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June 18

Angle grinder -lidl/aldi/netto

Barely a week goes by without one of the above supermarkets having an angle grinder on special offer - this confuses me as I don't consider it a household essential.. yet they still seem to sell. Question (bit of a straw poll but I hope you will humour me) - what do individuals use them for? (I mean 'household' use). Also does Walmart or whatever in the US have a similar obsession with the sale of this machine tool? Thanks.83.100.250.191 (talk) 00:03, 18 June 2010 (UTC)

I've used one to cut a long metal bolt, I also used one to trim a metal rod that was in the way of a light fixture. If you are handy, then it's a useful tool to have. And no, I have not seen any particular obsession here in the US, but that kind of thing goes in cycles. I hope they sell safety equipment with it (face shield), it can be a dangerous tool (always stay perpendicular to the rotation of the disk). Ariel. (talk) 01:44, 18 June 2010 (UTC)

I restore classic cars - angle grinders are great tools for hacking out bits of rusty sheet-metal, sawing heads off of stubbornly stuck bolts - all sorts of general metal cutting. I don't think I've ever seen one in WalMart - they might stock them, but it's just not the kind of store I'd look at when buying tools. Most of their stuff is cheap junk. SteveBaker (talk) 04:20, 18 June 2010 (UTC)

And don't forget that many men collect tools they have no use for and will never use...it's a guy thing, like women collecting shoes. StuRat (talk) 13:10, 18 June 2010 (UTC)

I find them remarkably useful for cutting bolts, rebar, plate, grinding rough metal, grinding down welds, etc. I have two, in fact, because my first one was too small for some of the work I was doing. That said, I obviously work with metals more than most people, and I wouldn't consider them a normal household implement. They're noisy and produce showers of incandescent sparks that can do bad things if they end up in your eye or in something flammable. Acroterion _(talk) 15:49, 18 June 2010 (UTC)

With the explosion of Harbor Freight and other 100% no-name import tool stores, things like this are becoming very common in the USA. Yes, you can get an angle grinder at most Wal-Mart stores (pneumatic or electric) and I wouldn't be surprised if I saw one in a rural supermarket either (if you can tell a difference between a Wal-mart and rural supermarket). What's becoming very popular is the "multi tool" (basically a vibrating dremel), the handle sits parallel to the path of vibration so you can use it for cutting, sanding, polishing, etc. As far as either of these being a "household item".... you would be surprised how many (probably bad) ideas you come up with when you have one! --144.191.148.3 (talk) 16:33, 18 June 2010 (UTC)

conservation of PH

Starting with neutral organic chemicals is it possible to turn the mixture acidic by any reaction (including bacteria etc) while keeping all reaction products in the final mixture? Ariel. (talk) 01:43, 18 June 2010 (UTC)

Probably not. Lots of compounds are highly pH sensitive. For example, amino acids can protonate or deprotonate at specific pH's. You'd need to post the specific reaction so we can check it, but the pH environment is generally very fundemental to the nature of compounds dissolved in solution. --Jayron32 01:52, 18 June 2010 (UTC)

If the solvent is ethyl acetate+water+etc then ester hydrolysis will make the solution turn acidic. A catalyst is usually needed which can be an enzyme [1] , a metal salt [2] or other things.

Is that what you meant.?83.100.250.191 (talk) 02:10, 18 June 2010 (UTC)

Or react acetic anhydride with water - the reaction products are acetic acid only.83.100.250.191 (talk) 02:19, 18 June 2010 (UTC)

Start with glucose and oxidise it to pyruvic acid. You can choose pathways where ethanol rather than CO2 is released. John Riemann Soong (talk) 15:39, 18 June 2010 (UTC)

Or even do use a CO2-producing pathway: it's soluble in water and would make the solution acidic. The extent is complete oxidation of any organic material in an enclosed container (to trap the product gases until cooled): CO2+H2O, CO2 dissolves in H2O, now you've got carbonic acid. DMacks (talk) 16:58, 19 June 2010 (UTC)

Or acyl chlorides and water. Provided you don't release so much HCl that some of it evaporates from solution of course. John Riemann Soong (talk)`

From one perspective, since the haloform reaction consumes base, it makes the solution more acidic. And the product (if you use chlorine) is chloroform and carboxylate. John Riemann Soong (talk) 17:14, 18 June 2010 (UTC)

Wine to vinegar. Physchim62 (talk) 00:39, 19 June 2010 (UTC)

Mobile phones in supermarkets

Hi. I live in the UK and I find that, almost without fail, my mobile never seems to get a signal when I am in my local supermarkets (Marks and Spencers, Sainsburys and Asda). I do not seem to get the same problem in other buildings (no matter how large) or in other shops. This has made me wonder whether there is anything about the building or contents (e.g. refrigeration units) of a supermarket that might prevent me getting a signal, or whether it might even be intentional for them to block the signal (although I can't see why). Any thoughts would be appreciated. GaryInLondon (talk) 02:40, 18 June 2010 (UTC)

There are ways to reduce or jam signals and there are businesses that do it to keep employees from using cell phones (they can only use them in the cell phone designated area). Some department stores who are worried about competitors may also jam phones and can be recognized if you start taking photographs and they ask you to stop. Ask the management. 71.100.0.224 (talk) 03:32, 18 June 2010 (UTC)

Does the building have a metal roof? Ariel. (talk) 03:46, 18 June 2010 (UTC)

Interesting; I'd like to know how widespread this practice is — in the US, radio jamming is illegal, including jamming a cell phone signal. Comet Tuttle (talk) 03:49, 18 June 2010 (UTC)

There's a difference between active jamming and natural attenuation of the signal. In the smaller traditionally-built supermarkets in rural northern England, mobile phones usually work, but I have a problem at home caused by very thick stone walls. Dbfirs 07:43, 18 June 2010 (UTC)

No problem getting a good signal in my local (large) branches of Sainsbury's and Asda, though a metal roof might well make a difference, as will the distance from the base station of course. You can find (clunky) maps of UK base stations here.--Shantavira|^{feed me} 09:11, 18 June 2010 (UTC)

I don't know about there, but supermarkets in the US are massive, with maybe a dozen aisles and fully stocked shelves between you and the outside when you're in the center, whereas the typical office building has a window within view at all times. So, the signal just has to go through more stuff. StuRat (talk) 12:59, 18 June 2010 (UTC)

I'd guess it's more to do with the distance from the base station than anything else, although a metal roof and cheap reinforced concrete construction won't help. Many UK supermarkets are built on cheap land with nothing else around but carparks, so it's hardly "hot territory" for the phone companies to ensure coverage. I can't imagine that the store is actually jamming coverage, because that costs money for no real benefit to the store. Physchim62 (talk) 01:51, 19 June 2010 (UTC)

I also don't believe that supermarkets are intentionally messing with cel-phones.

However, it's interesting as a thought experiment. I notice that many people in the supermarket call home to verify what they should buy and how much. If they weren't allowed to phone, would they buy more or less? APL (talk) 02:56, 19 June 2010 (UTC)

They'd buy less from that supermarket. 81.131.37.105 (talk) 14:19, 19 June 2010 (UTC)

As highlighted already, the Telecommunications Act prohibits interference with the EM spectrum so intentional suppression is illegal in the UK.

I'd agree with the previous points about the amount of metal in the structure interfering with the local infrastructure coverage.

ALR (talk) 19:10, 19 June 2010 (UTC)

Life on mars

Quick version: What I'd like is some old(er) sources which specifically make reference to the possibility of life on Mars, or the solar system in general, but before scientific consensus thought it was likely or possible. I specifically want to see HOW the topic is addressed. Did "science" say "it's not possible" or did they say "evidence suggests it's unlikely but more research is required". That kind of thing.

If that doesn't make enough sense, this is the "not so quick version". I'm writing an article about scientific discovery and basing it around the idea of "Life on Mars". When i was growing up, I didn't study astronomy or anything, but the impression I got from pretty much everything i ever read or heard was there was no life anywhere else in the solar system. This idea has been turned right on its head, quite recently in the scheme of things.

The point of my article is about how science constantly examines its beliefs and follows where the evidence leads. The idea that there might be life on Mars has shaken the scientific establishment but "believers" weren't persecuted and it wasn't ignored or covered up, it has been fervently pursued and is now one of the most exciting and important areas of research. I'm going to use this as contrast to the argument frequently made about science being scared of "supernatural" beliefs because they threaten the "established" beliefs of science. Vespine (talk) 05:40, 18 June 2010 (UTC)

I have to disagree with a part of what you wrote - the idea of life on Mars has not shaken up anything. Mainly because it's still just an idea - nothing has been found. (And the rock found on earth that might be from Mars doesn't count.) You'll have to wait for something to be found, and for best drama it will need to be something non-obvious, which some will say is proof of nothing, and others will say is proof, and only later will one or the other be known to be right. (That rock might turn out to be it.) It's far too early to use Mars for this. Also - it's very easy to forget about all the revolutions that turned out to be wrong, and where the establishment was right, and the "crank" was forgotten. There's a lot of selection bias going on here. Ariel. (talk) 05:59, 18 June 2010 (UTC)

The older view of course is that Mars was covered in irrigation canals and turned colors every spring as the plants sprouted. Rmhermen (talk) 06:06, 18 June 2010 (UTC)

well i disagree that "nothing" has been found. Extraterrestrial_life#Extraterrestrial_life_in_the_Solar_System several discoveries have been made, not just on Mars but several other places, which recently have made it more of a possibility. So anyway, this article makes it seem to me that the "possibility" has been considered for a long time, so where did my preconception of there being no other life in the solar system come from? I've discussed this with more then a couple of people and they all agreed with me that growing up you learned that Earth harbored the only life in the solar system.. Even watching cartoons we knew marvin the martian was a joke because there was no life on mars. Vespine (talk) 06:17, 18 June 2010 (UTC)

And? There still isn't life on Mars, nothing changed. And the link you posted says the same thing - no life (but some water). Your preconception, as you call it, is still correct as far as we know - no one has found any life. Ariel. (talk) 06:36, 18 June 2010 (UTC)

We're obviously not understanding each other. YES of course there is still no life found on Mars but now it is acknowledged as a real possibility, much more so then not too long ago. We weren't really actively looking for life on other bodies in the solar system, partly because we didn't have the technology, but partly because it seemed much less possible! Now what we've learned about extremophiles and astrobiology, it no longer seems so extremely unlikely! Not that I don't appreciate your input but if you still don't get what I'm trying to say, i don't need another reply from you telling me how wrong I am. I'm after sources specific to life in the solar system previous to say about two decades ago. Thanks.Vespine (talk) 08:58, 18 June 2010 (UTC)

Interesting - I always thought it was the reverse. After evolution, science assumed life was everywhere, including mars, and only after we got there and really looked around (i.e. now) do we no longer think there is life there. The viking missions (40 years ago) looked for life, so at least as far back as then it was thought mars had (or could have) life. And before that people looked for evidence via telescope. (And yes, we didn't understand each other. I think it's because we came from exactly opposite assumptions.) Ariel. (talk) 09:41, 18 June 2010 (UTC)

This section: Extraterrestrial life#Early_modern_period and the following one cover what you ask I think. It was pretty much assumed there was life on other planets, but when we actually got there and there was nothing, at that point the ideas started to shift the other way. Ariel. (talk) 10:00, 18 June 2010 (UTC)

Science can, and often does, entertain several conflicting theories when evidence is sparse. One sufficient evidence accumulates, we laugh at the theories that turned out to be wrong. I still like the idea (suggested long ago) that life on earth actually originated on Mars and was carried to earth by meteorites. Dbfirs 07:38, 18 June 2010 (UTC)

I disagree with the premise here. I don't think the possibility of there being life elsewhere in the solar system has changed much at all over the past 150 to 200 years - and certainly not in the last 50. But we've certainly changed where we think it might be:

• For the longest time everyone thought that Venus would be the most likely place - imagining lush swampy jungles and such like. But results from spacecraft showed Venus to be an exceptionally nasty place - and the possibility of life there was largely discounted. But recently, we've found 'extremophile' bacteria on earth, now people are starting to entertain the possibility of life on Venus once more!
• Now we're looking at icy moons far out around Jupiter and perhaps Saturn - and thinking that they are the likely places to look for life - when in the past, they'd have been considered to be completely impossible.
• The one constant through all of that was Mars - which was always considered to be a possibility for life - and is still considered a possibility today. The results we saw from the Viking survey missions of the 1970's showed much the same promise as we see today with the Mars Polar Lander with much the same tantalizing uncertainty. Our Life on Mars article has a reasonable 'history' section which explains that life on mars was stated as an explicit possibility in 1857 - and was probably thought to be a possibility by William Herschel as early as 1800.

What's really changed is that we've gone from highly speculative statements based on the appearance of the planet through a blurry telescope and horribly inaccurate estimates of surface temperatures from orbital data - to actually sending scientific instruments there and measuring things. Yes there is water on Mars - but no, there aren't any large canals flowing with water. What's also changed is our greater appreciation of how varied the conditions can be on earth and still have life flourish. I was watching a documentary the other night about how puddles of liquid CO2 exists at the bottom of some deep ocean trenches - and that there are small crabs and other animals that can live - even in close proximity to such nastiness! If that's possible - then life beneath the ice sheets of various moons of Jupiter and Saturn starts to look very much more plausible.

SteveBaker (talk) 11:40, 18 June 2010 (UTC)

That's actually some pretty good answers thanks, and some good sources. I also have recently read and watched a few things specifically about Enceladus and Europa which is what lead me to consider this question. So what I'm hearing is that probably my preconception, while growing up, that extraterrestrial life was not being expected in the solar system was a, common or not, misconception, not based on scientific consensus, but maybe just public opinion or pop culture or something. Thanks.Vespine (talk) 11:53, 18 June 2010 (UTC)

It's actually more interesting to me that the idea of life of Mars was rather quashed quite quickly in the 1960s. If you read sci fi from that era, the idea of life on Mars is presented as a not-that-far-out thing. I'm thinking of Stranger in a Strange Land, Martian Timeslip, etc. The life on Mars part of those stories are often the part that needs the least explanation. By comparison, by the late 1960s, 1970s, and so on, the idea that life would somehow actually be there seems to be quite hard to sustain, just ridiculous. Reading those stories now, and they sound quaint in their easy presumption that there could be life at all on Mars (creatures and plants and etc.), not just intelligent life. It was relatively recently that we found out that the planet was basically a dead desert, maybe with some frozen microbes hiding somewhere but that's it. --Mr.98 (talk) 13:30, 18 June 2010 (UTC)

I strongly disagree. If the scientific opinion in the late 1960's and early 1970's was that there couldn't be life on Mars, why did NASA spend a billion dollars (which would be an inflation-adjusted $5.4bn today) to send the Viking program there specifically to look for it? Those two missions launched in 1975 and must have started planning and budgeting in precisely the period you're talking about. To the contrary - scientists were rather of the opinion that they WOULD find life there - which is why the US taxpayer was convinced to spend so much. These days, comparable missions (such as the Phoenix lander and ill-fated Mars Polar Explorer) are funded on a shoe-string ($350 million). SteveBaker (talk) 14:01, 18 June 2010 (UTC)

Well, my timing might be off. But it's not too far. What I'm saying above is that in the late 1960s, it appears not to have been a big deal to assume there was life on Mars. At some point between then and, say, the 1990s, that changed. Whether that was in the mid-1970s or early-1970s or late-1970s, I don't know. --Mr.98 (talk) 16:59, 18 June 2010 (UTC)

It's possible you are talking of the time right after the Viking missions landed. When nothing was found, the idea of life on Mars become less popular. Ariel. (talk) 21:36, 18 June 2010 (UTC)

It's not even true that "nothing was found". In fact, the criteria that the designers of the mission set out for the positive detection of life by the on-board instruments were fully met - in a sense the instruments did indicate the presence of life. The flaw was in the experiment, which (it later emerged) could be fooled by non-biological processes which could plausibly be happening in Martian soil. It is most certainly NOT the case that the Viking landers proved that there was no life there - to the contrary, they produced evidence that it could be there - but sadly, due to the flaw in the tests they'd devised, the experiments didn't show that life must be there. That's not much to show for a billion dollar expenditure - but they did snap some cool photos and gather plenty of other scientific data so it wasn't a complete bust. SteveBaker (talk) 03:49, 19 June 2010 (UTC)

Again, Steve, I think we're talking past each other. I'm talking about large, multicellular life primarily, the sort of thing that excites the public imagination. There were no plants or critters. Imagining that there would be plants and critters on Mars seems to have been rather unimaginative in the 1960s. By the 1980s, nobody thinks there are any seriously there, and the question of "life" had receded into one about microbes. There's a big difference in the popular/public perception between microbes and critters. Nobody is saying Viking was a waste of money or time or anything. --Mr.98 (talk) 07:26, 20 June 2010 (UTC)

It's been a constant that there might be "life on mars", but the potential forms that life might take has constricted dramatically! As late as 1900 it would not have branded you as a crackpot to put forth a theory that the Martian canals were created by intelligent beings. APL (talk) 21:16, 18 June 2010 (UTC)

Also note that what people mean when they say "life" has changed. Early on, we were only concerned with intelligent life, or at least large animals. Some scum growing in a pond on some other planet wouldn't have been very interesting 100 years ago. Now that we could examine it's DNA, such scum would be extremely interesting, so there is far more interest in finding "any life" now than there was back then. StuRat (talk) 12:53, 18 June 2010 (UTC)

Radio Interference on a 'dead' radio.

On my journey to work in an urban environment, there is a specific spot where I get the sound of interference from my car radio speakers. It is a sort of clicking sound and is the typical sort of noise that one is used to hearing on occasions if a police car drives past, or there is known radio/electrcial activity nearby. My question arises because this happens when my car radio is TURNED OFF.

I have thought about this over several days, trying to work out how it happens and what processes are going on. But I always come up against the same problem . . . If there is no electrical current through my radio, what is generating the noise from my speakers?

I hope you can help. —Preceding unsigned comment added by 194.223.35.225 (talk) 07:12, 18 June 2010 (UTC)

Inductance? Dismas|^(talk) 07:23, 18 June 2010 (UTC)

What about the various beeps and bells your car makes? Are those piped through the speakers? Ariel. (talk) 07:23, 18 June 2010 (UTC)

Well it actually doesn't make many but I always assumed that those warning beep noises came directly from elsewhere - or how would I hear them if I had no car radio? Am I wrong? Are my speakers actually turned on while the radio itself is turned off? —Preceding unsigned comment added by 194.223.35.225 (talk) 07:28, 18 June 2010 (UTC)

It depends on the car, some have a dedicated speaker, others use the existing speakers. I think using the speakers is more common - it's easy to test, just make it beep and listen for where it comes from. Ariel. (talk) 09:43, 18 June 2010 (UTC)

On many (most?) cars speakers come standard. Radios are an option, but the speakers are difficult to install once the car has been assembled, so they get installed at the factory. APL (talk) 06:04, 19 June 2010 (UTC)

The interference is probably generated in your speaker coils by a large electromagnetic field. You could probably reproduce the effect at home by connecting a transformer to a household battery near to the car speakers. Dbfirs 07:31, 18 June 2010 (UTC)

Aaaah yes, of course: An electromagnetic field could be the energy that powers my speakers while also creating the souind. Thanks to both of you for showing me how this can happen. —Preceding unsigned comment added by 194.223.35.225 (talk) 08:00, 18 June 2010 (UTC)

You don't even need a strong electromagnetic field. Take any low-impedence speaker, grab a nine-volt battery, and hold a coin over the leads of the battery. When you generate a spark, you should hear the spark through the speaker. You have just made a basic radio. David E. Hughes performed these experiments in the 1870's, unfortunately he was basically ignored at the time, as no one saw any application for this novelty. We could easily have had broadcast radio several decades earlier had his work not been dismissed. Radio-frequency induction can occur with just about any speaker, and sometimes for unknown reasons, speakers can just start making sounds. Pay it no mind. --Jayron32 06:16, 19 June 2010 (UTC)

I was once in my kitchen with my boom box plugged in, but turned off, when it said, loudly, "How ya doin', good buddy ?". After I peeled myself off the ceiling, I realized it was just a stray CB transmission. StuRat (talk) 12:43, 18 June 2010 (UTC)

Poorly maintained CB radios are notorious for this sort of thing. (However I have to assume that modern digital units don't often have this problem.)

