The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
In principle, if I cover something metal that already shows a degree of rust with a clear sealant, will that clear sealant stop the rust from progessing? (I have a sculpture that has an element that is wrought-iron bulrushes. I am stripping the sculpture of old paint that has started to crack, and am scouring off the rust. However, I like the look of the rusted bulrush heads and would like to leave them as they are. I don't want them to rust further.) If the answer is no, is there any other way of stopping the rust at just this point? If the answer is yes, what type of clear sealant would be recommended? The sculpture sits outdoors in the Canadian climate all year round and is in direct sun. Everything else on the sculpture I am painting with a Tremclad primer and then a rustproofing paint for the top coat. Thanks // BL \\ (talk) 00:49, 4 September 2009 (UTC)[reply]
"Canadian climate"? Where in Canada? It's a huge place. Rusting is heavily dependent on local humidity, which is different throughout the country. --✶♏ݣ02:16, 4 September 2009 (UTC)[reply]
I would heat the thing pretty hot to make sure that all of the water has been driven off the surface - then - when it's cool again, apply a decent coat of some kind of varnish. If the varnish can exclude the air and water from the metal - then I don't see how the rust could spread. Rusting is the combining of oxygen with the metal - no more oxygen therefore means no more rust. SteveBaker (talk) 16:35, 4 September 2009 (UTC)[reply]
Hard to heat a 4-foot tall sculpture, unless you mean just to leave it in the sun. (We do have sun this week for the first time since about May.) Thanks for all the ideas. // BL \\ (talk) 23:20, 4 September 2009 (UTC)[reply]
Toxicity of lead(II) nitrate
Is lead(II) nitrate toxic enough that skin exposure to a single small drop of its solution, washed off after only 1 or 2 seconds, will cause fatal poisoning? --75.40.206.92 (talk) 00:53, 4 September 2009 (UTC)[reply]
Probably not lethal, per the compound's MSDS, if there's no cut, etc, and it's pure skin contact. However, we do not offer, and are not qualified to offer, medical advice, and it is advisable to seek proper advice from a doctor asap. Tim Song (talk) 01:03, 4 September 2009 (UTC)[reply]
These are medical questions that we are not qualified to, and will not, answer. Please seek medical advice from a medical professional. Tim Song (talk) 01:22, 4 September 2009 (UTC)[reply]
This is verging perilously close to seeking medical advice, which we can't give here. If you were handling the substance, you should have first read its Material Safety Data Sheet. If you don't have access to that, you can link to it here:[3]
You will note that in the section relevant to skin exposure, it instructs you to seek medical advice (it means face-to-face, from a qualified Medic, although it doesn't explicitly state that). Unless your question was indeed purely hypothetical, please do so. (Addendum: I swear those earlier answers weren't there when I posted mine.) 87.81.230.195 (talk) 02:41, 4 September 2009 (UTC)[reply]
No. It wasn't. The guy was probably dissatisfied w/ my response, so he rewrote the question & removed the response. Then you responded; then someone else undid the rewrite/removal. Hence the mess. Tim Song (talk) 03:10, 4 September 2009 (UTC)[reply]
I have a truckload of mulch which is part mulched branches and about half mulched green leaves. It rained a little and I noticed vapor coming off the pile. When I dug beneith the surface I was shocked to find a large amount of heat coming from the pile. Is the heat due to continued metabolism of the leaves? I can not imagine they have had time to start the process of decay sufficient to produce as much heat as is coming off the pile and besides they are still green. --Taxa (talk) 01:18, 4 September 2009 (UTC)[reply]
How long has it been there? I found this in Composting: "If the pile is built in a short period, and has a good mix of materials (C:N) and a coarse structure, with about 50% moisture ("like a squeezed out sponge"), the temperature should rise within days to as high as 60 °C (140 °F)." Looks like decay can begin pretty quickly. You might also check Decomposition. Makeemlighter (talk) 04:00, 4 September 2009 (UTC)[reply]
Yes, its the decay caused by the action of the bacteria which the material no longer has metabolism to prevent according to the article. Thanks for the links. --Taxa (talk) 05:56, 4 September 2009 (UTC)[reply]
Mustard stains turn pink?
So being the slob I am, I just got mustard all over my grey track pants. I went to the bathroom and sprayed a variety of household cleaners on my pants -- I figured I didn't care much if they had bleach stains; I just didn't want them to be yellow. Something even weirder happened: The mustard stains turned pink when I sprayed them with a particular foaming cleaner (containing, among other things, ammonium chloride). What's going on? --✶♏ݣ02:10, 4 September 2009 (UTC)[reply]
Most yellow mustard contains tumeric as a coloration agent (it gives it its bright yellow color). Tumeric is also a good acid-base indicator, in that it turns a brilliant vermillion in the presence of a strong base. Usually, there is enough acid (vinegar) in the mustard to keep the tumeric in its yellow form; but if you overwhelm the acid with enough soap, it will turn a bright red. My guess is that the ammonium chloride is of a high enough pH to turn the tumeric red. --Jayron3203:16, 4 September 2009 (UTC)[reply]
Many strong cleaners are very basic, especially the ones for floors, toilets etc. The indicator idea is right for turmeric (don't know about mustard)- to get the colour to change back soak in orange juice or something. To get rid of the stain is very difficult.83.100.250.79 (talk) 11:20, 4 September 2009 (UTC)[reply]
Unless it contains both ammonium chloride and, say, sodium hydroxide. Such bi-phase cleaners are a common way to keep ammonium around, since acid-ammonium compounds aren't volatile at all. However, once the two phases are mixed in the presence of a liquid, the whole mess is basic. It would be entirely appropriate for the ingredients label to list ammonium chloride if that was what they added to the mess to generate ammonia in situ, even if the actual cleaning agent is basic ammonia, which is what I suspect here. I should have been clearer; nearly ALL industrial cleaning agents (even if they list ammonium chloride as one ingredient) will have a very high pH. Prepared yellow hot dog mustard almost always contains tumeric as a coloring agent. Tumeric + strong base = bright red color. That is exactly where his pink came from. --Jayron3217:56, 4 September 2009 (UTC)[reply]
The 'borax-turmeric' complex is also convincing - and I suspect will be far more difficult to get rid (stable?) than just adding a bit of grapefruit juice. If the original questioner is reading this they should check for the presence of "boric acid" or "borate(s)" in their cleaner.
As an aside I think washing the clothes (using clothes washing powder) does eventually remove turmeric stains, though not always on the first wash.83.100.250.79 (talk) 18:13, 4 September 2009 (UTC)[reply]
Suppose I shoot two neutrons out of two neutron cannons at the same time and speed so that they traveled almost parallel but get closer and closer becasue of the slight angle of the cannons. As the neutrons got closer and closer what will they do when they touch? --Taxa (talk) 02:20, 4 September 2009 (UTC)[reply]
Neutrons do not repel each other with the electrostatic force, but they do repel each other according to the Pauli exclusion principle. As above, the only relevant way to describe their collisional interaction is quantum-mechanically. Nimur (talk) 03:59, 4 September 2009 (UTC)[reply]
Since neither of the above directly answer your question, I'll try. I believe the answer is that, depending on random quantum details, there are various possibilities. They either glide right through each other, bounce off each other, or briefly stick together and then keep going their separate ways. 24.174.30.146 (talk) 04:48, 4 September 2009 (UTC)[reply]
It should be noted that this situation is identical to sending two neutrons slowly toward each other (just in a different inertial reference frame). Rckrone (talk) 06:40, 4 September 2009 (UTC)[reply]
There are other possibilities besides the ones already mensioned. They could stick and form deuterium releasing an electon, an anti-neutrino and energy, or one of them or both could decay before collision. Dauto (talk) 15:21, 4 September 2009 (UTC)[reply]
My uncle on my mother's side was born with his feet facing completely the wrong way round, along with webbed toes. He also suffers from some minor mental handicaps, though my family suspect this is the result of the extensive and painful treatment he had to undergo to reverse the position of his feet.
I've searched everywhere and can find no reference to this disorder - my main question is; what is it, and is it hereditary in any way (e.g. is there any chance my or my sister's children could suffer the same fate)? —Preceding unsigned comment added by 94.195.129.212 (talk • contribs)
The best person to answer such a question is a physician. We can't advise whether the condition you described is hereditary. It sounds like your description is not quite correct, either; there are a wide variety of possible physical aberrations which might be close to what you have described, such as club foot, but "feet facing completely the wrong way round" sounds like an implausible scenario. Again, you should ask a physician about this, since we can't diagnose what the actual condition was. Nimur (talk) 04:00, 4 September 2009 (UTC)[reply]
It's not implausible at all. The genes that control development operate in a hierarchical way, and there are many cases of mutation of a high-level laterality-controlling gene leading to things of that sort. A quick scan of Pubmed didn't show any easily findable descriptions of a syndrome, though. Looie496 (talk) 04:20, 4 September 2009 (UTC)[reply]
Well, I understand if it's something you can't comment on. I'm not looking to sue wikipedia over some hysterical self-diagnosis though - I just wanted to know if those symptoms are similar to any kind of recognised disorder, and if they are, whether that same disorder can be passed along.
We can't diagnose this condition - we're not allowed to. We'd have to say that if someone was born this way - it would have to have been something that developed quite early on in the womb - but whether that was caused genetically - or perhaps due to some unfortunate chemical that the mother was exposed to - would require such a diagnosis. It seems to me that this would likely have happened so early in the developmental process that it would almost certainly be genetic - but then things like Thalidomide have cause non-genetic birth defects that early on...so it's possible that it was an environmental rather than a genetic cause. SteveBaker (talk) 16:25, 4 September 2009 (UTC)[reply]
Magnise Steel
What % of magnise should be available in Mn steel.
Let's say there's an hypothetical species that branches into two distinct lineages. After a while, the original species is extinct, but the two diverging lineages survive and diversify as each lineage adds new features and adaptations that weren't found in the common ancestor. You could infer that the features that are unique to both lineages developed after the split, but the ones they share in common are ones that were present before the split.
Would it be possible, using genetic engineering, to remove only the genes that are unique to each lineage, but keep the genes that are common to both of them and reproduce the genome of the extinct ancestor?
My guess would be that it would work better for simpler organisms and especially for ones that have a lot of different descendant species, but would it be possible to try it on more complex species that have been diverging for millions of years?
In the situation where a gene changed in one of the two lines, how would you be able to tell which of the two is the original version and which is the one that changed? If a certain gene has changed in both lines, so that the original version of the gene no longer exists in either line how would you recreate it assuming you could somehow find out it was missing? Rckrone (talk) 06:19, 4 September 2009 (UTC)[reply]
You may be better off also comparing an out group not descended but still related to see if its gene is the same or equivalent to one of the decedents. There may also be totally deleted genes that you not recover at all. Graeme Bartlett (talk) 06:47, 4 September 2009 (UTC)[reply]
Even if you can reconstruct the ancestral genome from an information-theoretic point of view, you're still a long way from being able to revive an ancient beastie. --Sean15:09, 4 September 2009 (UTC)[reply]
Taking the question as it is worded literally, if you removed the genes that were unique to each 'new' lineage and only used the genes that were common to both to recreate the ancestor organism, you would end up with an incomplete organism. Might be fun to look at but it wouldn't be the same as the original. --KageTora - (영호 (影虎)) (talk) 15:02, 5 September 2009 (UTC)[reply]
There appears to be a correlation between the shortness of an end product's half-life and how easy it is to create the product by fusion. Is this correlation imaginary or real? --Taxa (talk) 07:07, 4 September 2009 (UTC)[reply]
Palladium 109 has a half life of only 13.427 hours and decays to silver 105 with a half-life of 41.29 days which decays to palladium 105 which is stable.
Can the decay of pd 109 or ag 105 immersed in a container of deuterium produce traces of tritium? --Taxa (talk) 07:46, 4 September 2009 (UTC)[reply]
How does Palladium turn into silver? The number of nucleons decreases by 4, yet the atomic number changes from 46 to 47, are you sure you have your question correct? Graeme Bartlett (talk) 11:54, 4 September 2009 (UTC)[reply]
The Wikipedia article lists only the "most" stable isotopes of palladium without showing the decay chain. Pd (46)109 is not included in the chart so I can not check it out there. Elsewhere the decay product of pd (46)109 is listed as ag (47)105 and the product of ag (47)105 as pd (46)105. --Taxa (talk) 12:54, 4 September 2009 (UTC)[reply]
I am using pd 109 as an example because of the relatively short half-life of 13 hours but I mean to include all of the unstable isotopes of palladium. So would any of these decays result in the production of tritium if occurred in a container of deuterium? --Taxa (talk) 14:30, 4 September 2009 (UTC)[reply]
Nitrogen certainly isn't going to change into tritium, why would it? Perhaps you should explain what you actually want to know and we can then work out what the information you need it. --Tango (talk) 17:41, 4 September 2009 (UTC)[reply]
Actually you mean proton. However, all you need say is that nothing any isotope does when it decays can change deuterium into tritium, regardless of what the isotope is. --Taxa (talk) 19:00, 5 September 2009 (UTC)[reply]
My interest is with palladium decay chain and products and in particular what they do in a Deuterium environment but by the same token other isotope decay chains and products may spawn reactions or serve as catalysts. Whether they may do so to the extent of fusion or fission is the question. --Taxa (talk) 11:32, 6 September 2009 (UTC)[reply]
And I wouldn't describe that as nitrogen turning into tritium, it is nitrogen turning into carbon with tritium as a by-product. --Tango (talk) 23:14, 4 September 2009 (UTC)[reply]
That is the great news about such interactions - they leave a uni-directional trail. So if I wake up in the morning with tritium in my bottle of deuterium I can speculate that maybe there was some nitrogen in there that got hit by a cosmic ray. Likewise, if I had some palladium in there I might ask if any of the unstable isotopes of palladium were in there as well which decayed resulting in a similar thing. Unfortunately, I have not been able to find any papers exploring or even speculating on any possible explanation except that tritium was probably already in there to begin with. --Taxa (talk) 23:25, 4 September 2009 (UTC)[reply]
The n meant neutron, but it was produced in other high energy reactions involving cosmic rays, which are mostly protons. You conclusion is quite likely, that natural deuterium will likely contain tritium, unless it is especially aged to let it decay away. Graeme Bartlett (talk) 22:29, 5 September 2009 (UTC)[reply]
The question sis whether any of the decay products of the isotopes of palladium could cause fusion in an environment of Deuterium reslting in the presence of Tritium. The need for high temp and high presure or extreme temp, however, seems to prohibit this possibility. --Taxa (talk) 12:04, 6 September 2009 (UTC)[reply]
Inventions
Is there anywhere I could see a list of 20th/21st century inventions not invented in America? Am I mistaken in thinking most inventions are made in the US? TheFutureAwaits (talk) 07:57, 4 September 2009 (UTC)[reply]
I'm sure USA are near the top of the list, being one of the worlds leading developed countries, but I imagine Japan and several European countries are worthy competitors. Googling phrases like 'latest recent inventions' comes up with heaps of sites about recent technological advancements. I imagine that there are new things being invented all around the world, it's just you more likely get to hear about the succesful ones that are relevent to you and your life.91.109.206.248 (talk) 08:10, 4 September 2009 (UTC)[reply]
Off the cuff I would say that you are almost certainly misled in believeing most invetions begin in the US. The main problem here is that "invented" is a fairly subjective term, the closest possible thing I could think of that one could quantatively measure is patent applications and patents granted. But this should be treated with caution as one "invention" could be covered by one patent, whereas another could be covered by thousands. Patents granted 2005Patent applications 2005 These would suggest that japan leads the way with about 30% of granted patents, US following with 22%. Despite this it could be argued that patent applications may be a better measure of the competition in technological indstry, rather than its level of innovation.—Preceding unsigned comment added by 92.1.57.159 (talk • contribs)
I think this will be very hard to measure. Many inventions are quite useless. To be honest, many patents are quite useless - if you start to use the number of patents or of patent applications as an indicator of success, smart people will start to generate a large number of patents or patent applications. Researchers at public institutions often do not apply for patents for inventions that would be patented if developed in a large company. But look at some of the biggies. Radar and computers are (mostly) British. Rockets are (mostly) German and Russian. Much of current software technology is from the US (but MP3 is German). Lasers are mostly US. CDs are Dutch/Japanese. Penicillin is British. Assembly lines are (mostly) US. --Stephan Schulz (talk) 09:59, 4 September 2009 (UTC)[reply]
It depends how you define "inventions". You can definitely get statistics on patents approved, but whether these count as legitimate "inventions" is problematic. Additionally tons of "inventions" that we think of as being American have been, in their present forms, developed outside of the US. So modern solar cells were developed in the US in the 1950s, though a far more efficient model was worked out by the USSR in the 1970s, though most solar cells today are developed by Germany. Similarly, Americans may have invented the first microwave but it's likely that the patents that cover your current microwave are held by the Japanese (ditto your television and many other digital things).
The US does have a strong tradition of invention dating back to the 19th century, and the research labs of the post-WWII period certainly contributed a lot. It's not incorrect to say that the US has a disproportionate amount of inventing and innovation, though it is an exaggeration to be sure to suggest that all of the important inventions of the modern time came out of the US. --98.217.14.211 (talk) 13:38, 4 September 2009 (UTC)[reply]
A further point that complicates the matter is that something protected by a US patent is not necessarily invented in the US, nor by a US citizen. --Quest09 (talk) 15:49, 4 September 2009 (UTC)[reply]
And worse still, the existence of a patent doesn't prove that there is a novel invention behind it - many MANY patents are just junk. Until a patent is challenged in court and actually survives that challenge - you have no idea whether it's a truly novel and non-obvious invention or just some schmuck trying to make a quick buck. There are more patents in the US because there are more people patenting junk - laws that allow things like "business methods" and software algorithms to be patented - too few patent clerks to check each patent in sufficient detail - and a legal system that allows big companies to patent things that smaller companies invented and then suing them years later with a 'submarine patent'. The cause of the large number of patents is not some amazing national tendency to inventiveness - it's a sucky patent system! SteveBaker (talk) 16:15, 4 September 2009 (UTC)[reply]
Seeing that for popular inventions such as radio, telephone, computers, planes, etc just about every nation can throw in a somewhat valid claim, you'll find it very hard to get any agreement on that. Can I ask the other way round: Can you name just one invention that is undoubtably solely American?195.128.251.165 (talk) 22:54, 4 September 2009 (UTC)[reply]
Any of the application-specific technology for landing a man on the moon (well, most of that stuff, anyway) is pretty exclusively American. (Though, the engineers who worked on those projects may have had backgrounds or origins from other nations). But I doubt any other country can make a legitimate claim to inventing a Lunar Excursion Module before the USA. They might have hypothesized such an idea, or even built some prototypes, but none were actually functionally invented until Americans actually executed the lunar missions. Nimur (talk) 23:12, 4 September 2009 (UTC)[reply]
Could you have any kind of rocket engine without some Russian help? Very few things are invented completely from scratch, they usually build upon the work of others. It is usually difficult, if not impossible, to determine a unique inventor for a device in a way that can't be disputed. Should you credit the person that did the underlying work? The person that came up with the idea for the device? The person that came up with a way of implementing that idea? The person that actually made it work in practice? --Tango (talk) 23:23, 4 September 2009 (UTC)[reply]
Isn't that precisely the point though? You claim it is solely an American invention. Others claim it was just building on earlier inventions. Nil Einne (talk) 01:21, 6 September 2009 (UTC)[reply]
Quoting from above, which you replied to "Very few things are invented completely from scratch, they usually build upon the work of others. It is usually difficult, if not impossible, to determine a unique inventor for a device in a way that can't be disputed. Should you credit the person that did the underlying work? The person that came up with the idea for the device? The person that came up with a way of implementing that idea? The person that actually made it work in practice?". You say, because the aileron wasn't put on a plane, all prior inventions should be ignored, even if the American version was building on earlier inventions. (I don't know if it was.) Others say people made aileron's before that and the Americans were building on earlier inventions, no harm in that, but misleading to call it a solely American invention (perhaps you can call the American version the first successful invention, but that's quite different from calling it a solely American invention.) Another complication is what do you do with independent inventions? In other words, ultimately this discussion is going no where since don't agree on how you define a solely American invention. You are welcome to your opinion, but it's clear quite a number of people don't agree so it's ultimately just random opionions on what is an isn't a solely American invention Nil Einne (talk) 04:37, 6 September 2009 (UTC)[reply]
FYI: The method of roll control used on (almost) all the world's airplanes today (namely, the aileron) was first successfully developed and used by Glenn Curtiss as I already mentioned above. His design was based entirely on the Wright Brothers' wing-warping system (the arrangement of the control cables was nearly identical, but they actuated ailerons instead of warping the whole wingtip). The Wright Brothers, on the other hand, designed the wing-warping system completely on their own after watching seagulls fly, and did not build upon any other aileron or wing-warping control systems. Therefore the wing-warping system definitely qualifies as a solely American invention, and so does the aileron, since it was invented by an American inventor and based on another invention that was solely American. 98.234.126.251 (talk) 04:50, 7 September 2009 (UTC)[reply]
LK Lander? That it was never used is no slur on its "invention" per se.
And again, we're back to mincing words over what counts as an "invention" - to answer this question at all, we need a really rigorous definition for "invention." Nimur (talk) 17:26, 5 September 2009 (UTC)[reply]
I just found a couple more examples of inventions that were solely American: the phonograph was undisputably an all-American invention, and so was the nuclear reactor. Painkiller drugs for surgery were also first developed in the USA. So there were quite a few inventions that were solely the work of our American inventors.
