hard hat, gloves, and sturdy clothes. --Jayron32 01:19, 24 June 2011 (UTC)

(ec) Prepare yourself for a big surprise! They don't wear rubber boots -- they wear clothes made of steel wires. Amazing? Incredible? Well, what this does is, it allows the dangerous high-voltage electricity to flow around their body rather than through it. 67.169.177.176 (talk) 01:24, 24 June 2011 (UTC)

I don't know, but I bet they piss on the ground far less than the average person at that height above street level does (however low that percentage is normally already.) --188.29.15.168 (talk) 01:24, 24 June 2011 (UTC)

You betcha! If you piss on the ground when you have a 500 kV potential difference with it, you'll get charbroiled and won't even know what hit you. 67.169.177.176 (talk) 01:28, 24 June 2011 (UTC)

Not true; the urine breaks up into droplets. See MythBusters (2003 season)#Peeing on the Third Rail.--Shantavira|^{feed me} 06:08, 24 June 2011 (UTC)

FYI, a third rail "only" carries 500-800 volts (which can still be dangerous); a power line, on the other hand, can carry anywhere between 11 kV (your typical local distribution line on wooden poles) and 1150 kV (the high-voltage transmission line between Irkutsk and Alma-Ata). See the difference? 67.169.177.176 (talk) 21:50, 24 June 2011 (UTC)

I guess they didn't have 500 kV, which might be enough to create sparks between the droplets. Sometimes I wonder how large the current is when rain flows over the insulators of a high-voltage line. Icek (talk) 07:32, 24 June 2011 (UTC)

Large enough that you can get a corona discharge (which is AFAIK what causes that annoying buzzing sound that power lines sometimes make). 67.169.177.176 (talk) 21:42, 24 June 2011 (UTC)

Shockingly, peeing onto an electric fence is not recommended. I wouuuld know this from having not seen the live wire that zapped me. --Modocc (talk) 15:07, 24 June 2011 (UTC)

WP:OR I've heard of a worker who was fatally electrocuted when he (unknowingly) pissed on a live electric cable which was carrying "only" 11 kV (and was insulated, as well). 67.169.177.176 (talk) 21:36, 24 June 2011 (UTC)

Mythbusters agree on that one, the test above was for the third rail where a person would be too far that urine was bound to break up. (This is referenced in the above article I believe because I read it a few weeks ago.) For an electric fence the person can be much closer. I do agree that applying a low voltage situation to the high voltage of power lines doesn't work Nil Einne (talk) 05:51, 25 June 2011 (UTC)

Um, don't they just switch off the electricity in those power lines before the workers climb up? – b_jonas 13:37, 24 June 2011 (UTC)

It depends on the kind of work that is being done. For routine maintenance or inspection on very important wires, shutting them off is not necessarily an economical or desirable option (shutting off the electricity for an entire region, for example, can cause more danger to more people than it would to a properly trained operator). This is a pretty amazing video showing how inspections of high voltage transmission wires are done. As you can tell, they are very live — the operator is just kept away from anything that could ground them. He does not appear to have anything protective on (because he's not grounded). --Mr.98 (talk) 14:44, 24 June 2011 (UTC)

That hooded suit he's wearing is probably full of metal wires - it's a lighter version of the chain mail mentioned above. --Tango (talk) 22:52, 24 June 2011 (UTC)

Yeah, in the video, the guy says that the suit in the video is made out of 25% stainless steel thread. Red Act (talk) 02:46, 25 June 2011 (UTC)

Most electric utility workers you see working on poles next to the road are working on subtransmission lines of say 4kv to 34kv AC phase to phase. The transmission lines of 69kv, 138k and higher are a different kettle of fish. No practical amount of rubber protective gear would insulate a grounded worker from death when he touched an energized transmission line, so he works it deenergized or while isolated from ground, and the conductive suits come into play. If the transmission line worker were also touching something grounded, the conductive suit would not protect him from incineration. At the lower subtransmission and distribution voltages, insulation is practical and live line work is done commonly. The gear is beyond what an amateur could likely conjure up so do not attempt it. US utilities would typically require them while working on 12kv or 4 kv wires to wear a hardhat, approved safety glasses, fire retardant shirt and pants, "serviceable shoes" which have substantial soles and come high enough to provide ankle support (no sneakers or running shoes). No metal conductors under the protective gear. If they climb the wooden pole, they will use a climbing belt which goes around the pole and they would have "gaffs" attached to their boots which dig into the pole. They have to lean back for the belt and gaffs to hold, and they lean in too much, they will find themselves sliding down a splintery pole. If they are going to be near live high voltage wires they will wear thick rubber gloves tested to insulate to a higher voltage than the energized equipment in question (way thicker than dish washing rubber gloves), which have leather protective gloves outside them to protect from abrasion. They are likely to wear a harness for fall protection, with a rope which extends to break the fall in a shock absorbing way. The harness also allows them to be more easily lowered to the ground by rescuers if they are knocked unconscious. They are likely to additionally wear rubber sleeves which protect the arms. All this is heavy, cumbersome and hot, and there is a temptation to take short cuts, so there are commonly unannounced safety audits by supervisors. Mistakes and carelessness lead to death, severe burns, and amputations of burned limbs. A worker doing some switching operation at ground level might wear variations on the above equipment, less the climbing belt, gaffs, and harness, but adding an insulating cape and facemask, since a switching error could produce a huge fireball for a bit until fuses or breakers operated. Power voltages of 480 and up are good at sustaining an arc which incinerates everything in the room, besides the electrocution hazard. Edison (talk) 15:58, 25 June 2011 (UTC)

This is an interesting problem. A person of length L stands on the ground, wearing perfectly insulating shoes. He is right underneath a powerline at a height of H above the ground. The powerline is at a voltage of V, the angular frequency is omega. Estimate the current through the person. Count Iblis (talk) 18:36, 25 June 2011 (UTC)

Negligible. It's only going to be significant if you get arcing, where the air is turned into plasma and becomes much more conductive. --Tango (talk) 18:42, 25 June 2011 (UTC)

Which brings up another question: Do linemen who work on high-voltage power lines (300 kV and up) really walk around with a halo around their heads? 67.169.177.176 (talk) 18:49, 25 June 2011 (UTC)

muscle cramp consequences?

From time to time I get muscle cramps, usually in a calf or hamstring, at which time my body basically tells my brain that I need to do whatever it takes to straighten that muscle and prevent it from contracting further. After pulling my toes towards my knee (calf cramp) or straightening my leg (hamstring cramp), the cramp passes (unwinds, kinda) and the muscle returns to normal function. I think most people here have experienced this process, certainly any athletes. What I'm curious about is what would happen if I did not stretch out the cramping muscle? if I just let it continue to seize up and contract? Does the cramp impulse eventually dissipate? can the muscle actually damage itself through a prolonged contraction? I've always wondered about this but have never been quite curious enough to put up with the pain and cognitive dissonance (why aren't you straightening that muscle? this is an emergency!) to experiment on myself... The Masked Booby (talk) 02:17, 24 June 2011 (UTC)

I can speak (WP:OR) for foot, calf and quad, ab- and adductor cramps. I was not able to get out of bed easily for about 10 days post surgery, during which time I had horrendous cramping. There is a peak point (very painful) in a cramp and it can hold there for what seems like forever, but is probably measured in minutes, and then it fades. You can't think about much else when it is happening, and I can now understand how cramps can cause swimmers to drown. I am not suggesting this will be everyone's experience. The article Cramp says nothing about possible damage from them. Bielle (talk) 02:32, 24 June 2011 (UTC)

In corroboration of Bielle, I can also offer some personal experience. For a period during my teens, I suffered occasional calf muscle cramps when sitting on wooden chairs in my (very crowded) school chapel during longer Sunday services. Since there was already very little space to move, and because drawing attention to myself was something to be avoided, I just had to leave my muscle contracted and grit my teeth until the cramp passed of its own accord after a few (2-4) minutes (incautious tensing of the muscle for 10 minutes or so after it had would sometimes cause it to return). No apparent muscle (or tooth) damage resulted. {The poster formerly known as 87.91.2301.95} 90.201.110.36 (talk) 17:29, 24 June 2011 (UTC)

Sugar water injection

On season 3 episode 12 of the espionage television series Burn Notice, a character uses a syringe to inject another character with sugar water in order to deceive that other character into believing that he had been injected with a deadly poison when in fact he had been injected with something harmless. Is it really true that injected sugar water is harmless? And why would the character use sugar water rather than just plain water? Was the sugar an unnecessary detail by the writers? —SeekingAnswers (reply) 14:53, 24 June 2011 (UTC)

Typically, doctors will use saline when giving fluids intravenously. One of the main reasons for this is that they want a solution which is isotonic with blood, so that the cells don't swell up from water absorption (see picture on that page). With saline, the osmotic pressure of the solution is regulated by salt, but osmotic pressure can also be regulated by any solute, including sugar. Why did the writers specify sugar instead of saline? I'm not sure, but my guess is that they were making a connection to the concept of a placebo, which are sometimes colloquially referred to as "sugar pills". -- 174.24.222.200 (talk) 15:46, 24 June 2011 (UTC)

Another couple of questions then: How does one go about determining how much salt or sugar is necessary for the solution to be isotonic with blood? And why would swollen cells be bad — that is, what kind of symptoms would present themselves? —SeekingAnswers (reply) 01:28, 25 June 2011 (UTC)

Initially, it would have to be determined experimentally, for example with an osmometer, or by observing the effect of solutions of various concentrations on red blood cells. However, since osmotic pressure is a colligative property, once you figure out the concentration needed for one solute, you can figure it out for pretty much any other. Typical IV saline is 9g/L, which is about 0.154 M NaCl, or 0.307 M solute molecules (0.154 M Na⁺ + 0.154 M Cl^-). So you would need about a 0.3 M sugar solution. For a typical 10 mL syringe, this works out to about 1.05 g of sucrose (or 550 mg of glucose). A quick experiment with a kitchen scale shows this to be about 1/4 of a tsp of sucrose (probably about the amount of sugar in a small hard candy). - Regarding swollen cells, a temporary swelling of the cells isn't so much of a problem, (as it will likely reverse when the cells hit general circulation, and the hypotonic bolus is diluted out) but that if the solution is hypotonic enough, and the cells are bathed in it long enough, the cells may swell to the point at which the membranes rupture. This is called hemolysis, and if it happens to enough of the cells, can be fatal (although I doubt a ~10mL pure water bolus would cause enough damage to be fatal in most cases). -- 174.24.222.200 (talk) 17:56, 25 June 2011 (UTC)

Alternatively, IV bottles may also contain glucose. ~AH1 ^(discuss!) 16:18, 24 June 2011 (UTC)

Note that the sugar solution given in hospitals is highly diluted (with water). Injecting a stronger concentration of sugar could be deadly. StuRat (talk) 17:19, 24 June 2011 (UTC)

An strongish isotonic balanced, glucose injection would cause a sugar rush. A subject so primed could very well believe this to be the symptoms of poisoning. This sort of conviction was observed by doctors in the Nazi death camps during their experiments. During the the 1991 Iraqi missile attack on Israel, a number of people suffocated in independent incidents, thinking that carbon dioxide poisoning was confirmation of a gas attack and so dared not to take there gas masks off (they forgot to take the seals off the filtration canisters). [1] --Aspro (talk) 21:49, 24 June 2011 (UTC)

I'm not sure what you mean when you wrote "an strongish isotonic balanced." That doesn't seem to be proper English. Could you clarify? —SeekingAnswers (reply) 01:28, 25 June 2011 (UTC)

The sugar rush is unlikely to be true. I haven't looked over the article Hyperactivity#Sugar_consumption. Imagine Reason (talk) 14:04, 25 June 2011 (UTC)

Also questioning the normal (nondiabetic) person perceiving a "sugar rush" from glucose in the bloodstream. If he eats candy or drinks a 32 ounce sugar soft drink, there will be heightened glucose in the bloodstream, leading the pancreas to release insulin, preventing the blood sugar from going very high. Consider the old glucose tolerance test, in which the blood sugar goes high after a big dose of glucose orally, but promptly comes back down in the normal person. No strange sensation in the gluconormal. Edison (talk) 15:32, 25 June 2011 (UTC)

32 ounce, is that 2 pints? Can someone drink 2 pints of sugary drink? That is a huge dose, surely? Half a pint would be a more normal drink but still quite a hit of sugar. Or am I wrong about the quantity? Itsmejudith (talk) 21:37, 25 June 2011 (UTC)

It is a huge dose, but people really do drink it. Note that it's two American pints; if you're used to Imperial pints, those are bigger. --Trovatore (talk) 00:25, 26 June 2011 (UTC)

7-Eleven has drinks up to a gallon in size, although that one is called the "Team Gulp", implying it would be shared. The "Double Gulp" is 64 ounces, though, and I bet some people drink that solo: 7-Eleven#The_Big_Gulp. StuRat (talk) 02:43, 27 June 2011 (UTC)

fish

Do fish sleep? — Preceding unsigned comment added by 69.27.150.44 (talk) 15:30, 24 June 2011 (UTC)

If I remember correctly, they do, but they swim while they do; that might just be sharks though. Sir William Matthew Flinders Petrie | Say Shalom! 15:32, 24 June 2011 (UTC)

There is some information (but not a lot) at Sleep (non-human)#Sleep in fish and reptiles. Gandalf61 (talk) 15:41, 24 June 2011 (UTC)

Fish are incapable of closing their eyes, so they look awake when they sleep. Dolphins meanwhile sleep with one eye open. ~AH1 ^(discuss!) 16:17, 24 June 2011 (UTC)

Yeah, but the guy asked about fishies, not about sea-going mammals. :p It is nice to note though (they're just like cats then). Sir William Matthew Flinders Petrie | Say Shalom! 16:53, 24 June 2011 (UTC)

And yet, a sea-going mammal is more closely related to a bony fish than said fish is to the types of "fish" referenced in Flinders Petrie's reply. Yay Linnaean taxonomy! Buddy431 (talk) 04:26, 25 June 2011 (UTC)

There is a downloadable PDF at #14 "Sleep in fishes". Bus stop (talk) 17:01, 24 June 2011 (UTC)

This may or may not have bearing on the question (joke). According to our article, Luca Brasi (fictional character in Mario Puzo's novel The Godfather) "…sleeps with the fishes". Bus stop (talk) 17:18, 24 June 2011 (UTC)

In that case, the fish aren't necessarily sleeping. He's, er, sleeping. With fish around him. Grandiose (me, talk, contribs) 20:47, 24 June 2011 (UTC)

Precisely. He's "sleeping", and he's with the fishes. Or whatever the equivalent creatures are in the Hudson. David Feldman, author of a number of "Imponderables" books, titled one of them "Do Fish Sleep?" or some such. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:32, 24 June 2011 (UTC)

June 25

Halo effect?

