Wikipedia:Reference desk/Archives/Science/2010 July 17

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July 17

Different forms of lead - enviroment

RoHS states in the criticism section Another criticism is that less than 4% of lead in landfills is due to electronic components or circuit boards, while approximately 36% is due to leaded glass in monitors and televisions (RoHS removed lead from most circuit boards but not leaded glass).

My question is - what are the comparitive dangers of lead solder (lead tin alloy), and leaded glass (lead oxide in silicate/lead silicate) - specifically in landfills or other waste disposal - or more specifically does leaded glass leach lead to any extent? (refs please if possible). Thank you.87.102.32.76 (talk) 00:02, 17 July 2010 (UTC)

Encasing in glass (vitrification) is one way of isolating hazardous materials from the environment. I wouldn't expect leaching of leaded glass to be a significant problem. --Carnildo (talk) 01:14, 17 July 2010 (UTC)

Lead glass does indeed leach lead into drinks. Axl ¤ [Talk] 20:22, 18 July 2010 (UTC)

butterflies

do you have any idea where a butterfly might sleep at night? —Preceding unsigned comment added by Horseluv10 (talk • contribs) 01:28, 17 July 2010 (UTC)

According to this link butterflies usually sleep in trees. And if memory serves me, butterflies don't really "sleep." They need sunlight to be active, and when there's a lack of sunlight, they go into a sort of resting state that's not exactly sleeping. They don't move around, but they can if they need to. The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 01:41, 17 July 2010 (UTC)

Insects have a 24-hour rhythm of activity, see circadian rhythm. Specifically regarding sleep in insects: for bees, see this Nature paper. So bees clearly do sleep. I'd be surprised if lepidoptera don't. --Dr Dima (talk) 04:29, 17 July 2010 (UTC)

Moths in the daytime will probably be similar to butterflies at night. They just sit and rest. If you knock into them, they might fly for a little distance, but they land quickly and go back into their dormant stage. --Chemicalinterest (talk) 11:03, 17 July 2010 (UTC)

There is a very nice 1916 (!) paper by Rau and Rau, here, describing rest / sleep in insects. Very enjoyable to read, closer in style to J.-H. Fabre than to modern biology papers --Dr Dima (talk) 17:03, 17 July 2010 (UTC)

Getting peanut out of your body faster

I am mildly allergic to peanuts. If I eat them I don't swell up and die. But I do feel slightly out of breath and my joints ache (actually quite painful). Strangely, this only started about two years ago. Anyway, as you can imagine I do avoid peanuts. So I've been having my normal reaction to peanuts for the last few hours but I didn't eat any peanuts today. I was wondering what the hell was going on when I realized that maybe the fried chicken I had for dinner might have been fried in peanut oil. Sure enough, I looked up the restaurant online and, yup, peanut oil only. Anyway, I was wondering if there was anything I could do to make it get out of my body faster. Any suggestions? I've been drinking quite heavily (water that is).--162.83.139.249 (talk) 04:52, 17 July 2010 (UTC)

Yikes, we're just a bunch of semi-anonymous dopes with nothing better to do than answer questions from strangers. It sounds to me like you need some advice from an actual doctor who's examined you in person. If you're concerned about anaphylaxis, you should probably take your epi-pen and/or call 911/go to the hospital. Water wouldn't seem to be very helpful; oil and water don't mix, but don't take my word for it - ask the attending physician. Matt Deres (talk) 04:58, 17 July 2010 (UTC)

Nah, It'll pass in a few hours. Just really quite unpleasant. The worst part about it all is that I am in love with peanuts (mainly peanut butter). I used to eat PB&J sandwiches all the time. Maybe I developed the allergy from overexposure. Anyway, a really neat thing: I just read in Wikipedia's article on peanut allergy that they have developed peanut butter that has 100% of the allergen removed, though it isn't being marketed yet. I can't wait.--162.83.139.249 (talk) 05:03, 17 July 2010 (UTC)

I survived. All over. Kept me awake until 5:00 a.m.--162.83.139.249 (talk) 14:02, 17 July 2010 (UTC)

I'm glad you're alright. If peas aren't a problem, you might want to see if your local grocer carries "pea butter". I've heard it's almost indistinguishable from peanut butter; you can even use it for making peanut butter cookies and the like. Matt Deres (talk) 16:35, 17 July 2010 (UTC)

I agree with Matt, you need to consult a doctor. We can't give medical advice. --Tango (talk) 16:24, 17 July 2010 (UTC)

Excuse me for ranting a bit, but this hits on one of my pet peeves. We don't give medical advice, but that doesn't mean we have to advise people to consult a doctor on every occasion. "Dear Wikipedians, I stubbed my toe and it hurts, what should I do?" "We can't give medical advice, consult a doctor." Nuts. It's sufficient to say that we don't give medical advice -- advising people to consult a doctor is in itself medical advice. And very often it's bad advice -- doctors are an extremely expensive resource, at least in the USA. And -- and -- okay, enough, sorry. Looie496 (talk) 19:31, 17 July 2010 (UTC)