When I was growing up a neighbor (Briefly) had a CB that we could hear on just about everything we owned that had a speaker. Very strange. Intuitively you would think that this level of interference is impossible, but apparently it's not. APL (talk) 06:26, 19 June 2010 (UTC)

breasts full of milk

Can cats who have had their kittens taken away and have breasts full of milk die or be injured by the absence of nursing or else what happens to the milk? 71.100.0.224 (talk) 11:16, 18 June 2010 (UTC)

Very unlikely. I don't know about cats, but in humans (and cats are likely to be the same) the back-pressure eventually shuts down the milk production, and the lack of lactation does not stimulate any more milk production. It eventually gets reabsorbed. It hurts though - it can hurt a lot. See Breast engorgement which also discusses what you asked. Ariel. (talk) 11:30, 18 June 2010 (UTC)

Of course for most animals losing all their young even in a litter wouldn't generally be that uncommon an occurence. For the mother to not be able to survive this is needless to say unlikely Nil Einne (talk) 20:44, 18 June 2010 (UTC)

This newspaper in 1998 reported that El Niño weather left eight hundred dairy cows unmilked because of disrupted power, who died after becoming infected. Cuddlyable3 (talk) 21:39, 20 June 2010 (UTC)

Of course, dairy cattle are hardly a normal example of milk production in mammals (not that you said so). We actually have an article on mastitis in dairy cattle, which is apparently quite common. Matt Deres (talk) 21:47, 20 June 2010 (UTC)

I fixed your link -- it was missing a bracket. 67.170.215.166 (talk) 05:11, 21 June 2010 (UTC)

Thanks! Matt Deres (talk) 20:23, 21 June 2010 (UTC)

Why are there no Herring Gulls in Hampshire?

In my local area (Southampton, UK), seagulls are very common, it being near the coast, however, it is only the small gulls (Black-headed gulls I believe). When I go to coastal areas in other parts of the UK, there are always loads of the huge Herring Gulls...but for some reason, there do not appear to be any in Hampshire, which surprises me, as these gulls are usually common in urban areas, as they are well-fed by litter louts. We do have wheeliebins as opposed to black bags (the large gulls enjoy ripping those open) and waste in incinerated rather than going to landfill sites (another favourite haunt of gulls) now but I'm not sure that is the reason. The WP article on Herring Gulls shows they are found in every coastal area of Great Britain but I am not sure if there are other areas of the UK that don't have them.

GaryReggae (talk) 11:21, 18 June 2010 (UTC)

The lack of a local landfill and the presence of wheelie bins is certainly a possibility, IMO. Herring Gulls, as well as being longer and taller, are also far more 'substantial' birds - and need to eat a lot, for their size. Perhaps they are unable to eke out a living on discarded food items found in the streets? Has the sea been fished out where you are, as a matter of interest? If so, that's another possibility. Herring Gulls do prefer to feed their chicks on fresh fish. Strangely, the HG is actually declining as a species in the UK, despite the urban colonies in certain areas exhibiting massive yearly growth... --Kurt Shaped Box (talk) 17:13, 18 June 2010 (UTC)

Another possibility is that the Southampton herring gulls are all on the Isle of Wight! Southampton is actually quite a way from the open sea, so maybe the larger gulls have stayed closer to the open water, leaving the smaller gulls to pick up the urban food that's still available. Physchim62 (talk) 00:36, 19 June 2010 (UTC)

It is usually associated to food. There must be no fish-and-chip vans and outlets in Southampton. No fishing-trawlers. Normally along the Kent coast when getting your fish-and chips you have to watch out for the big gull awaiting his opportunity, usually perched above the van itself! MacOfJesus (talk) 21:45, 23 June 2010 (UTC)

Immunosuppression drugs -> skin like tissue paper?

About 20 years ago, my grandmother had a kidney transplant and, as a result of the immune suppression drugs that she takes, her skin is extremely delicate and very slight knocks or abrasions will remove it. Recently, while alighting from a motorcar, her ankle was caught in the seat-belt and the resulting pressure created a wound. Apparently, when her hosieries were removed at the hospital, her skin was in the mesh of her tights. I am not seeking medical advice; she is now receiving daily care from the NHS. I would like to know whether this is a known condition and whether it has a name? Is it a rare reaction to immunosuppression? --78.150.225.204 (talk) 13:51, 18 June 2010 (UTC)

Skin thinning and easy bruising are common side effects of corticosteroids (source), which are a widespread and very powerful class of immune suppressants. The medical term is skin atrophy. I personally have some nasty scars from when I was on prednisone. --Sean 14:56, 18 June 2010 (UTC)

Sodium bromide as salt substitute

Would sodium bromide be a good salt substitute? --Chemicalinterest (talk) 15:29, 18 June 2010 (UTC)

This link discusses an incident where sodium bromide was taken instead of sodium chloride (by accident). I'm not sure whether that toxicity is caused because there was too much sodium bromide, or if it's because NaBr itself is toxic. Regards, --—Cyclonenim | Chat  17:51, 18 June 2010 (UTC)

The Bromide article discusses some of the toxicity/biochemistry of this ion. DMacks (talk) 18:36, 18 June 2010 (UTC)

Salt substitutes normally replace the sodium metal cation not the chlorine halide anion. The usual substitutes are calcium, potassium or possibly magnesium, all of which are needed in human biology. This is to reduce the chance of hypernatremia, excessive sodium levels (natrium is the old name for sodium, its the source for sodium's symbol, Na). Excessive chlorine levels is hyperchloremia, which appears to be asymptomatic. As bromine is a sedative, it shouldn't be used. Selenium and iodine are toxic in more than trace amounts. The common polyatomic ions like nitrate or sulfate are also poisonous. Phosphate is probably safe. CS Miller (talk) 13:22, 19 June 2010 (UTC)

Windmill on an airplane

There was previously some discussion about whether net energy would be harvested from having a windmill on a car. Would a windmill on an airplane harvest energy in a steady wind? I imagine it could do so when the wind was gusting, due to the accelerating wind acting against the inertia of the plane. 92.15.14.87 (talk) 17:31, 18 June 2010 (UTC)

As mentioned in the other thread, the ram air turbine is a windmill that pops up if all the engines fail, and it generates emergency power so the pilot can at least have some flight instruments to read, and try to control the plane. But in ordinary flight, a windmill would create drag on the aircraft, and the aircraft's engines will have to use more energy to overcome this drag than the amount of energy the windmill can generate. This occurs regardless of whether the aircraft is flying into the wind or with the wind. It's a net loss, which is why you don't see windmills on airplanes. (Last point of clarification: The ram air turbine generates extra drag, too, but if the engines have all failed then you have much bigger things to worry about than the little windmill's extra drag.) Comet Tuttle (talk) 17:44, 18 June 2010 (UTC)

I meant steady wind and steady level flight also - no diving. What about on a glider? 92.15.14.87 (talk) 18:04, 18 June 2010 (UTC)

No net power can be harvested this way - there is no such thing as a free lunch. But if your glider needs electrical energy - then a windmill will rob you of some kinetic energy (and therefore make you lose height faster and ultimately glide less far) - but if you need electricity to power instruments or whatever, then that might be a trade-off that you're prepared to make. SteveBaker (talk) 18:39, 18 June 2010 (UTC)

A windmill on a glider will produce a less efficient glider. If you need juice for electronics, solar panels are a more elegant solution, given the big long wing surface. With the widespread introduction of large lithium-ion batteries, battery-powered electric propulsion is becoming possible, allowing self-launching and extended flight for gliders, but that's a windmill in reverse. Basically, any harvesting of energy via a windmill on any moving object will come at a cost of worse performance or higher energy consumption, all things being otherwise equal. Acroterion _(talk) 18:43, 18 June 2010 (UTC)

As mentioned in the other thread (and still true here), it's not necessarily true that adding a windmill will make your aircraft less efficient. It could add more drag than the power it produces, but it could also add less than that; it could even reduce the drag. What it can't do is give you enough power to preserve your steady-state flight without any other power source. That would be a perpetual motion machine. (In the case of a ground-based vehicle, though, even that's not true, because you can extract arbitrary amounts of energy from the motion of the air relative to the ground.) -- BenRG (talk) 19:11, 18 June 2010 (UTC)

One thing to consider that might be getting overlooked in some of the above... the speed of the wind relative to the ground is pretty unimportant. An airplane in flight is moving pretty fast through the air. So the effective wind is backwards relative to the plane, at whatever speed the plane's airspeed is at the moment. So you don't need to worry whether the wind will run out - there will always be wind, as long as the plane is moving fast enough to sustain flight. Friday (talk) 19:17, 18 June 2010 (UTC)

You can not harvest energy from a steady wind, you can only harvest it from a changing wind, or a wind that is different from something else (like the ground). See Dynamic soaring for a dramatic example. Ariel. (talk) 21:32, 18 June 2010 (UTC)

When we are flying, we have airspeed and ground speed. Whether we are flying into the wind or with the wind, we still fly at the same airspeed, and as far as the aircraft is concerned, that's all that's relevant. Therefore, assuming steady wind and steady level flight (we call that "straight and level"), the airplane will always be flying x miles per hour in relation to the air moving around it. In that respect, the airplane is already using (or fighting against) all of the wind energy available to it. If it's flying with the wind, it tracks faster along the ground (ground speed). If it's flying against the wind, it tracks slower. Adding a fan at that point would cause more drag, and slow the aircraft down (or cause it to require more power). Falconus^{p t c} 22:02, 18 June 2010 (UTC)

Some of the early biplanes like the de Havilland Tiger Moth and de Havilland Dragon Rapide had small wind driven generators to provide electrical power. MilborneOne (talk) 15:54, 19 June 2010 (UTC)

Someone mentioned drag. You would have two powers fighting against themselves. Either the plane would fall or the power received would be too weak to be significant. The energy received would be at the expense of dragging the plane. So, whatever energy would be received would be "lost". Every effort is made to reduce the drag to make the flight economical. Air has a very heavy drag effect. So the method you envisage to recover some of the energy would result in spending more!

The support teams of The Ras Taltan, a cycle race in Ireland incorpurating the Ring of Kerry, reported that the cycles strapped to their support cars had the effect of producing very low MPG in fuel consumption. MacOfJesus (talk) 21:31, 20 June 2010 (UTC)

The Komet fighter also had a ram-air turbine in the nose to provide electric power. 67.170.215.166 (talk) 05:15, 21 June 2010 (UTC)

Does abstinence cure any addiction?

Addiction of no matter what - sex, drugs, gambling. The idea behind it is that if you stay clean for a long time, your body will reset the addiction. --Quest09 (talk) 17:33, 18 June 2010 (UTC)

I'm not sure you can say abstinence cures addiction because usually people who abstain for years from, say, alcohol after becoming alcoholics can relapse on the first drink years later. If it was a cure, this wouldn't happen. Instead, it's just staying away from what weakens you. With respect to drugs, it's going to depend on the type of addiction: psychological or physical? Psychological addictions should be easier to remove by abstinence, but physical addictions often require weaning off the substance rather than a complete halt. Regards, --—Cyclonenim | Chat  17:47, 18 June 2010 (UTC)

Some would say yes, you can quit anything cold turkey if you have the willpower. Others would say no, you never truly cure an addiction unless you replace it with something else. There is probably a little truth in each, but since addiction is such a multi-faceted problem, there is no clear answer to your question. All we really know is what we have observed of the process, we don't have clear evidence of addiction at work inside the body, aside from chemical changes which are only a small part of the process. --144.191.148.3 (talk) 17:49, 18 June 2010 (UTC)

A distinction must be made between physiological dependence (Physical dependence), in which the balance of neuroactive chemicals in the brain is altered directly by the substance abuse, and behavioral addiction, in which the the balance of neuroactive chemicals in the brain has not necessarily been externally perturbed. In either case the etiology, the symptoms, the treatment, and the results vary greatly, so nothing general can be said without overgeneralizing the things grossly. --Dr Dima (talk) 18:17, 18 June 2010 (UTC)

My Google search for abstinence cure addiction found http://health.howstuffworks.com/addiction.htm/printable. I did not find there a definitive answer to your question, but I did find some interesting information.—Wavelength (talk) 02:53, 19 June 2010 (UTC)

This might be a language / definition problem. Does "cured" imply "permanently cured"? During the period of abstinence, by definition, one is not participating in the activity. This could be labeled "temporarily cured" (insofar as the person is not participating in the activity). But there is always the possibility of relapse. "Addiction" is subject to interpretation: broadly speaking, we can sub-categorize it into "physiological" and "psychological" dependence. The "cure" for addiction can be interpreted subjectively and may span these categories. For example, detoxification following a drug or alcohol addiction is typically the first step in treatment. For certain drugs, total "cold-turkey" abstinence techniques may actually be less effective than other methods (often a surrogate substance is used to help alleviate withdrawal symptoms - e.g., Opioid Replacement Therapy). Details depend on the type and circumstances of physical dependence. But "detox" is not the same as "cured" - it is obvious that relapse is a serious issue, because addiction has a significant psychological component, independent of physiological/chemical dependence. In the medical or psychological community, this problem of definition is sidestepped by using more precise terms. For example, a patient is classified based on the type of dependence, rather than simply saying that they are "addicted". This helps decide what kind of treatment is preferred. It is pretty rare (at least in the modern institution of psychology) to say that anybody is ever "cured" of a psychological issue, including addiction or substance abuse problems, because "cure" implies some kind of certainty that relapse will not happen. People who undergo treatment for addiction have various strategies to reduce the probability of relapse - again, based on the type of addiction and the circumstances, this might include total abstinence. Nimur (talk) 18:33, 19 June 2010 (UTC)

In studying the life of Saint Augustine, he stumbled on a number of positive steps towards a cure of addiction. However, the cure comes in steps. For The Alcoholics Anonymous there are twelve steps. Study C.G. Jung. All agree that there are steps towards a complete cure. Going-it-alone is a very hard road, and would not be possible for some kind of addictions, and because man is a gregarious creature the cure would needs be with others. MacOfJesus (talk) 20:51, 20 June 2010 (UTC)

'natural' alkyl halides?

Are there any natural alkyl halides produced by living organisms? Would I see ever see chlorine substituted on a random amino acid in a protein for instance? John Riemann Soong (talk) 18:11, 18 June 2010 (UTC)

I don't know any specific complex natural alkyl (sp³) halides off-hand, but maybe follow the links and refs in the "Occurrence" and "Biosynthesis" sections of our haloalkane article? DMacks (talk) 18:31, 18 June 2010 (UTC)

See also Organochloride#Natural_occurrence not much info, or Encylo..Britanica better. Not suprisingly things that live in salt water are a common source.

eg http://www.google.co.uk/search?hl=en&q=asparagopsis+taxiformis&meta= (mentioned in the britannica article) aka Limu kohu

There's a nice example of thr type of thing found here google books:Invitation to organic chemistry By A. William Johnson page 113, with both alkyl and alkenyl halide (carbon-iodide bonds are also common - but most I've seen are attached to benzene or similar)

If you want more then I recommend trying using google scholar http://scholar.google.co.uk/ (searching "natural product" + bromine/halogen , with marine/algae etc to narrow seems to work..) if you don't use scholar search returns a lot of results about metal halide lights for marine aquariums...

eg this worth reading (and lots more) turns up easily with aromatic, akenyl and alkyl halides.

Alternatively hunt down and marry a marine biochemist.. :) 87.102.32.15 (talk) 19:21, 18 June 2010 (UTC)

As for halogens in amino acids - I was going to say not likely - since most examples I know of tend to appear to be the result of electrophilic attack on double bonds eg terpene like compounds etc .. but no: [3] halogenated tyrosines found in marine animals - spongin in sponges and gorgonin in Gorgonians this time - again marine creatures.87.102.32.15 (talk) 19:49, 18 June 2010 (UTC)

For an sp3 halogenated amino acid look into "barbamide" structure- contains a trichloromethyl group that is thought to derive from a halogenated leucine [4], there are probably thousands of other examples.87.102.32.15 (talk) 21:01, 18 June 2010 (UTC)

Thyroxine is not an alkyl halide, but is a halo-organic formed naturally in the human body. Physchim62 (talk) 00:29, 19 June 2010 (UTC)

What's the selective pressure (or function) of the iodide substitutions? Is it for their EWG effect to make the molecule easier to cleave? Make the molecule exceptionally large, bulky and fat-soluble? Or? John Riemann Soong (talk) 16:27, 21 June 2010 (UTC)

Also I take it most of our iodine nutrition comes through the form of I- iodide and not elemental iodine :o -- does an enzyme oxidise iodide to some intermediate which can then grab electrons on an aromatic ring? Or does the iodide ion attack aromatic rings nucleophilically? (With the help of an enzyme, of course.) John Riemann Soong (talk) 16:29, 21 June 2010 (UTC)

As usual, you can start reading wikipedia to find leads to help answer your questions. The thyroxine article mentions some of the key enzymes, and also tells you another article to read. That article (as well as the ones about each enzyme) tell you more (with refs to scientific literature) about the chemical origin of the iodine atom and the chemistry of its reactions. What I don't see is information about "why iodine" (speculation on evolutionary pressures or hereditary tracing of the related regulatory pathways). DMacks (talk) 14:22, 22 June 2010 (UTC)

Amino acids in a vegan diet

Do vegans have any deficiency of particular amino acids in their diets, or do they have all of them? Thanks 92.15.14.87 (talk) 18:18, 18 June 2010 (UTC)

According to our article Legume: "Legumes contain relatively low quantities of the essential amino acid methionine. To compensate, some vegetarian cultures serve legumes along with grains, which are low in the essential amino acid lysine, which legumes contain. Thus a combination of legumes with grains forms a well-balanced diet for vegetarians." SteveBaker (talk) 18:29, 18 June 2010 (UTC)

Yeah, rice and beans, aside from being tasty, is likely to have the amino acids you need, all together in one meal. You can get all essential amino acids from plant material, but you have to know what you're doing. Whereas you can be an uneducated meat eater and easily get them all. Friday (talk) 18:45, 18 June 2010 (UTC)

Vegans who don't go to any special effort are most likely to be short on lysine, but as the other replies pointed out, eating legumes is a good solution. Soy protein in particular has nearly the same quality as beef protein, so vegans who eat lots of soy products don't need to worry about this. (There may be other issues with eating lots of soy, though.) Looie496 (talk) 21:37, 18 June 2010 (UTC)

While this is not something I've looked into myself very well, I saw something a few week back while researching for another answer. I can't seem to find the particular source (well one of the ones I did find may be it, but I seem to recall something that I didn't see in any of the sources I provided). But sources (some of these may be a bit biased but their citations and info seems resonable to me) like Protein combining, Vegetarian nutrition, [5], [6] [7] [8] [9] (unsure about this source, comment on tryptophan doesn't appear correct) suggest while you do want a balanced diet, it is rather hard to get insufficient essential amino acids even on a vegetarian or vegan diet provided you have sufficient calorific intake.

Even if you only eat potatoes, you could easily get essential amino acids in sufficient quantities (sources say 6-8 large potatoes), although your diet is likely to be deficient in other areas (and I find it doubtful many people in the developed world would choose such a diet not counting those who eat mostly chips of either kind of course). Rice seems a bit more iffy 7.5 cups of cooked rice seems quite a lot then again if it's the only thing your eating you may need that much to fulfill you calorific intake.

In any case, note there is no need to combine proteins in one meal to ensure sufficient protein intake or balanced protein intake, simply get enough thoroughout the day. Body builders and others who want a high protein diet obviously need to take a bit more care to ensure their protein intake isn't limited by a small intake of one essential amino acid.

But in summary although getting amino acids in sufficient quantities seems to be a common concern, from what I can tell it's not really generally that big a deal, even without great effort most vegetarians and vegans who have access to a resonable set of foods won't usually won't end up deficienct even without making much of an effort. Nil Einne (talk) 22:51, 18 June 2010 (UTC)

The things I'm familiar with vegans often being deficient in (if not careful) is not amino acids but rather iron (Anemia) as well as Vitamin B12 (Vitamin B12 deficiency). Buddy431 (talk) 01:55, 21 June 2010 (UTC)

Natural sea salt

Is natural sea salt any healthier than artificial salt? --75.25.103.109 (talk) 21:07, 18 June 2010 (UTC)

When you say artificial salt, do you mean to refer to a salt substitute? If not, I think sodium chloride is sodium chloride and it doesn't matter from whence it is derived, whether sea or flats. DRosenbach ^{(Talk | Contribs)} 21:26, 18 June 2010 (UTC)

(after ec)The term "artificial salt" is pretty meaningless. Sea salt contains sodium chloride (table salt) plus other stuff, depending where it came from. See Sea_salt#Taste_and_health. My understanding is, there is no evidence that sea salt is healthier than any other salt. Many people consume too much sodium, and eating sea salt won't change that. There is a widely held superstition that "natural" things are healthier than "artificial" things, but the people who go around believing such things usually can't explain what they even mean by those terms. A grizzly bear is very natural indeed but should not be considered safe. Friday (talk) 21:27, 18 June 2010 (UTC)

(ec2) That depends on the rest of your diet. It contains a lot more minerals other than sodium and chloride, but if you get adequate amounts of them from the other things you eat, it might not make much of a difference. Looie496 (talk) 21:28, 18 June 2010 (UTC)

(ec again!) Have you read Sea_salt#Taste_and_health? Sea salt contains some iodine which we need in our diet but standard table salt does not. As already mentioned, they are both almost entirely sodium chloride so there is little difference. 86.7.19.159 (talk) 21:30, 18 June 2010 (UTC)

You got that backwards - table salt usually has iodine added, and sea salt contains no significant iodine. Friday (talk) 21:33, 18 June 2010 (UTC)

Seaweed does, though. Kind of a lot of it if I recall correctly. No real relationship with sea salt, of course, except that you could argue that the saltiness in seaweed is sea salt, and you might expect the same type of consumer to eat it. --Trovatore (talk) 21:36, 18 June 2010 (UTC)

Iodine is not added to salt in the UK. Sea food is a source of iodine, especially seaweed. 92.15.4.168 (talk) 13:40, 19 June 2010 (UTC)

To my knowledge no one is artificially manufacturing salt. It would be a very expensive process, and salt is pretty cheap. Most table salt comes from salt mines where workers dig up giant deposits of salt from parts of the ocean that dried up eons ago. APL (talk) 21:51, 18 June 2010 (UTC)

Around here, most table salt comes from evaporation. They have big shallow ponds carved out of San Francisco Bay. The salt article doesn't seem to have a breakdown of how much is evaporated, versus mined, worldwide.