What is the psychology term used to describe when a person's head is encircled in a halo to improve their public image? (Not for religion or the Halo effect) For example, Obama is often portrayed in front of a brightened circle, or out of focus seal.Smallman12q (talk) 00:36, 25 June 2011 (UTC)

I'm not sure there is a term, but I will point out that there are similar photos of Bush as well (do a Google Image search for "Bush halo" -- it seems pretty common given the practice of putting seals in the background). (And for something else entirely, do a Google Image search of "Ashcroft Spirit of Justice".) --Mr.98 (talk) 02:07, 25 June 2011 (UTC)

Well, I think a psychologist would say that that is in fact an example of the halo effect in action. Looie496 (talk) 00:49, 26 June 2011 (UTC)

The halo effect has nothing to do with visual halos. --Mr.98 (talk) 14:00, 27 June 2011 (UTC)

Appeal to authority? Guilt (albeit positive) by association? Imagine Reason (talk) 14:03, 27 June 2011 (UTC)

It gives the appearance that the person is wearing a hat. Hats have been historically associated with power. Bit speculative. ~AH1 ^(discuss!) 01:46, 30 June 2011 (UTC)

Unknown bug

[2] Can anyone tell me what kind of bug this is? The photo was taken in the US state of Connecticut. It's roughly 5+ inches long. Thanks, Dismas|^(talk) 01:00, 25 June 2011 (UTC)

I believe that's a dobsonfly. Looie496 (talk) 03:29, 25 June 2011 (UTC)

Known "for its kingly features and intimidating tusks", apparently. I love Wikipedia.--Shantavira|^{feed me} 07:21, 25 June 2011 (UTC)

Thanks!! Dismas|^(talk) 13:50, 25 June 2011 (UTC)

Why are bird droppings white?

Why are bird droppings generally predominantly white, while those of most other creatures are predominantly brown? -- Jack of Oz ^{[your turn]} 03:03, 25 June 2011 (UTC)

Most mammals (including humans), as well as amphibians, excrete most of their nitrogen waste as urea, in urine. Fish tend to get rid of nitrogen waste as ammonia. Birds and reptiles metabolize nitrogen waste to uric acid. Uric acid is not very soluble in water, so birds don't excrete it dissolved in urine, the way mammals do urea. Rather, it is excreted with other solid waste, in the form of a white paste. Buddy431 (talk) 04:19, 25 June 2011 (UTC)

And because uric acid comes in the form of white crystals, hence the colour. Yes, I wanted to ask this additional question but found out from the article. --Ouro (blah blah) 07:28, 25 June 2011 (UTC)

Lovely, thanks both of you. -- Jack of Oz ^{[your turn]} 08:46, 25 June 2011 (UTC)

Is there anything else you guano know ? StuRat (talk) 18:32, 25 June 2011 (UTC)

Not at the moment, thanks. If I feel so moved, I'll go to the right place.  :) -- Jack of Oz ^{[your turn]} 21:48, 25 June 2011 (UTC)

No, much to the regret of gout sufferers, humans do not excrete urea, or even allantoin like pigs do, but the sparingly soluble uric acid. I remain curious whether the high uric acid levels help account for why so many predators spit humans out, as eating shark meat high in uric acid or other ammonia rich compounds can be harmful. Wnt (talk) 22:23, 25 June 2011 (UTC)

You're wrong - read the articles urea and uric acid. Urea is the waste product in mammals (including humans) for most sources of nitrogen. Uric acid is only the end product for the Purine metabolism. Most mammals further break uric acid (from the Purine metabolism) down into Allantoin via Urate oxidase. Birds and reptiles, on the other hand, convert nearly all of their nitrogenous waste into uric acid (and excrete it along with their feces). Buddy431 (talk) 03:34, 26 June 2011 (UTC)

From uric acid: "In humans and higher primates, uric acid is the final oxidation (breakdown) product of purine metabolism and is excreted in urine." This is also why humans get uric acid kidney stones. Now I should add, however, that I have some personal doubts about the perfect truth of this statement, because urate oxidase happens to have a "stop codon" right in the catalytic site that happens to use the sequence for selenocysteine, though it doesn't have a good SECIS. I have a feeling humans might just use the very low amounts of RNA produced for this gene to make some amount of functional protein for specialized purposes, and therefore can go on from uric acid in some small percentage of the total metabolism. But that's just personal speculation. Wnt (talk) 07:32, 26 June 2011 (UTC)

Right, the key words being purine metabolism. Humans excrete purine waste products as uric acid, but nearly all other nitrogen waste products as urea. Uric acid only counts for a small amount of human nitrogenous waste (though still enough to cause gout). On the other hand, birds and reptiles excrete nearly all of their nitrogenous waste as uric acid (as a solid, along with the feces). Buddy432 (talk) 03:00, 27 June 2011 (UTC)

Wow. Never so blind as when you think you know... I've looked it up, and yes, urea is described as 20-30 or 25-30 grams per day, whereas uric acid is 250 mg - 750 mg per day.^[3] So yes, indeed, urea is much more important than uric acid in terms of total nitrogen excretion! Wnt (talk) 04:49, 27 June 2011 (UTC)

I think maybe snakes excrete most of their nitrogen as uric acid. That's what sticks in my head from the "Nitrogen" chapter of Primo Levi's mostly-nonfiction-novel (if that makes sense) The Periodic Table. Levi recounts needing a quantity of the stuff, and contacting a zoo with a large snake to see if they'd give him his feces. The zookeepers were quite indignant that this nobody was asking for the precious snake crap, which of course was all spoken for. --Trovatore (talk) 16:55, 27 June 2011 (UTC)

Magnetic field of sun

please compair the magnetic field of sun and earth .Is there any major diffrence between them ?and why?--Akbarmohammadzade (talk) 05:13, 25 June 2011 (UTC)Iran

Is this a homework question? We have articles on the Solar magnetic field and the Earth's magnetic field, go have a read and if you still have specific questions then come back here. Cheers, Ouro (blah blah) 06:56, 25 June 2011 (UTC)

As I was decided to discuss about this subject Ibrought It,here I want to say my idea: The periodical variation of sun body and its convection ,make the sun to have global magnetic fields outside and inside of its body .the plasma body of sun make it not to be able to have magnetic poles such as earth ,in addition its rotation round its axies has defferenet speeds from equarter to pole. The major defference between earth magnetic field and sun's one is that earth has iron core and semi stable solid body . but the magnetic fields in sun are the result of movement of electeric particles .akbarmohammadzade--78.38.28.3 (talk) 07:35, 26 June 2011 (UTC)

The solar wind

It is supposed that the solar wind moves direct planetary orbital .but it might be all around any quarter of sun , then we can suppose that the kuiper belt be sphrical round solar system (not ring ). is it because of Einshtein general relativity that the solar wind have to move in such direction?--Akbarmohammadzade (talk) 05:31, 25 June 2011 (UTC)Iran

Huh? As we read in our article on the Kuiper belt, the belt resembles a torus with the main concentration extending to around ten degrees outside of the plane of the ecliptic. It is not spherical (hence the designation 'belt'). The Solar wind, which I believe radiates in all directions from the star, doesn't really have much to do with its shape as far as I know, though I might be wrong. That's all I could understand from your question. --Ouro (blah blah) 07:03, 25 June 2011 (UTC)

Have a look at Oort cloud. Plasmic Physics (talk) 11:09, 25 June 2011 (UTC)

Indeed, the Oort cloud is spherical. Neither the Oort cloud of the Kuiper belt have anything to do with solar wind, though. --Tango (talk) 13:25, 25 June 2011 (UTC)

And the radiation of particles, like anything else, occurs in all directions from the source. If the solar wind does push the planets outward in their orbit a bit, I would expect only a tiny effect, and for it not to be cumulative, since the orbital speed ultimately controls orbital distance. Think of it like a fan blowing a ball upward. It only moves up a bit, since gravity holds it down. StuRat (talk) 13:43, 25 June 2011 (UTC)

The solar wind doesn't have much effect on orbits, but radiation pressure does. It's particularly significant for asteroids. Also, the solar wind isn't going to completely spherically symmetrical because it is affected by the sun's magnetic field, which isn't spherically symmetrical. --Tango (talk) 18:47, 25 June 2011 (UTC)

well the O'ort belt is far from us , but we can see the effects of Kuiper belt where that first send water here to earth. ( in fact I am studying about the efects of solar wind on production of water in solar system , which cased the existance of life in this system) Akbarmohammadzade (talk 08:52, 26 June 2011 (UTC)

You may be interested in the Heliopause. ~AH1 ^(discuss!) 01:43, 30 June 2011 (UTC)

Standard enthalpy of formation

How much is C(g)'s standard heat of formation?--M940504 (talk) 10:24, 25 June 2011 (UTC)

The same as graphite's standard heat of vaporisation. Plasmic Physics (talk) 11:06, 25 June 2011 (UTC)

Use of figures from copyright protected references

I am referring to figures which I personally drafted in the first place and which ended up in published articles that I coauthored (e.g., in Journal of Inorganic Biochemistry, etc., not someone else's articles). Is this forbidden by Wikipedia? Figures certainly help to clarify concepts in any review-type article.

A am attempting to write an account of a specific area of chemistry. I see figures used this way in review articles all the time (e.g., page 8 of the Encyclopedia of Vitamin-E used images from a paper I coauthored, which was published in Biochimica et Biophysica Acta. originally). Jrwright72626 (talk) 11:27, 25 June 2011 (UTC)

See WP:DCM. This sort of question is generally better asked on the Help Desk. Tevildo (talk) 12:44, 25 June 2011 (UTC)

Yes, see the help desk in the first instance. DCM may not be necessary; it depends what you mean by 'figures', if, as one might think, you mean illustrations of some kind, then DCM may be necessary. Grandiose (me, talk, contribs) 12:49, 25 June 2011 (UTC)

DCM probably doesn't apply in this case, since most journal publications require authors to transfer their ownership/copyright of all published material to the journal. Figures that are reproduced in a review article without any substantial changes require the permission of the original journal (that's why it often says "reproduced with permission from ..."). I doubt that a journal would donate their materials to be freely reproduced on Wikipedia, and if a copyrighted image is found in an article it will most likely be removed. If you are interested in contributing figures to Wikipedia, it would probably be best to create new figures and publish them into the Wikimedia Commons so that they can be freely used. --- Medical geneticist (talk) 13:40, 25 June 2011 (UTC)

While the help desk is the best place for questions concerning using or contributing to wikipedia in general, the best place for this specific question is probably Wikipedia:Media copyright questions, I suspect you may be directed the if you asked at the help desk. Nil Einne (talk) 13:55, 25 June 2011 (UTC)

Medical geneticist is right -- I should create entirely new figures. I do have some photos and diagrams (of a spectroscopic display, electrophoretic separations, etc.) that have not been published anywhere. Obviously I could use those without having to go through a lot of letter writing. Jrwright72626 (talk) 16:19, 25 June 2011 (UTC)

Fortunately the US doesn't have database copyright, but for those unfortunately living in countries that do, I don't know if even redrafting a graph would be legal - it might be that the journal claims to own the results themselves. Though I would not criticize someone for posting the data here anyway, nor would I support any effort of Wikipedia to collude in the enforcement of such regulations. Wnt (talk) 21:10, 25 June 2011 (UTC)

Lasalocid

I looked for further information on this chicken food additive because a local stock food company has just recalled several batches after accidentally adding lasalocid to chicken mash and feed pellets. One of the warnings in their advertisement was that it should not be fed to dogs. I thought this might be a useful addition to the Wikipedia entry.

