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August 11

How to produce TiCL4 in industry

please tell me how to produce TiCl4 from Ilmenite ore in industry. why the producer usually produce TiCl4 from Rutile without Ilmenite. AND could you tell me how to separate Vanadium from crude TiCl4

Is this homework by any chance? Why not try looking at the pages I have linked for you and try to work it out for yourself?--Light current 03:02, 11 August 2006 (UTC)

How do you get Vanadium from TiCl₄? Isopropyl 13:57, 11 August 2006 (UTC)

You dont. Why dont you look at the pages Ive linked! 8-)--Light current 14:03, 11 August 2006 (UTC)

Alchemy. Titoxd^(?!?) 09:44, 12 August 2006 (UTC)

IMAGE TRANSFER CONSTANT.

I Wanna know what is

You wanna??? Try rephrasing the question--Light current 04:42, 11 August 2006 (UTC)

I think they want to know what "image transfer constant" means. I can't help, except to say it apparently has something to do with electronics ([1]). --Allen 04:51, 11 August 2006 (UTC)

Doesnt mean anything in my electronics knowledge!--Light current 05:01, 11 August 2006 (UTC)

Passengers boarding bridges.

tell me more about passengers boarding bridges, technology used in it. and also manufacturers—Preceding unsigned comment added by 59.144.44.56 (talk • contribs)

Tell you what? TRy rephrasing--Light current 05:45, 11 August 2006 (UTC)

Do you mean a jetway? Take a look at the article and its links.--Shantavira 07:13, 11 August 2006 (UTC)

solution of liquids inside vessels

A niece, who is very concerned about health issues, recently told me that she was avoiding buying mineral water in plastic bottles, because "the plastic gets dissolved" and was instead using only glass bottles.

This set me thinking about the whole issue of the solubility of vessels. I remember from my physics lessons in school that all vessels are dissolved to a certain extent by the contained liquid and also, though it may not be strictly relevant, that research in West Africa, where I worked for many years, indicated that when the local people stopped using the traditional iron cauldrons for their stews and went for more modern cooking appliances, they lost out on iron in their diet (derived from the cauldron).

I realize that the issues are extremely complex because they depend on: the nature of the vessel, whether wood, pottery, glass, platic; what the liquid is...anything from water, whiskey, sulphuric acid; maybe the environmental conditions such as temperature.

Even with water the nature of acidity and impurities in the water would presumably have an effect.

So to keep in simple, I am requesting as to whether anybody has statistical data on the solubility of different types of vessels in water (perhaps of different qualities) contained in the vessels. Are these rates to be considered signficant in any case in terms of ingestion by the drinker or are they, as one scientist told me over the phone last night, just of laboratory interest like the phenomenon that the glass in your window pane is gradually sliding downwards.85.12.64.148 08:50, 11 August 2006 (UTC)F.D. O'Reilly −Ihana enterprises

I might not be a full fledged scientist but I'd think that the plastic in most bottles will not dissolve, in any substantial amount, into the liquid it contains. Even if it did dissolve into the liquid it contained, you should remember that little children swallow plastic bits from their toys all the time, it simply passes through their system. PvT 09:27, 11 August 2006 (UTC)

Pharmaceutical companies spend quite a lot of time worrying about 'partition coefficients' - how much a given chemical prefers oily (hydrophobic) liquids to water. You can search for 'log P' or 'log D' values for compounds you're interested in. I'll bet that most plastics (or specifically the monomers) in water bottles have pretty high log P values (i.e. they much prefer oily solvents). They're unlikely to leach into water in significant amounts. Of course, I could be wrong. Ignoramibus 05:44, 16 August 2006 (UTC)

Who cares if plastic got into the water? Why does she care? Before you do anything, she has to tell you why it matters =D. Oh yeah, and glass doesn't flow =D. People just got that idea because the way they used to make windows would make the edges "bulge". So people see old windows, see that the bottom seems to be "thicker" and assume water is liquid. Cheers --mboverload@ 09:45, 11 August 2006 (UTC)

I ve learned something today: solid glass doesnt flow. But rock and mountains do (v slowly)--Light current 14:15, 11 August 2006 (UTC)

Yeh the sliding glass phenonemon is a myth that derives from the fact that early panes of glass are thicker at one end, because the technology wasn't accurate enough to produce flat glass, not because they changed shape. I would consider the effects of using iron pots, irrelavent to this case, as plastic and iron are extremely different physically and chemically. The only thing I have heard about plastic bottles is that the free radicals on the end of the polymerised chains cause carbondioxide to be absorded out of the water, and connect to then ends of the chains, but all that does is decrease fizziness. Anyway plastic is made of carbon and hydrogen neither of which are harmful (infact they are essential for survival) so I dont see any problems with ingesting microscopic amounts anyway. Philc _T^E_C^I 12:00, 11 August 2006 (UTC)

It's quite absurd to say that everything made out of carbon and hydrogen is completely safe. Thousands of hydrocarbons are toxic, including some in plastic containers. StuRat 00:49, 12 August 2006 (UTC)

There should be little concern that plastic will dissolve in water, or anything else you want to drink. But there is legitimate concern about plasticizers such as phthalates, which are non-polymeric chemical compounds added to the plastics to improve their physical properties. There are controversies surrounding the health effects of these compounds. --Ed (Edgar181) 12:49, 11 August 2006 (UTC)

It sounds to me as if your niece has succumbed to the plastic-dioxin hoax. --Ginkgo100 ^{talk · contribs · e@} 17:37, 11 August 2006 (UTC)

Plastics most definitely do give off chemicals into the liquid they contain. This seems to be particularly true if the liquid is acidic. Ever notice a total lack of plastic pickle jars ? There is a reason for this. Spaghetti sauce also usually comes in glass, as plastic bottles, especially soft ones, tend to absorb tomato color and odor, just as the sauce absorbs a plastic taste and odor. Soft plastics, like those used in two liter pop bottles, also seem worse than hard plastics. Time is another important factor. If you wait long enough, anything in a plastic bottle will acquire an unpleasant plastic taste. This is why water in plastic bottles has an expiration date. Temperature is also important. Keeping plastics cool would lower the speed at which the diffusion of chemicals into the contents takes place. However, avoid freezing, as the stress put on the bottle by the contents expanding actually increases diffusion of chemicals from the plastic. To be completely safe, avoid plastic wherever possible. Now, if anyone doubts what I've said here, get a plastic pop bottle, pop in a metal can, and pop in a glass bottle; store each under identical conditions for 10 years, then compare the three. The plastic bottle version will be completely flat and disgusting, while the pop in the can will be better (perhaps with a metallic taste) and the pop in the glass bottle will be exactly the same as when new. StuRat 19:53, 12 August 2006 (UTC)

You say that you have to avoid plastics to be safe, but you fail to give any reason to actually do so. --mboverload@ 00:49, 12 August 2006 (UTC)

Because they leach chemicals from the plastic to the liquid, some of which may be toxic. Put the question the other way, what exactly is the advantage of using plastic containers instead of glass ? Also, how do you explain bottled water having an expiration date, if not from leaching of chemicals into the water ? StuRat 19:53, 12 August 2006 (UTC)

yes there is a reason for no plastic pickle jars, and it has nothing to do with leaching of plastic components. a lot of plastics are actually rather permeable to oxygen, much more so than glass, so putting pickles in plastic would result in them not keeping as well. and the acidic point you have confused with items in metal jars, such as aluminium. here liquid acidity plays a role, becuase it reacts with the metal surface, contaminating the food with metal ions. Xcomradex 02:13, 12 August 2006 (UTC)

Acids dissolve many things, not just metals. And avoiding plastic bottles, because you don't want food that has been oxidized, is yet another good reason. StuRat 19:53, 12 August 2006 (UTC)

See, this is why I avoid this kind of "omg it's bad more me" thinking. It always turns out to be misinformation crud. --mboverload@ 09:37, 12 August 2006 (UTC)

A lot of people's opinions/facts here seem to contradict each other. Does anyone have a viable source for this information? --Proficient 13:39, 12 August 2006 (UTC)

Well, the source for the info that plastic water bottles have expiration dates on them is the bottles themselves, go look at some in the store. StuRat 19:56, 12 August 2006 (UTC)

It is true, however, that very few studies have been done in this field. The reason is that government food health regulation organizations, like the FDA, don't consider containers to be under their jurisdiction, and food companies, unless forced to do so, have no interest in paying for a study that may make them liable for damages and/or force them to change their packaging. StuRat 20:13, 12 August 2006 (UTC)

Well, in addition to the Snopes link I provided above, here is another. Why use plastic rather than glass? Because it's much lighter weight and less prone to breakage. Broken shards from a heavy jar are, I daresay, more dangerous to my health than plastic compounds in my food. I have indeed seen red pasta sauce packaged in plastic bottles, as well as items such as pickle relish. As for expiration dates on bottles, I had always assumed this was a marketing ploy, in which companies hope consumers will throw out old bottles and purchase new ones, although I could be wrong. --Ginkgo100 ^{talk · contribs · e@} 23:26, 12 August 2006 (UTC)

If you're going to go that far in finding risks in glass jars, how about empty plastic containers, set too close to the stove, catching fire, spreading to the rest of the house and killing your entire family ? Now, if we can keep the discussion reasonable, what are the risks of glass bottles which are used properly (which doesn't include smashing them and jumping up and down on the shards) ? StuRat 04:37, 13 August 2006 (UTC)

I once had a beer bottle with a splinter broken off the top. I decided not to take any chances and threw it down the sink.

Water that has been in a plastic container can indeed taste 'platicy', so I assume some of it does dissolve. I don't know if bits of plastic eaten by children are harmless because they pass through their system, but dissolved plastic may get absorbed (first into the blood and then where?). The quantities may be minute (I've had water stored in a plastic bottle for years and the bottle was still there :) ), but toxins can be dangerous at extremely low concentrations and I don't know if there might be a cumulative effect.

I've checked a Spa bottle and there is a date on the lid, but it doesn't say whether that is expiration or production, so I'll assume the latter. Also, I've tried your experiment. Be back with you in ten years. DirkvdM 10:07, 13 August 2006 (UTC)

You can tell if it's a production date or expiration date by whether it's long ago (production date) or in the future (expiration date). If the date just passed, then either you just bought it hot off the production line or it's quite old and that's the expiration date. As for kids eating chunks of plastic, some portion of the plastic would dissolve, or leach out, but the relatively short period inside the body (about a day) means that not much leaching will occur. A water bottle left on the shelf for years, especially if in the hot sunlight, on the other hand, has plenty of time to leach toxic chemicals into the water. StuRat 19:29, 14 August 2006 (UTC)

Potency of liquid explosives

With the recently foiled plot to blow up passenger airplaines by mixing liquid explosives, a danish expert on television explained that as little as 100ml explosives would be enough to blow up a plane. That's some pretty intense firepower, if you ask me. The article on organic peroxide isn't very helpful in determining how explosive it is, but I would assume the exact details on where on the plane the explosion is placed is important. Merely blowing a small hole in the fuselage clearly isn't enough.

Is the terrorists plan even feasible? Could a skilled pilot land a damaged plane on the sea, if the plane is only partially destroyed?

Merely blowing a small hole in the fuselage clearly isn't enough. Pardon 8-? Have you ever made a small hole in a balloon? What happens?--Light current 13:39, 11 August 2006 (UTC)

I was under the impression that the bulk of air travel is not by balloon these days? Blowing a small hole in a plane's hull will have extremely uncomfortable effects and will probably cause a few deaths, but it would not necessarily induce the plane to crash. dab (ᛏ) 13:51, 11 August 2006 (UTC)

I too must have miised it when they unpacked and inflated the planes at heathrow. Philc _T^E_C^I 20:25, 11 August 2006 (UTC)

What you mean you can breathe ok at 30000 ft?--Light current 14:06, 11 August 2006 (UTC)

no, why? dab (ᛏ) 14:18, 11 August 2006 (UTC)

Lack of oxygen after being sucked thro a window! (or decompression) See altitude sickness--Light current 17:29, 11 August 2006 (UTC)

I would have to side with the pessimists. A small hole in an otherwise smooth airframe travelling 450MPH at 30000' is nothing short of catastrophic. If you're lucky, the plane might make it down in one piece. If you're even more lucky, it will do so on a runway or other suitable facility. The article on Oplan Bojinka has more details relevant to the question at hand, which is how much damage could a little explosive do to an airliner. The 'successful' 1994 Manila Air bombing had 1/10th the intended quantity (for 'testing purposes') and was enough to kill one, injure 11, and force the plane to perform an emergency landing. --66.195.232.121 14:19, 11 August 2006 (UTC)

The effects of explosive decompression vary; see for example Turkish Airlines Flight 981 and Aloha Airlines Flight 243. --Lambiam^Talk 14:59, 11 August 2006 (UTC)

I would actually interpret the Philippine Airlines Flight 434 bombing differently: a bomb big enough to split a man in half makes a hole in the plane, and the plane lands succesfully. Death and injuries were caused by the explosion, not by the hole. The real damage to the plane comes from any avionics that are affected (hydraulic and electrical wires traveling throughout the plane). Bomb: death, fire: death, damage to avionics: death, air leakage: discomfort. The only place where decompression instantly kills you is Hollywood movies. Reading material: Cabin pressurization, [2][3][4] (from the first page of google results for plane hole myth). Weregerbil 15:04, 11 August 2006 (UTC)

The plane showed surprising resiliency, but it was only subject to 1/10th the nominal explosive volume. Decompression is one thing, a huge hole in a fuselage is quite another.

I commonly see the argument that a pinhole in a plane will take it down. My father has worked all his adult life as an aircraft mechanic. His job is repairing holes on the body of passenger jets. Every flight puts holes all over the plane. Lightning turns it into, as my father describes, swiss cheese. So, am I to believe that my father has not been working his whole adult life and not only made up the story of fixing holes in the plane's body but also faked the repair shop I visited him at and all those body sheets with little holes in them that he was filling in? --Kainaw ^(talk) 17:45, 11 August 2006 (UTC)

A pinhole wont take it down, but what about a 2" dia hole? See explosive decompression Also there is a way to stop a balloon exploding when puctured with a pin. Put a piece of sticky tape on the surface first then ouncture thro that. Does this tell you anything about the problem? It should!--Light current 17:51, 11 August 2006 (UTC)

....And dont say all planes should be wrapped in sticky tape!--Light current 18:02, 11 August 2006 (UTC)

A small hole would cause the cabin to decompress slowly. Note that the air is nowhere near a vacuum at the altitude planes fly, however. The problem becomes breathing in the thin air. The oxygen masks would drop, and that would allow the passengers to breath. The pilot would also likely decide to lose altitude to a point where people could breath without the oxygen masks. Also note that it takes some 10 minutes to die from total oxygen deprivation, while we are only talking about a slight reduction in the oxygen level (due to the thin air), so it might take hours for people to die, even if they had no oxygen masks and stayed at high altitude. Finally, an emergency landing would be made at the first available airport (not "in the sea", which would be deadly). The only likely deaths would be as a result of the explosion and from heart attacks, due to the stress. StuRat 18:21, 11 August 2006 (UTC)

Assuming you had oxygen to breathe, its a question of whether the low pressure or the rate of decompression, or the extremely low temperatures would kill you. Im not certian after looking at a number of our pages on related subjcts. I suppose it depends on how fit you are, and how long you are exposed to this environment. 8-(--Light current 18:36, 11 August 2006 (UTC)

A small hole wouldn't cause much of a temp drop, except right around it. I should think the heating system on board could easily keep pace with the heat loss through the hole, especially once the it was plugged (this might even happen automatically, if a blanket or pillow gets sucked up against it). Another effect would be noise. It might be quite loud near the hole, causing hearing damage to those nearby. StuRat 23:58, 11 August 2006 (UTC)

Loss of cabin pressure isn't a deadly incident, surely. But you all seem to think that a large nitroglycerin bomb going off inside an airplane would be a casual occurrence! A huge bomb blowing a gaping hole in the side of an aircraft at altitude is certainly cause for concern in my book.

Loss of cabin pressure at altitude (e.g. 35000ft) is certainly deadly. See Helios Airways Flight 522 and Payne Stewart for examples where death was most likely by hypoxia; alternatively if decompression occurs suddenly (e.g. as the result of an explosion or structural failure) the fuselage can be ripped open as happened on Turkish Airlines Flight 981. IIRC, at 35000ft hypoxia can incapacitate the pilot within 15-20 seconds without emergency oxygen following a rapid decompression. In this event the pilots rapidly don their oxygen masks and execute an emergency descent; their vision is likely to be impaired as the pressure drop causes tears to evaporate from the surface of the eye, and they may have suffered severe hearing damage or perforation of their eardrums. Meanwhile any passengers who have failed to get their oxygen masks on can expect to be suffering permanent effects within two minutes, as lowered pressure causes blood oxygen to diffuse back into the lungs. The outside temperature is roughly -56ºC so it is likely to get rather cold rather quickly, even with the heat turned up (although this would obviously depend on the size of the hole). As a result of the emergency descent (to below 18000ft to ensure the safety of passengers), fuel consumption will be drastically increased and range will be correspondingly shortened - if this occurred far from an airport there is a real likelihood of a crash or ditching attempt. --Yummifruitbat 03:11, 12 August 2006 (UTC)

Those are the type of things that would happen if a door was blown off, not from a small hole. The Helios timeline also shows that people were still awake 2.5 hours after the cabin pressure alarm went off. It was human error (failure to react to the situation) which downed that flight. StuRat 04:46, 13 August 2006 (UTC)

I won't be doing any guesswork here, just quote a guy from an 'national emergency team' (something along those lines) who said that a bomb could blow a hole in the hull that, if strategically placed, could crash the airplane. He didn't say where that place was and why it would crash the plane, though. DirkvdM 10:18, 13 August 2006 (UTC)

• Even if the cabin was depressurized don't they have really thick metal doors around the cabin>? meaning that the pilots could still land the thing without any problems?--71.247.125.144 14:58, 13 August 2006 (UTC)

I think you're saying the cockpit is a separate pressurized chamber from the passenger compartment. This is not the case, they share the same heating and A/C system, and those common ducts keep the pressure equal between the two parts of the plane. StuRat 19:21, 14 August 2006 (UTC)

Strength of HCL

There is an experiment for calculating the strength of HCL. It is a titration using NaOH. After the titration I used a formula with the figure 3.646. I multiplied this figure to the mL of NaOH. Where does this figure come from.

• Roughly speaking, because HCl and NaOH are a strong acid and base respectively (and of roughly equal strength in each direction), it takes 1 mol of HCl to neutralise 1 mol of NaOH, with a result that is pH neutral - 7. So if you have 10 mL of 1 M NaOH, then that's 0.01 mol of NaOH, which has to react with 0.01 mol of HCl. If that takes 5 mL of HCl, then you have 0.01 mol / 5 mL = 2 M, for example. Your calculation probably has that kind of reasoning hidden in it somewhere. Confusing Manifestation 15:05, 11 August 2006 (UTC)

Damn edit conflicts!! :)

So, the titration probably told you that $V_{NaOH}$ mL NaOH of a given molarity $M_{NaOH}$ neutralized $V_{HCl}$ mL HCl of unknown molarity $M_{HCl}$.

$M_{NaOH}$ has units of moles/L, and you want a value in moles, so you probably multiplied the number of mL of NaOH by ${\frac {M_{NaOH}}{1000}}$ (since you measured the NaOH in mL not L).

So, $N_{NaOH}=V_{NaOH}{\frac {M_{NaOH}}{1000}}$. $N_{NaOH}$ is the number of moles of NaOH used. Since NaOH and HCl both separate into only two ions, you can simply take $M_{HCl}=1000{\frac {N_{NaOH}}{V_{HCl}}}$ to get the molarity of HCl. I'm not sure which one of these numbers was 3.646, but it probably depended on what molarity of NaOH you were using to do the titration. --Bmk 15:09, 11 August 2006 (UTC)

The molar mass of HCl is given as 36.46 g/mol. Was there a factor of 0.1 mol/l for the NaOH? --Lambiam^Talk 15:24, 11 August 2006 (UTC)

Please don't confuse the strength of an acid with its concentration. I suspect the original question was to calculate the mass concentration of the HCl, with units in g/l. HCl is a strong acid at all times, but it can be made dilute or concentrated by altering the ratio of acid to water.--G N Frykman 17:52, 11 August 2006 (UTC)

Well, the question is ambiguous. Depending on the circumstances, titration could measure either "strength" or concentration. --Bmk 19:54, 11 August 2006 (UTC)

The strength of the acid - how much it ionises - would be calculated by conductivity measurements. Titration will only tell you the concentration of the acid, and won't tell you whether it is strong or weak.--G N Frykman 09:41, 12 August 2006 (UTC)

Thermodynamics

Hi, I have a question with a bet I am trying to settle, I cannot find the info on wikipedia. Is it possible for a fridge/air conditioner ect to produce more cold then heat? I thought a thermodynamics law stated that it was impossible for it to produce a net cold? Any answers? If so could you provide the law or some reference? Thanks

Hanez

A refrigerator merely sucks heat energy from the interior and dumps itoutside the case. You also have the heat produced by the compressor. So the answer is : it produces more heat than cold!--Light current 17:19, 11 August 2006 (UTC)

So, yes, Hanez, you are correct, it would violate the laws of thermodynamics for any device to lower the temperature of the universe. StuRat 18:08, 11 August 2006 (UTC)

So why do you need a fridge that big?--Light current 18:12, 11 August 2006 (UTC)

Maybe so you can put stars inside the fridge to induce cold fusion ? :-) StuRat 18:24, 11 August 2006 (UTC)

Stars are already (hot) fusion reactors 8-)--Light current 18:31, 11 August 2006 (UTC)

So cool them down, and then you have cold fusion, right ? :-) StuRat 23:53, 11 August 2006 (UTC)

Thanks for the responses. How about heat neutral? Is it possible for a dehumidifier or a fridge ect to produce the same amount of heat as it does cold? Or should it always be producing more heat than cold?

That would require 100% efficiency, which never exists in the real world. StuRat 23:53, 11 August 2006 (UTC)

You've never seen me at work, have you? Then again, some people claim I'm not for real, so may still be right. DirkvdM 10:23, 13 August 2006 (UTC)

You are 100% efficient at spouting nonsense, I'll have to grant you that. :-) StuRat 07:28, 16 August 2006 (UTC)

This concept will be much easier to understand if you stop thinking of "cold" as a substance. The best way to think of a refrigerator is an engine that works between two heat baths of different temperatures by taking in external energy. See heat engine. A refrigerator is a heat engine working in the opposite direction. --198.125.178.207 00:53, 12 August 2006 (UTC)

It's actually pretty humorous that the only thing air conditioners do is produce heat overall =D --mboverload@ 01:24, 12 August 2006 (UTC)

please do not pull tongues here! thans --Light current 04:34, 12 August 2006 (UTC)

And that's not even counting the global warming they cause. DirkvdM 10:23, 13 August 2006 (UTC)

Soda Water

I drink a lot of soda water. I do so to help me prevent from drinking soda. But also cause water is boring and I want to keep hydrated. So, for the latter reason, am I really hydrating myself with soda water? Here are the ingredients on one particular bottle:

table salt, sodium citrate, sodium bicarbonate, potassium bicarbonate, potassium sulfate, or disodium phosphate

Also, does milk hydrate? Thanks!!!

THe question is: are any of those substances diuretics?--Light current 17:23, 11 August 2006 (UTC)

What do you mean by "hydrated?" If you simply mean "not thirty" than pretty much anything with water in it will do. When energy drink makers talk about "hydration," it's a marketese way of refering to osmotic pressure. When you sweat, you give off not just water but salt. Your body needs to maintain a pretty stable ratio of both, so drinking pure water is not ideal. Electrolytes (ie, salt) help. If you're running long races or hiking in the desert, you need to care about this. Otherwise, it doesn't really matter. --Pyroclastic 17:34, 11 August 2006 (UTC)

Why cant you be hydrated even if you are thirty?--Light current 17:47, 11 August 2006 (UTC)

I'm way past thirty and still pretty hydrated. DirkvdM 10:26, 13 August 2006 (UTC)

Anything with water in it will "hydate" you, it isn't that scientific. — [Mac Davis] (talk)

Well, your statement certainly isn't. Sea water and whiskey contain water. DirkvdM 10:26, 13 August 2006 (UTC)

Purified water

On the North American cooking show Good Eats, in an episode on making stock, the host Alton Brown mentioned that distilled water was too pure to be good for dissolving the collagen and flavor compounds that are necessary for good stock. I was under the impression that very pure water is "hungry" to dissociate into ions and is therefore a very good solvent, not a poor one. Am I mistaken, or is Alton? --Ginkgo100 ^{talk · contribs · e@} 17:48, 11 August 2006 (UTC)

Pure water is an excellent solvent, but is reckoned not to be very good for making tea, for example. This is possibly due to the lack of dissolved air - boiling the water to distil it gets rid of most of the dissolved air. The degree of ionisation of water itself is always very small (it's called the ionic product of water) but it is a wonderful solvent for ionic substances.--G N Frykman 17:57, 11 August 2006 (UTC)

Yeah I think its bad to drink pure (deionised) water. It needs some minerals (or whisky).--Light current 18:16, 11 August 2006 (UTC)

Well, stock isn't intended as a beverage, but as a food base for sauces and soups. The idea is that some types of water will be better at dissolving substances in the meat, bones, and vegetables and therefore produce a higher quality stock. If the problem is dissolved air, would aerated distilled water be as effective as tap water or artesian water? --66.7.182.48 Ginkgo100 ^{talk · contribs · e@} 19:30, 11 August 2006 (UTC)

I say Alton Brown is just wrong. It doesn't matter. Once you dump the bones, meat, and vegetables in it's not "purified" anymore anyway. I will say that buying distilled water for food purposes is a waste of money. --GangofOne 19:51, 11 August 2006 (UTC)

His claim was that there was a negative benefit to using distilled water (as is not usually the case in cooking, since you want the purest ingredients possible) since normal water has a baseline of impurities that works toward bringing more flavor out of the stock. Also, saying that using purified/distilled water for food use is wasteful, is a matter of complete opinion as many culinary experts and food connoisseurs would argue the opposite and can easily tell the difference in food prepared with purified water versus typical tap water.