Even though it's evaporated from seawater, it's not ordinarily marketed as "sea salt". I don't know whether there are any special rules to qualify the product as "sea salt" or not. --Trovatore (talk) 23:04, 18 June 2010 (UTC)

I didn't realize that. I thought that all salt that came from evaporation was sold as "Sea Salt". I wonder what the difference is. It would be hilarious if it were just marketing. That is, the same salt, from the same source, sold as both table salt and sea salt, for different prices. APL (talk) 03:02, 19 June 2010 (UTC)

Sea salt is generally unpurified. Table salt, whether it is mined or evaporated from ocean water, goes through a purification process to be almost pure sodium chloride. So, if you take sea water, evaporate the water, and then use the leftover crystals directly, that's "sea salt". If you take that sea salt, further purify it and remove all the non-sodium chloride impurities, you have "table salt". --Jayron32 05:12, 19 June 2010 (UTC)

Assuming 'artificial salt' means refined rock salt (ie the mined type) there is difference that rock salt is very old and was laid down before man made polution, whereas sea salt has the potential to be polluted by more recent man made discharges. In practice I have no idea if this is a factor or whether there is regulation of sea salt purity.87.102.32.15 (talk) 22:55, 18 June 2010 (UTC)

So sea salt is sodium chloride with some contaminants, whereas table salt is slightly purer sodium chloride with different contaminants. Gandalf61 (talk) 09:16, 19 June 2010 (UTC)

You would be healthier adding no salt at all to your food. It's very likely that you get more than enough salt or sodium hidden in the processed foods you eat. I think the recently reduced UK target for salt consumption is 4g per day, but the true optimum is belived to be about 2.3g per day as far as I recall. I suggest you try estimating and adding up your total salt or sodium intake per day (from the nutritional information given on processed foods where available etc) - you will almost certainly have an unpleasant surprise. 92.15.4.168 (talk) 13:33, 19 June 2010 (UTC)

For a good salt substitute; try Ruthmol Salt. MacOfJesus (talk) 23:44, 19 June 2010 (UTC)

Most Salt substitute is potassium chloride. While it's true that most westerners consume much more sodium than they need, and that they could do to get more potassium, there are definite health implications involved with consuming too much potassium as well. I'd recommend having a good reason before using a salt substitute, and discus it with your doctor ahead of time. Buddy431 (talk) 01:45, 21 June 2010 (UTC)

Organic Materials

what are the molecular components from which organic materials are constructed?Sadiehyde (talk) 21:50, 18 June 2010 (UTC)

See functional group. --Chemicalinterest (talk) 21:57, 18 June 2010 (UTC)

Blossoms and leaves: coming and going

As I recall from my experience, spring blossoms on some deciduous trees appear first at the extremities and drop off last from the extremities, and spring leaves appear first at the extremities and autumn leaves drop off last from the extremities. To what extent is my memory correct? What is the scientific (possibly biochemical) reason for the blossoms and leaves behaving in those ways?—Wavelength (talk) 22:58, 18 June 2010 (UTC)

How much sunlight and shade do the extremeties see versus the interior branches? TenOfAllTrades(talk) 23:11, 18 June 2010 (UTC)

Apparently, they see more sunlight and less shade, but I do not know how much, either in absolute measurements or in relation to the amounts seen by the interior branches.—Wavelength (talk) 23:23, 18 June 2010 (UTC)

The distribution of plant hormones might have something to do with it eg Auxins I would guess that they dominate at growing tips and diffuse to the 'interior parts'. Also see Plant hormone - .. - Abscisic acid seems to be involved (in some cases) - though I'm not sure if it's causal (or the mechanism by which it is produced at growing tips..) . Maybe someone else can expand on this.87.102.32.15 (talk) 23:17, 18 June 2010 (UTC)

By the way I can't actually confirm what you remember - and there are growing tips all over the plant branches (potentially).. so .dunno. 87.102.32.15 (talk) 00:27, 19 June 2010 (UTC)

Neither do I believe that deciduous trees in general lose their blossom or leaves in this way. Richard Avery (talk) 14:16, 19 June 2010 (UTC)

As I understand it; It does depend on the weather and the soil and the altitude and of course the sunlight. The blossoms will tend to develop into fruit, or fall-off in frost early, or come off early in a storm. MacOfJesus (talk) 23:12, 19 June 2010 (UTC)

Blossoms will, after pollination will progress towards becoming fruit, and will fall-off when ripe unless weather conditions dictate otherwise. MacOfJesus (talk) 08:08, 20 June 2010 (UTC)

Plants that have their flowers in spikes such as a foxglove nearly always open from the bottom up. I think they go to seed from the bottom up too. Flower spikes that open from the top down are rare. 92.28.240.72 (talk) 10:14, 20 June 2010 (UTC)

Why is the speed of light relative to an observer constant regardless of the velocity of the source of light or of the observer?

The whole relativity thing depends on this phenomenon, so it would be interesting to know WHY this is the case.––220.253.96.217 (talk) 23:31, 18 June 2010 (UTC)

Because that explanation best fits the universe we observe. At some point, questions of "why" regarding fundamentals are philosophical rather than scientific. — Lomn 01:17, 19 June 2010 (UTC)

The two parts of this have two different answers. The reason it remains constant regardless of the velocity of the source is basically the same as the reason waves generated by a boat traveling through water remain constant regardless of the velocity of the boat. But the reason it remains constant regardless of the velocity of the observer is much deeper: it is a result of the Einstein equations for special relativity, which say that when an observer moves, the basic laws of physics only remain valid if time is rescaled, and the amount of rescaling is exactly what is needed to keep the apparent speed of light constant. Looie496 (talk) 01:28, 19 June 2010 (UTC)

Modern physics rejects Looie496's assertion that the reason the speed of light remains constant regardless of the velocity of the source is basically the same as the reason waves generated by a boat traveling through water remain constant regardless of the velocity of the boat. Looie496's presumption that there exists a medium (water) that light travels in is the old Luminiferous aether theory that has been disproven since 1887 by the Michelson–Morley experiment, Cuddlyable3 (talk) 11:27, 19 June 2010 (UTC) small tweak

Relativity does not presume that there is no such thing as space. Light as viewed in special relativity consists of oscillating electric and magnetic fields, and those fields are defined in spatial coordinates. Maxwell's equations for electromagnetic fields produce an oscillation that propagates across space according to the wave equation, which is the same equation that governs the propagation of waves across the surface of a body of water. Looie496 (talk) 17:08, 19 June 2010 (UTC)

The Wave equation to which you refer is derived by the classical mechanics of applying Hooke's law to an elastic medium, in which one finds a physically realizable value for the speed of wave propagation. Maxwell in 1865 published his equations believing in the rest frame of the luminiferous medium. They are laws of Classical electromagnetism. Maxwell was no more able than Robert Hooke to conceive the relativity of the speed of light though he knew an approximate value of c. Cuddlyable3 (talk) 23:42, 19 June 2010 (UTC)

The whole relativity thing depends on that only if you chose to follow the historical aproach (which most introductory books do) and postulate the constancy of the speed of light and get everything else from there. Alternately you could postulate, for instance, the Lorentz transformations and get everything else from there (including the constancy of the speed of light which is not a postulate on that approach). You might ask now why does the universe obey the Lorentz transformations? Well, it is a matter of space-time symmetries. The Lorentz transformations obey a set of symmetries which are generalizations of space rotations. Asking why the universe obeys Lorentz covariance (That's the technical name of the symmetry) is simmilar to asking why the universe is isotropic and homogeneous. The answer of couse is that's simply the way it is and we know that from empirical obsergations. There is no why. Dauto (talk) 03:11, 19 June 2010 (UTC)

I think it's important to distinguish "we don't know why, or even if there is a why" from "there is no why". The former would be a much more justified statement. --Trovatore (talk) 03:19, 19 June 2010 (UTC)

I think the latter is the better statement. Dauto (talk) 15:52, 19 June 2010 (UTC)

Why do you think that? Of course, it's a stronger statement, and we want to make the strongest statements we can justify. But I don't see that you have any justification for it whatsoever. --Trovatore (talk) 18:51, 19 June 2010 (UTC)

I agree with Trovatore. Lorentz invariance could easily end up having an explanation (in terms of some sort of pregeometry). -- BenRG (talk) 18:58, 19 June 2010 (UTC)

Of course there could be an explanation but ,like a three year old child, we could simply ask another 'why' question such as 'why is that pregeometry that way?'. Let's not kid ourselves, all scientific theories rely on some kind of axiom or priciple for which, within the framework of that theory, 'there is no why' is the only possible answer. Since there is no way around that, I believe that 'There is no why' is the better statement. Dauto (talk) 02:40, 20 June 2010 (UTC)

I very strongly disagree. Just because it's turtles all the way down doesn't mean you have to stop at the first turtle. Now, it would be different if you said "we're pretty sure this is the way it is, whether we know why or not", that would be a useful and practical statement. But insisting that "there is no why" reminds me of strong atheism, which I think is pretty ridiculous. --Trovatore (talk) 03:23, 20 June 2010 (UTC)

I think that "there's no why" is indeed the best answer to that kind of question. Why do you say strong atheists are ridiculous? It seems to be a point of view as viable as any of the world religions if not more. Dauto (talk) 17:05, 21 June 2010 (UTC)

Well, I think you're wrong. You have no justification for claiming there is no why. Or if you do, you haven't explained it. I think the same thing if you're claiming actively that there is no God, but I probably shouldn't have brought that up because it's not really the issue here. --Trovatore (talk) 23:15, 21 June 2010 (UTC)

While we're mincing words, "it is a result of the Einstein equations for special relativity..." This is accurate, but it is phrased in such a way that it sounds like one day Einstein just decided that he should write some equations to make the speed of light constant in all frames. The way the universe works is not a consequence of Einstein, or any other scientist's equations. The universe works the way it does - and Einstein's equations happen to explain this particular detail in a simpler and more consistent way than any other explanation. Universal principles are not a "consequence" of our mathematical effort to represent them. Instead of attributing this fact to the equations, we should say "if this fact were not true, there would be an inconsistency in the universe because of the way that electromagnetic waves work. This inconsistency was first resolved mathematically by Einstein." Nimur (talk) 18:40, 19 June 2010 (UTC)

If you're asking why we believe it: testing. If you're asking why it's true, special relativity explains it. — DanielLC 06:30, 19 June 2010 (UTC)

...And if you're asking "why it is the way it is instead of working out some other way", that answer lies at some level in either philosophy or religion. The most agnostic answer to the "big why" is probably the Anthropic principle which is a type of logical tautology. The Anthropic Principle states that the laws of the universe exist the way they do because we are observing them. To state it another way, the fact that humans exist to observe the universe is predicated on the fact that the laws of the universe cannot exist in any way other than what we are observing, because if they were different, the universe under THOSE laws could not have produced humans to observe them. Or, to put it a third way, if the universe obeyed different laws, it would not have produced an intelligent life form to ponder the universe. So the answer to "why" could just be that if it were different, it wouldn't exist in a way to allow us to observe those differences. --Jayron32 06:52, 19 June 2010 (UTC)

That's a pretty "extreme" statement of the strong anthropic principle" - as you have phrased it, Jayron, you discount the possibility of a null space within which certain physical laws could differ while still providing a universe suitable for intelligent life. Nimur (talk) 18:48, 19 June 2010 (UTC)

I agree. E.g., there is a formal description of Jayron32's brain, therefore any algorithm that aims to simulating it, defines the laws of physics of a a universe in which he lives. Count Iblis (talk) 19:16, 19 June 2010 (UTC)

Looking at the philosophical answer: Does this "big why", and what is said above "prove" the existance of God, as defined in Saint Thomas Aquinas' proofs of God's existance? Particularly so, if it is said that: the universe cannot exist in any way other than what we are observing. Also, defining how a person thinks in whatever method, could in itself be proving God's existance! If you assume that the observer observes that which is in reality, you could be proving God's existance. Neil Armstrong's statement 1969: "There is a Santa Claus"! However, there is a way around it! If you say that there is no reality outside yourself, and that the only thing I know is that "I" exist. But then, there is no light and no universe! And as for the speed of light: that is just a figment of one's imagination! MacOfJesus (talk) 20:50, 19 June 2010 (UTC)

I would start with e=mc^2 - once you have that relativity is required. The reason is that as an object gets faster it's mass goes up (since it's energy has mass), to speed it up even more requires even more energy, that additional energy makes it even heavier. Carry that to the end shows that at a speed of c the mass is infinite. That basically requires relativity. Because without it you could add speeds, for example .75c + .75c = 1.5c But we already showed that speeds above c mean infinite energy. So in a universe where mass and energy are interchangeable relativity is required. Ariel. (talk) 07:54, 20 June 2010(UTC)

Try studying Physics and Existentialism at the same time. MacOfJesus (talk) 08:05, 22 June 2010 (UTC)

To go back to the original point of the OP; Maybe it is because we observe by light, which is everywhere for the viewer so there is no start point as light is everywhere as the viewer cannot observe anything without it! MacOfJesus (talk) 11:58, 23 June 2010 (UTC)

Paper cuts vs. "normal" cuts

I've seemed to notice that paper cuts have more pain to them than your average minor cut, and a kid in my scout troop who accidentaly sliced his finger with a knife (almost bad enough for stitches) said it hurt less than some paper cuts he's gotten. What causes paper cuts to hurt worse than other "normal" cuts? Ks0stm ^(T•C•G) 23:49, 18 June 2010 (UTC)

From Paper cut: "Paper cuts can be surprisingly painful as they can stimulate a large number of skin surface pain receptors (nociceptors) in a very small area of the skin. Because the shallow cut does not bleed very much, the pain receptors are left open to the air, ensuring continued pain. This is exacerbated by irritation caused by the fibers in the paper itself, which may be coated in chemicals such as bleach. Additionally, most paper cuts occur in the fingers, which have a greater concentration of sensory receptors than the rest of the body."[10] Ariel. (talk) 00:15, 19 June 2010 (UTC)

semiconductor doping

If silicon chips are doped with arsenic, why doesn't touching them poison you? --75.25.103.109 (talk) 23:55, 18 June 2010 (UTC)

1. No one ever touches them. The part you see is a plastic cover, the silicon is inside.
2. There is a VERY tiny amount.
3. The arsenic is tightly bound in the silicon, and will not come out just because it's touched.

Ariel. (talk) 00:13, 19 June 2010 (UTC)

You don't get arsenic poison by touching a piece of arsenic elemental anyway; you get it by touching then ingesting, inhaling fumes or the volatile compounds such as arsenic trichloride, or intentional poisoning. --Chemicalinterest (talk) 10:58, 19 June 2010 (UTC)

The amounts are tiny, and by the time an electronic chip gets to you, the consumer, it is virtually impossible for any arsenic to be chemically active or in any way exposed to you. Arsenic would be tightly bound inside the semiconductor crystal lattice - see doping (semiconductor) - and the concentrations would be insignificantly small. Inside a semiconductor fab, arsenic gas may be released into an ion implantation chamber. This is usually an airtight device (hermetically sealed vacuum chamber). Arsine and Arsenic trifluoride are commonly released into the chamber. "Since these gases are all highly toxic or otherwise hazardous, additional input purging and trapping systems are needed to ensure that the all of the source gas is removed from the system before wafer loading or removal." Arsenic breaks out from these "extremely toxic" gases at high temperatures inside the ion implanting device. It then diffuses into the substrate (and is therefore deeply buried inside the silicon ("deep" can mean nearly 1 micron - but we can safely say that no arsenic will "rub off" the chip. (Microchip Manufacturing, Chp. 11 "Diffusion Sources"). Occasionally, an epitaxial layer will intentionally be doped with arsenic, but even during the processing, the gas is introduced in amounts of around 20-100 parts per million (relative to the already near-vacuum conditions inside the chamber). Again, safety devices are supposed to flush the chambers and input plumbing to ensure that the gas is totally purged before anybody is exposed to the wafers. At least one study has been published to investigate the effects of prolonged exposure to arsenic for people who work in the silicon fabs (factories) (and also, copper smelters, who are exposed to even higher concentrations because arsenic occurs naturally in copper ores). Here is Biological monitoring of arsenic exposure of gallium arsenide- and inorganic arsenic-exposed workers, (1989). It was found that these workers had "far higher" concentrations of arsenic than a control-group, but it seems that there was no conclusive evidence that even this elevated level of arsenic was unsafe. Nimur (talk) 19:08, 19 June 2010 (UTC)

I used to work in a wafer fab where we used arsine both for doping the semiconductor and for making passivating glass layers (ASG - arseno-slicate glass). Arsine smells of onions, and when a local farmer harvested his onion crop, we evacuated the clean room in double quick time... We also had one of the marketing guys ask the almost exact question above - "hey, if you've got arsenic on top of the chips, isn't that dangerous?" - to which I gave the somewhat innacurate answer "only if you eat a lot of them". --Phil Holmes (talk) 10:53, 20 June 2010 (UTC)

It's possible that an impurity was added to the arsine to make it easy to smell. I don't actually know if these gas compounds have an intrinsic smell. On the other hand, if a safety-odorant additive or impurity would interfere with the gas during silicon ion implantation, it might not be added... This guideline from the CDC says that "Arsine is a flammable and highly toxic gas with a garlic-like or fishy odor that does not provide adequate warning of hazardous levels." Nimur (talk) 17:24, 20 June 2010 (UTC)

I'd like to know if there is way to extract the arsenic to use as a poison without access to complex lab equipment. TheGoodLocust (talk) 22:32, 21 June 2010 (UTC)

And why do you want to know this -- are you planning to poison someone? In that case, I must warn you that today's forensic labs can detect arsenic unfailingly, and that attempted murder gets you a 20-to-life sentence. But if you're just looking for realistic ways to do it (for a detective novel or something), then subliming elemental arsenic (simply by heating) will separate it out from all the other microchip components. Keep in mind, though, that you're very likely to poison yourself in the process. 67.170.215.166 (talk) 02:17, 22 June 2010 (UTC)

Would I poison myself by inhaling it? How much circuit board would I need to poison people in a small room? What I mean to say is, could a person dump some in a fire and have it kill those in the room over a period of time? And no, I'm not planning on poisoning anyone. My dad actually got in trouble back in the 30's for reading a book on poisons! TheGoodLocust (talk) 03:44, 22 June 2010 (UTC)

You have to be much more concerned about Fluxide for solder in joining metals. If you are looking for a "useful" poison, poisonus plants are much more lethal. Also beware of the heavy metals getting into the system. Aluminium sauspans that are cleaned too well, is a no,no. MacOfJesus (talk) 23:35, 23 June 2010 (UTC)

Oh, I'm well aware of more useful poisons (have quite a few in my backyard actually) and could easily go into the forest to find some really deadly mushrooms that look like edible ones - it might be funnny to actually combine a poison with an ayahuasca analogue now that I think about it. I was just curious from a "Macguyver" perspective if I could throw some chips in a fire and poison a room full of people. I guess it might just be easier to mix some bleach and ammonia though. TheGoodLocust (talk) 04:00, 24 June 2010 (UTC)

June 19

Ammonia

What's a chemical which decomposes ammonia but which is harmless to humans? --75.25.103.109 (talk) 00:30, 19 June 2010 (UTC)

Sodium bicarbonate: it reacts to form sodium ammonium carbonate, which is harmless. --Chemicalinterest (talk) 00:49, 19 June 2010 (UTC)

sodium ammonium carbonate doesn't really exist - carbonate is too basic - so it will deprotonate ammonium.