Regards, Heather March — Preceding unsigned comment added by 218.101.90.35 (talk) 21:35, 25 June 2011 (UTC)

There are many references to this problem and I have amended the article with an appropriate reference from the Veterinary Record of the British Veterinary Association. Thanks for that Heather, for future reference it is usually better to leave a note like this on the 'talk' page of the article which will bring it to the attention of any watchers of that page. Richard Avery (talk) 10:12, 26 June 2011 (UTC)

Permian–Triassic extinction event

Hi, I couldn't help but compare the data of this event with human impact and climate change. The extinction figures were pretty much as they are today according to the estimates and there was afterwards a huge geological event which began as a *greenhouse effect* and countiniued into a super hot world that even any trace of humanity would probably not survive.

Let's say that at that time an intellegent life form became dominant over the earth causing the extinction event, not dissimilar to the corresponding present figures which are showing massive extinctions that we cannot even explain. Let's say that this civilisation caused a greenhouse effect, much in the way that present day earth is believed to be going. No coal seams are recovered from that time as though something not only made the trees extinct, but also performed the magic of making them disappear as well?

Excerpt:

"This pattern is consistent with what is known about the effects of hypoxia, a shortage but not a total absence of oxygen. However, hypoxia cannot have been the only killing mechanism for marine organisms. Nearly all of the continental shelf waters would have had to become severely hypoxic to account for the magnitude of the extinction, but such a catastrophe would make it difficult to explain the very selective pattern of the extinction. Models of the Late Permian and Early Triassic atmospheres show a significant but protracted decline in atmospheric oxygen levels, with no acceleration near the P-Tr boundary. Minimum atmospheric oxygen levels in the Early Triassic are never less than present day levels—the decline in oxygen levels does not match the temporal pattern of the extinction."

Is it not a good theory that intelligent life evolved and destroyed the planets ecology, themselves with it, and so on from there?

~ R.T.G 22:37, 25 June 2011 (UTC)

Note: Colony collapse disorder, Decline in amphibian populations etc etc ~ R.T.G 22:41, 25 June 2011 (UTC)

This makes a good sci-fi story, but there are problems. First, I'd think that sentient species at any time would have been fairly likely to invent clay pots, and the broken shards of clay pots should have turned up in sediments somewhere. Next, I'd kind of expect whatever species involved would develop a larger brain, which would be noted as remarkable by paleontologists - and I'd expect their remains to be found, because it's hard to destroy the Earth if you don't have numbers. And when found, shouldn't they have something, some weapon or possessions, some part of the time? Last, how do the Siberian Traps fit into this scheme? It seems as easy to believe that two spaceships were having a war and a stray shot found its way to Earth, creating the Traps and causing all the atmospheric changes. Wnt (talk) 23:56, 25 June 2011 (UTC)

To answer your question directly. No! it's not a good theory because there is no supporting evidence. The (It's all happened before theory) was popular in the sixties, hence the great thoughtfull song [Year 2525].190.148.136.161 (talk) 00:30, 26 June 2011 (UTC)

(ec) To get an idea of why it's pretty implausible, consider what the fossil record millions of years from now would look like if humans did end up wiping themselves out due to climate change sometime over the next few centuries. There would be more than a bit of evidence of our civilization: buildings, roads, technology, not to mention the shear scale of the number of humans that would leave their skeletal remains behind. You're suggesting some creatures had a climate impact on the planet on that scale or larger but left no trace at all of their existence. What was all that coal being burned by/for? Rckrone (talk) 00:35, 26 June 2011 (UTC)

I don't think that's true. What evidence do you think will be left in the fossil record millions of years from now? Perhaps a few human skeletons (fossilisation is a fairly rare event), which someone expert in mammals (assuming such still exist) might possibly note showed signs of little hard labour, but then again we'd expect most of the human skeletons that have ever existed to show signs of a normal workload. Perhaps they'd puzzle over the large skull and small pelvis? But I wouldn't expect any fossil record of our roads or buildings or technology, except maybe a curious thin layer (representing a very brief time) higher than usual in hydrocarbons and radioactive elements. If we're lucky. A million years is a very long time: flint cutting tools might survive, but concrete won't. Even looking at Roman artifacts in Britain, nowhere near that old, shows the problem of missing artifacts made from iron (which have long since corroded to nothing. Maybe, with all the digging we've done, we'll show up as a puzzling mismatch of eras for several layers in a few locations, followed by more sensible, chronological layers on top.

There was an interesting TV series exploring this topic not long ago. Was it Life after us? Or something like that. 86.164.67.252 (talk) 12:45, 27 June 2011 (UTC)

June 26

Hotspot underneath Iceland is the same one that produced the Siberian Traps?

In this article, it is mentioned that the hotspot that produced the Siberian Traps may be underneath Iceland now. But do have have 250 million years of continuous volcanism from today in iceland to the formation of the Siberian Traps, 250 million years ago? Count Iblis (talk) 00:46, 26 June 2011 (UTC)

The article you cited did not claim that the plume that caused the Siberian trapps is now under Iceland. It said that a gigantic impact in Antarctica may have caused the Sib. trapp by antipodal disruption and incidentally may also have contributed to the Iceland plume. 190.148.136.161 (talk) 01:49, 26 June 2011 (UTC)

Prehistoric Scotland says that there was a lot of volcanic activity around the Scotland area in that same time period. The Icelandic plume is thought to have migrated N-W. from that area helping to open the North Atlantic.190.148.136.161 (talk) 02:07, 26 June 2011 (UTC)

It's a bit of a jump to get from the Siberian Traps to the Iceland plume, although in between there is the High Arctic LIP, which was mainly active in the middle to late Cretaceous (so about 100 to 80 million years ago), and the North Atlantic LIP which was active from the latest Cretaceous up to the end of the Paleocene (about 70 to 55 mya). The iceland plume reached its current location in the Mid-Atlantic Ridge by the Miocene (about 15 mya). Some people have suggested [4] following plate reconstruction that the siberian traps are located exactly where the North Atlantic LIP was to erupt some 180 my later, but I'm not sure that this is the view of everyone working on these things. Mikenorton (talk) 18:14, 26 June 2011 (UTC)

thanks! Count Iblis (talk) 15:13, 27 June 2011 (UTC)

crossing over

If I stood, or sat in my rowboat, at the east side of the international date line (somewhere in the Pacific), and then I stepped or rowed to the other side of the line. Would today now be tommorrow or yesterday? 190.148.136.161 (talk) 00:59, 26 June 2011 (UTC)

If it is midday on Tuesday on the east side of the line then it is midday on Wednesday on the west side of the line. See International Date Line for more information. --Tango (talk) 01:20, 26 June 2011 (UTC)

Of course, today is still today on either side of the line. It is simply that our time-keeping convention is to call today Tuesday on one side of the line, and to call today Wednesday on the other side of the line. It's just an arbitrary change of co-ordinates. Gandalf61 (talk) 08:12, 26 June 2011 (UTC)

It affects business in the South Pacific. When it is Monday morning in New Zealand and Australia it is Sunday morning on some Pacific Islands and the businesses there then suffer. Some Pacific Islands have decided to move one day ahead to deal with this problem. Count Iblis (talk) 17:07, 26 June 2011 (UTC)

The way to remember which is which is always to remember that as land moves to the east it moves later in time. (i.e. the Sun rises up over it) So the west edge of the date line is the furthest point east in the world, and so it's the latest time zone.

My suspicion is that there are many small and large ways (also road conventions, negotiating teams, human rights issues, Whale Wars) in which it looks like Australia is becoming more of a regional power over much of the South Pacific. Wnt (talk) 04:21, 27 June 2011 (UTC)

Constitutional walk [close to speed of light] on Einstein’s treadmill:

Although the stepping positions in space would remain same but would the moving clock on such a treadmill be slowed down? As air time is involved in RUNNING therefore WALK should be considered in the scenario - non-broken connection between walker and walk belt 68.147.41.231 (talk) 03:21, 26 June 2011 (UTC) Eccentric Khattak No.1

Yes, a clock attached to the treadmill belt would run slow, as observed in the racewalker's inertial frame of reference.

The footfalls all occur at the same location in space according to the racewalker's frame of reference (or really the same two locations, since the racewalker has two feet), but they do not all occur at the same location according to the belt's frame of reference. In the belt's frame of reference, the footfalls occur at the locations of the footprints left behind on the belt, which in the belt's frame of reference are stationary.

The two frames of reference do not necessarily agree as to whether the person is running or walking. The event of a front foot landing and the event at around the same time of a rear foot leaving the belt occur at two different locations, so there's relativity of simultaneity to deal with. I.e., the two frames of reference may disagree as to whether the rear foot has left the belt yet as of when the front foot lands. Red Act (talk) 12:06, 26 June 2011 (UTC)

Also, unless the belt is moving less than half the speed of light (in the racewalker's frame of reference), walking instead of running would be impossible, because walking would require the feet to move faster than the speed of light. Red Act (talk) 12:41, 26 June 2011 (UTC)

The person can be walking in their frame no matter how fast the treadmill is going, it just won't necessarily be walking in the treadmill frame. Rckrone (talk) 16:03, 26 June 2011 (UTC)

How do you define "their frame" for someone walking? Is that the frame of their head? I don't think it is possible to walk (on solid ground or a treadmill) faster than around 0.5c, since your feet need to move faster than your overall speed (in the lab frame) in a walking motion. The same is true of a vehicle travelling on wheels - the top of the wheel moves at twice the speed of the vehicle, so it can't go faster than 0.5c (in that case, it is exactly 0.5c, I'm not sure exactly what the top speed would be for a walker). --Tango (talk) 18:30, 26 June 2011 (UTC)

Yeah, I do mean their head. That seems like the only reasonable way to define "their frame". In that frame there's clearly no problem with having one leg moving at say 3c/4 in one direction and the other leg moving at 3c/4 in the other, and then at some regular interval both quickly switching direction (if you ignore the difficulty of accelerating a leg so much). Here I'm imagining the body and two legs as 3 separate objects. From the lab frame the person would be running, since the lift of the back foot would be well before the fall of the front one. The two leg speeds would be 0 and 24c/25, but clearly each leg would be spending the majority of the time moving forward since the average speed is still 3c/4. I can't think of any reason why c/2 would be any more of a barrier with wheels, but things get messy trying to describe "rigid" bodies rotating like that. Rckrone (talk) 05:07, 27 June 2011 (UTC)

In the lab frame, if a car is moving at c/2 then the top of its wheels are moving at c, hence the car cannot move at c/2 or faster (in reality, if you tried the wheels would spin - what we've found is a fundamental limit to friction between the wheel and the road). --Tango (talk) 11:52, 27 June 2011 (UTC)

In the frame of the wheeled vehicle, all we have is a rotating object that has a speed of c/2 at the edge. There's nothing impossible about that (besides holding an object together under so much force). In the lab frame the top of the wheel is not moving at a speed of c, it's going at 4c/5. From this perspective the wheel is pretty distorted, seeing as more of the outside edge of the wheel is on the top than on the bottom at any given time. You can think of the wheel case is basically like having a lot of feet. Rckrone (talk) 15:43, 27 June 2011 (UTC)

Yeah, that was another poorly worded sentence on my part. I should have put "(in the treadmill belt's frame of reference)" after the phrase "walking instead of running" in my post, because otherwise it sounds like the racewalker's frame of reference is being used to define walking vs. running, since that's the only frame of reference mentioned in that sentence.

I'll spell out and explain the c/2 limit in detail to make it clear to everybody (hopefully). In any reference frame used to define "running" vs. "walking", assuming the left and right footfalls are evenly spaced in terms of time and distance, "walking" means that each foot spends at least 50% of the time (in that reference frame) in contact with the treadmill belt, so that the other foot is in contact with the belt both when the given foot lands and leaves the belt. In the treadmill belt's frame of reference, let t₁ and t₂ be two consecutive times at which the left foot lands, and let x₁ and x₂ be the corresponding locations at which the left foot lands. If the belt is moving at speed v in the lab frame, then in the treadmill belt's frame, the person is moving at speed v, which implies that (x₂-x₁)/(t₂-t₁) = v. For the racewalker to be walking in the treadmill belt's frame of reference, the earliest the left foot can leave the belt during that cycle is at t₁+(t₂-t₁)/2. That means that during the second part of that cycle, the left foot only has at most a duration of (t₂-t₁)/2 in which to cover a distance of x₂-x₁, meaning its average velocity during that second part of the cycle must be at least (x₂-x₁)/[(t₂-t₁)/2] = 2(x₂-x₁)/(t₂-t₁) = 2v, which would be superluminal if v > c/2. Red Act (talk) 07:06, 27 June 2011 (UTC)

A clock attached to the treadmill would obviously run slow relative to a clock on the wall of the room (which I assume is the reference frame the OP is interested it), the fact that someone is running on it makes no difference at all. I don't think that was the question, though. I think the question was whether a clock attached to the runner would run slow compared to the wall clock. If it was attached to the runner's torso, then it wouldn't since the torso isn't moving significantly relative to the wall (that lots of other things are moving really quickly doesn't matter, you just look at the two clocks). If it were attached to one of the runner's legs, then it gets a lot more complicated because the legs are accelerating. At some points they will be moving backwards at relativistic speeds, at some points they will be stationary and at some points they will be moving forwards at relativistic speeds. That means the clock on the legs will run slow compared to the wall clock, but I can't immediately calculate by how much. --Tango (talk) 13:34, 26 June 2011 (UTC)

The other replies have effectively already said this, but let me emphasize: time dilation only depends on the motion of the clock relative to the lab. It never makes any difference how the clock is "attached" to the lab (via a pair of rapidly moving legs and a treadmill, in this case). Likewise, it makes no difference if it's not attached at all for some of the time (air time). In general relativity, the legs and the treadmill do technically matter, but only because they gravitate, not because they're attached to the clock. -- BenRG (talk) 16:47, 26 June 2011 (UTC)

To all - Sorry about the confusion!