And as for the LK lander -- it was never tested in its intended application (i.e. to land on the Moon), so it doesn't count as an invention either. It's only an invention once it's been tested and found to be useful either in its intended application or in some other application, or else every failed idea and useless gadget in the world would count as an invention, which would take credit away from those (like Thomas Edison or the Wright Brothers) who made their inventions practical. 98.234.126.251 (talk) 00:09, 6 September 2009 (UTC)[reply]
I don't understand how nuclear reactions, or even a reaction pile, could possibly be considered as an "invention", I'd prefer a "technological development". The technology was developed by a huge team, not through one single person's idea. But if it's going to be labelled as an invention, then I'd say Lise Meitner was the inventor. Franamax (talk) 01:00, 6 September 2009 (UTC)[reply]
To both of you -- your arguments are bullshit. Enrico Fermi was living in the US and designing the reactor for the US government's Manhattan Project -- ain't that enough to make this an American invention? And Leo Szilard's "outline design" was just that, an outline, he never had it made into actual hardware, which is an absolutely necessary requirement for an idea to be considered an invention. And as for Lise Meitner, she only discovered nuclear fission, she never played a part in actually designing the nuclear reactor, so your claim that she was the inventor of the nuclear reactor is bullshit squared. According to your reasoning, then, it would be Leonardo da Vinci who invented the helicopter because he made the first design sketch, even though that design was never built, never tested, never flown, and indeed was incapable of controlled flight? Or it would be Rutherford who invented the TV because he first demonstrated that an electron beam can induce phosphorescence, even though his "TV tube" didn't actually show any pictures, but just glowed in the dark? You don't even know the difference between an "idea" and an "invention", do you? Or do you just not give a hoot about such fine distinctions? 98.234.126.251 (talk) 01:39, 6 September 2009 (UTC)[reply]
N.B. Our article implies Enrico Fermi was stateless from 1938 to 1944 (not an Italian citizen). In some ways this may be accurate given the situation at the time. Both of the above did of course take up American citizenship not that long after. But they do highlight another issue. Some inventions are made in another country (usually a developed one, often the US) by citizens of another country (who perhaps got most of their education in their country) and some of these don't choose to take up citizenship of the country were they made the invention (many do of course). Should their inventions be considered inventions of the country where they were when they made the invention (considering they likely had help etc), both countries, or what? Nil Einne (talk) 04:56, 6 September 2009 (UTC)[reply]
The pain killer example seems rather odd to me. According to anaesthesia and surgery, opium, alcohol, cannabis, aconitum and others have been used for a long while, by (depending on the combination) the Greeks, Romans, Chinese, Indians, and others long before the US existed. Because of the risks of with unstandard doses, attempts were made to standarise the doses as much as possible given the level of sophisticary at the time. Hanaoka Seishū evidentally is often credited as the first to perform surgery (specifically a masectomy) under general anaesthesia in 1804 albeit his work was not published to the Western world because of the isolation policy of Tokugawa Shogunate until they had already developed their own techniques. Moving on to a different area, inhalant anaesthetics were used by Arabic and Iranian/Persian physicians/surgeons and in Islamic Spain via narcotic soaked sponges (influenced of course particularly by the Greeks). (Some of the earlier anaesthetics were of course inhaled.) Of course it's questionable if there can really be called inventions per se but it's also clear that these were important in the development of later anaethesia methods and drugs. Coming to more modern times, Morphine was first extracted in Germany and we're getting closer and it was an important step forward allowing a great degree of standarisation although the lack of the hypodermic needle hindered its use. Diacetylmorphine (aka heroin) was synthesised in London from morphine albeit didn't become of interest until it was synthesised again in Germany (although I'm not sure if it was ever used much for surgery). Okay I'm getting a bit ahead of things there... The anaesthetic properties of nitrous oxide (itself discovered by a Englishman) was discovered by a Brit albeit first used (that we know of) by an American albeit for dentistry since it's too weak to be used as for general anaethesia (but shouldn't be ignored, since it's seems definite it did have an effect on later developments). Diethyl ether was possibly discovered by a Spainard and first synthesised by a German and its analgesic properties discovered by a Swiss although first used in surgery (that we know of) by Americans. Chloroform was discovered first by an American then independently by a Frenchman and a German, characterised by another Frenchman and its anaesthetic properties discovered by James Young Simpson and first used by him in his England, before spreading to Europe and eventually America (although as it later turned out, the Americans were fortunate they stuck with ether for so long given that chloroform was much more likely to kill the patient and was abandoned). John Snow (physician) from England was evidentally one of the first to study and calculate dosages for ether and chloroform, evidentally learning of ether from the Americans and chloroform of course from his compatriot and as his work was published in 1847/1848 (ether being first publicly demonstrated in the US in 1846), I don't think the Americans were far ahead of him. He was also instrumental in promoting and increasing it's acceptance in Britain from what I can tell I mean he used it on the queen (with her permission) for hecksake. Karl Koller (ophthalmologist) used cocaine as a local anaesthetic (although many of the early drugs/herbal products were used locally partially I guess since they were more likely to kill the patient if given generally because of the dose regulation and other issues) before he moved to the US. Coming to the modern developments Paul Janssen a Belgium appears to be credited as one of the pioneers of modern anaesthesia drugs [8]. There's obviously a fairly big gap between Janssen and morphine/ether/chloroform/nitrous oxide which I haven't looked at, primarily because I didn't come across much discussion of that in my reading but I think I've covered enough. Your broad statement is questionable. My guess is you were planning to claim that Americans were the first to use a form of general anaesthesia (specifically ether) that developed into our modern methods (which is a far more specific claim). This is true. It's clear however as others have emphasised with other examples that 1) These built on (or at least repeated) earlier efforts of using anaesthesia by a large number of people of different cultures and countries. 2) They wouldn't have happened if someone hadn't found ether, and as they were influenced by nitrous oxide if that hadn't been found and the effects of that hadn't be known it's not clear what would have happened either (you might argue someone else would have, but that's like arguing someone else would have used ether for general anaesthesia) 3) What we have today is the result of the efforts of a lot of people, many Americans of course but also a lot of other people 4) We know at least one Japanese person did use general anaesthesia before the Americans, even though his work was not an influence. This is not to belittle the accomplishments of those Americans involved but to acknowledge that their work can't be held as not being influenced by others nor (IMHO anyway) can it be considered the seminal work as although it was important, so was a lot of other things. Nil Einne (talk) 04:27, 6 September 2009 (UTC)[reply]
You're correct in saying that my statement should have been more specific. Yes, other nations had in fact used primitive forms of anaesthesia for surgery before we came up with the idea of using ether for that purpose. However, none of the methods you mentioned above could offer complete, relatively safe pain relief: aconitum is highly toxic, and alcohol/cannabis/opium can only numb the sensation of pain, not eliminate it completely. The first truly practical anaesthetic agent was ether, and its use for anaesthesia was pioneered by American surgeons (namely Crawford Long). Cocaine and heroin aren't safe to use for anaesthesia either, by the way. 98.234.126.251 (talk) 05:24, 7 September 2009 (UTC)[reply]
I took a look at the article about Hanaoka Seishu -- it says about his "anaesthetic" witches' brew that "The active ingredients in Tsūsensan were scopolamine, hyoscyamine/atropine, aconitine and angelicotoxin" -- which are deadly poisons and would have been extremely dangerous for routine use during surgery. It also says that "His wife, who participated in his experiments as a volunteer, lost her sight due to adverse side effects", which speaks volumes about the safety of his formulation. I for one would surely not wanna take that stuff before getting a broken bone reset -- even chloroform would've been safer, to say nothing of ether. 98.234.126.251 (talk) 03:49, 8 September 2009 (UTC)[reply]
Boy are they lying through their teeth! Quite apart from their rabid anti-Americanism and terrorist sympathies (which alone should have been enough for that site to be banned from the Internet), here's where they're factually wrong: the internal combustion engine was invented by Germans; the telephone was an American invention beyond doubt; the television was the work of a Hungarian, an American and a couple of Russians; and the radio was invented by an Italian who put together twoinventions by a German and a Russian inventor! In short, this website is a perfect example of "counterknowledge" in action! Man, those damned Scots are really trying to take credit for inventions that they never even made in the first place! 98.234.126.251 (talk) 00:48, 8 September 2009 (UTC)[reply]
Telephone was invented by Mr Bell; however due to funding he moved to the US were his idea!! was improved opon and consiquently the US due to funding and improvments of the idea claimed the invention. this is true with regard to many inventions both in the US and Europe as well as China Middle east ECT...a country such as US in mainly made up of Imagrants from Europe south america, unless you are native American indian then you are from Europe or another country around the globe. it is only recently after several genarations you could actually say i am American. Most say i am Irish American African American Mexican American French Amrican or something along those lines. The exAZmple of the telephone was far enough back that it was most likerly a european who had moved to America any way - only recently could you actually claim it was an American invention. Inventions of certain rifles would have been claimed by people like Henry Colt however it was proberly made by somebody working for him who had migrated to the country to the boss goes the spoilsChromagnum (talk) 07:20, 12 September 2009 (UTC)[reply]
Cliffs
Is there a maximum possible height for sheer (90 degree) cliffs made of solid rock? I'm asking specifically for Earth gravity although I'm sure on Mars it can be much greater. I think the pressure from the rest of the mountain would cause a cliff of a certain height to collapse? TheFutureAwaits (talk) 10:32, 4 September 2009 (UTC)[reply]
Based on a documentary about the Grand Canyon, I believe it has less to do with the sheerness of the cliffs and more to do with the angle of the minor fissures in the wall. If the fissures are highest at the face of the cliff and lower inside the rock, gravity pushes rock against rock and nothing much happens. If the fissures are lowest at the face and higher inside the rock, gravity slowly slides the rock above the fissure outwards - eventually causing a collapse. -- kainaw™12:33, 4 September 2009 (UTC)[reply]
That would be a factor, and the type of rock also would be. Theoretically, every cliff will eventually collapse, since the earth is constantly changing. But consider Half Dome in Yosemite. That's a long, sheer drop - and that baby has been around a looong time. But I think it's made of granite, which means it is likely to last a lot longer than cliffs of sedimentary rock, such as at the Grand Canyon. Baseball BugsWhat's up, Doc?carrots12:38, 4 September 2009 (UTC)[reply]
For a given type of rock, presumably at some point the density times the height of the column will overcome the compressive strength of the stuff at the bottom. My back of the envelope calculation for those factors in granite (density ~.04 lbs per in3, strength ~20,000 psi) gives a column of it a maximum height of around 40,000 feet. I'm sure there are complicating factors, though. --Sean15:47, 4 September 2009 (UTC)[reply]
Your value for the density of granite is too low. If almost 100,000 ft is possible, why, then did I see 7,000 ft somewhere as the upper limit for sheer cliffs? (and interestingly enough, for buildings using 1920s engineering, which are hollow) Sagittarian Milky Way (talk) 23:58, 6 September 2009 (UTC)[reply]
Not really, no. There wouldn't be a limit. First off, it makes no difference whatsoever if it's a sheer cliff or not - pressure depends only on what's directly above you. On that note, you're currently on top of about 3000 kilometers of solid rock - the Earth's mantle. Whereas it's only 100 km up to space, at which point you're practically weightless. --Pykk (talk) 17:20, 4 September 2009 (UTC)[reply]
Crap, that's wrong - I did the math. You're not very weightless at all at 100 km. (the shuttle's just apparently weightless because of its orbit) Anyway, the question would really be if the Earth's core could handle the pressure, I suppose. --Pykk (talk) 17:34, 4 September 2009 (UTC)[reply]
A sheer cliff vs. a slanted cliff would matter. It isn't just about pressure, its about distributing the force, and a slanted cliff would be more resistant to slight seismic and thermal disturbances. Of course, there's always the problem of keeping a solid rock "solid"; freeze-thaw cycles and other weathering processes induce cracks and weaknesses on short time scales.
You might be right. I don't know how and when I read a context describing the universe as if you have data that contain all characteristic of this universe and that each sub-data with similar characteristics can communicate each other. Perhaps in my dreams (joke).--Email4mobile (talk) 11:34, 4 September 2009 (UTC)[reply]
I just had a lecture on Virtual Work in my Applied Mechanics class, and the professor left me with certain basic conceptual doubts. He says the method of virtual Work can be applied to indeterminate systems, and its powerful advantage is that it can generate as many independent equation as one wants. Thus, it can be used to solve situations where Newton's laws fail (indeterminate systems) without losing the assumption of rigidity of the bodies involved. I wasn't convinced with this, and a private conversation after class tells me that this principle of using work (energy) is more fundamental than Newton's Laws, and is more powerful than it. I have several doubts. This principle was derived in my class using the Newton's laws, and no other assumptions. So how can this result in giving more equations than the Newton's Laws themselves? Is Virtual Work really powerful enough to generate as many equations as one wants, and solve indeterminate systems completely ? Is my professor conceptually right? I need solid, authoritative answers on this, and thanks in advance for the help. Rkr1991(Wanna chat?)13:06, 4 September 2009 (UTC)[reply]
My understanding of virtual work is that it is just a tool that can be used to solve problems that could otherwise be solved just fine using netwon's laws, but perhaps more with less effort. I didnt think virtual work was taught in most engineering programs. That might be why you didnt get a response. My professor wrote a book that included a lot on the topic. Do you by chance go to the university of arkansas? But, to answer your question virtual work is just an expression of newtonian laws. XM (talk) 05:08, 5 September 2009 (UTC)[reply]
No, VW only allows you to solve problems that could otherwised be solved using convential newtonian methods. You can generate infinate equations, but you could do this in newtonian methods too, but any equations past a point would be surpufolus and wouldnt do any good. That is, you can sum forces about the X, Y, and Z axis, giving you 3 equations, and then put a new axis up and sum forces about x1 y1 and z1 but those 3 new equations dont get you any further. I dont think your professor is communicating VW effectively. There is nothing magical or extra-newtonian about it XM (talk) 10:51, 6 September 2009 (UTC)[reply]
Queries about Strong Nuclear Force
Why the strong nuclear force is many(more than 50) times greater than that of Electrostatic force, if it is only has to overcome the proton-proton repulsion? Also, if it is so then why does it act on neutrons as they are chargeless, hence no repulsion, hence no need for external force? Even considering the revolution of nucleus around itself such high quantity of force may not be required!
Your question seems to presume that the Universe is an elegantly, carefully engineered machine, in which no forces or energy should be 'wasted' in order to achieve certain desirable results. Unfortunately, it doesn't work that way. Physical laws came first, and this Universe is the consequence; the laws weren't designed in advance to produce this particular Universe. (That said, if we wished to play the 'what-if' game, it's worth noting that we probably wouldn't be here if the strong force were weakened. Higher-mass isotopes which are stable in this Universe would tend to be radioactive Fusion reactions – particularly the ones which power our Sun – would have a lower energy yield. There would be a different preponderance of elements in the Universe and on Earth. All in all, a very different place.) TenOfAllTrades(talk) 14:47, 4 September 2009 (UTC)[reply]
Why is the proton about 2000 times heavier than an electron? It just is. Why is the strong force stronger than the electromagnetic force? It just is. Dauto (talk) 14:52, 4 September 2009 (UTC)[reply]
In such basic questions about the universe, "what" is a question for scientists but "why" is a question for theologians
The answer to "why is gold yellow?" used to be "it just is" but now it can be explained from relativistic quantum theory. Most physicists think the ratios of the strengths of the fundamental forces will also turn out to have an explanation because they seem too large to happen by accident. -- BenRG (talk) 14:32, 5 September 2009 (UTC)[reply]
Perhaps the only thing we have that's close to answering the 'why' question is the Anthropic principle. It basically says that if the universal constants like the strength of the strong force were any different - then in all likelyhood, life would fail to form and there would be nobody here to consider the question. Since we are here to ask the question, these properties must be almost exactly how they are. The strong force is what pulls two hydrogen nuclei together when they get close enough together. If it were weaker, it would be harder for protons to get together like that and we'd probably have no stars...or only much bigger stars or something...which pretty much means no life either. It's an answer - but not a very satisfying one. SteveBaker (talk) 03:07, 5 September 2009 (UTC)[reply]
I think you're confusing the strong force that acts on objects with color charge (quarks and gluons) with the residual strong force that acts on color-neutral objects like protons and neutrons. The latter is a lot weaker. I think it's comparable in strength to the electromagnetic force in the nucleus. -- BenRG (talk) 14:32, 5 September 2009 (UTC)[reply]
How are you measuring the strength of the forces? If you're referring to force, the strong strong force is sometimes stronger and sometimes weaker than the electrostatic force. Whether it is stronger or weaker depends on the charge, color charge, and distance of the objects the force is acting between. — DanielLC16:23, 5 September 2009 (UTC)[reply]
falling distance
How high of an object could a person realistically expect to survive jumping off of onto a cement sidewalk, grass covered dirt the deep part of a swimming pool? I understand that this question may not be answerable with the given criteria, but perhaps there is a study that you could push my way that has looked into something kind of like this. Googlemeister (talk) 16:50, 4 September 2009 (UTC)[reply]
The nature of the fall (feet-first versus head-first) makes a massive difference - a small difference in HOW you fall makes all the difference in the world to the outcome. So there aren't going to be hard-and-fast answers. Anyway OSHA sets a 'safe fall' limit of 6 feet in most circumstances - without specifying the nature of the surface and says that hundreds of workers in the US die each year as a result of falls from as little at 10 feet. However, there are people who have fallen from airplanes without a (working) parachute who have survived falls from heights that guarantee they reached 'terminal velocity' - which means that it doesn't matter whether they fell from 1,000' or 40,000' - the result would be the same. Vesna Vulović (allegedly) fell 33,000 feet and survived (just) - but there are plenty of well-substantiated accounts of people falling from 20,000 feet and surviving with relatively minor injuries. So the answer is somewhere between 6 feet and 33,000 feet - I don't think that helps much! SteveBaker (talk) 12:36, 5 September 2009 (UTC)[reply]
Those really high falls generally have extenuating circumstances. Usually there is something providing them more drag than you would have normally and they usually have something to break their fall. Terminal velocity for a skydiver in the standard position before their parachute opens is about 120mph - I doubt anyone has survived going from 120mph to 0mph in a fraction of a second. --Tango (talk) 12:52, 5 September 2009 (UTC)[reply]
Certainly there are extenuating circumstances! That's what I'm trying to say. Check out Nick Alkemade, Ivan Chisov and Alan Magee for example. That's my point - some people die from a 10' fall, others suffer no injury. Other people survive a 33,000' fall. Professor Splash can dive from 40' into one foot of water in a kiddies paddling pool without injury(!) - but if you dive (badly) from just one foot above the water into a swimming pool that's less than ~6' deep, you can whack your head on the bottom and die. Yet Dana Kunze holds the high dive record at 174 feet into water - Kevin Hines who tried to commit suicide by jumping 280 feet from the Golden Gate Bridge and survived although 98% of people who do that don't. It's all about the circumstances...which is what makes answering this question in anything other than the vaguest terms impossible. SteveBaker (talk) 19:18, 5 September 2009 (UTC)[reply]
Opal inlays
Would it be possible to use opal for guitar inlays, instead of pearl? The reason I post here is because I'm interested in the practicality, are there any reasons why such a material could not be used? I gave Google a preliminary search but couldn't find much. Any links to information online would also be appreciated! Thanks. Regards, --—Cyclonenim | Chat 17:00, 4 September 2009 (UTC)[reply]
I'd think that a sheet of opal as thin as a soundboard inlay would be very prone to breaking in normal use (never mind Townshendisms), and that broken or cracked opal would be sharp enough to cut fingertips. I guess you could cut a much deeper rebate in the soundboard, allowing for a thicker inlay, but I don't know what that would do to the sound. -- Finlay McWalter • Talk17:15, 4 September 2009 (UTC)[reply]
I'm concerned about the high water content of Opal and how that would affect the wood, if at all. @Jayron, I was aware of that but I always refer to it as pearl for the sake of effort (and I also couldn't remember the proper name!) ;) Regards, --—Cyclonenim | Chat 18:53, 4 September 2009 (UTC)[reply]
I don't think it is a problem - opals are not wet, the water is very well bound they do not leach water (the back could be coated anyway), a bigger problem might be the softness of the opal. Also did you mean electric guitar, or acoustic - electric would probably be easier.83.100.250.79 (talk) 19:01, 4 September 2009 (UTC)[reply]
Opal is quite heavy - on the body it might not be good - but as frets (is that the right word) it might be ok. I can't see any real issues with it though, except acoustics and possibly it wearing quite quickly.83.100.250.79 (talk) 23:30, 4 September 2009 (UTC)[reply]
I wouldn't be suprised if there are plastic opal simulants available - which would probably have better characteristics than the rock ( a web search confirms such things exist) - probably cheaper too.83.100.250.79 (talk) 23:44, 4 September 2009 (UTC)[reply]
static electricity - clothes
Is there a simple explanation for why natural fibres (eg cotton) produce far less static electricity than synthetic fibes (eg polyester) when in rubbing contact?83.100.250.79 (talk) 17:51, 4 September 2009 (UTC)[reply]
I was wondering about that - but does that help conduct the static away - to where? (my shoes insulate) - or does it prevent the static build up in the first place (like a sort of short circuit)?83.100.250.79 (talk) 23:28, 4 September 2009 (UTC)[reply]
In the 18th century Stephen Gray (scientist) learned that some substances conduct electricity well and other poorly. In terms of high voltage, low current static electricity, wood, hemp or cotton drain off a charge. They are sometimes thought of as insulators for low voltages, but when a small charge at high voltage is to be kept from draining to ground, Gray found that silk or glass were superb insulators. He could use a hemp thread as a conductor for static electricity, and insulate it by hanging it from silk threads. So I suggest that natural fibers allow quicker drainage of charge than silk, or synthetics such as polyester or nylon. Fabric softeners or dryer sheets leave a slightly conductive layer of chemical on the clothing to drain off the static charge. Edison (talk) 23:42, 4 September 2009 (UTC)[reply]
That's interesting - anyone know (or want to guess) why silk is different from cotton - I know silk is a protein, and cotton a carbohydrate (of sorts) - but both are quite good at hydrogen bond (absorbed water) which was suggested as a cause for the non-static nature of some natural fibres.83.100.250.79 (talk) 23:48, 4 September 2009 (UTC)[reply]
Experiments by 18th century scientists showed that on a slightly damp day, static charge drained away faster than on very dry days. So they would dry the apparatus in front of a fire on a dry winter day for maximum static buildup. Cotton, wood, or hemp still drained off the charge, however dry you made them, but glass or silk insulated even better. I believe the slight conductivity is a characteristic of the fiber and not of the moisture. Maybe at extreme heat some water is driven off, but the fiber would probably lose its normal appearance and properties. If charred, it would probably be somewhat conductive from the carbon, but if reduced to ash it might be an insulator. That would not be recommended for your clothes, however. Edison (talk) 19:36, 5 September 2009 (UTC)[reply]
Yes. There were 10 properties and I had to say if each one is physical or chemical. All of the other ones were easy properties like melting point or reactivity with acids, but I couldn't figure out those three. --75.39.193.64 (talk) 22:26, 4 September 2009 (UTC)[reply]
They are a bit tricky - taste is chemical - see taste - though obviously if something is hot (tea) or cold (ice) is a physical property - though that isn't actually a taste. There are chemical receptors on the the tongue...
Both magnetism and solubility are probably physical properties - though both depend on the chemistry - only certain chemicals can be magnetic , but if you are measuring how strong a magnet it that is definately a physical property.83.100.250.79 (talk) 23:24, 4 September 2009 (UTC)[reply]
In the standard High School chemistry text, chemical properties are those which require a "chemical change" to be seen; chemical properties describe how a substance combines with another substance, or decomposes into other substances. What a chemical property describes is how a substance undegoes changes into different substances. If the substance does not change into a new substance while observing the property, it isn't a chemical property. Thus "flammibility" is a chemical property, in that in order to observe if something is flammible, you have to, you know, change it into new stuff. However color is a physical property, because you can observe color by just looking at it. It does not require a change into a new substance to observe somethings color. Using THAT definition, the OP should easily be able to decide which properties are chemical and which are physical, without us having to do his homework for him. --Jayron3201:26, 5 September 2009 (UTC)[reply]
Gah I hated these questions in high school. All they do is confuse students and make them draw arbitrary lines of distinction where none exist. Picking up an object by itself is a chemical reaction (Van der Waals repulsion). Magnetism is chemical (it depends on electron configuration, and you can actually cause changes in it by excitement -- see nuclear magnetic resonance). Melting point in itself is a chemical property, naturally (relying on chemical bonds).
When I was in the classroom teaching, I tended to glaze over this section as well; the state-mandated End-of-course tests always had some questions on it, so I had to teach it as they expected, but it always left a "bad taste" in my mouth. Still, there is some internal logic to the physical/chemical divide, just not a lot once you really learn chemistry. It is actually a good example of the Lie-to-children, that is the use of inaccurate models for pedagogical purposes; in this case learning to recognize a distinction between irreversable changes where new substances form, verses changes which do not change the type of substance. The same unit usually covers other categorization schemes, which I found much more helpful to later studies in chemistry, such as the distinction between a pure substance and a mixture (you'd be surprised how HARD it is for many students to recognize that Milk is a mixture while water is a pure substance!), or between a homogeneous and heterogeneous mixture (Tyndall effect). The physical/chemical categorization scheme is shitty, but it comes up in class, and will appear on the test, so we should at least make our best attempt to make it work for students when the do have inevitable questions about it. --Jayron3211:55, 5 September 2009 (UTC)[reply]
Jacube seems to be a name for Hylocereus undatus in at least some areas of Mexico. Try Googling for Hylocereus jacube and Tamaulipas jacube and tasajo jacube. (Tasajo, reina de la noche, and junco tapatío appear to be other names commonly used for the plant in Mexico.) My Spanish isn't quite up to interpreting all the results. Deor (talk) 00:45, 5 September 2009 (UTC)[reply]
Stomach to Bladder
I'm trying to get an estimate of the time, after drinking a bolus of water (say 16 ounces), until it shows up (say 1-2 ounces ) in the bladder. Then, assuming an average adult human how long until 8 ounces and then how long until 14-15 ounces gets to the bladder. I realize that there are many variables that would influence/confound the timing so I'm just looking for a rough generalized estimate. OR with alternative beverage is acceptable ;) Thanks all. hydnjo (talk) 22:03, 4 September 2009 (UTC)[reply]
There are so many variables that I don't think we can even give a meaningful estimate. It could vary from a few minutes to a few days (if ever). --Tango (talk) 22:22, 4 September 2009 (UTC)[reply]
It's not really a meaningful question. Water doesn't go from the stomach to the bladder. Water goes from the stomach to the bloodstream, if absorbed, or to the colon and from thence elsewhere if not. If absorbed, it affects the state of hydration, and the kidney compensates, if needed, by increasing urine output. But the urine excreted is, if you will, "randomly chosen" from the blood traveling through the kidney, and won't directly correspond to the water just absorbed from the stomach. If the water absorption is going to trigger additional output, it will do so when it's absorbed, it doesn't have to "go" to the kidney to do it. There's no "travel" delay; it will happen right away. - Nunh-huh22:37, 4 September 2009 (UTC)[reply]
An addendum to Nunh-huh's thorough response — urine output from the kidneys is mostly (inversely) tied to the level of vasopressin (also called antidiuretic hormone) in the blood. If the body senses that it has too little water onboard, vasopressin is secreted to trigger its retention. (The regulation of vasopressin is a fairly complex process; our article gives a number of useful pointers.) TenOfAllTrades(talk) 23:30, 4 September 2009 (UTC)[reply]
To be more specific, I was trying to understand the body mechanics of one element of a urological exam which involved fasting, voiding, drinking, waiting and voiding again with some ultrasonic imaging of the bladder at various times. No medical advice being sought out, just some musing on my part about the drinking-waiting-voiding part. hydnjo (talk) 01:11, 5 September 2009 (UTC)[reply]
I don;t think anyone suggested you were seeking advice, medical or otherwise. In general, you fast before an imaging study (ultrasound or x-ray) to avoid complicating the view with undigested food; then it sounds like you void (to start with an empty bladder), then get imaged as the bladder fills (and is emptied??) What's the test's name? Anyway, it sounds like your question is how long it takes to fill a bladder, and that the answer depends on a lot of factors. Urine output should be on the order of 60 ml/hour. The average urinary bladder holds about 500-600 cc; you start to feel like you want to pee when it contains about 250-300 ml. So, as a ballpark figure, starting with an empty bladder, your bladder will be full enough to make you want to pee in about 5 hours, and be essentially full in about 10 hours. The more you drink, the more you decrease that waiting time. If you really wanted to speed up the process, you could hydrate with an IV. - Nunh-huh03:49, 5 September 2009 (UTC)[reply]
Thanks Nunh-huh - that's the answer to the question that I posed so poorly at the outset. The testing was done to investigate a urine retention issue but I don't know that it has a name. Your explanation has added the context I wanted. Thanks also Tango and Ten for your inputs :) hydnjo (talk) 11:30, 5 September 2009 (UTC)[reply]
September 5
Dead flies on outdoor plants
I've noticed that occasionally there are lots of dead flies on my outdoors plants (I've noticed them on basil, oregano, and thyme in particular). I occasionally just found one and thought, "well, I guess this just happens to be where he kicked the bucket," but the other day I found dozens of them. They look like normal houseflies, more or less, and are just sitting on the plants, clinging to them, dead. They aren't wrapped in a web or anything so obvious. What causes this? Is this some sort of fly life-cycle thing? Or some odd predator? Or what? We don't use pesticides on the plants. Any thoughts? Imagine a bunch of flies just sitting on a plant. Now imagine they happen to be dead. That's what it looks like. --98.217.14.211 (talk) 00:38, 5 September 2009 (UTC)[reply]
Houseflies and blowflies do not feed on green parts of live plants, but they may feed on the honeydew secretions of aphids if those are present on the plants. There may be some kind of pathogen (virus, bacterium, fungus, parasitic worm eggs, whatever) present in the honeydew and infecting the flies. I've never seen such a thing, so I have no good guesses as to what it may be. If it is a fungus, you would see fruiting bodies emerging from the dead flies. Otherwise, you'd just see dead flies. Sorry. --Dr Dima (talk) 02:59, 5 September 2009 (UTC)[reply]
"Actually happened" means nothing here, you're just asking about time zones, which are all about your reference point. From our article, "At 02:39 UTC on Monday July 21 (10:39pm EDT, Sunday July 20), 1969, Armstrong opened the hatch, and at 02:51 UTC began his descent to the Moon's surface." As always, it was a different day somewhere in the world... --98.217.14.211 (talk) 00:54, 5 September 2009 (UTC)[reply]
OK, no one's picked up on this thread for more than an hour, and a Google search for "there is no time in space" shows a shocking number of people who appear to be serious, so I guess I'd better spoil my own joke here. It's a line from a very famous episode of The Twilight Zone, the one where the aliens' guiding book, To Serve Man, turns out to be a cookbook. --Trovatore (talk) 02:22, 5 September 2009 (UTC)[reply]
As to the original question, if it is July 20 in the US, it can be July 20 or 21 in Australia or New Zealand, but not July 19. Eastern Standard Time in the US, for example, is 15 hours behind Eastern Standard Time in Australia. In all Australian and New Zealand time zones both the landing and the moon walk took place on July 21. --Anonymous, 05:22 UTC, September 5, 2009 (it's September 4 in western US time zones, but September 5 in Australia and New Zealand).