A mild dilute acid will convert ammonia to a salt - eg citric acid will form ammonium citrate - which will get rid of the ammonia smell, but does not decompose the ammonia.87.102.32.15 (talk) 02:36, 19 June 2010 (UTC)

It only deprotonates ammonia partially, so there is still a little odor. Try reacting smelly vinegar with smelly ammonia to produce the faintly odored ammonium acetate. --Chemicalinterest (talk) 10:54, 19 June 2010 (UTC)

Urine contains urea, which breaks down into ammonia. See also the urea cycle. Of course, in high enough concentrations, any substance can be harmful to humans. Nimur (talk) 19:12, 19 June 2010 (UTC)

Think they wanted something that decomposes ammonia, not decomposes to ammonia. Not sure now..83.100.252.174 (talk) 21:27, 19 June 2010 (UTC)

Vague definitions of harmful aren't needed here; he is obviously asking whether something that is not very toxic. --Chemicalinterest (talk) 20:09, 19 June 2010 (UTC)

Decomposes ammonia by removing odor, etc. --Chemicalinterest (talk) 22:41, 19 June 2010 (UTC)

Production of carbon tetrachloride

Can carbon tetrachloride be made by burning a candle in chlorine gas? In oxygen it forms carbon dioxide. --Chemicalinterest (talk) 00:54, 19 June 2010 (UTC)

Based on the article you linked, specifically the section on synthesis and the chlorination article it cites, one can generate CCl₄ through oxidation reactions using chlorine gas. However, those references suggest that one must use more specific reactants and conditions than simply applying heat to a candle in a chlorine gas atmosphere to obtain the desired products in substantial quantities. -- Scray (talk) 04:06, 19 June 2010 (UTC)

I would imagine that, if you burned a candle in chlorine gas, you would get all sorts of chlorinated products (including some carbon tetrachloride). To get a good yield of pure(ish) carbon tetrachloride, you would need a more specific reaction, such as the chlorination of methane mentioned in the article. Physchim62 (talk) 11:47, 19 June 2010 (UTC)

Potato Chips

How do potato chips companies get their chips crisp, even when they are the baked kind? When I thinly slice mine and cook whether it is frying or baking they come out like au gratin potatoes? —Preceding unsigned comment added by 71.137.252.51 (talk) 03:38, 19 June 2010 (UTC)

I don't think you can do the baked kind at home -- they actually powder the potatoes and mix them with other stuff to get something that will be crispy when baked. For the fried ones, it's simply a matter of frying them for a long time at a relatively low oil temperature -- there's an amazing amount of water in potatoes and you have to get it all out or your chips will be soggy. Looie496 (talk) 05:00, 19 June 2010 (UTC)

I haven't made potato chips, but when I fry French Fries, I get them quite hard and crispy. My method is to have plenty of oil to completely, really really submerge whatever you're frying (aka deep frying). Then you have to get the oil really really hot. You should have it on maximum heat on your stove's largest flame (if you have different sizes) and test the oil by dropping a single drop of water into it. If the water does not sizzle IMMEDIATELY when it hits the surface of the deep oil, you have to wait for the oil to get hotter. (when it's not hot enough, the drop of water will fall in, and only a moment or two later cause a reaction. you have to then wait for the oil to get hotter.) Once the oil is really really hot, so that a drop of water sizzles onto it (you should be testing every minute or two), you drop on whatever you're deep-frying, in this case potato chips: STAND BACK! It will splutter and sizzle like hell when you put the stuff in. But then it will settle down (you keep it on maximum heat) and just fry. You should be frying for about 4-8 minutes, you can stir occasionally, the oil won't pop out at you (juts don't get any water in it), all of this is on your stove's maximum heat, and you check that it's done by the color: your chips shoudl be "golden brown". When they are, turn off the heat and carefully remove the chips onto a kitchen towel (bounty, etc) or you can strain them with a strainer, leaving them oilier. Now, one thing is a little bit of oil will be all over your stove, so don't remove the pan until you've turned off the flame (and, if it's an electric stove, waited for it to cool) as it could ignite the oil - this happened to me. That's about it. So, my advice is really the opposite of the advice to "cook slowly for a long time". Then again, I haven't fried chips yet, so who knwos if this will work :) 92.229.14.159 (talk) 12:03, 19 June 2010 (UTC)

Harold McGee's On Food and Cooking explains both styles of cooking them. He says factory made crisps are cooked at a consistent, high temperature (~170C) for 3..4 minutes (they're on a submerged conveyor). Home cooked crisps (and factory made "kettle chips") are made in batches, with the oil starting at ~120C and rising to 175C in 8..10 minutes. He explains how the differences in the water and protein behaviour in these two environments account for the kettle chips being harder; this latter method largely resembles the double-frying method that's commonly used for making fully-fledged Belgian fries (example). As that recipe I cited notes, don't dump in such a massive lot of slices that the oil temperature plummets - use small to medium sized batches. In general, different cultivars have different water and starch content, so experimenting with locally available types is a good idea. It's very common to dry the cut potato before frying (to reduce spitting and promote rapid caramelisation) and for some cultivars people wash the cut slices before drying (to reduce excess starch) - I've heard of people who towel dry the cut slices and them leave them out for a couple of hours to really dry out (but overdo this and they'll burn, or disintegrate and contaminate the oil). -- Finlay McWalter • Talk 14:17, 19 June 2010 (UTC)

sperm sorting

I just want to ask a question about sperm sorting. I am not great with negotiating computers so I hope I am doing this right. I understand sperm sorting can be used to determine sex. I am wondering if it would also work to help males with balanced chromosome translocations. Up to 60% of an affected male's sperm will produce miscarriages. Since sex determination looks at the chromosomes or in some way sorts the x from the y sperm, I thought it might work for this too. Any help you can give me will be much appreciated. —Preceding unsigned comment added by Sallygartner (talk • contribs) 04:23, 19 June 2010 (UTC)

Have you read the obvious article Sperm sorting? Nil Einne (talk) 10:27, 19 June 2010 (UTC)

Yes, I have read the article. This does not specifically say it would help with chromosome problems. —Preceding unsigned comment added by Sallygartner (talk • contribs) 15:27, 19 June 2010 (UTC)

Well the article explains how sex sorting works which you seemed confused about. The sperm are dyed and given a different charge depending on amount of dye absorbed (which varies because of the differing amounts of DNA the dye binds to).

So if the sperm have a differing DNA complement, e.g. lack part of one or more chromosome (nullisomy), you may be able to detect them in this way (in particular if the X sperm have what seems a complete complement), but if the sperm chromosomes contain balance translocations, the DNA complement will be the same. [11] seems to discuss this somewhat although you'd need a subscription.

The article also mentions "DNA damage in sperm cells may be detected by using Raman spectroscopy. [1] It is not specific enough to detect individual traits, however.[1]" From the ref [12] it doesn't appear this will help with balanced translocations much since it's detecting DNA damage.

Nil Einne (talk) 16:05, 19 June 2010 (UTC)

This procedure exposes spermatozoa to a fluorescent dye (Hoechst 33342) and ultraviolet light? Both of those seem like things that could cause chromosomal or genetic damage. This issue seems to have been brought up letters to the journal Human Reproduction. This 2005 article states in its title, Hoechst 33342 stain and u.v. laser exposure do not induce genotoxic effects in flow-sorted boar spermatozoa, but I'm unconvinced. Nimur (talk) 19:22, 19 June 2010 (UTC)

I agree with you Nimur; the latter paper is pretty unconvincing. (The fulltext appears to be a free download.) Their statistics on chromosomal anomalies and sister chromatid exchanges are based on just eight piglets (four stained and four unstained, Table 2), and the amount of scatter in the data values suggests that they desperately need more data to get reliable estimates of the means. While none of their data are significant at p < 0.05, you really wouldn't expect it to be unless the effect size was enormous. TenOfAllTrades(talk) 22:39, 19 June 2010 (UTC)

why do gas (petrol) stations have the same characteristic roof over the filling area?

Why do gas (petrol) stations all have the characteristic roof (or covering) over the filling area. Specifically, it is flat, held up on pilons, and of a rectangular or other very "square" (right angled corners) footprint. There are many types of roofs on many buildings, but only gas stations have this type as a rule - why? Thank you. 92.229.14.159 (talk) 12:10, 19 June 2010 (UTC)

Maybe they are mass produced. --Chemicalinterest (talk) 12:12, 19 June 2010 (UTC)

Well this one [13] doesn't. Anyway while I don't know the specific answer to the question I would guess there are some considerations for a petrol station that many other buildings lack, in particular they need high roofs both to accomodate large vehicles and I presume to ensure fumes don't get trapped. The roofs also likely need a degree of fire resistance and perhaps resistance to the petrol (and probably some diesel) fumes. And they do need roofs so people can fill their cars up without getting wet and perhaps for other reasons. Ultimately it may be tradition and the lack of any real advantage to do something else as much as anything. Nil Einne (talk) 15:28, 19 June 2010 (UTC)

The roofs are serving the same purpose, so it's not surprising they use the same design. It's probably the best design for the job. It needs to be open on two sides for the vehicles to get in and out and it is beneficial for it to be open on the 3rd side as well for ventilation. That gives them two options for holding it up, columns or a cantilevered design. The former is far easier and there are no real disadvantages, so naturally they choose that. They have a choice between a flat roof or a sloping roof. Flat roofs are easier and cheaper, and clearly work, so naturally they choose flat roofs. Everyone (with a few exceptions, either due to different priorities or a different starting point) that designs petrol stations goes through the same thought process and naturally gets the same result. --Tango (talk) 16:01, 19 June 2010 (UTC)

Major gas (petrol) brands aim to provide a distinctive recognizable "welcoming" forecourt for self service. This corporate styling exercise includes a brand logo, pumps, card reader and uniform prefabricated roofs that provide shelter and lighting. Cuddlyable3 (talk) 16:29, 19 June 2010 (UTC)

I (op) don't buy these answers. They lead, perhaps, to the current design, but the current would be the second-to-last step following the above reasoning: the last step would be to add a sloping roof, so that the rain can roll off, instead of accumulating. Why isn't there such a slope? You can make it with $75 of corrugated sheet metal. There has to be something else. 92.229.14.11 (talk) 19:41, 19 June 2010 (UTC)

You're sort of right - see this image of a petrol station roof [14]

Here's another (much more modern) [15] exception to the rule.

Here's a hybrid of the two [16]

Here's some more 'old school' flat roof types [17] [18] [19] [20] street view of last one - looks flat - but has a slight internal slope and internal drainage this seems to be a fairly standard design where I am another - different shape but same internals

Note the internal drainage in most of these, I recommend you use an aerial photograph to look at the ones near where you live - it's clear that they are not just simple flat roofs at all; a key feature of the flat type roofs is central drainage that means less space taken up on the forecourt by drainage pipes (they can be close to the pumps near the pillars) - to do this with gutters only on the perimeter is slightly more complicated. 83.100.252.174 (talk) 21:16, 19 June 2010 (UTC)

In fact the old style flat roof seems to be going out of fashion (why?) example - I assumed this was a flat roof - becuase it used to be - but is now a sloping tiled roof - 83.100.252.174 (talk) 21:56, 19 June 2010 (UTC)

Flat roofs are bad because the rainwater doesn't run off quickly, and pools on the roof. This weight can damage the roof itself. --TammyMoet (talk) 07:33, 20 June 2010 (UTC)

C'mon, flat roofs are not level roofs, they always have a slight drainage slope either to one edge, two edges or toward a central gully. My belief has always been that the cost has driven the design. A huge, ugly, square, 'flat' roof is the cheapest option, don't waste money on fancy design if the fancy design is not going to attract custom - and when did anybody ever go down to the Whatever gas station because they loved the roof. Nah, you generally go to the cheapest or nearest. I think local building laws and regulations (in the UK) are now making for a better looking tiled and sloping roof. Caesar's Daddy (talk) 07:55, 20 June 2010 (UTC)

No you're right, they're not level but they're not really "flat" either. (I've owned one or two...) Water does indeed collect in the hollows, but the real issue is that rainwater (especially if the drain's blocked, or if you get really heavy rain) takes time to drain away. This weight causes the roof to fail eventually. Plus the fact that the tar cloth perishes over time, and needs replacing. Flat roofs may well be cheaper but take more maintenance than sloping roofs, and it may well be that this is the part that persuades people to replace them with a more traditional style roof. --TammyMoet (talk) 12:01, 20 June 2010 (UTC)

In snowy areas, how do they keep the weight of the snow from collapsing the roof? Do they heat it somehow, or does someone show up with a cherry picker and shovel it? Googlemeister (talk) 13:51, 21 June 2010 (UTC)

The solution to both rain and snow problems is very simple: they build the roof strong enough to take the load. I live in an area that doesn't get much of either, and the building code for flat roofs calls for being able to support ten inches of water or its equivalent in snow. Areas with serious snowfall require things to be even stronger. --Carnildo (talk) 00:37, 23 June 2010 (UTC)

Sloped roofs would lead to water dumping over onto people driving in and out, which they wouldn't like. That setup works okay on your house because it has an eaves trough and a fairly small footprint from which to collect the water. Matt Deres (talk) 14:52, 21 June 2010 (UTC

@ every other person in this thread, hypothesising and digressing does not answer the question!!! and I want to know the answer, ahhh if only I knew a petrol garage architect.

Spindle cell rhabdomyosarcoma

What is the outlook for metastatic spindle cell rhabdomyosarcoma? —Preceding unsigned comment added by 64.223.235.196 (talk) 13:47, 19 June 2010 (UTC) I am not asking for medical advice, just info. —Preceding unsigned comment added by 70.16.107.144 (talk) 14:10, 19 June 2010 (UTC)

Not sure if this will answer your question: "Two types of ERMS, botryoid and spindle cell rhabdomyosarcomas, tend to have a better prognosis (outlook) than the more common forms." Taken from this page. --TammyMoet (talk) 15:28, 19 June 2010 (UTC)

but does that apply to cases that have metastasized —Preceding unsigned comment added by 70.16.107.144 (talk) 16:15, 19 June 2010 (UTC)

I think that crosses the line into medical advice. Ask your oncologist. --TammyMoet (talk) 16:57, 19 June 2010 (UTC)

We understand that you are just looking for information, but honestly there is no way anyone on the Ref Desk can intelligently answer what the prognosis would be for any given person's metastatic cancer. There are simply too many variables. There is some information in the soft tissue sarcoma article, and this reference discusses factors associated with prognosis in metastatic rhabdomyosarcoma, but your best option (as usual) is to ask a physician. --- Medical geneticist (talk) 19:36, 19 June 2010 (UTC)

Simulator

I need to simulate a microprocessor based system. The system would have some external devices interfaced to the microprocessor. What are the software that can do this type of a simulation ? —Preceding unsigned comment added by 218.248.80.62 (talk) 14:05, 19 June 2010 (UTC)

Nisan and Schocken's The Elements of Computing Systems has a free multi-layered simulator (here) which has both hardware level simulation and a simulated CPU. People have designed various components in the book's HDL (a simplified counterpart of VHDL), which the forum should be able to help you find. -- Finlay McWalter • Talk 14:28, 19 June 2010 (UTC)

Something from Category:Electronic circuit simulators might help. DMacks (talk) 16:51, 19 June 2010 (UTC)

The Computing Ref Desk would be a better place for this question, but in short, what you are hoping to do is to create an emulator. There is software available to use as a starting point, but I'm not very familiar with it. Looie496 (talk) 17:43, 19 June 2010 (UTC)

Thanks. I will be posting to the computing RD. 59.93.207.169 (talk) 06:36, 20 June 2010 (UTC)

Radioactive minerals on other planets?

Has any attempt been made to find commercially exploitable radioactive minerals on any of the moons or planets of our solar system? Solar powered robots and rail-guns could parachute this back to Earth for atomic power. What about Mercury- could its high density mean that dense minerals such as Uranium might exist there?[Trevor Loughlin]80.1.88.6 (talk) 14:36, 19 June 2010 (UTC)

No attempt has been made. There's vanishingly little possibility that it would yield product at a lower cost than on earth. --Tagishsimon (talk) 14:40, 19 June 2010 (UTC)

Why would anybody do that when uranium still is a fairly common element on earth? Dauto (talk) 15:26, 19 June 2010 (UTC)

Something like Uranium is best found on the Earth - it's already here in great quantities. The closest serious idea to what you describe is finding Helium-3 on the Moon (deposited there by solar wind) for use in nuclear fusion (we need to invent a fusion reactor that actually produces more energy than it uses for that to be useful, of course). Apart from Helium-3, there isn't much on the Moon that we can't get easier on Earth, so most ideas about exploiting resources of the Moon are about either using them on the Moon or in space. There are lots of ideas about asteroid mining, including sending resources back to Earth - it's much cheaper (in terms of energy requirement) to get resources from an asteroid to Earth than from another planet (or even the Moon) to Earth, due to weaker gravity. --Tango (talk) 16:16, 19 June 2010 (UTC)

Mining of elements or isotopes in space so that they could be brought back to Earth makes no economic sense, and probably won't make one for many more years. Mining makes sense, however, if the materials are to be used locally. To build a research colony on Mars you would want to use Martian materials as much as possible, rather than the ones brought from Earth. Same goes for the water and oxygen used by the colony. --Dr Dima (talk) 02:32, 20 June 2010 (UTC)

Uranium on Earth is more common then silver so it's not exactly hard to come by. And considering we don't even use mining robots and interplanetary rail-guns on earth, it doesn't seem like sending them to space is something that's going to be happening any time soon. Vespine (talk) 01:00, 21 June 2010 (UTC)

I think that uranium and other radioactive elements have been mapped on the moon by detecting the gamma rays emitted. This can only work where the surface is exposed in a vacuum. Space: 1999 describes what happened when too much radioactivity in one spot on the moon (in fiction). (and could only happen in a really far fetched non realistic fiction) Graeme Bartlett (talk) 11:43, 21 June 2010 (UTC)

Purpose of Addiction

Why can the body become addicted to certain substances and what purpose does this serve? Addictions don't seen to benefit the body in any way. So why does the body crave something? Here I'm talking about physical addictions, not psychological ones. Thanks! Stripey the crab (talk) 14:53, 19 June 2010 (UTC)

You probably want to read Substance_dependence#Pathophysiology, such as the Role of dopamine subsection. --Tagishsimon (talk) 14:58, 19 June 2010 (UTC)

The neurotransmitter Dopamine is closely associated with reward-seeking behaviors including basic desires for survival such as sex, eating and family, without which none of us would be alive. It is also involved pathologically in physical addictions. Human neurobiology has not evolved enough to be fool-proof. Cuddlyable3 (talk) 15:57, 19 June 2010 (UTC)

Expanding on that, I think the original poster has as a premise the idea that everything in the body has some purpose, which is untrue. The human body has various weird properties that don't serve a great purpose; they just didn't interfere with our ancestors enough to stop them from being able to breed. See the "Evolutionary baggage" section of Evolution of the eye, or see Recurrent laryngeal nerve, a nerve that runs from your brain to your voice box to control it, but it idiotically goes down into your chest cavity first and then loops back up. Comet Tuttle (talk) 16:02, 19 June 2010 (UTC)

Right, addictions are malfunctions of the biological reward system caused by putting substances into the body that it is not equipped to handle. They don't have a purpose any more than the breakdown of a car after you put water into the gas tank has a purpose. Looie496 (talk) 16:49, 19 June 2010 (UTC)

See [21], in real life turkeys won't come across heads stuck onto sticks to make love with. We're little different, evolution hasn't fitted us to resist all drugs purified in a laboratory where analogues have a useful purpose in the brain. Dmcq (talk) 19:00, 19 June 2010 (UTC)

It maybe because we are creatures of habit, and we resist change. MacOfJesus (talk) 19:31, 19 June 2010 (UTC)

I think the answer to this question is a textbook example of proofs of evolution. It's a fundamental part of evolution, it perfectly explains why many of our biological systems are not perfect and often seem trivially fallible, cobbled together, or coopted or adapted from other purposes; because that's exactly what they are. Let see the creationists and ID-ers try to explain something like addiction, if there is one thing that addiction is NOT is intelligently designed. Vespine (talk) 00:45, 21 June 2010 (UTC)

Don't forget man has intelligence and free will, has an imagination to plan for the future. Please see C. G. Jung on the section under addiction. Some people managed a complete cure. MacOfJesus (talk) 14:13, 21 June 2010 (UTC)

For what it's worth, if I understand correctly, Jung never tried to validate any of his notions by means of testing. I mean, he never even tried. He was far from the scientific method. Comet Tuttle (talk) 18:36, 21 June 2010 (UTC)

If you look at the page I suggested under the section, you would find he ran clinics and had some addicts to treat. His methods and advice has proven itself as his patients went on to found the AA and The Oxford Group. He had a distinct empathy with the patient, respecting their dignity. Have you looked at the steps? Time has proved them. And as I said there has been some complete cures. Jung was top in his field and obtained a Ph.D from the top European University, and is today considered the Master of his Science, and one we go back to time and time again. His methods are the ones used in every such Clinics today! The methods you suggest in testing and validating would be counter-productive in the human subject. MacOfJesus (talk) 22:54, 21 June 2010 (UTC)

It is unlikely that any person would purposely become an addict, but a drug dealer might contribute to the addiction of another person and have the purpose of deriving continued business from the addict. (http://www.multilingualbible.com/2_timothy/3-6.htm; http://www.multilingualbible.com/2_peter/2-19.htm) -- Wavelength (talk) 00:55, 22 June 2010 (UTC)

Experiments in quantum mechanics?

What aspects of quantum mechanics have actually been experimentally verified?