We are actually supposed to say "If you are concerned about it - consult a doctor". Nobody who just stubbed their toe is still going to be complaining about it for long enough to ask for a diagnosis or treatment here on the Wikipedia ref desk. They will use several useful four letter words...hop around for a few minutes - and then recover completely - long before they can reach a keyboard. But if the pain has lasted long enough to ask a question here - perhaps they have actually broken a toe. We don't know that - we can't diagnose it - so we have to defer to a doctor. If someone asks about a stubbed toe and it's really broken - we absolutely shouldn't laugh it off and tell them not to worry or to take an asperin. So IF you are concerned about it - see a doctor (and if you aren't concerned about it and know it's so trivial that you don't need to see a doctor - then please stop wasting our time with stupid questions!) SteveBaker (talk) 15:27, 18 July 2010 (UTC)

It's not my fault you live in a country with a stupid health care system. --Tango (talk) 20:18, 17 July 2010 (UTC)

It's not the health care system, it's the people, unfortunately. Even if you save a person's life that does not mean that the said person will not proceed to sue you for physical and/or emotional distress. Doctors are at least to some extent protected by the system, Wikipedians are not at all. BTW why are we even discussing this? This has no relation to the OP question whatsoever. --Dr Dima (talk) 22:04, 17 July 2010 (UTC)

Look how defensive he is! I'll bet it is Tango's fault we have a stupid health care system! Get him! APL (talk) 05:15, 18 July 2010 (UTC)

Ignoring the asides, and regarding pea butter, yeah I've tried pea butter and the soy crap and many others. Yes you'll hear people say "it's almost like it; you can't tell the difference." Well let me tell you that it's not terrible but... not even close, not even in the same country of the same city of the same ballpark. It's about as close to real peanut butter as say, a tofu dog is compared to a Nathan's all beef hot dog, Armour domestic prosciutto is to Prosciutto de Parma; canned olives are to oil cured...--162.83.139.249 (talk) 01:53, 18 July 2010 (UTC)

Peppermint tea relaxes the spinchters and thus helps things remove more quickly from your rear end. By the way your diet sounds very unhealthy, I would never eat any of the things you favour. 92.24.178.184 (talk) 09:37, 18 July 2010 (UTC)

Almond butter is also out there - we had some in our kitchen at work. I can just about tell the difference between that and "JIF extra-crunchy" - but it's not more different than JIF than JIF is from (say) an up-market organic peanut butter. Since the difference is less than the difference between two different brands of peanut butter - that ought to be "good enough"...especially if you're going to despoil it with grape jelly (or ketchup...and don't say "yuck" until you've tried it!). SteveBaker (talk) 15:33, 18 July 2010 (UTC)

Trimming macaw toenails

Just been clipping my hyacinth macaw's toenails today. When you do it, you have to be careful not to knick the vein that runs all the way down the middle of the nail, apart from the last few mililmetres. What exactly is the purpose of this vein anyway? --95.148.107.17 (talk) 11:48, 17 July 2010 (UTC)

Your macaw's claws are not a solid keratin cone all the way through; they have a narrowing core of living tissue most of the way down, though it runs out before the extreme tip, from which the keratin grows, just as your own finger- and toe-nails grow from a nail bed of living tissue - human and other primates' nails are merely a specialized flattened form of claw. This living tissue needs a blood supply just like all such tissue. Apart from having a blood supply, this tissue will also have sensitive nerves (as you'll know if you've ever had a splinter under a nail), so cutting into this area may not only cause blood loss and damage that could result in future growth malformation of the claw, it will also hurt. 87.81.230.195 (talk) 16:35, 17 July 2010 (UTC)

Dementia.

Three years ago, my wife (now 64 years of age) was diagnosed as a Dementia patient. Her memory and motor co-ordination were affected. She now has no sense of balance and is confined to a wheel chair.Three months ago, she developed what I consider to be a unique problem. She constantly feels the urge to visit the toilet for a bowel movement. She has always been extremely regular, going to the toilet first thing in the morning, so that this latest development is extremely frustrating for both her and myself. To give some indication of the severity of the problem, I have been monitoring the number of times that I have to help her to the toilet on a daily basis. At present, the record stands at 51 times in a 24 hour period, with only one successful bowel movement. This has obviously affected our sleep pattern, so that we are now averaging a mere 3-4 hours sleep a night over the past two weeks. I have used medication prescribed by my GP, neurologist and a psychiatrist, as I was informed that the problem was caused by a short-circuit in the brain. No medication has had the slightest positive effect. I would like to know whether this problem has been encountered before and been successfully treated. If so, what medication or treatment was employed. —Preceding unsigned comment added by 196.30.31.182 (talk) 16:09, 17 July 2010 (UTC)

Unfortunately, we cannot give medical advice. Sorry. This seems like a serious problem, have you tried contacting a doctor? That would probably be the best thing to do. The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 16:20, 17 July 2010 (UTC)