There is a well-known (among protein biochemists) phenomenon of "salting in" proteins. First google hit: "Initial salting in at low concentrations is explained by the Debye-Huckel theory. Proteins are surrounded by the salt counter ions (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing activity of the solvent, which in turn, leads to increasing solubility. This theory predicts the logarithm of solubility to be proportional to the square root of the ionic strength." (source) For protein solubility, the pH of the water can also be important.
--JWSchmidt 22:35, 11 August 2006 (UTC)

but that is irrelevant, once you dump meat etc in the water (full of ions etc), you no longer have pure water. i'd say the amount of ions in the water (generally on the ppm level for most ions) contributes only the tiniest amount to the amount of ions in stock (which will be much much more). i'd say your cook is talking smack. Xcomradex 02:08, 12 August 2006 (UTC)

Well, that could very well be, but Alton is normally quite good with his science, is a trained chef, and makes copious use of various food scientists in his episodes, so he'd seem to be in a position to know. When you add something to distilled water, you are obviously adding impurities, but perhaps not the same kinds of impurities that would be found in "normal" water. Our article on distilled water is spectacularly uninformative and google searches are cluttered with nutcases pro- and anti- for drinking distilled water, so it's difficult to tell. Alton has a website, so I guess we could ask him to explain himself. Matt Deres 03:02, 13 August 2006 (UTC)

A link I added to a question on one of the Reference Desks about using honey in homemade beer said specifically not to use distilled water for beer.--Anchoress 03:06, 13 August 2006 (UTC)

But why? Just because somebody, an unknown person who has a computer, said that doesn't make it true. --GangofOne 04:10, 13 August 2006 (UTC)

1) I'm not saying it's true, I'm saying someone said it. 2) I don't know why, and I don't think I'm obligated to figure out why. 3) It wasn't just 'somebody, and unknown person who has a computer', it was the corporate website for a brewery, answering questions about how to optimise home brewing. Please don't jump down my throat for trying to be helpful. Anchoress 04:19, 13 August 2006 (UTC)

I assure you I am not, and have no interest in, attacking you. My only interest is a deeper understanding of reality. --GangofOne 06:56, 13 August 2006 (UTC)

According to The Complete Joy of Homebrewing, 3rd ed., by Charlie Papazian, whether distilled water is appropriate for homebrewing depends on whether you're doing a malt-extract beer or an all-grain beer. Malt extract contains adequate minerals, so distilled water is acceptable (p. 78). The chapter on "advanced homebrewing" (applying to all-grain brewing) does not explicitly state one should not use plain distilled water, but does imply it, because certain minerals are needed for a good mash. --Ginkgo100 ^{talk · contribs · e@} 22:00, 13 August 2006 (UTC)

British bombing plot explosives ingredients

Reportedly (I am not too impressed by the news media's facts), the bombers planned on using liquid mixtures in British sports drink bottles to make an explosion. Does anybody have any guesses to whether or not this is true, or what chemicals they were planning on using? — [Mac Davis] (talk)

There was a demonstration on the TV last night by a Professor of chemistry (or something like that) who took some simple ingredients making a mixture of 200 ml or so. He placed this on top of a (5mm?) steel plate, ignited it, and it made a neat hole about 30mm across. Draw your own conclusions.--Light current 18:43, 11 August 2006 (UTC)

So basically if the self destruct button on the plane is hidden behind a 5mm steel plate, you can punch hole in it and press the button. Otherwise you'll need something better. Philc _T^E_C^I 21:09, 11 August 2006 (UTC)

The article on the 2006 transatlantic aircraft plot mentions some possible mixtures. Some of the articles listed in the "see also" section describe what has been used in other strikes. Weregerbil 18:45, 11 August 2006 (UTC)

I read somewhere that a mixture of acetone and concentrated hydrogen peroxide was likely. --Pyroclastic 18:58, 11 August 2006 (UTC)

I thought of this as a possibility, but I don't know. --Bmk 19:58, 11 August 2006 (UTC)

Nitroglycerin has been used by terrorists in at least one aircraft bombing, although it did not succeed in destroying the aircraft. If carefully positioned in a vulnerable location, and possibly combined with other components to generate shrapnel, I'm sure this could potentially be used to cause a crash. --Yummifruitbat 23:13, 11 August 2006 (UTC)

Look up binary explosive. Also keep in mind that aircraft skin is made of aluminum and is a lot thinner than that 5mm steel plate. Something that can blow a one-inch hole in that plate can create a hole five feet across or more in an airplane. --Serie 21:51, 11 August 2006 (UTC)

I have no idea how aircraft keep a balance between internal and external air pressure. Would it be possible for a gas generator of the type used in airbags to produce so much gas in a short period of time that the skin of an aircraft could rupture and pop open? --JWSchmidt 22:43, 11 August 2006 (UTC)

I think such a device would need to produce a phenomenal amount of gas - remember that an aircraft fuselage is itself a pressure vessel and is designed to withstand a considerable pressure differential. I think causing a rapid (i.e. explosive) decompression would be more feasible, particularly since this has the potential to incapacitate the crew even if the aircraft is not destroyed by the explosion. --Yummifruitbat 23:13, 11 August 2006 (UTC)

bearing in mind a fire on board an aircraft is a rather serious issue, i'm sure simply spreading 100 mL or so burning flammable liquid around could cause a fair amount of disruption. and 100 mL nitroglycerin would cause a tremendous amount of damage, given (a) it is 1.5x more powerful than TNT, and (b) it has a reasonable density. so 100 mL nitroglycerin would be about 117g, which would be equivalent to around 175.5g TNT. for comparision, in a hand grenade there is about 180 g Composition B. so you could certainly do a lot of damage to a soft aluminium shelled aircraft. Xcomradex 02:03, 12 August 2006 (UTC)

just a thought, i bet a chemically aware terrorist could make some pretty clever bombs, say a concentrated solution of diazomethane or neat phenyldiazomethane. i imagine its the last thing sensors are looking for. or even something around organic azides, eg diazidomethane. i imagine we aren't getting the whole story out of the respective govts, especially since a lot of sensitive compounds (eg TATP?) become a lot less sensitive in solution. Xcomradex 02:24, 12 August 2006 (UTC)

and i am entertaining the thought of panclastite type explosives being what was going to be used, easily prepared from relatively inert and readily availible ingredients. Xcomradex 02:30, 12 August 2006 (UTC)

Instead of bombs, Andrew Sullivan [5] suggests instead that the weapons might be the "terrorist breakthrough" device called a "mubtakkar" that quickly evolves a large quantity of hydrogen cyanide gas. Via a report in Time magazine [6]. -Wfaxon 07:38, 12 August 2006 (UTC)

Speed of Smell

Is there any way to quantify the speed of smell? Here is a crude example but its the first to come to my mind; sometimes when I fart, I smell it right away...other times it takes a while. Well, not that I think about it wind, humidity prolly are factors in this. But is there anyway, in like a controlled in environment, that the speed of smell can be quantified?

It just depends how fast the smelly molecules are travelling. THis of course depends on the air velocity in the vicinity. If you were to fart downwind, the smell would travel woth the wind (hopefully) at its speed. I predict this question will attract a great many comments (some funny, some not).--Light current 18:47, 11 August 2006 (UTC)

Brownian motion ? :-) StuRat 23:46, 11 August 2006 (UTC)

I guess the speed of a fart would be the speed of any air currents that are present combined with entropy in the form of Brownian motion. Weregerbil 18:51, 11 August 2006 (UTC)

Yes I think you are correct. Plus of course the exit velocity from the offending orifice?--Light current 18:53, 11 August 2006 (UTC)

Well this is an odd question. Well if we're talking about the time it takes for the " smell " to reach you that would be depend on the speed at which the particles involved move. You should note that a cloud of particles isn't a " smell ", it becomes one when it interacts with the receptors in your nose. I think Olfaction might be a good read for you PvT 18:54, 11 August 2006 (UTC)

Besides air currents, the main factor affecting the "speed of smell" is simple diffusion. (A question for others with a better understanding of physics: Is there a known rate of diffusion in still air? Would it depend on air pressure?) A more concentrated odor will seem to travel faster than a less concentrated one because the threshold of molecules necessary to detect it will reach the nose faster. --66.7.182.48 Ginkgo100 ^{talk · contribs · e@} 19:27, 11 August 2006 (UTC)

I believe small molecules diffuse faster, and diffusion speeds up at higher temps and lower air densities. It some cases, the rate of diffusion in air is amazingly high. StuRat 23:44, 11 August 2006 (UTC)

For biomolecules, which are relatively heavy compared to air, stray air currents (caused by such things as breathing, moving, ventilation, farting, etc) are usually much more efficient at moving odors around than actual diffusion. In perfectly still air an odor could take many hours to cross a room. In practice people often use an effective diffusion rate which is really not diffusion at all, but an average rate of transport due to all the stray air currents. Dragons flight 00:05, 12 August 2006 (UTC)

I would have thought there are a few factors involved. Firstly, the volatility of the odor source, then the considerations described above on the air currents carrying the volatiles to the nasal epithelium. Then you have to consider the number of molecules required to activate the number of neurons required for our noses to recognise a smell. The next consideration is the rate at which the olfactory neuron can transduce the binding of the odor to its receptor, into an action potential (this is pretty quick when tested experimentally). Then you have to consider the neural circuitry (the details of which are currently unknown) as the activated olfactory neurons project to their glomeruli in the olfactory bulb and pass the signal on to mitral cells, which in turn project to regions of the cortex. Once there, we recognise the "smell". One would think the speed of the signal along the neural circuitry would be pretty repeatable, thus the variation would most likely be at the level of odor detection, reception and transduction, especially considering its know we undergo adaptation to odors (though the mechanism not fully understood). Rockpocket 01:52, 12 August 2006 (UTC)

We used to perform a simple experiment for our Year 9 pupils (UK: 13-year-olds) in which we took the lid off a gas jar of hydrogen sulphide in one corner of the laboratory, and got the pupils to note at what time they could detect the smell, and plot iso-smell (?) contour lines. It used to take about 20 minutes for the smell to get from the front to the back of the laboratory - which was way too fast for the theoretical speed of diffusion of hydrogen sulphide. There were many factors to consider, of course - the fidgeting boys, the heat each one was giving off, air currents from under the door and so on. When hydrogen sulphide became politically incorrect, as it were, we used a squirt of lemon-fragrance air freshener. --G N Frykman 09:34, 12 August 2006 (UTC)

Nice experiment! However, i guess you would also have consider the competition among kids to be the first to smell it and the natural variation among individuals to odour sensitivity. The interesting thing would be to see if different odor classes (that are thought to activate different receptor subclasses) but with the same volatility, showed different iso-osmic contours. That way we would begin to get an idea of the rate distinct odors are detected and transmitted. *starts writing grant* Rockpocket 20:31, 12 August 2006 (UTC)

I wouldn't tell them in advance what the odor is. Then, record when they say that they smell something and what they think that they smell, at that time. If they get the odor wrong, ignore their input. StuRat 20:44, 12 August 2006 (UTC)

Anything exceeding that smell would be, ehm, ultra-olfactoric? No article on that yet? Ultra-smelly? Nope. Suggestions? DirkvdM 11:31, 13 August 2006 (UTC)

Speakers

Can you assume that speakers are producing sound within the limits of their construction if there is no sound distortion? Or would it not be unreasonable to expect a speaker burst after cranking the volume a bit too high, even if it was producing clear sound just before bursting?  freshofftheufoΓΛĿЌ  19:44, 11 August 2006 (UTC)

I would say : yes--Light current 04:54, 12 August 2006 (UTC)

Without much knowledge about the science behind speakers, I would say no. --Proficient 13:53, 12 August 2006 (UTC)

think you will hear some bad noises before the speaker bursts. Thats the time to turn down--212.74.96.197 23:52, 12 August 2006 (UTC)

As someone who knows a fair bit about speaker application, I can say you certainly can damage them without hearing a thing beforehand. The chief killer of speakers is overheating and eventual distortion of the voice coil. A speaker is basically a big electric motor, that moves back and forth along its center axis, instead of spinning. Like anything (beisdes a Superconductor) that moves electricity, some energy is lost to heat. What happens to the heat, you ask? It builds up within the coil, and if it cannot dissipate fast enough it can cause breakdown of the magnet (leading to a dull ineffective speaker), or complete thermal runaway (leading to meltdown of the coil). Now, most well made speakers take this process into account and can dissipate the heat fast enough at peak output. Also, a cone built too thin, or a rubber surround that isnt wide enough, can fail prematurely due to heavy use with little warning. What's the moral of the story? Expect cheap speakers to fail, unless you listen very delicately. If you want something that sounds good AND lasts, do some research and pick out a well made brand. --24.210.26.146 23:58, 12 August 2006 (UTC)

no I dont go with this run away thing. you can burn the coil but thats if you put too meuch volts on it, but you will hear it long before that happens.--212.74.96.197 00:10, 13 August 2006 (UTC)

Right, but since more than 90% of the energy in most speakers is converted into heat energy, it seems to make sense that a speaker would "burn out" at high volumes. It would explain why speakers burst below max capacity after they have been used for a while, when natural corrosion isn't an issue. Thanks for the answers!  freshofftheufoΓΛĿЌ  06:13, 13 August 2006 (UTC)

Monogamy

As I was reading Brian Skyrms' book Evolution of the Social Contract and as he was discussing the evolutionary fitness of various strategies of division of a cake (greedy (2/3) vs. just (1/2) vs. modest (1/3)...) I wondered how monogamous relationships affect the evolutionary fitness of a species. On a naive level it seems that monogamous (especially lifetime monogamous relationships) would decrease the genetic variation of a species' off-spring, which seems (at least on my understanding of evolution) decrease the fitness. But likewise, if monogamy in that species is particularly helpful in raising well-adjusted adult members then that increases the fitness of the off-spring. Does anyone know of any semi-technical (or even technical, I guess I can attempt to read technical articles even though my major is philosophy) material on this subject? I'd imagine if you could find a species with monogamous relationships and a closely related species without that type of relationship, then you could get a beautiful study on how monogamy affects the evolutionary fitness of a species (insects would be great given their short life-time). And if my admittedly naive understanding of the complexities of evolution is wrong, then please point this out.--droptone 20:45, 11 August 2006 (UTC)

You should also factor in the venereal disease spread by polygamy. StuRat 23:38, 11 August 2006 (UTC)

There has been a significant amount of research on monogamy using rodents, for example, see: Prairie Vole. You might also be interested in this. --JWSchmidt 00:13, 12 August 2006 (UTC)

The thing is, long-term pair bonds for the purpose of raising offspring does not require monogamy. IIRC animal studies have shown that many of the animal species that supposedly mated for life had paired females who 'stepped out' with other males (bald eagles were an example they gave). Furthermore, another thing I read (sorry, don't have links and too lazy to look) said that something like 50% of Europeans with royal blood had DNA that indicated unknown paternity somewhere in their ancestry. Aaaand... it's the opinion of some paleo-sociologists or whatever they're called that this explains the evolution of the 'Alpha' vs 'Beta' males; 'cavewomen' chose Alpha males for their ability to protect and provide, but while the Alphas were out hunting, they were canoodling with the Beta males who were hanging around the camp. Remember, the postman always rings twice. Anchoress 00:21, 12 August 2006 (UTC)

But does the postman always bang twice ? :-) StuRat 19:35, 14 August 2006 (UTC)

The Strange Case of Diabetes, Genetics, and the MP

Recently my MP Dr Ian Gibson (who's a nice bloke, for a politician) said that a rise in diabetes in Norfolk may be due to inbreeding[7]. Now, naturally, us in Norfolk were not too happy about being portrayed as a bunch of inbred hicks, and scientifically I would question if Norfolk actually is significantly more inbred in this day and age than anywhere else in the UK. Dr Gibson later said his remarks were not meant to cause offence: he meant the term in a "scientific" sense (he has a degree in Genetics), which I guess means that he meant "the rise is caused by a small genetic pool" rather than the more unscientific and offensive "the rise is because my constituents are incestous". But I wonder if he's not using his badge as a geneticist to say "I didn't mean to offend, I meant something completely different because I'm a Scientist." Sorry for the long-winded question. Sum0 21:58, 11 August 2006 (UTC)

I read what Ian Gibson said and I think he was commenting on type 1 diabetes in much the same way that geneticists would normally discuss the possibility of a genetic basis for a disease. I doubt if he entertained any thoughts about incest in Norfolk. There can be a founder effect leading to high rates of certain genetic diseases is a population without any incest in a population. --JWSchmidt 22:17, 11 August 2006 (UTC)

I read about this story myself this morning and felt a bit sorry for Dr Gibson. Geneticists, among whose number i count myself, talk about "inbreeding" and "outbreeding" in a very matter-of-fact way, without any negative connotation the the general population may attach to the terms. Lab mice strains, for example, are divided into inbred and outbred lines, and these have implications on their fitness and use in disease models. His major mistake IMHO was, when referring to humans, was not using a less emotive term such as consanguinity, if indeed that was his point. As an aside, and at risk of offending our East Anglian friends, i used to live in rural Suffolk and remember as a child an elderly neighbour telling me how she never travelled more than 30 miles from her village until the age of 25, by which time she had already met her husband and had children. She also told me that people used to know which nearby village an individual was from based on their villiage characteristic, such as a squint, polydactyly or big ears. Of course, this is just the testimony of an old woman, but it did make me think Gibson has a point. Rockpocket 01:31, 12 August 2006 (UTC)

Heh, no offence taken. I wouldn't doubt that a century ago there would have been a lot of inbreeding, but there's obviously a lot more migration these days and so I wouldn't think inbreeding would still be a noticable factor. I have a strong interest in genetics myself, so the fact that I didn't "get" his reasoning puzzled me. Sum0 19:45, 12 August 2006 (UTC)

I agree, i would think these days the level of homozygosity in Norfolk would be not significantly different from another other rural-ish county (it would be interesting to compare diabetes rates with Suffolk, for example). Gibson's theory would not be a good explanation for a rise in type 1 diabetes, however, if the statistic has been consistantly higher in Norfolk - and since the environmental factors causing the disease are unknown - i guess a significant genetic influence can't be ruled out, due to a historically restricted population. Still, this whole saga is somewhat Partridge-esque. Rockpocket 22:53, 12 August 2006 (UTC)

Camera Zoom

Are there any cameras where the zoom mechanism is internal to the camera body, so that the final (first?) lens remains stationary? (I mean on normal commercial cameras, not wacky specialist ones). -- SGBailey 22:18, 11 August 2006 (UTC)

wow that would be cool..Wjlkgnsfb 02:58, 12 August 2006 (UTC)

Yeah! The Kodak EasyShare V570 has an internal zoom mechanism. --jpgordon^∇∆∇∆ 03:26, 12 August 2006 (UTC)

See also digital zoom (which is not true zoom) and click on "what links here" for a list of cameras.--Shantavira 06:52, 12 August 2006 (UTC)

Digital zoom is worse than no zoom at all, it just makes a big blurry mess, don't ever use it. StuRat 19:37, 12 August 2006 (UTC)

Except when taking pictures of UFOs and Nessie.  freshofftheufoΓΛĿЌ  19:40, 12 August 2006 (UTC)

Well, of course UFO pics are blurry. If you just had an anal probe you would be more concerned about getting home to your trailer park than focussing the camera, too, wouldn't you ? :-) StuRat 20:48, 12 August 2006 (UTC)

If they weren't blurry, the flying object could be identified and it would become an IFO. Wow! I make something up and we've got an article on it! DirkvdM 11:37, 13 August 2006 (UTC)

Smoking and lung cancer

Okay, I managed to find in tobacco smoking that a person who smokes tobacco is 25 times more likely than a non-smoker to develop lung cancer, but I can't seem to find the answer to this question: what pecentage of smokers die of and/or are diagnosed with lung cancer? Better still, good reference desketeers, does anybody happen to kow where I could find to access the approxiamate pecentage of all common causes of tobacco smokeing-correlated death among smokers, seperate from non-smokers? A pie chart (I like pie) would be striking gold. Many thanks in advance. – ClockworkSoul 22:37, 11 August 2006 (UTC)

http://www.cancer.org/docroot/PED/content/PED_10_2X_Smoking_and_Cancer_Mortality_Table.asp

Unfortunately, this only has cancers, not other causes of death, but take a look at the "PAR" column. Lung Cancer has an 88% PAR, which means that out of 100 cases of lung cancer, 88 were caused by smoking.

Also, you may want to check out some NCHS resources like this :http://www.cdc.gov/nchs/datawh/statab/unpubd/mortabs.htm

there's a ton of CDC/NCHS/NIH data to wade through on mortality...

August 12

Glow sticks, who invented them

My six year old son and I would like to know the chemist or inventor of the glow stick.

Glen

Hello Glen. Our article doesn't seem to mention the inventor. However, this google cache suggests:

In the early 1960s, some guy, a young chemist at Bell Labs in Murray Hill, N.J., was searching for a general way to explain chemiluminescence. Peroxides, with their potential to liberate large amounts of energy during some chemical reactions, seemed to be likely participants.

After a number of experiments, he found to his great excitement that oxalyl chloride mixed with hydrogen peroxide and a fluorescent dye produced chemical light. The efficiency was only about 0.1%, but it was the foundation from which sprang modern chemiluminescence. Chandross, unaware of the powerful potential of his discovery, never patented it.

At about the same time, chemist Michael M. Rauhut was manager of exploratory research at American Cyanamid in Stamford, Conn. He and his colleagues corresponded with Chandross about his oxalyl chloride chemistry, then went to work on the reaction--studying it and looking for avenues that would produce chemical light intense enough to be of practical use.

Rauhut and his colleague Laszlo J. Bollyky developed a series of oxalate esters. Ultimately, Rauhut designed a phenyl oxalate ester that, when mixed with hydrogen peroxide and a dye, gave a quantum yield of 5\--not as efficient as a firefly, but still brilliantly useful. They dubbed it Cyalume, and it became the trademark name for American Cyanamid's chemical light products.'

So there you have it, Edwin A. Chandross developed the chemistry and Rauhut & Bollyky applied it to make the first glowsticks. Rockpocket 01:10, 12 August 2006 (UTC)

Ed Chandross may have been doing research in the field around the time that glow sticks were commercialized, but credit is usually given to Naval Air Weapons Station China Lake for inventing the glow stick. Here is an article. -- C. S. Joiner (talk) 01:13, 14 August 2006 (UTC)

I've edited the article, with mentions of both theories. (NPOV in action ;) Ignoramibus 06:08, 16 August 2006 (UTC)

After communicating with Ed Chandross by e-mail, I withdraw my comment which was based on second-hand information from a former employee of China Lake. It does indeed appear that Ed Chandross holds the patent for inventing the glow stick. -- C. S. Joiner (talk) 01:45, 11 October 2006 (UTC)

• I think Ctenophores did, probabew million years earlier than any of these guys, see Chemoluminescence and Luciferase, on a side note, bioluminescent pigs, how cool is that?--71.247.125.144 14:53, 13 August 2006 (UTC)

.

Finally, I get to my question: the working it around with the glass rod had a term to describe it. Maybe it was something i love this djkgnv Thanks for your help

Aaadddaaammm 01:14, 12 August 2006 (UTC)

Perhaps agitation? I think agitation is usually used for liquids, not gummy substances, though. --Bmk 01:18, 12 August 2006 (UTC)

Sorry - didn't read carefully enough - I guess it was liquid while you were ----itating the solution. Perhaps it was agitation then. --Bmk 01:22, 12 August 2006 (UTC)

Wow thanks for the quick reply, but that's not the word... We "X"ed the liquid until it became gummy and then kept "x"ing it until it was completely solid. It was a really weird word that I've never heard before Aaadddaaammm 01:26, 12 August 2006 (UTC)

Based on your guess, could it be Trituration? Rockpocket 01:35, 12 August 2006 (UTC)

YES! Thank you! Wikipedia comes to the rescue again! I'm impressed! Aaadddaaammm 01:37, 12 August 2006 (UTC)

Well, we're not really an encyclopaedia, but a small community of smart guys, here on the Reference Desk.

Color in Complete Darkness

I clicked the random article button, as I usually do, to find new topics of interest. An article came up about how the color perceived in complete darkness is actually lighter than the color seen as black in a lit area because the brain relies partly on contrast, rather than solely on absolute color, to differentiate between objects and colors. A name was given for the color seen in complete darkness, and I should like to know what it was, but I can't figure out how to find the article. It would be greatly appreciated if an answer, or more helpfully, the actual article, could be sent to email redacted. Thank you,

Maverick —The preceding unsigned comment was added by 64.12.116.74 (talk • contribs) 01:42, 12 August 2006 (UTC)

De nuit tous les chats sont gris. (Did I get that right?) --Trovatore 01:47, 12 August 2006 (UTC)

La nuit, tous les chats sont gris. --Lambiam^Talk 06:46, 12 August 2006 (UTC)

In het donker zijn alle katjes grauw. Any more languages? DirkvdM 11:46, 13 August 2006 (UTC)

In der Nacht / bei Nacht / Nachts sind alle Katzen grau. --Lambiam^Talk 17:24, 13 August 2006 (UTC)

Even though complete darkness wouldn't have a color because color is a wavelength of the electromagnetic spectrum... yeah, I can't help you. — [Mac Davis] (talk)

Yeah. you must have light to percieve color. So there is no such thing as color in complete darkness. You may want to think a bit more about what you are asking, perhaps you mixed some facts. pschemp | talk 05:37, 12 August 2006 (UTC)

If you've forgotten the title of an article you visited recently, try looking through the history list of your browser. Could it have been Purkinje effect or scotopic vision?--Shantavira 07:01, 12 August 2006 (UTC)

Could it be eigengrau? Adambrowne666 11:53, 12 August 2006 (UTC)

Interesting. --Proficient 14:00, 12 August 2006 (UTC)

um if this is random color seen in perfect darkness due to the optic nerve firing or molecules in the cones (thus nothing is really actually seen) this statement in the article "the night sky looks darker than eigengrau because of the contrast provided by the stars." is odd since the night sky is nothing close to being in perfect darkness. Maybe the article needs some help.pschemp | talk 14:18, 12 August 2006 (UTC)

The claim is that the night sky with stars appears darker than eigengrau, not that the night sky is "perfect darkness." digfarenough (talk) 17:09, 12 August 2006 (UTC)

Eigengrau is exactly what I wass looking for, thank you. Also, for those of you who commented on complete darkness not having a color, you may notice that I asked about the color 'perceived' or 'seen' and opposed to the actual wavelength. Make sure you have _your_ facts straight and understand my question before you criticize, please.

central dogma

what are the situations where central dogma are not obeyed

Assuming you are referring to the Central dogma of molecular biology - (where DNA becomes RNA becomes protein) - then any retrovirus in the process of replicating violates this dogma. Raul654 04:51, 12 August 2006 (UTC)

Another crypsis question

Can anyone tell me the name of the creature, I think it's a spider, that has evolved to so resemble the creatures it preys on, I think it might be ants, that it is all but indistingishable from them?