By “Moving Clock”, I meant light clock [mini model] on the Runner’s head [fixed] not attached to the walk belt. As runner [walker] moves close to the speed of light and so the light clock therefore if time dilates then

Why a pulse doesn’t trace out longer path/ angled for stationary observer in Gym’s frame of reference?

Why same vertical bouncing of pulse between two mirrors for both moving [runner] and stationary observers? 68.147.41.231 (talk) 03:07, 27 June 2011 (UTC) Eccentric Khattak No.1

Let make it more simple – Let a person stands [on his Roll Skates] on aforementioned treadmill. Although a person seems stands still but the walk belt enable his wheels to roll on its smooth surface. 68.147.41.231 (talk)EEK No.1 —Preceding undated comment added 03:58, 27 June 2011 (UTC).

Just because a person is rolling along on a treadmill doesn't mean that he's moving. When you talk about something moving, you always have to specify what it is that the movement is relative to. In this case, the person, the treadmill, and the lab the treadmill is in all have the same comoving frame, i.e., none of them are moving relative to each other. In that lab frame, only the treadmill belt is moving (and the roller skate wheels). So as measured in the lab frame, the clock attached to the person's head does not exhibit time dilation, because its speed as measured in the lab frame is zero. However, that clock attached to the person's head would be running slow as measured in the belt's comoving frame, and a clock that moves along with the belt runs slow as measured in the lab frame. Red Act (talk) 04:24, 27 June 2011 (UTC)

If you're running on a treadmill, the only thing moving is the treadmill. And the treadmill is moving back and forth, just like the spaceship in the twins paradox, so it will end up with a different span of time like the accelerated twin. Wnt (talk) 04:26, 27 June 2011 (UTC)

When I said the treadmill wasn't moving relative to the lab frame, I meant the non-belt portion of the treadmill, not the belt. The belt is obviously moving relative to the lab frame, and moving relative to the non-belt part of the treadmill. I probably should have worded things differently. Red Act (talk) 04:36, 27 June 2011 (UTC)

"9,900 years hyperbolic orbit"?

At http://elenin.org/ we read that this comet "follows a 9,900 years hyperbolic orbit around our sun". That seems contradictory. To specify a number of years seems to imply periodicity. But "hyperbolic" seems to imply that it's not periodic. What is meant? Michael Hardy (talk) 04:34, 26 June 2011 (UTC)

At one Epoch the comet can be hyperbolic, while at another it can be a closed loop. The real orbit (or the best approximation to such) considers perturbations by all planets, a few of the larger asteroids, a few other physical usually small forces, and requires numerical integration. Comet Elenin's orbit will become closed because Jupiter's gravity will lower the eccentricity below 1 as Elenin is leaving the planetary region. -- Kheider (talk) 05:24, 26 June 2011 (UTC)

Confusion between orbit types is not the most surprising thing at http://elenin.org/. Further down the page, it speculates that Elenin is in fact a brown dwarf and that it will "preciptate major reactions within the Earth's core as well as on its surface that could very well lead to a global catastrophe". Apparently it is connected with the Nibiru collision theory and the whole 2012 "end of the world" thing. Gandalf61 (talk) 08:06, 26 June 2011 (UTC)

Diamond and Lonsdaleite

It is often said that Adamantane is the smallest molecule that technically, can be called a diamond. Is it really so, since it contains no carbon only moeities? I suggest a new basic diamondoid (SMILES): C1C2CC3CC1C14C5CC6CC(C5)C57C8CC9CC(C8)C3(C3CC1CC5C3)C47C269. A similiar case exists for Lonsdaleite, where its basic unit is bicyclo[2.2.2]octane. New basic Londsdaloid: C1C2CC3CC4CC5CC6CC7CC8CC9CC1C81CC8CC24C1(C57C8)C369. What are the major differences besides their size and mass? Plasmic Physics (talk) 04:41, 26 June 2011 (UTC)

I guess it depends on what you think the essential nature of diamond is. Is it being just carbon, or is it being a lattice of singly-bonded tetrahedral carbons? If you're single bonded tetrahedral carbon, you're going to have edge effects, where you cap the carbon with something else (like hydrogen). The question is how far in you allow the edge effects to penetrate. For example, for Adamantane, it's all edge. I would say that Adamatane *does* have a carbon-only moeity, which consists of the ten carbons bonded together. Yes, it's directly connected to hydrogens, but why should that matter? If you're just looking for an all-carbon moeity with tetrahedral structure, why doesn't neopentane count? Or 1-methyladamantane? -- 174.24.222.200 (talk) 18:20, 26 June 2011 (UTC)

Well, I didn't choose them, because neopentane is non-reprasentative of a singular allotrope; and I chose the ones I did because the central carbon forms closed hexagons with all four adjacent atoms, meaning at it contains five carbons which are only attatched to other carbons. That is what I meant by carbon only moeities, appologies for the confusion. Plasmic Physics (talk) 20:35, 26 June 2011 (UTC)

The simplest carbon-only moeties I can think of would be the fullerenes, but they have graphite-type bonding rather than diamond-type bonding. The problem is one of geometry; graphite- type bonding, with its planar 120 degree bonding, is relatively easy to bend back on itself and leave no open branches. With diamond-type bonding, being tetrahedral (three dimensional and 109.5 degrees), tends to create more branches the further and further you get from the "origin" as you branch out, it becomes impossible to cap it with only more carbons. Eventually, you need to cap it with some univalent atom to end the branching, so even a large diamond crystal (which is essentially a single molecule) has all of its branches terminated by hydrogen. If you are dealing with closed hexagons, you're back to fullerenes and graphite. --Jayron32 18:40, 27 June 2011 (UTC)

what is un-saturated polyester film

Dear Sir,

As per subject given up Kindly clearify my that what is diffrence between saturated and un-saturated polyester film . This question is asked because of in international harmonized code 3920-6310 of about polyester film which film shall applied for this code its not clear as fo as you are requested to please clerifiy me about diffrence between saturated and un-sturated polyester film and for which purpose these film shall be used.

Thanks and best regards usman hafeez -redacted-

LOL @ "un-sturated". StuRat (talk) 02:32, 27 June 2011 (UTC)

See Polyester and Polyester resin. Unsaturated polyesters are resins, generally used in structural applications (as "fibreglass"). I don't think it would be possible to make a _film_ from resin, so anything described as "polyester film" will almost certainly be made of a saturated polyester. Tevildo (talk) 11:27, 26 June 2011 (UTC)

Orbital speed and escape velocity

My book on physics says: "The higher the [circular] orbit of a satellite, the slower its speed and the longer its period." But it doesn't say anything about why this is so. My reasoning is that the escape speed farther from the earth is lower, so the speed of the satellite also needs to be lower, otherwise it won't stay in its orbit but escape. Is my reasoning correct? Lova Falk talk 09:50, 26 June 2011 (UTC)

Yes, it is. Plasmic Physics (talk) 10:21, 26 June 2011 (UTC)

Sort of. A better way to look at it is in terms of centripetal force. The centripetal force is the force that keeps the object on a circular path, in this case that is gravity. That article gives us a formula for centripetal force: F=mv²/r (r is distance from the centre of the orbit, m is the mass of the object and v is its velocity). If you equate that to Newton's Universal Law of Gravity, F=GMm/r² (M is the mass of whatever it is orbiting and G is the gravitational constant) and rearrange, you'll get v²=GM/r. That shows that as r increases, v decreases. That the orbital period will increase is obvious - it's travelling a longer distance at a slower speed, so it takes longer. --Tango (talk) 14:35, 26 June 2011 (UTC)

Looking for a good Scientific Paper

about the PRINCIPLES of the Imprinting phenomenon of Konrad Lorenz.

Many thanks. — Preceding unsigned comment added by 79.179.8.59 (talk) 12:45, 26 June 2011 (UTC)

I'm not sure what "principles" means, but in any case Google Scholar is often a good resource for digging up information of that sort. You can find a downloadable pdf of a 1958 Scientific American article here; or if you are looking for something more recent, this is a paper from 2011 that briefly describes the current state of the art. There is lots more available; the literature on that phenomenon is very extensive. Looie496 (talk) 17:11, 26 June 2011 (UTC)

Subterranean rivers

The concept of subterranean rivers somehow makes me feel as if I'm thinking about strange creatures from mythology, and I wonder if that's because I've found rather little information about them. Here we see one of a number of places in the Minneapolis/St. Paul area where such a stream emerges from underground at a point along the banks of the Mississippi River; at each such point there's a waterfall because the riverbanks in that vicinity are steep and high. From this map it looks as if this stream must flow under the campus of the University of St. Thomas. Obviously the locations of such things must be taken into account whenever a building is built on the land above it.

Where can I find maps of subterranean rivers in specified areas (Google Maps doesn't immediately give me those).

Leonardo da Vinci wrote that subterranean rivers flow from the Caspian Sea to the Black Sea. Is there any truth in that? Michael Hardy (talk) 19:38, 26 June 2011 (UTC)

If the mental picture you have is of an empty tube, filled with water, like a pipe or tunnel, that's extremely rare. Groundwater emerging from the terrain is almost always the outflow from an aquifer. Very occasionally, in the right circumstances, there can be flooded caves, but that's very rare. Anyone planning any building of reasonable size will perform a geotechnical survey which will determine the technical nature of the soil and the character of the water table (and other local hydrology) and will design the building's foundation accordingly. -- Finlay McWalter ☻ Talk 19:49, 26 June 2011 (UTC)

In cities it's not uncommon for natural rivers to be put into culverts and then built over, such that they become effectively subterranean rivers (see Subterranean rivers of London for some examples). It's mostly a matter of nomenclature whether these are really rivers or just drains. -- Finlay McWalter ☻ Talk 20:01, 26 June 2011 (UTC)

@Finlay: I don't think you would suspect that the stream in the map I linked to had been artificially put underground if you saw it close up.

Here's another one, maybe a mile and a half upstream from there. The stream flows out of the vertical face of a cliff maybe 30 feet below street level, and looking around you would see that the waterfall has been carved out over many centuries. Michael Hardy (talk) 22:11, 26 June 2011 (UTC)

Yes, but it could still be water flowing out of porous rocks, as opposed to a tube. If you fill a keg with sponges and water, then open the tap, water will flow out, but have you created a "river" ? StuRat (talk) 02:29, 27 June 2011 (UTC)

So if I want to find out whether a particular place where flowing water emerges from the ground is from a hollow channel or from porous rock, are there standard maps that I can find on the internet or in libraries that indicate that? Michael Hardy (talk) 20:34, 27 June 2011 (UTC)

The article on cave diving describes formations that are more river-ish in Florida and Yucatan (the first being karst limestone, the second cenotes where limestone has been impacted by the asteroid that killed the dinosaurs) I'm sure there must be many other good examples. Wnt (talk) 04:12, 27 June 2011 (UTC)

According to the internet one example of an underground river is in Battlefield Cavern, part of White Scar Caves in England. 92.29.127.234 (talk) 09:17, 27 June 2011 (UTC)

This site claims that a crypto-river has been tracked underneath the Nile. --TammyMoet (talk) 12:39, 27 June 2011 (UTC)

If people want to cite examples, there's Mammoth Cave in Kentucky, which IIRC was carved by a river flowing through it, under ground through most of its course. It's a tributary of the Ohio River. And in Bellefonte, Pennsylvania, a river emerges from the ground, which flows underground until it reaches that point and above ground downstream from there. Michael Hardy (talk) 17:32, 27 June 2011 (UTC)

Something else that relates is rivers that flow part-time. You may have a regular above-ground river at times, then perhaps it drops below the surface but continues to flow at other times, then stops entirely in the driest periods. Dotted lines are often used to show such intermittent rivers. StuRat (talk) 20:40, 27 June 2011 (UTC)

what is older?