The accumulation of helium in the core causes a gradual increase in the rate of fusion and gravitational self-compression, as helium is denser than hydrogen. Higher temperatures must be attained to resist this increase in gravitational compression and to maintain a steady state.
It makes sense - to get two hydrogen nuclei to fuse you have to overcome their mutual repulsion. In the sun, it's gravity & pressure that does that - so there is some region in which the suns gravity is strong enough and some other region where it's not. As the sun transforms hydrogen into denser helium - it gets gradually denser - the region throughout which hydrogen fusion can occur gets bigger - so more hydrogen fuses and you get more energy. I don't have a reference - but it sure makes good sense. SteveBaker (talk) 02:46, 5 September 2009 (UTC)[reply]
It's not just that there is more volume that can fuse, the part of that volume that was fusing before is now fusing faster because it is hotter/denser. --Tango (talk) 10:42, 5 September 2009 (UTC)[reply]
Here's a response I got from Yahoo Answers: "As the core of the sun converts hydrogen to helium, it becomes more hydrogen-depleted. This forces the core to contract and increase pressure in order to fuse enough hydrogen to counteract gravitational collapse. As it contracts, however, the density gets higher, increasing the gravitational pressure; so the core must also get hotter by fusing even more hydrogen than before in order to maintain the equilibrium. So the sun gets hotter over time. As you say, it is 30% hotter now then when the earth first formed." --Halcatalyst (talk) 14:14, 5 September 2009 (UTC)[reply]
It's incomprehensible! Why (to pick just one part of this so-called explanations) does becoming more hydrogen-depleted force the core to contract? We're told it does that in order to fuse enough hydrogen to counteract gravitational collapse! Why? Is it sentient or something? That's not an explanation - it's a mess. SteveBaker (talk) 18:47, 5 September 2009 (UTC)[reply]
It is pretty common to explain things using anthropomorphic language. The only problem with the explanation is that it isn't very detailed, but that isn't necessarily a bad thing - you have to get the level of detail right for your intended audience. The OP probably doesn't know much astrophysics and probably doesn't want to read the equivalent of a textbook on the subject, so you need to miss a few things out. If you want a slightly more complete version of the sequence of events (they are actually all happening at once, of course), here goes: The hydrogen gets depleted, which reduces the amount of fusion happening, that reduces the radiation pressure so gravity is stronger and the star contracts. As with any gas, it heats up as it contracts. That extra heat and density increases the amount of fusion taking place, increasing the radiation pressure and bringing the star into a new equilibrium. This new equilibrium position is hotter and, therefore, brighter. --Tango (talk) 19:02, 5 September 2009 (UTC)[reply]
It doesn't seem right to me intuitively that a reduction in the reaction rate would lead to a higher equilibrium reaction rate, although I guess it's not impossible. I would think the increase in the molar mass is mostly what drives the volume down and the temperature up. Rckrone (talk) 05:50, 6 September 2009 (UTC)[reply]
My question is this: how can the atomic mass of oxygen-16 be 15.9949146 u when both a proton and a neutron have masses greater than 1 u? Shouldn't the mass be greater than 16 u? Nkot (talk) 01:56, 5 September 2009 (UTC)[reply]
Black hoes can evaporate due to hawking radiation...so would it be possible for a particle to pass the event horizion but have the black hoe evaporate before the particle is absorbed into the singularity? like the particle gets sucked past the "point of no return" but the black hoe evaporates right after?
Also, if you have two black hoes close enough to each other such that their event horizons overlap at a single point...(perhaps the black hoes could be orbiting one another, so they dont fall into each other), what would happen to a particle that traverses a path where the gravitational forces are neutralized by the opposing black hoe--that is the black hoes are possitioned such that their event horizions are both tanget ( at the same point) as the path of the particle. What would happen to the particle, since it is effectively has passed the event horizions of both black hoes? XM (talk) 04:54, 5 September 2009 (UTC)[reply]
In my experience, hoes don't evaporate, absorb particles, or neutralize gravity, regardless of their color. They also don't have event horizons. Or did you mean black ho's? If you did, I have to tell you that they don't do any of these things either. :-D 98.234.126.251 (talk) 05:37, 5 September 2009 (UTC)[reply]
At first I thought XM's L key didn't work, but then it would have been back hoe. The question seems legitimate aside from the... typo?... so I guess I'll answer it. The short answer to all of the questions is that anything that passes the event horizon will hit the singularity because that's how the event horizon is defined. If you escape then by definition you didn't cross the event horizon. So the real question is whether an evaporating hole has an event horizon at all, and the answer to that seems to be yes, at least if you believe the Penrose diagram that was in Hawking's original paper (reproduced here). Hawking himself seems to have decided that he was wrong and there is no horizon or singularity really, but that view doesn't seem to be very popular right now. If the event horizons of two black holes overlap then you really have one black hole with one event horizon, and the no-hair theorem implies that it will quickly become spherical. There's only one singularity so there's no ambiguity about where the particle ends up. -- BenRG (talk) 18:45, 5 September 2009 (UTC)[reply]
Forget about the amusing if racist typographical error! This user has asked a question that is so profound I wonder why I didn't think of it myself! Because if the hole (presumably a very small one) evaporated quickly enough, the particle would have "seen inside" the black hole and then "escaped" as the event horizon moved past it, and this would violate "cosmic censorship" which states that not even information about the inside of the black hole can escape-some physicist think this is just as well since new laws of physics might enter our universe should a naked singularity ever occur.
My answer is that since the particle would effectively be moving near the speed of light (or above(?)) when inside the event horizon, and that the horizon shrinks according to how much hawking radiation it can shed, then there is no reason to suppose that the horizon can catch up with the particle. I could be wrong-can someone do the maths?80.2.195.218 (talk) 13:24, 10 September 2009 (UTC)[reply]
Hey, that's a fascinating possibility -- that information could actually escape from a shrinking black hole. Unfortunately I can't crunch the numbers on this -- my area of expertise is hydrocarbon/petroleum chemistry, not astrophysics -- but it does make sense intuitively that if a black hole is shrinking, then matter/information could escape from it. Note also that the "cosmic censorship" hypothesis has so far only been definitively proved for non-shrinking black holes. (I wonder if Hawking is logged in right now, maybe he could crunch the numbers for you, he's a genius at this kind of stuff.) Well, clear skies to you! 146.74.230.106 (talk) 21:29, 10 September 2009 (UTC)[reply]
leaving groups, chemical attacks, MOs, and stuff.
Sometimes I get the feeling that in some electron movement mechanisms, incoming electron density "pushes" existing electron density in the other direction ... so say in esterification an alkoxy oxygen's lone pair is "pushing" away the pi electrons onto the carbonyl oxygen, and the pi electrons happen to be mobile. So in fact, before that carbon converts to sp3, it's like the alkoxy oxygen's lone pair is participating in the pi system and pushing the existing bonding electrons away. (Okay this might be an unacceptable classical picture though.)
It was mentioned to me in passing half a year ago how nucleophile electrons attack antibonding orbitals ... and in fact I had totally forgotten about antibonding orbitals (as a mechanism for nucleophilic attack) until it was mentioned again. I guess the classical picture is kind of misleading, because the typical picture of SN2 seems to be of say, the better nucleophile "pushing" away the leaving group through backside attack, forming and breaking bonds simultaneously that way. Do those nucleophile electrons in fact, contribute to an antibonding orbital, that somehow negates the bonding between the LG and the carbon? If so, how does an antibonding orbital convert into a bonding orbital (presumably that as the LG leaves a bond must be formed simultaneously)? Is bond breaking and formation truly simultaneous? Will one aspect be slightly ahead?
Another thing that doesn't get discussed much is sp2-sp3 (and sp2->sp3) transitions ... it almost seems to be a factor (if you could somehow get stuff to happen during the transition, and how much it affects equilibrium. It seems to me that possibly in such transitions you could have stereochemistry-affecting effects. What does the hybridisation of the two central carbons look like when the bromonium ion is attackihg an alkene for instance? 1/2 sp3, 1/2sp2?
Also, is acid catalysis always a first order reaction? It seems to me that for example, in acid-catalysed esterification of carboxylic acids where the C=O bond is being restored and kicking out the LG, that the electron density (coming out from oxygen's previous lone pairs) pushes electron density away from the C-OH bond, and meanwhile, this also pushes electron density from the OH (part of COOH) onto a nearby "proton". That is, I'm thinking you don't have to wait for acid to protonate the leaving group, and THEN wait for bond displacement to occur -- acidic protons act like terminal electron acceptors that stabilise the LG. Which kind of mechanism would acid catalysis support? (I'm referring to protonation, such as OH protonation, to create a good LG, not protonation to increase the carbonyl carbon's electrophilicity.) John Riemann Soong (talk) 07:44, 5 September 2009 (UTC)[reply]
First of all I'm going to recommend another book if you haven't already read it, it's "Mechanism and Theory in Organic Chemistry" (Thomas H. Lowry, Kathleen Schueller Richardson) which covers the first three paragraphs of your question in very gory details.
also Transition state - should be the best search term - eg for google books.
First paragraph - the alkoxy (why is it not alchoxy, alchemy, alchohol, k?emistry) O lone pair does just what you say - interacting with the pi system - specifically the C p orbitals. For RC(=O)OR' + R''O- the transition state is close to sp2 C bonded to O- , R , R' with the R''O bonding via the p (pi) orbital.
I don't think your use of the term 'antibonding orbital' is right in all the contexts you use it specifically the ester example Doh. It is right, silly me (deleted stuff below)
Second paragraph:
In a pure Sn2 reaction bond breaking and formation is simultaneous, however in practice if one of the leaving groups is better than the other, asymmetry may develop.
Both views are right. ('classical' and molecular orbital - they're describing the same thing, the same 'movement' of electrons (or electron density) )
Yes - the nucleophile feeds electrons into the leaving groups antibonding orbital - weakening the bond. As the bond is weakened the leaving group will move away from the molecule (electron repulsion).
Curiously the antibonding orbtital for the leaving group is the bonding orbital for the attacking nucleophile (and vice versa) - it's like a see-saw.
The antibonding orbital for the leaving group is the mirror image of the bonding orbital, this might need a little more explanation if you're not familiar with it, both can be anti, or bonding orbitals depending on which side a group is attached.. In the absense of groups on either side both orbitals can be considered plain p orbitals of the same energy, did that make any sense?
More: once a leaving group has left (in Sn2) the bonding orbital it was using, becomes the new antibonding orbital - it relates to the mirror image thing.
Third paragraph:
Roughly yes, someway between sp2 and sp3. For the stereochemistry the vaguely similar epoxide ring opening reactions are a good source of data (epoxides being more stable)
Fourth paragraph - do you mean that reaction of the intermediate in esterification is a concerted reaction in which the OH leaves as it is protonated (1 step) rather than being protonated then leaving (2 steps) - this is quite likely (though depends on absolute conditions)
Yeah, that's what I meant. Basically I'm wondering whether this will allow protonation to occur more often, even though the pKa of a protonated alcohol is kinda low. I wonder this cuz I'm interested in improving the efficiency of longer-term esterification, in weakly or moderately acidic solutions [with acetic or phosphoric acid for example] that must be edible later on. Thus, if I had a pH of 2.7 (or say I somehow got my hand on food-grade phosphoric acid and lowered it to 2 or something), would protonation of the OH group occur more often than the general 2-step depiction would indicate? That is, as the carbonyl's pi system electrons are entering the antibonding orbital (is my conception correct? sp2 bond is being reformed though) of the C-OH bond, this makes the OH group more basic ... making it a terrible leaving group, of course. But wait! There's a hydronium ion nearby (as well as various other protons on HOH's) which basically neutralise the OH group's basicity as it forms, in a sort of concerted reaction. John Riemann Soong (talk) 15:35, 5 September 2009 (UTC)[reply]
Basically yes. (at least there's nothing above that is obviously wrong)
To expand a bit there's a good example of trans-esterification where a chemical buffer (acid base) mixture is used (in dehydrating conditions of course) - in an even more concerted reaction the acid part of the buffer "stands by" to protonate the leaving group (-OR) as it leaves, and the basic part of the buffer "stands by" to deprotonate the attacking alcohol as it attaches to the carbonyl - higher concentrations of buffer help here - but the reaction goes suprisingly well for what may be an effectively neutral solution. Note how both the presence of the acid and base help here. This helps to reduce the activation energy - though the chances of getting all the molecules in the right place mean the reaction is quite slow nevertheless (High concentrations of buffer help). The same method can be used for straight esterifiaction.
The only tricky with the above method is choosing weak acids and bases that will not get involved in the esterification reaction (ie not acetate, or boric acid) Triethyl amine (does not react with carbonyl permanently) is a good choice for the base. Have you heard of tertiary amine carbonium ions? see
R3N+C(=O)R'
They're useful (and often overlooked) intermediates in esterification reactions, especially when you want to avoid any strong acid - you can prepare them before hand from the amine and acid chloride in suitable conditions.
I would like to learn a bit more about the symbols used in this type of molecular diagram, example In this particular example, the wriggly line is the symbol that I don't know about. There surely is an article on wikipedia, but I can't locate it. Can somebody please supply a link? Thanks! --TrogWoolley (talk) 10:24, 5 September 2009 (UTC)[reply]
It relates to the stereochemistry, the atom attactched to squigly line can be in one of two positions (up or down with respect to the paper) - it's a variation of the Natta projection
Here's an example with the two types ('forward', and 'back') - they are the triangular line , and the dotted lines, if a squicgly line was used it would mean that it could be either.
Talking of such things - if you see a percentage above or near the squiggle especially something like "40% R" , or "30% S" this gives the ratio of the two enantiomers - labled "R", and "S" (the R and S should be explained somewhere in one of the linked articles)83.100.250.79 (talk) 19:06, 5 September 2009 (UTC)[reply]
I'll tell you what. Give yourself a half-inch cut on your arm and pour Listerine into it. Then cut your other arm and pour salt water into it. Tell us which one hurts the most! --TammyMoet (talk) 15:04, 5 September 2009 (UTC)[reply]
Even the effect of Listerine in the mouth is only temporary. Saltwater as a mouthwash may not be as potent as Listerine, but it will make your mouth and throat feel better for a little while, certainly better than plain water will. Baseball BugsWhat's up, Doc?carrots16:57, 5 September 2009 (UTC)[reply]
Salt water has applications to oral hygiene other than germ-killing. The salt water interacts with the gums and keeps them in an isotonic equilibrium, minimizing fluid loss. Listerine, or other antibacterial fluid, probably does not satisfy this property. Nimur (talk) 17:31, 5 September 2009 (UTC)[reply]
I think a salt water mouthwash would help kill bacteria. In the past food was preserved by salting. I imagine that salt shrivels up the germs by osmosis. It may, I guess, be less harmful to the healing socket wound than the more aggressive chemicals in mouthwash. I think, for example, that when you use an antiseptic cream on a wound, that it kells off a layer or two of healthy cells. 78.146.76.67 (talk) 11:44, 6 September 2009 (UTC)[reply]
Eating a packet of Ready Salted doesn't sterilise my mouth; is there any real evidence that a saltwater mouthwash would? Especially since the salt will be gone within minutes (unlike preserved food, which remained salted)? I'm not really convinced. Vimescarrot (talk) 17:11, 6 September 2009 (UTC)[reply]
Be sure not to use salt substitute which is potassium chloride instead of sodium chloride. Potassium chloride will damage cells and keep the wound from healing. DISCLAIMER: This is not medical advice. Please consult your doctor to obtain medical advice. --Taxa (talk) 17:14, 6 September 2009 (UTC)[reply]
Also, mixing potassium chloride with sugar and giving it a tap with a hammer can cause fire, so if you do use salt substitute, make sure you clean your mouth out before you eat anything with sugar in it. I think it was potassium chloride, anyway. The stuff you get in water purification tablets.....? --KageTora - (영호 (影虎)) (talk) 11:52, 7 September 2009 (UTC)[reply]
Saltwater rinse recommendations are empirical -- they are not shown to reduce bacterial load any more than tap water, and especially not in the fraction of a minute that rinses are typically used. Even chlorhexidine requires a concentration of 2% and 10 minutes to kill some of the more terrible periodontal pathogens. DRosenbach(Talk | Contribs)01:34, 8 September 2009 (UTC)[reply]
Please do not write in block capitals, it is harder to read and is interpreted as shouting. I'm afraid I do not understand the question. "Free space" is an idealised concept, it doesn't actually exist in reality. --Tango (talk) 13:46, 5 September 2009 (UTC)[reply]
I believe your question should have been worded as 'why is it that when an object is in orbit, why is it in a permanent state of freefall?'. The reason is that the Earth's gravitational pull is dragging on the object bit-by-bit, so that every time the object goes around the Earth it gets just that little bit lower. This is why the Shuttle et al., have to compensate every now and then by firing off their booster rockets to get it back into position. There is no such thing as a permanent orbit. Either something starts coming back down or it starts floating away. Even the moon is getting further and further away from us. --KageTora - (영호 (影虎)) (talk) 14:10, 5 September 2009 (UTC)[reply]
I am sorry, but that is completely wrong. The need to boost is because of atmospheric drag. If you are in a high enough orbit that there is no significant atmosphere, orbits are essentially permanent. The Earth's orbit around the Sun, for instance, will last essentially unchanged until the Sun dies. The Moon is moving away because of tidal forces, but it will never leave orbit entirely. Orbits work because the gravitational pull is always towards the centre of the body and the object orbiting is moving perpendicular to that direction. This means gravity changes the direction of the motion without changing the speed, so it ends up going around the body at constant speed. (This is for a circular orbit, a general elliptical orbit is a little more complicated, but the basis concept is the same.) --Tango (talk) 14:18, 5 September 2009 (UTC)[reply]
You may be making the common mistake of thinking that astronauts are in microgravity because they're out in space, which is 90% wrong: they would be subject to about 90% of the amount of gravity as they are on the ground if they were just standing still at their usual altitude. The reason they're in microgravity is because they're in free fall, as above. Newton's cannonball is an intuitive way to understand that astronauts are continually falling. --Sean15:15, 5 September 2009 (UTC)[reply]
In fact, when it's time to return to the ground, the spacecraft fires a rocket tangent to the orbit (adding no momentum towards the earth). After losing some of the angular momentum, the spacecraft just "falls" back to the ground, indicating that it is still completely under the control of Earth's gravity. Nimur (talk) 17:36, 5 September 2009 (UTC)[reply]
I'll offer some further explanation - astronauts appear weightless because they are "falling" at exactly the same rate as their spacecraft, so relative to each other they don't move at all, hence appearing to float. This is because all objects in a given gravitational field accelerate the same amount. The gravitational force is proportional to mass, but acceleration is given by F=ma (which implies a=F/m). That means the mass cancels out when you calculate acceleration, meaning acceleration does not depend on mass. --Tango (talk) 15:31, 5 September 2009 (UTC)[reply]
To be perfectly clear, "Free fall" does not necessarily imply that the spacecraft is plummeting towards earth. Plummeting is only one kind of free fall. If your "sideways" speed is high enough you can "fall" for ever without ever getting any closer to the ground. (You can sort of visualize this as falling towards the earth, but going sideways enough that you miss it entirely. ) APL (talk) 04:15, 6 September 2009 (UTC)[reply]
Houseflies aren't silent. They're quite noisy. But given that their flying speed is almost the same, any difference in their loudness would probably be attributed to their larger wingspan. Dougcard (talk) 04:14, 6 September 2009 (UTC)[reply]
There may be more to it than just size... It's true that a hornet is much more noisy than a wasp or a bee. On the other hand, the average fly is much larger--but in many cases more silent--than a typical mosquito. To confuse things further, mosquitoes (and probably many if not most flying insects) can apparently operate in more than one flight mode, some of which may be more silent or noisy than others. Just think of a helicopter that generates different noise levels while moving or in hovering position. Also, many sources of noise, in particular from oscillating or rotating objects are quite directional, so the perception of noise may depend on the relative position of the observer with respect to the emitter. Last but not least, we may be more sensitive to noises that are perceived as threatening (fear of mosquito bite) than to those that are considered benign or inconsequential. Michel M Verstraete (talk) 20:32, 9 September 2009 (UTC).[reply]
Maybe - key factors here are the sampling frequency, and possibly you will need a separate comparator.
The power supply will as standard match a single DC voltage, but for audio you want it to match an AC voltage.
What the thing does is monitor the output voltage, and compare it to a standard, if the voltage is less than the standard then the supply is switched on. What you need to do is disconnect the wires that compare the output sample the with the standard, and connect it so that the output sample is compared with an audio input (suitably scaled) - this is where the comparator comes it - the comparator compares the two voltage and supplies a switching voltage to the power transistors.
There's a chance that the whole set up is so well integrated that you won't be able to access the comparator voltage input, (ie a single chip solution) - most likely you will be able to use the recitfied power supply, and switching transistors, but will need a separate comparator. You will probably need to disconnect any smoothing capacitors from the output, (but not imput).
Also note that the switching frequency of the amp will limit the frequency responce, and that there might be a huge amount of switching noise. (a small capacitor in the output stage helps fix this, as does any inductance a loudspeaker has)
Some one who knows more about the specifics of computer smpa supplies will know how adaptable they are.
This should be a useful read [9] - note it says the switching frequency is typically 33kHz - that isn't really enough for high quality audio, but should be good for a subwoofer, or active woofer.83.100.250.79 (talk) 18:33, 5 September 2009 (UTC)[reply]
Another alternative is to use the powersupply as a powersupply for a conventional amp (replacing the old transformer) - extra capacitors in the output stage are a good idea here, the average computer power supply has the potential to outperform the average audio amp power supply if you can isolate the switching noise.83.100.250.79 (talk) 18:41, 5 September 2009 (UTC)[reply]
The smps is designed to deliver current at a given DC voltage. An AC current output will be needed to drive a loudspeaker i.e. positive and negative currents with average zero. Connect the smps output via a resistor to ground. Calculate the resistor value R ohms to drain I amps = half the available maximum current. THe resistor will dissipate IxIxR watts. Connect a large value electrolytic capacitor, typically 470µF 50V or more, from the smps output to the loudspeaker; this blocks DC current into the speaker. Inside the smps you need to access the reference voltage which is often given by a zener diode. Your AC audio signal will be added to the DC reference voltage. Depending on the circuit you can probably arrange that using a resistor and an input coupling capacitor. Cuddlyable3 (talk) 21:39, 5 September 2009 (UTC)[reply]
You read correctly. The arrangement described is a Class A driver that wastes power. A push-pull or Class B driver is difficult to construct with a smps that is designed only to "push". Cuddlyable3 (talk) 17:57, 6 September 2009 (UTC)[reply]
How about if there are two 12V supplies (I believe there are usually 2 12V rails, but not sure if they are powered separately, or have the same rating), both fixed to 6V (for O input) then one can go up whilst the other down, the speaker connected across the two outputs, I suppose the outputs would need to be connected to ground via a capacitor - getting complex..83.100.250.79 (talk) 18:12, 6 September 2009 (UTC)[reply]
neutron decay products
Why is it possible to have a giant neutron (as in neutron star or Black Hole) but not a giant proton and electron as products of a giant neutron decay? --Taxa (talk) 19:03, 5 September 2009 (UTC)[reply]
A neutron star is not a giant neutron, but many neutrons, with a skin of atomic matter. Protons repel each other, so it is very hard to make a collection of tons of pure protons. In fact the energy needed to bring them together will exceed their rest mass. I think there was a reference desk Question about this a year ago. Normally you will get a combination of electrons and protons - that is hydrogen, after all a neutron decay makes protons and electrons as well as the neutrino. Graeme Bartlett (talk) 22:13, 5 September 2009 (UTC)[reply]
Okay, so a behive of neutrons... What happens to the neutrons that decay? Do they turn into protons and electrons and if so where do they go? Do they follow the path of least resistance and get shot out in jets someplace? --Taxa (talk) 17:03, 6 September 2009 (UTC)[reply]
The pressure from gravity forces electrons and protons together into neutrons since neutrons can pack much closer than normal atoms can, which is how a neutron star forms. Neutrons in the core of a neutron star are much more stable than free neutrons and if they do decay the resulting protons and electrons would likely soon be forced back into neutrons. Neutron_star#Structure mentions the core might have electrons and protons mixed in. In the crust where the pressure is lower and normal matter can exist there's probably some transition back and forth. Rckrone (talk) 20:31, 6 September 2009 (UTC)[reply]
discrete solutions of 1H schrodinger
I've been trying to solve this using (unnormalised) formula similar to
Wavefunction = eΣan rn
And ignoring the angular component (eg taking δ2/δθ2 fn(r,θ,μ) to be zero ) ( because I'm not very good/lazy)
Which works and gives me solutions, mostly of the form
an+2(n+2)(n+3)=k1an+1+k2an
where k1,k2 are numbers (I believe there is a name for polynomials of this type but have forgotten - can anyone remember?)