Thanks, Adambrowne666 05:30, 12 August 2006 (UTC)

See our article on Ant mimicry. --Lambiam^Talk 05:43, 12 August 2006 (UTC)

Thank you, perfect. Adambrowne666 06:33, 12 August 2006 (UTC)

minto engine

i want to know more about

Uhh?--Light current 05:40, 12 August 2006 (UTC)

Do you mean the Mentos eruption? InvictaHOG 05:45, 12 August 2006 (UTC)

The user probably means the heat engine; see this reference. Could it be that this is the same device as the "Minto wheel" mentioned in MythBusters (season 2)? --Lambiam^Talk

Mother Earth News built a gigantic 20 foot high Minto Wheel in 1976. It was disappointing in that it rotated VERY slowly and had low efficiency. Perhaps better design could improve on their experience. See: http://my.voyager.net/~jrrandall/MintoWheel.html Edison 02:57, 15 August 2006 (UTC)

Follow this link for a video of a working Minto Wheel: http://www.youtube.com/watch?v=-fUlKBH1sY8

The MintoWheel Yahoo group has active discussions and an archive of information and internet links: http://tech.groups.yahoo.com/group/MintoWheel/

Drugs producing synaesthesia

Sir, could you, please, elaborate a list of drugs that produce synaesthesia with some limited additional information about them? Thanks.

I don't believe any chemicals produce true synaesthesia, which is a specific neurological condition. Some chemicals, the most well-known of which is LSD, are said to produce something akin to synaesthesia, though. Psychoactive mushrooms might produce such an effect (not sure) or perhaps peyote or other cacti, but I don't know much about those. In general though, I think it's safe to say that no chemical is going to alter your brain in such a way as to give you true synaesthesia. digfarenough (talk) 17:15, 12 August 2006 (UTC)

Thanks.

Myself and others have experienced synesthesia while under the influene of the research chemical DOC, u can find out more about it on erowid.com

Insecticides --- as Preservatives

Hello! Why do soft-drinks companies use insecticides in their products as preservative? Are there no alternatives to this? Often, it is beyond permissible limit... and regular consumption of which may lead to fatal disease. I want to know why can't this use be discarded altogether... There must be some other chemicals(i don't know though),which can replace insecticides. Or is the alternate one too expensive for the companies to use (it will definitely prevent them from making those dazzling ads.)??? Thanks,--Pupunwiki 09:00, 12 August 2006 (UTC)

unless you can produce a specific example, i'd say they don't. Xcomradex 09:40, 12 August 2006 (UTC)

This could be about the India cola thing ([8], see google news for more). There are a number of possible explanations: there is a farm within some kilometers of a cola bottling plant, and microscopic amounts of insectiside get carried around by wind. And/or local cola manufacturers have found a neat trick to kick Pepsi and Coke in the groin by spreading rumors. You'll probably eat more pesiticide in your daily bread and milk because they are produced on farms that handle pesticides. Weregerbil 12:44, 12 August 2006 (UTC)

Yes, this is concerning the India-cola thing. It's evident from here. .Looking forward for a better answer... Thanks,--Pupunwiki 13:37, 12 August 2006 (UTC)

an answer to what? he's already explained they do not add pesticides as preservatives. Xcomradex 13:43, 12 August 2006 (UTC)

Weregerbil is correct. Pesticides have been used heavily by indian farmers for a long time. As a result, there are significant levels of pesticides in ground water throughout India. Therefore, when Coca Cola and Pepsi add Indian water to their product, it contains some pesticides. You must have misread whatever you read if you think that they purposefully put pesticides in their products as "preservatives". It's a contamination issue. And by the way, you might be a bit more polite to people who have taken the time to answer your question. --Bmk 14:21, 12 August 2006 (UTC)

Sorry,I didn't mean to hurt anyone.Actually, both the print & electonic media in India have mentioned of pesticides being used as preservatives Like Dr. Ashish Tiwari of Bombay Hospital said, “These pesticides are used by the cola companies to preserve their products for a longer period as compared to other countries. "Some city medical experts believed the pesticides were in the form of preservatives that ensured a longer shelf life for the products, but this too was harmful for health they said".Though,the cola companies diagree to it.Even though, a question arises : Why can't the water used, be filtered properly during processing the products? These apart,I really want to know what are the preservatives used worldwide ? Again,if i have been rude to anyone untentionally, I apologize. Pupunwiki 18:02, 12 August 2006 (UTC)

I doubt if pesticides can be removed from water just by filtering the water. Also note that actions like the one taken by the gov of India are frequently just excuses to protect their own local industry from competition, without running afoul of WTO rules. StuRat 19:28, 12 August 2006 (UTC)

Yeah, sounds to me like it's just an excuse, like 'Yes, the pop contains pesticides, but they were put there on purpose because as a nation we don't drink our pop fast enough.'Anchoress 22:50, 12 August 2006 (UTC)

indeed, especially when one considers the mechanism of action of insecticides (eg. chlorpyrifos) and preservatives (eg. sodium benzoate) are completely different. Xcomradex 12:00, 13 August 2006 (UTC)

Though I believe that the pesticides/insecticides are not put in purposefully by the cola companies, I also believe that they were fully aware of the contamination issue and had deliberately turned a blind eye and/or did not have enough control on their bottlers. Most of the contaminants can be filtered out from water very cheaply.

Vicodin HP Tabs vs. Lorcet 10/650

ṬìňàHi, I have a pretty simple question if anyone could be of assistance. I have used search engines but haven't been able to find out anything helpful. I truly appreciate any assistance that someone would offer. My husbands' Doctor has been prescribing Lorcet 10/650 for his spinal problems for quite some time now. He has no problem with this medication as he normally only takes 1/2 tablet when his pain is difficult. He has never been one to take much medication but will;when necessary, take only 1/2 of a pill when needed. He doesn't have a high tolerance for pain meds but has been doing okay with the Lorcet. However; his last Dr. appt., he was written the exact same prescription, but upon having it filled at the pharmacy, we noticed the tablets looked different. We just assumed this was some form of generic. However; my husband was suffering with his pain a little more than usual last night and he took one (1) of the "different" tablets. It wasn't long before he began sweating, feeling nauseated, difficulty breathing, and finally vomiting. Now; I have looked at one of his prior prescription bottles vs.the new one and it does have different name. The new, white tablet has "Vicodin HP" whereas the older ones have Lorcet 10/650. It has now been quite a few hours and he still feels pretty bad. Is there anyone who could tell us what the HP stands for and what is the difference in the two? I know there has to be something different between the two and I sure do appreciate any assistance you could offer. Thanking you in advance, TH

Vicodin HP contains 10 mg of hydrocodone bitartate ("vicodin") and 660 mg of acetaminophen ("tylenol"). Judging by the numbers, Lorcet 10/650 contains the same amount of hydrocodone, but 10 mg less acetaminophen (a negligible difference if you're just taking 1 or .5 pills). So the pills are effectively the same, by my reckoning. The sweating, breathing difficulties, and vomiting are concerning and you should speak with your doctor rather soon about those. digfarenough (talk) 18:12, 12 August 2006 (UTC)

The most obvious problem is that he took double his usual dosage. I would avoid doing that again. However, even if the active ingredients are the same, there could be other diffs, like the rate at which the active ingredients are dispersed, or the inactive ingredients (which may be causing an allergic reaction). I recommend you try to get the old meds, unless they are no longer available. Your doctor or pharmacy should never change your medication without your permission, even when they claim "it's exactly the same". StuRat 19:18, 12 August 2006 (UTC)

Saving Private Ryan - white powder stuff stops bleeding

In the movie Saving Private Ryan, the squad attacks a machine gun nest. During this attack, Wade, the medic gets shot in the stomach. While the rest of the squad is trying to help him, I noticed they were ripping open packets of white powder and sprinkling it over the wound. What was that stuff? Where can I get it? I bet it would come in handy in a first aid kit. I assume it had something to do with stopping the bleeding.

I searched coagulant but didn't find anything, then looked in first aid kit, fustrated. I figured maybe someone just knows what it is.

Thanks. --69.138.61.168 21:14, 12 August 2006 (UTC)

Take a look at Sulfanilimide#History. --JWSchmidt 21:19, 12 August 2006 (UTC)

Also see styptic, if you are looking for something for your first aid kit.Tuckerekcut 22:03, 12 August 2006 (UTC)

Sodium hydroxide. — [Mac Davis] (talk)

I doubt that. --82.207.254.93 02:18, 13 August 2006 (UTC)

In the movie: sulfa antibiotic to prevent infection. To stop bleeding, a surgeon would now use something like microcrystaline collagen, but that was not available in WWII, and really is more for directed application than "sprinkling". - Nunh-huh 02:22, 13 August 2006 (UTC)

Sulfa for infection; pressure for the bleeding. B00P 21:31, 17 August 2006 (UTC)

I have read in a Vietnam War novel of troops using Hydrogen peroxide as an antiseptic. I'm not clever enough to say if this comes in a crystaline form - I used to have a bottle of the stuff for cleaning my contact lenses. Alansplodge (talk) 14:30, 8 January 2010 (UTC)

August 13

Headphones

I have been thinking about what kind of headphones I want. I want the best pair of headphones I can get for under $200. I want low impedance, I want durability, I want comfort, I want terrific sound quality. Right now I have my eye on some Sony MDR-7506'ers after dying over them a month ago. I will be listening to rock, and classical, and I will use these headphones a lot. Thanks, — [Mac Davis] (talk)

• I like Etymotic, but you're probably looking more for over-the-head models. Are you looking for noise cancelling, or will these be for home use? I've tried some Bose headphones, and the sound and noise-cancelling is phenomenal. This pair is in your price range. Deltabeignet 20:58, 13 August 2006 (UTC)

I would recommend looking where DJ equipment is found, for three reasons. A) DJs demand high volume and noise reduction, sturdiness of build, sound quality, and techno-modern appearance, and that's more variables than your average listener, or even headphone afficianado usually requires. B) There is a significant DJ community which supports a variety of high-quality brands. C) DJs generally don't have money to waste on gimmick products, so headphones marketed for DJs probably aren't as expensive as they would be if they were built with others in mind.  freshofftheufoΓΛĿЌ  11:37, 14 August 2006 (UTC)

Bigger and blacker is better

Do black men statistically have larger penes, or is it just made up? — [Mac Davis] (talk)

Have you looked at Human_penis_size#Race_and_penis_size?-gadfium 01:16, 13 August 2006 (UTC)

I once heard that the English complain more about condoms being too small. Then again, such things may be caused by either the size of the penis or the size of the brain. DirkvdM 12:02, 13 August 2006 (UTC)

Or condom companies knowing that a customer with an inflated ego is more likely to keep buying the ones that make him feel that he's "Extra Large". Confusing Manifestation 10:07, 14 August 2006 (UTC)

Libido

What hormones govern one's libido? Are each gender's totally different? — [Mac Davis] (talk)

It's mainly testosterone, in both sexes. Anchoress 01:14, 13 August 2006 (UTC)

gender and fetal development

I've just read a review (The Globe and Mail - August 12, 2006) af a new book (The Female Brain by Louann Brizendine. In the review, this statement is made: "In the beginning, actually, we are all the same: the fetal brain is female". I believe that this statement is incorrect even though I have seen it repeated often in many different sources, I'd like to know the correct answer. From conception, as I understand it, all the cells of female brains contain two Y chromosomes and all the cells of male brains contain one X and one Y chromosome? Therefore, from the moment of conception, a male brain would be male and a female brain would be female wouldn't it? When speaking of fetal development, however, perhaps it is true that in the early stages of development, male and female brains do not appear much different until testosterone (as is stated in the review) influences that development. Please give me the straight information about this or direct me to a source which will do so. Thanks.

That's probably a feminist talking. The brain really isn't "female" or "male," its just a developing brain. Woman is not the ultimate gender. — [Mac Davis] (talk)

See our sex differentiation article. The statement "the fetal brain is female" is misleading and inaccurate. It is a garbled version of pre-gene expression understanding of differentiation. The old version goes roughly like this:

• The fetal mammalian brain is undifferentiated. If exposed to testosterone from testes it becomes masculinized. Those brains not exposed to testosterone continue to develop without testosterone effect and become feminine. In a sense, there was no known difference between a brain destined to be female and a brain destined to be male before the testes start making testosterone at about the 7th week of gestation. In the late 1970s feminists made much of this, and this is the lineage of the statement you quote. However, it is certainly misleading, if not downright false, to claim that an undifferentiated 6 week fetal brain is the same as a female brain.

More recent molecular genetic research makes the statement even more ridiculously wrong, as it has now been shown that male and female brains express a number of gene activities differently even before testosterone levels rise enough to cause the differentiation described above. I would not believe anything else this author writes about biology. alteripse 02:02, 13 August 2006 (UTC)

And a point of clarification for our original questioner. You wrote, "all the cells of female brains contain two Y chromosomes", but you meant "all the cells of female brains contain two X chromosomes." (at least for humans!) - Nunh-huh 02:05, 13 August 2006 (UTC)

can this happen

can a star ever hit the earth?

No. Every star except the sun is too far away. Things like comets or meteorites can hit the earth and destroy all life forever though. Hyenaste ^(tell) 02:17, 13 August 2006 (UTC)

Ever? Take a look at this website about galactic collisions and Interacting galaxy. --JWSchmidt 02:43, 13 August 2006 (UTC)

Yes it could happen, but the chances are so small you would do a lot better to worry if your seat belt is fastened (but then again, that's true of almost every other risk, too). StuRat 03:21, 13 August 2006 (UTC)

Actually, if you want to be technical, a star can never hit the earth. The gravity of the star would pull the earth towards it, not the other way around. Emmett5 03:41, 13 August 2006 (UTC)

Unless it was a dwarf star. Hyenaste ^(tell) 03:48, 13 August 2006 (UTC)

Actually, if you want to be technical, it doesn't matter who pulls who, the Earth and the star would be hitting each other. Besides, the Earth was here first.

Where is "here"? In a universe with unknown boundaries filled with moving objects we have no fixed points of reference by which identify any one point, so identities such as "here" are completely arbitrary. Location in the cosmological context is entirely relative, so all one can really say is that two bodies — the Earth and Star X — are moving towards one another. – ClockworkSoul 07:33, 13 August 2006 (UTC)

Is this an Earth first argument?

I dont think any stars (or galaxies) are close enough to collide with the earth before it is absorbed when the sun entres the red giant stage. So no is the answer. Philc _T^E_C^I 10:29, 13 August 2006 (UTC)

You mean the ones we know of? The moment the Sun turn red giant is about 5 billion years away. Suppose a rogue star would travel at one millionth the speed of light (1000 km/h). It could then be 5 thousand lightyears away and still get here in time. At that distance it would have to be fairly sizeable for us to see it. So yes, it seems possible. DirkvdM 12:27, 13 August 2006 (UTC)

So that's the answer. When the Sun turns red giant, it will hit the Earth, but only very slowly. --Heron 12:50, 13 August 2006 (UTC)

The Sun will not absorb the Earth. So yes, it's possible that a star can hit the Earth. But the distance to even the nearest stars (besides the Sun) are huge, compared to the size of the stars, so it's extremely unlikely. --72.136.70.187 18:24, 13 August 2006 (UTC)

Sorry, my browser logged me out. --Bowlhover 18:26, 13 August 2006 (UTC)

Oh, thanks for that link, Bowlhover. I didn't realise that the Earth had an escape plan. --Heron 20:42, 13 August 2006 (UTC)

I've always liked the idea that you could sort of 'ride' a small body out of the solar system after the sun collapses, might be the only way a human being is ever going to get anywhere near another solar system, of course human beings will be lucky to last another thousand years, let alone 3.5 billion years, not to mention in about 3 billion years the Andromeda Galaxy is going to be knocking at our doorstep, and will probably wreak havoc on a galatic scale, spark massive changes in predicted orbits and so on, might give a small planetesimal on the outer edge of our solar system a chance to 'surf' the waves of gravitation right out into deep space. Of course within a few million years of the collision, the massive shifts in gravitation would begin to spark rapid star formation and collapse, and waves of radiation would probably fill the resultant galaxy, and I imagine whatever super massive black holes happened to be sitting in the center of such a galaxy would go into their active phase and start chewing up everything in sight, which gives our cold dark planetesimal another escape route. Since the outer arms of that galaxy would probably fragment and be blown off into even deeper space, and what's left of our galaxy would light up like a Quasar. And that's probably about 5 billion years right there, and there goes the neighborhood. Of course, the current Human population is about 6.534 billion, so chances are the Earth will dump us like a bad habit long before any of that stuff happens. So it really doesn't matter, but it's fun to think about.--71.247.125.144 16:40, 15 August 2006 (UTC)

If we really want to be remembered as a species, probably our best bet is to stick some recognizable feat of human civilization on as many Oort cloud objects as we can get to, maybe some sort of transmitter, or radioisotope, something to attract attention, while at the same time something that would be instantly recognized as not a natural phenomena. That way if it ever wandered into a stray galaxy some 80 or 90 billion years from now, someone might actually see it, of course that only works if by some fluke some debris from our galactic fender bender actually reaches another galaxy before the eventual heat death of the universe--71.247.125.144 16:40, 15 August 2006 (UTC)

Longest run on sentance, ever oooOooOoh--71.247.125.144 16:40, 15 August 2006 (UTC)

4G networking and application

Would someone plz tell me about the networking techniques involved in 4G mobile communication?

This question may be more appropriately posed at the Computing/IT Reference desk. --Lambiam^Talk 02:53, 13 August 2006 (UTC)

Animals with weird names

Are there any animals with weird names other than Proceratium_google, Goldenpalace.com_monkey, and Pachygnatha_zappa? Thanks! :) -Ravedave 05:57, 13 August 2006 (UTC)

Meh. It's gonna be a long list. But just cuz I don't have a date tonite, I think Homo erectus is a strange name, as are woodpecker, titmouse, and booby. Anchoress 06:00, 13 August 2006 (UTC)

axolotl - Nunh-huh 06:03, 13 August 2006 (UTC)

how about: [[9]] Adambrowne666 09:29, 13 August 2006 (UTC)

Also: atlascopcosaurus - I like your examples, though, Ravedave, I'd never heard of them Adambrowne666 09:33, 13 August 2006 (UTC)

Penis worm appeals to my inner teenager, as do bustards. I also like my boobies blue-footed. Henry^Flower 09:52, 13 August 2006 (UTC)

GoldenPalace.com Monkey: yikes, sponsored naming of a species? "This animal was brought to you by a casino?" What's next? Could you put your baby's name up for auction? Luckily my day is saved by the fact that the article speaks of 'pairs of titties' and even 'male titties'. :) DirkvdM 12:41, 13 August 2006 (UTC)

Would you care for some blue tits with your spotted dick ? (OK, that last one is more of a food, but I couldn't resist.) StuRat 08:52, 14 August 2006 (UTC)

• Just imagine what happens if they ever change their domain name--71.247.125.144 14:44, 13 August 2006 (UTC)

Does this count as weird: Stephen Nash's Titi Callicebus stephennashi? I remember reading an article about species that had been given weird names just for the humorous effect, which had quite a few examples. --Lambiam^Talk 17:39, 13 August 2006 (UTC)

Dracorex hogwartsia was named by children recently. Rmhermen 18:43, 13 August 2006 (UTC)

I think this must be the articlre mentioned above: http://www.nytimes.com/2005/02/20/weekinreview/20foun.html?ex=1266642000&en=072f74ff6a4493dd&ei=5088&partner=rssnyt I found it while googling for a mention I saw once of species names ending in tomii, dickii, and harrii, though it's not the article I was thinking of, it seems relevant. Malcolm Farmer 19:37, 13 August 2006 (UTC)

Supersaurus always struck me as funny. --Ginkgo100 ^{talk · contribs · e@} 22:10, 13 August 2006 (UTC)

Timber rattler= "Crotalus horridus horridus." Sounds like he made a bad impression on some naturalist. There is an extinct snake species named "Montypythonoides riversleighensis."Edison 17:42, 15 August 2006 (UTC)

For some reason, Scrotum humanum never really caught on. Still, as mentioned above, there are the everlasting favorites of elementary school biology, the tits and the boobies. —Ilmari Karonen (talk) 18:40, 15 August 2006 (UTC)

Anyone up for a crappie meal ? StuRat 19:37, 15 August 2006 (UTC)

I don't know why, but Felis cattus domesticus has always seems funny to me. Like they've just taken normal words and added "us"s. Aaadddaaammm 09:51, 16 August 2006 (UTC)

the doctors round mirrors

what are those round mirrors that were attached to a headband which doctors wore used for and do they have a name?

They were used for indirect laryngoscopy (before direct laryngoscopy became commonplace). Indirect laryngoscopy involved the use of a small laryngeal mirror (not unlike modern dental mirrors) that was inserted into the throat, in combination with the head mirror you speak of (used to illuminate the smaller mirror). If they had a name more specific than "head mirror", I don't know it. - - Nunh-huh 06:40, 13 August 2006 (UTC)

Just to make it a little more clear - the little mirrors that you normally see perched on their heads in pictures, when used, are swung around to cover their eye - there is a little hole in the center to see through. A light source was placed pointing at the mirror which reflected the light forward wherever they were looking (such as the mouth). Although some ENT doctors still use them, they have largely been supplanted by headlamps which perform the same purpose. InvictaHOG 00:04, 14 August 2006 (UTC)

Physics

Hello all. I'm studying for a test tomorrow, and this particular question has me stumped- i have bad notes, and the text book is even worse.

A box of mass 20 kg is dragged along a rough horizontal floor by means of a rope held at the angle of 30 degrees with the horizontal. The force of friction between the box and the floor is 50N. Uf the force exerted along the rope is 350 N, what is the net horizontal force on the box? What is the accelreation on the box?

I would like to know what formual to use, and what adjustments i would need to make. Thanks in advance.Cuban Cigar 08:53, 13 August 2006 (UTC)

• First you have to know how to how to break down the diagonal force into two forces: one would be vertical, and the other would be horizontal.
  • You can do it by trigonometry. You know one angle and the length of the diagonal of a right-angle triangle. You can calculate the horizontal using cos(30°)*350.
  • You can do it by using Pythagoras's theorem.
  • If you know that the height of an equilateral triangle is approximately (1.732/2) times the length of one of its sides, you can use that instead. An equilateral triangle has angles of 60°, so imagine one that's been cut in half. (The square root of 3 is approx. 1.732.)
• Next you have to know that two forces that act on the same object, but in opposite directions, cancel each other out. (Assuming the object doesn't spin or anything.) If the forces are in opposite directions but they don't equal each other, subtract the weaker force from the stronger force. That's the strength of the net force. The net force will be in the direction of the stronger force.
• Next you have to know that a Newton is a measure of force, which is mass (in kilograms) multiplied with acceleration (in metres per second squared).

Good luck. --Kjoonlee 09:47, 13 August 2006 (UTC)

I know some of this, but what really stumps me is the force between the object and the ground is 50N.

The friction (50 N) will counter the horizontal pull by its size of 50 N. So you should subtract it from cos(30°)*350. The results of that will be the net horizontal force acting on the box. :) --Kjoonlee 09:56, 13 August 2006 (UTC)

Well, to be honest, I *think* that's correct, but I'm not sure about the effects of friction. Will 50 N of friction really result in 50 N of horizontal force in resistance to the pull? Maybe I should read Friction. --Kjoonlee 10:02, 13 August 2006 (UTC)

Yes it will, because that's just what it means. The force of friction is by definition the force you have to overcome while dragging the object. If you exert a larger force, the object will accelerate. --Lambiam^Talk 17:50, 13 August 2006 (UTC)

50N will just be subtracted from the net force, it gives me the right answer. Thanks to everyone who helped.

How many atoms are there in a cell?

Aproximately... Thanks.

Please suitly emphazi, a human cell, an animal cell, a plant cell, a brain cell, a sex cell..... Benbread 11:06, 13 August 2006 (UTC)

A cellular tissue is composed mainly of water. Water molar mass is 18.02g/mol, which means that single molecula of water weights ${\frac {18.02g/mol}{6.02*10^{23}moleculae/mole}}=3*10^{-26}kg/molecula$.

"Typical cell mass 1 nanogram...", therefore signle cell has ${\frac {1*10^{-9}kg/cell}{3*10^{-26}kg/molecula}}=3.34*10^{16}moleculae/cell$.

Water molecula is composed of three atoms, so single cell has about $10^{17}$ atoms. Michagal 11:13, 13 August 2006 (UTC)

Thats more atoms in a cell than miles to the nearest star (not the sun) and back 250 times, and the same number as 20% of the grains of sand on the earth, or The worlds population multiplied by 2 million if random QI facts help you comprehend the magnitude of that number. Philc _T^E_C^I 11:23, 13 August 2006 (UTC)

What's with the "moleculae"? I've never heard that term before. Aaadddaaammm 09:54, 16 August 2006 (UTC)

Spaced out link

In answer to a question above, I made a link to a Dutch Wikipedia article, with a description that started with 'In', but the 'In' disappeared. Here's the format: [url|In ... bla bla]. This effect disappeared when I added a space, thus: [url| In ... bla bla]. Here are the real links (see source):

het donker zijn alle katjes grauw

In het donker zijn alle katjes grauw

Any idea what caused that? DirkvdM 11:52, 13 August 2006 (UTC)

wikisyntax? You don't put pipes (|) in external links, the link is separated from the description with a space (that's unambiguous since spaces do not appear in urls, they are rendered as '%20'). dab (ᛏ) 12:06, 13 August 2006 (UTC)

In an exolink you should not use a pipe but a space to separate the url from the text rendered:

In het donker zijn alle katjes grauw

(When you hover on your first link, you'll see that "|In" is taken to be part of the url.) Alternatively, use a wikilink like this:

In het donker zijn alle katjes grauw

--Lambiam^Talk 17:15, 13 August 2006 (UTC)

Silly me, I knew that. DirkvdM 10:16, 14 August 2006 (UTC)

Caffeine in breast milk

How long does it take for caffeine to enter breast milk after ingestion and/or how could one test for its possible impact in a breastfeeding baby? Is it possible a mother having one cup of tea could affect her baby soon after? We've googled this, but get contradictory answers. Thanks in advance. Adambrowne666 12:07, 13 August 2006 (UTC)

The half life of caffeine in humans is around 5-7 hours, but this is extended in pregnant women (18-20 hours), women on contraceptives (13 hours) and newborn babies (30 hours). caffeine is completely absorbed form the stomach within 45 minutes, and is widely distributed, which means is likely to be in breast milk. the test for caffeine in a newborn would be pretty drastic, i imagine a blood test or similar, but a test of the breast milk would be easier. i recommend reading caffeine, and talking to a doctor. Xcomradex 12:31, 13 August 2006 (UTC)

I would suggest that the mother gives up caffiene altogether (I would suggest this for most people) since like a lot of other drugs, the body becomes tolerant/dependant after a while and you receive no additional benefits from further drug use other than to achieve the same level arousal that a normal person has from day to day who does not use caffeine. --130.161.182.91 14:07, 13 August 2006 (UTC)

Why does the word 'addicted' change to tolerant/dependant when we're talking about legal drugs? DirkvdM 10:19, 14 August 2006 (UTC)

On the other hand, caffeine is used as a respiratory stimulant for newborn infants with apnea. The amount passed in breast milk is trivial and harmless. alteripse 18:21, 13 August 2006 (UTC)

Thank you! :blows kisses to alteripse:. Anchoress 20:02, 13 August 2006 (UTC)

It makes me feel all fuzzy inside when people read and/or quote text that I wrote. Thanks for making my hour! – ClockworkSoul 05:01, 14 August 2006 (UTC)

Thanks, all Adambrowne666 00:25, 15 August 2006 (UTC)

Anecdote re: speed of transfer from mother's digestive tract to her bloodstream to breast milk: a new mom went out to dinner at a restaurant and ate food containing a lot of ginger, garlic, and onion. Within an hour, she started to breast feed the baby, who was always a good feeder, but who screamed in outrage at the taste of the milk. Then tried to nurse again, baby screamed again. It was ok by the next day, but the mom kept apologizing to the baby all night. Or maybe the milk was still garlicky the next day but the baby had acquired the taste.Edison 17:56, 15 August 2006 (UTC)

Scientific Journal Access Through Wikipedia?