Given the OP is talking about such a serious problem and how past medication has failed, it's safe to assume that they have already spoken to a doctor. The best option is to continue seeing the doctor who has the best knowledge of your wife's case and talk about extending your current treatment arrangement or starting a new one. There's lots of information on the internet about dementia and it's treatment, but I must say that most forms of deteriorating dementia are not curable and are usually treated to sustain memory for as long as possible. I don't feel comfortable going into any more detail I'm afraid, so please go talk to your doctor. Regards, --—Cyclonenim | Chat  16:48, 17 July 2010 (UTC)

Besides, Draco, he wasn't even asking for medical advice, but medical information. Medicine is still a scientific topic that can be discussed. Even if the question is anecdotally phrased. —Preceding unsigned comment added by 92.19.107.38 (talk) 20:24, 17 July 2010 (UTC)

<removed duplicate question> SteveBaker (talk) 16:26, 17 July 2010 (UTC)

Wikipedia articles that may be relevant are Defecation#Neurological aspects, Dementia and Caregiving and dementia. Cuddlyable3 (talk) 18:45, 17 July 2010 (UTC)

Metric system

What's the point of the metric system? --138.110.206.102 (talk) 17:12, 17 July 2010 (UTC)

• Stablishing one system of units common to the whole world.
• Using a decimal system that makes it easier to use mathematical formulae. Dauto (talk) 17:14, 17 July 2010 (UTC)

See metric system. Looie496 (talk) 17:16, 17 July 2010 (UTC)

But it's so confusing with all the different prefixes and stuff. And the units are different magnitude than the regular units. 1 m isn't even close to 1 ft. --138.110.206.102 (talk) 17:22, 17 July 2010 (UTC)

Metric system units are easier to remember, as for example one metre is 100 centimetres, one tonne is 1,000 kg, and so on. It's also much easier to calculate than Imperial units, as it's difficult to remember how many feet there are in a mile but not so difficult to memorize the number of metres in a kilometre (1,000). ~AH1^(TCU) 17:27, 17 July 2010 (UTC)

5280. --138.110.206.102 (talk) 17:28, 17 July 2010 (UTC)

Yes, but that's not easier to remember than the metric units. All names within this system are based on the main unit, and are in base ten. For example, there's nanometre, mircron (or "micrometre", that's an exception), millimetre, centimetre, decimetre, decametre, kilometre, etc. In Imperial, you have to remember the number of fluid ounces in a pint, pints in a quart, quarts in a gallon, and so on. You don't have to remember these confusing conversions in metric. Instead of using actual full names, all you really have to remember in a series of metric units is one name, and the prefixes. ~AH1^(TCU) 17:38, 17 July 2010 (UTC)

You may be able to remember how many feet there are in a mile, but many people can't. Without looking it up, can you recall the conversion factor between fl. oz. and cubic in., both of which are units of volume? If you made a calculation and the result came out to be 1,023,514 in., would you be able to convert it to miles (a more familiar unit for lengths of that magnitude) in your head? Do you remember the conversion factor between avoirdupois oz. and troy oz.? With the metric system, there are many fewer redundant units for the same types of quantities, and the system of prefixes is uniform for all types of units. --173.49.11.154 (talk) 18:17, 17 July 2010 (UTC)

(ec)It's interesting that you say "1 m not close to 1 ft"--somehow you've chosen the foot as the standard, and you have to memorize arbitrary conversion factors from it to everything else (12 inches, 1/5280th mile, 1/3th yard). And a whole different set of conversion factors for other types of measurements (for pounds, 16 ounces and 1/2000th ton). And another set for volume (quick! how many drams in a gallon?). With metric, it's the same conversions for everything...less to know. And doing powes-of-ten conversions is easy because it matches our whole numbering system (just shift the decimal point) rather than multiplying or dividing by "less round" values.

OTOH, the whole idea of a "comfortable/recognizeable" unit is important when you're trying to use both--you just chose the wrong correspondence. A meter is about a yard (so a meter is 3 feet, rather than a 1:1 for your natural base unit, and an inch is 2.5 cm). A liter is about a quart (so a gallon is 4 liters). A kilogram is about 2 pounds. DMacks (talk) 18:24, 17 July 2010 (UTC)

The metric system is an international decimalised system of measurement used by most of the world except only Burma, Liberia, and the United States. Did you read the article Metric system ? Cuddlyable3 (talk) 18:35, 17 July 2010 (UTC)

However, 1 metre is approx. 1.1 yards (or 1yard and 3⅓inch). If you are used to the metric system then the US customary system and the British Imperial system (they are slightly different) are inconsistent and awkward to use. Now let me see. There are 12 inches to the foot, 3 feet to yard, 2 yards to the fathom, 110 fathoms to the furlong, 8 furlongs to the mile. There are 16 ounces to the pound, 14 pounds to the stone, 8 stones to the hundredweight, 20 hundredweight to the ton. There are 1000 millimetres to the metre, 1000 metres to the kilometre. There are 1000g to the kilogram, 1000kilogram to the metric ton. Now which is simpler? CS Miller (talk) 20:09, 17 July 2010 (UTC)