So, so far I have infinite solutions (using infinite range of a0)
But there is more because I want to normalise which I believe is "integral over all space of fn(r,θ,μ)fn*(r,θ,μ)" which I believe that this will only give non infinite integrals for certain values of a0 - and hence give "quantised solutions" (as wanted).
Can anyone give a clue on how to show which of the integrals will be finite. (Even though I have all the parameters from one of the equations above) - and hence can integrate the equation (giving another infinite polynomial) I haven't got a clue how to evaluate the integral... Thanks.83.100.250.79 (talk) 19:31, 5 September 2009 (UTC)[reply]
Can you be a little more specific about what you're trying to do? Is this energy eigenstates of the hydrogen atom? What's the integral you're trying to evaluate? Rckrone (talk) 05:34, 6 September 2009 (UTC)[reply]
As far as I can tell, the OP is asking for help in evaluating integrals of the type
Specifically, he suspects that the requirement that the above integral be finite will lead to only some allowed sets of . For physical reasons, the OP then hopes that some of these sets of will also satisfy the recursion relation he calculated initially and therefore produce allowed wavefunctions for his problem. Martlet1215 (talk) 10:56, 6 September 2009 (UTC)[reply]
That's it, unfortunately my notes are a bit mixed up and now I'm not sure the equations I wrote above are correct - the only way I'll be able to tell is to start again from the beginning. Nobody seems to have noticed an error though..83.100.250.79 (talk) 11:24, 6 September 2009 (UTC)[reply]
Thanks, unfortunately I've been having some technical difficulties - meaning that a correction to the above recurrence relation didn't get inserted, then wikipedia wouldn't let me edit (overnight) - as a result the solution you saw lacked an (n+2)(n+3) term. To add insult to injury my notes are a mess, and as I tried various formula to solve the differential, I've lost track of which one I was using (basically I'm working from memory and a few scraps of paper). I'll need to start again to get this sorted out.
I still can't find the equation I used - I think it may have been similar to wavefunction =f(x)eax where f(x) is a (possibly finite) polynomial. Maybe someone (with knowledge of what works in the long run) could suggest a good choice for a generic function to start with to solving the differential equation.83.100.250.79 (talk) 16:58, 6 September 2009 (UTC)[reply]
Like Rckrone said initially, it would help if you explicitly told us what you are trying to do. Is this the problem of finding the radial part of the energy eigenstates of the Hydrogen atom? Martlet1215 (talk) 10:54, 7 September 2009 (UTC)[reply]
You guessed right in your first post - I can get solutions to the differential equation (radial only time independant schrodinger), using a variety of different formulations eg e^f(x) , f(x) , f(x)e^ax etc , but I can't work out a way to find out which solutions are not good, becuase the wave function cannot be normalised.
f(x)e^ax seems the most promising so far (a is negative) since if f(x) is a finite polynomial the the integratl will be finite. However I'm having difficulty showing the conditions under which f(x) is finite, and still stuck on rejecting other solutions which I can't integrate (normalise) - I probably need a way to tell which integrals will be infinte (since I can reject all those)>83.100.250.79 (talk) 15:03, 7 September 2009 (UTC)[reply]
September 6
Human race vs Human species
More and more I hear people on the radio or in books speaking of the 'human race'. I tried to ignore it but recently I read it in a lot of well-informed science fiction stories and today I heard it on a science program! that was too much. We're a species. How come we call ourselves so often a race? Where did it come from? None of the articles about race and racism I could find on Wikipedia seem to address the problem. Is it merely a slip of the meaning of the word or has it got a deeper meaning? Thank you. 190.244.183.244 (talk) 02:36, 6 September 2009 (UTC)[reply]
I doubt it's "more and more" — it's always been a common phrase. Probably you've just been noticing it more.
I see nothing wrong with the term. Certainly it has nothing to do with racism; kind of the opposite, given that "the human race" includes all "races". But it has a harder, more martial, more mythical sound to it than species, and sometimes that's desired. Species is a coldly scientific word, and doesn't work well when the poetic or emotional or metaphysical aspects are connotations you want to get across. --Trovatore (talk) 02:57, 6 September 2009 (UTC)[reply]
As Trovatore says, it doesn't have any special meaning, it's just the colloquial usage. Words in the normal vulgar lexicon are often very different from their purely scientific meaning, and that's just how it is. Happens all the time. My pet peeve is decimate. ~ Amory (user • talk • contribs)03:32, 6 September 2009 (UTC)[reply]
The usage is very common and not at all new. It appears in "The Time Machine, by H. G. Wells [1898]" and in "Frankenstein, by Mary Wollstonecraft (Godwin) Shelley [1818]". And those are just the first two books that it happened to cross my mind to search. I'm certain that I could find others.
Besides, "Human Species" isn't quite right either. "Human" refers to a handful of species, we just happen to be the last one standing. APL (talk) 04:10, 6 September 2009 (UTC)[reply]
Perhaps the usage isn't completely nailed down, but using "human" to refer to all of genus Homo is common enough that the human article starts "This article is about modern humans. For other human species, see Homo (genus)." APL (talk) 17:39, 6 September 2009 (UTC)[reply]
"Race" comes from a word meaning "line", which could be broadly interpreted to include "species", although it's more normally used to mean "sub-species", i.e. varieties within a species - although, technically, every "variety" within the human species is unique from the DNA perspective, except for identical siblings. Baseball BugsWhat's up, Doc?carrots09:12, 6 September 2009 (UTC)[reply]
The trouble is that we're comparing one fairly vague term "race" with another vague term "species".
The scientific definition of 'species' is generally that two animals are of the same species if they can successfully interbreed. That would make all modern humans be a part of the same species. However, we say that lions and tigers are different species - despite the existance of ligar and tigons. Actually, that's a terrible example because ligars and tigons are generally infertile - but I happen to like the words "ligar" and "tigon"! Dogs and Wolves might be a better example.
Race (biology) has a somewhat better definition in biology (and all humans are of one race under that definition too) - but the use of the term Race (classification of human beings) in everyday speech has a different meaning. The trouble with the everyday meaning is that it takes a somewhat arbitary group of genes (the one for skin color, for example) and promotes that to higher significance than any other group you might pick. Why classify people according to their skin color rather than (say) their lactose-tolerance or their eye color? It doesn't make any kind of scientific sense. What we're really trying to capture is the place where the persons ancestors originated before the mass migrations of relatively modern times has caused that to become a largely irrelevent thing.
What environmental conditions will be required in order for future human evolution to favour an increase in brain complexity rather than a decrease? NeonMerlin[10]06:19, 6 September 2009 (UTC)[reply]
For traditional evolution to work, two things have to happen - firstly, there has to be a genetic mutation or a chance combination of genes that results in some physical change. Secondly, that change has to give the recipients of that mutation an enhanced probability of passing the gene(s) onto the next generation. So IF there is a genetic change that makes some people smarter than others - and IF that change means that they have more children than the average person - THEN the population will tend to become smarter. Sadly (perhaps) it's not clear that our intelligence is genetically determined...and it's far from clear that more intelligent people have more children. Perhaps very mentally deficient people are less likely to have kids - but there is some evidence that things are heading the way of the movie Idiocracy (it's a terrible movie - no need to watch it!)...the idea being that intelligent people are too busy with their exciting jobs to raise kids - where the dumb people have nothing better to do - so they have vast families. That would tend to produce an evolutionary pressure AGAINST rising intelligence.
But that's traditional evolution. Modern humans have a tendancy to break the rules. When there is a genetic mutation that might prevent some couple from having kids - we step in with medical treatments for infertility. If someone is too stupid to hold down a long term job - we don't allow them and their children to starve - we provide social security and food stamps and such - so they survive, despite that evolutionary pressure.
What I think is more relevent here is the concept of 'memetics' - the evolution of ideas. If two individuals have brains of identical make-up - but one is educated to modern standards and the other is brought up by wolves - we're going to say that the latter person is not as intelligent as the former. Education is memetics in action. Ideas that work are passed on by teachers to children - ideas that don't work fall by the wayside. Ideas evolve. Since humans are the carriers of these 'memes' - we can get more intelligent (well, depending on your definition of that tricky word) as time passes. I believe that is the fundamental flaw in the ideas behind Idiocracy - the brains of the kids who come from large families with stupid parents aren't measurably genetically different from the single child of a Nobel award winner - so providing we have an educational system that allows the efficient passing of memes from the brain of the Nobel prize winner into the brains of the kids of stupid parents, our "intelligence" can continue to evolve despite the lack of genetic improvement.
Efficient transfer of memes in a cognitive way, that is. The other six kinds of transmission listed in the article won't make us smarter, they'll just make more memes. 213.122.26.161 (talk) 14:12, 6 September 2009 (UTC)[reply]
APL may not have considered that much mating these days is recreational. Anything that causes intelligent people to procreate more will have the desired effect. Cuddlyable3 (talk) 13:51, 6 September 2009 (UTC)[reply]
Contrary to what SteveBaker says the Heritability of IQ article indicates intelligence is even more determined by genetics than height. Interesting the correlation between twins gets closer the older they are. It also lists a couple of genes which do contribute to intelligence though probably a very large number do, the number of repeats in bits which don't occur in genes also contributes though I didn't see that mentioned in the article. Dmcq (talk) 14:05, 6 September 2009 (UTC)[reply]
And anything I've read about it indicates rich people do tend to have more children and that correlates reasonably well with intelligence. But then so do the poor. It's the in betweeners that don't. Dmcq (talk)
"Practically, however, the upper bound of these correlations are given by the reliability of the test, which tends to be 0.90 to 0.95 for typical IQ tests..." how is the reliability of an IQ test tested? Is there an official prototype person with an IQ of 100, used for calibration, preserved at a constant temperature under a glass jar in Paris? 213.122.26.161 (talk) 14:22, 6 September 2009 (UTC)[reply]
Some people's results on repeated IQ tests vary a great deal, presumably because they were tested on days on which they had lot of intelligence, or an unusual lack of it. So for this method of testing the test to be a good one, it would have to be performed on a person whose intelligence was known to be constant. Even better, take a person whose intelligence varies over time by a known amount, and see if the test can pick up on the variations accurately. 213.122.26.161 (talk) 15:30, 6 September 2009 (UTC)[reply]
We can't have someone we know to have constant intelligence or that has a known variation in intelligence because our only measure of intelligence is the one we are testing. You have to just do the same experiment with lots of people. --Tango (talk) 17:28, 6 September 2009 (UTC)[reply]
Most people aren't much of a fan of the sort of things that would be required to manually affect human evolution. See eugenics. Evolution is a rather nasty business -- rapid "progress" is made only by the lack of reproduction (often death) of the great majority of individuals in a species. Most people aren't that interested in participating in that type of ethical system. Much of what we call "civilization" are safety nets so that just because you are born with poor eyesight or stubby legs or a slightly less-than-average brain, you don't have to actually die. Consider how much money we funnel to genetic diseases that affect a small minority of people—this is an act of humanity, not evolutionary fitness. There's no reason that eugenics couldn't be made to "work", but it would involve implementation on a horrific, probably impossible scale. --98.217.14.211 (talk) 14:37, 6 September 2009 (UTC)[reply]
Forgive me for avoiding the direct question, but I think it is important to point out whenever questions like this are asked that the minimum time it would take for any manipulation to have the tiniest noticeable effect is on the order of 1000 years. Thus, while such questions might be philosophically interesting, it's important to realize that they don't have any practical relevance. Looie496 (talk) 14:42, 6 September 2009 (UTC)[reply]
Well, not necessarily. It depends what you are trying to select for and what measures you are willing to take. If you're talking about one gene, and are willing to sterilize everyone else who doesn't have it, then you could do it in one generation. Again, nobody wants to do that, though. --98.217.14.211 (talk) 14:53, 6 September 2009 (UTC)[reply]
Where did you get that 1000 years from? If you look at dogs or cats selective breeding has made a huge difference in far far less time. Much of their breeding only started in the 19th century. Dmcq (talk) 15:22, 6 September 2009 (UTC)[reply]
What makes you say that? With drastic enough measures the average [something] of the human race could be changed noticeably in a single generation. To pick a horrific example, if tomorrow the all powerful eugenics king declared that white people were not allowed to reproduce, what would that do to mankind's average skin tone? APL (talk) 17:50, 6 September 2009 (UTC)[reply]
Well if you look at Human skin color it seems that people in Europe were probably dark coloured at the end of the last ice age and the white colour you see now mainly came about in the last 12000 years or so, a third of the change may have happened after the Egyptians stated their civilization so within the time of recorded history. And that was without any eugenics king declaring anything. Dmcq (talk) 18:10, 6 September 2009 (UTC)[reply]
A dog generation is about 1/10th of a human generation and usually includes multiple offsping, so dogs can probably evolve over 10 times faster than humans. And concerning the other points, it's true that you can get faster changes if you focus rigorously on one factor and select rigorously for it. So for example, if you sterilize everybody whose brain size is below the mean, you might get a perceptible increase in brain size in a hundred years. But for plausible interventions, it's difficult to get below 1000. Looie496 (talk) 18:26, 6 September 2009 (UTC)[reply]
Generation length is only one factor in evolution speed. One way to get fast evolution in humans would be to concentrate on just a small group. If you choose 100 people (50 male, 50 female - you might be tempted to have more women, but I don't think it would actually be a good idea) that are already above average in what it is you are interested in and you encourage early and plentiful reproduction you can get a generation every 20 years and remove people from the group that don't fit your requirements you could get pretty rapid selection. --Tango (talk) 18:52, 6 September 2009 (UTC)[reply]
The Ashkenazi intelligence article discusses the hypothesis that ashkenazi jews have greater intelligence on average than most other groups and that the difference is due to natural selection during the middle ages. Dmcq (talk) 20:22, 6 September 2009 (UTC)[reply]
Formula for subjective sound fading with distance, and adding
1) You are in a flat agricultural field (for example) with a speaker giving out, say, 60 decibels. What would be the formula for how the sound fades away the further away you stand from the source? 2) You have two speakers the both give out 60 decibels. If you put them close to each other, can you get more sound at any point than 60 decibels? What would you get? I realise I have not specified every parameter, so reasonable assumptions can be made. 78.146.76.67 (talk) 11:31, 6 September 2009 (UTC)[reply]
Calling sound levels "decibels" is a common error. The term 60 decibels is not a measurement unit; it just means a ratio 1,000. Possibly the OP should have posted "60 dB(SPL)" where SPL is the level reference of 20 micropascals (μPa). 0 dB(SPL) is barely audible. 1) In open air if a speaker gives 60 dB(SPL) at 1 meter one hears 60 - 1020 log(r) dB(SPL) at other distances r meters. 1) Two such speakers broadcasting noise can give 63 dB(SPL) at 1 meter. If they broadcast a single frequency tone then the received sound is spread in a complex interference pattern with peaks of 66 dB(SPL) at 1 meter in some directions. The agricultural field is assumed not to reflect any sound. Cuddlyable3 (talk) 12:56, 6 September 2009 (UTC)[reply]
Thanks, can I just check I understand the formula please? Have I calculated correctly: at 10 meters away the answer would be 50 dB(SPL), at 100 metres away it would be 40 dB(SPL), and at 1000 metres away it would be 30 dB (SPL)? And at a billion (thouand million) metres away the noise would be minus 30 dB (SPL) - that cannot be right! 78.146.76.67 (talk) 13:31, 6 September 2009 (UTC)[reply]
As dB is not an absolute measure, 0 dB has no particular physical meaning and is not the same as "no signal". Negative dB simply indicates that the ratio is increasingly smaller, and that your signal is increasingly less audible. — Lomn14:07, 6 September 2009 (UTC)[reply]
This is a suprisingly difficult thing to answer.
The energy transmitted is proportional to one over the square of the distance - that's nice, simple physics. If you double the distance you are from the speaker - you get one quarter of the sound energy. Easy!
However - you used the word "subjective" in your subject line and "decibels" in your question - and herein lies the tricky part.
The human ear doesn't report a doubling of sound energy as a doubling of percieved loudness...it depends on the duration and frequency of the sound waves as well as the amplitude. But very roughly - the sound has to have 10 times more energy behind it in order to sound twice as loud.
A decibel expresses the ratio of two sound levels - not some absolute number - there are many variations on the use of the term - read: Decibel#Acoustics_2 (or the entire decibel article if you're brave!). Typically, audio equipment is described in terms of 'dbA' - which is ten times the log-to-base-ten of the ratio of the sound energy produced to the quietest sound a human can hear. So a difference of 10 decibels sounds like a doubling in loudness - and a 60 dbA speaker can sound like 6 doublings in volume - 2x2x2x2x2x2 - 64 times louder than the quietest sound you can hear. A 70 dbA speaker would produce ten times as much sound energy - and sound twice as loud.
Incidentally - this is why listening to loud music can be so damaging to our hearing. The damage is done by the energy transmitted into our ears - but ten times the 'safe' amount of energy only sounds twice as loud.
Putting two speakers close together does indeed double the amount of sound energy - but a mere doubling of energy doesn't sound twice as loud to a human. There is also an ikky complication if the two speakers are playing anything like the same sound - interference. If both speakers were playing the exact same perfect sine wave then as you walked around them, the sound would get louder and quieter because at some places the sound waves would add together and in others they'd cancel out.
Thanks. You can imagine the speakers are giving out (different) traffic noise. I'd be very interested to know the formula for "adding" the noise of two different speakers which are at different distances. Also, as I wrote above, I think I must have misunderstood the formula given for the fading of noise with distance. (I'm ultimately trying to estimate the noise at particular coordinates from a non-straight road - probably best to model as several point souces of noise which correspond to individual cars on the road). 78.146.76.67 (talk) 13:46, 6 September 2009 (UTC)[reply]
If you do that, don't forget to take account of the fact that traffic slows down around tight corners - resulting in more vehicles tending to be there than on the straight parts - but also that the engine noise will vary with speed. If big trucks are to be considered, you'll need to consider the noise they make when engine-braking. You probably need to calculate the sound energy emitted by each point-source - use the inverse-square-law to calculate the total energy at any given point - then convert that into dbA's using the equation in the decibel article. SteveBaker (talk) 15:17, 6 September 2009 (UTC)[reply]
A more or less direct quote (after poor translation) from my physics book: The total sound intensity at a specified point is the sum of the intensities caused by single sound sources. This result can be can be applied to, among other things, combining the intensities of different kinds of noise sources. It is not valid if the waves have a phase relation. It should be noted that aside fading with the squared distance and reflection/absorption by ground and other surfaces, the sound fades due to absorption by air. The correct approach to this problem depends on whether you want a safe upper limit or accuracy. --194.197.235.240 (talk) 15:22, 6 September 2009 (UTC)[reply]
If you're serious about this there is professional acoustic modeling software that's used by architects, but I don't know anything about it. For a point source the 1/r² law implies a 20 dB drop for each factor-of-10 increase in distance; for example 80 dBA at 1 meter becomes 60 dBA at 10 meters and 40 dBA at 100 meters. When combining multiple sources it's the energy that adds linearly, not the perceived loudness (ignoring interference, which should be safe to do in this case). If L is a dB measure of loudness then the correct formula for combining them would be , but in most cases you can approximate that pretty accurately by . Aside from reflection off solid surfaces, the 1/r² law can be modified by temperature gradients above the ground, which can act as a converging or diverging lens. I suppose there wouldn't be much reflection or temperature variation out in a tilled field, but I'm not sure. -- BenRG (talk) 15:30, 6 September 2009 (UTC)[reply]
Sound normally fades faster than the inverse square law in a field because the sound is refracted upwards. If you have a clear sky and a cold night though the air will be colder near the ground so the sound is refracted down and it fades more slowly than inverse square. Interestingly sound is not in the main 'carried' by the wind downwards, what happens is that the air in the wind travels faster further away from the ground so making sounds refract down more downwind and refract up into the sky upwind. Dmcq (talk)
Thanks for all the above, especially to BenRG for his formula for combining several sound sources. I seem to recall reading on one of the Wikipedia articles that I read a day or two ago that subjective noise decreases with 1/r and not 1/r**2. Perhaps it would be easier if I considered the sound energy for the fading-with-distance and sound-adding calculations, and then after calculating the sound-energy for the X.Y points I was interested in, I then converted this sound energy into dB(SPL). In that case would the sound energy from different sources of traffic-noise simply add? I assume they would decay 1/r**2. How do you convert sound-energy into dB(SPL) and back please? 78.146.254.202 (talk) 09:19, 7 September 2009 (UTC)[reply]
Traffic noise goes down as 1/r (or in fact a bit faster than that normally because of refraction). The traffic noise is along a line source. There is a considerable amount of refraction reducing the noise because the air normally gets colder with height. A tilled field in sunlight would make the problem worse because it is dark and absorbs heat. That is why sound hardly travels at all on sunny days but you can hear foghorns from many miles away at night. Dmcq (talk)
I'm very interested in traffic noise going down by 1/r rather than 1/r**2 - the former should mean that sound from further away is less attenuated, and would make a big difference to the results of calculations. Do you have any sources, preferably online, that reinforce that idea please? I'm not sure that the two articles above do. Since I've been brought up from a schoolboy to believe that things attenuate by 1/r**2, I need to have a clear explanation for 1/r rather than 1/r**2. Thanks. 89.242.115.9 (talk) 20:23, 7 September 2009 (UTC)[reply]
1/r2 comes about like this: If you imagine a point source of sound (or light or heat or almost anything with waves) out in the middle of nowhere - and imagine it producing one short BEEP! of sound. That sound radiates outwards in all directions equally so at any given moment the sound wave is the surface of a sphere that's growing at the speed of sound. Well, the initial burst of sound energy is spread out over that entire surface - so the amount of sound energy at any given point on the surface is equal to the initial sound energy divided by the area of the sphere - which is 4 pi times the radius squared. Hence - the sound at any point at a distance 'r' is proportional to 1/r2. However, we've been talking about sound ENERGY - and as I explained above - the human ear isn't a very linear device. The formula in decibel and A-weighting (which weights the results based on frequency) relates the percieved VOLUME to the incident ENERGY - and it's not a simple relationship...but I suppose if you imagined that the ear was percieving that volume was proportional to the square of the amount of energy - then volume would be proportional to 1/r - but I don't think that's true.
At any rate, this is a horribly complicated business. Firstly, you don't know your source data to enough precision. Just how much noise does a vehicle make? You have everything from a prius running in all-electric mode - up to an 18 wheeler doing engine braking - and everything in-between. Then you have the number and mix of vehicles on your road - the effects of corners and hills changing their engine speeds and causing them to bunch up in some places and spread out in others. You don't know the distribution of frequencies within those sounds. Then you have the effects of refraction and reflection of the ground - and absorption of sound by the ground, trees, etc - which is different for sounds of different frequencies and different frequency components within a single sound. When you get to the end of all of that - then you have to consider that humans don't perceive sound in a simple way - you have to turn incident energy into dBa numbers using the A-weighting approach. There are so many unknowns in that set of variables that it's going to take a really expert person to get the error bars down to something manageable - or else you're going to have answers that have a couple of orders of magnitude of error associated with them! SteveBaker (talk) 11:25, 8 September 2009 (UTC)[reply]
That's assuming a steady stream of traffic. Why not try google with something like 'traffic noise attenuation with distance'? You'll get some more complex formula that do an accurate job up to a hundred meters or so - after that atmospheric conditions make a large difference. It is a popular study. Dmcq (talk) 00:30, 8 September 2009 (UTC)[reply]
Defunct Sciences
Hello. I'm looking for a list (or group) of studies which were once considered scientific but are now considered (by the vast majority) as defunct. An example I could think of is alchemy; does anyone know any others?
I wonder if reading lines on your palms or bumps on your head would qualify? (Now, I'm seeing Daffy Duck disguised as a swami - "No bumps? We make some!" [pulls out hammer and whacks Porky over the head a few times]). Baseball BugsWhat's up, Doc?carrots14:09, 6 September 2009 (UTC)[reply]
I would like to ask if there is or if it is possible to create a list of chemicals (not only chemical elements) by density? Of course, list of only those chemicals, that have an article in Wikipedia (and when the density is given in the article).
There are vastly too many known chemical compounds to list...millions of them at least. You need to narrow your criteria before there could be any chance of finding such a list. (eg: If you wanted the 100 densest or the 100 least dense, maybe we could help). SteveBaker (talk) 15:00, 6 September 2009 (UTC)[reply]
Since you are restricitng your request to chemicals on Wikipedia, the answer is -- maybe. You will need to either get a Wikipedia database dump and run a program on you own computer, or write a "bot" and get permission to use it. In either case, you will process all articles that include the {{chembox}} template. You do this by going to Special:WhatLinksHere/Template:Chembox. After you get your list the first time, you can look at the "what links here" page occasionally to see if thre are any new chemicals, and update your list. As steve baker said, there are a LOT of chemicals, so if you want to place your in Wikipedia itself, you will need to use multiple subpages. -Arch dude (talk) 16:53, 6 September 2009 (UTC)[reply]
You can save yourself a lot of effort because density is related to the average atomic weight of a compound. For liquids and solids this produces one set of data, for gases another set of lighter densities.
Thus without even looking I can tell you that C6H12O6 (glucose) has a very similar density to H2O (water) , C2H5OH (ethanol), diamond is higher (C). Fe2O3 (rust) is higher still, and PbO (lead oxide) is very high.