A meteorite or gold? Or... were they formed at the same time? — Preceding unsigned comment added by 92.30.142.163 (talk) 21:16, 26 June 2011 (UTC)

Gold is a chemical element, so it will have been created in a supernova and will have been essentially unchanged ever since (gold rarely even bonds with other elements in compounds). Some of it may have come from the radioactive decay of other elements, but I believe that is a very small proportion. Meteorites, on the other hand, are lots of compounds stuck together. Meteorites will have formed during the early period of the formation of the solar system, which was some time (ie. millions, maybe billions of years) after the supernova that seeded the solar nebula with heavy elements. --Tango (talk) 21:27, 26 June 2011 (UTC)

(edit conflict)Your question really is asking to compare apples to oranges. A meteorite is defined as any extraterrestrial object, whether rock or metal, that has fallen to the Earth's surface. These have been falling to Earth since its formation, and many of the meteorites that fall are remnants from the early solar system before the earth was formed, but technically they are not meteorites until they land on Earth.

Gold, on the other hand, is an element; it is formed in the heaviest stars as they turn to supernovae. Gold we find on Earth was formed as stars exploded over and over during the billions of years before the formation of our solar system. Thus, in the strictest definition, you could say that gold is "older" than meteorites, but again, it is not really a good question to ask. Some meteorites may even contain gold. -RunningOnBrains^(talk) 21:36, 26 June 2011 (UTC)

I'd say almost all gold on Earth is older than meteorites on Earth, having been created by supernovae before the formation of our solar system (and thus before any meteorites here), but there could be some more recently created gold that drifted into our solar system and fell to Earth since it formed, and therefore could possibly be newer than some terrestrial meteorites. Also, gold can be created as the end product of radioactive decay, so there might be some newer gold from that source. As for the broader question of gold versus meteorites throughout the universe, that's a different story. I would think there were many meteorites prior to the first supernova, so they might win, in that case. StuRat (talk) 02:21, 27 June 2011 (UTC)

Meteorites need elements heavier than helium in order to form, so they must have come after the deaths of the first stars. The first stars are predicted to have been really large and would have gone supernova, producing gold. See Population III. Therefore gold existed in the universe before meteorites did (well, before meteors did - they weren't meteorites until there were planets from them to crash into!). --Tango (talk) 12:48, 27 June 2011 (UTC)

If the questioner is wondering about specific formations of gold, e.g. nuggets, veins, etc. Then it is worth noting that these are usually relatively recent geologic formations (e.g. 10s or 100s of million of years ago). The geologic processes that give rise to mineral veins are still ongoing, so a gold deposit could be of virtually any age. As discussed above, the gold atoms where created in supernova before the birth of our solar system, but specific gold deposits are likely to have been put in place much more recently. Dragons flight (talk) 17:46, 27 June 2011 (UTC)

Asperger's syndrome and stalking

Are there any empirical studies relating Asperger's syndrome and stalking? And what are the results..? --helohe (talk) 23:55, 26 June 2011 (UTC)

I don't know if there are, but I can tell you that I have definitely never stalked or considered doing so to anyone. Plasmic Physics (talk) 00:00, 27 June 2011 (UTC)

But, are you an aspie? — Preceding unsigned comment added by Wikiweek (talk • contribs) 13:17, 27 June 2011 (UTC)

Yes, this downloadable paper from 2007 directly addresses that question, and its introduction reviews earlier relevant literature. The results "show that the diagnosis of ASD is pertinent when individuals are prosecuted under stalking legislation in various jurisdictions". I will leave it to you to figure out what that means. Looie496 (talk) 02:06, 27 June 2011 (UTC)

I think the previous sentence from that paper is an even better one to quote here: "Individuals with [autistic spectrum disorders] were more likely to engage in inappropriate courting behaviours..., and were more likely to focus their attention upon celebrities, strangers, colleagues, and ex-partners ..., and to pursue their target longer than controls." Red Act (talk) 04:05, 27 June 2011 (UTC)

June 27

What is the biggest Humpback whale ever found?

What is the biggest humpback whale ever found? Neptunekh2 (talk) 00:46, 27 June 2011 (UTC)

According to this, "maximum reliably recorded adult lengths are in the 16-17 meter range". ~ Mesoderm (talk) 01:29, 27 June 2011 (UTC)

life and reproduction

Would it be scientifically accurate to say that by having a child, I am perpetuating 3.5 billion years of successful reproduction, and therefore extending a 3.5 billion year long lineage by one generation? The Masked Booby (talk) 02:49, 27 June 2011 (UTC)

That's probably roughly right, although the lineage conceivably might have been a lot longer than that if life on Earth started here via exogenesis. Note that in any event, exactly how many generations it took to create you isn't precisely defined, because sexual reproduction can mix the genes of individuals of widely different ages. There's presumably also a little vagueness in the generation count due to it being a little vague as to when during the process of abiogenesis there began existing clearly defined cells, with clearly defined parent cells. However, the vast majority of generations of your ancestors since life began involved asexual reproduction of single-celled organisms, so the vagueness in the number of generations wouldn't be that large of a percentage. Red Act (talk) 03:57, 27 June 2011 (UTC)

The simple answer is "Yes". Now, if the OP is trying to figure out how many generations that translates to, it gets slipperier. Just among my own 16 great-great-grandparents, there is 37-year gap from oldest to youngest. That's more than the average length of a "generation" (20-30 years) just by itself. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:24, 27 June 2011 (UTC)

Actually more than one: your mitochondria have their own proud parentage. But if we credit that, we should also consider horizontal gene transfer which, in a sense, means that we could have parentage through many small bits of many different microbes in the billions of years past - before at last converging on some common ancestor(s) of all life in yet earlier generations. Wnt (talk) 04:30, 27 June 2011 (UTC)

A microbe called Adam? :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:43, 27 June 2011 (UTC)

Rock-hard stools and fake fruit juice

As a child I learned by experience that drinking too much fake fruit juice led to terrible stools so rock-hard I could only pass them by pulling them out piece by piece with my fingers. So I've long since avoided anything but real fruit juice - though on two or three occasions at hotels or social events I've forgotten this precept until unpleasantly reminded that it still applies even as an adult. But looking over the web it seems like fruit juice is commonly recommended to people with fecal impaction (which sounds like a more serious version of this), and it seems like advertisements for stool softeners have grown very common in the U.S. in recent years. (the effect of home budget cutbacks...?) So in the interest of all the kids who haven't learned by trial and error yet I'm curious - can someone think of evidence that might link this problem to some ingredient in fake fruit juice? The first guess that comes to mind is high fructose corn syrup... yet I get exposed to so much of that in other forms without any similar effect ever happening. Unfortunately, because of when and how I was exposed, I don't know the ingredients of the products involved, though one of the worst culprits vaguely resembled orange juice. I couldn't find anything on PubMed in a few basic searches... but I'm not sure what I'm looking for. Wnt (talk) 05:56, 27 June 2011 (UTC)

For making that discovery I'd like to shake your hand ... or maybe not. :-) StuRat (talk) 06:23, 27 June 2011 (UTC)

But, seriously, if everyone who drank such drinks had that reaction, it would be widely known already. You must have had an allergy or unusual reaction. Also, I would bet that parents who give their kids fake juice also don't tend to give them enough fiber and provide a generally poor diet, overall, so any of those factors could contribute. StuRat (talk) 06:23, 27 June 2011 (UTC)

I don't see anything on PubMed about allergy causing fecal impaction. While it may not be a universal reaction I somehow doubt it's all that rare, judging by the prevalence of hard stools. Wnt (talk) 06:31, 27 June 2011 (UTC)

As a past participant in the F-plan diet, I can tell you that juicing oranges removes the fibre from them and leaves you with the water and other bits. If you want to get the benefit of the orange you need to eat the whole flesh (OK you can leave as much as the white pith as you wish to) and not to juice it. So real fruit juice could have the same effect, particularly if you're not drinking a great deal anyway.--TammyMoet (talk) 12:36, 27 June 2011 (UTC)

Interesting. When I get real orange, grape, or apple juice, it's not uncommon for me to run through 1-2 liters in 24 hours, but it never caused this effect. But I'm getting the impression the underlying biology is more variable than I thought. Frankly, I'd been thinking that the reaction might be universal and widely known, since after all there are things like olestra (and I think adulterated olive oil...) which are widely sold and which have equally disturbing effects. Wnt (talk) 15:04, 27 June 2011 (UTC)

WIMPs

There is a huge amount of conjecture and speculation about weakly interacting massive particles in the literature, going back to mirror matter hypotheses in the 1950s. Has there ever been any evidence for their actual existence? 76.254.22.47 (talk) 07:13, 27 June 2011 (UTC)

Have you read Weakly interacting massive particles#Experimental detection? Red Act (talk) 07:21, 27 June 2011 (UTC)

Neutrinos are WIMPs so the answer is yes! But so far no smoking gun evidence for other kinds of WIMPs has been found. Dauto (talk) 07:54, 27 June 2011 (UTC)

That's not true and the Wiki-articles on this subject are out of date. The DAMA-Libra results which were originally received by a lot of scepticism have been confirmed by the COGENT results, and very recently COGENT has also reported an annual modulation. These are consistent with light WIMPS of a mass of about 8 GeV to which other DM direct detection experiments are not sensitive to. There are a lot more physicists taking these results serious than a few years ago. Because you first had the DAMA results, then the confirmation of these results by DAMA-Libra and then later the completely independent experiment COGENT. Count Iblis (talk) 15:08, 27 June 2011 (UTC)

Thanks for that information. I had heard of the DAMA results but wasn't too impressed. I will definably look into the COGENT experiment which I hadn't heard of before. Dauto (talk) 16:28, 27 June 2011 (UTC)

After reading about CoGeNT (Which seems to be part of the CDMS II experiment), I have to say that I don't think that is the smoking gun evidence just quite yet, though we may be getting tantalizingly close to it. Dauto (talk) 19:01, 27 June 2011 (UTC)

Difference between curd and yoghurt

difference between curd and yoghurt... their nature and formation..... acidic nature.... — Preceding unsigned comment added by Simplyds (talk • contribs) 12:13, 27 June 2011 (UTC)

Have you read the Wikipedia articles on curd and yoghurt? The differences are easy to discover. Oddly, the acidity of these foodstuffs seems harder to determine. After a bit of a look round I found this which is a bit heavy but has info on yoghurt, and this one has info on milk curd. Richard Avery (talk) 12:55, 27 June 2011 (UTC)

Capturing CO2

Could the CO2 expelled by a car be captured? Wikiweek (talk) 12:18, 27 June 2011 (UTC)

Sure, by attaching a hose to the exhaust pipe and routing it somewhere. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:57, 27 June 2011 (UTC)

Yes Buggs, I'm thinkin' the "somewhere" leaves your response a bit open-ended, and not even clever. Caesar's Daddy (talk) 13:13, 27 June 2011 (UTC)

I've seen this done in garages, when the mechanics have to run the engine for awhile to test something. The hoses presumably route the CO, CO2, soot, and whatever else, to the outside of the building. Given that, it ought to be possible to capture it. Although, as noted, it's not "pure" CO2 emitting from a car, but a variety of things. So it might be possible to capture the contents of the exhaust, but by what process would you separate the various products from each other? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:37, 27 June 2011 (UTC)

Somewhere to a CO2 parallel universe, where it disappears? But would it be practical? You'll still need some way of compressing it... — Preceding unsigned comment added by Wikiweek (talk • contribs) 13:14, 27 June 2011 (UTC)

You can bubble the CO2 through lime water which sequesters it as Calcium carbonate. This is a simple kind of carbon dioxide scrubber which I will let people read and follow links from on their own time. Attaching such systems to cars, however, is impractical and expensive, which is why it isn't done. --Jayron32 18:30, 27 June 2011 (UTC)

Several by-products of combustion are already captured in a catalytic converter, but CO2 is not one of them because out of all the by-products, CO2 is one of the least harmful. Vespine (talk) 00:42, 28 June 2011 (UTC)

Catalytic converters work by reducing nitrogen and sulfur oxides to less harmful gasses. Such oxides make up a miniscule amount of the exhaust, which is still mostly carbon dioxide; so to deal with the CO2 would require a MUCH larger system. Furthermore, the primary danger of CO2 is as a greenhouse gas, and its not clear that a reduced product (in this case likely methane, CH4) would be any less harmful. The problem with carbon sequestration in calcium carbonate is that you have to, very frequently, change out the chalk and replace the lime. Quite messy business for something you want to just "work" without any outside help, like a catalytic converter does. --Jayron32 02:55, 28 June 2011 (UTC)

Note that a catalytic converter does not 'capture' anything. As the name implies, it contains one or more large-surface-area catalysts that encourage the conversion of certain exhaust components into less-noxious chemicals. (This generally includes the combustion of unburned or partially-burned fuel, the oxidation of carbon monoxide into less-toxic carbon dioxide, and the breakdown of nitrogen oxides into nitrogen and oxygen.) TenOfAllTrades(talk) 14:56, 28 June 2011 (UTC)

It's not very practical to capture the carbon dioxide from the tailpipe as the car is being driven down the street, for the reasons listed above. A more practical approach may be to use carbon credits and carbon trading. Under such a system, anyone driving (or perhaps manufacturing or selling) a car would have to pay a company to extract the equivalent amount of carbon dioxide from the air and sequester it. This approach has the possibility of being far more efficient, but requires the political will to pass the legislation to make it mandatory. I believe there are companies which will currently do this on a voluntary basis, but, of course, most drivers won't participate. StuRat (talk) 17:29, 28 June 2011 (UTC)

General Fusion

What are the main reasons it will fail? 20.137.18.50 (talk) 12:33, 27 June 2011 (UTC)

Well, it might fail to solve some of the technological challenges required to make fusion happen in the first place. Or it might achieve a repeatable fusion reaction that consumes more energy than it releases. Or it might solve all those problems, but still not be an economically feasible process. Gandalf61 (talk) 12:49, 27 June 2011 (UTC)

Private companies based on fusion have failed in the past because the capital R&D costs are very high and the guarantee of economical success is nonexistent. They have an additional downside from government or university work in that they are reliant on investment funds but they are trying to develop proprietary technology. So generally they need hype but have difficulty providing the details about how they made it happen, which is a sure recipe for suspicion. There was an ICF company in the early 1970s that failed after cycles of this sort — it turned out that ICF was hard, and that generating sustained research funds from private donors was hard. Universities and governments have typically dominated in this field because their funding mechanisms are not profit-based. You can still get useful results even if you don't get closer to getting a profit in those contexts, but that is not a good business model.