Out of the units you mentioned, the only ones that are commonly used are inches, feet, yards (in football), and miles for length and ounces, pounds, and tons for weight. Fathoms, furlongs, stones, and hundredweights are only used very rarely. --138.110.206.102 (talk) 21:21, 17 July 2010 (UTC)

Oh - but it's much worse than that. Csmiller says that there are 14lbs to the stone and 8 stones to the hundredweight. That means that there are 112 lbs in a hundredweight...but hold on...aren't there 100 lbs in a hundredweight? Well - it depends which side of the atlantic you happen to live on - it's 112lbs in the UK and 100lbs in the US.

There was a time when that didn't matter much unless you were shipping stuff from the US to the UK or vice-versa. But in this era of universal communications where we don't even know that Csmiller is a Brit (I presume), we can easily be talking at cross-purposes. If someone asks "How many pounds are there in a hundredweight", the answer is quite complicated.

Then 138.110.206.102 comes along and tells us that the imperial system isn't so complicated because such-and-such units are not used anymore because (presumably) (s)he is an American - and is unaware that many British people still very commonly use the 'stone' when talking about human bodyweight and hardly use the gallon much at all anymore when it's really common in the US.

This "imperial system of measurements" that everyone is talking about isn't any kind of standard at all - it's a complete mess that causes immense amounts of confusion when used on the Internet where people are too stupid to realize that when an American says "My car does 35 miles per gallon" that a Brit is likely to think "Well, that's not so terrible - I thought Americans all drove gas-guzzlers"...but that's because a car that does 35 miles per UK gallon would be doing an impressive 42 miles per US gallon because US gallons are much smaller. A 35mpg car in the US is really a gas-guzzling 29mpg car in the UK.

As a final note: My wife was a nurse in the UK and France - where drug dosages are measured in grams (g). When she studied to get her license to practice in the US, she was horrified to discover that over here, drugs are measured in 'grains' - and also use the abbreviation 'g'!!! When US drug companies ship overseas, they are required (of course) to label them in grams ('g'). When drugs are imported from overseas, they have to be re-labelled because of that, but the standard for doing that is change the abbreviation for 'grams' to 'gr' so as not to confuse medical people who are used to using grains! Now - how many people in the US buy cheap drugs over the Internet from Canada, Mexico and elsewhere? It would be really interesting to discover how many people have died because of that incredible piece of stupidity! SteveBaker (talk) 14:44, 18 July 2010 (UTC)

Wow, what a mess! Before I read this I've always thought that when dealing with mass measurements, "gr" was ambiguously the abbreviation of "grain" and that "g" could always be unambiguously interpreted as "gram". I, too, now wonder how many people have been killed by that confusion! --173.49.11.154 (talk) 16:15, 18 July 2010 (UTC)

As it happens, most tablets are marked in milligrams (mg) - even if the amount is 1000mg (ie, one gram). Since people don't mark things in 'milligrains' - this doubtless lessens the confusion. However, liquid drugs (where the quantities involved are much larger) do still have this confusion. But they don't label tablets with 'mgr' - so who knows what horrible messes are still possible! SteveBaker (talk) 16:49, 18 July 2010 (UTC)

Yes, I was using the UK system, not the US system. BTW, yards are still used in the UK. Normally in sports - pitch lengths and golf green lengths, and road distances under about 1/4 mile. CS Miller (talk) 22:28, 18 July 2010 (UTC)

My original point with that list is that there is with the traditional systems no way of inferring how to go from one unit, say 'foo', to the next unit up, 'baz', without consulting a reference book, or remembering the conversion factor. With the metric system there is one base unit of measurement for any quantity, say 'foo'. With the metric system I know that, without knowing what a 'foo' measures, that 1000 milli-foo will be 1 foo, and that 1000 foo is 1 kilo-foo. CS Miller (talk) 22:53, 18 July 2010 (UTC)

The idea behind the metric system was, as Looie points out, twofold. First was to develop a universal standard, so that the US and the UK and France and Japan all knew that if you said something was a given length or weight, it was. This is in contrast to systems that were sometimes quite localized, and a "pound" or a "foot" could mean different things in different places. Second was to develop a system that was decimalized, because it is easier to do many calculations with decimalized systems than non-decimalized. 12 inches to a foot, three feet to a yard, dividing inches into 1/16ths, 5280 feet to a mile... this is a pain, quite arbitrary, and makes it hard to covert between units (how many 1/16ths of an inch are there in a mile? Not the easiest calculation to do in your head). Decimalization lets you just change prefixes and do things in orders of 10. That's pretty easy to do. As for what feels "intuitive" to you—it's entirely what you grow accustomed to using. I find miles intuitive but that's just because I've grown accustomed to thinking in terms of them. It's entirely arbitrary. Which is not to say that in all fields decimalization is easier; in time, for example, there is a strong argument that decimalization doesn't actually save much effort on calculations, and in fact impedes certain types of calculations. --Mr.98 (talk) 20:20, 17 July 2010 (UTC)