If that's a contentious question with a debatable answer, where might one find a list of the most well-known experiments of quantum mechanics? 96.255.178.76 (talk) 15:56, 19 June 2010 (UTC)

If I may add the contra-positive: what open questions still exist in quantum mechanics that have not been experimentally verified? Zunaid 16:20, 19 June 2010 (UTC)

The double-slit experiment is a famous one that demonstrates wave-particle duality, which is a fundamental feature of quantum mechanics. Pretty much all of quantum mechanics has been experimentally verified - that's a requirement to be considered a scientific theory. --Tango (talk) 16:25, 19 June 2010 (UTC)

Many of these experiments are still open to contending interpretations. Cuddlyable3 (talk) 16:35, 19 June 2010 (UTC)

Indeed. Things like the Copenhagen interpretation aren't theories, they are interpretations of theories. Theories have evidence for them, interpretations don't (once you get significant evidence for an interpretation over the others, that interpretation just becomes part of the theory and you stop using the word "interpretation"). --Tango (talk) 16:40, 19 June 2010 (UTC)

Spin (physics) has been confirmed experimentally - so much so that it's used in NMR spectroscopy , Electron paramagnetic resonance spectroscopy, as well as Magnetic resonance imaging. The Stern–Gerlach experiment is the classic experiment. These are examples of quantisation of spin.

Quantum tunnelling is an example of an experimentally obtained results that are explained in terms of a quantum mechanical wavefunction. I'm not aware of other explanations - but that doesn't mean they don't exist - 'QM' represents a good theoretical basis for this phenonoma though.83.100.252.174 (talk) 16:52, 19 June 2010 (UTC)

The list is too long even to summarize. Our article on Theoretical and experimental justification for the Schrödinger equation is probably the best resource here as far as I can see, but it is written at a pretty advanced level. (The Schrödinger equation is the basic mathematical formulation of quantum mechanics). Looie496 (talk) 16:54, 19 June 2010 (UTC)

Quantum mechanics is a rather wide umbrella term that can cover any theory in physics which is based on the principles of the wave function, gauge symmetry and quantum field theory. We have quantum mechanical theories of three of the four fundamental forces - electromagnetism, the strong force and the weak interaction. All of these have been extensively tested. In particular, the quantum theory of electromagnetism, quantum electrodynamics, has been verified to a higher degree of precision than any other theory in physics, I think. These quantum theories together make up the Standard Model of particle physics. A confirmation of the existence of the Higgs boson would fill one of the few experimental gaps in this model. However, what we lack is a quantum mechanical theory of gravity. There are various candidate theories, but each of these is either inconsistent with known facts, too vague to be testable, or not testable with current technology. Gandalf61 (talk) 16:55, 19 June 2010 (UTC)

Quantum mechanics (like special relativity) is a simple set of rules that one requires one's physical theories to follow. It's not a physical theory by itself. A theory that follows the rules might be called "quantum" (or "relativistic"). The basic quantum-mechanical (and relativistic) rules are ludicrously well confirmed; basically every high-energy physics experiment in the last century tests these rules. As for individual quantum theories, it depends on the theory; it's the same as asking "how well has physics been tested?".

Gauge symmetry is not an intrinsically quantum idea. It happens that the most famous gauge theory (the Standard Model) is also quantum, but Maxwell's electrodynamics is a U(1) gauge theory, and the equivalence principle in general relativity is related to the gauge principle. -- BenRG (talk) 18:26, 19 June 2010 (UTC)

An experiment proposed by David Deutsch in which an observer is able to reversibly forget the outcome of a measurement, while not forgetting that the measurment was performed, thus disproving the Copenhagen Interpretation (because the measured system would be back in the original state, rather than its wavefunction having irreversibly collapsed because of the measurement), has not yet been performed. Count Iblis (talk) 16:58, 19 June 2010 (UTC)

David Deutsch's Request for a Photon Experiment Cuddlyable3 (talk) 17:12, 19 June 2010 (UTC)

As far as I can tell that page was not written by Deutsch but by some random Internet crank. Deutsch himself is also kind of crankish. -- BenRG (talk) 18:26, 19 June 2010 (UTC)

That experiment was not designed to test quatum mechanics. I t was not designed to test an interpretation of quatum mechanics either. It was designed to test a misunderstanding view of an interpretation of quatum mechanics. Neither quantum mechanics nor any of its main stream interpretations has nothing to say about observers forgeting the outcome of an experiment. Dauto (talk) 02:18, 20 June 2010 (UTC)

Forget the cranck experiment. Quantum mechanics in the MWI does make an unambiguous prediction in case of the thought experiment proposed by Deutsch. Count Iblis (talk) 17:25, 20 June 2010 (UTC)

You can experimentally verify quantum theory any time you want. The only problem is that for the more complicated parts, it's difficult to take accurate enough measurements and you have to spend a lot of time learning how to do the math. If you pursue a university-level course in physics (which is an excellent idea, and I encourage everyone to try!), electronics, optics, certain branches of chemistry, and so on, you will undoubtedly have class and laboratory work where you apply quantum theories to your measurements. As has been stated above, "quantum mechanics" is an umbrella term for an entire class of mathematical methods that describe certain physical measurements (typically measured in the regime of atomic or sub-atomic systems). Probably the simplest experiment, which is even conducted in introductory chemistry or physics classes in high school, is measuring photoelectric effect. Here is a version you can probably do with home equipment. I recall other experiments in physics, ranging from measuring mass-to-charge ratios (Oil drop experiment); magnetic field effects on optics; double slit experiments; and so on. Where I went to school, we had an undergraduate physics lab where we did basic quantum physics experiments, and as we got more advanced, we had access to a nuclear reactor, a TUNL nuclear lab, a semiconductor fab, and so on; so as undergraduate physicists, we had the opportunity to do some serious nuke and quantum experimental lab work. As I got farther and farther down in size/farther up the energy spectrum, experimental verification required need bigger and more expensive devices; and after awhile I lost interest in independently verifying every theory. Inevitably, you have to accept on faith that just about all of quantum theory has been pretty darned well confirmed experimentally by other scientists - there simply isn't enough time to verify the whole of the modern body of scientific knowledge yourself. If such experimental facilities are unavailable, there are dozens of exercises you can do as a student to experimentally verify the basic quantum principles yourself. One of the big "transitions" in comprehending modern physics is understanding exactly what is meant by an "observable." In physics, especially in quantum mechanics, the whole purpose is to sit around and think about invisible, tiny concepts that are literally on the edge of "existing." (What exactly is energy, for example?) You have to figure out some way to do something so that you end up making an observation that either verifies or refutes some mathematical representation of what you thought is occurring. In other words, if somebody tells you that "atomic nuclei exist" or "atomic nuclei don't exist", how do you design an experiment to prove this one way or the other? (Hint). As you refine this experiment farther and farther, you start describing more details of the atomic nucleus, and applying more sophisticated methods until you explain every last decimal-place of accuracy that you can measure with your machine. After just a few decimal places (for most experiments), you need quantum mechanics. Invariably, at some point, you reach the limit of your experimental accuracy (and have to find someone to pay for a better machine). Or, you become an applied physicist and worry about different kinds of problems. Nimur (talk) 20:42, 19 June 2010 (UTC)

What exactly is energy? Cuddlyable3 (talk) 22:51, 19 June 2010 (UTC)

Energy is a thing that is quantized. It affects other things, an effect we call work. Energy can have a position (also quantized), but its position is best described by a wave-function; so its position is uncertain with respect to the amount and character of the energy. We know from experiment that energy is a conserved quantity in all interactions - or at least, if energy disappears, something else manifests to keep things balanced. Like all questions of physics and philosophy, this question at some point will devolve into "... and here is a set of data we measured experimentally, can you see the pattern?" Nimur (talk) 15:18, 20 June 2010 (UTC)

Using the links I see you wrote "Energy is a Concept that (is a) Photon. It affects Matter, an effect we call Work (physics)." But was energy around before there were any humans to have concepts i.e. which came first, the energy or the concept? Does a falling body receive energy from gravity and if so are photons involved? Cuddlyable3 (talk) 21:21, 20 June 2010 (UTC)

Well, a photon is a quantum of energy for a particular kind of interaction. And, strictly speaking, a photon isn't "energy" - it's a particle that carries energy during an electromagnetic interaction. It was sloppy of me to "imply" that all energy is in the form of photons - this is clearly not the case. In my defense, I never actually said that, but your expansion of my wikilinks demonstrates that my explanation was not clear. There are actually many different kinds of quantized energy - phonons, photons, and so on. You can even say that other things "are" energy, if you want - in a sense, a hadron is also a bundle of "energy", combined in a particular way out of even more elementary "things" (I'm reluctant to use the term "particle" because even elementary particles seem to be nothing more than particular immutable combinations of energy, momentum, spin, and so on). Combinations of these "things" result in more macroscopic properties, like mass, charge, velocity, and so on. As far as your other question - energy, like the rest of the universe, existed before humans ever conceived or explained it. And as for gravity - gee, that's a tough one, because we still don't have a quantum theory of gravity. But, I wouldn't be surprised if we are able at some point to come up with an unencumbered, experimentally verifiable way to say that "yes, when an object changes its position relative to another object with mass, an exchange of gravitational energy is mediated by a particle." At present, we have no such theory that can tie up the loose-end implications of such a statement. At present, the best we have is general relativity, which does not (in its vanilla incarnation) imply that a particle exchange mediates the warping of space-time to cause the effects we call gravity. Nimur (talk) 22:46, 20 June 2010 (UTC)

By far the coolest experiments which both verifies the predictions of some models of QM and actually falsifies the predictions of some other models of QM are the Bell test experiments, which test Bell's theorem. It takes quite a bit of work for someone new to figure out what is going on there, but the results are actually quite profound. The short answer is that you can even determine experimentally between certain interpretations of quantum mechanics (what had been long thought to fall under the heading of "philosophy" more than physics—like the Einstein/Bohr debate), much less between QM and the "classical" theories (the latter of which is so old of an experimental achievement as to no longer be interesting). --Mr.98 (talk) 07:21, 20 June 2010 (UTC)

June 20

Oxidation of antimony

Would the antimony in a pewter spoon be oxidized as it is dissolved in hydrochloric acid? --Chemicalinterest (talk) 00:46, 20 June 2010 (UTC)

Yes it should oxidize to SbCl₃. FWiW 67.170.215.166 (talk) 05:18, 20 June 2010 (UTC)

Antimony is pretty inert to non-oxidizing acids such as hydrochloric acid, although you might get a slow reaction due to dissolved oxygen. Physchim62 (talk) 08:46, 20 June 2010 (UTC)

Here's one source of Sb reactivity towards acid [22] - no reaction with dilute acids (does react with dilute nitric acid). Also here [23] . The oxide does dissolve and is produced by heating in air. 77.86.115.161 (talk) 10:52, 20 June 2010 (UTC)

"Dilute acids have no effect on Sb; concentrated oxidizing acids react readily, e.g. conc HNO₃ gives hydrated Sb₂O₅, aqua regia gives a solution of SbCl₅, and hot conc H₂SO₄ gives the salt Sb₂(SO₄)₃." Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 645. ISBN 978-0-08-022057-4.. If you look at the electrode potentials, you will see that elemental antimony will not reduce H⁺ to hydrogen. Physchim62 (talk) 11:06, 20 June 2010 (UTC)

Sorry to the art appreciators, but I want to dissolve a fine pewter spoon in hydrochloric acid to get the reducing agent tin(II) chloride. I know the copper will be left behind, but will the antimony? That was the context of my question. --Chemicalinterest (talk) 11:09, 20 June 2010 (UTC)

Yes, excluding any antimony in the alloy that was already oxidised.. Haven't you got any lead free solder? It's usually almost all tin plus very small amounts of silver or copper.77.86.115.161 (talk) 11:12, 20 June 2010 (UTC)

No, I only have lead solder. --Chemicalinterest (talk) 11:42, 20 June 2010 (UTC)

Yes, the antimony should be left behind. There's very little antimony in pewter anyway, usually less than 1%, just enough to harden the tin. So your tin(II) chloride should be 98–99% pure (at least when it's fresh), which should be perfectly adequate for your purposes. Physchim62 (talk) 11:18, 20 June 2010 (UTC)

Why don't Harleys ever have headlamps in other shapes?

In March, I promised a Harley dealer that I would buy a Harley once any model came with headlights in shapes other than circulars. Apparently, I will never buy a Harley then. But that was the dealer's opinion. What's with 2010 Harleys looking the same as the 1960 Harleys? I promise, they would make great time machines because they wouldn't look as out-of-place in the past as a DeLorean would.

But will Harley motorcycles ever get a different headlamp shape in any future model? Or will the 2060 models be just as at-home in 2010 as the 2010 models are today? The Harleys reek of old-schoolness, and just like so many things in life, that style ought to get old sooner or later.

PS: I tried calling the customer care phone # for Harley-Davidson but their offices were already closed. That's why I asked here instead. --Let Us Update Wikipedia: Dusty Articles 01:10, 20 June 2010 (UTC)

Unfortunately, the Official Reference Desk Crystal Ball is currently out-of-order, so we are unable to answer your question. We apologise for the inconvenience. --Tango (talk) 01:31, 20 June 2010 (UTC)

Okay, I can see the part of being unable to answer when Harleys will ever have headlight shapes other than circular-types, but why don't they have other headlight shapes already? At least that's a past/present question, so you don't need a crystal ball for that. --Let Us Update Wikipedia: Dusty Articles 01:38, 20 June 2010 (UTC)

Just a guess from a marketing angle: One of the Harley's most essential characteristics is that it looks like a Harley. If one didn't have a single big round headlight, it wouldn't look like a Harley any more. A 2010 Harley is expected to look like a 1960 Harley, or a 1940 Harley for that matter. PhGustaf (talk) 01:54, 20 June 2010 (UTC)

Does a Ford need to look like a Ford? --Let Us Update Wikipedia: Dusty Articles 19:03, 20 June 2010 (UTC)

PhGustaf is right: 2010 Harleys are supposed to look like a 1940 Harley. New technology is integrated, often at great cost to keep it looking like it is not there. For instance, the ABS doesn't use the "grate sensor" that the Bosch system typically uses. Instead, they use special bearings with a pickup on the outer ring. The only visible part is an extra wire. Pretty smart.

So, I'd expect to see Harley come out with HID lamps that fit the old-style housing, rather than moving forward on looks. You can see this on bikes like the Rocker C and on bikes that aren't aimed for the main market- I'm talking about the V-Rod here. In fact, the V-Rod doesn't have an entirely round headlight, it's more of a teardrop shape.

WP:TLDR applies. tedder (talk) 04:34, 20 June 2010 (UTC)

Oh, TL;DR? In that case, at what part of my original post did you stop reading at? --Let Us Update Wikipedia: Dusty Articles 06:30, 20 June 2010 (UTC)

TLDR was in regard to my reply, not yours. I figured it rambled enough that I lost you tedder (talk) 09:04, 20 June 2010 (UTC)

Nah, I've been trying to solve that age-old question for who knows how long. After nurturing my curiosity for a long time, there'd be no way that your answer(s) would be rambles. I'll be Googling for images of concept Harleys now; depictions of what they may look like in 2020, 2030, and 2040. If I have trouble, I'll check back here to see if you or anyone can find links to them. --Let Us Update Wikipedia: Dusty Articles 09:51, 20 June 2010 (UTC)

The same reason as the odd firing order characteristic of Harleys; if it went hmmmm or wheeeee, instead of blat-blat-blat, it wouldn;t be a Harley. Acroterion _(talk) 16:42, 20 June 2010 (UTC)

A simple answer: Because people buy them. If twenty years from no people only buy 5-wheeled purple-fringed dingbats with triangle headlights, then Harley will make...No, they wouldn't. Can you see a Hell's Angel on a bike with purple fringe? 75.41.110.200 (talk) 05:23, 21 June 2010 (UTC)

smelly vitamins.

what, exactly, makes multi-vitamins smell they way they do? why are some so pungent and others not? i assume it's the amount of variety of ingredients, but most have that same "vitamin smell" not matter what they contain. —Preceding unsigned comment added by 67.83.46.55 (talk) 08:24, 20 June 2010 (UTC)

Is it yeast which is a good (and I suspect common) basis for a multivitamin pill..? 77.86.115.161 (talk) 10:18, 20 June 2010 (UTC)

Multivitamins without yeast also smell. B vitamins have a quite horrible smell, for one. -- Aeluwas (talk) 10:42, 20 June 2010 (UTC)

Which of the B vitamins are responsible for the smell?77.86.115.161 (talk) 10:48, 20 June 2010 (UTC)

Yeast extract is the main component of the vast majority of Vitamin B supplements, and it does have quite a distinctive smell. You can get it as brewers yeast tablets. If you can, try and take a smell of these tablets to see if that's the smell you're referring to. --TammyMoet (talk) 14:29, 20 June 2010 (UTC)

Try Marmite! MacOfJesus (talk) 14:15, 21 June 2010 (UTC)

butterfly / moth

I found this butterfly / moth (picture) just sitting on the pavement today, at risk of getting stepped on so I carefully moved it to my garden on a card. It seems weak and just sits on the card now, it doesn't move around or anything except for its antennas. It tried once to fly and just fluttered to the ground and landed on its back. I have two questions

• a) What species it is?
  
• b) Is there anything I can do to help it? I feel very sad about this. If I just let it go it will fall to the floor and probably get stepped on.
  

Thank you for your help 82.43.90.93 (talk) 12:46, 20 June 2010 (UTC)

Cinnabar moth. Maybe you can get it to take some honey, or sugar water? --TammyMoet (talk) 14:33, 20 June 2010 (UTC)

Is it possible that it has laid it's eggs and will die anyway (anyone know when these lay their eggs?)

In the UK, usually around June since, according to Richard South, the caterpillars "feed[s] in July and August on ragwort (Senecio jacobaea)" - which they certainly do as I know from collecting and raising them as a youth.

The male and female of this species look very similar, and I can't tell which yours is. If you're concerned about helping it to reproduce (assuming it hasn't already) the best course would be to take it to somewhere that ragwort is growing, preferably in as close to a rural/unpolluted situation as possible, and leave it on a plant - you may see some of the very colourful caterpillars there. The moth, incidentally, is one of the few British species that habitually fly (in a rather weak fashion) in the daytime. 87.81.230.195 (talk) 02:37, 21 June 2010 (UTC)

Of course you could just let it die, it could possibly be a weak, unfit or diseased individual. Just as squishig a bug in the past could have dire consequences on life in the present, if it just happens to be a direct ancestor of say: the human race. In the same way, you playing "God" with nature and helping a weak or unfit individual to breed and possibly then compete with other individuals which just might have otherwise gone onto evolve into another intelligent race in another billion years, but will instead not flourish because of your direct actions. In a slight variation of, but still quite fittingly called "butterfly effect". Of course i'm not "serious", but it's a thought isn't it? Vespine (talk) 05:54, 21 June 2010 (UTC)

uv / urine

http://www.amazon.co.uk/Urine-Off-Finder-Black-Light/dp/B001I0617W

Does this only work for cats? 77.86.115.161 (talk) 15:36, 20 June 2010 (UTC)

Cats, dogs, rats; probably more. Any particular animal in mind? Try googling for blacklight giraffe urine etc. Be aware though: urine is a bit difficult to detect using a black light. The room must be very dark, and it's easy to get false positives from other substances[24]. 88.112.56.9 (talk) 18:42, 20 June 2010 (UTC)

ok so does healthy human urine fluoresce (noticeably - not in a uv spectrometer), and if so what causes it? And what does coffee/tea/milk/cocoa do? 77.86.115.161 (talk) 19:30, 20 June 2010 (UTC)

All urine (including human) fluoresces under UV light -- in fact, there are special UV fluorescence kits for detecting urine stains. Don't know what causes it, though; prob'ly a trace component that I don't remember. FWiW 67.170.215.166 (talk) 05:24, 21 June 2010 (UTC)

The presence of natural fluorophores in human urine is the cause of its fluorescence. The major ones include, 4-pyridoxic acid, riboflavin and various pterins and porphyrins. Fluorescence is observed mostly within the 300 nm - 450 nm excitation wavelength range, and it is highly variable between different individuals. Rockpocket 11:36, 21 June 2010 (UTC)

Thanks> 77.86.115.161 (talk) 12:04, 21 June 2010 (UTC)

Risk of catastrophic methane explosion in Gulf of Mexico

This article and this video say that a methane gas buildup under the Gulf of Mexico ocean floor will explode with devastating consequences... Is this credible or is it just fear mongering? Thanks very much for your input! --User298576392 (talk) 18:04, 20 June 2010 (UTC)

Why would methane explode? The ocean isn't filled with oxidizers. The ocean would also carry away the heat from the methane, preventing it from reaching an ignition temperature. --Chemicalinterest (talk) 18:21, 20 June 2010 (UTC)

In all honesty - it walks and talks like a conspiracy theory.77.86.115.161 (talk) 19:33, 20 June 2010 (UTC)

The article doesn't say that the methane will ignite, just that there may be enough to create a vast bubble that would rise all at once and generate a tsunami when it reaches the surface. Seems unlikely to me, but let's at least get the story straight. Looie496 (talk) 23:17, 20 June 2010 (UTC)

Yeah, let's get the story straight – or as straight as you can get bovine excrement! Methane deposits are commonly associated with oil wells, and this one is no exception, but any substantial quantity of methane would sit on top of the oil. If there was going to be some "supersonic tsunami" (doncha just lurve the alliteration), it would already have happened. Physchim62 (talk) 23:46, 20 June 2010 (UTC)

I checked my universities' Geology department on this, To Quote the PHD who incidently was a survivor of the rig in Ixtoc I oil spill "Its Crap" Weaponbb7 (talk) 21:17, 21 June 2010 (UTC)

I haven't read the article, but this sounds similar to a limnic eruption? Is the bottom of the Gulf supersaturated with methane (I don't know)? If so then perhaps a volcanic eruption or something else to mix the cold/warm waters (e.g. underwater rock shelf collapse) might allow a massive methane burp. Just throwing out some possibilities/theories. TheGoodLocust (talk) 22:26, 21 June 2010 (UTC)

The methane still won't ignite because there's not enough free oxygen down there to allow combustion; and since it won't ignite, it won't make much of an explosion (a BLEVE at most rather than a real detonation), much less a tsunami. 67.170.215.166 (talk) 02:39, 22 June 2010 (UTC)

Ignite? I never said it would ignite, but a massive enough methane burp might look like an explosion. Unlike the limnic eruptions we've seen in some places (e.g. Nyos), such an eruption would probably not cause as much loss of life since I think the methane would float up into the air rather than suffocating those the ground. TheGoodLocust (talk) 03:40, 22 June 2010 (UTC)

Why is the power output of a series-connect array of solar cells so affected by partial shading?