I didn't say I had such a list - just that we'd stand a better chance of finding some kind of list for you if you could narrow the criteria. SteveBaker (talk) 02:42, 8 September 2009 (UTC)[reply]
Children with diarrhea have a mean whole gut transit time of 5.5-7.3 hours, and 14.1-15.5 hours during the recovery period.[12] Another study in ill preterm babies found that those fed small amounts of milk had a WGTT of about 32 hours at 3 weeks and 21 hours at 6 weeks.[13] Here's more about baby poo than you'd ever want to know:[14] That study of healthy children found the transit time in under threes is about 30 hours, and in those aged 3-4 it is 36 hours. Fences&Windows02:38, 9 September 2009 (UTC)[reply]
LiFePo4
Sometimes when I find a site with a fairly low price for LiFePo4 the cells are not encased or does not include a charger. Where can I find encased technology of good or best quality with a charger at the lowest price? -- Taxa (talk) 16:58, 6 September 2009 (UTC)[reply]
LiFePo4? Am I to understand that it includes polonium? If so, where did you find those cells, especially at a "fairly low price"? Polonium is very expensive, mind you. 98.234.126.251 (talk) 06:01, 7 September 2009 (UTC)[reply]
Do a search on both spellings and see if you get any results that include polonium. You probably will not since Li and Fe as part of the term modify its sufficiently to make the distiction between Po4 and PO4. -- Taxa (talk) 01:01, 9 September 2009 (UTC)[reply]
Well, the article Lithium iron phosphate battery has a list of manufacturers at the bottom -- maybe some of them might let you order the batteries (and charger) by mail-order catalog at wholesale prices. (You know that for the very lowest prices, buying straight from the manufacturer is usually the best option when possible.) But then again, maybe they don't do that. The only way to find out for sure is to check the company websites. FWiW 98.234.126.251 (talk) 06:21, 7 September 2009 (UTC)[reply]
guys I have a project on Low noise amplifier .Plz can smebdy suggest a very basic tutorial starting right from the basics with circuit diagram
What do you consider "basic"? I would suggest Chapter 11 in Gray & Meyer for a theoretical overview, and I think Planar Microwave Engineering has an entire chapter on LNAs. Are you simulating this design in SPICE, building the circuit out of discrete components or designing for an ASIC, or simply studying the topic for general overview? The design methodology for LNAs will vary dramaticallly depending on what your actual needs are - first of all, what are you amplifying? Voltage amplifiers and current amplifiers have different topologies for best noise characteristics. Next, what are your power, bandwidth, operating frequency? These will also help you select a topology. How do you define "low noise" (e.g. 80 dB, 130 dB, spurs, noise floor, intermodulation, total harmonic distortion, etc.) You might be best served by a basic introduction to amplifiers in general (specifically electronic amplifier), and pay close attention to the relationship between different figures of merit and the noise performance. Then, you can "zoom in" on low-noise topologies and see some tricks to get the noise figure lower. Nimur (talk) 20:17, 6 September 2009 (UTC)[reply]
Here's a tutorial from National Semi, on Youtube. They're pitching their own tools, though, so you have to parse through some commercial product placement; but they have Bob Pease hosting, so it's probably worth it. He "can't tell you how to make a low noise amplifier", but he's going to "talk about how not to make a high-noise amplifier" with his classic awesome hand-drawn notes. Nimur (talk) 20:32, 6 September 2009 (UTC)[reply]
Actually that probably isn't right - looking at the methods for gold refining it looks like the urea is being oxidised by the nitric acid (catalysed by nitrous acid present in aqua regia). Looking... (seems this only works in dilute HNO3)
In concentrated acid it would be easy to assume that everything is converted to N2 , CO2 and H2O , in which case an equation would be fairly easy to get. Is that what you had in mind.?83.100.250.79 (talk) 21:55, 6 September 2009 (UTC)[reply]
Interesting. It could be that the nitric acid was not very concentrated after all (it's 1/4 of a.r.) - but N2? That's weird. IIRC only really dilute nitric acid does that.Tim Song (talk) 18:20, 8 September 2009 (UTC)[reply]
NO2, NO, and NO2+ / NO+ would all be likely to react with the amine group on urea
That's just a speculation, NO+ would make N2 by the same process, both being electrophilic attack on the NH2 ... finally subsitution of H2O at the C=0 ... giving CO(OH)2 (carbonic acid)
Cl2 may also react with urea (as do hypochlorites). There are examples of nitrous acid reacting with urea[16], so NO+ should react as well. The real reaction will be more complicated.83.100.250.79 (talk) 21:03, 9 September 2009 (UTC)[reply]
Relativity and Existence
The star Beta Comae Berenices is about 30 light years away. I was born about 25 years ago. Does this mean from the perspective of Beta Comae Berenices I do not exist? TheFutureAwaits (talk) 22:28, 6 September 2009 (UTC)[reply]
You do, they just won't know it until another 5 years or so. I doubt they're watching your house. But they could be watching TV broadcasting signals. For them, Disco is still all the rage here, as far as they know. Baseball BugsWhat's up, Doc?carrots22:39, 6 September 2009 (UTC)[reply]
I'm not sure if that's right. If that's true then you're saying everything beyond a person's immediate influence is predetermined as it has already happened but they have yet to experience it. TheFutureAwaits (talk) 22:48, 6 September 2009 (UTC)[reply]
"Predetermined?" Well, let's take an example closer to home. At the ballpark, the concession stands have the game on TV. However, due to FCC concerns and such, there is a slight delay, maybe 7 seconds. So if you happen to be watching the game through an exit portal and also watching the TV, you might see the batter hit the ball somewhere. Then you turn to watch the TV, and 7 seconds later you'll see the batter hit the ball. So it's "predetermined" in the sense that what the electromagnetic waves are carrying has already happened. That's going to be the case, whether the delay is 7 seconds or 30 years. Baseball BugsWhat's up, Doc?carrots00:44, 7 September 2009 (UTC)[reply]
Not really...on the earth, the time would be so instantaneous that it truly is action/reaction, rather than having something happen to you then 5 minutes later you experience it. Ks0stm(T•C)00:00, 7 September 2009 (UTC)[reply]
It just depends on how you define existing yet. In the reference frame there that's stationary relative to us (and probably in the frame of the star itself) your birth is in the past even though someone there couldn't receive information of the event for another 5 years. I don't know what you want to call that. However there are some reference frames at that point in which your birth is still in the future (frames moving very quickly away from Earth). Deciding in what situations you qualify as existing isn't necessarily a easy question. For example a proponent of four dimensionalism would say that you exist regardless of where they happen to be in time and space. Rckrone (talk) 23:54, 6 September 2009 (UTC)[reply]
If an explosion equal to 100 trillion666 megatons happened 30 light years away now, would we even know about it, let alone exist? So maybe you don't exist there yet, but it's inevitable that you will. Like the above poster said, it depends on your point of view/philosophy and your reference frame. Sagittarian Milky Way (talk) 00:25, 7 September 2009 (UTC)[reply]
This is entirely a "Tree falling and no one listening debate" and it centers on the fact that people are confusing an event with information about an event. You were born 25 years ago. Information about your birth has not yet reached Beta Comae Berenices. That doesn't mean that according to (hypothetical) people at Beta Comae Berenices you do not exist, it just means they don't know that you exist. There's lots of things that have happened that you have no knowlegde of. It doesn't mean they didn't happen. --Jayron3203:57, 7 September 2009 (UTC)[reply]
Something to keep in mind is that there is a distinction between events that are in your light cone and events that aren't. A past event in your light cone is unambiguously in the past regardless of reference frame. Any event outside your light can be in the past, present or future depending on your reference frame. For example TheFutureAwaits' birth is outside the light cone of someone who is on Beta Comae Berenices right now. If they're stationary relative to Earth, TFA's birth is 25 years in the past as it is to us here on Earth now (although they can't yet know about it). But if that observer were to suddenly accelerate away from Earth to faster than (5/6)c, then TFA's birth would suddenly become a future event. That's not something that can happen with the Giants game I missed last week. Rckrone (talk) 04:44, 7 September 2009 (UTC)[reply]
No, I think your obfuscating the reality of the situation with fancy physics; your still confusing the actual event (TFA's birth) with the receiving information about his birth, which can be played around with. By accelerating at (5/6) c, what you are doing is essentially outrunning the information, thus dilating the delay of that information reaching you to infinity (by keeping the information outside of the "light cone" forever). However, that doesn't change when the event happened, it just changes when the information arrives. Still the same tree, still the same sound, your just running away before you can hear it...--Jayron3204:54, 7 September 2009 (UTC)[reply]
Yeah. You're right. Darn that whole "Lack of a priviledged reference frame" thing. Sometimes the tree makes a sound before it even lands... --Jayron3205:46, 7 September 2009 (UTC)[reply]
If the article is incorrect or confusing, we need to edit it to make it more correct and clear. Always remember that while simultaneity is not absolute, causality is always preserved. The hypothetical observer outside the light-cone could not have been impacted by the OP's birth yet, because of causality; but they could have predicted it (assuming they had sufficient prior information) and therefore be aware of it (speculatively) before confirmation arrives. If their predictions were wrong, they would have no way of knowing until (at least) after the light cone from the OP's birth "arrives" at their location. Nimur (talk) 15:20, 7 September 2009 (UTC)[reply]
One mistake people sometimes make in these things is thinking of objects as points in spacetime. Objects are lines in spacetime. The situation is like this:
| |
X * here-and-now
BCB -> |\ |
| \|
| * birth of TheFutureAwaits
|
The event marked X is the earliest point on BCB's worldline where your birth or subsequent events could have a causal effect. So, from the perspective of Beta Comae Berenices when? "Right now"? Meaningless. At the time the light we're now seeing from it was emitted? That's about 35 years prior to X. Same cosmological time as determined by CMB anisotropy? Around 5 years before X. I can't think of any other reasonable question to ask along these lines.
Forget the relativity of simultaneity. Different coordinate systems assign different coordinates to the same point. That's all there is to the relativity of simultaneity. It's not "wrong" as such, just meaningless. It's a statement about coordinate systems, and coordinate systems don't exist. -- BenRG (talk) 12:15, 7 September 2009 (UTC)[reply]
"Now" does have meaning in the context of a particular frame. (I would point out there's a difference between "meaningless" and "not particularly useful". I would agree that it's often not a particularly useful way to think about the relationship between two events.) In this case I was using "now on BCB" to mean the point that's at the same time as here, according to the Earth frame. I wasn't as clear about that as I could've been. Rckrone (talk) 17:42, 7 September 2009 (UTC)[reply]
But cause and effect travel at, at most, the speed of light. What good is existance if it doesn't make a mote of a difference to the most sensitive detector? (at least temporarily, or, if you're receeding fast enough, indefinately/forever) You can't even be aware of the existance of an event without it causing an effect (otherwise, how did you notice?) TheFutureAwaits exists, to an omniscient observer outside spacetime. But so do the 2012 Olympics (probably). I think we can agree, using the usual Plain English sense of the language, the 2012 Olympics don't exist yet. There is a very high probability that there will be a day, that they exist. That means, for now, they don't exist. That doesn't stop from people from planning or predicting events that don't exist because we're trying to make them exist, or finding out what will exist before it does. And for high likelyhood things (like Greenwich sun meridian crossings?) it's only natural to list tomorrow's and 2010's as fact, but technically they are just as much fiction as Moby Dick until they occur, in the flesh. Interestingly enough, on the last one Ockham's Razor says shut up. Sagittarian Milky Way (talk) 01:16, 8 September 2009 (UTC)[reply]
I think any attempt to naturally generalize plain English language, which is based on a classical picture, to the relativistic case is going to be problematic. In the classical case, events fall into only two categories: past and future (ignoring border cases), and so there are a bunch of equivalent ways we can define the concept of events that haven't happened yet. Some of them are as events that can't affect us now, events the we can still affect, or events that are forward in time from where we are now. In the relativistic case those three aren't equivalent (and the last one depends on your reference frame which makes it kind of problematic). I don't think there's a natural way to resolve the ambiguity without just deciding on some new definitions. Rckrone (talk) 06:57, 8 September 2009 (UTC)[reply]
Would these tomatoes growing at a sewage works be safe to eat?
I just saw this article. Would the tomatoes be safe to eat? I understand that the sludge is eventually turned into compost which is presumably safe to grow food plants in, but what about these plants that are growing directly on the waste? Spin Dryer (talk) 23:27, 6 September 2009 (UTC)[reply]
Food has been grown with feces as fertilizer for thousands of years. That's not a problem. Pathogens won't go through them. More worrisome are things like heavy metals that might also be in waste water. --98.217.14.211 (talk) 23:57, 6 September 2009 (UTC)[reply]
That's the story that was told to me by someone who worked at a sewage farm. At the place he worked, they apparently had some very large, very healthy-looking tomato plants with nice-looking fruit growing in unexpected places. The staff were told that the tomatoes were unsafe to eat (and not to even think about picking them) due to the possibility of contamination by heavy metals and other chemicals from the various cleaning products that people routinely flush/put down the sink. --Kurt Shaped Box (talk) 09:24, 7 September 2009 (UTC)[reply]
People don't actually flush that much nasty stuff down the sink. The main problem with heavy metals is purely 'natural': they bioaccumulate. In other words, are enriched upwards in the food chain - which we're at the top of. So our feces would normally contain many, many times more heavy metal than the corresponding amount of plant-mulch or cow dung. --Pykk (talk) 19:23, 7 September 2009 (UTC)[reply]
In the US, people put all kinds of stuff down the sink. Maybe not so much things like Mercury, but there are all kinds of traces of medications in the water. Googlemeister (talk) 13:33, 8 September 2009 (UTC)[reply]
I think it's important to understand (given the OPs second comment) that AFAIK the danger comes from contamination. It's difficult to grow something in sewage and ensure you don't get any of it on the stuff you are growing. Washing is not guaranteed to get it all off and you may only need a small amount and I presume it may even penetrate the surface somewhat. anyway. I expect this is particularly a problem with leafy vegetables but low hanging fruit like tomatoes will still have some risk. Nil Einne (talk) 09:08, 7 September 2009 (UTC)[reply]
Certainly bugs can penetrate fruit skin. My father was a ship's doctor in the Royal Navy in WW2 and had to deal with a Dysentery outbreak caused by sailors eating water melon stored by traders underwater in the then infected Sweet Water Canal. The sailors seemed to think if they washed the melon and cut the skin it was good enough to sterilise the interior. --BozMotalk09:28, 7 September 2009 (UTC)[reply]
Hmm, even if true it hardly proves that the pathogens got through the unbroken rind. Enough of them might have stuck to the rind after washing, and then when the sailors cut into it, they carried them into the meat on the knife. I don't know for sure that the pathogens can't get through, but I have to say it seems a little unlikely to me given the thickness of watermelon rind and the size of ameobae, combined with the existence of a plausible alternative explanation. --Trovatore (talk)
The answer is on the image description page - "The Space Shuttle Challenger crewmember remains are being transferred from 7 hearse vehicles to a MAC C-141 transport plane". Nanonic (talk) 23:34, 6 September 2009 (UTC)[reply]
According to recent news reports (one example), the Emperor Norton Bridge has been closed because of cracks in the cables that support the deck. Is it accurate to say that there's currently a problem with the "suspension" of this suspension bridge, or would that be a bit of a colloquialism? Nyttend (talk) 02:59, 7 September 2009 (UTC)[reply]
To answer your question, no you would not be correct, because according to that article they "found a crack in one of the eyebars on the side of the structure." I interpret that to mean the actual bridge part, along where the original work was planned. If there was a crack in the cables, I think you'd be correct in saying it, not like Suspension (vehicle) of cars but rather in the actual hanging of the thing. ~ Amory (user • talk • contribs)04:19, 7 September 2009 (UTC)[reply]
Actually, that wasn't the article I consulted; it was something on the Road Runner website. Here is a story from the San Francisco Chronicle, stating that the link "helps hold up the east span". Nyttend (talk) 03:20, 8 September 2009 (UTC)[reply]
I understand an eyebar to be part (or indeed all) of the vertical suspension members of a suspension bridge. Thus I think it would be fine to say that the bridge. Saying there is a problem with the "suspension of this suspension bridge" is probably a bit unhelpful; I'd tend to use the phrase "problem with a vertical suspension link", or somesuch. However, since the eastern span of the bridge, which is where the fault was found, is a combination of "a double-tower cantilever span, five medium-span truss bridges, and a 14-section truss causeway", I'm not convinced that the explanation necessarily relates to suspension at all - though I'm not satisfied that I understand the design of the double-tower cantilever span ... is is cable stayed? --Tagishsimon(talk)21:27, 8 September 2009 (UTC)[reply]
I see that the first image in eyebar explains quite well the space of eyebars in truss sections. So now my view is that although the eyebars are under tension and so can be thought of as suspension members, to describe them as such without more context would probably serve to mislead. --Tagishsimon(talk)21:31, 8 September 2009 (UTC)[reply]
Radioactivity in the early Earth.
From what I know radioactive heating was a major source of heat for the early Earth, and still is today to a lesser extent. My question is, was the radioactivity billions of years ago (when the Earth formed) enough to cause harm to humans if we lived then. Would it be more/less then the fallout from a nuclear blast? —Preceding unsigned comment added by 66.133.196.152 (talk) 06:20, 7 September 2009 (UTC)[reply]
From what I know, the sources of radiation were buried deep under the surface (as they are today) and heating the Earth from within. And since ionizing radiation is strongly absorbed by rocks (from what I've heard way back when, a layer of granite just 1 foot thick can absorb gamma rays almost completely), the radiation at the Earth's surface would be negligible, since all of it would've been converted to heat. The heating from the radiation, on the other hand, would be a whole different story -- since it was strong enough to melt rocks, it would surely burn any living creature to a crisp. 98.234.126.251 (talk) 06:35, 7 September 2009 (UTC)[reply]
Ehhh, if I lived billions of years ago, I'd be more concerned about the radiation I'd receive from the sun due to a lack of ozone rather than radioisotope decay emerging from the earth's core. Primitive earth was probably devoid of ozone, so heavy amounts of solar radiation would be kill a human pretty quickly.
You should also consider that there's no one set quantity of fallout that's released from any nuclear bomb. The fallout quantity depends on the yield, which can vary. Dougcard (talk) 06:39, 7 September 2009 (UTC)[reply]
Much less than a nuclear blast by the time there were humans. That comes trivially from the maths of half lives. Out of interest Rutherford showed without background radiation the world would cool completely in about 10 million years. The fact that the core is still molten etc at 5 billion years is because of radioactive decay generating heat which has nowhere to go. --BozMotalk09:21, 7 September 2009 (UTC)[reply]
It's also worth pointing out that Ernest Rutherford was an atomic physicist, not a geophysicist or planetary scientist. Modern theory have proposed a variety of mechanisms for cooling other than blackbody radiation, including nuclear decay heating and latent heat of fusion from liquid-to-solid crystallization. So, I would take Rutherford's estimate with a grain of salt; modern geophysical theory seems a little more reliable. A common misconception is that all physicists know everything, and are good at back-of-the-envelope calculations. If only we could put the most famous theoretical physicists on the Wikipedia Science Reference Desk to see how their domain-specific expertise translates into general-purpose problem solving skill... Nimur (talk) 15:28, 7 September 2009 (UTC)[reply]
If the radiation is hot enough to melt metal and rocks, it is far more radioactive than the radiation in a nuclear blast. Nuclear radiation is bad for humans and other living things (as they say) but it's not much on a geophysical scale. --98.217.14.211 (talk) 20:07, 7 September 2009 (UTC)[reply]
Not really true I am afraid. It keeps rocks molten because it heats them incredibly slowly over thousands of years but the heat is locked in. At any instant the level is way less than a nuclear blast--BozMotalk21:07, 7 September 2009 (UTC)[reply]
drug/biochemical for feeling refreshed
I understand that adenosine is one of the causative agents of drowsiness and sleepiness. Is there a chemical that gives you the feeling of being refreshed, like after a long nap or a really, really good sleep? And of course I'm not talking about a simple adenosine antagonist like caffeine, since I quite suspect that adenosine antagonism doesn't give you that refreshed feeling.
If this chemical exists, in what natural sources could I find it, and is it capable of passing the blood-brain barrier? If this chemical were say, used as a study drug, would there be any long-term ill effects? John Riemann Soong (talk) 07:52, 7 September 2009 (UTC)[reply]
There is no drug that causes you to feel refreshed in the sense of completely substituting for sleep. There is, however, a wide class of drugs that make you feel awake and energized, including amphetamine, cocaine, and other so-called "psychomotor stimulants". Looie496 (talk) 15:27, 7 September 2009 (UTC)[reply]
But those are adenosine antagonists, which I specifically excluded! And I want to exclude compounds that give you a "buzz" or make you feel charged with energy, which is not how I feel when I wake up from a long nap (relaxed). Is the feeling of refreshedness perhaps due to the fact that adenosine is still active (but exiting the system), with various neurostimulants coming in, which induces an interesting competitive effect? John Riemann Soong (talk) 15:57, 7 September 2009 (UTC)[reply]
The hypothesis I favor (which comes from Giulio Tononi) says that sleep actually produces structural changes in the brain. While we are awake, synaptic connections get steadily stronger as we store memories, and this change gradually unbalances the brain's activity patterns. During sleep, a process takes place that gradually weakens the synapses. If that's correct, then there is no obvious way for a drug to duplicate the process. (And by the way, psychomotor stimulants are not adenosine antagonists, they are dopamine agonists, a whole different class of drug.) Looie496 (talk) 19:51, 7 September 2009 (UTC)[reply]
How much noise do moving cars and other vehicles make?
Also depends heavily on the make of the vehicle. I remember the first time I saw a Prius, it was cruising through a grass parking lot using only its electric motor. It came up behind me and passed slowly by - surprised the hell out of me when a large white object entered my peripheral vision because I hadn't heard a damn thing! 218.25.32.210 (talk) 02:04, 8 September 2009 (UTC)[reply]
U,S, and other government websites should have some figures, since in the U.S. associations advocating for blind people are demanding that electric cars make noise so they can hear them coming, and I have read statements by spokesmen for companies planning to manufacture and sell electric cars related to this. See [20], [21],[22]. Maybe they could just require them to put in one of those giant window shaking 200 watt sound systems and play brain thumping noise/music all the time. Edison (talk) 15:50, 8 September 2009 (UTC)[reply]
The following web site [[23]] exhibits a scale with the noise level of a wide range of sources, including a car (65-70 dB) and a diesel truck (85-90 dB). I assume that these would be relatively normal, modern vehicles passing by. I have measured levels of the order of 120 dB for a car with a broken exhaust pipe that sounded more like a very loud (and unpleasant) jet engine at a distance of 2-3 m. At that level, noise can be damaging to your ear especially if endured for sustained periods of time. Michel M Verstraete (talk) 20:06, 9 September 2009 (UTC).[reply]
Bouncing soap bubbles, electrical?
Bubbles colliding with each other in the air typically bounce off of each other -- although they can sometimes hit in a way that causes them to join and assume a more minimal double-bubble configuration and sometimes, more rarely, the two will join as a single larger, and most minimal, sphere.
Soap bubbles typically break if they touch dry wood, metal, stone, plastic or skin. They break if they touch sheer silk fabric or smooth nylon but they typically bounce off of wool and raw silk seems to be excellent for bouncing them as well.
Are these exceptions all examples of electrical repulsion? Is there some other explanation (i.e. the fine hairs of the wool are just not enough contact to pop the bubble, the lanolin in the wool and natural oils in raw silk are a factor?)
I am an entertainer with a show that I call Bubble Magic. I've read C.V. Boys classic work on Soap Bubbles and other science literature but I've never seen a scientific explanation for the apparent repulsion between bubbles and wool or bubbles and other materials. 79.193.226.55 (talk) 10:14, 7 September 2009 (UTC)[reply]
What a good set of questions. It is possible for bubbles to bounce off surfaces without contact or electrical forces just from the mechanics of the air between them. Clearly, static and other electrical forces (even van der Waals) could play a part, so could fibre geometry and surface absorbency. I think the film structure of the bubble is fairly well know (with hydro-phobic tails pointing outwards). One thing to try would be to compare dry cleaned wool with natural wool. There is a huge difference in fire resistance (dry cleaned wool is quite hard to burn, natural wool is easy to burn) so I think dry cleaned wool probably has little lanolin. Have you tried other waxy material? --BozMotalk11:21, 7 September 2009 (UTC)[reply]
I have tried other waxy materials including paraffin, bees wax, and even pure lanolin with no success (the bubbles popped) but the lack of "wetting" does seem to be a factor and so it may contribute in some way. Sheer silk (my Hawaiian shirts) seem to grab and quickly drink the drop at the bottom of the bubble ... then it pops. Once a bubble has popped on, even a good wool surface (navy pea coat) that wet spot is no longer a good place to bounce one.
But the two bubbles approaching each other in the air have a very different surface geometry than does the fine-haired wool carpet so it's difficult to see one answer to the question.
The hydrophobic ends of the soap molecules at the surface, I believe, have no great charge to them ... maybe the nearby water molecules attached to those soap molecules that are now all aligned with the same face (charge) aimed outward? What can you say about the "mechanics of the air between them"? 79.193.226.55 (talk) 11:35, 7 September 2009 (UTC) —Preceding unsigned comment added by 79.193.226.55 (talk) 11:34, 7 September 2009 (UTC)[reply]
In the complete absence of any electrical forces I do not think that two bubbles would ever be able to squeeze out the thin layer of air between them. They would deform, the air would squash and they would spring apart. Even in classical fluid dynamics the equations suggest a smooth ball cannot touch a flat wall because of the air cushion, only surface irregularities allow it to happen. But I suspect there will always be electrical forces. --BozMotalk12:08, 7 September 2009 (UTC)[reply]
For your show of course you should be able to charge up bubbles positively and negatively. Any static charge would dominate. All that requires is a metal hoop to blow through, standing on a nylon carpet and having one earthed boot. A bit of judicious shuffling should do the trick. --BozMotalk12:11, 7 September 2009 (UTC)[reply]
Thank you for that! Simply compressed air could account for much of what we see with or without electrical forces. I'll take that with me as I continue to watch what they do in various situations.