Nobody seems to have mentioned that it incorporates (not by chance) conversion factors of 1. eg 1 cubic meter of water weighs 1 metric tonne, or 1 cubic centimetre of water weights 1 gram (ie based on water of density 1 unit). Extensions of the metric system ie SI units do similar things, Centigrade is based on the properties of pure water: melting and boiling point 100 divisions. Kelvins retain the same scale but are offset. also Move a force of 1 newton through 1 meter and you've done 1 joule of work. Compare with the various conversion factors for 1 footpound.87.102.32.76 (talk) 20:36, 17 July 2010 (UTC)

Indeed. Consider a dam, 100metres high, 1km wide, with a water-pool 10km long. It is 300 metres above sea-level. How much energy is stored in it? The answer is - the volume of water is 100m*1km*10km. That is 1 km³ or 1 million m³. 1m³ is one ton or 1000kg, so there is 10⁹kg of water. Energy [ Joules ] = mass * gravity * height, or E = mgh. g is 9.83 m·s^-2, which is normally approximated as 10. Therefore, there are 10⁹ * 10 * 300 Joules, or 3 PetaJoules, or 833 million kWhr.

Consider a dam, 100 yards high, 1mile wide, with a water-pool 10 miles long. It is 300 yards above sea-level. How much energy is stored in it? The answer is the volume of water is 100yards * 1 mile * 10 miles. That is 3.1 billion cubic yards. 1 cubic yard of water weighs 1685.5 lb, so there is 5.2 trillion pounds. E (BTU) = m (pounds) * g * h (yards), where g = 0.003855 BTU/yard/foot. So E = 5.2 trillion * 0.003855 * 300, or 6 trillion BTU.

Now, which is easier? CS Miller (talk) 21:37, 17 July 2010 (UTC)

This point is often overstated. Yes, the nice value for the density of water under standard conditions is a timesaver when doing mental arithmetic (mental arithmetic specifically; it hardly matters to a computer) on problems that involve water.

But while water is pretty important, it's not the only substance we want to know about. Suppose you want to estimate how fast air pressure goes down with increasing elevation? The density of water won't help you at all; you need to memorize something if you're going to do it in your head. (What I remember is the volume of one mole of an ideal gas at standard temperature and pressure; 22.4 liters).

Similarly, sure, the conversion factor between meters and kilometers is easier to do mental arithmetic with than the one between feet and miles. But if you're doing anything more complicated than just multiplying or squaring them (say, if you want to know the surface area of a sphere rather than the volume of a cube) there's a good chance you're going to be reaching for the calculator anyway. Summary — sure, it's true that certain common calculations are easier to do in your head in the metric system, but this was more important when more of them had to be done in our heads. --Trovatore (talk) 21:54, 17 July 2010 (UTC)

Okay, okay. So the metric system makes immeasurable (he-he) sense. No wonder then that the US and UK are reluctant. hydnjo (talk) 20:52, 17 July 2010 (UTC)

The UK uses the metric system. Dauto (talk) 21:57, 17 July 2010 (UTC)

No, it kinda uses the metric system because certain situations use pints, BTU, feet and yards. Regards, --—Cyclonenim | Chat  22:29, 17 July 2010 (UTC)

We use pints for milk and beer (they aren't the same size as US pints, though) and feet for the height of people (and stone and pounds for the weight of people, never just pounds like in the US). I've never seen someone use BTU. Yards are used for some things (the signs warning you of an approaching junction on a motorway are 100, 200 and 300 yards from the junction, for example), but they are pretty rare. Miles are used for large distances, especially on roads. The size of anything being sold will always have the metric equivalent on the label, under EU law. --Tango (talk) 23:05, 17 July 2010 (UTC)

BTU is used on some older boilers like the one in my house. Newer ones probably use SI units. Regards, --—Cyclonenim | Chat  13:43, 18 July 2010 (UTC)

Well, it is not uncommon for people to use non-metric system units even in countries that have a metric system tradition. For instance, in Brazil it is common to use cups, tea spoons and table spoons for culinary situations. The point is that the metric system is used in the UK and people there don't find themselves confused about how big a metre is. Dauto (talk) 23:10, 17 July 2010 (UTC)

I find it amusing that there are people who defend imperial units with almost religious fervor.. "I'll give you my inches when you pry them from my cold dead hand!". lol Vespine (talk) 23:50, 17 July 2010 (UTC)

For some possible origins of the word "inch", this could almost literally be true! Mitch Ames (talk) 09:59, 18 July 2010 (UTC)

Indeed. What I find most ironic is that those same people are likely the ones who would roll their eyes when hearing a Brit describe the old pound system ("12 pence to a shilling, twenty shillings to a pound... that's nuts! How do they ever make change?") Matt Deres (talk) 03:24, 18 July 2010 (UTC)