I am trying to understand why, in a series-connected array of solar cells in which one cell is faulty or shaded, the power output of the array should fall by more than the power of the one "lost" cell. To my thinking the current corresponding to the maximum power point (Impp) will be the same in each case (with or without the lost cell), so each "live" cell will continue to produce its same power output. Can someone please explain the physics of the disproportionately large decrease? Many thanks. 89.211.215.17 (talk) 18:07, 20 June 2010 (UTC)

I think the cell has resistance, so it functions like a resistor, impeding the current from flowing. If it was just a piece of metal, it would have almost no resistance and so the power output would only go down 1 cell. --Chemicalinterest (talk) 18:19, 20 June 2010 (UTC)

I'm fairly certain that the 'silicon' is acting as a Photoresistor as well, in addition to the photo-voltaic effect.77.86.115.161 (talk) 18:19, 20 June 2010 (UTC)

In series you can only get the current from the total that every cell can produce. If one is reduced somehow by shading etc, the max current is reduced, and the other cells are not used to their full capacity, the could make a higher current, but the reduced one limITs it. Graeme Bartlett (talk) 11:30, 21 June 2010 (UTC)

Remote video camera

Hi. I want to set up a video camera outside, so that I can watch the footage on my TV. I am therefore going to need a setup where I can receive the pictures remotely. My TV has SCART, HDMI and RF inputs and my PVR has a S-Video, SCART and RF inputs (it would be nice to be able to record the video, but not crucial). I also have a camcorder that I could use for the vidoe capture, which has HDMI and S-Video outputs. I have done loads of searches for "remote camera", "RF wireless camera", "remote webcam", "wireless camera" etc, etc but I can't find anything obvious. It would be nice if the picture could be encrypted between the camera and the receiver, but again not critical. Any thoughts would be greatly appreciated. Thanks GaryInLondon (talk) 19:31, 20 June 2010 (UTC)

Have you tried connecting an S-video cable from camcorder to PVR, and a SCART cable from PVR to TV? Cuddlyable3 (talk) 20:44, 20 June 2010 (UTC)

Interesting that your searches didn't work. There are lots of wireless video systems available, mainly designed for security purposes -- try searching for "wireless security camera" or "wireless surveillance camera". If you really need to be able to use your existing camera, though, that's out of my knowledge range. Looie496 (talk) 23:23, 20 June 2010 (UTC)

Another search is "wireless video sender" or just "video sender" eg - these can be got at relatively low price for transmission of standard video signals - the issue is that they require a power supply, and typically are built for indoor use only. Using one could still have much wiring though.77.86.115.161 (talk) 23:36, 20 June 2010 (UTC)

Are you sure this has to be on your TV set? Doing this with a computer would be vastly easier. There are tons of WiFi "web cams" out there which would do this job perfectly - so long as you don't mind watching the results on a computer screen. You could even watch it over the internet while away from home. If you absolutely must see it on your TV, there are ways to get the video output from your computer to drive the TV. SteveBaker (talk) 02:54, 21 June 2010 (UTC)

Seeing the past

If you traveled faster then the speed of light, could you see the past? --92.244.142.112 (talk) 19:33, 20 June 2010 (UTC)

Yes (if it were possible to do so). But you can look back in time without traveling faster than light. Kittybrewster ☎ 19:53, 20 June 2010 (UTC)

How can you look back in time? Bus stop (talk) 19:56, 20 June 2010 (UTC)

Light takes a finite time to travel to your eyes, so the further (distance) out you look, the further back in time you see. e.g. we can see what very young galaxies looked like in the early universe just by having very powerful telescopes looking out to vast distances. Zunaid 19:59, 20 June 2010 (UTC)

Hence, a light year is a measurement of distance rather than an amount of time. Kittybrewster ☎ 20:04, 20 June 2010 (UTC)

By that reasoning we see our hand as it looked in the past. The light took time to travel from our hand to our eyes. Bus stop (talk) 20:45, 20 June 2010 (UTC)

True. Maybe the OP wanted to know why we can't travel faster than light? Assuming there are no wormholes which I certainly assume in the absence of evidence for them. Kittybrewster ☎ 20:51, 20 June 2010 (UTC)

Nicéphore Niépce invented a way to see the past, now we can see it moving and even reconstruct a historic event in 3-D, and maybe soon we will be able to step into one. Cuddlyable3 (talk) 20:40, 20 June 2010 (UTC)

And by this reasoning we are not really seeing the past. We are seeing an artifact that relates to the past. Bus stop (talk) 20:49, 20 June 2010 (UTC)

Television beats Paul Revere any day. Kittybrewster ☎ 21:32, 20 June 2010 (UTC)

If you could travel faster than light, you could not only see the past (which is possible anyway as others pointed out), you could go to it. Looie496 (talk) 21:49, 20 June 2010 (UTC)

Indeed but you might have to leave your mass behind. Kittybrewster ☎ 21:52, 20 June 2010 (UTC)

Using a tachyonic antitelephone you can send signals into your own past. Count Iblis (talk) 23:22, 20 June 2010 (UTC)

Let's be super-clear about this. There is no such thing as a tachyon. The laws of physics as we understand them do not permit faster than light travel - and it's highly unlikely that there are wormholes. So if you want a clear science-based answer - and not science fiction - then the boring answer is that because you cannot possibly travel even as fast as light - let alone faster - we simply cannot say what you'd hypothetically be able to see. It's an utterly meaningless question - and any attempt to answer it is absolutely guaranteed to be bogus. SteveBaker (talk) 02:50, 21 June 2010 (UTC)

We might not be able to describe what you'd see outside the window of your superluminus ship, but once you arrived at, say, Proxima Centauri fifteen minutes later, it's safe enough to say that you could see into your own personal past with the appropriate telescope. Even if you'd be too far away at that point to resolve enough details to actually pick yourself out.

Sure, our question-asker is not likely to ever pilot such a ship, since they're probably completely impossible, but there's educational value in these sorts of hypotheticals. For instance, understanding this concept may lead them to wonder what would happen if the Centaurians simply put up a giant mirror for us. APL (talk) 03:38, 21 June 2010 (UTC)

Woah, I never thought of that. So if WASP-12b was highly polished, archeologists could use Hubble to see the Romans? 81.131.52.86 (talk) 09:52, 21 June 2010 (UTC)

Well, kind of. The timing works out more or less. I don't know how to do the math to figure out how big of a telescope you'd need to see individual Romans in a giant disco-ball nine-hundred light-years away, but I'm pretty sure it would be far bigger than anything we could ever hope to actually build. APL (talk) 20:41, 21 June 2010 (UTC)

To OP (and Steve, whom I'm sure knows this), you actually can have faster-than-light particles (tachyons) in some models, except for us forward-time folk they look exactly like forward-time particles. In one model for antimatter, a positron is simply an electron going faster-than-light backward-in-time, which is the cause of the antimatter weirdness that we observe in our forward-time universe. That said, a tachyon can't slow down to slower than the speed of light any more than we can speed up faster than it.

A thought experiment: if a person was going backward in time from 2012 to 2008 in the middle of the city, what would he look like, how would he behave, were you to see him on the street in 2010 inside his time-machine-telephone-booth? SamuelRiv (talk) 03:57, 21 June 2010 (UTC)

I keep hearing about these models in physics but I've yet to see any of them in a Victoria's Secret show. Yes, that was my useless comment for the night. --mboverload@ 08:35, 21 June 2010 (UTC)

Ammonia-based life

What substances would be poisonous to ammonia-based life but harmless to humans? --75.25.103.109 (talk) 23:47, 20 June 2010 (UTC)

I had a hunch but don't really know much about hypothetical "ammonia based life", took me all of about 5 seconds to verify: Googling the term found our article Hypothetical_types_of_biochemistry#Ammonia which confirms the most obvious answer would be simply oxygen. If this was a homework question, you fail. Vespine (talk) 00:07, 21 June 2010 (UTC)

nitrite reacts very quickly with ammonia to produce dinitrogen. Graeme Bartlett (talk) 11:21, 21 June 2010 (UTC)

June 21

How the planet and why is divided to different countries; who made this? God, humans or nature?

I would like to know who has created the countries of the plant - God, humans or the nature or is it because we have different knids of humans?

Best regards Daniel daniel.sarbalavand —Preceding unsigned comment added by 213.7.13.253 (talk) 07:39, 21 June 2010 (UTC)

Countries are by definition human constructs. Some religions say their God created or ordained some countries like Isreal...I think.

Also, I would shy away from saying there are "different kinds of humans". I know you didn't mean it in a bad way but it evokes very a very negative response. Plus it doesn't make a whole lot of sense since we're all the same species... --mboverload@ 08:03, 21 June 2010 (UTC)

Some modern countries - mainly in Europe and much of Asia - originated from ethnic groups with a shared genetic and/or cultural heritage (including a shared language) which usually dates back many thousands of years. In some cases - for example, island states - their boundaries were largely shaped by natural geographical features. In the Americas and Africa, the boundaries of many modern countries were determined by colonialists in the 19th century and earlier, who divided up large areas into smaller areas that could be administered more effectively, and those boundaries have endured. Other countries are, in effect, empires or confederations, containing many different ethnicities (such as India or China). The article on Borders explains this further. Ghmyrtle (talk) 08:27, 21 June 2010 (UTC)

Shy away also from the example of Israel as a country because of its ambiguity. Israel may mean[25] 1) an ancient kingdom of the Hebrew tribes at the southeastern end of the Mediterranean Sea; founded by Saul around 1025 BC and destroyed by the Assyrians in 721 BC or 2) A Jewish republic in southwestern Asia at eastern end of Mediterranean; formerly part of Palestine, created by UN mandate in 1947. Cuddlyable3 (talk) 08:29, 21 June 2010 (UTC)

It's not ambiguous - the borders changed at varying times in history. But the basic location has not changed. Ariel. (talk) 08:59, 21 June 2010 (UTC)

The frontier between Spain and France has always been delimitated by the Pyrenees mountain range, all modifications of that frontier were in parts that are easy to cross. So, if God created mountains, then you can say that the frontier between Spain and France was created by God.

I dem for stuff like the great plains in the West part of Russia, preventing any invasion from Europe; the swamps and rought terrain in Central America, preventing contact between Maya civilization/Aztec civilization and Inca civilization.

There was this documental in TV saying how one of those precolumbian civs had discovered the wheel but they couldn't use it because it was all rough terrain and they hadn't animals big enough to pull a cart, and the other civ had big animals that could easily pull a cart (llamas?) but they hadn't discovered the wheel. Because of the bad terrain they never entered in contact and they could never discover the chariot and conquer all of the American continent and join all of it in a common culture that could unite the land in a single country and culture (kind of what Alexander the Great tried to do with Greek culture, Napoleon and Hitler with Europe, Greek with the Aegean Sea, Romans with the Mediterranean, etc).

Similar problems for Africa, with too many jungles and deserts to make it feasible to create a single African culture.

Arguibly, the European Union exists only because the European countries all have a common culture, and that culture was obtained by cultures managing to conquer all or most of the continent, then other cultures absorbing them and conquering stuff again, etc, until all countries get at least a part of the common culture that results from all the mixes. This was possible due to the mix of mountains and fertile plains in Europe, which allows for small civs to develop, conquer, and get conquered, and make it impossible to keep the terrain conquered for too long (too many connections with paths of invasion allowing Muslims, Turks, Huns, etc. to enter, too many thick forests and snow in the North, etc). So, again, if God created Europe's geography, it was God's fault that the European Union exists, and that there no things like the African Union or the Asian Union (the American Union kind of exists, but there is one for the Latin-conquered part, and another for the English/French conquered part). --Enric Naval (talk) 09:20, 21 June 2010 (UTC)

History of Belgium 81.131.52.86 (talk) 10:01, 21 June 2010 (UTC)

See country, nation, government, sovereignty, nation state, and sovereign state. These all mean slightly different things. "Country" by itself is ambiguous. "Nation" is not much better. But it seems safe to at least say that government, sovereignty, states, and nation states are all human inventions. Nations and territories are clearly influenced by geography, history, mass migrations, linguistics, and so on, but one should take care to avoid geographic determinism in explaining how nations, cultures, etc, came to exist in their current forms. Pfly (talk) 10:10, 21 June 2010 (UTC)

See Category:Territorial evolution.—Wavelength (talk) 13:24, 21 June 2010 (UTC)

Hi OP. Just so you know, science has definitively discounted "God" as the answer to any question about "who did" something. (except in fiction). In point of fact, some things humans made, the rest nature made - God made, makes, did, and does nothing, except in the fiction written or believed by humans. This is, at least in my estimation, the upshot of the enlightenment (an end to this kind of superstition), and, if you ask me, the major source of progress in the past few hundred years. The first step to everything you see around you, from the computer you're typing on, the mass produced furniture you're probably sitting at, the electricity powering your house, the first step toward all of this was realizing that the answer was not, is not, and will never be "God wanted it this way." 92.230.234.54 (talk) 15:01, 21 June 2010 (UTC)

One irrelevant wikilink hardly excuses this complacent atheist rant. Cuddlyable3 (talk) 19:18, 21 June 2010 (UTC)

Agreed. DRosenbach ^{(Talk | Contribs)} 04:26, 22 June 2010 (UTC)

Indeed we do have "different kinds of humans." That would be because culturally we are different. Bus stop (talk) 15:09, 21 June 2010 (UTC)

"Different kind of humans", is almost suggesting segration / apartide /. The science of countries and their boundries is often originating in battles and war. Study the deeds of you property and you will discover it depends on who won which battle/war. I haven't mentioned God, just humans and their wars. How scientific is that? MacOfJesus (talk) 00:16, 22 June 2010 (UTC)

Historically cultures coincided with national borders to a large degree, though I wouldn't include the bookstore. Bus stop (talk) 01:21, 22 June 2010 (UTC)

Exploration of the ocean bed

While mankind contonues to research outer space, water bodies, land ceaselessly and while scientists explore the deposits undergound, why have we not vigorously studied the various ocean beds/ ocean floors? recently i read a book ( which the scientists on this site would rubbish as figment of imagination) which goes on to talk about the wonders that lies below the ocean bed. even assuming whats written in the book is too fantastic to be true, why havent we the common public heard much about ocean floor/ ocean bed research? why dont we actually study and see what lies beneath? im not taking about scouting the ocean bed for fictitous treasures. Im talking about excavation of the ocean floor and studying what actually lies beyond that. do people involve in such studies?--Fragrantforever 09:05, 21 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

Natural resources on and below the ocean floors have been extensively studied and, where it is commercially feasible, extracted too. See our articles on offshore drilling and deep sea mining. Gandalf61 (talk) 09:24, 21 June 2010 (UTC)

..and, for further information, Physical oceanography and Category:Physical oceanography. Ghmyrtle (talk) 09:28, 21 June 2010 (UTC)

Three-quarters of the Earth's surface is ocean, and most of the ocean bed lies thousands of feet down. Studying it in detail is a lot of work. Looie496 (talk) 21:21, 21 June 2010 (UTC)

Exploring the ocean depths is a lot harder than exploring space. There's nothing but a thin little sheet of air between you and the heavens. Between you and Poseiden's relm, however, is quadbilliontrillionsinkwtftillion metric tons of water and everything suspended in it. Frankly, I'll stick with my 100 dollar kids telescope. I can see a lot farther. --mboverload@ 01:06, 22 June 2010 (UTC)

the supernova

i copied this question from above, because it`s seems that no one will answer it there, especially after it has transported to the archives. and it is better to see this before answering, thanks any way --Abbad Dira (talk) 11:13, 21 June 2010 (UTC).

quote: "The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions"

can these flares makes a notable changes in the star magnitude? --Abbad Dira (talk) 07:35, 16 June 2010 (UTC).

Sure, that's what variable stars are all about in some form or another. Luminous blue variable stars, in particular, appear relevant. Dwarf novae may also be. — Lomn 12:57, 21 June 2010 (UTC)

No antimony nitrate

Why doesn't antimony nitrate have an article? Is it subject to hydrolysis and therefore unstable? --Chemicalinterest (talk) 11:31, 21 June 2010 (UTC)

There's a antimony(III) nitrate CAS 20328-96-5 , it does hydrolyse in water, basic nitrates are also known.

77.86.115.161 (talk) 12:33, 21 June 2010 (UTC)

Just because something has a CAS number (and plenty of suppliers pretending to sell it) doesn't mean that it actually exists! This paper from 1996 says that only a basic nitrate is known for antimony. Physchim62 (talk) 13:00, 21 June 2010 (UTC)

We'd better tell the CRC press - they list in in [26] ! (there's more info here [27]) 77.86.115.161 (talk) 13:12, 21 June 2010 (UTC)

It probably is only stable in nitric acid. --Chemicalinterest (talk) 13:03, 21 June 2010 (UTC)

Why I asked was because Physchim62 posted a response at WP:RD/S#Oxidation of antimony that nitric acid oxidizes antimony to antimony pentoxide. I was wondering whether the Sb₂O₅ would react with additional nitric acid to produce antimony nitrate. --Chemicalinterest (talk) 13:07, 21 June 2010 (UTC)

No it doesn't seem to - there's a possibility of covalent Antimony(v) nitrate compounds being made under extreme conditions such as using sources of Nitronium ion, or other very reactive compounds.

eg SbF(NO₃)₄ is mentioned here [28], more closer to a pure nitrate is SbO(NO₃)₃.DMSO [29]

I can't find a Sb(NO₃)₅ made under any conditions. It might exist - but not via nitric acid.77.86.115.161 (talk) 13:41, 21 June 2010 (UTC)

Looking at periodic properties, you might be interested in this 1877 account of an attempted preparation of anhydrous Sn(NO₃)₂! From the description given, it is clear than the Sn(II) was oxidized to Sn(IV) before the anhydrous salt could be prepared. Simple Sn(NO₃)₂ is still unknown, although basic nitrates are known. Tin tetranitrate is covalent. Physchim62 (talk) 14:29, 21 June 2010 (UTC)

Wouldn't iron(II) nitrate be unstable too because the iron(II) would be oxidized to iron(III)? --Chemicalinterest (talk) 15:00, 21 June 2010 (UTC)

Often.. Using nitric acid plus iron or 'iron(II) hydroxide' would oxidise iron to iron(III) though a preparation exists using cold dilute nitric acid, but , nitrate is not an effective oxidising agent in neutral solutions (ie it's a slow reaction)- so iron(II) nitrate can be prepared eg type of reaction that might make it _{unfortunately Ag+ is an oxidant..}

ferrous nitrate can be expected to be unstable in acid solutions.

It does exist though but in solution "..is very unstable and decomposes when heated even slightly, forming basic ferric nitrate and liberating nitric oxide. To prepare a pure ferrous nitrate, decomposition of a ferrous sulphate solution by barium or lead nitrate is employed" [30]87.102.11.212 (talk) 15:11, 21 June 2010 (UTC)

Indeed. In practice, the oxidation of iron(II) to iron(III) is quite slow compared to the time it takes you to do the necessary reactions. Also, [Fe(H₂O)₆]²⁺ is not very acidic (unlike the iron(III) equivalent), so there is no particular tendency to form basic salts. Physchim62 (talk) 15:24, 21 June 2010 (UTC)

animal tool use

Obviously humans use tools, and a few other animals can make and use tools, but are humans unique in that they are the only animals that use tools to make other (better) tools? Googlemeister (talk) 14:21, 21 June 2010 (UTC)

That is the distinction that I've heard many times before. Animals (and early humans) had tools that just happened to be fit for the job when they were found. Humans figured out how to make tools that can increase the effectiveness of other tools and then learned to manufacture tools from raw materials. -- kainaw™ 14:29, 21 June 2010 (UTC)

Wild chimps have been observed stripping the leaves from a stick, and chewing on the end to make a better termite-grabbing stick. Captive chimps can use a small stick to grab a larger stick to grab some food.