I have charged bubbles and seen dramatic effects as a result. I often perform in science centers and when I can, I get a hold of a Van de Graff generator. If you blow a stream of bubbles to it they will act as though they are being pulled in ... until ... the first one pops and then, suddenly the others reverse course! They take on the charge (presumably delivered to them by the splash of the first one) that is now the same charge as that of the dome of the Van De Graff ... these retreating bubbles invariably chase me since I'm the closest available place to discharge their excess ... I will sometimes dodge them for a few steps but then they catch me like little kamikazees. I'll try the trick with the carpet and boot ... 79.193.226.55 (talk) 12:53, 7 September 2009 (UTC)[reply]
I expect you could get a good effect with a piece of PVC pipe rubbed with a piece of wool. The trick of an uncharged bubble being attracted to the charged object, picking up (or giving up) electrons, then spraying ionized droplets on the other bubbles, which then chase uncharged objects or people, is brilliant. Edison (talk) 21:58, 7 September 2009 (UTC)[reply]
Prions have no genetic material as far as we know, thus, the notion of "growing" is only partially applicable. Prions (specifically, the misfolded prion protein, or PrPSc) induce changes in the folding of otherwise normal cellular protein (PrPC); thus, their propagation in a culture would depend on the abundance and availability (for direct contact) of the PrPC, and the stability of the PrPSc under culture conditions. I don't think anyone has identified an efficient system for detecting PrPSc in simple cell culture (in the way that a shell vial assay {is that really a red link??!!} may be used for detecting viruses). Attempts have been made to develop in vitro tests for prions, such as PMCA and various immunoassays (e.g. PMID 19060956). --Scray (talk) 20:24, 7 September 2009 (UTC)[reply]
Not a real dictionary word (yet or probably ever).. But [24] "The test method was developed by British Rail and Mebon Paints and the term Prohesion is derived from a key concept of this development namely Protection is Adhesion."
Sometimes, and yes, respectively. Beta particles are nothing more than electrons (negative or positive), so beta decay absolutely must consider the mass of the electrons. (The inverse process, electron capture, also involves electrons.) Tables of atomic masses always include the mass of electrons for neutral, ground-state atoms. TenOfAllTrades(talk) 15:27, 7 September 2009 (UTC)[reply]
Well, it sort of includes the mass of those electrons. Considering that electrons have roughly 1/1856th (give or take) the mass of a proton, and most atomic masses aren't often reported much past the 4th decimal place, so electrons don't often show up, unless we're dealing with hyper-accurate atomic masses (which are available, but not often used in standard calculations). --Jayron3218:53, 7 September 2009 (UTC)[reply]
I understood the original question somewhat differently... First of all, nuclear forces are relevant only to account for the stability of the nuclei, not to explain the interactions between these nuclei and the electrons of a given atom. Second, there are two main classes of nuclear reactions: fission and fusion. Fission is a process where single individual heavy nuclei (e.g., Uranium, Plutonium, etc) break down in pieces as part of a stochastic process, which can sometime be accelerated by external stimulation (e.g., by neutrons). In some of these cases of disintegration, beta particles (electrons) may be released. Fusion requires multiple light nuclei (e.g., Hydrogen, Helium, etc) to merge together: the old nuclei are now bound together by nuclear forces to form a new, singular nucleus. This process only takes place at very high temperature where materials are already either strongly ionized or in a state of plasma. I am not aware that electrons play any role in stimulating (or hindering) such nuclear reactions. In any case, as already pointed out above, the actual mass of electrons in neutral atoms is minuscule compared to the mass of the nucleus. If these various answers do not answer your question, please clarify or elaborate on what you are looking for. Michel M Verstraete (talk) 19:47, 9 September 2009 (UTC).[reply]
Insect Identification
I was wondering if anyone would be able to identify this insect. It was squashed and captured on a piece of tape.
(Possibly) Pertinent Information:
I found the insect crawling on my desk.
The body measures approximately 3mm in length, and 2mm in width.
I am located in Toronto, Canada. Today's temperature is 21 Celsius, relative humidity @ 73%.
Images:
I will refrain from embedding the images as they are quite large and may break the page.
However, the body of the German cockroach measures at least 1.3cm long (according to the wikipedia article). The body of the sample I captured measures around 0.3cm long.
Impact of the type of cigarettes smoked on the decrease in life expectancy
I have a hard time finding numbers concerning the decrease in human life expectancy caused by smoking which numerically examines the differences between the type of product used. I am particularly interested in the difference between average-yield cigarettes with filters and unfiltered and/or high-yield cigarettes. I found an AP article concerning a study conducted in India which claimed that the decrease was roughly 20 years for long-term smokers of unfiltered "bidi" type cigarettes. One must however consider that bidi smokers usually don't have access to healthcare which as good as that commonly available in countries such as the UK - hence the difference might be much lower in the UK, for example. I suppose that the decrease caused by unfiltered cigarettes in "developed countries" is in the range of 11 to 16 years. Thanks for your help. —Preceding unsigned comment added by Binrapt (talk • contribs) 16:57, 7 September 2009 (UTC)[reply]
Careful there. The lack of health care cuts both way. Life expectancy in India is about 10 years below life expectancy in the UK. So people will die earlier even without cigarettes - in other words, any particular harmful custom has less lifespan to take away in the first place. If you die at age 3 from amoebic diarrhea, you cannot die of tobacco-caused vascular diseases at age 60. --Stephan Schulz (talk) 20:13, 7 September 2009 (UTC)[reply]
Anemia/obesity connection
Don't worry, this isn't a request for medical advice; I'm just curious. Is there any kind of anemia that is associated with / is exacerbated by / tends to occur with obesity? +Angr20:29, 7 September 2009 (UTC)[reply]
Well, at the risk of sounding as though I'm not taking the question seriously, you do see these 600lb+ guys on talkshows who seem to forget just how much food they consume on a daily basis when asked directly - claiming that they 'don't eat more than anyone else' and that there must be some sort of genetic/glandular cause for their obesity... --Kurt Shaped Box (talk) 22:29, 7 September 2009 (UTC)[reply]
I also misread it exactly the same way. It is like a magic trick where the audience is misdirected by expectation or "attentional set." Edison (talk) 15:37, 8 September 2009 (UTC)[reply]
It's plausible. I vaguely remember reading about malnutrition and obesity, since people who don't manage their diets well probably aren't eating the right stuff either. But you proably knew that already. 98.14.222.125 (talk) 23:39, 7 September 2009 (UTC)[reply]
No. Type II diabetes/metabolic syndrome is associated with increased ferritin levels, which is a surrogate marker for iron overload, which is negatively associated (weakly!) with anaemia. See [25]. --NorwegianBluetalk20:31, 8 September 2009 (UTC)[reply]
It's been suggested, but it doesn't seem to be the case: "Overweight and obesity were associated with changes in serum iron, TS, and ferritin that would be expected to occur in the setting of chronic, systemic inflammation. However, overweight and obese persons were not more likely to be anemic compared with normal-weight persons."[26]Fences&Windows04:08, 9 September 2009 (UTC)[reply]
Snapping a street light by repeated poking with finger
Is it true that you could snap a street light - I mean a street light on a long mostly vertical pole or tube - by repeatedly pushing it gently with your finger at its resonant frequency? 89.242.115.9 (talk) 20:32, 7 September 2009 (UTC)[reply]
I once saw a group of three college guys "tackling" a sequence of metal light poles by all three simultaneously bumping the pole with their shoulders (one high, one low, one in the middle). This resulted in a wave of energy travelling swiftly up the pole, and a sharp mechanical snap when the weave reached the top, knocking out the light. They scored 4 out of 4 that I saw. There was not a huge amount of force, but the transient shock at the top was impressive. There are legends (doubtful) of Nikola Tesla shattering bridges or buildings with mechanical resonators. I would not rule out the possibility of say a 2 pound force repeatedly applied at a resonant frequency causing resonant motion of a metal light pole, if it is a modern flexible one. An old cast iron one or one on a wooden pole? No way. The designers should have damped out such resonance, to avoid large amplitude resonance in wind, but see Tacoma Narrows Bridge (1940) for a famous example of failure to deal with resonance in a bridge. Edison (talk) 21:56, 7 September 2009 (UTC)[reply]
Well, what is "snapping" and what is "gently"? You can certainly excite it to fairly violent movement with repeated pushing with one hand (and if I can do it with my hand, Big Van Vader can do it with a finger). It will not snap the pole, but it may shed some of the glass components on top. --Stephan Schulz (talk) 21:58, 7 September 2009 (UTC)[reply]
The idea that you can break anything by gently stimulating it at its resonant frequency is deeply flawed. The biggest problem is that each time you 'poke' the object, you have to put in more energy than the object can dissipate during the next cycle of oscillation. If you don't put in that minimum amount, the oscillation cannot grow. Tesla was a clever guy - but he had a tendency to be taken in by simple ideas and to blow them out of all proportions - then to lie about his results, reporting what he THOUGHT they should be - not what they actually were. He had enough successes to become famous - even revered - but in many ways he was a complete nut-job. His theories on resonance are an excellent example of that. The basic idea is true - there are things that will resonate to destruction (the canonical example being the opera singer shattering a glass with nothing more than her voice)...but that doesn't translate to being able to destroy massive objects with tiny forces. SteveBaker (talk) 02:30, 8 September 2009 (UTC)[reply]
Tesla also thought you could transmit electricity through the earth, as I recall. That's not a very practical idea. Edison got a few things wrong too. Both of those guys are examples of the principle that in order to get good ideas, you have to have lots of ideas - some of which will be wrong. Edison, for example, promoted DC while Tesla promoted AC. Guess who won that battle. Baseball BugsWhat's up, Doc?carrots15:59, 8 September 2009 (UTC)[reply]
When I was a kid, we used to knock out lights in parks and playgrounds by kicking the pole behind the maintenance hatch. We didn't know then what exactly was going on, but I suppose there was a relay attached to the inside wall of the pole opposite the hatch, and a sharp kick would break the circuit for just long enough that the mercury vapour lamp would then need to restart, which takes a few minutes.--Rallette (talk) 06:09, 8 September 2009 (UTC)[reply]
Not sure if they had it when Rallette was a kid but don't modern street lights have a collision detection mechanism that cuts the power when it's hit by something (ie. car)? --antilivedT | C | G11:18, 8 September 2009 (UTC)[reply]
It would be quite possible to design a metal lamp post which was quite tall, which was strong enough to support itself and a large wind loading, but was underdamped, if that made it a buck cheaper and it was not a specified quality which was tested for by the purchaser. The same folks who put lead in childrens' products, antifreeze in tooth paste, make cribs which strangle babies, build school buildings which collapse in low level earth tremors, and put melamine in pet food, might just market underdamped lightposts. Edison (talk) 15:45, 8 September 2009 (UTC)[reply]
I was thinking of poking the metal pole when it is at the end of its movement, like pushing a child's swing at the end of its swing. The pole would break through metal fatigue, as when you bend a piece of wire such as a paperclip back and forth. 78.147.7.217 (talk) 21:34, 8 September 2009 (UTC)[reply]
What's the technical term for a fight between two animals where neither combatant is fighting to its full capability in order to ensure that neither is killed or permanently maimed (with the rationale that 'if I go all out on him, he'll go all out on me and we'll kill each other')?
I've been watching gull videos on YouTube again tonight and I've discovered more examples of the previously-discussed 'tug-o-war beak wrestling' - e.g. here and here and I had a moment of realization that that purpose of these conflicts may actually be to ensure that neither bird can attack with its beak (because, let's face it - two gulls could rip each other up pretty badly if they really went at it), whilst both attempt to overpower the other and get him into a position where he can be 'submitted' and forced to disengage and fly away - all with minimal bloodshed. Kind of like a gull version of our submission wrestling, where the object is to get the other guy to tap out, rather than put him into intensive care. I don't know if this is obvious to anyone else - but it never really clicked with me until now...
I've looked for a WP article discussing this behaviour (in animals in general - not just gulls) but all I've found is references to human combat. Any ideas, guys? --Kurt Shaped Box (talk) 01:55, 8 September 2009 (UTC)[reply]
The term that occurs to me is "ritual combat", and I'm pretty sure that's what ethologists call it, however our ritual combat is a redirect to an article that doesn't mention animals. Looie496 (talk) 02:28, 8 September 2009 (UTC)[reply]
Well, it's probably a form of intrasexual selection, though that isn't the name of the combat itself. It's of note that almost all intraspecies fighting is of the nature you describe—it is rarely meant to be fatal, and instead is about posturing, submission, etc. (Interspecies is a totally different question.) There is a lot of discussion of this in On Killing (specifically, that there are other options than "fight" and "flight"—"posturing" and "submission"). --98.217.14.211 (talk) 02:50, 8 September 2009 (UTC)[reply]
Perhaps relevant aphorism: I read once that -- due to the large difference in how serious their weaponry is -- when fighting for mates, "doves are hawks and hawks are doves". --Sean16:22, 8 September 2009 (UTC)[reply]
Funnily enough, I saw a video on YouTube of two hawks fighting last year - it was less violent than in the gulls. One hawk had the other one pinned on its back and proceeded to gently 'beak tap' it until it gave up. I suppose the perception that "I've got you at my mercy and I am now in the position to deliver a fatal blow if I so wished" is enough to bring the fight to an end. It looks to me as though that's what happened in the second gull video - when one bird had the other by the neck/throat. --Kurt Shaped Box (talk) 20:17, 8 September 2009 (UTC)[reply]
Based on the animal videos I've seen, the same thing goes for wolves, lions, and other large predators. So yeah, I suppose that's because they're more likely to kill one another during ritual combat than other animals. Funny thing, though, in Jack London's Call of the Wild, dogs and wolves do fight one another to the death (and I mean dogs vs. dogs or wolves vs. wolves, not wolves vs. dogs). That's a pretty odd thing, considering that he actually did spend a long time in the far north and prob'ly witnessed enough dog-fights to become an expert on the subject. 98.234.126.251 (talk) 05:59, 9 September 2009 (UTC)[reply]
I think Dawkins mentioned this in The Selfish Gene, though I can't find a definite attribution. IIRC, his example was in rattlesnakes, who rarely, if ever, strike one another when fighting over a mate. A single bite would almost certainly be deadly, yet both combatants refrain and therefore increase their risk of losing, but increase their odds of living. In a way, this is a kind of invisible Green-beard effect. That's part of the gene-centered view of evolution, though, so other theorists will have different explanations. Matt Deres (talk) 16:37, 8 September 2009 (UTC)[reply]
Space shuttle landing stuff
In the article, Space Shuttle Columbia disaster, in the section "Destruction during re-entry," it gives a sort of play by play of the events of the landing up to and including the disintegration of the orbiter. Like this:
* 8:53:26 (EI+557) – Columbia crossed the California coast west of Sacramento. Speed: Mach 23; altitude: 231,600 feet (70.6 km; 43.86 mi).
Anyway, is there anything similar out there for one of the sucessful landings? I've looked but I can't find anything. I'm really amazed that the Columbia made it across California in a minute and a half, and I got so into looking at the data that I nearly forgot that this mission was going to end in disaster. It seems that this list was made for some commission looking into the accident, so maybe no one has made anything for one of the many times that things went right.
Thanks for your time. I always appreciate the effort that goes into anwering these questions.
The ill-fated mission didn't result in the shuttle re-entering any faster or slower than it should have done - so the timeline for a successful mission would be pretty similar. However, they don't always come in on the exact same track - so there would be differences of location - if not of speed. http://spaceflight.nasa.gov/realdata/sightings/ offers data for an upcoming landing - in order that amateur 'shuttle-spotters' will know when and where to look. I don't think that's precisely what you want but the interactive applet has a gazillion options for finding out where pretty much any NASA vehicle is at any time - or when it will cross a particular state. That MAY enable you to figure out what you want to know. SteveBaker (talk) 10:58, 8 September 2009 (UTC)[reply]
You may want to login into the NASA system and ask them that question directly: See 42. You may have to wait for 2 weeks to get an answer, but you should get reliable information. Michel M Verstraete (talk) 19:19, 9 September 2009 (UTC).[reply]
The NASA TV channel worked for me last night - at 8:11pm central time the shuttle and space station zipped across the Texas skies right on cue. The sun had only just set and the sky was still pretty bright - yet they were easily the brightest objects in the sky - crossing from horizon to horizon in just a few minutes. The shuttle was about a hand's-breadth in front of the space station and you could easily tell them apart with the naked eye. With binoculars, you can see the big solar panels and really get a feel for just how gigantic the ISS has become. Very impressive...also a complete waste of money - but that's another story! SteveBaker (talk) 13:43, 9 September 2009 (UTC)[reply]
Thanks for all the responses. I have gotten ever closer to the info I want, and if I put it together I should have something interesting. Maybe I should share it? —Preceding unsigned comment added by 169.231.32.17 (talk) 08:59, 10 September 2009 (UTC)[reply]
Hello.
I am wondering if anyone can direct me to a manufacturer of equipment for quickly drying a powder that is highly heat sensitive. The powder must remain below 30 C. Our current method is; after reprecipitating the product using water to dissolve and acetone to crash out for purification, we air dry in a humidity-reduced room, then dry under vacuum in pans until the product is a consistent weight. Some method of drying the product more quickly without heating it is necessary. A small amount of water hydration will remain, but the excess moisture needs to be removed. Thank you in advance for your help. 134.217.112.15 (talk) 15:49, 8 September 2009 (UTC)[reply]
Agitate the pans, and heat them to 30 C (or whatever safe temperature is below the decomposition temperature of your product). The evaporation of water from the material will tend to chill the remaining material, reducing the rate of further evaporation (even under vacuum). Agitation ensures that water remains uniformly distributed over the exposed surface (maximizing evaporation), and will encourage the breakup of water-retaining clumps. Sifting through screens or shaking in the presence of inert metallic or ceramic balls will have a similar effect. TenOfAllTrades(talk) 22:32, 8 September 2009 (UTC)[reply]
You could put it in a round-bottom flask and dry it under vacuum in a warm-water bath, with constant agitation; that's the method we use in our lab for drying heat-sensitive materials. Caution: drawing too much of a vacuum could chill the flask so much that it condenses moisture from the air and rehydrates the material. You should experiment with different suction pressure / water temperature combinations to see which one gives the shortest drying time without condensing moisture from the air. 98.234.126.251 (talk) 05:36, 9 September 2009 (UTC)[reply]
Have you investigated Fluidized bed techniques? Although these seem more commonly used for other purposes, it seems to me that they might also be efficacious for this one. Try searching the technical literature using this term. Actually, some of TenOfAllTrades's procedures may approach this area. 87.81.230.195 (talk) 19:58, 9 September 2009 (UTC)[reply]
Beginning of science: Aristotle or Galileo
Apparently, people with a humanistic background tend to consider Aristotle as the [] of science. On the other hand, people versed in the natural science consider Galileo the first scientist.--Mr.K.(talk)16:07, 8 September 2009 (UTC)[reply]
It depends largely on what you define "science" as being. Strictly speaking, Aristotle bears little resemblance to a "scientist" by a primarily modern definition (he explained how he thought the world worked, and paid some attention to natural history, but he exhibited nothing like an empiricist ethos). Galileo looks a LOT more like a "scientist" than Aristotle did, though calling him the "first" is problematic (he was not totally novel, just very famous). In any case, the "science" of the Early Modern (Scientific Revolution) period looks a lot more like modern science than does Ancient "science", though even the Early Modern stuff looks pretty quaint compared to, say, 19th-century science (which is for all intents and purposes "modern", even though many of the things we currently associate with science are firmly rooted in the late 20th century). --98.217.14.211 (talk) 16:31, 8 September 2009 (UTC)[reply]
It really depends on what tradition you are following. There were lots of early Arabic chemists, for example, doing real "Science" as before 1000 (see Muhammad ibn Zakariya al-Razi (aka Rhazes) in the 900's and Geber in the 700s. Even in Europe, Roger Bacon set out the basic precepts of the scientific method in the 13th century, 250 years before Galileo. If ANYONE is the father of modern western scientific thought, Roger Bacon is probably it, but even then I wouldn't make that assertion too strongly. --Jayron3221:04, 8 September 2009 (UTC)[reply]
The greeks frowned on doing experiments - believing that you could simply think up all of the answers from first principles. That kind of thing works great for mathematics - but sucks when it comes to the physical sciences. Aristotle wasn't a scientist by any modern definition. SteveBaker (talk) 21:16, 8 September 2009 (UTC)[reply]
I agree generally, but there are important exceptions. Hippocrates (who might actually be a group of people, but it doesn't matter) was an amazing observer of empirical facts; and Archimedes was certainly open to experimenting. Looie496 (talk) 23:47, 8 September 2009 (UTC)[reply]
Aristotle seems a pompous fool. No one person delayed the rise of the scientific method more than "the philosopher," as Aristotle was known many centuries after his time. Galileo was an empiricist and scientist. Edison (talk) 02:51, 9 September 2009 (UTC)[reply]
For woman, does size matter?
I don't know many couples where the man is shorter than the woman. A well-known exception is Sarkozy and Bruni. Is that so important that the man is taller? On the other hand, I know several couples where the woman is making more money, is more intelligent, has more culture than the man. Mr.K.(talk)16:09, 8 September 2009 (UTC)[reply]
I know plenty of couples like that - assuming Mr.K. means an interest in the arts, etc. by "having culture". Why do you ask? --Tango (talk) 00:33, 9 September 2009 (UTC)[reply]
I was just interested in seeing some actual examples. But you may be right — if we define culture as meaning an interest in the arts, then surely some examples can be found. While that may be the most common and basic definition of culture, it is by no means the only definition of culture. As we well know, culture often embraces the decidedly un-cultural. Maybe I'm nitpicking or being pedantic. But much of what passes for culture challenges our definition of culture. Bus stop (talk) 00:55, 9 September 2009 (UTC)[reply]
I agree that culture is far more than just the arts, but in the context of a person "having culture" I can't think of anything else that could be intended. --Tango (talk) 01:19, 9 September 2009 (UTC)[reply]
Two facts come into play here. First, because men are generally taller than women, the great majority of couples would have a taller man even if pairing were completely random. Second, there is (with many exceptions) a broad statistical association between tallness and social dominance, and a broad statistical tendency for men to be dominant (in the technical sense of the word) in relationships. Looie496 (talk) 18:31, 8 September 2009 (UTC)[reply]
Males are typically taller, but I think even that is possibly a RESULT of the thousands of years of selective breeding, not the cause of it. I think since women are the ones that give birth and breastfeed they are vulnerable at those times and so males play the role of the provider and protector. Males and females instinctually look for signs of health and virility in a partner, basically how suitable they will be for breeding with. A lot of what we find "attractive" these days stems from those ancient subconscious instincts. Some of those factors now get distorted, warped and manipulated by modern society since we no longer need to rely on "basic instincts" for survival. I think height is definitely one of the factors used as a indicator of health and vigour specifically in males. It's the iconic superman, fit and upright. In females the main factors are typically youth, breasts and hips, height is not necessary to make a good mother. In many other species the female is the bigger of the 2, I don't think there is any reason why female humans couldn't be the bigger gender on average if we bred that way for thousands of years, I think that baby nursing is the thing that prevented that from happening. Now I think there is definitely more of a trend away from the "classic" large hourglass shaped mother figure. It used to be that unless a woman had big hips she was much less likely to survive her first child birth, these days with modern paediatrics pretty much any woman can give birth relatively safely, so being skinny and tall is no longer a breeding liability. To specifically answer the question, no i do not believe it is "important" but it is a very strong left over instinct for a lot of humans. There will be expeptions to the rules as there always are, and the rules will slowly shift over time, but anyone claiming it is "important" is doing so based on reasons of purely human construct. Just like the belief that it is important to marry into your race. Vespine (talk) 23:08, 8 September 2009 (UTC)[reply]
"...signs of health and virility", yep. I once knew a couple who got married and between them probably maxed out the weight limit on a typic elevator. There's really no accounting for attractiveness. There's no absolute rule. Baseball BugsWhat's up, Doc?carrots00:13, 9 September 2009 (UTC)[reply]
Of course I wasn't suggesting there were any absolute rules, but that's a far cry from claiming there are no observable trends. Otherwise advertising wouldn't so heavily rely on sex to sell things. And as the above points out, in the scheme of things it makes perfect sense for two obese people to marry. The scenario which does not follow the trend is if a skinny person marries an obese person, but even the fact that this happens sometimes doesn't disprove the "trend", deviations from the norm are perfectly expected in any biological system, what would truly be strange is if there were no deviations from the norm. And I use the term "norm" in the purely statistical meaning of "average", not as an antonym of abnormal, that's an entierly different discussion. Maybe it is because people associate "norm" with good and "outside the norm" with bad that they are reluctant to admit the observable trends, but I think that's a fallacious association. "The norm" is not intrinsically superior to "outside the norm", it just means "average". Vespine (talk) 23:53, 9 September 2009 (UTC)[reply]
Aversion and fear
If you are afraid of something - dog, plane, spider or whatever - and you avoid any contact with or even approaching it, does your fear get bigger? If yes, why does it grow? Logically, if you don't have any contact with something, shouldn't the tendency be to loose any feeling towards it? --Mr.K.(talk)16:10, 8 September 2009 (UTC)[reply]
I don't know if it would grow, but there's a good evolutionary reason why it wouldn't lessen over time (or at least not quickly). Let's say you come across an animal you've never seen before in the woods, and it nearly eats you. Even if you don't come across another one for years, if one day you do, it's important for your survival that you vividly remember your terrifying experience and stay away or else this time you might be lunch. That fear instinct is very important, so it can be hard to overcome even if we know rationally that a certain fear is illogical. Rckrone (talk) 18:02, 8 September 2009 (UTC)[reply]
The thing is that for somebody with a phobia, you think about the thing even if you don't have contact with it. A person with a spider phobia can lie in bed imagining that a spider might be about to crawl on them, and the idea can be so vivid that it is as fearsome as the actual event. This probably isn't a functionally useful phenomenon; it comes from having an overactive fear system. Looie496 (talk) 18:15, 8 September 2009 (UTC)[reply]
On the contrary — 'refreshing' the memory that way may be one of the mechanisms by which a person retains (evolutionarily-useful) responses to seldom-occuring but dangerous aspects of their environment (per Rckrone). I forget the original author, but I once heard an anology along the lines of: "Consider a small mammal living in the forest. Every time he sees a shadow move, he jumps. Nine times out of ten, it's the wind in the leaves, but one time out of ten it's a lion. The reflex action is still useful, because the penalty for jumping when the leaves twitch is much smaller than the penalty for not jumping when a lion pounces." Obviously, one can be too sensitive, to the point where one is leaping at shadows all the time and not eating; that's going to take an evolutionary penalty. But it's not clear where to draw the line between useful wariness and harmful paranoia. TenOfAllTrades(talk) 19:38, 8 September 2009 (UTC)[reply]
It could also be what psychologists call superstitious behavior. Running and hiding when you hear a noise averted the supposed danger. You run and hide everytime you hear a similar noise, and, lo and behold you angain "avoid being eaten," reinforcing the connection between fleeing the noise and staying uneaten. The counteracting principles are habituation and experimental extinction (of the learned response, not the wee fleeing creature). In humans, Cognitive behavioral therapy is a modern technique for lessening such self perpetuating associations.Edison (talk) 22:28, 8 September 2009 (UTC)[reply]
I think that's basically a different way to saying the same thing that I did. Concerning evolutionary utility, that's valid to a degree: there is data showing that phobias tend to focus on things that it is useful for monkeys to fear, for example snake and spider phobias are much more common than gun phobias. But it's important to keep in mind that not everything evolution produces is functional -- because each individual is a random mix of genes from the population, every so often you're going to get a combination of things that don't fit together very well. Looie496 (talk) 23:55, 8 September 2009 (UTC)[reply]
Having no fear can get you killed. Just ask Steve Irwin. Fear of spiders and snakes makes basic sense. These are two types of creatures that can hurt you, and if you avoid them you're less likely to get a venomous bite. The same principle, by the way, applies to speaking in public. Baseball BugsWhat's up, Doc?carrots00:10, 9 September 2009 (UTC)[reply]
Irwin did not die because he had no fear. Stingrays are not a creature that are particularly worthy of fear. I bet more people are killed by horses each year then stingrays. Googlemeister (talk) 14:17, 9 September 2009 (UTC)[reply]
Standard therapy for phobias of all kinds is gradual supervised contact with the feared object. Exposure builds up "evidence" that the item is harmless, thus outweighing the fear (based on a real experience or not) that it is dangerous. Constantly avoiding the feared object gives the person a one-sided view, reinforced by each occasion of deliberate avoidance. (If you don't leave home because you believe there are man-eating tigers in your (Northern Hemisphere densely populated) street, you will never find out that there are none). - KoolerStill (talk) 15:04, 9 September 2009 (UTC)[reply]
how to pump a longboard (skateboard)
i have heard that it is possible to "pump" a long board. in doing so you can basically move your longboard forward without ever having to push with your foot. when i heard this was possible i searched around the internet trying to find a good explentation on how to do this. i found websites but when i tryed i waas unsuccesfull. i figured if i knew exaclty why this is possible i would understand it better and might be able to pump my longboard. so exactly why is it possible? does it have to do with your momentum or is it something else? it would also help if someone could sugest a really good web site where i could get further explinations on how to preform this.