Actually (although I'm first to defend the switch to metric currency), there were aspects of the old system that made sense. With 240 pennies in a pound, you could easily and exactly have 1/2, 1/3rd, 1/4th, 1/5th. 1/6th, 1/8th, 1/10th, 1/12th, 1/16th. 1/20th, 1/24th, 1/30th, 1/50th, 1/60th, 1/80th, 1/120th and 1/240th of a pound. With 100 pennies in a pound (or cents a dollar), you only have 1/2, 1/4th, 1/5th, 1/10th, 1/20th, 1/25th, 1/50th and 1/100th. In an era before calculators, this was a useful thing. SteveBaker (talk) 04:35, 18 July 2010 (UTC)

How did you make change for 1/50th of a pound in the pre-decimal system? APL (talk) 05:13, 18 July 2010 (UTC)

You cannot. SteveBaker is wrong: one cannot have exactly 1/50th of a 240-penny pound.Cuddlyable3 (talk) 11:26, 18 July 2010 (UTC)

Sorry - you're right - I made a boo-boo. SteveBaker (talk) 14:18, 18 July 2010 (UTC)

Looks like a typo - 1/40th could be in there, but isn't. Vimescarrot (talk) 14:26, 18 July 2010 (UTC)

There are many reasons to prefer metric:

• Consistency: If I mention a unit you don't know (maybe a 'Henry' - the SI unit of inductance) - you still immediately know that 1000 millihenry is 1 henry, and you'd expect that in the equation for inductance (which involves volts, amps and seconds) that there wouldn't be any funny constants in there (1 henry is one volt times one second divided by one amp). But in non-metric units, you have no idea how many ounces there are in a hundredweight unless you also know how many pounds there are in a hundredweight and how many ounces in a pound. You know that the imperial unit of 'power' is the horsepower, and that power is energy divided by time...but you can't take imperial units of energy (btu's) and imperial units of time (seconds) and immediately know how many btu's per second makes a horsepower. But with metric units, you know that a watt is one joule per second.
• Memorable Ratios: With imperial you have to memorize an immense number of arbitary names and conversion factors - with metric, there are base units and multipliers and they are all simply related by powers of 10 or 1000. Do you know the number of millibars in a psi?
• Abbreviations: The SI units have standard abbreviations (m,g,s etc) that are completely unambiguous and uniform across all different languages - where in imperial units, there are all sorts of confusing collisions - and 'pound' in English abbreviated 'lb' - but is 'livre' in France and abbreviated 'l'. Within the US alone, 'mi', 'ml', 'm' and 'M' are all used as abbreviations for 'mile'. But no matter where you go in the world, a kilometer is always 'km'.
• Standardization: All SI users agree on how big a meter a kilogram and a second are. But in imperial, there are lots of different miles, tons, hundredweights, ounces, pints and gallons. If I tell you that my car does 35 miles per gallon - you can't tell what that means without first asking whether I'm talking US gallons or UK gallons.
• Comprehensiveness: There are no imperial units for oddball things like inductance. The Henry is defined by the kilogram, meter and second...but there is no unit of inductance that's specified in terms of pound, foot and second. This is also true for volts, ohms, amps and watts. All electrical units that are used in the imperial-unit world are metric.
• Lack of ambiguity: If I tell you that one person measured the pressure in a vessel as 1at - and someone else measured it at 0.96784atm, you could easily assume that the pressure had changed between those two measurements - but an 'at' is a 'technical atmosphere' and an 'atm' is an 'atmosphere' - they are different units for pressure - both present in the imperial system. But 10Pa is 10 pascals...no matter what. Since there are no other units of pressure, it's utterly unambiguous and (so long as you've learned the system), incapable of confusion.
• Rigor: There is confusion in the imperial system between 'pound' and 'pound-force' - and between 'ounce' and 'fluid ounce' and (most egregious) between 'calorie' and 'Calorie'. In the super-formal SI system, kilograms and newtons are clearly different units - and kilogram and liter are also cleanly distinguished and 'cal' and 'kcal' are hard to confuse.

SteveBaker (talk) 04:35, 18 July 2010 (UTC)

Steve makes an excellent case for the superiority of SI units, but I'm still happy to use my Imperial units here in the UK alongside and in preference to the imposed metric system (with which I am also conversant). Perhaps I'm a dinosaur, but my species hasn't died out yet. Dbfirs 09:24, 18 July 2010 (UTC)

Imperial units are also imposed on people in many situations. For example, in the UK, street signs are still marked in miles and miles-per-hour because the cost to replace all of those millions of signs (and to do it all on the same day!) would be immense. Also, if you are an aircraft pilot - even in a country that is 100% switched over to the metric system - you are forced to think of aircraft altitudes in feet because that's the international standard and aircraft altimeters have a scale that shows thousands of feet with no metric equivalent. Ships are a similar deal - with speeds almost always being measured in nautical miles per hour (knots) instead of km/hr. A nautical mile is one arc-second in latitude - so if you are figuring out your latitude in degrees, then - in an age before calculators - it was simplest to use nautical miles - and hence, knots for speed. The cost and effort of converting aircraft over to the metric system would be spectacularly high right now - with minimal benefits. However, as aircraft transition from mechanical/pneumatic instruments over to computer screens - and paper charts are replaced by GPS, the cost of transitioning will decline sharply. However, it would still require international agreement and that would be virtually impossible to obtain. This kind of 'lock-in' effect makes a complete transition to the metric system almost impossible in countries that have not already been using it for a couple of hundred years.