This is a separate question from the specific technical one. The general difficulty with fusion is that the tolerances for imperfections (either in keeping the plasma off of the walls in MCF, or compressing it in ICF) are very low, for any imperfection rapidly leads to either incredible inefficiency or rapid cooling, both of which make generating a gain in net energy unlikely. Now I don't know much about Magnetized target fusion but it seems to be an attempt to average out the difficulties of both. Whether it actually works to that end, or whether it simply means you are trying to solve two different and difficult problems at the same time, remains to be seen, I think. The track record for fusion is not great: every problem solved usually results in the discovery of two more problems. This is why the two current most favored efforts (NIF and ITER) are basically based on the idea of scaling it up to monstrous sizes so that hopefully the imperfections become less important. --Mr.98 (talk) 13:52, 27 June 2011 (UTC)

I don't like your will there. That's very pessimisitic. It could fail, for a variety of reasons from physics to politics, but that's far from certain. i kan reed (talk) 17:05, 28 June 2011 (UTC)

I think the OP is just expressing the fact that so far every attempt at commercializing fusion (much less getting even net energy) has failed over the past five decades. There are little reasons to be optimistic with fusion — the history of fusion research is filled with people saying "this shouldn't be too hard — give us 5 years!" again and again and again and again. It turns out that controlled fusion is genuinely hard. --Mr.98 (talk) 18:44, 28 June 2011 (UTC)

What's so hard about putting a star in a bottle ? :-) StuRat (talk) 19:13, 28 June 2011 (UTC)

bond angles

how "flexible" are bond angles (or equilibrium bond angles, because they can move)? I mean in large molecules like polymers, they can easily bend (such as polyethylene) and we see a lot of images showing structures like DNA bending as if its a simple rope or something.also, the covalent bonds in liquid glasses such as SiO sre still present but apear to be somehow looser than the solid form.. if the bond angles (or equilibrium bond angles) are more flexible when the olecules are larger,why is it that way. is everything about molecular geometry only true for smaller molecules? thanks.--Irrational number (talk) 12:44, 27 June 2011 (UTC)

• Some bonds are free to move as a swivel. allowing large molecules to bend.
• Large molecules have many bonds. The slight flexibility of each of them can add up to a large flexibility for the larger molecule.

Dauto (talk) 17:14, 27 June 2011 (UTC)

Do these materials(large molecules) naturaly tend to bend too?-Irrational number (talk) 18:26, 27 June 2011 (UTC)

There are two conflicting things here. First, a long simple alkane is indeed very floppy, and bends quite alot. However, that bending only works if the molecule is dimensionally constrained; essentially long straight chains are the "floppiest". When there is a network of bonding within a molecule in three dimensions, it can constrain the bonding. The carbons in an alkane are in the same hybridization as the carbons in diamond, and yet diamond is very much NOT flexible. In DNA, the three-dimensional structure constrains the DNA chain into a relatively rigid double helix, though the entire chain does have some flex to it. Look at other macromolecules like proteins. Some proteins are very flexible, while others are not. The difference is the presence of large numbers of cysteine bases, which form disulfide bonds and constrain the structure of the protein; proteins with lots of disulfide crosslinking (like keratin) tend to be relatively inflexible. --Jayron32 18:28, 27 June 2011 (UTC)

There are cubane, propellanes, cyclobutane at 90 degrees ... even cyclopropane at 60 degrees. It's hard to think of a molecule that forces C-C bonds at a smaller angle than that, but if you do ... odds are someone's done research on it. ;) The bonds have a preferred angle, yes, but generally carbons seem to prefer association of any sort over none at all. But the strain on such structures is enormous - of course, in a long piece of plastic, the deformation of any one bond is absolutely miniscule by comparison. Wnt (talk) 18:46, 27 June 2011 (UTC)

how did biblical figures probably walk on water

if not by magic, then what is the most likely mechanism biblical figures used to walk on water? — Preceding unsigned comment added by 188.29.96.144 (talk) 13:38, 27 June 2011 (UTC)

There is not universal agreement that Jesus was literally walkig on the water. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:40, 27 June 2011 (UTC)

They probably didn't... AndyTheGrump (talk) 13:42, 27 June 2011 (UTC)

The could have used floating sandals, as in the illustration in our article on Walking on water.--Shantavira|^{feed me} 13:49, 27 June 2011 (UTC)

The article Jesus' walk on water gets into specifics of the Bible story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:52, 27 June 2011 (UTC)

I think Jesus walked on water using the same levitation mechanism by which Yoda levitated, i.e., the levitation was enabled by the imagination of the storyteller. But see levitation for real levitation mechanisms, and levitation (paranormal) for other mythological levitation. Red Act (talk) 14:08, 27 June 2011 (UTC)

A sandbar close to the surface of the water could give the appearance of walking on water especially if seen from another water-going vessel—perhaps at a distance, and perhaps with the lower portion of the body blocked from view by the water-going vessel upon which one finds oneself. Bus stop (talk) 19:37, 27 June 2011 (UTC)

Maybe they thought life is a state of mind. Richard Avery (talk) 19:48, 27 June 2011 (UTC)

Modern magicians use a clear plastic support, just below the water. Plastic wasn't available then, so perhaps glass was used. Unlike the sandbar, this can fool people right there, as clear objects can become virtually invisible, once submerged, especially with waves at the top. Also note that in Biblical times it was common for religious figures to use magic tricks to convince people they had God(s) on their side. The magic contest between Moses and the Egyptian high priest, where each turned their staff into snake(s), shows this nicely (some Christian fundamentalists might argue that Moses' trick was the real thing, but who argues that the Egyptian priest was really using the power of Egyptian gods ?). StuRat (talk) 19:54, 27 June 2011 (UTC)

You have to be careful with that trick. The nature of waves in shallow water is different from deeper water. In Superman II there was a scene that showed the evil General Zod walking on water. They got a little too close with the camera, and although you couldn't see the platform he was walking on, you could see its effect in the rippling of the water. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:39, 27 June 2011 (UTC)

But, of course, you were merely seeing the effect on the waves from the supporting force field. StuRat (talk) 04:21, 28 June 2011 (UTC)

Egyptian fundamentalists of course. If Wikipedia had been around in Old Testament times, there might have been a heated debate. Wanderer57 (talk) 21:28, 27 June 2011 (UTC)

If the internet had been around in O.T. times, God would simply have posted the Ten Commandments in His blog. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:35, 27 June 2011 (UTC)

If it was a wiki, I'd hate to think of all the edit wars on that one. StuRat (talk) 04:21, 28 June 2011 (UTC)

He would probably have added "Thou shalt not annoy others with your constant twittering." Googlemeister (talk) 13:21, 28 June 2011 (UTC)

And his Admin policy would have been strict. "Disemvowellement? No, I think you misheard." {The poster formerly known as 87.81.230.195} 90.201.110.117 (talk) 17:18, 28 June 2011 (UTC)

painkillers for waxing

What would be more effective pain relief for waxing of intimate areas? Paracodal or ibuprofen? I've been advised to take something before my appt and these are the two options in my drawer! Thanks. (just so you know, I take both occasionally and am not allergic to either and have never had any adverse reactions in the past and this is not a request for "medical advice", you can just give me science!) 195.27.52.146 (talk) 15:15, 27 June 2011 (UTC)

It really is a request for medical advice, actually. Who advised you? In many countries only a medical practitioner would be able to advise. In others, perhaps a pharmacist. Itsmejudith (talk) 15:51, 27 June 2011 (UTC)

I feel that this is a specific question about the action of the two drugs. In this case, there is a very clear answer. Ibuprofen primarily reduces inflammation and fever. Neither of those will be of much help in reducing upcoming pain in sensitive nerve endings. Paracodal contains paracetamol, which specifically reduces pain by reducing the sensitivity of nerve endings. Both are "pain relievers", but they relieve different kinds of pain. If this doesn't completely answer the question, please delete it and mark this as a true request for medical advice. -- kainaw™ 18:41, 27 June 2011 (UTC)

This sounds like a request for medical advice to me. I have no idea, for example, whether the practitioner might be relying on your yelps and screams as feedback about whether he/she is pulling too hard, and by suppressing them you could make something gruesome happen. IMHO if something is so painful you need a drug to suppress the pain, your body is trying to gently hint to you that perhaps it is not a good idea. Wnt (talk) 18:50, 27 June 2011 (UTC)

I don't think you need a medical license to suggest cosmetics, so I would go with a skin cream or shaving cream containing menthol and/or eucalyptus and/or aloe. The menthol a pain-killer, the eucalyptus is an antiseptic to prevent infection, and the aloe is a painkiller and will help you heal after. The advantage of a topical cream is that it's much stronger where you need it, while anything you take orally is distributed around your body, so very little of it will actually go to the skin in question. I do agree with Wnt, though, that if they advise stronger painkillers, they aren't doing it right. It shouldn't be that painful. StuRat (talk) 20:08, 27 June 2011 (UTC)

Why not use Lidocaine/prilocaine?

The lidocaine/prilocaine combination is indicated for dermal anaesthesia. Specifically it is applied to prevent pain associated with intravenous catheter insertion, blood sampling, superficial surgical procedures; and topical anaesthesia of leg ulcers for cleansing or debridement.[3] Also, it can be used to numb the skin before tattooing as well as laser hair removal.

Count Iblis (talk) 22:32, 27 June 2011 (UTC)

Kainaw is right, that's just what I wanted to know. To the rest, waxing is notoriously painful and taking a couple of painkillers before doing it is pretty much standard advice from the practitioners. Wnt—there's no such thing as "pulling too hard" when it comes to waxing! That's the whole point.  :) Thanks for all the responses! 195.27.52.146 (talk) 06:44, 28 June 2011 (UTC)

communication over vast distances

Is it in any way possibly to send information over vast distances (in a reasonable amount of time). Even better, is this also applicable to traveling? 66.229.227.191 (talk) 15:19, 27 June 2011 (UTC)

The question is vague. By typing this comment, I'm sending information to people in distant countries, if they happen to be looking at this page. By using my cell phone, I can talk to those people. Did you mean vaster or faster than that? Michael Hardy (talk) 20:43, 27 June 2011 (UTC)

No form of communication or transportation is faster than the speed of light, which severely limits interstellar travel. Red Act (talk) 15:39, 27 June 2011 (UTC)

A wormhole would be useful but there is no reason to believe that they actually exist. Dauto (talk) 17:19, 27 June 2011 (UTC)

The speed of light is fast enough if you transmit yourself using the message. Ultimately, we are just information stored in the brain and all that can in principle be transmitted. If the message that defines you travels 10,000 light years and upon arrival you are recreated using the received message, you would not experience the 10,000 years. Count Iblis (talk) 17:32, 27 June 2011 (UTC)

You wouldn't experience anything. If such technology existed, allowing a copy of a human brain's "state" to exist, it would be reasonable to describe it as a fork(). A copy of the state would be created and begin new processing. But it does not change the processing-state of the original copy. Needless to say, hypothetical technology to serialize the complete state of a human brain, transmit it by any method, and restore functionality by running it on a "virtual machine" is still science-fiction. Much work remains to precisely define the type of "machine" and its "instruction set" or "state." Even once these tasks are complete, building a replica and designing a "scanner/copier" will be additional, complex tasks. Nimur (talk) 17:43, 27 June 2011 (UTC)

Add to that the fact that you would only be able to travel to places that have a receiver. Dauto (talk) 19:28, 27 June 2011 (UTC)

If it takes 10,000 years to get there, they might have a receiver built by then. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:33, 27 June 2011 (UTC)

Indeed, so if e.g. the Earth were to face some disaster, we could transmit signals that contain the information to recreate our civilization elsewhere. That would be easy to do if we have transformed to a machine civilization. If the signal is powerful enought it can be picked up millions of lightyears away in some nearby galaxy. They can then download our programs and eventually our entire civilization can be rebuilt there.

A limiting factor here is the data rate. Perhaps the best strategy is to have a radio beacon repeatedly transmitting an easy to decode message that tells listeners to look out for a laser beam. Using a visible light laser, one can transmit more than 10^14 bits/second. So, more than 10^21 bits of information can be transmitted per year and if we use higher frequency beams much more than that.