Is it possible for Wikipedia to subsribe to scientific journals (particularly review ones - since these aren't "original research") as an institution so that its member could improve it better? --130.161.182.91 14:03, 13 August 2006 (UTC)

• I doubt it, Journal Access is usually on the expensive side, and this is, for the most part, a non-for-profit site.. also usually Journal Access is usually authorized by either IP or passcode, since wikipedia can't provide an IP to it's users, and since a password would never remain private, I'm just not sure how it could be made to work. Besides, I have Journal Access through my university, and I assume I'm not the only one who does--71.247.125.144 14:41, 13 August 2006 (UTC)

I'm not sure how the access could be licensed to be distributed to editors, either. Would be nice though. --Ginkgo100 ^{talk · contribs · e@} 22:16, 13 August 2006 (UTC)

Note that WP:NOR only applies to people attempting to publish their own original research on Wikipedia. It's perfectly fine to cite original research that's already been published in a journal. Citing OR is good, including it is bad. —Keenan Pepper 00:55, 14 August 2006 (UTC)

If you are not already aware, there are many free full-text journals and collections of research papers avaiable on the web. A random selection of some of my collection of links about this:

http://citeseer.ist.psu.edu/

http://www.doaj.org/

http://cogprints.org/perl/search/simple

http://www.citebase.org/search

http://ideas.repec.org/search.html

http://www.publist.com/

My favourite site is Citeseer, which deals with a wide range of things. I do not know if there is a wikipedia list about free journals, but their ought to be. 81.104.12.50 21:00, 15 August 2006 (UTC)

Diesel

What products form after diesel has been burnt?

Combustion of hydrocarbons always yields carbon dioxide and water. Additives and incomplete combustion result in other products as well. Isopropyl 14:48, 13 August 2006 (UTC)

carbon dioxide, water, incomplete combustion (anything except a bright blue flame with no smoke) also leaves carbon and carbon monoxide. Philc _T^E_C^I 15:24, 13 August 2006 (UTC)

Assuming you are asking about the differences in combustion products versus gasoline engines, classic diesels engines produced a fair amount of soot, although modern diesels burn much more cleanly than their predecessors. StuRat 08:42, 14 August 2006 (UTC)

Common name for Gordionus violaceus

Does anyone know what is the common name for Gordionus violaceus?

I can't find a name for it, but if it helps, it Gordiona seem to be parasitic worms, and here is callasified as a horse hair worms. Philc _T^E_C^I 18:14, 13 August 2006 (UTC)

I doubt the species has a common name. We have an article on Nematomorpha. --Lambiam^Talk 20:36, 13 August 2006 (UTC)

Assuming that violaceus refers to the colour, you could try calling it the "Violet horse hair worm". --Lambiam^Talk 20:43, 13 August 2006 (UTC)

kineto baric force and biefeld brown question

I have heard of something called a kineto-baric force that can move things useing electric fields and produce pressure. apparently its similar to electrokinetics except it needs no conductor and can only push things i think. I dont understand physics so could someone explain it to me in simple terms. Also does anyone know if this is mainstream accepted as i can find no skeptical or sites disproving it. It doesnt seem like anti-gravity stuff though, just another method of electro-propulsion. here are the links

http://science.radioelectronics.biz/electrokinetics/electrokineticPropulsion.html

http://www.rexresearch.com/zinsser/zinsser.htm

http://jnaudin.free.fr/lifters/files/ElectrograviticsElectrokineticsValone.pdf this has a mention of its relation to electrokinetics

There is a section on this website http://www.seaspower.com/Movingbeyond-LaViolette.htm "Kineto-baric Field Propulsion. German scientist Rudolph Zinsser discovered that sawtooth electromagnetic waves could be made to push distant objects. He produced a radio tube circuit that transmitted 45 megahertz radio waves having a sharp rise and gradual fall. His experiments demonstrated that these waves could exert impulses of up to 104 to 105 dyne seconds, which is equivalent to the application of about 1 to 3 ounces of force for a period of one second. He found that this force could be generated with an amazingly low input power, the output-force–to–input-power ratio surpassing that of conventional propulsion methods by several powers of ten. His projections imply a thrust of 1350 pounds force per kilowatt."

Secondly could the biefeld brown effect move non conductive substances like plastic or stone if a means to cause the ion wind, or thrust could be produced on its surface?

Thank you for your time Robin research

"Kineto-baric force" seems to be a term unknown to physics (just did a tiny search), but this sounds rather like a more recent claim by Eugene Podkletnov. Be this as it may, if you read the talk pages at Wikipedia:WikiProject Physics-Wikipedia:WikiProject Pseudoscience you'll see that there has been quite a bit of unflattering discussion of several of the other topics discussed at some of the websites you cited. At least three of the four websites you mention can probably be safely regarded as "fringe-science"/cranky websites, as I would think should be fairly obvious:

1. rexresearch.com says that it promotes "suppressed/dormant/emerging science, inventions, technologies, experiments", which is a pretty good hint that stuff discussed there may not be mainstream :-/
2. seaspower.com says that "Space Energy Access Systems, Inc. (SEAS) is in the process of identifying and testing new technologies that claim to be over unity"; see perpetual motion machine for the meaning of "over-unity"; I hardly need add that proposals which would violate of the laws of thermodynamics are highly unlikely to belong to the canon of generally accepted mainstream science;
3. Paul LaViolette, the fellow mentioned in the page you cited, is a "UFO researcher"; Etheric stargate says that it promotes "Zodiac cryptogram and books and scientific discoveries of Paul LaViolette on interstellar communication, cosmology, mythology, ether physics," and Starburst Foundation claims "the closing of the last ice age our ancient ancestors endured one of the most lethal global catastrophes to have occurred in the course of human history."
4. jnaudin.free.fr says "Dear new explorers and experimenters, You are WELCOME in the JLN Labs web site dedicated to the search of Free-Energy solutions..."; note that "free-energy" as in "low to no-cost energy", especially alleged extraction of vacuum energy to do useful work, belongs to the "over-unity" fringe and is certainly far from the mainstream; note that this website has also promoted MEG, another putative over-unity device.

See also

1. Biefeld-Brown_effect-Reactionless drive-Lifter (ionic propulsion device)-John Hutchison-Teleforce-Free energy suppression (a conspiracy theory) and their talk pages (among others)
2. List of pseudoscientific theories#Physics
3. Crank dot (not often updated, but gives some idea of the amount of stuff which is "out there")

Summing up: it would be a serious mistake to assume that just because you can't find comments on weird topic X at a mainstream website like The National Academies (formerly the National Academy of Science), that X must be mainstream science! I would hope this commonsense principle would be obvious, but took the trouble to reply since it seems that it might not be.---CH 23:54, 14 August 2006 (UTC)

Why wet things are dark

Hi, why are they? Whenever I wet a napkin with a "clear" liquid - water - it darkens. Why on earth? Thanks! -- 88.91.136.190 18:09, 13 August 2006 (UTC)

Because water makes the lights go out, you silly. — [Mac Davis] (talk)

Assuming you have a flashlight or something ;-), probably because water refracts light, changing the frequency of reflected light? Anchoress 20:04, 13 August 2006 (UTC)

Read The Straight Dope's answer, then come back here if you need a second opinion. --Heron 20:24, 13 August 2006 (UTC)

I would like to know the Ph.D. thesis version. — [Mac Davis] (talk)

Here is a second opinion already: more light goes through (as you can see when you look through the wet cloth to a light source – the wet spots appear lighter), and therefore less is reflected. And that is because the light bounces less (not more). Third opinions, anyone? --Lambiam^Talk 20:30, 13 August 2006 (UTC)

The same thing is true of things that are wet while being opaque (e.g. wet paint), so I don't think it has anything to do with refraction. I always assumed that the chemical properties (or I guess colloidal properties) of the molecules of water that interact with the other material are less transparent to light, and thus appear darker.  freshofftheufoΓΛĿЌ  03:13, 14 August 2006 (UTC)

This was asked before, but those answers don't satisfy me. My explanation was that dry cloth scatters the reflected light because of all the tiny hairs on it. Those will get flattened (stick to the cloth) when wet, so the reflection is more directional. most of the time you will not look at the cloth in exactly that angle, so it appears darker. But I tested this and I didn't find the brighter reflection that should be there at the right angle, so I didn't dare give that answer. I'm being a little bolder this time. DirkvdM 11:30, 14 August 2006 (UTC)

This may be a stretch, but it's not completely off the wall. A lot of the color in textiles come from chemical dyes, which are subject to oxidation and reduction. Perhaps the presence of water induces a reduction reaction, dulling the dyes. Thus, when you get your cloth or paper wet, it becomes darker. This reaction is reversible, though... detergent operates by releasing an oxidizing agent to re-oxidize the dyes, hence so much commercial advertisement for "brighter colors" after washing. Nimur 16:43, 14 August 2006 (UTC)

Thanks for many, yet few answers. I do urge you to take into account the darkening of wet wood, so the thesises regarding dye can be ignored, or so I think. There was one answer here that appealed to me, the "first second" opinion. To my limited knowledge, one more easily sunburns when bathing. The question is just if that is caused from being wet, plus the limited depth of one's skin under water - or simply from the light bouncing off the water, and striking the body which is so very close. Now, whatever way one looks at this, LIGHT IS LOST. It may be absorbed by the wettened material at a greater rate than before... I really don't know the answer to this. Can Oxford be contacted? 88.91.136.190 18:07, 14 August 2006 (UTC)

Is sunburn increased when you are just wet? Or is it when you are in the water, thus getting a double-dose of UV as it gets reflected off the surfaces around you (similar to snow blindness)?  freshofftheufoΓΛĿЌ  18:46, 14 August 2006 (UTC)

I suspect that being wet makes you feel cool and thus stay in the sun longer. If dry, you would get hot and go indoors before getting sunburned. StuRat 20:48, 14 August 2006 (UTC)

Being wet doesn't make you sunburn faster. Being on or near water does, however.Anchoress 21:14, 14 August 2006 (UTC)

It's an interesting question. Also, why does a white bird feather go grey when you dip it in clear acohol? It has to do with the index of refraction of the materials that the light travels through, as well as on the arrangement of the molecules in the material, which can alter reflected or transmitted light according to the differing interfaces and the distances between them. Reflection depends on differences in index of refraction. When you change the air/material interface to a water/material interface then the difference in refractive indices decreases, so there is less scattered reflection of light. Structural colour (as opposed to pigment) effects will also alter as the diffraction of light changes, so that phenomena such as colour caused by constructive interference will change. On top of that, the light reflected from the molecules in the material has to pass throught a water/air interface back to your eye, which reflects some of it back into the material. In the end, yes, more light "stays inside" and less comes back at you, and the light that does return will have a different "wave composition" from when the material is wet. You can observe some of these physical effects if you change the "wetting agent" from say water to alcohol to colourless oil. To add to the above, pigments may change their light absorption properties when they "get wet". --Seejyb 21:40, 14 August 2006 (UTC)

The reason that you sunburn quicker in the water is because of the compression of light caused by the waves. You know when you see that moving pattern of sunlight on the bottom of a pool, where the waves compress/rarefact the light because of the shifting angles of incidence on the surface? These magnifications intensify UV and Infared light also, burning you faster. As for the paper towel, i think that in THAT case the color change is mostly due to the tiny fibers being flattened. --Classic1977 09:43, 6 September 2006

Questions about "self surgery".

Since our article is a bit devoid of the information I seek: What, exactly, are some useful methods for self surgery? Like, how to fix your own dislocated shoulder, or how to extract a foreign object from your abdomen, or how to treat an infection in the wilderness.

Actually, does Wikipedia have like...A WikiSurvival project or something similar, for questions much like this? --Abnerian 22:35, 13 August 2006 (UTC)

Any instructions that could make it easier for people to do something as blatantly hazardous as performing surgery on themselves would probably be a legal liability. But you might try googling 'wikisurvival' or something, it might exist elsewhere. And I'm sure there are lots of sites that feature survival first aid etc.Anchoress 22:38, 13 August 2006 (UTC)

One should be able to treat dislocation (medicine) without resort to surgery, but, as our article states: Such manipulation should not be attempted without sufficient training, as it is possible to greatly increase the severity of the injury through improper attempts at care. For a shoulder you will need extra training because you can't perform this in the usual way on yourself anyway. For surgery, it helps to have some insight into human anatomy. This is also true for self-surgery. Further useful stuff is some surgical instruments, including needles for sewing up afterwards (don't forget the surgical yarn), ways of sterilizing them, materials for making the neighbourhood of the incision antiseptic, materials for handling and stopping the flow of blood, and for bandaging. Roughly speaking, there are no methods that are specifically useful for self-surgery; the best methods are the same ones used for surgery in general, except that the patient must remain conscious, or else the surgeon too passes out. --Lambiam^Talk 23:37, 13 August 2006 (UTC)

For dislocation, you really need somebody else to do it for you while you scream in pain. — [Mac Davis] (talk)

Not for Jack Bauer. --mboverload@ 02:49, 14 August 2006 (UTC)

I once saw someone in a movie set his dislocated shoulder by wedging his arm between branches and then throwing his body away from that. Might work in principle, and if you're alone in a survival situation it might be worth a try because you'd be useless with a dislocated shoulder. The SAS survival handbook doesn't tell. It just says to put your foot in the patient's armpit and pull. I don't see anyone doing that to themselves. Then again, autofellatio seems to be possible, so who knows. :) DirkvdM 11:43, 14 August 2006 (UTC)

Oh, and my mother once dislocated her little toe, causing it to point sideways. The way she told this, she 'simply pushed it back'. DirkvdM 11:46, 14 August 2006 (UTC)

How to relax my over-exercised muscles without drinking alcohol?

I have ethical objections to alcohol as I've known three or four drinkers who have ruined theirs and other peoples lives because of it. Also its bad for your physical and mental health. However after taking a lot of exercise over the past few days my muscles are very tense and ache slightly. Is there anything else that I could eat or drink that would relax them please? I am not into massage. Thanks.

Maybe smoke something? It is normal, by the way, if your muscles feel tense after much exercise; it does not necessarily mean they are actually not relaxed. For some people a hot bath helps, although others report it aggrevates the condition. The best remedy is a couple of good nights of sleep. --Lambiam^Talk 23:42, 13 August 2006 (UTC)

Just rest. Sleep is probably the best, (and cheapest!). P.S.:(did I read "taking exercise" right? Do we need to have Exercise (drug)?) — [Mac Davis] (talk)

The expression 'to take exercise' is a turn of phrase common in the UK. Anchoress 00:31, 14 August 2006 (UTC)

Though I'd buy it if they sold it!  freshofftheufoΓΛĿЌ  03:01, 14 August 2006 (UTC)

Its like taking tea and scones albeit with a bit more sweat involved. Rockpocket 06:11, 14 August 2006 (UTC)

That may depend on the tea and scones. DirkvdM 11:59, 14 August 2006 (UTC)

Thanks for the alcohol-education. We didn't know that it can develop into a bad habit. But you finally got around to an actual question, so I'll give an answer to that. Meditation. What I do is lie down on bed and put a folded towel in my back (not too thick) and neck (getting that right takes practise because the sensation changes as you relax more). Then, first I tense up the muscles in my toes. Next, I very gradually let the tension move up to my ankles, legs, body, neck, and then down to my fingers, where I let it 'flow out of my body' (it actually feels like that). Then I focus on relaxing the muscles in my toes (this is a bit harder, but somehow the preparatory tensing helps) and then up again, through my body and out through my fingers. This whole process takes a minute or two. After that, my muscles are very relaxed and I can start meditating. Provided the towel in my neck doesn't feel wrong, as a result of which I have to rearrange it, which ruins the effect. The more experience you get with this, the better the effect will be. Same for the meditation itself. But that makes too much sense to point out. :) DirkvdM 11:56, 14 August 2006 (UTC)

Have you tried ibuprofen or naproxen?Tuckerekcut 21:03, 14 August 2006 (UTC)

You are most likely asking about delayed onset muscle soreness (DOMS). Incidence and severity reduced by a gradually increasing exercise regime, and by eating after exercise. Also by NSAIDs. Opioid analgesics reduce the soreness only for as long as they would work for any injury. Local rubs like methyl salicylate reduce the discomfort by couter-irritation, but recovery is not hastened. The natural course of DOMS is not reduced by massage, stretching, homeopathy, local heat or cold, or electrical stimulation. --Seejyb 22:03, 14 August 2006 (UTC)

Well answered, Seejyb. BenC7 02:15, 17 August 2006 (UTC)

Drink at least 20 oz of water after exercise; eat after exercise, especially protein, salt, and carbohydrates. Eat something like pasta with a chunks of steak on top, seasoned with salt. Use ice or a cold pack directly onto the sore muscles, followed by the high heat of a steamy shower. If you are not taking a multivitamin daily, start taking one. Do not rely on creams or expensive store bought products, this works just fine if you follow the above directions. I take Kyokushin Karate and have encountered many a sore muscle and tried many 'remidies'...the simpliest things always work, believe me. --69.138.61.168 03:51, 15 August 2006 (UTC)

Straight after exercise jump into icy water, it helps with the recovery process. Einstein's shadow 11:47, 17 August 2006 (UTC) (Copied from below by 68.100.203.44 05:45, 19 August 2006 (UTC).)

August 14

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casimir effect scale up

Can the casimer effect in theory if not practice yet be scaled up in size and effect range? could we in theory make a repulsive or attractive force from it that could act on larger objects? Is there debate on this subject or is it a flat out no. How then if not by this are scientist proposing right or wrong to produce propulsive force from vacuum energy -- Restless

No. In the Casimir effect, two very closely spaced neutrally charged parallel electrically conducting plates mutually attract because their presence changes the mode structure of the quantum zero point field (ZPF) relative to free space. If the plates are a distance d apart, the force per unit area <cool math stuff I couldn't get to work, sorry> is the reduced Planck’s constant and c is the speed of light in vacuum. The attraction between the two parallel plates can be understood in terms of the pressure of zero-point energy being greater outside the two plates, than in between—the plates snap together. This force is so so small. That is why the Casmir effect could never be scaled up—the mass of the plates would be greater, while the energy pressure continues to stay the same. ...unless you could get them closer and closer together. What would be that limit? Probably the Planck length Where is the article on the Casmir effect?? — [Mac Davis] (talk)

Try Casimir effect. --Lambiam^Talk 06:18, 14 August 2006 (UTC)

I swear I tried that, even though I thought it was spelled "Casmir." — [Mac Davis] (talk)

What if you could somehow increas the radiation pressure of the zero-point field in one area, would that be able to cause a larger version of the casimir effect? you also never aswered how people are trying to produce propulsive force from zero point energy. restless

Look up for my response to a poster inquiring about some cranky stuff he found at some websites which promote "free energy from the vacuum schemes". Basically, vacuum energy is a legitimate topic in mainstream physics, but the idea that you can use it to do useful work is highly suspect, and in particular, claims that you can use vacuum energy to build a device which would violate the laws of thermodynamics (the term used by many cranks is "over-unity") is definitely cranky.---CH 23:59, 14 August 2006 (UTC)

Hmmm for a mathemetician with with no physics degrees that i have seen in your profile CH, you fling the word crank around alot. SEAS is run by a guy called tom valone I wouldnt call that a crank myself. And hal puthoff who while controverisal in some areas is a well acknowledged expert in vacuum energy [he hosted the NASA talks on alternative energy sources in 2001] agrees with many of these ideas. Just because you dont like his ideas doesnt make him a crank. Furthermore if you look at vacuum energy on this site even it is a huge resevoir of energy, so much that it should be bending time and space. That sounds like energy that can be put to work to me so this fact is not highly suspect, if it were NASA , british aerospace project greenglow, the calphysics institute, the institute for advanced studies in austin and a number of other institutes that are looking into what is not-known [and not highly suspect as you put it] is wether or not we can work with this energy or not with the tools we have at this moment in time. You cannot dismiss this fact. Dont get me wrong i do not beleive in free energy I only beleive that with the right tools we can make the vacuum energy do certain things, perhaps a novel system of propulsion by causeing the waves to effect, or changing them into negative energy like in the casimir effect, but not free energy. Also in closeing attacking the people of these websites is a logical fallicy, you are not disproving the argument only attacking the people. I will not say anything further exept that firstly the statement above is biased, secondly the person posting has no physics qualifications. Commenter

Birthday

In honor of my birthday (august 14th) I will ask a trivia question and review anyones article of choice if they get it correct. What is the probability that someone shares the same birthday as me if I am in a room with 22 other people? -Ravedave 02:15, 14 August 2006 (UTC)

$1-\left({\frac {364}{365}}\right)^{22}$ --Bmk 02:34, 14 August 2006 (UTC)

yup thats it. Birthday Paradox. Which article Do you want reviewed? -Ravedave 02:38, 14 August 2006 (UTC)

The way you've phrased it, 100% (certainly someone somewhere shares your birthday, whether you're in a room with 22 people, or five people, or alone on the top of the Eiffel Tower). But what you probably meant (what is the likelihood that at least one of 22 randomly chosen people will be born on a given day, in this case 14 August) would give an answer more like 6%. (The probability that any one person was born on a certain date (other than 29 February) is about 1/365 or more precisely 4/1461; they are independent events so they are added, so the probability is 88/1461 = 6%). Note that what you have proposed is not the birthday paradox, which asks for the probability of two of 23 people sharing a birthday, rather than specifying the date in advance. Happy Birthday. - Nunh-huh 02:39, 14 August 2006 (UTC)

I relized that shortly after I posted it, however Birthday paradox does have the equasion dmk provided. -Ravedave 02:41, 14 August 2006 (UTC)

And if you prefer digits...0.058571325264343345847099029333104. But I like Nunh-huh's 100% answer. --Bmk 02:46, 14 August 2006 (UTC)

And happy birthday by the way. --Bmk 02:47, 14 August 2006 (UTC)

Now for a harder question: What is the probability it will be your birthday on any given day, if you attend a restaurant that gives away free birthday meals on that day (one that doesn't check ID) ? :-) StuRat 08:35, 14 August 2006 (UTC)

I'd say that won't be a constant, it will be a function of how often you visit the restaurant and how good the waiters are at remembering your face. 1/365, because we're all scrupulously honest round here, right? ;-) -- AJR | Talk 12:46, 14 August 2006 (UTC)

Bmk would probably prefer you said 1/365.2425. JackofOz 03:25, 15 August 2006 (UTC)

Unless you're born on February 30. Then it's 1/1461... TERdON 08:34, 22 August 2006 (UTC)

I think you mean Feb 29th. Our calendar never has a Feb 30. StuRat 06:46, 23 August 2006 (UTC)

No, TERdON couldn't have meant 29 Feb. That date is already included in my 365.2425 calculation. Maybe he/she was just overcompensating for the loss of Pluto as a planet. :--) JackofOz 02:18, 25 August 2006 (UTC)

Insect identification

Strange insect

I found this insect which had apparently crawled out of my lawn onto the side of the curb and emerged from its chrysalis. After a few hours it flew away. Anyone know what it is? Thanks, --Bmk 02:21, 14 August 2006 (UTC)

Some sort of Cicada apparently. Pretty interesting bugs. -Ravedave 02:29, 14 August 2006 (UTC)

Thanks! I think that's the one! The picture on the cicada page was great. Extra points to anyone who can tell me what species this one is. It was seen in upstate NY, USA. --Bmk 02:58, 14 August 2006 (UTC)

I looks like the one in the template to me which is of the genus Tibicen. I am guessing the one in your picture has light color becuase it hasnt matured. -Ravedave 04:21, 14 August 2006 (UTC)

Compare this picture. --Lambiam^Talk 06:26, 14 August 2006 (UTC)

Check out http://www.boingboing.net/2006/07/24/online_bug_identific.html for bug ID services. --Kjoonlee 10:21, 14 August 2006 (UTC)

Tibicen it appears to be! Extra points all around. Thanks folks --bmk

As a side, somewhat irrelevant note, cicadas are what makes the loud, constant buzzing noise in many forest areas. In the Florida (where I live) wilderness it is easily identified if cicadas are in proximity (which they mostly are) and an appropriate nickname for their sound would be the white noise of the wilderness. Not many people I know actually know where this sound comes from, but if they read this now they know. Also, when I traveled to Costa Rica I found gargantuan cicadas that where nearly half a foot long. Pretty amazing, huh?--Porsche997SBS 20:24, 26 August 2006 (UTC)

non-chlorine bleach

Does it clean as effectively as chlorine bleach?

Depends on what you're cleaning. I've never tried laundry, but fo whackin' out a person, no, the chlorine bleach works much better. — [Mac Davis] (talk)

What do you do when your clothes start to smell?  freshofftheufoΓΛĿЌ  11:14, 14 August 2006 (UTC)

Stop using the stuff. DirkvdM 12:06, 14 August 2006 (UTC)

Reasons for car batteries going flat?