SteveBaker (talk) 14:18, 18 July 2010 (UTC)

I just have to respond to some nonsense there. Road signs won't all be changed on the same day. Signs with both units are installed over a longer period, then gradually replaced with simply metric signs as needed after the change. Every major nation involved in aviation is already metric except the USA. Why would the USA make it impossible to obtain agreement? Australia and Canada made total transitions from Imperial to metric in the latter half of the 20th century, so it can be done. HiLo48 (talk) 21:20, 18 July 2010 (UTC)

I don't think the cost is the main thing preventing changing to kilometres on UK roads. Bigger factors are: the public resistance to any kind of change, drivers not being familiar with the new units and the change it would require to speed limits (you could put up signs saying 48.3 km/h, but it would be pretty silly. More likely would be increasing the speed limit to 50 km/h, which will result in protests from people concerned about road safety. The alternative is reducing it to 45 km/h, which would result in protests from people that think it's just a way of getting more money from speeding fines). --Tango (talk) 15:41, 18 July 2010 (UTC)

I'm still trying to push my road safety idea, which is to reduce every limit by 1mph. 87.81.230.195 (talk) 17:27, 18 July 2010 (UTC)

Ireland metricated its roads in 2005 - see Roads in Ireland just before the TOC. CS Miller (talk) 22:20, 18 July 2010 (UTC)

I somewhat object to US customary units being referred to as Imperial. Going "meta" for a moment, I have to wonder why it is that refdesk discussions so often seem to be Brits discussing amongst themselves. There are many many fewer British citizens than Americans, but somehow there seem to be more of them represented on the refdesk (and perhaps as WP editors in general). Is there something about the endeavor that specifically appeals to the British character? --Trovatore (talk) 20:08, 18 July 2010 (UTC)

Isn't the US system sometimes called English Units, not Imperial Units in the US? CS Miller (talk) 22:20, 18 July 2010 (UTC)

Yes, an that really annoys me. Why would anyone call a unit "English" when it is only used in the US? --Tango (talk) 23:28, 18 July 2010 (UTC)

Imperial units are the non-metric units used in the (former) British Empire. US customary units are the non-metric units used in the US. They are different units and it is completely wrong to use one name to refer to the other set of units. As for Brits being overrepresented on the ref desks: I believe we are overrepresented on Wikipedia in general. I don't know why. --Tango (talk) 23:28, 18 July 2010 (UTC)

The basic problem with the metric system is that the units are based on a scientific calculation rather than on something "human", which is where inches, feet, and yards came from. You can say someone is 5 or 5 1/2 or 6 feet tall and it makes some sense. Saying someone is 1.8 meters tall seems less exacting somehow. Same problem with F vs. C in temperatures. F has a finer gradient than C does. Also, there is a fundamental flaw with metrics: Just try dividing a meter by 3. With a foot, a yard, or a mile it's no problem. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:46, 21 July 2010 (UTC)

I concur with Bugs. 'Imperial' and other 'traditional' systems are the end result of hundreds if not thousands of years of cultural evolution, resulting in unit sizes and inter-relationships well (though not necessarily maximally) suited to their applications by and to people and their affairs, unlike a universally applied system derived in part from such things as the distance from the Equator to the North pole. Given the increasing ubiquity of computing devices that should be capable of instant conversions (though not with the fallibility of humans who might forget to employ them), there should be no major problems running them in parallel (bar the odd lost Martian probe). 87.81.230.195 (talk) 16:58, 21 July 2010 (UTC)

How portions of the brain are identified

In the left hemisphere of the brain are located Broca's and Wernicke's regions. Are the corresponding regions in the right hemisphere similarly named -- i.e. right hemisphere Broca's, etc. -- or are these right hemisphere regions referred to with specific designations. —Preceding unsigned comment added by 216.106.212.60 (talk) 19:53, 17 July 2010 (UTC)

My understanding is that usually only the regions in the hemisphere that is dominant for language (Usually, but not always, the right) are referred to as Broca's area and Wernicke's area -- our article on Wernicke's area seems to confirm this. I suspect that if you were to look through the literature, you'd find some inconsistencies, though. Looie496 (talk) 01:13, 18 July 2010 (UTC)

See Lateralization of brain function and Functional specialization (brain). The language centers of the brain, as well as the logical areas seem to be mostly in the left hemisphere. ~AH1^(TCU) 02:11, 18 July 2010 (UTC)

They are almost always in the left hemisphere in right-handed people. In people who are left-handed, they can be on either side, or you can even get mixed dominance in rare cases. Looie496 (talk) 02:18, 18 July 2010 (UTC)

Fast neutron reactor meltdowns

One can endlessly find statements that reactors cannot detonate "like nuclear bombs", because they use slow-neutron chain reactions, and for a weapon-sized explosion you need a fast-neutron chain reaction. With a slow-neutron reactor, the worst you can get is fuel that heats to the point of melting (meltdown), or in some scenarios the production of flammable hydrogen gas (which, if ignited, could cause trouble).