However, I don't know if they've used a tool to make/improve another tool. CS Miller (talk) 18:03, 21 June 2010 (UTC)

Tool making (as opposed to just tool use) has been observed in several species (primarily primates, but others too). I've never heard of other animals using tools to make tools, though. Past experience suggests we'll find animals that do sooner or later - that's what's happened every other time we've come up with something we think only humans do. --Tango (talk) 18:29, 21 June 2010 (UTC)

Oh, I should give a link to: Tool use by animals. --Tango (talk) 18:30, 21 June 2010 (UTC)

if I sterilise my kitchen knife with the flame from my gas stove, will I ruin it?

I have a big stainless steel kitchen knife. As far as I know, it doesn't have a means of being sharpened. The knife has been in some pretty disgusting situations (due to people putting it in the same part of the sink where food gets stuck and sits for days and I had no time to wipe it down with bleach and wait 20 minutes, so I just took the range support off the stove and lit up a gas flame (there's a hole underneath the burner) and ran the knife through the base of the flame.

I didn't run it through until it was red hot but I had some water droplets on the side of the knife and I basically watched the droplets boil off as my "diagnostic". The thing I'm wondering is whether I can ruin my blade if I heat it up too long? And I noticed particles coming off as I washed it -- I hope I didn't melt any temperature-sensitive protective coatings or anything. John Riemann Soong (talk) 15:18, 21 June 2010 (UTC)

You definately can ruin it - see Tempering - I don't know what sort of knife it is and is can depend on that, but the cutting edge will probably dis-benefit from any tempering (lose hardness).

Cleaning the knive is the best way to sterilise it - eg hot water + washing up liquid. If the blade is attached to a separate handle the join is one place to watch out for for build up of gunk.

See also Sterilization (microbiology) - boiling water after properly cleaning it is a better bet. As is alcohol. Also hydrogen peroxide, bleach, or steam (from a kettle) are good ideas.

If the particle where little grey or dark flakes then you might have oxidised it - in the long term this reduces the polish on the blade which is a bad thing. It could have been carbonised dirt, or burnt lacquer too...

If it was me and I had to clean it quickly I would have scrubbed it, then poured boiling water on it.

Was it stainless steel or carbon steel knife? 87.102.11.212 (talk) 15:29, 21 June 2010 (UTC)it.87.102.11.212 (talk) 15:29, 21 June 2010 (UTC)

Stainless steel. I had too much of a microbio reflex... then I realised a knife is meant to be sharp. John Riemann Soong (talk) 15:55, 21 June 2010 (UTC)

Heating it until the water is gone should get it hot enough on the surface; once it starts changing colors it has reached around 400F. --Chemicalinterest (talk) 15:37, 21 June 2010 (UTC)

Tin(II) hydroxide and related compounds

After adding more ammonia, I got a grayish precipitate

I reacted tin(II) sulfate (probably some of it oxidized to tin(IV) sulfate) with some ammonium hydroxide to get a tan precipitate. I reacted it with more and I got a gray precipitate. Tin(II) oxide states that it is black, so is it a mixture of tin(II) oxide and tin(IV) oxide? Thank you. --Chemicalinterest (talk) 15:40, 21 June 2010 (UTC)

No, well maybe a little ;) what you have is hydrated form of the oxide, that is a precipitate which is somewhere between tin(II) oxide and tin(II) hydroxide. Now filter it off, let it dry and then heat it – you might have a surprise... Physchim62 (talk) 16:05, 21 June 2010 (UTC)

"This hydrate is white, burns like tinder when suddenly heated" ! Are you trying to burn chemicalinterest's house down ?!

(ec repeat info) Hydrated tin(ii) oxide is white too. see p345 - if it's the hydrated oxide heating (boiling) should turn it black.87.102.11.212 (talk) 16:09, 21 June 2010 (UTC)

Will it turn red... I'll try it.--Chemicalinterest (talk) 16:16, 21 June 2010 (UTC)

is it possible to fool a plant cell into thinking a gold nanoparticle is a starch particle?

Racking for ideas... my group has lots of experience with animal cells, but not plant cells. This afternoon we are going to see how plant cells with their cell walls digested are going to behave around gold nanoparticles treated with TAT and other membrane-penetrating proteins (normally used on animal cells). At the same time I am brainstorming for other ideas. It will be very exciting if plant cells have vestigial endocytosis capabilities that get activated.

I'm also wondering how plant cells take in starch. Do they? After all, when sugar is transported up and down stems through the phloem, it's through the form of starches and not simple sugars, right?

Basically anything that would get relatively large nanoparticles (20-60 nm) into cells. (Excitingly, we may soon have a means of using much smaller particles -- 2-10 nm without suffering aggregation problems usually associated with them, if we probe the right ligands.) We know animal cells endocytose particles that large -- up to a limit of 100 nm, but they get stuck in endosomes and usually remain unprocessed for hours (by that time, since we are using particle tracking the cells have apoptosed on our microscopes). Is it crazy perhaps to try to maybe enter through plasmodesmata machinery? (If that's how starches are transported?) Very few people in my group are plant specialists.

I was thinking of coating the particle with various carbohydrate-like polymers (or even just lots of monomer ligands) that would make the particle look like useful food for a plant cell. Despite being quite large. Normally I know plants rely on bacteria, protists or fungi to digest nutrients for them. John Riemann Soong (talk) 16:11, 21 June 2010 (UTC)

erm Plant sap says sugars in sap not starch .. it's a fascinating idea of coating gold like a sugar coated pill to confuse the plant though. I'm not a biologist - maybe the bigger picture includes starch transportation.87.102.11.212 (talk) 16:15, 21 June 2010 (UTC)

Agreed, plant sap is a mixture of sugars (usually sucrose), water, hormones and minerals. No sugar polymerism I'm afraid. Plasmodesma are about 60nm in size so you might just be able to squeeze large nanoparticles through, but I have absolutely no idea how you'd go about it. Regards, --—Cyclonenim | Chat  16:21, 21 June 2010 (UTC)

Hmm. I'm thinking of culturing some plant cells on a microscope slide, then selectively rupturing the cell wall of the cells on one end of the slide. We then treat the slide with nanoparticle buffer -- the nanoparticles will be treated with movement protein? The particles will enter through the ruptured end and spread the rest of the cells through plasmodesmata and there hopefully will be no endosomes trapping them.

We could also go the whole hog and basically digest the cell wall of most of the cells, but since plant viruses usually enter through mechanically ruptured cells -- does the cell membrane need to be broken too? I don't know if chemical digestion will work. Of course selectively and mechanically rupturing plant cells sounds a little difficult -- but then so is injecting probes directly into cells, and plant cells are kinda big anyway. Anyone have tips? One thing I do NOT want to do is trigger mass apoptosis -- do I have to worry about ruptured cells releasing apoptotic factors?

(We're going to all this trouble over gold because nanorods are excellent optical rotational probes that respond differentially to polarised light depending on their orientation. And they're less toxic than quantum dots and they don't bleach like fluorophores. We want to see the rods interact with the cytosol and not just stay in a confined endosome.) John Riemann Soong (talk) 17:03, 21 June 2010 (UTC)

This is well beyond my level so I can't comment specifically on techniques, but there are numerous journal entries out there showing gold particles within plant cells ( here's one ), maybe it's worth collaborating with these people to see how they introduced the particles into the cells? They could have just been injected, but they may have used other methods too. Regards, --—Cyclonenim | Chat  17:45, 21 June 2010 (UTC)

effect of color of iris on image formation

Ever noticed black outline around the eye of tiger! know its reason? that black outline minimizes light's intensity, so tiger is able to see its prey in glare also..

willn't the color of iris in human eye (or in any other animal) have any effect on image formation ? isn't it so that person with black iris could see thing more clearly than a person with light-colored iris, in too much light? And vice versa?

and i believe that every thing that happens or is in the world is/was for some reason, so do the iris of human. Thanx .....--Myownid420 (talk) 17:49, 21 June 2010 (UTC)

See our article Iris (anatomy), specifically the section Genetic and physical factors determining iris color, for what causes the color of the human iris. On your last point, it is doubtless true that everything in the world exists for some reason, but it doesn't have to be for a good reason. Comet Tuttle (talk) 18:40, 21 June 2010 (UTC)

There are many, many different human iris colorations, which would suggest that any evolutionary effect is minimal. Physchim62 (talk) 19:23, 21 June 2010 (UTC)

Two things occur to me (pardon the personal research), light does not pass through the iris, only through the 'hole' (pupil) in the centre so it is difficult to see how the colour of the iris can affect the received light. Why not ask someone who wears coloured contact lenses. Coloured in the sense that the iris part is a distinctly different colour from their normal iris colour. Here [31] is what I mean. Richard Avery (talk) 06:35, 22 June 2010 (UTC)

wood

I have noticed that when wiping off an unfinished solid wood stool with a clean wet paper towel that a yellowish stain comes off onto the paper towel. What is the yellowish stain since the wood is unfinished? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 18:27, 21 June 2010 (UTC)

Among other things, wood contains tannins. This could be part of your yellowish stain. Pro bug catcher (talk • contribs). 19:27, 21 June 2010 (UTC)

If it's a bar stool, or used to be, there's a couple of other things I can think it could be, lol. :) Vespine (talk) 00:23, 22 June 2010 (UTC)

Cell disruption, movement proteins and apoptosis

My grad student sort of likes the plasmodesmata idea; we're now looking at particular movement protein papers to see if anything like this has been attempted before. But I want to ask -- do plant cells have responses against movement proteins? I don't know which viral proteins are particularly targeted. I want to know how much nanoparticles treated with movement protein can be added before I start eliciting defence responses.

Also anyone have tips for controlled cell disruption on one end of a plant cell culture (on a microscope slide) while leaving most of the cells alive and not in the process of apoptosis? In particular I'm thinking of using our glass-washing sonicator. I could dip the slide in a solution with mild surfactant while in the sonicator. I know the part that is not exposed to the sonicator solution will still feel sound waves, but they will be much less damaging, right? John Riemann Soong (talk) 18:38, 21 June 2010 (UTC)

Anyone have suggestions on surfactant? I don't want to completely dissolve the cell membrane of the targeted cells -- I need to leave the gap junctions intact. John Riemann Soong (talk) 20:06, 21 June 2010 (UTC)

Erm, I think this is getting to be a particularly specialized homework question! Physchim62 (talk) 21:22, 21 June 2010 (UTC)

It's not going to be marked (unless this is specifically the OP's students PhD work!) so I'd see it more of a problem solving question. Regards, --—Cyclonenim | Chat  21:34, 21 June 2010 (UTC)

I just want some quick and dirty immunology tips. Having to deal with plant defences is relatively new to us. I had to think up this idea all by myself, which probably means I'll probably have a good chance of going somewhere wrong. I just only finished my 2nd year of undergrad, so I don't want to slow down the greater project too much but I want to still be able to conduct my experiment. I want to pull it off so that way I can get my group to look at plants more often. John Riemann Soong (talk) 21:50, 21 June 2010 (UTC)

Amount of water that "sticks" to dipped object.

I would like to determine the (theoretical or real) amount of water that stays on a surface that has been dipped in water (or a water based solution). For the real value, I suppose I could weight the object before and after it has been dipped (and before the water/solution dries). Can anyone point to the theory behind this? Other methods? Or perhaps point to known answers for different objects? I want to determine this for sugar maple and aspen leaves, dipped in a sucrose solution. Ideally to figure the amount of sucrose per unit of leaf surface added by dipping. Pro bug catcher (talk • contribs). 19:24, 21 June 2010 (UTC)

The relevant property is probably surface tension. --Tango (talk) 20:58, 21 June 2010 (UTC)

We have a good article on wetting, which is the phenomenon you are asking about. My understanding is that you can't calculate it from theory (except in idealized textbook cases), you have to find a way to measure it. Physchim62 (talk) 21:13, 21 June 2010 (UTC)

Operating of Transverse flux motor

I'm trying to understand what makes a transverse flux motor move.. for example [32] which seems typical - I can understand figures 4 and 5 ie with current applied causes magnetic field goes through the rotor... But the only way I can understand this working is on a reluctance motor principle (with more than one set of current windings) - operating on a sort of stepper principle - ie a synchronous type motor. (or maybe AC drive with sets of magnets in alternating pole direction where current reversal causes alternate rotor poles to allign , again by the reluctance principle..) Can shed more light on this? 87.102.11.212 (talk) 20:46, 21 June 2010 (UTC)

CALORIE BURN RATE FOR EXERCISE

In starting a new exercise program, I'm trying to determine how many calories are burned per each push-up I do.

I don't remember where I read that 2,600 calories equals one pound and that one calorie equals 4.184 joules. That doesn't help me in converting push-ups to calories burned. I also remember reading, but don't remember where, that there is a conversion of weight lifted to horsepower used, where the horsepower equals a calorie equivalent.

Basically, what I want to know is; for a man weighing 255 pounds, approximately how many calories would he burn doing a correct form push-up? Buzz27 (talk) 21:00, 21 June 2010 (UTC)

You can get a lower bound by figuring out how much the man's center of gravity goes up during the push up, in feet; multiply that by 255, and you have a figure in foot-pounds, a unit of energy, which you can convert to calories in Google or something. (Be careful that there are two units called the calorie that differ by a factor of a thousand.)

But remember that the body is not perfectly efficient, so this figure is really just a lower bound. Also there are important secondary effects that are not necessarily linear in the number of push-ups — to the extent that the exerciser gets his heart rate and metabolism up, they may remain elevated for a number of hours. Also, if he builds muscle, that will increase his basal metabolism (but also possibly make him hungrier). --Trovatore (talk) 21:08, 21 June 2010 (UTC)

(expand) I'm willing to try in metric.. If your arms are A meters long, and you weigh K kilograms, each push up need AKg/2 (centre of bodies mass is ~1/2 along between shoulders and feet) (g~10) = 5AK. So if arms =0.6m and weight = 100kg thats 0.6x100x5=60x5=300Joules (or 0.3kJ) (or ~1/14 calories)

That's just for a push-up I get hot when doing push ups so I'm not 100% efficient. Anyone know how to guess human efficiency?87.102.114.9 (talk) 21:17, 21 June 2010 (UTC)

A pound of fat is about 4000 Calories. A push-up burns somewhere in the neighborhood of 1 Calorie. Unless you have incredibly strong arms, doing push-ups is not useful for burning calories -- their value is in improving your muscle strength in the arms, pectorals, and core. Looie496 (talk) 21:11, 21 June 2010 (UTC)

If you are saying that one pushup burns one food calorie, then pushups would be a great way to burn fat since someone in shape can do 100 pushups in less then 5 minutes, which is approximately the same calorie burn rate that someone running a 7 minute mile would get. If you mean the non-food calorie, then pushups are pretty worthless way to burn fat in the short term. Googlemeister (talk) 21:23, 21 June 2010 (UTC)

Pushups, and other upper-body exercises, are always going to be lousy ways of burning calories. The muscles involved in a pushup (chiefly pectoralis major and the triceps muscle) really aren't very big, and so aren't up to the job of doing lots of work and burning lots of energy. This is all because you're a biped, several million years divorced from swinging through the trees. If you want to burn calories, you need to use the big muscles of the body - chiefly the gluteus maximus, the hamstring and quadriceps groups in the thigh, the muscles of the lower abdomen, and the heart. Running, walking, cycling, skiing, and dancing use these, as do common gym machines like a stair climber or cross trainer. Even exercises like swimming and rowing, which recruit the arms and upper body too, are still heavily leg/ab/gleut biased. There's an easy (well...) way to verify this - go to the gym and use two machines - the stationary bike and the stationary hand bike. Do 100 calories-worth of exercise on each (per the little meter thing, which is sufficiently accurate for our purposes here). The 100 calories on the (leg) bike is pretty straightforward; the 100 calories on the hand bike is (even if you're pretty fit) a soul-destroying slog. I don't believe anyone ever got fit, or lost significant weight, doing pushups. My advice instead would be to check with your doctor that you're healthy to exercise, then visit a gym and have the (usually pretty well trained) exercise coach people there design a balanced program for you, that matches your fitness and meets your goals. -- Finlay McWalter • Talk 22:02, 21 June 2010 (UTC)

My personal experience (obviously OR) is that the exercises most suited for weight loss are the ones that work the whole body. In the gym, try one of the elliptical cross-trainers where you push and pull on the handlebars at the same time as you run on the foot pedals. Those burn 100 calories (as measured by the self-reporting LED display; who knows how accurate those are) with considerably less sensation of effort than a treadmill or a leg-only elliptical.

Swimming is (again in my personal anecdotal experience) a truly excellent weight-loss exercise. I think one of the reasons is that, for many exercises, the limiting factor to how hard you can work is thermal stress. In the pool, the water carries that right away, assuming they keep it at a good temperature for lap swimmers (somewhere around 70 degrees F). --Trovatore (talk) 22:09, 21 June 2010 (UTC)

Well, you should theoretically burn more calories than the physics would say since some types of exercise will up your metabolism for the rest of the day as the body repairs itself. Also, as you build muscle your resting metabolism will be higher. I'd recommend you do body weight squats instead of pushup since you'll be using bigger muscles and moving more weight. Personally, if you do decide to do body weight exercises (nothing wrong with that), then you may want to look into HIIT - that should ramp up your metabolism if you can handle it. Consult your doctor before starting any exercise program...blah...blah...blah....TheGoodLocust (talk) 22:16, 21 June 2010 (UTC)

I've read that what TheGoodLocust wrote: "as you build muscle your resting metabolism will be higher" is actually the dominant way you lose weight by exercising. The calories you burn during exercise are completely irrelevant. You can't reason in the naive way, assuming that the body has a contant metabolic rate and then say that if you burn X alories, you'll lose Y grams of fat. A few years ago this theory was put to the test in a BBC Horizon documentary. Students were given a diet containing twice the amount of calories they normally ate (about 5000 Kcal/day for most of them). The weight gain after a month was minimal, ranging from a few kg to 10 kg. After a few weeks all the weight gain was lost as the students returned to their normal diet.

What happened was that the students with the lowest weight gain increased their metabolic rate, partially due to growing more muscles (without exercising, simply as a respons to increased calory intake). So, this experiments confirmed that the weight does not respond strongly to any attempt to change your energy balance, because your body will counteract that by adjusting your metabolic rate. You have to go to extremes like eating 5000 kcal per day without doing any exercise to see even a modest weight gain of a few kg.

This is not that surprising as without such a mechanism, you could starve to death by eating one slice of bread less every day in a few years time. To lose weight by dieting, you really must eat significantly less calories; the body then cannot compensate for that. In the Horizon documentary, it was mentioned that any weight loss by dieting is temporary. The number of fat cells more or less sets your weight. Your body regulates the metabolic rate such that the fat cells are filled to some fixed degree. If you have lost a huge amount of weight by dieting, then your fat cells are still there, but they are empty. If you then eat a normal diet, say 2000 kcal per day, your body will then slowly start to fill your fat cells; it won't take long before you're be back at your old weight.

My personal experience corroborates this picture. Since about 2 years ago, I've doubled my exercise time. I now run for about half a hour, five times per week. On the two resting days I do brisk walking. I also eat a little less than I did two years ago. But my weight was 63 kg two years ago and now it is 62 kg. The only thing that has significantly changed is my fitness. I can jog for more than an hour without getting tired (I really need to do fast running for more than 15 minutes to feel that I'm exercising at all). My resting heart rate has dropped to 40 bpm (in fact yesterday evening it was 37 bpm). It was around 48 bpm two years ago. Count Iblis (talk) 02:20, 22 June 2010 (UTC)

Yes, that was part of my point, the other idea I was trying to communicate was that certain high intensity exercise programs (e.g. HIIT) will cause your metabolism to spike for 24-48 (?) hours as your body repairs itself from the damage (e.g. microtears). TheGoodLocust (talk) 05:54, 22 June 2010 (UTC)

Well, it's very individual. At some points in my life I have been very successful at losing weight via exercise, at other times not so much. I really don't think it's mainly about muscle gain, partly because my experience is that when I have more muscles I'm also hungrier.

I'm sure Iblis is right that it's not as simple as just subtracting two numbers (not that you can accurately calculate them anyway). But in my experience is nevertheless that exercise can be effective, even if I can't be sure of the exact mechanism.

I recall that there is some research that indicates that exercise actually changes your "set point", the weight that your body tries to maintain. Alternatively, it may reduce low-level anxiety that would otherwise induce you to eat, and it also shouldn't be forgotten that time you spend exercising is time that you're not snacking. --Trovatore (talk) 06:05, 22 June 2010 (UTC)

I've also read that sleeping more helps to lose weight. It has been known for a long time that people with sleeping disorders tend to be fatter. But recently it was reported that people who simply ecide to sleep less tend to be fatter. There is a link with sleeping enough and getting enough exercise that works both ways. I have noted that I sleep a little more too now that I'm exercising more.