Hi

The battery in my car keeps going flat if i don't use it for a couple of days. Yet I've had the battery tested and they say there is nothing wrong with it. Could there be another reason?

Probably your Alternator. Unless you are leaving your lights on. :) -Ravedave 04:15, 14 August 2006 (UTC)

I should probably explain more. Your Alternator is what charges your battery when you are driving. So if its not chanrging your battery then it will go dead from beign used, but not charged. Also I have heard of stuff like hood lights staying on. -Ravedave 04:24, 14 August 2006 (UTC)

If it is the alternator, and you have full gauges, the battery voltage will read a bit low. Look for that. StuRat 08:29, 14 August 2006 (UTC)

Also, you could have an intermittent short circuit. For example, I had an 83 Trans Am which had an intermittent short in the passenger power door lock, which would eventually drain the battery. StuRat 08:26, 14 August 2006 (UTC)

Is it winter where you are? Old car batteries tend to go flat if just left in the cold.

Actually, batteries last longer in the cold. However, if they do go completely dead, they can freeze and split open, and thus be destroyed, by the cold. Also, it takes more juice to start a cold car, due to the sluggish cold oil, so a poorly charged battery will become more apparent in cold weather. StuRat 19:43, 14 August 2006 (UTC)

Make sure you didn't put it in backwards! I always do that with my batteries.  freshofftheufoΓΛĿЌ  11:13, 14 August 2006 (UTC)

and if you've recently put in car electronics, you might have stuffed the wiring up so it draws current even when the ignition is off. it happens. Xcomradex 12:01, 14 August 2006 (UTC)

There have been cases where the car's key fob receiver gets repeatedly activated, either by an external radio source (case study here) or by the fob itself being left overnight near the car (can't find a ref. for this, but read it a few days ago). This keeps the car's electrical systems continually awake and quickly drains the battery. --Heron 17:34, 14 August 2006 (UTC)

Sometimes car batteries just get old and need replacing! BenC7 02:16, 15 August 2006 (UTC)

As a person who has delt with bad car batteries (and bad cars) more times than I would like to admit, there are MANY reasons your battery might go bad. A bad alternator is the most likely cause, but also there are cells inside a batter that hold about 3/4 H2SO4 and 1/4 water. If the water evaporates, the battery efficiency is severely compromised. You can rememedy this by pouring a small amount of distilled water into the cells (NOT TAP WATER, this will cause a violent reaction that will spew acid on you) of a completely cold battery. Also, sometimes the terminals become corroded, which will cause bad connections between the power cables and the terminals; a solution of 1/2 baking soda and 1/2 water will take that corrosion right off in most cases. Frequent jumping and subsuquent light driving also ruins batteries because they cannot retain a good change, and then you have to jump them again...a cycle of pain. Sometimes batties just wear out...for a good one, 5-7 years or more, a cheap one, about 2 years. Hope that helps. --69.138.61.168 03:45, 15 August 2006 (UTC)

There is a rectifier in the alternator which converts the AC current to DC, if this is defective, the alternator will run AC current through the battery which will ruin it.

Check the glove box light and the trunk light. Make sure they are not staying on.

Wouldn't adding any water to concentrated H2SO4 cause a highly exothermic reaction (generates heat) that could splash acid on you? --Shanedidona 13:00, 23 August 2006 (UTC)

Chronic cough

My 6 years old daughter has chronic cough for more than one month. (Her cough starts when she goes to bed, during night and before she wakes up.)First it started with having caught cold and treated with antibiotic but her cough continued. When she was only 5 months years old, she was hospitalized by diagnosis of "Whooping cough" for 2 months. Now is there any relation between her chronic cough and this childhood disease? Is it a symptom of other disease or as her doctor says it could be an allergy?

As usual, you might get better answers by paying a person with years of expertise, accountability, and far more information about your daughter, rather than anonymouse volunteers with unknown qualifications whom you cannot hold responsible. You don't specify some important details, but let's assume you are a middle class American mother and you daughter is basically healthy and growing well with no serious disease since pertussis in infancy. Some of the likely possibilities:

• She hasn't finished recovering from her viral respiratory infection
• She has an asthmatic cough from an environmental trigger (outdoor or indoor source)
• She has an asthmatic cough from a persistent sinusitis
• She has a habit cough (this is the typical age) or a psychogenic cough

There are many uncommon possibilities

• A foreign body in a bronchus
• Persistent gastroesophageal reflux
• Tuberculosis or rarer lung infections
• Tic or other neurologic cause
• Cystic fibrosis
• Hypersensitivity pneumonitis (e.g., histoplasmosis, or your local favorite)
• A vascular malformation in the chest
• Several types of immunodeficiency

There are many more rarer possibilities that you don't even want to know about. If she definitely had pertussis in infancy it is unlikely to recur. How certain was that diagnosis? Despite immunization?

If it isn't gone in a another couple of weeks, go see someone more knowledgeable and responsible than we are. alteripse 11:44, 14 August 2006 (UTC)

If she's had a chronic cough for more than a month, the time to see the pediatrician is NOW. StuRat 21:16, 14 August 2006 (UTC)

Another possibility, especially since you said this only happens when she lies down to sleep, is acid reflux disease. This means that the valve at the top of the stomach fails to prevent acid from entering the esophagus. During the day, gravity performs this function, but not when you lie down. StuRat 21:22, 14 August 2006 (UTC)

Oops, I see that was already listed, under the name gastroesophageal reflux. StuRat 21:24, 14 August 2006 (UTC)

Is her bed next to an outside wall? That's often the coldest part of the house, and I've sometimes had persistent nocturnal coughing for that reason. —Tamfang 07:12, 15 August 2006 (UTC)

Formula for calculating the Heating Load in KW of Convectional oven

Dear sir,

I am intrested to know that how to know the heating load in KW of convectional Heating oven if I know the Volume of Oven in Cumbic Meter and Weight of Material which has been put inside the oven and set temperature upto what time. I am also intrested to know, How Much Initial heating time effect the Heating load.

As I know the Heating Load is depend upon Set Temperature, Volume of Heating oven, Materail in side the Oven, Air Inside the oven, Thickness of Insulation, Heating up time, Ambient temperature. I am really intrested to know the optimum formula for calculating the heating load of conveyorised and batch oven.

Biggest cells, and hen's eggs?

How big is the biggest cell (animal, plant, or fungus) please? I remember as a schoolboy wondering about unfertilized hen's eggs. Now while it is extremely unlikely they are just one large cell, just how many cells do they have in them?

The largest known cell is actually the Ostrich Egg, I'm pretty amazed by that as well. PvT 10:46, 14 August 2006 (UTC)

Contrary to popular belief, and to thier names, ostrich and hen's eggs (and any other poultry eggs) are not single cells. In the yolk of the egg, there is just one single cell - that of the embryo, which divides and grows during the incubation of the egg. As for your original question, I'd say that the biggest cells would be those of some single celled organisms, such as algaes. Martinp23 12:14, 14 August 2006 (UTC)

I would have to say that some plant cells are large enough to actually see with a nude eye. I recall those are the largest known. — [Mac Davis] (talk)

Caulerpa (a green alga) are pretty big. Each plant is a single cell (albeit with multiple nuclei) and the whole organism can grow to be about 3 meters long. TenOfAllTrades(talk) 15:13, 14 August 2006 (UTC)

Looks like we have our answer!! — [Mac Davis] (talk)

It says in the Ostrich entry that the eggs are the world's largest single cells. If that is not true, then the entry needs to be changed. I'm rather sceptical as a cell that size would have tremendous problems with respiration. But if it is the case, what do the yolk and egg correspond to? If there is just one little cell in an unfertilized egg, where is it? And the sac (correct spelling I think) containing the yolk, or the membrain inside the shell, how were those made? It could have been made of specialized cells. Cells<-->eggs are still a mystery. If an Ostrich egg truely is a cell then it must be bigger in volume than the algae cell, even if its 3m long.

I thought that in an unfertilised bird's egg the yolk is one great big haploid cell, with no cell membrane between the chromosome-containing non-yolky clear cytoplasm on one side, and the rest of the yolk - a telolecithal cell which will undergo meroblastic cleavage. Is that right? Strange how difficult it is to get real hard facts on this. A fertilised egg, by the time it is laid, is multicellular (already 60000 cells), and the blastodermal cells are separated from the yolk that has no nucleus, so that does not count as a single cell. How long can a giraffe's spinal nerves be (bonus: has only one nucleus), and how big are the the neurons of giant squids? What would be the size of the (multinucleate) muscle cells of an elephant or a whale? --Seejyb 23:36, 14 August 2006 (UTC)

Electrical Engineering

My question is a very ODD one .

The question is : -

Out of AC and DC voltages which poses a repulsive shock and which an attractive shock ?

Please reply soon .

I'm not sure what you mean by a "repulsive" or "attractive" shock. They both are pretty unpleasant if the voltage is high enough, so I guess they're both pretty repulsive to me :). But seriously, I think what you may be referring to is the way that strong electric currents cause muscles to contract, resulting in a person being unable to release the source of the voltage (the actual reason is that flexors are usually stronger than extensors, so when they both contract, the flexors win). Other than that, I think you should read our article on electricity to get the basics down. --Bmk 12:54, 14 August 2006 (UTC)

I think I know what the confusion is here. In modern electric fences, they frequently turn the voltage on and off every second or so. This allows people who get zapped by them to let go, and thus survive. This is unrelated to A/C versus D/C, however. StuRat 21:10, 14 August 2006 (UTC)

Can you be more specific with your question? --Proficient 21:36, 17 August 2006 (UTC)

Neither is very attractive -- in fact both are quite shocking and repulsive! (sorry!)--Light current 05:44, 19 August 2006 (UTC)

Why the male Warbler builds unused nests?

Protonotaria citrea - (Boddaert, 1783) Prothonotary Warbler Unique Identifier: ELEMENT_GLOBAL.2.100372 Element Code: ABPBX07010

I have read :

The Prothonotary Warbler is a small songbird of the New World warbler family. It breeds in hardwood swamps in southern Canada and the eastern United States, nesting in a cavity. The male often builds several incomplete unused nests in his territory; the female builds the real nest. It winters in the West Indies, Central America and northern South America. This bird was named after officials in the Roman Catholic Church known as the protonotarii, who wore golden robes.

Most activities in the animal kingdom have a biological advantage, I was wondering if the male bird does this activity, as a method of fooling predators. ie, the predator will see the false nest and attempt to steal eggs from that nest....

Any information about this would be much appreciated.

It is an interesting division of labour. The male typically selects several potential nesting sites in advance, and "illustrates" their suitability by building a dummy nest, using moss. It's a bit like a real-estate agent dressing up a place for viewers. When a female arrives, the male shows her around, and if she is sufficiently impressed by one of these sites, she'll turn it into a real nest. As a male you always wonder: "What does woman want?" By selecting several sites, the male increases the likelihood that the female will like one of them. --Lambiam^Talk 01:10, 15 August 2006 (UTC)

This piece of 'equipment'?

I have been challenged to find out the name of this piece of equipment, I can only guess it is used somewhere in science but having looked through various lists on here of science equipment and clicking on the ones that I hadn't heard of hasn't actually got me anywhere. The piece of equipment is linked below.

http://img136.imageshack.us/my.php?image=6iu2.jpg

I'm guessing the image is probably somewhere on wiki. Thanks. ~~

Warning. The link opens a popup that crashes Konqueror. DirkvdM 12:15, 14 August 2006 (UTC)

Looks like an empty Stevenson screen. DirkvdM 12:15, 14 August 2006 (UTC)

Thanks, I found the exact image on google images when I searched it so I guess that you're right. Sorry if it crashes Konqueror, I'd only tried it on Firefox. ~~

Crashes Konqueror 3.2 on Mac OS X Tiger as well. O_o --M1ss1ontomars2k4 ^{(T | C | @)} 23:05, 23 August 2006 (UTC)

gold - precious metal

what makes gold so precious? what quality does it have that is of so much value?

1) It is scarce. That alone makes people want it. Which makes it more scarce, etc. Which is a bloody shame, because this jewellery-nonsense forces up the prices also for

2) practical implementations. It is one of a sel;ct group of chemicals that are not very reactive. In plain English, it doesn't rust. For that reason it is used for electrical connections because they are especially prone to rust, which reduces their conductivity, their very reason for existence. DirkvdM 12:24, 14 August 2006 (UTC)

Practicality aside, if you've ever held 99.9% pure gold in the sunlight, it is just so incredibly pretty! I think that's the real reason :) --Bmk 12:56, 14 August 2006 (UTC)

Because it's so non-reactive, it's one of a very few elements that are commonly found in the pure form (nuggets). This meant that it was one of the first elements to be discovered in antiquity, so people started figuring out how to make pretty things out of gold long before they did so with other things. Result: several millennia of accumlated cultural mystique. --Pyroclastic 19:10, 14 August 2006 (UTC)

Gold just has lots of practical applications in industry. For the same reason copper is actually rather valuable — a couple bucks a pound. --Cyde Weys 17:03, 14 August 2006 (UTC)

Gold is quite ductile (soft), which makes it easy to work with. It's also highly electrically conductive, which makes it good for wiring (except it costs too much for most wiring), and, as previously noted, it doesn't oxidize, like iron (to form rust), silver (to form tarnish), copper (to form that nasty green stuff), or aluminum (to form white spots). If it was plentiful enough (and thus cheap), we might even make car body panels out of it. StuRat 21:04, 14 August 2006 (UTC)

Copper is so valuable that it's being stolen frequently. Recently, a nearby school had ten classrooms flooded because thieves broke in to steal the copper pipes. User:Zoe|(talk) 02:19, 15 August 2006 (UTC)

copper is also running out, hence the price hike. Xcomradex 07:59, 15 August 2006 (UTC)

I thought i would throw in that Silver is a better room temperature conductor than gold, and that gold car panels would be impractically soft and heavy, high grade aluminum would be a more feasible corrosion-resistant choice. --66.195.232.121 13:37, 15 August 2006 (UTC)

Silver wouldn't be as good as gold for electrical use, because it tarnishes, and the silver oxide would prevent electricity from flowing across electrical contacts. Gold isn't any softer than the plastic body panels used on many cars. And aluminum gets those ugly white spots of aluminum oxide. StuRat 18:47, 15 August 2006 (UTC)

Technically silver tarnish is really Silver Sulfide, as it reacts slowly with Hydrogen Sulfide found in trace amounts in the air. Over time the black tarnish builds up.

I never thought about copper being valuable, but then you must think about the prices of some higher end heat sinks to see its value. --Proficient 21:41, 17 August 2006 (UTC)

Human Decomposition

How long do you have to wait until all that's left of a corpse is a skeleton? --Burbster 12:09, 14 August 2006 (UTC)

Longer than you'll live if it's in a bog. So if ou don't slide into the bog yourself, you'd decompose before the other body. More in general, this depends to a large degree on how much oxygen the body is exposed to. And the temperature also makes a big differnce. This was asked before, but I can't find the thread. DirkvdM 12:29, 14 August 2006 (UTC)

This depends enormously on its environment. See decomposition. --Shantavira 12:30, 14 August 2006 (UTC)

If the environment is a vat of strong acid, a few seconds. If the environment is a inter-galactic void, never. StuRat 20:59, 14 August 2006 (UTC)

Depends on the molarity of the strong acid. It might take considerably longer than a few seconds. --Amanaplanacanalpanama 21:41, 16 August 2006 (UTC)

Okay, let's say instead for three different environments: Out in the open air at moderate humditiy, in a shallow grave and in a coffin buried deep underground. --Burbster 23:32, 16 August 2006 (UTC)

You're asking purely for academic reasons? Rentwa 20:11, 26 August 2006 (UTC)

The 'save' button is teasing me

Because three questions up Konqueror crashed, I switched to Mozilla and now I notice the strange effect that when I hit the 'save page' button, the screen moves up a bit. Only when I hit it a second time does it work. Is the button teasing me? DirkvdM 12:31, 14 August 2006 (UTC)

I've had the same thing for a while now, on my Linux machine. --Zeizmic 12:36, 14 August 2006 (UTC)

Because the questioner is using Konqueror, I assume he is using KDE. I use Firefox in KDE and have no issues with the save button. --Kainaw ^(talk) 16:59, 14 August 2006 (UTC)

I have issues like this occasionally with Firefox on Windows. My only guess is that, for whatever reason, when you try to click the button it instantaneously re-renders the page such that the new location of the save button is no longer under the mouse pointer, and thus, it doesn't get clicked. This might be JavaScript-related. --Cyde Weys 17:02, 14 August 2006 (UTC)

This occasionally happens with all my Windows applications. Clicking on the scroll bar clears it for me.--Shantavira 17:31, 14 August 2006 (UTC)

I am indeed using KDE (under Suse). And it might indeed have something to do with Javascript. Between the edit frame and the options above it, there is some space. When I hit the save button, this space disappears. It might indeed re-render then. But when I hit the top of the save button, it doesn't move up enough and there is no problem (the button works). I don't have Javascript enabled for Konqueror, so that may be it. Nothing to do with the OS, the DE or the browser. DirkvdM 17:50, 14 August 2006 (UTC)

This actually has to do with your Wikipedia preferences. If you go to your preferences and the Editing tab, at the very bottom is a option saying "Prompt me when entering a blank edit summary". If you checked it, then if you enter nothing or enter /*(text)*/ in the edit summary and click save, at the top you will get a message telling you: "You have not provided an edit summary. If you click Save again, your edit will be saved without one." Only if you click save again, it will save. --Yanwen 18:14, 14 August 2006 (UTC)

No, that's not it - I don't have that checked. It is Javascript. I just disabled it and the problem is gone. DirkvdM 09:05, 15 August 2006 (UTC)

If mountains have effect on earth Consistency and stabilizing?

the earth has move (in orbit) and shake. if mountain effect it and other things similar these? —The preceding unsigned comment was added by 194.225.166.13 (talk • contribs) .

I'm not exactly sure what you're asking, but let me point out a few things that may be relevant. The overall shape of the Earth is practically a perfect sphere: the equatorial bulge is small and Mount Everest is even smaller. I don't see how mountains could have any "stabilizing" effect on earthquakes. In fact, the same tectonic activity that produced the mountains could also produce earthquakes, so I'd say earthquakes are more likely to occur in mountainous regions, not less. —Keenan Pepper 16:06, 14 August 2006 (UTC)

I think the question is if mountains cause earthquakes. The answer would then be that they are both caused by tectonic plate movement and volcanic activity.

• The plates of the Earth's crust move about (extremely slowly) and collide with each other, pushing up mountains (like the Himalaya). This causes friction, which also causes earthquakes.
• Below that crust is lava, which sometimes breaks through and causes volcanoes, another type of mountain (like the ones in Indonesia). And this also causes earthquakes.

So mountains don't really cause earthquakes, but the two have a common cause, so that's why earthquakes occur in mountainous areas. If your English isn't good enough to read these articles, you might want to have a look at the Simple English Wikipedia. It is not quite as extensive as the 'normal' Wikipedia, though. DirkvdM 18:13, 14 August 2006 (UTC)

Although I'm not quite sure what the question is, I suspect it may be related to the recent news item that the 2004 Indian Ocean earthquake had perceptibly altered GPS satellite orbits. --Lambiam^Talk 00:52, 15 August 2006 (UTC)

I think the question-asker may be referring (knowingly or unknowingly) to Milankovitch cycles rather than earthquakes. Do mountains have an effect on orbital parameters? might be what is being asked, I think - much like if you stick a blob of something to a ball it will affect how it spins. With regards to the Earth, the answer is no. If the earth was scaled down to 7 or 8 centimetres across, it would be smoother than a billiard ball. Mountains are not large enough with respect to the Earth to make any difference to its orbit, spin, precession, etc. BenC7 02:32, 15 August 2006 (UTC)

He could also be asking about isostasy. Titoxd^(?!?) 07:24, 17 August 2006 (UTC)

Instrument

http://img136.imageshack.us/my.php?image=6iu2.jpg

Could someone kindly tell me what this scientific instrument is...it looks like a beehive but i`m relatively sure it`s not.

That is a weather station, where anyone interested in measuring the weather puts instruments such as barometers and thermometers, where they are subjectedto the atmosphere but protected from the elements. Martinp23 14:40, 14 August 2006 (UTC)

Are you the same person? We just had this question a few hours ago. The answer is Stevenson screen. — [Mac Davis] (talk)

artificial insemination

Can all animals be inseminated artificially?

Yes. Its really the phallus that is artificial, not the semen. I guess the insemination is artificial. Anyway, it doesn't matter if there was copulation involved, the sperm just has to get to the egg. — [Mac Davis] (talk)

Technically, some animals, such as Cnemidophorus lizards, cannot be artificially inseminated, because they don't reproduce sexually. See Parthenogenesis. —Keenan Pepper 16:09, 14 August 2006 (UTC)

Well, you need more than the sperm and the egg. You also need a womb (if you want a baby to come out of it, that is). So you indeed have to enter something in a female, be it a fertilised egg, as it is done with humans, or with a functional dildo, so to say. I can imagine that with some animals that would be problematic, like very small animals (without killing them, which would defeat the purpose). Or with very big ones. Try inseminating a whale (a sperm whale of course :) ). DirkvdM 18:26, 14 August 2006 (UTC)

It might be very difficult for microscopic animals. I wonder if anyone does this for any reason. Also remember that creatures such as sponges and corals are animals. Maybe they could be "artifically inseminated", but it would be much different that the process for a horse or a pig. ike9898 19:49, 14 August 2006 (UTC)

There may be a technical problem for Diplozoon paradoxum. For an illustration of the fused animals, see da:Dobbeltdyr (Diplozoon paradoxum) or the middle of the bottom line of the image at Flatworm. --Lambiam^Talk 00:35, 15 August 2006 (UTC)

Many animals fertilize externally, in which situation this question is a non sequitur. --Ginkgo100 ^{talk · contribs · e@} 03:46, 15 August 2006 (UTC)

Maximum velocity of a sailing ship

Can a ship powered only by sail exceed the wind velocity? If so, what is the maximum speed it can reach relative to the wind velocity? --Cyde Weys 16:59, 14 August 2006 (UTC)

If the water current exceeds the wind velocity then the ship can lower its sails and go as fast as the water current. -- C. S. Joiner (talk) 17:25, 14 August 2006 (UTC)

And a more serious answer can be found here: "the motion of the boat creates its own apparent wind, which combines the windspeed vector and the hull speed vector. Sailing into the wind, this can quickly add up to apparent winds of far greater than the true windspeed" -- C. S. Joiner (talk) 17:37, 14 August 2006 (UTC)

Per Csjoiner, yes—modern racing hulls are efficient enough to exceed the wind speed when on a broad or beam reach. (Most sail boats are fastest on a beam reach, though may not be able to exceed the wind's speed.) Ice boats, because they travel on a very low friction surface, can usually easily exceed the wind's speed when reaching. TenOfAllTrades(talk) 17:44, 14 August 2006 (UTC)

The reason for this is that the boat is (at least when on a beam reach or closer to the wind) not mainly powered by the direct force of the wind on the sail. It is driven by the bernoulli effect of the wind blowing across the wing-like shape of the filled sail, and thus is not limited by the velocity of the wind. --198.125.178.207 18:25, 14 August 2006 (UTC)

Hold on. Sailing into the wind? That won't get you anywhere, or do I get the English sailing terms wrong? (If not, the article needs correcting.) But even sailing upwind (at an angle of up to about 45° to the wind) isn't very fast - it just feels very fast. Sailing downwind is a lot faster and quieter. But that way you just get pushed by the wind and you miss out on the wing-effect. Indeed, broad or beam reach (getting the wind from the side) is fastest. That way you can indeed exceed the speed of the wind. Which sounds counterintuitive, but so does the ability to sail upwind (close hauled). Both are possible thanks to the wing-effect.

By the way, if things go just right, the bough can be lifted on to of the bough wave. This has happened to me once (in a Valk or 'falcon' - I thought we had an article on that) and it's a wonderful feeling, like you're flying. What is this called and is this an indication one is exceeding the wind speed?

About the Points of sail article, I disagree with calling running downwind a 'don't go zone'. Getting 'gull wing' right is one of the nicer moments of sailing. DirkvdM 18:45, 14 August 2006 (UTC)

"Sailing into the wind" is indeed a not uncommon (but potentially confusing) way of expressing "sailing upwind". You also hear "sailing against the wind" (which makes me wonder who was the winner), possibly influenced by German gegen den Wind segeln or similar expressions in other Germanic languages. --Lambiam^Talk 00:21, 15 August 2006 (UTC)

Sodium azide interferes with SDS-PAGE?

If you have experience with SDS-PAGE, have you ever had a problem with having too much sodium azide in your samples? Would you suspect this would interfere at high concentrations? ike9898 19:10, 14 August 2006 (UTC)

• What is the nature of your problem, and what concentration of azide are you using? I can say, however, that I regularly use azide in my peptide samples to prevent bacterial contamination, and I've never had any problem with them (none, at least, that I traced to the presence of azide). – ClockworkSoul 21:33, 14 August 2006 (UTC)

Formatting an External Harddrive

I have an external USB hard drive. It is currently in NTFS, but I want to format it in FAT32 so that I can use it with my Linux dual boot. Windows XP doesn't let you format it into anything but NTFS and I'm a Linux noob running Ubuntu. I tried GParted, but it doesn't seem to be able to manage externals. Any help? --Russoc4 20:18, 14 August 2006 (UTC)

This is probably a better question for the Computing Reference Desk -- C. S. Joiner (talk) 20:23, 14 August 2006 (UTC)

Oh dear. I didn't realize they made one! Thanks for your help. --Russoc4 20:25, 14 August 2006 (UTC)

Give it to one of your friends that runs a Mac, it only takes a few clicks. — [Mac Davis] (talk)

In the command prompt 'format [drive letter]: /FS:FAT32'

P = I*V

And now for a completly unrelated question to the one above...

I know that Power in Watts = Current * Voltage. I know that current is the flow of electrons and voltage is the potential energy to push the electrons, , but I'm not sure what that means in practice. Lets say you have a 100W lightbulb. Is there any different in powering it with 20 amps and 5 volts compared to 2 amps and 50 volts? How about for a DC motor? What role do each current and voltage play when powering a motor? I've been wondering about this for a while, but I keep forgetting to ask it.--Russoc4 20:25, 14 August 2006 (UTC)

One quick response--while 20A*5V = 2A*50V in power output, they would work differently based on the limitations of real world material. 20 amps is a lot to send through wires.