My question is whether fast neutron reactors would act differently in this regard, in terms of becoming supercritical with a fast neutron chain reaction. Obviously the lack of material and tamping, etc., is not going to get you kiloton-range nuclear reaction even in the worst case scenario. But could you get 10-100 ton TNT equivalent from a fast neutron chain reaction in a reactor that had, say, 20%-90% enriched U-235?

My gut feeling is "no", because the assembly time would be too slow even if there was enough material, but I don't really know how low of a fizzle it would be. If the goal is only 10-100 tons of TNT equivalent, that doesn't require exactly perfect conditions.

Any thoughts on this? I haven't found anything specifically on it by Googling. --Mr.98 (talk) 21:41, 17 July 2010 (UTC)

See: Delayed neutron, and also this section, in particular: "Thermal expansion of the fuel itself at increased power can provide quick negative feedback." Basically if it started to heat up it would shut itself down. Ariel. (talk) 05:01, 18 July 2010 (UTC)

I'm not sure I buy that? I mean there are a lot of conditions where it is imaginable that the increased heat would not necessarily cause the fuel to move apart. And if the supercriticality happened too quickly (e.g. all control rods immediately removed, or some kind of reflector was put into place), it would still be a fizzle, which could be quite a large boom (in human terms), yes? --Mr.98 (talk) 18:05, 18 July 2010 (UTC)

I am not familiar with the fast neutron reactor type, but your typical nuclear fuel rod is only enriched to around 5-10% U235, not 20-90%. Is that highly enriched fuel something specific to a fast neutron reactor? Googlemeister (talk) 13:13, 19 July 2010 (UTC)

Animal Allergies

I was wondering, are there any records of animals having allergies to such things as dust, pollen or shed hair like some humans? And if so, how would this affect their behavior? I'm talking about allergies like hay fever, with symptoms like itchy eyes, runny noses and headaches. Are humans the only animals to have these problems? Thanks! Stripey the crab (talk) 23:04, 17 July 2010 (UTC)

Well this is just an anecdote but my friend had a beagle with really bad hay fever, she used to have to give it antihistamines every day or else it's eyes would get all sore and weepy. I can't see why allergies would be a purely "human" condition. Vespine (talk) 23:33, 17 July 2010 (UTC)

The causes described in the allergy article do not seem to point to uniquely human factors. Do other animals suffer from pruritus and irritation following a mosquito bite? ~AH1^(TCU) 02:08, 18 July 2010 (UTC)

The mechanisms underlying allergies are universal across animals (or at least vertebrates; not sure about others). But allergies happen when the mechanism is hyperactive. There's a fine line: the weaker the response, the higher the susceptibility to infection; the stronger the response, the higher the incidence of allergy. Different species face different infection risks and therefore have different levels of immune response. Just about any animal will show an allergic response if you provoke it strongly enough, though -- for example by injecting some sort of foreign protein into its bloodstream. Looie496 (talk) 02:25, 18 July 2010 (UTC)

My dog was at one point referred to a dog allergist by our vet. On the other hand I'm not fully convinced it wasn't an elaborate scam. Rckrone (talk) 16:49, 18 July 2010 (UTC)

Assuming that allergies are mostly caused by the lack of exposure to stuff in childhood thanks to sterilized environments...animals eat dirt and chew on dead animals. Might not be as big a problem with them....right? --mboverload@ 23:13, 18 July 2010 (UTC)

Loudspeaker distortion

What is a typical level of distortion in a hi-fi loudspeaker system and does it depend upon frequency?--88.104.91.109 (talk) 23:21, 17 July 2010 (UTC)

Distortion is measured in total harmonic distortion, that article says anything below 1% is considered "High Fidelity" so depends what you mean by "typical". THD is calculated based on a standardized test which does not consider frequency however I do believe the frequency would effect distortion, especially if the sound falls out side the "sweet spot" in the speaker's frequency response. Vespine (talk) 23:43, 17 July 2010 (UTC)

Essentially all loudspeakers produce more distortion than electronics, and 1–5% distortion is not unheard of at moderately loud listening levels. Human ears are less sensitive to distortion in the bass frequencies, and levels are usually expected to be under 10% at loud playback. Distortion which creates only even-order harmonics for a sine wave input is sometimes considered less bothersome than odd-order distortion. See the article Audio system measurements. Cuddlyable3 (talk) 11:15, 18 July 2010 (UTC)