thanks —Preceding unsigned comment added by 76.235.215.200 (talk) 17:45, 8 September 2009 (UTC)[reply]
It is just momentum shifting, like using a swing or twirling a hula hoop. I was going to go into a detailed description, but thought I'd check to see if Google was nice and found one on ehow here (can't link straight to ehow - it is blocked). -- kainaw™18:11, 8 September 2009 (UTC)[reply]
Note: this is presented as observation and not advice, since falling is fairly likely while practicing a new technique. It reminds me of a way of skating along while keeping the iceskates parallel, but shifting from one edge to the other. On the board if the axis of the board points to the right, then a push to the right by dropping a bit and rising back up, will result in some forward resultant. Flip the board a bit to the left and pump left. Edison (talk) 22:23, 8 September 2009 (UTC)[reply]
Asian (Indian) elephants and African elephants
Often in the media, we see Asian (Indian) elephants being used as a beast of burden (and other positive interactions with humans). However, I have never seen the same for African elephants. Is there a reason for this? Are Asian elephants easier to "domesticate" while the African elephant can not? —Preceding unsigned comment added by 69.77.185.91 (talk) 18:36, 8 September 2009 (UTC)[reply]
(after ec)According to this - "When the Belgians in colonial times intended to stub the jungle of Belgian Congo, they employed Indian mahouts, who successfully caught and trained the African elephants according to the Asian method. Nowadays safaris on the backs of African riding elephants become more and more popular in Africa". This article says that despite the common belief in Africa that they're untamable, the African Elephant is "with patience, quite trainable" and also notes that Hannibal battled the Romans with AEs. Well, I don't suppose that he would've have done that unless they could be reliably trained not to panic and run amok when the javelins started flying and indiscriminately trample both friend and foe on the battlefield... --Kurt Shaped Box (talk) 19:58, 8 September 2009 (UTC)[reply]
There also may be the consideration as to whether the benefits of African Elephant's extra strength and work capability when compared to other beasts of burden justified its huge daily food requirements. --Kurt Shaped Box (talk) 21:03, 8 September 2009 (UTC)[reply]
Well, throw enough spears at any large animal and it's eventually going to lose its cool - but the point that I was trying to make is that unless the elephants could be conditioned not to behave like this for the most part, they'd be absolutely useless as war mounts and a complete liability on the battlefield. The fact that it was even possible to lead them into battle in the first place shows that they can be trained... --Kurt Shaped Box (talk) 15:02, 9 September 2009 (UTC)[reply]
The point I was making was that although they can be trained to some extent, they frequently have been a liability on the battle-field. In contrast, I don't think (arguing somewhat from ignorance here) horses have been criticised as much for this. AlmostReadytoFly (talk) 15:32, 9 September 2009 (UTC)[reply]
Agreed there. A panicked, out of control horse isn't going to accidentally (or deliberately) kill/maim 15 guys in the space of a minute or so as it tries to flee. As a side issue, I wonder how rogue elephants on the battlefield were dealt with in ancient times? Did the soldiers try to kill the beast, or did they get out of its way as fast as possible and let it run off into the distance (then perhaps attempt to catch it again later once it had had time to calm down)? --Kurt Shaped Box (talk) 20:21, 9 September 2009 (UTC)[reply]
Be careful not to confuse "domestication" and "taming". Strictly, a species is only domesticated when it is bred in captivity and the captive-bred population shows physical and/or mental modifications from the wild population. By contrast, wild-breeding animals can be tamed, and trained, to the extent that their species' and their individual innate natures render them amenable to being so.
In all history, only the long-vanished Indus Valley Civilization (aka the Harrapans) are known to have successfully domesticated the (Indian) Elephant. Otherwise, elephants have been successfully bred in captivity only rarely, and most of the (mostly female) working elephants in India and elsewhere have been caught and tamed, although some have been born to tamed females allowed to mate with wild males. Our articles on Domestication and on the Asian Elephant are guilty of some loose and inconsistant language in this regard. 87.81.230.195 (talk) 19:28, 9 September 2009 (UTC)[reply]
As a separate point, note that although African elephants were used as war elephants in the Mediterranean sphere (to which Asian Elephants were also imported), these were usually the North African Forest Elephant, a species or sub-species now extinct (not least because of this exploitation) which was somewhat smaller and probably more tameable than the surviving African Forest Elephant and even larger African Bush or Savannah Elephant. 87.81.230.195 (talk) 19:41, 9 September 2009 (UTC)[reply]
Biochemistry question: What does oxygen do in this case?
After oxidating glucose into CO2 and water, oxygen helps it become stable because of the oxygen even though the accumulative G0 value is largely NEGATIVE...how's that possible? —Preceding unsigned comment added by 93.183.239.108 (talk) 19:25, 8 September 2009 (UTC)[reply]
Per the lead paragraph of our article on energy density, "hydrogen has a higher energy density per unit mass than does gasoline, but a much lower energy density per unit volume." However, for the strictest possible interpretation of "most efficient manner" (that is, matter-antimatter annihilation), they'd be identical, as mass is the only consideration in such a case. — Lomn00:43, 9 September 2009 (UTC)[reply]
I think the OP meant the most amount of work you can extract in the most efficient manner from those 2 - otherwise efficiency doesn't mean much (as Lomn pointed out). --antilivedT | C | G01:14, 9 September 2009 (UTC)[reply]
The work done by an engine typically comes from heat energy produced in some exothermic reaction, so you could do work by annihilating hydrogen or gasoline just as you could by burning them (and a lot more of it). Rckrone (talk) 03:11, 9 September 2009 (UTC)[reply]
Which is why we engineers say: "What a bloody stupid answer, the OP is CLEARLY not talking about matter/antimatter or direct matter-to-energy conversion."...this is merely confusing an otherwise clear answer - which is "Hydrogen, by mass. Gasoline, by volume." SteveBaker (talk) 13:34, 9 September 2009 (UTC)[reply]
Steve, I'm not sure if I should take offense at this or not (particularly as an engineer). I led the original answer with precisely "hydrogen by mass, gasoline by volume", and then added antimatter as the addendum. — Lomn16:27, 9 September 2009 (UTC)[reply]
Then the question devolves into a request for clarification about the intended meaning of "efficiency" - if the OP meant thermodynamic efficiency, then Lomn's theoretical answer is valid. If the OP meant "practical, realizable, efficient combustion in an engine, in 2009", then clearly an analysis of matter-antimatter reactions is irrelevant. Again, the practical considerations start to become convoluted by details other than the raw thermal energy released from oxygen-fuel combustion: does manufacturing and carrying around the necessary, custom equipment to perform hydrogen combustion count against the overall "efficiency" score, or are we again only talking about the net energy released? Fuel efficiency will suffer, because 1 kg of hydrogen can not be stored as easily (ergo, as "efficiently") as 1 kg of gasoline. The OP did not state explicitly, but I think their question was implicitly asking for the molar heat of combustion, normalized by the mass-per-mole, for oxygen-fuel combustion of 1 kg each. The answer to this question was helpfully provided and referenced below, by 83.100.250.79. Nimur (talk) 17:50, 9 September 2009 (UTC)[reply]
I would combine a unit mass of hydrogen plus unlimited oxygen for the one case, and the same unit mass of gasoline plus oxygen for the other case. Chemists are welcome to chime in with respect to the energy liberated in each case. Naively, I would bet on hydrogen. Edison (talk) 02:40, 9 September 2009 (UTC)[reply]
And just for fun semtex exploding gives about 4 MJ/kg. But of course the clever thing about semtex was not the energy yield but the fact is couldn't be detected by a sniffer dog... --BozMotalk13:20, 9 September 2009 (UTC)[reply]
Nerves and eyes
Pathways from eye to brain, with midline-crossing pathways in blue, and ipsilaterally projecting pathways in red.
Most parts of the body are connected to the "other" side of the brain, so the right leg is handled by the left brain, et cetera... I know this is different for the eyes, but are they entirely the same side, do the muscles go with one and the optic nerve with the other, or some combination? SDY (talk) 02:17, 9 September 2009 (UTC)[reply]
Through the marvel of hemidecussation, the left half of each retina goes to the left hemisphere and contrariwise. It is said to be a sharp split at the center of each retina. Not sure how the fovea centralis splits, but presumably the same. This shows up in the Michael Gazzaniga experiments with split brain patients. If an object is to your left, it is processed by the right hemisphere, and the left hemisphere knows of it only if the corpus callosum has not been severed. Optic fibers cross over at the optic chiasma. In movies of split-brain patients, the hemisphere controlling speech would produce verbalizations which were mere guesses regarding visual stimuli presented to the other hemisphere, but the non-speaking hemisphere would cross-cue by shaking the head, whereupon the speaking hemisphere would change to the answer the nonspeaking hemisphere had seen. We seem to have two brains, each quite capable on its own. Edison (talk) 02:33, 9 September 2009 (UTC)[reply]
(ec) Our article on the optic chiasm explains this, although not very well. Basically, both eyes send some input to both sides of the brain. The way I always remember it is each side of the brain gets input from the opposite side of the world. The right side of the brain gets input from the left side of the world; the left side of the brain gets input from the right side of the world. If you work it out, the consequence is that the left side of the retina in both eyes projects to the left side of the brain, and the right side of the retina in both eyes projects to the right side of the brain. This arrangement may seem bizarre at first, but it has the very useful property of causing the visual input to each side of the brain to come from the same place where tactile input to that side usually comes from, and where motor output from that side goes. Looie496 (talk) 02:41, 9 September 2009 (UTC)[reply]
(ec again, yikes) The "final common pathway" for eye movement is a set of small brainstem nuclei, but huge areas of the brain are involved in eye movement control. By the way this picture is a beautiful illustration of the left-right pathways, too bad we don't have one as nice. Looie496 (talk) 02:53, 9 September 2009 (UTC)[reply]
It might be useful to note here that while one-sided numbness and paralysis caused by stroke is evidence of a defect in the opposite side of the brain, blindness in either eye caused by stroke is associated with a defect in the same side of the body as the eye.Mrdeath5493 (talk) 07:12, 9 September 2009 (UTC)[reply]
They do have that effect. Most of the mass of ordinary matter (~90%?) comes from the strong force, and most of the rest from kinetic energy of the quarks. All other contributions including the Higgs interaction are a small (~1%?) correction on top of that. I think the W and Z bosons also get small masses from QCD (the Higgs mechanism article says they do). However the masses you get this way don't match what is observed, and the Higgs field was introduced to make up for that difference. The Standard Model attributes all mass discrepancies to the same Higgs field, though you could explain them in other ways (like additional Higgs fields or, in most cases, explicit mass terms). I'm not sure where the idea came from that the Higgs field is the source of all mass. It would be better to say that the Higgs field is the source of all the mass that we don't understand. John Baez points out that of ~25 adjustable parameters in the Standard Model, 22 describe the Higgs or its interactions with other fields, so it's probably hiding a lot of beyond-Standard-Model physics. -- BenRG (talk) 17:53, 9 September 2009 (UTC)[reply]
Pass the veggie dogs please!
I've been a vegetarian for 14 years, for ethical reasons. My family had dogs when I was growing up, but I never had my own dog as an adult until now. (The arrangements have been made; she'll be coming to live with me in a few weeks.) I would like her to live on a vegetarian diet as well. What I'm wondering is this: Can a dog truly be as healthy on vegetarian dog food as on regular dog food, or is there still some legitimate controversy about that? How much more expensive is it to keep a dog on a vegetarian diet? The dog is about three years old and has been eating a non-vegetarian diet up to this point; would that present any particular problems or challenges? - Lydia's Alpha-to-Be —Preceding unsigned comment added by 71.104.238.248 (talk) 03:37, 9 September 2009 (UTC)[reply]
Well, some people at least maintain that some dogs can thrive on vegetarian or vegan diets. Watch out for dilated cardiomyopathy due to L-carnitine or taurine deficiency. Never own a cat. - Nunh-huh04:04, 9 September 2009 (UTC)[reply]
Yes, I'm well aware that cats are carnivores and aren't biologically equipped to eat a plant-based diet, and if I ever did happen to have a cat in my life, I would respect that and buy something meat-based. However, since dogs are omnivores (like humans) I've heard that they can thrive on a vegetarian diet. Of course, the typical diet of canines in the wild has more animal protein than that of primates in the wild, so I don't imagine it would be a strict equivalence. Of course I would talk to the vet before making the final decision on Lydia's diet (and I could always make a change one way or the other based on her health, our finances, new advances in dog food, etc.), but I just wanted to get an idea early on, while we still have a couple months to figure out exactly how she's going to fit into our lives. Thanks for your answers! - Lydia's Alpha-to-Be —Preceding unsigned comment added by 71.104.238.248 (talk) 06:47, 9 September 2009 (UTC)[reply]
Dogs are indeed omnivores - not herbivores - their primary diet is meat - although they'll eat vegetable matter if they are hungry enough and there is nothing else available. Humans are also omnivores - but our primary diet isn't (or at least, shouldn't) be meat. So we do much better on an artificially herbivorous diet than dogs do. I don't think it's fair on the dog to try to make it be what it isn't. Trust me - dogs have no ethical desire to avoid eating meat. Even our 10 year old labrador - who is the gentlest, most mild-mannered dog you'll ever meet - has absolutely no compunction in chasing down a squirrel, ripping its head off and feasting on it's still warm-and-twitching body. If you don't like that dogs behave like this - then the remedy is for you to avoid owning one - rather than trying to change it's ethics to match yours. Dogs eat meat and chew bones...it's what they do...it's by FAR their greatest joy in life...it's what they live for. SteveBaker (talk) 12:58, 9 September 2009 (UTC)[reply]
I agree with SteveBaker. While an ovo-lacto-vegetarian diet won't kill a dog (the way it will a cat), it's really unfair, maybe even cruel, to the dog to force it into a dietary lifestyle it's incapable of understanding or appreciating. If you were still at the point of merely considering getting a dog, I'd advise you to get a rabbit or guinea pig or some other thoroughly vegan pet instead. As it is (your getting a dog is now irreversible), please allow your dog to eat what makes her happy, the same way you eat what makes you happy. +Angr14:03, 9 September 2009 (UTC)[reply]
Agreed. I very much doubt that domestic dogs, cats and whatever else really care enough about their owners' moral, ethical, religious or socio-political views to make personal sacrifices. --Kurt Shaped Box (talk) 14:40, 9 September 2009 (UTC)[reply]
On the other hand, How much meat do pet dogs usually get anyway? Aren't most cheap dog foods little more than vitamin enriched, meat flavored, corn meal? A quick look at some ingredients lists leads me to believe that some of the popular brands are mostly grains with some lard mixed in for flavor. If the brands of vegan dog food on the market have found some good replacement for the lard flavor (have they?), then how's the dog even going to know?
(Personally, I still wouldn't try it with a cat. The risks are a lot higher, and I frankly don't trust quality-control on pet foods at all. But what do I know? I've never had any particular inclination to make myself a vegetarian, let alone a pet.)APL (talk) 14:51, 9 September 2009 (UTC)[reply]
As pack animals, dogs will be loyal to you no matter what you put them through - but you have a responsibility to return the favor by keeping them happy. Dogs are the least vegetarian animals I can think of! The evidence of their carnivorous tendencies is everywhere. It's not about dog food...most of the dry food doesn't look like it's ever been need an actual animal. That's not the point. Dogs need to chew to keep their teeth in good shape - the various plastic toys and fake bone-like products don't seem to interest them much. That means that they need real bones and chewable rawhide toys and things like (my dog's favorites) pig ears just to keep their teeth healthy. Our dogs occasionally get those two foot long cow bones - which they'll (hilariously) laboriously haul around the house and try to hide from each other as they gradually gnaw this 10lb bone down to nothing over a period of weeks. One of those will entirely consume their waking hours for almost that entire time - it's hard to imagine how they are not utterly passionate about that behavior. When dogs sleep - you can see their feet twitching and they make tiny dream-barking noises as their jaws move and their cheeks puff out...then you see their jaws moving with little dream biting and chewing motions. There can be little doubt that they even DREAM of hunting small furry animals. Truly - find a good home for your dog and get a rabbit (I recommend an English rabbit) - they are very cool: you can train them - treat them like a cat or small dog - and feed them vegan stuff and they'll be very happy and healthy.) SteveBaker (talk) 15:55, 9 September 2009 (UTC)[reply]
Anecdotally, a friend of mine in Scotland, who had grown up on a working farm with dogs and was in addition a bright and unsentimental woman, fed her Alsatian and Golden Retriever on a vegetarian diet, carefully balanced, with appropriate added supplements, and bones to gnaw. My friend was not herself a vegetarian, and I can't remember her specific motivations, but the two dogs (whom I often looked after) thrived physically and mentally, and their faeces were markedly less smelly than is generally the case with meat-fed dogs. I agree that one should not do this without specialised knowledge and/or vetinarian advice. As it happens, another Scottish friend, my landlady for a time, kept a wild rabbit (rescued as a kit) as a perfectly contented and agreeable house-pet in her upstairs flat, though I agree an outside hutch might be considered more usual. 87.81.230.195 (talk) 19:00, 9 September 2009 (UTC)[reply]
The key there is probably the "and bones to gnaw" part. If bones are large, fresh and uncooked (required to avoid choking risks) - the dogs get a good deal of nutrition and 'meaty stuff' from the marrow inside the bones. If she had cut off the bone supply - I'd imagine the problems would begin right there. On a farm, the dogs may well have been 'self feeding' too - catching rabbits and squirrels, rats & mice - that kind of thing. SteveBaker (talk) 20:15, 9 September 2009 (UTC)[reply]
On the subject of dogs and bones, do you remember a time a few years back when 'they' were saying that dogs should never be allowed to gnaw on bones - due to the risk of sharp bone splinters being swallowed and causing internal injuries? I don't know if that was just one particular school of thought on the matter (I've never owned a dog, so I wasn't really paying it a huge amount of attention) but I definitely remember 'dog experts' on TV saying it several times. --Kurt Shaped Box (talk) 20:37, 9 September 2009 (UTC)[reply]
Wasn't that strictly for poultry bones? And seriously, if bones were regularly killing dogs, wouldn't we have ended up evolving dogs that did not engage in such dangerous behavior? 65.121.141.34 (talk) 21:16, 9 September 2009 (UTC)[reply]
The issue is with thin cooked bones. Cooked chicken bones are certainly not good - raw is fine though. Large bones are OK cooked. Dogs have evolved to gnaw bones - that's why they have not evolved toothpaste. SteveBaker (talk) 02:38, 10 September 2009 (UTC)[reply]
I would say that your primary ethical consideration here is to that one living creature you are bringing into your life, not to every other living thing on Earth whose life you wish to spare also. This is especially so since a dog will give you unconditional love and devotion and do anything to be part of your "pack". Dogs will eat pretty much anything, and most are also incredibly stoic, so they won't show signs of dicomfort until they have gotten pretty sick. While it certainly may be possible to create a perfect vegan dog food, the danger I see is in subtle deficiencies building up over time, such as the cardiomyopathy mentioned above. She won't tell you about her discomfort until it's too late. The safest way to go IMO is to use the highest quality of food you can afford, and don't worry about the meat components too much. Meat should always provide the best balance of nutrients for a dog, it's what they've been eating for thousands of years. It's true that they'll find certain types of grass and spend 20 minutes eating them (fibre? micronutrients?), and it's true that they'll eat any kitchen scrap you give them (mostly because they've been staring at you while you cook, trying to figure out how to get up on the counter where the human food is) - but if they can catch a squirrel, they'll ignore the corn cobs.
And if your dog is used to one type of food, you should be very careful if you're changing over to another, their guts will be set up to process the food they're used to. Franamax (talk) 20:17, 9 September 2009 (UTC)[reply]
Start by giving the dog the same diet as it has been used to - enough trauma with the move itself. Then using the many thoughtful suggestions above, gradually alter the dog's diet to one that is more in keeping with your beliefs. Abrupt diet changes can cause intestinal distress resulting in diarrhea and you wouldn't want that along with all of the other distress of a having a new household member. hydnjo (talk) 21:18, 9 September 2009 (UTC)[reply]
Making the dog of a vegan eat only a vegan diet, which it would not choose if given a choice, is a bit like baptising the dog and feeding it the eucharist. Or declaring the dog is an athiest, or a Tory. The moral choice of avoiding meat and animal products just will not give the dog the moral glow it gives the human. My father would feed his hunting dogs steak which had gone out of date in the freezer of a restaurant, but they also ate cornbread he baked for them. They would also eat green plants they found in their prowls. The vet's advice is the thing to give heed to. Edison (talk) 22:50, 9 September 2009 (UTC)[reply]
I think this, and all similar sentiments above, is missing the point. Sure, the dog won't have the same moral objection toward eating meat that a vegetarian or vegan might have. But this is irrelevent. Some dogs don't apparently have moral objections to mauling children, but we don't let them get away with that while saying things like "well we might feel morally happy about not mauling children but the dogs don't share our viewpoints". Very few, if any, ethical vegans or vegetarians are going to hold the belief "it is wrong for me to cause the suffering and death of animals but it is fine for everyone else". Most ethical vegans or vegetarians will think "it is wrong for anybody to cause the suffering and death of animals" and they will acknowledge that it happens "in the wild" but view this as an unfortunate result of evolution. Someone who owns a dog has every right and is, indeed, behaving quite admirably, to want to give their own dog a healthy lifestyle with minimal impact on the lifestyles of other creatures. Maelin (Talk | Contribs) 06:40, 10 September 2009 (UTC)[reply]
How to charge the batteries and measure current?