The following is my own speculation on this :). It could be that sleeping time counts as "virtual fat" for your body. The whole point of having a fat reserve is that you could survive for a certain amount of time on your fat reserve. What matters to your body is that amount of time, not the amount of fat. Now, your body will respond to eating less by adjusting the metabolic rate; if you eat too little then the body cannot compensate for that and you'll lose weight.

The rate at which you lose weight is then determined by what the minimum average metabolic rate over a day can be. During sleep the body can throttle down the metabolic rate more than during daytime without compromizing on how well you can function. So, the longer you sleep, the longer you can last on the same fat reserve, so you would need less fat reserves to survive for the same amount of time. The body can gauge how well it sleeps uder normal circumstances and use that to control the amount of fat reserves via complicated feedback processes.

What may enter in the calculation here is that if you were to eat far less than you need, you would become very tired and sleepy; your body will want to sleep a lot more to save energy. But if you sleep bad under normal circumstances, you may not respond to this by actually sleeping a lot more than someone who sleeps well under normal circumstances. If the body takes this into account under normal circumstances as well, then the amount of virtual fat your body calclates you have if you sleep well will be larger, so you would lose/gain more weight by sleeping more/less. Count Iblis (talk) 15:28, 22 June 2010 (UTC)

Faraday cage from water?

Is water/salt water conductive enough to be used as an effective faraday cage? How much protection would it provide against emp/super-emp weapons? If not what could be added to it to increase conductivity enough to provide adequate protection? I suppose I could put my cell phone in some tupperware, submerge it, and try to call it, but I think that'd be an apples to oranges comparison. Cheers. TheGoodLocust (talk) 22:10, 21 June 2010 (UTC)

Well if you dropped the device 100 meters deep in the sea water it would protect against EMP. You could reduce the skin depth by adding more salt, upto 30% should increase conductivity. Graeme Bartlett (talk) 01:39, 22 June 2010 (UTC)

Well, I figured the sea would do a good job at that, seems to keep Cthulu in check after all, and I'm assuming would work on the super emps too (plus submarines seem like faraday cages in their own right), but I was actually more curious about smaller scale applications - how many inches of salt/sea water would be required to provide emp and/or super emp protection? TheGoodLocust (talk) 03:52, 22 June 2010 (UTC)

The skin depth for a typical metal will be about 1/3000th the typical value for sea water, so 1 mm of aluminum shielding will be about the same as 3 m of sea water. I'm not sure how much shielding one needs for a nuclear EMP, but that ratio suggests it would probably be better to stick with metal shielding for most applications. Dragons flight (talk) 07:53, 22 June 2010 (UTC)

Thank you, very helpful. TheGoodLocust (talk) 08:23, 22 June 2010 (UTC)

Lots of water would be needed, although you're looking at a different effect. Water attenuates the signal so essentially absorbs the energy, a faraday cage routes the signal around the space inside it, through mutual interference.

ALR (talk) 08:17, 22 June 2010 (UTC)

Ah, well, I meant submerge a non-conductive container into sea water (e.g. tupperware), and which should conduct the signal around it. TheGoodLocust (talk) 08:23, 22 June 2010 (UTC)

Yes, I appreciate that you meant you had some way to provide watertight integrity, although a non conductive container will just allow EM waves to pass through it, so you're dependent on the mass of water to attenuate. Part of how a faraday cage works is that the metal thickness allows the cage to act as an antenna, the weight of water would be too much to achieve that.

Deep enough to protect the device the container would be crushed.

ALR (talk) 08:41, 22 June 2010 (UTC)

ALR (talk) 08:41, 22 June 2010 (UTC)

Bacteria in Spoiled Milk

Foodborne illness mentions a number of the most common offending pathogens—which, if any, is most likely to be contracted from drinking spoiled milk?

Alfonse Stompanato (talk) 23:33, 21 June 2010 (UTC)

I suspect the mind would be the most "common offending pathogen" you could get from drinking spoiled milk. In other words, I think people would worry themselves sick over nothing - the human digestive system is truly an amazing thing and with modern pasteurization methods I don't think you could get botulism from it and, I believe, with botulism you are actually getting sick from the waste products of the bacteria, which might not qualify as a "pathogen." TheGoodLocust (talk) 00:30, 22 June 2010 (UTC)

Soured milk is apparently an ingredient in many recipes, thus I doubt it is bad for you in any direct way. I'm not exactly sure the difference between "soured" and "spoiled" milk; it seems the terms are used inter-changeably.-RunningOnBrains^(talk) 03:38, 22 June 2010 (UTC)

It all depends on what gets into the milk. For example, S. aureus is a major cause of mastitis in cows, humans, and other mammals, and an important cause of foodborne illness, primarily as a source of a pre-formed toxin that causes self-limited form of gastroenteritis (example: PMID 327532). Unpasteurized milk can be a source of brucellosis and other pathogens in some parts of the world. That being said, commercially-pasteurized milk is extremely safe when stored and consumed according to its labeling. -- Scray (talk) 04:01, 22 June 2010 (UTC)

Yeah, there's a big difference between soured milk and spoiled milk. Leave a quart of milk sitting on a warm counter for a few days and there's a good chance you'll be able to smell the difference: butyric acid, which is a marker of spoiled milk, is one of the most obnoxious odors known to man. Looie496 (talk) 04:08, 22 June 2010 (UTC)

June 22

basic physics question about inertia, riding the bus, balance, etc.

When I ride the city bus I stand perpendicular (facing out the window) to the direction of movement (forward). Knowing that we will soon be approaching a stop, I shift my weight to my rear (nearer the back of the bus) leg. Then, as the bus rapidly decelerates, I gradually shift my weight to my front (neared to front of the bus) leg and thereby disperse the change in inertia? velocity? momentum? in a controlled fashion. Done properly, I never need grasp a handrail no matter how abruptly the bus stops. At no time am I off-balance.

What I want to know is: from a Physics standpoint, what exactly is going on here? How can I properly describe this sequence of events? As a layperson, I can sum it up by just saying "shifting my weight and maintaining my balance" but I'm very curious to hear a detailed explanation of the physics involved. Any takers?

Thank you! —Preceding unsigned comment added by 218.25.32.210 (talk) 01:14, 22 June 2010 (UTC)

You are making sure the reactive force on your feet from the floor (well, the total of the forces on each foot) points through your centre of mass (by moving your centre of mass), so that it does not produce a torque. The direction of that force will usually simply be "up", but when the bus accelerates/decelerates the direction changes. You can think of this simply as a change in the direction that is "up", since the equivalence principle tells us that acceleration is indistinguishable from gravity (without external reference, so let's assume the bus's windows are so dirty you can't see out - not a big assumption on the buses I use!). --Tango (talk) 02:05, 22 June 2010 (UTC)

When the bus is not accelerating (bus stationary or moving at constant speed) there are only two forces acting on your body – your weight acts downwards, and the floor of the bus exerts an upward force equal to your weight but opposite in direction. The vector representing the upwards force passes through your center of mass.

When the bus is accelerating there is an extra force – a horizontal force exerted on your feet by the floor of the bus. (If the floor of the bus was slippery with water or ice this horizontal force would not exist. When the bus accelerated you would slide towards the rear, and when the bus stopped you would slide towards the front.)

The horizontal force exerts a torque about your center of mass. When the bus stops, this torque tries to make you rotate (fall forwards.) When the bus is increasing speed, the torque tries to make you rotate in the other direction (fall backwards.) You prevent this from happening by leaning forwards or backwards so that the upwards force exerted on your feet is no longer through your center of mass and exerts a torque on your body. By adjusting the position of your center of mass you can ensure that the torque exerted by the horizontal force on your feet is equal and opposite to the torque exerted by the upward force on your feet. When the two torques cancel you do not rotate (neither fall forwards nor backwards.) Dolphin (t) 02:41, 22 June 2010 (UTC)

I'm not sure that you'd need an external reference (clear windows). All you need to keep from falling over is that the total force vector (gravity + other acceleration) points from your center of gravity to some point on the floor between your feet. This is certainly made easier by seeing the relative motion of a fixed reference frame, but theoretically, at least, it wouldn't be necessary. -- 174.24.195.56 (talk) 15:30, 22 June 2010 (UTC)

A few more questions on quantum mechanics.

Is the observer effect a basic part of quantum theory or a particular interpretation of it? Is the observer effect falsifiable? Is the ensemble interpretation incompatible with the observer effect? And is quantum entanglement a possible explanation for why individual photons might still exhibit interference in a Mach-Zehnder interferometer, regardless of whether they're being observed? ☯  Zenwhat (talk) 02:43, 22 June 2010 (UTC)

To answer your first question: it depends what you mean by "observer effect". If you mean the effect in which observing a system disturbs it (or, in more QM terms, any interaction between two initially isolated systems leavs them in an entangled state) then yes, I think this is a basic part of quantum theory. If you mean wavefunction collapse then I think this is interpretation dependent - in the many-worlds interpretation, for example, there is no objective wavefunction collapse - the apparent collapse of the wavefunction is an illusion due to the fact that an observation implicitly selects one out of a multitude of universes. Gandalf61 (talk) 09:36, 22 June 2010 (UTC)

Another way to look at that is using the classical Schrodinger's cat thought experiment - but without the observer having "special" status:

• The poison gas container became entangled between being closed and being open when it "observed" the quantum event that set off the trap.
• The cat became entangled by "observing" the poison gas canister and is simultaneously dead and alive.
• When the outside experimenter opens the box to look at the cat (and thereby "collapses the wavefunction"), he/she merely becomes a part of the entanglement - and is now the entanglement of an experimenter who is sad for the loss of the cat with an experimenter who is pleased that the cat is OK.
• When the experimenter phones the cat's owner to tell of the sad/happy news - that person on the other end of the line also becomes entangled.
• The telephone system also became entangled between two states where more or less electricity was used for the phone call - the air in the laboratory is entangled between one set of sound vibrations and another - the photons of light reflecting off of the cat and the experimenter are entangled between the two states and head outwards through the laboratory windows entangling other things that they interact with.

In this view, wave functions are not collapsed by some special "observer" - they merely entangle the observer along with everything else. The observer has no special status - which is a much more comfortable position than proposing that human brains are somehow "special". The entanglement ripples outwards (in truth, at the speed of light), affecting more and more things. Since every quantum scale event in the universe is simultaneously entangling different parts of the universe into different states, you effectively have the many-worlds interpretation where every possible quantum event creates an entire new copy of the universe that is an 'entanglement' of all of the other copies. SteveBaker (talk) 10:47, 22 June 2010 (UTC)

Fossil fish

Hello, does anyone know what kind of fish this is? Thanks, --The High Fin Sperm Whale 03:25, 22 June 2010 (UTC)

It tells you right in the file description. TheGoodLocust (talk) 03:46, 22 June 2010 (UTC)

He's the one who uploaded the file, so I think he wants a more specific answer than the file description. ☯  Zenwhat (talk) 03:57, 22 June 2010 (UTC)

I would imagine that HFSW knew that, since it is his photo. "Ray-finned fish" is not a very specific description. There are more species of ray-finned fishes than all other vertebrates put together. Anyway, I'm certainly not an expert, but it looks very generic to me. Looie496 (talk) 04:00, 22 June 2010 (UTC)

Yes, I would like to know the order, genus, or, preferably the species. --The High Fin Sperm Whale 04:03, 22 June 2010 (UTC)

Have you tried at Wikipedia:WikiProject_Fishes#Related_WikiProjects eg fishes, biology or tree of life.87.102.66.101 (talk) 12:52, 22 June 2010 (UTC)

One would almost certainly have to know the location / geological formation from which the fossil came to assign it to a particular genus or species. Do you have that information? Deor (talk) 15:03, 22 June 2010 (UTC)

Geophysics survey

Following up on the question about "Faraday cage from water": Would the electromagnetic sensors used for geophysical surveying (such as ground-penetrating radar, or induction-based electromagnetic sensors) be useful for detecting magnetic/conductive materials (e.g. iron ore deposits, manganese nodules, or the occasional Electra 10-E) underwater? 67.170.215.166 (talk) 03:55, 22 June 2010 (UTC)

Perhaps in freshwater, but I think it is unlikely to work at sea. I imagine some advanced form of sonar would be necessary for the latter. TheGoodLocust (talk) 07:08, 22 June 2010 (UTC)

read magnetotellurics which can detect material of different conductivities in the earth. Careful measurement of the magnetic field with Aeromagnetic surveys can reveal iron ore deposit below water, but it would not be economical to mine. Your ground penetrating radar would suffer too much attenuation in water to be useful. Graeme Bartlett (talk) 10:59, 22 June 2010 (UTC)

Potato battery

A recently published article has been making the rounds on the Internet lately, with bold claims of "The treated potato battery generates energy that is five to 50 times cheaper than commercially available batteries". But reading the study I did some calculations and with the 225cm² of Zn surface area in their potato cell at ~1.2mWh/cm² (their data) the total power capacity of their potato cell is only 270mWh, less than half of the most basic Zinc-Carbon AA battery, yet they proclaimed "at maximal performance the treated Zn/Cu-potato cell is markedly more economical than a typical 1.5 V AA alkaline or D batteries." Is my calculation correct? Can anyone decipher how they arrived at the cost analysis and conclusion? Is this article (at least its claims) completely hogwash? --antilived^{T | C | G} 06:50, 22 June 2010 (UTC)

I think the idea is that you have more than one cell, and their combined cost is lower than a regular battery. That said, the idea is nonsense anyway. There were people talking about how much potatoes cost, and sorts of other nonsense. The power comes from the metal. NOT the potato. The potato does nothing. Just replace it with some salt water. Ariel. (talk) 06:53, 22 June 2010 (UTC)

You'd have to pay for the metal rods and wires and cost your time too. By the way can I interest you in some stone soup?, a couple of potatoes now would give it some body. Dmcq (talk) 10:29, 22 June 2010 (UTC)

50 times cheaper - I cannot disagree with this claim - the cost of the battery is that of the metal plates they are using, plus the boiled potato - compare with convention batteries - they don't just use zinc plate - but specially prepared zn powder, plus MnO2, plus construction costs - to what is a quite sophisticated finished product - the potato battery just uses the raw materials - it will without doubt be much cheaper. I don't know if they've included transportation costs...

Second claim more economical - no idea what 'economical' means in this context - probably a repeat of the above correct claim.

Summary: Not hogwash - but not actually a practiable energy source. (see below)

Note: This battery would be fine for a digital watch, but I'm fairly certain that it would have serious problems driving a substantial load - eg radio loudspeaker, or even tiny electric motor. A led is not a demanding load. Otherwise it's interesting to note the suitability of boiled plant matter as a ion conudctive material.87.102.66.101 (talk) 13:11, 22 June 2010 (UTC)

monofilament cutting string

In SciFi stories sometimes they have monofilament strings that are just one atom wide and can cut through anything. But wouldn't the material that was cut just immediately vacuum weld back together again? (You don't get a better vacuum than that, and the cut piece are exactly in the right spot to join right back together.) I'm guessing metals would do that? But would more complicated molecules? Say a piece of wood? Would it depend on what kind of bond the molecule used? Ariel. (talk) 07:12, 22 June 2010 (UTC)

Yes, this idea pops up in Sci-Fi books/comics/manga/anime/movies/cartoons a lot; see this partial (but very impressive) list. A "monofilament" (a molecule, really) one atom thick makes no sense, however, as it has a strength of a single molecule. The work needed to tear it is about the same as the work required to move a couple of electrons from one orbital to another, that is, something of order of 10^-18 Joule. So no, that won't cut anything. If you take a bunch of, say, nylon molecules side by side, however, then you have a fishing line. The thicker it is, the stronger it is. And yes, you can get some nasty cuts from the fishing line if you are not careful. --Dr Dima (talk) 08:24, 22 June 2010 (UTC)

I'd imagine having such low mass would be a major hindrance as well. If one could increase the strength of the electromagnetic force in the filament then that should get rid of the strength issues (it is sci fi after all), but that would still leave the mass problem, which I suppose could be countered by increasing the acceleration of the weapon. TheGoodLocust (talk) 08:37, 22 June 2010 (UTC)

Yes, you can do that, but the cutting implement will not be a monofilament string anymore; rather, it would be an ion beam. Yes, an ion beam can cut solid materials. --Dr Dima (talk) 08:52, 22 June 2010 (UTC)

By the way, if we return to the original idea of a very thin monofilament string, you can see that it is unlikely to work by doing a simple dimensional analysis. Note that, for a given force applied to the filament, the pressure it exerts on the surface you are trying to cut is proportional to the force applied to the filament divided by the filament diameter to the first power. However, the maximal force the filament can withstand is roughly proportional to its cross-section, so to its diameter squared. Assuming you pull on the filament with the maximal force it allows without breaking, then, for the same cutting configuration, the pressure will increase as the first power of the diameter. That is, the larger is the filament diameter the higher is the pressure it exerts on the surface you are trying to cut. Indeed, I've never heard of anyone getting cut by walking into a spiderweb; but a snapping steel cable will cut a person clean in two. --Dr Dima (talk) 09:04, 22 June 2010 (UTC)

...and to finish that thought: Spider's web is gram-for-gram stronger than steel...so if the idea of thinner (being "sharper") is better - then spiders web ought to cut more easily than a cheese wire - which in turn ought to cut better than a steel cable. SteveBaker (talk) 10:24, 22 June 2010 (UTC)

Inner asteroid belt?

Is there any reason there is no asteroid belt within the Mars, Earth, Venus, Mercury and the Sun? Just chance, or some does physical principal exclude this possibility?80.1.88.13 (talk) 08:00, 22 June 2010 (UTC)[Trevor Loughlin]

Well, I'm totally guessing here since I've never taken any astronomy classes, but I'd imagine that as matter accretes into planets they'll move closer to the sun. Once this happens I think the complex gravitational interactions between the planets, sun, and asteroids would tend to throw the remaining asteroids in the core of the system into each other to make more planets, into the existing planets to increase their mass or into the sun. The outer asteroid belt wouldn't be subject to such chaotic gravitational forces as frequently and should remain relatively stable. TheGoodLocust (talk) 08:32, 22 June 2010 (UTC)

Jupiter perturbs orbits and makes planet-formation difficult. Being further away allows the asteroids to accrete into planets. So implies our Asteroid_belt#Origin article, anyway. Vimescarrot (talk) 10:36, 22 June 2010 (UTC)

In this close the planets will muck up the orbits and make them unstable, even though Mars etc are smaller, they would be much closer to an inner belt and have a huge impact. Graeme Bartlett (talk) 10:54, 22 June 2010 (UTC)

Ferrofluid heart assist jacket?

Some researchers have created experimental powered jackets surrounding the heart to give about 10% assistance in the case of heart failure. Could the power limitations be overcome by using a ferrofluid filled jacket (surrounding the heart, as before) powered by superconducting magnets external to the patients body?[Trevor Loughlin]80.1.88.13 (talk) 08:20, 22 June 2010 (UTC)

I can't comment on the physics, but I doubt the FDA would approve such a device with that kind of liquid in it. Perhaps someone qualified can comment on the FDA's views on the chemicals used in ferrofluids.--mboverload@ 09:28, 22 June 2010 (UTC)

Ferrofluids tend to be things like oil or water with nano-scale particle of iron, magnetite or hematite suspended in it. Certainly stuff like that would be pretty disasterous to have inside your body if the surrounding container leaked. I think the toughest problem would be to find a material flexible enough to pump the heart millions of times without breaking - that is also biologically tolerated. For a short-term emergency, it ought to be OK - but not for long-term use. SteveBaker (talk) 10:17, 22 June 2010 (UTC)

A superconducting electromagnet has significant size, weight and power consumption. Besides its non-portability it raises safety issues, see MRI#Safety, and it would be unacceptable for a patient with a medical implant such as a pacemaker. Cuddlyable3 (talk) 10:31, 22 June 2010 (UTC)

If I had tubes of magnetic fluid wrapped around my heart I don't think I'd want to go anywhere near a superconducting magnets. APL (talk) 15:21, 22 June 2010 (UTC)

Metal mesh interfere with WiFi signal?

Could a laptop stand fashioned from this mesh interfere with the laptop's WiFi signal? --89.243.136.23 (talk) 09:35, 22 June 2010 (UTC)

If it is just a stand it won't have much effect, but if the mesh blocks the line of sight to the wireless router it could well seriously degrade the signal. Graeme Bartlett (talk) 10:50, 22 June 2010 (UTC)

power electronics

what's the difference between a volotage regulator and voltage stabilizer? —Preceding unsigned comment added by K.saikishan (talk • contribs) 10:53, 22 June 2010 (UTC)

A voltage stabilizer appears to be the name of a finished product (ie a box with inputs and outputs). A voltage regulator is a more general term which can refer to a single component, integrated chip, or finished product.87.102.66.101 (talk) 13:15, 22 June 2010 (UTC)

Cheetah attacks

Have there ever been any reports of Cheetahs attacking humans? Your article on the Cheetah doesn't give any details on this. 202.129.232.194 (talk) 13:41, 22 June 2010 (UTC)

Yes http://www.google.co.uk/search?hl=en&q=cheetah+human+attack&meta= eg [33] [34]

87.102.66.101 (talk) 15:20, 22 June 2010 (UTC)