It may also help, when thinking about this topic, to remember V = I*R, therefore, P = I²*R, which might make more intuitive sense when thinking about the "roles" of current-voltage-resistance in motor power. -- Scientizzle 21:00, 14 August 2006 (UTC)

One difference between powering a 100 W light bulb with 5 V 20 A or 50 V 2 A is that you would have to use different bulbs. Another difference is that the low voltage case would need power supply wires that have more copper in them, but could get away with less insulation. Since insulation is generally cheaper than copper, higher voltages are generally preferred. In the case of electric motors, the windings for a high voltage motor will have comparatively many turns of thin wire, while the low voltage motor will have fewer turns of thick wire. --Gerry Ashton 23:13, 14 August 2006 (UTC)

Nowadays bulbs may say "100W" while they have much lower wattage but equivalent luminosity, an unfortunate development. Let's assume it is a "true" 100W bulb, which has been designed for use at 120V. Then the current going through will be 100W/120V = 0.833A. It's resistance, using Ohm's Law, is then 120V/0.833A = 144Ω. The latter is an actual physical characteristic of the lamp, independent of the voltage applied. If instead of 120V we apply 60V, we get a current of 60V/144Ω = 0.417A, and a power of 0.417A × 60V = 25W, only a quarter of what it says on the bulb. Likewise, if we apply 240V, we get a power consumption of 400W in the split second before the filament melts. The point is that the wattage listed is not an invariant physical characteristic, but only applies within the design parameters. --Lambiam^Talk 23:48, 14 August 2006 (UTC)

In many real materials, resistance is a function of temperature. So the 144Ω figure may only apply at the temperature which the filament reaches in operation at that voltage. So it's even more design-specific than you suggest. In general, a bulb will have an output $O(T)$ (e.g., blackbody radiation) and a resistance $R(T)$. At equilibrium, $P=V^{2}/R=O$, or $V^{2}=O(T)R(T)$. Since output tends to increase very rapidly with temperature, even if $dR/dT<0$ we expect to find a balance. (In fact, resistance tends to increase with temperature due to increased disorder within the material.) Of course, even this is a simplification since in reality there will be temperature variations (and thus resistivity variations) within the wire and the current may create complex patterns that are harder to analyze. The important bit with respect to the initial question is that for most things as simple as light bulbs, once you pick the voltage the current is determined, so you can't just "go to" half the voltage and twice the current and "see what happens". Hope this helps. --Tardis 06:49, 15 August 2006 (UTC)

Well, all these answers do help put it into perspective. thanks. --Russoc4 15:38, 15 August 2006 (UTC)

Don't fall into the trap of thinking that P=I*V is true for AC. It is strictly true only for DC. For AC, it is true only for a load which is purely resistive. A resistive load could be a heater or an incandescent light bulb. Any load which is reactive, containing net inductance or capacitance, will consume power less than I*V. High voltage power lines (such as 345 kv) are likely to be capacitive (combination of resistance and capacitance) and the current will lead the voltage. Residential loads, with motors and air conditioners, are likely to be inductive combination of resistance and inductance. In an inductive load the current waveform will lag behind the voltage waveform. The electric meter on your house bills for energy used in kilowatt hours; the reactive current is basically free. Commercial and industrial customers are billed if their power factor is too reactive. The reactive current is termed VARs for "volt-amps reactive" and the power company hates them, since they heat up transformers and distribution lines just like revenue-producing watts. They install capacitor banks to improve the power factor towards unity (neither inductive nor capacitative). Edison 16:51, 15 August 2006 (UTC)

G2B2... what does it mean?

Trying to figure out what G2B2 means in a medical context, as an adjective applied to a woman, or as a status associated with a woman. --MattShepherd 20:37, 14 August 2006 (UTC)

Perhaps if you provided the specific context in which you heard this term it would be easier for us to figure out what it means. Was it on a lab sheet? ...in a text book? Did you overhear it? Tuckerekcut 20:46, 14 August 2006 (UTC)

Asked in passing by a translator friend, who didn't give me much else to go on. I'll figure it out. --MattShepherd 20:55, 14 August 2006 (UTC)

Did you mean G2P2? It is shorthand for an obstetrical history. "G" (for gravida) refers to the number of pregnancies. "P" (for para) refers to the number of live births. Some include an "A" or "SA" for abortions/miscarriages. G2P1 means 2 pregnancies, 1 delivery (and currently pregnant with the second). G1P2 means 1 pregnancy with a set of twins delivered. - Cybergoth 21:30, 14 August 2006 (UTC)

It might refer to a GABA A receptor structure: a γ2 and a β2 subunit. --Lambiam^Talk 23:30, 14 August 2006 (UTC)

The way you describe the circumstance in which the term is used would indicate the pregnancy related meaning. "G" does refer to the number of times the woman has fallen pregnant. As noted, the second letter is a capital "P", but these days a somewhat complicated four-digit "code" follows it. The first digit after the P indicates the number of full-term pregnancies (those that lasted > 37 weeks), the second, the number of pregnancies where a premature baby was born (20-37 weeks' pregnancy), the third, the number of pregnancies ending before 20 weeks (spontaneous or induced abortion), and the fourth indicates the number of children living at present. An example would be "G5 P3115", analysed as: G5 = times pregnant, P3xxx = 3 times full-term pregnancies, Px1xx = 1 premature delivery, Pxx1x = 1 miscarriage before 20 weeks, and Pxxx5 = 5 living children. Note that this does not indicate in what sort of combination(s) the 5 living children come from, all one can say is that out of 5 pregnancies, 4 lasted to a viable gestational age. They could all have been twin pregnancies, with three kids having died, one from prematurity, one poisoned by her husband, and one in battle. The coding does not allow for indicating twins, triplets, and such. Note also that if the first three numbers following the P add up to 1 less than the G, then it indicates that the woman is presently pregnant. --Seejyb 01:04, 15 August 2006 (UTC)

broken neon

Do broken neon tubes release a dangerous amount of mercury vapor? I was in a convenience that had a broken neon sign and I'm wondering if I should bother with going to the doctor. KeeganB

According to neon sign, only some neon signs use mercury and it's a drop of it at that. Spread out to an entire convenience store, it's probably fine. AEuSoes1 21:05, 14 August 2006 (UTC)

And since it is elemental mercury in the sign, instead of a vapor, you are in less danger of mercury poisoning than if it were methylmercury or similar. Hyenaste ^(tell) 23:43, 14 August 2006 (UTC)

Doesn't elemental mercury produce a poisonous vapor? Anyway, I forgot to point out that the duplicates of this sign produced blue light, which it caused by mercury. KeeganB

I wouldn't worry to much about your mercury exposure. I myself have come into contact with a solution which contained a small amount of the mercury salt mercury(II)chloride without even knowing what it was till much later. As far as I know elemental mercury is actually quite safe compared to its salts. Seeing how very little is in the tube to begin with I wouldn't think that you have anything to worry about at all short term or long term. PvT 12:36, 15 August 2006 (UTC)

I don't have a scientific basis for questioning that mercury is every bit as deadly as its present reputation. The term "mad as a hatter" is supposed to refer to recognition centuries ago that exposure to mercury caused brain damage. But a few decades ago everyone in chemistry class got to roll some of it around in the palm of his hand and it felt really cool. It would also coat a penny and make it look like a dime. In the late 19th century, gold miners would make up snowball-like wads of gold ore and mercury with their bare hands to extract the precious metal. Electrical experimenters used it all the time for low resistance low friction contact points is circuits. Mr. Wizard on TV kid science shows used mercury many times this way, as for a "jumping spring." 19th century photographers used it to make Daguerrotypes. It was in fever thermometers, which many a child bit through and got mercury in the mouth. It is in the silver amalgam fillings which have been in the mouths of many millions of Americans for many decades. For these reasons, I have to feel a little skepticism about the deadly peril of the vapor from a drop of spilled mercury. Edison 17:05, 15 August 2006 (UTC)

• You're right on the first point, you don't have the "scientific basis" for understanding the difference between mercuric nitrate, dimethylmercury, methylmercury, and mercury the element. If I were to follow the reasoning you have just outlined, I would have to conclude that the toxicity of chlorine gas is a myth, after all, people consume sodium chloride all the time, and don't do anything other than raise their blood prease, therefore chlorine isn't really toxic, that's just media hype, bah, brain hurt.--71.247.125.144 03:05, 17 August 2006 (UTC)

Mercury is what is known as a heavy metal poison. What is dangerous about it is it bioaccumulates. This means any taken in to the body is not eliminated very quickly, so if you are exposed to it as a very young child most of it will still be in you when you are very old. Other poisons, like cyanide, will allow you to recover from a less than fatal dose as the poison will be eliminated after a time, a few days maybe. Poisons which bioaccumulate won't do that. Sicne Mercury is a liquid, it has a higher vapor pressure than solids so you can inhale enough to be significant. The amount in a neon tube is not very much, you would have to hang around the convenience store a long time (weeks) with a neon tube breaking nearly every day to have a chance of having problems.

Mammals and body temperature

Could someone explain why, say, my cat has a different body temperature than myself, even though we share a great deal of temperature-sensitive biochemistry? Peter Grey 23:29, 14 August 2006 (UTC)

Seriously, doesn't it seem odd that mammals have so many genes in common, and these genes govern chemical reactions highly sensitive to temperature, and yet different species have different normal body temperatures? Peter Grey 18:14, 19 August 2006 (UTC)

digression:individual temperature

Try reading body temperature, particularly the section on variations in body temperature between different mammals. That should give you a start. :-) Anchoress 00:36, 15 August 2006 (UTC)

Thermoregulation discusses temperature variation for an individual, not variations across species. Peter Grey 02:22, 15 August 2006 (UTC)

On a related subject, I remember seeing a chart purporting to show how you can read the temperature in a room from the posture of a resting cat. Wish I could find that again! —Tamfang 06:53, 15 August 2006 (UTC)

They also find the warmest and coolest location in the house. I once found my cat sleeping in the bathroom sink. I thought it's little walnut brain had blown a fuse until I realized the ceramic sink was connected to thick metal pipes filled with cool water, and probably stayed cool all day long. StuRat 07:41, 15 August 2006 (UTC)

Mushroom clouds

Was the Trinity test the first instance in which the iconic mushroom cloud seared its image into humanity's collective consciousness, or did scientists even before the first nuclear explosion have an idea of what the resultant cloud would look like? --Cyde Weys 23:34, 14 August 2006 (UTC)

Read our article Mushroom cloud; it suggests that they should have known the answer if they asked the question. Probably they were smart enough to figure it out anyway without experimental evidence. I don't remember reading anywhere that they actually wondered or speculated about this aspect, although it appears unlikely to me that they wouldn't have. --Lambiam^Talk 00:03, 15 August 2006 (UTC)

Note that much smaller conventional explosions also produce mushroom clouds, so people would have known about them long ago. I would even think, under the right circumstances, that a volcano could produce a mushroom cloud. StuRat 00:33, 15 August 2006 (UTC)

Yeah, I've had the experience of seeing an explosion complete with a mushroom cloud less than a mile away. — [Mac Davis] (talk)

Somebody lit a match near the Porta-potties after the chili bake off ? StuRat 07:34, 15 August 2006 (UTC)

Image-google 'volcano "mushroom cloud"' for some nice examples. DirkvdM 09:15, 15 August 2006 (UTC)

Before the Trinity explosion, they did a trial run with 100 tons of TNT to get an idea of what a large explosion would do, and how the radioactive fallout would behave. That explosion also generated a mushroom cloud. --Serie 22:46, 15 August 2006 (UTC)

Orphaned comment

I'm not sure where this belongs, because it was added to the Science Ref desk after this date had been transcluded:

Straight after exercise jump into icy water, it helps with the recovery process. Einstein's shadow 11:47, 17 August 2006 (UTC)

August 15

the direction of the Earth's orbit

The Earth follows a path around the Sun. Given that the globe is spinning, how would one describe or calculate the direction of its orbit in terms of planetary coordinates?

Or, to put it another way: imagine an axis through the Earth which always points in the direction of the planet's orbit around the Sun. Would the points this axis describes on the surface of the Earth form a meaningful pattern, and how would it be described? --Halcatalyst 02:13, 15 August 2006 (UTC)

I think I understand what you are asking. You would need to realize that the Earth's orbit isn't "pointing" in one direction, like a curved line with an arrow on the end. You need to think in terms of Vectors. One vector points in a straight line out into space, based on the direction the earth is going at that specific moment (inertia). The other vector points in a straight line towards the sun, representing the acceleration of the earth towards the sun (gravity). When you combine the effect of these two vectors, the earth follows a circular path around the sun. BenC7 02:45, 15 August 2006 (UTC)

Yes. I'm interested in the vector of inertia, and the pattern it would trace on the Earth's surface over time. --Halcatalyst 02:57, 15 August 2006 (UTC)

If we're talking about the velocity vector of the earth here, during a single rotation, it doesn't change significantly in the solar coordinate system, so as the earth rotates on it's 23.5 degree-tilt axis, it will trace out a circumference of the earth. Because the earth keeps its axial orientation (in the solar frame) over the course of a year, the circle will slowly rotate on the earth's surface (at the equinoxes it will trace along the equator, at the solstices, it will trace a "perpendicular" circumference), and the trace will wander around between the + and - 23.5 degrees latitude. Over a long time, it will travel through every point (approximately) between the latitudes +23.5 and -23.5 degrees. Actually, I don't know - does anyone know if the earth's rotation is in any kind of resonance with its orbit around the sun? If so, it will only have a limited "rosetta" pattern on the earth's surface, rather than hitting every point. --Bmk 03:24, 15 August 2006 (UTC)

Good point, but the slowing of the rotation (from something like 22 hours in the dinosaur age?) implies that there is no resonance. So, yeah, the curve is space-filling. —Tamfang 06:48, 15 August 2006 (UTC)

I guess so, unless the earth's orbit is slowing down to match? I don't know. --Bmk 16:08, 15 August 2006 (UTC)

Since nothing is working on our orbit in the way that tidal friction works on our rotation, it is believed that the length of the year can be changing only if the gravitational constant is changing, as some theories suggest, but consensus says that's not happening either. —Tamfang 06:42, 16 August 2006 (UTC)

Actually, according to general relativity, orbiting bodies give off gravitational radiation, which does slow the orbit. In GR, there are no stable orbits! Also, there is the effect of interplanetary gas dragging on the planet. Of course, both of these effects are extremely small, and they probably have a negligible effect, but nonetheless, they exist. --Bmk 17:44, 16 August 2006 (UTC)

• Thanks for a good discussion! --Halcatalyst 20:02, 17 August 2006 (UTC)

See analemma. B00P 21:11, 17 August 2006 (UTC)

Warm vs cold blooded

Hi

My question is about energy use in cold blooded animals vs warm blooded animals. I have written;

"A lucky 70 kg snake might find a 15 kg pig to eat. This would provide
it with enough energy for about three months of living, give or take. 
If you or I, on the other hand, ate 15 kg of bacon, this would sustain 
us for a bit more than a week."

Do these numbers seem reasonable? What numbers would you use?

Thanks very much for your help

Aaadddaaammm 03:18, 15 August 2006 (UTC)

It sounds erroneous to me. The normal number is 2000 kcal/day, or of course 14000 per week. 15000 grams of bacon would then have to have less than one (dietary) calorie per gram... and as can be seen on most nutrition labels (at least in the US), protein has 4 and fat 9 calories/gram. Maybe if, somehow, 80%-90% of bacon was indigestible, this would work out; otherwise it's off by quite a bit. --Tardis 06:53, 15 August 2006 (UTC)

I don't know about you, but if I ate 15 kg of bacon I would feel very, very sick and would wish that I would die. --Lambiam^Talk 09:11, 15 August 2006 (UTC)

Yeah, we can't eat 15 kg of meat at once. Maybe 1 kg a day would be quite reasonable sustinance. - Rainwarrior 19:20, 17 August 2006 (UTC)

Brain in computer

Is it possible to use a brain as a computer hardware? If yes, is it currently researched?

Impossible. Will be for a long while. — [Mac Davis] (talk)

In principle any nontrivial information-processing device can emulate any other (given enough storage), but the structure of an organic brain is so different from that of a digital computer that it's hard to imagine circumstances in which anyone but an extremely mad scientist would ever try it. —Tamfang 06:46, 15 August 2006 (UTC)

I find the reverse to be much more interesting, a human brain that could instantly access info from a computer. For example, think about what could be accomplished by combining the creativity of the human brain with all the misinformation in Wikipedia ! StuRat 07:28, 15 August 2006 (UTC)

That's not a terrible idea, but it wouldn't really be all that interesting, you wouldn't really be connected, you'd just be using your mind to do the equivalent of clicking a mouse, I imagine it would work a bit like Hawking's blink control. Wouldn't have to be much more sophisticated than a Cochlear implant. Of course the only thing that would do is turn your brain into a glorified tracking ball, which might just cut down on the instances of carpal tunnel syndrome--71.247.125.144 16:05, 15 August 2006 (UTC)

I picture something far more ambitious, many years from now, where you would think of a question ("What's the capital of Sri Lanka ?"), and instantly know the answer, much like AskJeeves worked, when it worked. On the other hand, if it doesn't work, maybe you would instantly see a Columbo movie, LOL. StuRat 19:06, 15 August 2006 (UTC)

Some kinds of information could be expressed as new senses, e.g. you might feel the state of your bank account as you feel that of your stomach. Me, I'm hoping for a four-dimensional virtual eye. —Tamfang 01:46, 18 August 2006 (UTC)

No, because it would be wetware. --Lambiam^Talk 08:52, 15 August 2006 (UTC)

A brain in a computer or a computer in a brain - both come down to the same problem of useful information exchange. 'Reading' a brain is very crude at the moment. And 'writing', afaik, hasn't gone beyond giving a stimulus to a part of the brain to elicit a response of some muscle. Also very crude. That is getting info out of (or into) a brain, next is making sense of it. So far, all we can say is that 'there is some activity' in some part of the brain when certain functions are performed. We first need to understand the brain, and we're not quite there yet.

Scientists currently have an implant into the visual cortex which allows the blind to "see" with a grid of points. It's a very small grid right now, so only allows them to see if a person is in front of them, not actually identify the person, but this could be improved to the point where complete images of either the real world or a computer generated world could be supplied to the brain. StuRat 19:01, 15 August 2006 (UTC)

However, if this were possible, it would open up a path to one of the most desired things, namely eternal life. The machine and the brain would merge. The sum of the two would hold the personality. But the machine can expand indefinitely (in principle) and live forever (and be easily repaired and such). So if the brain would die, that would be like a minor stroke and we would live on inside a computer happily ever after. Also, since we could then interconnect, we would merge more and more and eventually all become one. Cool! Or boring? DirkvdM 09:31, 15 August 2006 (UTC)

Presumably non-mad scientists are working on it. Check out [10]. 130.188.8.13 13:02, 15 August 2006 (UTC)

Souls in the Great Machine by Sean McMullen. Yup, using brains as computer hardware.Ohanian 13:34, 15 August 2006 (UTC)

So it's not possible for the time being but maybe in 100 years? Thank for the fast reply.

100 years seems too short...how about 1000 years? --Bowlhover 01:42, 16 August 2006 (UTC)

"The machine and the brain would merge. The sum of the two would hold the personality." That supposes that one's personality resides in the brain. I will grant that one's intellect is most likely in the brain, but personality encompasses far more than intellect. Emotion, physiology, one's soul and countless other factors make up a personality. Does anyone know exactly where these qualities exist? Can anyone know? Do they even exist in a physical place at all, or are they trans-physical? I believe merging a computer and a brain might preserve a person's knowledge, but the actual person would not be merged. — Michael J 18:07, 19 August 2006 (UTC)

electric shock abdominator

Oh, does anyone know about those late nite TV ads for those 'abdominator' style muscle toners that you wear like a cummerbund and it gives you electric shocks to induce muscle twitch and supposedly then get you in shape from all the 'exercise' youve been doing? What is that device called?—Preceding unsigned comment added by 211.26.193.93 (talk • contribs)

I hope you're not interested in buying one. They are utterly useless. --mboverload@ 07:01, 15 August 2006 (UTC)

There's also one that shocks your face to exercise facial muscles. Sounds dangerous to me. And if you find it difficult to exercise now, just wait until it requires repeated electrical shocks. StuRat 07:16, 15 August 2006 (UTC)

A mobile version could chase you around and you'd be running for your life - plenty exercise. So once again, StuRat, don't knock it until you've thought it through. :) DirkvdM 09:36, 15 August 2006 (UTC)

But what is it called folks? The closest I can find (if it's not an abdomenizer) is a microcurrent electrical neuromuscular stimulator.--Shantavira 12:33, 15 August 2006 (UTC)

How do plants defend themselves from microbes?

Since plants don't have a circulation system, what methods do plants employ to defend themselves from microbes? Thanks. --Demonesque 07:08, 15 August 2006 (UTC)

for starters, Phytoalexin. and don't forget plants do have Xylem. Xcomradex 08:03, 15 August 2006 (UTC)

And several plants produce pheromones that alert their neighbours they may come under attack. --Lambiam^Talk 08:49, 15 August 2006 (UTC)

And some plants have proteases. Eg. pawpaw has something like 50% dry w/w papain which is thought to be a defence mechanism against microbes and burrowing insects. Aaadddaaammm 09:23, 15 August 2006 (UTC)

Here's the latest on woad [11] Woad really produces this chemical if you scrunch up some leaves. Perhaps grazing animals and insects don't like blue tongues? --Zeizmic 12:33, 15 August 2006 (UTC)

One defense mechanism is cell death. They kill the cells arounf the microbe and stop it spreading. This results in little spots all over the leaf. The official term is Hypersensitive response [12]. David D. (Talk) 18:30, 15 August 2006 (UTC)

Not exactly answering the question, but plants are often in close proximity to fungi in the soil, some of which have antibiotic properties, which creates a somewhat safer environment for the plants.B00P 21:18, 17 August 2006 (UTC)

Gravity

If the Sun was to suddenly disappear, light would take so many minutes to reach earth, but would the gravity take affect at the exact time or at the speed of light or slower. I guess what i'm asking is what speed dose gravity travel at?

Gravity travels at exactly the speed of light. See General Relativity.

Please don't make your answer too hasty. We don't really know. — [Mac Davis] (talk)

Well, general relativity and string theory both say it travels at exactly the speed of light. If fact I don't think there are any theories of quantum gravity that say anything different and the only theory that does say something different it Newtonian gravity.

Well we know it doesn't travel instantaneously and it does seem to travel at around the speed of light. --Cyde Weys 18:19, 15 August 2006 (UTC)

Remember to sign your posts, people! And I can't remember what it the answer was, but i think this has been asked before - check through the archives - i think the title was "speed of gravity". Aaadddaaammm 09:26, 15 August 2006 (UTC)

Here it is. DirkvdM 09:39, 15 August 2006 (UTC)

Also, see Gravitational Radiation. --Bmk 16:14, 15 August 2006 (UTC)

You also have to take into account the cause and effect of this sudden disappearance. It is difficult to see how this could happen without an accompanying explosion so big that it would render your question irrelevant. (In other words, hypothetical questions are almost impossible to answer without a lot more detail of various other factors. And even then...)--Shantavira 17:18, 15 August 2006 (UTC)

The question is, is it possible for the sun to leave faster than the speed of light? I am not expert but I do not know if that scenerio can even happen under the current model of the universe. HighInBC 21:39, 27 August 2006 (UTC)

Bibliography on Wikipedia

I am writing a scientific literature overview in the subfield of AI and will have a compilation of several hundred article titles available, sorted by year of publication/alphabetically. It is often a serious problem to find references to all the work that has been done in a specific scientific field and I think that a list of scientific papers published on a particular topic would be very useful to the scientific community. Authors could add references to their own papers once published etc. and people could contribute missing information, e.g., sometimes the title of the article/paper is known but it is impossible to find out where it has been published or whether it is publicly accessible. Googling for every single publication ever published is a nightmare and in the scientific community we depend on people who are willing to do just that and write a good survey for a widely accessible journal. I think that having a wiki list of published work would be very helpful as it would make surveying the area a bit less obscure and make it easier for young researchers as well.

I am wondering whether this is an acceptable idea for Wikipedia and if anyone else thinks it would be helpful.

I agree that it would be a good idea, maybe with papers sorted by keywords; although I find the majority of (physics) papers don't list keywords in the abstracts.

I think the most useful structure would eventually evolve through common effort. If several people knowledgable in the field start contributing, it shouldn't take long before we get a useful database. Lots of research topics are already covered in Wikipedia and one could just attach relevant bibliographies to those.

microbiology

what are the micro organisms useful in controlling air pollution?and in what way?

what are the microbes that produce light?and in what way they are useful?--hima 13:00, 15 August 2006 (UTC)vedula.himaja

Please take a short amount of time to familiarize yourself with the instructions at the top of the page. We're pleased to help out with most questions, but I'm afraid that we have to ask you to Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. TenOfAllTrades(talk) 13:11, 15 August 2006 (UTC)

it is not at all a home work question....it is asked in one of my descriptive exams...ive been searching it from hours on net so ive kept it here

Google is an effective search tool. For your first question, searching with the keywords microbes control air pollution will pull up a number of relevant links. A similar search should lead you to answers to your second question, bioluminescence will also be helpful. TenOfAllTrades(talk) 13:48, 15 August 2006 (UTC)

what is PRBS

In Telecoms there is a method of testing circuits by using PRBS. What is PRBS and what is the difference between PRBS23 and PRBS15 etc. Thank You

PRBS stands for pseudo random binary sequence and is intended to simulate random data being sent. The 15 or 23 could refer to the word length but Im not sure.--Light current 18:10, 15 August 2006 (UTC)

A PRBS can be generated by a linear feedback shift register. It's a kind of pseudorandom noise. It has statistical properties similar to random data--for example, different run lengths of 1's and 0's occur with the expected frequencies, and the autocorrelation of a PRBS with a delayed version of itself is 0 (unless the delay is a whole number of periods). The number usually refers to the length of the shift register. The length of a PRBSn pattern is $2^{n}-1$. Xilinx has some good application notes on how to setup the LFSR to generate different lengths of PRBS pattern.-- The Photon 02:32, 19 August 2006 (UTC)

Leuconostoc and Weissella

These microorganism are useful for what purpose ? Thanks

Knowing nothing about the genera in question, and with the risk of seeming a smartass, I'd say the obvious answer is "making more of themselves". —Ilmari Karonen (talk) 15:12, 15 August 2006 (UTC)

Did you read Leuconostoc? There is at least one answer there.--Shantavira 17:22, 15 August 2006 (UTC)

Leuconostoc can also cause some pretty bad infections in humans - InvictaHOG 09:47, 24 August 2006 (UTC)

Do insects have brains?