Hello friends!, I know a lot of methods still available to measure the current stored in a Battery. But i need a simple method or atleast understandable. I have 4 AA size 1.2V, 850mAh NiCd batteries. I designed a charger circuit with charging voltage of 5V and charging current of 240mA for 4 batteries in series. So that each battery gets 240/4 = 60mA. Since my battery has 850mAh rating, now I don't know how long do I have to charge or how much charging current is actually needed?. I need atleast 4.8V,250mA for my main project ciruit to work.And my batteries with the above rating doesn't even supply power for more than 10 minutes even when it's been charged for more than 8 to 10hrs. So with my current battery rating,the backup should atlaeast last for 3 hours?What could be the problem?. In charger circuit, I use a 22 (1 watt)Ohm current limiting resistance in series with the input 5V source to get a current of 240mA. All 4 batteries are connected in series while charging.when I read the voltage of the battery, it shows 1.26V(1 battery) when charged fully and 1.1V when everything was drained!. For my main project, it consumes 250mA current with 4.8V requirement. ...In my case, is the battery actually charging or do I need more current rating for my design.? Please help me —Preceding unsigned comment added by Balan rajan (talk • contribs) 05:29, 9 September 2009 (UTC)[reply]
Current is not stored in a battery, charge is. The rating is for milliampere-hours, which (someone check my math) 1 milliampere-hour = 3.6 coulombs. A battery with a rating of 850 mAh will supply a current of 1 milliampere for 850 hours, or 850 milliamperes for 1 hour, or some combination thereof, such that milliamperes X hours = 850. The time to charge the battery will depend a lot upon how much current the charger itself operates on. Assuming a perfect system, if your charging current is 60mA (240 mA divided by 4 in series, if I am reading that right), then the battery should be fully charged in 850/60 = 14 hours, ten minutes, give or take. It will probably take somewhat longer than that given inherent losses in the system, so lets say 16-17 hours for a full charge. 8-10 hours would not nearly be long enough. Also, you do not indicate what your discharging circuit current is. If I draw 8.5 amps out of a fully charged, 850mAh rated battery, it'll be fully drained in 6 minutes... SO it looks like a combination of a) not enough charging time and b) too high a load on the battery when being discharged. --Jayron3205:47, 9 September 2009 (UTC)[reply]
Although not as explosive it actually takes more a complex design to charge NiCd/NiMH batteries than Li-ion ones. Seeing that you probably aren't too advanced in electronics (all components get the total current if they're series, see Kirchoff's circuit laws), you should probably use an off-the-shelf charger for now. Also, batteries don't have perfect reciprocity, they tend to drain a lot faster under high current (ie. 1mA load might last 850 hours, but 850mA load probably won't last an hour), so you should take that into account too. --antilivedT | C | G11:28, 9 September 2009 (UTC)[reply]
Well, you're probably not charging the batteries at all - that's the problem. The best way to charge NiCads is to use a constant current source, not a constant voltage source, as you're trying. Commercial chargers provide this, which is why they're better. As you describe your set up, you have 4 ~1.2V batteries in series, a total of ~4.8V. That voltage is dropped by a 22 ohm resistor, meaning that the current flowing is I=V/R=0.2/22=9mA. With this current, they'll take about 100 hours or so to charge. As the batteries charge, their voltage will increase slightly and so the current will drop further and the charging will take longer. So we see this circuit just won't work. With a constant current charger this problem does not occur. It's then easiest to work out when they're fully charged by feeling them - they will get slightly warm when they have charged up. --Phil Holmes (talk) 14:38, 9 September 2009 (UTC)[reply]
There is a limit to how fast a battery should be charged or discharged to avoid damage, explosion, or shortened service life. Isn't there some rule of thumb of using the ampere hour rating divided by 10 to get a charge rate for Nicads? That would imply 85 ma for 10 hours to charge the 850 mah cells. The charge should taper off so that the current drops to a mere trickle when the battery is are charged, rather than continuing to raise to voltage to force the same current through a fully charged battery. That would eventually cause loss of moisture in the electrolyte, outgassing, overheating, and explosion unless the venting system was adequately vented. Edison (talk) 22:41, 9 September 2009 (UTC)[reply]
Glucose oxidation
I'm rephrasing the question because it seems that it wasn't completely clear the last time around.
The oxidation of glucose to CO2 and water has a very large accumulative G0' value and yet glucose is quite stable in the presence of oxygen, why is this so?
(ec)The editor above is absolutely correct. The stability is because at room (or body for that matter) temperature, there is insufficient energy to overcome the activation energy. Gasoline, or even hydrogen mixed with oxygen has incredible potential energy, but the activation energy is such that the mixture can exist for an indefinite period of time. Something either needs to bring the energy above the activation energy, such as a spark provided to the fuel-oxygen mixture, or the activation energy needs to be decreased, such as with the presence of an enzyme. Glucose is oxidized through a series of reactions, using a large number of highly specialized enzymes, each of which not only lowers the activation energy so the reaction can proceed, but also ensures only the desired product results from the reaction. Enzymes not only allow the reaction to proceed at the temperatures present in a biological system, but also prevent the ligands from reacting with or into any undesired chemicals. TheSeeker 4Talk18:14, 9 September 2009 (UTC)[reply]
How can matter exist?
From my understanding of chemistry (mostly learned a few years ago in high school), I do not understand how matter can exist if the protons and electrons are so small in the atoms that make up matter. I skimmed the atom page, but didn't see any real answer, although there probably isn't one yet. How can matter exist if there's basically nothing in the atoms (correct me if I don't know what I'm talking about = ])? EVAUNIT-66618:24, 9 September 2009 (UTC)[reply]
(EC with bugs)Fundemental particles (the quarks that make up protons and neutrons, and leptons of which the electron is one example) are essentially point-particles(dimensionless). However, the interactions between these particles occurs at measurable distances, and the distances of those interactions defines the size of things like atoms and molecules. So, even though the parts that fundementally make up an atom have no size at all, because these particles exist at a definable distance, THAT distance defines the size of the atom, which in turn gives volume to matter. For example, though an individual electron is essentially volumeless, the electrons orbit an atom in the electron cloud, the interactions between electrons and protons, and between electrons and each other define the size and shape of this cloud, and THIS is what gives an individual atom a real volume (see atomic radius. Put a group of atoms together, and they way that they interact with each other defines the bulk volume of matter, and thus you have the world you see around you.
Does the solar system exist? Most of the solar system is not occupied by planets, moons, or other heavenly bodies. Does a galaxy exist? Even though stars can be thought of as large, most of the galaxy (I think) is composed of fairly empty space.
Furthermore, the speed of electrons, combined with their very small orbits, places them almost "everywhere at once." I think this gives the substantiality to matter.
One finds it difficult to walk through walls not because the wall or the person is terribly dense, although the person could be dense in a different sense, but rather because of the likelihood that the fast moving electrons comprising the atoms of the of the human will "just happen" to be in a position in their orbit to encounter the fast moving electrons in the atoms comprising the wall. Bus stop (talk) 18:56, 9 September 2009 (UTC)[reply]
Nonsense! Superman was always perfectly law-abiding. They probably just hadn't passed that law yet, I imagine it was still stuck in committee. (Superman really wasn't that good at politics). Franamax (talk) 19:42, 9 September 2009 (UTC)[reply]
Forgetting the ongoing absurdity of a man flying, "The Mysterious Cube" has to be in the top echelon of the most preposterous episodes in the series. A scientist friend of Superman's convinces him that he could pass through solid objects, through the power of super-concentration. Now, maybe that could be theoretically possible, given that Superman can fly faster than light and see through anything (except Lois' dress). All well and good. Except that when he passes into the ultra-dense material comprising the cube, his suit comes with him. Apparently his super-suit had a mind of its own. Baseball BugsWhat's up, Doc?carrots03:41, 10 September 2009 (UTC)[reply]
Thinks look solid - because even though they are mostly vacuum - they still block and reflect light perfectly well. They feel solid because the electrons in orbit around the atoms of that chair you're sitting on are negatively charged and they repel the negatively charged electrons of your rear-end. Hence things feel solid. The mass of the atom is almost entirely centered in the middle...but they weigh what they should - so they are heavy enough to seem solid. Between those things - matter does indeed behave like it was solid. However, truly "solid" materials - something like a neutron star - which have all of the atoms squished together without all of those gaps - seems like really bizarre 'stuff'. As our article points out - the entire mass of all of humanity - crushed to the density of a neutron star would be smaller than a sugar cube. Neutron stars have so much gravity that they bend light by enough that you can stand 'in front' of one and see all the way around the back of it! SteveBaker (talk) 20:10, 9 September 2009 (UTC)[reply]
Well, indeed, but the article you cite says "They are a relatively short-lived phenomenon, lasting a few tens of thousands of years." A few tens of thousands of years is actually a very long time by our standards. So I'm guessing that in a hundred years another picture of the formation might look almost identical? — Sam 63.138.152.155 (talk) 19:03, 9 September 2009 (UTC)[reply]
For the linked picture of the butterfly (often called by its less romantic name, the Bug Nebula), the explosion which created the nebula occurred roughly two thousand years ago. The expanding cloud is now (mostly) a very, very long way from its parent star, so it feels very little gravitational attraction and will be moving outwards at a (nearly) constant rate. So, figure in another hundred years the nebula will be about five percent broader, and a little bit dimmer. The difference will be perceptible (if you have two photographs, side by side) but not particularly dramatic. TenOfAllTrades(talk) 19:36, 9 September 2009 (UTC)[reply]
The pillars in that photo at right are about 100 Trillion kilometers tall. The dust would have to be moving at an impressive speed for the picture to change very much in 100 years! SteveBaker (talk) 02:35, 10 September 2009 (UTC)[reply]
Oxymuriate of mercury
This substance is frequently mentioned in nineteenth-century medical texts - what's it's modern name? Mercury (II) chloride is one obvious suggestion, but that's "corrosive sublimate", and the "oxy" might suggest it contains oxygen. Thanks in advance. Tevildo (talk) 21:57, 9 September 2009 (UTC)[reply]
To confuse things oxymuriatic acid is actually (probably) chlorine gas. see [28] this is Humphrey Davies discovery that chlorine gas (oxymuriatic acid) is not what it was thought it was.. 83.100.250.79 (talk) 22:27, 9 September 2009 (UTC)[reply]
Drug dealers are usually members of a union or professional organisation, such as the Royal Society of Skag Peddlers. Their websites will probably have statistics on the qualifications of their members.
As far as I know, cocaine isn't worth synthesising from scratch, so the chemistry is pretty basic acid-base reactions and purification. LSD requires a bit of tinkering, and MDMA is a proper synthesis job.
Apparently, most LSD produced in America is made by a handful of experienced chemists in northern California, many of whom have been at it since the sixties. They can get away with it because there are so few of them, they all know each other, and they only make small quantities (because that's all you need, it seems). I once read that federal agents uncovered a drug production lab housed in a grain silo buried underground.
I reckon the overall answer is this: most drug producers don't know loads, just what they need to. But certain drugs need skill to make, and are made by a few specialists.
I would guess, not very. You don't need much formal training is chemistry to just follow a recipe and make the drugs. The training is required to do research and come up with new knowledge (about new chemicals, new ways to make old chemicals, explanations of why certain things are the way they are, etc.). Drug manufacturers don't generally do that kind of stuff. It is similar to how you don't need to be an automotive engineer to work in a car factory. --Tango (talk) 22:42, 9 September 2009 (UTC)[reply]
I'm curious whether the field would weed out those who didn't have some sort of (non-monetary) interest in science (albeit black market science)? Actually my main reason of wondering this was just as Malcolm X thought his bookie would've been a NASA scientist if he had been born white, whether many of the "top" drug makers would've been found in top schools had they been born into more privilege. Presumably, the less skilled you are (or the less you know what's going on), the less your purity and the less your yield. (higher grade => higher prices?) John Riemann Soong (talk) 22:49, 9 September 2009 (UTC)[reply]
A chapter of Freakonomics discusses the retail (not manufacture) of illegal drugs in a Chicago housing project. JT (the area manager for the Black Disciples gang) is a college graduate who could evidently, in other circumstances, have done well for himself in the licit business world, and who runs the gang like a Harvard Business School grad. -- Finlay McWalter • Talk23:01, 9 September 2009 (UTC)[reply]
I just want to note that it REALLY depends on the drugs in question and the type of manufacture. As far as I can tell there are entirely different methods of production and people involved in the production of cocaine, LSD, ecstasy, and methamphetamine, and the skill required is likely quite different as well. My suspicion is that in terms of theoretical knowledge, meth makers are probably pretty low on the list—any old hillbilly seems able to set up a meth lab (albeit not the most safe one). --98.217.14.211 (talk) 23:55, 9 September 2009 (UTC)[reply]
The meth synthesis is easy if you start with pseudoephedrine, which comes from decongestant pills. People who do that generally just follow recipes. I don't know about the other drugs. Looie496 (talk) 00:00, 10 September 2009 (UTC)[reply]
I would think that the best drug makers would be the best technicians as opposed to the best engineers or chemists. The reaction pathways are already known, and recipes to achieve those reactions are known. All that remains is to select the best pathway and recipe in terms of safety and purity of yield, then do it properly each time. The incentives for performance are avoiding blowing up your house and avoiding angry dealers whose customers have all been driven insane by the latest batch. A chemist might understand the reaction energetics perfectly but not notice the crud at the rim of the bucket. An engineer might want to scale the process up or use too expensive of gear for the low-volume element. A technician will perfect the recipe.
That's different from drug marketers, many of whom should probably have gone to Harvard so they could do benign things like devastate the world financial system instead. ;) But I'd hire up a really good lab assistant anytime to cook up the best drugs. Franamax (talk) 01:43, 10 September 2009 (UTC)[reply]
Clarification: In the documentary "Extreme Ice" the way the exact location of the camera was maintained was to fasten it to rock above the ice flow. This was probably okay for showing what happened each hour for over a year and maybe even in the event of an earthquake because the field of view is so wide. Doubtful even an institution would have use for lengthier time lapse but then we still spend a lot of money to drill holes in the ice to get data that goes back lots of years. I'm speaking theoretically in the event someone wanted data that required the exact location from the object being recorded. -- Taxa (talk) 01:11, 10 September 2009 (UTC)[reply]
I'm sorry, your question is not very clear. What do you mean by "location"? And do you mean "How will" or "How do"? "Will" implies the future, and Wikipedia is not a crystal ball. However, if you mean how astronomers are able to take pictures of celestial bodies as they were 100 years ago, it is because even light does not move instantly. Light moves at a constant rate. The reflected light off of a celestial body may have been reflected off of the body 100 years ago, but is only reaching earth now. Therefore, astronomers looking through telescopes see the celestial body as it was when the light reflection they are viewing was reflected off of its surface. For example, if the sun suddenly disappeared, we, on Earth, would still see the sun for about eight minutes after it actually happened. Intelligentsium00:58, 10 September 2009 (UTC)[reply]
At a distance of 100 light years an astronomer almost certainly sees light emitted not reflected from a celestial bodies, and that is definitely so in the case of viewing our Sun. Cuddlyable3 (talk) 11:44, 10 September 2009 (UTC)[reply]
(ec)I'm thinking this has more to do with a question of whether it is possible to take a comparison picture in 2109 at exactly the same location in space, relative to the sun, given the somewhat eccentric and very slightly chaotic earth orbit. I'm wondering of how much importance to comparative astronomy is the change of location of the camera base due to earth orbit. --Tagishsimon(talk)01:01, 10 September 2009 (UTC)[reply]
Obviously, without a lot of expensive and impractical spacecraft, it's going to be impossible to get perfectly repeatable positioning. However, the size of the error due to the earth going around the sun - and the sun moving around the perimeter of our galaxy are very small indeed compared to the distance between stars. Stars in our local group are moving at almost the exact same speed as us around the edge of the galaxy - so the closest stars are moving the most slowly relative to us. Their relative positions will change very little over very long timescales. For stars at much longer distances, the amount of change compared to the distance between us means that those stars move VERY little relative to us. Take some hard numbers: The sun is moving at about 20 km/second relative to our neighboring stars. Over 100 years, the sun (and therefore the earth) will have moved 100x356x24x60x60x20 kilometers - that's 63 billion km - about six lightyears relative to the other stars in a region perhaps 20,000 lightyears across. So most of those stars won't move more than one part in several thousand compared to us...that's measurable - but not huge. The entire galaxy is of course spinning - we're going to have moved about 60 light years over the next 100 years compared to more distant galaxies...our galaxy is moving at about the same kind of speed relative to the other galaxies closest to us - but now we're talking about looking at objects like other galaxies...those are at distances measured in the millions of lightyears. Truly, our motion over 100 years is negligable to their distances. SteveBaker (talk) 02:26, 10 September 2009 (UTC)[reply]
You may want to check those numbers - a light year is just shy of ten trillion kilometers, so we'd move less than a hundredth of a light year in a century. If we take the diameter of the solar system as twice the semimajor axis of Neptune's orbit (screw you, Pluto, and your Kuiper belt buddies, too!) 63 billion km is only seven times the width of the solar system. That's enough that you could see slight shifts in the apparent positions of a few of the nearer stars, but even the nearest stars are almost a hundred times that distance from us. TenOfAllTrades(talk) 02:38, 10 September 2009 (UTC)[reply]
Yeah - that didn't seem right...oh - I see what happened. I slipped between meters and kilometers halfway through the mental arithmetic! Never trust a software guy without a calculator! Thanks for the double-check! Anyway - the point is made - we move a TINY distance compared to the distances to the objects we're observing. SteveBaker (talk) 02:49, 10 September 2009 (UTC)[reply]
Preventing/Dissuading housecats from slaughtering houseplants...? Hizzelp!
So I've got 4 wonderful little housecats and a ~100sqm apartment (a bit crowded, yes, but they are all street-rescues from urban China). Until recently, I've had houseplants scattered around on high shelves and the occasional wall-mounted planter or hanging basket, but what I'd really like to do is green the place up to the max... which would require plants be placed on counters, tables, and the like.
To date, whenever my cats have been presented with an opportunity to reach one of my plants (say, by careless placement of a chair or box) they have proceeded to go all Paul Bunyan / Mike Mulligan & Mary Anne.
Has anyone had success deterring this behavior? The cats already know it's not acceptable, so only do it when I'm sleeping or at work. Is this driven by the rarity of the occurrence? In other words, if they had a wide selection of targets would the urges eventually be satisfied? Or do I need to be more proactive?
I'd be thinking boredom as the first problem, too many cats, small place. What other interesting things are there for cats to do at your place? If they can't pursue their traditional activities (chasing/hiding/jumping), they will do other and weirder things.
As for deterrence, cayenne pepper sprinkled onto the soil? Water an ashtray and pour a bit of the foul water onto the plant (bet they've never attacked an ashtray!) I think you need to solve the boredom problem first though. Franamax (talk) 01:53, 10 September 2009 (UTC)[reply]
Oh yes, if the cats really do know that wrecking your plants is unacceptable - and think about it, did you really scold the right one at the right time, so that they learned the right lesson? They don't always have very good memory and understanding of causality. The cats themselves form a peer group, so they will be watching each other to see who gets awsy with what. Anyway, when a cat really does think it has got your measure, then specific destructive acts are usually commentary on what the cat sees as the latest thing you did to piss it off. In other words, the cats are engaged in a power struggle with you, so it's best to appease them rather than punish them. ;) Franamax (talk) 02:14, 10 September 2009 (UTC)[reply]
If they're chewing them up, there are sprays made from bitter melon that might work. These should be non-toxic unlike some of the other bitter sprays, so it should be safe for both the cats and the plants. I've never used them myself, but was actually thinking about trying it on electrical cords as a precaution. If they're urinating in the pots, then I've read in many books that covering the dirt with marbles work well. --Wirbelwindヴィルヴェルヴィント (talk) 04:28, 10 September 2009 (UTC)[reply]
Strange haze around the ISS
I just finished watching a visible pass of the International Space Station and Space Shuttle Endeavour. I noticed that there was a strange glowing haze around the ISS to one side, in the shape of a crescent moon. My guess is that it's some kind of out-gassing or perhaps the remnants of a burn they just did (wouldn't they do some kind of burn shortly after the departure of a shuttle?). I was worried that the station has depressurized and what I was seeing was the atmosphere leaking into space, but NASA would know about that and there is no mention of such a catastrophe having occurred on their website or on NASA TV.
I took photographs of the ISS, but they're long exposure so the station shows up as a bright streak. You can still see a bit of a haze around the station, but you can't see the shape that the haze took, so these pictures don't really show what I observed very well at all.
Whatever it was, it was following the station in its orbit because it kept pace with it as it moved across the sky. It made it appear as though the station had a comet-like "tail". I've seen dozens of ISS passes and I've never seen anything like that.
Ah! I'm too late. Yes, most often, if you see a large gas plume coming out of a manned space vehicle, it is... urine. This is a disaster for scientific instrumentation. A professor of mine was principle investigator on a Space Shuttle mission to study plasma ion effects in the high ionosphere; in at least one experiment, the trailed antenna became so coated in urine ions that it directly affected the scientific measurements. So much for the vacuum of space... Nimur (talk) 08:19, 10 September 2009 (UTC)[reply]
history of the octet rule ... and proving that something is an element
It is the 19th century. You don't have any NMR, or mass spectroscopy. How do you prove that something is an element? Couldn't you say that the substances in your hypothetical compound are too bound together to release them by most known means? For example, in Davy's conclusion that HCl did not in fact contain oxygen, how did he defeat the idea that the oxygen was just really really strongly bonded to the other compounds.
The other thing is that I'm really confused at how people came to realise the octet rule. I mean, not long ago, Descartes was thinking that elements bonded to each other via hooks. How did people discover the chemical bond and the octet rule before the discovery of the electron? How did people propose enantiomers, Kekule structures and structural isomers and acetylation reactions before they had even discovered the electron?
It is clear that in the latter 19th century, people recognised the principles of unsaturation, electrophilic and nucleophilic attack ... but I can't really see how people discovered them if they didn't know the electron existed. How did people discover carbonyl reactions if they had no idea of partial charge and bond polarity? John Riemann Soong (talk) 03:09, 10 September 2009 (UTC)[reply]
The "Octet rule" is a historical artifact from early versions of the Periodic Table of the Elements, especially John Newlands's "Law of Octaves" which observed that, when arranged in order of atomic weight (protons and "atomic number" would not be elucidated for many years) chemical elements would repeat their properties every 8 elements. If you arrange the elements in order of atomic weight, then the 3rd, 11th, and 19th elements (lithium, sodium, and potassium) all display strikingly similar properties, as do other elements spaced similarly. Furthermore, Gilbert N. Lewis and Irving Langmuir devised important atomic models which basically connect this empirical observation with the electronic structure in the atom.
As to your first question, reliable methods of calculating the molar mass of a substance predates understanding of actual atomic structure by almost a century. Since elements cannot be broken down into smaller substances, you just keep doing things like electrolysis or other similar processes until you don't produce any new subtances with smaller molar masses. Once you rigorously show that something cannot break down anymore, you likely have an element. However, some early models of atomic structure were based on the theory that there was exactly one element, hydrogen, and that ALL other "elements" were merely increasingly more complex conglomerations of hydrogen. Its an easy mistake to make, since the molar masses of nearly all elements are simply interger multiples of the molar mass of hydrogen. See Prout's hypothesis for more on this reasonable, but ultimately dead-end theory. --Jayron3204:29, 10 September 2009 (UTC)[reply]
Another general comment is that you don't need to know how something works to know that it does work. The actual nature of a bond ("covalent electrons") isn't needed to recognize that "something" holds molecules together in certain ways, and using certain chemicals, those things can change, and then eventually one sees patterns in what kinds of chemicals cause certain changes. For example, you don't have to know that "unsaturation" means two shared covalent pairs, you just have to see that one "unsaturation" in a molecule absorbs one hydrogen molecule or dihalogen molecule. The names of many old concepts are based on observed behavior, not on the now-known chemical structure: if something is "saturated" it cannot absorb any further. DMacks (talk) 04:36, 10 September 2009 (UTC)[reply]
If you are interested in understanding the nature of the chemical bond, one could do no better than to go to The Source, which in this case is the book The Nature of the Chemical Bond by Linus Pauling. The section on covalent and ionic bonding in EVERY single general chemistry textbook for the past 50 years is basically cribbed directly from Pauling's work. --Jayron3204:39, 10 September 2009 (UTC)[reply]
heat of fusion of aluminum oxide...
Need this to solve my thermodynamics problem set, but google is being obnoxious. In fact, the scientific community as a whole is being obnoxious. How the hell are we missing the heat of fusion for such a common substance? And why isn't there an easily-available database somewhere? Why does "aluminum oxide" + "heat of fusion" turn up no useful results? John Riemann Soong (talk) 03:42, 10 September 2009 (UTC)[reply]
This source from google books: [30] does not give the value directly, but notes that liquid Aluminum Oxide is a well studied material, which may mean that enthalpy of fusion data may be availible. I would check the footnotes of that reference for more details. However, it may also be that such data has never been reliably measured given Aluminum Oxides rediculously high melting point. It could just be that its hard to do a reliable calorimetry experiment to find the heat of fusion of a material that melts at a higher temperature than your measuring devices do! --Jayron3204:04, 10 September 2009 (UTC)[reply]
q: how were michelson and morley able to get the initial interference pattern if their did not exist any path difference initially??
I don't think it matters whether the two paths are perfectly identical. Interference fringes will be seen in the field of view and the object of the experiment is to see whether the fringes move when the apparatus is rotated. They don't. Cuddlyable3 (talk) 11:27, 10 September 2009 (UTC)[reply]
temperature-dependent heat capacity of aluminum
I note that aluminum exhibits a relatively significant temperature-dependence ... a lot of books and internet pages mention this, but won't give me a function. Can someone give me a function? If I extrapolated experimental data onto excel, what minimum degree polynomial would be useful? John Riemann Soong (talk) 06:34, 10 September 2009 (UTC)[reply]
As far as I remember, the reason is as follows. Alumin(i)um has a relatively high Debye temperature (about 400 K), that is, some of its phonon modes have energies well above the room temperature (about 295 K). As a result, at room temperature the heat capacity of aluminium is below the 3Nk value of Dulong-Petit law, and growing with temperature. Please see our article on Debye model, or Ashcroft & Mermin textbook. You can use the formulae derived in the framework of the Debye model. You should also be aware that the heat capacity of a solid may actually exceed 3Nk close to the melting point, and that there is also a (small) electron contribution to the aluminium heat capacity that is not accounted for by the Debye model. --Dr Dima (talk) 08:33, 10 September 2009 (UTC)[reply]
How to calculate the density of a gas
How do you calculate the density of hydrogen at 50 Celsius and 0.5 MPa? This is not a homework question, I need it for work. I suppose you perhaps could use the ideal gas law pV=nRT but dont know how. Thank you! Wikifantast (talk) 06:47, 10 September 2009 (UTC)[reply]
In this particular example, the wriggly line is the symbol that I don't know about. There surely is an article on wikipedia, but I can't locate it. Can somebody please supply a link? Thanks! --TrogWoolley (talk) 10:24, 5 September 2009 (UTC)
Resolved
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