The power of radio transmitter and the laser beam must be large, but that's not a problem for a machine civilization capable of using all the power that the Sun emits. The laser beam can be split into separate parts that are aimed at many of the nearby galaxies. The beam divergence can be made small enough such that the beam's width is exactly the size of the galaxy upon arrival (the brighness of the beam would then be similar to the apparent brighness of a star at a distance of the order of the diameter of that galaxy, so it would be easy to detect).

Our survival then depends on there being just one civilization capable and willing to recreate us among the many hundreds of nearby galaxies. Count Iblis (talk) 00:16, 28 June 2011 (UTC)

If light-speed communication is too slow for you then superluminal communication is the page to look at for more information. Apparently the prospects are not good. --Antiquary (talk) 19:21, 27 June 2011 (UTC)

Biology

Why do some birds migrate even though they are warm blooded ? — Preceding unsigned comment added by Ssmagic (talk • contribs) 16:27, 27 June 2011 (UTC)

It doesn't have anything to do whether an animal is warm blooded or cold blooded. Many species of all kinds migrate. See animal migration for details. --- Medical geneticist (talk) 16:32, 27 June 2011 (UTC)

Humans are warm-blooded, but we still find it desirable to take many steps in order to avoid being cold. Why should it be any different for animals? There are many different adaptations to cold, including migration and hibernation. Dragons flight (talk) 17:01, 27 June 2011 (UTC)

Humans also migrate, at least in their older years... --Jayron32 18:21, 27 June 2011 (UTC)

Apart from seeking more comfortable temperatures, some bird species have to migrate because the availability of their preferred or obligatory food sources are greatly affected by the changing seasons. If, for example, a bird lives on insects, it would likely find very slim pickings during a Northern European winter, making migration to, say, North Africa, advantageous. Our article Bird migration describes in detail this and several other reasons for the phenomenon. {The poster formerly known as 87.81.230.195} 90.197.66.204 (talk) 19:46, 27 June 2011 (UTC)

Another frequent reason for migration is reproduction. They often migrate from a wide area to a small one, where their greater population density helps them find a desirable mate. Then, there is sometimes "safety in numbers" where they raise the chicks, or perhaps they breed in an inaccessible area to deter predators. StuRat (talk) 20:29, 27 June 2011 (UTC)

In general, birds migrate because of the reasons above, not because it's cold. There are plenty of birds that hang around in winter when there's a food source. You might say the cold and snow are indirect reasons for the migration. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:31, 27 June 2011 (UTC)

I suppose you could argue that those species which migrate to warmer climates in winter never developed (or lost) the adaptations that would allow them to survive cold weather (right up to penguins that can survive winter in Antarctica). So, at this point, they do need to migrate to avoid the cold, among the other reasons. StuRat (talk) 04:17, 28 June 2011 (UTC)

Penguins migrate to a degree too though, don't they? Googlemeister (talk) 18:35, 28 June 2011 (UTC)

"The swallow may fly south for the winter, yet it is no stranger to our land..." Albval (talk) 19:36, 28 June 2011 (UTC)

hello (identifying #7 plastic)

how do they tell #7 plastics apart at recycling centers — Preceding unsigned comment added by Tsp12345 (talk • contribs) 19:38, 27 June 2011 (UTC)

That's a good question. The plastic recycling article is rather hazy on the subject, simply saying that they're separated based on their resin identification code. This article says the manual sorting process is too expensive and isn't sufficiently reliable, and talks about two technologies that can identify some plastic types. It's not clear if these automatic methods are in widespread use. In my own area, it seems they only want drinks bottles; everything else (tubs, trays, lids, caps, films, bags, etc.) they don't take. I imagine that if (or when) most retail products contain RFID tags, the separation of some post-consumer waste (bottles, tubs, trays at least) may become more easily automated. -- Finlay McWalter ☻ Talk 19:51, 27 June 2011 (UTC)

Some recycling programs will only accept properly marked (i.e. with the correct code) plastics for recycling. Some plastics, if kept with the same type, can be melted down and reused in the same application; however this requires proper sorting. While "pure" plastics can fetch greater prices on resale, they are also much more labor intensive to ensure proper purity; some cheaper reuses (for example, shredded and used as mulch) fetch much less on the open market, but then again are much cheaper to process. Plastic recycling has more information, and the economics of recycling are quite complex, especially when coupled with the "social pressures" to recycle even when it is not financially feasible to do so. --Jayron32 20:22, 27 June 2011 (UTC)

I added to the title to make it actually useful. StuRat (talk) 20:25, 27 June 2011 (UTC)

I found a few sources via Google Books. Several of them say that Near Infrared (NIR) and Middle Infrared (MIR) spectroscopy can be used with some success, but that it doesn't work with plastics that have black/grey dyes in them, because those absorb the NIR wavelength; also MIR cannot be used for high-speed processing.[5][6][7][8] Other techiniques measure the density or melting point, or use chemical markers.[9][10]] ... Anyways, I would suggest searching Google books for identifying plastics recycling, and you'll probably turn up quite a bit more information. Cheers. ~ Mesoderm (talk) 20:36, 27 June 2011 (UTC)

weird plastic taste in coffee

Hi, I'm a total coffee philistine, but one thing I can't handle is the plastic taste that you get from some containers. Basically I brew up several cups, and store them in my plastic container (Sistema brand, in Australia), but of late, I've noticed the ghastly plastic gunky taste is getting in the coffee, even though it didn't originally. I've been using them for several months without incident, and now, suddenly, nearly every coffee comes out awful. Why does this happen? Surely plastic is inert, so it shouldn't get into food. Has this problem ever been investigated with plastic containers? Also, is there any cure? It's been emotional (talk) 21:04, 27 June 2011 (UTC)

I used to drink coffee out of various plastic and foam containers and noticed the same thing. Given that many plastics (or byproducts of burning/heating them) act as endocrine disruptors or mutagens, I didn't feel like taking any chances and started drinking out of ceramic, glass, or metallic containers. I no longer have to deal with the unpleasant plastic taste (which I notice every time I drink out of plastic containers now), and I don't have to worry about the health effects of drinking a hot liquid out of a plastic container. ~ Mesoderm (talk) 21:13, 27 June 2011 (UTC)

I agree with glass (not leaded crystal) or ceramic (unpainted ceramic, that is). Metal, however, can also react with beverages, so they often coat this inside of metal containers with plastic to prevent this, and we're back to the original problem (unless you have a gold or platinum bottle :-) ). I use glass, myself. Specifically, I buy Everfresh juices and reuse the glass bottles: [11]. StuRat (talk) 22:32, 27 June 2011 (UTC)

To answer your question, there are several chemicals that can leach out of plastic bottles into the contents. More leaching is expected with more heat, more flexing of the bottle, more time, and more acidic content (a highly alkaline drink might be a problem, too, but there aren't many of those). In your case, pouring hot coffee into it might be the problem. StuRat (talk) 22:35, 27 June 2011 (UTC)

Thanks, very astute of you, StuRat. Thanks to all of you. It's been emotional (talk) 23:11, 27 June 2011 (UTC)

Don't they have ceramic coffee pots coffee pots in Australia? Or even teapots? (I see that "coffee pot" re-directs to "Coffeemaker", which are of course not coffee pots. Coffee pots are similar to tea pots, but designed for coffee. Usually taller and more cylindrical than teapots in my experience). 2.97.219.42 (talk) 10:15, 28 June 2011 (UTC)

In US English, at least, a coffee pot (that's 2 words in US English) is the container into which the freshly brewed coffee pours from the coffee maker (also 2 words), and a tea pot (also 2 words) is where the tea is steeped. So, neither is the storage container asked about here. StuRat (talk) 13:14, 28 June 2011 (UTC)

is it any easier to catch a bullet at the top of its arc if you throw it up than if you shoot it up?

If I take a bullet in my hand, and throw it up a couple of feet for you to catch, is it any easier for you to catch it than if we repeat the same thing, but, in a very still place, you happen to be on top of a cliff and the arc of the bullet I shoot from somewhere far far away looks, relative to you, exactly the same on paper as when I threw it up to you from a couple of feet below? I mean, because the top of the parabola should look the same. — Preceding unsigned comment added by 188.28.68.234 (talk) 22:10, 27 June 2011 (UTC)

From a pure physics standpoint, velocity is velocity; the round has no memory that it used to be going very fast; and so, near the top of a parabola, vertical velocity approaches zero. "Engineering details" may confound this simplistic viewpoint: a round fired from a gun will be hot; it may be wobbling; it may have deformed during firing or flight. It will also be hard to aim very precisely due to error propagation (a longer time in flight means that tiny error in aim will result in large error in position). The safety factor should be considered, too - if you miscalculate, or if wind, non-ideal turbulence, or any other parameter changes the expected peak location of the trajectory, your experimenter will be in a very dangerous position. Nimur (talk) 22:18, 27 June 2011 (UTC)

Well, the bullet still wouldn't be going very fast, even if your calcs are off a bit. However, the variability is enough that you couldn't reliably get the bullet to reach the peak of it's trajectory within reach of the target person on top of the cliff. So, it would be easier to catch if hand thrown. StuRat (talk) 22:25, 27 June 2011 (UTC)

Also if the bullet is shot out of a rifle it might be spinning pretty fast, which might make it harder to grab. Rckrone (talk) 23:15, 27 June 2011 (UTC)

I think what the OP meant by "easier" is purely the act of nabbing the bullet, given that you just happen to be in the right place at the right time. At the very top of its arc, at least for one moment, it will have zero or near-zero vertical velocity, before it starts to fall again. So if you were next to the bullet and had a butterfly net or something, grabbing it should be just as "easy" as if it were thrown up in the air. Obviously, this only works if you've thrown or shot it pretty much straight-up. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:26, 27 June 2011 (UTC)

The difference that comes to my mind is that you couldn't see it if it originated at a distant point. In one instance you could maintain eye contact for the length of the trajectory. In the other instance you would only be able to establish eye contact at a fairly late point in its trajectory. This would introduce an added difficulty. Human vision is inadequate to the task of tracking a fast-moving small object especially at a considerable distance. While the object would still be small if tossed from only a few feet away, the tracking of such an object by the eyes of humans is still within normal operating range. Bus stop (talk) 23:33, 27 June 2011 (UTC)

You might, if it were painted international orange or something. Maybe the OP needs to clarify what he means by "easier". My concept of this would be that you could fly like Superman and be able to spot the bullet and to be at the top of the arc and grab it. However, Superman could grab it as soon as it leaves the rifle without doing himself any harm (unless it was made of kryptonite). So the OP needs to comment further. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:49, 27 June 2011 (UTC)

Let's formulate this as a problem. Let's say we have a .38 Special, with a muzzle velocity of about 600 feet per second, which is pointed upward and fired. How accurately must the muzzle velocity and direction be controlled in order to produce an error of less than 1 foot in any direction in the location of the trajectory peak? Extra credit: how does the necessary directional accuracy compare to the maximum possible accuracy of a .38 Special? Looie496 (talk) 23:49, 27 June 2011 (UTC)

No one has specifically said it so I'll add it. Both bullets will be experiencing a constant downward acceleration of 9.8m/s² . So yes, the "top" of the parabola of the fired bullet will be identical to the parabola formed by a thrown bullet from the point where the thrown bullet's velocity matches that of the fired bullet. As stated above however, this is only given "perfect" conditions of no friction or turbulence (etc...) which of course don't exist in real life. Vespine (talk) 00:30, 28 June 2011 (UTC)

A bullet shot straight up will still travel a few thousand feet. If a bullet travels 5000 feet, then to be accurate to within 1 foot (assuming there is no wind or other atmoshperic effects) you will need accuracy of .01 degrees to be within a foot. I don't think most handguns would have that level of accuracy and even a sniper rifle would be tricky. Of course a sniper rifle would probably go a lot higher then 5000 feet since it has a much higher muzzle velocity. Googlemeister (talk) 13:13, 28 June 2011 (UTC)

miami

do they have central heating in most houses in miami and what kind — Preceding unsigned comment added by Superhands99 (talk • contribs) 22:40, 27 June 2011 (UTC)

It does get chilly enough in winter to need some form of heating, but, due to the relatively low amount of heating needed, electrical heating is common (the cost of electrical heating is prohibitive in colder climates). Electric baseboard heating is one common form. StuRat (talk) 22:56, 27 June 2011 (UTC)

Miami recently set a record because 10 straight days failed to reach 65 F in January.[12] I think little heating is required. Miami has a climate of 149 heating degree days versus Detroit (6224) or Duluth (9371). Rmhermen (talk) 00:58, 28 June 2011 (UTC)

Even 65°F is a bit cold, especially for the elderly. But, of course, those are the highs. The record low is 27°F: (pick "Record Low" check box). At those temps you can die without some form of heat. StuRat (talk) 04:10, 28 June 2011 (UTC)

It's my understanding that many homes in Miami area, especially the older ones, don't have heating systems. Presumably, on really cold days (by their standards), they use space-heaters or blankets or something. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:13, 28 June 2011 (UTC)