This is the dumbest question I asked. I'll be happy if you answer me.

Himanyo 17:51, 15 August 2006 (UTC)

Yes. very small ones to fit inside their heads (probably)--Light current 18:08, 15 August 2006 (UTC)

Read brain, especially the section on invertebrates.--Shantavira 18:16, 15 August 2006 (UTC)

Although calling it a "brain" might be a bit too generous, perhaps "nerve cluster" ? StuRat 18:49, 15 August 2006 (UTC)

The correct term is ganglion or ganglia. The illustration in the insect article would possibly be more helpful than the brain article. BenC7 23:36, 15 August 2006 (UTC)

I once read a very interesting book about the apparently very clever things insects can do being due to the following very simple and ingenious rules, things that could be encoded onto only a few neurons I imagine. Sorry, I've forgotten the title and author. Humans, on the other hand, have the overheads of language, and a model of the world enabling them to reason. They need a big brain to code things into language and also maintain a model of the world. (They have a much more complicated software programme than ants - ants are just machine code.) Without these overheads ants can do similarly clever things by instinct which can be encoded compactly into a small brain.

Then there is the "hive mind", where the modest brainpower of each individual combines to do things collectively, which no individual could do alone. In humans, for example, no human could go to the moon alone, but collectively, we can do it together. StuRat 23:10, 18 August 2006 (UTC)

I think in ants at least, the ants are again just blindly following simple but ingenoius rules. I have been thinking that a statistical software program is smarter than humans, but because it does not encode things into language or reason then it does not seem so.

New Pollen?

I live in the commonwealth of massachusetts. Ive never had allergy problems before. However, just recently, Ive been displaying symptoms of allergic reactions. Nasal congestion, swollen face, etc. So Ive looked at differnt pollen websites and cant find any info to help me. SO my question is what, if any new pollen comes out around this time of year in the northeast. Ive been fine all summer so it must be some plant/weed that gets release mid to late summer. Of course there is always the chance that I just recently became allergic to something. I know the whole deal how none of your are doctors and I should seek medical attention for real help, so lets just get past that.

THanks!!!

There is a section on the weather page of the Globe that gives a pollen count for the next day or two, maybe you should see if your discomfort follows a trend that parallels this count. For what it's worth, people develop new allergies all the time. Isn't IgE a bitch?Tuckerekcut 00:04, 16 August 2006 (UTC)

The most prevalent pollen allergen in the northeast US at this time of year is ragweed.--Mark Bornfeld DDS 00:17, 16 August 2006 (UTC)

Treatment of Erythrasma skin rash

I take as read all the precautions etc about this kind of medical advice.

I saw a dermatologist today and she noticed that I had a erythrasma infection in my armpits. It did not seem to be harmful but it can spread. It is, according to my internet research, caused by Corynebacterium minutissimum, a bacteria. She told me to spray it twice a day for a fortnight with Daktarin, which is a UK trade name for a spray powder that contains "miconazole nitrate Ph Eur 0.16% w/w" and which is usually used for the fungal infection known as athlete's foot and other names.

I wondered afterwards why a treatment for fungus would be used with a bacterial infection, and reading the miconazole article suggests that it does have a mild anti-bacterial action also.

But I wonder if I could instead just use an antibacterial spray, as this should be more powerful in zapping the germs. I'm also aware of the nitrates and remember that these are carcinogenic - or is that nitrites?

My question is - is there such a thing as an antibacterial spray that is safe to be used regularly on the skin? I do have some antibacterial creams, but sprays are quicker and more convenient to use. One of them contains chlorhexidine gluconate, which according to the article you should not get near your ears or eyes. The other is based on cetrimide. I want to know more about this before speaking to a pharmacist so I don't end up with something only designed to be used once on wounds. Thank you.

According to the Merck Manuals, "Topical drugs such as clindamycin and miconazole cream are also effective" [for the treatment of Erythrasma]. For the rest, you should really ask your dermatologist. --Lambiam^Talk 00:00, 16 August 2006 (UTC)

You can certainly use just about any antiseptic to reduce skin fauna (Clorhexidine and Betadine soaps work well, many spreays and ointments are available), but you don't necesserily want to. Natural microbial fauna might be more effective in keeping out pathological strains than you could be even with diligent cleaning. It may have been that your doctor told you to use the antifungal to reduce the chance of a new infection with fungus, assuming that your body can fight off the erythrasma itself. I would strongly suggest you take the advice of your physician, maybe call her office if you want more answers. If you do decide to go against her advice, though, I would stick to plain old soap and water.Tuckerekcut 00:01, 16 August 2006 (UTC)

If you truly want to ignore the advice of your doctor (and go with 'free' advice), I find that 100% Tea Tree Oil (Melaleuca Oil) is quite effective for these things. --Zeizmic 13:50, 16 August 2006 (UTC)

defense

what's the best way to defend against terrorism weapons made out of soda or other soft drinks? = >?

Prohibit production of soda and soft drinks. You can also kill all the terrorists. — [Mac Davis] (talk)

on a plane, banning them is the best option. People can buy a $1 soft drink on the other side if they want to, or a $2 one guaranteed by the manufacturer on of the plane.

In public places, it's impossible and pointless. Wjlkgnsfb 22:25, 15 August 2006 (UTC)

C'mon guys, be serious. It is just plain stupid if you wanted to ban soft drink transportation onto a plane. That is moronic. How would that save lives? All that would do is prove that once again, we give in a little bit more. We sacrifice more of our liberties. — [Mac Davis] (talk)

lets see you come up with an effective, efficient, cheap detection system to verify that soft drink cans don't actually contain explosives. The simplest solution is to travel light, and buy what you need on the airplane itself or before/after your trip. Wjlkgnsfb 23:13, 15 August 2006 (UTC)

Unfortunately, defense against soda offers no protection whatsoever against processed cheese or underwear. --Lambiam^Talk 23:47, 15 August 2006 (UTC)

And by no means... never mix the two together. The deadly combination may just take off a hand or an arm. — [Mac Davis] (talk)

From the terrorism article: "Terrorism is the systematic use or threatened use of violence to intimidate a population or government...". Nobody even has to get hurt for terrorism to work: it becomes terrorism when the populace is scared. Thousands of people might have died over the course of this era of terrorism, but hundreds of millions of people have to change the way they go about their lives. That is the true effect of terrorism, and they (the instigators) couldn't have done it without us.Tuckerekcut 23:52, 15 August 2006 (UTC)

lol. 68.20.38.241 01:26, 16 August 2006 (UTC)

People change how they live because they care about living and/or the lifes of others. If that is a "win" for terrorism, the only way to defeat terrorism is to stop caring what happens. No matter how many are kidnapped or killed, just stop caring and terrorism will fail in the end. It is my opinion that not caring if people live or die is terrible, so I feel that is a win for terrorism too. Apparently, terrorism wins no matter what. --Kainaw ^(talk) 00:57, 16 August 2006 (UTC)

Sadly, but well said. I think the only way to stop terrorism is to eliminate all the terrorists. And for all you folks following the news out there, I'll give you a hint - the correct answer is not "kill all the terrorists". See hydra for more details. --Bmk 01:14, 16 August 2006 (UTC)

How about special planes for people from Muslims countries ? The terrorists wouldn't see much point in blowing up those planes (that would actually be bad PR for them), and would have a hard time getting onto the other planes. This may seem extreme, but I, and I assume many others, are to the point of just not wanting to fly anymore. I can't bring any carrry-on luggage, and the airlines feel free to lose my luggage and serve me a tiny portion of contaminated water, if any, while keeping me in a hot plane for hours, after waiting in security lines for hours, and they still can't seem to protect us. StuRat 02:03, 16 August 2006 (UTC)

Which ones are the "Muslim countries"? --68.64.100.100 03:52, 16 August 2006 (UTC)

Those with a majority Muslim population. Do you need a list ? StuRat 06:45, 16 August 2006 (UTC)

I believe I once heard that most muslim (and other) terrorist actions take place in the home country of the terrorists and kill mostly muslims. Anyway the question was about terrorists, not muslims. DirkvdM 12:33, 16 August 2006 (UTC)

And has your fevered brain imagined there is some huge threat from non-Muslim terrorists ? Most people would be entirely satisfied if we could stop Muslim terrorists. All those Buddhist terrorists will just have to wait. :-) StuRat 20:02, 16 August 2006 (UTC)

My (fevered or not) brain doesn't see much of a threat in terrorism. The attacks, that is, what politicians and the media do is a different matter - they're the real terrorists. I think I have made that clear enough in previous discussions. The total worldwide deathtoll is negligible compared to real threats, like malaria and cars. And the 'war on terrorism', of course. The fact that recently most attacks have been by muslims is at least in part a result of the narrow statistical basis. It may well be that just a few years ago most terrorists were catholics. It takes just a few attacks to tip the balance. Of course the war on terrorism 'helps' here, too. I f you keep on attacking muslims they will keep on counterattacking and you've got yourself a self-fulfilling prophecy. DirkvdM 07:31, 18 August 2006 (UTC)

So, by your def, the Chechens who blew up the Russian school, children included, are "not real terrorists" and we should just ignore this type of thing ? The facts don't support your argument, attacks on US civilians have dropped off dramatically since the war on terrorism began. Prior to that, they were spiraling ever upwards. And you can't just ignore something due to the current death toll, the potential death toll is much greater. Using your logic, AIDS should have been ignored in the 1980's, because the death toll, at the time, was small, even though it was entirely predictable that it would spread and kill millions, just like unopposed terrorism will. StuRat 18:44, 18 August 2006 (UTC)

Just so we're very clear about how terrible the above suggestion is, the people arrested in the recent 'liquid explosives' plot were mostly British. Those arrested in the Canadian terrorist conspiracy were mostly Canadian. Or are you suggesting that British and Canadians should only be allowed to fly on their own airlines. BA and Air Canada would really like that - they would make a huge profit. DJ Clayworth 17:09, 17 August 2006 (UTC)

How about special planes for muslims and people who won't eat pork? The pork hating terrorist will be very happy to kill their sworned pork hating enemies (the joos) and leave the rest of us alone. We can call the new airline No Pork Airways.Ohanian 04:51, 16 August 2006 (UTC)

There seems to be a view around here that terrorist = Muslim = terrorist. That may be someone's idea of a sick joke, but it just incites hatred for all Muslims, the vast majority of whom have nothing but abhorrence for terrorism. JackofOz 10:46, 16 August 2006 (UTC)

The only terrorists I fear are those who don't eat pork. I propose a new airline where the interior of the planes are laced with lard. And all the drinks contains traces of lard. I feel safer in the plane this way. Ohanian 14:49, 16 August 2006 (UTC)

Alas, that is not just 'around here'. After the end of the USSR, the US (and other western countries) needed another enemy (to distract from interior problems). The attacks on the WTC and the pentagon were a godsend. The only problem was that it's an enemy you can't point out easily. So first Al Qaeda was invented (the term is a US invention), but that was too small and hard to fight, so it changed to 'muslims in general'. Nice and identifiable. DirkvdM 12:33, 16 August 2006 (UTC)

On a more general note, and this was in a way already said above, the best defence against terrorism is to ignore it. I understand that that was a method used by Thatcher against the IRA (if so, for once she got something right). The point of terrorism is to instill fear. If the media ignore everything you do, there's not point in doing it, so it will stop. So the media and the politicians telling us to be afraid of something that barely kills anyone (if you look at the big picture) are the real terrorists. DirkvdM 12:33, 16 August 2006 (UTC)

The US tried ignoring it; they ignored the first attack (bomb) on the World Trade Center, they ignored the attacks on the US embassies in Africa, and they ignored the attack on the USS Cole. If they had also ignored the 9-11 attacks, the next attacks likely would have been with WMD. StuRat 20:24, 16 August 2006 (UTC)

Actually, the US arrested, tried and convicted those responsible for the 1993 bombing of the WTC. They are sitting in a maximum security prison even now. That was before the US just imprisoned suspected terrorists without trials.Edison 17:10, 17 August 2006 (UTC)

By ignored, I don't mean "took no action whatsoever", that would be beyond stupid. What I meant was "took no action capable of preventing further attacks". Those actions include, but are not limited to, removing the terrorists and their Taliban supporters from their base in Afghanistan. After that was done, terrorist attacks against US civilians dropped off dramatically. StuRat 21:48, 17 August 2006 (UTC)

Yeah, but we only got peace with the IRA by talking to them. And I don't think the current threat is organised enough for there to be anyone worth talking to about it. And to the 'hilarious' suggestions of all-muslim-country airlines, the problem is 'home-grown' terrorists. Skittle 13:18, 16 August 2006 (UTC)

Home-grown terrorists may be the problem in the UK, but not in the US. I don't think any of the 9-11 attackers were born in the US. The UK needs to arrest all the clerics who preach terrorism, and keep them locked up, to stop the home-grown thing. StuRat 20:18, 16 August 2006 (UTC)

What you mean arrest people for saying things you disagree with? So much for Land of the Free, Home of the Brave. DJ Clayworth 17:12, 17 August 2006 (UTC)

The Right to Free Speech most definitely does not include the right to advocate murdering civilians, as I'm sure the voters would agree in any referendum. StuRat 19:30, 17 August 2006 (UTC)

A bit more on the IRA broadcast ban. That was also aimed at Sinn Féin, a law that forbade tv and radio (not newspapers) to air comments by Sinn Féin members, so it was more of a political thing. They could be shown, however, so the BBC decided to show the interviews and have the voices dubbed over, thus circumventing the law. So een though the basic idea made sense, it was halfharted, misdirected and done to hastily, not in cooperation with the media, which only pissed them off. Don't ever do that to the media. It will always backfire - they're too powerful, which is a central issue here. There's a little bit on this way at the bottom of Prevention of Terrorism Act (Northern Ireland). Could do with some expansion (maybe a separate article even), but I know too little to write that.

But most importantly, the ban drew so much attention that it actually hepled the IRA get more attention. Just as the whole war on terrorism now is a godsend for terrorists all over the world. They only need to plan a terrorist attack and make sure they are found out. I wonder if that is what was done here. DirkvdM 13:32, 16 August 2006 (UTC)

No offense everyone, but this wasn't really a science question to begin with, and I doubt turning this topic into a political message board is a good idea...Honsetly, let's nip this now and focus on more seagull bagel & masterbation questions. Can't get enough of those... -- Scientizzle 15:53, 16 August 2006 (UTC)

Back to pop-bottle explosives then, there's an interesting article in The Register today about the chemistry of making binary liquid explosives. Ojw 21:30, 17 August 2006 (UTC)

What is the difference between group velocity and phase velocity?

Despite reading the articles I am still not clear what the difference is between Group velocity and Phase velocity, relating to waves and sound. Could anyone explain it in simpler laymen's terms please?

Before reading the article I never knew these existed, despite having a GCE A-level in physics, grade B. 62.253.44.31 22:37, 15 August 2006 (UTC)

The phase velocity is the velocity at which a wave of a single frequency will propagate. The phase velocity is the velocity with which most people are innately familiar; "wave velocity" or "velocity of propagation," really means "phase velocity." When you combine waves of several different frequencies, something different happens: you get interference. In an extreme example, you can combine several waves such that they cancel out everywhere except in a small area of space. This destructive wave interference is by the way, how active noise-cancelling headphones work. The envelope of the resulting "wave packet" is not really a proper wave—it's the result of the interference of several component waves. The envelope of the wave packet, the peak of constructive interference, can travel at a different speed from the phase velocity, the velocity of each of its individual component waves. Group velocity. Get it? — [Mac Davis] (talk)

So if I use an analogy of a long line of cars moving slowly along on a congested road, then would the phase velocity would be the speed the cars are moving at? If one of the cars leaves the road, then the car behind will quickly move up, then the one behind that and so on, so that this gap moves like a travelling wave (or sp? traveling wave) along the line of cars. Would the speed at which this gap moves be the wave velocity?

I always thought a soliton would be a group wave, until I read the complex article and it totally confused me... --Zeizmic 12:01, 16 August 2006 (UTC)

The analogy of a line of cars might work, but not as you stated it; it is sort of a complicated analogy since it is a longitudinal wave (i.e. compression wave). Really, the best way to think of group and phase velocity is that the shape of the wavelet changes. The group velocity is sort of the "average" speed of the whole little pulse. The phase-velocity is how fast each frequency component moves. Phase-velocity is different for each frequency component; and it determines how different the pulse will look at the other end. Perhaps even with your physics background, you never got as much Fourier analysis as your colleague electrical engineers; wavelet analysis must use some rigorous mathematical Fourier transforms to get numerical results. Nimur 22:54, 16 August 2006 (UTC)

I didnt realise that different frequencies had different speeds. Now it makes more sense. If this is the case, then why is the speed of sound given as (as far as I recall) 330 metres per second, and not a different speed for specific frequencies? And would it be possible to construct a sound-prism?

So let me see if I get this right please - on an AM radio broadcast, the carrier signal is moving at one speed (the speed of light presumably), but the modulated sound signal is moving at another speed. Is that correct?

And if you drop a pebble into the middle of a large pond and watch the ripples spread out, is it correct that the ripples are moving at phase velocity, not group velocity?

Yes, yes, and yes... The trick here is that in most materials (i.e., in air, for example), the group and phase velocities are nearly equal. So, when you say that the speed of sound is 330 m/s, you mean that is the average, rough approximation. When the phase and group velocities are not equal, the packet changes shape - this can be detected as distortion. Yes, your AM radio broadcast carrier gets distorted; remember, the speed of light in AIR is less than the speed of light in vacuum (how much less? Depends on the frequency); and if you were unlucky enough to be transmitting through certain types of glass you probably would not be able to recover the original signal. But, for most "normal circumstances" (...if normal means anything in science...) the phase and group velocities are close or equal. Nimur 13:24, 20 August 2006 (UTC)

Let me give an example of when phase and group velocities are very different: waveguides (image). They are pipes through which you feed electromagnetic waves. A waveguide has a "cutoff frequency" – waves with frequencys lower than that will die out as they try to propagate along the guide. Frequencys above the cutoff do all propagate, but with different phase velocities. If you start at a high frequency and decrease it, the phase velocity will increase. Actually, as you approach the cutoff frequency, the phase velocity will increase to infinity (yes, much higher than the speed of light in vacuum). An infinite phase velocity means that whenever, at one point along the guide, the field has a maximum, it will have its maximum at all other points aswell. The group velocity, however, will always be less than or equal to the speed of light in vacuum. (Otherwise you could send information faster than the speed of light in vacuum, which, as we know, isn't possible.) —Bromskloss 01:57, 21 August 2006 (UTC)

See [13] java applet--Light current 02:13, 21 August 2006 (UTC)

Also, phase velocity is w/k whereas group velocity is dw/dk (ie the differential of the phase velocity)--Light current 02:16, 21 August 2006 (UTC)

August 16

"Black threads" in tilapia (edible fish) ?

I regularly eat freshwater, farm raised tilapia. It often contains what I would describe as "black threads". They seem to break apart easily. What are they ? Two thoughts I had were some kind of worm and blood vessels. I cook the fish before eating it, but still, if it's worms I think I'll switch to some other type of fish. I can try to take a pic, but they are quite small and my digicam is so-so, so I'm not sure how well they will show up. StuRat 01:28, 16 August 2006 (UTC)

Are you sure its not what was in the intestines of the tilapia? — [Mac Davis] (talk)

Sounds like veins to me. But it would depend on how thick they are. BenC7 04:44, 16 August 2006 (UTC)

I agree - it sounds like the blood vessels. - Cybergoth 22:36, 16 August 2006 (UTC)

I think I've seen the same, and I'd say it's veins / blood vessels. Nimur 23:28, 16 August 2006 (UTC)

Good, I'm not so grossed out now. StuRat 03:39, 17 August 2006 (UTC)

Safety Glasses

I recently sustained an eye injury, and my doctor insists I wear protective lenses to prevent something happening to the other eye and rendering me entirely blind. I've gotten polycarbonate lenses, which work well enough, but a friend of mine (whose father is, he says, a welder) wears a nifty set of dark glasses that are, he claims, actually shop goggles, capable of defending against flying metal debris. I handled them, though, and they seemed like the same sort of thin plastic thing you could get at WalMart. They must have been reasonably high quality, though, since they were so good at cutting out glare without effecting much else. What do you think? If I got a pair, would they really protect me? If so, can anyone offhand point me to a source? Black Carrot 05:44, 16 August 2006 (UTC)

I think having 100% coverage is more important than the material. So, try to get glasses that cover the sides as well as the front. Most object flying towards the eye can be stopped by any glasses, so long as the object actually hits the glasses. StuRat 07:43, 16 August 2006 (UTC)

Polycarbonate is the toughest thing you can get for protective eyeware. The side-shields are necessary when you are working with flying debris. In Canada, nobody gets away with working on a job site without approved eyeware. --Zeizmic 11:56, 16 August 2006 (UTC)

They've got great coverage. In fact, that's part of why I'm interested in them - my damaged eye is still very sensitive to light at the edges, even though it doesn't really get an image, so I've been wearing those huge post-surgery shield glasses for awhile. The glasses my friend has, though, hug the edges of the eyesocket, so they keep out just as much peripheral light. As for the material, though, what do you figure these might be made of, and does it sound like they might actually be an acceptable substitute for the approved material? About the worst thing I can think of is having my glasses actually shatter into my eyes. Black Carrot 16:29, 16 August 2006 (UTC)

Polycarbonate is strong -- it's the stuff they make bulletproof glass out of. And based on the mechanical properties described in the article, it's a very ductile material, so you don't need to worry about it shattering: if something hits your glasses hard enough to go through, it's got enough energy to continue through your brain and exit the back of your skull. --Serie 23:20, 16 August 2006 (UTC)

Well, right. I recognize that. It's the glasses my friend has that I'm not sure about. I'm asking whether anyone can suggest based on the information I have (related to welding, full coverage, cut out glare, thin and flexible, etc.) what they might be made of, how strong they might be, and perhaps where I can get a pair cheaply if the first two work out. Black Carrot 05:33, 17 August 2006 (UTC)

Bananas inducing gag reflex

I have an unusual question, but I'm sure you're used to that around here.

When I eat a banana, it often induces my gag reflex. I have nothing against the taste of banana, and, yes I do chew it (ie. not deepthroating a banana!). Any suggestions what might cause this?

Aaadddaaammm 09:43, 16 August 2006 (UTC)

Do you get similar sensations from other squishy foods? Sometimes the physical mouthfeel of food can be a very negative sensation. I don't mind the chemical taste of broccoli but the wet slippery squishy slightly grainy feel of it boiled...YUCK! Oh, and thanks for mentioning the chewing issue, that was my first thought when I started reading your question :-) Weregerbil 12:24, 16 August 2006 (UTC)

Try steaming it, or stir-frying it with a bit of garlic and some salt. Crispy broccoli isn't squishy! :-) Anchoress 05:42, 17 August 2006 (UTC)

A fellow programmer here had his gall bladder removed. Now, he throws up every time he eats bananas. He doesn't know why (and is upset because he normally had a banana for breakfast every day). I wonder if there is a relation between your problem and his. --Kainaw ^(talk) 13:00, 16 August 2006 (UTC)

The old banana gag : peel it and throw it some place, to see if someone shall fall. Please subscribe to a good insurance first :) -- DLL ^{.. T} 19:11, 16 August 2006 (UTC)

Bananas give me a similar feeling (like I want to gag), which is why I don't like them. I attribute it to the texture. Ironically, my husband, who won't eat fresh tomatoes because of the texture, enjoys bananas. --Ginkgo100 ^{talk · e@} 20:24, 16 August 2006 (UTC)

I feel queasy and often have a gagging reflex when I eat a banana or anything banana flavored. I avoided banana for a long time and eventually mentioned this to an allergist. It turns out that I was diagnosed as allergic to bananas and that this is actually a relatively common symptom for this relatively common food allergy. For me, eating bananas produces no effects (rashes, swelling, etc) other than nausea. Maybe you have the same issue? (The preceding comment is not meant to reflect any medical advise. Please consult your physician.) -- C. S. Joiner (talk) 21:19, 16 August 2006 (UTC)

Two suggestions:

1) Make sure you don't eat any of the little strands that are between the meat and the peel.

2) If the sliminess bothers you, try eating them in oatmeal. I've noticed that this counters the effect, and I don't end up with my mouth feeling like it's coated with slime. StuRat 21:55, 16 August 2006 (UTC)

I had a cat who would put his ears down and run from the room whenever a banana was peeled, making me wonder what banana-related trauma he suffered before we got him. :-) StuRat 21:59, 16 August 2006 (UTC)

Lots of cats (such as my cat) do not like bananas either. Nimur 22:49, 16 August 2006 (UTC)

Bananas shouldn't leave your mouth feeling like slime unless they're under-ripe. Try giving them a day or two more before you peel them. (Not too long, though. Waiting till they're black is waiting too long, unless you're making a banana cake). And broccoli should never be boiled. No wonder you find it distasteful. Steaming (and light steaming at that) is the only humane thing to do to a broccoli, if you don't want to eat it raw. JackofOz 01:24, 17 August 2006 (UTC)

I disagree. All bananas leave a slimy feeling in my mouth. I suspect they have something in them which isn't water soluble (perhaps a potassium compound ?). I rarely eat a plain banana, for this reason. StuRat 03:33, 17 August 2006 (UTC)

Numerical study of rotational effects for rotors

Numerical study of rotational effects for rotors It has been recognized that rotational effects can increase lift and at the mean time delay dynamic stall. Studying such phenomenon is very important for predicting rotor performance and optimising rotor shapes. A quantitative study of rotational effects has increasing needs for industrial usage. The project will focus on (1) numerical development of a modified Quasi-3D model based on the previous Quasi-3D model and (2) study the rotational effects at different spanwise distances and different angles of attack. please help me that how to design things(CFD/EFD etc ) that would help me in this research

When asking for free help, it is best not to cut&paste the exact assignment. Otherwise people might feel that they are being taken advantage of. In fact, I remember there is something about this at the top of the discussion. --Zeizmic 15:18, 16 August 2006 (UTC)

Time course of evolution

Over what period of time or number of generations have evolutionary changes been seen? Specifically, have Sherpas and other peoples living in higher elevations shown genetic adaptation to the high altitude conditions? Thanks!24.5.103.166 17:01, 16 August 2006 (UTC) Scott

Modern humans are not under as strict selective pressures as other species (due to healthcare, the welfare state, and other societal considerations etc). This, combined with long lifespans, means "evolutionary changes" among humans are very difficult to quantify over generational timescales. Founder effects precipitate "evolutionary changes", but are often not advantageous (evolution does not occur with forethought, remember). There are examples of genetic variation that could, one could hypothesise, shape modern human evolution over quite short generation times, in the absence of modern healthcare. Consider the potential selective advantage of the CCR5-Δ32 allele during a global HIV/AIDS pandemic, for example. Rockpocket 17:35, 16 August 2006 (UTC)

Outside of humans, there are many animals that have shown changes due to both natural selection (classical evolution) and human-controlled selected (breeding). For example, the common pet hedgehog has an abnormally high chance of being albino because humans have purposely overbred albino hedgehogs. In the natural world, there was an article from National Geographic last month about evolutionary changes in the birds on the Galapagos Islands (the Darwin Species). Also, I recently read about some green-brown tree frogs that are beginning to have the ability to turn white. If it propagates throughout the tree frog population and doesn't die out as a weird mutation, it will be another evolutionary step for them. --Kainaw ^(talk) 17:51, 16 August 2006 (UTC)

There's always the same story about birch butterflies growing darker with pollution that darkens boughs. -- DLL ^{.. T} 18:59, 16 August 2006 (UTC)

Bacteria becoming resistant to antibiotics is a form of evolution. And, like Kainaw said, since you didn't specifically ask for natural evolution (natural selection), breeding animals to give them the characteristics we want them to have can also be seen as evolution. Actually, I think that farmers must have come up with the idea of evolution from the time they started doing that, thousands of years ago. The notion of evolution is a whole lot older than Charles Darwin (his father was a protagonist of the idea, for one). DirkvdM 19:02, 16 August 2006 (UTC)

You mean Charles Darwin's grandfather, not his father (who was an immensely large society doctor, like his grandfather, but not a reknown scientist, unlike his grandfather). Darwin did not invent the idea of evolution, of course, but is the one credited with the development of natural selection in particular as the mechanism of evolution, and propelled it into serious scientific discussion. But in any case selection by itself is not the idea of evolution, per se, which generally indicates population-wide effects and speciation, which breeders generally did not have any grasp of. It is actually quite a conceptual leap from manipulation of passive stocks to the idea that organisms can transmute into other organisms over generations, though it seems obvious once you know it. --Fastfission 00:16, 17 August 2006 (UTC)

Did I just become a referenced source? [14] Black Carrot 19:54, 16 August 2006 (UTC)

I don't think so, and if you have, its been misinterpreted. Its unlikely that the tree frogs Kainaw refers to have recently evolved the ability to turn white. Most frogs and reptiles have this capacity so some extent (see chromatophore), they just don't tend to use it that often. Moreover, even if they recently acquire this trait, its unlikely it would become fixed in the population. There would be no obvious selective advantage to it. Infact, it is more likely to be disadvantageous, as the dearth of naturally occuring albinos demonstrates.

However, there are some interesting examples of pigmentary adaptation that has evolved over (relatively) short time periods. My particular favorite is the Rock pocket mouse. See also a recent study on Peromyscus [15]. Rockpocket 20:18, 16 August 2006 (UTC)

Actually, it was Black Carrot's question that led me to hunt down the article on white tree frogs in our library. Going from memory, the study (which didn't have conclusions - only study data) showed that tree frogs in northern Florida and southern Georgia were increasingly turning white when on white surfaces. Tree frogs found in other areas turned green. So, they wanted a grant to study if this is an evolutionary step in the tree frogs or have they always turned white and nobody noticed. I don't remember who it was and I don't know if they got the grant. But, I remember the tree frogs turning white. I just remember weird facts and lose the source of them all the time. --Kainaw ^(talk) 20:16, 16 August 2006 (UTC)

Sorry, Kainaw, i accidently edited my comment after you reply. The grant you mention is asking the right question, of course, but i would be very surprising if it was a novel adaptive trait. There could be the result of subtle variation in chromatophore distribution or hormonal control. However, if this was a genuine novel trait, i would guess it is a subsequence of selection for another function of the gene involved, rather than selection for the colour change per se. This is usually the case with pigmentary variations that are not obviously cryptic in purpose. Rockpocket 20:32, 16 August 2006 (UTC)

Humans do show evolutionary adaptations to different environments. For high altitude, there are three responses. Humans who are from sea-level populations react to high altitude with increased concentration of red blood cells (and thus thicker blood) and a higher respiration rate. I don't remember the details of the other two reactions, but peoples from the Andes mountains have a reaction similar to that of sea-leve peoples, while Sherpas and other peoples from the Himalyan Plateau have a different reaction entirely. The time scales for these changes aren't known, but the Andes changes could not have taken more than 15,000 years. --Serie 23:36, 16 August 2006 (UTC)

I don't believe there is any evidence that these physiological adaptations are genetically encoded and thus a result of natural selection. Athletes from all populations undergo high altitude training to obtain the same effect. A similar example is from the Moken sea gypsies. This remarkable study showed that Moken children have underwater visual acuity that is more than twice as good as that of European children. This, it was suggested, could be the result of a novel evolutionary adaptation to underwater vision. This would have been an amazing find, but just this year the same authors demonstrated that it is actually a skill that can be learned, irrespective of genetic background [16]. Of course, there is no doubt that human populations have evolved under selective pressures (or the lack thereof) - differences in skin tone between Equatorial and Northern European populations demonstrate that. Its just that correlating positive selection of an allele to phenotype is tricky at the best of times in outbred human populations. Putting a time scale on it is even harder. Rockpocket 01:04, 17 August 2006 (UTC)

It is common for people to confuse evolution with adaptation. A single person will never ever evolve. All of your evolution was done when your father's sperm hit your mother's egg. Everything after that is mere adaptation. Unfortunately, "evolution" is often used in place of "adaptation" in what should be credible sources. It confuses the issue and fuels the fire for anti-evolution people who want to find any reason at all to prove that science is wrong. --Kainaw ^(talk) 01:15, 17 August 2006 (UTC)

There have been a few recent papers on selection in the human genome in different population, like this one.--Peta 00:19, 17 August 2006 (UTC)

Other things which seem to have evolved recently [17] MeltBanana 00:27, 17 August 2006 (UTC)

Fastfission, you say that "It is actually quite a conceptual leap from manipulation of passive stocks to the idea that organisms can transmute into other organisms over generations." Technical terminology aside, isn't it more likely to be the other way around? People started breeding animals for certain traits because they understood that could be possible. So they had some idea of selection. Extending that to natural selection does require some intelligence, but until not too long ago, intelligence was no guarantee to become a 'scholar', so there must have been quite a few highly intelligent farmers. Over thousands of years quite a few of those must have figured this out. Of course, lack of means to spread the knowledge meant the insight was probably lost when they died, so we won't know about them. But they must have existed. DirkvdM 06:43, 17 August 2006 (UTC)

how to check qulaity of cyanoacrylate or super glue

i would like to know how do you check the quality of cyanoacrylate used as glue. i want to know the chemical tests possible and the common man's test, if any. what are the basic things to make sure that we get a good qulaity glue. i am looking for a super glue which sets in 1 to 2 seconds. thank you.

To check, apply a drop to two blocks of glass, press together for two seconds, and try to pull them apart. If you succeed, the glue was not super. --Lambiam^Talk 18:08, 16 August 2006 (UTC)

Yes, but if you don't succeed that doesn't mean it is superglue because you might not be strong enough. The basic idea is right though (and rather obvious). I've once seen on Klokhuis (great show - I wrote the stub :) ) how glue manufacturers test this. They glued two strips of wood (or whatever material you want it for) together, overlapping, attached one end to a hook and hung weights on the other end, adding to it until it broke. If the breakage was in the wood, the glue was stonger than the wood, and therewould be little point in making it stronger than that. DirkvdM 19:11, 16 August 2006 (UTC)

living rocks

While watching a presentation on the History Channel called the Grand Canyon the narrator referred to the rocks along the Colorado River as "living rocks." What does the term living rocks mean? James L Barden

Well, they eat, drink, and love women. — [Mac Davis] (talk)

Living rocks! Damn straight! Well, except sometimes. --Trovatore 18:37, 16 August 2006 (UTC)

Living rocks are cactii. I doubt that is what the narrator was referring to. --Kainaw ^(talk) 18:40, 16 August 2006 (UTC)

Becuase there aren't any cactii anywhere near the Grand Canyon?--152.163.100.74 18:50, 16 August 2006 (UTC)

What is a cactius, anyway? —Tamfang 06:41, 17 August 2006 (UTC)

Next one - what are living daylights? DirkvdM 19:13, 16 August 2006 (UTC)

I have one link that may be tangentially helpful - this PDF file has a section entitled "Blood of the Living Rocks: What Colors the Sandstone Red", but it never really says why it is using that term. --LarryMac 19:24, 16 August 2006 (UTC)

"Living rock" means "in its native condition and site" OED, e.g. the Sphinx is hewn out of the living rock. So I would guess the narrator meant that what looked like individual rocks were actually part of the bedrock.--Shantavira 19:37, 16 August 2006 (UTC)

Some other, and possibly more obviously illustrative examples, would be the sculpture of Mount Rushmore, and the Treasury at Petra.- Nunh-huh 19:42, 16 August 2006 (UTC)

I suspect they mean the rocks change over time (from erosion) or appear to change (due to lighting conditions). They could also mean there are living things on the rocks, like lichen. StuRat 21:42, 16 August 2006 (UTC)

'Living Rock' appears to be some sort of not-very-scientific jargon that is applied to the canyonlands. [18] There appears to be lots of literature using this, but it is not defined anywhere. By the pictures, I'll go with the natural sculptures carved out of the bedrock.--Zeizmic 23:54, 16 August 2006 (UTC)

EMP's affect on a crystal radio

Would an electromagnetic pulse adversely affect a crystal radio, which uses a passive circuit? --Dynamite Eleven 18:50, 16 August 2006 (UTC)

I don't see why it wouldn't be overloaded and fried just like any other electronic equipment. StuRat 20:07, 16 August 2006 (UTC)

Depends how much power was incident on the crystal radio's antenna, of course. Nimur 22:41, 16 August 2006 (UTC)

In its simple form, a crystal radio does not contain electronic components. It should hold up better than current electronic radios. This is not directly related to its being passive. A sufficiently powerful EMP will evaporate your cast-iron stove; it is all a matter of degree. --Lambiam^Talk 22:54, 16 August 2006 (UTC)

Cellphones......and the jammers there of

I remember reading an article, not sure where, about commercial radio frequencies, where the author claimed that your average person with a reasonable amount of engineering experiance could probably buy $11 or $12 worth of electronics from a radioshack and be able to build a device that could blackout all cellphone reception in an area the size of Manhattan, is this true? and if it is, how would you do it?--152.163.100.74 19:08, 16 August 2006 (UTC)

Flood the frequencies that the phones work on with extremely powerful garbage signals. Not too hard to create, but it will not "black out" the phones. It just makes the phone's signals appear weak in comparison. What I think would be cool is a system that collects signals and then repeats them at higher power on a delay. That should confuse the phones and towers. --Kainaw ^(talk) 20:03, 16 August 2006 (UTC)

You could enclose the entire area in a Faraday cage. Some secure agencies have taken to integrating one into their buildings structure, but it's not exactly feasible to build one to block all of Manhattan. It rather sounds like something that an evil genius might devise. Hmm... – ClockworkSoul 20:43, 16 August 2006 (UTC)

If you were to flood the frequencies enough, all that the mobile phones would pick up would be a load of noise, and no communications. I know this to be true, as I recently stayed on a military singals base, and when they had the radio transmitters on high power, the comms of civilian networks in the area would break down, with mobiles failing to ocnnect or send SMS. Martinp23 20:47, 16 August 2006 (UTC)

Twenty years ago, cell phones used simple technology that could be jammed by sending out high-power at the system operation frequency. Modern cell phones use CDMA, or Code Division Multiple Access, which makes "brute force" jammers very ineffective. So, perhaps ten years ago, a $10 dollar home-made 50 watt sine wave transmitter could jam the system. CDMA is actually extremely effective at evading exactly such high-power, "dumb" jamming (it was developed for electronic warfare; it also serves to prevent thousands of legitimate cell-phone calls from "jamming" each-other.. One feature of CDMA coding is to divert power to frequency sidebands where the jam tone has no effect. To jam such systems, you would need a more sophisticated, digitally controlled jammer, which would cost more than $10 or $20 dollars (perhaps more like... several tens of thousands of dollars, or several months to years of home-made re-engineering). In addition, your home-engineer would now need to diversify his expertise from basic analog circuit design to include software, radio frequency electronics, and other areas of expertise. Nimur 22:36, 16 August 2006 (UTC)

P.S. User:Martinp23 mentions a jammer that exists on a military base. Without doubt, such jammers do exist. However, they operate as I described above (digitally controlled, CDMA-aware systems) and certainly are not home-made. I also doubt their operational range is more than a few hundred yards; if larger areas are covered, it is probably using multiple independent jamming devices. Nimur 22:40, 16 August 2006 (UTC)

Ring tones

Ladies and Gentlemen,

This is a question in reference to the wikipedia article entitled "ring tones". When making a telephone call, does the ring tone that the caller hears correspond and occur at the same time the ring of the phone recieving the incoming call? In other words, if the caller hears eight dial tones, will the person receiving the call hear his or her phone ring eight times simultaneously? If not, why?

Thank you for your assistance WJK August 16, 2006

Not necessarily - it all depends on:

• • the length of the ring tone (recieving)
  • the length of the ring tone (sending)

The first one varies according to phone brand/personal preference and the latter according to country. At certain times (when a certain ring tone in a certain country is used), both will be the same, but at most other times they will be different. Martinp23 20:52, 16 August 2006 (UTC)

If I ring my mobile phone from my home phone, my mobile starts ringing very slightly before I hear the rings in the home phone. The delay is very slight, however. I live in Australia. BenC7 02:21, 17 August 2006 (UTC)

Hair bleaching question

I currently have 3-foot long hair that's a mess of different colours after various dye/bleachjobs over the last couple of years. There's reds, browns, blondes, oranges, bits that look black, etc. In short, it's horrible. Is it possible to simply bleach all the different pigments out of it with peroxide, leaving it white-blonde again? Ta. --Kurt Shaped Box 23:08, 16 August 2006 (UTC)

From what I'm reading about hair dye, hydrogen peroxide opens up the hair cuticle and allows whatever proteins or compounds that are coloring your hair to escape. If this is true, I wouldn't think it matters whether the color is natural or synthetic as long as it's behaving the same way. And if your hair is as beautiful as you say, would it really matter if your bleach job failed? :D Hyenaste ^(tell) 23:40, 16 August 2006 (UTC)

I don't think so, but you should ask a hairdresser. Anchoress 23:51, 16 August 2006 (UTC)

Depends. How much damage are you willing to do to the structure of your hair? --Serie 00:01, 17 August 2006 (UTC)

I would think you would have more luck dying it black, which can cover any colors already there. And, in the future, only change your hair color when you're on the run from the cops. :-) StuRat 03:26, 17 August 2006 (UTC)

August 17

Where is the center of earth's land?

Hello,

I was wondering, what is the "average place of land"?

This is how I would define it :

Consider earth as a ball with radius R.

Let A be that part of the surface where there is land.

Define ${\vec {v}}=\int _{A}{\vec {r}}d\sigma$

where ${\vec {r}}$ is a threedimensional vector from the origin to that point on the surface.

The average place would then be $R{\frac {\vec {v}}{||{\vec {v}}||}}$

My guess would be somewhere in Africa?? Evilbu 00:12, 17 August 2006 (UTC)

Don't think just because it is in the center of the map, it is the center of land. I believe it would be in the Middle East, or the Indian subcontinent, but that's just my mind-model with weighting and the shape of the Earth in mind. Probably more accuratley somewhere in the Indian Ocean. — [Mac Davis] (talk)

Well, it will be somewhere inside the earth, deep within the surface, by the given definition. Of course I don't know exactly where, but given that the pacific ocean is the biggest region with no land, it will probably be somewhere on the other side from the center of the earth from the Pacific ocean. --Bmk 02:41, 17 August 2006 (UTC)

Nevermind, I retract that comment. I reread the definition, and it would indeed be on the surface :) --Bmk 03:11, 17 August 2006 (UTC)

I take that the centre of the ball is the origin. Assuming ${\vec {r}}$ is distinct from zero, the definition given results in a vector of length R, so that is not inside. --Lambiam^Talk 03:19, 17 August 2006 (UTC)

Wikipedia, the encyclopedia anyone can edit....

as long as they have a 4 year degree in math and physics. Isn't it a bit elitest of wikipedia to write all the science and math articles filled with equations and other things that no one can be expected to understand? isn't it contrary to the personal liberty of all peoples that wikipedia should be written in such a way as to restrict knowledge from the common man?--Milboage 00:28, 17 August 2006 (UTC)

If you don't have an advanced understanding of high maths and physics, why on earth would you attempt to write an edit that required such knowledge? Monolingual Basque people are free to edit this too, but they refrain from doing so because they don't understand it, just as you don't understand integrals and trigonometry or whatever. It's inappropriate to require all physics articles to either stick with basic arithmetic or explain the basics of calculus anytime they need to demonstrate a proof just so Joe Everyman can understand it. Why not take a class or (heh) read up the Wikipedia article if you're so interested in a subject? Hyenaste ^(tell) 00:44, 17 August 2006 (UTC)

You can always contribute to the Simple English Wikipedia! --Ed (Edgar181) 01:00, 17 August 2006 (UTC)

I have often complained about this. I know that no math geeks will ever be able to wrap their brain around this complaint, but I'll try again. Being able to recite an equation is not intelligence. Being able to mix and match equations is not intelligence. It is no more complicated than playing with Legos. Being able to take an equation and explain it without math is intelligence. Einstein wasn't a genius because he looked at a graph of energy to mass ratios and realized that it was a constant relationship with a constant equal to the square of the speed of light. He was a genius because he was able to explain relativity without using equations. Steven Hawking is similar. Read A Brief History of Time and notice how few equations there are. Even when he uses one, he quickly dismisses it and goes on to explain the concept in plain English. Unfortunatly, Wikipedia has a bunch of math geeks who are quick to delete any attempt to explain the equations. Why? They claim, "It is right there in the equation! You don't need to explain it!" They will never understand that it isn't a matter of "need". It is a matter of intelligence - even genius - to explain the math concepts without formulas. So, in my opinion, the math geeks just feel inferior and delete anything that they can't do themselves. --Kainaw ^(talk) 01:10, 17 August 2006 (UTC)

Isn't math a simplification of English? One equation of medium complexity = a paragraph of english, to use an equation. Math and english can mesh perfectly if you use the right words, but physics professors sometimes lack in that area.

Well it might help you if you got your words right too. The plural of LEGO is LEGO. No such things as LEGOS. pschemp | talk 03:58, 17 August 2006 (UTC)

If you think you understand relativity "in plain English", you're wrong. Can't be done. Some of the motivations? Sure. Some of the consequences? Those, too. The theory itself? You're only fooling yourself. Until you get into the equations, you simply don't really understand it, period. And that goes for lots of other things.

I agree. In addition, it would be impossible to understand quantum electrodynamics using only words. — [Mac Davis] (talk)

Now, it's a valid criticism that in many cases there is accessible material to present, and it's not presented, or not as clearly as it could be. That's absolutely an area for improvement. But it doesn't mean the specialized material shouldn't be there. --Trovatore 01:24, 17 August 2006 (UTC)

Math is of extreme importance to some people. Equations are little meaningless symbols that describe the world around us. Einstein was not a genius because he was able to explain relative without using equations, because he was. You can't just say something you know, you have to write it down, and the language of the universe is mathematics. Stephen Hawking mentioned that in his book a few times I believe. His book was popularized physics, meaning it is meant for the sole purpose of mass nonfiction entertainment. Who the hell would want to read a mathbook for fun? Well real mathematicians and physicists do. I do. If you've ever cracked open a college quantum physics text book... there's quite a bit of math. In fact it is almost all integrals, differentials, partial derivatives, and summations and deltas and dot products. The last time I checked M-theory they had a layman, and smartman section :) That's good. — [Mac Davis] (talk)

I sympathize with both "camps" here - and I think there is plenty of room for compromise. For every complex physics or mathematics article, there can be a full mathematical treatement as well as an English interpretation of the idea intended for those unwilling or unable to go through the mathematics. No need for an "either or", I think. BTW, one of my favorite quotes by Feynman here is that "if you can't explain it to a college freshman, you don't understand it yourself" (inexact quote, too lazy to look up). On the other hand, as someone mentioned, "mathematics is the language of the universe". --Bmk 02:32, 17 August 2006 (UTC)

The issue I see is that some level of simplification is required to make complex topics more understandable to the general public. For example, when explaining atoms, the model of electrons in circular orbits about the nucleus is easiest to understand. The probability wave function, orbital shells and energy quanta concepts should only be introduced after the basics are understood. However, when academics get hold of an article, they frequently delete any simplified explanation because it's "wrong". This leaves the general public incapable of understanding the article. StuRat 02:56, 17 August 2006 (UTC)

• It is wrong, it's much simpler to say that the universe is a large poorly lit christmas bulb that's over 200 billion AUs wide, but we can't put that in an article--71.247.125.144 03:24, 17 August 2006 (UTC)

• So then you're in the camp that says "no simplifications can ever be permitted, and if that means the general public can't understand our articles, well, screw 'em". StuRat 03:44, 17 August 2006 (UTC)

Well, no. To have an article on, say, the exterior derivative without equations would be doubly useless: Serious students couldn't get any useful information from it, and casual readers, if they ever cared about such a thing, would have to spend hours reading other dense articles just to understand the "plain English" explanation. Further, as someone pointed out above, though every article can be edited by everyone, not every article should be edited by everyone. You should only edit articles you actually know something about, and if your knowledge of math doesn't go beyond college algebra then you shouldn't be editing math articles. But let me hasten to add that this isn't because math is special, or because I'm a snotty nerd with a math degree. I don't know jack about Hindi phonology, so I don't edit it. The same should go for everyone and every subject.

That said, there's a good argument for, where possible, giving both a technical and non-technical explanation. The articles on relativity do a fine job of that, as do articles on several other well-known physics topics. Unfortunately that's just not always practical. It really does take a rare talent to convey these advanced ideas in simple ways, and for many of them it's just not worth the effort (see above r.e. "exterior derivative"). --George 05:06, 17 August 2006 (UTC)

"The untrained man reads a paper on natural science and thinks: ‘Now why couldn't he explain this in simple language.’ He can't seem to realize that what he tried to read was the simplest possible language – for that subject matter. In fact, a great deal of natural philosophy is simply a process of linguistic simplification – an effort to invent languages in which half a page of equations can express an idea which could not be stated in less than a thousand pages of so-called ‘simple’ language." —Thon Taddeo in A Canticle for Leibowitz

Science fiction: stellar explosions and disc formation.

In many science fiction television programs, particularly - in my memory - star trek, when a stellar object such as a planet or star, etc. explodeds the ejecta forms a two-dimensional disc which rapidly expands from the centre of the explosion. Is there a scientific basis underlying this effect, or is it purely artistic license? I looked at accretion disc, but it only appears to deal with collapsing matter, not mentioning ejected matter; ejecta is also no help. Thanks in dadpants,
-somesortamoniker. 88.144.1.63 02:09, 17 August 2006 (UTC)

Nah, I think it's just for visual coolness. I have nothing to back this up, except the intuition that nothing would cause such a violent asymmetry in the explosion. --Bmk 02:38, 17 August 2006 (UTC)

I first noticed this in Star Wars, when the Death Star exploded. It had a deep equatorial trench, however, which might be presumed to cause that effect. A rapid rotation might also cause such an effect. In general, however, if a spherical object exploded, I would expect a spherical debris field. StuRat 02:41, 17 August 2006 (UTC)

I should mention that planets don't usually spontaneously explode, so if they do, there's a mighty funky mechanism at work, probably available only from Starfleet command, which means it could look like anything. --Bmk

I second visual coolness. — [Mac Davis] (talk)

When there's gravity and an atmosphere about, there's lots of interesting shapes that explosions can take, mushroom clouds, dust rings. In space, they should probably just explode apart in all directions, and the fires would probably disappear quickly as the oxygen escapes. I think it was just modeled after explosions on earth that produce an outwardly expanding shock wave, and figured it looked more interesting given a planar shape than a spherical one. The earliest one of these I can think of in movies would probably have been from the end of Alien. - Rainwarrior 04:06, 17 August 2006 (UTC)

Doner kebabs

Why do they taste so nice when I eat them, yet make my stomach feel soo bad up to 12 hours later? --Kurt Shaped Box 05:53, 17 August 2006 (UTC)

Has every single donair you've ever eaten made you feel this way? If yes, then you might be allergic to something in them. If it's just one vendor, and you don't actually get sick from them, I'd guess either it's that they're using homous and you aren't used to eating beans, or the yogourt sauce (tzatziki, although it has a different name) is a bit off. Anchoress 06:02, 17 August 2006 (UTC)

The ones round here (UK) are mutton, salad and garlic mayo in a pita bread. I always feel bloated and usually wake up early the next morning with heartburn. I know, I should probably just stop eating the damn things. --Kurt Shaped Box 06:07, 17 August 2006 (UTC)

Could also be the raw onions (some places use them) or maybe cuz they're so greasy? Some people get upset stomachs from that. Anchoress 06:04, 17 August 2006 (UTC)

Yup, raw red onions usually - and they are greasy. --Kurt Shaped Box 06:07, 17 August 2006 (UTC)

If mutton disagrees with you, might I suggest making them out of seagull meat ? :-) StuRat 06:12, 17 August 2006 (UTC)

How many gulls would be required to make up one elephant leg? By all accounts, they're pretty lean birds --Kurt Shaped Box 06:21, 17 August 2006 (UTC)

The more the better, clean out the whole neighborhood ! :-)StuRat 07:00, 17 August 2006 (UTC)

why does water boil at low pressure?

Why does water boil at low pressure?

I assume you are asking why water boils at lower temps, when under lower pressure. This is also true of other liquids. Basically, pressure "pushes" the water molecules together to form a liquid. With less pressure, you reduce this effect. High temps cause rapid movement of water molecules, which makes them "break free" from the bonds that hold the water together as a liquid. So, temp and pressure both interact with each other to determine the boiling point of any substance. StuRat 06:27, 17 August 2006 (UTC)

Figured that, never could find any reference on it, though

poltergiests are in my water!

Sometimes when water is cold and in a bottle, un opened, it rapidly turns to slush upon opening

If it's below the freezing temp (at normal air pressure), the higher pressure in a sealed container may keep it from freezing, until the bottle is opened, then the lower pressure allows it to freeze. StuRat 06:58, 17 August 2006 (UTC)