Or they could just use their aircos as heaters :) . Count Iblis (talk) 02:36, 28 June 2011 (UTC)

That's right. I live in Florida (Not in Miami, though) and every house I've ever lived in has has a AC/heating unit, with one single exception. Dauto (talk) 03:21, 28 June 2011 (UTC)

June 28

Multiple sclerosis

What is meant by t1 or t2 lesion load? how does it differ from active lesion? — Preceding unsigned comment added by 199.224.149.10 (talk) 04:32, 28 June 2011 (UTC)

I can't give a detailed answer, but I can tell you that T1 and T2 are different ways of carrying out an NMR examination. This paper describes them in detail, if you can make sense of it. Looie496 (talk) 05:15, 28 June 2011 (UTC)

To explain in better detail, see Magnetic_Resonance_Imaging#Basic_MRI_scans. T1 and T2 refer to two different MRI techniques (the MR in MRI is the same MR as in NMR and the terms (NMR and MRI) are occasionally used interchangably, though mostly NMR is reserved for the analytical chemistry technique, while MRI is used for the medical diagnostic technique. The authors of this paper are really refering to MRI). The technical details of each can be found in the article I cited, but for the purpose of the OPs question, and for the purpose of understanding that paper, the T1 and T2 lesion loads are merely the number of lesions detectable on a T1 scan versus a T2 scan. Each type of scan has different sensitivities, so they have different applications; some times you'll want to do a T1 scan and sometimes a T2 scan. The paper you cited is the results of various experiments to determine the ideal parameters for using MRI to detect multiple sclerosis lesions. --Jayron32 05:27, 28 June 2011 (UTC)

Colloquial medical expressions

When someone dies of a "hole in the heart", what did kill him? And what about the classical - "dying of old age"? Does that simply mean "old person died, don't know why"? Wikiweek (talk) 14:39, 28 June 2011 (UTC)

The former may often be ventricular septal defect -- Finlay McWalter ☻ Talk 14:43, 28 June 2011 (UTC)

From Death_by_natural_causes: "Old age is not a scientifically recognized cause of death; there is always a more direct cause although it may be unknown in certain cases and could be one of a number of aging-associated diseases." SemanticMantis (talk) 14:49, 28 June 2011 (UTC)

In the case of a "hole in the heart" due to injury, as in a bullet wound, it might be in any part of the heart, or perhaps nearby, say in the aorta or vena cava. In this case the victim is likely to hemorrhage to death, with the loss of blood pressure probably actually causing brain death. StuRat (talk) 16:19, 28 June 2011 (UTC)

Quantum superposition

Hello,

How does quantum superposition fit in with the principle of contradiction? It seems like QS can allow for a statement and its negation to be jointly true (i.e., "Schrödinger's cat is dead" and "Schrödinger's cat is alive" are both true at the same time). Does this mean the principle of contradiction is wrong?

Thank you. Leptictidium (mt) 15:09, 28 June 2011 (UTC)

The principle of contradiction is logically sound. What is not clear is what is meant when you state that the cat is alive or that it is dead. Are those two states truly logic opposites to each other? QM says that these statements are not the logic negation of each other since a third state is also possible, namely the cat might be in quantum superposition state. Dauto (talk) 15:34, 28 June 2011 (UTC)

But QS is not a state in and as of itself, it's merely a superposition of states, right? Leptictidium (mt) 15:36, 28 June 2011 (UTC)

No, it is really a real state. If |a> and |b> are two orthonormal states, then so are |a'> = 1/sqrt(2) [|a> + |b>] and |b'> = 1/sqrt(2) [|a> - |b>]. Count Iblis (talk) 15:40, 28 June 2011 (UTC)

Quantum mechanics makes a clear, definitional distinction between the state of the system, and the observable state of the system. We have an article on this concept: observable. Something that is still a superposition of states is not observable. When you measure the state, you are observing one of many possible states. Nimur (talk) 15:45, 28 June 2011 (UTC)

Sorry, but that's plain nonsense. You can transform any observable using any arbitrary unitary transform to yield another observable. That such observables (whose eigenstatstes are superpositions of the previous ones) can't in practice be measured is not an issue, in principle you can measure a cat in a superposition of being dead and alive. Count Iblis (talk) 17:40, 28 June 2011 (UTC)

Therefore, no truly logic opposites can exist, since there will always be a third state possible. Yes? --Leptictidium (mt) 15:57, 28 June 2011 (UTC)

No. Count Iblis (talk) 17:41, 28 June 2011 (UTC)

Logic opposites are possible but the opposite of an electron with spin up is NOT an electron with spin down. The logis opposite of an electron in a spin up state is an electron that is not in a spin up state but could conceivably be in a superposition of states between spin up and spin down. A familiar example might help. The logic opposite of moving northward is NOT moving southward. That opposite would be not moving northward which might mean you are moving northwestward. Dauto (talk) 16:30, 28 June 2011 (UTC)

I prefer to phrase it this way. For example, let's take electron spin in the hydrogen atom. It can either take the value +1/2 or -1/2. When it is not measured, I do not say, "the particle is both spinning with +1/2 and -1/2." Instead, I phrase it as "the particle's spin is not measured. Here are the probabilities that it may be +1/2: (math); and that it may be -1/2: (math)." I think this simple choice of phrase makes quantum mechanics seem a lot less silly. But, if you want to say "the particle is both spinning up and not spinning up," (or, "the cat is both alive and dead"), you can very well phrase it that way. It's still silly. Nimur (talk) 16:08, 28 June 2011 (UTC)

Who said QM is not supposed to sound silly? If the electron is in a quantum superposition of a spin up and a spin down state than it is truly both at the same time. Dauto (talk) 16:15, 28 June 2011 (UTC)

You guys are all basing your statements on only one of the many possible Interpretations of quantum mechanics, specifically the common Copenhagen interpretation, which deals with such things as things existing in multiple states simultaneously, and with observation causing "collapse of the wavefunction" to produce the result; that is that the observation itself causes the result, somewhat non-mechanisticly. There are other, perhaps equally valid interpretations, such as the Ensemble interpretation, which takes a more agnostic view on the connection between quantum mechanics and reality. The mental gymnastics which is sometimes required (such as our simultaneously alive-and-dead cat) to make the Copenhagen interpretation work is philosophically unsatisfying. It is perhaps really much better to just state that our knowledge of the cat's living/dead state is incomplete without observation. In any instant, it may be alive or it may be dead, but it will be definately one or the other of them, irrespective of our observation. What changes is which variables we feed into our equations to decide if it is alive or dead; once we observe the cat. The distinction is deciding whether or not the event occurs only at the moment of observation or at some impossible-to-determine time before the observation. While philosophically the second proposition feels better, the first proposition actually makes the mathematics much simpler, since it gives us a specific point in time to determine when the "event" occurs; since it doesn't actually matter "when" prior to our observation, and since it is literally impossible to know "when" without observing it (i.e. you literally cannot determine the living/dead state of the unobserved cat unambigously from first principles, you can ONLY determine it empirically via observation), the first proposition works better for the purposes of making the math work. The end result is it doesn't really matter (from a scientific point of view) which "interpretation" works better for you, philosophically (that's why these are "interpretations" and not theories or laws or models, they don't require rigourous proof), the equations yield the same results either way, which is just the probability of the cat being dead as a function of time, and nothing more. What quantum mechanics does is destroy our belief in the "clockwork universe", that somehow given a perfect knowledge of initial conditions, one can deterministicly predict exact outcomes of any event before it happens. QM clearly shows this to be not true; one can only predict the probability of any event happening; even perfect knowledge of initial conditions cannot, for example, predict the exact time when a single discreet particle will decay. --Jayron32 16:48, 28 June 2011 (UTC)

Example: Deutsch' thought experiment involving superpositions of entire observers observing different outcomes. Here one considers observing the z-component of a spin that is polarized in the x-direction. If the whole system of observer plus spin is isolated from the environment, the entire system will be a superposition of the two outcomes. Then the observer in each branch forgets, in a reversible way, the outcome of the measurement, by dumping the information back on the spin. That then restores the spin to its initial state. The observer, however, does keep the information that a measurement of the z-component was carried out.

The observer can then verify that the spin is polarized in the x-direction after this procedure, even though he remembers measuring the z-component. This then proves that when the z-component was measured, both sectors in which different outcomes were obtained really exist (if only one sector really exists after measurement, the spin would not be restored to its original state). Count Iblis (talk) 18:00, 28 June 2011 (UTC)

Another example: Quantum mechanics in a timeless universe. Many theoretical physicists believe that time doesn't exist (my opinion is that those that do think time exists mostly haven't thought this issue through to its logical conclusion). Then the world today can, in this interpretation, be said to exist in the early universe as a complicated non-local superposition. Count Iblis (talk) 18:28, 28 June 2011 (UTC)

MRI question

Would an MRI be better at finding bullet fragments then an xray? Googlemeister (talk) 15:45, 28 June 2011 (UTC)

You probably need to define "better." MRIs are bulkier, more expensive, and harder to transport than a standard x-ray radiograph imager. Nimur (talk) 15:47, 28 June 2011 (UTC)

There are risks with taking MRIs of bodies containing magnetic metals. Even though bullets are typically made of non-metallic lead, there may be fragments of magnetic metal from the shell casing, and steel ammunition is sometimes used (e.g. in shotgun pellets). Studies show that the metal fragments are unlikely to move much, but there is a risk of damage to internal organs.[13][14] --Colapeninsula (talk) 15:55, 28 June 2011 (UTC)

"Non-metallic lead" ? I assume you mean "non-magnetic". StuRat (talk) 16:10, 28 June 2011 (UTC)

Better as in more likely to find the bullet fragments, the bulkyness of an MRI vs an xray machine is probably not of paramount importance (unless you are talking about military field applications I suppose) since both are too large to fit into your standard ambulance and cost usually isn't the biggest concern of someone with a bullet in them. I did not consider that some ammunition was steel. I guess I need to read up on that. Googlemeister (talk) 16:07, 28 June 2011 (UTC)

I would expect bullet fragments to show up quite nicely on an X-ray, so no need to resort to the more expensive MRI. StuRat (talk) 16:11, 28 June 2011 (UTC)

To expand on StuRat's statement, I would expect that (ignoring all other factors such as cost and complicatedness of use, complications due to magnets, and other issues) that an X-ray would be equally as good as an MRI in finding bullet fragments, that is once the image is obtained, a trained professional should have no more trouble finding a bullet in the image with an X-ray image than with an MRI image. If we include the other issues already noted above, the X-ray is probably better than an MRI for this application. --Jayron32 16:14, 28 June 2011 (UTC)

Here's a useful link: a research paper that performed comparative virtual autopsy using MRI and CT, and comparing them to the X-ray radiography: Image-guided virtual autopsy findings of gunshot victims performed with multi-slice computed tomography (MSCT) and magnetic resonance imaging (MRI) and subsequent correlation between radiology and autopsy finding (2003). Nimur (talk) 16:17, 28 June 2011 (UTC)

I think there needs to be some clarification on your use of the term "x-ray" -- CT scan machines emit ionizing radiation, as do conventional x-ray machines, so what exactly would be your criteria for separating the two? Projectional x-ray images (such as a chest x-ray or a dental panoramic radiograph) would not locate the bullet fragments in 3 dimensions, making localization of the fragments for surgical removal difficult. A full body CT scan (or CT scan of that portion of the body known to possess the fragments would allow the practitioner to see the fragments in an axial slice. Whether or not MRI would be better or worse, though, I cannot say, because (as a dentist) I'm completely unfamiliar with MRIs. DRosenbach ^{(Talk | Contribs)} 17:00, 28 June 2011 (UTC)

With traditional X-rays, they take two, at 90 degree angles, to locate objects in 3D. For example, one from the front and one from the side. StuRat (talk) 17:43, 28 June 2011 (UTC)

Multiple Alleles

Hello. If the dominance hierarchy of coat colour in Netherland Dwarfs is C (dark gray) > c^ch (chinchilla) > c^h (light gray) > c (albino), why do c^chc^ch and c^chc code for light gray instead of chinchilla and why do c^hc^h and c^hc code for point restricted instead of light gray? Thanks in advance. --Mayfare (talk) 17:36, 28 June 2011 (UTC)

Because binary genetics (even multiple allele binary genetics) is rarely useful for anything more than pedagogical purposes; that is it is helpful in demonstrating the basic principle, but in actual practice, the physical traits expressed by genes are often the result of complex effects, sometimes in the second or third order (for example, the gene doesn't directly code for the structure of the pigment, it codes for the structure of a component of the pigment, or it codes for the structure of a substance that is involved in the manufacture of the pigment some several steps back from the pigment itself). In particular, broad traits such as pigmentation represent what are called polygenic traits which are coded by multiple genes. For some analogs in humans, see Eye_color#Genetics and List_of_human_hair_color_genes, which lists for humans some 12 genes responsible for hair color; you'll also note that many of these genes code for things OTHER than hair color as well, that is there are not only multiple genes which determine hair color, there are multiple traits coded for by each gene (of course, depending on how you define "trait"). I would expect the genetics of other mammals to be similarly complex. --Jayron32 19:09, 28 June 2011 (UTC)